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living organisms produce compounds of many types via their metabolisms which are believed to adaptively shape - shift with changing environment across a long evolutionary history .
elucidation of design principles behind such complex systems is a major goal in natural science . toward this end , so far , the structure of metabolic networks has been actively investigated using network analysis from the viewpoint of statistical mechanics . as a result , striking structural properties such as scale - free ( heterogeneous ) connectivity and hierarchical organization have been revealed , and possible origins have been discussed via several models ( e.g. , reviewed in refs .
in addition to considering metabolic networks , however , it is also important to consider how metabolites are distributed among species in order to elucidate design principles of metabolisms such as adaptive mechanisms .
the metabolite distributions have the following advantages .
since living organisms have specific metabolite compositions due to metabolisms adaptively changing with respect to the environment , we can estimate environmental adaptation ( adaptive evolution ) using metabolite distributions .
moreover , they are also useful for characterizing species relationships , which are highly linked to ecological systems . in metabolite distributions ,
thus , identification of structures and construction of a theory ( model ) for evolutionary mechanisms are key challenges for a deeper understanding of metabolism .
flavonoids are especially interesting examples when considering metabolite distributions among species .
secondary metabolites including flavonoids , alkanoids , terpenoids , phenolics , and other compounds are widely observed in angiosperms , and are not essential for preserving life unlike basic metabolites such as bases , amino acids , sugars , and fatty acids ( building blocks of dna , protein , carbohydrate , and fat , respectively ) . however , secondary metabolites play additional roles aiding survival in diverse environments .
therefore , distributions of secondary metabolites are believed to be significantly different among species due to adaptation to environments , implying high species specificity @xcite . for this reason ,
secondary metabolites help us to understand environmental adaptation and adaptive evolution .
moreover , secondary metabolites , especially flavonoids , are often used as markers in chemotaxonomy , which is a taxonomic classification based on metabolite compositions of species that has been used for many years @xcite . however , taxonomic classifications using secondary metabolites at higher levels ( e.g. family and order levels ) are known to be inherently more difficult than those at lower levels ( e.g. species levels ) @xcite .
although the metabolite distribution provides important insights into metabolism as discussed above , it has not caught as much attention as metabolic networks .
this was mainly because knowledge of secondary metabolites was not widely available .
in recent years , however , the whole picture of species - flavonoid relationships has become available in the knapsack database @xcite and partly in metabolomics.jp @xcite .
we now can investigate metabolite distributions among species using these websites . in this paper , we focus on flavonoids , which are a class of secondary metabolites , and investigate metabolite distribution among species . in order to comprehensibly describe species - flavonoid relationships ,
bipartite networks are utilized .
they are useful for representing two different objects , which correspond to species and flavonoids in this case .
we first investigate degree distributions in species - flavonoid networks in several families , and show power - law distributions of the number of flavonoids in a species and the number of shared species of a flavonoid .
a simple model is next proposed for explaining a possible origin of the heterogeneous distributions ( power - law distributions ) , and it is compared to real data . furthermore , intuitive descriptions and mathematical evidence are provided for the emergence of heterogeneous distributions .
we finally mention the characteristics of well - shared ( hub ) isoflavonoids in fabaceae ( bean family ) as an example .
in addition , we discuss the possibility of more effective selection of discriminative metabolites and taxonomic classifications at higher levels by considering this heterogeneous distribution , and speculate on the evolution of flavonoid diversity .
a total of 14378 species - flavonoid pairs were downloaded from metabolomics.jp @xcite ( http://metabolomics.jp/wiki/category:fl ) , in which 4725 species and 6846 identified flavonoid structures are linked by a published journal article . in other words , only published data were utilized .
the species - flavonoid pairs are by no means comprehensive : no plant species has been ` completely ' investigated for its biosynthetic activity , and many flavonoid molecules whose descriptions have yet to be published are also thought to exist . the taxonomy ( family ) of a species was assigned according to the taxonomicon ( http://taxonomicon.taxonomy.nl ) .
we here focus on the six largest families in terms of the number of reported flavonoids : fabaceae ( bean family ) , asteraceae ( composite family ) , lamiaceae ( japanese basil family ) , rutaceae ( citrus family ) , moraceae ( mulberry family ) , and rosaceae ( rose family ) .
in particular , we can discuss in detail species - flavonoid relationships in fabaceae because this family is well researched .
flavonoids consist of backbone structures and their modifications . on the above website
, flavonoids are classified into nine groups according to their backbone structures : fl1 : chalcone , fl2 : flavanone , fl3 : flavone , fl4 : dihydroflavonol , fl5 : flavonol , fl6 : flavan , fl7 : anthocyanin , fli : isoflavonoid , fln : neoflavonoid . in order to comprehensibly
investigate the distribution of flavonoids ( metabolites ) among species , we here utilize bipartite networks ( hereinafter called _ species - flavonoid networks _ ) , which is useful for representing two different objects ( species and flavonoids in this case ) .
bipartite networks are defined as graphs having two different node sets ( species and flavonoids ) in which edges are only drawn between one node set and the other node set ( inter - connectivity ) .
note that there is no edge between nodes belonging to the same node set ( intra - connectivity ) . in the species - flavonoid networks
, an edge is drawn between a species node and a flavonoid node when the species has the flavonoid .
we show a partial species - flavonoid network for lamiaceae ( the japanese basil family ) in fig . [
fig : sample_net ] as an example .
the node degrees of species nodes ( squares ) and flavonoid nodes ( circles ) are extremely varied . in order to characterize the tendency of connectivity , we investigated frequency distributions of the node degree ( degree distribution ) in species - flavonoid networks . in bipartite networks
, we can find distributions of two types due to the two types of nodes ( species nodes and flavonoid nodes ) .
the number of edges for species nodes and flavonoid nodes correspond to the number of flavonoids in a species @xmath0 and the number of shared species of a particular flavonoid @xmath1 , respectively . as shown in fig .
[ fig : degree_dist ] , the frequency distributions of @xmath0 and @xmath1 roughly follow a power law , implying heterogeneous distribution of flavonoids among species .
that is , most flavonoids are shared by a few species ; however , a few flavonoids are conserved in many species .
most species have flavonoids of a few types ; however , a few species have flavonoids of many types .
furthermore , the heterogeneous distributions of flavonoids among species characterized by the power - law statistics are approximately conserved between family - based species - flavonoid networks , suggesting a scale - free feature . regarding the number of metabolites in a species following power - law distributions
a similar result has been additionally reported in @xcite .
this finding might provide insights into environmental adaptation and adaptive evolution because compositions of secondary metabolites including flavonoids are strongly influenced by environmental conditions . by considering heterogeneous distribution of flavonoids
, we might be able to detect useful metabolites relating to such adaptations .
in particular , the heterogeneous distribution of the number of shared species predicts that most flavonoids are important for characterizing such adaptations at a species level .
however , this finding also tells us of the difficulty in finding metabolites that reflect adaptations at higher levels ( e.g. family and order levels ) . in general ,
taxonomic classification ( characterization of living organisms ) based on secondary metabolites including flavonoids is empirically believed to be more difficult at higher levels than at lower levels ( e.g. species level ) @xcite .
this difficulty , driving from the heterogeneous distributions is that most flavonoids are species - specific .
thus , most flavonoids contribute to taxonomic classification at lower levels rather than that at higher levels . as a result
, we possibly extract overrated and/or underrated information when exhaustively considering flavonoids ( metabolites ) at higher levels .
hub flavonoids might play an essential role in characterizing biological features ( e.g. environmental adaptation ) at higher levels because of their conservation ; thus , hub flavonoids are expected to be more appropriate and beneficial markers for characterization of biological features at higher levels .
we here speculate on a possible origin of heterogeneous distributions of flavonoids ( metabolites ) among species using a simple model .
we believe that the heterogeneous distribution was acquired through evolutionary history .
the origin of heterogeneity might provide insights into the evolution of flavonoid diversity .
we consider two simple evolutionary mechanisms as follows .
( i ) new flavonoids are generated by variation of existing flavonoids . in evolutionary history , species accordingly obtain new metabolic enzymes via gene duplications @xcite and horizontal gene transfers @xcite , and the metabolic enzymes synthesize new flavonoids through modification of existing flavonoids with substituent groups and functional groups .
( ii ) flavonoid compositions of new species are inherited from those of existing ( ancestral ) species .
new species are believed to emerge by mutation of ancestral species , and they are similar to the ancestral species as a result . for this reason , there might be the above inheritance of flavonoid compositions from ancestral species to new species . with consideration for the above two mechanisms ,
we propose a simple model with two parameters @xmath2 and @xmath3 reproducing heterogeneous distributions of flavonoids among species .
our model is defined by the following procedure : \(a ) we set an initial species - flavonoid network represented as a complete bipartite graph with @xmath4 species and @xmath4 flavonoids ( fig .
[ fig : model ] a ) .
\(b ) with the probability @xmath2 , event i corresponding to the emergence of a new species occurs .
an existing species is selected at random ( fig .
[ fig : model ] b ) .
a new species emerges due to mutation of the randomly selected existing species , and the flavonoids of the existing species are inherited by the new species as their candidate flavonoids ( fig .
[ fig : model ] c ) . on considering divergence of flavonoid compositions ,
the new species finally acquires flavonoids with equal probability @xmath3 for each of the candidates ( fig .
[ fig : model ] d ) .
however , if new species accordingly have no flavonoids , then such species are neglected ( removed ) because of the observation condition ( species without flavonoids are not included in our data set ) .
in contrast to event i , event ii corresponding to the emergence of a new flavonoid occurs with the probability @xmath5 . a species - flavonoid pair is uniformly selected at random ( fig .
[ fig : model ] e ) .
then , the species receives a new flavonoid ( fig .
[ fig : model ] f ) .
\(c ) the procedure ( b ) is repeated until the number of species and the number of flavonoids are equivalent to @xmath6 and @xmath7 , respectively .
this model does not consider the loss of nodes ( extinctions ) , which is an important mechanism in evolutionary systems .
in particular , the degree distributions may become different due to such extinctions @xcite .
in species - flavonoid networks , however , this mechanism tends to be nonessential for the following reason . in plant evolution , genome doubling ( polyploidity )
is a major driving force for increasing genome size and the number of genes @xcite .
duplicated genes typically diversify in their function , and some acquire the ability to synthesize new compounds .
indeed , more than 50,000 molecular structures are elucidated in the entire plant kingdom ( mostly secondary metabolites ) @xcite , compared to a few thousand primary metabolites in higher animals .
the population of flavonoids , the representative group in plant secondary metabolites , is therefore expected to increase , indicating that we can dismiss the effect of node losses . .
( ( b ) ( d ) ) event i : the emergence of a new species .
the gray square represents a randomly selected existing species .
the black square indicates a new species emerging due to duplication of existing species .
the dashed lines are possible pairs of the new species and flavonoids .
( ( e ) ( f ) ) event ii : the emergence of a new flavonoid .
the thick edge between gray nodes corresponds to a randomly selected existing species - flavonoid pair .
the black circle is a new flavonoid . ]
our model is essentially adjusted through only one parameter @xmath3 because the parameter @xmath2 only controls the number of species and the number of flavonoids .
when we set the number of species @xmath6 and the number of flavonoids ( metabolites ) @xmath7 , the parameter @xmath2 can be estimated as @xmath8 .
the emergence of heterogeneous ( power - law ) distributions in evolving systems might be caused by ` rich - get - richer ' or preferential mechanisms : the increase of a statistic is proportional to the statistic itself @xcite .
we here explain that the model has ` rich - get - richer ' mechanisms .
we first mention the number of flavonoids in a species @xmath0 .
when event ii occurs , @xmath0 increases .
the number of flavonoids of species @xmath9 , @xmath10 , increases when a randomly selected species - flavonoid pair includes species @xmath9 .
thus , species with many flavonoids tend to be selected in such a case . as a result ,
such species acquire more flavonoids , implying a ` rich - get - richer ' mechanism .
the origin of this preferential mechanism is similar to that in the dorogovtsev - mendes - samukhin ( dms ) model @xcite .
however , our model is essentially different from the dms model because the dms model does not describe bipartite relationships .
this is mathematically described as follows .
we consider the time evolution of @xmath10 .
let @xmath11 be the total number of species - flavonoid pairs at time @xmath12 ; the probability that species @xmath9 with @xmath10 flavonoids is chosen is equivalent to @xmath13 because the pair is randomly selected .
in addition , event ii occurs with the probability @xmath5 .
therefore , the time evolution of @xmath10 is described as @xmath14 moreover , we focus on the time evolution of @xmath11
. the number of pairs @xmath11 increases in events i and ii . in the case of event
i , @xmath11 increases by @xmath15 , where @xmath16 is the number of species at time @xmath12 , because flavonoids of the randomly selected existing species are inherited by the new species with the probability @xmath3 .
note that the expected number of flavonoids of randomly selected species is @xmath17 . in the case of event
ii , @xmath11 increases by 1 .
the events i and ii occur with the probabilities @xmath2 and @xmath5 , respectively .
therefore , the time evolution of @xmath11 is written as @xmath18 since @xmath19 , the solution of this equation with the initial condition @xmath20 is @xmath21 indicating that @xmath11 is approximately proportional to time @xmath12 for large @xmath12 and relatively small @xmath3 . substituting eq .
( [ eq : approx_l ] ) into eq .
( [ eq : dn_f / dt ] ) , we have @xmath22 suggesting the preferential mechanism : the increase of @xmath10 is proportional to @xmath10 . from this equation , using the mean - field - based method @xcite , we immediately obtain the power - law distribution of @xmath0 : @xmath23 we next consider the number of shared species of a flavonoid @xmath1 .
when event i occurs , @xmath1 increases .
the number of shared species of a flavonoid @xmath9 , @xmath24 , might increase when a randomly selected species has flavonoid @xmath9 .
thus , flavonoids shared by many species tend to be selected in such a case . as a result ,
such flavonoids are shared by more species , reflecting a ` rich - get - richer ' mechanism .
the origin of this preferential mechanism is analogous to that in the duplication - divergence ( dd ) model @xcite .
however , our model is also different from the dd model in that the dd model does not describe bipartite relationships .
this is mathematically explained as follows .
we consider the time evolution of @xmath24 .
the probability that each flavonoid @xmath9 is shared by a new species is equivalent because a resulting new species obtains flavonoid @xmath9 with the probability @xmath3 when one of @xmath24 species with flavonoid @xmath9 is randomly selected .
in addition , event i occurs with the probability @xmath2 .
since @xmath25 , therefore , the time evolution of @xmath24 is described as @xmath26 implying the preferential mechanism : the increase of @xmath24 is proportional to @xmath24 .
like for @xmath0 , we immediately have the power - law distribution of @xmath1 : @xmath27 we compare frequency distributions of the number of flavonoids of a plant species @xmath0 and the number of shared species of a flavonoid @xmath1 between our model and real data .
we consider the frequency distributions obtained from the whole data set .
the parameter @xmath2 is derived from @xmath8 . since @xmath28 and @xmath29 in the actual species - flavonoid network ,
the parameter @xmath2 becomes 0.41 .
[ fig : comparison ] shows the comparison of the frequency distribution between real data and the model with @xmath30 .
the parameter @xmath3 is selected by minimizing the distributional distance ( the inset in fig . [
fig : comparison ] ) , which corresponds to the sum of tail - weighted kolmogorov - smirnov statistics ( distances ) @xcite for two distributions [ @xmath31 and @xmath32 between the predicted distributions and the empirical distributions .
[ fig : net_compari ] shows the comparison of the network structure between real data and our model . here , we chose the species - flavonoid network for rutaceae ( the citrus family ) as an example because of its reasonable size .
as shown in these figures , the model is in good agreement with real data , indicating that the two mechanisms in our model are a possible origin of the heterogeneous distribution .
the power - law statistics are conserved among families as shown in fig .
[ fig : degree_dist ] , suggesting that the evolutionary mechanisms might be universal among families . .
the green circles indicate the real frequency distribution of the number of shared species of a flavonoid @xmath1 .
the solid lines correspond to the predicted frequency distributions averaged over 100 realizations of the model with @xmath30 .
the inset shows the distributional distance between predicted distributions and empirical distributions with the parameter @xmath3 . ]
( b ) . filled squares and open circles correspond to plant species and flavonoids , respectively .
the networks are drawn by yed @xcite . ] in our model , the parameter @xmath3 means the probability that flavonoid compositions of new species , which emerge due to mutations of an existing ( ancestral ) species , are inherited from ancestral species . as above , the inheritance probability is relatively small ( @xmath30 ) , suggesting high divergence of flavonoid composition from ancestral species .
this might be because new species eventually acquire adaptive compositions of flavonoids different from those ancestral species in different environments in evolutionary history .
in particular , species habitats might be strongly reflected in the composition of secondary metabolites because such metabolites play crucial roles in survival in diverse environments .
for this reason , flavonoid compositions are expected differ between new species and ancestral species . in this manner
, our model can estimate the divergence degree of flavonoids from metabolite distributions .
in addition , our model might also be applied to wide - range metabolites among species because the emergence mechanisms , considered in the model , are possibly also similar in the case of other metabolites such as other secondary metabolites ( e.g. alkanoids , terpenoids , and phenolics ) and lipids , which are important from the viewpoints of pharmacodynamics and dietetics .
thus , we can predict that heterogeneous distributions are observed in not only flavonoids but also other metabolites . furthermore
, our model also helps to estimate the divergence degree of such metabolites .
we here investigate hubs in species - flavonoid networks .
in particular , hubs for flavonoid nodes might be key characteristics at higher levels because such flavonoids are well conserved among species at higher levels .
as an example , we focus on fabaceae ( the bean family ) , already well investigated as the source of isoflavonoids .
hubs are defined using a @xmath33-score that characterizes disagreement with an average @xcite .
if network connectivity is determined at random like in a random graph , the degree distribution approximately follows a normal distribution .
then , we can find nodes with large numbers of edges , which are hardly in agreement with the normal distribution , using the @xmath33-score .
thus , we define hubs as nodes with more than @xmath34 edges , where @xmath35 is the average number of edges over all flavonoid nodes or species nodes and @xmath36 is the standard deviation of @xmath35 .
@xmath37 is a threshold value used to determine hubs , and we set @xmath38 @xcite . fig .
[ fig : specificity ] shows the degree of specificity @xmath39 for each flavonoid class , defined as @xmath40 where @xmath41 is the ratio of flavonoid class @xmath9 in a target flavonoid set , and @xmath42 is the ratio of flavonoid class @xmath9 in the whole data set .
a positive @xmath39 indicates a discriminative flavonoid class @xmath9 . as shown in this figure
, there are significantly many isoflavonoids .
it is well known that isoflavonoids are predominantly found in fabaceae @xcite , in good agreement with the result obtained from our analysis .
the presence of dominant flavonoids is also predicted by our model .
species have many similar flavonoids due to the evolutionary mechanism : new flavonoids are generated by modification of existing ( ancestral ) flavonoids .
this result also supports the reliability of our model . in particular , the significance of isoflavonoids is clearer in the case of hub flavonoids . here , we can also observe discriminative anthocyanins .
this class of flavonoid serves as pigments in plants , and some are well conserved across many species . in fabaceae , thus , we also expect to characteristically observe anthocyanins as typified by chrysanthemin in black beans . in the case of whole flavonoids , however , anthocyanins are relatively less conspicuous , unlike the case for hub flavonoids . and the case of hub flavonoids [ the item fabaceae ( hub ) " ] are shown . ] as explained in the previous section , we have possibilities of extracting overrated and/or underrated information using whole flavonoids due to the heterogeneous distribution .
to detect higher - level - specific ( e.g. family - specific ) characters based on whole flavonoids , we need to assume the number of shared species of a flavonoid with a normal ( homogeneous ) distribution .
however , the statistics follow a power - law distribution as shown in fig .
[ fig : degree_dist ] b , indicating that the assumption is not appropriate .
therefore , we might extract more appropriate information at higher levels from hub ( well - shared ) flavonoids rather than whole flavonoids .
as an example , let us show hubs of isoflavonoids significantly more distributed within fabaceae .
table [ table : hub_flavonoid ] shows the list of the top 20 isoflavonoids in fabaceae ranked by the number of shared species .
as shown in this table , the hub flavonoids are shared among species of diverse types . in hub flavonoids ,
moreover , we find genistein and daizein , which are believed to be origins of all isoflavones @xcite .
most of the other hub flavonoids are synthesized via simple modifications of genistein and daizein .
this result might support a hypothesis from our model : hub ( well - shared ) flavonoids are ancient . [
table : hub_flavonoid ] our model has an assumption : new flavonoids are generated by modification of existing ( ancestral ) flavonoids .
if this assumption is appropriate , we can expect hub ( well - shared ) flavonoids to have relatively simple modifications . as explained in the previous section , flavonoids consist of backbone structures and their modifications .
thus , we can estimate the complexity of modification for flavonoids using their masses in the case where two flavonoids share backbone structures . in order to test this hypothesis
, we investigate correlations between masses of flavonoids and the number of shared species @xmath1 ( fig .
[ fig : mass ] ) . as an example
, we here focus on backbone structures of two types for isoflavonoids : isoflavone and isoflavan ( highly observed in fabaceae ) . as shown in this figure , there are negative correlations , implying relatively simple modification of hub flavonoids .
this result suggests validity of the assumption in the model .
in addition , this result also suggests that we can predict the number of shared species of a flavonoid using its mass .
this might be useful for detecting well - shared flavonoids . .
( a ) isoflavone ( spearman s rank correlation @xmath43 with @xmath44 ) .
( b ) isoflavan ( spearman s rank correlation @xmath45 with @xmath46 ) ]
we have found heterogeneous distributions of flavonoids among species , and this is conserved among several families : fat - tailed distributions of the number of flavonoids in a species and the number of shared species of a flavonoid . in particular
, we can extract more appropriate and beneficial flavonoid compositions with consideration for the heterogeneous distribution .
this finding might be useful for taxonomic classification and characterization of living organisms using secondary metabolites including flavonoids at higher levels .
furthermore , a simple model has been proposed for describing a possible origin of the heterogeneous distribution .
it has been shown that the ` rich - get - richer ' mechanisms inducing heterogeneous distributions are led by simple evolutionary mechanisms .
the model estimates the divergence degree of several metabolites including flavonoids , and it predicts heterogeneous distribution of such metabolites among species .
we furthermore have found relatively simple modifications of well - shared flavonoids via the model .
our model helps with understanding the evolution of metabolite diversity .
we thank j.b .
brown who kindly helped with the proofreading of this paper .
k.t . was partially supported by a research fellowship for young scientists from the japan society for the promotion of science .
the work was also supported by a grant - in - aid for scientific research on priority area
systems genomics " from the ministry of education , culture , sports , science and technology , japan . | we investigate the distribution of flavonoids , a major category of plant secondary metabolites , across species .
flavonoids are known to show high species specificity , and were once considered as chemical markers for understanding adaptive evolution and characterization of living organisms .
we investigate the distribution among species using bipartite networks , and find that two heterogeneous distributions are conserved among several families : the power - law distributions of the number of flavonoids in a species and the number of shared species of a particular flavonoid . in order to explain the possible origin of the heterogeneity , we propose a simple model with , essentially , a single parameter . as a result
, we show that two respective power - law statistics emerge from simple evolutionary mechanisms based on a multiplicative process .
these findings provide insights into the evolution of metabolite diversity and characterization of living organisms that defy genome sequence analysis for different reasons .
flavonoid , metabolism , power law , bipartite graph model , evolution 89.75.da , 89.75.hc |
there is an intricate mutual dynamical dependence between the central massive black hole ( mbh ) and the nuclear region of the host galaxy .
centres of galaxies act as resonant cavities , and the mass of the central mbh contributes to the formation and locations of the resonances @xcite,@xcite .
resonances can either halt or enhance radial gas flow , and thus can control fueling of the nucleus @xcite . among resonantly - induced features ,
nuclear spirals form naturally as a gas response to non - axisymmetry in the gravitational potential of a galaxy @xcite,@xcite .
in fact , recent high - resolution observations often find in the innermost few hundred parsecs of disc galaxies nuclear spirals @xcite,@xcite that are likely to continue inward to within a few parsecs from galaxy s centre @xcite,@xcite . because of their ubiquity , nuclear spirals were invoked as the mechanism by which material is transported to the central mbh @xcite . in this paper , i present implications of @xcite and @xcite for the diagnostic role of nuclear spirals , and i confront model predictions with the most recent observations .
nuclear spirals form naturally as morphology of waves in gas , generated by a rotating asymmetry in the galactic gravitational potential .
generation and propagation of waves is governed by dynamical resonances , whose presence and positions depend on the central mass distribution in the galaxy .
simple linear approximation enables to describe the morphology of nuclear spiral for most typical rotation curves @xcite : + @xmath0 , with a linear inner rise , reflecting solid - body rotation in the innermost parts of the galaxy , i.e. constant - density core , +
@xmath1 , same as @xmath0 but with a central mbh of mass consistent with the observed correlations ( e.g. @xcite ) , +
@xmath2 , a pure power - law , corresponding to a central density cusp . +
these three representative rotation curves are presented in the upper panels of fig.1 , while the shapes of the nuclear spirals generated by a rotating bisymmetry in the potential are shown in the lower panels of fig.1 .
if there is no central mbh , and if the rotation curve rises linearly in its innermost parts ( case @xmath0 ) , the nuclear spiral will not extend to the centre of the galaxy ( fig.1 , left column ) .
if there is a mbh in the centre ( case @xmath1 ) , the nuclear spiral extends to the centre , and it tightly winds around the central mbh ( fig.1 , central column ) . if there is a central density cusp ( case @xmath2 ) , the nuclear spiral extends to the centre , but it unwinds towards the centre ( fig.1 , right column ) .
rotation curves @xmath0 and @xmath2 appear similar , but their corresponding nuclear spirals are diametrically different .
ubiquity of nuclear spirals in galaxies may indicate that approximating the inner rise of the rotation curve by a straight line is often inadequate .
moreover , nuclear spiral tightly winding around the galactic centre may indicate the presence of a mbh there .
nuclear spirals are resonant phenomena , and they can be generated by very small departures from axial symmetry in galaxies .
aside for asymmetries in stellar distribution , other asymmetries may contribute to the overall galactic gravitational potential .
if mbhs in centres of galaxies form by merging of smaller black holes , then there should be a few black holes of mass one or two orders of magnitude smaller than that of the central ones , orbiting around the centre of a typical galaxy ( e.g. @xcite,@xcite ) .
these black holes constitute a weak perturbation in the gravitational potential , which can generate wave phenomena in gas within a disc close to the centre of a galaxy .
a single orbiting black hole about ten times less massive than the central black hole generates a three - arm spiral pattern in the central gaseous disc , with density excess in the spiral arms up to 3 - 12% ( @xcite : see fig.2 , left and central panels ) .
dusty filaments that have been discovered recently in the centres of galaxies ( e.g. @xcite,@xcite ) have luminosity lower from their surroundings by @xmath3% , therefore spiral patterns in gas generated by the most massive orbiting black holes should be detectable .
interestingly , one of the best investigated nuclear spirals in ngc 1097 ( @xcite,@xcite ) has three arms ( fig.2 , right panel ) , difficult to generate by the observed bisymmetric bar only .
mbh in circular orbit of 1 kpc radius perpendicular to the galactic plane .
darker shading represents higher density .
units on axes are in kpc .
right panel : vlt naco j - band image of the nuclear spiral in ngc 1097 after subtraction of radial intensity gradient by ellipse fitting .
the side of the box is 8 arcsec , corresponding to about 0.55 kpc . ]
in the present - day universe , 10 - 20 per cent of galaxies show nuclear activity of seyfert type .
this activity is orders of magnitude weaker than that of quasars , and internal , dynamical factors are likely to play a role in triggering it .
extensive morphological studies had no success in pointing out the mechanism that triggers the nuclear activity , but they might have focused on features on too large scales .
a typical local active galactic nucleus ( agn ) consumes about 0.01 of fuel per year ( e.g. @xcite ) , most likely coming from gas inflow .
this corresponds to about @xmath4 during its @xmath5-yr long activity .
therefore there is no need to transport gas from the outskirts of a galaxy in order to feed a local agn , but significant redistribution of gas in the innermost tens and hundreds of parsecs should be expected . in strong bar ,
the nuclear spiral has the nature of a shock in gas @xcite , which can trigger gas inflow throughout the spiral .
note however , that analogously to gas flow in the region of straight principal shocks in the bar ( e.g. @xcite,@xcite ) , not all gas in the region of nuclear spiral shows radial inflow ( fig.3 ) . in fact , most of the volume is dominated by outflow of low - density gas , but inflow of dense post - shock gas in the spiral dominates the budget .
therefore exclusive use of tracers of dense gas ( e.g. molecular emission ) can result in biased estimates of integrated radial flow of galactic gas .
right panel of fig.4 shows line - of - sight velocities expected for the standard model 8s20 of nuclear spiral from @xcite , when viewed at inclination of 60 , and after subtracting contribution of circular motion .
large streaming motions are expected , of amplitude of up to 50 .
this amplitude can only be achieved when shocks in gas are involved .
recently , the same algorithm has been applied to the kinematics of nuclear spiral in ngc 1097 observed with the integral field unit gmos on the very large telescope @xcite .
strong streaming motions of amplitude about 50 that show spiral morphology , have been observed .
_ that observation confirms presence of shocks in nuclear spirals . _ note that the modelled kinematical spiral arms do not overlap with the spiral gas morphology ( fig.4 , left panel ) .
this is because the matter distribution is point - symmetric , while the velocity vectors point - antisymmetric .
the shift between the kinematical and morphological spiral arms predicted by the models is consistent with that observed in ngc 1097 @xcite .
hydrodynamical models of nuclear spiral shocks indicate the rate of inflow in the innermost parsecs of a galaxy up to 0.03 @xcite .
this inflow is sufficient to feed luminous local agn , and the feeding can continue over long timescales .
nuclear spiral shock is less tightly wound than what the linear theory predicts , hence loosely wound spirals in the classification developed in @xcite may indicate spiral shocks .
interestingly , when in that classification one groups together grand - design nuclear spirals ( explicitly linked to shocks in bars ) and loosely wound spirals , they occur considerably more often in active than in non - active galaxies @xcite,@xcite .
hydrodynamical models of nuclear spirals presented here assume that galactic gas is a continuous medium , which can be statistically approximated by isothermal fluid
. one may expect that this approximation breaks down at scales small enough , but it is still likely to hold on 10-pc scale , because continuous dusty nuclear spiral arms extend down to within that distance from the nucleus .
perhaps this approximation is most appropriate for the dynamic interstellar medium , in which dense clouds continuously form and disperse .
the shape of nuclear spiral can serve as an indicator of the presence of a mbh in a galaxy s centre , and as an estimator of its mass .
the amplitude of the spiral can constrain asymmetries in the galaxy s potential , like orbiting remnant black holes left from the time of galaxy formation .
nuclear spirals in galaxies can either be weak density waves which can not feed the nucleus , or strong dissipative shocks , which can generate gas inflow large enough to power luminous local agn .
nuclear spiral shocks should be revealed in kinematical observations by strong streaming motions , and such motions of amplitude consistent with theoretical predictions have been recently observed .
this observation makes a sound argument in support of gas inflow in nuclear spirals , which can serve as a mechanism feeding the central mbh and leading the the agn phenomenon .
e. athanassoula : mnras * 259 * , 345 ( 1992 ) p. englmaier , i. shlosman : apj * 528 * , 677 ( 2000 ) j. etherington , w. maciejewski : mnras * 367 * , 1003 ( 2006 ) k. fathi , t. storchi - bergmann , r.a .
riffel et al : apj * 641 * , l25 ( 2006 ) r.r .
islam , j.e .
taylor , j. silk : mnras * 340 * , 647 ( 2003 ) w. maciejewski : gas dynamics in central parts of galaxies . in : _ galactic & stellar dynamics
, eas publication series vol 10 , ed by c.m .
boily et al ( edp sciences , les ilis 2003 ) pp 316 w. maciejewski : mnras * 354 * , 883 ( 2004 ) w. maciejewski : mnras * 354 * , 892 ( 2004 ) w. maciejewski , p.j .
teuben , l.s .
sparke , j.m .
stone : mnras * 329 * , 502 ( 2002 ) p. martini , m.w .
regan , j.s .
mulchaey , r.w .
pogge : apjs * 146 * , 353 ( 2003 ) p. martini , m.w .
regan , j.s .
mulchaey , r.w .
pogge : apj * 589 * , 774 ( 2003 ) b.m .
peterson : _ an introduction to active galactic nuclei _ , ( cambridge univ .
press , cambridge 1997 ) r.w .
pogge , p. martini : apj * 569 * , 624 ( 2002 ) m.a .
prieto , w. maciejewski , j. reunanen : aj * 130 * , 1472 ( 2005 ) m.w .
regan , j.s .
mulchaey : aj * 117 * , 2676 ( 1999 ) s. tremaine , k. gebhardt , r. bender et al : apj * 574 * , 740 ( 2002 ) m. volonteri , f. haardt , p. madau : apj * 582 * , 559 ( 2003 ) | recent high - resolution observations indicate that nuclear spirals are often present in the innermost few hundred parsecs of disc galaxies .
my models show that nuclear spirals form naturally as a gas response to non - axisymmetry in the gravitational potential .
some nuclear spirals take the form of spiral shocks , resulting in streaming motions in the gas , and in inflow comparable to the accretion rates needed to power local active galactic nuclei . recently streaming motions of amplitude expected from the models
have been observed in nuclear spirals , confirming the role of nuclear spirals in feeding of the central massive black holes . |
9. ‘13TH’ In her ferocious, intellectually galvanizing activist documentary, Ava DuVernay takes a hard look at race in the United States through the 13th Amendment of the Constitution. You may think you’ve heard it all before; you haven’t. [Read the review]
10. ‘FROM THE NOTEBOOK OF …’ One of the high points of this year’s New York Film Festival, this 48-minute masterwork from Robert Beavers is quite a few years old but new to me. (It was apparently finished in 1971 and reworked in 1998.) Here, Mr. Beavers considers the nature of cinema using light and shadow, various mattes and apertures — including a window spilling sun on a desk — a meditation that at times has the quality of a holy confession.
Other Loves
“Aquarius” (from Kleber Mendonça Filho); “Autumn” and “The Dreamer” (Nathaniel Dorsky); “Bagatelle II” (Jerome Hiler); “Certain Women,” especially Kristen Stewart (Kelly Reichardt); “Creepy” (Kiyoshi Kurosawa); “The Fits” (Anna Rose Holmer); “The Illinois Parables” (Deborah Stratman); “Into the Inferno” (Werner Herzog); “Jackie” and “Neruda” (Pablo Larraín); “Krisha” (Trey Edward Shults); “La La Land,” if mostly its finale (Damien Chazelle); “Loving” (Jeff Nichols); “Mountains May Depart” (Jia Zhangke); “Paterson” (Jim Jarmusch); “Sunset Song” (Terence Davies); “20th Century Women” (Mike Mills).
A. O. Scott
Last spring, with #OscarsSoWhite in the rearview mirror and Donald J. Trump’s victory on the as-yet-unglimpsed horizon, I reviewed Jeremy Saulnier’s “Green Room.” It struck me at the time as a smart, brutal, slightly contrived thriller about members of a rock band battling a gang of white-supremacist punks in the Northwest. In retrospect, though, it seems possible that this scrappy little indie (which just missed making the list below) was something more than a bit of nasty fun. Maybe it was a harbinger, an unheeded political signal amid the pop-cultural noise, a pre-emptive allegory of battles to come.
Am I reading too much into it now, or was I not paying close enough attention then? If so, I’m hardly the only one. Relevance is one of the great shibboleths of criticism, and after a real-life event as dramatic and complex as this year’s election, the temptation to seek clues and answers in works of popular art is almost overwhelming. Think pieces promising to tell us “How [insert title here] Explains Trump” popped up after Nov. 8 like mushrooms after a rainstorm, and entertainment has been mined for signs and symptoms of working-class disaffection, coastal-elitist bubble-think, fake-news gullibility and every other real and imaginary affliction of the American body politic. But cinema is better at exploring than explaining, and the screen is more like a prism or a kaleidoscope than a mirror or a window. We seldom get the news from movies.
Which is not to deny that they are useful tools for reckoning with reality. In a time of confusion, the best films can offer clarity, comfort and a salutary reminder of complexities that lie beyond the bluster and expedience of political discourse and conventional journalism. We go to the movies — and we still go quite a lot, by the way, in spite of the seductions of the couch and the streaming queue — in search of escape from reality. We’re also looking for alternative routes to the truth, for sparks of imagination that can ignite or illuminate our own thinking when it gets muddled or stale. ||||| Other Loves
“Aquarius” (from Kleber Mendonça Filho); “Autumn” and “The Dreamer” (Nathaniel Dorsky); “Bagatelle II” (Jerome Hiler); “Certain Women,” especially Kristen Stewart (Kelly Reichardt); “Creepy” (Kiyoshi Kurosawa); “The Fits” (Anna Rose Holmer); “The Illinois Parables” (Deborah Stratman); “Into the Inferno” (Werner Herzog); “Jackie” and “Neruda” (Pablo Larraín); “Krisha” (Trey Edward Shults); “La La Land,” if mostly its finale (Damien Chazelle); “Loving” (Jeff Nichols); “Mountains May Depart” (Jia Zhangke); “Paterson” (Jim Jarmusch); “Sunset Song” (Terence Davies); “20th Century Women” (Mike Mills).
A. O. Scott
Last spring, with #OscarsSoWhite in the rearview mirror and Donald J. Trump’s victory on the as-yet-unglimpsed horizon, I reviewed Jeremy Saulnier’s “Green Room.” It struck me at the time as a smart, brutal, slightly contrived thriller about members of a rock band battling a gang of white-supremacist punks in the Northwest. In retrospect, though, it seems possible that this scrappy little indie (which just missed making the list below) was something more than a bit of nasty fun. Maybe it was a harbinger, an unheeded political signal amid the pop-cultural noise, a pre-emptive allegory of battles to come.
Am I reading too much into it now, or was I not paying close enough attention then? If so, I’m hardly the only one. Relevance is one of the great shibboleths of criticism, and after a real-life event as dramatic and complex as this year’s election, the temptation to seek clues and answers in works of popular art is almost overwhelming. Think pieces promising to tell us “How [insert title here] Explains Trump” popped up after Nov. 8 like mushrooms after a rainstorm, and entertainment has been mined for signs and symptoms of working-class disaffection, coastal-elitist bubble-think, fake-news gullibility and every other real and imaginary affliction of the American body politic. But cinema is better at exploring than explaining, and the screen is more like a prism or a kaleidoscope than a mirror or a window. We seldom get the news from movies.
Which is not to deny that they are useful tools for reckoning with reality. In a time of confusion, the best films can offer clarity, comfort and a salutary reminder of complexities that lie beyond the bluster and expedience of political discourse and conventional journalism. We go to the movies — and we still go quite a lot, by the way, in spite of the seductions of the couch and the streaming queue — in search of escape from reality. We’re also looking for alternative routes to the truth, for sparks of imagination that can ignite or illuminate our own thinking when it gets muddled or stale.
The 11 releases listed below were not only my most memorable movie-watching experiences of the year; they were also, in ways I can’t always specify, helpful. They stirred my curiosity, troubled my sleep and increased the range of my understanding. Sometimes they just made me feel better. ||||| Hollywood is the world’s best money-laundering machine. It takes in huge amounts of money from the sale of mass-market commodities and cleanses some of it with the production of cinematic masterworks. Earning billions of dollars from C.G.I. comedies for children, superhero movies, sci-fi apocalypses, and other popular genres, the big studios channel some of those funds into movies by Wes Anderson, Sofia Coppola, Spike Lee, Martin Scorsese, James Gray, and other worthies. Sometimes there’s even an overlap between the two groups of movies, as when Ryan Coogler made “Creed,” or when Scorsese made the modernist horror instant-classic “Shutter Island,” or when Clint Eastwood makes just about anything.
There used to be more of an overlap, both before the age of television, when Hollywood was the only audiovisual game around, and in the age of television, when Hollywood was still the prime source of feature films. At that time—a time that has only recently passed into history—the laundering of Hollywood money took place inside Hollywood, which is how Howard Hawks, John Ford, Alfred Hitchcock, Douglas Sirk, Joseph Mankiewicz, Fritz Lang, Frank Tashlin, Jerry Lewis, Elaine May, Michael Cimino, and the other geniuses of the system were able to make their movies.
The machine is now more complex—the connection between Hollywood and the best movies is circuitous and intricate. Spike Lee’s “Chi-Raq” was produced by Amazon Studios, not by Hollywood, but its stars, technicians, facilities, distribution network, and movie theatres are Hollywood by-products. Barry Jenkins’s “Moonlight” and James Gray’s “The Lost City of Z” (coming in 2017) were produced by Plan B, the company co-founded by Jennifer Aniston, Brad Pitt, and Brad Grey; though Scorsese’s uproariously bitter comedy “The Wolf of Wall Street” was made with private financing, it was ultimately released by Paramount.
Many independent filmmakers who started out with their own money and that of friends and family are now working with Hollywood without actually being a part of it. Alex Ross Perry’s third feature, “Listen Up Philip,” starred Jason Schwartzman and Elisabeth Moss, both of whom have made their names and their livings within the system; he followed it with “Queen of Earth,” starring Moss and Katherine Waterston; and his new feature, “Golden Exits,” premièring at Sundance in January, stars Emily Browning, Analeigh Tipton, Chloë Sevigny, Mary-Louise Parker, and Lily Rabe, along with Schwartzman. Joe Swanberg’s latest round of films (“Drinking Buddies,” “Happy Christmas,” and “Digging for Fire”) has featured such actors as Anna Kendrick, Jake Johnson, Olivia Wilde, Ron Livingston, Rosemarie DeWitt, and Orlando Bloom; his forthcoming film, “Win It All,” will star Johnson and Keegan-Michael Key. Sophia Takal’s recently released drama “Always Shine” stars Mackenzie Davis and Caitlin FitzGerald. Dustin Guy Defa’s new feature, “Person to Person” (also premièring next month at Sundance), stars Michael Cera, Abbi Jacobson, Philip Baker Hall, Olivia Luccardi, and Isiah Whitlock, Jr., along with Tavi Gevinson and actors known mainly for independent films, such as Bene Coopersmith and Buddy Duress. Josephine Decker’s new film, “Movie No. 1,” stars Molly Parker and Miranda July, who, in 2011, made her film “The Future” with Hamish Linklater as her co-star.
Most of these actors make their living from Hollywood movies or television series, which frees them up to take on projects made on a very low budget. This is all to the good. Hollywood and independent filmmaking have engaged in an important division of labor: Hollywood specializes in making money, the independents specialize in making movies. Although there are still plenty of good movies produced by the studios, even at the most overtly commercial levels (“Pete’s Dragon,” “Doctor Strange,” and “Ant-Man,” for instance, are delights), and although, conversely, the mere fact of working independently on a low budget is no guarantee of artistic quality, there are many more boldly conceived and originally realized films emerging from the independent scene than from Hollywood.
This is, and should be, no surprise. My list for the best films of the year has hardly any Hollywood movies on it. I’m not sure exactly how to define the term, but I have maybe four or five major-studio releases out of thirty-five selections. It’s a commonplace to wring hands on the subject of how bad Hollywood has become, but it’s more than counterbalanced by how good independent films have become. And yet, the critic on my shoulder whispers, whereas everyone goes to the local multiplex to see studio movies, how many people ever see those independent films?
Answer: it doesn’t matter at all. What matters is what excites a viewer, what excites a critic. It’s a critic’s job to say, when necessary, that some movies being made widely available and being widely promoted—and sometimes even widely praised—are not good at all, and that some of the best movies being made might take a viewer a little work to find. It doesn’t matter that an overwhelming majority of viewers may never find many of the best movies in their local theatres—because they can find many of them streaming at home. Given the prominence of television as a presumptive artistic counterpart (or rival) to movies, there’s less reason than ever to disdain small screens at home as a primary mode of watching films.
My list sticks to films that have had what’s formally considered a theatrical release, a week-long run in New York, in 2016. Some of the best movies I’ve seen this year aren’t included solely because of the vagaries of theatrical distribution (or, rather, non-distribution), including two virtual top-ten films, “collective:unconscious” and “The Arbalest,” which were released by streaming video (the producer of the former, Dan Schoenbrun, discusses the subject at IndieWire and mentions the movie’s availability for free on a variety of sites). In all likelihood, neither film will get a regular theatrical release this year or ever—yet, by way of their streaming platforms, they’re available to far more viewers nationally than would ever be likely to catch them in a New York theatrical release. There’s also a phantom entry for the best movie of the year, the top of the list, what you might call a Movie Zero: “A Quiet Passion,” Terence Davies’s bio-pic about Emily Dickinson, which premièred at the Berlin Film Festival in February and screened at both The New Yorker Festival and the New York Film Festival in October. I thought it would get a year-end qualifying run, at least to promote Cynthia Nixon’s starring performance for awards consideration. That didn’t happen, and it’s now scheduled to be released here in March. Spoiler alert: I’d be surprised if it doesn’t top next year’s list.
The point of criticism is the long haul—as seen in the resurgence of interest in Julie Dash’s “Daughters of the Dust,” currently playing at Film Forum, where it was released twenty-five years ago. I know . . . this doesn’t do Dash any good. Her career, which should have been propelled into varied and ceaseless activity by that film, didn’t get going as it should have—or, rather, producers didn’t come forward to enable her to make another feature—and I can’t help but think that, if critics had done their jobs more astutely and more vigorously back then, things might have gone differently. Had Dash made more films, it would have been good for her, for the movies, and for the world—the world of enthusiastic moviegoers, a coterie of cinephiles. But the fact of good movies being available widely doesn’t help the world at large, and it’s an enduring critical delusion (as well as a mode of demagogy) to assume and assert that it does.
Great movies made and put into wide release by Hollywood have had no effect on anything but the experience of watching great movies, as understood by the few people who recognize the terms of their greatness. This year’s best example is “Sully.” Though
There may well be viewers who go to see an Eastwood film expecting that it will make their day, and they might choose to take the story of “Sully” as they’d prefer it to be, as the legend of an unambiguously confident American military hero. Yet that’s not what Eastwood actually presents in the movie; there’s little or nothing in the way of Trump’s personality or actions in the movie’s protagonist, but rather a great deal of Hillary Clinton’s character. This paradox shows that Eastwood-the-filmmaker is far greater and more important than Eastwood-the-talker—and that the essence of the art of cinema is for movies to surpass and even defy filmmakers’ intentions. “Sully” proved to be very popular, and very successful; it didn’t change the political landscape at all.
That’s one reason that the usual run of overtly political movies, in which the liberal consensus finds itself reflected back upon itself with confident self-satisfaction, strikes me as both an aesthetic regression and a political frivolity. The dream of restoring Hollywood filmmaking to what it once was, of Making Hollywood Great Again, is noxious nostalgia that omits the unbearable circumstances in the world at large that went hand in hand with the best of classic Hollywood, the prejudices and the exclusions on which its films depended. It’s also why fretting over the decline in the artistry of wide releases is irrelevant at best, destructive at worst. (The best movies being made now, such as “Moonlight,” could never have been made in classic Hollywood—not even close.) In 2014, Ava DuVernay made “Selma,” an excellent movie about the struggle in the nineteen-sixties for voting rights, which (outrageously) hasn’t at all stopped officials from passing new laws specifically designed to suppress the vote of black citizens.
I wonder whether this year-end glance at the world of movies would have turned out the same way had a few tens of thousands of votes in three states gone to a different candidate. Maybe the error would have been to believe that a system in which so much depended on so little (and so few) was anything but fundamentally shaky, if not terminally rotten. In any case, movies, and art over all, don’t help, can’t help, aren’t meant to help—in the short term or in specific terms. The good they do reaches deep into the marrow of the soul of a relatively few people and does so spontaneously, unexpectedly, irresistibly, decisively, and sometimes even unconsciously. The changes that the best movies wreak may not be perceptible in any reasoned public discourse close to the time of their release. But, for just that reason, these movies are all the more essential and enduring—they bring about changes in mood, tone, emotional tenor or temperature, changes in the inner life, in the inner inner life. That was also true in times that seemed better, too.
Best Movies of 2016
Best Undistributed Film
“Coma” (Sara Fattahi)
“Hermia and Helena” (Matías Piñeiro)
“Yourself and Yours” (Hong Sang-soo)
“Univitellin” (Terence Nance)
Best Director
Zach Clark
Barry Jenkins
Clint Eastwood
Maya Vitkova
Whit Stillman
Best Actress
Addison Timlin (“Little Sister”)
Agyness Deyn (“Sunset Song”)
Kate Beckinsale (“Love & Friendship”)
Samantha Robinson (“The Love Witch”)
Krisha Fairchild (“Krisha”)
Best Actor
Keith Poulson (“Little Sister”)
David Maloney (“Men Go to Battle”)
Tom Hanks (“Sully”)
Josh Brolin (“Hail, Caesar!”)
Parker Sawyers (“Southside with You”)
Best Supporting Actor
Mahershala Ali (“Moonlight”)
Tom Bennett (“Love & Friendship”)
Alden Ehrenreich (“Hail, Caesar!”)
Trevante Rhodes (“Moonlight”)
Tyler Hoechlin (“Everybody Wants Some!!”)
Aaron Eckhart (“Sully”)
Best Supporting Actress
Ellen Burstyn (“Wiener-Dog”)
Lily Gladstone (“Certain Women”)
Zoey Deutch (“Everybody Wants Some!!”)
Blake Lively (“Café Society,” Woody Allen)
Michelle Williams (“Manchester by the Sea”)
Best Ensemble Cast
“Moonlight”
“Everybody Wants Some!!”
“Wiener-Dog”
“Hidden Figures”
“Happy Hour”
“Hail, Caesar!”
