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active regions are complex , dynamic objects and are prominent manifestations of solar activity . understanding the nature , origin , and development of these regions is one of the most important outstanding questions in solar physics .
helioseismology provides us with a means to probe the layers of the sun below the surface of active regions , and has the potential to yield important clues about their structure and evolution .
in particular , helioseismology can give us information about the flows and dynamical structures associated with active regions , about the depth and extent of thermal disturbances beneath sunspots and other surface phenomena , and about the nature of the magnetic fields that rise to form active regions .
the frequencies of global oscillations change with the overall level of solar activity @xcite ; this is by now very well established ( see review by * ? ? ? * and references therein ) .
the frequencies of both low degree modes ( e.g. * ? ? ?
* ) and medium degree modes ( e.g. * ? ? ?
* ; * ? ? ?
* ; * ? ? ?
* ) increase with solar activity level , and this frequency increase is stronger at higher frequencies .
though high degree global mode measurements are not routinely made , some sets of high degree mode frequency measurements have been made , and these are found to increase with activity as well @xcite .
the use of so - called ` ring diagrams ' @xcite to study solar structure is by now a well - established technique in helioseismology ( see review by * ? ? ?
* ) . in this paper
, we will discuss the changes to mode parameters in ring diagrams between active regions and the surrounding quiet sun .
ring diagrams prove useful for studying the effects of solar activity on helioseismic modes for two reasons .
first , rings are measured on a localized patch of the sun , providing both temporal and spatial resolution .
this allows us to isolate phenomena associated with solar activity from the surrounding sun .
second , measurements can be made to much higher degree much more easily than with global mode analysis .
ring diagrams were first used by @xcite to measure flow rates near the solar surface .
rings have been used subsequently by a number of authors to study the near - surface dynamics of the sun ( e.g. * ? ? ?
* ; * ? ? ?
* ; * ? ? ?
ring diagrams have also been used to study the thermal structure beneath sunspots and in the near - surface layers @xcite .
the effects of active regions on ring diagram mode parameters have been studied in previous works .
@xcite found that the high degree mode frequencies obtained from ring diagrams were enhanced in active regions .
@xcite found that the mode widths were also enhanced in active regions , while the amplitudes were suppressed , and @xcite found that the relation between the change in width and mode amplitude was very nearly linear . @xcite assumed that the relation between activity and mode parameter variation was quadratic , and found a peak increase in mode frequency at around 5mhz , with a corresponding maximum change in width and amplitude . in this work
, we study the properties of 264 active region ring diagrams from solar cycle 23 .
this sample gives us a statistically significant number of measurements over a substantial range of activity levels from all phases of the solar cycle , when compared to earlier works .
the data are resolved line - of - sight velocity measurements of the solar surface taken by the michelson doppler imager ( mdi ) on board the _ solar and heliospheric observatory _ ( soho ) spacecraft @xcite .
ring diagrams are constructed from small , @xmath0 patches of the solar disk , tracked to move with the solar differential rotation .
the regions are tracked across the solar disk center .
the observation cadence is 1 minute , and the patches are tracked for 8192 minutes .
they are projected onto a rectangular grid using postel s projection and corrected for the distortion in the mdi optics .
the doppler cubes are then fourier transformed to obtain a three dimensional power spectrum .
a more detailed discussion of the construction of ring diagrams can be found in @xcite and @xcite .
the spectra are fit in the same way as @xcite .
the functional form is from @xcite ; it is an asymmetric lorentzian profile with terms for advection in both transverse directions and for azimuthally asymmetric power distribution .
fits are done at constant frequency , so that to interpret these measurements as discrete normal modes , we interpolate along each ridge to integer values of the degree @xmath1 .
errors are treated in the same way as @xcite .
target active regions are selected from the noaa active region catalog .
ring diagrams require higher resolution dopplergrams than the usual mdi ` medium-@xmath1 ' data that are collected continuously .
we use full - disk dopplergram data which are one of mdi s ` high rate ' data products , produced mainly during yearly two to three month dynamics run campaigns .
we require a data coverage of greater than 80% .
the noaa active region catalog includes sunspot classifications according to the mt . wilson scheme .
wilson classifications are @xmath2 , @xmath3 , @xmath4 , and @xmath5 , and combinations of these .
the noaa catalog lists active regions for each day that they are visible , and in the case where the classification changes , we take the classification closest to center disk crossing . in our sample ,
90% of the active regions are classified as either @xmath2 , which are unipolar groups , or @xmath3 , which are simple bipolar groups .
ring diagrams suffer from a number of systematic effects .
these arise primarily from foreshortening when away from disk center , and secular changes in the characteristics of the mdi instrument .
these effects can be minimized by studying the mode parameters of an active region relative to a quiet sun region , tracked at the same latitude and as near in time as possible . for this sample ,
two quiet regions were chosen for each active region , one on either side of the active region . in order to characterize the level of activity in our rings
, we use a measure of the total unsigned line - of - sight magnetic flux .
this measure is the magnetic activity index ( mai ) , which is described in @xcite and is a measure of the strong magnetic unsigned flux in the ring diagram aperture . in brief
, the mai is the spatial and temporal average of all mdi magnetogram pixels with a flux greater than 50 g , taken over the same aperture and time range as the velocity data for the ring diagrams .
the activity in each region , then , is characterized by a single number , and differential measurements can be characterized by the difference in mai , @xmath6 , between the active region and the quiet comparison region .
we also fit a linear trend in time to the spatial averages of the magnetograms .
this gives a rough measure of the growth or decay of the active region , and we refer to this quantity as the growth parameter .
mode parameters for all rings and comparison regions were fit using the profile from @xcite .
we interpolate the ridge fits to integer values of @xmath1 , and take the differences in frequency @xmath7 .
the sense of the differences are active minus quiet . in figure
[ fig : dnu ] , we show averages of the scaled frequency differences @xmath8 for the @xmath9-mode and the first three @xmath10-modes
. the frequency ranges chosen have relatively small errors and were fit in most regions in the sample .
the behavior seen in figure [ fig : dnu ] is nevertheless representative of the rest of the data in our sample .
the majority of @xmath6 values are fairly small this is in part due to the fact that the majority of active regions do not have particularly large mai values , but also due to the fact that , at high activity levels in particular , it is sometimes difficult to find a suitable quiet region for comparison .
the comparison regions therefore sometimes have fairly significant mai values .
we confirm earlier results finding that , in the presence of magnetic fields , helioseismic frequencies increase .
we find that , for small and intermediate magnetic field strengths ( @xmath11 g ) , the relationship is linear . for the @xmath10-mode differences , the correlation coefficients mostly range between 0.6 and 0.7 .
the @xmath9-mode frequencies have larger errors , and the correlation coefficients are correspondingly lower .
the best fit linear regression lines are also shown .
the reduced @xmath12 values computed from the residuals are large between 3 and 15 for sets of averages .
thus , the computed errors in the fitted frequencies do not completely account for the observed scatter in the frequency differences .
it is possible that a linear relation does not completely account for the dependence of frequency on @xmath6 , but we have tested a variety of higher order polynomials and other functional forms without substantially reducing the @xmath12 values .
when fitting higher order polynomials , the best fits return essentially the same linear fits as shown in figure [ fig : dnu ] , with negligibly small non - linear coefficients .
other functional forms generally increased the @xmath12 values . as a test of the assumption of linearity
, we apply an anderson - darling test to the residuals from the linear best fits .
the residuals from the linear regression fit fail an anderson - darling test at the 1% level .
this implies either that the errors are non - gaussian , or that the relation between magnetic activity and shift in frequency is not entirely linear . at high magnetic field strengths ( @xmath13 g ) , a visual inspection of figure [ fig : dnu ] might suggest a ` saturation ' effect in the frequency shifts .
evidence for such an effect in thermodynamic perturbations beneath active regions has been suggested @xcite . in this case , however , we do not find that the outliers at high field strengths are statistically significant .
fitting different slopes at low and high activity does not change the @xmath12 values of the residuals , and removing the high activity regions from the sample does not substantially change either the @xmath12 values or the anderson - darling @xmath14 statistic of the residuals .
further , we have tested whether or not the presence of some comparison regions with significant activity is introducing bias .
we find that , when the sample is divided between quiet and moderately active comparison regions , the frequency differences are indistinguishable .
it must be noted , however , that a saturation effect is not _
inconsistent _ with our data , either
. a larger sample of high field strength regions will be required to adequately address this problem . to show the behavior of the dependence of frequency on activity , we fit a straight line to each individual mode difference as a function of mai : @xmath15 the slopes @xmath16
are shown in figure [ fig : nuslope ] .
the slopes in frequency shifts are seen to increase with frequency .
it is notable , however , that the slopes are not a pure function of frequency different @xmath17-ridges have slightly different dependences on frequency . at high frequency , there is some indication that the slopes turn over .
it has been observed in mdi data @xcite and in helioseismic and magnetic imager ( hmi ) data @xcite that for frequencies above the acoustic cutoff , the slopes of frequency with magnetic field strength do in fact become negative . in our own sample , however , the quality of the fits do not permit us to extend our work much beyond the acoustic cutoff .
we have examined the differences between different classes of sunspots in the centers of active regions .
the majority of the active regions in our sample are classified as @xmath2 or @xmath3 types . when subdivided by type , the linear correlation is somewhat changed ( though the correlation coefficients are not ) , and the distribution of the residuals for for the @xmath2-type active regions now satisfy an anderson - darling test for normality at the 15% level .
the residuals for the @xmath3-type active regions do pass the 10% test , but do not do as well as the @xmath2-types .
the slopes of the fits and the correlation coefficients are not changed by a statistically significant amount . in figure
[ fig : ars ] we show examples of @xmath18 separated by active region type , and the residuals to a linear fit . the differences in the slopes between the @xmath2-type regions and the @xmath3-type regions are shown in figure [ fig : comp ] .
there is a small but systematic trend with frequency in the slopes . for @xmath19 mhz ,
@xmath2-type spots have very slightly smaller slopes @xmath16 , while they are slightly larger for modes with @xmath20 mhz .
we have also subdivided the sample in a number of different ways to attempt to determine if the mode parameters are sensitive to other variables than the total magnetic field strength in the region .
the fitted parameters were checked for secular trends with time , or for any dependencies on the latitude of the region .
we have found no statistically significant differences in the mode parameters or their behavior with increasing activity , either as a function of time over solar cycle 23 or as a function of latitude .
we can also split the sample in two using the growth parameter of the mai as a rough measure of whether or not a given active region is growing or decaying .
the statistical properties of these two sub - samples are indistinguishable from their parent sample .
the confidence level for all of these claims is at the 95% level or greater .
it is by now well established that helioseismic frequencies below the acoustic cutoff frequency are enhanced in the presence of magnetic fields . in this work , we have measured mode frequencies for a large sample of active regions using ring diagram analysis .
we find , consistent with most earlier work , that shifts in frequency are linearly correlated with the magnetic activity measured at the surface .
these correlations hold for all mode sets and for the whole range of frequencies studied .
both @xcite and @xcite have presented frequency shifts with ring diagrams at various levels of magnetic activity .
our results are generally quantitatively consistent with theirs , though we do not find any evidence of a quadratic dependence of the mode parameters on activity , as @xcite did .
@xcite find what appears to be a much cleaner relation with frequency than we do , in spite of the fact that they use the same frequency fitting technique and data from the same instrument .
this is most likely due to the much smaller number of regions used in that study . our finding that the helioseismic frequencies of different active region types may be drawn from different statistical populations is novel , but it is not immediately clear what the significance of this result is .
it implies that the surface geometry , not only strength , of the magnetic fields in an active region may determine the oscillation characteristics of the sun .
it has been shown that the inclination of the magnetic fields can affect the amount of acoustic power absorption ( e.g. * ? ? ?
observational evidence for this has been found using helioseismic holography @xcite and time - distance analysis .
it is possible that we are seeing this effect averaged out over the much larger region sampled in ring diagram analysis .
although we do find that the slopes @xmath16 are slightly different for the two different active region types , the fact that these differences appear to be simply a function of frequency implies that it is very unlikely do be due to changes in the thermal structure in the regions typically resolved in ring diagram structure inversions . in the region where the upper turning points of the modes are located , however , it is possible that a different thermal stratification in different sunspot types would give rise to a difference such as the one we have detected , since upper turning points are shallower with increasing frequency .
the direct effects of magnetic fields also have an effect on the upper turning points , as was shown by @xcite in the case of horizontal magnetic fields .
the errors in the measurement of the mais are small , but it is possible that small systematic errors arise from the fact that the calculation is restricted to the line - of - sight fields .
different surface field configurations could give rise to somewhat different systematic errors .
it is difficult to estimate how large this effect could be at present , but continuously available high - resolution data becoming available from the helioseismic and magnetic imager ( hmi ) on the solar dynamics observatory ( sdo ) is allowing full vector inversions for magnetic fields .
this will allow us to more accurately compute the total magnetic fields in active regions .
csb is supported by a nasa earth and space sciences fellowship nnx08ay41h .
sb is supported by nsf grants atm 0348837 and atm 0737770 to sb .
this work utilizes data from the solar oscillations investigation/ michelson doppler imager ( soi / mdi ) on the solar and heliospheric observatory ( soho ) .
soho is a project of international cooperation between esa and nasa .
mdi is supported by nasa grants nag5 - 8878 and nag5 - 10483 to stanford university .
-mode and first three @xmath10-modes , as a function of the difference in mai .
the differences are with respect to a quiet region near the active region .
the range of frequencies over which the averages were taken is shown in each panel .
the straight lines are the best linear fits to the data .
[ fig : dnu],width=672 ] -mode and the first three @xmath10-modes as a function of the change in magnetic activity @xmath22 .
the frequency ranges are shown in panels a ) d ) .
blue points denote @xmath2-type sunspots , red points denote @xmath3-type sunspots .
histograms of the residuals are also shown in panels e ) h ) .
[ fig : ars],width=672 ] -type active regions and @xmath3-type active regions . panels a ) and b ) show the slopes @xmath16 fit to the sample of @xmath2-type spots and @xmath3-type spots , respectively .
panel c ) shows the differences @xmath23 between the two sets of slopes .
the differences are shown as a function of frequency up to @xmath21 mhz .
the sense of the difference is @xmath24 .
different colors are used for different radial orders @xmath17 , and are the same as figure [ fig : nuslope ] .
panel d ) shows a histogram of the differences from panel c ) . the solid line is the normal curve with the mean and standard deviation of the data
; the dashed line shows the best fit gaussian .
[ fig : comp],width=672 ] | high degree solar mode frequencies as measured by ring diagrams are known to change in the presence of the strong magnetic fields found in active regions .
we examine these changes in frequency for a large sample of active regions analyzed with data from the michelson doppler imager ( mdi ) onboard the soho spacecraft , spanning most of solar cycle 23 .
we confirm that the frequencies increase with increasing magnetic field strength , and that this dependence is generally linear .
we find that the dependence is slightly but significantly different for active regions with different sunspot types . |
climate change affects health through multiple pathways such as less clean air , less safe drinking water , availability of foods and extreme heat ( 1 ) . increasing global temperatures are expected to impact on yields of food crops and increase global food insecurity ( 2 ) , which could have a bigger impact on health(3 ) .
hence , there is strong public health incentive for mitigating climate change ( 4 , 5 ) .
the uk climate change act 2008 sets a target to cut the total annual greenhouse gas emissions ( ghges ) by 80% by 2050 , compared with 1990 levels ( 6 ) .
uk food production and consumption is responsible for 1830% of total ghge ( 6 ) .
different food groups have different carbon footprints , with livestock ( particularly sheep and cows ) and dairy footprints orders of magnitude higher than cereals , fruit and vegetables ( 7 ) .
therefore , changing the food that we eat can have a substantial impact on ghge in the uk ( 8) . it is not clear , however , whether such changes would lead to healthier diets ( 911 ) . the government report
food 2030 highlights that providing healthy and sustainable diets is an overarching objective and the government should provide stewardship by adopting these principles for food provided in the government sector ( 12 ) .
the public sector spends about 2.4 billion per year for food and catering services in schools , hospitals , armed forces , prisons and government agencies .
the highest percentage of public sector spending for food is on school dinners ( 29% ) ( 13 ) .
this is an area of food provision which has received a great deal of attention recently due to the new school food plan ( 14 ) and recent changes around free school meals .
the uk government introduced a policy on universal free school meals for children in reception , year 1 and year 2 in state - funded schools in england from september 2014 ( 15 ) .
it is expected that the uptake of primary school meals will increase significantly with the new policy , which will impact on the total ghge of primary school meals and the nutritional quality of meals eaten by children .
the nutritional quality of primary school meals in england has been assessed previously ( 16 , 17 ) .
these studies have used food composition tables to estimate nutrients in school foods consumed in a representative sample . for the analyses in this paper ,
we have added measures of ghge to this dataset and developed a novel method to estimate the uncertainty around ghge of primary school meals ( both school lunches and packed lunches ) , based on uncertainty about the parameter estimates for ghge for different food groups .
this study aims to answer the following three research questions :
1:what is the contribution of primary school meals to the total greenhouse gas emissions ( ghges ) in england?2:are school lunches associated with more or less ghges than packed lunches?3:are healthy primary school meals less ghg intensive than unhealthy meals ? what is the contribution of primary school meals to the total greenhouse gas emissions ( ghges ) in england ? are school lunches associated with more or less ghges than packed lunches ?
the primary school food survey ( psfs ) data set , a survey conducted in 139 primary schools in england ( 18 ) , was used in this study .
the survey involved 6,690 students who ate school lunches and 3,488 students who brought packed lunches .
this survey was commissioned and funded by the children s food trust ( formerly the school food trust ) .
it involved selecting a random sample of 290 primary schools ( from the department for children , schools and families database ) stratified according to region , school type and postcode .
of the 290 schools , 50% agreed to take part and six schools withdrew later .
reasons given by schools to refuse participation are listed in the appendix 4 of the psfs full technical report ( 18 ) .
they visited each school for five days in a week and collected details of 10 pupils having a school lunch from different service points or rooms and five children per day having packed lunches in the same schools .
nutritional information for all the foods served to the school lunch tray or brought in the packed lunch box by each participating student on that day was recorded .
this dataset included the name of the food item , a unique food code , weight of the serving and nutritional information for key macro and micro nutrients .
nutritional analysis of the foods was estimated with reference to the food standards agency nutrient databank ( 19 ) . in the psfs dataset
we conducted a systematic review to estimate the ghges associated with the production of 100 g of different food groups ( 20 ) .
this systematic review involved searching peer - reviewed and grey literature from 1995 - 2012 on ghges associated with the production and consumption of food items ( estimated by life cycle analysis ) .
the overall environmental burden of products is reported in global warming potential ( gwp ) a cumulative value for main greenhouse gases such as carbon dioxide ( co2 ) , methane ( ch4 ) and nitrous oxide ( n20 ) .
this systematic review provides ghge values for food items listed in a commonly used food frequency questionnaire ( ffq ) ( 21 ) . if the food item was not available in the ghge dataset the average value for that group was used ( e.g. for apricot the average value of all fruits was used ) .
the systematic review does not provide ghge values directly for composite food items ( i.e. foods that are made from more than one primary ingredient , such as pizza or chicken curry ) .
the ghge values of composite foods were estimated by allocating ghge values of ingredients using a recipe for that food item .
recipes were sourced initially from the mccance and widdowson ( 22 ) series of food composition tables ( which contribute to the uk nutrient databank ) , supplemented with standardised searches of google .
this approach was adopted from a previous study conducted by scarborough et al ( 8) .
we categorised all of the meals in the psfs by the five food categories in the eatwell plate ( 23 ) , thereby allowing an assessment of the main sources of ghge in the primary school food sector .
these five groups are : bread , rice , potatoes , pasta and other starchy foods , fruits and vegetables , meat , fish , eggs , beans and other non - dairy sources of protein , milk and dairy foods and foods and drinks high in fat and/or sugar .
each food code in the psfs was allocated in to the relevant category of the eatwell plate using the national food guide and its food group classification ( 24 ) , which provides a list to classify food in to the five food groups of the eatwell plate .
the composite foods were split between the different eatwell plate categories by estimating the proportion of weight for each raw ingredient , using data from the recipes identified using the method described earlier .
our primary measure used to identify healthy primary school meals was achievement of target levels of salt , saturated fat and free sugar .
this measure takes account of three nutrients that the who considers to be related to non - communicable diseases ( 10 , 25 ) .
since this measure does not account for micronutrient quality of foods ( which previous research has suggested should be considered if sustainability of diets is addressed ( 26 ) ) , we also use a secondary measure which considers both macro and micronutrients ( achieving any 7 or more standards from the 14 nutrient based standards set for primary school meals ) ( 16 ) .
the psfs report provides reference values for a primary school meal for these 14 nutrients - energy , protein , carbohydrate , non - milk extrinsic sugars , fats , saturated fatty acids , fibre , sodium , vitamin a , vitamin c , folate , calcium , iron and zinc ( 16 ) .
there is no accepted , gold standard method to categorise healthy and unhealthy meals and any definition will have practical challenges when assigning meals in to a specific category .
the average ghges per school and packed lunch was estimated by aggregating all the items served per child on to their lunch tray on that day and these values were used to estimate the total ghges from primary school meals in england , per year .
the number and proportion of meals which met nutrient based criteria are presented for both packed lunches and school lunches .
mean ghge value for healthy meals and unhealthy meals were estimated for both packed lunches and school lunches and compared using t - tests .
there are two main types of uncertainties associated with this analysis : 1 ) uncertainty due to sampling error ( introduced by the representative sample from the psfs ) , 2 ) the uncertainty due to parameters we used to estimate nutritional values and ghge values .
a novel method was developed to estimate the uncertainty due to ghge values . for point estimates of results ,
the ghge value used is the mean of the ghge values reported for each food group in the literature , as identified by the systematic review .
but for the uncertainty analysis a monte carlo simulation with 1000 iterations ( 27 ) was conducted , where the individual ghge parameters identified from the systematic review are allowed to vary randomly from the selection identified in the literature .
the primary school food survey ( psfs ) data set , a survey conducted in 139 primary schools in england ( 18 ) , was used in this study .
the survey involved 6,690 students who ate school lunches and 3,488 students who brought packed lunches .
this survey was commissioned and funded by the children s food trust ( formerly the school food trust ) .
it involved selecting a random sample of 290 primary schools ( from the department for children , schools and families database ) stratified according to region , school type and postcode .
of the 290 schools , 50% agreed to take part and six schools withdrew later .
reasons given by schools to refuse participation are listed in the appendix 4 of the psfs full technical report ( 18 ) .
they visited each school for five days in a week and collected details of 10 pupils having a school lunch from different service points or rooms and five children per day having packed lunches in the same schools .
nutritional information for all the foods served to the school lunch tray or brought in the packed lunch box by each participating student on that day was recorded .
this dataset included the name of the food item , a unique food code , weight of the serving and nutritional information for key macro and micro nutrients .
nutritional analysis of the foods was estimated with reference to the food standards agency nutrient databank ( 19 ) . in the psfs dataset
we conducted a systematic review to estimate the ghges associated with the production of 100 g of different food groups ( 20 ) .
this systematic review involved searching peer - reviewed and grey literature from 1995 - 2012 on ghges associated with the production and consumption of food items ( estimated by life cycle analysis ) .
the overall environmental burden of products is reported in global warming potential ( gwp ) a cumulative value for main greenhouse gases such as carbon dioxide ( co2 ) , methane ( ch4 ) and nitrous oxide ( n20 ) .
this systematic review provides ghge values for food items listed in a commonly used food frequency questionnaire ( ffq ) ( 21 ) .
if the food item was not available in the ghge dataset the average value for that group was used ( e.g. for apricot the average value of all fruits was used ) . the systematic review
does not provide ghge values directly for composite food items ( i.e. foods that are made from more than one primary ingredient , such as pizza or chicken curry ) .
the ghge values of composite foods were estimated by allocating ghge values of ingredients using a recipe for that food item .
recipes were sourced initially from the mccance and widdowson ( 22 ) series of food composition tables ( which contribute to the uk nutrient databank ) , supplemented with standardised searches of google .
this approach was adopted from a previous study conducted by scarborough et al ( 8) .
we categorised all of the meals in the psfs by the five food categories in the eatwell plate ( 23 ) , thereby allowing an assessment of the main sources of ghge in the primary school food sector .
these five groups are : bread , rice , potatoes , pasta and other starchy foods , fruits and vegetables , meat , fish , eggs , beans and other non - dairy sources of protein , milk and dairy foods and foods and drinks high in fat and/or sugar .
each food code in the psfs was allocated in to the relevant category of the eatwell plate using the national food guide and its food group classification ( 24 ) , which provides a list to classify food in to the five food groups of the eatwell plate .
the composite foods were split between the different eatwell plate categories by estimating the proportion of weight for each raw ingredient , using data from the recipes identified using the method described earlier .
our primary measure used to identify healthy primary school meals was achievement of target levels of salt , saturated fat and free sugar .
this measure takes account of three nutrients that the who considers to be related to non - communicable diseases ( 10 , 25 ) .
since this measure does not account for micronutrient quality of foods ( which previous research has suggested should be considered if sustainability of diets is addressed ( 26 ) ) , we also use a secondary measure which considers both macro and micronutrients ( achieving any 7 or more standards from the 14 nutrient based standards set for primary school meals ) ( 16 ) .
the psfs report provides reference values for a primary school meal for these 14 nutrients - energy , protein , carbohydrate , non - milk extrinsic sugars , fats , saturated fatty acids , fibre , sodium , vitamin a , vitamin c , folate , calcium , iron and zinc ( 16 ) .
there is no accepted , gold standard method to categorise healthy and unhealthy meals and any definition will have practical challenges when assigning meals in to a specific category .
the average ghges per school and packed lunch was estimated by aggregating all the items served per child on to their lunch tray on that day and these values were used to estimate the total ghges from primary school meals in england , per year .
the number and proportion of meals which met nutrient based criteria are presented for both packed lunches and school lunches .
mean ghge value for healthy meals and unhealthy meals were estimated for both packed lunches and school lunches and compared using t - tests .
there are two main types of uncertainties associated with this analysis : 1 ) uncertainty due to sampling error ( introduced by the representative sample from the psfs ) , 2 ) the uncertainty due to parameters we used to estimate nutritional values and ghge values .
a novel method was developed to estimate the uncertainty due to ghge values . for point estimates of results ,
the ghge value used is the mean of the ghge values reported for each food group in the literature , as identified by the systematic review .
but for the uncertainty analysis a monte carlo simulation with 1000 iterations ( 27 ) was conducted , where the individual ghge parameters identified from the systematic review are allowed to vary randomly from the selection identified in the literature .
in the psfs dataset , there were 1,556 unique food items consumed by 6,690 students . in total 38,148 food items
in packed lunches there were 943 unique food items consumed and in total 17,272 food items were consumed by 3,481 students .
sample was equally distributed among age groups and sex did not have a significant impact on the mean ghges per meal .
the ghge values of individual school meals were normally distributed with a long tail . for school lunches the interquartile range was 0.40 - 0.80 and for packed lunches it was 0.46 0.86 kgco2e ( table 1 ) . in both , school lunches and packed lunches
the contribution of the meat , fish and alternatives category to ghges is much higher than its contribution by weight . around 62% of
the weight of packed lunches was from fruit and vegetables ( primarily due to the large serving sizes of fruit juices , which make up 44% of the weight of packed lunches ) ( figure 1 ) .
the mean ghge value per school lunch was estimated as 0.72 kgco2e ( table 2 ) .
of the 4.2 million primary school children in england around 39% take school lunches ( 16 ) .
therefore , the annual ghge from primary school lunch is approximately 224 million kgco2e per year .
the mean ghge value per packed lunch is 0.70 kgco2e and 61% of primary school children take packed lunches on 190 school days per year .
table 2 shows that for both school lunches and packed lunches around 90% of the uncertainty around the mean ghge value is due to the uncertainty around ghge parameters .
uncertainty intervals around the estimate of total ghges from school lunches ( including packed lunches ) is 455 million 892 million kgco2e per year .
table 3 shows that when healthy meals are defined by salt , saturated fat and sugar levels , the mean ghge of healthy school lunches was 0.54 ( 0.47 1.46 ) kgco2e and the mean ghges of unhealthy school lunches was 0.81 ( 0.57 1.44 ) kgco2e .
similarly the mean ghges of healthy packed lunches ( 0.39 kgco2e ) was lower than the mean ghges of unhealthy packed lunches ( 0.72 kgco2e ) .
previous studies have highlighted the importance of considering micro - nutrient levels when looking at opportunities to reduce the ghge from meals ( 26 ) .
the primary school food nutrient based standards had values for 14 macro and micro - nutrients ( 16 ) .
the psfs report used the achievement of 7 - 10 nutrients as an indicator to measure the improvement of school meals over time .
there were 4,312 school lunches ( 64.5% ) which achieved at least seven nutrient based standards ( out of 14 ) and therefore we used this definition to create a second method to classify meals as healthy .
table 3 also shows results of comparing the mean ghge of healthy meals vs non - healthy meals for both school lunches and packed lunches and the uncertainty when micro - nutrients are considered to define healthy meals .
the mean ghge for healthy school lunches was 0.79 kgco2e ( 0.56 1.44 ) compared to 0.59 kgco2e ( 0.42 1.04 ) for unhealthy lunches . among packed lunches the mean ghge of healthy lunches ( 0.83 kgco2e ) was higher than the mean ghge of unhealthy lunches ( 0.60 kgco2e ) . reducing ghges from meals could help to reduce nutrients such as saturated fat , salt and sugar .
but as shown in table 4 these healthy meals with lower ghges have less fibre and micronutrients - iron , calcium , zinc and folate . under the second definition ,
healthy meals have higher levels of fibre and micronutrients , but the ghge is also increased .
in the psfs dataset , there were 1,556 unique food items consumed by 6,690 students . in total 38,148 food items
in packed lunches there were 943 unique food items consumed and in total 17,272 food items were consumed by 3,481 students .
sample was equally distributed among age groups and sex did not have a significant impact on the mean ghges per meal .
the ghge values of individual school meals were normally distributed with a long tail . for school lunches the interquartile range was 0.40 - 0.80 and for packed lunches it was 0.46 0.86 kgco2e ( table 1 ) . in both , school lunches and packed lunches
the contribution of the meat , fish and alternatives category to ghges is much higher than its contribution by weight . around 62% of
the weight of packed lunches was from fruit and vegetables ( primarily due to the large serving sizes of fruit juices , which make up 44% of the weight of packed lunches ) ( figure 1 ) .
the mean ghge value per school lunch was estimated as 0.72 kgco2e ( table 2 ) .
of the 4.2 million primary school children in england around 39% take school lunches ( 16 ) .
therefore , the annual ghge from primary school lunch is approximately 224 million kgco2e per year .
the mean ghge value per packed lunch is 0.70 kgco2e and 61% of primary school children take packed lunches on 190 school days per year .
table 2 shows that for both school lunches and packed lunches around 90% of the uncertainty around the mean ghge value is due to the uncertainty around ghge parameters .
uncertainty intervals around the estimate of total ghges from school lunches ( including packed lunches ) is 455 million 892 million kgco2e per year .
table 3 shows that when healthy meals are defined by salt , saturated fat and sugar levels , the mean ghge of healthy school lunches was 0.54 ( 0.47 1.46 ) kgco2e and the mean ghges of unhealthy school lunches was 0.81 ( 0.57 1.44 ) kgco2e .
similarly the mean ghges of healthy packed lunches ( 0.39 kgco2e ) was lower than the mean ghges of unhealthy packed lunches ( 0.72 kgco2e ) .
previous studies have highlighted the importance of considering micro - nutrient levels when looking at opportunities to reduce the ghge from meals ( 26 ) .
the primary school food nutrient based standards had values for 14 macro and micro - nutrients ( 16 ) .
the psfs report used the achievement of 7 - 10 nutrients as an indicator to measure the improvement of school meals over time .
there were 4,312 school lunches ( 64.5% ) which achieved at least seven nutrient based standards ( out of 14 ) and therefore we used this definition to create a second method to classify meals as healthy .
table 3 also shows results of comparing the mean ghge of healthy meals vs non - healthy meals for both school lunches and packed lunches and the uncertainty when micro - nutrients are considered to define healthy meals .
the mean ghge for healthy school lunches was 0.79 kgco2e ( 0.56 1.44 ) compared to 0.59 kgco2e ( 0.42 1.04 ) for unhealthy lunches . among packed lunches the mean ghge of healthy lunches ( 0.83 kgco2e ) was higher than the mean ghge of unhealthy lunches ( 0.60 kgco2e ) . reducing ghges from meals could help to reduce nutrients such as saturated fat , salt and sugar .
but as shown in table 4 these healthy meals with lower ghges have less fibre and micronutrients - iron , calcium , zinc and folate . under the second definition ,
healthy meals have higher levels of fibre and micronutrients , but the ghge is also increased .
this study found that the total ghges due to primary school meals in england is 578.1 million kgco2e a year , equivalent to more than 578,000 economy class return air journeys between london and new york ( 28 ) .
school lunches have a marginally higher ghge mean value than packed lunches , but the overall emission is higher from packed lunches as more primary school children take packed lunches .
the study also investigated whether healthier school meals were associated with less or more ghges . when we used a common definition to define healthy meals ( lower levels of salt , saturated fat and sugar ) results suggest that healthy school lunches and packed lunches are low in ghges , but are also lower in fibre and some micronutrient levels .
this difference in ghge in healthy and unhealthy meals could be due to several reasons .
for example it could be associated with the amount of food items included in the meal and therefore with the total energy of the meal . to test this
, we estimated the ghge per set amount of energy in a primary school meal .
the mid - point of the energy reference range for primary school meals is 530kcal .
we estimated the ghge for a 530kcal meal in both healthy and unhealthy groups . when ghge per 530 kcal is estimated in healthy and unhealthy school meals classified according to salt , sugar and saturated fats , the healthier meals has more ghges .
we also used a secondary method to define healthy and unhealthy meals using seven out of 14 nutrient standards . when ghge per 530kcal is estimated in healthy and unhealthy school meals classified according to seven out of 14 standards , still
healthy meals had a higher ghge value ( 0.85 ) compared to unhealthy meals ( 0.77 kgco2e ) .
but there is no change in the previous conclusion of comparison between healthy and unhealthy school lunches , based on this definition .
it is not straight forward to provide a reason for the difference in ghge values in healthy and unhealthy meals . if all students adopted a healthy school lunch defined by low salt , sugar and saturated fat ( with a mean ghge value of 0.54 kgco2e ) , the total ghge from primary school meals would be 441.2 million kgco2e , saving 136.9million kgco2e compared to the current total emissions from primary school meals .
this is equivalent to avoiding more than 139,000 economy class return air journeys between london and new york ( 28 ) .
this study also showed that 106 million kgco2e ( 30% of the ghges associated with packed lunches ) are from fruit juices .
these could be removed by replacing fruit juice with tap water , which has also been recommended as a priority in another government policy- the government buying standards for food and catering services published by the public health england ( 29 ) .
it is argued that cultural backgrounds should be given a central attention if we try to promote healthier and sustainable food choices in multi - ethnic communities ( 30 ) .
these are important lessons for the uk which has a diverse community with immigrants from different parts of the world .
no previous studies have estimated the carbon footprint of the primary school food sector , in any country . however , a number of studies have estimated the total carbon footprint of the food system in the uk ( 8 , 31 , 32 ) .
these studies have estimated that total ghge due to food consumption in the uk is around 95mtco2e / year ( 33 ) .
the total emissions from primary school lunches in england , as estimated in this paper represent about 0.6% of that , which is to be expected since primary school children represent 6.5% of the population in the uk and the school lunch only represents a third of their food intake in 190 days in a year .
the literature suggests that policy options should aim to reduce ghge intensive meat meals to achieve both environmental goals and health benefits ( 34 ) .
there are mixed findings on whether moving to a healthier diet or moving towards recommended dietary guidelines would reduce ghges ( 36 ) .
the previous literature has also reported that sometimes , despite containing large amounts of plant - based foods , high nutritional quality diets do nt always have the lowest ghge values ( 37 ) .
tom et al 2015 found that reducing caloric intake levels and shifting current us diet to recommended food patterns based on the us dietary guidelines would increases energy use by 38 % and ghges by 6 % ( 38 ) .
the difference in ghge in healthy and unhealthy meals could be impacted by several factors such as the type of food items and energy levels in the meals and therefore it is important to consider all these aspects , when making recommendations for sustainable healthy diets .
previous studies have also highlighted that changing diets to make them sustainable could compromise the micro - nutrient levels(26 ) .
a paper from horgan et al showed that it is very difficult to meet all dietary recommendations , especially for fibre and sodium ; reducing ghge makes it even more difficult , using adult diets from the uk national diet and nutrition survey ( 39 ) .
our results also support these findings and challenge the statement of healthy meals are always environmentally friendly
. therefore this analysis supports findings from other papers which suggest that the association between ghge reduction and nutritional quality is complex and may not always be synergistic ( 9 , 10 , 39 ) . for this study
a method that has not been used before was used to address the uncertainty due to ghge parameters of food .
use of ghge values of food to create databases combining ghge values and nutrition information is a relatively new discipline . therefore researchers need to develop methods in order to incorporate uncertainty in final results appropriately .
the ghge estimates are from a systematic review , which included papers from a wide variety of sources , countries and different production systems .
we have included the ghge of all primary school food items served to trays and we did not consider leftover food .
disposal of food waste also contributes to the ghge and therefore we underestimate the ghge associated with primary school meals .
the psfs collected data between february and april 2009 and therefore this dataset does not allow us to assess any seasonal variations in school meals .
this study is based on actual meals consumed by school children and differs from many other published studies which examine computer generated meals .
this study provides valuable insights in to the ghges of consumed meals and could be useful for policy decisions regarding food provision in the public sector .
we have established methods to define healthy diets or healthy foods , but not individual meals .
a systematic review by marshall et al shows that there are more than 80 different diet quality indices for children and they have used food only standards , nutrient only standards or combination of both of them to assess the healthiness of diets ( 40 ) .
in this dataset , we have data only for a single meal of the day , per child and it is difficult to draw conclusions about healthiness of diets using these existing tools .
no previous studies have estimated the carbon footprint of the primary school food sector , in any country . however , a number of studies have estimated the total carbon footprint of the food system in the uk ( 8 , 31 , 32 ) .
these studies have estimated that total ghge due to food consumption in the uk is around 95mtco2e / year ( 33 ) .
the total emissions from primary school lunches in england , as estimated in this paper represent about 0.6% of that , which is to be expected since primary school children represent 6.5% of the population in the uk and the school lunch only represents a third of their food intake in 190 days in a year .
the literature suggests that policy options should aim to reduce ghge intensive meat meals to achieve both environmental goals and health benefits ( 34 ) .
there are mixed findings on whether moving to a healthier diet or moving towards recommended dietary guidelines would reduce ghges ( 36 ) .
the previous literature has also reported that sometimes , despite containing large amounts of plant - based foods , high nutritional quality diets do nt always have the lowest ghge values ( 37 ) .
tom et al 2015 found that reducing caloric intake levels and shifting current us diet to recommended food patterns based on the us dietary guidelines would increases energy use by 38 % and ghges by 6 % ( 38 ) .
the difference in ghge in healthy and unhealthy meals could be impacted by several factors such as the type of food items and energy levels in the meals and therefore it is important to consider all these aspects , when making recommendations for sustainable healthy diets .
previous studies have also highlighted that changing diets to make them sustainable could compromise the micro - nutrient levels(26 ) .
a paper from horgan et al showed that it is very difficult to meet all dietary recommendations , especially for fibre and sodium ; reducing ghge makes it even more difficult , using adult diets from the uk national diet and nutrition survey ( 39 ) .
our results also support these findings and challenge the statement of healthy meals are always environmentally friendly
. therefore this analysis supports findings from other papers which suggest that the association between ghge reduction and nutritional quality is complex and may not always be synergistic ( 9 , 10 , 39 ) .
for this study a method that has not been used before was used to address the uncertainty due to ghge parameters of food .
use of ghge values of food to create databases combining ghge values and nutrition information is a relatively new discipline . therefore researchers need to develop methods in order to incorporate uncertainty in final results appropriately .
the ghge estimates are from a systematic review , which included papers from a wide variety of sources , countries and different production systems .
we have included the ghge of all primary school food items served to trays and we did not consider leftover food .
disposal of food waste also contributes to the ghge and therefore we underestimate the ghge associated with primary school meals .
the psfs collected data between february and april 2009 and therefore this dataset does not allow us to assess any seasonal variations in school meals .
this study is based on actual meals consumed by school children and differs from many other published studies which examine computer generated meals .
this study provides valuable insights in to the ghges of consumed meals and could be useful for policy decisions regarding food provision in the public sector .
we have established methods to define healthy diets or healthy foods , but not individual meals .
a systematic review by marshall et al shows that there are more than 80 different diet quality indices for children and they have used food only standards , nutrient only standards or combination of both of them to assess the healthiness of diets ( 40 ) .
they require data obtained from 24 hour dietary recalls or food frequency questionnaires . in this dataset
, we have data only for a single meal of the day , per child and it is difficult to draw conclusions about healthiness of diets using these existing tools .
this paper demonstrates that changes in the primary school food sector can have an impact on uk greenhouse gas emissions , and that meals that are lower in salt , saturated fat and sugar are associated with fewer greenhouse gas emissions .
however , the results suggest that lowering greenhouse gas emissions in school meals may compromise fibre levels and micronutrient quality . these methods can be used to estimate the greenhouse gas emissions of other government food procurement sectors including hospitals , prisons and the military .
| background / objectiveschool meals represent the largest sector in government food procurement in the uk .
this paper aims to quantify , simultaneously , the nutritional quality and carbon footprint of meals provided by primary schools in england.methodsthe school food trust conducted the primary school food survey 2009
( psfs ) in a nationally representative sample of 139 primary schools in england .
the survey included 6,690 students who consumed school lunches and 3,488 students who brought packed lunches .
we estimated the total greenhouse gas emissions ( ghges ) per kg of the food items contributing to those lunches based on the results of a systematic review of life cycle analyses.resultsin both school lunches and packed lunches the meat , fish and alternatives group contributed the largest share of ghges .
the mean ghge value per school lunch was estimated to be 0.72 ( 95% uncertainty interval 0.52 - 1.34 ) kgco2e and per packed lunch as 0.70 ( 0.58 - 0.94 ) kgco2e .
the total ghges due to primary school meals in england per year is 578.1 million kgco2e ( 455 million-892 million).conclusionif all children achieved a healthy meal defined by having a low level of salt , free sugars and saturated fat the total ghges from primary school meals would be 441.2 million kgco2e ( 384 1,192 ) , saving 136.9million kgco2e compared to the current total emissions from primary school meals .
this paper demonstrates that changes in the primary school food sector can have an impact on uk greenhouse gas emissions . |
SECTION 1. SHORT TITLE.
This Act may be cited as the ``Boat Protection Act of 1996''.
SEC. 2. PROTECTION OF VESSEL HULL DESIGNS.
Title 17, United States Code, is amended by adding at the end
thereof the following new chapter:
``CHAPTER 12--PROTECTION OF VESSEL HULL DESIGNS
``Sec.
``1201. Definitions.
``1202. Subject matter of protection.
``1203. Ownership and transfer.
``1204. Duration of protection.
``1205. Exclusive rights in plugs or molds.
``1206. Limitation on exclusive rights: reverse engineering; first
sale.
``1207. Limitation on exclusive rights: innocent infringement.
``1208. Plug or mold notice.
``1209. Enforcement of exclusive rights.
``1210. Remedies for infringement.
``1211. Relation to other laws.
``Sec. 1201. Definitions
``As used in this chapter--
``(1) `vessel hull' has the meaning given that term in
regulations which the Register of Copyrights shall issue;
``(2) a `plug' means a device or model used to make a mold
for the purpose of exact duplication, regardless of whether the
device or model has an intrinsic utilitarian function that is
not only to portray the appearance of the product or to convey
information;
``(3) a `mold' means a matrix or form in which a substance
for material is used, regardless of whether the matrix or form
has an intrinsic utilitarian function that is not only to
portray the appearance of the product or to convey information;
``(4) a plug or mold is `fixed' in a vessel hull when its
embodiment in the vessel hull, by or under the authority of the
owner of the plug or mold, is sufficiently permanent or stable
to permit the vessel hull to be perceived, reproduced, or
otherwise communicated for a period of more than transitory
duration;
``(5) a plug or mold is `original' if it is the independent
creation of a person who did not copy it from another source;
``(6) to `commercially exploit' a plug or mold is to sell,
offer for sale after the plug or mold is fixed in a vessel
hull, or otherwise distribute to the public for profit vessel
hulls embodying the plug or mold;
``(7) the `owner' of a plug or mold is--
``(A) the person who created the plug or mold;
``(B) the legal representative of that person if
that person is deceased or under a legal incapacity;
``(C) the employer of that person if that person
created the plug or mold within the scope of that
person's employment; or
``(D) a party to whom the rights of the person,
representative, or employer described in subparagraph
(A), (B), or (C) are transferred in accordance with this chapter;
``(8) an `innocent purchaser' is a person who purchases a
vessel hull or a product in which a vessel hull is contained in
good faith and without having notice of protection under this
chapter with respect to that vessel hull or product;
``(9) having `notice of protection' means having actual
knowledge that, or reasonable grounds to believe that, a plug
or mold fixed in a vessel hull is protected under this chapter;
and
``(10) an `infringing vessel hull' is a vessel hull which
is made, imported, or distributed in violation of the exclusive
rights of the owner of a plug or mold under this chapter.
``Sec. 1202. Subject matter of protection
``(a) Nationality Requirements.--
``(1) In general.--An original plug or mold fixed in a
vessel hull is eligible for protection under this chapter if--
``(A) on the date on which the plug or mold is
first commercially exploited, the owner of the plug or
mold is a national or domiciliary of the United States,
or is a national, domiciliary, or sovereign authority
of a foreign nation that is party to a treaty affording
protection to plugs or molds to which the United States
is also a party, or is a stateless person, wherever
that person may be domiciled;
``(B) the plug or mold is first commercially
exploited in the United States; or
``(C) the plug or mold comes within the scope of a
Presidential proclamation issued under paragraph (2).
``(2) Presidential proclamations.--Whenever the President
finds that a foreign nation extends, to plugs or molds of
owners who are nationals or domiciliaries of the United States
or to plugs or molds on the date on which the plugs or molds
are first commercially exploited, protection--
``(A) on substantially the same basis as that on
which the foreign nation extends protection to plugs or
molds of its own nationals and domiciliaries and plugs
or molds first commercially exploited in that nation,
or
``(B) on substantially the same basis as provided
in this chapter, the President may by proclamation
extend protection under this chapter to plugs or
molds--
``(i) of owners who are, on the date on
which the plugs or molds are first commercially
exploited, nationals, domiciliaries, or
sovereign authorities of that nation, or
``(ii) which are first commercially
exploited in that nation.
``(b) Exclusion for Products Not Original.--Protection under this
chapter shall not be available for a plug or mold that--
``(1) is not original; or
``(2) consists of designs that are staple, commonplace, or
familiar in the vessel manufacturing industry, or variations of
such designs, combined in a way that is not original.
``(c) Other Exclusions.--In no case does protection under this
chapter for a plug or mold extend to any idea, procedure, process,
system, method of operation, concept, principle, or discovery,
regardless of the form of which it is described, explained,
illustrated, or embodied in the plug or mold.
``Sec. 1203. Ownership and transfer
``(a) Vesting of Rights in Owner.--The exclusive rights in a plug
or mold under the chapter shall vest in the owner of the plug or mold.
``(b) Transfer of Rights.--The exclusive rights in a plug or mold
under this chapter may be transferred in whole or in part by any means
of conveyance or by operation of law, and may be bequeathed by will or
pass as personal property by the applicable laws of intestate
succession.
``(c) Conflicting Transfers.--In any case in which conflicting
transfers of the exclusive rights in a plug or mold are made, the
transfer first executed shall be void as against a subsequent transfer
which is made for a valuable consideration and without notice of the
first transfer, unless the first transfer is recorded in the Copyright
Office within 3 months after the date on which it is executed, but in
no case later than the day before the date of such subsequent transfer.
``(d) Protection Excluded for United States Government.--Plugs or
molds prepared by an officer or employee of the United States
Government as part of that person's official duties are not protected
under this chapter, but the United States Government is not precluded
from receiving and holding exclusive rights in plugs or molds
transferred to the Government under subsection (b).
``Sec. 1204. Duration of protection
``(a) Commencement of Protection.--The protection provided for a
plug or mold under this chapter shall commence on the date on which the
plug or mold is first commercially exploited.
``(b) Term of Protection.--Subject to the provisions of this
chapter, the protection provided under this chapter to a plug or mold
shall continue for a term of 10 years beginning on the date on which
such protection commences under subsection (a).
``Sec. 1205. Exclusive rights in plugs or molds
``Subject to the other provisions of this chapter, the owner of a
plug or mold has the exclusive rights to do and to authorize any of the
following:
``(1) Reproduce the plug or mold by optical, electronic, or
any other means.
``(2) Import or distribute a vessel hull in which the plug
or mold is embodied.
``(3) Induce or knowingly cause another person to do any of
the acts described in paragraphs (1) and (2).
``Sec. 1206. Limitation on exclusive rights: reverse engineering; first
sale
``(a) Reverse Engineering.--Notwithstanding the provisions of
section 1205(1), it is not an infringement of the exclusive rights of
the owner of a plug or mold to reproduce the plug or mold solely for
the purpose of teaching, analyzing, or evaluating the concepts or
techniques embodied in the plug or mold or the design or organization
of components used in the plug or mold.
``(b) First Sale.--Notwithstanding the provisions of section
1205(2), the owner of a particular vessel hull lawfully made under this
chapter, or any person authorized by such owner, is entitled, without
the authority of the owner of the plug or mold, to sell or otherwise
dispose of that vessel hull.
``Sec. 1207. Limitation on exclusive rights: innocent infringement
``(a) In General.--Notwithstanding any other provision of this
chapter, an innocent purchaser of an infringing vessel hull--
``(1) shall incur no liability under this chapter with
respect to the importation or distribution of units of the
infringing vessel hull that occurred before that innocent
purchaser had notice of protection with respect to that vessel
hull; and
``(2) shall be liable only for a reasonable royalty on each
unit of the infringing vessel hull that the innocent purchaser
imports or distributes after having notice of protection with
respect to that vessel hull. The amount of the royalty referred
to in paragraph (2) shall be based on wholesale cost and shall be
determined by voluntary negotiation between the parties, mediation, or
binding arbitration, or, if the parties do not resolve the issue, by
the court in a civil action for infringement.
``(b) Subsequent Purchases.--The immunity from liability and
limitation on liability referred to in subsection (a) shall apply to
any person who directly or indirectly purchases an infringing vessel
hull from an innocent purchaser.
``(c) Applicability Only to Products Purchased Before Notice of
Protection.--The provisions of subsections (a) and (b) apply only with
respect to units of an infringing vessel hull that an innocent
purchaser purchased before having notice of protection with respect to
that vessel hull.
``Sec. 1208. Plug or mold notice
``(a) Affixation Notice.--The owner of a plug or mold provided
protection under this chapter may affix notice to the plug or mold or
to the vessel hull embodying the plug or mold in such manner and
location as to give reasonable notice of such protection. The Register
of Copyrights shall prescribe by regulation, as examples, specific
methods of affixation and positions of notice for purposes of this
section, but these specifications shall not be considered exhaustive.
The affixation of such notice is not a condition of protection under
this chapter but shall constitute prima facie evidence of notice of
protection.
``(b) Contents of Notice.--The notice referred to in subsection (a)
shall consist of--
``(1) the words 'plug or mold', or the letters PM in a
circle;
``(2) the year in which the plug or mold was first fixed in
a vessel hull; and
``(3) the name of the owner or owners of the plug or mold
or an abbreviation by which the name is recognized or is
generally known.
``Sec. 1209. Enforcement of exclusive rights
``(a) Infringers.--Except as otherwise provided by this chapter,
any person who violates any of the exclusive rights of the owner of a
plug or mold under this chapter shall be liable as an infringer of such
rights.
``(b) Civil Action for Infringement.--The owner of a plug or mold
protected under this chapter shall be entitled to institute a civil
action for any infringement of the exclusive rights in that plug or
mold under the chapter.
``(c) Enforcement of Right To Import.--
``(1) Regulations.--The Secretary of the Treasury and the
United States Postal Service shall separately or jointly issue
regulations for the enforcement of the right to import set
forth in section 1205. These regulations may require, as a
condition for the exclusion of articles from the United States,
that the person seeking exclusion--
``(A) obtain a court order enjoining, or an order
of the International Trade Commission under section 337
of the Tariff Act of 1930 excluding, importation of the
articles; or
``(B) furnish proof that the plug or mold involved
is protected under this chapter and that the
importation of the articles would infringe the rights
in the plug or mold under this chapter, and also post a
surety bond for any injury that may result if the
detention or exclusion of the articles proves to be
unjustified.
``(2) Seizure and forfeiture of infringing articles.--
Articles imported in violation of the right to import set forth
in section 1205 are subject to seizure and forfeiture in the
same manner as property imported in violation of the customs
laws. Any such forfeited article shall be destroyed as directed
by the Secretary of the Treasury or the court, as the case may
be, except that the articles may be returned to the country of
export whenever it is shown to the satisfaction of the
Secretary of the Treasury that the importer had no reasonable grounds
for believing that his or her acts constituted a violation of the law.
``Sec. 1210. Remedies for infringement
``(a) Injunctive Relief.--Any court having jurisdiction of a civil
action arising under this chapter may grant temporary and permanent
injunctions on such terms as the court may deem reasonable to prevent
or restrain infringement of the exclusive rights in a plug or mold
under this chapter.
``(b) Actual Damages and Profits.--Upon finding for the owner of
the plug or mold, the court shall award the owner actual damages
suffered by the owner as a result of the infringement. The court shall
also award the owner the infringer's profits that are attributable to
the infringement and are not taken into account in computing the award
of actual damages. In establishing the infringer's profits, the owner
of the plug or mold is required to present proof only of the
infringer's gross revenue, and the infringer is required to prove his
or her deductible expenses and the elements of profit attributable to
factors other than the plug or mold.
``(c) Statutory Damages.--At any time before final judgment is
rendered, the owner of the plug or mold may elect, instead of actual
damages and profits as provided in subsection (b), an award of
statutory damages for all infringements involved in the action with
respect to any one plug or mold for which any one infringer is liable
individually, or for which any two or more infringers are liable
jointly and severally, in an amount not more than $250,000 as the court
considers just.
``(d) Recovery of Costs by Prevailing Party.--In any action for
infringement under this chapter, the court in its discretion may allow
the recovery of full costs, including reasonable attorneys' fees, to
the prevailing party.
``(e) Time Limitation on Bringing Actions.--An action for
infringement under this chapter shall not be maintained unless the
action is commenced within 3 years after the claim accrues.
``(f) Destruction or Other Disposition of Infringing Articles.--As
part of the final judgment or decree, the court may order the
destruction or other disposition of any infringing vessel hulls, and
any plugs, molds, or other articles by means of which such vessel hulls
may be reproduced.
``Sec. 1211. Relation to other laws
``(a) Other Rights Not Affected.--Nothing in this chapter shall
affect any right or remedy held by any person under chapters 1 through
11 of this title, or under title 35.
``(b) References in Chapters 1 Through 11.--References to `this
title' or `title 17' in chapters 1 through 11 of this title shall be
deemed not to apply to this chapter.
``(c) Preemption.--The provisions of this chapter shall preempt the
laws of any State to the extent those laws provide any rights or
remedies with respect to a plug or mold which are equivalent to those
provided by this chapter, except that such preemption shall be
effective only with respect to actions filed on or after January 1,
1998.
``(d) Applicability of Title 28 Provisions.--The provisions of
sections 1338, 1400(a), and 1498(b) and (c) of title 28 shall apply
with respect to exclusive rights in plugs or molds under this chapter
to the same extent as those provisions apply to mask works.''.
SEC. 3. TECHNICAL AMENDMENT.
The table of chapters of title 17, United States Code, is amended
by adding at the end thereof the following new item:
``12. Protection of Vessel Hulls Designs.......................1201.''.
SEC. 4. EFFECTIVE DATE.
The amendments made by this Act shall take effect on January 1,
1997.
SEC. 5. AUTHORIZATION OF APPROPRIATIONS.
There are authorized to be appropriated such sums as may be
necessary to carry out this Act and the amendments made by this Act. | Boat Protection Act of 1996 - Sets forth copyright provisions regarding the protection of vessel hull designs.
Defines: (1) "plug" as a device or model used to make a mold for the purpose of exact duplication, regardless of whether the device or model has an intrinsic utilitarian function that is not only to portray the appearance of the product or to convey information; (2) "mold" as a matrix or form in which a substance for material is used, regardless of whether the matrix or form has an intrinsic utilitarian function that is not only to portray the appearance of the product or to convey information; and (3) "commercially exploit" for purposes of this Act as the sale or offer for sale of a plug or mold after it is fixed in a vessel hull or otherwise distributed to the public for profit vessel hulls.
Extends protection to an original plug or mold fixed in a vessel hull, if: (1) the owner of the plug or mold is a national or domiciliary of the United States or of a foreign nation which is party to a protection treaty to which the United States is also a party on the date on which the plug or mold is first commercially exploited; (2) the plug or mold is first commercially exploited in the United States; or (3) the plug or mold comes within the scope of a presidential proclamation extending reciprocal protection to the works of foreign nationals, domiciliaries, or sovereign authorities.
Vests exclusive rights in such plugs or molds in the owner who may transfer (in whole or in part) or bequeath such interest. Recognizes the first registered transfer in case of a conflict.
Sets the protection term for plugs or molds at ten years from the date of first commercial exploitation.
Grants the owner of a plug or mold the exclusive rights to: (1) reproduce the plug or mold; (2) import or distribute a vessel hull in which it is embodied; and (3) cause another to perform such acts. Provides that it is not an infringement of the owner's exclusive rights: (1) to reproduce a plug or mold for purposes of teaching, analyzing, or evaluating concepts, techniques, design, or organization of components in it; or (2) to sell or otherwise dispose of a vessel hull lawfully made under this Act (without the authority of the owner of the plug or mold). Limits the liability of an innocent purchaser of an infringing vessel hull.
Permits the owner of a plug or mold to place on it a specified notice of protection, which is not a condition of protection but shall constitute prima facie evidence of notice of protection.
Entitles the owner of a plug or mold whose protection has been infringed to institute a civil action. Authorizes the award of attorney's fees to a prevailing party.
Directs the Secretary of the Treasury and the U.S. Postal Service to issue regulations for the enforcement of the right to import a vessel hull in which the plug or mold is embodied. Permits the impoundment and seizure of vessel hulls imported in violation of the owner's exclusive rights.
Sets forth remedies for infringement, including temporary and permanent injunctive relief, actual damages, the award of an infringer's profits to the owner, impoundment orders, and the award of statutory damages instead of actual damages or profits in an amount not to exceed $250,000, under specified conditions.
Authorizes appropriations. |
in the last decade a wide variety of modified theories of gravity has been studied with the aim of solving or smoothing some puzzling features of conventional gravity and cosmology .
the reasons for considering such a modified gravitational schemes rely mainly on two damages that are intrinsic features of general relativity ( gr ) . on one hand ,
it is widely accepted by high energy physicists that the description of the gravitational field provided by general relativity must be doomed at scales of the order of the planck length , where the spacetime structure itself must be represented in terms of a quantum regime . on the other hand , and in the opposite extreme of the physical phenomena , gr also faces an intriguing dilemma in connection with the late cosmic speed up stage of the universe .
one of the newest extended theories of gravity is the so called @xmath0 gravity , which is a theory formulated in a spacetime possessing absolute parallelism @xcite .
the first investigations within this framework can be traced back to refs .
@xcite@xcite , where an ultraviolet deformation of einstein gravity was considered with the aim of smoothing singularities , namely the initial singularity of friedmann - robertson - walker ( frw ) cosmological models .
after that , the attention was focused in low energy deformations of gr which serve to tackle those aspects of the cosmological evolution connected with the late speed up stage of the universe in spatially flat models @xcite@xcite .
quite more recently , some fundamental aspects of @xmath0 theories , like the presence of extra degrees of freedom and the lack of lorentz invariance , had been addressed in refs .
@xcite@xcite . in spite of their success in smoothing the big - bang singularity @xcite ,
the ultraviolet deformations in the context of the @xmath0 theories fail to smooth singularities of gr vacuum solutions like black holes @xcite . for this reason
, we introduced in ref .
@xcite a more general theory in which the singularities of einstein theory receive a more appropriate treatment , even those that emerge from vacuum solutions of einstein equations . in this framework
the gravitational action is chosen , in close analogy with the born - infeld ( bi ) procedure used in electrodynamics , as the determinant of a particular combination of the torsion tensor that assures the correct low energy limit given by gr .
both the bi theory and the @xmath0 s mentioned above are based on actions built with just first derivatives of the dynamical field -the vierbein @xmath1- , so assuring second order motion equations .
most of the gravitational theories with absolute parallelism lack the invariance under local lorentz transformations of the vierbein .
this means that they should be regarded as theories describing the dynamics of the vierbein field rather than the metric field ( which is invariant under local lorentz transformations of the vierbein ) . as a consequence ,
the symmetry of the metric tensor is not enough to suggest the form of the vierbein , which could be elusive in many physically meaningful solutions . in this article
we will examine this issue by working out the proper vierbein field for closed and open frw cosmologies .
for this purpose , in section 2 we introduce the teleparallel equivalent of general relativity , that constitutes the geometrical pillar on which the @xmath0 and bi theories of gravity , also summarized there , are built . in section 3
we explain the lack of invariance of these theories under local lorentz transformation of the vierbein field in a cosmological context , discuss about the meaning of this feature , and work out the proper vierbein field for closed and open frw cosmologies . finally , in section 4 we display the conclusions .
in this section we will focus the attention on two gravitational schemes based on absolute parallelism . on one hand
, we will discuss a family of modified teleparallel theories constructed as a deformation of the einstein - hilbert lagrangian in weitzenbck spacetime the so called @xmath0 gravities. on the other hand , we will consider a quite different ultraviolet modification of gr with determinantal structure : born - infeld gravity .
we will start by introducing the geometrical concepts that serve as the building blocks of both schemes .
the basic idea is that gravity can be described by providing the spacetime with a torsion @xmath2 , @xmath3 , where @xmath4 is a vierbein ( a basis of the cotangent space ) in a @xmath5-dimensional manifold .
the vierbein @xmath4 is the co - frame of an associated basis @xmath6 in the tangent space .
if @xmath7 and @xmath8 are respectively the components of the 1-forms @xmath9 and the vectors @xmath10 in a given coordinate basis , then the relation between frame and co - frame is expressed as @xmath11 contracting with @xmath12 one also gets @xmath13 the components @xmath14 of the torsion tensor in the coordinate basis is related to the 2-forms @xmath15 through the equation @xmath16 this means that the spacetime is endowed with a connection @xmath17 ( since @xmath18 ) . the first term in eq .
( [ wei ] ) is the weitzenbck connection .
the metric is introduced as a subsidiary field given by @xmath19 where @xmath20 .
( [ metric ] ) can be inverted with the help of eq .
( [ coframe ] ) to obtain @xmath21 which means that the vierbein is orthonormal .
teleparallelism uses the weitzenbck spacetime , where the connection is chosen as @xmath22 as a consequence of the choice of the weitzenbck connection ( [ wei1 ] ) , the riemann tensor is identically null .
so the spacetime is flat : the gravitational degrees of freedom are completely encoded in the torsion @xmath2 . in terms of parallelism
, the choice of the weitzenbck connection has a simple meaning .
in fact , the covariant derivative of a vector yields @xmath23 in particular , eq .
( [ orto ] ) implies that @xmath24 ; so , the weitzenbck connection is metric compatible .
in general , eq . ( [ transport ] ) means that a given vector is parallel transported along a curve if its projections on the co - frame remain constant .
so , the vierbein parallelizes the spacetime .
of course , this nice criterion of parallelism would be destroyed if local lorentz transformations of the co - frame were allowed in the theory .
teleparallelism is a dynamical theory for the vierbein , which is built from the torsion . according to eq .
( [ metric ] ) , a set of dynamical equations for the vierbein also implies a dynamics for the metric .
this dynamics coincides with einstein s dynamics for the metric when the teleparallel lagrangian density is chosen as @xcite @xmath25=\frac{1}{16\pi g}\;e\;(t-2\lambda)\ ; , \label{lagrangiant}\ ] ] where @xmath26 , and @xmath27 stands for the absolute value of the determinant . in eq .
( [ lagrangiant ] ) we have defined the _
weitzenbck invariant _ as @xmath28 the tensor @xmath29 appearing in the last equation is defined according to @xmath30 in fact , the lagrangian ( [ lagrangiant ] ) just differs from the einstein - hilbert lagrangian with cosmological constant @xmath31 in a total derivative @xmath32=e\ t-2\;\partial _ { \nu } ( e\;t_{\sigma } ^{\ \
\sigma \nu } \,)\ ; , \label{divergence}\ ] ] where @xmath33 is the scalar curvature for the levi - civita connection . when gr dresses this costume , the gravitational degrees of freedom are gathered in the torsion instead of the levi - civita curvature .
it is a very curious and fortunate fact that both pictures enable to construct a gravitational action with the same physical content .
however , it is remarkable that the lagrangian ( [ lagrangiant ] ) involves just first derivatives of its dynamical field , the vierbein . in some sense
, the teleparallel lagrangian picks up the essential dynamical content of einstein theory without the annoying second order derivatives appearing in the last term of eq .
( [ divergence ] ) .
such lagrangian is a better starting point for considering modified gravity theories , since any deformation of its dependence on @xmath34 will always lead to second order dynamical equations . on the contrary ,
the so called @xmath35 theories lead to fourth order equations .
analogously to the @xmath35 scheme , a @xmath0 theory replaces the weitzenbck invariant @xmath34 in eq .
( [ lagrangiant ] ) with a general function @xmath0 .
so , the dynamics is described by the action @xmath36where @xmath37 is the matter lagrangian density .
undoubtedly , the whole family of actions gathered in ( [ action ] ) constitutes a vast territory worth to be explored , specially when one is aware that the dynamical equations arising by varying the action ( [ action ] ) with respect to the vierbein components @xmath38 are of second order .
this distinctive feature makes weitzenbck spacetime a privileged geometric structure to formulate modified theories of gravitation .
in fact , the dynamical equations for the vierbein tell how the matter distribution organizes the orientation of the basis @xmath9 at each point , in such a way that the field lines of @xmath39 realize the parallelization of the manifold .
after this vierbein field is obtained , one uses the assumption of orthonormality to get the metric ( [ metric ] ) . let us deal now with born - infeld gravity
this high energy modification of einstein gravity is based on the born - infeld procedure used first in the context of electrodynamics , and is governed by the @xmath40-dimensional action in weitzenbck spacetime given by @xcite @xmath41 , \label{acciondet}\]]where @xmath42 is quadratic in the weitzenbck torsion , and reads @xmath43 being @xmath44 and @xmath45 non - dimensional constants .
such a combination ensures the correct gr limit since both terms in @xmath46 have trace proportional to the weitzenbck invariant @xmath47 . in order to show this fact , we can factor out @xmath48 from expression ( [ acciondet ] ) and use the expansion of the determinant , @xmath49where @xmath50 and @xmath51 is the identity .
this last equation expresses the fact that in any number of dimensions we have @xmath52hence , at the lowest order we retrieve the low energy regime described by the einstein theory with cosmological constant @xmath53 $ ] .
due to the fact that general relativity is a theory for the metric , it is invariant under local lorentz transformations of the vierbein .
however , the equivalence between teleparallelism ( [ lagrangiant ] ) and gr dynamics , expressed in the eq .
( [ divergence ] ) , implies that @xmath34 changes by a boundary term under local lorentz transformations .
because of this reason , the teleparallel equivalent of gr does not provide the manifold with a parallelization but only with a metric . on the contrary , in a @xmath0 theory the boundary term " in @xmath34
will remain encapsulated inside the function @xmath54 .
this means that a @xmath0 theory is not invariant under local lorentz transformations of the vierbein .
so , a @xmath0 theory will determinate the vierbein field almost completely ( up to global lorentz transformations ) . in other words ,
a @xmath0 theory will describe more degrees of freedom than the teleparallel equivalent of gr .
this is an important issue in the search for solutions to the @xmath0 dynamical equations , since pairs of vierbein fields connected by local lorentz transformations ( i.e. , leading to the same metric tensor ) are _ inequivalent _ from the point of view of the theory .
clearly , the same considerations are also valid for born - infeld gravity because the determinantal action ( [ acciondet ] ) is constructed with quadratic combinations of the torsion tensor , which fails to be invariant under a local lorentz change of the tetrad . due to the lack of local lorentz invariance ,
the vierbein fields solving the equations of theories with absolute parallelism are harder to obtain than the metric field .
in fact , the considerations of symmetry about the form of the metric can be of little help to determine which among a set of locally lorentz related frames is the right one to solve the dynamical equations .
as an example , we will find here the adequate frames in order to deal with frw universes with non flat spatial sections .
for these geometries , the line element can be described in hyper - spherical coordinates as @xmath55 , \label{metesferica}\ ] ] where @xmath56 for the closed universe and @xmath57 for the open universe . here
, one is tempted to think that the vierbein that solves the dynamical equations could have the form @xmath58 however , this choice turn out to be incompatible with the field equations coming from the actions ( [ action ] ) and ( [ acciondet ] ) , because the vierbein ( [ naive ] ) does not correctly parallelize the spacetime .
the symptom that the choice ( [ naive ] ) will not work is the form acquired by the weitzenbck invariant in such case , which turn out to be @xmath59.\ ] ] this form of @xmath34 would be unable of giving a proper reduced lagrangian for the dynamics of the scale factor @xmath60 , as a consequence of its dependence on @xmath61 .
this @xmath62-dependent weitzenbck invariant is not consistent with the isotropy and homogeneity of the frw cosmological models .
we shall here sumarise the technique in order to obtain the parallelized frames . for details , we refer the reader to ref .
@xcite .
the procedure starts taking the _ naive _ frame of eq .
( [ naive ] ) and performing on it a suitable local lorentz transformation .
this transformation will locally twist the diagonal frame ( [ naive ] ) to convert it in a global well defined parallel field . for the closed universe ( @xmath63 ) ,
the local lorentz transformation consist in a local rotation of the spatial tetrad @xmath64 , with euler angles @xmath65 ; thus both frames are related via the euler matrix @xmath66 where @xmath67 as usual , the angular coordinates range in the intervals @xmath68 , @xmath69 and @xmath70 . the aspect of the so locally rotated frame is now @xmath71\notag \\
\mathring{e}^{3 } & = & - s ( \theta)s ( \phi)d\psi - s ( \psi ) [ ( s ( \psi ) c ( \phi ) + c ( \psi ) c ( \theta ) s ( \phi ) ) \ d\theta + ( c ( \psi ) c ( \phi ) - s ( \psi ) c ( \theta ) s ( \phi ) ) \ s ( \theta )
\ d\phi ] , \notag \\ \label{autop1}\end{aligned}\ ] ] where , of course , @xmath72 and @xmath73 .
a similar procedure is applicable to the open frw universe ; take the same rotation ( [ rotacion ] ) starting from the spatial part of the naive vierbein ( [ naive ] ) with @xmath57 , but now replace the euler angle @xmath61 by @xmath74 .
the transformed fields read ( here we put @xmath75 and @xmath76 ) @xmath77 \notag \\ \breve{e}^{3 } & = & s(\theta)s(\phi)d\psi + sh(\psi ) \ [ ( i\ sh(\psi)c ( \phi ) + ch(\psi)c(\theta)s(\phi))\ d\theta + ( ch(\psi)c(\phi ) -i\ sh ( \psi)c(\theta)s(\phi ) ) s(\theta ) \ d\phi ] .\notag
\\ \label{autop3}\end{aligned}\ ] ] then , as the frame field of 1-forms we take @xmath78 where the @xmath79 s allude to the dreibein @xmath80 and @xmath81 , @xmath82 , of eqs .
( [ autop1 ] ) and ( [ autop3 ] ) respectively .
the fact that the naive vierbein ( [ naive ] ) is connected with ( [ autop4 ] ) by a local rotation guarantees that the latter still describes the spatially curved frw metric given in eq .
( [ metesferica ] ) .
the weitzenbck invariant associated to the vierbein ( [ autop4 ] ) is@xmath83where the positive sign corresponds to the closed case and the negative to the open one , and @xmath84 is the hubble rate . ) can be summarized in the expression @xmath85 .
see ref .
@xcite for the flat case . ]
the absence of angular vestiges in ( [ invarcerrado ] ) foretell that the vierbein ( [ autop4 ] ) will be adequate to solve the dynamical equations .
let us prove this statement first for the @xmath0 schemes represented by the action ( [ action ] ) . for this purpose
, we must replace the vierbein ( [ autop4 ] ) in the field equations coming from the variation of the action ( [ action ] ) with respect to the components of the vierbein .
when varying with respect to the temporal component we obtain the modified version of friedmann equation , which turns out to be @xmath86 the non trivial equations for the spatial sector are equal to @xmath87 in the right hand side of the equations appear the energy density @xmath88 and the pressure @xmath89 of the fluid that fills the spacetime in a homogeneous and isotropic way , i.e. , the energy - momentum tensor reads @xmath90 in the comoving frame .
note that eq .
( [ friedcerrada ] ) is of first order in time derivatives of the scale factor , irrespective of the function @xmath54
. equations ( [ friedcerrada ] ) and ( [ espcerradas ] ) are two differential equations for just one unknown function @xmath60 ; so , they can not be independent .
the way to see that this is indeed the case , is to take the time derivative of ( [ friedcerrada ] ) and combine it with the conservation equation , @xmath91 to obtain eq .
( [ espcerradas ] ) .
conversely , if the system ( [ friedcerrada ] ) and ( [ espcerradas ] ) is consistent , then the conservation of energy in the matter sector is given automatically and eq .
( [ densidad de energia ] ) holds .
a further characterization of the scale factor dynamics depends on the particular choice of the function @xmath0 , but the general considerations about the correctness of the frames ( [ autop4 ] ) are valid for all @xmath54 s .
the frames ( [ autop4 ] ) are also valid for other theories with absolute parallelism , because they reflect the procedure of parallelization performed in the frw manifold .
we shall use them now in order to study the dynamics of the curved frw models in four dimensional born - infeld gravity . for simplicity
, we will work in the subspace of the parameter space @xmath92 defined by the condition @xmath93 ( see eq .
( [ tensorf ] ) ) .
the dynamics of the scale factor is encoded in the modified friedmann equation , which emerges from the replacement of the ansatz ( [ autop4 ] ) in the motion equation coming from varying the action ( [ acciondet ] ) with @xmath94 respect the temporal component of the tetrad @xmath95 , and it looks @xmath96 in the last equation , the signs @xmath97 refer again to the close and open cases respectively , and the bars mean absolute value .
again , the equation coming from the spatial sector is just the time derivative of ( [ 00k=1 ] ) combined with the conservation equation ( [ densidad de energia ] ) , so we can ignore it in the analysis .
an exact solution of the motion equation ( [ 00k=1 ] ) is beyond our present scope .
however , the main physical features can be derived if one thinks about eq .
( [ 00k=1 ] ) as an energy conservation equation of the type @xmath98 the potential @xmath99 can be found easily , and it can be written as @xmath100 , \label{potbik=1}\ ] ] where we have defined the two constants @xmath101 and @xmath102 .
additionally , the two constants @xmath103 and @xmath104 indicate present date values of the involved quantities , and @xmath105 is the barotropic index of the perfect fluid with state equation @xmath106 . in fig .
[ potenciales ] we can see the potentials ( [ potbik=1 ] ) for a radiation - dominated universe ( i.e. , @xmath107 ) , with @xmath108 , so @xmath109 .
the curves in black refers to the closed case and the ones in grey to the open case .
the behavior of gr is depicted in dashed lines for both cases .
while the gr potentials become divergent as @xmath110 , we see that the bi dynamics behave drastically different in that ( high energy ) limit .
as the scale factor tends to zero , the bi potentials go to zero with null derivative . in fig .
[ potenciales ] , we display the curves for three nominal values of the bi parameter , @xmath111 , @xmath112 and @xmath113 .
note that the energy level in eq .
( [ efpotk=1 ] ) is null , so the closed universe possesses a turning point in the low energy regime , where the potential is null . the non divergence of the bi potentials in the regime when @xmath110 denotes a very nice feature of the theory
actually , in that limit we have @xmath114 so the eq .
( [ efpotk=1 ] ) has , in the same limit , the solution @xmath115 then , in born - infeld cosmology we obtain that the early universe is characterized by an inflationary stage of geometrical nature .
the exponential behavior of the scale factor is driven by the bi parameter through the maximum hubble rate defined according to @xmath116 .
the existence of this early inflationary stage does not require the presence of the inflaton , and it seems to be an intrinsic feature of the bi regularization procedure .
in fact the spacetime so obtained is regular and there is not big bang singularity in it , because the scale factor tends to zero when the proper time @xmath117 .
in this article we have discussed certain conceptual features related with the lack of local lorentz invariance in gravitational theories with absolute parallelism and illustrated its consequences by means of two examples . in every gravitational theory possessing absolute parallelism , the spacetime structure is materialized in the coframe field @xmath118 which defines an orthonormal basis in the cotangent space @xmath119 of the manifold @xmath120 at each point @xmath121 . as an example we analyzed the dynamics of frw models in the so called @xmath0 theories , which are enjoying a growing popularity in our days .
when @xmath122 , i.e. , when one considers general relativity in weitzenbck spacetime , the basis @xmath118 at two different points of the manifold are completely uncorrelated , and it is not possible to define a global smooth field of bases unambiguously .
this is so because the theory is invariant under the local lorentz group acting on the coframes @xmath118 . in turn , when @xmath123 , local lorentz rotations and boosts are not symmetries of the theory anymore .
because of this lack of local lorentz symmetry , the theory picks up a preferential global reference frame constituted by the coframe field @xmath118 that solves the field equations . in such case
, the bases at two different points become strongly correlated in order to realize the parallelization of the manifold . nevertheless , the appearance of a preferred reference frame is a property coming from the symmetries of the spacetime , and it is not ruled by the specific form of the function @xmath0 .
for instance , when one is dealing with frw cosmological spacetimes , the field of frames that will lead to consistent field equations will be given by ( [ autop4 ] ) , whatever the function @xmath0 be .
additionally , the fields ( [ autop4 ] ) are also valid in more general theories with absolute parallelism which are not related with the @xmath0 schemes , for instance , born - infeld gravity ( [ acciondet ] ) . in this framework
, we have seen that the behavior of the early universe is characterized by an inflationary stage of infinite duration and geometrical character .
the exponential form of the scale factor is ruled by the bi parameter @xmath124 and it does not rely on the existence of the inflaton . finally , and due to the very nature of the born - infeld action , the spacetime results free of the big bang singularity .
f. fiorini wants to thank the organizers of the 8th alexander friedmann international seminar for their hospitality at rio de janeiro .
this research was supported by conicet and universidad de buenos aires . | the vierbein ( tetrad ) fields for closed and open friedmann - robertson - walker cosmologies are hard to work out in most of the theories featuring absolute parallelism .
the difficulty is traced in the fact that these theories are not invariant under local lorentz transformations of the vierbein .
we illustrate this issue in the framework of @xmath0 theories and born - infeld determinantal gravity .
in particular , we show that the early universe as described by the born - infeld scheme is singularity free and naturally inflationary as a consequence of the very nature of born - infeld gravitational action . |
CLOSE Debbie Reynolds, the Academy Award nominated actress known for her role in the musical 'Singin' in the Rain,' passed away just one day after her daughter Carrie Fisher's death.
Carrie Fisher gives a kiss to her mother, Debbie Reynolds, in the photo room of the 20th Screen Actors Guild Awards in January 2015. (Photo: Dan MacMedan, USA TODAY)
Can you really die of a broken heart?
Late Wednesday, the stunning word came that vivacious entertainer Debbie Reynolds had passed away at 84 — one day after her daughter Carrie Fisher, 60, another cherished actress and author, died.
Reynolds' son, Todd Fisher, said the stress of his sister's death was insurmountable. It "was too much" for Reynolds, Fisher told the Associated Press. "She said, 'I want to be with Carrie.' And then she was gone," he said.
“She’s now with Carrie and we’re all heartbroken."
Reynolds was at Fisher's home in Beverly Hills planning the funeral for her daughter, who died Tuesday after a heart attack on a plane last week, when she may have suffered a stroke, according to TMZ.
Dying of a broken heart is "absolutely real," grief expert David Kessler tells USA TODAY. "I think it's extremely underdiagnosed. I think it's more common than we believe."
The scenario plays out most often among elderly couples who have shared a deep and enduring bond for decades, Kessler notes. One spouse passes away, and within days — and sometimes hours — the other spouse succumbs.
For parent and child, "it's less seen, but not surprising," Kessler says.
CLOSE Turns out, people really do suffer from broken hearts. Stress cardiomyopathy, also known as broken heart syndrome, is brought on by the response to a stressful event, such as the death of a loved one or divorce. VPC
The American Heart Association agrees, classifying broken heart syndrome as a medical condition also called stress-induced cardiomyopathy. Women are more likely than men to be stricken, the association says, and will experience sudden, severe chest pain, which is a reaction to a surge of stress hormones triggered by an emotionally painful event. The heart temporarily enlarges, but unlike a heart attack, there is no evidence of blocked heart arteries.
While the condition is usually treatable, it can lead to severe, short-term heart muscle failure.
Kessler has his own powerful insight into the agony of losing a child. His 21-year-old son died three months ago. "I now have a personal understanding on the deepest level" of trying to soothe an aching heart, he says.
The Los Angeles-based grief expert says he worked with Fisher a number of times. Fisher and Reynolds "were so close. I would not be surprised if part of this was broken heart syndrome."
He recalled Fisher bringing a friend into her home to live out her final days. Fisher "was someone who was very comfortable with death. She took life and death personally," he says.
For everyday people struggling to process the parade of high-profile deaths in 2016, they should not feel unnerved that they are distressed by the loss of someone they never knew such as a celebrity, Kessler says. "Your grief is a reflection of a connection that has been lost .... not necessarily someone you met. If your heart feels connected, it will grieve."
CLOSE Fans gathered around Debbie Reynolds star on the Hollywood Walk of Fame on Wednesday night, to remember the acting and dancing legend. Reynolds died on Wednesday at the age of 84, one day after the death of her daughter, actress Carrie Fisher. (Dec. 29) AP
As for rumblings about celebrity deaths "coming in threes," that isn't statistically accurate, Kessler says. "But our minds like to see patterns and organize it that way."
Kessler offers these words of advice for those particularly shaken by the double hit of Fisher and Reynolds: Do something to help yourself feel more comfortable. "Even though we may not know them, do not take this life for granted. Let me call my mother and tell her how much I love her."
Follow Miller on Twitter @susmiller.
Read or Share this story: http://usat.ly/2iHdoqp ||||| There’s been an outpouring of grief on the web as celebrities pay tribute to Debbie Reynolds, Hollywood icon and mother of Carrie Fisher. Reynolds died Wednesday afternoon, one day after her daughter passed away at the age of 60. She was 84.
A talented singer and actress, Reynolds appeared in many movies and stage productions spanning decades. She is survived by a son Todd and her granddaughter Billie.
Younger audiences will remember Reynolds as Grace Adler’s showbiz mom from “Will & Grace.”
Close friend Carol Channing wrote: “She was beautiful and generous. It seems like only yesterday she was having lunch here at the house and we were discussing
the possibility of working together in a new show. I have such fond memories of appearing with her here at the McCallum Theater in Palm Springs. So many laughs. My prayers go out to the family. She will be missed.”
Added Reynolds’ costar Rip Taylor: “I was blessed to work with this remarkable woman for 45 almost 50 years. That makes for a very rare bond and unique relationship. She was generous to a fault, never caring who got the laugh from the audience. I Will always love her. I am absolutely devastated tonight!”
Related Harrison Ford Remembers Carrie Fisher During Mark Hamill's Walk of Fame Star Ceremony Carrie Fisher Wins 2018 Grammy for Best Spoken Word
Read some of the online tributes below:
This is a beautiful love story to witness in my 58 years. I miss them both so much. Love is everlasting pic.twitter.com/AeIVGaGl9k — Todd Fisher (@tafish) December 29, 2016
Todd Fisher, Carrie’s brother and Reynolds’ son, wrote: “This is a beautiful love story to witness in my 58 years. I miss them both so much. Love is everlasting.”
Debbie Reynolds, a legend and my movie mom. I can't believe this happened one day after Carrie. My heart goes out to Billie. — Albert Brooks (@AlbertBrooks) December 29, 2016
Albert Brooks wrote: “Debbie Reynolds, a legend and my movie mom. I can’t believe this happened one day after Carrie. My heart goes out to Billie.”
Debbie Reynolds was pure class. She was loving, talented, beautiful, unsinkable. I feel sorry for anyone who never got a chance to meet her. pic.twitter.com/XrIDFuLfYU — Larry King (@kingsthings) December 29, 2016
Larry King wrote: “Debbie Reynolds was pure class. She was loving, talented, beautiful, unsinkable. I feel sorry for anyone who never got a chance to meet her.”
So heartsick. Debbie went to be with Carrie. It's such a devastating 1,2 punch. She was my "mom" for years & I loved her dearly.A legend. — Debra Messing (@DebraMessing) December 29, 2016
Debra Messing wrote: “So heartsick. Debbie went to be with Carrie. It’s such a devastating 1,2 punch. She was my “mom” for years & I loved her dearly. A legend.”
It is beyond astonishing that both @carrieffisher & @DebbieReynolds1 have left this earth. I overwhelmingly adored & admired them both. 😢🌹🌹 pic.twitter.com/emLn1ZvwUd — Sean Hayes (@SeanHayes) December 29, 2016
Sean Hayes wrote: “It is beyond astonishing that both @ carrieffisher & @ DebbieReynolds1 have left this earth. I overwhelmingly adored & admired them both.”
The combination of the loss of @carrieffisher & then her mom @DebbieReynolds1 is too much. I'm really at a loss here… #toomuch16 — Eric McCormack (@EricMcCormack) December 29, 2016
Eric McCormack wrote: “The combination of the loss of @ carrieffisher & then her mom @ DebbieReynolds1 is too much. I’m really at a loss here… # toomuch16“
#DebbieReynolds has just died. This is too hard to comprehend. Beautiful, talented, devoted to her craft, she follows Carrie, dead days ago. — Bette Midler (@BetteMidler) December 29, 2016
Bette Midler wrote: “ # DebbieReynolds has just died. This is too hard to comprehend. Beautiful, talented, devoted to her craft, she follows Carrie, dead days ago.”
Mark Hamill wrote: #CruelCruelYear
Debbie Reynolds was one of the last of Hollywood Royalty. It breaks my heart that she is gone. I'd hoped that my grieving was done for 2016. — William Shatner (@WilliamShatner) December 29, 2016
William Shatner wrote: “Debbie Reynolds was one of the last of Hollywood Royalty. It breaks my heart that she is gone. I’d hoped that my grieving was done for 2016.”
I can't imagine what Carrie Fisher and Debbie Reynolds' family are going through this week. I send all of my love. — Ellen DeGeneres (@TheEllenShow) December 29, 2016
Ellen wrote: “I can’t imagine what Carrie Fisher and Debbie Reynolds’ family are going through this week. I send all of my love.”
Anna Kendrick wrote: “American treasure.”
Carrie, watching her mother from the wings. pic.twitter.com/QWE2YnQLJD — Martha Plimpton (@MarthaPlimpton) December 29, 2016
Martha Plimpton wrote: “Carrie, watching her mother from the wings.”
The most incredible love is when one can't live without the other…#RIP #DebbieReynolds — Constance Zimmer (@ConstanceZimmer) December 29, 2016
Constance Zimmer wrote: “The most incredible love is when one can’t live without the other… # RIP # DebbieReynolds“
Debbie Reynolds, God is holding you and Carrie in his hands.
We will always speak your name🌈
Love you, Debbie Allen — Debbie Allen (@msdebbieallen) December 29, 2016
Debbie Allen wrote, “Debbie Reynolds, God is holding you and Carrie in his hands. We will always speak your name.”
Damn. RIP Debbie Reynolds. Legendary entertainer. I'm sure broken hearted by the loss of her daughter. — Dane Cook (@DaneCook) December 29, 2016
Dane Cook wrote: “Damn. RIP Debbie Reynolds. Legendary entertainer. I’m sure broken hearted by the loss of her daughter.”
That is the saddest thing. So sorry for the whole family. Rip #CarrieFisher and #DebbieReynolds. 💔 — Ricki Lake (@RickiLake) December 29, 2016
Ricki Lake wrote, “That is the saddest thing. So sorry for the whole family. Rip #CarrieFisher and #DebbieReynolds.”
Painfully sad – there are no words 4 loss of Debbie Reynolds & Carrie Fisher. 2 vibrant, talented – moving spirits. #RIPC #RIPD #sagaftra — Gabrielle Carteris (@TheGabrielle_C) December 29, 2016
Gabrielle Carteris wrote: “Painfully sad – there are no words 4 loss of Debbie Reynolds & Carrie Fisher. 2 vibrant, talented – moving spirits.”
Debbie Reynolds helped light my passion for performing with Singin' in The Rain. She will always be an icon. Rest with Carrie, Debbie. — Grant Gustin (@grantgust) December 29, 2016
Grant Gustin wrote: “Debbie Reynolds helped light my passion for performing with Singin’ in The Rain. She will always be an icon. Rest with Carrie, Debbie.”
i love you billie. so so much. rest in peace, debbie reynolds. — Ariana Grande (@ArianaGrande) December 29, 2016
Ariana Grande wrote: “i love you billie. so so much. rest in peace, debbie reynolds.”
There are no words. Just that we all want 2 surround Billie with loving strength & support. Please give her space media. Please. Please. — Jamie Lee Curtis (@jamieleecurtis) December 29, 2016
Jamie Lee Curtis wrote: “There are no words. Just that we all want 2 surround Billie with loving strength & support. Please give her space media. Please. Please.”
FEW B4 HER, OR THE FEW WE SHALL EVER C AGAIN! NOW HER & HER DAUGHTER CAN SOAR 2GETHER IN GODS GR8 VAST KINGDOM! R.I.P. DEBBIE REYNOLDS — Corey Feldman (@Corey_Feldman) December 29, 2016
Corey Feldman wrote: “FEW B4 HER, OR THE FEW WE SHALL EVER C AGAIN! NOW HER & HER DAUGHTER CAN SOAR 2GETHER IN GODS GR8 VAST KINGDOM! R.I.P. DEBBIE REYNOLDS”
So sad to learn of @DebbieReynolds1 passing …an American icon and Hollywood legend. pic.twitter.com/OHh7VtsAAW — Gloria Gaynor (@gloriagaynor) December 29, 2016
Gloria Gaynor wrote: “So sad to learn of @DebbieReynolds1 passing …an American icon and Hollywood legend.”
What a tragedy! First Carrie, now her legendary mother Debbie Reynolds- my deepest and condolences to their family!! https://t.co/swJhKQg368 — Mira Sorvino (@MiraSorvino) December 29, 2016
Mira Sorvino wrote: “What a tragedy! First Carrie, now her legendary mother Debbie Reynolds- my deepest and condolences to their family!!”
So blown away and saddened by this Debbie Reynolds news a day after her daughter, Carrie passes away. So much luv & strength to their family — Dwayne Johnson (@TheRock) December 29, 2016
Dwayne Johnson wrote: “So blown away and saddened by this Debbie Reynolds news a day after her daughter, Carrie passes away. So much luv & strength to their family.”
THIS IS TRAGIC 😩 I 💖‘d DEBBIE,SHE WAS TUFF FUNNY,TOLD“BEST”OLD 40′s-50′s SHOW BIZ STORIES& LIVED THROUGH HOLLYWOOD 🐂💩…A HUGE TESTAMENT 2HER — Cher (@cher) December 29, 2016
This is beyond heartbreaking.
Debbie was an Idol …I Have Seen
Singing in The Rain a million times.
Loved all her films…WORDS
ARE INADEQUATE — Cher (@cher) December 29, 2016
Beautiful , sweet, Debbie Reynolds. Could the bond between mother and daughter have been s… https://t.co/KyUQ3ZbnVP pic.twitter.com/ZqktGezKid — Rita Wilson (@RitaWilson) December 29, 2016
Debbie Reynolds cd sing, dance & gave dazzling performances. RIP doesn't sound right for her or Carrie-I hope they're somewhere having fun — Mia Farrow (@MiaFarrow) December 29, 2016
Gary Marsh, the president and CCO of Disney Channel wrote: “Through her role as the magical Grandmother Agatha Cromwell in four ‘Halloweentown’ movies, Debbie Reynolds became as beloved by Disney Channel viewers as she was by their parents and grandparents. We join the film, theatre, recording and TV community in extending our condolences to her family.” ||||| # DebbieReynolds has just died. This is too hard to comprehend. Beautiful, talented, devoted to her craft, she follows Carrie, dead days ago. ||||| Image copyright AP Image caption Debbie Reynolds (left) with her daughter and fellow actress Carrie Fisher
Debbie Reynolds, who starred opposite Gene Kelly in the 1952 musical Singin' in the Rain, has died a day after the death of her daughter, Carrie Fisher.
The US actress, 84, had been rushed to hospital with a suspected stroke.
Her son, Todd Fisher, said the stress of his sister's death had been too much for her and in her last words, she had said she wanted to be with Carrie.
US actress Bette Midler said Reynolds was "devoted to her craft" and that her death was "too hard to comprehend".
Actress Debra Messing said Reynolds, her on-screen mother in sitcom Will and Grace, had been an "inspiration".
"A legend of course," she wrote in a statement. "The epitome of clean-cut American optimism, dancing with Gene Kelly as an equal, a warrior woman who never stopped working.''
Actor Rip Torn, who worked with Reynolds in her Las Vegas stage show, said: "I was blessed to work with this remarkable woman for 45 almost 50 years. That makes for a very rare bond and unique relationship.
"She was generous to a fault, never caring who got the laugh from the audience. I will always love her."
Veteran comic actress Carol Channing agreed: "She was beautiful and generous. It seems like only yesterday she was having lunch here at the house and we were discussing the possibility of working together in a new show."
Media playback is unsupported on your device Media caption Carrie Fisher tells Debbie Reynolds, "I love you momma"
For Star Trek actor William Shatner, Reynolds was one of the last of the Hollywood royalty.
"It breaks my heart that she is gone," he wrote. "I'd hoped that my grieving was done for 2016.
Reynolds had been at her son's house in Beverly Hills - apparently discussing the arrangements for Carrie Fisher's funeral - when she was taken ill.
She was admitted to Cedars-Sinai Medical Centre suffering from breathing difficulties and her death was confirmed a few hours later. It is thought she suffered a stroke.
Carrie Fisher, renowned for her role as Princess Leia in the Star Wars series, had died aged 60 the day before, after spending three days in a Los Angeles hospital.
She never regained consciousness after suffering a massive heart attack on board a flight from London to Los Angeles on Friday.
Speaking to the Associated Press news agency about his mother, Todd said: "She's now with Carrie and we're all heartbroken.''
Celebrity news site TMZ reported that Reynolds cracked while discussing plans for Carrie's funeral with her son, telling him: "I miss her so much; I want to be with Carrie."
Can you die from a broken heart? By Stephen Evans, BBC News
Image copyright PA
Some people talk about "broken heart syndrome", known more formally as stress cardiomyopathy or takotsubo cardiomyopathy. According to the British Heart Foundation, it is a "temporary condition where your heart muscle becomes suddenly weakened or stunned. The left ventricle, one of the heart's chambers, changes shape."
It can be brought on by a shock. "About three quarters of people diagnosed with takotsubo cardiomyopathy have experienced significant emotional or physical stress prior to becoming unwell," the charity says.
This stress might be bereavement but it could be a shock of another kind. There are documented cases of people suffering the condition after being frightened by colleagues pulling a prank, or suffering the stress of speaking to a large group of people. It's speculated that the sudden release of hormones - in particular, adrenaline - causes the stunning of the heart muscle.
This is different from a heart attack, which is a stopping of the heart because the blood supply is constricted, perhaps by clogged arteries.
Read more here
How does grief cause physical pain?
Media playback is unsupported on your device Media caption "Funny and vital": Fans in Hollywood mourn Debbie Reynolds
Image copyright Getty Images Image caption Singin' in the Rain guaranteed Reynolds Hollywood legend status
Reynolds was leading lady in a succession of major Hollywood musicals and comedies in the 1950s and 60s.
She rose to stardom with Singin' in the Rain, at the age of only 19.
She received a best actress Academy Award nomination for the 1964 musical The Unsinkable Molly Brown.
Her other films included 1973 animated film Charlotte's Web, in which she provided the voice for the eponymous spider.
In 2015 she was given a lifetime achievement award by the Screen Actors Guild. The award was presented to her by her daughter.
Reynolds married singer Eddie Fisher in 1955 and had two children, Carrie and Todd. The couple divorced in 1959 after news emerged of his affair with movie star Elizabeth Taylor.
Reynolds married twice more.
Image copyright Getty Images Image caption Reynolds (left) had a complex relationship with her daughter Carrie Fisher [pictured in 1972]
The actress has a sometimes strained relationship with her actress daughter, who wrote about it in her semi-autobiographical novel Postcards from the Edge.
The pair stopped speaking to each other for many years but became closer later in life.
In an interview last month with US radio network NPR, Fisher said her mother was "an immensely powerful woman" whom she admired "very much".
As people gathered to pay their respects to the actress at Hollywood's Walk of Fame, one couple, Jose and Daniela Barrera, appeared to speak for many after a year marked by celebrity deaths.
"It's just, you know, a sad time I guess," Jose told the Reuters news agency. "With the closing of the year and so many deaths in the year, it's just sad."
"It was so sad," added Daniela. "It was a shocker. I mean, what were the odds of this happening? It was incredible finding out, sad." ||||| This article is over 2 years old
Oscar-nominated star told her son ‘that she would like to be with Carrie again’, 15 minutes before she had a severe stroke
Hollywood legend Debbie Reynolds has died aged 84, just one day after the death of her daughter, famed actor and author Carrie Fisher.
Her death was confirmed by her son, Todd Fisher.
Debbie Reynolds: her life and career – in pictures Read more
“The last thing she said this morning was that she was very, very sad about losing Carrie and that she would like to be with her again,” Fisher said. “Fifteen minutes later she suffered a severe stroke.”
Reynolds died just hours after she was taken to Cedars Sinai medical center from her son’s house in Beverly Hills on Wednesday afternoon.
“The only thing we’re taking solace in is that what she wanted to do was take care of her daughter, which is what she did best,” he added.
On Friday, Carrie Fisher reportedly suffered a heart attack on a flight from London to Los Angeles. Reynolds posted on her Facebook page on Christmas Day that Fisher was in a stable condition.
Carrie Fisher died two days later.
On Tuesday, Reynolds addressed Fisher’s death on Facebook, writing: “Thank you to everyone who has embraced the gifts and talents of my beloved and amazing daughter. I am grateful for your thoughts and prayers that are now guiding her to her next stop. Love Carries Mother.”
Facebook Twitter Pinterest Billie Lourd, Carrie Fisher and Debbie Reynolds at the Screen Actors Guild awards in Los Angeles last year. Photograph: Kevin Mazur/Getty Images
Further tributes came from Joely Fisher, a daughter of Reynolds’ ex-husband Eddie Fisher, and Carrie Fisher’s half-sister, who tweeted a picture of herself and Reynolds with the words “God speed mama”.
Joely Fisher (@MsJoelyFisher) God speed mama pic.twitter.com/XsO5zqN8w6
“So heartsick. Debbie went to be with Carrie. It’s such a devastating 1, 2 punch,” tweeted Debra Messing. Reynolds played Messing’s mother on the sitcom Will & Grace. “She was my ‘mom’ for years & I loved her dearly. A legend.”
Messing’s co-star Eric McCormack, who played Will, tweeted a short time later: “The combination of the loss of Carrie Fisher & then her mom Debbie Reynolds is too much. I’m really at a loss here.”
Albert Brooks, who directed and co-starred with Reynolds in 1996’s Mother, was another of the star’s “children” who paid tribute on Wednesday.
Albert Brooks (@AlbertBrooks) Debbie Reynolds, a legend and my movie mom. I can't believe this happened one day after Carrie. My heart goes out to Billie.
Hollywood veteran Carl Reiner, who acted alongside Reynolds in the 1959 comedy The Gazebo, and later directed Carrie Fisher in the 1990 comedy Sibling Rivalry, tweeted: “How shocked we were to learn that Debbie Reynolds passed away just a day after her daughter Carrie. I loved & worked [with] both of these icons.”
Carol Channing, who performed with Reynolds on stage, told the Press Association: “She was beautiful and generous. It seems like only yesterday she was having lunch here at the house and we were discussing the possibility of working together in a new show.”
Actor Rip Taylor, who had also performed with Reynolds in Las Vegas, said: “I was blessed to work with this remarkable woman for 45, almost 50 years. That makes for a very rare bond and unique relationship. She was generous to a fault, never caring who got the laugh from the audience. I will always love her.”
In 2011, Reynolds and Fisher appeared together for an extensive interview on the Oprah Winfrey show. During the interview, mother and daughter spoke about their admiration for each other.
Fisher said: “I believe my mother knows now but if she doesn’t, it would be good if she did: that I take her advice, that I follow her example, that I respect who she is … and if I’m like her in any way then I’m happy that I am.”
Earlier on Wednesday, Winfrey tweeted a photo from the interview, saying: “Remembering the good times with Carrie and her mother.”
Oprah Winfrey (@Oprah) Remembering the good times with Carrie and her mother. #RIPCarrie pic.twitter.com/aplDPUrfhm
Fellow chatshow host Ellen DeGeneres added her tribute, expressing concern for the relatives of both women.
Ellen DeGeneres (@TheEllenShow) I can't imagine what Carrie Fisher and Debbie Reynolds' family are going through this week. I send all of my love.
The Academy of Motion Picture Arts and Sciences was among the organisations paying tribute on social media, tweeting: “An actress, a trailblazer and hero, rest in peace Debbie Reynolds.”
Actor and singer Bette Midler also hailed Reynolds on Twitter, saying she was “beautiful, talented, devoted to her craft”.
Reynolds began her rise to stardom at 16, when she caught the eye of Warner Bros during a beauty pageant, but her first breakout role was co-starring with Gene Kelly in Singin’ in the Rain. She was nominated for an Academy Award for her work in 1964’s The Unsinkable Molly Brown.
Debbie Reynolds, the Hollywood aristocrat who was a vitamin boost for the heart | Peter Bradshaw Read more
Reynolds had her two children, Carrie and Todd, with her first husband, singer Eddie Fisher. The couple divorced after Fisher had an affair with Elizabeth Taylor. She married and divorced twice more.
Carrie Fisher memorialized her tumultuous relationship with Reynolds in her semi-autobiographical novel, Postcards From the Edge. Reynolds wanted to play the role of the mother in the film adaptation of the book, but director Mike Nichols cast Shirley MacLaine instead.
mia farrow (@MiaFarrow) Debbie Reynolds cd sing, dance & gave dazzling performances. RIP doesn't sound right for her or Carrie-I hope they're somewhere having fun
Fisher spoke about her mother’s declining health in May, telling People magazine that the star had been “a little more frail” during the filming of their documentary Bright Lights: Starring Carrie Fisher and Debbie Reynolds.
Todd Fisher told ABC News in June that Reynolds had suffered a “small stroke” while in the hospital recovering from an operation. | – Hollywood is a sadder place with the loss of beloved star Debbie Reynolds, who died Wednesday, just a day after the death of daughter Carrie Fisher. The 84-year-old Reynolds is believed to have suffered a stroke at son Todd Fisher's home while planning her daughter's funeral, the BBC reports. Todd Fisher said the grief and stress of Carrie's death had been too much for his mother and the last thing she said was that "she was very, very sad about losing Carrie and that she would like to be with her again," per the Guardian. Experts say that in extremely stressful events like the death of a spouse or a child, it really is possible to die from a broken heart, with a surge of hormones creating a condition the American Heart Association calls stress-induced cardiomyopathy. Grief expert David Kessler tells USA Today that dying of a broken heart is not only "absolutely real," he believes it is "extremely underdiagnosed." Kessler, who worked with Fisher several times, says the condition is more often seen among couples who were married for many decades, but Reynolds and her daughter were so close that he "would not be surprised if part of this was broken heart syndrome." Some reactions to Reynolds' death: Bette Midler: "This is too hard to comprehend. Beautiful, talented, devoted to her craft, she follows Carrie, dead days ago." Debra Messing, Reynolds' "daughter" on Will & Grace: "So heartsick. Debbie went to be with Carrie. It's such a devastating 1,2 punch. She was my "mom" for years & I loved her dearly. A legend." Albert Brooks, who played her son in Mother: "Debbie Reynolds, a legend and my movie mom. I can't believe this happened one day after Carrie. My heart goes out to Billie." SAG-AFTRA president Gabrielle Carteris: "We have lost a unique talent and a national treasure. Coming so close to the death of her daughter, Carrie Fisher, this is truly a double tragedy. Their imprint on our culture is profound and they both will live on." Co-star Rip Taylor: "I was blessed to work with this remarkable woman for 45, almost 50 years. That makes for a very rare bond and unique relationship. She was generous to a fault, never caring who got the laugh from the audience. I will always love her," he said, per Variety. |
the term composite lymphoma ( cl ) was introduced by custer in the mid-1950s to describe cases of 2 distinct lymphomas concurrently arising in a single patient .
the incidence of cl is low with an estimated 14.7% of lymphoma cases representing cl .
typically , cl consists of 2 distinct non - hodgkin lymphomas ( nhl ) or a classic hodgkin lymphoma with an nhl ; however , case reports of 2 hodgkin lymphomas also exist . in cases of lymphoma
, diagnostic accuracy relies heavily on a pathologist 's expertise and is of great clinical consequence as it determines prognosis and selection of treatment regimen .
cl presents a unique challenge to clinicians as little data exist in regards to treatment protocols and outcomes .
here we discuss a case of a cl involving both a t - cell and a b - cell nhl and we will review the literature on the diagnostic evaluation and treatment of such a cl .
a 49-year - old woman recently diagnosed with anemia presented to the university of california irvine medical center with a chief complaint of progressively worsening cough .
she described her cough , which began a month prior to her admission , as initially mild and dry ; however , 2 days prior to admission , her symptoms changed and her cough became both more intense and productive of white sputum . on the day of admission , she began experiencing shortness of breath associated with subjective fevers and chills , prompting her to seek medical attention .
upon further questioning , she disclosed decreased appetite and approximately 13 pounds of weight loss over the last month .
anemia had been diagnosed 1 month ago by her primary care physician ; at that time , her hemoglobin level was 9 mg / dl and this was attributed to heavy menses .
the patient also denied a history of smoking , radiation exposure , or a personal or family history of malignancy . on admission ,
initial blood work revealed a hemoglobin level of 6 mg / dl with an mcv of 71.0 fl , but no leukocytosis .
there was moderate anisocytosis , slight polychromasia , multiple microcytes , and rouleaux formation on peripheral blood smear .
her chemistries were notable for hyponatremia ( 129 meq / l ) , and she had a creatinine level of 1.1 mg / dl , total bilirubin of 2.6 mg / dl , and ldh of 179 iu / l .
further chemistries revealed a total protein level of 10.0 g / dl and notably elevated kappa ( 61 mg / l ) levels but normal lambda ( 12.80
chest radiograph showed a soft tissue density in the left hilum concerning for lymphadenopathy ( fig 1a , b ) .
the patient was started on empiric antibiotics and a work - up for tuberculosis was begun . given the significantly elevated protein levels on her serum protein electrophoresis , urine protein electrophoresis , and immunofixation
serum protein electrophoresis revealed a band with restricted mobility in the gamma region as well as a band in the beta region .
urine protein electrophoresis also showed 2 bands , both with restricted mobility in the gamma region .
serum immunofixation revealed 2 iga kappa proteins and 1 free kappa light chain monoclonal protein .
urine immunofixation showed 1 iga kappa protein and 1 free kappa light chain monoclonal protein .
a chest computed tomography ( ct ) to further characterize chest radiographic findings demonstrated extensive anterior and middle mediastinal lymphadenopathy as well as bilateral supraclavicular lymphadenopathy .
in addition , mildly prominent left hilar and right axillary lymph nodes as well as bilateral pleural effusions were seen .
microscopically , lymph node staining with hematoxylin and eosin stain revealed a sinus histiocytosis pattern where mixed b - cells were found forming aggregates and both t - cells and plasma cells were found arranged in clusters and sheets around vessels ( fig 2 ) .
in addition , there were patchy ebv - positive cells , mostly around the follicles .
t - cells formed the dominant population which did not show any aberrant loss of surface antigen expression and were positive for cd2 , cd3 , cd4 , cd5 , cd7 , and cd8 both on immunohistochemistry ( ihc ) and flow cytometry .
the b - cells were positive for cd20 and pax-5 and some were notably enlarged and positive for ish - ebv .
cd138 and mum-1 were used to highlight numerous plasma cells which appeared to be kappa light chain restricted .
myd88 l265p mutation was negative , and pcr confirmed the b - cell immunoglobulin heavy change to be clonally rearranged , although t - cell beta and gamma clonal rearrangement was not detected .
the histologic features of hypervascularity with dominant t - cell population that showed aberrant loss of bcl-2 are consistent with a t - cell lymphoma , most likely peripheral t - cell lymphoma .
the presence of monotypic plasmacytic proliferation with mixed small and large b - cells is consistent with a low - grade b - cell lymphoma with exuberant plasmacytic differentiation .
the differential diagnosis includes marginal zone b - cell lymphoma with increased plasma cells and lymphoplasmacytic lymphoma the latter of which was suspected in this case .
given these findings , the patient was diagnosed with cl consisting of peripheral t - cell lymphoma not otherwise specified and lymphoplasmacytic lymphoma .
the patient underwent staging bone marrow biopsy which revealed a hypercellular marrow with active trilineage hematopoiesis and moderate myeloid hyperplasia but no evidence of b - cell or t - cell lymphomatous involvement .
dose - adjusted epoch - r ( etoposide , prednisone , vincristine , cyclophosphamide , doxorubicin , and rituximab ) with monthly prophylactic intrathecal hydrocortisone , methotrexate , and cytarabine was administered and to date the patient has received a total of 5 cycles .
pet - ct after the second cycle showed a partial response to therapy with significant reductions in both level iv node , and anterior mediastinal lymph node conglomerate ( fig 1c , d ) .
given the aggressive nature of her disease including the t cell component of her lymphoma , she was referred to a bone marrow transplant center and planned for autologous bone marrow transplant after completion of her sixth cycle of chemotherapy .
cl is increasingly being recognized in part due to the greater use of adjunctive laboratory techniques such as flow cytometry , ihc , and molecular and cytogenetic assays . to date combinations of nearly all common lymphomas
the most commonly reported cases involve 2 b - cell nhl or a b - cell nhl with a hodgkin lymphoma .
what makes this case unique is the bilineage involvement of both a t - cell nhl and a b - cell nhl . to date
less than 100 such cases have been described , representing less than 1% of all reported lymphoid malignancies . among these cases , the most frequent b - cell nhl identified was diffuse large b - cell lymphoma , whereas peripheral t - cell lymphoma not otherwise specified and angioimmunoblastic t - cell lymphoma were the most commonly identified t - cell nhl .
the diagnosis of cl is primarily based on histology and given the complexity of biopsy tissue architecture , where mixtures of infiltrates of different lymphoma types can occur , many cases of cl are likely missed .
the application of ihc adds considerable diagnostic specificity being able to both confirm clonality and cell subtype .
newer molecular techniques using pcr to detect immunoglobulin heavy chain ( igh ) and t - cell receptor gene rearrangements can confirm clonalities of both b- and t - cell components and further aid in the diagnosis of a cl .
flow cytometry is another ancillary method proven to have certain advantages such as the ability to distinguish between different cell phenotypes simultaneously and determine clonality of different cell populations .
this was demonstrated in a study by demurtas et al . who used flow cytometry to successfully identify 17 cl cases among a total of 1,332 lymphomas .
lastly , ebv testing , as was performed in this case , has been shown to be a useful adjunct .
the pathogenesis of cl is poorly understood and , given its rarity , even less is known about the formation of composite t - cell and b - cell lymphomas . although it is possible that some cases are due to mere coincidence , the majority is likely not , and multiple mechanisms have been proposed to explain how these 2 lymphomas arise simultaneously .
one theory involves transformative mutations occurring in pluripotent stem cells destined to give rise to both b and t lymphocytes .
this theory is supported by the discovery of syngeneic mutations present in both b - cell and t - cell populations in several cl cases .
an example of this is the discovery of loss - of - function mutations in tet ( ten - eleven translocation ) 2 , a tumor suppressor gene , which has been found to predispose both mice and humans to the development of a mixed b / t - cell cl .
has further supported this hypothesis with the discovery of the ccnd1 gene ( cyclin d1 ) mutations in both b- and t - cell populations .
some have suggested that chronic stimulation of b- and t - cells with either common antigens or cytokines could mediate transformation of both lineages .
lastly , virally induced transformation has been suggested as a possible etiology , specifically in ebv - positive lymphomas . a study by zettl et al . which investigated 17 cases of t - cell lymphoma suggested that immunosuppression induced by a t - cell lymphoma may lead to ebv - associated b - cell lymphoma .
cases of cl present a unique challenge to clinicians since , aside from case reports and small case series , no large therapeutic studies have been conducted .
a further complicating matter is the uncertainty that often arises when interpreting imaging studies . in cases of metastatic disease ,
it is often not feasible to determine which lymphoma component has spread , therefore making it difficult to stage properly . nevertheless , the focus of therapy should be directed towards the more aggressive component of the cl .
specifically , in cases of mixed t - cell and b - cell lymphoma , some data exist to support the role of anti - cd20 antibodies in regimens ; however , this again is limited to case reports .
schmitz et al . analyzed 320 patients with t - cell lymphomas treated within trials of the german high - grade non - hodgkin lymphoma study group and found a significant benefit of chop plus etoposide in patients aged < 60 years with a normal ldh level .
as this case demonstrates , cl presents similarly to most lymphomas ; however , it presents new challenges with regards to the management and prognosis .
much remains to be learned and more studies are needed to help develop treatment protocols not only for combined b - cell and t - cell cl but cl as a whole .
all authors have been personally and actively involved in substantive work leading to the manuscript and will hold themselves jointly and individually responsible for its content .
a.r . was the primary author documenting the patient 's care and composing the case report .
j.j . and d.j . are the attending hematologists who follow the patient regularly as an outpatient and contributed to the editing of the manuscript .
was also involved in the patient 's inpatient care and editing process of the manuscript . | composite lymphoma ( cl ) is a rare disease with 2 distinct lymphomas concurrently arising in a single patient with an estimated incidence of 14.7% of newly diagnosed lymphomas per year .
cl most commonly involves 2 b - cell non - hodgkin lymphomas ( nhl ) or a b - cell nhl with a hodgkin lymphoma .
our case is unique in that it was a bilineage cl with both a t - cell and b - cell nhl , which has only been reported in a few case reports . a 49-year - old woman presented with several months of progressive cough , weight loss , dyspnea , and supraclavicular lymphadenopathy .
computed tomographic imaging done upon admission to the hospital found that she had extensive anterior and middle mediastinal lymphadenopathy as well as bilateral supraclavicular lymphadenopathy .
the patient underwent an excisional biopsy on the supraclavicular lymph node and was found to have a composite lymphoma involving both a t - cell and b - cell nhl .
her final pathological diagnosis was peripheral t - cell lymphoma and lymphoplasmacytic lymphoma .
the patient was found to have stage iiib disease .
her hiv , hepatitis panel , and tuberculosis tests were all negative .
she then underwent chemotherapy with dose - adjusted epoch - r ( etoposide , prednisone , vincristine , cyclophosphamide , doxorubicin , and rituximab ) .
the patient showed a complete response and was then referred to a bone marrow transplant center for an autologous hematopoietic stem cell transplant .
cl is a rare disease composed of at least 2 distinct lymphomas concurrently arising in a single patient .
due to the complexity in having to treat multiple types of lymphoma simultaneously cl presents challenges with treatment and assessing prognosis . |
Smetlivy was in the Aegean Sea at the time of the 'near-miss'. Pic: File
A Russian warship has been forced to fire warning shots at a Turkish vessel to avoid a collision, officials have claimed.
The Defence Ministry in Moscow has alleged that the unnamed Turkish ship failed to respond to warnings issued by the Smetlivy navy destroyer in the Aegean Sea.
In a statement, it said the warship had been unable to establish radio contact with the approaching seiner, while visual signals and flares also went unacknowledged.
When the Turkish fishing vessel was 600 metres away and the warning shots were fired, it sharply changed course and ended up passing the warship within 540 metres.
"Only by luck was tragedy avoided," the ministry warned.
Play video "Putin: Downed Jet A 'Blow'" Video: Putin: Downed Jet A 'Blow'
Turkey's Foreign Minister, Mevlut Cavusoglu, has said the matter is being investigated - but stressed his country wants to "solve the tension" with Russia through dialogue.
Ankara's military attache was summoned by Russia over this latest incident, which unfolded 14 miles (22km) away from the Greek island of Lemnos.
Following that meeting, a Russian spokesman said: "The Turkish military diplomat was given a tough explanation about the potentially disastrous consequences from Ankara's reckless actions towards Russia's military contingent fighting against international terrorism in Syria."
It is the latest episode in the ongoing diplomatic stand-off between the two countries, with Vladimir Putin claiming Turkey shot down a Russian warplane to protect oil supplies arriving from Islamic State territory.
Play video "Turkey And Russian Relations Tense" Video: Turkey And Russian Relations Tense
The Russian President has described that incident as a "huge mistake", with the Kremlin adamant that the downed jet was in Syrian airspace at the time.
However, Turkey has claimed the warplane had encroached on its territory, despite repeated warnings not to do so.
Mr Putin has called for a series of sanctions to be implemented against Turkey, and Russian tourists are now being urged not to travel on holiday.
Fruit and vegetable imports have also been banned. ||||| MOSCOW (AP) — Russia's Defense Ministry says a Russian destroyer has used small arms fire to ward off a Turkish fishing ship and prevent a collision in the Aegean Sea.
A ministry statement says the guided missile destroyer Smetlivy was unable to establish radio contact Sunday with the approaching Turkish seiner, which also failed to respond to visual signals and flares. So when the ship was 600 meters (660 yards) away, the destroyer fired and the Turkish vessel quickly changed course, passing within 540 meters.
Tensions between Moscow and Ankara have been heightened since a Turkish jet downed a Russian bomber along the Syrian border last month, and this could further strain relations.
The Defense Ministry said it summoned the Turkish military attache in Moscow over the incident. | – A Russian destroyer fired warning shots at a Turkish fishing boat Sunday in the latest tensions between the two nations, reports Reuters. Russia's Defense Ministry says its warship, the Smetlivy, was just trying to avoid a collision with the unnamed vessel after repeated attempts to warn it over the radio and with what the AP calls "visual signals and flares" failed; the fishing boat changed course quickly after the Smetlivy opened fire, but the two ships came within about 600 yards of each other. Moscow has summoned the Turkish military attache in the incident, which took place in the Aegean Sea, about 14 miles off the Greek island of Lemnos, notes Sky News. |
the anterior open - bite can be defined as the presence of negative overbite between the incisal edges of the maxillary and mandibular teeth , with the posterior teeth in occlusion14 . generally , an anterior open - bite is a kind of malocclusion that causes esthetic problems , impairs mastication and articulation , thus creating unfavorable conditions for a child 's emotional development5 . in the mixed dentition ,
the prevalence of open - bite can reach 17%6 , caused by factors such as the partial eruption of the incisors , abnormal size of lymphoid tissue provoking alterations in the tongue 's posture , persistence of infantile swallow , and the occurrence of oral habits7 . according to many authors ,
the incidence decreases with age6,8,9 , stabilizing around 2% in caucasian and 16% in black african - american teenagers10 .
this decrease accounts for normal occlusal development , neural maturation of the child favoring the cessation of oral habits , the decrease in size of adenoids , and the establishment of normal adult swallow2,11 . in the etiology of the anterior open - bite
there are factors related to oral habits , abnormal size or function of the tongue , oral breathing , vertical growth pattern ( predisposing to open - bite ) , and congenital or acquired diseases11 . among the most frequent habits are finger - sucking , pacifiers , altered labial postures and tongue habits2 .
vertical malocclusions result from the interaction of several etiologic factors , with genetic and/or environmental origin
. the prognosis may be good to poor according to the severity and associated etiology . swallowing with tongue thrusting
is frequently observed in children up to ten years old with or without open - bite .
other aspects that may break the oral balance , as adenoid hypertrophy , increased tonsils , allergy , excess of nasal cartilage , septal deviation , and chronic coryza , may lead to mouth breathing and anterior tongue positioning during swallowing , thereby affecting the position of incisors , both inducing buccal movement and limitating their correct eruption13 .
there are three types of open - bite malocclusion in the mixed dentition period(1 ) : dentoalveolar , skeletal and a combined open - bite .
most skeletal open - bites are probably at least partially attributable to abnormal perioral muscle function14 . in skeletal open - bite
there are craniofacial dysplasias , characterized by a counter - clockwise rotation of the palatal process , associated with a longer anterior face height , large gonial angle , short ramus , and maxillary and mandibular dentoalveolar hyperplasia1,2,11,15 .
many authors emphasize that the skeletal open - bite should be treated early in the mixed dentition3,4,16 , since besides interfering with facial growth , the early treatment improves facial appearance and the child 's self - esteem , reducing the possibility of relapse and thereby increasing the stability17 . taking this into account , the long - term stability of anterior open - bite patients aged nearly 12 years old treated with fixed appliances and without extractions was studied18 .
the authors concluded that 61.9% of the patients presented stable occlusion . in another study , lopez - gavito , et al.10 , in 1985 , longitudinally followed 41 patients treated with fixed appliances and headgear for 10 years post - retention , and observed 35% of relapse of approximately 3 mm or more .
english16 , in 2002 , stated that , if no treatment is performed , maintenance of the malocclusion in patients with vertical growth pattern with anterior open - bite may result in further need of surgical treatment .
the treatment of the open - bite in the late mixed dentition , with a severe tongue thrust or posture problem , may be unsuccessful , and depends on the severity of the malocclusion and the possibility of dentoalveolar compensation7,19 .
in addition , a long retention phase is necessary before abnormal perioral muscle function can be reduced .
the objective of this work was to document a clinical case of anterior open - bite presented in the mixed dentition , successfully treated by orthodontic and orthopedic methods , emphasizing the importance of early treatment as a means of preventing the need for orthognathic surgery .
a female patient , 5 years and 2 months old , with an excessive vertical growth , presenting an anterior open - bite with contact only in the molar region attended our clinic ( figures 1 and 2 ) .
this malocclusion was classified as dentoskeletal , initially related to a thumb - sucking resulting in secondary tongue thrust .
the patient presented a vertical growth pattern of the face , as can be seen in table 1 .
the treatment proposed was a fixed palatal crib soldered on the bihelix appliance ( figure 3 ) , and high pull traction on the mandible for 16 hours a day , applying 500 g of force , during the entire treatment , in an attempt to rotate the mandible counter - clockwise with an intrusive force in the posterior region . following this 3-year process ,
right after she was subjected to full fixed appliance , with edgewise mechanotherapy , over a 9 month period . at the end of the treatment
, it could be noticed , by the clinical characteristics ( figures 5 and 6 ) and also by the cephalometric measures ( table 1 ) , that the initial proposal was successful .
the anterior open - bite was corrected , followed by dentoalveolar and growth pattern compensation .
these outcomes could be explained by changes in dental inclinations and by the increase of the posterior facial height , which minimized the effects of the longer anterior face height ( table 1 ) .
the concern about facial vertical dimensions derives from the fact that they are more difficult to treat , and the results obtained are less stable15,20 .
an anterior open - bite may have a good or poor prognosis , depending on its etiology and severity .
relapse can reach 25% . a prolonged habit , such as digital sucking , can lead to arrest of the vertical development of the alveolar process , lateral constriction of the maxilla due to increased activity of the perioral muscles , and a more inferior posturing of the tongue .
this situation , in the majority of cases , causes posterior crossbite , high palate , extrusion of the posterior teeth and anterior displacement of the maxilla . if this condition remains for a lengthy period , the alterations may persist , even after the habit has been stopped9,21
therefore , during the mixed dentition , it is very important to treat patients adequately3,4 , in order to avoid severe dental changes .
these changes may become definitive , reducing the efficiency of the therapeutic methods , thus providing orthognathic surgery as the only option for treatment22 .
the interruption of a habit can sometimes be traumatic to children , due to its importance in compensating psychological needs .
its sudden interruption can lead to a transfer to another habit , sometimes less socially accepted and more harmful to the child23 . to a motivated patient , who sincerely wants to break a habit not psychologically significant , an appliance will work as a " reminder " , and will help to break the habit . if the habit is compulsive , then psychological help is also required .
patients with open - bite often present incompetent upper lip and a compensatory hyperactive lower lip , orbicularis oris and tongue musculature .
the anterior seal , necessary for swallowing , is obtained between the upper and lower incisors , contributing to maintenance of the negative overbite .
an individual with an excessive vertical growth has a good likelihood of developing an anterior open - bite , and the degree of its severity can be altered by unfavorable environmental factors , such as habits and mouth breathing7 .
this case has been stable , and it is believed that it will remain so ( figures 7 and 8) .
this may be explained by the fact that treatments were conducted at the appropriate period of development , thus establishing perioral muscular equilibrium , matching the final period of facial growth .
the combination of orthodontic and orthopedic treatments was necessary to achieve the best results , as previously suggested7 .
it must be pointed out that this patient , if not treated at the correct moment , could have required orthognathic surgery . | a clinical case with anterior open - bite , treated in the mixed dentition , is presented .
this approach demonstrates one of the possible approaches of treatment , which is capable of interfering with growth and redirecting its vectors .
orthodontic and orthopedic methods were used , consisting of slow maxillary expansion , through a fixed palatal crib soldered in a bi - helix appliance , and high - pull traction on the mandible for 16 hours a day .
after eight years of follow - up , stable outcomes were accomplished .
these results may be explained by the fact that treatments were performed at the appropriate period of development , thus establishing perioral muscular equilibrium , matching the final period of facial growth .
the combination of orthodontic and orthopedic treatments was necessary to prevent the need of further orthognathic surgery treatment . |
a sudden quench of the hamiltonian parameters is perhaps the simplest form of out - of - equilibrium dynamics that a closed quantum system can experience .
experiments with `` virtually isolated '' cold atomic species in optical lattices @xcite have transformed this seemingly theoretical dream into a rich and lively stage . several fundamental issues of theoretical quantum statistical physics , like the onset of thermalization which is generally expected to occur for a closed quantum system after a sudden quench @xcite , or the `` breakdown of thermalization '' @xcite expected when the system is integrable or nearly integrable , are now of experimental relevance @xcite .
we refer the reader to a recent review @xcite for an extensive introduction to such non - equilibrium quantum dynamics issues .
the issue we want to tackle in this paper is the following .
suppose you perform a quantum quench of the hamiltonian parameters , abruptly changing , at @xmath0 , from @xmath1 .
if @xmath2 denotes the initial quantum state at @xmath0 , and @xmath3 the eigenstates of @xmath4 with energy @xmath5 , the ensuing quantum dynamics would lead to averages for any given operator @xmath6 given by : @xmath7 where @xmath8 and @xmath9 . the first ( time - independent ) term in the previous expression
dominates the long - time average of @xmath10 , and is usually known as _ diagonal average _
@xcite @xmath11 to calculate it , in principle , we should take the sum over all the ( many - body ) eigenstates @xmath12 of @xmath4 an exponentially large number of states , calculating for each of them the overlap @xmath13 and the associated diagonal matrix element @xmath14 .
luckily , @xmath15 can be calculated for many problems , notably those that can be reduced to quadratic fermionic problems , by circumventing in one way or another exponentially large sums : for instance , through a detour to time - dependent single - particle green s function and the use of wick s theorem , see e.g. @xcite . but suppose that you want to know more than just the diagonal average @xmath15 , and pretend to have information on the whole distribution of the values of @xmath16 accessed after the quench @xcite , i.e. , @xmath17 of which @xmath15 is just the average : @xmath18 .
here there is , evidently , a problem : knowing the distribution of @xmath19 requires exploring the full many - body hilbert space , summing over the eigenstates @xmath12 , and this exhaustive enumeration would restrict our calculations to exceedingly small sample sizes , although all information on @xmath13 and @xmath14 might in principle be easy to calculate , or in any case accessible , for instance by just solving a one - body problem ( hence , for much larger sizes ) .
a similar problem occurs in considering , for instance , the corresponding generalized gibbs ensemble ( gge ) average @xcite @xmath20 where @xmath21 are lagrange multipliers which constrain the mean value of each of the constants of motion @xmath22 to their @xmath0 value , @xmath23 $ ] , @xmath24 , @xmath25 is the gge partition function , and @xmath26 . once again , for `` quadratic problems '' this average is rather simply calculated in terms of single - particle quantities , but the corresponding distribution @xmath27 requires a difficult sum over the hilbert space .. these tricks however would not work , for instance , for the microcanonical distribution . ] concerning the issue of thermalization after a quantum quench , we might indeed expect that , if the system is well described by a gge ensemble , not only the mean values of @xmath28 and @xmath29 are equal , i.e. , @xmath30 , but also the two distributions should be closely related ; at least this is what a good statistical ensemble should do . quite generally , we might formulate the problem as follows : how can we obtain information on weighted distributions ( or density of states ) @xmath31 with positive weights @xmath32 , when both @xmath32 and @xmath33 are `` easily calculated '' , but the sum over @xmath34 runs over an exponentially large `` configuration space '' ? as discussed before , examples of this are the diagonal distribution , where @xmath35 , the gge distribution , where @xmath36 , but also the microcanonical distribution , where @xmath32 is a window characteristic function for the microcanonical shells , etc . a monte carlo algorithm to perform such exponentially
large sums in configuration space seems unavoidable .
we stress that this is so even if one is considering quenches in free - fermion models , where the relevant many - particle states @xmath3 and matrix elements are easy to write down and calculate .
the alternative of using exact diagonalization methods would put a strong limit on the size of the problem which can be studied . in this paper
we introduce a monte carlo method obtained by a rather natural extension of the wang - landau algorithm ( wla ) @xcite which will allow us to compute weighted distributions of the form of eq . .
the wang - landau algorithm , proposed in 2001 by f. wang and d.p .
landau , is a monte carlo method designed to compute the density of states of a classical statistical mechanics problem .
the algorithm performs a non - markovian random walk to build the density of states by overcoming the prohibitively long time scales typically encountered near phase transitions or at low temperatures . besides the classical ising and potts models studied in the original papers @xcite ,
the method has been applied to the solution of numerical integrals @xcite , folding of proteins @xcite and many other problems . here
is the plan of the paper . in sec .
[ sec : wwla ] we show how the wla can be extended to compute weighted density of states . in sec .
[ sec : wl - quantumquenches ] we show how the weighted - wla can be used to compute distributions related to quantum quenches with quadratic fermionic models
. finally , sec .
[ sec : conclusions ] contains a summary and future perspectives .
let us consider a system with a discrete configuration space , where configurations can be labeled with an index @xmath34 . given a physical observable @xmath37 , we define its weighted ( coarse - grained ) density of states : @xmath38 with @xmath39 a _ positive _ weight . here
@xmath40 is a kronecker delta , or , if the possible values of @xmath33 are too dense to keep them all , a suitable histogram - window - function coarse - graining of the dirac s delta .
when @xmath41 , we recover the usual density of states @xmath42 , and the wla can be used to estimate it @xcite .
we will now show that , by properly modifying the wla , we can compute @xmath43 for generic @xmath39s . to understand the gist of the approach , consider a generic positive function @xmath44 which is our best guess for the desired @xmath43 , and set up a markov chain random walk in which , given a state @xmath34 , a new state @xmath45 is generated with a trial probability @xmath46 , which we will take to be symmetric , @xmath47 , and accepted with probability : @xmath48 \;.\ ] ] with this standard metropolis monte carlo prescription , we know that , after an initial transient , we will visit the configurations @xmath34 with an equilibrium distribution @xmath49 fulfilling the detailed balance condition and given by : @xmath50 where @xmath51 is a normalization constant . as in the wla @xcite , while the random walk goes on , we collect a histogram @xmath52 , updating @xmath53 at each visited state @xmath34 . at equilibrium , after @xmath54 steps , the `` mean '' histogram will then be given by : @xmath55 exactly as for the wla @xcite , if our guess for @xmath44 is a good approximation to @xmath56 , the histogram @xmath52 will be `` almost flat '' ( see below ) .
obviously , during the random walk , together with the histogram @xmath52 we also update our guessed @xmath44 .
therefore , closely inspired by the wla @xcite , we propose the following algorithm : 1 .
fix a modification factor @xmath57 , and set @xmath58 and @xmath59 for all values of @xmath19 ; 2 .
start the monte carlo procedure using eq . and
update at each step the histogram and the weighted density of states with the rules @xmath60 and @xmath61 ; 3 . stop the random walk when @xmath52 is `` almost flat '' ( for instance @xcite , when @xmath62 for all values of @xmath19 , where @xmath63 is the mean histogram value ) . for the previous observations , at the end of this step @xmath64 is a good approximation to @xmath65 with a discrepancy of order @xmath66 ; 4 .
reduce the value of @xmath67 , reset @xmath68 and restart the procedure from step ( 1 ) using the @xmath69 just obtained .
stop this loop when @xmath66 is smaller than the desired discrepancy @xmath70 .
a similar extension of the wla has been already been introduced for the particular case in which @xmath39 is the boltzmann distribution , with the aim of computing the free energy profile as a function of a reaction coordinate @xcite . in the present paper , we will use this algorithm to compute distributions where the weights are not boltzmann - like , but rather associated to quantum quenches .
let us return for a moment to the original wla .
a first trivial observation is that , as it should be , the weighted - wla with @xmath71 coincides with the wla . in many situations , when the size of the configuration space is too big and the density of states ranges over too many orders of magnitude , it is convenient , in computing @xmath42 , to run many wla over small domains @xmath72 $ ] .
but then the update rule of the standard wla has to be changed to avoid that , during the random walk , @xmath73 leaves the domain @xmath74 .
this trick was already used in the first papers by wang and landau , when dealing with the largest sizes @xcite . to avoid leaks from @xmath74 , the empirical solution was to reject any proposal to states @xmath45 with @xmath75 , without any update of @xmath76 and @xmath52 . with this prescription , however , there are `` boundary effects '' , actually a systematic underestimation of the density of states at the borders of the intervals @xcite .
schulz _ et al . _
@xcite showed phenomenologically that such boundary effects are eliminated by using the rather obvious update rule : given a proposal @xmath45 , if @xmath77 is outside the interval we remain in @xmath34 and we update @xmath52 and @xmath78 using the state @xmath34 , otherwise we accept @xmath45 with the usual rule .
this update rule is just what is obtained , rigorously , by using our weighted - wla .
indeed , the density of states in a restricted range @xmath74 is proportional to a weighted density of states in which @xmath79 when @xmath80 , and zero otherwise . with these weights ,
the update rule of our weighted - wla is exactly the one obtained phenomenologically by schulz _ et al .
_ @xcite .
in this section we come back to the initial problem of computing the distributions @xmath28 and @xmath29 related to quantum quenches . we will show that with the weighted - wla we can compute these distributions for sizes inaccessible with an exhaustive enumeration .
we concentrate on quantum quenches in two models possessing a free fermionic description .
the first model we considered is the fermionic anderson model with disorder in the local potential : @xmath81 where @xmath82 ( @xmath83 ) creates ( destroys ) a fermion at site @xmath84 , @xmath85 is the nearest - neighbor hopping integral and @xmath86 is an uncorrelated on - site random potential uniformly distributed in the range @xmath87 $ ] .
we assume periodic boundary conditions .
it has been mathematically proven @xcite that , for hamiltonians like @xmath88 and in presence of any @xmath89 , all the single - particle eigenstates of @xmath90 are exponentially localized .
the second model we considered still describes spinless fermions hopping on a chain , but now the hopping is long - ranged @xcite : @xmath91 where @xmath92 is a ( real ) hopping integral between sites @xmath93 and @xmath94 .
we will take the @xmath95 s to be random and long - ranged , with a gaussian distribution of zero mean , @xmath96 , and variance given by : @xmath97 here @xmath98 is a real positive parameter setting how fast the hoppings variance decays with distance .
notice that , for @xmath99 , we have @xmath100 for any @xmath98 , hence the model has also on - site gaussian disorder ; by increasing the distance between the two sites @xmath101 , the variance of the hopping integral decreases with a power law .
the peculiarity of this long - range - hopping model is that , although being one - dimensional and regardless of the value of @xmath102 ( which hereafter is fixed to @xmath103 ) , it has an anderson transition from ( metallic ) extended eigenstates , for @xmath104 , to ( insulating ) power - law localized eigenstates for @xmath105 @xcite .
physically , this is due to the fact that , for small @xmath98 , long - range hoppings are capable of overcoming the localization due to disorder . having access , in the same model , to physical situations in which the final eigenstates are extended ( @xmath104 ) or localized ( @xmath105 ) will clearly show the role that spatial localization plays in disrupting the ability of the gge to describe the after - quench dynamics .
physically , spatial localization prevents the different `` modes '' of the system from having an infinite reservoir .
for the considered quenches , we use as initial hamiltonian @xmath106 the clean chain with @xmath107 and the same boundary conditions of the final hamiltonian , i.e. , periodic boundary conditions when quenching to @xmath108 and open boundary conditions when quenching to @xmath109 .
the corresponding initial state @xmath2 will be the filled fermi sea , i.e. , the ground state of @xmath106 with @xmath110 , where @xmath111 is the number of fermions .
the reason behind this simple choice for @xmath106 is that the `` stationary state '' reached does not depend , qualitatively , on the initial hamiltonian being ordered or not , see ref .
the final hamiltonian will be the anderson model @xmath108 with @xmath112 , or the long - range hopping chain @xmath109 with @xmath113 or @xmath114 .
in all cases the particle number is a constant of motion , therefore @xmath110 for any time @xmath115 . to get a smoother size dependence of the computed quantities ,
the smaller size realizations are obtained by cutting an equal amount of sites at the two edges of the largest realization .
the two hamiltonians , being quadratic in the fermion operators , can be diagonalized for any chain of size @xmath116 in terms of new fermionic operators @xmath117 where @xmath118 are the wave functions of the eigenmodes of energy @xmath119 : @xmath120 .
the energies @xmath119 and the associated wave functions @xmath118 are obtained , for any given disorder realization of a chain of size @xmath116 by numerically diagonalizing the @xmath121 one - body hopping matrix . given an observable @xmath37 , consider the two distributions introduced before : @xmath122 where @xmath123 is the dirac s delta , @xmath124 are the many - body eigenstates of @xmath4 , @xmath125 , @xmath126 , and @xmath127 is the occupation of the single - particle eigenstate @xmath128 in the many - body eigenstate @xmath12 .
these functions give the weighted distributions of @xmath14 in the diagonal and gge ensembles .
let us discuss a few technical details on the implementation we made , before discussing the physics emerging from our calculations .
notice that the sum over @xmath34 is effectively restricted to the canonical hilbert space @xmath129 with a fixed number of particles @xmath130 in the diagonal ensemble , since @xmath131 if @xmath132 .
no such restriction is in principle present in the gge case , where the sum over @xmath34 runs over the grand - canonical hilbert space . by definition ,
the distributions are such that @xmath133 and @xmath134 , where the integration is over the domain of @xmath14 . as customary in any numerical finite - size study ,
one really needs to consider a coarse - grained version of these distributions , obtained by splitting the domain of @xmath19 into small intervals @xmath135 of amplitude @xmath136 .
such a coarse - grained distribution has exactly the form of a weighted density of states , see eq .
, with @xmath137 in the diagonal case , and @xmath138 in the gge case . the configuration space @xmath139 ( i.e. , the canonical hilbert space @xmath129 for the diagonal distribution and the full hilbert space for the gge ) over which the two weighted distributions are defined is discrete and grows exponentially with the system size .
the weighted - wla is therefore the appropriate tool for the numerical computation of @xmath28 and @xmath29 .
the eigenstates @xmath12 which appear in the definition of @xmath28 have a fixed number of fermions @xmath111 ( the same of the initial state ) , while in @xmath29 the number of particles can change . in the weighted - wla , for the diagonal ensemble , we use therefore a `` particle conserving '' proposal scheme : given a state @xmath12 , the state @xmath140 is given by moving at random a fermion in one of the unoccupied single - particle eigenstates .
in this case , the ratio @xmath141 which appears in eq . ,
is equal to : @xmath142 where the coefficient @xmath143 is the square of the determinant of a @xmath144 matrix ( see ( * ? ? ?
d ) for the explicit expression of @xmath143 ) . for the gge case , instead
, we do not have restrictions on the number of fermions and , given a state @xmath12 , we generate a state @xmath140 by changing the occupation of a randomly selected single - particle eigenstate @xmath128 . in this case :
@xmath145 where the @xmath146 ( @xmath147 ) sign appears when the mode @xmath128 is initially occupied ( empty ) .
let us recall that the lagrange s multipliers @xmath21 are obtained by requiring @xmath148 .
this condition , written explicitly , reads : @xmath149_{\nu \mu } \right|^2 } - 1 \;,\ ] ] where @xmath150 and @xmath151 are @xmath121 matrices whose elements @xmath152 and @xmath118 are the single - particle wavefunctions of the initial hamiltonian @xmath153 and the final one @xmath4 , and @xmath154 is the occupation of the @xmath155th eigenstate of @xmath153 in the initial state .
the difference in the computational effort on computing the ratio @xmath141 in the two ensembles is evident : in the diagonal case at each step we have to compute the determinant of a @xmath144 matrix , while in the gge we have just to recover the value of @xmath156 ( they can be computed and stored before the monte carlo calculation because their number is @xmath116 ) . here
we will show results for sizes up to @xmath157 , where both @xmath28 and @xmath29 can be computed and compared .
( for the gge ensemble , we could reach @xmath158 without problem . ) in the numerical computations we used a minimum value of the wl parameter @xmath159 , and we split the domain of @xmath19 in @xmath116 bins .
notice that the domain of @xmath19 in @xmath29 is always larger than the domain of @xmath28 because , in the gge , the many - body eigenstates do not have a restriction on the number @xmath160 of fermions . in the next two subsections
we show the results obtained with the weighted - wla for the calculation of @xmath28 and @xmath29 for two observables , the total energy and the local density .
the physical picture emerging from the calculation of the full distribution function of the after - quench energy and local - density confirms and extends the results discussed in ref .
in particular , we find clear differences between the diagonal and gge distributions , even at the level of the variances , whenever a disorder - induced spatial localization is at play in the after - quench hamiltonian .
the first observable we consider is the total energy : here @xmath161 , where @xmath162 are the single - particle occupations of the eigenstate @xmath12 . in fig .
[ fig : rho - gge - d ] we show the distributions @xmath163/l$ ] and @xmath164/l$ ] , computed for @xmath165 and @xmath157 , for the three cases we have studied , i.e. , quenches from an initially ordered half - filled chain @xmath106 towards : 1 ) a long - range hopping hamiltonian @xmath109 with extended eigenstates ( @xmath166 , top ) , 2 ) @xmath109 with localized eigenstates ( @xmath167 , center ) , and 3 ) an anderson hamiltonian @xmath108 with a disorder width @xmath112 ( bottom ) .
/l$ ] and @xmath168/l$ ] computed with the weighted - wla .
the gray curves are obtained with @xmath165 , while the black ones with @xmath157 .
the solid vertical lines are the average energy after the quench , i.e. @xmath169 , for @xmath157 .
the three panels are obtained starting from the ground states of clean chains and quenching to different disordered hamiltonians : panel ( a ) long - range hopping with @xmath166 ( extended eigenstates ) , panel ( b ) long - range hopping with @xmath167 ( localized eigenstates ) and panel ( c ) anderson model with @xmath112 . for the computations we used a single disorder realization and , to get a smoother size dependence ,
the smaller size realization is obtained by cutting an equal amount of sites at the two edges of the larger realization .
these distributions are obtained for a single realization of the couplings , but we verified that , for large sizes , the results are self - averaging
. , scaledwidth=85.0% ] observe , first , that the distributions @xmath170 and @xmath171 shown in fig .
[ fig : rho - gge - d ] have identical average ( denoted by a solid vertical line ) @xmath172 this result comes directly from the fact that the energy does not fluctuate in time ( i.e. , the diagonal energy coincides with the average energy @xmath173 ) and gge fixes the occupation of the fermionic eigenstates in such a way as to exactly reproduce @xmath173 .
the form of the two distributions , however , differs considerably , most notably at the extremes of the spectrum , and for the anderson model case .
let us now consider the fluctuations of the energies in both distributions . in the diagonal ensemble
the variance is : @xmath174 where the expression on the right - hand side holds only for the hamiltonian ( it would not apply to arbitrary operators , because @xmath175 ) .
an entirely similar expression applies to the gge case .
since the energy is an extensive operator , it is reasonable to ask what happens to the fluctuations in the energy - per - site @xmath176 , which are simply given by @xmath177 , and @xmath178 .
on pretty general grounds , for quenches of local non - integrable hamiltonians , it is known @xcite that @xmath179 in the thermodynamic limit , @xmath180 . indeed , as shown in fig .
[ fig : sigmae - gge - d ] both @xmath181 and @xmath182 decrease to @xmath183 for @xmath180 for the three considered cases . for our quadratic problems ,
however , we can say a bit more .
first of all , from the explicit expression in eq .
after very simple algebra ( mainly using wick s theorem ) , we arrive at : @xmath184 where @xmath185 is the @xmath0 one - body green s function .
the off - diagonal elements of @xmath186 play here an important role , and the second term in @xmath181 originates from the fact that , by definition , gge does not include correlations between different eigen - modes , i.e. , @xmath187 , when @xmath188 .
( empty circles ) and @xmath189 ( solid triangles ) as a function of the size @xmath116 .
the data are obtained using the same set of quenches used in fig .
[ fig : rho - gge - d ] and the values are computed using eqs . .
error bars are calculated by averaging over 20 different realizations of the disorder .
the dashed lines are power law fits @xmath190 , where @xmath191 for the anderson case , while , for the quench to @xmath109 , @xmath192 when @xmath193 , and @xmath194 when @xmath195 .
notice the observable difference between @xmath196 and @xmath197 when the final eigenstates are localized.,scaledwidth=85.0% ] let us first consider the anderson model case .
assuming , as done so far , a bounded distribution of disorder , we are guaranteed that a finite bound @xmath198 exists such that @xmath199 for any @xmath116 . with this assumption ,
it is easy show that @xmath182 has to go to zero at least as @xmath200 for @xmath180 .
indeed , the occupation factors appearing in @xmath182 are such that @xmath201 . hence : @xmath202 the same statement can be made for @xmath181 , because the difference between the two variances has a similar upper bound : @xmath203 where we used that @xmath204 .
nevertheless , although both @xmath181 and @xmath182 go to @xmath183 as @xmath200 for the anderson model , they do so with a different pre - factor , see fig .
[ fig : sigmae - gge - d ] and comments below . for the quenches to @xmath109 ,
a bound @xmath198 for the single - particle spectrum is in principle not defined : one can think of rare realizations in which the hopping is large at arbitrarily large distances , which would give an unbounded distribution of eigenvalues @xmath205 .
indeed , the behavior of both @xmath181 and @xmath182 suggest , see fig .
[ fig : sigmae - gge - d ] , that the power - law approach to @xmath183 might be slower than @xmath200 , i.e. , as @xmath206 with @xmath207 ( we find @xmath208 for the case @xmath166 and @xmath194 for @xmath167 ) . while this might be a finite - size artifact , we find it intriguing that such deviations are quite clearly seen for quenches to @xmath109 : they might be due to the power - law nature of the hopping integral variance .
concerning the similarity between @xmath181 and @xmath182 , we observe that the two essentially coincide for the case of a quench to @xmath109 with extended eigenstates , while there is a small discrepancy for the quench to @xmath109 with localized eigenstates , and a quite clear different pre - factor in the anderson model case , @xmath209 and @xmath210 with @xmath211 .
this different pre - factor can be understood by analyzing the term @xmath212 which appears in eq . .
in fig . [
fig : occandmatrices ] , panel ( b ) , we show the structure of the matrix @xmath213 for the three quench cases .
we divide this matrix into four sectors , one for each sign of the single - particle energies @xmath214 and @xmath215 : in two of these quadrants the product @xmath216 is positive ( top - right and bottom - left ) , and in the others is negative .
for quenches to @xmath109 this matrix is almost equally distributed in all the four sectors : the sum @xmath212 has cancellations , leading to @xmath217 for large sizes . for quenches to @xmath108 , on the contrary
, the matrix @xmath213 is mainly concentrated in the sectors in which @xmath218 , leading to @xmath219 . as a function of the single - particle energy @xmath119 .
panel ( b ) : representation of the matrix @xmath220 . for the diagonal and off - diagonal elements we add a black pixel when the value exceeds their mean value . for the diagonal elements the mean value is @xmath221 , while for the off - diagonal elements the mean value is @xmath222 , where @xmath160 is the number of fermions in the initial state , and we used the relation @xmath223 ( see ( * ? ? ? * app .
the vertical and horizontal lines indicate the indexes at which the single - particle energies @xmath214 and @xmath215 change sign , and the signs shown in the four quadrants are those of the product @xmath224 .
for the two panels we used @xmath157 and the same quenches used in fig .
[ fig : rho - gge - d ] and fig .
[ fig : sigmae - gge - d].,title="fig:",scaledwidth=85.0% ] + panel ( a ) + as a function of the single - particle energy @xmath119 .
panel ( b ) : representation of the matrix @xmath220 . for the diagonal and off - diagonal elements we add a black pixel when the value exceeds their mean value . for the diagonal elements the mean value is @xmath221 ,
while for the off - diagonal elements the mean value is @xmath222 , where @xmath160 is the number of fermions in the initial state , and we used the relation @xmath223 ( see ( * ? ? ?
the vertical and horizontal lines indicate the indexes at which the single - particle energies @xmath214 and @xmath215 change sign , and the signs shown in the four quadrants are those of the product @xmath224 . for the two panels we used @xmath157 and the same quenches used in fig .
[ fig : rho - gge - d ] and fig .
[ fig : sigmae - gge - d].,title="fig:",scaledwidth=85.0% ] + panel ( b ) + finally , let us comment on one aspect of the distributions shown in fig .
[ fig : rho - gge - d ] which can be easily understood from the single - particle occupations shown in fig .
[ fig : occandmatrices ] .
we see that , when the after - quench hamiltonian is the anderson model , @xmath225 has both mode ( i.e. , maximum value ) and average very close to the ground state energy : the quench excites mostly the low - energy part of the many - body spectrum .
on the contrary , for both the quenches towards @xmath109 , mode and average are almost in the middle of the many - body spectrum ; there , indeed , the quench is more dramatic : we are going from the ground state of a chain with nearest - neighbor hopping to a disordered chain with long - range hopping .
this is evident by looking at the occupations @xmath226 as a function of the single - particle energy @xmath119 , shown in fig .
[ fig : occandmatrices ] , panel ( a ) . by definition ,
only the eigenstates of @xmath153 with @xmath227 are occupied in @xmath228 .
the quench to @xmath108 only slightly modifies the initial occupations : @xmath229 , apart for fluctuations due to disorder , goes smoothly from @xmath103 , in the lower part of the single - particle spectrum , to @xmath183 , in the highest part of the spectrum . on the contrary , for the quenches towards @xmath109 , the single - particle spectrum is entirely excited , both the positive and the negative energy part .
this explains why , for these quenches , the after - quench energy @xmath230 is near the center of the many - body spectrum .
let us now consider the local density @xmath231 , perhaps the simplest one - body observable . for definiteness , we concentrate on @xmath232 , the center of the chain .
it is important to stress that we are going to consider the fluctuations of @xmath233 _ before _ any possible average over the sites @xmath84 : averaging over the sites @xmath84 an intensive local operator would effectively send to zero the fluctuations in the thermodynamic limit @xcite , while we will show that , for a fixed @xmath84 , finite fluctuations survive in the thermodynamic limit when the eigenstates are localized , due to disorder .
the diagonal and gge distributions @xmath234 and @xmath235 are now constructed using the matrix elements @xmath236 , where @xmath237 are , as before , the single - particle occupations of the eigenstate @xmath12 . in fig . [ fig : rho - n - gge - d ] we plot @xmath238 $ ] and @xmath239 $ ] , computed for the three quenches discussed before .
the case of a quench to @xmath109 with @xmath240 ( localized eigenstates ) is quite peculiar .
the values that @xmath241 can assume is actually split in two separated domains , one just above @xmath242 and one just below @xmath243 , and the mean value is exactly in the middle , where no values of @xmath244 happen to fall .
this is due to the strong spatial localization of the eigenstates . as we show in fig .
[ fig : wl - local - occ ] , at fixed @xmath84 , the value of @xmath245 is strongly localized in a single eigenstate @xmath246 . this implies that the value @xmath247 has a strong jump when we move from a state @xmath12 in which @xmath248 , to the state @xmath12 in which @xmath249 . for the quench to @xmath108 , with @xmath112 ,
the localization is not strong enough to produce such a gap : we however expect this to happen for larger values of the disorder amplitude @xmath250 . at the center of the chain , @xmath232 , for the diagonal ensemble and the gge , and for @xmath157 ( black curves ) or @xmath165 ( gray curves ) . in panel
( a ) , we plot @xmath238/l$ ] and @xmath239/l$ ] , while in panels ( b ) and ( c ) @xmath238 $ ] and @xmath239 $ ] .
the vertical lines are the diagonal and gge average of @xmath251 , which coincide for the local density .
the three panels are obtained using the same quenches of fig .
[ fig : rho - gge - d].,scaledwidth=85.0% ] as a function of the eigenstates index @xmath128 , at fixed site @xmath232 .
we have taken @xmath157 and the three panels are obtained using the same quenches of fig .
[ fig : rho - gge - d].,scaledwidth=85.0% ] since @xmath233 is a one - body operator , the diagonal and gge averages coincide @xcite , and therefore , the mean value of the two distributions is the same : @xmath252 we also note that , for this observable , @xmath253 for any positive integer @xmath254 , and therefore @xmath255 .
however , this does not allow us to conclude that the two distributions @xmath234 and @xmath235 coincide , since , unlike the case of the total energy , we have that , for instance : @xmath256 the variance of the two distributions can be computed by exploiting again wick s theorem .
we find that : @xmath257 in fig .
[ fig : sigmalocaldensity - gge - d - new ] we plot @xmath258 and @xmath259 as a function of size .
we see that , in both ensembles , the variances vanish as @xmath200 when quenching to @xmath109 with @xmath193 ( extended eigenstates ) while they are _ finite _ when quenching to @xmath108 and to @xmath109 with @xmath195 , i.e. , when the final hamiltonian has localized eigenstates .
these results agree with the findings of ref .
@xcite , who show that , for large @xmath116 , the variance of few - body intensive ( but not site - averaged ) observables remains finite both in the microcanonical ensemble and in the diagonal ensemble for the aubry - andr model . from the equation for @xmath258 , we see that it is related to an inverse participation ratio ( ipr ) : the sum is over the eigenstates @xmath128 , each @xmath128 weighted with the corresponding occupation factor @xmath260 depending on the initial state .
it is therefore easy to realize that : @xmath261 where the last equality defines the ipr at fixed site @xmath84 .
this shows that , whenever the ipr goes to zero , i.e. , when the final hamiltonian has delocalized eigenstates , @xmath258 goes to zero as well . for a final hamiltonian with localized eigenstates
we have instead the opposite : there is at least one eigenstate @xmath246 localized around @xmath84 , and therefore there is a single - particle wavefunction @xmath262 which does not vanish in the thermodynamic limit ; if the initial occupation @xmath263 of this eigenstate is such that @xmath264 , then @xmath258 remain finite in the thermodynamic limit . concerning @xmath259 , eq .
can be rewritten as : @xmath265 where @xmath266 denotes the mean squared time - fluctuations of the single - particle green s function @xmath267 @xcite : @xmath268 @xmath269 being the time fluctuation with respect to the long - time average @xmath270 .
physically , @xmath271 is the averaged long - time fluctuation of the local density @xmath272 . in refs .
@xcite we have shown that if the final hamiltonian has extended eigenstates , then @xmath273 for large sizes , while @xmath266 remains finite when the final hamiltonian has localized eigenstates .
this explains all the features shown in fig .
[ fig : sigmalocaldensity - gge - d - new ] , in particular the clear difference between @xmath259 and @xmath258 in all cases .
( circles ) and @xmath258 ( triangles ) as a function of size .
the data are obtained using the same set of quenches used in fig .
[ fig : sigmae - gge - d ] and the values are computed using eq . .
error bars are calculated by averaging over 20 different realizations of the disorder .
the dashed lines are power - law fits @xmath274 , where @xmath191 in both cases.,scaledwidth=85.0% ]
in this paper we have introduced a monte carlo method obtained by a rather natural extension of the wang - landau algorithm @xcite which allows to compute quite general weighted distribution functions of the form relevant to quantum quenches , see eq . .
we have used this approach to analyze quantum quenches for free - fermion hamiltonians in presence of disorder . for these systems , thanks to wick s theorem , after - quench expectation values and time averages require a modest computational effort , proportional to a power - law of the size @xmath116 @xcite
. however , the calculation of full probability distributions like the diagonal ensemble distribution @xmath275 , eq . , or the gge one @xmath276 , eq .
would still require a sum over an exponential number of terms , hence unfeasible beyond very small sizes . although quadratic , hence with an extensive number of conserved quantities , these free - fermion problems are not described by the gge ensemble whenever the disorder is such that the after - quench eigenstates are localized .
more precisely , while the gge ensemble is known to correctly capture the long - time average of any one - body operator , almost `` by construction '' @xcite , it does not capture correlations induced by the spatial localization of the eigenstates .
our study further explored this issue by explicitly calculating and comparing the full probability distributions of both the energy and the local density in the two relevant ensembles . concerning the energy ,
we have explicitly verified that the form of the two distributions for the diagonal and gge ensembles differs considerably , most notably at the extremes of the spectrum , and for the anderson model case .
more in detail , we have verified that , regardless of the final hamiltonian , the averaged fluctuations of the energy - per - site , @xmath277_{\mathrm{av}}$ ] and @xmath278_{\mathrm{av}}$ ] , go to zero in the thermodynamic limit , see fig .
[ fig : sigmae - gge - d ] , in agreement with the general analysis of refs .
nevertheless , we find that there is a clearly detectable difference in the two variances when the final hamiltonian has localized eigenstates .
in addition to the energy , we studied the local density distributions . for this
observable , it was already known that , even in presence of disorder and localization , the gge expectation value coincides with the diagonal average @xcite , a property true , more generally , for any one - body operator @xcite .
our numerical results confirm that even if the averages of @xmath279 and @xmath280 coincide , the two distributions are different when localization is present , with clearly detectable differences already at the level of the variance , see fig . [
fig : sigmalocaldensity - gge - d - new ] : @xmath258 and @xmath259 differ by a quantity which represents the averaged long - time fluctuations of the local density @xcite , which remain finite whenever the final hamiltonian has localized eigenstates . other many - body operators , like density - density correlations , might be analyzed in a similar way . here ,
even the average values are not in general well described by the gge distribution whenever localization is at play @xcite : we expect , once again , clearly visible discrepancies between the diagonal and gge distributions in such cases . in conclusion ,
as explained above , the weighted - wla we have presented circumvents the difficulty associated to the exponentially large hilbert space to be visited , even when the relevant ingredients entering the distribution matrix elements and overlap between states can be calculated quite effectively . in principle
, the applicability of the method is not limited to `` quadratic fermion problems '' of the type we have considered in the paper : if , by bethe ansatz , or any other exact technique or even by a suitable quantum monte carlo approach , one would be able to calculate matrix elements and overlaps , the method we have illustrated would provide an effective monte carlo sampling of the relevant distribution functions .
we acknowledge discussions with a. laio , a. russomanno and a. silva .
research was supported by miur , through prin-2010llkjbx-001 , by snsf , through sinergia project crsii2 136287 1 , by the eu - japan project lemsuper , and by the eu fp7 under grant agreement n. 280555 .
10 marcos rigol , vanja dunjko , vladimir yurovsky , and maxim olshanii . relaxation in a completely integrable many - body quantum system : an _ ab initio _ study of the dynamics of the highly excited states of 1d lattice hard - core bosons . , 98:050405 , 2007 .
pedro ojeda , martin e. garcia , aurora londoo , and n. y. chen .
monte carlo simulations of proteins in cages : influence of confinement on the stability of intermediate states . , 96(3):1076 1082 , 2009 .
evelina b. kim , roland faller , qiliang yan , nicholas l. abbott , and juan j. de pablo .
potential of mean force between a spherical particle suspended in a nematic liquid crystal and a substrate .
, 117(16):77817787 , 2002 .
m. mller and j.j .
de pablo .
simulation techniques for calculating free energies . in _ computer simulations in condensed matter systems : from materials to chemical biology volume 1 _ , volume 703 of _ lecture notes in physics _ , pages 67126 .
springer berlin heidelberg , 2006 .
alexander d. mirlin , yan v. fyodorov , frank - michael dittes , javier quezada , and thomas h. seligman . transition from localized to extended eigenstates in the ensemble of power - law random banded matrices .
, 54:32213230 , oct 1996 . | we present here an extension of the wang - landau monte carlo method which allows us to get very accurate estimates of the full probability distributions of several observables after a quantum quench for large systems , whenever the relevant matrix elements are calculable , but the full exponential complexity of the hilbert space would make an exhaustive enumeration impossible beyond very limited sizes . we apply this method to quenches of free - fermion models with disorder , further corroborating the fact that a generalized gibbs ensemble fails to capture the long - time average of many - body operators when disorder is present . |
SECTION 1. SHORT TITLE.
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under part Q, not less than $600,000,000 shall be used
for grants for the purposes specified in section
1701(b), not more than $200,000,000 shall be used for
grants under section 1701(d), and not more than
$350,000,000 shall be used for grants under section
1701(e).''.
(i) Purposes.--Section 10002 of the Public Safety Partnership and
Community Policing Act of 1994 (42 U.S.C. 3796dd note) is amended--
(1) in paragraph (4), by striking ``development'' and
inserting ``use''; and
(2) in the matter following paragraph (4), by striking
``for a period of 6 years''.
(j) COPS Program Improvements.--
(1) In general.--Section 109(b) of the Omnibus Crime
Control and Safe Streets Act of 1968 (42 U.S.C. 3712h(b)) is
amended--
(A) by striking paragraph (1);
(B) by redesignating paragraphs (2) and (3) as
paragraphs (1) and (2), respectively; and
(C) in paragraph (2), as so redesignated, by
inserting ``, except for the program under part Q of
this title'' before the period.
(2) Law enforcement computer systems.--Section 107 of the
Omnibus Crime Control and Safe Streets Act of 1968 (42 U.S.C.
3712f) is amended by adding at the end the following:
``(c) Exception.--This section shall not apply to any grant made
under part Q of this title.''.
SEC. 3. REPORT BY INSPECTOR GENERAL REQUIRED.
(a) Report.--Not later than 180 days after the date of the
enactment of this Act, the Inspector General of the Department of
Justice shall submit to Congress a report on the Public Safety and
Community Policing (``COPS ON THE BEAT'') grant program authorized by
part Q of title I of the Omnibus Crime Control and Safe Streets Act of
1968 (42 U.S.C. 3796dd et seq.), including the elements described in
subsection (b).
(b) Elements of Report.--The report submitted under subsection (a)
shall include information on the following, with respect to the grant
program described in such subsection:
(1) The effect of the program on the rate of violent crime,
drug offenses, and other crimes.
(2) The degree to which State and local governments awarded
a grant under the program contribute State and local funds,
respectively, for law enforcement programs and activities.
(3) Any waste, fraud, or abuse within the program.
(c) Random Sampling Required.--For purposes of subsection (a), the
Inspector General of the Department of Justice shall audit and review a
random sampling of State and local law enforcement agencies. Such
sampling shall include--
(1) law enforcement agencies of various sizes;
(2) law enforcement agencies that serve various
populations; and
(3) law enforcement agencies that serve areas of various
crime rates.
Passed the House of Representatives May 15, 2007.
Attest:
LORRAINE C. MILLER,
Clerk. | COPS Improvements Act of 2007 - (Sec. 2) Amends the Omnibus Crime Control and Safe Streets Act of 1968 to expand the authority of the Attorney General to make grants for public safety and community policing programs (COPS ON THE BEAT or COPS program). Revises grant purposes to provide for: (1) the hiring or training of law enforcement officers for intelligence, anti-terror, and homeland security duties; (2) the hiring of school resource officers; (3) school-based partnerships between local law enforcement agencies and schools to combat crime, gangs, drug activities, and other problems facing elementary and secondary schools; (4) innovative programs to reduce and prevent illegal drug (including methamphetamine) manufacturing, distribution, and use; (5) criminal gang enforcement task forces; and (6) enhanced community policing and crime prevention grants that meet emerging law enforcement needs.
Allows COPS program grants to be used to hire former members of the Armed Forces to serve as career law enforcement officers for community-oriented policing, particularly in communities adversely affected by a recent military base closing.
Authorizes the Attorney General to make grants to: (1) assign community prosecutors to handle cases from specific geographic areas and address counterterrorism problems, specific violent crime problems, and localized violent and other crime problems; and (2) develop new technologies to assist state and local law enforcement agencies in crime prevention.
Grants the Office of Community Oriented Policing Services exclusive authority to perform functions and activities under the COPS grant program.
Authorizes the Attorney General to renew COP program grants if grant recipients can demonstrate significant progress in achieving the objectives of the initial grant application.
Requires the Attorney General to select one or more institutions of higher education, including historically Black colleges and universities, to conduct a scientific study of the effectiveness of the programs, projects, and activities funded by the COPS program. Requires such institutions to report on on their studies to the Attorney General not later than four years after the enactment of this Act. Requires the Attorney General to report to Congress on such studies.
Increases and extends through FY2013 the authorization of appropriations for the COPS program. Increases from 3 to 5% the amount of funds available for technical assistance. Specifies amounts to be made available for hiring officers and prosecutors, and for technology grants.
(Sec. 3) Requires the Inspector General of the Department of Justice to report to Congress on the COPS program, including information on: (1) the effect of the program on the rate of violent crime, drug offenses, and other crimes; (2) the degree to which state and local governments awarded a COPS grant contribute funds for law enforcement programs and activities; and (3) any waste, fraud, or abuse in the program. Requires the Inspector General to audit and review a random sampling of state and local law enforcement agencies in preparing such report. |
the microscopic gist of the macroscopic second law is often pictured as a system s seeking out _ more _ phase - space states .
so it seems a bit odd that the idealized nonequilibrium steady states generated by molecular dynamics behave in the opposite way@xcite .
the @xmath2 states from such atomistic simulations soon become constrained to an ever - shrinking strange attractor .
the compensating additional heat - reservoir states are never seen explicitly .
instead they are _ modelled _ by time - reversible friction coefficients .
these coefficients control temperature or energy and induce steady - state behavior in the system under study . unlike _ real life _ , the underlying laws of physics are mostly time - reversible , which means it is puzzling that physics gives a good accounting of real - world observations .
time - reversible mechanical models ( molecular dynamics ) provide clear examples of this conundrum . to illustrate the irreversible behavior of such time - reversible models let us consider the simplest case , a one - dimensional harmonic oscillator ( with unit mass and force constant ) exposed to a temperature gradient@xcite , @xmath3 .
the oscillator s motion is subject to a time - dependent friction coefficient @xmath4 imposing weak control over the oscillator s kinetic energy @xmath5 and its fluctuation , @xmath6 .
this oscillator model@xcite generates a three - dimensional `` flow '' satisfying the three ordinary differential equations of motion : @xmath7 \ ; \
\dot \zeta = a [ \ ( p^2/t ) - 1 \ ] + b [ \ ( p^4/t^2 ) - 3(p^2/t ) \ ] \ .\ ] ] the superior dots in the motion equations indicate comoving time derivatives . _ at thermal equilibrium _ where @xmath8 is constant
the parameters @xmath9 are chosen to promote the control of the second and fourth velocity moments@xcite : @xmath10 from the visual standpoint this parameter choice appears to provide an ergodic coverage of the oscillator phase space .
liouville s continuity equation in phase space can be used to show that these motion equations are consistent with gibbs canonical distribution ; @xmath11 _ away from equilibrium _ the heat - reservoir temperature field @xmath12 is an explicit function of the oscillator coordinate @xmath13 and @xmath14 is the maximum value of the temperature gradient .
plane to the next .
these @xmath2 phase - space cross sections for the conducting oscillator correspond to four values of the maximum temperature gradient : @xmath15 . both @xmath13 and @xmath16
range from @xmath17 to @xmath18 in all the cross sections .
, width=528 ] see * figure 1 * for sample numerical @xmath2 cross sections of the three - dimensional flow in @xmath19 space .
the @xmath2 points are plotted whenever @xmath20 changes sign .
notice that the equations of motion for this heat - conduction model are _ time - reversible_. to see this start out with a solution of the equations forward in time , @xmath21 .
then change the signs of the momentum @xmath16 , @xmath20 , as well as the direction of time , @xmath22 .
these steps provide a new `` reversed '' solution of exactly the same motion equations .
the nonequilibrium @xmath2 cross - sections with @xmath23 shown in * figure 1 * look like inhomogenous ( or `` multifractal '' ) strange attractors . and they are . in these flows , as in a wide variety of time - reversible nonequilibrium steady states , the fractal strange attractors satisfy the second law of thermodynamics , with an overall hot - to - cold heat current .
the reversed flows , topologically similar fractals , are mechanically unstable , with exponentially growing phase volume , and with a heat - flow direction violating the second law .
these repellor states are unobservable numerically due to this ( lyapunov ) instability , and can only be collected by storing , and then reversing , a time series of attractor states@xcite .
the construction of the flow cross - sections is equivalent to applying a time - reversible `` map '' @xmath24 from one penetration of the zero @xmath20 plane to the next , @xmath25 .
such two - dimensional maps provide relatively simple ( two - dimensional rather than three ) pictures of the chaos generated by the conducting oscillator . because the penetrations of the differential equations are proportional to the `` flux '' through the sampling plane @xmath26 at @xmath27 , rather than just the `` density '' , there are unoccupied white `` nullclines '' in the cross sections wherever the flux @xmath28 vanishes .
`` maps '' have long been used in dynamical systems theory to illustrate and explain ergodicity ( closely approaching all of a system s states ) and lyapunov instability ( the exponentially - fast growth of small perturbations ) .
arnold s cat map@xcite and the baker map are the best - known examples . for clarity
let us recall the action of the baker map .
the square shown at the left is first squeezed twofold in the @xmath29 direction and stretched twofold in the perpendicular direction .
after a cut along the @xmath29 line the two halves are joined together in the new arrangement shown at the right .
the changed spacings of the points reflect the squeezing and stretching induced by the map .
, width=480 ]
in the dynamical systems literature the discontinuous `` baker map '' , composed of area - preserving cutting and kneading operations , provides a simple illustration of `` chaos '' , the exponentially diverging growth induced by the mapping of small perturbations .
the familiar `` cat map '' is another well - known discontinuous mapping of the unit square into itself .
both these map types illustrate lyapunov instability , @xmath30 , where the proportionality constant exceeds unity , leading to divergence .
many - to - one mappings , such as @xmath31 , in the presence of chaos are enough to produce the strange attractors associated with nonequilibrium steady states .
even one - to - one volume - preserving mappings , as in the simplest baker map above , are enough to generate lyapunov unstable chaos . in the equilibrium baker map each half of a @xmath32 square
is mapped from a @xmath33 rectangle to two @xmath34 disjoint rectangles . in order to follow our criterion for time reversibility detailed in the next section
we use a _ rotated _ version of the baker map , illustrated in * figure 2*. the mapping is as follows : + if(q.lt.p ) then + qnew = + 1.25d00*q - 0.75d00*p +
dsqrt(1.125d00 ) + pnew = -0.75d00*q + 1.25d00*p - dsqrt(0.125d00 ) + endif + if(q.gt.p ) then + qnew = + 1.25d00*q - 0.75d00*p - dsqrt(1.125d00 ) + pnew = -0.75d00*q + 1.25d00*p + dsqrt(0.125d00 ) + endif + the result of 100,000 iterations of this map is a near uniform covering of the @xmath35 square , as is shown in * figure 3*. are plotted here .
the uniform area conservation of the map is analogous to the equilibrium phase - volume conservation described by liouville s theorem .
, width=480 ] the _ dissipative _ baker map@xcite , with changes in _ area _ as well as shape , is a better model for _ nonequilibrium _ molecular dynamics and statistical mechanics . in those disciplines the phase - space density responds to heat transfer . in the oscillator example above the action of a heat reservoir with temperature @xmath36
is represented by the time - reversible frictional force , @xmath37 $ ] .
the resulting change in comoving phase volume @xmath38 follows from the continuity equation : @xmath39 \ .\ ] ]
the dissipative baker map is deterministic , time - reversible , and likewise produces mirror - image attractor - repellor multifractal pairs .
these are the same qualities associated with nonequilibrium molecular dynamics algorithms ever since the early 1970s , though they passed unrecognized until the 1980s.@xcite
the conducting oscillator is just one example of the deterministic , time - reversible flows that represent a nonequilibrium steady state with a chaotic multifractal attractor .
the time - reversed state , with the momentum , friction coefficient , and the time all changed in sign , is an exactly similar mirror - image multifractal structure , an unstable zero - measure repellor .
more complicated maps with these same properties can be constructed by concatenating time - symmetric combinations of reversible mappings @xmath40 like @xmath41 where each of the mappings satisfies the time - reversibility criterion : @xmath42 with the four operations performed from right to left . here
@xmath43 indicates the time - reversal operation @xmath44 .
this reversibility criterion states that the sequence of four steps [ 1 ] iterate forward ; [ 2 ] reverse velocities ; [ 3 ] iterate backward ; [ 4 ] reverse velocities
returns to the original @xmath2 state .
the simplest time - symmetric mappings satisfying this criterion are shears and reflections.@xcite it is interesting to note that _ numerical _ implementations almost never return _ exactly _ to their initial state after the four - step sequence above .
in fact the _ lack _ of an exact return is a ( somewhat misleading ) @xcite measure of algorithmic accuracy@xcite .
the similarities between small - system dynamics and macroscopic dissipative behavior motivate the study of relatively simple flows and maps capable of generating the complexity associated with irreversible strange attractors . at the same time this complexity often exhibits a compelling beauty .
the prototypical cat and baker maps are relatively simple , but their discontinuities are not at all representative of the attractor types shown in * figure 1 * .
the time is ripe for a fresh look at such problems .
the snook prize problem for 2015 is to formulate and analyze an interesting time - reversible ergodic map relevant to statistical mechanics , in two or three dimensions .
it is desirable that the map generates a multifractal .
entries can be submitted to the authors , to the los alamos ar@xmath45iv , or to computational methods in science and technology .
the author(s ) of the most interesting entry received prior to 1 january 2016 will receive the prize s cash award of $ 500 us .
the publisher of computational methods in science and technology ( cmst.eu ) has generously offered an additional prize award of $ 555.5@xmath46 us subject to the terms and conditions published in cmst .
w. g. hoover and c. g. hoover , _ simulation and control of chaotic nonequilibrium systems _
( world scientific publishers , singapore , 2015 ) .
h. a. posch and wm .
g. hoover , `` time - reversible dissipative attractors in three and four phase - space dimensions '' , physical review e * 55 * , 6803 - 6810 ( 1997 ) .
w. g. hoover , j. c. sprott , and c. g. hoover , `` nonequilibrium molecular dynamics and dynamical systems theory for small systems with time - reversible motion equations '' , molecular simulations ( in preparation , 2015 ) .
w. g. hoover , o. kum , and h. a. posch , `` time - reversible dissipative ergodic maps '' , physical review e * 53 * , 2123 - 2129 ( 1996 ) .
j. kumick , irreversibility in a simple reversible model
, physical review e * 71 * , 016115 ( 2005 ) = ar@xmath45iv nlin/0510016 . l. ermann and d. l. shepelyansky , `` arnold cat map , ulam method , and time reversal '' , physica d * 241 * , 514 - 518 ( 2012 ) = ar@xmath45iv 1107.0437 . w. g. hoover and c. g. hoover , `` comparison of very smooth cell - model trajectories using five symplectic and two runge - kutta integrators '' , computational methods in science and technology * 21*(to appear , 2015 ) = ar@xmath45iv 1504.00620 .
d. faranda , m. f. mestre , and g. turchetti , `` analysis of roundoff errors with reversibility test as a dynamical indicator '' , international journal of bifurcation and chaos * 22 * , 1250215 ( 2012 ) = ar@xmath45iv 1205.3060 . | the _ time reversibility _ characteristic of hamiltonian mechanics has long been extended to nonhamiltonian dynamical systems modeling nonequilibrium steady states with feedback - based thermostats and ergostats .
typical solutions are multifractal attractor - repellor phase - space pairs with reversed momenta and unchanged coordinates , @xmath0 .
weak control of the temperature , @xmath1 and its fluctuation , resulting in ergodicity , has recently been achieved in a three - dimensional time - reversible model of a heat - conducting harmonic oscillator .
two - dimensional cross sections of such nonequilibrium flows can be generated with time - reversible dissipative maps yielding sthetically interesting attractor - repellor pairs .
we challenge the reader to find and explore such time - reversible dissipative maps .
this challenge is the 2015 snook - prize problem . |
A nurse working in a northeastern Italian hospital has been arrested as part of an investigation into the deaths of 38 patients who, cops said, she may have injected with potassium chloride because they or their family members were "annoying,"
Coworkers suspected Daniela Poggiali, 42, because patients would suddenly worsen and die during her shift. They described her as a "cold, polished" person who sometimes sedated patients who bothered her during her shift. They also suspected she gave patients laxatives to embarrass the colleagues who worked after her.
"We wondered whether these deaths could be so frequent without anyone doing anything," a coworker told Corriere della Sera.
The investigation and arrest resulted from the death of a 78-year-old patient who was found to have died from a potassium chloride injection, the New York Post reported. But homicide may be more difficult to prove in the case of the earlier victims.
Prosecutors told Corriere that potassium leaves no trace after a few days, making it challenging to investigate.
Police searched Poggiali's phone and found a photo of the nurse giving a thumbs up next to the body of a patient moments after that patient's death, Corriere reported.
[H/T NY Post, Photo: Twitter] ||||| These crawls are part of an effort to archive pages as they are created and archive the pages that they refer to. That way, as the pages that are referenced are changed or taken from the web, a link to the version that was live when the page was written will be preserved.Then the Internet Archive hopes that references to these archived pages will be put in place of a link that would be otherwise be broken, or a companion link to allow people to see what was originally intended by a page's authors.The goal is to fix all broken links on the web . Crawls of supported "No More 404" sites. | – Italian police have arrested a nurse who possibly killed up to 38 patients because they or their families "annoyed" her, officials say. Daniela Poggiali, 42, was arrested Friday in connection with 11 patient deaths and had already been under suspicion of killing another in April, the New York Post and ANSA report. Police then found a selfie on her phone of Poggiali giving a thumbs-up beside a dead patient in northeast Italy. "I can assure you in that all my professional years of seeing shocking photos, there were few such as these," says a prosecutor. Poggiali was originally suspected of killing a 78-year-old woman who had entered the hospital with minor health issues and allegedly died from a potassium overdose—which can trigger cardiac arrest and be hard to trace because it leaves the body soon after death. Now police believe she may have killed up to 38 patients who "needed extra care or had pushy relatives," reports ANSA. Co-workers, who had already noticed patient deaths during Poggiali's shifts, describe her as "a cold, polished" person who worked hard, Gawker reports. They also say she had been accused of giving patients heavy laxatives to make life harder for the next nurse on duty. (Read about a hospital shooting that was really a botched mercy killing.) |
with the current trend toward esthetic dentistry , composites have added a whole new dimension .
resin based composites are widely used in restorative dentistry as both direct and indirect restorations in anterior and posterior teeth .
the clinical performance of composite materials has improved with the development of more wear - resistant formulations , the newer generation dentin bonding agents and improved light curing and surface - sealing systems . when existing composite resin restoration fails , due to caries , fracture , color change or inadequate contour , the treatment choice consists of either total replacement or repair of an existing restoration .
total replacement is often undesirable as it invariably increases the cavity size and traumatizes the pulp . hence , repair is more practical than replacing the restoration as it reduces pulpal trauma and is cost - effective .
repair of composite restorations is often accomplished by placing new composite over the old composite .
this repair is often challenging as there are few , if any , reactive double bonds in the old composite for bonding to the new composite.1 although the importance of a good bond between the old and new resin material has been accepted , repair bond strengths have been variable and unpredictable , as stated in many studies.2 - 4 a variety of chemical , mechanical surface treatments and bonding agents have been evaluated to improve the repair strength of composites .
most studies have indicated that the surface roughness of composite has a great influence on repair strength than using a bonding agent.5 - 7 surface treatment by diamond bur or sandblasting achieved the highest bond strength.8 sandblasting7 and application of multistep adhesive primers9 greatly improved the bonding . until date , there is no consensus exist in the most appropriate way to prepare the surface to obtain maximum bond strength .
hence , the present study has compared the effects of different surface treatments and bonding agents on shear bond strength ( sbs ) of composite repair , and also evaluated the mode of failure of repaired composites : cohesive or adhesive or both .
in this study , two repair adhesive systems namely all - bond 2 adhesive system ( bisco ) and clearfil repair adhesive system ( kurarey ) were used to repair the substrate of aged composite with fresh composite after various surface treatments either with diamond bur or with air abrasion unit .
clearfil ap - x microhybrid composite resin was used as to prepare test composite specimens .
the substrates for sixty test specimens were fabricated by placing uncured microhybrid composite into the retentive cavity of the acrylic resin surrounded by stainless steel cylinder .
the substrate was cured for 40 s with light intensity of 450 mw / cm2 .
specimens were first stored in 37c water for 48 h then boiled in water for 8 h and again stored in 37c water for 3 weeks to again the material .
the aged specimens were divided into three groups of 20 each and surface treated as follows .
group i : no surface treatment , group ii : abraded with a coarse , tapered , rounded end diamond bur and group iii : air - abraded with 50 aluminum oxide at 80 psi for 3 s using extra - oral sandblaster unit ( apm - sterengold , usa ) .
the specimens were then subdivided into two sub groups of 10 each and each sub group is subjected to either clearfil repair ( sub group a ) or all - bond 2 adhesive systems ( sub group b ) according to manufacturer s recommendations . a hollow translucent polyethylene tube of 6 mm internal diameter was centered on pre - treated surface of each specimen , and the fresh microhybrid composite was then applied in 2 mm increments and light cured for 40 s. the repaired specimens were stored in distilled water at 37c for 24 h and then additionally thermocycled for 300 cycles between 5c and 55c with a dwell time of 30 s and transfer time of 5 s. after 24 h specimens were subjected to shear bond test using hounsfield universal testing machine ( instron , usa ) at a cross head speed of 1 mm / min .
fractured surfaces of the specimens were examined under stereomicroscope at 10 magnification to evaluate the mode of failure : cohesive ( figure 1 ) or adhesive ( figure 2 ) .
the results were analyzed statistically using one - way analysis of variance and for pairwise comparison using scheffes multiple comparison tests .
the mean sbs ( mpa ) values with a standard deviation of all the main groups were depicted and compared in the graph 1 .
group iii ( air - abrasion ) has showed the highest sbs values than other groups .
the mean sbs values of all sub groups were depicted and compared in the graph 2 and table 1 .
group iiia ( air - abrasion followed by clearfil repair ) has showed the highest sbs of all groups and in all the main groups , sub groups a ( clearfil repair ) showed better results than sub groups b ( all - bond 2 ) .
the mode of failure of fractured specimens was adhesive for group i and cohesive in group ii and iii specimens ( table 2 ) .
comparison of three groups ( i , ii , iii ) with respect to shear bond strength . comparison of sub group a and sub group b in each main group .
when repairing the old restorations , a frequently asked question is whether the repair material bonds adequately to the existing restorations .
composite repair often presents a different challenge ; while there is no oxygen - inhibited layer , if any , few unreacted double bonds remain in the old composites for bonding to the new composite .
thus , the potential for chemical bonding between old and fresh composite layers decreases over time.1 improving the bond strength between new and old composite usually , requires increased surface roughness to promote mechanical interlocking and coating with repair adhesives to advance surface wetting and chemical bonding .
mechanical and/or chemical treatments to roughen the surface include roughening with diamond bur,7,10,11 carbide bur,12 silicon carbide paper,9,11 green carborundum stone,8 air abrasion with 50 aluminum oxide particles,5,10,13 etching with 37% phosphoric acid gel,12,13 hydrofluoric acid8 and 1.23% acidulated phosphate fluoride gel.5 diamond bur is preferred by most clinicians for preparing enamel and composite surface prior to acid etching.11,12 air - abrasion or sandblasting is an old technology that is finding a new place in modern science based dentistry . at present , the newer air abrasion unit available is microetcher ii intraoral sandblaster ( danville engineering , california ) .
it uses 50 aluminum oxide particles at 80 psi pressure and was found effective to improve the repair bond strength.5,14,15 hence in the present study diamond bur and extra - oral sandblaster using same particle and pressure were used for mechanical surface roughening .
the use of bonding agents has improved the repair bond strength16 and most clinicians tend to use the adhesive system that they have already in their practice rather than acquiring a special bonding system for composite repair procedures .
hence , in the present study two different adhesives namely all - bond 2 system ( bisco ) and clearfil repair ( kuraray ) were tested .
all - bond 2 system is a universal bonding system used to bond composite to enamel , dentin , metal alloy , amalgam , porcelain and composite .
it is a fourth generation adhesive system.17 clearfil repair is a unique adhesive used for intraoral repairs of fractured porcelain or composite restorations .
it is a fifth generation adhesive system consisting of self - etch primer , adhesive and porcelain bond activator with silane coupling agent.9 to simulate aging of the composite in the oral cavity , short term water storage followed by boiling , then 3 weeks water storage was used in the present study.9 the shear bond test is considered as an appropriate method for quantifying the adhesion and bonding of repair materials because of its simplicity18 and hence used in the present study .
the results of the present study showed the least mean sbs value of 16.7 2.5 mpa in group i when there is no mechanical roughening of substrate subsurface .
this bond strength is not clinically acceptable and should be above 18 mpa.4,19 this is due to decreased surface area for bonding and reduced penetration of new composite to interlock mechanically to the surface of old composite.7,12,13,20 this was further confirmed with mode of failure being adhesive ( figure 2 ) .
when different mechanical surface treatments were compared , air abrasion has improved the repair bond strength resulting in cohesive mode of failure ( figure 1 ) .
this could be due to increased surface roughness with large micro - retentive areas which enhances the wettability for adhesive system.5,6,10,15,21 application of clearfil repair adhesive system after any mechanical surface treatment has improved the bond strength values significantly than all - bond 2 , especially when applied after air - abrasion .
this could be due to deeper penetration of adhesive , in the presence of silane coupling agent , into micro - retentive areas created by air abrasion.8,15,22 a silane that is used with clearfil se primer is 3-methoacryloxy propyl trimethoxy silane .
when silane is applied to the exposed filler particles following surface roughening of composite resin , it gets deposited on the filler . in the presence of water ,
methoxy groups of silane are hydrolyzed to silinol ( -si - oh ) groups that can bond to other silinols by the formation of a siloxane bond ( -si - o - si ) .
then the methacrylate group of silane form covalent bonds with repair resin when it is polymerized , thereby completing the coupling process.23 silane also enhances the wetting ability of the adhesive over the irregularities created by surface roughening.15,24 in group i , application of all - bond 2 adhesive system without any prior mechanical roughening resulted in clinically accepted repair as this system involve the use of 32% phosphoric acid which created interstices resulting in improved mechanical attachment.12 with clearfil repair system , its se primer lacks etching ability when compared to phosphoric acid .
overall air - abrasion of aged composite substrate followed by application of clearfil repair adhesive system yielded the highest repair bond strength than the any other combinations tested in the present study .
within the limitation of the study , the following conclusions were drawn :
mechanical surface treatment of the composite substrate significantly improves the repair bond strength especially with air - abrasionamong the repair adhesive systems tested , clearfil repair yielded a higher bond strength .
mechanical surface treatment of the composite substrate significantly improves the repair bond strength especially with air - abrasion among the repair adhesive systems tested , clearfil repair yielded a higher bond strength .
hence , surface treatment with air abrasion followed by bonding with clearfil repair adhesive system can be attempted clinically for the repair of composite restorations . | background : enhancement of bond strength between new and old composite usually requires increased surface roughness of old composite to promote mechanical interlocking and subsequent coating with bonding agents to improve surface wetting and chemical bonding .
so this study was carried out to evaluate and compare the effects of different surface treatments and repair materials on the shear bond strength ( sbs ) of composite repairs the mode of failure of repaired composites whether cohesive or adhesive was also evaluated.materials and methods : the substrates for 60 composite specimens were fabricated and aged with water treatment and subjected to various surface treatments .
the surface treatment regimens used in the study were : no surface treatment , abraded with diamond bur , air abraded ( sandblasted ) with 50 aluminum oxide particles .
specimens were then repaired with fresh composite using either clearfil repair or all - bond two adhesive systems .
specimens were water stored , thermocycled and tested for sbs using universal testing machine .
fractured specimens were then examined under stereomicroscope to determine the mode of failure.results:it was clearly showed that surface roughening of the aged composite substrate with air abrasion , followed by the application of clearfil repair adhesive system ( group iiia ) yielded the highest repair bond strength ( 32.3 2.2 mpa).conclusion : surface treatment with air abrasion followed by bonding with clearfil repair adhesive system can be attempted clinically for the repair of composite restorations . |
Funny or Die didn’t pull any punches with their take on the Duggar scandal. In a video titled "The Duggars Respond to Sexual Abuse Scandal," two comedians dressed as Jim Bob and Michelle Duggar sit down to explain their take on In Touch magazine "Scooby Doo-ing around and bringing up all this pickle again."
"With more kids than an NBA team, we were bound to have one troubled kid," says Greg David Jones, donning a polo shirt and side part to play Duggar patriarch Jim Bob.
UPDATED: Josh Duggar Molestation Allegations: A Timeline of Events
The sketch’s writer and director Erin Gibson fluffs up her "split bang" to play wife Michelle, the self-described "baby factory for the Duggar family."
"When Josh was a teenager, he made a mistake," Gibson claims. "He mistaked two girls on their 'tutus.'"
"That’s what we call breasts," Jones clarifies.
NEWS: Jessa Duggar's Father-In-Law Encourages Josh Duggar: 'Hang In There'
"Here’s the thing, some other girls did come forward, and some of them were our daughters. But honestly, if you asked me which one, I don’t know, the brunette with the curly hair?" Gibson fires, addressing the rumors that Josh’s younger sisters might be some of his minor victims. "We did the right thing and immediately waited three years before we called the authorities."
The two also mocked the family’s statements on the scandal.
"It has been terrible for us and Josh, but those are the only three people affected by these mistakes," Gibson concludes.
EXCLUSIVE: Mama June Shannon Reacts to TLC Pulling '19 Kids and Counting': 'I Feel Cheated Still!'
Fallout from the scandal continues to affect the family’s hit TLC show, as Hulu announced on Thursday that they had pulled the episodes from their streaming service and were redirecting fans to the network’s website. As of May 28, clips of 19 Kids and Counting are still available to stream on the TLC website.
Hulu CEO Mike Hopkins told CNNMoney that the service followed TLC's lead in taking the show offline "for the time being."
"We're partners. We license the show from them," Hopkins said. "And of course, as you know, they took it off of their platforms, so we did the same."
WATCH: Is TLC Planning a '19 Kids and Counting' Spinoff? ||||| CLOSE Skip in Skip x Embed x Share Reality TV stars from the Duggar family, Jim Bob and Michelle Duggar, appeared on television for the first time since the shocking revelations that their son confessed he groped five underage girls, including his own sisters. VPC
Megyn Kelly interviews Jim Bob Duggar and Michelle Duggar at their home in Tontitown, Ark. (Photo: Fox News/Getty Images)
Jim Bob and Michelle Duggar, the Christian conservative reality-TV stars reeling from a family molestation scandal, appeared on television Wednesday night for the first time since the shocking revelations that their son confessed he groped underage girls years ago, including his own little sisters.
In their first TV interview since the revelations two weeks ago, the Duggars talked about how son Josh Duggar, now 27, came to them at age 14 and tearfully told them that he had "improperly touched" some of their daughters.
"We were shocked, we were devastated," Michelle Duggar told Megyn Kelly on Fox News. "As parents we felt, we're failures. We tried to raise our kids to do what's right — to know what's right. And yet one of our children made really bad choices."
Still, they insisted their son is not and was not a pedophile, because he was too young at the time of his offenses. Josh was never charged with a crime.
For the first time, the couple acknowledged that four of the victims were their daughters, including younger sisters Jill and Jessa, who also spoke to Kelly. A fifth was a family friend.
The daughters are upset that Josh's secret came out, since it affected them as well. The Duggars insisted that Josh had sought and received forgiveness from all the victims, that all had moved on and put the episode behind them.
"Every victim should have the right to tell their own story, not by a tabloid," said Jim Bob Duggar.
Kelly said at the conclusion of the hour that the rest of the daughters' interview will air on another Duggar special on her show on Friday night.
Under Kelly's questioning, the Duggars defended their actions in delaying reporting Josh to the authorities, saying they were trying to protect their son and their daughters. They eventually took him to police because "we felt it was an important step for Josh to confess to police because he broke the law," Jim Bob said.
But the police didn't act at the time, and by the time Josh was reported to state child protection authorities, the statute of limitations for any possible criminal act had expired.
The Duggars said that in 2002 and 2003, when he was 14 and 15, Josh had groped the girls while they slept (the girls slept in the same room), and that he did this more than once even after his first confession to his parents.
They got him out of the house and sent him to a non-professional Christian-based counseling program in Little Rock, Ark. Jim Bob said it was "the best decision" they made, because Josh became "closer to God" as a result. "It was a turning point in his life," he said.
Josh asked for forgiveness from his victims, some of whom were too young to understand what was wrong or what had happened or why Josh had to leave, said Michelle Duggar.
Kelly pressed them about why they launched a reality show about their family in 2008 given this past.
"When we were asked to do the show, all of this had been taken care of five years before," Jim Bob said. "We had no fears because everything was resolved and ...it was a sealed juvenile record and this stuff under law can't be brought out."
The Duggars believe the bigger story is how those records were released (under a Freedom of Information Act), and they threatened to sue, to "protect juvenile records because mistakes juveniles make when they're young should be sealed," Jim Bob said.
"We trusted (the authorities) and our children poured out their hearts and then to have their trust betrayed and have everything turned over to a tabloid and twisted?" said Michelle.
Kelly also pressed them on the widespread criticism that they lectured others about sin while covering up their own sins.
"Everybody has things in their past in their families," Michelle said. "Our son violated God's principles, and it was terrible what Josh did, it was inexcusable but it was not unforgivable," added Jim Bob.
The Duggars believe they are the victims of a witch hunt because of their religion (they're Baptists) and their politics. "This is more about... there's an agenda and there's people that are twisting (the allegations) to hurt and slander," Michelle said.