“Dog Eat Dog”
Best Screenplay
“Love & Friendship”
“Moonlight”
“Manchester by the Sea”
“Happy Hour”
“Wiener-Dog”
Best Cinematography
“Moonlight”
“Men Go to Battle”
“Sully”
“No Home Movie”
“Embrace of the Serpent”
Best Editing
“Sully”
“Knight of Cups”
“Dog Eat Dog”
Best Dog
“Wiener-Dog”
“Paterson” (Jim Jarmusch)
“Krisha”
“Little Sister” | – The year's best-of lists are flooding in, and Richard Brody of the New Yorker is among those out with picks for the best movies of 2016. Here are the top 10 of the 35 he names, with the director noted: Little Sister (Zach Clark) Moonlight (Barry Jenkins) Sully (Clint Eastwood) Viktoria (Maya Vitkova) Love & Friendship (Whit Stillman) Men Go to Battle (Zachary Treitz) Wiener-Dog (Todd Solondz) Kate Plays Christine (Robert Greene) Happy Hour (Ryusuke Hamaguchi) Knight of Cups (Terrence Malick) Here are the top 10 from Manohla Dargis of the New York Times: No Home Movie (Chantal Akerman) Toni Erdmann (Maren Ade) Moonlight (Barry Jenkins) O.J.: Made in America (Ezra Edelman) My Golden Days (Arnaud Desplechin) I Am Not Your Negro (Raoul Peck) Arrival (Denis Villeneuve) The Handmaiden (Park Chan-wook) 13th (Ava DuVernay) From the Notebook of ... (Robert Beavers) Read Brody's explanation of his picks here, and Dargis' here. AO Scott and Stephen Holden also give their picks at the Times. |
maximising the cardiac output ( co ) by fluid infusion benefits patients undergoing cardiac surgery , but they may not tolerate large volume of fluid due to impaired cardiac performance . hence ,
colloids are widely used in cardiac perioperative setting , however , higher cost and potential risks of colloids are still unresolved .
hypertonic solution infusion has been shown to benefit cardiac surgery patients and was associated with a higher excretion of body fluid excess when compared with colloid infusion .
perioperative administration of lactate based hyperosmolar solutions benefited cardiac surgery patients by improving cardiac performance , oxygen delivery and inducing negative fluid balance .
lactate was suspected to contribute to these benefits as per the findings of previous studies .
we conducted this study to evaluate the effect of hyperosmolar sodium lactate ( hsl ) infusion on haemodynamics and fluid balance in comparison with 6% hydroxyethyl starch ( he s ) infusion .
this prospective , randomised , open - labelled study aimed to evaluate the efficacy and the safety of a scientifically - formulated and patent - protected hsl solution ( totilac ) , manufactured by finusolprima farma indonesia ( for innogene kalbiotech pte ltd ) compared to he s 6% ( voluven , fresenius kabi ) during coronary artery bypass grafting ( cabg ) surgery .
composition and profile of the he s 6% solution and hsl solution male and female patients , aged 18 - 75 years undergoing cabg surgery were enrolled .
we excluded the patients who needed combined operations and intra - aortic balloon pump , patients with severe arrhythmia ( ventricular tachycardia , atrial flutter with rapid response , heart block ) , the presence of severe haemodynamic imbalance , severe bleeding and/or re - operation , liver dysfunction as indicated by serum glutamic oxaloacetic transaminase and serum glutamic pyruvic transaminase > 2 times normal value ) and renal failure ( creatinine level > 180 mol / l ) .
signed informed consent was obtained from all eligible patients or the next of kin if the patient was not able to comprehend or unable to accept and sign informed consent .
patients underwent routine monitoring including 5-lead electrocardiography , radial , central venous pressure ( cvp ) , pulmonary artery ( pa ) catheters , pulse oximetry , blood , urine and temperature monitoring .
following pre - medication with intravenous midazolam ( 2.5 - 5 mg ) , anaesthesia was induced with 3 - 5 mg / kgbw propofol , titrated and adjusted based on patients haemodynamic status and clinical condition and 1 - 2 g / kgbw sufentanil . a dose of 0.1 - 0.2 mg / kgbw pancuronium bromide was administered for intubation .
anaesthesia and haemodynamic stability during surgery was maintained with continuous infusion of 1.0 - 1.5 mg / kgbw of propofol as baseline hypnosis , coupled with titration of inhalational anaesthesia agent ( sevoflurane ) .
then propofol was continued as post - operative sedation with patient warming and improvement in co. intravenous bolus of sufentanil was administered in case of poor analgesia and/or increase in blood pressure or heart rate at 30% or more .
nitroglycerin was continuously infused only for a tight indication , such as for patients with left main coronary artery occlusion or low ejection fraction ( < 40% ) with multiple coronary occlusions , or if there were any signs of revascularisation injury .
the infusion rate was modulated according to the blood pressure at 0.5 to 2 g / kgbw / h .
co / cardiac index ( ci ) , pulmonary vascular resistance ( pvr)/pulmonary vascular resistance index ( pvri ) and systemic vascular resistance ( svr)/systemic vascular resistance index ( svri ) were also measured and monitored intermittently by pa catheter to ensure that the haemodynamic status was normal during the infusion .
for cardiopulmonary bypass ( cpb ) , the extracorporeal circuit consisted of a roller pump ( sarns 8000 ) and a membrane oxygenator ( capiox sx ) .
patients were cooled to 31 - 32c and received intermittent antegrade normothermic blood cardioplegia , a mixture of 400 - 600 ml of oxygenated blood with graduated doses of potassium - magnesium solution .
standard systemic heparinisation ( 3 mg / kgbw ) was performed and an activated clotting time of greater than 480 s was maintained during cpb .
randomisation was conducted by an independent nurse and random allocation was concealed within a thick envelope .
study drug was administered by a nurse according to random allocation ; hence the investigator was blind about the treatment .
similar dose of hsl or he s solutions were administered at 3 ml / kgbw within 15 min at the beginning of surgery ( after induction and fasting fluid replacement ) .
the haemodynamic parameters were recorded on baseline and immediately after study fluid administration including heart rate ( hr ) , systolic and diastolic blood pressure , mean arterial pressure ( map ) , co , ci , cvp , pulmonary capillary wedge pressure ( pcwp ) , mean pulmonary arterial pressure , svr and pvr .
laboratory parameters including arterial ph , pao2 , paco2 , bicarbonate ( hco3 ) , haemoglobin and haematocrit levels , blood electrolytes ( sodium , potassium , chloride , magnesium ) , blood glucose and blood lactate were recorded .
intra - operative fluid input , urine output , bleeding volume and fluid balance were also measured at the end of surgery .
any adverse event during the study period was documented . sample size calculation in this study was based on the anticipated minimal difference of ci between control and treatment group ( delta value ) .
previous trials in cardiac surgery showed that hypertonic solution would result ci differences of 0.3 l / min / m compared to isotonic crystalloid solution .
based on a two - tailed t - test with 5% of significance level and assuming standard deviation of 0.4 , with 10% drop - out and power 80% , we required a total of 100 patients ( 50 in hsl group and 50 in he s group ) .
statistical assessment of haemodynamic status and laboratory parameters was carried out through repeated measures analysis of variance ( anova ) .
the within - group ( hsl vs. he s ) changes between baseline and loading dose was evaluated using anova .
all statistical analyses were performed using statistical package for the social sciences version 15 , 2006 ( spss inc . ,
one hundred patients undergoing cardiopulmonary bypass graft ( cabg ) surgery , 50 in hsl group and 50 in he s group , were enrolled in this study , however , only 98 ( 50 patients in hsl group and 48 patients in he s group ) were included for analysis .
two patients in he s group were not included in the analysis due to incomplete data ( 1 patient ) and protocol violation ( 1 patient ) .
the demographics and baseline between hsl and he s group were comparable [ table 2 ] .
baseline characteristics and intra - operative data systolic and diastolic blood pressure , map , cvp , pcwp , pvr / pvri showed similar changes between the two groups two groups ( p > 0.05 ) , while the increase of heart rate ( p = 0.024 ) , co ( p = 0.002 ) , ci ( p = 0.001 ) were higher in hsl than he s group [ table 3 ] .
svr / svri were significantly lower in hsl than he s group ( p = 0.03 and p = 0.002 respectively ) [ table 3 ] .
the analysis evaluating the influence of co - variates such as systolic and diastolic pressure , cvp , svri , pvri , map , ph , hco3 and lactate on ci changes due to the treatment showed that svri was the most significant parameter related to the hsl treatment and also to the observed changes in ci between two treatment groups ( p < 0.001 ) .
pvri and hco3 levels level also influenced the changes of ci between two groups ( p = 0.029 and 0.031 , respectively ) .
haemodynamic evolutions the total fluid intake was not different between hsl and he s group although the amount of crystalloid infusion was lower in hsl than he s group ( 0.024 ) [ table 4 ] .
the cumulative urine output was higher in hsl than he s group although it was not significant .
hence , the total fluid output throughout the surgery was comparable between hsl and he s group .
the fluid balance was more negative in hsl group ( 445.94 815.30 ) , whereas the fluid balance was still positive in he s group ( 108.479 1219.91 ) ; the difference was significant between the two groups ( p = 0.009 ) .
laboratory parameters before and after study drugs administration baseline data of biochemical parameters was similar between hsl and he s group ( p > 0.05 ) .
the changes of serum potassium , magnesium , haemoglobin , pao2 , paco2 , sao2 levels , glucose level before and after study drug infusion were comparable between hsl and he s group ( p > 0.05 ) .
serum sodium level was higher in hsl than he s group ( p < 0.0001 ) .
blood lactate and ph were increased higher in hsl than he s group ( p < 0.001 ) .
arterial hco3 level increased in hsl group but decreased in he s group , the difference between both groups was significant ( p < 0.001 ) .
base excess reached normal level in hsl group , whereas in he s group it decreased to a more negative base excess , the difference between both groups was obviously very significant ( p < 0.001 ) [ table 5 ] .
the number of patients requiring vasodilators and or inotropes was numerically less in hsl than he s group , although it was not statistically different [ table 6 ] .
utilization of concomitant drugs no adverse events related to study drug infusion was noticed in both groups during the study period .
maximizing the co by perioperative intravascular expansion during cardiac surgery is associated with a better improvement of tissue perfusion , reduced post - operative morbidity and length of stay .
patients undergoing cardiac surgery may not tolerate large volumes of fluid required for haemodynamic stabilisation due to reduction of cardiac performance .
hence , small volume infusion with an adequate intravascular expansion effect and ability to remove extracellular fluid excess may benefit these patients .
colloids have been widely used in perioperative cardiac surgery and were associated with lower net post - operative weight gain , however , high cost and potential risk of colloid usage are still unsolved issues .
a study in cardiac surgery comparing colloid with hypertonic saline infusion found that excretion of excess body fluid was higher in hypertonic saline group than colloid and avoiding tissue oedema . in this study , we used he s 6% as a reference solution because this solution has been widely used during perioperative cardiac surgery .
similar volumes of hypertonic sodium lactate and he s 6% was administered during cardiac surgery .
lactate plays an important role as an energy substrate for cardiac cells and many studies showed that lactate administration directly improved cardiac performance .
previous studies have showed that administration of hsl for post cardiac surgery patients resulted in better cardiac performance and tissue perfusion when compared with hypertonic sodium chloride 3% . until now
, we did not find any publication comparing the efficacy of hsl with colloid in cardiac surgery setting , therefore we conducted this study .
this study revealed that hsl infusion resulted higher increase of ci with lower svri than he s infusion despite comparable intravascular volume expansion , as indicated by comparable changes in map and cvp in both groups .
multivariate analysis showed that the decrease of svri was mostly associated with the improvement of ci and this finding was consistent with the previous studies .
the decrease of pvr / pvri and also alkalinizing effect of hsl also contributed to improved cardiac performance .
the increase in myocardial contractility directly related to the increase in cardiac performance and lactate has been shown to improve cardiac contractility . unfortunately in this study , we did not record the cardiac contractility after study fluid infusion , but we strongly feel that the lactate contributed for the improvement of cardiac performance .
the decrease of vascular resistance after hypertonic solution infusion has been attributed to its hypertonicity , and we postulate that the same mechanism worked during hsl infusion in this study .
previous studies have showed that the intravascular volume expansion after hyperosmolar solution infusion as indicated by the improvement of map and cvp contributed for increasing ci however the vascular expansion was comparable between hsl and he s group in this study . in this study ,
lower total fluid input with comparable total fluid output resulted in a much negative fluid balance in hsl group , whereas it became positive in he s group .
this effect is could be due to a redistribution of interstitial fluid and mobilisation of intracellular fluid from swollen endothelial cells to intravascular space .
reduction of endothelial cell swelling and mobilisation of extra vascular fluid into intravascular space following hypertonic solution administration were beneficial during cardiac surgery because it would reduce tissue oedema and improve microcirculation .
overall , hsl could be considered as an ideal fluid in cardiac surgery due to its ability to maintain haemodynamic status and improve ci with negative fluid balance .
the goal of perioperative fluid therapy is not only to maintain the effective circulatory volume , but also to avoid fluid overload whenever possible .
tissue oedema in surgical patients should be minimised because it increases the morbidity and mortality .
the infusion of hsl was well - tolerated since there was no adverse event during this study and laboratory parameters were still in normal range in both groups .
sodium level increased and chloride level decreased after hsl infusion , however the average levels were still within the normal limits .
in contrast , in he s group sodium level slightly decreased and chloride levels increased .
hypernatremia , one of the potential side - effects of hyperosmolar fluid infusion , was not found in this study , as also was the case in previous studies .
osmolality and electroneutrality principles were suspected responsible for the decrease of plasma chloride level after sodium lactate infusion . after study drugs administration , arterial ph , hco3 and
base excess reached normal levels in hsl group , whereas in he s group base excess and hco3 were almost unchanged and still below normal range .
this finding indicated that hsl infusion could completely reverse tissue acidosis , whereas he s infusion did not improve the existing tissue acidosis .
reversal of tissue acidosis in this study could be due to mild alkalinisation effect of hsl .
this was an expected result , considering that infusion of hsl will increase the strong ion difference as a consequence of higher sodium and lower chloride in the hl patients after lactate gets metabolised .
number of patients requiring concomitant supportive drug during cardiac surgery such as vasodilator and inotropes was numerically less in hsl group .
however the difference was not significant as and the sample size might not be adequate in this respect .
this study had some limitations including lack of double - blinding as well as the absence of the data expressing cardiac contractility after hsl or he s infusion .
another limitation was that for measurement of the effect of study drugs on haemodynamic status , measurement of the extra vascular lung water also is desirable and could not be measured due to lack of suitable monitors
this study had some limitations including lack of double - blinding as well as the absence of the data expressing cardiac contractility after hsl or he s infusion .
another limitation was that for measurement of the effect of study drugs on haemodynamic status , measurement of the extra vascular lung water also is desirable and could not be measured due to lack of suitable monitors
this study demonstrated that hsl administration was safe and resulted in better improvement of ci and much lower vascular resistance with negative intra - operative fluid balance during cabg surgery when compared with he s infusion . | background and aim : no solution has been determined ideal for fluid therapy during cardiac surgery .
previous studies have shown that hyperosmolar sodium lactate ( hsl ) infusion has improved cardiac performance with smaller volume infusion , which resulted in negative fluid balance .
this study compared the effects between a patent - protected hsl infusion and hydroxyethyl starch ( he s ) 6% on haemodynamic status of the patients undergoing cardiac surgery.methods:in this open - label prospective controlled randomized study , patients were randomly assigned to receive loading dose of either hsl or he s 6% , at 3 ml / kgbw within 15 min , at the beginning of surgery .
haemodynamic parameters and fluid balance were evaluated , while biochemical parameters and any adverse effect were also recorded .
haemodynamic and laboratory parameters were analyzed through repeated measures analysis of variance .
statistical assessment of fluid management was carried out through student t - test .
all statistical analyses were performed using the statistical package for the social sciences version 15 , 2006 ( spss inc .
, chicago , il).results : out of 100 enrolled patients in this study ( 50 patients in each arm ) , 98 patients were included in analysis ( 50 in hsl group ; 48 in he s group ) .
cardiac index increased higher in hsl group ( p = 0.01 ) , whereas systemic vascular resistance index decreased more in hsl than he s group ( p = 0.002 ) .
other haemodynamic parameters were comparable between hsl and he s group .
fluid balance was negative in hsl group , but it was positive in he s group ( 445.94 815.30 ml vs. + 108.479 1219.91 ml , p <
0.009).conclusion : administration of hsl solution during the cardiac surgery improved cardiac performance and haemodynamic status better than he s did . |
cutaneous t - cell lymphomas ( ctcl ) account for roughly 3% of non - hodgkin s lymphoma ( nhl ) and are a heterogenous group of disorders characterized by clonal accumulation of malignant cd4 or cd8 t - lymphocytes in the skin . according to a recent review of the seer database and other registries , the incidence of ctcl is on the rise ; approximately 6.4 per million persons will be diagnosed with ctcl each year.1 mycosis fungoides ( mf ) and its leukemic variant , szary syndrome ( ss ) , make up the majority of ctcl .
treatment algorithms have been developed for mf and ss and include combined or sequential therapies with multiple skin - directed as well as systemic agents.2 the nccn and eortc also have developed guidelines in the management of mf and ss .
decisions in initial or subsequent therapies such as skin - directed therapy , radiation therapy , photopheresis , anti - neoplastic therapies , biologic therapies , or combined - modality treatment incorporate the disease stage , overall prognosis , and quality - of life of the patient . for early - stage patients in whom
remission is likely , the goal of therapy is to avoid long - term treatment - related toxicities ; for patients with aggressive disease , approaches often include skin - directed as well as systemic therapies , including biologic or targeted therapy , and chemotherapy .
staging of patients with mf and ss is essential both for its prognostic value and for decisions in management .
the most commonly used staging system for mf / ss is based on a tumor - node - metastasis - blood ( tnmb ) classification ( table 1).3 when mf is grouped by stage , patients with patch - plaque disease ( stages ia , ib , and iia ) have an excellent survival of more than 12 years ; those with tumors or erythroderma ( stages iib / iii ) have a median survival of approximately 4 years ; however , those with stage iv which includes patients with lymph node or visceral involvement , the median survival is less than 3 years.4 similarly , ss has a median survival of less than 3 years.5,6 kim et al showed that advanced age , t stage , and presence of extracutaneous disease correlated with a reduction in survival.7 many patients die not from their disease , but the infectious complications they develop , likely due to impaired immunity as well as from immunosuppressive effects of systemic therapies .
one unique feature of this disease is that as the malignant t - cell clone expands , it does so at the expense of normal t - cells , creating an immunodeficiency in numbers of functional t - cells , as well as decreased production of th1-type cytokines , and decreased nk cell activity.8 an important treatment paradigm is to introduce treatments that do not cause further immune suppression .
denileukin diftitox ( ontak ; eisai inc . ) is a biological therapeutic agent that is essentially a fusion protein toxin .
a fusion protein toxin combines a targeting ligand such as a growth factor with a cytocidal moiety such as a plant or bacterial toxin .
denileukin diftitox uses a truncated diphtheria toxin ( dab389 ) as the toxophore and this is fused to the full - length sequence of the il2 protein .
once bound to the il2r , denileukin diftitox is internalized via receptor - mediated endocytosis in an acidified vesicle . upon internalization and acidification
, denileukin diftitox is proteolytically cleaved within the endosomes to liberate the enzymatically active portion of the diphtheria toxin .
the fragment of diphtheria toxin is translocated across the endosomal membrane into the cytosol where it inhibits protein synthesis via adp - ribosylation of elongation factor-2 , ultimately resulting in cell death.9,10 the story of the birth of denileukin diftitox is an interesting one , and it is worthwhile to review its development .
denileukin diftitox was born out of the ongoing discovery of il2 and its receptors , and novel bioengineering .
since the cloning of the autocrine t - cell growth factor , il2 , in 1983 , the il2 receptor ( il2r ) has been the subject of major investigation .
targeting of il2r has subsequently been explored for its therapeutic potential as well as to help elucidate signal transduction pathways .
we know now that the il2r is a complex comprised by three parts : the alpha chain ( cd25 ) which is required for high affinity binding , the beta chain ( cd122 ) which participates in il2 and il15 signal transduction , and the common gamma chain ( cd132 ) which participates in downstream signal transduction of il2 and other cytokines.1114 the generation of an anti - cd25 ( anti - tac ) antibody has helped identify populations of cells where il2r is expressed.15 in a normal subject , the il2r is expressed mostly at a low level in less than 5% of normal circulating peripheral blood mononuclear cells ( pbmc ) .
however , the greatest level of expression of cd25 is seen in the setting of t - cell malignancies such as cutaneous t - cell lymphoma , and adult t - cell leukemia .
it is also highly expressed in hairy cell leukemia , hodgkin s disease , as well as some b - cell nhls and histiocytic proliferations .
indeed , high- or intermediate affinity il2r isoforms are expressed in at least 50% of ctcl and 25% to 50% of b - cell non - hodgkin s lymphomas when tissue is examined by flow cytometry , and thus make the il2r an attractive target for therapy.16 in 1995 sakaguchi et al discovered that the high affinity il2 receptor alpha chain was a reliable cell surface marker for regulatory t - cells ( tregs).17 cd4 cd25 cells were found to be anergic , failing to proliferate when stimulated by anti - cd3 antibodies .
they also suppressed the growth of cd4 cd25 t - cells in vitro , as well as an admixture of conventional t - cells .
interestingly , although il2 was required for their growth and survival , tregs did not produce il2 themselves.18 since ctcl is considered by some to be a malignant proliferation of t - regs,19 the rationale behind targeting cd25 is even more robust . abnormalities of il2r were also detected in autoimmune diseases such as rheumatoid arthritis , systemic lupus erythematosus , aplastic anemia , and insulin - dependent diabetes . increased expression of cd25 was also detected in the serum of patients during solid organ allograft rejection , and in those with graft - versus - host disease ( gvhd ) . since the cloning of the il2r receptor , work has been done to exploit the receptor as a target for therapy in t - cell malignancies , gvhd , and other autoimmune diseases .
daclizumab is a humanized anti - tac monoclonal antibody that has been tested in leukemia and lymphoma . in cell lines
, it was thought that daclizumab blocked the interaction of il2 and its receptor resulting in cytokine - deprivation - mediated apoptotic cell death.20 additionally , based on in vivo data from mouse models , it was thought that daclizumab also exerted an effect through an fcr receptor mechanism.21 clinical trials using daclizumab in adult t - cell leukemia and lymphoma ( atl ) was associated with partial responses predominantly in patients with smoldering or chronic atl .
unfortunately , unlike other therapeutic monoclonal antibodies used in the treatment of human malignancies , daclizumab did not seem to have strong cytocidal activity .
therefore , other strategies were needed to make use of il2r targeting in t - cell malignancies .
in order to target the delivery of a cytocidal moiety to il2r - bearing cells , human il2 was fused to truncated diphtheria toxin ( dt ) . unlike daclizumab ( anti - tac ) , which is a mab directed against the cd25 component of the receptor , dab486-il2 contained the full - length sequence of il2 as the ligand for the il2r .
the original fusion protein toxin used a fragment of dt containing methionine plus the first 485 amino acids of dt resulting in the molecule dab486-il2.9,22,23 while this molecule had clinical activity ( 1 complete response , 2 partial responses , out of 18 patients ) , the maximum tolerated dose ( mtd ) was only 0.1 mg / kg / day , due to transaminase elevations.24 five of 18 patients experienced fever associated with administration of the fusion protein toxin that responded to acetaminophen .
the anti - tumor effect of dab486-il2 did not correlate with pre- or post - treatment antibodies to dt , dab486-il2 , or il2 .
modifications were made to dab 486-il2 by removing 97 amino acids from the native part of the toxin containing the disulfide bond , resulting in an increase in half - life and tolerance in animals .
this resulted in a 5-fold greater affinity for il2r and a 10-fold increase in potency.25,26 the resulting dab389-il2 fusion protein toxin is otherwise known as denileukin diftitox .
denileukin diftitox binds to il2r in the same way as il2 because it contains the full - length sequence of il2 .
this optimized fusion protein toxin binds to a high- or intermediate - affinity receptor.27,28 intermediate affinity receptors have beta ( cd122 ) and gamma ( cd132 ) subunits and bind il2 with kd 10 , and high - affinity receptors have the addition of the alpha ( cd25 ) subunit and bind il2 with kd 10 .
once denileukin diftitox binds to il2r , this molecule is internalized into the cell where the truncated diphtheria toxin is cleaved off , liberated into the cytosol , and induces cell death by causing apoptosis . a phase i clinical trial using dab389-il2 in patients with lymphomas expressing il2r ( cd25 or cd122 ) resulted in an mtd of 27 g / kg / day.25 unlike with the first generation fusion protein toxin
the dose - limiting toxicities that were seen included asthenia , fever , nausea and vomiting .
in addition , some of the ctcl patients who were treated in this trial exhibited signs and symptoms of capillary leak syndrome with edema , hypotension and hypoalbuminemia .
again , the presence of antibodies to dt , dab389-il2 , or il2 pre- and post - treatment did not prevent treatment responses .
the half - life of dab 389-il2 was found to be 72 minutes with monophasic clearance , and there was no dose accumulation with repeated doses of the drug . in this trial ,
35 patients had ctcl ( 30 mf , 4 large cell ctcl , and 1 cutaneous ptcl ) , and most were heavily pretreated .
of the 35 ctcl patients , 4 ( 11% ) had a complete response , and 8 ( 24% ) had a partial response .
the median time to response was 2 months and the duration response ranged from 2 to 39 + weeks ( median 10 months ) .
there was no obvious correlation with the expression of cd122 or cd132.25 in another phase i / ii trial using dab 389-il2 that enrolled a more homogenous group of 35 patients with mf , a dose and schedule of dab 389-il2 given over 5 consecutive days of a 21-day cycle was explored .
thirteen patients ( 37% ) achieved an objective response , including a complete response in 5 patients ( 14% ) .
complete response was achieved in patients with extensive erythroderma and tumor - stage mycosis fungoides.29 a smaller trial of 4 heavily pre - treated ctcl patients who received either 9 ( 1 patient ) or 18 ( 3 patients ) g / kg / day of dab 389-il2 for 5 days of a 21-day cycle showed striking results.30 one patient achieved a complete pathological response , and another patient had a complete clinical response , and the other 2 patients had partial responses . similar to prior trials , the duration of response ranged from 5 to 11 + months .
these trials formed the basis of the pivotal phase iii trial of denileukin diftitox.31 this randomized , blinded , multicenter , parallel group study was designed to evaluate the efficacy , safety , and pharmacokinetics of two doses of denileukin diftitox in patients with previously treated , advanced or refractory ctcl .
the inclusion criteria required that patients have 20% of lymphocytes within the skin biopsy stain positive for cd25 .
patients were randomized to receive either denileukin diftitox 9 or 18 g / kg / day administered on 5 consecutive days every 3 weeks for up to 8 cycles , and were stratified by stage ( ie , iia or iib ) .
all patients were monitored for toxicity and clinical efficacy , the latter being assessed by changes in disease burden and quality of life measurements .
the study enrolled 71 patients , and 48 ( 68% ) had advanced disease ( stage iib or greater ) .
overall , 21 ( 30% ) of the 71 patients with ctcl treated with denileukin diftitox had an objective response ( 20% partial response and 10% complete response ) .
there was no difference in the overall response rate between the 9 or 18 g / kg / day cohorts ; however , a subset analysis of patients with stage iib disease or higher , showed a trend towards higher response ( p = 0.07 ) .
quality - of - life improvements following denileukin diftitox therapy were seen both in responders and in nonresponders , and this was mainly a result of clinical improvements in pruritus in 68% of the patients . in patients who responded , the use of rescue medications such as topical steroids or oral antihistamines was also decreased .
fifty of the 71 patients were classified as nonresponders ; however only 2 ( 3% ) of patients had progression of disease .
the remainder of the patients had stable disease ( 32% ) , or withdrew due to intolerance to the therapy ( 35% ) before they could be assessed .
the authors commented that even in patients who were classified as stable disease , had a significant initial response to therapy .
it is again noteworthy that the majority of patients had detectable levels of antidenileukin diftitox and/or anti - il2 after treatment with denileukin diftitox , however , the presence of these antibodies did not impair the response to treatment .
curiously , higher antidenileukin diftitox antibody levels were associated with a lower incidence of rash , hypoalbuminemia , and transaminase elevations , but did not correspond to infusion - related reactions .
it is thought that the development of antibodies to denileukin diftitox may contribute to the increase in clearance of denileukin diftitox that was observed by cycle 3 .
negro - vilar et al reported preliminary results of a placebo - controlled phase iii trial of up to 8 cycles of denileukin diftitox in 144 patients with stage ia to iii disease , the largest ctcl trial to date.32 patients with at least 3 prior treatments were included .
overall response rates for the placebo , low - dose ( 9 g / kg ) , and high - dose ( 18 g / kg ) treatment arms were 16% , 38% , and 49% , respectively , with median times to progression of 4 , 26 , and greater than 32 months , respectively . in an unpublished meta - analysis of three phase iii clinical trials of denileukin diftitox for the treatment of ctcl , negro - vilar also reported there was no correlation between cd25 expression and response.33
since the expression of il2r has been largely thought to be important in t - cell targeting of denileukin diftitox , strategies to upregulate il2r expression have been explored .
retinoids have demonstrated efficacy in the treatment of mf / ss and have antiproliferative , antiangiogenic , immune - modulating , and cellular effects.34 in vitro studies demonstrated that the retinoid receptor ( rxr ) retinoid , bexarotene , at biologically relevant concentrations of 10(6 ) m to 10(8 ) m , upregulated both the p55 and p75 subunits o f the il2r and the susceptibility of t - cell leukemia cells to denileukin diftitox.35,36 in a phase i dose - escalation trial , denileukin diftitox 18 g / kg 3 days was administered in combination with oral bexarotene ( 75 to 300 mg / day ) every 21 days to patients with relapsed or refractory mf / ss.36 the overall response rate was 70% , and responders included patients who had stable disease or no response on denileukin diftitox alone .
cd25 expression on cd4 cells was measured by immunohistochemistry or flow cytometry at baseline and after 7 days of bexarotene .
modulation of the il2r was seen with doses of bexarotene 150 mg daily and higher .
all 4 patients who achieved a cr and 1 of 3 patients who achieved a pr had evidence of > 50% upregulation after bexarotene treatment .
arginine butyrate is a histone deacetylase ( hdac ) inhibitor that also has been shown to increase il2r - beta ( cd122 ) subunit gene and protein expression.37 while low dose arginine butyrate showed no growth inhibitor effect of its own , combination studies with denileukin diftitox in vitro showed an increase in cytotoxicity . since hdac inhibitors are clinically active compounds in ctcl , combination therapies to test potential synergism with denileukin diftitox are warranted .
ctcl affects numerous dimensions of quality of life ( qol ) due to relentless painful , pruritic and disfiguring lesions .
qol was evaluated as a secondary endpoint in heavily pretreated advanced and/or recurrent ctcl patients enrolled in the multicenter randomized phase iii trial of denileukin diftitox by olsen et al using the functional assessment of cancer therapy - general ( fact - g ) scale.31,38 fact - g was developed to measure health - related qol in patients with cancer.39 this tool measures four domains of quality of life : physical , functional , social and emotional well - being , as well as patient - physician relationships .
the physical well - being scale assesses energy level , pain and side effects of treatment .
the ability to sleep , work and participate in desired leisure activities are addressed in the functional well - being subscale . the relationship - with - physician subscale measures satisfaction with interaction and care provided by the physician . in the study by olsen et al
the 71 patients who received denileukin diftitox were administered the fact - g questionnaire at baseline prior to the start of therapy and prior to each treatment cycle .
in addition , along with each fact - g measurement , patients were asked to rate the appearance of their skin on a 7-point global severity scale .
because the symptom of pruritus was not specifically addressed in the physical well - being subscale of the fact - g , patients were also asked to rate severity of pruritus on a 10-cm visual analog scale.38 in the 21 patients who achieved a complete or partial response to denileukin diftitox , the fact - g and most individual subscale scores improved during the study period reaching statistical significance by cycle 3 ( p < 0.05 ) and were significantly higher than scores of non - responders at the completion of the study ( p < 0.041).38 additionally for responders , skin and pruritus severity scores showed significant improvement at study end compared with baseline measurements .
nonresponders also showed brief improvement in qol while receiving denileukin diftitox , but this declined with the discontinuation of therapy .
overall , the most commonly reported adverse events ( ae ) in the pivotal study by olsen et al were flu - like symptoms ( 85% ) .
other common aes were acute hypersensitivity - type reactions , asthenia , nausea / vomiting ( which led to dehydration in some patients ) , and infectious complications .
the frequency of hypersensitivity reactions that occurred during or within 24 hours of drug administration was 60% and improved with steroid , antihistamine , and acetaminophen pre - medication prior to subsequent cycles .
it should be noted that routine pre - medication was prohibited in this study . in clinical use
, the routine use of pre - medication does reduce this complication significantly , however .
the incidence of serious infusion reactions across 3 clinical studies ( n = 234 patients ) was 8.1% .
various pre - medication protocols have been proposed including one by dang et al40 and consists of dexamethasone 4 mg iv , diphenhydramine 25 to 50 mg iv , and acetaminophen 650 mg po .
vascular leak syndrome was reported in 25% of patients and was defined as hypotension , hypoalbuminemia , and peripheral edema .
the vascular leak syndrome occurred within the first 14 days of treatment and was usually self - limited .
patients responded well to judicious use of diuretics for edema , and slow hydration for hypotension .
serum albumin <3 g / dl and pre - exisiting edema seemed to predict the development of vascular leak syndrome .
the authors recommend an additional clinical evaluation of the patient for changes in weight and fluid shifts at least one time within the first 10 days after treatment begins .
the us food and drug administration boxed warning states that denileukin diftitox should only be administered in a facility equipped and staffed for cardiopulmonary resuscitation .
all adverse events in the pivotal phase iii study were most severe during the first two cycles of treatment and then diminished significantly .
hepatic transaminase levels were commonly elevated , with 19% of patients experiencing grade 34 elevations .
most elevations were observed during the first therapy cycle and diminished during all subsequent cycles .
there was no significant bone marrow suppression , although lymphocyte counts fluctuated transiently in 70% of patients .
infections were reported but were considered typical infections of ctcl patients , and not related to denileukin diftitox . postmarketing reports of serious events include thyrotoxicosis as reported by ghori et al41 clinical thyrotoxicosis was described in 8 patients treated at a single center ; 4 patients developed thyrotoxicosis within days of the first cycle of denileukin diftitox therapy , and 4 patients after the second cycle .
symptoms of tremor , tachycardia , nausea , diarrhea , and weight loss should trigger suspicion of this condition which resolves after drug discontinuation .
loss of visual acuity and color vision is another black box warning and may have to do with retinal changes , however the mechanism of this rare phenomenon is not known.42 lastly , rhabdomyolysis has been reported in the context of severe vascular leak,43 and the authors also have independently experienced this complication in two of their patients .
denileukin diftitox has made great strides in the treatment of ctcl since its development 20 years ago .
the reported response rates range from 30% to 50% , and treatment definitely improves the quality of life of these patients
the toxicity profile and unfavorable schedule of administration have prevented its use as upfront treatment , however , denileukin diftitox may be more effective if used earlier in the course of the disease . while the initial response rate of denileukin diftitox was 38% in early - stage ctcl , the median number of prior treatments was five . in less
heavily treated patients , however , the response rate was considerably higher , 63% and 48% , for early and late stage ctcl , respectively .
this suggests that the response rate may be higher in patients who are treated earlier in the course of their disease .
we are only now beginning to understand how to utilize denilekin diftitox in combination therapy .
due to non - overlapping toxicity profiles , denileukin diftitox has also been successfully been combined with chop ( cyclophosphamide , doxorubin , vincristine and prednisone ) for peripheral t - cell lymphoma , suggesting that chemotherapy combinations that incorporate this immunotoxin may eventually have a place in the treatment of advanced ctcl .
it would also be useful to predict which patients would benefit most from treatment with denileukin diftitox .
initally , it was thought that the presence of cd25 was required for entry of the drug into the malignant t - cells , however , recent evidence has shown durable responses in patients with cd25 disease . regardless of these limitations , this unique immunotoxin has proven itself effective for the treatment of ctcl , a chronic disease with considerable morbidity and mortality . | denileukin diftitox ( ontak ) is indicated for the treatment of patients with persistent or recurrent cutaneous t - cell lymphoma ( ctcl ) , a rare lymphoproliferative disorder of the skin .
denileukin diftitox was the first fusion protein toxin approved for the treatment of a human disease .
this fusion protein toxin combines the il2 protein with diphtheria toxin , and targets the cd25 subunit of the il2 receptor , resulting in the unique delivery of a cytocidal agent to cd-25 bearing t - cells .
historically , immunotherapy targeting malignant t - cells including monoclonal antibodies has been largely ineffective as cytocidal agents compared to immunotherapy directed against b - cells such as rituximab .
this review will summarize the development of denileukin diftitox , its proposed mechanism of action , the pivotal clinical trials that led to its fda approval , the improvements in quality of life , and the common toxicities experienced during the treatment of patients with ctcl .
ctcl is often a chronic progressive lymphoma requiring the sequential use of treatments such as retinoids , traditional chemotherapy , or biological response modifiers .
the incorporation of the immunotoxin denileukin diftitox into the sequential or combinatorial treatment of ctcl will also be addressed . |
null | severe developmental and reproductive disorders in wild animals have been linked to high exposure to persistent environmental chemicals with hormonal activity .
these adverse effects of environmental estrogens have raised considerable concern and have received increasing attention .
although numerous chemicals with the capacity to interfere with the estrogen receptor ( er ) have been identified , information on their molecular mechanism of action and their relative potency is rather limited . for the endometrium ,
the lack of information is due to the lack of a suitable experimental model .
we investigated the functions of phytoestrogens in an endometrial - derived model , ruca - i rat endometrial adenocarcinoma cells .
the cells were cultured on a reconstituted basement membrane to preserve their functional differentiation and estrogen responsiveness .
we assessed the relative binding affinity to the estrogen receptor of the selected phytoestrogens coumestrol , genistein , daidzein , and the putative phytoestrogen mangostin compared to estradiol by a competitive scatchard analysis .
the following affinity ranking was measured : 17beta - estradiol > > > coumestrol > genistein > daidzein > > > mangostin .
in addition , we investigated the capacity of these compounds to promote the increased production of complement c3 , a well - known estradiol - regulated protein of the rat endometrium .
all substances tested increased the production of complement c3 , although different concentrations were necessary to achieve equivalent levels of induction compared to estradiol .
mechanistically we were able to demonstrate that the increase of complement c3 production was mediated by primarily increasing its steady - state mrna level .
these findings indicate that ruca - i cells represent a sensitive model system to elucidate relative potencies and functions of environmental estrogens in an endometrium - derived model.imagesfigure 2figure 3figure 4figure 5figure 6 |
among the health care services covered by medicare , reimbursements for hop services have shown the largest rate of growth since the inception of the program . from 1974 , the first full year of coverage for disabled medicare enrollees , through 1983 , hop reimbursements rose from $ 0.3 billion to $ 2.7 billion , an average annual rate of increase of 26 percent . similarly , during the same period , all medicare expenditures showed an average annual rate of growth of about 20 percent . with the advent of the medicare pps in october 1983 ,
hop expenditures rose to $ 4.1 billion , an average annual rate of increase of 23 percent . during the same period ,
pps legislation restructured the payment system by which short - stay hospitals are reimbursed for inpatient services rendered to medicare beneficiaries .
the new system gives short - stay hospitals the incentive to hold costs down because they earn a profit when their costs fall below the prospective payment or absorb a loss when their costs exceed the prospective payment . as a result ,
health care decisions being made in response to pps are expected to have a profound impact on other providers of health care , especially hospital outpatient facilities .
for example , the physicians ' practice costs and income survey ( health care financing administration , 1983 - 85 ) indicates that physicians treating medicare patients are being encouraged to shorten lengths of hospital stays , reduce ancillary services , and foster outpatient testing .
preliminary findings from studies on the impact of the pps suggest these reasons for hop services being the fastest growing segment of the health care industry : there are direct financial incentives for hospitals to shift care to ambulatory settings when it is clinically appropriate and cost efficient .
surgical and diagnostic technological innovations have enabled hospitals to perform more procedures on an ambulatory basis .
for example , preadmission review for medical necessity , appropriateness , and quality of care encourage treatment in the safest and most cost - effective setting .
the addition of ambulatory surgical benefits under medicare and the repeal of the part b deductible for home health agency services have encouraged the use of outpatient services ( omnibus budget reconciliation act , 1980 , public law 96 - 499 ) .
the shift of patient care to an outpatient setting has reduced the risk of nosocomial infections .
trends in the number of supplementary medical insurance enrollees and the amounts of covered charges and reimbursements for the years 1974 through 1985 are shown in table 1 . from 1974 to 1983
, reimbursements for hop services to medicare beneficiaries increased from $ 0.3 billion to $ 2.7 billion ( figure 1 ) , an average annual rate of growth ( aarg ) of about 26 percent .
for all medicare reimbursements during this period , the aarg was 20 percent . from 1983 through 1985 , reflecting the first 2 full years of the medicare prospective payment system , hop reimbursements rose from $ 2.7 billion to $ 4.1 billion , an aarg of about 23 percent .
the average hop reimbursement per enrollee grew from $ 14 in 1974 to $ 92 in 1983 , and then rose to $ 136 in 1985 .
the use of hospital outpatient services under medicare is shown in table 2 for 1985 , displaying covered charges , percent distribution , and average charge per enrollee , by type of service , sex , race , and type of enrollment .
nearly one - half of all medicare hop charges ( $ 6.5 billion ) were for three services radiology ( $ 1.4 billion or 22.2 percent ) , end stage renal disease ( esrd ) ( $ 0.9 billion or 13.2 percent ) , and laboratory ( $ 0.8 billion or 12.9 percent ) ( figure 2 ) .
hop charges for operating room services ( $ 0.4 billion ) accounted for about 7 percent of all hop charges for medicare beneficiaries , reflecting the increasing number and variety of surgical procedures performed in an outpatient setting .
there were substantial differences by race and type of entitlement in the charge per enrollee for hop services .
the total charge per enrollee for persons of races other than white ( $ 338 ) was 66 percent higher than that for persons of the white race ( $ 203 ) .
the total charge per disabled enrollee ( $ 474 ) was 149 percent higher than that for the aged ( $ 191 ) .
this difference was reflected , for the most part , in the use of esrd services that accounted for 44 percent of all hop charges among the disabled , but only 6 percent among the aged .
charges for esrd services represented 34 percent of all charges for persons of races other than white compared with 9 percent for white persons .
hospital outpatient clinic and emergency room visits and charges for 1985 under medicare ( table 3 ) , are shown by sex , race , and type of enrollment .
users of hop services in 1985 made 5.7 million visits to clinics and almost 7.0 million visits to emergency rooms .
although data are not shown in the tables , the rate of use of clinic services by medicare beneficiaries declined about 7 percent from 1983 ( 204 visits per 1,000 enrollees ) to 1985 ( 190 visits per 1,000 enrollees ) .
this finding is contrary to the expected shift in hospital services from the inpatient to the outpatient setting .
the rate of emergency room services , however , showed a moderate increase of about 13 percent from 1983 ( 206 visits per 1,000 enrollees ) to 1985 ( 232 visits per 1,000 enrollees ) .
the average charge per visit in 1985 was slightly higher for emergency room services ( $ 43 ) than for clinic services ( $ 41 ) .
substantial differences exist in the rate of use ( visits per 1,000 enrollees ) of clinic and emergency room services by race and type of entitlement .
persons of races other than white used clinic and emergency room services 4.6 times and 1.5 times more , respectively , than did white persons .
disabled beneficiaries used clinic and emergency room services 2.6 times and 2.2 times more , respectively , than did aged beneficiaries . for aged medicare beneficiaries ( table 4 ) , hospital outpatient covered charges and reimbursements are shown for 1985 , by area of residence .
the average hop reimbursement per aged enrollee in the united states was $ 118 . by region ,
the average hop reimbursement per enrollee was highest in the northeast ( $ 131 ) and lowest in the south ( $ 102 ) , a difference of 28 percent . by state , massachusetts had the highest average reimbursement per enrollee ( $ 217 ) and south dakota the lowest ( $ 66 ) , a difference of 229 percent ( figure 3 ) .
presented in table 5 are hospital outpatient covered charges and reimbursements for disabled medicare beneficiaries , excluding those for end stage renal disease .
the average medicare hop reimbursement per disabled enrollee in the united states , excluding enrollees with esrd , was $ 132 .
this figure was 12 percent higher than the average for aged enrollees ( $ 118 ) . by region ,
the average reimbursement per disabled enrollee was highest in the northeast ( $ 165 ) and lowest in the south ( $ 105 ) , a difference of 57 percent . by state , the average reimbursement per enrollee ranged from $ 288 in the district of columbia to $ 73 in alabama , a difference of 295 percent ( figure 4 ) . for medicare beneficiaries receiving hospital outpatient services in 1985 ,
the 10 leading ( most frequently reported ) principal diagnoses are displayed in table 6 .
data include the number of bills , covered charges , reimbursements , and average charges and reimbursements per bill . among all medicare beneficiaries using hop services , the 10 leading principal diagnoses accounted for 8.9 million bills or 27 percent of all hop bills ( 33.6 million ) . similarly , the 10 leading principal diagnoses accounted for 26 percent ( $ 1.1 billion ) of all medicare hop reimbursements ( $ 4.1 billion ) .
diabetes was the most frequently reported diagnosis , comprising 18 percent ( 1.6 million ) of all bills for hop services ( figure 5 ) .
cataract was the most costly leading principal diagnosis , accounting for 14 percent ( $ 0.6 billion ) of all hop reimbursements .
the average reimbursement per bill for cataract was $ 728 , or six times higher than the average hop bill ( $ 121 ) . for 1985 ,
table 7 presents the leading ( most frequently reported ) surgical procedures performed on medicare beneficiaries in hospital outpatient departments .
utilization is measured by the number of bills , covered charges , and average charges and reimbursements per bill . among all aged and disabled beneficiaries ,
the 10 leading hop surgical procedures accounted for 43 percent ( 1.3 million ) of all hop surgical procedures ( 2.9 million ) .
the 10 leading hop surgical procedures accounted for about two - thirds ( $ 0.6 billion ) of all medicare reimbursements for hop surgery ( $ 0.9 billion ) .
the average reimbursement per bill for the 10 leading surgical procedures ( $ 489 ) was 53 percent higher than the average reimbursement for all bills for surgical procedures ( $ 317 ) .
the most frequent surgical procedure was operation on lens ( 0.45 million ) , which accounted for 15 percent of all hop surgical procedures ( 2.9 million ) .
the highest average charge per bill ( $ 1,521 ) was for operations on lens ( figure 6 ) .
the average hop reimbursement per bill was highest for operations on lens ( $ 966 ) , more than three times higher than the average for all surgical procedures ( $ 317 ) .
the next highest average reimbursement per procedure was for operations on the breast ( $ 437 ) .
disabled medicare enrolleesdisabled enrollees are separated into two groups . in the first group are persons entitled to cash disability benefits for at least 24 months ; some of these enrollees have end stage renal disease ( esrd ) .
the second group of disabled persons has not been entitled to cash disability benefits for 24 months .
these enrollees are entitled to medicare because they have esrd and meet certain social security insured status requirements .
eligibility for medicare coverage begins with the third month after the beginning of a course of renal dialysis.hospital outpatient servicesmajor hospital outpatient services covered by supplementary medical insurance include services in an emergency room or outpatient clinic , laboratory tests billed by the hospital , x - rays and other radiology services billed by the hospital , medical supplies such as splints and casts , drugs and biologicals that can not be self - administered , and blood transfusions .
physical therapy services must be furnished under a plan set up and reviewed periodically by a physician . for outpatient speech pathology services ,
are persons entitled to cash disability benefits for at least 24 months ; some of these enrollees have end stage renal disease ( esrd ) .
the second group of disabled persons has not been entitled to cash disability benefits for 24 months .
these enrollees are entitled to medicare because they have esrd and meet certain social security insured status requirements .
eligibility for medicare coverage begins with the third month after the beginning of a course of renal dialysis .
major hospital outpatient services covered by supplementary medical insurance include services in an emergency room or outpatient clinic , laboratory tests billed by the hospital , x - rays and other radiology services billed by the hospital , medical supplies such as splints and casts , drugs and biologicals that can not be self - administered , and blood transfusions .
physical therapy services must be furnished under a plan set up and reviewed periodically by a physician . for outpatient speech pathology services ,
the hospital outpatient data are derived from a 5-percent sample of bills for services performed in hospital outpatient departments during 1985 .
the bills were tabulated by the health care financing administration 's central records as of december 1986 . it is estimated that these bills represent about 98 percent of the eventual reimbursements for hospital outpatient services in 1985 .
data for the years 1974 - 85 are based on bills recorded 12 months following the year of service .
. payments for hospital outpatient services are based on interim rates that may be adjusted after the end of the hospital 's accounting year , calculated on reasonable costs of operation .
the hospital outpatient figures in this report reflect bills for covered services whether or not a reimbursement was made by the medicare program . | presented in this article are program data on the use and cost of hospital outpatient ( hop ) services rendered to aged and disabled medicare beneficiaries during calendar year 1985 .
trend data are also presented for calendar years 1974 - 85 .
the data shown in this article focus on charges , reimbursements , and reimbursements per enrollee as a means of measuring the cost of hop services .
the data provide information to help identify trends and patterns of care for monitoring the medicare hop benefit and for evaluating the impact of the inpatient hospital prospective payment system ( pps ) on the use and cost of hop services . |
Mitt Romney wants President Obama to apologize for his campaign's suggestion that the Republican candidate could have broken the law by making inaccurate statements to the Securities and Exchange Commission.
Romney told ABC News' Jonathan Karl late this afternoon that Obama should clean up his campaign staff after officials coordinated an effort to imply that Romney committed a felony by saying he left Bain Capital in 1999, though The Boston Globe reported this week that Romney was listed as the company's CEO until 2002 on official files.
"The president needs to take control of these people," Romney said. "He ought to disavow it and rein in these people who are running out of control."
Romney added, "He sure as heck ought to say that he's sorry for the kinds of attacks that are coming from his team."
Romney insisted that he abandoned the private-equity firm he founded to run the Olympics and that, after 1999, he had "no role whatsoever in the management" of Bain even though SEC documents listed him as president, chairman of the board and sole stockholder.
"I left any responsibility whatsoever, any effort, any involvement whatsoever in the management of Bain Capital after February of 1999," Romney said.
Romney didn't answer when he was asked if he thought there was anything wrong with being associated with Bain after 1999, a period that has been the source of Obama's attack ads on Bain-backed companies that either outsourced jobs or went bankrupt.
Obama, himself, told an ABC News affiliate, WJLA in Washington, D.C., that Romney should "absolutely" answer the questions that have been raised about Bain.
"My understanding is that Mr. Romney attested to the SEC, multiple times, that he was the chairman, CEO and president of Bain Capital, and I think most Americans figure if you are the chairman, CEO and president of a company that you are responsible for what that company does," Obama told WJLA. "Ultimately, Mr. Romney, I think, is going to have to answer those questions because, if he aspires to being president, one of the things you learn is you are ultimately responsible for the conduct of your operations. But again, that's probably a question that he's going to have to answer, and I think that's a legitimate part of the campaign."
Romney's campaign has been under siege by both the Obama campaign and media outlets that have obtained records showing Romney's ties to Bain after he ostensibly "left" in 1999. The Washington Post reported that between 1999 and 2001, Romney signed six Bain documents with the SEC.
Though the campaign said Romney didn't "participate" in management decisions during that time, the Boston Herald wrote then that "Romney said he will stay on as a part-timer with Bain, providing input on investments and key personnel decisions. But he will leave running day-to-day operations to Bain's executive committee."
Romney gave five brief interviews to TV networks today in a hastily arranged fashion as the Bain attacks dominated the media narrative, capping a week of bad press for Romney that also included rising calls for him to release more of his tax records.
In each interview, Romney tried to shine the spotlight back on the economy, accusing Obama of diverting attention away from the sputtering recovery by unearthing new attacks.
"Why the president continues, and his people continue, to make these kinds of charges and tried to turn this into something big is clear to the American people," Romney said. "Because the president's failed to do the job that he was elected to do, which was to get this economy turned around." ||||| Mitt Romney aggressively counter-punched against reports that he controlled Bain Capital for three years longer than he has previously claimed, giving five separate television interviews on Friday defending himself and slamming President Barack Obama’s campaign for alleging that he might be a “felon.”
An animated and sometimes irritated Romney conceded that he continued to nominally head Bain Capital — the subject of relentless attacks against him by Democrats — after 1999 and had the option to return to managing the daily operations of the firm when the Olympics was over. He also stuck to his guns regarding his tax returns, saying he would release two years’ worth (2011 and 2010) and no more.
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reset Romney counter-punches on Bain Obama: Romney should answer on Bain
(Also on POLITICO: Obama: Bain is fair game)
“I was the owner of an entity that is filing those information — that information, but I had no role whatsoever in the management of Bain Capital after February of 1999, not that that would have been a problem, to have said that I was with the firm beyond that, but I simply wasn’t,” Romney said on CNN.
On Friday night, Romney’s answers had already proven to be unsatisfactory to the Obama campaign.
“The Obama campaign is not satisfied with Romney’s answer. They still want to see Romney’s tax returns as well as minutes from Bain meetings,” NBC White House correspondent Kristen Welker reported. From Obama’s camp, Welker said: “We expect the American people would want to see more information.”
But the presumptive GOP standard bearer insisted that he took no active role in the company following 1999. Kicking off the latest round in the Bain wars, the Boston Globe reported on Thursday that Romney’s name appeared as CEO of Bain on Securities and Exchange Commission documents until 2002.
Romney took pains to try to distinguish owning the company from managing it, while at the same time not disparaging Bain.
“Well, there’s nothing wrong with being associated with Bain Capital, of course,” the Republican continued on CNN when pressed by interviewer Jim Acosta. “But the truth is that I left any role at Bain Capital in February of ’99.”
The GOP standard bearer also demanded an apology from Obama after deputy campaign manager, Stephanie Cutter, labeled him a possible “felon” for allegedly misrepresenting himself on government documents.
“He sure as heck ought to say that he’s sorry for the kinds of attacks that are coming from his team,” Romney said on ABC. “It’s very disappointing on his part. It’s beneath the dignity of the presidency of the United States to go out and say the kind of things that are being said, and even Democrats are saying that.”
To CNN’s Acosta, Romney called the attacks on his record “disgusting” and “demeaning.”
“Is that’s really what expected of the campaign of the sitting president of the United States? … Is this up to the standards that’s expected of the president of the United States?” Romney asked.
Romney also avoided questions about his vice presidential pick. Speculation accelerated about the possibility of him tapping former George W. Bush Secretary of State Condoleezza Rice after the Drudge Report’s banner headline naming Rice as a surprise leading contender on Thursday night, after a long day of Bain headlines critical of Romney.
Romney didn’t back away when asked by ABC’s Jonathan Karl if he stands by his primary pledge to select an anti-abortion rights vice presidential nominee, a position that would seem to knock Rice out of contention, who has described herself as favoring abortion rights. ||||| 3 years ago
(CNN) - Following a week of some of the sharpest attacks yet on his management of the financial firm Bain Capital, Mitt Romney offered a vocal defense Friday of his tenure there and strongly disputed reports he left the firm years later than he has previously said.
"There's nothing wrong with being associated with Bain Capital, of course," Romney said in an interview with CNN's Jim Acosta. "But the truth is that I left any role at Bain Capital in February of 1999."
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The Democratic criticisms, combined with a series of recent news articles looking into what is and isn't known of Romney's complicated financial portfolio, are simply "an effort on the part of the president's campaign to divert attention from the fact that the president has been a failure when it comes to reigniting the American economy," Romney said of President Barack Obama.
Romney stopped short of saying Obama's campaign was lying in recent ads hitting at his Bain tenure. Democrats have charged that Bain - under Romney and after - profited when companies owned by Bain closed and when jobs were outsourced overseas.
Obama's campaign, he said, is "putting out information which is false and deceptive and dishonest" in their advertisements.
Related: Why is 1999 so important to 2012?
Financial documents filed with the Security and Exchange Commission, including some obtained and reviewed by CNN, list Romney in various capacities with Bain after what Romney has repeatedly said was his February 1999 departure from the firm. That month, he took the reins of the Salt Lake City Olympic games and "relinquished all management authority and role in Bain Capital," he said in the interview.
Democrats, however, have pointed to the fact that his name appears on Bain Capital financial documents until 2002 as evidence Romney did not actually leave the firm. In 2002, Romney signed a retirement package with the firm and was no longer an owner of the company.
Obama deputy campaign manager Stephanie Cutter charged in a conference call with reporters this week that Romney "through his own words and his own signature was misrepresenting his position at Bain to the SEC, which is a felony," or was otherwise "misrepresenting his position at Bain to the American people to avoid responsibility for some of the consequences of his investments."
Presented with Cutter's felony suggestion, Romney asked if that is "really what's expected from the campaign of the sitting president of the United States?"
"Is this the level that the Obama campaign is willing to stoop to? Is this up to the standards expected of the presidency of the United States?" he asked. "It's disgusting, it's demeaning it's something which I think the president should take responsibility for and stop."
In the interview, Romney also lent greater clarity to his intentions surrounding release of his tax returns. In January, Romney released his 2010 return and an estimate of his 2011 tax year liability.
Related: Romney team defiant in response to Bain attack
"The law requires us to put out a full financial disclosure and that I've done," he said, adding that the most recent year will be released "as soon as the accountants have that ready.
"And that's what we're going to put out," he said. "People always want to get more and we're putting out what is required plus more that is not required. And those are the two years that people are going to have and that's all that's necessary for people to understand something about my finances."
Also see:
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McDonnell furiously defends Romney from Obama salvo
Biden to Romney: 'Show your papers'
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Barbour: If in Romney’s position, I would release tax docs
Watch The Situation Room with Wolf Blitzer weekdays at 4pm to 6pm ET and Saturdays at 6pm ET. For the latest from The Situation Room click here. ||||| Mitt Romney challenged President Obama Friday to "rein in" his campaign team after a senior aide suggested the Republican candidate may have committed a felony in his SEC filings. In an interview with Fox News, Romney called the comment "absurd" and "beneath the dignity of the presidency," and charged that the Obama team is just trying to deflect from all the sour economic news to "save the president's skin."
The Republican presidential candidate spoke to Fox News amid a tumultuous debate between the campaigns and in the media over Romney's tenure at private-equity firm Bain Capital. That debate has led to charges of lying on both sides but cranked up Thursday following a Boston Globe article that said documents show Romney was in charge at Bain for three years longer than he had claimed.
In a comment Romney's campaign says crossed a red line, Obama's deputy campaign manager Stephanie Cutter alleged that Romney was either misrepresenting his position at Bain to the Securities and Exchange Commission, "which is a felony," or misrepresenting to the American people.
"It's ridiculous," Romney told Fox News on Friday, in response to the charge. "And of course it's beneath the dignity of the presidency and of his campaign."
Romney added: "He really needs to rein in his team and to finally take responsibility for what they're saying. This is really absurd."
Romney, though, claimed the attacks are part of a "pattern."
"There are a lot of people in this country who are really hurting, and the president has been unsuccessful in getting people back to work, and so they're casting about in some way to try and make attacks and try and save the president's skin, save his campaign. That's simply not going to work," Romney said. "He's going to have to finally confront the American people with the failures of his policies and talk about the way forward."
The Romney campaign on Thursday had called on Obama's campaign to apologize.
But the Obama campaign has not done so. Far from it, Obama in an interview with WJLA-TV said Friday that Romney needs to better explain his tenure at Bain.
"Ultimately Mr. Romney, I think, is going to have to answer those questions, because if he aspires to being president, one of the things you learn is, you are ultimately responsible for the conduct of your operations," Obama said. "But again that's probably a question that he's going to have to answer and I think that's a legitimate part of the campaign."
The 2001 SEC filing showed Romney as Bain's "sole shareholder, sole director, chief executive officer and president" though the campaign had said he left in 1999 to lead the 2002 Winter Olympic Games. The period is relevant because that's when Bain was involved with companies that created jobs overseas or went bust -- and a period when Romney said he was not actively with the company.
The Romney campaign, though, stands by statements that the candidate left Bain in 1999, saying there are just "technical and legal reasons" why his name stayed on the documents. A campaign spokeswoman told Fox News on Friday that Romney was not in a management role after 1999. Bain Capital offered a similar explanation.
Obama challenged that in his interview with WJLA. "Now, my understanding is that Mr. Romney attested to the FCC, multiple times, that he was the chairman, CEO and president of Bain Capital and I think most Americans figure if you are the chairman, CEO and president of a company that you are responsible for what that company does," he said.
Romney, though, said he's still waiting to engage in the "meaningful debate" he says Obama pledged after Romney clinched the GOP nomination.
"I'm waiting for that to start. All we've seen so far from his campaign has been one attack after the other," Romney said.
Asked about past comments in which he's called Obama a "nice guy," Romney said with a chuckle: "He's straining that generous comment."
Meanwhile, Romney said in response to Democratic criticism about his disclosure of personal finances that he will release one more year's worth of tax returns. He said two years' worth -- that would be 2010 and 2011 -- is "plenty."
Romney also challenged Obama's latest claims that the GOP candidate is not serious about deficit reduction because of his support for tax cut extensions for top earners. Romney said Obama "ought to look in the mirror because this president has raised the deficit and raised the debt for this country."
Romney also declined to comment on the vice presidential nominee selection process. Speculation has centered of late on former Secretary of State Condoleezza Rice, though she has said definitively she is not interested in the job. ||||| Presumptive GOP presidential nominee Mitt Romney joined CBS News in a series of interviews with all five networks Friday. CBS News
(CBS News) President Obama should apologize for his campaign's suggestion that Mitt Romney is either a criminal or a liar, the presumptive GOP nominee told CBS News' Jan Crawford in an interview Friday.
The president "ought to apologize for what he's doing," Romney told Crawford. The former Massachusetts governor sat down with all five networks one day after Mr. Obama's deputy campaign manager Stephanie Cutter posed two damning outcomes for the former Massachusetts governor from Thursday's Boston Globe story, which alleged that Romney continued to head the private equity firm Bain Capital three years after he claimed to have left.
Romney says Obama owes him an apology
Cutter said in a conference call Thursday with reporters that if the allegations are true, then Romney is either a felon for "misrepresenting his position at Bain" to the Securities and Exchange Commission, or "he was lying to the American people."
Asked by Crawford whether he believes Mr. Obama owes him an apology for Cutter's remarks, Romney said, "Absolutely - my goodness!
"What kind of president would have a campaign that says something like that about the nominee of another party?" Romney said. "This is reckless and absurd on his part, and it's something that's beneath his dignity. I hope he recognizes that even fellow Democrats have said that.
"Look - the president needs to talk about the direction he'd take the country, and stop these kinds of ads and attacks that are so disparate from what the American people want to talk about," Romney concluded, adding later that the president "has demeaned the leadership which he should be bringing to this country."
Romney's history at Bain has long plagued his presidential ambitions; on Friday, pressure began to mount for him to release his tax returns for a closer look into his assets and professional history with the firm. In an interview with CBS News on Thursday, the president argued such questions were appropriate, and merely "the nature of runnin' for president."
Read the transcript from the full interview here. ||||| His credibility under attack, Republican presidential hopeful Mitt Romney insisted on Friday that he had "no role whatsoever in the management" of a private equity firm after early 1999, and demanded that President Barack Obama apologize for campaign aides who persist in alleging otherwise.
President Barack Obama speaks at a campaign event at Green Run High School in Virginia Beach, Va., Friday, July 13, 2012. Obama is spending the day in Virginia campaigning. (AP Photo/Susan Walsh) (Associated Press)
President Barack Obama pauses while speaking at a campaign event at Green Run High School in Virginia Beach, Va., Friday, July 13, 2012. Obama is spending the day in Virginia campaigning. (AP Photo/Susan... (Associated Press)
President Barack Obama holds a baby as he greets the overflow crowd before a campaign event at Green Run High School in Virginia Beach, Va., Friday, July 13, 2012. Obama is spending the day in Virginia... (Associated Press)
President Barack Obama, accompanied by and Sen. Mark Warner, D-Va., left, talks with Cari Beauregard, right, and Jennifer Farlin, second from right, at Rick's Cafe in Virginia Beach, Va., Friday, July... (Associated Press)
President Barack Obama picks up Kerry Christophe III during a stop at Rick's Cafe in Virginia Beach, Va., Friday, July 13, 2012. Obama is spending the day in Virginia campaigning. Sen. Mark Warner, D-Va.,... (Associated Press)
FILE - In this July 11, 2012 file photo, Republican presidential candidate, former Massachusetts Gov. Mitt Romney speaks in Houston, Texas. President Barack Obama and Republican rival Mitt Romney's campaigns... (Associated Press)
"This is simply beneath the dignity of the presidency of the United States," Romney said in an interview on ABC, one of several he granted to network and cable stations in hopes of extinguishing the controversy.
Under pressure from Democrats and even some Republicans to release tax returns going back several years, Romney indicated he wouldn't do so. "You can never satisfy the opposition research team of the Obama organization," he told CBS.
Romney said after he left Bain Capital he retained ownership "until we were able to negotiate a departure" from the company he had founded. "I had no role whatsoever in the management of Bain Capital after February of 1999," he said, adding that officials at the company and independent fact-checkers had said the same thing.
He also said, "I was an owner, and being a shareholder doesn't mean you're running the business." He said he couldn't recall attending any Bain management meetings after he moved to Salt Lake City to oversee the Olympic Games.
The precise role Romney played at the firm between 1999 and 2001 is important not only because critics have raised questions about his truthfulness, but also because Bain was sending jobs overseas during that period.
That, in turn, goes to the core issue of the race for the White House in dreary economic times, Romney's claim that as a former businessman, he has the ability to create jobs and finally pull the country out of a downturn that has lingered throughout Obama's term. The Obama campaign has criticized Romney as running a firm that pioneered job outsourcing.
Some Securities and Exchange Commission documents have surfaced suggesting Romney played an active role in the Boston-based company through 2002. The filings with the SEC place Romney in charge of Bain Capital from 1999 to 2001, the period in which it outsourced jobs and ran companies that fell into bankruptcy.
Obama himself had stepped into the controversy a few hours before Romney's comments were aired.
"Now, my understanding is that Mr. Romney attested to the SEC multiple times that he was the chairman, CEO and president of Bain Capital. And I think most Americans figure if you're the chairman, CEO and president of a company that you are responsible for what the company does," Obama said in an interview with WJLA-TV in Virginia as he campaigned across the battleground state.
The president said the questions that have been raised in numerous media reports and highlighted by his own campaign aides were a legitimate part of the race for the White House.
"Ultimately, I think, Mr. Romney is going to have to answer those questions because if he aspires to being president, one of the things you learn is you're ultimately responsible for the conduct of your operations," the president said.
But Romney said that was "Chicago-style politics at its worst," and accused the president and his campaign of trying to shift attention from the persistently sluggish economy and unemployment of 8 percent or higher for more than 40 months.
Romney was particularly harsh when asked about a claim by Obama deputy campaign manager Stephanie Cutter suggesting he might be guilty of a felony for misrepresenting his position at Bain to the SEC.
"Is this the level that the Obama campaign is willing to stoop to?" he responded on CNN. "Is this up to the standards expected of the presidency of the United States?"
The Obama campaign said it would not apologize.
Romney acknowledged that he would have benefitted financially from Bain's operations even after he left management of the firm to others. That could open him up to criticism that he gained from investment in companies that sent jobs overseas.
"All of the investors participate in the success or failure of various investments, just like you do as a shareholder of an enterprise," Romney said.
One Romney aide said earlier in the week that any suggestion that Romney had shipped jobs overseas was a lie, and the campaign has said repeatedly the break with the private equity firm came in 1999.
Yet documents surfaced for the second straight day that seemed to indicate Romney played an active management role in Bain Capital after that date, when he and company officials say he left the firm to run the Olympic.
Annual reports filed by Bain Capital with the state of Massachusetts said he had a role in the firm as late as 2001. The company's 2002 report did not list Romney among the firm's managing partners, suggesting he was no longer with Bain by that point.
Obama spent much of his day challenging Romney over taxes and spending, telling one audience that if Republicans are unwilling to let tax cuts lapse for the wealthiest Americans, they're "not serious" about reducing the deficit.
Appearing in Hampton Roads, Va., Obama renewed calls to extend Bush-era tax breaks for those earning $250,000 or less while the two sides argue about higher earners, affecting the top 2 percent of Americans. But he charged Republicans with balking, and holding middle-class cuts "hostage."
"If you say you want to bring down the deficit, but you're not willing to let tax cuts lapse for the top 2 percent, it tells me you're not serious about deficit reduction," Obama said at a campaign rally. He said lawmakers should "go ahead and help middle-class families right now. And so far, I have not gotten an OK from the other side on that. And that tells me I guess they're not that serious about deficit reduction."
Romney and other Republicans argue that raising taxes on anyone would be a mistake given the fragile state of the recovery.
But for now, the dispute over outsourcing and the timing of Romney's departure from the firm he created took a central role in the race.
Separately, Bain Capital issued a statement saying that Romney "remained the sole stockholder for a time while formal ownership was being documented and transferred to the group of partners who took over management of the firm in 1999."
The dispute expanded to the television ad wars already under way.
Romney unveiled a scathing commercial this week declaring there was no truth to the accusations and saying that in 2008, "candidate Obama lied about Hillary Clinton." It showed the secretary of state _ then Obama's rival for the Democratic nomination _ saying "shame on you, Barack Obama."
Obama responded on Friday with an ad that accused the Republican of favoring a 25 percent tax cut for millionaires, tax breaks for oil companies and corporations that move jobs overseas and a tax increase for working families. By contrast, it says, the president wants "the wealthy to pay a little more so the middle class pays less."
______
Kuhnhenn reported from Hampton Roads, Va. Associated Press writer Steven Braun contributed to this report.
______
Follow Jim Kuhnhenn on Twitter: http://www.twitter.com/jkuhnhenn | – Mitt Romney went on the offensive in a big way today over his tenure at Bain, giving a series of TV interviews to insist that he stopped having any management role in 1999 and to demand that President Obama apologize because of his advisers' "disgusting" attacks on him over the issue. Some of his quotes: “"There's nothing wrong with being associated with Bain Capital, of course," he told CNN. "But the truth is that I left any role at Bain Capital in February of 1999." So why was he still listed as holding key positions at Bain after that? "I still retained an ownership interest," he said on CBS. "I had the capacity if I were not on leave, if I were actually wanting to run the business to do so, but I did not." “There is a difference between being a shareholder, an owner if you will, than a person who is running an entity.” "This is simply beneath the dignity of the presidency of the United States," he said on ABC, when asked about an Obama adviser who suggested Romney was guilty of a felony. "He really needs to rein in his team and to finally take responsibility for what they're saying," he told Fox News. “What kind of a president would have a campaign that says something like that about the nominee of another party?” Does Obama owe him an apology? "Absolutely—my goodness!" Politico and the AP have roundups. Click to read one columnist's view that Romney has changed his story over the years. |
SECTION 1. SHORT TITLE.
This Act may be cited as the ``The Defense Communities Assistance
Act of 2009''.
SEC. 2. SENSE OF CONGRESS.
It is the sense of the Congress, that as the Federal Government
implements base closures and realignments, global repositioning, and
grow the force initiatives, it is necessary to assist local communities
coping with the impact of these programs at both closed and active
military installations. To aid communities to either recover quickly
from closures or to accommodate growth associated with troop influxes,
the Federal Government must provide assistance to communities to
effectively implement the various initiatives of the Department of
Defense.
SEC. 3. PERMANENT AUTHORITY TO CONVEY PROPERTY AT MILITARY
INSTALLATIONS TO SUPPORT MILITARY CONSTRUCTION AND
AGREEMENTS TO LIMIT ENCROACHMENT.
Section 2869(a)(3) of title 10, United States Code, is amended by
striking ``shall apply only during the period'' and all that follows
through ``September 30, 2008'' and inserting ``without limitation on
duration''.
SEC. 4. EXTENSION OF AUTHORITY TO PURCHASE MUNICIPAL SERVICES FOR
MILITARY INSTALLATIONS IN THE UNITED STATES.
(a) Permanent Authority.--Chapter 146 of title 10, United States
Code, is amended by inserting after section 2465 the following new
section:
``Sec. 2465a. Contracts for procurement of municipal services for
military installations in the United States
``(a) Contract Authority.--Subject to section 2465 of this title,
the Secretary concerned may enter into a contract for the procurement
of municipal services described in subsection (b) for a military
installation in the United States from a county, municipal government,
or other local governmental unit in the geographic area in which the
installation is located.
``(b) Covered Municipal Services.--The municipal services that may
be procured for a military installation under the authority of this
section are as follows:
``(1) Refuse collection.
``(2) Refuse disposal.
``(3) Library services.
``(4) Recreation services.
``(5) Facility maintenance and repair.
``(6) Utilities.
``(c) Exception From Competitive Procedures.--The Secretary
concerned may enter into a contract under subsection (a) using
procedures other than competitive procedures if--
``(1) the term of the proposed contract does not exceed 5
years;
``(2) the Secretary determines that the price for the
municipal services to be provided under the contract is fair,
reasonable, represents the least cost to the Federal
Government, and, to the maximum extent practicable, takes into
consideration the interests of small business concerns (as that
term is defined in section 3(a) of the Small Business Act (15
U.S.C. 632(a))); and
``(3) the business case supporting the Secretary's
determination under paragraph (2)--
``(A) describes the availability, benefits, and
drawbacks of alternative sources; and
``(B) establishes that performance by the county or
municipal government or other local governmental unit
will not increase costs to the Federal Government, when
compared to the cost of continued performance by the
current provider of the services.
``(d) Limitation on Delegation.--The authority to make the
determination described in subsection (c)(2) may not be delegated to a
level lower than a Deputy Assistant Secretary for Installations and
Environment, or another official of the Department of Defense at an
equivalent level.
``(e) Congressional Notification.--The Secretary concerned may not
enter into a contract under subsection (a) for the procurement of
municipal services until the Secretary notifies the Committees on Armed
Services of the Senate and the House of Representatives of the proposed
contract and a period of 14 days elapses from the date the notification
is received by the committees. The notification shall include a summary
of the business case and an explanation of how the adverse impact, if
any, on civilian employees of the Department of Defense will be
minimized.
``(f) Guidance.--The Secretary of Defense shall issue guidance to
address the implementation of this section.''.
(b) Clerical Amendment.--The table of sections at the beginning of
such chapter is amended by inserting after the item relating to section
2465 the following new item:
``2465a. Contracts for purchase of municipal services for military
installations in the United States.''.
(c) Extension of Pilot Program.--Section 325(f) of the Ronald W.
Reagan National Defense Authorization Act for Fiscal Year 2005 (Public
Law 108-375; 10 U.S.C. 2461 note) is amended by striking ``September
30, 2010'' and inserting ``September 30, 2020''.
SEC. 5. REIMBURSABLE ACTIVITIES UNDER THE DEFENSE-STATE MEMORANDUM OF
AGREEMENT PROGRAM.
Section 2701(d)(1) of title 10, United States Code, is amended by
inserting before the period at the end the following: ``and the
processing of property transfers before or after remediation, provided
the Secretary shall not condition funding based on the manner in which
a State exercises its enforcement authority, or its willingness to
enter into dispute resolution prior to exercising that enforcement
authority.''.
SEC. 6. INDEMNIFICATION OF TRANSFEREES OF CLOSING DEFENSE PROPERTIES.
Section 330(a)(1) of the National Defense Authorization Act for
Fiscal Year 1993 (Public Law 102-484; 10 U.S.C. 2687 note), is amended
by striking ``cost or other fee'' and all that follows through
``contaminant,'' and inserting ``cost, statutory or regulatory
requirement or order, or other cost, expense, or fee arising out of any
such requirement or claim for personal injury, environmental
remediation, or property damage (including death, illness, or loss of
or damage to property or economic loss) that results from, or is in any
manner predicated upon, the release or threatened release of any
hazardous substance, pollutant, or contaminant''.
SEC. 7. REQUIREMENT FOR NO-COST ECONOMIC DEVELOPMENT CONVEYANCES.
(a) Repeal of Certain Requirements.--Subsection (a) of section 3006
of the National Defense Authorization Act for Fiscal Year 2002 (Public
Law 107-107; 115 Stat. 1350), and the amendments made by that
subsection, are hereby repealed. Effective as of the date of the
enactment of this Act, the provisions of section 2905 of the Defense
Base Closure and Realignment Act of 1990 (part A of title XXIX of
Public Law 101-510; 10 U.S.C. 2687 note) that were amended by section
3006(a) of the National Defense Authorization Act for Fiscal Year 2002,
as such provisions were in effect on December 27, 2001, are hereby
revived.
(b) Regulations.--Not later than 60 days after the date of the
enactment of this Act, the Secretary of Defense shall prescribe
regulations to implement the provisions of section 2905 of the Defense
Base Closure and Realignment Act of 1990 revived by subsection (a) to
ensure that the military departments transfer surplus real and personal
property at closed or realigned military installations without
consideration to local redevelopment authorities for economic
development purposes, and without the requirement to value such
property.
(c) Report.--Not later than 180 days after the date of the
enactment of this Act, the Secretary of Defense shall submit to
Congress a report on the status of current and anticipated economic
development conveyances, projected job creation, community
reinvestment, and progress made as a result of the enactment of this
section. | Defense Communities Assistance Act of 2009 - Expresses the sense of Congress on the necessity of assisting local communities coping with the impact of base closures and realignments and other military actions.
Extends permanently (under current law, terminated at the end of FY2008) the authority of the Secretary of the military department concerned to convey, for certain purposes, real property on a military installation determined to be excess to the needs of the Department of Defense (DOD).
Authorizes the Secretary concerned to contract for the procurement of municipal services for a U.S. military installation from a county, municipal government, or other local governmental unit in the area. Authorizes such Secretary to so contract using procedures other than competitive procedures, under certain conditions and after congressional notification.
Amends the Ronald W. Reagan National Defense Authorization Act for Fiscal Year 2005 to extend through FY2020 a pilot program for the purchase of certain municipal services for military installations.
Amends the National Defense Authorization Act for Fiscal Year 1993 to broaden the indemnification provided to transferees of military properties.
Reinstates provisions of the Defense Base Closure and Realignment Act of 1990 which allow military departments to transfer surplus real and personal property at closed or realigned military installations without consideration to local redevelopment authorities when used for economic development purposes, without the requirement to assess the property's value. |
water is the most important liquid on earth .
although its uniform phase already exhibits many fascinating properties and is currently an area of intensive research , the importance of the _ inhomogeneous _ phase in the chemical and biological sciences is even greater : as a solvent , water is ubiquitous in physical chemistry , biochemistry and electrochemistry .
the associated phenomena include hydrophobic interactions @xcite , protein folding @xcite , the electrochemical interface @xcite , and phase transitions of confined liquids @xcite .
due to the complex interplay of hydrogen bonding , long - range polar interactions , and short - range excluded volume effects , developing a tractable theory to describe the solvent in the aforementioned systems remains a challenge @xcite . despite the importance , inherent interest , and extensive experimental study of water , most existing theories of the inhomogeneous phase of water
either lack the accuracy to describe the above phenomena in a quantitatively satisfying way or become computationally prohibitive .
the latter is particularly true for applications to complex systems , such as dissolved biomolecules or electrochemical interfaces .
simple dielectric continuum theories @xcite capture the dielectric response of the solvent at long length scales , but fail to describe more subtle effects at interfaces , such as the reorganization of the hydrogen - bond network or the binding of water molecules to solutes .
atomistic theories , on the other hand , describe such local effects quite well , but require the explicit treatment of many solvent molecules and also demand long simulation times to calculate statistically reliable thermodynamic averages .
since the full - fledged _ ab initio _ molecular dynamics description of the solvent is only feasible for the smallest solutes , generally additional approximations become necessary in practice : bernholc and coworkers , for example , have introduced a clever scheme which employs the full _ ab initio _ description only for a few solvent molecules adjacent to the solute and use rigid geometries and frozen electron densities for the remaining molecules @xcite . in other studies , combination of _ ab initio _
methods for the solute with classical force field approaches @xcite for the solvent yields additional simplifications . despite the simplifications which such hybrid approaches allow , the need to compute many configurations to sample phase - space properly ultimately limits the size of systems which can be studied and thus the applicability of such approaches .
ideally , one would have a rigorous description of the solvent which is able to combine the advantages of continuum theories ( large system sizes and _ implicit _ thermodynamic averaging ) with an explicit geometric description of the solvent molecule . here , we show that just such a theory can be developed for liquid water by starting with the quantum mechanical free - energy functional for both the electrons and nuclei which comprise the liquid and , by `` integrating out '' the electrons , proceeding to construct a density functional in terms of atomic site densities alone .
such `` classical '' density - functional theories , which are founded on a number of exact theorems @xcite , have been applied successfully to the study of simple liquids in the past @xcite .
historically , application of this method begins with a hard sphere reference system that is usually augmented by terms that capture weak long - range attractive forces @xcite .
unfortunately , a hard sphere reference system is a poor starting point for the description of water because of the strong anisotropic short - range interactions arising from the molecular structure , including effects such as hydrogen bonding . to remedy this , chandler and coworkers @xcite introduced a density - functional theory for general molecular liquids in terms of a set of densities , one for each `` interaction site '' on the molecule ( typically atomic centers ) .
although their theory successfully predicted the correct hydrogen - bonded structure of ice @xcite , it suffered from a significant flaw : to make calculations tractable , the `` united atom approximation '' , which takes all of the sites on the molecule to sit at a single point , had to be invoked .
this severe oversimplification of the molecular structure prohibited the description of dielectric properties and stalled the further development of this promising approach . in @xcite , we eliminated the need for the united atom approximation by writing the free energy of a general molecular liquid as a functional of a set of effective potentials in which fictitious non - interacting molecules move .
this advance allows for the exact evaluation of the entropy associated with the geometric structure of the molecules in a numerically feasible way and forms the basis for the construction of a new class of accurate density functionals for fully interacting _ molecular _ liquids .
in this work , we apply our general theory of molecular liquids to water and demonstrate how an accurate free - energy functional can be developed to reproduce the equation of state , the experimental site - site correlation functions , and the macroscopic dielectric response . the organization of the work is as follows .
section 2 gives a brief review of the general theory of molecular liquids introduced in @xcite .
section 3 discusses the application of this approach to the particular case of water and introduces new computational techniques to simplify calculations of triatomic liquids .
section 4 presents results obtained using this new microscopically - informed continuum theory to study the behavior of water in a parallel plate capacitor . here
, we explore the differences between capacitor plates consisting either of purely repulsive hard walls or of walls with a local region of attraction .
we also explore the dielectric response of water in both the linear and the nonlinear regimes of the applied field . comparing our results to previous works based on explicit molecular simulations
, we find quite encouraging agreement .
section 5 then concludes this work .
in @xcite , we showed that the grand free energy @xmath0 of an assembly of interacting identical molecules ( consisting of @xmath1 atoms or `` interaction sites '' each ) can be expressed as a functional of a set of effective potentials @xmath2 , in which a corresponding set of fictitious non - interacting molecules move .
specifically , we wrote @xmath3= \omega^{(ni)}[\mathbf{\psi}]- \sum_{\alpha=1}^{m}\int d^{3}r \left ( \psi_{\alpha}(\mathbf{r})-\phi_{\alpha}(\mathbf{r})+\mu_{\alpha}\right ) n_{\alpha}(\mathbf{r } ) \nonumber\\ + u[\mathbf{n } ] . \label{fullomega}\end{aligned}\ ] ] here , @xmath4 is the site - dependent external potential ( with @xmath5 referring to the different atomic sites on each molecule ) , @xmath6 is a site specific chemical potential and @xmath7 $ ] denotes the excess free energy due to inter - molecular interactions , which is a functional of the set of site densities @xmath8 . finally , @xmath9 $ ] is the grand free energy of an assembly of noninteracting molecules in a set of effective potentials @xmath10 .
this free energy is known explicitly and is _ exactly _ @xmath11=-k_{b}tn_{l } \int d^{3m}r\;s(\{\mathbf{r}_\alpha\ } ) e^{-\beta\sum_{\alpha=1}^{m}\psi_{\alpha}(\mathbf{r}_{\alpha } ) } \label{freeeni},\end{aligned}\ ] ] where @xmath12 is the reference density at vanishing chemical potentials ( which we will later take to be the bulk liquid density ) and @xmath13 , which describes the geometry of the molecule , is the intra - molecular distribution function .
note that we take the densities in ( [ fullomega ] ) to be themselves functionals of the effective fields via @xmath14.\ ] ] finally , the effective potentials which minimize @xmath15 $ ] determine the equilibrium site densities and allow for the calculation of various equilibrium properties of the liquid .
the introduction of effective potentials instead of site density fields as fundamental variables in the density - functional theory of classical molecular liquids allows for the first time a computationally tractable approach to treat the non - interacting system exactly .
this parallels the introduction of kohn - sham orbitals as fundamental variables in the density - functional theory of electronic structure @xcite . in both cases ,
the construction of highly accurate density functionals is made possible by mapping a system of interacting particles onto a fictitious system of noninteracting particles with the same equilibrium densities .
we mention that our approach of minimizing the free energy with respect to a set of _ effective potentials _ is known in the electronic structure context as the optimized effective potential method @xcite . in @xcite , we also present a recipe for the construction of the excess free energy functional @xmath16 in ( [ fullomega ] ) . as usual with density - functional theories , this construction is difficult . as in our previous work ,
we follow the lead of kohn and sham and construct a free - energy functional that reproduces established results for the homogeneous phase in the limit of vanishing external fields .
namely , we expand @xmath16 in a power series about the uniform liquid , and formally group all terms except the quadratic part , which is analogous to the hartree energy in electronic - structure theory , into an unknown functional @xmath17 $ ] , which is then the analogue to the electronic exchange - correlation functional , whose form , being unknown , must ultimately be treated in some approximate way . to proceed , we separate the kernel of the quadratic part of @xmath16 into a long - wavelength part @xmath18 , known analytically for the case of rigid molecules , and a remainder @xmath19 , to be determined from experimental data .
the next paragraph describes @xmath18 in detail , and the set of functions @xmath19 will be constructed below such that the resulting functional reproduces the experimental correlation functions in the uniform phase .
when these two parts are determined , they combine with @xmath20 to give @xmath16 as @xmath21=\frac{1}{2}\sum_{\alpha,\gamma=1}^{m}\int d^{3}r \int d^{3}r'\ ; n_{\alpha}(\mathbf{r})\left\ { k_{\alpha\gamma}(\mathbf{r},\mathbf{r ' } ) \right .
\nonumber\\ \left .
+ c_{\alpha\gamma}(\mathbf{r},\mathbf{r'})\right\ } n_{\gamma}(\mathbf{r ' } ) + f^{ex}[\mathbf{n } ] .
\label{u}\end{aligned}\ ] ] the derivation of @xmath18@xcite considers a collection of rigid neutral molecules with each interaction site carrying a partial charge @xmath22 with _ no _ assumptions regarding the form of the non - electrostatic part of the interaction the theory neither is perturbative in the interaction strength nor presupposes a decomposition into pairwise interaction potentials . in @xcite , we then prove rigorously that , for a certain class of liquids including all diatomic liquids and also water , the leading order term in a long - wavelength expansion of @xmath23 , the hessian of u for rigid molecules , is @xmath24 where @xmath25 is the macroscopic dielectric constant and @xmath26 is the dielectric constant of a system with intra - molecular correlations only . because @xmath18 now captures the singular long - wavelength features of the response function , @xmath19 , which we define as the difference between @xmath23 ( given by the experimental correlation functions ) and the sum of @xmath18 and @xmath27 ,
must now be smooth near the origin and thus amenable to numerical approximations .
as discussed below , we define @xmath20 such that its hessian matches the constant term in the long - wavelength expansion of @xmath23 . therefore , the functions @xmath19 have to _ vanish _ for small @xmath28 . next , to approximate @xmath20 , we begin by noting that in the case of zero external fields all densities are equal and the first quadratic term ( @xmath29 ) in ( [ u ] ) vanishes because of charge neutrality . anticipating that , by definition
, the matrix function @xmath30 vanishes in the long - wavelength limit , @xmath20 then captures all of the internal energy of the uniform phase ( and the long - wavelength limit of the non - singular part of the hessian @xmath23 ) and can be expressed as @xmath31 , with @xmath32 being the volume and @xmath33 the average molecular density . due to
the presence of multiple density fields , generalizing the above expression for @xmath20 to the inhomogeneous case is more difficult than for the analogous exchange - correlation energy in electronic structure theory .
moreover , because of the strong correlations induced by excluded volume effects , _ purely local _
excess functionals fail to describe the liquid state @xcite .
we therefore approximate @xmath20 with a simplified _ ansatz _ in the spirit of weighted density - functional theory @xcite , but generalized to multiple species , @xmath34=\int d^{3}r\sum_{i}p_{i } f^{ex}\left(\sum_{\gamma=1}^{m}b_{\gamma}^{i}\overline{n}_{\gamma}(\mathbf{r})\right ) , \label{fex}\ ] ] where we introduce the weighted densities @xmath35 , with @xmath36 being a `` smoothing '' parameter ultimately fit to the experimental surface tension . to reduce to the correct form in the uniform case
, @xmath37 and @xmath38 must fulfill @xmath39 and @xmath40 . for the scalar function @xmath41
, we use a polynomial fit to various bulk thermodynamic properties of the liquid . the condition that @xmath30 vanishes in the long - wavelength limit subsequently fixes @xmath37 and @xmath38 . for a given @xmath42 , this then completely specifies our approximation to @xmath20 .
next , relating @xmath43 to the density - density correlation functions through the ornstein - zernike relation gives the matrix function @xmath30 for a given @xmath42 .
finally , we can determine the smoothing parameter @xmath42 by adjustment until calculations of the liquid - vapor interface give the correct surface tension .
assuming rigid bonds of fixed length ( and thus rigid angles as well ) the intra - molecular distribution function of a water molecule ( normalized to integrate to the volume of the system ) is @xmath44 where @xmath45 is the oxygen - hydrogen bond length taken from the spc / e @xcite model of water , @xmath46 is the bond angle between the hydrogens and taken to be the tetrahedral angle like in the spc / e model .
also , the label @xmath47 refers to the oxygen atom and the labels @xmath48 and @xmath49 to the two hydrogens , and we define @xmath50 .
contrary to the case of diatomic molecules , where the assumption of rigid bonds turns @xmath51 into a convolution , numerical evaluation of ( [ freeeni ] ) proves more challenging in the triatomic case because of the complex , nine - dimensional form of @xmath52 . to address this , we observe here that @xmath51 for water can _ also _ be brought into a `` convolution form '' by making use of the following mathematical identity , which is readily derived using the addition theorem for spherical harmonics , @xmath53 where @xmath54 and @xmath55 are unit vectors , @xmath56 is an arbitrary angle , @xmath57 is a legendre polynomial and the @xmath58 s denote the spherical harmonics .
( to prove ( [ mathid ] ) , first expand the delta function as a sum of pairs of legendre polynomials on the interval @xmath59 $ ] and then use the spherical - harmonic `` addition theorem '' to express @xmath60 as a sum of pairs of spherical harmonics . ) substituting ( [ mathid ] ) and ( [ swater ] ) into ( [ freeeni ] ) results in a computationally efficient form for the non - interacting free energy @xmath51 , @xmath61 where @xmath62 and @xmath63 , given by @xmath64 are now convolutions and can be efficiently evaluated with fast - fourier - transform techniques .
transformation to fourier space greatly simplifies the above convolutions , @xmath65\nonumber\\ f^{(2)}_{lm}(\mathbf{k})=(-i)^{l}j_{l}(|\mathbf{k}|b)y_{lm}(\hat{\mathbf{k } } ) { \mathcal f}[e^{-\beta\psi_{2}(\mathbf{r } ) } ] , \label{ffts}\end{aligned}\ ] ] where @xmath66 denotes the spherical bessel functions of the first kind and @xmath67 $ ] denotes the fourier transform of @xmath68 . to evaluate ( [ omeganiconv ] ) numerically ,
we first choose a maximum value of @xmath69 , @xmath70 , after which we truncate the infinite sum .
in general , the choice of @xmath70 depends on the density profile that has to be represented .
we find in the capacitor calculation presented below that the interaction site densities for water adjacent to the capacitor wall are fairly smooth in the linear response regime and can be sufficiently resolved with @xmath71 .
if strong external fields are applied , sharp features in the density profile develop and we use @xmath72 to be absolutely sure of a highly converged description . first , we approximate @xmath41 as a sixth - order polynomial , @xmath73 and adjust its coefficients to reproduce the seven conditions represented by ( a ) the thermodynamic stability of liquid and vapor phases , ( b ) their coexistence , ( c ) the experimental liquid and vapor densities , ( d ) the experimental bulk modulus of the liquid ( @xmath74 ) and ( e ) the derivative of the bulk modulus with respect to the pressure @xmath75 at standard temperature and pressure ( @xmath76c and @xmath77atm ) .
table [ fexinput ] summarizes the experimental input used to determine the coefficients @xmath78 , and table [ fexcoeffs ] gives the actual numerical values of the coefficients used in our calculations below .
( clearly , not all of the digits given in the table are significant , we give them only to make our results numerically reproducible . )
the values in the table are given in atomic units ( @xmath79 , @xmath80 ) as this is the system which our software employs .
c c c c + @xmath81 & @xmath82 & @xmath74 & @xmath83 + @xmath84 $ ] & @xmath84 $ ] & @xmath85 $ ] & ( dimensionless ) + + 997.1 & 0.023 & 2.187 & 5.8 + l l l + @xmath86 & @xmath87 $ ] & @xmath88 + @xmath89 & @xmath90 $ ] & @xmath91 + @xmath92 & @xmath93 $ ] & @xmath94 + @xmath95 & @xmath96 $ ] & @xmath97 + @xmath98 & @xmath99 $ ] & @xmath100 + @xmath101 & @xmath102 $ ] & @xmath103 + @xmath104 & @xmath105 $ ] & @xmath106 + next , we can determine the coefficients in the integrand in ( [ fex ] ) from knowledge of the constant term in the long - wavelength expansion of the hessian @xmath23 .
the entries in this term ( which is a matrix ) are related to various material response properties such as as the bulk modulus , but unfortunately , we do not have access to data for all of the material properties . in the absence of data , we take this matrix to be proportional to its value for the non - interacting case with a proportionality constant set to ensure the correct bulk modulus .
this then fixes the integrand in ( [ fex ] ) and allows it to be written entirely in terms of rational numbers in the form , @xmath107 next , to construct the matrix @xmath29 we use the partial charges of the spc / e water model @xcite , i.e. @xmath108 ( @xmath109 being the proton charge ) and the fact that the dielectric constant of the liquid with intra - molecular correlations _ only _ is @xmath110 , where @xmath111 is the dipole moment of an spc / e water molecule .
also , we employ the experimental value @xcite , @xmath112 , for the macroscopic dielectric function of liquid water at standard conditions described above . the use of @xmath29 as leading order term is only justified for _ long - wavelength _ ( small @xmath28 ) properties of the liquid : we therefore cut off its slowly decaying , large @xmath28 tail by multiplying it in fourier space with a crossover function @xmath113 given by @xmath114 with @xmath115 bohr , chosen to keep the @xmath30 functions as band - width limited as possible .
then we determine @xmath30 as described above using the partial structure factor data for the uniform liquid from figure 1 in @xcite . the best , explicit partial structure factor data which we have found are measured at standard pressure , but at a temperature @xmath116c , which differs slightly from the standard temperature ( @xmath76c ) employed in this work . comparing experimental radial distribution functions at various temperatures
@xcite , we find that the differences remain smaller than 10% over a temperature range of 30 kelvin .
we therefore expect an overall error of no more than one or two percent due to this difference in temperatures .
next , adjusting the smoothing parameter to give the experimental surface tension of @xmath117n / m@xcite , measured at standard conditions , yields @xmath118 ( to all the digits used in our software ) . finally , to provide a computationally transferable representation of @xmath30 , we parametrize each component @xmath19 by a sum of gaussians in fourier space @xmath119 table [ cfunccoeffs ] summarizes the resulting fitting coefficients ( to all decimal places used in our software ) . to reproduce the full matrix , note that @xmath30 is symmetric and that the identity of the hydrogens imposes @xmath120 .
figure [ cfunctions ] compares our extracted @xmath30 functions to the resulting numerical fits , the latter of which are used in all of the calculations presented below .
l l l l l + & & @xmath121 & @xmath122 & @xmath123 + & & @xmath90 $ ] & @xmath124 $ ] & @xmath125 $ ] + + & @xmath48 & @xmath126 & @xmath127 & @xmath128 + & @xmath49 & @xmath129 & @xmath130 & @xmath131 + & @xmath132 & @xmath133 & @xmath134 & @xmath135 + & @xmath136 & @xmath137 & @xmath138 & @xmath139 + & @xmath140 & @xmath141 & @xmath142 & @xmath143 + & @xmath144 & @xmath145 & @xmath146 & @xmath147 + + & @xmath48 & @xmath148 & @xmath149 & @xmath150 + & @xmath49 & @xmath151 & @xmath152 & @xmath153 + & @xmath132 & @xmath154 & @xmath155 & @xmath156 + & @xmath136 & @xmath157 & @xmath158 & @xmath159 + & @xmath140 & @xmath160 & @xmath161 & @xmath162 + & @xmath144 & @xmath163 & @xmath164 & @xmath165 + + & @xmath48 & @xmath166 & @xmath167 & @xmath168 + & @xmath49 & @xmath169 & @xmath170 & @xmath171 + + & @xmath48 & @xmath166 & @xmath167 & @xmath168 + & @xmath49 & @xmath169 & @xmath170 & @xmath171 + ( thick dashed curve ) , @xmath172 ( thick dash - dotted curve ) and @xmath173 ( thick dotted curve ) and the corresponding parametrized forms ( thin solid curves ) given by ( [ fits ] ) and table [ cfunccoeffs ] . note that @xmath174 is not shown , since it would be visually indistinguishable from @xmath173 . ] in sum , to compute the free - energy functional for a given set of effective potentials @xmath175 , one first evaluates the intra - molecular contribution via ( [ omeganiconv ] ) and ( [ ffts ] ) .
next , one determines the site densities via ( [ eq : getns ] ) , which allows one to evaluate the second term in ( [ fullomega ] ) trivially .
finally , one evaluates the last term in ( [ fullomega ] ) according to ( [ u ] ) , with @xmath29 given by ( [ k ] ) , @xmath30 parameterized by the coefficients in table [ cfunccoeffs ] , and @xmath20 computed according to ( [ fex ] ) , ( [ fex ] ) , ( [ fexh2o ] ) .
to demonstrate the ability of our density - functional theory to describe water in an inhomogeneous environment and to capture the dielectric response of the liquid , we study the behavior of the liquid in a parallel plate capacitor .
we carry out our study at standard temperature and pressure described above , taking the system to be homogeneous in the two dimensions parallel to the capacitor plates . along the perpendicular direction , we impose periodic boundary conditions , defining a unit cell containing _ two _ parallel plate capacitors with opposing externally applied electric fields .
this arrangement makes the electrostatic potential a periodic function and eliminates undesired electrostatic interactions between the capacitors .
each capacitor has a plate separation of @xmath176 ( 200 bohr ) and the total length of the cell is @xmath177 ( 800 bohr ) .
in our study we consider both purely repulsive , `` hard - wall '' plates as well as `` attractive '' plates with a region of attraction near the plates .
for the hard - wall case , the plates are essentially infinite potential hard walls acting on both the oxygen and hydrogen sites of the water molecules . as a practical numerical matter , to reduce aliasing effects in the use of the numerical fourier transform we approximate such walls by purely repulsive gaussian potentials of sufficiently narrow width and large amplitude so that the results below are insensitive to the width and amplitude of the gaussian employed .
in particular , we use @xmath178 with @xmath179 and @xmath180 . for the attractive case ,
we employ a `` 9 - 3 '' ( planarly integrated lennard - jones ) potential acting on the oxygens _ only _ , specifically , @xmath181\ ] ] with @xmath182 ev , @xmath183 and @xmath184 .
this potential has its minimum at a distance of 3 from the wall at a depth @xmath185 ev .
we choose this depth as typical of the interactions in such systems .
for instance , berkowitz and co - workers @xcite employ a corrugated potential with an average depth of about 0.40 ev , which is also in the range of a couple of tenths of an electron volt . to determine the thermodynamic state of the system
we then expand the density fields on a real space grid with 8192 sampling points ( @xmath186 points / ) , and minimize the grand free energy ( [ fullomega ] ) using standard numerical conjugate gradient techniques without any preconditioning .
we begin with a brief discussion of our results for the hard wall case as an idealized reference for comparison .
figure [ zerofield ] shows our results for oxygen and hydrogen equilibrium density profiles in the absence of an externally applied electrostatic displacement ( @xmath187 ) and compares them to the density profiles of hydrogen and oxygen sites in a relatively weak external field ( @xmath188 ) .
the zero - field profiles exhibit an extended gas phase region up to a distance of @xmath189 from the plates .
this `` lingering '' gas phase region exists because molecules can , at very little free - energy cost , minimize the influence of the repulsive plates by leaving the system .