Appearing on conservative-friendly news channel, the Duggars told Kelly on her show, The Kelly File, that they still believe they can save their top-rated series about their huge family, 19 Kids and Counting, from the cancellation ax.
But they're not too worried if it goes away, because they and their family will do just fine moving on with their lives, they said.
The TLC network has pulled the show's reruns from its schedule but has not decided whether to dump it outright, despite the damage caused by Josh's dark secret and his parents' role in hushing it up in Arkansas years ago.
The Duggars' interview with Kelly was their first public discussion of the scandal that has deeply damaged their show, their children, their pious image and their conservative GOP politics since InTouch magazine published a story May 21 based on police reports obtained under a Freedom of Information request to Arkansas authorities.
(Photo: Richard Drew/ AP)
Hours later, the Duggars and Josh, now 27, acknowledged the scandal on their Facebookpage without going into details, apologized and fervently reconfirmed their faith.
Josh Duggar also hurriedly resigned from the influential GOP ally, the Family Research Council in Washington, where he worked as a lobbyist for Christian causes and against gay marriage and abortion rights.
While TLC ponders what to do about the lucrative and popular show, the Duggars have been the targets of withering social-media criticism as hypocrites for promoting their family's moral purity while hiding Josh's self-described "inexcusable" past behavior.
Read or Share this story: http://usat.ly/1M6eW5S ||||| NEW YORK (AP) — Reality TV star Jessa Duggar told Fox News Channel on Wednesday that she was a victim of her older brother Josh Duggar, who fondled five girls when he was a teenager.
This photo provided by FOX News shows, Jim Bob Duggar, left, of the TLC series "19 Kids and Counting," before an interview speaking with FOX News Channel’s Megyn Kelly on Wednesday, June 3, 2015. The... (Associated Press)
This photo provided by FOX News shows, FOX News Channel’s Megyn Kelly sitting down with the Duggar children of the TLC program "19 Kids and Counting," on Wednesday, June 3, 2015. Kelly's interview with... (Associated Press)
This photo provided by FOX News shows, FOX News Channel’s Megyn Kelly, from left, Jim Bob, and Michelle Duggar of the TLC program "19 Kids and Counting," during an interview for "The Kelly File" on Wednesday,... (Associated Press)
Jessa Duggar, featured like her brother in the family's TLC series, "19 Kids and Counting," told Fox in an interview conducted in Arkansas on Wednesday that she wanted to defend him. She said allegations he's a child molester or pedophile are "so overboard and a lie," Fox reported.
The Associated Press generally does not identify victims of sexual mistreatment. But Jessa Duggar is speaking publicly, in an interview that Fox's Megyn Kelly also conducted with her parents, Jim Bob and Michelle Duggar. While Fox distributed Jessa Duggar's quote Wednesday, it didn't show it during the one-hour special about the case, with Kelly instead saying Fox would air the interviews with Jessa Duggar and her sister Jill Duggar on Friday.
The Duggar parents said Josh Duggar, who's now 27, fondled four of his sisters and a family baby sitter when he was a teenager and confessed to them. The fondling was done over the girls' clothes and, except in two cases, happened when the girls were asleep, Jim Bob Duggar said.
Josh Duggar apologized for unspecified bad behavior two weeks ago when the story came to light and resigned as a lobbyist for the Family Research Council, a conservative Christian group.
"I would do anything to go back to those teen years and take different actions," Duggar wrote online. "In my life today, I am so very thankful for God's grace, mercy and redemption."
He has not spoken publicly about fondling his sisters or the baby sitter and was not featured in Fox's interviews.
"He's very sorry," Michelle Duggar said in the interview, wiping away tears.
She said the fondling devastated her and her husband and made them question whether they had failed as parents.
Arkansas police last month said they had destroyed a record outlining a nearly decade-old investigation into Josh Duggar. No charges were filed in the abuse, which happened in 2002 and 2003. Police began investigating the abuse in 2006 when tipped by a family friend but concluded the statute of limitations had lifted.
Jim Bob Duggar said that before that investigation he had taken Josh Duggar to a Christian counselor and separately had him tell the stories to a state police officer near their home.
"We had all resolved it, we had forgiven, we had moved on in life," Michelle Duggar said.
"19 Kids and Counting" is one of TLC's most popular shows, coming off a season of strong ratings after featuring the weddings of Jessa Duggar and Jill Duggar. TLC pulled reruns of the show off the air when allegations concerning Josh Duggar surfaced two weeks ago. The network has said no decision has been made about whether the series will continue.
Jim Bob Duggar said the family is "fine whether they film us or not."
"We're just going to go on and live life," he said. "We're going to go on and serve God and make a difference in the world."
The couple criticized the leaking of police records on the case as "an unprecedented attack on our family" that should be investigated.
Michelle Duggar said her daughters "have been victimized more by what has happened in the last couple of weeks than they were 12 years ago because, honestly, they didn't even understand and know that anything had happened until after the fact when they were told about it."
Jim Bob Duggar is a former state representative in Arkansas. Some of the state's Republicans, including presidential candidate Mike Huckabee, have expressed support for the family. | – Two weeks after the skeleton burst out of the Duggar family closet, Jim Bob and Michelle Duggar have opened up about the Josh Duggar molestation scandal. In an interview with Megyn Kelly on Fox News, they talk about how they felt and what they did when they discovered their oldest son had "improperly touched" four of his sisters and a babysitter. Some highlights: "As parents, we felt, we're failures," Michelle Duggar said. "Here we've tried to raise our kids to do what's right, to know what's right, and yet one of our children made some really bad choices. I think as a parent, we were just, we were devastated." But this "was not rape or anything like that," Jim Bob said. "It was touching someone over the clothes. It was, like, a few seconds, and then he came to us and crying told us what happened." The abuse continued even after Josh first confessed the abuse in 2002, and they had to put up "safeguards" at home, the Duggars admitted. Jim Bob said Josh was eventually "pulled from the home" for a Christian counseling program. "It was after that third time he came to us, is where we really felt like, 'You know what? We have done everything we can as parents to handle this in-house,'" Jim Bob said. "'We need to get help.'" The couple said they aren't sure whether 19 Kids and Counting will continue, but Jim Bob defended the decision for the family to star in a reality show despite their shocking secret. "We had a clean bill of health from the state. We had no fear," he said. The record was sealed, he added, and "they said it would never be brought out." The Duggars describe the document leak that exposed the scandal as an "unprecedented attack" on their family and believe they're being targeted because of their religion. "Every one of us has done things wrong. That's why Jesus came," Michelle says. "There's an agenda, and there's people that are purposing to try to bring things out and twisting them to hurt and slander." Kelly also spoke to two Duggar daughters, and she says the rest of the interview will be aired on Friday night, USA Today reports. In quotes that Fox has released, Jessa Duggar says she was victimized by her older brother, but calling him a child molester is "so overboard and a lie," the AP reports. Click to watch Funny or Die spoof the scandal or to read about the latest police report to be leaked. |
one disadvantage of the original kohonen learning rule is that it has no potential ( or objective , or cost ) function valid for the general case of continuously distributed input spaces .
ritter , martinetz and schulten @xcite gave for the expectation value of the learning step ( @xmath6 denotes the voronoi cell of @xmath0 ) @xmath7 the following potential function @xmath8 this expression is however only a valid potential in cases like the end - phase of learning of travelling - salesman - type optimization procedures , i.e. input spaces with a discrete input probability distribution and only as long as the borders of the voronoi tesselation @xmath9 are not shifting across a stimulus vector ( fig .
[ clfig1 ] ) , which results in discontinuities .
.,height=188 ] as kohonen pointed out @xcite , for differentiation of ( [ cl_wrkpot ] ) w.r . to a stimulus vector @xmath10
, one has to take into account the movement of the borders of the voronoi tesselation , leading to corrections to the oringinal som rule by an additional term for the winner ; so ( [ cl_wrkpot ] ) is a potential function for the winner relaxing kohonen rather than for som .
this approach has been generalized @xcite to obtain infomax maps , as will be discussed in section [ clau_sec4 ] .
for a gaussian neighbourhood kernel @xmath11 it is illustrative to look at limiting cases for the kernel width @xmath12 .
the limit of @xmath13 implies @xmath4 to be constant , which means that all neurons receive the same learning step and there is no adaptation at all . on the other hand
, the limit @xmath14 gives @xmath15 which coincides with the so - called vector quantization ( vq ) @xcite which means there is no neighbourhood interaction at all .
the interesting case is where @xmath12 is small , which corresponds to the parameter choice for the end phase of learning . defining @xmath16 , we can expand ( @xmath17-expansion of the kohonen algorithm @xcite )
@xmath18 here we have written the sum over the two next neighbours in the one - dimensional case ( neural chain ) , but the generalization to higher dimensions is straightforward .
( note that instead of evaluating the gaussian for each learning step , one saves a considerable amount of computation by storing the powers of @xmath17 in a lookup table for a moderate kernel size , and neglecting the small contributions outside . using the @xmath19 kernel instead of
the `` original '' @xmath20 kohonen kernel reduces fluctuations and preserves the magnification law better ; see @xcite for the corrections for a non - gaussian kernel . )
if we now restrict to a travelling salesman setup ( periodic boundary 1d - chain ) with the case that the number of neurons equals the number of stimuli ( cities ) , then the potential reduces to @xmath21 this coincides with the @xmath22 limit ( the limit of high input resolution , or low temperature ) of the durbin and willshaw elastic net @xcite which also has a local ( universal ) magnification law ( see section [ clau_sec3 ] ) in the 1d case @xcite , that however astonishingly ( it seems to be the only feature map where it is no power law ) is not a power law ; low magnification is delimited by elasticity ) . as the elastic net is troublesome concerning parameter choice @xcite for stable behaviour esp . for serial presentation ( as a feature map model would require ) , the connection between elastic net and wrk should be taken more as a motivation to study the wrk map . apart from ordering times and reconstruction errors , one quantitative measure for feedforward structures
is the transferred mutual information , which is related to the magnification law , as described in the following section .
information theory @xcite gives a quantitative framework to describe information transfer through feedforward systems .
mutual information between input and output is maximized when output and input are always identical , then the mutual information is maximal and equal to the information entropy of the input . if the output is completely random , the mutual information vanishes . in noisy systems ,
maximization of mutual information e.g. leads to the optimal number of redundant transmissions .
linsker @xcite was the first who applied this `` infomax principle '' to a self - organizing map architecture ( one should note he used a slightly different formulation of the neural dynamics , and the algorithm itself is computationally very costly ) .
however , the approach can be used to quantify information preservation even for other algorithms .
this can be done in a straightforward manner by looking at the magnification behavoiur of a self - organizing map .
the magnification factor is defined as the number of neurons ( per unit volume in input space ) .
this density is equal to the inverse of the jacobian of the input - output mapping .
the remarkable property of many self - organizing maps is that the magnification factor ( at least in 1d ) becomes a function of the local input probability density ( and is therefore independent of the desity elsewhere , apart from the normalization ) , and in most cases even follows a power law .
while the self - organizing map shows a power law with exponent @xmath23 @xcite , an exponent of 1 would correspond ( for a map without added noise ) to maximal mutual information , or on the other hand to the case that the firing probability of all neurons is the same .
in higher dimensions , however , the stationary state of the weight vectors will in general not decouple , so the magnification law is no longer only of local dependence of the input probability density ( fig .
[ clfig2 ] ) .
networks , the neural density in general is not a local function of the stimulus density , but depends also on the density in neighbouring regions .
, height=222 ]
as pointed out in @xcite , the prefactor @xmath24 in the wrk learning rule can be replaced by a free parameter , giving the generalized winner relaxing kohonen algorithm @xmath25 the @xmath26 restricts the modification to the winner update only ( the first term is the classical kohonen som ) . the subtracted ( @xmath27 , winner relaxing case ) resp . added ( @xmath28 , winner enhancing case ) sum corresponds to some center - of - mass movement of the rest of the weight vectors .
the magnification law has been shown to be a power law @xcite with exponent @xmath29 for the winner relaxing kohonen ( associated with the potential ) and @xmath30 for the generalized winner relaxing kohonen ( see fig .
[ clfig3 ] ) . as stability for serial update
can be acheived only within @xmath31 , the magnification exponent can be adjusted by an _ a priori _ choice of parameter @xmath32 between @xmath24 and @xmath33 . , including the special cases som ( @xmath34 ) and wrk ( @xmath35 ) .
, height=215 ] although kohonen reported the wrk to have a larger fraction of initial conditions ordered after finite time @xcite , one can on the other hand ask how fast a rough ordering is reached from a random initial configuration . here the average ordering time can have a minimum @xcite for negative @xmath32 corresponding to a near - infomax regime . as in many optimization problems
, this seems mainly to be a question whether the average , the maximal ( worst case ) , or the minimal ( parallel evaluation ) ordering time is to be minimized .
cortical receptor fields of an adult animal show plasticity on a long time - scale which is very well separated from the time - scale of the signal processing dynamics .
therefore , for constant input space distributions ( which in principle can be measured ) the magnification law could be accessed experimentally by measuring the neural activity ( or the number of active neurons ) by any electrical or noninvasive technique .
especially the auditory cortex is well suitable for a direct comparison of mathematical modelling due to its 1-d input space .
owls and bats have a large amplitude variation in their input probability distribution ( their own `` echo '' frequency is heard most often ) and are therefore pronounced candidates for experiments . in a refined step ,
experimental and theoretical investigations on the nonlinear modifications of the learning rules have to be done . on the experimental side
, it has to be clarified which refinements to long - term - potentiation and long - term - depletion have to be found for the weight vectors in a neural map architecture
. mechanisms that can be included as modifications are modified winner updates ( as for gwrk ) , probabilistic winner selection @xcite , or a local learning rate , depending on averaged firing rates and reconstruction errors @xcite . on the theoretical side , it is obvious that the same magnification exponent can be obtained by quite different algorithms .
the relation between them and the transfer to more realistic models should be investigated further .
j. c. claussen , winner relaxing and winner - enhancing kohonen maps : maximal mutual information from enhancing the winner , preprint ( 2002 ) .
t. graepel , m. burger , and k. obermayer , phys .
e 56 , 3876 ( 1997 ) . | self - organizing maps are models for unsupervised representation formation of cortical receptor fields by stimuli - driven self - organization in laterally coupled winner - take - all feedforward structures .
this paper discusses modifications of the original kohonen model that were motivated by a potential function , in their ability to set up a neural mapping of maximal mutual information . enhancing the winner update , instead of relaxing it , results in an algorithm that generates an infomax map corresponding to magnification exponent of one .
despite there may be more than one algorithm showing the same magnification exponent , the magnification law is an experimentally accessible quantity and therefore suitable for quantitative description of neural optimization principles .
self - organizing maps are one of most successful paradigms in mathematical modelling of special aspects of brain function , despite that a quantitative understanding of the neurobiological learning dynamics and its implications on the mathematical process of structure formation are still lacking . a biological discrimination between models may be difficult , and it is not completely clear @xcite what optimization goals are dominant in the biological development for e.g. skin , auditory , olfactory or retina receptor fields .
all of them roughly show a self - organizing ordering as can most simply be described by the self - organizing feature map @xcite defined as follows : every stimulus in input space ( receptor field ) is assigned to a so - called winner ( or center of excitation ) @xmath0 where the distance @xmath1 to the stimulus is minimal . according to kohonen ,
all weight vectors are updated by @xmath2 this can be interpreted as a hebbian learning rule ; @xmath3 is the learning rate , and @xmath4 determines the ( pre - defined ) topology of the neural layer . while kohonen chose @xmath5 to be 1 for a fixed neighbourhood , and 0 elsewhere , a gaussian kernel ( with a width decreasing in time ) is more common .
the self - organizing map concept can be used with regular lattices of any dimension ( although 1 , 2 or 3 dimensions are preferred for easy visualization ) , with an irregular lattice , none ( vector quantization ) @xcite , or a neural gas @xcite where the coefficients @xmath5 are determined by rank of distance in input space . in all cases , learning can be implemented by serial ( stochastic ) , batch , or parallel updates . |
the reconstruction of an unknown quantum state from a suitable set of measurements is called quantum tomography @xcite , which is a particularly important method in the study of quantum mechanics and its various applications . since the characterization of the states is the central tasks in quantum - state engineerings and controls , this technique is of great importance in the current quantum information processing . recently ,
many theoretical analysis and experimental demonstrations have been devoted to implement the desirable quantum - state tomographies for , e.g. , the polarization states of photons @xcite , the electronic states of trapped ions @xcite , and the solid - state qubits @xcite , etc .
however , all these tomographic reconstructions are based on the destructively - projective ( dp ) measurements , and thus are very operational - complicated .
this is because that each kind of dp measurements , e.g. , @xmath2 , is required to be performed many times on many copies of the reconstructed state for determining just one of the elements ( e.g. , @xmath3 in the state @xmath4 ) in the density matrix @xmath5 . besides the usual dp measurements , quantum state
could also be detected by other strategies , typically such as the so - called quantum nondemolition ( qnd ) measurements . basically , qnd measurement is a nondestructive detection , as the measurement - induced back - action noises could be effectively suppressed by repeatedly hiding them in certain observables which are not of interests .
the basic criteria for a qnd measurement is that the repeated measurements of an observable @xmath6 of the same system should yield the identical result .
this means that the measured observable must be commutative with the hamiltonian @xmath7 describing the interaction between the measured system and the detector , i.e. , @xmath8=0 $ ] .
historically , qnd measurement is proposed to explore the fundamental limitations of measurements , and has been demonstrated in various branches of physics , such as in the detection of gravitational waves @xcite , quantum optics @xcite , telecommunications @xcite , and quantum control @xcite , etc . in recent years , the qnd measurement has also been successfully applied to probe the atomic qubits in the cavity quantum electrodynamics ( qed ) @xcite .
furthermore , this technique was extensively used to the circuit qed systems @xcite for nondestructively reading out the superconducting qubits .
this qnd measurement is implemented by measuring the transmission of the driven microwave signals through a transmission line resonator , which is dispersively coupled to the detected qubits .
this is because that the detected qubits can cause sufficiently large state - dependent shifts of the resonator frequency .
thus by detecting the signals of the shifted frequency of the resonator , the qubit state will be read out . however , the qnd measurements in the above works @xcite are only utilized to effectively distinguish the different logic states of the detected qubit(s ) , which is ( are ) not prepared initially at their superposed state .
motivated by the above experiments , recently we proposed a new scheme to nondestructively detect the superposition of these logic states by the qnd measurements @xcite . by taking account of the full quantum correlations between the resonator and dispersively - coupled qubit(s ) , our proposal shows that each detected peak marks one of the logic states and the relative height of such a peak is related to its corresponding superposed probability .
this means that one kind of the qnd measurements can determine all the diagonal elements of the density matrix of the measured quantum state @xmath5 .
similarly , the non - diagonal elements of @xmath9 could be determined by other kinds of qnd measurements by performing the suitable unitary operations to transfer them into the measurable diagonal locations .
therefore , the proposed tomographic reconstructing approach is high efficient for @xmath0 ( @xmath1 ) qubits , as the number of the kinds of the qnd measurements required is significantly decreased .
for example , to tomographically reconstruct a two - qubit state , the proposed @xmath10-kind qnd measurements are sufficient .
this is significantly simpler than the previous schemes ( requiring @xmath11-kind measurements ) based on either the dps @xcite or the individual dispersive readouts of the logic states @xcite .
the paper is organized as follows : sec .
ii gives our generic model of the transmissions of a driven resonator . in sec .
iii , we provide a detailed analysis of the qnd measurement of a single - qubit state by probing the transmissions of the driven resonator .
next , we show how to use these qnd measurements to tomographically reconstruct an unknown single - qubit state in the experimental circuit - qed system .
the extensions to the two - qubit case are given in sec .
iv , where the advantage of our proposal ( compared with the previous approach based on the dp measurements ) will be explicitly revealed .
the possible generalization to the @xmath0-qubit situation and summarizations of our main results are finally given in sec .
for the detection of the states of the qubits , we investigate the photon transmission of a driven resonator by studying the steady - state properties of the resonator - qubits dynamics . for generality , we consider a cavity - qed system consisting of @xmath0 qubits .
the hamiltonian reads @xmath12,\end{aligned}\ ] ] where @xmath13 and @xmath14 are ladder operators for the photon field and the @xmath15th qubit respectively . also , @xmath16 is the cavity frequency , @xmath17 the @xmath15th qubit transition frequency , and @xmath18 the coupling strength between the @xmath15th qubit and the resonator .
suppose that the cavity is coherently driven by @xmath19 where @xmath20 is the real amplitude and @xmath21 the frequency of the applied external driving . under the born - markov approximation ,
the dynamics of the whole system with the dissipations and dephasings is described by the following master equation @xcite @xmath22+\kappa \mathcal { d}[a]\varrho_n+\sum_{j=1}^n\gamma_{1,j } \mathcal { d}[\sigma_{-_j}]\varrho_n\nonumber\\ & & + \sum_{j=1}^n\frac{\gamma_{\phi , j}}{2 } \mathcal{d}[\sigma_{z_j}]\varrho_n,\\ & & h_n = h+h_d.\nonumber\end{aligned}\ ] ] here , @xmath23 is the density operator and the dissipation superoperator is defined by @xmath24{\varrho_n}=a{\varrho_n}a^\dagger - a^\dagger a{\varrho_n}/2-{\varrho_n}a^\dagger a/2 $ ] , which describes the effects of the environment on the system .
the parameters of the last three terms in eq .
( 3 ) correspond to photon decay rate @xmath25 , the @xmath15th qubit decay rate @xmath26 , and the @xmath15th qubit pure dephasing rate @xmath27 , respectively . in
what follows , we begin with the master equation ( 3 ) to calculate the frequency - dependent transmission of the cavity , which is proportional to the steady - state mean photon number @xmath28 in the cavity . technically , to satisfy the basic criteria for the desirable qnd measurements of the @xmath0-qubit system
, we assume that the conditions @xmath29 should be satisfied for assuring the effective dispersive coupling @xmath30 between the @xmath15th qubit and the cavity .
these conditions assure also that the inter - bit interactions are negligible .
above , @xmath31 denotes the detuning between the @xmath15th qubit and the cavity , and @xmath32 the detuning between the @xmath15th and @xmath33th qubits .
for contrast , we first calculate the transmission spectrum of a driven empty cavity .
the hamiltonian of the simplified system reduces to ( @xmath34 throughout the paper ) @xmath35 after the time - dependent unitary transformation defined by the operator @xmath36 , we get the effective hamiltonian @xmath37 where @xmath38 is the detuning of the cavity from the driving . consequently , we get the master equation for such a driven empty cavity @xmath39 + \kappa(\hat{a}\varrho_0\hat{a}^\dagger-\hat{a}^\dagger\hat{a}\varrho_0/2-\varrho_0\hat{a}^\dagger\hat{a}/2),\end{aligned}\ ] ] where @xmath40 is the density matrix of the empty cavity . from the above master equation ,
one can easily obtain the equations of motion for the expectation values of the relevant operators , such as mean photon number inside the cavity @xmath41 : [ eq : whole ] @xmath42 with @xmath43 the steady - state solution of eq .
( 8) gives @xmath44 obviously , the transmission spectrum of an empty cavity , which is proportional to @xmath28 , is well - known lorentzian : centered at @xmath45 with the half - width @xmath25 .
certainly , when @xmath21 does not sufficiently match the cavity frequency , no photon penetrates the cavity and thus no transmission is recorded .
now we investigate the case , in which a single qubit with transition frequency @xmath46 is dispersively coupled to the cavity mode . in the frame rotating at drive frequency @xmath21 characterized by the transformation @xmath47 , the hamiltonian of the system reads @xmath48 with @xmath49 and @xmath50 . under the born - markov approximation ,
the master equation for the single - qubit plus the driven resonator is @xmath51+\kappa \mathcal { d}[a]\varrho_1+\gamma_{1,1 } \mathcal { d}[\sigma_{-_1}]\varrho_1 \nonumber\\&&+ \frac{\gamma_{\phi,1}}{2 } \mathcal{d}[\sigma_{z_1}]\varrho_1.\end{aligned}\ ] ] the desirable quantity @xmath28 can be determined by solving the following coupled equations of motion : [ eq : whole ] @xmath52 @xmath53 @xmath54 and @xmath55 it is obvious that the additional measurement - induced dephasing rate @xmath56 does not influence the solution of the equations . as the decay @xmath57 of the qubit is significantly less than the decay rate @xmath25 of the driven cavity , the average of @xmath58 could be safely assumed to be unchanged during the measurement .
in fact , the characterized time of the detection is determined mainly by the decay of the cavity @xmath25 .
such a quantity is about @xmath59 mhz @xcite , which is obviously larger than @xmath60 mhz @xcite .
experimentally , the time interval of completing a single qnd measurement is about @xmath61ns @xcite , this is significantly shorter than the lifetime : @xmath62@xmath63s and the decoherence time : @xmath64ns @xcite .
therefore , during such a readout the decay of the qubit is negligible , i.e. , @xmath65 . under the steady - state condition
, we obtain @xmath66\nonumber\\ & & \times[(\frac{\kappa^2}{4}+\frac{\gamma_{1,1}\kappa}{2}+\gamma_1 ^ 2-\delta_{dr}^2)^2\nonumber\\ & & + ( \kappa\delta_{dr}+\gamma_{1,1}\delta_{dr}+\gamma_{1,1}\gamma_1)^2]^{-1},\end{aligned}\ ] ] which is strongly related to the the initial state of qubit , thus the qubit state could be determined by the cavity transmission . .
five cases of the qubit states for @xmath67 , and @xmath68 are shown . for comparison , the empty cavity ( emc ) transmission
is also plotted in black line .
the peak shifts by @xmath69 or @xmath70 correspond to single logic state @xmath71 or @xmath72 . for the superposition states , the double - peak relative heights ( in contrast to the peak height of the empty cavity transmission ) present clearly the superposed probabilities of the two logic states . here
, the parameters are selected as : @xmath73mhz @xcite.,width=302,height=226 ] the measured cavity transmission ( normalized to the peak height of the empty cavity transmission ) versus the probe frequency detuning are plotted in fig . 1 .
generally , the qubit is assumed to be prepared initially in the state @xmath74 . obviously , when @xmath75 , or @xmath68 , it reduces to the single logic state @xmath72 or @xmath71 .
compared with the empty cavity transmission ( plotted as the dark line in fig . 1 )
, one observes that qubit - resonator coupling leads to a right ( left ) shift of the single peak in the transmission spectrum by a quantity @xmath76 ( @xmath77 ) , which is dependent of the logic states for @xmath78 ( @xmath79 ) .
thus , the shifts of the peaks can be used to mark the logic states of the qubit . however ,
when the qubit is in the superposition of the two logic states , e.g. , @xmath80 , and @xmath81 , respectively , we see that the situation is very different from the case for the single logic states . in this case
, the spectrum shows two peaks whose locations coincide with that for the single logic states , but the relative heights of these two peaks correspond clearly to the superposed probabilities , i.e. , @xmath82 and @xmath83 , respectively .
this provides an effective approach to directly measure the superposed probabilities of a superposed state . above investigation
indicates that , partial information of the qubit state , i.e. , the diagonal elements of the relevant density matrix , can be directly obtained by only one kind of the qnd measurements . while , to extract the full information of an unknown qubit state , one should tomographically reconstruct all the elements of its density matrix .
basically , to completely define a @xmath84-dimensional density matrix @xmath9 , one needs to determine @xmath85 real parameters .
therefore , to determine an unknown qubit state , the key point is to identify these parameters by virtue of the tomographic technique .
now we demonstrate how to perform the tomographic construction of an arbitrary single - qubit state @xmath86 , whose density matrix operator reads @xmath87 a more efficient and widely used technique is to parameterize the density matrix @xmath88 on a bloch sphere @xcite , @xmath89 here , @xmath90 denotes the identity matrix , @xmath91 the pauli matrices , and @xmath92 real parameters .
therefore , in order to determine the single - qubit state , we must identify the three components @xmath93 of the bloch vector @xmath94 . as discussed in the previous section , two diagonal elements @xmath95 and @xmath96 of the density matrix @xmath97 can be directly determined by the two measured occupation probabilities @xmath82 , @xmath83 in the direct qnd measurements .
this means that the parameter @xmath98 can be determined by the relation @xmath99 @xmath100 . to obtain the other two parameters @xmath101 and @xmath102
, we need to determine the non - diagonal elements . to this end , we perform the single - qubit operations : @xmath103 and @xmath104 , to transfer them to the the relevant diagonal locations , respectively . for example , after the operation @xmath105 , the density matrix @xmath88 is changed to @xmath106 now , performing another kind of qnd measurements the parameters @xmath107 and @xmath108 can be measured . consequently , the coefficient @xmath102 can be determined via the relation @xmath109 .
similarly , by performing the quantum operation @xmath110 on the original density matrix @xmath88 , another new density matrix @xmath111 can be obtained and the coefficient @xmath101 can be similarly determined .
note that here the number of the unitary operations required for implementing the quantum state tomography ( based on the qnd measurements ) is the same as the previous approach ( based on the usual dp measurements ) .
thus , for the single - qubit case the complexity of the present approach is the same as that in the previous one .
note that here , as the same as that in the previous approach based on the dp measurements , three kinds of qnd measurements are still required for the present reconstructions .
one is directly applied , another is applied after the @xmath105 operation , and the final one is applied after the @xmath110 operation , thus the efficiency is not enhanced . the remaining task is to implement the single - qubit operations required above for transferring the non - diagonal elements to the diagonal locations .
we work with a circuit - qed system wherein a superconducting charge qubit is coupled to the fundamental mode of a transmission line resonator @xcite .
let the qubit work at its degeneracy point and neglect the fast oscillating terms under the rotating - wave approximation ( rwa ) .
following ref .
@xcite , under one displacement transformation , the effective hamiltonian of the resonator plus qubit system can be written as @xmath112 with the detuning of the qubit transition frequency from the drive @xmath113 and the rabi frequency @xmath114 .
next , supposing that this system works in the dispersive regime , i.e. , @xmath115 , after the transformation @xmath116}$ ] , then the above hamiltonian becomes @xmath117 first , if the condition @xmath118 is satisfied , then the hamiltonian ( 19 ) produces a rotation of the qubit about the @xmath119 axis , i.e. , @xmath105 could be generated by choosing the evolution time @xmath120 .
second , if the driving is sufficiently detuned from the qubit and its amplitude is also sufficiently large enough , then another approximate hamiltonian @xmath121 can be obtained by further performing a transformations @xmath122 , with the coefficient @xmath123 , on the hamiltonian ( 19 ) . obviously , the desirable operation @xmath124 can be implemented by the evolution under the hamiltonian ( 20 ) with the duration @xmath125 .
third , the desirable operation @xmath110 could be constructed as : @xmath126 .
it should be pointed out that the durations @xmath127 ( or @xmath128 ) of the single - qubit operations required above for implementing the desirable tomographies is estimated as @xmath129ps using the experimental parameters : @xmath130mhz @xcite , and @xmath131 @xcite .
this is significantly less by at least two orders than the qubit decoherence time , which is measured as @xmath132ns @xcite .
therefore , the required gate operations are accessible and the proposed tomographic reconstructions are experimentally feasible . as an example , we assume that the three parameters @xmath133 , @xmath134 , @xmath135 are obtained through the above reconstructions , then the reconstructed state @xmath88 can be written as @xmath136 , whose real @xmath137 and imaginary @xmath138 parts ( i , j=0 , 1 ) are graphically represented in fig . 2 . for a single - qubit state .
the real @xmath137 and imaginary @xmath138 parts of the density matrix elements @xmath139 ( i , j=0 , 1 ) are plotted in ( a ) and ( b ) , respectively.,width=302,height=151 ]
we extend the above sing - qubit qnd measurements to the two - qubit case .
the transition frequencies of the two qubits are represented as @xmath46 and @xmath140 , respectively . in the above dispersive condition ( 4 ) and in a framework rotating at @xmath141 ,
the effective hamiltonian of the present complete system is @xmath142 where @xmath143 and @xmath144 , @xmath145 .
similarly , the relevant master equation reads @xmath146+\kappa \mathcal { d}[a]\varrho_2+\sum_{j=1,2}\gamma_{1,j } \mathcal { d}[\sigma_{-_j}]\varrho_2\nonumber\\ & & + \sum_{j=1,2}\frac{\gamma_{\phi , j}}{2 } \mathcal{d}[\sigma_{z_j}]\varrho_2.\end{aligned}\ ] ] and the equations of motion for the mean values of various expectable operators are [ eq : whole ] @xmath52 @xmath147 @xmath148 @xmath149 @xmath150 @xmath151 @xmath152 @xmath153 again , due to the relatively - long decoherence times of the qubits and their sufficiently short measured times , the additional measurement - induced dephasing and decay rates of the qubits are also unimportant .
thus , the expectable values of the qubit operators can still be regarded as unchanged , i.e. , @xmath154 and @xmath155 , during the desirable qnd measurements . as a consequence
, one can easily solve the above eqs .
( 23a - e ) and finally obtain the exact steady - state distribution of the intracavity photon number @xmath156-\sum_{j}{b_je_j(d_j+b_jg_j ) } } { \sum_{j , j'}b_je_j(d_{j'}f+d_ja)-{(b_1e_1-b_2e_2)^2 } -ad_1d_2f}\right\},\nonumber\\ j , j'=1,2 , j\neq{j'}.\end{aligned}\ ] ] here , @xmath157 , @xmath158 , and @xmath159 . for certain slected two - qubit states with @xmath160 , @xmath161 , @xmath162 , @xmath163 , @xmath164 , @xmath165 , @xmath166 , @xmath167 @xmath168 , and @xmath164 , @xmath165 , @xmath166 , @xmath167 @xmath169 ,
respectively . for comparison , the empty cavity ( emc ) transmission is also plotted in black line . here , the parameters are @xmath170mhz @xcite . in ( b ) only the parameters @xmath70 and @xmath171 are modified as @xmath172 and @xmath173 . in this case , the relative heights of the peaks are exactly equivalent to the corresponding probabilities of the single logic states superposed in the measured superposition state.,width=302,height=226 ] we now investigate the above distributions schematically for various typically selected two - qubit initial states .
first , we assume that the two - qubit is initially prepared at only one of the four logic states , i.e. , in the generic expression @xmath174 only one of the four probability amplitudes equals @xmath68 , e.g. , @xmath175 , @xmath176 @xmath177 @xmath178 .
3 shows clearly that single peaks reveal the inputs of these four single logic states , and they can also be distinguished by the shifts of the central frequencies of the transmission spectrum . the peaks with frequency shifts : @xmath179 , @xmath180 , @xmath181 , and @xmath182 mark the state @xmath183 , @xmath184 , @xmath185 , and @xmath186 , respectively .
thus the pulls of the cavity are strongly dependent of the states of the qubits . for these single logic states the heights of the single peaks
are exactly equivalent and of unity value , which is the same as that for the emc .
next , for the superposition of the four single logic states the situations are quite different .
for example , fig .
3 ( a ) also shows that , if the two - qubit is prepared initially as one of the bell states : @xmath187 , @xmath166 , @xmath188 , @xmath189 , then the transmitted spectrum of the cavity reveals two peaks ; their locations are respectively at the positions for the single states @xmath183 and @xmath186 , but have the same relative heights . moreover ,
for a more generic superposed state @xmath187 , @xmath166 , @xmath188 , @xmath190 one can see that four peaks are exhibited simultaneously .
the central positions of these peaks locate at the corresponding positions of single logic states @xmath191 , and @xmath192 , respectively . here , the relative heights of the peaks marking the states @xmath183 and @xmath186 are exactly equivalent to the superposed probabilities @xmath165 and @xmath193
. however , the relative heights of the peaks marking the states @xmath184 and @xmath185 deviate from the corresponding superposed probabilities @xmath166 and @xmath188 .
this is because these two peaks are not well distinguished due to the contributions from these two logic states overlap . as a consequence ,
each peak is higher a little than the expected one , i.e. , the superposed probability of the relevant logic state . while , such a situation does not exist for the @xmath183 and @xmath186 peaks ( the relative heights of them equal to the expected ones ) , as they are separated sufficiently far from the others . in fig .
3 ( b ) we modify the relevant parameters such as @xmath172 and @xmath173 .
then we find that each peak of the transmission of the cavity is well separated from the others , and thus its relative height is exactly equal to the expectable superposed probability of the corresponding logic state in the measured two - qubit state .
the two - qubit state tomography is done in the same way as that for the single - qubit state .
the only difference is that now there are @xmath11 real parameters to be determined in the 4-dimensional density matrix operator @xmath194 , and thus more operations are required to transfer the nondiagonal elements in @xmath194 to the diagonal locations .
generally , the 4-dimensional density matrix for a two - qubit state @xmath174 in a complete basis @xmath195 , @xmath196 , @xmath197 , @xmath198 can be represented as @xmath199 which can also be rewritten as @xmath200 with @xcite @xmath201 here , @xmath202 are the pauli operators and @xmath203 identity matrix , and what we want to determine is sixteen real parameters @xmath204 . note that the first and second subscripts of the matrix elements @xmath205 ( i , j=1 , 2 , 3 , 4 ) in eq .
( 25 ) and @xmath204 in eq .
( 26 ) is labeled for the first and second qubits , respectively . as in the above discussion
, performing the qnd measurements on the two - qubit state @xmath194 can directly determine all the four diagonal elements : @xmath96 , @xmath206 , @xmath207 and @xmath208 , respectively , by the measured results @xmath165 , @xmath166 , @xmath188 and @xmath193 .
as a consequence , the parameters @xmath209 , @xmath210 , @xmath211 and @xmath212 can be determined by @xmath213 to determine the other @xmath214 parameters , we need to perform certain unitary operations to transfer them to the diagonal locations for other qnd measurements .
it is well - known that , arbitrary two - qubit operation assisted by arbitrary rotations of the single qubits generate an universal set of quantum gates .
so the key to implement the above required operations for tomographies is to realize a two - qubit gate .
again , for the experimental circuit qed system with two superconducting charge qubits , such a gate could be implemented by using the so - called flicforq protocol @xcite . in fact , if the cavity is driven by two external fields satisfying the sideband matching condition : @xmath215 , then an effective hamiltonian @xmath216 can be induced in a quadruply rotating framework . here ,
@xmath217 with @xmath218 , and @xmath219 , @xmath220 , @xmath221 .
obviously , the evolution under the above hamiltonian with the duration , e.g. , around @xmath129ps , for the experimental parameters @xcite , can produce a two - qubit operation : @xmath222.\ ] ] on the other hand , the typical single - qubit gates , e.g. , @xmath223 , and @xmath224 ( j=1 , 2 ) can be relatively easy to produce using the similar approaches presented in sec .
with such a two - qubit operation and these single - qubit gates , we show in table i how to perform the desirable unitary operations for transferring the non - diagonal elements to the diagonal locations .
for example , by performing a selected operational sequence @xmath225 on the original density matrix @xmath194 , we have a new density matrix @xmath226 , and the new diagonal elements are @xmath227 then , by the qnd measurements the values of @xmath228 , @xmath229 , and @xmath230 are given directly . as a consequence , the desirable parameters @xmath209 , @xmath231 , @xmath232 and @xmath233 can be obtained by the relations : @xmath234 similarly , other non - diagonal elements can also be determined . clearly , here
only six kinds of qnd measurements are sufficient to tomographically reconstruct a two - qubit state .
this is obviously simpler than the previous tomographies based on the usual dp measurements , wherein @xmath11 kinds of measurements are probably required @xcite .
thus , the present tomographies is essentially high efficient . after performing all the qnd measurements listed in the table
, a two - qubit state can be completely reconstructed .
for example , a two - qubit state @xmath194 having the following representation : @xmath235 which can be effectively reconstructed by these parameters @xmath236 determined by six kinds of qnd measurements . the simulated reconstructions are graphically shown in fig . 4 , where @xmath137 and @xmath138 are the real and imaginary parts of the reconstructed state @xmath194 in the bases @xmath237 , @xmath196 , @xmath197 , @xmath238 , with @xmath239 .
for a two - qubit state .
the real @xmath137 and imaginary @xmath138 parts @xmath240 of the density matrix elements in the complete bases are plotted in ( a ) and ( b ) , respectively.,width=302,height=151 ] .the operational combinations before the qnd measurements to determine the parameters for tomographically reconstructing a two - qubit state .
the subscript @xmath241 of @xmath242 is labeled for the operation of qubit @xmath243 . [
cols="<,^,>",options="header " , ]
generally , the quantum state tomographic constructions demonstrated above can be extended for @xmath0 ( with @xmath244 ) qubits in a straightforward manner .
this is because that the proposed qnd measurements can be directly applied to determine all the diagonal elements of the arbitrary @xmath0-qubit state ; the individual superposed logic states can be inferred from the relevant positions of the measured peaks , and the probabilities of the corresponding computational bases superposed in the measured state could be extracted from the relative heights of the peaks ( when they separate sufficiently from the others ) .
moreover , all the required operations for the tomographic reconstructions can be implemented from the universal set of the logic gates demonstrated . in summary , we have proposed a scheme to perform the quantum state tomographies by qnd measurements .
differing from the usual tomographies based on the dp measurements , here the qnd measurements are utilized .
since all the diagonal elements of the density matrix of an unknown quantum state can be simultaneously determined by a single kind of qnd measurements , the efficiency of the present tomographic reconstruction is definitely better for more qubits .
specifically , our proposal is demonstrated with the current circuit qed setup with a few charge qubits , and could be generalized to other systems , in principle .
this work was supported in part by the national science foundation grant no .
10874142 , 90921010 , and the national fundamental research program of china through grant no .
2010cb923104 , and the fundamental research funds for the central universities no .
swjtu09cx078 , and a*star of singapore under research grant no .
wbs : r-144 - 000 - 189 - 305 . | we propose a high efficiency tomographic scheme to reconstruct an unknown quantum state of the qubits by using a series of quantum nondemolition ( qnd ) measurements .
the proposed qnd measurements of the qubits are implemented by probing the the stationary transmissions of the dispersively - coupled resonator .
it is shown that only one kind of qnd measurements is sufficient to determine all the diagonal elements of the density matrix of the detected quantum state .
the remaining non - diagonal elements of the density matrix can be determined by other spectral measurements by beforehand transferring them to the diagonal locations using a series of unitary operations .
compared with the pervious tomographic reconstructions based on the usual destructively projective ( dp ) measurements ( wherein one kind of such measurements could only determine one diagonal element of the density matrix ) , the present approach exhibits significantly high efficiency for @xmath0-qubit ( @xmath1 ) .
specifically , our generic proposal is demonstrated by the experimental circuit - quantum - electrodynamics ( circuit - qed ) systems with a few josephson charge qubits .
pacs number(s ) : 42.50.pq , 03.65.wj , 03.67.lx , 85.25.cp |
the doppler velocity technique now has two decades of success in enabling extrasolar planetary detections .
it has produced candidates with masses approaching that of earth , and has been especially successful in detecting long period planets . in recent years , doppler velocity confirmations have proven vital to gaining an understanding of the planetary candidates discovered by photometric space missions , especially kepler .
doppler velocity campaigns are responsible for 31% of the 1854 confirmed planetary discoveries in the past three decades , but they account for 87% of the 330 confirmed planets with periods longer than 1 year@xcite .
ground - based facilities , furthermore , are amenable to the operation of long - term surveys due to their relativity low construction and operational costs along with their ability to be upgraded as instrumentation improves . in order to find analogs of our own solar system , we need to extend the catalog of successful radial velocity ( rv ) planet detections to encompass longer - period planets ( particularly true jupiter analogs ) and smaller mass , short - period planets .
this means observing efforts must increase their temporal baselines and cadence of observation to more effectively populate each planet s rv phase curve .
the automated planet finder , located at the mt .
hamilton station of uco / lick observatory , combines a 2.4-m telescope with a purpose - built , high - resolution echelle spectrograph , and is capable of 1@xmath0 doppler velocity precision@xcite .
eighty percent of the telescope s observing time is specifically dedicated to the detection of extrasolar planets .
this time is shared evenly between two exoplanet research groups , one at uc santa cruz and one at uc berkeley .
time is allocated in whole night segments , with a schedule developed quarterly by the telescope manager .
target lists and operational software are developed separately as the two exoplanet groups are focused on different types of planet detection / follow up . for
a description of the uc berkeley planet detection efforts , please see fulton et .
al , 2015@xcite .
the remaining 20% of telescope time is dedicated to at - large use by the university of california community .
all users are allowed to request specific nights if it is beneficial to their science goals ( for example : to obtain rv values while a planet transits its star ) , and such requests are taken into account by the telescope manager when setting the schedule .
the apf leverages a number of inherent advantages to improve efficiency .
for example , its levy spectrometer , a high - resolution prism cross - dispersed echelle spectrograph with a maximum spectral resolving power of r@xmath1 , is optimized for high precision rv planet detection @xcite . a full description of the design and the individual components of the apf is available in vogt et al .
( 2014 ) @xcite .
to support long - running surveys , we have developed a dynamic scheduler capable of making real - time observing decisions and running the telescope without human interaction . through automation and optimization
, we increase observing efficiency , decrease operating costs and minimize the potential for human error .
the scheduler s target selection is driven by balancing scientific goals ( what we _ want _ to observe based on scientific interest , required data quality , and desired cadences ) and engineering constraints ( what we _ can _ observe based on current atmospheric conditions and physical limitations of the telescope ) . to address these criteria ,
we need to know how the velocity precision extracted from a given stellar spectrum depends on inputs that can be monitored before and during each observation .
we have assessed the influences of the various inputs by analyzing 16 months of data taken on the apf between june 2013 & october 2014 .
the plan of this paper is as follows : in [ sect : data ] we describe the current apf radial velocity catalog , paying special attention to the variety of spectral types and the frequency of observations . in
[ sect : inputs ] we evaluate the relations between velocity precision and parameters including stellar color and v band magnitude , airmass , seeing , date of observation and atmospheric transparency and we explain how these relations inform the nightly decision - making process executed by the observing software . in [ sect : dismissedinputs ] we outline the parameters that were assumed to be important prior to on - sky observations , but that have since been determined to have little relevance . in [ sect : heimdallr ] we describe how the relevant relations are integrated into the scheduling software , and we discuss its structure , its dependencies , and its capabilities . in
[ sect : compare ] we discuss other automated and semi - automated observatories and highlight both the similarities and differences between those systems and that employed by the apf . finally we conclude in [ sect : campaigns ] by reviewing the application of the apf s automated observing strategy to the telescope s current and upcoming observing scientific campaigns .
this paper differs from most publications discussing precision radial velocity work in that all of the plots , equations and discussions presented are based on individual , un - binned exposures of stars .
it is well known that pulsation modes ( p - modes ) in stars cause oscillations on the stellar surface , adding noise to the rv signal . it has also been well documented that the noise imparted by these p - modes in late - type stars can be averaged over by requiring total observation times longer than the @xmath2 minute periods typical of the pulsation cycles @xcite
. thus the majority of radial velocity publications , especially those dealing with exoplanet detections , present _ binned _ velocities and error values .
that is , they take multiple , individual _ exposures _ of a star during the night and then combine ( bin ) them to create one final _ observation _ with its own velocity and internal error estimate @xcite .
the binned observations therefore contain more photons than any individual exposure , but , more importantly , average over the pulsation modes on the star , and therefore exhibit a measurably smaller scatter ( figure [ fig : bin_unbin ] ) .
these terms , exposure and observation , will be used specifically throughout this paper to help make clear to the reader whether we are talking about an exposure - a single instance of the shutter being open and collecting photons from the star , or an observation - the combination of all exposures taken of a star over the course of a night .
similarly , exposure time will refer to the open shutter time during one exposure and observation time will refer to the total open shutter time spent on a target between all exposures . in the case of the star s observation consisting of only one exposure , then the observation time is equivalent to the exposure time .
our radial velocity dataset for the rv standard star hd 185144 showing the individual exposures ( open circles in black ) and the resulting binned velocities ( solid circles in red ) .
the binned velocities have a much smaller rms value ( 0.99 @xmath0 for the first 120 days and 1.72 @xmath0 over the entire 400 day span , compared to the 1.72 @xmath0 and 2.06 @xmath0 exhibited by the un - binned data over the same respective time spans ) due to their increased signal - to - noise .
additionally the individual exposures are each @xmath360 seconds long while the binned velocities span at least @xmath35min , so they average over the p - modes of the star
. this paper uses the individual exposure data when carrying out all further analyses and calibrations .
the change in the rms values between the first 120 days and the full data set is largely due to a change in observing strategy .
after the first 4 months we started observing hd 185144 less frequently and with fewer exposures in each observation to allow for more targets to be observed each night.,height=302 ] the apf s star list is made up of legacy targets first observed as part of the lick - carnegie exoplanet campaign using the hires spectrograph on the keck i telescope .
stars for the lick - carnegie survey were selected based on three main criteria : * spectral type between g and m : stars with spectral types earlier than f5 experience oscillations that can produce pseudo - keplerian signals , and are fast rotators with few spectral lines so they are avoided * single stars : no stars with companions closer than 5 " , as this can lead to scattered light from the nearby companion making its way into the spectrograph slit and contaminating the target star s signal * quiet stars : only stars without large amounts of emission in the ca ii h & k line cores are permitted , as core emission in these lines is an indicator of stellar chromospheric activity @xcite which complicates the data reduction process and can produce pseudo - keplerian signals .
the resulting lick - carnegie target list is comprised of @xmath31800 stars , which have been monitored using keck / hires over the past two decades .
when creating the initial target list for the apf , the lick - carnegie star list was culled for targets with v magnitudes brighter than 12 and declinations above -20@xmath4 . in order to efficiently prove the apf s capabilities , we selected stars with suspected short - period planets ( p < 100 days ) that required only 1 - 2 more rounds of phase coverage to verify . the presence and the false - alarm probabilities of these short - period ,
keplerian signals were determined by analyzing the existing keck / hires rv datasets using the publicly available systemic console @xcite .
systemic allows users to fit planetary signals to rv data and derive the orbital properties , while also providing tools to handle error estimation and assess orbital stability .
this selection process resulted in a list of 127 stars .
the calibrations described in this paper are based on data taken with the apf between june 2013 and october 2014 .
the data set includes precision doppler observations of 80 of the 127 stars selected from the lick - carnegie survey and this is before the development / inclusion of the dynamic scheduler , thus all data in this paper were obtained using fixed star lists .
our precision doppler observations encompass spectra of 80 stars and incorporate 600 hours of open shutter time .
the stars span spectral types from early g to mid m , have 3.5 < v < 12 , and are all located within 160 pc ( figure [ fig : apf_cmd ] ) . every apf star has a set of observations containing between one and seven hundred exposures .
individual exposures are restricted to a maximum length of fifteen minutes to avoid cosmic ray accumulation and to minimize uncertainty when calculating the photon - weighted midpoint times .
additionally , we enforce a total observing time limit of one hour per target per night to ensure that telescope time is not wasted on observing faint objects when conditions are poor . for each individual exposure , the @xmath5 ( the average fwhm of the star over the integration time ) of the guide camera s seeing disk
is logged in the fits image header , along with the total number of photons from the exposure meter and the total exposure time .
colors , magnitudes and distances for the stars are obtained from simbad @xcite .
color - magnitude diagram for stars observed with apf and used in the analysis described herein .
color coding represents the number of exposures that have been obtained for each star .
our dataset spans a wide range in color and magnitude and contains stars with spectral types from f6 to m4.,height=302 ] all spectra are analyzed using the data reduction techniques described in detail by butler et al .
( 1996)@xcite , which produces a measurement of the stellar rvs and associated internal uncertainties .
the reduction pipeline analyzes each exposure s extracted spectrum in 2 chunks and determines the radial velocity shift for each chunk individually .
the final reported velocity is the average over all the chunks , while the internal uncertainty is defined as the rms of the individual chunk velocity values about the mean , divided by the square root of the number of chunks .
thus the internal uncertainty represents errors in the fitting process , which are dominated by the photon noise .
the internal uncertainty does not include potential systematic errors associated with the instrument , nor does it account for astrophysical noise ( or `` jitter '' ) associated with the star and , therefore , represents only a lower limit to the accuracy of the data for finding companions .
we use the apf s 737 individual exposures of hd 185144 ( sigma draconis , hr 7462 ) , a bright rv standard star , to estimate the precision with which we can measure radial velocities .
it should be noted that the radial velocity values produced by our analysis pipeline are all relative velocities and thus have a mean value of zero .
we examine the unbinned , or individual , exposures , finding that star s mean internal uncertainty is @xmath6 @xmath0and that the mean of the absolute values of its velocity measurements is @xmath7 @xmath0 . because @xmath8 includes effects from the internal uncertainty _ in addition _ to other sources of error such as the stellar jitter and the instrument systematics ,
its value is always higher than the internal uncertainty value for a given exposure .
the difference between these two parameters implies an additional quadrature offset of @xmath9 @xmath0 , which we then generalize as @xmath10 @xmath0(figure [ fig:185144_unc ] ) .
we take this offset value to represent the additional error contributions from all other systematics , including the known 5 - 15 minute pulsation modes of the star that the binned data averages over and the systematics from the instrument . if , instead , we compared the mean internal uncertainty to the standard deviation of the velocity measurements ( @xmath11 @xmath0 ) we would require a larger additional offset term ( @xmath12 @xmath0 ) @xmath0 for hd 185144 .
this value is notably smaller than the standard deviation of the individual velocities , @xmath11 @xmath0 , because we deliberately acquired 6 observations of hd 185144 in order to both average over the pulsation modes and achieve a high precision for the final binned observations . ] .
we note , however , that the data are strongly affected by the velocities of exposures that fall in the outlying , non - gaussian tail .
we thus choose to determine our error estimate using the mean of the absolute values of the velocity measurements ( instead of the standard deviation of the velocities ) as it mitigates the influence of the outliers .
we use the relations of wright et al .
( 2005)@xcite , which presents radial velocity jitter estimates at the 20@xmath13 percentile , median and 80@xmath13 percentile levels to assess the expected stellar activity for hd 185144 .
we find an estimated median jitter of @xmath14 @xmath0 , and a 20@xmath13 percentile value of @xmath15 @xmath0 .
noting that the @xmath16 percentile value matches the @xmath17 for our exposures , obtained over a timespan of 400 days , suggests that the star is in fact intrinsically quiet .
that is to say , we expect only 20% of stars with the same evolution metric , activity metric ( both described by wright 2005 ) and b - v color as hd 185144 to have activity levels less than @xmath15 @xmath0 .
given that we measure @xmath7 @xmath0 , hd 185144 is , at a minimum , much quieter than expected based on its color , activity and evolution .
even so , it is reasonable to expect that some fraction of the observed uncertainty is due to the star itself ( astrophysical noise ) or currently unknown planets rather than instrumental effects , thus indicating that the instrument is performing very well .
radial velocities from apf exposures on the star hd 185144 [ g9v , @xmath18 = 4.68 ] , 737 points in total .
the internal uncertainty estimates produced by the data reduction pipeline are noticeably smaller than the actual spread in the data .
the internal error does not account for telescope systematic errors or sources of astrophysical noise in the star .
our average internal uncertainty is @xmath19 = 1.0 @xmath0(blue line ) but we find the mean absolute value of the hd185144 velocity measurements to be @xmath8 = 1.8 @xmath0(purple line ) .
we adopt an estimate that the additional systematic uncertainty in our velocity precision is @xmath20 = 1.5 @xmath0 .
, height=302 ] to verify that the size of the offset between @xmath19 and @xmath8 is not specific to the hd 185144 data set , we compare the mean values of these parameters for every star observed by the apf during the time span of figure [ fig:185144_unc ] .
that is , we apply the same procedure detailed above for hd 185144 to all stars observed during the same date range , and then compute and compare the mean values of @xmath19 and @xmath8 for each star s set of exposures ( figure [ fig : muabs_meanintunc ] ) .
as expected , the values for the mean of the absolute radial velocity values are always higher than the mean internal uncertainty values because @xmath8 includes the effects of the internal uncertainty combined with additional sources of error such as the stellar jitter and instrument systematics .
additionally some of these stars are planet hosts , and thus display even higher @xmath8 values because of the planet s influence . however the quietest , non - planet hosting stars are able to reach @xmath8 values of slightly less than 2 @xmath0 , suggesting that the additional error offset value determined using hd 185144 ( @xmath10 @xmath0 ) is appropriate .
mean values of @xmath19 and @xmath8 for each star observed during the same time span as the hd 185144 analysis presented in figure [ fig:185144_unc ] .
the @xmath8 values are always larger because they include the internal uncertainty _ in addition _ to other effects such as stellar jitter and instrument systematics . for bright , quiet stars it is possible to reach @xmath8 values of 1.8 @xmath0.,height=302 ]
to create an efficient and scientifically informative exoplanet survey we must balance scientific interest in a range of target stars with the observing limitations presented by the weather and the telescope s physical constraints .
there are a number of criteria of astronomical importance . for each star ,
the following parameters are utilized by the scheduling software to determine whether the star is given a high rating for observation : * observing priority - a numerical rating that reflects the observers assessment of potential keplerian signals in the rv data . * desired cadence - dictates the desired wait time between observations of a specific target . * desired precision - the average allowable internal velocity uncertainty for measurements of a specific target .
both observing priority and cadence are determined via the observers examination of the star s existing data set . as mentioned in section [ sect : data ] , we use the publicly available systemic console to analyze our rv data sets .
the console produces a lomb - scargle periodogram from the selected rv data set , which displays peaks corresponding to periodic signals in the data . when a peak surpasses the analytic _ false alarm probability _
( fap ) threshold defined by this method , the observers note the period and the half - amplitude of the signal and use those values to decide upon an observing cadence and desired level of precision that will fill out the signal s phase curve quickly and with data points of the appropriate snr .
the desired precision is further refined if the observers have some knowledge of the star s stellar activity , as this sets a lower limit to the attainable precision .
details on the fitting procedures and the statistical capabilities of the systemic console are described in detail in meschiari et .
al , 2009 . for each star
, this information ( along with other characteristics such as right ascension , declination , the v magnitude and the b - v color ) is stored in an on - line google spreadsheet accessible to team members and the telescope software .
this database of target stars drives the survey design and target selection while also being easily accessed , understood and updated by observers . in perfect conditions ( no clouds , no loss of light due to seeing )
all stars that are physically available and deemed in need of a new observation ( based on their cadence ) are simply ranked by observing priority and position in the night sky and then observed one after another , until dawn .
cloud cover and atmospheric turbulence , however , make such conditions rare .
furthermore , stars with low declinations spend only short periods at low air mass .
consequently there are a substantial number of constraints that affect the quality of an exposure . in order to maximize the scientific impact of each night s exposures ,
the conditions must be evaluated dynamically , and data taken only when the desired precision listed in the database is likely to be attainable . to identify the targets that can be expected to attain their desired precision within the one hour observing time limit
, the observing program must link the night - time conditions and the physical characteristics of each star with the resulting internal uncertainty over a given exposure time . to this end
, we first relate the internal uncertainty of a given exposure to the number of photons that fall in the iodine ( i@xmath21 ) line - dense region of the spectrum ( i.e. the @xmath22 bandpass ) where our radial velocity analysis is performed .
we fit the relation between internal uncertainty and photons in the iodine region separately for the g and k star data set ( comprised of 2790 g star exposures and 957 k star exposures ) and the m star data set ( comprised of 837 m star exposures ) .
because information on a star s rv value comes from the location of its spectral lines , we expect the m stars - which contain many more spectral lines - to achieve better precision for the same number of photons .
this expectation is validated by figure [ fig : i2_uncert ] where a vertical offset between the g / k star best - fit line and the m star best - fit line is evident .
comparing the zero points for the best - fit lines ( table 1 ) , we find a factor of 2 difference between the stellar groups .
thus the m stars reach the same level of internal uncertainty with half the number of photons required by the g and k star population . additionally , the slopes of both best - fit lines are close to the _
m_= -2 expected for shot - noise limited observations with _
-1.58 and -1.73 for the g / k and m stars , respectively .
the fact that the slopes are shallower than _
m_= -2 , indicating performance better than shot - noise limited , is reasonable as the internal uncertainty only accounts for the errors resulting from the extraction of the spectrum from the original fits files .
we emphasize that this is just a piece of the error budget , and does not include other random or systematic errors . observations of g ( blue ) , k ( green ) and m ( red ) type stars during the 1.5 years of apf / levy observations .
we plot the individual 2,790 g star exposures , 957 k star exposures and 837 m star exposures .
the gray diamonds represent m star data obtained using keck / hires as part of the lick - carnegie planet survey where the keck / hires pixels have been scaled to match the same /pixel scale as the apf / levy ( @xmath23 /pixel ) .
we find that the g and k stars have the same zero point and the same slope , so we combine these two data sets for this analysis .
the green and blue dashed line represents the best - fit to the apf / levy s combined g and k star dataset , while the red line shows the best - fit to the apf / levy m star data set which is fit separately due to the increase of spectral lines in later spectral types .
as expected , the apf / levy m stars show higher data precision for the same number of photons in the @xmath24 region of the spectrum . the percent errors quoted on the figure
are calculated using the scatter in the difference between the observed @xmath24 photons and the @xmath24 photons from the best - fit lines , so they represent the scatter of the sample and not the error on the mean .
the dark gray line is the best - fit to the keck / hires m star data set . comparing this to
the red line reveals that the apf requires 5.75x fewer photons in the @xmath24 region to achieve velocity precision comparable to keck / hires on m stars down to at least m@xmath25=10.,height=377 ] the functional form of these best - fit lines is given by equation [ eq : i2_unc ] .
note that the numeric values for each variable ( in the case of eq [ eq : i2_unc ] , a and b ) are listed in table 1 .
this format will be used for all relations presented in
[ sect : inputs ] .
functional form of the fits applied in figure [ fig : i2_uncert ] : @xmath26 the gray points in figure [ fig : i2_uncert ] correspond to spectra of m stars obtained with keck / hires since november 2002 as part of the lick - carnegie planet search .
there are 168 stars represented , all with b - v @xmath27 1.2 , resulting in 8872 individual exposures . in order to compare these individual velocities to those obtained on the apf in a meaningful way , we rescale the keck / hires pixels so that they represent the same range of per pixel as those on the the apf / levy .
this involves two different scaling factors as the hires instrument underwent a detector upgrade in 2004 that changed its pixel size from 24@xmath28 to 15@xmath28 , resulting in different sampling values . applying these factors
means that all of the data shown in figure [ fig : i2_uncert ] represents the median number of @xmath29 per pixel , where each pixel covers @xmath23 - the native value for the apf / levy in the @xmath24 region .
the figure shows that for m stars , the apf requires @xmath35.75x fewer photons in the @xmath30 region to achieve velocity precision comparable to keck@xcite , which is proportional to the ratio of the resolutions , @xmath31 . for hires , the `` throughput '' ( the resolving power times the angular size of the slit ) is 39,000 `` @xcite and for the apf it is 114,000''@xcite .
normally hires was used with the 0.861 `` slit giving a filled aperture resolution of 45k while for the levy a 1 '' slit is used , so the ratio of the resolutions is 2.5 .
the levy demonstrates a larger than expected improvement over hires which could be explained by the increased number of lines in the iodine region for m dwarfs .
further investigation is beyond the scope of the current paper but we plan to include such analysis in a future publication .
we note that the excellent seeing at mk means that some data were observed with a much higher effective r , up to 90k , which may explain the large scatter we see in figure 5 . ]
speed estimates for the apf / levy , carried out last year@xcite , show that the telescope and instrument together are approximately 6x slower than keck / hires .
combining these two effects indicates that the apf has essentially the same speed - on - sky as keck / hires for precision rvs of m stars .
this is not altogether unexpected , as hires was never specifically optimized for precision rv work .
the apf s levy spectrograph was purpose - built for high - precision , rv science and therefore features much higher spectral resolution and finer wavelength sampling than hires . both of these factors , as well as the significantly higher system efficiency of the apf / levy optical train over that of keck / hires@xcite ,
combine to make apf as fast as keck / hires for precision rv work on m dwarfs , at least down to m@xmath25=10 . where n@xmath32 is the median number of photons per pixel in the i@xmath21 region for a given exposure , and @xmath33 is the estimated internal uncertainty for the resulting radial velocity value . to assess whether the exposures of these stars represent a gaussian distribution , we compare the standard rms and the scatter calculated using a tukey s biweight method around each fit .
the tukey s biweight scatter provides a more robust statistic for data drawn from a non - gaussian distribution as it less heavily weights the outliers , which are assumed not to be part of a normal distribution @xcite . for the g and k star fit ,
the standard rms is 0.182 while the biweight scatter is 0.186 .
similarly , for the m stars , the standard rms is 0.151 while the biweight scatter comes out to 0.155 . in the limit of a true gaussian distribution
, these two metrics would produce the same result . employing a bootstrap analysis of each method
, we find the standard deviation of both the rms and the biweight scatter of the g and k star sample to be 0.002 .
similarly , the standard deviation of both the rms and the biweight scatter of the m star sample is 0.003 .
noting the similarity of these standard deviations with the actual offsets found between the rms and biweight scatter , we determine that the observations for both sets of stars are drawn from a mostly gaussian distribution . knowing the median number of photons per pixel in the iodine region required to achieve a given level of rv precision enables us to determine the expected exposure time for a star _ if _ we know how quickly those photons accumulate . to determine this rate and the relation between the final exposure meter value and the number of photons in the @xmath24 region ( used to set upper bounds on observing time ) we study a subset of the year of apf data described in section [ sect : data ] .
cuts are applied to the main data set to select only those observations taken on clear nights and in photometric conditions , as non - photometric data will induce skew in the results .
first , we select only exposures with seeing @xmath34 , which results in 935 individual observations .
we then perform separate , multi - variate linear regressions on the photon accumulation rate in the @xmath24 region of the spectrum and the photon accumulation rate for the exposure meter ( eq [ eq : linregress_i2 ] , eq [ eq : linregress_expmeter ] ) on all remaining data points . in each case , we calculate the variance of deviations from the best - fitting relation for all of the data .
we also calculate the variance for all of the points on a given night .
we then reject nights using the f - ratio test .
namely , if the standard deviation of a given night is more than twice the standard deviation of the population as measured by the tukey s biweight then all observations from that night are rejected .
this results in data sets of 865 exposures used in the @xmath24 photon accumulation rate regression and 816 exposures in the exposure meter photon accumulation rate regression .
points that fall significantly below the regression line are most likely due to clouds while those falling above the line are likely due to erroneous readings from the exposure meter .
once the nights with large variance have been removed , we repeat the regressions on the remaining points to determine the actual fits described in section [ sec : regressions ] . in figures [ fig : linregress_i2 ] and [ fig : linregress_expmeter ] the points in color are those used to perform the linear regressions , while the points in gray are those we rejected after they were deemed non - photometric .
figure [ fig : i2_expmeter ] uses the same set of data as figure [ fig : linregress_expmeter ] in order to keep only the normally distributed exposure meter readings . to determine the predicted observation time of a star
, we perform a multi - variate linear regression using the trimmed dataset resulting from the procedure described in the previous section .
the regression estimates the rate at which photons accumulate in the pixels of the iodine region of the spectrum , and accounts for [ 1 ] the star s v magnitude , [ 2 ] its b - v color , [ 3 ] slit loss due to the current seeing conditions , [ 4 ] the airmass based on the star s location and [ 5 ] the modified date of the observation ( figure [ fig : linregress_i2 ] ) .
the modified date is calculated by subtracting the maximum date from each observation following the selection process described above .
this makes the zero point of the relationship the value at the time of the last photometric observation .
we use the modified date parameter to address the degradation of the telescope s mirror coatings over time . when the mirrors are recoated it will introduce a discontinuity in this parameter , and we will then adjust the zero point of all regression fits based on the new throughput estimates and watch for any changes that develop in the slope of the regressions . the multi - parameter fit over these five variables results in a best - fit plane ,
of which we present a projection in figure [ fig : linregress_i2 ] . to help visualize the goodness of fit
, we plot the data on one axis , the linear regression combination on the other and place a 1:1 line on top .
this approach is also used when plotting the linear regression in figure [ fig : linregress_expmeter ] .
multi - variate linear regression of the iodine pixel photon accumulation rate which incorporates stellar color , stellar magnitude , atmospheric seeing and airmass .
colored points are used in calculating the regression , while gray points have been rejected as non - photometric data as described in section [ sec : dataselection ] .
the black line is a 1:1 relationship , and the grey dashed line shows the relation offset by one standard deviation , which is the limit we use operationally .
the strong correlation between the data and the regression line enables prediction of the rate of photon accumulation in the spectrum s iodine region ( a value not calculated until the data reduction process ) using the stellar properties and ambient conditions . we can thus estimate the observation time required to meet a specific median i2 photon value , and , in conjunction with figure [ fig : i2_uncert ] , a radial velocity precision.,height=302 ] the regression gives : @xmath35 with @xmath36 where r@xmath37 is the photon accumulation rate in the iodine region , _ z _ is the angle of the star relative to zenith
, mjd is a modified julian date and @xmath38 is the fraction of the starlight that traverses the spectrograph slit . by dividing the number of @xmath30 region photons necessary to meet our desired rv precision ( derived from eqn [ eq : i2_unc ] ) with the photon accumulation rate in the @xmath30 region calculated using eqn [ eq : linregress_i2 ] , we can determine the predicted observation time for a star for a specified internal uncertainty in a given set of conditions .
these predicted observation times account for atmospheric conditions such as seeing and airmass , but do not address the issue of atmospheric transparency .
the apf lacks an all - sky camera with sufficient sensitivity to assess the brightness of individual stars , meaning that we can not evaluate the relative instantaneous transparency of different regions of the sky .
instead we must determine the transparency during each individual observation by comparing the rate of photon accumulation we observe with what is expected for ideal transparency .
although the @xmath24 region photons provide a straightforward way to determine the predicted exposure times , the number of iodine region photons is available only after the final fits file for an observation has been reduced to yield a radial velocity measurement .
thus we can not monitor in real time the rate at which they are registered by the detector to assess the cloud cover .
instead , we compute a transparency estimate during each exposure using the telescope s exposure meter . the exposure meter is created by using series of 2d images from the guider camera that are updated every 1 - 30 seconds depending on the brightness of the target . rather than guiding on light reflected off a mirrored slit aperture , as is traditionally done
, the apf uses a beamsplitter to provide 4% of incoming light to the guider camera as a fully symmetric , unvignetted seeing disk .
this allows a straightforward way to monitor how well the telescope is tracking its target and provide realtime corrections to both under and over guiding - both of which smear out the telescope s point spread function on the ccd and result in broader full width at half maximum values for spectral lines .
guide cameras that utilize the reflected light off of a mirrored slit aperture are significantly more sensitive to these problems in good seeing , as the majority of the light falls through the spectrograph slit . in our experience , the loss of 4% of the star s light is acceptable if it ensures that the telescope s guiding is steady throughout the night and across the different regions of the sky .
after each guiding exposure is completed , the guide camera then passes the 2d fits images it creates to the sourceextractor software @xcite which analyzes each image and provides statistics on parameters such as the flux and full - width at half - maximum ( fwhm ) , which are in turn used to evaluate the current atmospheric seeing .
these guide camera images are also used to meter the exposures .
each image is integrated over the rectangular aperture corresponding to the utilized spectrograph slit , with background photons ( determined using adjacent , background - estimating rectangles ) subtracted off to determine the number of star - generated photons accumulated by the guide camera .
analysis of the existing apf data suggests that the exposure meter rate ( much like the iodine photon accumulation rate ) depends on the star s color , its v magnitude , the atmospheric seeing ( in the form of slit losses ) , the airmass and the date of observation . a multi - variate linear regression to the exposure meter rate over these five terms results in the correlation displayed in figure [ fig : linregress_expmeter ] .
because the exposure meter is rapidly updated , we can monitor photon accumulation in real - time during an observation .
atmospheric seeing is already incorporated into the @xmath39 term in the linear regression ( eqns [ eq : v_corr ] , [ eq : linregress_expmeter ] ) , so any decrease from the expected exposure meter rate likely stems from an increase in clouds and corresponding decrease in atmospheric transparency .
the ratio of expected exposure meter rate to observed exposure meter rate provides a slowdown " factor that the scheduler tracks throughout the night and multiplies by the predicted ` clear night ' observation times calculated using eqn [ eq : linregress_i2 ] to determine a best guess exposure duration .
multi - variate linear regression to the exposure meter photon accumulation rate , as measured on the apf guider , which incorporates stellar color , stellar magnitude , atmospheric seeing and airmass .
colored points are used in calculating the regression , while gray points have been rejected as described in section [ sec : dataselection ] .
the black line is a 1:1 relation , and the grey dashed line shows the relation offset by one standard deviation , which is the limit we use operationally .
the strong correlation permits prediction of the expected exposure photon accumulation rate for a given star in photometric conditions , and thus provides a measure of the transparency .
any decrease in exposure photon accumulation rate from what is predicted is presumed to arise from decreases in atmospheric transparency brought about by cloud cover.,height=302 ] the regression in figure [ fig : linregress_expmeter ] gives : @xmath40 where r@xmath41 is the photon accumulation rate on the exposure meter , @xmath42 , @xmath43 , @xmath44 and c@xmath41 have the same meanings as in eqn [ eq : linregress_i2 ] but for the exposure meter photon accumulation rate instead of the iodine photon accumulation rate , _ z _ is the star s zenith angle , and v@xmath45 is defined in eqn [ eq : v_corr ] . finally , because of the scatter seen in figures [ fig : linregress_i2 ] and [ fig : linregress_expmeter ] , we must ensure that exposures end when photons sufficient to achieve the desired rv precision have accumulated instead of continuing on for extra seconds or minutes .
photons in the @xmath24 region ca nt be monitored during the observation .
however the apf data set shows a strong relationship between the number of photons obtained in the @xmath24 region of the spectrum and the photons registered by the exposure meter , which is monitored in realtime .
the telescope s guide camera , which is used for the exposure meter , has a broad bandpass and is unfiltered .
this generates a strong color - dependent bias when comparing the guider photons to those that fall in the much narrower @xmath24 region .
we apply a quadratic b - v color correction term to produce the relation shown in figure [ fig : i2_expmeter ] . combining this with the equations identified in figure [ fig : i2_uncert ] ,
we obtain relations that allow us to relate the desired internal precision to the corresponding number of photons in the iodine region of the spectrum , and then to the number of photons required on the exposure meter .
the resulting exposure meter threshold is used to place an upper limit on the exposure .
this is particularly useful on nights with patchy clouds , where the cloud cover estimate calculated during the previous observation can be significantly higher than the cloud cover in other parts of the sky - resulting in artificially high predicted observation times . in this case , the exposure meter can be used to stop an observation if the desired photon count is reached early , improving efficiency .
color - corrected relationship between the photons in the @xmath24 region of the spectrum and the photons registered by the exposure meter .
the black line shows the best - fit , and the grey dashed line shows the relation offset by one standard deviation , which is the limit we use operationally . to increase telescope efficiency
, we require a way to ensure observations do nt continue when the number of iodine region photons necessary to achieve the desired internal uncertainty has already been achieved .
as described in section [ sec : regressions ] there is no way to measure the @xmath24 region photon accumulation in real time .
however , the tight correlation between @xmath24 photons and photons on the exposure meter ( which does update in real time ) displayed here allows us to set a maximum exposure meter value based on our desired precision level .
thus the observation software will end the exposure when the specified exposure meter value is met , even if the open shutter time falls short of the predicted observation time .
this is particularly useful for cases where the cloud cover used in calculating the predicted observation time is actually more than the cloud cover on the target , which would result in an erroneously long observation.,height=302 ] fit applied in figure [ fig : i2_expmeter ] : @xmath46 where r is the ratio of photons on the exposure meter to photons in the iodine region of the spectrum .
the above relations are combined to enable the scheduling algorithm to select scientifically optimal targets .
the following list summarizes the combination scheme . +
* steps to determining an object s predicted observation time and exposure meter cut - off * 1 .
query spreadsheet for stellar attributes ( v , b - v , required precision , ra , dec , observing priority ) .
2 . use equation [ eq : i2_unc ] to determine the desired number of photons in the @xmath30 region of the spectrum .
3 . use equation [ eq : linregress_i2 ] to calculate the observation time required to obtain the desired total number of @xmath24 region photons in ideal transparency conditions .
4 . multiply the slowdown factor , calculated during the previous observation using eqn [ eq : linregress_expmeter ] , with the ideal transparency observation time estimates to get the predicted observation time in current conditions .
calculate the exposure meter threshold based on the required number of @xmath30 region photons using eqn [ eq : i2_expmeter ] .
we find scatters of 11.5% and 11.1% in figures [ fig : linregress_i2 ] and [ fig : i2_expmeter ] respectively ( table 1 ) .
this means that , even on a photometric night , we may not accumulate the number of photons in the @xmath24 region necessary for the desired precision as the photon arrival rate could be too low . to increase the likelihood of getting enough photons to reach the desired number of photons in the @xmath24 region
, we increase the observation time estimate and the exposure meter threshold by 11.5% and 11.1% , or one standard deviation . by implementing this padding factor
we ensure that 84% of the time we observe a target , we will obtain the desired number of @xmath30 photons .
however , this does not necessarily guarantee that we will achieve the desired internal uncertainty , due to the scatter in the relation between the @xmath24 region photons and the uncertainty estimates seen in figure [ fig : i2_uncert ] and quantified in table 1 . using these predicted observation times
, the scheduler can evaluate whether any potential target can be observed at its desired precision within the one - hour observation time limit .
combining the predicted observation times with the targets coordinates determines whether it will remain within the allowed @xmath47 elevation range during the exposure .
stars that satisfy all these criteria are then ranked based on their observing priority , time past cadence requirement , and distance from the moon , with the highest scoring star being selected for observation .
the scheduler then transmits the necessary information for the selected star , including its expected observation time and exposure meter threshold , to the observing software , breaking up the total observation time into a number of individual exposures if necessary .
exposures obtained during 2013 and 2014 indicate that some factors initially suspected to be important need not impact target selection considerations .
for example , the original observing protocol avoided targets within 45@xmath4 of the direction of any wind above 5 mph to avoid wind shake in the telescope .
we find , however , no discernible increase in the internal uncertainty ( indicated by the color scale in figure [ fig : wind_plot ] ) as a function of wind speed or direction .
this resilience likely stems from an effective wind shielding mode for the dome shutters , which opens them just enough to ensure that there is no vignetting of the target star @xcite .
in addition , substantial effort has been put into tuning the telescope s servo motors in order to stiffen " the telescope and thus mitigate the effect of wind gusts that do manage to enter the dome @xcite .
windspeed ( point size ) and direction ( azimuthal position ) plotted for 3155 individual exposures reveals no strong correlation between pointing near / into the wind and the estimated internal uncertainty displayed in the color bar .
the exposures represented in this figure were obtained before we had the means to determine condition - based exposure times .
thus all exposures were run until the reached their exposure meter threshold , or up to a static maximum exposure time of 900s and then terminated , regardless of the number of photons collected by the exposure meter .
this means the wind based effects are not being mitigated by longer exposure times , and wind direction can thus be ignored when deciding which stars are considered viable targets for the next observation.,height=302 ] we also previously assigned higher priority to targets with elevation in the 60 - 70@xmath4 range , removing scientifically interesting targets that were closer to the horizon from consideration . as shown in figure [ fig : el_error ] , however , there is no significant loss in velocity precision as a function of elevation from 90@xmath4 down to 20@xmath4 thanks to the telescope s atmospheric dispersion corrector ( adc ) which works down to 15@xmath4 .
the telescope has a hard observing limit of 15@xmath4 because of the adc s range and because working at lower elevations leads to vignetting by the dome shutters .
we still enforce an elevation range of @xmath47 to avoid mechanical problems in telescope tracking at the high elevations .. working at elevations approaching our lower limit does result in longer predicted observation times ( due to the airmass term ) which can result in stars being skipped over in favor of other , higher elevation targets .
the radial velocity precision as a function of the elevation shows no strong correlation , once we compare observations with a fixed exposure meter value . as our linear regressions in figure 4 and 5 account for the decline in the photon accumulation rate with decreasing elevation
, we do not need to add an additional term to account for other elevation effects such as increased seeing .
similar to the figure [ fig : wind_plot ] , the observations presented here were taken before the adaptive exposure time software was in use .
thus every exposure has a static maximum exposure time of 900s and the low elevation effects are not being mitigated by allowing for longer exposures .
the telescope s adc only functions down to 15@xmath4 , the same elevation at which the telescope begins to vignette on the dome shutter , thus providing the lower limit for our observations.,height=302 ] finally , we no longer assign a weighting value to the slew time necessary to move between targets .
the apf is capable of moving at 3@xmath48 in azimuth and 2@xmath48 in elevation , which means that a direct slew to a target across the sky would take only one minute .
because the ccd takes approximately 40 seconds to read out each observation , this slew time factor is small enough to be considered unimportant .
furthermore , with the introduction of the wind shielding mode , the telescope s movement was altered so that it must first drop to a safe elevation " of @xmath49 before rotating to the target azimuth and then moving upwards to the appropriate elevation .
this is done to protect the primary mirror from falling debris while the dome shutters are reconfigured to minimize wind - effects for the next observation during the slew .
an additional result is that all slews take approximately the same amount of time , which provides justification for discounting slew time as an input to target selection .
in section [ sect : inputs ] , we described a method to predict observation times for targets given their precision requirements and the current atmospheric conditions . to automate the determination of these observation times and the selection of the optimal target at any time throughout the night we have implemented a dynamic scheduler ( written in python ) called heimdallr .
heimdallr runs all of the apf s target selection efforts and interfaces with pre - existing telescope control software so that , once it submits an observation request , it waits until that set of exposures is completed before reactivating .
telescope safety , system integrity , and alerts about current weather conditions are monitored by two services called apfmon and checkapf .
each of these software sets has the ability to override heimdallr if they detect conditions that pose a threat to , or represent a problem with , the telescope .
this ensures that the facility s safety is always given priority .
additionally , while directing the night s operations , heimdallr uses other pre - existing utilities including openatnight , prep - obs and closeup which , as their names suggest , open the facility prior to nightfall ( or when night time conditions warrant ) , prepare the instrument and optical train for observing , and close the facility , securing the telescope when conditions warrant .
the setting of the guider camera , the configuration of dome shutters and the control of telescope movement to avoid interference with the cables wrapped around the telescope base is handled by yet another utility called scriptobs . typically , heimdallr initiates in the afternoon and prompts the instrument control software to focus the instrument by obtaining a dewar focus cube ( series of exposures of the quartz halogen lamp taken through the iodine cell ) using the standard observation slit .
once the software determines a satisfactory value for the instrument s dewar position ( via a simple linear least squares parabolic fit to the focus values ) , it proceeds to take all of the calibration exposures that are required by the data reduction pipeline . upon completing these tasks ,
heimdallr then waits until dusk , at which point it consults checkapf to ensure that there are no problematic conditions in the weather and then apfmon to ensure facility readiness . if both systems report safe conditions , it then opens the dome , allowing the telescope to thermalize with the outside air .
heimdallr runs a main loop that continuously monitors a variety of keywords supplied by the telescope . at 6@xmath4 twilight ,
the telescope is prepped for observing and begins by choosing a rapidly rotating b star from a pre - determined list .
the b star has no significant spectral lines in the @xmath24 region and serves as a focus source for the telescope s secondary mirror while also allowing the software to determine the current atmospheric conditions ( as described in section [ sec : regressions ] ) . at 9@xmath4 twilight
, heimdallr accesses the online database of potential targets and parses it to obtain all the static parameters described in section 3.1 .
it then checks the current date and time and eliminates from consideration those stars not physically available .
the scheduler then employs the stars coordinates , b - v colors and v magnitudes , combined with the seeing and atmospheric transparency determined during the previous observation , to calculate the predicted observation time for each target given their desired precision levels .
stars unable to reach the desired precision within the one hour maximum observation time are eliminated from the potential target list .
the remaining stars are ranked based on scientific priority and time past observing cadence .
the star with the highest score is passed to scriptobs to initiate the exposure(s ) .
when the exposures finish , heimdallr updates the star s date of last observation in the database with the photon - weighted midpoint of the last exposure and begins the selection process anew . when the time to 9@xmath4 morning twilight becomes short enough that no star will achieve its desired level of precision before the telescope must close , heimdallr shuts the telescope using closeup and initiates a series of post - observing calibration exposures .
once the calibrations finish , heimdallr exits .
in addition to making dynamic selections from the target database during the night , heimdallr can also be initiated in a fixed list or ranked fixed list operational mode .
the fixed list mode allows observers to design a traditional starlist that heimdallr will move through , sending one line at a time to scriptobs .
any observations that are not possible ( due to elevation constraints ) will be skipped and the scheduler will simply move to the next line .
the ranked fixed list option allows users to provide a target list that heimdallr parses to determine the optimal order of observations .
that is , after finishing one observation from the list , the scheduler will then perform a weighting algorithm similar to what is employed by the dynamic use mode to determine which line of the target list is best observed next .
heimdallr keeps track of all the lines it has already selected , so that they do not get initiated twice , and will re - analyze the remaining lines after each observation to select the optimal target .
this option is especially useful for observing programs that have a large number of possible targets but do nt place a strong emphasis on which ones are observed during a given night .
there are a number of automated and semi - automated facilities that perform similar observations .
examples include harps - n , carmenes , the robo - ao facility at palomar and the las cumbres observatory global telescope ( lcogt ) network . in order to place the apf s operations in context relative to these other observatories
, we will briefly discuss the approaches of these other dedicated radial velocity facilities ( carmenes , harps - n , and the nres addition to lcogt ) and of the more general facility with queue scheduling ( robo - ao ) .
we will then highlight the common approaches along with discussing what is simpler for our facility as it is dedicated to a single - use .
radial velocity surveys generally require tens or hundreds of observations of the same star to detect planetary companions .
traditionally , high - precision velocities were obtained on shared - use facilities and observing time was limited .
more recently , however , purpose built systems ( such as harps ) have presented the opportunity to obtain weeks or months of contiguous nights .
the harps - n instrument , installed on the telescopio nazionale galileo at roque de los muchachos observatory in the canary islands , is a premier system for generating high - precision velocities . at present , it is primarily devoted to kepler planet candidate follow up and confirmation .
the system allows users to access xml standard format files that define target objects using the short - term - scheduler gui ( sts ) to guide the process and then assemble the objects into an observing block .
when an observer initiates an observation , these blocks and their associated observing preferences are passed to the harps - n sequencer software , which places all of the telescope subsystems into the appropriate states , performs the observation , and then triggers the data reduction process @xcite .
thus , while the building of target lists has been streamlined , nightly observation planning still requires attention from an astronomer or telescope technician .
the forth - coming calar alto carmenes instrument is expecting first light in 2015 .
+ carmenes will also be used to obtain high - precision stellar radial velocity measurements on low - mass stars .
its automated scheduling mechanism relies on a two - pronged approach : the off - line scheduler which plans observations on a weekly to nightly time scale based on target constraints that can be known in advance , and the on - line scheduler which is called during the evening if unexpected weather or mechanical situations arise and require adapting the previously calculated nightly target list @xcite .
finally , the lcogt network will soon implement the network of robotic echelle spectrographs ( nres ) , six high resolution optical echelle spectrographs slated for operation in late 2015 .
like all instruments deployed on the lcogt network , the scheduling and observing of nres will be autonomous .
users submit observing requests via a web interface which are then passed to an adaptive scheduler which works to balance the requests observing windows with the hard constraints of day and night , target visibility , and any other user specified constraints ( e.g. exposure time , filter , airmass ) .
if the observation is selected by the adaptive scheduler , it creates a block " observation tied to a specific telescope and time .
this schedule is constructed 7 days out , but rescheduling can occur during the night if one or more telescopes become unavailable due to clouds , or if new observing requests arrive or existing requests are canceled . in this event , the schedule is recalculated , and observations are reassigned among the remaining available sites @xcite .
robo - ao is the first fully automated laser guide star adaptive optics instrument .
it employs a fully automated queue scheduling system that selects among thousands of potential targets at a time with an observation rate of @xmath50 objects @xmath51 .
its queue scheduling system employs a set of xml format files which use keywords to determine the required settings and parameters for an observation .
when requested , the queue system runs each of the targets through a selection process , which first eliminates those objects that can not be observed , and then assigns a weight to the remaining targets to determine their priority in the queue at that time .
the optimal target is chosen , and the scheduler passes all observation information to the robotic system and waits for a response that the observations were successfully executed .
once the response is received , the observations are marked as completed and the relevant xml files are updated @xcite .
we have designed this system based on our rv observing program carried out over the past 20 years at keck and other facilities .
this experience , coupled with the preexisting software infrastructure , has guided the development of both the dynamic scheduler software itself and our observing strategy .
comparison to these other observing facilities and the strategies they employ emphasizes some shared design decisions .
for example , the apf has a similar target selection approach to that of the robo - ao system .
both utilize a variety of user specified criteria to eliminate those targets unable to meet the requirements and then rank the remaining targets , passing the object with the highest score to the observing software .
additionally , as is common with all of the observing efforts mentioned above , our long term strategy is driven by our science goals and is in the hands of the astronomers involved with the project .
several differences are also notable .
the first is that we lack an explicit long term scheduling component in our software .
our observing decisions are made in real time in order to address changes in the weather and observing conditions that occur on minute to hour time scales , and to maximize the science output of nights impacted by clouds or bad seeing .
however , for a successful survey there must also be a longterm observing strategy for each individual target .
we address this need via a desired cadence and required precision for every potential target . by incorporating the knowledge of how often each star needs to be observed and a way to assess whether the evening s conditions are amenable to achieving the desired precision level , heimdallr adheres to the longterm observing strategy outlined by our observing requirements and does nt need to generate separate multi - week observing lists .
a second difference is that the final output of the scheduler is a standard star list text file , one line in length .
this format has been in use in uco - supported facilities such as lick and keck observatories for more than 20 years , and thus is familiar to the user community .
the file is a simple ascii text file with key value pairs for parameters and a set of fixed fields for the object name and coordinates .
this permits ready by - eye verification of the next observation if desired and allows the user to quickly construct a custom observing line that can be inserted into the night s operations if needed .
observers can furthermore easily make a separate target list in this format for observations when not using the dynamic scheduler ( see sec [ sect : modes ] ) finally , we use a google spreadsheet for storing target information and observing requirements , as opposed to a more machine - friendly format such as xml .
although lick observatory employs a firewall to sharply limit access to the apf hosts , it only operates on the incoming direction .
thus it is straightforward and non - compromising from a security standpoint for our internal computers to send a request to google and pull the relevant data back onto the mountain machines .
this approach provides team members with an accessible , easy - to - read structure that is familiar and easily exportable to a number of other formats .
google s version control allows for careful monitoring of changes made to the spreadsheet and ensures that any accidental alterations can be quickly and easily undone .
the use of the google software also allows interaction with a browser , so no custom gui development is required .
therefore , we are taking advantage of existing software to both minimize our development effort , and make it as easy as possible to have the scientists update and maintain the core data files that control the observations .
the apf has operated at high precision for over a year , and has demonstrated precision levels of @xmath52 @xmath0on bright , quiet stars such as sigma draconis@xcite . the telescope s slew rate permits readout - limited cycling and 80 - 90% open shutter time , allowing for 50 - 100 doppler measurements on clear nights .
heimdallr s design dovetails with the need to automate the continued selective monitoring of more than 1,000 stars observed at high doppler precision at keck over the past 20 years @xcite .
the apf achieves a superior level of rv precision and much - improved per - photon efficiency in comparison to keck / hires for target stars with v < 10 . as a primary user
, we can employ the apf on 100 + nights per year in the service of an exoplanet detection survey . at present
, 127 stars have been prioritized for survey - mode observation with the apf .
this list emphasizes stars that benefit from the telescope s more northern location , and gives preference to stars that display prior evidence of planetary signals .
we adopt a default cadence of 0.5 observations per night . when a star is selected , it is observed in a set of 5 - 15 minute exposures with the additional constraint that the total of a night s sequential exposures ( the observation time ) on the star is less than an hour . additionally , information obtained at keck has , in some cases , permitted estimates for the stellar activity of specific target stars . in these cases ,
observation times can be adjusted to conform to a less stringent desired precision . with its ability to predict observation times
, heimdallr readily achieves efficiencies that surpass the use of fixed lists , and indeed , its performance is comparable to that of a human observer monitoring conditions throughout the night .
heimdallr is readily adopted to oversee a range of observational programs , and a particularly attractive usage mode for apf arises in connection with nasa s transiting exoplanet survey satellite ( tess ) mission .
tess is scheduled for launch in 2017 , and is the next transit photometry planet detection mission in nasa s pipeline @xcite .
transit photometry observations of potential planet signatures generally require follow - up confirmation , with rv being the most common .
currently there is a dearth of high - precision rv facilities in the northern hemisphere , and harps - n is heavily committed to kepler planet candidate follow up .
nasa recently announced plans to develop an instrument for the 3.5 m wiyn telescope at kitt peak observatory capable of extreme precision doppler spectrography to be used for follow up of tess planet candidates @xcite .
however such an instrument will require time for development and commissioning and thus is not a viable candidate for pre - launch observations of tess target stars .
the apf s year - round access to the bright stars near the north ecliptic pole , which will obtain the most observation time from tess , makes it an optimal facility to conduct surveys in support of the satellite s planet detection mission . at present , comparatively little is known about the majority of tess s target stars .
we have little advance knowledge of which stars host properly inclined , short - period transiting planets observable by the satellite .
we will thus start with a default value for the observing cadence and be poised to adapt quickly should hints of planetary signatures start to emerge .
additionally , initial desired precisions ( and the corresponding observation times ) must rest on the suspected stellar jitter of the targets .
the availability of on - line databases to track all of the science - based criteria will be crucial for moving back and forth quickly between this project and further lick - carnegie follow up .
evaluations of the value of apf coverage are governed by three scientific criteria ( priority , cadence and required precision ) , along with supporting physical characteristics ( ra , dec , v and b - v ) for each target .
thus when beginning rv support for tess , heimdallr can easily be instructed to reference the tess database when determining the next stellar target ( instead of the lick - carnegie list ) .
tess observations also provide an excellent test bed for experimenting with alternate observational strategies .
for example , sinukoff et al .
( 2014)@xcite stated that obtaining three 5-minute exposures of a star spaced approximately two hours apart from one another during the night results in a 10% increase in precision over taking a singe 15 minute exposure .
the tess stars that will be monitored by the apf are all located in the north ecliptic pole region , meaning that the slew times will be almost negligible .
it is thus likely that an observing mode that subdivides exposures to improve precision could be very valuable . in short ,
the apf is extremely well matched to the tess mission .
we are pleased to acknowledge support from the nasa tess mission through mit sub award # 5710003702 .
we are also grateful for partial support of this work from nsf grant ast-0908870 to ssv , and nasa grant nnx13af60 g to rpb .
this material is based upon work supported by the national aeronautics and space administration through the nasa astrobiology institute under cooperative agreement notice nnh13zda017c issued through the science mission directorate .
this research has made use of the simbad database , operated at cds , strasbourg , france .
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, _ society of photo - optical instrumentation engineers ( spie ) conference series _ * 9143 * , 20 ( 2014 ) . | we report initial performance results emerging from 600 hours of observations with the automated planet finder ( apf ) telescope and levy spectrometer located at uco / lick observatory .
we have obtained multiple spectra of 80 g , k and m - type stars , which comprise 4,954 individual doppler radial velocity ( rv ) measurements with a median internal uncertainty of 1.35 @xmath0 .
we find a strong , expected correlation between the number of photons accumulated in the 5000 - 6200 iodine region of the spectrum , and the resulting internal uncertainty estimates .
additionally , we find an offset between the population of g and k stars and the m stars within the data set when comparing these parameters . as a consequence of their increased spectral line densities ,
m - type stars permit the same level of internal uncertainty with 2x fewer photons than g - type and k - type stars . when observing m stars , we show that the apf / levy has essentially the same speed - on - sky as keck / hires for precision rvs . in the interest of using the apf for long - duration rv surveys , we have designed and implemented a dynamic scheduling algorithm .
we discuss the operation of the scheduler , which monitors ambient conditions and combines on - sky information with a database of survey targets to make intelligent , real - time targeting decisions .
: jennifer burt , uco / lick observatory , 1156 high st , santa cruz , usa , 95060 ; e - mail : |
in the 1960 s , belinskii , khalatnikov , and lifshitz ( bkl ) developed a formalism to analyze the approach to the singularity in spatially inhomogneous cosmologies @xcite .
they argued that , while one can construct , over any short time interval , a local kasner solution @xcite , this type of solution can not be maintained indefinitely since terms inconsistent with it can not remain subdominant .
rather , the generic solution will behave as a spatially homogeneous mixmaster cosmology @xcite at every spatial point . for a long time , this analysis remained controversial , primarily due to its non - rigorous nature .
recently , in a series of papers @xcite , we and our collaborators have used an analytic method , simpler than but not unrelated to that of bkl , along with detailed numerical simulations to provide strong support for the bkl picture .
in addition , our methods have clarified how einstein s equations control the approach to the singularity .
the essence of our method of consistent potentials ( mcp ) developed originally by grubisi and moncrief @xcite is to solve the velocity term dominated ( vtd ) equations obtained by neglecting all terms containing spatial derivatives in einstein s equations .
we then substitute the asymptotic form of the vtd solution ( with spatially dependent parameters ) into the neglected terms .
if these terms are all exponentially small , the vtd solution is consistent .
this in turn supports a conjecture that the approach to the singularity is asymptotically vtd ( avtd ) i.e. , at almost every spatial point , the full solution comes arbitrarily close to a vtd solution as the singularity is approached @xcite . on the other hand , if one or more of the neglected terms grows exponentially , then the vtd solution is inconsistent so that the conjectured behavior is not avtd .
if two or more previously neglected terms will alternately always grow for any range of vtd solution parameters , then the mcp predicts that the solution will be oscillatory and the oscillations will persist forever .
if there exists a range of parameter values consistent with a vtd solution almost everywhere , the prediction is that oscillations will persist only until the parameters are driven into the consistent range @xcite . for the mcp to predict the correct behavior , the only dynamically significant time dependences , sufficiently close to the singularity
, must be the linear ones from the vtd solutions which appear in the arguments of the exponential potentials .
perhaps surprisingly then , the mcp predictions have been verified by numerical simulation of the full einstein equations in all models we have studied so far @xcite .
the previous discussion of the application of the mcp makes no appeal to an invariant description of the system .
one then wonders whether or how this picture depends on the choice of variables and of spacetime slicing .
there is also an issue of the nature of oscillatory behavior observed in spatially inhomogeneous cosmologies @xcite .
the bkl claim is that these models should evolve as a vacuum bianchi type ix ( mixmaster ) universe at every spatial point . in the mcp
applied to the minisuperspace ( mss ) picture of vacuum , homogeneous bianchi type ix models , the vtd is the kasner solution .
this solution is inconsistent with maintaining exponential smallness of the three exponential wall terms in the mss potential leading to the usual infinite sequence of bounces off a closed triangular potential @xcite .
however , we found that vacuum @xmath0 symmetric cosmologies on @xmath1 exhibit oscillations between two potentials ( rather than three ) at every spatial point @xcite . at the time
, we did not know if these represented `` true '' mixmaster oscillations or something else . in this paper
, we shall describe spatially homogeneous bianchi type ix universes on @xmath4 as @xmath0 symmetric cosmologies with the same topology by rewriting the bianchi type ix spatial metric in a coordinate frame @xcite .
the objective of this exercise is to see how the standard mixmaster oscillations are described in the @xmath0 variables used in our previous studies .
we find that the relationship between the mss and @xmath0 descriptions of the mixmaster universe is not trivial . in the coordinate representation of the bianchi type ix homogeneous space ,
one of the killing vectors is still manifest and is taken to play the role of the spatial @xmath0 symmetry .
the norm of that killing vector is the key variable in our previous description of generic , spatially inhomogeneous @xmath0 models .
here we find its behavior to be dominated by the largest logarithmic scale factor ( lsf ) of the standard bkl description .
the bounces off one of the @xmath0 potentials occur when the time derivative of the dominant lsf changes sign .
this is what happens in the standard mss picture in a bounce off any of the three potential walls .
the other @xmath0 potential causes a bounce when one lsf loses its dominant place to another in the mss picture .
this correspondance will be discussed extensively in this paper .
although numerical analysis of inhomogeneous @xmath0 symmetric cosmologies revealed only the two types of bounces described above , our study of the @xmath0-mss correspondance for the mixmaster universe demonstrates that a third type of bounce can occur at the end of a bkl era @xcite when the monotonically decreasing smallest lsf starts increasing and overtakes the middle one .
this yields a qualitative prediction not yet observed numerically which can distinguish between local mixmaster dynamics and other oscillatory behavior . in section
ii , we shall review the mss picture and , in section iii , the @xmath0 variables .
note that in this paper , we shall often use `` @xmath0 '' to refer to properties of the @xmath0 symmetric cosmologies .
the correspondance between the @xmath0 models and the mixmaster models will be discussed in section iv with the implications of the correspondance given in section v. conclusions will be drawn in section vi .
a vacuum , diagonal bianchi type ix mixmaster cosmology is described by the metric @xcite @xmath5 where the scale factors @xmath6 , @xmath7 , and @xmath8 are functions of @xmath9 only and @xmath10 it is often convenient to define the lsf s @xmath11 , @xmath12 , and @xmath13 by @xmath14 the @xmath15 symmetry ( [ bianchi9 ] ) may be realized in a coordinate frame by @xmath16 on @xmath17 .
the choice of time coordinate @xmath18 where @xmath19 is comoving proper time , is that used by bkl .
an alternate , but equivalent description , was given by misner @xcite in terms of the mss variables @xmath20 , the logarithmic volume , and @xmath21 , the anisotropic shears , where @xmath22 this variable choice conveniently allows einstein s equations to be obtained by variation of the superhamiltonian @xmath23\ ] ] where @xmath24 is the determinant of the spatial metric @xmath25 with conjugate momenta @xmath26 while @xmath27 is the scalar curvature of @xmath25 and @xmath28 is the hamiltonian constraint . with @xmath29 , @xmath30
canonically conjugate to @xmath20 , @xmath21 respectively , and the time coordinate choice @xmath31 , eq .
( [ generalh0 ] ) becomes @xmath32 for the mss potential @xmath33 when @xmath34 is exponentially small , the metric is locally ( neglecting the topology ) the kasner solution .
generically , in the evolution toward the singularity , one of the first three terms on the right hand side of eq .
( [ msspot ] ) the one associated with the largest lsf will grow .
a `` bounce '' off the exponential potential will change the sign of the time derivative of the dominant lsf changing one kasner solution into another .
conservation of momentum in the bounce was first used by bkl to relate the two asymptotic kasner solutions . in terms of the lsf s , einstein s evolution equations for the mixmaster model are ( for overdot indicating @xmath35 ) @xmath36 , \nonumber \\
\ddot \zeta & = & { 1 \over 2 } \left [ \left ( e^{2 \gamma } - e^{2 \alpha } \right)^2 - e^{4 \zeta } \right ] , \nonumber \\
\gamma & = & { 1 \over 2 } \left [ \left ( e^{2 \alpha } - e^{2 \zeta } \right)^2 - e^{4 \gamma } \right].\end{aligned}\ ] ] if the initial kasner solution is characterized by a given @xmath37 and the dominant potential term is @xmath38 , then from eqs .
( [ mixeqs ] ) the final asymptotic kasner solution with @xmath39 will have @xmath40 , @xmath41 , @xmath42 .
various schemes exist to encode this information @xcite . if , initially , @xmath43 , then initially @xmath44 while @xmath45 , @xmath46 since the ( collapsing ) kasner solution generically has only one expanding direction .
this means that @xmath11 increases while the others decrease . after a typical bounce
, the above bounce rules yield @xmath47 , @xmath48 while @xmath49 has increased but is still negative . in subsequent bounces
, @xmath11 and @xmath12 will continue to oscillate while @xmath13 decreases monotonically but with ever decreasing @xmath50 .
( each kasner regime between the bounces is called an epoch . )
eventually , @xmath49 will change sign .
this is called the end of an era . if @xmath51 prior to this era ending bounce , we find that , asymptotically , @xmath52 after the bounce . subsequently , @xmath12 and @xmath13 oscillate while @xmath11 decreases monotonically .
this sequence of eras apparently @xcite persists indefinitely .
part of a typical mixmaster evolution is shown in fig . 1 .
@xmath0 symmetric cosmologies on @xmath2 are described by the metric @xcite @xmath53 where the symmetry direction is @xmath54 , and the other spatial directions are @xmath55 .
the metric variables are assumed to be functions of @xmath56 , @xmath57 , and @xmath9 .
the norm of the killing field is @xmath58 , @xmath59 are the `` twists '' , @xmath60 is the determinant of the 2-metric @xmath61 and @xmath62 is parametrized by @xmath63 and @xmath64 via @xmath65 \ .\ ] ] note that the metric @xmath66 differs from that for @xmath67 spatial topology given in @xcite .
it is convenient to make a canonical transformation from the twists and their conjugate momenta @xmath68 to the twist potential @xmath69 and its conjugate momentum @xmath70 .
it is also convenient to define the spacetime slicing by zero shift and lapse @xmath71 where @xmath72 is the determinant of the 2-metric @xmath73 .
einstein s equations are found by variation of @xmath74 \nonumber \\ & & \left .
+ 2e^\lambda e^{ab}\varphi , _
a\varphi , _
b+{1 \over 2 } e^\lambda e^{-4\varphi } e^{ab}\omega , _
a\omega , _
b \right\ } \right ] \end{aligned}\ ] ] where @xmath75 is the hamiltonian constraint and the overall trigonometric factor comes from @xmath76 .
an excellent approximation to the behavior seen in numerical simulations of these models ( albeit on @xmath67 rather than @xmath17 ) is that at each spatial point a kasner - like phase characterized by @xcite @xmath77 ( where @xmath78 , @xmath79 , @xmath80 , @xmath81 , @xmath82 , @xmath83 , and @xmath84 are functions of @xmath56 and @xmath57 but independent of @xmath9 ) is followed by a `` bounce '' off one of the three potentials @xmath85 in eqs .
( [ u1pots ] ) , the potentials are defined to be identical to those in @xcite .
( it is possible to incorporate the prefactor @xmath76 from eq .
( [ hu1 ] ) into the potentials .
however , this factor depends on topology . in section
v we shall see that only the ( subdominant ) logarithm of this factor would appear in the variables of interest and would not affect the qualitative behavior . )
if one assumes incident and final asymptotic solutions of the form ( [ vtdsoln ] ) at a given spatial point and that @xmath70 , @xmath69 , @xmath63 , and @xmath86 are constant in time through the bounce , the remaining momenta @xmath87 , @xmath88 , and @xmath89 at that point will change during a bounce off one of the potentials according to the following rules : \(1 ) for a bounce off @xmath90 , @xmath91 with the other momenta conserved .
\(2 ) for a bounce off @xmath92 , @xmath93 these rules are obtained by recognizing that , for @xmath64 large and negative , @xmath94 is dominated by @xmath95 so that @xmath96 where @xmath97 is approximately constant in time
. then @xmath98 defines the direction ( in a local mss ) in which the conjugate momentum changes sign during a bounce with momenta in the plane orthogonal to that direction conserved .
\(3 ) for a bounce off @xmath99 , @xmath100 with the other momenta conserved .
\(4 ) in all cases , the momenta must satisfy an asymptotic form of the hamiltonian constraint ( [ hu1 ] ) given by @xmath101 eq .
( [ h0lim ] ) is obtained from eq .
( [ hu1 ] ) by assuming that all terms containing exponential potentials are exponentially small . in numerical simulations performed so far @xcite ,
the dominant local behavior is oscillation of @xmath102 due to bounces off @xmath90 and @xmath92 .
a bounce off @xmath99 has been seen only if @xmath103 initially .
note that the rule ( [ v2rules ] ) for a bounce off @xmath92 becomes @xmath91 if @xmath104 implying @xmath105 ( from eq .
( [ h0lim ] ) ) .
our simulations provide strong support for bkl s claim that the approach to the singularity in generic cosmological spacetimes is oscillatory .
the remaining question then is whether or not this oscillatory behavior represents local mixmaster dynamics .
by writing the mixmaster metric ( [ mixmetric ] ) ( denoted @xmath106 in this section ) in the coordinate frame on @xmath17 given by eq .
( [ sigmas ] ) and comparing it to the @xmath0 metric ( [ u1metric ] ) ( denoted @xmath107 in this section ) , each @xmath0 variable @xmath102 , @xmath64 , @xmath108 , @xmath69 , or @xmath63 and its conjugate momentum may be expressed in terms of the bkl scale factors @xmath6 , @xmath7 , and @xmath8 and their time derivatives .
the explicit killing direction @xmath54 will be identified with the @xmath0 symmetry direction @xmath109 so that @xmath110 or @xmath111 the twists @xmath112 and @xmath113 in @xmath107 are determined from @xmath114 and @xmath115 so that @xmath116 then the @xmath0 model 2-metric ( here denoted as @xmath61 ) is found from @xmath117 comparison of eqs .
( [ mixmetric ] ) and ( [ u1metric ] ) with eqs .
( [ e2phi ] ) and ( [ betas ] ) , computation of the determinant of @xmath72 , and the expression of @xmath62 in terms of @xmath63 and @xmath64 ( see eq .
( [ eab ] ) ) leads to @xmath118 @xmath119}},\ ] ] @xmath120 \cos(2\theta ) + ( a^2-b^2)c^2 \cos(2\phi ) } \over { a^2 b^2 + a^2 c^2 + b^2 c^2 - a^2 b^2 \cos ( 2 \theta ) + ( a^2 - b^2 ) c^2 \cos [ 2(\theta -\phi ) ] } } \ .\ ] ] we note that @xmath121 our gauge condition in @xcite ( modified for @xmath17 ) is @xmath122 . but
this is the `` 2-dimensional lapse . ''
the 3-dimensional lapse is @xmath123 so that @xmath124 which is just the usual bkl lapse condition @xcite .
this means that the time variable @xmath9 chosen in @xmath0 models is the same as the usual bkl time @xmath9 .
it is now necessary to consider the canonical transformation which replaces @xmath59 and its conjugate momentum @xmath68 subject to the constraint @xcite @xmath125 by @xmath69 and its canonically conjugate momentum @xmath70 where @xmath126 for @xmath127 . in these variables ,
@xmath68 may be found from the einstein equation for the time derivative of @xmath59 @xcite : @xmath128 we find @xmath129 to give @xmath130 where @xmath131 is an as yet undertermined function of time .
the momentum conjugate to @xmath69 is defined by an integrability condition @xcite so that @xmath132 \right \ } .\end{aligned}\ ] ] it is easily checked that @xmath133 as is required . from the @xmath0 symmetric model hamiltonian ( [ hu1 ] ) , we obtain @xmath134 so that @xmath135 where @xmath136 is a constant .
the other momenta @xmath87 , @xmath88 , @xmath89 , @xmath86 may also be found from the equations of motion for @xmath137 , @xmath138 , @xmath139 , @xmath140 respectively and are given for completeness in the appendix .
given all the variables , it becomes a simple matter to construct all the terms in the @xmath0 hamiltonian ( [ hu1 ] ) .
in particular , we shall consider @xmath141 } \right\}^2 \nonumber \\ & & /\left [ { 2\left ( { c^2\cos ^2\theta + b^2\cos ^2\phi \;\sin
^2\theta + a^2\sin
^2\phi \;\sin ^2\theta } \right ) } \right]^2,\end{aligned}\ ] ] @xmath142\sin ^2(2\phi ) \left ( { b\dot a - a\dot b } \right)^2 } \right.\nonumber \\ & & + 4\cos ^2\theta \left ( { b^2\cos ^2\phi + a^2\sin ^2\phi } \right ) \left [ { ac\dot b\cos ^2\phi + b\left ( { c\dot a\sin ^2\phi -a\dot c } \right ) } \right]^2 \nonumber \\ & & + 4\left ( { a^2-b^2 } \right)c\cos ^2\theta \cos \phi \sin \phi \sin ( 2\phi ) \left ( { a\dot b - b\dot a } \right)\left [ { -ac\dot b\cos ^2\phi } \right .
\nonumber \\ & & \left .
{ + b\left ( { a\dot c - c\dot a\sin ^2\phi } \right ) } \right ] } \right\}/\left\ { { 2a^2b^2\left [ { c^2\cos ^2\theta + \sin ^2\theta \left ( { b^2\cos ^2\phi + a^2\sin ^2\phi } \right ) } \right]^2 } \right\},\end{aligned}\ ] ] @xmath143\dot b } \right .
\nonumber \\ & & + b^3\cos \phi \sin ^2\theta \sin ( \theta -\phi ) \left ( { c\dot a - a\dot c } \right)+b\cos ( \theta -\phi ) \left [ { c^3\dot a\cos \theta \sin ( \theta -\phi ) } \right .
\nonumber \\ & & \left .
{ -a^3\dot c\sin ^2\theta \sin \phi } \right ] } \right\}^2/\left\ { { \left\ { { a^2\left [ { c^2\cos ^2(\theta -\phi ) + b^2\sin ^2\theta } \right ] } \right . }
\nonumber \\ & & \left .
{ + b^2c^2\sin ^2(\theta -\phi ) } \right\}^2\left [ { c^2\cos ^2\theta + \sin ^2\theta \left ( { b^2\cos ^2\phi + a^2\sin ^2\phi } \right ) } \right ] } \right\ } , \end{aligned}\ ] ] and the factor @xmath144+b^2c^2\sin ^2(\theta -\phi ) } \right\ } .\ ] ]
as was described in @xcite , the key to the dynamics of the @xmath0 models is the behavior of the variable @xmath102 . in the approach to the singularity , one bkl scale factor always dominates .
the nature of mixmaster dynamics is that a bounce occurs when one scale factor is @xmath145 ( with the corresponding lsf @xmath146 ) .
the other scale factors are @xmath147 with the corresponding lsf s large and negative
. we shall thus refer to scale factors and functions thereof as `` order unity '' ( @xmath148 ) or `` exponentially small '' ( @xmath147 ) . during the kasner epochs ( away from the bounces ) ,
all the scale factors are exponentially small .
assume that during a kasner epoch @xmath149 and define @xmath150 , @xmath151 , and @xmath152 so that @xmath153 , @xmath154 , and @xmath155 are @xmath156 .
the following discussion can be changed to reflect any other ordering of the scale factors by performing the appropriate permutation while keeping in mind that different scale factors will be associated with different @xmath157 dependences . from eq .
( [ e2phi ] ) , we see that @xmath102 is dominated by the largest lsf . for our chosen ordering , @xmath158.\ ] ] since the ( _ ersatz _ ) spatial dependence appears in the logarithm , the spatially homogeneous behavior dominates at any particular spatial point .
note also that if @xmath153 and @xmath155 are exponentially small , @xmath159 at a generic spatial point .
figure 2 shows a superposition of @xmath102 constructed from eq .
( [ e2phi ] ) on the same graph as fig . 1 .
the scale factors are obtained from a numerical simulation of the mixmaster ode s @xcite .
note that @xmath102 changes sign in two ways .
if @xmath160 ( @xmath161 ) , @xmath102 will `` bounce '' when the scale factor which dominates it bounces .
this is the usual mixmaster bounce .
however , @xmath137 also changes sign , after the usual bounce , when the now - increasing scale factor ( @xmath7 in our case ) becomes as large as the decreasing dominant scale factor ( @xmath6 in our case ) . evaluating @xmath90 from eq .
( [ u1v1mix ] ) when @xmath149 , we find , for @xmath153 , @xmath154 , and @xmath155 exponentially small , that @xmath162 i.e. bounces off @xmath90 correspond to the usual mixmaster bounces .
this is not surprising since @xmath90 comes from terms in the spatial scalar curvature .
( it appears in the `` kinetic '' part of the hamiltonian constraint because the canonical transformation @xmath163 interchanges momentum and configuration variables . )
if we assume the kasner time dependence@xmath164 , @xmath165 , and @xmath166 ( recalling that @xmath167 while the kasner solution is @xmath168 , for @xmath169 a constant , etc . ) , we find in evaluating @xmath92 from eq .
( [ u1v2mix ] ) that the dominant scale factor @xmath6 does not appear so that ( for @xmath155 exponentially small ) , @xmath170 implying that @xmath92 is exponentially small unless @xmath171 is order unity rather than exponentially small . but
@xmath172 corresponds to the change in the dominant scale factor from @xmath6 to @xmath7 as @xmath6 decreases while @xmath7 increases after the standard mixmaster bounce .
thus bounces off @xmath92 in terms of the @xmath0 variables correspond to the change in the identity of the dominant scale factor as seen in the behavior of @xmath102 in fig . 2 .
figure 3 illustrates the interplay among @xmath90 , @xmath92 , and @xmath102 which is very similar to that seen in generic @xmath0 models ( see figs .
25 in @xcite ) .
an effect not mentioned in our previous studies of generic @xmath0 models appears when we consider the variable @xmath64 . for @xmath149 , and @xmath153 and @xmath154 exponentially small but @xmath155 not necessarily @xmath147 , we find from eq .
( [ zequiv ] ) that @xmath173 i.e .
@xmath64 decreases monotonically ( is dominated by the most negative lsf ) unless the era ends and @xmath8 grows to be as large as @xmath7 so that @xmath174 . the behavior of @xmath64 is shown in fig . 4 for the same simulation as in the other figures
figure 5 shows @xmath11 , @xmath12 , @xmath13 , and @xmath64 in the region of a bounce which changes the sign of @xmath79
. the bounce rules ( [ v2rules ] ) imply that such a sign change is possible if @xmath175 .
of course , @xmath176 will eventually cause a bounce off @xmath99 .
this rise of @xmath64 , qualitatively indicating the end of a mixmaster era , has not been observed in previously published simulations of @xmath0 models @xcite .
however , in fig .
6a of @xcite , it is seen that @xmath79 changes during bounces off @xmath92 .
it is also seen that the magnitude of @xmath79 decreases at such bounces just as in fig .
presumably , if the simulations could be followed to larger @xmath9 , @xmath64 would eventually begin to increase as @xmath79 changes sign .
6a of @xcite also shows @xmath108 decreasing monotonically with decreasing magnitude of the slope @xmath80 .
the bounce rules ( [ v2rules ] ) do not permit the sign of @xmath80 to change since eq .
( [ h0lim ] ) may be used to show that @xmath177 is always @xmath178 . in @xcite ,
it was argued that all terms in @xmath179 ( from eq .
( [ hu1 ] ) ) containing spatial derivatives , except for @xmath92 , were proportional to @xmath180 . if @xmath149 in a mixmaster model , @xmath181 $ ] which is always exponentially small since @xmath182 and @xmath183
of course , @xmath184 which is always exponentially small .
thus , we have shown that all the observed generic @xmath0 behavior described in @xcite is characteristic of mixmaster behavior expressed in @xmath0 variables . in order for this to be correct
, we also expect the remaining variables @xmath69 and @xmath63 and all the momenta to be of order unity at all times so that , generically , they may be regarded as approximately constant in time .
this assumption underlies the mcp .
we find that @xmath69 is independent of the scale factors with @xmath185 we consider the approximate forms of the remaining variables for the case @xmath149 with @xmath153 , @xmath154 , and @xmath155 exponentially small .
we find @xmath186
describing a mixmaster universe as a @xmath0 symmetric cosmology has yielded significant insight into the observed behavior of generic @xmath0 models .
the oscillations in @xmath102 observed in the generic models are precisely what would be expected from local mixmaster dynamics .
perhaps of greater interest , a new effect
the signature for the end of an era as seen in the rise of @xmath64has been predicted .
observation of this effect in longer running simulations of generic @xmath0 models or in models with an era change at some spatial point early in the simulation would provide strong evidence that the observed oscillations are indeed due to local mixmaster dynamics . because the rise in @xmath64 is expected to be dramatic , any numerical uncertainties
( see the discussion of numerics in @xcite ) should be irrelevant .
simulations to look for this effect are in progress .
one question which remains in our larger program to analyze the approach to the singularity is the dependence of the mcp picture and our interpretation of the results on our choice of spacetime slicing and variables .
while the @xmath0 description of a bianchi type ix mixmaster model uses the same slicing so that no conclusions may be drawn on that issue , we clearly have two completely different descriptions of the same mixmaster model .
both descriptions are characterized by intermittent kasner ( or vtd ) behavior with bounces off exponential potentials changing one kasner solution into another . however , the three traditional bkl lsf s are replaced in the @xmath0 description by a single variable @xmath102 whose oscillations follow the change from one kasner epoch to the next .
the @xmath0 variable @xmath64 clearly signals an era change which is not obvious when following the usual bkl lsf s . in the study of generic collapse , we conjecture that , in any convenient variables which allow detection of local vtd behavior , the mcp will predict correctly whether or not the model is avtd . in addition , it should also be possible to identify local mixmaster dynamics through the comparison of the departures from avtd behavior with the description of a homogeneous mixmaster universe in the same variables .
using the evolutions equations for the @xmath0 variables , we find the corresponding momenta to be @xmath187 @xmath188 } \right ) \nonumber \\ & & \left . { \left .
{ -4a^2b^2c^2\sin ^2\theta \sin ^2(\theta -\phi ) \sin ^2\phi } \right ] } \right\}{{\dot a } \over a } \nonumber \\ & & + \left\ { { 2\sin \theta \left [ { ( c^2\cos ^2\theta + a^2\sin ^2\theta \sin
^2\phi ) \left ( { -a^2b^2+a^2c^2-b^2c^2 } \right . } \right . } \right .
\nonumber \\ & & \left . { + a^2b^2\cos ( 2\theta ) + ( a^2+b^2)c^2\cos [ 2(\theta -\phi ) ] } \right ) \nonumber \\ & & \left .
{ \left . { + 4a^2b^2c^2\sin ^2\theta \cos ^2(\theta -\phi ) \cos ^2\phi } \right ] } \right\}{{\dot b } \over b } \nonumber \\ & & + \left\ { { 8a^2b^2c^2 } \right.\cos ^2\theta + \left ( { -a^2b^2+a^2c^2+b^2c^2+a^2b^2\cos ( 2\theta ) } \right .
\nonumber \\ & & \left . { + ( a^2-b^2)c^2\cos [ 2(\theta -\phi ) ] } \right)\left [ { -a^2-b^2 } \right .
\nonumber \\ & & \left .
\left . \left.+(a^2-b^2)\cos
( 2\phi ) \right ] \right\ } \sin ^3\theta { { \dot c } \over c } \right\}/\left\ { { \left [ { a^2b^2+a^2c^2+b^2c^2 } \right . } \right .
\nonumber \\ & & -a^2b^2\cos ( 2\theta ) + ( a^2-b^2)c^2\cos [ 2(\theta -\phi ) ] \left [ { c^2\cos ^2\theta } \right .
\nonumber \\ & & \left .
{ + \sin ^2\theta ( b^2\cos ^2\phi + a^2\sin ^2\phi ) } \right ] } \right\},\end{aligned}\ ] ] @xmath189 \right\ } \nonumber \\ & & / \left\{{a\,b\,c\ , \left [ { c}^2\,{\cos^2 \theta } + { \sin^2 \theta } \ , \left ( { b}^2\,{\cos^2 \phi } + { a}^2\,{\sin^2 \phi } \right ) \right ] } \right\},\end{aligned}\ ] ] @xmath190 \nonumber \\ & & / \left\{{a\,b\,c\ , \left [ { c}^2\,{\cos^2 \theta } + { \sin^2 \theta } \ , \left ( { b}^2\,{\cos^2 \phi } + { a}^2\,{\sin^2 \phi } \right ) \right ] } \right\ } .\end{aligned}\ ] ]
we would like to thank the institute for theoretical physics at the university of california / santa barbara for hospitality .
bkb would like to thank the institute for geophysics and planetary physics of lawrence livermore national laboratory and the max planck institut fr gravitationsphysik for hospitality .
this work was supported in part by national science foundation grants phy9732629 , phy9800103 , phy9973666 , and phy9407194 .
some of the computations discussed here were performed at the national center for supercomputing applications at the university of illinois .
figure 1 . the lsf s for a portion of a typical mixmaster trajectory . note that , prior to @xmath191 , @xmath11 and @xmath13 oscillate while @xmath12 decreases monotonically .
this `` era '' ends when @xmath12 starts to increase .
now @xmath13 decreases monotonically while @xmath11 and @xmath12 oscillate .
it is clear that another era has ended ( but off the scale ) near @xmath192 since @xmath13 is seen to oscillate again .
the @xmath0 symmetric model variable @xmath102 superposed on the mixmaster trajectory segment of fig .
it is clear that @xmath102 always tracks the largest lsf and that @xmath137 changes sign both at the original `` bounces '' of the lsf s and when a different scale factor becomes the largest .
the @xmath0 symmetric model variable @xmath64 superposed on the mixmaster trajectory segment of fig . 1 .
note that @xmath64 decreases monotonically except at the end of an era when it increases .
details of the rise of @xmath64 in fig . 4 .
( a ) a standard lsf bounce ( in @xmath12 ) causes @xmath138 to become more negative .
this is a bounce off @xmath90 .
( b ) the next bounce in @xmath102 , off @xmath92 occurs when @xmath193 and causes @xmath138 to become positive .
( c ) the next bounce ( in @xmath11 ) causes @xmath138 to increase .
( d ) @xmath64 reaches a maximum when the now increasing smallest lsf @xmath13 equals the middle one @xmath12 . | previous studies @xcite have provided strong support for a local , oscillatory approach to the singularity in @xmath0 symmetric , spatially inhomogeneous vacuum cosmologies on @xmath1 .
the description of a vacuum bianchi type ix , spatially homogeneous mixmaster cosmology ( on @xmath2 ) in terms of the variables used to describe the @xmath0 symmetric cosmologies indicates that the oscillations in the latter are in fact those of local mixmaster dynamics .
one of the variables of the @xmath0 symmetric models increases only at the end of a mixmaster era .
such an increase therefore yields a qualitative signature for local mixmaster dynamics in spatially inhomogeneous cosmologies . # |
membranous nephropathy is an immune - mediated glomerular disease that is the most common form of nephrotic syndrome in adults .
membranous nephropathy has the potential to progress to end - stage renal failure ; however , it also spontaneously resolves in about 30% of patients.1 its onset is insidious , with edema being the most common presenting symptom .
the primary sign of membranous nephropathy is proteinuria , with higher levels of urine protein correlated with greater risk of disease progression.1 initial treatment of membranous nephropathy involves management of the accompanying edema , hypertension , and often hyperlipidemia , most commonly through the use of diuretics , angiotensin - converting enzyme inhibitors and/or angiotensin receptor blockers , and statins , respectively.1 such treatments , along with dietary management of proteinuria , may be sufficient in patients with disease at low risk of progressing .
however , immune suppression via corticosteroids , cyclosporine , and alkylating agents is generally required for patients with higher - risk disease ( characterized by persistent / high - grade proteinuria and/or deteriorating renal function).1 unfortunately , such therapies can be associated with significant toxicity , and many patients experience recurrence or develop resistance to treatment.2 synthetic adrenocorticotropic hormone ( acth ) analogs have been used in europe with some success for the treatment of nephrotic syndrome of various etiologies , including idiopathic membranous nephropathy.36 in the united states , the natural acth , h.p .
union city , ca , usa ) has recently been shown to induce remission , defined as stabilization or improvement of renal function ( by estimated glomerular filtration rate ) and resolution of proteinuria , in patients with idiopathic membranous nephropathy.7 herein , we describe a case in which 13 months of treatment with acthar resulted in a sustained remission of membranous nephropathy in a patient with refractory disease .
at an initial visit in september 2006 , a 46-year - old white male presented with edema , blood pressure indicative of hypertension ( 144/94 mmhg ) , heart rate of 76 beats per minute , and creatinine of 1.4 mg / dl ( 123.76 mol / l ) .
he had experienced sudden onset of edema in his feet and legs 5 weeks prior to this initial visit , which caused him serious concern . at a height of 5 feet 8 inches ( 172.72 cm ) and weighing 235 lbs ( 105.75 kg ; up about 35 lbs [ 15.75 kg ] from his usual weight ) , his body mass index was 35.7 .
g / l ) and cholesterol at 307 mg / dl ( 7.9513 mmol / l ; low - density lipoprotein , 224 mg / dl [ 5.8016 mmol / l ] ) .
he was negative for cancer screening , hepatitis b and c panel , antinuclear antibody , rheumatoid factor , and rapid plasmid reagin .
he was started on olmesartan medoxomil - hydrochlorothiazide 40/25 mg for hypertension and proteinuria and simvastatin 40 mg for elevated cholesterol .
the patient was scheduled for a kidney biopsy for nephrotic range proteinuria in october 2006 , which resulted in a diagnosis of idiopathic membranous glomerulopathy .
lisinopril 40 mg twice daily was added to his medication regimen . at this time , his creatinine was at 1.3 mg / dl ( 114.92 mol / l ) . the patient s membranous glomerulopathy progressed from october 2006 to july 2009 , as revealed by laboratory results . during this period
, he remained on an angiotensin receptor blocker ( olmesartan medoxomil - hydrochlorothiazide ) and angiotensin - converting enzyme inhibitor ( lisinopril ) treatment regimen .
since no improvement was observed , he then received cyclosporine a for 6 months , to which he was relatively adherent .
no improvement was observed 3 months after initiation of cyclosporine a , so prednisone was added .
three months later , he developed shingles and was admitted to the hospital due to what was felt to be complications of cyclosporine a plus prednisone .
both cyclosporine a and prednisone were tapered off after the patient requested all immunosuppressive medications be stopped .
three months later , he agreed to be treated with mycophenolate , which he received for approximately 12 months but only during the last 3 months did he take it as prescribed .
the patient was agreeable to trying acthar ( 80 usp u / ml ) and received treatment from september 2009 to october 2010 ; his laboratory values during this period are summarized in table 1 .
acthar was self - administered subcutaneously at an initial dose of 40 u every 72 hours .
after 3 months , the dose was increased to 80 u every 72 hours . in april 2010
g / l ) , and he required additional antihypertensive therapy . by july 2010 ,
thus , it took approximately 10 months of acthar treatment to improve his urinary protein levels . by october 2010
g / l ) . as shown in table 1 , in addition to the decline in urinary protein levels
, the patient experienced decreases in creatinine and albumin levels , an increase in creatinine clearance , and modest weight gain while receiving treatment with acthar .
first , one year of acth treatment has been shown in european studies to be sufficient for resolving proteinuria.36 in addition , the patient s laboratory results indicated clinically significant improvement in his signs of membranous nephropathy . finally , the patient reported that his quality of life had improved , and he was not experiencing any symptoms of membranous nephropathy .
g / l ) in december 2010 , with slight elevation to 451 mg / dl ( 45.1 g / l ; still within normal range ) in march 2011 , to 189 mg / dl ( 18.9
his protein to creatinine ratio was 0.58 in january 2012 , and at that time his medications were limited to an angiotensin - converting enzyme inhibitor ( lisinopril ) and angiotensin receptor blocker ( olmesartan medoxomil - hydrochlorothiazide ) . as of may 1 , 2012 ,
his blood pressure was 124/78 mmhg , he weighed 199 lbs ( 89.55 kg ) , his heart rate was 81 beats per minute , and there was no evidence of edema .
current medications include olmesartan medoxomil - hydrochlorothiazide 40/12.5 mg once daily , lisinopril 40 mg once daily , and simvastatin 40 mg once daily .
at the time of diagnosis of membranous nephropathy , this patient had serious health concerns . however , after 10 months of acthar treatment , his proteinuria resolved and several other signs and symptoms of membranous nephropathy improved . since treatment with acthar was halted , this patient has remained stable and has not required any additional treatment for 1.5 years . in conclusion , the results described in this case report suggest that , in agreement with the data obtained during previous studies , acthar appears to be an effective treatment strategy for patients with refractory membranous nephropathy . | treatment options for refractory membranous nephropathy are limited .
herein we describe the case of a 46-year - old white male with membranous nephropathy who progressed during 3 years of treatment with antihypertensive agents ( specifically angiotensin - converting enzyme inhibitors and angiotensin receptor blockers ) , diuretics , simvastatin , prednisone , cyclosporine a , and mycophenolate mofetil . prior to initiation of treatment with h.p .
acthar gel , his proteinuria level was 9,520 mg / dl ( 952.0
g / l ) but it decreased to 2,948 mg / dl ( 294.8
g / l ) after 10 months of acthar therapy .
after 13 months , treatment with acthar was halted as his 24-hour urinary protein was 1,628 mg / dl ( 162.8 g / l ) ; by 15 months , it was 407 mg / dl ( 40.7 g / l ) .
the patient has remained free of signs and symptoms of membranous nephropathy for 1.5 years .
these results support the use of acthar as an effective and safe therapy for patients with refractory membranous nephropathy . |
For months, Goldman Sachs and the Securities and Exchange Commission had been involved in secret talks over allegations that the Wall Street bank defrauded customers in selling them investments designed to fail.
Then, after a crucial meeting last month between lawyers for Goldman and the SEC, the agency came to a fork in the road. Even after SEC lawyers had told Goldman in writing they were prepared to file a federal suit, the firm gave no ground, declining to ask for a settlement, according to three people familiar with the case. The agency could prolong negotiations in hopes of reaching a deal Goldman would accept, as the SEC had often done in previous cases, or take the bank to court.
Endorsing the recommendation of investigators, the SEC's five-member commission voted 3 to 2 to proceed with the civil suit, taking a high-stakes gamble that pits Wall Street's top regulator against its most storied bank. The case, filed Friday,
has provoked a counteroffensive from Goldman, which says it was blindsided by the suit. Goldman's defenders are suggesting that the suit may have been designed to help make the case for the Obama administration's push this month for legislation to overhaul financial regulation.
SEC officials say that they told Goldman last summer the agency would probably bring action, and that the bank did not show any contrition. At the same time, they say they wanted to use the Goldman case to make a broader statement about the agency's renewed intention of holding prominent financial firms accountable for misconduct.
Neither SEC officials nor Goldman executives would discuss the internal dynamics of the case on the record. But people in both camps were preparing Monday for an epic court battle that could offer a chance for both sides to restore their reputations after they were sullied during the financial crisis.
Victory for the SEC, Wall Street's top regulator, would help restore credibility after it was sharply criticized for not aggressively enforcing securities laws. Victory for Goldman could help the firm answer critics who allege it epitomized the excesses that led the financial sector into its worst crisis in decades.
On Monday, the case reverberated around the world. Financial regulators in London and Germany said they would open investigations to see if Goldman's sale of mortgage securities broke local laws.
Goldman's domestic legal troubles could be compounded abroad as foreign regulators open probes into the investment. London's Financial Services Authority and Germany's BaFin regulatory agency said Monday that they were coordinating with the SEC. The Royal Bank of Scotland lost an estimated $850 million and the Duesseldorf-based IKB Deutsche-Industriebank lost more than $100 million on mortgage-related securities set up by Goldman. [Story, A7.]
The SEC's suit centers on a development central to the financial crisis: the creation of exotic investments that allowed firms to bet on the direction of the housing market.
The suit asserts that Goldman defrauded investors when it sold them a subprime-mortgage investment in 2007 that was secretly designed to lose value. The agency alleges that Goldman created and marketed the investment without telling its clients that Paulson & Co., a prominent hedge fund, had helped the bank assemble the investment while at the same time was placing bets that it would lose value. The bank received $15 million from Paulson & Co. for its services.
Goldman has denied the allegations, releasing three statements since Friday rebutting the SEC's points. ||||| The Securities and Exchange Commission decided to sue Goldman Sachs Group Inc. over the objections of two Republican commissioners, suggesting an unusual split at the agency that could politicize one of its most prominent cases in years.
People familiar with the matter said the five-member commission held a lengthy meeting Wednesday to debate the civil-fraud charges against Goldman, and ultimately voted 3-2 in favor of pushing forward. The charges were filed Friday.
Normally the agency prefers to have unanimous support when bringing enforcement actions against the firms it regulates. Word of the SEC split could exacerbate partisan tensions in Washington ... | – The decision to go after Goldman split the SEC along party lines and came only after months of secret talks broke down. Though the commission generally aims for unanimity, they voted, 3-2, to proceed with the civil suit despite opposition from two Republican members. The tiebreaker was an Independent commissioner appointed by President Obama. Word of the rift threatens to politicize the case and widen the gulf between Dems and Republicans over the financial overhaul the White House is pushing, the Wall Street Journal notes. Though Goldman insists the suit came as a surprise, the Washington Post claims the case came after months of secret talks with Goldman's lawyers. The SEC says they informed the bank they'd bring legal action last summer. The talks reached an impasse last month when Goldman refused to give ground or show contrition, the commission says. |
SECTION 1. SHORT TITLE.
This Act may be cited as the ``Biliteracy Education Seal and
Teaching Act'' or the ``BEST Act''.
SEC. 2. FINDINGS.
Congress finds the following:
(1) The people of the United States celebrate cultural and
linguistic diversity and seek to prepare students with skills
to succeed in the 21st century.
(2) It is fitting to commend the dedication of students who
have achieved proficiency in multiple languages and to
encourage their peers to follow in their footsteps.
(3) The study of world languages in elementary and
secondary schools should be encouraged because it contributes
to a student's cognitive development and to the national
economy and security.
(4) Recognition of student achievement in language
proficiency will enable institutions of higher education and
employers to readily recognize and acknowledge the valuable
expertise of bilingual students in academia and the workplace.
(5) California has pioneered the first State system in the
Nation to recognize students for achieving proficiency in
multiple languages. In 2012, California awarded a Seal of
Biliteracy to over 10,000 graduating high school seniors in 37
school districts.
(6) Students in every State should be able to benefit from
a Seal of Biliteracy program.
SEC. 3. STATE SEAL OF BILITERACY PROGRAM.
(a) Establishment.--The Secretary of Education shall award grants
to States to establish or improve a Seal of Biliteracy program to
recognize student proficiency in speaking, reading, and writing in both
English and a second language.
(b) Grant Application.--In order to receive a grant under this
section, a State shall submit an application to the Secretary at such
time, in such manner, and containing such information and assurances as
the Secretary may require, including--
(1) a description of the criteria a student must meet to
demonstrate proficiency in speaking, reading, and writing in
both English and a second language;
(2) assurances that a student who meets the requirements
under paragraph (1)--
(A) receives a permanent seal or other marker on
the student's secondary school diploma or its
equivalent; and
(B) receives documentation of proficiency in the
student's official academic transcript; and
(3) assurances that a student is not charged a fee for
submitting an application under subsection (c).
(c) Student Participation in a Seal of Biliteracy Program.--To
participate in a Seal of Biliteracy program, a student must submit an
application to the State that serves the student at such time, in such
manner, and containing such information and assurances as the State may
require, including assurances that the student--
(1) will receive a secondary school diploma or its
equivalent in the year the student submits an application; and
(2) has met the criteria established by the State under
subsection (b)(1).
(d) Student Eligibility for Application.--A student who gained
proficiency in a second language outside of school may apply to
participate in a Seal of Biliteracy program under subsection (c).
(e) Use of Funds.--Grant funds made available under this section
shall be used for administrative costs of establishing or improving and
carrying out a Seal of Biliteracy program and for public outreach and
education about that program.
(f) Grant Terms.--
(1) Duration.--A grant awarded under this section shall be
for a period of 2 years, and may be renewed at the discretion
of the Secretary.
(2) Renewal.--At the end of a grant term, the recipient of
such grant may reapply for a grant under this section.
(3) Limitations.--A grant recipient under this section
shall not have more than 1 grant under this section at anytime.
(4) Return of unspent grant funds.--Not later than 6 months
after the date on which a grant term ends, a recipient of a
grant under this section shall return any unspent grant funds
to the Secretary.
(g) Report.--Not later than 9 months after receiving a grant under
this section, a grant recipient shall issue a report to the Secretary
describing the implementation of the Seal of Biliteracy program.
(h) Definitions.--In this section:
(1) ESEA definitions.--The terms ``secondary school'',
``Secretary'', and ``State'' have the meanings given those
terms in section 9101 of the Elementary and Secondary Education
Act of 1965 (20 U.S.C. 7801).
(2) Second language.--The term ``second language'' means
any language other than English, including Braille and American
Sign Language.
(3) Seal of biliteracy program.--The term ``Seal of
Biliteracy program'' means any program established under
section 3 of this Act.
(i) Authorization of Appropriations.--There is authorized to be
appropriated to the Secretary $10,000,000 for each of fiscal years 2015
through 2019 to carry out this section. | Biliteracy Education Seal and Teaching Act or the BEST Act - Directs the Secretary of Education to award renewable two-year grants to states to establish or improve a Seal of Biliteracy program to recognize student proficiency in speaking, reading, and writing in both English and a second language. Requires students who wish to participate in such a program to submit an application to their state that includes assurances that they: (1) will receive a secondary school diploma or its equivalent in the year they apply; and (2) have met the state's criteria for demonstrating proficiency in speaking, reading, and writing in both English and a second language. Requires states to provide participating students who demonstrate that proficiency: (1) a permanent seal or other marker on their secondary school diploma or its equivalent, and (2) documentation of that proficiency on their official academic transcript. Allows students who gain proficiency in a second language outside of school to participate in such programs. Prohibits states from charging students an application fee. |
Published on Jan 29, 2014
Buzzfeed Australia sent us some snacks! Obviously, we had to try them on camera.
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BuzzFeed is the world's first true social news organization. Featuring tasty, short, fun, inspiring, funny, edgy, interesting videos from theBuzzFeed. /BuzzFeedVideo is BuzzFeed's original YouTube Channel, with a focus on producing great short-form BuzzFeed videos for YouTube (and the world!). BuzzFeed Video will entertain, educate, spark conversation, inspire and delight. Subscribe to BuzzFeedVideo today and check us out at http://buzzfeed.com ||||| Published on Feb 7, 2013
Men At Work's official music video for 'Down Under'. Click to listen to Men At Work on Spotify: http://smarturl.it/MenAtWorkSpotify?I...
As featured on Contraband: The Best of Men At Work. Click to buy the track or album via iTunes: http://smarturl.it/MAWContraband?IQid...
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More From Men At Work
Who Can It Be Now: https://youtu.be/SECVGN4Bsgg
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---------
Lyrics:
Travelling in a fried-out Kombi
On a hippie trail, head full of zombie
I met a strange lady, she made me nervous
She took me in and gave me breakfast
And she said:
Do you come from a land down under
Where women glow and men plunder
Can't you hear, can't you hear the thunder
You better run, you better take cover." |||||
A jar of the Australian spread Vegemite in New York in 2006. (Brendan McDermid/Reuters)
Start typing the sentence “Vegemite tastes like …” into Google and the search engine quickly gives you three suggestions for completing your thought.
The first option is “soy sauce,” an apt description of the salty brown sludge so popular in Australia.
The second is “beer,” which also makes sense considering Vegemite is made from leftover brewers’ yeast extract.
The third suggestion, however, is less than obvious.
According to Google, at least, Vegemite tastes like sadness.
Why a breakfast spread would be associated with sadness is a peculiarly Australian tale of poverty and addiction. And the answer lies somewhere in the overlap between the search engine’s three suggestions.
Vegemite is a cousin, so to speak, of Marmite, the yeast-based spread invented at the beginning of the 20th century in England. The British B-vitamin spread was wildly popular Down Under until its supply was interrupted by World War I. Conflict offered local food manufacturer the Fred Walker Co. — which would later become Kraft — a window of opportunity. The company hired a young chemist named Cyril P. Callister to develop Australia’s own version of Marmite, according to the Vegemite Web site.
For nearly a century, Vegemite has been a barometer of Australia’s culture and economy. From the contest to come up with its name to its iconic advertisements, memorable radio limericks and nostalgia-inducing “Happy Little Vegemites” commercials, the product charts changes in Australian society over the 20th century.
In 1981, the Australian rock band Men at Work memorialized the spread in their song “Down Under,” which contains a line about a Vegemite sandwich.
“Vegemite started as a wartime substitute for Marmite, but it’s now as symbolic of Australia as Sydney Harbour Bridge and the koala,” the BBC reported in 2012.
To outsiders, however, the malty toast-topper tastes terrible.
In 2011, President Obama risked angering Australians by saying that he found Vegemite to be “horrible.”
Jars of Vegemite are seen on the production line during the brand’s 90th year, at the Vegemite factory in October 2013 in Melbourne, Australia. (Graham Denholm/Getty Images)
But during the past week, the beloved breakfast spread has been pulled into a much more serious and particularly Australian debate over alcoholism and the rights of the indigenous.
On Sunday, Indigenous Affairs Minister Nigel Scullion warned that Vegemite was being used to make bootleg booze in indigenous communities where there is a ban on selling alcohol.
Calling the condiment “a precursor to misery,” Scullion told Brisbane’s Courier-Mail that some indigenous Australians were using Vegemite to brew bathtubs full of moonshine.
“Adults and even young children are getting drunk on the home brew, which at times is mixed with orange juice,” the newspaper reported. “Senator Scullion said children in some communities were too hung-over from all-night benders to go to school.”
In some instances, people had bought as many as 20 jars of Vegemite for the purpose of home brewing, according to the Sydney Morning Herald.
Australia’s indigenous population suffers from a significantly higher rate of alcohol abuse, according to the country’s Bureau of Statistics and Institute of Criminology, and indigenous Australians are up to eight times more likely to die due to alcohol than their peers, according to recent research.
Australian Prime Minister Tony Abbott and Russian President Vladimir Putin meet Jimbelung the koala before the start of the first Group of 20 meeting on Nov. 15, 2014, in Brisbane, Australia. (Andrew Taylor/G20 Australia via Getty Images)
In the interview, Scullion mentioned the possibility of a legislative ban on Vegemite in certain communities but said the government preferred for local leaders and businesses to crack down on the problem instead.
Scullion added that he was tired of hearing about “people’s rights” rather than dealing with problems related to alcohol abuse, such as domestic violence and child neglect.
“Wouldn’t it be terrible to ban Vegemite?” he told the Courier-Mail. “Well it’s a precursor to misery in (some) communities.”
The newspaper also quoted police union president Ian Leavers on the problem of Vegemite moonshine.
“Where there is a will, there is always a way and in indigenous communities I have seen alcohol brewed from many things such as Vegemite,’’ he said. “While we cannot just go out and ban everything that could possibly be used to make illegal alcohol, at the same time common sense needs to take place and if people are purchasing large quantities of an item that could be used for brewing illegal alcohol, questions should always be asked.”
The mere suggestion of banning Vegemite caused a stir in Australia.
On Sunday, shortly after Scullion’s comments were published, his boss, Prime Minister Tony Abbott came out to reassure Aussies that nobody was going to pry the Vegemite from their hands.
“The last thing I want to see is a Vegemite watch going on,” Abbott said, “because Vegemite, quite properly, is for most people a reasonably nutritious spread on your morning toast or on your sandwiches.”
To some of Abbott’s critics, however, the breakfast spread skirmish is just another example of the prime minister’s harsh policies toward the indigenous.
Although Abbott has so far made good on a campaign promise to spend a week of each year living among Aborigines — conducting meetings from a tent in Australia’s vast Northern Territory last September — he has also drawn criticism for pulling funding from aboriginal communities and calling their culture mere “lifestyle choices.”
Great to be in Arnhem Land – looking forward to the days ahead. pic.twitter.com/IozhB0zSTk — Tony Abbott (@TonyAbbottMHR) September 14, 2014
“What we can’t do is endlessly subsidize lifestyle choices if those lifestyle choices are not conducive to the kind of full participation in Australian society that everyone should have,” Abbott said in March, according to the Guardian. “If people choose to live miles away from where there’s a school, if people choose not to access the school of the air, if people choose to live where there’s no jobs, obviously it’s very, very difficult to close the gap.”
“Fine, by all means live in a remote location, but there’s a limit to what you can expect the state to do for you if you want to live there,” added the prime minister, a feisty politician who once ate a raw onion whole on live television and earned the nickname “the bomb-thrower.”
Opposition politicians called Abbott’s decision and comments “deeply disturbing and highly offensive.”
Some anti-alcoholism advocates, meanwhile, say that Scullion’s comments exaggerate the problem.
“We’re talking about an isolated problem in a couple of communities around a very large nation, and a nation where there is a very large number of Aboriginal communities, and every community is different,” John Boffa of the Northern Territory-based People’s Alcohol Action Coalition told the BBC.
For now, at least, all of Australia can enjoy Vegemite: the beloved breakfast spread with an aftertaste of sadness. ||||| Sale of Vegemite could be restricted in dry communities, following reports of the spread being used to make homemade alcohol. Photo: Eddie Jim
The government's idea to reduce the availability of Vegemite from remote communities has been labelled as "bizarre" by the West Australian shadow minister for Aboriginal Affairs.
The yeast spread has been reportedly identified as a key ingredient in homemade alcohol in dry remote communities.
Federal Indigenous Affairs Minister Nigel Scullion said that local communities needed to take a greater responsibility in restricting excessive sales of the product after he was earlier reported describing Vegemite as a "precursor to misery".
While the true extent of the Vegemite issue in remote communities is not known, it is believed that in 2010 a man died in Queensland after drinking a Vegemite-based alcoholic brew.
Indigenous Affairs Minister Nigel Scullion. Photo: Alex Ellinghausen
WA shadow minister for Aboriginal Affairs Ben Wyatt, said aside from very isolated cases, Vegemite should not be perceived as a threat to remote communities.
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He questioned the logic of the federal government's approach towards Vegemite.
"It is bizarre," he said.
WA Labor spokesman for Aboriginal Affairs, Ben Wyatt.
"Scullion takes tens of millions of dollars out of remote aboriginal communities and then has this absurd reaction in respect to Vegemite.
"Are potatoes going to be banned?
"It seems to be that they have an approach that is built around bizarre reactions to individual issues rather than a comprehensive strategy underwritten by federal government responsibility and support."
One remote WA general shopkeeper, who did not want to be named, said she didn't understand why the federal government was suggesting that Vegemite should be restricted or removed from shops in communities.
"I prefer Promite," she said.
"We do have some jars of Vegemite here but they've gone out of date.
"What does that tell you?"
The owners of Vegemite, Mondelez, a US-based multinational food company, declined to comment. ||||| Story highlights Vegemite reportedly being used to make moonshine in remote, alcohol-restricted Aboriginal communities
Australian Indigenous Affairs Minister calls for local restrictions on Vegemite sales, calling it a "precursor to misery"
(CNN) Australian Prime Minister Tony Abbott has warned against restricting the sale of popular toast spread Vegemite in remote indigenous communities after reports it was being used to make moonshine.
Indigenous Affairs Minister Nigel Scullion first suggested local communities should regulate Vegemite purchases after reports from Aboriginal health organizations that the yeast-based spread was being bought in bulk to make homemade alcohol in some remote indigenous communities in the northeastern state of Queensland, where alcohol is banned.
Scullion described the spread as a "precursor to misery" in local newspaper the Courier Mail on Saturday, saying children in some communities were too unwell from excess consumption of the Vegemite-based home-brew to attend school.
"Businesses in these communities also have a responsibility to report any purchase that may raise their own suspicions," he later added.
But Abbott told reporters at a press conference in Queensland on Sunday that he had no plans to institute a "Vegemite watch".
Read More ||||| Vegemite could be ending up in more than sandwiches, following reports of the yeast extract being used to make homemade alcohol in dry communities across Queensland and the Northern Territory.
The problem has been described as prolific in some areas in the Northern Territory, with reported instances of people buying up to twenty jars of Australia's favourite spread at a time, for the brewing of homemade alcohol.
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Link Bega may be tempted to part-fund its Vegemite buy via a share issue. Photo: Eddie Jim
Indigenous Affairs Minister Nigel Scullion said the goal was for local communities to take a greater responsibility in restricting excessive sales of high-yeast products, rather than impose a legislative ban on the food products.
"The government is not seeking to place any restrictions on Vegemite or any other yeast product that may be used in home brew in remote communities," he said.
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Link Nigel Scullion said the focus was on restricting the sale of such products, and not banning it altogether. Photo: Alex Ellinghausen
"Our priority has always been to get kids to school, make communities safer and get people into jobs. Businesses in these communities also have a responsibility to report any purchase that may raise their own suspicions."
There are 19 communities across Queensland where alcohol is limited or banned.
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In 2013 the Queensland government said it was considering removing alcohol bans in certain communities, due to a growing increase in the production of homemade alcohol.
At the time there were also reports of other food and drinks, like Ribena juice, being used to produce alcohol.
"They're using a whole range of products and items that can be used to essentially ferment and turn into alcohol," said Selwyn Button, from the Queensland Aboriginal and Islander Health Council to the ABC in November 2013.
"It's anything that they can get their hands on that has the ability to ferment," he said, adding that the ingredients used in homemade alcohol are heavy in sugar and carbohydrates, common risk factors for health conditions like type 2 diabetes.
According to the Vegemite website, the spread was first produced in 1922 when the Fred Walker Company, which would later become Kraft Food Company, "hired a young chemist to develop a spread from one of the richest known natural sources in the Vitamin B group – brewer's yeast."
Brewer's yeast is a key ingredient used in the production of beer and ale.
The Queensland Aboriginal and Islander Health Council has been contacted for comment. | – In news that may prompt reanalysis of Men at Work lyrics, an Australian politician is trying to crack down on Vegemite, which the Washington Post calls "the beloved breakfast spread with an aftertaste of sadness." Indigenous Affairs Minister Nigel Scullion wants to restrict access to Vegemite because aboriginal health groups are reporting that the yeast-based spread is being scooped up in bulk to make moonshine, CNN reports. Describing the iconic spread as a "precursor to misery," Scullion says that Vegemite has been associated with domestic violence cases and even kids showing up to school hungover, the BBC notes. "Businesses in these communities … have a responsibility to report any purchase that may raise their own suspicions," Scullion says. Alcohol is banned in 19 indigenous Aussie communities due to health and social problems from excessive consumption, CNN notes. In the Northern Territory, where converting Vegemite to hooch is said to be prevalent, some people have been buying up to 20 jars of Vegemite at a time, the Sydney Morning Herald reports. But per WAToday.com, another Australian pol is calling Scullion's attempt to restrict sales "absurd" and "bizarre." And PM Tony Abbott denies Vegemite is to blame for the country's social ills, telling reporters in Queensland yesterday, "This is a deregulatory government and the last thing I want to do is to have a Vegemite watch," per CNN. "Because Vegemite, quite properly, is for most people a reasonably nutritious spread on your morning toast or on your sandwiches." Based on this BuzzFeed taste test, it doesn't look like America will face a Vegemite epidemic anytime soon. (Does anyone in Australia even eat Vegemite anymore?) |
the x - ray magnetic circular dichroism ( xmcd ) is now well established as a selective probe of the magnetic properties even in complex systems .
xmcd can yield local quantitative information through a wide range of powerful calculation techniques .
for instance within the multiplet framework , the xmcd spectra at the l@xmath2 transition metal ( tm ) and m@xmath3 rare earth ( r ) edges can be accurately reproduced @xcite .
it allows one to evaluate the local transition metal 3@xmath1 and rare earth 4@xmath4 magnetic moments .
moreover , the sum rules @xcite can provide , in favorable cases , a separate determination of both orbital and spin magnetic moments .
however these atomic approaches fail at the tm k edge , where the excited electron is promoted to the delocalized @xmath5 states . for final delocalized band states ,
the scattering processes encountered by the photoelectron can be treated in a one - electron picture within the multiple - scattering framework .
this theory was first applied to the calculation of the x - ray absorption spectra , and recently it has been implemented to calculate the xmcd spectra , in particular at the transition metal k edge . since the xmcd arises from the interplay between the spin - polarization and the spin - orbit coupling , these effects have to be included in the model .
@xcite used a fully relativistic multiple - scattering formalism and obtained good results in the near - edge region .
this formalism was recently extended to the exafs range @xcite . on the other hand ankudinov and rehr , using a multiple - scattering approach where the scattering by the atomic sites is fully relativistic and the propagation between sites is non - relativistic , calculated the extended structure in xmcd at the l@xmath2 edges of gd in good agreement with experiments @xcite . however , in this case , the edge region was not well reproduced .
more recently we performed calculations including both the near - edge and exafs regions in the same multiple - scattering formalism with application to the fe k edge @xcite .
we showed that the spin - polarization of the @xmath1-states of the neighboring ions highly contributes to the signal structure and accounts for the first positive peak in the fe xmcd spectrum .
this contribution arises from the scattering of the photoelectron due to the spin - orbit potential of the neighbors and the absorber .
the role of the spin - orbit interaction of the 3@xmath1 states on the neighboring sites was also reported by igarashi and hirai @xcite using tight - binding calculations , and later on by guo within an itinerant electronic model @xcite .
these authors showed that the xmcd at the tm k edge in fe and ni is determined by the orbital moment on the 3@xmath1 states through the @xmath5-@xmath1 hybridization . by including the coulomb interaction between the 3@xmath1 electrons , the xmcd spectra seem to be quite well reproduced .
if these techniques now offer a reasonable description of the dichroic spectrum in pure metals , the interpretation of the xmcd at the tm k edge in rare earth - transition metal compounds is still open . in particular
, the xmcd signal in the near - edge region may present very different features with respect to the allied rare earth .
recent experiments performed at the fe k edge in r@xmath6fe@xmath7b compounds were analyzed considering the xmcd spectra as the addition of the magnetic contributions of both fe and r sublattices @xcite .
it was proposed that fe k edge xmcd is induced by the splitting of the 5@xmath1 band , due to the exchange interaction with the 4@xmath4 states , through the @xmath5-@xmath1 hybridization . in the course of our studies at the l@xmath2 rare earth edges in gdni@xmath0 and tbni@xmath0 @xcite , non negligible xmcd signals compared to ni metal have been observed at the ni k edge whereas ni does not satisfy the stoner criterion in the rni@xmath0 compounds @xcite .
these results give information on the rare earth influence on the dichroic spectra of the k edge of ni .
however , the understanding of the xmcd at the k edge of the transition metal in r - tm intermetallics is far from being achieved and a better description of the rare earth role has yet to be given . in this paper
we report a comparative study of the co k edge xmcd spectra between co metal and rco@xmath8 metallic alloys with magnetic and non magnetic rare earth . in most of these compounds ,
the co has a strong magnetic moment , in the rco@xmath0 compounds for instance , it is comparable to that of co metal .
the choice of different rare earths allows us to observe the sensitivity of the xmcd spectrum to the magnetic and chemical environment of the absorbing site . for co metal , laco@xmath0 and tbco@xmath0 ,
calculations of the xmcd signal have been carried out within the multiple - scattering model using a semi - relativistic approach @xcite .
these calculations require the knowledge of the atomic potential which was obtained within the local density approximation using the linear muffin - tin orbital ( lmto ) basis - set within the atomic sphere approximation and including the so called combined correction term @xcite . the second section of the present paper deals with the xmcd experimental results observed at the co k edge in co metal and various r - co compounds .
the third section presents the calculations of the crystal potentials by means of the linear muffin - tin orbital method within the local - density approximation , and the multiple - scattering calculations of the x - ray absorption and the dichroic signal of co metal , laco@xmath0 and tbco@xmath0 .
the last section summarizes and concludes our paper .
like most of the rare earth - transition metal binary alloys , the r - co phase diagrams present a large number of well - defined compounds .
the different crystallographic structures of these compounds are based on the cacu@xmath0-like hexagonal lattice including simple r or co atom substitutions along with layers shifts .
the magnetism of the rare earth - transition metal systems has been extensively studied in the past two decades ( see for instance refs .
it relies on a combination of 4@xmath4 localized and 3@xmath1 itinerant magnetism giving rise to a wide range of magnetic properties , some of them well suited for technical applications .
the band structure of the r - tm metallic alloys is characterized by the hybridization of the 3@xmath1 and 5@xmath1 bands @xcite .
the hybridization leads to a ferromagnetic coupling between 4@xmath4 and 3@xmath1 moments in light rare earth compounds and ferrimagnetic in heavy rare earth compounds @xcite .
the hybridized states are located at the top of the 3@xmath1 band and at the bottom of the 5@xmath1 band .
the fermi level lies in this region where the density of states varies strongly .
starting from the pure 3@xmath1 metal , the progressive introduction of the rare earth induces a decrease in the 3@xmath1 magnetism and for given concentrations the stoner criterion is no more satisfied .
the critical concentration for the onset of the 3@xmath1 magnetism is rni@xmath0 for the nickel - based alloys whereas it corresponds to rco@xmath6 for the rco@xmath8 compounds .
the rco@xmath6 compounds crystallize in the mgcu@xmath6-type cubic structure ( laves phases ) . in yco@xmath6 and luco@xmath6 , co is non magnetic whereas in compounds with magnetic rare earths the co moment of about 1 @xmath9 , is induced by exchange interactions between 3@xmath1 and 4@xmath4 spins .
the curie temperature reaches a maximal value of 395 k in gdco@xmath6 and rapidly decreases with the spin value of the rare earth . on the contrary , in the rco@xmath0 compounds ( cacu@xmath0-like structure ) the co moment , as deduced from magnetization studies , is approximately 1.64 @xmath9 and the strong co - co exchange interaction leads to very high curie temperatures ( t@xmath10 @xmath11 950 k ) .
the extremely large co anisotropy favors the @xmath12 axis and competes with that of the rare earth .
for instance in tbco@xmath0 , a spin reorientation from the basal plane to the @xmath12 axis above 440 k is observed @xcite . in the solid solutions r(ni@xmath13co@xmath8)@xmath0 , which also crystallize in the cacu@xmath0 structure ,
the co magnetic moment for high @xmath14 values is comparable to that in the rco@xmath0 compounds .
the curie temperatures then progressively decrease when substituting co by non magnetic ni ions .
the xmcd measurements at the co k edge have been performed in laco@xmath0 , tbco@xmath0 , dy(ni@xmath15co@xmath16)@xmath0 and tbco@xmath6
. their crystallographic structures and magnetic properties are reported in table [ tab1 ] .
table [ tab2 ] gives the equivalent positions with their coordinates and the point symmetry group for the cacu@xmath0-type hexagonal structure .
all these compounds were prepared at the laboratoire de magntisme louis - nel , by rf - melting in a cold crucible from the stoichiometric proportions of pure elements . in order to minimize oxidation ,
the melting was performed under neutral argon atmosphere . for transmission mode xmcd experiments ,
the samples were then crushed into powder and layered onto a thin kapton foil .
the powders were previously analyzed by x - ray diffraction using a debye - scherrer method .
the co sample consists in a thin metallic foil .
the xmcd measurements were carried out at lure , on the energy dispersive beam - line d11 @xcite .
the polychromator consists of a curved si(111 ) crystal which focuses the x - ray beam in the middle of the electromagnet poles .
higher harmonics are rejected by a sio@xmath6 plane mirror located downstream of the photodiode array detector .
right circularly polarized x - ray beam is selected by 1 mm - wide slits positioned 3 mrad below the orbit plane .
the circular polarization rate of the incoming radiation is estimated at @xmath17 .
the xmcd spectra are recorded in transmission mode by selecting one polarization and reversing the magnetic field , applied along the photon propagation direction .
the applied magnetic field intensity is about 0.4 t. the samples are oriented so that the magnetic field is applied perpendicular to the plane of the sample .
for low temperature measurements ( down to 10 k ) , the sample can be mounted in a helium cryogenerator inserted between the electromagnet poles .
the spectra have been measured at room temperature in co metal , laco@xmath0 and tbco@xmath0 and at 10 k in tbco@xmath6 and dy(ni@xmath15co@xmath16)@xmath0 .
the xmcd spectra at the co
k edge are presented on figure [ cokexp ] for co metal , laco@xmath0 and tbco@xmath0 along with other r - co compounds .
the origin of the energy scale has been chosen at the inflexion point of the absorption edge .
all xmcd spectra have been normalized to the edge jump of the absorption edge . in tbco@xmath6 and in dy(ni@xmath15co@xmath16)@xmath0 at 10 k ( @xmath18t@xmath19 ) , the magnetization of the co sublattice is smaller than the magnetization of the rare earth sublattice and antiferromagnetically coupled with it , giving rise to a reverse xmcd signal with respect to co metal or laco@xmath0 and tbco@xmath0 compounds .
in order to keep the same sign convention than in co metal the xmcd spectra of tbco@xmath6 and dy(ni@xmath15co@xmath16)@xmath0 were multiplied by -1 as indicated on figure [ cokexp ] .
the dichroic signal at the co k edge in co metal exhibits a one - peak structure centered about 5 ev above the absorption edge .
the full width at half maximum is about 5 ev .
the xmcd spectrum of laco@xmath0 , where the rare earth is not magnetic , is close to that of co metal .
it presents a negative one - peak structure at about 5 ev in addition to a weak positive contribution in the middle of the broad negative structure . on the other hand ,
the xmcd spectra obtained from magnetic r - based compounds strongly contrast with that of co metal and laco@xmath0 .
the dichroic signal consists of a three - peaks structure , two negative and one positive in the middle of the negative ones .
the central peak exhibits now a huge amplitude , comparable to that of the negative dips . when switching from an hexagonal - based compound ( tbco@xmath0 ) to its cubic - based counterpart ( tbco@xmath6 ) , sizeable changes in the xmcd signal
are also observed .
the central positive feature in tbco@xmath6 seems of larger amplitude and wider than in tbco@xmath0 . at higher energy , all
xmcd co k edge spectra exhibit a positive bump located about 20 ev above the absorption edge , which may be ascribed to magnetic exafs .
the behavior of the xmcd signal at the co k edge in r - co compounds , with respect to co metal , clearly shows the r influence on the dichroism . in order to obtain a deeper insight into such a behavior
, we performed multiple - scattering calculations at the co k edge in co metal , laco@xmath0 and tbco@xmath0 .
the co k edge xmcd spectra were calculated within the multiple - scattering framework including the spin - orbit coupling .
the cross section is calculated from the dirac - green function according to eq .
( 3 ) in ref.@xcite . a fully relativistic core - state wave function has been used .
the determination of the cross section requires the calculation of the atomic potential which has been carried out within the self - consistent lmto approach ( see section [ sublmto ] ) .
the influence of the relativistic effects , that is the spin - orbit interaction , is obtained by the series expansion of the dirac - green function .
to zero - th order in @xmath20 we find the absorption cross section @xmath21 in the absence of relativistic effects .
the expansion carried out up to second order in @xmath20 provides 5 terms .
only the fourth term of this expansion contributes to xmcd .
this term will be denoted as @xmath22 according to the notation in ref .
@xcite . in order to take into account the finite core - hole lifetime @xmath23
, the spectra must be convoluted by a lorentzian with a half width at half maximum ( hwhm ) @xmath24 . within the green function formalism
, this convolution is achieved in calculating the green function for complex energies @xmath25 .
we have to consider also the fact that only the transitions into the empty states , located above the fermi energy , are allowed .
thus , the convolution by the @xmath24-width lorentzian must be carried out from e@xmath26 instead of @xmath27 .
we will see later on that the right choice of the fermi energy is of crucial importance when comparing the calculated spectra to the experimental ones .
the total absorption cross - section can be written as the sum of two contributions according to eq .
( 21 ) in ref .
@xcite .
@xmath28\ ] ] where the sum is carried out over the two spin states _
s_. @xmath29 is defined as the _ atomic _ contribution to x - ray absorption and @xmath30 stands for the influence of the _ neighbors _ surrounding the absorption site .
the atomic contribution @xmath29 is the absorption due to an isolated atom , and does not exhibit oscillations .
the dichroic cross section defined as @xmath31 is shown to be equal to the sum of three terms : @xmath32\right]\ ] ] where @xmath33 describes the purely _ atomic _ contribution to xmcd ( related to the fano effect ) , @xmath34 provides the _ local _ contribution due to the spin polarization of the @xmath5-states on the absorbing site and @xmath35 is the contribution due to the scattering of the photoelectron by the spin - orbit potential of the _ neighbors _ and the absorber itself @xcite .
the @xmath5 , @xmath1 , @xmath4 , ... orbitals of each atom of the cluster give a specific contribution to @xmath35 .
the expansion of @xmath35 into orbitals and sites is useful to determine the physical origin of some peaks of the xmcd spectra .
the calculations were carried out at idris ( orsay ) .
the crystal potentials were calculated within the local density approximation using a lmto basis set .
the electronic structure is selfconsistent and the total energy is converged beyond 0.1 mry . the spin - orbit coupling is not included in the calculations . for the brillouin zone integration of the density of states we used the tetrahedron method with about 300 @xmath36-points in the irreducible part of the brillouin zone ( ibz ) @xcite .
the calculated co density of states ( dos ) is presented on figure [ dos]a .
the result is consistent with previous calculations performed by jarlborg _
_ in co - hcp using the same lmto formalism @xcite .
the similarities between the spin @xmath37 and the spin @xmath38 dos show the rigid band like behavior of co metal .
the calculated co spin moment 1.57 @xmath39co agrees well with the experimental value of about 1.6 @xmath9 .
the selfconsistent fermi level is located at -1 ev . the calculations on rco@xmath0 class compounds were first performed on gdco@xmath0 . while not measured in the present study , this compound serves as a reference for our lmto calculations of the rco@xmath0 .
the muffin - tin radii r@xmath40 of both gd and co were derived from the values given by yamaguchi and asano @xcite by expanding the radii so that the total volume occupied by the muffin - tin spheres in the unit cell is equal to the volume of the unit cell itself , while keeping the ratio r@xmath40(gd)/r@xmath40(co ) constant . under this condition , the muffin - tin spheres on two neighboring sites overlap each other . the r muffin - tin radius in the other rco@xmath0 compounds has been deduced from that of gd in gdco@xmath0 by scaling the rare earth radius to the volume of the unit cell , keeping the co muffin - tin radius constant throughout the rco@xmath0 series .
the muffin - tin radii used for the calculations are summarized in table [ tab3 ] .
our calculated gdco@xmath41 dos , presented in figure [ dos]c , is comparable to that of keller _ et al . _
@xcite , although the energy resolution of the latter is not as accurate as in the present study .
the 4@xmath4 spin moment is coupled antiferromagnetically to the mainly @xmath1-character moment of the co conduction band , as expected for rare earth - transition metal alloys .
the fermi energy is located at e@xmath42=-2 ev .
the calculated spin moments on co sites , of 1.28 @xmath39co and 1.37 @xmath39co respectively on 2c and 3 g sites , are slightly smaller than those previously reported by yamaguchi and asano @xcite but agree with a larger moment on the 3 g site .
the total spin moment calculated on the gd site is 7.06@xmath39gd , this value is also smaller than the values reported in ref .
the gd 4@xmath4 spin moment deduced from our calculations is 6.69 @xmath39gd .
the reduction of the 4@xmath4 spin moment compared to the 7 @xmath43 expected for the free ion comes from the @xmath4(gd)-@xmath1(co ) hybridization in the band structure calculation .
figures [ dos]b and [ dos]d show the calculated dos of laco@xmath0 and tbco@xmath0 respectively . for laco@xmath0
the fermi energy is located at -2.5 ev .
the calculated co spin moments are 1.33 @xmath39co and 1.50 @xmath39co on the 2c and 3 g sites respectively
. a weak moment of 0.4 @xmath39la is also calculated on the la site , which is mainly due to the 5@xmath1 states .
for tbco@xmath0 the fermi energy is located at -1.66 ev and the calculated co moments are 1.37 @xmath39co and 1.41 @xmath39co on 2c and 3 g atomic sites , respectively .
the values of the co moments calculated in laco@xmath0 and tbco@xmath0 are very consistent with those obtained in gdco@xmath0 .
the spin moment calculated at the tb sites is 5.88 @xmath39 tb .
compared with the moment calculated on the gd site in gdco@xmath0 , this value appears quite coherent . here
also the @xmath4(tb)-@xmath1(co ) hybridization leads to a reduction of the 4@xmath4 spin moment which reaches 5.63 @xmath39 tb .
the xmcd calculations have been carried out with the numerical program described in ref .
the converged potential included in the multiple - scattering calculations are those calculated by lmto .
the xmcd program uses touching muffin - tin spheres without overlap .
the absence of overlap is required for the multiple - scattering calculations to be convergent .
because of the difference in the muffin - tin radii between lmto and multiple - scattering potentials , there is an interstitial volume between the spheres in the multiple - scattering calculations .
this volume is represented by a muffin - tin potential v@xmath44 which is calculated as the average potential , in the interstitial region , due to all the charges in the cluster ( including the interstitial region ) .
this interstitial potential v@xmath44 is the energy origin of the multiple - scattering calculations , and has no reason to be the same as the energy origin of the lmto calculations .
this ambiguity can be avoided by using full potential codes that do not make the muffin - tin approximation . however , no such codes are available at the moment for xmcd . the muffin - tin radii used in the multiple - scattering calculations are presented on table [ tab3 ] . for laco@xmath0 and tbco@xmath0 ,
they have been deduced using the procedure proposed by yamaguchi and asano for gdco@xmath0 @xcite .
note that the r@xmath40(r)/r@xmath40(co ) ratio has the same value than in lmto calculations for tbco@xmath0 while it is slightly smaller in laco@xmath0 .
the calculations for hcp co metal have been performed using a cluster of 105 atoms .
the absorption , @xmath45 , and dichroic , @xmath46 , spectra calculated first without introducing the fermi level are presented in figures [ cocalc]a and [ cocalc]b .
figure [ cocalc]b also presents the contribution of @xmath33 , @xmath34 and @xmath35 to the dichroic cross section .
the xmcd spectrum consists in a three - peaks structure near the absorption edge , followed by weak exafs oscillations appearing about 10 ev above the edge .
the first two peaks in the xmcd spectrum come mainly from the @xmath35 contribution . as aforesaid ,
this contribution comes from the scattering due to the spin - orbit potential on the neighbors and the absorbing site .
quite similar results have been previously reported at the fe k edge @xcite .
the third peak at 5 ev results from the sum of the three contributions , @xmath33 , @xmath34 and @xmath35 which have comparable amplitudes . as we shall see later in laco@xmath0 and tbco@xmath0 , in this energy region @xmath33 and @xmath35 are always in phase opposition with @xmath34 .
@xmath34 originates form the polarization of the @xmath5-states on the absorbing site .
the expansion of the @xmath35 cross section into the @xmath47 components and sites of the whole cluster is presented on figure [ cocalc]c .
the scattering due to the @xmath1 spin - orbit potential mainly accounts for the first two peaks in the near - edge region of the xmcd signal .
the amplitude of the oscillations due to the scattering by the spin - orbit potential on the @xmath5 orbitals starts to significantly increase above the edge and a large peak is calculated around 8 ev .
the negative peak around 5 ev in the @xmath35 cross section results from the well balanced contributions of the @xmath5 and @xmath1 orbitals . in order to compare the calculated spectra to the experimental ones
, the fermi energy has to be included . in figure [ cocalcexp ]
the absorption and dichroic experimental spectra are presented along with the calculated ones with and without introducing the fermi energy .
absorption and xmcd spectra are all normalized to the edge jump at the absorption edge so that the absorption edge jump is 1 .
the fermi energy was chosen at 1.2 ev by fitting both the absorption and the xmcd spectra to the experimental ones in the near - edge region .
the fermi energy of the multiple - scattering calculations is not the same as that of the lmto calculations because of the difference in the energy origin between the two approaches .
the effect of the fermi energy clearly shows up , especially for the xmcd spectrum : the first two peaks have vanished and only subsists the negative peak around 5 ev .
the xmcd spectrum is broadened around e@xmath26 as expected from the truncated lorentzian convolution .
it may be noticed that in ref .
@xcite , the xmcd spectrum calculated at the k edge in fe metal with e@xmath26=0 ev keeps a positive peak at low energy , mainly coming from the @xmath35 contribution , which fits well the derivative - like behavior of the measured xmcd spectrum . the higher fermi level found in co
metal leads to the collapse of this second peaks in the near - edge region of the co k edge xmcd spectrum .
it is worth noting that a higher fermi level in co metal is coherent with the higher occupancy of the co @xmath1 band ( @xmath48 ) compared to fe ( @xmath49 ) . in the near edge region
the calculation reproduces rather well the structure of the absorption and xmcd experimental spectra .
the calculated spectra present a slight shift to the high energies .
this shift is very likely due to the difficulty to properly fit in the energy between calculated and experimental spectra . for the xmcd spectrum the calculation yields the expected one - peak feature with however a narrower width than the experimental one . in the region between 10 ev and 30 ev
the calculated oscillations are not resolved in the experimental spectrum , where only a large bump is observed . the extended energy spectra are presented on figure [ coexafs ] .
the slight shift in energy of the exafs oscillations is again noticed between experiment and calculation in both the absorption and the xmcd spectra .
though the exafs structures are strongly damped in the measured spectra , the agreement between experiment and calculation remains rather satisfactory .
the agreement in the intensity of the calculated and experimental peak around 5 ev is very likely fortuitous . indeed in the calculation
the degree of circular polarization is set equal to 1 , while experimentally the polarization rate of the incoming beam , estimated at 0.65 , reduces the signal intensity .
this is confirmed in the energy range 10 - 30 ev where the intensity of the calculated oscillations is to small to account for the bump observed experimentally .
consequently it turns out that in the high energy region the calculated amplitude of the oscillations is always overestimated , in the dichroic spectrum but also in the absorption one .
these effects might be related to a current limitation of the xmcd program which does not include the inelastic scattering processes undergone by the photoelectron in the metal .
the multiple - scattering calculations in the laco@xmath0 and tbco@xmath0 compounds have been carried out on a 117 atoms cluster for each co atomic site .
the total spectrum results from the weighted sum of the spectrum on each site with respect to its multiplicity in the unit cell .
calculations have been performed only in the near edge energy domain since the extended structures are poorly resolved in the absorption and dichroic experimental spectra .
the absorption and dichroic spectra calculated without the fermi level for laco@xmath0 are presented on figures [ laco5calc]a and [ laco5calc]b .
the different components , @xmath33 , @xmath34 and @xmath35 , to the xmcd cross section are also shown . in the energy region -10 to 0 ev , the @xmath35 contribution is responsible for the first two peaks as already observed in co metal . around the third negative peak at 5 ev ,
the @xmath33 and @xmath34 contributions are comparable to those calculated in co metal whereas @xmath35 is reduced by more than a factor 2 .
the reduction of @xmath35 and the phase opposition between @xmath33 , @xmath35 and @xmath34 give rise to the positive cusp located in the middle of the negative peak , characteristic of the laco@xmath0 xmcd spectrum ( cf . fig .
[ laco5calcexp ] ) .
figure [ laco5calc]c presents the contribution to the @xmath35 cross section of the @xmath5 , @xmath1 and @xmath4 shells of the la first neighbors and of the @xmath1 shell of the co first neighbors . in the near - edge region and just above the edge , @xmath35 is dominated by the scattering processes due to the @xmath1 contribution of co and la .
the peculiar decrease of the total @xmath35 cross section around 5 ev comes from the existence of a positive peak in the la @xmath1 orbital component , while the co @xmath1 and la @xmath5 components give rise to negative structures . at
higher energies features on @xmath35 come essentially from the la @xmath5 shell contribution .
the normalized absorption and xmcd cross sections calculated with a fermi energy of 0 ev are compared on figure [ laco5calcexp ] with the experimental spectra .
the calculated dichroic spectrum was divided by an arbitrary factor in order to fit the experimental one . besides the reduction of the signal due to the circular polarization rate
, this correction accounts for the fact that the magnetic saturation of the powdered sample of laco@xmath0 is not reached under an applied field of 0.4 t. the agreement for the absorption spectrum is far from being excellent but the dichroic signal is well reproduced , especially the structure at 5 ev .
it can be noticed that the total width of the spectrum agrees well with the observed one . above 10 ev discrepancies between the calculations and the measured spectrum
are observed , as for co metal the experimental signal presents a large bump instead of well resolved structures .
the absorption and xmcd calculated spectra without the fermi level for tbco@xmath0 are illustrated on figure [ tbco5calc]a and [ tbco5calc]b .
figure [ tbco5calc]b also shows the contributions of @xmath33 , @xmath34 and @xmath35 to the total xmcd cross section .
the structures of the xmcd signal in the low energy region arise , as in laco@xmath0 , from @xmath35 .
the first negative peak has a structure and an amplitude very similar to those obtained in laco@xmath0 or co metal .
the second positive peak presents a double structure which results from the mixing of the co @xmath1 and tb @xmath1 shell positive contributions and the negative tb @xmath4 shell contribution as shown in figure [ tbco5calc]c . in figure
[ tbco5calc]c are represented only the contributions to the @xmath35 cross section from the @xmath5 , @xmath1 and @xmath4 shells of the tb first neighbors and the @xmath1 shell of the co first neighbors .
the addition of the contributions , of smaller intensity , coming from the other atoms of the cluster does not change quantitatively the structure of the spectra .
it may be noted that the tb @xmath4 shell contribution is not negligible in the near edge region .
compared to the laco@xmath0 xmcd spectra , the third negative peak around 5 ev comes almost exclusively from @xmath35 . in this energy region @xmath33 and @xmath34 having roughly the same amplitude and opposite sign cancel each other .
this negative structure can be mainly assigned to the tb @xmath1 shell contribution .
this contribution along with the tb @xmath5 and @xmath4 contributions , of lower intensity , give rise also to the positive bump in @xmath35 which immediately follows the negative peak .
when the fermi level is included in the calculation , the structures near the absorption edge are smeared out .
the calculated spectra which best fit with the experimental ones are obtained with e@xmath26=3 ev .
experimental and calculated spectra are presented in figure [ tbco5calcexp ] .
the calculated absorption spectrum presents structures which are not resolved in the experimental one .
the calculated dichroic spectrum was scaled to the experimental one . as for laco@xmath0
, this correction accounts for the non - saturation of the magnetization .
the two peaks at 6 and 10 ev in the experimental xmcd spectrum are quite well reproduced by the calculations , in particular their widths . at higher energies ,
we find incoherences again between the calculation and the measured spectrum .
calculations within the multiple scattering approach of the dichroic signal at the co k edge in pure co metal reproduce with a rather good agreement the structures of the experimental spectrum .
in particular the one - peak structure near the edge is well accounted for with a fermi energy of 1.2 ev .
the co k edge spectrum , calculated without the fermi level presents strong similarities with the fe k edge spectrum calculated in the same conditions . in the present theoretical approach it is possible to separate the local contributions to the dichroic cross section from those coming from the surrounding atoms . when these contributions are examined it
is confirmed that the scattering by the spin - orbit potential of the @xmath1 shell of the neighboring atoms creates strong structures in the low energy range of the spectrum .
this is in agreement with igarashi and hirai calculations .
the local contributions , atomic contribution and contribution due to the spin polarization of the @xmath5-states , give structures at higher energies typically around 5 ev .
however as soon as the fermi level is introduced in the calculations , low energy structures partially ( fe ) , or completely ( co ) , disappear .
present calculations show that the negative structure observed in the co metal xmcd spectrum at the co k edge results from a well balanced mixing between local , @xmath33 and @xmath34 , and surrounding , @xmath35 , contribution .
it may be noted that , in this energy range , the contributions to @xmath35 , arising from the spin - orbit coupling in the @xmath1 and @xmath5 shells have comparable intensities .
the calculated co k edge xmcd spectra in laco@xmath0 , and tbco@xmath0 reproduce , with an excellent agreement in the near edge region , the structures of the experimental spectra . as for co metal the signal structure in laco@xmath0
is accounted for by a balanced mixing between local and surrounding contributions . in this last contribution
the rare earth atoms , via the spin - orbit coupling on the la @xmath1 and @xmath5 shells , significantly influence the structure . in the case of tbco@xmath0
the multiple - scattering calculations stress the major role of the contributions due to the neighbors , @xmath35 in the structure of the spectrum around 5 ev .
more precisely , the expansion of the @xmath35 cross section into the @xmath47 orbital components allowed us to evidence that the first negative peak in the xmcd spectrum at the co k edge originates almost exclusively from the spin - orbit potential on the tb @xmath1 states .
this result points out that the structures of the xmcd spectrum at the k edge of the transition metal in the r - tm alloys are induced to a large extent by the rare earth when the rare earth is magnetic .
the xmcd at the co k edge in the r - co compounds , which probes the empty @xmath5-states on co sites , thus detects the spin - orbit interaction on the rare earth @xmath1-states .
this process is very likely mediated through the hybridization .
the similarities observed in the density of states above the fermi level , between the tb(@xmath1 ) and the co(@xmath5)-dos in tbco@xmath0 ( cf . fig .
[ tbco5doszoom ] ) underline the existence of a co(@xmath5)-r(@xmath1 ) hybridization .
the closer resemblance between co-2c(@xmath5 ) and tb(@xmath1 ) is related to the shorter distance leading to a larger orbital overlapping between the co-2c tb compared to co-3g tb .
effects of the environment can be expected to exist at the l@xmath2 edges of the transition metal as well , like in the re - tm alloys where the re(5@xmath1 ) and tm(3@xmath1 ) band are hybridized .
for instance , it is very likely that magnetic exafs structure can reflect these effects and recent theoretical investigations on the magnetic exafs at the l@xmath2 edges of pure fe are very promising @xcite .
however a proper experimental evidence presents great difficulties as the white lines dominate the spectra at these edges .
moreover , in the soft x - ray energy range , surface defaults which are far from being negligible in the re - tm alloys may disturb the interpretation of the spectra .
though the xmcd spectra are quite well reproduced in the near region , a better agreement has yet to be obtained in the exafs region both in the absorption and dichroic spectra .
an improvement planned for the future is the use of an optical potential to take into account the exchange and inelastic interactions on the photoelectron .
more precisely , the interpretation depends on whether we consider fully or semi - relativistic theories . in a fully relativistic framework
, xmcd depends only on the projection of the relativistic photoelectron wavefunction over the @xmath5 states of the absorber . in a semi - relativistic framework ,
the photoelectron is considered to propagate to all sites of the cluster , where it is scattered by the local spin - orbit interaction .
when the @xmath5-component of this semi - relativistic wavefunction is calculated , it has a contribution from the non - relativistic wave function ( @xmath33 and @xmath34 ) and a contribution due to the spin - orbit scattering by all the atoms of the cluster ( @xmath35 ) . | the x - ray magnetic circular dichroism ( xmcd ) has been measured at the co k edge in hcp - co and r - co compounds ( r = la , tb , dy ) . the structure of the experimental xmcd spectra in the near - edge region has been observed to be highly sensitive to the magnetic environment of the absorbing site .
calculations of the xmcd have been carried out at the co k edge in co metal , laco@xmath0 and tbco@xmath0 within the multiple - scattering framework including the spin - orbit coupling . in the three systems , the xmcd spectra in the near - edge region
are well reproduced . the possibility to separate the local effects from those due to the neighboring atoms in the xmcd cross section makes possible a more physical understanding of the spectra .
the present results emphasize the major role played by the @xmath1 states of the tb ions in the xmcd spectrum at the co k edge in the tbco@xmath0 compound . |
firefighting is one of the most hazardous , physically demanding , and psychologically stressful occupations .
it is therefore not surprising that low back pain and related musculoskeletal injuries are very common in firefighters and the leading cause of early retirement [ 1 , 2 ] .
obesity affects more than one - third of career firefighters [ 3 , 4 ] and has been linked with an increased risk of low back pain in the general population . in the general population , obesity has also been associated with poor performance on physical fitness tests , such as back muscular endurance [ 6 , 7 ] , which has been reported to be predictive of future incidence of low back pain . in the general population ,
poorly conditioned back and core muscles have been associated with low back pain , as individuals with low back pain have reduced strength , endurance , atrophy , fatty infiltration , and abnormal activity in various back and core muscles [ 811 ] .
the fire service joint labor management wellness - fitness initiative of the international association of fire fighters and international association of fire chiefs recommends screening for obesity and the assessment of musculoskeletal fitness , including muscular endurance .
however , the relationships between obesity , low back pain , and back muscular endurance have not been assessed in firefighters .
given the link between back muscular endurance , obesity , and low back pain in the general population , along with the high incidence of low back pain in firefighters , exploring the impact of obesity on back muscular endurance in firefighters is warranted .
the purpose of this study was to assess the relationships between obesity and measures of back and core muscular endurance in firefighters .
a cross - sectional study was conducted with firefighters from a municipal fire department in the united states .
data for this study were obtained from baseline assessments within a randomized controlled trial of progressive resistance exercise training for the low back ( grant no .
male career firefighters ( n = 83 ) were recruited from the entire population of firefighters ( n = 573 ) of tampa fire rescue ( tampa , fl , united states ) . the study sample consisted of 10 captains , 5 lieutenants , 13 driver - engineers , 8 paramedics , and 47 firefighters without additional rank .
participants were recruited by presentations , email notices , posted information , and word - of - mouth .
the university of south florida institutional review board approved the experimental protocol and all participants provided informed consent . candidates with interest in the study underwent telephone screening that included questions related to work status and health history , and those deemed eligible were invited to our laboratory for additional screening .
on - site screening included various self - reported health history questionnaires and a physical examination .
inclusion criteria for participation were being 18 years of age or older and an active , full - duty firefighter . candidates with cardiovascular or orthopedic contraindications to exercise , history of systemic inflammatory disease or spinal surgery , clinically meaningful current low back pain or disability , inability to participate in physical activity , presence of red flags for potential serious condition related to low back pain , abnormal resting blood pressure or heart rate , currently receiving care for spinal pain disorder / injury , currently diagnosed with or receiving care for a psychological or psychiatric disorder , currently performing progressive resistance exercises for the low back or core muscles , active workers ' compensation or personal injury case , simultaneous enrollment in another clinical trial , drug or alcohol abuse within the past year , or any other condition that would put the candidate at increased safety risk or otherwise make the candidate unsuitable for this study were excluded .
self - reported physical exercise was assessed by the question , over the past three months , on average , how many days per week have you performed any physical exercise ? this question was adapted from a specific item described in the minimum data set of the fire service joint labor management wellness - fitness initiative guidelines .
body mass ( kg ) , measured with a calibrated electronic scale ( life measurement , inc . , concord , ca , united states ) , and body height ( cm ) , measured with a stadiometer ( novel products inc . ,
rockton , illinois , united states ) , were used to calculate bmi ( bmi ( kg / m ) = body mass ( kg)/body height ( m ) ) .
body fat percentage was assessed using whole - body air displacement plethysmography ( bod pod , life measurement , inc . , concord , ca , united states ) with estimated thoracic gas volume according to the manufacturer 's guidelines .
air displacement plethysmography , when compared with both hydrostatic weighing and dual - energy x - ray absorptiometry , agrees within 1% body fat when the average of multiple study means is calculated . also , the correlations between air displacement plethysmography and both hydrostatic weighing and dual - energy x - ray absorptiometry are strong across multiple studies ( r = 0.780.94 ) .
isometric back extension muscular endurance was assessed with the modified biering - sorensen test . for the modified biering - sorensen test
, the participant was positioned on a variable angle roman chair ( conner athletic products , jefferson , ia , united states ) at the horizontal position , with the anterior superior iliac spines aligned to the superior edge of the pelvic restraint pad of the machine .
the hands were placed behind the head , ankles were positioned under the ankle pad , and legs were held as straight as possible .
the participant was then instructed to elevate the torso to a horizontal position ( figure 1 ) .
as soon as the horizontal position was attained , the examiner began timing with a stopwatch .
the participant was verbally encouraged by the examiner to hold the position as long as possible .
if the participant 's torso dropped 10 below the horizontal position , the participant would be given a maximum of two warnings to reestablish the position .
if the participant was unable to do so , the examiner stopped the test , and time was recorded in seconds .
the modified biering - sorensen test has been shown to be a reliable measure of isometric back extension muscular endurance .
after a four - minute rest , isometric core muscular endurance was assessed with the plank test ( figure 2 ) . for the plank test
, the participant was positioned as follows : prone position on a floor mat ; upper body elevated and supported by the elbows ; hips and legs elevated off the floor so that the neck , trunk , and lower extremities aligned in the sagittal plane ( straight body alignment maintained from shoulder through hip , knee , and ankle ) ; body supported on forearms and toes ; elbows directly under the shoulders ; ankles maintained at 90 ; scapulae stabilized with elbows at 90 ; spine in a neutral position throughout the assessment .
as soon as the participant lifted the torso off the mat , a test examiner began timing with a stopwatch .
the participant was verbally encouraged by the test examiner to hold the test position as long as possible .
if the participant was unable to maintain the test position , the participant would be given a maximum of two warnings from the examiner to reestablish the position .
if the participant was unable to do so , the examiner stopped the test , and time was recorded in seconds .
the plank test has been shown to be a reliable measure of isometric core muscular endurance .
data were analyzed using sas ( statistical analysis system , version 9.2 , cary , nc , united states ) and spss version 20 ( ibm corporation , armonk , ny , united states ) .
several analyses were conducted to assess the impact of obesity on back and core muscular endurance .
first , differences between the nonobese and obese participants on various measures were assessed with independent t - tests .
participants were categorized into one of two groups based on bmi values : nonobese - bmi < 30 kg / m , obese - bmi 30
kg / m . due to differences in age between the groups , age was included as a covariate in the models for back and core muscular endurance comparing obese with nonobese participants .
additionally , associations between dependent variables ( back and core muscular endurance ) and independent variables ( age , self - reported amount of any physical exercise per week , bmi , body fat percentage , fat mass , and fat - free mass ) were assessed by calculating pearson correlation coefficients for bivariable comparisons .
lastly , three separate multivariable stepwise regression analyses were conducted for both back and core endurance , each using one of three measures for obesity ( bmi , body fat percentage , or fat mass / fat - free mass ) along with age and self - reported physical exercise as independent variables .
multiple measures of obesity were selected because of the potentially different application for each measure .
for example , bmi is an indirect measure of body composition that is frequently used as an efficient test in occupational , health , and fitness settings .
body fat percentage , fat mass , and fat - free mass provide more direct markers of body composition , yet require specialized testing equipment .
multiple measures of obesity were not included within the same stepwise regression model because the bivariable correlations among these measures were moderate to strong , ranging from r = 0.45 to r = 0.96 ( table 2 ) .
due to the low bivariable correlations among the included independent variables within each of the multivariable stepwise regression analyses , collinearity was not deemed an issue and , therefore , variance inflation factor was not considered .
in addition to the analyses used to assess the impact of obesity on muscular endurance , the rate at which bmi misclassified subjects as obese or nonobese was also assessed by calculating false negative and false positive rates .
misclassifications of obesity were based on standard body fat percentage criteria for defining obesity ( obese 25% body fat ; not obese < 25% body fat ) .
age , physical exercise , obesity , and muscular endurance data of the participants stratified by obesity category according to bmi are summarized in table 1 .
the mean bmi of all the firefighters was 28.1 kg / m , which is in the overweight range . according to standard bmi categories
, 21.7% ( n = 18 ) of the participants had a normal bmi , 49.4% ( n = 41 ) were overweight , and 28.9% ( n = 24 ) were obese . based on body fat percentage , 57.6% of the participants were nonobese and 42.4% of participants were obese .
obese firefighters according to bmi categories had poorer back and core muscular endurance times compared with the nonobese firefighters .
of the 83 participants , 19 ( 22.9% ) were misclassified by bmi according to body fat percentage criteria .
a total of 15 ( 42.9% ) participants were misclassified by bmi as nonobese when they were actually obese ( i.e. , false - negative misclassifications )
. a total of 4 ( 8.3% ) participants were misclassified by bmi as obese when they were actually nonobese ( i.e. , false - positive misclassifications ) .
bivariable pearson 's correlation coefficients ( r ) comparing age , physical exercise , bmi , body fat percentage , fat mass , fat - free mass , and muscular endurance data are presented in table 2 . for back muscular endurance ,
significant negative correlations were noted with age , bmi , body fat percentage , and fat mass . for core muscular endurance ,
significant negative correlations were noted with bmi , body fat percentage , fat mass , and fat - free mass . for back muscular endurance ,
the obesity measure was the only significant independent variable in the three stepwise multivariable regression models , which accounted for 1619% of the variance in back muscular endurance ( table 3 ) . with a 1-point increase in bmi , back muscular endurance decreases by 2.9 seconds . with a 1-point increase in body fat percentage , back muscular
endurance decreases by 1.2 seconds . with a 1-point increase in fat mass , back muscular
the obesity measure and age were significant independent variables in all three of the stepwise multivariable regression models , which accounted for 2937% of the variance in core muscular endurance ( table 4 ) . with a 1-point increase in bmi , core muscular
core muscular endurance decreases by 4.4 seconds . with a 1-point increase in fat mass ,
the findings of this study indicate that obesity has a significant negative impact on back and core muscular endurance in firefighters , regardless of which measure of obesity is assessed .
similar trends were observed for the relationships between all markers of obesity ( bmi , body fat percentage , or fat mass / fat - free body mass ) assessed in this study and back and core muscular endurance .
first , the biomechanical strategies required for the muscular endurance tests used in this study are likely impacted by body mass . the modified biering sorensen and
the plank tests depend on gravity 's action on body mass for the entire load and the ability to support body mass against gravity for an extended period of time .
thus , individuals with high bmi values are likely at a biomechanical disadvantage during these tests given the higher body loads that need to be supported against gravity .
it is unclear if the same relationship between bmi and back and core muscular endurance exists when testing strategies are used that are not dependent on gravity 's effect on body mass and exercise load .
the lack of significant relationships between fat - free mass and muscular endurance measures in the bivariable and multivariable regression models may indicate that overall body mass may play a larger role than muscle mass in back and core muscular endurance performance testing .
other conceivable explanations for the poorer muscular endurance times in obese firefighters include possible differences between obese and nonobese individuals in physiology and morphology of the back and core muscles , general fitness levels , perceived exertion levels on fitness tests , and familiarity with physical fitness exercise , along with a possible negative influence of other comorbidities associated with obesity . considering that the multivariable regression models for back and core muscular endurance accounted for only 1619% and 2937% of the variance , respectively ,
these models do not account for a large portion of the variance in back and core muscular endurance .
therefore , other factors that were not measured in this study may be involved in performance on the muscular endurance tests . also ,
because the total portion of variance accounted for in the models was low , back and core muscular endurance should be directly assessed and should not be predicted from age , self - reported amount of any physical exercise per week , and measures of obesity .
the present study 's findings on the relationship of body composition and back muscular endurance in firefighters appear to be similar to the relationships observed in the general population .
we uncovered four previous studies that assessed relationships between back muscular endurance ( as assessed by some version of the biering sorensen test ) and body composition in the general population [ 6 , 7 , 16 , 17 ] . in three of these four studies [ 6 , 7 , 16 ] , significant moderate negative correlations between measures of body composition ( bmi and body fat percentage ) and back muscular endurance were observed . in the present study ,
bmi and body fat percentage were elevated in a large proportion of participants , indicating a high prevalence of overweight or obese firefighters in this study . in the current study ,
29% of the firefighters were obese according to bmi , and 42% of firefighters were obese according to body fat percentage .
these findings are consistent with previous studies of obesity in firefighters which reported that approximately 34% of firefighters are obese according to bmi [ 3 , 4 ] and approximately 48% are obese according to body fat percentage .
in the present study , bmi misclassified 42.9% of obese firefighters ( according to body fat percentage criteria defining obese as 25% ) as nonobese ( i.e. , false negative diagnosis ) . such misclassifications appear to be common in male firefighters , as a previous study reported a false negative rate of 32.9% . given the relatively high rate of mismatch between bmi and body fat percentage , assessing both bmi and body fat percentage is reasonable since each method may give unique information on the health status of firefighters .
in addition to the relationship between obesity and poor back and core muscular endurance observed in the present study , obesity has been linked with decreased job performance and increased risk of disability in firefighters . a recent study assessed fitness parameters among firefighters , including bmi , body fat percentage , and performance on a physical ability test that consisted of climbing stairs , rolling , lifting , pulling , threading a hose coupling to a hydrant , and advancing a hose , wielding a sledgehammer , and rescuing a mannequin . in this study ,
poor performance on the physical ability test was correlated with high bmi ( r = 0.34 , p < 0.01 ) and high body fat percentage ( r = 0.36 , p < 0.01 ) .
a longitudinal study of firefighters reported that obesity was a significant risk factor for job disability , and that every unit increase in bmi was associated with a 5% increase in risk of job disability .
this study also reported that obese firefighters ( bmi 30 ) had a hazard ratio of 2 for an adverse employment event , defined as injured - duty status , termination of duty , resignation , premature retirement , or death , when compared to those with a bmi < 27 . whether obesity is associated with increased risk for musculoskeletal disorders , such as low back pain , in firefighters is unknown and requires further study .
first , this study enrolled a relatively small number of participants , which limited the number of independent variables that could be considered in multivariable regression models .
the study sample was powered based on potential differences in outcomes of the randomized trial , not the regression models of this cross - sectional analysis .
also , the present study only enrolled male participants from a single fire department in the southeastern united states , and it is unclear if results can be generalized to firefighters in other settings .
the cross - sectional , observational design used in this study can only report on associations observed at the time of measurement and is therefore unable to establish causation between back and core muscular endurance and body composition .
additionally , it is unclear if performance on the back and core muscular endurance tests reflects the ability to perform physical activities required of firefighters .
although physical factors such as back and core muscular endurance and obesity measures are associated with low back pain , other factors that are associated with low back pain , such as psychosocial occupational factors , were not measured in this study .
finally , the measure of self - reported physical activity used in this study , although a part of the minimum data set established by the fire service joint labor management wellness - fitness initiative , has yet to be validated .
obesity as measured by increased bmi and body fat percentage is associated with decreased back and core muscular endurance in firefighters , which is consistent with findings in the general population . given the relationship between increased incidence of low back pain in obese individuals and individuals with poor back muscular endurance , exercise programming for back injury prevention in firefighters should address improving both body composition and muscular endurance .
additional research is needed to assess the impact of exercise training and improving body composition on increasing back and core muscular endurance , improving job performance , and reducing risk for low back pain in firefighters . | the purpose of this study was to assess the relationships between obesity and measures of back and core muscular endurance in firefighters .
methods .
a cross - sectional study was conducted in career firefighters without low back pain .
obesity measures included body mass index ( bmi ) and body fat percentage assessed with air displacement plethysmography .
muscular endurance was assessed with the modified biering sorensen ( back ) and plank ( core ) tests .
relationships were explored using t - tests and regression analyses .
results . of the 83 participants enrolled , 24 ( 29% )
were obese ( bmi 30 ) . back and
core muscular endurance was 27% lower for obese participants .
significant negative correlations were observed for bmi and body fat percentage with back and core endurance ( r = 0.42 to 0.52 ) .
stepwise regression models including one obesity measure ( bmi , body fat percentage , and fat mass / fat - free mass ) , along with age and self - reported physical exercise , accounted for 1719% of the variance in back muscular endurance and 2937% of the variance in core muscular endurance . conclusions .
obesity is associated with reduced back and core muscular endurance in firefighters , which may increase the risk of musculoskeletal injuries .
obesity should be considered along with back and core muscular endurance when designing exercise programs for back pain prevention in firefighters . |
owing to the increasing availability of high - dimensional datasets , regression models for multivariate response and high - dimensional predictors have become important tools . in this article , we describe two procedures where a random target variable @xmath0 depends on explanatory variables or covariates within a cluster - specific regression model . each cluster is represented by a parametric conditional distribution , the entire dataset being modeled by a mixture of these distributions .
it provides a rigorous statistical framework .
the model assumes that each observation @xmath1 originates from one of @xmath2 disjoint classes and that the data @xmath3 are independent and identically distributed such that if @xmath4 belongs to class @xmath5 , the target variable @xmath6 results from a conditional regression model @xmath7 with an unknown matrix of coefficients @xmath8 and independent errors @xmath9 with an unknown diagonal covariance matrix @xmath10 .
we work with high - dimensional dataset , in other words the number of parameters to estimate @xmath11 is larger than the number of observed target values @xmath12 .
two ways are considered in this paper , coefficients sparsity and ranks sparsity .
the first approach consists in estimating the matrix @xmath8 by a matrix with few nonzero coefficients .
the well - known lasso estimator , introduced by @xcite for linear models , is the solution chosen here .
we refer to @xcite for an overview of the lasso estimator and to @xcite for stability selection results . in the second approach
, we consider the rank sparsity in @xmath8 .
this approach dates back to the @xmath13 s and was initiated by @xcite for the linear model .
@xcite introduced the term of reduced - rank regression for this class of models .
for more recent works , we refer to @xcite and to @xcite . nevertheless , the linear model is appropriate for homogeneous observations , which is not always the case .
we extend in this paper those methods to mixture regression models .
an important example of high - dimensional dataset is functional dataset .
we refer to ramsay and silverman s book @xcite for an overview .
moreover , a lot of recent works have been done on regression models for functional datasets : for example , we refer to @xcite for a study with scalar response and functional regressors . in this paper , we focus on the projection of functions into a well - suited wavelet basis .
indeed , they handle many types of functional data , because they represent global and local attributes of functions and can deal for example with discontinuities .
moreover , a large class of functions can be well represented with few nonzero coefficients for a suitable wavelet , which leads to sparse matrix of coefficients and then to sparse regression matrix .
we propose here two procedures for clustering high - dimensional or functional datasets , where the high - dimension or functional random target variable @xmath0 depends on high - dimensional or functional predictors @xmath14 with a cluster - specific regression model .
remark that we estimate the number of components , model parameters and cluster proportions . in the case of a large number of regressor variables , we use variable selection tools in order to detect relevant regressors . since the structure of interest
may often be contained into a subset of available variables and many attributes may be useless or even harmful to detect a reasonable clustering structure , it is important to select the relevant variables .
moreover , removing irrelevant variables enables us to get an easier model and can largely enhance comprehension .
our two procedures are mainly based on three recent works .
firstly , we refer to the article of @xcite , which studies finite mixture regression model .
even if we work on a multivariate version of it , the model considered in the article of @xcite is adopted here .
the second , the article of @xcite , deals with model - based clustering in density estimation .
they propose a procedure , called lasso - mle procedure , which determines the number of clusters , the set of relevant variables for the clustering and a clustering of the observations , with high - dimensional data .
we extend this procedure to regression models .
finally , @xcite suggests a low rank estimator for the linear model . to consider the matrix structure , we develop this last approach to mixture models .
we consider a finite mixture of gaussian regression models .
the two procedures we propose follow the same sequence of steps .
firstly , a penalized likelihood approach is considered to determine potential sets of relevant variables . introduced by @xcite , the lasso is used to select variables .
varying the regularization parameter , it constructs efficiently a data - driven model collection where each model has a reasonable complexity .
the second step of the procedures consists in refitting parameters by a less biased estimator , focusing on selected variables .
then , we select a model among the collection using the slope heuristic , which was developed by @xcite .
the difference between the two procedures is the refitting step . in the first procedure ,
later called lasso - mle procedure , the maximum likelihood estimator is used/ the second procedure , called lasso - rank procedure , deals with low rank estimation . for each model in the collection , a subcollection of models with conditional means estimated by various low rank matrices is constructed .
it leads to sparsity for the coefficients and for the rank , and considers the conditional mean within its matrix structure .
the article is organized as follows .
section [ gaussianmixtureregression ] deals with gaussian mixture regression models . the model collection that we consider is described . in section [ twoprocedures ] ,
the two procedures that we propose to solve the problem of high - dimensional regression data clustering are described .
section [ illustrativeexample ] presents an illustrative example , to highlight each choice done in the two procedures .
section [ functionaldatasets ] states the functional data case , with a description of the projection proposed to convert these functions into coefficients data .
we end this section by studying simulated and benchmark data .
finally , a conclusion section ends this article .
the model used is a finite gaussian mixture regression models .
@xcite describe this model when the deterministic predictors @xmath15 are multivariate and the target variable @xmath16 is scalar . in this section , it is generalized to multivariate response .
let us mention that this model has already been introduced , we refer for example to @xcite . in this paper , we deal with high - dimensional data .
[ clustering ] we observe @xmath17 independent couples @xmath18 , which are realizations of random variables @xmath19 . here , @xmath20 are fixed or random covariates and @xmath21 is a multivariate response variable .
conditionally to @xmath22 , @xmath6 is a random variable of unknown conditional density @xmath23 .
the random response variable @xmath21 depends on a set of explanatory variables , written @xmath20 , through a regression - type model .
if @xmath6 , conditionally to @xmath22 , originates from an individual in class @xmath24 , we assume that @xmath25 where @xmath26 , @xmath27 is the matrix of class - specific regression coefficients and @xmath28 is diagonal , positive definite in @xmath29 .
we consider in the following the gaussian regression mixture model : * conditionally to the @xmath30 s , @xmath6 s are independent , for all @xmath31 ; * each variable @xmath6 follows a law of density @xmath32 , with @xmath33 we have denoted by @xmath34 the proportion of the class @xmath24 . for all @xmath35 , for all @xmath36 , for @xmath37 , @xmath38_m= \sum_{j=1}^{p } [ \mathbf{b}_{k}]_{m , j } \xi_{j}$ ] is the @xmath39th component of the conditional mean of the @xmath24th mixture component .
we prefer to work with a reparametrized version of this model whose penalized maximum likelihood estimator is scale - invariant and easier to compute .
indeed , it is not equivariant under scaling of the response .
more precisely , consider the transformation @xmath40 for @xmath41 which leaves the model invariant .
a reasonable estimator based on transformed data @xmath42 should lead to estimator which are related to the first ones up to the homothetic transformation .
this is not the case for the maximum likelihood estimator of @xmath43 and @xmath44 .
secondly , the optimization of the loglikelihood is non - convex and hence , it leads to computational issues .
then , we reparametrize the model described above by generalizing the reparametrization described by stdler et al .
@xcite .
for all @xmath35 , define new parameters @xmath45 where @xmath46 , @xmath47 is the cholesky decomposition of the positive definite matrix @xmath48 .
remark that @xmath47 is a diagonal matrix of size @xmath49 .
the model with its reparametrized form then equals * conditionally to the @xmath30 s , @xmath6 s are independent , for all @xmath31 ; * each variable @xmath6 follows a law of density @xmath50 , with @xmath51 for the sample @xmath52 , the log - likelihood of this model is equal to , @xmath53 and the maximum log - likelihood estimator ( mle ) is @xmath54 since we deal with the high - dimension case ( @xmath55 ) , this estimator has to be regularized to get stable estimates .
therefore , we propose the @xmath56-norm penalized mle @xmath57 where @xmath58 where @xmath59_{m , j}|$ ] and with @xmath60 to specify .
this estimator is not the usual @xmath56-estimator , called the lasso estimator , introduced by @xcite .
it penalizes the @xmath56-norm of the coefficients matrices @xmath61 and small variances simultaneously , which has some close relations to the bayesian lasso ( see @xcite ) .
moreover , the reparametrization allows us to consider non - standardized data .
notice that we restrict ourselves in this article to diagonal covariance matrices which are dependent of the clusters .
we assume that the coordinates of the @xmath6 are independent , which is a strong assumption , but it allows us to reduce easily the dimension .
we refer to @xcite for different parametrization of the covariance matrix .
nevertheless , because we work with high - dimensional data ( @xmath62 and @xmath49 are high and @xmath17 is small ) we prefer a parsimonious model from the diagonal family .
we allow different volume clusters because they are capable to detect many clustering structures , as explained in @xcite .
suppose that there is a known number of clusters @xmath24 and assume that we get , from the observations , an estimator @xmath63 such that @xmath64 well approximates the unknown conditional density @xmath65 .
we look at this problem as a missing data problem : if we denote by @xmath66 the component membership , with @xmath67_1,\ldots , [ \boldsymbol{z}_{i}]_k)$ ] for @xmath1 is defined by @xmath68_k= \left\ { \begin{array}{ll } 1 & \text { if } i \text { originates from mixture component } k ; \\ 0 & \text { otherwise ; } \end{array } \right.\ ] ] the complete data are @xmath69 .
thanks to the estimation @xmath63 , we use the maximum a posteriori principle ( map principle ) to cluster data . specifically , for all @xmath1 , for all @xmath70 , consider @xmath71 the posterior probability of @xmath72 with @xmath4 coming from the component @xmath24 , where @xmath73 .
then , data are partitioned by the following rule : @xmath74_k= \left\ { \begin{array}{ll } 1 & \text { if } \hat{\boldsymbol{\tau}}_{i , k}(\hat{\theta } ) > \hat{\boldsymbol{\tau}}_{i , l}(\hat{\theta } ) \text { for all } l\neq k \text { ; } \\ 0 & \text { otherwise . }
\end{array } \right.\ ] ] first , we introduce a generalized em algorithm to approximate @xmath75 defined in .
then , we discuss initialization and stopping rules in practice , before studying convergence of this algorithm . from an algorithmic point of view
, we use a generalized em algorithm to compute the mle and the @xmath56-norm penalized mle .
the em algorithm was introduced by @xcite to approximate the maximum likelihood estimator of mixture model parameters .
it is an iterative process based on the minimization of the expectation of the likelihood for the complete data conditionally to the observations and to the current estimation of the parameter @xmath76 at each iteration @xmath77 . using to the karush - kuhn - tucker conditions , we extend the second step to compute the maximum likelihood estimators , penalized or not , under rank constraint or not , as it was done in the scalar case in @xcite .
all those computations are available in appendix [ em ] .
we therefore obtain the next updating formulae for the lasso estimator defined by .
remark that it includes maximum likelihood estimator .
let denote by @xmath78 the euclidean ineer product .
if we denote , for all @xmath79 , for all @xmath70 , for all @xmath80 , for all @xmath81 , @xmath82^{\text{(ite)}}_{k , m } = \sqrt{\boldsymbol{\tau}^{(\text{ite})}_{i , k } } [ \boldsymbol{y}_i]_m;\\\nonumber & [ \boldsymbol{\widetilde{x}}_i]^{\text{(ite)}}_{k , j } = \sqrt{\boldsymbol{\tau}^{(\text{ite})}_{i , k } } [ \boldsymbol{x}_i]_j ; \\\nonumber & \delta_{k , m } = \left ( -n_k \langle [ \mathbf{\boldsymbol{\widetilde{y}}}_.]^{\text{(ite)}}_{k , m},[\boldsymbol{\phi}_k]^{\text{(ite)}}_{m , . }
[ \mathbf{\boldsymbol{\widetilde{x}}}_.]^{\text{(ite)}}_{k , . }
\rangle \right)^2 - 4 ||[\mathbf{\boldsymbol{\widetilde{y}}}_.]^{\text{(ite)}}_{k , m}|| _ 2 ^ 2 ; \\ \label{s } & [ \boldsymbol{s}_{k}]_{j , m}^{(\text{ite})}=-\sum_{i=1}^{n } [ \boldsymbol{\widetilde{x}}_i]^{\text{(ite)}}_{k , j } [ \boldsymbol{p}_k]^{(\text{ite})}_{m , m } [ \boldsymbol{\widetilde{y}}_i]^{\text{(ite)}}_{k , m } + \sum_{\genfrac{}{}{0pt}{}{j_2=1 } { j_2\neq j}}^{p } [ \boldsymbol{\widetilde{x}}_i]^{\text{(ite)}}_{k , j } [ \boldsymbol{\widetilde{x}}_i]^{\text{(ite)}}_{k , j_2 } [ \boldsymbol{\phi}_k]^{(\text{ite})}_{m , j_2 } ; \\ \nonumber & n_{k } = \sum_{i=1}^{n } \boldsymbol{\tau}_{i , k}^{(\text{ite } ) } ; \\ \nonumber\end{aligned}\ ] ] and if we denote by @xmath83 $ ] the largest value in @xmath84 such that the update of @xmath85 leads to improve the expected complete penalized log likelihood , we update the parameters by @xmath86_{m_1,m_2}^{\text{(ite+1 ) } } & = & \left\ { \begin{array}{lll } & \frac{n_k \langle [ \mathbf{\boldsymbol{\widetilde{y}}}_.]^{\text{(ite)}}_{k , m } , [ \boldsymbol{\phi}_k]_{m,.}^{(\text{ite } ) } [ \mathbf{\boldsymbol{\widetilde{x}}}_.]^{\text{(ite)}}_{k , . }
\rangle + \sqrt{\delta}_{k , m}}{2 n_k ||[\mathbf{\boldsymbol{\widetilde{y}}}_.]^{\text{(ite)}}_{k , m}||_2 ^ 2 } & \text { if } m_1=m_2=m;\\ & 0 & \text { elsewhere;}\\ \end{array } \right.\\ \label{phi } [ \boldsymbol{\phi}_k]_{m , j}^{\text{(ite+1 ) } } & = & \left\ { \begin{array}{lll } & \frac{-[\boldsymbol{s}_{k}]^{(\text{ite})}_{j , m}+ n\lambda \pi^{(\text{ite})}_{k } } { ||[\mathbf{\boldsymbol{\widetilde{x}}}_.]^{\text{(ite)}}_{k , j}||_{2}^2 } & \text { if } [ \boldsymbol{s}_{k}]^{(\text{ite})}_{j , m}>n \lambda \pi^{(\text{ite})}_{k } ; \\ & -\frac{[\boldsymbol{s}_{k}]^{(\text{ite})}_{j , m}+ n\lambda \pi^{(\text{ite})}_{k } } { ||[\mathbf{\boldsymbol{\widetilde{x}}}_.]^{\text{(ite)}}_{k , j}||_{2}^2 } & \text { if } [ \boldsymbol{s}_{k}]^{(\text{ite})}_{j , m } < -n \lambda \pi_{k}^{(\text{ite } ) } ; \\ & 0 & \text { else ; } \end{array } \right.\end{aligned}\ ] ] in our case , the em algorithm corresponds to alternate between the e - step which corresponds to the computation of and the m - step , which corresponds to the computation of , and .
remark that to approximate the mle under rank constraint , we use an easier em algorithm which is described in details in appendix . in the e - step ,
we compute the a posteriori probability of each observation to belong to each cluster according to the current estimations . in the m - step ,
we consider each observation within its estimated cluster , and consider the linear regression estimators under rank constraint by keeping the biggest singular values .
we initialize the clustering process with the @xmath24-means algorithm on couples @xmath87 , for all @xmath1 .
according to this clustering , we compute the linear regression estimators in each class . then , we run a small number of times the em - algorithm , repeat this initialization many times and keep the one which corresponds to the highest log - likelihood .
to stop the algorithm , we propose to run it a minimum number of times , and to specify a maximum number of iterations to make sure that it will stop . between these two bounds ,
we stop if a relative criteria on the log - likelihood is small enough and if a relative criteria on the parameters is small enough too .
those criteria are adapted from @xcite . by those rules ,
we are trying to attain a local optimum as close to a global optimum of the likelihood function as possible .
we address here the convergence properties of the algorithm described in paragraph [ algogem ] .
although convergence to stationary points has been get for the em algorithm ( see @xcite ) , it is not true without conditions hard to verify for generalized em algorithm .
results we propose are quite similar to the one get by @xcite , because algorithms are similar .
we refer the interested reader to this article for proof of the following results , when @xmath88 .
same ideas are working for any values of @xmath49 .
[ prop1 ] the algorithm described in paragraph [ algogem ] has the descent property : @xmath89 the proposition [ prop1 ] is clear by construction of @xmath90 , the m - step of the algorithm as a coordinate - wise minimization .
[ prop2 ] assume that @xmath91 for all @xmath1 .
then , for @xmath92 , the function @xmath93 is bounded from above for all values @xmath94 .
this is true because we penalize the log - likelihood by @xmath95 , where @xmath96 , then small variances are penalized also .
the penalized criteria therefore stays finite whenever @xmath10 , @xmath35 .
this is not the case for the unpenalized , which is unbounded if the variance of a variable tends to @xmath97 .
we refer for example to @xcite .
[ cor ] for the algorithm described in paragraph [ algogem ] , @xmath98 decreases monotonically to some value @xmath99 .
according to this corollary , we know that the algorithm converges to some finite value , depending on initial values . [ thm ] for the algorithm described in paragraph [ algogem ] , every cluster point @xmath100 of the sequence @xmath101 , generated by the algorithm , is a stationary point of the function @xmath102 .
this theorem proves that the algorithm converges to a stationary point .
we refer to @xcite for the definition of a stationary point for non - differentiable functions .
corollary [ cor ] is deduced from proposition [ prop1 ] and proposition [ prop2 ] .
theorem [ thm ] is more difficult to prove .
we deal with high - dimensional data where we observe a sample of small size @xmath17 and we have to estimate many coefficients ( @xmath103 ) .
then , we have to focus on variables that are relevant for the clustering .
the notion of irrelevant indices has to be defined .
a couple @xmath104 is said to be _ irrelevant _ for the clustering if @xmath105_{m , j } = \ldots = [ \boldsymbol{\phi}_{k}]_{m , j}=0 $ ] , which means that the variable @xmath106 does not explain the variable @xmath107 for the clustering process .
we also say that the indices @xmath108 is irrelevant if the couple @xmath104 is irrelevant .
a _ relevant _ couple is a couple which is not irrelevant : at least in one cluster @xmath24 , the coefficient @xmath109_{m , j}$ ] is not equal to zero .
we denote by @xmath110 the indices set of relevant couples .
remark that @xmath111 .
we denote by @xmath112 the complement of @xmath110 in @xmath113 . for all @xmath35 ,
we denote by @xmath114}$ ] the matrix of size @xmath115 with @xmath97 on the set @xmath112 .
be also define by @xmath116 the model with @xmath2 components and with @xmath110 for indices set of relevant couples : @xmath117 } \boldsymbol{x } ) ^t(\boldsymbol{p}_k\boldsymbol{y}-\boldsymbol{\phi}_k^{[j ] } \boldsymbol{x } ) } { 2 } \right ) , \right.\\ & \hspace{1cm}\left .
\theta=(\pi_1,\ldots , \pi_k,\boldsymbol{\phi}_1^{[j]},\ldots , \boldsymbol{\phi}_k^{[j ] } , \boldsymbol{p}_1,\ldots,\boldsymbol{p}_k ) \in \theta_{(k , j ) } = \pi_k \times \left ( \mathbb{r}^{q \times p } \right)^k \times \left(\mathbb{r}_+^{q } \right)^k \right\}. \nonumber \end{aligned}\ ] ] we construct a model collection by varying the number of components @xmath2 and the indices set of relevant couples @xmath110 .
the subset @xmath110 is constructed with the lasso estimator defined in .
nevertheless , to be consistent with the definition of relevant couples , the group - lasso estimator could be preferred , where coefficients @xmath118_{m , j},\ldots,\boldsymbol{\phi}_{k}]_{m , j}\}$ ] are groupped .
we focus here on the lasso estimator , but the group - lasso approach is described in appendix .
it gives mainly the same results , but the lasso estimator leads to consider also isolated irrelevant couples .
the goal of our procedures is , given a sample @xmath119 , to discover the relation between the variable @xmath120 and the variable @xmath121 .
thus , we have to estimate , according to the representation of @xmath116 , the number of clusters @xmath2 , the relevant variables set @xmath110 , and the parameter @xmath122 . to overcome this difficulty , we want to take advantage of the sparsity property of the @xmath56-penalization to perform automatic variable selection in clustering high - dimensional data .
then , we compute another estimator restricted on relevant variables , which will work better because it is no longer an high - dimensional issue .
thus , we avoid shrinkage problems due to the lasso estimator .
the first procedure takes advantage of the maximum likelihood estimator , whereas the second one takes into account the matrix structure of @xmath123 with a low rank estimation .
this procedure is decomposed into three main steps : we construct a model collection , then in each model we compute the maximum likelihood estimator and finally we select the best one among the model collection .
the first step consists of constructing a model collection @xmath124 in which @xmath116 is defined by equation , and the model collection is indexed by @xmath125 .
we denote by @xmath126 the possible number of components .
we assume that we could bound @xmath127 without loss of generality .
we also note @xmath128 . to detect the relevant variables and construct the set @xmath129
, we penalize the log - likelihood by an @xmath56-penalty on the mean parameters proportional to @xmath59_{m , j}|$ ] . in @xmath56-procedures ,
the choice of the regularization parameters is often difficult : fixing the number of components @xmath130 , we propose to construct a data - driven grid @xmath131 of regularization parameters by using the updating formulae of the mixture parameters in the em algorithm
. we can give a formula for @xmath132 , the regularization parameter , depending on which coefficients we want to shrink to zero , for all @xmath133 : @xmath134_{m , j } = 0 \hspace{0.5 cm } \leftrightarrow & \hspace{0.5 cm } [ \boldsymbol{\lambda}_{k}]_{j , m}= \frac{|[\boldsymbol{s}_{k}]_{j , m}|}{n \pi_{k } } ; \end{aligned}\ ] ] where @xmath135_{j , m}$ ] is defined by .
then , we define the data - driven grid by @xmath136_{j , m } , k\in \{1,\ldots , k\ } , j \in \{1,\ldots , p\ } , m \in \{1,\ldots , q\}\right\}. \label{grid}\end{aligned}\ ] ] we could compute it from maximum likelihood estimations .
then , for each @xmath137 , we could compute the lasso estimator defined by @xmath138 for a fixed number of mixture components @xmath130 and a regularization parameter @xmath137 , we could use an em algorithm , recalled in appendix [ em ] , to approximate this estimator . then , for each @xmath130 and for each @xmath137 , we could construct the relevant variables set @xmath139 .
we denote by @xmath140 the collection of these sets .
the second step consists of approximating the mle @xmath141 using the em algorithm for each model @xmath142 .
the third step is devoted to model selection . rather than selecting the regularization parameter
, we select the refitted model . instead of using an asymptotic criterion , as bic or aic
, we use the slope heuristic described in @xcite , which is a non - asymptotic criterion for selecting a model among a model collection .
let us explain briefly how it works .
firstly , models are grouping according to their dimension @xmath143 , to obtain a model collection @xmath144 .
the dimension of a model is the number of parameters estimated in the model . for each dimension
@xmath143 , let @xmath145 be the estimator maximizing the likelihood among the estimators associated to a model of dimension @xmath143 . also , the function @xmath146 has a linear behavior for large dimensions .
we estimate the slope , denoted by @xmath147 , which will be used to calibrate the penalty .
the minimizer @xmath148 of the penalized criterion @xmath149 is determined , and the model selected is @xmath150 .
remark that @xmath151 .
note that the model is selected after refitting , which avoids issue of regularization parameter selection . for an oracle inequality to justify the slope heuristic used here , see @xcite .
whereas the previous procedure does not take into account the multivariate structure , we propose a second procedure to perform this point .
for each model belonging to the collection @xmath116 , a subcollection is constructed , varying the rank of @xmath123 .
let us describe this procedure . as in the lasso - mle procedure
, we first construct a collection of models , thanks to the @xmath56-approach . for @xmath152
, we obtain an estimator for @xmath122 , denoted by @xmath153 , for each model belonging to the collection .
we could deduce the set of relevant columns , denoted by @xmath139 and this for all @xmath130 : we deduce @xmath140 the collection of relevant variables set .
the second step consists to construct a subcollection of models with rank sparsity , denoted by @xmath154 the model @xmath155 has @xmath2 components , the set @xmath110 for active variables and @xmath156 is the vector of the ranks of the matrix of regression coefficients in each group : @xmath157 where @xmath158 } \boldsymbol{x } ) ^t(\boldsymbol{p}_k\boldsymbol{y}-(\boldsymbol{\phi}_k^{r_k})^{[j ] } \boldsymbol{x } ) } { 2 } \right ) ; \\
\theta&=(\pi_1,\ldots , \pi_k,(\boldsymbol{\phi}_1^{r_1})^{[j]},\ldots , ( \boldsymbol{\phi}_k^{r_k}))^{[j ] } , \boldsymbol{p}_1,\ldots,\boldsymbol{p}_k ) \in \theta_{(k , j , r)}\\ \theta_{(k , j , r ) } & = \pi_k \times \psi_{(k , j , r ) } \times \left(\mathbb{r}_+^{q } \right)^k ; \\
\psi_{(k , j , r ) } & = \left\{\left .
( ( \boldsymbol{\phi}_1^{r_1})^{[j]},\ldots , ( \boldsymbol{\phi}_k^{r_k})^{[j ] } ) \in \left(\mathbb{r}^{q \times p } \right)^k \right| \text{rank}(\boldsymbol{\phi}_k)=r_k \text { for all } k \in \{1,\ldots , k\ } \right\ } ; \end{aligned}\ ] ] and @xmath159 .
we denote by @xmath160 the possible number of components , @xmath140 a collection of subsets of @xmath161 and @xmath162 the set of vectors of size @xmath130 with rank values for each mean matrix .
we compute the mle under the constrained ranks thanks to an em algorithm .
indeed , we constrain the estimation of @xmath61 , for the cluster @xmath24 , to have a rank equals to @xmath163 , by keeping only the @xmath163 largest singular values . more details are given in section [ em2 ] .
it leads to an estimator of the mean with row sparsity and low rank for each model .
as described in the above section , a model is selected using the slope heuristic .
this step is justified theoretically in @xcite .
those two procedures have both been implemented in matlab , with the help of benjamin auder and the matlab code is available .
we run the em algorithm several times : once to construct the regularization grid , twice for each regularization parameter for the lasso - mle procedure ( once to approximate the lasso estimator , and once to refit it with the maximum likelihood estimator ) and more times for the lasso - rank procedure ( we vary also the ranks vector ) .
if we look at every regularization parameters in the grid defined in , there are @xmath164 values and then we compute the em algorithm @xmath165 times , which could be large .
even if each em algorithm is fast ( implemented with c ) , repeat it numerous times could be time - consuming .
we propose to the user to select relevant regularization parameters : either a regular subcollection of @xmath131 , to get various sparsities , or focus on the large values of regularization parameters , to get sparse solutions .
the model collection constructed by the lasso - mle procedure is included in the model collection constructed by the lasso - rank procedure : @xmath166 then , the second procedure will work better .
nevertheless , it is time - consuming to construct all those models , with various rank vectors and maybe it is not necessary , depending on the data .
it is known that the framework of low - rank arises in many applications , among which analysis of eeg data decoding @xcite , neural response modeling @xcite . however , in some data the low - rank structure could be not adapted and then not needed .
we illustrate our procedures on four different simulated dataset , adapted from @xcite .
firstly , we present the models used in these simulations . then , we validate numerically each step and we finally compare the results of our procedures with others . remark that we propose here some examples to illustrate our methods , but not a complete analysis .
we highlight some issues which seem important .
moreover , we do not illustrate the one - component case , focusing on the clustering .
if , on some dataset , we are not convinced by the clustering , we could add to the model collection models with one component , more or less sparse , using the same pattern ( computing the lasso estimator to get the relevant variables for various regularization parameters and refitting parameters with the maximum likelihood estimator , under constrained ranks or not ) and then we select a model among this collection of linear and mixture models .
let @xmath167 be a sample of size @xmath17 distributed according to multivariate standard gaussian .
we consider a mixture of two components . besides , we fix the number of active variables to @xmath168 in each cluster .
more precisely , the first four variables of @xmath120 are explained respectively by the four first variables of @xmath121 .
fix @xmath169 and @xmath170 for all @xmath171 , where @xmath172 denotes the identity matrix of size @xmath49 .
the difficulty of the clustering is partially controlled by the signal - to - noise ratio ( denoted snr ) . in this context
, we could extend the natural idea of the snr with the following definition , where @xmath173 denotes the trace of the matrix @xmath174 .
@xmath175 remark that it only controls the distance between the signal with or without the noise and not the distance between the both signals .
we compute four different models , varying @xmath17 , the snr and the distance between the clusters .
details are available in the table [ tablerecap ] .
.description of the different models .
[ cols="^,^,^,^,^,^",options="header " , ] because the models are constructed on the learning sample , the mape are lower than for the test sample .
nevertheless , results are similar , saying that models are well constructed .
this is particularly the case for the model 1 , which is more consistent over a new sample . to conclude this study
, we could highlight the advantages of our procedure on these data .
it provides a clustering of data , similar to the one done with supervised clustering in @xcite , but we could explain how this clustering is done .
this work has been done with the lasso - mle procedure
. however , the same kind of results have been get with the lasso - rank procedure .
in this article , two procedures are proposed to cluster regression data . detecting the relevant clustering variables , they are especially designed for high - dimensional dataset .
we use an @xmath56-regularization procedure to select variables and then deduce a reasonable random model collection .
thus , we recast estimations of parameters of these models into a general model selection problem . these procedures are compared with usual criteria on simulated data : the bic criterion used to select a model , the maximum - likelihood estimator and the oracle when we know it . in addition , we compare our procedures to others on benchmark data .
one main asset of those procedures is that it can be applied to functional dataset .
we also develop this point of view .
in those appendices , we develop computing for em algorithm updating formulae in section [ em ] , for lasso and maximum likelihood estimators and for low ranks estimators . in section [ grouplasso ] ,
we extend our procedures with the group - lasso estimator to select relevant variables , rather than using the lasso estimator
. introduced by @xcite , the em ( expectation - maximization ) algorithm is used to compute maximum likelihood estimators , penalized or not .
the expected complete negative log - likelihood is denoted by @xmath176 in which @xmath177_k \log\left ( \frac{\det(\boldsymbol{p}_k)}{(2 \pi)^{q/2 } } \exp \left(- \frac{1}{2 } ( \boldsymbol{p}_k \boldsymbol{y}_i - \boldsymbol{x}_i\boldsymbol{\phi}_k)^t ( \boldsymbol{p}_k \boldsymbol{y}_i - \boldsymbol{x}_i\boldsymbol{\phi}_k ) \right ) \right)\\ & + [ \boldsymbol{z}_i]_k \log(\pi_{k } ) ; \end{aligned}\ ] ] with @xmath178_k$ ] are independent and identically distributed unobserved multinomial variables , showing the component - membership of the @xmath179 observation in the finite mixture regression model .
the expected complete penalized negative log - likelihood is @xmath180 [ [ calculus - for - updating - formula ] ] calculus for updating formula + + + + + + + + + + + + + + + + + + + + + + + + + + + + + * e - step : compute @xmath181 , or , equivalently , compute for @xmath35 , @xmath1 , @xmath182_k|\textbf{y } ) \\ & = \frac{\pi_{k}^{(\text{ite } ) } \det \boldsymbol{p}_k^{(\text{ite } ) } \exp \left ( -\frac{1}{2}\left ( \boldsymbol{p}_k^{(\text{ite } ) } \boldsymbol{y}_i-\boldsymbol{x}_i \boldsymbol{\phi}_k^{(\text{ite})}\right)^t\left(\boldsymbol{p}_k^{(\text{ite } ) } \boldsymbol{y}_i-\boldsymbol{x}_i \boldsymbol{\phi}_k^{(\text{ite})}\right ) \right ) } { \sum_{r=1}^{k}\pi_{k}^{(\text{ite})}\det \boldsymbol{p}_k^{(\text{ite } ) } \exp \left ( -\frac{1}{2}\left(\boldsymbol{p}_k^{(\text{ite } ) } \boldsymbol{y}_i-\boldsymbol{x}_i \boldsymbol{\phi}_k^{(\text{ite})}\right)^t\left(\boldsymbol{p}_k^{(\text{ite } ) } \boldsymbol{y}_i-\boldsymbol{x}_i \boldsymbol{\phi}_k^{(\text{ite})}\right ) \right ) } \end{aligned}\ ] ] this formula updates the clustering , thanks to the map principle . *
m - step : improve @xmath183 .
+ for this , rewrite the karush - kuhn - tucker conditions .
we have @xmath184_k \log \left ( \frac{\det(\boldsymbol{p}_k)}{(2 \pi)^{q/2 } } \exp \left ( -\frac{1}{2 } ( \boldsymbol{p}_k \boldsymbol{y}_i - \boldsymbol{x}_i \boldsymbol{\phi}_k)^t(\boldsymbol{p}_k \boldsymbol{y}_i - \boldsymbol{x}_i \boldsymbol{\phi}_k ) \right ) \right ) \left| \textbf{y } \right .
\right ) \nonumber\\ & - \frac{1}{n } \sum_{i=1}^{n } \sum_{k=1}^{k } e_{\theta^{(\text{ite } ) } } \left ( [ \boldsymbol{z}_i]_k \log \pi_{k } |\textbf{y } \right ) + \lambda \sum_{k=1}^{k } \pi_{k } ||\boldsymbol{\phi}_k||_1 \nonumber\\ = & - \frac{1}{n } \sum_{i=1}^{n } \sum_{k=1}^{k } -\frac{1}{2 } ( \boldsymbol{p}_k \boldsymbol{y}_i - \boldsymbol{x}_i \boldsymbol{\phi}_k)^t ( \boldsymbol{p}_k \boldsymbol{y}_i - \boldsymbol{x}_i \boldsymbol{\phi}_k)e_{\theta^{(\text{ite } ) } } \left ( [ \boldsymbol{z}_i]_k |\textbf{y } \right)\nonumber\\ & - \frac{1}{n } \sum_{i=1}^{n } \sum_{k=1}^{k } \sum_{m=1}^q \log \left ( \frac{[\boldsymbol{p}_k]_{m , m}}{\sqrt{2 \pi } } \right ) e_{\theta^{(\text{ite } ) } } \left [ [ \boldsymbol{z}_i]_k |\textbf{y } \right ] \nonumber\\ & - \frac{1}{n } \sum_{i=1}^{n } \sum_{k=1}^{k } e_{\theta^{(\text{ite } ) } } \left ( [ \boldsymbol{z}_i]_k |\textbf{y } \right)\log \pi_{k } + \lambda \sum_{k=1}^{k } \pi_{k } ||\boldsymbol{\phi}_k||_1 .
\end{aligned}\ ] ] firstly , we optimize this formula with respect to @xmath185 : it is equivalent to optimize @xmath186 + we obtain @xmath187 with @xmath188 $ ] being the largest value in the grid @xmath189 , with @xmath190 , such that the function is not increasing . + to optimize with respect to @xmath191 , we could rewrite the expression : it is similar to the optimization of @xmath192_{m , m } ) - \frac{1}{2 } ( \boldsymbol{p}_k \boldsymbol{\widetilde{y}}_i - \boldsymbol{\widetilde{x}}_i \boldsymbol{\phi}_k)^t(\boldsymbol{p}_k \boldsymbol{\widetilde{y}}_i - \boldsymbol{\widetilde{x}}_i \boldsymbol{\phi}_k ) \right ) + \lambda \pi_{k } ||\boldsymbol{\phi}_k||_1\ ] ] for all @xmath35 , which is equivalent to the optimization of + @xmath193_{m , m } ) + \frac{1}{2n } \sum_{i=1}^n \sum_{m=1}^q \left ( [ \boldsymbol{p}_k]_{m , m } [ \boldsymbol{\widetilde{y}}_i]_{k , m } - [ \boldsymbol{\phi}_k]_{m , . }
[ \boldsymbol{\widetilde{x}}_i]_{k , . }
\right ) ^2 + \lambda \pi_{k } ||\boldsymbol{\phi}_k||_1 ; \ ] ] where @xmath194 .
the minimum in @xmath195_{m , m}$ ] is the function which vanishes its partial derivative with respect to @xmath195_{m , m}$ ] : @xmath196_{m , m } } + \frac{1}{2n } \sum_{i=1}^n 2 [ \boldsymbol{\widetilde{y}}_i]_{k , m } \left ( [ \boldsymbol{p}_k]_{m , m } [ \boldsymbol{\widetilde{y}}_i]_{k , m } - [ \boldsymbol{\phi}_k]_{m , . } [ \boldsymbol{\widetilde{x}}_i]_{k,.}\right)=0\ ] ] for all @xmath35 , for all @xmath36 , which is equivalent to + @xmath197_{m , m}^2 \sum_{i=1}^n [ \boldsymbol{\widetilde{y}}_i]_{k , m}^2 - \frac{1}{n_k } [ \boldsymbol{p}_k]_{m , m } \sum_{i=1}^n [ \boldsymbol{\widetilde{y}}_{i}]_{k , m } [ \boldsymbol{\phi}_k]_{m , . } [ \boldsymbol{\widetilde{x}}_i]_{k,.}&=0\\ \leftrightarrow -1 + [ \boldsymbol{p}_k]_{m , m}^2 \frac{1}{n_k } || [ \mathbf{\boldsymbol{\widetilde{y}}}]_{k , m } ||_2 ^ 2 - [ \boldsymbol{p}_k]_{m , m}\frac{1}{n_k } \langle[\widetilde{\textbf{y}}]_{k , m } , [ \boldsymbol{\phi}_k]_{m , . }
[ \widetilde{\textbf{x}}]_{k , . } \rangle&=0.\end{aligned}\ ] ] + the discriminant is @xmath198_{k , m},[\boldsymbol{\phi}_k]_{m , . }
[ \widetilde{\textbf{x}}]_{k , . }
\rangle \right)^2 - \frac{4}{n_k } ||[\mathbf{\boldsymbol{\widetilde{y}}}]_{k , m}||_2 ^ 2.\ ] ] then , for all @xmath35 , for all @xmath36 , @xmath199_{m , m}= \frac{n_k \langle [ \widetilde{\textbf{y}}]_{k , m } , [ \boldsymbol{\phi}_k]_{m , . }
[ \widetilde{\textbf{x}}]_{k , . } \rangle + \sqrt{\delta}}{2 n_k
||[\mathbf{\boldsymbol{\widetilde{y}}}]_{k , m}||_2 ^ 2}.\ ] ] + we could also look at the equation as a function of the variable @xmath123 : according to the partial derivative with respect to @xmath109_{m , j}$ ] , we obtain for all @xmath36 , for all @xmath35 , for all @xmath79 , @xmath200_{k , j } \left([\boldsymbol{p}_k]_{m , m } [ \boldsymbol{\widetilde{y}}_i]_{k ,
m } - \sum_{j_2 = 1}^{p } [ \boldsymbol{\widetilde{x}}_i]_{k , j_2 } [ \boldsymbol{\phi}_k]_{m , j_2}\right ) -n\lambda \pi_{k } \text{sgn}([\boldsymbol{\phi}_k]_{m , j})=0,\ ] ] where @xmath201 is the sign function . then , for all @xmath202 , @xmath203_{m , j } = \frac{\sum_{i=1}^{n } [ \boldsymbol{\widetilde{x}}_i]_{k , j } [ \boldsymbol{p}_k]_{m , m } [ \boldsymbol{\widetilde{y}}_i]_{k , m } - \sum_{\genfrac{}{}{0pt}{}{j_2=1}{j_2\neq j}}^{p } [ \boldsymbol{\widetilde{x}}_i]_{k , j } [ \boldsymbol{\widetilde{x}}_i]_{k , j_2 } [ \boldsymbol{\phi}_k]_{m , j_2 } - n\lambda \pi_{k } \text{sgn}([\boldsymbol{\phi}_k]_{j , m})}{||[\mathbf{\boldsymbol{\widetilde{x}}}]_{k , j}||_{2}^2}.\ ] ] + let , for all @xmath202 , @xmath204_{j , m}=-\sum_{i=1}^{n } [ \boldsymbol{\widetilde{x}}_i]_{k , j } [ \boldsymbol{p}_k]_{m , m } [ \boldsymbol{\widetilde{y}}_i]_{k , m } + \sum_{\genfrac{}{}{0pt}{}{j_2=1 } { j_2\neq j}}^{p } [ \boldsymbol{\widetilde{x}}_i]_{k , j } [ \boldsymbol{\widetilde{x}}_i]_{k , j_2 } [ \boldsymbol{\phi}_k]_{m , j_2}.\ ] ] then @xmath205_{m , j}&= \frac{-[\boldsymbol{s}_{k}]_{j , m}- n\lambda \pi_{k } \text{sgn}([\boldsymbol{\phi}_k]_{m , j})}{||[\mathbf{\boldsymbol{\widetilde{x}}}]_{k , j}||_{2}^2 } \\ & = \left\ { \begin{array}{lll } & \frac{-[\boldsymbol{s}_{k}]_{j , m}+ n\lambda \pi_{k } } { ||[\mathbf{\boldsymbol{\widetilde{x}}}]_{k , j}||_{2}^2 } & \text{if } [ \boldsymbol{s}_{k}]_{j , m}>n \lambda \pi_{k}\\ & -\frac{[\boldsymbol{s}_{k}]_{j , m}+ n\lambda \pi_{k}}{||[\mathbf{\boldsymbol{\widetilde{x}}}]_{k , j}||_{2}^2 } & \text{if } [ \boldsymbol{s}_{k}]_{j , m } < -n \lambda \pi_{k}\\ & 0 & \text{elsewhere . }
\end{array } \right.\end{aligned}\ ] ] from these equalities , we could write the updating formulae . for @xmath206 , @xmath207 ,
let @xmath208_{j , m}^{(\text{ite})}=-\sum_{i=1}^{n } [ \boldsymbol{\widetilde{x}}_i]_{k , j } [ \boldsymbol{p}_k]^{(\text{ite})}_{m , m } [ \boldsymbol{\widetilde{y}}_i]_{k , m } + \sum_{\genfrac{}{}{0pt}{}{j_2=1 } { j_2\neq j}}^{p } [ \boldsymbol{\widetilde{x}}_i]_{k , j } [ \boldsymbol{\widetilde{x}}_i]_{k , j_2 } [ \boldsymbol{\phi}_k]^{(\text{ite})}_{m , j_2 } ; \\ &
n_{k } = \sum_{i=1}^{n } \boldsymbol{\tau}_{i , k } ; \\ & ( [ \boldsymbol{\widetilde{y}}_{i}]_{k,.},[\boldsymbol{\widetilde{x}}_i]_{k , . } ) = \sqrt{\boldsymbol{\tau}_{i , k } } ( \boldsymbol{y}_i,\boldsymbol{x}_i).\end{aligned}\ ] ] to take into account the matrix structure , we want to make a dimension reduction on the rank of the mean matrix .
if we know to which cluster each sample belongs , we could compute the low rank estimator for linear model in each component .
indeed , an estimator of fixed rank @xmath209 is known in the linear regression case : denoting @xmath210 the moore - penrose pseudo - inverse of @xmath174 and @xmath211_r = u d_r v^t$ ] in which @xmath212 is obtained from @xmath143 by setting @xmath213 for @xmath214 , with @xmath215 the singular decomposition of @xmath174 , if @xmath216 , an estimator of @xmath217 with rank @xmath209 is @xmath218_r$ ] .
we do not know the clustering of the sample , but the e - step in the em algorithm computes it . [ em2 ] we suppose in this case that @xmath28 and @xmath34 are known , for all @xmath35 .
we use this algorithm to determine @xmath61 , for all @xmath35 , with ranks fixed to @xmath219 . *
e - step : compute for @xmath35 , @xmath1 , @xmath220_k|y ) \\ & = \frac{\pi_{k}^{(\text{ite } ) } \det \boldsymbol{p}_k^{(\text{ite } ) } \exp \left ( -\frac{1}{2}\left ( \boldsymbol{p}_k^{(\text{ite } ) } \boldsymbol{y}_i-\boldsymbol{x}_i \boldsymbol{\phi}_k^{(\text{ite})}\right)^t\left(\boldsymbol{p}_k^{(\text{ite } ) } \boldsymbol{y}_i-\boldsymbol{x}_i \boldsymbol{\phi}_k^{(\text{ite})}\right ) \right)}{\sum_{r=1}^{k}\pi_{k}^{(\text{ite})}\det \boldsymbol{p}_k^{(\text{ite } ) } \exp \left ( -\frac{1}{2}\left(\boldsymbol{p}_k^{(\text{ite } ) } \boldsymbol{y}_i-\boldsymbol{x}_i \boldsymbol{\phi}_k^{(\text{ite})}\right)^t \left(\boldsymbol{p}_k^{(\text{ite } ) } \boldsymbol{y}_i-\boldsymbol{x}_i \boldsymbol{\phi}_k^{(\text{ite})}\right ) \right ) } \end{aligned}\ ] ] * m - step : assign each observation to its estimated cluster , by the map principle applied thanks to the e - step .
we say that @xmath221 comes from component number @xmath222 .
then , we can define @xmath223 , in which @xmath224 and @xmath225 correspond to the observations belonging to the cluster @xmath24 .
we decompose @xmath226 in singular value : @xmath227 .
then , the estimator is @xmath228 .
one way to perform those procedures is to consider the group - lasso estimator rather than the lasso estimator to select relevant variables .
indeed , this estimator is more natural , according to the relevant variable definition .
nevertheless , results are very similar , because we select grouped variables in both case , selected by the lasso or by the group - lasso estimator . in this section ,
we describe our procedures with the group - lasso estimator , which could be understood as an improvement of our procedures .
our both procedures take advantage of the lasso estimator to select relevant variables and to reduce the dimension in case of high - dimensional dataset .
first , recall what is a relevant variable .
a variable indexed by @xmath229 is _ irrelevant _ for the clustering if @xmath230_{m , j } = \ldots = [ \boldsymbol{\phi}_{k}]_{m , j}=0.\ ] ] a _ relevant _ variable is a variable which is not irrelevant .
we denote by @xmath110 the set of relevant variables .
the _ group - lasso estimator _ for mixture regression models with regularization parameter @xmath152 is defined by @xmath233 where @xmath234_{m , j}||_2 ; \ ] ] where @xmath235_{m , j}||_2 ^ 2 = \sum_{k=1}^k |[\boldsymbol{\phi}_k]_{m , j}|^2 $ ] and with @xmath132 to specify . however , depending on the dataset , it could be interesting to look for which variables are equal to zero first . one way
could be to extend this work with lasso - group - lasso estimator , described for the example for the linear model in @xcite .
the first step consists of constructing a collection of models @xmath236 in which @xmath237 is defined by @xmath238 where @xmath239 } x ) ^t(\boldsymbol{p}_ky-\boldsymbol{\phi}_k^{[\widetilde{j } ] } x)}{2 } \right),\ ] ] and @xmath240 the model collection is indexed by @xmath241 .
denote by @xmath160 the possible number of components .
we could bound @xmath127 without loss of estimation .
denote also @xmath242 a collection of subsets of @xmath243 , constructed by the group - lasso estimator . to detect the relevant variables and construct the set @xmath244 , we will use the group - lasso estimator defined by . in the @xmath56-procedures ,
the choice of the regularization parameters is often difficult : fixing the number of components @xmath130 , we propose to construct a data - driven grid @xmath131 of regularization parameters by using the updating formulae of the mixture parameters in the em algorithm .
then , for each @xmath137 , we could compute the group - lasso estimator defined by @xmath245_{m , j}||_2 \right\ } .\ ] ] for a fixed number of mixture components @xmath130 and a regularization parameter @xmath132 , we could use a generalized em algorithm to approximate this estimator . then , for each @xmath130 and for each @xmath137 , we have constructed the set of relevant variables @xmath246 .
we denote by @xmath242 the collection of all these sets .
we propose a second procedure to take into account the matrix structure . for each model belonging to the collection @xmath237
, a subcollection is constructed , varying the rank of @xmath123 .
let us describe this procedure . as in the group - lasso - mle procedure
, we first construct a collection of models , thanks to the @xmath56-approach .
we obtain an estimator for @xmath122 , denoted by @xmath249 , for each model belonging to the collection .
we could deduce the set of relevant variables , denoted by @xmath250 and this for all @xmath130 : we deduce @xmath242 the collection of set of relevant variables .
the second step consists in constructing a subcollection of models with rank sparsity , denoted by @xmath251 the model @xmath252 has @xmath2 components , the set @xmath250 for active variables and @xmath156 is the vector of the ranks of the matrix of regression coefficients in each group : where @xmath254 } \boldsymbol{x } ) ^t(\boldsymbol{p}_k\boldsymbol{y}-(\boldsymbol{\phi}_k^{r_k})^{[\widetilde{j } ] } \boldsymbol{x } ) } { 2 } \right ) ; \\
\theta=&(\pi_1,\ldots , \pi_k,\boldsymbol{\phi}_1^{r_1},\ldots , \boldsymbol{\phi}_k^{r_k } , \boldsymbol{p}_1,\ldots,\boldsymbol{p}_k ) \in \pi_k \times \psi_k^r \times \left(\mathbb{r}_+^{q } \right)^k ; \\
\psi_k^r= & \left\{(\boldsymbol{\phi}_1^{r_1},\ldots , \boldsymbol{\phi}_k^{r_k } ) \in \left(\mathbb{r}^{q\times p } \right)^k | \text{rank}(\boldsymbol{\phi}_1 ) = r_1,\ldots , \text{rank}(\boldsymbol{\phi}_k)=r_k \right\ } ; \end{aligned}\ ] ] and @xmath255 .
denote by @xmath126 the possible number of components , @xmath242 a collection of subsets of @xmath243 and @xmath162 the set of vectors of size @xmath130 with rank values for each mean matrix .
we could compute the mle under the rank constraint thanks to an em algorithm .
indeed , we could constrain the estimation of @xmath61 , for all @xmath24 , to have a rank equal to @xmath163 , in keeping only the @xmath163 largest singular values .
more details are given in section [ em2 ] .
it leads to an estimator of the mean with row sparsity and low rank for each model .
m. misiti , y. misiti , g. oppenheim and j - m poggi . clustering signals using wavelets .
in francisco sandoval , alberto prieto , joan cabestany and manuel graa , editors , _ computational and ambient intelligence _ ,
volume 4507 of _ lecture notes in computer science _ , pages 514521 .
springer berlin heidelberg , 2007 . | finite mixture regression models are useful for modeling the relationship between response and predictors arising from different subpopulations . in this article , we study high - dimensional predictors and high - dimensional response and propose two procedures to cluster those observations according to the link between predictors and the response .
to reduce the dimension , we propose to use the lasso estimator , which takes into account the sparsity and a maximum likelihood estimator penalized by the rank , to take into account the matrix structure . to choose the number of components and the sparsity level , we construct a model collection ,
varying those two parameters and select a model among this collection with a non - asymptotic criterion .
we extend these procedures to functional data , where predictors and responses are functions . for this purpose
, we use a wavelet - based approach .
for each situation , we provide algorithms and apply and evaluate our methods both on simulated and real dataset , to understand how it works in practice . |
The big Caravan of People from Honduras, now coming across Mexico and heading to our “Weak Laws” Border, had better be stopped before it gets there. Cash cow NAFTA is in play, as is foreign aid to Honduras and the countries that allow this to happen. Congress MUST ACT NOW! ||||| US president Donald Trump tweeted at length about immigration today, following up on yesterday’s references to “caravans” of people heading toward the US border with Mexico.
Border Patrol Agents are not allowed to properly do their job at the Border because of ridiculous liberal (Democrat) laws like Catch & Release. Getting more dangerous. “Caravans” coming. Republicans must go to Nuclear Option to pass tough laws NOW. NO MORE DACA DEAL! — Donald J. Trump (@realDonaldTrump) April 1, 2018
Mexico has the absolute power not to let these large “Caravans” of people enter their country. They must stop them at their Northern Border, which they can do because their border laws work, not allow them to pass through into our country, which has no effective border laws….. — Donald J. Trump (@realDonaldTrump) April 2, 2018
There is little connection between the approaching “caravan” and the US program Deferred Action for Childhood Arrival (DACA) cited by the US president. DACA only applies to immigrants who entered the US illegally as minors more then 10 years ago.
The caravan is a group of Central American men, women and children. They number up to 1,000, according to organizers, and are currently traveling through Mexico with the goal of eventually crossing into the US.
Their hope, as Buzzfeed’s Adolfo Flores reports, is that strength in numbers will protect them from the violent cartels that migrants sometimes encounter on the journey north, as well present a logistical challenge for immigration authorities hoping to turn them away.
Hundreds of Central American migrants attend a mass in Tapachula, Mexico on March 25, 2018. (Reuters/Jose Torres)
Hundreds of Central American migrants attend a mass on March 25, 2018. (Reuters/Jose Torres)
Hundreds of Central American migrants take part in a Via Crucis on Palm Sunday from Tapachula, Mexico on March 25, 2018. Their banner reads “We are all America no to the discrimination.” (Reuters/Jose Torres)
Central American migrants arrive at in Ixtepec, Oaxaca, Mexico, before continuing their journey to the US on March 30. (Reuters/Jose Jesus Cortes)
Central American migrants gather before continuing their journey to the US in Ixtepec, Oaxaca, Mexico March 30, 2018. (Reuters/Jose Jesus Cortes)
Central American migrants gather before continuing their journey to the US (Reuters/Jose Jesus Cortes)
Central American migrants gather before continuing their journey to the US on March 31. (Reuters/Jose Jesus Cortes)
Central American migrants gather in Ixtepec, Oaxaca on March 31, 2018. (Reuters/Jose Jesus Cortes)
Central American migrants rest in Ixtepec, Oaxaca on March 31. (Reuters/Jose Jesus Cortes) ||||| President Donald Trump railed against immigrants, Mexico, and Democrats in a series of tweets on Sunday and Monday that suggested a caravan of immigrants reportedly traveling toward the U.S. are trying to take advantage of a program they would not qualify for.
At the White House Easter Egg roll on Monday, Trump told reporters: “The Democrats have really let them down. They really let them down. It’s a shame. A lot of people have taken advantage of DACA. It’s a shame,” according to a pool report.
Trump’s statements appear to have come after Fox News reported on a caravan of over 1,000 Central American migrants that is currently traveling through Mexico. The migrants’ trek was first reported by BuzzFeed News.
The 2018 caravan is being organized by a humanitarian volunteer group called Pueblos Sin Fronteras, or People Without Borders. The group organized two similar caravans in 2017 and has aided migrants and refugees on the move for over 15 years, according to its website. The group hopes that by traveling in such a large group they will be able to avoid some of the dangers that befell travelers who take the often perilous route through Mexico to the southern border of the United States.
Alex Mensing of Pueblos Sin Fronteras told ABC News that many of the caravan travelers are fleeing violence and that they are hoping to reach U.S. ports of entry in Arizona, California, or New Mexico where they will claim asylum and likely be detained.
But starting on Sunday morning, Trump unleashed a flurry of tweets about the caravans – and seemed to conflate the group with DACA. Here are the facts.
Trump blames “Catch & Release”
Trump first tweeted that “caravans” are heading toward the Southern U.S. border, but patrol agents “are not allowed to properly do their jobs.” Trump blamed that inability to work on “ridiculous liberal (Democrat) laws like Catch & Release.”
The majority of migrants traveling in the 2018 caravan are originally from Honduras, according to BuzzFeed, and many are fleeing the political unrest that followed the 2017 elections there. Some two-thirds of the migrants reportedly hoping to seek asylum when they reach the U.S.
During an appearance on Fox and Friends, the union chief of the National Border Patrol Council, Brandon Judd, suggested the “catch and release” policy was partly to blame. Under the policy, unlawful immigrants are released from detention while they await hearings in immigration court. Judd also said that immigrants can also be released if they claim asylum.
“Once they enter the country, even if we are standing at the border with our hands out saying, ‘Don’t enter, don’t enter,’ all they have to do is cross one foot into the border and we have to take them into custody,” he said. “If they ask for asylum or say I fear to go back to my country, then we have to process them under ‘credible fear’ which allows them to be released into our country.”
In a February 2017 memo, then Department of Homeland Security Secretary John Kelly said the administration was ending “catch and release,” but a Reuters report from last June showed that it was easier said than done.
The Trump Administration’s attempt to end “Catch & Release” has been hampered by the reality that immigration authorities don’t have the space to hold every immigrant who is detained at the border, according to Reuters.
Mexico denies it “is doing very little” to stop illegal immigration
In tweets on Monday Trump blamed Mexico for allowing people to travel to the U.S., suggesting he would end the North American Free Trade Agreement in an effort to stem the flow of migrants.
The BuzzFeed report notes that “no one has made any effort to stop” the migrants as they travel through Mexico without authorization. About one third of the migrants traveling plan to stay in the country rather than continue on to the U.S.
Luis Videgaray Caso, Mexico’s Secretary of Foreign Affairs, responded in a tweet on Sunday, saying that Mexican authorities work with their American counterparts on migration “every day.”
Caravan of immigrants not eligible for DACA
In his tweets, Trump also declared the end of a deal on DACA, a program that has protected young immigrants who were brought to the U.S. by their parents from deportation. Trump suggested that the immigrants who made up the caravan were coming to America in hopes of taking advantage of the program, which he effectively ended in September 2017. Efforts to offer DACA recipients permanent protections have stymied in Congress, in part due the to strict provisions Trump wants included in any deal. Trump has tried to shift the blame to Democrats, but it is not that simple.
It should be noted that the migrants who are traveling in the caravan, no matter their age, would not qualify for DACA.
The Trump administration stopped accepting new applications for the Deferred Action for Childhood Arrivals program, or DACA, on Sept. 5, 2017. Under the president’s orders, renewal applications for people who already benefitted from the program needed to have been turned in by Oct. 5, 2017.
Legal challenges have kept the program alive, to an extent. The administration is still not accepting new applications, but people who have already benefitted from the program can reapply. According to U.S. Citizenship and Immigration Services, all renewal requests will be adjudicated under the guidelines that were set forth when the program was first established. | – President Trump returned to one of his favorite recent themes on Tuesday, complaining about a "caravan" of immigrants in Mexico moving toward the US border. "The big Caravan of People from Honduras, now coming across Mexico and heading to our 'Weak Laws' Border, had better be stopped before it gets there," Trump tweeted. "Cash cow NAFTA is in play, as is foreign aid to Honduras and the countries that allow this to happen. Congress MUST ACT NOW!" So what exactly is this "caravan" Trump is worried about? Some details: The caravan: There is indeed a group of about 1,200 people, mostly from Honduras, walking north through Mexico, and BuzzFeed reports that most hope to reach the US and request asylum. (See photos of the group via Quartz.) The caravan left on March 25 and is organized by a group known as People Without Borders, which has organized similar caravans in previous years, per Time. |
Boy sings 'ain't no homo gonna make it to heaven' in church; Pastor receiving death threats: report Viral video shows congregation applaud after young boy's performance
A young boy sings an anti-gay hymn in a church identified as the Apostolic Truth Tabernacle Church in Greensburg, Indiana.
An Indiana pastor is reportedly fielding death threats after footage surfaced of his congregation going wild for a tiny tot singing an anti-gay hymn.
The clip went viral on Wednesday and features a young boy crooning a song about God and bible verses, including the lyrics, “Ain’t no homo gonna make it to heaven.”
Since it hit the blogosphere, the church, identified as the Apostolic Truth Tabernacle Church in Greensburg, Indiana, has received harassing phone calls, and its pastor, Jeff Sangl, has even gotten death threats at home, members told TMZ.com.
The website reports the church is “on lockdown” and members are taking turns watching over the property.
Sangl fears for his safety and he and his wife fled for vacation Wednesday morning without telling anyone where they were going, one member told TMZ.com.
Representatives of the church could not be reached for comment by the Daily News.
Viewers online were jolted by the video — and by how young its star appears to be.
Gawker writer Neetzan Zimmerman likened the video to child abuse.
“What makes this particular demonstration of intolerance so shocking is just how young this congregant is. Believing him to be no older than five, some are calling the church’s treatment of the boy out-and-out child abuse.”
Others were appalled by the congregation’s overwhelmingly positive response to the performance.
“Listen to the applause he’s getting for spouting hate!” wrote one commenter on YouTube.
Author Anne Rice posted the video on her Facebook page, writing: “In this country, Christians can teach toddlers to hate and to persecute, and we, through the automatic tax exemption for churches, foot the bill.”
Despite the uproar and reported threats, church members told TMZ.com they don’t regret that the video surfaced online.
“The people who are upset just don’t reach the word of God,” an unnamed member of the church told the website. “If we don’t teach the children the truth early they will never learn.
“Of course we applauded a child who is singing a song about God.”
[email protected] ||||| Toddler's 'Ain't No Homos' Song Puts Church on Lockdown Pastor Gets Death Threats
EXCLUSIVE
Members of an Indiana church say they've been flooded with death threats since video of a 3-year-old proudly singing, "Ain't no homos gonna make it to heaven" ... was posted on the Internet.Multiple members of thein Greensburg, Indiana tell TMZ the church office has been getting harassing calls and the pastor has received death threats at his home. They also say a prayer meeting scheduled for this evening at church had to be moved to a secret location.We're told they are looking into increasing security, but for now the congregation is handling it ... taking turns watching over the church.One member says Pastoris extremely worried about his safety -- and this morning he and his wife left for vacation without telling anyone where they were going.Despite the threats, all the members we spoke to have no regrets about the song getting posted online -- in fact one said, "The people who are upset just don't read the word of God. If we don't teach the children the truth early they will never learn."As for the thunderous applause after the hate-filled song -- we're told, "Of course we applauded a child who is singing a song about God." ||||| Church on lock-down after shocking video shows boy, 4, singing 'ain't no homos gonna make it to Heaven'
A church in rural Indiana has gone on lock-down and its pastor has fled into hiding after a shocking video emerged of a four-year-old boy singing a homophobic song.
The clip shows the child receiving raucous applause and a standing ovation as he chants 'ain't no homos gonna make it to heaven.'
On Wednesday, members of Apostolic Truth Tabernacle Church in Greensburg, Indiana, said they have received death threats over the publication of the video.
Scroll down for video
Backlash: The shocking video has sent Pastor Jeff Sangl (right) into hiding over the negative attention focused on his congregation at the Apostolic Truth Tabernacle Church
Lock-down: Members of the Apostolic Truth Tabernacle Church in rural Greensburg, Indiana, are guarding their church and are reportedly meeting in secret because of the video
In the grainy footage recorded by a cellphone, a young boy approaches the microphone and sings: 'I know the the Bible’s right, somebody’s wrong/ the Bible’s right, somebody’s wrong/ Romans one, twenty six and twenty seven/ Ain’t no homos gonna make it to Heaven.'
Men in suits rise to their feet and begin cheering and applauding. Pastor Jeff Sangl grins and nods approvingly.
Three times the boy sings the verse -- which is a takeoff on lyrics written by Bishop G.E. Patterson, the late leader of the nation's largest black Pentecostal church.
The original lyrics read: 'I've told you time and time again, you can't make it to Heaven while you sippin' on gin' and 'I've told you once, I've told you twice, you can't make it to Heaven with a sweetheart and a wife.'
Applause: The boy received enthusiastic approval from Pastor Sangl (right) and the members of his church, who rose to their feet and cheered when he sang the 'homos' lyric
The Bible verse the boy refers to, Romans 1:26-27, reads: 'Because of this, God gave them over to shameful lusts. Even their women exchanged natural sexual relations for unnatural ones. In the same way the men also abandoned natural relations with women and were inflamed with lust for one another. Men committed shameful acts with other men, and received in themselves the due penalty for their error. '
Even as criticism of the church pours in, members of the congregation are standing by the boy's performance.
'The people who are upset just don't read the word of God. If we don't teach the children the truth early they will never learn,' one congregant told TMZ.com .
After the video went public, Pastor Sangl, who is seen urging the boy on, suddenly left for an unplanned vacation and no one is sure where he's gone.
Members of the congregation say they've received death threats.
Pastor Sagl posted a statement on the church's website on Wednesday that said the church doesn't teach hate. However, he added: 'We are a strong advocate of the family unit according to the teachings and precepts found in the Holy Bible.'
The video comes after a two pastors in North Carolina drew national criticism. One said he believed parents should hit their children if they act gay. Another said gays should be put in pens so homosexuality will die out.
| – A video of a 4-year-old boy singing "Ain’t no homo gonna make it to heaven" in front of his cheering Indiana church has gone viral—and now the Apostolic Truth Tabernacle Church is dealing with some unpleasant fallout, reports the New York Daily News. The church has been barraged by nasty phone calls and even death threats. In response, the church says it is on "lockdown," with members guarding the building around the clock, and pastor Jeff Sangl and his wife took off suddenly on vacation yesterday without telling anyone where they were going. “Of course we applauded a child who is singing a song about God,” one member of the congregation tells TMZ."If we don’t teach the children the truth early they will never learn." The original lyrics of the song, by the late leader of America's largest black Pentecostal church, condemned drinking and adultery with verses like "You can't make it to heaven with a sweetheart and a wife," notes the Daily Mail. |
magnetic ordering phenomena of both classical and quantum antiferromagnets on non bipartite lattices are a fascinating subject . the simplest and most frequently studied model of this type is the heisenberg antiferromagnet on a triangular lattice ( haft ) . while the question of whether or not the typical features of this model have been observed in experiments is still a controversial issue @xcite , the theoretical understanding of these features has advanced rapidly during recent years @xcite . in contrast to antiferromagnets on bipartite lattices , the haft exhibits non collinear magnetic order in its classical and most likely also in its quantum ground state . as a consequence
, the order parameter of the haft is represented locally by a set of three mutually orthogonal unit vectors or , alternatively , by a rotation matrix which defines the local orientation of this set relative to some fixed frame of reference .
renormalization group ( rg ) studies of appropriate nonlinear sigma ( nl@xmath6 ) models @xcite have revealed a number of interesting properties of the haft .
the symmetry of the model was found to be dynamically enhanced from @xmath7 to @xmath8 , and in a two loop rg calculation for the classical haft @xcite , the temperature dependence of the correlation length @xmath0 was obtained as @xmath9 where @xmath10 is the lattice constant , @xmath11 .
the prefactor @xmath12 is left undetermined by the rg calculation .
it follows from topological considerations that the order
parameter field of the haft allows for excitations of the form of @xmath13 vortices @xcite .
a numerical study of the classical haft @xcite has revealed that these vortices become abundant above a threshold temperature @xmath14 and that they unbind for @xmath15 , similarly as the @xmath16 vortices in the planar @xmath17 model above the kosterlitz
thouless ( kt ) transition temperature @xmath18 @xcite .
further evidence for this similarity beween the dissociation mechanism of the @xmath13 vortices and that of the @xmath16 vortices has been provided by kawamura and kikuchi @xcite . in recent work @xcite , we have studied the influence of the vortices on the partition function of the classical haft on the basis of the nl@xmath6 model . while a true kt
type phase
transition can be ruled out for the haft , our results suggest that for @xmath15 the vortices will affect the properties of the haft rather drastically . in particular , the disorder induced by the unbinding of the vortices can be expected to lead to a crossover from the t dependence eq .
( [ 1 ] ) of the correlation length in the low temperature regime @xmath19 to a kt type behavior @xmath20 in the high temperature regime .
it is the aim of the present paper to supplement our recent analytical study @xcite , which was based on a continuum description of the haft by a monte carlo ( mc ) simulation of the original lattice model .
a similar study has recently been published by southern and young @xcite . while we closely follow the method of these authors , our conclusions will be quite different from theirs . in the next section
, we first give a brief account of the technique we used .
subsequently we present the results for the correlation length @xmath0 and the antiferromagnetic susceptibility @xmath1 .
while these quantities are directly accessible to simulations in the high temperature regime , where the disordering effect of the vortices limits the range of the correlations , the key quantity to be computed in the low temperature regime is the spin stiffness @xcite . our numerical results for this last quantity will be presented and discussed in section iii .
finally , we summarize the evidence for a vortex induced crossover transition in section iv .
the classsical hamiltonian of the triangular heisenberg antiferromagnet can be defined as @xmath21 here , the @xmath22 are three dimensional unit vectors and the sum extends over all distinct pairs of nearest neighbor sites of a triangular lattice of @xmath23 sites .
the exchange constant has been set to unity .
the classical ground state of the hamiltonian eq .
( [ 3 ] ) is a coplanar arrangement in which the spins on the three sublattices are oriented at @xmath24 relative to each other , @xmath25 here , @xmath26 , @xmath27 are a pair of mutually orthogonal unit vectors and @xmath28 can be any one of the six vectors pointing towards the corners of the hexagonal brillouin zone of the triangular lattice , e.g. @xmath29 . the correlation length @xmath0 can be obtained assuming a ornstein zernicke form for the structure factor @xmath30 @xmath31 is then the susceptibility of the system at the ordering wavevector .
the spin correlations @xmath32 in eq .
( [ 5 ] ) can be determined by mc techniques .
we used the local algorithm described by kawamura and miyashita @xcite .
the lattice is divided into independent sublattices .
then , the spins of each of these sublattices are updated sequentially . for a given spin
, a new direction is chosen at random and the standard metropolis rule is used to decide whether the new direction is to be accepted . if it is discarded , a precessional motion through a randomly chosen angle about the direction of the local mean field is performed .
we apply this method to systems of linear sizes @xmath33 . for the smaller systems , @xmath34 , we discard the first @xmath35 sweeps for equilibration and average over the next @xmath36 sweeps . for @xmath37 , we average over @xmath38 sweeps after discarding the initial @xmath39 sweeps , and for @xmath40 , the average is over @xmath41 , and @xmath36 sweeps are discarded .
a selection of results for the correlation length @xmath0 and for the antiferromagnetic susceptibility @xmath1 which have been obtained by averaging over 3 - 5 independent runs of these lengths is tabulated in table [ tab_ksi_chi ] .
as will become apparent shortly , the data shown in this table are crucial in checks of theoretical predictions for the temperature dependence of @xmath0 and @xmath1
. to exhibit possible finite size effects , the table contains two pairs of data for each temperature which correspond to two different system sizes @xmath42 , @xmath43 . in general ,
@xmath0 and @xmath1 decrease with @xmath44 , but increase with the system size @xmath42 .
if , for a given temperature @xmath45 and a given system size @xmath46 , the data for @xmath0 and @xmath1 exhibit no size dependence upon doubling the system size , then one can conclude that the system size @xmath46 suffices to obtain size independent data for all @xmath47 .
data which are size independent by this criterion are marked by an asterisk in table [ tab_ksi_chi ] .
obviously , we can not exclude that the data for the lowest temperature @xmath48 obtained for the @xmath49 system are still size dependent . certainly , however , our data for @xmath48 are lower bounds to the thermodynamic limits of @xmath0 and @xmath1 at this temperature . to facilitate the comparison of our data with the rg predictions we include in table [ tab_ksi_chi ] the values for @xmath0 and @xmath1 which result from fits of the expressions eq .
( [ 1 ] ) and eq . (
[ 6 ] ) to these data @xcite . in figs .
[ ksi - t ] and [ chi - t ] , we show our complete sets of results for the correlation length and for the antiferromagnetic susceptibility as functions of the temperature .
obviously , for any given system size @xmath42 , there is an inflection point in the sequences of data for @xmath0 and @xmath1 .
this point defines a temperature @xmath50 below which both @xmath0 and @xmath1 begin to exhibit finite size effects . in fact , as can be seen in fig .
[ ksi - t ] , the correlation length increases linearly with the system size for sufficiently low temperatures @xmath51 . figs .
[ ksi - t ] and [ chi - t ] also contain fits of different theoretical predictions to the numerical data .
the dashed lines represent fits of the rg result , eq .
( [ 1 ] ) , to our data for @xmath0 and of the form @xmath52 proposed by southern and young @xcite on the basis of rg calculations , to our data for @xmath1 . in these rg predictions , the constants @xmath12 and @xmath53 are the only undetermined parameters . in our fits , we neglect the data points for temperatures @xmath54 which contain finite size effects . in agreement with southern and young
@xcite we find @xmath55 and @xmath56 .
the solid lines represent fits of the kt forms eq .
( [ 2 ] ) and @xmath57 to the data . with the kt form for @xmath0 , eq . ( [ 2 ] ) , the last expression follows from the general relation @xmath58 for the structure factor at the ordering wave vector , if @xmath59 is assumed to take the value @xmath60 as for a proper kt transition . for the threshold temperature ,
we use the value @xmath61 , which we can be inferred from the temperature dependence of the spin stiffness as will be discussed in the next section .
this leaves the constant @xmath62 which is common to the expressions eq .
( [ 2 ] ) and eq . ( [ 7 ] ) and the constant factors @xmath63 and @xmath64 of eq . ( [ 2 ] ) and eq . ( [ 7 ] ) as fit parameters . as before ,
we ignore data points for @xmath54 in our fits .
the results are @xmath65 , @xmath66 and @xmath67 .
obviously , for temperatures @xmath68 , the @xmath69-temperature dependence of the kt forms fits the data better than the @xmath70-temperature dependence predicted by the rg analysis . in figs .
[ ksi - wt ] and [ chi - wt ] we plot @xmath0 and @xmath1 logarithmically against @xmath71 so that the kt forms eq .
( [ 2 ] ) and eq . ( [ 7 ] ) appear as straight lines .
these lines are seen to fit the data quite well in the temperature interval @xmath72 , whereas the agreement between the curves representing the rg forms is restricted to a narrow interval around @xmath73 . in particular
, we emphasize that for @xmath48 , the rg predictions are incompatible with the data points for @xmath0 and @xmath1 which are listed in table [ tab_ksi_chi ] with their respective errors . in this context
, we recall that if our data for @xmath48 do not represent the thermodynamic limits of @xmath0 and @xmath1 , they are certainly lower bounds to these limits . hence , the discrepancy between the rg predictions and the true values of @xmath0 and @xmath1 may even be larger than has been inferred here .
we note that the fit of the kt form , eq .
( [ 7 ] ) , to the data for the susceptibility @xmath1 is better than that of the rg form , eq .
( [ 2 ] ) , to @xmath0 .
this may be attributable to the lower quality of the data for @xmath0 which are obtained indirectly from the ornstein - zernicke expression eq .
( [ 5 ] ) in the limit @xmath74 . in summary
, we observe that our results combined with the earlier findings of kawamura and miyashita @xcite support the view that in the temperature range @xmath15 the spin correlations of the haft are decisively influenced by unbound vortices , so that a perturbative treatment of the model is inadequate in this temperature regime
. it should be obvious , however , that in the above analysis of our numerical results we have been guided by our previous prediction @xcite that , in the case of the haft , the vortex unbinding mechnism leads to a kt - type temperature dependence of the correlation length above a crossover temperature @xmath75 . while we do not claim to have found compelling evidence for this prediction , we regard our numerical results as strong support for it .
to further corroborate the above view and in order to get insight into the low temperature regime , where the correlation length exceeds the accessible system sizes , we also determined the spin stiffness @xmath2 in our simulations .
the diagonal components @xmath76 , of the spin stiffness tensor are the second derivatives of the free energy density @xmath77 with respect to the twist angles @xmath78 of the spins around three mutually orthogonal axes @xmath79 @xcite , @xmath80 ( { \bf u } \cdot { \bf e}_{ij})^2 > \nonumber \\ & - & \frac{2}{\sqrt{3 } t l^2 } < \left [ \sum_{<i , j > } { \bf s}_i \times { \bf s}_j \cdot { \bf e}_{\alpha } ( { \bf u } \cdot { \bf e}_{ij } ) \right]^2 > \;\ ; . \label{8}\end{aligned}\ ] ] here , @xmath81 is the lattice direction along which the twist is applied and @xmath82 is the direction of the bond between nearest neighbor lattice sites @xmath83 and @xmath84 .
the prefactor in eq .
( [ 8 ] ) has been chosen such that eq .
( [ 8 ] ) is the stiffness per unit area . in the simulation , the thermal averages on the right hand side of eq .
( [ 8 ] ) are replaced by averages over configurations which are generated by a large number of successive mc sweeps . for a finite system
, the ordered spin structure will change its orientation in space in the course of the simulation . in a sufficiently large number of sweeps
, one will therefore measure the average spin stiffness @xmath85 since there is no long range order in the haft for any finite temperature , @xmath2 must vanish for the haft in the thermodynamic limit for any finite temperature .
however , for finite system sizes @xmath42 , @xmath2 will be finite for sufficiently low temperatures such that @xmath86 . according to eq .
( [ 1 ] ) , this condition should be satisfied for system sizes @xmath87 up to temperatures of the order of unity , unless the constant @xmath12 is exceedingly small as has been suggested by southern and young @xcite .
as we have argued above , the results for @xmath88 in the high temperature regime , @xmath15 , should not be interpreted as evidence for such a small value of @xmath12 .
in fact , a naive integration of the 2loop renormalization group equations which starts with the microscopic parameters of the haft as initial values yields the result eq .
( [ 1 ] ) with @xmath89 . in our simulations ,
we determine the three @xmath90 separately in each sweep and thus obtain the averages @xmath2 for each sweep . in fig .
[ rho - t ] , we show the average spin stiffness as a function of the temperature for system sizes @xmath91 .
the steep drop in @xmath2 which occurs as @xmath44 increases beyond @xmath5 is consistent with the rapid decrease of @xmath0 in the same temperature regime in which the vortices become unbound @xcite .
in contrast to the spin stiffness of the planar xy model , @xmath2 does not saturate in the low temperature regime @xmath19 with increasing system size @xmath42 but decreases with increasing @xmath42 .
this behavior is to be expected , since in contrast with the correlation length of the xy model , the correlation length of the haft remains finite for low temperatures , where the vortices are bound in pairs . as @xmath92 , our data for @xmath2 approach the correct limiting value @xmath93 . in fig .
[ rho - l ] , we display @xmath2 for various temperatures and system sizes .
the data are averages over 3 - 5 independent runs of lengths comparable to those which we have described above , error bars indicate the standard deviation . in the low temperature regime ,
the thermodynamics of the classical haft should be captured by the appropriate nl@xmath6 model @xcite . on the basis of a renormalization group treatment of this model , azaria _ et al .
_ @xcite have made detailed predictions for the dependence of the spin stiffness on the linear system size @xmath42 and the correlation length @xmath0 . in their mc study of the classical haft
, southern and young @xcite found excellent agreement with the predicted @xmath42 dependence of the spin stiffness tensor at the temperature @xmath94 . in order to be able to compare our numerical results with the predictions of the rg analysis of the nl@xmath6 model
, we integrated the two loop rg equations of azaria _ et al . _
@xcite starting from the initial conditions @xmath95 and @xmath96 . here ,
@xmath97 and @xmath98 are the two main components of the spin stiffness tensor with respect to the reference frame of the local order parameter @xcite . by the above initial conditions we identify @xmath97 and @xmath99 with their microscopic values on the scale of the lattice constant @xmath10 .
we find that in the temperature regime under consideration , @xmath100 , the average stiffness @xmath2 varies linearly with @xmath101 to a very good approximation on the scale @xmath102 covered by our simulations , see fig .
[ rho - lnksi ] below . from the rg equations
, one can also infer that the slope @xmath103 decreases from @xmath104 to @xmath105 , when @xmath42 increases from a value of the order of the lattice constant , @xmath106 , to a value of the order of the correlation length , @xmath107 . in fig .
[ rho - l ] , the straight lines are least squares fits to the data .
the slopes of these lines , normalized to the maximal theoretical slope @xmath104 , are tabulated in table [ gefaelle ] . for @xmath108 ,
the slopes are seen to be rather close to their maximal value which obtains , when @xmath42 is of the order of the lattice constant .
this is not unexpected since according to the rg calculations , the correlation length is many orders of magnitude larger than our maximal system size @xmath49 for these temperatures .
the larger values of @xmath109 which we find for @xmath110 are incompatible with the rg theory .
hence we conclude that for @xmath111 unbound vortices , not being taken into account by the rg analysis , begin to limit the range of the spin correlations in the haft .
if one defines the correlation length @xmath0 through the matching condition @xmath112 , then the result of the integration of the two loop rg equations can be cast into the following form @xmath113 this is shown for two different temperatures in the two graphs in fig .
[ rho - lnksi ] .
obviously , the function @xmath114 depends weakly on l. the relation eq .
( [ 10 ] ) makes it possible to obtain the correlation length from the monte carlo simulation , even in the low temperature regime where @xmath0 is much larger than the system size @xmath42 . inserting our mc data for @xmath115 into eq .
( [ 10 ] ) and solving for @xmath0 , we obtain the data points shown in fig .
[ reklame ] for @xmath116 .
this figure also includes the data for @xmath117 which have already been shown in fig .
[ ksi - t ] .
the dashed and solid lines in fig . [ reklame ] represent fits of the rg and kt forms , eqs .
( 1 ) and ( 2 ) , to the mc data for @xmath116 and @xmath117 , respectively .
we have shown that the mc simulation of the haft yields compelling evidence for the influence of vortices on the spin correlations and hence on the thermodynamics of this model . in agreement with earlier findings by kawamura and miyashita @xcite
we find that the disordering effect of the vortices sets in rather abruptly at a temperature @xmath5 . up to this temperature ,
our data for the spin stiffness @xmath2 and the ensuing temperature dependence of the correlation length @xmath0 are consistent with the predictions of the rg analysis of the haft which ignores the existence of topological defects such as vortices . for @xmath15 , however , the simulation yields temperature dependences of the correlation length @xmath0 and the antiferromagnetic susceptibility @xmath1 which are incompatible with the rg predictions . instead ,
in this temperature regime , the temperature dependences of @xmath0 and @xmath1 which follow from the kt picture of unbinding vortex pairs provide satisfactory fits of the data .
a rapid increase of the density of unbound vortices for @xmath118 had already been found by kawamura and miyashita in their simulation of the haft @xcite .
it had not been clear , however , whether this phenomenon would lead to the same temperature dependences of the correlations of the haft as had been predicted for the planar xy model by kosterlitz and thouless @xcite . in our recent analytical study @xcite ,
we were led to the conclusion that this should indeed be the case .
the present numerical study fully supports this conclusion . as we have discussed in ref .
@xcite , the crossover transition from the rg type behavior to the kt type behavior of the correlations of the haft can not imply a phase transition in the proper sense , because the correlation length is finite both below and above the transition temperature @xmath75 .
the results shown in fig .
[ reklame ] indicate , however , that the transition happens in a very narrow interval around @xmath75 .
therefore we consider it possible that the derivative of the correlation length with respect to the temperature develops a discontinuity at @xmath75 in the thermodynamic limit .
h. kadowaki , h. kikuchi , and y. ajiro , j. phys .
c : solid state phys .
* 2 * , 4485 ( 1990 ) ; k. takeda , k.miyake , k. takeda , and h. hirakawa , j. phys .
. jpn . * 61 * , 2156 ( 1992 ; n. kojima _
et al . _ , j. phys .
. jpn . * 62 * , 4137 ( 1993 ) .
.[tab_ksi_chi ] correlation length @xmath0 and antiferromagnetic susceptibility @xmath1 for system sizes @xmath119 , @xmath120 , and @xmath121 for various temperatures .
the statistical error represents the standard deviation over 3 - 5 independent runs .
the two last columns contain the rg predictions for @xmath0 and @xmath1 .
asterisks indicate agreement of the results for different system sizes , see main text . [ cols=">,>,>,>,>,>,>",options="header " , ] | we have simulated the classical heisenberg antiferromagnet on a triangular lattice using a local monte carlo algorithm .
the behavior of the correlation length @xmath0 , the susceptibility at the ordering wavevector @xmath1 , and the spin stiffness @xmath2 clearly reflects the existence of two temperature regimes a high temperature regime @xmath3 , in which the disordering effect of vortices is dominant , and a low temperature regime @xmath4 , where correlations are controlled by small amplitude spin fluctuations . as has previously been shown , in the last regime , the behavior of the above quantities agrees well with the predictions of a renormalization group treatment of the appropriate nonlinear sigma model . for @xmath3 , a satisfactory fit of the data
is achieved , if the temperature dependence of @xmath0 and @xmath1 is assumed to be of the form predicted by the kosterlitz thouless theory .
surprisingly , the crossover between the two regimes appears to happen in a very narrow temperature interval around @xmath5 .
+ pacs numbers : 75.10.hk , 75.50.ee , 75.40.mg |
LIGONIER (KDKA) – Emergency crews were called to Idlewild Park Thursday after a young boy fell off a roller coaster.
According to emergency dispatchers, the initial call came in just before noon at the Westmoreland County amusement park.
According to police sources, the 3-year-old boy was ejected from the Rollo Coaster while riding with his brother. It happened on the last turn at the highest point, approximately 12 feet.
Sources say he landed on the tracks near a fence, and that he was initially unresponsive and discolored. However, the boy was conscious when he was flown to Children’s Hospital, and reportedly spoke to family members.
Park official Jeff Croushore said that it happened on the coaster’s middle section.
“Our thoughts and prayers are with the boy and his family, a full investigation has begun to determine the cause of this incident,” he said.
The Rollo Coaster is a wooden ride built in 1938. Officials say rides are inspected daily.
Records show the Rollo Coaster was last inspected on Aug. 6.
The ride has been shut down. Ligonier Police and Westmoreland County detectives are investigating.
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Stay Up To Date, Follow KDKA On Twitter ||||| A young boy tumbled from a wooden roller coaster at a Pennsylvania theme park Thursday and was airlifted to a hospital with unknown injuries, a park spokesman said.
The accident occurred on the Rollo Coaster ride at the Idlewild & Soak Zone in Ligonier, about 50 miles east of Pittsburgh, spokesman Jeff Croushore said at an afternoon news conference.
"He was talking, he was alert with his family," Croushore said of the boy. He could not confirm the extent of the child's injuries or his age.
The victim was not identified, although a local fire station dispatcher earlier told NBC News the child was about 3 years old.
Chopper 11 over scene at Idlewild Park after child falls off roller coaster in Ligonier, Pennsylvania. WPIX
The Rollo Coaster was built in 1938 and includes a height restriction of 48 inches — or 36 inches if accompanied by an adult.
Croushore said the accident occurred at the middle section of the ride, but did not know the height of the drop.
The coaster transports riders "up and down along a wooded hillside" and swooping curves, according to the Idlewild website.
The Pennsylvania Amusement Ride Safety Division has shut down the attraction, and an investigation has been opened, said supervisor Joseph Filoromo.
An inspector had already been at the park Thursday, but Croushore said rides are inspected daily.
"Our thoughts and concerns are with the injured boy and his family," IdleWild & SoakZone said in a statement.
The accident follows other incidents at amusement parks and fairs this summer — including one in Tennessee that injured three girls when their Ferris wheel bucket overturned and another in Kansas in which a 10-year-old boy was killed on a 169-foot water slide. ||||| A 3-year-old was flown to the hospital Thursday after what was reported to emergency dispatchers as a fall from a roller coaster at the Idlewild and SoakZone amusement park.
Spokesman Jeff Croushore provided few details other than to say the injury happened on the Rollo Coaster, an older-style wooden ride.
VIDEO: Watch the latest report from Kelly Brennan and Beau Berman
The child was conscious and talking while being treated at the park, Croushore said. He was flown to Children's Hospital of Pittsburgh of UPMC. No information about his condition is being released.
Sources told Pittsburgh's Action News 4 reporter Ashlie Hardway that the boy suffered head and chest injuries.
The injury happened in "the middle part" of the ride, Croushore said. He declined to be more specific, and he had no information to offer regarding whether the injury was a result of a malfunction or the rider's behavior.
The Rollo Coaster will remain closed, pending further investigation by Ligonier police and Westmoreland County detectives. Idlewild remained open to customers.
When asked about a report that an inspector from the state Bureau of Ride and Measurement Standards visited the park Thursday, the spokesman said, "Our rides are inspected daily, and we're not going to go into that right now, but safety is always our No. 1 priority."
VIEW: ?Current inspection notice for Idlewild coaster (PDF)
Amy Bellan was at the park Thursday and said her son first road the coaster last year when we was 2-years-old.
"Their height restrictions are only 36 inches. So unfortunately they don't have seatbelts on there. It's only a bar," Bellan said.
Built in 1938, the coaster has a height requirement of 36 inches. Riders under 48 inches must be accompanied by an adult. The ride doesn't require seat belts.
Shanna Leeman, who grew up near Idlewild Park and now has a season pass with her family, said she was in line for the Rollo Coaster with her husband and two kids and was behind a woman with three kids when she witnessed a worker bend the rules.
"One of the three children was under the 48 inches and unable to ride without a parent, and (the worker) told the mother that, and he looked around, and said, 'But I don't see my supervisor around' and he turned his head and let them get on the ride," Leeman said.
A spokesman for the Pennsylvania Department of Agriculture said the 'Rollo Coaster was last inspected Saturday by a private, certified inspector and it passed the inspection.
The department is working with Idlewild staff and police to investigate and an inspector is at the park to inspect the ride and examine the inspection history.
Parents told Pittsburgh's Acton News 4 that the issue may not be with the ride, but with the people who run it.
"I knew it was going to happen some time or another with the attendant just letting them go on," Leeman said.
Idlewild responded late Thursday to Leeman’s accusations:
"Ride operators are trained to strictly adhere to all height requirements for all rides and attractions. We were not made aware of this guest’s claim prior to this point. However, all guest concerns are taken seriously. Right now, our focus is on the current investigation into today’s incident and our thoughts and prayers continue to be with the boy and his family."
FULL STATEMENT from Department of Agriculture:
"This afternoon, the Pennsylvania Department of Agriculture learned of this morning’s incident at Idlewild. Our thoughts are with the child involved in this incident. At this point, the department is working with the amusement park’s staff and local officials to investigate. As part of that investigation, the department has an inspector on site to inspect the ride, and we are examining the inspection history. At this point, we know the ride was most recently inspected by a private certified inspector on August 6, 2016, and that it passed that inspection.
"This ride is one of more than 10,200 across the commonwealth that is registered with the state. There are more than 1,650 inspectors that the department has trained and certified to monitor rides in an effort to strengthen public safety. The department has inspected and registered amusement rides under the Amusement Ride Safety Act since 1984.
"Attached is the most recent notification of inspection for the ride that the incident occurred on, listed under Pennsylvania amusement registration number 1209."
Related: Water slide death in Kansas raises questions about amusement park safety
Related: Mechanical flaw cited after girls fall off Ferris wheel at county fair | – A young boy was hospitalized with unknown injuries after falling off an 80-year-old wooden roller coaster Thursday at Pennsylvania's Idlewild & Soak Zone, NBC News reports. The boy hasn't been identified, but he may have been around 3 years old. According to KDKA, the boy was riding the Rollo Coaster with his brother when he fell. It's unclear how far the boy fell, though a spokesperson for the amusement park says the fall happened in the "middle part" of the ride, WTAE reports. The boy was flown to a local children's hospital. "He was talking, he was alert with his family," NBC quotes the spokesperson as saying. The Rollo Coaster has been shut down while the boy's fall is investigated. Riders as short as 3 feet are allowed on the roller coaster as long as they have an adult with them. The Idlewild spokesperson says the park's rides are inspected every day. |
immunoglobulin light - chain amyloidosis ( al ) is the most common type of systemic amyloidosis.1 the use of high - dose chemotherapy followed by autologous stem cell transplantation ( asct ) has been recognized as an important therapy that has dramatically changed the perspective of al amyloidosis care.2 since a plasma cell dyscrasia is the underlying cause of al amyloidosis,3 asct has also been adopted for the treatment of this entity , aiming to induce a hematological and organ response by providing time for the involved organs to slowly clear out some of the amyloid protein that translates into survival prolongation.4 because the depth of response is a critical determinant of treatment outcome , different strategies have been employed , hoping to increase the proportion of patients who ultimately achieve a complete hematological response after asct .
these strategies have included the use of induction chemotherapy before asct , especially for those patients with > 10% bone marrow plasma cells.5 a recent , single - arm , prospective clinical trial investigated the role of bortezomib and dexamethasone induction followed by asct for newly diagnosed al amyloidosis.6 the study was successful to show unprecedentedly high hematologic responses .
a hematologic very good partial response or better was seen in 77% of 35 patients at 6 months but was reported in 100% for the 27 patients who completed all planned therapy . while exciting results were noted , also new emerging complications after asct were seen ( gvhd - like syndrome ) .
the mechanisms by which this complication occurred remain uncertain . here , we describe the first case of acquired von willebrand syndrome ( avws ) in a patient with al amyloidosis who received cyclophosphamide , bortezomib and dexamethasone induction followed by asct . interestingly , this patient also developed a gvhd - like process in the skin that was successfully treated with steroids and a secondary igm monoclonal gammopathy .
a previously healthy , 56-year / old male presented with asymptomatic hypoalbuminemia detected on routine screening 2-years prior and subsequently developed asymmetric inflammatory polyarthritis ( mcp s , wrists and shoulders ) and proteinuria .
further investigations led to the diagnosis of al amyloidosis ( stage i ) with a concurrent low - grade b - cell neoplasm on bone marrow and no evidence of lymphadenopathy .
pre - treatment studies revealed lambda light chain of 3030 mg / l ( normal range 5.7126.3 ) , free kappa 59.3 mg / l ( normal range 3.319.4 ) and ratio of 0.02 ( normal range 0.261.65 ) , 24 hr urine collection showed 9.86 g / day of proteinuria with 0.16 g / day of monoclonal igg lambda and free lambda light chain .
nt - pro - bnp and high - sensitive troponin - t were normal , serum ldh was normal , crp was elevated ( 23.6 mg / l ) , creatinine was 108 mol / l , alp was normal and hemostasis study was normal ( pt , inr , ptt and factor x activity were all normal ) .
treatment with cyclophosphamide , bortezomib and dexamethasone ( cybord ) was initiated , achieving very good partial response ( vgpr ) after 3 cycles of therapy .
stem cell mobilization was successfully performed followed by autologous stem cell transplantation with bortezomib / melphalan conditioning .
at-2 months post - asct the patient developed an erythematous rash affecting more than 50% of the body surface area .
bm biopsy showed normal cellularity and adequate megakaryocytes , no evidence of plasma or lymphoproliferative disorders were seen .
treatment with prednisone at 1mg / kg was initiated leading to complete resolution of these symptoms . at day-100 ,
serum protein electrophoresis , however , showed the presence of a secondary igm lambda monoclonal gammopathy .
four months post - asct patient presented to er with prolonged epistaxis . prior to this time
laboratory investigations revealed prolonged ptt ( 45.5 s ) , and decrease von willebrand factor activity ( vwf : act ) , von willebrand factor antigen ( vwf : ag ) , and factor viii activity ( fviii : c ) levels .
vwf : act ( gp1b ) 12 iu / dl ( normal range : 41144 ) , vwf : ag 31 iu / dl ( normal range : 40185 ) , fviii : c 14 iu / dl ( normal range : 54147 ) .
factor ix and xi levels were normal , fxii was slightly decreased at 30 iu / dl .
mixing studies for vwf : act and fviii : c showed no inhibitory effect on normal plasma consistent with a non - neutralizing vwf antibody against non - functional vwf domains .
vwf propeptide to vwf antigen ratio ( vwfpp : ag ) was increased at diagnosis ( 7.7 ) suggesting increased vwf clearance ( vwfpp measured by vwfpp - specific monoclonal antibody enzyme - linked immunosorbent assay ( elisa ) using the gti diagnostics kit .
lupus type inhibitor was not detected , and fibrinogen and all other measured factor levels were normal .
g / l , platelets 110 10e9 , creatinine 139 umol / l , ana- , rf- , hep b and hep c negative , cryoglobulin and agglutinin testing negative . based on these investigations ,
no coagulation factor replacement was required and desmopressin ( ddavp ) challenge test demonstrated a good increase in von willebrand factor and factor viii levels , without rapid clearance ( factor levels were measured at 30 mins , 1 and 4 hours ) ( table 1 ) . the patient was treated with prednisone at 1mg / kg with slow dose tapering .
no further bleeding has been reported and normalization of von willebrand factor levels is maintained at 12 months .
acquired von willebrand syndrome ( avws ) is a rare hemorrhagic disorder that usually occurs in patients with no previous personal or family history of bleeding . 7 according to the isth registry , 48% and 15% of 186 avws cases that qualified for the registry were associated with lymphoproliferative and myeloproliferative disorders.8 among lymphoproliferative disorders avws is most commonly associated with monoclonal gammopathy of undetermined significance ( mgus ) in up to 23% of cases.9 in our patient , the pathogenic aetiology of underlying avws seemed to be increased clearance of fviii - vwf complex due to non - neutralizing autoantibodies to vwf given the lack of inhibitory effect on normal plasma on vwf : act and fviii : c mixing studies ( 37 c 2 hours of incubation ) .
our patient demonstrated a decrease vwf ag : act ratio ( 0.45 ) , similar to type 2 von willebrand disease ( vwd ) and loss of high and intermediate molecular weight ( hmw ) multimers , which has been described in avws.8 ( figure 2 ) vwfpp levels and vwfpp : ag ratio were measured and demonstrated increased ratio at diagnosis ( 7.7 , normal range 0.52.0 ) and normal ratio ( 0.9 ) in remission suggesting increase clearance of vwf had a role in awvs for our patient .
interestingly , ddavp was able to stimulate enough secretion of vwf from endothelial wiebel - palade bodies to overcome the clearance of vwf by the autoantibody , resulting in normalization of vwf : ag and vwf : act levels , and reappearance of hmw multimers .
the decrease ( but still abnormal ) vwfpp : ag ratio ( 5.3 ) also reflects the increased secretion stimulated by ddavp relative to clearance that remained constant .
vwfpp is cleaved in the trans - golgi but remains stored together with mature vwf in platelet -granules and endothelial cell weibel - palade bodies in equimolar amounts .
after release , vwfpp dissociates from the mature vwf subunit , circulates with a steady - state half - life , and serves as a marker of vwf secretion.10 a high vwf : pp / ag ratio has been proposed by scott et al.,11 as a simple method to distinguish avws due to decreased vwf synthesis from that due to increased clearance .
federici et al.8 characterized in their paper some differences in avws caused by igg - mgus versus igm mgus .
although the paper reported on only 8 igg - mgus and 2 igm mgus , they reported a higher vwf : pp / ag compared to controls in igg mgus but not in igm mgus .
in addition , a normal multimeric pattern was seen in the igg mgus cases but selective loss of large and intermediate multimers in the igm - mgus cases.12 our case of igm mgus associated awvs differs in that high vwfpp : ag was seen , although the loss of high and intermediate molecular weight multimers is similar to that reported by federici et al.8 the treatment goals in avws are to control acute bleeds , to prevent bleeding in high - risk situations , and to obtain long - term remission . in this case , ddavp was able to stimulate enough endogenous secretion of vwf to overcome the clearance caused by the anti - vwf antibody , and maintain normal vwf levels at 1 and 4 hours following ddavp administration .
in other cases of avws , ddavp is often ineffective for treatment as the anti - vwf antibody is either neutralizing , or the clearance of vwf : ag by the anti - vwf antibody is much greater than the amount of endogenous vwf : ag that can be secreted by weibel - palade bodies .
however , in our case , the anti - vwf antibody is non - neutralizing and clearance by this antibody is not so rapid such that the ddavp - stimulated release of endogenous vwf can overcome the anti - vwf antibody - mediated clearance .
this is evidenced by the increased vwf levels following ddavp stimulation and the decreased vwfpp : ag ratio .
bleeding and bruising are common in immunoglobulin light chain ( al ) amyloidosis and can occur through a number of mechanisms , thus avws is not often considered when bleeding symptoms occur .
kos et al,13 recently reported a small series of cases where the association of active al amyloid and the appearance of awvs was noted . in our current report , in contrast , this association was observed even in the setting of complete haematological response . to our knowledge
this is the first case report of post - transplant igm lambda secondary mgus treated with high dose prednisone .
however , a previous report by lazarchick et al.,14 described a 41 y / o male who after undergoing allogeneic bone marrow transplantation for the treatment of acute myeloid leukemia was admitted with worsening chronic gvhd and subsequently was found to have markedly reduction of von willebrand factor antigen consistent with a diagnosis of avws .
our current report also illustrates the emerging complications for patients with al amyloidosis receiving bortezomib - containing regimens prior to stem cell transplantation .
further data in this regard is needed to better understand the mechanisms by which these complications occur and how to minimize the morbidity related to these events . | acquired von willebrand syndrome ( avws ) is a rare hemorrhagic disorder that occurs in patients with no prior personal or family history of bleeding . here
, we describe a case of avws occurring after autologous stem cell transplantation ( asct ) .
interestingly , avws developed after bortezomib - based induction and conditioning regimens .
recent evidence suggests that the proximity of the bortezomib therapy to the collection of stem cells with consequent depletion of regulatory t cells after the conditioning regimen could explain some of the unusual autoimmune complications reported in patients receiving bortezomib prior to asct .
in addition , this patient developed a secondary mgus post - asct , which may have also contributed to the avws . to the best of our knowledge ,
this is the first case of post - asct avws reported .
prospective data is needed to better elucidate the mechanisms by which these unusual complications occur in patients receiving bortezomib prior to asct . |
the silicon tri - gate transistor used in this work is fabricated using standard cmos technology , similar to previously reported devices @xcite .
the channel , defined by the top gate , is 11 nm high , 42 nm wide and 54 nm long . on both sides of this gate , 25 nm
long si@xmath70n@xmath71 spacers form barriers to the highly doped source and drain regions . with a background boron doping of @xmath72/@xmath73 in the silicon channel ,
about 10 boron atoms are expected under the gate and about 10 under the spacers . in a dilution refrigerator at a base temperature of 40 mk ,
hole transport and rf gate reflectometry measurements give complementary insights in the static and dynamic behaviour of the two - hole system of interest .
the hole temperature was measured from quantum - dot transport at @xmath44 300 mk .
the noise floor of the transport measurement ( @xmath44100 fa ) allows us to detect currents with a total tunnel rate down to 500 khz .
a surface mount 270 nh inductor , attached to the top gate , forms a tank circuit together with a parasitic capacitance of @xmath440.3 pf .
tunnel events in the transistor with a tunnel rate higher than or equal to the resonant frequency of 583 mhz result in a change of the reflected amplitude and/or phase of this resonator .
furthermore , low intensity light was directed to the silicon chip through an optical fiber to enable the use of the lower doped substrate as a back gate . in order to estimate the location of the two atoms ,
we have extracted the relative capacitive coupling to the different electrodes .
the hole temperature of @xmath44300 mk gives @xmath74 for the acceptor - lead tunnel rate , thereby justifying a thermally broadened fit @xcite .
the reflectometry line width shows a relative coupling to the top gate ( @xmath75 ) and drain ( @xmath76 ) of [email protected] ev / v and [email protected] ev / v respectively , thereby placing this atom roughly halfway between these two electrodes , under the @xmath77 spacer .
this relatively weak coupling to the top gate supports our identification of the acceptor atom , as gate - induced quantum dots are known to have gate couplings above @xmath440.7 ev / v @xcite .
the second boron atom has to be located closer to the centre of the channel , as the tunnelling to both electrodes is too slow to be detected .
= 1.93 v and @xmath78 = -777 mv . * e * , ( * f * ) amplitude ( phase ) shift for the linecuts on the red ( inter - acceptor singal ) and blue ( acceptor - lead singal ) dotted lines in * c * ( * d*).,width=332 ] in the rf gate reflectometry experiments shown in figs .
[ fig : figure1 ] , [ fig : figure2 ] , and [ fig : figure3 ] , a driving frequency of 583 mhz is used , which is close to the resonant frequency and ideal to distinguish the acceptor - lead and inter - acceptor transitions .
the full frequency response of the reflected signal from the lc - circuit reveals more information about the tunnel rates involved in the experiment @xcite .
frequency domain measurements of the amplitude and phase response around the resonance of the lc circuit are shown in fig .
[ fig : figures1 ] .
these measurements show that the acceptor - lead signal mainly changes the amplitude of the reflected signal , while the inter - acceptor signal mainly reduces the resonant frequency .
this difference in response of the lc - circuit can be explained by a difference in tunnel rate between these two processes @xcite .
when the tunnel rate is much faster than the resonant frequency ( @xmath79 ) , the tunnel process will predominantly add capacitance to the circuit ( dispersive response ) , which in turn shifts the resonance to a lower frequency .
this is observed for the inter - acceptor tunneling process , thereby revealing a tunnel rate much faster than the resonant frequency .
when the tunnel rate is of the order of the resonant frequency ( @xmath80 ) , the tunnel process will predominantly add resistance to the circuit ( dissipative response ) .
this added resistance can either bring the circuit closer or further away from its ideal matching condition , depending on the initial impedance of the circuit , thereby either reducing or increasing the reflection amplitude .
a reduction in reflection amplitude is observed for the acceptor - lead tunneling process , thereby revealing a tunnel rate of the order of the resonant frequency .
= [email protected] ghz .
the inset shows a schematic representation depicting the excitation from the bonding to the anti - bonding singlet state with microwaves.,width=332 ] to find the tunnel coupling between the two acceptor atoms , we probe the resonance between the bonding and anti - bonding singlet @xmath81 states , as shown in the inset of fig .
[ fig : figures2 ] , in accordance with a measurement on two electrons on a hybrid donor - quantum dot system @xcite . here
we make use of the bias - tee coupled to the drain lead , as shown in fig .
[ fig : figure1]a .
the inter - acceptor signal is probed with rf gate reflectometry , while continuous wave microwaves are applied to the drain electrode .
when the transition between the bonding and anti - bonding @xmath81 states is excited by the applied microwaves , the occupation of the bonding state is lowered , while the occupation of the anti - bonding state is increased .
as the bonding and anti - bonding singlet states give rise to an opposite response of the resonator @xcite , the observed @xmath2 is expected to decrease when the occupation in the anti - bonding state is increased and completely disappear when the occupations in the system become unpolarised . in order to keep the input power of the applied microwaves constant during the experiment , the splitting of the acceptor - drain signal is also probed during the experiment .
the splitting of this signal has no dependence on the microwave frequency and is solely dependent on the microwave power applied at the drain . using this measurement we can calibrate for any frequency dependent losses in the system and use the same input power for every frequency .
the response of the inter - acceptor tunnel signal is shown in fig .
[ fig : figures2 ] as @xmath82 , with @xmath83 being the signal without microwaves .
the resonance dips at a frequency of the [email protected] ghz , which demonstrates a tunnel coupling between the atoms of [email protected] ghz .
the width of this resonance indicates a @xmath84 for these charge states of @xmath44 200 ps , similar to what was found for a two - electron system on a hybrid donor - quantum dot @xcite
. -states . * a * , magnetic field dependence of the energy levels of a hole bound to a single boron acceptor in silicon with a compressive strain of 1.2@xmath8510@xmath86 parallel with the magnetic field and an electric field of 0.6 mv / m perpendicular to the magnetic field . * b * , magnetic field dependence of the energy levels of a hole bound to a single boron acceptor in silicon with a compressive strain of 0.6@xmath8510@xmath86 parallel with the magnetic field and an electric field of 1.2 mv / m perpendicular to the magnetic field . dashed lines show the linear projection of the high magnetic field zeeman effect , showing a change in @xmath26 in * b*.,width=332 ] in bulk silicon the single hole ground state of an acceptor atom is fourfold degenerate , consisting of heavy hole and light hole states . the effect of strain , electric field and magnetic field on these states
is well described by bir et al .
strain and electric field split the heavy and light hole manifolds , leading to a splitting of @xmath26 at zero magnetic field .
a magnetic field splits all four spin - states , where this zeeman effect strongly depends on the local environment of the atom .
the two atoms probed in the experiments are found to have heavy hole ground states .
the @xmath26 is assumed to be different for the two acceptors , as they experience a different local environment . as an example
, the zeeman effect is calculated for two different local environments where the heavy holes form the ground state at zero magnetic field , shown in fig .
[ fig : figures3 ] . for the first example we consider
the situation where a compressive strain of 1.2@xmath8510@xmath86 is present parallel to the magnetic field and an electric field of 0.6 mv / m is present perpendicular to the magnetic field , see fig .
[ fig : figures3]a . in fig .
[ fig : figures3]b the situation with half of the strain and double the electric field is considered . in this second example
, we note that if a linear approximation is taken for the hole - spin states in the high magnetic field region and traced back to zero magnetic field ( dashed lines ) , a different heavy - light hole splitting is found than at zero magnetic field .
this effect , caused by a rotation of the quantization axis of the angular momentum of the hole , has been observed in our experiment presented in fig .
[ fig : figure4 ] . for the doubly occupied and positively charged acceptor state ( a@xmath87 ) the exchange energy between two holes from the same manifold
far exceeds the heavy - light hole splitting ( @xmath88 ) . due to this exchange interaction
, only 6 out of the 16 possible two - hole states can be bound to a boron atom in silicon @xcite .
a similar sixfold manifold is found for two - holes bound to two closely placed boron atoms @xcite and the neutral states of two holes bound to group ii acceptors @xcite . as these six states are build from combinations of different spin states , one heavy hole singlet state , one light hole singlet state and four light / heavy - quadruplet states
are found , which we will write as : & _
= 1/ ( - ) , + &
_ = 1/ ( - ) , + & ^2-_= 1/ ( - ) , + & ^-_= 1/ ( - ) , + & ^+_= 1/ ( - ) , + & ^2+_= 1/ ( - ) , where @xmath89 represent the heavy hole states and @xmath90 represent the light hole states . furthermore , when an exchange interaction between the heavy and light holes is introduced , @xmath23 , the q@xmath91 state splits into a singlet and triplet state @xcite . in fig .
[ fig : figures4]a an example of the magnetic field dependence of the a@xmath20-states of an acceptor is shown , using the a@xmath92 states from fig .
[ fig : figures3]b and neglecting any exchange between the light and heavy holes ( @xmath23 = 0 ) . the colors in the figure
show the heavy - hole ( red ) and light - hole ( blue ) character of these states , where the states built from one heavy and one light hole turn purple .
the splitting between the heavy hole singlet and the light hole singlet ( @xmath93 - @xmath94 = 2@xmath26 ) is found to be different in the high magnetic field limit compared to the zero magnetic field splitting , in line with was found in fig .
[ fig : figures3]b .
energies for the same local environment as in fig .
[ fig : figures3]b and @xmath95 . a clear difference in splitting between the s@xmath16 and s@xmath28 states in the low and high magnetic field limit is visible . *
b * , the ( 1,1)-configuration product states of the two single hole states described in fig.[fig : figures3]a and [ fig : figures3]b.,width=332 ] in the situation where each hole is bound to a different acceptor , the two hole state can be described as a product state of the single particle states , leading to an energy spectrum of 16 states divided into 4 fourfold degenerate manifolds at zero magnetic field . each fourfold manifold splits into a singlet and a triplet state when an exchange interaction is introduced . in our experiments
the heavy - hole manifold has the lowest energy at zero magnetic field and can be described as : & _
= 1/ ( , - , ) , + & ^-_= , , + & ^0_= 1/ ( , + , ) , + & ^+_= , .
the energy splitting to the next two manifolds is given by the @xmath26 of each acceptor , where these two - hole states consist of one heavy and one light hole state .
finally , the light - hole manifold is split from the heavy - hole manifold by the sum of both @xmath26 s . in fig .
[ fig : figures4]b an example of such a ( 1,1 ) level configuration is shown for a combination of the a@xmath92-states presented in fig .
[ fig : figures3]a and [ fig : figures3]b .
although many level crossings are observed , we highlight the fact that in this situation where the heavy holes form the ground state manifold , the ground state in the ( 1,1 ) region remains the t@xmath96 state for any positive magnetic field . in the transport measurements shown in fig.[fig
: figure4 ] the ( 1,1)@xmath97(2,0 ) transition energies at zero magnetic field and as a function of magnetic fields up to 3 t are probed . in these experiments , a voltage of + 10 mv
is applied to the drain , while the current is measured at the source .
this bias direction gives a transport direction for the holes from the drain to the source .
from the rf gate reflectometry experiments , as shown in fig .
[ fig : figure2 ] , it is deduced that the acceptor with a charge transition from 0 to 1 hole has a stronger tunnel coupling to the drain ( detectable with rf reflectometry ) than the acceptor with a charge transition from 1 to 2 holes ( not detectable with rf reflectometry ) .
it follows that the probed sequential tunnelling involves the ( 1,1)@xmath97(2,0 ) transition , where the two observed bias triangles are formed by the two following hole charge transfer processes : ( 1,0 ) ( 1,1 ) ( 2,0 ) ( 1,0 ) , + ( 2,1 ) ( 1,1 ) ( 2,0 ) ( 2,1 ) .
the current measured within the bias triangle region is around 5 pa at the baseline at zero magnetic field and declining to the measurement noise floor of @xmath44 100 fa at the other side of the triangle , indicating a total tunnel rate of the sequential tunnel process around 30 mhz and lower .
we recall that the resonant tunnel - rate between the ( 1,1 ) and ( 2,0 ) s@xmath16 states was measured at 4.3 ghz and the tunnel - rate from the drain to the acceptor was found to be around the resonant frequency of 583 mhz , indicating that the tunnel - rate between the second acceptor and the source is the limiting tunnel process
. however , we note that due to off - resonant tunneling or tunneling between two states consisting of different spins , the inter - acceptor tunnel rate can be strongly suppressed , thereby possibly becoming the limiting tunnel process .
furthermore , the ratio between this inter - acceptor tunnel rate and the relaxation rate of each excited state in the ( 1,1)-configuration determines if this excited state will have any effect on the measured current .
the transport measurement presented in fig .
[ fig : figure4 ] can be explained by only taking the heavy - hole manifold of the ( 1,1)-configuration into account .
this indicates that any state which includes any light - hole has a fast relaxation to the heavy hole ground state , which matches with the fast light - to - heavy hole relaxation process observed as a relaxation hotspot in fig .
[ fig : figure3 ] . the shift in phase response of the reflected signal as shown in fig .
[ fig : figure2]b is ascribed to the addition of a quantum capacitance ( @xmath98 ) to the lc - circuit @xcite when holes can tunnel between the two atoms , given by : @xmath99 where @xmath100 is the difference in capacitive coupling from the top gate to each acceptor , found to be 0.14 ev / v in the transport measurements , @xmath101 is the electron charge , @xmath15 is the energy detuning between the two acceptors , and @xmath29 is the tunnel coupling between the ( 1,1 ) and ( 2,0 ) s@xmath16 states . all other tunnel couplings between ( 1,1 ) and ( 2,0 ) states are considered to be much smaller and therefore not contributing to a change in the detected reflected signal .
the total phase shift ( @xmath102 ) is determined by the difference in occupation , given by the boltzmann distribution , of the lower and upper branch of the heavy hole singlet state : @xmath103 where @xmath104 and @xmath105 are the energies of the bonding and anti - bonding singlet states respectively and @xmath106 describes the energies of all the involved states . using eq .
[ eq : eqm1 ] and [ eq : eqm2 ] , the magnetic field dependence of the phase shift caused by the inter - acceptor tunneling is calculated as shown in fig .
[ fig : figure2]c .
we note that although the crossing of the q@xmath91 state and the s@xmath16 state has some influence on the boltzmann distribution of the s@xmath16 states , this influence is not distinguishable in the measurement .
however , for completeness , we have displayed the @xmath46 crossing point in fig .
[ fig : figure2]c , as found in the relaxation - hotspot measurement together with an estimated g - factor of the q@xmath91 state . to t@xmath96 relaxtion ( blue ) or with the s@xmath16 to q@xmath107 relaxation ( red ) .
both fits have a comparable value for @xmath108 . *
b * , comparison of the modeled relaxation mechanisms on a larger scale of magnetic field and @xmath109.,width=332 ] at magnetic fields much higher than the @xmath110 mixing point the dominant relaxation mechanism comes from either the relaxation to the ( 1,1 ) t@xmath96 state or the relaxation to the ( 2,0 ) q@xmath107 state , given by eq .
[ eq : eq1 ] . in fig .
[ fig : figures5]a the fits of the relaxation rate data with a combination of eqs .
[ eq : eq1 ] and [ eq : eq2 ] is given for the relaxation process to the t@xmath96 state ( blue ) and the q@xmath107 state ( red ) are shown .
our data is insufficient to determine if a @xmath111 or @xmath112 relaxation mechanism is dominant at high magnetic fields .
the relaxation amplitudes extracted from these two fits , which are interpreted as the relaxation time at a field of 1 t relative to the corresponding level - crossing , is found to be 0.5 @xmath66s for @xmath113 and 5 @xmath66s for @xmath63 .
both of these values are in good agreement with the theoretical predictions for light - heavy hole relaxation ( @xmath109 = 0.14 @xmath66s at 1 t @xcite ) and heavy - heavy hole relaxation ( @xmath109=40 @xmath66s at 0.5 t @xcite ) .
[ fig : figures5]b shows the extracted relaxation rates on a larger scale of @xmath114 , demonstrating the more than 3 orders of magnitude increase in relaxation rate at the hotspot .
furthermore , it reveals that if this hotspot behavior can be moved to a higher magnetic field , by increasing the heavy - light hole splitting or decreasing the g - factor , relaxation times longer than 1 ms could be achieved at magnetic fields around 0.5 t .
the observed relaxation hotspot is explained by the mixing of the bonding s@xmath16 state and the ( 2,0 ) q@xmath45 state , which allows a light - to - heavy hole relaxation to the ( 1,1 ) t@xmath17 state .
this relaxation process is expected to have a @xmath111 dependence and furthermore depends linearly on the light hole character of the mixed state .
here we show the calculation of the light hole character of the probed state . around the anti - crossing we can write the energies of the lower ( - ) and upper ( + ) states as : @xmath115 where @xmath116 is the energy splitting between the states in the absence of mixing ( @xmath117 - @xmath94 ) ,
@xmath94 is taken as the reference energy ( @xmath118 ) .
we define the amount of light hole character of each state as the chance to measure it as the q@xmath91 state in the basis of q@xmath91 and s@xmath16 , written as @xmath119 and given by : @xmath120 the relaxation measurement is performed at zero detuning , which is the original position of @xmath94 in the absence of mixing .
the state probed here can be written as a combination of the + and - states , depending on their relative energy difference with the measurement point @xmath121 .
we note that @xmath122 = @xmath123 = @xmath124 and also that @xmath125 is equal to @xmath126 , which gives the total light hole character at the zero energy point as : @xmath127 as used in eq . [ eq : eq2 ] .
the key properties of acceptor - based spin - orbit qubits , such as the dipole coupling and decoherence time between the chosen qubit states , are predicted to strongly depend on changes to the symmetry of the silicon crystal and the confinement of the hole @xcite .
unstrained silicon ensemble measurements have established an electric dipole coupling of 0.26 debye @xcite and relaxation and coherence times in the micro - second regime @xcite .
these acceptor systems are promising for fast electrically - driven spin - orbit qubits with a strong coupling to cavities and phonons @xcite , although a longer coherence time would be desirable .
an optimal regime , where the coherence and relaxation times are prolonged while the strong electric dipole coupling is maintained , has been predicted in the small strain regime , giving a small splitting and strong mixing between the heavy and light hole states @xcite .
the possibility to lengthen the acceptor relaxation time has been demonstrated in experiments on intentionally heavily strained bulk samples , where @xmath109 times up to 100 ms are measured @xcite .
the access to and control over single atoms , as has been demonstrated here , is necessary to probe the physics in an environment with a small local strain , which is the crucial regime for the realisation of acceptor qubits .
the device has been designed and fabricated by the tolop project partners , see http://www.tolop.eu . this work was supported by the arc centre of excellence for quantum computation and communication technology ( ce110001027 ) and the arc discovery project ( dp120101825 ) . | two - level quantum systems with strong spin - orbit coupling allow for all - electrical qubit control and long - distance qubit coupling via microwave and phonon cavities , making them of particular interest for scalable quantum information technologies . in silicon , a strong spin - orbit coupling exists within the spin-3/2 system of acceptor atoms and their energy levels and properties are expected to be highly tunable . here we show the influence of local symmetry tuning on the acceptor spin - dynamics , measured in the single - atom regime .
spin - selective tunneling between two coupled boron atoms in a commercial cmos transistor is utilised for spin - readout , which allows for the probing of the two - hole spin relaxation mechanisms .
a relaxation - hotspot is measured and explained by the mixing of acceptor heavy and light hole states .
furthermore , excited state spectroscopy indicates a magnetic field controlled rotation of the quantization axes of the atoms .
these observations demonstrate the tunability of the spin - orbit states and dynamics of this spin-3/2 system .
single impurities in semiconductors offer an extensive variety of spin systems @xcite , desirable for the emerging fields of quantum technologies , such as quantum communication @xcite , quantum sensing @xcite , and quantum information @xcite . impurities with spin-1/2 , such as phosphorus in silicon , are promising two - level spin systems for quantum technologies @xcite .
alternatively , impurities with spin-3/2 offer the possibility to isolate a two - level system whose quantum properties strongly depend on the specific splitting and mixing of the spin-3/2 states , thereby providing a highly tunable quantum system .
several spin-3/2 impurities have been investigated in recent studies , such as single co atoms @xcite and si vacancies in silicon carbide @xcite , as well as spin-3/2 hole quantum dots @xcite . however , the adjustability of impurity spin-3/2 systems has not yet been demonstrated . here
this tunability is shown using the until now little explored spin-3/2 system of a single acceptor in silicon , which has a level configuration and environmental couplings predicted to yield highly tunable qubits @xcite .
of particular interest is the possibility to tune the acceptor system to a regime with a large dipole coupling whilst being robust against charge noise @xcite . by using a silicon cmos transistor to access the single acceptor regime @xcite , which allows excellent control over the environment of the atom , this work demonstrates control over the level configuration of a single acceptor in silicon and probes the resulting influence on the spin - dynamics of the acceptor states .
a predicted strong spin - orbit coupling for the heavy hole ( @xmath0 ) and light hole ( @xmath1 ) states makes acceptors in silicon good candidates for spin - orbit qubits @xcite .
this type of qubit is advantageous for the all - electrical qubit control by local gates @xcite and the long - range qubit coupling via the interaction with microwave resonators @xcite .
the level configuration of the acceptor atom is predicted to strongly depend on the local strain , electric field , magnetic field , and the proximity of the atom to an interface @xcite . as a consequence
the essential properties of possible two - level quantum systems created from these levels , such as the electric dipole coupling , relaxation time and coherence time , can be drastically changed @xcite . so far spin - dynamic experiments on acceptor ensembles in bulk silicon have been hindered by a large inhomogeneous broadening , originating from the random heavy - light hole splitting induced by each atom s local environment @xcite . by addressing individual acceptor atoms , which is essential to operate them as qubits , this effect of inhomogeneous broadening
is circumvented .
single acceptor measurements have demonstrated the effects of electric field @xcite , local strain @xcite , a nearby interface @xcite , magnetic field @xcite , and hubbard - like interactions between two acceptors @xcite . here
we demonstrate the ability to tune the level configuration and , as a consequence , the hole spin dynamics of an acceptor atom , thereby showing the fundamental versatility of this spin-3/2 system .
for this study a two - hole system confined to two boron atoms in a state - of - the - art silicon cmos transistor ( see supplementary information a for fabrication details ) is investigated using a combination of single hole transport @xcite and dispersive radio - frequency ( rf ) gate reflectometry techniques @xcite ( see fig .
[ fig : figure1]a ) . the crossover point between one hole on each acceptor , the ( 1,1 ) state , and both holes on one acceptor , the ( 2,0 ) state ,
is used to probe the spin state of the double hole system , making use of spin selective tunneling @xcite .
magnetic field dependent measurements of the relaxation rate and the excited state spectrum of the two - hole system show that the quantization axis of the angular momentum can be rotated with the applied field , which strongly tunes the mixing and splitting between the heavy and light hole states .
the amount of control over the level configuration of a single acceptor atom demonstrated here is an essential step towards an acceptor qubit . .
the signals of a boron atom ( black arrow ) and an unintentional quantum dot ( grey arrows ) are identified.,width=332 ] rf gate reflectometry @xcite is used to detect individual acceptors .
the charging of a boron atom in the nano - transistor is observed as a shift of the phase , @xmath2 , or the amplitude , @xmath3 , of the reflection from a lc - circuit connected to the top - gate , when driven near the resonance frequency with @xmath4 .
this shift is caused by a change in admittance of the lc - circuit induced by tunneling of holes when a localized site in the transistor changes its charge occupation @xcite . in a map of topgate voltage ( @xmath5 ) and backgate voltage ( @xmath6 ) in the presence of a small drain voltage ( @xmath7 = 1 mv ) , shown in fig .
[ fig : figure1]b , some charging lines appear far below the onset of hole transport current @xmath8 .
these lines are identified as the charging of localized sites which are only strongly tunnel coupled to one of the electrodes .
the slopes of these lines correspond to the capacitive coupling ratio to the top and back gate .
multiple lines with equal slopes ( grey arrows in fig .
[ fig : figure1]b ) imply the charging of several charge states of the same localized state , here likely to be an unintentional quantum dot at the si / sio@xmath9 interface @xcite .
in contrast , a boron atom can bind no more than two holes @xcite .
a single charging line , unaccompanied with any counterparts of equal slope ( black arrow in fig . [ fig : figure1]b ) , indicates the charging of the first hole onto a single boron atom .
the location of this atom is estimated by comparing the capacitive couplings to the four transistor electrodes ( see supplementary information b ) , which reveal a position not directly beneath the top gate , but instead close to the drain lead .
this verifies that this charging line does not come from the charging of a gate - defined quantum dot . a sudden electrostatic shift in the charging signal of this acceptor , shown in fig . [ fig : figure2]a , is the signature of the charging of another localized site nearby . further measurements of this state , presented later in this paper , show that this site is a second boron atom .
the negative @xmath2 found within the break of the line indicates the tunneling of holes between the two atoms .
a detailed study of the reflected signal in the frequency domain shows that the acceptor - lead tunnel rate is comparable to the resonant frequency ( 583 mhz ) of the lc - circuit ( supplementary information c ) .
in contrast , the inter - acceptor tunnel rate is found to be much faster than this resonant frequency .
the tunneling of holes from either lead to the second acceptor atom is not observed , likely due to tunnel rates much slower than the resonant frequency . the magnetic field dependence of the inter - acceptor tunneling , shown in fig . [ fig : figure2]b , reveals the number of holes bound to the acceptor atoms . we observe the signature of pauli spin blockade in the reflected signal @xcite when a magnetic field is applied along the axis of the nanowire that forms the top gate of the transistor ( y - direction in fig .
[ fig : figure1]a ) .
approximately at 0.25 t the reflectometry signal starts to weaken due to spin - selective tunneling associated with the increasing thermal population of a triplet state .
this observation of spin - selective tunneling indicates the presence of an even number of holes bound to the two acceptor atoms , from which it is concluded that the inter - acceptor tunneling corresponds to the ( 1,1)@xmath10(2,0 ) transition . to describe the two - hole system we use a theoretical framework to construct the ( 1,1 ) and ( 2,0 ) states from single hole states ( supplementary information d ) .
the four lowest energy states of a single hole bound to an acceptor in silicon can be described by angular momenta of @xmath11 ( heavy holes ) and @xmath12 ( light holes ) .
a distortion of the symmetry of the wave function can lift the degeneracy of heavy and light holes @xcite .
our experiments are consistent with heavy hole ground states for both acceptors , with energy splitting @xmath13 between the heavy and light hole states of acceptor @xmath14 .
the total energy of the two - hole system at zero magnetic field is shown as a function of the energy level detuning @xmath15 between the atoms in fig .
[ fig : figure2]d . to interpret our measurements
it is sufficient to only consider the lowest spin manifold for the ( 1,1)-configuration ( right side of fig .
[ fig : figure2]d ) , where one heavy hole resides on each acceptor , forming a singlet state , s@xmath16 , and three triplet states , t@xmath17 , t@xmath18 , and t@xmath19 .
for the ( 2,0)-configuration ( left side of fig .
[ fig : figure2]d ) , which is the doubly occupied acceptor a@xmath20 state , the exchange energy between holes with the same angular momentum ( @xmath21 , @xmath22 ) or different angular momenta ( @xmath23=@xmath24 ) are treated in the limit where @xmath21 , @xmath25 @xmath23 , which is the only regime consistent with our data . in analogy to the two - hole states of neutral group ii acceptors @xcite and of two closely spaced boron atoms @xcite ,
the lowest energy manifold in the ( 2,0)-configuration consists of six states , split by @xmath26 and @xmath23 .
the ground state is the heavy hole singlet , s@xmath16 .
four states consisting of one heavy and one light hole , q@xmath27 , with @xmath14 denoting the angular momentum , are @xmath26 higher in energy and split by @xmath23 into singlet and triplet states , as shown in fig .
[ fig : figure2]d .
the sixth state is the light hole singlet state , s@xmath28 , another @xmath26 higher in energy . at zero magnetic field
the tunnel coupling @xmath29 between the ( 1,1 ) and ( 2,0 ) s@xmath16 states gives rise to the inter - acceptor reflectometry signal , where @xmath29 is measured by a microwave excitation experiment to be [email protected] ghz ( supplementary information c ) @xcite . at a finite magnetic field , which we label @xmath31 ,
the ( 1,1 ) t@xmath17 state becomes the ground state at the zero detuning point .
since the pauli principle forbids tunneling between the atoms in the t@xmath17 state , the reflectometry becomes suppressed in this regime .
using the tunnel coupling @xmath29 and the thermal occupation of the two - hole states ( see supplementary information e ) , this magnetic field dependence of the reflectometry signal is simulated @xcite , as shown in fig .
[ fig : figure2]c .
@xmath31 is found to be [email protected] t , which provides an effective land g - factor ( @xmath32=@xmath33 ) of the t@xmath17 state of [email protected] , using the zeeman energy of @xmath34 , where @xmath35 is the bohr magneton .
noteworthy is that in bulk silicon the t@xmath17 state is expected to have @xmath36=3 and @xmath37 , which indicates that in our experiment the @xmath32 is strongly suppressed in this low magnetic field regime .
such a situation occurs when the quantization axis of the angular momentum is not aligned with the applied magnetic field , indicating that this quantization does not come from the magnetic field but instead from either local strain , electric field , or a nearby interface .
a pulsed measurement technique was used to measure the spin dynamics of the two - hole system .
the reflectometry signal originating from the inter - acceptor tunneling in the s@xmath16 state can be recovered at magnetic fields above @xmath31 by pulsing the system into the ( 2,0 ) region .
such a recovered signal is indicated by a white circle in fig .
[ fig : figure3]a , where the time - averaged amplitude and phase response of the reflected signal are displayed for an applied voltage pulse of 0.8 mv to the drain for 40 out of every 200 ns and at a magnetic field of 1.5 t. this indicates a finite population of the s@xmath16 excited state at the zero detuning point , which is utilised to explore the spin - dynamics of the two - hole system using time resolved spectroscopy .
fig .
[ fig : figure3]b shows the time dependence of the phase response with a voltage pulse applied between the @xmath38 and @xmath39 points , as marked in fig .
[ fig : figure3]a , and averaged over @xmath40 pulse sequences .
the observed exponentially decaying signal corresponds to the relaxation of the s@xmath16 state .
this ability to sense the two - hole spin state could be utilized in a readout scheme for a single hole spin state , in analogy to the scheme first demonstrated by koppens et al .
@xcite .
fig .
[ fig : figure3]c shows the relaxation rate t@xmath41 of the s@xmath16 state as a function of magnetic field . in the high magnetic field regime ( @xmath421.5 t ) , t@xmath41 increases monotonically with magnetic field .
this t@xmath41 behavior is well approximated by a power - law dependence on magnetic field , which is usually expected for spin - lattice relaxation processes @xcite .
on the other hand , in the low magnetic field regime ( @xmath431.5 t ) , t@xmath41 reaches a maximum at @xmath440.8 t. this implies a different spin - dynamic mechanism , likely arising from the specific interactions within this spin-3/2 acceptor system . from the magnetic field dependence of t@xmath41
we determine what relaxation mechanisms are relevant in the probed double - acceptor system .
fig .
[ fig : figure3]d illustrates the magnetic field dependence of the two - hole spin eigenenergies at zero detuning . while the ( 1,1 ) t@xmath17 level is the ground state at magnetic fields above @xmath31 , the ( 2,0 ) q@xmath45 level also falls below the s@xmath16 state above another critical magnetic field @xmath46 .
the relaxation rates from the s@xmath16 state to the t@xmath17 and q@xmath45 states , @xmath47 and @xmath48 , are expressed by a power law dependence on magnetic field : @xmath49 } } = a_{\text{st[q ] } } \left(\left(b - b_{\text{s}\rightarrow\text{t[q ] } } \right)^2 + ( 2t_\text{st[q]})^2 \right)^{\gamma_\text{st[q]}/2 } \label{eq : eq1}\ ] ] where @xmath50}$ ] is the relaxation amplitude for the @xmath51}$ ] process and @xmath52}$ ] is the tunnel coupling between the s@xmath16 and the ( 1,1 ) t@xmath17 [ ( 2,0 ) q@xmath45 ] state .
while @xmath54 is expected to be negligible , the spin - orbit interaction for light and heavy holes is expected to give a sizable @xmath55 .
theoretical reports predict different magnetic field power laws for these relaxation process with @xmath56=5 ( kramers degenerate ) and @xmath57=3 ( non - kramers degenerate ) @xcite .
both these relaxation rates monotonically increase with magnetic field like the observed t@xmath41 above @xmath441.5 t. however , this dataset is insufficient to conclude which relaxation process is dominant in this high magnetic field range and the best fit with both the @xmath47 and @xmath48 are shown in fig .
[ fig : figure3]c ( supplementary information f ) .
the non - monotonic magnetic field dependence of @xmath58 in the low magnetic field regime indicates the existence of another relaxation mechanism .
the heavy - light hole mixing plays an important role in the spin relaxation around the resonance between the s@xmath16 and ( 2,0 ) q@xmath45 state . in the vicinity of @xmath46 ,
the finite @xmath55 hybridises the s@xmath16 and ( 2,0 ) q@xmath45 states , resulting in new spin eigenstates , both containing a finite light hole component .
this light hole character opens a light - to - heavy hole relaxation path to the ( 1,1 ) t@xmath17 state , which is expected to be much faster than the heavy - to - heavy hole relaxation process between s@xmath16 and t@xmath17 @xcite .
since this relaxation mechanism strongly depends on the light - hole component in the hybridised states ( see supplementary information g ) , the relevant transition rate @xmath59 can be written as : @xmath60 where @xmath61 is the relaxation amplitude between the q@xmath45 and t@xmath62 states , which , as mentioned , is expected to be much larger than @xmath63 .
the non - monotonic magnetic field dependence of the lorentzian peak and the large relaxation amplitude @xmath61 give a satisfactory explanation for the observed t@xmath41 hotspot around 0.8 t. a combination of the monotonic rate @xmath47 and non - monotonic rate @xmath59 is used to fit the full magnetic field dependence of t@xmath41 , as shown by a solid black line in fig .
[ fig : figure3]c . in this fit @xmath46
is found at [email protected] t , @xmath55 is found in magnetic field units to be [email protected] t and we extracted a ratio between the relaxation amplitudes @xmath64 .
the here observed spin - relaxation hotspot can be used as a rapid initialization of the spin - state of the acceptor atom , where the measured ratio @xmath65 of more than three orders of magnitude demonstrates the excellent tunability of the acceptor system .
similar hotspots , caused by the mixing of spin and orbital degrees of freedom , have been predicted and measured for systems with a strong spin - orbit coupling in iii - v semiconductors @xcite .
furthermore , @xmath55 is expected to mainly originate from the spin - orbit coupling of the heavy and light hole states .
therefore , the strong mixing between the s@xmath16 and q@xmath45 states , as observed in our experiment , points to the presence of a strong spin - orbit coupling for the acceptor states and thereby shows the potential to use them as electrically drivable spin - orbit qubits . to understand the environment of the acceptor atoms we investigate the two - hole excited state spectrum .
due to their fast relaxation rate , these excited states are not accessible by the reflectometry technique and instead we use single hole transport spectroscopy @xcite to probe the two - hole energy spectrum . in fig .
[ fig : figure4]a the transconductance signal as a function of @xmath5 and @xmath6 at zero magnetic field shows a bias triangle ( contour marked by a solid line ) , demonstrating sequential hole tunneling via both acceptors in series .
lines parallel to the triangle baseline ( arrows in fig .
[ fig : figure4]a ) are attributed to transitions from the ( 1,1 ) ground state to ( 2,0 ) excited states ( supplementary information d ) .
the observed ( 2,0 ) spectrum matches the expected energy spectrum of a doubly charged acceptor state , shown in fig .
[ fig : figure4]b .
this supports our identification of the second confinement site as an acceptor atom , which is further validated since our measurement is not compatible with the regular spaced excited state spectrum expected for quantum dots .
the ( 2,0 ) @xmath26 and @xmath23 are extracted as 110@xmath3010 @xmath66ev and 36@xmath305 @xmath66ev respectively .
the measured @xmath26 reflects the effect of local fields on the symmetry of the acceptor states .
however , the direction of the resulting quantization axis for the angular momenta is unknown , which makes it impossible to predict the exact zeeman interaction for low magnetic fields @xcite .
the extracted @xmath23 reflects the mixing between light and heavy holes , associated with the spin - orbit coupling .
we can compare this to @xmath55 , taking into account that this tunnel coupling carries an additional component , as the s@xmath16 state at zero detuning is in a superposition of ( 1,1 ) and ( 2,0 ) states .
converting @xmath55 to an energy scale using 1.5 @xmath67 3 , gives @xmath55 in the range of 3 to 7 @xmath66ev .
although somewhat lower than @xmath23 , likely caused by the rotation of the quantization axis at this magnetic field as discussed later , both these parameters show a strong spin - orbit coupling , which is crucial to envision electrical manipulations of the acceptor spin states .
next we discuss the magnetic field dependence of the transition energy spectrum , as shown in fig .
[ fig : figure4]c , which is measured on a cut through the bias triangle at @xmath6=1.4 v ( dotted line in fig .
[ fig : figure4]a ) . the baseline of the triangle , indicated with a solid line in fig .
[ fig : figure4]c , changes its slope twice .
the first change around 0.25 t indicates the singlet - triplet crossing at @xmath31 , in agreement with the observation of spin blockade in fig .
[ fig : figure2]b .
the second change around 0.50 t indicates the change of the ( 2,0 ) ground state from s@xmath16 to q@xmath45 , corresponding to the same anti - crossing that generates the relaxation hotspot in fig .
[ fig : figure3]b , but here occurring in the negative detuning region and therefore at a lower magnetic field . in the high magnetic field regime ( @xmath421 t )
we observe well established resonance lines .
the number of resolvable features is larger than at zero magnetic field , indicating spin split excited states . in this regime
the zeeman energy dominates over @xmath26 and therefore the quantization axis of the angular momenta of the two - hole states align with the external magnetic field . ignoring any mixing terms other than the s@xmath16 mixing ,
the magnetic field dependence of the transition energies can be easily described by using @xmath0 for heavy holes and @xmath1 for light holes to calculate the zeeman shifts , as shown in fig .
[ fig : figure4]d . using this model ,
the g - factors and @xmath26 can be extracted by fitting the slopes and position of the transition lines in fig .
[ fig : figure4]c respectively . for the doubly occupied acceptor
we find @xmath68 of 0.85 and @xmath69 of 1.07 and @xmath26 of 30 @xmath66ev .
for the single occupied acceptor only the heavy hole states play a role in the transitions for which we extract @xmath68 of 1.05 .
our observations allow for the characterization of the acceptor system in both the low and high magnetic field regimes , which shows the extent of tuning of the acceptor states .
the detected level configurations indicate a symmetry transition of the acceptor spin-3/2 system as a function of magnetic field .
the g - factors found in the high magnetic field regime are close to those found for bulk boron acceptors @xcite , which is in stark contrast to the effective g - factor found at low magnetic fields in the spin blockade experiment of fig .
[ fig : figure2]b .
furthermore the @xmath26 of the doubly occupied acceptor is about four times smaller in the high magnetic field regime than at zero magnetic field .
these changes demonstrate that the quantization - axis in the high magnetic field regime differs from the quantization axis at zero magnetic field , thereby strongly influencing the g - factor and heavy - light hole splitting .
a further indication of the rotating quantization axis is the decaying amplitude of the ( 1,1 ) t@xmath17 to ( 2,0 ) s@xmath16 transition , which completely disappears at a magnetic field around 2 t. the observation of the reduced mixing between these states is well explained by the enhancement of the spin - blockade effect when the angular momentum becomes quantized along the magnetic field .
the here demonstrated possibility to change the quantization axis and strongly influence the g - factor , heavy - light hole splitting and relaxation rate of the acceptor states by controlling the atoms environment with an external field , is a fundamental requirement for reaching the optimal conditions for acceptor - based qubits @xcite . in conclusion ,
the interactions between heavy and light hole states of individual acceptor atoms in silicon have been analysed , establishing the evaluation of the effect of local fields on the wave function symmetry and thereby on the level configurations and spin - dynamics of acceptor atoms . mixing between light and heavy holes
is found to strongly influence the spin - dynamics of the two - hole system , leading to a hotspot in the spin - relaxation rate .
furthermore it is shown that the quantization axis of the holes can be rotated by applying a magnetic field , thereby significantly tuning the g - factor and heavy - light hole splitting .
we have shown access to and control over the heavy and light hole states of individual acceptors and found evidence of a strong spin - orbit coupling in this system , thereby demonstrating the fundamental principles to implement acceptor atom spin - orbit qubits . |
SECTION 1. LIABILITY OF BUSINESS ENTITIES PROVIDING USE OF FACILITIES
TO NONPROFIT ORGANIZATIONS.
(a) Definitions.--In this section:
(1) Business entity.--The term ``business entity'' means a
firm, corporation, association, partnership, consortium, joint
venture, or other form of enterprise.
(2) Facility.--The term ``facility'' means any real
property, including any building, improvement, or appurtenance.
(3) Gross negligence.--The term ``gross negligence'' means
voluntary and conscious conduct by a person with knowledge (at
the time of the conduct) that the conduct is likely to be
harmful to the health or well-being of another person.
(4) Intentional misconduct.--The term ``intentional
misconduct'' means conduct by a person with knowledge (at the
time of the conduct) that the conduct is harmful to the health
or well-being of another person.
(5) Nonprofit organization.--The term ``nonprofit
organization'' means--
(A) any organization described in section 501(c)(3)
of the Internal Revenue Code of 1986 and exempt from
tax under section 501(a) of such Code; or
(B) any not-for-profit organization organized and
conducted for public benefit and operated primarily for
charitable, civic, educational, religious, welfare, or
health purposes.
(6) State.--The term ``State'' means each of the several
States, the District of Columbia, the Commonwealth of Puerto
Rico, the Virgin Islands, Guam, American Samoa, the Northern
Mariana Islands, any other territory or possession of the
United States, or any political subdivision of any such State,
territory, or possession.
(b) Limitation on Liability.--
(1) In general.--Subject to subsection (c), a business
entity shall not be subject to civil liability relating to any
injury or death occurring at a facility of the business entity
in connection with a use of such facility by a nonprofit
organization if--
(A) the use occurs outside of the scope of business
of the business entity;
(B) such injury or death occurs during a period
that such facility is used by the nonprofit
organization; and
(C) the business entity authorized the use of such
facility by the nonprofit organization.
(2) Application.--This subsection shall apply--
(A) with respect to civil liability under Federal
and State law; and
(B) regardless of whether a nonprofit organization
pays for the use of a facility.
(c) Exception for Liability.--Subsection (b) shall not apply to an
injury or death that results from an act or omission of a business
entity that constitutes gross negligence or intentional misconduct,
including any misconduct that--
(1) constitutes a crime of violence (as that term is
defined in section 16 of title 18, United States Code) or act
of international terrorism (as that term is defined in section
2331 of title 18) for which the defendant has been convicted in
any court;
(2) constitutes a hate crime (as that term is used in the
Hate Crime Statistics Act (28 U.S.C. 534 note));
(3) involves a sexual offense, as defined by applicable
State law, for which the defendant has been convicted in any
court; or
(4) involves misconduct for which the defendant has been
found to have violated a Federal or State civil rights law.
(d) Superseding Provision.--
(1) In general.--Subject to paragraph (2) and subsection
(e), this Act preempts the laws of any State to the extent that
such laws are inconsistent with this Act, except that this Act
shall not preempt any State law that provides additional
protection from liability for a business entity for an injury
or death with respect to which conditions under subparagraphs
(A) through (C) of subsection (b)(1) apply.
(2) Limitation.--Nothing in this Act shall be construed to
supersede any Federal or State health or safety law.
(e) Election of State Regarding Nonapplicability.--This Act shall
not apply to any civil action in a State court against a business
entity in which all parties are citizens of the State if such State
enacts a statute--
(1) citing the authority of this subsection;
(2) declaring the election of such State that this Act
shall not apply to such civil action in the State; and
(3) containing no other provisions. | Exempts a business entity from civil liability for any injury or death occurring at such entity's facility in connection with the use of such facility by a nonprofit organization if: (1) the use occurs outside of the scope of the business of the entity; (2) the injury or death occurs while the facility is being used by the organization; and (3) the entity authorized the organization's use of the facility. Provides an exception for an injury or death that results from an entity's act or omission that constitutes gross negligence or intentional misconduct, including crimes of violence or acts of international terrorism, hate crimes, sexual offenses, and misconduct that violates Federal or State civil rights laws.
Provides that this Act shall not apply in a State that enacts a statute to that effect if all parties to an action are citizens of that State. |
GREENBELT, Md. (WUSA 9) -- A federal judge has banned the Washington Redskins' controversial nickname from being spoken in his courtroom or written in his opinions.
Senior District Judge Peter J. Messitte, chambered in Greenbelt, Maryland, made his position - if not his reasoning - clear on the front page of a recent decision in a lawsuit against the team that's unrelated to the name.
In a page-one footnote of a July 8 opinion in Barrett Green v. The Washington Redskins, Messitte wrote, "Pro Football's team is popularly known as the Washington "Redskins," but the Court will refrain from using the team name unless reference is made to a direct quote where the name appears. Pro Football's team will be referred to hereafter simply as 'the Washington Team.'"
The judge did not write an explaination as to how he reached his decision.
But during a hearing in November, Messitte was slightly more blunt. According to a transcript, the judge brought up the issue after a lawyer introduced the team's general counsel.
federal judge has banned the Washington Redskins' controversial nickname from being spoken in his courtroom
"We're going to call them the Washington Football team hear (sic) in this court," Messitte was recorded as saying. "Have (sic) a local rule that tell (sic) us about the way words are used. No need to get into a big political issue with you on that. For now, that's what we'll call them."
Reached by phone Monday afternoon, Messitte's judicial assistant told WUSA 9 the judge would not be commenting on his linguistic decision.
"So far as I know," explained John Banzhaf, a George Washington University law professor, "this is the first federal judge to ban the use of the word."
Banzhaf, who thinks the nickname should be changed, says while the judge's decision has no weight in the trademark fight, it does add to public arguments.
"The very fact that he singled this word out - not Atlanta Braves, or the Vikings, or the Fighting Irish - as a slur, a racial slur, says the 'R' word is different," said Banzhaf.
The team is appealing a ruling by the US Patent and Trademark Office that found the nickname is disparaging.
In March, team owner Dan Snyder launched a foundation to support Native Americans, funding more than 40 projects across the country so far, the team said.
Snyder has vowed not to change the team's name; the team has said an "overwhelming majority" of Native Americans do not find the nickname offensive.
"We did our homework, unlike a lot of people," Snyder told reporters in April. "And we understand the issues out there and we're not an issue. The real issues are real life issues, real life needs and I think it's time that people focus on the reality."
In a letter to U.S. Senate Majority Leader Harry Reid (D-NV) in May, team president Bruce Allen wrote that a majority of Americans are in favor of keeping the name.
A team spokesman Monday told WUSA 9 the team would have no comment about Judge Messitte's nickname ban.
Read or Share this story: http://on.wusa9.com/1mcJapm ||||| In THR's annual Sports Issue, the exec talks to THR about WME's $2.4 billion deal for his old shop — sports management behemoth IMG — and the scariest person he ever faced at the negotiating table.
This story first appeared in the July 25 issue of The Hollywood Reporter magazine.
Sean McManus, 59, brought the NFL back to CBS in 1998 after a four-year absence. And he's spearheaded a succession of significant rights deals since, including SEC football, NCAA men's basketball, the PGA Championship and U.S. Open tennis. Here, he talks to THR about the NCAA and NFL concussion controversies, WME's $2.4 billion deal for his old employer — sports behemoth IMG — and the scariest person he ever faced at the negotiating table.
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Did you ever have aspirations to be in front of the camera like your dad, legendary ABC sportscaster Jim McKay?
I did a little bit. I had a reel-to-reel tape recorder and I used to watch Yankee games — I was a big Yankees fan — and turn the sound down and do commentary and play it back to my father and he would give me little pointers. And when I got to be about 12 years old I thought, "Maybe I should do something different, this is a pretty big legend to follow."
What's the most important lesson you learned at IMG that you use in this job?
In a negotiation, both sides should feel like winners. When I was representing the Orange Bowl or the British Open or Wimbledon, there were times when we had all the leverage on our side because these were events that a lot of people wanted to acquire. And we would always convince our clients that they were better off doing a deal that maximized dollars but still left a reasonable profit for the other side. There were times that we could have squeezed a lot harder than we did. If you try to acquire every penny that you can it usually comes back to haunt you. That's a lesson I learned from [IMG executives] Mark McCormack and Barry Frank. That builds relationships, so the next time you're negotiating and you don't have all the leverage, the person with whom you are negotiating will remember that.
STORY THR Sports Issue Cover: RGIII Fronts Thursday Night Football Preview
The 2018 and 2022 World Cups are moving to Fox and Telemundo in a $1.2 billion deal. Did you have any interest in it?
CBS Sports Network isn't at a point where bidding that much money for a property like that makes sense. But I think ESPN has done a terrific job promoting it. An awful lot of people were talking about where they were going to be at 6 o'clock [on June 22 for the U.S.-Portugal match]. In my town of New Canaan, Conn., they put up a tent right on the main street for a viewing party. Now if you had said to me even a month ago that this World Cup game was going to be so important that there's going to be a viewing party in your hometown, I would have laughed at you.
Is there a rights package you would like that you don't have?
There are a lot I would like, but there aren't any that make economic and programming sense at the moment. I would love to be in a position to bid for the NBA, but with our college basketball and golf schedules, there's no room. To have an opportunity to bid on baseball would have been fun also — but again, with the NFL and all the programming commitments we have during the summer, it just didn't make sense for us. Plus, I work for a man, Leslie Moonves, who really believes that you should not lose a lot of money on sports rights.
PHOTOS Touchdown! Hollywood's Best Football Movies
So CBS makes money on the NFL?
Yes, the NFL has been a profitable franchise for us, and we anticipate that being true going forward.
Even though the increase for the current deal was more than 60 percent to $1 billion through 2022?
It's a big increase. Even though we are paying more money in rights, it still makes sense because many advertisers need the NFL. They just can't afford for almost six months every year not to advertise in the most successful and attractive programming on TV. Listen, the NFL got an enormous increase. Could they have extracted a bit more? Probably. But I think they understand that you don't want to create a deal that is so onerous for a network that they are not actively coming back and negotiating next time around.
PHOTOS Inside ESPN's New 'SportsCenter' Studio
ESPN is launching the SEC Network in August, but you have 10 more years on your SEC deal. What if ESPN came to you and offered to buy out the SEC deal? You only pay $55 million a year for the SEC. I bet ESPN would pay more.
I can't imagine why we would do it. We don't do it strictly for the profit that we make. We also do it for the promotional value and the prestige that is inherent in having the No. 1 college football package four out of the last five years. And three of the highest-rated games in the regular season last year were SEC games. We're very, very happy with it. And were we approached by someone who wanted to buy it, I think we'd give a pretty quick no.
What effect has the concussion controversy had on the NFL?
It hasn't had an effect on our NFL business yet. I think we've been responsible in covering it. The last time we had the Super Bowl, we did two pieces on the issue of player safety. We had former players like Ray Lucas, Sean Salisbury and Charlie Brown come in and talk about the issue. When it is a story to be covered, we cover it. [Analyst and former player] Boomer Esiason has been very outspoken on the issue of player safety. So we certainly don't ignore it. It's a subject that deserves a lot of attention.
You played football as a child. Would you let your son play?
I did let my son play football. He chose hockey, baseball and golf, but he played football for one year as a seventh grader. And he was playing against the eighth and ninth graders. So that might have had something to do with his initial lack of interest in the sport. But on a Sunday afternoon, unless he has a hockey game, he's watching the NFL. And some of my fondest memories were as a 10- and 11-year-old playing football. And I've loved the game since then.
PHOTOS Hollywood's Connections to the NFL
Should college athletes be paid?
That's a very complicated question. For college athletes, who spend an enormous amount of time playing their sport, the college experience should be made easier from an economic standpoint, whether that's a larger stipend, help with transportation, an insurance policy. I do think you change the dynamic when they are employees instead of students. And I understand that a lot of them are students in name only. But the vast majority of student athletes are just that — they are not the football players and the basketball players. They are swimming and diving or doing tennis or wrestling. And trying to figure out which college athletes should share directly in the enormous revenues that are generated is not easy. Do you pay just the starting lineup? Do you pay the top performers? And if you're going to pay the quarterback on the football team, do you pay the nationally ranked gymnast on the women's gymnastic team? I think everybody believes that the system needs to be adjusted in terms of how athletes are taken care of. But what's good and fair for the starting quarterback at Alabama is very different than what's good and fair for the kid on the volleyball team. It's not as simple as a lot of people like to make it.
There is a lot of pressure on the Washington Redskins to change their name. How will CBS analysts address that controversy this fall?
We haven't talked to them yet. Generally speaking, we do not tell our announcers what to say or not say. Up to this point, it has not been a big issue for us. Last year, it was simmering; now it's reaching a hotter level. But we probably will not end up dictating to our announcers whether they say Redskins or don't say Redskins. We leave that up to them and our production team. There are times when something becomes important enough that we talk to them, and between now and the start of football season we'll decide what is the right thing to do.
WME recently bought IMG, where you used to work. Any tips for Ari Emanuel?
It would be presumptuous of me to give Ari Emanuel advice on any subject. But if I were to give one piece of advice, it would be respect your clients because in the end they are your business.
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Who is the toughest negotiator you've ever faced?
I would say Don King was the scariest person with whom I've negotiated, especially when I was in his townhouse at about 8 p.m., just him and me negotiating a deal for a fight. I was a 28-year-old vp of programming for NBC Sports, so sitting across from Don King and having him pound the table was frightening. The most intimidating was that same year, 1981, with Primo Nebiolo, the head of the International Amateur Athletics Federation. He looked exactly like Benito Mussolini. I was told that shortly into my presentation he would start reading the newspaper. And so when Nebiolo picked up the newspaper, I stopped talking. And for about 30 seconds he kept reading. Then he looked over the top of the newspaper, and I still wasn't talking. So he put the newspaper down and he never picked it back up.
Did you hear from rival TV sports executives after the Thursday night deal?
I did. I heard from a number of them — "Congratulations, happy for you, but we're not going away," that sort of thing. And that's not uncommon. We're all good friends. I count [NBC Sports Group chairman] Mark Lazarus, [Fox executives] David Hill and Eric Shanks, and [ESPN president] John Skipper as good friends. I sent John Skipper a note on the World Cup. I sent Eric Shanks a note on the Super Bowl this year. And I sent Mark Lazarus a note on the Olympics. We're all incredibly competitive, but we also root for each other because in the end, if one of us is doing well, all of us are doing well. But I did, I heard from a number of them.
Did you hear from all of the people you just named?
I'll just say that I heard from a number of them. I think people were surprised that we got it because most believed that as a network we probably needed it the least. In the end, what people learned was that we may have needed it the least, but we wanted it the most.
What's the best life lesson your dad taught you?
I would say to be yourself because the camera never lies. That was something he said all the time, and it applies more directly to his profession than mine. But in the end, the person that you are is going to come out. And if you're a phony, you're going to be found out. | – CBS Sports announcers will likely be able to use the term "Redskins"—or, if they'd rather, not—during the upcoming NFL season, chairman Sean McManus says. "Generally speaking, we do not tell our announcers what to say or not say," McManus tells the Hollywood Reporter. Even as the issue is "reaching a hotter level," he adds, "we probably will not end up dictating to our announcers whether they say Redskins or don't say Redskins. We leave that up to them and our production team." Still, he leaves the door open a bit, saying, "between now and the start of football season we'll decide what is the right thing to do." One place the Washington Redskins name will not appear? That would be in one federal judge's court documents. In his ruling on a recent lawsuit brought against the team—a suit not focusing on the team's name—Maryland Senior District Judge Peter Messitte wrote the "Pro Football's team will be referred to hereafter simply as 'the Washington Team.'" During a November hearing, Messitte was also recorded as barring the name from being spoken. WUSA 9 spoke with a law professor who said that to his knowledge, Messitte "is the first federal judge to ban the use of the word." |
obesity is characterized by an excessive accumulation of fat in the adipose tissue ( 1 , 2 ) .
a product of the obese ( ob ) gene , called leptin , is released primarily from adipocytes and plays a key role in regulating body weight ( 3 ) . in most obese subjects
, leptin fails to perform its physiological functions in spite of its high serum levels ( 4 , 5 ) .
obesity is linked with several disorders including cardiovascular diseases ( cvds ) , certain types of cancer ( 6 ) , type 2 diabetes , and it raises the risk of pulmonary defects ( 7 ) .
demonstrated that leptin resistance leads to increased parasympathetic tone , which in turn causes bronchoconstriction and obesity - associated asthma ( 8) . another previous study described a link between hypoventilation and adiposity ( 9 ) .
phipps et al . proposed that hyperleptinemia is a cause of respiratory failure in obese leptin - resistant subjects ( 10 ) .
it has been suggested that a derangement of leptin expression in adipocytes may affect the lungs and promote asthma ( 11 ) .
interestingly , a previous study reported the highest levels of serum leptin occur in asthmatic obese patients compared to the other human groups including non - obese controls , obese subjects , and asthmatic non obese patients ( 12 ) .
serum leptin elevation has already been shown to be an established marker of leptin resistance in severe obesity ( 4 ) .
this might lead to the creation of an imbalance between -1 antitrypsin ( a1at ) and ne activity ( 13 , 14 ) .
a severe deficiency of serum a1at is important in the development of chronic obstructive pulmonary disorder ( copd ) and asthma , which might be due to the degradation of lung tissue elastin by ne - enhanced activity ( 15 , 16 ) .
briefly , on the basis of the facts described above , it could be postulated that leptin resistance with a protease - antiprotease imbalance may be vital for the obesity predisposition to pulmonary disorders including , among others , asthma and copd .
the first part highlights body weight regulation and the disruption of leptin s physiological function in obesity .
leptin was first identified in 1994 in the obese ( ob / ob ) mouse model .
it is a 16 kda non glycated protein consisting of 167 amino acids and is primarily expressed in adipose tissues ( 17 ) .
it is encoded by the obese gene ( ob gene ) , located on chromosome number 7 in humans , and is responsible for regulating the balance between food intake and energy expenditure ( 18 ) . during starvation ,
leptin levels go down , which increases appetite and decreases energy consumption . on the other hand , with sufficient energy stores
leptin regulates energy expenditure and food intake by communicating with the central nervous system ( cns ) via its receptor ( ob - rb ) located in the hypothalamus ( 20 ) .
the hypothalamus is the key site for leptin detection as it contains two types of neurons : type 1 expresses appetite suppressing peptides derived from pro - opiomelanocortin ( pomc ) precursors , whereas type 2 produces appetite stimulating peptides such as neuropeptide y ( npy ) and agouti - related peptide ( agrp ) .
leptin suppresses appetite by counteracting npy and agrp , whereas leptin activates pomc mrna expression , which enhances the release of a potent appetite - suppressing peptide , alpha - melanocyte stimulating hormone ( -msh ) ( 21 , 22 )
. mechanisms of leptin action and dysfunction are shown in figures 1 and 2 , respectively .
this shows shows that during normal physiological states , leptin binds with its receptors in the brain and suppresses appetite by counteracting npy and agrp , however , leptin also induces pomc mrna expression .
abbreviations : agrp , agouti - related peptide ; mrna , messenger ribonucleic acid ; npy , neuropeptide y ; ob , leptin ; ob - rb , leptin receptor ; pomc , pro - opiomelanocortin .
this figure shows that in obesity , leptin can not bind with its receptors situated in the brain ( hypothalamus ) , resulting in adiposity signals arrived due to the stimulation of npy and agrp expression with a concomitant decrease of pomc mrna expression .
the leptin failure leads to severe obesity that is associated with various disorders including insulin resistance , t2d , cvd , hypertension , and asthma .
abbreviations : agrp , agouti - related peptide ; cvd , cardiovascular disease ; npy , neuropeptide y ; ob , leptin ; ob - rb , leptin receptor ; pomc , pro - opiomelanocortin ; t2d , type 2 diabetes .
some studies have shown that obese ( ob / ob ) mice are leptin deficient , and diabetic ( db / db ) mice have mutated leptin receptors contributing to leptin dysfunctions ( 23 , 24 ) . a rare genetic disorder has been reported in obese humans , which might be due to a mutation in the leptin gene and can be treated with exogenous leptin administration .
it has been identified that 12 pakistani , 5 turkish , 1 austrian , and 2 egyptian obese subjects are leptin deficient because of leptin gene mutations ( 25 ) . on the other hand ,
several previous studies have reported that most obese individuals have elevated serum leptin levels , which are positively correlated with body mass index ( bmi ) ( 26 , 27 ) . despite having increased serum leptin levels , leptin fails to retain its appetite - suppressing effect of reducing weight in obese subjects .
approximately 30 fold higher leptin concentrations were required for weight reduction in obesity ( 28 )
. the failure of leptin to function in severely obese subjects may be due to extracellular circulating factors .
an interaction between circulating leptin and serum leptin interacting proteins ( slips ) contributes to leptin failures ( 4 , 29 ) .
this leptin appetite suppressing effect , which is markedly impaired in obese subjects , is shown in figure 2 .
gcsf is a member of the interleukin-6 ( il-6 ) family that includes il-6 and oncostatin - m ( osm ) cytokines ( 30 , 31 ) .
in addition to leptin s control of energy homeostasis by stimulating its hypothalamic receptor , the janus kinase / signal transducer and activator of transcription ( jak / stat ) signaling is essential in peripheral tissues , especially in the liver . this is vital because it affects differential expression of the target genes of acute phase proteins ( apps ) , including a1at ( 13 ) . using a wide range of techniques
, it has been shown that osm induces a functional response after 24 hours via stat3 binding to the stat sequence ( 32 ) .
moreover , different reports using gel shift and luciferase assays have identified that a perfect consensus for stat present in the 3'-a1at enhancer region was capable of binding the transcription factor stat3 ( 33 ) .
for other cell types such as monocytes and macrophages , lipopolysaccharides ( lps ) up - regulate the a1at gene , which is also stimulated in the lung epithelial tissues in response to osm ( 34 , 35 ) . in hepg2 cells ,
the a1at gene regulation occurs at the transcriptional stage , which is mediated primarily via hepatocyte promoters containing the stat3 sequence ( 32 ) .
the a1at levels were stimulated up to three folds by two il-6 and osm in hepg2 cell lines ( 35 ) .
it was suggested that the short and long leptin receptor isoforms were expressed in hepg2 hepatic cells , which supports the hypothesis that , like osm cytokines , leptin might act to regulate few gene targets in hepatocytes ( 36 ) .
recently , jiang s laboratory demonstrated that the expression of the a1at gene was leptin - dependent in mouse models and leptin stimulation increases the a1at levels both at the mrna and protein levels via the jak / stat3 pathway in cultured hepatic hep1 - 6 cell lines ( 13 ) . a specific tyrosine residue , tyr 1138 , in the intracellular domain of the leptin receptor ( ob - rb ) mediates the activation of stat3 ( 37 ) .
the binding of the leptin - ligand causes the ob - rb to undergo homo - oligomerization and subsequently binds to jak2 .
only ob - rb possesses the stat - binding site . in vivo studies have demonstrated that stat3 is the major transcriptional factor in signaling .
binding of ob - rb with jak2 leads to the jak2 autophosphorylation and the phosphorylation of tyr985 , tyr1077 , and tyr 1138 on the ob - rb receptor .
the phosphorylation of tyr1138 recruits stat3 proteins to the ob - rb - jak2 complex .
tyrosine - phosphorylated stat3 molecules can dimerize and translocate into the nucleus to activate the transcription of target genes in peripheral tissues such as vascular endothelial cells and hepg2 liver cells ( 35 , 38 ) .
this shows shows that leptin binds with its receptors on hepatocytes , successively stat3 molecules dimerize and translocate into the nucleus and bind with the promoter region of the serpin gene in order to up - regulate the acute phase protein expression , including a1at .
abbreviations : a1at , alpha-1-antitrypsin ; jak - stat3 , janus kinase signal transducer and activator of transcription .
leptin was first identified in 1994 in the obese ( ob / ob ) mouse model .
it is a 16 kda non glycated protein consisting of 167 amino acids and is primarily expressed in adipose tissues ( 17 ) .
it is encoded by the obese gene ( ob gene ) , located on chromosome number 7 in humans , and is responsible for regulating the balance between food intake and energy expenditure ( 18 ) . during starvation ,
leptin levels go down , which increases appetite and decreases energy consumption . on the other hand , with sufficient energy stores
leptin regulates energy expenditure and food intake by communicating with the central nervous system ( cns ) via its receptor ( ob - rb ) located in the hypothalamus ( 20 ) .
the hypothalamus is the key site for leptin detection as it contains two types of neurons : type 1 expresses appetite suppressing peptides derived from pro - opiomelanocortin ( pomc ) precursors , whereas type 2 produces appetite stimulating peptides such as neuropeptide y ( npy ) and agouti - related peptide ( agrp ) .
leptin suppresses appetite by counteracting npy and agrp , whereas leptin activates pomc mrna expression , which enhances the release of a potent appetite - suppressing peptide , alpha - melanocyte stimulating hormone ( -msh ) ( 21 , 22 )
. mechanisms of leptin action and dysfunction are shown in figures 1 and 2 , respectively .
this shows shows that during normal physiological states , leptin binds with its receptors in the brain and suppresses appetite by counteracting npy and agrp , however , leptin also induces pomc mrna expression .
abbreviations : agrp , agouti - related peptide ; mrna , messenger ribonucleic acid ; npy , neuropeptide y ; ob , leptin ; ob - rb , leptin receptor ; pomc , pro - opiomelanocortin .
this figure shows that in obesity , leptin can not bind with its receptors situated in the brain ( hypothalamus ) , resulting in adiposity signals arrived due to the stimulation of npy and agrp expression with a concomitant decrease of pomc mrna expression .
the leptin failure leads to severe obesity that is associated with various disorders including insulin resistance , t2d , cvd , hypertension , and asthma .
abbreviations : agrp , agouti - related peptide ; cvd , cardiovascular disease ; npy , neuropeptide y ; ob , leptin ; ob - rb , leptin receptor ; pomc , pro - opiomelanocortin ; t2d , type 2 diabetes .
some studies have shown that obese ( ob / ob ) mice are leptin deficient , and diabetic ( db / db ) mice have mutated leptin receptors contributing to leptin dysfunctions ( 23 , 24 ) . a rare genetic disorder has been reported in obese humans , which might be due to a mutation in the leptin gene and can be treated with exogenous leptin administration .
it has been identified that 12 pakistani , 5 turkish , 1 austrian , and 2 egyptian obese subjects are leptin deficient because of leptin gene mutations ( 25 ) . on the other hand ,
several previous studies have reported that most obese individuals have elevated serum leptin levels , which are positively correlated with body mass index ( bmi ) ( 26 , 27 ) . despite having increased serum leptin levels , leptin fails to retain its appetite - suppressing effect of reducing weight in obese subjects .
approximately 30 fold higher leptin concentrations were required for weight reduction in obesity ( 28 ) .
the failure of leptin to function in severely obese subjects may be due to extracellular circulating factors .
an interaction between circulating leptin and serum leptin interacting proteins ( slips ) contributes to leptin failures ( 4 , 29 ) .
this leptin appetite suppressing effect , which is markedly impaired in obese subjects , is shown in figure 2 .
gcsf is a member of the interleukin-6 ( il-6 ) family that includes il-6 and oncostatin - m ( osm ) cytokines ( 30 , 31 ) .
in addition to leptin s control of energy homeostasis by stimulating its hypothalamic receptor , the janus kinase / signal transducer and activator of transcription ( jak / stat ) signaling is essential in peripheral tissues , especially in the liver .
this is vital because it affects differential expression of the target genes of acute phase proteins ( apps ) , including a1at ( 13 ) . using a wide range of techniques
, it has been shown that osm induces a functional response after 24 hours via stat3 binding to the stat sequence ( 32 ) .
moreover , different reports using gel shift and luciferase assays have identified that a perfect consensus for stat present in the 3'-a1at enhancer region was capable of binding the transcription factor stat3 ( 33 ) .
for other cell types such as monocytes and macrophages , lipopolysaccharides ( lps ) up - regulate the a1at gene , which is also stimulated in the lung epithelial tissues in response to osm ( 34 , 35 ) . in hepg2 cells ,
the a1at gene regulation occurs at the transcriptional stage , which is mediated primarily via hepatocyte promoters containing the stat3 sequence ( 32 ) .
the a1at levels were stimulated up to three folds by two il-6 and osm in hepg2 cell lines ( 35 ) .
it was suggested that the short and long leptin receptor isoforms were expressed in hepg2 hepatic cells , which supports the hypothesis that , like osm cytokines , leptin might act to regulate few gene targets in hepatocytes ( 36 ) .
recently , jiang s laboratory demonstrated that the expression of the a1at gene was leptin - dependent in mouse models and leptin stimulation increases the a1at levels both at the mrna and protein levels via the jak / stat3 pathway in cultured hepatic hep1 - 6 cell lines ( 13 ) . a specific tyrosine residue , tyr 1138 , in the intracellular domain of the leptin receptor ( ob - rb ) mediates the activation of stat3 ( 37 ) .
the binding of the leptin - ligand causes the ob - rb to undergo homo - oligomerization and subsequently binds to jak2 .
binding of ob - rb with jak2 leads to the jak2 autophosphorylation and the phosphorylation of tyr985 , tyr1077 , and tyr 1138 on the ob - rb receptor .
the phosphorylation of tyr1138 recruits stat3 proteins to the ob - rb - jak2 complex .
tyrosine - phosphorylated stat3 molecules can dimerize and translocate into the nucleus to activate the transcription of target genes in peripheral tissues such as vascular endothelial cells and hepg2 liver cells ( 35 , 38 ) .
this shows shows that leptin binds with its receptors on hepatocytes , successively stat3 molecules dimerize and translocate into the nucleus and bind with the promoter region of the serpin gene in order to up - regulate the acute phase protein expression , including a1at .
abbreviations : a1at , alpha-1-antitrypsin ; jak - stat3 , janus kinase signal transducer and activator of transcription .
in obesity , the disruption of leptin - mediated signaling occurs that may lead to lung function failure by concomitant increases in body weight .
olson et al . suggested that leptin stimulates lung ventilation , whereas leptin deficiencies lead to hypoventilation in obese subjects ( 11 ) .
the relationship between obesity and asthma is complex and involves several mechanisms ( 9 ) .
a few recent studies have indicated the highest levels of leptin occur in the sera of asthmatic obese patients relative to the other groups such as asthmatic non obese patients , normal obese subjects , and non - obese subjects without asthma or other pulmonary complications .
report 14.5 , 40 , and 76% increases in serum leptin in asthmatic obese patients compared to obese subjects without asthma and non - obese subjects , with and without asthma , respectively ( 12 ) .
wahab and colleagues have indicated significant increases in serum leptin levels in obese asthmatic patients ( 25.8 11.1 ng / ml ) compared with non - obese asthmatic patients ( 8.8 11.1 ng / ml ) ( 39 ) .
another study has shown the maximum serum leptin levels in obese asthmatic patients ( 19.37 14.04 ng / ml ) is elevated compared with non - obese asthmatic patients ( 6.37 2.46 ng / ml ) and healthy controls ( 6.50 3.51 ng / ml ) ( 40 ) .
demonstrated maximum serum leptin levels in copd cases , both in incitement and static conditions , relative to the other groups .
their calculations indicated that , compared to the non obese control subjects , there were 90.34 , 68.75 , and 64% increases in serum leptin levels in obese with copd , obese without copd , and non - obese with copd cases , respectively ( 41 ) . therefore , these previous investigations clearly indicate that leptin resistance is linked to respiratory / pulmonary - related complications and may contribute to the development of a unique asthma phenotype in obese patients .
an elegant study reported that leptin stimulates a1at expression at both the mrna and protein levels via the jak2-stat3 pathway in liver hepg 2 and hep 1 - 6 cell lines .
alternatively , serum levels of a1at are reduced in obese leptin - resistant subjects with parallel increases in neutrophil elastase ( ne ) activity ( 13 ) .
elevated serum ne levels are also related to airway constriction in obese subjects ( 42 ) . in the same obese subjects , increases in c - reactive protein ( crp )
have also been reported ( 42 ) , which induce leptin resistance via crp - leptin adduct formation ( 29 ) .
an imbalance of a1at and ne leads to lung tissue impairments ( 14 , 43 ) .
in short , previously published data raise the possibility that the protease - antiprotease balance is leptin dependent , and due to the leptin resistance protective capacity of a1at , it could be arrested to counteract ne activity .
consequently , the degradation of lung tissues , especially elastin , occurs by ne overactivity , which could lead to pulmonary related problems in the susceptible obese population .
this hypothesis is summarized as : leptin resistance in asthmatic obese patients may reduce serum alpha 1 antitrypsin levels . in turn ,
ne enhances , which can lead to the development of pulmonary - related complications including asthma and copd due to the degradation of proteins in lung tissues . exploring mechanisms underlying the derangement of protease
antiprotease counterparts will aid in devising personalized interventional therapy for particular obese patients prone to lung complications .
this option is preferred over generalizing treatment for all patients suffering from respiratory complications , including non - obese subjects .
in short , previously published data raise the possibility that the protease - antiprotease balance is leptin dependent , and due to the leptin resistance protective capacity of a1at , it could be arrested to counteract ne activity .
consequently , the degradation of lung tissues , especially elastin , occurs by ne overactivity , which could lead to pulmonary related problems in the susceptible obese population .
this hypothesis is summarized as : leptin resistance in asthmatic obese patients may reduce serum alpha 1 antitrypsin levels . in turn ,
ne enhances , which can lead to the development of pulmonary - related complications including asthma and copd due to the degradation of proteins in lung tissues . exploring mechanisms underlying the derangement of protease
antiprotease counterparts will aid in devising personalized interventional therapy for particular obese patients prone to lung complications .
this option is preferred over generalizing treatment for all patients suffering from respiratory complications , including non - obese subjects . | contextunder normal physiological conditions , leptin regulates body weight by creating a balance between food intake and energy expenditure .
however , in obesity , serum leptin levels increase and become defective to retain energy balance.evidence acquisitionelevated serum leptin levels are regarded as an established marker of obesity .
it is also reported that obese asthmatic patients have maximum serum leptin levels compared to other groups such as non - obese asthmatics , and normal obese and non obese subjects without asthma .
in addition to having an appetite suppressing effect , leptin also regulates certain acute - phase protein expressions including -1 antitrypsin ( a1at ) in the liver.resultsa1at is a protease inhibitor that counterbalances the activity of the neutrophil elastase ( ne ) enzyme .
a1at reductions in obese - leptin resistant subjects lead to increased ne activity .
the overactivity of ne degrades lung tissue proteins , which may lead to pulmonary disorders including asthma.conclusionson the basis of prior studies , it could be hypothesized that , in obese asthmatic patients , the highest degree of leptin failure / resistance might lead to the creation of an imbalance between ne and its inhibitor a1at . to ascertain this , large scale prospective studies are warranted to assess the comparative serum leptin and a1at levels and ne activity in asthmatic non - obese and obese patients , simultaneously .
such studies might help to devise novel interventional therapies for the treatment of pulmonary - related problems including asthma , chronic obstructive pulmonary disorder ( copd ) , and other lung defects in susceptible obese subjects in the future . |
chronic psychological pressures due to work - related stress are likewise among those that can lead to mental , physical , and behavioral complications and jeopardize an individual s health status ( 2 ) . long - term exposure to negative stressors not only affects physical and mental health but also endangers a person s whole life ( 3 ) .
wang et al . in their study on mental health status introduced work - related stress as a crucial factor leading to mental disorders ( 4 ) . in this respect ,
emergency medical service ( ems ) providers are exposed to numerous risks due to time constraints in performing their duties and making decisions in critical situations as well as other negative stressful physical , emotional , and mental stimuli ( 58 ) . in this
regard , froutan et al . in their study argued that working in pre - hospital emergency situations was unique and stressful and could lead to work - related stress , thus negatively influencing organizational performance ( 9 ) .
the results of the related literature have similarly indicated a nearly 22% prevalence rate of post - traumatic stress disorder among emergency medical technicians .
approximately 6.8% of emergency technicians have also reported to be at risk of job burnout ( 10 , 11 ) .
resilience is considered an appropriate strategy to improve mental health status in individuals ( 12 ) . in this
regard , cutter stated that programs associated with reducing the risks in this area should be oriented toward reinforcing the numerous positive characteristics of resilient populations and give attention to the concept of resilience in terms of chain management in accidents , emergencies , and injuries ( 13 ) .
in fact , one of the underlying factors improving resilience is positive coping , which refers to a dynamic process to adapt positively to bitter and unpleasant experiences ( 14 , 15 ) .
accordingly , sveen identified positive coping strategy as a method to enhance the levels of resilience ( 16 ) .
similarly , yong argued that positive adaptation was significantly correlated with levels of resilience as well as other dimensions , including ardency , vigor , and optimism ( 17 ) .
nowadays , attitudes and theories put forth by authorities regarding pre - hospital emergency care seek to establish and reinforce characteristics of positive coping in ems personnel in the face of risks associated with accidents and emergencies .
in fact , what prevents an individual from breaking down because of stress is the use of methods that can modify the stressors . it also should be noted that such efficient methods arise from multiple characteristics of resilience such as positive coping ( 18 ) .
given the limited understanding of positive coping mechanisms adopted by ems personnel to deal with work - related stress and tensions , as well as factors affecting it , in real environments and considering that such understanding as well as determining effective factors are of utmost importance , the main questions of how does such a mechanism take place in real environments ? and what are the factors affecting coping with stress and tensions ? have yet to be addressed .
therefore , the purpose of this study was to achieve a better and deeper understanding of the concept of positive coping used by the ems providers .
qualitative research design with latent content analysis is generally used to study the viewpoints of persons experiencing specific events and situations ( 19 ) .
consequently , such a method was used , and a synopsis of the experiences of the ems staff was obtained based on collected data that centered on the viewpoint of the interviewees .
the study did not have a priori hypothesis , and the inductive method was used to obtain the different codes and categories .
later they were theoretically ordered based on their properties and dimensions ( 20 , 21 ) .
hence , we interviewed 28 pre - hospital care professionals ( including 20 emergency technicians , three anesthesiology assistants , and five nurses ) from the city of mashhad ( table 1 ) .
the inclusion criteria consisted of having previous experience with injury patients , and , in order to have diversity , we choose subjects from various age groups with different education levels , work experiences , and job positions .
the exclusion criteria were unwilling to participate in the study and having pervious education on positive coping .
data collection was done using unstructured interviews that included general ( e.g. , please describe one of your experience of your one day duty in the emergency service ) and specific questions , ( e.g. , please speak about your own experience about coping strategies to deal with a crisis ; at the time of a crisis , what problems and issues do you face ? ; and how do you provide clinical services during a crisis ? if required , the interviewee was requested to elaborate upon his or her responses .
each interview lasted about 4060 minutes and was done in persian by the first author , while being recorded with the interviewers consent .
the interviewer is an expert in qualitative research and trained in qualitative courses and workshops .
the aim of the interviewers was to obtain a deep knowledge of the experiences of the medical staff , and so the interviews , which consisted of data collection , data analysis , and participants selection , persisted until data saturation was reached .
the framework qualitative data analysis method was used to analyze the data , and this encompasses several dissimilar nonetheless vastly interconnected stages ( 22 ) . in the initial or familiarization stage , after the interviews were completed , the transcribed data verbatim was analyzed several times .
the second step identifies a thematic framework stage , which consisted of grouping the transcripts into meaningful units .
the summarized meaningful units were code labeled constituting the manifest content . in the third or indexing stage , we compared and contrasted the codes based on their similarities and differences and sorted them into categories and then subcategories and organized all the pertinent codes into data extracts within the named categories . in the fourth or charting stage , we studied the organized extracts for each category and pondered as to whether they formed a coherent pattern .
next , we deliberated upon whether the validity of individual categories with respect to the data set and whether our candidate categories precisely echoed the meaning shown in the data set as a whole .
two researchers independently examined data for different categories . in the fifth or mapping and interpretation stage , we defined and further refined the categories .
the ethics committee of the mashhad university of medical sciences approved this research project in april 2016 ( code : ir.mums.rec.1395.99 ) . before starting the study ,
the participants were informed about the purpose of the study , and they were assured they could withdraw from the study whenever they desired without repercussions .
maximum variation of sampling was used to validate the dependability and credibility of the data ( 23 ) along with member checking and peer debriefing .
a summary of the interviews was given to nine participants to confirm the researchers accurately depicted their viewpoints and experiences .
peer checking was done by two doctoral nursing students who received the transcriptions and a summary of the analysis process .
if there were any differences , then they were resolved by discussions ( 24 ) .
our lengthy presence in the field ( from april 2016 to november 2016 ) allowed us to create trusting and supportive communication links with the interviewees ; thus allowing us to accurately collect data .
qualitative research design with latent content analysis is generally used to study the viewpoints of persons experiencing specific events and situations ( 19 ) .
consequently , such a method was used , and a synopsis of the experiences of the ems staff was obtained based on collected data that centered on the viewpoint of the interviewees .
the study did not have a priori hypothesis , and the inductive method was used to obtain the different codes and categories .
later they were theoretically ordered based on their properties and dimensions ( 20 , 21 ) .
, we interviewed 28 pre - hospital care professionals ( including 20 emergency technicians , three anesthesiology assistants , and five nurses ) from the city of mashhad ( table 1 ) .
the inclusion criteria consisted of having previous experience with injury patients , and , in order to have diversity , we choose subjects from various age groups with different education levels , work experiences , and job positions .
the exclusion criteria were unwilling to participate in the study and having pervious education on positive coping .
data collection was done using unstructured interviews that included general ( e.g. , please describe one of your experience of your one day duty in the emergency service ) and specific questions , ( e.g. , please speak about your own experience about coping strategies to deal with a crisis ; at the time of a crisis , what problems and issues do you face ? ; and how do you provide clinical services during a crisis ? if required , the interviewee was requested to elaborate upon his or her responses .
each interview lasted about 4060 minutes and was done in persian by the first author , while being recorded with the interviewers consent .
the interviewer is an expert in qualitative research and trained in qualitative courses and workshops .
the aim of the interviewers was to obtain a deep knowledge of the experiences of the medical staff , and so the interviews , which consisted of data collection , data analysis , and participants selection , persisted until data saturation was reached .
the framework qualitative data analysis method was used to analyze the data , and this encompasses several dissimilar nonetheless vastly interconnected stages ( 22 ) . in the initial or familiarization stage , after the interviews were completed , the transcribed data verbatim was analyzed several times .
the second step identifies a thematic framework stage , which consisted of grouping the transcripts into meaningful units .
the summarized meaningful units were code labeled constituting the manifest content . in the third or indexing stage , we compared and contrasted the codes based on their similarities and differences and sorted them into categories and then subcategories and organized all the pertinent codes into data extracts within the named categories . in the fourth or charting stage , we studied the organized extracts for each category and pondered as to whether they formed a coherent pattern .
next , we deliberated upon whether the validity of individual categories with respect to the data set and whether our candidate categories precisely echoed the meaning shown in the data set as a whole .
two researchers independently examined data for different categories . in the fifth or mapping and interpretation stage , we defined and further refined the categories .
the ethics committee of the mashhad university of medical sciences approved this research project in april 2016 ( code : ir.mums.rec.1395.99 ) . before starting the study
, the participants were informed about the purpose of the study , and they were assured they could withdraw from the study whenever they desired without repercussions .
maximum variation of sampling was used to validate the dependability and credibility of the data ( 23 ) along with member checking and peer debriefing .
a summary of the interviews was given to nine participants to confirm the researchers accurately depicted their viewpoints and experiences .
peer checking was done by two doctoral nursing students who received the transcriptions and a summary of the analysis process . if there were any differences , then they were resolved by discussions ( 24 ) .
our lengthy presence in the field ( from april 2016 to november 2016 ) allowed us to create trusting and supportive communication links with the interviewees ; thus allowing us to accurately collect data .
in the present study , the experiences and perceptions of participants adopting positive coping mechanisms against terrible accidents , emergencies , and disasters have been explored . in this respect ,
data analysis led to the establishment of four main concepts , including work engagement , smart capability , positive feedback , and crisis pioneering ( table 2 ) .
work engagement was one of the extracted concepts in the analysis of experiences and perceptions of participants in the present study .
this category was comprised of two subcategories of loyalty to system and accountability towards victims . in this respect , it was argued that special bias toward their profession among ems personnel has caused them to act loyally . in terms of loyalty to the system , the study participants believed that they had used all their vigor and abilities in order to fulfill organizational goals and serve the public . in this
11 ) stated : we have a kind of enthusiasm and eagerness towards pre - hospital emergency ... we have not left the profession because other people starting such a profession may not have the necessary competence in this respect ... we pay homage to this profession .
the ems personnel also assumed themselves to be in charge of dealing with the medical conditions of victims , and they had accepted their share of responsibility in terms of performing the related procedures .
they also believed that the life of victims was a heavy responsibility on their shoulders . in this respect , one of the participants ( no .
19 ) said : during the mission , i was taking care of the breathing and consciousness of a baby suffering from a burn ... but i noticed a sudden reduction in vital signs
i have a heavy responsibility ... there is too much stress .... another category in the present study was smart capability .
in this respect , the pre - hospital emergency personnel felt empowered in terms of providing proper care for victims through their own competence , expertise , and skills .
judgment / decision - making , optimism , and self - efficacy were extracted as the subcategories associated with smart capability .
the study participants believed that if victims lives were threatened , they should seize the opportunity and incubate them based on their own judgment and quick decisions ; because loss of time would cause death . in this
26 ) reiterated : ... the victim with a chest burn needed cardiopulmonary resuscitation ( cpr ) ... abroad and deep burn all over his chest had made cardiac massage useless ... the injured victim was in urgent need of scartomy
i immediately did it .... in terms of the necessity to make quick decisions in order to intubate the victim , one of the participants ( no .
17 ) also stated : ... in the first minutes , the victim was confused ...
she answered us slowly in a wrap - up , i diagnosed her with decreased level of consciousness ... i made up my mind ...
then i quickly intubated the victim ... the second subcategory of smart capability was optimism among medical emergency personnel .
the ems technicians argued that they could make use of more effective coping strategies in the face of mental pressures . in their hard and demanding missions , such personnel attempted to assure adequate clinical services . considering psychological traumas
in this regard , an emergency technician added : ... some of the missions are demanding and difficult ... but problems associated with the scenes of an accident are transient ... my colleague and i could save the victim s life with concentration and effort .... in terms of self - efficacy , the study participants believed that , although the scenes of accidents and emergencies were replete with tensions and stress , they endeavored to control all steps of the missions and tackle possible barriers undermining the delivery of clinical services . in this respect , one of the medical emergency personnel ( no .
15 ) said : people were agitated at the scene of the accident ... they had made everything difficult for us
i controlled them with calmness and high self - confidence ... i also asked them to leave the scene
so we could help the victims .... positive feedback was one of the other extracted concepts in the given analysis .
satisfaction of victims with clinical services , positive views by authorities , and employee motivation . during the interviews with the ems personnel , these two points were highlighted : pre - hospital emergency is the frontline of care and treatment in which the most serious emergency cases are accommodated and how services are provided in the emergency department as a symbol of the general status of services in society .
the given personnel assumed that quality of examination as well as clinical services provided along with their effectiveness could lead to patient satisfaction and , as a result , employee satisfaction .
in this regard , one of the medical emergency personnel ( no . 13 ) added : ...
i rushed to examine a two - year boy who had drowned in cold water
i started cardiopulmonary resuscitation ( cpr ) the child fortunately recovered he had defecated ... i took off his clothes ...
i covered him with my jacket ... that day ... saving the life of a child motivated me
i decided to be more determined in my profession and work hard despite problems and enjoy .... positive views by authorities were the final subcategory extracted from the analysis of positive feedback .
the study participants cited further support by authorities and their involvement in decision - making by authorities as other factors affecting positive feedback . in this respect , one of the ems personnel ( no .