( recall that ( [ fullomega ] ) is written in the grand canonical ensemble , so that the system can exchange particles with an external reservoir . ) as soon as a relatively weak external electric displacement is applied , however , it becomes favorable for the dipolar molecules to enter the system because they can lower their energy by partially aligning with the field within the capacitor . for
even quite small fields , this effect causes the capacitor to fill with liquid , thereby eliminating most of the gas phase region .
the result of this is then an almost rigid shift of the density profiles toward the capacitor plates , with an appearance and general shape which remains nearly fixed over a large range of fields .
considering the fine details of the density profiles , we note that , contrary to our previous results for diatomic liquids , a relatively small ( barely noticeable in the figure ) asymmetry exists at zero external field between the oxygen and hydrogen site densities so that there is a non - vanishing electrostatic charge density in the vicinity of the capacitor plates even in the absence of an externally applied electric field .
( note : because the oxygen site carries a charge which is double in magnitude compared to the hydrogen site and because there are two independent but identical hydrogen sites , the magnitude of the charges carried by the oxygen and hydrogen density fields are directly proportional to the curves in the figure , _ with the same constant of proportionality _ for each . ) by symmetry , the net charge which the plates induce must integrate to zero ; however , a finite surface dipole remains with a corresponding potential jump which we find in the zero - field hard - wall case to be + @xmath190 v across the solid - liquid interface , with the potential being higher in the solid .
figure [ d197 ] shows the equilibrium density profiles in a relatively strong ( @xmath191 ) external field directed from left to right in the figure .
the relative abundance of oxygen sites close to the left plate ( which carries a positive external charge to generate the field ) and of hydrogen sites next to the right plate ( which carries a negative external charge ) indicates that the water molecules exhibit a strong tendency to align their dipoles with the applied field .
interestingly , this leads to quite different density profiles on the opposite sides of the capacitor . on the left ( positive ) plate , the first peak in the oxygen density
is followed by a peak in the hydrogen density of similar shape , width and height .
this we interpret to be a direct consequence of alignment of the molecules with the field and the rigid intra - molecular bonding between hydrogen and oxygen atoms , an effect quite similar to what was observed in our previous study of liquid hydrogen chloride@xcite .
the distance between these peaks , 0.65 , is within about 10% of 0.58 , what one expects from the basic geometry of the water molecule assuming that the molecules fully align with the field . on the right ( negative )
plate , we again find a well - defined peak in the oxygen density , though the peak is somewhat stronger than on the left .
we find also that the hydrogen density , rather than being also sharply peaked , is now spread significantly around the oxygen peak .
this case is different , because the hydrogen sites , now pointing away from the liquid region , can not form hydrogen bonds if the molecules align fully with the field .
figure [ ljzerofield ] compares the zero - field results for the hard - wall plates with those of the attractive plates .
there is no longer a `` lingering '' gas phase region because the minimum in the interaction potential ( acting only on the oxygen sites in this case ) with the plates sets the location of the main peak in the oxygen density .
this minimum , as described above , occurs at a distance of about 3 from the attractive walls and corresponds well with the peaks in the oxygen and hydrogen density profiles .
the height of the oxygen peak is larger than the density in the bulk by a factor of @xmath192 , which is similar to the results of molecular dynamics calculations of water adjacent to platinum surfaces @xcite and experimental findings @xcite .
finally , there is also a net dipole layer in our attractive case leading now to a significantly stronger potential jump at the liquid - solid interface of @xmath193 v , with the potential in the solid again being higher .
this value is typical of realistic systems : from molecular dynamics data of water adjacent to a platinum surface@xcite , we extract a potential jump of @xmath194 v with the potential being higher in the solid . when a strong field ( again , @xmath191 ) is applied to the capacitor with attractive walls ( figure [ phild197 ] )
, we find a rearrangement of the liquid structure which exhibits various quantitative differences compared to the hard - wall case : the oxygen peaks are now significantly more pronounced ( reaching values near 4 and 5 times the equilibrium liquid density , as opposed to the previous peak values near 1.5 and 2.2 ) as the oxygen atoms settle into the attractive potential wells near the walls .
also , the peak near the positive plate is also now notably broader ( with a width of 1.6 at the value of the equilibrium , as opposed to the previous value of 1.0 ) . finally , the hydrogen peak is significantly less pronounced relative to the oxygen peak and the peak position is now less displaced ( 0.4 ) from the oxygen peak position . despite these quantitative differences , however , the qualitative features at strong fields are quite similar in the attractive and the hard - wall cases .
namely , on the left ( positive ) plate we find a well - defined peak in the oxygen density followed by a corresponding peak in the hydrogen density , and on the right ( negative ) plate there is a well - defined oxygen peak which is surrounded by a more diffuse peak in the hydrogen density .
also , as with the hard wall case , we find that the hydrogen peak is off - center from the oxygen peak and displaced toward the negative plate to which it is attracted .
this suggests that , at these large field strengths , general features are independent of the exact form of the liquid - solid interaction .
in fact , we note that this sort of asymmetry between positive and negative plates is also evident in molecular dynamics calculations which , at fields near @xmath195 , also tend to show that , near the positive plate , the oxygen density exhibits peaks which are followed by peaks of similar appearance in the hydrogen density , whereas , near the negative plate , there is a well - defined peak in the oxygen density but that the hydrogen density exhibits either a broader peak or multiple sub - peaks in the vicinity of the main oxygen peak@xcite
. the equilibrium site densities also determine the dielectric function of water @xmath196 with @xmath197 being the total electric field given by the sum of the electric displacement and the induced electric field .
although @xmath197 has a complicated form close to the walls , it rapidly approaches the constant value @xmath198 as the distance from the walls increases , where @xmath75 is the induced polarization . in the present one - dimensional geometry
, @xmath75 is proportional to the induced surface charge which appears in the equilibrium density profiles .
figure [ dielectric ] shows our calculated results for @xmath25 plotted as a function of @xmath197 in units of mv / m ( equivalent to 1 mv / nm or 0.1 mv / ) to simplify comparison with the results of previous studies .
the figure shows that the results from our density - functional theory are well - described by self - consistently screened nonlinear electrostatics ( solid curve ) , which gives the polarization @xmath75 as the self - consistent solution to the equation @xmath199 , where @xmath200 is the response of a gas of noninteracting dipoles in a local field @xmath197 and
@xmath201 ensures that the correct linear response is recovered when @xmath202 is weak .
the solid curve reproduces our data well and so represents a convenient analytic guide to the eye for our results .
figure [ dielectric ] compares our results to booth s analytical result for the nonlinear dielectric response of water @xcite .
this result ( dashed curve in the figure ) was obtained by extending onsager s and kirkwood s theories of polar dielectrics to high field strengths @xcite and also reproduces quite well explicit molecular dynamics results for high fields .
it fails , however , at small fields , eventually giving an incorrect linear dielectric constant of about @xmath203 .
we find very good agreement with this established result for fields larger than @xmath204 mv / m .
we also compare our results to various molecular dynamics calculations @xcite and find very good agreement , except at zero field , where the results of the molecular dynamics calculations often show a wide range of results , some differing significantly from the experimental dielectric constant of @xmath205 depending on the model potentials and numerical methods employed@xcite .
the zero - field dielectric constant , we , of course , reproduce exactly by construction .
our results , therefore , appear to be reliable over a broad range of applied fields .
this work demonstrates how to apply a new , general kohn - sham classical density - functional approach for molecular liquids to what is arguably the liquid of greatest scientific interest , water .
the resulting theory has the quite tractable computational cost of the problem of a noninteracting gas of molecules in a self - consistent external potential and gives an exact account of the entropy associated with the alignment of the molecular dipole moment with an external field . after constructing the functional and giving a complete numerical parameterization of all quantities so that our results are numerically reproducible
, we demonstrate the tractability of the approach by applying it to the behavior of water in parallel plate capacitors , with either hard - wall or attractive plates , over a range of applied fields through which the dielectric constant @xmath25 of water varies by over a factor of two .
we provide results for the distribution of oxygen and hydrogen atoms near the capacitor plates and find an asymmetry between the response at negatively and positively charged plates in general qualitative agreement with molecular dynamics results . from the resulting charge distributions ,
we extract predictions of the dielectric constant of water over a wide range of field strengths ( 0 to 800 mv / m ) and find results in very good agreement with both previous theoretical and molecular dynamics calculations .
the aforementioned exact treatment of the entropy cost of aligning the molecules with the field is critical in producing this accurate treatment of dielectric saturation effects . with a successful framework in place
, there is now a firm basis for future improvements .
given that we now have a good treatment of the internal structure of the water molecule , the primary area remaining for improvement is our choice to employ for this first work a somewhat simplistic weighted - density functional form in ( [ fex ] ) .
the direct route to improve upon this is to leverage much of the existent work in simple fluids , both in traditional weighted density - functional theories@xcite and in fundamental measure theory@xcite .
another clear area for improvement would be the inclusion of additional , ionic species into the functional to allow for screening by electrolytes , which should be relatively straightforward . in sum , we present a new framework for a computationally tractable continuum description of water which captures , within a unified approach with a firm theoretical foundation , molecular - scale correlations , entropic effects , microscopic dielectric screening , surface tension , bulk thermodynamic properties , and dielectric saturation .
this description thus includes _ a priori _ all of the various effects which are generally added _ a posteriori _ to continuum models of water . although less detailed than current explicit molecular treatments of the solvent , freed from the need for computing thermodynamic averages , a sufficiently accurate continuum approach such as we present has the potential to open up much larger and complex systems to theoretical study .
as such , the new framework is an ideal starting point for a variety of new investigations into a wide class of subjects , which include protein folding , molecular motors , membrane physics , drug design , the electrochemical interface , liquid - phase catalysis and fuel cells .
t.a.a . was supported in part by nsf grant no .
che-0113670 , and j.l .
acknowledges support by doe grant no .
de - fg02 - 07er46432 . | we present an accurate free - energy functional for liquid water written in terms of a set of effective potential fields in which fictitious noninteracting water molecules move . the functional contains an _ exact _ expression of the entropy of noninteracting molecules and thus provides an ideal starting point for the inclusion of complex inter - molecular interactions which depend on the _ orientation _ of the interacting molecules .
we show how an excess free - energy functional can be constructed to reproduce the following properties of water : the dielectric response ; the experimental site - site correlation functions ; the surface tension ; the bulk modulus of the liquid and the variation of this modulus with pressure ; the density of the liquid and the vapor phase ; and liquid - vapor coexistence . as a demonstration , we present results for the application of this theory to the behavior of liquid water in a parallel plate capacitor .
in particular , we make predictions for the dielectric response of water in the nonlinear regime , finding excellent agreement with known data . |
( 2s,4r)-1-tert - butyl 2-methyl 4-hydroxypyrrolidine-1,2-dicarboxylate
( 5.00 g , 20.4 mmol ) was dissolved in anhydrous ch2cl2 ( 200 ml ) at room temperature under n2 . to the
solution
were added 4-nitrobenzoic acid ( 3.41 g , 20.4 mmol ) and dicyclohexylcarbodiimide
( dcc ) ( 5.06 g , 24.5 mmol ) .
a catalytic amount of n , n-(dimethylamino)pyridine ( dmap ) ( 125 mg , 1.0 mmol ) was added to the
reaction mixture , and the resulting mixture was stirred vigorously
for 12 h. the white precipitate was filtered , and the solvent was
removed in vacuo .
the resulting crude oil was purified by silica gel
column chromatography ( 02% ch3oh / ch2cl2 v / v ) to yield compound 1 ( 6.1 g ) as a
colorless oil ( 76% yield ) .
the minor cis rotational
isomer was distinctly observed for a few resonances : h
nmr ( 600 mhz , cdcl3 ) 8.328.30 ( d , j = 8.8 hz , 2h ) , 8.208.18 ( d , j = 8.7 hz , 2h ) , 5.585.57 ( m , 1h ) , 4.564.52 ( t , j = 7.8 hz , minor ) , 4.474.43 ( t , j = 8.1 hz , major ) ( sum of major and minor = 1h ) , 3.913.85
( m , 1h ) , 3.79 ( s , minor ) , 3.78 ( s , major ) ( sum of major and minor
= 3h ) , 3.733.70 ( m , 1h ) , 2.612.58 ( m , 1h ) , 2.402.32
( m , 1h ) , 1.47 ( s , minor ) , and 1.44 ( s , major ) ( sum of major and minor
= 9h ) ; c nmr ( 151 mhz , cdcl3 ) 173.0 ,
164.4 , 153.9 , 151.1 , 135.2 , 131.2 , 124.0 , 81.2 , 74.7 , 74.0 , 58.2 ,
52.7 , 36.9 , and 28.6 ; esi ms : [ m + na ] calcd for c18h22n2o8na 417.1 , found 417.0 ;
hrms ( lifdi - tof ) m / z [ m ] calcd for c18h22n2o8 394.1376 ; fragments observed : [ m c7h5no4 ] calcd for c11h17no4 227.1158 , found 227.1146 ( loss of nitrobenzoate ) ;
[ m c7h3no3 ] calcd for c11h19no5 245.1263 , found
245.1234 ( loss of nitrobenzoyl ) ( major fragment ) ; [ m c5h8o2 ] calcd for
c13h14n2o6 294.0852 , found
294.0865 ( loss of boc ) ( second most prominent fragment ) .
compound 1 ( 3.4 g , 8.6
mmol ) was dissolved in anhydrous ch2cl2 ( 20
ml ) under a nitrogen atmosphere .
trifluoroacetic acid ( cf3cooh ) ( 20 ml ) was added to the solution , and the resulting reaction
mixture was stirred at room temperature for 6 h. the solvent was removed
in vacuo .
the crude oil thus obtained was washed with cold ether ( 3
15 ml ) to obtain compound 2 ( 1.8 g ) as a white
solid ( 74% yield ) : h nmr ( 600 mhz , d2o )
8.468.37 ( d , j = 7.2 hz , 2h ) , 8.348.28
( d , j = 7.1 hz , 2h ) , 5.77 ( m , 1h ) , 4.874.82
( m , 1h ) , 4.614.54 ( m , 1h ) , 3.903.74 ( m , 2h ) ,
2.902.84
( m , 1h ) , and 2.682.64 ( m , 1h ) ; c nmr ( 151 mhz ,
d2o / dmso - d6 ( 9:1 ) )
171.2 , 162.2 , 153.1 , 137.4 , 133.9 , 126.3 , 76.8 , 60.1 , 55.8 , 53.2 ,
and 36.7 ; hrms ( lifdi - tof ) m / z [ m
+ h ] calcd for c12h13n2o6 281.0774 , found 281.0763 .
crystals were obtained from the
slow evaporation of a solution of approximately 10 mg of compound 2 in 500 l of d2o ( table 3 ) .
the absolute
structure parameter refined to nil indicating the true hand of the
data had been determined consistent with
known chiral centers .
the structure was solved
using direct methods and refined with full - matrix , least - squares procedures
on f. all non - hydrogen atoms were refined
with anisotropic displacement parameters .
four symmetry unique molecules
of the zwitterion and four water molecules of hydration were located
in the asymmetric unit .
the water and ammonium h atoms were located
from the difference map and treated with x h and h
all other hydrogen atoms were treated as idealized
contributions with geometrically calculated positions and with uiso equal to 1.2 , or 1.5 for methyl , ueq of the attached atom .
the methylene h atom
torsion angles were derived from the refined c c bond positions
and assuming idealized tetrahedral sp geometry .
structural information has been deposited with
the cambridge crystallographic data centre under deposition no . | ( 2s,4r)-4-hydroxyproline(4-nitrobenzoate )
was synthesized .
the crystal structure revealed an exo ring pucker ,
with the nitrobenzoate pseudoaxial on the pyrrolidine envelope and
antiperiplanar to c and c c
h
bonds .
the unit cell exhibited variation in ch / co and ch / co torsion angles , with a 15 increase in torsion angle
( 148 to 163 ) observed to result in a 0.018 decrease
in ch / co bond
length , consistent with favorable c
h
*c o hyperconjugative interactions increasing
with greater orbital overlap . |
immunohistochemistry is no different from any other technique : an experimental approach for which the quality of the results relies entirely on the analyte , reagents , precise experimental technique , correct application of controls and , ultimately , an accurate interpretation of the data based on all of the aforementioned factors . in this article , the essential nature of appropriate controls in immunohistochemical assay is discussed .
the sine qua non of validating research findings is the use of appropriate controls in the design and performance of experiments and assays .
unfortunately , in the case of immunohistochemistry , although the need for controls is well established ( baskin 2009 ; burry 2000 , 2010 ; 2011 ; frevert et al . 2013 ) , it is the experience of the authors that critical controls are often not performed or reported in ensuing publications .
this neglect has resulted in the publication of unverified and irreproducible findings in the literature ( couchman 2014 ; collins and tabak 2014 ) .
contributing to this problem is the fact that many high - impact journals that publish immunohistochemical data do not require authors to report controls for immunohistochemistry and , what is perhaps more regrettable , the controls that are published often are inappropriate or misinterpreted . realizing that controls are an essential component of experimental design in all scientific investigations
, we insist that valid interpretations of immunohistochemical assays can not be made in the absence of minimally appropriate controls .
. simply stated , an immunohistochemical assay that lacks controls can not be validly interpreted .
it s equally important not to conclude that a molecule is present when in fact it is not , as it is to conclude that it is absent when in fact it is present .
it is important to understand that controls either positive or negative can never prove the identity or the presence or absence of a molecule in a tissue sample using immunohistochemical techniques . with proper controls , however ,
the investigator can build a convincing case for the presence or absence of a probed molecule .
this is the best that can be done , but it must be done correctly to be credible and reproducible . to get a snapshot of the attitude of many journals for the importance of controls in papers that incorporate immunohistochemical methods
, we examined a sample of 29 articles that had immunohistochemical data in the journal of histochemistry & cytochemistry and 71 additional publications in eight other high - impact cell biology and pathology - oriented journals that routinely publish data and images based on immunohistochemistry .
specifically , we were interested to know the extent to which control results are readily identifiable in articles that included immunohistochemistry in these journals .
of the 100 articles in nine journals , up to 80% of papers do not mention controls and 89% of guidelines for authors for these journals do not require or even mention controls .
this informal survey sheds light on one reason that controls are often omitted from publications : journals ( and , by inference , their reviewers and editors ) either do not understand the basic principles of immunohistochemical controls or they do not consider them sufficiently important to require inclusion in their articles .
this sadly influences investigators to have an uncritical attitude towards using valid controls in their studies .
accordingly , we recommend that the guidelines for authors for all journals should include a requirement that controls must be described and included in manuscripts that report results of immunohistochemical studies . to avoid inaccurate conclusions on a false - positive or a false - negative result
, a minimum of a positive and a negative control should be run for all immunohistochemical assays .
moreover , journals and their editors should require reviewers to comment on whether appropriate minimal positive and negative controls were used . here , we briefly describe these controls and how they should be correctly interpreted .
essential to valid interpretation of immunohistochemical staining is the selection of antibodies that have been validated to detect specific epitopes .
this issue is perhaps the most critical control and is discussed extensively elsewhere ( gore 2013 ; fervert et al 2013 ; saper 2009 ; saper and sawchenko 2003 ) .
the case for specificity is often established independent of binding to epitopes in tissues or cells .
this usually involves the separation of proteins that differ in size , charge , or conformation using gel electrophoresis .
the proteins are then transferred from the gel to a membrane ( i.e. , western blot ) , where they are stained with an antibody and/or antibodies specific to the target protein to resolve the issue of the cross - reactivity of antibodies ( marchalant et al . 2014 ) .
although this specificity is usually provided by the manufacturer of the antibody , ideally the proteins separated in the western blot should be obtained from the same tissue or cells as the antibody will be used for immunohistochemistry .
the latter is often not feasible for an investigator but , nevertheless , the investigator must realize that this meaning of specificity applies only to the property of antibodies ( either polyclonal or monoclonal ) to recognize specific epitopes but does not prove the identity for binding of a stained targeted molecule in a tissue sample .
unfortunately , the so - called absorption control is often incorrectly offered to as a negative control as support for the specificity of immunostaining of a targeted molecule .
this procedure is carried out by mixing the antibody with the target protein before applying the antibody to the tissue slice .
if immunohistochemical staining in the tissue is blocked by this procedure , the staining observed with the unabsorbed antibody is often considered to be specific .
however , this result only demonstrates that the antibody is specific for the molecule to which it was generated a fact already demonstrated by western blots but does not demonstrate that the antibody is binding to the same target molecule in the tissue .
unfortunately , in the spirit of considering the need for controls , reviewers often ask for absorption controls but this result ( i.e. , blocking of immunostaining ) is a weak control for making conclusions about the identity of targeted molecules in the tissue ( holmseth et al .
positive controls in immunohistochemistry protocols are specimens containing the target molecule in its known location ( e.g. , specific cell type , intracellular compartment , among others ) and whose histomorphology and cytomorphology can be visualized by a stain
( i.e. , the fluorochrome of a chromogenic molecule ) . generally , these characteristics are initially deduced from other experimental evidence , including fractional western blots , over - expression , knock - down , experiments on cells , or studies carried out on transgenic animals known to express the target molecule .
conversely , the antibody should not produce staining in genetically engineered mice where the target molecule has been confirmed to be deleted . by and large ,
the use of cell lines , especially those transfected to over - express a target , are not recommended as appropriate positive controls , as many assays lack the appropriate dynamic range and calibration to ensure appropriate comparison between a cell line and tissue .
the most rigorous positive control is the positive anatomical control ; i.e. , where the presence of the antigen in the specimen is known a priori and is not the target of the experimental treatment .
this can be a known site of expression of the target molecule in the specimen ( i.e. , internal positive control ) or a separate specimen ( e.g. , a slide ) that is known to contain the molecule targeted by the antibody ( i.e. , external positive control ) .
for example , an assay that uses an antibody that is claimed to be specific for insulin should include sections of pancreas that have islets of langerhans ; the antibody should target and visualize only the insulin - producing islet beta cells .
the antibody should have been demonstrated not to cross - react with closely related molecules of the insulin - like peptide family .
interpretation of positive controls can be problematic in the case of antibodies that are directed against molecules that are expressed ubiquitously or are expressed at very low levels , and this criterion for specificity may be impossible in clinical settings .
nevertheless , in the absence of such controls , the investigator is obligated to ( and journals should demand ) that authors be circumspect about interpretations derived from such assays .
the goal of a negative control is to demonstrate that the reaction visualized is due to the interaction of the epitope of the target molecule and the paratope of the antibody / affinity reagent .
it is absolutely critical for investigators to be wary of claims made about the specificity of antibodies used for immunohistochemistry , especially for antibodies obtained from commercial sources .
although a manufacturer may demonstrate specificity of an antibody by western blot analysis , one can not conclude that immunohistochemistry with the same antibody reveals the same target molecule in a tissue sample .
thus , in addition to the molecule targeted by the antibody , the results of an immunohistochemical assay ( e.g. , stain ) can reveal the presence of structurally related molecules as well as the binding of the antibodies used in the assay ( both primary and secondary ) nonspecifically to other cellular and tissue components .
accordingly , journals should require of authors to demonstrate ( or cite evidence ) that the antibody recognizes a protein within the tissue of interest that migrates appropriately in the gel electrophoresis and stains with antibodies specific to the target protein , as demonstrated by a western blot .
unfortunately , a common negative control seen in many articles in the literature is to perform the immunohistochemical assay with a primary antibody in tandem with a specimen that is not exposed to the primary antibody ; that is to say , with the primary antibody omitted .
investigators claim and , regrettably , journal reviewers and editors accept this as control for the specificity of the staining for the antigen targeted by the antibody .
the absence of staining when the primary antibody is omitted is a control for nonspecific binding of the secondary antibody ; this result is not evidence for the specificity of staining with the primary antibody .
however , in some instances , it is an important additional control in assay development . it does not distinguish between staining that results from immunoglobulins binding at antigen binding sites in the f(ab)2 variable regions ( e.g. , implicit for specific binding and immunoglobulins interacting with cell and tissue components in the fc region ) or due to nonspecific mechanisms .
the proper negative control in this instance is substitution of serum or isotype - specific immunoglobulins at the same protein concentration as the primary antibody .
regrettably , the use of isotype - specific immunoglobulins ( or normal or preimmune serum ) as a substitute for the primary antibody has fallen out of favor as a negative control for staining specificity . in the instance of a non - commercial polyclonal antibody , pre - immune sera should be used , and when pre - immune sera is not available ( commercial poly - clonal antibodies and all monoclonal antibodies ) an isotype - specific immunoglobulin should be appropriately substituted .
this control should be an absolute minimum requirement by journals for publishing studies that incorporate immunohistochemistry .
it should be understood , however , that so - called specific antibodies , both polyclonal and monoclonal , can also bind nonspecifically due to fc binding and other mechanisms , leading to the possibility that both specific and non - specific staining observed with such an antibody in a tissue section could not be validly distinguished without further controls ( i.e. , some of the staining is specific and some is non - specific ) . in this situation ( where the primary antibody appears to show nonspecific binding )
, an absorption control can be useful in distinguishing specific from non - specific staining ; the staining that is absent when the absorbed antibody is used ( against a background of persistent , non - specific staining ) is likely to indicate specific antibody binding sites .
recognizing that the omission or improper use of controls is a serious problem limiting the validity as well as the reproducibility of much published data derived from the use of immunohistochemistry , we recommend that biomedical journals include specific requirements regarding the inclusion of controls for immunohistochemistry in their instructions for authors , as an element of describing immunohistochemical assays .
the guidelines outlined in this article are the first step in defining a standard of practice for immunohistochemistry .
additional articles will outline additional points that should be addressed to ensure adequate validation and description of immunohistochemical assays . the end product of this larger effort will be a unified manuscript outlining the specification of immunohistochemical assays in the peer - reviewed literature , and the individual articles will serve as the in - depth information on each of those points . although reproducibility is a concern , the validity of reported results is the more serious problem .
the findings with a poor antibody can generate reproducible , but invalid , conclusions if proper controls are absent .
reproducibility can become a problem when different antibodies to the same antigen produce different results and controls are lacking to sort out the validity of different findings . in table 1 , we outline the elements with reference to controls that journal editors should require to be included in submitted manuscripts that report immunohistochemical data . the results of a positive control and a negative control as well as data supporting the claimed specificity of the primary antibodies for the target molecules should be reported .
essential elements pertaining to controls in immunohistochemical assays that should be included in peer - reviewed manuscripts*. additional recommendations concerning immunohistochemical assays will be defined in additional articles in this series .
characterization of antigen - antibody specificity should rely on confirmation of a one - protein : one - antibody relationship , or determination of the presence of shared epitopes .
approaches such as absorption control and the omission of a primary antibody should never be accepted as sole negative controls for specificity of staining in the absence of clear statements by the authors that these controls do not unequivocally demonstrate specificity of staining .
the points outlined in table 1 can be cited by authors as support for the validity of interpretations of the immunohistochemistry reported in their publications . | immunohistochemistry is widely used in biomedical research to localize specific epitopes of molecules in cells and tissues .
the validity of interpretations based on immunohistochemistry requires appropriate positive and negative controls that are often not reported in publications .
this omission may lead to incorrect interpretations and irreproducible results in the literature and contribute to wasted time , effort , and resources as well as erosion of confidence in scientific investigation by the general public , legislative bodies and funding agencies .
the present article summarizes essential controls required for validation of immunohistochemical findings and represents a standard of practice for the use of immunohistochemistry in research and diagnostic investigations .
adherence to the guidelines described in the present article can be cited by authors as support for the validity of interpretations of the immunohistochemistry reported in their publications . |
when analyzing and processing a signal , such as a sound wave or digital picture , it is often useful to represent the signal in terms of a basis .
for instance , a sound wave can be represented in terms of its harmonic frequencies by a fourier series . with this representation
, the sound wave can be processed to remove static by setting to 0 the high frequency coefficients , or be compressed for smaller storage on a computer by discretizing the coefficients and setting small coefficients to 0 .
representing a function with respect to a basis is also useful in transmitting signals , as all that is needed to be sent are the basis coefficients instead of every value of the function .
there is a problem with this transmission procedure though when error is introduced into the system .
if one of the basis coefficients is lost or corrupted during transmission , then an entire dimension is lost and can not be recovered .
this is where using a frame instead of a basis can be useful .
a frame is essentially a redundant coordinate system in that a frame uses more vectors than necessary when representing a signal .
however , this redundancy helps to mitigate the error due to the loss of coordinates through transmission by effectively spreading the loss over the whole space instead of localizing it to certain dimensions . given @xmath7 , a _
tight frame for @xmath0 _ is a sequence @xmath8 with @xmath9 such that there exists a constant @xmath10 satisfying @xmath11 where , @xmath12 is the standard inner product on @xmath0 ( the dot product ) .
thus , a frame allows for the exact reconstruction of a vector from the sequence of frame coefficients @xmath13 .
we call a tight frame @xmath14 a _ finite unit tight frame , or funtf _ , if @xmath15 for all @xmath16 .
note that in the case @xmath17 , a sequence @xmath18 is a funtf if and only if it is an ortho - normal basis .
funtfs are the most useful frames for signal processing , as they minimize mean squared error due to noise @xcite .
this has motivated the study of funtfs and in particular has led to interest in finding ways to construct funtfs . in @xcite , using a potential energy concept inspired from physics , it is proven that there exists a finite unit tight frame of @xmath19 vectors for @xmath0 for all natural numbers @xmath20 .
an explicit construction for funtfs is given in @xcite , and in @xcite the method of spectral tetris is introduced to explicitly construct funtfs as well other types of frames .
in the context of differential geometry and topology , the word `` frame '' has a different meaning .
a moving frame for the tangent bundle of a smooth manifold can be thought of as a basis for the tangent space at each point on the manifold which moves continuously over the manifold .
to avoid confusion , we will refer to moving frames in this context as moving bases .
if @xmath7 and @xmath21 is an @xmath4-dimensional smooth manifold , then a _ vector field _ is a continuous function @xmath22 such that @xmath23 for all @xmath24 .
that is , a vector field continuously assigns to each point @xmath25 , a vector @xmath26 in the tangent space @xmath27 .
thus , a moving basis for the tangent bundle of a @xmath4-dimensional smooth manifold @xmath21 is a sequence of vector fields @xmath28 such that @xmath29 is a basis for @xmath30 for all @xmath31 . of particular interest in the theory of vector fields and
moving bases is the case where the underlying manifold @xmath21 is the @xmath4-dimensional sphere @xmath5 .
note that @xmath1 can be represented by the unit circle in @xmath32 and that @xmath33 can be represented by the unit sphere in @xmath34 .
the famous hairy ball theorem states that if @xmath4 is even then there does not exist a nowhere zero vector field for @xmath5 . as a moving basis for @xmath5 would consist of @xmath4 nowhere zero vector fields , the manifold @xmath5 can not have a moving basis when @xmath4 is even . on the other hand , it can be simply proven that @xmath1 , @xmath2 , and @xmath3 all have a moving basis for their tangent space . to give a brief sketch of this proof
, we identify @xmath1 with the unit circle of the complex numbers @xmath35 , @xmath2 with the unit sphere of the quaternions @xmath36 , and @xmath3 with the unit sphere of the octonions @xmath37 .
each of these division algebras contain the real numbers , so in particular we have that @xmath38 , @xmath39 , and @xmath40 .
now for each of the cases @xmath41 , we can pick a basis @xmath42 for the tangent space @xmath43 . to move this basis @xmath44 from @xmath45 to a different point @xmath46
, we simply multiply each vector in the basis by @xmath47 giving @xmath48 .
this gives a moving basis for @xmath5 for the cases @xmath41 .
this proof will not work for other values of @xmath4 as @xmath35 , @xmath36 , and @xmath37 are the only finite dimensional division algebras over @xmath49 besides @xmath49 itself .
the question of does @xmath5 have a moving basis for its tangent bundle for any other values of @xmath4 was an important open problem in differential topology and was solved negatively in 1958 by michel kervaire and independently by raoul bott and john milnor .
@xmath5 has a basis for its tangent space at each point which moves smoothly over @xmath5 if and only if @xmath50 .
this motivates us to question what happens when we weaken the condition of basis to that of finite unit tight frame . by combining the two definitions of the word `` frame '' ,
we are led to studying tight frames which vary smoothly over a manifold . as the reconstruction formula ( [ recform ] ) uses an inner product ,
we need to consider riemannian manifolds , where the riemannian metric gives a smoothly varying inner product for the tangent space at each point on the manifold .
note that any smooth submanifold of @xmath0 is naturally a riemannian manifold where the riemannian metric is given by the standard inner product on @xmath0 .
[ frame ] let @xmath21 be an @xmath4-dimensional riemannian manifold with riemannian metric @xmath51 for each @xmath52 .
let @xmath20 , and @xmath53 be a vector field for all @xmath54 .
we say that @xmath14 is a _ moving tight frame _ for the tangent bundle of @xmath21 if @xmath55 is a tight frame for @xmath56 for all @xmath52 .
that is , for all @xmath57 , there exists @xmath10 such that @xmath58 we say that @xmath14 is a _ moving finite unit tight frame ( funtf ) _ for the tangent bundle of @xmath21 if it is a moving tight frame and @xmath59 for all @xmath16 and @xmath52 .
if @xmath7 is even , then the sphere @xmath5 does not have a nowhere zero vector field .
as a moving funtf consists of unit vector fields , no even dimensional sphere can have a moving funtf for its tangent bundle . on the other hand , we will show that every odd dimensional sphere has a moving funtf for its tangent bundle .
the concept of a moving tight frame was first applied in 2009 when p. kuchment proved that particular vector bundles over the torus , which arise in mathematical physics , have natural moving tight frames but do not have moving bases @xcite . in @xcite
, it was shown that the dilation theorem for tight frames in @xmath0 can be extended to moving tight frames .
the relationship between frames for hilbert spaces and manifolds was also considered in a different context by dykema and strawn , who studied the manifold structure of collections of funtfs under certain equivalent classes @xcite
. for terminology and background on vector bundles and smooth manifolds see @xcite . for terminology and background on frames for hilbert spaces see @xcite and @xcite .
most of the research contained in this paper was conducted at the 2010 research experience for undergraduates in matrix analysis and wavelets organized by dr david larson .
the first author was a research mentor for the program , and the second and third authors were participants .
we sincerely thank dr larson for his advice and encouragement .
before discussing moving tight frames , we give some basic results about how to check whether or not a sequence of vectors is a tight frame for a hilbert space . for @xmath7 ,
we denote the unit vector basis for @xmath0 by @xmath60 .
as the reconstruction formula ( [ recform ] ) is linear , it holds for all @xmath61 if and only if it holds for the vectors in the orthonormal basis @xmath60 .
furthermore , if @xmath62 and @xmath61 , then @xmath63 if and only if @xmath64 for all @xmath65 .
this leads us to the following fact .
[ factbasis ] let @xmath66 .
the sequence @xmath14 is a tight frame for @xmath0 if and only if there exists a constant @xmath10 such that @xmath67 given @xmath7 and @xmath68 , we will be interested in identifying when a sequence @xmath69 is a tight frame for the subspace @xmath70 .
however , fact [ factbasis ] may only be used to check if a sequence of vectors is a tight frame for the entire space , not just a subspace .
we will use the following fact to get around this problem .
[ factunion ] let @xmath7 and @xmath71 such that @xmath72 .
if @xmath73 is a tight frame for @xmath74 with frame constant @xmath10 and @xmath75 , then @xmath76 is a tight frame for @xmath77 with frame constant @xmath78 if and only if @xmath79 is a tight frame for @xmath0 with frame constant @xmath78 .
to apply fact [ factunion ] , we need to know the frame constant for a given finite unit tight frame .
this is given by the following fact , which can be deduced from fact [ factbasis ] by summing over @xmath80 .
[ factcoef ] let @xmath81 such that @xmath9 .
if @xmath8 is a finite unit tight frame for @xmath0 then @xmath82 is the frame constant for @xmath14 .
we identify the sphere @xmath5 with the unit vectors in @xmath83 .
that is , @xmath84 . with this representation ,
it is very easy to identify the tangent space @xmath85 for each @xmath46 .
we first note that if @xmath46 , then the vector @xmath47 is normal to the tangent space @xmath85 .
thus , as @xmath5 is a manifold of 1 less dimension than @xmath83 , if @xmath86 , then a vector @xmath87 is in the tangent space @xmath85 if and only if @xmath88 is orthogonal to @xmath47 .
that is , if @xmath89 and @xmath90 then @xmath91 if and only if @xmath92 .
for example , in the case of the circle , if @xmath93 then @xmath94 is the unit vector in the tangent line @xmath95 which points counter - clockwise .
thus , we can create a unit vector field for @xmath96 by switching the two coordinates and including a negative sign in the first coordinate .
this method can be used to create vector fields for higher dimensional spheres as well . given any @xmath7 , we create a unit vector field for @xmath97 by switching pairs of coordinates and inserting a negative sign into one coordinate of each pair . for example
, the map @xmath98 is a unit vector field on @xmath99 . to formalize this , if @xmath100 and @xmath101 then we define @xmath102 to be the operator defined by @xmath103 .
as we are only interested in @xmath104 when it switches pairs of coordinates and multiplies one of the coordinates in each pair by @xmath105 , we restrict ourselves to the set , @xmath106 note that the condition that @xmath107 guarantees in particular that @xmath108 for all @xmath109 .
thus , the set @xmath110 is exactly the collection of operators which switches pairs of coordinates and multiplies one of the coordinates in each pair by @xmath105 .
the next lemma shows that the operators in @xmath110 can be used to construct tangent vectors .
recall that @xmath113 if and only if @xmath114 .
we have that , @xmath115 thus , @xmath114 and hence @xmath113 .
the vector @xmath116 is formed by permuting the coordinates of @xmath47 and multiplying half the coordinates by @xmath105 .
none of these operations changes the norm , and thus @xmath117 as @xmath118 . by lemma [ lemmatangentsphere ] ,
if @xmath119 , then we may define a unit vector field @xmath120 by @xmath121 for all @xmath122 . in the introduction we used division algebras over @xmath49 to prove that @xmath1 , @xmath2 , and @xmath3 each have a moving basis for their tangent bundle .
however , for @xmath50 it is also possible to choose @xmath123 such that @xmath124 is a moving orthonormal basis for @xmath5 . indeed , if @xmath125 then @xmath126 is an orthonormal basis for @xmath95 , and if @xmath127 then @xmath128 is an orthonormal basis for @xmath129 . constructing a moving orthonormal basis for @xmath130
can be done similarly . as no other sphere
has a moving basis for its tangent bundle , we now focus on moving funtfs .
a funtf is able to reconstruct every vector in @xmath0 exactly , and hence the vectors that comprise a funtf are in this respect , distributed uniformly across @xmath131 .
thus , it is natural to assume that wether or not a set of vector fields of the form @xmath124 is a moving funtf depends on wether or not the set @xmath132 in some respect uniformly switches pairs of coordinates and in some respect uniformly inserts negative signs . with this in mind
, we introduce the following definition . verifying that a particular set @xmath133 is balanced requires checking many different equations , and it is not immediately obvious that balanced sets always exist .
however , the following lemma shows that the entire set @xmath110 itself is balanced
. let @xmath7 .
we first count the number of ways to choose an operator @xmath146 .
we may count @xmath147 ways to choose @xmath148 from @xmath149 .
if @xmath150 is the first element of @xmath151 then there are @xmath152 choices for @xmath153 from @xmath154 .
continuing in this manner gives @xmath155 ways to choose @xmath156 for an operator @xmath146 .
for each @xmath157 , there are two ways to choose @xmath158 .
as there are @xmath4 of these pairs , we have that , @xmath159 .
let @xmath134 such that @xmath135 .
we now count the elements in the set @xmath160 . given a choice of @xmath161 and setting @xmath162 and @xmath163 , there are @xmath164 choices for @xmath165 such that @xmath146
. as there are 2 choices for @xmath166 , we have that @xmath167 thus condition @xmath168 is satified .
we now show that condition @xmath169 is satisfied .
let @xmath144 such that @xmath170 are all distinct integers . for all @xmath109 and @xmath171 ,
we let @xmath172 if @xmath173 and @xmath174 otherwise . we define a map @xmath175 by @xmath176 .
it is simple to check that this is a bijection , and hence @xmath177 .
lemma [ lemmabalanced ] gives in particular that for all @xmath7 there exists a balanced subset of @xmath110 .
the following theorem then proves that there exists a moving funtf for @xmath6 for every @xmath7 .
let @xmath7 and @xmath133 . note that for all @xmath178 , we have that @xmath179 . by facts [ factunion ] and [ factcoef ] , for each @xmath122
, @xmath180 is a funtf for @xmath181 if and only if @xmath182 is a tight frame for @xmath183 with frame bound @xmath184 .
assume that @xmath133 is not balanced .
we will show that @xmath185 is not a funtf for @xmath186 by proving that @xmath182 is not a tight frame for @xmath183 .
as @xmath132 is not balanced , it fails either condition @xmath168 or condition @xmath169 .
we first assume that @xmath132 fails condition @xmath168 .
we have that there exists @xmath134 such that @xmath187 .
we will use fact [ factbasis ] to show that @xmath188 is not a tight frame for @xmath189 by showing that the reconstruction formula applied to @xmath190 is not orthogonal to @xmath191 .
we let @xmath192 .
@xmath193 thus , @xmath194 is not a tight frame for @xmath183 by fact [ factbasis ] and hence @xmath195 is not a moving funtf for @xmath6 .
we now assume that @xmath132 fails condition @xmath169 .
there exist distinct integers @xmath144 such that @xmath196 .
we will show that @xmath194 is not a tight frame for @xmath189 by showing that the reconstruction formula applied to @xmath197 is not orthogonal to @xmath198 .
we let @xmath192 .
@xmath199 thus , @xmath194 is not a tight frame for @xmath183 by fact [ factbasis ] and hence @xmath195 is not a moving funtf for @xmath6 .
thus , if @xmath133 is not balanced then @xmath195 is not a moving funtf for @xmath6 .
thus , @xmath207 is a tight frame for @xmath201 with frame bound @xmath208 by fact [ factbasis ] .
this gives us that @xmath209 is a tight frame for @xmath85 for all @xmath46 by fact [ factunion ] , and hence @xmath124 is a moving funtf for @xmath6 . by lemma [ lemmabalanced ] and theorem [ thmmain ]
, we have for all @xmath7 , that @xmath210 is a moving funtf for @xmath6 .
thus , as in the proof of lemma [ lemmabalanced ] , @xmath6 has a moving funtf of @xmath211 vector fields for all @xmath7 .
the natural next step is to find funtfs comprised of fewer vector fields .
that is , our goal is to now find a proper subset of @xmath110 which is balanced . 1 .
if @xmath216 then @xmath217 and @xmath218 for all @xmath219 + 2 . if @xmath137 and @xmath220 then there exists @xmath216 and @xmath109 such that @xmath221 + 3 .
if @xmath222 then @xmath223 for all @xmath109 + essentially , @xmath224 would be a set of ways to pair up the components of @xmath183 such that any two components are paired up by exactly one permutation from @xmath224 .
assuming we have created such a set @xmath224 , we may define a set @xmath132 by @xmath225 that is , we define @xmath132 by pairing up each permutation in @xmath224 with all possible sequences @xmath226 such that @xmath227 .
due to the restrictions on @xmath224 , it is straightforward to check that the resulting set @xmath132 will be balanced .
the set @xmath224 contains @xmath228 elements , and for each choice of @xmath216 there are @xmath229 choices for @xmath226 .
thus , @xmath230 .
all that remains is to show that such a set @xmath224 exists . to create @xmath224
, we will construct a @xmath231 symmetric matrix @xmath232 such that every row ( and column ) of @xmath232 is a permutation of @xmath233 and the diagonal of @xmath232 is constant 0 . given such a matrix @xmath234_{1\leq i , j\leq 2n}$ ] , for all @xmath235 we let @xmath236 be the column number whose entry in the @xmath237th row of @xmath232 equals @xmath238 .
then we may set @xmath239 .
we have that @xmath168 is satisfied as @xmath232 has 0 diagonal and is symmetric .
we have that @xmath169 is satisfied as if @xmath137 with @xmath220 then @xmath240 .
we have that @xmath241 is satisfied as each row of @xmath232 is a permutation of @xmath233 .
thus , to create @xmath224 , we need to construct a @xmath231 symmetric matrix @xmath232 such that every row ( and column ) of @xmath232 is a permutation of @xmath233 and the diagonal of @xmath232 is constant 0 .
we create @xmath234_{1\leq i ,
j\leq 2n}$ ] by defining @xmath242 for each @xmath243 by if we switch the variables @xmath237 and @xmath238 in the definition of @xmath246 , we leave @xmath246 unchanged .
hence , @xmath232 is symmetric . setting @xmath247
if @xmath248 guarantees that @xmath232 has constant 0 diagonal . to show that each row of @xmath232 is a permutation of @xmath233 we first consider @xmath249 .
the sequence @xmath250 is a permutation of @xmath251 and hence @xmath252 is a permutation of @xmath253 .
the @xmath237th row of @xmath232 is formed by concatenating @xmath254 as the @xmath255th element of the sequence @xmath252 then switching the @xmath237th and the @xmath255th element .
thus the @xmath237th row of @xmath232 is a permutation of @xmath233 when @xmath256 . for the case @xmath257
, we have that @xmath258 is a permutation of @xmath251 as @xmath259 and @xmath228 are relatively prime , and hence @xmath260 is a permutation of @xmath253 .
the @xmath255th row of @xmath232 is formed by concatenating @xmath254 as the @xmath255th element of the sequence @xmath261 , and hence is a permutation of @xmath262 .
thus , we have formed a matrix @xmath232 satisfying all our desired properties , and the proof is complete . | frames for @xmath0 can be thought of as redundant or linearly dependent coordinate systems , and have important applications in such areas as signal processing , data compression , and sampling theory .
the word `` frame '' has a different meaning in the context of differential geometry and topology .
a moving frame for the tangent bundle of a smooth manifold is a basis for the tangent space at each point which varies smoothly over the manifold .
it is well known that the only spheres with a moving basis for their tangent bundle are @xmath1 , @xmath2 , and @xmath3 . on the other hand , after combining the two separate meanings of the word `` frame '' , we show that the @xmath4-dimensional sphere , @xmath5 , has a moving finite unit tight frame for its tangent bundle if and only if @xmath4 is odd .
we give a procedure for creating vector fields on @xmath6 for all @xmath7 , and we characterize exactly when sets of such vector fields form a moving finite unit tight frame . |
quantum hypothesis testing ( qht ) is a fundamental topic in quantum information theory @xcite , playing a non - trivial role in protocols of quantum communication and quantum cryptography @xcite .
the typical formulation of qht is given in terms of quantum state discrimination @xcite , where a certain number of generally non - orthogonal quantum states ( the quantum hypotheses ) have to be discriminated by means of a quantum measurement .
in particular , the simplest scenario regards the statistical discrimination between two non - orthogonal quantum states , corresponding to the ` null ' and the ` alternative ' quantum hypotheses , occurring with some a priori probabilities . in _
symmetric testing _ , these hypotheses have the same cost @xcite and the goal is to minimize the mean error probability of confusing them by suitably optimizing the quantum measurement . for such a basic problem , we know closed analytical formulae identifying both the minimum error probability , given by the helstrom bound @xcite , and the optimal quantum detection , expressed in terms of the helstrom matrix @xcite .
furthermore , we can also use an easier - to - compute bound which becomes tight in asymptotic conditions .
this is the recently - introduced quantum chernoff bound @xcite , for which we know simple formulae in the case of multi - mode gaussian states @xcite , ( i.e. , those states with gaussian wigner function @xcite ) . in this paper , we consider _ asymmetric _ qht , where two quantum hypotheses have different associated costs @xcite . in this approach
, we aim to minimize the probability that the alternative hypothesis is confused for the null hypothesis , an error which is known as ` false negative ' .
this minimization has to be done by suitably constraining the probability of another possible error , known as a ` false positive ' , where the null hypothesis is confused for the alternative hypothesis .
this is clearly the best approach for instance in medical - type testing , where the null hypothesis typically represents absence of a disease , while the alternative corresponds to the presence of a disease .
asymmetric qht is typically formulated as a multi - copy discrimination problem , where a large number of copies of the two possible states are prepared and subjected to a collective quantum measurement . from this point of view , the aim is to maximize the error - exponent describing the exponential decay of the false negatives , while placing a reasonable constraint on the false positives . for this calculation , we can rely on two mathematical tools .
the first is the quantum relative entropy @xcite between the two states , while the other is the recently - introduced quantum hoeffding bound ( qhb ) @xcite , which performs the optimization of the error - exponent while providing a better control on the false positives . in this work ,
we start by giving some basic notions on asymmetric qht and briefly reviewing the qhb , also showing how its computation simply reduces to the quantum fidelity @xcite in the presence of pure states .
then , we provide a general recipe for computing this bound in the case of multimode gaussian states , for which it can be expressed in terms of their first- and second - order statistical moments . in the general multimode case
, we derive a relation between the qhb and other easier - to - compute bounds , which are based on well - known mathematical inequalities .
finally , we derive analytical formulas and numerical results for the most important classes of one - mode and two - mode gaussian states . by developing the theory of asymmetric qht for gaussian states
, our work could be useful in tasks and protocols involving gaussian quantum information @xcite , including technological applications of quantum channel discrimination ( e.g. , quantum illumination @xcite or quantum reading @xcite ) where we are interested in increasing our ability to accept one specific quantum hypothesis .
in binary qht we consider a quantum system which is prepared in some unknown quantum state @xmath0 , which can be @xmath1 or @xmath2 .
for instance we can imagine one party , say alice , who prepares such a system .
this system is then passed to bob , who does not know which choice alice has made .
thus , bob must decide between the following two hypotheses @xmath3 in order to discriminate between these two hypotheses , i.e. , distinguish between the two states , bob applies a quantum measurement , generally described by a positive operator valued measure ( povm ) . without loss of generality
, bob can always reduce his measurement to be a dichotomic povm @xmath4 with @xmath5 @xcite . the outcome @xmath6 , with povm operator @xmath7
, is associated to the null hypotheses @xmath8 , while the other outcome @xmath9 , with povm operator @xmath10 , is associated with the alternative hypothesis @xmath11 . since the two quantum states @xmath1 and @xmath2 are generally non - orthogonal , there is a non - zero error probability to confuse the two hypotheses .
we can identify two different types of error : type - i and type - ii errors , with associated conditional error probabilities . by definition , the type - i error , also known as a ` false - positive ' , is where bob accepts the alternative hypothesis @xmath11 when the null hypothesis @xmath8 holds .
we have a corresponding error probability expressed by @xmath12 then , the type - ii error or ` false - negative ' is where bob accepts the null hypothesis @xmath8 when the true hypothesis is the alternative@xmath13 .
this error occurs with conditional probability@xmath14 note that we can introduce other probabilities , but they are fully determined by @xmath15 and @xmath16 .
for instance , we may also consider the ` specificity ' or ` true - negativity ' of the test which is the success probability of identifying the null hypothesis , i.e. , @xmath17 which is simply given by @xmath18 .
similarly , we may also consider the ` sensitivity ' or ` true - positivity ' of the test which is the success probability of identifying the alternative hypothesis , i.e. , @xmath19 .
the costs associated with the two types of error can be very different especially in the medical and histological settings .
for instance , in a medical test , @xmath8 is typically associated with no illness , while @xmath20 with the presence of the disease .
it is therefore clear that we would like to have tests where the false - negative probability ( or rate ) @xmath16 is the lowest possible , so that ill patients are not diagnosed as healthy . for this reason , in a medical setting , hypothesis testing is almost always asymmetric , meaning that we aim to minimize one of the two conditional error probabilities .
in general we can formulate the problem of qht as an @xmath21-copy discrimination problem @xcite .
this means that alice has @xmath21 quantum systems which are prepared in two possible multi - copy states@xmath22 these systems are passed to bob who performs a collective measurement on them . as before , this general povm can be chosen to be dichotomic @xmath23 with @xmath10 .
the error probabilities now depend on the number of copies @xmath21 .
in particular , the probability of false positives is given by@xmath24 and the probability of false negatives is@xmath25 in the limit of a large number of copies @xmath26 , these probabilities go to zero exponentially , i.e. , we have@xmath27 where the coefficients @xmath28 are called the ` error - exponents ' or ` rate limits ' @xcite .
bob s aim is to maximize the error exponent @xmath29 , so that the error probability of false negatives @xmath30 has the fastest exponential decay to zero .
this must be done while controlling the rate of false positives . here
a well known result is the ` quantum stein lemma ' @xcite which connects @xmath29 with the quantum relative entropy between the single - copy states @xmath1 and @xmath2 . for a large number of copies @xmath31
, there is a dichotomic povm such that the error probability of the false positives is bounded @xmath32 and the error probability of false negatives goes to zero with error - exponent@xmath33 more powerfully , we may use the notion of the qhb @xcite . for @xmath31 , there is a dichotomic povm such that the error - exponent of false positives is lower - bounded by a positive parameter@xmath34 and the error - exponent of false negatives satisfies@xmath35 where @xmath36 is the qhb defined by@xmath37 where @xmath38 is the ` s - overlap ' between the single - copy states @xmath1 and @xmath2 .
note that the quantum hoeffding bound enforces a stronger constraint on false - positives , since these are bounded at the level of the error - exponent and not at the level of the error probability as happens for the quantum relative entropy bound .
asymmetric testing becomes very simple when one of the states ( or both ) is pure . in this case
, we can in fact relate the qhb to the quantum fidelity between the two states .
let us start by considering the case where only one of the states is pure , e.g. , @xmath39 .
we can write @xcite@xmath40 where @xmath41 is the fidelity between @xmath42 and @xmath2 .