2 ) stated : ... our participation in decision - making for the ems bases with the authorities ... good treatment by authorities due to their satisfaction with us ... can heavily motivate us to stay in this profession .
another characteristic unique to the concept of positive coping is crisis pioneering , which has two subcategories : readiness to perform new missions and volunteer actions to counter crises . in this regard , the participants argued that , if they were near the accident site and there were a high number of victims , they would announce their readiness to the ems center . in this regard , a participant ( no .
the ems center messaged an accident with a high number of victims in critically bad conditions we were close to the scene of accident ... we coordinated with the ems center and then went straight to the scene of the accident ... in terms of volunteering to counter the crises , one of the medical emergency technicians said that : ... the personality traits of emergency personnel are such that they quickly volunteer if everyone asks for help ... we go and rescue people ... for example although it was very difficult to access the city of bam following the earthquake ... and there were so many problems ... we were dispatched to the scene through the system as volunteers ...
work engagement was one of the extracted concepts in the analysis of experiences and perceptions of participants in the present study .
this category was comprised of two subcategories of loyalty to system and accountability towards victims . in this respect , it was argued that special bias toward their profession among ems personnel has caused them to act loyally . in terms of loyalty to the system , the study participants believed that they had used all their vigor and abilities in order to fulfill organizational goals and serve the public . in this
11 ) stated : we have a kind of enthusiasm and eagerness towards pre - hospital emergency ... we have not left the profession because other people starting such a profession may not have the necessary competence in this respect ... we pay homage to this profession . the ems personnel also assumed themselves to be in charge of dealing with the medical conditions of victims , and they had accepted their share of responsibility in terms of performing the related procedures .
they also believed that the life of victims was a heavy responsibility on their shoulders . in this respect , one of the participants ( no .
19 ) said : during the mission , i was taking care of the breathing and consciousness of a baby suffering from a burn ... but i noticed a sudden reduction in vital signs
another category in the present study was smart capability . in this respect , the pre - hospital emergency personnel felt empowered in terms of providing proper care for victims through their own competence , expertise , and skills .
judgment / decision - making , optimism , and self - efficacy were extracted as the subcategories associated with smart capability .
the study participants believed that if victims lives were threatened , they should seize the opportunity and incubate them based on their own judgment and quick decisions ; because loss of time would cause death . in this regard , one of the ems personnel ( no .
26 ) reiterated : ... the victim with a chest burn needed cardiopulmonary resuscitation ( cpr ) ... abroad and deep burn all over his chest had made cardiac massage useless ... the injured victim was in urgent need of scartomy
i immediately did it .... in terms of the necessity to make quick decisions in order to intubate the victim , one of the participants ( no .
17 ) also stated : ... in the first minutes , the victim was confused ...
she answered us slowly in a wrap - up , i diagnosed her with decreased level of consciousness ...
then i quickly intubated the victim ... the second subcategory of smart capability was optimism among medical emergency personnel .
the ems technicians argued that they could make use of more effective coping strategies in the face of mental pressures . in their hard and demanding missions , such personnel attempted to assure adequate clinical services . considering psychological traumas
an emergency technician added : ... some of the missions are demanding and difficult ... but problems associated with the scenes of an accident are transient ... my colleague and i could save the victim s life with concentration and effort .... in terms of self - efficacy , the study participants believed that , although the scenes of accidents and emergencies were replete with tensions and stress , they endeavored to control all steps of the missions and tackle possible barriers undermining the delivery of clinical services . in this respect , one of the medical emergency personnel ( no .
15 ) said : people were agitated at the scene of the accident ... they had made everything difficult for us
i controlled them with calmness and high self - confidence ... i also asked them to leave the scene
it included three subcategories of effectiveness of clinical service delivery , satisfaction of victims with clinical services , positive views by authorities , and employee motivation . during the interviews with the ems personnel , these two points were highlighted : pre - hospital emergency is the frontline of care and treatment in which the most serious emergency cases are accommodated and how services are provided in the emergency department as a symbol of the general status of services in society .
the given personnel assumed that quality of examination as well as clinical services provided along with their effectiveness could lead to patient satisfaction and , as a result , employee satisfaction . in this
i rushed to examine a two - year boy who had drowned in cold water
i started cardiopulmonary resuscitation ( cpr ) the child fortunately recovered he had defecated ... i took off his clothes ... i covered him with my jacket ... that day ... saving the life of a child motivated me
i decided to be more determined in my profession and work hard despite problems and enjoy .... positive views by authorities were the final subcategory extracted from the analysis of positive feedback .
the study participants cited further support by authorities and their involvement in decision - making by authorities as other factors affecting positive feedback . in this respect , one of the ems personnel ( no .
2 ) stated : ... our participation in decision - making for the ems bases with the authorities ... good treatment by authorities due to their satisfaction with us ... can heavily motivate us to stay in this profession .
another characteristic unique to the concept of positive coping is crisis pioneering , which has two subcategories : readiness to perform new missions and volunteer actions to counter crises . in this regard , the participants argued that , if they were near the accident site and there were a high number of victims , they would announce their readiness to the ems center . in this regard , a participant ( no .
the ems center messaged an accident with a high number of victims in critically bad conditions we were close to the scene of accident ... we coordinated with the ems center and then went straight to the scene of the accident ... in terms of volunteering to counter the crises , one of the medical emergency technicians said that : ... the personality traits of emergency personnel are such that they quickly volunteer if everyone asks for help ... we go and rescue people ... for example although it was very difficult to access the city of bam following the earthquake ... and there were so many problems ... we were dispatched to the scene through the system as volunteers ...
using the experiences of pre - hospital emergency personnel and the analysis of data obtained in the present study , we extracted four main categories of work engagement : smart capability , crisis pioneering , and positive feedback .
this preliminary study done in iran employed a qualitative content analysis method to examine the experiences of pre - hospital emergency personnel in terms of positive coping and to address the research question of how are the experiences and perceptions of pre - hospital emergency personnel towards positive coping ? according to the results of the present study , pre - hospital emergency personnel had a particular bias toward their profession , and they had made attempts to fulfill their duties in this respect .
they also believed that this profession must remain in the hands of qualified people who continue their activities in order to save the lives of victims .
in fact , the ems personnel showed emotional reactions to their profession and affiliated organization , and they tried to carry out their duties with higher quality through a sense of accountability toward the victims . in this regard
, the results of studies by avery and rurkkhum showed that performance was not simply reduced to competence , eligibility , or skills in employees ; rather it was dependent upon the way personnel displayed emotional reactions in their profession and affiliated organization ( 25 , 26 ) . in the study by macey et al .
, the findings also showed that employees with higher levels of work engagement were encouraged by intrinsic stimuli such as opportunities for job promotion , value , and fair treatment rather than financial rewards or other extrinsic factors ( 27 ) .
in fact , employees endowed with high levels of work engagement considered their profession significant , motivating , and challenging because they were inclined to apply their knowledge , skills , and resources to develop their work skills ( 28 , 29 ) . in this respect ,
modi claimed that work commitment and engagement were beyond passive loyalty , and they included active bonds with an organization in which personnel tended to make considerable efforts to achieve organizational welfare as one example of staff loyalty ( 30 ) .
smart capability was similarly taken into account as one of the factors affecting the ems personnel in the face of crises that could lead to the development of resistance in difficult conditions .
judgment / decision - making by ems personnel along with their skills were of utmost importance such that they could use their own knowledge and skills to perform independent nursing interventions for patients based on their self - esteem and self - confidence . in this respect ,
studies by moadab and nasirpour revealed that medical emergency personnel played the role of an implementer ( 31 , 32 ) , and their interventions as well as health care services were provided based on their independent judgment , decision - making skills , and prioritization ( 32 ) . because ems personnel need to be empowered decision - makers in the variable conditions of victims and uncertain clinical environments , the authority and the rights granted to them in decision - making abilities gives them a sense of empowerment .
the results of this study in terms of giving authority and rights to make decisions were consistent with the findings by white . in this regard ,
the author concluded that this community of personnel could better control the environment , and they could easily make and implement decisions ( 33 ) .
however , krairikshh reported that the amount of official authority did not have a significant effect on performance and clinical decisions in nurses ( 34 ) .
another reason for the capability of the ems personnel was their optimism to deal with crises .
based on the study results , emergency technicians persisted in reaching the goals when they were challenged on missions due to having a sense of self - confidence . in their views , adversities in missions
in fact , optimism in medical emergency personnel was considered as one of their most important individual factors affecting the choice of strategies to meet the challenges raised during missions . in this regard
, studies have shown that optimistic individuals go through the daily events of their lives with a more positive manner , and they anticipate more positive consequences ( 35 ) .
other results associated with the present study have shown that ems technicians were required to be flexible in order to adapt themselves with accidents and crises through planning , especially when encountered by difficult missions .
the results of a study by thompson also showed that optimistic people make use of control strategies such as attempt , controlled thought , and logical analysis ( 36 ) .
considering self - efficacy as another reason for the capability of the ems personnel , the results of this study have indicated that medical emergency personnel make used of their own competence and expertise in missions and controlled the circles of people around the scenes of accidents .
lalianpour stated that , when individuals had the required capabilities , they were endowed with a sense of self - efficacy , or they felt they had the essential competence and expertise for successful fulfillment of their duties ( 37 ) .
crisis pioneering was one of the other concepts obtained from the experiences of medical emergency personnel with positive coping .
the results of the present study showed that the pioneering characteristics of the ems personnel could lead to more stability in their professions . in this
regard , crunt stated that people who pioneered in doing activities had initiative and expanded the scope of their roles .
empirical evidence also suggested that the given category was positively correlated with organizational consequences such as job performance and stress tolerance in demanding and difficult occupations ( 38 ) .
another concept extracted from the experiences of medical emergency personnel in terms of positive coping was receiving positive feedback .
the findings of this study have shown that victim satisfaction with clinical services provided by the ems personnel was considered as positive feedback .
in fact , dissatisfaction of people with healthcare services would bring about adverse consequences that could lead to their disconnection with the pre - hospital emergency system and creation of negative feedback towards the ems personnel .
in a study conducted by bovdorksy et al . in the united states , it was found that the quality of health care delivery could have the greatest effect on the level of satisfaction in victims ( 39 ) .
focusing on the relationship between patients levels of satisfaction compared with those in nurses , tzeng reported that nurses levels of satisfaction were directly correlated with those in patients ( 40 ) . in this respect ,
omidvari stated that patient satisfaction leads to a sense of contentment in health care personnel . in line with the findings of this study
, the present study also showed that patient satisfaction could provide positive feedback in personnel according to their experiences , which ultimately could lead to improvement of positive coping skills and resilience in stressful situations and crises ( 41 ) .
considering the concept of positive feedback , another concept extracted from the experiences of the ems providers was the attitudes of authorities to personnel . according to the considerable and serious tasks assigned to ems centers in terms of maintaining and promoting public health ,
authorities were required to involve medical emergency personnel in the decision - making processes of the organization .
today , one organizational strategy is to grant more responsibilities for decision - making to the personnel because their participation will enhance organizational performance ( 42 ) .
the results of the present study suggest that medical emergency personnel have considered collaborative decision - making by authorities as one of the best working conditions affecting motivation , job satisfaction , and promotion of quality of services .
however , zandi showed that nurses have little feeling toward taking part in decision - making processes ( 43 ) .
the experiences of the ems personnel in this study revealed that several factors such as behaviors of authorities could have a positive effect on their motivation .
in fact , officials could satisfy motivation through its recognition and prediction in medical emergency personnel . in this
regard , vali estimated that one - third of the working and operational staff in the ems centers had low levels of work - related motivation ( 44 ) . therefore , managers and officials should consider the fact that motivated human forces can have an effect on the survival and dynamicity of an organization as well as the fulfillment of its policies and strategies ( 45 ) .
meanwhile , managers who accentuate human values believe that increased efficiency is the result of improved motivation ( 46 ) .
although the results of the studies in terms of understanding the experiences of pre - hospital emergency personnel toward positive coping in the face of crises can not be generalized worldwide , and it can be only applied to similar cultures and situations , such research studies can have their own conclusions and implications .
first , this study has shown that different factors can have an effect on the formation of positive coping in medical emergency personnel .
the results of this study have also shown that some factors such as work engagement were consistent with the results of similar studies , but factors such as positive feedback , pioneering crisis , and smart capability were considered as the underlying factors affecting positive coping . given the fact that efficient methods such as positive coping can prevent debilitating stress in an individual , pre - hospital emergency authorities should seek to build and strengthen positive coping characteristics in pre - hospital medical emergency personnel to deal with the risks associated with accidents , emergencies , and injuries through adopting regular and dynamic policies . | introductionit is important to gain a thorough understanding of positive coping methods adopted by medical emergency personnel to manage stressful situations associated with accidents and emergencies .
thus , the purpose of this study was to gain a better understanding of positive coping strategies used by emergency medical service providers.methodsthis study was conducted using a qualitative content analysis method .
the study participants included 28 pre - hospital emergency personnel selected from emergency medical service providers in bases located in different regions of the city of mashhad , iran , from april to november 2016 .
the purposive sampling method also was used in this study , which was continued until data saturation was reached . to collect the data ,
semistructured open interviews , observations , and field notes were used.resultsfour categories and 10 subcategories were extracted from the data on the experiences of pre - hospital emergency personnel related to positive coping strategies .
the four categories included work engagement , smart capability , positive feedback , and crisis pioneering .
all the obtained categories had their own subcategories , which were determined based on their distinctly integrated properties.conclusionthe results of this study show that positive coping consists of several concepts used by medical emergency personnel , management of stressful situations , and ultimately quality of pre - hospital clinical services .
given the fact that efficient methods such as positive coping can prevent debilitating stress in an individual , pre - hospital emergency authorities should seek to build and strengthen positive coping characteristics in pre - hospital medical emergency personnel to deal with accidents , emergencies , and injuries through adopting regular and dynamic policies . |
an imbalance between pro- and anti - angiogenic factors inducing the formation of new blood vessels from a pre - existing vasculature ( angiogenesis ) has been described as a hallmark of cancer ( hanahan and weinberg , 2011 ) .
hence , targeting angiogenesis might plausibly reduce intra - tumoral levels of oxygen and nutrients , resulting in tumor starvation and thus in reduced tumor growth ( folkman , 1971 ) .
anti - angiogenic therapies have been rapidly translated with great expectations from preclinical cancer models to clinical practice ( carmeliet and jain , 2011 , crawford and ferrara , 2009 , ferrara and kerbel , 2005 ) .
for example , the identification of vascular endothelial growth factor ( vegf - a ) and its receptors as rate - limiting factors for normal and pathological angiogenesis has led to the development of bevacizumab ( avastin ) , a humanized monoclonal antibody targeting vegf - a ( ferrara et al . , 2004 , ferrara and kerbel , 2005 ) . some cancer types , such as colorectal ( hurwitz et al . , 2004
) , renal cell ( motzer et al . , 2007 ) , and pancreatic neuroendocrine carcinomas ( pnets ) ( raymond et al . , 2011 ) ,
have shown encouraging responses to this therapeutic strategy . however , numerous other cancer types , in particular breast cancer , seem to be poorly responsive to anti - angiogenic regimens . indeed , metastatic breast cancer patients treated with standard chemotherapy plus bevacizumab benefit from only 1 or 2 months of progression - free survival .
the rapid onset of resistance evidently prevents any overall survival benefit ( kerbel , 2009 , miller et al
these data underline the importance of deciphering the molecular mechanisms underlying intrinsic or adaptive resistance to anti - angiogenic therapy . when blocking the vegf - a signaling axis in preclinical models , e.g. , with bevacizumab , tumors escape by activating alternative pro - angiogenic signaling pathways , including signaling by fibroblast growth factors ( fgfs ) , platelet - derived growth factors ( pdgfs ) , bv8/prokineticin , and interleukin-17 ( il-17 ) ( bergers and hanahan , 2008 , casanovas et al . , 2005 , chung et al . , 2013 ,
in order to counteract the activation of these alternative pro - angiogenic pathways , several multi - kinase inhibitors , targeting vegf - dependent and independent pro - angiogenic signaling pathways , are currently in clinical use or in clinical trials .
for example , sorafenib , a multi - kinase inhibitor targeting raf , vegf receptors ( vegfrs ) 13 , pdgf receptors ( pdgfrs ) and , c - kit , and flt-3 , is currently used for the treatment of hepatocellular carcinoma .
sunitinib , blocking vegfr13 , pdgfr/ , c - kit , and flt-3 , is employed for the treatment of renal cancer .
both inhibitors show significant anti - tumor efficacy in preclinical tumor models and in cancer patients ; however , they also suffer from resistance development based on thus far unknown mechanisms ( pez - ribes et al .
transient benefits are rapidly followed by tumor recurrence , sometimes associated with drug resistance and heightened tumor invasiveness ( bergers and hanahan , 2008 , ebos and kerbel , 2011 , pez - ribes et al .
, 2009 , sennino and mcdonald , 2012 , singh and ferrara , 2012 ) .
nintedanib ( bibf-1120 ) is an even - wider - spectrum angiokinase inhibitor targeting vegfr13 , pdgf/ , and fgf receptors ( fgfrs ) 14 , as well as flt-3 and src family kinases ( hilberg et al . , 2008 ) .
nintedanib has recently shown promising results in pre - clinical models of lung cancer , ductal adenocarcinoma of the pancreas , and pnet ( awasthi et al . , 2015 , bill et al . , 2015 ,
furthermore , nintedanib has demonstrated excellent tolerance and potent activity in a phase i clinical trial in early her2-negative breast cancer ( quintela - fandino et al . , 2014 ) and in a phase iii study in non - small - cell lung cancer ( nsclc ) , leading to its approval as a second - line treatment in combination with docetaxel for advanced nsclc ( mccormack , 2015 , reck et al . ,
we report that tumors treated with nintedanib or sunitinib do not revascularize during the development of therapy resistance . instead
, the cells located in avascular areas escape the lack of oxygen by shifting their metabolism toward a hyperglycolytic state and by producing lactate .
conversely , the cells localized in the vicinity of blood vessels utilize the lactate for oxidative phosphorylation . the data
2008 ) as an alternative route to develop resistance to anti - angiogenic therapy in mouse models of breast cancer and of insulinoma .
notably , interference with glycolysis or disruption of metabolic symbiosis reinstalls nintedanib s efficacy in repressing tumor growth .
nintedanib is a potent angiogenesis inhibitor that represses endothelial cell proliferation and induces their apoptosis ( ec50 < 10 nm ) , yet with limited direct effects on tumor cells ( hilberg et al . , 2008 ) . a stable murine breast cancer cell line ( py2 t ) established from a breast tumor of an mmtv - pymt transgenic mouse ( waldmeier et al
. , 2012 ) displayed an ec50 of 8 m in vitro , which is above the pharmacologically achievable concentration in mice ( hilberg et al .
, 2008 , roth et al . , 2009 ; figure s1a ) . to study the tumor - suppressive efficacy of nintedanib in vivo
, py2 t cells were orthotopically implanted into the mammary fat pad of immune - competent syngeneic fvb / n female mice .
when tumors reached a volume of 1520 mm , where the angiogenic switch had already taken place ( figure s1b ) , daily treatment with nintedanib was initiated ( 50 mg / kg ; p.o . ) . during the first week of treatment ( short - term [ st ] treatment ) ,
tumor volumes as well as tumor weights in nintedanib - treated animals were significantly reduced ( figures 1a and 1b ) .
this nintedanib - responsive phase was associated with decreased cell proliferation and increased apoptosis ( figures 1c1f ) . however , after 3 weeks of treatment ( long - term [ lt ] treatment ) , tumors escaped this therapeutic effect and showed an enhanced tumor growth with increased cell proliferation and reduced apoptosis ( figures 1a and 1c1f ) . apparently , py2 t breast cancer cells escaped nintedanib treatment despite its broad range of inhibitory activities .
next , we investigated whether angiogenesis had been reactivated in lt - treated py2 t tumors , thereby escaping nintedanib treatment .
intriguingly , microvessel density was found decreased both after st and lt nintedanib regimen , indicating a potent and stable anti - angiogenic effect of nintedanib , even in a phase of drug - refractory exponential tumor growth ( figures 2a , 2b , and s2a ) .
the numbers of blood vessels became more variable following lt nintedanib treatment , potentially indicating an initiation of revascularization .
however , immunofluorescence co - staining for cd31 and cleaved caspase 3 ( ccasp3 ) revealed increased apoptosis in endothelial cells after st and lt nintedanib treatment , demonstrating the sustained anti - angiogenic efficacy of nintedanib even after lt treatment ( figures 2c and 2d ) .
this therapy - resistant tumor growth was not specific for the multi - kinase inhibitor nintedanib ; in a head - to - head comparison , py2 t tumors treated with nintedanib and sunitinib displayed comparable tumor growth and reduced microvessel densities after lt treatment ( figures s2b s2d ) .
next , we assessed whether py2 t tumors compensate for the lack of blood vessels with increased pericyte coverage .
pericytes promote the maturation and stabilization of blood vessels through pdgfr signaling and thus influence the responsiveness to anti - angiogenic therapy ( hellstrm et al . , 1999 ) .
interestingly , despite its inhibitory activity on pdgfr signaling , nintedanib did not affect the pericyte coverage of blood vessels resisting nintedanib treatment ( figures 2e and s2e ) .
nintedanib also did not affect the functionality of the remaining blood vessels as determined by the injection of fluorescence - labeled lectin ( figures 2f and s2f ) .
consistent with decreased tumor perfusion , pimonidazole staining revealed a significant increase in tumor hypoxia not only in the st - treated , nintedanib - responsive tumors but also in the lt - treated , nintedanib - resistant tumors ( figures 2 g and 2h ) .
these data demonstrate a potent anti - angiogenic activity of nintedanib and suggest a mechanism of therapy resistance by which tumors escape anti - angiogenic therapy in the absence of any revascularization . to investigate the molecular mechanisms underlying the resistance against nintedanib treatment , we isolated by flow cytometry endothelial and tumor cells from nintedanib - treated and untreated tumors at different time points of resistance development . to facilitate the isolation of tumor cells , py2 t cells were transduced with a retroviral construct expressing a truncated , non - functional form of murine cd8 ( misteli et al . , 2010 ) .
a cd45cd8 population could only be identified in py2t - cd8 tumors and not in wild - type py2 t tumors ( figure s3a ) .
after st ( 1 week ) and lt ( 3 weeks ) treatment with nintedanib , cd45cd8 tumor cells and cd45cd8cd31podoplanin endothelial cells were sorted by flow cytometry ( figures s3b s3d ) .
surprisingly , endothelial cell gene expression profiles between st and lt nintedanib - treated tumors did not markedly differ , mainly reflecting endothelial cells undergoing apoptosis ( data not shown ) . in contrast
, gene expression analysis of isolated tumor cells revealed a marked difference between untreated and treated groups .
the genes resulting from the comparison between lt nintedanib - treated and untreated tumor cells were subjected to kyoto encyclopedia of genes and genomes ( kegg)-pathway analysis , which showed an enrichment of metabolic pathways , in particular glycolysis ( figure 3a ) .
gene set enrichment analysis ( gsea ) ( subramanian et al . , 2005 ) also showed an enrichment of glycolysis gene expression , especially when comparing the gene expression profiles of lt versus untreated tumor cells , yet also when comparing st versus untreated tumor cells ( figure 3b ) .
glycolysis gene enrichment also became evident when the gene expression profiles associated with a core set of glycolytic enzymes were visualized using a heatmap .
indeed , hierarchical clustering correctly interrelated the three different treatment conditions ( figure 3c ) .
qrt - pcr analysis confirmed the upregulated expression of most of the glycolytic enzymes upon st and lt nintedanib treatment , whereas the expression of genes implicated in mitochondrial biogenesis and oxidative phosphorylation was unaffected ( figures 3d and 3e ) . because nintedanib - treated tumors exhibited enhanced hypoxia compared to size - matched , vehicle - treated tumors ( figures 2 g and 2h ) , we hypothesized that hypoxia could be a determinant of tumor cell heterogeneity and a direct inducer of the glycolytic shift . as expected ,
when compared with normoxic cultures , py2 t cells cultured for 3 days in hypoxic conditions ( 1% o2 ) exhibited a significantly increased expression of nine out of ten glycolysis - related transcripts analyzed ( figure s3e ) .
together , the data suggest a metabolic adaptation to anti - angiogenic therapy , in which hypoxic tumor cells shift to a hyperglycolytic state to survive and proliferate at reduced oxygen and nutrient supply . considering the highly glycolytic phenotype of nintedanib - treated tumor cells , we analyzed lactate production in py2 t tumors .
total lactate production was not increased in nintedanib - treated tumors compared to vehicle - treated tumors ( figure s4a ) , possibly explained by a fast metabolic utilization of lactate .
the alternation between highly hypoxic and normoxic areas in nintedanib - treated tumors ( figure 2h ) , together with comparable levels of lactate between nintedanib and vehicle - treated tumors , suggested the establishment of lactate - based metabolic symbiosis ( sonveaux et al . , 2008 ) .
in such symbiosis , hypoxic glycolytic cells use glucose to produce high levels of lactate that is rapidly exported through monocarboxylate transporter 4 ( mct4 ) , mainly a lactate exporter .
oxidative cells located in perfused areas express mct1 , mainly a lactate importer , allowing them to take up lactate and directly fuel their krebs cycle .
these cells do not rely on glycolysis , and glucose can bypass them and diffuse to hypoxic areas , where it is taken up by glycolytic cells expressing high levels of hypoxia - induced glucose transporter 1 ( glut1 ) to produce lactate .
we assessed the establishment of metabolic symbiosis during the development of resistance against nintedanib - mediated anti - angiogenic therapy in the py2 t transplantation model of breast cancer .
immunofluorescence staining for mct1 and mct4 demonstrated a diffuse baseline expression of mct1 that remained unchanged during nintedanib treatment , whereas mct4 was highly expressed in non - vascularized areas of lt nintedanib - treated tumors and to a lesser extent in st - treated tumors ( figures 4a and s4b s4d ) .
similar results were observed in sunitinib - treated tumors ( figure s4e ) . to assess the generality of our findings , we analyzed microvessel densities and mct4 expression in tumors of rip1tag2 transgenic mice that have been treated with nintedanib ( bill et al . , 2015 ) .
the rip1tag2 transgenic mouse model of pnet is highly sensitive to anti - angiogenic therapies and has been instrumental for compound testing and subsequent successful translation to the treatment of patients with pnets ( tuveson and hanahan , 2011 ) . with rip1tag2 mice ,
nintedanib treatment was initiated at 10 weeks of age , which prolonged median survival from 24 days in control - treated animals to 55 days in nintedanib - treated animals .
comparable to the py2 t breast cancer model , rip1tag2 mice also developed resistance to nintedanib therapy and did not display any revascularization in therapy - refractory tumors ( figure s4f ) , and mct4 expression was also only found in tumors after prolonged nintedanib treatment ( figure s4
g ) . to further assess the establishment of metabolic symbiosis in nintedanib therapy - resistant tumors , we assessed by immunofluorescence microscopy analysis the expression and localization of markers for hypoxia ( pimonidazole ) , glucose uptake ( glut1 ) , lactate export ( mct4 ) , mitochondrial biogenesis , and oxidative phosphorylation ( pgc1 and cox iv ; lebleu et al . , 2014 , wu et al . ,
notably , the mean shortest distance between mct4-expressing cells and the nearest blood vessel was increased in lt tumors , although not with statistical significance ( figure 4b ) , indicating the expression of mct4 in hypoxic areas .
indeed , the expression of hypoxia - induced glut1 correlated with the expression of hypoxia - induced mct4 and with the hypoxia - marker pimonidazole in the hypoxic areas of nintedanib lt tumors ( figures 4c4 g , s4h , and s4i ) . the expression of mct4 co - localized with pimonidazole as well ( figures 4h , 4i , and s4j ) . on the other hand ,
the expression of pgc1 and cox iv did not specifically localize with vascularized or non - vascularized areas yet increased in st and lt nintedanib - treated tumors ( figures s4k and s4n ) .
curiously , the co - expression of mct4 with pgc1 and cox iv was decreased and unchanged , respectively , in st nintedanib - treated tumors , yet it was unchanged with pgc1 and increased with cox iv comparing lt vehicle and nintedanib - treated tumors ( figures s4l , s4 m , s4o , and s4p ) .
these results suggest a first wave of tumor hypoxia and glycolysis followed by a homeostasis of metabolic symbiosis between anaerobic glycolysis and aerobic oxidative phosphorylation during prolonged anti - angiogenic therapy .
the small molecule 3-(3-pyridinyl)-1-(4-pyridinyl)-2-propen-1-one ( 3po ) inhibits the glycolytic activator phosphofructokinase-2/fructose-2,6-bisphosphatase 3 ( pfkfb3 ) in endothelial cells ( schoors et al . , 2014 ) .
its combined activity as a glycolysis and endothelial cell inhibitor made it a prime compound to overcome glycolysis - induced resistance to anti - angiogenic therapy .
whereas single treatment with nintedanib significantly repressed tumor growth in py2t - transplanted mice , single treatment with 3po only marginally delayed it ( figures 5a and 5b ) .
notably , the combined treatment with nintedanib and 3po showed an additive effect on tumor growth inhibition .
this combined effect was not mediated by an additive anti - angiogenic effect , because the microvessel densities between the nintedanib single and the nintedanib plus 3po combination treatments were not significantly altered ( figure 5c ) .
consistent with its ability to normalize blood vessels , single treatment with 3po significantly increased pericyte coverage and thus vessel functionality , possibly explaining the limited repression of tumor growth despite the significant decrease in microvessel density ( figure 5d ; schoors et al . , 2014 ) .
this effect was abrogated upon combined 3po and nintedanib treatment . to determine the early effects of 3po treatment on nintedanib - treated tumors ,
py2t - transplanted mice were first treated with nintedanib for 8 days and then subjected to treatment with 3po and nintedanib for subsequent 5 days . whereas nintedanib significantly repressed tumor growth upon st treatment , 3po treatment did not add further tumor repression ( figures s5a and s5b ) . however , the extent of tumor hypoxia and the rate of tumor cell apoptosis specifically in the hypoxic tumor areas significantly increased upon combined nintedanib/3po treatment ( figures s5c s5e ) . collectively , these results suggest that the inhibition of glycolysis is one avenue of overcoming resistance to anti - angiogenic therapy with multi - kinase inhibitors . to determine whether the inhibition of metabolic symbiosis could overcome the development of resistance against anti - angiogenic therapy , we generated py2 t cell lines that were devoid of mct4 by crispr / cas9-mediated knockout of the slc16a3 gene ( mct4 is known as solute carrier 16 a3 [ slc16a3 ] ) .
2 ) , which showed targeted recombination in the slc16a3 gene and did not express mct4 protein anymore , were used for further experimentation ( figure s5f ) . the loss of mct4 expression in these clones significantly repressed tumor growth as compared to wild - type cells under treatment , with nintedanib treatment leading to an additive effect in repressing tumor growth kinetics and final tumor weights ( figures 5e and 5f ) .
these results were confirmed by short hairpin rna ( shrna)-mediated ablation of mct4 expression ( shmct4 ) in py2 t cells ( figure s5
g ) . the loss of mct4 expression in shmct4 cell lines significantly retarded tumor growth kinetics and final tumor weights under treatment with nintedanib as compared to shctrl cells ( figures s5g s5i ) . however , after a first delay , shmct4 tumors resumed growth .
immunofluorescence staining for cd31 did not reveal any increase in microvessel density in nintedanib - treated shmct4 tumors , excluding an escape route by revascularization ( figure s5j ) .
instead , we observed an increase of mct4 expression both at the protein and mrna level in nintedanib - treated shmct4 tumors ( figures s5k and s5l ) , suggesting that cells with poor shrna - mediated knockdown efficiency developed a selective growth advantage and elicited tumor recurrence .
the results presented above beg the question whether , in py2 t tumor cells , hypoxia - induced glycolysis is directly affected by treatment with nintedanib and 3po or the loss of mct4 expression . thus , we performed extracellular flux analysis by seahorse
methodology to determine the oxygen consumption rate ( ocr ) as a measure of oxidative phosphorylation and the extracellular acidification rate ( ecar ) as a measure of glycolysis . as expected , under hypoxic conditions ,
py2 t cells exhibited increased ecar ( glycolysis ) and decreased ocr ( oxidative phosphorylation ) as compared to normoxic conditions ( figures 6a and 6b ) . when directly quantified
, hypoxic cells had reduced atp - coupled ocr , increased ecar , unchanged glycolytic capacity , and decreased glycolytic reserve as compared to cells cultured under normoxia ( figures 6c6f ) . to determine any effects of therapeutic treatments on the rates of glycolysis and oxidative phosphorylation , the ratios between ecar and ocr were determined in wild - type or mct4 knockout py2 t cells cultured under normoxia or hypoxia and treated with solvent , nintedanib , or 3po .
these experiments revealed that nintedanib did not affect the ratio between ecar and ocr ( figure 6 g ) , whereas 3po reduced this ratio , i.e. , it decreased glycolysis and increased oxidative phosphorylation under hypoxic , but not normoxic , conditions ( figure 6h ) .
the genetic ablation of mct4 expression also reduced ecar / ocr only under hypoxic growth conditions ( figure 6i ) , which also resulted into increased tumor cell apoptosis and cell - cycle arrest ( figures 6j and 6k ) .
taken together , the data show that anti - angiogenic resistance can occur via the establishment of metabolic symbiosis and that interfering with metabolic symbiosis can overcome resistance to anti - angiogenic therapy with multi - kinase inhibitors .
( 2016 ) ; this issue of cell reports and jimnez - valerio et al .
( 2016 ) ; this issue of cell reports , we report the intriguing finding that a glycolytic shift underlies the development of resistance to anti - angiogenic therapy with multi - kinase inhibitors . notably , in response to the efficient repression of tumor angiogenesis , tumors compartmentalize into hypoxic regions at a distance from blood perfusion and into normoxic regions in the vicinity of mature and functional blood vessels .
the hypoxic tumor cells exhibit high glucose uptake by the hypoxia - induced expression of glut1 , and they efficiently generate and export lactate by the hypoxia - induced expression of the lactate exporter mct4 .
conversely , the normoxic tumor cells take up the lactate produced by the hypoxic tumor cells and oxygen from nearby blood vessels and fuel both into oxidative phosphorylation ( figure 7 ) .
such aspect of metabolic intra - tumoral heterogeneity is portrayed by the concept of metabolic symbiosis ( sonveaux et al . , 2008 ) . here
, we have analyzed the efficacy of the angiokinase inhibitors nintedanib and sunitinib in a preclinical mouse model of breast cancer and in the rip1tag2 transgenic mouse model of pancreatic neuroendocrine cancer .
treatment of py2 t tumor - bearing mice and of rip1tag2 mice with the angiogenesis inhibitors has led to a significant therapeutic response , characterized by increased tumor and endothelial cell apoptosis , decreased tumor cell proliferation , and reduced tumor size . however , despite the potent anti - angiogenic efficacies , the treated tumors rapidly escape therapy . evasive resistance to anti - angiogenic therapy has previously been reported to rely partially on the redundancy of pro - angiogenic growth factors leading to tumor revascularization ( bergers and hanahan , 2008 , chung et al .
intriguingly , the nintedanib- and sunitinib - resistant tumors do not show any evidence of revascularization .
rather , with the reduction in tumor perfusion , hypoxia is increased in resistant tumors and microarray gene expression analysis reveals a metabolic shift to glycolysis in the resistant tumor cells .
indeed , glycolysis and glucose - transport - related genes are well known targets of hypoxia - induced cellular adaptations ( harris , 2002 ) , and glycolysis induction has been recently described in response to vegf inhibitors ( curtarello et al . , 2015 ,
the tumor cells shift to glycolysis as a mechanism underlying resistance against anti - angiogenic therapy offers the opportunity of defeating therapy - resistance by interfering with glycolysis . indeed , in this and in the accompanying reports ( allen et al .
2016 ) , combination therapy involving angiokinase inhibitors with 3po ( our work ) , a glycolytic flux inhibitor ( clem et al . , 2008 ,
schoors et al . , 2014 ) , or with rapamycin , an mtor and glycolysis inhibitor ( presented in the accompanying papers by allen et al . and jimnez - valerio et al . ) , surmounts resistance to treatment
however , combination treatment of nintedanib with 2-deoxyglucose , a competitive inhibitor of the production of glucose-6-phosphate from glucose ( wick et al . , 1955 ) , did not delay tumor growth , most likely due to the fact that we have been unable to supply the very high concentrations of 2-deoxyglucose in tumors that would be pharmacologically active ( data not shown ) .
dichloroacetate ( dca ) , a drug inhibiting pyruvate dehydrogenase kinase and thus promoting glucose oxidation over glycolysis by increasing the pyruvate flux into mitochondria ( michelakis et al . , 2010 ) , also has not shown any effect on tumor growth ( data not shown ) .
hence , the pharmacological targeting of glycolysis in the context of anti - angiogenic therapy may be more complex than anticipated .
along these lines , despite a clear hypoxia - response pattern to nintedanib therapy , high - throughput metabolomic analysis of tumor lysates from treated mice has failed to show any significant differences in central carbon metabolism between nintedanib lt and untreated tumors ( data not shown ) . however
, this snapshot analysis ex vivo may be obscured by the concomitant presence of cells using hypoxia / glycolysis or oxidative phosphorylation within the same tumor , thus averaging out the metabolites specific for the distinct cellular subpopulations . in a comparable way
, metabolic flow analysis with labeled substrates of glycolysis and oxidative phosphorylation is hampered by the lack of a technique to directly measure the metabolites of localized cell subpopulations within a tumor .
we have thus used established markers for angiogenesis , hypoxia , metabolite transport , and mitochondrial function to visualize the distinct metabolic compartments . moreover ,
we have analyzed the hypoxia - induced metabolic shift between glycolysis and oxidative phosphorylation in cultured tumor cells by seahorse technology and have found that inhibition of glycolysis by 3po as well as the genetic ablation of mct4 expression repress hypoxia - induced glycolysis and induce cell - cycle arrest and apoptosis .
regions with higher oxygen partial pressure metabolize lactate produced in hypoxic areas and thus increase the diffusion capacity of oxygen and glucose . indeed , increased expression of mct4 has been correlated with poor prognosis in melanoma and breast cancer ( doyen et al . , 2014 , ho et al . , 2012 ) .
accordingly , the genetic ablation of mct4 expression in py2 t tumors treated with nintedanib show significantly delayed tumor growth .
our data therefore suggest that ( 1 ) despite the broad range of activities of the multi - kinase inhibitors nintedanib and sunitinib , tumors can still escape treatment ; ( 2 ) nintedanib and sunitinib resistance does not occur via tumor revascularization but is induced by a metabolic shift toward glycolysis and the establishment of metabolic symbiosis ; and ( 3 ) nintedanib and sunitinib treatment should be used in combination with glycolysis / metabolic symbiosis inhibitors for lt efficacy ( figure 7 ) .
along these lines , it has been recently reported that the genetic disruption of mct1 or mct4 represses breast tumor growth ( morais - santos et al . , 2015 ) and sensitizes glycolytic tumor cells to treatment with phenformin , an inhibitor of mitochondrial complex i ( marchiq and pouyssgur , 2016 ) .
however , complicating things , a recent investigation of metabolic changes in tumors after cessation of sunitinib or sorafenib therapy has revealed a metabolic shift to lipid synthesis and blockade of lipidogenesis has inhibited tumor regrowth ( sounni et al . , 2014 ) . in conclusion , the data presented here and in the accompanying reports underscore the variety of evasive responses to anti - angiogenic and likely to other targeted therapies .
the establishment of metabolic symbiosis adds not only another level of complexity but also a number of druggable targets to the design of combinatorial therapies .
the results also emphasize the importance of intra - tumoral heterogeneity as therapy response , in particular with regard to oxygen and nutrient availability .
such heterogeneity likely masks critical adaptation mechanisms when performing cross - sectional analysis without spatial resolution .
fvb / n mice were kept and bred under specific pathogen - free ( spf ) conditions . the generation and characterization of rip1tag2 transgenic mice has been described elsewhere ( hanahan , 1985 ) .
all experiments were performed following the rules and legislations of the cantonal veterinary office and the swiss federal veterinary office ( sfvo ) under license numbers 1878 , 1907 , and 1908 .
py2 t murine breast cancer cells were cultured as previously described ( waldmeier et al . , 2012 ) .
5 10 cells were orthotopically injected into the mammary gland number 9 of 7- to 11-week - old female fvb / n mice under isoflurane / oxygen anesthesia .
tumor length ( l ) and width ( w ) were assessed three times per week using a vernier caliper , and tumor volume ( v ) was calculated using the formula v = 0.543 l w. see the supplemental experimental procedures .
subconfluent py2 t cells were transfected with 2 g of mct4 crispr / cas9 ko plasmid and 2 g of mct4 hdr plasmid ( santa cruz biotechnology ; sc-429828 and sc-429828hdr , respectively ) .
successfully transfected cells were selected by puromycin treatment ( 5 g / ml ) and fluorescence - activated cell sorting ( facs ) sorted based on their rfp expression .
single clones were derived and validated using pcr primers flanking the sequences targeted by the guide rnas , subsequent sequencing , and western blot analysis .
prior to in vivo experiments , the rfp and puromycin resistance cassettes were removed using infection with adenovirus - expressing cre recombinase ( ad - cre ) . for details , see the supplemental information .
data analysis and graph generation was performed using graphpad prism 6 ( graphpad prism software ) .
for immunofluorescence analysis , each data point represents one field of view and the mean is displayed .
statistical significance of in vitro experiments was calculated using student s t test or anova test , as indicated in the figure legends .
, non - significant ; p < 0.05 ; p < 0.01 ; p < 0.001 ; p < 0.0001 .
; supervision , g.c . ; project administration , g.c . ; funding acquisition , r.b . and g.c . | summarydespite the approval of several anti - angiogenic therapies , clinical results remain unsatisfactory , and transient benefits are followed by rapid tumor recurrence . here , we demonstrate potent anti - angiogenic efficacy of the multi - kinase inhibitors nintedanib and sunitinib in a mouse model of breast cancer .
however , after an initial regression , tumors resume growth in the absence of active tumor angiogenesis .
gene expression profiling of tumor cells reveals metabolic reprogramming toward anaerobic glycolysis .
indeed , combinatorial treatment with a glycolysis inhibitor ( 3po ) efficiently inhibits tumor growth .
moreover , tumors establish metabolic symbiosis , illustrated by the differential expression of mct1 and mct4 , monocarboxylate transporters active in lactate exchange in glycolytic tumors . accordingly
, genetic ablation of mct4 expression overcomes adaptive resistance against anti - angiogenic therapy .
hence , targeting metabolic symbiosis may be an attractive avenue to avoid resistance development to anti - angiogenic therapy in patients . |
a key feature of the microscopic domain is the compton wavelength for a particle of rest mass @xmath23 , which is @xmath24 .
( strictly , this is the _ reduced _ compton wavelength , though we refer to these quanitites interchangeably throughout this paper . ) in the @xmath25 diagram of fig .
[ mr ] , the region corresponding to @xmath26 might be regarded as the ` quantum domain ' in the sense that the classical description breaks down there .
a key feature of the macroscopic domain is the schwarzschild radius for a body of mass @xmath23 , which corresponds to the size of a black hole of this mass and is @xmath27 .
the region @xmath28 might be regarded as the ` relativistic domain ' in the sense that there is no stable classical configuration in this part of fig .
[ mr ] . [ mr ] despite being essentially relativistic results , it is interesting that both these expressions can be derived from a semi - newtonian treatment in which one invokes a maximum velocity @xmath29 but no other relativistic effects .
the compton line can be derived from the heisenberg uncertainty principle ( hup ) , which requires that the uncertainty in the position and momentum of a particle satisfy @xmath30 , by arguing that the momentum of a particle of mass @xmath23 is bounded by @xmath31 .
this implies that one can not localize it on a scale less than @xmath32 and is equivalent to substituting @xmath33 and @xmath34 in the uncertainty relation . in sec .
[ sec.3 ] , we discuss more rigorous ways of determining the compton scale , even in non - relativistic quantum theory , though there is always some ambiguity in the precise numerical coefficient . the expression for the schwarzschild radius
is derived rigorously from general relativity but exactly the same expression can be obtained by equating the escape velocity in newtonian gravity to @xmath29 .
the compton and schwarzschild lines intersect at around the planck scales , @xmath35 and naturally divide the @xmath25 diagram in fig . [ mr ] into three regimes , which for convenience we label quantum , relativistic and classical .
( as discussed in appendix [ appendixa ] , a more comprehensive discussion involves three dichotomies classical / quantum , non - relativistic / relativistic , weak - gravitational / strong - gravitational and different combinations of these then give @xmath36 possible regimes . )
there are several other interesting lines in fig .
[ mr ] . the vertical line @xmath37 marks the division between elementary particles ( @xmath38 ) and black holes ( @xmath5 ) , since the event horizon of a black hole is usually required to be larger than the compton wavelength associated with its mass .
the horizontal line @xmath39 is significant because quantum fluctuations in the metric should become important below this @xcite .
quantum gravity effects should also be important whenever the density exceeds the planck value , @xmath40 , corresponding to the sorts of curvature singularities associated with the big bang or the centres of black holes @xcite .
this implies @xmath41 , which is well above the @xmath42 line in fig .
[ mr ] for @xmath43 , so one might regard the shaded region as specifying the ` quantum gravity ' domain .
this point has recently been invoked to support the notion of planck stars @xcite and could have important implications for the detection of evaporating black holes @xcite .
although the compton and schwarzschild boundaries correspond to straight lines in the logarithmic plot of fig .
[ mr ] , this form presumably breaks down near the planck point due to quantum gravity effects .
one might envisage two possibilities : either there is a smooth minimum , so the the compton and schwarzschild lines in some sense merge , or there is some form of phase transition or critical point at the planck scale , so that the separation between particles and black holes is maintained .
which alternative applies could have important implications for the relationship between elementary particles and black holes @xcite .
one way of obtaining a smooth transition between the compton and schwarzschild lines is to invoke the generalized uncertainty principle ( gup ) @xcite .
as one approaches the planck point from the left , this implies that the compton wavelength is replaced by an expression of the form @xcite
@xmath44 \ , , \ ] ] where @xmath45 is a dimensionless constant ( normally assumed to be positive ) .
this might be regarded as a ` generalized ' compton wavelength , the last term representing a small correction due to gravitational effects .
even if the gup is rejected , gup - type phenomenology can be obtained via an alternative route , by extending the de broglie relations to super - planckian energies @xcite .
less attention has been paid to what happens when the black hole radius approaches the intersect point from the right .
one possibility is that the schwarzschild radius is replaced by @xmath46\ ] ] for some constant @xmath47 , so that the gravitational mass , which is distinct from the bare mass @xmath23 , is given by is @xmath48 @xcite .
this is termed the generalized event horizon ( geh ) and represents a small perturbation of the schwarzschild radius in the limit @xmath49 .
although eqs .
( [ gup2 ] ) and ( [ geh1 ] ) apply in different regimes ( @xmath4 and @xmath50 , respectively ) , the expressions for @xmath51 and @xmath52 are mathematically identical if @xmath53 and @xmath54 .
although there is no reason for anticipating these values , the factor of two in the expression for the schwarzschild radius is precise , whereas the coefficient associated with the compton wavelength is somewhat arbitrary , so this motivates an alternative approach in which the free constant in eq .
( [ gup2 ] ) is associated with the first term rather than the second .
it then becomes @xmath55 \ , , \ ] ] which is mathematically identical to the expression for @xmath52 given by eq .
( [ geh1 ] ) .
what happens as one approaches the planck point from the left and right are therefore linked .
the suggestion that there is some connection between the uncertainty principle on microscopic scales and black holes on macroscopic scales is termed the black hole uncertainty principle ( bhup ) correspondence @xcite and it is manifested in a unified expression for the compton wavelength and schwarzschild radius . we also describe this as the compton - schwarzschild correspondence when discussing an interpretation in terms of extended de broglie relations @xcite . more generally , this correspondence might allow any unified expression @xmath56 which has the asymptotic behaviour @xmath57 for @xmath58 and @xmath59 for @xmath49 .
one could envisage many other unified expressions satisfying this condition but they would only be well motivated if based upon some final theory of quantum gravity .
the bhup correspondence suggests that there is a different kind of positional uncertainty for an object larger than the planck mass , related to the existence of black holes .
this is not unreasonable since the compton wavelength of a particle is smaller than the planck length in this region , so its physical meaning is unclear .
in addition , an outside observer can not localize an object on a scale smaller than its schwarzschild radius .
there are three important mathematical features of the bhup correspondence @xcite .
the first is the smooth transition between the compton and schwarzschild lines in fig .
[ mr ] , as indicated by the broken line .
the second is the duality between the two lines under the transformation @xmath2 .
the third is the implication that there could be black holes in the sub - planckian regime ( @xmath38 ) with radius @xmath32 for @xmath58 . in this paper , we are mainly concerned with the second feature , most of our considerations being independent of the bhup correspondence .
however , our conclusions have important implications for the other two features and we discuss these elsewhere @xcite .
the black hole boundary in fig . [ mr ] assumes there are three spatial dimensions but many theories suggest that dimensionality could increase on small scales . in particular ,
superstring theory is consistent only in @xmath60 spacetime dimensions , even though our observable universe is @xmath61-dimensional . in current string theory models ,
ordinary matter is described by open strings , whose end - points are confined to a @xmath62-dimensional @xmath63-brane , while gravity is described by closed strings that propagate in the bulk @xcite .
it is therefore possible for our universe to be either a @xmath64-brane or a @xmath63-brane , which is compactified on @xmath65 extra dimensions . in either case , current experiments would be unable to directly probe the higher - dimensional nature of spacetime if the compactification scales were sufficiently small .
however , there is a crucial qualitative difference between the two scenarios . in the first
, matter is confined to the three visible dimensions ; in the second , it can probe at least some of the extra dimensions at high energies and this more general scenario is considered in this paper . an additional motivation for this
is that the @xmath64-brane of the first scenario is expected to have some thickness in quantum theory and this might be interpreted as an effective compactification scale for the confined matter .
this motivates us to consider the behavior of black holes and quantum mechanical particles in spacetimes with extra directions . for simplicity , we begin by assuming that all the extra dimensions in which matter is free to propagate are compactified on a single length scale @xmath7 . if there are @xmath6 extra dimensions , and black holes with @xmath66 are assumed to be approximately spherically symmetric with respect to the full @xmath10-dimensional space , then the schwarzschild radius is given by @xcite @xmath67 for @xmath68 , so the slope of the black hole boundary in fig .
[ mr ] becomes shallower .
the question now arises of whether the @xmath23 dependence of @xmath14 is also affected by the extra dimensions .
the usual assumption is that it is not , so that one still has @xmath11 . in this case , the intersect of the schwarzschild and compton lines is changed , so that the effective higher - dimensional planck mass decreases ( allowing the possibility of tev quantum gravity ) and the effective higher - dimensional planck length increases @xcite .
however , in this paper we will argue that in some circumstances one expects @xmath69 for @xmath70 .
in this case , the effective planck length is changed but not the planck mass , so that there can be no tev quantum gravity regime . on the other hand ,
the duality between @xmath14 and @xmath15 is preserved and we will see that this has interesting physical implications .
the plan of the paper is as follows .
[ sec.2 ] reviews the interpretation of the uncertainty principle in three dimensions ( @xmath71 ) .
[ sec.3 ] then considers how this relates to the derivation of the standard expression for the compton wavelength .
[ sec.4 ] discusses the ( well - known ) expression for the schwarzschild radius for a ( @xmath72)-dimensional black hole .
[ sec.5 ] then derives the equivalent result for the effective compton wavelength , emphasizing that this depends crucially on the form assumed for the wave function in the higher - dimensional space .
[ sec.6 ] shows how the expression for the higher - dimensional compton wavelength can be related to a ` compton temperature ' , which is dual to the hawking temperature of a black hole in @xmath72 dimensions .
[ sec.7 ] explores the consequences of our claim for the detectability of primordial black hole evaporations and recent @xmath16-particle scattering results .
[ sec.8 ] gives some general conclusions and suggestions for future work .
a more complete discussion of fig .
[ mr ] is presented in the appendix .
in the form originally derived by heisenberg , the uncertainty principle states that the product of the ` uncertainties ' in the position and momentum of a quantum mechanical particle is of order of or greater than the reduced planck s constant @xmath73 @xcite .
more generally , the rigorous definition of the uncertainty @xmath74 for an operator @xmath75 is the standard deviation for a large number @xmath76 of ( absolutely precise ) repeated measurements of an ensemble of identically prepared systems described by the wave vector @xmath77 : @xmath78 formally , this expression corresponds to the limit @xmath79 and is generally @xmath80-dependent .
thus , the uncertainty @xmath74 does not correspond to incomplete knowledge about the value of the property @xmath81 for the system , since @xmath77 need not possess a definite value of @xmath81 .
consistency with the hilbert space structure of quantum mechanics requires that the product of the uncertainties associated with arbitrary operators @xmath82 and @xmath83 satisfy the bound @xcite @xmath84|\psi\rangle|^2 + |\langle \psi|[\hat{a},\hat{b}]_{+}|\psi\rangle|^2 } \geq \frac{1}{2}|\langle \psi|[\hat{o}_1,\hat{o}_1]|\psi\rangle| \ , , \end{aligned}\ ] ] where @xmath85 $ ] is the commutator of @xmath82 and @xmath83 and @xmath86_{+}$ ] is the anticommutator of @xmath87 and @xmath88 .
this formulation , which was first presented in refs .
@xcite , can also be given a measurement - independent interpretation since , from a purely mathematical perspective , @xmath89 and @xmath90 represent the ` widths ' of the wave function in the relevant physical space or phase space , regardless of whether a measurement is actually performed .
for the operators @xmath91 and @xmath92 , defined by @xmath93 and @xmath94 , the commutation relation @xmath95 = i\hbar$ ] gives @xmath96 where @xmath97 and @xmath98 correspond to the standard deviations of @xmath99 in position space and @xmath100 in momentum space , respectively .
this formulation of the uncertainty principle for @xmath91 and @xmath101 was first given in refs .
@xcite and , for this choice of operators , the @xmath80-dependent terms in eq .
( [ sup ] ) are of subleading order , in accordance with heisenberg s original result .
the underlying wave - vector in the hilbert space of the theory is identical in either the physical or momentum space representations , which correspond to different choices for the basis vectors in the expansion of @xmath80 @xcite .
although @xmath97 and @xmath98 do _ not _ refer to any unavoidable ` noise ' , ` error ' or ` disturbance ' introduced into the system by the measurement process , this was how heisenberg interpreted his original result @xcite . in order to distinguish between quantities representing such noise and the standard deviation of repeated measurements which do not disturb the state @xmath102 prior to wave function collapse
, we use the notation @xmath103 for the former and @xmath104 for the latter .- dependent .
however , we adopt heisenberg s original notation , in which the state - dependent nature of the disturbance is not explicit . ] in this notation , heisenberg s original formulation of the uncertainty principle may be written as @xmath105 ignoring numerical factors .
it is well known that one can heuristically understand this result as reflecting the momentum transferred to the particle by a probing photon .
however , such a statement must be viewed as a postulate , with no rigorous foundation in the underlying mathematical structure of quantum theory .
indeed , as a postulate , it has recently been shown to be manifestly false , both theoretically @xcite and experimentally @xcite . despite this , the heuristic derivation of eq .
( [ hup_xp ] ) may be found in many older texts , alongside the more rigorous derivation of eq .
( [ sup ] ) from basic mathematical principles ( see , for example , @xcite ) .
unfortunately , it is not always made clear that the quantities involved in each expression are different , as clarified by the pioneering work of ozawa @xcite .
an excellent discussion of the various possible meanings and ( often confused ) interpretations of symbols like ` @xmath106 ' is given in @xcite . throughout the rest of this paper , unless explicitly stated , we consider only uncertainties of the form @xmath104 , defined in eq .
( [ sd ] ) , and uncertainty relations derived from the general formula eq .
( [ sup ] ) .
unfortunately , eq . ( [ sup ] ) is also sometimes referred to as the generalized uncertainty principle or generalized uncertainty relation ( see , for example , @xcite ) . to avoid confusion , throughout this paper we use the term _ general _ uncertainty principle to refer to the most general uncertainty relation obtained from the hilbert space structure of standard non - relativistic quantum mechanics ( for arbitrary operators ) and the term _ generalized _ uncertainty principle to refer to the amended uncertainty relation for position and momentum in non - canonical theories .
the compton wavelength is defined as @xmath107 and first appeared historically in the expression for the compton cross - section in the scattering of photons off electrons .
subsequently , it has arisen in various other contexts and it is important to distinguish these when discussing how the expression for the compton wavelength is modified in higher - dimensional models . the reduced compton wavelength @xmath108 appears naturally in the klein - gordon and dirac equations but the non - reduced expression is relevant in processes which involve turning photon energy ( @xmath109 ) into mass ( @xmath110 ) .
other arguments associate the compton wavelength with the _ localisation _ of a particle and this will be relevant when we come to discuss the modifications required with extra dimensions . generally speaking ,
the arguments are of two types , involving either the relativistic energy - momentum relation , together with the de broglie relations , or the uncertainty principle for position and momentum from non - relativistic quantum mechanics , together with some ` relativistic ' arguments of a more dubious nature .
we briefly review the former argument in sec .
[ sec.3.1 ] , for the sake of completeness , but it is the latter which chiefly concerns us in this paper and its primary deficiencies are discussed in detail in sec .
[ sec.3.2 ] . in sec .
[ sec.3.3 ] , we present an original alternative argument for identifying the maximum possible uncertainty in the momentum @xmath111 with the rest mass of the particle in order to obtain a minimum value of the position uncertainty @xmath112 .
[ sec.3.4 ] gives some additional comments about the relation between the compton and schwarzschild lines in the standard 3-dimensional case .
the relativistic energy - momentum relation is @xmath113 , where @xmath114 is the magnitude of the particle s @xmath12-momentum , @xmath23 is its rest mass and @xmath115 is the lorentz factor .
one interpretation of the compton wavelength formula is that when @xmath116 , the particle possesses sufficient energy to pair - produce copies of itself and its antiparticle .
combining this condition with the de broglie relation @xmath117 and @xmath118 gives @xmath119 , so we require @xmath120 to prevent this .
thus @xmath14 acts as a fundamental barrier beyond which pair - production occurs rather than further localization of the wave packet of the original particle . while it is true that the particle has sufficient energy to produce copies of itself for @xmath121 , it is also necessary that both the @xmath12-momentum in a given inertial frame and the @xmath122-momentum in any inertial frame are conserved for physically allowed transitions .
additional quantum numbers may need to be conserved , depending on the particle s properties and the precise details of the quantum field theory that describes its interactions .
an allied argument uses the fact that , in order to determine some physical property of a quantum particle , we must probe it using another kind of quantum particle . the simplest example is probing a particle of rest mass @xmath23 with a photon in order to determine its position . when the photon energy is greater than twice the rest energy of the particle whose position we wish to determine , @xmath123 , the interaction may again result in pair - production of particles of rest mass @xmath23 , rather than further localization of the original wave packet @xcite .
the same caveats hold as before , regardless of what type of particle we probe or probe with .
likewise , it is well known that attempts to confine a particle within a radius less than its compton wavelength result in pair - production @xcite , even if the energy required is derived from a confining potential ( rather than a probe particle ) , as required for the resolution of the klein paradox @xcite .
thus @xmath14 sets the distance scale at which qft becomes essential for understanding the behavior of a particle of a given rest mass , regardless of how we localize it @xcite . in summary
, while the de broglie wavelength marks the scale at which non - relativistic quantum effects become important and the classical concept of a particle gives way to the idea of a wave packet , the compton wavelength marks the point at which relativistic quantum effects become significant and the concept of a single wave packet corresponding to a state in which the particle number remains fixed becomes invalid @xcite .
@xmath14 is an effective minimum width because , on smaller scales , the concept of a single quantum mechanical particle breaks down and we must switch to a field description in which particle creation and annihilation occur in place of further spatial localization .
if one assumes that nothing can travel faster than the speed of light , then the momentum of a particle of rest mass @xmath23 is bounded by @xmath31 in newtonian theory .
the uncertainty principle then implies that the particle can not be localised on a scale less than the compton wavelength to within a numerical factor .
more precisely , if @xmath124 , then the relations @xmath125 yield @xmath126 since the momentum of a particle is _ not _ bounded by @xmath31 in relativity , the numerical factor is imprecise .
neveretheless , there are strong theoretical reasons , stemming from detailed calculations in quantum field theory , as well as compelling observational evidence @xcite , for believing that this argument is at least qualitatively correct . unfortunately , the above derivation is purely heuristic and has no rigorous mathematical foundation .
one problem is that the mass @xmath23 of a particle is a parameter in non - relativistic quantum mechanics and _ not _ an operator , so we can not identify it with either the expectation value @xmath127 or the standard deviation @xmath128 of _ any _ operator @xmath75 . even if identifying @xmath31 with the expectation value of the momentum operator @xmath129 for a given wave packet _ were _
permissible , there is no guarantee that the corresponding standard deviation @xmath98 would be of the same order of magnitude . for example
, it is possible to imagine a wave packet defined by a very narrow peak , centred at @xmath130 , but with spread @xmath131 .
however , from the general formula for @xmath74 we see that @xmath132 , which implies @xmath133 if @xmath134 and @xmath135 .
this may be expected for a wave function that is symmetric , or almost symmetric , about @xmath136 .
one would expect a similar result for ( almost ) spherically symmetric wave packets in any number of dimensions , with @xmath98 being replaced by @xmath137 , and this scenario is considered in detail in sec .
[ sec.3.3 ] .
we wish to place the identifications ( [ ident ] ) on a firmer theoretical footing , so that we may apply the same logic to quantum systems in a higher - dimensional space with compact extra dimensions . this will enable us to derive approximate results for such a scenario _ without _ the need for detailed qft calculations in higher - dimensional spacetimes with compact extra dimensions . in a non - relativisitic theory ,
the inequality @xmath138 may be obtained by combining the non - relativistic expression for the @xmath12-momentum , @xmath139 with a maximum speed @xmath140 . in conjunction with the de broglie relations , @xmath141 eq .
( [ 3-mom ] ) implies @xmath142 and , using @xmath143 , we again recover eq .
( [ compton ] ) .
however , since the speed limit is put in by hand , _ without _ introducing additional relativistic effects , such as lorentz invariance , the compton limit ( [ compton ] ) must also be inserted by hand as a lower bound on the de broglie wavelength of the position operator eigenfunctions .
likewise , the constraint ( [ k^2_bound ] ) must be imposed as an upper bound on the wavenumber of momentum operator eigenfunctions .
mathematically , this can be achieved by defining position and momentum operators , @xmath144 and @xmath145 , and their eigenfunctions in the position space representation , in the usual way , @xmath146 and then introducing an infrared cut - off in the expansion for @xmath147 in terms of @xmath148 or for @xmath149 in terms of @xmath150 : @xmath151 these integrals being zero for @xmath152 . in the momentum space representation , @xmath144 and @xmath145 and their eigenfunctions
take the form @xmath153 and consistency requires us to introduce an ultraviolet cut - off in @xmath154 : @xmath155 the ultraviolet cut - off , @xmath156 , implies an infrared cut - off , @xmath157 , and vice - versa , so that the extension of @xmath158 in position space is bounded from below by the compton wavelength , the extension of @xmath149 in @xmath154-space is bounded from above by the corresponding wavenumber , and the extension of @xmath159 in momentum - space is bounded by @xmath138 .
since @xmath160 and @xmath161 are scalars , we may write these as @xmath162 and @xmath163 , respectively , where @xmath164 and @xmath165 . for approximately spherically symmetric wave packets , we expect @xmath166 @xmath167 the commutator of @xmath144 and @xmath145 is @xmath168 = i\hbar \ , , \end{aligned}\ ] ] which implies @xmath169 by eq .
( [ sup ] ) . from eqs .
( [ r^2_sd])-([p^2_sd ] ) , it is therefore reasonable to make the identifications @xmath170 where we will henceforth refer to the compton wavelength as the compton radius and restrict consideration to quasi - spherically symmetric distributions , the precise meaning of this term being explained in sec .
[ sec.5 ] . under these conditions ,
the uncertainty relation for position and momentum _ does _ allow us to recover the standard expression ( [ compton ] ) .
thus , we have demonstrated that the existence of an effective cut - off for the maximum attainable energy / momentum in non - relativistic quantum mechanics implies the existence of a minimum attainable width for ( almost ) spherically symmetric wave functions , and this may be identified with the compton radius for @xmath124 . for non - spherically symmetric systems we may still consider the ( maximum ) upper bound on each momentum component , @xmath171 , as giving rise to a ( minimum ) lower bound for the spatial extent of the wave packet in @xmath172 spatial direction . as we shall also see in sec .
[ sec.5 ] , this has important implications for the physics of such systems in the presence of compact extra dimensions , and holds for all particles with masses @xmath4 . the argument given above is not the usual justification for the compton wavelength formula in non - relativistic quantum mechanics .
however , the compton radius clearly has a rigorous theoretical foundation in qft , as well as strong empirical support , and is best thought of in a relativistic context as marking the onset of pair - production , as discussed in sec .
[ sec.3.1 ] . even in a non - relativistic context ,
in which we do not assume the cut - offs used in eqs .
( [ r - space_exp ] ) and ( [ k - space_exp ] ) , @xmath173 still implies @xmath174 .
that is , if the width of the wavefunction in position space is less than the compton wavelength , its width in momentum space is larger than the rest mass multiplied by the speed of light .
this implies that the width of @xmath175 in energy space is of order or greater than the rest mass - energy of the particle @xmath176 . under these circumstances , a significant fraction of the measurements of @xmath177 in an ensemble of identically prepared systems will yield values @xmath178 , so it makes sense , even in the non - relativistic limit , to regard @xmath179 as a fundamental phenomenological barrier .
localizing the wave function of the particle on length scales @xmath180 ensures that the corresponding spread in momentum space , @xmath181 , is sufficient to yield a significant proportion of states with energies sufficiently high to produce pairs .
this is perhaps the best way to understand why the heuristic argument for the compton wavelength formula works , even though it represents an essentially relativistic result derived in a non - relativistic theory .
the advantage of the various non - relativistic arguments given above is that they can be readily extended to the higher - dimensional case with extra compactified dimensions .
the results obtained are phenomenologically robust , despite being ` derived ' in the approximate low - energy theory . the standard ( @xmath12-dimensional ) compton and schwarzschild lines transform into one another under both of the substitutions @xmath2 ( interchanging sub - planckian and super - planckian _ mass _ scales ) and @xmath182 ( interchanging sub - planckian and super - planckian _ length _ scales ) . in the log - log plot of fig .
[ mr ] , these correspond to reflections in the lines @xmath183 and @xmath42 , respectively .
there is an ambiguity in whether one interprets the schwarzschild line as a lower bound on the localization of mass _ outside _ a black hole @xcite or an upper bound on the localization of mass _ inside _ it @xcite . in the first case
, only the @xmath2 transformation correctly preserves the direction of the associated inequalities ; in the second case , only the @xmath182 transformation does so .
note that each line maps into itself , with the upper / lower and left / right half - planes interchanging , under the combined t - duality transformation @xmath184 t - dualities arise naturally in string theory and are known to map momentum - carrying string states to winding states and vice - versa @xcite .
in addition , since they map sub - planckian length scales to super - planckian ones , switching to the dual description for @xmath185 allows the description of physical systems in an otherwise inaccessible regime @xcite .
though it is unclear what role t - duality may play , at a fundamental level , in relating point particles and black holes , these considerations reinforce the suggestion that there may be such a connection .
the black hole boundary in fig .
[ mr ] assumes there are three spatial dimensions but many theories , including string theory , suggest that dimensionality could increase on sufficiently small scales @xcite . for simplicity , we first assume that the extra dimensions are associated with a single length scale @xmath7 . if the number of extra dimensions is @xmath6 , then , in the newtonian approximation , the gravitational force between two masses @xmath186 and @xmath187 is @xmath188 where @xmath189 is the higher - dimensional gravitational constant and @xmath190 is the number of spacetime dimensions in the relativistic theory .
this becomes @xmath191 for @xmath192 , so one recovers the inverse - square law there .
the higher - dimensional nature of the gravitational force is only manifest for @xmath193 .
this follows directly from the fact that general relativity can be extended to an arbitrary number of dimensions , so we may take the weak field limit of einstein s field equations in @xmath194 dimensions to obtain the newtonian gravitational potential generated by a mass @xmath23 as @xcite @xmath195 for @xmath193 .
this becomes @xmath196 for @xmath192 . in the newtonian limit ,
the effective gravitational constants at large and small scales are different because of the dilution effect of the extra dimensions .
there are two interesting mass scales associated with the length scale @xmath7 : the mass whose compton wavelength is @xmath7 , @xmath197 and the mass whose schwarzschild radius is @xmath7 , @xmath198 these mass scales are reflections of each other in the line @xmath37 .
an important implication of eq .
( [ v1 ] ) is that the usual expression for the schwarzschild radius no longer applies for masses below @xmath199 .
if the black hole is assumed to be ( approximately ) spherically symmetric in the higher - dimensional space on scales @xmath200 , the expression for @xmath15 must be replaced with @xmath201 where @xmath202 therefore , the slope of the black hole boundary in fig .
[ mr ] becomes shallower for @xmath203 .
strictly speaking , the metric associated with eq .
( [ higherbh ] ) is only valid for infinite extra dimensions , since it assumes asymptotic flatness @xcite . for black hole solutions with compact extra dimensions
, one must ensure periodic boundary conditions with respect to the compact space . however , eq . ( [ higherbh ] ) should be accurate for black holes with @xmath204 , so we adopt this for the entire range @xmath205 as a first approximation .
similar problems arise , even in the newtonian limit , since eq .
( [ v2 ] ) is also only valid for infinite extra dimensions and does not respect the periodicity of the internal space . in practice , we expect any corrections to smooth out the line around @xmath206 , so that the true metric yields the asymptotic forms corresponding to the schwarzschild radius of a @xmath61-dimensional black hole on scales @xmath207 and a @xmath208-dimensional black hole on scales @xmath204 . this behavior is indicated in fig .
2(a ) for various values of @xmath6 . the intersect with the compton boundary (
assuming this is unchanged ) then becomes @xmath209 this gives @xmath210 and @xmath211 for @xmath212 but @xmath213 and @xmath214 for @xmath215 . in principle , @xmath216 could be of order @xmath217 tev , making it accessible by the large hadron collider ( lhc ) . according to standard arguments
@xcite , this would allow quantum gravity effects to be detectable in accelerator experiments , providing @xmath218 clearly , @xmath219 is excluded on empirical grounds but @xmath220 is possible .
one expects @xmath221 in m - theory @xcite , so it is interesting that @xmath7 is of order a fermi if all of these dimensions extend beyond the planck scale .
@xmath222 cm as @xmath223 since this is the smallest scale which can be probed by the lhc .
the above analysis assumes that all the extra dimensions have the same size .
one could also consider a hierarchy of compactification scales , @xmath224 with @xmath225 , such that the dimensionality progressively increases as one goes to smaller distances @xcite .
in this case , the effective _ average _ length scale associated with the compact internal space is @xmath226 and the new effective planck scales are @xmath227 @xmath228 where @xmath229 and @xmath230 . for @xmath231 , the effective schwarzschild radius is then given by @xmath232 this situation is represented in fig .
clearly , the planck scales are not changed as much in this case as in the scenario for which the @xmath6 extra dimensions all have the same scale . [ mr2 ] the relationship between the various key scales ( @xmath233 ) in the above analysis is illustrated in fig .
[ fig7 ] for the case of one extra spatial dimension ( @xmath219 ) .
this suggests that the duality between the compton and schwarzschild length scales is lost if one introduces extra spatial dimensions .
however , this raises the issue of whether the expression for the standard compton wavelength should also be modified in the higher - dimensional case and we now address this .
we argue that , in this scenario , a phenomenologically important length scale is the _ effective _ compton wavelength , which may be identified with the minimum effective width ( in @xmath12-dimensional space ) of the higher - dimensional wave packet @xmath234 .
in this section , we consider whether the effective compton wavelength in a ( @xmath235)-dimensional spacetime with @xmath6 compact dimensions scales like @xmath236 , as in the @xmath12-dimensional case , or according to a different scaling law . if we use the term in the sense discussed in sec . 3 , to describe the localisabiity of a particle , we find that this depends crucially on the degree to which the wave packet of the particle is ` pancaked ' in the extra dimensions , i.e. on the degree of asymmetry between its size in the infinite and compact dimensions . in 3-dimensional space with cartesian
coordinates @xmath237 , the uncertainty relations for position and momentum are @xmath238 for spherically symmetric distributions , we have @xmath239 where the axes are arbitrarily orientated , so that the relations ( [ 3d_urz ] ) are each equivalent to @xmath240 in @xmath10 spatial dimensions , we also have @xmath241 so that for distributions that are spherically symmetric with respect to the three large dimensions we obtain @xmath242 the exponent on the right is @xmath243 , rather than @xmath72 , because there is only _ one _ independent relation associated with the large spatial dimensions due to spherical symmetry . assuming , for simplicity , that the extra dimensions are compactified on a single length scale @xmath7 , then spherically symmetric wave functions are only possible on scales @xmath244 in position space or @xmath245 in momentum space . in this case , we may identify the standard deviations in the extra dimensions ( i.e. in both position and momentum space ) with those in the infinite dimensions , @xmath246 for all @xmath247 , so that eq .
( [ ( 3+n)-d_ur_combined ] ) reduces to ( [ 3d_ur_sphersymm ] ) . following the usual identifications
, this gives the standard expression for the compton wavelength in a higher - dimensional context .
however , this is not the only possibility .
the condition of spherical symmetry in the three large dimensions implies that the directly observable part of @xmath175 is characterized by a single length scale , the 3-dimensional radius of the wave packet @xmath248 .
one can therefore consider states for which the wave function occupies a ( @xmath243)-dimensional volume and define a length scale @xmath249 as the _ average _ radius across these @xmath243 dimensions : @xmath250 this volume is of special interest because it is the only one that can be constructed from all @xmath243 _ independent _ length scales associated with the wave packet .
+ in this scenario , @xmath251 and @xmath252 , for at least some @xmath247 .
such states may be considered ` quasi - spherical ' in the sense that they are spherically symmetric with respect to the three large dimensions but pancake - shaped ( and possibly extremely irregular ) from the higher - dimensional perspective .
they are also degenerate with fully spherically symmetric wave packets of radius @xmath249 , in that they are associated with the same length scale . in this case
, we have @xmath253 where @xmath254 denotes the spread of the wave function in the three infinite dimensions of momentum space .
this relation comes from combining the _ single _ independent 3-dimensional uncertainty relation , associated with the large dimensions , with the @xmath6 independent uncertainty relations associated with the compact dimensions . with respect to the full @xmath10-dimensional space , the wave packet need not be spherically symmetric .
let us now restrict ourselves to states for which @xmath255 where the @xmath256 are dimensionless constants satisfying @xmath257 this ensures that @xmath258 and restricts us to the higher - dimensional region of the @xmath25 diagram
. conditions ( [ ( 3+n)-d_ur ] ) then reduce to @xmath259 which together with eq .
( [ x ] ) ensures @xmath260 note that the @xmath256 have no intrinsic relation with the constants @xmath261 used to characterize the hierarchy of length scales in sec .
[ sec.4 ] , and we are still considering the case in which all extra dimensions are compactified on a single length scale @xmath7 .
they simply paramaterize the degree to which each extra dimension is ` filled ' by the wave packet ( e.g. if @xmath262 , the physical spread of the wave packet in the @xmath172 extra dimension is @xmath263 ) .
were we to consider a similar parameterization in the hierarchical case , it would follow immediately that @xmath264 .
equation ( [ ( 3+n)-d_ur*1 ] ) now becomes @xmath265^{1/(1+n ) } \ , .\end{aligned}\ ] ] the validity of this bound is subject to the quasi - spherical symmetry condition ( [ volume ] ) but it is _ stronger _ than the equivalent condition ( [ 3d_ur_sphersymm ] ) for fully spherically symmetric states . by definition ,
such a wave packet is also quasi - spherically symmetric in momentum space , in the sense that it is spherically symmetric with respect to three infinite momentum dimensions , but not with respect to the full @xmath10-dimensional momentum space . for fully spherically symmetric states
, we must put each @xmath256 equal to a single value @xmath266 , where @xmath267 and @xmath268 for the 3-dimensional part of the wave function because the momentum space representation @xmath269 is given by the fourier transform of @xmath270 .
hence , a wave function that is totally spherically symmetric in the @xmath72 dimensions of position space will also be totally spherically symmetric in the @xmath72 dimensions of momentum space .
therefore , considering spherically symmetric wave functions with @xmath271 and @xmath272 ( corresponding to @xmath273 ) just restores the standard compton formula in a higher - dimensional context . for quasi - spherically symmetric states , defined by eq .
( [ ( 3+n)-d_ur_combined * * ] ) with @xmath274 for at least some @xmath247 , the volume occupied by the particle in the @xmath6 extra dimensions of momentum space is @xmath275 in these states , this volume remains fixed but the total volume also depends on the 3-dimensional part @xmath181 , which may take any value satisfying eq .
( [ ( 3+n)-d_ur_combined * * ] ) . the underlying physical assumption behind the mathematical requirement of fixed extra - dimensional volume
is discussed further in sec .
[ sec.5.2 ] . however , the idea is that , since the extra - dimensional space can only be probed indirectly for example , via high - energy collisions between particles whose momenta in the compact directions can not be directly controlled the net effect of any interaction is likely to leave the total extra - dimensional volume occupied by the wave packet unchanged , even if its 3-dimensional part can be successfully localized on scales below @xmath7 .
this is the mathematical expression of the fact that we have no control over the extra - dimensional part of _ any _ object - including that of the apparatus used to probe a ` test ' higher - dimensional system . as such , complete spherical symmetry in the full higher - dimensional space
can not be guaranteed and the most natural assumption is that asymmetry persists between the 3-dimensional and extra - dimensional parts of the wave function . since @xmath276 we have @xmath277 where @xmath278 is defined by eq .
( [ r * ] ) . restricting ourselves to the higher - dimensional region of the @xmath25 diagram , @xmath279
we see that , for @xmath280 , this gives @xmath281 for _ any _ choice of the constants @xmath256 , with the extreme limits @xmath282 and @xmath283 corresponding to @xmath284 and @xmath285 , respectively .
the first of these corresponds to the scenario @xmath286 , which recovers the standard planck length bound on the minimum radius of a planck mass particle . in other words ,
if _ all _ the extra dimensions are compactified on the planck scale , both the standard @xmath12-dimensional compton and schwarzschild formulae hold all the way down to @xmath263 , giving the familiar intersect .
however , if @xmath287 , then @xmath288 for a planck mass particle is larger than the planck length and may be as large as the critical value @xmath289 .
this occurs when the higher - dimensional part of the wave packet completely ` fills ' the extra dimensions . in general ,
the upper bound on the minimum value of @xmath249 occurs when the wave packet is space - filing in the compact directions and each of these is compacified on some scale @xmath287 . at @xmath280 ,
this gives @xmath283 , which lies in the range @xmath290 . for @xmath291 ,
the same scenario gives @xmath292 , which corresponds to the effective 3-dimensional region of the @xmath25 plot . in this region ,
the assumption of quasi - sphericity breaks down and the 3-dimensional and higher - dimensional parts of the wave packet effectively decouple with respect to measurements which are unable to probe the length / mass scales associated with the extra dimensions .
we may therefore set @xmath293 as the strongest _ lower _ bound on @xmath249 , since this is the _ upper _ bound on the value of @xmath288 .
to reiterate , this comes from combining two assumptions : ( a ) the wave function of the particle is quasi - spherically symmetric in the sense of eq .
( [ volume ] ) with respect to the _ entire _ higher - dimensional space on scales @xmath294 ; and ( b ) wave packet is space - filling in the @xmath6 additional dimensions of position space .
note that the unique 3-dimensional uncertainty relation and each of the @xmath6 independent uncertainty relations for the compact directions still hold individually .
however , the higher - dimensional uncertainty relations are satisfied for any choice of the constants @xmath256 in the range specified by eq .
( [ x ] ) and the remaining 3-dimensional relation @xmath295 is satisfied automatically for any @xmath181 satisfying eq .
( [ ( 3+n)-d_ur_combined * * ] ) . in the limit @xmath285 for all @xmath247 ,
in which the wave packet completely fills the compact space , it is straightforward to verify that @xmath296 when @xmath297 , so that the 3-dimensional and @xmath10-dimensional formulae match seamlessly
. thus , for @xmath298 , we have @xmath299 but the genuine 3-dimensional radius of the wave packet is of order @xmath300 and , for @xmath301 , we have @xmath302 . under these conditions , the 3-dimensional uncertainty relation is superseded , as a lower bound on the value of @xmath249 , by the limit obtained by combining _
all _ the bounds arising from each of the separate uncertainty relations , so that @xmath303 it straightforward to demonstrate that all the inequalities in this subsection hold in the range @xmath304 , which corresponds to @xmath305 in eq .
( [ inequalityseries ] ) .
we now make the identifications ( [ p_ident ] ) , so that @xmath306 this implies that , when extrapolating the usual arguments for the compton wavelength in non - relativistic quantum theory to the case of compact extra dimensions , we should identify the _ geometric average _ of the spread of the wave packet in @xmath243 spatial dimensions with the particle radius , but its spread in the large dimensions of momentum space with the rest mass .
however , there is clearly a problem with identifying the standard deviation of the _ total _ higher - dimensional momentum , @xmath307 , with the rest mass of the particle .
since the standard deviations of the individual extra - dimensional momenta are bound from below by @xmath308 , we have @xmath309 .
also , pair - production is avoided for @xmath310 , so @xmath311 is required for consistency . since @xmath7 must be very small to have avoided direct detection
, @xmath312 must be large and the above requirement contradicts known physics as it requires _ all _ known particles to have masses @xmath313 .
likewise , were we to associate @xmath314 with a single length scale via the usual up , the minimum value of the standard deviation of the total higher - dimensional position vector @xmath315 would be bounded from above by @xmath316 , which automatically rules out the existence of particles larger than the extra dimensions .
the manifest asymmetry of the wave packet in position space on scales less than @xmath7 ( and on scales greater than @xmath317 in momentum space ) therefore _ requires _ identifications of the form eq .
( [ p_ident ] ) in order for the standard compton formula to hold for @xmath318 in a higher - dimensional setting .
what happens to the standard formula below this scale is unclear .
if the wave packet is able to adopt a genuinely spherically symmetric configuration in the full higher - dimensional space ( including momentum space ) , then the above arguments suggest the identifications @xmath319 and @xmath320 for @xmath321 , so that the usual compton formula holds all the way down to @xmath322 .
the possible short - comings of this approach are that it would be valid only for spherically symmetric states and that it requires a change in the identification of the rest mass and particle radius at @xmath323 , i.e. @xmath324 and @xmath325 , where @xmath248 and @xmath254 denote 3-dimensional quantities , as before .
as wave packets will generally be asymmetric on scales @xmath318 , it is reasonable to assume that the asymmetry will persist , even when we are able to ( indirectly ) probe length / energy scales associated with the extra dimensions .
for example , suppose that we try to localize a particle in 3-dimensional space by constructing a spherically symmetric potential barrier .
we then gradually increase the steepness of the potential well , increasing the energy and localizing the particle on ever smaller length scales . in principle
, we may even shrink the 3-dimensional radius below the scale of the internal space .
but what about the width of the wave packet in the compact directions ?
since we did not design our initial potential to be spherically symmetric in @xmath72 spatial dimensions having no direct manipulative control over its form in the extra dimensions it is difficult to imagine that we would suddenly obtain a fully spherically symmetric potential in higher - dimensional space , simply by increasing the energy at which our ` measuring device ' operates .
similarly , we may imagine confining a particle within a spherically symmetric region of 3-dimensional space by bombarding it with photons from multiple angles .
increasing the energy of the photons then reduces the radius of the sphere . but how can we control the trajectories of the probe photons in the internal space ?
since , again , in the compact space , we do not have direct manipulative control over the apparatus that creates the photons , it is impossible to ensure anything other than a random influx of photons ( with random extra - dimensional momenta ) in the @xmath6 compact directions . in this case
, we would expect to be able to measure the average photon energy and to relate this to a single _ average _ length scale , but we can not ensure exact spherically symmetry with respect to all @xmath72 dimensions , or measure the spread of the wave packet in each individual extra dimension .
na " ively , we may expect the single ( measured ) length scale to be given by the geometric average over all @xmath72 dimensions , @xmath326^{1/(3+n)}$ ] , for wave packets that are spherically symmetric in the large directions but irregular in the compact space .
however , the arguments proposed above suggest that the key length scale is @xmath327^{1/(1+n)}$ ] , with only independent uncertainty relations contributing to the composite measurement .
this makes sense , since it is obvious that , were we able to isolate our measurements of the 3-dimensional part of the wave packet , this would yield only a single length scale @xmath248 ; any ` smearing ' of this measurement due to the spread of the wave packet in the extra dimensions must be due to the @xmath6 additional _ independent _ widths , @xmath328 . in the most extreme case
, we may expect the combined effects of our experimental probing of the extra dimensions to cancel each other out , leaving the total volume of the wave packet in the compact space unchanged .
this justifies eq .
( [ volume * ] ) but does not alter the reduction of the 3-dimensional volume and , hence , of the _ overall _ volume of the wave packet , when the energy of the probe particles / potential barrier is increased .
together , these considerations lead to the scaling predicted by eq .
( [ hd_compton+ ] ) . as eq .
( [ hd_compton+ ] ) corresponds to the maximum possible asymmetry for which a single length scale can be associated with @xmath175 , this should give the highest possible lower bound on the size of a quantum mechanical particle in a spacetime with @xmath6 compact extra dimensions .
thus , the problem of defining a single quantum radius for a particle in a semi - compactified higher - dimensional space is analogous to the problem of defining a single radius for asymmetric wave packets in the 3-dimensional case .
quantum states expected to give rise to highly asymmetric wave packets include those corresponding to spinning particles , which should form a pancake in both position and momentum space .
hence , it may be necessary , even in a 3-dimensional context , to modify the standard expression for the compton wavelength for such states to give more than one characteristic length scale ( with differing rest mass dependences ) , corresponding to the widths of the particle in , for example , the directions parallel and perpendicular to the spin axes .
a related question is , how can we ascribe a wave function @xmath175 to a black hole with a schwarzschild radius @xmath329 ( cf .
casadio @xcite ) ? in the classical theory , with only infinite dimensions ,
a schwarzschild black hole is the unique spherically symmetric vacuum solution @xcite .
however , in the quantum mechanical case , our previous analysis suggests that it may be possible to associate multiple quasi - spherically symmetric wave packets with the unique classical solution , just as we can for classical ( spherically symmetric ) point particles .
the investigation of both these points lies beyond the scope of this paper and is left for future work .
finally , if we interpret the compton wavelength as marking the boundary on the @xmath330 ) diagram below which pair - production rates becomes significant , we expect the presence of compact extra dimensions to affect pair - production rates at high energies .
specifically , we expect pair - production rates at energies above the ( lower ) mass scale associated with the compact space , @xmath331 , to be enhanced relative to the 3-dimensional case .
this is equivalent to ` raising ' the compton line , i.e. decreasing its ( negative ) gradient on the @xmath25 diagram .
a more detailed , fully relativistic , analysis would be needed to confirm whether this is a generic result for massive scalar fields ( corresponding to uncharged matter ) .
however , there is tentative theoretical evidence that enhanced pair - production may be a generic feature of higher - dimensional theories in which some directions are compactified ( see , for example , @xcite ) but the available literature on this subject is sparse . to summarize our results for higher - dimensional black holes and fundamental particles , we have @xmath332 @xmath333 for @xmath6 extra dimensions compactified on a single length scale @xmath7 , and these lines intersect at @xmath334 , where @xmath335 when @xmath287 .
the crucial point is that there is no tev quantum gravity in this scenario since the intersect of the compton and schwarzschild lines still occurs at @xmath322 .
the effective planck length is reduced to @xmath289 but this does not allow the production of higher - dimensional black holes at accelerators .
thus , the constraint ( [ nconstraint ] ) on the scale @xmath7 in the conventional picture no longer applies .
also , whereas the lhc probes the full higher - dimensional space in the standard case , it only probes the fourth spatial dimension ( or , at most , a subset @xmath336 of the available extra dimensions ) if the bhup correspondence remains valid in higher dimensions .
[ mr3 ] this scenario is illustrated in fig .
3(a ) for extra dimensions compactified on a single length scale @xmath7 and in fig .
3(b ) for a hierarchy of length scales . in the latter case , the expressions ( [ hd_compton*])-([hd_schwarz ] )
must be modified to @xmath337 @xmath338 where @xmath339 is the largest compact dimension and @xmath340 is defined in eq .
( [ effectiveschwarz ] ) .
in this section , we define an ` intrinsic ' temperature for a fundamental particle whose mass is localized within a _ minimum _ radius @xmath14 and compare this to the hawking temperature of a black hole , whose mass is localized within a _ maximum _ radius @xmath15 .
we then consider heuristic derivations of both temperatures in the 3-dimensional case using the hup .
finally , these arguments are extended to the higher - dimensional case , using the uncertainty relations for quasi - spherically symmetric wave packets derived in sec .
[ sec.4 ] . in 3-dimensional space
, we may use the usual mass - temperature relation @xmath341 to define the ` compton temperature ' of a fundamental particle , @xmath342 where @xmath343k is the planck temperature .
( in this section all equations are order of magnitude relations . )
this may be interpreted as the ` rest mass temperature ' of a particle localized within a radius @xmath344 .
equation ( [ t_c ] ) is consistent with the uncertainty principle ( [ 3d_ur_sphersymm ] ) together with the identifications @xmath345 hence , the compton temperature is the _ maximum _ temperature for a particle at rest , in the sense that the associated temperature would be lower than @xmath346 if its wave packet were localized on some scale @xmath347 .
this may be compared with the hawking temperature of a black hole of mass @xmath23 and radius @xmath15 in three dimensions , @xmath348 this expression is consistent with the uncertainty principle , using the relations @xmath349 note that here we identify the _ maximum _ possible spatial extent of the wavefunction with the schwarzschild radius .
this is based on the assumption that it is associated with a ( classical ) point - like mass at the central singularity which is causally disconnected from the region beyond @xmath15 .
it is therefore impossible to localize the mass of the black hole on scales @xmath350 , since the horizon is a global feature of spacetime .
this may be contrasted with the fundamental particle case , in which the mass can not be localized on scales @xmath351 .
hence @xmath352 may be interpreted as the _ minimum _ temperature for a black hole from the perspective of an external observer , in the sense that , were the mass of the black hole to be localized on a smaller scale ( e.g. due to a fluctuation in the horizon size ) , the temperature of the horizon would increase .
clearly , the hawking and compton temperatures coincide at @xmath322 , giving @xmath353 . in general
, they are dual under the transformation @xmath354 in this analysis , we assume that the mass scale @xmath355 marks a division between elementary particles and a black holes , so that the expressions for the compton and hawking temperature only apply for @xmath356 and @xmath357 , respectively . in a scenario
in which there is no such division , so that elementary particles can be interpreted as sub - planckian black holes , @xmath346 would itself be interpreted as a hawking temperature @xcite .
the situation changes radically in the higher - dimensional case .
if all the extra dimensions have the same compactification scale @xmath7 , then the hawking temperature is modified to @xcite @xmath358 here @xmath359 is the @xmath10-dimensional planck mass , given by eq .
( [ revisedplanck ] ) , and the second relationship follows from the definitions @xmath360 the higher - dimensional hawking temperature line now intersects the 3-dimensional compton temperature eq .
( [ t_c ] ) line at @xmath361 , giving @xmath362 as the revised planck temperature . in refs .
@xcite , eq .
( [ t_h_hd ] ) was derived from the relations @xmath363 where @xmath364 , which reduce to eq .
( [ t_h_ident ] ) for @xmath71 .
the @xmath23 dependence could also be obtained from the surface gravity , since this scales as @xmath365 . as discussed in sec .
[ sec.5 ] , we expect the usual 3-dimensional uncertainty principle to hold all the way to the planck point @xmath366 for particle wave packets that are spherically symmetric with respect to all @xmath72 spatial dimensions . for black hole wave functions that are totally spherically symmetric in the @xmath10-dimensional space on scales @xmath367 , one might therefore expect standard identifications like ( [ t_h_ident+ ] ) to be valid if one makes the substitutions @xmath368 , @xmath369 , where @xmath370 and @xmath314 denote the uncertainties in the _ total _
@xmath10-dimensional position and momentum , respectively .
however , in sec .
[ sec.5.2 ] , the total spherical symmetry of the wave packet in @xmath72 dimensions led us to identify the particle rest mass with the maximum value of the uncertainty for the total higher - dimensional momentum , @xmath371 .
this resulted in inconsistencies ( i.e. to all known particles having masses @xmath311 and radii @xmath372 ) .
likewise , the total spherical symmetry of the black hole wave packet in @xmath72 dimensions suggests the identification @xmath373 , which implies that all black holes should have @xmath374 and @xmath375 , thus rendering the @xmath61-dimensional part of the @xmath25 diagram inaccessible . the solution ( as before ) is to consider seriously the manifest asymmetry between the 3-dimensional and extra - dimensional parts of the wave packet and to combine the individual uncertainty relations for each dimension to obtain eq .
( [ ( 3+n)-d_ur_combined***a ] ) for quasi - spherically symmetric systems . applying this to ` particles ' with masses @xmath5 ( i.e. black holes ) leads us to identify @xmath376 with the _
3-dimensional _ part of the wave function .
clearly , this gives the standard expression ( [ higherbh ] ) for @xmath15 in @xmath208-dimensional spacetime .
then the identification @xmath377 recovers the expression for the higher - dimensional hawking temperature derived in refs .
@xcite . for fundamental particles in higher - dimensional space
, this suggests the identifications @xmath378 which reduces to eq .
( [ t_c_ident ] ) for @xmath71 .
together with @xmath379 , this leads to @xmath380 this is the only definition which is consistent with our previous argument that the particle rest mass should be identified with the 3-dimensional part of the momentum spread for a quasi - spherical symmetric wave packet , so that eqs .
( [ t_c_ident ] ) , ( [ x ] ) and ( [ ( 3+n)-d_ur_combined***a ] ) are self - consistent . in this scenario , the lines corresponding to the higher - dimensional compton and hawking temperatures in the @xmath25 diagram now intersect at @xmath322 , giving @xmath381 .
physically , we may interpret this as implying that , even with compact extra dimensions , evaporating black holes form planck mass relics with radii of order @xmath382 and temperatures @xmath383 .
this suggests that , in the quantum mechanical description , attempts to either increase or decrease the energy of the relics , always increase the radius of the corresponding wave packet above @xmath289 , while the temperature always increases .
the crucial difference is that particle / anti - particle pairs are absorbed in the former case , creating a schwarzschild black hole , whereas , in the latter , mass - energy is carried away by the pair - production of particles and the relic itself becomes a particle , with no event horizon .
furthermore , these actions are symmetric , in that a mass shift of fixed magnitude results in corresponding ( fixed ) changes in radius and temperature .
alternatively , our picture suggests that attempts to localize the relic wave packet on scales @xmath384 will result in pair - production of fundamental particles , whereas attempts to localize it on scales @xmath385 lead to the production of microscopic black holes . in other words , we can multiply particles by squashing them and black holes by pulling them apart . although the results obtained above assume that the extra dimensions are compactified on a single cale @xmath7 , we note that similar arguments apply when there is a hierarchy of compactification scales . in this case
@xmath386 , defined in eq .
( [ t * ] ) , is replaced by @xmath387 , where @xmath388 , in all relevant formulae , which are then valid for @xmath231 , or the equivalent mass range , as before .
in this section we consider two possible observational consequences of retaining the duality between the compton and schwarzschild expressions .
the first relates to the detectability of exploding primordial black holes ( pbhs ) .
there is still no unambiguous detection of such explosions but it has been claimed that some short - period gamma - ray bursts could be attributed to pbhs @xcite . the second relates to high - energy scattering experments and the enhancement of pair - production at at accelerators on scales below @xmath7 . in the standard ( @xmath71 ) model ,
pbhs complete their evaporation at the present epoch if they have an initial @xmath389 g and an initial radius @xmath390 cm , comparable to the size of a proton @xcite . for most of their lifetime these pbhs are producing photons with energy @xmath391 mev , so the extragalactic @xmath392-ray background at this energy places strong constraints on the number of such pbhs and thereby their current explosion rate . in principle , these pbhs could also contribute to cosmic - ray positrons and antiprotons , although there are other possible sources of these particles @xcite .
if there are @xmath6 extra dimensions , each with compactification scale @xmath7 , then the mass and temperature of a pbh terminating its evaporation today will change if the critical radius @xmath393 is less than @xmath7 . from eq .
( [ t_h_hd ] ) and the higher - dimensional black - body formula , the mass loss rate should then be @xmath394 leading to a black hole lifetime @xmath395 thus the critical mass of the pbhs evaporating at the present epoch and the associated temperaure become @xmath396 so both the critical mass and the associated temperature are increased compared to the @xmath12-dimensional case ( @xmath71 ) .
if there is a hierarchy of extra dimensions , the value of @xmath6 in the above equations must be replaced by @xmath397 , which is the dimensionality for which @xmath398 ( @xmath336 ) .
this means that the standard limits on their number density must also be changed , though we do not discuss this further here .
an important point from an observational perspective is that the black holes evaporating at the present epoch are necessarily higher dimensional if @xmath399 cm . in the tev quantum gravity scenario , for example ,
( [ nconstraint ] ) implies @xmath399 cm providing @xmath400 .
this condition is necessarily satisfied in m - theory because the maximum number of compactified dimensions is @xmath401 .
figure 4 shows the @xmath25 diagram for a scenario in which there are three compactified dimensions . in the case of compactified extra dimensions
, another uncertainty arises due to the fact that quanta emitted in the compact directions may simply be reabsorbed due to the periodic boundary conditions .
[ mr3 ] we now consider the consistency of our phenomenologically general results with respect to the leading higher - dimensional theory of fundamental physics : string theory .
in particular , we focus on their consistency with minimum - radius results for higher - dimensional , non - relativistic and quantum mechanical particle - like objects , known as @xmath16-particles .
the end points of open strings obey neumann or dirichlet boundary conditions ( or a combination of both ) and are restricted to @xmath62-dimensional submanifolds , where @xmath403 , called @xmath63-branes .
although these are composite rather than fundamental objects , they have dynamics in their own right and an intrinsic tension @xmath404 , where @xmath405 denotes the string coupling and @xmath406 is the fundamental string length scale @xcite .
thus , @xmath407-branes , also referred to as @xmath16-particles , are point - like , and possess internal structure only on scales @xmath408 .
this may be seen as the analogue of the compton wavelength in @xmath407-brane models of fundamental particles . at high energies
, strings can convert kinetic into potential energy , thereby increasing their extension and counteracting attempts to probe smaller distances .
therefore , the best way to probe @xmath63-branes is by scattering them off each other , instead of using fundamental strings as probes @xcite .
@xmath16-particle scattering has been studied in detail by douglas _
et al _ @xcite , who showed that slow moving @xmath16-particles can be used to probe distances down to @xmath409 in @xmath410 spacetime dimensions .
this result may be obtained heuristically as follows @xcite .
let us consider a perturbation of the metric component @xmath411 induced by the newtonian potential @xmath412 of a higher - dimensional particle of mass @xmath23 .
in @xmath16 spacetime dimensions , this takes the form @xmath413 where @xmath106 is the spatial extension of the particle and @xmath189 is the @xmath16-dimensional newton s constant , so that the horizon is located at @xmath414 ( for convenience , we set @xmath415 throughout this section . ) in spacetimes with @xmath6 compact spatial dimensions , this is related to the @xmath61-dimensional newton s constant via @xmath416 , so that , for @xmath190 , we simply recover the formula for the higher - dimensional schwarzschild radius ( [ higherbh ] ) .
however , we may also use eq .
( [ dpart-2 ] ) to derive the minimum length obtained from @xmath16-particle scattering in @xcite by first setting @xmath417 , where @xmath418 is the time taken to test the geometry , and instead using the higher - dimensional newton s constant derived from string theory , @xmath419 @xcite .
this gives @xmath420 combining this with the spacetime uncertainty principle , which is thought to arise as a consequence of the conformal symmetry of the @xmath63-brane world - volume @xcite , @xmath421 we then have @xmath422 for @xmath410 , this gives @xmath423 , as claimed .
combining results from string theory and higher - dimensional general relativity by setting @xmath424 with @xmath425 , we obtain @xmath426 which gives @xmath427 as the modified planck length for @xmath428 .
in fact , eqs .
( [ dpart-5])-([dpart-6 ] ) suggest that the minimum positional uncertainty for @xmath16-particles _ can not _
be identified with the modified planck length obtained from the intersection of the higher - dimensional schwarzschild line , @xmath429 , and the standard compton line , @xmath430 , in any number of dimensions .
hence , the standard scenario is _ incompatible _ with @xmath16-particle scattering results .
however , it is straightforward to verify that , if @xmath431 , we have @xmath432 , so that the intersection of the higher - dimensional schwarzschild and compton lines is equal to the minimum length scale that can be probed by @xmath16-particles . in this scenario , @xmath433 , and we note that @xmath434 for @xmath435 , as required for consistency , but , in general , @xmath436 ( or equivalently @xmath287 ) , requires @xmath437 .
we have addressed the question of how the effective compton wavelength of a fundamental particle defined as the minimum possible positional uncertainty over measurements in _ all _ dimensions scales with mass if there exist @xmath6 extra compact spatial directions . in @xmath61-dimensional spacetime , the compton wavelength scales as @xmath430 , whereas the schwarzschild radius scales as @xmath438 , so the two are related via @xmath439 . in higher - dimensional spacetimes with @xmath6 compact extra dimensions , @xmath429 on scales smaller than the compactification radius @xmath7 , which breaks the symmetry between particles and black holes if the compton scale remains unchanged .
however , we have argued that the effective compton scale , defined in terms of minimum positional uncertainty , depends on the form of the wavefunction in the higher - dimensional space . if this is spherically symmetric in the three large dimensions , but maximally asymmetric ( i.e. pancaked ) in the full @xmath72 spatial dimensions , then the effective radius scales as @xmath440 rather than @xmath236 on scales less than @xmath7 and this preserves the symmetry about the @xmath322 line in ( @xmath441 ) space . in this scenario ,
the effective planck length is reduced but the planck mass is unchanged , so quantum gravity and microscopic black hole production are associated with the standard planck energy , as in the 3-dimensional scenario . on the other hand , one has the interesting prediction that the compton line which marks the onset of pair - production is ` lifted ' , relative to the 3-dimensional case , in the range @xmath442 , so that extra - dimensional effects may become visible via enhanced pair - production rates for particles with energies @xmath443 .
this prediction may be consistent with minimum length uncertainty relations obtained from @xmath16-particle scattering amplitudes in string theory . also , as indicated in fig . 4
, the existence of extra compact dimensions has crucial implications for the detectability of black holes evaporating at the present epoch . since these have the size of a proton , they are _ necessarily _ higher - dimensional for @xmath399 cm .
our results naturally suggest a definition for the intrinsic ` quantum ' temperature of a fundamental particle , here referred to as the ` compton temperature ' , which is associated with the spatial localization of a particle s wave packet within a minimum ( i.e. compton ) radius .
this scales as @xmath444 in ( @xmath194)-dimensional spacetime . using the dimensional dependence of @xmath14 and @xmath15
, we find that this is related to the hawking temperature @xmath352 of a black hole via @xmath445 in arbitrary dimensions , so that a particle of mass @xmath4 has the same temperature as a black hole with dual mass @xmath446 .
the above analysis assumes that the compton and schwarzschild lines retain simple power - law forms until their intersection point in figs . 1 or 2(a)-(b ) .
no allowance is made for deviations from the hup , as postulated by the gup , and no attempt is made to smooth the transition at the planck point , as postulated by the bhup correspondence .
these effects would obviously entail different temperature predictions in the planck regime even in the @xmath12-dimensional case .
our main intention is to examine the consequences of the above analysis for the temperature predicted by the bhup correspondence in the higher - dimensional case . in this paper
, we have assumed that non - relativistic quantum mechanical particles obey the standard heisenberg uncertainty principle ( hup ) in each spatial direction .
the modified expression for the _ effective _ compton line , which retains a simple power - law form until its intersection with the higher - dimensional schwarzschild line in the ( @xmath441 ) diagram , is seen to arise from the application of the hup to maximally asymmetric wave functions .
these are spherically symmetric with respect to the three large dimensions but pancaked in the compact directions .
no allowance has been made for deviations from the hup , as postulated by various forms of generalised uncertainty principle ( gup ) , proposed in the quantum gravity literature , and no attempt has been made to smooth out the transition between particle and black hole states at the planck point , as postulated by the black hole uncertainty principle ( bhup ) correspondence @xcite . as discussed in a separate paper @xcite , these effects would entail different temperature predictions in the planck regime even in the @xmath12-dimensional case .
our main intention here has been to examine the consequences of the existence of extra dimensions in the ` standard ' ( i.e. hup - based ) scenario .
* acknowledgments * we thank the research center for the early universe ( resceu ) , university of tokyo , for hospitlaity received during this work .
we thank pichet vanichchapongjaroen , shingo takeuchi and tiberiu harko for helpful discussions during the preparation of the manuscript .
we have three dichotomies for the physical systems discussed in this paper : classical / quantum , non - relativistic / relativistic and weak - gravitational / strong - gravitational .
this gives @xmath36 possible regimes , according to the values of different combinations of the characteristic mass @xmath447 , length @xmath448 and time @xmath449 scales of the system considered .
these are shown below , together with examples of physical formulae from the corresponding regime : systems that fall within the ranges described by eqs .
( [ class ] ) , ( [ non - rel ] ) and ( [ non - grav ] ) can be classified as classical , non - relativistic and weakly - gravitational .
these include all systems described by newton s laws in the absence of gravity .
systems described by newtonian gravity fall into the ranges specified by eqs .
( [ class ] ) , ( [ non - rel ] ) and ( [ grav ] ) , etc .
systems for which @xmath453 can be adequately described by classical equations of motion via the correspondence principle @xcite and we can ignore relativistic effects in systems with @xmath454 . the formulae on the right - hand side of eq .
( [ non - grav ] ) refer to spherically symmetric bodies of mass @xmath23 and to cosmic strings of mass per unit length @xmath455 . for @xmath456 ,
the deficit angle of the spacetime surrounding the string core is small @xcite and for an observer at a distances @xmath457 from a spherically symmetric body , its gravitational field may be ignored .
fundamental particles typically fall into this category , since our observations are limited to the region @xmath458 , for @xmath58 .
hence , these may be described by quantum mechanics if they fall into the regimes specified by eqs .
( [ quant ] ) and ( [ non - rel ] ) or by quantum field theory if they fall into those specified by eqs .
( [ quant ] ) and ( [ rel ] ) .
quantum gravity applies to systems lying within the ranges specified by eqs .
( [ quant ] ) , ( [ rel ] ) and ( [ grav ] ) . to adequately illustrate each of the eight regimes , we would need to combine the @xmath25 diagrams used throughout this paper with a @xmath459-axis to give a 3-dimensional representation . in light of the discussion above
, the compton line may be seen as marking the boundary in the @xmath25 plane between the quantum@xmath460non - relativistic@xmath460weak - gravitational and the quantum@xmath460relativistic@xmath460weak - gravitational regimes , whereas the schwarzschild line marks the boundary between regions corresponding to the classical@xmath460non - relativisitic@xmath460strong - gravitational and classical@xmath460relativistic@xmath460strong - gravitational regimes .
the exception , for both lines , is the area around the point of intersection , close to the planck point @xmath366 , in which we expect quantum@xmath460relativisitic@xmath460strong - gravitational effects to become important .
b. carr , _ the black hole uncertainty principle correspondence _
, in 1st karl schwarzschild meeting on gravitational physics , eds .
p. nicolini , m. kaminski , j. mureika , m. bleicher , pp 159 - 167 ( springer ) , arxiv:1402:1427 ( 2015 ) .
j. polchinski , _ string theory .
1 : an introduction to the bosonic string _ , cambridge univ . pr . , cambridge ( 1998 ) .
p. kanti , _ black holes in theories with large extra dimensions : a review _ , int . j. mod .
a. 19 , 4899 - 4951 ( 2016 ) , arxiv : hep - ph/0402168 . n. arkani - hamed , s. dimopoulos and g. dvali . _ the hierarchy problem and new dimensions at a millimeter _ , phys .
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a 67 , 042105 , ( 1 - 6 ) ( 2003 ) , arxiv : quant - ph/0207121 . l. a. rozemat _ et al _ , _ violation of heisenberg s measurement - disturbance relationship by weak measurements _ , phys .
lett.109 , 100404 ( 2012 ) .
s. baek _ et al _ , _ experimental violation and reformulation of the heisenberg s error - disturbance uncertainty relation _
3 , 2221 ( 2013 ) .
e. scheibe , _ the logical analysis of quantum mechanics _ , pergamon press , oxford ( 1973 ) .
d. b. cline , d. a. sanders and w. hong , _ further evidence for gamma - ray bursts consistent with primordial black hole evaporation _
, astrophys .
j. * 486 * , 169 ( 1997 ) .
b. j. carr , k. kohri , y. sendouda and j. yokoyama , _ new cosmological constraints on primordial black holes _
d * 81 * , 104019 ( 2010 ) , arxiv:0912.5297 [ astro-ph.co ] .
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a * 4 * , 1587 ( 1989 ) ; t. yoneya , _ string theory and space - time uncertainty principle _ , prog .
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103 * , 1081 ( 2000 ) , hep - th/0004074 .
a. jevicki and t. yoneya , _ space - time uncertainty principle and conformal symmetry in d particle dynamics _ ,
b 535 , 335 ( 1998 ) , hep - th/9805069 . | in three spatial dimensions , the compton wavelength @xmath0 ) and schwarzschild radius @xmath1 ) are dual under the transformation @xmath2 , where @xmath3 is the planck mass .
this suggests that there is a fundamental link termed the black hole uncertainty principle or compton - schwarzschild correspondence between elementary particles in the @xmath4 regime and black holes in the @xmath5 regime . in the presence of @xmath6 extra dimensions ,
compactified on some scale @xmath7 , one expects @xmath8 for @xmath9 , which breaks this duality .
however , it may be restored in some circumstances because the effective compton wavelength depends on the form of the @xmath10-dimensional wavefunction .
if this is spherically symmetric , then one still has @xmath11 , as in the @xmath12-dimensional case . the effective planck length is then increased and the planck mass reduced , allowing the possibility of tev quantum gravity and black hole production at the lhc . however , if the wave function is pancaked in the extra dimensions and maximally asymmetric , then @xmath13 , so that the duality between @xmath14 and @xmath15 is preserved . in this case , the effective planck length is reduced but the planck mass is unchanged , so tev quantum gravity is precluded and black holes can not be generated in collider experiments .
nevertheless , the extra dimensions could still have consequences for the detectability of black hole evaporations and the enhancement of pair - production at accelerators on scales below @xmath7 .
though phenomenologically general for higher - dimensional theories , our results are shown to be consistent with string theory via the minimum positional uncertainty derived from @xmath16-particle scattering amplitudes .
@xmath17 @xmath18 _ @xmath19 the institute for fundamental study , the tah poe academia institute " , + naresuan university , phitsanulok 65000 , thailand + _ _ @xmath20 thailand center of excellence in physics , ministry of education , bangkok 10400 , thailand + _ _ @xmath21 astronomy unit , queen mary university of london , mile end road , london e1 4ns , u.k .
+ _
_ @xmath22research center for the early universe ( resceu ) , graduate school of science , + university of tokyo , tokyo 113 - 0033 , japan _ |
SECTION 1. SHORT TITLE.
This Act may be cited as the ``Save America's Jobs Act of 2002''.
SEC. 2. PREVENTION OF CORPORATE EXPATRIATION TO AVOID UNITED STATES
INCOME TAX.
(a) In General.--Paragraph (4) of section 7701(a) of the Internal
Revenue Code of 1986 (defining domestic) is amended to read as follows:
``(4) Domestic.--
``(A) In general.--Except as provided in
subparagraph (B), the term `domestic' when applied to a
corporation or partnership means created or organized
in the United States or under the law of the United
States or of any State unless, in the case of a
partnership, the Secretary provides otherwise by
regulations.
``(B) Certain corporations treated as domestic.--
``(i) In general.--The acquiring
corporation in a corporate expatriation
transaction shall be treated as a domestic
corporation.
``(ii) Corporate expatriation
transaction.--For purposes of this
subparagraph, the term `corporate expatriation
transaction' means any transaction if--
``(I) a nominally foreign
corporation (referred to in this
subparagraph as the `acquiring
corporation') acquires, as a result of
such transaction, directly or
indirectly substantially all of the
properties held directly or indirectly
by a domestic corporation, and
``(II) immediately after the
transaction, more than 80 percent of
the stock (by vote or value) of the
acquiring corporation is held by former
shareholders of the domestic
corporation by reason of holding stock
in the domestic corporation.
``(iii) Lower stock ownership requirement
in certain cases.--Subclause (II) of clause
(ii) shall be applied by substituting `50
percent' for `80 percent' with respect to any
nominally foreign corporation if--
``(I) such corporation does not
have substantial business activities
(when compared to the total business
activities of the expanded affiliated
group) in the foreign country in which
or under the law of which the
corporation is created or organized,
and
``(II) the stock of the corporation
is publicly traded and the principal
market for the public trading of such
stock is in the United States.
``(iv) Partnership transactions.--The term
`corporate expatriation transaction' includes
any transaction if--
``(I) a nominally foreign
corporation (referred to in this
subparagraph as the `acquiring
corporation') acquires, as a result of
such transaction, directly or
indirectly properties constituting a
trade or business of a domestic
partnership,
``(II) immediately after the
transaction, more than 80 percent of
the stock (by vote or value) of the
acquiring corporation is held by former
partners of the domestic partnership
(determined without regard to stock of
the acquiring corporation which is sold
in a public offering related to the
transaction), and
``(III) the acquiring corporation
meets the requirements of subclauses
(I) and (II) of clause (iii).
``(v) Special rules.--For purposes of this
subparagraph--
``(I) a series of related
transactions shall be treated as 1
transaction, and
``(II) stock held by members of the
expanded affiliated group which
includes the acquiring corporation
shall not be taken into account in
determining ownership.
``(vi) Other definitions.--For purposes of
this subparagraph--
``(I) Nominally foreign
corporation.--The term `nominally
foreign corporation' means any
corporation which would (but for this
subparagraph) be treated as a foreign
corporation.
``(II) Expanded affiliated group.--
The term `expanded affiliated group'
means an affiliated group (as defined
in section 1504(a) without regard to
section 1504(b)).''
(b) Modification of Rates of Corporate Tax.--
(1) In general.--The Secretary of the Treasury shall
prescribe rates of tax under section 11 of the Internal Revenue
Code of 1986 (relating to tax imposed on corporations) which
result in a net decrease in revenues for a taxable year equal
to the net increase in revenue (if any) for that year as a
result of the amendment made by subsection (a).
(2) Estimates and subsequent adjustments.--The rates of tax
prescribed under paragraph (1) shall be determined on the basis
of estimates made by the Secretary of the Treasury. Adjustments
shall be made in such rates for succeeding taxable years to the
extent prior estimates resulted in revenues which were in
excess of or less than the revenues required under paragraph
(1).
(c) Effective Dates.--
(1) In general.--The amendment made by this section shall
apply to corporate expatriation transactions completed after
September 11, 2001.
(2) Special rule.--The amendment made by this section shall
also apply to corporate expatriation transactions completed on
or before September 11, 2001, but only with respect to taxable
years of the acquiring corporation beginning after December 31,
2003. | Save America's Jobs Act of 2002 - Amends the Internal Revenue Code by determining that acquiring corporations in "corporate expatriation transactions" shall be considered domestic corporations. Defines a "corporate expatriation transaction" as, with certain exceptions, one in which a "nominally foreign corporation" acquires substantially all of the properties held by a domestic corporation and in which, immediately after the transaction, more than 80 percent of the stock of the acquiring corporation is held by former shareholders of the domestic corporation. Lowers the 80 percent threshold to 50 percent when the acquiring "nominally foreign corporation" lacks substantial business activities in the foreign country in which it was created and organized compared to the total activities of the "expanded affiliated group" and the stock is publicly traded, with the principal market of trading being the United States. Defines the terms "nominally foreign corporation" and "expanded affiliated group."Applies similar rules to partnership transactions.Establishes that a series of related transactions relevant to the Act shall be handled as a single transaction.Directs the Secretary of the Treasury to prescribe tax rates that result in a net decrease in revenues for a taxable year equal to any increase in revenue that occurs due to the implementation of this Act. |
ORLANDO, Fla. - A truck that sent a large piece of scrap metal flying off an Interstate 4 overpass and onto a minivan had its load properly secured, News4Jax sister station WKMG learned Monday from the Florida Highway Patrol.
Troopers are still investigating the crash but believe speed might have been a factor.
Now, 36-year-old Jesus Escobar, the man whose minivan became the target of a four-ton hunk of scrap metal that fell out of the toppled truck, is suffering from several injuries.
Escobar's lawyer, Dutch Anderson, said Escobar will spend at least the next three weeks of summer sitting inside of his home and wearing a brace around his collar because of a fractured neck. Anderson said he also had his head nearly scalped from the crash.
"He had a horrible laceration that goes from one side of his head to the other," he said.
Escobar was going to his construction job Saturday, traveling off of Interstate 4 and onto State Road 528 near Orlando, when, at the same time, the driver of the semitruck hauling scrap metal was traveling onto I-4. The truck driver hit a guardrail, the semi overturned and the huge hunk of metal fell off the overpass and on top the van below.
"Clearly, this is something that never should have happened," Anderson said.
Escobar woke up in a hospital, not remembering a thing. But he's thankful no one else was with him in his now mangled minivan, and no other vehicles were caught up in the crash, Anderson said.
"One of the first things he said to me," Anderson said, "was, 'I'm glad it was me.' And I was like like, 'Jesus, what do you mean you're glad it was you?' He said, 'That's the exit everybody takes to go to SeaWorld with their kids. So if it had been somebody with a family full of children, it would have been a catastrophe.'"
Now, the Escobar family attorney is hoping to reach a settlement.
The driver of the truck was cited for careless driving. He was driving a truck that had a logo on its side: Trademark Metals Recycling.
WKMG dug into the truck company's to see if its drivers have a history of careless driving. But a search of records with the U.S. Department of Transportation and Orange County Clerks office turned up nothing.
Trademark Metals Recycling has not returned messages seeking comment.
Copyright 2017 by WKMG ClickOrlando - All rights reserved. ||||| by: WFTV Web Staff Updated: Jul 16, 2017 - 12:21 PM
0
ORANGE COUNTY, Fla. - When 36-year-old Jesus Armando Escobar was exiting off Interstate 4 onto State Road 528, he had no idea what was about to happen on the overpass above him.
Antonio Santiago Wharton, 33, of Kissimmee, was driving a Mack truck loaded down with scrap metal at about 7:35 a.m. Saturday.
Related Headlines Pasco County sinkhole stops growing; residents grab belongings
As he negotiated the curve, he lost control of the truck, hit the guardrail and overturned the vehicle, the Florida Highway Patrol said.
© 2017 Cox Media Group. © 2017 Cox Media Group.
A 7,000 pound metal pipe flew off Wharton’s truck, tumbled off the overpass and landed squarely on the roof of Escobar’s Pontiac Van.
The force of the impact crushed the driver side roof of the van, troopers said.
Somehow, Escobar, the father of three, was able to walk away from the crash with only minor injuries.
If he had been sitting in any other seat, he would have likely been killed, officials said.
Theodore Olson, with AATR Orlando, said he's seen a lot of wrecks, but nothing like this.
"I've seen crushed cars before, but nothing in this kind of circumstance, where, like, they were up on on upper bridge and it rolled out of a container and crushed a car," Olson said. "I thought it was a fatality, to be honest with you. But they came out and said, 'Nope, he's only got scratches.'"
Wharton was ticketed for careless driving, troopers said.
Escobar was released from the hospital Saturday night. His wife told Channel 9's Lauren Seabrook that he doesn't remember the crash.
© 2017 Cox Media Group. ||||| A driver escaped serious injury after a heavy iron pipe from a truck crashed down on top of a van.
A driver escaped serious injury after a heavy iron pipe from a truck crashed down on top of a van.
Troopers said the truck driver, Antonio Wharton, took the curve too fast from the Beachline to I-4 West, hitting the barrier wall and tipping over.
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A huge iron pipe was dumeped over the side just as Jesus Escobar was driving on the ramp leaving I-4 west and heading toward the Beachline east.
Wharton was ticketed for careless driving.
"(You're) not expecting anything from the sky to fall down. You're looking for other vehicles, and here comes this scrap metal, boom, right on top of the car. By an absolute miracle, he survives." Trooper Steven Montiero said.
Troopers were amazed that Escobar was alert after the crash.
"That driver had just enough room in that driver compartment to walk away," Montiero said.
Dave McDaniel spoke on the phone Monday afternoon with Escobar's wife. She said he's exhausted and needs rest. She is consulting with an attorney.
Montiero was not working Saturday but simply happened to drive up on the scene and was stunned when he read the other troopers notes.
"That the driver of the van was alert and walking around. And he only had a little scratch on his forehead," Montiero said. "See something like this and expect this is not survivable. But, by the grace of God, this driver did survive that crash."
AlertMe | – Jesus Armando Escobar, 36, was exiting a Florida interstate on Saturday morning at the same time Antonio Santiago Wharton, 33, was driving a Mack truck loaded with scrap metal on the overpass above him. Wharton lost control of the truck going around the curve and it overturned, dumping a 7,000-pound metal pipe off the overpass and onto the roof of Escobar's van. Yet somehow, the father of three suffered only minor injuries—despite the fact that the roof of the van on the driver's side was crushed by the nearly four-ton piece of scrap metal, WFTV reports. "I thought it was a fatality, to be honest with you. But they came out and said, 'Nope, he's only got scratches,'" says a worker with AATR Orlando, a towing service. A state trooper who saw the scene and read other troopers' notes tells WESH Escobar was "alert and walking around" soon after the accident. Authorities say Escobar, who was released from the hospital the same day the accident happened, may have been killed had he been in any other seat. "That's the exit everybody takes to go to SeaWorld with their kids. So if it had been somebody with a family full of children, it would have been a catastrophe," Escobar's lawyer says Escobar, who doesn't remember the incident, told him. The lawyer tells News4Jax his client's injuries include a significant head laceration and a neck fracture that will keep him in a neck brace for weeks, and says the family is hoping to reach a settlement in the case. Wharton received a careless-driving ticket; the load was properly secured, but authorities are investigating whether speed was an issue. (In another miraculous incident, a new dad fell 47 stories and survived.) |
recently , in refs .
@xcite , it was suggested that the nontrivial topological charge of qcd vacuum , @xmath2 can be probed by measuring asymmetric electric currents , due to an event - by - event @xmath9- and @xmath10-violation , in the non - central heavy - ion collision experiments such as rhic , fair , and lhc .
their main idea is that unequal numbers of the chirally left- and right - handed quarks , @xmath11 proportional to the @xmath2 in terms of the axial ward - takahashi identity @xcite , can produce the asymmetric electric current under a strong magnetic field @xmath12 . interestingly enough , a possible experimental evidence was already reported by star collaboration at rhic @xcite .
moreover , in ref .
@xcite , using the lattice qcd simulation , the electromagnetic ( em ) current fluctuation as well as local chirality were explored at finite @xmath8 , resulting in that the fluctuations become insensitive to the external magnetic field as @xmath8 increases . in ref .
@xcite , it was also shown that the electric current , induced by the external magnetic field with the nontrivial @xmath2 , reads @xmath13 where the @xmath14 represents the chiral chemical potential and contains the information on the @xmath2 inside of it .
in fact , this is a consequence of the em axial anomaly @xcite . in the present report , based on our previous work @xcite
, we investigate the cme at low @xmath8 , employing the instanton vacuum configuration with the nontrivial @xmath2 , which relates to the finite instanton - number fluctuation , i.e. the number difference between the instantons and anti - instantons in the grand canonical ensemble , @xmath15 resulting in the @xmath10-violation . to this end , we first write the effective action derived from the instanton vacuum configuration as a functional of @xmath1 @xcite . using generic functional external - source and linear schwinger methods ,
we compute the relevant physical quantities , the vacuum expectation values of the local chiral density @xmath3 , chiral charge density @xmath16 , em current @xmath17 , induced by the external magnetic field . in order to consider the @xmath8-dependence of the relevant quantities , we also employ the harrington - shepard caloron to obtain the @xmath8-dependent constituent - quark mass .
fianlly , the standard fermionic matsubara formula is taken into account for the anti - perioidc sum over the euclidean time , i.e. @xmath8 .
we consider all the relevant physical quantities up to @xmath18 .
in this section , we briefly introduce a @xmath9- and @xmath10-violating effective action @xmath19 , derived by diakonov _
et al . _ from the instanton vacuum configuration in the large @xmath20 limit at zero temperature ( @xmath21 ) @xcite .
employing a dilute grand canonical ensemble of the ( anti)instantons with a finite instanton - number fluctuation , @xmath22 , which corresponds to a @xmath10-violating vacuum , but a fixed total number of the pseudo - particles @xmath23 , the @xmath19 can be written in momentum space with euclidean metric as follows : @xmath24f^{2}(k ) } { \rlap{/}{k}-im}\right],\end{aligned}\ ] ] from the effective action , we can obtain the following two self - consistent ( saddle - point ) equations with respect to the @xmath25 : @xmath26,\end{aligned}\ ] ] where the @xmath25 is approximated as @xmath27 in the last line of eq .
( [ eq : sdp ] ) with account of the fact @xmath28 in the thermodynamic limit @xcite .
the momentum - dependent constituent - quark mass is defined as @xmath29 @xcite . by adding and subtracting the instanton @xmath30 and anti - instanton ( @xmath31 ) contributions in eq .
( [ eq : sdp ] ) , we can obtain an expression for @xmath32 as a function of relevant parameters : @xmath33 taking into account all the ingredients discussed so far , finally , we can write the relevant effective action with @xmath34 for further investigations : @xmath35,\end{aligned}\ ] ] where the @xmath36 denotes the trace over color , flavor and lorentz indices . according to the axial ward - takahashi identity @xcite
, the @xmath2 is proportional to the number difference between the chirally left- and right - handed quarks , @xmath37 .
hence , the nontrivial @xmath2 indicates the chirality flip .
note that , similarly , if a chirally left - handed quark is scattered from an instanton to an anti - instanton , the quark helicity is flipped to the right - handed one , and vice versa .
this means that the nonzero @xmath1 results in @xmath38 . in this way
, the @xmath2 can be considered to be proportional to the @xmath1 : @xmath39 @xcite .
the @xmath32 in eq .
( [ eq : del ] ) can be rewritten in terms of a real and small parameter @xmath40 , which satisfies the condition @xmath41 , for convenience as follows : @xmath42
in this section , we compute relevant physical quantities for the cme in the presence of the external magnetic field , using the effective action given in the last section .
they are the vacuum expectation values ( v.e.v . ) of the local chiral density @xmath43 , chiral charge density @xmath44 , and electromagnetic ( em ) current @xmath45 , which are defined as follows : @xmath46 the @xmath43 and @xmath44 represent the strength of the parity breaking in a system , whereas the @xmath45 here the em current induced by the external magnetic field .
it is very convenient to compute these quantities employing the effective action with corresponding pseudoscalar ( @xmath47 ) , axial vector ( @xmath48 ) , and vector ( @xmath49 ) external sources .
hence , the effective action can be rewritten as : @xmath50,\ ] ] where @xmath51 with @xmath52 and @xmath53 .
the @xmath54 indicates the covariant quark momentum , gauged by the photon field as @xmath55 .
note that we have written the external sources @xmath47 and @xmath56 , which correspond to the @xmath43 and @xmath44 , to be proportional to the @xmath32 , since they signal the nontrivial topological charge @xmath2 as the parity - breaking quark mass @xmath57 does .
first , we calculate the v.e.v . of the chiral density , using the standard functional method as follows : @xmath58\gamma_{5 } \right\},\ ] ] where we have performed the trace of over the color and flavor indices .
since we are interested in the response of the nonperturbative vacuum to the external magnetic field for the nonzero topological charge @xmath2 , we only collect the terms proportional to the @xmath32 and the photon field strength tensor @xmath59 . in order to perform the trace over the lorentz index in the r.h.s .
( [ eq : cd1 ] ) under the external em field , we employ the linear schwinger method @xcite . according to that , the quark propagator in the presence of the instanton background can be written up to @xmath60 , which is equivalent up to @xmath61 , as follows : @xmath62 } { k^{2}+(1+\delta^{2})m^{2 } } \cr & \times & \left[1-\frac{\tilde{m}(\sigma\cdot f)+i\left(1-\frac{\delta}{4}\gamma_{5 } \right)\hat{m}(k)\gamma_{\mu}k_{\nu}f_{\mu\nu}-2i\delta m\gamma_{5}\rlap{/}{k}}{k^{2}+(1+\delta^{2})m^{2}}\right].\end{aligned}\ ] ] here , @xmath63 .
we define relevant functions related to the momentum - dependent quark mass : @xmath64 after a straightforward trace manipulation , one arrives at a simple expression for the chiral density : @xmath65 where the subscripts @xmath66 and @xmath32 in the l.h.s . of eq .
( [ eq : cd2 ] ) indicate the fact that we picked up only the terms proportional to the @xmath59 and @xmath32 as explained above . in deriving eq .
( [ eq : cd2 ] ) , to make the problem easy , we assumed a static external em field , which is assigned for example as in ref .
@xcite : @xmath67 where the external em field consists of the classical ( @xmath68 ) in the symmetry gauge and fluctuation ( @xmath69 ) parts .
we take the @xmath70 as small and constant em potentials . among the em field strength tensors ,
@xmath71 and its dual remain finite , while others disappear .
the relevant integral @xmath72 in eq .
( [ eq : cd2 ] ) reads : @xmath73^{2}},\ ] ] as understood from eq .
( [ eq : cd2 ] ) , the parity breaking of the vacuum becomes enhanced quadratically with respect to the @xmath32 and @xmath74 .
similarly to the @xmath43 , we can compute the v.e.v . of the chiral charge density as follows : @xmath75\gamma_{4}\gamma_{5}\right\}.\ ] ] by solving eq .
( [ eq : ccd1 ] ) and picking up relevant terms , one is lead to a compact expression for it as follows : @xmath76 where we have used the fact that only the @xmath77 is nonzero in our symmetric - gauge em field . from eq .
( [ eq : ccd2 ] ) , we observe that the chiral charge density increases linearly with respect to the @xmath32 as well as the @xmath74 .
the integral @xmath78 is written as : @xmath79^{2}}.\ ] ] finally , we attempt to compute the v.e.v . of the em current , induced by the external magnetic field in the presence of the nontrivial topological charge : @xmath80\gamma_{\mu}\right\}.\ ] ] expectedly , we can obtain a very similar expression for the @xmath81 to that for the v.e.v .
of the chiral charge density : @xmath82(ia_{\nu})\mathcal{f}_{b},\end{aligned}\ ] ] where the definition of the @xmath78 is the same with that given in eq .
( [ eq : fb ] ) .
considering eq .
( [ eq : emc2 ] ) and assuming finite values for @xmath83 , we can write the induced em currents for @xmath84 separately for its transverse ( @xmath85 ) and longitudinal ( @xmath86 ) components : @xmath87 the @xmath88 increases linearly as the @xmath74 grows , which is the indication of the cme as in eq .
( [ eq : emc ] ) . equating the transverse and longitudinal components
, we have the ratio as follows : @xmath89 from eq .
( [ eq : jjj ] ) , if we assume that @xmath90 along the @xmath91-direction , in other words , the strengths of the fluctuations @xmath70 in eq .
( [ eq : a ] ) are almost the same to each other , it is obvious that the transverse components of the induced em current are much smaller than those of the longitudinal ones , @xmath92 , due to the fact that @xmath93 .
this tendency is just consistent with that given in the recent lattice qcd simulation @xcite .
considering the general expression for the induced em current in eq .
( [ eq : emc ] ) , the induced em current along the @xmath91-direction in eq .
( [ eq : joa ] ) can be rewritten as @xmath94b_{0},\ ] ] and gives the following expression for the chiral chemical potential , @xmath95 comparing eqs .
( [ eq : ccd2 ] ) and ( [ eq : joa ] ) , it can be easily shown that the v.e.v .
of the chiral charge density is the same with the third and fourth components of the induced em current in the leading contributions in @xmath32 : @xmath96 where we have used the result from eq .
( [ eq : jjj2 ] ) .
( [ eq : na ] ) for @xmath97 is consistent with that given in refs .
@xcite for a homogeneous magnetic field .
to investigate the physical quantities in hand at low but finite temperature ( @xmath98 ) , we want to discuss briefly how to modify the instanton variables , @xmath99 and @xmath100 at finite @xmath8 .
we will follow our previous work @xcite and refs .
@xcite to this end .
we write the instanton distribution function at finite @xmath8 with the hs caloron as follows : @xmath101.\ ] ] using the instanton distribution function in eq .
( [ eq : ind ] ) , we can compute the average value of the instanton size , @xmath102 straightforwardly as follows @xcite : @xmath103^{\frac{1}{2 } } -a_{n_c}t^2}{2\bar{\beta}\gamma n},\ ] ] where @xmath104 . substituting eq .
( [ eq : rho ] ) into eq .
( [ eq : ind ] ) , the distribution function can be evaluated further as : @xmath105,\,\,\,\ , \mathcal{m}(t)=\frac{1}{2}a_{n_c}t^2+\left[\frac{1}{4}a^2_{n_c}t^4 + \nu\bar{\beta}\gamma n \right]^{\frac{1}{2}}.\ ] ] finally , in order to estimate the @xmath8-dependence of the constituent - quark mass @xmath106 , it is necessary to consider the normalized distribution function , defined as follows : @xmath107}{\gamma(\nu)}.\ ] ] now , we want to employ the large-@xmath108 limit to simplify the expression of @xmath109 . since the parameter @xmath110 becomes infinity as @xmath111 , and the same for @xmath112 . in this limit , as understood from eq .
( [ eq : nid ] ) , @xmath109 can be approximated as a @xmath32-function @xcite : @xmath113.\ ] ] considering the constituent - quark mass is represented by @xcite @xmath114 = \sqrt{n(t)}\,\bar{\rho}^{2}(t),\ ] ] we can modify the @xmath106 as a function of @xmath8 as follows : @xmath115\equiv m_{0}(t)\ ] ] where we will use @xmath116 mev as done for zero @xmath8 .
first , we present the numerical results for the local chiral density @xmath117 in eq .
( [ eq : cd2 ] ) as a function of @xmath74 in the left panel of fig . [ fig2 ] .
there , we depict them for different temperatures , @xmath118 mev , separately . as a trial , we choose @xmath119 , which gives @xmath120 in eq .
( [ eq:44 ] ) . in other words ,
the @xmath9- and @xmath10-violation effects are about @xmath121 in comparison to non - violating quantities . moreover , since the @xmath3 is almost linearly proportional to @xmath122 , one can easily estimate it for different @xmath40 ( or @xmath32 ) values .
obviously as shown in the figure , the @xmath123 grows rapidly with respect to @xmath74 , manifesting the cme . as @xmath8 increases , the strength of the curve decreases . at the same time ,
the slope of the curve , @xmath124 , gets smaller .
this tendency means that the @xmath117 becomes insensitive to the external magnetic field as @xmath8 gets higher , and the same for the cme .
the reason for this tendency can be understood by the decreasing instanton effect . in the right panel of fig .
[ fig2 ] , we show the @xmath117 as a function of @xmath8 for different strengths of the magnetic fields , @xmath125 . as shown there , the strength of a curve depends on that of the magnetic field .
as @xmath8 increases , the @xmath117 becomes small , indicating that the instanton effect is reduced .
in other words , decreasing tunneling effect corresponding to @xmath126 . thus , unless there is another mechanism to make the @xmath2 nontrivial , such as the sphaleron , the @xmath117 as well as the cme decrease monotonically with respect to @xmath8 for a finite @xmath74 value .
interestingly , the @xmath117 decreases much faster for the larger @xmath74 value , since the @xmath8-dependence of the quantity becomes more obvious and strengthened .
[ cols="^,^ " , ]
in the present report , we have investigated the chiral magnetic effect ( cme ) .
we have observed the followings : * the transverse em current induced by the external magnetic field is far smaller than that of the longitudinal one , @xmath127 , and their ratio is proportional to @xmath32 , @xmath128 @xcite .
* we obtain a relation such that the strength of the chiral charge density is the same with that of the induced em current in the @xmath91- and @xmath129-directions : @xmath130 as long as the lorentz invariance remains unbroken @xcite . * the correct relation between the fourth component of the em field and the the chiral chemical potential
is found : @xmath131 . *
the cme , represented by the local chiral density and induced em current , becomes insensitive to the external magnetic field as @xmath8 increases .
this can be understood by that the instanton , i.e. tunneling effect gets diminished with respect to @xmath8 : @xmath126 @xcite . *
the local chiral density and induced em current as functions of @xmath8 decrease faster for the larger external magnetic field , since the decreasing instanton effect is strengthened . for more details on the present report
, one can refer ref .
this report is prepared for the proceeding for the international workshop _ hadron and nuclear physics _ ( hnp2009 ) , 16@xmath13219 nov 2009 , osaka , japan .
the author appreciate the hospitality during his stay at rcnp , osaka university , japan , and the financial support from a. hosaka of rcnp .
he also thanks k. fukushima , m. m. musakhanov , and c. w. kao for fruitful discussions .
this work was supported by the nsc96 - 2112-m033 - 003-my3 from the national science council ( nsc ) of taiwan .
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b * 203 * , 299 ( 1988 ) . | in this talk , we report our present work on the chiral magnetic effect ( cme ) under a strong magnetic field @xmath0 at low temperature . to this end
, we use the instanton vacuum with the finite instanton - number fluctuation @xmath1 , which relates to the nontrivial topological charge @xmath2 .
we compute the vacuum expectation values of the local chiral density @xmath3 , chiral charge density @xmath4 and induced electromagnetic current @xmath5 .
we observed that the longitudinal em current is much larger than the transverse one , @xmath6 , and the @xmath4 equals to the @xmath7 .
it also turns out that the cme becomes insensitive to the magnetic field as @xmath8 increases , since the instanton effect decreases . |
SECTION 1. SHORT TITLE.
This Act may be cited as the ``Rural Health Outreach Grants
Amendments Act''.
SEC. 2. ESTABLISHMENT OF PROGRAM OF GRANTS FOR RURAL HEALTH OUTREACH.
Title III of the Public Health Service Act (42 U.S.C. 241 et seq.)
is amended by adding at the end the following new part:
``Part P--Rural Health Outreach Grant Program
``SEC. 399B. RURAL HEALTH OUTREACH GRANT PROGRAM.
``(a) In General.--The Secretary may make grants to demonstrate new
and innovative models of outreach and health care services delivery in
rural areas that lack basic health services. Grants will be awarded for
one of the following: direct provision of health services to rural
populations (especially for those who are not currently receiving those
services), or to enhance access to and utilization of existing
available services.
``(b) Missions of the Outreach Projects.--Projects under subsection
(a) should be designed to address the needs of a wide range of
populations living in rural communities including, but not limited to,
the poor, farmers, farm workers, senior citizens, individuals with
disabilities, pregnant women, infants, adolescents, and rural
populations with special health care needs. The program could include
projects to:
``(1) Provide, enhance, or revitalize emergency medical
services in rural communities.
``(2) Provide ambulatory health and/or mental health
services in health professional shortage areas and in frontier
areas.
``(3) Enhance the health and safety of farmers through
direct health services for farm families, and migrant and
seasonal farm workers.
``(4) Provide direct health services to enhance health care
services to senior citizens.
``(5) Provide direct health services that will reduce
infant mortality in rural communities.
``(c) Composition of Program.--
``(1) Consortium arrangements.--Participation in the
program established in subsection (a) requires the formation of
consortium arrangements among three or more separate and
distinct entities to carry out an outreach project.
``(2) Certain requirements.--
``(A) A consortium under paragraph (1) must be
composed of three or more existing health care
providers or a combination of three or more health care
and social service providers. Consortium members may
include such entities as: hospitals, public health
agencies, home health providers, mental health centers,
rural health clinics, social service agencies, health
profession(s) schools, educational institutions,
emergency medical centers/providers, and community and
migrant health centers.
``(B) All public and private entities, both
nonprofit and for-profit may participate as members of
a consortium arrangement under paragraph (1).
``(C) A grant under subsection (a) will be made to
only one entity in a consortium under paragraph (1).
The grant recipient must be a nonprofit or public
entity which meets one of the following requirements:
``(i) Applicants must be located outside of
a Metropolitan Statistical Area as defined by
the Federal Government.
``(ii) Applicant must be located in a rural
census tract. (This provision applies to
counties that are technically classified as
Metropolitan Statistical Areas or considered as
part of a Metropolitan Statistical Area but
large parts of the counties are rural.)
Organizations located in the rural areas of the
counties mentioned previously are eligible for
participation in the program.
``(d) Review Criteria.--An outreach application under this section
may be evaluated based on the following criteria:
``(1) The extent to which the applicant has proposed a new
and innovative approach to health care in the rural area.
Services shall be directed as population groups that are
unserved or underserved.
``(2) The extent to which the applicant has justified and
documented the needs for the project and developed measurable
goals for meeting the needs.
``(3) The extent to which the applicant has clearly defined
the roles and responsibilities for each member of the
consortium and developed a workable plan for managing the
consortium's activities.
``(4) The level of local commitment and involvement with
the project, including the extent of cost participation by the
applicant and/or other organizations.
``(5) The feasibility of the project to continue after
Federal grant support is completed.
``(6) The extent of the evaluation component.
``(e) How Project Funds Are To Be Expended.--
``(1) Grantees under subsection (a) will be required to use
at least 85 percent of the total amount awarded for outreach
and care services.
``(2) 60 percent of funds must be spent in rural areas.
This provision is designed accordingly--when a consortium is
purchasing goods and services, priority should be given to
purchases in rural areas.
``(3) Grant funds may not be used for purchase,
construction, or renovation of real property or to support the
delivery of inpatient services.
``(4) Grant funds may be used for equipment and vehicles
when such equipment is essential to carrying out the outreach
project.
``(5) Individual grant awards will be limited to a total
amount of $300,000 per year. Projects will be federally funded
for three years.
``(6) Applicants must demonstrate that existing levels of
institutional and other support are not reduced or supplanted
by the availability of these grant funds.
``(f) Authorization of Appropriations.--For the purpose of carrying
out this section, there are authorized to be appropriated $25,000,000
for fiscal year 1994, and such sums as may be necessary for each fiscal
year thereafter.''. | Rural Health Outreach Grants Amendments Act - Amends the Public Health Service Act to authorize grants to demonstrate new and innovative models of outreach and health care services delivery in rural areas that lack basic health services.
Conditions grants on formation of consortia of at least three health care providers or at least three social service providers.
Authorizes appropriations. |
SECTION 1. SHORT TITLE.
This Act may be cited as the ``Declaration of Official Language Act
of 2001''.
SEC. 2. ENGLISH AS OFFICIAL LANGUAGE.
(a) In General.--Title 4, United States Code, is amended by adding
at the end the following new chapter:
``CHAPTER 6--LANGUAGE OF THE GOVERNMENT
``Sec.
``161. Declaration of official language.
``162. Preserving and enhancing the role of the official language.
``163. Duties of citizenship.
``164. Reform of naturalization requirement.
``165. Exceptions.
``166. Preemption.
``167. Construction.
``168. Enforcement.
``169. Prohibition.
``Sec. 161. Declaration of official language
``English is the official language of the Government of the United
States.
``Sec. 162. Preserving and enhancing the role of the official language
``The Government of the United States shall preserve and enhance
the role of English as the official language of the United States of
America. Unless specifically stated in applicable law, no person has a
right, entitlement, or claim to have the Government of the United
States or any of its officials or representatives act, communicate,
perform or provide services, or provide materials in any language other
than English. If exceptions are made, that does not create a legal
entitlement to additional services in that language or any language
other than English.''.
``Sec. 163. Duties of citizenship
``All United States citizens should be encouraged to read, write,
and speak English to the extent of their physical and mental abilities.
``Sec. 164. Reform of naturalization requirements
``(a) It has been the long-standing national belief that full
citizenship in the United States requires fluency in English. English
is the language of opportunity for all immigrants to take their
rightful place in American society.
``(b) The Immigration and Naturalization Service shall--
``(1) enforce the established English language proficiency
standard for all applicants for United States citizenship, and
``(2) conduct all naturalization ceremonies entirely in
English.
``Sec. 165. Exceptions
``This chapter does not apply to the use of a language other than
English for--
``(1) religious purposes,
``(2) training in foreign languages for international
communication,
``(3) use of non-English terms of art in government
documents,
``(4) law enforcement, or
``(5) scientific terminology.
``Sec. 166. Preemption
``This chapter preempts any Federal law, regulation, policy
guidance, agency ruling or determination, or any other Federal action
or policy which is inconsistent with this chapter.
``Sec. 167. Construction
``This Act is not intended to affect programs in schools designed
to encourage students to learn foreign languages.
``Sec. 168. Enforcement
``(a) Cause of Action.--Whoever is injured by a violation of this
chapter may, in a civil action, obtain appropriate relief.
``(b) Attorney's Fees.--In any action under this chapter, the court
may allow a prevailing party, other than the United States, a
reasonable attorney's fee as part of costs.
``Sec. 169. Prohibition
``No agency or department of the United States shall require the
government of any State or subdivision thereof, or any person or
organization, to communicate or provide materials in any language other
than English.''.
(b) Clerical Amendment.--The table of chapters for title 4, United
States Code, is amended by adding at the end the following new item:
``6. Language of the Government............................. 161''.
SEC. 3. REPEAL OF BILINGUAL EDUCATION ACT.
(a) Repeal of Bilingual Education Act.--The Bilingual Education Act
(20 U.S.C. 7401 et seq.) is repealed.
(b) Termination of Office of Bilingual Education and Minority
Languages Affairs.--
(1) In general.--The Office of Bilingual Education and
Minority Languages Affairs in the Department of Education is
terminated.
(2) Repeal of conforming provisions.--Sections 209, 216,
and 413(b)(1)(A) of the Department of Education Organization
Act are repealed.
(c) Unobligated Funds.--At the end of the transition period
described in subsection (d)(2), the Secretary shall deposit in the
general fund of the Treasury any funds that have not been awarded or
obligated for grants under the Bilingual Education Act (20 U.S.C. 7401
et seq.).
(d) Transitional Provisions.--
(1) Completion of programs during current school year.--
Subsection (a) shall not apply to any program under the
Bilingual Education Act (20 U.S.C. 7401 et seq.) until
completion of the most recent school year of the program that
commences after the date of the enactment of this Act.
(2) Assistance for transition to special alternative
instructional programs.--During the 1-year period beginning on
the date of the enactment of this Act, the Secretary of
Education may assist local educational agencies in the
transition of children enrolled in programs assisted under the
Bilingual Education Act (20 U.S.C 7401 et seq.) to special
alternative instructional programs (as such programs are
described in section 7501 of the Elementary and Secondary
Education Act of 1965 (20 U.S.C. 7601) that do not make use of
the native language of the student.
SEC. 4. CONSTRUCTION.
Nothing in this Act shall be construed as requiring that a State or
local educational agency develop, implement, provide, or maintain a
program of bilingual education.
SEC. 5. RELEASE FROM DECREE.
Any consent decree entered into with a State, locality, or local
educational agency, and either the Department of Health, Education, and
Welfare, or the Department of Education that requires such State,
locality, or local educational agency to develop, implement, provide,
or maintain any form of bilingual education is void.
SEC. 6. EFFECTIVE DATE.
Except as provided in subsections (c) and (d) of section 3, this
Act shall take effect on the date of the enactment of this Act.
SEC. 7. REPEAL OF BILINGUAL VOTING REQUIREMENTS.
(a) In General.--
(1) Bilingual election requirements.-- Section 203 of the
Voting Rights Act of 1965 (42 U.S.C. 1973aa-1a) is repealed.
(2) Voting rights.--Section 4 of the Voting Rights Act of
1965 (42 U.S.C. 1973b) is amended by striking subsection (f).
(b) Conforming Amendments.--
(1) References to section 203.--The Voting Rights Act of
1965 (42 U.S.C. 1973 et seq.) is amended--
(A) in section 204, by striking ``or 203,''; and
(B) in the first sentence of section 205, by
striking ``, 202, or 203'' and inserting ``or 202''.
(2) References to section 7.--The Voting Rights Act of 1965
(42 U.S.C. 1973 et seq.) is amended--
(A) in sections 2(a), 3(a), 3(b), 3(c), 4(d), 5, 6,
and 13, by striking ``, or in contravention of the
guarantees set forth in section 4(f)(2)'';
(B) in paragraphs (1)(A) and (3) of section 4(a),
by striking ``or (in the case of a State or subdivision
seeking a declaratory judgment under the second
sentence of this subsection) in contravention of the
guarantees of subsection (f)(2)''; and
(C) in paragraphs (1)(B) and (5) of section 4(a),
by striking ``or (in the case of a State or subdivision
which sought a declaratory judgment under the second
sentence of this subsection) that denials or
abridgments of the right to vote in contravention of
the guarantees of subsection (f)(2) have occurred
anywhere in the territory of such State or
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twenty years after i. i. rabi proposed its model for the description of a two - level atom interacting with a single mode of radiation field inside a qed cavity @xcite , r. h. dicke made the generalization for @xmath0 two - level atoms @xcite .
shortly after their proposals , both models were approximated to simpler ( and integrable ) hamiltonians by means of the rotating - wave approximation ( rwa ) , i. e. the jaynes - cummings ( jc ) , and the tavis - cummings ( tc ) models @xcite .
the dicke model has been a topic of discussion for several years , thanks to its most important trait : the prediction of the superradiant phase transition at finite temperature , which in the limit of zero temperature leads to a quantum phase transition ( qpt ) @xcite .
however , along many years several authors have pointed out that this phase transition can not be achieved in a qed cavity systems due to a no - go theorem @xcite , opening an active discussion , which is far from closed @xcite .
the dicke hamiltonian is composed of three terms , one describing a monochromatic quantized radiation field inside the cavity , a second one related with the relative atomic population , and a third which describes the interaction between them .
it reads ( from now on we set @xmath1 ) @xmath2 here , the frequency of the radiation mode is @xmath3 , associated with the number operator @xmath4 .
for the atomic part , @xmath5 is the excitation energy of the single two - level system , while @xmath6 , @xmath7 , @xmath8 are collective atomic pseudo - spin operators obeying the su(2 ) algebra .
the @xmath6 operator quantifies the relative atomic population . besides
, it holds that if @xmath9 is the eigenvalue of @xmath10 , then @xmath11 ( the pseudo - spin length ) defines the symmetric atomic subspace which includes the ground state .
finally , in the case of cavity qed systems , the interaction parameter @xmath12 would depend principally in the atomic dipolar moment .
as mentioned before , the most representative feature of the model is its second - order qpt in the thermodynamic limit , a paradigmatic example of quantum collective behavior .
when the atom - field interaction reaches the critical value @xmath13 , its ground state goes from a normal ( @xmath14 ) , with no photons and no excited atoms , to a superradiant phase ( @xmath15 ) , where the number of photons and excited atoms becomes comparable to the total number of atoms in the system , i.e. a macroscopic population of the upper atomic level .
being the simplest non - integrable atom - field system exhibiting quantum chaos , the dicke model became a paradigm in quantum optics , first , and later in the quantum information community , as it describes more generally the interaction of a set of @xmath0 two - level systems ( qubits ) interacting with a bosonic field , like quantum dots , bose - einstein condensates , and polaritons to circuit qed systems @xcite .
thanks to the advance in sophisticated experimental techniques to control quantum systems , the superradiant qpt was observed experimentally in several systems during the last years . for the dicke model it was first simulated by means of a bose - einstein condensate in an optical cavity @xcite .
also , an open version of the model was realized employing raman transitions @xcite , and dynamical non - equilibrium superradiant phase transition has been also observed @xcite .
moreover , by means of superconducting qed the rabi model @xcite and few - atoms dicke - like models @xcite have been explored in this direction .
more than ten years ago , c. emary and t. brandes built approximate solutions of the dicke model by means of the holstein - primakoff realization of the su(2 ) algebra in the thermodynamic limit @xcite .
this approach describes the behavior of the model for the ground- and low energy - states , exhibiting the superradiant qpt easily and showing the presence of chaos in the spectrum of the hamiltonian .
besides , the truncated holstein - primakoff approach makes it possible to extract the critical exponents for the ground - state energy per particle , the fraction of excited atoms , the number of photons per atom , their fluctuations , and the concurrence @xcite .
enhanced by these experimental and theoretical results , and thanks to its algebraic properties , the dicke model has become an excellent tool from the theoretical point of view for exploring several features of quantum many - body systems with collective degrees of freedom , e.g. , the qpt , the excited - state quantum phase transitions
@xcite and their relation with the thermal phase transition @xcite , the onset of quantum chaos and its correspondence to the classical limit @xcite , quantum quenches @xcite and the problem of equilibrium and thermalization in isolated many - body quantum systems @xcite , to name a few .
this is the motivation for looking for as many analytical or semi - analytical descriptions of the spectra and observables of the model as it is possible .
the truncated holstein - primakoff approximation decouples the low energy modes into two independent harmonic oscillators .
it is valid when the number of excitations is small compared with the number of atoms , allowing for a description of a few low energy states far from the qpt @xcite .
the lack of a general analytical description is rooted in the fact that the dicke model does not have as many integrals of motion as degrees of freedom , being in this sense non - integrable , unlike the tc model .
numerical calculations provide useful results in truncated subspaces @xcite . on the other hand
, it has been recently shown that , thanks to being restricted to the single qubit case , the rabi model can be considered as integrable @xcite , though the controversy about this fact remains @xcite .
a similar method to the one which was used for the rabi model in order to show its integrability , has been recently applied to the dicke model with three @xcite and two atoms @xcite . however , a concise analytic solution of the dicke model is far to be obtained , and in the general case is quite probably impossible . in this work
we construct second integrals of motion in the dicke model employing the born - oppenheimer approximation ( boa ) @xcite .
they are useful and predictive within the non - chaotic energy regime and within a wide range of values of the external parameters , coupling and frequencies , both in the normal and superradiant phases .
the boa validity relies on the fact that part of the system oscillates faster than the other one , causing an effective decoupling where the slow ( adiabatically changing ) variables enters in the fast dynamics as simple parameters . as the dicke model has a one bosonic and one fermionic degree of freedom , two versions of the approximation
are used , depending on which one is the faster .
similar approaches have already been reported in the rabi model , the dicke model , as well as for the jc and tc modes . in the rabi model
the fast atomic boa has been employed to determine the entanglement of a single atom respect the bosonic field @xcite , and to unveil previously unnoticed aspects of the rwa in the jc model @xcite . in the dicke model
the fast atomic boa was applied to study its ground - state properties , like the finite size scaling of the entanglement between the components of the system and other physical observables @xcite .
also , it has been used to study the finite size dependence of the tunneling driven ground - state energy splitting in the superradiant phase @xcite .
the fast boson boa has been applied to the rabi model in @xcite , and then extended to develop the so called generalized rwa @xcite . also , in refs.@xcite the fast boson boa has been employed to describe the different phases that can be found in the dicke model realization in bose - einstein condensates in optical cavities @xcite . in this contribution
, we extend the use of the boa to higher energies in the dicke model , and show that it can describe the regular , non - chaotic energy regime of the model , which extends from the ground - state to an upper energy ( above or below the esqpt critical energy ) , depending strongly on the level splitting and the frequency of the field @xcite . in both cases ,
the fast boson and fast atomic boa , we explicitly derive the approximate second integral of motion that makes regular the low energy regime of the dicke model , and show its range of applicability in the model parameter space .
the boa extends the theoretical tools to describe the , so far unexplained , whole non - chaotic or regular energy region of the dicke model , far beyond the region of validity of the quadratic approximation of the holstein - primakoff description .
we give stringent numerical evidence showing that the boa , and the second integrals of motion coming from it , shed new light in the study of the quantum dynamics of the model .
this contribution extends the study presented in ref.@xcite by some of us , where the basic idea was introduced and complementary results were given for the fast pseudospin boa .
the paper is organized as follows , in section 2 the fast pseudospin approximation and the fast boson one are presented , and their low energy frequencies are calculated .
these frequencies are compared in section 3 with the exact ones to establish the region of validity of the approximations in the dicke model parameter space . in section 4
we derive a semiclassical approach for the slow variables , which allows us to obtain analytic results for the expectation values of observables .
these results are extensively compared in section 5 with exact results coming from the numerical diagonalization of the dicke hamiltonian . in the region of applicability
the numerical results are nicely reproduced by the approximations , giving a simple framework to understand them . in section 6
the adiabatic invariants associated with the two fast - slow approximations are unveiled and numerical tests are presented , showing them as approximated integrals of motion both in the semiclassical and quantum versions of the dicke model until the appearance of chaos in the energy and parameters space . in this same section ,
the requantization of the semiclassical slow variable is presented and the resulting spectra are compared with the exact ones which come from numerical diagonalizations , showing again , a remarkable accord . finally in section 7
we give our conclusions .
the dicke hamiltonian commutes with the @xmath16 operator , defining different subspaces with fixed @xmath17 . as mentioned before
, the maximum value @xmath11 designates the symmetric subspace where the ground - state lies . inside this subspace ,
the hamiltonian only has two degrees of freedom , one for the collective atomic degree of freedom ( pseudospin ) and one for the bosons .
an effective decoupling between them can occur as a consequence of the different temporal scales in their respective intrinsic dynamics , in two different ways .
one when the pseudospin dynamics is much faster than the bosonic one , and the second in the opposite case . in the following two subsections we present the two approaches separately . to derive in a simple way the approximations , we start with a quantum - classical approach , quantum for the fast variables and classical for the slow ones . in the following sections
full quantum and full classical results are presented in the framework provided by the fast - slow approximations .
for the sake of clarity , let us consider the dicke hamiltonian in terms of classical boson variables , i.e. by substituting the annihilation [ creation ] operators according to @xmath18 [ @xmath19 @xmath20 if we _ freeze _
the bosonic slow variables , a simple hamiltonian for the pseudospin variables is obtained , which can be easily diagonalized by considering a rotation ( @xmath21 ) around the @xmath22-axis @xmath23 the rotation angle @xmath21 can be positive or negative depending on the sign of @xmath24 .
the previous hamiltonian describes the precession of the pseudospin around the rotated @xmath25 axis with angular velocity @xmath26 , and can be easily diagonalizad by considering eigenstates of the rotated operator @xmath27 @xmath28|jm'\rangle , \label{hmp}\ ] ] with @xmath29 .
the eigenvalues , @xmath30 , depend on the , up to now , _ frozen _ bosonic variables . if we let these variables evolve , these eigenvalues define , for each @xmath31 , an effective hamiltonian for the slow bosonic variables , which has the standard form of a classical particle moving in a conservative potential @xmath32 we have manipulated the dicke hamiltonian to obtain two effective dynamics for the pseudospin and boson variables respectively , where the other variables enter as simple parameters .
this approach will be self consistently valid only if the frequency of the precessing pseudospin @xmath33 is much larger than the frequency of the bosonic variables , @xmath34 , which evolve according to the effective hamiltonian @xmath35 .
a detailed analysis of the validity of this approach is presented below .
an important consequence of this approach is that the dynamics of the semi - classical model and the spectrum in the quantized version , are organized in a finite number of bands , each characterized by the quantum number @xmath31 .
each band is associated to a different effective hamiltonian , @xmath36 , for the bosonic variables , and since the energy of the effective hamiltonian is only lower bounded , each band extends infinitely in energy .
this band structure provides a useful description of the regular part of the energy spectra , up to a point where the approximation breaks down . to determine the values of the fast and slow frequencies ( @xmath37 and @xmath34 ) as a function of coupling and energy , and to be able to establish the range of validity of the previous approach
, we analyse the dynamics of the slow bosonic variables and focus our attention on the effective potential @xmath38 . the minimum of the potential @xmath39 , for @xmath31 integer or half integer according to @xmath17 ,
is given by @xmath40 & { \mbox{for $ -j\leq m'\leq -j / f^2$}}\\ m'\omega_o & { \mbox{otherwise } } \end{array}\right .
\label{eq : eminm}\ ] ] where @xmath41 with @xmath42 , the critical value separating the normal and superradiant phases . the value of @xmath24 which minimize the potential is @xmath43 the form of the potentials @xmath39 is illustrated in fig.[fig:1 ] for two representative cases in the normal ( @xmath44 ) and superradiant ( @xmath45 ) phases . in both cases the smaller the value of @xmath31 , the lower the associated potential . in the normal phase , the potentials for all @xmath31 have their minima at @xmath46 , whereas in the superradiant phase , the potentials for the values of @xmath31 in the interval @xmath47 present a spontaneous breaking of the parity symmetry ( @xmath48 ) , and the potentials have two degenerate minima .
the right - hand side well , with @xmath49 , corresponds to a positive rotation angle @xmath21 , whereas the left - hand side , with @xmath50 , is associated to a negative @xmath21 angle . for @xmath51 the parity symmetry of the potentials
is spontaneously restored and the minima are located again at @xmath46 . [ cols="^,^ " , ] in fig.[fig:13 ] , the peres lattice of operator @xmath52 is shown for the case @xmath53 , @xmath54 [ the same parameters used in panel ( a ) of fig.[fig:8 ] ] . it can be seen that the finite bands are associated to the quantum number @xmath55 ( dashed lines ) .
the colors of the points in the peres lattice indicate the uncertainty @xmath56 .
observe that the lowest states of every band and all the members of the lowest band ( @xmath57 ) have very low uncertainty , which indicates that these hamiltonian eigenstates are , in some extent , also simultaneous eigenstates of operator @xmath52 . finally , we discuss the full quantum treatment that can be performed from the fast - slow approximations . in the case of the fast pseudospin approximation , once the pseudospin part has been diagonalized by considering a rotation around the @xmath22 axis , we are left with the hamiltonian @xmath58 , eq.([hmp ] ) , for each @xmath31 .
this hamiltonian can be quantized in the standard way to obtain a schrdinger equation @xmath59 or alternatively , if we are interested only in the energy spectrum , a standard bohr - sommerfeld quantization can be employed @xmath60 where @xmath61 is a closed path in the classical phase space associated to the hamiltonian @xmath36 . in any case
the result is a spectrum associated to the band @xmath31 of the complete spectrum . with @xmath62 .
the exact spectrum is shown by solid light lines , the blue and green ( color online ) lines are for the positive and negative parity sector respectively .
the dashed black lines are the results of the fast pseudospin boa using the bohr - sommerfeld quantization rule .
right panel shows a closer view of the region around the critical coupling , the red dashed line indicates the critical energy of the esqpt.,title="fig:",scaledwidth=50.0% ] with @xmath62 .
the exact spectrum is shown by solid light lines , the blue and green ( color online ) lines are for the positive and negative parity sector respectively .
the dashed black lines are the results of the fast pseudospin boa using the bohr - sommerfeld quantization rule .
right panel shows a closer view of the region around the critical coupling , the red dashed line indicates the critical energy of the esqpt.,title="fig:",scaledwidth=25.0% ] fig.[fig:14 ] shows the results of the latter approach , compared with numerical exact results for couplings ranging from 0 until the superradiant phase , in the case @xmath63 .
only the lowest 20 energy states are plotted .
the five states with higher energies look broken because they have avoiding crossing with other higher states not shown .
the approximate results reproduce remarkably well the exact spectrum , except in the critical esqpt energy region of the superradiant phase , where the tunneling effects , not considered by the bohr - sommerfeld quantization rule , become relevant . in ref.@xcite ,
results using the same approach are given and it is shown that the approximate and exact spectrum get closer as the number of two - level systems @xmath17 increases . for the fast - boson approach , the procedure is similar , after diagonalizing the fast boson variable by using the shift transformation , we are left , for every quantum number @xmath64 , with an effective hamiltonian for the pseudospin variables ( [ hnp ] ) . by considering the pseudospin components as @xmath65 quantum operators , the resulting hamiltonian is a particular version of the lipkin - meshkov - glick model that can be numerically diagonalized , giving the spectrum associated to band @xmath64 .
it is interesting to note that the same lmg model is obtained for each band @xmath64 , and the only difference between the bands spectra is an additive simple constant @xmath66 .
but for @xmath54 with @xmath67 , and the approximate results are obtained from the fast boson approximation.,scaledwidth=70.0% ] in fig.[fig:15 ] we compare the approximate spectrum obtained from the previous approach with the exact one obtained numerically , we use a ratio @xmath54 and couplings from @xmath68 until @xmath69 .
similar to the fast pseudospin case , the agreement is very good .
a complete survey of the born - oppenheimer approximation ( boa ) applied to the dicke model has been presented .
the study includes both the case when the fast variable is the pseudospin one and the case when the fast variable is the bosonic one .
the ranges of validity of both versions of the boa were unveiled .
it was found that in the normal phase a simple criterion is @xmath70 for the fast boson boa and @xmath71 for the fast pseudospin one , but in the superradiant phase , as a consequence of the change in the fundamental effective excitations , the criterion changes to @xmath72 and @xmath73 for the fast boson and fast pseudospin boa s respectively ( @xmath74 with @xmath75 ) .
more restrictive and detailed criteria were obtained by comparing the low energy frequencies coming from the boa s with those obtained from a quadratic approximation around the minimal energy configuration .
ample numerical tests were presented to show the effectiveness of these criteria and the ability of the boa s to reproduce the exact results of the dicke model , both in its classical and quantum version .
it was found that in the boa s reproduce very well the exact results in the normal and superradiant phase , from the ground state until the energy where chaos appears in the model .
the approximations explain in a clear way the appearance of independent energy bands in the regular part of the spectrum in a wide region of the model parameter space .
quantitative discrepancies are found , but they are reduced for larger ratios @xmath76 in the case of the fast boson boa and @xmath77 in the case of the fast pseudospin one .
the adiabatic invariants associated to the two different boa s were explicitly identified and they were found to give very approximate hamiltonian commuting operators in the quantum version of the model and very approximate conserved quantities in its classical one .
our results show that the boa is very efficient to explore and explain the phenomenology observed in the regular regime of the dicke model , up to energies where chaos appears and no other approximation known so far is valid .
besides the understanding of the spectrum in a wide region above the ground - state , these results provide a valuable tool to study dynamics in the dicke model .
in particular , we expect that the second adiabatic invariant determines the non - equilibrium dynamics and the further thermalization after a quench , leading the system to a generalized gibbs ensemble , instead of a standard gibbs ensemble , within the region in which either the fast boson or the fast pseudospin approximation is valid .
also , as we have foreseen in this work , the properties of the esqpts in this model are delimited by the existence ( or not ) of the second adiabatic invariant . within the region
in which the boa is valid , the critical behavior is the corresponding to a system of just one degree of freedom , showing a logarithmic divergence in the density of states .
it is worth to note that the same kind of critical behavior has been recently reported in the rabi model , in the limit in which the atomic frequency is much larger than the frequency of the field @xcite , that is , in a region in which the fast pseudospin approximation is expected to hold .
a. r. is supported by spanish grants no .
fis2012 - 35316 and fis2015 - 63770-p ( mineco / feder ) , m. a. b - m , s.l - h , b. lc , j. c - c and j.g .
h acknowledge financial support from mexican conacyt project cb166302 and dgapa - unam project in109417 .
s.l - h . acknowledges financial support from mexican conacyt project cb2015 - 01/255702 and from conacyt fellowship program for sabbatical leaves .
in this appendix we derive the lowest energy frequencies of the slow variables for the two boa s , by expanding the effective hamiltonians around the minimal energy configurations until quadratic terms , @xmath78 , and using the very well known result for the frequency of quadratic hamiltonians @xmath79 .
we expand the potential @xmath39 appearing in the effective hamiltonian ( [ hmp ] ) , around the minimal energy configuration given in eq.([eq : qmin ] ) .
when the potential is a double well ( @xmath47 ) this expansion gives @xmath80 therefore the boson frequency is @xmath81 when the potential has a single minimum at @xmath46 , the expansion of the potential around it , yields @xmath82 from where the boson frequency can be easily obtained @xmath83 to find the slow pseudospin frequencies , we express the effective hamiltonian ( [ hnp ] ) in terms of the canonical variables shown in eq.([eq : cano ] ) @xmath84.\ ] ] then , we expand this hamiltonian around the minimal energy configuration given in eq.([eq : minconfb ] ) .
for @xmath44 , the minimal energy configuration in terms of the canonical variables is @xmath85 .
the expansion of the hamiltonian until quadratic terms is @xmath86 from this expression we obtain the pseudospin frequency @xmath87 for @xmath45 , the minimal energy configuration in terms of variables @xmath88 and @xmath89 reads @xmath90 . expanding the hamiltonian around this point gives @xmath91 therefore the pseudospin frequency is @xmath92
in this appendix we present in detail the calculations yielding to the expressions for the expectation values of selected observables shown in section 4 .
first , we calculate the denominator appearing in the expressions for the expectation values , which is proportional to the semiclassical approximation to the density of states [ @xmath93 or weyl s formula @xmath94 .
\label{eq : nua}\ ] ] the integration over @xmath95 can be performed , by expressing the delta function in terms of the zeros of the equation @xmath96 , @xmath97 from where , we obtain @xmath98 since @xmath99 , the integration over variable @xmath95 gives @xmath100 provided that @xmath101 are real numbers .
this latter condition is guaranteed by the classically allowed integration region @xmath102 , defined by @xmath103 .
the boundaries of this integration region are obtained by solving @xmath104 , which implies the following quadratic equation for the variable @xmath105 @xmath106 whose solutions are @xmath107 where we have used the definition @xmath74 with @xmath108 . for energies inside the double
well potential , @xmath47 and @xmath109 [ see panel ( b ) of fig.[fig:1 ] ] , the classically allowed region is formed by two disconnected intervals @xmath110 \cup [ q_+(e , m'),q_-(e , m')].\ ] ] for any other case the classical allowed region is given by the interval @xmath111.\ ] ] to calculate the expectation value of the bosonic number operator , we substitute @xmath112 to obtain @xmath113.\ ] ] as before , we express the delta function in terms of the zeros of its argument ( [ eq : zerosp ] ) , to obtain @xmath114 the integration over variable @xmath95 is straightforward @xmath115 where we have used , the interval defined above @xmath102 to guarantee that @xmath101 are real numbers . by using , in the numerator of the integrand , the explicit expression of the potential @xmath39 ( [ eq : vm ] ) , we obtain after some direct simplifications the result @xmath116 to calculate the expectation value of @xmath117 , we take advantage of the inverse rotation @xmath118 to evaluate @xmath119 where we have used @xmath120 , @xmath121 , and the definition of @xmath122 in eq.([eq : beta ] ) . with this result
the expectation value of @xmath117 for each @xmath31 and given energy @xmath123 is @xmath124.\ ] ] the integral appearing in the previous expression @xmath125=\int dq \frac{\omega_o \
m'}{\sqrt{w_o^2+(\frac{2\gamma q}{\sqrt{j}})^2}}\int dp \delta[e - h_{m'}(p , q)],\ ] ] has the same integral over the variable @xmath95 that we have already calculated before ( [ eq : nua ] ) .
therefore , using the result of eq.([eq : nuar ] ) , we obtain @xmath126 as in the previous case , first we calculate the denominator appearing in the expression for the expectation values , which is proportional to the semiclassical approximation to the density of states @xmath127 @xmath128 \\&=\int d\phi\int_{-j}^j d j_z \left(\frac{\delta(j_z - j_{z+})}{\left|\partial h_{n'}/\partial j_z\right|_{j_{z+}}}+\frac{\delta(j_z - j_{z-})}{\left|\partial h_{n'}/\partial j_z\right|_{j_{z-}}}\right),\end{aligned}\ ] ] where @xmath129 are the solutions of the equation @xmath130 , given by @xmath131 where we have used the definition @xmath132 , with @xmath133 . calculating the derivatives @xmath134 and evaluating them in @xmath129
, we obtain @xmath135 therefore the integral reads @xmath136 to perform the integration over the variable @xmath137 , we have to investigate when the solutions @xmath129 are in the interval @xmath138 $ ] .
we can distinguish two cases depending on the value of @xmath139 .
if @xmath140 , the two solution @xmath129 are in the interval @xmath141 $ ] if and only if the square root argument appearing in the denominator is greater or equal than 0 : @xmath142 .
the previous condition is satisfied in two intervals around @xmath143 and @xmath144 @xmath145\cup [ \pi-\phi_o,\pi+\phi_o],\ ] ] where @xmath146 is the solution of the equation @xmath147 , given by @xmath148.\ ] ] therefore in this case , @xmath140 , the integral over @xmath137 gives @xmath149\cup [ \pi-\phi_o,\pi+\phi_o ] } d\phi \frac{2}{\sqrt{\mathcal{f}(\cos\phi)}}.\ ] ] now , since the dependence on @xmath150 in the integrand enters through @xmath151 , the integral over @xmath152\cup [ \pi-\phi_o,\pi+\phi_o]$ ] , can be expressed as four times the integral in the interval @xmath153 $ ] . in this way
the final form for the integral is @xmath154 for @xmath155 , only the solution @xmath156 is in the interval @xmath157 $ ] , and that for any value of @xmath158 $ ] .
therefore in this case the integral takes the form @xmath159 gathering the previous results , we obtain the eq.([eq : denfb ] ) . the expectation value of @xmath6 , @xmath160,\ ] ] can be calculated similarly . by expressing the dirac delta in terms of the roots of its argument , @xmath129 , we obtain @xmath161 as before , in the case @xmath162 the two roots are in @xmath141 $ ] for @xmath150 in the region defined above , therefore the integral gives @xmath163 the sum of the roots is @xmath164 , yielding to the expression @xmath165 for @xmath155 , since only the root @xmath156 is in the interval @xmath141 $ ] and @xmath150 is not restricted , the expectation value is @xmath166 the summary of these results is shown in eq.([eq : jzfb ] ) . to calculate the expectation value of the boson number operator , @xmath167 ,
we write it in terms of the @xmath168 and @xmath169 operators @xmath170 to calculate @xmath171 , where we have used that @xmath172 and @xmath173 . with the previous result
, the expectation value of the number of photons in the fast boson approximation reads @xmath174\nonumber\\ & = n'+\frac{2\gamma^2 } { 2\pi \nu^{a}(e , n')j\omega } \displaystyle\int dj_zd \phi ( j^2-j_z^2)\cos^2\phi \delta\left[(e - h_{n'}\left(\vec{j}\right)\right],\end{aligned}\ ] ] where we have expressed the @xmath175 component in terms of the canonical variables @xmath176 .
the two cases previously identified have to be considered separately to evaluate the integral of the second term . in the case
@xmath177 the integral is @xmath178\nonumber\\ & = \frac{2\gamma^2 } { 2\pi \nu^{a}(e , n')j \omega } 4\int_{0}^{\phi_o}\frac{j^2-j_{z+}^2+j^2-j_{z-}^2}{\omega_o\sqrt{\mathcal{f}(\cos\phi)}}\cos^2\phi d\phi.\nonumber\end{aligned}\ ] ] now , by using the expressions for the roots @xmath129 and the definition of @xmath179 , we obtain @xmath180 by substituting this result in the integral , we obtain @xmath181 recalling that @xmath74 with @xmath108 , we simplify the factor in front of the previous integral to obtain the following expression for the expectation value of @xmath182 , valid in the case @xmath177 @xmath183 for @xmath155 , the integral is @xmath178\nonumber\\ & = \frac{2\gamma^2 } { 2\pi \nu^{a}(e , n')j \omega } \int_{0}^{2\pi}d\phi\frac{j^2-j_{z+}^2}{\omega_o\sqrt{\mathcal{f}(\cos\phi)}}\cos^2\phi .\nonumber\end{aligned}\ ] ] by using the expression for the root @xmath156 and the definitions of @xmath184 and @xmath185 , the previous integral simplifies to yield the following expression @xmath186 the previous results are gathered in eq(.[eq : aafb ] ) .
the full classical dicke hamiltonian that we use in this contribution is the one obtained from a semiclassical approximation to the quantum propagator written in terms of coherent states @xcite @xmath187 where @xmath188 with @xmath189 and @xmath190 bloch ( for the pseudospin ) and glauber ( for the bosons ) coherent states respectively @xmath191 ) @xmath192 we consider canonical variables @xmath193 and @xmath194 , related to the complex coherent parameters through @xmath195 the expectation value of the hamiltonian , written in terms of the previous variables define the classical hamiltonian @xmath196 with classical hamilton equations given by @xmath197 @xmath198
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. gen . * 39 * , 3085 ( 2006 ) . | adiabatic invariants are introduced and shown to provide an approximate second integral of motion for the non - integrable dicke model , in the energy region where the system exhibits a regular dynamics .
this low - energy region is always present and has been described both in a semiclassical and a full quantum analysis .
its peres lattices exhibit that many observables vary smoothly with energy , along lines which beg for a formal description .
it is shown how the adiabatic invariants provide a rationale to their presence in many cases .
they are built employing the born - oppenheimer approximation , valid when a fast system is coupled to a much slower one . as the dicke model has a one bosonic and one fermionic degree of freedom , two versions of the approximation
are used , depending on which one is the faster . in both cases
a noticeably accord with exact numerical results is obtained .
the employment of the adiabatic invariants provides a simple and clear theoretical framework to study the physical phenomenology associated to this energy regime , far beyond the energies where the quadratic approximation can be employed .
_ keywords _ : dicke model , born - oppenheimer approximation , integrability . |
the importance of accurate simulation of the plastic deformation of ductile metals in the design of structures and components to performance and failure criteria is well known .
plasticity models describe the influence of elastic and inelastic deformation on stress within a body that undergoes a specific displacement / loading path .
these models are conventionally constructed with parameters , such as elastic constants , yield stress and work hardening , fitted to experimentally measured data .
crystal plasticity ( cp ) is a particular form of a plasticity model that takes into account some details of the underlying crystal structure . in cp
, characteristics of the motion of dislocations ( nanometer scale line imperfections in the crystal structure of a material ) influence the deformation experienced by the material .
early cp models connected plastic strain rate to burgers vectors , velocity and line length density of inherent material dislocations @xcite .
more recent models cast this response in a finite deformation framework , and decompose the plastic portion of the velocity gradient into separate contributions from various families of dislocations , each associated with a specific slip system @xcite .
given the nanoscale nature of the underlying defects that govern plastic deformation in metals , it is logical to consider whether simulation methods that explicitly model these defects , such as atomistic simulation and discrete dislocation dynamics ( dd ) see _
e.g. _ @xcite and @xcite , can be used to improve the fidelity of cp constitutive relations .
the connection between dislocation interaction and plasticity was pioneered by @xcite , @xcite , and @xcite . since that time
, a number of researchers have made connections between dislocation mechanisms and crystal plasticity , see _
e.g. _ @xcite .
a number of recent efforts have made comparisons of molecular dynamics results with continuum plasticity simulations .
@xcite compared atomistic simulation of fcc nickel with both cp and macroscopic internal state variable theories for the case of simple shear .
this comparison revealed qualitative similarities between the different methods , but also quantitative differences due to the presence of thermal vibrations that occur for atomistic simulation at room temperature .
in particular , it was observed that a much narrower stress distribution arose for the finite element analyses than for that extracted from atomistics .
this connection to thermal vibration was verified through additional simulations at low temperature ( @xmath010k ) .
efforts have also been made by vitek @xcite , grger _
et al._@xcite , and weinberger _ et al._@xcite to directly use atomistic simulation results to parameterize microscale yield response and cp models in body - centered cubic ( bcc ) metals .
vitek and coworkers examined the non - schmidt behavior of the slip systems of group vb and vib systems using a finnis - sinclair inter - atomic potential . in their work ,
et al._used bond order potentials to model the behavior of screw dislocations in mo and w , quantifying a stress / loading - direction dependency to the critical resolved shear stress and characterizing the resulting non - schmid behavior .
et al._leveraged this approach to fit parameters of a single crystal yield constitutive model to zero - temperature molecular statics simulation results .
they then combined this parameterization with experimental data to develop a temperature and stress dependent model for the evolving plastic strain rate .
this approach is particularly well - suited for bcc metals , where lattice friction for individual dislocations represents a significant barrier to glide .
dislocation dynamics has also been recently employed to make comparisons between continuum plasticity and lower - level simulation methods . @xcite built on the insights of vitek _
et al._and grger _
et al._in developing a three - dimensional discrete dd model to characterize the relationship between dislocation glide behavior and macro - scale plastic slip in single crystal bcc ta . for fcc metals , where interactions between dislocations and with other obstacles , _ e.g. _ precipitates ,
strongly dictate the speed of dislocation motion and resulting rate of plastic deformation , atomistic simulation is limited in its ability to simulate a significant quantity of dislocations . in this regime , dd can play a useful role in providing relevant characteristics used in the fitting of cp model parameters .
such a connection was exploited by @xcite , who employed simple boundary value problems to compare the predictions of nonlocal plasticity theories with dd results .
@xcite later used both atomistic simulation and dd in a hierarchy of modeling methods , with results from atomistics used to quantify individual dislocation mobilities for use in dd simulations , and dd results to quantify parameters related to work hardening within a cp framework .
these researchers successfully used this combined approach to predict the mechanical response of an aluminum single crystal deformed under uniaxial compressive loading along the [ 421 ] crystal direction .
the computed strain - stress response agreed well with experimental data that was not used in model calibration .
in addition to md and dd , other methods such as phase field crystal methods using diffusive dynamics have also proven useful in simulating plastic behavior with near atomic detail , see , _ e.g. _ [ berry2012defect ] and [ wang2016developing ] .
while these efforts have achieved some degree of success , they have been limited in how they use the data from the evolution of explicit dislocations to enhance the fidelity of the plasticity models considered . in general , only the global stress - strain response of a system containing a distribution of dislocations is used to parameterize the hardening behavior ; no local information is used to connect the two models . in particular , a direct comparison of the dislocation density tensor field ( ddt ) resulting from the evolution of the dislocation distribution in the case of dd and from the plastic deformation in the case of cp has not been considered thus far .
however , the inclusion of the ddt as an independent field or a parameter in the flow rules and yield criteria of single - crystal plasticity models has been explored , see @xcite , and can be used to model length - scale effects @xcite , predict different dislocation microstructures @xcite , and allows comparison with ebsd and x - ray micro - diffraction data @xcite .
a comparison of the dislocation density tensor field resulting from corresponding dd and cp simulations is the primary contribution of this work .
an attendant development is the means of extracting the ddt field from both methods and the associated length - scale at which one may resolve the dd - based densities . after a review of the basic theory and the two simulation methods in sec .
[ sec : theory ] and sec .
[ sec : method ] , we compare corresponding simulations resulting from both methods in sec . [
sec : results ] . to make the comparison meaningful
we make the two models as consistent as possible given the different formulations .
first , by using nominally _ homogeneous _ compression and shear loading simulations , we calibrate a simple , representative flow rule for the cp model based on the dd response in sec .
[ sec : calibration ] . to eliminate dynamic effects we consider loading rates where both the dd and cp results are relatively insensitive to changes of rate .
another key predicate for consistency is the appropriate scale for the comparison based on the averaging volume used to translate discrete dislocations in dd into a density field .
we hypothesize that there exists a range of volumes where a field is resolved and remains practically indistinguishable for small changes in the averaging volume .
this notion of an _ intermediate asymptotic scale _
, refer to @xcite , for the dislocation density field is crucial to this work .
then , after parameter calibration and estimation of minimal asymptotic scale , we compare the spatially - varying ddt field , as well as the global response , resulting from dd and cp simulations ( sec . [
sec : comparison ] ) .
such comparison is performed for torsion of wires with square cross section .
the rationale behind this choice is that , on the one hand , torsion induces a deformation state which is _ inhomogeneous _ within the cross section , and therefore its plastic component can be associated with _ geometrically necessary _ dislocation microstructures . on the other hand ,
the deformation state is homogeneous along the twist axis , therefore allowing meaningful averages along this direction for all fields extracted from dd and cp .
this comparison of inhomogeneous loading in dd is enabled by method of @xcite and the model code @xcite , which treats the boundary effects of a finite system with interacting dislocations .
( other efforts along these lines can be found in [ devincre2015physically ] . )
we conclude with a discussion of the results and insights on how aspects of cp models can be improved using dd simulation in the final section . to our knowledge ,
comparison of dd and cp response at the levels of both overall stress - strain response and microstructural fields has not been investigated before .
the dislocation density tensor ( ddt , @xmath1 ) introduced by @xcite is a measure of the geometrically necessary dislocation density in a region of a crystal .
the ddt is a fundamental quantity connecting the individual dislocations at the micro - scale to the macroscopic elastic and plastic deformation gradient fields , which are the essential kinematic ingredients in the macroscopic phenomenological theory of plasticity , see , e.g. , @xcite .
the dislocation density tensor @xmath1 is defined by its relationship with the ( total ) burgers vector @xmath2 for oriented area @xmath3 @xmath4 where @xmath5 is the dislocation - free reference configuration and @xmath6 is the intermediate ( or _ lattice _ ) configuration where the loop closure @xmath2 for area @xmath7 is measured .
is defined by nanson s formula @xmath8 . as in [ cermelli2001 ] , the curl of a tensor field @xmath9 is defined @xmath10 for all constant vectors @xmath11 , so that @xmath12 , where @xmath13 is the permutation tensor . the associated version of stokes theorem is @xmath14 . ]
this definition relies on stokes theorem and the usual multiplicative decomposition , originally due to @xcite , of the deformation gradient @xmath9 , @xmath15 where the deformation gradient @xmath16 is the derivative of the motion @xmath17 with respect to the reference coordinates @xmath18 , refer to fig . [ fig : configurations ] . as denoted in eq .
( [ eq : burgers_def_b ] ) , the ddt @xmath1 , being the curl of the plastic deformation @xmath19 maps ( oriented ) elements of area @xmath20 in the reference configuration @xmath21 to infinitesimal burgers vectors @xmath22 in the incompatible lattice configuration .
the primary kinematic assumption of crystal plasticity is the rate of plastic deformation is of the form : @xmath23 where @xmath24 is the slip rate on plane @xmath25 and the schmid tensors @xmath26 reside in the intermediate configuration and are associated with the crystallographic planes in which glissile dislocations reside .
( here , @xmath27 is the slip direction and @xmath28 is the slip plane normal . )
this leads to an overall deformation rate given by @xmath29 in the finite deformation context .
[ fig : configurations ] shows one such slip plane for an edge dislocation with the slip direction @xmath30 aligned with the burgers vector @xmath2 . in truth ,
[ fig : configurations ] is a very much simplified picture of plasticity with the one dislocation shown representing a family of parallel dislocation lines as nye envisaged ; however , the essential irreversibility of macro - plasticity is a manifestation of both dislocation motion and entanglement . under the assumption of linearized kinematics ( @xmath31 , small strain and rotation ) ,
the total deformation gradient can be written as @xmath32 where @xmath33 and @xmath34 are the elastic and plastic distortions , respectively .
in particular , the process of imposing a relative displacement @xmath35 to the two sides of a cut in surface @xmath36 ( refer to fig . [
fig : configurations ] ) results in the plastic distortion tensor , as in @xcite @xmath37 if the relative displacement is constant over @xmath36 , the defect is a volterra dislocation and it models a crystal dislocation with burgers vector @xmath38 . in this case , the dislocation density tensor is concentrated on the closed line bounding @xmath36 : @xmath39 where @xmath40 . particularly germane to the present study is volume average of the dislocation density tensor . the average of eq .
( [ alpha_dd ] ) over a region @xmath41 with volume @xmath42 centered at @xmath43 can easily be obtained by virtue of the sifting property of the dirac-@xmath44 , that is @xmath45 where the line integral now extends over the portion of the dislocation line inside @xmath41 . here
, @xmath46 is at the scale of dislocations embedded in lattice and the field @xmath47 is at a larger length scale where continuous fields can be obtained .
this definition classifies dislocation lines into geometrically necessary or statistically stored depending on whether the line is open or closed within the volume @xmath41 . in previous studies
@xcite we derived a generalization of eq .
( [ eq : alpha_ap ] ) , @xmath48}_{\check{{\boldsymbol{\alpha}}}({\mathbf{x } } ) } = \sum_{\ell } { \mathbf{b}}_\ell \otimes \int_\ell \ , { \delta}{\left({\mathbf{x}}- { \mathbf{y}}\right ) } \ , { \mathrm{d}}{\mathbf{x}}\\ & \approx \sum_{\ell } { \mathbf{b}}_\ell \otimes \biggl [ \sum_{(ab ) \in \ell } { \mathbf{x}}_{ab } \underbrace{\int_{0}^1 { \delta}{\left(\lambda { \mathbf{x}}_{ab } + { \mathbf{x}}_b - { \mathbf{y}}\right ) } { \mathrm{d}}\lambda}_{\phi_{ab}({\mathbf{y } } ) } \biggr ] = \sum_{\ell } { \mathbf{b}}_\ell \otimes \left [ \sum_{(ab ) \in \ell } { { \mathbf{x}}_{ab } \phi_{ab}{\left({\mathbf{y}}\right ) } } \right ] , \end{aligned}\ ] ] which uses bell - shaped smoothing kernels @xmath49 that are not necessarily piecewise constant .
this definition is evaluated using a quadrature based on straight segments @xmath50 of length @xmath51 with tangents @xmath52 . in a similar fashion
the local line density @xmath53 can be estimated : @xmath54 given that the kernel function has compact support , we can use its radius of influence to estimate the range of length scales for the estimated dislocation density to be smooth and yet resolved the variations in the system .
in fact , we will estimate the minimum of the range of intermediate asymptotic scales in order to maximize the resolution of trends in the dislocation density tensor field . in averaging via eq .
( [ eq : hardy_alpha ] ) to find the minimum number of dislocation lines in a given volume to obtain smooth density field and to compare with cp results , we are also making the conjecture that this is the scale of cp .
it bears mentioning that in our previous work @xcite we demonstrated that the definition of @xmath1 , eq .
( [ eq : alpha_ap ] ) , satisfies the fundamental extensive property of the burgers vector , namely that the resultant burgers vector of a burgers circuit is the sum of burgers vectors of all individual dislocation lines crossing the enclosed surface .
we also showed that nye s original definition of dislocation density and eq .
( [ eq : alpha_ap ] ) become equivalent when certain conditions regarding the spacing between the dislocations and curvature of dislocations are obeyed .
consistency , for example @xmath55 where @xmath56 is the average density , implies the requirement that @xmath57 given ( a ) the localization @xmath58 is based on a partition of unity @xmath59 , ( b ) exact integration of the line integral , and ( c ) the integration weights equal to kernel volumes @xmath60 .
for a piece - wise constant basis @xmath61 with compact support on a cubical region , exact integration is simply @xmath62 given the two intersection points @xmath63 of the segment with the boundary of the cube where @xmath64 $ ] .
if either end of the segment does not intersect the cube and instead is in the interior of the cube then @xmath65 .
we employed the discrete dislocation dynamics ( dd ) method developed by @xcite , as implemented in the computer program model @xcite .
a brief explanation of the method is given here ; a full account of the method can be found in [ po2014recent ] .
the crystal plasticity model was implemented in the finite deformation code albany @xcite .
given the aim of this work to compare and correlate dd and cp , we have maximized the commonalities of the two modeling techniques . for both models ,
we use : ( a ) isotropic elasticity with the slip planes of a cubic lattice , ( b ) acceleration is ignored in the balance of linear momentum , however there are dynamic / viscous effects in each model , ( c ) the momentum balance is solved on finite element meshes with corresponding boundary conditions . in this mode , both the response of cp , governed by its flow rule , and that of dd , governed by its mobility equation , are relatively insensitive to loading rate .
the formula allows to construct a continuum dislocation density field from dd simulations , which can be directly compared to the corresponding quantity defined in sec .
[ sec : cp ] in the cp framework . in general ,
dd approaches treat dislocation lines explicitly , with lines decomposed into discrete edges ( segments ) bounded by vertices .
given the formulas in sec .
[ sec : theory ] , the dislocation density field @xmath66 can be computed for a network of dislocations ; however , their evolution from a given initial configuration must be computed from a closure equation yielding the dislocation velocity @xmath67 as a function of the local stress state .
such an equation of motion for the discrete dislocation configuration can be obtained from thermodynamic considerations @xcite . for fcc metals and by neglecting inertia terms , the equation of motion can be written as : @xmath68 eq .
( [ eq : pmep ] ) expresses the balance of the total configurational force per unit line of dislocation , and is comprised of : a viscous drag contribution , is a function of velocity itself , _
i.e._the relation between drag force and dislocation velocity is non - linear ; however , for the simulations presented here we assume that @xmath69 is a constant material coefficient . also of note
is the fact that the drag coefficient is in general a second - order tensor exhibiting anisotropy depending on the crystal structure , and that it may also depend on the local dislocation character ( _ i.e._edge versus screw ) , and on the type of dislocation motion ( _ i.e._glide versus climb ) .
as described in [ po2014recent ] , the method used here utilizes lagrange multipliers to constrain climb processes , which are often only active at very high temperatures .
approaches that do incorporate climb include the works by @xcite , @xcite and @xcite .
] @xmath70 , and a mechanical contribution , @xmath71 , the peach - koehler force .
in contrast to cp , the assumption of linearized kinematics adopted in dd allows to write the ( small - strain ) stress field @xmath72 appearing in the peach - koehler force as the sum of two terms : ( a ) a dislocation - dislocation interaction term which can be computed accurately using the peach - koehler stress equation @xcite and ( b ) a correction term which accounts for the mechanical boundary conditions imposed to the simulation domain .
the dd formulation used in this work solves eq .
( [ eq : pmep ] ) in weak / variational form for the dislocation velocity field using the finite element method , refer to @xcite .
the numerical implementation is based on discretization of dislocation lines into segments connecting pairs of nodes .
segment shape functions and nodal degrees of freedom are then used for the unknown dislocation velocity field @xmath67 , so that eq .
( [ eq : pmep ] ) , upon assembly over the dislocation network , is transformed into a discrete system of equations for the nodal velocities .
finally , the nodal velocities are used to update the nodal positions and evolve the dislocation configuration in time . in our cp model
we use kirchhoff-st.venant elasticity @xmath73 with elastic lagrange strain @xmath74 .
this elastic constitutive relation reduces to @xmath75 in the limit of small strain and rotation .
the elastic modulus @xmath76 with cubic symmetry is @xmath77 where @xmath78 is the dyad @xmath79 , which we reduce to isotropy by setting @xmath80 , @xmath81 , @xmath82 for correspondence with the dd simulations . for the plastic behavior , the kinematic assumption in eq .
( [ eq : plastic_rate ] ) can be seen as a plastic flow rule of the form found in ( * ? ? ?
a particularly simple hardening rule for the rate of slip @xmath24 for slip system @xmath25 is @xmath83 subject to a @xmath84 threshold and ( isotropic ) hardening modulus @xmath85 . here
@xmath86 is the shear stress resolved on the slip plane with normal @xmath28 and the cauchy stress is simply @xmath87 .
the implicit update algorithm largely follows @xcite .
given a solution to momentum balance , we recover a dislocation density field by first using a local , element - wise l@xmath88 projection to move @xmath89 data at the integration points to the element nodes . then using the finite element basis functions @xmath61 to interpolate @xmath89 on _ each element _ , which allows differentiation with respect the reference coordinates @xmath18
, we obtain : @xmath90 where @xmath91 indexes nodes , @xmath92 is the permutation tensor , @xmath93 and @xmath94 are basis vectors in the spatial and reference frames ( respectively ) , and we have dropped the subscript @xmath95 for clarity .
chain rule provides the spatial gradient @xmath96 in terms of the partial derivatives of the basis @xmath61 with respect to the local coordinates @xmath97 @xmath98 where @xmath99 is the jacobian of the local @xmath100-to - referential @xmath18 coordinate map .
lastly , we average the local node values to obtain a unique value for every node and hence a continuous plastic deformation curl field .
alternately a global l@xmath88 projection could be used .
for our comparison studies we chose face - centered cubic single crystals of cu .
its 12 slip systems are defined by the schmid tensors @xmath101 .
as mentioned , we employ an isotropic elasticity model with effective poisson ratio @xmath102 and shear modulus @xmath103 gpa .
given that model is a dimensionless code , we adopt the same normalization in our results .
lengths are normalized to the material s burgers vector @xmath104 = 2.556 , stress - like quantities are normalized by @xmath105 , the drag coefficient is set at @xmath106 pa - s , and time is normalized by @xmath107 fs . after preliminary studies , over a wide range initial ( fully gissile ) dislocation densities and loading rates , we chose an initial dislocation density of @xmath108 @xmath109 , consisting of prismatic dislocation loops with @xmath110-type burgers vectors lying in @xmath111 planes , and loading rate of @xmath112 dimensionless inverse - time units ( corresponding to @xmath113 sec@xmath114 ) to approximate the rate - independent loading regime . from the initial dislocation density
we employ a length - scale @xmath115 to non - dimensionalize @xmath1 fields . given that initially
the dislocation network consists entirely of loops , the total dislocation density tensor starts at zero .
note , eq .
( [ eq : pmep ] ) introduces a time - scale to dd and eq .
( [ eq : flow_rule ] ) introduces time - scale to cp , yet neither has inertia so scaling time can lead to self - similar solutions dependent only on loading and not the rate of loading . for dd , this limit is achieved when the dislocation interactions and collisions are sufficiently resolved . for cp
, time - scale and loading rate invariance is apparent only as @xmath116 and also for small strains with a linear flow rule , as in @xcite and @xcite .
we examine the response of dd and cp for strains up to 1% , well below the limit of validity of the linear elastic model in dd . in sec .
[ sec : calibration ] we use homogeneous compression and shear loading results from dd to calibrate the cp flow rule and to estimate a minimum asymptotic scale . then , in sec .
[ sec : comparison ] we compare the dislocation density fields and global response resulting from inhomogeneous loading due to torsion . for all comparisons an ensemble of 10 replicas of the dd systems are used to alleviate sensitivity to initial dislocation arrangement . with the given elastic constants and symmetries , we use compression and ( simple ) shear loading dd and cp simulations to calibrate the hardening parameters of the flow rule specified in eq .
( [ eq : flow_rule ] ) . for these nominally homogeneous loading cases
we employed a cube of dimensions @xmath117 oriented with the @xmath118 crystal directions . in compression , the top face of the cube ( the face with outward normal in the @xmath119 direction ) is displaced in @xmath120 and the bottom face @xmath121 ( face with normal in the @xmath122 direction ) is fixed ; the @xmath123 and @xmath124 lateral faces are constrained in their normal directions to promote homogeneous deformation and allow for expansion . in shear , the top face is displaced in @xmath125 while fixed in @xmath126 and @xmath121 ; the bottom face is fixed in @xmath125 , @xmath126 and @xmath121 and all lateral faces are fixed in @xmath126 and @xmath121 .
[ fig : compression_reaction_vs_strain ] shows the stress - strain response for compression .
the initial slope of the dd response , 2.54@xmath105 , compares well with the expected young s modulus of @xmath127= 2.68@xmath105 .
likewise , fig .
[ fig : shear_reaction_vs_strain ] shows the stress - strain response for simple shear loading . in this case , the initial slope is 0.92@xmath105 near the expected value 1.00@xmath105 .
these results imply that the initial distribution of dislocations minimally affects the material s elastic response . after approximately 0.001 strain in compression and 0.004 strain in
shear the total line density starts to rise rapidly which corresponds to a distinct decrease in the slope of the stress - strain response . using direct fits to the dd response we determined that the slope of this plastic regime was 0.12@xmath105 in the compression case and 0.42@xmath105 in the shear case and that the onset of plastic response was at 0.00125 and 0.0031 strain , respectively .
these values were used as initial guesses in calibrating the cp model .
[ fig : compression_reaction_vs_strain ] and [ fig : shear_reaction_vs_strain ] also show that the calibrated cp stress - strain response compares well to that of dd using the hardening parameters : @xmath128 = 1 ( inverse time units ) , @xmath84 = 0.11 gpa = 0.0022 @xmath105 , and @xmath85= 30.5 gpa = 0.635 @xmath105 , for all slip systems @xmath129 $ ] .
we employed the exponent @xmath130=4 which was the highest value that offered numerical stability .
( the issue of instability upon approaching the rate independent limit @xmath116 is well - known , as discussed by @xcite , @xcite and @xcite . )
lastly , by using a kernel estimator , eq .
( [ eq : hardy_alpha ] ) , positioned near the center of a @xmath131 system we were able to estimate the asymptotic region for the dislocation density tensor field using the compression case .
[ fig : asymptotic_scale ] shows that three relevant components of @xmath1 converge to near constant , non - trivial values for kernel radii above @xmath132 500 @xmath133 , which is also well below the system size used for this study . for comparing the predictions of the dd and cp models we simulated the torsion of a @xmath134 = @xmath135 rectangular wire .
the torsion was effected by a twisting displacement of the top relative to the bottom faces , with the bottom face fully fixed and the lateral faces traction - free .
both @xmath118 and @xmath136 crystallographic orientations of the lateral faces of the wire are explored . since the elastic response is isotropic , only slip plane orientation relative to the loading distinguishes these two cases . the general solution for the stress and displacement fields in an isotropic elastic wire due to torsion
are : @xmath137 and @xmath138 in terms of a warping function @xmath139 . given the warping function characteristic of our prismatic wire with square cross - section , the torsional modulus @xmath140 relating the torsional moment @xmath141 to the twist per axial distance @xmath142 is @xmath143 where @xmath144 is the side length of the square cross - section .
the torque - twist response for both models are shown in fig .
[ fig : torsion_reaction ] .
the correspondence between the calibrated cp model and the dd response for the @xmath118 orientation of the wire is similar to that shown in fig . [
fig : shear_reaction_vs_strain ] for shear . for the @xmath136 oriented wire
, however , the dd response shows a delayed onset of significant plasticity , as evidenced both by the torque - twist response as well as the line density evolution , whereas the cp torque - twist for this orientation is nearly the same as for @xmath118 .
[ fig : torsion_evolution ] shows the evolution of the dislocation network with twist for the @xmath118 case .
the dislocations are primarily screw dislocations on different glide planes .
they reach their shown locations after a series of cross slip events from a few initial common sources .
clearly , between twist @xmath145 radians and @xmath146 radians , the initial random network multiplied through frank - read mechanisms ( no nucleation model is employed ) and aligned with the diagonals of the square cross - section .
this regime also corresponds to the apparent onset of plasticity shown in fig .
[ fig : torsion_reaction ] . fig .
[ fig : torsion_shear_stress]a shows the dislocation network and resulting line density at distinctly plastic state , twist angle @xmath147 = 0.06 radians for both the @xmath118 and @xmath136 cases . in the @xmath118 case ,
dislocation lines spanning the diagonals of the wire s square cross - section pile up ; whereas , in the @xmath136 case shown , the majority of the lines are vertical and span the opposing face mid - lines while a minority span one pair of the diagonal corners as in the @xmath118 case . clearly from the line networks themselves and the resulting line density ,
the dislocation lines in the @xmath136 case are more dispersed spatially and less numerous in total than in the @xmath118 case .
( note these networks are still dense relative to the nominally homogeneous cases where there is no tendency for dislocations to accumulate in any particular region of the body . ) in dd , dislocation lines are generated in high stress regions near the corners of the wire in torsion and migrate to the low / zero stress basins shown in green in fig .
[ fig : torsion_shear_stress]b , given the peach - kohler forces in eq .
( [ eq : pmep ] ) . for the two cases , the orientations of the slip planes relative to the wire are different , but elastic stress field is same , up until yield , due to the isotropic moduli assumption . the resolved shear stress ( rss )
is plotted in fig .
[ fig : torsion_shear_stress]b for both cases . in the @xmath118 case
the diagonal basin in rss is dominant and in the @xmath136 case the vertical basin is dominant but broader than in the @xmath118 .
since our system size and total line density are at the threshold of being able to be resolved given the estimated minimum asymptotic scale , we average the dd data through the @xmath121-axis since slices of the solution are nominally equivalent along the twist axis .
[ fig : torsion100 ] and fig .
[ fig : torsion110 ] show the two dimensional projection of the in - plane components of the dislocation density tensor for the @xmath118 and @xmath136 orientations of the wire , respectively . in general , the @xmath1 fields generated with dd and cp are only comparable up to a divergence - free / solenoidal field _
i.e._@xmath89 gradient of scalar function does not contribute to @xmath1 ( which follows directly from a helmholtz decomposition of @xmath89 ) . also , the solutions have nominal 90 degree rotation and inversion symmetry .
the fields resulting from both dd and cp have comparable magnitudes . and yet , the @xmath1 fields generated by dd have significant components in the center of wire , unlike cp . in the @xmath118 orientation case ,
the magnitudes of @xmath1 components are similar ; but in the @xmath136 case the weak pattern correspondence breaks down due to more dispersed nature of dislocation line density .
as mentioned , in dd lines are generated at high stress regions at the lateral edges of the prismatic wire and migrate to the rss basins either diagonal or crossing the midpoints of the wire s cross - section . in contrast , in a cp simulation , a background of mobile , geometrically necessary dislocations are assumed to be present everywhere and plastic slip occurs in regions of high stress . in cp
there is no mechanism for explicit generation of dislocations nor compatibility of plastic slip induced by the motion of the implicit dislocation network .
hence , the dislocation density field produced by cp only responds to the regions of high rss , and there is no driving force for migration / flow of dislocation density to low rss basins .
as a last comparison , fig .
[ fig : torsion_m_comp ] shows the sensitivity of the dislocation density field for the @xmath118 case predicted by cp to the flow rule exponent @xmath130 .
clearly the significant dislocation density approaches the center of the cross - section and the `` @xmath148 '' pattern becomes more prominent and sharper with increased @xmath130 showing better correspondence with the dd results .
an explanation for this better correspondence is discussed in the concluding section . due to numerical issues with the form the simple flow rule it was not possible to increase @xmath130 to further improve the correspondence with the dd results .
in this work , we have established that a simple cp model calibrated to dd data can produce similar microstructural fields as well as overall response .
this similarity is predicated on resolving the dislocation density field at a scale above the intermediate asymptotic length scale intrinsic to the material with its native dislocation population . for the material we examined , cu with line density @xmath149 m@xmath150 , we established that the minimum asymptotic scale is approximately 500 @xmath133 .
physically , the asymptotic scale is determined by how densely dislocation lines pack after being generated at high rss regions and migrating to low rss regions . in particular , we estimated the scale at which continuum dislocation density fields should appear with nominally homogeneous simulations where there is little difference between high and low rss regions . this estimate proved robust in constructing dislocation density fields in the inhomogeneous loading cases we considered . for the finite systems we examined , it appears that the dislocation pile - ups on particular slip planes reach a characteristic spacing due to the fact that forces between dislocations scale as @xmath151 , while forces due to the applied stress scale as @xmath133 ( refer to chap .
21 in @xcite ) . is the burgers vector of the material . ]
hence , we conjecture that the asymptotic scale for the dislocation density is strongly dependent on material and less dependent on the particular loading case . by examining eq .
( [ eq : hardy_alpha ] ) and eq .
( [ eq : hardy_rho ] ) , the connection between the dislocation line density @xmath152 and dislocation density tensor @xmath1 can be seen .
clearly @xmath152 indicates the general magnitude of @xmath1 , _
i.e._there are no @xmath1 contributions where @xmath152 is zero ; but , @xmath1 adds vectorial information from the line direction as well as from the burgers vector , see eq .
( [ eq : hardy_alpha ] ) in contrast , with a cp model the dislocation density @xmath1 results from the curl of the plastic deformation gradient through the cp flow rule , eq .
( [ eq : flow_rule ] ) .
so , unlike the explicit representation of dislocation lines in dd , cp , through its flow rule , conflates generation and migration and only creates mobile slip in high stress / deformation gradient regions .
moreover it simulates the hardening due to entanglement of dislocation lines with the flow rule .
a loose correspondence can be made between the cp flow rule and the dynamics of the dislocation lines that governs dd evolution .
the peach - kohler forces driving the dislocation dynamics are analogous to the resolved shear stresses driving plastic evolution in the flow rule so that the dislocation line velocity is proportional to the peach - kohler force , and the plastic slip rate is proportional to the local resolved shear stress . from our results , is it clear that , although the global response of corresponding dd and cp models can be made the same , the microstructural dislocation density tensor field is much more sensitive to details of the calibrated flow rule .
although algorithmic stability issues prevented us from exploring the response of flow rules with high exponents , we were able to show that increased exponent tends to improve the qualitative similarity of the in - plane @xmath1 fields for a prismatic wire in torsion where there is a strong tendency for the dislocation network to align with geometric features .
it stands to reason that this improvement will saturate before the @xmath116 limit is reached , where plastic slip , and by analogy dislocation velocity , is insensitive to rss magnitude .
in fact , it is hard to imagine how a flow rule could be constructed to perfectly represent the @xmath1 patterns seen with dd unless some compatibility of the plastic slip representing dislocation motion is enforced .
this modeling direction is currently being developed within the framework of _ continuum dislocation theory _ , as in @xcite , @xcite and @xcite , where dislocation densities are independent field quantities evolving according to transport equations , and plastic slip is computed from dislocation fluxes . in general , the continuum field , @xmath1 given by eqs . and
, captures the ( geometrically necessary ) dislocation density and is a quantitative measure useful in understanding the microstructures that result from large strains in the plastic regime .
this tensor can be used in the yield function of macroscopic phenomenological theories of plasticity to reproduce realistic dislocation microstructures .
such models form alternatives to the crystal - plasticity formulations based on active slip systems .
for example , @xcite include the ddt in the yield function , and develop a rate - independent macroscopic theory based on material symmetry .
as the authors demonstrate , inclusion of ddt in the yield function introduces an additional length - scale into the macroscopic theory . using this length - scale as a parameter ,
@xcite have shown the formation of dislocation microstructures with spatially localized ddt similar to our work . for similar structures ,
the value of the length - scale in the theory are also similar to the range of intermediate asymptotic length scales that we estimated are needed to obtain a field description of the ddt from the dd simulations .
this suggests that performing dd simulations to evaluate the ddt tensor may serve as a practical tool for calibrating and validating the phenomenological theories of plasticity . also the correspondence between dd and cp
could perhaps be improved by using a flow rule with explicit dependence on the ddt computed from the plastic deformation gradient .
an analysis along these lines is left for future work .
the authors would like to acknowledge helpful discussions with j. ostien , a. mota , f. abdeljawad , h. lim , and r. sills ( sandia ) , and support from sandia national laboratories advanced simulation and computing / physics & engineering models ( asc / p&em ) program .
sandia national laboratories is a multi - program laboratory managed and operated by sandia corporation , a wholly owned subsidiary of lockheed martin corporation , for the u.s .
department of energy s national nuclear security administration under contract de - ac04 - 94al85000 .
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, 61(10):37093723 , 2013 . | the importance of accurate simulation of the plastic deformation of ductile metals to the design of structures and components is well - known .
many techniques exist that address the length scales relevant to deformation processes , including dislocation dynamics ( dd ) , which models the interaction and evolution of discrete dislocation line segments , and crystal plasticity ( cp ) , which incorporates the crystalline nature and restricted motion of dislocations into a higher scale continuous field framework .
while these two methods are conceptually related , there have been only nominal efforts focused on the system - level material response that use dd - generated information to enhance the fidelity of plasticity models . to ascertain to what degree the predictions of cp are consistent with those of dd , we compare their global and microstructural response in a number of deformation modes . after using nominally homogeneous compression and shear deformation dislocation dynamics simulations to calibrate crystal plasticity flow rule parameters ,
we compare not only the system - level stress - strain response of prismatic wires in torsion but also the resulting geometrically necessary dislocation density fields . to establish a connection between explicit description of dislocations and the continuum assumed with crystal plasticity simulations , we ascertain the minimum length - scale at which meaningful dislocation density fields appear .
our results show that , for the case of torsion , the two material models can produce comparable spatial dislocation density distributions .
keywords : : : dislocation dynamics , crystal plasticity , dislocation density tensor |
recently , we introduced chem1d , a program for electronic structure calculations on one - dimensional ( 1d ) molecules .
@xcite unlike previous workers who used softened@xcite or otherwise altered@xcite interelectronic interactions in their studies of 1d chemical systems , chem1d employs the unadorned coulomb operator @xmath0 .
this potential introduces a non - integrable singularity which requires special treatment . building on compelling arguments from the mathematical physics community ,
@xcite our program avoids coulombic divergences by solving the schrdinger equation with dirichlet boundary conditions that require the wavefunction to vanish wherever two particles electrons or nuclei touch .
the dirichlet conditions have three chemically interesting consequences .
first , that molecular energies are spin - blind , i.e. they are invariant with respect to spin - flips .
second , that a `` super - pauli '' exclusion rule applies , i.e. an orbital can not be occupied by more than one electron .
third , that the nuclei become impenetrable , i.e. electrons are unable to tunnel through them .
@xcite the severity of these effects means that this model does not reflect the same type of experimental systems as the `` quasi-1d '' methods characterised by softened coulomb interactions , which permit the nuclei to be penetrable and electrons to pair within spatial orbitals .
this reflects situations where the 1d confinement is not strict , and so they are well suited to modelling confined experimental systems such as ultracold atoms confined within a 1d trap.@xcite in contrast , the coulomb interaction used in this work describes particles which are _ strictly _ restricted to move within a 1d sub - space of three - dimensional space
. early models of 1d atoms using this interaction have been used to study the effects of external fields upon rydberg atoms@xcite and the dynamics of surface - state electrons in liquid helium .
@xcite this description of 1d chemistry also has interesting connections with the exotic chemistry of ultra - high magnetic fields ( such as those in white dwarf stars ) , where the electronic cloud is dramatically compressed perpendicular to the magnetic field.@xcite in these extreme conditions , where magnetic effects compete with coulombic forces , entirely new bonding paradigms emerge .
@xcite unfortunately , our previous investigation @xcite of 1d chemistry suffered from debilitating numerical stability issues .
the chem1d program uses basis sets related to the exact wavefunctions @xcite of the hydrogen molecule cation but these quickly develop near - linear - dependence problems that prevent chem1d from achieving basis set convergence even for relatively modest molecular systems .
in this paper we describe leglag , a more numerically stable version of chem1d , which can be applied to a wider range of molecules to gain deeper insight into 1d chemistry . in sec . [
sec : theory ] we introduce the orthogonal set of basis functions which leglag employs and then briefly discuss the structure of the program . in sec .
[ sec : results ] we undertake an extensive study of 1d molecules , identifying multiple classes of stable species and the factors which lead to their stability . finally , in sec .
[ sec : rules ] , we present a set of rules that govern chemical bonding in 1d .
unless otherwise stated , atomic units are used throughout . the ground state of the molecule .
black circles represent the nuclei .
each coloured region represents a singly - occupied orbital and the corresponding coloured diamond shows the most likely position of the electron.,scaledwidth=45.0% ]
under dirichlet boundary conditions , nuclei are impenetrable to electrons and each electron in a molecule is therefore confined to a ray or line segment by the nuclei closest to it . in this way , the @xmath1 nuclei divide 1d space into two semi - infinite domains and @xmath2 finite domains .
each domain supports a set of orbitals that vanish at the boundaries of the domain and outside it .
figure [ fig : orbital_example ] illustrates this for a small diatomic molecule . in order to specify the constitution of a molecule
, we employ a notation in which atomic symbols indicate nuclei and subscripts indicate the numbers of electrons in the intervening domains .
for example , is a triatomic with a lithium , boron and hydrogen nucleus arranged from left to right in that order .
there is one electron to the left of the lithium nucleus , four electrons between the lithium and the boron nuclei , three electrons between the boron and the hydrogen nuclei and one electron to the right of the hydrogen nucleus . in the present work ,
we consider only ground states and assume that the @xmath3 electrons within a domain singly occupy the @xmath3 lowest - energy orbitals .
there are three types of domain left , right and middle and we require a set of basis functions for each .
the functions should vanish at the domain boundaries and form a complete set .
chem1d uses the functions [ eq : chem1dbasis ] @xmath4 where @xmath5 , @xmath6 and @xmath7 are the reduced coordinates in the left , right and middle domains respectively , @xmath8 and @xmath9 are the positions of the leftmost and rightmost nuclei , and @xmath10 and @xmath11 are the center and halfwidth of a middle domain , @xmath12 is an exponent , and @xmath13 is the pochhammer symbol .
@xcite the @xmath14 and @xmath15 functions are used in the left and right domains , respectively . @xmath16 and @xmath17
are used in the middle domains .
one disadvantage of these functions is their increasing linear dependence as the size of the basis set grows , which creates numerical instability in the orthogonalisation step of the pople - nesbet hartree - fock ( hf ) method .
@xcite this limits the size of basis set that can be employed before unacceptable numerical precision is lost .
a second disadvantage of this basis set is that , because the @xmath16 and @xmath17 functions are increasingly peaked around the middle of the domain , they struggle to describe details of the molecular orbitals near domain boundaries .
this becomes particularly problematic when the domain contains more than one electron .
@xcite in contrast , leglag uses the basis functions [ eq : lrm - bf ] @xmath18 where @xmath19 and @xmath20 are second - order associated laguerre and legendre polynomials .
@xcite ( our package s name stems from its use of legendre and laguerre polynomials . )
the @xmath21 , @xmath22 and @xmath23 functions are used in the left , right and middle domains , respectively , and are mutually orthogonal .
the @xmath23 are evenly distributed across the domain , as fig .
[ fig : bf_comparison ] shows . in earlier work , we discovered @xcite that hf calculations @xcite give unexpectedly accurate results in 1d .
it also appears , in contrast to the situation in 3d,@xcite that the mller - plesset ( mp ) perturbation series @xcite in 1d often converges rapidly to the exact energy .
@xcite however , to perform such calculations it is necessary to evaluate the integrals [ eq : ints ] @xmath24 where @xmath25 , @xmath26 is a density component , @xmath27 is the kinetic energy operator and @xmath28 is the kronecker delta function .
@xcite if the four basis functions are in the same domain , the singularity of the coulomb operator causes @xmath29 to diverge .
however , the antisymmetrized integral @xmath30 is finite and can be found from quasi - integrals @xcite using @xmath31 because @xmath22 is the image of @xmath21 under inversion through the molecular mid - point , formulae involving only @xmath22 and @xmath23 can be found from the equivalent formulae involving @xmath21 and @xmath23 .
we will therefore not discuss the former .
integral formulae are given in appendix [ app : ints ] and most of the necessary special functions are evaluated by calling external libraries .
however , because we invariably need a range of values for the @xmath32 and @xmath33 parameters in the tricomi confluent hypergeometric functions @xcite @xmath34 required for coulomb integrals involving the @xmath21 functions , it is more efficient to compute these functions recursively
. it has been shown that backwards recurrence in the @xmath32 parameter is numerically stable and our algorithm exploits this.@xcite to obtain the starting values for this recurrence we use an asymptotic expansion that is valid when @xmath35 is large and positive.@xcite our numerical experiments have shown that for arguments @xmath36 this expansion converges at an unacceptable rate .
our algorithm therefore uses miller s method@xcite when @xmath37 .
we detect and avoid computing negligible integrals using the coulomb upper bound@xcite @xmath38 where @xmath39 is the maximum potential of @xmath40 in the domain of @xmath41 and @xmath42 is the integral of @xmath43 .
the @xmath44 and @xmath45 values can be found using expressions in section [ app : prop ] .
aside from integral evaluation , leglag closely follows the algorithms employed in chem1d . for a comprehensive description of these ,
see the paper by ball and gill .
@xcite leglag has been implemented using the python programming language ( version 3.41 ) in combination with the cython language extension for compute - intensive bottlenecks .
it employs the external numpy library for data structures and linear algebra operations and the scipy library for computing some of the special functions .
a significant feature of leglag is that it can be easily controlled by external python scripts . in generating the data presented in sec .
[ sec : results ] , we have made extensive use of scripts that use the numerical function minimiser available in scipy to optimize molecular geometries . the exclusion potential ( red ) of a atom ( blue ) .
the blue regions show the occupied orbitals when computing the exclusion potential at the position of the red dot.,scaledwidth=45.0% ] in 3d , the molecular electrostatic potential@xcite ( mesp ) is the limit of the ratio of the coulomb energy of a test particle to the magnitude of its charge , as that charge approaches zero .
it is a potent tool for understanding chemical behaviour and can reveal , for example , electrophilic or nucleophilic regions . unfortunately , however , the mesp diverges at all points in a 1d system except where the electron density vanishes .
@xcite therefore , to define a meaningful potential in a 1d molecule , we must insist that the test particle create a new dirichlet node at its position .
we call the resulting potential the `` exclusion potential '' to emphasise that , in contradistinction to the 3d analog , the test particle in 1d excludes electrons from its neighbourhood and thereby significantly perturbs the system . figure [ fig : potential_construction ] shows the exclusion potential for a atom as well as the perturbed orbitals for a given position of the test particle .
note how the dirichlet node created by the test particle compresses the right orbital , and prevents the electron which occupies it from extending to the right .
@l * 3d .. 3.6 * 3d .. 2.3 * 3d .. 1.3 atom & 3ctotal energies & 3cionization energies & 3celectron affinities + & & & & & & & & & + h & 0.500000 & 0.500000 & 0.500000 & 13.606 & 13.606 & 13.606 & 3.893 & 3.939 & 3.961 + he & 3.242922 & 3.244986 & 3.245611 & 33.822 & 33.878 & 33.895 & & & + li & 8.007756 & 8.01112 & 8.01179 & 4.486 & 4.517 & 4.522 & 1.395 & 1.410 & 1.414 + be & 15.415912 & 15.4226 & 15.4236 & 10.348 & 10.400 & 10.408 & & & + b & 25.35751 & 25.3671 & 25.3684 & 2.068 & 2.09 & 2.099 & 0.64 & 0.65 & 0.65 + c & 38.09038 & 38.105 & 38.107 & 4.670 & 4.719 & 4.73 & & & + n & 53.569 & 53.59 & 53.6 & 1.1 & 1.1 & 1.1 & 0.3 & 0.3 & 0.3 + o & 71.9293 & 71.95 & 71.96 & 2.516 & 2.548 & 2.556 & & & + f & 93.1 & 93.2 & 93.2 & 0.5 & 0.5 & 0.5 & & & + ne & 117.31 & 117.35 & 117.35 & 1.5 & 1.5 & 1.5 & & & +
to begin to understand the nature of chemical bonding in 1d , we have performed an extensive search for stable molecules . after presenting accurate atomic energies
, we will discuss the structures of a wide variety of small molecules and a small set of polymeric systems .
the periodic table in 1d has only two groups@xcite and we will frequently refer to alkalis ( , , , which have an odd number of electrons and a permanent dipole moment ) and nobles ( , , , which have an even number of electrons , are symmetrical and have no dipole . ) all of the calculations that we report use 30 basis functions in each of the left and right domains and 50 functions in each of the finite domains .
we will refer to this as the ( 30,50 ) basis set .
we report only the digits that have converged as the basis set is increased to the ( 30,50 ) set .
our first task was to choose the exponent @xmath46 in @xmath47 and @xmath48 that yields the best energies as the basis set is increased .
we expected that @xmath46 would be determined largely by the innermost ( and lowest - energy ) orbitals , and that therefore @xmath49 , where @xmath50 is the nuclear charge of the atom in question .
we were therefore surprised to find that this is not the case and that , except for hydrogen , the optimal exponent is always close to @xmath51 , a compromise that attempts to describe both the compact inner orbitals and the diffuse outer orbitals .
after this discovery , we used @xmath51 for all atoms . in our first foray into 1d chemistry , @xcite we used multiple - precision arithmetic in mathematica@xcite to compute the near - exact hf , mp2 and mp3 energies , ionisation energies and electron affinities of the ground - state atoms up to .
our subsequent ( double - precision ) chem1d program was often unable to reproduce these energies , principally because of its inadequate basis functions .
table [ tab : atoms ] shows that our ( double - precision ) leglag calculations are much more successful in capturing the energies but the ( 30,50 ) basis still struggles for the largest atoms and , in particular , fails to yield any significant figures for the electron affinity of . @l
* 3d .. 2.3 * 3d .. 3.6 * 3d .. 3.6 & 3cbond length & 3ctotal energy & 3cdissociation energy + & & & & & & & & & + & 2.636 & 2.637 & 2.638 & 1.184572 & 1.185418 & 1.185728 & 184.572 & 185.418 & 185.728 + & 2.025 & 2.027 & 2.027 & 3.880313 & 3.882619 & 3.883301 & 137.39 & 137.633 & 137.691 + & 5.345 & 5.323 & 5.320 & 8.544163 & 8.547920 & 8.548659 & 36.407 & 36.800 & 36.871 + & 5.152 & 5.141 & 5.142 & 8.681782 & 8.686367 & 8.687589 & 174.025 & 175.25 & 175.80 + & 3.966 & 3.961 & 3.962 & 16.079548 & 16.08707 & 16.08845 & 163.636 & 164.50 & 164.85 + & 8.880 & 8.810 & 8.806 & 26.020047 & 26.0310 & 26.0329 & 95.492 & 96.1 & 96.1 + & 3.298 & 3.296 & 3.296 & 25.957601 & 25.96793 & 25.96949 & 100.093 & 100.85 & 101.13 + & 10.349 & 10.238 & 10.235 & 25.863890 & 25.8736 & 25.8748 & 6.382 & 6.5 & 6.5 + & 6.666 & 6.635 & 6.633 & 38.756672 & 38.7721 & 38.7745 & 166.290 & 167.4 & 167.9 + & 14.316 & 14.268 & 14.257 & 54.22372 & 54.244 & 54.247 & 52.470 & 53 & 53 + & 5.407 & 5.392 & 5.392 & 54.218224 & 54.2379 & 54.2407 & 149.222 & 150.2 & 150.5 + & 19.20 & 18.168 & 18.131 & 54.0703 & 54.089 & 54.091 & 1.3 & 1 & 1 + & 10.468 & 10.383 & 10.378 & 72.590721 & 72.616 & 72.620 & 110.787 & 112 & 112 + & 4.606 & 4.586 & 4.584 & 11.260655 & 11.266223 & 11.267543 & 9.977 & 10.118 & 10.144 + & 11.174 & 11.170 & 11.003 & 28.600892 & 28.6126 & 28.6145 & 0.461 & 0.5 & 0.5 + & 8.693 & 8.644 & 8.637 & 16.064647 & 16.07183 & 16.07326 & 49.134 & 49.59 & 49.69 + & 7.050 & 7.000 & 6.996 & 23.452479 & 23.46286 & 23.46460 & 28.811 & 29.16 & 29.22 + & 13.330 & 13.228 & 13.157 & 33.418876 & 33.4323 & 33.4343 & 53.611 & 54.1 & 54.2 + & 14.007 & 13.999 & 13.778 & 33.379031 & 33.3922 & 33.3941 & 13.766 & 14.0 & 14.0 + & 10.435 & 10.358 & 10.336 & 46.140625 & 46.1588 & 46.1614 & 42.486 & 43.0 & 43 + & 8.956 & 8.892 & 8.884 & 61.588547 & 61.6112 & 61.6143 & 11.788 & 12.3 & 12.4 + & 19.552 & 19.258 & 19.229 & 61.63192 & 61.654 & 61.658 & 44.7 & 45 & 45 + & 21.546 & 21.092 & 21.099 & 61.5802 & 61.602 & 61.605 & 3.5 & 3 & 3 + & 14.943 & 14.769 & 17.748 & 79.987067 & 80.015 & 80.019 & 49.98 & 51 & 51 + & 12.566 & 12.566 & 12.381 & 40.776885 & 40.7932 & 40.7955 & 3.464 & 3.6 & 3.6 + & 20.571 & 19.884 & 19.869 & 68.9851 & 69.010 & 69.014 & 0.2 & 0 & 0 + & 19.349 & 19.233 & 19.003 & 50.733908 & 50.753 & 50.756 & 18.891 & 19 & 19 + & 16.040 & 16.009 & 15.779 & 63.457101 & 63.481 & 63.484 & 9.21 & 9 & 9 + & 26.480 & 25.946 & 25.912 & 78.949 & 78.977 & 78.981 & 22 & 22 & 22 + & 27.514 & 26.939 & 26.869 & 78.933 & 78.961 & 78.96 & 6 & 6 & 6 + & 21.138 & 20.799 & 20.735 & 97.3018 & 97.34 & 97.34 & 14.9 & 15 & 15 + & 22.880 & 24.906 & 24.801 & 91.660 & 91.69 & 91.70 & 1 & 1 & 1 + & 30.301 & 31.892 & 33.989 & 107.14 & 107.18 & 107.19 & 10 & 10 & 10 + & 29.583 & 28.780 & 28.727 & 125.50 & 125.54 & 125.55 & 0 & 0 & 0 + variation of diatomic bond lengths ( in bohrs ) with the number of electrons in the middle domain .
data are grouped according to the character of the molecule : aligned alkali - alkali , opposed alkali - alkali , and alkali - noble .
quadratic least - square fits are shown as dotted lines.,scaledwidth=45.0% ] notwithstanding the deficiencies of the ( 30,50 ) basis for the largest atoms , leglag is able to treat a far wider variety of molecular systems than is possible in chem1d and we have surveyed the diatomics with atoms up to oxygen and with all possible electronic configurations that can be generated from the ground - state atoms .
table [ tab : diatomics ] reports the bond lengths and energies of the diatomics that we have found to be stable , i.e. lower in energy than their constituent atoms .
this set of results , which greatly extends our previous efforts , @xcite allows us significantly more insight into the mechanics of 1d bonding .
there appear to be four major factors that govern the binding between two atoms : 1 .
valence attraction to an alkali nucleus 2 .
nuclear shielding 3 .
dipole interactions 4 .
number of occupied domains and we now discuss each of these in turn , and pictorial representations can be seen in figure [ fig : bonding_diagrams ] .
valence - nucleus attraction ( fig . [ fig : bonding_diagrams]a ) is strongest on the electron - deficient side of the alkali ; on the other side of an alkali , or on either side of a noble , such an interaction is shielded too effectively .
the four configurations of the hb molecule , viz . , , and ,
illustrate this .
the first three are bound and , in each , at least one of the atoms presents its electron - deficient side to the other atom .
the fourth configuration , in which each atom presents its electron - rich side to the other , is unstable .
it follows that two nobles will not bind , as neither has an electron - deficient side . in 3d ,
noble gas atoms can bind weakly through dispersion interactions , @xcite but we have not seen evidence of this in 1d .
this may be an artefact of the ( 30,50 ) basis but we believe that such binding , if it exists , is likely to be very weak . nuclear shielding ( fig .
[ fig : bonding_diagrams]b ) is also critical .
lighter atoms bind more strongly because their nuclei are less shielded and this is true _ a fortiori _ of the completely unshielded h atom . as the shielding increases ,
binding energies drop rapidly , and bond strengths in nitrogen - containing molecules like and are in the millihartree ( m@xmath52 ) range .
dipole interactions ( fig .
[ fig : bonding_diagrams]c ) also influence bond strengths .
the and molecules each hold a single electron in the internuclear domain and , naively , one might expect that would be more strongly bound because of its shorter bond and greater attraction between the bonding electron and nuclei . however , the bond strength in , where the atomic dipoles are favourably aligned , exceeds that in by roughly 50 m@xmath52 .
similar arguments explain the relative strengths in and .
the rare instances , e.g. , where a diatomic forms with opposed dipoles are driven by the attraction between two electron - deficient sides . the number of occupied domains ( fig .
[ fig : bonding_diagrams]d ) is also relevant , as the very different bond energies in the hb diatomics show .
why , for example , is is so much more weakly bound than , despite both having favourable dipole alignments ?
the answer is that the six electrons are squeezed into two domains in , rather than three in . to form the former from the latter ,
the electron from the left domain is promoted into a high - energy orbital in the right domain and this incurs a large energy cost . in our earlier
work,@xcite we discovered a few surprisingly long bonds .
however , the results in table [ tab : diatomics ] show that gargantuan bond lengths are not at all uncommon in 1d .
figure [ fig : bondlengths ] reveals a strong correlation between the length of the middle domain of a diatomic and the number of electrons occupying it . if the data are grouped into those with aligned dipoles , those with opposed dipoles and those with a noble atom , strong parabolic trends emerge .
similar behaviour is found for estimates of atomic radii .
@xcite this similarity might suggest that there is no significant distortion of atomic densities during the formation of a diatomic molecule .
figure [ fig : diatomic_densities ] depicts the difference in a selection of diatomic electron densities and the corresponding sum of atomic densities , showing that , in the majority of cases , this is true .
more specifically , this assertion is true when the bonding alkali , i.e. the alkali with its electron deficient side in the bonding domain , is heavier than . in these cases
we see the outermost electron of the other atom occupies the position of the lumo of the bonding alkali .
the orbital that this electron occupies does not appreciably change in shape , however . as a result
the bond length is completely determined by the shape of the atomic species .
the exception to this are those diatomics where the bonding alkali is an atom .
the unshielded proton of the atom is significantly more reactive than other species , an effect we also see when looking at bond strengths .
this results in the outer electron of the other atom occupying an orbital similar to the lumo of the atom , rather than the homo of its parent atom .
this creates a noticeable distortion of the atomic electron densities in such cases .
the fact that each electron is largely isolated within its local domain provides little opportunity for complicated interelectronic interactions . as a result , we find that the qualitative and quantitative effects of electron correlation are usually small .
the correlation energy in 1d constitutes a much smaller fraction ( typically less than 0.1% ) of the total energy than in 3d .
moreover , it largely cancels between reactants and products so that correlated bond energies are typically within 1 m@xmath52 of their uncorrelated values .
correlated bond lengths are also similar to uncorrelated ones , especially in relative terms .
accordingly , we use hf structures henceforth .
we also undertook a systematic search for stable triatomic molecules , examining all possible electronic configurations generated by ground - state atoms up to , and including , carbon .
many stable species emerge , and we report bond lengths , total energies , atomisation energies and bond energies for some of these in table [ tab : triatomics ] . for the reasons discussed above , we report atomisation and bond energies only at the hf level . in our earlier exploration@xcite of 1d reactivity , we concluded from a small set of atomisation energies that the bonds in a triatomic abc are similar in strength to those in ab and bc .
we argued that the small deviations could be rationalised by considering the a c dipole interaction .
the results in table [ tab : triatomics ] largely support this view .
for example , the h li and li li bond strengths in are 39 and 52 m@xmath52 , which are slightly higher than those in ( 36 m@xmath52 ) and ( 49 m@xmath52 ) , and this increased stability can be ascribed to the favourable dipole alignment .
in contrast , the li
h and h b bond strengths in fall from 36 and 100 m@xmath52 to 20 and 84 m@xmath52 , respectively , because the boron dipole is opposed to those of the lithium and hydrogen atoms .
the molecule also has opposed dipoles and the b
c bond energy drops from 9 m@xmath52 in the diatomic to 7 m@xmath52 in the triatomic .
we have also found two classes of triatomic that one might have expected to be unstable .
the first consists of a noble flanked by two alkalis with aligned dipoles ( e.g. and ) and the second consists of two nobles on one side of an alkali ( e.g. and ) .
such molecules contain bonded atoms that do not form stable diatomics , e.g. the moiety in or the moiety in .
the exclusion potentials in fig .
[ fig:1he2he2li2_h2he3b3_potential ] show the attractive force which binds these unusual abc triatomics . in each case , the diatomic fragment bc generates a small positive potential in its left domain which can then interact favourably with the valence electron of a. @l * 2d .. 2.3 * 3d .. 2.6 * 1d .. 2.3 * 2d .. 1.3 & 2cbond length & 3ctotal energy & & & + & & & & & & & & + & 17.620 & 3.296 & 26.458006 & 26.468322 & 26.469874 & 100.497 & 0.404 & + & 2.795 & 8.942 & 26.735055 & 26.74627 & 26.74818 & 310.500 & 215.008 & 89.366 + & 13.090 & 9.665 & 29.101690 & 29.11340 & 29.11529 & 1.260 & 0.799 & + & 2.025 & 16.294 & 41.972376 & 41.9891 & 41.9917 & 139.071 & & 1.680 + & 5.336 & 8.860 & 16.604027 & 16.611622 & 16.61313 & 88.514 & 39.380 & 52.107 + & 5.243 & 7.048 & 24.126866 & 24.13849 & 24.14078 & 203.198 & 174.387 & 29.172 + & 5.387 & 13.356 & 34.094432 & 34.1091 & 34.11168 & 229.167 & 175.556 & 55.142 + & 3.946 & 7.047 & 24.111979 & 24.12320 & 24.12529 & 188.310 & 159.500 & 24.674 + & 10.289 & 13.443 & 33.925825 & 33.9393 & 33.9414 & 60.560 & 6.949 & 54.178 + & 9.099 & 14.048 & 34.040693 & 34.0553 & 34.0579 & 108.382 & 82.704 & 12.890 + & 10.281 & 19.510 & 51.24102 & 51.2605 & 51.2631 & 26.006 & 7.115 & 19.62 + & 9.205 & 19.492 & 51.39508 & 51.4159 & 51.4192 & 113.018 & 74.956 & 17.53 + & 6.649 & 6.649 & 39.422734 & 39.4393 & 39.44217 & 332.352 & 166.062 & 166.062 + & 6.632 & 16.058 & 64.12276 & 64.1480 & 64.1517 & 174.867 & 165.657 & 8.577 + & 2.027 & 10.290 & 29.244835 & 29.25684 & 29.25879 & 144.404 & 138.023 & 7.014 + & 11.009 & 4.601 & 14.503682 & 14.511311 & 14.513255 & 10.081 & 0.104 & + & 4.601 & 8.737 & 19.317942 & 19.327327 & 19.329411 & 59.507 & 10.373 & 49.530 + & 10.949 & 13.320 & 36.662290 & 36.6778 & 36.6805 & 54.103 & 0.492 & 53.642 + & 5.210 & 5.524 & 16.749370 & 16.75602 & 16.759498 & 233.857 & 197.450 & 59.832 + & 5.191 & 10.017 & 34.055957 & 34.07025 & 34.07275 & 190.692 & 184.310 & 16.667 + & 5.619 & 3.338 & 33.985753 & 33.999903 & 34.002215 & 120.488 & 20.395 & 84.081 + & 5.533 & 6.789 & 46.820115 & 46.83917 & 46.84223 & 221.976 & 55.686 & 185.569 + & 4.574 & 12.299 & 26.677407 & 26.68967 & 26.69200 & 10.817 & & 0.840 + & 4.514 & 20.723 & 36.623610 & 36.6388 & 36.6414 & 15.423 & & 5.45 + & 8.69 & 8.966 & 24.127495 & 24.13851 & 24.140705 & 104.226 & 55.092 & 55.092 + & 8.833 & 7.04 & 31.51126 & 31.52547 & 31.52797 & 79.832 & 51.021 & 30.698 + & 8.715 & 14.190 & 41.440738 & 41.457727 & 41.46047 & 67.717 & 53.951 & 18.583 + & 8.948 & 10.461 & 54.201813 & 54.2238 & 54.2272 & 95.918 & 53.432 & 46.784 + & 7.077 & 7.075 & 31.482743 & 31.49682 & 31.49927 & 51.318 & 22.507 & 22.507 + & 13.937 & 19.704 & 58.75720 & 58.7802 & 58.7835 & 34.426 & 15.54 & 20.66 + & 3.983 & 10.32 & 41.445882 & 41.46312 & 41.46577 & 172.461 & 166.08 & 8.825 + & 12.580 & 19.444 & 66.15358 & 66.1798 & 66.1834 & 22.652 & 3.761 & 19.19 + & 25.12 & 3.288 & 51.3170 & 51.3367 & 51.3397 & 10.198 & 1.9 & + & 10.164 & 6.747 & 64.126951 & 64.15210 & 64.15578 & 179.060 & 12.770 & 172.678 + & 9.794 & 18.02 & 66.69221 & 66.7183 & 66.7221 & 1.39 & & 0.93 + & 30.000 & 12.358 & 66.1349 & 66.1608 & 66.1644 & 4.00 & 0.5 & + & 16.126 & 16.129 & 88.82132 & 88.8553 & 88.8597 & 15.916 & 6.71 & 6.71 + left exclusion potential ( red ) of ( left ) and ( right ) and electron density ( blue ) of ( left ) and ( right).,title="fig:",scaledwidth=45.0% ] left exclusion potential ( red ) of ( left ) and ( right ) and electron density ( blue ) of ( left ) and ( right).,title="fig:",scaledwidth=45.0% ] table [ tab : tetraatomics ] presents results for the stable tetra - atomic molecules formed by dimerising , and .
these results confirm that the length and strength of a bond are largely independent of its environment but , as in the triatomic study , we find significant increases in some bond strengths as a result of favorable dipole interactions .
for example , in , the central bond is approximately 50 m@xmath52 stronger than that in , and the right bond is almost four times as strong as in .
however , this effect is not universal .
for example , the dipoles in are all aligned , yet the individual bonds are not strengthened and , indeed , the central bond is weaker than in the corresponding diatomic .
this is because the central domain houses five electrons , forcing the bond to be long ( @xmath53 18 bohrs ) and greatly reducing the dipole stabilisation . in most of the stable species
abcd , the central pair bc is also a stable diatomic .
however , this is not the case in and . in both of these ,
the central bond is significantly weaker than in the other tetra - atomics and they are therefore analogous to the loosely associated triatomics in table [ tab : triatomics ] .
we also found two molecules , and , where each individual bond is present in a stable diatomic but the overall tetra - atomic is not bound .
the exclusion potential of the fragment , which is present in both and , becomes positive beyond 8 bohr to the right of the h atom and this provides the driving force for bonding in the molecule .
however , remains unbound because of the unfavourable dipole interactions between the left boron atom and the other atoms .
similar dipole interactions also appear in .
it is possible that the and fragments in , or the and fragments in associate weakly at a very large separation but that the ( 30,50 ) basis can not adequately describe this . @l
* 3d .. 2.3 * 3d .. 2.6 * 1d .. 1.3 * 3d .. 1.3 & 3cbond length & 3ctotal energy & & & & + & & & & & & & & & & + & 3.284 & 23.316 & 10.349 & 51.822463 & 51.842 & 51.845 & 107.48 & & 1.0 & 5.5 + & 8.880 & 18.08 & 3.290 & 51.980101 & 52.0013 & 52.0048 & 198.034 & 90.492 & 2.449 & + & 9.085 & 2.795 & 9.828 & 52.115557 & 52.1361 & 52.1392 & 333.182 & 75.51 & 231.308 & 22.682 + & 3.356 & 2.715 & 10.35 & 51.99337 & 52.0142 & 52.0173 & 278.35 & 82.682 & 171.879 & 2.84 + & 8.979 & 19.70 & 3.297 & 51.993816 & 52.015 & 52.019 & 211.6 & 77.3 & 16.1 & 98.6 + & 9.253 & 18.48 & 10.340 & 51.901493 & 51.923 & 51.926 & 119.429 & 73.090 & 17.56 & 6.41 + & 8.880 & 9.99 & 8.88 & 52.06129 & 52.083 & 52.087 & 212.18 & 74.54 & 21.20 & 81.1 + & 3.298 & 8.854 & 10.155 & 51.999949 & 52.0210 & 52.0244 & 217.728 & 99.060 & 88.595 & 21.238 + & 10.348 & 9.128 & 9.825 & 51.907673 & 51.9280 & 51.9311 & 125.255 & 6.587 & 75.332 & 23.818 + in our early work on 1d chemistry , @xcite we examined the bond length and energy within the hydrogen nanowire an infinite chain of alternating protons and electrons using a periodic hf calculation . using leglag
, we can study the same system as the extrapolated limit of a sequence of finite chains and we can also examine other homogeneous , or heterogenous , polymers .
for each polymer , we studied a range of short oligomers and fit their properties to the functions of the type @xmath54 , where @xmath3 is the number of monomer units in the oligomer .
we then extrapolated these functions to the infinite polymer , i.e. @xmath55 . for computational efficiency , we used the ( 30,30 ) basis set , rather than the ( 30,50 ) set used above .
our results are summarised in table [ tab : polymers ] and we report only the digits that have converged as the basis set is increased to the ( 30,30 ) set .
results for the hydrogen polymer agree with our periodic calculations @xcite and confirm that the bond becomes longer ( stretching from around 2.6 bohrs to 2.8 bohrs ) and stronger upon polymerisation .
the lengthening / strengthening trend is ubiquitous and results from a competition between growing numbers of repulsive interelectronic interactions ( which are reduced if the polymers expand by a few percent ) and an accumulation of favourable dipole interactions ( which stabilise the polymer relative to the monomers ) .
however , not all of the polymers in table [ tab : polymers ] follow this pattern and the and polymers are notable exceptions . in both of these
, the inter - monomer bonds are exceptionally long and the resulting stabilisation is small .
because these new bonds do not arise in stable diatomics , these `` polymers '' are better viewed as loose aggregates .
@l * 1d .. 2.3 * 1d .. 2.6 @ * 2d .. 2.2 * 1d .. 2.6 * 1d .. 1.3 & 2cmonomer & 4cpolymer + & & & & & & + & 2.636 & 1.184572 & 2.798 & 2.798 & 1.420210 & 235.638 + & 8.693 & 16.064647 & 9.0 & 9.0 & 16.13383 & 69.18 + & 5.152 & 8.681782 & 5.46 & 5.46 & 8.752991 & 71.209 + & 8.880 & 26.020047 & 9.6 & 9.6 & 26.0474 & 27.4 + & 13.330 & 33.418876 & 14.0 & 14.0 & 33.447 & 28 + & 2.025 & 3.880313 & 2.025 & 10 & 3.882261 & 1.948 + & 3.298 & 25.957601 & 3.3 & 20 & 26.0 & 0 +
our studies reveal that chemistry in 1d is largely local . the combination of particle impenetrability and strong shielding causes distant particles to have very little effect on each another and , as a result , the functional groups in 1d chemistry are essentially the diatomic units within a molecule .
this reduction requires us to understand the bonding in diatomic molecules and has led us to three simple rules which describe all of the bound diatomics reported in table [ tab : diatomics ] : * two alkalis with aligned dipoles bind * two alkalis with unaligned dipoles bind if their nuclear charges differ by at least two * a noble binds to an alkali s electron - deficient side strong bonds result from three ingredients : * light atoms * aligned atomic dipoles * low electron occupations in each domain the first ingredient improves electron - nuclear attraction ( because of reduced shielding ) ; the last also enhances coulombic attraction and also reduces kinetic energy .
in general , a polyatomic is strongly bound if all of its constituent diatomics are separately stable .
there are interesting exceptions ( such as the stable triatomic and the unstable tetra - atomic ) but it is true for all of the tightly bound triatomics that we have identified .
curiously , the rule incorrectly predicts and to be strongly bound when , in fact , it turns out that one of their constituent bonds is insufficiently strong to overcome the unfavourable dipole interactions .
fortunately , this is the only example that we have found where the rule fails .
using our newly developed electronic structure program for 1d molecules , leglag , we have performed an extensive survey of 1d chemistry . by adopting improved basis functions ,
we have been able to identify and characterise a wide variety of stable molecules and a small set of polymers .
many of these are novel structures and , prior to this work , would not have been expected to exist .
we have also developed an understanding of the bonding interactions in these molecules and we have identified the most significant factors that contribute to their stability .
this has allowed us to formulate a set of simple rules which predict whether a putative 1d molecule is stable .
is grateful for an australian postgraduate award .
thanks the australian research council for a discovery early career researcher award ( de130101441 ) and a discovery project grant ( dp140104071 ) .
p.m.w.g .
thanks the australian research council for funding ( grants no .
dp140104071 and dp160100246 ) .
p.f.l . and p.m.w.g .
also thank the nci national facility for grants of supercomputer time .
it is convenient to define the parity function @xmath56 the potential to the left of @xmath72 is @xmath79 and the potentials to the right(+ ) or left( ) of @xmath73 are @xmath80\ ] ] where @xmath81 is the gauss hypergeometric function.@xcite these potentials , which are illustrated in fig .
[ fig : pot ] , are monotonically decreasing and behave asymptotically as @xmath82 .
potential @xmath84 to the right of @xmath85 with @xmath86 ( left ) and to the right of @xmath87 with @xmath88 ( right ) . from top to bottom , @xmath89.,title="fig:",scaledwidth=45.0% ] potential @xmath84 to the right of @xmath85 with @xmath86 ( left ) and to the right of @xmath87 with @xmath88 ( right ) . from top to bottom , @xmath89.,title="fig:",scaledwidth=45.0% ] the coulomb integral@xcite between densities @xmath91 and @xmath92 in different domains with @xmath93 is given by @xmath94 where @xmath81 and @xmath95 are the laplace transforms of @xmath96 and @xmath97 and @xmath98 . in this way , we find that each of the integrals , and is @xmath101 for large @xmath102 .
consequently , for domains that are far apart , many of the higher coulomb integrals are negligible and can be safely neglected using the bound .
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2015 , * 17 * , 3196 ; mol .
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2015 , * 113 * , 1843 ] , we perform a larger - scale study of chemical structure in one dimension ( 1d ) .
we identify a wide , and occasionally surprising , variety of stable 1d compounds ( from diatomics to tetra - atomics ) as well as a small collection of stable polymeric structures .
we define the exclusion potential , a 1d analogue of the electrostatic potential , and show that it can be used to rationalise the nature of bonding within molecules .
this allows us to construct a small set of simple rules which can predict whether a putative 1d molecule should be stable . |
Exclusive: Lindsay Lohan: I Don't Regret Anything I've Done
Lindsay Lohan is quickly becoming the girl who cried "comeback" -- but she swears this time she's serious about getting her act together.
The 26-year-old Liz & Dick actress opens up in the new issue of Us Weekly about repeatedly hitting bottom and trying to work her way back up to the top amid legal woes and personal drama.
PHOTOS: Lindsay Lohan in court
"I want to be known as an actress, not a troubled starlet," she told Us Weekly reporter Jennifer Peros during a sitdown interview in Los Angeles. "People can think what they want, and the only thing I can do is prove them wrong."
Easier said than done. Over the last several years, the former child star has endured a seemingly endless string of public humiliations, including but not limited to five stints in rehab, six arrests, multiple career setbacks, and countless family fights, some of which culminated in frantic calls to the police. But Lohan says she's a better person -- and a better actress -- for all of it. Even the 20,274 minutes of jail time.
PHOTOS: How Lindsay's face has changed
"[I regret] nothing, because then I wouldn't have been able to cry in scenes at the drop of a hat," she explains to Us. "I have it tattooed: LIVE WITHOUT REGRETS. I'm not saying I wanted to go to a jail cell, but I've drawn from all of it."
PHOTOS: Lindsay's biggest OMG moments
For much more from Lindsay Lohan -- including what she learned from rehab and community service, plus her plans for kids, love, and the future -- pick up the new issue of Us Weekly, on stands now. ||||| Lindsay Lohan I Want NOTHING to Do With My Half-Sister
Lindsay Lohan -- I Want Nothing to Do with My Half-Sister
EXCLUSIVE
Don't count on a Lohan family reunion any time soon --has ZERO plans to meet her newly-announced 17-year-old half-sister ... in fact, she wants nothing to do with her ... ever.Lindsay is telling friends, she's 100% done with the "circus" that is her father-- and does NOT want to meet her half-sister Ashley.TMZ broke the story ... Michael took a DNA test on national TV to determine whether he fathered Ashley back in 1995 with a former mistress -- and the results came back positive.We’re told Lindsay has been aware of the paternity dispute for a while -- since it's been going back and forth for years -- but did not know her father had taken a DNA test until we broke the story.Lindsay has not communicated with Michael since he leaked the recorded phone call during her fight with Dina last month -- and no longer wants anything involving him in her life, lovechildren included.Lindsay says she's doing much better now without her father's drama -- and she wants to keep it that way.We're told Lindsay has no ill feelings toward Ashley -- but finds the entire situation "disgusting" ... especially because Michael had the affair while he was still married to (and having kids with) Dina.For his part, MiLo tells TMZ, "I am sorry to hear Lindsay feels that way. I met Ashley and she is a good kid. But we all have our choices to make in life, as well as our own prerogatives. Who knows, maybe someday things will change. Regardless, I want the best for all my kids." ||||| Lindsay Lohan sat down with Jay Leno on Tuesday to talk about her latest movie, "Liz & Dick."
Following appearances on “Good Morning America” and “Late Night with Jimmy Fallon,” Lindsay Lohan continued to hit the media circuit with a stop at “The Tonight Show,” where she opened up about canceling on Barbara Walters and her latest movie, “Liz & Dick.”
Lohan’s “Tonight Show” appearance came days after she backed out from a scheduled interview with “20/20’s” Barbara Walters, a move that irked the veteran journalist.
“You canceled Barbara Walters, and Barbara looked a little … upset,” host Jay Leno observed. “So what happened there?”
The actress, whose actions of late have landed her on numerous tabloids, said the timing for the interview just “wasn’t right, right now.”
Lindsay Lohan's Highs and Lows
“I love her, I’m a big fan of Barbara Walters,” Lohan said. “So when it’s right, she knows she’ll be the first person I sit down with.”
During the wide-ranging interview, which managed to incorporate Tim Tebow, Thanksgiving traditions and Lohan’s half-sister, the actress spoke candidly about her life in the limelight, stating she “never” regrets entering showbiz at the tender age of three.
“I love doing it, it makes me happy,” Lohan said. “I think I had to step back and take myself out of everything and kind of get my head straight … you get caught up in everything, it’s important to kind of find yourself.”
Top Entertainment Photos
The “Mean Girls” star also touched on her latest movie, Lifetime's Elizabeth Taylor biopic “Liz & Dick,” and how she went about preparing for her role. Lohan confided to Leno that she “became good friends” with Taylor’s nurse, who eagerly shared little anecdotes about the big screen star.
“It was nice to kind of have the inside things that I didn’t know about Elizabeth,” Lohan gushed. “When she was home in bed she would karaoke sometimes to [radio station] 103.1!”
To see more of Leno’s interview with the “Liz & Dick” actress, check out the clips below:
||||| Barbara Walters, Lindsay Lohan, and Jay Leno Credit: Astrid Stawiarz/Getty; Dimitrios Kambouris/WireImage.com; Brian To/WireImage.com
Barbara Walters is dumbfounded as to why Lindsay Lohan abruptly pulled out of an appearance on ABC's 20/20, scheduled to air Nov. 16.
The esteemed TV journalist, 83, spoke about the cancelation for the first time on The View Nov. 12. "My interview with Lindsay is canceled. She has new PR people, a very well-known group that we do business with all the time," Walters explained.
PHOTOS: Lindsay Lohan's multiple court appearances
"'Why is it canceled?'" Walters asked Lohan's rep. "'Lindsay doesn't feel up to it.' Well, I mean, she has a lot of problems, and it was just one more. I said, 'Poor girl, I hope when she feels like it, she will do it with us.'"
Walters felt slighted, however, when she discovered that Lohan will be promoting her new Lifetime movie, Liz & Dick, on The Tonight Show With Jay Leno instead. "If they'd said to me 'You know, Barbara, she isn't up to the kinds of questions that you might ask' . . . I wouldn't feel quite as disappointed as I do today."
PHOTOS: How Lindsay Lohan's face has changed
According to Walters, she would have conducted "a wonderful, wonderful interview" comparing Lohan's life to the late Elizabeth Taylor (who passed away in March 2011). Additionally, the 26-year-old "could have set a lot of things straight" and rehabbed her public image, Walters said.
"I like Lindsay Lohan very much. I've known her for years since she was a very little girl," Walters explained. "She said whenever she did an interview, she would sit down and do it with me."
PHOTOS: Lindsay Lohan look-alikes
In June, Walters conducted the first part of her interview with Lohan on the set of Liz & Dick in L.A. "Even then, the producers were a little worried about whether or not she would be able to finish the film. When I saw her, she was in very good shape," the View co-host recalled. "We were supposed do the major interview last week. . . We were very excited about it. I spent a lot of time, doing a lot of homework, watching the actual movie. . . and then her longtime press agent resigned. That should have been a clue."
PHOTOS: Lindsay Lohan's biggest OMG moments
Walters, who flashed her binder full of research as proof of her hard work, said she deserved "a more honest explanation" from Lohan's new representatives. "As far as Jay goes, I love Jay. More power to him," Walters said. "I think I would have helped her. I think to go on Jay Leno and be adorable and amusing, there's still all the problems with her."
Lohan will appear on The Tonight Show With Jay Leno Nov. 20, five days before the premiere of Liz & Dick. | – Lindsay Lohan went on the Tonight Show last night to talk to Jay Leno ... days after canceling an interview with Barbara Walters that had been scheduled for 20/20 last Friday. "The timing wasn’t right, right now," a fidgety Lohan explained to Leno when he pointed out that Walters was quite upset over the situation. "I love her, I’m a big fan of Barbara Walters," Lohan continued. "So when it’s right, she knows she'll be the first person I sit down with." Er, make that ... the second person? More from her Leno interview: "I guess I could give her one word of advice: Good luck with my dad," Lindsay said of the secret half-sister the world recently learned about. "That's great for him," she said of Tim Tebow's virginity, after Leno brought up a tabloid story about the two of them doin' it. On why she wanted to play Elizabeth Taylor so badly: "I relate to her, you know, her part of the life that was all in front of the cameras." She says Taylor once sent her a ring and invited her to dinner, but she was too nervous to attend. From another recent interview with Us: "I want to be known as an actress, not a troubled starlet," she says. But when it comes to her past, "[I regret] nothing, because then I wouldn't have been able to cry in scenes at the drop of a hat. ... I'm not saying I wanted to go to a jail cell, but I've drawn from all of it." Click to see how the critics feel about Lohan in Liz & Dick. |
supermassive black holes ( sbhs ) reside at the centers of most large galaxies .
the masses of these sbhs are tightly correlated with the luminosity @xcite , mass @xcite , and velocity dispersions @xcite of the spheroidal components of their host galaxies .
large galaxies form hierarchically from the merger of smaller galaxies , and sbh mergers are expected to accompany the mergers of their hosts .
the final stages of these sbh mergers are driven by the emission of copious amounts of gravitational radiation .
conservation of linear momentum implies that the final black holes produced in sbh mergers must recoil with linear momentum equal in magnitude and opposite in direction to that of the anisotropically emitted gravitational radiation .
early estimates of these gravitational recoils or `` kicks '' using post - newtonian ( pn ) techniques @xcite and black - hole perturbation theory @xcite suggested that they would not exceed several hundred km / s in magnitude .
more recently , progress in numerical relativity ( nr ) @xcite has allowed relativists to simulate the mergers of highly spinning , comparable - mass black holes . for non - spinning binaries , ensuing studies identified a maximum recoil of @xmath2 @xcite
. simulations of spinning black holes , however , resulted in one of the greatest surprises of numerical relativity ; for equal - mass binaries with opposite spins in the orbital plane gravitational recoils can approach 4,000 km / s @xcite , greater than the escape velocity of even the most massive galaxies .
this theoretical result seems at first difficult to reconcile with observations indicating that almost all large galaxies host sbhs .
one solution to this problem is to align the sbh spins before merger into configurations that lead to small recoils .
gravitational radiation extracts energy and angular momentum from the orbit of the binary sbhs , causing them to merge on a timescale @xmath3 , where @xmath4 is the binary separation .
this timescale becomes longer than the age of the universe at separations @xmath5 pc , implying that some mechanism other than gravitational radiation is required to escort the sbhs to this separation ( the `` final - parsec problem '' ) @xcite .
one such mechanism is the transfer of orbital angular momentum from the sbh binary to surrounding gas .
this gas forms a circumbinary disk about the sbhs , and can be transferred through the gap onto accretion disks about the individual sbhs @xcite .
if the angular momentum of the circumbinary disk is misaligned with the sbh spins , the lense - thirring effect causes inclined annuli in the individual accretion disks to differentially precess about the sbh spins .
bardeen and petterson @xcite showed that viscous dissipation causes this differentially precessing gas to settle into the equatorial planes of the sbhs . on longer timescales , these warped accretion disks torque the sbh spins into alignment with the orbital angular momentum of the gas at large radii , presumably that of the circumbinary disk from which both accretion disks are being fed @xcite .
bogdanovi et al .
@xcite suggested that this alignment could reduce gravitational recoils to less than 200 km / s , in contrast to the @xmath6 km / s recoils expected for sbhs in the `` superkick '' configuration ( spins in opposite directions lying in the equatorial plane ) @xcite .
dotti et al .
@xcite tested this suggestion by performing a series of n - body smoothed particle hydrodynamics ( sph ) simulations of two @xmath7 sbhs inspiraling due to dynamical friction exerted by a @xmath8 circumnuclear disk in their orbital plane .
one of the sbhs began at the center of the circumnuclear disk , while the second sbh spiraled inwards from an initial separation of 50 pc to a final separation of @xmath9 pc .
gas particles within the bondi - hoyle radii @xcite of the sbhs were accreted , and assumed to fuel warped accretion disks as described in perego et al . @xcite .
on a timescale of @xmath10 1 - 2 myr , the sbh spins became aligned to within @xmath11 ( @xmath12 ) of their orbital angular momentum for a cold ( hot ) circumnuclear disk @xcite .
if the partially aligned spin configurations found in these simulations were preserved as the sbhs inspiraled and merged , the median recoils predicted by nr simulations would be @xmath13 km / s for dimensionless spins @xmath14 ( @xmath15 ) with an initially uniform distribution of magnitudes @xmath16 $ ] .
the assumption that sbh spin distributions remain unchanged between @xmath17 ( where the sph simulations end ) and @xmath18 ( where the nr simulations begin ) , needs further examination . here
@xmath19 is the schwarzschild radius of a sbh of mass @xmath20 . because of the steep scaling @xmath21 mentioned previously , the sbhs decouple from their circumbinary disk and spiral inwards purely under the influence of gravitational radiation at a binary separation @xmath22 @xcite , where @xmath23 is the total mass of the binary .
schnittman @xcite integrated pn equations of motion and spin precession from an initial binary separation @xmath24 to a final separation @xmath25 ( in geometrical units where @xmath26 ) and discovered that partially aligned sbh spin distributions during this portion of the inspiral are strongly influenced by the presence of spin - orbit resonances .
these resonances are special spin configurations in which both sbh spins and the orbital angular momentum jointly precess at the same frequency in a common two - dimensional plane . for binary sbhs with mass ratio @xmath27 and
dimensionless spins @xmath14 , at each separation @xmath4 there exist two one - parameter families of spin - orbit resonances : one with @xmath28 and the other with @xmath29 , where @xmath30 is the angle between the components of @xmath31 and @xmath32 perpendicular to the orbital angular momentum @xmath33 .
the first of these families ( @xmath34 ) has @xmath35 , where @xmath36 , while the second family ( @xmath29 ) has @xmath37 . as sbhs inspiral due to the emission of gravitational radiation ,
they can become captured into nearby spin - orbit resonances , substantially altering the sbh spin distributions between @xmath38 and @xmath39 . in previous work , we examined the influence of this pn portion of the inspiral on the expected distribution of sbh final spins @xcite and recoils @xcite .
we found that if the spin of the more massive sbh was more closely aligned with the orbital angular momentum ( @xmath35 ) , the sbhs were more likely to be captured into the @xmath34 family of resonances .
this alignment of the sbh spins prior to merger causes them to add constructively , enhancing the spin of the final black hole .
symmetry requirements imply that gravitational recoils are suppressed when the sbh spins are aligned with each other prior to merger @xcite , so this pn alignment also reduces the predicted distribution of recoils .
the opposite is true when @xmath37 ; sbhs are preferentially captured into the @xmath29 family of resonances , reducing the final spins and enhancing the gravitational recoils .
recent equal - mass nr simulations by lousto and zlochower ( @xcite ; henceforth lz ) have qualitatively and quantitatively changed the predicted dependence of gravitational recoils on the sbh spins @xmath14 .
the maximum possible kick , extrapolated to maximal initial spins , is now @xmath40 km / s , and this kick occurs not in the previously described `` superkick '' configuration but for spins with @xmath41 . in light of these new findings , it is worth investigating whether pn spin alignment still has as dramatic an effect on the expected recoil distribution as we found previously .
this investigation is the subject of this paper . in section
[ s : pn ] we revisit our analysis of how pn evolution affects binaries that are evolved from an initial separation of @xmath42 down to a final separation of @xmath25 .
we clarify the reason why spin - orbit resonances are also effective at suppressing kicks consistent with the new lz results . in section [ s
: param ] we set up a more extensive set of monte carlo simulations of sbh inspirals .
we focus on a specific choice for the initial distribution of sbh parameters @xmath43 , and justify this choice based on astrophysical considerations . in section [ s : res ]
we present the final distributions of recoil velocities resulting from our monte carlo simulations , and our predictions for the fraction of remnant sbhs that are ejected from their host galaxies .
we summarize these results and discuss the sources of uncertainty in our analysis in section [ s : disc ] .
the recent lz simulations @xcite have two potentially important consequences from an astrophysical point of view .
first of all , the maximum possible `` hang - up '' kick magnitude is about 25% larger than predicted by the ordinary , `` no hang - up '' superkick formula : 4,900 km / s rather than 3,750 km / s .
secondly , the largest kick occurs for a configuration in which the spins are partially aligned with the orbital angular momentum . because of the gas - dynamical alignment arguments summarized above , this configuration seems more likely than the superkick configuration .
we would therefore expect an enhancement in the statistical likelihood of gravitational recoils ejecting remnant sbhs from galaxies as reported by lz .
we confirm this enhancement , but show that even in hang - up kick scenarios spin - orbit resonances can significantly change the likelihood of large recoil velocities as the sbhs inspiral from sub - parsec scales to about @xmath44 .
the largest `` superkick '' recoil velocities are obtained for nearly equal - mass sbhs .
furthermore , the lz kick formula is most reliable for mass ratios close to unity , since all 48 of the new nr simulations were carried out for @xmath45 @xcite .
we therefore begin our study of the likelihood of very large kicks by considering comparable - mass binaries .
resonance effects are not present for @xmath46 , but astrophysical binaries are not expected to be precisely equal in mass .
for this reason we have performed monte carlo pn evolutions of 900 black hole binaries with mass ratio close to but not exactly equal to one ( we choose @xmath47 to facilitate comparisons with schnittman @xcite and our own earlier work @xcite ) .
we considered binaries where the two black holes have the same dimensionless spin magnitude @xmath48 , and selected five equally - spaced values of @xmath49 in the range @xmath50 $ ] .
for each of the five values of @xmath49 we further selected six equally - spaced initial values of @xmath51 in the range [ @xmath52 , @xmath12 ] and six values in the range [ @xmath54 , @xmath55 , for a total of sixty monte carlo simulations .
each simulation is started by assuming uniform distributions in @xmath56 $ ] and @xmath57 $ ] .
we begin at an initial separation @xmath58 and use the pn equations of motion to evolve the binaries down to a final separation @xmath59 ( cf .
section ii of @xcite for details of the pn evolution ) .
to quantify the effect of pn spin alignment , we compute the recoil velocity distribution that would result from applying kick formulae to our binaries _ before _ the pn evolution ( at @xmath58 ) and close to merger ( at @xmath59 ) .
we calculate the component @xmath60 of the recoil velocity parallel to @xmath33 using both the new lz `` hang - up '' formula @xcite and the older kick formula from campanelli et al . @xcite .
we calculate the components @xmath61 , @xmath62 perpendicular to @xmath33 from the fitting formula of @xcite : cf .
( 1 ) in @xcite .
we then compute the probability that the total recoil velocity is greater than @xmath63 km / s for each of our sixty monte carlo simulations ( twelve values of @xmath51 and five values of @xmath49 ) .
this value of @xmath64 is comparable to the escape velocity from a giant elliptical galaxy @xcite ; we will consider more realistic escape velocities that depend on the host galaxy s mass in section [ s : res ] .
the results are plotted in figure [ fig : p1000 ] .
figure [ fig : p1000 ] confirms lz s conclusion that the `` hang - up '' effect increases ejection probabilities if the spin of the heavier companion is partially aligned with the orbital angular momentum ( @xmath65 ) whereas the ejection probabilities are reduced for partial antialignment of @xmath66 ( @xmath67 ) ; cf .
their fig . 2 .
by comparing the dashed lines in the upper left and right panels of figure [ fig : p1000 ] , we see that , if we ignore the effect of resonances ( as the authors of the lz papers did ) , ejection probabilities for the aligned cases @xmath68 are only mildly dependent on @xmath51 and roughly double because of the hang - up kick effect . these ejection probabilities can be larger than @xmath69 for spins @xmath70 and @xmath47 .
on the other hand , a comparison of dashed and solid lines in each panel shows that ejection probabilities are dramatically reduced in the aligned case if we apply the kick formula ( as we should ) close to merger , rather than at large separations .
the relevance of resonant effects depends on @xmath51 : if the initial angle between the larger black hole and the orbital angular momentum @xmath71 , recoil velocities larger than @xmath72 km / s would almost never occur . even for more modest alignments ( @xmath73 ) ,
such large kicks only occur for large values of @xmath49 .
recoils are even smaller for @xmath74 , as all components of the kick are proportional to @xmath75 ( see eq . ( 11 ) of @xcite ) .
note that this kick suppression only applies when on average @xmath35 ; for initial values of @xmath37 the recoil is enhanced , not suppressed , as demonstrated by the lower two panels of fig .
[ fig : p1000 ] , where @xmath76 .
interestingly , the kick enhancement appears to saturate : while ejection probabilities approach zero as we fix @xmath51 at ever smaller values , they are essentially independent of @xmath77 if we apply the kick formula close to merger .
figure [ fig : p1000 ] also indicates that kick suppression via alignment ( @xmath78 ) is more efficient than enhancement via antialignment ( @xmath79 ) .
we shall quantify this asymmetry in more detail below .
it may seem surprising that pn spin alignment so dramatically suppresses the recoil velocities predicted by the new lz kick formula , since many of the spin - orbit resonances depicted in figure 1 of @xcite have values of @xmath80 comparable to that of the new `` maximum recoil '' configuration in the presence of the hang - up effect .
we can understand the effectiveness of pn kick suppression by recognizing that it results from the alignment of the perpendicular components of the sbh spins _ with each other _
( @xmath81 ) , not from the spins aligning with the orbital angular momentum ( @xmath82 , as bogdanovi et al .
@xcite argued would occur due to the torque exerted by a warped circumbinary disk ) . to illustrate this point , we consider maximally spinning ( @xmath83 ) binaries with @xmath47 in figure [ fig : deltaphi ] .
dotted histograms refer to recoil distributions computed before the pn evolutions ( at @xmath58 ) , and solid histograms refer to the corresponding distributions computed after evolving the binaries down to @xmath59 .
let us first focus on the left panel .
the black curves in the upper histogram show that black holes with isotropic spin distributions ( flat distributions in @xmath84 , @xmath85 , and @xmath86 ) maintain these isotropic distributions as they inspiral down to @xmath59 .
the thick blue ( thin red ) curves in the upper histogram corresponds to the subset of this isotropic distribution with the 30% lowest ( highest ) initial values of @xmath51 .
careful comparison of the solid and dotted curves reveals that recoils are suppressed ( enhanced ) for low ( high ) initial values of @xmath51 .
this tendency is seen much more clearly in the middle and lower panels , where @xmath51 has the indicated initial value while @xmath32 retains its isotropic initial distribution .
if @xmath87 is partially aligned with @xmath33 , as in the middle histograms , then @xmath88 ( the angle between the two spins ) and @xmath86 will be strongly peaked around @xmath89 at the end of the evolution and kicks will be reduced .
if instead @xmath87 is partially antialigned with @xmath33 ( as in the lower histograms ) , then @xmath88 and @xmath86 will be strongly peaked around @xmath90 at the end of the evolution and the kicks will be enhanced ( cf . the discussion in @xcite ) .
the crucial element for producing alignment here is the fact that @xmath91 .
this is illustrated in the right - hand panels of figure [ fig : deltaphi ] , which are the same as the corresponding left - hand panels , except that @xmath92 has been reset to a flat distribution @xmath93 $ ] after the pn inspiral ( but before the recoil velocities are computed ) .
this nearly eliminates the kick suppression ( for initially aligned binaries ) or enhancement ( for initially anti - aligned binaries ) .
we demonstrated in the previous section that the new fitting formulae for gravitational recoils provided in the lz papers @xcite did not alter our earlier conclusion @xcite that pn spin alignment can dramatically affect the distribution of recoil velocities for specific initial values of @xmath94 and @xmath51 and an initially isotropic distribution for @xmath32 . in this section
, we describe a more astrophysically motivated choice for these initial parameters .
the effect of pn spin alignment on this new distribution will be presented in section [ s : res ] .
the origin of sbhs is poorly understood theoretically and poorly constrained observationally .
lynden - bell @xcite recognized that the central objects of mass @xmath95 believed to power quasars would quickly collapse into sbhs .
haehnelt and rees @xcite explained the quasar luminosity function by assuming that such massive sbh seeds promptly formed at the centers of dark - matter ( dm ) halos whose formation rates could be predicted using the press - schechter formalism @xcite . more recent theoretical work
has called into question whether the high - redshift seeds of sbhs were truly this massive . while some maintain that massive central concentrations of gas at the centers of pre - galactic disks can directly collapse into @xmath96 sbh seeds @xcite
, others argue that metal - free gas will fragment into population iii stars with characteristic masses @xmath97 @xcite .
volonteri , haardt , and madau @xcite , also using the press - schechter formalism to estimate halo mass functions and merger rates , showed that @xmath98 seeds occupying @xmath99 overdensities at redshift @xmath100 could grow into sbhs that would reproduce both the quasar luminosity function at @xmath101 and the observed local @xmath102 relation @xcite between sbh mass and galaxy velocity dispersion .
a future space - based interferometer such as lisa or the european new gravitational wave observatory ( ngo / elisa ) will be able to distinguish between these two different scenarios for sbh formation by observing the gravitational waves emitted during high - redshift mergers @xcite . given this uncertainty in the high - redshift population of sbh seeds , in this paper we restrict our attention to sbh mergers in the low - redshift ( @xmath103 ) universe .
stewart et al .
@xcite used a high - resolution n - body simulation to calculate the merger rates of dm halos in the redshift range @xmath104 .
they fit their results for the rate at which a larger galaxy of mass @xmath105 merges with smaller galaxies with masses between @xmath106 and @xmath105 to the function @xmath107 where the normalization @xmath108 is binned by mass , and the mass - ratio dependence is given by @xmath109 with the indices @xmath110 and @xmath111 determined from the simulation . this same functional form can be used for the merger rates of both dm halos of mass @xmath112 and galaxies with stellar mass @xmath113 , although the fitted values of the parameters will be different .
table 1 of stewart et al .
@xcite provides numerical estimates of these parameters binned by stellar mass ; we use the functions [ e : mparam ] @xmath114 which approximate the values listed in this table .
note that the total rate of mergers diverges in the limit @xmath115 for @xmath116 , although the rate at which the galactic mass increases remains finite .
the press - schechter formalism also predicts that the number of dm halos and thus the number of mergers diverges as their mass goes to zero .
volonteri , haardt , and madau @xcite address this issue in their merger trees by only keeping track of halos with masses above an effective mass resolution @xmath117 that evolves with redshift , but always remains a small fraction of the largest progenitor mass . because we are only interested in sbh mergers at low redshift
, we neglect galaxies with @xmath118 .
this corresponds to neglecting sbhs with @xmath119 , since sbhs are about a fraction of @xmath120 of the stellar mass of their host spheroids @xcite .
sbhs less massive than this value are poorly constrained observationally , and even if present in a halo may have difficulty reaching the galactic center , since the dynamical friction time scales as the inverse of the sbh mass .
we assume that sbh mergers occur promptly following the merger of their host galaxies .
( [ e : mrate ] ) gives the rate at which individual galaxies of stellar mass @xmath113 merge with smaller galaxies ; to determine the total rate of mergers in a cosmological volume also requires an estimate of the galactic stellar mass function @xmath121 .
we use the mass function determined from the @xmath122 sample of the cosmos survey @xcite ; this mass function , as shown in the left panel of figure 14 of @xcite , is quite similar to earlier mass functions derived from the sloan digital sky survey @xcite .
the total rate per unit cosmological volume @xmath123 at which galaxies with stellar masses between @xmath124 and @xmath113 merge is given by @xmath125 we use this rate function as part of a monte carlo approach to generate a representative sample of sbh mergers .
we choose a random number @xmath126 from a flat distribution in the interval @xmath127 , then find the stellar mass @xmath113 for which @xmath128 .
values of @xmath129 correspond to stellar masses @xmath130 , while values @xmath131 correspond to stellar masses @xmath132 above which the galactic luminosity function is exponentially suppressed .
we next choose a second random number @xmath133 , also from a flat distribution @xmath134 , and find the value of @xmath135 for which @xmath136 .
values of @xmath137 correspond to nearly equal - mass mergers ( @xmath138 ) , while values @xmath139 correspond to mergers with the smallest galaxies to host sbhs ( @xmath140 ) .
the sbh masses are then determined from the masses of their host galaxies , @xmath141 and @xmath142 .
histograms of our sbh mass ratio distribution are given by the solid black curves in the upper panels of fig .
[ fig : eject1000log ] . our assumption that the sbh mass is @xmath120 that of its host galaxy s stellar mass is strictly true only for elliptical galaxies , since observations suggest that sbh masses are uncorrelated with galactic disks and pseudobulges @xcite .
the most massive galaxies are primarily ellipticals , while smaller galaxies are a mixture of ellipticals and spirals @xcite .
a more sophisticated monte carlo treatment would draw galactic bulge fraction from an observed distribution as a function of galactic mass , and only correlate the sbh mass with this bulge component .
such a treatment is beyond the scope of this paper .
this procedure for determining the sbh mass ratio @xmath143 is considerably more elaborate than that used in the lz papers @xcite .
they assumed that the probability of having a sbh mass ratio between @xmath94 and @xmath144 was simply @xmath145 , with the function @xmath146 given by eq .
( [ e : mrat ] ) with @xmath147 and @xmath148
. this assumption seems to be based on a misinterpretation of stewart et al .
@xcite , which defines @xmath146 as being proportional to the total number of mergers between a mass ratio of @xmath94 and 1 .
the lz papers did not need to introduce an explicit cutoff at small mass ratios , because the total number of mergers remained finite under their assumption .
this finite number of mergers allowed them to calculate the probability that the gravitational recoil would be in a particular velocity interval . given the infinite rate of mergers predicted by eq .
( [ e : mrate ] ) as @xmath149 , we would predict an infinite number of mergers with @xmath150 km / s in the absence of a cutoff , since @xmath151 as @xmath152 .
this cutoff is well justified physically because dm halos of arbitrarily small mass can not host stars , let alone sbhs .
the accretion and merger history of sbhs determines the magnitude and direction of their spins . in this section
we discuss some astrophysical predictions on sbh spin magnitude and direction . here
we present a short overview of the literature to show that sbh spin magnitudes are strongly dependent on the underlying assumptions about gas accretion . because of these uncertainties , in this paper we simply assume @xmath153 for @xmath154 , 0.75 , and 1.0 , and we provide predictions for each of these three values .
schnittman @xcite showed that the amount of pn spin alignment is insensitive to the spin magnitude for @xmath155 ( see fig .
11 in his paper ) . at large separations
where @xmath156 , eq .
( 3.5 ) of @xcite indicates that the constraint for defining a spin - orbit resonance depends only on @xmath80 , not @xmath157 .
we therefore expect that pn spin alignment should not be particularly sensitive to our assumption that @xmath158 , although additional numerical studies would be required to confirm this expectation . volonteri et al . @xcite examined the distribution of sbh spin magnitudes using cosmological merger trees constructed within the press - schechter formalism .
they found that binary mergers alone lead to broad distributions of the dimensionless spin magnitude peaked around @xmath159 , but that when accretion is included the spins reach much larger values .
accretion from geometrically thin disks leads to spin distributions sharply peaked around @xmath160 @xcite , as the bardeen - petterson effect @xcite aligns the sbh spins with the disks on a timescale @xcite @xmath161 much shorter than the salpeter time @xmath162 on which the spin magnitudes change . here
@xmath163 is the radiative efficiency normalized by a typical value @xmath164 and @xmath165 is the agn luminosity in units of the eddington value @xmath166 ( @xmath167 is the proton mass , @xmath168 is the thomson cross section for elastic scattering ) .
accretion from geometrically thick disks leads to much broader spin distributions , because spin alignment occurs on the longer salpeter time .
sbhs that accrete from a thick disk may also have a smaller maximum spin @xmath169 , as ordered magnetic fields in the plunging region interior to the innermost stable orbit may extract angular momentum that would be advected by the sbh in the thin - disk case @xcite .
volonteri et al .
@xcite assumed that after each major merger , sbhs accreted continuously from disks with well defined angular momentum until their mass increased by an amount @xmath170 , where @xmath171 is the circular velocity of the host galaxy s dm halo in units of 150 km / s .
moderski and sikora proposed an alternative scenario , in which gas was accreted in small discrete episodes with random orientations with respect to the sbh spin .
this `` chaotic accretion '' scenario leads to sbh spins that fluctuate about @xmath172 , and was originally motivated by the conjecture of wilson and colbert @xcite that only radio - loud agn ( approximately 10% of all agn ) are powered by highly spinning sbhs .
king et al .
@xcite suggested that the mass accreted in each of these discrete episodes might be determined by the mass of the accretion disk interior to the radius @xmath173 pc at which the disk becomes self - gravitating .
star formation at @xmath174 would stir the gas flow , implying that each event would have essentially random orientations .
recent high - resolution n - body / sph simulations of galactic accretion disks which include star formation support this suggestion @xcite .
these simulations follow gas flows from galactic scales of @xmath175 kpc all the way down to @xmath176 pc , and show that the orientation of the inner nuclear disk varies on @xmath177 myr timescales , that are comparable to the alignment timescale @xmath178 of eq .
( [ e : tal ] ) .
berti and volonteri @xcite explored how chaotic accretion would affect sbh spin evolution in a cosmological context , also incorporating the results of nr simulations available at the time .
the nr simulations implied that sbh spin distributions would now be broadly peaked about @xmath179 in the absence of accretion , but that the full range of spin magnitudes @xmath180 was now possible once both standard and chaotic accretion were permitted .
this differs from the spin magnitude distributions used in the lz papers @xcite , which as shown in figure 7 of @xcite are peaked around @xmath181 .
these spin distributions were determined from the n - body / sph simulations of dotti et al .
@xcite , which were restricted to equal - mass binaries , and began with an initially uniform distribution of spin magnitudes @xmath16 $ ] .
although the @xmath182 myr duration of these simulations is long compared to the alignment time @xmath178 on which the spin directions change , it is less than the salpeter time @xmath183 on which the spin magnitudes change .
one might therefore be concerned that these distributions have not converged to the value they should have at @xmath184 , where the gravitational - wave driven stage of the inspiral begins .
the residual misalignment of the sbh spins with their orbital angular momentum at @xmath38 has been less thoroughly investigated than the spin magnitudes .
we review some of these studies below . to encompass all possible scenarios with regard to astrophysical spin alignment prior to @xmath185 , in our simulations we will consider : * uniform symmetric distributions in @xmath186 and @xmath85 drawn in the range @xmath187 $ ] ( @xmath188 ; strong alignment ) and @xmath189 $ ] ( weak alignment )
. we will refer to these cases as the `` 10/10 '' and `` 30/30 '' scenarios . * a uniform distribution in @xmath186 and @xmath85 with asymmetric range for the angles : @xmath190 $ ] , @xmath191 $ ] . in this `` 10/30 '' scenario
the primary is more strongly aligned with the orbital angular momentum . * a uniform distribution in @xmath186 and @xmath85 with @xmath192 $ ] , @xmath193 $ ] .
this `` 30/10 '' scenario could result from the secondary orbiting close to the inner edge of a circumbinary disk , so that it ends up being more aligned than the primary with the orbital angular momentum . in order to justify these assumptions , here we review some literature on astrophysical predictions for the spin orientation resulting from sbh mergers .
dotti et al .
@xcite performed simulations where one @xmath7 sbh is initially at rest at the center of a @xmath8 circumnuclear disk .
the second sbh , also with @xmath194 , began at an initial separation of @xmath195 pc with orbital angular momentum that was already aligned or anti - aligned with that of the circumnuclear disk .
this is consistent with the sph simulations of larwood and papaloizou @xcite , which suggest that the mass - quadrupole moment of the sbh binary will induce differential precession in an inclined circumbinary disk .
viscous dissipation will then cause this differentially precessing disk to settle into the equatorial plane of the binary .
it is unclear whether this mechanism will operate at the large initial separation of the dotti et al .
simulations before the sbh binary becomes gravitationally bound .
dynamical friction causes initially eccentric or retrograde orbits to circularize as the second sbh inspirals to a final separation @xmath196 pc .
accretion during this inspiral aligns the spins of both sbhs to within @xmath11 of the orbital angular momentum for a cold circumnuclear disk , and to within @xmath12 for a hot disk with greater pressure support , and hence more isotropic gas velocity dispersion @xcite .
these simulations did not include star formation or cooling , and the internal energy of the gas particles was chosen to prevent gravitational fragmentation .
these choices suppress chaotic accretion and the dynamical instabilities found in hopkins et al .
@xcite , that cause the direction of the angular momentum of the inner disk to fluctuate on @xmath10 myr timescales .
these estimates should therefore be considered lower bounds on the residual misalignment between the sbh spins and their orbital angular momentum . after the simulations of dotti et al .
@xcite end , but before the gravitational - wave driven stage of the inspiral begins at @xmath42 , the sbhs open a gap and form a true circumbinary disk .
high - resolution hydrodynamical simulations indicate that the gas surface density will be sharply truncated at radii less than twice the semi - major axis of the binary @xcite .
mass can flow from the inner edge of this circumbinary disk onto the individual sbhs @xcite .
accretion rates are generally higher for the less massive sbh , which is further from the center of mass and hence closer to the inner edge of the disk .
this point is absolutely crucial for the pn spin alignment that is the subject of this paper , as it is the _ relative _ value of @xmath51 and @xmath197 that determines whether gravitational recoils are suppressed or enhanced .
one might expect that the higher accretion rate onto the smaller sbh would lead to closer alignment between its spin and that of the orbital angular momentum .
alternatively , it is possible that the spin of the more massive sbh would be more influential in determining the direction of the warp in the circumbinary disk that torques the sbh spins .
the relative value of @xmath51 and @xmath197 in the presence of a circumbinary disk remains very much an open question .
a final complication is the growth of the binary s orbital eccentricity through its interaction with the circumbinary disk .
although dynamical friction damped the orbital eccentricity at the large separations of the dotti et al .
simulations @xcite , after the formation of a circumbinary disk the orbital eccentricity again grows to a limiting value @xmath198 @xcite .
gravitational radiation circularizes the binary after it decouples from the circumbinary disk @xcite , but the binary could still have considerable residual eccentricity @xmath199 when the frequency of the fundamental gw harmonic reaches @xmath200 hz @xcite .
we will neglect residual eccentricity during the inspiral and any effects it might have on pn spin alignment .
we carried out a systematic study of the probability that gravitational recoils eject sbhs from their host galaxies . we generated a population of binaries with astrophysically motivated mass ratios using the monte carlo prescription described in section [ ss : massrat ] . to quantify the effect of sbh spin magnitudes , we computed ejection probabilities for three fixed values of @xmath48 : @xmath49=0.5 , 0.75 , and 1 . to account for all possibilities
given the great uncertainty in the spin - alignment distributions , we considered the four cases described in section [ sss : dir ] : two `` symmetric '' cases ( 10/10 , 30/30 ) and two `` asymmetric '' cases ( 10/30 and 30/10 ) . our results for @xmath201 are summarized in figure [ fig : eject1000log ] .
this figure has four panels : our simulated binaries are binned by mass ratio @xmath94 in the top panels , and by the stellar mass @xmath113 of the larger host galaxy in the bottom panels . in the right panels we assume that
a gravitational recoil greater than @xmath63 km / s is needed to eject a recoiling sbh from its host galaxy , while in the left panels we adopt a prescription that depends on the stellar mass @xmath113 .
the gravitational potential of a real galaxy is the sum of contributions from its stellar mass and dm halo ; although the dm halo is more massive , the more concentrated stellar contribution is dominant for large elliptical galaxies @xcite .
modeling elliptical galaxies with the density profiles of terzi and graham @xcite , gualandris and merritt @xcite find that escape velocities have typical values @xmath202 , where @xmath203 is the effective radius that contains half the galaxy s total luminosity .
combining this with the observed relation @xmath204 yields the approximate expression @xcite @xmath205 this is the prescription we used to calculate escape velocities in the left panels of figure [ fig : eject1000log ] .
each panel of figure [ fig : eject1000log ] has 7 histograms : the solid black curve corresponds to the total distribution of simulated binaries , while the 6 dashed and/or dotted colored curves correspond to the distributions of ejected sbhs given the 6 different spin - alignment distributions indicated in the keys to the figure .
pn spin alignment can play an important role for asymmetric distributions , as can be seen by comparing the distributions of ejected binaries calculated from spins _ before _
( thin - line dashed and dash - dotted histograms ) or _ after _ ( thick - line histograms ) the pn evolution from @xmath58 to @xmath59 . as expected , the fraction of ejected binaries decreases in the 10/30 case , while it increases in the 30/10 case . however , the kick reduction in the 10/30 case is more significant than the kick enhancement in the 30/10 case : in other words , _ pn resonances are more effective at reducing recoils when the primary is more aligned with the orbital angular momentum than they are at increasing recoils when the secondary is more aligned with the orbital angular momentum_. for the symmetric distributions ( 10/10 and 30/30 ) , pn spin alignment has a marginal effect on the ejection probabilities . for clarity ( and to save computational time ) , in these symmetric cases we only plot the distribution of ejected binaries that results by applying the recoil formula to the initial distribution at @xmath58 .
comparing the left and right panels of figure [ fig : eject1000log ] allows us to understand the effects of the mass - dependent escape velocity of eq .
( [ vescmerritt ] ) on the ejection probability .
the most obvious effect is the steep decrease in the ejected fraction from near unity at @xmath206 to less than 10% for @xmath207 .
this is very natural : heavier galaxies should be more effective at retaining recoiling sbhs .
somewhat more surprising is that despite the constant escape velocity , the escape fraction also increases as @xmath208 in the bottom right panel .
this is a consequence of our decision to neglect sbhs with @xmath209 that reside in galaxies with @xmath210 .
because of this choice , sbhs in galaxies with @xmath211 only undergo comparable - mass ( @xmath212 ) mergers , elevating the fraction of large recoils since kicks are proportional to @xmath75 at leading order ( see eq .
( 11 ) of @xcite ) . a second effect of the mass - dependent escape velocity of eq .
( [ vescmerritt ] ) is the possibility of ejecting recoiling sbhs for mass ratios as low as @xmath213 , as can be seen in the top left panel of figure [ fig : eject1000log ] .
the larger host galaxy can have a mass as small as @xmath214 for these mass ratios , corresponding to an escape velocity @xmath215 km / s by eq .
( [ vescmerritt ] ) .
this accounts for the nonzero escape probabilities for @xmath216 .
we also note that in preparing these figures we have not evolved any pn inspirals for @xmath217 , even for those histograms labeled with @xmath218 that correspond to evolved distributions .
this explains why the thin and thick lines corresponding to the initial and final histograms coincide for @xmath217 .
the gravitational - wave inspiral time is inversely proportional to the binary s symmetric mass ratio @xmath219 @xcite , making it hard to preserve accuracy over long pn time evolutions for @xmath216 .
however , schnittman @xcite showed that spin - orbit resonances only become important inside a `` resonance locking '' radius @xmath220 ^ 2 $ ] .
we are therefore justified in treating all binaries with @xmath221 ( for which pn evolutions from @xmath58 to @xmath59 become problematic ) as if the inspiral did not happen : that is , we can compute recoils of binaries with @xmath222 by simply applying the recoil formula at @xmath223 .
we examine how the fraction @xmath224 of ejected sbhs depends on the sbh spin magnitude @xmath49 in figure [ fig : ejectratio ] .
the two top panels in this figure were produced using the same distributions shown in the left panels of figure [ fig : eject1000log ] ; the fraction @xmath224 is calculated by dividing the histograms for each spin distribution by the solid black histogram showing the total distribution .
as expected , the ejected fractions are smaller for lower values of @xmath49 , since the kick magnitudes are reduced while the escape velocities remain fixed .
ejections from host galaxies with @xmath225 ( @xmath226 ) are nearly eliminated for @xmath227 ( 0.5 ) .
pn spin alignment remains effective for these lower spin magnitudes ; for certain values of @xmath113 , the ejected fraction is reduced by almost an order of magnitude .
careful scrutiny of the left panels of figure [ fig : ejectratio ] reveals that pn kick enhancement for the 30/10 case drives @xmath224 above that of the 30/30 case , except at the highest values of @xmath113 for the @xmath154 and 0.75 distributions .
mergers involving the most massive host galaxies are dominated by small values of @xmath94 , for which pn spin alignment is ineffective .
it is also interesting to note that pn spin alignment is suppressed as @xmath228 ( the thin and thick lines converge in this limit in the right panels of figure [ fig : ejectratio ] ) .
schnittman @xcite showed that pn spin alignment increased as @xmath94 increased from 1/9 up to 9/11 ( see figure 10 of @xcite ) .
symmetry implies that pn spin alignment must vanish for equal - mass binaries , since the labeling of the sbhs is arbitrary for @xmath229 and it is therefore impossible to distinguish @xmath35 from @xmath37 .
this limiting behavior implies that the effects of spin alignment must be maximized for some mass ratio in the range @xmath230 , which is precisely what we observe in the right panels of figure [ fig : ejectratio ] .
these near - unity mass ratios are also expected to yield the largest kicks , which emphasizes the importance of including the effects of pn spin alignment in future studies of gravitational recoils .
a final summary of our results is provided in table [ t : fej ] , where we calculate the percentage of ejected binaries for each spin distribution .
although the precise amount of spin alignment depends on the value of @xmath49 , we see that kicks are suppressed ( enhanced ) by @xmath1 ( 20% ) when the escape velocities are given by eq .
( [ vescmerritt ] ) .
the kick suppression or enhancement is even more dramatic for the case of a constant escape velocity @xmath231 km / s .
the ejected fraction is lower overall for this choice of escape velocity , which is larger than the mean value predicted by eq .
( [ vescmerritt ] ) . the kick suppression or enhancement is greater because the effects of pn spin alignment are most pronounced at the high velocity tail of the kick distribution , as shown in the left panel of figure [ fig : deltaphi ] .
ccccccc @xmath49 & @xmath232 & @xmath233 & @xmath234 & @xmath235 & @xmath236 & @xmath237 + + 0.50 & 0.76 & 7.21 & 2.95 & 1.59 & 6.03 & 7.81 + 0.75 & 3.86 & 19.28 & 9.208 & 5.310 & 17.79 & 21.41 + 1.00 & 11.22 & 34.26 & 19.49 & 13.70 & 33.60 & 37.11 + + 0.50 & 0 & 0.39 & 0 & 0 & 0 & 0.002 + 0.75 & 0 & 10.30 & 2.21 & 0.13 & 7.70 & 12.92 + 1.00 & 2.21 & 27.57 & 12.18 & 4.19 & 26.87 & 31.22 +
we demonstrated in previous work @xcite that the alignment of sbh spins with each other during the pn stage of the inspiral can dramatically suppress the predicted distribution of gravitational recoils .
this mechanism can reinforce the kick suppression that results from the alignment of the sbh spins with their orbital angular momentum through interaction with a circumbinary disk at an earlier stage of the inspiral @xcite .
recent nr simulations @xcite showed that gravitational recoils are maximized not in the previously claimed `` superkick '' configuration in which the spins lie in the orbital plane , but in a new `` hang - up '' configuration in which the angle between the spins and orbital angular momentum is @xmath238 .
the primary conclusion of this paper is that kick suppression due to pn spin alignment remains highly effective despite the new dependence of the gravitational recoil on sbh spins .
it is difficult to make very robust quantitative predictions about the magnitude of this effect , as the recoil distribution is highly sensitive to sbh spin distributions that are theoretically uncertain and poorly constrained observationally .
some sph simulations have shown that sbh spins can grow to large magnitudes and rapidly align with the orbital angular momentum through coherent accretion from a massive circumnuclear disk @xcite , but other simulations that include gas cooling and star formation indicate that the direction of the angular momentum of the accreted gas will vary chaotically on timescales comparable to the alignment time , leading to smaller spin magnitudes and larger misalignments with the orbital angular momentum @xcite .
our results show that the predicted fraction of recoiling sbhs that are ejected from their host galaxies can vary from @xmath239 to @xmath240 depending on the adopted distribution of sbh spins .
although somewhat frustrating from a theoretical perspective , the strong dependence of the ejected fraction on sbh spins implies that observational studies of recoils may place promising constraints on the highly elusive sbh spin distribution .
* we need to determine how effectively realistic circumbinary disks can align sbh spins with their orbital angular momentum .
such circumbinary disks may not remain geometrically thin , and may gravitationally fragment or collapse into stars .
these possibilities could have significant quantitative effects on the sbh spin distribution at the onset of the pn stage of the inspiral .
* we need to develop a better understanding of the interaction between unequal - mass sbhs and a circumbinary disk .
one could argue that the spin of either the primary or the secondary might align more efficiently with the orbital angular momentum .
whether pn spin alignment leads to kick suppression or enhancement depends crucially on the _ relative _ values of @xmath51 and @xmath197 . *
we need to carefully consider how the merger rate , mass - ratio distribution , and escape velocity depend on host - galaxy mass .
our results shown in figs . [ fig : eject1000log ] and [ fig : ejectratio ] demonstrate the sensitivity of the ejected fraction to assumptions about these galactic properties .
although challenging , steady theoretical and observational progress is being made on all of these issues .
once astrophysicists can provide more accurate predictions of sbh spin distributions at @xmath241 , when sbhs decouple from their circumbinary disks , relativists will be able to evolve the binaries through merger and more accurately predict gravitational recoils . including the pn stage of the inspiral will be an important ingredient in this grand theoretical undertaking .
* _ acknowledgements .
_ * we thank mike blanton , massimo dotti , mike eracleous , david hogg , carlos lousto , david merritt , jeremy tinker , marta volonteri , and yosef zlochower for useful conversations .
this work was supported by nsf grants phy-090003 , phy-0900735 and phy-1055103 , fct projects ptdc / fis/098032/2008 and ptdc / fis/098025/2008 , the ramn y cajal programme and grant fis2011 - 30145-c03 - 03 of the ministry of education and science of spain , the fp7-people-2011-cig grant cbheo , no .
293412 , the sherman fairchild foundation to caltech , projects icts - cesga-221 of the centro de supercomputacin de galicia , aect-2011 - 3 - 0007 by the barcelona supercomputing center , and the erc starting grant erc-2010-stg - dybho .
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because of enhanced gravitational - wave emission in the so - called `` hang - up '' configurations , this maximum recoil occurs when the black - hole spins are partially aligned with the orbital angular momentum .
we revisit our previous statistical analysis of post - newtonian evolutions of black - hole binaries in the light of these new findings .
we demonstrate that despite these new configurations with enhanced recoil velocities , spin alignment during the post - newtonian stage of the inspiral will still significantly suppress ( or enhance ) kick magnitudes when the initial spin of the more massive black hole is more ( or less ) closely aligned with the orbital angular momentum than that of the smaller hole .
we present a preliminary study of how this post - newtonian spin alignment affects the ejection probabilities of supermassive black holes from their host galaxies with astrophysically motivated mass ratio and initial spin distributions .
we find that spin alignment suppresses ( enhances ) ejection probabilities by @xmath1 ( 20% ) for an observationally motivated mass - dependent galactic escape velocity , and by an even greater amount for a constant escape velocity of 1,000 km / s .
kick suppression is thus at least a factor two more efficient than enhancement . |
trapping and manipulation of ultracold atoms is of significant importance due to applications of cold atoms in several areas such as study of quantum degenerate gases @xcite , quantum information processing @xcite , atom interferometry @xcite , precession measurement @xcite etc .
an atom with finite value of its magnetic dipole moment can be trapped in an inhomogeneous static magnetic field at the position of the minimum potential energy @xcite .
the potential energy of an atom in a magnetic field b is given as @xmath0 , where @xmath1 is the zeeman hyperfine quantum number for the state with hyperfine number @xmath2 , @xmath3 is the lande - g factor for the hyperfine state , and @xmath4 is the bohr magneton @xcite .
depending on the sign of the product @xmath5 , the atom can seek either the minimum of the field or the maximum of the field to achieve the minimum potential energy .
the states with @xmath6 are called low field seeking states , whereas the states with @xmath7 are called high field seeking states . since maxwell s equation @xmath8 together with earnshaw s theorem denies the existence of the maximum of the magnetic field in free space , the trapping with static magnetic field is possible only for atoms in low field seeking states at the minimum of the magnetic field .
therefore , the trapping geometries achievable using the static magnetic field alone remain limited . to overcome this limitation , zobay and
garraway @xcite proposed the use of the radio frequency ( rf ) field in the presence of the static magnetic field to generate the adiabatic dressed state potentials for an atom .
these potentials , referred as ` rf - dressed potentials ' in short , offer extensive control over potential landscapes and trapping geometries through rf field parameters such as amplitude , polarization , frequency and phase .
this can meet the enormous demand of versatility required for trapping and manipulation of the cold atoms for various purposes ranging from the study of fundamental physics to matter wave interferometry based precision measurements @xcite .
these potentials show good flexibility and versatility for trapping and manipulation of cold atoms on miniaturized scale as well @xcite .
it turns out that these dressed state potentials are inherently inhomogeneous due to position dependent direction and magnitude of the static magnetic field which controls the rabi frequency . since the first proposal by zobay and garraway @xcite ,
the atom trapping in these rf - dressed potentials has been studied theoretically as well as experimentally by several groups world wide @xcite . using this approach ,
atoms have been trapped in different geometries which include the double well @xcite , quasi - two dimensional traps @xcite and ring traps @xcite .
+ the trapping geometries with controlled rotation of atom cloud on a circular path ( _ i.e. _ ring shape ) are of considerable interest for several purposes which include the study of super - fluidity in low - dimensional systems @xcite , measurement of quantum mechanical phases @xcite , and the realization of a cold atom gyroscope @xcite for high precision measurement of rotation . in this work
, it is theoretically shown that , using the static magnetic field of a quadrupole trap and rf fields of different polarizations and phases , some novel two - dimensional rf - dressed potentials for an atom can be generated with the support of a suitable dipole trap .
the generated anisotropic two - dimensional time - dependent potentials may be useful for the controlled rotation and oscillation of the cold atom cloud on the circular path . + this article is organized as follows .
the section [ theory ] presents the general theoretical background to calculate the adiabatic dressed state potentials for an atom interacting with a rf field in the presence of a static magnetic field .
the eigenvalues of the atom - field interaction hamiltonian , which give the rf - dressed potentials , are calculated for the rf field of any arbitrary polarization in the presence of a static magnetic field of a quadrupole trap .
the section [ discussion ] describes the well known rf - dressed potentials for different cases of the rf fields whereas section [ results ] shows our proposed trapping potentials that can also be achieved through rf dressing .
the rf - dressed potentials obtained for different cases are plotted to show the trapping and manipulation geometries achievable for the cold atoms .
finally , the conclusion of our work is presented in section [ conclusion ] .
the origin of the adiabatic dressed state potential due to interaction of an atom with the rf field in the presence of a static magnetic field has been described earlier in several research works @xcite .
it can be understood well within the frame work of semi - classical theory as described in the following .
the dressed state potentials presented here have been worked out with example of @xmath9 atoms .
+ we assume the static magnetic field due to a quadrupole magnetic trap is given as @xcite , @xmath10 and time - dependent rf field @xmath11 is given as , @xmath12 where @xmath13 , @xmath14 , and @xmath15 are the basis unit vectors in the laboratory coordinate system .
the parameter @xmath16 is the quadrupole field gradient along the z - axis .
+ neglecting the effect of gravity and the kinetic energy of the atom , the time dependent hamiltonian for the atom having hyperfine angular momentum * f * and interacting with a magnetic field @xmath17 is given by @xcite @xmath18 where magnetic field * b(r , t ) * in this equation is sum of static and time - dependent fields given by eqs .
( [ eq : quadfield ] ) and ( [ eq : rffieldshort ] ) , and it can be expressed as , @xmath19 with @xmath20 being an unit vector along the direction of the static field . + in order to evaluate adiabatic potentials for an atom in the magnetic field given by eq .
( [ magfield ] ) , we follow the theoretical approach as described earlier @xcite . in this approach , first , the hamiltonian of eq .
( [ eq : hamiltonian ] ) is evaluated in a new coordinate system whose one basis vector is parallel to the local magnetic field direction . in this new local coordinate system ,
represented by unit basis vectors @xmath21 , the unit vector @xmath22 is along the direction of local static magnetic field ( @xmath20 ) , and the other two unit vectors ( _ i.e. _ @xmath23 and @xmath24 ) are perpendicular to @xmath25 as well as to each other . due to variation of @xmath26 in space , these unit vectors @xmath21 turn out to be position dependent when expressed in laboratory coordinate system . in this new local coordinate system ,
the appearance of static magnetic field of the quadrupole trap is @xmath27 and that of rf field is @xmath28 .
the hamiltonian in eq .
( [ eq : hamiltonian ] ) in this local coordinate system is given as , @xmath29.\ ] ] here @xmath30 , @xmath31 and @xmath32 are components of @xmath33 along @xmath34 and @xmath22 axes . since @xmath22 is the unit vector along the vector @xmath20 ( _ i.e. _ the direction of the local static field ) , it represents the local quantization axis .
+ in the next step the hamiltonian is transformed to a frame rotating about @xmath32 by applying the unitary transformation @xmath35 , which modifies the state @xmath36 to @xmath37 as @xmath38 and the schrodinger equation as @xmath39 where @xmath40 we can write the time variation of rf field as @xmath41 , @xmath42 and @xmath43 , where @xmath44 and @xmath45 are the phases of the rf field along the @xmath24 and @xmath22 unit vectors . after applying the rotating - wave approximation , we get the time independent hamiltonian using eq .
( [ eq : hrt ] ) as , @xmath46.\end{gathered}\ ] ] here @xmath47 and @xmath48 are the raising and lowering operator for the hyperfine angular momentum respectively . for an atom in @xmath49 manifold with f=2 and @xmath50 , the interaction hamiltonian can be written in matrix form as , @xmath51 the diagonalization of the matrix in eq .
( [ eq : hr ] ) gives the energy eigenvalues of the hamiltonian @xmath52 in eq .
( [ eq : hrti ] ) .
these eigenvalues give the adiabatic dressed state potentials ( v ) for the atom - radiation system .
after diagonalizing the matrix in eq .
( [ eq : hr ] ) , the dressed state potential for zeeman sub - level @xmath49 can be written as , @xmath53 } .\ ] ] now identifying the detuning ( @xmath54 ) and rabi frequency ( @xmath55 ) of the rf field by @xmath56 and @xmath57 ) as , @xmath58 it is important to note that rabi frequency given by eq .
( [ eq : omega ] ) does not have contribution from the parallel component of the rf field @xmath59 .
thus , components of the rf field perpendicular to the local static field ( _ i.e. _ @xmath60 and @xmath61 ) are only important for the evaluation of rabi frequency . for a time
varying rf field at frequency @xmath62 with its x- , y- and z - components in the laboratory coordinate system described by @xmath63 the calculation of the rabi frequency involves the calculation of @xmath60 and @xmath61 .
this is briefly discussed as follows .
+ in the laboratory coordinate system , the unit vectors along x- , y- , and z - axes ( _ i.e. _ @xmath13 , @xmath14 , and @xmath15 ) can be expressed in the column vector form as , @xmath64 for the quadrupole magnetic trap with its static magnetic field given by the eq .
( [ eq : quadfield ] ) , the basis vectors of the local coordinate system ( _ i.e. _ @xmath23 , @xmath24 and @xmath22 ) can also be expressed in as column vectors in the laboratory coordinate system as @xcite , @xmath65 where @xmath66 , @xmath67 , @xmath68 , and @xmath69 .
+ the rotation matrices @xmath70 and @xmath71 defined by @xmath72 and @xmath73 can be used to relate these basis vectors @xmath21 to the basis vectors @xmath74 as following : @xmath75 , @xmath76 and @xmath77 ; @xmath78 , @xmath79 and @xmath80 . using the above transformation matrices @xmath70 or @xmath71 , any arbitrary vector ( such as applied rf magnetic field ) expressed in one basis set ( either @xmath74 or @xmath21 ) can be transformed into a vector expressed in the other basis set .
thus the rf magnetic field vector , which is given in laboratory coordinate system by eq .
( [ eq : rffield ] ) , is transformed to a vector @xmath81 in the local coordinate system .
the vector @xmath81 is given as , @xmath82 evidently , the first and second elements of the column vector in eq .
( [ eq : rotmatrf ] ) give @xmath60 and @xmath61 , which are required to evaluate rabi frequency using eq .
( [ eq : omega ] ) . the third element of the column vector @xmath81 represents rf field along vector @xmath83 . hence using eq .
( [ eq : omega ] ) and eq .
( [ eq : rotmatrf ] ) , one gets the expression for the rabi frequency as @xmath84 ( _ i.e. _ eq . ( [ eq : omegafinal ] ) ) , the dressed state potential ( eq . ( [ eq : pot_compact ] ) ) for an atom , interacting with the rf field and static quadrupole trap field , can be obtained .
the eqs . ( [ eq : pot_compact ] ) and ( [ eq : omegafinal ] ) provide a general expression for the rf - dressed potential ( v ) for an atom in a zeeman hyperfine sub - level @xmath49 interacting with a static magnetic field @xmath26 ( given by eq .
( [ eq : quadfield ] ) ) and a rf field @xmath11 given by eq .
( [ eq : rffield ] ) . in this section ,
the formalism developed in the previous section has been utilized to obtain the rf - dressed potentials for selected configurations of rf field and static magnetic field of a quadrupole trap .
based on this , different geometries for trapping and manipulation of cold atoms have been discussed , with a particular example of @xmath85 atom in @xmath86 state .
+ the quadrupole trap suffers from majorana losses which occur at the trap centre ( _ i.e. _ location of zero magnetic field ) . to avoid these losses
, one can try to trap cold atoms at a plane @xmath87 ( away from the centre of quadrupole trap ) using some external potential , such as potential of a sheet type red - detuned laser beam .
this can confine atoms in xy - plane at @xmath87 @xcite .
the sheet potential with a tight confinement along vertical direction ( _ i.e. _ z - direction ) results in two - dimensional ( 2d ) motion of atoms in xy - plane .
the vertical confinement can also be made strong enough to hold atoms against gravity . at this
shifted position , the magnitude of the field is given as @xmath88 where @xmath89 .
+ a number of 2d trapping geometries can be realized by considering the various forms of rf field in the presence of static magnetic field of the quadrupole trap given by eq .
( [ eq : modfield ] ) .
for example , a double - well potential can be generated by taking a linearly polarized rf field along x - axis , _ i.e. _ @xmath90 , in the presence of above static field . the double - well type rf - dressed potential for an atom in the state @xmath49 can be evaluated from eqs .
( [ eq : pot_compact ] ) and ( [ eq : omegafinal ] ) as @xmath91},\ ] ] where @xmath92 ( color online ) rf - dressed adiabatic potential ( eq .
( [ eq : dwpot ] ) ) showing double - well trapping geometry for the @xmath85 atom in the state @xmath86 , for different parameters as @xmath93=150 g / cm , @xmath94=0.7 g , @xmath95 mhz and @xmath9610 @xmath97 . plot ( a ) shows the variation in the potential with position along x - axis without rf field ( single well ) as well as with rf field ( double well ) for two different values of frequencies ( @xmath981.0 mhz and @xmath981.5 mhz ) of rf field .
the graphs ( b ) and ( c ) show the iso - potential contours in the xy - plane for the single well and double well potentials ( @xmath981.5 mhz ) respectively .
the color contrast in contours reveal the variation in potential from minimum ( red ) to maximum ( blue ) values through intermediate values shown by orange , yellow and green .
, width=325 ] fig .
[ fig : doublewell ] shows the plot of double well potential given by eq .
( [ eq : dwpot ] ) . by varying the quadrupole field gradient @xmath93 as well as the frequency @xmath62 of the rf field , the separation between the wells ( d ) can be varied .
the relation that governs this dependence can be extracted from the criterion of the potential minimum of eq .
( [ eq : dwpot ] ) .
it is given as @xmath99 figure [ fig : doublewell ] shows the double well potential along the x - axis , whereas it is obvious that with a y - polarized rf field , the double well potential along the y - axis can be generated .
the depth of the potential can be changed by changing the amplitude of the rf field ( _ i.e. _ @xmath94 or @xmath100 ) .
the generation of such type of a double well potentials has been experimentally realized using a rf field and a ioffe - pritchard trap @xcite .
the double well potential as a beam splitter for a bose - einstein condensate has also been demonstrated in a miniaturized trap @xcite .
this double well as a beam splitter has advantage over the static magnetic field beam splitter due to its robustness and coherence preserving properties .
further , it can be shown that incorporating a rf field along z - axis ( i.e. @xmath101 ) , the symmetric double well potential can be converted to asymmetric double well potential with unequal depth of two wells .
such type of potential can be useful for unequal splitting of atom cloud as well as for tunnelling studies @xcite .
+ ( color online ) the ring shaped trapping geometry with the rf - dressed potential of eq .
( [ eq : ringpot ] ) for the @xmath85 atom in the state @xmath86 .
the trapping parameters are @xmath93=150 g / cm , @xmath94=@xmath100=0.7 g , @xmath95 mhz and @xmath9610 @xmath97 . the elevated plot shows the actual variation of the potential with x and y coordinates , whereas the carpet shows the iso - potential contours in the xy - plane at @xmath9610 @xmath97 .
the color contrast in the contours reveal the variation in potential from minimum ( red ) to maximum ( blue ) values through the intermediate values shown by orange , yellow and green colors .
the ring radius is nearly 140 @xmath97.,width=325 ] similarly , a well known trapping geometry with rf - dressed potentials is a ring shaped trapping potential @xcite .
the ring shaped trapping potential can be generated by using a circularly polarized rf field of the form @xmath102 , with @xmath103 , and static magnetic field given by eq .
( [ eq : modfield ] ) . for these fields , the eqs .
( [ eq : pot_compact ] ) and ( [ eq : omegafinal ] ) evidently result the rf - dressed potential ( for an atom in the state @xmath49 ) with spatial variation given as , @xmath104},\ ] ] where @xmath105 is given by eq .
( [ eq : delta0 ] ) . the potential given by eq .
( [ eq : ringpot ] ) is independent of polar angle @xmath106 and its plot in the xy - plane is shown in fig .
[ fig : ring ] . from the graph , it is evident that minimum of the potential lies on a circular ring in the xy - plane . the radius ( r ) of this ring
can be obtained @xcite as @xmath107 ( color online ) variation in the ring radius ( r ) in the ring shaped trapping potential with the quadrupole field gradient @xmath93 for different frequencies of rf field , for @xmath85 atom in @xmath86 state .
the other parameters are @xmath103=0.7 g and @xmath9610 @xmath97.,width=325 ] from the expression of the ring radius ( _ i.e. _ eq . ( [ eq : radius ] ) ) , it is obvious that the radius of the ring trap can be varied by varying @xmath62 as well as @xmath93 .
[ fig : ringradius ] shows the variation of this radius with @xmath93 for different values of @xmath62 .
it is preferable to change the radius by varying the quadrupole field gradient only , rather than by sweeping the frequency @xmath62 @xcite . during the frequency sweep
, the non - adiabatic landau - zener transitions may become significant and increase the loss of trapped atoms due to transition of atoms to untrappable states .
alternatively , the radius of ring can be varied by varying the position of trapping plane ( @xmath108 ) at a fixed @xmath93 @xcite . +
further , instead of a circularly polarized rf field , if an elliptically polarized rf field is chosen , the generated potential is split arcs . with a rf field of the form @xmath109 , with @xmath110 , and static field as given by eq .
( [ eq : modfield ] ) , the rf - dressed potential for split arcs trapping geometry is given as , ( color online ) the plots of rf - dressed potential of eq .
( [ eq : splitarcpot ] ) showing the split arcs trapping potential for the @xmath85 atom in the state @xmath86 .
the other parameters are @xmath93=150 g / cm , @xmath94=0.7 g , @xmath100=0.14 g , @xmath95 mhz and @xmath9610 @xmath97 .
the elevated plot shows the actual variation of the potential whereas the carpet shows the iso - potential contours .
the color contrast in contours reveal the variation in potential from minimum ( red ) to maximum ( blue ) values through intermediate values shown by orange , yellow and green.,width=325 ] @xmath111 where @xmath112.\ ] ] the plot of eq .
( [ eq : splitarcpot ] ) is shown in the fig .
[ fig : arc ] for unequal values of @xmath94 and @xmath100 .
it can be pointed out that the orientation of the arcs is dependent on the values of @xmath94 , @xmath100 and phase ( @xmath113 ) .
heathcote _ et . al . _
@xcite experimentally demonstrated the variation in orientation of split arcs by varying the relative phase between the components of the rf field .
+ the ring trap for cold atomic gases are promising for studying low dimensional systems where one or more dimensions are quantum mechanically restricted for motion .
the ring trap geometry can also be useful for cold atom based inertial sensors such as atom gyroscope @xcite .
in this section , we discuss our proposed two - dimensional trapping potentials that can be generated with appropriate choice of rf field and its phase .
these potentials described in the following may be useful for various purposes .
it is expected that split arcs with unequal depth of trapping potential may be useful to study quantum mechanical tunneling with cold atoms trapped in the arcs .
we note that such arcs with unequal potential depth can be created by incorporating the z - component in the rf field .
thus , if the rf field is taken as @xmath114 , with @xmath110 , and static field as given by eq .
( [ eq : modfield ] ) , the rf - dressed potential can be written as @xmath115 where @xmath116 ) showing the asymmetric split arcs for different values of @xmath101 : ( a ) @xmath101=0.07 g , ( b ) @xmath101=0.14 g , and ( c ) @xmath101=0.35 g. the other parameters are @xmath93=150 g / cm , @xmath94=0.7 g , @xmath100=0.07 g , @xmath1170 , @xmath95 mhz , @xmath9610 @xmath97 , and @xmath85 atom in @xmath86 state . the color contrast in contours reveal the variation in potential from minimum ( red ) to maximum ( blue ) values through intermediate values shown by orange , yellow and green.,width=325 ] ( color online ) the iso - potential contours of eq .
( [ eq : pot_asy_split_arcs ] ) showing the asymmetric split arcs for different values of the phase angles @xmath118 : ( a ) @xmath118=@xmath119 , ( b ) @xmath118=@xmath120 , and ( c ) @xmath118=@xmath121 .
the other parameters are @xmath93=150 g / cm , @xmath94=0.7 g , @xmath100=0.07 g , @xmath1220.14 g , @xmath95 mhz , @xmath9610 @xmath97 , and @xmath85 atom in @xmath86 state . the color contrast in contours reveal the variation in potential from minimum ( red ) to maximum ( blue ) values through intermediate values shown by orange , yellow and green.,width=325 ] the contours of the rf - dressed potentials given by eq .
( [ eq : pot_asy_split_arcs ] ) for different values of @xmath101 and @xmath118 are shown in fig .
[ fig : assymetric_split_field ] and fig .
[ fig : assymetric_split_angle ] respectively .
these graphs clearly reveal that split arcs become asymmetric by incorporation of z - component in the rf field .
the ultracold atoms trapped in these split arcs potentials may be a good tool to study tunnelling and josephson oscillations @xcite with tunnelling along circular path . as described in ref .
@xcite , the asymmetry of the two trapping potentials can be used to control josephson oscillations of population between trapping potentials . by increasing the asymmetry ,
the josephson oscillations can be suppressed and self trapping can be reached . in our proposed asymmetric split arc potential ,
the asymmetry can be controlled by adjusting the amplitude and phase of third rf component of the field .
the separation between the minima of arcs depends upon the arc length which can be controlled by controlling the radius of the ring as well as the phase angle @xmath118 .
the @xmath118 dependent separation between potential minima along the arcs is shown in fig .
[ fig : assymetric_split_angle ] . an asymmetric ring potential can be generated by the use of a rf field of the form @xmath114 , with @xmath103 , in the presence of the static magnetic field given by eq .
( [ eq : modfield ] ) .
the incorporation of z - component in the rf field results in anisotropy in the isotropic ring potential . for these rf and static magnetic fields ,
the dressed state potential for an atom ( _ e.g. _ @xmath85 ) in the state @xmath49 can be calculated to be @xmath123 where @xmath124 ) and ( [ eq : omegatilt ] ) are shown in fig .
[ fig : tilt ] , for different values of rf field amplitude @xmath101 at a given value of @xmath118 . due to presence of z - component in the rf field ( _ i.e. _ @xmath101 ) , a potential well is formed at a particular position on the ring . in an earlier work @xcite , the asymmetric ring potential , due to presence of this z - component in rf field ,
has been experimentally observed in a rf - dressed quadrupole trap .
+ the depth of the potential well on the ring is dependent on the value of @xmath101 , whereas the position of the well ( _ i.e. _ potential minimum ) on the ring is dependent on the phase angle @xmath118 .
[ fig : tilt ] shows that , as @xmath101 is increased , the ring shaped potential becomes more asymmetric ( _ i.e. _ tilted ) with increased well depth .
the atoms from the whole ring can be forced to drain to this well position by suitably adjusting the value of @xmath101 .
this makes the transfer of cold atoms very convenient to a particular site on the ring . by changing the value of @xmath118
, the position of potential minimum ( _ i.e. _ the well ) can be changed to our choice , which can act as a ` conveyor belt ' for the cold atom cloud .
the transport of the atoms along the ring may also be useful in areas such as atom - interferometry for rotation sensing @xcite . as discussed earlier in section [ discussion ] , the ring traps provide the confinement to atom cloud from two dimensions which makes the motion of atoms in quasi - one - dimension along the circular path .
such systems may be useful to study non - linear atom interferometry , where confinements of bose condensates to low dimensions may result in increased non - linear interactions and hence improved measuring sensitivity @xcite . + as discussed before in this article , the inclusion of a z - component in the rf field used for generation of the ring trap geometry results in a potential well on the ring .
the atoms from the whole ring can be accumulated in this well .
since the position of this potential well on the ring is dependent on the phase angle @xmath118 , by varying the value of @xmath118 with time , the position of the well ( and atom cloud trapped in it ) can be moved along the circumference of the ring .
this rotational motion of the atom cloud seems controllable by controlling the phase modulation in the z - component of the rf field . in the following ,
we consider two types of phase modulations in the z - component of the rf field .
one is the linear phase modulation and the other is the periodic phase modulation .
these phase modulations can result in two different types of rotational motion of potential well and atom - cloud trapped in it , which are discussed in the following description . + the linear phase modulation in the z - component of rf field results in rotation of the potential well on the ring circumference at a rate which is determined by the modulation frequency . for the @xmath125 atoms in @xmath49 state ,
first , we consider here the linear phase modulated rf field of the form @xmath126 where the value of modulation frequency @xmath127 is very small compared to @xmath62 , so that the modified potential due to phase modulation can be adiabatically followed by the atoms . using the rf field as in eq .
( [ eq : rflinearphasemod ] ) with @xmath103 , and the static field as in eq .
( [ eq : modfield ] ) , the eqs .
( [ eq : potential ] ) , ( [ eq : delta ] ) and ( [ eq : omegafinal ] ) result in rotating potential ( @xmath128 ) of the form @xmath129 where @xmath130 ) for the parameters @xmath93=150 g / cm , @xmath131 g , @xmath95 mhz , and @xmath9610 @xmath97 .
the contours are plotted for different values of time t ( in seconds ) : ( a ) t=@xmath132 , ( b ) t=@xmath133 , ( c ) t=@xmath134 , ( d ) t=@xmath135 , ( e ) t=@xmath136 , ( f ) t=@xmath137 ; with @xmath127=1 hz .
the contours show the rotation of potential minimum with time.,width=325 ] in eq .
( [ eq : omegalinear ] ) , the last term in the rabi frequency expression contains the time dependence , which result the potential of eq .
( [ eq : linearphasepot ] ) to be time dependent such that position of the potential minimum changes with time .
the contours in fig .
[ fig : rotation ] show that position of the minimum of potential @xmath128 moves along the circular path on the ring with time .
thus , the linear phase modulation discussed above converts the ring potential into a rotating well potential .
the rate of rotation is governed by the modulation parameter @xmath127 . as the rotation takes place , experimentally
, it is likely that temperature of the cloud increases due to non - adiabatic following of the potential by atoms in the cloud .
this may lower the life - time of the atoms in the trap .
however , this rotation provides excellent opportunities to study motion dependent physics phenomenon like super - fluidity in the condensate cloud .
+ next , we consider the periodic phase modulation , in which the phase of the z - component of the rf field is considered to vary periodically . taking the modulation frequency @xmath138 , the rf field can be expressed as @xmath139 using the rf field as in eq .
( [ eq : rfperiodicphasemod ] ) with @xmath103 , and static field as in eq .
( [ eq : modfield ] ) , the eqs .
( [ eq : potential ] ) , ( [ eq : delta ] ) and ( [ eq : omegafinal ] ) result in oscillating potential ( @xmath140 ) ( for @xmath85 atom in @xmath49 state ) of form @xmath141 where ( color online ) the contours of rf - dressed potential of eq .
( [ eq : periodicphasepot ] ) for the parameters @xmath93=150 g / cm , @xmath131 g , @xmath95 mhz , and @xmath9610 @xmath97 .
the contours are plotted for different values of time t ( in seconds ) : ( a ) t=@xmath132 , ( b ) t=@xmath142 , ( c ) t=@xmath143 , ( d ) t=@xmath144 , ( e ) t=@xmath145 , ( f ) t=@xmath146 , ( g ) t=@xmath147 , ( h ) t=@xmath148 , ( i ) t=@xmath149 ; with @xmath138=1 hz . the contours show the oscillation of potential minimum with time along the circular path.,width=302 ] @xmath150 ) and eq .
( [ eq : omegaperiodic ] ) shown in fig .
[ fig : minimaintime ] that the position of minimum of the potential moves along the ring circumference and completes its one rotation in time duration @xmath151 . after a complete rotation in time @xmath152 ,
the sense of rotation gets reversed .
the next rotation is completed in same duration @xmath152 , but , with sense of rotation in opposite direction .
this continues , and the sense of rotation of potential minimum keeps on changing after a time interval of @xmath152 .
thus , the atom cloud trapped in this potential makes an oscillatory motion along the circumference of the ring , with a time period of oscillation as @xmath153 . + the rotating potential described above can be utilized to initiate motion of the bose condensate ( or cold atom cloud ) along the circular path to study super - fluidity , which is otherwise achieved using laser beams of appropriate frequency to transfer momentum from photons to atoms @xcite .
the use of laser beams to initiate the rotation of cloud also leads to some heating of the cloud due to finite scattering rate .
a rotating cloud in the ring can serve as a singly charged vortex state with vortex core coinciding with centre of the ring .
such singly charged vortices have also been proposed to serve as qubits in quantum information processing @xcite .
we have discussed various types of rf - dressed adiabatic potentials for ultracold atoms which can be realized by superimposing an appropriately designed rf field on the static magnetic field of a quadrupole trap . using this scheme in presence of a supporting two - dimensional dipole trap , apart from the familiar double well and ring trap potentials , some interesting anisotropic ( static as well as time - dependent ) two - dimensional potentials can be generated with rf fields of various polarizations and phase modulations .
the generated time - dependent ( i.e. moving ) 2d potentials can facilitate the rotation as well as oscillation of the trapped atom cloud along the circular path .
various possible applications of these proposed potentials in transporting atom cloud and in studying josephson oscillations , super - fluidity and vortex states using bose condensates in low dimensional geometries have been discussed .
we thank h. s. rawat , v. b. tiwari and s.p .
ram for the careful reading of the manuscript and fruitful suggestions .
arijit chakraborty acknowledges the financial support by the homi bhabha national institute , india . | in this work , the rf - dressed potentials generated using a static magnetic field of a quadrupole trap and various radio frequency ( rf ) fields , have been theoretically investigated for trapping and manipulations of cold atoms in a two - dimensional ( 2d ) geometry .
it is shown that , in this scheme , the rf fields of some particular polarizations and phases can give rise to some novel static and time - dependent anisotropic two - dimensional potentials which are useful to trap and manipulate the cold atoms in the 2d geometry .
the generated time - dependent 2d potentials , rotating on the circular ring , can be used for the controlled rotation and oscillation of the cold atom cloud on the circular ring path .
the ultracold atoms trapped in these potentials may be used to investigate the interesting physics phenomena such as tunnelling and super - fluidity . |
chronic inflammation ,
a key mechanism in the pathogenesis of cancer
and cardiovascular disease , induces lipid peroxidation , which in turn generates
a spectrum of reactive electrophiles capable of causing extensive
damage to dna and proteins , resulting in toxic and mutagenic events .
malondialdehyde is the principal and most studied product of lipid
peroxidation ( figure 1 ) . under physiological conditions , malondialdehyde can react
with dna to form adducts mainly to deoxyguanosine and deoxyadenosine ,
with the predominant one being 3-(2-deoxy--d - erythro - pentafuranosyl)pyrimido[1,2-]purin-10(3h)-one deoxyguanosine ( m1dg , figure 1 ) .
m1dg is
a premutagenic lesion and has been shown to induce g t and
g a mutations in dna ; these mutations
are believed to be important steps in carcinogenesis , contributing
to the etiology of human cancer .
while m1dg may serve
as a valuable biomarker in studies
of the role of inflammation in human disease , its sensitivity to changes
in inflammation - inducing exposures is not clear .
for instance , cigarette
smoke contains high levels of pro - oxidants , such as reactive oxygen
and nitrogen species , and it is plausible
to expect that levels of m1dg would be elevated in dna
from smokers as compared to nonsmokers .
indeed , many studies demonstrated
that levels of urinary f2-isoprostane 8-epi - pgf2 , a reliable urinary biomarker of oxidative
stress , are elevated in smokers , and chronic inflammation is a
major contributing factor in the pathogenesis of cigarette smoke - associated
diseases , including lung cancer .
however , existing
reports on m1dg levels in smokers and nonsmokers are inconsistent :
some studies demonstrate that levels of m1dg are modestly
elevated in smokers , whereas other studies show no differences .
these inconsistencies may be , at least in part , due to differences
in the methodologies used by different research groups .
analytical
methods that have been used to detect and quantify m1dg
in human biological samples include gas chromatography mass
spectrometry , immunoslot blot , and p - postlabeling technique as well as liquid chromatography
tandem
mass spectrometry ( lc ms / ms ) . by using these
methods
, m1dg has been detected in liver , pancreas , breast ,
leukocytes , and lymphocytes from human subjects , with the levels of
this adduct ranging from 1 to 120 adducts/10 nucleotides ,
depending on the sample type , subject characteristics or exposures ,
and applied methodologies for m1dg analysis .
one of the potential issues with some methodologies could be overestimation
of m1dg levels , due to either lack of specificity or artifactual
formation .
thus , to better understand the role of m1dg in human diseases , there is a need for a robust , specific ,
and sensitive method that can be applied in large population studies
investigating relationships between relevant exposures and health
outcomes .
it should be noted that the latest lc ms / ms - based
methods
for m1dg measurement provide high sensitivity and selectivity ;
however , the published assays involve the use of custom - made immunohistochemistry
columns to purify samples prior to analysis .
our goal in this study was to develop a new robust
and sensitive mass spectrometry - based method for the analysis of m1dg in human leukocyte dna , with the initial primary focus
on modifying the sample preparation procedure to exclude the immunohistochemistry - based
purification step .
m1dg and [ c3]m1dg were purchased from toronto research
chemicals ( north york , ontario , canada ) . reagents and enzymes for
dna isolation were obtained from qiagen sciences ( germantown , md ) .
calf thymus dna was purchased from worthington biochemical corporation
( lakewood , nj ) .
all other chemicals and solvents were purchased from
sigma - aldrich chemical co. ( milwaukee , wi ) .
the synthesis of 5,6-dihydro - m1dg was performed
by reacting m1dg with nabh4 , employing a previously
described protocol .
briefly , m1dg ( 5 mg ) was dissolved in 2 ml of
a meoh / h2o ( 2:8 , v / v ) solution , 1.3 mg of nabh4 was added , and the mixture was stirred for 30 min at room temperature .
the final product was isolated and purified on a phenomenex bondclone
c18 column ( 3.9 300 mm , 10 m ) .
h nmr ( d - dmso , 500 mhz ) of 5,6-dihydro - m1dg was consistent with that previously reported : 7.93 ( s , 1h , h2 ) , 7.29 ( dt , j = 8.4 , 1.9 hz , 1h , h8 ) , 6.08 ( dd , j = 7.8 , 6.1 hz , 1h , h1 ) , 5.48 ( m , 1h , h7 ) , 4.34 ( m , 2h , h6 ) , 4.05 ( br s , 1h , h3 ) ,
3.81 ( m , 1h , h4 ) , 3.50 ( m , 2h , h5 ) ,
2.482.17 ( m , 2h , h2 ) .
a similar procedure
was employed to synthesize 5,6-dihydro-[c3]m1dg from [ c3]m1dg ,
and h nmr similar to that of 5,6-dihydro - m1dg was obtained for the product ; mhm / z 309 . the yields for 5,6-dihydro - m1dg and 5,6-dihydro-[c3]m1dg
blood
samples from 25
smokers and 25 nonsmokers were obtained from the methodology
and development of tobacco related biomarkers
collection
of these samples was approved by the university of minnesota human
research protection programs institutional review board ( irb study
no . 0908m70881 ) .
all subjects were at least 18 years old , not pregnant
or breastfeeding , and were in good physical and mental health .
additional
criteria for smokers included smoking at least 10 cigarettes per day
( cpd ) , having been a smoker for at least 5 years with no change greater
than 50% in cpd or brand in the last year , and not using any other
tobacco products in the last 6 months .
nonsmokers were required to
have smoked less than 100 cigarettes in their lifetime and were not
using any tobacco products regularly .
dna isolation from
human blood samples was performed using the commercial protocol for
dna purification from buffy coat ( qiagen , valencia , ca ) with several
modifications .
briefly , 3 ml of red blood cell lysis solution was
added to 1 ml of buffy coat prepared from 10 ml of blood .
the leukocyte
pellet was collected by centrifugation ( 3000 g , 10 min ) and mixed with 5 ml of cell lysis solution .
proteinase
k ( 2 l of 20 mg / ml solution ) was added , and the mixture was
incubated at room temperature overnight with gentle shaking .
the following
day , 50 l of rnase a solution ( 4 mg / ml ) was added , and the
sample was incubated at room temperature for 2 h. protein precipitation
solution ( 1.5 ml ) was added to the cell lysate , and the sample was
vortex - mixed for 30 s and centrifuged ( 3000 g , 10 min ) to remove proteins .
dna was precipitated from the supernatant
by the addition of 5 ml of isopropanol .
the dna pellet was washed
with 2 ml of 70% ethanol in h2o and then 2 ml of 100% ethanol .
dna was dried under a stream of nitrogen and stored at 20
c until use .
potential rna contamination was assessed by hplc
analysis of enzymatically hydrolyzed dna samples for uridine .
addition of antioxidants
during dna isolation did not affect the measured m1dg levels ,
suggesting that artifactual formation of m1dg is minimal
during this step .
the dna samples
were dissolved in 1 ml of 25 m tris - hcl ( ph 7.4 ) buffer containing
5 m cacl2 and 5 m mgcl2 . the resulting
solution was mixed with 25 fmol [ c3]m1dg ( internal standard ) , followed by the addition of micrococcal
nuclease ( 1 unit ) , phosphodiesterase i ( 0.003 units ) , and alkaline
phosphatase ( 0.25 units ) .
the mixed solution was then incubated overnight
at 37 c . the next day ,
25 l of hydrolysate was taken
for the analysis of deoxyguanosine by hplc , which was used to calculate the amount of dna as described previously .
the remaining volume of hydrolysate was incubated
with 50 l of nabh4 ( 2 mg / ml ) at room temperature
for 30 min to reduce m1dg and [ c3]m1dg to their corresponding 5,6-dihydro derivatives .
after the incubation
, samples were loaded on bond elut pba cartridges
( 100 mg , agilent technologies , lake forest , ca ) activated with 1 ml
of meoh and 1 ml of h2o .
the cartridges were washed with
1 ml of h2o and 1 ml of 3% meoh sequentially and finally
eluted with 2 ml of 25% meoh . the 25% meoh fraction containing analytes
was collected and concentrated to dryness in a centrifugal evaporator .
the residue was redissolved in 20 l of deionized h2o and subjected to column purification on an agilent 1100 hplc system
equipped with a zorbax sb c18 column ( 5 m , 150
0.5 mm , agilent technologies , wilmington , de ) .
the mobile phase consisted
of 15 mm nh4oac and ch3cn , with a gradient from
4 to 27% ch3cn within 15 min , increased to 33% ch3cn over 2 min , then returned to 4% ch3cn in 1 min and
held for 15 min at this composition , at a flow rate of 12 l / min .
the detection wavelength was set at 254 nm , and the column temperature
was maintained at 25 c .
benzamide ( 2 g / ml ) , which has
similar retention time ( 15.5 min ) to that of 5,6-dihydro m1dg under the described hplc conditions , was used as a uv marker .
the fraction eluting at 1517 min was collected ( supporting information , figure s1 ) , evaporated
to dryness , and redissolved in h2o prior to analysis by
lc nsi hrms / ms . to assess possible artifactual
m1dg formation during the sample preparation , 5 fmol of n5-deoxyguanosine was added to calf thymus dna ,
and the sample was enzymatically hydrolyzed and purified as described
above .
ms / ms analysis was carried out on a tsq
vantage triple quadrupole mass spectrometer ( thermo scientific , waltham ,
ma ) interfaced with an agilent 1100 capillary hplc system ( agilent ,
palo alto , ca ) .
analysis was performed on an agilent zorbax sb c18 column at a flow rate of 12 l / min with the temperature
maintained at 30 c .
the mobile phase consisted of 15 mm nh4oac and ch3cn with a linear gradient from 4 to 35% ch3cn over a period
of 18 min and then returned to 4% ch3cn followed by 15
min re - equilibration .
the esi source was operated in positive ion
mode , monitoring m / z 306.2 [ m +
h ] 190.2 [ c8h8n5o ] for 5,6-dihydro - m1dg and corresponding
ions at m / z 309.2 193.2
for 5,6-dihydro-[c3]m1dg .
the collision
gas was ar at 1 mtorr with collision energy of 12 ev .
the quadrupoles
were operated at a resolution of 0.2 ( q1 ) and 0.7 ( q3 ) da . the lc nsi hrms / ms was performed
on an ltq orbitrap velos instrument ( thermo scientific , waltham , ma )
interfaced with a nano2d lc hplc ( eksigent , dublin , ca ) system
using nanoelectrospray ionization .
, 10 cm length , 15 m orifice )
created by hand packing a commercially available fused - silica emitter
( new objective , woburn , ma ) with luna c18 bonded separation
media ( phenomenex , torrance , ca ) . the mobile phase consisted of 5
mm nh4oac and ch3cn .
a 5 l injection
loop was used , and the sample ( 3 l ) was loaded onto the capillary
column with a 1000 nl / min flow under the initial conditions for 5.5
min .
separation on the capillary column was performed using a linear
gradient at a flow rate of 300 nl / min with increasing ch3cn from 2 to 33% over 12 min , followed by ramping to 98% ch3cn within 1 min and holding at this composition for additional 2
min .
the gradient was then returned to 2% ch3cn ( initial
condition ) in 1 min , and the system was re - equilibrated at this mobile
phase composition for 6 min at 1000 nl / min before next injection .
the capillary
temperature was 350 c , and the s - lens rf level was set at 40% .
the analysis was performed using accurate mass extracted ion chromatograms
of m / z 190.0723 [ c8h8n5o ] and 117.0546 [ c5h9o3 ] ( parent ion m / z 306.1 ) for 5,6-dihydro - m1dg and corresponding
fragments ( m / z 193.0824 and 117.0546 )
for 5,6-dihydro-[c3]m1dg with a
mass tolerance of 2 ppm . the scan events were performed using higher - energy
collisional dissociation ( hcd ) fragmentation with a normalized collision
energy of 20 units , isolation widths of 1 da for both the analyte
and internal standard , and product ion spectra acquisition at a resolution
of 50 000 .
the quantitation of m1dg was based on
the peak area ratio of 5,6-dihydro - m1dg ( m / z 306.1 190.0723 ) to 5,6-dihydro-[c3]m1dg ( m / z 309.1 193.0824 ) , the constructed calibration
curves , and the amount of internal standard added .
a calibration
curve was constructed before each analysis using a series of standard
solutions of 5,6-dihydro - m1dg and 5,6-dihydro-[c3]m1dg .
the calibration standard solutions
contained a constant amount of 5,6-dihydro-[c3]m1dg ( 2.5 fmol on column ) and varying amounts of 5,6-dihydro - m1dg ( 0.005 , 0.025 , 0.1 , 0.5 , 2.5 , and 5 fmol on column ) .
accuracy
was determined by adding different amounts of m1dg ( 0.025 ,
0.1 , 0.5 , 2.5 fmol ) and 2.5 fmol of internal standard to 200 g
of calf thymus dna in 1 ml of 25 m tris - hcl ( ph 7.4 ) buffer
containing 5 m cacl2 and 5 m mgcl2 , followed by hydrolysis and purification as described above .
samples
at each level of added m1dg were analyzed in triplicate . to characterize method precision ,
0.5 fmol of
m1dg and 2.5 fmol of internal standard were added to 200
g of calf thymus dna , followed by the described hydrolysis
and purification protocol .
the precision was determined as intraday
and interday coefficients of variation ( % cv ) , which were calculated
based on the analyses of three aliquots of the samples on three separate
days .
trace levels of m1dg were present in calf thymus
dna ; these levels were quantified and subtracted from the levels of
m1dg measured in the samples during the method characterization .
the limit of detection ( lod ) was determined using standard solutions
of 5,6-dihydro - m1dg .
the limit of quantitation ( loq ) was
established in calf thymus dna samples by adding m1dg ( 0.005 ,
0.01 , 0.025 , and 0.05 fmol ) and internal standard ( 2.5 fmol ) to calf
thymus dna samples , followed by hydrolysis and purification , and analyzing
each sample in triplicate .
the loq was defined by identification of
the lowest m1dg level that produced a coefficient of variation
( cv ) lower than 5% .
recovery was
determined by comparing the results of samples to
which [ c3]m1dg ( 2.5 fmol ) was added
to 200 g of calf thymus dna at the beginning and at the end
of sample preparation procedure .
two - tailed
unpaired student s t - test was used for two
group comparison . a p value less than 0.05 was considered
significant .
the purpose
of this study was to develop a robust and sensitive analytical procedure
for the analysis of m1dg by lc
the developed
protocol is outlined in scheme 1 . the addition
of nabh4 after enzymatic hydrolysis was used to increase
the detection sensitivity by reducing m1dg to 5,6-dihydro - m1dg . in agreement with the previous
report , the detection sensitivity of
5,6-dihydro - m1dg increased 12-fold as compared to that
of m1dg .
because it has been previously reported that m1dg can form a conjugate with tris buffer , we tested the stability of m1dg upon overnight
incubation in tris - hcl and in other two buffers commonly used in dna
hydrolysis : mops and sodium succinate buffer .
the subsequent reduction
with nabh4 and quantification of the formed 5,6-dihydro - m1dg showed no difference among the three tested buffers , suggesting
no effect of tris - hcl on the sensitivity of our assay .
m1dg
conjugate in aqueous solutions at room temperature or due to deconjugation of this product during the nabh4 reduction step .
we initially used low - resolution
triple quadrupole mass spectrometry
( lc esi
ms / ms ) , monitoring m / z 306.2 190.2 for 5,6-dihydro - m1dg and m / z 309.2 193.2 for 5,6-dihydro-[c3]m1dg . by using this method ,
an loq
of 3.3 fmol ( on - column ) was achieved in calf thymus dna ( data not
shown ) .
however , when the method was applied to human leukocyte dna ,
high noise levels and co - eluting peaks were observed for both 5,6-dihydro - m1dg and its internal standard , with no obvious peak being detected
at the retention time of 5,6-dihydro - m1dg ( figure 2a ) .
analysis of the same human leukocyte dna sample
using the high resolving and accurate mass capabilities of the orbitrap
detector produced clear peaks for both 5,6-dihydro - m1dg
and its internal standard without any baseline noise or coeluting
peaks ( figure 2b ) .
the product scans of the
analytes using hcd fragmentation generated two major fragments for
5,6-dihydro - m1dg at m / z 190.0723 and m / z 117.0546 and
two major fragments for 5,6-dihydro-[c3]m1dg at m / z 193.0824 and m / z 117.0546 ( supporting
information , figure s3 ) . because of the higher signal intensities ,
the transitions m / z 306.1
190.0723 and
m / z 309.1
193.0824 were selected for quantitation of 5,6-dihydro - m1dg and 5,6-dihydro-[c3]m1dg , respectively ;
the peak area ratios between the two major fragments of 5,6-dihydro - m1dg were used to confirm its identity , and the corresponding
ratio was used to confirm the identity of the internal standard ( supporting information , figure s3 )
. chromatograms
obtained upon analysis of m1dg in the
same human leukocyte dna sample by using ( a ) lc esi ms / ms
and ( b ) lc nsi hrms / ms .
the calf thymus dna that was
used for the method development contained 13 fmol of m1dg / mg dna .
this value was subtracted during the analysis of data
obtained for the samples used for method characterization . by using
the developed lc nsi
hrms / ms method , an lod of 5 amol
( on - column ) was obtained . the instrument response and
the 5,6-dihydro - m1dg/5,6-dihydro-[c3]m1dg
ratio were linear in the 0.0055 fmol ( on - column ) range of
m1dg ( r = 0.9997 , figure 3a ) .
the loq was 25 amol on - column based on a cv
of 3.21% .
the accuracy of measured levels of 5,6-dihydro - m1dg ( expressed as % of added m1dg ) at 0.025 , 0.1 , 0.5 ,
and 2.5 fmol was 99.6 , 103 , 100 , and 100% , respectively , exhibiting
excellent linearity ( r = 0.9981 , figure 3b ) .
the recovery of the
assay was 41.3 3.47% ( n = 5 ) .
( a ) linearity of 5,6-dihydro - m1dg/5,6-dihydro-[c3]m1dg peak area
ratio at constant level of 5,6-dihydro-[c3]m1dg ( 2.5 fmol on - column ) and varying levels of 5,6-dihydro - m1dg ( from 5 to 5000 amol on - column ) .
( b ) relationship between
added m1dg and measured 5,6-dihydro - m1dg in
calf thymus dna ( r = 0.998 ) in the range
from 0.025 to 2.5 fmol of m1dg per 200 g of dna ;
m1dg originally present in the calf thymus dna was determined
and subtracted from each value .
the method was applied to the analysis of leukocyte dna samples
from 50 human subjects . to investigate the potential effect of cigarette
smoking on levels of m1dg in human leukocyte dna , samples
from 25 smokers and 25 nonsmokers were selected for this analysis .
typical chromatograms upon analysis of m1dg in human leukocytes
from a smoker and a nonsmoker are presented in figure 4 .
the results of m1dg levels from the 50 subjects
are summarized in table 1 .
the yield of dna
in this study averaged 136 55 g , which was sufficient
to detect and quantify the m1dg adduct in all samples .
the levels of m1dg in the analyzed samples ranged from
0.004 to 9.15 adducts/10 nucleotides , averaging ( sd )
2.02 2.17 adducts/10 nucleotides .
levels of m1dg in leukocyte dna from smokers averaged 64.9 71.9
fmol / mg dna and in nonsmokers , 56.5 58.8 fmol / mg dna , or 2.16
2.40 and 1.89 1.96 adducts/10 nucleotides ,
respectively .
although the average m1dg level in smokers
was slightly higher than that in nonsmokers , this difference was not
significant .
hrms / ms chromatograms obtained
upon
analysis of 5,6-dihydro - m1dg in human leukocyte dna from
a ( a ) smoker and ( b ) nonsmoker .
measurement of lipid
peroxidation - induced dna damage in populations
with varying environmental and occupational exposures and lifestyle
and dietary habits could greatly advance our understanding of the
role of these factors in the induction of chronic inflammation and
the associated diseases . in this study
hrms / ms
method for the analysis of m1dg , the major dna adduct derived
from the lipid peroxidation product malondialdehyde , in human leukocyte
dna . this robust and sensitive method was successfully applied to
the analysis of leukocyte dna from 25 smokers and 25 nonsmokers .
studies
are underway to investigate how the levels of this highly mutagenic
adduct in humans are related to various exposures and disease risk . in the process of method development
, we initially explored the
use of low - resolution triple quadrupole mass spectrometry and were
able to quantify m1dg in calf thymus dna at levels as low
as 3.3 fmol , which was comparable to the previously developed lc
. however , application of the method
to human leukocyte dna produced high background noise and co - eluting
peaks , leading to inaccurate quantitation of the adduct levels in
these samples . as an alternative
, we employed an accurate mass high - resolution
orbitrap mass spectrometer , which proved to be highly sensitive and
selective in a previous study on another dna adduct , 7-ethylguanine .
after the transition to hrms / ms , both
capillary - esi at a flow rate
of 10 l / min and nano - esi at a flow rate of 300 nl / min were
investigated , with nano - esi showing at least 50-fold increase in sensitivity
compared to that of capillary - esi .
moreover , nano - esi has been shown
to be more tolerant of salt contamination than conventional esi .
however ,
it has been reported that substantial ion suppression can occur at
flow rates as low as 50 nl / min . in our
developed method , a flow rate of 300 nl
/ min is used and therefore
the analysis could be susceptible to signal suppression if sufficient
purification of the sample is not performed .
indeed , analysis of m1dg in samples that underwent only one purification step , extraction
on bond elut pba cartridges , showed a 4-fold signal decrease due to
ion suppression effect ( data not shown ) compared to samples that were
also subjected to a column purification step ( scheme 1 ) .
we also investigated mass tolerance , which reflects measurement
and calibration errors of the orbitrap instrument . changing the mass
tolerance setting for ion extraction from 10 to 5 to 2 ppm did not
alter the peak area of the analyte ( supporting
information , figure s4 ) .
consequently , the mass tolerance was
set at 2 ppm to achieve better selectivity and accuracy .
overall ,
the transition to high - resolution ms / ms improved the sensitivity of
the method by approximately 130-fold compared with the originally
used low - resolution ms / ms .
moreover , the baseline noise and occurrence
of co - eluting peaks were completely eliminated , greatly improving
selectivity of the method ( figures 2 and 3 ) .
the average m1dg level determined
in our study was 2.02 2.17 adducts/10 nucleotides ,
which is comparable to the previously reported levels .
the lowest dna yield among the analyzed human
leukocyte dna samples was 39 g , and m1dg was reliably
quantified in that sample .
the sensitivity and selectivity of the
developed method indicates that measurement of m1dg in
even lower amounts of dna is possible in future studies .
although
the average m1dg levels were slightly different
between smokers and nonsmokers in this study ( table 1 ) , the observed difference was not statistically significant .
this is consistent with the results of several studies that compared
m1dg levels in leukocyte dna from smokers and nonsmokers .
for instance , peluso et al . reported that m1dg levels per
10 nucleotides were 4.8 0.4 in leukocyte dna of
current smokers , 4.2 0.7 in ex - smokers , and 3.7 0.4
in nonsmokers ; however , the differences were not statistically significant .
another study investigating the effect of formaldehyde
exposure on leukocyte m1dg levels in a group of italian
pathologists found that the levels of m1dg per 10 nucleotides tended to increase in smokers compared to nonsmokers ,
4.5 1.3 vs 3.8 0.9 , respectively , but without reaching
statistical significance .
cigarette smoke
is a rich source of exposure to free radicals capable of inducing
oxidative damage to dna and promoting oxidative stress in smokers .
however , the levels of m1dg in humans may also be affected
by such factors as age , gender , diet , environmental or occupational
exposures , alcohol consumption , and inflammatory diseases .
for instance ,
m1dg has been reported to be lower in leukocyte dna of
women as compared to men : 5.1 0.4 adducts/10 nucleotides
vs 6.7 1.1 adducts/10 nucleotides , respectively .
the potential contribution of the diet to the
measured m1dg is exemplified by the findings of a study
in which levels of this adduct in leukocyte dna of female subjects
who consumed a diet rich in polyunsaturated fatty acids were nearly
20-fold higher than in the control group .
in addition to the potential contribution of the mentioned demographic
and lifestyle factors , a small sample size in the studies that compared
m1dg in smokers and nonsmokers , including the present study ,
may have prevented detection of statistically significant differences
between these two groups .
furthermore , m1dg analysis in
different cell types that are characterized by different lifespans
may potentially reveal differences between smokers and nonsmokers
and should be considered in future studies .
availability of
a validated and accurate method for the detection
and quantitation of m1dg in humans may be extremely useful
not only for investigations of the role of environmental exposures
or lifestyle factors in health outcomes but also for the prevention ,
prognosis , and diagnosis of diseases associated with inflammation
and oxidative stress .
reported that m1dg levels in the normal breast tissue of women with breast
cancer were increased 2- to 3-fold compared to the normal tissue of
women without breast cancer . in another
study , m1dg levels in lymphocyte dna of thalassemia patients
were 4-fold higher than in healthy control subjects , which indicates
elevated oxidative stress and lpo - induced dna damage in internal organs .
further applications of the developed methodology
to measure m1dg levels in specific cohorts could facilitate
our understanding of the importance of malondialdehyde - induced dna
damage in these and other diseases . in summary , we developed
a novel lc
hrms / ms method
for the quantitation of m1dg in human leukocyte dna , and
successfully applied this method to the analysis of m1dg
in leukocyte dna from 50 human subjects .
our approach features a unique
application of high - resolution mass spectrometry to achieve the requisite
sensitivity and specificity .
the method can be used in future studies
aimed at understanding the pathophysiological role of m1dg in humans . | malondialdehyde
( mda ) , an endogenous genotoxic product formed upon
lipid peroxidation and prostaglandin biosynthesis , can react with
dna to form stable adducts .
these adducts may contribute to the development
of such inflammation - mediated diseases as cancer and cardiovascular
and neurodegenerative diseases .
the predominant mda - derived dna adduct
formed under physiological conditions is 3-(2-deoxy--d - erythro - pentafuranosyl)pyrimido[1,2-]purin-10(3h)-one deoxyguanosine ( m1dg ) . in this study
, we developed
a novel liquid chromatography ( lc)nanoelectrospray ionization
( nsi)high - resolution tandem mass spectrometry ( hrms / ms ) method
for the analysis of m1dg in human leukocyte dna .
after
enzymatic hydrolysis of dna , m1dg and the added internal
standard [ 13c3]m1dg were reduced
to their 5,6-dihydro derivatives by addition of sodium borohydride
to the hydrolysate and purified by solid - phase extraction and column
chromatography .
the 5,6-dihydro derivatives in the purified samples
were analyzed by lc
nsi
hrms / ms using higher - energy
collisional dissociation ( hcd ) fragmentation , isolation widths of
1 da for both the analyte and internal standard , and a resolution
of 50 000 .
the detection limit of the developed method is 5
amol on - column , and the limit of quantitation is 0.125 fmol / mg dna
starting with 200 g of dna .
method accuracy and precision were
characterized .
the developed method was further applied to the analysis
of leukocyte dna from 50 human subjects .
m1dg was detected
in all samples and ranged from 0.132 to 275 fmol / mg dna , or 0.004
to 9.15 adducts per 108 bases .
this unique and highly sensitive
hrms / ms - based method can be used in future studies investigating the
pathophysiological role of m1dg in human diseases . |
let us first summarize the results of @xcite for the gluon channel only ( @xmath23 ) .
the starting point is the bfkl equation @xcite with nl@xmath1 corrections @xcite continued to @xmath20 dimensions , as described in more detail in @xcite . in particular , we consider running coupling evolution at the level of the one - loop @xmath24-function @xmath25 so that @xmath26 where @xmath27 is normalised according to the @xmath3 scheme .
note first that , the ultraviolet ( uv ) fixed point of eq .
( [ beta ] ) at @xmath28 separates the evolution ( [ alfa ] ) into two distinct regimes , according to whether _ (
i ) _ @xmath29 or _
( ii ) _ @xmath30 . in the regime _ ( i ) _
@xmath31 runs monotonically from @xmath32 to @xmath28 for @xmath33 and is thus infrared ( ir ) free and bounded , while in the regime _
( ii ) _ @xmath31 starting from @xmath34 in the uv limit , goes through the landau pole at @xmath35 , and reaches @xmath32 from below in the ir limit .
the main result of @xcite is a factorisation formula for the bfkl gluon density in @xmath20 dimensions .
if the gluon is initially on - shell , and the ensuing ir singularities are regulated by @xmath36 in the ( unphysical ) running coupling regime _ ( i ) _ mentioned above , then the gluon density at scale @xmath37 factorises in the form @xmath38 where @xmath39 is the saddle point value of the anomalous dimension variable @xmath40 conjugated to @xmath41 and the factor @xmath42 which is perturbative in @xmath31 and @xmath43 is due to fluctuations around the saddle point .
the expression of @xmath39 for @xmath44 is determined by the analogue of the bfkl eigenvalue function , namely at nl@xmath1 level by the equation @xmath45 = { \omega}\;,\ ] ] where , by definition , @xmath46 and the detailed form of the kernels is found in refs .
@xcite on the basis of refs .
the result ( [ factor ] ) is proven in @xcite from the fourier representation of the solutions of the nl@xmath1 equation by using a saddle - point method in the limit of small @xmath47 , which singles out @xmath39 as in eq .
( [ gammabar ] ) .
let us now make the key observation that due to the infinite ir evolution down to @xmath48 the exponent in eq .
( [ factor ] ) develops @xmath17 singularities according to the identity @xmath49 which produces single and higher order @xmath43-poles in the formal @xmath50 expansion of the denominator .
however , such singularities are not yet in minimal subtraction form , because we can expand in the @xmath43 variable the leading and nl parts of @xmath39 , as follows : @xmath51 + \cdots \;. \nonumber\end{aligned}\ ] ] while the @xmath52 part is already in minimal subtraction form , the terms @xmath53 and higher need to be expanded in the variable @xmath54 in order to cancel the series of @xmath43-poles generated by the denominator : [ denomexp ] @xmath55 and similarly for the higher order terms in @xmath43 .
therefore , by replacing eqs .
( [ gammaexp ] ) and ( [ denomexp ] ) into eq .
( [ factor ] ) , we are able to factor out the minimal subtraction density in the form @xmath56 where now the @xmath43-independent @xmath3 anomalous dimension is @xmath57 \ , , \nonumber\end{aligned}\ ] ] and contains some nnl@xmath1 terms related to the @xmath43-dependent ones in square brackets in eq .
( [ gammaexp ] ) . correspondingly , the coefficient @xmath58 in eq .
( [ rg ] ) has a _ finite _
@xmath52 limit , at fixed values of @xmath59 and @xmath60 .
therefore , we are able to reach the physical uv - free regime _
( ii ) _ , and we obtain @xmath61 \;,\ ] ] which is the result for the @xmath11 factor at nl@xmath1 level we were looking for .
a few remarks are in order .
firstly , the expansion coefficients @xmath62 and @xmath63 are simply obtained from the known form of the @xmath43-dependence of @xmath64 in eq .
( [ chi0 ] ) , while @xmath65 is not explicitly known , because the @xmath43-dependence of @xmath66 in eq .
( [ chi1 ] ) has yet to be extracted from the literature @xcite .
we quote the results @xmath67 in particular @xmath62 , together with the ll@xmath1 form of @xmath68 yields the result of ref .
@xcite [ r0 ] @xmath69 \\
\label{r0b } & = \left\ { \frac{\gamma(1-{\gamma_{\mathrm{l}}})\chi_0({\gamma_{\mathrm{l } } } ) } { \gamma(1+{\gamma_{\mathrm{l}}})[-{\gamma_{\mathrm{l}}}\chi_0'({\gamma_{\mathrm{l } } } ) ] } \right\}^{1/2 } \exp\left\{{\gamma_{\mathrm{l}}}\,\psi(1)+\int_0^{{\gamma_{\mathrm{l}}}}{\mathrm{d}}\gamma'\ ; \frac{\psi'(1)-\psi'(1-\gamma')}{\chi_0(\gamma')}\right\ } \;,\end{aligned}\ ] ] while @xmath63 and @xmath65 provide the new nl@xmath1 contribution to @xmath11 of @xcite .
secondly , the anomalous dimension in the @xmath2-scheme takes contributions from @xmath70 only , namely takes nl@xmath1 corrections too , which however coincide @xcite with those obtained by the known fluctuation expansion at @xmath52 . ]
@xmath71 and is therefore independent of the kernel properties for @xmath44 . on the other hand , by eqs .
( [ gammamsbar ] ) and ( [ rk ] ) , @xmath72 is related to @xmath73 by the expression @xmath74 whose origin is tied up to the identity ( [ denomexp ] ) .
indeed , we have separated terms of order @xmath43 or @xmath75 into minimal subtraction and coefficient contributions : therefore , their @xmath41-evolution should cancel out in the @xmath52 limit , which is the content of eq .
( [ gammams ] ) . using eqs .
( [ gammaq0 ] ) and ( [ gammams ] ) , the well known relations @xcite for nl@xmath1 anomalous dimensions can be extended to subleading levels , as generated by the @xmath43-expansion .
thus the difference @xmath76 \;.\ ] ] is computed up to nnl@xmath1 level as outlined above , even if the dynamical @xmath52 nnl@xmath1 contributions to the @xmath40 s are not investigated here .
we conclude that , while the anomalous dimension in the @xmath2-scheme ( which is roughly a `` maximal '' subtraction one ) only depends on the @xmath52 properties of the bfkl evolution , the @xmath3 coefficient and anomalous dimension both depend on higher orders in the @xmath43-expansion of the kernel eigenvalue , which generate subleading contributions .
the result in eq .
( [ diffanomdim ] ) of @xcite directly provides the scheme change for the gluon anomalous dimension at nnl@xmath1 level .
a problem exists concerning the magnitude of the scheme change summarized above in the small-@xmath1 region .
in fact , the explicit form of the coefficients @xmath77 , @xmath62 , @xmath65 , @xmath63 exhibit leading pomeron singularities of increasing weight , indicating that a small-@xmath1 resummation is in principle required for the scheme - change too . as a consequence , any resummed evolution model should provide , in principle , information on the corresponding @xmath43-dependence for a rigorous relation to the @xmath3 factorisation scheme , a task which appears to be practically impossible . in order to circumvent this difficulty
, we remark that @xmath11 in eq .
( [ r0b ] ) is directly expressed as a function of the variable @xmath40 , and that the leading pomeron singularity occurs because of the saddle point identification @xmath78 .
it is then conceivable that such a singularity will be replaced by a much softer one if the effective anomalous dimension variable becomes @xmath79 at resummed level .
a replacement similar to this one was used in anomalous dimension space in the study of the scheme - change of @xcite . in our framework
, we are able to ensure in general that @xmath80 is the relevant variable by assuming that the @xmath81 normalisation change occurs in a @xmath0-factorised form , i.e. , by taking the `` ansatz '' @xmath82 where @xmath83 is a properly chosen @xmath40- and @xmath15-dependent coefficient and @xmath84 denotes the unintegrated gluon density in @xmath40-space in the @xmath2-scheme .
the latter is directly provided by the @xmath85 small-@xmath1 bfkl equation , possibly of resummed ( rgi ) type .
it is then clear that , at ll@xmath1 level , @xmath83 in eq .
( [ ktansatz ] ) takes the saddle point value @xmath86 , which therefore should coincide with the expression ( [ r0 ] ) in order to reproduce eq .
( [ schemerel ] ) .
furthermore , the nl@xmath1 expression ( [ rk ] ) can be reproduced too , by a properly chosen @xmath87 term in the expression of @xmath83 ; and similarly for further subleading terms in the @xmath15-expansion of @xmath83 .
in other words , eq .
( [ ktansatz ] ) can be made equivalent to eq .
( [ rk ] ) at any degree of accuracy in the logarithmic small-@xmath1 hierarchy , but has the advantage that the effective anomalous dimension is order by order dictated by @xmath88 , possibly in rgi resummed form , and is therefore much smoother than its ll@xmath1 counterpart . by the argument above , we expect the @xmath15-expansion of the @xmath0-factorized scheme - change ( [ ktansatz ] ) to be more convergent than ( [ rk ] ) in the small-@xmath1 region .
this encourages us to implement it at leading level ( @xmath89 ) , in which we have @xmath90 where @xmath91 is pictured in fig .
[ f : rho].a .
for @xmath92 it is close to a @xmath93-function and for negative @xmath94 it oscillates with a damped amplitude for larger @xmath95 and with increasing frequency .
the difference of @xmath96 and @xmath97 involves a weight function distributed around @xmath98 which , convoluted with @xmath99 , includes automatically the rgi resummation effects of the @xmath2-scheme .
a word of caution is however needed about the accuracy of ( [ llconv ] ) in the finite-@xmath1 region , where subleading terms in the @xmath15-expansion of @xmath83 in eq .
( [ ktansatz ] ) are needed , and are left to future investigations .
( solid ) and its asymptotic estimates for @xmath100 ( dashed ) . _
( b ) _ sketch of the fastest convergence contour in the complex @xmath40-plane of the integral in eq .
( [ d : rho ] ) for @xmath101 , including the cuts and two saddle points that provide the dominant contributions to @xmath102 for very negative @xmath94.,title="fig:",scaledwidth=55.0% ] ( solid ) and its asymptotic estimates for @xmath100 ( dashed ) . _
( b ) _ sketch of the fastest convergence contour in the complex @xmath40-plane of the integral in eq .
( [ d : rho ] ) for @xmath101 , including the cuts and two saddle points that provide the dominant contributions to @xmath102 for very negative @xmath94.,title="fig:",scaledwidth=40.0%,scaledwidth=35.0% ] even if @xmath103 is in a sense a small quantity because the first two @xmath94-moments of @xmath104 must vanish the numerical evaluation of ( [ llconv ] ) is delicate because of the large oscillations of @xmath102 in the negative @xmath94 region . for @xmath105
the fastest convergence contour is shown in fig .
[ f : rho].b , where two saddle points @xmath106 of order @xmath107 are found . a saddle point evaluation @xmath108}{{{\textstyle\frac{1}{2}}}\sqrt{\chi_0^{(0 ) } { } ' \big(\gamma_{{\mathrm{sp}}}(\tau)\big ) } } \right\ } \;,\ ] ] provides a good estimate for the contributions from the diagonal parts of the contour , while we integrate numerically the remaining part of the contour .
the result ( [ rhosp ] ) is @xmath109-independent , but the constant of integration @xmath110 is determined numerically , e.g. , @xmath111 .
the function @xmath112 is also computed entirely numerically for @xmath113 . in order to illustrate the difference between small-@xmath1 gluon distributions in the @xmath2 and @xmath3 factorisation schemes , we consider a toy gluon density obtained by inserting a valence - like inhomogeneous term @xmath114 in the rgi equation of @xcite , as follows resummation scheme introduced in ref .
@xcite , where we perform the @xmath15-shift also on the higher - twist poles of the nl@xmath1 eigenvalue ; we denote it @xmath115 .
the running coupling , as a function of the momentum transfer @xmath116 , is cutoff at @xmath117 . ] @xmath118 and solving the corresponding evolution for the unintegrated gluon density @xmath119 where @xmath120 .
the normalisation @xmath121 is set so that the inhomogeneous term has a momentum sum - rule equal to @xmath122 .
the solution of the rgi equation approximately maintains the sum - rule for the full resulting gluon , though not exactly because of some higher - twist violations .
we then define the integrated densities @xmath123 which are shown in fig .
[ fig : toy - gluon ] in comparison to cteq ( nlo ) and mrst ( nnlo ) fits for the @xmath3 gluon at two scales .
note that we have not attempted to fine - tune the inhomogeneous gluon term to get good agreement at large @xmath1 since in any case we neglect the quark part of the evolution which is likely to contribute non - negligibly there . and
@xmath124 in the @xmath2 and @xmath3 schemes , compared to mrst2004 ( nnlo ) @xcite and cteq6m1 ( nlo ) @xcite . at the higher @xmath125 value
we also show the @xmath126 approximation to the full @xmath3 evaluation.,title="fig:",scaledwidth=48.0% ] and @xmath124 in the @xmath2 and @xmath3 schemes , compared to mrst2004 ( nnlo ) @xcite and cteq6m1 ( nlo ) @xcite . at the higher @xmath125 value
we also show the @xmath126 approximation to the full @xmath3 evaluation.,title="fig:",scaledwidth=49.0% ] one observes that the difference between the @xmath2 and @xmath3 schemes is modest compared to that between the cteq and mrst fits and , in particular , there is no tendency for the @xmath3 density to go negative .
this is despite the violently oscillatory nature of @xmath102 , which might have been expected to lead to significant corrections .
this can in part be understood from the approximate form of @xmath96 @xmath127 \;,\ ] ] which is obtained by expanding the scheme - change in the anomalous dimension variable @xmath128 to first non - trivial order .
we can see that this approximation is pretty good in the small-@xmath1 region for reasonable values of @xmath129 ( @xmath130 ) , corresponding to an effective @xmath131 .
value we do not show the @xmath126 approximation , because in general it breaks down for low @xmath125 . ] splitting function in the @xmath2 and @xmath3 schemes together with the uncertainty band for the @xmath2 scheme that comes from varying the renormalisation scale for @xmath132 by a factor @xmath133 , in the range @xmath134 ; shown for two @xmath125 values.,title="fig:",scaledwidth=48.0% ] splitting function in the @xmath2 and @xmath3 schemes together with the uncertainty band for the @xmath2 scheme that comes from varying the renormalisation scale for @xmath132 by a factor @xmath133 , in the range @xmath134 ; shown for two @xmath125 values.,title="fig:",scaledwidth=48.0% ] we can also use our usual techniques @xcite for extracting the splitting function itself in the @xmath3-scheme .
the results are shown in fig .
[ fig : split ] , where the @xmath3 curve is supposed to be reliable in the small-@xmath1 region only ( @xmath135 ) , because at finite @xmath1 the @xmath15-dependence of the scheme change will become important .
it appears that the splitting function is more sensitive to the scheme - change than the density itself . at the lower @xmath125 value
the difference between the @xmath3-scheme and the @xmath2-scheme ( with @xmath115 resummation ) is nearly the same as the renormalisation scale uncertainty and so might not be considered a major effect .
recall however that the scale uncertainty is nnl@xmath1 whereas the factorisation scheme change is a nl@xmath1 effect , so that while the renormalisation scale uncertainty decreases quite rapidly as @xmath125 is increased ( right - hand plot ) , the effect of the factorisation scheme change remains non - negligible . at small @xmath1
, most of the difference between the @xmath3 and @xmath2 splitting functions seems to be due to the @xmath3 splitting function rising as a larger power of @xmath136 .
one can check this interpretation by estimating the factorisation - scheme dependence of the asymptotic @xmath137 behaviour , using the @xmath126 approximation .
we find @xmath138 where the numerical value is given for @xmath139 , and is in rough agreement with what is seen in the left - hand plot of fig .
[ fig : split ] .
let us now discuss the inclusion of quarks in the resummed , small-@xmath1 flavour singlet evolution .
resummation effects will be included via the unintegrated gluon density as discussed before , while the scheme - change to the @xmath3-quark will be an ( approximate ) @xmath0-factorised form of the one arising at first non - trivial ll@xmath1 level . in order to better specify the scheme change
, we first recall @xcite that the quark density in a physical @xmath2-scheme corresponding to the measuring process @xmath140 ( e.g. @xmath141 or @xmath142 in dis ) which we call @xmath140-scheme is defined , at nl@xmath1 level , by @xmath0-factorisation of some @xmath143 impact factor @xmath144 , as follows : @xmath145 by then working out this convolution in terms of the eigenvalue function @xmath146 of @xmath144 , one directly obtains a nl@xmath1 resummation formula for the @xmath43-dependent @xmath147 anomalous dimension in the @xmath140-scheme : @xmath148^{-1 } \frac{{\mathrm{d}}}{{\mathrm{d}}t } q_{{\varepsilon}}^{(p)}(t ) \equiv \gamma_{qg}^{(p)}\big({\alpha_\mathrm{s}}(t),{\omega};{\varepsilon}\big ) \;,\ ] ] where , in the @xmath52 limit , @xmath149 has been obtained in closed form in various cases @xcite , including sometimes the @xmath43-dependence .
the @xmath3-scheme is then related to the @xmath140-scheme by the transformation @xmath150 where we set @xmath151 and @xmath152 at nl@xmath1 level , so that @xmath153 .
we thus obtain , by the definition ( [ d : gammap ] ) and by eq .
( [ schemerel ] ) , @xmath154 + \gamma_{qg}^{({\overline{\mathrm{ms}}})}({\alpha_\mathrm{s}},{\omega } ) \nonumber \\ & = \left[{\gamma_{\mathrm{l}}}\big(\frac{{\bar{\alpha}_\mathrm{s}}}{{\omega}}\big ) + { \varepsilon}\hat{d } \right ] c_{qg}^{(p)}({\alpha_\mathrm{s}},{\omega};{\varepsilon } ) + \gamma_{qg}^{({\overline{\mathrm{ms}}})}({\alpha_\mathrm{s}},{\omega } ) \ ; , \label{d : gammams}\end{aligned}\ ] ] where @xmath155 and @xmath156 is universal and @xmath43-independent , so that the process dependence of @xmath157 is carried by the perturbative , scheme - changing coefficient @xmath158 .
the coefficient @xmath158 in eq .
( [ d : gammams ] ) can be formally eliminated by promoting @xmath43 to be an operator in @xmath129-space , as follows : @xmath159 so that the square bracket in eq .
( [ d : gammams ] ) in front of @xmath158 just vanishes ( this procedure is rigorously justified in @xcite ) .
that implies that the l.h.s . of eq .
( [ d : gammams ] ) and @xmath160 are to be evaluated at values of @xmath161 which modifies @xmath162 at relative ll@xmath1 level . therefore , even if @xmath156 is by itself a nl@xmath1 quantity , the subtraction of the coefficient part in eq .
( [ d : gammams ] ) affects the scheme change at relative leading order , contrary to the gluon case of eqs .
( [ gammamsbar ] ) and ( [ diffanomdim ] ) .
the replacement ( [ epsop ] ) was used in @xcite in order to get an `` exact '' expression of @xmath156 at nl@xmath1 level ( that is , resumming the series of next - to - leading @xmath15-singularities @xmath163^n$ ] ) .
the main observation is that , by expanding @xmath160 in the @xmath40 variable around @xmath164 with coefficients @xmath165 , and by converting eq .
( [ d : quark ] ) to @xmath40-space , we obtain @xmath166 where @xmath167 is the fourier transform of @xmath168 and @xmath169 turns out to be the _ universal _
function @xmath170 \left [ \frac{{\mathrm{e}^{{\varepsilon}\psi(1)}}\gamma^2(1+{\varepsilon})\gamma(1-{\varepsilon})}{\gamma(1 + 2{\varepsilon } ) } \right ] \equiv { { \mathcal{h}}^{\mathrm{rat}}}({\varepsilon } ) { { \mathcal{h}}^{\mathrm{tran}}}({\varepsilon})\ ; , \ ] ] which we factorise into parts with rational and transcendental coefficients .
note that the universality of @xmath171 , which is proportional to the residue of the characteristic function @xmath146 at the collinear pole @xmath172 , is due to the interesting fact that one can define @xcite a universal @xcite , off - shell @xmath173 splitting function in the collinear limit @xmath174 , for any ratio @xmath175 of the corresponding virtualities .
we then realise from eq .
( [ qdotgamma ] ) that the terms in the r.h.s . with at least one derivative @xmath176
are of coefficient type , and vanish by the replacement ( [ epsop ] ) . the remaining one , proportional to @xmath171 , is universal and , by ( [ epsop ] ) , yields the nl@xmath1 result @xcite @xmath177 where we have factorised @xmath31 by the commutator @xmath178={\alpha_\mathrm{s}}$ ] and we have defined the quantity @xmath179 which has transcendental coefficients and differs from unity by terms of order @xmath180 or higher , in the @xmath181 region @xcite .
the complicated expression ( [ gqgmsbar ] ) has been evaluated iteratively @xcite , but not resummed in closed form .
however , it can be drastically simplified in the @xmath0-factorised framework by neglecting the transcendental corrections @xmath182 , on the ground that the resummed anomalous dimension is small .
in fact , by setting @xmath183 and @xmath184 , eq .
( [ gqgmsbar ] ) reduces to the expression @xmath185 which is just the borel transform of @xmath186 \;.\ ] ] since @xmath187 $ ] we obtain from ( [ borel ] ) what we call the `` rational '' approximation nl@xmath188 ( first derived in @xcite ) @xmath189 this result can be further interpreted in @xmath0-factorised form @xmath190 by using the characteristic function @xmath191 which yields the result in eq .
( [ gqgratgamma ] ) at the ll saddle point .
finally , since the exponentials in ( [ hms ] ) generate translations in @xmath41 , our rough estimate of the resummed @xmath5 is provided by the simple formula [ pqgrat ] @xmath192 \label{qdot } \\ & = \int_x^1 \frac{{\mathrm{d}}z}{z } \ ; p_{qg}^{({\overline{\mathrm{ms}}})}\big({\alpha_\mathrm{s}}(t),z\big ) g\big(t,\frac{x}{z } \big ) \;.\end{aligned}\ ] ] by replacing in eq .
( [ qdot ] ) the resummed gluon density @xcite and by performing the necessary deconvolution @xcite we obtain the results in fig . [
f : toypqg ] , compared to nlo and nl@xmath1 @xcite results .
@xmath193 splitting function for two values of @xmath129 and in various approximations : at two - loop [ dashed ] , the rgi resummed rational one in eq .
( [ pqgrat ] ) [ solid ] and with the addition of the first transcendental correction [ dash - dotted ] , the rational nl@xmath1 approximation [ dotted ] and the complete nl@xmath1 one [ dash - dot - dotted],title="fig:",scaledwidth=49.0% ] @xmath193 splitting function for two values of @xmath129 and in various approximations : at two - loop [ dashed ] , the rgi resummed rational one in eq .
( [ pqgrat ] ) [ solid ] and with the addition of the first transcendental correction [ dash - dotted ] , the rational nl@xmath1 approximation [ dotted ] and the complete nl@xmath1 one [ dash - dot - dotted],title="fig:",scaledwidth=49.4% ] a proper comparison of the curves in fig .
[ f : toypqg ] can be made only in the small-@xmath1 region @xmath135 because eqs .
( [ gqgmsbar ] ) and ( [ pqgrat ] ) do not include the finite-@xmath1 perturbative terms .
we then notice that small-@xmath1 resummation effects in @xmath194 are sizeable even around @xmath195 and somewhat larger than the gluonic ones .
they are anyway much smaller than the corresponding ones of the nl@xmath1 result , thus showing that the resummed anomalous dimension variable is pretty small , as already noticed in the gluon case .
we can also check how good the `` rational '' resummation is , by calculating the effect of the first @xmath182 transcendental correction , which is also shown in fig .
[ f : toypqg ] .
it appears that the difference is indeed not large and anyway much smaller than the difference between the results of nl@xmath188 in eq .
( [ gqgratgamma ] ) and nl@xmath1 @xcite , both shown in fig .
[ f : toypqg ] . to sum up
, we have proposed here a @xmath0-factorised form of the @xmath196 scheme - change ( eqs .
( [ ktansatz ] ) and ( [ qkt ] ) ) which allows a convergent leading log hierarchy , because of the smoothness of the resummed anomalous dimension . applying the leading scheme change to the gluon density and
in an approximate way to the quark density we have provided predictions for the @xmath197 and @xmath147 splitting functions in the @xmath3-scheme and for the corresponding densities .
we find that the gluon density itself is rather insensitive to the scheme change , while its splitting function is somewhat sensitive .
resummation effects for the @xmath3 quark are more important , but anyway much smaller than those at nl@xmath1 level .
we are thus confident that the scheme change can be calculated in a reliable way in a fully resummed approach as well .
we thank john collins for a question about positivity of the gluon in the @xmath3 scheme which motivated us , in part , to push forwards with these investigations .
this research has been partially supported by the polish committee for scientific research , kbn grant no . 1 p03b 028 28 , by the u. s. department of energy , contract no . de - ac02 - 98ch10886 and by miur ( italy ) .
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m. ciafaloni , d. colferai and g. p. salam , jhep * 0007 * ( 2000 ) 054 . | we investigate the relationship of `` physical '' parton densities defined by @xmath0-factorisation , to those in the minimal subtraction scheme , by comparing their small-@xmath1 behaviour .
we first summarize recent results on the above scheme change derived from the bfkl equation at nl@xmath1 level , and we then propose a simple extension to the renormalisation - group improved ( rgi ) equation . in this way we are able the examine the difference between resummed gluon distributions in the @xmath2 and @xmath3 schemes and also to show @xmath3 scheme resummed results for @xmath4 and approximate ones for @xmath5 .
we find that , due to the stability of the rgi approach , small-@xmath1 resummation effects are not much affected by the scheme - change in the gluon channel , while they are relatively more sensitive for the quark gluon mixing .
bnl - nt-06/4 + dff 432/01/06 + lpthe-06 - 01 + hep - ph/0601200 + january 2006 * minimal subtraction vs. physical factorisation schemes + in small-@xmath6 qcd * m. ciafaloni@xmath7 , d. colferai@xmath7 , g.p .
salam@xmath8 and a.m. stato@xmath9 + @xmath7 _ dipartimento di fisica , universit di firenze , 50019 sesto fiorentino ( fi ) , italy _ ; + + @xmath8 _ lpthe , universit pierre et marie curie
paris 6 , universit denis diderot
paris 7 , cnrs umr 7589 , 75252 paris 75005 , france _ + @xmath9 _ physics department , brookhaven national laboratory , upton , ny 11973 , usa _ ; + and + _
h. niewodniczaski institute of nuclear physics , krakw , poland _
+ predictions of perturbative quantum chromodynamics for dglap @xcite evolution kernels in hard processes have been substantially improved in the past few years , both by higher order calculations for any bjorken @xmath1
@xcite and by resummation methods in the small-@xmath1 region @xcite .
however , higher order splitting functions are factorisation - scheme dependent : while the nnlo results and standard parton densities @xcite are obtained in the minimal subtraction ( @xmath3 ) scheme , the resummed ones are in the so - called @xmath2-scheme , in which the gluon density is defined by @xmath0-factorisation of a physical process . therefore , in order to compare theoretical results , or to exploit the small-@xmath1 results in the analysis of data , we need a precise understanding of the relationship of physical schemes based on @xmath0-factorisation and of minimal subtraction ones , with sufficient accuracy . the starting point in this direction is the work of catani , hautmann and one of us ( m.c . ) @xcite , who calculated the leading-@xmath10 ( ll@xmath1 ) coefficient function @xmath11 of the gluon density in the ( dimensional ) @xmath2-scheme referred originally @xcite to the fact that the initial gluon , defined by @xmath0-factorisation , was set off - mass - shell ( @xmath12 ) in order to cutoff the infrared singularities .
it turns out @xcite , however , that the effective anomalous dimension at scale @xmath13 is independent of the cut - off procedure , whether of dimensional type or of off - mass - shell one .
] versus the minimal subtraction one , namely @xmath14 where @xmath15 is the moment index conjugated to @xmath1 , the @xmath3 density @xmath16\ ] ] factorises a string of minimal - subtraction @xmath17 poles starting from an on - shell massless gluon , @xmath18 is the ll@xmath1 bfkl @xcite anomalous dimension , and the explicit form of @xmath11 will be given shortly .
the purpose of the present letter is to show how to generalise the relation ( [ schemerel ] ) to possibly resummed subleading - log levels and to quarks .
we first summarize the essentials of such generalisation at next - to - leading @xmath19 ( nl@xmath1 ) level , following the detailed analysis of the bfkl equation in @xmath20 dimensions of two of us @xcite .
we then propose a simple extension of the method to the renormalisation group improved ( rgi ) approach @xcite . on this basis , we show the effect of a @xmath2 to @xmath3 scheme change on a toy resummed gluon distribution and we calculate a full @xmath3 small-@xmath1 resummed @xmath4 evolution kernel as well as a small-@xmath1 resummed @xmath5 evolution kernel in an approximation to the @xmath3 scheme . |
if r - parity conserving supersymmetry exists below the tev - scale , new particles will be produced and decay in cascades at the lhc .
the lightest supersymmetric particle will escape the detectors , thereby complicating the full reconstruction of the decay chains .
however , the masses of the particles in a cascade like @xmath0 can be determined from endpoints of kinematical distributions @xcite . here , @xmath1 denotes a ( left - handed ) squark , @xmath2 a ( right - handed ) slepton , whereas @xmath3 and @xmath4 denote the lightest neutralinos , the latter being stable .
the observed leptons and quark ( jet ) are denoted @xmath5 , @xmath6 and @xmath7 , where the subscripts `` n '' and `` f '' denote `` near '' and `` far '' .
attention is focused on the msugra benchmark point sps 1a ( line ) @xcite @xmath8 and in particular two points on the line , sps 1a ( @xmath9 ) with @xmath10 and @xmath11 , and sps 1a ( @xmath12 ) with @xmath13 and @xmath14 .
the resulting low - energy masses entering in the cascade ( [ eq : cascade ] ) are given in table [ sps1a - masses ] @xcite .
a second effect , not discussed above , is very clear by comparison of the errors on the masses obtained with and without the lc measurement : fixing the lsp mass strongly reduces the errors on all the masses .
this comes from the fact that the endpoint method determines mass _ differences _ much better than the actual masses themselves , a feature due to the way masses enter the endpoint expressions ; in terms of differences of masses ( squared ) .
actually , the errors on the masses obtained when the lhc and the lc are combined , tables [ table : lhc+lc alpha][table : lhc+lc beta ] , are very close to the errors on the mass differences as obtained by the lhc alone .
the removal of ambiguities , and the higher precision are crucial for an extrapolation to the gut scale @xcite , a major goal of studying the spectroscopy of supersymmetric particles at future accelerators .
9 h. baer , c. h. chen , f. paige and x. tata , phys .
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_ , in _ proc .
of the aps / dpf / dpb summer study on the future of particle physics ( snowmass 2001 ) _ ed .
n. graf , eur .
j. c * 25 * ( 2002 ) 113 [ econf * c010630 * ( 2001 ) p125 ] [ arxiv : hep - ph/0202233 ] . b. k. gjelsten , d. j. miller and p. osland , jhep * 0506 * ( 2005 ) 015 [ arxiv : hep - ph/0501033 ] .
j. a. aguilar - saavedra _ et al . _
[ ecfa / desy lc physics working group ] , arxiv : hep - ph/0106315 . b. c. allanach , g. a. blair , s. kraml , h. u. martyn , g. polesello , w. porod and p. m. zerwas , arxiv : hep - ph/0403133 . | the measurements of kinematical endpoints , in cascade decays of supersymmetric particles , in principle allow for a determination of the masses of the unstable particles . however , in this procedure ambiguities often arise .
we here illustrate how such ambiguities arise .
they can be resolved by a precise determination of the lsp mass , provided by the linear collider . |
attention - deficit hyperactivity disorder ( adhd ) is one of the most common behavioral and neurodevelopmental disorders which is characterized by hyperactivity , impulsivity , and inattention in children and adolescents .
prevalence of adhd among school - aged children in different studies varies between 5 and 12% [ 1 , 2 ] , whereas the prevalence of this disorder declines with increasing age .
children with adhd are at increased risk of antisocial behavior , learning disabilities , drug abuse , impaired academic performance , impaired executive functions , communication disorders , speech problems , and comorbid psychiatric disorders [ 5 , 6 ] .
although , the pathogenesis of adhd is still unknown , primary and secondary factors are estimated to be implicated in adhd pathogenesis .
some of these factors , which are associated with adhd , are pregnancy and birth related risk factors which are classified into three groups including prenatal , perinatal , and postnatal risk factors . regarding prenatal risk factors ,
a large number of studies have shown that maternal exposure to alcohol , tobacco , and cocaine during pregnancy increases the risk of adhd .
on the other hand , some studies showed that prenatal viral infections are associated with increased risk of adhd [ 10 , 11 ] .
various studies have demonstrated that preeclampsia , maternal anemia , lower serum level of iron and iodine , and trauma to abdomen during pregnancy are associated with increased risk of adhd development [ 10 , 12 ] .
regarding perinatal risk factors , a number of risk factors such as prematurity , low birth weight , and breech delivery are estimated to be associated with increased risk of adhd .
postnatal risk factors include postnatal viral infections such as measles , varicella , and rubella increasing the risk of developing adhd .
additionally , several other factors such as breast - feeding , head injury in early childhood and adolescence , encephalitis , convulsion and endocrine disorder are estimated to be risk factors for development of adhd [ 13 , 14 ] .
although the association of breastfeeding and adhd is not established , some studies have shown that adhd is more common in children with lower rates of breast feeding .
the role of other factors such as unintended pregnancy , x - ray exposure , and previous abortion is not established .
in addition to the mentioned factors , several sociodemographic factors such as maternal education , family income , male gender , and maternal age at pregnancy are known to be predictive factors for developing adhd [ 12 , 13 ] .
some studies have shown that maternal emotional stress during pregnancy is related to increased risk of psychobehavioral disorders such as adhd .
prematurity , maternal alcohol consumption , and smoking are associated with adhd symptoms [ 15 , 16 ] .
with respect to destructive complication of adhd and its negative effects on psychosocial behavior of children with this disorder , we aimed to determine the adhd risk factors among the school - aged children in bandar abbas .
this case - control study was carried out among 404 children aged 411 years that were selected by cluster sampling in southern iran in 2012 .
this study was approved by the ethics committee of hormozgan university of medical sciences ( hums ) .