( [ relfcs ] ) implies @xmath43 . by using the latter inequality in eq .
( [ qhb2 ] ) , we derive the fidelity - bound@xmath44 more specifically , in the discrimination of two pure states , we find that the previous fidelity - bound becomes tight @xmath48 in fact , for pure states @xmath49 and @xmath50 , and for any @xmath51 , we can write@xmath52 therefore we can replace @xmath53 in the qhb of eq .
( [ qhb2 ] ) , which implies eq .
( [ fidtight ] ) @xcite .
a bosonic system of @xmath54 modes is a quantum system described by a tensor product hilbert space @xmath55 and a vector of quadrature operators @xcite @xmath56 these operators satisfy the vectorial commutation relations @xcite@xmath57:=\mathbf{\hat{x}\hat{x}}% ^{t}-(\mathbf{\hat{x}\hat{x}}^{t})^{t}=2i\mathbf{\omega}~ , \label{commquad}%\ ] ] where @xmath58 is the symplectic form , defined as@xmath59{cc}% 0 & 1\\ -1 & 0 \end{array } \right ) ~. \label{symplectic_form}%\ ] ] correspondingly , a real matrix @xmath60 is called ` symplectic ' when it preserves @xmath58 by congruence , i.e. , @xmath61 . by definition , we say that a bosonic state @xmath0 is ` gaussian ' when its phase - space wigner representation is gaussian @xcite .
in such a case , we can completely describe the state by means of its first- and second - order statistical moments .
these are the mean value or displacement vector @xmath62 , and the covariance matrix ( cm ) @xmath63 with generic element@xmath64 where @xmath65 denotes the anticommutator .
the cm is a @xmath66 real symmetric matrix , which must satisfy the uncertainty principle @xcite@xmath67 an important tool in the manipulation of gaussian states is williamson s theorem @xcite : for any cm @xmath63 , there is a symplectic matrix @xmath60 such that@xmath68 where@xmath69{cc}% 1 & 0\\ 0 & 1 \end{array } \right ) .\ ] ] the matrix @xmath70 is the ` williamson form ' of @xmath63 , and the set @xmath71 is the ` symplectic spectrum ' of @xmath72 .
according to the uncertainty principle , each symplectic eigenvalue must satisfy the condition @xmath73 , with @xmath74 for all @xmath75 if and only if the gaussian state is pure .
our goal is to find a general recipe for the calculation of the qhb for gaussian states .
we start from the general formula in eq .
( [ qhb2 ] ) involving the logarithm of the @xmath45-overlap @xmath76 defined in eq .
( [ sover ] ) . given two @xmath54-mode gaussian states , @xmath1 and @xmath2 ,
we can write an explicit gaussian formula for the @xmath45-overlap in terms of their statistical moments ( @xmath77 , @xmath78 ) and ( @xmath79 , @xmath78 ) . this is given by @xcite@xmath80 , \label{soverlap}%\ ] ] where @xmath81 is the difference between the mean values , while @xmath82 and @xmath83 depends on the cms @xmath78 and @xmath84 .
in particular , introducing the two real functions @xmath85 we can write the formulas@xmath86 and@xmath87~\mathbf{s}_{0}^{t}\nonumber\\ & + \mathbf{s}_{1}\mathbf{~}[\oplus_{k=1}^{n}\lambda_{1-s}(\nu_{k}% ^{1})\mathbf{i}]~\mathbf{s}_{1}^{t } , \label{sigma}%\end{aligned}\ ] ] where @xmath88 and @xmath89 are the symplectic spectra of the two states , with @xmath90 and @xmath91 being the symplectic matrices which diagonalize the two cms according to williamson s theorem , i.e.,@xmath92 substituting eq .
( [ soverlap ] ) into eq .
( [ qhb2 ] ) , corresponds to explicitly computing the logarithmic term @xmath93 , yielding@xmath94 in particular for zero - mean gaussian states we have @xmath95 and the previous expression simplifies to@xmath96 note that computing the @xmath45-overlap @xmath76 and its logarithmic form @xmath97 could be difficult due to the presence of the symplectic matrices , @xmath90 and @xmath91 , in the term @xmath98 in eq .
( [ sigma ] ) .
a possible solution is to compute an upper bound , known as the ` minkowski bound ' , which is based on the minkowski determinant inequality @xcite and depends only on the two symplectic spectra @xcite .
specifically , we have @xmath99 , where@xmath100 ^{-n } , \label{sum_bound}%\ ] ] and@xmath101\nonumber\\ & \times\lbrack\left ( y+1\right ) ^{1-s}-\left ( y-1\right ) ^{1-s}% ] \}^{1/n}. \label{psi}%\end{aligned}\ ] ] another easy - to - compute upper bound is the ` young bound ' @xmath102 , which is based on young s inequality @xcite and satisfies @xmath103 where @xcite@xmath104 and@xmath105 ^{-\frac{1}{2}}~. \label{gamma}%\ ] ] taking the negative logarithm of eq .
( [ boundscomp ] ) , we can write the following inequality for the qhb@xmath106 where @xmath107 in the specific case where one of the two gaussian states is pure , we can compute their fidelity @xmath41 and apply the upper bound given in eqs .
( [ fqhb ] ) and ( [ qhbf2 ] ) , which becomes tight when both states are pure [ see eq .
( [ fidtight ] ) ] . in particular , for two multimode gaussian states @xmath108 and @xmath2 , we can easily write their fidelity @xmath41 in terms of the statistical moments @xcite@xmath109 where @xmath110 . as a result
, we can use eq .
( [ qhbf2 ] ) with@xmath111 .\ ] ]
in this section , we examine the case of one - mode gaussian states .
this means we fix @xmath112 in the previous formulas of sec . [ sec_asygauss ] , with matrices becoming @xmath113 , vectors becoming 2-dimensional , and symplectic spectra reducing to a single eigenvalue .
for instance , the @xmath45-overlap can be more simply computed using the expressions@xmath114 in particular , here we shall derive the analytic formulas for the qhb for two important classes : coherent states ( in sec .
[ sec_amp ] ) and thermal states ( in sec .
[ sec_thermal ] ) . assuming that we impose a good control on the rate of false positives ( so that @xmath121 ) , then the error - exponent for the false negatives
is simply given by @xmath122 .
more explicitly , this corresponds to an asymptotic error rate@xmath123 note that , if we have poor control on the rate of false positives , i.e. , @xmath124 , then the qhb @xmath125 is infinite .
this means that the probability of false negatives @xmath30 goes to zero super - exponentially , i.e. , more quickly than any decreasing exponential function . in this section
we derive the qhb for one - mode thermal states @xmath126 and @xmath127 , with variances equal to @xmath128 and @xmath129 , respectively ( in our notation , @xmath130 , where @xmath131 is the mean number of thermal photons ) .
these gaussian states have zero mean ( @xmath132 ) and cms in the williamson form @xmath133 and @xmath134 ( so that @xmath135 ) .
thus , we can write@xmath136 and derive@xmath137 this is the @xmath45-overlap to be used in the qhb of eq .
( [ qhb2 ] ) . given two arbitrary @xmath138 and @xmath139 , the maximization in eq .
( [ qhb2 ] ) can be done numerically .
the results are shown in fig .
[ picthermal ] for thermal states with variances up to @xmath140 vacuum units ( equivalent to @xmath141 mean thermal photon ) . from the figure
we can see an asymmetry with respect to the bisector @xmath142 which is a consequence of the asymmetric nature of the hypothesis test .
the bottom - right part of the figure is related to the minimum probability of confusing a nearly - vacuum state ( @xmath143 ) with a thermal state having one average photon ( @xmath144 ) . by contrast , the top - left part of the figure is related to the probability of confusing a thermal state having one average photon ( @xmath145 ) with a nearly - vacuum state ( @xmath146 ) .
these probabilities are clearly different . as null hypothesis , and @xmath147 as alternative hypothesis .
we consider low thermal variances @xmath148 and we have set @xmath149 for the false positives.,scaledwidth=50.0% ] we are able to derive a simple analytical result when we compare a thermal state with the vacuum state .
let us start by considering the vacuum state to be the null hypothesis ( @xmath150 ) while the thermal state is the alternative hypothesis ( @xmath151 ) .
in this specific case , we find@xmath152 and we get@xmath153 since @xmath154 is a constant , the maximization of @xmath155 over @xmath156 corresponds to minimizing the function @xmath157 , whose minimum occurs at @xmath158 . as a result
, we have@xmath159 since @xmath130 , we can write the qhb in terms of the mean number of thermal photons , i.e.,@xmath160 this is the optimal error exponent for the asymptotic probability of false negatives , i.e. , of confusing a thermal state with the vacuum state .
in this section we consider two important classes of two - mode gaussian states .
the first is the class of einstein - podolsky - rosen ( epr ) states , also known as two - mode squeezed vacuum states . the second ( broader )
class is that of two - mode squeezed thermal ( st ) states , for which the computation of the qhb is numerical .
the expression of the qhb in the case of epr states is easy to derive . since epr states are pure , the qhb @xmath125 is given by @xmath164 of eq .
( [ qhbf2 ] ) . as a result
, we need only to compute the fidelity between the two states .
an epr state has zero mean and cm@xmath165{cc}% \mu\mathbf{i } & \sqrt{\mu^{2}-1}\mathbf{z}\\ \sqrt{\mu^{2}-1}\mathbf{z } & \mu\mathbf{i}% \end{array } \right ) , \label{vepr}%\ ] ] with @xmath166 , @xmath167 is the @xmath113 identity matrix and@xmath168{cc}% 1 & 0\\ 0 & -1 \end{array } \right ) .\ ] ] given two epr states with parameters @xmath169 and @xmath170 , their fidelity is computed via eq .
( [ fid_formulanew ] ) , yielding@xmath171 where @xmath172 .
after simple algebra , we find@xmath173 to be used in eq .
( [ qhbf2 ] ) . in this section
we consider symmetric st states @xmath174 , which are gaussian states with zero mean and cm@xmath175{cc}% \mu\mathbf{i } & c\mathbf{z}\\ c\mathbf{z } & \mu\mathbf{i}% \end{array } \right ) , \label{symcm}%\ ] ] where @xmath166 and @xmath176 @xcite ( in particular , without loss of generality , we can assume @xmath177 ) .
these are called symmetric because they are invariant under permutation of the two modes @xcite .
note that , for @xmath178 , we have no correlations , and the st state is a tensor - product of thermal states , i.e. , @xmath179 .
for @xmath180 the correlations are maximal , and the st state becomes an epr state , i.e. , @xmath181 . finally , for @xmath182
, we have maximal separable correlations . in other words
, @xmath183 is the separable st state with the strongest correlations ( e.g. , highest discord ) . the symplectic decomposition of a symmetric st state is known . from the cm of eq .
( [ symcm ] ) , one can check that the symplectic spectrum is degenerate and given by the single eigenvalue @xmath184 the symplectic matrix @xmath60 which diagonalizes @xmath185 in williamson form @xmath186 is given by@xmath187{cc}% \omega_{+}\mathbf{i } & \omega_{-}\mathbf{z}\\ \omega_{-}\mathbf{z } & \omega_{+}\mathbf{i}% \end{array } \right ) , \label{diags}%\ ] ] where@xmath188 as a result , the s - overlap between two symmetric st states , @xmath1 and @xmath2 , can be computed using the simplified formulas@xmath189 where @xmath128 ( @xmath129 ) is the degenerate eigenvalue of @xmath1 ( @xmath2 ) , computed according to eq .
( [ degeig ] ) , and @xmath90 ( @xmath91 ) is the corresponding diagonalizing symplectic matrix , computed according to eqs .
( [ diags ] ) and ( [ omedef ] ) .
let us start with simple cases involving the asymmetric testing of correlations with specific st states .
first we consider the asymmetric discrimination between the uncorrelated thermal state @xmath190 as null hypothesis and the correlated ( but separable ) st state @xmath191 as alternative hypothesis .
a false negative corresponds to concluding that there are no correlations where they are actually present @xcite .
it is straightforward to derive their degenerate symplectic eigenvalues which are simply @xmath192 and @xmath193 .
then , we have @xmath194 , while @xmath91 can be easily computed from eqs .
( [ diags ] ) and ( [ omedef ] ) . by substituting these into eqs .
( [ stseq1 ] ) and ( [ stseq2 ] ) , we can compute the s - overlap @xmath195 and therefore the qhb @xmath125 via eq .
( [ qhb2 ] ) .
the results are plotted in fig .
[ pic ] , for values of thermal variance @xmath196 up to @xmath140 ( i.e. , from zero to @xmath141 mean photon ) and small values of the parameter @xmath47 , bounding the rate of false - positives .
as expected , the qhb improves for decreasing @xmath47 and increasing @xmath197 . and the st state @xmath198 with maximal separable correlations .
we plot the qhb as a function of the thermal variance @xmath196 and the false - positive parameter @xmath47 . as we can see the qhb improves for lower @xmath47 and for higher @xmath196.,scaledwidth=50.0% ]
now let us consider the asymmetric discrimination between @xmath199 and the epr state @xmath200 , i.e. , the most correlated and entangled st state @xcite .
thanks to the simple symplectic decomposition of the epr state ( @xmath162 ) , we can further simplify the previous eqs .
( [ stseq1])-([stseq2 ] ) and write@xmath201 with @xmath202 being given by eq .
( [ vepr ] ) . as before , we compute the qhb which is plotted in fig .
[ pic2 ] , for @xmath203 and @xmath204 .
as expected the qhb improves for decreasing @xmath47 and increasing @xmath196 .
note a discontinuity identifying two regions , one where the qhb is finite , and the other where it is infinite ( white region in the figure ) . and the epr state @xmath205 .
we plot the qhb as a function of the thermal variance @xmath196 and the false - positive parameter @xmath47 .
the qhb improves for lower @xmath47 and for higher @xmath196 . in particular
, there is a threshold value after which the qhb becomes infinite ( white region).,scaledwidth=48.0% ] in fact , by expanding the term @xmath206 in eq .
( [ qhb2 ] ) for @xmath207 , that we find @xmath208 where@xmath209 for values of @xmath47 and @xmath196 such that @xmath210 , we find that the term @xmath206 diverges at the border , making the qhb infinite .
for a given @xmath47 , this happens when @xmath211 finally , we consider the most general scenario in the asymmetric testing of correlations with st states .
in fact , we consider two generic st states , @xmath212 and @xmath213 , with the same thermal noise but differing amounts of correlation .
for this computation , we use eqs .
( [ degeig])-([omedef ] ) with @xmath214 or @xmath215 , to be replaced in eqs .
( [ stseq1])-([stseq2 ] ) , therefore deriving the s - overlap and the qhb . at small thermal variance ( @xmath216 ) and for the numerical value @xmath149
, we plot the qhb as a function of the correlation parameters @xmath217 and @xmath215 . as we can see from fig .
[ pic3 ] , the qhb is not symmetric with respect to the bisector @xmath218 ( where it is zero ) and increases away from this line . ) but different correlations @xmath217 and @xmath215 . setting @xmath149 , we plot the qhb as a function of @xmath217 and @xmath215 .
we can see that the qhb increases orthogonally to the bisector @xmath218.,scaledwidth=48.0% ]
in this work we have considered the problem of asymmetric quantum hypothesis testing by adopting the recently - developed tool of the quantum hoeffding bound ( qhb ) . after a brief review of these notions ,
we have shown how the qhb can be simplified in some cases ( pure states ) and estimated using other easier - to - compute bounds based on simple algebraic inequalities .
in particular , we have applied the theory of asymmetric testing to multimode gaussian states , providing a general recipe for the computation of the qhb in the gaussian setting . using this recipe ,
we have found analytic formulas and shown numerical results for important classes of one - mode and two - mode gaussian states . in particular , we have studied the behavior of the qhb in the low energy regime , i.e. , considering gaussian states with a small average number of photons .
our results could be exploited in protocols of quantum information with continuous variables . in particular
, they could be useful for reformulating gaussian schemes of quantum state discrimination and quantum channel discrimination in such a way as to give more importance to one of the quantum hypotheses
. this asymmetric approach could be the most suitable in the development of quantum technology for medical applications .
this work has been supported by epsrc ( ep / j00796x/1 ) .
g.s . has been supported by an epsrc dta grant .
the authors thank c. ottaviani and s. pirandola for enlightening discussions . for brevity
we do not consider the other case where the st state is the null hypothesis and the thermal state is the alternative hypothesis .
this case is included in the our final analysis for generic st states . | we consider the asymmetric formulation of quantum hypothesis testing , where two quantum hypotheses have different associated costs . in this problem ,
the aim is to minimize the probability of false negatives and the optimal performance is provided by the quantum hoeffding bound . after a brief review of these notions , we show how this bound can be simplified for pure states .
we then provide a general recipe for its computation in the case of multimode gaussian states , also showing its connection with other easier - to - compute lower bounds .
in particular , we provide analytical formulae and numerical results for important classes of one- and two - mode gaussian states . |
a mapping @xmath1 , where the dependence on the continuous parameter is smooth , is called a _ semidiscrete surface_. let us connect @xmath2 with @xmath3 by segments for all possible pares @xmath4 .
the resulting piecewise smooth surface is a _ piecewise ruled surface_. in this paper we study infinitesimal and higher order flexibility conditions for such semidiscrete surfaces . by _
flexions _ of a semidiscrete surface @xmath5 we understand deformations that isometrically deform corresponding ruled surfaces and in addition that preserve all line segments connecting @xmath2 with @xmath3 .
many questions on discrete polyhedral surfaces have their origins in classical theory of smooth surfaces .
flexibility is not an exception from this rule .
the general theory of flexibility of surfaces and polyhedra is discussed in the overview @xcite by i. kh .
sabitov . in 1890
@xcite l. bianchi introduced a necessary and sufficient condition for the existence of isometric deformations of a surface preserving some conjugate system ( i.e. , two independent smooth fields of directions tangent to the surface ) , see also in @xcite . such surfaces can be understood as certain limits of semidiscrete surfaces . on the other hand ,
semidiscrete surfaces are themselves the limits of certain polygonal surfaces ( or _ meshes _ ) . for the discrete case of flexible
meshes much is now known .
we refer the reader to @xcite , @xcite , @xcite , and @xcite for some recent results in this area . for general relations to the classical case
see a recent book @xcite by a. i. bobenko and yu .
b. suris .
it is interesting to notice that the flexibility conditions in the smooth case and the discrete case are of a different nature .
currently there is no clear description of relations between them in terms of limits .
the place of the study of semidiscrete surfaces is between the classical and the discrete cases .
main concepts of semidiscrete theory are described by j. wallner in @xcite , and @xcite .
some problems related to isothermic semidiscrete surfaces are studied by c. mller in @xcite .
we investigate necessary conditions for existence of isometric deformations of semidiscrete surfaces .
to avoid pathological behavior related to noncompactness of semidiscrete surfaces we restrict ourselves to compact subsets of the following type .
an _ @xmath6-ribbon surface _ is a mapping @xmath7\times \{0,\ldots , n\ } \to\r^3 , \qquad ( i , t ) \mapsto f_i(t).\ ] ] we also use the notion @xmath8 while working with a rather abstract semidiscrete or @xmath6-ribbon surface @xmath5 we keep in mind the two - dimensional piecewise - ruled surface associated to it ( see fig . [ part ] ) .
@xmath9 in present paper we prove that any 2-ribbon surface ( as a ruled surface ) is flexible and has one degree of freedom in the generic case ( theorem [ 2-ribbon flex ] ) .
this is quite surprising since generic 1-ribbon surfaces have infinitely many degrees of freedom , see , for instance , in @xcite , theorem 5.3.10 .
we also find a system of differential equations for the deformation of 2-ribbon surfaces ( system a and corollary [ 111c ] ) .
in contrast to that , a generic @xmath6-ribbon surface is rigid for @xmath10 . for the case
@xmath11 we prove the following statement ( see theorem [ inf ] and corollary [ lambdah ] ) .
* infinitesimal flexibility condition . *
+ _ a 3-ribbon surface is infinitesimally flexible if and only if the following condition holds : @xmath12 where @xmath13 and @xmath14 _ _ remark . _ throughout this paper we denote the derivative with respect to variable @xmath15 by the dot symbol . having this condition
, we also show how to construct inductively the variational isometric conditions of higher orders .
finally , we show that an @xmath6-ribbon surface is infinitesimally or finitely flexible if and only if all its 3-ribbon subsurfaces are infinitesimally or finitely flexible ( see theorems [ n - ribbon - infini ] and [ n - ribbon - fini ] ) .
we say a few words in the case of developable semidiscrete surfaces whose flexions have additional surprising properties .
* organization of the paper . * in section 1
we discuss flexibility of 2-ribbon surfaces .
we study infinitesimal flexibility questions for 2-ribbon surfaces in subsections 1.2 and 1.3 . in subsection 1.2
we give a system of differential equations for infinitesimal flexions , prove the existence of nonzero solutions , and show that all the solutions are proportional to each other . in subsection 1.3
we define the variational operator of infinitesimal flexion which is studied further in the context of finite flexibility for 2-ribbon surfaces . in subsection 1.4
we prove that a 2-ribbon surface is finitely flexible and has one degree of freedom if in general position . in section 2
we work with @xmath6-ribbon surfaces .
subsection 2.2 gives infinitesimal flexibility conditions for 3-ribbon surfaces .
subsection 2.3 studies higher order variational conditions for 3-ribbon surfaces .
finally , subsection 2.4 shows the relations between flexibility of @xmath6-ribbon surfaces and infinitesimal and flexibility of 3-ribbon subsurfaces contained in it ( in both infinitesimal and finite cases ) .
we conclude the paper with flexibility of developable semidiscrete surfaces in section 3 . in this case
flexions have additional geometric properties . * necessary notions and definitions . * within this paper we traditionally consider @xmath15 as a smooth argument of a semidiscrete surface @xmath5 .
the time parameter for deformations is @xmath16 .
a _ perturbation _ of a semidiscrete ( @xmath6-ribbon ) surface is a smooth curve @xmath17 in the space of all sufficiently smooth semidiscrete surfaces .
we assume that the curve is parameterized by @xmath18 $ ] for some positive @xmath19 such that @xmath20 .
denote by @xmath21 the _ infinitesimal perturbation _ of a semidiscrete ( @xmath6-ribbon ) surface @xmath5 along the curve @xmath22 , i. e. the tangent vector @xmath23 .
we say that a perturbation is a _ flexion _ if it does not change the inner geometry of the surface obtained by joining all the pairs @xmath24 and @xmath25 by straight segments .
in the case of semidiscrete ( @xmath6-ribbon ) surfaces a surface is flexible if the the following quantities are preserved by the perturbation : @xmath26 ( for all possible @xmath27 and @xmath15 in the case of an @xmath6-ribbon surface ) .
we say that an infinitesimal perturbation is an _
infinitesimal flexion _ if it does not change the inner geometry of the surface infinitesimally . in other words ,
the first derivatives of the quantities listed above are all equal to zero .
in this section we describe flexions of 2-ribbon surfaces .
such surfaces are defined by three curves @xmath28 , @xmath29 , and @xmath30 .
our main goal here is to prove under some natural genericity assumptions that any 2-ribbon surface is flexible and has one degree of freedom .
our first point is to describe the system of differential equations ( system a ) that determines infinitesimal flexions corresponding to finite flexions and find solutions to this system ( see subsections 1.1 and 1.2 ) . further via solutions of system a we define the variational operator of infinitesimal flexion @xmath31 ( in subsection 1.3 ) . finally , to show finite flexibility of 2-ribbon surfaces we study lipschitz properties for @xmath31 ( in subsection 1.4 ) .
in this small subsection we collect some useful relations . for any infinitesimal flexion of a 2-ribbon surface @xmath5
the following properties hold : @xmath32 for a semidiscrete or @xmath6-ribbon surface @xmath5 and a @xmath33-curve @xmath22 the operations @xmath34 , @xmath35 , and @xmath36 commute , so we do not pay attention to the order of these operations in compositions .
the first three equations follow from the fact that infinitesimal flexions preserve the norm of tangent vectors to the curves @xmath29 , @xmath37 , and @xmath30 .
the invariance of the lengths of @xmath38 and @xmath39 implies the fourth and the fifth equations .
equations ( [ e8 ] ) and ( [ e9 ] ) follows from invariance of angles between the vectors @xmath40 and @xmath41 and the vectors @xmath40 and @xmath41 . finally , the last two equations hold since the angles between @xmath38 and @xmath42 and @xmath39 and @xmath42 are preserved by infinitesimal flexions and therefore @xmath43 ( in addition we use equations ( [ e8 ] ) and ( [ e9 ] ) respectively ) . in this subsection
we write down a system of differential equations ( system a ) which describe infinitesimal flexions of a 2-ribbon surface in general position .
we show the existence of infinitesimal flexions and prove that they are proportional to each other ( theorem [ 1-d - inf ] ) .
let @xmath44 denote by _ system a _ the following system of differential equations @xmath45 in proposition [ inner ] below we show an explicit formula for the function @xmath46 , it is @xmath47 in our notation of section 2 .
note also that @xmath48 and @xmath49 in system a. the remaining part of this subsection is dedicated to the proof of theorem [ 1-d - inf ] on the structure of the space of infinitesimal flexions . in proposition
[ condition ] we show that any infinitesimal flexion satisfies system a. then in proposition [ existence ] we prove that any solution of system a with certain initial data is an infinitesimal flexion . finally , in proposition [ 111 ] we show the uniqueness of the solution of system a for a given initial data .
after that we prove theorem [ 1-d - inf ] .
let us show that any infinitesimal flexion satisfies system a. [ condition ] let @xmath50 , @xmath38 , and @xmath39 be linearly independent .
then for any infinitesimal flexion @xmath34 the functions @xmath51 satisfy system a. we start the proof with the following general lemma . [ additional ] for any infinitesimal flexion @xmath34 we have the equalities @xmath52 the functions @xmath53 , @xmath54 , and @xmath55 are infinitesimally preserved by infinitesimal flexions , hence @xmath56 , @xmath57 , and @xmath58 vanish . the invariance of angles between @xmath50 and @xmath38 , and @xmath50 and @xmath39 yield the equations @xmath59 and @xmath60 , respectively .
_ proof of proposition [ condition ] .
_ from lemma [ additional ] the functions @xmath56 , @xmath57 , and @xmath58 are equivalent to zero , thus @xmath61 , @xmath62 , and @xmath63 are equivalent to zero as well .
let us prove the expression for @xmath64 and @xmath65 .
note that @xmath66 thus equations ( [ e8 ] ) and ( [ e6 ] ) imply @xmath67 to obtain the expression for @xmath64 rewrite @xmath68 and @xmath69 in the basis consisting of vectors @xmath50 , @xmath38 , and @xmath39 . the same strategy works for the functions @xmath65 . now we study expressions for @xmath70 and @xmath71 . from lemma
[ additional ] we know that @xmath72 and @xmath73 and hence @xmath74 and @xmath75 .
therefore , the equations for @xmath70 and @xmath71 are satisfied . in order to get an expression for @xmath76
, we first note that @xmath77 , since the function @xmath78 is an invariant of an infinitesimal flexion .
so we get @xmath79 rewrite @xmath80 second , we have @xmath81 third , we get @xmath82 fourth , @xmath83 after a substitution of the four above expressions and simplifications we have @xmath84 further , we get @xmath85 from the last two identities , by substituting @xmath86 and @xmath72 ( see lemma [ additional ] ) , we obtain the expression for @xmath76 . the expression for @xmath87 is calculated in a similar way .
this concludes the proof .
further we prove that any solution of system a with certain initial data is an infinitesimal flexion .
[ existence ] let @xmath5 be a 2-ribbon surface , @xmath88\to \r^3 $ ] for @xmath89 .
assume that the function @xmath90 has no zeros on @xmath91 $ ] .
then any infinitesimal perturbation @xmath34 of @xmath5 satisfying system a and the boundary conditions @xmath92 is an infinitesimal flexion . by the definition of an infinitesimal flexion
it is enough to check that the following 11 functions are preserved by the infinitesimal perturbation : @xmath26 ( for all possible admissible @xmath27 ) .
_ invariance of @xmath53 , @xmath54 , @xmath55 , @xmath93 , and @xmath94_. from system a we have @xmath95 and hence all five functions under consideration are constants .
so it is enough to show that they vanish at some point : we show this at point @xmath96 .
@xmath97 _ invariance of @xmath98 and @xmath99_. note that @xmath100 hence @xmath101 .
similar reasoning shows that @xmath102 .
_ invariance of @xmath103 and @xmath104_. let us prove that @xmath105 .
first , note that @xmath106 recall that @xmath107 .
let us substitute the expression for @xmath64 from system a and rewrite @xmath69 in the basis of vectors @xmath50 , @xmath38 , and @xmath39 .
one obtains @xmath108 hence @xmath109 it follows that @xmath103 is invariant under the infinitesimal perturbation .
the proof of the invariance of @xmath110 is analogous .
_ invariance of @xmath111 and @xmath112_. let us prove that @xmath113 .
@xmath114 we have already shown that @xmath115 and @xmath116 . hence @xmath117 we rewrite the last @xmath118 in the last expression in the basis @xmath119 and get @xmath120 let us rewrite @xmath121 , @xmath122 , and @xmath123 in terms of @xmath124 .
first , we have : @xmath125 the second equality holds since we have shown that @xmath126 .
if we rewrite @xmath68 in the basis @xmath127 , we get the following : @xmath128 second , we have @xmath129 third , with @xmath130 and the expression for @xmath76 from system a we get : @xmath131 finally , we combine these three expressions and arrive at @xmath132 it is clear that the coefficients of @xmath133 and @xmath134 vanish identically . let us study the coefficient of @xmath135 .
consider the following mixed product @xmath136 , it is identical to zero
. let us rewrite @xmath68 in the second position of the mixed product in the basis @xmath137 , @xmath38 , @xmath39 .
we get the relation @xmath138 we apply this identity to the first two summands of the coefficient of @xmath135 and get the following expression for the coefficient of @xmath135 : @xmath139 we rewrite this as @xmath140 let us study the expression in the brackets .
@xmath141 the second equality holds by the jacobi identity .
hence the coefficient of @xmath135 is zero .
therefore , @xmath142 and @xmath111 is invariant under the infinitesimal perturbation .
the proof of the invariance of @xmath143 repeats the proof for @xmath111 .
so we have checked the invariance of all the 11 functions in the definition of an infinitesimal flexion .
hence the infinitesimal perturbation @xmath34 is an infinitesimal flexion . in the following proposition
we prove that system a has a unique solution for any single 2-ribbon surface @xmath5 ( not for a deformation ) and initial data for @xmath144 at one point @xmath145 .
recall that @xmath15 is an argument of @xmath5 .
[ 111 ] let @xmath5 be a 2-ribbon surface , @xmath88\to \r^3 $ ] for @xmath89 . for any collection of initial data @xmath146 there exists a unique solution of system a. this solution is extended for all @xmath147 , where @xmath148 the system of differential equations for @xmath149 is a system of homogeneous linear equations with variable coefficients and hence for any collection of initial data it has a unique solution .
the initial conditions of the last proposition can be reformulated in terms of infinitesimal flexion @xmath150 at a single point @xmath151 itself .
[ 111c ] let @xmath5 be a 2-ribbon surface , @xmath88\to \r^3 $ ] for @xmath89 .
for any collection of initial data @xmath152 there exists a unique solution of system a. this solution is extended for all @xmath147 , where @xmath148 the corollary follows directly from proposition [ 111 ] after obtaining the initial values @xmath153 from the vectors @xmath154 : @xmath155 now we have all the ingredients to prove the general theorem on the structure of the space of infinitesimal flexions .
[ 1-d - inf ] consider a 2-ribbon surface defined by curves @xmath88\to \r^3 $ ] for @xmath89 , where @xmath28 and @xmath30 are @xmath156-smooth and @xmath29 is @xmath33-smooth .
assume that the function @xmath157 has no zeroes on @xmath91 $ ] .
the space of infinitesimal flexions of such surfaces @xmath158up to isometries@xmath159 is one - dimensional .
_ uniqueness . _
any infinitesimal flexion is isometrically equivalent to an infinitesimal flexion which satisfies @xmath92 consider functions @xmath144 defined by equations ( [ g_i ] ) . by proposition [ condition ]
these functions satisfy system a. hence by corollary [ 111c ] , the functions @xmath144 are uniquely defined by @xmath5 and the initial conditions for infinitesimal flexions .
recall that elements of an arbitrary euclidean vector @xmath160 are uniquely determined by its scalar products with an arbitrary basis : @xmath161 therefore , the infinitesimal flexion is uniquely defined by the functions @xmath144 .
hence the dimension of infinitesimal flexions is at most one ( the parameter @xmath22 is the unique parameter of this flexion ) .
_ existence .
_ by corollary [ 111c ] there exists an infinitesimal deformation satisfying system a and the initial values @xmath162 by proposition [ existence ] this infinitesimal deformation is an infinitesimal flexion . since the function @xmath163 has no zeroes , @xmath164 is a nonzero vector and hence the infinitesimal deformation is nonvanishing .
let us fix an orthonormal basis @xmath165 in @xmath166 .
suppose that we know the coordinates of a 2-ribbon surface @xmath167\times \{0,1,2\ } \to\r^3 $ ] in this basis .
denote the coordinate functions for @xmath50 , @xmath38 , and @xmath39 as follows @xmath168 denote by @xmath169 the banach space @xmath170)^9 $ ] with the norm latexmath:[\[\|(h_1,\ldots , h_9)\|=\max\limits_{1\le i \le 9}(\max(\sup @xmath5 is defined by the curves @xmath172 , @xmath38 , and @xmath39 up to a translation .
so the space @xmath169 is actually the space of all 2-ribbon surfaces with one endpoint fixed , say @xmath173 .
we say that a point @xmath174 is in _ general position _ if the determinant @xmath175 for any point in the segment @xmath91 $ ] .
this condition obviously corresponds to @xmath176 denote by @xmath177\times \omega^1_9 \to \omega^1_9 $ ] the variational _ operator of infinitesimal flexion _ in coordinates @xmath178 : @xmath179 for ( @xmath180 ) . here
@xmath181 is a solution of system a at point @xmath5 with the initial conditions corresponding to @xmath182 i. e. , @xmath183 note that the variational operator of infinitesimal flexion @xmath31 is autonomous , it does not depend on time parameter @xmath16 .
let us show in brief how to find the coordinates of the perturbation @xmath21 in the basis @xmath184 satisfying @xmath185 first , one should solve system a with the above initial data , then substitute the obtained solution @xmath186 to equations ( [ e11 ] ) .
now we have the coordinates of @xmath187 , @xmath188 , and @xmath189 .
having the additional condition @xmath190 one can construct @xmath191 , @xmath192 , and @xmath193 : @xmath194 in previous subsection we showed that any @xmath195-ribbon surface in general position is infinitesimally flexible and the space of its infinitesimal flexions is one - dimensional .
the aim of this subsection is to show that a 2-ribbon surface in general position is flexible and has one degree of freedom .
we start with the discussion of the initial value problem for the following differential equation on the set of all points @xmath169 in general position ( here @xmath16 is the time parameter ) : @xmath196 to solve the initial value problem we study local lipschitz properties for @xmath31 .
consider a banach space @xmath197 with a norm @xmath198 and let @xmath199 be a subset of @xmath200\times e$ ] .
we say that a functional @xmath201 _ locally satisfies a lipschitz condition _
if for any point @xmath202 in @xmath199 there exist a neighborhood @xmath203 of the point and a constant @xmath204 such that for any pair of points @xmath205 and @xmath206 in @xmath203 the inequality @xmath207 holds .
first we verify a lipschitz condition for the following operator .
define @xmath208\times \omega^1_9 \to \omega^1_9 $ ] by @xmath209 where @xmath210 are defined by equations ( [ g_i ] ) .
[ g1 ] the functional @xmath211 locally satisfies a lipschitz condition at any point in general position .
consider a point @xmath212 .
the element @xmath186 itself satisfies a linear system of differential equations ( system a ) .
the coefficients of this system depend only on a point of @xmath213 .
since the point @xmath214 is in general position , there exists an integer constant @xmath204 such that for a sufficiently small neighborhood @xmath215 of @xmath214 the dependence is @xmath204-lipschitz , i.e. , for @xmath216 and @xmath217 from @xmath215 all the coefficients satisfy the inequality @xmath218 hence the solutions for @xmath219 $ ] satisfy the lipschitz condition on @xmath215 as well : for some constants @xmath220 we have @xmath221 from system a we know that the @xmath222 linearly depend on @xmath223 , therefore , we get the lipschitz condition for the derivatives : for some constants @xmath224 we have @xmath225 thus there exists a real number @xmath226 such that for all points @xmath216 and @xmath217 in @xmath215 , @xmath227 therefore , @xmath211 satisfies a lipschitz condition on @xmath215 .
lemma [ g1 ] and expression ( [ e11 ] ) directly imply the following statement .
[ d1 ] the functional @xmath31 locally satisfies a lipschitz condition at points in general position .
now we prove the following theorem on finite flexibility of 2-ribbon surfaces in general position .
[ 2-ribbon flex ] consider a 2-ribbon surface defined by a @xmath33-curve @xmath29 and @xmath156-curves @xmath28 and @xmath30 defined on a segment @xmath91 $ ] .
assume that @xmath90 does not have zeros on @xmath91 $ ] .
then the set of all flexions of such surface @xmath158up to isometries@xmath159 is one - dimensional .
as we show in corollary [ d1 ] , the operator @xmath31 satisfies a lipschitz condition in some neighborhood of the point @xmath216 related to @xmath50 , @xmath38 , and @xmath39 . from the general theory of differential equations on banach spaces (
see for instance the first section of the second chapter of @xcite ) it follows that this condition implies local existence and uniqueness of a solution of the initial value problem for the following differential equation @xmath228 in some neighborhood of @xmath214 .
since the 2-ribbon surface @xmath229 with a fixed endpoint @xmath230 is uniquely defined by @xmath231 , we get the statement of the theorem .
in this section we study necessary flexibility conditions of @xmath6-ribbon surfaces .
we find these conditions for 3-ribbon surfaces , and we show how they are related to the conditions for @xmath6-ribbon surfaces . in this subsection
we prove certain relations that we further use in the proof of the statement on infinitesimal flexibility conditions for 3-ribbon surfaces . as we have shown in section 1 the notions of finite flexibility and infinitesimal flexibility
coincide for the 2-ribbon case . still in this subsection
we say _ infinitesimal flexions _ of a 2-ribbon surface to indicate that an infinitesimal flexion of an @xmath6-ribbon surface coincides with finite flexions of all its 2-ribbon surfaces .
consider the following function @xmath232 this function plays a central role in our further description of the flexibility conditions of @xmath0-ribbon and @xmath6-ribbon surfaces ( see theorem [ inf ] and theorem [ n - ribbon - infini ] ) .
let @xmath233 be the infinitesimal flexion of @xmath47 . via this function
we describe monodromy conditions for finite flexibility .
proposition [ inner ] and corollary [ discr ] deliver necessary tools to describe continuous and discrete parts of the monodromy condition on @xmath47 . here
we study the dependence of the infinitesimal flexion @xmath234 on the argument @xmath15 .
[ inner ] * ( on continuous shift . ) * suppose @xmath50 , @xmath38 , and @xmath39 are linearly independent on the segment @xmath235 $ ]
. then for an infinitesimal flexion @xmath236 the following condition holds : @xmath237 this is a direct consequence of the next lemma .
[ rel ] let @xmath50 , @xmath38 , and @xmath39 be linearly independent , then we have @xmath238 note that @xmath239 let us prove the statement of the lemma for an arbitrary point @xmath151 . without loss of generality
we fix @xmath240 and @xmath241 ( this is possible since any flexion is isometric to a flexion with such properties and isometries of flexions do not change the functions in the formula of the lemma )
. then @xmath242 is proportional to @xmath243 , and hence there exists some real number @xmath244 with @xmath245 thus we immediately get @xmath246 let us express the summands for @xmath247 .
we start with @xmath248 .
first we note that @xmath249 equation ( [ e8 ] ) implies @xmath250 from equation ( [ e4 ] ) we have @xmath251 the function @xmath252 is invariant of an infinitesimal flexion , therefore : @xmath253 and hence @xmath254 now we decompose @xmath255 in the last formula in the basis of vectors @xmath256 , @xmath257 , and @xmath258 : @xmath259 therefore , after substitution ( [ ei ] ) of @xmath260 we apply ( [ eii ] ) , ( [ eiii ] ) , ( [ eiv ] ) , and the last expression and get @xmath261 similar calculations for the summand @xmath262 ( applying equations ( [ e3 ] ) , ( [ e5 ] ) , and ( [ e9 ] ) and the conditions @xmath240 and @xmath241 ) show that @xmath263 further we have @xmath264 therefore , @xmath265 and consequently @xmath266 thus lemma [ rel ] holds for all possible values of @xmath151 .
any 3-ribbon surface contain 2-ribbon surfaces as a subsurfaces .
each of them has an infinitesimal flexion @xmath267 ( @xmath268 ) .
here we show the relation between @xmath269 and @xmath270 for the same values of argument @xmath15 .
first , in proposition [ curvatures ] we show a relation for @xmath271 and @xmath272 .
second , in proposition [ phipsi ] we give a link between @xmath271 and @xmath267 .
this will result in the formula of corollary [ discr ] on the relation between @xmath269 and @xmath270 .
we start with a formula expressing @xmath272 via @xmath271 .
[ curvatures ] we have the following equation : @xmath273 we do calculations at a point @xmath151 again assuming that @xmath274 and @xmath241 ( by choosing an appropriate isometric representative of the deformation ) .
let us show that @xmath275 .
first , note that @xmath276 secondly we show that the inner products of @xmath277 and the vectors @xmath256 , @xmath278 , and @xmath279 are all zero ( this would imply that @xmath280 ) . from equation ( [ e9 ] ) we have @xmath281 further , from equations ( [ e5 ] ) , we get @xmath282 finally , from the equation @xmath283 we obtain @xmath284 therefore , @xmath285 , and hence @xmath286 . from equation ( [ e1 ] ) and
equation ( [ e7 ] ) we get @xmath287 therefore , for some real number @xmath288 we have @xmath289 by a similar reasoning ( since we have shown that @xmath290 ) we get @xmath291 since @xmath292 , at point @xmath151 we have @xmath293 hence , @xmath294 and , therefore @xmath295 .
this implies @xmath296 and @xmath297 the last two formulas imply the statement of proposition [ curvatures ] .
now let us relate @xmath271 and @xmath233 .
[ phipsi ] suppose @xmath50 , @xmath38 , and @xmath39 are linearly independent .
then the following equation holds : @xmath298 we restrict ourselves to the case of a point . without loss of generality
we assume that @xmath240 and @xmath299 .
so as we have seen before , there exists @xmath244 such that @xmath300 and hence @xmath301 let us calculate @xmath302 .
decompose @xmath303 since @xmath304 we get @xmath305 by equation ( [ e6 ] ) we have @xmath306 hence after the substitution of @xmath242 in the first summand one gets @xmath307 therefore , we obtain @xmath308 since the statement does not depend on the choice of the basis and invariant under isometries , we get the statement for all the points .
we introduce the abbreviations @xmath309 let us show a formula of a discrete shift .
[ discr]*(on discrete shift . ) * suppose @xmath50 , @xmath38 , and @xmath39 are linearly independent .
then the following holds : @xmath310 the statement follows directly from propositions [ curvatures ] and [ phipsi ] . in this subsection
we write down the infinitesimal flexibility monodromy conditions for 3-ribbon surfaces ( via continuous shifts of proposition [ inner ] and discrete shifts of corollary [ discr ] ) . recall that @xmath311 and @xmath312[1111 ] [ inf ] consider a 3-ribbon surface @xmath5 with linearly independent @xmath172 , @xmath38 , and @xmath39 at all admissible points .
the surface @xmath5 is infinitesimally flexible if and only if for any @xmath313 and @xmath314 in the interval @xmath315 $ ] we have @xmath316 by corollary [ discr ] we get relations between @xmath317 and @xmath318 for @xmath268 .
on the other hand , proposition [ inner ] relates @xmath319 and @xmath320 for @xmath268 .
these four relations define the monodromy condition for @xmath321 that is the condition in the theorem and , therefore , it holds if a surface is infinitesimally flexible .
suppose now the condition holds .
then the flexion is uniquely defined by the value of @xmath269 at a point @xmath151 .
let us simplify the expressions for @xmath322 and @xmath323 performing the following normalization for a fixed parameter @xmath16 .
denote @xmath324 here the semidiscrete surface @xmath5 is flexible if and only if @xmath325 is flexible .
in addition for the semidiscrete surface @xmath325 we get @xmath326 for all arguments @xmath15 . therefore we get the expressions for @xmath322 and @xmath323 as follows : @xmath327 and @xmath328 notice that this expression holds momentary , i.e. only for a fixed time parameter @xmath16 , so it can not be use for finite deformations . in this subsection
we say a few words about higher order variational conditions of flexibility for 3-ribbon surfaces .
we give an algorithm to rewrite these conditions in terms of the coefficients of the infinitesimal flexion defined by the system of differential equations ( system a ) .
we introduce a further auxiliary function by letting @xmath329 [ lambdah ] a 3-ribbon surface is infinitesimally flexible if and only if the following condition holds : @xmath330 this condition is obtained from the condition of theorem [ inf ] by differentiating w.r.t @xmath314 at the point @xmath313 .
therefore , these conditions are equivalent . from the infinitesimal flexibility condition of corollary [ lambdah ] one constructs many other conditions of flexibility .
if a 3-ribbon surface has a flexion , depending on a parameter @xmath16 , then @xmath331 at all points .
this implies the following statement .
if a 3-ribbon surface is flexible then for any positive integer @xmath332 we have @xmath333 where @xmath334 .
let us briefly describe a technique to calculate @xmath335 . +
* step 1 . * to simplify the expressions we write : @xmath336
further we let @xmath337 here we are interested in derivatives at an arbitrary value of a curve argument @xmath15 but at a fixed parameter of deformation @xmath338 . note that @xmath339 .
the functions @xmath340 and @xmath341 are calculated from the initial data for the @xmath0-ribbon surface @xmath5 .
let us find the expressions for @xmath342 . without loss of generality we fix @xmath343 for a starting point @xmath96 .
we find @xmath244 from corollary [ discr ] ( on discrete shift ) .
first , we have @xmath344 therefore , from corollary [ discr ] we have @xmath345 all the functions @xmath342 are found as the corresponding solutions of two systems of differential equations ( system a for @xmath268 ) according to corollary [ 111c ] . since @xmath346 , these solutions are compatible . for the functions
@xmath347 we have @xmath348 to avoid cross products in the above expression we use lagrange s formula : @xmath349 * step 2 .