, 935 preschool children were selected using cluster sampling and all of them were screened by conners ' parents and teachers rating scales . out of them , 271 children were positive for adhd according to conners ' questionnaire and those who were positive for adhd ( 271 ) were interviewed by a child and adolescent psychiatrist and 208 children who met dsm - iv criteria for adhd were enrolled in this study .
the total possible score was 84 and children with a parent or teacher questionnaire total score above 70 were considered as positive and referred to ebne - sina hospital , the only behavioral and neuroscience center in hormozgan province .
all of the selected children were interviewed by a specialist in child and adolescent psychiatry .
the cases were selected among patients who met the diagnostic criteria of dms - iv for adhd and controls were chosen among healthy children .
their parents were asked to answer the questionnaire including maternal and pregnancy related risk factors for adhd such as the mother age at pregnancy , thyroid disease , the length of pregnancy , exposure to x - ray , infectious disease , eclampsia , abnormal uterine bleeding , abdominal trauma , medication intake , alcohol and tobacco consumption during pregnancy , and previous abortion , as well as neonatal and infantile related risk factors such as unwanted pregnancy , type of delivery , hyperbilirubinemia , phototherapy , blood exchange , low birth weight ( less than 2.5 kg ) , feeding ( breastfeeding or formula feeding ) , childhood asthma , dysentery , epilepsy , head trauma , and thyroid disease .
in addition , parents ' educational level , economic level , and presence of psychiatric disease in children and their parents were documented .
data was analyzed using statistical procedures for social sciences ( spss ; version 19 ) by descriptive analysis such as mean , standard deviation and percentile frequency .
a total of 404 children met the enrollment criteria , including 208 children as case group and 196 as controls .
the mean age of participants in case and control groups was 6.48 1.95 and 5.77 1.232 years , respectively .
there was no significant difference between both groups ( p > 0.05 ) . among adhd children , 150 ( 59.3% ) were boys and 58 ( 38.4% ) were girls . among controls , 103 ( 40.7% ) and 93 ( 61.6% ) were boys and girls , respectively .
chi - square demonstrated that adhd was significantly higher among boys than girls ( p < 0.0001 , or : 3 , 95% ci : ( 1.346.635 ) ) .
the results showed that a history of trauma to abdomen during pregnancy was significantly higher among mothers who had children with adhd .
maternal , pregnancy , neonatal risk factors for adhd , and maternal and paternal history of psychiatric disorders are listed in tables 1 and 2 . as shown in table 3 , among neonatal and childhood risk factors , childhood head trauma and epilepsy
this cross - sectional case - control study was performed to determine the risk factors of adhd .
symptoms of adhd almost present in early childhood after 3 years of age and before 7 .
it may be continued to adulthood and affect the interpersonal impairments , academic performance , and work and family problems .
untimely diagnosis and treatment of this disorder can lead to cognitive and behavioral impairments . in recent years , numerous investigations have been done to identify the etiology of this disorder and the related factors . in the current study ,
this finding was consistent with the results of other studies conducted by kim et al . and
there are converging lines of evidence regarding the role of genetic factors in developing adhd .
moreover , our results showed that adhd was more frequent among those children of nonrelated parents compared to related parents
. this could be due to the increased chance of distribution of genetic role and mutation when children are born to nonrelated parents .
controversial findings have been reported about the role of thyroid hormones in adhd [ 23 , 24 ] , while some lines of evidence revealed that adhd is more frequent in patients with a generalized resistance to thyroid hormones compared to normal population .
our finding showed that thyroid disease was not significantly higher among patients with adhd compared to control children .
screening of adhd children for thyroid disease is not recommended unless the symptoms of hypo / hyperthyroidism are observed .
our results showed that alcohol and tobacco exposure during pregnancy would increase the risk of adhd .
there are few studies regarding the association of preeclampsia in pregnancy and adhd in their children .
some studies have shown that pregnancy complications are associated with increased risk of offspring adhd [ 10 , 31 ] . however , amiri reported that a history of preeclampsia and infections during pregnancy were not significantly higher among mothers of children with adhd .
our findings revealed that trauma to abdomen , previous abortion , unwanted pregnancy , preeclampsia , and cesarean section were significantly higher among patients with adhd compared to control subjects . but
x - ray exposure , infectious disease , dysentery , and vaginal bleeding at pregnancy were not associated with increased risk of adhd .
various studies demonstrated that low birth weight among adhd children was significantly higher than normal children [ 28 , 32 ] .
but in this study , low birth weight was not significantly higher in children with adhd .
the results of our study demonstrated that prevalence of adhd among formula - fed patients was significantly higher than breast - fed children .
some lines of evidence demonstrated that fatty acid compositions of human breast milk such as docosahexaenoic acid and arachidonic acid have an important role in brain development [ 33 , 34 ] . the results of our study may be due to the role of fatty acids in brain growth during neonatal and infancy stages .
in addition , a review by mazza and colleagues reported that fatty acids are associated with other psychotic disorders .
our results showed that epilepsy and trauma to head were significantly higher among adhd children than control group . on the other hand , the difference of the frequency of childhood asthma , dysentery , and thyroid disease was not significant between both groups .
our result was consistent with a study conducted by gerring and colleagues that reported that adhd was more frequent among patients who presented with moderate and severe head injuries .
furthermore , another finding that was consistent with our results was reported by dunn and colleagues ; they demonstrated that children with epilepsy are at increased risk of adhd in the future .
recently , various studies examine the effect of methylphenidate on seizure frequency among patients with concomitant adhd and epilepsy .
these evidences showed that methylphenidate is an effective and safe medication for patients with both epilepsy and adhd [ 39 , 40 ] .
although in this study we tried to eliminate the overestimation or underestimation of adhd by parents of children , whoever they are , a limitation in our study could be the probable recall bias by the parents . in conclusion
, our study demonstrated that parental psychiatric disorders , previous abortion , unwanted pregnancy , cesarean delivery , maternal alcohol and tobacco exposure during pregnancy , epilepsy , and head trauma were significantly more among adhd children than control group .
accordingly , avoiding alcohol , tobacco , and unnecessary x - ray during pregnancy and elective cesarean delivery are recommended as well as feeding by breast milk instead of formula .
however , it must be taken into consideration that alcohol and tobacco exposure , previous abortion , and unwanted pregnancy may be results of maternal and paternal adhd . | background . attention - deficit hyperactivity disorder ( adhd ) is one of the most common psychiatric disorders among children .
the aim of this study was to evaluate risk factors for adhd in children . method . in this case - control study , 404 children between 4 and 11 years old were selected by cluster sampling method from preschool children ( 208 patients as cases and 196 controls ) .
all the participants were interviewed by a child and adolescent psychiatrist to survey risk factors of adhd . results . among cases ,
59.3% of children were boys and 38.4% were girls , which is different to that in control group with 40.7% boys and 61.6% girls .
the chi - square showed statistically significance ( p value < 0.0001 ) .
the other significant factors by chi - square were fathers ' somatic or psychiatric disease ( p value < 0.0001 ) , history of trauma and accident during pregnancy ( p value = 0.039 ) , abortion proceeds ( p value < 0.0001 ) , unintended pregnancy ( p value < 0.0001 ) , and history of head trauma ( p value < 0.0001 ) .
conclusions .
findings of our study suggest that maternal and paternal adverse events were associated with adhd symptoms , but breast feeding is a protective factor . |
this is the first reported case of metastasizing nodular hidradenoma in a child in the medical literature .
less than five cases of hidradenoma have been reported in children , none of which were malignant .
its malignant counterpart is quite rare ; with only 50 cases reported in adults , and none in children .
early diagnosis and wide surgical resection are the mainstay in the management of this malignant tumor , which is not responsive to chemotherapy and radiotherapy ( rt ) .
an 8-year - old girl presented to a district hospital in november 2008 with a painless lemon - sized scalp swelling since three months .
she presented a year later to our referral hospital with another recurrence at the margins .
she underwent excision of the lesion at our hospital in november 2010 and the histopathology of the excised specimen revealed recurrent hidradenoma of scalp . in august 2011
the pathology of the specimen showed evidence of bilateral high parietal bone erosion , osseous infiltration , and extradural extension .
histopathology of excised scalp tumor with periosteum revealed skin - covered tumor mass composed of several nodules of tumor cells , which had eosinophilic to clear cytoplasm with round to ovoid nuclei .
the tumor tissue was infiltrating the periosteum and reaching up to the resected margins [ figures 1 and 2 ] .
microphotograph showing multiple lobules of tumor cells seen in the dermis with intact epidermis ( h and e 40 ) microphotograph showing cellular tumor with infiltrative borders ( h and e 100 ) the patient presented with recurrence yet again in 2012 [ figure 3 ] .
the flesh - colored , ulcerated scalp mass had grown to a larger size measuring approximately 13 10 12 cm . computed tomography and
magnetic resonance imaging done between june and august 2012 revealed a large heterogeneously enhancing mass in the left parieto - occipital region with epidural component and invasion of left transverse sinus [ figure 4 ] .
clinical photograph of the patient ( a ) axial t1w image showing large soft tissue mass in the scalp causing erosion of left parieto - occipital bones and invasion into the extradural space with buckling of white matter .
( b ) coronal t2w image showing multiple radiating flow voids within the mass chemotherapy was started with 5fluorouracil ( 5fu ) and cisplatin , but was discontinued after two cycles due to poor response .
she also received 20 gy of rt in 5 sequences in september 2012 with no visible improvement .
her parents decided to take her back to their native village and never returned for follow - up thereafter .
malignant nodular hidradenoma ( mnh ) is an extremely rare ( 0.005% among all epithelial neoplasms of skin ) and little understood tumor of sweat glands . to date , reported cases in the medical literature number just over 50 , mostly as case reports or isolated small series . in 1865 , cornil documented the first case of sweat gland carcinoma . reviewing
the literature , gates et al . assigned a total of eight cases to the nineteenth century .
cooley reported a series of 11 well - documented cases of malignant adnexal tumors . in 1968 ,
berg and mcdivitt presented the largest series to date , of 17 cases of hidradenoma among 102 sweat gland carcinomas and were the first to offer classification of this entity .
the cell of origin of this tumor is still debatable , whether from eccrine cells , apocrine cells , or folliculosebaceous apocrine unit ( fsau ) cells .
it is increasingly being recognized that most of these tumors have cells from any or all the three units .
these tumors have been variously named as clear cell eccrine carcinoma , nodular hidradenoma , malignant clear cell hidradenoma , solid cystic adenocarcinoma , malignant acrospiroma , and clear cell myoepithelium tumor .
a major predicament faced by the clinicians is the inability to distinguish the malignant variety from its benign counterpart , hidradenoma a frequently occurring adnexal tumor with favorable prognosis .
in contrast , malignant hidradenoma , especially the metastasizing type is extremely aggressive with a very poor clinical outcome .
the distinction is based on lack of circumscription ; infiltrative manner of spread ; nuclear pleomorphism ; perineural and lymphovascular invasion ; and increased mitotic numbers as well as hematogenous spread to distant nodes , other organs , bones , and lungs .
immunochemistry studies have been attempted , but because of paucity of cases , no definite data is yet available . ki67 and phh3 may have a role to play in the diagnosis and differentiation of benign , atypical , and malignant hidradenomas .
this distinction is of importance for prognostic evaluation , particularly in cases of atypical and malignant variety .
atypical hidradenoma has lower ki-67 values compared with metastasizing adnexal carcinoma and malignant hidradenoma ( p value 0.002 ) .
a few other immunostaining markers such as c5/6 , ck15 , ema , and p-53 have been found positive in malignant cutaneous adnexal neoplasms and apocrine carcinomas .
metastasizing malignant hidradenoma has not been reported in childhood till date , although three cases of benign hidradenoma in children aged 1 , 3 , and 13 years have been documented .
this patient happens to be the first such case that appeared at the age of 8 years .
the tumor recurred every time after surgical excision ( 5 times ) and was so aggressive that it spread to extradural space , vertebrae , humerii , and lungs in a span of less than 4 years .
hidradenoma typically presents as a slow - growing painless , firm , subcutaneous nodule or plaque .
it may be flesh colored , violet , or reddish with intact normal overlying skin ; occasionally showing surface ulceration . more often than not , the diagnosis is based on histopathologic features alone .
malignant hidradenomas have mostly been reported to arise de novo , although a few cases have arisen in pre - existing benign hidradenoma .
metastases to bones , lungs , and other viscera may occur in as high as 60% of patients .
mnhs are usually large , poorly demarcated , and asymmetric as compared with the typically well - demarcated benign variety .
however , definitive histologic features , that distinguish hidradenomas from its benign counterpart or other related malignant tumors are lacking , and diagnosis is based on the extent of invasion .
tumor necrosis , areas of high cellularity , and focal or diffuse areas of marked cytologic atypia are present in some cases . there may be angiolymphatic invasion . additionally , in some cases
, nuclear anaplasia may be minimal to moderate and at times even absent in both the primary and the metastases .
standard treatment of hidradenoma is wide surgical excision that extends 2 cm beyond tumor margins .
of late , wider excision extending to 5 cm beyond margins has been recommended to reduce incidence of residual cells .
since no uniform treatment guidelines for mnh are established and adjuvant therapies have also not been very effective , targeted therapy using molecular biology techniques might be the answer for this rare but aggressive tumor .
mnhs are usually large , poorly demarcated , and asymmetric as compared with the typically well - demarcated benign variety .
however , definitive histologic features , that distinguish hidradenomas from its benign counterpart or other related malignant tumors are lacking , and diagnosis is based on the extent of invasion .
tumor necrosis , areas of high cellularity , and focal or diffuse areas of marked cytologic atypia are present in some cases . there may be angiolymphatic invasion . additionally , in some cases
, nuclear anaplasia may be minimal to moderate and at times even absent in both the primary and the metastases .
standard treatment of hidradenoma is wide surgical excision that extends 2 cm beyond tumor margins .
of late , wider excision extending to 5 cm beyond margins has been recommended to reduce incidence of residual cells .
use of mohs microsurgery has also been suggested . since no uniform treatment guidelines for mnh
are established and adjuvant therapies have also not been very effective , targeted therapy using molecular biology techniques might be the answer for this rare but aggressive tumor .
| an 8-year - old girl presented with a scalp swelling .
the swelling was recurrent , reappearing everytime after local excision .
she underwent surgery and the histopathologic diagnosis was malignant hidradenoma .
this very rare and aggressive tumor is known to occur in elderly population and is histopathologically distinct from its commonly occuring benign counterpart .
malignant hidradenoma is resistant to chemotherapy and radiotherapy .
we empahsize that being cognizant of the possibility of this rare tumor would assist in timely action in the form of wide resection , with possible reduction in morbidity and mortality . |
hot cores are compact ( 0.1 pc ) , warm ( @xmath5 100300 k ) , dense ( 10@xmath6 h nuclei ) clouds of gas and dust near or around sites of recent star formation ( see e.g. * ? ? ?
* ; * ? ? ?
* ; * ? ? ?
the hot - core phase is thought to last about 10@xmath7 yr @xcite to 10@xmath8 yr @xcite and represents the most chemically rich phase of the interstellar medium , characterized by complex molecules like , , , and .
the complex chemical and physical processes occurring in the hot - cores are not fully understood . until recently hot cores were thought to be associated with high - mass protostars ( m@xmath9 8 @xmath10 ) only and to represent an important phase in their evolution toward ultracompact and compact h ii regions .
the central energizing source for a number of hot cores have been identified using high angular resolution mid - infrared ( mir ) and millimeter continuum observations ( e.g. * ? ? ?
* ; * ? ? ?
these detections strengthen the idea of hot molecular cores ( hmcs ) as representing a stage in the evolutionary sequence of massive protostars .
however , there are non - negligible examples of hot cores that are in the vicinities of uc h ii regions and appear to be only externally heated .
for these sources it may well be argued that the hot cores can also arise as chemical manifestations of the effect of the uc h ii regions on their environments , rather than being only the precursors of uc h ii regions .
the chemical models are still far from providing a unique interpretation of the hot core chemistry , and would benefit from high angular resolution continuum and spectroscopic observations suitable to understand the temperature and density distributions of the cores . in particular , the strong sensitivity of surface and gas - phase chemistry to dust temperature and gas density highlights the importance of the study of the abundances of complex molecules in different regions with varied physical characteristics .
furthermore , all the existing chemical models assume the hot cores to be internally heated and have radially varying density and temperature profiles @xcite ; the models do not yet provide a consistent treatment of the externally heated hot cores .
we present high angular resolution ( 1 ) interferometric observations with the berkeley - illinois - maryland association ( bima ) array of the well - studied hot core associated with the uc h ii region g34.26 + 0.15 located at a distance of 3.7 kpc @xcite .
the h ii region is a prototypical example of cometary morphology , which may be due to the bow - shock interaction between an ambient molecular cloud and the wind from an energetic young star moving supersonically through the cloud @xcite .
observations with the vla @xcite show that the highly compact molecular cloud appears to be wrapped around the head of the cometary h ii structure , with the ionization front advancing into the cloud .
g34.26 + 0.15 has been extensively studied in radio continuum @xcite and radio recombination lines @xcite . at radio continuum frequencies
, it exhibits several components : two uc h ii regions called a & b , a more evolved h ii region with a cometary shape named component c , and an extended ring - like h ii region with a diameter of 1 called component d @xcite .
molecular gas has been mapped in , hco@xmath11 , so , and co @xcite . the hot core associated with g34.26 + 0.16 has been the target of chemical surveys using single - dish telescopes @xcite in which complex molecules characteristic of hot cores were detected .
molecular line observations suggest that the hot core does not coincide with the h ii region component c ; it is offset to the east by at least 2 and shows no sign of being internally heated @xcite .
based on narrow - band mid - infrared imaging of the complex , @xcite concluded that the same star is responsible for the ionization of the h iicomponent c and heating the dust but is not interacting with the hot core seen in molecular emission . at a resolution of 12 , @xcite also found the peak of the 350 emission to be coincident with the component c of the uc h ii region . in this paper
we use the bima observations to study the energetics , chemistry and kinematics of the molecular gas contributing to the hot core emission associated with g34.26 + 0.15 .
observations of the source g34.26 + 0.15 were acquired with the ten - element bima interferometer between 1999 december and march 2000 at three frequency bands centered approximately at 87 , 107 and 109 ghz using the a & b configurations of the array . due to technical difficulties
only nine antennas could be used for the observations at 87 ghz .
table [ obsdetails ] presents a log of the observations , including the typical system temperatures in the different configurations presented here .
the primary fwhm of the array is between 132 and 106 at frequencies between 87 and 109 ghz .
the correlator was configured to split each frequency into four windows per sideband , two of which had bandwidths of 100 mhz and 64 channels each and the remaining two had bandwidths of 50 mhz and 128 channels each .
the sources uranus , 1830 + 063 and 1771 + 096 were observed as the primary flux calibrator , the phase calibrator and the secondary calibrator , respectively .
however owing to the consistently poor quality of 1830 + 063 observations and the sparsity of uranus observations , we have used 1771 + 096 as both the phase and primary flux calibrator .
the flux of 1771 + 096 was determined from each of the six datasets , using the miriad task bootflux with uranus as the primary calibrator .
the average final flux for 1771 + 096 is 2.3 jy ; we estimate the absolute flux calibration error to be 10% . the pointing and phase center used for mapping the region around g34.26 + 0.15
is @xmath12 = 18@xmath1353@xmath141855 @xmath15 = 114582 and the @xmath16 = 58 .
the data were reduced using the miriad @xcite software package .
continuum maps were constructed by averaging over spectral windows that did not contain line emission . in order to achieve better phases
the continuum maps were iteratively self calibrated .
the spectral line maps within a particular spectral window were made by first fitting a low - order polynomial to the visibilities in the channels not contaminated by any line emission and then subtracting the fit to the continuum from the individual channels .
the observed spectral lines were identified using the spectral line catalog by @xcite . we have detected multiple transitions of methanol ( ) , two transitions of ethyl cyanide ( ) and single transitions of methyl formate ( ) , dimethyl ether ( ) , formamide ( ) , , ocs ( and its @xmath17s , @xmath18c isotopomers ) , so , so@xmath1 and the hydrogen recombination line h53@xmath2 .
table [ speclines ] presents spectroscopic details of the molecular lines that were detected in the present data set .
table [ basic_results ] summarizes the basic results of the bima observations : synthesized beam sizes , the peak intensity , the peak brightness temperature , the central velocity ( @xmath19 ) , the velocity width ( @xmath20 ) and the achieved rms per channel of the interferometric maps , for each of the observed spectral lines .
the @xmath19 and @xmath20 were determined from gaussian fits to the line profiles .
in addition to the 10% error in absolute calibration we estimate the statistical errors in intensities to be @xmath21% .
figure [ cont_cont ] shows an overlay of the @xmath222.8 mm continuum image with the @xmath222 cm continuum emission observed by @xcite .
the 2.8 mm continuum is peaked at the nominal map center ( @xmath12 = 18@xmath1353@xmath141855 , @xmath15 = 114582 ) and coincides with the cometary component c of the g34.26 + 0.15 uc h ii region complex @xcite . as will be discussed in sec .
[ intmap_peak ] the continuum peak detected at 2.8 mm does not coincide with the emission peaks of the lines originating in the hot molecular gas .
although continuum at 2.8 mm shows a single peak , most of the radio continuum maps at cm wavelengths show the component c to consist of two emission peaks c1 and c2 , separated by @xmath23 .
however @xcite suggest that c1 and c2 are not two separate continuum components , but they correspond to two regions of maximum emission in the nebula .
recently @xcite mapped the g34.26 + 0.15 region at 43 ghz using vla and they find a single peak similar to the millimeter maps . based on the radio continuum spectrum the flux density due to the free - free emission from the components a & b is expected to be @xmath24 mjy at 100 ghz @xcite .
this is consistent with our observations where we do detect some emission from the uc components a and b , though these components are not resolved in our maps . at 107 ghz ( @xmath3 mm )
we measure a peak flux density of 2.9 jy / beam and an integrated intensity of 6.7@xmath25 jy estimated by fitting a gaussian of 16@xmath2614 to the central source .
in addition to the given statistical error for the continuum flux density , there is a 0.7 jy error corresponding to the uncertainty in the absolute flux calibration .
the 2.8 mm continuum flux density measured here is consistent with previous observations at similar resolutions @xcite .
@xcite measured an integrated radio continuum flux of 5 jy at 1.3 cm ( 24 ghz ) for the component c , which , when combined with the 2.8 mm flux indicates a spectral index of 0.2 .
this spectral index is significantly flatter than the index of 0.45 derived by @xcite for the combined emission of all 3 components of the uc h ii region . at a resolution of 1 ,
the 2.8 mm emission is clearly dominated by the free - free emission from component c of the uc h ii region and does not arise from an embedded source that could be energizing the hmc internally .
dust emission may be responsible for the eastern extension of the emission at a 10% level .
figure [ allmap ] shows the integrated intensity maps of the different spectral line emission detected in the region around g34.26 + 0.15 overlaid with the continuum emission at @xmath3 mm and the positions of the h@xmath1o and oh masers detected in the region @xcite .
the emission from none of the molecular species coincides with the positions of the h@xmath1o and oh masers . at a resolution of 1 the integrated intensity distribution for the different chemical species
primarily show three kinds of morphological structures : _ single - peaked , double - peaked _ and _ irregular_. figure [ peaks ] shows the positions of the absolute maxima of the integrated intensities for the different species overlaid with the @xmath3 mm continuum map of g34.26 + 0.15 .
the absolute positional accuracy is estimated to be 01 .
we note that it is possible to identify primarily two regions where the maxima due to the transitions of the different species are localized : the first lying slightly to the south - east of the continuum peak and the second lies to the north - east of the 2.8 mm continuum peak . _
( a ) single - peaked : _ the spectral lines of ( with the exception of the @xmath2715@xmath28 e2 transition ) , , nh@xmath1cho , so and ocs , as well as the h53@xmath2 recombination line show well - defined single peaked structures
. also shows a single - peaked structure though it is somewhat poorly defined as compared to the rest . of these spectral lines
only the peaks of the h53@xmath2 and the emission coincide with the peak of the continuum at @xmath3 mm , while the peaks due to and ocs occur to the north - east of the continuum peak .
the peak due to so lies 1 to the south - east of the 2.8 mm continuum peak .
the peaks of and nh@xmath1cho lie close enough ( @xmath5 04 south - east ) to but not exactly at the position of the 2.8 mm continuum peak . at a first glance
, it appears that the more abundant species with higher optical depths tend to show a single - peaked structure .
we revisit the question of optical thickness of the lines in sec .
[ kintemp ] .
_ ( b ) double - peaked : _ the spectral lines of ch@xmath29ch@xmath1cn and show rather well - defined double - peaked structure .
figure [ peaks ] suggests that the peaks corresponding to the two transitions of occur at rather different positions .
in fact , they correspond to the two peaks that appear in both transitions , with essentially reversed ratios of relative intensities .
the double - peaks of are also not aligned with those of , as emission as a whole is somewhat shifted to the north of the continuum peak and extends more along the east - west direction in contrast to the emission . _
( c ) irregular shaped : _ the integrated intensity distribution of o@xmath18cs , oc@xmath17s and so@xmath1 appear to be irregularly shaped and do not have enough signal - to - noise in order to show well - defined peaks .
the positions shown in figure [ peaks ] correspond to the absolute maxima within the emitting region and represent the approximate location of the enhancement in emission .
these should not be taken too literally as peaks having significance comparable to the peaks for the single - peaked species .
figure [ peaks ] shows that almost all peak positions to the north - east of the continuum peak correspond to single - peaked emission structure . among the tracers peaking to the south - east ,
only and so are single - peaked and is double - peaked .
the remaining tracers have irregular intensity distribution with absolute maxima at the indicated positions .
these two primary locations of the peaks of the spectral lines , ( fig . [ peaks ] ) may either correspond to different emitting clumps or they could be manifestation of the differences in the temperature and density that leads to the variation of the chemical abundances within the same clump .
we revisit both these concepts in sec .
[ discussion ] . in sec .
[ chemabund ] we derive the chemical abundances of the different chemical species at the two nominal peak positions identified by the @xmath30@xmath31a@xmath11 peak to the north - east and the 1211 peak to the south - east of the continuum peak .
figure [ velmap ] shows the centroid velocity distribution of some of the selected species for which the signal to noise was sufficient over large areas to generate the maps . with the exception of the hydrogen recombination line and the limited sensitivity line , the center velocity of all molecular lines changes from 56 in the south - west to 62 in the north - east over a spatial scale of 0.08 pc in a direction approximately with a position angle of 40@xmath32 . the direction and magnitude of the velocity gradient match well with other measurements of molecular gas velocity gradients towards g34.26 + 0.15 .
using observations at angular resolutions similar to the present dataset @xcite derived a velocity gradient of @xmath33 pc@xmath34 , while @xcite and @xcite observed a velocity gradient of 6@xmath35 on 0.3 to 0.75 pc scales . @xcite derived a velocity gradient of 15@xmath36 on 0.2 to 0.3 pc scales . @xcite observed similar velocity gradients as we find , using only .
sio emission primarily tracing outflow activity was not detected at the position of the hot core , it rather appears to surround the hot core @xcite .
this implies that shocks do not play an important role in regulating the hot core chemistry in g34.26 + 0.15 .
the ionized and molecular gas in g34.26 + 0.15 show rather different velocity gradients , both in direction and magnitude .
the hot molecular gas consistently shows this sw - ne velocity gradient , while the ionized gas has a total gradient of @xmath37 in a direction perpendicular to the symmetry axis of the cometary uc h iiregion @xcite .
a smaller velocity gradient is detected in the ionized gas parallel to the symmetry axis , _ i.e. _ along the east - west direction .
in addition , the ionized gas shows typical velocity widths of @xmath38 @xcite .
the hydrogen recombination line , h53@xmath2 shows an emission peak exactly coincident with the continuum peak at @xmath3 mm and a velocity gradient similar to the minor component of the velocity gradient as identified in the ionized gas .
similar to all the other recombination lines detected in the region , the h53@xmath2 line has a linewidth much larger than all the other molecular species .
these large widths of the recombination lines show conclusively that the ionized gas is driven primarily by the h ii region dynamics .
comparison of figs .
[ allmap ] and [ velmap ] show that the observed velocity gradient in the hot molecular gas is along the minor axis of the source emission for all species .
this is also consistent with the results of @xcite . for a core with significant rotation
, the velocity gradient is expected to be along the major axis of the source .
this argues strongly against the velocity gradients arising due to the gravitationally bound rotation of a circumstellar slab or disk as was proposed by @xcite .
several authors have interpreted the observed velocity distribution of the uc h iiregion g34.26 + 0.2c in terms of mainly two models : the moving star bow shock model and the champagne outflow model .
however , @xcite point out that none of these models satisfactorily explain the observed velocities in the region .
these authors proposed a model in which the velocities in the region are governed by the stellar winds from the components a and b. further , the ionized gas which is photoevaporated directly from the hot , dense uc molecular core by the exciting star of the cometary h ii region g34.26 + 0.2c , flows from the molecular core toward a region of lower density to the west . in this model , it is further proposed that the molecular core and the components a and b are at a slightly larger distance from the earth than g34.3 + 0.2c .
the velocity pattern derived from the various species observed here is consistent with the wind and photoevaporation " model proposed by @xcite , and this further strengthens the conclusions of @xcite , which were derived based only on the velocity patterns of .
hot cores are typically proposed to be precursors of high mass stars ( e.g. * ? ? ?
the center of the hot core is identified with a collapsing , and rapidly accreting high mass protostar .
high angular resolution mid - infrared ( mir ) observations have successfully detected the energizing sources for several hot cores like g11.94 - 0.62 , g45.07 + 0.13 , g29.96 - 0.2 etc .
@xcite . using sub - arcsecond resolution centimeter and millimetre molecular line and continuum observations the existence of multiple deeply embedded uc and hypercompact h iiregions contributing to the formation of the hmcs g10.47 + 0.03 and g31.41 + 0.31 have been substantiated @xcite .
most of the hmcs thus represent a stage in the evolutionary sequence of massive protostars .
however , in the case of the hot molecular gas in g34.26 + 0.15 the existing continuum observations in mid - infrared , far - infrared , sub - millimeter and millimeter have consistently shown the peak of the dust emission to be coincident with the uc h ii region component c and not at the position of the hot core @xcite . in particular , using mir observations with 12 resolution @xcite have reported non - detection of any mir source associated with the hmc in g34.26 + 0.15 .
thus g34.26 + 0.15 similar to the orion compact ridge and w3(oh ) @xcite represents the alternative scenario for hot cores , which are externally heated and viewed upon as manifestation of gas shocked and heated by the expanding ionization front and the stellar winds arising from the h ii regions .
medium angular resolution mir and fir observations further suggest that the hmc is isolated from the component c of the h ii region and is heated by stellar photons from a and b components and not shocks @xcite . @xcite compared the and c@xmath39o peaks with the peaks seen in arcsecond resolution observations by @xcite and found that none of the peaks coincide with either component c of the h ii region or with each other .
these suggest that the hot molecular gas detected in g34.26 + 0.15 traces a layer of a core that is being externally heated by shocks and stellar photons
. however , non detection of sio emission from the position of the hot core rules out any significant role played by shocks in determining the hot core chemistry @xcite . the arcsecond resolution continuum and molecular line observations presented in this paper
provide further evidence to this proposed model of the hot core in g34.26 + 0.15 being externally heated .
the continuum map at 2.8 mm shows a single peak coincident with the radio continuum peak , and it is offset from the peaks of all molecular lines .
the molecular line maps extending over a region of 9@xmath2612 ( @xmath40 ) show that ( i ) the emission from different species are not centrally peaked , ( ii ) the molecular peaks are not co - spatial , ( iii ) none of the molecular line emission peaks at the continuum peak and ( iv ) none of the molecular line peaks coincide with the h@xmath1o and oh masers , tracing locations of shocks due to the propagation of the ionization front from the uc h iiregions , detected in the region @xcite .
the relative offsets between the peaks in the different molecular line emission further brings out the possibility of there being multiple hmcs within the beam .
we note that the ne and the se peaks detected in the g34.26 + 0.15 region are separated along the north - south direction by 08 , which at a distance of 3.7 kpc translates to 0.014 pc . for comparison , the hot core and the compact ridge regions in the orion - kl cloud at a distance of 450 pc
are separated by 0.018 pc .
we consider the angular resolution of the present observations to be insufficient to either clearly resolve or rule out the possibility of the two peaks being two different cores .
these results differ substantially from the single - dish observations which have so far suggested that the emission from the different molecular species originate from within a single bound core .
the observations of g34.26 + 0.15 presented here , with the highest angular resolution to date , suggest multiple externally heated hmcs , a hypothesis which is a matter of further study . in the absence of observations of multiple transitions of molecular species at 1resolution
, it is not possible to derive the density and temperature distributions appropriate to decipher factors contributing to the relative offsets of the different emission peaks .
availability of such temperature and density profiles is also crucial for deriving accurate estimates for the abundance profiles for the detected complex molecular species .
existing and recent high angular resolution observations of the hmc associated with g34.26 + 0.15 strongly favour that the source is externally heated .
however there are no observations available that constrain ( i ) the geometry of the hot core material with respect to the external heating source ; ( ii ) the density structure of the core material , _
e.g. _ whether it shows a simple gradient in a particular direction or it is clumpy or it is a uniform density swept up region ; or ( iii ) the geometry and multiplicity of the core along the line of sight .
we propose the present dataset as a building block for future observations which would help clarify some of the outstanding issues . the rather unconventional " and complicated geometry of the hmc associated with g34.26 + 0.15 poses further challenge to deriving a consistent chemical model for the source .
all existing chemical models for hmcs , including those constructed specifically for g34.26 + 0.15 ( e.g. * ? ? ?
* ; * ? ? ?
* ) explicitly consider a centrally energized spherical cloud forming a massive protostar in two stages involving collapse to high densities ( @xmath41 ) followed by a warm - up phase resulting in the rich chemistry of the hot cores .
the models for the hmc in g34.26 + 0.15 are primarily based on single dish observations and assume that the source consists of a hot ultracompact core ( ucc ) with a radius less than 0.025 pc and @xmath42 , a compact core ( cc ) with a radius of about 0.1 pc and a density of 10@xmath8 , surrounded by a massive halo extending out to 3.5 pc with a h@xmath1 density that falls off as r@xmath43 ( e.g. * ? ? ? * and the references therein ) .
the latest chemical model for g34.26 + 0.15 by @xcite is more sophisticated in terms of using the density and temperature profiles derived from the dust continuum observations .
these density and temperature profiles are subsequently used as inputs for the chemical model .
however , the density and temperature distributions are primarily constrained by single - dish continuum observations and the model considers a centrally peaked spherically symmetric structure that is isothermal up to a radius of 0.05 pc ( @xmath44 ) .
further it assumes the core of the region to be collapsing to form a massive protostar .
most of these assumptions do not conform to the results of high angular resolution molecular line observations presented in this paper and also by @xcite and @xcite .
similar arguments may be invoked to show the inappropriateness of the radiative transfer models developed by @xcite for the hmc in g34.26 + 0.15 .
in the absence of high resolution multi - line spectroscopic observations suitable to derive the temperature and density distributions , we have adopted a simplistic approach to derive an estimate of the kinetic temperature from the observed brightness temperatures . using the brightness temperatures of oc@xmath17s 98 ( 50 k ) and ocs 98 ( 96 k ) at the position of the intensity peak of oc@xmath17cs ( table [ basic_results ] ) , and the relative abundance of the isotopomers @xmath45/@xmath46 @xmath47 @xcite we derive @xmath48 and @xmath49 . hence ocs
98 is optically thick and its peak brightness temperature ( 167 k ) is a reasonably good estimate of the gas kinetic temperature .
we further note that the peak brightness temperature of 3@xmath504@xmath51 a@xmath11 , the brightest and the most optically thick of the methanol lines observed here is 187 k : the peak brightness temperatures of so and are 147 k and 143 k , respectively . thus beyond the calculated high opacity values of ocs 98 , the rather high peak brightness temperatures of 3@xmath504@xmath51 a@xmath11 , so and suggest that all these lines are optically thick and their peak brightness temperatures provide a firm lower limit to the true kinetic temperature of the ucc of g34.26 + 0.15 . based on these , we estimate the kinetic temperature to be 160@xmath52 k and use 160 k for the subsequent analysis
. most of the available estimates of kinetic temperature of the hot core region g34.26 + 0.15 are rotation temperatures derived using a variety of molecules . based on an lvg analysis of ch@xmath29cn
@xcite derived a gas temperature between 80175 k , while using the k - ladder of the same molecule @xcite estimated a kinetic temperature of @xmath53 k. @xcite derived a rotation temperature of 125 k from c@xmath1h@xmath54oh observations , while @xcite derived a rotation temperature of @xmath55 k from ammonia observations .
the errorbars in the kinetic temperatures available from literature are rather large and they are all consistent with our derived value of 160@xmath52 k. the higher angular resolution of our observations better probe the small clumps in contrast to the other observations .
we note that the molecules of which rotational transitions were used to derive the kinetic temperatures have similar dipole moments
. however , comparison with temperatures derived from single dish observations with the present results is uncertain due to multiple issues : beam dilution , contamination from large scale emission , etc .
we have derived the column densities of the different observed species assuming local thermal equilibrium ( lte ) , the kinetic temperature to be 160 k , and the observed transitions ( with the exception of ocs 98 ) to be optically thin .
the assumption of a single temperature instead of a temperature profile leads to inaccuracies in our estimates of abundances .
however , given the non - centrally peaked geometry of the hot molecular gas as detected in our observations and the lack of dust continuum data , as well as observations of multiple spectral lines constraining the density and temperature profiles , resolving these uncertainties is beyond the scope of this paper .
we propose the use of these abundances in combination with upcoming high angular resolution complementary observations in order to provide constraints for future chemical models .
based on the peak brightness temperatures presented in table [ basic_results ] we conclude that in all likelihood , so , and @xmath56@xmath57 transitions are also optically thick . in the absence of observations of rarer species , we use the estimated column densities as lower limits and/or guidelines . for both and
we adopt the largest among the column densities derived from the different observed transitions .
the @xmath30@xmath31 a@xmath58 transition gives the highest column density and it has a peak brightness temperature of 82 k , which suggests that it is still optically thin .
the column density of ocs 98 is derived by using the oc@xmath17s column densities and assuming the relative galactic abundance of @xmath45/@xmath46 @xmath47 .
table [ colden ] presents the observed column densities and abundances of the different species at the positions of the north - eastern ( ne ) and south - eastern ( se ) peaks , abundances of nh@xmath29 @xcite , @xcite , along with abundances of different species in other prototypical " hot cores .
the present dataset does not provide an independent estimate of the total molecular hydrogen column density , , in the ultracompact core ( ucc ; * ? ? ?
* ) of g34.26 + 0.15 .
estimates of in the core , mostly based on a number of single - dish and interferometric observations of different chemical species , vary by almost an order of magnitude . using the peak nh@xmath29 abundance of 2@xmath2610@xmath59 @xcite and the observed nh@xmath29 column density of 7@xmath2610@xmath39 @xcite , @xcite estimated to be 4@xmath60 .
in contrast based on nh@xmath29 @xcite and ch@xmath29cn @xcite observations , the is estimated to be 3@xmath61 .
the lower h@xmath1 column densities deduced by @xcite are however consistent with the non - detection of c@xmath39o at the center of the core . following @xcite here
we adopt the of the ucc within g34.26 + 0.15 to be 4@xmath2610@xmath62 in order to calculate the observed abundances of the observed chemical species relative to molecular hydrogen ( table [ colden ] ) .
the and observations that have angular resolution comparable to our observations justify the adopted value of .
the derived column densities of the complex molecules like , , and agree reasonably well with the previous observations ( at 13@xmath268resolution ) by @xcite .
following table [ colden ] we find that at the two rather clearly segregated peak positions within the inner regions of the hmc in g34.26 + 0.15 , the abundances of , , , , and so@xmath1 differ by factors @xmath63 .
we have detected several of the n- , o- and s - bearing parent and daughter molecules in the g34.26 + 0.15 hot core region . here
we discuss the relative abundances of the different species in the light of the abundances observed in a few well - known hot core regions ( table [ colden ] ) .
we also compare the abundances relative to a few well - known chemical models for hot cores , these include : chemical models for g34.26 + 0.15 by @xcite and @xcite , both at @xmath64 = 10@xmath65 yr after the grain mantle evaporation ; and the model for the orion compact ridge at @xmath64 = 3.3@xmath66 yr by @xcite .
the model by @xcite though not fine - tuned for g34.26 + 0.15 , is relevant because previous chemical study by @xcite suggested that the observed abundances can be explained reasonably well by this model at @xmath67 yr .
the chemical model for g34.26 + 0.15 presented by @xcite is essentially an improvement of the model by @xcite in terms of using latest collision rates and chemistry .
however for the model by @xcite column densities are available only for the entire source , rather than explicitly for the ucc or the inner regions of the hmc in g34.26 + 0.15 . since , the enhanced angular resolutions of the present bima observations enables us to probe the inner regions of the hmc directly , the column density calculations for the ucc by @xcite are still relevant for our work .
further we note the column densities of the entire source ( core+halo ) as estimated by these two models agree reasonably well .
figure [ modelcomp ] compares the abundances of the different species relative to the molecular hydrogen abundance as observed at the ne peak of g34.26 + 0.15 with abundances predicted by the different chemical models . in the following sections we discuss the abundances of the o- , n- and s - bearing molecular species separately and compare them with abundances seen in other hot cores .
we have detected , and .
figure [ modelcomp ] shows that there is a huge discrepancy between the abundances of as predicted by @xcite and @xcite , with the latter model reproducing the observed abundances in g34.26 + 0.15 exactly .
all the chemical models predict the relative abundance / to be between 10@xmath68 and 10@xmath43 and do not reproduce the high abundance ratio of 0.1 as observed in most hot cores ( table [ colden ] ) . on the other hand a relative abundance of / @xmath69
is predicted by all the models , which is more or less consistent with the observed range of values in the other hot cores .
most of the chemical models for hot cores , including those considered in this paper rely solely on gas - phase chemistry to account for the formation of the large o - bearing complex molecules .
however , @xcite have shown that the gas - phase processes are highly inefficient in producing and can never reproduce the observed abundances .
recently @xcite has proposed a slower warm - up phase of the hot core and a combination of grain - surface and gas - phase chemistry in the hot cores , which better reproduce the observed abundances of .
table [ colden ] suggests that the abundances of the n - bearing species , , , , , and in g34.26 + 0.15 lie within the range of values seen in other hot cores .
discovery of ice has lead to the conclusion that is indeed a parent species evaporated from the grain mantle .
presence or absence of in the grain mantle plays an important role in determining the abundances of the different daughter species @xcite .
figure [ modelcomp ] suggests that while @xcite reproduces the abundance seen in g34.26 + 0.15 ; both @xcite and @xcite fall short by a factor of @xmath21 or more , with the latter model being much worse . ,
a symmetric top molecule , is likely to form via radiative association of ch@xmath70 with hcn or cn with ch@xmath29 @xcite .
the chemical models for the ucc of g34.26 + 0.15 @xcite and the orion compact ridge @xcite predict abundances 3050 times lower than the observed value in g34.26 , while the core+halo model of @xcite predicts an even lower abundance ( fig . [ modelcomp ] ) .
the high abundances of nitrile molecules like as found in many hot cores can not be reproduced by gas phase reactions alone .
hydrogenation of accreted and to produce that when evaporates , is proposed to be a more viable path for formation in hot cores @xcite .
the chemical model for orion compact ridge by @xcite predicts an abundance that is 10 times lower than observed in g34.26 .
no predictions for the abundance of are available from the other two chemical models in consideration here .
is thought of as a cold - cloud tracer but should also be formed efficiently in the hot gas if c@xmath1h@xmath1 is evaporated from grain mantles @xcite .
figure [ modelcomp ] shows that all the chemical models predict an abundance larger by more than a factor of 100 than the value observed in g34.26 .
this is consistent with our estimate that is optically thick ( sec .
[ kintemp ] ) in g34.26 + 0.15 .
is most likely formed by atom addition to hco on grain mantles and then evaporate @xcite .
@xcite found to be formed upon uv photolysis and warm - up of h@xmath1o::co:= 100:50:10:110 mixture .
however , most of the chemical models so far do not consider either or as parent species and there are no predictions of abundances available so far . based on single - dish observations of g34.26 + 0.15 and subsequent chemical modeling
, @xcite inferred that the ocs emission , which requires rather high excitation energy , can not be produced in the extended halo ; the rotation temperature derived from so@xmath1 warrants a core origin ; and the so lines are more likely to arise from the halo .
we estimate both ocs and so to be optically thick and to have peak brightness temperatures characteristic of the inner regions .
table [ colden ] shows that abundance of ocs as observed in g34.26 + 0.15 is larger than those observed in many hot cores .
the abundance of so in g34.26 + 0.15 is similar to that in orion , while sgr b2(n ) and g327.60.3 show much lower abundances .
note that the so abundance derived here is likely a lower limit due to the optically thick so line .
the so@xmath1 abundance in g34.26 + 0.15 , is similar to the abundance seen in sgr b2(n ) and both are lower by a factor of 10 than the values seen in orion and g327.30.6 .
it was initially pointed out by @xcite and @xcite that the relative abundance ratios of so , so@xmath1 and h@xmath1s could be used to estimate the age of the hot cores of the massive protostars .
however , @xcite has re - considered this issue and conclude that none of these ratios can be used by itself to estimate the age , since the ratios depend at least as strongly on the physical conditions and on the adopted grain mantle composition as on time .
figure [ modelcomp ] shows that all the chemical models under consideration here predict very similar ocs abundances , although somewhat less than that observed in g34.26 + 0.15 .
the model by @xcite reproduces the observed so abundance in g34.26 + 0.15 reasonably well , while the other two models predict abundances lower by factors of 510 .
since we estimate so in g34.26 + 0.15 to be optically thick , it is hard to reconcile to the higher abundance derived observationally .
the model by @xcite reproduces the observed abundances of so@xmath1 for g34.26 + 0.15 , while the models by @xcite and @xcite respectively overestimates and underestimates the observed values .
none of the chemical models considered here reproduce the abundances of all the observed species satisfactorily .
these models like all the other chemical and radiative transfer models for hmcs assume the energizing source to be at the center , with centrally peaked temperature and density profiles .
in addition , there are reasonable arguments in favor , as well as , against the complex molecule formation mechanisms ( grain - mantle evaporation , grain - surface chemistry , gas - phase chemistry ) .
thus , from the physical point of view all these models are not directly applicable to g34.26 + 0.15 , which as our observations show is externally heated and additionally might be harboring multiple unresolved hmcs .
there are two main uncertainties in our estimates of the column densities of the different species : _
( i ) _ we have assumed a single kinetic temperature , rather than a temperature profile , the value of which may also be off by 50 k for some of the species and _ ( ii ) _ the estimate is also not accurate .
both of these uncertainties can only be addressed with complementary observations at comparable angular resolutions .
the errorbars drawn at the 50% level in fig .
[ modelcomp ] attempt to quantify these uncertainties in addition to the statistical errors and the errors in absolute calibration .
since the difference in abundances between the ne and se peaks of g34.26 + 0.15 never exceeds a factor of 3 and the discrepancy between the observed and predicted abundances are of the order of factors of 10 or more , our conclusions would not have been significantly different had we compared the observed abundances at the se peak with the model predictions .
further , we have shown that the abundances observed in g34.26 + 0.15 are not atypical compared to other galactic hot cores .
thus , discrepancies by factors of 10 to 100 between the abundances observed in g34.26 + 0.15 and the predictions of the chemical models can not be explained by the estimated errors in abundance calculations .
given the inappropriateness of the existing chemical models and uncertainties in the derived relative abundances we consider any age / timescale related discussion for the hmc in g34.26 + 0.15 beyond the scope of this paper .
despite the present consensus on the contemporaneous existence of and bearing grain mantles , chemical differentiation in hot core regions is also well - established from observations .
such chemical differentiation was prominently noticed in the two clumps in the orion - kl cloud core , very close to the luminous and massive young stellar object , irc2 : the hot core and the compact ridge . while the warmer and
denser hot core shows unusually high abundances of h - rich complex n - bearing molecules like ch@xmath1chcn and , the compact ridge is characterized by high abundances of large oxygen - bearing molecules like , and . however , later observations of the orion - kl hot cores by @xcite suggest that the chemical differentiation is probably not as drastic as it was first thought to be . similar chemical differentiation is observed between the two hot cores w3(h@xmath1o ) and w3(oh ) in the w3 region @xcite .
these sources are spatially offset by about 0.06 pc and yet they exhibit clear signs of n / o differentiation .
both sources show emission from , h@xmath1co , , and , but only the maser source shows significant emission from , , and so2 @xcite , as well as from hcn @xcite and @xcite .
several chemical models have partially explained the chemistry of both the hot core & the compact ridge @xcite in orion . @xcite
have shown that the evaporation of rich grain mantles inhibit high abundances of o - bearing large molecules , though the already injected alcohols remain abundant for much longer .
this leads to the formation of n - rich hot cores .
@xcite further showed that in collapsing cores both n - rich and o - rich species tend to co - exist .
however , it might be possible to derive the age of the cores based on the relative abundance of the two types of species because is found to be more abundant at earlier times whereas hcn and form later on @xcite .
observational detection of large number of daughter species in hot cores suggest that the chemical timescale needs to be shorter than the dynamical timescale , _
i.e. , _ the cores need to be gravitationally supported up to 10@xmath65 yrs @xcite . within the inner regions of g34.26 + 0.15
we find that the n - bearing species tend to peak to the south - east , while the peaks of the o - bearing species are concentrated to the north - east of the continuum peak .
the ne and the se peaks are primarily separated along the north - south direction by 08 , which at a distance of 3.7 kpc translates to 0.014 pc . for comparison , the hot core and the compact ridge regions in the orion - kl cloud at a distance of 450 pc are separated by 0.018 pc .
thus , given the larger distance to the source and the angular resolution of the present observations , the possibility of the two emission peaks actually belonging to two different cores , one being n - rich and the other being o - rich , can not be ruled out .
although the two peak positions in g34.26 do not show large difference in abundances , differences in the abundances of , , and show contrasts quite similar to what is seen in orion - kl @xcite .
additional high angular resolution observations of molecular lines are required to derive a better estimate of the temperature distribution , in order to improve the derived abundances at the two peak positions seen within the inner regions of the hmc in g34.26 + 0.15 .
we have presented high angular resolution mapping observations of the hmc in g34.26 + 0.15 tracing different chemical species characteristic of hot cores .
the higher angular resolution enables us to probe the inner regions of the hot molecular gas .
the observations presented here is only a first step and needs to be augmented by observations of standard temperature and density sensitive molecular transitions to constrain the physical attributes of the region which can then be used as constraints for future chemical models .
we do not detect any evidence for an energizing source at the center of the hot core , the continuum peak at 2.8 mm is consistent with the free - free radio continuum emission from component c of the uc h iiregion .
the intensity distribution of the various molecular tracers do not peak at the same position , the peaks of none of the distributions is located either at the position of the continuum peak or the positions of the h@xmath1o and oh masers .
the temperature and density distributions of the inner regions of the hot cores can not be determined from the present observations .
based on intensity and velocity distribution , only component c , the most evolved of the h iiregions associated with g34.26 + 0.15 appears to influence the energetics of the hot molecular gas .
the kinematics of the hot core as derived from the velocity distribution of the molecular tracers is not strongly influenced by the h ii region dynamics . within the inner regions of the hot core in g34.26
+ 0.15 we find that the nitrogen and oxygen - bearing species tend to show a dichotomy and peak at different positions , separated by 08 , the spatial separation being similar to the two hot / warm cores identified in the orion .
we propose that as in orion and in w3(oh ) , ( i ) these peak positions may indeed be separate regions of chemical enrichment , resolution of which would require even higher angular resolution observation and ( ii ) may arise due to the external influence of the neighboring h ii regions .
we have estimated the abundances of the observed molecular species at the two peak positions assuming a single kinetic temperature of 160 k under conditions of lte .
the high angular resolution observations presented here , provides overwhelming evidence in favour of the hot molecular gas at spatial scales of 0.018 pc being externally heated .
this together with the clumpiness of the region and possible existence of multiple hmcs in the region , implies geometries more complicated than those considered by the state - of - art chemical models . for the sake of completeness
, we follow @xcite to derive a crude upper limit for the luminosity of the internal energizing source if any , using the kinetic temperature derived in this paper and stefan - boltzmann law .
the luminosity of the hypothetical and so far undetected internal source is estimated to be 8.9@xmath2610@xmath65 @xmath71 and this corresponds to a o7.5 zams star @xcite .
comparison of the abundances observed in g34.26 + 0.15 with currently available somewhat inappropriate chemical models for hot cores by @xcite , @xcite , and @xcite suggest that the nitrogen richness of the region can only be explained by the evaporation of ammonia - rich ice - mantles .
however , this implies that the abundances of the oxygenated daughter species be suppressed in the presence of ammonia , which is not the case in g34.26 + 0.15 .
this can mean any of the following ( i ) the oxygenated species in question are also formed on grain mantles , ( ii ) the two regions are actually separate from each other or ( iii ) there may be additional gas - phase processes which can progress efficiently even in the presence of ammonia to create high abundances of oxygenated daughter species , which the chemical models do not yet consider
. comparison of abundances observed in a few hot cores ( in addition to g34.26 + 0.15 ) and the chemical models show that the chemical models do not yet consistently explain the abundances of all species in any of the hot cores
. the complicated geometry of g34.26 + 0.15 makes direct comparison of the observed abundances with the chemical models even more difficult .
one of the major caveats of the estimates of the abundances presented here in the hot molecular gas is the assumption of a single kinetic temperature characterizing the emission of the different species .
this is a consequence of the lack of complementary observations of molecular species at high angular resolutions to study the temperature and physical structure of the hot molecular gas . in order to understand the true nature of the different peak positions in g34.26 + 0.15
as identified in the bima data and to provide proper physical constraints for the chemical models for the region , sub - arcsecond resolution observations are necessary .
this material is based upon work supported by the national science foundation under grant no .
this research has made use of nasa s astrophysics data system .
lwl acknowledges support from the laboratory for astronomical imaging at the university of illinois and nsf under grant ast-0228953 .
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+ so & @xmath98@xmath99 & 109.2522200 & 21.05 & 1.510 + lccccccc line & beam & @xmath100 & @xmath101 & @xmath19 & @xmath20 & rms + & ( arcsec ) & ( jy beam@xmath34 ) & ( k ) & ( ) & ( ) & ( mjy beam@xmath34 ) + h53@xmath2 & 148@xmath26125 & 0.454 & 42 & @xmath102 & @xmath103 & 66.3 + @xmath75 @xmath30@xmath31 a@xmath76 & 148@xmath26125 & 0.934 & 82 & @xmath104 & @xmath105 & 69.1 + @xmath75 @xmath30@xmath31 a@xmath11 & 148@xmath26125 & 0.952 & 83 & @xmath106 & @xmath107 & 69.6 + @xmath78 @xmath79@xmath80 e & 102@xmath26085 & 0.240 & 31 & @xmath108 & @xmath109 & 35.6 + @xmath81 @xmath82@xmath83 & 102@xmath26085 & 0.218 & 26 & 49.3 & & 55.1 + @xmath84 @xmath85@xmath86 & 102@xmath26085 & 0.383 & 46 & @xmath110 & @xmath111 & 106 .
+ @xmath87 98 & 102@xmath26085 & 0.394 & 50 & @xmath112 & @xmath113 & 86.1 + @xmath75 @xmath56@xmath57 a@xmath11 & 102@xmath26085 & 1.48 & 187 & @xmath114 & @xmath115 & 44.9 + @xmath89 @xmath90@xmath91 & 102@xmath26085 & 0.365 & 46 & @xmath116 & @xmath117 & 45.3 + @xmath94 @xmath95@xmath96 & 102@xmath26085 & 0.198 & 25 & @xmath118 & @xmath119 & 45.3 + @xmath75 @xmath27@xmath77 e2 & 102@xmath26085 & 0.643 & 81 & @xmath120 & @xmath121 & 94.9 + @xmath88 9 - 8 & 099@xmath26089 & 0.165 & 20 & 55.6 & & 67.5 + @xmath97 1211 & 099@xmath26089 & 1.23 & 143 & @xmath122 & @xmath123 & 64.3 + so @xmath98@xmath99 & 099@xmath26089 & 1.27 & 147 & @xmath124 & @xmath125 & 123.1 + ocs 98 & 099@xmath26089 & 1.44 & 167 & @xmath114 & @xmath126 & 127.0 + @xmath89 @xmath92@xmath93 & 099@xmath26089 & 0.360 & 42 & @xmath127 & @xmath128 & 65.2 + lllllllll & 3.4(17 ) & 8.5(-7 ) & 2.6(17 ) & 6.4(-7 ) & 1.4(-7 ) & 4.0(-7 ) & 2.0(-7 ) & 2.0(-5 ) + & 2.9(16 ) & 7.3(-8 ) & 2.7(16 ) & 6.8(-8 ) & 1.4(-8 ) & 3.0(-8 ) & 1.0(-9 ) & 2.0(-6 ) + & 5.7(16 ) & 1.4(-7 ) & 3.4(16 ) & 8.5(-8 ) & 8.0(-9 ) & 1.9(-8 ) & 3.0(-9 ) & 3.4(-7 ) + & 7.0(18 ) & 1.8(-5 ) & & & 6.7(-8 ) & 5.7(-7 ) & & + & 1.3(16 ) & 3.3(-8 ) & & & 4.0(-9 ) & 5.0(-9 ) & 3.0(-8 ) & 7.0(-7 ) + & 1.3(15 ) & 3.2(-9 ) & 2.7(15 ) & 6.8(-9 ) & 3.0(-9 ) & 5.0(-9 ) & 6.0(-10 ) & 4.0(-7 ) + & 5.1(13 ) & 1.3(-10 ) & 1.3(14 ) & 3.3(-10 ) & 1.8(-9 ) & 6.0(-9 ) & 5.0(-9 ) & 3.0(-11 ) + nh@xmath1cho & & & 2.5(15 ) & 6.2(-9 ) & 1.4(-10 ) & 3.0(-10 ) & 2.0(-10 ) & 2.0(-8 ) + so@xmath1 & 5.8(15 ) & 1.4(-8 ) & 1.5(16 ) & 3.7(-8 ) & 1.2(-7 ) & 1.6(-7 ) & 3.0(-8 ) & 2.0(-7 ) + oc@xmath17s & 1.8(15 ) & 4.4(-9 ) & 2.2(15 ) & 5.6(-9 ) & & & 3.0(-10 ) & 1.0(-9 ) + o@xmath18cs & 2.0(15 ) & 5.1(-9 ) & 1.4(15 ) & 3.5(-9 ) & & & 7.0(-10 ) & 7.0(-10 ) + ocs & 3.9(16 ) & 9.7(-8 ) & 4.9(16 ) & 1.2(-7 ) & 1.1(-8 ) & 3.0(-8 ) & @xmath1292.0(-9 ) & @xmath1292(-9 ) + so & 4.4(16 ) & 1.1(-7 ) & 5.3(16 ) & 1.3(-7 ) & 1.9(-7 ) & 3.0(-7 ) & 2.0(-8 ) & @xmath1293(-9 ) + mm continuum image the contour levels are -3 , 3 , 10 , 20 , 30 , 40 , 50 , 70 , 90 , 100 , 120 , 140 of the noise level of 20 mjy beam@xmath34 . for the @xmath130 cm continuum image
the contour levels are at -3 , 3 , 5 , 10 , 20 , 30 , 40 , 80 , 120 , 180 , 250 , 350 , 450 , 600 , 800 , 850 times the noise level of 0.3 mjy beam@xmath34 .
the synthesized beams are shown on the right - hand corner of the plot .
the synthesized beam at @xmath3 mm is 100@xmath26085 with p.a .
= 35 and the beam at @xmath130 cm is 048@xmath26041 with p.a.=21 .
[ cont_cont],width=283 ] .
the noise levels ( in jy beam@xmath34 ) are : _ ( a ) _ 0.58 , _ ( b ) _ 0.40 , _
0.26 , _ ( d ) _ 0.45 , _ ( e ) _ 0.61 , _ ( f ) _ 0.58 , _ ( g )
_ 0.30 , _ ( h ) _ 0.48 , _
( i ) _ 30 , _ ( j ) _ 0.24 , _
( k ) _ 0.50 , _ ( l ) _ 0.35 , _ ( m ) _ 0.58 , _
( n ) _ 0.22 , _ ( o ) _ 0.46 and _ ( p ) _ 0.32 . the contour levels in panels _ ( a ) , ( f ) , ( g ) , ( h ) , ( i ) , ( j ) , ( m ) , ( n ) _ and _ ( o ) _ are in steps of the noise level , starting from twice the noise level .
the contour levels in the remaining panels are in steps of twice the noise level , starting from twice the noise level .
the negative contours are not shown to simplify the image .
the synthesized beams are shown on the left hand corner of each panel .
the filled @xmath131 mark the positions the components a , b , and c @xcite of the uc h ii region g34.3 + 0.2 .
the squares and diamonds signify positions of h@xmath1o and oh masers respectively @xcite .
[ allmap],width=566 ] mm .
the symbols with additional circles around them denote that these correspond to single - peaked intensity distributions .
the errorbars on the left hand bottom corner show the positional uncertainty .
[ peaks],width=377 ] .
the errorbars correspond to 50% errors in abundance estimates .
@xcite corresponds to the chemical model for the orion compact ridge at @xmath132 yr .
@xcite corresponds to the chemical model for the ultracompact core , for which = 2.7@xmath133 at @xmath67 yr .
@xcite corresponds to a chemical model for the entire source g34.26 + 0.15 , for a line of sight through the center of the core at @xmath67 yr , with = 3.6 10@xmath134 .
[ modelcomp],width=377 ] | we present high angular resolution ( @xmath0 ) multi - tracer spectral line observations toward the hot core associated with g34.26 + 0.15 between 87109 ghz .
we have mapped emission from ( i ) complex nitrogen- and oxygen - rich molecules like , , , , , ; ( ii ) sulfur - bearing molecules like ocs , so and so@xmath1 ; and ( iii ) the recombination line h53@xmath2 .
the high angular resolution enables us to directly probe the hot molecular core associated with g34.26 + 0.15 at spatial scales of 0.018 pc . at this resolution
we find no evidence for the hot core being internally heated .
the continuum peak detected at @xmath3 mm is consistent with the free - free emission from component c of the ultracompact h ii region .
velocity structure and morphology outlined by the different tracers suggest that the hot core is primarily energized by component c. emission from the n- and o - bearing molecules peak at different positions within the innermost regions of the core ; none are coincident with the continuum peak .
lack of high resolution complementary datasets makes it difficult to understand whether the different peaks correspond to separate hot cores , which are not resolved by the present data , or manifestations of the temperature and density structure within a single core .
based on the brightness temperatures of optically thick lines in our sample , we estimate the kinetic temperature of the inner regions of the hmc to be @xmath4 k. comparison of the observed abundances of the different species in g34.26 + 0.15 with existing models does not produce a consistent picture .
there are uncertainties due to : ( i ) the unavailability of temperature and density distribution of the mapped region within the hot core , ( ii ) typical assumption of centrally peaked temperature distribution for a hot core with an accreting protostar at the center , by the chemical models , an aspect not applicable to externally heated hot cores like g34.26 + 0.15 and ( iii ) inadequate knowledge about the formation mechanism of many of the complex molecules . |
SECTION 1. SHORT TITLE.
This Act may be cited as the ``Kids in Disasters Well-being,
Safety, and Health Act of 2007''.
SEC. 2. DEFINITION.
In this Act, the terms ``child'' and ``children'' mean an
individual or individuals, respectively, who have not attained 18 years
of age.
SEC. 3. ESTABLISHMENT OF COMMISSION.
There is established a commission to be known as the ``National
Commission on Children and Disasters'' (referred to in this Act as the
``Commission'').
SEC. 4. PURPOSES OF COMMISSION.
The purposes of the Commission are to--
(1) conduct a comprehensive study to examine and assess the
needs of children as they relate to preparation for, response
to, and recovery from all hazards, including major disasters
and emergencies;
(2) build upon the investigations of other entities and
avoid unnecessary duplication, by reviewing the findings,
conclusions, and recommendations of other commissions, Federal,
State, and local governments, or nongovernmental entities,
relating to the needs of children as they relate to preparation
for, response to, and recovery from all hazards, including
major disasters and emergencies; and
(3) submit a report to the President and Congress on
specific findings, conclusions, and recommendations to address
the needs of children as they relate to preparation for,
response to, and recovery from all hazards, including major
disasters and emergencies.
SEC. 5. COMPOSITION OF COMMISSION.
(a) Members.--The Commission shall be composed of 10 members, of
whom--
(1) 1 member shall be appointed by the President;
(2) 1 member, who is of a different political party than
that of the member appointed under paragraph (1), shall be
appointed by the President;
(3) 2 members shall be appointed by the majority leader of
the Senate;
(4) 2 members shall be appointed by the minority leader of
the Senate;
(5) 2 members shall be appointed by the Speaker of the
House of Representatives; and
(6) 2 members shall be appointed by the minority leader of
the House of Representatives.
(b) Chairperson and Vice-Chairperson Selection.--The Chairperson
and Vice Chairperson shall be elected from among members of the
Commission.
(c) Governmental Appointees.--An individual appointed to the
Commission may not be an official or employee of the Federal
Government.
(d) Commission Representation.--The Commission shall include--
(1) representatives from private nonprofit entities with
demonstrated expertise in addressing the needs of children as
they relate to preparation for, response to, and recovery from
all hazards, including major disasters and emergencies; and
(2) State emergency managers and local emergency managers.
(e) Qualifications.--Members appointed under subsection (a) shall
include--
(1) individuals involved with providing services to
children, including health, education, housing, and other
social services, including grant and entitlement programs;
(2) individuals with experience in emergency management,
including coordination of resources and services among State
and local governments, the Federal Government, and
nongovernmental entities;
(3) individuals with philanthropic experience focused on
the needs of children;
(4) individuals with experience in providing donated goods
and services, including personnel services, to meet the needs
of children and families as they relate to preparation for,
response to, and recovery from all hazards, including major
disasters and emergencies; and
(5) individuals who have conducted academic research into
related issues.
(f) Appointments.--All members of the Commission shall be appointed
not later than 90 days after the date of enactment of this Act.
(g) Initial Meeting.--The Commission shall meet and begin the
operations of the Commission not later than 120 days after the date of
enactment of this Act.
(h) Quorum and Vacancy.--
(1) Quorum.--A majority of the members of the Commission
shall constitute a quorum, but a lesser number of members may
hold hearings.
(2) Vacancy.--Any vacancy in the Commission shall not
affect its powers and shall be filled in the same manner in
which the original appointment was made.
SEC. 6. DUTIES OF COMMISSION.
The Commission shall--
(1) conduct a comprehensive study that examines and
assesses the needs of children as they relate to preparation
for, response to, and recovery from all hazards, including
major disasters and emergencies, including specific findings
relating to--
(A) children's physical and mental health;
(B) child care, including in private for-profit and
nonprofit settings;
(C) child welfare;
(D) elementary and secondary education;
(E) sheltering, temporary housing, and affordable
housing;
(F) transportation;
(G) entitlement and grant programs;
(H) juvenile justice;
(I) evacuation; and
(J) relevant activities in emergency management;
(2) identify, review, and evaluate existing law relevant to
the needs of children as they relate to preparation for,
response to, and recovery from all hazards, including major
disasters and emergencies;
(3) identify, review, and evaluate the lessons learned from
past disasters and emergencies relative to addressing the needs
of children; and
(4) submit a report to the President and Congress on the
Commission's specific findings, conclusions, and
recommendations to address the needs of children as they relate
to preparation for, response to, and recovery from all hazards,
including major disasters and emergencies, including specific
recommendations on the need for planning and establishing a
national resource center on children and disasters,
coordination of resources and services, administrative actions,
policies, regulations, financing, and legislative changes as
the Commission considers appropriate.
SEC. 7. POWERS OF COMMISSION.
(a) Hearings.--The Commission may hold such hearings, meet and act
at such times and places, and receive such evidence as may be necessary
to carry out the functions of the Commission.
(b) Information From Federal Agencies.--
(1) In general.--The Commission may secure directly from
any executive department, bureau, agency, board, commission,
office, independent establishment, or instrumentality of the
Federal Government such information, suggestions, estimates,
and statistics as the Commission considers necessary to carry
out this Act.
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the Commission to carry out its duties.
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assistance provided for under paragraph (1), departments and
agencies of the United States may provide to the Commission
such services as they may determine advisable and as authorized
by law.
(d) Contracting.--The Commission may enter into contracts to enable
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SEC. 8. STAFF OF COMMISSION.
(a) In General.--The Chairperson of the Commission, in consultation
with the Vice Chairperson, in accordance with rules agreed upon by the
Commission, may appoint and fix the compensation of a staff director
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States Code.
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instrumentality of the Federal Government may detail, without
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be without interruption or loss of civil service status or privilege.
(c) Consultant Services.--The Commission is authorized to procure
the services of experts and consultants in accordance with section 3109
of title 5, United States Code, but at rates not to exceed the daily
rate paid a person occupying a position at level IV of the Executive
Schedule under section 5315 of title 5, United States Code.
SEC. 9. TRAVEL EXPENSES.
Each member of the Commission shall serve without compensation, but
shall receive travel expenses, including per diem in lieu of
subsistence, in accordance with applicable provisions in the same
manner as persons employed intermittently in the Government service are
allowed expenses under section 5703 of title 5, United States Code.
SEC. 10. FEDERAL ADVISORY COMMITTEE ACT APPLICABILITY.
The provisions of the Federal Advisory Committee Act shall apply to
the Commission, including the staff of the Commission.
SEC. 11. REPORTS OF COMMISSION; TERMINATION.
(a) Interim Report.--Not later than December 31, 2008, the
Commission shall submit to the President and Congress an interim report
containing specific findings, conclusions, and recommendations required
under this Act as have been agreed to by a majority of Commission
members.
(b) Final Report.--Not later than 24 months after the date of the
enactment of this Act, the Commission shall submit to the President and
Congress a final report containing specific findings, conclusions, and
recommendations required under this Act as have been agreed to by a
majority of Commission members.
(c) Termination.--
(1) In general.--The Commission, and all the authorities of
this Act, shall terminate 180 days after the date on which the
final report is submitted under subsection (b).
(2) Records.--Not later than the date of termination of the
Commission under paragraph (1), all records and papers of the
Commission shall be delivered to the Archivist of the United
States for deposit in the National Archives.
SEC. 12. AUTHORIZATION OF APPROPRIATIONS.
There is authorized to be appropriated to carry out this Act,
$2,000,000 for each of fiscal years 2008 and 2009.
Passed the House of Representatives November 6, 2007.
Attest:
LORRAINE C. MILLER,
Clerk. | Kids in Disasters Well-being, Safety, and Health Act of 2007 - Establishes the National Commission on Children and Disasters, which shall: (1) conduct a comprehensive study that assesses childrens' needs as they relate to preparation for, response to, and recovery from all hazards, including major disasters and emergencies; (2) identify, review, and evaluate existing law relevant to such needs; (3) identify, review, and evaluate the lessons learned from past disasters relative to addressing such needs; and (4) report to the President and Congress on its findings and recommendations to address such needs, including regarding the need for a national resource center on children and disasters, coordination of resources and services, administrative actions, policies, regulations, financing, and legislative changes.
Sets forth provisions regarding the Commission's powers, staffing, reporting and record-keeping requirements, and termination. Authorizes appropriations. |
null | we studied the effects of weight loss and non - weight - bearing exercise ( swimming ) on blood and organ lead and essential metal concentrations in rats with prior lead exposure .
nine - week - old female sprague - dawley rats ( n = 37 ) received lead acetate in their drinking water for 2 weeks , followed by a 4-day latency period without lead exposure .
rats were then randomly assigned to one of six treatment groups : weight maintenance with ad libitum feeding , moderate weight loss with 20% food restriction , and substantial weight loss with 40% food restriction , either with or without swimming .
blood lead concentrations were measured weekly .
the rats were euthanized after a 4-week period of food restriction , and the brain , liver , kidneys , quadriceps muscle , lumbar spinal column bones , and femur were harvested for analysis for lead , calcium , copper , iron , magnesium , and zinc using atomic absorption spectrophotometry .
both swimming and nonswimming rats fed restricted diets had consistently higher blood lead concentrations than the ad libitum controls .
rats in the substantial weight loss group had higher organ lead concentrations than rats in the weight maintenance group .
rats in the moderate weight loss group had intermediate values .
there were no significant differences in blood and organ lead concentrations between the swimming and nonswimming groups .
organ iron concentrations increased with weight loss , but those of the other metals studied did not .
weight loss also increased hematocrits and decreased bone density of the nonswimming rats .
the response of lead stores to weight loss was similar to that of iron stores because both were conserved during food restriction in contrast to decreased stores of the other metals studied .
it is possible that weight loss , especially rapid weight loss , could result in lead toxicity in people with a history of prior excessive lead exposure.imagesfigure 1figure 2figure 3figure 4figure 5 |
Tim Tebowed and Denver rose as one.
The Broncos quarterback's 80-yard touchdown pass to receiver Demaryius Thomas on the first play of overtime against Pittsburgh both clinched Sunday's game and wrote another improbable chapter in Tebow's book of clutch plays to win high-pressure games.
His performance also borrowed a little magic from another famous book.
The devout Christian's stat line in Sunday's game mirrors the numbering of the Biblical passage that Tebow at times had painted on to his black eye paint during his career at the University of Florida -- John 3:16.
The passage reads, according to the New American Standard Bible, "For God so loved the world, that He gave His only begotten Son, that whoever believes in Him shall not perish, but have eternal life."
Officially, Tebow passed for 316 yards against the Steelers, completing 10 of 21 pass attempts -- meaning he passed for 31.6 yards per completion.
After his final pass was caught and brilliantly taken downfield by Thomas, Tebow shrugged off three bad weeks -- when he threw for just one touchdown and four interceptions -- and took a knee and prayed in his classic style.
"First and foremost, I just want to thank my savior, the Lord, Jesus Christ," Tebow said at the postgame press conference. "I am so thankful for the platform God has given me."
Next up for those on the Tebow bandwagon, a trip to New England to tackle Tom Brady and the Patriots in the AFC divisional playoff game on Saturday. ||||| Focused crawls are collections of frequently-updated webcrawl data from narrow (as opposed to broad or wide) web crawls, often focused on a single domain or subdomain.
You are using unsupported browser. Some features may not work correctly. Upgrade to a modern browser , such as Google Chrome
Trends has upgraded to a newer version, which is not supported by this device. | – This might just be a weird coincidence, or Tim Tebow's dramatic defeat of the Steelers last night may have been a miracle in more ways than one. The polarizing Denver quarterback wound up throwing for 316 yards, which, if you toss in a colon in the right spot, mirrors the call number of a famous bible verse, John 3:16. That's a verse Tebow occasionally wrote on his face while playing at the University of Florida, Fox News reports. Not weird enough for you? Well, Tebow threw those 316 yards over the course of 10 completions, meaning he averaged 31.6 yards per completion. Wait, there's more: John Ourand of the Sports Business Journal tweeted that the TV rating for the last 15 minutes of the game was—you guessed it—a 31.6. Was this some kind of divine product placement? Probably not, but if it was it worked: As of this writing, John 3:16 is No. 1 on Google Trends. |
Gwyneth Paltrow, the actress and founder of online lifestyle brand Goop, thinks that nasty, anonymous online commenters should take a look at themselves first before they post.
“The Internet is an amazing opportunity, socially. We have this opportunity to mature and learn, which is the essence of being on earth — to being the closest person we can be to our actual, real, truest self,” she said ahead of her surprise appearance at the Code Conference today. “But the Internet also allows us the opportunity to project outward our hatred, our jealousy. It’s culturally acceptable to be an anonymous commenter. It’s culturally acceptable to say, ‘I’m just going to take all of my internal pain and externalize it anonymously.'”
Of all the celebrities out there, Paltrow receives a particularly curious reception online, and she’s well aware of it. She is beloved and obsessed-over (the success of her Goop project comes largely from people wanting to live like her, have lunch in Paris or moisturize their bodies like she would).
At the same time, there seems to be some frustration and even aggression aroused by her lanky-blonde-perfect-frittata persona. Consider a recent headline: “Gwyneth Paltrow Joins Instagram, Will Probably Do This Better Than the Rest of Us, Too.”
In February, the newly hired editor of anonymous image-sharing site Whisper promoted one of his company’s user-submitted posts that included a picture of Paltrow’s face overlaid with text alleging that she was having an affair, an image that then went viral.
“It’s taken me a long time to get to the point where I can see these things and not take it as a personal affront and a hurt. I see myself as a chalkboard or a whiteboard or a screen, and someone is just putting up their own projection on it,” she said.
“It has nothing to do with me. They have an internal object, and they’re putting it on me. I kind of look at it as, ‘Wow this is an interesting social experiment.’ You’re talking about a blind stranger having feelings about you. It can only be projection.”
The conversation about celebrity and the Internet, she said, is part of a larger one about “containment and self-regulation” online.
“Our culture is trying to wrestle with the idea that everybody has a voice, and how it’s unimportant and really important at the same time,” said Paltrow. “We’re in this very adolescent phase. It’s dangerous, [because] we lack the capacity to say, ‘Why does this matter to me, and who am I in this?’ ‘Why am I having opinions about Angelina Jolie’s operation?’ ‘What is unhealed in me?’ ‘Why am I using the Internet to do this?'”
She compared the experience of living through vitriolic Internet commenters to surviving a war.
“You come across [online comments] about yourself and about your friends, and it’s a very dehumanizing thing. It’s almost like how, in war, you go through this bloody, dehumanizing thing, and then something is defined out of it,” she said. “My hope is, as we get out of it, we’ll reach the next level of conscience.”
This year may be a tipping point for Internet trolls, she hopes: “It’s almost like we’re being given this test: Can you regulate yourself? Can you grow from this? Can you learn? You can make it as bloody as you want to, but is that the point?”
And yet, for Paltrow, the Internet can also be a source of great good. Though the Goop team won’t disclose specific details, Paltrow said her e-commerce business is profitable, and that the “open rate” (meaning subscribers that actually open Goop emails) for the Goop newsletter, which reaches people in 120 different countries, is more than double the industry average.
“I started it across all those categories kind of by accident. But it set me up really well to have a lifestyle brand,” she said. “I have big goals in mind for what I want it to be. I finally have been able to find the self-confidence that I really can do this, and I’m doing it.”
Paltrow said she was initially hesitant about speaking at the Code Conference, where she would be onstage among tech CEOs.
“At first, I thought, wow, I don’t belong in this group. But, you know, I’m really excited about my Web business and where we are with it,” she said. “I think we’re achieving a new or newish paradigm — and we’re actually achieving it — this mix of content and commerce.”
Her goal for Goop this year is to “do more of it, and do it better,” she said. So far, Paltrow has not yet taken venture capital for her site, where posts are signed “Love, gp.” Instead, she said she has used her own money, as well as “my blood, sweat and tears.”
“When I look at new companies, we’re kind of the opposite of, let’s just build it, build it quick and sell it,” said Paltrow. “Because my name is so attached to it — because it really is mine — it’s important that it be something real.” ||||| BEImages/Matt Baron
Well, this could all get a bit meta if any of you leave comments that are in any way negative on this post, but—here goes! Last night, Gwyneth Paltrow—Goop Overlord, Conscious Uncoupler—made a surprise appearance at the inaugural Code Conference in Rancho Palos Verdes, California, alongside the likes of Sergey Brin and Satya Nadella. (The conference is co-run by Vanity Fair contributing editor Kara Swisher.)
Paltrow has had great success with her weekly Goop newsletter (its “open rate”—that is, the percentage of subscribers who actually open her missives—is, according to Paltrow, “more than double the industry average”), and her e-commerce business is currently turning a profit. But while Paltrow sees the great opportunities available thanks to the Internet, and has clearly reaped the benefit of such, she told Re/code, the tech-news site hosting the conference, that she was also keenly aware of the Internet’s dark underbelly: comment threads.
“The Internet is an amazing opportunity, socially. We have this opportunity to mature and learn, which is the essence of being on Earth—to being the closest person we can be to our actual, real, truest self,” she said. “But the Internet also allows us the opportunity to project outward our hatred, our jealousy. It’s culturally acceptable to be an anonymous commenter. It’s culturally acceptable to say, ‘I’m just going to take all of my internal pain and externalize it anonymously.’”
Does this mean Gwyneth actually reads the thousands of posts written about her each week? Gwyn, are you reading this right now!??!? (If so, hi! Uh, that “Gwyneth Responds to Chris Martin Lyrics” post from last week was all in good fun! Also, want to meet up for some bruschetta and white wine? You can pick the place and time. Do you eat bruschetta?! Is bruschetta healthy?! We know you won’t answer these questions in the comments, clearly, but e-mail us, maybe?)
Paltrow went on to say that she has become somewhat immune to the onslaught of comments.
“It’s taken me a long time to get to the point where I can see these things and not take it as a personal affront and a hurt. I see myself as a chalkboard or a whiteboard or a screen, and someone is just putting up their own projection on it,” she said. “It has nothing to do with me. They have an internal object, and they’re putting it on me. I kind of look at it as, ‘Wow this is an interesting social experiment.’ You’re talking about a blind stranger having feelings about you. It can only be projection.”
The experience of reading about herself online over the years is analogous to what it’s like for veterans of war, she reportedly said.
“You come across [online comments] about yourself and about your friends, and it’s a very dehumanizing thing. It’s almost like how, in war, you go through this bloody, dehumanizing thing, and then something is defined out of it,” she said. “My hope is, as we get out of it, we’ll reach the next level of conscience.”
So, the next time you’re about to leave an anonymous, caps-lock comment on a Kim Kardashian photo post, imagine a mini-Gwyneth on your shoulder, drinking a mini-kale smoothie, shaking her head. We’ll all be on that next level of conscience in no time. ||||| Gwyneth Paltrow isn't who you'd expect to speak at a big tech conference featuring Microsoft and Google honchos. But on Tuesday, she gave a short and impassioned speech about the dark side of the Internet.
The actress was the surprise guest at Re/Code's Code Conference outside of Los Angeles. She spoke about the anonymity of the Internet — and its ability to allow "objectification and dehumanization" of others, especially celebrities.
"It's like the scabs from your high-school wounds being ripped off on a daily basis," Paltrow said.
Actress Gwyneth Paltrow was a surprise speaker at the Code Conference on Tuesday. Asa Mathat / Re/code
A visibly nervous Paltrow started off self-deprecating — she promised that she wouldn't talk about Javascript or Ruby On Rails — but she relaxed as she went on about the effect Internet trolls have had on her life and those of her celebrity friends.
Paltrow acknowledged that some abuse goes along with being a public figure: "When you go back through history, it's always happened. From a spiritual leader to Katharine Hepburn ..."
But the nature of the Internet adds a disturbing layer, she said. Paltrow gave one chilling example: A celebrity friend who posted a "normal photo" on Instagram received a comment from a user who expressed a desire to "rape and disembowel" her.
Paltrow, who specifically slammed Facebook for its "foundation of objectification," didn't go into many details about the online abuse she herself has taken.
But in February, a user of the anonymous secrets-sharing app Whisper posted a message alleging that Paltrow was cheating on husband Chris Martin — a claim that her rep quickly denied. The following month, Paltrow earned Internet scorn for calling her separation from Martin a "conscious uncoupling."
"At a certain point when you've been made fun of and excoriated and dragged through the mud ... for 20 years ... you realize it's not really about you," Paltrow said.
Instead, Paltrow said, she has accepted she "cannot be more than an external representation" of whatever hurts the trolls keep inside themselves.
Paltrow said she thinks about how her children will grow up in an online world, and wonders: "Perhaps the Internet has been brought to us as a test of our own emotional evolution."
Paltrow hopes that evolution will bring changes to the Internet and the way we live online.
"It's no accident that as the Internet grows, and the voices get softer and softer because there are so many of them ... we're drawn to authenticity." | – Gwyneth Paltrow ... tech expert? The actress spoke at the Code Conference yesterday, rubbing elbows with tech CEOs, thanks to her Web business, Goop. Before her surprise appearance, she talked to re/code (the tech news site hosting the conference, Vanity Fair notes) about Goop (it's profitable, though she won't give exact numbers, and the "open rate" for her newsletter emails is more than double the industry average), but she also spoke quite a bit about mean online commenters on the Internet. One quote that's getting her some negative attention: "You come across [online comments] about yourself and about your friends, and it’s a very dehumanizing thing. It’s almost like how, in war, you go through this bloody, dehumanizing thing, and then something is defined out of it. My hope is, as we get out of it, we’ll reach the next level of conscience." The quote, of course, led to headlines like "Gwyneth Paltrow: Celebrities Who Have Dealt with Mean Internet Comments Are Almost Like War Veterans." (Even re/code acknowledged that Paltrow "compared the experience of living through vitriolic Internet commenters to surviving a war.") NBC News notes that her actual speech focused on the same themes, but her comparison there wasn't as dramatic: She said reading mean comments was like having "the scabs from your high-school wounds being ripped off on a daily basis." (Paltrow's last ill-advised comment had to do with working moms.) |
the dft calculations were performed in siesta using a supercell of the cu(001 ) with a 4x4 surface and 4 atoms thick slab .
calculational details include a real space cutoff of 200 ry , gamma points approximation , double / single - z polarized ( dzp / szp ) basis set for the c ( dzp ) , h(dzp ) , and cu(szp ) atoms .
computational details for the vibrational frequencies , electron - phonon coupling , and electron - hole pair damping can be found in ref .
@xcite . for the nudged elastic band ( neb )
calculation more refined computational parameters were necessary , a 5x5 surface , 600 ry cutoff , 3x3 k - points , and the dzp basis set for all species . using the refined parameters changed vibrational frequencies by less than 10 % .
although the neb calculation is fairly converged with computational parameters , the calculated barrier is still approximate because of the basis set superposition error inherent in the siesta method .
we therefore use the experimental barrier height in the main text .
the equilibrium configuration of c@xmath0h@xmath0 on cu(001 ) and the relaxation of the cu atoms is shown schematically in fig .
[ fig : c2h2config ] .
the results for the vibrational energies @xmath23 and electron - hole damping rates @xmath24 , @xmath25 are shown in tab .
i of the main text .
the calculated equilibrium configuration of the chemisorbed c@xmath0h@xmath0 molecule on cu(001 ) is in agreement with ref . :
@xmath127 , @xmath128 and bond angle cc - h is @xmath129 .
the acetylene atom displacements for all modes are illustrated in fig .
[ fig : vibmodes ] , where only four cu atoms nearest to the acetylene molecule are shown as blue balls . calculated equilibrium configuration of c@xmath0h@xmath0 on cu(001 ) .
the c - c and ch bond lengths and c - ch bond angle are given in the text . ] [ cols="^,^,^",options="header " , ] we calculate the anharmonic coefficients @xmath130 and find the modes coupled effectively .
figure 3 of the main text shows the dependence of coefficients @xmath131 and @xmath132 on mode numbers @xmath133 and @xmath134 .
these coefficients indicate the most effective ways of decay of the symmetric ch stretch mode # 1 and asymmetric ch stretch mode # 2 .
these modes are known to be responsible for the high - energy threshold @xmath90 mev , they are excited directly by the tunneling electrons .
the symmetric ch stretch mode # 1 decays most efficiently via excitation of a pair of equivalent phonons : # 4 ch asymmetric in - plane bend or wag , # 5 in - plane bend or scissor , # 6 out - of - plane bend or asymmetric rotation , # 7 cartwheel .
coupling of the symmetric ch stretch mode # 1 with the symmetric rotation mode # 11 is ineffective since the corresponding anharmonic coefficient is @xmath135 times smaller than that for a coupling with the pair of out - of - plane bend or asymmetric rotation mode # 6 .
the asymmetric ch stretch mode # 2 decays most efficiently via excitation of a pair of non - equivalent phonons , e.g. , the pair of the asymmetric rotation # 6 and cartwheel mode # 7 .
this simple estimation of the anharmonic coefficient shows that the rotation of the acetylene molecule is initiated via excitation of the asymmetric rotation mode # 6 .
there are two processes leading to the excitation of the reaction coordinate mode # 6 , the excitation of a pair of the asymmetric rotation phonons or the excitation of one asymmetric rotation phonon and one phonon of the cartwheel mode # 7 .
in this section we derive explicitly the excitation rate of the reaction coordinate mode . as we have shown in supplementary material [
appendix : springrod ] , the excitation process of the vibrational mode of the acetylene molecule involves two possible pathways , via excitation of the reaction coordinate mode and the auxiliary idler mode or via double excitation of the reaction coordinate mode ( terms @xmath136 and @xmath137 respectively , in eq .
( 8) of the main text ) .
we discuss here both of the scenarios using the keldysh diagram technique . in both cases under consideration
the frequencies of the vibrational modes are far from the resonance , @xmath138 and the anharmonic interaction between them can be treated as weak . in what follows
we derive the excitation rate of the rc mode due to the process described by @xmath136 ; the excitation rate due to @xmath137 can be obtained replacing the index @xmath139 of the idler phonon in all formulas below , with the index @xmath140 of the rc phonon . for the description of the effective stationary occupation densities of the rc mode we use the kinetic equation.@xcite the anharmonic component of the excitation rate of the rc mode
is given by the one - loop polarization operator .
neglecting the temperature corrections , it reads @xmath141 \rho_{\mathrm{ph}}^{(i)}(\varepsilon ) d\varepsilon , \end{gathered}\ ] ] where @xmath142 is the density of states of the rc and high - frequency modes and @xmath143 are the corresponding occupation densities .
formula ( [ eq : ga ] ) describes the energy transfer rate to the hindered rotation mode of an adsorbate due to the anharmonic coupling with the ch stretch mode
. we proceed with the calculation of a total excitation rate @xmath144 of the rc mode @xmath145 after making a substitution of ( [ eq : ga ] ) into ( [ gtot ] ) the total rc excitation rate takes the form @xmath146 the second term in eq .
( [ phongenrate ] ) shows a threshold dependence on bias voltage , because it is proportional to the high - frequency mode occupation numbers @xmath147 .
it can be shown that the first term in ( [ phongenrate ] ) can be omitted due to the fact that @xmath148 .
the total excitation rate of the rc phonons due to the anharmonic term @xmath136 is then @xmath149,\end{gathered}\ ] ] and due to @xmath137 is @xmath150 note that both rates are proportional to the ch stretch mode excitation rate @xmath151 and to small phonon densities of the rc and idler vibrational modes far from the resonance .
in this section we calculate the excitation rate of the rc phonons @xmath152 using pauli master equations . as discussed in supplement [
appendix : double ] , depending on the height of the rotational barrier , two possible processes can lead to initiation of the rotations of the acetylene molecule on cu(001 ) . in this section
these processes will be considered separately as they involve ladder climbing of two different types . in case
when the rotational barrier height is @xmath153 , the one - step ladder climbing process takes place @xcite .
the excitation rate of this process @xmath154 is given by ( [ eq : phongenrate2 ] ) and the relaxation rate is @xmath155 , thus the pauli master equation can be written as @xmath156p_{m}.\end{gathered}\ ] ] the stationary solutions ( in respect to @xmath157 ) for @xmath158 states in the localization potential of the rc mode can be written as @xmath159 , @xmath160 .
reaction rate @xmath52 is defined as a probability rate to overcome the localization potential barrier and in our notations it is the excitation rate from the first excited level @xmath161 if the rotational barrier height is @xmath162 then the excitation rate is assumed to be dominated by the two - phonon anharmonic coupling with the high - frequency mode .
the pair of rc phonons excitation rate @xmath163 is given by ( [ eq : phongenrate3 ] ) and the de - excitation process is dominated by the single phonon relaxation rate @xmath155 .
then , according to ref .
, the pauli master equation takes form @xmath164p_{m}.\end{gathered}\ ] ] the stationary solutions ( in respect to @xmath157 ) for @xmath165 states in the localization potential of the rc mode can be written as @xmath159 , @xmath166 and @xmath167 reaction rate @xmath52 in this case is a sum of the excitation rates from the first excited state @xmath168 and from the second excited state @xmath169 , @xmath170 the reaction rate in both cases is a quadratic function of the rc phonon excitation rate which is a feature of the two - step ladder climbing process and differs only in a proportionality coefficient . for a more accurate estimation of proportionality coefficient between the second power inelastic tunneling current and rotation rate we need to take into account the fact that the inelastic tunneling current is a sum of several components which arise from the scattering of tunneling elections on all relevant vibrational modes . in our case
we are interested in two ch stretch modes , symmetric # 1 and asymmetric # 2 . according to our dft calculation the inelastic transmission through these modes are @xmath171 ( s@xmath21v)@xmath18 and @xmath172 ( s@xmath21v)@xmath18 . in what follows we will take this into account . introducing the probability factors
to excite the symmetric ch stretch mode @xmath173 and the asymmetric one @xmath174 . substituting the expression for the excitation rate of the rc phonons ( [ eq : phongenrate2 ] ) and ( [ eq : phongenrate3 ] ) into eqs .
( [ eq : rb1 ] ) and ( [ eq : rb2 ] ) correspondingly and using the expression for the high - frequency phonons @xmath175 occupation densities we obtain the proportionality coefficient @xmath176 [ eq . ( 9 ) of the main text ] between the excitation reaction rate and the phonon generation rate @xmath177 .
@xmath178 using @xmath179 mev , @xmath180 ps@xmath18 , @xmath181 ps@xmath18 , @xmath182 ps@xmath18 , @xmath183 mev ( @xmath184 ) we obtain @xmath185 s. it is @xmath186 times larger than the coefficient @xmath187 s obtained from the best fit of the experimental data .
moreover , in case of a lower reaction barrier @xmath153 the process of double excitation of the reaction coordinate phonons gives a contribution to the linear part @xmath51 of the rotation probability .
the rotation rate can be estimated then as @xmath188 .
then the impact of this process into the proportionality coefficient @xmath71 can be written as @xmath189 using the same parameters as above for the coefficient @xmath176 , we arrive to the estimated value of @xmath190 , which is three orders of magnitude larger than the value of @xmath71 obtained from the fitting of the experimental data .
evidently , this makes the case of a lower reaction coordinate barrier @xmath153 hardly possible .
analogously , the coefficient @xmath191 between @xmath192 and @xmath193 , @xmath194 using @xmath195 mev , @xmath196 ps@xmath18 , @xmath197 ps@xmath18 , @xmath198 mev we obtain that @xmath199 s , @xmath200 times larger than the best fit value @xmath187 s. thus the estimated value of the coefficient @xmath85 is slightly larger than the value obtained from the fit of the experimental data .
we believe that our simpler model overestimates the anharmonic coupling coefficients @xmath201 ; for a better agreement with the experimental data we have to take @xmath202 times smaller values @xmath203 mev .
in this section we show that in the limit of a low temperature @xmath66 the excitation rate of phonons excited simultaneously via tunneling electron scattering can be written in the same form as for the single - electron excitation .
@xcite in order to calculate an excitation rate of coherent phonons we use the keldysh - green s function method.@xcite the kinetic equation for phonons takes the form @xmath204\frac{d\omega}{2\pi},\ ] ] where @xmath205 ; @xmath206 is a total number of phonons in corresponding mode .
@xmath207 are phonon keldysh - green s functions and @xmath208 are phonon polarization operators .
the former are given by @xmath209 where @xmath210 is the vibration occupation function of @xmath139-th mode to be determined self - consistently from the kinetic equation .
substituting @xmath211 in the kinetic equation , we obtain @xmath212.\end{gathered}\ ] ] at low temperatures , @xmath213 the occupation density takes the form @xmath214 , where @xmath215 and @xmath216 are the excitation and relaxation rates of the corresponding phonon modes .
then @xmath217 .
the self - energy @xmath218 , expanded to the second order in @xmath219 [ see eq .
( 10 ) of the main text ] reads @xmath220 where @xmath221 are the keldysh - green s functions of the electrons of the adsorbate . substituting @xmath222 and taking into account that @xmath223 , we arrive to the following expressions for the polarization operators @xmath224 in full analogy we obtain the expression for @xmath225 .
total coherent phonon excitation rate @xmath226 takes the same form for both modes @xmath227 the expression in a limit @xmath66 and @xmath228 can be approximated as @xmath229 where @xmath230 and @xmath231 is the relaxation rate of the coherent phonons .
we can use the inverse lifetime of the coherent modes @xmath232 and @xmath233 and rewrite @xmath234 , where @xmath235 and @xmath236 is the efficiency of the coherent process .
equation ( [ eq : g_coh_2 ] ) shows that the total coherent phonon excitation rate takes the form of a single - phonon excitation rate @xmath114 @xcite , where the single vibrational frequency is replaced by the sum of two vibrational frequencies .
4ifxundefined [ 1 ] ifx#1 ifnum [ 1 ] # 1firstoftwo secondoftwo ifx [ 1 ] # 1firstoftwo secondoftwo `` `` # 1''''@noop [ 0]secondoftwosanitize@url [ 0 ]
+ 12$12 & 12#1212_12%12@startlink[1]@endlink[0]@bib@innerbibempty link:\doibase 10.1021/jp025712l [ * * , ( ) ] link:\doibase 10.1103/physrevb.75.205413 [ * * , ( ) ] http://link.aps.org/abstract/prb/v70/e125414 [ * * , ( ) ] @noop * * , ( ) @noop * * , ( ) | we study the elementary processes behind one of the pioneering works on stm controlled reactions of single molecules [ stipe et al .
, phys . rev
. lett . * 81 * , 1263 ( 1998 ) ] . using the keldysh - green function approach for the vibrational generation rate in combination with dft calculations to obtain realistic parameters
we reproduce the experimental rotation rate of an acetylene molecule on a cu(100 ) surface as a function of bias voltage and tunneling current .
this combined approach allows us to identify the reaction coordinate mode of the acetylene rotation and its anharmonic coupling with the c - h stretch mode .
we show that three different elementary processes , the excitation of c - h stretch , the overtone ladder climbing of the hindered rotational mode , and the combination band excitation together explain the rotation of the acetylene molecule on cu(100 ) .
tunneling electrons from a scanning tunneling microscope ( stm ) form an atomic source of electrons for electronic and vibrational excitations which can be used to manipulate individual atoms and molecules in a controlled manner @xcite .
the study of acetylene c@xmath0h(d)@xmath0 rotation on the cu(001 ) surface @xcite was the first comprehensive and systematic experiment on a single adsorbate manipulation made in combination with stm inelastic electron tunneling spectroscopy ( stm - iets ) .
this method has been established as an indispensable experimental method to gain insight into the vibrationally mediated motions and reactions of single molecules with stm ( see , e.g. , ref . and references therein ) .
the observed in ref .
rotation yield per electron as a function of bias voltage for c@xmath0h@xmath0(d@xmath0 ) exhibits a threshold at 358 ( 266 ) mv .
this corresponds to the excitation of the ch(d ) stretch mode which is not a rotational mode . in this respect
it is very different from , e.g. , the rotation of a single oxygen molecule on pt(111 ) surface @xcite , where the hindered rotational mode can be directly excited by tunneling electrons @xcite . that the onset of a molecular motion / modification is caused by a vibrational mode that is not directly responsible for the observed motion is not unique .
many other examples have been established , e.g. , the migration of co on pd(110 ) @xcite .
the rotation of c@xmath0h(d)@xmath0/cu(001 ) @xcite also demonstrates several peculiar features which have not been previously understood . in this paper
we revisit the experimental findings of ref . .
based on dft calculations and the keldysh diagram technique we clarify the vibrational modes and elementary physical processes behind the characteristic features of the acetylene d@xmath0 on cu(001 ) will be analyzed elsewhere , it can be done analogously to the current approach . ] rotation on cu(001 ) .
rotation yield per electron as a function of bias voltage at fixed tunneling current @xmath1 na .
circles are experimental data from ref . .
blue dashed line is the linear process a , eq.([eq : ra ] ) , red dash - dotted line is the nonlinear process b , eq.([eq : rb ] ) , and green dotted line is the combination band process c , eq.([eq : rc ] ) .
black solid line corresponds to a sum of all processes .
lines are calculated via eqs .
( [ rabc],[eq : ra],[eq : rb ] ) with @xmath2 , @xmath3 , and @xmath4 , the ch mode generation rate eq.([eq : giet ] ) , is calculated via the keldysh technique @xcite , the parameters are specified in the text . ] the experimental data @xcite on the c@xmath0h@xmath0/cu(001 ) rotation is summarized as symbols in figs .
[ fig : yvsv ] and [ fig : yvsi](a ) .
the higher threshold at 358 mev , see fig .
[ fig : yvsv ] , corresponds to excitation of the ch stretch mode .
in addition , a lower threshold with a much smaller rotation yield is clearly seen at @xmath5 mev , we note that this does not correspond to any vibrational energy of the c@xmath0h@xmath0/cu(001 ) , see below .
the third feature is the crossover from a single to two - electron process with increasing tunneling current above 10 na , see fig .
[ fig : yvsi](a ) .
this crossover can not be attributed to a resonant inelastic electron - molecule scattering with rotational excitation as in the case of o@xmath0/pt(111 ) @xcite , because of the evident absence of direct excitation of the hindered rotational modes . moreover
, the crossover can not be attributed to coherent ladder climbing since the reaction order ( number of electrons needed ) does not approache one at high bias @xcite .
rotation yield per electron @xmath6 as a function of tunneling current ( panel a ) .
symbols show the experimental data from ref . .
lines are the calculated results for different bias voltages : @xmath7 ( black solid line ) , 449 ( red dashed ) , 500 ( green dash - dotted ) , and 600 mv ( blue dotted ) .
thin dash - dotted lines are the linear and nonlinear contributions to the rotation yield for @xmath8 mv . the calculations are done with the same parameters as in fig.[fig : yvsv ] .
the dependencies of the hybridization parameter @xmath9 on current for different bias voltages are shown in panel b. ] the identification of the precursor to rotation is not straightforward since the molecule has a number of low frequency vibrational modes . the hindered rotational mode of c@xmath0h@xmath0 on cu(001 ) @xmath10 mev , whereas the thermally measured barrier for rotation is relatively high @xmath11 mev @xcite .
for this low - energy rotational mode to directly induce rotations , a multi ( 5 - 6)-electron processes is expected , whereas in the experiment , as explained above , only a two - electron process is observed at larger tunneling currents .
c c c c c c c c c c @xmath12 & mode & & @xmath13 & @xmath14 & @xmath15 & @xmath16 + & & & @xmath17s@xmath18 & + & & & & + & & this & & eels & iets + & & work & ref . &
ref .
& ref .
& + 1 & ch stretch sym & 371 & 379 & 364 & 358 & 1.0 & -0.01 & 0.01 & 0 + 2 & ch stretch asym & 368 & 375 & 357 & 358 & 0.7 & 1.66 & -1.66 & 0 + 3 & cc stretch & 167 & 171 & 164 & n.o.@xmath19 & 2.2 & 0 & 0 & 0 + 4 & ch in - plane bend + & or wag , asym & 131 & 132 & 141 & n.o .
& 0.2 & 1.16 & -1.16 & 0 + 5 & ch in - plane bend + & or scissor , sym & 111 & 117 & 118 & n.o . & 1.5 & 0 & 0 & 0 + * 6 * & * ch out - of - plane bend * + & * or asym rotation * & * 100 * & * 101 * & * 78 * & n.o . &
* 0.7 * & * 0 * & * 0 * & * -1.06 * + 7 & out - of - plane bend + & or cartwheel & 71 & 75 & n.o . & n.o . & 0.2 & -0.24 & -0.24 & 0 + 8 & in - plane bend or wag & 58 & n.p.@xmath20 & n.o . &
n.o . & 2.0 & 1.26 & -1.26 & 0 + 9 & molecule - cu stretch & 50 & n.p . &
52 & n.o . & 0.05 & 0 & 0 & 0 + 10 & in - plane rotation & 29 & n.p . & n.o . & n.o .
& 1.8 & -0.35 & 0.35 & 0 + * 11 * & * out - of - plane rotation * & * 28 * & n.p . & n.o . & n.o . & * 0.2 * & * 0 * & * 0 * & * 1 * + 12 & out - of - plane bend & 23 & n.p . & n.o . & n.o . & 0.04 & -0.04 & -0.05 & 0.03 + + + to analyse the mechanisms of rotation of a single c@xmath0h@xmath0/cu(001 ) by tunneling electrons we performed dft calculations on a 4@xmath214 cu(001 ) surface with one adsorbed acetylene molecule .
the calculations of relaxed geometries , vibrational energies , and electron - hole pair damping rates were carried out with siesta @xcite .
other details of the dft calculations are presented in the supplementary material , sec .
i ( _ sm - i _ in what follows ) .
we also estimated the energy barrier @xmath22 for c@xmath0h@xmath0 rotation on cu(001 ) to 100 mev using the nudged elastic band method .
the results for the vibrational energies @xmath23 and electron - hole damping rates @xmath24 , @xmath25 are given in tab .
[ tab : vibmodes ] , in comparison with the previous theoretical @xcite and experimental @xcite results .
the last three columns of tab .
[ tab : vibmodes ] show ( in relative units ) the components of each modes angular momentum @xmath26 , where @xmath27 , @xmath28 are the atomic positions ( in the acetylene molecule ) and masses , @xmath29 the center - of - mass , and @xmath30 the atomic displacements in the vibrational mode @xmath12 . the high frequency modes ( # 1 & 2 in tab .
[ tab : vibmodes ] ) are the symmetric and antisymmetric ch stretch modes .
the higher threshold energy of the rotation yield @xmath31 at @xmath32 mv and the corresponding peak in the @xmath33 plot , observed in ref .
, indicate that inelastic excitation by tunneling electrons of these modes is a trigger for rotation . along the reaction pathway
there are only two frustrated rotation modes which has angular momentum in the ( 001 ) direction , # 6 and # 11 .
the full hamiltonian of the system can be written as a sum of the electronic and vibrational ( phonon ) parts , @xmath34 where the electronic part @xmath35 depends on the normal coordinates of the molecule @xmath36 . using the newns - anderson type hamiltonian @xcite ,
we write @xmath37 where the indices @xmath38(@xmath39 ) and @xmath40 denote a substrate ( tip ) and the adsorbate , respectively ; the corresponding energy levels are @xmath41 and @xmath42 .
electronic tunneling matrix elements @xmath43 ( tip - adsorbate ) and @xmath44 ( substrate - adsorbate ) give rise to a stationary tunneling current between the tip and the substrate through the adsorbate orbital at applied bias voltage @xmath45 .
the electron occupation functions in the substrate and tip are assumed to be fermi distributions with the same temperature @xmath46 but different chemical potentials @xmath47 and @xmath48 , @xmath49 . in order to clarify the interaction parts of the full hamiltonian ( [ eq : hfull ] ) behind the experimental results on the acetylene rotation , it is convenient to split the rotation rate into three partial processes , @xmath50 where the rates @xmath51 and @xmath52 are , respectively
, the one- and two - electron processes with a higher threshold @xmath53 mv , and @xmath54 is the one - electron process with a lower threshold @xmath55 mv . to describe the generation of high frequency ch stretch modes , the adsorbate orbital energy in the 1st term of eq .
( [ eq : he ] ) can be expanded @xcite to the first order as @xmath56 where @xmath57 is an electron - phonon constant and @xmath58 the unperturbed adsorbate energy , @xmath59 is the annihilation operator of the vibrational mode @xmath60 with the frequency @xmath61 mev , which is directly excited by the inelastic tunneling current ; we use the experimental value from ref . in the estimates below . ] .
the high frequency vibration generation rate then reads @xcite @xmath62 where @xmath63^{-1}$ ] , @xmath64 is the inverse lifetime of the phonon mode @xmath65 due to electron - hole pair excitation , given in tab .
[ tab : vibmodes ] . at @xmath66
@xcite @xmath67 our next task is to find the mechanisms of the energy transfer between the high frequency ch stretch mode and the reaction coordinate ( rc ) hindered rotational mode .
the first possibility is the direct over - barrier rotation excitation due to an inelastic tunneling generation of the stretch mode @xmath68 @xcite .
the rotation rate corresponding to such single - electron process can be described @xcite as a linear function of the ch stretch mode generation rate , @xmath69 a good fit to the experimental data is given by @xmath70 , see fig .
[ fig : yvsv ] .. the physical meaning of @xmath71 is the probability of a ch stretch vibration to excite the c@xmath0h@xmath0 rotation over the barrier .
this value is in reasonable agreement with the well established case of the migration of co on pd(110 ) @xcite .
however , this mechanism can not describe the two - electron process . in principle , the direct over - barrier rotation excitation from the second excited level of the ch stretch mode provides a two - electron process .
however , this process can be discounted since the short lifetime @xmath72 ps gives a nearly two orders of magnitude smaller rate .
another possibility for the energy transfer is an anharmonic interaction of the ch stretch mode with the reaction coordinate mode . in the simplest case this can be described as a cubic coupling .
we expand the vibrational hamiltonian @xmath73 in eq .
( [ eq : hfull ] ) up to cubic terms to account for the coupling between the directly excited ( @xmath74 ) and the reaction coordinate ( rc ) ( @xmath75 ) modes , @xmath76 where @xmath77 are the anharmonic coupling constants , and @xmath78 is possibly some auxiliary ( idler ) vibrational mode excited simultaneously with the rc mode . of the symmetric ch stretch mode # 1 ( left panel ) and asymmetric stretch mode # 2 ( right panel ) with other vibrational modes of acetylene on cu(001 ) surface .
the color scheme is explained in the colorbar to the right .
corresponding modes are given in table [ tab : vibmodes ] .
mode # 6 is the asymmetric rotation , and mode # 11 is the symmetric rotation .
[ fig : kappas ] ] dft calculation of the anharmonic coupling constants is prohibitively time - consuming .
we thererfore construct ( see in _ sm - ii&iii _ ) a simpler model which takes into account only the pair interactions between the nearest neighbors as springs on rods ; the results for the coupling coefficients are shown as colors in fig [ fig : kappas ] . the symmetric ch stretch mode # 1 couples most efficiently with a pair of the asymmetric rotations # 6 .
in contrast , asymmetric ch stretch mode # 2 couples strongly with a pair of non - equivalent phonons , i.e. , asymmetric rotation # 6 and cartwheel mode # 7 .
the coupling to the symmetric rotation mode # 11 is ineffective and the coefficients are approximately two orders of magnitude smaller .
thus , the asymmetric rotation # 6 ( ch out - of - plane bend ) is the most probable candidate for being the acetylene / cu(001 ) rotation precursor .
two different pathways responsible for the two - electron partial process @xmath79 are possible . if the barrier height is @xmath80 , only the second term in eq . (
[ eq : hph ] ) contributes . in this case
the rotation starts from the excitation of the high energy symmetric ch stretch mode # 1 and two successive decays into pairs of rc mode ( # 6 ) are needed to overcome the barrier .
such a overtone ladder climbing process ( see fig .
[ fig : ladderclimbing ] ) was first discussed for a desorption of co molecules in ref . .
low - frequency mode ladder climbing process .
] if @xmath81 , one pair of the rc stretch excitations is enough to cross the barrier which just gives a correction to the single - electron rate @xmath82 . in this case , the only possibility for a two - electron process comes from the third term in eq .
( [ eq : hph ] ) .
the rotation starts from the excitation of the high energy antisymmetric ch stretch mode ( # 2 ) , and two successive decays into pairs of rc mode ( # 6 ) and idler mode ( # 7 ) are needed to overcome the barrier .
this corresponds to the usual single - step ladder climbing process @xcite . in both cases
the generation rate of rc phonons ( pairs of phonons ) is proportional to the generation rate of the ch stretch phonons , @xmath83 ( see more detail in _ sm - iv _ ) .
analysing the pauli master equations for the one- and two - step rc potential ladder climbing processes shows that the rotation rate is @xmath84 with different formulas for the coefficient @xmath85 depending on the corresponding anharmonic coupling coefficients @xmath86 and the ratio of the rc and idler modes linewidth to the detuning @xmath87 ( @xmath88 ) , because the anharmonic decay of the stretch mode is nonresonant , see _ sm - v_. the fitted value @xmath89 reproduce the experimental data above the higher threshold @xmath90 mv well , see fig .
[ fig : yvsv ] . the hybridizations parameters @xmath91 mev , @xmath92 mev were fixed from the tunneling current @xmath93 na and the fraction of the inelastic component @xmath94 at @xmath7 mv . to simulate higher current levels ,
the same parameters were used except @xmath9 which changes as a function of bias and tunneling current as shown in fig .
[ fig : yvsi](b ) . the calculated rotation rate as a function of tunneling current underlines the importance of the two - electron process at high currents and voltages , see fig .
[ fig : yvsi](a ) . from the dash - dotted lines in fig .
[ fig : yvsi](a ) which shows the one and two - electron contributions where only the one - electron process , excitation of the c - h mode followed by the anharmonic mode coupling to the rc mode , is responsible for the reaction yield at low current below around @xmath95 na .
the anharmonic coupling coefficients described above allows for a theoretical extimation of @xmath85 . if @xmath81 , the estimate is @xmath96 s , which is about 7 times larger than the best fit value . however , as noted above , the double excitation of the reaction coordinate mode gives in this case a contribution to @xmath51 .
the resulting value of the coefficient @xmath71 is then @xmath97 , i.e. , @xmath98 times larger than the fitted value @xmath99 .
this allows us to exclude the case of a lower rotational barrier from consideration since it would give rise to a much faster one - electron process than seen experimentally .
the only possibility left is that @xmath80 .
the theoretical estimate for @xmath85 is then @xmath100 s , i.e. , approximately 5 times larger than the fitted value .
we believe , due to approximations , this value to be in reasonable agreement with the experiment . as can be seen from fig .
[ fig : yvsv ] , below the higher energy threshold @xmath101 the rotation rate per electron is very low but non zero above a lower threshold of @xmath102240 mev .
this can be attributed to an inelastic electron tunneling processes which involves a simultaneous combination band @xcite generation of two coherent phonons @xmath103 . assuming that the adsorbate energy in eq .
( [ eq : he ] ) is now a function of these vibrational modes , @xmath104 , and expanding it in a taylor series @xmath105 where @xmath106 and , @xmath107 and @xmath108 are annihilation operators of the vibrational modes with frequencies @xmath109 and @xmath110 , and @xmath111 damping rates @xmath112 , @xmath113 .
the analysis of this mechanism using the keldysh - green s functions shows that the total coherent phonon excitation rate takes the form of a single - phonon excitation rate @xmath114 @xcite , eq .
( [ eq : giet ] ) , where a single vibrational frequency is simply replaced by the sum of two vibrational frequencies .
this gives for the reaction rate , instead of eq .
( [ eq : ra ] ) , @xmath115 where @xmath116 @xmath117 and the coefficient @xmath118 depends on the parameters of the system as explained in _ sm - vi_. although it is difficult to make a theoretical estimate of this coefficient , the fitted value to the experimental data is @xmath3 .
thus , the combination band single - electron process is about @xmath119 slower than the process with rotation excitation via ch stretch vibration .
this is in reasonable agreement with the fact that the process eq .
( [ eq : hcomb ] ) occurs in the next order of the perturbation theory compared with the process eq .
( [ eq : ea ] ) .
the over - barrier rotation mode excitation occurs due to an inelastic tunneling generation of a coherent pair of phonons , e.g. the in - plane bend or wag mode @xmath120 mev and in - plane bend or scissor mode @xmath121 mev ( modes # 4 and 5 ) .
another possibility is that the second of these phonons is the asymmetric out - of - plane rotation @xmath122 mev ( mode # 6 ) .
the latter , being a hindered rotation mode , may simplify the resulting molecule rotation . to conclude , we show that the precursor for the acetylene rotation on cu(001 ) is the out - of - plane bend ( or asymmetric rotation ) mode @xmath102100 mev ( # 6 in table [ tab : vibmodes ] ) .
rotation with a higher threshold voltage 358 mv occurs if enough energy stored in the high - frequency ch stretch mode excited by tunneling electrons is transferred to the rotational mode ( reaction coordinate ) .
the anharmonic coupling of the ch mode with the hindered rotation mode is found to be responsible for a crossover from a single to multiple electron process for tunneling currents higher than 10 na .
the lower threshold voltage for rotation at 240 mv is attributed to a combination band process of inelastic scattering of tunneling electrons on a pair of lower - energy vibrational excitations of the acetylene molecule .
this work was supported in part by the russian ministry of education and science and the russian academy of sciences .
h.u .
was supported by a grant - in - aid for scientific research ( grants no .
s-21225001 and no .
b-1834008 ) from japan society for the promotion of science ( jasp ) . 22ifxundefined [ 1 ] ifx#1 ifnum [ 1 ]
# 1firstoftwo secondoftwo ifx [ 1 ] # 1firstoftwo secondoftwo `` `` # 1''''@noop [ 0]secondoftwosanitize@url [ 0 ]
+ 12$12 & 12#1212_12%12@startlink[1]@endlink[0]@bib@innerbibempty http://dx.doi.org/10.1038/352600a0 [ * * , ( ) ] link:\doibase 10.1126/science.261.5123.886 [ * * , ( ) ] http://link.aps.org/abstract/prl/v78/p4410 [ * * , ( ) ] http://www.sciencemag.org/cgi/doi/10.1126/science.279.5358.1907 [ * * , ( ) ] link:\doibase 10.1103/physrevlett.81.1263 [ * * , ( ) ] `` , '' in http://www.panstanford.com/books/9789814241502[__ ] , ( , ) chap . , pp
. link:\doibase 10.1103/physrevb.62.r13306 [ * * , ( ) ] link:\doibase 10.1126/science.1069016 [ * * , ( ) ] http://link.aps.org/abstract/prb/v70/e125414 [ * * , ( ) ] link:\doibase 10.1063/1.479863 [ * * , ( ) ] link:\doibase 10.1021/jp025712l [ * * , ( ) ] link:\doibase 10.1016/s0039 - 6028(87)81048 - 8
[ * * , ( ) ] http://stacks.iop.org/0953-8984/14/i=11/a=302 [ * * , ( ) ] link:\doibase 10.1103/physrevb.75.235441 [ * * , ( ) ] http://prola.aps.org/abstract/pr/v178/i3/p1123_1 [ * * , ( ) ] http://dx.doi.org/10.1016/0038-1098(80)90677-8 [ * * , ( ) ] link:\doibase 10.1103/physrevb.55.4825 [ * * , ( ) ] link:\doibase 10.1016/s0039 - 6028(01)01893 - 3 [ * * , ( ) ] link:\doibase 10.1038/nmat3176 [ * * , ( ) ] link:\doibase 10.1103/physrevb.86.035440 [ * * , ( ) ] @noop * * , ( ) link:\doibase 10.1063/1.477531 [ * * , ( ) ] * rotation of a single acetylene molecule on cu(001 ) by tunneling electrons in stm : supplementary materials * yulia e. shchadilova,@xmath123 sergey g. tikhodeev,@xmath124 magnus paulsson,@xmath125 and hiromu ueba@xmath126 + the details are given for * dft calculation of the vibrational modes of acetylene molecule on cu(001 ) surface and the inelastic tunneling ; * third order anharmonic terms in the vibrational hamiltonian which are responsible for the energy transfer between the vibrational modes ; * model calculation of the anharmonic coupling constants ; * anharmonic excitation rate of the hindered rotational phonons using keldysh diagram technique ; * pauli master equation approach to calculate the probability of rotations due to anharmonic decay of high frequency ch stretch mode ; * keldysh - green s function derivation of the combination band two - phonon rotation excitation .
pacs numbers : 68.37.ef , 68.43.pq |
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exceeds 150 percent but not 300 percent, 50
percent of such credit; and
``(iii) if such Indian unemployment rate
does not exceed 150 percent, 0 percent of such
credit.
``(B) Special rule for large projects.--In the case
of a qualified Indian reservation property which has
(or is a component of a project which has) a projected
construction period of more than 2 years or a cost of
more than $1,000,000, subparagraph (A) shall be applied
by substituting `during the earlier of the calendar
year in which the taxpayer enters into a binding
agreement to make a qualified investment or the first
calendar year in which the taxpayer has expended at
least 10 percent of the taxpayer's qualified
investment, or the preceding calendar year' for `during
the calendar year in which the property is placed in
service or during the immediately preceding 2 calendar
years'.
``(C) Determination of indian unemployment.--For
purposes of this paragraph, with respect to any Indian
reservation, the Indian unemployment rate shall be
based upon Indians unemployed and able to work, and
shall be certified by the Secretary of the Interior.
``(6) Coordination with nonrevenue laws.--Any reference in
this subsection to a provision not contained in this title
shall be treated for purposes of this subsection as a reference
to such provision as in effect on the date of the enactment of
this paragraph.''.
(2) Lodging to qualify.--Paragraph (2) of section 50(b) of
such Code (relating to property used for lodging) is amended by
striking ``and'' at the end of subparagraph (C), by striking
the period at the end of subparagraph (D) and inserting ``;
and'', and by adding at the end the following subparagraph:
``(E) new reservation construction property.''.
(c) Recapture.--Subsection (a) of section 50 of such Code (relating
to recapture in case of dispositions, etc.), is amended by adding at
the end the following new paragraph:
``(6) Special rules for indian reservation property.--
``(A) In general.--If, during any taxable year,
property with respect to which the taxpayer claimed an
Indian reservation credit--
``(i) is disposed of; or
``(ii) in the case of reservation personal
property--
``(I) otherwise ceases to be
investment credit property with respect
to the taxpayer; or
``(II) is removed from the Indian
reservation, converted, or otherwise
ceases to be Indian reservation
property,
the tax under this chapter for such taxable year shall
be increased by the amount described in subparagraph
(B).
``(B) Amount of increase.--The increase in tax
under subparagraph (A) shall equal the aggregate
decrease in the credits allowed under section 38 by
reason of section 48(c) for all prior taxable years
which would have resulted had the qualified investment
taken into account with respect to the property been
limited to an amount which bears the same ratio to the
qualified investment with respect to such property as
the period such property was held by the taxpayer bears
to the applicable recovery period under section 168(g).
``(C) Coordination with other recapture
provisions.--In the case of property to which this
paragraph applies, paragraph (1) shall not apply and
the rules of paragraphs (3), (4), and (5) shall
apply.''.
(d) Basis Adjustment To Reflect Investment Credit.--Paragraph (3)
of section 50(c) of such Code (relating to basis adjustment to
investment credit property) is amended by striking ``energy credit or
reforestation credit'' and inserting ``energy credit, reforestation
credit, or Indian reservation credit other than with respect to any
expenditure for new reservation construction property''.
(e) Certain Governmental Use Property To Qualify.--Paragraph (4) of
section 50(b) of such Code (relating to property used by governmental
units or foreign persons or entities) is amended by redesignating
subparagraphs (D) and (E) as subparagraphs (E) and (F), respectively,
and by inserting after subparagraph (C) the following new subparagraph:
``(D) Exception for reservation infrastructure
investment.--This paragraph shall not apply for
purposes of determining the Indian reservation credit
with respect to reservation infrastructure
investment.''.
(f) Application of At-Risk Rules.--Subparagraph (C) of section
49(a)(1) of such Code is amended by striking ``and'' at the end of
clause (ii), by striking the period at the end of clause (iii) and
inserting ``, and'', and by adding at the end the following new clause:
``(iv) the qualified investment in
qualified Indian reservation property.''.
(g) Clerical Amendments.--
(1) Section 48 of such Code is amended by striking the
heading and inserting the following:
``SEC. 48. ENERGY CREDIT; REFORESTATION CREDIT; INDIAN RESERVATION
CREDIT.''.
(2) The table of sections for subpart E of part IV of
subchapter A of chapter 1 is amended by striking the item
relating to section 48 and inserting the following:
``Sec. 48. Energy credit; reforestation
credit; Indian reservation
credit.''.
(h) Effective Date.--The amendments made by this section shall
apply to property placed in service after December 31, 2001. | Indian Reservation Economic Investment Act of 2001 - Amends the Internal Revenue Code to allow an Indian reservation investment credit based on specified amounts. Includes qualified personal property and qualified real property used or located outside an Indian reservation which is connected to existing tribal infrastructure in the reservation, including roads, power lines, water systems, railroad spurs, and communication facilities as a reservation infrastructure investment. Limits the credit based on the Indian unemployment rate. Provides for recapture of the credit in certain cases. |
Here’s a question you won’t hear debated by the panelists on sports-talk shows: Why are so few women among the panelists on sports-talk shows?
Women have made strides in virtually every area of sports journalism over the past two decades or more. They cover sports for newspapers and Web sites, write columns and host studio programs. They are ubiquitous as sideline reporters on game broadcasts and they’re a growing presence as the sports anchor on local newscasts.
But they don’t, generally speaking, get to offer their opinions on the air. The usual sports-chat topics — quarterback controversies, coaching decisions, draft projections and the like — are still the province of men. And those outspoken male pundits are increasingly responsible for shaping the narrative that drives the 24-hour sports news cycle, where strong opinions and hot takes rule the day.
Don’t women have opinions, too?
Guys have lots of them, and in the testosterone jungle that is sports chatter, some of the things they say about women can be pretty ugly. Maybe having a few women around wouldn’t hurt.
Fox Sports reporter Erin Andrews. (Jason Merritt/Getty Images)
Last month, Kirk Minihane of Boston radio station WEEI called Fox sports reporter Erin Andrews “a gutless b----” for the crime — this is sports radio, remember — of expressing a mild opinion during an interview with pitcher Adam Wainwright during baseball’s All-Star Game. Minihane apologized for his comment.
Then there was ESPN commentator Stephen A. Smith, who suggested on ESPN2’s “First Take” last month that women were responsible for “provoking” men into acts of domestic violence, such as Baltimore Ravens running back Ray Rice’s beating of his fiancee. Faced with a massive backlash, Smith also apologized and was suspended for a week by ESPN.
Sports talk usually doesn’t get that sexist, but it also doesn’t regularly offer many opinions from the other sex, either. A few clips from the highlight reel:
●ESPN, the self-proclaimed “Worldwide Leader in Sports,” has had just two female panelists (Jackie MacMullan and Jemele Hill) among the 33 regular and guest panelists who have appeared on “Around the Horn,” its signature daily debate show, since the program started in 2002. “The Sports Reporters,” another ESPN blabfest, is somewhat better: It has put seven women on as regular or semi-regular panelists over the program’s 26-year run. (ESPN declined to comment for this story.)
●Among the top 100 sports-radio programs ranked by the trade magazine Talkers last year — a list containing 183 hosts and co-hosts — only two women made an appearance (Fox Sports Radio co-host Amy Van Dyken, whose program was ranked No. 76; and Dana Jacobson of CBS Sports Radio at No. 99).
●Of the 143 sports pundits whose picks and predictions are tracked by the Web site Pundittracker, only one is a woman (Ramona Shelburne, a columnist for ESPN.com’s Los Angeles site).
Is it the supply that’s lacking — that is, a pool of women who want to mix it up with the men on the air? Or is it the demand — a lack of interest among the overwhelmingly male sports audience to hear opinions from women? Or is it something else, such as timidity and sexism on the part of sports-media executives (overwhelmingly male) to give the ladies a shot?
CBS Sports Radio host Dana Jacobson, who once worked for ESPN. (Lorenzo Bevilaqua/ESPN via AP)
Answer: Maybe all of the above.
“Sports are still unquestionably positioned as a male domain, so the default experts are men,” said Marie Hardin, dean of Penn State’s communications department and an expert on sports media. “I’m not saying that women haven’t made great strides in opportunities to compete, to coach” — just this week the NBA’s San Antonio Spurs made Becky Hammon the first female assistant coach in major pro sports — “and to be part of the media around sports, but their numbers are too low to change the overall cultural sentiment around sports.”
Some of this is self-perpetuating, she says: Men have long dominated sports broadcasting, and men tend to hire other men.
And, she notes, fans have their own self-fulfilling expectations. Research by several scholars, including Hardin, indicates that sports viewers (typically but not entirely men) prefer to hear male voices when they watch sports, especially sports played by men. Women who comment on men’s sports are perceived as somewhat less credible. And women who comment on women’s sports are ranked even lower by fans, she said.
Hardin notes that the roles women have been able to achieve on sports broadcasts, such as hosts facilitating the conversation among pundits, don’t position women as the authoritative “voice” on a TV broadcast. The big jobs — play-by-play announcers, analysts, panel pundits — tend to go overwhelmingly to men. Throughout the long history of televised sports, only a tiny number of women, such as ESPN’s Pam Ward and Beth Mowins, have ever been play-by-play announcers on major men’s sports.
The only job dominated by women in TV sportscasting — its “pink-collar ghetto,” as Hardin puts it — is sideline reporting, a lesser role than the announcer or color commentator. It’s mostly younger women who fulfill these roles, reinforcing the perception that the job is primarily window dressing. Fox recently demoted its veteran NFL sideline reporter, Pam Oliver, after she dared to turn 53. She was replaced by Andrews, who is 36.
A different dynamic may be at play in sports radio. Women just aren’t clamoring to become hosts of the pugnacious call-in shows that dominate the format, says Chuck Sapienza, vice president of programming for ESPN 980 and Sportstalk570, two Washington-area stations owned by Redskins owner Daniel Snyder.
“Most women interested in broadcasting are interested in TV,” he says. “We try [to attract women]. We try a lot. It’s next to impossible.”
Sapienza regularly asks would-be interns and young job candidates about their career ambitions. Many of the young men want to break into, or move up in, sports radio. But Sapienza says, “I’ve never had a young woman tell me she wants to be a radio talk-show host. They want to be on �?SportsCenter.’ They want to be sideline reporters.”
Part of it, he reasons, may also be because of the absence of role models. There are no women on sports radio who approach the stature of Jim Rome, Dan Patrick or Mike Francesa, all major sports-radio stars. Nanci Donnellan, known as “the Fabulous Sports Babe,” once had a nationally syndicated radio show, but has had health problems in recent years. She now has an overnight show on an AM station in Tampa, WHFS.
The good news? If the playing field still isn’t exactly level for women, the balance may at least be starting to improve. Slowly.
Christine Brennan, a USA Today sports columnist, points out that women have begun to appear more frequently on TV as expert commentators and analysts on men’s sports. Among others: Dottie Pepper, a former pro golfer-turned-broadcaster, offered her views about Tiger Woods’s back problems on ESPN the other day; former soccer player Julie Foudy was an expert commentator on the recent World Cup; WNBA star Kara Lawson has weighed in on the NBA on ESPN.
“This would not have happened five years ago,” Brennan says. “ESPN would never have asked a woman to comment on a man. These are all breakthroughs in their own way.”
Brennan herself is proof of the improving climate. A one-time panelist on “The Sports Reporters,” she is a regular sports commentator on NPR and on such ABC News shows as “Good Morning America” and “Nightline.” “I’m doing more TV in my 50s than I did in my 30s and 40s,” she says.
Having more women on sports broadcasts isn’t just a question of equity, she argues, it’s smart business.
“TV sports has just about maxed out the male audience,” Brennan says. “If you want to grow your ratings, you’ve got millions of girls and women in this country who are growing up to be consumers of sports news and products. They’re obviously used to hearing a man talk about sports. But maybe there’s a 12-year-old girl somewhere who hears a woman’s voice and says, �?Let’s watch.’ And the sport and the network have just created a new fan.”
Lesley Visser, the veteran CBS sports reporter, takes the long view.
Back in the 1970s, when she became the first woman to cover the NFL as a reporter for the Boston Globe, Visser noted the surprised and occasionally hostile reception she’d get from the players, coaches, team officials and fans. The credentials on her press passes to games read, “No Women or Children in the Press Box.”
After she became a TV reporter in the 1980s, Visser started racking up firsts: the first woman to report on an NBA broadcast, the first to do a Final Four game, the first at a Super Bowl.
It’s not unusual to see a woman covering any of those events now.
“It takes time for a culture to change,” says Visser, 60. ”People don’t smoke as much as they once did, but they didn’t all stop smoking the day after we learned it was bad for you. It takes time.”
And this, too, will change, she says: “I think it’s coming. Is it moving fast enough for me? No. But it’s coming.” ||||| When the NFL on July 24 announced its suspension of Baltimore Ravens running back Ray Rice for allegedly knocking his then-fiance out cold in an Atlantic City casino in February, the league's discipline — just a two-game ban — drew a tidal wave of criticism.
The blowback came from far and wide after the league's announcement, with critics arguing that Rice's light suspension illustrated a lack of respect for women in general and for victims of domestic violence in particular.
But the outcry had another ripple effect. It made targets of female media members who voiced their opinions on Twitter. While the NFL's treatment of Rice demonstrated a lack of justice, common sense and compassion, the week since his suspension has underscored one truth as starkly as ever: On social media, women in the sports news business are forced to wade into a unique cesspool of sexual harassment, sports-fueled aggression and Internet anonymity.
A Twitter user named Matt Hayden told ESPN's Samantha Ponder she was proof "that female sports reporters are better off seen and not heard, that's why they're hired anyway."
After ESPN's Michelle Beadle blasted comments her colleague Stephen A. Smith made about Rice, she was called a "bitch" and a "c*nt" who deserved the beatings an ex-boyfriend gave her and would hopefully be "Patty Hearst'd" after ESPN eventually suspended Smith from the air for a week.
Male reporters, too, face trolling on Twitter and other platforms from aggressive sports fans. Reporters who are racial or ethnic minorities face their own distinct form of nastiness. And it's all part of larger social issues that extend well beyond sports or news. But it's been painfully apparent over the last week that the special brand of ugliness reserved for female sports reporters revolves specifically around their sex, looks and other attributes that don't apply to men.
Sports Illustrated editor and writer Richard Deitsch, who covers sports media, follows the industry as closely as anyone, frequently casts light on the treatment of its women and says the problem is only getting worse. Deitsch says he hears from women in the business "almost on a daily basis," and when it comes to social media, the overall trend is a negative one.
"What I've found in the last six to 12 months is that the intensity of the conversation these women are facing has gone up and the intensity generally leads to more negative comments than positive comments," Deitsch told Mashable. "I do think the attacks and the coarseness of the attacks have gotten more intense."
'The worst it's ever been'
Baltimore Ravens running back Ray Rice, alongside his wife Janay, speaks to the media about arrest for domestic assault. Image: Patrick Semansky/Associated Press
Sports radio host Amy Lawrence criticized the NFL's suspension of Rice on her program and paid the price online.
"I barely got the words out of my mouth before the reaction started flooding in," Lawrence wrote on her blog on July 28. "The phone lines, my Facebook page, and my Twitter feed blew up ... by far, the most vicious reaction was directed at me personally. I was called bitch, gold-digger, hack, idiot, dumb broad, delusional, ugly, clueless, and the worst host on CBS Sports Radio among other things."
Lawrence continued: "I was sexually harassed and called names I would never speak or print. In my 10 years of network radio, that was the worst it’s ever been."
While the problem may be worsening, it's not new. Justine Gubar, an Emmy-winning investigative producer who works for ESPN, traveled to Columbus, Ohio, in 2011 for a story about rules violations by iconic Ohio State coach Jim Tressel. Upset Buckeyes fans found her name, attacking her professionally and personally online. Her personal phone number was published online, fans left nasty voicemails on her home and mobile phones and her Facebook and Twitter page were inundated with abuse.
"Not only was it about the work I was doing, but everyone felt the need — and these were all men — to comment on the way I looked," Gubar told Mashable. "I'm not sure how that was relevant to the work I was doing, and the crazy thing was that a lot of this was on Facebook so I could see exactly who the people insulting me were and what they looked like. They weren't exactly model material."
Ohio Stadium is filled with fans Saturday, Nov. 18, 2006, after a college football game between top-rated Ohio State and No.2 Michigan in Columbus, Ohio. Image: Amy Sancetta/Associated Press
In mid-July, Fox announced it will replace longtime NFL sideline reporter Pam Oliver after 19 years with Erin Andrews on pro football broadcasts beginning this season. This provoked grumblings and some backlash that the network did so for cosmetic reasons. Both Oliver and Andrews are women, and both are well-respected professionally, but they also are very different in some ways.
Andrews is 17 years Oliver's junior, tall and blond. Oliver is 53 years old and, unlike Andrews, has never been the subject of slobbery Internet posts about her 'busting out of a teeny bikini.'
Many fans online blasted Fox for the swap, saying it was motivated by age, looks and even race. In some cases this had a twist of irony — as detailed here and pointed out by ESPN's Jemele Hill — given that Oliver's TV appearances in the last few years had regularly been accompanied by gleeful mockery of her looks on Twitter.
I'll say this: Considering some of the things I've seen some of you tweet about her, don't rally for Pam Oliver now #TooLate — Jemele Hill (@jemelehill) July 14, 2014
It's bad — but why?
Fox replaced Pam Oliver, left, with Erin Andrews, right, as its NFL sideline reporter for this season after Oliver had been on the job for 19 years. Both Oliver and Andrews have been the targets of sports fans on social media. Image: LM Otero/Charles Sykes/Associated Press
The misogynistic tendencies leads to two clear questions. First, why do male sports fans seem extra motivated to launch hyper-personal attacks online against women in sports media?
"That is a question that has yet to be answered through academic research, but the socialization of organized team sports as a masculine domain and rite of passage into manhood for many young boys probably plays a part," Edward Kian, a professor of sports media at Oklahoma State University, told Mashable via email. "In other words, many of the guys who sucked at organized sports and stopped playing at younger ages wrongly believe they are better than high-level female athletes in those sports. You see and hear this in the gym regularly, and it is laughably pathetic."
Public figures of all sorts are just a click away from the entire world, thanks the Internet and social media, as has been documented ad nauseam. And Sports Illustrated's Deitsch points to all of this being layered on top of a sports media ecosystem that increasingly relies on 24/7 coverage and passionate debate, saying that trickles down to fans.
"I think with sports being so turbo-charged based on opinion, the topic lends itself to debate and intensity," he told Mashable. "Certain networks capitalize on that debate and intensity for monetization reasons and that inevitably works its way onto social media."
Indeed, Beadle was attacked online after tweeting vehement criticism of comments regarding the Ray Rice suspension that her ESPN colleague Smith had made on First Take. (That's the network's bloviation-based daytime talk show that features incessant arguing between hosts and has veered into foot-in-mouth territory before.)
A problem with no clear solution
Which brings us to the second qeustion: How can the sexist vitriol be combated? Free speech law complicates policing online insults that fall short of outright threats — and that doesn't even take into account the practicality of doing so on networks with hundreds of millions of users. Twitter offered Mashable just a generic statement on reporting abusive content and striving to create a better service, while Facebook pointed toward its publicly available "community standards" and protocols for reporting abuse.
There's also the debate over whether it's better to ignore trolls completely — or at least as much as possible — or expose them through retweets and scathing replies. Both approaches have merits and shortcomings, but neither is perfect. And simply quitting a platform like Twitter isn't feasible for people who communicate for a living.
Unfortunate as it is, the vitriol faced by women in sports media appears to be one of the ugliest downsides to a digital age that's radically changed the sporting world for better and worse over the past few years.
The past several days starkly illuminated all of this after, as many commentators of all stripes agreed, the NFL fumbled a prime opportunity to send a message to its millions of fans about the consequences of abusing women — physically or online.
BONUS: 50 Stunning Sports Photos From 2013 ||||| Starting in 1996, Alexa Internet has been donating their crawl data to the Internet Archive. Flowing in every day, these data are added to the Wayback Machine after an embargo period. ||||| CBS Sports will make television history in September when it debuts the first all-female sports talk show, the network confirmed exclusively to The Big Lead.
The weekly show, which will air on CBS Sports Network, will not only feature an all-female cast, but will also be produced and directed by women.
“We’re really excited and proud to be launching the first ever all female sports talk show,” David Berson, the President of CBS Sports told The Big Lead. “We have been discussing and developing the show for well over a year. Internally and externally, there’s been universal enthusiasm and across-the-board support.”
Berson would not confirm any names connected to the show – it’s still unclear if the as-yet titled show will have one central host – but people familiar with the show’s plans who spoke on the condition of anonymity because the details were supposed to remain confidential revealed to The Big Lead six names who are expected to be regulars: CBS Sports veteran Lesley Visser, Dana Jacobson (who previously worked at ESPN), CBS NFL analyst Amy Trask, and sideline reporters Allie LaForce, Tracy Wolfson and Jenny Dell.
CBS would not reveal the show’s format, but sources say it will be something akin to The View meets Pardon the Interruption. It’s difficult to find a comparison for something this groundbreaking, but Berson did say it was going to be “a sports talk show featuring women; it’s not intended to be a women’s sports issue show.”
Unlike other networks, which are skittish to bring competitors onto their shows, Berson noted that the show would include “personalities from other media companies” as well as current and former athletes and team executives.
“It’s long overdue,” Berson said. “We feel we’re the right network and place for it with a tremendously respected roster of female sports journalists.”
Related: CBS Sports Network is Doing a 4-Hour NFL Pregame Show
Related: Tim Brando is Done at CBS Sports After 18 Years
Related: Bruce Feldman Leaving CBS Sports for Fox Sports | – The first all-female sports talk show is coming to television on CBS Sports—to be hosted, directed, and produced by women, The Big Lead reports. "We have been discussing and developing the show for well over a year," says David Berson, President of CBS Sports. "Internally and externally, there’s been universal enthusiasm and across-the-board support." He didn't reveal who will host the still-untitled show, due to start in September, but anonymous sources say Lesley Visser, Dana Jacobson, and Amy Trask will rule the desk, with Jenny Dell, Tracy Wolfson, and Allie LaForce on the sidelines. It will be "a sports talk show featuring women; it’s not intended to be a women’s sports issue show," says Berson. Other sources "say it will be something akin to The View meets Pardon the Interruption," reports The Big Lead—which got a snarky reaction at The Week: "Seriously: Would you ever see a male-led sports talk show described as 'akin to The View'?" The news comes just after Paul Farhi at the Washington Post called for more female sports panelists on TV ("Don’t women have opinions, too?") and about two weeks after another women-in-sports-media story made headlines: Baltimore Ravens running back Ray Rice got a two-game suspension for knocking out his girlfriend at a casino, and female reporters received vicious attacks on social media for calling it too light a punishment, reports Mashable. |
Image copyright Marcio Cabral Image caption Mr Cabral said flashes and a long exposure were needed to capture the scene
A winning entry in the Wildlife Photographer of the Year competition has been disqualified for featuring a taxidermy specimen.
The image, known as The Night Raider, shows an anteater moving towards a termite mound in a Brazilian reserve.
London's Natural History Museum, which runs the competition, says the use of stuffed animals breaches its rules.
The photographer, Marcio Cabral, denies he faked the scene and claims there is a witness who was with him on the day.
Other photographers and tourists were in the park at the same time and therefore "it would be very unlikely anyone wouldn't see a stuffed animal being transported and placed carefully in this position", he told BBC News.
But Roz Kidman Cox, the chair of judges for Wildlife Photographer of the Year (WPY), was stern in her criticism.
"This disqualification should remind entrants that any transgression of the rules and spirit of the competition will eventually be found out," she said.
Image copyright NHM Image caption The taxidermy specimen is held at a visitors’ centre at an entrance to the park
The Night Raider picture won the Animals In Their Environment category in the 2017 WPY awards. It was taken in Emas National Park.
The green lights are click beetles hoping to lure termites into being their prey with a bioluminescent display.
The anteater's appearance was described in the citation caption as being serendipitous - a "surprise bonus" that walked into the shot. But the Natural History Museum (NHM) says third parties recently raised concerns the image was staged - that the hungry interloper is in fact a static model that can be seen at a visitors' centre at an entrance to the reserve.
When alerted to this possibility, the museum asked five scientists to review the winning photo and to compare it with the centre's display model.
These experts, who included the NHM's own taxidermy specialist and South American mammal and anteater researchers, worked independently of each other, but they all came to the same conclusion - that the two animals were one and the same.
The scientists found the markings, the postures, the morphologies and even the positioning of the fur tufts to be just too similar.
Nature's reality
The NHM says Mr Cabral fully cooperated with the investigation, supplying RAW images for inspection that were taken "before" and "after" the winning scene. But none of these included the anteater.
"Unfortunately, I do not have another image of the animal because it is a long exposure of 30 seconds and ISO 5000," Mr Cabral said.
"After the flashes were fired, the animal left the place, so it was not possible to make another photo with the animal coming out of the place that is totally dark."
The WPY rules state that "entries must not deceive the viewer or attempt to misrepresent the reality of nature". And it is on this basis that The Night Raider has been stripped of its title and removed from display in the competition's UK tour.
Roz Kidman Cox has been a judge on WPY for more than 30 years. She told the BBC: "I find it disheartening and surprising that a photographer would go to such lengths to deceive the competition and its worldwide following.
"The competition places great store on honesty and integrity, and such a breach of the rules is disrespectful to the wildlife-photography community, which is at the heart of the competition."
Iberian wolf
This is not the first time the WPY judges have had to disqualify a winning entry. In 2009, they threw out the grand prize photo that supposedly depicted a wild Spanish wolf jumping over a gate.
A similar investigation concluded that the pictured animal was not wild at all, but a tame wolf from a zoo.
Ms Kidman Cox said the judges were always alert to the possibility that photos might be staged but that the artifice could be very hard to spot if the featured animals were in a natural pose in a low-lit scene.
"The judges themselves are chosen to include a range of skills and expertise, both biological and photographic, and are well able to question the veracity of an image," she added.
"The rules also make it clear that the competition champions honest and ethical photography, and they are translated into a number of languages to prevent any misunderstanding."
Mr Cabral describes his exclusion as a sad decision and one he will continue to contest.
The visitors' centre is locked at night and has guards and so he could not have had access to the model, the photographer says. He intends to return to Emas National Park later this year to collect evidence that he believes will exonerate him.
[email protected] and follow me on Twitter: @BBCAmos ||||| A prestigious wildlife photography competition has been rocked by scandal after one of the winners was disqualified for allegedly deploying a taxidermied anteater to stage the photo.
On Friday, the London Natural History Museum, which runs the Wildlife Photographer of the Year competition, announced "The Night Raider" by photographer Marcio Cabral had been disqualified after a thorough investigation.
"I find it disheartening and surprising that a photographer would go to such lengths to deceive the competition and its worldwide following," said the chair of the competition's jury, Roz Kidman Cox.
"The competition places great store on honesty and integrity, and such a breach of the rules is disrespectful to the wildlife photography community, which is at the heart of the competition."
Cabral, however, denies he faked the night photo, taken in Brazil's Emas National Park, with the photo winning the competition's 2017 "Animals in Their Environment" category.
"Marcio had been visiting the National Park for three years waiting for the right conditions to capture the glowing termite mounds," read the entry. "After days frustrated by rain, he was in for a surprise.
"A giant anteater ambled out of the darkness and stayed just long enough for Marcio to take a single picture, using a long exposure and flash to highlight his unexpected companion."
But according to the competition, an "anonymous source" came forward in March this year, "questioning the authenticity of the image". A subsequent investigation obtained photos of a taxidermied anteater on display at the entry to the national park (below). ||||| Natural History Museum takes down picture, but Marcio Cabral is adamant he did not fake it
The dramatic photograph of an anteater approaching a glowing termite mound in the dead of night was originally considered a worthy winner of a Wildlife Photographer of the Year award. The prize has now been withdrawn after judges noticed a problem: the anteater pictured is almost certainly a stuffed animal kept outside a visitor centre.
The Natural History Museum, which administers the awards, has disqualified the Brazilian wildlife photographer Marcio Cabral for attempting to deceive judges by submitting a picture of a taxidermy specimen in the “animals in their environment” category.
Facebook Twitter Pinterest The stuffed anteater that is kept on display at a visitor centre at the Emas National Park, Brazil. Photograph: NHM
After a “thorough investigation” involving two mammal experts and a taxidermy specialist from the museum, in addition to two South American experts, it was concluded that the photograph features the dead anteater that greets visitors at the entrance to Brazil’s Emas National Park.
“The five scientists, working independently of each other, all concluded that there are elements of the animal’s posture, morphology, raised tufts of fur and patterns on the neck and head that are too similar for the images to show two different animals,” said a spokesperson for the museum.
If he did fake this it’s a sign of desperation Brent Stirton, Wildlife Photographer of the Year
The investigation followed a tip-off from a third party that the photograph, entitled The Night Raider, broke competition rules, which demand that “entries must not deceive the viewer or attempt to misrepresent the reality of nature”.
Cabral, who strongly denies using a stuffed animal in the image, claimed in his original submission that he had spent three years waiting for the right conditions to capture the glowing termite mounds. According to his original caption, the photographer spent days frustrated by rain in Emas National Park before a “giant anteater ambled out of the darkness” and stayed “just long enough” for him to take a single photo.
The museum said Cabral co-operated with the investigation and supplied image files taken before and after the winning shot. None of them included the anteater.
According to the museum, Cabral also offered a witness who claims he also saw the animal alive, but the investigators were unconvinced.
Roz Kidman Cox, a member of the 2017 judging panel, issued a stern warning to others who submit dubious images in an attempt to win awards: “I find it disheartening and surprising that a photographer would go to such lengths to deceive the competition and its worldwide following.”
“The competition places great store on honesty and integrity, and such a breach of the rules is disrespectful to the wildlife photography community, which is at the heart of the competition.”
The image had been on display at the Natural History Museum since October as part of a paid exhibition. On Friday morning it was removed from the gallery wall and replaced with a notice explaining the alleged falsification.
Wildlife Photographer of the Year 2017 – the winners Read more
Fellow photographers were baffled by Cabral’s apparent attempt to dupe judges. “If that’s true, he’s just done himself so much more harm than is necessary,” said Brent Stirton, who won the overall Wildlife Photographer of the Year prize in the same awards ceremony. “There are plenty of experts in our field and sooner or later, if you do that kind of thing, it catches up with you.”
Stirton said winning such an award can make a “huge difference for people who on their way up”. “For the wildlife world, this is their Oscars. This is a big deal. Guys spend their whole career trying to win one of these ones. It’s one that counts.
“I’m just a bit sorry for this guy. I’m not sure if he did fake this, but if he did it’s a sign of desperation. I don’t want to be that guy because that kind of stain will follow you around. Even if you take the greatest wildlife picture ever taken, people are going to doubt it.”
Stirton said fake images would usually be detected: “A great deal of us are just photographers and we rely on genuine experts to know how animals behave. Those people spend their whole life looking at those animals. If you think you can slip one past those guys, it’s optimistic at best and arrogant at worst.
“Why take that kind of risk? Because surely if you do that and collect an award, in the back of your mind you’re waiting to be uncovered?”
This is not the first time the competition has been hit by accusations of fakery. In 2010, the overall winner lost his award following claims that he hired a tame wolf to feature in the winning photo. | – It's that moment every wildlife photographer hopes for: an image in which the resident fauna wanders perfectly into frame. And that supposedly happened to such great effect for Marcio Cabral in Brazil's Emas National Park that his photo "The Night Raider," which depicts an anteater staring down a glowing termite mound, took first place in the "Animals in Their Environment" category of the London Natural History Museum's photo competition—a contest the Guardian says "for the wildlife world … is their Oscars." But as BuzzFeed reports, that anteater likely didn't just "amble" into the shot after all, as Cabral claimed: The photographer has been disqualified for his win after allegations that he placed a stuffed anteater into the photo (see the image up close for yourself here). After an "anonymous source" came forward, five specialists were brought in to independently compare the anteater in Cabral's pic to a taxidermied anteater at the park's entrance. Their findings: "There are elements of the animal's posture, morphology, raised tufts of fur, and patterns on the neck and head that are too similar for the images to show two different animals." Cabral continues to insist it was a live anteater he captured, and he even claims to have a witness who saw it. Organizers aren't budging—no one will take Cabral's spot in the winner's circle, contest organizers say, and he's barred from taking part in the competition again. "I find it disheartening and surprising that a photographer would go to such lengths to deceive the competition and its worldwide following," the head of the contest's jury says. (Two hunters in Brazil were killed by giant anteaters.) |
SECTION 1. SHORT TITLE.
This Act may be cited as the ``Farm to School Act of 2015''.
SEC. 2. ACCESS TO LOCAL FOODS: FARM TO SCHOOL PROGRAM.
Section 18(g) of the Richard B. Russell National School Lunch Act
(42 U.S.C. 1769(g)) is amended--
(1) in paragraph (1)--
(A) by striking the paragraph designation and
heading and all that follows through ``In this
subsection, the'' and inserting the following:
``(1) Definitions.--In this subsection:
``(A) Agricultural producer.--The term
`agricultural producer' means a farmer, rancher, or
fisher (including of farm-raised fish).
``(B) Eligible school.--The''; and
(B) in subparagraph (B) (as so redesignated), by
inserting ``, including the summer food service program
for children under section 13 and the early care and
afterschool portions of the child and adult care food
program under section 17,'' after ``under this Act'';
(2) in paragraph (2), by striking ``and nonprofit entities
through grants and technical assistance'' and inserting ``land-
grant colleges and universities, and nonprofit entities through
grants, technical assistance, and research'';
(3) in paragraph (3)--
(A) in subparagraph (A)--
(i) in clause (i), by inserting ``and
technical assistance'' after ``training'';
(ii) by redesignating clauses (vi) and
(vii) as clauses (vii) and (viii),
respectively; and
(iii) by inserting after clause (v) the
following:
``(vi) implementing agricultural literacy
and nutrition education;''; and
(B) by striking subparagraph (C) and inserting the
following:
``(C) Improved procurement and distribution.--
``(i) In general.--In awarding grants under
this subsection, the Secretary shall seek to
improve local food procurement and distribution
options for agricultural producers and eligible
schools.
``(ii) Aggregation, processing,
transportation, and distribution.--In advancing
local food procurement options and other farm
to school objectives, the Secretary may provide
funding for projects that include innovative
approaches to aggregation, processing,
transportation, and distribution.
``(D) Awards.--
``(i) Maximum amount.--The total amount
provided to a grant recipient under this
subsection shall not exceed $200,000.
``(ii) Term.--The term of an award shall
not exceed 3 years.
``(iii) Purpose and scope.--In making
awards under this subsection, the Secretary
shall seek to make awards of diverse amounts
and duration in order to best match the award
to the purpose and scope of the project to be
funded.
``(E) Limitation.--The Secretary may not award a
grant under this subsection if the grant funds would be
used solely for the purpose of carrying out a
conference.'';
(4) in paragraph (5)--
(A) by redesignating subparagraphs (A) through (G)
as clauses (i) through (vii), respectively, and
indenting the clauses appropriately;
(B) in clause (ii) (as so redesignated), by
striking ``lunches'' and inserting ``meals'';
(C) in the matter preceding clause (i) (as so
redesignated), by striking ``To the maximum extent
practicable'' and inserting the following:
``(A) In general.--To the maximum extent
practicable'';
(D) in clause (vi) (as so redesignated), by
striking ``and'' at the end;
(E) by redesignating clause (vii) (as so
redesignated) as clause (viii);
(F) by inserting after clause (vi) (as so
redesignated) the following:
``(vii) expand the selection of local
commodities for eligible schools; and''; and
(G) by adding at the end the following:
``(B) Tribal community projects.--In the case of
projects serving tribal communities, the Secretary
shall, to the maximum extent practicable, give highest
priority to projects that best use products from tribal
agricultural producers, as determined by the
Secretary.'';
(5) in paragraph (7)--
(A) by redesignating subparagraphs (A) through (C)
as clauses (i) through (iii), respectively, and
indenting appropriately;
(B) by striking the paragraph designation and
heading and all that follows through ``nonprofit
entities--'' and inserting the following:
``(7) Technical assistance and research.--
``(A) In general.--The Secretary shall provide
technical assistance, research, and information to
assist eligible schools, State and local agencies,
Indian tribal organizations, agricultural producers or
agricultural producer groups, and nonprofit entities--
'';
(C) in subparagraph (A) (as so designated)--
(i) in clause (ii) (as so redesignated), by
striking ``and'' at the end;
(ii) in clause (iii) (as so redesignated),
by striking the period at the end and inserting
``; and''; and
(iii) by adding at the end the following:
``(iv) to increase awareness of, and
participation in, farm to school programs among
agricultural and aquaculture producers or
agricultural producer groups, including
beginning, veteran, and socially disadvantaged
farmers and ranchers.''; and
(D) by adding at the end the following:
``(B) Review.--
``(i) In general.--Not later than 1 year
after the date of enactment of the Farm to
School Act of 2015 and every 3 years
thereafter, the Secretary shall review and
submit to the Committee on Agriculture and the
Committee on Education and the Workforce of the
House of Representatives and the Committee on
Agriculture, Nutrition, and Forestry of the
Senate a report that describes the progress
that has been made in identifying and
eliminating regulatory and other barriers
related to developing farm to school programs.
``(ii) Requirements.--In preparing the
report, the Secretary shall examine--
``(I) the direct and indirect
regulatory compliance costs affecting
the production and marketing of locally
or regionally produced agricultural
food products to school food programs;
and
``(II) barriers to local and
regional market access for small-scale
production.'';
(6) in paragraph (8)--
(A) in subparagraph (A), by striking ``$5,000,000''
and inserting ``$15,000,000''; and
(B) by adding at the end the following:
``(C) Administration.--Of the funds provided to the
Secretary under subparagraph (A), not more than 5
percent may be used to pay administrative costs
incurred by the Secretary in carrying out this
subsection.''; and
(7) in paragraph (9), by striking ``2011 through 2015'' and
inserting ``2016 through 2021''. | Farm to School Act of 2015 This bill amends the Richard B. Russell National School Lunch Act to reauthorize the Department of Agriculture's (USDA's) Farm to School Program through FY2021 and modify the program. The program currently provides grants and technical assistance to schools, state and local agencies, Indian tribal organizations, agricultural producers, and nonprofit entities to improve access to local foods in schools. The bill makes schools participating in the Summer Food Service Program for children, the early care and afterschool portions of the Child and Adult Care Food Program, and the School Breakfast Program eligible to participate in the program. It also permits USDA to provide land-grant colleges and universities with grants, research, and technical assistance under the program. The purposes for grants awarded under the program are expanded to include agricultural literacy and nutrition education. The bill requires USDA to provide technical assistance, research, and information to increase awareness of and participation in farm to school programs among agricultural producers. In awarding grants, USDA must improve local food procurement and distribution options for agricultural producers and eligible schools. USDA is permitted to fund projects that include innovative approaches to aggregation, processing, transportation, and distribution. The bill establishes new limitations on the amount and duration of grants. The bill also establishes reporting requirements and limits funds that may be used for administrative costs. |
SECTION 1. SHORT TITLE.
This Act may be cited as the ``Combating Terrorism Financing Act of
2007''.
SEC. 2. INTERSTATE TRANSPORTATION OF CRIMINAL PROCEEDS AND ``REVERSE''
MONEY LAUNDERING.
(a) In General.--Section 1957(a) of title 18, United States Code,
is amended to read as follows:
``(a)(1) Whoever, in any of the circumstances set forth in
subsection (d)--
``(A) conducts or attempts to conduct a monetary
transaction involving property of a value greater than $10,000
that is derived from specified unlawful activity, knowing that
the property is derived from some form of unlawful activity; or
``(B) conducts or attempts to conduct a monetary
transaction involving property of a value greater than $10,000,
with the intent to promote the carrying on of specified
unlawful activity,
shall be punished as provided in subsection (b).
``(2) Whoever, in the any of the circumstances set forth in
subsection (d), transports, attempts to transport, or conspires to
transport more than $10,000 in currency in interstate commerce--
``(A) knowing that the currency was derived from some form
of unlawful activity; or
``(B) knowing that the currency was intended to be used to
promote some form of unlawful activity,
shall be punished as provided in subsection (b).''.
(b) Penalty.--Section 1957(b) of title 18, United States Code, is
amended--
(1) in paragraph (1), by striking ``paragraph (2)'' and
inserting ``paragraphs (2) and (3)''; and
(2) by inserting after paragraph (2) the following:
``(3) The maximum period of incarceration for a person convicted of
an offense under subsection (a)(1)(B) must not exceed the statutory
maximum for the offense being promoted.''.
(c) Conforming Amendment.--Section 1957(f) of title 18, United
States Code, is amended--
(1) in paragraph (2) by striking ``and'' after the
semicolon;
(2) in paragraph (3), by striking the period and inserting
``; and''; and
(3) by inserting at the end the following:
``(4) the term `conducts' has the same meaning as it does
for purposes of section 1956 of this title.''.
(d) Heading.--
(1) In general.--Section 1957 of title 18, United States
Code, is amended in the heading by inserting ``or in support of
criminal activity'' after ``specified unlawful activity''.
(2) Chapter analysis.--The item relating to section 1957 in
the chapter analysis for chapter 95 of title 18, United States
Code, is amended to read as follows:
``1957. Conducting monetary transactions in property derived from
specified unlawful activity or in support
of criminal activity.''.
SEC. 3. FREEZING BANK ACCOUNTS OF PERSONS ARRESTED FOR OFFENSES
INVOLVING THE MOVEMENT OF MONEY ACROSS INTERNATIONAL
BORDERS.
Section 981(b) of title 18, United States Code, is amended by
adding at the end the following:
``(5)(A) If a person is arrested or charged in connection
with an offense described in subparagraph (C) involving the
movement of funds into or out of the United States, the
Attorney General may apply to any Federal judge or magistrate
judge in the district in which the arrest is made or the
charges are filed for an ex parte order restraining any account
held by the person arrested or charged for not more than 30
days, except that the time may be extended for good cause shown
at a hearing conducted in the manner provided in rule 43(e) of
the Federal Rules of Civil Procedure. The court may receive and
consider evidence and information submitted by the Government
that would be inadmissible under the Federal Rules of Evidence.
``(B) The application for the restraining order referred to
in subparagraph (A) shall--
``(i) identify the offense for which the person has
been arrested or charged;
``(ii) identify the location and description of the
accounts to be restrained; and
``(iii) state that the restraining order is needed
to prevent the removal of the funds in the account by
the person arrested or charged, or by others associated
with such person, during the time needed by the
Government to conduct such investigation as may be
necessary to establish whether there is probable cause
to believe that the funds in the accounts are subject
to forfeiture in connection with the commission of any
criminal offense.
``(C) A restraining order may be issued pursuant to
subparagraph (A) if a person is arrested or charged with any
offense for which forfeiture is authorized under this title,
title 31, or the Controlled Substances Act.
``(D) For purposes of this paragraph--
``(i) the term `account' includes any safe deposit
box and any account (as defined in section 5318A(e)(1)
and (e)(2)) at any financial institution;
``(ii) the term `account held by the person
arrested or charged' includes an account held in the
name of such person, and any account over which such
person has effective control as a signatory or
otherwise.
``(E) Restraint pursuant to this paragraph shall not be
deemed a seizure for purposes of subsection 983(a) of this
title.
``(F) A restraining order issued pursuant to this paragraph
may be executed in any district in which the subject account is
found, or transmitted to the central authority of any foreign
state for service in accordance with any treaty or other
international agreement.''.
SEC. 4. USING BLANK CHECKS IN BEARER FORM TO SMUGGLE MONEY.
Section 5316 of title 31, United States Code, is amended by adding
at the end the following:
``(e) Monetary Instruments With Amount Left Blank.--For purposes of
this section, a monetary instrument that has the amount left blank
shall be considered to have a value in excess of $10,000 if the
instrument was drawn on an account that contained or was intended to
contain more than $10,000 at the time the instrument was being
transported, or at the time it was negotiated or was intended to be
negotiated.''.
SEC. 5. PROHIBITING MONEY LAUNDERING THROUGH HAWALAS, OTHER INFORMAL
VALUE TRANSFER SYSTEMS, AND CLOSELY RELATED TRANSACTIONS.
Section 1956(a)(1) of title 18, United States Code, is amended by
striking ``For purposes of this paragraph, a financial transaction''
and inserting ``For purposes of this paragraph and section 1957, a
financial transaction or a monetary transaction''.
SEC. 6. SECTION 1957 VIOLATIONS INVOLVING COMMINGLED FUNDS AND
STRUCTURED TRANSACTIONS.
Section 1957 of title 18, United States Code, is amended by adding
after subsection (f) the following:
``(g) The Government may satisfy the $10,000 requirement in
subsection (a)(1) by showing that--
``(1) the monetary transaction involved the transfer,
withdrawal, encumbrance, or other disposition of more than
$10,000 from an account in which more than $10,000 in proceeds
of specified unlawful activity was commingled with other funds;
or
``(2) the defendant conducted a series of monetary
transactions in amounts under $10,000 that exceeded $10,000 in
the aggregate and that were closely related to each other in
terms of such factors as time, the identity of the parties
involved, the nature or purpose of the transactions or the
manner in which they are conducted.''. | Combating Terrorism Financing Act of 2007 - Amends the federal criminal code to: (1) expand prohibitions against conducting monetary transactions over $10,000 for the purpose of engaging in interstate criminal activities; (2) authorize the Attorney General to obtain a 30-day ex parte court order freezing the bank account of any individual arrested or charged for crimes involving the movement of funds into or out of the United States; (3) expand money laundering prohibitions to include monetary transactions; and (4) include monetary transactions involving commingled funds or structured transactions in prosecuting interstate transfers of funds greater than $10,000 for criminal purposes.
Includes within the requirement to report monetary transactions exceeding $10,000 blank monetary instruments in bearer form drawn on accounts found to contain more than $10,000. |
Egyptian businessman Mahmoud Abdel-Salam Omar accused of sexually abusing hotel maid at The Pierre
Vic Nicastro for News Egyptian businessman Mahmoud Abdel-Salam Omar, accused of groping maid at The Pierre hotel, is led by NYPD detectives from the 19th Precinct early Tuesday.
The hotel maid allegedly groped by an Egyptian businessman, immediately reported it to a supervisor but was told to wait a day to speak to security, sources said Tuesday.
The supervisor's decision explains why Sunday night's alleged assault was not reported to police until Monday morning.
Mahmoud Abdel-Salam Omar, 74, the former head of the Bank of Alexandria and now chairman of a leading Middle Eastern salt company, is accused of locking the 44-year-old maid inside his $900-a-night room at The Pierre on Sunday.
Channeling his inner Dominique Strauss-Kahn, Omar called for room service requesting tissues and answered the door in his pajamas, police sources said.
When the maid - whom he had not specifically asked for - arrived at his 10th-floor room, he asked her to put the box of tissues on a table, sources said. As she moved toward the table, he locked the door.
"He locked her in the room and had her trapped," a police source said. "He grabbed her breasts, groped her. He was grinding against her."
Omar then asked the maid for her phone number, a police source said. After she gave him a made-up number he let go, and she fled the room.
The incident happened about 6 p.m. on Sunday but was not reported to police until Monday morning.
In a statement Monday night, hotel management said they made the safety "of our guests and staff," a priority.
"We take all complaints very seriously and investigate thoroughly. This incident has been formally reported to the New York Police Department and is under investigation. We will fully comply with the investigation as requested," the statement read.
Despite the delay, investigators believe the woman's story.
"Experienced NYPD detectives found the complainant to be credible," said Paul Browne, the NYPD's top spokesman.
Omar was arrested at the hotel Monday afternoon and charged with sexual abuse, unlawful imprisonment, forcible touching and harassment, officials said.
The financier paused briefly as he was led out of the 19th Precinct stationhouse early Tuesday and stared mutely at reporters with a stunned expression.
"He's an old man," said a friend who tried to visit Omar in the police station but was turned away. "He's a good man and also a grandfather."
At the posh hotel, news of the alleged attack spread quickly.
"When I came in they were all talking about it," said a bellman, who declined to give his name. "When she came to his room, he got carried away. He started grabbing at her. He wouldn't let her go."
The maid has worked at the hotel for about a year, co-workers said. She did not return to her job Monday.
"I don't want to say it, but he tried to rape her," the bellman added. "It's a total copycat of what happened with the French guy."
Strauss-Kahn, the former head of the International Monetary Fund and a leading French presidential candidate, was arrested May 14 for allegedly forcing himself on a maid at the Sofitel in Manhattan.
He remains under house arrest in a posh Tribeca townhouse.
Omar was head of the Bank of Alexandria in Egypt before becoming chairman of the Egyptian salt company El-Mex Salines Co.
"They were saying the guest was a very nice guy, and then this," said a shocked housekeeper at the hotel. "Human beings are strange."
With Kerry Wills
[email protected] ||||| A former chairman of one of Egypt's major banks was arrested Monday on charges of sexually abusing a maid at a Manhattan hotel, just weeks after the arrest of former International Monetary Fund chief Dominique Strauss-Kahn on similar allegations, police said.
Mahmoud Abdel Salam Omar is accused of sexually abusing the maid at The Pierre, a luxury hotel near Central Park and Fifth Avenue on the Upper East Side, police said.
The maid was called to Omar's room Sunday night to drop off tissues, police said. But once inside the 74-year-old's room, police said Omar would not let her leave and touched her inappropriately. The encounter was not reported until Monday, police said.
Paul Browne, a spokesman for the New York City Police Department, said detectives found the complainant to be credible.
There was no immediate information on whether Omar had an attorney. He was being held Monday night at a police precinct.
Police said further details will be released at the suspect's arraignment, expected to take place Tuesday.
Omar is the former chairman of Egypt's Bank of Alexandria, but is currently an executive with El-Mex Salines Co., according to the salt production company's website.
The Pierre said it will "fully comply with the investigation," according to a statement read over the phone by a hotel manager. "The Pierre's priority is the safety of our guests and staff," the statement also said.
The Pierre is owned by Taj Hotels Resorts and Palaces of India.
The hotel attack comes about two weeks after Strauss-Kahn quit as managing director of the IMF, on May 18, after he was charged with sexually assaulting a maid at a different city hotel, the Sofitel, near Times Square. He has denied the allegations, but is under house arrest as he awaits trial. | – The high-profile arrest of Dominique Strauss-Kahn apparently wasn't enough to convince one exec that he should keep his hands off New York City's maids. Prominent Egyptian banker Mahmoud Abdel Salam Omar was arrested yesterday and charged with sexually abusing a maid at a Manhattan hotel, barely 2 weeks after the former IMF chief was arrested on similar charges, AP reports. Police say the maid was called to the 74-year-old executive's room at the Pierre to drop off tissues, but once she was inside the room, he refused to let her leave and groped her. "When she came to his room, he got carried away. He started grabbing at her. He wouldn't let her go," a hotel bellman tells the New York Daily News. "It's a total copycat of what happened with the French guy." Omar, the former chairman of one of Egypt's biggest banks, is being held on charges of sexual abuse, unlawful imprisonment, forcible touching, and harassment. |
Son of the Late Dana Plato Commits Suicide
or leave a comment of your own See what other readers have to say about this story –
First Joni Richardson endured the death of her daughter-in-law, Diff'rent Strokes star Dana Plato, in 1999. Now almost exactly 11 years later, Plato's son, Tyler Lambert, committed suicide at the age of 25."It's a shame that such a talented human being would do this with his life," Richardson tells PEOPLE. "He had all the opportunities in the world and we just can't understand it."According to Richardson, her grandson, a cameraman and amateur songwriter, had long struggled with his mother's premature death at age 36. Plato died of a prescription pill overdose on May 8, 1999. It was around the time of Mother's Day, Richardson notes, making the anniversary that much harder.Lambert died of a gunshot wound to the head on May 6. At the time, Richardson claims, he had been experimenting with drugs and alcohol, a factor she believes contributed directly to his death."He was talking so sweet to me on the phone that morning," she says. "But you never can tell what's in their mind."She adds that Lambert's body is being cremated, and there will be no memorial."Our lives have just been wrapped around him," Richardson says. "It's just devastating." ||||| Tyler Lambert once aspired to follow his famous mother, "Diff'rent Strokes" actress Dana Plato, into show business. Instead, like her, he took a detour into drugs and eventual suicide.
Johnny Whitaker, Plato's former manager and a friend of the family, told ABCNews.com he once tried to intervene in Lambert's drug use.
"I did say, 'You know your mother had a problem, which means you may have a problem because it is a family disease,'" said Whitaker, a former child actor who played Jody on "Family Affair" and is now a certified drug counselor. "Dana passed away because of the disease. And when the toxicology reports come in, I'm sure they will show something."
Lambert, 25, committed suicide on May 6, just days before Mother's Day and the 11th anniversary of Plato's 1999 death from a drug overdose.
In the days leading up to Lambert's suicide, a long-time family friend told Whitaker that Lambert had "become very withdrawn and hadn't talked to anybody for three or four days." The same friend told Whitaker that Lambert always said, "he wanted to be with Mom."
The Tulsa, Okla., office of the Chief Medical Examiner confirmed to ABCNews.com that Lambert died last week from a self-inflicted shotgun wound to the head. Toxicology test results are still pending.
Whitaker said Lambert's family once asked him to talk to the young man, an aspiring rapper and singer, about his drug use. At the time Lambert only admitted to using marijuana, Whitaker said.
"I kept the door open and let him know I would be there," Whitaker said. "He wasn't ready to work on it."
Lambert was just 14 when his mother took her own life, overdosing on prescription pills on May 8, 1999. She was 34 when she died.
Plato married Lambert's father, Lanny Lambert. in 1984. Tyler was born a year later. The couple divorced in 1990, and Lanny Lambert was given custody of Tyler.
Even though Lambert mostly grew up with his paternal grandmother, Joni Richardson, he was attached to his mother.
"Dana did absolutely adore her son," Whitaker said.
But he also said Lambert thought he had a closer relatonship with his mother than he really did.
"They didn't," Whitaker said. "Emotionally they did. Physically and actually, they didn't."
Nonetheless, Lambert struggled every Mother's Day.
"Mother's Day was always a difficult time, not only because it was Mother's Day but the anniversary of Dana's death," Whitaker said.
Dana Plato's Difficult Life
Plato appeared to have a bright future ahead of her when she landed the role of Kimberly Drummond on "Diff'rent Strokes." The show was a hit from its 1978 premiere, and Plato charmed audiences. But she was written off the series in 1984 amid rumors of drug use, and she struggled to find other roles.
In 1989, Plato bared all for Playboy and began starring in B-movies. From there, she dabbled in softcore pornography, including a 1997 feature based on her "Diff'rent Strokes" past.
Meanwhile, legal and substance abuse problems plagued the actress. In 1991 she was arrested attempting to rob a video store at gunpoint, and the following year she was arrested for forging a Valium prescription.
Plato's drug addiction eventually took her life -- she died after overdosing on Vanadom and Vicodin.
Troubled Stars of the 1980s
Here are the stories of nine other child stars from 1980s TV who ended up plagued with problems.
Andrew Koenig
In February, family and friends found "Growing Pains" actor Andrew Koenig's body in a Vancouver, British Columbia park, after he went missing for nearly two weeks.
His father Walter Koenig, an actor best known for his role as Chekov on "Star Trek," said his son killed himself after a liftetime suffering from depression.
Though the 80s made him a star, Koenig had been trying to escape his fame as "Growing Pains" goofball Richard "Boner" Stabone.
At the time of his disappearance, his father told ABC News: "He's been depressed. He's trying to get ahead in this business, and he's been working at it a long time."
The younger Koenig, who appeared on "Star Trek: Deep Space Nine" and played The Joker in 2003's "Batman: Dead End," hated being known for his "Growing Pains" role and "Star Trek" connection, according to his friend, writer/producer Lance Miccio.
"When I introduced him to people, he said, 'Never say my dad's Chekov and never say I played Boner,'" Miccio told ABCNews.com. "He didn't want to be known as Boner his whole life. That's something that affected him."
Tracey Gold
Koenig's "Growing Pains" co-star, Tracey Gold, has also whethered the ups and downs of Hollywood. Gold rocketed to teen stardom after being cast as Carol Seaver in the series.
But while she thrived on TV, behind the scenes, Gold struggled with anorexia. In 1992, her mother, Bonnie Gold, told People magazine that she burst into tears when she visited her daughter on the "Growing Pains" set in 1985 and was shocked to find she had wasted away to 90 lbs.
After seeking treatment in the early '90s, Gold transitioned from "Growing Pains" to acting in TV movies. But in 2004, she was arrested for driving under the influence after she rolled her SUV, carrying her husband and her three young sons, down a California highway embankment.
Gold's 7-year-old son, Sage, sustained the worst injuries, a broken clavicle and a head wound. The actress spent five hours in prison before being released on $50,000 bail. Gold later plead guilty to a felony DUI charge and was sentenced to one month in a work release program, 240 hours of community service, and three years of probation.
MacKenzie Phillips
In September 2009, actress Mackenzie Phillips revealed to Oprah Winfrey that her rock star father, John Phillips, raped her at age 18, sparking a 10-year-long consensual sexual relationship. Phillips, 49, the former star of '70s-'80s sitcom "One Day at a Time," said she was first raped by her father, the lead singer of the Mamas and the Papas, in a hotel room while passed out after a drug binge. (She also has a history of substance abuse issues.)
The relationship continued long after she married Jeff Sessler when she was 19-years-old, and ended only when she became pregnant and feared her father was the baby's father, Phillips said. Her father paid for an abortion. "I woke up that night from a blackout to find myself having sex with my father," Phillips said on "Oprah," reading an excerpt from her new book, "High on Arrival." "I don't know how it started."
Corey Feldman
During the 1980s, television was Corey Feldman's oyster. After landing a starring role in a McDonald's commercial at age three, he appeared in dozens of television shows, including "Mork and Mindy," "One Day at a Time," "Cheers" and "Eight is Enough." Feldman successfully crossed over into film, co-starring in box office boons like '85's "The Goonies" and '86's "Stand By Me."
But Feldman's success couldn't solve his problems. He worked constantly to escape parents who he claimed abused him, and at age 15, was granted legal emancipation from Sheila and Robert Feldman. Neverending exposure to the Hollywood lifestyle led to an appetite for drugs, and in 1990, Feldman was arrested for heroin possession -- twice. He went to rehab the following year.
"It took people a long, long time to forgive me. I was just a kid making mistakes like any other kid," he told the Phoenix New Times in 2000.
These days, Feldman's back on his feet. In 2002, he channeled his trials and tribulations in the business into a solo album, "Former Child Actor" and appeared on the first season of VH1's "The Surreal Life." He currently stars in the A&E; reality TV series "The Two Coreys" with fellow '80s child star, Corey Haim.
Jodie Sweetin
"Full House" sweetheart Jodie Sweetin didn't grow up to resemble her goody-two-shoes character at all. At age 22, the star of the '80s and '90s sitcom developed a debilitating daily meth habit that she kept a secret from her then-husband, LAPD officer Shaun Holguin.
In 2005, after a night of partying landed her in the hospital, Sweetin sought treatment. Once sober, she divorced Holguin and married Cody Herpin, the father of her daughter Zoie.
But in November 2008, Sweetin split with Herpin. Last year, she came out with the book "unSweetined," in which she reveals she kept the meth, cocaine and ecstasy binges going while she claimed to be sober. In one passage, she talks about breaking into tears while addressing a crowd at Wisconsin's Marquette University about her "trials and tribulations."
"I talked about growing up on television and about how great my life was now that I was sober, and then midspeech I started to cry," Sweetin writes. "The crowd probably thought that the memories of hitting rock bottom were too much for me to handle. Or maybe they thought the tears were just a way for an actor to send a message that drugs are bad. I don't know what they thought."
"I know what they didn't think," she continues. "They didn't think I was coming down from a two-day bender of coke, meth, and ecstasy and they didn't think that I was lying to them with every sentence that came out of my mouth."
Dustin Diamond
Who would've expected Screech to turn into a sexual freak? Dustin Diamond, who played the loveable nerd Samuel "Screech" Powers on "Saved by the Bell" and its precursor, "Good Morning Miss Bliss," through the late '80s and '90s, seemed allergic to scandal as a teen.
But in 2006, Diamond released a sex tape, "Screeched," aka "Saved By the Smell." It depicted the TV nerd in more detail than any fan wanted to see, and Diamond was panned for participating in the decidedly un-sexy endeavor.
His manager, Roger Paul, told the New York Daily News that he hoped the tape would raise Diamond's profile and help him get back into acting of the non-pornographic variety. Still, Diamond's relying on his past to get him through the present. Last year, he released "Behind the Bell," a book about his sitcom days in which he claims that drugs and sex were the rule on the "Saved by the Bell" set.
Gary Coleman
Plato's "Diff'rent Strokes" co-star, Gary Coleman, has seen his fair share of troubles. While he turned into a pop culture icon thanks to his signature line on the show, "What'choo talkin' 'bout, Willis?," Coleman became infamous for his problems with the law.
In 1989, Coleman sued his parents and former manager over misappropriation of his $3.8 million trust fund.Though he won a ruling in excess of $1.2 million in 1993, Coleman filed for bankruptcy six years later, and blamed his financial problems on mismanagement of his trust.
Coleman has also been cited for disorderly conduct multiple times, and in 1998, was charged with assault after punching bus driver Tracy Fields. He plead no contest and was ordered to pay Fields' hospital fees. Most recently, in January, he was arrested on a domestic violence assault warrant in Utah, and spent a night in jail.
Adam Rich
Adam Rich may have charmed audiences as adorable Nicholas Bradford on "Eight Is Enough," but in real life, his shenanigans have been far from cute.
After leaving "Eight Is Enough" in 1981, Rich made a handful of guest appearances on shows including "CHiPS" and "Baywatch." Apparently, those guest roles didn't give him enough dough. In 1991, he was arrested for breaking through a pharmacy window in an attempt to steal drugs. He was bailed out of jail by his "Eight is Enough" dad, Dick Van Patten, only to be arrested for shoplifting again.
Rich pleaded no contest to both charges, but his legal troubles didn't end there. In 2003, he racked up a misdemeanor DUI arrest after almost smashing into a police car in Los Angeles, and also plead no contest to those charges.
Jaimee Foxworth
Jamiee Foxworth's post-'80s TV career is one her "Family Matters" dad would probably condemn.
After playing youngest daughter Judy Winslow on the sitcom from 1989 to 1993, Foxworth was written out of the show with no explanation. The actress turned to drugs and alcohol and attempted to supplement her meager funds by starring in pornographic movies under the name Crave.
In 2008, Foxworth sought help for her substance abuse problems by participating in VH1's "Celebrity Rehab With Dr. Drew." She gave birth to a baby boy in May 2009 and told People magazine, "I've been through a lot of pain in the past and … I now look forward to years of joy to share with my child." | – The curse of child stars appears to have hit a second generation. Tyler Lambert, 25-year-old only child of Dana Plato, who played Kimberley on the popular sitcom Diff'rent Strokes, killed himself with a shotgun last week. The suicide just before Mother's Day came 11 years to the day after Lambert's troubled mother committed suicide with a drug overdose, ABC reports. His grandmother told People he had been experimenting with drugs and alcohol. |
a 65-year - old caucasian woman with a medical history of primary biliary cirrhosis presented with fever , chills , increasing shortness of breath , abdominal pain with distension , nausea , and vomiting for 5 days .
she denied any cough , chest pain , palpitations , bipedal edema , paroxysmal nocturnal dyspnea , or obstipation .
vital signs on admission were as follows : blood pressure 136/61 mmhg , pulse 108/min , respiratory rate 30/min , temperature 38.2c , and oxygen saturation of 95% on room air . on physical examination , she was anicteric with rales over the left lung base with decreased breath sounds .
her liver function tests revealed an elevated aspartate aminotransferase ( ast ) of 101 iu / l , total bilirubin of 2.5 mg / dl with a direct bilirubin of 0.8 mg / dl , decreased serum albumin of 2.5 g / dl , and normal alkaline phosphatase , alanine transaminase , and gamma - glutamyl transferase levels .
plain and upright abdominal radiography was negative for any air - fluid levels or free gas under the diaphragm .
computed tomography of the abdomen showed cirrhotic liver with portal hypertension , splenomegaly , esophageal varices , and moderate ascites .
we considered the differential diagnosis of pneumonia , peritonitis due to viscus perforation , and sbp .
sbp due to l. monocytogenes was diagnosed on the basis of abdominal tenderness and ascitic fluid neutrophil count of more than 250/mm with cultures positive for listeria and absenceof secondary causes of peritonitis .
she was given ampicillin and gentamycin for the peritonitis based on the antibiotic sensitivity report from the ascitic fluid culture .
after the initiation of antibiotics , her repeat paracentesis 48 h later , showed marked decrease in neutrophils from 8,075/mm initially to 168/mm with sterile blood and ascitic cultures .
she was discharged from the hospital after a prolonged stay of more than 1 month for multiorgan dysfunction .
cirrhosis leads to general immune dysfunction with a specific cirrhosis - associated immune dysfunction syndrome which is a systemic state of immune dysregulation .
liver houses 90% of the reticuloendothelial cells ( such as kupffer and sinusoidal endothelial cells ) that are crucial to the eradication of bacteria .
l. monocytogenes is a gram - positive , motile , aerobic , or facultative anaerobic bacillus .
listeria has been known to have predilection for newborns and immunocompromised adults such as pregnant patients , elderly , those on immunosuppressive therapies or continuous peritoneal dialysis cancer , or aids patients ( 6 , 7 ) .
the use of proton pump inhibitors has also been implicated as a risk factor for sbp ( 8) .
human cases of listeria are usually linked to transmission from food products such as dairy or meat products .
clinically , listeria manifests as septicemia , meningitis , endocarditis , gastroenteritis , or peritonitis ( 6 , 9 , 10 ) .
described the first case of sbp due to listeria in 1977 ( 6 , 11 ) .
listeria should be suspected as a cause of sbp when the patient has diphtheria - like organisms on ascitic / blood cultures , iron overload / hemochromatosis , exposure to farm animals , or poor reaction to empiric therapy within 4872 h ( 3 ) .
at least 50 cases of l. monocytogenes sbp have been described in the medical literature , with many of them found in spain .
this relatively high prevalence of l. monocytogenes in spain is theorized to be secondary to the ingestion of dairy products , raw fruits , and vegetables in that region .
it has also been found in brazil , mexico , taiwan , australia , israel , and france ( 12 ) .
diagnosis of sbp is made with a polymorphonuclear cell count > 250 cells / mm without an intra - abdominal source of infection .
sbp can present with hyperthermia or hypothermia , chills , tachypnea , tachycardia , abdominal pain and tenderness , vomiting , diarrhea , or ileus with a leukocytosis on complete blood count .
other possible presentations include worsening of liver function , altered mental status from hepatic encephalopathy , shock , renal failure , or gastrointestinal bleed .
typical organisms are gram - negative agents such as e. coli and klebsiella pneumoniae , and gram - positive microbe such as streptococcus pneumoniae which account for about 95% of cases ( 6 ) .
patients with negative ascitic fluid culture and ascitic fluid polymorphonuclear cell count > 250 cells / mm have culture negative sbp and should still be treated the same as a culture - positive patient .
those patients with bacterascites ( positive cultures with a normal ascitic polymorphonuclear cell count ) are either colonized secondary to infections outside the peritoneum or early progression of sbp .
these patients should be treated as if they have systemic infection if they exhibit signs / symptoms of sbp .
if not , it is recommended that a second paracentesis be performed once the culture comes back positive .
if ascitic fluid neutrophil count is > 250 cells / mm , then the patient should be treated for sbp .
if the wbc count is less than 500 cells / mm , the patient should be followed up .
all patients with suspected sbp should have blood cultures drawn before the initiation of antibiotic therapy ( 13 ) .
empiric treatment for sbp is usually recommended with a third generation cephalosporin such as cefotaxime , but it does not provide adequate coverage for listeria
( 6 ) .
trimethoprim - sulfamexothazole and erythromycin have been used successfully in the past in patients with penicillin allergy ( 2 ) .
repeat paracentesis is recommended 2 to 3 days after the initiation of therapy in order to determine therapeutic response on top of clinical progression .
a decrease of 25% in ascitic fluid wbc count on repeat paracentesis in 48 h is desirable .
if the patient is not responding by this time period , resistant organisms or secondary peritonitis should be suspected . in patients on norfloxacin
prophylaxis , gram - positive organisms are usually suspected and cefotaxime is the initial drug of choice . the optimal length of therapy for listeria sbp has not yet been determined but is suggested to be longer than 1014 days ( 6 , 10 ) . in our case , we treated the patient with ampicillin for 28 days .
albumin with antibiotics has been shown to decrease the occurrence of hepatorenal syndrome from 30 to 9% compared to the use of antibiotics alone .
the european association for the study of the liver suggests that albumin be administered at admission because it has been shown to decrease the incidence of hepatorenal syndrome and has a survival benefit .
it has been particularly recommended in those patients with serum bilirubin > 4 mg / dl or serum creatinine > 1 mg / dl ( 13 ) .
in patients who survive an initial episode of sbp ,
norfloxacin prophylaxis is indicated in cirrhotic patients with acute gastrointestinal bleed ( with or without ascites ) , as primary prophylaxis in patients with low total protein in ascitic fluid , and as secondary prophylaxis in cirrhotic patients with previous episodes of sbp ( 3 , 13 ) .
the authors have not received any funding or benefits from industry or elsewhere to conduct this study . | listeria is an uncommon cause of spontaneous bacterial peritonitis ( sbp ) in the united states .
listeria should be suspected as a cause of sbp when the patient has diphtheria - like organisms on ascitic / blood cultures , iron overload / hemochromatosis , exposure to farm animals , or poor response to empiric therapy within 4872 h. diagnosis of sbp is made if the ascitic fluid shows polymorphonuclear cell count > 250 cells / mm3 without an intra - abdominal source of infection .
ampicillin with or without an aminoglycoside is the treatment of choice .
trimethoprim - sulfamethoxazole is recommended for prophylaxis in patients with a previous episode of listeria sbp . |
the majority of rtms treatment studies target the dlpfc the ( dorsolateral ) prefrontal cortex is implicated in regulating affective states , providing cognitive control over stress and emotion responsiveness .
a variety of studies has shown that a series of daily sessions of high frequency ( hf)-rtms delivered to the left dlpfc or low frequency ( lf)-rtms applied to the right dlpfc are effective in reducing symptoms in clinically depressed populations .
rtms can either activate or suppress motor , sensory , or cognitive functions , depending on the brain location and parameters of its delivery : lf - rtms ( < 1hz ) is considered to
inhibit cortical regional activity , while hf - rtms ( > 1hz ) activates cortical areas .
the stimulation effects not only affect neuronal activities in the stimulated regions primarily but also those connected to them secondarily the vast majority of rtms studies in major depression target the left dlpfc with hf stimulation .
the rationale to use the dlpfc as the rtms target area originates from brain imaging research , where patients with unipolar depression show prefrontal abnormalities ( predominantly on the left ) . decreased neuronal activities in the ( dorsolateral ) prefrontal regions , as well as in the rostral anterior cingulate cortex ( acc ) areas , closely connected to the dlpfc ,
these frontal hypoactivities result in apathy , psychomotor slowness , and impaired executive functioning . besides dysfunctional
frontocingulate networks , other neuronal pathways between the orbital and medial prefrontal cortex , the amygdala , and hippocampus are implicated in the pathophysiology of mood disorders .
endocrinological disturbances and hypothalamic - pituitary - adrenal ( hpa ) system deregulations are commonly found .
the most consistently described biological abnormality in chronic major depression is a failing negative feedback system resulting in hypercortisolism
( figure 1 ) .
brain imaging results suggest that antidepressant response to rtms might vary as a function of stimulation frequency and may depend on pretreatment prefrontal brain metabolism . for instance
, the stimulation of prefrontal regions with lower metabolic activity with hf - rtms may significantly improve clinical outcome .
however , opposite results , where higher baseline metabolic activities in the dlpfc bilaterally were associated with better clinical outcome , have been reported as well .
additionally , higher baseline activities in the acc are not only predictive for treatment outcome in pharmacological antidepressant trials , electrophysiological imaging studies , and sleep deprivation studies , but high pretreatment acc activities were also a positive clinical predictor in hf - rtms treatment protocols .
concerning the neurobiological effects , rtms seems to influence metabolic activity of the acc . whereas right - sided lf - rtms showed metabolic acc decreases , left - sided hf - rtms treatment resulted in higher acc metabolic activity , especially in those subdivisions of the acc which are strongly interconnected with dlpfc areas .
however , in some reports successful hf - rtms treatment did not result in significant acc metabolic increases .
furthermore , luborzewski et al failed to demonstrate neurochemical acc alterations post hf - rtms , and loo et al demonstrated that one session of lf - rtms seemed rather to deactivate the acc than to activate it . altogether , the majority of successful rtms treatment studies correspond with pathophysiological models of major depression that are based on dysfunctions within fronto - cingulate networks , although the direction of the changes is not consistent over studies .
an important aspect of the physiology of rtms could be related to the endocrinological response of the hpa axis .
keck proposed that rtms influences occur at the hypothalamic level , suggesting that the ( dorsolateral ) prefrontal cortex participates in the rtms - induced blunted response of hpa activity .
hf - rtms would inhibit cortisol - releasing hormone synthesis and release ( figure 2 ) .. some studies have examined this hypothesis in depressed patients . for instance , in a sample of severely depressed patients , salivary cortisol concentrations decreased immediately after one active left dlpfc hf - rtms session and not after sham rtms .
pridmore observed normalization of the dexamethasone suppression test in a small sample of medicated depressed subjects after multiple sessions of hf - rtms .
in addition , in a sham - controlled left prefrontal hfrtms trial , szuba et al found acute mood and serum thyroid - stimulating hormone elevations in drug - free depressed patients after each active stimulation session .
these observations could imply that the clinical effects of rtms act in a similar way to pharmacological interventions : clinical improvement after antidepressant treatment has been associated with a normalization of hpa system function and different antidepressants may act in the same way in attenuating the hpa axis .
however , it has to be noted that in depressed patients hpa system abnormalities are not consistently observed .
only a few studies have examined the rtms effects on neurotransmitter systems in major depression . because rtms treatment resulted in psychomotor symptom improvement , such as a reduction in motor slowness in bodily movement and speech ,
increased voice volume , and facial inexpressivity , some authors suggested that a possible working mechanism of action could be by activating the dopaminergic system .
indeed , several brain imaging studies using dopaminergic ligands point to an rtms - related release in endogenous dopamine when stimulating prefrontal cortical areas , although others found no impact on the dopaminergic system at all . in major depression ,
the serotonergic system has been extensively investigated , and serotonin ( 5-ht ) is an important excitatory transmitter involved in hpasystem regulation . in a severely depressed medication - resistant sample ,
successful clinical outcome after hf - rtms treatment was associated with dlpfc 5ht2a receptor upregulation and hippocampal 5-ht2a receptor downregulation , measured with 123i-5-ir91150 spect interestingly , this prefrontal increase of this type of postsynaptic receptor agrees with treatment response findings after treatment with selective serotonin uptake inhibitors ( ssris ) and electroconvulsive therapy ( ect ) . as clinical recovery is reported to be associated with increased brain - derived neurotrophic factor ( bdnf ) expression in the hippocampus , it was suggested that the observed 5-ht2a receptor downregulation in the hippocampus would be associated with bdnf increases in this area comparable to the effects of most pharmacological antidepressant agents .
however , as rtms responders seem to be resistant to acute mood changes after trypthophan depletion , it may be possible that the neurobiological influence of rtms does not only depend on the central availability of serotonin to exert antidepressant effects .
in short , whether the rtms effects are attributed to the modulation of only the serotonergic system remains unclear .
a beneficial treatment outcome has been related to glutaminergic increases under the stimulated area ( left dlpfc ) in depressed patients . from an electrophysiological point of view , stimulation of the dlpfc might influence 5-ht2a receptors in the hippocampus via ( glutaminergic ) pyramidal neurons .
furthermore , research on the chronic effects of tms on hippocampal evoked potentials demonstrates that tms is accompanied by changes in the local hippocampal inhibitory circuits ( g - aminobutyric acid , gaba ) .
the implication of glutaminergic / gabaergic deficits in major depression has been proposed , but to date the influence of rtms on the glutaminergic/ gaba system has only been demonstrated in healthy individuals . a single active hf - rtms session increased glutamate / glutamine levels in the prefrontal cortices , suggesting that this application may act via the stimulation of the glutaminergic prefrontal neurons . concerning the inhibitory effects , active rtms resulted in increases in cortical inhibition ; however , in this study only the left motor cortex was stimulated .
brain and endocrinological data indirectly suggest that a clinical beneficial rtms outcome affects neurotrophic factors in the brain .
animal studies already demonstrated increases in the expression of bdnf in the rat hippocampus after the application of long - term hfrtms similar to antidepressant drug treatment and ect in a sample of drug - resistant depressed patients , zanardini et al reported on a normalizing rtms effect of initially decreased serum bdnf .
yukimisa et al demonstrated that changes in serum bdnf correlated positively ( rs=0.34 ) with changes on the 17-item hamilton depression rating scale in all depressed patients treated with hf - rtms .
these trend - like correlations were found to be significant when comparing responders with nonresponders ; an increase of bdnf levels was only observed in those patients who clinically responded to the hf - rtms treatment .
neurobiological data support the choice of the left dlpfc as a valid rtms target site to intervene with the neuronal pathways deregulated in major depression .
the observed changes in a depressionrelated neurocircuitry seem to agree with other successful treatment modalities , such as pharmacological antidepressant treatment and ect .
although further research is required , biological data indicate that depressed patients with some kind of preserved
cortico- subcortical neurocircuitries could be susceptible to rtms treatment . displaying a metabolically more active fronto - cingulate network at baseline
this observation is consistent with the hypothesis that the synchronized modulation of dysfunctional fronto - cingulate pathways is critical for illness remission . in short
, successful rtms treatment seems to result in a cascade of neurobiological changes in brain areas linked with the stimulated area , supporting the integrative model of action depicted in figures 1 and 2 .
whether the rtms effects are modulated by nt systems or neurotrophic factors remains to be clarified . | for nearly two decades now , transcranial magnetic stimulation ( tms ) has been available as a noninvasive clinical tool to treat patients suffering from major depression . in this period ,
a bulk of animal and human studies examined tms parameters to improve clinical outcome .
however , the neurobiological mechanisms underlying mood changes remain an important focus of research .
in addition to having an effect on neuroendocrinological processes , neurotransmitter systems , and neurotrophic factors , tms may not only affect the stimulated cortical regions , but also those connected to them .
therefore , we will review current human data on possible neurobiological mechanisms of repetitive ( r ) tms implicated in the deregulated neurocircuitry present in unipolar depression . furthermore , as the rtms application can be considered as a
top - down neuronal intervention , we will focus on the neuronal pathways linked with the stimulated area and we will present an integrative model of action . |
Richard Simmons Sues the Nat'l Enquirer The Sex Change Story Was a Malicious Lie
Richard Simmons Sues the National Enquirer Over False Sex Change Story (UPDATE)
2:25 PM PT -- The National Enquirer says Richard Simmons' lawsuit is ironic ... since he claims to support LGBTQ rights, and is now claiming he was defamed by its story he was transitioning to a woman.
What's really ironic is ... Simmons said exactly that in his lawsuit -- that the Enquirer was gambling he wouldn't sue because it would make it seem like he thinks there's something wrong with people who transition.
The Enquirer adds, "We stand by our reporting about Mr. Simmons, and intend to vigorously defend this lawsuit and win public vindication of our reports."
Richard Simmons is suing American Media for a story claiming he was transitioning to become a woman.
Simmons claims defamation and invasion of privacy against the National Enquirer for writing what he calls "cruel and malicious" stories.
Simmons claims in his lawsuit the publications knew the information was false but felt Simmons would never sue because it would make him appear unsympathetic to people who transition ... as if something were wrong with it. Simmons says in the suit they "miscalculated."
The suit claims the stories were based on a source who Richard says has been blackmailing, extorting and stalking him for several years.
One of the stories claimed Simmons was now a woman, had a boob job and was "considering having a vagina built by doctors." The story claimed he was living as a woman named Fiona.
The suit claims Simmons warned the publications the story was false but they were "coldly oblivious to the damage their cruel stories would cause ... " ||||| STATEMENT FROM THE NATIONAL ENQUIRER:
For decades, Richard Simmons has used his outrageous behavior to build his brand and his bank account.
For Mr. Simmons to claim that his privacy has been invaded is hypocritical when his entire livelihood is based upon the public consumption of his image.
To wit, Mr. Simmons signed a lucrative merchandising deal with a major branding company in April to handle licensing of his name and likeness.
At the same time, he protests that he is entitled to privacy and therefore should not be subjected to scrutiny of the media, which has raised reasonable questions about his health and whereabouts since he disappeared from the public eye almost four years ago.
This is a legitimate news story that demands coverage. It is the business of The National ENQUIRER — and has been for the past 90 years — to report on what goes on behind the closed doors of Hollywood.
Moreover, Mr. Simmons is raising a false equivalency in suggesting that The ENQUIRER’s coverage of gender identity somehow implies that the publication has a stance or position on this. We do not.
Indeed, it is ironic that Mr. Simmons claims to be an avid supporter of the LGBTQ community while at the same time alleges that he was defamed by The ENQUIRER report that he had transitioned into a female.
At the end of the day, how Mr. Simmons lives his life is news and of interest to our readers.
Our story was based on credible sources who were in Mr. Simmons’ inner circle. The photos provided to The ENQUIRER are real — and speak for themselves.
We stand by our reporting about Mr. Simmons, and intend to vigorously defend this lawsuit and win public vindication of our reports.
We will also aggressively pursue our ongoing investigation into his life and who is really behind this bizarre and meritless lawsuit.
Story developing. ||||| In a libel complaint, the fitness star says the publication knew its source wasn't credible and that he has "a legal right to insist that he not be portrayed as someone he is not."
Richard Simmons isn't missing. For those looking for the fitness guru, try Los Angeles Superior Court, where Simmons is now standing up for truth and privacy in a huge libel lawsuit against the National Enquirer, Radar Online and American Media, Inc. Simmons is targeting a series of "cruel and malicious" articles published between June 2016 and March of this year that suggested he was transitioning from a male to a female, including reports of "shocking sex surgery," breast implants, hormone treatments and consultations on medical castration.
The complaint filed on Monday paints the tabloids' conduct as "particularly egregious," a cynical calculation that Simmons wouldn't sue because he wouldn't want to appear as frowning upon the act of transitioning from one gender to another.
"National Enquirer and Radar Online have miscalculated," reads the complaint, a copy of which was obtained by The Hollywood Reporter. "The National Enquirer and Radar Online have cheaply and crassly commercialized and sensationalized an issue that ought to be treated with respect and sensitivity. Principles of freedom of speech and press may protect their prerogative to mock and degrade the LGBTQ community. But freedom to speak is not freedom to defame. Mr. Simmons, like every person in this nation, has a legal right to insist that he not be portrayed as someone he is not. Even the most ardent supporter of sexual autonomy and LGBTQ rights is entitled to be portrayed in a manner that is truthful."
Neville Johnson, the attorney for Simmons, continues, "The law of defamation and false light invasion of privacy exist to vindicate this elemental right. The law protects the right of every person to be treated with decency and dignity, free from the deliberate propagation of falsehoods that have no motivation other than exploitation. It is to vindicate that right, and the rights of all persons to be portrayed with dignity and honesty with regard to their sexual identity, that Mr. Simmons files this lawsuit."
The lawsuit raises provocative issues. Past courts have grappled with the question of whether being called gay is actually a stain on one's reputation. Other courts have dealt with public accusations of cosmetic surgery in the reputational context. Results have been mixed. For instance, Tom Cruise once won a default judgment against a porn actor who claimed an affair, while a New York appeals court in 2012 ruled that defamation suits premised on one's sexuality are "based on the flawed premise that it is shameful and disgraceful to be described as lesbian, gay or bisexual."
Here, Simmons is bringing the first-ever defamation lawsuit over published reports of a sex change and framing it as a stand for dignity and the right to have a gender identity.
Equally as interesting is Simmons' target — a publication that has routinely annoyed celebrities and has become closely aligned with President Donald Trump thanks to Trump's friendship with its owner, David Pecker. (Famously, Trump wondered last year on the campaign trail why the National Enquirer hadn't ever won a Pulitzer.)
The National Enquirer has employed a peculiar strategy when it comes to celebrity gossip. Since public figures must demonstrate "actual malice" — knowing falsity or reckless disregard for the truth — to prevail in defamation cases, the publication looks to make its reports defensible. A recent Buzzfeed feature about the magazine quoted editorial director Dylan Howard as saying that sources are given polygraph tests and asked to sign a contract testifying the information provided is true. As Buzzfeed puts it, "Ultimately, the actual veracity of the story matters less than the existence of sworn testimony of its veracity."
But according to Simmons' suit, AMI publications can hardly shield itself from accusations of being reckless. Not when there are good reasons to be dubious about the credibility of a source and not in the face of contrary information.
Simmons admits to retreating from his 40-year career in television and fitness in early 2014. His absence from the media spotlight garnered attention itself, including from the celebrated podcast, Missing Richard Simmons. Others may have looked to capitalize on the situation.
"Starting from around May 2015, Mauro Oliveira, an individual who has blackmailed, extorted and stalked Mr. Simmons for several years with the intention of destroying the career and reputation of Mr. Simmons, contacted several press outlets, including the National Enquirer and Radar, and offered information on Mr. Simmons' disappearance in exchange for a fee," states the complaint.
Oliveira allegedly told the publication different stories about Simmons during multiple contacts. According to the complaint, the National Enquirer was told on one occasion that Simmons' absence was due to him being held hostage by a housekeeper who engaged in witchcraft. On another occasion, it was a sex change.
"All of these assertions were untrue, and were merely attempts by Mr. Oliveira to gain a profit in exchange for providing a false narrative about Mr. Simmons' leave of absence," continues the complaint. "While pitching around these ideas, Mr. Oliveira was simultaneously blackmailing Mr. Simmons, sending him emails and threatening to destroy his reputation with damaging press coverage unless Mr. Simmons paid Mr. Oliveira to stop."
As the National Enquirer began preparing its story about a sex change in June 2016, according to the court papers, the publication provided Simmons' publicist, Tom Estey, a copy of the unpublished article for review. Estey warned AMI's general counsel that they should "be prepared for a lawsuit."
Nevertheless, allegedly using Oliveira as its sole source, the National Enquirer published on article on June 8.
"The cover of the article, 100% entirely dedicated to the false story about Mr. Simmons' transition, included an old image of Mr. Simmons from 2013 (before his disappearance), dressed in costume as a female, which he has done openly over the years consistent with his well-known and longstanding burlesque-style entertainment persona," states the complaint. "Accompanying the image of the 2013 photo of Mr. Simmons was a large bold headline, taking up half of the cover page, proclaiming 'Richard Simmons: He's Now a Woman!'"
Radar is said to have followed this up with five articles itself recycling information.
Just two days later, after the National Enquirer's initial story, Oliveira is said to have recanted his story about Simmons' gender transition via an email to Simmons and his manager. The email stated that Oliveira had been "misrepresented and betrayed and that such allegations were pure fabrications by others not [himself.]'"
Oliveira allegedly demanded money, and said that if Simmons paid him, he would be prepared to "go on record to discredit the story and defend Richard Simmons."
As the complaint (read in full here) puts it, "This email — part of a longstanding pattern of harassment of Mr. Simmons by Mr. Oliveira — further demonstrates that Mr. Oliveira was obviously not credible, and any reliance on him as a source was reckless and malicious."
Despite Simmons' denials, the Olivera email turned over to AMI and several more follow-up threats and demands for retractions, the National Enquirer "doubled-down" with a new article on June 15 repeating the sex-change allegation. Radar would post a story as late as March 22, 2017, stating that Simmons was "the latest Hollywood star to secretly undergo a sex change" and that he has "opted for a breast implant surgery, hormone therapy, and a host of other invasive changes to create the transformation the Enquirer reported."
Simmons is now bringing four counts of libel as well as an invasion of privacy-false light charge. He's asking that defendants be enjoined and restrained from continuing to disseminate articles about how Simmons underwent a sex change plus demanding an unspecified amount of compensatory and punitive damages. He also wants an apology and retraction.
An AMI spokesperson responds, "While we have not seen Mr. Simmons’ complaint, we stand by our reporting about him, all of which was based on solid sourcing, photos and videos. Should he choose to proceed with his lawsuit, we will defend it vigorously, and we look forward to the public vindication of our reports." | – Richard Simmons has a bone to pick with the tabloids. According to the Hollywood Reporter, the fitness guru filed a lawsuit against the National Enquirer, Radar Online, and American Media, Inc. after a series of stories claiming Simmons underwent a “shocking sex surgery” began appearing in June of 2016. Simmons, who returned to the public eye in April after a three-year hiatus, called the articles “cruel and malicious,” and claims that the National Enquirer bet on him ignoring the stories so he wouldn’t appear unsympathetic toward people transitioning genders. The complaint says they “miscalculated," and that "the National Enquirer and Radar Online have cheaply and crassly commercialized and sensationalized an issue that ought to be treated with respect and sensitivity.” TMZ reports that the tabloids' articles claimed Simmons was living as a woman named Fiona. Simmons’ complaint alleges that Mauro Oliveira, the source used in the National Enquirer’s reporting, was a longtime stalker of the celebrity who tried to sell stories about Simmons for a fee. It claims that while pitching false stories to the tabloids, Oliveira simultaneously attempted to blackmail Simmons, “threatening to destroy his reputation with damaging press coverage unless Mr. Simmons paid Mr. Oliveira to stop." National Enquirer released a statement defending its "credible sources who were in Mr. Simmons’ inner circle," and saying, “We stand by our reporting about Mr. Simmons, and intend to vigorously defend this lawsuit and win public vindication of our reports.” |
. (Photo: KING)
SEATTLE -- A group of attorneys has filed a class action lawsuit against the Washington State Department of Transportation, claiming the billing process for bridge tolls violates due process.
For all the times a week she's driven across the 520 bridge, Amy Funchess never guessed how much she would end up owing WSDOT.
Before she got her Good To Go pass, Funchess says she traveled across the bridge many times but only received two tolling bills in the mail.
When she called Good To Go a couple months ago to ask about her balance, she was stunned with what she learned.
"Lo and behold, they told me about all these civil penalties I had. And I said 'How much would those be?' And they said 'Oh, you're up around $900.' And I about fell over in my chair," Funchess said.
Funchess, an attorney, consulted a friend, attorney Catherine Clark of Seattle, who had heard the same story from other lawyers.
"I honestly think it's people who aren't thinking the process through," Clark said.
So Clark and her colleagues, attorney Mary Anderson of Bellevue, and attorney Laurie Shiratori of Seattle, filed a class action lawsuit this week claiming WSDOT and Electronic Transaction Consultants are violating a driver's right to due process, by failing to notify her of her bills and the penalties owed for not paying them.
"It's sporadic. Some things get sent, some do not," said Clark. "The civil penalty do not refer to the toll bill that was issued. The toll bill doesn't include dates on which they are allegedly sent. It's very confusing for people and it should be that hard."
KING 5 has aired a series of stories exposing the confusion and the billing problems with Good To Go.
Clark accuses WSDOT of using a specific Washington Administrative Code as a crutch, which says "a toll bill MAY be sent to the registered owner of the vehicle."
But there is no requirement.
"The position that they take is a WAC that says we may send you a bill," said Clark. "Which suggests it's a discretionary idea. We don't think it's discretionary. We think it's a constitutional right that I'm entitled to notice or anyone is entitled to notice."
KING 5 reached out to WSDOT to comment on the lawsuit. A spokesperson said WSDOT had not yet been served.
The whole process makes Funchess reluctant to take the 520 bridge at all.
"Untrusting, to be quite honest, a little bit violated," she said. "They stole from me."
Funchess said Good To Go offered no appeals process, no payment plan, and that if she didn't pay up, Department of Licensing would not renew her tabs.
Read or Share this story: http://www.king5.com/story/news/2015/01/29/520-bridge-toll-class-action-lawsuit-billing-problems/22553149/ ||||| Originally published January 30, 2015 at 10:29 PM | Page modified January 31, 2015 at 7:36 PM
The steady drumbeat of 520 bridge toll horror stories has finally boiled over into a class action lawsuit, exactly as a judge predicted it would, five years ago.
Five years ago, when the state was setting up the photo-toll system on the 520 bridge, a local judge made an unusually bold prediction.
If you put both the toll fines and appeals process on that bridge under the control of the state roads agency, you will get sued by outraged citizens, the judge told state lawmakers in Olympia. And you easily could lose.
“Since the birth of our democracy, it has been well settled that government cannot take from its citizens without due process of law,” Barbara Linde, who was then chief judge of King County’s District Court system but who is now in Superior Court, scolded legislators at a 2010 hearing.
“In my view, it will only be a matter of time before an aggrieved citizen — and there will be many aggrieved citizens — brings a class-action lawsuit,” she said (italics mine).
Once again, the person nobody listens to turns out to be right.
On Thursday, three law firms filed exactly that class- action suit. It argues that the 520 bridge’s tolling fines and bureaucratic appeals process are so tilted against the people that they are unconstitutional, as well as in violation of consumer laws.
“People are being gouged by the government in ways no private business could get away with,” summed up attorney Mary Anderson.
The suit is derived from toll horror stories in the news for the past three years. They go like this: Commuter crosses bridge, has some glitch with photo-tolling account or never gets bills in the mail and — wham! — commuter is hit with eye-watering fines. There’s no place to appeal but a merciless administrative review set up by the transportation agency itself.
I have told some of these stories, and I hear new ones every week. (My email in-tray would be a rich class-action client pool.) The main grievance is that the state feels it isn’t obligated to send out toll bills. And that the fines, $40 on each missed toll, are so steep they can turn minor account snafus into multi-thousand-dollar collection actions.
Take Nicola Livic, of Redmond. He has a transponder on his car, linked to a credit card to automatically pay his tolls. But when his credit-card number was changed by the bank (due to a fraud issue), his online account stopped working.
No big deal. Except that the motor-vehicle department had his mailing address wrong (his ends with a box number, #44, that somehow got dropped.) So all the subsequent mailings alerting him to new tolls and his growing fines never reached him.
The total damage by the time he realized what was going on: $3,545. Less than $300 of that is for actual tolls.
When he appealed at the state Department of Transportation (DOT)’s University District office, he was told that ignorance of fines was a poor defense.
“It felt like a kangaroo court,” Livic says. “I’m culpable for not monitoring my Good-To-Go account as closely as I should. But the punishment is way out of whack for an address error that wasn’t mine.”
It used to be that a missed toll payment was like a parking ticket. You could go to a local court where an elected judge with significant leeway would hear you out.
But in 2010, the DOT requested that these cases be switched from the courts to an administrative process set up by the DOT. It enlisted administrative-law judges to staff the toll courts, but didn’t give them much flexibility on how they could rule.
Crucially, fines collected now go to the DOT. An average of $65,000 just in fines is assessed on the 520 bridge each day.
Judge Linde warned lawmakers back in 2010: You’re setting this up so DOT designs the system, issues the infractions and oversees the appeal process. Plus it gets the fine money.
“It will be anything but the independent process that citizens expect,” she said.
I’ve argued that fining people $40 for each $4 missed payment is a level of gouging you won’t see from the worst payday-loan shop. Better would be to charge no fines but attach unpaid toll bills to license-tab renewals, as they do in British Columbia. Tough but fair.
What happens now? The person who was right in the first place made a guess about that, too.
Judge Linde noted in 2010 that the inevitable class-action suit would be weighed by judges who tend to take a dim view of “tossing citizens into an administrative process.” There’s a big risk the state will lose, she said then. If so, it will put the taxpayers on the hook for “having to repay toll penalties, along with triple damages and attorneys’ fees.”
Or the state Legislature could act, now, and try to fix all this. They sure can’t say they weren’t warned.
Danny Westneat’s column appears Wednesday and Sunday. Reach him at 206-464-2086 or [email protected]
Four weeks for 99 cents of unlimited digital access to The Seattle Times. Try it now! ||||| . (Photo: KING)
POULSBO, Wash. -- A Poulsbo man says he is still reeling from paying his son's Good To Go bill, which amounted to more than $18,000.
Tom Rose says his son, who just got his first job, had been crossing the 520 bridge every day for work, and neglected to get a Good To Go pass.
"He thought he'd be bill later for it," said Rose. "And the way the things were going, he was living hand to mouth. He thought he was picking the lesser of two evils. He could save up and pay for them later."
Rose says his son never received a bill. He learned the total of what he owed when he tried to sell his car: more than $18,000. $1,360 in tolls, more than $16,000 in penalties.
When both father and son contacted the WSDOT's Good To Go office, they say they were told they could try to go before an administrative judge, but it probably wouldn't do them any good.
KING 5 has been hearing similar stories from other drivers. The billing has been so inconsistent with Good To Go that a group of attorneys filed a class action lawsuit this week, claiming WSDOT was violating due process. But so far, none of the cases we've heard of was worse than Tom Rose's son.
"They need to pay their tolls. We all need to do our part," Rose said. "But to not have a proper recourse, and not have the administrative process correct, is really an affront. It's almost an abuse."
We asked WSDOT to check its records. A spokesperson looked into the matter and found while they did try to send the bills out to Rose's son, the bills were returned to them. They clearly did not have a good address for the driver.
Because of that they say they are willing to work with him. Rose's son will have to pay the tolls, but they will try and find a resolution on the penalties.
"We would welcome any type of remediation in this. A second look, that would be great," said Rose.
Related: Attorneys file class action lawsuit over Good To Go billing process
Read or Share this story: http://www.king5.com/story/news/local/2015/01/30/520-bridge-good-to-go-poulsbo-18000/22623259/ | – A Washington state man received a wee shock when he saw his outstanding toll-bridge bill: more than $18,000. His dad, Tom Rose, says the young man was working his first job and crossing the 520 bridge daily without a Good to Go pass—figuring he'd pay later, KING-TV reports. But the Washington State Department of Transportation didn't have the son's right address, so no bill came in the mail. The guy only learned of the $1,360 in tolls and over $16,000 in penalties when trying to sell his car. "He was living hand to mouth," Rose says of his son. "He thought he was picking the lesser of two evils. He could save up and pay for them later." Luckily WSDOT says it's willing to strike a deal on the man's penalties, but there are other cases of high Good to Go bills. In fact, a recent class-action lawsuit claims that Good to Go billing violated due process by not always notifying a driver of her outstanding bills and penalties, notes KING-TV. Other drivers have felt WSDOT's billing wrath and learned they can't complain in local courts, where elected judges might rule in their favor; billing complaints go to a "merciless administrative review set up by the transportation agency itself," writes Danny Westneat in the Seattle Times. As for WSDOT, it has no comment on the lawsuit and says it hasn't been served yet. |
the study took place in mauritania , one of the key countries for the implementation of preventive control and hosting desert locust permanent habitats ( popov et al .
the country is also historically an important locust migration route between the sahel and the maghreb in africa ( ceccato et al . 2007 ) .
the study was conducted during and shortly after two successive annual rainy seasons ( between july and december ) , in 2012 and in 2013 .
the studied areas are annually monitored by the survey teams of the national anti - locust center of mauritania and correspond to the traditional desert locust breeding and gregarization areas ( popov et al .
field sampling was oriented by locust presence in these areas ( see fig . 1 and cisse et al .
1.sampling sites in mauritania where desert locust adults were found ( n = 130 ) .
the gray lines show the isohyetes of mean annual rainfall in mm ( data from agrymet / rim ) .
sampling sites in mauritania where desert locust adults were found ( n = 130 ) .
the gray lines show the isohyetes of mean annual rainfall in mm ( data from agrymet / rim ) .
the sampling methodology used to estimate the desert locust adult densities was consistent with the fao guidelines ( cressman 2001 ) .
at least ten samples were taken at an individual site ( survey stop ) where green vegetation was present .
each sample consisted of counting the number of individuals in a foot transects of 100 m in length and 1 m in width .
parallel transects were separated by at least 50 m. the average number of locusts per 100 m was determined from the ten samples and converted to density per hectare .
the collected data were focused on locust behavior ( isolated or scattered solitarious adults ; grouped transiens or gregarious adults ) and body - coloration ( usually brown for solitarious adults ; bright pink for transiens , pink , or yellow for gregarious adults ) ( symmons and cressman 2001 ) .
phase polyphenism confers to locust species , and desert locust in particular , considerable variation in behavioral , morphological , anatomical , and physiological characteristics , as population densities and environmental conditions of the habitat area change ( pener and simpson 2009 ) .
the extreme gregarious adult forms are noticeably different from the extreme solitarious adult forms in various traits such as coloration , wing length , hind femur length , a bulge in the cheeks , a depression in the crest of the pronotum , a shortening of the prozona , and a constriction in the thorax ( duranton and lecoq 1990 ) . in the transiens adult forms ( congregans or dissocians , depending on phase change direction ) ,
phase characteristics are independently and continuously induced or shifted to either direction in response to changes in the density of the population ( rao 1942 , pener and simpson 2009 ) . also , the swarm migration and group oviposition are well known as typical gregarious - phase characteristics . in the field
, prominence was given to behavior rather than appearance in characterizing the phase status of individuals because body color and morphological changes could occur later ( rogers et al .
also , during these 2 yr of field work , no major outbreak was in progress .
( 2013 ) , with a solitarious status or gregarious status ( hence including most transiens forms ) .
samples were conducted in 148 sites and adult locust found in 130 sites ( fig . 1 , also described in cisse et al .
the vegetation variables of status and cover were collected for each site following the fao guidelines ( cressman 2001 , cisse et al .
if mixed dry and green vegetation was found with no signs of new growth , it was noted
green or shooting. the cover vegetation variable was based on the density of the vegetation compared with bare soil : it was denoted as
we assessed the prediction of desert locust adult phase with the statistical model using adult density , vegetation status and cover as established in cisse et al .
this prediction model is a multivariate logistic regression model of the form : logit[p(gregarious ) ] adult density + vegetation status + adult density : vegetation cover .
table 1 presents the results of its adjustment from historical data realized in cisse et al .
( 2013 ) . by introducing the new field observations as explanatory variable in this adjusted statistical model
, we could compute the probability that each sampled population of desert locust adult was gregarious according to its density and the status and cover of the vegetation .
we then compared these predictions with the phase status observed in the field according to behavior .
the probability of being gregarious from the model was compared with the characterized phase status through a simple confusion matrix .
data were analyzed with the statistical software r version 3.2.2 ( r development core team 2015 ) .
( 2013 ) of the form : logit[p(gregarious ) ] adult density + vegetation status + adult density : vegetation cover.coefficientestimatesez valuepr(>|z|)intercept1.89971680.039710347.839<2e16adult density0.00255450.000141318.082<2e16greening vegetation0.08145730.17160300.4750.635shooting vegetation1.99471650.30273576.5894.43e11dry vegetation0.68886790.22303443.0890.002green vegetation0.08929480.05119911.7440.081adult density : low cover0.00326990.00038438.509<2e16adult density : medium cover0.00036970.00015202.4310.015vegetation cover from cisse et al ( 2013 ) .
( 2013 ) of the form : logit[p(gregarious ) ] adult density + vegetation status + adult density : vegetation cover .
the study took place in mauritania , one of the key countries for the implementation of preventive control and hosting desert locust permanent habitats ( popov et al .
the country is also historically an important locust migration route between the sahel and the maghreb in africa ( ceccato et al . 2007 ) .
the study was conducted during and shortly after two successive annual rainy seasons ( between july and december ) , in 2012 and in 2013 .
the studied areas are annually monitored by the survey teams of the national anti - locust center of mauritania and correspond to the traditional desert locust breeding and gregarization areas ( popov et al .
field sampling was oriented by locust presence in these areas ( see fig . 1 and cisse et al .
1.sampling sites in mauritania where desert locust adults were found ( n = 130 ) .
the gray lines show the isohyetes of mean annual rainfall in mm ( data from agrymet / rim ) .
sampling sites in mauritania where desert locust adults were found ( n = 130 ) .
the gray lines show the isohyetes of mean annual rainfall in mm ( data from agrymet / rim ) .
the sampling methodology used to estimate the desert locust adult densities was consistent with the fao guidelines ( cressman 2001 ) .
at least ten samples were taken at an individual site ( survey stop ) where green vegetation was present .
each sample consisted of counting the number of individuals in a foot transects of 100 m in length and 1 m in width .
parallel transects were separated by at least 50 m. the average number of locusts per 100 m was determined from the ten samples and converted to density per hectare .
the collected data were focused on locust behavior ( isolated or scattered solitarious adults ; grouped transiens or gregarious adults ) and body - coloration ( usually brown for solitarious adults ; bright pink for transiens , pink , or yellow for gregarious adults ) ( symmons and cressman 2001 ) .
phase polyphenism confers to locust species , and desert locust in particular , considerable variation in behavioral , morphological , anatomical , and physiological characteristics , as population densities and environmental conditions of the habitat area change ( pener and simpson 2009 ) .
the extreme gregarious adult forms are noticeably different from the extreme solitarious adult forms in various traits such as coloration , wing length , hind femur length , a bulge in the cheeks , a depression in the crest of the pronotum , a shortening of the prozona , and a constriction in the thorax ( duranton and lecoq 1990 ) . in the transiens adult forms ( congregans or dissocians , depending on phase change direction ) ,
phase characteristics are independently and continuously induced or shifted to either direction in response to changes in the density of the population ( rao 1942 , pener and simpson 2009 ) . also , the swarm migration and group oviposition are well known as typical gregarious - phase characteristics . in the field
, prominence was given to behavior rather than appearance in characterizing the phase status of individuals because body color and morphological changes could occur later ( rogers et al .
also , during these 2 yr of field work , no major outbreak was in progress .
( 2013 ) , with a solitarious status or gregarious status ( hence including most transiens forms ) .
samples were conducted in 148 sites and adult locust found in 130 sites ( fig . 1 , also described in cisse et al .
the vegetation variables of status and cover were collected for each site following the fao guidelines ( cressman 2001 , cisse et al .
if mixed dry and green vegetation was found with no signs of new growth , it was noted
green or shooting. the cover vegetation variable was based on the density of the vegetation compared with bare soil : it was denoted as
we assessed the prediction of desert locust adult phase with the statistical model using adult density , vegetation status and cover as established in cisse et al .
this prediction model is a multivariate logistic regression model of the form : logit[p(gregarious ) ] adult density + vegetation status + adult density : vegetation cover .
table 1 presents the results of its adjustment from historical data realized in cisse et al .
( 2013 ) . by introducing the new field observations as explanatory variable in this adjusted statistical model
, we could compute the probability that each sampled population of desert locust adult was gregarious according to its density and the status and cover of the vegetation .
we then compared these predictions with the phase status observed in the field according to behavior .
the probability of being gregarious from the model was compared with the characterized phase status through a simple confusion matrix .
data were analyzed with the statistical software r version 3.2.2 ( r development core team 2015 ) .
( 2013 ) of the form : logit[p(gregarious ) ] adult density + vegetation status + adult density : vegetation cover.coefficientestimatesez valuepr(>|z|)intercept1.89971680.039710347.839<2e16adult density0.00255450.000141318.082<2e16greening vegetation0.08145730.17160300.4750.635shooting vegetation1.99471650.30273576.5894.43e11dry vegetation0.68886790.22303443.0890.002green vegetation0.08929480.05119911.7440.081adult density : low cover0.00326990.00038438.509<2e16adult density : medium cover0.00036970.00015202.4310.015vegetation cover from cisse et al ( 2013 ) .
( 2013 ) of the form : logit[p(gregarious ) ] adult density + vegetation status + adult density : vegetation cover .
the study took place in mauritania , one of the key countries for the implementation of preventive control and hosting desert locust permanent habitats ( popov et al .
the country is also historically an important locust migration route between the sahel and the maghreb in africa ( ceccato et al . 2007 ) .
the study was conducted during and shortly after two successive annual rainy seasons ( between july and december ) , in 2012 and in 2013 .
the studied areas are annually monitored by the survey teams of the national anti - locust center of mauritania and correspond to the traditional desert locust breeding and gregarization areas ( popov et al .
field sampling was oriented by locust presence in these areas ( see fig . 1 and cisse et al .
1.sampling sites in mauritania where desert locust adults were found ( n = 130 ) .
the gray lines show the isohyetes of mean annual rainfall in mm ( data from agrymet / rim ) .
sampling sites in mauritania where desert locust adults were found ( n = 130 ) .
the gray lines show the isohyetes of mean annual rainfall in mm ( data from agrymet / rim ) .
the sampling methodology used to estimate the desert locust adult densities was consistent with the fao guidelines ( cressman 2001 ) .
at least ten samples were taken at an individual site ( survey stop ) where green vegetation was present .
each sample consisted of counting the number of individuals in a foot transects of 100 m in length and 1 m in width .
parallel transects were separated by at least 50 m. the average number of locusts per 100 m was determined from the ten samples and converted to density per hectare .
the collected data were focused on locust behavior ( isolated or scattered solitarious adults ; grouped transiens or gregarious adults ) and body - coloration ( usually brown for solitarious adults ; bright pink for transiens , pink , or yellow for gregarious adults ) ( symmons and cressman 2001 ) .
phase polyphenism confers to locust species , and desert locust in particular , considerable variation in behavioral , morphological , anatomical , and physiological characteristics , as population densities and environmental conditions of the habitat area change ( pener and simpson 2009 ) .
the extreme gregarious adult forms are noticeably different from the extreme solitarious adult forms in various traits such as coloration , wing length , hind femur length , a bulge in the cheeks , a depression in the crest of the pronotum , a shortening of the prozona , and a constriction in the thorax ( duranton and lecoq 1990 ) . in the transiens adult forms ( congregans or dissocians , depending on phase change direction ) ,
phase characteristics are independently and continuously induced or shifted to either direction in response to changes in the density of the population ( rao 1942 , pener and simpson 2009 ) . also , the swarm migration and group oviposition are well known as typical gregarious - phase characteristics . in the field
, prominence was given to behavior rather than appearance in characterizing the phase status of individuals because body color and morphological changes could occur later ( rogers et al .
also , during these 2 yr of field work , no major outbreak was in progress .
( 2013 ) , with a solitarious status or gregarious status ( hence including most transiens forms ) .
samples were conducted in 148 sites and adult locust found in 130 sites ( fig . 1 ,
the vegetation variables of status and cover were collected for each site following the fao guidelines ( cressman 2001 , cisse et al .
if mixed dry and green vegetation was found with no signs of new growth , it was noted
drying. if the vegetation present was yellow only , it was noted dry. vegetation could also be completely green or
shooting. the cover vegetation variable was based on the density of the vegetation compared with bare soil : it was denoted as
we assessed the prediction of desert locust adult phase with the statistical model using adult density , vegetation status and cover as established in cisse et al .
this prediction model is a multivariate logistic regression model of the form : logit[p(gregarious ) ] adult density + vegetation status + adult density : vegetation cover .
table 1 presents the results of its adjustment from historical data realized in cisse et al .
( 2013 ) . by introducing the new field observations as explanatory variable in this adjusted statistical model
, we could compute the probability that each sampled population of desert locust adult was gregarious according to its density and the status and cover of the vegetation .
we then compared these predictions with the phase status observed in the field according to behavior .
the probability of being gregarious from the model was compared with the characterized phase status through a simple confusion matrix .
data were analyzed with the statistical software r version 3.2.2 ( r development core team 2015 ) .
( 2013 ) of the form : logit[p(gregarious ) ] adult density + vegetation status + adult density : vegetation cover.coefficientestimatesez valuepr(>|z|)intercept1.89971680.039710347.839<2e16adult density0.00255450.000141318.082<2e16greening vegetation0.08145730.17160300.4750.635shooting vegetation1.99471650.30273576.5894.43e11dry vegetation0.68886790.22303443.0890.002green vegetation0.08929480.05119911.7440.081adult density : low cover0.00326990.00038438.509<2e16adult density : medium cover0.00036970.00015202.4310.015vegetation cover from cisse et al ( 2013 ) . logistic regression model from cisse
et al . ( 2013 ) of the form : logit[p(gregarious ) ] adult density + vegetation status + adult density : vegetation cover . vegetation cover from cisse et al ( 2013 ) .
from the 130 sites where adult locusts were found , we observed 98 sites with solitarious adults and 32 sites with gregarious adults . regarding vegetation status , 104 sites were green , 5 shooting , and 21 drying .
vegetation cover was low in 50 sites , medium in 51 , and dense in 29 sites .
comparison with the model showed eight errors of prediction for the phase status ( table 2 , fig .
the model predicted solitarious for one of the gregarious observations leading to a false negative rate of 3.8% ( table 2 ) .
the false positive rate was a bit higher ( 6.7% ) with seven solitarious observations predicted as gregarious .
altogether , these tests led to a relatively small overall error of prediction of 6.1% ( 1overall accuracy , table 2 ) .
2.comparison of observed phase status in the field with the model prediction of the phase status from density , vegetation cover , and status ( expressed as a probability of being gregarious ) .
table 2.confusion matrix of the model prediction from density , vegetation cover , and status ( prediction threshold taken at 0.5 of probability to observe gregarious locusts ) versus the observed phase status in the fieldpredicted solitariouspredicted gregariouserrorsobserved solitarious977false positive rate = 7/104 = 6.7%observed gregarious125false negative rate = 1/26 = 3.8%errorsfalse omission rate = 1/98 = 1.0%false discovery rate = 7/32 = 21.9%overall accuracy = 122/130 = 93.8% comparison of observed phase status in the field with the model prediction of the phase status from density , vegetation cover , and status ( expressed as a probability of being gregarious ) .
confusion matrix of the model prediction from density , vegetation cover , and status ( prediction threshold taken at 0.5 of probability to observe gregarious locusts ) versus the observed phase status in the field
this study allowed checking the robustness of our previous findings on desert locust adult gregarization thresholds focusing on historical data analysis ( cisse et al .
2013 ) . despite the diversity of field workers who contributed to the collection of historical data in mauritania
the false negative predictions would be the most problematic in a management context as it would indicate that gregarious individuals are solitarious .
fortunately , the model presented a low rate of false negatives with these new data .
this indicates that an operational use of this model could help in determining if a given locust density and vegetation situation is at risk or not .
treatments could be decided on this base , though the locust density measure might be another source of errors .
indeed , a certain amount of caution should be exercised when the results of foot transects are extrapolated to an entire area of green vegetation .
this method may be appropriate for homogenous distribution but is not likely to account entirely for clumpiness in locust distribution within the green vegetation .
several studies have recognized that preventive control strategy is the only effective strategy ( duranton and lecoq 1990 , lecoq 2004 , van huis et al .
locust control should never be spontaneous ; it must be rational , based on a risk assessment .
this requires a cross - analysis process of locust densities and environmental factors , mainly vegetation , rainfall and time factor ( beginning , middle , or end of seasonal rainy period ) .
the staff involved in implementation of the preventive control strategy needs specific indicators for when or where chemical treatment should be done . in this respect , the statistical model of cisse et al .
a simple routine that transforms locust density and vegetation status and cover into a probability to find gregarious locusts could be incorporated into the custom geographic information systems , ramsesv4 ( reconnaissance and management system of the environment of schistocerca ) , that is used to analyze field data for decision - making in each desert locust affected country ( cressman and hodson 2009 ) .
lastly , the statistical model could be improved further by analyzing data of all locust - affected countries according to our methodology . from this ,
this study was supported by funds from the fao commission for controlling the desert locust in the western region ( clcpro ) . | previous studies investigated the effect of vegetation on density thresholds of adult desert locust gregarization from historical data in mauritania .
we examine here the prediction of locust phase based on adult density and vegetation conditions using the statistical model from cisse et al . compared with actual behavior of desert
locust adults observed in the field in mauritania . from the 130 sites where adult locusts were found , the model predicted the phase of desert locust adults with a relatively small error of prediction of 6.1% .
preventive locust control should be rational , based on a risk assessment .
the staff involved in implementation of the preventive control strategy needs specific indicators for when or where chemical treatment should be done . in this respect , we show here that the statistical model of cisse et al
. may be appropriate . |
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ALBUQUERQUE, N.M. — The first hint that the service Saturday at Sunset Memorial Park wasn’t a typical funeral came when eulogist Michael Flowers got cheers when he spoke of the dearly departed.
Another giveaway came from the prominent bright colors, T-shirts, sandals and ubiquitous black pork pie hats that broke up the typical formal black.
The funeral for Walter White, the fictional chemistry teacher turned meth kingpin in AMC’s television drama “Breaking Bad,” drew about 200 mourners to the cemetery after a funeral procession that rolled 80 cars deep down Second Street in the North Valley.
Leading the procession were a few Bernalillo County Sheriff’s deputies, followed by a tan, beat-up RV made famous in the show, a hearse and then around 80 diehard fans. The procession shut down streets and took 10 minutes to pass.
The show recently ended its historic run after five seasons of filming in Albuquerque. White died in the last episode.
The funeral benefited Albuquerque’s Health Care for the Homeless and was to be broadcast to millions of viewers via YouTube. However, YouTube cut the stream 15 minutes before the funeral after Sony and AMC determined it was featuring some copyrighted material, according to an employee working on the live stream.
The lack of eavesdropping YouTube viewers made for an intimate evening at the park near Menaul and Edith, which was cast in golden light just before the sun set.
“We all need closure,” said eulogist and “Breaking Bad” set decorator Michael Flowers to the assembled mourners. “… The show is over – and what the hell are we going to do on Sunday nights?”
Nick Gerlich came to the funeral from Amarillo, Texas, and showed a couple of friends more than 40 sites from the show, culminating in White’s funeral.
He said the funeral gives him “closure, I guess, in a strange kind of way. A way of paying respects to someone you feel like you know really well.”
Other mourners came from as far away as Switzerland, Mexico City and Ireland.
Bryan Whitney came to Albuquerque from Ireland primarily for his brother’s wedding.
“But when we heard this was on,” he said, “we booked a little early.”
Whitney said the show has a huge following in Ireland, and it spread quickly among his group of friends to become a major Sunday affair.
He said he feels lost, at least in terms of television entertainment, now that White is dead.
Vernon’s Steakhouse created an endowment fund to raise money for Albuquerque’s Health Care for the Homeless, and attendees were asked to pay their respects to White through donations ranging from $10 to $10,000.
Tickets for the funeral’s nighttime reception at the speakeasy-style steakhouse were $100 per person, and vendors had everything from chicken-and-waffle-flavored chocolate to the original Albuquerque Journal papers featuring Walter White’s obituary. Every guest received two drinks made with blue ice, and some attendees smoked cigars on plush couches outside in front of a live band. Fans of the show from Boston and Rhode Island attended the reception.
“The show was shocking and twisted and amazing, and it had that psychological connection,” Vicki Kowal of Albuquerque said at the gathering. “Losing him (Walter) and that whole show and those characters is a loss. It felt good and befitting that we had the funeral.”
Bracelets at the funeral were given out for $10, and bidding started at $10,000 for a painting by the steakhouse’s resident artist, Gabriel Ballantine, of the various faces of the deceased protagonist.
Sunset Memorial Park officials agreed to hold the funeral only after being assured that they could remove the memorial, a square tombstone to be installed away from real graves, should it become an attraction.
“We are a cemetery first and foremost. Our allegiance lies with our families that have allowed us to bury their loved ones here,” said general manager Vaughn Hendren. “Being a cemetery, we see families bringing loved ones – kids, if you will – who have died from drug abuse.”
Hendren said the cemetery recently buried one such drug overdose victim.
Journal Staff Writer Nicole Perez contributed to this report. ||||| Crawl of outlinks from wikipedia.org started March, 2016. These files are currently not publicly accessible. Properties of this collection. It has been several years since the last time we did this. For this collection, several things were done: 1. Turned off duplicate detection. This collection will be complete, as there is a good chance we will share the data, and sharing data with pointers to random other collections, is a complex problem. 2. For the first time, did all the different wikis. The original runs were just against the enwiki. This one, the seed list was built from all 865 collections. | – A fake funeral was held Saturday for Breaking Bad character Walter White in Albuquerque, offering some 200 fans a chance to pay their last respects to a show that, as one attendee put it, "brought people into Albuquerque, it brought attention into Albuquerque, and it brought money into Albuquerque." The funeral also raised $17,000 for a local charity, with mourners paying to shovel dirt onto an empty coffin. Nevertheless, not everyone was happy about the event, especially family members of those buried at Sunset Memorial Park, KOB.com reports. That's because the funeral may have been fake, but the coffin, the gravesite it was laid in, and the headstone were all very real. "My son is buried about 15 yards from where the makeshift gravesite is," says one father. "This is a place of mourning. It’s not a spectacle." But officials at Sunset Memorial Park say they will remove the memorial if it becomes too much of a tourist attraction. "We are a cemetery first and foremost," says the general manager, per the Albuquerque Journal. "Our allegiance lies with our families that have allowed us to bury their loved ones here." At least one petition is already calling for the gravesite to be taken down. |
in early march 2003 , a 26-year - old man was admitted to a general medical ward of the prince of wales hospital ; he had been ill for 1 week with fever , chills , and rigor .
his previous health had been good , and he had no history of recent travel .
physical examination showed a temperature of 40.2c and bronchial breath sounds at the right upper zone lung field .
chest x - ray confirmed right upper lobe consolidation ( figure , part a ) .
chest radiographs performed a , at admission , b , on day 4 , and c , on day 16 of hospitalization for index sars case - patient , prince of wales hospital .
a complete blood profile on admission showed a leukocyte count 3.1 x 10/l , absolute neutrophil count 2.0 x 10/l , lymphocyte count 0.7 x 10/l , platelet count 112 x 10/l , and hemoglobin 14.7 g / dl .
the patient had mild renal impairment , with a creatinine of 119 mol / l , urea and electrolytes within normal limits , and alanine transaminase mildly elevated at 90 iu / l ( normal < 58
a diagnosis of atypical or viral pneumonia was suspected because of the low leukocyte count and normal c - reactive protein .
other laboratory tests were performed , including blood , sputum , and urine cultures , nasopharyngeal aspirate for influenza and parainfluenza , indirect immunofluorescence for respiratory syncytial viral antigen detection , and atypical pneumonia titer ( for adenovirus , psittacosis , q fever , influenza a and b , and mycoplasma ) .
the patient was housed in a general medical ward with no specific isolation facility . after admission his high fever and productive cough , now with thick , yellowish sputum , persisted .
he also complained of progressive dyspnea , headache , dizziness , generalized malaise , and myalgia .
his pulse and blood pressure were normal , and his oxygen saturation was approximately 98% on room air . a sputum culture yielded normal oral flora , and sputum smears were negative for acid - fast bacilli .
nasopharyngeal aspiration was negative for influenza viruses a and b , respiratory syncytial virus , adenovirus , and parainfluenzavirus types 1 , 2 , and 3 , with the use of commercial immunofluorescence assay .
a chest radiograph on day 4 showed progression of pneumonia , with consolidation changes over the right upper and lower lobes ( figure , part b ) .
a repeat complete blood profile showed a leukocyte count of 5.4 x 10/l with persistent lymphopenia and a platelet count of 98 x 10/l .
amoxicillin - clavulanate was therefore changed to intravenous cefotaxime , 1 g every 8 h ; clarithromycin ( 500 mg twice a day ) was continued .
as the patient s condition deteriorated progressively and he had difficulty in expectorating sputum , salbutamol , 0.5 g four times a day , driven by a jet nebulizer at 6 l of oxygen per min , was given to assist mucociliary clearance .
starting from day 6 , the patient s fever and chest condition gradually improved . however , over the next 2 weeks , 138 persons ( mostly healthcare workers ) who had been in contact with him had onset of a similar illness with high fever and pneumonia .
the patient was subsequently confirmed to be the index case - patient in this hospital outbreak of sars ( 1 ) .
further history showed that he had visited a hotel in kowloon , hong kong , where a 64-year - old physician from southern china had stayed for 2 days ; this physician later died of severe atypical pneumonia 10 days after admission to a regional hospital in kowloon ( 2 ) .
the cause of the illness was not known at the time of the physician s death .
our patient was identified as the index case - patient 5 days after the onset of this large outbreak at the prince of wales hospital , as he was the first patient who had the characteristic clinical , radiologic , and laboratory features of sars and had epidemiologic links with other infected persons .
after 8 days , use of the nebulized bronchodilator was stopped because of the possibility of enhancing sars transmission , and the patient was isolated in a private room with negative - pressure ventilation .
after the patient completed a 7-day course of cefotaxime and a 10-day course of clarithromycin , his pneumonia recovered gradually , and serial chest radiographs confirmed resolution of his consolidation ( figure , part c ) .
an immunofluorescence test for antibody against sars - cov subsequently confirmed an elevated titer of 1:5,120 in convalescent - phase serum collected on day 21 of illness .
convalescent - phase serum was negative for other atypical pneumonia organisms , including adenovirus , psittacosis , q fever , influenza a and b , and mycoplasma .
repeat complete blood count showed that lymphocytes and thrombocytes had returned to normal , along with serum creatinine and alanine transaminase levels .
the patient was isolated in a private room until day 27 of his hospital stay , when his nasopharyngeal aspirate and urine samples were confirmed to be negative for sars - cov .
repeat chest radiograph at follow - up 2 weeks later showed no residual parenchymal opacity , and the patient remained asymptomatic .
this report describes the index patient responsible for the hospital outbreak in the prince of wales hospital ( 2 ) .
he was linked to spread of the virus to more than 100 persons ( 1 ) .
this outbreak , together with similar events in canada ( 3 ) , singapore ( 4 ) and other cities where the source of infection was also related to the chinese physician ( 5 ) , led to increased awareness of this emerging global infection caused by a novel coronavirus ( 6 ) .
the super - spread event in prince of wales hospital caused by this patient was related to failure to apply isolation precautions , as the disease had not been recognized during the early part of his admission .
the use of a nebulized bronchodilator may also have enhanced the spread of the virus in the ward , and this practice was stopped for patients with suspected sars after this incident ( 7 ) .
this case report illustrates the natural history of sars in a young , previously healthy patient who received no specific therapy .
his clinical features and laboratory parameters were similar to those of other patients with sars ( 25 ) .
his clinical course followed a typical pattern with progression of pneumonia during the 2nd week of his illness ( 8) .
he was treated presumptively for bacterial community - acquired pneumonia with conventional antimicrobials ( 9 ) , without antiviral agents or corticosteroids .
he started to improve by the 3rd week and subsequently recovered uneventfully . during the global outbreak in 2003 , treatment of sars was empiric .
several groups have reported the use of ribavirin ( 25,7,8 ) and corticosteroids ( 2,3,7,8,10,11 ) with generally favorable outcomes .
ribavirin has been associated with substantial adverse reactions , including hemolytic anemia , elevated transaminases , and bradycardia ( 4 ) , and has demonstrated no in vitro activity against sars - cov ( 12 ) .
further studies , preferably with a randomized , placebo - control design , are needed to address treatment of this disease , which has high attack rates and is frequently fatal . | during the global outbreak of severe acute respiratory syndrome ( sars ) in 2003 , treatment was empiric .
we report the case history of the index patient in a hospital outbreak of sars in hong kong .
the patient recovered after conventional antimicrobial therapy .
further studies are needed to address treatment of sars , which has high attack and death rates . |
SECTION 1. SHORT TITLE.
This Act may be cited as the ``Meat and Poultry Products
Traceability and Safety Act of 2006''.
SEC. 2. TRACEABILITY OF LIVESTOCK AND POULTRY.
(a) Livestock.--Title I of the Federal Meat Inspection Act (21
U.S.C. 601 et seq.) is amended by adding at the end the following:
``SEC. 25. TRACEABILITY OF LIVESTOCK, MEAT, AND MEAT PRODUCTS.
``(a) Definition of Traceability.--In this section, the term
`traceability' means the ability to retrieve the history, use, and
location of an article through a recordkeeping and audit system or
registered identification.
``(b) Requirements.--
``(1) In general.--Amenable species presented for slaughter
for human food purposes, and the carcasses or parts of
carcasses and the meat and meat food products of those species,
shipped in interstate commerce shall be identified in a manner
that enables the Secretary to trace--
``(A) each animal or group of animals of the
amenable species (as determined by the Secretary to be
appropriate for each amenable species) to any premises
or other location at which the animal was held at any
time before slaughter; and
``(B) each carcass or part of a carcass and meat
and meat food product of the amenable species forward
from slaughter through processing and distribution to
the ultimate consumer.
``(2) Traceability system.--The Secretary shall establish a
traceability system for all stages of production, processing,
and distribution of meat and meat food products that are
produced through the slaughter of amenable species described in
paragraph (1).
``(c) Prohibition or Restriction on Entry.--The Secretary may
prohibit or restrict entry into any slaughtering establishment
inspected under this Act of any amenable species not identified as
prescribed by the Secretary under subsection (b).
``(d) Records.--
``(1) In general.--The Secretary may require that each
person, firm, and corporation required to identify an amenable
species under subsection (b) maintain accurate records, as
prescribed by the Secretary, regarding the purchase, sale, and
identification of the amenable species.
``(2) Access.--Each person, firm, and corporation described
in paragraph (1) shall, at all reasonable times, on notice by a
duly authorized representative of the Secretary, allow the
representative to access to each place of business of the
person, firm, or corporation to examine and copy the records
described in paragraph (1).
``(3) Duration.--Each person, firm, and corporation
described in paragraph (1) shall maintain records required to
be maintained under this subsection for such period of time as
the Secretary prescribes.
``(e) False Information.--No person, firm, or corporation shall
falsify or misrepresent to any other person, firm, or corporation, or
to the Secretary, any information as to any premises at which any
amenable species or carcasses of amenable species were held.
``(f) Alteration or Destruction of Records.--No person, firm, or
corporation shall, without authorization from the Secretary, alter,
detach, or destroy any records or other means of identification
prescribed by the Secretary for use in determining the premises at
which any amenable species or carcasses of amenable species were held.
``(g) Relation to Country of Origin Labeling.--Nothing in this
section prevents or interferes with implementation of the country of
origin labeling requirements of subtitle D of the Agricultural
Marketing Act of 1946 (7 U.S.C. 1638 et seq.).''.
(b) Poultry.--The Poultry Products Inspection Act is amended by
inserting after section 23 (21 U.S.C. 467e) the following:
``SEC. 23A. TRACEABILITY OF POULTRY AND POULTRY PRODUCTS.
``(a) Definition of Traceability.--In this section, the term
`traceability' means the ability to retrieve the history, use, and
location of an article through a recordkeeping and audit system or
registered identification.
``(b) Requirements.--
``(1) In general.--Poultry presented for slaughter for
human food purposes and poultry products shipped in interstate
commerce shall be identified in a manner that enables the
Secretary to trace--
``(A) each poultry or group of poultry (as
determined by the Secretary to be appropriate) to any
premises or other location at which the poultry was
held at any time before slaughter; and
``(B) each poultry product forward from slaughter
through processing and distribution to the ultimate
consumer.
``(2) Traceability system.--The Secretary shall establish a
traceability system for all stages of production, processing,
and distribution of poultry and poultry food products that are
produced through the slaughter of poultry described in
paragraph (1).
``(c) Prohibition or Restriction on Entry.--The Secretary may
prohibit or restrict entry into any slaughtering establishment
inspected under this Act of any poultry not identified as prescribed by
the Secretary.
``(d) Records.--
``(1) In general.--The Secretary may require that each
person, firm, and corporation required to identify poultry
under subsection (b) maintain accurate records, as prescribed
by the Secretary, regarding the purchase, sale, and
identification of the poultry.
``(2) Access.--Each person, firm, and corporation described
in paragraph (1) shall, at all reasonable times, on notice by a
duly authorized representative of the Secretary, allow the
representative to access to each place of business of the
person, firm, or corporation to examine and copy the records
described in paragraph (1).
``(3) Duration.--Each person, firm, and corporation
described in paragraph (1) shall maintain records required to
be maintained under this subsection for such period of time as
the Secretary prescribes.
``(e) False Information.--No person, firm, or corporation shall
falsify or misrepresent to any other person, firm, or corporation, or
to the Secretary, any information as to any premises at which any
poultry or carcasses of poultry were held.
``(f) Alteration or Destruction of Records.--No person, firm, or
corporation shall, without authorization from the Secretary, alter,
detach, or destroy any records or other means of identification
prescribed by the Secretary for use in determining the premises at
which any poultry or carcasses of poultry were held.
``(g) Relation to Country of Origin Labeling.--Nothing in this
section prevents or interferes with implementation of the country of
origin labeling requirements of subtitle D of the Agricultural
Marketing Act of 1946 (7 U.S.C. 1638 et seq.).''.
SEC. 3. TECHNICAL CORRECTIONS.
(a) In General.--The Federal Meat Inspection Act (21 U.S.C. 601 et
seq.) is amended--
(1) by striking ``cattle, sheep, swine, goats, horses,
mules, or other equines'' each place it appears and inserting
``amenable species'';
(2) by striking ``cattle, sheep, swine, or goats'' each
place it appears and inserting ``amenable species'';
(3) by striking ``cattle, sheep, swine, and goats'' each
place it appears and inserting ``amenable species'';
(4) by striking ``cattle, sheep, swine, goats, or equines''
each place it appears and inserting ``amenable species'';
(5) by striking ``cattle, sheep, swine, goat, or equine''
each place it appears and inserting ``amenable species''; and
(6) by striking ``cattle, sheep, swine, goat, or other
equine'' each place it appears and inserting ``amenable
species''.
(b) Effective Date.--The amendments made by subsection (a) shall
take effect on the day after the effective date of section 794 of the
Agriculture, Rural Development, Food and Drug Administration, and
Related Agencies Appropriations Act, 2006. | Meat and Poultry Products Traceability and Safety Act of 2006 - Amends the Federal Meat Inspection Act and the Poultry Products Inspection Act to direct that amenable species presented for slaughter for human consumption, and the carcasses or parts of carcasses and the meat and food products of those animals, shipped in interstate commerce be identified in a manner that enables the Secretary of Agriculture to trace: (1) each animal or group of animals to any location at which the animal was held at any time before slaughter; and (2) each carcass or part of a carcass and food product forward from slaughter through processing and distribution to the ultimate consumer.
Authorizes the Secretary to: (1) prohibit or restrict entry to a slaughtering establishment of an animal not so identified; and (2) require that each person, firm, or corporation required to identify livestock maintain accurate records.
Directs the Secretary to establish a traceability system for all stages of production, processing, and distribution of meat and meat food products and poultry and poultry food products. |
non - motile , non - spore - forming , gram - negative coccobacilli bacteria are a serious public health problem around the world , especially in developing countries ( 1 , 2 ) . brucellosis is an endemic disease in the middle east , the mediterranean countries , and east asia ( 1 , 3 ) .
annually , 10,000 people are infected with this disease in turkey ( 2 ) . the world health organization ( who ) has reported about that every year
, 500,000 new cases of brucellosis were diagnosed in the above regions ( 4 , 5 ) .
this inflicts irreparable economic damage on the health systems of these countries . due to the implementation of health programs , the prevalence of brucellosis
however , brucellosis is an endemic disease in southeast european countries , such as croatia and macedonia ( 8) .
there are currently six classical species ( pathogenic species of both animals and human ) within the genus brucella , namely , brucella abortus ( preferred hosts are cattle and buffalos ) , brucella melitensis ( goats , sheep , and camels ) , brucella ovis ( sheep ) , brucella canis ( dogs ) , brucella suis ( swine , horses , cattle , wild hares , wild boars ) , and brucella neotomae ( desert wood rats ) ( 9 ) . brucella suis and brucella neotomae are endemic to southeast europe .
this study designed primers and probes for all six classical species . following the recommendations of the who published in 1989 ,
the gold standard for the treatment of brucellosis is combinatorial treatment , i.e. , doxycycline - rifampin are used for six weeks , or doxycycline is taken for six weeks together with streptomycin for 23 weeks ( 10 ) .
moreover , some studies have shown that recurrence rates of 510% occur due to inappropriate treatment ( 14 , 15 ) .
so , these factors , such as the high rate of recurrence , resistance to rifampin ( because tuberculosis is endemic in some parts of countries ) , and toxic side effects ( damage to the middle ear , nephrotoxicity resulting from the use of streptomycin ) , have led to trying new treatment options for brucellosis .
fluoroquinolones and macrolides , gentamicin , ciprofloxacin , cotrimexazole , tetracycline , tigecycline , and erythromycin are being used as new anti - microbial agents ( 16 , 17 ) .
so , the best anti - microbial pattern recommended for the treatment of human brucellosis has become important .
recently , microarray hybridization of pre - amplified deoxyribonucleic acid sequences to arrayed species - specific oligonucleotides has been used as a fast technique for the detection and identification of bacterium ( 18 ) .
microarrays are powerful techniques for the rapid and parallel detection of microorganisms genomes in deferential samples , such as blood .
pcr amplification products ( pcr results ) could be analyzed in comparison by mistreatment high - density oligonucleotide microarrays .
powerful analytical devices having hundreds or thousands of probes connected to solid support ( 19 ) .
this ability and practicality facilitate the recognition of brucella antibiotic resistance genes , because gold standard detection ( brucella culture ) need long time ( 12 weeks ) ( 20 ) .
therefore , rapid phenotypic determination of antibiotic susceptibility pattern is not possible by disk diffusion methods ( 21 ) .
thus , evaluating antibiotics patterns and brucella detection appear to be necessary techniques by molecular methods in brucellosis .
so , the aims of this study were to design long oligo microarray probes for the complete diagnosis of brucella spp . and to obtain genetic profiles for antibiotic resistance in bacteria at the same time .
studied via the national center for biotechnology information ( ncbi ) genome database ( http://www.ncbi.nlm.nih.gov/genome ) and the refseq complete genome regarding the six strains were detected throughout the related files of genemarks , version 2.5 m .
then , for each refseq , a complete genome was retrieved from ncbi nucleotide database ( http://www.ncbi.nlm.nih.gov/nuccore ) to study the sequence length and total genes involved within a complete genome .
as inclusion / exclusion criteria to identify and design primers and microarray - based long oligonucleotides probes . the best server to show clear similarities among different brucella spp . is the gviewer server ( 22 ) .
therefore , the primers and probes were designed based on aleleid 7.83 ( premier biosoft , usa ) for the detection of brucella species antibiotics resistance gene . this study designed antibiotics resistance gene solid - phase primers with similar melting temperatures of 60 c in table 2 .
we designed a long oligonucleotide probe , as described in table 3 . to design the probe , lengths of 4053 bp
the specificity of primer and microarray probes had been approved by the basic local alignment search tool ( blast , ncbi , usa ) . for chloramphenicol antibiotics resistance gene ,
the relation between increased drug resistance to chloramphenicol and genes was unknown . but shaw et al .
published a study in nature and showed the catb gene as a chloramphenicol - resistant gene ( 23 ) .
the most encountered are the tet family genes ( 24 , 25 ) , i.e. , tet(a ) , tet(b ) , tet(c ) , tet(s ) , tet(p ) , tet(o ) , tet(l ) , tet(m ) , and tet(w ) .
in addition , aac(3)-ia and aac(6)-ib - cr4 genes represent gentamicin and kanamycin , respectively ( 28 , 29 ) .
the gene sequence studied via the ncbi genome database ( http://www.ncbi.nlm.nih.gov/genome ) was used to design the primers and probes .
the provided microarray probes were rechecked by ncbi blast tool software and the physical - chemical and structural characteristics , such as g , tm , h , and hairpins of designing microarray probes , were tested via the online tool of oligoanalyzer 3.1 ( < https://eu.idtdna.com/calc/analyzer > ) .
other default parameters were performed in this study , including target type : dna , oligo conc : 0.25 m , na+ concentration : 50 mm , nucleotide type : dna , sequence type : linear , temperature : 25 c , max foldings : 25 , suboptimality : 50% , start position : 0 and stop position : 0 .
finally , the accurate and standard long oligonocleotides probes were selected for use in designing a diagnostic dna microarray chip .
this article designed 16 primer oligonucleotides sequence with the same temperature program for use dna microarray detection ( table 2 ) .
therefore , we designed 16 long oligonucleotides probes for dna microarray methods ( table 3 )
. there has been extensive scientific research that has shown a wide range of zoonotic infections , which are caused by different strains of brucella ( 3134 ) .
the identification of these bacteria can be very critical in the medical society ( 35 ) . because of some antibiotic - resistant genes , the prevalence of brucellosis is increasing , and , as a result
, it is necessary to develop a rapid identification technique that can replace culture and biochemical tests . in this study , by using suitable primers and the microarray method , some resistant antibiotics were identified among brucella spp . in a short time .
it was observed that some species that carried the tet family gene showed resistance to tetracycline although the majority of spp .
had the tet+ gene , which means that there was a high level of tectracycline resistance in this period .
in fact , this kind of resistance causes bacteria to acquire new genes , which are responsible to code a protein that protects bacterial ribosomes from the action of tetracyclines .
however , resistance to aminoglycoside was detected by probes that were designed based on acc(3 ) , acc(6 ) , and ant genes .
regarding the mechanism of chloramphenicol resistance , there is its enzymatic inactivation by acetylation mainly via acetyltransferases or , in some cases , by chloramphenicol phosphotransferases . in the present study ,
brucella neotomae 5k33 included the highest number of genes ( 3129 genes ) and nucleotide sequences ( 3.3 mb ) in table 1 , was selected as standard sample for designing long oligonocleotides microarray probes .
so , an accurate , rapid , sensitive , and specific diagnostic tool results a definite treatment that may lead to the reduction of unnecessary costs for public health around the world .
one of the most efficient molecular diagnostic technology is the dna microarray , which makes a reliable diagnosis regarding microbial agents of various infectious diseases at the same time ( 15 ) .
dna microarray technology includes several stages , the most important of which is designing probes . regarding this stage
, scientists can use a wide range of databases , tools , and servers for microarray probes .
this technology is a valuable method to use the obtained information for alleleid tool to retrieve invaluable raw data in the form of designing microarray probes . by comparing the genome sequence of six brucella species ,
designing microarray probes is a versatile process that can be done in a wide range of selections . since , the long oligo microarray probes are the best choices for specific diagnosis and definite treatment , this group of probes was designed in the present survey . moreover ,
probes can be designed in two forms , i.e. , general and specific . in the past ,
microbial resistance was a complicated issue in hospitals and health centers throughout the world , but the microarray diagnostic method can be a solution in this matter , because today s microarray probes are designed for normal virulence or multi - drug resistance genes ( 3641 ) . | brucella spp . is a common zoonotic infection referred to as brucellosis , and it is a serious public health problem around the world .
there are currently six classical species ( pathogenic species in both animals and humans ) within the genus brucella . the ability and practicality facilitated by a microarray experiment help us to recognize brucella spp . and its antibiotic resistant gene
. rapid phenotypic determination of antibiotic resistance is not possible by disk diffusion methods .
thus , evaluating antibiotics pattern and brucella detection appear necessary technique by molecular methods in brucellosis .
so , the aim of this study was to design a microarray long oligonucleotides probe and primer for the complete diagnosis of brucella spp . and obtaining genetic profiles for antibiotic resistance in bacteria at the same time . in this study , we designed 16 antibiotic - resistant gene solid - phase primers with similar melting temperatures of 60 c and 16 long oligonucleotide probes
. these primers and probes can identify tetracycline- , chloramphenicol- , and aminoglycoside - resistant genes , respectively .
the design of microarray probes is a versatile process that be done in a wide range of selections .
since the long oligo microarray probes are the best choices for specific diagnosis and definite treatment , this group of probes was designed in the present survey . |
SECTION 1. SHORT TITLE.
This Act may be cited as the ``Transportation Security and Redress
Act'' or ``TSARA''.
SEC. 2. JUDICIAL REVIEW PROCEDURES FOR PERSONS DELAYED OR PROHIBITED
FROM BOARDING.
(a) Exclusive Remedy.--Except as provided in subsection (b), no
court of the United States or of any State or political subdivision
thereof shall have jurisdiction over any claim, including a
constitutional claim, related to or arising out of a decision to delay
or prohibit a person from boarding a commercial aircraft because such
person has been identified as a threat by the Transportation Security
Administration or the Terrorist Screening Center. Any petition filed
under subsection (c) shall be the sole and exclusive judicial remedy
for any claim described in this section against the United States, any
United States Government department or agency, or any component or
official of any such department or agency.
(b) Exclusive Jurisdiction and Time of Filing.--
(1) Exclusive jurisdiction of the united states court of
appeals.--Any petition for review under subsection (c), as well
as any claims arising out of the same facts and circumstances
that could have been set out in such petition, including any
challenge to an individual's identification as a threat by the
Transportation Security Administration or the Terrorist
Screening Center, shall be filed only in the United States
Court of Appeals for the District of Columbia Circuit or in the
court of appeals of the United States for the circuit in which
the person resides or where such person's principal place of
business is located.
(2) Scope of review.--The court of appeals in which the
petition is filed shall have jurisdiction to decide all
relevant questions of law. The court of appeals shall have
exclusive jurisdiction to affirm, amend, modify, or set aside
any part of the final decision under review, and may order the
Transportation Security Administration or Terrorist Screening
Center to conduct further proceedings.
(3) Time for filing.--The petition filed under subsection
(c), as well as any claims related to such petition, must be
filed not later than 60 days after a final order or final
decision is issued pursuant to the administrative redress
process established by section 44903, 44909, or 44926 of title
49, United States Code. The court of appeals may allow the
petition to be filed after the 60th day only if good cause is
shown for not filing by the 60th day.
(c) Petition for Review.--A petition for review may be filed by any
person who challenges a final administrative redress decision by the
Transportation Security Administration to delay or prohibit such person
from boarding a commercial aircraft because such person has been
identified as a threat by the Transportation Security Administration or
the Terrorist Screening Center. No petition may be filed under this
subsection unless and until the person filing such petition has
exhausted the administrative redress process established by section
44903, 44909, or 44926 of title 49, United States Code.
(d) Requirement for an Administrative Record and Procedures for
Judicial Review.--Notwithstanding any other provision of law, the
following procedures shall apply to a petition filed pursuant to
subsection (c):
(1) The United States shall file with the court of appeals
an administrative record, which shall consist of the
information the United States relied upon in support of the
final decision under review, as well as any information the
petitioner has submitted pursuant to the administrative redress
process established by section 44903, 44909, or 44926 of title
49, United States Code.
(2) All unclassified information contained in the
administrative record that is not otherwise privileged or
subject to statutory protections shall be provided to the
petitioner, and no discovery shall be permitted.
(3) The administrative record may include unclassified
information subject to privilege or statutory protections,
which the United States may submit in camera and ex parte.
(4) Sensitive security information contained in the
administrative record may only be provided to petitioner's
counsel pursuant to a protective order in accordance with the
regulations and orders issued pursuant to section 114(r) of
title 49, United States Code.
(5) The administrative record may also include classified
information, which the United States shall submit to the court
ex parte and in camera. The United States shall provide an
unclassified summary of the classified information to the
petitioner's counsel pursuant to a protective order, taking
into account the circumstances of the case, including the
petitioner's ability to respond to the basis for the final
order or final decision, unless the head of the department or
agency whose classified information is at issue, or his
designee, determines in his discretion that providing a summary
could damage the national security of the United States.
(6) The administrative record may also include information
obtained or derived from orders issued pursuant to the Foreign
Intelligence Surveillance Act of 1978, as amended (50 U.S.C.
1801 et seq.), without regard to subsections (c), (e), (f),
(g), and (h) of section 106, subsections (d), (f), (g), (h),
and (i) of section 305, subsections (c), (e), (f), (g), and (h)
of section 405, and section 706, of that Act. Whenever the
United States intends to use such information against an
aggrieved person, it shall provide an in camera and ex parte
notice to the court concerning such use.
(7) Whenever the court of appeals receives a notice
pursuant to subsection (d)(6), the court shall review, in
camera and ex parte, the application, order, and any other
materials that may be submitted by the United States.
(8) If the court determines that the order was not lawfully
authorized, or the information was not obtained in conformity
with the order, it shall exclude such information from
consideration as part of the administrative record.
(9) Any classified information, sensitive security
information, law enforcement sensitive information, or
information that is otherwise privileged or subject to
statutory protections, that is part of the administrative
record, or cited by the court in any decision, shall be treated
by the court and the parties consistent with the provisions of
this subsection, and shall remain under seal and preserved in
the records of the court to be made available in the event of
further proceedings. In no event shall such information be
released as part of the public record.
(10) After the expiration of the time to seek further
review, or the conclusion of further proceedings, the court
shall return the administrative record, including any and all
copies, to the United States. All privileged information or
other information in the possession of petitioner's counsel
that was provided by the United States pursuant to a protective
order shall be returned to the United States, or the
petitioner's counsel shall certify its destruction, including
any and all copies.
(e) Scope of Review.--The court of appeals shall decide any
petition for review filed under subsection (c) based solely on the
administrative record submitted by the United States, including any
information which may have been filed with the court in camera and ex
parte, and any information submitted by the petitioner during the
administrative redress process established by section 44903, 44909, or
44926 of title 49, United States Code. The court shall uphold a final
decision issued pursuant to the administrative redress process by the
Transportation Security Administration unless such decision was--
(1) arbitrary and capricious, an abuse of discretion, or
otherwise not in accordance with law;
(2) contrary to constitutional right, power, privilege, or
immunity;
(3) in excess of statutory jurisdiction, authority, or
limitation, or short of statutory right;
(4) lacking substantial support in the administrative
record taken as a whole, including in the classified
information submitted to the court; or
(5) not in accord with procedures required by law.
(f) Supreme Court Review.--A decision by the court of appeals under
this section may be reviewed by the Supreme Court under section 1254 of
title 28, United States Code.
(g) Rule of Construction.--Nothing in this section shall be
construed as limiting, superseding, or preventing the invocation of,
any privileges or defenses that are otherwise available at law or in
equity to protect against the disclosure of information.
SEC. 3. DEFINITIONS.
In this Act:
(1) The term ``classified information'' means any
information or material that has been determined by the United
States Government pursuant to an Executive order, statute, or
regulation, to require protection against unauthorized
disclosure for reasons of national security and any restricted
data, as defined in paragraph r. of section 11 of the Atomic
Energy Act of 1954 (42 U.S.C. 2014(y)).
(2) The term ``national security'' means the national
defense and foreign relations of the United States.
(3) The term ``sensitive security information'' shall have
the meaning set forth in sections 114(r) and 40119 of title 49,
United States Code, and the regulations and orders issued
pursuant thereto.
(4) The term ``aggrieved person'' shall have the meaning
set forth in sections 1801(k), 1821(2), and 1841(3) of title
50, United States Code.
SEC. 4. APPLICATION TO PROCEEDINGS.
(a) Effective Date.--The amendments made by this Act shall take
effect on the date of the enactment of this Act, and shall apply to any
pending claim by a person who challenges a final decision by the
Transportation Security Administration to delay or prohibit such person
from boarding a commercial aircraft because he has been identified as a
threat by the Transportation Security Administration or the Terrorist
Screening Center.
(b) Conforming Amendment.--The procedures set forth in section 2(d)
shall also apply to any petition to review a final order entered
pursuant to section 46110 of title 49, United States Code. | Transportation Security and Redress Act or TSARA This bill grants to the U.S. Court of Appeals for the District of Columbia Circuit and certain other U.S. courts of appeals exclusive jurisdiction to review any claims against the United States or a federal agency arising out of a decision to delay or prohibit a person from boarding a commercial aircraft because that person has been identified as a threat by the Transportation Security Administration (TSA) or the Terrorist Screening Center. A petition for review may be filed by any person who challenges a final administrative redress decision by the TSA to delay or prohibit a person from boarding a commercial aircraft because identified as a threat. No petition may be filed until the person filing has exhausted the administrative redress process. The court of appeals shall decide any petition for review based only on the administrative record submitted by the United States which shall consist of the information the United States relied upon in support of the final decision under review, as well as any information the petitioner has submitted pursuant to the administrative redress process. The court shall uphold a final decision issued pursuant to such process by the TSA unless such decision was: arbitrary and capricious, an abuse of discretion, or otherwise not in accordance with law; contrary to constitutional right, power, privilege, or immunity; in excess of statutory jurisdiction, authority, or limitation, or short of statutory right; lacking substantial support in the administrative record taken as a whole, including in the classified information submitted to the court; or not in accord with procedures required by law. A decision made by a court of appeals under this bill may be reviewed by the Supreme Court. |
A 34-year-old man has filed an $800,000 lawsuit against a Albany construction company, claiming the owner fired him after he refused to attend weekly Bible study.
Ryan Coleman’s lawsuit states that he discovered only after he was hired as a painter for Dahled Up Construction that the job entailed more than just fixing up homes. According to Coleman and his lawsuit, owner Joel Dahl told him all employees were required to partake in regular Bible study sessions led by a Christian pastor during the work day, while on the clock.
Coleman told Dahl that the requirement was illegal, but Dahl wouldn’t budge, according to the lawsuit. In order to keep his job, Coleman obliged for nearly six months but ultimately told Dahl he couldn’t go, the suit says.
“I said ‘I’ve kept an open mind, and it’s just not my thing.’ And he said, ‘Well, I’m going to have to replace you,'” Coleman told The Oregonian/OregonLive.
“He said ‘You’re not going to tell me how to run my own company,’” Coleman continued. “I said ‘I’m not trying to tell you how to run your own company, but you’re not going to tell me what god to pray to.’”
Coleman said his religious beliefs are indigenous: He’s half Caucasian and half Native American, with Cherokee and Blackfoot heritage.
Coleman worked for the small construction company from October 2017 to this past April, when he was fired, the suit states.
“This is so illegal,” said Corinne Schram, a Portland attorney representing Coleman. “Unless you are a religious organization like a church, you cannot force your employees to participate in religious activities.”
Dahl's Albany attorney, Kent Hickam, doesn't dispute that Dahl requires all of his employees to attend Bible study, but says it’s legal because Dahl pays them to attend.
“Mr. Dahl feels that it’s unfortunate that he (Coleman) is now trying to exploit Mr. Dahl’s honorable intentions for unjustified financial gain,” Hickman said.
Dahl told The Oregonian/OregonLive that he’d struggled with drugs and alcohol and served time in prison for attempted second-degree assault. He said he’s been clean and sober for seven years. He started his company in 2016, with the idea of helping other convicted felons or people who’ve battled addictions rebuild their lives.
“I’m a second-chance employer,” Dahl said. (Joel Dahl says he’s not related to another second-chance employer, Dave Dahl of Dave’s Killer Bread.)
God is a big part of Joel Dahl’s life. The company's Facebook page features photos of recently completed home remodels -- often alongside praise to God or Jesus.
After stripping a 106-year-old home down to the studs and renovating it to look brand new, one post states: “Fixing up this old house at times I was discouraged ‘cause there was so much to fix. But Me and God did this together and we got er done.”
Another post expresses gratitude for the work that has come to Dahled Up Construction: "Just finished these 2 roofs ... Look at God go. He is so awesome.”
Coleman said he’s served prison time for delivery of methamphetamine and child neglect but has now been clean and sober for nearly four years. Earlier this week, he won back full custody of his two children, he said.
Coleman’s past left him fearful that he wouldn’t be able to find other work, so he said stuck with the weekly, hourlong Bible study sessions for six months, until he took a stance and said he wouldn’t go.
Coleman's legal team has started a web page, where it plans to offer updates about the case. Members of the public can also sign the page, in a show of support for Coleman. The page can be viewed here.
The lawsuit was filed last week in Linn County Circuit Court. Read the lawsuit here.
-- Aimee Green
[email protected]
o_aimee ||||| ALBANY, Ore. – A man is suing an Albany construction company claiming he was fired for not attending Bible study.
Ryan Coleman said he was hired by Dahled Up Construction Inc. in October 2017. Soon after he started working there, he said he discovered his boss Joel Dahl required employees to attend a Christian Bible study during work time.
Coleman, who is not a practicing Christian, told Dahl he was not comfortable attending and that it was it illegal for him to require his employees to do so.
However, he said Dahl insisted he attend. Coleman said he believed he had no other choice and went to the Bible study in order to keep his job.
In April, Coleman said he once again told Dahl on the phone that he had a right not to attend the Bible study, and was then fired by Dahl.
Coleman claims Dahl and his company discriminated against him due to his religious beliefs and is asking for $800,000 in damages.
Dahl’s attorney Kent Hickman told the Oregonian that Dahl does require all his employees to attend Bible study and said it is legal because he pays them to attend. | – An Oregon man who says he was fired from his construction job for refusing to attend Christian Bible study is appealing to a higher power: the court. In a lawsuit filed this month, Ryan Coleman, 34, says he didn't find out about the weekly Bible study requirement until after Joel Dahl of Albany-based Dahled Up Construction hired him as a painter in late 2017, OregonLive reports. He says he went along with it for about six months before telling Dahl, "It's just not my thing." Dahl's response, per Coleman, "He said, 'well, I'm going to have to replace you." That was in April, KEZI reports. Now, Coleman is seeking $800,000—$50,000 in lost earnings and $750,000 for "severe emotional distress, anguish, humiliation, anger, shame, and anxiety," per the lawsuit's ironically titled "prayer for relief." Dahl's attorney, accusing Coleman of seeking "unjustified financial gain," concedes that Dahled Up employees are required to go to Bible study. But it's legal, he argues, because they're still on the clock when they attend. Colman's attorney disagrees: "This is so illegal," she says, adding that only religious organizations could have such a requirement. Dahl, who admits to past legal problems, says he's a "second-chance employer," with OregonLive noting that "God is a big part of Joel Dahl's life." |
SEOUL, South Korea — Kim Jong-un , catapulted into prominence after Kim Jong-il ’s sudden death, paid respects at his father’s glass coffin on Tuesday, as the regime stepped up a campaign to portray the impoverished country as standing behind its young new leader.
Kim Jong-un’s visit to the Kumsusan mausoleum, where the body was lying in state, was his first public appearance since his father’s death on Saturday pushed him to the forefront of the North Korean leadership, whose inner workings and power struggles remain a mystery to the outside world.
Televised images and photographs from North Korea showing streams of weeping soldiers and citizens who filled plazas in Pyongyang to mourn the death of Kim Jong-il. Combined with an outpouring of effusive praise for the son, the official coverage of the mourning seemed to reflect a calculated propaganda message meant to depict a smooth transition.
The son was inheriting not only the mantle of power but also a cult of personality from his father: the media began calling him “another leader sent from the heaven,” a description until now reserved for his father.
The North announced the death on Monday. The outside world, caught off guard, scrambled to figure out where a regime with a food crisis and nuclear weapons would be headed under a young and inexperienced leader, whose command of loyalty among hard-line generals and Workers’ Party officials — all veterans of bloody power games — remains untested.
“Comrade Kim paid his respect with a grief-stricken heart,” the North’s official news agency, K.C.N.A., said in a brief dispatch.
The North’s state television showed Kim Jong-il’s body covered with a red blanket and his head on a white pillow. The coffin was surrounded by white chrysanthemums and Kimjongilia, a flower named after the deceased leader.
Kim Jong-un was accompanied by a group of senior party and military officials, giving the outside world a hint of whom Mr. Kim was relying on during a critical transition. But the list included no new or unusual names.
Paying a tribute and swearing to uphold the wishes of a dead ancestor is a crucially important political gesture for the son. The Kim family, starting with Mr. Kim’s grandfather, Kim Il-sung, the North’s founding president, has ruled the country for more than six decades.
In a lengthy editorial, North Korea’s main party daily, Rodong Sinmun, legitimized the third-generation dynastic succession by calling Korea “the Kim Il-sung nation” and “the Kim Jong-il Korea.” It called Kim Jong-un “the spiritual pillar and the lighthouse of hope” for the military and the people.
State radio said: “The respected comrade Kim Jong-un’s ideology equals General Kim Jong-il’s ideology and will.”
Crowds of people, some wailing and some grim-faced, placed flowers at monuments around the Pyongyang, the North Korean capital, The Associated Press reported. Flags flew at half-staff and shops were closed.
China and Russia, North Korea’s Cold War-era allies, quickly moved to indicate support for the new leadership of the government in Pyongyang. The United States and South Korea remained cautious but called for a peaceful and stable transition in North Korea.
President Hu Jintao of China visited the North Korean Embassy in Beijing to express condolences. President Dmitri A. Medvedev of Russia sent a message of condolence to Kim Jong-un.
“We offer our condolences to the North Korean people,” the South Korean government said in a statement. “We hope that North Korea will recover stability soon and South and North Korea can work together for peace and prosperity on the Korean peninsula.”
Unification Minister Yu Woo-ik said that South Korea would not send a delegation to Mr. Kim’s funeral on Dec. 28. But he said the government would allow visits to the North by the families of the late President Kim Dae-jung, who held a landmark summit with Mr. Kim in 2000, and the former chairman of Hyundai, Chung Mong Hun, who had business ties with North Korea.
Kim Jong-il died of a heart attack brought about by overwork and stress, according to the North’s media. Because of the age and inexperience of his son, who is believed to be in his late 20s, the world is watching how the transition will proceed.
For policy makers in the region, the worst case scenario would be an unruly power struggle accompanied by a breakdown of command and control over the country’s nuclear weapons.
But the transition also offers opportunities for Washington and the government in Seoul, said David Straub, deputy director of the Shorenstein Asia-Pacific Research Center at Stanford University. Kim Jong-un is the first North Korean leader who was educated at least partly in the West. He studied in Switzerland as a teenager.
“There will be new leaders in North Korea. They will be younger,” he said. “U.S. officials will need to consider what signals to send to North Korea and when and how best to do this to maximize the chances for positive change in North Korea.” ||||| Dow Jones Reprints: This copy is for your personal, non-commercial use only. To order presentation-ready copies for distribution to your colleagues, clients or customers, use the Order Reprints tool at the bottom of any article or visit www.djreprints.com
U.S. officials aggressively lobbied China, Russia and Japan and suspended a food-aid plan for North Korea following the death of the country's leader, aiming to gain a diplomatic foothold as control over the authoritarian, nuclear-armed country appeared to pass to Kim Jong Il's untested young son.
North Korea officially returned to its customary silence on Monday after announcing the death of its supreme leader early in the day, underscoring the world's anxiety over its trajectory under Kim Jong Eun, the former ruler's youngest son, whom state media says will now lead the isolated country.
The U.S. doesn't have a clear ... | – Kim Jong Un made his first public appearance today since the death of his father, paying his respects at the Pyongyang mausoleum where Kim Jong Il lies in state in a glass coffin, reports the New York Times. The younger Kim was accompanied by senior party and military officials, while mourners in the street praised him and the official state media touted his legitimacy—indicating that North Korea's transition of power so far appears to be on track. The United States appears divided over how much to push Pyongyang for reform at this delicate time, reports the Wall Street Journal. Some advocate pressuring the young leader now, as he is still consolidating power, while others believe foreign countries should back off and let North Korea stabilize, as a new generation of leaders might be more open to change. Kim Jong Il's official funeral will be held Dec. 28, but foreign delegations will not be invited. “There will be new leaders in North Korea. They will be younger,” said one intelligence expert. “US officials will need to consider what signals to send to North Korea and when and how best to do this, to maximize the chances for positive change in North Korea.” |
The Wikipedia page of North Carolina Republican Congresswoman Renee Ellmers was edited by a federal government IP address to accuse her of having an affair with Republican Majority Leader Kevin McCarthy.
“Ellmers is alleged to have been involved in an extra-marital affair with Republican House Majority Leader Kevin McCarthy since 2011,” the edited article read. The sources listed for the allegation were a Breitbart article (which didn’t allege anything of the sort) and a blog post by conservative blogger Charles C. Johnson.
The edit was reversed by another editor, calling them “not reliable sources”. But the Washington Free Beacon’s Lachlan Markay noticed something interesting about the IP address behind the anonymous edit…
Umm. Someone using a DHS IP address edited Renee Ellmers’ Wikipedia page to allege an affair with McCarthy pic.twitter.com/U88gCiCaK6 — Lachlan Markay (@lachlan) October 8, 2015
Indeed, inputting the IP address used to edit Ellmers’ Wikipedia page (216.81.94.68) into any free IP look-up service reveals that the edits came from a Department of Homeland Security computer. Ironically, Ellmers and McCarthy both were advocates of passing a “clean” DHS funding bill earlier this year, rather than holding up the bill to try to defund President Obama’s executive actions on immigration as conservatives wanted.
[Image via screengrab]
——
>>Follow Alex Griswold (@HashtagGriswold) on Twitter
Have a tip we should know? [email protected] ||||| Kevin McCarthy, a Republican from California, is the current majority leader in the House, and was the heavy favorite to replace the departing John Boehner as Speaker. That was, at least, until he suddenly removed his name from consideration today, leaving fellow Republicans on Capitol Hill in “chaos” and “tears.”
McCarthy announced that he would no longer seek the position as Speaker at about 12:30 today. It was so unexpected that several of McCarthy’s colleagues in the House told reporters that people were “stunned” and in tears. Peter King, who normally only opens his mouth to tell a lie, reported to the Washington Post’s Robert Costa that members of the House were crying in a cloakroom.
Did McCarthy simply not want what is now commonly considered “the worst job in “Washington,” or was there more to it? Very shortly after McCarthy’s announcements, conservative-interest sites began reporting that a rumor has been circulating, with increasing intensity in recent weeks, that McCarthy was engaged in an affair with North Carolina republican House member Renee Ellmers.
Brietbart News stated that the rumor has been “circulating” for “some time,” while Red State’s Erick Erickson, in an article that has for some reason since been deleted, reported that a “guy out in America who has emails for a massive number of members of Congress” recently sent a mass email to members with links that allege the affair. Erickson described the rumor as becoming “louder buzz over the past few days with more and more people on and off the hill talking about it.”
The earliest online evidence the rumor seems to be Got News, the website run by controversial rightwing muckraker Charles C. Johnson, who, on Sept. 25, weeks before the rumor was reported elsewhere, wrote that McCarthy and Ellmers were in a “long running” affair that was “something of an open secret in Washington.”
Adding onto the speculation is the existence of a letter written by Walter Jones, a Republican also from North Carolina, and sent to Republican Conference chairman Cathy McMorris-Rodgers on Wednesday, arguing that “Republican leaders or potential Republican leaders must step down because of skeletons in their closets.”
McCarthy and Ellmers—both of whom are married—have so far denied the existence of the affair, but a source who spoke to Gawker said that he witnessed the two together, acting affectionately, at a fundraiser a few months ago.
“The best way to describe it would be Joe Biden shoulder massage thing,” the source said. “But without any of the awkwardness. I don’t do that to anyone but my wife.”
The same source said that he has been hearing the rumor for at least six months, meaning it at least predates the Johnson blog post. Today, it has spread so fast that an IP address registered to Homeland Security was logged altering Ellmers’ Wikipedia page to mention the affair.
Gawker has reached out to the offices of McCarthy and Ellmers and will update this story if they respond. If you’ve heard anything about Kevin McCarthy’s resignation and/or his alleged affair, or have any insight into the origin of the rumor, email me at [email protected].
[image via Getty] ||||| After dropping out of the race for speaker of the House, Rep. Kevin McCarthy (R-Calif). said he did not want to be a "distraction" from the committee investigating the attack on Americans in Benghazi. (AP)
After dropping out of the race for speaker of the House, Rep. Kevin McCarthy (R-Calif). said he did not want to be a "distraction" from the committee investigating the attack on Americans in Benghazi. (AP)
Thirty minutes beforehand, John A. Boehner had no idea.
About 11:30 a.m. on Thursday, just before House Republicans were scheduled to choose his successor, the House speaker sat down with reporters from his native Ohio. He smoked a Camel. He talked about buying a car, a regular-guy moment to savor after nine years of being driven by the Capitol Police.
And Boehner was certain that his top deputy — the affable, attentive, unobjectionable Majority Leader Kevin McCarthy (R-Calif.) — was about to win.
There had been reasons to doubt that. Last month, McCarthy had embarrassed Republicans by suggesting that the House committee to investigate the deaths of four Americans in Benghazi, Libya, was designed to score political points. Two days before, a back-bencher who opposed McCarthy circulated a vague letter asking whether any top Republicans had committed “misdeeds.” One day before, McCarthy had been formally rejected by the House’s hard-right caucus.
Still, after all that, McCarthy had the votes. Boehner was sure. After all, who else was there?
It was the soundbite heard 'round Capitol Hill: House Majority Leader and presumptive House speaker nominee Rep. Kevin McCarthy, R-Calif., has dropped out of the race for speaker. The Washington Post's Elise Viebeck explains the sudden news — and what happens next. (Julie Percha/The Washington Post)
“I’m confident he’ll win today,” he said, according to the account of a reporter from the Gannett News Service.
The reporters left. Boehner went to perform a ceremonial duty, opening the House for the day. Then, at 12:03 p.m., a pair of staffers pulled him into an office to tell him he was wrong.
On Thursday, Capitol Hill was still struggling to make sense of McCarthy’s sudden withdrawal from the race for speaker. It was caused, in part, by a party at war with itself. The same hard-line conservatives who hounded out Boehner had hounded out his likely successor before he had even held the speaker’s gavel.
On Thursday, McCarthy seemed like a bystander at his own big moment, so much so that he did not even warn his allies that he was about to give up.
“I’m not the one,” McCarthy told the other Republicans, who’d come expecting a vote.
He said it so softly that many members couldn’t hear him at all.
Republicans including Rep. Darrell Issa (R-Calif). and Rep. Jason Chaffetz (R-Utah) - who is running for House speaker - say what it means that Rep. Kevin McCarthy (R-Calif.) is no longer seeking his party's nomination. (AP/C-SPAN)
Boehner had announced his resignation on Sept. 25, after four tumultuous years as speaker. His obvious successor was McCarthy, 50.
The golden era of his candidacy lasted all the way until Sept. 29.
“Everybody thought Hillary Clinton was unbeatable, right?” McCarthy told Fox News Channel’s Sean Hannity, who had challenged him to state a promise that Republicans had delivered on. “But we put together a Benghazi special committee, a select committee. What are her numbers today? Her numbers are dropping.”
With that comment, McCarthy seemed to cast doubt on the credibility of the Benghazi committee, which discovered that Clinton had used a private e-mail account to conduct business as secretary of state. To Democrats, he seemed to be admitting that one of Congress’s most sacred duties — to investigate crimes and failings in government — had been perverted into a lab for political-opposition research.
Two days later, McCarthy said he didn’t mean what he had said.
But it was too late for many conservatives. Part of the speaker’s job was to avoid do-overs, to go on TV and say the right thing.
“We seem to continually lose the communication battle,” said Rep. Jason Chaffetz (R-Utah), who jumped into the race to oppose McCarthy. “The president has a huge bully pulpit. The Democratic nominee will obviously have a big megaphone. . . . You’ve got to win the argument in the public, then you have the ability to govern.”
Last weekend, in private, McCarthy began to worry that he didn’t have the votes.
He would need 218 votes to become speaker when the formal vote was held in late October. But no Democrats were going to back him. That meant McCarthy could afford to lose only 29 of the 247 House Republicans.
On Thursday, the GOP would hold its internal vote, a crucial test of McCarthy’s strength. In his internal projections, he wasn’t getting what he needed. “I knew I could get 200-and-some votes. But getting 218 was not easy,” McCarthy said in an interview Thursday evening.
That meant McCarthy needed to win over some of the House’s professional “no” votes, the same conservatives who had defied Boehner in votes over the debt limit, the “fiscal cliff” and the federal budget.
This was a job McCarthy had never been good at. He was a walking personification of the problem that had felled Boehner — a human symbol of the GOP’s inability to keep order.
McCarthy had recruited many of those conservatives, visited their districts, knew their families, bought them pizza. And, yet, even when he was the official party whip, they defied him.
On Tuesday night, he went back to the same people, seeking a different result.
McCarthy walked into a third-floor ballroom at the Capitol Hill Club, a bastion of the Republican establishment just south of the Capitol. Waiting for him were dozens of conservatives, including the crucial House Freedom Caucus — a group which says it has about 40 members (the exact number, and the full caucus membership list, are both secret). The Freedom Caucus had pledged to vote as a bloc if 80 percent of them could agree on one candidate.
I’m my own man, McCarthy told them. I’m not John Boehner. I’m committed to creating a more inclusive House.
He laid out plans to create a “kitchen cabinet” consisting of leaders drawn from conservative groups such as the Freedom Caucus.
But they wanted him to make specific promises. Rep. Tim Huelskamp (R-Kan.), the leader of the House Tea Party Caucus, asked McCarthy to publicly oppose efforts by establishment groups — the U.S. Chamber of Commerce and others — to run radio and TV ads criticizing conservatives who defied their own leaders.
McCarthy would not commit to a public pledge.
Earlier that day, Rep. Walter B. Jones (R-N.C.) — an antiwar libertarian who was often an outsider in his own party — wrote a letter to another leader of the House GOP, Rep. Cathy McMorris Rodgers (Wash.).
In the letter, Jones said any candidate for speaker should withdraw “if there are any misdeeds he has committed since joining Congress that will embarrass himself, the Republican conference or the House of Representatives.”
In interviews on Thursday, Jones said he didn’t have any hard proof of misconduct by McCarthy or any of the other candidates. Given a chance to confront McCarthy about possible misdeeds at the forum Tuesday night, Jones instead confronted him about an occasion where one of McCarthy’s staffers had been rude to one of his own staffers about the renaming of a post office.
The next day, the Freedom Caucus met to decide.
A few of them were willing to give McCarthy a chance, including some of those who McCarthy had recruited in 2010. But the vast majority couldn’t do it. Their constituents had been calling to complain that McCarthy was too much like Boehner.
That left two other choices: Chaffetz and Rep. Daniel Webster (R-Fla.).
On paper, there was not much to recommend Webster: He was little-known in the House and was in danger of losing his seat entirely because of redistricting.
His appeal as a leader was that, in effect, he was promising not to lead them.
Elect me, he had told members, and every House member would be part of the team. No orders from on high.
They chose Webster.
If the Freedom Caucus followed through on its promise to vote as a bloc, that meant McCarthy might have lost 40 votes. Which would mean he couldn’t win.
“When they went with Webster, I kind of realized I can’t get this thing,” McCarthy said Thursday.
Still — in public and private — McCarthy insisted he would win.
“I look forward to being able to get their votes,” he said after the Freedom Caucus rejected him. “My door is always open. Every voice needs to be heard. I’m very confident we’ll all get back together.”
At 8 a.m. Thursday, there was another meeting with about 75 House members, a last sales pitch. It didn’t go well.
“The next election is the most vital one in recent history. If the liberal left keeps controlling the White House, we’re never going to retrieve the country we know and love,” Rep. Dana Rohrabacher (R-Calif.) said he told McCarthy. He was still stuck on the Benghazi comments. “Kevin, you just had a verbal blunder that has dramatically damaged our cause. I just cannot support you for speaker — just a few days after you said something so harmful to that cause.”
As Rohrabacher recalled, McCarthy then stood up to speak.
“I’ve learned from this mistake. I hope you all will forgive me,” McCarthy said, according to Rohrabacher. “I will make sure it doesn’t happen again.”
Rohrabacher said he rose again.
“Kevin, you need to not be in this race,” he said.
In the rest of the House, the morning went on as usual. In his office, Boehner was regaling the Ohio reporters with a list of his accomplishments and joking about a little wind-up monkey that he kept on his desk. It was a reminder of how he felt sometimes, always running around to keep the House going.
“You don’t have to be the monkey anymore,” Boehner said his scheduler had told him, according to an account by Deirdre Shesgreen of Gannett. The speaker had decided to give the toy to a congressman’s young daughters.
But elsewhere, McCarthy had made a decision that would change those plans. He didn’t want to be speaker if it meant being constantly worrying he’d lose the job.
The meeting began with a prayer and the Pledge of Allegiance. Then McCarthy got up and started talking in a normal voice, without a working microphone. “Speak up!” people yelled.
He spoke. It was quiet. “I think McCarthy just pulled out of the race. . . . ” Rep. Bill Huizenga (R-Mich.) wrote on Twitter, still unsure.
Then Boehner spoke, saying that the election was postponed and the meeting was adjourned. Later he said he would stay on until a new speaker was chosen. Winding up instead of winding down.
In the big room, the Republicans were still quiet. Everybody filed out. Later, Rep. Peter T. King (R-N.Y.) reported seeing members cry in the “cloakroom,” a space off the House floor that is off-limits to the public. “A banana republic,” he called his own party.
McCarthy left and tried to persuade Rep. Paul Ryan (R-Wis.), the former vice-presidential candidate, to do what he couldn’t. “I think Ryan is the best one to bring us together. Paul Ryan has the cachet. They know of his brain work, they know he has a national following. He just has the respect,” McCarthy said. ||||| Getty Behind McCarthy's decision to bail 'They’re going to eat you and chew you up.'
The doubts haunted Kevin McCarthy.
Publicly, he projected an air of confidence, the appearance of the man who would be the next speaker of the House. But in private, his allies told him the pursuit for power was changing him and he wasn't himself. Some said that even if he won, he couldn't govern.
Story Continued Below
"We need somebody to get us 247," McCarthy said in an extensive interview with POLITICO Thursday, referring to the total number of House Republicans. "And I was never going to be able to get 247."
The majority leader's longtime allies — the people he recruited and helped get elected to Congress — told him they were getting hammered back home, and that it would be difficult to back him on the House floor.
Other friends said McCarthy's pursuit of the speaker’s gavel had become a staggering weight on his shoulders and was already starting to change him.
Conservatives — namely members of the House Freedom Caucus — were making demands he believed he simply couldn’t deliver on.
And, of course, there was Benghazi. The California Republican’s monumental blunder – his claim that the panel was created to undermine Hillary Clinton’s presidential campaign – became an unavoidable distraction.
McCarthy went back and forth in his head, and with his staff. Should he stay in the race? Did he even want to? And with a limited mandate – winning the speakership with probably just 220 votes, essentially the bare minimum – could he be an effective speaker?
"We all worked to get the majority. And I had a lot of friends that were really supportive that said, 'Why do you want to do it during this time? This time will be the worst time. They’re going to eat you and chew you up,'" McCarthy said in the interview. "But I also felt with what we had in front of us, we need somebody to get us [all 247 Republicans united], and I was never going to be able to get 247.”
McCarthy came up with two options. He could drop out of the race. Or he could cobble together 218 GOP votes in the closed meeting Thursday of House Republicans to nominate the speaker — proving he had the support to win a floor vote for speaker.
In the hours leading up to the party nominating contest, McCarthy concluded the job was not for him. Even if he could win, he'd be unable to move a must-pass debt ceiling increase. He figured he'd have an equally hard time shepherding through a critical spending deal.
The party, as he would say after the announcement that left the entire Capitol dumbfounded, needed a new face.
He had missed his moment.
A McCarthy aide delivered the news to a shocked Boehner just moments before he made the announcement publicly.
“For the betterment of the conference, if we are going to have all these battles about wanting to do something, it's easier if we have someone who comes and unites us,” McCarthy said during the interview. “And there’s something to be said about a fresh face.”
With that, McCarthy's unusually rapid ascent through House leadership ranks came to an abrupt halt.
Washington is filled with men and women who never go for the brass ring, only to regret it years later. McCarthy, however, seemed at peace.
“The conference is in an odd place,” McCarthy said, as he scrolled through messages on his BlackBerry. “Sometimes you gotta hit the bottom to be able to come back. This gives us a real fresh start – a new start gives a fresh start. Having a fresh face brings the conference together. There are hurt feelings about past things on all sides, I tried to do some healing there.
"Look, I think it’s just best for the conference," he added. "I don’t want to go through these tough things and still have more problems.”
There was an immediate effort by senior Republicans to try to convince Rep. Paul Ryan (R-Wis.) to reconsider his resistance to the speakership. He is seen as one of the only House Republicans who has the stature to unite all factions in the conference. Ryan immediately put out a statement saying he, too, wasn’t the guy.
McCarthy will remain majority leader, the No. 2 in the unruly conference, where he will be in charge of the House floor, committees and policy. Rep. Steve Scalise (R-La.), who mounted an aggressive bid to replace McCarthy as majority leader, will remain as majority whip.
While it wasn’t the only factor, the House Freedom Caucus’ decision to vote as a bloc was a huge blow to McCarthy’s count and his ego. Ohio Rep. Jim Jordan, who was poised to run for House majority leader, cast doubt on whether McCarthy could win the speakership. Members of the House Freedom Caucus met privately with McCarthy days before the planned vote, and threatened to overthrow him as speaker if he did not accede to their demands.
McCarthy said when the Freedom Caucus endorsed Florida Rep. Daniel Webster “that showed how tough of a hill I had to climb.”
McCarthy said he’s not sure if he will endorse a candidate for speaker, but there’s already talk about a caretaker to hold the speaker’s gavel until the end of 2016.
The leading candidates are Minnesota Rep. John Kline, a close ally of Boehner who chairs the Education and Workforce Committee; Texas Rep. Mac Thornberry, the chairman of the Armed Services Committee; Michigan Rep. Candice Miller, the chairman of the House Administration Committee; Oklahoma Rep. Tom Cole, a senior member of the Appropriations Committee and former chairman of the National Republican Congressional Committee; and Rep. Greg Walden, the current chairman of the NRCC.
Authors: | – There might be somebody out there who can unite all 247 House Republicans, but Kevin McCarthy says it definitely isn't him. The House majority leader tells Politico that his shock decision not to seek the nomination for speaker came after friends said to him: "Why do you want to do it during this time? This time will be the worst time. They're going to eat you and chew you up." He says that while he could have won the speakership with around 220 votes, he "was never going to be able to get 247," which would have left him unable to pass crucial measures like the debt ceiling increase. A big factor was the decision of the House Freedom Caucus to back Rep. Daniel Webster for the job, which could have left McCarthy without enough votes, reports the Washington Post. There could be murkier factors involved: On Wednesday, Rep. Walter Jones called for candidates who've committed "misdeeds" to withdraw from the race, and rumors are circulating that he was referring to an alleged affair between McCarthy and fellow GOP Rep. Renee Ellmers, Gawker reports. Her Wikipedia page was edited on Thursday to say she has allegedly been having an affair since 2011. The edit, which came from a Department of Homeland Security IP address, was quickly reversed to remove the claim, Mediaite reports. Jones says he doesn't have any proof of misconduct involving McCarthy or any other candidates, the Post reports. (McCarthy's Benghazi comments didn't help his cause.) |
in the previously reported cases of presumptive p. tenuis nematodiasis , cervical scoliosis and analgesia were attributed to continuous dorsal gray column lesions , whereas general proprioceptive ( gp ) ataxia and upper motor neuron ( umn ) paresis were associated with surrounding white matter involvement.6 , 8 in nonequine aberrant hosts , p. tenuis lesions tend to involve the spinal cord white matter even when camelids display similar cervical scoliosis.11 the apparent predilection for the dorsal gray matter lesions in the horse can not be fully explained although positive tropism via neurotransmitters abundant in this area of the spinal cord has been proposed.6 this case displayed both clinical ( analgesia , scoliosis , gp ataxia / umn paresis ) and histopathological signs ( dorsal gray column and lateral white matter lesions ) consistent with equine verminous myelitis.6 the c4 spinal cord lesion site is also identical to the region in which a larva of the metastrongyloidea ( presumed to be p. tenuis ) was previously identified.6
antemortem diagnosis of verminous myelitis is often challenging as acute onset of asymmetric spinal cord disease can result from neoplasia , trauma , or infection with bacteria , viruses , fungi , or protozoa.12 parasites that have been identified in the brain or spinal cord of horses include rhabditid nematodes ( halicephalobus gingivalis ) , strongyloid nematodes ( strongylus vulgaris , s. equinus , angiostrongylus cantonensis , p. tenuis ) , spiruroid nematodes ( draschia megastoma ) , filarid nematodes ( setaria spp . ) , and warble fly larvae ( hypoderma spp.).7 , 10 , 12 , 13 concurrent cerebrospinal fluid xanthochromia , pleocytosis , and increase in total protein occur inconsistently and are neither sensitive nor specific for nematodiasis .
although eosinophilic pleocytosis supports a diagnosis of parasitic infection , eosinophils are not always found in the csf of horses with verminous encephalitis as might be expected.14 , 15 , 16 marked malacia and inflammation result from a combination of mechanical damage due to migration as well as host immune response forming characteristic parasitic migration tracts that may be visible only microscopically on postmortem examination.12 , 17
routine laboratory testing including cbc , biochemistry profile , and urinalysis was not performed due to its limited utility to differentiate between causes of nematodiasis .
h. gingivalis is only occasionally detected in urine due to renal infestation or in biopsies of granulomas of skin or head ( not present in this case);18 larva , however , have rarely been detected in routine cerebrospinal fluid analysis.19 additional signs of infestation with the soil dwelling saprophyte ( uveitis , sinusitis , osteomyelitis , and mastitis)18 were not detected .
hypoderma can cause skin warbles , and in horses can cause signs of encephalitis more commonly than signs of myelitis due to predilection for the brain ( 15/16 cases ) based on apogeotropism , for example , the more vertical position of the head and neck.20 the filly in this report had no contact with cattle or fields previously inhabited by cattle , a common predisposing variable.20
strongylus vulgaris has been associated with two separate clinical syndromes , acute severe forebrain disease , evidenced by blindness , circling , dementia , and dysphagia , due to parasiteinduced embolic showers14 , 21 and a more chronic syndrome due to larval migration through the spinal cord and brain , which could not be excluded as a cause of the filly 's clinical signs .
single case reports of asymmetric brain disease and cauda equina syndrome in the united states have been attributed to draschia megastoma
16 and setaria labiatopapillosa
15 respectively .
kumri , a fairly common syndrome of spinal ataxia due to nematodiasis in central and southeast asia.22 the lone case of equine meningoencephalomyelitis due to a. cantonensis in the united states occurred in a miniature horse with fever and signs of brainstem , cerebellum , and spinal cord dysfunction.17 an increasing prevalence of infection of the definitive host , rattus norvegicus population in new orleans offered a possible explanation for exposure to the protostrongylid previously only reported in asia.17
within the metastrongyloidea , only angiostrongylidae and protostrongylidae families display neurotropism and infect the central nervous system ( cns).7 of the 7 genera within the family protostrongylidae , only p. tenuis and elaphostrongylus can infect host cns , and the latter has never been reported in north america.23 in north america , parelaphostrongylus tenuis is an endemic parasite of whitetailed deer ( odocoileus virginianus ) .
a prevalence of 86% in that species might actually underestimate the true widespread nature of this nematode based on current methods of testing gastropod intermediate hosts.24
no effective commercial antemortem test for equine p. tenuis myelitis exists . when interpreted in the context of physical examination findings and history , advanced imaging has the potential to suggest the presence of nematodiasis , but molecular confirmation is needed for an accurate diagnosis .
recent use of mri has been able to aid diagnosis of human nematodiasis due to a. cantonensis ,
25 a nematode closely related to p. tenuis.17 the large size of the equine neck , however , precludes the routine use of mri in equine cervical diagnostic testing .
the positive pcr result for p. tenuis is the first definitive identification of the protostrongylid worm in an equine spinal cord and only the second definitive identification of p. tenuis in the equine central nervous system.10 in a previously reported and confirmed p. tenuis verminous encephalitis case , multiple larvae , eggs , and both a male and female adult metastrongylid were identified phenotypically.7
immune response and clearance of the aberrant parasite before necropsy or formalin fixation of the tissue before pcr testing were possibly responsible for the inability to confirm p. tenuis in previous cases , which had a more chronic course of infection than this case . in a recent study evaluating sensitivity of pcr for detection of p. tenuis dna in formalinfixed neural tissues from 38 goats , camelids or wild ungulates with characteristic histologic lesions of p. tenuis , only 19 cases were pcr positive.26
p. tenuis dna can therefore be detected with pcr from formalinfixed , paraffinembedded tissue even if a nematode is not visible in the sample .
absence of the nematode at time of sample collection , small size of sample tested , and extended time of tissue in formalin fixation were potential reasons for negative results . in this case prompt euthanasia
might have preserved the p. tenuis dna before a full immune response could eliminate it .
cases of p. tenuis nematodiasis in horses range in age from 6 months to 3 years6 , 8 and cases in cattle range in age from 3 to 7 months.4 , 5 no clear explanation exists why juvenile animals seem to be overrepresented ; but the prognosis for horses remains worse .
no horse has ever recovered from p. tenuisassociated cns infection despite successful use of the combination treatment of moxidectin , fenbendazole , and dexamethasone in calves with meningitis .
one horse is alive after 10 years , but severe scoliosis persists ( personal communication aj ) .
the chronicity and locally extensive nature of gray column lesions in horses with scoliosis may preclude recovery after clinical signs occur ; therefore , whitetailed deer and gastropods should be kept away from equine pastures .
| there are reports of horses with acute onset acquired cervical scoliosis and cutaneous analgesia .
the underlying dorsal gray column myelitis that produces these neurologic signs has been only presumptively attributed to migration of parelaphostrongylus tenuis within the spinal cord . despite previous confirmation brain by polymerase chain reaction testing , of p. tenuis within the brain of horses by polymerase chain reaction testing , genetic testing has failed to definitively identify the presence of this parasite in cases of equine myelitis .
this case report provides molecular confirmation via polymerase chain reaction of p. tenuis within the cervical spinal cord of a horse with scoliosis and cutaneous analgesia . |
SECTION 1. SHORT TITLE.
This Act may be cited as the ``Chlorine Zero Discharge Act of
1993''.
SEC. 2. ZERO DISCHARGE OF TOXIC PERSISTENT AND BIOACCUMULATIVE
SUBSTANCES.
(a) Findings.--The Congress finds that--
(1) substances that persist and/or bioaccumulate in the
environment, build to higher and higher concentration over
time, reaching their greatest levels in the tissues of species
high on the food chain, including humans;
(2) toxic substances that persist and/or bioaccumulate in
the environment are biologically active in infinitesimal
quantities, causing reproductive failure, birth defects,
developmental impairment, hormonal disruption, behavioral
disorders, immune suppression, and cancer at low doses, and
mixtures of these substances may cause these effects at even
lower doses;
(3) regulatory approaches that permit even limited
production and discharge of toxic substances that persist and/
or bioaccumulate result in the accumulation of these substances
in the environment and food chain over time and subsequent
damage to the health of humans and other species;
(4) the most favored method of preventing the continued
contamination of the environment from persistent or
bioaccumulative toxic substances is to phaseout their
production and/or use over time and replace these substances or
the processes that produce them, or both, with safer
alternatives;
(5) among the persistent and/or bioaccumulative toxic
substances of greatest concern are organochlorines discharged
in the production of pulp and paper as a result of the use of
chlorine or any other chlorinated oxidizing agents in the pulp
and paper manufacturing process;
(6) the Great Lakes Water Quality Agreement between the
United States and Canada concludes that ``the discharge of
toxic substances in toxic amounts be prohibited and the
discharge of any or all persistent toxic substances be
virtually eliminated''; and
(7) in the Sixth Biennial Report on Great Lakes Water
Quality, the International Joint Commission on Great Lakes
Water Quality concluded that ``the concepts of virtual
elimination and zero discharge are consistent and a clear
statement or direction to take to achieve the Agreement's
purpose. The overall strategy or aim regarding persistent toxic
substances is virtual elimination, and the tactic or method to
be used to achieve the aim is through zero input or discharge
of those substances created as a result of human activity.
(b) Zero Discharge of Organochlorine Compounds, Byproducts, or
Metabolites.--Title III of the Federal Water Pollution Control Act is
amended by redesignating section 519 as section 520 and by inserting
the following after section 518:
``SEC. 519. DISCHARGE OF ORGANOCHLORINE COMPOUNDS, BYPRODUCTS, OR
METABOLITES.
``(a) Zero Discharge.--(1) Effective 5 years after the enactment of
this section, each pulp and paper manufacturing facility shall achieve
zero discharge into water of organochlorine compounds, byproducts, or
metabolites formulated as a result of the use of chlorine or any other
chlorinated oxidizing agent in the pulp and paper manufacturing
process.
``(2) Effective 5 years after enactment of this section, all
existing and new permits under this Act for paper and pulp mills which
use chlorine or any other chlorinated oxidizing agent shall require
compliance with the zero discharge requirement set forth in paragraph
(1).
``(b) Safe Alternatives Assistance.--Within one year after the
enactment of this section, the Administrator shall evaluate
alternatives to the use of organochlorines in the manufacturing of pulp
and paper, and shall publish a report on the transfer of technology in
the pulp and paper industry from organochlorine to chlorine-free
technology as a model for pollution prevention. Within 18 months after
the enactment of this section, the Agency shall begin providing
technical information and support to assist permit applicants in the
use of alternatives to organochlorine compounds in the production of
pulp and paper.
``(c) Report to Congress on Organochlorine Zero Discharge
Candidates.--Within 18 months after the enactment of this section, the
Administrator shall complete a report to Congress on nonpoint sources
and industrial discharges of organochlorine compounds and their
byproducts and metabolites into water. The report shall include a
listing of all types or categories of nonpoint sources and industrial
organochlorine discharges into water and their byproducts and
metabolites. The report shall also include a listing of the annual
quantities of each organochlorine compound discharged into water
nationally and by permitted facility, together with a list of each
permitted facility's location and quantities of combined organochlorine
compound discharges into water. The report shall contain
recommendations for achieving a zero discharge policy for important
categories of organochlorine pollution sources. In order to develop
such recommendations, the Administrator shall convene an advisory
panel. The advisory panel shall conduct public hearings and solicit
public and expert comment. The panel shall consist of 15 members,
including at least 1 independent expert in each of the fields of public
health, occupational health, technology change, toxics use reduction,
and ecology, 2 affected citizens, and technical and policy experts from
industry, labor, public interest groups, and State environmental
agencies.
``(d) Definition.--For the purposes of this section, the term `zero
discharge' means absolutely no output or release, including nonpoint
source output or release, into water. The term `zero discharge' does
not mean a less than detectable output or release.''. | Chlorine Zero Discharge Act of 1993 - Amends the Federal Water Pollution Control Act to require pulp and paper manufacturing facilities to achieve zero discharge into water of organochlorine compounds, byproducts, or metabolites formulated as a result of the use of chlorine or any other chlorinated oxidizing agent in the pulp and paper manufacturing process.
Requires permits for paper and pulp mills which use chlorine or chlorinated oxidizing agents to require compliance with the zero discharge requirement.
Directs the Administrator of the Environmental Protection Agency to: (1) evaluate alternatives to the use of organochlorines in pulp and paper manufacturing and to publish a report on the transfer to chlorine-free technology in the pulp and paper industry as a model for pollution prevention; and (2) provide technical information and support to assist permit applicants in the use of such alternatives. |
testosterone is responsible for secondary sex characteristics , sexual desire and erection . also , it increases metabolic processes in the muscles , bones , bone marrow , immune system and brain ( 1 ) .
therefore , a reduction in the level of testosterone leads to symptoms that are caused by the decrease of these processes .
total testosterone levels in men consist of three parts : ( a ) testosterone that binds strongly to shbg ( sex hormone binding globulin ) ; this accounts for almost 80% of total testosterone and serves as a reserve source ; ( b ) testosterone also binds to albumin , but this binding is weak and easily available ; ( c ) and free testosterone ( 2 ) .
free testosterone and testosterone bound to albumin are biologically active and are 20% of total testosterone ( 2 , 3 ) .
testosterone levels in men aged 40 is reduced ( 4 ) , and the total testosterone level is reduced 0.3% annually ( 5 , 6 ) . the average amount of testosterone in men of 75 years of age is 66% of men aged 25 ( 6 - 8 ) .
the decline of testosterone levels with aging , on one hand , is related to testis dysfunction ( leydig cell mass reduction , a decrease in performance of the remaining cells , as well as reduced testis circulation ) , and on the other hand , to reduced testosterone - stimulating hormones , including gnrh from the hypothalamus and gonadotropin from the pituitary gland ( 5 , 9 ) .
andropause is the gradual reduction of the male sex hormone ( testosterone ) with increasing age , and its symptoms are sexual dysfunction , weakness , fatigue , insomnia , loss of motivation , mood disorders and reduction of bone density ( 10 ) . recently ,
the serum level of testosterone is different in individuals , however , in most experiments 10 nmol / l to 35
nmol / l has been found to be within the normal range ( 2 ) .
one of the issues facing older people is finding the lower level of testosterone that causes andropause ( 11 ) .
so , to diagnosis andropause , in addition to testosterone serum levels , clinical symptoms should be considered ( 12 ) . besides considering the possible benefits of testosterone therapy in older men for andropause treatment , possible complications including benign prostatic hyperplasia , prostate cancer , exacerbation of sleep apnea , gynecomastia
andropause has been widely considered in recent years by the medical societies ( 14 ) .
some studies of testosterone therapy have mentioned significant progress in reducing the symptoms ( 11 , 15 )
. however , the benefit of testosterone therapy in this age group still faces uncertainty ( 16 ) . because there are few studies in our country ( iran ) about andropause and testosterone therapy in men over 50 years of age , the results of this study are important in the treatment of men with andropause .
the aim of this study is to evaluate the effect of testosterone in the treatment of andropause in men .
the study population included 80 men over fifty years old , who were referred to the private office of the researcher in 2014 in sanandaj , iran .
exclusion criteria included suspicion of having prostate cancer , prostate disease , urinary tract infection and the risk of active urinary retention . before starting the study , serum testosterone levels of the men
were measured by radio immunoassay and the adam ( androgen deficiency in the aging male ) questionnaire was completed via interview .
the adam questionnaire consists of 10 questions with yes or no answers . in this questionnaire
the answer of yes to questions 1 or 7 , or the answer of yes to three questions from questions 8 to 10 , confirmed testosterone deficiency .
if the answer to questions 1 or 7 and questions 8 to 10 were negative , then the patient was considered healthy .
the men were treated with testocaps capsules manufactured by schering - plough , with one 40 mg capsule per day for a period of six months . at the end of months 1 , 3 and 6 after the intervention , serum testosterone levels were measured and the adam questionnaire was completed again , simultaneously .
based on the adam questionnaire results and the serum testosterone levels of the men , treatment of andropause was determined by an urologist and recorded in a checklist .
descriptive statistics ( frequency and percentage , mean , standard deviation ) and paired t - test were used to compare levels of testosterone . to determine the correlation between age and testosterone levels ,
the pearson correlation was used . finally to compare the treatment process during the treatment period
the mean age of patients was 56.57 3.21 years , with an age range of 51 - 67 years .
of the total , 70% were urban dwellers , 38% were smokers and 20% used alcohol . also , 17.5% had an underlying chronic disease such as hypertension or diabetes ( table 1 ) .
( % ) . analyzing the adam questionnaire before the treatment stage , 100% of patients had andropause .
after the first month of treatment , the andropause rate was 87.5% , and in the third month it was 55% .
testosterone levels in the subjects before treatment was 240.6 nmol / l , and at the end of months one , three and six after the intervention the trend was positive . at the end of the sixth month ,
anova data , this increase of testosterone levels was statistically significant ( p = 0.0001 ) ( table 3 ) .
the findings also showed that there is a significant and inverse correlation between age and testosterone levels before and after the treatment , namely , the level of testosterone is reduced with increasing age ( table 4 ) .
in our study , oral administration of testosterone increased testosterone levels in men over 50 years who were suffering from andropause . over time
, there was no need to increase the dose of medicine to constant changes in testosterone levels and clinical symptoms . in a study by ko et al .
( 16 ) , oral administration of testosterone decanoate had an effect in the short term , but its effect was low . in the treatment procedure ,
serum testosterone levels are rarely kept higher than average levels . in a study by bae et al .
, intramuscular injection of testosterone had a greater impact than oral use and increased the levels of testosterone in men with andropause ( 17 ) . in another study ,
bae et al . found that men who consumed testosterone pills with meals had higher serum testosterone levels than those who consumed the pill after meals ( 18 ) . in a study by tan et al . , testosterone therapy increased the strength and durability of erection and improved sexual performance of men with andropause ( 19 ) . also , in a study by legros et al .
the aim of ronald`s study was increasing the level of testosterone in men with andropause to a normal range of 400 - 700 ng / dl , and also reducing the symptoms of andropause ( 21 ) . in this study
, at the end of the intervention , testosterone levels reached 578 ng / dl , and the symptoms of andropause were reduced .
also in this study , there was an inverse relationship between age and testosterone levels .
testosterone levels in all stages of treatment and at 1 , 3 and 6 months after treatment was reduced . in a study conducted by michel et al .
, they showed that with increasing age approximately 20% of the testosterone levels of men by age 60 and 50% of men by age 80 are reduced ( 22 ) .
changes in testosterone levels in different races may be due to a low - fat diet and high consumption of carbohydrates .
although , dietary protein increases testosterone levels and reduces its age - related effects ( 23 ) . in analyzing the adam questionnaire before treatment ,
after six months it was 0% and all patients had improvement in sexual desire . in a study by matsumoto et al .
( 24 ) , testosterone therapy in older men increased muscle strength , physical activity , penile erectile function , libido , cognitive function and quality of sleep , and also reduced depression . in a study by bae et al .
, intramuscular injections of testosterone in patients with andropause increased adam questionnaire scores , especially sexual desire scores ( 17 ) . in a study by zhang et al .
( 25 ) , six months after the end of treatment the effect of testosterone on increasing the quality of life was observed . in a study by legros et al .
, the quality of life of older men was improved with testosterone therapy ( 20 ) . also in a review study conducted by bassil et al .
( 26 ) , the benefits of testosterone therapy were stated as increased sexual function , bone density , muscle mass , improved mood , quality of life and cognitive function , as well as increase in power .
these findings are consistent with the findings of this study . the use of testosterone therapy increased acne , oily skin , gynecomastia , risk of prostate cancer , cardiovascular disease and lipid changes , and also increased the hematocrit levels ( 19 , 26 - 28 )
of course , to evaluate the risks of using testosterone was not the aim of our study .
treatment with testosterone in men over 50 years with andropause will increase testosterone levels and also quality of life , sexual desire , erection , energy levels , ability to exercise and feel the joy of life more than before . | background : andropause is the gradual reduction of the male sex hormone ( testosterone ) with increasing age .
its symptoms are sexual dysfunction , weakness , fatigue , insomnia , loss of motivation , mood disorders and reduction of bone density .
treatment of andropause with testosterone has been recently considered.objectives:the aim of this study was to evaluate the effect of testosterone in the treatment of andropause in men.patients and methods : for men who met the inclusion criteria ( 50 years of age and older ) laboratory tests and clinical examinations were conducted by an urologist in order to diagnose prostate cancer , prostate disease , urinary tract infection and active urinary retention . after obtaining consent ,
the patients were enrolled in the study .
data were analyzed using spss version 20 .
descriptive statistics ( frequency and percentage , mean , standard deviation ) and the paired t - test were used to compare levels of testosterone . to determine the correlation between age and testosterone levels ,
the pearson correlation was used . finally , to compare the treatment processes during the treatment period the repeated measures anova was used.results:the mean age of patients was 56.57 3.21 years .
a total of 31 patients ( 39% ) were smokers , among them 30% smoked daily , 2.5% weekly and 6% smoked for fun .
the mean testosterone level before treatment was 240.6 125.4 and at 1 , 3 and 6 months after treatment the level was raised , so that at the end of the sixth months it was 578.7 141.7 .
the level of increase was statistically significant ( p = 0.0001).conclusions : treatment with testosterone in men over 50 years with andropause will increase testosterone levels and also quality of life , sexual desire , erection , energy levels , ability to exercise and feel the joy of life more than before .
depression was decreased and they had sleepy feelings after dinner . |
RIO DE JANEIRO — Nico Delle Karth, an Austrian sailor preparing for the 2016 Summer Olympics, said it was the foulest place he had ever trained.
Garbage bobbed on the surface, everything from car tires to floating mattresses. The water reeked so badly of sewage that he was afraid to put his feet in it to launch his boat from shore.
“I’ve never seen anything like this before,” Mr. Delle Karth said of Guanabara Bay in Rio de Janeiro, where the Olympic sailing and windsurfing events will take place.
Even as Brazil scrambles to finish an array of stadiums for the start of the 2014 World Cup soccer tournament in less than a month, it is already coming under scathing criticism for its handling of the next mega-event on its plate, the 2016 Summer Games.
Francesco Ricci Bitti, president of the influential association representing various Summer Olympic sports, said the Rio Games were in “the most risky position” of any Olympics he could remember. John D. Coates, an International Olympic Committee vice president, said last month that Rio’s preparations were “the worst I have experienced,” with construction yet to begin on the Deodoro sports complex, the second most important site after Olympic Park.
Photo
Guanabara Bay, nestled between Sugarloaf Mountain and other granite peaks, offers the kind of a postcard image Rio’s authorities want to celebrate as hosts of the 2016 Summer Olympics. But it has become a focal point of complaints, turning Rio’s polluted waters into a symbol of frustrations with the troubled preparations for the Olympics.
“Welcome to the dump that is Rio,” Germany’s sailing team said in one typically blunt assessment of the site for the Olympic regatta.
Brazilians training here agree.
“It can get really disgusting, with dog carcasses in some places and the water turning brown from sewage contamination,” said Thomas Low-Beer, 24, a Brazilian Olympic hopeful who sails in the bay. He shuddered when recalling how his dinghy crashed into what he believed was a partly submerged sofa, capsizing him into the murky Guanabara.
Though international officials complain that Brazil has had almost five years since winning its Olympic bid to make headway, some of the delays stem from chronic problems the nation has long fought.
Well-financed efforts to clean up the bay have proved disappointing for decades, undercut by mismanagement and allegations of corruption. The political rivalries among local, state and federal layers of government have led to infighting, including an impasse over who should pay for certain Olympic projects. Protests over forced evictions to make way for the Olympics have slowed construction.
The Olympics are hardly the only pressing concern for a country grappling with an economic slowdown. The World Cup begins on June 12, and several of the 12 stadiums where soccer games are supposed to be held are not finished, while a number of transit projects will not be completed until after the tournament. Underscoring the troubles, a construction worker died in an electrical accident this month — the eighth worker killed in an accident at a World Cup stadium site.
Preparing for the Olympics may prove even more challenging. Brazilian officials had contended that 2007 Pan-American Games venues could be refurbished at low cost. But last year they had to demolish the cycling venue because it failed to meet Olympic standards. Now Rio plans to build a new structure costing 10 times as much as the original.
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Strikes have delayed repairs at the Engenhão stadium, a Pan-American Games venue intended for 2016 track and field events, after it was closed last year over fears that its roof might collapse. Violent clashes between striking workers and security personnel have also delayed work on Olympic Park, the main cluster of venues.
Some officials say the situation is more precarious than the troubled run-up to the 2004 Olympics in Athens.
“I think in terms of time available, we are even worse,” said Mr. Ricci Bitti, president of the Association of Summer Olympic International Federations.
Mr. Ricci Bitti and other Olympic officials have publicly asserted that there is no Plan B, that the Games will not be moved from Rio. Still, Brazilian officials have reacted to criticism with statements that have not exactly reassured Olympic officials.
Eduardo Paes, the mayor of Rio, told reporters that he and other authorities were “pretty sure” they would deliver on their promises to have the venues ready in time.
Brazil’s sports minister, Aldo Rebelo, lashed out at unconfirmed reports that Olympic officials were considering moving the Games.
“You can be guaranteed it is nothing but a bluff,” Mr. Rebelo said. Pointing to large sponsorship agreements for the Rio games, he said, “I doubt the Olympic Committee wants to lose that business.”
Of all the challenges Brazil faces, cleaning up Guanabara Bay may be the toughest.
Officials vowed to tackle the problem after the United Nations Earth Summit here in 1992 drew scrutiny of Rio’s foul waters. The Rio state government secured more than $1 billion in loans from Japan’s government and the Inter-American Development Bank for cleanup projects, but they have not been even remotely successful, according to environmental experts. The State Environmental Institute in Rio de Janeiro estimates that more than 10 percent of the trash here is not collected, much of it flowing into the bay through canals and degraded rivers.
Vast amounts of raw sewage leak into the waters. Officials set a goal of treating as much as 80 percent of it by the 2016 Olympics, but less than 40 percent is currently treated.
State environmental officials have acknowledged they would fall short of that goal, The Associated Press reported over the weekend, citing a letter sent to federal authorities requesting more funding to battle pollution.
Calling the bay “dark, brown and stinking,” Lars Grael, 50, a Brazilian sailing legend who won two Olympic medals, said he had encountered human corpses on four occasions while sailing in the bay. He told reporters that officials should move the sailing events to a resort area hours away by car.
The authorities here insist that nothing of the sort will happen. Carlos Portinho, Rio’s top environmental official, said the criticism of Guanabara Bay was exaggerated, contending that recent tests had shown that fecal contamination in the Olympic regatta area was within “satisfactory” standards in Brazil.
Acknowledging that reversing pollution in the bay was a “long-term project,” Mr. Portinho said that officials had deployed three small “ecoboats” to collect garbage; by the Olympics, he said, 20 or 30 might be operating. He said that new sewage treatment plants were being built, while floating “ecobarriers” would facilitate the collection of trash in the bay.
Brazilian environmental experts say the efforts are a fraction of what needs to be done.
“The government could deploy aircraft carriers to collect the bay’s garbage and the problem would not be solved,” said Mario Moscatelli, a biologist. “The bay is still a latrine. It’s an insult to Rio’s people to say it will be clean for the Olympics.”
In 2008, China grappled with an algal bloom that threatened the Olympic sailing at the Beijing Olympics. But Chinese authorities deployed about 1,000 boats, compared with the dozens that could ultimately constitute Rio’s garbage fleet.
“China did a really good job cleaning up the water,” said Ian Barker, a former Olympian who is a coach with Ireland’s sailing team.
As for the few boats now collecting trash in Rio’s bay, he said, “that seems to be the sum total of what they’ve done so far, which is not even scratching the surface.” ||||| RIO DE JANEIRO (AP) — Sailing's governing body may conduct independent water-quality tests in Rio de Janeiro's polluted Guanabara Bay, the sailing venue for the 2016 Olympics and the site of Rio's first test event in 2½ months.
In this May 15, 2014 photo, kids play in the polluted waters of Guanabara Bay in Rio de Janeiro, Brazil. Little progress has been made in the clean up of the bay, and with just over two years to go until... (Associated Press)
In this May 15, 2014 photo, trash floats on a polluted water channel that flows into the Guanabara Bay in Rio de Janeiro, Brazil. In its 2009 Olympic bid, officials promised that the city's waterways... (Associated Press)
In this May 15, 2014 photo, untreated sewage creates a dark streak on the sand as it flows into the water of Guanabara Bay in Rio de Janeiro, Brazil. Brazil will not make good on its commitment to clean... (Associated Press)
In this May 15, 2014 photo, trash floats on a polluted water channel that flows into the Guanabara Bay in Rio de Janeiro, Brazil. With just over two years to go until the Rio Olympics, nearly 70 percent... (Associated Press)
In this May 15, 2014 photo, trash litters a forested area on the shores of Guanabara Bay in Rio de Janeiro, Brazil. The country will not make good on its commitment to clean up Rio de Janeiro's sewage-filled... (Associated Press)
In this May 15, 2014 photo, a man jumps into the polluted waters of Guanabara Bay in Rio de Janeiro, Brazil. Brazil will not make good on its commitment to clean up Rio de Janeiro's sewage-filled Guanabara... (Associated Press)
Any hope Brazil would be able to clean up the sewage-filled bay soon was quashed in a document obtained by The Associated Press over the weekend.
In a May 7 letter to sports minister Aldo Rebelo, Rio's state environment secretary Carlos Francisco Portinho acknowledged in a best-case scenario that pollution flowing into the bay could be cut to "over 50 percent" — well below the promised reduction of 80 percent.
Alastair Fox, head of competitions for the international sailing federation, told the AP the body is likely to test on its own, hoping to allay athletes' health concerns.
The tests could also push Rio organizers to move more quickly on the problem.
Fox said he hoped the International Olympic Committee would do independent testing, although the IOC indicated to the AP it had no such plans.
"If the IOC are not conducting water-quality tests, then I think it is very likely the ISAF will," Fox said Monday in an email. "Certainly compared to most sailing venues, the water quality is very, very bad."
Danish Olympian Allan Norregaard, a bronze medalist at the 2012 Olympics, told the AP that Guanabara was "the most polluted place I've ever been." Other sailors interviewed by the AP called it an "open sewer."
The bay and similar concerns about Rio's iconic Copacabana and Ipanema beaches add to the disarray plaguing South America's first Olympics.
The IOC has sent a special troubleshooter to monitor progress, and last month IOC vice president John Coates said Rio's preparations were the "worst" in memory.
Spending on Rio has reached $17 billion and is expected to rise.
Nearly 70 percent of Rio's sewage goes untreated into its waters. Exposure to fecal matter can cause hepatitis A, dysentery, cholera and other diseases.
The visible problem involves old couches, tires and dead animals floating in the 148-square mile (383-square kilometer) bay. State officials are using garbage boats to collect floating debris, with the detritus weaving giant blankets of human and industrial waste along noxious shorelines.
"If someone picks up a bag, or hits a sofa or something like that, then clearly that is going to affect them in the race," Fox said.
"We've seen numbers from teams of the fecal content in the Guanabara Bay, which clearly are not safe," Fox added. "For us, that's a matter of concern. We've been assured again by the organizers that they are doing everything they can."
IOC spokesman Mark Adams said the Olympic body would not test.
"To confirm, we are not conducting any independent testing, as testing is already being done by Rio," Adams said in a brief email to the AP.
The IOC did not respond to repeated requests to interview IOC Medical Director Dr. Richard Budgett about potential health risks to athletes. In March, Nawal El Moutawakel, head of the IOC inspection team in charge of preparing Rio, said she had been assured the bay could be "clean from garbage."
"I don't think we will forgive ourselves if we let the athletes compete in an environment that is not safe and secure," she said.
Malcolm Page, a two-time Olympic gold medalist and chairman of the sailing federation's Athletes' Commission, said he trusted state tests, but welcomed independent testing.
"If the Brazilians are happy to receive any of that independent help, it only makes dealing with the problem easier and removes any sugar-coating," he said. "The sailors are certainly worried about it."
An analysis last year of a decade's worth of government data on Guanabara and other waterways showed that sewage pollution indicators consistently spiked far above acceptable limits, even under Brazilian laws that are far more lenient on pollution than those in the United States or Europe.
Fox said at least five courses — three inside the bay and two in the open Atlantic — would be used at the test event beginning Aug. 2. He said courses outside the bay had always been planned, not driven by the pollution problems.
Fox said plans call for the medal race — the final race where the gold, silver and bronze medals are decided — to be held in Guanabara near Flamengo Beach, a venue convenient for fans.
Signs around that beach warn against swimming.
Mario Moscatelli, a biologist and outspoken environmentalist, said retrieving the floating garbage in the bay was fine, but did not address the problem of untreated sewage.
In an open letter to Brazilian President Dilma Rousseff, he asked for the "release of the funds needed to recover the environmental assets, which are being used in Rio as garbage dumps and latrines."
___
Associated Press writer Jenny Barchfield contributed to this report.
___
Stephen Wade on Twitter: http://twitter.com/StephenWadeAP | – With the clock ticking on Rio's 2016 Olympics and tongues wagging about its lack of preparedness, the New York Times today turns to a rather disgusting item on the Games' checklist that Brazil seems to have missed: Guanabara Bay, the site of the sailing and windsurfing events. Despite Brazil's promise in its Olympic bid to clean up the bay, sewage (of which 60% is untreated) and garbage flow into it unchecked and might well give Olympians incentive to move a little faster, even though the stench makes many hesitate to so much as dip a toe in. And with the first test events just months away, sailing officials tell the AP that they want independent water testing. This after the AP obtained a letter from Rio state's environment secretary acknowledging that at most pollution flowing into the bay could be cut by half—not the 80% Brazil promised. "It can get really disgusting, with dog carcasses in some places and the water turning brown from sewage contamination," says one Olympic hopeful who ran into a sofa while sailing in the bay; the German sailing team called it "the dump that is Rio." One Brazilian sailing legend (who says he's seen human corpses on four occasions while sailing in the bay) wants the events moved to waters hours away, but officials insist progress is being made and that fecal contamination levels are "satisfactory." Malarkey, says one biologist: "The bay is still a latrine. It’s an insult to Rio’s people to say it will be clean for the Olympics." |
the error function @xmath4 is defined by @xcite @xmath5 and its inverse @xmath6 , which we will denote by @xmath7 satisfies @xmath8 = \operatorname{erf}\left [ \mathfrak{i}(x)\right ] = x.$ ] the function @xmath9 appears in several problems of heat conduction @xcite . in @xcite
we considered the function @xmath10 and its inverse @xmath11 satisfying @xmath12 = n\left [ s(x)\right ] = x.\ ] ] it is clear from ( [ erf ] ) and ( [ n ] ) that@xmath13\ ] ] and therefore@xmath14 in @xcite we showed that@xmath15 \label{ds}\ ] ] and @xmath16 where @xmath2 is a polynomial of degree @xmath17 satisfying the recurrence @xmath18 the same approach was employed by carlitz in @xcite . from ( [ 2.3 ] ) , it follows easily that for a fixed value of @xmath17 @xmath19 from ( [ sj ] ) and ( [ sn ] ) , we conclude that@xmath20 since@xmath21 we have@xmath22 it follows from ( [ ider ] ) that estimating @xmath23 for large values of @xmath17 is equivalent to finding an asymptotic approximation of the polynomials @xmath2 when @xmath24 .
the objective of this work is to study @xmath2 asymptotically as @xmath1 for various ranges of @xmath25 we shall obtain different asymptotic expansions for @xmath1 and ( i ) @xmath26 ( ii ) @xmath27 and ( iii ) @xmath28 the paper is organized as follows : in section [ section2 ] we approach the problem using a singularity analysis of the generating function @xcite of the polynomials @xmath29 in section [ section3 ] we apply the wkb method to the differential - difference equation ( [ 2.3 ] ) . in @xcite
, we used this approach in the asymptotic analysis of computer science problems and in @xcite to study the krawtchouk polynomials .
finally , in section [ section4 ] we analyze ( [ 2.3 ] ) again using the ray method @xcite and obtain an asymptotic approximation valid in various regions of the @xmath30 domain . in @xcite , @xcite , @xcite , we employed the same technique to analyze asymptotically other families of polynomials and in @xcite , @xcite to study some queueing problems .
in @xcite we obtained the exponential generating function @xmath31-\frac{x^{2}}{2}\right\ } , \ ] ] which implies that@xmath32\right\ } \frac{dz}{z^{n+1}},\ ] ] where the integration contour is a small loop around the origin in the complex plane . using ( [ ds ] ) , we have@xmath33\frac { dz}{z^{n+1}}\\ & = e^{-x^{2}/2}\frac{1}{\sqrt{2\pi}n^{\prime}(x)}\frac{n!}{2\pi\mathrm{i}}\oint\limits_{\left\vert z\right\vert < r}\frac{1}{z^{n+1}}ds[n(x)+zn^{\prime } ( x)]\\ & = \frac{n!}{2\pi\mathrm{i}}\oint\limits_{\left\vert z\right\vert < r}\frac{n+1}{z^{n+2}}s[n(x)+zn^{\prime}(x)]dz\end{aligned}\ ] ] and therefore@xmath34\frac{dz}{z^{n+2}}. \label{pn1}\ ] ] since @xmath35 has singularities at @xmath24 and @xmath36 we consider the functions@xmath37 we have@xmath38 and@xmath39 changing variables to @xmath40 n^{\prime}(x)\ ] ] in ( [ pn1 ] ) , we obtain@xmath41 ^{-(n+2)}dw,\ ] ] or , @xmath42 ^{n+2}}dw , \label{contour}\ ] ] where @xmath43 is a small loop about @xmath44 in the complex plane , with @xmath45 to expand ( [ contour ] ) for @xmath1 with a fixed @xmath46 we employ singularity analysis .
the function @xmath47 has singularities at @xmath48 by ( [ erf ] ) , we have@xmath49 , \quad\mathcal{j}\rightarrow\infty,\ ] ] so that@xmath50 and by symmetry we have@xmath51 the integrand in ( [ contour ] ) thus has singularities at @xmath52 and @xmath53 but for @xmath54 the former is closer to @xmath55 we expand ( [ contour ] ) around @xmath52 by setting @xmath56 and using@xmath57 ^{-(n+2)}\sim\left [ z_{1}(x)\right ] ^{-(n+2)}\exp\left [ -\sqrt{\frac{\pi } { 2}}e^{x^{2}/2}\frac{\delta}{z_{1}(x)}\right ] .
\label{13}\ ] ] then , we deform the contour @xmath43 in ( [ contour ] ) to a new contour @xmath58 that encircles the branch point at @xmath52 ( see figure [ fig12 ] ) .
this leads to@xmath59 ^{-(n+2)}\frac{1}{n}\label{14}\\ & \times\frac{1}{2\pi\mathrm{i}}\int\limits_{0}^{\infty}\left ( \upsilon ^{+}-\upsilon^{-}\right ) \exp\left [ -\sqrt{\frac{\pi}{2}}\frac{e^{x^{2}/2}}{z_{1}(x)}\delta\right ] d\delta,\nonumber\end{aligned}\ ] ] where@xmath60 here @xmath61 corresponds to the approximation of @xmath62 for @xmath63 above or below the right branch cut in figure [ fig12 ] .
for @xmath17 large we have@xmath64 and then evaluating the elementary integral in ( [ 14 ] ) leads to @xmath65 as @xmath1 with@xmath66 ^{-\left ( n+1\right ) } = \frac{n!}{\sqrt{2\ln\left ( n\right ) } } \left [ \frac{e^{-x^{2}/2}}{\zeta\left ( x\right ) } \right ] ^{n+1}\label{15}\ ] ] and @xmath67 \sim\exp\left ( -\frac{x^{2}}{2}\right ) \left [ x^{-1}+o\left ( x^{-3}\right ) \right ] , \quad x\rightarrow\infty.\label{zeta}\ ] ] in figure [ xo1 ] we plot @xmath68 $ ] and @xmath69 $ ] .
we see that the approximation is very good for @xmath70 but it becomes less precise as @xmath71 this is because our previous analysis assumes that @xmath1 with @xmath72 if either @xmath73 or @xmath74 we must modify it , which we will do next . when @xmath75 or more generally when @xmath76 the singularities at @xmath52 and @xmath77 are nearly equidistant from @xmath55 on the scale @xmath78 @xmath79 we have@xmath80 and ( [ 15 ] ) simplifies to @xmath81 but , to this we must add the contribution from @xmath53 which corresponds to replacing @xmath82 by @xmath83 and multiplying by @xmath84 the right hand side of ( [ 17 ] ) .
we note from ( [ z1- ] ) that @xmath85 so that the integrand in ( [ contour ] ) is antisymmetric with respect to the map @xmath86 thus , for @xmath1 and @xmath27 we get @xmath87 with@xmath88 .\label{18}\ ] ] as @xmath89 the alternating term becomes negligible and ( [ 18 ] ) matches to ( [ 15 ] ) , as @xmath90 in figure [ x=0 ] we plot the ratio @xmath91 /\ln\left [ \psi_{2}(y,40)/40!\right ] $ ] and verify the accuracy of ( [ 18 ] ) . letting @xmath92 in ( [ 14 ] ) using ( [ 15 ] )
yields@xmath93 which differs from ( [ large x ] ) .
this suggests that another scale must be analyzed , where @xmath94 and @xmath17 are both large .
thus , we consider the case of @xmath92 , with @xmath95 now the singularity at @xmath52 in ( [ contour ] ) becomes close to @xmath96 since @xmath97 we use the form ( [ pn1 ] ) and expand @xmath98 $ ] for @xmath99 and @xmath71 setting @xmath100 with @xmath101 we obtain @xmath102=\sqrt{2}\mathcal{j}\left\ { 1+\sqrt{\frac{2}{\pi}}\left [ ze^{-x^{2}/2}-\zeta\left ( x\right ) \right ] \right\ }
\\ = \sqrt{2}\mathcal{j}\left [ 1+\sqrt{\frac{2}{\pi}}e^{-x^{2}/2}\left ( z-\frac{1}{x}+o\left ( x^{-3}\right ) \right ) \right ] \\ \sim\sqrt{2}\sqrt{-\ln\left [ \sqrt{\frac{2}{\pi}}e^{-x^{2}/2}\left ( \frac { 1}{x}-z\right ) \right ] } \\ \sim\sqrt{2}\sqrt{\frac{x^{2}}{2}+\ln(x)-\frac{1}{2}\ln\left ( \frac{2}{\pi } \right ) -\ln\left ( 1-\xi\right ) } .\end{gathered}\ ] ] thus , we have@xmath103 here the contour @xmath58 is a small loop about @xmath104 now we again employ singularity analysis , with the branch point at @xmath105 determining the asymptotic behavior for @xmath106 a deformation similar to that in figure [ fig12 ] leads to@xmath107 for @xmath108 this collapses to ( [ large x ] ) . by examining ( [ 15 ] ) and
( [ 20 ] ) , we can obtain the following approximation@xmath109 ^{n+1},\label{21}\ ] ] which is more uniform in @xmath94 , since it holds both for @xmath70 and @xmath110 for @xmath17 large and for @xmath92 with @xmath17 fixed .
however , we must still use ( [ 18 ] ) if @xmath17 is large and @xmath94 is small . in figure [ xlarge ]
we plot @xmath68 $ ] and @xmath111 $ ] and confirm that ( [ 21 ] ) is a better approximation than ( [ 15 ] ) for large values of @xmath25
we shall now rederive the results in the previous section by using only the recurrence ( [ 2.3 ] ) and ( [ large x ] ) .
we apply the wkb method to ( [ 2.3 ] ) , seeking solutions of the form @xmath112
with@xmath113 b(x , n),\quad n\rightarrow\infty .
\label{3.1}\ ] ] thus , we are assuming an exponential dependence on @xmath17 and an additional weaker ( e.g. , algebraic ) dependence that arises from the function @xmath114 using ( [ 3.1 ] ) in ( [ 2.3 ] ) leads to @xmath115 + o\left ( \frac{\partial^{2}b}{\partial n^{2}}\right ) \\ & = \left [ x+a^{\prime}(x)\right ] b(x , n)+\frac{1}{n+1}\frac{\partial } { \partial x}b(x , n).\end{aligned}\ ] ] expecting that @xmath116 and @xmath117 we set@xmath118 and@xmath119 to solve ( [ 3.3 ] ) we let@xmath120 to find that@xmath121 solving this separable ode leads to@xmath122 , \label{3.7}\ ] ] where @xmath123 is a constant of integration . to fix @xmath124
we assume that expansion ( [ 3.1 ] ) , as @xmath74 will asymptotically match to ( [ large x ] ) , when this is expanded for @xmath106 in view of ( [ 3.1 ] ) this implies that@xmath125 , \quad x\rightarrow\infty,\ ] ] so that@xmath126 in view of ( [ 3.7 ] ) this is possible only if @xmath127 and then from ( [ zeta ] ) we have@xmath128 \sim\ln(x),\quad x\rightarrow\infty . \label{3.8}\ ] ] we next analyze ( [ 3.4 ] ) . using ( [ 3.8 ] )
to compute @xmath129 we obtain@xmath130 solving this first order pde by the method of characteristics , we obtain@xmath131 , \ ] ] where @xmath132 is at this point an arbitrary function .
however , since @xmath17 is large and @xmath133 we need only the behavior of @xmath132 for large values of its argument .
we again argue that by matching to ( [ large x ] ) we have @xmath134 b(x , n)\sim x^{n},\quad x\rightarrow\infty,\ ] ] and using ( [ 3.8 ] ) we get@xmath135 and thus@xmath136 so that@xmath137 combining our results , we have found that @xmath138 } } \left [ \frac{e^{-x^{2}/2}}{\zeta\left ( x\right ) } \right ] ^{n+1},\quad n\rightarrow\infty . \label{3.11}\ ] ] this applies for @xmath70 and @xmath139 where we can regain the results of the singularity analysis ( [ 15 ] ) by simply using@xmath140 } \sim\sqrt{\ln ( n)},\quad n\rightarrow\infty.\ ] ] formula ( [ 3.11 ] ) is also valid for @xmath141 and @xmath74 where it reduces to ( [ large x ] ) .
however , ( [ 3.1 ] ) breaks down for @xmath90 we thus consider the scale @xmath78 @xmath142 and set@xmath143 with which ( [ 2.3 ] ) becomes@xmath144 for fixed @xmath145 we seek an asymptotic solution of ( [ 3.13 ] ) in the form@xmath146 where @xmath147 will have a weaker ( e.g. , algebraic or logarithmic ) dependence on @xmath148 from ( [ 3.13 ] ) we obtain , using ( [ 3.14 ] ) , @xmath149 \label{3.15}\\ & = \left [ 1-\frac{1}{n}+o\left ( n^{-2}\right ) \right ] \frac{\partial } { \partial y}q(y , n)+\frac{y}{n}q(y , n).\nonumber\end{aligned}\ ] ] if @xmath147 has an algebraic dependence on @xmath17 , then @xmath150 should be roughly @xmath151 relative to @xmath152 @xmath153 roughly @xmath154 and so on .
thus , we expand @xmath147 as@xmath155 where @xmath156 have a very weak ( e.g. , logarithmic ) dependence on @xmath17 and balance terms in ( [ 3.15 ] ) of order @xmath157 and @xmath158 to obtain@xmath159 and@xmath160 \label{3.18}\\ & = \frac{\partial}{\partial y}q_{1}(y , n)-\frac{\partial}{\partial y}q_{0}(y , n)-yq_{0}(y , n).\nonumber\end{aligned}\ ] ] solving ( [ 3.17 ] ) yields @xmath161 where @xmath162 must be determined . we could solve ( [ 3.18 ] ) , using ( [ 3.19 ] ) , but its solution would involve another arbitrary function of @xmath17 .
thus , considering higher order terms will not help in determining @xmath163 instead , we employ asymptotic matching to ( [ 3.11 ] ) . expanding ( [ 3.11 ] ) for @xmath73 and comparing the result to ( [ 3.12 ] ) as @xmath89 with ( [ 3.14 ] ) , ( [ 3.16 ] ) and ( [ 3.19 ] )
, we conclude that @xmath164 but then our approximation for @xmath165 is not consistent with @xmath166 for odd @xmath148 we return to ( [ 3.13 ] ) and observe that the equation also admits an asymptotic solution of the form@xmath167 where , analogously to ( [ 3.17 ] ) , we find that @xmath168 so that another asymptotic solution to ( [ 3.13 ] ) is@xmath169 we argue that any linear combination of ( [ 3.14 ] ) and ( [ 3.21 ] ) is also a solution and that the combination which vanishes at @xmath170 for odd @xmath17 has @xmath171 and @xmath172 as in ( [ 3.20 ] ) .
we have thus obtained , for @xmath173 @xmath174 , \quad n\rightarrow\infty.\ ] ] this agrees with ( [ 18 ] ) , obtained by singularity analysis in section 2 . to summarize ,
we have shown how to infer the asymptotics of @xmath2 using only the recursion ( [ 2.3 ] ) and the large @xmath94 behavior ( [ large x ] ) .
our analysis does need to make some assumptions about the forms of various expansions and the asymptotic matching between different scales .
we shall now find a uniform asymptotic approximation for @xmath2 using a discrete form of the ray method @xcite .
this approximation will apply for @xmath94 and/or @xmath17 large .
we seek an approximate solution for ( [ 2.3 ] ) of the form @xmath175 , \label{anszat}\ ] ] where @xmath176 as @xmath106 since @xmath177 @xmath178 we see that we must have@xmath179 as @xmath180 using ( [ anszat ] ) in ( [ 2.3 ] ) , we have@xmath181 as @xmath139 where we have used@xmath182 to solve ( [ eikonal ] ) , we use the method of characteristics , which we briefly review .
given the first order partial differential equation@xmath185 we search for a solution @xmath186 by solving the system of characteristic equations@xmath187 with initial conditions@xmath188 = 0 , \label{initial1}\ ] ] and@xmath189 where we now consider @xmath190 to all be functions of the variables @xmath191 and @xmath192 for the eikonal equation ( [ eikonal ] ) , we have@xmath193 and therefore the characteristic equations are@xmath194 and@xmath195 solving ( [ charac1 ] ) subject to the initial conditions@xmath196 we obtain@xmath197 , \nonumber\\ p=\sqrt{\frac{\pi}{2}}\exp\left ( \frac{s^{2}}{2}+b\right ) \left ( t+s\right ) \left [ \operatorname{erf}\left ( \frac{t+s}{\sqrt{2}}\right ) -\operatorname{erf}\left ( \frac{s}{\sqrt{2}}\right ) \right ] \label{char0}\\ + \exp\left ( -\frac{1}{2}t^{2}-st+b\right ) -t - e^{b}+a,\quad\quad q=-\frac { 1}{2}t^{2}-st+b\nonumber\end{gathered}\ ] ] from ( [ initial ] ) we have@xmath198 which is consistent with ( [ initial1])@xmath199 therefore,@xmath200 , \label{rays}\]]@xmath201 \label{pq}\\ + s\exp\left ( -\frac{1}{2}t^{2}-st\right ) -\left ( t+s\right ) , \quad\quad q=-\frac{1}{2}t^{2}-st+\ln\left ( s\right ) .\nonumber\end{gathered}\ ] ] in figure [ rays ] we sketch the rays @xmath202 for @xmath203 .$ ] using ( [ pq ] ) in ( [ eqf ] )
we have@xmath204 \label{eqf1}\\ & + s\left [ 1+\frac{1}{2}t^{2}+st-\ln\left ( s\right ) \right ] \exp\left ( -\frac{1}{2}t^{2}-st\right ) -\left ( t+s\right ) .\nonumber\end{aligned}\ ] ] using ( [ a , b ] ) in ( [ initial2 ] ) , we get @xmath205 and solving ( [ eqf1 ] ) subject to ( [ f(0,s ) ] ) , we obtain@xmath206 \label{f(t , s)}\\ & \times s\left [ 1+\frac{1}{2}t^{2}+st-\ln\left ( s\right ) \right ] -\left ( \frac{1}{2}t^{2}+st\right ) + f_{0}\nonumber\end{aligned}\ ] ] or , using ( [ rays]),@xmath207 n+\frac{1}{2}\left ( s^{2}-x^{2}\right ) \left ( n+1\right ) + f_{0}. \label{f(x , n , s)}\ ] ] to solve the transport equation ( [ transport ] ) , we need to compute @xmath208 and @xmath209 as functions of @xmath191 and @xmath192 use of the chain rule gives@xmath210 and hence,@xmath211 where the jacobian @xmath212 is defined by @xmath213 using ( [ rays ] ) , we can show after some algebra that@xmath214 using @xmath215 in ( [ transport ] ) , we have@xmath216 or@xmath217 and using ( [ charac1 ] ) , we obtain@xmath218 since @xmath219 we have@xmath220 where we have used ( [ inversion ] ) and ( [ j ] ) .
thus,@xmath221 and therefore@xmath222 for some function @xmath223 since from ( [ initial ] ) we have @xmath224 while ( [ j1 ] ) gives @xmath225 we conclude that @xmath226 and hence @xmath227 .
\label{g(t , s)}\ ] ] using ( [ j1 ] ) we can write ( [ g(t , s ) ] ) as@xmath228 .
\label{g(n , s)}\ ] ] replacing @xmath229 and @xmath230 in ( [ anszat ] ) by ( [ f(x , n , s ) ] ) and ( [ g(n , s ) ] ) , we obtain @xmath231 as @xmath139 with @xmath232 \frac{s^{n}}{\sqrt{n+1+ns^{-2 } } } , \label{phi}\ ] ] where @xmath233 is still to be determined . eliminating @xmath191 from ( [ rays ] ) we get@xmath234 = 0,\label{eqs}\ ] ] which defines @xmath235 implicitly . for every @xmath236 there
exist only two solutions @xmath237 and @xmath238 of ( [ eqs ] ) ( see figure ) .
since @xmath4 is an odd function , it follows that @xmath239 although we have @xmath240 $ ] for @xmath241 and @xmath242 $ ] for @xmath243 the two approximations are comparable when @xmath94 is small and therefore we must add their contributions .
we shall now find the constant @xmath244 in ( [ phi ] ) by using ( [ large x ] ) .
we rewrite ( [ eqs ] ) as@xmath245 ^{-2}\label{s1}\ ] ] and for a fixed value of @xmath246 consider the limit @xmath71 it follows from ( [ s1 ] ) that @xmath247 and therefore we consider an expansion of the form@xmath248 using ( [ s3 ] ) in ( [ s1 ] ) , we obtain@xmath249 and therefore@xmath250 solving ( [ s4 ] ) we have@xmath251 } , \quad x\rightarrow\infty,\label{spxlarge}\ ] ] where @xmath252 denotes the lambert function , defined by @xcite@xmath253 = z,\quad\forall z\in\mathbb{c}\ ] ] and having the asymptotic behavior@xmath254 ^{2}\right ) , \quad z\rightarrow\infty.\label{wasympt}\ ] ] using ( [ spxlarge ] ) and ( [ wasympt ] ) in ( [ phi ] ) , we obtain@xmath255 from stirling s formula@xmath256 n^{n}e^{-n},\quad n\rightarrow\infty,\label{stirling}\ ] ] and @xmath257 n^{n},\quad n\rightarrow\infty,\ ] ] we conclude that@xmath258 and thus@xmath259 \sqrt{\frac{2\pi s^{2}}{\left ( n+1\right ) s^{2}+n}}.\label{phi1}\ ] ] using ( [ s(0,n ) ] ) , we have @xmath260 as @xmath261 with@xmath262 + \phi\left [ x , n ;-
s_{p}(-x , n)\right ] , \quad n\rightarrow\infty.\label{pfinal}\ ] ] in figure [ ray0 ] we compare @xmath263 $ ] and @xmath264 $ ] for @xmath265 and in figure [ raylarge ] for @xmath266 we note that the asymptotic approximation ( [ pfinal ] ) is more uniform than ( [ 15 ] ) , ( [ 18 ] ) and ( [ 20 ] ) but it is less explicit since @xmath267 must be obtained numerically . next , we compare the results of this section with those in the previous two sections .
we first consider @xmath54 with @xmath70 and @xmath106 from ( [ eqs ] ) , we have@xmath268 } , \label{snlarge}\ ] ] where @xmath269 was defined in ( [ zeta ] ) . using ( [ snlarge ] ) and ( [ wasympt ] ) in ( [ phi1 ] )
, we get@xmath270 ^{n+1},\ ] ] which agrees with ( [ 15 ] ) after taking ( [ stirling ] ) into account .
now we consider the limit @xmath139 with @xmath271 and @xmath272 from ( [ eqs ] ) , we have@xmath273 using ( [ sp ] ) , ( [ s(0,n ) ] ) and ( [ wasympt ] ) in ( [ phi1 ] ) , we find that@xmath274 and therefore@xmath275\ ] ] agreeing with ( [ 18 ] ) . finally , we consider the limit @xmath1 with @xmath276 @xmath277 @xmath278 from ( [ eqs ] ) , we have@xmath279 } .
\label{s2}\ ] ] using ( [ s2 ] ) and ( [ wasympt ] ) in ( [ phi1 ] ) , we have@xmath280 which agrees with ( [ 20 ] ) . | we analyze the sequence of polynomials defined by the differential - difference equation @xmath0 asymptotically as @xmath1 .
the polynomials @xmath2 arise in the computation of higher derivatives of the inverse error function @xmath3 .
we use singularity analysis and discrete versions of the wkb and ray methods and give numerical results showing the accuracy of our formulas .
msc - class : 33b20 ( primary ) 34e20 , 33e30 ( secondary ) .
keywords : inverse error function , differential - difference equations , singularity analysis , discrete wkb method . |
the study of resonance production plays an important role both in pp and heavy - ion high energy collisions . in pp collisions
, it contributes to the general understanding of hadron production mechanisms and provides a reference for tuning qcd - inspired models . in heavy - ion collisions , due to their short lifetime ( few fm/@xmath3 ) , resonances can decay inside the fireball , and studying the interactions of their decay products with the surrounding medium allows one to estimate its temperature and investigate its time evolution @xcite .
moreover , resonances produced in the early stages of the collision can show signals of chiral symmetry restoration in terms of modifications of their mass and/or width @xcite .
alice @xcite is the lhc experiment mainly devoted to the study of ultra - relativistic heavy - ion collisions , in order to investigate the properties of the quark - gluon plasma ( qgp ) .
its excellent capabilities for particle identification @xcite over a wide @xmath4 range ( from @xmath50.1 to @xmath510 @xmath6 ) , make it a very well suited device for the study of resonances .
results are presented for @xmath0 ( identified by charged @xmath7 decay channel ) , @xmath1 ( k@xmath8k@xmath9 decay channel ) and @xmath2 ( @xmath10 decay channel ) measurements done with a sample of data collected by alice in 2010 . section [ sec : analysis ] briefly describes the analysis procedure and section [ sec : results ] shows some results .
section [ sec : conclusions ] presents the conclusions and an outlook .
the data analysis is carried out using a sample of minimum - bias pp data collected by alice during 2010 , with a size ranging from 25 to 155 million events , for the different resonances analyzed . in order to minimize the background , particle identification selection criteria for the decay products
are used , which are based on their d@xmath11d@xmath12 measured by the time projection chamber ( tpc ) and their @xmath13 measured by the time of flight ( tof ) detector . due to their very short lifetime
, resonance decay products can not be distinguished from the particles coming from the primary vertex , and their yield can only be measured by computing the invariant mass spectrum of all primary tracks and then subtracting the combinatorial background . for the @xmath0 ,
the combinatorial background is estimated from like - sign @xmath7 pairs and then subtracted from the unlike - sign @xmath7 .
the resulting distribution is fitted with a breit - wigner function plus a straight line to account for a remaining residual background ( figure [ fig : peaks ] left ) .
the raw yields of @xmath1 and @xmath2 are extracted by fitting the invariant mass distributions with a function composed by a polynomial to describe the background , plus a voigtian , i.e. the convolution of a gaussian and a breit - wigner ( figure [ fig : peaks ] right ) .
this choice is necessary to take into account the resolution in invariant mass , since it ranges between 1 and 2 @xmath14 and is therefore comparable with the nominal widths of these resonances ( 4.25 and 9.1 @xmath14 , respectively ) .
the raw yields of @xmath0 , @xmath1 and @xmath2 in pp collisions are corrected for reconstruction efficiency , acceptance and branching ratio and then normalized to the number of inelastic collisions in the analyzed sample @xcite .
figure [ fig : spectra ] shows the resulting spectra , compared with phojet @xcite and some widely used pythia @xcite tunes : d6 t @xcite , atlas - csc @xcite and perugia-0 @xcite . for the @xmath0 , pythia
d6 t shows the best agreement , while phojet and atlas - csc produce a softer spectrum .
the @xmath1 is well reproduced by d6 t below 2.5 @xmath6 and by phojet and atlas - csc above this limit .
both mesons are underestimated by perugia-0 .
in contrast , all models underestimate the @xmath2 yield . figure [ fig : ratios ] shows the @xmath15k@xmath9 and @xmath16k@xmath9 ratios , for different energies and different colliding systems @xcite . including alice measurements @xcite . both ratios do not vary with @xmath17 .
spectral distributions @xmath18 has been determined for @xmath0 , @xmath1 and @xmath2 resonances through their hadronic decay channels .
spectra show different levels of agreement with various event generators : mesons are reasonably well reproduced ( except by perugia-0 ) while the @xmath2 is underestimated in all cases
. ratios of @xmath1 and @xmath0 to k@xmath9 do not increase with respect to lower energies .
other resonances studies are ongoing to complement the picture for pp collisions at 7 tev : @xmath19 , @xmath20 and @xmath21 .
the analysis of pb pb collisions at @xmath22 @xmath23 has also started with the extraction of @xmath1 signal for @xmath24 @xmath6 , both in central and peripheral events .
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( alice collaboration ) , _ | the study of resonance production in pp collisions helps understanding hadronization mechanisms and tuning the qcd - inspired particle production models . in pb
pb collisions , resonances allow one to probe the temperature and time evolution of the fireball .
transverse momentum spectra have been analyzed for @xmath0 , @xmath1 and @xmath2 resonances using data from pp collisions at 7 tev collected by the alice detector .
a comparison with monte carlo event generators shows different levels of agreement for meson spectra , while @xmath2 is always underestimated . |
optical beam guiding , deflection and cloning has attracted a great deal of attention due to its tremendous applications in optical imaging , optical switching , optical lithography , laser machining , and free - space communication technologies .
the guiding and steering of an optical beam is made possible by virtue of a refractive index of the medium .
several techniques such as mechanical @xcite , thermal @xcite , electrical @xcite , acousto - optical @xcite and all optical @xcite have been proposed to control the refractive index for beam deflection .
however , all - optical methods have been paid much effort owing to many striking features such as high speed , efficiency , and quick nonlinear response time .
the nonlinear optical interactions between light and matter creates a new avenue to control over beam propagation dynamics through a medium .
this is feasible as the absorptive and dispersive properties of the medium can be modified by the strength of the interactions .
such manipulation of dispersion and absorption leads to many novel phenomena including electromagnetically induced transparency ( eit ) @xcite , coherent population trapping(cpt ) @xcite , saturated absorption techniques @xcite or lasing without inversion(lwi ) @xcite .
the sharp refractive index changes near the centre of the transparency window for the eit medium is the key concept for beam deflection @xcite .
the ability to control of light deflection is also possible by use of transverse magnetic field through an atomic medium @xcite .
further a suitable spatially dependent control field can be used to modulate the refractive index along the transverse direction .
this spatially modulated refractive index generates several effects such as induced focusing @xcite , waveguiding @xcite and anti - waveguiding @xcite .
most of the eit - based schemes for producing beam deflection and guiding have low transmission due to presence of medium absorption @xcite .
therefore , finding an alternative medium which displays gain with the desired variation of refractive index is a challenging task . in this context , active raman gain(arg ) media
have attracted a lot of attention @xcite . recently
zhu _ et al . _
@xcite have theoretically studied the beam deflection in an arg medium .
they have used spatially inhomogeneous pump beam to deflect a weak probe beam .
they have found that the deflection angle is increased by an order of magnitude as compared to eit medium .
nonetheless the probe field experiences a large amount of gain during the propagation through a @xmath1-type arg medium @xcite .
this large gain makes the probe beam propagation unstable and thus limits the practical application @xcite .
moreover , the input spot sizes for individual gaussian profiles of pump and probe beams are equal to @xmath2 cm and @xmath3 mm , respectively .
hence , the diffraction spreading of such beams are not relevant since rayleigh length is much larger than the length of the medium . focusing laser beams into smaller spots @xcite and increasing the spatial resolution of arbitrary images
@xcite is a fundamental problem in all - optical image processing @xcite .
distortion and absorption holds the fundamental limitation for the creation , detection , or propagation of small images .
this limitation affects the applications such as efficient transfer and conversion of small images @xcite , steering @xcite or optical manipulation of light beams @xcite .
here we address these issues by considering the propagation of diffraction - limited beams and arbitrary images through a controllable arg medium . in this paper
we exploit an anti - waveguide mechanism @xcite to show beam steering , splitting , and cloning of an arbitrary images in an inhomogeneously broadened medium . to facilitate these processes
, we use spatial inhomogeneous pump beam to write an anti - waveguide inside the medium for co - propagating probe beam . at two - photon raman detuning condition , the refractive index and gain of the probe susceptibility are high at the peak of the gaussian pump beam whereas at wings both are very small .
the high refractive index together with gain allow to deflect the probe beam when it is launched at the wings of the pump beam .
the control field parameters such as detuning and intensity can be used to control the transmission intensity and width of the deflected probe beam .
next , we reveal splitting of a single super - gaussian probe beam into two gaussian beams by use of two - peak pump beam structure .
the bright(cladding ) and dark(core ) regions of the pump field profile induces a high(cladding ) and low(core ) refractive index of the probe field which lead to formation of an anti - waveguide structures inside the medium .
more specifically , the super - gaussian probe beam guided out from the core where it was injected .
the diffraction - limited probe beam gets focus in the cladding due to the converging refractive index .
we also observe that the transmitted probe beam gets the shape of the pump beam with finesse two times larger than the initial finesse of the pump beam .
further , we demonstrate the cloning of a doughnut - shaped pump beam structure onto the probe beam .
our numerical simulation shows that the cloned probe has a controllable gain with high finesse .
furthermore , our scheme can be employed for cloning the arbitrary pump images to the probe beam even though the pump images are severely distorted due to diffraction .
it follows that our findings can greatly improve the device performance on beam steering , splitting and image cloning beyond the diffraction limit .
the article is organized as follows . in the next section ,
we introduce the physical model and basic equations of motion for a four - level system . in sec .
iii , an approximate expression for a linear susceptibility of a weak probe field is derived using perturbative approach .
we include the thermal motion of the atoms by averaging the susceptibility over maxwell - boltzmann velocity distribution . in sec .
iv , we describe the beam propagation equations for the evolution of both pump and probe fields under paraxial approximations . in sec .
v , we discuss our results based on numerical simulation .
we first explain the spatially dependent susceptibility for different shapes of the pump beam and advantage of a uniform control beam .
we then perform numerical integration of the beam propagation equations in order to demonstrate steering , splitting and cloning of an optical beam .
obtained results are summarised in the final section .
( color online ) ]
the schematic of the system under consideration for the generation of steering , splitting and cloning of an optical beam is illustrated in fig.[fig : fig1](a ) where three co - propagating fields interact within the inhomogeneously broadened medium .
the electrical dipole allowed transitions @xmath4 , @xmath5 , and @xmath6 form a four - level @xmath0-type atomic system as shown in fig.[fig : fig1](b ) . the transitions @xmath7 , @xmath8 and @xmath9 are generally forbidden electric dipole transitions .
the atomic transitions @xmath10 , @xmath5 , and @xmath11 are driven by a pump field with frequency @xmath12 , a weak probe field with frequency @xmath13 and a control field with frequency @xmath14 , respectively .
this generic level configuration can be found for example in energy levels of @xmath15rb which contain ground levels @xmath16 , @xmath17 and excited levels @xmath18 and @xmath19 , respectively @xcite .
we define three co - propagating electric fields as follows : @xmath20 where , @xmath21 are slowly varying envelopes , @xmath22 is the unit polarization vector , and @xmath23 is the wave number of electric fields .
the index @xmath24 denotes the pump , probe , and control fields , respectively . under the action of three coherent fields ,
the interaction hamiltonian of the system in the dipole and rotating wave approximation is given by @xmath25 where @xmath26 , @xmath27 , @xmath28 are the single - photon detunings of the pump , probe , and control fields , respectively .
the atomic transition frequencies are denoted by @xmath29 .
the rabi frequencies of pump , probe and control fields are defined as @xmath30 where the @xmath31 are the corresponding dipole moment matrix elements of transitions @xmath32 .
the dynamical evolution of the atomic system can be described by the density matrix equations @xcite , @xmath33+\mathcal{l}\rho\,.\end{aligned}\ ] ] where the liouvillian matrix @xmath34 , defined in eq .
( [ liouvillian ] ) , describes the relaxation by radiative and non - radiative decay @xmath35 .
\end{aligned}\ ] ] the radiative decay rates from the excited states @xmath36 and @xmath37 to ground states @xmath38 and @xmath39 are labeled by @xmath40 and @xmath41 , @xmath42 and the collisions dephasing rate @xmath43 describes redistribution of populations between ground levels .
the decay rate of the atomic coherence is defined as @xmath44+\gamma_{_{c}},~i\notin \{\alpha,\beta\}\,.\end{aligned}\ ] ] substituting the interaction hamiltonian of eq.([heff ] ) and the liouvillian matrix of eq.([liouvillian ] ) in the density matrix eq.([master ] ) , the equations of motion for the four - level atomic system can be described as @xmath45\rho_{_{21 } } - { { i } } g \rho_{_{23 } } + { { i } } g^ { * } \rho_{_{31 } } + { { i } } \omega^ { * } \rho_{_{41}}\,,\nonumber\\ \dot{\rho}_{_{33}}&=-(\gamma_{_{13}}+\gamma_{_{23}})\rho_{_{33 } } + { { i } } g \rho_{_{13 } } - { { i } } g^ * \rho_{_{31 } } + { { i } } g\rho_{_{23 } } - { { i } } g^*\rho_{_{32}}\,,\nonumber\\ \dot{\rho}_{_{31}}&=-\left[\gamma_{_{31 } } - { i}{\delta_{_{1}}}\right]\rho_{_{31 } } + { { i } } g \rho_{_{21 } } + { { i } } g ( \rho_{_{11}}- \rho_{_{33 } } ) \,,\nonumber\\ \dot{\rho}_{_{32}}&=-\left[\gamma_{_{32 } } - { i}{\delta_{_{2}}}\right]\rho_{_{32 } } + { { i } } g\rho_{_{12 } } - { { i } } \omega \rho_{_{34 } } + { { i } } g ( \rho_{_{22 } } - \rho_{_{33}})\,,\nonumber\\ \dot{\rho}_{_{34}}&=-\left [ \gamma_{_{34 } } - { i}({\delta_{_{2}}}-{\delta_{_{3}}})\right]\rho_{_{34 } } + { { i } } g \rho_{_{14}}+ { { i } } g \rho_{_{24 } } - { { i } } \omega^*\rho_{_{32 } } \,,\nonumber\\ \dot{\rho}_{_{41}}&=-\left [ \gamma_{_{41}}- { i}({\delta_{_{r}}}+{\delta_{_{3}}})\right]\rho_{_{41 } } + { i}\omega \rho_{_{21}}- { { i } } g\rho_{_{43 } } \,,\nonumber\\ \dot{\rho}_{_{42}}&=-\left [ \gamma_{_{42}}- { i}{\delta_{_{3}}}\right]\rho_{_{42 } } + { { i } } \omega ( \rho_{_{22 } } - \rho_{_{44}})- { { i } } g \rho_{_{43 } } \ , , \end{aligned}\ ] ] together with population conservation condition @xmath46 and two - photon raman detuning @xmath47 . in the next section , we obtain the analytical expression for the linear susceptibility of the probe field in a compact form with the assumption of equal decay rates from excited states , _
i.e. , _ @xmath48 .
in this section , we derive an approximate solution of linear susceptibility of the probe field in a hot atomic medium .
the analytical solution of the atomic coherence @xmath49 for the probe field can be obtained by solving the density matrix eqs.([full_density ] ) in the steady state condition .
we assume that all atoms are prepared initially in the ground state @xmath38 . due to the presence of large detuning of the strong pump and weak probe fields , most of the atoms populate at their ground state @xmath38 while other states @xmath50 , remain empty at later time .
hence the system turns to an arg configuration for the probe field . since
raman gain process is basically a second - order process , we therefore expand the density matrix elements to first order in the probe field @xmath51 and to second order in the pump field @xmath52 but all orders in the control field @xmath53 in the weak probe field limit .
the perturbation expansion of the density matrix can be expressed as @xmath54 where , @xmath55 describes the solution in the absence of all three optical fields and @xmath56 denotes the @xmath57-th order solution .
now we substitute the above expression in the eqs.([full_density ] ) and equate the coefficients of @xmath51 , @xmath58 , @xmath59 ( @xmath60 ) , and constant terms . as a result
, we obtain a set of 12 coupled simultaneous linear algebraic equations to determine the expression of @xmath61 .
we use back substitution method to solve these algebraic equations in order to derive the probe coherence @xmath49 .
the different terms in the expression of the probe coherence are given in appendix [ app - a ] .
the atomic coherence @xmath49 will yield the probe susceptibility @xmath62 at frequency @xmath13 @xmath63 where @xmath64 is the atomic density of the medium .
the above analysis is valid for stationary atoms . while for a hot atomic system
, the thermal motion of the atoms causes inhomogeneous broadening of the atomic spectra .
the thermal velocity @xmath65 of the atom can be included in the susceptibility expression([chi_32 ] ) by introducing velocity - dependent field detunings @xmath66 .
the term @xmath67 is the doppler shift experienced by an atom with a velocity component @xmath65 in the direction of the beam propagation of the fields .
we have assumed the wave vectors of the three fields are nearly equal ( @xmath68 ) .
the negative sign in the velocity - dependent field detuning @xmath69 indicate that atom and field are co - propagating .
the susceptibility of a hot atomic vapour system needs to be averaged over the entire velocity distribution of atoms and it is given by @xmath70 the velocity distribution of the atom is assumed to obey the maxwell - boltzmann distribution @xmath71 the doppler width @xmath72 at temperature @xmath73 defined by @xmath74 where @xmath75 is the atomic mass and @xmath76 is the boltzmann constant .
doppler broadening plays a crucial role to control the width of the absorption or gain window of the thermal media @xcite .
the spectral features of window become narrower in a doppler broadened medium as compared with the homogeneous medium .
the steepness of the refractive index due to the narrowing of resonance window can be useful in many applications such as slow light , storage of light and high resolution spectroscopy .
thus we include atomic velocity effect on the beam propagation dynamics through arg medium by considering doppler averaging in the susceptibility expression .
the propagation of co - propagating pump and probe fields with amplitudes @xmath77 and @xmath78 along the @xmath79-direction are governed by maxwell s wave equations . under slowly varying envelope and paraxial wave approximations , the beam propagation equations for pump and probe field can be expressed in the following form @xmath80 the velocity - averaged susceptibility @xmath81 is included only in the probe beam equation , whereas this effect is very negligible on the pump beam propagation under the weak probe field @xcite .
the second partial derivatives in the transverse directions @xmath82 represent a paraxial diffraction .
the diffraction of beam or image is inevitable since its constituent plane wave components acquire different phases during its propagation .
the spatially dependent refractive index of the fields can be used to suppress or even reverse due to diffraction .
we use a suitable spatially dependent pump field to produce spatially dependent refractive index for the probe field . for this purpose , we choose the transverse spatial profile of the pump beam as a laguerre - gaussian with charge @xmath83 , denoted by lgp@xmath84 .
the profile of pump beam can be written as @xmath85 \nonumber\\ & \times \exp\left [ - i(m+1)\tan^{-1}\bigg({\frac{z}{z_r}}\bigg ) + im\theta \right ] \,,\end{aligned}\ ] ] where @xmath86 is an initial peak amplitude , @xmath83 is the azimuthal index .
the beam width is defined as @xmath87 , where @xmath88 is the beam waist at @xmath89 , and @xmath90 is the rayleigh length . the radial distance from the axis of the beam
is given by @xmath91 .
note that for the azimuthal index @xmath92 , the laguerre - gaussian pump ( lgp@xmath93 beam reduces to a gaussian pump beam ( gp@xmath94 .
figure [ fig : figure2 ] shows the intensity distribution of the pump field against radial position @xmath95 at different lengths of the medium .
the lgp@xmath96 beam exhibits a dark spot in the centre and a bright profile in the annular region .
this makes intensity profile in contrast to gp@xmath97 beam .
it is clearly shown in fig.[fig : figure2 ] that diffraction induced distortion of the pump beam profile is not severe even after 5 cm of propagation .
therefore , phase modulation imposed on the probe beam due to the spatially varying pump beam is effective throughout the length of the medium .
the probe beam possess a gaussian profile @xmath98^f}\,,\end{aligned}\ ] ] at an entry face of the medium .
the initial peak amplitude and the width of the probe field are denoted by @xmath99 and @xmath100 and @xmath101 is the initial location of the centre of the probe beam along the @xmath95 direction .
we have chosen the initial intensity of the probe beam such that it gets absorbed inside the medium without pump and control fields .
the integer values of @xmath102 decides the input profile of the probe beam - either a gaussian @xmath103 or a super - gaussian @xmath104 .
( color online ) ]
in order to elucidate the effect of position dependent characteristic of the pump field on the probe beam dynamics , we first numerically explore the behaviour of velocity - averaged probe susceptibility under different detuning and intensity of the control field .
[ fig : figure3 ] shows the spatial variation of probe dispersion and gain plotted against transverse axis @xmath95 at @xmath105 plane . here
two different transverse profiles of pump beam namely gaussian ( gp@xmath106 and laugerre - gaussian ( lgp@xmath107 have been used .
we begin with gaussian pump beam and study the usefulness of uniform control field @xmath53 on the spatially modulated probe susceptibility . in absence of a control field ,
the position dependent refractive index of the probe is zero under two - photon raman condition whereas the spatial gain profile of the probe field takes the shape of the pump beam profile .
the spatially dependent pump structure generates a probe gain profile which is one of the key components in realising the deflection of the probe beam if it is off - centered with respect to the pump beam . in absence of the control field @xmath108 , the gain profile of the probe field is fifteen times larger than in case of control field @xmath109
. this large gain can create modulation instability of system @xcite .
therefore a controllable gain of the medium is required to avoid the modulation instability .
it is clear from fig .
[ fig : figure3 ] that the position dependent probe gain can be substantially suppressed by a uniform control field with @xmath110 .
this restricted probe gain is accompanied by a gaussian shaped spatial refractive index .
the gradient of the refractive index is dependent on the sign of the control field detuning . at red control field
detuning , the slope of the spatial refractive index attains maximum at the line centre and decreases gradually toward the wings .
hence , a convex lens like refractive index can be mimiced in the arg medium for @xmath111 . on the contrary
the blueshifted the control field detuning @xmath112 can generate a concave refractive index profile onto the medium . therefore the refractive index gradient allows us to focus or defocus the probe beam towards the centre of the pump beam . as a result the probe field propagates through the gain window with narrowing or broadening , respectively .
hence a control field can prepare a gain medium with suitable spatial refractive index for encompass the probe beam deflection to a great extent .
next we consider higher order lgp@xmath113 mode to investigate the spatial inhomogeneous character of @xmath81 in the presence of uniform control beam .
the grey double dashed dotted line in fig .
[ fig : figure3a ] and [ fig : figure3b ] shows the transverse variation of probe refractive index as well as gain , respectively .
the position dependent refractive index and gain both increase in the bright region whereas it decreases at the dark region of the doughnut shaped pump beam .
in other words , lgp@xmath113 induces a diverging gradient index in the region @xmath114 0.005 cm whereas a converging gradient index exists in regions 0.005 @xmath115 0.02 cm of the medium . thus bright and dark regions of lgp@xmath113 resembles a waveguide and anti waveguide structure inside the atomic medium .
fig.[fig : figure3a ] is also show that the waveguide and anti - waveguide features are accompanied with gain and absorption , respectively . as a result ,
the probe beam is guided out from dark region and confined at bright region in the course of propagation inside the medium .
hence the shape of the pump beam profile can be efficiently transfered to the transmitted probe beam .
we have simulated numerically the propagation equations for pump ( [ beam_eq_control ] ) and probe ( [ beam_eq_probe ] ) beams by split step operator method @xcite to demonstrate the spatial susceptibility as well as diffraction effects on the beam s propagation dynamics .
first , we study how the deflection of a probe beam can be controlled by a spatial dependence of the pump rabi frequency .
the shape and position of a probe beam is given by eq ( [ profile_probe ] ) at the entry face of the medium .
[ fig : figure4a ] shows the spatial evolutions of the probe beam with @xmath116 mm and @xmath117 m when the peak of pump beam is centered at the origin @xmath118 with @xmath119 m .
initially the overlap area between the probe and pump beam is very negligible .
the overlap area is gradually increased due to the broadening of both the beams during propagation .
it is evident from this figure that after a propagation of one rayleigh length , the probe beam progressively enters the pump region .
the bright region of the pump beam tends to refract the probe beam into it and subsequently enhances the probe beam amplitude . as a result
, the probe beam is focused towards the high intensity region of the pump and remains confined there .
ii is noteworthy that the probe beam gains the initial shape of the pump beam and retains this shape as it propagates along the @xmath79 axis .
similarly , if the peak position of the probe beam is shifted along the positive @xmath95-direction then it can be dragged by the pump beam towards the pump line centre .
[ fig : figure4b ] exhibits the effect of control field detuning onto the propagation dynamics of a probe pulse at @xmath120 cm .
it is seen that the deflected probe beam becomes narrower at redshifted detuning as compared to a blue - shifted detuning .
therefore the sign of the detuning of the control field gives an additional flexibility to control the width of the deflected probe beam .
thus the arg medium not only acts as an effective beam deflector but also can act like a lens with a wide focal length tunability .
( color online ) ] next , we demonstrate the spatial evolution of single super - gaussian probe as well as double gaussian pump beam with different propagation distance @xmath79 . at the entrance face of the medium , the probe beam
is launched in the dark region of the double gaussian pump beam as shown in fig .
[ fig : figure5 ] .
the position dependent pump beam creates two gain peaks together with converging refractive index in the probe susceptibility which is similar to the grey double dashed dotted line in fig.[fig : figure3 ] .
the gain and spatial inhomogeneity of the refractive index is accountable for this splitting of a single super - gaussian probe beam into two gaussian beams .
the converging lens effect in the intense regions of the pump leads to focusing of the cloned probe beam towards it .
the finesse of the transmitted probe beam can be defined as the ratio of the spacing between peaks to the width of peaks .
the transmitted probe beam width is reduced by a factor of 1.5 and the peaks separation are increased by 0.7 mm as compared to the initial shape of the pump beam .
hence the finesse of the cloned image has doubly enhanced as compared with initial pump image . noticeably from fig .
[ fig : figure5 ] the transmitted probe beam structure is preserved even though the pump beam suffers distortion due to diffraction . in this section ,
we investigate the efficient transfer of images between two co - propagating orthogonal polarized optical beams .
we adopt all - optical anti - waveguide mechanism to clone the images from pump to probe beam .
an all - optical anti - waveguide structure can be formed inside the medium with use of lgp@xmath113 beam which has zero intensity at the beam centre .
the dark and bright regions of lgp@xmath113 beam give rise to minimum and maximum refractive index gradient on the probe susceptibility . as a results
a diverging and converging refractive index is formed in the core and cladding region of the anti - wave guide structure .
thus an all - optical anti - waveguide for a probe beam is generated by the co - propagating doughnut - shaped strong pump beam . in order to demonstrate the cloning mechanism in arg medium ,
the centre of the dark region of the doughnut pump beam is the initial location of probe beam .
the diverging refractive index gradient and diffraction leads to the probe beam leaving the core region and slowly enter the high intensity regions of the pump beam .
therefore each wing of the probe beam profile experiences gain and converging gradient of refractive index in the cladding region .
thus the probe energy is guided into the annular ring of the doughnut - shaped beam and leaving a zero intensity in the dark region .
hence the transmitted probe beam profile acquires a doughnut - shaped profile as shown in fig .
[ fig : figure6 ] .
we have found that the transmitted structure of probe beam is twice as sharp compared to the lgp@xmath113 beam structure .
the spatial evolution of probe beam at different propagation distances are similar to that in fig .
[ fig : figure5 ] .
( color online ) ] fig .
[ fig : figure7 ] shows the cloning of an arbitrary images and its diffraction effects through an arg medium . in order to elucidate the arbitrary image cloning
, we consider the probe beam as a plane wave whereas the pump beam carries complex image such as three letters arg " structured at the entrance face of the medium .
the two - dimensional transverse profile of the pump beam creates gain for the probe beam wherever two - photon raman condition is satisfied .
hence the transverse pattern of the pump beam can be efficiently transferred to the probe beam .
the cloned probe beam also experiences focusing effects at the high intensity regions of the pump beam .
thus the transmitted probe beam has better resolution than the original pump beam images as can be seen in fig .
[ fig : figure7]b . fig .
[ fig : figure7]c illustrates that the diffraction induced distortion severely affects the pump beam images and is completely distorted after a propagation of 2 cm .
in conclusion , we have studied diffractionless steering , splitting and cloning of an optical beam in a doppler broadened four level @xmath0-type raman gain medium using a spatially inhomogeneous pump beam .
the spatial pump beam profile gives rise to transverse modulation in the refractive index and gain for the probe beam .
the modulated refractive index along with gain can optically form anti - waveguide structure inside the medium .
the properties of anti - waveguide structure such as refractive index and gain can be controlled by the application of control field which lead to steering of the probe beam very efficiently .
we further demonstrated that a single probe beam can be split into two gaussian modes when it is injected at the centre between two gaussian modes of pump beam .
we found that the probe beam profile has acquired the shape of the pump beam and propagates without usual diffraction .
we next show that the transfer of doughnut - shaped pump image onto a low power gaussian - shaped probe beam can be possible with high finesse . finally , by numerical simulations we have established that an arbitrary image with three letters arg " imprinted on pump beam can be cloned on to the transmission profile of the probe .
the finesse of cloned image has increased twice as compared to the initial resolution of pump images .
thus this scheme might be useful in optical switching , optical lithography , and optical imaging processing .
tnd acknowledges science and engineering board of india for financial support ( sr / s2/lop-0033/2010 ) .
the related @xmath121th - order contributions for @xmath122are obtained as @xmath123}\\ { \rho}_{_{34}}^{^{(12 ) } } & = \frac { { i}{\rho}_{_{14}}^{^{(9 ) } } + { i}{\rho}_{_{24}}^{^{(6 ) } } - { i}{\omega^*}{\rho}_{_{32}}^{^{(12 ) } } } { \left [ \gamma_{_{34 } } - { i}({\delta_{_{2}}}-{\delta_{_{3}}})\right ] } \\ { \rho}_{_{12}}^{^{(9 ) } } & = \frac{{i}{\rho}_{_{32}}^{^{(3 ) } } -{i}{\rho}_{_{13}}^{^{(2 ) } } - { i}{\omega}{\rho}_{_{14}}^{^{(9 ) } } } { \left [ \gamma_{_{c } } + { i}{\delta_{_{r}}}\right ] } \\ { \rho}_{_{14}}^{^{(9 ) } } & = \frac { i{\rho}_{_{34}}^{^{(1 ) } } -{i}{\omega^{*}}{\rho}_{_{12}}^{^{(9 ) } } } { \left [ \gamma_{41 } + { i}({\delta_{_{r}}}+{\delta_{_{3}}})\right]}\\ { \rho}_{_{33}}^{^{(6 ) } } & = \frac { i ( { \rho}_{_{13}}^{^{(2 ) } } - { \rho}_{_{31}}^{^{(1 ) } } ) } { \left [ \gamma_{_{13 } } + \gamma_{_{23 } } \right]}\\ { \rho}_{_{24}}^{^{(6)}}&= { \rho}_{_{44}}^{^{(6)}}={\rho}_{_{22}}^{^{(6)}}=0\\ { \rho}_{_{13}}^{^{(2 ) } } & = { \rho}_{_{31}}^{^{(1)}}= \frac { -{i}}{\left [ \gamma_{_{13 } } + { i}{\delta_{_{1}}}\right ] } \\ { \rho}_{_{32}}^{^{(3 ) } } & = { \rho}_{_{34}}^{^{(1)}}=0 \end{aligned}\ ] ] @xmath124}}{(\gamma_{_{13}}+\gamma_{_{23}})(\gamma_{_{31}}^2+{\delta_{_{1}}}^2 ) } + \frac{{[\gamma_{_{34 } } - { i}({\delta_{_{2}}}-{\delta_{_{3}}})][\gamma_{_{41 } } + { i}({\delta_{_{r}}}+{\delta_{_{3 } } } ) ] } -|\omega|^2}{(\gamma_{_{31 } } + { i}{\delta_{_{1}}})\left[(\gamma_{_{c } } + { i}{\delta_{_{r}}})(\gamma_{_{41 } } + { i}({\delta_{_{r}}}+{\delta_{_{3}}}))+|\omega|^2\right]}\right]\end{aligned}\ ] ] 99 i. cindrich , appl . opt .