* define @xmath350 as before , the functions @xmath351 and @xmath352 are calculated from the initial data for the 3-ribbon surface @xmath5 .
first , let us find the expressions for @xmath353 by induction on @xmath332 .
_ induction base .
_ for @xmath354 we get the formulae from step 1 . _ induction step . _
suppose that we know the expressions for @xmath332 let us find @xmath355 .
we have @xmath356 the expression in the left hand part is a function that is known by induction .
the last two summands of the hand right part are also expressed inductively after rewriting @xmath357 , and @xmath358 in the basis @xmath359 , @xmath360 , @xmath361 . secondly , decomposing @xmath362 in the basis @xmath359 , @xmath360 , @xmath361 we get @xmath363 * step 3 . * note that @xmath364 and @xmath365 [ aalg ] suppose that we get a rational polynomial expression @xmath366 in variables @xmath367 , @xmath368 , @xmath369 , and @xmath370 .
then @xmath371 is also a rational polynomial expression in variables @xmath367 , @xmath368 , @xmath369 , and @xmath370 .
steps 13 give all the tools to write the expression for @xmath371 explicitly . for any positive integer @xmath332
the function @xmath372 is a rational polynomial expression in variables @xmath367 , @xmath368 , @xmath369 , and @xmath370 .
therefore , we can apply steps 13 and proposition [ aalg ] to calculate @xmath373 using induction on @xmath332 .
we conclude this subsection with a few words on sufficient conditions for flexibility .
we start with an open problem .
find a sufficient condition for flexibility of semidiscrete and @xmath6-ribbon surfaces . for the case of @xmath0-ribbon surfaces we have the following conjecture .
consider a @xmath0-ribbon surface @xmath5 .
let @xmath374 for all non - negative integers @xmath332 ( where @xmath375 ) .
then @xmath5 is locally flexible .
we also conjecture that it is enough to take only a finite number of these conditions .
then the following question is actual : _ what is the number of independent conditions of isometric deformation _ ?
let us finally describe a relation between ( finite and infinitesimal ) flexibility of @xmath6-ribbon surfaces and flexibility of all 3-ribbon subsurfaces contained in them .
we start with theorem on infinitesimal flexibility .
[ n - ribbon - infini ] consider an @xmath6-ribbon surface satisfying the genericity condition : @xmath376 , @xmath377 , and @xmath378 are not coplanar at any admissible point @xmath151 and integer @xmath27 .
then this surface is infinitesimally flexible if and only if any 3-ribbon surface contained in the surface is infinitesimally flexible .
the proof is straightforward .
all the conditions for infinitesimal flexion are exactly the conditions for 3-ribbon surfaces of theorem [ inf ] . for the finite flexibility we have the following .
[ n - ribbon - fini ] consider an @xmath6-ribbon surface satisfying the genericity condition : @xmath376 , @xmath377 , and @xmath378 are not coplanar at any admissible point @xmath151 and integer @xmath27 .
then this surface is flexible if and only if any 3-ribbon surface contained in the surface is flexible .
we think of this theorem as of a semidiscrete analogue to the statement of the paper @xcite on conjugate nets and all @xmath379-meshes that they contain . in this paper
we do not study phenomena related to non - compactness and hence we restrict ourselves to the case of compact @xmath6-ribbons surfaces .
the `` only if '' part of the statement is straightforward .
we prove the converse by induction on the number of ribbons in a surface .
_ induction base .
_ by assumption any 3-ribbon subsurface contained in the surface is flexible .
it has one degree of freedom , since by theorem [ 1-d - inf ] any 2-ribbon subsurface of a 3-ribbon surface has at most one degree of freedom , while the genericity condition holds in a certain neighborhood of a starting position .
_ induction step .
_ suppose we know that any @xmath380-ribbon subsurface is flexible and has one degree of freedom in some neighborhood ( for @xmath381 ) .
let us prove the statement for any @xmath382-ribbon subsurface .
we consider a @xmath382-ribbon subsurface as the union of two @xmath380-ribbon subsurfaces that intersect in a @xmath383-ribbon subsurface . by the induction assumption
this @xmath383-ribbon surface has one degree of freedom compatible with the flexions of both @xmath380-ribbon subsurfaces .
therefore , the flexion of the @xmath383-ribbon subsurface is uniquely extended to the both @xmath380-ribbon subsurfaces .
this implies flexibility of the @xmath382-ribbon with one degree of freedom .
suppose that all ribbons of a semidiscrete surface are developable , i.e. the vectors @xmath376 , @xmath384 , and @xmath385 are linearly dependent .
we call such semidiscrete surfaces _ developable_. in this section we describe an additional property for flexions of developable semidiscrete surfaces .
this fact gives a surprising corollary concerning the flexion of a 2-ribbon developable surface .
the degree of freedom for a flexion of a generic 2-ribbon developable surface is 1 , as can easily be seen from the genericity condition for 2-ribbon surfaces .
so a flexion is unique up to the choice of a parameter .
denote by @xmath392 the angle between @xmath38 and @xmath39 .
consider a flexion of a 2-ribbon developable surface @xmath5 .
let us choose the parameter @xmath22 of the flexion such that @xmath393 changes linearly in @xmath22 .
then for any @xmath15 the value @xmath394 changes linearly in @xmath22 . for the surface of @xmath395
we get @xmath397 since @xmath398 and @xmath399 . now
the statement of the corollary for @xmath395 follows from proposition [ inner ] and the inner geometry expression of proposition [ devel ] for the function under integration ( that is actually @xmath400 )
. * acknowledgement . *
the author is grateful to j. wallner for constant attention to this work , a. weinmann for good remarks .
this work has been performed at technische universitt graz within the framework of the project `` computational differential geometry '' ( fwf grant no .
s09209 ) . a. i. bobenko , t. hoffmann , w. k. schief , _ on the integrability of infinitesimal and finite deformations of polyhedral surfaces _ , discrete differential geometry , a. i. bobenko , p. schrder , j. m. sullivan , g. m. ziegler , ( eds . ) , series : oberwolfach seminars , v. 38 ( 2008 ) , pp .
6793 .
mller , j. wallner , _ semi - discrete isothermic surfaces _ , geometry preprint 2010/02 , tu graz , february 2010 .
h. pottmann , j. wallner , _ infinitesimally flexible meshes and discrete minimal surfaces _ , monatshefte math .
, v. 153 ( 2008 ) , pp
. 347365 . | in this paper we study necessary conditions of flexibility for semidiscrete surfaces . for 2-ribbon semidiscrete surfaces
we prove their one - parametric finite flexibility . in particular we write down a system of differential equations describing flexions in the case of existence .
further we find infinitesimal criterions of @xmath0-ribbon flexibility .
finally , we discuss the relation between general semidiscrete surface flexibility and @xmath0-ribbon flexibility . |
With his gravelly Tennessee drawl and his trademark straw panama hat, R.A. "Bob" Hoover was an icon of American aviation prowess and heroism.
One of his most flamboyant escapades was escaping the Nazis in World War II by stealing one of their planes.
The legendary aviator died at his home near Los Angeles on Tuesday, at age 94, according to the Aircraft Owners and Pilots Association.
Hoover was born January 24, 1922 in Nashville, Tenn., and began flying at age 15. In his early years, Hoover taught himself aerobatic flying and vanquished recurring air sickness through the force of repetition, according to a 2010 Smithsonian interview.
His precise flying and technical skill as a test pilot earned Hoover the title of the "greatest stick-and-rudder man who ever lived." That superlative was given to him by General James "Jimmy" Doolittle, his close friend and leader of the April 1942 Doolittle Raid on Tokyo.
An Army Air Corps and later Air Force veteran of both World War II and the Korean War, Hoover was awarded the Distinguished Flying Cross for rescuing a damaged B-26 from a beach in Sicily.
After being shot down in 1944, Hoover spent 16 months in a Stalag Luft I, a German prisoner of war camp on the northeastern coast of Germany, according to the National Aviation Hall of Fame. Hoover jumped a barbed wire fence while the guards were distracted by a staged fight. He stole a lightly-damaged Focke-Wulf Fw 190, flying it to freedom before ditching the plane in a field in the Netherlands.
After the war, Hoover became a test pilot and flew through a time when flying records would fall one-by-one and new aircraft were being developed to go higher, faster and farther.
In October 1947 he flew the chase plane alongside Gen. Chuck Yeager as he broke the sound barrier, traveling past Mach 1, for the first time in the skies over Southern California. As Yeager's backup, Hoover always expressed regret that he wasn't the first.
He spent the most tense days of the Cold War testing fighters at North American Aviation. Hoover served as captain of the 1966 U.S. Acrobatic Team in Moscow.
After leaving the aerospace business, Hoover became an hallmark of the air show and race circuit.
He flew in more than 2,500 civilian and military air shows in the U.S. and around the world, according to the Smithsonian, thrilling those on the ground with his trademark routine: Shutting off one or both of the engines on his North American Rockwell Shrike Commander 500S, while performing loops and dives.
A precise aviator, Hoover famously was able to pour a glass of iced tea in the middle of a barrel role. Hoover's famous green and white stunt plane sits prominently under the wing of the Concorde supersonic airliner at the National Air and Space Museum Annex in Chantilly, Va. ||||| Legendary pilot Bob Hoover, a world famous air show performer and former Air Force test pilot who flew captured enemy planes at Wright Field, died Tuesday, according to media reports.
He was 94 years old.
“It’s easy to call him an icon, but he truly is,” said Ron Kaplan, enshrinement director at the National Aviation Hall of Fame at Wright-Patterson Air Force Base. “He has influenced more individuals than probably … any single person in aviation.”
Hoover had a reputation as “a great test pilot so at the dawn of the jet age he was literally off the wing of Chuck Yeager” flying a chase plane as Yeager broke the sound barrier above the California desert in 1947, said Kaplan.
Hoover, a Nashville, Tenn., native, had expected to fly the Bell X-1 before Yeager on the historic test flight but was replaced when he buzzed an aircraft traffic control tower in Springfield while stationed at Wright Field, Kaplan said.
“You could tell he would be a little wistful knowing that he could have been at the controls of the X-1 and not for the glory but really for the challenge of it because he was consummate test pilot,” Kaplan said.
The pilot’s health had been failing in recent weeks, according to Kaplan. Hoover planned to travel from his California home to attend the NAHF enshrinement dinner this month at the National Museum of the U.S. Air Force but declined a week before because of health concerns, Kaplan said.
The Experimental Aircraft Association on its website announced Hoover’s death Tuesday.
During World War II, Hoover flew 58 combat missions before he was shot down and spent 16 months in a German POW camp. Hoover escaped and flew an abandoned Nazi fighter to Holland, according to his NAHF biography.
After the war, he flew captured German and Japanese planes and test aircraft at Wright Field in Dayton.
In 1950, he began a 36-year affiliation with North American Aviation and Rockwell International.
The acrobatic champion performed on the air show circuit around the world for decades. “Bob Hoover was a superb pilot, and most professional aerobatic pilots I know consider him to be unmatched,” said Timothy Gaffney, a National Aviation Heritage Alliance spokesman.
Memorial service arrangements were pending, EAA said. ||||| Bob Hoover (1922 - 2016)
Robert A. "Bob" Hoover, a World War II fighter pilot who became an aviation legend for his skills as a test pilot and for his appearances in air shows, has died at age 94, according to multiple news sources.
Hoover died early Tuesday, said Bill Fanning, a close family friend for many years and fellow pilot.
"He was every pilot's icon," Fanning said, recalling his friend as one of the premier test pilots of the 1950s and '60s. "Bob tested everything. He flew them all."
Hoover was known for being the chase pilot for Chuck Yeager, who set an aviation record by breaking the sound barrier in 1947. Hoover went on to set his own transcontinental and “time to climb” speed records.
Click to get weekly celebrity death news delivered to your inbox.
The famous General Jimmy Doolittle who was a pioneering pilot himself, called Hoover the “greatest stick-and-rudder man who ever lived.”
Hoover’s plane was shot down during World War II and he spent 16 months in a German POW camp. He escaped the camp by stealing a German plane and flying it to the Netherlands.
Hoover became the backup pilot for his friend Chuck Yeager and flew chase for Yeager during his famous Mach 1 flight. He flew flight tests for the F-86 Sabre and the F-100 Super Sabre.
Hoover later became a legend flying at air shows across the country. He retired from performing at air shows in 1999 at the age of 77.
The Smithsonian Air and Space Museum tweeted, “We mourn the passing of our friend Robert A. “Bob” Hoover, "The Greatest Stick and Rudder Man Who Ever Lived.”
We invite you to share condolences for Bob Hoover in our Guest Book. ||||| It’s a special kind of sand that makes a guy like Bob Hoover stand out among a generation of heroes. Born in 1922, Hoover was a fighter pilot in the Second World War. He flew in North Africa before pulling a primo assignment piloting a Spitfire out of Sicily. After getting shot down over the Mediterranean, Hoover spent more than a year as a German prisoner in Stalag Luft 1 before making a run for it as the Russians advanced on the camp.
Not content to spend the remainder of the war learning Russian, or hiding in a German barn, Hoover stole a German Focke Wulf 190 and flew like mad to get behind the Western front. In his appropriated German plane, Hoover had to avoid allied aircraft (lest he get shot down by unwitting friendly fire) all the way to Holland, where he landed in a field and was promptly surrounded by pitchfork-wielding locals convinced he was a Nazi flyer. His incredible exploits during the war alone are enough to qualify a guy as pretty damned impressive in my eyes. But Hoover was just getting started.
Unlike so many of his peers, Hoover didn’t leave the cockpit after the war. He stayed on with the Air Corps as it became the Air Force, serving as a test pilot, and eventually as both Chuck Yeager’s wingman and the backup pilot for his famous Mach 1 flight in the Bell X-1. Even after leaving the service, Hoover continued to fly and test military aircraft as a civilian test pilot.
While Hoover had a remarkable gift for flying the wings off high-performance military aircraft (sometimes literally), it was in civilian aviation where Hoover cemented his legend. After a stint flying for aircraft manufacturers, Hoover made for the air racing and air show circuit, where he performed in everything from P-51 Mustangs to cumbersome, twin-engine Commander utility planes. As it turned out, Hoover’s great talent wasn’t making high-performance planes scream for mercy, it was making crowds scream for more after watching Hoover’s impossibly graceful flights in totally pedestrian aircraft.
Engine-out aerobatic flights and perfect one-wheel touch-and-go landings aside, Hoover might be most famous for executing a perfect roll in his twin-engine commander while pouring a glass of iced tea. YouTube is packed to the gills with videos of his antics. Like this one. And this one. And this one. He was many things, but most of all, Hoover was a hell of a pilot—and with his air shows, he inspired a great many more to try to fill his shoes.
Bob Hoover died this morning, at the age of 94. My Facebook feed—usually a spattering of politics and off-road trucks and friendly idiocy—was instead filled with kind words and videos of Hoover, modestly and warmly being his own quiet kind of hero. The last thing we need is fewer heroes, but seeing friends from a dozen countries and hobbies and political outlooks come together early in the morning to give this good man a tip of the hat on his passing is one last act of inspiration from a guy who seemed to have an endless well of the stuff. ||||| Bob Hoover, a World War II fighter pilot who escaped a POW camp and flew to freedom by stealing a German airplane and who spent decades testing aircraft, thrilling spectators at air shows and training military aviators, died Oct. 25 at a hospital in Torrance, Calif. He was 94.
The cause was congestive heart failure, said his daughter-in-law, Lynn Hoover.
Mr. Hoover, who learned to fly as a teenager in Tennessee, was among the country’s most revered pilots. The renowned World War II airman Gen. Jimmy Doolittle once called Mr. Hoover “the greatest stick-and-rudder man who ever lived.”
In 1947, Mr. Hoover was a test pilot flying alongside Chuck Yeager when Yeager broke the sound barrier. Mr. Hoover taught dive-bombing maneuvers to Air Force pilots during the Korean War.
He flew more than 300 varieties of airplanes and knew virtually every significant figure in the history of aviation, from Orville Wright to Charles Lindbergh to Neil Armstrong, the first astronaut to walk on the moon. During his decades as a stunt pilot, Mr. Hoover handled his plane so smoothly that he could pour a cup of tea while executing a 360-degree roll. One of the airplanes he used for aerobatics, a North American Rockwell Shrike Commander 500S, is housed in the National Air and Space Museum’s Steven F. Udvar-Hazy Center in Chantilly, Va.
Bob Hoover at the National Air and Space Museum, where he received an award for lifetime achievement in 2007. (Marvin Joseph/The Washington Post)
“He had such an intuitive sense of how to fly an airplane,” Dorothy S. Cochrane, a curator at the Air and Space Museum, said in an interview. “He had a stunning ability to be a part of the airplane and to figure out what was wrong and how to get out of it and recover. He just had that ability not only to do it himself but to communicate to others.”
As recently as last year, actor Harrison Ford credited lessons learned from Mr. Hoover with helping him survive a crash landing of a vintage airplane on a California golf course.
During World War II, while based in North Africa and southern Europe, Mr. Hoover flew 58 missions as a fighter pilot with the Army Air Forces. On his 59th, on Feb. 9, 1944, he was shot down off the coast of southern France and was plucked from the sea by a German patrol boat.
He spent more than a year in a German prison camp before he and a fellow American climbed the fence and fled into the nearby woods. With the war coming to an end, German civilians were more cooperative, and a farm woman gave Mr. Hoover and his fellow escapee a gun.
“She said it would do us a lot more good than it did her, and she was right,” Mr. Hoover later told the Los Angeles Daily News.
He and his friend came upon a field with hundreds of damaged German warplanes. Mr. Hoover found one that had a full gas tank.
When a German mechanic approached, Mr. Hoover’s friend pulled the gun on him.
Hoover with Chuck Yeager, left, on the 50th anniversary of the historic flight that broke the sound barrier. (Reuters/Reuters)
“We told him unless he could get us airborne fast, we were going to kill him,” Mr. Hoover recalled years later.
The German plane’s engine started, but Mr. Hoover’s buddy refused to get aboard, vowing never to fly in another airplane. Instead, he took his chances on foot — and years later was reunited with Mr. Hoover.
The stolen plane had a German cross painted on the side, and Mr. Hoover was fearful of being attacked by Allied forces as he flew along the coast of Germany toward the Netherlands.
“I didn’t have any maps or charts,” he said in a 2007 interview with the publication Airport Journals. “I knew that if I turned west and followed the shoreline, I would be safe when I saw windmills.”
He landed in a field and was quickly surrounded by Dutch farmers with pitchforks. Soon afterward, a British army truck rolled up, and Mr. Hoover was taken to safety.
Hailed as a hero, he noted that the prison camps were loosely guarded during the waning days of the war. “People made it sound like a great escape,” he said, “but the guards had deserted us.”
Robert Anderson Hoover was born Jan. 24, 1922, in Nashville. His father was an office manager and bookkeeper.
Mr. Hoover began taking flying lessons at 15 and joined the Tennessee Air National Guard at 18.
After World War II, while serving in the newly formed Air Force, he was one of the test pilots selected for a project to break the sound barrier with the new Bell X-1 rocket-powered aircraft. When Yeager accomplished the feat in 1947, Mr. Hoover was flying the “chase plane” and took the first photographs of Yeager’s faster-than-sound flight.
He received the Distinguished Flying Cross, Purple Heart and other decorations before leaving the military in 1948. He then became a test pilot for General Motors, North American Aviation and North American Rockwell.
He lived for years in Palos Verdes Estates, Calif., and appeared at air shows around the world, flying a yellow P-51 Mustang or his white-and-green Shrike. In Moscow in 1966, he was briefly detained because he outshone Soviet pilots while flying a Russian-built plane.
In one of his most daring maneuvers, Mr. Hoover turned off the engines of his airplane and flew it like a glider, coming to a silent stop on the runway.
After a 1989 accident, in which his airplane was filled with the wrong fuel, Mr. Hoover invented a new kind of nozzle to prevent such mistakes from happening again.
His wife of 68 years, the former Colleen Humrickhouse, died in February. Survivors include two children, Anita Eley of Greeley, Colo., and Robert A. Hoover Jr. of El Segundo, Calif.; three grandchildren; and two great-grandsons.
In 1994, federal officials threatened to ground Mr. Hoover for failing medical tests. The outpouring from flying fans was so great that he was reexamined, and his pilot’s license was reinstated. He retired from aerobatics in his late 70s and piloted his last plane when he was 85.
Filmmaker Kim Furst premiered a documentary about Mr. Hoover, “Flying the Feathered Edge,” in 2014. Mr. Hoover published an autobiography, “Forever Flying,” in 1996.
In his book, Mr. Hoover wrote, “Hell, I would fly an old Dodge truck if they put wings on the side.” | – One of America's greatest aviation heroes has died, reports Yahoo. Bob Hoover, a World War II fighter pilot who escaped the Nazis by stealing one of their planes, died of congestive heart failure Tuesday near Los Angeles, reports the Washington Post. He was 94. Born in Tennessee, Hoover was flying by age 15 and soon learned how to perform loops and dives, reports CNNMoney. He put those skills to use in 58 combat missions during World War II before he was shot down in 1944 and spent 16 months in German POW camp Stalag Luft I. He eventually arranged for a mock fight to break out, scaled a barbed wire fence while guards were distracted, and jumped into a Nazi plane, which he flew to the Netherlands. He didn't have a map, but "I knew that if I turned west and followed the shoreline, I would be safe when I saw windmills," he once said. His triumphs didn't end there. In 1947, he was Chuck Yeager's wingman as he broke the sound barrier for the first time. He then became a premier test pilot before flying in more than 2,500 air shows around the globe. Among his greatest tricks: pouring a glass of iced tea during a barrel roll. Gen. Jimmy Doolittle once described Hoover as the "greatest stick-and-rudder man who ever lived," but "he was every pilot's icon," a family friend tells Legacy.com. "He has influenced more individuals than probably … any single person in aviation," a rep for the National Aviation Hall of Fame adds, per the Dayton Daily News. (This man survived the only mass escape from a Nazi death camp.) |
spin - dependent electronic transport and use of the spin degree of freedom of electrons in hybrid magnetic structures have recently been subject of highly interesting field termed spintronics .
this developing field has emerged from many exciting phenomena , the giant magneto - resistance being the most well known example , which has made it attractive for applications as well as fundamental studies @xcite .
typical studied systems are based on the use of ferromagnetic metals ( f ) and/or external magnetic fields to inject , manipulate and detect spin - polarized electrons inside a mesoscopic normal metal ( n ) .
an important characteristic of mesoscopic systems is the appearance of shot noise , the fluctuations of current through the system due to the randomness of the electronic scattering processes and the quantum statistics . shot noise and nonlocal correlations of the current fluctuations contain additional information on the conduction process which is not gainable through a mean current measurement .
in ferromagnetic - normal metal structures , in which the spin of electrons plays an essential rule , current fluctuations are due to the randomness of both charge and spin transport processes .
thus , shot noise measurements are expected to provide information about spin - dependent scattering processes and spin accumulation in the system .
together with the importance of noise in spintronic devices in view of applications this motivates our study of spin - polarized shot noise . in the past years
, shot noise has been extensively studied in a wide variety of hybrid structures involving normal metals , semiconductors and superconductors@xcite . however , there are few studies devoted to shot noise in ferromagnet - normal metal systems . results of earlier studies of current fluctuations in fnf double barrier systems in the coulomb blockade regime@xcite and fif ( i being an insulator ) systems @xcite can be understood in terms of well known results for the corresponding normal - metal systems for two spin directions@xcite .
tserkovnyak and brataas studied shot noise in double barrier fnf systems with noncollinear magnetizations in f - terminals @xcite .
they found that the shot noise has a non - monotonic behavior with respect to the relative angle of the magnetizations for different scattering regimes and different types of fn junctions .
the effect of spin flip scattering on spin - polarized current fluctuations has been considered in refs . .
mishchenko @xcite found that in a perfectly polarized two - terminal double barrier system spin - flip scattering leads to a strong dependence of shot noise on the relative orientation of the magnetizations in f - terminals . in ref .
we have proposed a four - terminal spin - valve system of tunnel junctions to study spin - dependent shot noise and cross- correlations simultaneously .
it has been found that the cross - correlations between currents in terminals with opposite spin polarization can be used to measure directly the spin - flip scattering rate .
recently , there have been also studies of the current fluctuations of spin - polarized entangled electrons in quantum dots and wires @xcite and in quantum dots attached to the ferromagnetic leads in the coulomb blockade @xcite , kondo @xcite and sequential tunneling @xcite regimes . in this paper , we study current fluctuations in a three terminal diffusive fnf system in the full range of spin polarizations and the spin - flip scattering intensity .
based on the boltzmann - langevin @xcite kinetic approach , we develop a semiclassical theory for spin - polarized transport in the presence of the spin - flip scattering . we obtain the basic equations of charge and spin transport , which allow the calculation of mean currents and the correlations of current fluctuations in multi - terminal diffusive systems . applying the developed formalism to a three - terminal geometry , we find that current correlations are affected strongly by spin - flip scattering and spin polarizations .
we focus on the shot noise of the total current through the system and the cross - correlations measured between currents of two terminals .
we demonstrate how these correlations deviate from the noise characteristics of the unpolarized system , depending on the spin - flip scattering rate , the polarizations of the terminals and their magnetic configurations ( relative directions ) .
our results provide a full analysis for spin - dependent shot noise and cross - correlations in terms of the relevant parameters .
the structure of the paper is as follows . in section
ii we extend the boltzmann - langevin equations to the diffusive systems , in which spin - flip scattering takes place and which are connected to ferromagnetic terminals .
we find the basic equations of the charge and the spin currents and the correlations of their fluctuations .
in section iii we apply this formalism to the three terminal system .
we obtain the fano factor and the cross - correlations between currents through two different terminals .
section vi is devoted to the analysis of the calculated quantities .
we present analytical expressions for the fano factor and the cross - correlations in different important limits .
finally , we end with some conclusion in section v.
in this section we extend the semiclassical boltzmann - langevin kinetic approach @xcite to cover spin - polarized transport . in the presence of spin - flip scattering the boltzmann - langevin equation
is written as @xmath0 + i_{\alpha}^{{\text { sf}}}[f_{\alpha},f_{-\alpha } ] + \xi^{{\text { imp}}}_{\alpha}+\xi^{{\text { sf}}}_{\alpha } , \label{bls}\end{aligned}\ ] ] where the fluctuating distribution function of spin @xmath1(@xmath2 ) electrons @xmath3 depends on the momentum @xmath4 , the position @xmath5 , and the time @xmath6 .
( [ bls ] ) contains both normal impurity and spin - flip collision integrals which are given by the relations @xmath7=\omega
\int \frac{d{\bf p}^{\prime } } { ( 2\pi h)^3 } [ j_{\alpha \alpha}({\bf p}^{\prime},{\bf p})- j_{\alpha \alpha}({\bf p},{\bf p}^{\prime } ) ] , \label{is } \\ * & & i_{\alpha}^{{\text { sf}}}[f_{\alpha},f_{-\alpha}]= \omega \int \frac{d{\bf p}^{\prime } } { ( 2\pi h)^3 } [ j_{-\alpha \alpha}({\bf p}^{\prime},{\bf p})- j_{\alpha -\alpha}({\bf p},{\bf p}^{\prime } ) ] .
\nonumber \\ * & & \label{issf}\end{aligned}\ ] ] here @xmath8 , $ ] where @xmath9 is the elastic scattering rate from the state @xmath10 into @xmath11 ; @xmath12 is the volume of the system .
the corresponding langevin sources of fluctuations due to the random character of the electron scattering are given by @xmath13 , \label{ksis } \\ * & & \xi^{\text { sf}}_{\alpha}=\omega \int \frac{d{\bf p}^{\prime}}{(2\pi h)^3 } [ \delta j_{-\alpha \alpha}({\bf p}^{\prime},{\bf p})- \delta j_{\alpha -\alpha}({\bf p},{\bf p}^{\prime } ) ] , \label{ksisfs}\end{aligned}\ ] ] where the random variable @xmath14 is the fluctuation of the current @xmath15 with @xmath16 $ ] being the mean current .
we will assume that all scattering events are independent elementary processes and thus the correlator of the current fluctuations @xmath17 is that of a poissonian process : @xmath18 due to the non - vanishing spin - flip collision integral in ( [ bls ] ) , the equations for the distributions of electrons with opposite spin directions are coupled .
the coupled equations can be transformed into two decoupled equations for the charge @xmath19 and spin @xmath20 distribution functions , which read @xmath21 + i^{{\text { sf}}}_{{\text { c}}({\text { s } } ) } [ f_{{\text { c}}{(\text { s})}}]+ \xi^{{\text { imp } } } _ { { \text { c}}({\text { s}})}+ \xi^{{\text { sf}}}_{{\text { c}}({\text { s}})}. \label{blfp}\end{aligned}\ ] ] here we have introduced different collision integrals : @xmath22=\omega\int \frac{d{\bf p}^{\prime } } { ( 2\pi h)^3}[j^{{\text { imp}}}_{{\text { c}}({\text { s}})}({\bf p}^{\prime},{\bf p})- j^{{\text { imp}}}_{{\text { c}}({\text { s}})}({\bf p},{\bf p}^{\prime})],\nonumber \\ * & & \label{if}\\ * & & i_{\text { c}}^{{\text { sf}}}[f_{\text { c } } ] = \omega\int \frac{d{\bf p}^{\prime } } { ( 2\pi h)^3}[j_{\text { c}}^{{\text { sf}}}({\bf p}^{\prime},{\bf p})- j_{\text { c}}^{{\text { sf}}}({\bf p},{\bf p}^{\prime } ) ] , \label{isff}\\ * & & i^{{\text { sf}}}_{\text { s}}[f_{s}]=-\omega\int \frac{d{\bf p}^{\prime } } { ( 2\pi h)^3}w^{{\text { sf}}}({\bf p},{\bf p}^{\prime } ) [ f_{\text { s}}({\bf p}^{\prime})+f_{\text { s } } ( { \bf p})],\nonumber \\ * & & \label{isffp}\end{aligned}\ ] ] where @xmath23,\end{aligned}\ ] ] and we assumed @xmath24 , @xmath25 @xmath26 the corresponding langevin sources of fluctuations are given by @xmath27 in the following we assume that all the quantities are sharply peaked around the fermi energy and instead of @xmath4 use the quantities @xmath28 the energy and @xmath29 the direction of the fermi momentum .
then , for elastic scattering of electrons the following relation holds @xmath30 where @xmath31 is the density of states in the fermi level . for a diffusive conductor
we apply the standard diffusive approximation to the kinetic equations ( [ blfp ] ) where the charge and spin distribution functions are split into the symmetric and asymmetric parts : @xmath32 substituting this form of @xmath33 in eqs .
( [ blfp ] ) and averaging subsequently over the fermi momentum direction first weighted with one and then with @xmath29 , we obtain @xmath34 .
\label{df0}\end{aligned}\ ] ] in the same way from eqs .
( [ fnex ] ) and ( [ blfp ] ) , for @xmath35 , we obtain @xmath36 , \label{dfp0}\end{aligned}\ ] ] where different relaxation times of normal impurity and spin - flip scatterings are defined as @xmath37 here we used the identity @xmath38 for the elastic scattering . in obtaining eqs .
( [ df]-[dfp0 ] ) we have disregarded terms @xmath39 in the expressions @xmath40 , since we are only interested in the zero frequency noise power .
the terms of the electric field @xmath41 are eliminated by substituting @xmath28 by @xmath42 in the arguments of @xmath43 , respectively , where the charge and spin potentials are expressed as @xmath44 and @xmath45 , with @xmath46 being the spin - dependent electro - chemical potential .
we also used the identities @xmath47 which follows from the conservation of number of spin @xmath1 electrons in each normal impurity scattering process@xcite .
in contrast to this , we note that the integral @xmath48 does not vanish , reflecting the fact that spin is not conserved by the spin - flip process . combining eqs .
( [ df ] ) , ( [ df0 ] ) and ( [ dfp ] ) , ( [ dfp0 ] ) the equations for the symmetric parts of the mean charge and spin distribution functions are obtained as @xmath49 where @xmath50 is the spin - flip length .
note , that in general charge and spin diffusion constants given by @xmath51 are different .
using eqs .
( [ fnex ] ) the charge and spin current densities can be expressed as @xmath52 .
the corresponding fluctuating potentials are given by @xmath53 .
using these identities and integrating eqs .
( [ df]-[df0 ] ) over @xmath28 we obtain diffusion equations for the charge potential and current density , @xmath54 which also imply @xmath55 in the same way eqs .
( [ dfp]-[dfp0 ] ) give us diffusion equations of spin potential and current density : @xmath56 where @xmath57 are the charge and spin conductivities . here
@xmath58 are the langevin sources of fluctuations of the charge and spin current densities , and @xmath59 are additional terms in the expressions for the divergence of charge and spin currents fluctuations eqs .
( [ dj ] ) and ( [ djp ] ) , due to the non - conserved nature of spin - flip process .
now we calculate possible correlations between the currents @xmath60 and @xmath61 . from eqs .
( [ ksis]-[poisson ] ) for the correlations of different fluctuating sources we obtain @xmath62 where @xmath63 \nonumber \\ * & & [ { \bar j}_{\alpha \alpha}({\bf n},{\bf n}^{\prime \prime},\varepsilon)+ { \bar j}_{\alpha \alpha}({\bf n}^{\prime \prime},{\bf n},\varepsilon ) ] , \label{gssp } \\ * & & g^{\text { sf}}_{\alpha\alpha^{\prime}}= \int d{\bf n}^{\prime \prime}[\delta _ { \alpha\alpha^{\prime } } \delta({\bf n}-{\bf n}^{\prime})- \delta _ { \alpha-\alpha^{\prime } } \delta({\bf n}^{\prime}-{\bf n}^{\prime \prime})]\nonumber \\ * & & [ { \bar j}_{-\alpha \alpha}({\bf n},{\bf n}^{\prime \prime})+ { \bar j}_{\alpha -\alpha}({\bf n}^{\prime \prime},{\bf n } ) ] . \label{gsfssp}\end{aligned}\ ] ] from eqs .
( [ ksiimsf ] ) , ( [ ksiimsfs ] ) and ( [ ksicor]-[gsfssp ] ) we calculate the correlations between the fluctuating sources @xmath64 , which can be used together with eqs .
( [ jcs ] ) and ( [ isp ] ) to obtain the results , @xmath65 , \label{jsjs } \\ * & & <
j_{{\text { c}}l}^{c}({\bf r},t ) j_{\text { s}m}^{c}({\bf r}^{\prime } , t^{\prime})>= \delta_{lm } \delta({\bf r}-{\bf r}^{\prime } )
\delta(t - t^{\prime})\sigma_{\text { c } } \nonumber \\ * & & \times \sum _ { \alpha}\alpha\pi_{\alpha \alpha}({\bf r } ) , \label{jsjsp } \\ * & & < i_{\text { c}}^{\text { sf}}({\bf r},t ) i_{{\text { c}}({\text { s}})}^{\text { sf}}({\bf r}^{\prime},t^{\prime})>\nonumber \\ * & & = < j_{{\text { c}}(\text { s})m}^{c}({\bf r}^{\prime } , t^{\prime } ) i_{{\text { c}}(\text { s})}^{\text { sf}}({\bf r}^{\prime},t^{\prime } ) > = 0 , \label{iis } \\ * & & < i_{\text { s}}^{\text { sf}}({\bf r},t ) i_{\text { s}}^{\text { sf}}({\bf r}^{\prime},t^{\prime } ) > = \delta_{lm } \delta({\bf r}-{\bf r}^{\prime})\delta(t - t^{\prime})\sigma_{\text { c } } \\ * & & \times \frac{1}{d_{\text { c}}\tau^{+}_{\text { sf } } } \sum _ { \alpha } \pi_{\alpha -\alpha}({\bf r } ) , \label{isis}\end{aligned}\ ] ] where @xmath66 . \label{pi}\ ] ] the diffusion equations ( [ delf]-[del2fip ] ) and eqs . ( [ jsjs]-[pi ] ) are a complete set of equations , which in principal can be solved for a multi - terminal mesoscopic diffusive conductor connected to an arbitrary number @xmath67 of metallic and/or ferromagnetic terminals held at constant potentials . the distribution function @xmath68 of the terminal @xmath69 biased at the voltage
@xmath70 determines the boundary conditions of the diffusive equations . in the case where the terminal @xmath71 is connected by a tunnel junction to the diffusive conductor at the point @xmath72 ,
the ferromagnetic character of the terminal can be modeled by a spin - dependent conductance @xmath73 .
the fluctuating spin @xmath1 current through the junction is given by @xmath74 .
$ ] as the boundary condition this current should match to the value calculated from the diffusive equations @xmath75 , where @xmath76 is the junction area . here
@xmath77 and @xmath78 are the spin @xmath1 symmetric part of the distribution function and current density respectively . from the solutions of the diffusion equations
the mean charge and spin currents and the correlations of the corresponding fluctuations can be obtained .
( [ delf]-[del2fip ] ) and ( [ jsjs]-[pi ] ) are valid for an arbitrary @xmath79 in the diffusive limit . in the following
we will consider the more realistic case of @xmath80 , where the effect of spin - flip scattering on the conductivity of the diffusive metal is neglected . in this case ,
@xmath81 and hence @xmath82 . for simplicity
, we also assume that the spin - flip scattering is isotropic , i. e. , @xmath83 does not depend on the directions @xmath29 , @xmath84 , which implies @xmath85 . in the next section we use the above developed formalism to calculate spin - polarized current correlations in a diffusive three - terminal system .
we consider the three - terminal spin valve system as shown in fig .
[ zbfig1 ] .
the system consists of a diffusive normal wire ( n ) of length @xmath86 connected by tunnel junctions to three ferromagnetic terminals f@xmath87 ( @xmath88 ) .
the terminal f@xmath89 is held at the voltage @xmath90 and the voltage at the terminals f@xmath91 is zero .
the tunnel junction @xmath92 connecting f@xmath87 to n has a spin dependent tunneling conductances @xmath93 , which equivalently can be characterized by a total conductance @xmath94 , and the polarization @xmath95 .
inside the wire we account for both , normal impurity and spin flip scattering .
the length @xmath86 is much larger than @xmath96 providing a diffusive motion of electrons .
the spin - flip length @xmath97 is assumed to be much larger than @xmath98 , but arbitrary as compared to @xmath86 .
we study the influence of the spin - flip scattering on shot noise of the current through the wire and cross - correlations between currents through the terminals f@xmath99 and f@xmath100 .
to start we write the solutions of eqs .
( [ del2fi ] ) and ( [ del2fip ] ) in terms of the charge ( spin ) potentials @xmath101 and @xmath102 , at the connecting points @xmath103 and @xmath104 inside the wire : @xmath105 where the charge and spin potential functions are defined as @xmath106}}{\sinh{\lambda } } , \label{pfs0 } \\ * & & \phi_{{\text s}l } ( x)=\frac{\sinh{(\lambda x / l)}}{\sinh{\lambda}}. \label{pfsl}\end{aligned}\ ] ] here the parameter @xmath107 is the dimensionless measure of the spin - flip scattering inside the n - wire .
an expression for the fluctuations of the current through the wire @xmath108 is obtained if we take the inner product of @xmath109 in eq .
( [ j ] ) with @xmath110 and integrate over the volume of the wire : @xmath111 where we also used eqs .
( [ dj ] ) and ( [ del2fi ] ) . in a similar way by volume integration of the products @xmath112 in eq .
( [ deljp ] ) , and using eqs .
( [ djp ] ) and ( [ del2fip ] ) we obtain @xmath113 , which yields the fluctuations of spin currents at @xmath103 and @xmath104 : @xmath114 note , that as a result of the spin - flip scattering the spin current and , hence , its fluctuations are not conserved through the wire . using eqs .
( [ delis1 ] ) , ( [ delics ] ) , ( [ pfs0 ] ) and ( [ pfsl ] ) a relation between the fluctuation of the spin currents at the two different points is obtained , @xmath115 \nonumber\\ * & & + \delta i^{c}_{\text s}(0 ) + \delta i^{c}_{\text s}(l ) , \label{delis0l}\end{aligned}\ ] ] where @xmath116 ( @xmath117 being the area of the wire ) is the conductance of the wire and @xmath118 . in the limit @xmath119 , the conservation of the spin current
is retained and @xmath120 , as is seen in eq .
( [ delis0l ] ) . in the boltzmann - langevin formalism , the fluctuation of spin @xmath1 currents through junction @xmath92 are written in terms of the intrinsic current fluctuations @xmath121 due to the random scattering of electrons from the tunnel barriers and the potential fluctuations @xmath122 at the junction points : @xmath123 using this relation the fluctuations of charge and spin currents through the terminals can be expressed in terms of the fluctuating spin and charge potentials at the connection points and the corresponding intrinsic currents fluctuations . denoting @xmath124 as the intrinsic fluctuations of the charge ( spin ) current through the tunnel junction @xmath92 , we obtain @xmath125 now we have to apply the currents conservation rules at the junction points . for spin - conserving tunnel barriers charge and spin currents fluctuations are conserved . at the pint @xmath104 the rules apply as equality of the expressions for @xmath108 given in eqs .
( [ deli1 ] ) and ( [ deli1n ] ) , and @xmath126 in eqs .
( [ delis1 ] ) and ( [ delis1n ] ) . at the point @xmath103 , they read @xmath127 which in combination with eqs .
( [ deli1]-[delis0l ] ) and ( [ deli1n]-[delisi ] ) lead to @xmath128 the solution of this system of equations gives us the fluctuations of the potentials in the connecting nodes which can be replaced into eqs .
( [ deli1n]-[delisi ] ) to obtain the fluctuations of the charge and spin currents through different terminals in terms of @xmath129 , @xmath130 , @xmath131 , and @xmath132 .
in particular , the fluctuations of the charge currents have the form @xmath133 where @xmath134 , @xmath135 , @xmath136 , @xmath137 , and @xmath138 are functions of @xmath139 , @xmath140 , and @xmath141 .
the currents correlations @xmath142 , are expressed in terms of the correlations of different fluctuating currents appearing in eqs .
( [ delif ] ) . to calculate the correlations of the currents @xmath131 and
@xmath132 we have to determine the mean distribution function @xmath143 .
this is achieved by solving eqs .
( [ delf ] ) , ( [ delfs ] ) and imposing the boundary conditions that @xmath144 in the terminal f@xmath145 held in equilibrium at the voltage @xmath146 is given by the fermi - dirac distribution function @xmath147 .
from the solutions of eqs .
( [ delf ] ) , ( [ delfs ] ) we obtain @xmath148 , \label{fms}\end{aligned}\ ] ] where @xmath149 are coefficients which have to be determined by the boundary conditions . integrating of ( [ fms ] ) over the energy @xmath28 the mean electro - chemical potential of spin @xmath1 electrons is obtained : @xmath150v , \label{fims}\end{aligned}\ ] ] which also could be obtained from the solutions of eqs .
( [ del2fi ] ) , ( [ del2fip ] ) . in the presence of the tunnel junctions
the boundary conditions are imposed by applying the mean currents conservation rules at the connection points . using eqs .
( [ barj ] ) , ( [ barjp ] ) , ( [ fims ] ) we obtain the mean charge and spin currents through the n wire : @xmath151 in terms of the charge and spin potentials at the connection points @xmath152 , @xmath153 , @xmath154 , @xmath155 , we have the following relations for the mean currents @xmath156 using eqs .
( [ imc]-[iim ] ) and the currents conservations relations at the point @xmath103 , @xmath157 , and @xmath158 , we find @xmath159\cosh{\lambda } \nonumber \\ * & & + [ \frac{g_n}{g_{23}}(1+\frac{g_n}{g_{1}})\lambda^2 + ( \frac{g_1}{g_{n}}+q_{1})q_{23}]s\nonumber \\ * & & -p_1p_{23}\frac{g_n}{g_{23 } } , \label{aa } \\ * & & \frac{1}{c}= [ 2\frac{g_n}{g_{23}}+(1+\frac{g_n}{g_{1}})q_{23 } + \frac{g_1}{g_{23 } } ( 1+\frac{g_n}{g_{23 } } ) q_{1 } ] \nonumber \\ * & & \times \cosh{\lambda } + \frac{g_n}{g_{23}}(1+\frac{g_n}{g_{1}}+\frac{g_n}{g_{23 } } ) \lambda^2s \nonumber \\ * & & + [ q_{1}+q_{23}(1+\frac{g_1}{g_{n}}q_{1})]s -2p_1p_{23 } , \label{ccc } \\ * & & \frac{b}{c}= -(q_{23}+\frac{g_1}{g_{23}}q_{1})\cosh{\lambda } \nonumber \\ * & & -[\frac{g_n}{g_{23}}\lambda^2+\frac{g_1}{g_{n } } q_{1}q_{23}]s , \label{bb } \\ * & & \frac{c}{c } = -\frac{g_1}{g_{23}}(\frac{g_n}{g_{1}}\lambda^2s + q_1\cosh{\lambda})p_{23}-q_{23}p_1 , \\ * & & \frac{d}{c}=\frac{g_1}{g_{23}}\lambda(\frac{g_n}{g_{1 } } \cosh{\lambda}+q_1 s)p_{23 } -\frac{g_n}{g_{23}}\lambda p_1 , \label{dd}\end{aligned}\ ] ] where @xmath160 , @xmath161,@xmath162 , @xmath163 , @xmath164 .
replacing @xmath165 given by eq .
( [ fms ] ) in eqs .
( [ pi ] ) we can calculate the correlations in eqs .
( [ jsjs]-[isis ] ) , which can be used to calculate all the possible correlations between @xmath131 and @xmath132 , given by eqs .
( [ delic ] ) and ( [ delics ] ) .
calculations lead to the following results @xmath166 \label{s},\\ * & & s_{\text s}(0)= \langle\delta i^{c}_{\text s}(0)\delta i^{c}_{\text s}(0)\rangle= 2g_n [ \frac{a}{t}(1-a ) \nonumber \\ * & & + \frac{b}{2}(1 - 2a ) + \frac{1}{2\lambda^2}(\frac{1}{s^2}-\frac{1}{t})b^2 \nonumber \\ * & & + \frac{c^2-d^2}{2s^2 } -\frac{1}{s}(cd\lambda s+\frac{c^2+d^2}{2}\cosh{\lambda } ) ] , \\ * & & s_{\text s}(l)=\langle\delta i^{c}_{\text s}(l)\delta i^{c}_{\text s}(l)\rangle= 2g_n [ \frac{a}{t}(1-a ) \nonumber \\ * & & + ( \frac{1}{t}-\frac{1}{2})b(1 - 2a ) + ( 1-\frac{1}{t}+\frac{1/s^2 - 1/t}{2\lambda^2})b^2 \nonumber \\ * & & + \frac{c^2-d^2}{2s^2 } -\frac{1}{s}(cd\lambda s+\frac{c^2+d^2}{2}\cosh{\lambda } ) ] , \\ * & & s_{\text s}(0l)=\langle\delta i^{c}_{\text s}(0)\delta i^{c}_{\text s}(l)\rangle=-2g_n [ \frac{a}{t}(1-a ) \nonumber\\ * & & + \frac{b}{2s}(1 - 2a ) + ( \frac{1/t-1}{2\lambda^2s}-\frac{1}{2s})b^2 + \frac{c^2-d^2}{2st } \nonumber\\ * & & -\frac{1}{t}(cd\lambda s+\frac{c^2+d^2}{2}\cosh{\lambda } ) ] , \\ * & & s(0)= \langle\delta i_{\text { c}}^{c}\delta i^{c}_{\text s}(0)\rangle= g_n[(1 - 2a-2b)d+(1 - 2a \nonumber\\ * & & -b)(\lambda c + \frac{\cosh{\lambda}}{s}d ) + \frac{1}{\lambda}bc+ ( d -\frac{\cosh{\lambda}}{\lambda s } c)b],\\ * & & s(l)=\langle\delta i_{\text { c}}^{c}\delta i^{c}_{\text s}(l)\rangle= -g_n[(1 - 2a - b ) ( \lambda sc \nonumber\\ * & & + \frac{1+s\cosh{\lambda}}{s}d ) -(\frac{\cosh{\lambda}}{s}-1 ) ( sd+\frac{\cosh{\lambda}}{\lambda}c)b ] .
\label{sl}\end{aligned}\ ] ] in writing these equations , we have for simplicity dropped the time dependence of the correlators and implicitly assumed , that the correlators are symmetrized ( which leads to a factor of 2 ) .
since we will be solely interested in the zero - frequency noise correlations , we also dropped the time integration . to obtain the noise in the terminals we have to specify the correlators of the intrinsic fluctuations at the tunnel junctions . assuming the tunnel junctions to be spin conserving , we obtain for the correlations of the intrinsic fluctuation of charge and spin currents @xmath167 where @xmath168 is the mean current of spin @xmath1 electrons . using the results ( [ s]-[didsj ] ) and eqs . ( [ deli1n]-[delisi ] ) with the solutions of eqs .
( [ sys1]-[sys4 ] ) the correlation of the currents of the form @xmath169 is obtained . in terms of the coefficients introduced in ( [ delif ] )
it has the form @xmath170 + c_{i}c_{j}s_{\text { c}}+c_{i0}c_{j0}s_{\text s}(0 ) \nonumber \\ * & & + c_{il}c_{jl } s_{\text s}(l ) + ( c_{i}c_{j0}+c_{i0}c_{j})s(0 ) + ( c_{i}c_{jl } \nonumber \\ * & & + c_{il}c_{j})s(l ) + ( c_{i0}c_{jl}+c_{il}c_{j0})s_{\text s}(0l ) .
\label{sijf}\end{aligned}\ ] ] in this way we obtain the fano factor @xmath171 and the cross correlations @xmath172 measured between the currents through f@xmath173 , f@xmath174 . in the general case for arbitrary @xmath175 , @xmath140 and
@xmath141 the expressions of @xmath176 and @xmath172 are too lengthy to be given here and in the next section we will present analytical expressions of @xmath176 and @xmath172 in some important limits only .
for simplicity in the following we will consider the junctions to have the same tunneling conductances @xmath177 , @xmath178 . if the amplitude of the polarizations @xmath179 are also the same we distinguish the following different configurations .
the two terminals f@xmath173 and f@xmath174 have either parallel or anti - parallel polarizations .
we take the signs of @xmath180 and @xmath181 to be positive in the parallel configuration . in this case
there are two different configurations depending on whether @xmath182 is positive ( parallel to @xmath180 , @xmath181 ) or negative ( anti - parallel to @xmath180 , @xmath181 ) . on the other hand for the antiparallel configuration of f@xmath173 and f@xmath174 the sign of @xmath182 is not essential and the two cases of @xmath182 and @xmath183 are equivalent .
thus there are three independent configurations of the polarizations corresponding to @xmath184 , @xmath185 and @xmath186 .
we denote these configurations by @xmath187 , @xmath188 , and @xmath189 , respectively .
we analyze the dependence of @xmath176 and @xmath190 on the spin flip scattering intensity @xmath141 for different configurations and amplitude of the polarizations .
we show how the spin flip scattering affects both @xmath176 and @xmath172 and produces a strong dependence on the magnetic configuration of the f terminals .
let us start with analyzing of the shot noise .
[ zbfig2 ] illustrates the typical behaviour of the shot noise with respect to the spin flip scattering intensity and configuration of the polarizations . here
@xmath176 versus @xmath141 is plotted for a given magnitude of the polarization @xmath191 in the terminals for the different magnetization configurations .
different columns i - iii belong to different values of the tunnel contact conductances @xmath192 .
clearly , for a finite @xmath141 the fano factor @xmath176 is changes drastically with the relative orientation of the polarizations . for strong spin flip scattering ,
@xmath193 the fano factor reduces to @xmath194 independent of the polarization of the terminals .
( [ fn ] ) is the result for a all - normal metal three terminal system ( @xmath195 ) @xcite which reduces to @xmath196 and @xmath197 in the limits of small and large @xmath192 , respectively .
this is expected since the strong spin flip intensity destroys the polarization of the injected electrons . at finite @xmath141
the curves belonging to different configurations differ from each other and the largest difference occurs as @xmath141 approaches zero . in this limit , using eqs .
( [ sijf ] ) and ( [ i1 m ] ) we obtain the following results for the different configurations @xmath198 \nonumber \\ * & & + \frac{16g_{+}^3}{3x_{+}^4g^2}\{q^3(qg+\frac{21}{2})g^5 + \frac{3}{2}q[q(22 + 7q)g+36+\frac{51}{2}q]g^3 \nonumber \\ * & & -\frac{81}{32}q[(6q-32)g^2 + 11g+6 ] + \frac{243}{8}(\frac{4}{3}g^2 + 3g+1 ) \ } , \label{frpp}\end{aligned}\ ] ] @xmath199 + \frac{8g_{-}^3}{qx_{-}^4g^2 } [ \frac{2}{3}q^5g^6 \nonumber \\ * & & + 7q^4g^5 + q^3(3q+26)g^4 + \frac{3}{2}q^2(9q+32)g^3 \nonumber \\ * & & + \frac{1}{3}q(-\frac{83}{8}q^2 + 86q+137)g^2 + 9(-\frac{17}{16}q^2+\frac{15}{4}q+2)g \nonumber \\ * & & + \frac{q^2}{8}-7q+17 ] , \label{frpm}\end{aligned}\ ] ] @xmath200 + \frac{8g_{0}^3}{x_{0}^4g^2 } [ \frac{2}{3}q^4g^6+\frac{7}{3}q^3(q+2)g^5 + q^2(3q^2 \nonumber \\ * & & + 18q+8)g^4 + q(\frac{11}{6}q^3 + 25q^2 + 24q+\frac{32}{3})g^3+\frac{1}{3}(\frac{13q^4}{8 } \nonumber \\ * & & + 55q^3 + 44q^2 + 96q+16)g^2 + ( \frac{q^4}{16}+\frac{57}{8}q^3+q^2 \nonumber \\ * & & + \frac{57q}{4}+16)g + \frac{9}{8}q^3-q^2 + 2q+8]\ , .
\label{frpz}\end{aligned}\ ] ] here we defined @xmath201 , @xmath202 , and @xmath203 .
the total conductances of the system normalized by @xmath204 for the three configurations in the limit @xmath119 are given by @xmath205 in fig .
[ zbfig3 ] we show the polarization dependence of the fano factor in the limit of small spin - flip scattering intensity , @xmath206 for the different magnetic configurations of the terminals . at @xmath207
the fano factor for different conductances @xmath192 takes the normal state value @xmath208 , see eq .
( [ fn ] ) , independent of the polarizations configuration . for finite polarizations
@xmath176 of different configurations differ from each other and the normal state value . as @xmath191 increases
, the fano factor of the configuration @xmath209 deviates substantially from those of the other two configurations and reaches the full poissonian value @xmath210 as @xmath191 approaches @xmath210 .
this is independent of the tunnel conductances @xmath192 .
thus for perfectly polarized terminals the fano factor takes the value @xmath210 in the limit of small spin - flip scattering rate . to understand this effect
we note that in the limit @xmath211 , the system constitutes an ideal three terminal spin valve due to the antiparallel configuration of the polarizations at its two ends . in the absence of the spin flip scattering there in no current through the n - wire since for the up - spin electrons provided by the terminals f@xmath173 and f@xmath174 , there is no empty state in the terminal f@xmath212 in the energy range @xmath213 .
for very small but finite @xmath141 only those of electrons which undergo spin - flip scattering once can carry a small amount of current .
these spin - flipped electrons are almost uncorrelated and pass through the normal wire independently giving rise to full poissonian shot noise .
similar effects have been found before for two @xcite and four @xcite terminal spin - valve systems . for arbitrary @xmath192 and @xmath191
, @xmath176 has a complicated dependence on @xmath141 and the corresponding expressions are to lengthy to be presented here .
simpler expressions are obtained for perfectly polarized junctions .
setting @xmath214 in eqs .
( [ sijf ] ) and ( [ i1 m ] ) yield for the fano factors of the different configurations @xmath215 , \label{flpp}\end{aligned}\ ] ] @xmath216 , \label{flpm}\end{aligned}\ ] ] @xmath217 -\frac{g_{0}}{x^2}[4g^2 + 2g-\lambda^2 + \frac{8g_{0}}{g } ( g^3(\frac{1}{\lambda^2}-1)-2g^2 \nonumber \\ * & & + g(\frac{1}{4}\lambda^2 - 1)+\frac{3}{8}\lambda^2 ) + \frac{4g^2_{0}}{g^2}(g^4(1-\frac{2}{\lambda^2 } ) + g^3(\frac{7}{2}-\frac{2}{\lambda^2 } ) \nonumber \\ * & & + \frac{g^2}{4}(17-\lambda^2 ) + g(1-\frac{3}{4}\lambda^2 ) -\frac{9}{16}\lambda^2)]\ , .
\label{flpz}\end{aligned}\ ] ] here we defined @xmath218 and the dimensionless total conductances are now given by @xmath219 the strong dependence of @xmath176 on @xmath141 , and the magnetic configuration is also shown in fig .
[ zbfig4 ] , where @xmath176 versus @xmath141 is plotted for different polarization @xmath182 of the terminal f@xmath212 , and fixed @xmath220 . as in fig .
[ zbfig2 ] different columns i - iii present results for different values of @xmath192 . in each column @xmath182 varies from top to bottom in the interval @xmath221 to @xmath210 . in the limit of large @xmath141
, the fano factor tends to the the normal state value ( [ fn ] ) determined by the conductance @xmath192 only . the deviations from this normal state value at finite @xmath141 depend on @xmath182 and @xmath192
. for small values of @xmath192 ( column iii ) , with decreasing @xmath141 from large values @xmath176 first decreases below the normal state value @xmath208 and then starts to increase again .
thus , there is a minimum of the fano factor @xmath176 occurring at a value of @xmath141 which continuously decreases from @xmath222 to @xmath223 as @xmath182 increases from @xmath221 to @xmath210 . decreasing @xmath141 further
, @xmath176 increases to a maximum value at @xmath223 .
the maximum of @xmath176 at @xmath223 continuously decreases with increasing @xmath182 and becomes a minimum when @xmath224 . for antiparallel fully polarized terminals , i. e. @xmath225 ,
decreasing @xmath141 leads to the strongest variation of @xmath176 , see eq .
( [ flpm ] ) and @xmath176 reaches the poissonian value @xmath210 as @xmath141 approaches zero . comparing plots for @xmath225 of columns (
i - iii ) , we see that this effect is independent of the contact conductances @xmath192 , which is in agreement with the discussion in connection with fig .
[ zbfig3 ] .
increasing @xmath182 from @xmath221 decreases the effect of spin flip process in the current and the noise , and , hence , leads to a reduction of the shot noise at @xmath226 .
the maximum value of @xmath176 thus drops below the poissonian value . for large values of @xmath192 ( column i )
the maximum of @xmath176 is shifted from zero to a finite @xmath227 as @xmath182 increases from @xmath221 to @xmath210 , while for small @xmath192 the maximum @xmath176 always occurs at @xmath223 as described above . for @xmath228 ( column ii )
the situation is in between the large and small @xmath192 behavior , increasing @xmath141 leads first to a maximum of the fano factor followed by a minimum .
comparing the first and the second row of fig .
[ zbfig4 ] , we observe the effect of spin - flip scattering is more pronounced for negative @xmath182 than for positive @xmath182 .
this can be understood , because for parallel magnetization directions the non - equilibrium spin accumulation in the ferromagnetic wire is smaller .
the spin - flip scattering decreases the spin - accumulation and , hence , has the largest effect for anti - parallel magnetizations .
let us now discuss the effect of spin flip scattering on the cross correlations measured between the currents through the terminals f@xmath173 and f@xmath174 .
we distinguish two different cases of parallel ( @xmath229 ) and antiparallel ( @xmath230 ) magnetizations of f@xmath173 and f@xmath174 . for the parallel case and when @xmath231 the two terminals f@xmath173 , f@xmath174 are completely equivalent and hence @xmath232 .
this can be used with eq .
( [ sumdeli ] ) to obtain that in this case the fano factor and the cross - correlation factor @xmath233 are related as ( see also ref .
@xcite ) @xmath234 thus @xmath235 has the same qualitative dependence on @xmath141 as @xmath176 . since @xmath236
the cross - correlations are always negative as expected @xcite .
the fano factor for the perfectly polarized parallel case is presented in fig .
[ zbfig4 ] and the cross - correlations for this case can be deduced from these plots using eq .
( [ ff23 ] )
. we will now analyze the cross - correlations @xmath235 for @xmath220 and different values of @xmath182 . from eqs .
( [ sijf ] ) and ( [ i1 m ] ) one can see that in the limit of large spin - flip scattering @xmath237 , the cross - correlations reduces to its all - normal system value @xmath238 which is independent of the polarizations .
alternatively , this result could have been obtained using eqs .
( [ fn ] ) and ( [ ff23 ] ) .
on lowering @xmath141 the amplitude of the cross - correlations @xmath239 decreases ( large @xmath192 , column i ) or increases ( small @xmath192 , column iii ) with respect to the normal value . for @xmath225
, @xmath235 vanishes in the limit @xmath240 , irrespective of the the value of the contacts conductance @xmath192 .
this case corresponds to the vanishing of the total mean current @xmath241 . from this observation
we conclude that in the expression of @xmath235 , the cross - correlation @xmath172 vanishes faster than the mean current @xmath241 , as @xmath119 .
thus , for @xmath225 @xmath239 has a minimum at @xmath223 for both cases of small and large @xmath192 .
increasing @xmath182 from @xmath221 , the minimum is shifted to a finite @xmath227 for large @xmath192 , it stays always at @xmath223 for small @xmath192 . for small @xmath192
, @xmath239 has also a maximum at @xmath227 which corresponds to the minimum of the fano factor . for @xmath242 ( column ii )
the behavior of @xmath235 is between that for small and large @xmath192 .
comparing of the plots in top ( @xmath243 ) and down ( @xmath244 ) rows in fig .
[ zbfig4 ] shows that the most strong variation of the cross - correlation happens when the magnetization of f@xmath212 is anti - parallel to those of f@xmath91 . for the antiparallel case
@xmath230 the effect of spin - flip scattering is more interesting , since it contains the correlations between currents of opposite spin directions produced by the spin - flip scattering . in fig .
[ zbfig5 ] we plot @xmath235 versus @xmath141 for different values of the magnitude @xmath245 and @xmath192 .
we take @xmath224 which corresponds to a maximum spin accumulation in the n - wire due to the terminal f@xmath212 . for @xmath214
the cross - correlations are solely due to the spin flip - scattering . in this case
@xmath235 vanishes in the limit of @xmath119 . at finite @xmath141
the spin - flip scattering induces correlations between the electrons with opposite spins and hence @xmath235 becomes finite . with increasing @xmath141 the magnitude of @xmath235 increases and approaches the all - normal system value of @xmath195 when @xmath246 .
for @xmath247 the value of @xmath239 for vanishing @xmath141 depends on the values of @xmath191 and @xmath192 as @xmath248 decreasing @xmath191 from @xmath210 to @xmath249 , @xmath239 increases from zero to a maximum value .
the maximum absolute value is equal to the normal value for large @xmath192 ( column i ) , while it is larger than the normal value for small @xmath192 ( column iii ) .
in conclusion , we have investigated the influence of spin polarization and spin - flip scattering on current fluctuations in a three - terminal spin - valve system . based on a spin - dependent boltzmann - langevin formalism , which accounts for spin - flip scattering in addition to the usual scattering at impurities and tunnel junctions , we have developed a semiclassical theory of current fluctuations in diffusive spin - valves .
this theory allows the calculations of spin - polarized mean currents and correlations of the corresponding fluctuations in multi - terminal systems of diffusive wires and tunnel contacts .
we have applied this formalism to a three - terminal system consisting of a diffusive normal wire connected at the ends to one and two ferromagnetic terminals , respectively .
we have found a strong deviation of the current correlations from the all - normal system values .
the shot noise of the total current through the system and the cross - correlations between currents of two different terminals depend strongly on the spin - flip scattering rate and the spin polarization and change drastically with reversing the polarizations in one or more of the terminals .
the strongest variation of the shot noise occurs , when the polarizations of the two terminals connected to one end of the normal wire are antiparallel with respect to the terminal on the other end . for small spin - flip scattering intensity
, the fano factor deviates substantially from the normal value and can reach the full poissonian value for perfectly polarized terminals even if the tunnel contact resistances are negligible .
we have further demonstrated the effect of spin - polarization and spin - flip scattering on the cross - correlations measured between currents of two adjacent terminals in two cases where the terminals have parallel and antiparallel polarizations . for antiparallel orientations of the contact polarizations
, the noise allows a direct determination of the spin - flip scattering processes in the normal wire .
the study of noise and cross - correlations therefore allows to extract information on the spin - flip scattering strength , which is of importance for spintronics applications .
we acknowledge discussions with c. bruder , t. kontos and h. schomerus .
m. z. thanks c. bruder and his group members for hospitality at the university of basel where this work was initiated .
w. b. was financially supported by the rtn spintronics , by the swiss nsf and the nccr nanoscience .
j. c. egues , g. burkard , and d. loss , phys .
lett . * 89 * , 176401 ( 2002 ) ; h. -a .
engel and d. loss , phys .
b * 68 * , 195321 ( 2002 ) ; d. loss and e. v. sukhorukov , phys . rev
. lett . * 64 * , 1035 ( 2000 ) ; g. burkard _
et al . , _ phys .
b * 61 * , r16303 ( 2000 ) . | we study fluctuations of spin - polarized currents in a three - terminal spin - valve system consisting of a diffusive normal metal wire connected by tunnel junctions to three ferromagnetic terminals . based on a spin - dependent boltzmann - langevin equation
, we develop a semiclassical theory of charge and spin currents and the correlations of the currents fluctuations . in the three terminal system , we show that current fluctuations are strongly affected by the spin - flip scattering in the normal metal and the spin polarizations of the terminals , which may point in different directions .
we analyze the dependence of the shot noise and the cross - correlations on the spin - flip scattering rate in the full range of the spin polarizations and for different magnetic configurations .
our result demonstrate that noise measurements in multi - terminal devices allow to determine the spin - flip scattering rate by changing the polarizations of ferromagnetic terminals . |
population synthesis models and stellar evolutionary isochrones are the tools which give age estimates for galaxies and star clusters , thus providing a constraint on the age of the universe .
the models , however , are dependent upon the transformations from effective temperature ( @xmath12 ) , surface gravity , and abundance to observed colors and magnitudes . in the case of metal - poor giants ,
these transformations remain inconclusive , despite considerable efforts in the past . in 1966 , johnson produced a remarkable set of tables that gives color - color sequences in @xmath13 passbands for local dwarfs , giants , and supergiants ( of nearly solar metallicity , since metal - poor stars are rare in the disk ) , based on his and his collaborators extensive photometry efforts .
he calculated the absolute flux in each passband to obtain bolometric corrections and effective temperatures . for giants ,
this temperature scale has been subsequently revised ( dyck et al . 1996 ; dibenedetto 1993 ; ridgway et al . 1980 )
but the color - color sequences are still used in many contexts , including assigning colors to theoretical isochrones and computing colors for integrated light population models .
since 1966 , new passbands have become standard for broadband photometry .
these are the cousins ( 1980a , b ) @xmath2 and @xmath3 filters at roughly 0.68@xmath14 m and 0.79@xmath14 m , and the cit ( elias et al .
1982 ; `` cit '' stands for california institute of technology ) @xmath15 filter at 1.6@xmath14 m . with these new filters ,
it is clear that more comprehensive color - color tables are necessary .
one powerful way to generate a complete color - color table is to compute theoretical line - blanketed stellar spectra and convolve them with filter response functions to synthesize colors ( e.g. buser & kurucz 1979 ; bell & gustafsson 1978 , 1989 ; kurucz 1992 ) .
the only major detriment to this approach is that , owing to the complexity of the problems of opacity and convection , the theoretical fluxes match imperfectly with real stellar fluxes .
systematic color drifts can be seen when theoretical results are compared to an empirical color - color table ( cf .
worthey 1994 ) .
empirical tables are therefore of primary interest , for use by themselves or for use as a check of the theoretical color calibrations .
the most complete empirical calibration attempted to date was done by green ( 1988 ) for use in the revised yale isochrones ( green et al .
1987 ) . for green s work ,
solar neighborhood @xmath0 photometry was assembled , and a temperature scale was attached via the @xmath16 color .
the extension to different metallicities was accomplished by using theoretical color results .
the green calibration is imperfect ; while problems with fitting isochrones ( corbally 1996 ) may be due to the temperature of the evolutionary tracks rather than the color calibration , the green colors differ from other literature calibrations ( worthey 1994 ) .
a problem with bolometric corrections ( tiede , frogel , & terndrup 1995 ; mould 1992 ) has also been noticed , but the color calibration has not yet been redone . as part of an effort to redo this color calibration ,
a literature search conducted by worthey and fisher ( 1996 ) discovered a paucity of observations in the @xmath2 and @xmath3 passbands for metal - poor giants .
new observations at the michigan - dartmouth - mit ( mdm ) observatory were proposed to help fill this @xmath17 gap and to provide empirical relations between the various colors for different metallicities .
we selected globular clusters of known metallicity , with previous @xmath18 ( and sometimes @xmath19 ) photometry , and specifically stars observed in @xmath1 by frogel et al .
( 1983 ) and cohen et al .
( 1978 ) . in order to extend the metallicity range of our data to higher [ fe / h ] values , ngc 6791 was added to the list .
unreduced @xmath1 photometry exists and , we expect , will soon be available to complete the color sequence for this cluster .
the approach in this paper is to concentrate _ only _ on the frogel et al .
( 1983 ) and cohen et al .
( 1978 ) stars in the globular clusters and on ngc 6791 giants previously studied by garnavich et al .
( 1994 ) . in this way
, we reduce a daunting array of data to a manageable size while retaining full ability to construct @xmath20 color sequences from the results .
we describe the observations and data reduction in the next section . in section 3.1
, we give our photometry results and , in section 3.2 , compare them with data found in the literature .
section 3.3 contains a discussion of the empirical color - color relations for the metal - poor giants .
section 4 contains concluding remarks .
the observations were obtained during the nights of april 11 , 12 , and 13 , 1997 , at the mdm observatory mcgraw - hill 1.3 m telescope . a schott glass @xmath0 filter set fabricated to match the johnson - cousins system was used with a uv - coated tek 1024 ccd .
landolt ( 1992 ) standard stars were regularly observed along with fields that were chosen to overlap previous frogel et al .
( 1983 ) and cohen et al .
( 1978 ) @xmath1 target stars in globular clusters , and garnavich et al .
( 1994 ) red giants in open cluster ngc 6791 .
the initial processing of the raw ccd images was done with the routines in the iraf ccdproc package . for each of the three nights
, 10 biases were combined for the bias subtraction .
the flats were produced by combining between 3 and 6 twilight flat images per night per filter .
the processed data were reduced using dophot ( schechter et al . 1993 ) . because the point spread function ( psf ) of the stars varied with position on the ccd , we adjusted the values of some of the input parameters of dophot to obtain accurate photometry results .
in particular , we used the variable psf feature of dophot and , in some cases , lowered dophot s sensitivity with respect to detecting nearby neighbors of stars .
the latter was done in order to avoid false multiple detections of individual , slightly elongated stellar images .
dophot s photometry output contains a list of aperture corrections for stars with small photometric errors and without nearby neighbors . in order to apply the correct aperture correction for each of our target stars , we selected from this list the stars far away from the cluster , so as to avoid aperture corrections influenced by the higher sky value in the immediate vicinity of the cluster . with the fairly large field of view of the ccd
, this method left us with between roughly 10 and 240 isolated stars with high s / n ratios for the various images . using these stars , the dependence ( if any ) of the aperture correction upon position on the ccd was determined , using a linear fit in @xmath21 and @xmath22 .
the f - test ( cf .
press et al .
1992 ) was used to determine if fits which included @xmath21- and @xmath22-terms were statistically different from a constant value for the aperture correction applied over the whole chip . during our three photometric nights
, we observed a total of 10 landolt ( 1992 ) fields , at airmass values ranging from @xmath23 to @xmath24 . using the iraf photcal package , we applied standard star solutions for all three nights of the form @xmath25 @xmath26 @xmath27 @xmath28 @xmath29 where the @xmath30 , @xmath31 , and @xmath32 are the fitted constants , @xmath33 is the airmass of the exposure taken with the respective filter , the lowercase magnitudes are instrumental , and the uppercase ones are the final calibrated magnitudes .
the rms errors for the fits for the three nights are given in table 1 , and the residuals between the calculated magnitudes and the ones given by landolt ( 1992 ) are plotted in fig .
[ resids ] .
roughly two - thirds of the program stars were observed only on one night ( usually 3 ccd frames per filter , 2 frames for the @xmath19 filter ) , but about one - third of the stars were observed on two nights .
for all the stars , the @xmath34 magnitudes and colors were averaged arithmetically .
the photometric scatter between nights 2 and 3 , based on 8 stars in ngc 6791 , is around 0.01 mag for @xmath35 and about 0.015 mag for @xmath36 colors . with only 8 stars ,
the estimated error of our photometry for these nights is the photometric scatter divided by @xmath37 , which is around 0.004 mag and 0.005 mag for @xmath35 and @xmath36 colors , respectively .
these values are consistent with the rms of the standard star solutions ( table 1 ) . however , for 7 globular cluster stars in common between nights 1 and 2 , the colors matched to a photometric scatter of 0.03 mag for all colors , significantly larger than what the standard star solutions imply .
the @xmath5 colors for these stars were also systematically different by 0.05 mag . for these reasons , night
1 data were dropped whenever possible .
only two stars were observed in night 1 alone , and these are marked in table 2 .
reduced magnitudes and errors for our program giants ( luminosity class 3 ) are given in table 2 .
the `` err1 '' column gives a magnitude error estimate based on the number of observations and the scatter between individual measurements .
the error is quantized in 0.005-mag steps .
colors involving the @xmath19 filter should be assumed to have 50% larger errors than the `` err1 '' entry would suggest .
the `` err2 '' column contains an entry if one or more filters had few observations or if there was extra scatter between measurements .
for instance , an entry of `` .03ui '' means that any color involving @xmath19 or @xmath3 should be considered to have an error of 0.03 mag .
table 3 contains the dereddened ( via cardelli et al .
1989 ) photometry results .
star identifications are given along with [ fe / h ] and @xmath38 from harris ( 1996 ) .
infrared photometry is from cohen et al .
( 1978 ) and frogel et al .
their raw photometry results were used , also dereddened using cardelli et al .
this allows full @xmath20 color sequences to be constructed .
we conducted a literature search to compare our photometry to previous studies whenever possible . for @xmath4
, we found 20 globular cluster stars in common with pre-1975 photometry ( no more recent data were discovered ) .
the median @xmath39 is @xmath40 .
by contrast , three ngc 6791 stars in common with harris & canterna ( 1981 ) compare with @xmath41 .
it thus seemed that @xmath42 increased with increasing [ fe / h ] values , and we considered various filter defects that could generate this metallicity trend .
however , the behavior is counter to that expected from a red leak , and the uv coating on the ccd should make the overall @xmath19 filter response fairly similar to the original , so we believe that we have approximated the landolt standard system very well , as implied by the standard star solutions .
the other colors did not display such a trend .
literature @xmath5 values were found for 42 program stars ( cathey ( 1974 ) ; arp ( 1955 ) ; arp ( 1962 ) ; kaluzny ( 1993 , private communication ) ; cudworth ( 1995 , private communication ) ; harris & canterna ( 1981 ) ; kinman ( 1965 ) ; kaluzny & rucinski ( 1995 ) ) , and the overall average @xmath43 . concentrating on the most recent data , the three ngc 6791 stars in common with harris & canterna ( 1981 ) give @xmath44 , and the three stars in common with kaluzny & rucinski ( 1995 ) give @xmath45 .
@xmath46 photometry of 13 ngc 6791 stars in common with garnavich et al .
( 1994 ) yields an average @xmath47 mag , but we are less concerned with this offset because of the relatively low accuracy of 0.05 mag claimed by these authors .
the major goal of this study is to explicitly reveal the metallicity dependence of broad - band colors .
for instance , @xmath48 has long been used to estimate the metallicity of faint stars ( e.g. van den bergh 1962 ) .
figures [ ubvk ] , [ bvvk ] , [ vrvk ] , [ vivk ] , [ jkvk ] , and [ hkvk ] show the various dereddened colors versus @xmath49 for giants of widely differing metal abundances , including the globular cluster giants from this work .
@xmath49 is chosen because it is an excellent temperature indicator for gkm giants , with a large color range compared to its observational uncertainty .
in addition , the best model fluxes show no metallicity sensitivity .
that is , one temperature - @xmath49 conversion is applicable to stars of all abundances , at least in the 4000k to 5000k range ( e.g. bessell et al .
1989 , 1991 ; kurucz 1992 ; bell & gustafsson 1989 ) .
a fit to the effective temperature @xmath49 relation of ridgway et al .
( 1980 ) is @xmath50 where @xmath51 is @xmath12 in degrees kelvin .
the range is valid over @xmath52 , or @xmath53 k. this approximate formula is given as a convenience for readers , but they should be aware that the cubic curve can deviate from the ridgway et al .
calibration by as much as about 0.08 mag in @xmath54 , which corresponds to about 60 k in effective temperature .
serious users may want to refer to the original temperature calibration table .
our photometry plus the worthey & fisher ( 1996 ) literature photometry , all dereddened , produced relations summarized here as six formulae giving colors as a function of @xmath49 and [ fe / h ] .
much of the literature photometry comes from the machine readable version of morel & magnenat ( 1978 ) and is on the johnson system .
the @xmath17 data were transformed using the relations given by m. s. bessell ( 1979 ) .
[ fe / h ] values were obtained from mcwilliam ( 1990 ) and cayrel de strobel et al .
the fits below are non - linear least - squares regressions as described by press et al .
some data were rejected in a 2.5-@xmath55 rejection loop , but never more than a few percent were discarded .
most of the literature data are photographic with quoted error of @xmath56 , whereas the data of this work have errors more on the order of @xmath57 .
consequently , we included a weighting factor of @xmath58 to our data .
this value is derived from the conservative estimate that our errors are up to 60% of the literature errors .
theoretical colors from worthey ( 1994 ) were included at low statistical weight ( @xmath59 of the literature datapoints ) to provide guidance in regions with no stars .
these 48 `` stars '' are included in the total n ( number of datapoints ) below , except for the @xmath60 equation ( theory data produce a large range in v - i for a given v - k which is not reflected in observational data ) .
different combinations of coefficients were compared using the f - test and only statistically significant terms were retained .
the fits are good _ only _ in the regime @xmath61 , but cover the range of galactic [ fe / h ] values for giants . note that , although we omit stars with @xmath62 } < 0 $ ] in the plots for the sake of clarity , all metallicities are included in the derivation of the fits .
@xmath63}^{2 } \nonumber\\ & & + \ 0.3752 \ ( v - k)_{0 }
\ { \rm [ fe / h ] } \ - \ 0.0868 \ ( v - k)_{0}^{2 } \ { \rm [ fe / h ] } ; \\ & & ( n = 428 , rms = 0.082 ) \nonumber\\ & & \nonumber\\ ( b - v)_{0 } & = & \ 0.1116 \ + \ 0.4013 \ ( v - k)_{0 } \ + \ 0.3509 \ { \rm [ fe / h ] } \nonumber\\ & & - \ 0.0823 \ ( v - k)_{0 } \
{ \rm [ fe / h ] } + \ 0.01298 \ ( v - k)_{0 } \
{ \rm [ fe / h]}^{2};\\ & & ( n = 625 , rms = 0.062 ) \nonumber\\ & & \nonumber\\ ( v - r)_{0 } & = & \ -0.0040 \ + \ 0.2271 \ ( v - k)_{0 } \ + \ 0.0100 \ { \rm [ fe / h]};\\ & & ( n = 301 , rms = 0.021 ) \nonumber\\ & & \nonumber\\ ( v - i)_{0 } & = & \ 0.1595 \ + \ 0.3387 \ ( v - k)_{0 } \ +
\ 0.004291 \ ( v - k)_{0}^{3 } \nonumber\\ & & + 0.004255 \ ( v - k)_{0}^{2 } \
{ \rm [ fe / h ] } \ - \ 0.005596 \ { \rm [ fe / h]^{3}};\\ & & ( n = 267 , rms = 0.026 ) \nonumber\\ & & \nonumber\\ ( j - k)_{0 } & = & \ 0.0231 \ + \ 0.2613 \ ( v - k)_{0 } \
+ \ 0.009869 \ ( v - k)_{0 } \ { \rm [ fe / h ] } ; \\ & & ( n = 642 , rms = 0.029)\nonumber\\ & & \nonumber\\ ( h - k)_{0 } & = & \ -0.0190 \ + \ 0.04402 \ ( v - k)_{0 } ; \\ & & ( n = 446 , rms = 0.020)\nonumber\end{aligned}\ ] ] the @xmath64 fit contains an [ fe / h ] term that is statistically significant , but only at the @xmath65 level .
the real behavior of @xmath64 is probably more subtle than the simple fit can reproduce .
the @xmath66 color equation contains a very significant @xmath67}$ ] term .
this indicates a metallicity dependence of the @xmath66 color , which is usually assumed to be a pure temperature indicator .
fitting the @xmath60 data produced a somewhat surprising result . at first glance
, one might assume that the data may be well represented by a metallicity - independent , linear fit in @xmath49 ( see fig .
[ vivk ] ) .
we find , however , a more complex behavior with respect to both metallicity and @xmath49 .
the functional dependence of @xmath60 upon [ fe / h ] is weak , but significant .
there is a possibility that an error in the assumed @xmath38 values of the various clusters could affect the fitting results .
we investigated the effect an @xmath38 error of @xmath680.02 would have on datapoints but found that the resulting shifts in color are small compared to the spread due to different metallicities . in order to demonstrate the magnitude and direction of the shift of the datapoints in the color - color diagrams due to a reddening error
, we provide the reddening vectors for @xmath69 ( see figures [ ubvk ] through [ hkvk ] ) .
this value is , of course , far beyond a reasonable error in @xmath38 , but lower values produced vectors which were too small to be visible in the figures .
the vectors were created using the reddening curve by cardelli et al .
( 1989 ) .
our photometry is good enough to show separation of @xmath48 sequences for globular clusters of differing metallicities in figure [ ubvk ] .
m92 stars ( at [ fe / h]@xmath70 ) values are from harris ( 1996 ) . ] lie to numerically smaller ( i.e. , bluer ) @xmath48 from the other globular clusters .
there is also a hint that m3 ( [ fe / h]@xmath71 ) and m13 stars ( [ fe / h]@xmath72 ) lie blueward of m5 ( [ fe / h]@xmath73 ) .
this illustrates the metallicity sensitivity of @xmath48 and also confirms our optimistic assessment of our photometric accuracy .
our m92 data are significantly bluer in @xmath48 than literature data of similar [ fe / h ] in the range @xmath74 .
stars in this region have higher @xmath12 and are thus fainter since they lie further toward the subgiant branch .
it is likely that the discrepancy is due to the fact that the literature data are photographic , but more ccd data are needed to verify this .
included in the figure are the @xmath48 fits for several [ fe / h ] values .
figure [ bvvk ] also clearly displays a dependence of @xmath75 color upon [ fe / h ] .
it is interesting to note that all the fits for the various values of metallicity intersect in the region @xmath76 .
figures [ vrvk ] and [ jkvk ] show a much weaker dependence of @xmath64 and @xmath66 on [ fe / h ] , as indicated by the equations above .
there is a hint that the @xmath64 sequence shows a divergence for different metallicity ranges around @xmath77 , but more data are needed to make sure .
the interesting behavior of @xmath60 is displayed in figure [ vivk ] .
giants with solar [ fe / h ] fall toward numerically lower @xmath60 values than the ones with [ fe / h ] @xmath78 for @xmath79 . at @xmath80 , however , the solar metallicity curve lies above the ones representing the lower metallicity ranges .
furthermore , stars with [ fe / h ] @xmath81 fall toward lower @xmath60 than solar [ fe / h ] stars throughout the range of @xmath49 .
another noteworthy result is the non - linear dependence of @xmath60 on @xmath49 .
it is apparent from the plot that the fits approximate the datapoints very well .
since this @xmath60 behavior was unexpected , we examined the possibility of single datasets overly influencing the fit , but when the function was refit without the walker ( 1994 ) and the da costa & armandroff ( 1990 ) m15 data , as well as the theoretical points , it remained unchanged .
it is worth mentioning that the dependence of @xmath60 on metallicity is a significantly lower - amplitude effect than the one on @xmath49 .
@xmath60 therefore remains a useful color index for temperature determination .
figure [ hkvk ] shows the opposite case : @xmath82 displays no sensitivity to metal abundance . in this plot ,
stars of all abundances overlie the same locus .
it is most likely that both colors , @xmath82 and @xmath49 , have negligible metallicity sensitivity ( rather than the alternative that both have measureable sensitivities , but the sensitivities conspire to look similar in the color - color plot ) .
the @xmath82 plot has a very small range compared to its observational error .
we have presented color sequences and analytical color - color fits for giants as a function of [ fe / h ] .
the well - known metallicity sensitivity of @xmath48 is clearly visible in fig .
our data underscore this high sensitivity , especially in the higher @xmath12 regime .
a somewhat weaker dependence upon [ fe / h ] was found for @xmath75 .
this color shows an interesting metallicity degeneracy at @xmath83 .
the colors @xmath64 , @xmath60 , and @xmath66 are much less influenced by metallicity , while @xmath82 is solely a function of @xmath49 ( and thus @xmath12 ) .
the dependence of @xmath66 and @xmath60 on [ fe / h ] was a surprising result ; more data would certainly be useful to confirm our findings .
the extremely weak metallicity dependences of @xmath64 and @xmath60 make these viable temperature indicators , with the advantage of only requiring an optical detector as opposed to an optical / ir combination .
this research was funded in part by nasa through grant hf-1066.01 - 94a from the space telescope science institute , which is operated by the association of universities for research in astronomy , inc .
, under nasa contract nas5 - 26555 .
thanks to brent fisher for a good deal of hard work in mining the gold out of the literature photometry ore .
we would also like to thank mario mateo for his helpful comments regarding dophot and aperture corrections .
finally , thanks to the anonymous referee for his / her insightful comments and suggestions .
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tiede , g. p. , frogel , j. a. , & terndrup , d. m. 1995 , , 186 , 50.06 van den bergh , s. 1962 , , 67 , 486 walker , a. r. , 1994 , aj , 108 , 555 worthey , g. & fisher , b. 1996 , , 28 , 1366 , # 72.05 worthey , g. 1994 , , 95 , 107 m3 & ii-18 & 14.105 & 0.400 & 0.935 & 0.515 & 0.980 & 0.015 & & i-21 & 13.075 & 1.150 & 1.340 & 0.700 & 1.355 & 0.030 & & iii-77 & 13.365 & 1.060 & 1.255 & 0.620 & 1.250 & 0.015 & 0.03u & iii-28 & 12.815 & 1.150 & 1.355 & 0.695 & 1.335 & 0.015 & 0.03ui & ii-46 & 12.755 & 1.455 & 1.510 & 0.770 & & 0.015 & 0.03u & iv-25 & 13.680 & 0.820 & 1.105 & 0.630 & 1.200 & 0.015 & m92 & iv-2 & 13.500 & 0.285 & 0.970 & 0.505 & 1.095 & 0.030 & & iv-10 & 13.455 & 0.335 & 0.920 & 0.560 & 1.100 & 0.015 & & iv-114 & 13.865 & 0.255 & 0.810 & 0.540 & 1.045 & 0.015 & & iii-82 & 13.375 & 0.395 & 0.935 & 0.575 & 1.150 & 0.015 & & ii-70 & 13.120 & 0.400 & 0.985 & 0.590 & 1.165 & 0.015 & & iii-4 & 14.155 & & 0.755 & 0.470 & 0.935 & 0.015 & & xi-19 & 12.870 & 0.530 & 1.070 & 0.605 & 1.190 & 0.015 & 0.03ui & x-49 & 12.220 & 0.855 & 1.270 & 0.680 & & 0.015 & & viii-43 & 14.615 & 0.070 & 0.750 & 0.485 & 0.970 & 0.015 & m13 & i-24 & 12.955 & 0.845 & 1.055 & 0.675 & 1.275 & 0.015 & & i-23 & 13.200 & 0.570 & 0.935 & 0.615 & 1.175 & 0.015 & & i-18 & 13.950 & 0.465 & 0.855 & 0.590 & 1.115 & 0.015 & & i-2 & 14.290 & 0.395 & 0.840 & 0.550 & 1.045 & 0.015 & m5 & ii-50 & 13.880 & 0.630 & 1.005 & 0.570 & 1.105 & 0.015 & 0.02v & iii-3 & 12.470 & 1.475 & 1.440 & 0.770 & 1.450 & 0.015 & & iii-16 & 14.235 & 0.265 & 0.780 & 0.485 & 0.950 & 0.015 & & iii-53 & 13.545 & 0.525 & 0.940 & 0.540 & 1.070 & 0.015 & & iii-56 & 13.365 & 0.685 & 1.005 & 0.565 & 1.120 & 0.015 & & iii-78 & 12.650 & 1.320 & 1.380 & 0.730 & 1.400 & 0.015 & & iv-19 & 12.610 & 1.320 & 1.380 & 0.715 & 1.375 & 0.015 & & iv-3 & 14.955 & 0.285 & 0.810 & 0.520 & 0.990 & 0.015 & & iv-28 & 14.395 & 0.550 & 0.945 & 0.520 & 1.025 & 0.015 & & iv-86 & 14.970 & -0.045 & 0.590 & 0.375 & 0.755 & 0.015 & 0.03u & iv-81 & 12.280 & 1.725 & 1.580 & 0.830 & 1.545 & 0.015 & & iv-47 & 12.425 & 1.510 & 1.430 & 0.755 & 1.430 & 0.015 & & iv-59 & 12.690 & 1.200 & 1.280 & 0.665 & 1.255 & 0.015 & & i-25 & 13.595 & 0.780 & 1.040 & 0.585 & 1.125 & 0.015 & & i-20 & 12.555 & 1.335 & 1.350 & 0.700 & 1.320 & 0.015 & & i-14 & 13.010 & 1.080 & 1.200 & 0.655 & 1.245 & 0.015 & & i-68 & 12.500 & 1.510 & 1.430 & 0.750 & 1.420 & 0.015 & & i-67 & 13.985 & 0.310 & 0.770 & 0.485 & 0.915 & 0.015 & & i-55 & 13.645 & 0.490 & 0.885 & 0.525 & 1.010 & 0.015 & & i-1 & 14.185 & 0.285 & 0.770 & 0.475 & 0.935 & 0.015 & & ii-9 & 12.595 & 1.335 & 1.350 & 0.715 & 1.370 & 0.015 & 0.03v ngc 6791 & r17 & 14.575 & 1.770 & 1.530 & 0.800 & 1.510 & 0.010 & & r4 & 14.000 & 1.415 & 1.580 & 1.355 & & 0.010 & 0.015r & r19 & 14.140 & 1.975 & 1.630 & 0.895 & 1.740 & 0.010 & & r23 & 14.875 & 1.520 & 1.385 & 0.700 & 1.305 & 0.010 & & r9 & 14.130 & 1.985 & 1.595 & 0.885 & 1.705 & 0.010 & & r24 & 14.980 & 1.750 & 1.450 & 0.785 & 1.460 & 0.010 & & r22 & 14.525 & 1.580 & 1.390 & 0.710 & 1.355 & 0.015 & & r12 & 13.835 & 2.040 & 1.650 & 0.930 & 1.920 & 0.010 & 0.015r & r11 & 14.600 & 1.765 & 1.500 & 0.775 & 1.475 & 0.010 & 0.02b & r3 & 14.070 & 2.220 & 1.710 & 0.965 & 1.940 & 0.015 & 0.03u & r21 & 14.720 & 1.700 & 1.470 & 0.770 & 1.445 & 0.015 & 0.03u & r25 & 14.715 & 1.490 & 1.395 & 0.715 & 1.340 & 0.015 & & r10 & 14.570 & 1.765 & 1.585 & 0.800 & 1.540 & 0.015 & & r16 & 13.740 & 2.055 & 1.635 & 0.865 & 1.730 & 0.015 & m3 & ii-18 & -1.57 & 0.01 & 14.075 & 0.393 & 0.925 & 0.508 & 0.965 & 2.348 & 11.727 & 0.645 & 0.088 & i-21 & & & 13.045 & 1.143 & 1.330 & 0.693 & 1.340 & 3.098 & 9.947 & 0.795 & 0.088 & iii-77 & & & 13.335 & 1.053 & 1.245 & 0.613 & 1.235 & 3.008 & 10.327 & 0.795 & 0.118 & iii-28 & & & 12.785 & 1.143 & 1.345 & 0.688 & 1.320 & 3.188 & 9.597 & 0.815 & 0.098 & ii-46 & & & 12.725 & 1.448 & 1.500 & 0.763 & & 3.478 & 9.247 & 0.875 & 0.108 & iv-25 & & & 13.650 & 0.813 & 1.095 & 0.628 & 1.185 & 2.873 & 10.777 & 0.765 & 0.128 m92 & iv-2 & -2.29 & 0.02 & 13.440 & 0.271 & 0.950 & 0.490 & 1.065 & 2.417 & 11.023 & 0.630 & 0.085 & iv-10 & & & 13.395 & 0.321 & 0.900 & 0.545 & 1.070 & 2.522 & 10.873 & 0.620 & 0.095 & iv-114 & & & 13.805 & 0.241 & 0.790 & 0.525 & 1.015 & 2.392 & 11.413 & 0.590 & 0.075 & iii-82 & & & 13.315 & 0.381 & 0.915 & 0.560 & 1.120 & 2.532 & 10.783 & 0.660 & 0.125 & ii-70 & & & 13.060 & 0.386 & 0.965 & 0.575 & 1.135 & 2.627 & 10.433 & 0.660 & 0.105 & iii-4 & & & 14.095 & & 0.735 & 0.455 & 0.905 & 2.102 & 11.993 & 0.540 & 0.065 & xi-19 & & & 12.810 & 0.516 & 1.050 & 0.590 & 1.160 & 2.657 & 10.153 & 0.690 & 0.095 & x-49 & & & 12.160 & 0.841 & 1.250 & 0.665 & & 2.927 & 9.233 & 0.750 & 0.115 & viii-43 & & & 14.555 & 0.056 & 0.730 & 0.470 & 0.940 & 2.142 & 12.413 & 0.490 & 0.015 m13 & i-24 & -1.54 & 0.02 & 12.895 & 0.831 & 1.035 & 0.660 & 1.245 & 2.842 & 10.053 & 0.720 & 0.105 & i-23 & & & 13.140 & 0.556 & 0.915 & 0.600 & 1.145 & 2.577 & 10.563 & 0.650 & 0.115 & i-18 & & & 13.890 & 0.451 & 0.835 & 0.575 & 1.085 & 2.477 & 11.413 & 0.640 & 0.105 & i-2 & & & 14.230 & 0.381 & 0.820 & 0.535 & 1.015 & 2.327 & 11.903 & 0.600 & 0.105 m5 & i-1 & -1.29 & 0.03 & 14.095 & 0.264 & 0.740 & 0.453 & 0.890 & 2.015 & 12.080 & 0.525 & 0.113 & i-14 & & & 12.920 & 1.059 & 1.170 & 0.633 & 1.200 & 2.980 & 9.940 & 0.785 & 0.093 & i-20 & & & 12.465 & 1.314 & 1.320 & 0.678 & 1.275 & 3.085 & 9.380 & 0.815 & 0.153 & i-25 & & & 13.505 & 0.759 & 1.010 & 0.563 & 1.080 & 2.675 & 10.830 & 0.705 & 0.113 & i-55 & & & 13.555 & 0.469 & 0.855 & 0.503 & 0.965 & 2.365 & 11.190 & 0.605 & 0.103 & i-67 & & & 13.895 & 0.289 & 0.740 & 0.463 & 0.870 & 2.085 & 11.810 & 0.515 & 0.053 & i-68 & & & 12.410 & 1.489 & 1.400 & 0.728 & 1.375 & 3.350 & 9.060 & 0.855 & 0.113 & ii-9 & & & 12.505 & 1.314 & 1.320 & 0.693 & 1.325 & 3.215 & 9.290 & 0.825 & 0.103 & ii-50 & & & 13.790 & 0.609 & 0.975 & 0.548 & 1.060 & 2.600 & 11.190 & 0.685 & 0.083 & iii-3 & & & 12.380 & 1.454 & 1.410 & 0.748 & 1.405 & 3.360 & 9.020 & 0.855 & 0.113 & iii-16 & & & 14.145 & 0.244 & 0.750 & 0.463 & 0.905 & 2.155 & 11.990 & 0.515 & 0.063 & iii-53 & & & 13.455 & 0.504 & 0.910 & 0.518 & 1.025 & 2.405 & 11.050 & 0.625 & 0.093 & iii-56 & & & 13.275 & 0.664 & 0.975 & 0.543 & 1.075 & 2.535 & 10.740 & 0.645 & 0.073 & iii-78 & & & 12.560 & 1.299 & 1.350 & 0.708 & 1.355 & 3.200 & 9.360 & 0.825 & 0.103 & iv-3 & & & 14.865 & 0.264 & 0.780 & 0.498 & 0.945 & 2.155 & 12.710 & 0.565 & 0.073 & iv-19 & & & 12.520 & 1.299 & 1.350 & 0.693 & 1.330 & 3.190 & 9.330 & 0.815 & 0.103 & iv-28 & & & 14.305 & 0.529 & 0.915 & 0.498 & 0.980 & 2.455 & 11.850 & 0.645 & 0.123 & iv-47 & & & 12.335 & 1.489 & 1.400 & 0.733 & 1.385 & 3.345 & 8.990 & 0.895 & 0.123 & iv-59 & & & 12.600 & 1.179 & 1.250 & 0.643 & 1.210 & 2.950 & 9.650 & 0.755 & 0.083 & iv-81 & & & 12.190 & 1.704 & 1.550 & 0.808 & 1.500 & 3.580 & 8.610 & 0.895 & 0.133 & iv-86 & & & 14.880 & -0.066 & 0.560 & 0.353 & 0.710 & 1.630 & 13.250 & 0.365 & -0.037 ngc 6791 & r17 & 0.20 & 0.13 & 14.175 & 1.677 & 1.395 & 0.700 & 1.309 & & & & & r4 & & & 13.600 & 1.322 & 1.445 & 1.255 & & & & & & r19 & & & 13.740 & 1.882 & 1.495 & 0.795 & 1.539 & & & & & r23 & & & 14.475 & 1.427 & 1.250 & 0.600 & 1.104 & & & & & r9 & & & 13.730 & 1.892 & 1.460 & 0.785 & 1.504 & & & & & r24 & & & 14.580 & 1.657 & 1.315 & 0.685 & 1.259 & & & & & r22 & & & 14.125 & 1.487 & 1.255 & 0.610 & 1.154 & & & & & r12 & & & 13.435 & 1.947 & 1.515 & 0.830 & 1.719 & & & & & r11 & & & 14.200 & 1.672 & 1.365 & 0.675 & 1.274 & & & & & r3 & & & 13.670 & 2.127 & 1.575 & 0.865 & 1.739 & & & & & r21 & & & 14.320 & 1.607 & 1.335 & 0.670 & 1.244 & & & & & r25 & & & 14.315 & 1.397 & 1.260 & 0.615 & 1.139 & & & & & r10 & & & 14.170 & 1.672 & 1.450 & 0.700 & 1.339 & & & & & r16 & & & 13.340 & 1.962 & 1.500 & 0.765 & 1.529 & & & & | new johnson - cousins @xmath0 photometry of giants in globular clusters is combined with @xmath1 photometry on the cit system to produce color sequences for giants from the globular clusters m3 , m5 , m13 , and m92 .
@xmath0 data are also presented for giants in the metal - rich open cluster ngc 6791 .
these data fill a gap in the literature , especially for the @xmath2 & @xmath3 bands .
we provide the empirical relations between broad band colors for various [ fe / h ] values for metal - poor giants .
the color sequences for @xmath4 and @xmath5 show clear separations for different [ fe / h ] values .
we also find weak , though unexpected , metallicity dependences of @xmath6 , @xmath7 , and @xmath8 colors .