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a. d. bandrauk , h. shen , journal of physics a : mathematical and general * 27 * , 7747 ( 1994 ) . | we propose an all - optical anti - waveguide mechanism for steering , splitting , and cloning of an optical beam beyond the diffraction - limit .
we use a spatially inhomogeneous pump beam to create an anti - waveguide structure in a doppler broadened @xmath0-type four - level raman gain medium for a co - propagating weak probe beam .
we show that a transverse modulated index of refraction and gain due to the spatially dependent pump beam hold the keys to steering , splitting and cloning of an optical beam .
we have also shown that an additional control field permits the propagation of an optical beam through an otherwise gain medium without diffraction and instability .
we further discuss how finesse of the cloned images can be increased by changing the detuning of the control field . |
the study of transition and noble metal clusters has focused considerable attention along the last years due to the different properties detected respect to their corresponding bulk - phases .
additionally , these cluster properties have demonstrated to be strongly dependent on the cluster size . on the other hand , noble metal clusters , and silver clusters in particular , present important applications from the scientific and technological point of view in interesting researching fields such as catalysis @xcite , and optics @xcite .
the structural and electronic properties of silver clusters @xcite have been widely studied , however unlike the optical properties @xcite .
the optical absorption spectra of silver clusters have been studied for more than two decades ago .
et al . _
@xcite found that ag@xmath1 ( n@xmath240 ) clusters show a simple dominant peak in the low energy region , exceptions were attributed to the coexistence of low energy isomers .
these results were confirmed theoretically for small - sized silver clusters ( n=5 - 8 ) @xcite .
on the other hand , idrobo _ et al . _
@xcite have recently carried out calculations of the absorption spectra of ag@xmath0 for different structural isomers , however no full agreement with experiments was found . on the other hand , experimental optical spectroscopy , aided by recent advances in the corresponding theoretical tools ,
has proved to be a powerful means for obtaining information about the geometrical and electronic structure of molecules and small clusters .
since the structure of a cluster is generally not directly accessible experimentally , its characterization must be done with a combination of experiment and theory . in previous works
we have shown how a comparison of the measured optical spectrum with theoretical calculations for different isomeric forms of a given cluster can provide a useful diagnosis of the geometrical structure of the cluster @xcite .
however , conventional optical absorption spectroscopy experiments for studying transition and noble metal clusters are difficult due to several technical issues , such as the extremely low density of the produced clusters , and theoretical spectroscopy is a perfect framework to complement most of experimental analysis . in this paper
, we present calculations of the optical absorption spectra of the three most stable isomeric forms of the ag@xmath0 cluster up to 8 ev by using an extremely accurate technique for treating the electronic excitations : the time - dependent density functional theory ( tddft ) @xcite under the formalism developed by casida _
et al . _
@xcite .
our motivations for this work have been the following : ( a ) first , to show a comparison between the present first - principles tddft results and the available experimental measurements , in order to improve the description of previous theoretical studies by reducing the numerical uncertainty ; ( b ) since significant differences have been found among the spectra of the different isomers of ag@xmath0 ( see fig .
[ p1 ] ) , to propose the comparison of experimental and tddft absorption spectra as a powerful tool to elucidate between the different isomeric forms of small clusters ; and ( c ) finally , to predict ag@xmath0 photoabsorption spectrum for energies higher than 5.5 ev , a range of energies which has not been considered in previous experimental or theoretical studies for this system ( our calculations extend the range of excitation energies up to 8 ev ) .
used for the calculation of the photoabsorption spectra .
the ground - state structure is labelled as g - s , and the two closest in energy isomers as iso1 and iso2 , respectively .
[ p1],width=245 ]
prior to the calculation of the photoabsorption spectra , the lowest energy geometrical structure of each isomer was determined by using the density functional theory @xcite .
the ion - electron interaction is modelled by replacing the ionic cores ( 1s@xmath32s@xmath3p@xmath43s@xmath3p@xmath4d@xmath54s@xmath3p@xmath6d@xmath55s@xmath7 krypton like core ) by pseudopotentials within the relativistic scheme of hartwigsen and coworkers @xcite , previously validated for several metal elements in pure and organometallic clusters @xcite .
this pseudopotential is built in such a way that is separable by construction , is highly accurate , and has an analytical form that can be specified by a small number of parameters . for exchange and correlation effects
we have used the generalized gradient approximation ( gga ) @xcite . as initial geometries for the structural optimization of the ag@xmath0 isomers
were considered the three most stable structures previously obtained by fernndez _
et al . _
starting from those geometries we performed structural relaxations by making use of the broyden algorithm @xcite with a convergence criterion of @xmath8 ev / in the net forces on every atom .
the structural relaxations , performed with the abinit package @xcite , did not produce significant variations with respect to the original structures . in order to test the influence of using a well - tailed exchange - correlation potential in the structural properties we have additionally checked the simple gga by comparison with a functional with improved asymptotic behavior : the van leeuwen baerends ( lb94 ) gga functional @xcite , which led to practically identical optimized structures . the geometries obtained , which are then used in the calculations of the photoabsorption spectra ,
are shown in fig .
[ p1 ] .
once the ground - state structures of the different isomers were established , we performed the calculation of the excitation spectra . for this purpose
, we have used the tddft formalism @xcite , implemented in the real space code octopus @xcite .
the theoretical foundations underlying the tddft calculations , as well as the computational scheme , have been presented elsewhere @xcite , and here we only summarize the main points .
the photoabsorption spectrum is calculated by using the formalism developed by casida @xcite .
application of this technique to obtain the oscillator strengths requires a previous calculation of the ground state electronic structure , that is , the occupied electronic states , and also the unoccupied states .
the whole set of occupied states , joint to twenty extra unoccupied states for each spin channel , were necessary to reach convergence of the excitation spectra for an energy range up to 8 ev .
after that , each excitation peak is broadened by a lorentzian profile to give the photoabsorption cross section @xmath9 where @xmath10 is the energy , @xmath11 are the discrete excitation energies obtained by the casida method , and the value of the parameter @xmath12 determines the full width at half maximum . we have performed the calculations of the photoabsorption spectra with the gga , using the perdew - burke - ernzerhof parameterization @xcite of electronic correlation .
the corresponding occupied and unoccupied single
particle states are used in the casida method with the adiabatic lda exchange correlation kernel .
although not entirely consistent , this is a common practice because the use of a better kernel does not significantly affect the results as long as the single particle orbitals have been calculated with a suitable static @xmath13 potential @xcite .
this computational framework has been used successfully in the calculation of the optical spectra of atoms and clusters @xcite . in the case of free atoms ,
the energies for one - particle low - energy excitations agree with experiment to within 5 - 10 per cent @xcite . for clusters of s
p metals , the errors in the position of the absorption peaks are usually in the 0.1 - 0.2 ev range @xcite , and the results are also very reasonable for carbon and bn clusters @xcite , and transition metal , organometallic , and molecular and van der waals clusters @xcite , even in the high - energy range .
this formalism , used in combination with both adiabatic local density ( alda ) and gga approximations for the xc effects , has provided successful results , establishing this technique for the calculation of excitations in this kind of nanoscale systems as an effective tool in the characterization of a great number of cluster properties and behaviors , such as the elucidation of ground - state structures , the characterization of dimeric growths in molecular clusters , and the theoretical justification of collective electronic behaviors @xcite .
( upper pannel ) , and three experimental spectra of ag@xmath0 measured in a ne matrix at 6 k @xcite , and ar matrices at 10 @xcite and 28 k @xcite ( lower pannels ) .
the computed spectrum has been broadened using lorentzian profiles with a width of 0.05 ev .
[ p3 ] ] fig .
[ p1 ] shows the calculated equilibrium structures of the three lowest - energy isomers of the ag@xmath0 system , starting from the geometries obtained by fernndez _
et al . _
the results do not reveal significant variations respect the original structures ; where , during the relaxation process , all the atoms in the clusters are free to move .
the obtained g - s configuration is based in a seven - atom pentagonal bypiramid , as predicted in previous references @xcite .
the ordering of the most stable isomers presented here do not fully agree with these previous studies , but is in complete agreement with the accurate structural analysis given by fernndez _
( for a more detailed description about the structures see ref .
however , this factor can be due to the small differences in the total energy detected between the different , almost energy - degenerated , isomers shown in the recent literature ( in the range of mev ) . in the present study the gap in the total energy between the g - s structure and the two most stable isomers is 0.08 and 0.15 ev for iso1 and iso2 structures , respectively .
nevertheless , and according to the previous theoretical studies , the ground - state of this kind of systems has demonstrated to be highly sensitive to the common dft numerical implementations .
figure [ p2 ] shows the photoabsorption cross sections for the three most stable isomers of ag@xmath0 up to 8 ev as obtained by tddft under the casida formalism .
the finite width of the absorption peaks in an experiment linked to the accessible resolution is mostly determined by the temperature . in our calculations , on the other hand , the width of the peaks is an artifact and may be reduced or enlarged by modifying the @xmath12 parameter .
we have broadened the peaks in the way shown in the figure ( with @xmath12=0.05 ev ) , so as to simulate the approximate resolution yielded by most of the experiments of photoabsorption and photodissociative spectroscopy @xcite .
all three spectra are rich in features in the whole energy region up to 8 ev from the begining of the absorption .
three regions can be clearly distinguished in all the spectra ( separated by dashed lines superposed to each profile in the picture ) .
a region of no absorption at all covers the energy range up to 2 ev ( common to all isomers ) , a region of strong absorption is observed at energies between 2 and 6 ev , and another region of weaker absorption at energies larger than 6 ev , with an absorption strength dependent on the isomer in particular . to our knowledge , no experimental or theoretical study has been carried out for ag@xmath0 in a range of excitation energies up to 8 ev . in the region between 2 and 6 ev , where the absorption strength is more pronounced ,
the spectra are dominated by a sharped profile
whose position rather varies between the different clusters , and formed by pronounced peaks at 3.6 , 4.2 and 4.6 ev . for the iso1 and iso2 isomers an additional peak at 5.2 ev
is found , not present for the g - s structure .
although this wide absorption region is always located between 2 and 6 ev , and despite of other previous tddft theoretical photoabsorption studies in metallic clusters @xcite , it can not be interpreted as a collective plasmon since it is possible to differenciate each single - particle excitation forming the profile .
it is noticeable that the most pronounced peaks forming this strong absorption region between 2 and 6 ev are given for the iso2 isomer , due to the degeneracy of intermediate electronic states arising from its high symmetry .
in fact , the spectra of the other two isomers , where the electronic degeneracy of the intermediate occupied states is much lower , do not present such distinct absorption peaks . on the other hand , in the high excitation energy region ( 6 - 8 ev )
all the isomers show a first zone of moderate absorption up to 7 ev , which is not dependent on the particular geometry , and a final part where the strength of the absorption increases . as in previous papers @xcite
, we propose that at this energy range the high excitation energies can be interpreted for this system in terms of the contributions between transitions involving strongly hybridated @xmath14 electronic orbitals .
it is noticeable that this effect is less important for the iso2 structure , where , according to its high symmetry and kohn sham levels diagram , the @xmath15 hybridation is rather pronounced . the low energy response of these isomers up to 5.5 ev can be compared with the experimental results of the refs .
@xcite , @xcite , and @xcite for the measured spectra of medium - size silver clusters trapped in noble gas matrices at several temperatures .
figure [ p3 ] shows the experimental absorption cross sections of ag@xmath0 in a ne matrix at 6 k , and ar matrices at 10 and 28 k ( lower pannels ) , and the tddft spectrum for the obtained ag@xmath0 g - s structure ( upper pannel ) .
the estimated uncertainties of the relative cross sections in this kind of experiments use to be around 10% ( the uncertainties in the absolute cross sections are even larger ) .
the experimental absorption cross sections show a clear three peaks structure , where the relative strength of the peaks depend strongly on the temperature and the matrix surrounding the trapped cluster , but not their excitation energies .
the peaks arise at 3.2 , 3.7 and 4.4 ev , with a region of no absorption up to 5.5 ev .
the tddft spectrum , for the g - s isomer , shows a similar three peaks profile located at 3.6 , 4.2 and 4.6 ev . as we can appreciate in fig .
[ p3 ] , there exist a very good agreement between the calculated and the experimental peak positions if we just allow for a constant shift of around 0.2 - 0.4 ev .
this shift to the red of the experimental spectra can be justified by the additional effect of the nobel gas matrices to the photoabsorption response , which has been quantified by fedrigo _
et al . _
@xcite , and sieber _ et al . _
@xcite in 0.2 - 0.25 ev .
however , most of authors coincide in that value of the shift may not be appropriate because additional contributions could arise , such as compression effects of the cluster by the matrix , or matrix - induced polarization of the cluster charge density @xcite . on the other hand , previous authors suggest that the deviation in the experimental photoabsorption spectra of the small silver clusters showing several isolated peaks , instead of only one pronounced excitation detected in large - sized clusters @xcite , is due to the presence of several isomers in the experimental beams @xcite .
however , the present study reveal theoretical spectra for three different ag@xmath0 isomers where such isolated peaks are found . from these results , we can conclude that the presence of these distinct peaks in experimental spectra is not only due to the existence of several isomeric forms in the experimental samples since it seems to be an intrinsic optical property of this kind of aggregates .
other discrepancy sources in the spectrum may be due to additional factors : ( i ) the error introduced in the calculation by the necessarily approximated exchange and correlation potential , ( ii ) the expectable influence of the silver clusters coupling to the surrounding noble metal matrices , and ( iii ) the possible presence in the experimental sample of a mixture of various isomers , coinciding with other authors .
the calculated spectrum for this isomer provides the best matching with experiment , and this confirms the assignment of the ground state structure as predicted even by the total energies .
we then conclude that the calculated spectrum of the most stable isomer obtained provides a very accurate description of the experimental cross section and permits to conjecture with a high confidence that the isomer present most abundantly in the ag@xmath0 cluster beams has that structure .
this is reasonable , since this is indeed the calculated lowest energy isomer .
we have performed calculations of the optical absorption cross sections of three structural isomers of ag@xmath0 . for that purpose
we have first employed dft to optimize the geometries of those isomers . for each of those structures
tddft has been used to calculate the photoabsorption spectrum . in the calculations
, we used the generalized gradient approximation for the exchange and correlation potential , relativistic norm - conserving pseudopotentials , and the casida formalism to calculate the excitation spectrum . this approach yields spectra for the different isomers that are significantly different .
the spectrum corresponding to the most stable structure obtained matches well the experimental results , and we conclude that this is the isomer predominantly present in the laboratory cluster beams ; confirmation comes from the fact that this is the isomer with the lowest calculated energy . the efficiency of dft and tddft for the calculation of both ground state and spectroscopic features of molecules and clusters permits to use these theoretical methods , as we have shown here , as a complement to the experimental analysis , which in many occasions lacks some important information , such as the precise geometrical atomic arrangement of the probed systems .
the center for atomic - scale materials design is funded by the lundbeck foundation .
the authors wish to acknowledge additional support from the danish research agency through grant 26 - 04 - 0047 and the danish center for scientific computing through grant hdw-0107 - 07 .
j. i. m and e. m. f. wish also to acknowledge the interesting scientific discussions with professors j. a. alonso and l. c. balbs .
e. m. fernndez , m. b. torres and l. c. balbs , in _ recent advances in the theory of chemical and physical systems _ ; j. p. julien _ et al .
_ ( eds . )
_ progress in theoretical chemical and physics _ , 15 .
springer , netherlands p. 407
( 2006 ) .
s. fedrigo , w. harbich and j. butter , _ phys .
b _ * 47 * , 10706 ( 1993 ) ; s. fedrigo , w. harbich , j. belyaev and j. butter , _ chem .
_ * 211 * , 166 ( 1993 ) ; w. harbich , _ philos . mag .
b _ * 79 * , 1307 ( 1999 )
. x. gonze , j. m. beuken , r. caracas , f. detraux , m. fuchs , g. m. rignanese , l. sindic , m. verstraete , g. zerah , f. jollet , m. torrent , a. roy , m. mikami , ph .
ghosez , j. y. raty and d. c. allan , _ comput .
sci . _ * 25 * , 478 - 492 ( 2002 ) ; the abinit code is a common project of universit catholique de louvain , corning incorporated , and other contributors ( url _ http://www.abinit.org_ ) . | the optical absorption spectrum of the three most stable isomers of the ag@xmath0 system was calculated using the time - dependent density functional theory , with the generalized gradient approximation for the exchange and correlation potential , and a relativistic pseudopotential parametrization for the modelling of the ion
electron interaction .
the computational scheme is based on a real space code , where the photoabsorption spectrum is calculated by using the formalism developed by casida .
the significantly different spectra of the three isomers permit the identification of the ground - state configuration predominantly present in the laboratory beams in base to a comparison between the calculated photoabsorption spectrum of the most stable configuration of ag@xmath0 and the measured spectra of medium - size silver clusters trapped in noble gas ar and ne matrices at different temperatures .
this assignment is confirmed by the fact that this isomer has the lowest calculated energy . |
Colorado passed a medical aid in dying measure Tuesday that will allow adults suffering from terminal illness to take life-ending, doctor-prescribed sleeping medication.
The ballot initiative passed overwhelmingly, by a two-thirds, one-third split, according to unofficial returns. Supporters claimed victory an hour after polls closed in Colorado.
“Today is bittersweet for our family,” said Melissa Hollis Brenkert, who watched her sister die painfully from a brain tumor. “Passage of Prop 106 means that Coloradans will now have options when facing pain and suffering at the end of their lives.”
Opponents, though, vowed to keep fighting to protect the elderly and people with disabilities, who they said are the law’s targets. “We are deeply disappointed and concerned about Colorado legalizing doctor-assisted suicide,” said Jeff Hunt, vice president of public policy for Colorado Christian University. “The fight is not over.”
Proposition 106, the “End of Life Options” measure, models Oregon’s “Death with Dignity” law, passed 22 years ago. With 87 percent of votes counted, the initiative had 1,508,202 votes, or 64.5 percent, compared with 827,676 or 35.4 percent, against.
Two physicians would have to agree the person is mentally competent and has fewer than six months to live, and the person choosing to die would have to self-administer the dosage of secobarbital, historically used in low doses as a sleeping pill. People with dementia or Alzheimer’s would not be eligible for the prescription.
“My dad wanted this option for peace of mind in his dying days and, ultimately, for the opportunity of a gentle passing,” said Julie Selsberg, who worked on the campaign. “Now we know that Coloradans believe that offering the option of medical aid in dying is the kind, compassionate, safe and just thing to do.”
The measure was among the most emotionally charged initiatives on the state ballot. Colorado would join four other states that have followed Oregon with similar laws or court action — Washington, Vermont, Montana and California.
The “Yes on Colorado End-of-Life Options” campaign has raised $4.8 million, including from Compassion & Choices Action Network. The face of the campaign was Brittany Maynard, who chose to die under Oregon’s law in 2014 instead of letting an aggressive brain tumor continue to “torture her to death.” Her husband, Dan Diaz, has spent the last two years talking to lawmakers and working with Compassion & Choices to change law in other states. He and Brittany had to move to Oregon from California so she could die peacefully, he said.
Opponents said the proposal lacks safeguards — it does not require that a doctor is present at time of death, does not prevent “doctor shopping,” and does not prevent an heir from plotting the death of a relative to gain inheritance. The Archdiocese of Denver donated $1.1 million to the “No Assisted Suicide Campaign,” and said “human life is sacred at every stage and should be protected.”
Some advocates for the disabled community also were opposed, saying such a law could lead insurance companies to determine it is more cost-effective to provide medical aid in dying than lifelong medical care.
Even the language used on campaign signs and in television ads this fall has been controversial. People in favor of the initiative use the terms “dying with dignity” and “right to die,” but named their Colorado ballot measure the more neutral “end-of-life options. Opponents of the proposed law call it “physician-assisted suicide.”
The Secretary of State’s Office listed the measure as “medical aid in dying,” which is the term physicians are likely to use. ||||| Terminally ill people with six months or less left to live will be able to buy medicine to end their lives thanks to a vote Tuesday.
9NEWS is projecting that Proposition 106 will pass.
ELECTION RESULTS
The measure was modeled after Oregon’s “Death with Dignity” law that’s been in place for the last two decades. Five states in the U.S. have laws like this.
“This is a historic day for all Coloradans, and an especially tremendous victory for terminally ill adults who worry about horrific suffering in their final days,” Compassion & Choices Action Network President Barbara Coombs Lee said in a statement. “We are delighted the significant investment paid off and are proud to have lent the expertise and resources to empower the voters of Colorado. We congratulate Colorado for becoming the sixth state where more people have peace of mind at the end of life and fewer suffer unnecessarily.”
Compassion and Choices, a national group based in Denver, backed the measure. The opposition was primarily funded by Catholic organizations.
Copyright 2016 KUSA | – Proposition 106 has passed in Colorado, making the state the nation's sixth to legalize assisted suicide, reports 9NEWS. Adults who are terminally ill, with less than six months to live, and found to be mentally competent, can request life-ending medication—a high dose of secobarbital used in sleeping pills—from a doctor, reports the Denver Post; those with dementia or Alzheimer's aren't eligible. The measure passed with two-thirds support with 63% of votes counted, per the Post. Advocates called it a "tremendous victory," while "disappointed" critics promised that "the fight is not over." |
FILE -- In this Oct. 31, 2010 file photo, Holocaust survivor Samuel Willenberg poses for a picture at his studio, during an interview with the Associated Press in Tel Aviv, Israel. Willenberg, the last... (Associated Press)
JERUSALEM (AP) — Samuel Willenberg, the last survivor of Treblinka, the Nazi death camp in occupied Poland where 875,000 people were systematically murdered, has died in Israel at the age of 93.
Only 67 people are known to have survived the camp, fleeing in a revolt shortly before it was destroyed.
Treblinka holds a notorious place in history as perhaps the most vivid example of the "Final Solution," the Nazi plan to exterminate Europe's Jews. Unlike at other camps, where some Jews were assigned to forced labor before being killed, nearly all Jews brought to Treblinka were immediately gassed to death.
Only a select few — mostly young, strong men like Willenberg, who was 20 at the time— were spared from immediate death and assigned to maintenance work instead at the camp, located northeast of Warsaw.
On Aug. 2, 1943, a group of Jews stole some weapons, set fire to the camp and headed to the woods. Hundreds fled, but most were shot and killed by Nazi troops in the surrounding mine fields or captured by Polish villagers who returned them to Treblinka.
"The world cannot forget Treblinka," Willenberg told The Associated Press in a 2010 interview.
He described how he was shot in the leg as he climbed over bodies piled at the barbed wire fence and catapulted over. He kept running, ignoring dead friends in his path. He said his blue eyes and "non-Jewish" look allowed him to survive in the countryside before arriving in Warsaw and joining the Polish underground.
After the war Willenberg moved to Israel and became a surveyor for the Housing Ministry. Later in life, he took up sculpting to describe his experiences. His bronze statues depicted Jews standing on a train platform, a father removing his son's shoes before entering the gas chambers, a young girl having her head shaved, and prisoners removing bodies.
"I live two lives, one is here and now and the other is what happened there," Willenberg said. "It never leaves me. It stays in my head. It goes with me always."
His two sisters were killed at Treblinka. He described his survival as "chance, sheer chance."
The Nazis and their collaborators killed about 6 million Jews during the Holocaust. The death toll at Treblinka was second only to Auschwitz — a prison camp in southern Poland where more than a million people died in gas chambers or from starvation, disease and forced labor.
His daughter said he died on Friday. He is survived by a daughter and grandchildren. ||||| Media playback is unsupported on your device Media caption Treblinka survivor Samuel Willenberg recounts the Treblinka uprising in 2011
Samuel Willenberg, the last survivor of Nazi Germany's Treblinka death camp in Poland, has died in Israel aged 93.
Only one of 67 people known to have survived the camp, he escaped by clambering over bodies piled up by a fence as the Nazis shot prisoners during a mass break-out.
In 2013, he returned to the site to mark 70 years since his escape.
About 870,000 people died in the gas chambers at Treblinka - more than anywhere else except Auschwitz.
Mr Willenberg urged the world never to forget Treblinka.
Image copyright AP Image caption Mr Willenberg escaped from Treblinka by clambering over the bodies of his dead friends
Image copyright Getty Images Image caption Mr Willenberg regularly returned to Treblinka to guide youth tour groups
In October 1942, aged 19, he was among 6,000 Jews from the Opatow ghetto who arrived by train at the camp.
They were told they were at a transit camp and had to undress and shower before being sent onward. In reality, the shower rooms were gas chambers.
But because he was a bricklayer he was assigned to manual labour duties and escaped an early death. His job was to sort through the belongings of the people sent to the gas chambers.
After the war Mr Willenberg - whose two sisters were killed at the camp - moved to Israel and became a surveyor.
"I live two lives, one is here and now and the other is what happened there,'' he said. `"It never leaves me. It stays in my head. It goes with me always."
Most of Treblinka's guards were never prosecuted for their part in the crimes there.
Treblinka's commandant, Franz Stangl, was sentenced to life imprisonment in October 1970 following his trial in the west German city of Duesseldorf.
Today nothing remains of the extermination camp apart from the ashes of the mostly Jewish men, women and children murdered there. ||||| These crawls are part of an effort to archive pages as they are created and archive the pages that they refer to. That way, as the pages that are referenced are changed or taken from the web, a link to the version that was live when the page was written will be preserved.Then the Internet Archive hopes that references to these archived pages will be put in place of a link that would be otherwise be broken, or a companion link to allow people to see what was originally intended by a page's authors.The goal is to fix all broken links on the web . Crawls of supported "No More 404" sites. | – The last survivor of the Nazi death camp Treblinka—which systematically murdered 875,000 people during World War II, a gruesome toll eclipsed only by Auschwitz—died Friday at his home in Israel at the age of 93. Samuel Willenberg, born in Poland in 1923, was a physically fit bricklayer at the time of his arrival at Treblinka and was sent to work instead of immediately gassed like most prisoners, reports the BBC. He said it was "chance, sheer chance" that on Aug. 2, 1943, shortly before the camp was destroyed, he managed to escape during a mass revolt, reports the AP. The then-20-year-old had to climb over bodies to mount a fence and then keep running even as friends were shot alongside him. He was one of just 67 people known to have survived Treblinka. Willenberg credits his blue eyes and "non-Jewish" looks with his ability to evade capture in the following weeks as he made his way back to Poland and joined the uprising there (his mother was an Orthodox Christian but converted to Judaism, notes Haaretz). Both his sisters were killed at the camp, and he's survived by a daughter and grandchildren. Eventually Willenberg settled down in Israel and worked as a surveyor, and he told the AP in 2010: "I live two lives, one is here and now and the other is what happened there. It never leaves me. It stays in my head. It goes with me always." He regularly visited the area to guide youth tour groups and said, "The world cannot forget Treblinka." (The Nazis tried to destroy evidence of Treblinka in 1943, but archaeologists uncovered some of its secrets.) |
This beloved novel, a #1 New York Times bestseller, will soon be a major motion picture starring Danielle Macdonald and Jennifer Aniston.
For fans of John Green and Rainbow Rowell comes this powerful novel with the most fearless heroine—self-proclaimed fat girl Willowdean Dickson—from Julie Murphy, the acclaimed author of Side Effects May Vary.
With starry Texas nights, red candy suckers, Dolly Parton songs, and a wildly unforgettable heroine—Dumplin’ is guaranteed to steal your heart.
Dubbed “Dumplin’” by her former beauty queen mom, Willowdean has always been at home in her own skin. Her thoughts on having the ultimate bikini body? Put a bikini on your body. With her all-American-beauty best friend, Ellen, by her side, things have always worked . . . until Will takes a job at Harpy’s, the local fast-food joint. There she meets Private School Bo, a hot former jock. Will isn’t surprised to find herself attracted to Bo. But she is surprised when he seems to like her back.
Instead of finding new heights of self-assurance in her relationship with Bo, Will starts to doubt herself. So she sets out to take back her confidence by doing the most horrifying thing she can imagine: entering the Miss Teen Blue Bonnet Pageant—along with several other unlikely candidates—to show the world that she deserves to be up there as much as any twiggy girl does.
Along the way, she’ll shock the hell out of Clover City—and maybe herself most of all. ||||| Published on Nov 14, 2018
Directed by Anne Fletcher, DUMPLIN’ follows an outspoken plus-sized teenage girl named Willowdean (Danielle Macdonald), who’s known as Will to her friends and Dumplin’ to her mother (Jennifer Aniston), a former beauty queen who now runs the local Miss Teen Blue Bonnet pageant. In her small Texas town, Will confidently ignores comments about her weight and listens to Dolly Parton songs obsessively. But when she decides to enter her mother’s pageant in protest, her bold move encourages other contestants to follow in her footsteps, redefining the town’s traditions in the process.
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Dumplin' | Official Trailer [HD] | Netflix
http://youtube.com/netflix ||||| Published on Nov 30, 2018
Dolly Parton explains how she got involved with Jennifer Aniston to do the soundtrack for Dumplin' and reveals why her husband got so excited about her making music for the film.
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Dolly Parton's Husband Wants a Threesome with Jennifer Aniston
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#JimmyFallon ||||| CLOSE Dolly Parton‘s husband wants his wife and Jennifer Aniston to be more than creative collaborators. Time
Jennifer Aniston was one of the viewers blown away when Dolly Parton talked about a threesome on "The Tonight Show Starring Jimmy Fallon." (Photo: Getty Images)
Only Dolly Parton could go on a national talk show and talk about a threesome involving Jennifer Aniston.
Yes, that happened.
Parton, 72, blew up "The Tonight Show Starring Jimmy Fallon" Monday night as she discussed writing the music for Aniston's Netflix film "Dumplin' " (streaming Friday) and how excited her husband of 52 years, Carl Thomas Dean, was about the concept.
“I love her to death,” Parton said of Aniston, 49, who stars in and produced the movie. “My husband is crazy about her, and he was more excited that I was going to do a movie with her than he was that I got the chance to write all this music. I think he fantasizes, like, a threesome.”
More: Jennifer Aniston talks 'Dumplin',' real-life mother drama and telling off a terrible 2018
Then Parton made a clever quip (seen in the NSFW clip below) about her husband being too old for the situation, causing Fallon to collapse in surprised laughter.
Aniston, too, was pretty stunned by Parton's comments.
“My mouth just dropped,” Aniston tells USA TODAY. “And then I laughed my (butt) off. That’s Dolly. “
Fully composed by Tuesday, Aniston says the comments were just Dolly being her classic, outrageous self, which is why the colorful country music legend looms so large in "Dumplin'," the story of a plus-size teenager (Danielle Macdonald) who enters a pageant organized by her former beauty queen mother (Aniston).
News & views: It's time to leave Jennifer Aniston alone
Also: Hear Jennifer Aniston's Southern accent as a former pageant queen in Netflix's 'Dumplin' ''
Here's the hilarious NSFW video clip:
“It was hilarious, I think it’s flattering. And that’s Dolly's sense of humor,” says Aniston. “No one in the world can get away with saying anything like that about their partner on live television, except Dolly. I mean, that is a quote."
While Aniston and Parton have laughed about the line together ("It's been discussed all day, shall we say"), they haven’t exactly set aside time on Google Calendar for any nocturnal activities.
“That was just talk-show fodder,” says Aniston.
Jennifer Aniston is headed to Netflix, starring as a former beauty queen in "Dumplin'." (Photo: Bob Mahoney, Netflix)
What is real is the friendship between Aniston and Parton.
Besides an epic seven-hour meal shared at Aniston’s house, the two are pen pals. Dolly doesn’t text. She writes letters.
“They’re beautiful, all on stationary with this Dolly (letterhead). She’s so old-fashioned,” says Aniston. “I give her a phone call back after she writes. I like talking to her on the phone.”
Read or Share this story: https://www.usatoday.com/story/life/people/2018/12/04/jennifer-aniston-responds-dolly-partons-outrageous-threesome-joke/2209346002/ | – Dolly Parton's husband was pretty excited when he found out his wife of 52 years was going to be working with Jennifer Aniston on Dumplin', an upcoming Netflix film based on the best-selling book. "My husband is crazy about her," Parton explained on Monday while promoting the movie on the Tonight Show. "I think he kind of fantasizes, like, a threesome." (See the whole clip in our gallery or here for the rest of her NSFW comments, which sent Jimmy Fallon to the ground in hysterics.) Now Aniston has responded. "My mouth just dropped. And then I laughed my (butt) off. That’s Dolly," she tells USA Today. "It was hilarious, I think it's flattering. And that's Dolly's sense of humor. No one in the world can get away with saying anything like that about their partner on live television, except Dolly." (Aniston recently opened up about "reckless" tabloid speculation.) |
the prevention of perinatal transmission of hiv is one of the most successful public health interventions of the last few decades .
the use of maternal combination antiretroviral therapy ( cart ) , when combined with infant postnatal prophylaxis , has reduced transmission rates to less than 1% in developed countries [ 1 , 2 ] .
this is a remarkable achievement , but concerns remain regarding toxicity in these infants after exposure to multiple antiretrovirals ( arv ) in utero , during delivery , and in early infancy .
spontaneous preterm delivery and low birth weight have been associated with hiv infection during pregnancy .
although not a uniform finding across studies , the use of protease inhibitors ( pi ) during pregnancy may increase the incidence of preterm delivery [ 46 ] .
mitochondrial and nuclear genotoxicity are associated with in utero exposure to nucleoside reverse transcriptase inhibitors ( nrti ) [ 7 , 8 ] .
in addition , laboratory adverse events ( ae ) have been described in arv - exposed infants , including hematologic cytopenias and disruption of liver function .
transient macrocytic anemia was the most common side effect in infants exposed to zidovudine ( zdv ) pre- and postnatally in the landmark pactg 076 study [ 11 , 12 ] , and several reports describe profound neonatal anemia after arv exposure in utero [ 13 , 14 ] .
other studies have confirmed the link between arv exposure and neonatal neutropenia , lymphopenia , and thrombocytopenia [ 1520 ] .
liver dysfunction is described less frequently , although several studies have demonstrated elevated neonatal aspartate aminotransferase ( ast ) , alanine aminotransferase ( alt ) , and bilirubin after exposure to perinatal arv [ 2125 ] .
increasing complexity of maternal cart correlates with an increased risk for hematologic and hepatic ae [ 15 , 17 , 21 , 22 , 2628 ] . as new arv and
more complex cart regimens are administered for the prevention of perinatal hiv transmission , it is important to identify the toxicities associated with both established and novel regimens in order to inform best choices [ 2931 ] .
prior studies have compared infant ae after exposure to different classes of arv , for example , nonnucleoside reverse transcriptase inhibitor- ( nnrti- ) based cart and pi - based cart [ 22 , 27 ] . in this study , we examine infant ae after exposure to different maternal drugs within arv classes .
this study was approved by the colorado multiple institutional review board and exempted from informed consent .
this was a retrospective chart review of 190 pregnancies complicated by hiv infection that were managed by the children 's hospital immunodeficiency program ( chip ) in denver .
chip is the reference center for the care of hiv - infected pregnant women in colorado and neighboring states .
data were abstracted for all pregnancies from 1997 to 2009 that resulted in a live infant birth .
maternal data collected included demographics , arv use , illicit drug use , mode of delivery , hematologic and hepatic laboratory values , cd4 count , and viral load .
undetectable viral load was defined as < 400 copies / ml , as this was the lower limit of detection for the earliest data .
duration of maternal viremia during pregnancy was defined as the number of days from the estimated conception date until either the date of the first undetectable viral load measurement after which all subsequent viral load measurements were undetectable or , if there was no sustained viral suppression , the number of days between the estimated conception date and the date of infant birth .
infant data collected included gestational age ( preterm defined as < 37 weeks ) , birth weight ( small for gestational age ( sga ) defined as < 3rd percentile of expected weight for gestational age ) , postnatal arv prophylaxis , laboratory values ( hemoglobin , neutrophil count , platelets , ast , alt , and total bilirubin ) , and hospitalizations or illnesses .
infant complete blood count and liver function panel was assessed at birth ( age 07 days ) and at 4 weeks ( 2 weeks ) .
laboratory toxicities were graded using the division of aids table for grading the severity of adult and pediatric adverse events .
if the medical record did not specify an upper limit of normal for ast and alt , the limits imposed were 60
iu / l and 65 iu / l for ast and alt , respectively , as these are the limits used by the children 's hospital colorado laboratory .
infant infection status was monitored using hiv rna and/or dna pcr at birth , 2 weeks , 4 weeks , 6 weeks , and 4 months of age and hiv antibody testing starting at 12 months of age and repeated every 36 months until seroreversion was demonstrated .
pregnant women received a clinician - prescribed antenatal arv regimen that consisted of cart ( 3 arv from 2 arv classes ) in most cases ; modifications during the pregnancy were based on viral genotype , virologic response , safety , and tolerability , as previously described [ 3335 ] .
pi serum levels were routinely monitored and doses adjusted to achieve a trough above the 25th percentile for nonpregnant adults .
infant arv exposure was assigned based on the maternal arv received for 28 days during the 35 days immediately prior to delivery , thereby setting a minimum period of in utero drug exposure occurring near the time of infant laboratory assessment .
other maternal arv received before the 35 days immediately prior to delivery was not accounted for in the analysis .
most infants were prescribed postnatal prophylaxis consisting of six weeks of zdv . in some infants ,
zdv was replaced by stavudine ( d4 t ) due to anemia , neutropenia , or both . in situations where the risk of perinatal transmission was increased ,
infants received two- or three - drug arv . a detailed description of the infant postnatal prophylaxis prescribed and associated adverse events has been previously reported .
the analysis included infants with at least one laboratory value at either birth or 4 weeks .
the statistical analyses require that all observations ( infants ) are independent of one another or the results may be biased .
given that twins have identical exposure in utero and in order not to underestimate associations between ae and arv , the twin with the lower grade toxicity was excluded from each pair .
maternal and infant characteristics were compared using t - tests , chi - square tests , and fisher 's exact tests , as appropriate . because most infants were exposed to an antenatal arv regimen containing two nrti and a pi , ae
were compared between infants exposed to different nrti and between infants exposed to different pi . the number of infants exposed to nevirapine ( n = 10 ) was too small for comparison .
logistic regression was used to model grade 1 laboratory ae and grade 3 laboratory ae ( yes / no ) as a function of maternal arv received for 28 days during the 35 days immediately prior to delivery and any confounding variable that changed the odds ratio ( or , 95% confidence interval ) by > 20% . confounding variables used in the multivariate analyses include preterm birth , infant exposure to zdv monoprophylaxis versus combination prophylaxis , mechanism of delivery , maternal race and ethnicity , maternal illicit drug use , and duration of maternal viremia during the pregnancy .
one hundred and sixty - five mothers were managed at chip for 190 pregnancies , resulting in 196 live births . of these ,
163 infants ( 5 twins ) had at least one laboratory value available for analysis .
the analysis cohort consisted of 158 mother / infant pairs after excluding one infant from each twin pair .
severe maternal immune suppression was rare ; only 7% of women had a cd4 count < 200 cells / mm in early pregnancy .
one hundred twenty - seven women ( 80% ) received cart for at least 28 days prior to delivery .
pi - based cart was received by 77% of women , including lopinavir with ritonavir ( lpv / r , 37% ) , nelfinavir ( nfv , 26% ) , atazanavir ( atv , 10% , including 2% without ritonavir ) , and saquinavir ( 4% ) .
the majority of women received zdv ( 63% ) , but 13% , 9.5% , and 4% received d4 t , tenofovir ( tdf ) , and abacavir ( abc ) , respectively .
there were few differences in maternal and infant characteristics between the two largest treatment groups , lpv / r versus nfv ( supplementary table 1 in the supplementary material available online at http://dx.doi.org/10.1155/2016/9848041 ) .
laboratory ae in the first four weeks of life were common , with three quarters of infants having an ae ( any grade ) at either birth or 4 weeks .
the frequency of an ae grade 3 in any laboratory category was 12% at birth and 16% at 4 weeks .
neutropenia was most common , with 25% and 42% of infants having any grade ae , and 13% and 9% having grade 3 ae , at birth and 4 weeks , respectively ( figure 1 ) .
anemia was the next most common , with 9% and 42% of infants having any grade ae , but only 1% and 0% having grade 3 ae , at birth and 4 weeks , respectively .
the 26 ( 17% ) infants born preterm were more likely than term infants to develop an ae of any grade ( 93% versus 71% , p = 0.03 ) or grade 3 ( 46% versus 17% , p = 0.003 ) at either birth or 4 weeks .
no infants suffered a serious bacterial infection or a bleeding disorder as a complication of neutropenia or thrombocytopenia , and no infants developed liver failure as a result of hepatic inflammation .
rates of infant laboratory ae relative to antenatal exposure to maternal arv were compared in a multivariate analysis . at birth ,
infants exposed to maternal nfv compared to lpv / r had a higher rate of anemia ( or 7.4 ( 95% ci 1.439.0 ) , p = 0.02 ) , neutropenia ( or 10.6 ( 95% ci 1.766.4 ) , p = 0.01 ) , and any ae ( or 5.3 ( 95% ci 1.914.9 ) , p = 0.002 ) ( figure 2 ) .
this association was maintained when limited to infants exposed to the same maternal nrti backbone ( zdv and lamivudine ) ( table 3 ) .
the difference was primarily the result of grade 1 ae ; rates of grade 3 ae remained relatively low in both groups ( 9% versus 14% of lpv / r - exposed versus nfv - exposed infants , resp . ;
exposure to maternal atv was also associated with a higher rate of any laboratory ae compared to lpv / r ( or 4.2 ( 95% ci 1.017.5 ) , p = 0.046 ) with the difference primarily due to higher rates of neutropenia ( or 18.3 ( 95% ci 1.2267.8 ) , p = 0.03 ) ( figure 2 ) . at 4 weeks
, there were no longer significant differences in ae between infants exposed to different pi ( table 4 ) .
additional maternal and infant characteristics were examined to determine whether variables not included in the multivariate analysis might contribute to differences in infant ae at birth for the nfv and lpv / r groups , which had a sample size large enough for analysis ( supplementary table 1 ) .
the mean estimated duration of maternal viremia was longer in the nfv - exposed group than in the lpv / r - exposed group ( 172 versus 125 days , p = 0.05 ) .
however , the association of infant ae with nfv versus lpv / r exposure remained significant when duration of maternal viremia was included as a covariate in the multivariate analysis ( or 7.9 ( 95% ci 2.426.2 ) , p = 0.0007 ) .
in addition , a univariate analysis demonstrated that the duration of maternal viremia did not correlate with the frequency of infant ae ( or 1.0 ( 95% ci 0.991.0 ) , p = 0.57 ) .
nfv was prescribed in an earlier time period ( 19972007 ) ; lpv / r was first prescribed in 2003 and surpassed nfv as the most commonly used pi at our center by 2004 .
other variables did not differ including the duration of antenatal exposure to nfv or lpv / r or the proportion of women who received the pi prior to conception ( supplementary table 1 ) .
most women were treated with zdv , but a substantial number received abc , d4 t , or tdf ; therefore , rates of infant ae were compared between these groups .
there were no significant differences at birth in rates of anemia , neutropenia , thrombocytopenia , or liver enzyme elevation between infants exposed to maternal zdv compared with abc , d4 t , or tdf ( supplementary table 2 ) .
rates of preterm birth and sga for infants exposed to different maternal pi were compared in a univariate analysis .
no significant differences were found in rates of preterm birth ( 5/16 ( 31% ) , 9/58 ( 16% ) , and 5/37 ( 14% ) , p = 0.26 ) or sga ( 2/16 ( 13% ) , 7/56 ( 13% ) , and 4/35 ( 11% ) , p > 0.99 ) between infants exposed to atv , lpv / r , and nfv , respectively , although the small sample size limited the power to detect a difference .
low - grade laboratory ae were common at birth and 4 weeks in the cart - exposed infants , but grade
anemia and neutropenia made up the majority of ae , and neutropenia comprised nearly all grade 3 ae .
our results are in agreement with those of previous studies , which showed frequent , but low - grade , hematologic abnormalities among arv - exposed infants .
pacheco et al . reported significantly decreased infant hemoglobin and neutrophil values , and mussi - pinhata et al .
described anemia at hospital discharge in 24% of arv - exposed infants , although in both studies nearly all ae were of grade 1 or 2 [ 17 , 23 ] .
described grade 3 anemia or neutropenia in less than 10% of arv - exposed infants in the first six weeks of life .
four infants in our study required a blood transfusion due to anemia , all of whom were born at 32 weeks of gestation .
preterm infants are likely to require blood transfusion even when unexposed to arv , with about 80% of us infants with birth weight < 1500 grams requiring at least one transfusion .
none of the infants born 37 weeks of gestation in this study developed clinically significant ae .
although the majority of ae in these hiv- and arv - exposed infants were of low grade , the mechanism underlying the ae is not fully understood and the long term effects of these early toxicities are unknown .
we found increased infant laboratory ae at birth associated with exposure to maternal nfv and atv compared with lpv / r .
the difference was observed even when the analysis was restricted to mother / infant pairs with the same nrti background . at 4 weeks
, no difference was detectable between these groups , suggesting that the effect is either transient or masked by the effect of postnatal arv .
the association of laboratory ae with particular antenatal arv within the pi class is reported here for the first time . of note , bellon cano et al .
described increased anemia , thrombocytopenia , and liver enzyme elevation after exposure to pi - based cart ( of which most regimens contained nfv ) compared with two or three nrti or nnrti - based cart .
fetal hematopoiesis may be more susceptible to the effects of pi , as it occurs mainly in the liver and peripheral lymphoid tissues .
pi cross the placenta to some degree ; albeit due to their large molecular weight and high protein binding capacity , they do not reach therapeutic levels in cord blood .
cord blood to maternal plasma ratios for atv , nfv , and lpv range between 0.130.24 , 0.160.22 , and 00.49 , respectively .
amniotic fluid to maternal plasma ratios have been described for nfv ( 0.140.44 ) and lpv ( 0.08 ) [ 39 , 40 ] .
although serum levels for some pi may be low during pregnancy , in this cohort plasma pi levels were routinely monitored during pregnancy and doses adjusted to achieve a trough above the 25th percentile for nonpregnant adults .
therefore , the difference in infant ae is not likely attributable to differences in maternal pi drug levels . because this was a retrospective study , it is possible that the maternal receipt of various pi could be a marker for another confounding variable that contributed to infant ae .
examination for potential confounding variables between the nfv and lpv / r groups identified that on average women receiving nfv had a longer duration of viremia than women receiving lpv / r .
however , viremia did not correlate with increased risk of infant ae , and inclusion of maternal viremia as a covariate did not alter the relationship of infant ae with exposure to nfv versus lpv / r .
owing to its limited antiviral activity , nfv is no longer recommended for use in pregnant women .
however , there may be rare clinical scenarios in which nfv use might be considered , such as for patients who can not tolerate or have resistance to other arv that are included in the preferred and alternative regimens for pregnancy .
we found that atv exposure was associated with a higher incidence of neutropenia compared with lpv / r .
however , infants in this study who were exposed to atv did not show increased rates of liver enzyme elevation or hyperbilirubinemia compared with infants exposed to other pi .
. who described a series of twenty - three infants exposed in utero to atv , nine of whom developed elevated serum bilirubin concentrations at birth and five required phototherapy in the first three days of life .
our data need to be further confirmed in larger studies , because they were derived from only sixteen infants exposed to atv , resulting in an or with relatively large confidence intervals .
although zdv is commonly associated with hematologic side effects in exposed infants , we did not find more hematologic ae at birth among infants exposed to antenatal zdv compared with those exposed to abc , d4 t , or tdf , but the number of infants exposed to the alternative nrti was small .
few studies compare infant toxicities after in utero exposure to different nrti , although vivanti et al . demonstrated decreased genotoxicity in cord blood of infants exposed in utero to tdf versus zdv .
preterm birth has been described previously in association with in utero exposure to pi [ 46 ] .
we did not find an association of preterm birth or sga with lpv / r , nfv , or atv , but the power to detect differences was limited by our small sample size . in addition , data describing other risk factors for preterm birth or sga were not available in our data set .
perry et al . recently showed no differences in preterm birth or birth weight in infants exposed to maternal lpv / r versus atv ; this study did not report infant laboratory outcomes .
mothers and infants were not randomized to various arv in our study ; they received a regimen that was clinically appropriate based on severity of disease , tolerability , viral response to therapy , and risk of perinatal hiv transmission .
although two groups of infants for whom we found a significant difference in ae ( those exposed to lpv / r and nfv ) were cared for in different time periods , we also found differences between the effect of lpv / r and atv exposure , whose use was roughly contemporaneous . despite these limitations , this study permits comparison of infant ae within classes of arv , whereas most similar studies have compared between classes of arv .
in summary , when used in maternal cart for prevention of perinatal transmission of hiv , nfv and atv were associated with increased infant ae compared to lpv / r . as atv use in pregnant women
is increasing , larger , preferably randomized studies of infants exposed to lpv / r versus atv / r are needed to evaluate laboratory ae and to clarify any association with prematurity .
investigations into the safest maternal arv regimens and timing of arv initiation are important for optimizing outcomes for hiv - exposed infants , especially those with higher risk of hematologic and hepatic toxicity , such as preterm infants and infants in resource - limited settings . | combination antiretroviral therapy ( cart ) is successfully used for prevention of perinatal hiv transmission . to investigate safety
, we compared adverse events ( ae ) among infants exposed to different maternal cart regimens .
we reviewed 158 hiv - uninfected infants born between 1997 and 2009 , using logistic regression to model grade 1 ae and grade 3 ae as a function of maternal cart and confounding variables ( preterm , c - section , illicit drug use , race , ethnicity , infant antiretrovirals , and maternal viremia ) .
frequently used cart regimens included zidovudine ( 63% ) , lamivudine ( 80% ) , ritonavir - boosted lopinavir ( 37% ) , nelfinavir ( 26% ) , and atazanavir ( 10% ) . at birth ,
anemia occurred in 13/140 infants ( 9% ) , neutropenia in 27/107 ( 25% ) , thrombocytopenia in 5/133 ( 4% ) , and liver enzyme elevation in 21/130 ( 16% ) .
corresponding rates of ae at 4 weeks were 59/141 ( 42% ) , 54/130 ( 42% ) , 3/137 ( 2% ) , and 3/104 ( 3% ) , respectively .
serious ae ( grade 3 ) exceeded 2% only for neutropenia ( 13% at birth ; 9% at 4 weeks ) . compared with infants exposed to maternal lopinavir / ritonavir , infants exposed to nelfinavir and atazanavir had a 5-fold and 4-fold higher incidence of ae at birth , respectively . in conclusion , hematologic and hepatic
ae were frequent , but rarely serious .
in this predominantly protease inhibitor - treated population , lopinavir / ritonavir was associated with the lowest rate of infant ae . |
during liver surgery , the inflow occlusion maneuver to prevent blood loss as well as the liver manipulation itself have been shown to induce a cascade of molecular events , referred to as ischemia - reperfusion injury ( iri ) .
iri leads to the activation of kupffer cells ( kcs ) , the release of reactive oxygen species ( ros ) and proinflammatory cytokines , microcirculatory disturbances , and eventually liver dysfunction and failure [ 110 ] .
pharmacological preconditioning has been shown to be effective via mechanisms including , but not limited to , the direct neutralization of ros , upregulation of anti - inflammatory , and downregulation of proinflammatory signaling pathways [ 1127 ] . during iri , intestinal endotoxins ( lps ) leak through the altered gut membrane into the portal circulation and enhance the phagocytosis in hepatic kcs [ 2835 ] .
this interrelation between intestinal lps and hepatic kcs makes the gastrointestinal tract an attractive target for the pharmacological preconditioning strategies against hepatic iri .
we hypothesized that an oral pharmacological preconditioning supplement , tailored not only to exert direct ros - scavenging activity but also to stabilize the gut epithelium during iri , would tackle the warm hepatic iri in a porcine model . to the best of our knowledge
, this work is the first report of an oral pharmacological preconditioning against hepatic iri in a larger animal model .
german landrace pigs ( 32.3 0.9 kg ) were given access to standard laboratory chow ( ssniff r / m - h , ssniff spezialditen , soest , germany ) and tap water ad libitum before experiments .
all experimental procedures were reviewed and approved by the responsible authority ( regierungsprsidium karlsruhe , baden - wrttemberg , germany ) according to the animal welfare legislation ( 8 abs .
i s. 1206 ) ) and were performed according to institutional guidelines at the ruprecht - karls university of heidelberg .
after premedication with azaperone ( stresnil , janssen - cilag pharma , wien , austria , 1 - 2 mg / kg , i.m . ) and midazolamhydrochloride ( dormicum 15 mg/3 ml , roche , grenzach - wyhlen , germany , 0.50.7 mg / kg , i.m . )
, anesthesia was induced with esketaminhydrochloride ( ketanest s 25 mg / ml , parke - davis , berlin , germany , 10 mg / kg i.v . ) and midazolam hydrochloride ( 11.4 mg / kg i.v . ) .
after endotracheal intubation , animals were ventilated with a mixture of 1.52.0 l / min oxygen , 0.51.0 l / min air , and 0.75%1.5% isoflurane ( isofluran - baxter , baxter , unterschleiheim , germany , semiopen ventilation ) . for analgesia , piritramide ( dipidolor ,
janssen - cilag , neuss , germany , 3.75 mg / h intravenously ) was administered .
body temperature was maintained using warming blankets ( warmtouch , maleinckrodt medical gmbh , hennet / sieg , germany ) and monitored by continuous rectal temperature probes .
systemic hemodynamic parameters , including mean arterial pressure ( map ) and central venous pressure ( cvp ) , were measured continuously ( stetham transducer , hellige monitoring , freiburg , germany ) by indwelling polypropylene catheters ( braun , melsungen , germany ) in the common carotid artery and internal jugular vein , respectively . heart rate ( hr ) was monitored by body surface electrocardiogram recordings .
experimental groups were given a preconditioning oral nutritional supplement ( pons , 70 g per serving , fresenius kabi , germany ) containing glutamine , green tea extract ( the resource , method of extraction , and composition of green tea extract has been published elsewhere ) , vitamin c , vitamin e , beta carotene , selenium , zinc , and carbohydrates ( 1 sachet = 70 g ) ( table 1 ) dissolved in 250 ml tap water 24 hrs ( p.o . ) and 12 hrs ( p.o . ) before the operation .
the animals were then fasted overnight . on the day of operation and after performing a midline laparotomy , a third dose of pons was applied via a jejunostomy tube . the portal vein and common hepatic artery were then mobilized and encircled by elastic bands .
two hrs after the administration of the third dose of pons , the portal vein and the common hepatic artery were closed with yasargil clamps ( aesculap , tbingen , germany ) for 40 min to induce warm ischemia .
serial blood samples were drawn and spun at 0.5 , 3 , 6 , and 8 hrs after reperfusion and serum samples were kept at 20c for the analysis of transaminases ( aspartate aminotransferase ( ast ) and alanine aminotransferase ( alt ) ) serum concentrations with standard enzymatic methods .
the changes in bile production during each time interval were documented and the amount of the newly produced bile was plotted at the end of each time interval to assess the bile flow rate over time .
liver tissue was taken 8 hrs after reperfusion for histology ( hematoxylin and eosin ( h&e ) staining ) and immunohistochemistry ( tnf- , myeloperoxidase , cleaved caspase-3 ) .
hemodynamic parameters ( hr , map , cvp , pvf , haf ) were continuously monitored throughout the experiments ; ultrasonic probes ( transsonic system inc , new york , ny , usa ) were used for the measurement of portal venous flow ( pvf ) and hepatic arterial flow ( haf ) .
the experimental design is outlined in figure 1 . after the completion of experimental procedures 8 hrs after reperfusion
, animals were sacrificed in deep anesthesia through the intravenous application of a high dose of potassium chloride .
liver samples were fixed by perfusion with 5% paraformaldehyde in krebs - henseleit bicarbonate buffer ( 118 mmol / l nacl , 25 mmol / l nahco3 , 1.2 mmol / l kh2po4 , 1.2 mmol / l mgso4 , 4.7 mmol / l kcl , and 1.3
mmol / l cacl2 ) at ph 7.6 , embedded in paraffin , and processed for light microscopy ( h&e ) 8 hrs after warm ischemia . in order to assess the histomorphological changes , 40 areas of 0.15 mm
were evaluated per slide using a point - counting method as described previously : grade 0 , minimal or no evidence of injury ; grade 1 , mild injury , including cytoplasmic vacuolation and focal nuclear pyknosis ; grade 2 , moderate to severe injury with extensive nuclear pyknosis , cytoplasmic hypereosinophilia , and loss of intercellular borders ; grade 3 , severe necrosis with disintegration of hepatic cords , hemorrhage , and neutrophil infiltration . to describe leukocyte infiltration into the hepatic tissue , a scale from 1 to 4
was used : grade 1 , < 10 leukocytes / field ( focal infiltration ) ; grade 2 , 1020 ( mild infiltration ) ; grade 3 , 2150 ; grade 4 , > 50 leukocytes / field .
paraffin sections from liver tissue obtained 8 hrs after reperfusion were deparaffinized in xylene and rehydrated with graded ethanol .
antigen retrieval was performed via microwave pretreatment in edta buffer ( ph 9.0 ) three times for 5 min . the specimens were then cooled and treated with 30% hydrogen peroxidase ( h2o2 ) in phosphate - buffered saline ( pbs)final h2o2 concentration : 1%to block endogenous peroxidases .
sections were incubated with rabbit polyclonal anti - mouse tumor necrosis factor - alpha ( tnf- ) antibody ( biosource europe , nivelles , belgium ) at the dilution of 1 : 500 , and rabbit polyclonal anti - cleaved caspase-3 antibody ( dcs , hamburg , germany ) at a 1 : 200 dilution . after incubation ,
secondary biotinylated polyclonal rabbit anti - mouse immunoglobulin ( dako , hamburg , germany ) was applied at a dilution of 1 : 200 for 1 hr followed by streptavidin - biotin complex . for myeloperoxidase ( mpo )
immunohistochemistry analysis , the sections were pretreated with proteinase k ( 1 : 40 dilution ) and then blocked with bovine serum albumin .
they were then incubated with the primary antibody , a polyclonal rabbit anti - mpo antibody ( dako , carpinteria , ca , usa ) at a dilution of 1 : 200 , for 60 min at room temperature .
a biotinylated swine anti - rabbit antibody ( diluted 1 : 300 ) was used as the secondary antibody .
positive cells for immunohistochemistry were counted in 10 microscopic fields per slide and slides were evaluated with a semiquantitative technique , relating the score of 0 to 4 points to the fraction of stained cells : scale 0 , 0% cells ; 1 , < 5% cells ; 2 , 5%20% cells ; 3 , > 20%40% cells ; 4 , > 40% positive cells as described elsewhere .
mean values sem were compared using one - way anova with the students - newman - keuls post hoc test for the analysis of differences in hemodynamic values , vascular flow measurements , bile production , and transaminases .
differences in histological grading of injury as well as in immunohistochemical staining were tested by the mann - whitney rank sum test .
p < 0.05 was selected prior to the investigation as the criterion for significance of differences between groups .
hematocrit , body weight , and temperature were not different between control and pons groups ( n = 6 in each group ) ( table 2 ) .
continuous postperfusion monitoring of the hemodynamic parameters ( hr , map , cvp , pvf , haf ) also showed no significant differences between the two groups ( table 2 ) .
while serum alt increased in controls after warm ischemia / reperfusion to the liver , pons prevented this effect ; the difference between the two groups started to be significant 6 hours after reperfusion ( 49 3 u / l in controls versus 35 3 u / l in pons ; p = 0.01 ) .
this difference continued to exist until the end of experiments , 8 hrs after perfusion ( 50 3 u / l in controls versus 33 4 u / l in pons ; p = 0.02 ) .
the difference between the groups was significant 8 hrs after reperfusion ( 140 52
u / l in controls versus 46 7 u / l in pons ; p = 0.01 ) ( figure 2 ) .
there was significantly more severe necrosis with disintegration of hepatic cords , hemorrhage , and neutrophil infiltration ( the median grade for necrosis and leukocyte infiltration were 3 and 4 , resp . ) in control tissue taken 8 hrs after reperfusion .
pons decreased the severity of the above - mentioned histomorphological changes in the liver ( the median grade of necrosis and leukocyte infiltration of 1 ; p < 0.001 ) ( figure 3 ) . bile flow rate ( ml / hr ) was significantly higher in the pons group 8 hrs after reperfusion ( figure 2 ) .
the immunohistochemical analysis of sections obtained 8 hrs after reperfusion indicated positive staining for tnf- , mpo , and cleaved caspase-3 .
pons reduced the number of positively stained hepatocytes against all of three above enzymes ( figure 4 ) .
the manipulation of the liver during hepatic surgery activates kupffer cells , which leads to the release of proinflammatory cytokines , including tumor necrosis factor - alpha ( tnf- ) and interlukin-1 ( il-1 ) as well as free radicals , thus initiating an inflammatory cascade [ 27 ] .
this phenomenon is usually further complicated through the application of the pringle maneuver ( hepatic inflow occlusion ) in an attempt to prevent blood loss during the hepatic transection .
the cumulative effect induces warm iri to the liver , which results , depending on the duration of ischemia , in microcirculatory disturbances , liver cell damage , and in severe cases liver failure .
several approaches have been proposed to pharmacologically tackle hepatic iri ; none , however , has found its way into clinical routine yet . to prevent iri
, it is important to neutralize reactive oxygen and nitrogen species , either by administering radical scavengers or by enhancing the capacity of endogenous redox defense systems
. a vast variety of dietary constituents can exert radical scavenging effects in vivo . among all , hydrophilic ascorbic acid ( vitamin c ) and lipophilic -tocopherol ( vitamin e ) are the important components of the human antioxidant system .
carotenoids , the principal dietary source of vitamin a in humans , polyphenolic compounds in green tea extract [ 36 , 44 ] , selenium , and zinc all exert antioxidant action ; a synergism among the different antioxidants as part of an antioxidant network has been shown [ 4749 ] .
large amounts of gram - negative bacteria and endotoxins ( lps ) are normally present in the intestines .
a reduction in splanchnic blood flow and ischemia damages the intestinal wall and changes the permeability of the gut membrane , leading to excessive leakage of lps and bacterial translocation into the portal circulation .
scavenger receptors , including the scavenger receptor cystein - rich ( srcr ) superfamily members that are expressed on kcs , are involved in the bactericidal action by binding and endocytosis of endotoxin [ 51 , 52 ] .
the cd11/cd18 receptor of kcs , the pattern recognition receptors ( prrs ) cd14 , and the toll - like receptor 4 ( tlr4 ) in combination with the adaptor protein md2 are reported to be essentially involved in the lps - associated kc activation [ 50 , 53 ]
. this may reflect an evolutionary adaptation by kcs to their local hepatic environment and strategic anatomic position in the portal circuit , which is optimal for the removal of endotoxin and , thus , for the protection of the host .
glutamine has been shown to have a positive impact on the intestinal barrier by reducing permeability and bacterial translocation and preserving mucosal integrity [ 55 , 56 ] .
it can , therefore , prevent kupffer cell activation and results in a more favorable outcome .
however , we did not measure blood lps levels or histology of intestine , which might have further documented the protective effects of pons on intestine . in many models of liver injury ,
tnf- levels are elevated and correlate with injury ; the inhibition of tnf- activity can attenuate liver injury , protect hepatic morphology , and decrease mortality .
mpo has been shown to be largely responsible for the neutrophil - induced parenchymal cell killing .
released from the neutrophil 's azurophilic granules , mpo can generate hypochlorous acid , a diffusible oxidant and chlorinating agent that gives rise to other toxic species , such as chloramines .
apoptotic cell death can trigger neutrophil transmigration , severely aggravating apoptotic cell injury ; caspase inhibitors can have a significant overall protective effect on hepatic iri . in the present study
, we have shown that the oral administration of consecutive doses of a preconditioning supplement in experimental pigs significantly reduced the transaminases compared to controls after hepatic warm iri .
furthermore , pons resulted in significantly milder histological changes as well as a significant increase in bile production .
the milder histological changes as well as improved sinusoidal bile production after pons represents reduced postreperfusion injury .
this has been further proved by the immunohistochemical analysis of the tissues obtained 8 hrs postreperfusion ; pons reduced the expression of tnf- , mpo , and cleaved caspase-3 .
pons most likely exerts these protective effects via different mechanisms including direct antioxidative effects of its various antioxidant constituents including vitamin c , vitamin e , -carotene , polyphenolic compounds in green tea extract , selenium and zinc .
furthermore , pons most likely exerts an inhibitory effect on lps - associated kc activation through glutamine . to the best of our knowledge
, this work is the first report of an oral pharmacological preconditioning against hepatic iri in a larger animal model .
the application of an oral nutritional substance in pigs is safe , reproducible , and well - deals with the current obstacles faced within the context of hepatic surgery and warm iri .
tailoring such clinically - oriented experiments may finally help improve bench - to - bedside preconditioning protocols . | background .
several approaches have been proposed to pharmacologically ameliorate hepatic ischemia / reperfusion injury ( iri ) .
this study was designed to evaluate the effects of a preconditioning oral nutritional supplement ( pons ) containing glutamine , antioxidants , and green tea extract on hepatic warm iri in pigs .
methods .
pons ( 70 g per serving , fresenius kabi , germany ) was dissolved in 250 ml tap water and given to pigs 24 , 12 , and 2 hrs before warm ischemia of the liver .
a fourth dose was given 3 hrs after reperfusion .
controls were given the same amount of cellulose with the same volume of water .
two hours after the third dose of pons , both the portal vein and the hepatic artery were clamped for 40 min . 0.5 , 3 , 6 , and 8 hrs after reperfusion , heart rate ( hr ) , mean arterial pressure ( map ) , central venous pressure ( cvp ) , portal venous flow ( pvf ) , hepatic arterial flow ( haf ) , bile flow , and transaminases were measured .
liver tissue was taken 8 hrs after reperfusion for histology and immunohistochemistry .
results .
hr , map , cvp , haf , and pvf were comparable between the two groups .
pons significantly increased bile flow 8 hrs after reperfusion .
alt and ast were significantly lower after pons .
histology showed significantly more severe necrosis and neutrophil infiltration in controls .
pons significantly decreased the index of immunohistochemical expression for tnf- , mpo , and cleaved caspase-3 ( p < 0.001 ) . conclusion .
administration of pons before and after tissue damage protects the liver from warm iri via mechanisms including decreasing oxidative stress , lipid peroxidation , apoptosis , and necrosis . |
dynamic data driven application systems ( dddas ) @xcite aim to integrate data acquisition , modeling , and measurement steering into one dynamic system .
data assimilation is a statistical technique to modify model state in response to data and an important component of the dddas approach .
models are generally discretizations of partial differential equations and they may have easily millions of degrees of freedom .
the model equations themselves are posed in functional spaces , which are infinitely dimensional . because of nonlinearities , the probability distribution of the state is usually non - gaussian .
a number of methods for data assimilation exist @xcite .
filters attempt to find the best estimate from the model state and the data up to the present .
we present a combination of the ensemble kalman filter ( enkf ) @xcite and the sequential importal sampling ( sis ) particle filter ( pf ) @xcite .
the enkf is a monte - carlo implementation of the kalman filter ( kf ) .
the kf is an exact method for gaussian distributions .
however , it needs to maintain the state covariance matrix , which is not possible for large state dimension .
the enkf and its variants @xcite replace the covariance by the sample covariance computed from an ensemble of simulations .
each ensemble member is advanced in time by the model independently until analysis time , when the data is injected , resulting in changes in the states of the ensemble members .
particle filters also evolve a ensemble of simulations , but they assign to each ensemble member a weight and the analysis step updates the weights .
the kf and the enkf represent the probability distributions by the mean and the covariance , and so they assume that the distributions are gaussian .
this shows in the tendency of enkf to smear distributions towards unimodal , as illustrated in sec .
[ sec : numerical ] below .
so , while the enkf has the advantage that it can make large charges in the state and the ensemble can represent an arbitrary distribution , the enkf is still essentialy limited to gaussian distributions . on the other hand ,
the pf can represent non - gaussian distributions faithfully , but it only updates the weights and can not move ensemble members in the state space . thus
a method that combines the advantages of both without the disadvantages of either is of interest .
the design of more efficient non - gaussian filters for large - scale problems has been the subject of significant interest , often using gaussian mixtures and related approaches @xcite .
the predictor - corrector filter presented here uses an enkf as a predictor to move the state distribution towards the correct region and then a pf as corrector to adjust for a non - gaussian character of the distribution .
nonparametric density estimation is used to compute the weights in the pf .
the combined predictor - corrector method appears to work well on problems where either enkf of pf fails , and it does not degrade the performace of the enkf for gaussian distributions .
predictor - corrector filters were first formulated in @xcite . related results and some probabilistic background can be found in @xcite .
a common procedure to construct an initial ensemble is as a sum with random coefficients @xcite , @xmath0 where @xmath1 is an orthonormal basis in the space state @xmath2 equipped with the euclidean norm @xmath3 .
the elements of @xmath4 are column vectors of values of functions on a mesh in the spatial domain .
the basis functions @xmath5 are smooth for small @xmath6 and more oscillatory for large @xmath6 .
if the the coefficients @xmath7 sufficiently fast , the series ( [ eq : random - smooth ] ) converges and @xmath8 is a random smooth function in the limit as @xmath9 .
the sum ( [ eq : random - smooth ] ) defines a gaussian random variable with the eigenvalues of its covariance matrix equal to @xmath10 .
possible choices of @xmath11 include a fourier basis , such as the sine or cosine functions , or bred vectors @xcite . on the state space @xmath4
, we define another norm by @xmath12 note that if @xmath13 , @xmath14 is just the original norm @xmath15 on @xmath4 .
we generally use @xmath16 adapted to the smoothness of the functions in the initial ensemble , @xmath17 as @xmath18 .
a weighted ensemble of @xmath19 simulations @xmath20 is initialized according to ( [ eq : random - smooth ] ) , with equal weights @xmath21 .
the ensemble members are advanced by the model and at given points in time , new data is injected by an _
analysis step_. the data consists of vector @xmath22 of measurements , observation function @xmath23 , also called forward operator , here assumed to be linear , which links the model state space with the data space , and data error distribution , here assumed to be gaussian with zero mean and known covariance @xmath24 .
the value of the observation function @xmath25 is what the data vector would be in the absence of model and data errors .
the value of the probability density of the data error distribution at the data vector @xmath22 for a given value of the observation function @xmath25 is called _ data likelihood _ and denoted by @xmath26 .
the probability distribution of the model state before the data is injected is called the _ prior _ or the _ forecast _ , and the distribution after the data is injected is called the _ posterior _ or the _ analysis_. assuming the forecast probability distribution has the density @xmath27 , the density @xmath28 of the analysis is found from the bayes theorem , @xmath29 where @xmath30 means proportional . instead of working with densities ,
the probability distributions are approximated by weighted ensembles .
we will call the following analysis step algorithm _
enkf - sis_. * predictor . * given a forecast ensemble @xmath31 the members @xmath32 of the analysis ensemble are found from the enkf , @xmath33 where @xmath34 are randomly sampled from the data distribution , and @xmath35 is the forecast ensemble covariance,@xmath36 this is the enkf from @xcite , extended to weighted ensembles by the use of the weighted sample covariance ( [ eq : wc ] ) .
* corrector . * the analysis members @xmath32
are thought of as a sample from some _ proposal distribution _
, with density @xmath37 .
ideally , the analysis weights @xmath38 should be computed from the sis update as @xcite @xmath39 however , the ratio of the densities is not known , so it is replaced by a noparametric estimate inspired by @xcite , giving @xmath40 the bandwidth @xmath41 is the distance from @xmath32 to the @xmath42-th nearest member @xmath43 , measured in the @xmath44 norm .
[ c]cc & + ( a ) prior and data likelihood densities & ( b ) posterior from enkf + & + ( c ) posterior from sis & ( d ) posterior from enkf - sis ) .
enkf - sis was able to approximate the optimal solution better than either sis or enkf alone .
, width=288 ] fig .
[ fig : bimodal ] demonstrates a failure of enkf for non - gaussian distributions , while sis and enkf - sis do fine .
we construct a bimodal prior in 1d by first sampling from @xmath45 and assigning the weights by @xmath46 the data likelihood is gaussian .
the ensemble size was @xmath47 .
the next 1d problem demonstrates that enkf - sis is doing better that either enkf or sis alone in filtering for the stochastic differential equation @xcite @xmath48 where @xmath49 is white noise .
the parameter @xmath50 controls the magnitude of the stochastic term .
the deterministic part of this differential equation is of the form @xmath51 where the potential @xmath52 .
the equilibria are given by @xmath53 ; there are two stable equilibria at @xmath54 and an unstable equilibrium at @xmath55 .
the stochastic term of the differential equation makes it possible for the state to flip from one stable equilibrium point to another ; however , a sufficiently small @xmath50 insures that such an event is rare . a suitable test for an ensemble filter will be to determine if it can properly track the model as it transitions from one stable fixed point to the other .
from fig .
[ fig : bimodal ] , it is clear that enkf will not be capable of describing the bimodal nature of the state distribution so it will not perform well when tracking the transition . also , when the ensemble is centered around one stable point , it is unlikely that some ensemble members would be close to the other stable point .
it is known that sis can be very slow in tracking the transition and enkf can do better @xcite .
[ fig : rsode_results ] demonstrates that enkf can outperform both .
the solution @xmath8 of ( [ eq : rsode ] ) is a random variable dependent on time , with density @xmath56 .
the evolution of the density in time is given by the fokker - planck equation , which was solved numerically on a uniform mesh from @xmath57 to @xmath58 with the step @xmath59 .
at the analysis time , the optimal posterior density was computed by multiplying the probability density of @xmath8 by the data likelihood following ( [ eq : bayes - dens ] ) and then scaling so that again @xmath60 , using numerical quadrature by the trapezoidal rule .
the data points were taken from one solution of this model , called a reference solution , which exhibits a switch at time @xmath61 .
the data error distribution was normal with the variance taken to be @xmath62 at each point . to advance the ensemble members and the reference solution , we have solved ( [ eq : rsode ] ) by the explicit euler method with a random perturbation from @xmath63 added to the right hand side in every step @xcite .
the simulation was run for each method with ensemble size @xmath64 , and assimilation performed for each data point .
[ sec : hd ] [ c]cc$ ] .
the vertical axis is the value of function @xmath8 .
the level of shading on each vertical line is the marginal density of @xmath8 at a fixed @xmath65 , computed from a histogram with 50 bins .
while enkf completely ignores the non - gaussian character of the posterior and centers the distribution around @xmath55 , enkf - sis shows darker bands at the edges .
, title="fig:",width=201 ] & $ ] .
the vertical axis is the value of function @xmath8 .
the level of shading on each vertical line is the marginal density of @xmath8 at a fixed @xmath65 , computed from a histogram with 50 bins .
while enkf completely ignores the non - gaussian character of the posterior and centers the distribution around @xmath55 , enkf - sis shows darker bands at the edges .
, title="fig:",width=201 ] + ( a ) & ( b ) + $ ] .
the vertical axis is the value of function @xmath8 .
the level of shading on each vertical line is the marginal density of @xmath8 at a fixed @xmath65 , computed from a histogram with 50 bins .
while enkf completely ignores the non - gaussian character of the posterior and centers the distribution around @xmath55 , enkf - sis shows darker bands at the edges .
, title="fig:",width=201 ] & $ ] .
the vertical axis is the value of function @xmath8 .
the level of shading on each vertical line is the marginal density of @xmath8 at a fixed @xmath65 , computed from a histogram with 50 bins .
while enkf completely ignores the non - gaussian character of the posterior and centers the distribution around @xmath55 , enkf - sis shows darker bands at the edges .
, title="fig:",width=201 ] + ( c ) & ( d ) [ c]cc$ ] .
the vertical axis is the value of function @xmath8 .
the level of shading on each vertical line is the marginal density of @xmath8 at a fixed @xmath65 , computed from a histogram with 50 bins .
while enkf and enkf - sis create ensembles that are attracted to the data value @xmath66 , sis can not reach so far because there are no such members in this relatively small ensemble of size @xmath47 .
, title="fig:",width=201 ] & $ ] .
the vertical axis is the value of function @xmath8 .
the level of shading on each vertical line is the marginal density of @xmath8 at a fixed @xmath65 , computed from a histogram with 50 bins .
while enkf and enkf - sis create ensembles that are attracted to the data value @xmath66 , sis can not reach so far because there are no such members in this relatively small ensemble of size @xmath47 .
, title="fig:",width=201 ] + ( a ) & ( b ) + $ ] .
the vertical axis is the value of function @xmath8 .
the level of shading on each vertical line is the marginal density of @xmath8 at a fixed @xmath65 , computed from a histogram with 50 bins .
while enkf and enkf - sis create ensembles that are attracted to the data value @xmath66 , sis can not reach so far because there are no such members in this relatively small ensemble of size @xmath47 .
, title="fig:",width=201 ] & $ ] .
the vertical axis is the value of function @xmath8 .
the level of shading on each vertical line is the marginal density of @xmath8 at a fixed @xmath65 , computed from a histogram with 50 bins .
while enkf and enkf - sis create ensembles that are attracted to the data value @xmath66 , sis can not reach so far because there are no such members in this relatively small ensemble of size @xmath47 .
, title="fig:",width=201 ] + ( c ) & ( d ) finally , typical results for filtering in the space of functions on @xmath67 $ ] of the form@xmath68 are in figs . [
fig : b - enkf ] and [ fig : sis - fail ] .
the ensemble size was @xmath47 and the dimension of the state space was @xmath69 .
the fourier coefficients were chosen @xmath70 to generate the initial ensemble from ( [ eq : random - smooth ] ) , and @xmath71 for the norm in the density estimation .
[ fig : b - enkf ] again shows that enkf can not handle bimodal distribution .
the prior was constructed by assimilating the data likelihood@xmath72{l}% 1/2\mbox { if } u(\pi/4)\mbox { and }
\\ \quad\quad u\left ( 3\pi/4\right ) \in\left ( -2,-1\right ) \cup(1,2)\\ 0\mbox { otherwise } \end{array } \right.\ ] ] into a large initial ensemble ( size 50000 ) and resampling to the obtain the forecast ensemble size @xmath47 with a non - gaussian density .
then the data likelihood @xmath73 was assimilated to obtain the analysis ensemble .
[ fig : sis - fail ] shows a failure of sis .
the prior ensemble sampled from gaussian distribution with coefficients @xmath70 using ( [ eq : random - smooth ] ) and ( [ eq : sin ] ) , and the data likelihood was @xmath74 .
we have demonstrated the potential of a predictor - corrector filter to perform a successful bayesian update in the presence of non - gaussian distributions , large number of degrees of freedom , and large change of the state distribution .
open questions include convergence of the filter in high dimension when applied to multiple updates over time , mathematical convergence proofs for the density estimation and for the bayesian update , and performance of the filters when applied to systems with a large number of different physical variables and modes , as is common in atmospheric models .
darema , f. : dynamic data driven applications systems : a new paradigm for application simulations and measurements . in : bubak , m. , van albada , g.d . ,
sloot , p.m.a . ,
dongarra , j.j .
iccs 2004 , lncs , vol . 3038 , pp .
springer ( 2004 ) mandel , j. , beezley , j.d . : predictor - corrector and morphing ensemble filters for the assimilation of sparse data into high dimensional nonlinear systems . in : 11th symposium on integrated observing and assimilation systems for the atmosphere , oceans , and land surface ( ioas - aols ) , cd - rom , paper 4.12 , 87th american meteorological society annual meeting , san antonio , tx , http://ams.confex.com/ams/87annual/techprogram/paper_119633.htm ( 2007 ) | an ensemble kalman filter ( enkf , the predictor ) is used make a large change in the state , followed by a particle filer ( pf , the corrector ) , which assigns importance weights to describe a non - gaussian distribution .
the importance weights are obtained by nonparametric density estimation .
it is demonstrated on several numerical examples that the new predictor - corrector filter combines the advantages of the enkf and the pf and that it is suitable for high dimensional states which are discretizations of solutions of partial differential equations .
* key words : * dynamic data driven application systems , data assimilation , ensemble kalman filter , particle filter , tracking , non - parametric density estimation , bayesian statistics |
SECTION 1. SHORT TITLE.
This Act may be cited as the ``Jean Lafitte National Historical
Park and Preserve Boundary Adjustment Act of 2007''.
SEC. 2. JEAN LAFITTE NATIONAL HISTORICAL PARK AND PRESERVE BOUNDARY
ADJUSTMENT.
(a) In General.--Section 901 of the National Parks and Recreation
Act of 1978 (16 U.S.C. 230) is amended in the second sentence by
striking ``of approximately twenty thousand acres generally depicted on
the map entitled `Barataria Marsh Unit-Jean Lafitte National Historical
Park and Preserve' numbered 90,000B and dated April 1978,'' and
inserting ``generally depicted on the map entitled `Boundary Map,
Barataria Preserve Unit, Jean Lafitte National Historical Park and
Preserve', numbered _____, and dated ________,''.
(b) Acquisition of Land.--Section 902 of the National Parks and
Recreation Act of 1978 (16 U.S.C. 230a) is amended--
(1) in subsection (a)--
(A) by striking ``(a) Within the'' and all that
follows through the first sentence and inserting the
following:
``(a) In General.--
``(1) Barataria preserve unit.--
``(A) In general.--The Secretary may acquire any
land, water, and interests in land and water within the
area, as depicted on the map described in section 901,
by donation, purchase with donated or appropriated
funds, transfer from any other Federal agency, or
exchange.
``(B) Limitations.--
``(i) In general.--Any private land located
in the area, as depicted on the map described
in section 901, may be acquired by the
Secretary only with the consent of the owner of
the land.
``(ii) Boundary adjustment.--On the date on
which the Secretary, under subparagraph (A),
completes the acquisition of a parcel of
private land located in the area, as depicted
on the map described in section 901, the
boundary of the historical park and preserve
shall be adjusted to reflect the acquisition.
``(iii) Jurisdiction of national park
service.--Any Federal land acquired in the
areas shall be transferred without
consideration to the administrative
jurisdiction of the National Park Service.
``(iv) Easements.--To ensure adequate
hurricane protection of communities located in
the area, any land in the area identified on
the map that is acquired or transferred shall
be subject to any easements that have been
agreed to by the Secretary and the Secretary of
the Army.'';
(B) in the second sentence, by striking ``The
Secretary may also'' and inserting the following:
``(2) French quarter.--The Secretary may'';
(C) in the third sentence, by striking ``Lands,
waters, and interests therein'' and inserting the
following:
``(3) Acquisition of state land.--Land, water, and
interests in land and water''; and
(D) in the fourth sentence, by striking ``In
acquiring'' and inserting the following:
``(4) Acquisition of oil and gas rights.--In acquiring'';
(2) by striking subsections (b) through (f) and inserting
the following:
``(b) Resource Protection.--With respect to the land, water, and
interests in land and water of the Barataria Preserve Unit, the
Secretary shall preserve and protect--
``(1) fresh water drainage patterns;
``(2) vegetative cover;
``(3) the integrity of ecological and biological systems;
and
``(4) water and air quality.''; and
(3) by redesignating subsection (g) as subsection (c).
(c) Hunting, Fishing, and Trapping.--Section 905 of the National
Parks and Recreation Act of 1978 (16 U.S.C. 230d) is amended in the
first sentence by striking ``, except that within the core area and on
those lands acquired by the Secretary pursuant to section 902(c) of
this title, he'' and inserting ``on land, and interests in land and
water managed by the Secretary, except that the Secretary''.
(d) Administration.--Section 906 of the National Parks and
Recreation Act of 1978 (16 U.S.C. 230e) is amended--
(1) by striking the first sentence; and
(2) in the second sentence, by striking ``Pending such
establishment and thereafter the'' and inserting ``The''.
SEC. 3. REFERENCES IN LAW.
(a) In General.--Any reference in a law (including regulations),
map, document, paper, or other record of the United States--
(1) to the Barataria Marsh Unit shall be considered to be a
reference to the Barataria Preserve Unit; or
(2) to the Jean Lafitte National Historical Park shall be
considered to be a reference to the Jean Lafitte National
Historical Park and Preserve.
(b) Conforming Amendments.--Title IX of the National Parks and
Recreation Act of 1978 (16 U.S.C. 230 et seq.) is amended--
(1) by striking ``Barataria Marsh Unit'' each place it
appears and inserting ``Barataria Preserve Unit''; and
(2) by striking ``Jean Lafitte National Historical Park''
each place it appears and inserting ``Jean Lafitte National
Historical Park and Preserve''. | Jean Lafitte National Historical Park and Preserve Boundary Adjustment Act of 2007 - Amends the National Parks and Recreation Act of 1978 to adjust the boundary of the the Barataria Preserve Unit of the Jean Lafitte National Historical Park and Preserve in Louisiana and to acquire land necessary for the adjustment by transfer or exchange from a federal agency or, from a land owner, by donation or purchase (but only with an owner's consent).
Subjects any acquired or transferred land in the area to any easements that have been agreed to by the Secretary and the Secretary of the Army in order to ensure adequate hurricane protection of the communities located in the area.
Revises provisions concerning hunting, fishing, and trapping. |
a serious and frequent complication of transplantation new - onset diabetes after transplantation ( nodat)is associated with increased cardiovascular morbidity and mortality that is observed in kidney transplant patients [ 1 , 2 ] as well as with decreased graft and patient survival [ 35 ] .
thus , pretransplant identification of patients at high risk of developing nodat would be greatly advantageous by enabling the modification of nodat by the use of less diabetogenic immunosuppressive drugs or implementation of lifestyle - change interventions .
several clinical trials have revealed that lifestyle - change interventions were effective in preventing type 2 diabetes mellitus [ 6 , 7 ] and that they may be applicable in nodat cases too .
we previously reported that the posttransplant increase in body mass index and body fat percentage is associated with the development of nodat [ 8 , 9 ] , indicating that lifestyle - change interventions are useful for preventing nodat .
the postload plasma glucose level during an oral glucose tolerance test ( ogtt ) is a strong predictor for the development of diabetes in the future [ 10 , 11 ] .
furthermore , we have recently reported that ogtt can be a useful predictor of nodat development .
hba1c is much easier to test and examine than ogtt and has been increasingly used for assessing chronic glycemia in patients with diabetes , diagnosing diabetes mellitus , and identifying those who may be at high risk for developing diabetes in the future [ 1316 ] .
furthermore , several studies showed the efficacy of hba1c in the detection of posttransplant diabetes mellitus [ 1719 ] .
however , hba1c values are strongly influenced by anemia and erythropoietin ( epo ) treatment [ 2022 ] .
further , kidney transplant candidates are frequently administered epo injections for the treatment of anemia ; hence , the pretransplant hba1c level should be cautiously interpreted .
although tatar et al . showed that the pretransplant hba1c level can be used to identify the high - risk group of nodat , the utility of hba1c as a predictor for the development of nodat has not been completely elucidated . in our previous study ,
hence , in this study , we evaluated the predictive power of the pretransplant hba1c level for the development of nodat in patients receiving tacrolimus - based immunosuppressive treatment .
we retrospectively identified 193 consecutive patients who received living donor kidney transplants in our hospital between march 2000 and january 2012 .
seventy - four patients were excluded from this study for the following reasons : pretransplant diabetes mellitus ( n = 27 ) , recipient age < 18 years ( n = 8) , insufficient data on hba1c ( n = 3 ) , early graft or patient loss ( n = 8) , and cyclosporine - based immunosuppressive regimen ( n = 28 ) .
pretransplant diabetes was defined as the use of insulin or oral antihyperglycemic medications or fasting plasma glucose levels 126 mg / dl .
finally , a total of 119 patients were included in this study ( figure 1 ) . for subgroup analysis
, we identified 85 patients receiving no or low - dose ( 6,000 iu / week ) epo . to avoid detection bias ,
systematic , standardized , and periodic examinations of posttransplant glucose tolerance were performed on all patients regardless of pretransplant hba1c levels .
hba1c was measured basically within 3 months prior to transplantation by high performance liquid chromatography ( hplc ) method and estimated as a national glycohemoglobin standardization program ( ngsp ) value .
the hba1c ( japan diabetes society ( jds ) ) was converted to hba1c ( ngsp ) using the officially certified equation : ngsp ( % ) = 1.02 jds ( % ) + 0.25% .
the clinical data were collected retrospectively from the hospital data system and from clinical records in august 2013 .
patients received immunosuppressive treatment consisting of prednisolone , tacrolimus , mycophenolate mofetil or mizoribine , and basiliximab .
prednisolone was started at 1 mg / kg with subsequent tapering to 0.2 mg / kg 1 month after transplantation .
tacrolimus was initiated 2 days before transplantation and adjusted to maintain the initial trough level of 1012 ng / ml and the long - term target trough level of 68 ng / ml . mycophenolate mofetil or mizoribine was started on the day after transplantation .
acute rejection was confirmed by graft biopsy and treated with intravenous methylprednisolone ( 250 or 125 mg / day ) for 3 days followed by deoxyspergualin 5 mg/[kgday ] for 5 days .
nodat was defined according to the american diabetes association as the presence of diabetes symptoms in addition to casual plasma glucose levels 200 mg / dl or fasting plasma glucose levels 126 mg / dl .
fasting was defined as the absence of caloric intake for at least 8 h. in this study , patients with transient elevations of fasting plasma glucose levels immediately after transplantation or during times of acute illness were not diagnosed with nodat .
patients who started to receive insulin or oral antihyperglycemic medications after transplantation were also diagnosed as nodat .
all doses of epo were presented as recombinant human epo per week . for the conversion of darbepoetin alfa dosage to recombinant human epo , a ratio of 1 g darbepoetin alfa to 200 iu recombinant human epo ratio was used .
recombinant epo is generally used with a dose of 4,500 , 6,000 , or 9,000 iu / week . in this study ,
low - dose and high - dose epo were defined as 0 < epo 6,000 iu / week and epo > 6,000 iu / week , respectively .
data are expressed as means ( standard deviation ) or median ( range ) as appropriate .
statistical significance was determined using student 's t - test for normally distributed data , wilcoxon 's signed rank test for skewed data , and fisher 's exact test for dichotomous data .
univariate and multivariate logistic regression analyses were used to assess the association of several parameters with the incidence of nodat .
predictive discrimination of hba1c was assessed using a receiver - operating characteristic ( roc ) curve on the basis of maximizing sensitivity and specificity .
analyses were performed using jmp pro 10 ( sas institute , cary , nc ) .
the baseline data of the patients who did and did not develop nodat are presented in table 1 . of the 119 patients included in this study , 17 patients ( 14.3% ) developed nodat within 1 year of transplantation .
there were no differences in donor age , gender , cause of chronic renal failure , or pretransplant body mass index .
univariate logistic regression analysis showed that recipient age , gender , and hba1c were significant predictors for the development of nodat . in the multivariate analysis ,
the association between the pretransplant hba1c level and development of nodat did not reach statistical significance ( p = 0.07 ) , after adjusting for recipient age and gender , the 2 factors of p < 0.05 ( table 2 ) .
for 29 of the 119 patients included in this study , epo doses were > 6,000 iu / week ; the epo doses of 5 patients were not available . therefore , these 34 patients were excluded from the subgroup analyses of patients receiving no or low - dose epo . of the 85 patients
multivariate logistic regression subanalysis revealed that the pretransplant hba1c level was an independent predictor for the development of nodat ( table 3 ) .
the roc analyses showed that the area under the roc curve was 0.75 and the cut - off level of hba1c which gave the maximum sensitivity and specificity was 5.2% ( figure 2 ) .
the sensitivity , specificity , positive predictive value , and negative predictive value of hba1c at the cut - off point were 64% , 78% , 30% , and 94% , respectively ( table 4 ) .
in this study , we found that even in patients with chronic renal failure , who had several predispositions for fluctuated hba1c levels , pretransplant hba1c was associated with nodat development ; moreover , pretransplant hba1c levels were an independent predictor of nodat development in patients receiving no or low - dose epo .
our subgroup analysis further revealed that the cut - off value for hba1c was 5.2% and indicated that the risk of nodat development was significantly higher in patients with hba1c levels above this cut - off .
pretransplant hba1c levels were a significant predictor of nodat for patients receiving no or low - dose epo ; however , this association was not observed during the whole group analysis .
this inconsistency might be due to a high degree of variability in hba1c levels in patients receiving high - dose epo .
uzu et al . reported that high - dose epo strongly influenced hba1c levels , and therefore pretransplant hba1c levels might be difficult to apply to these patients .
our study has several points in common with those of a study by tatar et al . that revealed the predictive value of pretransplant hba1c for nodat development within 1 year after kidney transplantation .
both the studies excluded recipients aged < 18 years and included recipients with similar baseline characteristics , including equivalent age , sex , and pretransplant hba1c level . the major difference between these two studies was the study design : our study excluded patients who had received a cyclosporine - based immunosuppressive regimen because our previous study had showed that all patients who developed nodat had received a tacrolimus - based immunosuppressive regimen .
furthermore , in our study , the incidence rate of nodat development was lower ( 14.3% ) than that in tatar 's study ( 25.9% ) , and pretransplant bmi and fasting plasma glucose levels were not associated with nodat development .
these inconsistencies might be due to the difference in race , considering that all the included patients in our study were japanese with low bmis .
a weakness of our study is that the predictive value of pretransplant hba1c was determined only for the subgroup patients who did not receive epo or patients who received only low - dose epo .
however , we believe that this point is also an original strong point of our study because most of the kidney transplant candidates received epo therapies , and pretransplant hba1c level should be interpreted after considering the epo dose .
the cut - off point of 5.2% , which was derived by the subgroup analysis on the basis of maximizing sensitivity and specificity , was considered clinically acceptable , because it could identify the low- and high - risk groups with reasonable predictive values as a predictor of short - term nodat development .
the risk of nodat development in patients receiving no or low - dose epo with an hba1c 5.2% was 6.34-fold higher than in patients with an hba1c < 5.2% , which is higher than the reported odds ratio of impaired glucose tolerance based on a ogtt . according to the american diabetes association , prediabetes is defined as 5.7% hba1c 6.4% in the general population .
the cut - off value derived from this study was lower than that for the general population , which is most likely due to the influence of epo ; this is consistent with reports suggesting that the target hba1c level should be lowered to 5.1% for patients with hematocrit
the auc of 0.75 , sensitivity of 64% , and specificity of 78% compare favorably with previously reported values in the general population , indicating that hba1c values are indeed useful and can be applied to clinical practices in transplant settings , although the cut - off level of 5.2% needs to be further evaluated .
although several reports suggest that the hba1c level can be interpreted after using a correction formula ( hba1c 1.19 in those with low epo dosages , i.e. , < 100 iu/[kgweek ] , and hba1c 1.38 in those with high epo dosages , i.e. , 100 iu/[kgweek ] ) , this formula is complicated to use in the clinical setting , as it requires clinicians to calculate the corrected hba1c value each time .
this formula is even less practical with regard to recently developed epo drugs that have a longer elimination half - life because the dosage for these new drugs must first be converted into the comparable recombinant human epo dose before the correction formula can be applied . in this study , 29 out of a total of 119 patients received high - dose epo ( > 6,000 iu / week ) therapy . by excluding this minority group ,
these results indicate that the pretransplant hba1c level , which has been considered difficult to interpret in patients with chronic renal failure , can be used as a useful predictor of nodat by excluding patients receiving maximum dose epo .
the uremic state was also a well - known factor to affect the hba1c levels measured by hplc method .
carbamylated hemoglobin , which was greatly elevated in uremia , was significantly correlated with chromatographically determined glycosylated hemoglobin .
indeed , hba1c levels measured by hplc should be interpreted with much caution in uremia .
on the other hand , smith et al . also reported that hemodialysis had no effect on the hba1c levels measured by hplc although the slight increases were observed in the settings of chronic renal failure and continuous ambulatory peritoneal dialysis .
furthermore , hba1c values measured by hplc have been widely utilized for patients with chronic renal failure [ 22 , 27 ] and shown to be associated with increased death risk in the patients undergoing maintenance hemodialysis [ 30 , 31 ] .
based on these results , we believe that hba1c can be a useful tool even for patients with uremia . in this study ,
fasting plasma glucose levels were comparable between the groups , whereas in the study by tatar et al .
, pretransplant fasting blood glucose levels were reported as an independent predictor of nodat development . as the predictive value of fasting plasma glucose for the development of type 2 diabetes remains controversial [ 32 , 33 ]
hepatitis c virus ( hcv ) infection is also an important risk factor of the development of type 2 diabetes , as we have previously reported . in this study , however , only 3 of the 119 patients had hcv infections ; hence , the association between hcv infections and nodat development could not be statistically investigated .
this was a retrospective single - center study , and the sample size was small . because of the small sample size
, the predictive power of hba1c according to the epo dose could not be fully compared .
for the same reason , we could not fully assess the utility of hba1c in patients receiving high - dose epo .
furthermore , we could not compare the efficacy of hba1c with that of other indexes such as oral glucose tolerance tests .
however , we believe that pretransplant hba1c levels are easy to obtain and can be a useful tool to identify patients at high risk for the development of nodat .
our results reveal that the pretransplant hba1c level is an important predictor for the development of nodat for patients receiving epo doses of 6,000 iu / week .
there are several restrictions for the use of the hba1c level as a predictor of nodat before kidney transplantation , especially in patients receiving high - dose epo treatment . in the future ,
longer - term prospective studies with larger sample sizes should be conducted to confirm our findings and examine the use of the pretransplant hba1c level for patients receiving high - dose epo .
the clinical impact of improving the identification of patients at high risk of developing nodat prior to transplantation is high , as it would allow for the individual adaptation of immunosuppressive treatments and implementation of lifestyle - change interventions . | aims . to evaluate the predictive power of pretransplant hba1c for new - onset diabetes after transplantation ( nodat ) in kidney transplant candidates , who had several predispositions for fluctuated hba1c levels
.
methods .
we performed a retrospective study of 119 patients without diabetes who received kidney transplantation between march 2000 and january 2012 .
univariate and multivariate logistic regression analyses were used to investigate the association of several parameters with nodat .
predictive discrimination of hba1c was assessed using a receiver - operating characteristic curve .
results .
seventeen patients ( 14.3% ) developed nodat within 1 year of transplantation .
univariate logistic regression analysis revealed that recipient age , gender , and hba1c were predictors of nodat . in the multivariate analysis ,
the association between pretransplant hba1c and nodat development did not reach statistical significance ( p = 0.07 ) . to avoid the strong influence of high - dose erythropoietin on hba1c levels , we performed subgroup analyses on 85 patients receiving no or low - dose ( 6000 iu / week ) erythropoietin .
hba1c was again an independent predictor for nodat .
receiver - operating characteristic analysis revealed a cut - off value of 5.2% with an optimal sensitivity of 64% and specificity of 78% for predicting nodat .
conclusions .
our results reveal that the pretransplant hba1c level is a useful predictor for nodat in patients receiving no or low - dose erythropoietin . |
<greek-th> x
SECTION 1. EXTENDING AVAILABILITY OF SCHIP ALLOTMENTS FOR FISCAL YEARS
1998 THROUGH 2001.<greek-th> x
(a) Retained and Redistributed Allotments for Fiscal Years 1998 and
1999.--Paragraphs (1)(B)(ii), (2)(A)(i), and (2)(A)(ii) of section
2104(g) of the Social Security Act (42 U.S.C. 1397dd(g)) are each
amended by striking ``fiscal year 2002'' and inserting ``fiscal year
2004''.<greek-th> x
(b) Extension and Revision of Retained and Redistributed Allotments
for Fiscal Year 2000.--<greek-th> x
(1) Permitting and extending retention of portion of fiscal
year 2000 allotment.--Paragraph (2) of such section 2104(g) is
amended--<greek-th> x <greek-th> x
(A) in the heading, by striking ``and 1999'' and
inserting ``through 2000''; and<greek-th> x
(B) by adding at the end of subparagraph (A) the
following:<greek-th> x
``(iii) Fiscal year 2000 allotment.--Of the
amounts allotted to a State pursuant to this
section for fiscal year 2000 that were not
expended by the State by the end of fiscal year
2002, 50 percent of that amount shall remain
available for expenditure by the State through
the end of fiscal year 2004.''.<greek-th> x
(2) Redistributed allotments.--Paragraph (1) of such
section 2104(g) is amended--<greek-th> x
(A) in subparagraph (A), by inserting ``or for
fiscal year 2000 by the end of fiscal year 2002,''
after ``fiscal year 2001,'';<greek-th> x
(B) in subparagraph (A), by striking ``1998 or
1999'' and inserting ``1998, 1999, or
2000'';<greek-th> x
(C) in subparagraph (A)(i)--<greek-th> x
(i) by striking ``or'' at the end of
subclause (I), <greek-th> x
(ii) by striking the period at the end of
subclause (II) and inserting ``; or''; and
<greek-th> x
(iii) by adding at the end the following
new subclause:<greek-th> x
``(III) the fiscal year 2000
allotment, the amount specified in
subparagraph (C)(i) (less the total of
the amounts under clause (ii) for such
fiscal year), multiplied by the ratio
of the amount specified in subparagraph
(C)(ii) for the State to the amount
specified in subparagraph
(C)(iii).'';<greek-th> x
(D) in subparagraph (A)(ii), by striking ``or
1999'' and inserting ``, 1999, or 2000'';<greek-th> x
(E) in subparagraph (B), by striking `` or 1999''
and inserting ``, 1999, or 2000''; and<greek-th> x
(F) by adding at the end the following new
subparagraph:<greek-th> x
``(C) Amounts used in computing redistributions for
fiscal year 2000.--For purposes of subparagraph
(A)(i)(III)--<greek-th> x
``(i) the amount specified in this clause
is the amount specified in paragraph
(2)(B)(i)(I) for fiscal year 2000, less the
total amount remaining available pursuant to
paragraph (2)(A)(iii);<greek-th> x
``(ii) the amount specified in this clause
for a State is the amount by which the State's
expenditures under this title in fiscal years
2000, 2001, and 2002 exceed the State's
allotment for fiscal year 2000 under subsection
(b); and<greek-th> x
``(iii) the amount specified in this clause
is the sum, for all States entitled to a
redistribution under subparagraph (A) from the
allotments for fiscal year 2000, of the amounts
specified in clause
(ii).''.<greek-th> x <greek-th> x <greek-th> x <greek-th>
x <greek-th> x <greek-th> x
(3) Conforming amendments.--Such section 2104(g) is further
amended--<greek-th> x <greek-th> x
(A) in its heading, by striking ``and 1999'' and
inserting ``, 1999, and 2000''; and<greek-th> x
(B) in paragraph (3)--<greek-th> x
(i) by striking ``or fiscal year 1999'' and
inserting ``fiscal year 1999, or fiscal year
2000''; and<greek-th> x
(ii) by striking ``or November 30, 2001,''
and inserting ``November 30, 2001, or November
30, 2002'', respectively.<greek-th> x
(c) Extension and Revision of Retained and Redistributed Allotments
for Fiscal Year 2001.--<greek-th> x
(1) Permitting and extending retention of portion of fiscal
year 2001 allotment.--Paragraph (2) of such section 2104(g), as
amended in subsection (b)(1)(B), is further amended--
<greek-th> x
(A) in the heading, by striking ``2000'' and
inserting ``2001''; and<greek-th> x
(B) by adding at the end of subparagraph (A) the
following: <greek-th> x
``(iv) Fiscal year 2001 allotment.--Of the
amounts allotted to a State pursuant to this
section for fiscal year 2001 that were not
expended by the State by the end of fiscal year
2003, 50 percent of that amount shall remain
available for expenditure by the State through
the end of fiscal year 2005.''.<greek-th> x
(2) Redistributed allotments.--Paragraph (1) of such
section 2104(g), as amended in subsection (b)(2), is further
amended--<greek-th> x
(A) in subparagraph (A), by inserting ``or for
fiscal year 2001 by the end of fiscal year 2003,''
after ``fiscal year 2002,'';<greek-th> x
(B) in subparagraph (A), by striking ``1999, or
2000'' and inserting ``1999, 2000, or
2001'';<greek-th> x
(C) in subparagraph (A)(i)--<greek-th> x
(i) by striking ``or'' at the end of
subclause (II), <greek-th> x
(ii) by striking the period at the end of
subclause (III) and inserting ``; or''; and
<greek-th> x
(iii) by adding at the end the following
new subclause:<greek-th> x
``(IV) the fiscal year 2001
allotment, the amount specified in
subparagraph (D)(i) (less the total of
the amounts under clause (ii) for such
fiscal year), multiplied by the ratio
of the amount specified in subparagraph
(D)(ii) for the State to the amount
specified in subparagraph
(D)(iii).'';<greek-th> x
(D) in subparagraph (A)(ii), by striking ``or
2000'' and inserting ``, 2000, or 2001'';<greek-th> x
(E) in subparagraph (B), by striking `` or 2000''
and inserting ``, 2000, or 2001''; and<greek-th> x
(F) by adding at the end the following new
subparagraph:<greek-th> x
``(D) Amounts used in computing redistributions for
fiscal year 2001.--For purposes of subparagraph
(A)(i)(III)--<greek-th> x
``(i) the amount specified in this clause
is the amount specified in paragraph
(2)(B)(i)(I) for fiscal year 2001, less the
total amount remaining available pursuant to
paragraph (2)(A)(iv);<greek-th> x
``(ii) the amount specified in this clause
for a State is the amount by which the State's
expenditures under this title in fiscal years
2001, 2002, and 2003 exceed the State's
allotment for fiscal year 2001 under subsection
(b); and<greek-th> x
``(iii) the amount specified in this clause
is the sum, for all States entitled to a
redistribution under subparagraph (A) from the
allotments for fiscal year 2001, of the amounts
specified in clause (ii).''.<greek-th> x
(3) Conforming amendments.--Such section 2104(g) is further
amended--<greek-th> x
(A) in its heading, by striking ``and 2000'' and
inserting ``, 2000, and 2001''; and<greek-th> x
(B) in paragraph (3)--<greek-th> x
(i) by striking ``or fiscal year 2000'' and
inserting ``fiscal year 2000, or fiscal year
2001''; and<greek-th> x
(ii) by striking ``or November 30, 2002,''
and inserting ``November 30, 2002, or November
30, 2003'', respectively. <greek-th> x
(d) Effective Date.--This section, and the amendments made by this
section, shall be effective as if this section had been enacted on
September 30, 2002, and amounts under title XXI of the Social Security
Act (42 U.S.C. 1397aa et seq.) from allotments for fiscal years 1998
through 2000 are available for expenditure on and after October 1,
2002, under the amendments made by this section as if this section had
been enacted on September 30, 2002.<greek-th> x <greek-th><greek-th> x
08 | Amends title XXI (State Children's Health Insurance) (SCHIP) of the Social Security Act to revise the rule for redistribution and extended availability of FY1998 and 1999 allotments to States, permitting and extending retention of half of the FY 2000 allotment, and permitting and extending retention of half of the FY 2001 allotment. |
WASHINGTON — New immigration proposals advanced by the White House Thursday drew mostly tepid responses from a Republican Party that has waged fierce internal battles over the issue for decades.
The top GOP leaders in the House and Senate each responded with noncommittal statements that treated the proposal — which called for major cuts to legal immigration and a border wall in exchange for a path to citizenship for young immigrants brought to the United States illegally as children — as more of a broad suggestion rather than a starting point for legislation.
“This framework builds upon the four pillars for reform that the president has consistently put forth, and indicates what is necessary for the president to sign a bill into law,” Senate Majority Leader Mitch McConnell, R-Ky., said. “I am hopeful that as discussions continue in the Senate on the subject of immigration, members on both sides of the aisle will look to this framework for guidance as they work towards an agreement.”
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A spokesman for House Speaker Paul Ryan expressed gratitude to the president Thursday for "showing leadership on this issue" and said that they believe "his ideas will help us ultimately reach a balanced solution.”
A large group of senators are currently working on their own bipartisan negotiations, and Republicans and Democrats had both warned in the run-up to the White House proposal that they were unlikely to reach a deal if talks ventured too far beyond DACA and border security. Democrats and immigration advocacy groups immediately denounced Trump's plan in fiery terms on Thursday night, making it unlikely it can serve as the basis for a bill.
Senator Marco Rubio, R-Fla., suggested in a statement on Friday that lawmakers should focus on passing narrow legislation addressing "the most immediate problems" created by the end of DACA along with border security issues, and move on to other topics later.
"The reaction, from both sides, to the President's outline is a reminder that the more an immigration bill tries to do, the harder it is to pass," he said.
On the right, some conservative websites and groups blasted the proposal as too lenient. Breitbart’s homepage was splashed with headlines about “amnesty” that portrayed Trump’s plan to eventually grant citizenship to up to 1.8 million unauthorized immigrants as a betrayal of his campaign promises. Numbers USA, an advocacy group that seeks lower immigration levels and had backed a House GOP proposal with a much narrower path to legal status for DACA recipients, rejected the White House plan outright. Some immigration hawks complained that the cuts to legal immigration, which would grandfather in existing green card applications, would not occur fast enough.
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Congressman Steve King, R-Iowa, generally considered the furthest right member of the House on immigration, declared that "illegals have no right to be here" on Twitter and accused the White House of releasing a plan that "negotiates away American sovereignty."
“I have some concerns,” Rep. Jim Jordan, R-Ohio, a member of the conservative House Freedom Caucus, told FOX News. He said the “focus” of any bill had to be on cutting immigration levels and border security and that he was wary of any deal that would tilt more toward helping DACA recipients.
Shortly before the White House plan dropped, Sen. Ted Cruz, R-Texas, reiterated his position that he would not support any path to citizenship for Dreamers, telling reporters it was “inconsistent with the promises we made to the men and women who elected us,” according to Bloomberg.
But some Republican senators who had been working on their own DACA fixes praised Trump’s plan, including Thom Tillis of North Carolina, who called it a “realistic framework,” and James Lankford of Oklahoma, who called it a “responsible solution.”
The strongest praise came from Sens. Tom Cotton, R-Ark., and David Perdue, R-Ga. The two are close allies of the White House and the plan seemed to draw on their prior legislation, the Trump-backed RAISE Act, which would reduce immigration by up to half by eliminating the diversity visa lottery and some family categories of immigration.
“We all want a good deal, and here it is,” Perdue said in a statement. ||||| WASHINGTON (Reuters) - U.S. President Donald Trump said on Friday he was willing to shift his stance on immigration to push through a deal that protects illegal immigrants brought to the country as children from deportation and offer them citizenship.
A woman protests to call for a new DREAM Act to replace DACA in Los Angeles, California U.S. January 17, 2018. REUTERS/Lucy Nicholson
In an interview with CNBC broadcast on Friday, Trump also said Republican senators who have taken a tough approach to immigration, including Tom Cotton, John Cornyn and David Perdue, could agree to the plan to offer citizenship within 10 to 12 years to so-called “Dreamers.”
“They’ve really shifted a lot, and I think they’re willing to shift more, and so am I,” the Republican president told CNBC in an interview from the World Economic Forum in Davos. “We’re going to see. If we make the right deal, I think they will.”
“These are people that have very strong opinions on DACA (the Deferred Action for Childhood Arrivals program) and on immigration generally. And I happen to think they’re largely right,” said Trump.
Senior White House officials outlined an immigration plan on Thursday, hours after the Trump interview was taped, that would offer a path to citizenship for up to 1.8 million of the illegal immigrants. The proposal includes measures to curb some legal immigration programs and provide a border wall with Mexico.
FILE PHOTO: "Dreamers", undocumented immigrants who arrived in the U.S. when they were children, stand near the double steel fence that separates the U.S and Mexico at the border in Tijuana, Mexico, during the annual pre-Christmas "Posada" celebration organised by immigrants and organisations from the U.S. and Mexico, December 16, 2017. REUTERS/ Jorge Duenes/File Photo
The White House described the offer to more than double the number of Dreamers who would be protected from deportation as a major concession aimed at attracting enough votes for an immigration deal from Democrats.
To appeal to Republicans, the plan would slash family sponsorship of immigrants, tighten border security and provide billions of dollars in funding for a border wall with Mexico, one of Trump’s signature campaign promises - and proposals that have largely failed to gain traction with Democrats before.
Trump’s framework was quickly slammed by Democrats as a non-starter. House Democratic leader Nancy Pelosi said it held Dreamers “hostage to a hateful anti-immigrant scheme” and accused the Trump administration of a campaign “to make America white again.”
FILE PHOTO: 'Dreamers' react as they meet with relatives during the 'Keep Our Dream Alive' binational meeting at a new section of the border wall on the U.S.-Mexico border in Sunland Park, U.S., December 10, 2017. REUTERS/Jose Luis Gonzalez/File Photo
The deal also was panned by both pro-immigration groups, who called the proposal a bad trade-off, and conservative groups, who criticized the expansion of “amnesty” for illegal immigrants.
Trump, who was heading back from Davos, undermined any illusions of bipartisanship by taunting Senate Democratic leader Chuck Schumer on Twitter. Earlier this week, Schumer and Democrats backed a deal to reopen the government after a weekend shutdown if Republicans agreed to take up an immigration bill protecting the Dreamers.
“DACA has been made increasingly difficult by the fact that Cryin’ Chuck Schumer took such a beating over the shutdown that he is unable to act on immigration!” Trump tweeted.
Critics said the Trump framework was not helpful to the bipartisan Senate negotiations on an immigration deal.
“It looks like President Trump has no intention of actually working on a bipartisan deal that protects Dreamers and makes sensible changes to our immigration laws. He’s trying to turn our nation against immigrants,” Democratic Senator Chris Murphy said.
Republican Senators Cotton and Perdue on Thursday praised the framework. But Representative Jim Jordan, a member of the House of Representatives conservative Freedom Caucus, said on Friday the focus of any plan must prioritize border security issues over DACA. “I have some concerns frankly. It’s all about where the focus is,” he told Fox News. ||||| "This plan flies in the face of what most Americans believe," Senate Minority Leader Chuck Schumer said via social media. | Andrew Harnik/AP Photo Schumer rejects Trump’s immigration proposal The White House plan to win over Democrats by providing citizenship for Dreamers in exchange for sharp restrictions on legal immigration isn’t working.
Senate Minority Leader Chuck Schumer opposes the immigration framework released by the White House — a potentially fatal blow for the prospective legislation in the closely divided Senate.
The New York Democrat on Friday accused President Donald Trump of using a proposed path for citizenship for young undocumented immigrants as cover for making sweeping — and damaging — changes to the legal immigration system.
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"This plan flies in the face of what most Americans believe," Schumer said on Twitter. While Trump "finally acknowledged that the Dreamers should be allowed to stay here and become citizens, he uses them as a tool to tear apart our legal immigration system and adopt the wish list that anti-immigration hard-liners have advocated for for years."
The one-page proposal released by the White House on Thursday would allow as many as 1.8 million young immigrants to become citizens, while also calling for $25 billion in spending on a border wall and security as well as sharply restricting family-based immigration and eliminating a visa lottery system. White House officials are hoping the Senate will put it up for a vote, but it appears doomed to fail.
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White House press secretary Sarah Huckabee Sanders quickly shot back, tweeting that Schumer prefers "open borders & sanctuary cities over law & order and popular, common sense reforms."
Soon after, Trump himself piled on with a personal insult aimed at Schumer.
“DACA has been made increasingly difficult by the fact that Cryin’ Chuck Schumer took such a beating over the shutdown that he is unable to act on immigration!” Trump tweeted.
Schumer's remarks further cement the Democratic opposition, leaving little clarity on how Congress will clinch an agreement to preserve expiring legal protections for the Deferred Actions for Childhood Arrivals program. House Minority Leader Nancy Pelosi called it "anti-immigrant," and Senate Minority Whip Dick Durbin (D-Ill.) said Trump's plan would institute Trump's "hard-line immigration agenda — including massive cuts to legal immigration — on the backs of these young people."
“President Trump and Republicans cannot be allowed to use Dreamers as a bargaining chip for their wish list of anti-immigrant policies," said Sen. Dianne Feinstein (D-Calif.).
A bipartisan group of senators plans to continue meeting over the next two weeks to try to strike a deal that can pass the Senate with overwhelming support, with hopes that would force the House to swallow it and Trump to sign it. But Republican and Democratic lawmakers are also meeting separately in partisan groups, making the prospects of an aisle-crossing deal murky at best given the political tensions in the Capitol following a three-day government shutdown.
In the Senate, “there’s probably 50 groups right now," said Sen. Thom Tillis (R-N.C.). "Next week could be a very pivotal point in time where we start looking at a specific baseline bill and build on it.”
Senate Majority Leader Mitch McConnell has committed to an immigration debate in February, but lawmakers have no idea where they will start. It could even be a blank bill that is constructed through the amendment process.
“The word that the majority leader used is neutral," said Sen. Jeff Merkley (D-Ore.). "I don't know if that means there’s nothing in it or it’s yet to be determined by the majority leader."
Though many Republicans have coalesced behind Trump's framework over the past day, that won't be enough to make it law. The GOP controls just 51 votes in the Senate and would need to get at least nine Democrats behind Trump's plan for it to pass, a near-impossibility given Schumer's opposition.
Still, Republicans hoped that Trump's offer to provide a pathway to citizenship to the Dreamers could unlock gridlock on Capitol Hill.
“The more information we have about what he’s thinking, the better," said Sen. Lindsey Graham (R-S.C.).
Trump's willingness to provide citizenship to undocumented immigrants has received some criticism on the right from groups like Heritage Action for America. But the plan did receive support from key conservative barometers in the Senate, including GOP Sens. Tom Cotton of Arkansas and David Perdue of Georgia.
“I appreciate the president putting forth a clear framework on immigration that includes many of my key concerns — ending chain migration and the Diversity Visa lottery, as well as increasing border security," said Sen. Jim Inhofe (R-Okla.), another border hawk, on Friday morning. | – An immigration plan touted as a "compromise" by the White House upon its release Thursday appears unlikely to become a reality as Democrats—and even many Republicans—have major problems with it. Politico reports Senate Minority Leader Chuck Schumer decried President Trump's plan "as a tool to tear apart our legal immigration system" that "flies in the face of what most Americans believe." The plan provides a path to citizenship for up to 1.8 million Dreamers but also commits $25 billion to Trump's wall and border security, severely restricts family-based immigration, gets rid of the visa lottery system, and more. House Minority Leader Nancy Pelosi calls the plan "anti-immigrant," and Sen. Dianne Feinstein says "Republicans cannot be allowed to use Dreamers as a bargaining chip for their wish list of anti-immigrant policies." While the White House needs nine Democratic votes in the Senate for its plan to pass, it's unclear it will even get full support from Republicans, who largely range from tepid on the plan to flat-out opposed, NBC News reports. Senate Majority Leader Mitch McConnell calls the plan a "framework for guidance," and House Speaker Paul Ryan says it "will help us ultimately reach a balanced solution." Meanwhile, conservative groups and websites are characterizing it as a betrayal of Trump's campaign promises on immigration by providing "amnesty" for Dreamers. Regardless, Trump said Friday he thinks Republicans will ultimately come around on his plan. “They’ve really shifted a lot, and I think they’re willing to shift more, and so am I,” Reuters quotes the president as saying. |
it is now generally accepted that the universe is currently undergoing a period of accelerated expansion . the most popular approach to modeling
the current epoch is to postulate a new energy component of the universe , dark energy , which has negative pressure and hence drives the acceleration .
possible dark energy candidates include the cosmological constant @xcite , which has well known fine tuning issues , quintessence fields ( see for example @xcite and references therein ) and elastic dark energy @xcite .
an alternative approach is to modify the theory of gravity , and there have been a number of attempts to construct late time accelerating solutions to the gravitational field equations by modifying gravity at large distances / late times .
one such class of models are found by considering a gravitational action that contains an arbitrary function @xmath0 of the ricci scalar . the first modified gravity model to be considered introduced quadratic terms into the gravitational action @xcite .
such models can give rise to early - time inflationary solutions to the gravitational field equations , where the hubble parameter is initially @xmath1 , and slowly rolls towards a stable minkowski vacuum state .
modified gravity models which yield late - time acceleration have been considered recently .
an important example is the cddtt model @xcite , for which @xmath2 .
this function has a de - sitter vacuum solution to the field equations , which might be associated with the current epoch of the universe with a suitable tuning of the mass scale @xmath3 .
however , it has been shown that this model can not satisfy local gravity constraints @xcite , and also has an instability @xcite .
in addition to the cddtt model , a number of modified gravity functions have been proposed which give rise to late time acceleration @xcite , and some progress has been made in understanding general properties of these models , for example the behaviour of metric perturbations @xcite and the cosmological evolution of generic @xmath0 functions @xcite have been considered .
any @xmath0 model must satisfy certain conditions in order to exclude the possibility of ghost degrees of freedom and other instabilities .
these conditions are @xmath4 , which ensures that there are no ghost degrees of freedom in the model , and @xmath5 , which prevents instabilities from arising in the early universe @xcite .
it seems also sensible to impose @xmath6 , which ensures that there is no cosmological constant , and @xmath7 for large @xmath8 , since we want any modification to gravity to only become significant at late times .
in addition to these conditions , it has been shown that if a standard matter era ( for which @xmath9 ) is to be a fixed point then further conditions must be satisfied @xcite .
recently , a number of models have been studied in the literature which satisfy the above constraints , at least for @xmath10 .
specifically the following functions have been considered @xcite , @xmath11 , \end{aligned}\ ] ] where @xmath12 is the current vacuum curvature of the universe , @xmath13 are dimensionless constants , and @xmath14 . in ref.@xcite , the @xmath15
is defined differently to ( @xmath16 ) , and in ref.@xcite the precise formula was slightly different to ( @xmath16 ) . however , both models considered in @xcite have the same expansion in the limit @xmath17 , which will be the important point in this paper .
the model @xmath18 represents a modification to general relativity that is a power law in @xmath8 , whilst @xmath19 contains exponential corrections .
these models both have late - time accelerating epochs , and can satisfy local tests of gravity .
they can also satisfy the conditions discussed in ref.@xcite .
although the models ( @xmath16,@xmath20 ) possess many desirable features , an additional issue has arisen recently with regards to their suitability as viable gravitational models @xcite .
specifically , it has been suggested that if we look for solutions to the gravitational field equations that are perturbations around known general relativistic solutions , then the ricci scalar oscillates over very short timescales , and the amplitude of these oscillations will increase without bound to the past @xcite . if true , this presents us with a number of issues , amongst which are that the small perturbation will become much larger than the general relativistic solution at some time in the past , violating the perturbative assumption , and @xmath8 will become negative at some finite time .
such phenomena would most likely lead to significant problems in reproducing the standard cosmology .
the aim of this paper is to study the two models ( @xmath16,@xmath20 ) in detail .
we find that since @xmath8 oscillates over such small timescales , the linearized analysis presented in refs.@xcite will not necessarily yield a solution that is indicative of the full solution for all times .
we then solve the gravitational field equations numerically and semi - analytically and show that the ricci scalar undergoes asymmetric oscillations , and will drift away from the general relativistic limit .
we note that non - linear oscillations have been considered in @xmath0 models previously , see ref.@xcite .
in this section we consider the modified gravity action @xmath21 which yields the following field equations @xmath22 f'(r ) = { t_{\mu\nu } \over m_{\rm pl}^{2 } } , \ ] ] @xmath23 where primes denote differentiation with respect to @xmath8 , @xmath24 is the energy momentum tensor and @xmath25 is the reduced planck mass . the hss and ab models can be expanded as @xmath26 for @xmath27 , where @xmath12 acts as a small ` cosmological constant ' ( although there is no true constant in these models since globally @xmath6 ) .
@xmath28 , @xmath29 and @xmath30 are all small functions of @xmath8 , in the sense that the dimensionless parameters @xmath31 , @xmath29 and @xmath32 all satisfy @xmath33 , @xmath34 and @xmath35 for @xmath36 . for the hss and ab models , we have @xmath37 where @xmath12 is the current vacuum curvature of the universe , and @xmath38 and @xmath39 are parameters that are smaller than @xmath12
. these expansions are valid for @xmath40 and @xmath41 for the hss and ab models respectively . for the rest of this paper
, we will drop the subscripts @xmath42 and @xmath43 , and use @xmath44 or @xmath45 and @xmath46 or @xmath47 , which should be obvious in context .
we will explicitly state which model is being studied in each section .
finally , we note that we will frequently make use of the notation @xmath48 , which is the general relativistic solution to the field equations @xmath49 .
in particular during the matter era we have @xmath50 , and during the radiation era @xmath51 .
in this section , we review the perturbative analysis that has been used in refs.@xcite to derive approximate solutions to the gravitational field equations for the ab and hss models .
the full field equations are a set of non - linear , fourth order differential equations for the scale factor , and solving these equations directly is difficult ( although see for example ref.@xcite for an attempt to do so for the cddtt model ) . the approach taken in this section is to look for solutions to the field equations that are perturbations around known general relativistic solutions , that is we look for a solution to ( @xmath52 ) of the form @xmath53 , where @xmath54 is some small perturbation .
this approach involves linearizing the equation in @xmath55 . in doing so
, the following expansions are used @xmath56 in which case ( @xmath52 ) becomes @xmath57 to linear order in @xmath55 . unless otherwise stated , in ( @xmath58 ) and for the remainder of this paper @xmath59 is taken to be a function of @xmath48 only , @xmath60 .
the function @xmath61 is @xmath62 which is a function of @xmath48 only and is small .
the field equation ( @xmath58 ) is an inhomogeneous , second order differential equation for @xmath55 .
the solution is the linear sum of a particular solution to ( @xmath58 ) and the solution to the homogeneous equation @xmath63 which can be written approximately as @xmath64 where @xmath65 is the scale factor . in ref.@xcite , a solution to ( @xmath66 ) was derived for the hss model .
using @xmath46 and @xmath44 , the equation for @xmath55 reads @xmath67 a wkb solution can obtained for the matter era , @xmath68 , \ ] ] and for the radiation era @xmath69 , \ ] ] where @xmath70 are constants .
we have solved equation ( @xmath71 ) numerically , and @xmath72 is shown in fig.[fig:1 ] , taking a pure matter era as an example , so @xmath50 .
we have used time coordinates such that @xmath73 , and have chosen @xmath74 and @xmath75 .
we have evolved backwards in the time coordinate , over the range @xmath76 , using the initial conditions @xmath77 , @xmath78 , where @xmath79 . by solving equation ( @xmath71 ) numerically , we have found that @xmath55 oscillates symmetrically around zero , confirming the behaviour expected from the wkb solutions .
however , in fig.[fig:1 ] we have not exhibited the actual oscillations of @xmath8 explicitly , since they are of too high frequency to be resolved , and so have only presented @xmath48 and the upper and lower envelopes of the oscillations . from fig.[fig:1
] , we see that the lower envelope appears to have a turning point , indicating that in this approach after this time the oscillatory component @xmath55 will come to dominate over @xmath48 , and hence the ricci scalar will become negative at some point in the past . in refs .
@xcite , a similar analysis has been considered for the model @xmath80 .
if we use @xmath47 in ( @xmath66 ) , we find the following equation @xmath81 which has the wkb solution @xmath82 , \ ] ] during the matter era and @xmath83,\ ] ] for the radiation era , where @xmath84 are constants .
we have solved equation ( @xmath85 ) numerically , taking @xmath50 , using time coordinates with @xmath86 and choosing @xmath87 .
the resulting @xmath88 is shown in fig.[fig:2 ] , using the initial conditions @xmath89 , @xmath90 over the time range @xmath91 .
once again , we have shown only the envelopes of the oscillations of @xmath8 .
these solutions exhibit similar oscillatory and growing behaviour as found for the hss model . using this approach for both the hss and ab models ,
we find similar behaviour for @xmath8 .
specifically , @xmath55 undergoes rapid oscillations , and both the amplitude and frequency of these oscillations increases to the past .
since the amplitude of @xmath55 grows without bound as @xmath92 , it follows that @xmath55 will violate the condition @xmath93 at some point in the past , at which point the perturbative analysis will break down . beyond this
, we can not assume that @xmath88 is a solution to the gravitational field equations .
this oscillatory behaviour presents us with a number of problems .
the first is that since @xmath55 grows to the past , it will eventually satisfy @xmath94 . beyond this point
, @xmath8 will periodically be negative , and when @xmath8 is negative we can no longer use the expansion @xmath95 .
this is a problem particularly relevant for the hss model , since for @xmath96 there will be a point at which @xmath97 , which is a singular point in the field equations . the second problem associated with the oscillatory behaviour of @xmath55
is that the frequency grows to the past without bound .
it has been pointed out in ref.@xcite that this issue can be ameliorated by introducing an additional term @xmath98 into the action , where @xmath99 is a mass scale .
this will provide a cut off in the frequency growth at @xmath100 .
+ + +
in this section , we first show that the above linearized analysis is only valid over a very limited range of @xmath8 , and that the gravitational field equations are generically non - linear . to see this , we first write ( @xmath52 ) as @xmath101 where we have expanded the function @xmath95 , and neglected the term @xmath102 .
both of these assumptions are acceptable if we consider a regime where @xmath36 . in section [ sec : am1 ] , we linearized this equation in @xmath55 , and in doing so we neglected the term @xmath103 , which was assumed to be second order .
however , since @xmath55 oscillates with high frequency @xmath104 , it follows that the term @xmath105 will not remain small , since it will grow like @xmath106 to the past .
hence the accuracy of the above linearized analysis will begin to reduce when @xmath103 is of the same order as @xmath107 . beyond this point , we can no longer use the linearized equation for @xmath55 , and we must include these non - linear terms . for the ab model , we can explicitly show the range of @xmath55 over which the linearized analysis is valid . to see this , we consider the expansions ( @xmath108-@xmath109 ) . as an example , we take @xmath110 , which was expanded as @xmath111 . for the ab model
this reads @xmath112 .
we compare this to our actual function @xmath113 , given by @xmath114 , and we see that the expansion of @xmath115 is only valid in the very limited range @xmath116 . once this condition is violated , we can no longer use the linearized equation ( @xmath58 ) for @xmath55 . since in general we will have @xmath117 , then it follows that the linearized analysis will break down for the ab model long before @xmath118 .
the above reasoning suggests that although the linearized analysis successfully predicts the oscillatory behaviour of these models , we can only trust the solution for a limited range of @xmath8 , and beyond this the field equation for @xmath8 is inherently non - linear .
we conclude that we can not find a solution to ( @xmath52 ) for which @xmath119 for all @xmath8 . therefore in this section
, we do not consider solutions to the field equations that are perturbations around the general relativistic ricci scalar , but rather look for full numerical solutions to ( @xmath52 ) .
however , it is not just a second order differential equation for @xmath8 , but rather a fourth order non - linear equation for the scale factor @xmath65
. therefore we will treat ( @xmath52 ) , @xmath120 and @xmath121 as a set of coupled non - linear differential equations for @xmath8 , @xmath122 and @xmath123 .
we stress that we are not making the assumption that @xmath124 , and the only assumption that we will make is that during the matter era @xmath125 .
we do so because we wish to compare the full numerical results obtained here with the results of the linearized analysis of the section [ sec : am1 ] , where the vacuum curvature was neglected .
we have checked that introducing the vacuum curvature does not significantly effect our results , since we can absorb it into the energy momentum tensor .
we look for solutions to these equations for two sets of initial conditions .
first we perturb @xmath8 initially from its general relativistic limit , and compare the full numerical solution to the linearized analysis of the previous section .
we then set the initial conditions such that @xmath8 , @xmath123 and @xmath122 are initially exactly their general relativistic values , and observe how the hss and ab models evolve backwards through the matter era .
for the hss model , using the example of a pure matter era for which @xmath126 , we find @xmath127 together with the equations for @xmath122 and @xmath123 . the trace of the energy - momentum tensor @xmath128 is related to @xmath123 and @xmath122 through the conservation equation @xmath129 .
specifically , during the matter era we have @xmath130 . to derive ( @xmath131 ) from ( @xmath52 ) , we have used @xmath132 in ( @xmath133 ) .
the only assumptions made are that @xmath134 and that ignoring the @xmath12 term will not significantly effect our results , which is valid throughout our numerical calculation .
it is clear that @xmath135 is not a solution of these equations , and hence the hss model will not exactly mimic general relativity .
as we will see , even if we set the initial conditions such that @xmath8 , @xmath122 and @xmath123 are initially equal to their general relativistic values , if we evolve this model backwards in time then they will deviate from @xmath49 .
we have solved the coupled differential equations ( @xmath131 ) , @xmath120 and @xmath121 numerically over the range @xmath76 , taking @xmath75 , @xmath73 and @xmath136 as before .
we have found that we can only evolve the ricci scalar over a small range of @xmath137 . as we will see in the next section , this is because the ricci scalar will generically evolve to a singularity at some finite point in the past .
for now , we will ignore this singular behaviour and solve ( @xmath131 ) for @xmath8 over a small dynamical range .
the ricci scalar , obtained using a stiff differential equation solver , is shown in fig.[fig:3 ] .
here we have chosen the initial conditions @xmath138 , @xmath139 , @xmath140 , and @xmath141 , where @xmath142 , and evolved backwards in the time coordinate .
these initial conditions are the same as those chosen in the previous section , so that we can compare the full solution found here to the solution found using the linearized approximation @xmath88 . in fig.[fig:3 ] , we have exhibited the envelope of the oscillations of the ricci scalar , and the general relativistic solution @xmath48 . from the envelope functions , we see asymmetric oscillations of @xmath8 about @xmath48 .
we note that the solution obtained in this section is significantly different to the one obtained in the linearized analysis , shown in fig.[fig:1 ] .
specifically , in fig.[fig:3 ] we find that there is no turning point in the lower envelope in the time range considered .
conversely , we find that the upper envelope function increases at a faster rate than predicted in the linearized analysis .
we have also plotted @xmath143 for this model in fig.[fig:4 ] , which is the fractional difference between the hubble parameter @xmath122 for the hss model and the general relativistic hubble parameter during the matter era , @xmath144 .
we see that @xmath145 oscillates asymmetrically and not exactly around its general relativistic limit @xmath146 .
the amplitude of these asymmetric oscillations is highly suppressed but increasing to the past , and unless @xmath147 is chosen to be sufficiently small these oscillations may come to dominate @xmath122 . for the scale factor ,
we have again plotted the fractional difference @xmath148 in figs.[fig:5 ] and [ fig:6 ] , and we see that @xmath123 deviates from the general relativistic scale factor , but this deviation @xmath149 is highly suppressed .
however , as with the hubble parameter , @xmath149 grows to the past , and hence may become significant at some earlier time .
having solved the system of equations for @xmath8 , @xmath122 and @xmath123 by perturbing @xmath8 initially from the general relativistic limit , we now solve with no initial perturbation , that is we take the initial conditions @xmath150 , @xmath139 , @xmath140 , and @xmath141 , where @xmath151 . the solution to equation ( @xmath131 ) is shown in figs.3(a - d )
. again we have taken @xmath152 , @xmath73 and evolved over the time regime @xmath153 .
we see that @xmath8 oscillates , and @xmath122 and @xmath123 deviate from their general relativistic values .
however , once again @xmath149 and @xmath154 are suppressed , and this model closely mimics general relativity over this range of time . we can perform similar calculations for the ab model .
taking once again @xmath50 as a specific example , we find @xmath155 we obtain ( @xmath156 ) by using @xmath47 in equation ( @xmath133 ) . we have solved this equation numerically , along with the equations for @xmath122 and @xmath123 , using the same differential equation solver as for the hss model , taking @xmath157 and using the initial conditions @xmath158 , @xmath159 , @xmath140 and @xmath141 . as in section
[ sec : am1 ] , for the ab model we only solve equation ( @xmath156 ) over the very small time range @xmath91 , due to the presence of a singularity . by solving ( @xmath156 ) over this limited dynamical range , we find asymmetric oscillations of @xmath8 , @xmath122 and @xmath123 .
the envelope of the oscillations of @xmath8 are shown in fig.[fig:11 ] .
once again , we see no turning point in the lower envelope , suggesting that @xmath8 does not become negative for these models .
we also observe that the upper envelope grows faster than predicted by the linear analysis .
the hubble parameter and scale factor undergo asymmetric , suppressed oscillations which grow to the past , as seen in figs.4(b - d ) .
we also solve equation ( @xmath156 ) without perturbing @xmath8 , @xmath122 and @xmath123 from their general relativistic limits initially , and evolving the system backwards over the same time regime @xmath91 .
the results are shown in figs.5(a - d ) .
we find that @xmath8 oscillates , and @xmath143 and @xmath148 grow , indicating that @xmath123 and @xmath122 both diverge from their general relativistic limits .
however , this divergence is highly suppressed , as was found in the hss model .
so far , we have considered two approaches to solving the modified gravitational field equations .
it has been found that the linearized approach , in which the ansatz @xmath88 with @xmath93 is used in ( @xmath52 ) , will not give a solution that is indicative of the full solution , since non - linear terms can not be neglected due to the rapid oscillations of the ricci scalar .
the second approach considered was to solve the full gravitational field equations numerically .
in doing so , it was found that the ricci scalar undergoes non - linear oscillations , very closely ( but not exactly ) about its general relativistic limit .
however , we found that solving the gravitational field equations over significant timescales is impossible due to some kind of singularity at a finite time . in this section , we consider neither a linearized analysis nor a full numerical study of the field equations . instead , under sensible assumptions
, we show that the trace of the gravitational field equations for both the ab and hss models reduces to a non - linear wave equation , and hence that @xmath8 undergoes asymmetric oscillations about its general relativistic limit , in agreement with the results of section [ sec : s10 ] .
moreover we find that there is a singularity in @xmath8 at a finite time in both models .
since the approach taken is model specific , we consider the ab and hss models separately .
we begin by substituting @xmath47 into ( @xmath52 ) , giving @xmath160 next , we define @xmath161 , so @xmath162 and ( @xmath163 ) becomes @xmath164 where we have assumed that @xmath165 and hence neglected the vacuum energy .
next , by defining @xmath166 , we can write ( @xmath167 ) as @xmath168 to solve this equation , we write it as @xmath169 @xmath170 if we now introduce the fast time coordinate @xmath171 which is the timescale associated with the oscillations of the ricci scalar , then we can write ( @xmath172 ) as @xmath173 where primes denote derivatives with respect to @xmath174 , and we have defined @xmath175 .
if we solve equation ( @xmath176 ) for @xmath177 , then we can deduce @xmath8 from the relation @xmath178 note that ( @xmath179 ) is of the form @xmath180 , however we have not assumed that @xmath181 to deduce this expression .
if we now define @xmath182 , then we can write ( @xmath176 ) as @xmath183 + \ ] ] @xmath184 equation ( @xmath185 ) is a non - linear , second order inhomogeneous differential equation for @xmath186 , and the full solution is the sum of the particular solution to ( @xmath185 ) and the solution to the corresponding homogeneous equation given by setting the right hand side to zero .
@xmath187 is now the general relativistic limit , but it is clear that this is not an exact solution . we will find that @xmath186 undergoes asymmetric oscillations governed by the homogeneous equation , around the particular solution of ( @xmath185 ) .
we now calculate the oscillatory and drift components of @xmath186 .
we begin by calculating the drift of @xmath186 away from @xmath187 .
to do so , we make the assumption that the derivative terms @xmath188 and @xmath189 in ( @xmath185 ) are subdominant and hence can be neglected . with this assumption , ( @xmath185 ) reduces to an algebraic equation for @xmath186 , @xmath190 + \epsilon e^{t/\epsilon m_{\rm pl}^{2}}(1+x ) \log ( 1+x)\ ] ] @xmath191 if we assume that @xmath192 , then by expanding @xmath193 in ( @xmath194 ) we find the following expression for @xmath186 , @xmath195 \right ) .\ ] ] this solution is valid if we only consider terms linear in @xmath186 , that is we consider terms of order @xmath196 only .
taking the derivative of @xmath186 , we find that @xmath189 and @xmath188 are given by @xmath197 since @xmath189 and @xmath188 are much smaller than @xmath186 ( they are suppressed by a factor of @xmath198 and @xmath199 relative to @xmath186 respectively ) , then it follows that our original assumption that we can neglect derivative terms of @xmath186 in ( @xmath185 ) is valid , and ( @xmath200 ) is an approximate solution to ( @xmath185 )
. the solution to the homogeneous equation , obtained by setting the left hand side of ( @xmath185 ) to zero , will give the oscillatory component of @xmath186 and hence @xmath8 .
we will first show that the last two terms on the left hand side of ( @xmath200 ) , are highly suppressed , and hence can be neglected for @xmath201 .
to do so , we write @xmath202 , @xmath203 and @xmath204 in terms of @xmath137 , @xmath205 and the corresponding homogeneous equation to ( @xmath200 ) can be approximately written as @xmath206 + \epsilon e^{t/\epsilon m_{\rm pl}^{2}}\log ( 1+x ) = 0 .\ ] ] we see that the last two terms on the left hand side of ( @xmath207 ) have a common factor of @xmath199 and hence can be neglected .
we arrive at the following equation for @xmath186 , @xmath208 where @xmath209 is a small function of @xmath174 . in ( @xmath210 )
, we will assume that @xmath211 and @xmath212 , since the oscillations of @xmath122 and @xmath123 are suppressed by a factor of @xmath213 and can therefore be neglected . with this assumption , ( @xmath210 )
reduces to an equation purely in terms of @xmath186 and its derivatives .
equation ( @xmath210 ) describes an anharmonic , non - linear oscillator with a small negative damping term , and hence we have shown analytically that the ricci scalar will undergo asymmetric oscillations , in agreement with the results of section [ sec : s10 ] .
we henceforth describe the oscillator considered here as the logarithmic oscillator .
the potential @xmath214 for the logarithmic and simple harmonic oscillators are shown in figs.6(a , c ) .
the logarithmic potential will give rise to wave solutions that are not symmetric . before continuing
, we observe that if we expand @xmath8 as @xmath88 for @xmath215 , then @xmath186 can be expanded as @xmath216 , and ( @xmath210 ) becomes @xmath217 if we write ( @xmath218 ) in terms of @xmath137 , then it reduces to the linearized equation ( @xmath85 ) .
we have solved the non - linear equation ( @xmath210 ) numerically , using the initial conditions @xmath219 , @xmath220 , and evolved over the range @xmath221 .
this range of @xmath174 and choice of initial conditions are the same as were chosen in section [ sec : s10 ] , where the full gravitational field equations were solved numerically . in fig.@xmath222(a ) , we compare the ricci scalar @xmath223 obtained in this section to that found by solving the full gravitational field equations numerically in section [ sec : s10 ] .
it is clear that the results obtained in this section closely mimic the full numerical solution . in fig.@xmath222(b ) we compare @xmath224 to @xmath225 , where @xmath8 is the ricci scalar obtained by solving the full gravitational field equations numerically .
we see that the fractional difference between @xmath55 and @xmath226 remains small throughout the dynamical range considered . using this approach ,
we have found that we can only evolve @xmath186 and hence @xmath8 backwards in the time coordinate @xmath137 over the same limited dynamical range as in section [ sec : s10 ] .
however , by solving equation ( @xmath210 ) we can see why this is the case .
in fig.[fig : l26 ] , we have perturbed @xmath186 from @xmath187 and evolved backwards in the @xmath174 coordinate .
we see that the amplitude of the oscillations of @xmath186 increase due to the presence of the damping term in ( @xmath210 ) , and after a finite time @xmath227 .
since @xmath228 and @xmath229 , then it follows that both @xmath8 and @xmath230 will be singular at this point .
we conclude that wide ranges of initial conditions @xmath231 and @xmath232 will give rise to a singularity in the field equations as we evolve backwards in time .
that is not to say that all initial conditions will lead to this problem , and there exists an extremely restricted range of @xmath231 and @xmath232 at the beginning of the matter era that will not give rise to singular behaviour at some finite time in the past . instead of evolving backwards over the matter era ,
if we choose @xmath231 appropriately at the beginning of the matter era and evolve forwards in time , @xmath186 ( and hence @xmath8 ) will be well behaved and regular . to find the allowed initial conditions
, we can first use the fact that @xmath233 is the lower bound . to obtain an upper bound ,
we assume that the damping term in ( @xmath210 ) is negligible and consider @xmath234 this expression can be multiplied by @xmath189 and integrated to obtain the following expression , @xmath235 = e , \ ] ] where @xmath236 is a constant of integration .
the values of @xmath186 at the peaks and troughs of its wavetrain can be obtained from ( @xmath237 ) by setting @xmath238 and solving the algebraic equation @xmath239 .\ ] ] for a given @xmath236 , there will be two solutions for @xmath186 , corresponding to the maxima and minima of the wave .
we have deduced that @xmath240 is the minimum value that @xmath186 can take in order to avoid singularities , and substituting this into ( @xmath241 ) gives @xmath242 .
as we have stated , ( @xmath241 ) will yield two solutions for any particular @xmath236 , and so finding the second solution for @xmath242 will give us the maximum value of @xmath186 .
this solution is @xmath243 , and hence we conclude that in order to obtain a matter era free from singularities , we must impose the condition that @xmath244 at the beginning of the matter era . in terms of @xmath225
, this corresponds to the range @xmath245 .
since we will generically encounter a singularity if we evolve @xmath186 backwards in the time coordinate @xmath137 , we now solve equation ( @xmath210 ) by taking @xmath186 initially at some early time and evolving forwards in the @xmath174 coordinate , which corresponds to evolving forwards in the standard time coordinate @xmath137 .
in doing so , @xmath186 and hence @xmath8 will remain regular .
we take as initial conditions @xmath246 , @xmath247 and evolve over the range @xmath248 . by solving ( @xmath210 ) , we obtain @xmath249 , which is the oscillatory component of @xmath186 . the full solution to ( @xmath185 )
is approximately given by @xmath250 , where @xmath251 is the drift term given in ( @xmath200 ) .
in fig.[fig : fg9](a - d ) we compare @xmath226 to @xmath55 .
we see that there are two competing effects ; the non - linear oscillations , which are initially large but quickly decay , and the drift away from @xmath252 , which grows as we evolve forwards in the time coordinate .
the approximate solution obtained in this section closely mimics the full numerical solution .
however , the predicted drift begins to deviate from the full solution at late times .
however , this only occurs when the approximation @xmath201 is no longer valid . as an aside
, we conclude this section by considering a constant energy momentum tensor , that is we take @xmath253 . for this ricci scalar , we have @xmath254 , @xmath255 and @xmath256 .
using these in ( @xmath176 ) , we obtain the following equation for @xmath177 , @xmath257 the case of constant @xmath48 was discussed in ref.@xcite using the perturbative analysis of section [ sec : am1 ] , and it was found that the ricci scalar contained an exponentially growing component , suggesting an instability in this model . here , we solve ( @xmath258 ) for @xmath177 and obtain the ricci scalar from @xmath259 .
the solution is presented in figs.[fig : f7](a - b ) , where we have taken @xmath260 , @xmath73 , @xmath261 and evolved over the time regime @xmath262 .
we see that @xmath8 undergoes damped , rapid oscillations about its general relativistic limit .
we find no exponential growth , contrary to the claim made in ref.@xcite . in this section , we consider a similar calculation to that presented above , but now for the hss model .
we first re - write the trace of the gravitational field equations in terms of a dimensionless function and a fast time coordinate .
we then derive approximate expressions to describe the oscillations and drift of the ricci scalar away from its general relativistic limit .
we begin by substituting @xmath132 into ( @xmath52 ) , which gives @xmath263 where we have neglected the term @xmath12 . to transform equation ( @xmath264 ) into an oscillator equation
, we must make a series of field redefinitions . by first defining @xmath265
we write ( @xmath264 ) as @xmath266 + { n+1
\over 3n}{t \over m_{\rm pl}^{2}}\alpha
u^{2n/(2n+1)}\approx 0 .\ ] ] next , by introducing a fast time coordinate @xmath267 and defining @xmath268 , we can write ( @xmath269 ) in terms of @xmath270 and @xmath174 as @xmath271 @xmath272 where primes denote differentiation with respect to @xmath174 , and @xmath175 .
this is a non - linear , inhomogeneous second order differential equation for @xmath186 , and by solving for @xmath186 we obtain the ricci scalar from the relation @xmath273 .
as before , we can deduce both the oscillatory component of @xmath8 and the drift away from @xmath48 .
we now take as a specific example a pure matter era and set @xmath75 , in which case
we can write @xmath274 and @xmath275 . we also make the assumption that @xmath276 , which implies that @xmath277 where we have neglected the third term on the left hand side of ( @xmath278 ) , which is negligible . as in the ab model , an approximate expression for the drift can be found by solving the full inhomogeneous equation ( @xmath279 ) .
we take as an ansatz @xmath280 with this choice , @xmath189 and @xmath188 are of order @xmath281 and @xmath282 , and hence the derivative terms in ( @xmath279 ) can be neglected if we only consider terms of order @xmath283 . as a result
, it reduces to an algebraic expression for @xmath186 , which is solved by ( @xmath284 ) ( this can be verified by direct substitution ) .
having calculated the drift by solving ( @xmath279 ) , the oscillatory component of @xmath186 can be obtained by neglecting the last term on the right hand side of ( @xmath279 ) ( since it is of order @xmath285 ) , and solving the equation @xmath286 this equation describes the non - linear oscillations of @xmath186 around @xmath187 , that is around the general relativistic limit @xmath287 .
we have solved equation ( @xmath288 ) , using the initial conditions @xmath289 , @xmath247 , over the range @xmath290 and taking @xmath136 , and the results are exhibited in fig.(@xmath291 ) .
we compare the ricci scalar obtained in this section , given by @xmath292 , to the ricci scalar found in section [ sec : s10 ] , and find that they are in close agreement . as in the ab model , by using this method we find that we can only evolve @xmath186 backwards over a very limited dynamical range , and this is once again due to the presence of a singularity . in fig.@xmath293 , we see that as we evolve @xmath186 , after a finite time @xmath227 , and since @xmath292 , we find that as @xmath227 , @xmath294 .
this singularity arises due to the initial conditions that we have imposed . as in the ab model , to evade this singularity we will instead choose initial conditions at an early time and evolve forwards through the matter era . by doing so , @xmath186 will remain regular throughout . to find the initial conditions that @xmath186 may take in order to evade this singularity , we perform the same steps as in the ab model . we first observe that @xmath295 is a lower bound , and the upper bound can be obtained from the expression @xmath296 where
we have neglected the damping term and terms of order @xmath285 in ( @xmath288 ) . by substituting @xmath227 , we find that @xmath297 , and hence the upper bound for @xmath231 is found by solving ( @xmath298 ) for @xmath242 . doing so , we arrive at @xmath299 , which for @xmath75 is given by @xmath300 . in terms of @xmath292
, this corresponds to the choice @xmath301 at the beginning of the matter era . with this in mind
, we now solve ( @xmath288 ) by evolving forwards in the fast time coordinate @xmath174 , which corresponds to evolving forwards in the @xmath137 coordinate .
we solve ( @xmath288 ) over the range @xmath302 , with initial conditions @xmath303 and @xmath247 . by solving ( @xmath288 )
we obtain the oscillatory component @xmath249 of @xmath186 , and hence @xmath304 , where @xmath251 is given in ( @xmath284 ) . in fig.([fig : fg11 ] ) we compare @xmath186 obtained in this section to @xmath305 , where @xmath8 is the ricci scalar obtained solving the full field equations numerically . as in the ab model , there are two effects ; the non - linear oscillations of @xmath186 ( and hence @xmath8 ) which decay as we evolve forwards in time , and a drift in @xmath186 away from its general relativistic limit @xmath187 .
it is clear that the approximate solution obtained in this section closely mimics the full solution of section [ sec : s10 ] .
in section [ sec:2 ] , we have calculated the ricci scalar for the hss and ab models , and have found that it will undergo non - linear oscillations and will drift away from the general relativistic limit @xmath135 as one goes back in time . from the ricci scalar
we can now calculate the hubble parameter for the two models , using @xmath306 .
we look for a solution of the form @xmath307 , where @xmath308 .
a solution of this form must exist in order for these models be viable ; they must have a matter era for which @xmath309 for example , in order for normal structure formation to take place .
linearizing in @xmath154 , we find the following expression @xmath310 next , by using the time coordinate @xmath174 , where @xmath311 , we obtain @xmath312 where @xmath313 is the general relativistic scale factor .
this expression can be integrated to obtain @xmath154 , @xmath314 where @xmath315 is a constant of integration , and we have taken the slowly varying factor @xmath316 outside the integral , which is a good approximation for @xmath317 . we see that @xmath154 contains two terms ; one describing the oscillations of @xmath122 due to @xmath55 , and a term that goes like @xmath318 .
the oscillatory component is suppressed by a factor of @xmath319 , and hence the oscillations of @xmath8 will not have a significant impact on the hubble parameter .
we note in obtaining @xmath154 , we have not had to specify either @xmath55 or @xmath174 , and hence ( @xmath320 ) is valid for any model for which @xmath321 , including the hss and ab models . in a similar manner , we can also consider the scale factor . by writing @xmath322 and expanding as @xmath323
, we have at linear order @xmath324 next , by introducing the fast time coordinate @xmath174 , we write ( @xmath325 ) as @xmath326 and by using ( @xmath320 ) and integrating , we arrive at the following approximate expression for @xmath149 , @xmath327 where @xmath328 is a constant of integration .
@xmath149 possesses an oscillatory term due to the rapid oscillations of @xmath55 , which is suppressed by a factor of @xmath329 .
we conclude that the rapid oscillations of the ricci scalar has no significant impact on the scale factor for models in which @xmath321 .
in this paper we have solved the gravitational field equations for the hss and ab models numerically and by using an alternative perturbative analysis .
we have shown that the oscillations of the ricci scalar are inherently non - linear , although they can be modeled as linear waves in a certain regime . however , for the ab model this linear regime is particularly restricted .
rather than using the earlier perturbative analysis , we have re - written the trace of the gravitational field equations as a damped , driven , non - linear oscillator . by solving this new equation ,
we have found that the ricci scalar does indeed oscillate with high frequency , as predicted in ref.@xcite . as the amplitude and frequency of these waves grow to the past
, we see non - linear behaviour becoming increasingly important .
we have also found that the ricci scalar does not exactly oscillate around its general relativistic limit , but rather there is a highly suppressed drift .
in section [ sec : s10 ] , we solved the full gravitational field equations for both models numerically . by specifying the initial conditions at late times and evolving backwards
, we observed that in general the ricci scalar would evolve to a singularity after a finite time .
this is another important consequence of the non - linear terms in the field equations , since no such behaviour was observed when using the linearized approach . by using our oscillator equation
, we were able to explain why this singularity occurs , and found that it can be avoided by choosing initial conditions at some early time and evolving forwards .
we were able to derive the allowed initial conditions for both the ab and hss models .
we have found that although the singularity could potentially be evaded with a suitable choice of initial conditions , the resulting ricci scalar is likely to be unstable to perturbations away from a perfect matter era . to obtain a viable modified gravity model ,
it is clear that some method of regularizing this singularity is required .
finally , we have considered the effect of the oscillations of @xmath8 on the hubble parameter and scale factor .
we have found that the oscillatory components of @xmath122 and @xmath123 are suppressed by factors of @xmath319 and @xmath330 respectively , where @xmath331 .
we have concluded that @xmath154 and @xmath149 will remain small , in spite of the potentially large oscillations of @xmath8 .
this conclusion is generic to models which have @xmath332 .
although we studied specifically the hss and ab models in this paper , we believe that many of the results obtained are generic to @xmath0 theories of gravity which satisfy @xmath332 .
we expect that the procedure adopted in section [ sec:2 ] , that is writing the trace of the gravitational field equations as a non - linear oscillator equation , will generalize to all models for which @xmath332 , and if that is the case then the singularity encountered in this paper will be a common feature of @xmath0 models .
sa is supported by a stfc studentship .
we would like to thank a. starobinsky for helpful comments on an earlier draft of the paper . during the preparation of this manuscript we became aware that a. frolov has arrived at similar conclusions @xcite . | we study cosmological expansion in f(r ) gravity using the trace of the field equations .
high frequency oscillations in the ricci scalar , whose amplitude increases as one evolves backward in time , have been predicted in recent works .
we show that the approximations used to derive this result very quickly breakdown in any realistic model due to the non - linear nature of the underlying problem . using a combination of numerical and semi - analytic techniques
, we study a range of models which are otherwise devoid of known pathologies .
we find that high frequency asymmetric oscillations and a singularity at finite time appear to be present for a wide range of initial conditions .
we show that this singularity can be avoided with a certain range of initial conditions , which we find by evolving the models forwards in time .
in addition we show that the oscillations in the ricci scalar are highly suppressed in the hubble parameter and scale factor . |
african swine fever ( asf ) is a highly fatal disease of domestic pigs and can cause mortality of up to 100% of affected pigs .
the disease is caused by double - stranded dna virus with an icosahedral symmetry that belongs to genus asfivirus and family asfarviridae . since its first description in kenya in the early 1920s ,
the disease has been reported in several countries around the world , remaining endemic in sardinia , and in 2007 outbreaks was reported in georgia , russia , and neighbouring countries .
the epidemiology of asf is complex , transmission is direct and vector - borne , and the disease has well - recognized sylvatic and domestic cycles . in sub - saharan africa , asfv is maintained by long - term , inapparent infection of wildlife hosts such as bush pigs ( potamochoerus porcus ) and warthogs ( phacochoerus africanus ) which are infected via tick bites of the argasid tick vector ( ornithodoros complex ) .
asf is highly contagious and is transmitted by direct contact between infected pigs and susceptible ones or by contact with or ingestion of infectious secretions / excretions .
the virus is highly resistant in tissues and the environment , contributing to its transmission over long distances through swill feeding and fomites ( e.g. , contaminated material , vehicles , or visitors to pig premises ) . in subacute cases pigs
chronically , survivors are characterized by emaciation , stunted growth , hemorrhagic necrosis of the skin overlying bony protuberances , followed by abscessation , and deep ulceration .
acute disease caused by the virus is characterized by high fever , hemorrhages in the reticuloendothelial system , and high morbidity and mortality rates with consequent economic losses . unlike domestic swine , asfv infections of wild swine are asymptomatic with low viraemia titers .
the wild swine and soft ticks of the genus ornithodoros act as a virus reservoir .
this large natural reservoir of virus poses a constant threat to domestic pig populations worldwide .
pig farming is one of the fastest growing livestock activities in the rural areas of uganda and has become very attractive through the country as a means of increasing food , but income and employment have on several occasions been hampered by asf .
according to reports , uganda has the largest and fastest growing pig production in eastern africa with the pig population standing at 3.2 million .
but asf is an economically important and frequently lethal disease of domestic pigs which has hampered the development of the pig industry .
the aim of the study was to elucidate the patterns of asf outbreaks in uganda based on the spatial and temporal retrospective data retrieved from monthly reports from district veterinary officers ( dvos ) to the central administration at the ministry of agriculture , animal industry and fisheries ( maaif ) for the years spanning 20012012 to give an insight in the epidemiology of the disease in uganda .
retrospective data on asf outbreaks in uganda during 20012012 were retrieved from maaif , uganda .
the information was based on the monthly asf disease surveillance reports from the dvos . for the period considered under this study , uganda had a differing number of districts ( 80120 ) .
the lowest administrative units reporting asf outbreaks in uganda are districts , and , in this work , these were used as epidemiological units of asf outbreaks and classified as adjacent to the national park(s ) and international border(s ) .
the national parks considered in this study included : queen elizabeth national park ( qenp ) , lake mburo national park ( lmnp ) , murchison falls national park ( mfnp ) , kidepo valley national park ( kvnp ) , rwenzori mountains national park ( rmnp ) , kibale national park ( kinp ) , mount elgon national park ( menp ) , bwindi impenetrable national park ( binp ) , mgahinga gorilla national park ( mgnp ) , and semuliki national park ( snp ) .
rainfall values and the seasons for the different months , districts , and years ( 20012008 ) were obtained from the meteorological department , ministry of energy , water and mineral resources , uganda . for convenience of data handling and presentation , seven geographical regions , which in most cases vary by rainfall , agroecology , and farming production systems , were considered .
the months of the year were categorized as having below average rainfall ( dry season ) , above average rainfall ( wet season ) , and average rainfall ( neither wet nor dry season ) based on long term mean monthly rainfall over the period 20012008 . a nonparametric test ( kruskal - wallis rank test ) was used to assess the effect of season on asf ( stata 12.0 ) .
arcgis ( version 10 ) was used to plot the district distribution of asf outbreaks ( 20012012 ) .
semistructured questionnaires on the occurrence of asf outbreaks and the perception of risk factors and characteristics of these outbreaks were administered to the dvos in their respective districts .
questions included whether there are cases of pig deaths or sickness , percentage of the pig population affected , rating of asf as an important disease , seasons when incidence is most frequent , and actions taken to control asf .
questions were answered by ticking prewritten choices , whilst additional information was supplied in the extra spaces provided .
opinions and data were collected , entered into excel 2010 , summarized , coded , and analyzed .
perceived risk factors were scored on a likert scale and categorized as less or not important ( below 25% ) , important ( 26100% ) , or not applicable so as to estimate the corresponding odds ratios ( ors ) as described previously .
both descriptive statistics ( contingency tables ) and inferential statistics such as confidence interval for odds ratio were computed so as to quantify the major reason for pig movement in the area .
the regional monthly reports of asf outbreaks from districts during the years 20012012 are summarized in table 1 .
the total number of districts which reported asf was 59 with a total of 388 outbreaks .
the number of reported asf outbreaks was highest ( 68 ) in 2011 and lowest ( 6 ) in 2009 .
more outbreaks were reported during the months of february ( 43 ) , march ( 42 ) , june ( 40 ) , and january ( 38 ) than during the remaining months of the year .
the months of october ( 19 ) , may ( 20 ) , and september ( 26 ) had the lowest number of outbreaks reported . in the districts and regions
where rainfall data were available ( table 2 ) , it was apparent that the occurrence of asf was significantly associated with dry season ( p = 0.01 ) , when mean monthly rainfall ( mm ) was below average and the times when animal movement are more frequent .
the central region reported the highest number of asf outbreaks ( 181 ) followed by the eastern ( 100 ) , northern ( 60 ) , western ( 23 ) , southwestern ( 12 ) , and west nile ( 12 ) .
however , there was no asf outbreak reported in the northeastern region throughout the period covered by the study .
it should be noted that outbreaks were sporadic in the southwest and west nile regions throughout the study period .
a total of 201 outbreaks were reported in districts adjacent to the national parks representing 51.8% of the total outbreaks reported during the period ( 20012012 ) as summarized in table 4 .
uganda is landlocked and shares borders with southern sudan ( 435 km ) on the northern side , democratic republic of congo ( drc , 765 km ) on the western side , tanzania ( 396 km ) and rwanda ( 169 km ) on the southern side , and kenya ( 933 km ) on the eastern side ( figure 1 ) .
the total number of districts adjacent to the international borders reporting asf outbreaks was 18 .
eighty ( 20.6% ) asf outbreaks occurred in 18 districts along the international borders compared to 308 outbreaks that occurred in districts that did not share an international border .
the number of asf outbreaks varied between the different international borders , the highest being adjacent with drc ( 31 outbreaks in eight districts ) and tanzania borders ( 26 outbreaks in 2 districts ) while only 3 districts bordering kenya reported 13 outbreaks .
the lowest number of asf outbreaks was reported among the districts bordering rwanda ( one outbreak in one district ) and southern sudan ( 9 outbreaks in 4 districts ) .
opinions among the dvos about the characteristics of occurrence and control of asf in uganda are summarized in table 5 . in
all the 29 districts visited , all the dvos reported that farmers valued pigs in their areas and that pig farming ranked third in relation to all the other livestock .
asf was ranked as the second most important disease of pigs after helminthiasis . when faced with problems of pig health ,
all dvos reported that they diagnose by use of clinical signs , and only 15 combined the use of clinical signs and laboratory testing .
it was however established that the majority of laboratory testing is done at the national disease diagnostics and epidemiological center in entebbe with few sending samples to the college of veterinary medicine , makerere university .
twenty - five ( 86.2% ) and 22 ( 75.9% ) of the dvos reported that the source of asf outbreaks was as a result of pig movements due to trade ( odds ratio or 15.5 , confidence interval ci 4.949.1 ) and pig restocking ( odds ratio or 6.6 , confidence interval ci 2.517.3 ) , respectively .
however , the majority of the dvos blamed a neighbouring district as a source of their own outbreaks . only 2 dvos attributed the outbreaks to wild pigs
. only 1 dvo ( kasese ) reported a source of a former outbreak as from a neighbouring country ( drc ) .
this study aimed at elucidating the patterns of african swine fever outbreaks in uganda based on the spatial and temporal retrospective data retrieved from monthly reports from dvos .
the study also aimed at describing the perceptions of dvos on the characteristics of asf outbreaks in their areas by use of a questionnaire .
our research findings have proved that asf is endemic in uganda since throughout the study period asf was reported .
a report by the oie has also indicated that asf is an endemic disease in uganda .
the distribution of asf outbreaks showed no specific patterns ; however , there was a significant difference in the regions on reported asf outbreaks with the central region being the most affected ( 181 outbreaks ) , and yet it has the highest pig population .
this could be the reason leading to a surge in movement of pigs by traders from most parts of the country to the central region , hence the highest number of outbreaks .
the eastern region reported 100 outbreaks followed by northern ( 60 ) and western ( 23 ) with southwestern and west nile reporting only 12 outbreaks each .
. this difference could be partly because of the proximity to the central administration at maaif , methods used in reporting , misdiagnosis , the different husbandry practices , and vigilance in disease control , animal movements , distribution of pig markets , and other virus transmission dynamics . in the north - eastern region the majority of the population being majorly pastoralists could be the reason that no asf was reported in that region .
more so , the north - eastern region has the lowest number of pigs and the lowest region household average in uganda . in the present study
, there was a tendency to a seasonal pattern with higher frequency of asf outbreaks reported during the months with lower or without rainfall .
rainfall distribution in uganda has been shown to follow 14 distinct climate zones , which often span beyond the administrative partitions .
an exact analysis of time - specific rainfall data from a smaller number of districts confirmed that outbreaks were more common during the dry season compared to the parts of the year with average and above average rainfall ( normal and wet season ) .
the spatial and temporal patterns of asf outbreaks indicate that the virus can survive during periods without reports of asf outbreaks .
this could be partly because of underreporting or most importantly due to the transmission dynamics of the virus .
the spreading of the infection through introduction of infected pigs , either during the incubation period or by persistently infected pigs , has been described as one of the most important transmission routes .
in addition , the fact that the virus is spread through both the sylvatic and the domestic cycles could be a reason for the observed patterns of outbreaks .
the sylvatic cycle involves wild species of swine spreading the virus by soft ticks of the genus ornithodoros .
in africa the major host for the asf virus is the warthog , but all wild species of swine in africa can be silent carriers . the ornithodoros ticks can survive for a long time and can harbour the virus for several years with only a gradual decrease of infectivity . in commercial farms it is unlikely for the domestic pigs to come in contact with wild pigs and their ticks , but this is considered more common in traditional free - ranging systems .
a previous study carried out in mubende district located in central uganda suggested that free ranging and tethering could have an influence on the occurrence of asf outbreaks . in uganda asfv
has been detected in the wild suids and in ornithodoros ticks in rakai district , and in the same study eight pcr - positive pigs were found with no known clinical disease . in the intermediate cycle asfv has been found in ticks collected in pig stys that have been empty of pigs for four years .
the domestic cycle involves domestic pigs spreading the virus to other domestic pigs through direct or indirect contact . in the infected domestic pig
the virus is shed in enormous amounts in all bodily secretions and excretions , tissues , and blood 24 to 48 hours before clinical symptoms are shown .
transmission through direct contact can occur up to 30 days after infection , whereas blood is infective for eight weeks and in putrefied blood as long as 15 weeks .
meat from infected pigs or contaminated pork products is another important source of infection due to the virus 's long persistence in tissues .
the virus has been found in lymphoid tissues in domestic pigs for up to three
recovered pigs might remain persistently infected for 6 months and during this time act as a source of transmission to susceptible pigs .
in addition , symptomatic carrier animals play an important role in the persistence and dissemination of the disease in endemic areas . in a recent study conducted in gulu district in northern uganda ,
it was found out that in most rural areas , local slaughter places are small and poorly equipped and waste is directly accessible to other animals such as dogs or roaming pigs and that many pig owners sell their pigs as soon as they suspect asf among them .
this could be one of the major modes of transmission and sources of outbreaks in other rural areas of uganda . in this study ,
a total of 201 outbreaks were reported in districts adjacent to the national parks representing 51.8% of the total outbreaks reported during the study period ( 20012012 ) with some national parks being more involved than others .
this emphasizes the role of the wild suids in the epidemiology of asf in uganda .
however , the results of this study can not conclude on the dynamics of transfer of asfv between domestic pigs and wild suids in uganda .
eighty asf outbreaks were reported in 18 districts along the international borders compared to 308 outbreaks reported in districts that did not share an international border . the number of asf outbreaks varied between the different international borders , the highest being adjacent with drc ( 31 outbreaks in eight districts ) and tanzania borders ( 26 outbreaks in 2 districts ) . though the occurrence of asf does not entirely depend on proximity to international borders
, it is important to consider control of cross - border movements in the animal disease control programme in uganda .
the authors think that the porous nature along the two borders and the geography of the eastern part of the drc could be the cause of uncontrolled animal movements , hence the observed high number of asf outbreaks .
a recent study has reported a genetic similarity in asf disease outbreaks in uganda and kenya in 2003 , 2006 , and 2007 emphasizing the role of cross - border animal movements in the epidemiology of asf .
the perceptions of the dvos on risk factors were highly suggestive that trade and restocking were the most important risk factors for the occurrence of asf outbreaks .
a combination of findings from the spatial and temporal studies and dvo - based analysis of risk factors and characteristics of asf outbreaks in uganda indicates that the risk is highest during the dry season .
this could be as a result of lack of or limited feed resources by the farmers that lead to the sale of pigs or even due to the dynamics of pig movement in search of feeds .
twenty - seven of the 29 dvos that responded reported that the asf outbreaks in their districts originated from a neighbouring district indicating the role of animal movement in disease spread .
furthermore , this could probably be due to pig farmers ' and traders ' failure to adhere to quarantine measures when instituted during asf outbreaks .
one dvo ( kasese ) reported the source of a previous outbreak to be across the border ( drc ) .
this could be due to the porous nature of the border and lack of vigilance to enforce animal movement control .
this could justify the high number of outbreaks along the drc border compared to other international borders during the study .
the authors affirm that with regard to the validity of the data presented in this paper , the dvos are well trained and experienced in animal disease surveillance and control measures , and it is highly likely that the information obtained through extracts from the regular reports to the central administration at maaif and through the questionnaire is too reliable .
this study has found out that pig movement in the form of trade and restocking is an important factor in the transmission of asf in uganda .
more detailed and systematic studies should be undertaken to investigate further other specific risk factors and patterns of occurrence of asf in uganda . | african swine fever ( asf ) is a contagious viral disease , which can cause up to 100% mortality among domestic pigs . in uganda
there is paucity of information on the epidemiology of the disease , hence a study was carried out to elucidate the patterns of asf outbreaks .
spatial and temporal analyses were performed with data collected monthly by the district veterinary officers ( dvos ) and sent to the central administration at maaif from 2001 to 2012 . additionally , risk factors and the associated characteristics related to the disease were assessed based on semistructured questionnaires sent to the dvos .
a total of 388 asf outbreaks were reported in 59 districts . of these outbreaks , 201 ( 51.8% )
were reported in districts adjacent to the national parks while 80 ( 20.6% ) were adjacent to international borders .
the number of reported asf outbreaks changed over time and by geographical regions ; however , no outbreak was reported in the north - eastern region .
asf was ranked as second most important disease of pigs , and it occurred mostly during the dry season ( p = 0.01 ) .
pig movements due to trade ( or 15.5 , ci 4.949.1 ) and restocking ( or 6.6 , ci 2.517.3 ) were the major risk factors .
asf control strategies should focus on limiting pig movements in uganda . |
the metabolic syndrome refers to a group of symptoms including obesity , high blood pressure , insulin resistance , and hyperlipidemia , in which the role of central obesity is critical [ 1 , 2 ] . the increased prevalence of obesity in both industrialized and developing countries is associated with a surge in the preponderance of metabolic syndrome . in north america ,
55% of 97 million adults are either overweight or obese ( with a body mass index ( bmi ) 25 ) . in a study of 12363 us men and women using the national cholesterol education program adult treatment panel iii guidelines ,
the metabolic syndrome was diagnosed in 22.8% and 22.6% of the men and women , respectively .
the metabolic syndrome can be present in different forms , according to the combination of the various components of the syndrome , and it is well established that the metabolic syndrome increases the risk for the development of cardiovascular disease , type ii diabetes , and cancer [ 57 ] .
it is not yet known how the metabolic syndrome is triggered or how the different components are causally linked , but insulin resistance is strongly suspected as a common pathophysiologic link [ 8 , 9 ] .
it is clear that there is a positive correlation between body weight and insulin resistance ; moreover , the risk of developing all the metabolic abnormalities is strongly associated with insulin resistance .
dramatic increases in the prevalence of obesity during the second half of the last century have squarely placed adipose tissue at the center of scientific interest .
this tissue now is not considered only as passive reservoir for storing excess energy substrates . instead
, adipose tissue is currently regarded as a highly metabolically active tissue that secretes many cytokines .
adipose tissue - derived cytokines or adipokines are involved in regulation of many vital processes such as energy metabolism , inflammation , and atherosclerosis .
thus , increased levels of adipokines and proinflammatory cytokines , such as tnf- , have prominent roles in the pathogenesis of the metabolic syndrome .
many studies confirm that the presence of the metabolic syndrome or any of its components correlates with the levels of adipokines .
several studies have established an inverse relationship between the amount of physical activity and proinflammatory cytokines in obesity , diabetes , and the metabolic syndrome .
many believe that the beneficial effect of exercise is partly mediated through changes in the adipokines profile , that is , by increasing anti - inflammatory cytokines and decreasing proinflammatory ones [ 1113 ] .
this effect has been described at the levels of gene expression , protein ligands , and receptor bindings .
for instance , exercise increases insulin sensitivity through reduction of resting levels of tnf- and crp and augmentation of adiponectin levels .
this review summarizes some of the recent findings on the role of adipokines in obesity and the metabolic syndrome and how exercise may affect these changes .
unfortunately , there are not enough data available for most of the adipokines ; thus , we selected adiponectin , leptin , tnf- , and il-6 as there is a reasonable amount of data on exercise induced changes on the profile of these adipokines .
human adiponectin consists of 244 amino acids and has a distinct domain structure with a collagen - like and a globular c1q - like domain ( similar to the complement component c1q ) .
this adipokine circulates in the blood in at least three homomeric complexes : trimer ( low - molecular weight form , lmw ) , hexamer ( medium molecular weight form , mmw ) , and higher order multimers ( high molecular weight form , hmw ) [ 16 , 17 ] .
plasma concentrations reveal a sexual dimorphism , with females having higher levels than males . the hmw form may be the most biologically active form regulating glucose homeostasis [ 19 , 20 ] .
although some studies show that the hmw form has a greater association with cardiovascular diseases , it has similar utility for the identification of insulin resistance and metabolic disturbances as does total adiponectin .
as opposed to other adipocytokines , plasma levels of adiponectin inversely correlates with body mass index ( bmi ) , intra - abdominal fat , and indices of insulin resistance .
plasma levels of adiponectin decrease with weight gain and are increased by weight loss [ 24 , 25 ] .
many studies suggest that adiponectin is an important regulator of insulin sensitivity and glucose homeostasis , with several reports confirming an inverse relationship between insulin resistance and type ii diabetes with plasma adiponectin levels [ 2629 ] .
it decreases hepatic glucose production and improves glucose uptake and fatty acid oxidation in skeletal muscles [ 30 , 31 ] .
adiponectin stimulates insulin secretion in vivo while hypoadiponectinemia is associated with beta cell dysfunction [ 33 , 34 ] .
other studies show that adiponectin has anti - inflammatory effects , such as inhibition of endothelial nuclear factor kappa b ( nf-b ) , suppression of phagocytic activity , and tnf- production in macrophages [ 26 , 35 , 36 ] .
it also reduces the progression of atherosclerosis by decreasing the expression of adhesion molecules , reducing proliferation of vascular smooth muscle , and blocking transformation of macrophages to foam cells [ 37 , 38 ] . crossing adiponectin transgenic mice with leptin deficient ob / ob or apoe - deficient mice resulted in amelioration of insulin resistance , improved beta cell degranulation , increased expression of molecules involved in fatty acid oxidation , and attenuation of atherosclerosis .
, adiponectin administration enhances insulin effects , improves glucose metabolism , and increases fatty acid oxidation and weight reduction .
adiponectin exerts its function through activation of two kinds of receptors , adiponectin receptor 1 ( adipor1 ) and adiponectin receptor 2 ( adipor2 ) .
adipor1 receptors are found in different tissues and are connected to activation of 5 amp - activated protein kinase ( ampk ) pathways while adipor2 receptors are mostly expressed in the liver and mainly linked to the activation of peroxisome proliferator - activated receptor alpha ( ppar- ) , reducing inflammation and oxidative stress .
adenoviral selective expression of adipor1 receptors in db / db mice leads to activation of ampk and decreased expression of gluconeogenic enzymes such as glucose-6-phosphatase and phosphoenolpyruvate carboxykinase 1 .
increased expression of enzymes regulating glucose uptake ( such as glucokinase and ppar- ) results from enhanced hepatic expression of adipor2 receptors .
conversely , disruption of these receptors reduces the activity of related pathways and leads to significant glucose intolerance and aggravation of diabetes that is accompanied by increased hepatic triglyceride , inflammation , and oxidative stress .
the adiponectin gene is located on chromosome 3q27 , which is related to type ii diabetes and the metabolic syndrome [ 43 , 44 ] .
several common genetic variations of the human adiponectin gene have been identified . however , a limited number of single nucleotide polymorphisms ( snps ) have been associated with obesity , type ii diabetes and coronary artery disease [ 43 , 4547 ] .
the accumulated evidence thus supports the idea that obesity related diseases result from an interaction between genetic and environmental causes .
since exercise reduces insulin resistance and facilitates glucose metabolism , several studies have attempted to establish a relationship between exercise , adiponectin levels ( or the expression of adiponectin receptors ) , and improvements in insulin function . however , in interpreting the findings of these experiments , it is necessary to consider the intensity and duration of the exercise protocols used and the diversity of human subjects .
overall , it would appear that acute episodes of mild or moderate exercise in healthy , lean subjects do not affect adiponectin levels [ 4850 ] .
a decrease in adiponectin levels occurs after acute strenuous rowing by young athletes ; however , longer bouts of exercise are accompanied by increased expression of adiponectin mrna levels in skeletal muscle . in case of obese individuals , jamurtas et al .
evaluated the effects of a submaximal aerobic exercise bout on adiponectin , resistin , and insulin sensitivity in nine healthy overweight males .
they found no significant correlation between assessed variables except among insulin level and insulin sensitivity ( decreased postexercise insulin levels and increases in insulin sensitivity ) .
investigated the influence of acute exercise of various intensities on changes in the concentrations of total adiponectin and adiponectin oligomers ( hmw versus combination of lmw and mmw ) in nine middle - aged abdominally obese men .
high intensity exercise decreased total adiponectin concentrations mainly by reducing lmw and mmw adiponectin levels without changing hmw adiponectin .
conversely , a recent study of plasma adiponectin levels in inactive , abdominally obese men showed that both acute and short term ( one week ) aerobic exercise training significantly increased plasma values .
chronic exercise protocols in both healthy and insulin resistant subjects also produced conflicting results in the literature , as shown in table 1 , which summarizes the results of some exercise protocols on adiponectin levels .
the hormone leptin , whose nomenclature is derived from the greek word leptos ( means thin ) , is a 16 kda protein that has a primary role in suppressing appetite and increasing energy expenditure through metabolism .
leptin is primarily made in adipose tissue and its circulating levels correlate with body fat stores .
it is also expressed in the placenta , ovaries , mammary epithelium , bone marrow , and lymphoid tissues [ 56 , 57 ] . in humans
so far , six types of receptors have been recognized for leptin ( ob - ra - ob - rf ) that are all encoded by a single gene ( lepr ) .
ob - re does not encode a transmembrane domain and is secreted and circulates in human plasma and represents the primary leptin - binding activity .
ob - ra and ob - rc have significant roles in transporting leptin across the blood brain barrier .
ob - rb is the only receptor isoform that signals by intracellular mechanisms and this receptor is scattered throughout the central nervous system ( cns ) , particularly in hypothalamus , where it regulates energy homeostasis and neuroendocrine function [ 61 , 62 ] .
obesity and metabolic derangement in db / db mice are the consequences of dysfunctional ob - rb receptors .
janus - activated kinase ( jak ) , signal transducers and activators of transcription ( stat ) , insulin receptor substrate , and the mitogen - activated protein kinase ( mapk ) pathways are important leptin intracellular signaling mechanisms .
the binding of leptin to its receptor leads to the formation of the ob - r / jak2 complex and activation of stat3 , which is phosphorylated and migrates to the nucleus presumably to affect changes in gene expression .
binding of leptin receptors to jak2 also results in jak2 autophosphorylation , which in turn phosphorylates insulin receptor substrate proteins and involvement of phosphatidyl inositol 3-kinase to activate downstream signals .
leptin is one of the best - known hormone markers for obesity and is very sensitive to levels of energy intake , particularly in energy deficient states .
two or three days of fasting lowers human plasma leptin levels even before any loss in body fat mass occurs [ 67 , 68 ] . decreased leptin levels set off a series of biological reactions , including a reduction of sympathetic nervous system activity , thyroid hormones , hypothalamic gonadotropin - releasing hormones , insulin - like growth factor i ( igf - i ) , and augmentation of growth hormone ( gh ) and adrenocorticotropic hormone ( acth ) , to reduce energy expenditure and prevent weight loss [ 6973 ] .
conversely , adequate leptin levels promote energy expenditure through different effects on the endocrine ( e.g. , growth , reproduction , and immune system ) and autonomic nervous system .
leptin deficiency in animals ( ob / ob mice ) and humans results in increased food intake , decreased energy expenditure , and infertility . in spite of the appetite - lowering effects of leptin ,
the majority of obese individuals ( except for rare cases of congenital leptin deficiency ) show hyperleptinemia .
. the precise mechanisms of leptin unresponsiveness in obese individuals are yet to be determined ; however , several mechanisms have been proposed to explain this phenomenon . using an animal study , el - haschimi et al .
suggested that leptin may be unable to reach sites of action in the hypothalamus and/or that an intracellular reduction of leptin - mediated stat signaling occurs .
increased expression of suppressor of cytokine signaling-3 ( socs-3 ) , an inhibitor of postreceptor leptin signaling that lessens most of the obrb signaling at chronically high levels of circulating leptin , is proposed as another mechanism . increased
expression of socs-3 occurs in the vastus lateralis muscle of obese individuals and diet - induced obese animals .
similarly , socs3 deficient mice are protected against the development of hyperinsulinemia and insulin resistance during high fat diet induced obesity .
these animals have increased expression of skeletal muscle insulin receptor substrate-1 ( irs-1 ) and akt phosphorylation that results in increased skeletal muscle glucose uptake . persistent chronic inflammation and increased level of tnf-
may also play a role in hyperleptinemia of obese individuals as a positive correlation has been shown between tnf- and leptin levels in both human and rodents [ 80 , 81 ] . the regulatory role of insulin and the effect of chronic hyperinsulinemia in increased leptin levels
the stimulatory effect of insulin on leptin expression and secretion has been shown [ 82 , 83 ] ; however , such studies in human being were inconclusive . because of the multifaceted role of leptin in human metabolism
acute and short - term bouts of exercise do not affect leptin levels in healthy individuals .
however , longer durations of exercise ( 60 min ) that are associated with increased energy expenditure ( 800 kcal ) can decrease leptin concentrations . in an experiment with 45 men who participated in one of three competitive exercise protocols with approximately 1400 , 5000 , and 7000 kcal energy expenditure ,
only the participants in the last two categories had reduced serum leptin levels ; prompting the authors to conclude that only prolonged endurance exercise with large energy expenditure reduces circulating serum leptin levels .
short - term exercise training ( 12 weeks ) is not associated with significant changes in leptin levels , yet there are variable reports when training courses last more than 3 months . generally speaking , those training protocols which lower adiposity will result in diminished leptin levels .
an important point of interest in measuring leptin levels is paying attention to diurnal variations in its blood levels .
kraemer et al . determined leptin levels in 15 healthy postmenopausal women at baseline , exercise , and recovery point intervals .
blood sampling with the same time intervals but without exercise was performed one month later as a control group . even though no difference was detected between two groups
they emphasized the need to account for diurnal variations in measuring leptin levels over the course of exercise trials .
diabetic patients seem to be more responsive to the leptin lowering effects of exercise , as acute and short bouts of exercise can reduce leptin levels in such patients .
reported a decrease in leptin levels after an acute episode of exercise in diabetic ( not healthy ) subjects , as measured after 6 weeks of training .
this increased sensitivity to exercise - induced lowering effect of plasma leptin levels remains in the offspring of diabetic patients .
table 2 summarizes some of the clinical trials which have studied the effects of exercise on leptin levels in different groups of people .
it is also secreted by other immunogenic cells such as cd4 lymphocytes and natural killer cells and plays major roles in cell death ( apoptosis ) , inflammation , and induction of acute phase reactants . in obese individuals ,
expression levels of the tnf gene are higher in abdominal adipose tissue compared to subcutaneous fat , and , importantly , greater tnf gene expression occurs in the adipose tissues of obese animals and humans .
for instance , in both ob / ob and diet - induced obese mice , genetic deletion of tnf- or its receptors significantly reduced insulin resistance and improved insulin signaling in muscle and adipose tissue .
also , based on a community - based cohort study , it is proposed that the prevalence of insulin resistance increases with greater levels of resistin and tnf- and is inversely related to adiponectin levels .
diabetic patients have high activity of tnf- in the plasma and skeletal muscles [ 9698 ] . at a cellular level , tnf - dependent activation of stress - related kinases
some of these stress - related kinases also promote further production of tnf , perpetuating a positive feedback mechanism for sustained tnf activity and chronic insulin resistance . targeted disruptions of genes encoding tnf or tnf receptors
on the other hand , visceral fat obesity is associated with decreased concentrations of insulin - sensitizing and anti - inflammatory adipokines . during lipolytic activity ,
more fatty acids are released from visceral adipose tissue compared to subcutaneous adipose tissue [ 102 , 103 ] , as visceral fat has a higher metabolic rate and has increased susceptibility to lipolytic enzymes .
antilipolytic activity of insulin also has a lesser influence on visceral fat ( table 3 ) .
increased tnf level induces hepatic uptake of these fatty acids in a process that is accompanied by reduced fatty acid oxidation and triglyceride export .
direct drainage of visceral fat - induced ffas through porta vein is another factor in the pathogenesis of fatty liver . indeed
it is generally believed that the chain of reactions leading to hepatocyte fatty degeneration begins with increased levels of tnf and insulin resistance , which precede fat accumulation . during hepatic insulin resistance
, hepatic glucose production is no longer downregulated by insulin , resulting in increased hepatic glucose production and stimulation of increased insulin secretion .
insulin resistance increases adipocyte lipolysis , resulting in the release of large amounts of fatty acids into the blood and exacerbation of hepatic steatosis and insulin resistance ( figure 1 ) .
tnf- also promotes the incorporation of fatty acids into diacylglycerol , which may contribute to the development of tnf- induced insulin resistance in skeletal muscle .
tnf is also a potent inducer of mitochondrial ros and increases ros production in fatty hepatocytes . in order to mitigate or reverse this chronic oxidative stress , adaptive mechanisms such as
the controlled transfer of protons can uncouple mitochondrial respiration across the inner mitochondrial membrane , thereby dissipating the proton gradient and reducing the harmful effects of ros .
the inner mitochondrial membrane uncoupling proteins play important roles in thermogenesis of brown adipose tissue and in regulating the disposal of mitochondrial ros in other tissues .
decreases in the mitochondrial membrane potential reduce atp synthesis and make cells susceptible to necrotic cell death .
these events lead to local inflammatory reactions by attracting inflammatory cells , leading to the histopathology of nonalcoholic steatohepatitis .
a large body of evidence shows an inverse relationship between plasma levels of inflammatory adipokines and the amount of physical activity . even though acute episodes of exercise might be associated with increased levels of inflammatory cytokines , exercise training reduces circulating levels of inflammatory markers , even in lean individuals .
controlling the release and activity of at least two cytokines , namely , tnf- and il-6 , could contribute to the natural protective effects of physical activity in the metabolic syndrome .
exercise confers protection against tnf- induced insulin resistance while it reduces crp , il-6 , and tnf- levels and increases anti - inflammatory substances such as il-4 and il-10 [ 115 , 116 ] .
the association between the metabolic syndrome and inflammation is well documented [ 117 , 118 ] . the reduction in tnf- by exercise may be exerted through both il-6 ( muscle - derived ) dependent and independent pathways [ 119 , 120 ] .
furthermore , exercise induced increases in epinephrine levels can also blunt the tnf- response by a poorly defined mechanism .
weight reduction through exercise ( and diet ) decreases the volume and number of adipocytes and also reduces the number of endothelial and macrophage cells that are lodged inside adipose tissue that produce proinflammatory mediators .
increased production of anti - inflammatory mediators by adipocytes and decreased hepatic production of fibrinogen and other proinflammatory mediators are other consequences of exercise - induced weight reduction .
weight loss also influences the immune system by reducing the number of mononuclear cells in the circulation ; these are important sources of proinflammatory cytokines .
the effect of exercise training on reducing the expression of tnf- in white adipose tissue has been shown in several animal studies , as well [ 123125 ] .
table 4 summarizes the results of some clinical trials that measured tnf- after exercise training in humans .
il-6 belongs to a family of cytokines that collectively have an important role in immune reactions , hematopoiesis , and metabolism .
il-6 has both pro- and anti - inflammatory effects and is classified as an adipokine as well as a myokine and causes a wide range of sometimes contradictory effects .
the physiologic nature of target cells and specific in vivo conditions are confounding factors in determining its final biological effect .
indeed , il-6 is a good example of a chemical that is able to cause cross talk amongst different tissues .
there are conflicting reports about the effect(s ) of il-6 on lipid and glucose metabolism and insulin sensitivity .
fernandez - real et al . demonstrated a positive association between il-6 concentrations and the fasting insulin resistance index in 228 healthy volunteers .
subcutaneous injections of recombinant human il-6 also increase blood glucose and glucagon levels without changes in c - peptide levels , supporting the idea that il-6 alters insulin sensitivity .
moreover , il-6 impairs insulin signaling in adipocytes and reduces insulin - dependent glucose uptake by reducing glut4 expression and irs-1
. the disturbing effect of il-6 on insulin signaling also occurs in mouse hepatocytes and human hepatocarcinoma cells .
these data collectively suggest that il-6 impairs insulin sensitivity . on the other hand , carey et al .
reported that infusion of il-6 to seven healthy males accelerated glucose removal with no effects on endogenous glucose production during a hyperinsulinemic - euglycemic clamp study .
they also reported that il-6 improved basal and insulin - stimulated glucose uptake by myocytes , an effect that was mediated by translocation of glut4 transporters to the plasma membrane .
similarly , an acute infusion of il-6 improved insulin sensitivity and glucose removal in animal studies .
one explanation for this discrepancy in the effects of il-6 effect on glucose metabolism could be the time course of il-6 elevation .
chronic elevation of il-6 levels in obese and type ii diabetics may be associated with insulin resistance , while acute transient increase can enhance insulin sensitivity . however , this speculation is not supported in an animal study in which chronic infusion ( 14 days ) of il-6 increased insulin sensitivity .
il-6 mrna is upregulated in contracting skeletal muscle , and the transcriptional rate of the il-6 gene is also markedly enhanced by exercise .
physical training augments the expression of il-6 receptors in human skeletal muscle and sensitizes them to il-6 at rest .
of interest is that connective tissue located in and around working muscles may have an additional role in the production and secretion of il-6 to the plasma .
availability of energy resources can also affect intramuscular il-6 mrna levels in response to exercise as this response is higher under glycogen depleted conditions and following prolonged and strenuous activities .
lipid turnover , lipolysis , and fat oxidation , via activation of amp - activated protein kinase are enhanced by il-6 .
this is supported by studies showing that il-6 deficient mice ( il-6/ ) develop mature onset obesity and have disturbed carbohydrate and lipid metabolism that is partly reversed by il-6 replacement .
the lipolytic effect of il-6 on fat metabolism was confirmed in two clinical studies of healthy and diabetic subjects [ 142 , 145 ] .
a recent study reported that exercise - induced increases in il-6 production could improve insulin secretion through stimulating glucagon - like peptide-1 ( glp-1 ) secretion , a hormone that induces insulin secretion .
this newly explained mechanism adds to the importance of il-6 as a mediator of cross talk between different tissues .
collectively , it can be inferred that il-6 has regulatory effects on metabolism of both adipose and muscular tissue and is a mediator of cross talk between these two compartments .
excessive production of il-6 , as an adipokine , in obesity and diabetes , has an adverse effect on glucose metabolism and insulin sensitivity .
on the other hand , as a muscle - secreted il-6 myokine , it enhances glucose disposal and lipolysis and mediates the beneficial effects of physical activity . another theory for explaining
the increased amounts of il-6 in obesity and insulin resistance states is that elevated levels of il-6 are a secondary defense response to higher amounts of tnf-. in other words , tnf- , as an important pathophysiological culprit in obesity , stimulates il-6 release . alternatively
, increased amounts of il-6 may represent a compensatory mechanism in insulin resistance conditions for maintaining glucose homeostasis .
furthermore , increased levels of il-6 may be a response to impaired il-6 signaling , which is poorly defined in many clinical studies of obesity , insulin resistance , and diabetes .
interleukin-6 ( il-6 ) is the first cytokine to be released into the circulation during exercise , and its levels increase in an exponential fashion in response to physical exertion .
exercise - induced increases in plasma il-6 correlate with the muscle mass involved in exercise activity and also with the mode , duration , and , especially , the intensity of exercise .
the infusion of recombinant human il-6 ( rhil-6 ) into human subjects simulates the exercise induced il-6 response in the prevention of endotoxin - induced increase in plasma tnf- .
il-6 inhibition of lps - induced tnf- production has also been shown in cultured human monocytes and il-6 deficient knockout mice [ 151 , 152 ] .
furthermore , il-6 stimulates the release of other anti - inflammatory cytokines including il-10 and il-1ra . these and other experiments suggest that the anti - inflammatory effects of exercise are partly mediated through increased levels of il-6 . focusing on the results of clinical trials that have measured
first , the magnitude of il-6 increment is higher after moderate to severe exercise in untrained individuals .
second , exercise decreases blood levels of il-6 in the metabolic syndrome and obese patients , while normal weight individuals experience increased levels of il-6 when it is released as a myokine .
genetic polymorphism is another confounding factor which might explain differences in exercise - induced il-6 variations .
table 5 summarizes the results of some experiments in which il-6 was part of laboratory outcomes in clinical studies .
in reviewing the information on the effects of exercise on adipokine levels ( figure 2 ) , several drawbacks hinder lining a general conclusion .
. these standards could be different among patients with various bmi levels as obese individuals may benefit more than normal - weight people from a certain level of physical activity .
the in vivo interaction between different adipokines is another point which has mostly been ignored in isolated cytokines measurements .
for instance , higher levels of adiponectin hinder the secretion of tnf- and il-6 , while tnf- negatively affects adiponectin production and enhances il-6 production .
there are also many other adipokines which yet have not been investigated in this context .
unraveling the complex physiology and relations between various adipokines can lead to a better understanding of sport physiology . | the lack of adequate physical activity and obesity created a worldwide pandemic .
obesity is characterized by the deposition of adipose tissue in various parts of the body ; it is now evident that adipose tissue also acts as an endocrine organ capable of secreting many cytokines that are though to be involved in the pathophysiology of obesity , insulin resistance , and metabolic syndrome .
adipokines , or adipose tissue - derived proteins , play a pivotal role in this scenario . increased secretion of proinflammatory adipokines leads to a chronic inflammatory state that is accompanied by insulin resistance and glucose intolerance
. lifestyle change in terms of increased physical activity and exercise is the best nonpharmacological treatment for obesity since these can reduce insulin resistance , counteract the inflammatory state , and improve the lipid profile .
there is growing evidence that exercise exerts its beneficial effects partly through alterations in the adipokine profile ; that is , exercise increases secretion of anti - inflammatory adipokines and reduces proinflammatory cytokines . in this paper
we briefly describe the pathophysiologic role of four important adipokines ( adiponectin , leptin , tnf- , and il-6 ) in the metabolic syndrome and review some of the clinical trials that monitored these adipokines as a clinical outcome before and after exercise . |
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