@xmath9 is metal - insensitive .
the above colors are plotted as a function of @xmath10 , and a literature @xmath11 relation is given . |
let us imagine to divide the hilbert space @xmath1 of a given quantum system into two parts @xmath2 and @xmath3 such that @xmath4 .
when the system is in a pure state @xmath5 , the bipartite entanglement between a and its complement b , can be measured in terms of the rnyi entropies @xcite s_a^(n)=11-n_a^n , [ renyidef ] where @xmath6 is the reduced density matrix of the subsystem a , and @xmath7 is the density matrix of the whole system .
the knowledge of @xmath8 as a function of @xmath9 identifies univocally the full spectrum of non - zero eigenvalues of @xmath10 @xcite , and provides complementary information about the entanglement to the one obtained from the von neumann entanglement entropy @xmath11 .
furthermore , the scaling of @xmath8 with the size of a in the ground - state of a one - dimensional system is more suited than @xmath11 to understand if a faithful representation of the state in term of a matrix product state can be or can not be obtained with polynomial resources in the length of the chain @xcite . for a one - dimensional critical system
whose scaling limit is described by a conformal field theory ( cft ) , in the case when a is an interval of length @xmath12 embedded in an infinite system , the asymptotic large @xmath12 behavior of the quantities determining the rnyi entropies is @xcite @xmath13 where @xmath14 is the central charge of the underlying cft and @xmath15 the inverse of an ultraviolet cutoff ( e.g. the lattice spacing ) .
the prefactors @xmath16 ( and so the additive constants @xmath17 ) are non universal constants ( that however satisfy universal relations @xcite ) .
the central charge is an ubiquitous and fundamental feature of a conformal field theory @xcite , but it does not always identify the universality class of the theory . a relevant class of relativistic massless quantum field theories are the @xmath0 models , which describe many physical systems of experimental and theoretical interest .
the one - dimensional bose gas with repulsive interaction , the ( anisotropic ) heisenberg spin chains , the ashkin - teller model and many others are all described ( in their gapless phases ) by @xmath0 theories . these are all free - bosonic field theories where the boson field satisfies different periodicity constraints , i.e. it is compactified on a specific target space .
the two most notable examples are the compactification on a circle ( corresponding to the luttinger liquid field theory ) and on a @xmath18 orbifold ( corresponding to the ashkin - teller model @xcite ) .
the critical exponents depend in a continuous way on the compactification radius of the bosonic field .
a survey of the cfts compactified on a circle or on a @xmath18 orbifold is given in fig .
[ fig14 ] , in a standard representation @xcite .
the horizontal axis is the compactification radius on the circle @xmath19 , while the vertical axis represents the value of the @xmath18 orbifold compactification radius @xmath20 .
the two axes cross in a single point , meaning that the theories at @xmath21 and at @xmath22 are the same .
( the graph is not a cartesian plot , i.e. it has no meaning to have one @xmath19 and one @xmath20 at the same time . ) for some values of @xmath19 and @xmath20 , we report statistical mechanical models and/or field theories to which they correspond . in the following
we will consider the ashkin - teller model that on the self - dual line is described by @xmath23 $ ] and the xxz spin chain in zero magnetic field that is described by @xmath24 $ ] .
we mention that different compactifications have been studied @xcite , but they correspond to more exotic statistical mechanical models and will not be considered here .
theories corresponding to a free boson compactified on a circle ( horizontal axis ) and on an orbifold ( vertical axis ) as reported e.g. in refs .
@xcite . for some values of @xmath19 and @xmath20 ,
the corresponding statistical mechanical models are reported .
the xxz spin chain in zero magnetic field lies on the horizontal axis in the interval @xmath25 $ ] .
the self - dual line of the ashkin - teller model lies on the vertical axis in the interval @xmath23$].,scaledwidth=90.0% ] according to eq .
( [ renyi : asymp ] ) , the central charge of the cft can be extracted from the scaling of both the rnyi and von neumann entropies . in the last years , this idea has overcome the previously available techniques of determining @xmath14 , e.g. by measuring the finite size corrections to the ground state energy of a spin chain @xcite .
however , the dependence of the scaling of the entropies of a single block only on the central charge prevents to extract from them other important parameter of the model such as the compactification radius .
it has been shown that instead the entanglement entropies of disjoint intervals are sensitive to the full operator content of the cft and in particular they depend on the compactification radius and on the symmetries of the target space .
thus they encode complementary information about the underlying conformal field theory of a given critical quantum / statistical system to the knowledge of the central charge present in the scaling of the single block entropies .
( oppositely in 2d systems with conformal invariant wave - function , the entanglement entropy of a single region depends on the compactification radius @xcite . )
this observation boosted an intense theoretical activity aimed at determining rnyi entropies of disjoint intervals both analytically and numerically @xcite .
a part of this paper is dedicated to consolidate some of the results already provided in other works where they either have been studied only on very small chains , with the impossibility of properly taking into account the severe finite size corrections @xcite or have been tested in the specific cases of spin chains equivalent to free fermionic models @xcite .
an important point to recall when dealing with more than one interval is that the rnyi entropies in eq .
( [ renyidef ] ) measure only the entanglement of the disjoint intervals with the rest of the system .
they do _ not _ measure the entanglement of one interval with respect to the other , that instead requires the definition of more complicated quantities because @xmath26 is in a mixed state ( see e.g. refs .
@xcite for a discussion of this and examples ) .
furthermore , it must be mentioned that some results about the entanglement of two disjoint intervals are at the basis of a recent proposal to `` measure '' the entanglement entropy @xcite .
we consider the case of two disjoint intervals @xmath27\cup [ u_2,v_2]$ ] . by global conformal invariance , in the thermodynamic limit , @xmath28 can be written as _
a^n = c_n^2 ( ) ^6(n-1/n ) f_n(x ) , [ fn ] where @xmath29 is the four - point ratio ( for real @xmath30 and @xmath31 , @xmath29 is real ) @xmath32 the function @xmath33 is a universal function ( after being normalized such that @xmath34 ) that encodes all the information about the operator spectrum of the cft and in particular about the compactification radius .
@xmath16 is the same non - universal constant appearing in eq .
( [ renyi : asymp ] ) .
furukawa , pasquier , and shiraishi @xcite calculated @xmath35 for a free boson compactified on a circle of radius @xmath19 f_2(x)= , [ f2 ] where @xmath36 are jacobi theta functions and the ( pure - imaginary ) @xmath37 is given by x= ^4,(x)=i .
[ mapping ] @xmath38 is a universal critical exponent related to the compactification radius @xmath39 . or @xmath40 for any conformal property one could also define @xmath41 as sometimes done in the literature .
however , corrections to scaling are not symmetric in @xmath42 and this is often source of confusion .
a lot of care should be used when referring to one or another notation . ]
this has been extended to general integers @xmath43 in ref .
@xcite @xmath44 ^ 2}\ , , \label{fnv}\ ] ] where @xmath45 is an @xmath46 matrix with elements @xcite _ rs = _ k=1^n-1 ( ) _
k / n , [ gammadef ] and _ y=. [ betadef ] @xmath38 is the same as above , while @xmath47 is the riemann - siegel theta function @xmath48\,.\ ] ] the analytic continuation of eq .
( [ fnv ] ) to real @xmath9 for general values of @xmath38 and @xmath29 ( to obtain the von neumann entanglement entropy ) is still an open problem , but results for @xmath49 and @xmath50 are analytically known @xcite .
the function @xmath33 is known exactly for arbitrary integral @xmath9 also for the critical ising field theory @xcite .
however , in the following we will need it only at @xmath51 ( i.e. @xmath35 ) for which it assumes the simple form @xcite f_2^is(x)=1 ^ 1/2 .
[ cftf2 ] in ref .
@xcite , it has been proved that in any cft the function @xmath33 admits the small @xmath29 expansion f_n(x)=1 + ( ) ^ s_2(n)+ ( ) ^2s_4(n)+ , [ fexpintro ] where @xmath52 is the lowest scaling dimension of the theory .
the functions @xmath53 are calculable from a modification of the short - distance expansion @xcite , and in particular it has been found @xcite s_2(n)=n 2 _ j=1^n-1 1 ^ 2 , [ s2cft ] where the integer @xmath54 counts the number of inequivalent correlation functions giving the same contribution .
this expansion has been tested against the exact results for the free compactified boson ( ising model ) with @xmath55 $ ] ( @xmath56 ) and @xmath57 ( @xmath58 ) .
all the results we reported so far are valid for an infinite system .
numerical simulations are instead performed for finite , but large , system sizes . according to cft @xcite
, we obtain the correct result for a chain of finite length @xmath59 by replacing all distances @xmath60 with the _ chord distance _ @xmath61 ( but different finite size forms exist for excited states @xcite ) .
in particular the single interval entanglement is @xcite @xmath62^{-c(n-1/n)/6}\,,\ ] ] and for two intervals , in the case the two subsystems @xmath63 and @xmath64 have the same length @xmath12 and are placed at distance @xmath65 , the four - point ratio @xmath29 is x=()^2 .
[ xfs ] in this paper we provide accurate numerical tests for the functions @xmath33 in truly interacting lattice models described by a cft with @xmath0 . in sec .
[ sec2 ] we derive the cft prediction for the function @xmath35 of a free boson compactified on an orbifold describing , among the other things , the self - dual line of the at model when @xmath66 $ ] . in order to check this result
, we needed to develop a classical monte carlo algorithm in sec .
[ atmc ] based on the ideas introduced in ref .
this algorithm is used in sec .
[ atres ] to determine @xmath35 for several points on the self - dual line .
we also consider the xxz spin - chain in zero magnetic field to test the correctness of eq .
( [ fnv ] ) . in order to extend the results of ref .
@xcite to longer chains , we have used a tree tensor network algorithm that has allowed us to study chains of length up to @xmath67 with periodic boundary conditions . in this way , we have been able to perform a detailed finite size analysis that was difficult solely with the data from exact diagonalization reported in ref .
the analysis also shows that only through the knowledge of the unusual corrections to the leading scaling behavior @xcite we are able to perform a quantitative test of eq .
( [ fnv ] ) .
the tree tensor network algorithm is described in sec .
[ ttn : sec ] , while the numerical results are presented in sec .
[ xxz : sec ] .
the various sections are independent one from each other , so that readers interested only in some results should have an easy access to them without reading the whole paper .
in a quantum field theory @xmath68 for integer @xmath9 is proportional to the partition function on an @xmath9-sheeted riemann surface with branch cuts along the subsystem @xmath69 , i.e. @xmath70 where @xmath71 is the partition function of the field theory on a conifold where @xmath9 copies of the manifold @xmath72 are coupled along branch cuts along each connected piece of @xmath69 at a time - slice @xmath73 @xcite .
specializing to cft , for a single interval on the infinite line , this equivalence leads to eq .
( [ renyi : asymp ] ) @xcite , whose analytic continuation to non - integer @xmath9 is straightforward .
when the subsystem @xmath69 consists of @xmath74 disjoint intervals ( always in an infinite system ) , the @xmath9-sheeted riemann surface @xmath75 has genus @xmath76 and can not be mapped to the complex plane so that the cft calculations become more complicated .
however , for two intervals ( @xmath77 ) , when for a given theory the partition function on a generic riemann surface of genus @xmath78 with arbitrary _ period matrix _ is known , @xmath68 can be easily deduced exploiting the results of refs .
@xcite . in fact , a by - product of the calculation for the free boson @xcite is that the @xmath79 period matrix is always given by eq .
( [ gammadef ] ) .
although derived for a free boson , the period matrix is a pure geometrical object and it is only related to the structure of the world - sheet @xmath80 and so it is the same for any theory .
this property has been used in ref .
@xcite to obtain @xmath33 for the ising universality class for any @xmath9 , in agreement with previously known numerical results @xcite .
when also @xmath51 , the surface @xmath81 is topologically equivalent to a torus for which the partition function is known for most of the cft .
the torus modular parameter @xmath37 is related to the four - point ratio by eq .
( [ mapping ] ) .
thus , the function @xmath35 is proportional to the torus partition function where @xmath37 is given by eq .
( [ mapping ] ) and with the proportionality constant fixed by requiring @xmath82 .
this way of calculating @xmath83 is much easier than the general one for @xmath84 @xcite and indeed it has been used to obtain the first results both for the free compactified boson @xcite and for the ising model @xcite . for a conformal
free bosonic theory with action @xmath85 the torus partition functions are known exactly both for circle and orbifold compactification @xcite .
we now recall some well - known facts in order to fix the notations and derive the function @xmath35 for the ashkin - teller model .
the bosonic field @xmath86 is said to be compactified on a circle of radius @xmath19 when @xmath87 . the torus partition function ( and the one on the @xmath9-sheeted riemann surface )
should be derived with this constraint .
it is a standard cft exercise to calculate the resulting torus partition function @xcite z_circle()= , where @xmath88 is the dedekind eta function and @xmath89 . using eq .
( [ mapping ] ) and some properties of the elliptic functions , eq .
( [ f2 ] ) for @xmath35 follows @xcite . when specialized at @xmath90 ( or @xmath91 ) , @xmath35 has the simple form f_2^xx(x)= , [ f2xx ] that describes the xx spin - chain ( that is equivalent to free fermions via the non - local jordan - wigner transformation ) .
the concept of orbifold emerges naturally in the context of theories whose hilbert space admits some discrete symmetries . let us assume that @xmath92 is a discrete symmetry . for the free bosonic theory ,
the simplest example is the one we are interested in , i.e. the @xmath18 symmetry .
it acts on the point of the circle @xmath93 in the following way @xmath94 for the partition function of a theory on the torus , we introduce the notation @xcite ( 2,2 ) ( 0,-4)(15,15 ) ( 3.5,-14)@xmath95 ( -9,1.5)@xmath95 where the @xmath95 denotes the boundary conditions on the two directions on the torus . the full partition function , given a finite discrete group @xmath92 , is @xmath96 where @xmath97 denotes the number of elements in the group .
the generalization to higher genus riemann surfaces is straightforward ( but it is not so easy to obtain results , see e.g. @xcite ) .
now we specialize eq .
( [ modout ] ) to the case of the @xmath18 symmetry .
since the action ( [ fba ] ) is invariant under @xmath98 , we have the torus partition function for the free boson on the orbifold @xcite z_orb= ( ( 2,2 ) ( 0,-4)(15,15 ) ( 3.5,-14)@xmath99 ( -9,1.5)@xmath99 + ( 2,2 ) ( 0,-4)(15,15 ) ( 3.5,-14)@xmath99 ( -9,1.5)@xmath100 + ( 2,2 ) ( 0,-4)(15,15 ) ( 3.5,-14)@xmath100 ( -9,1.5)@xmath99 + ( 2,2 ) ( 0,-4)(15,15 ) ( 3.5,-14)@xmath100 ( -9,1.5)@xmath100 ) .
standard cft calculations lead to the result @xcite @xmath101 where all the @xmath37 arguments in @xmath36 and @xmath102 are understood . at the special point @xmath90 ( or @xmath91 ) we get @xmath103 thus , from the orbifold partition function , using the last identity and normalizing such that @xmath104 , we can write the funcion @xmath105 as f_2^at(x)=(f_2(x)-f_2^xx(x))+(f_2^is(x))^2 , [ atf2 ] where @xmath35 is given in eq .
( [ f2 ] ) , @xmath106 is the same at @xmath90 ( cf .
( [ f2xx ] ) ) and @xmath107 is the result for ising ( cf . eq .
( [ cftf2 ] ) ) . as a consequence of the @xmath108 symmetry of @xmath35 ,
also @xmath109 displays the same invariance . for small @xmath29 , recalling that @xmath110}$ ] , @xmath111 and @xmath112
, we have f_2^at(x)-1~ the critical ashkin - teller model lies in the interval @xmath113 and so @xmath114 .
thus we have @xmath115 along the whole self - dual line . @xmath105 for various values of @xmath38 in the allowed range
is reported in fig .
[ log_curve ] , where the behavior for small @xmath29 is highlighted in the inset to show the constant @xmath116 exponent . for the ashkin - teller model on the self - dual line for some values of @xmath38 .
inset : @xmath117 in log - log scale to highlight the small @xmath29 behavior .
the black - dashed line is @xmath118 . ]
the two dimensional ashkin - teller ( at ) model on a square lattice is defined by the hamiltonian @xmath119 where @xmath120 and @xmath121 are classical ising variables ( i.e. can assume only the values @xmath122 ) . also the product @xmath123 can be considered as an ising variable .
the model has a rich phase diagram whose features are reported in full details in baxter s book @xcite .
we review in the following only the main features of this phase diagram . under any permutation of the variables
@xmath124 the at model is mapped onto itself . at the level of the coupling constants
, this implies that the model is invariant under any permutation of @xmath125 . for @xmath126 ,
the at model corresponds to two decoupled ising models in @xmath127 and @xmath37 variables . for @xmath128
it reduces to a single ising model with coupling constant @xmath129 . for @xmath130
it corresponds to the four - state potts model .
it is useful to restrict to the symmetric ashkin - teller model where @xmath131 @xmath132 the full phase diagram is reported in fig .
[ phadia ] ( in units of the inverse temperature @xmath133 ) .
the model corresponds to two decoupled critical ising models at @xmath126 and @xmath134 . for @xmath135 it is equivalent to a critical ising model in the variable @xmath123 with critical points at @xmath136 . for @xmath137
there are two critical ising points at @xmath138 . on the diagonal @xmath139
the system corresponds to a 4-state potts model which is critical at @xmath140 .
the different kinds of orders appearing in the phase diagram are explained in the caption of fig .
[ phadia ] .
all the continuous lines in fig .
[ phadia ] are _ critical lines_. the blue lines c - is are in the ising universality class .
the line starting from afis belongs to the antiferromagnetic ising universality class . on the red line abc
the system is critical and the critical exponents vary continuously @xcite . ) .
the red abc line is the self dual line .
the point @xmath141 at @xmath126 corresponds to two uncoupled ising models .
the point @xmath142 is the critical four - state potts model at @xmath143 . at @xmath135
there are two critical ising points at @xmath144 , one ( is ) ferromagnetic and the other ( afis ) antiferromagnetic . for @xmath137
there is another critical ising point at @xmath145 .
all continuous lines are critical .
the blue lines @xmath146 and the one starting at @xmath147 are in the ising universality class .
the red line is critical with continuously varying critical exponents .
the region denoted by i corresponds to a ferromagnetic phase for all the variables . in the region ii , @xmath148 , @xmath37 , and @xmath149 are paramagnetic . in the region
iii only @xmath123 is ferromagnetic and in region iv @xmath123 exhibits antiferromagnetic order while @xmath127 and @xmath37 are paramagnetic . ]
the at model on a planar graph can be mapped to another at model on the dual graph . when specialized to the square lattice , the phase diagram is equivalent to its dual on the self - dual line : @xmath150 on this line , the symmetric at model maps onto an homogeneous six - vertex model which is exactly solvable @xcite .
it follows that on the self - dual line the model is critical for @xmath151 and its critical behavior is described by a cft with @xmath0 . along the self - dual line
the critical exponents vary countinuously and are exactly known . for later convenience
it is useful to parametrize the self dual line by a new parameter @xmath152 e^4j=,e^4k=1 - 2 , with @xmath153 . in terms of @xmath152 ,
the orbifold compactification radius is @xcite = 2r_orb^2== , [ etaat ] where @xmath154 is the equivalent of the luttinger liquid parameter for the at model . a swendsen - wang type cluster algorithm for
the at model has been proposed in ref .
@xcite and then re - derived in a simpler way by salas and sokal @xcite . here
we partly follow the derivation of salas and sokal and we restrict to the symmetric at hamiltonian ( [ sat ] ) and assume @xmath155 . using the identities for ising type variables _
i_j=2__i_j-1 , _
i_j=2__i_j-1 , we can rewrite eq .
( [ sat ] ) as -h = j_ij(2__i_j+ 2__i_j-2)+k _ ij(2__i_j-1)(2__i_j-1 ) . for convenience
we shift the interaction ( [ sat ] ) by @xmath156 . in order to write the boltzmann weight associated to a specific configuration we use @xmath157 and the analogous identity for the @xmath37 variables .
the boltzmann weight of a given link @xmath158 is then _
j+__i_j]+ + & & + [ 1 - 2e^-2(j+k)+e^-4j]__i_j__i_j .
[ atw ] the key idea for the swendsen - wang algorithm is to introduce two new auxiliary ising - type variables @xmath159 and @xmath160 living on the link @xmath158 .
we redefine the boltzmann weight on the link @xmath158 as @xcite _ ij&&(_i,_j,_i,_j , m_ij , n_ij)= e^-4j_m_ij 0_n_ij0 + + & & + [ e^-2(j+k)-e^-4j ] [ _ _ i _ j_m_ij1_n_ij0+__i_j
_ m_ij0_n_ij1]+ + & & + [ 1 - 2e^-2(j+k)+e^-4j]__i _ j__i _ j _ m_ij1_n_ij1 .
[ atwc ] summing over @xmath159 and @xmath160 we obtain the weight in eq .
( [ atw ] ) .
( [ atwc ] ) has a graphical interpretation in terms of clusters .
in fact we can divide the links of the lattice in `` activated '' ( if @xmath161 ) or `` inactive '' ( if @xmath162 ) .
the same considerations hold for the @xmath160 variables .
therefore , each link of the lattice can be activated by setting @xmath161 or @xmath163 .
the active links connect different lattice sites forming clusters .
there are clusters referring to the @xmath127 variables ( called @xmath127-clusters ) and to the @xmath37 variables ( @xmath37-clusters ) .
isolated lattice sites are clusters as well .
obviously , the lattice sites belonging to the @xmath127-clusters ( @xmath37-clusters ) have the same value of @xmath127 ( @xmath37 ) .
the partition function of the extended model defined by the weight ( [ atwc ] ) can be written as z=_,=1_m , n=1_ijw _ ij(_i,_j,_i,_j , m_ij , n_ij ) .
we now proceed to the following definitions .
we divide all the links into three classes : we define @xmath164 the total number of inactivated links ; @xmath165 the total number of links connecting sites which belong only to one type of clusters either a @xmath127-cluster or a @xmath37-cluster .
we define @xmath166 the total number of links on which @xmath167 and @xmath9 are both equal to @xmath168 .
furthermore we introduce the quantities @xmath169\,,\\ b_2\equiv [ 1 - 2e^{-2(j+k)}+e^{-4j}]\,.\end{aligned}\ ] ] the following step is to perform the summation over @xmath170 in eq .
( [ atwc ] ) .
this is readily done , obtaining the final expression for the partition function @xmath171 where we denoted with @xmath172 the number of @xmath127-clusters and with @xmath173 the total number of @xmath37-clusters . in the counting of @xmath37-clusters ( @xmath127-clusters )
we included all the lattice sites connected by a link on which @xmath161 ( @xmath163 ) .
isolated sites ( with respect to @xmath167 or @xmath9 or both ) count as single clusters .
the links where @xmath174 contribute to both types of clusters
. lattice .
green lines are @xmath127-clusters and red dashed lines are @xmath37-clusters .
links in blue are double links .
periodic boundary conditions on both directions are used.,scaledwidth=50.0% ] we are now in position to write the swendsen - wang algorithm for the symmetric at model . the monte - carlo procedure can be divided in two steps . in the first one , given a configuration for @xmath175 variables , we construct a configuration of the @xmath176 variables . in the second step we update the @xmath175 variables at given @xmath176 .
the details of the step one are * if @xmath177 and @xmath178 , we choose @xmath179 with the following probabilities : * * @xmath180 with @xmath181 , * * @xmath182 with @xmath183 , * * @xmath184 with @xmath183 , * * @xmath185 with @xmath186 , * if @xmath177 and @xmath187 , the probabilities are * * @xmath182 with @xmath188 , * * @xmath185 with @xmath189 , * if @xmath190 and @xmath178 , the probabilities are * * @xmath182 with @xmath188 , * * @xmath185 with @xmath189 , * if @xmath190 and @xmath187 we choose @xmath185 with probability @xmath168 . in the step two , given the configuration of @xmath176 generated using the rules above we build the connected @xmath127-clusters and @xmath37-clusters .
the value of @xmath127 ( @xmath37 ) spins are required to be equal within each @xmath127-cluster ( @xmath37-cluster ) .
we choose randomly the spin value in each cluster and independently of the value assumed on the other clusters .
this completes the update scheme .
( note a typo in ref .
@xcite : the minus sign in step 2 and 3 of the update is missing . ) in ref . @xcite
also the so called embedded version of the cluster algorithm is introduced .
its implementation is slightly easier compared to the direct algorithm . in the embedded algorithm instead of treating both @xmath127 and @xmath37 at the same time , one deals with only one variable per time .
let us consider the boltzmann weight of a link @xmath158 at fixed configuration of @xmath37 @xmath191 the model defined by this weight can be simulated with a standard swendsen - wang algorithm for the ising model using the effective coupling constant @xmath192 this is no longer translation invariant , but this does not affect the effectiveness of the cluster algorithm for the ising model as long as @xmath193 .
the same reasoning applies to the case of fixed @xmath127 .
thus , the embedded algorithm is made of two steps * for a given configuration of @xmath37 variables , we apply a standard swendsen - wang algorithm to @xmath127 spins .
the probability arising in the update step is @xmath194 .
* for a given configuration of @xmath127 variables , we update @xmath37 with the same algorithm and probability @xmath195 .
direct and embedded algorithms are both extremely effective procedures to sample the at configurations . however , very important for the following , eq .
( [ atpf ] ) for the partition function does not hold anymore for a @xmath9-sheeted riemann surface and we do not know whether it is possible to write the embedded algorithm for this case . in this section
we summarize the method introduced by caraglio and gliozzi @xcite to obtain the rnyi entropies via simulations of classical systems and we generalize it to the at model .
the partition function @xmath196 of a @xmath197-dimensional quantum system at inverse temperature @xmath198 can be written as an euclidean path integral in @xmath199 dimensions @xcite .
thus for the @xmath9-th power of the partition function one has @xmath200e^{-\sum\limits_{k=1}^n s(\phi_k)}\end{aligned}\ ] ] where @xmath201 is a field living on the @xmath202-th replica of the system and @xmath203 is the euclidean action ( @xmath37 is the imaginary time . )
the actual form of the action is not important , but for the sake of simplicity we restrict to the case of nearest - neighbor interactions @xmath204 and the function @xmath205 is arbitrary .
we recall that @xmath68 can be obtained by considering the euclidean partition function over a @xmath9-sheeted riemann surface with branch cuts along the subsystem @xmath69 @xcite .
( this equivalence is also the basis of all quantum monte carlo methods to simulate the block entanglement in any dimension @xcite . )
caraglio and gliozzi constructed this @xmath9-sheeted riemann surface for the lattice model in the following way .
let us consider a square lattice ( for simplicity ) and take the two points of its dual lattice surrounding @xmath69 ( that in 1 + 1 dimension is just an interval with two end - points ) .
the straight line joining them defines the cut that we call @xmath206 .
the length of @xmath206 is equal to the length of @xmath69 .
let us consider @xmath9 independent copies of this lattice with a cut .
the @xmath9-sheeted riemann lattice is defined by assuming that all the links of the @xmath202-th replica intersecting the cut connect with the next replica @xmath207 . to get the partition function over the @xmath9 sheeted riemann surface
we define the corresponding coupled action s^n(_k)=_k=1^n_ij f(_k(i),_k(j))+ _
ij f(_k(i),_k+1 ( modn)(j ) ) . [ act ] this definition can be used in any dimension , even though we will use here only @xmath208 . finally ,
calling @xmath71 the partition function over the action ( [ act ] ) , @xmath209 is given by @xmath210 following ref .
@xcite we introduce the observable @xmath211 where @xmath212 and @xmath213 are the euclidean actions of the model defined on the @xmath9-sheeted lattice and on the @xmath9 independent lattices respectively .
the sum is restricted to links crossing the cut , as the presence of @xmath206 in the arguments stresses .
it then follows _
n=^n_a , where @xmath214 stands for the average taken onto the uncoupled action @xmath215 . we can now discuss our improvement to the procedure highlighted so far . the practical implementation of eq .
( [ obs ] ) to calculate @xmath68 is plagued by severe limitations : analyzing the monte - carlo evolution of the observable , one notices that it shows a huge variance because it is defined by an exponential .
direct application of eq .
( [ obs ] ) is possible then only for small lengths of the subsystem @xmath69 . in order to overcome this problem ,
let us consider the quantity @xmath216 and imagine to divide the subsystem in @xmath59 parts to have @xmath217 , with the lengths of the various parts being arbitrary .
moreover we define a set of subsystems @xmath218 .
then it holds @xmath219 eq .
( [ trick ] ) is very useful because each term in the product can be simulated effectively using a modified version of ( [ obs ] ) if we choose the length of @xmath220 to be small enough .
in fact , by definition , we have @xmath221 where @xmath222 is the modified observable @xmath223 we stress that in eq .
( [ trick1 ] ) the expectation value in the l.h.s must be taken on the coupled action on the riemann surface with cut @xmath224 .
the disadvantage of eq .
( [ trick ] ) is that , to simulate large subsystems , one has to perform @xmath59 independent simulations and then build the observable taking the product of the results .
if the dimension of each piece @xmath220 is small this task requires a large computational effort .
another important aspect is the estimation of the monte carlo error : if each term in ( [ trick ] ) is obtained independently , the error in the product is @xmath225 if the lengths of the intervals @xmath220 are all equal , then the single terms of the summation in eq .
( [ error ] ) do not change much and the total error should scale as @xmath226 .
caraglio and gliozzi @xcite used another strategy to circumvent the problem with the observable in eq .
( [ obs ] ) .
the trick was to consider the fortuin - kastelayn cluster expansion of the partition function of the ising model .
the analogous for the at model was reported in the previous section @xmath227 where @xmath228 are the @xmath229-cluster configurations .
going from @xmath9 independent sheets to the @xmath9-sheeted lattice , the type of links and their total number do not change , but the number of clusters does change , and so we get the cluster expression of observable ( [ obs ] ) for the at model @xmath230}\ , , \label{cobs}\end{aligned}\ ] ] where @xmath231 ( @xmath232 ) denote the total number of @xmath127-clusters ( @xmath37-clusters ) on the riemann surface with cut @xmath224 . since the clusters are non local objects , they represent `` improved '' observables and the variance for the monte carlo history of eq .
( [ cobs ] ) is much smaller than in the naive implementation .
for a single interval of length @xmath12 in a finite system of length @xmath233 .
data have been obtained by monte carlo simulations using the embedded algorithm .
the orange points correspond to the susy model and the green ones to the @xmath234 parafermions .
the black crosses at @xmath235 are data obtained using the direct algorithm .
inset : behavior of the statistical error of @xmath236 vs @xmath12 for the susy model .
the blue - dashed line is the expected form @xmath237 . ]
we first present the results for the ashkin - teller model for a single interval .
although these results do not provide any new information about the model , they are fundamental checks for the effectiveness of the monte carlo algorithms .
we performed simulations using both algorithms described in the previous section : the direct cluster algorithm and the embedded one . when using the direct algorithm ,
measures are performed using the observable ( [ cobs ] ) , while for the embedded algorithm we used the observable in eq .
( [ obs ] ) . in fig .
[ example ] we report the results of the simulations of @xmath236 for the susy model ( @xmath238 in fig . [ fig14 ] ) and for the @xmath234 parafermions ( @xmath239 ) both for @xmath233 .
the orange and green points are obtained using the embedded algorithm . to check the implementation of the cluster observable
, we report at @xmath235 the data obtained using the direct algorithm and eq .
( [ cobs ] ) .
the perfect agreement between the two results confirms the correctness of both implementations .
note that @xmath236 is a monotonous function of @xmath12 , in contrast with the parity effects found for the xxz spin chain @xcite that also corresponds to a vertex model @xcite . in the inset
we show the behavior of the statistical error of the observable ( [ obs ] ) in the susy case as function of the subsystem length @xmath12 .
it agrees with the prediction in eq .
( [ error ] ) and its absolute value is extremely small , smaller than the size of the points in the main plot in fig .
[ example ] .
analogous results have been obtained for all the critical points on the self - dual line using both algorithms .
as function of @xmath240 for different @xmath12 and @xmath59 .
three points on the self - dual line are reported : four - states potts model , uncoupled ising , and susy . the dashed lines are fits to the function @xmath241 ( @xmath242 for the 4-states potts model ) where @xmath154 is @xmath243 respectively for the four - states potts model , ising , and susy . in the inset we report @xmath16 for @xmath244 for the susy point .
the dashed lines are fit to @xmath245 , with @xmath246 fixed . ]
the results for @xmath236 in a finite system are asymptotically described by the cft prediction ( [ snfs ] ) with @xmath51 and @xmath0 .
it is then natural to compute the ratio c_2(l_c)= , [ c2l ] that is expected to be asymptotically a function of the chord - length @xmath247 $ ] .
this allows to extract the non - universal quantity @xmath248 and to check the form of the corrections to the scaling . in fig .
[ c2 ] we report the results for @xmath249 for the susy point , for the two uncoupled ising models , and for the four states potts model .
it is evident that for large @xmath240 , @xmath249 approaches a constant value around @xmath250 .
this is a first confirmation of the cft predictions on the self - dual line .
the previous results also provide a test for the theory of the corrections to the scaling to @xmath84 .
it has been shown @xcite that for gapless models described by a luttinger liquid theory , the corrections to the scaling have the form @xmath251 ( or @xmath252 for finite systems ) where @xmath154 is the luttinger parameter , related to the circle compactification radius @xmath253 . on the basis of general cft arguments @xcite , it has been argued that this scenario is valid for any cft and so also for the at model with @xmath154 replaced by the dimension of a proper operator .
it is then natural to expect that for the at model this dimension is @xmath154 in eq .
( [ etaat ] ) , also on the basis of the results for the ising model @xcite .
the dashed lines in fig .
[ c2 ] are fits of @xmath249 with the function @xmath254 .
the agreement is always very good , except for the four - state potts model , for which the exponent of the leading correction @xmath154 assumes the smallest value and so subleading corrections enter ( as elsewhere in similar circumstances , see e.g. @xcite ) .
in fact , the fit with the function @xmath255 is in perfect agreement with the data ( but the presence of another fit parameter makes this result not so robust ) .
this analysis confirms that @xmath154 is the right exponent governing the corrections to the scaling . versus the four point ratio @xmath29 for the susy model .
the red points are extrapolations obtained using the finite - size ansatz ( [ ansatz ] ) .
the blue - dashed line is the @xmath256 prediction .
inset : @xmath257 vs @xmath258 for the four values of @xmath29 used in the extrapolation ( @xmath259 ) .
the dashed lines are fits to finite - size ansatz ( [ ansatz ] ) . ] in the inset of fig .
[ c2 ] we also report the values of @xmath16 for @xmath244 as a function of @xmath240 .
@xmath16 becomes smaller as @xmath9 increases as for the @xmath260 @xcite , xx @xcite , and ising @xcite spin - chains .
the dashed lines are fits to the expected scaling behavior @xmath252 of the corrections , that reproduce perfectly the data . in this section
we investigate the entanglement entropy of two disjoint intervals and check the correctness of our prediction ( [ atf2 ] ) for the at model on the self - dual line . as for all other cases studied so far numerically ( i.e. heisenberg @xcite , ising @xcite , and xy @xcite chains ) ,
strong scaling corrections affect the determination of the scaling function @xmath33 .
cft predictions have been confirmed only using the general theory of corrections to the scaling @xcite . in order to determine the function @xmath33
, we consider the ratio f^lat_n(x)= ( 1-x)^c(n-1/n)/6 , [ flat ] and , on the basis of the general cft arguments @xcite , we expect that the the leading correction to scaling can be effectively taken into account by the scaling ansatz @xmath261 for the ising model it has been found @xmath262 @xcite .
since for @xmath91 the at hamiltonian reduces to two uncoupled ising models , one naively expects @xmath263 along the whole self - dual critical line of the at model .
as function of @xmath264 for different models ( ising , susy , @xmath234 parafermions , and four - states potts model ) .
the blue - dashed line is the cft prediction .
the ( colored ) points close to the curve are extrapolations obtained with the finite - size scaling ansatz ( [ ansatz ] ) .
the black crosses are the monte carlo data used for the fits .
the block lengths used range from @xmath265 to @xmath266 . ]
hereafter we only consider @xmath267 .
we start our analysis from the susy point that ( assuming @xmath263 ) should have the smaller corrections to scaling . in fig .
[ susy_f2 ] we show monte carlo data at @xmath268 ( @xmath233 ) for @xmath257 plotted against the four point ratio @xmath29 defined as in eq .
( [ xfs ] ) .
we report with the blue dashed line the asymptotic cft result ( cf .
( [ atf2 ] ) ) . as in all other cases considered in the literature @xcite , the curves for @xmath35 at @xmath268 are not symmetric functions of @xmath269 , as instead the asymptotic cft prediction must always be @xcite .
this is due to the non - symmetrical finite - size corrections @xmath270 in eq .
( [ ansatz ] ) .
we extrapolate the result at @xmath271 using the ansatz ( [ ansatz ] ) and @xmath272 .
the extrapolations are reported as red points in fig .
[ susy_f2 ] .
there is a very good agreement between the extrapolations and the theoretical curve .
since the correction exponent @xmath272 is rather large , and so the corrections small , even small subsystems such as @xmath268 are enough to obtain a good extrapolation . in the inset of fig .
[ susy_f2 ] we report the monte carlo data for @xmath273 against @xmath274 .
the linear behavior in this inset confirms the validity of the ansatz ( [ ansatz ] ) and the reported straight lines are the fits giving the extrapolations reported in the main panel . versus @xmath275 .
the dashed lines are fits to the finite - size scaling ansatz ( [ ansatz ] ) fixing the value of @xmath276 .
left : the same plot in log - log scale .
, title="fig : " ] versus @xmath275 .
the dashed lines are fits to the finite - size scaling ansatz ( [ ansatz ] ) fixing the value of @xmath276 .
left : the same plot in log - log scale .
, title="fig : " ] we also investigate other points on the self dual line , namely the @xmath277-states potts model ( @xmath278 ) , the parafermion @xmath234 ( @xmath279 ) , the uncoupled isings ( @xmath91 ) . in fig .
[ all ] we report @xmath280 at fixed @xmath281 versus @xmath264 for all the mentioned models .
we report @xmath281 because it is the value of @xmath29 providing the most stable estimate , but also other values have been studied .
indeed , on one hand , the computational cost of the simulations decreases going toward @xmath282 ( the reason being evident from the definition of @xmath29 for which smaller lattice sizes are needed ) . on the other hand , scaling corrections become more severe in the region @xmath283 , as clear from the results for the susy model in fig .
[ susy_f2 ] .
thus @xmath281 represents the best compromise between these two drawbacks .
the dashed curves in the left panel of fig . [ fits ] are fits of the data with eq .
( [ ansatz ] ) obtained by fixing the value of @xmath284 to its predicted value ( cf .
( [ atf2 ] ) ) . there is a very good agreement with the full theoretical picture , confirming in particular the correctness of the exponent governing the leading correction to the scaling . for the @xmath234 parafermions and for the four - state potts model
, we needed very large values of @xmath12 in order to show the correct asymptotic behavior ( the range of @xmath12 reported in the plot is in fact @xmath285 ) .
this is made clearer in the right panel of fig .
[ fits ] where the same data are shown in log - log scale . in fig . [ all ]
we reports the fits obtained by fixing only the exponent of the corrections @xmath263 and leaving @xmath276 free . for all considered values of @xmath38 , the extrapolation of @xmath286 to @xmath271
is compatible ( within error bars ) with the expected result @xmath276 .
we finally study the correction amplitude @xmath270 in eq .
( [ ansatz ] ) .
this function is the main reason of the asymmetry in @xmath269 for @xmath257 and knowing its gross features could greatly simplify future analyses .
for the ising model , it has been found that @xmath287 for small @xmath29 , that is the same behavior of @xmath117 . since along the whole self - dual line @xmath288
, we would expect f_2(x)~x^1/4 .
[ f2hyp ] for the ising model ( i.e. @xmath91 ) , this scenario has been already verified with high precision @xcite .
obtained as @xmath289 as function of @xmath29 .
we show data for @xmath235 and various models ( susy , @xmath234 parafermions , ising model and the model corresponding to @xmath290 ) .
the blue - dashed lines are asymptotic fits to @xmath291 . ] in fig .
[ sub ] we report @xmath270 obtained as @xmath292 as function of @xmath29 ( in logarithmic scale to highlight the small @xmath29 behavior ) .
all data correspond to @xmath235 and various values of @xmath59 .
for the two largest values of @xmath38 ( @xmath234 parafermionic theory at @xmath279 and for the ising model at @xmath91 ) , we observe an excellent agreement with our conjecture @xmath287 .
however decreasing the value of @xmath38 , i.e. for the susy model at @xmath293 and for the model at @xmath290 , the behavior of @xmath270 is not as linear as before , especially for high value of @xmath29 .
nonetheless for @xmath294 the data confirm the behavior @xmath295 .
furthermore , it seems that for any @xmath296 , subleading terms in the expansion for small @xmath29 appear and they are vanishing only for the ising model .
this section is divided into two parts .
first we explain in a self contained way how to extract the spectrum of the reduced density matrix of some specific bipartitions of a pure state encoded in a tree tensor network ( ttn ) .
we only recall the basic definitions introduced in ref . @xcite and refer the reader to the literature for complementary works on the subject @xcite .
secondly we quickly recall how to use ttn to calculate the ground state of the anisotropic heisenberg spin - chain .
lattice and a @xmath297 lattice.,scaledwidth=80.0% ] we consider a one dimensional lattice @xmath298 made of @xmath299 sites , where each site is described by a local hilbert space @xmath300 of finite dimension @xmath197 . in this work
the state is the ground state @xmath301 of some local hamiltonian @xmath302 defined on @xmath298 , but in general it could be an arbitrary pure state @xmath303 defined on the lattice @xmath298 .
a generic state @xmath304 can always be expanded as @xmath305 where the @xmath306 coefficients @xmath307 are complex numbers and the vectors @xmath308 denote a local basis on the site @xmath309 .
we refer to the index @xmath310 that labels a local basis for site @xmath311 ( @xmath312 ) as a _ physical _ index . in the case
we are interested in , the tensor of coefficients @xmath307 in eq .
( [ eq : local_expansion ] ) is the result of the contraction of a ttn . as shown in fig .
[ fig : smalltree ] for lattices of @xmath313 and @xmath297 sites , a ttn decomposition of @xmath307 consists of a collection of tensors @xmath314 that have both _
bond _ indices and _ physical _ indices .
the tensors are interconnected by the bond indices according to a tree pattern .
the @xmath74 physical indices correspond to the leaves of the tree . upon summing over all the bond indices , the ttn produces the @xmath315 complex coefficients @xmath307 of eq .
( [ eq : local_expansion ] ) .
lattice in fig .
[ fig : smalltree ] .
( ii ) graphical representation of the constraints in eqs . ( [ eq : const1 ] ) and ( [ eq : const3 ] ) fulfilled by the isometric tensors .
, width=302 ] the tensors in the ttn will be constrained to be _ isometric _ , in the following sense . as shown in fig .
[ fig : isometric ] for the @xmath313 lattice of fig .
[ fig : smalltree ] , each tensor @xmath314 in a ttn has at most one upper leg / index @xmath316 and two lower indices / legs @xmath317 , so that its entries read @xmath318 ( everything can be generalized to tensors with more upper and lower legs @xcite ) .
then we impose that _ _ 1 , _ 2 ( w)__1 , _ 2^(w^)^_1 , _
2_ = _ . [ eq : isometry ] for clarity , throughout this paper we use diagrams to represent tensors networks as well as tensor manipulations .
for instance , the constraints for the tensors @xmath319 and @xmath320 of the ttn of fig .
[ fig : smalltree ] for a @xmath313 lattice , namely @xmath321 are represented as the diagrams in fig .
[ fig : isometric](ii ) .
we refer to a tensor @xmath314 that fulfills eq .
( [ eq : isometry ] ) as an _ isometry_. an intuitive interpretation of the use of a ttn to represent a state @xmath5 can be obtained in terms of a coarse - graining transformation for the lattice @xmath298 .
notice that the isometries @xmath314 in fig .
[ fig : smalltree ] are organized in layers .
the bond indices between two layers can be interpreted as defining the sites of an effective lattice . in other words ,
the ttn defines a sequence of increasingly coarser lattices @xmath322 , where @xmath323 and each site of lattice @xmath324 is defined in terms of several sites of @xmath325 by means of an isometry @xmath326 , see fig .
[ fig : coarsegrain ] . in this picture
, a site of the lattice @xmath324 effectively corresponds to some number @xmath327 of sites of the original lattice @xmath328 .
for instance , each of the two sites of @xmath329 in fig .
[ fig : coarsegrain ] corresponds to @xmath330 sites of @xmath328 .
similarly , each site of lattice @xmath331 corresponds to @xmath277 sites of @xmath328 . for a @xmath297 lattice @xmath328 with periodic boundary conditions ( the blue external circle )
is associated with a coarse - graining transformation that generates a sequence of increasingly coarse - grained lattices @xmath332 , @xmath333 and @xmath334 ( the inner circles ) .
notice that in this example we have added an extra index to the top isometry @xmath335 , corresponding to the single site of an extra top lattice @xmath334 , which we can use to encode in the ttn a whole subspace of @xmath336 instead of a single state @xmath5.,width=302 ] the use of isometric tensors , and the fact that each bond unambiguously defines two parts @xmath337 of the chain which are connected only through that bond as displayed in fig .
[ fig : bond ] , implies that the rank of that bond in the ttn is given by the schmidt rank @xmath338 of the partition @xmath337 @xcite .
thus the reduced density matrix @xmath10 for a set @xmath69 of sites of @xmath298 is @xmath339 where @xmath340 are the eigenvalues of @xmath10 .
it follows then the rnyi entanglement entropies @xmath8 are @xmath341 and @xmath141 @xcite . here
we show that in the case of the @xmath297 lattice of fig .
[ fig : smalltree ] there are three classes of indices , identified by their position in the ttn .
i ) physical bonds connect a single spin with the rest of the lattice , ii ) bond indices of the first layer connect a block of two adjacent spins to the rest of the lattice , iii ) bond indices of the third layer of the lattice connect four adjacent spins , to the other half .
this implies that the rank of the index is the schmidt rank of the respective partition .
, width=226 ] in the following we denote the ranks of the tensor @xmath326 , @xmath342 as @xmath343 .
in general , they fulfill @xmath344 meaning that @xmath326 projects states in @xmath345 into the smaller hilbert space @xmath346 . for a critical chain , the logarithmic scaling of the entanglement entropy ( cf .
( [ renyi : asymp ] ) ) implies that the rank of the isometries should at least grow proportionally to the length of the block represented by the effective spins @xmath347 which means that while moving to higher layer of the tensor network the rank of the isometries increases .
this also implies that the leading cost of the computation is concentrated in contracting the first few layers of the ttn .
if @xmath348 and we describe a pure state ( so that the rank of the @xmath349 is one ) the maximal rank of the tensors in the ttn is @xmath350 in ref .
@xcite it has been shown that i ) a ttn description of the ground state of chain of length @xmath74 with periodic boundary conditions can be obtained numerically with a cost of order @xmath351 .
ii ) from the ttn it is also straightforward to compute the spectrum @xmath352 of the reduced density matrix @xmath10 ( cf . eq .
( [ eq : rhoa ] ) ) when @xmath69 is a block of contiguous sites corresponding to an effective site of any of the coarse - grained lattices @xmath353 . fig .
[ fig : specteval ] illustrates the tensor network corresponding to @xmath10 for the case when @xmath69 is one half of the chain .
many pairs of isometries are annihilated .
in addition , the isometries contained within region @xmath69 can be removed since they do not affect the spectrum of @xmath10 . from the spectrum @xmath352
, we can now obtain the rnyi entropies @xmath8 .
the leading cost for computing the spectrum of the reduced density matrix @xmath10 for this class of bipartitions is due to the contractions of the first layers of the ttn .
when the bipartition is such that @xmath69 is a quarter of the chain , this implies a cost proportional to @xmath354 , where @xmath355 . of the reduced density matrix @xmath10 for a block @xmath69 that corresponds to one of the coarse - grained sites .
( i ) tensor network corresponding to @xmath10 where @xmath69 is half of the lattice .
( ii ) tensor network left after several isometries are annihilated with their hermitian conjugate . (
iii ) since the spectrum of @xmath10 is not changed by the isometries acting on @xmath69 , we can eliminate them and we are left with a network consisting of only two tensors , which can now be contracted together .
the cost of this computation is proportional to @xmath356.,width=340 ] it is also possible to compute the reduced density matrix @xmath10 when @xmath69 is composed of two disjoint subintervals @xmath357 and @xmath358 , where now each of the two intervals is a block of contiguous sites corresponding to an effective site of the coarse grained lattice .
the cost of this computation is again dominated by contracting the upper part of the tensor network , and the most expensive case is obtained by considering @xmath69 as the collection of two @xmath359 spins blocks , separated by @xmath359 spins .
the tensor network corresponding to this @xmath10 is shown in fig .
[ fig : spectevaltwoblocks ] .
also in this case many pairs of isometries are annihilated .
the isometries contained within the composed region @xmath69 can also be removed since they do not affect the spectrum of @xmath10 .
the cost of contracting this tensor network is proportional to @xmath360 < \mathcal{o}(\chi^6)$ ] .
of the reduced density matrix @xmath10 when @xmath69 corresponds to two coarse - grained sites separated by one coarse grained site from both sides .
( i ) tensor network corresponding to @xmath10 where @xmath69 is a quarter of the lattice .
( ii ) tensor network left after several isometries are annihilated with their hermitian conjugate . (
iii ) since the spectrum of @xmath10 is not changed by the isometries acting on @xmath69 , we can eliminate them and we are left with a network consisting of only few tensors , which can now be contracted together .
the cost of contracting this tensor network is proportional to @xmath361 < \mathcal{o}(\chi^6)$].,width=340 ] in the previous subsection we have shown how to extract the spectrum of the reduced density matrix for a single and a double spin block from a ttn state . in this manuscript
we are interested in reduced density matrices calculated on the ground - state of the anisotropic heisenberg spin chain ( xxz model ) in zero magnetic field , defined by the hamiltonian h=_j=1^l [ ^x_j^x_j+1+^y_j ^y_j+1+^z_j^z_j+1 ] , [ hxxz ] where @xmath362 are the pauli matrices at the site @xmath363 .
periodic boundary conditions are assumed .
we are interested in gapless conformal phases of the model , that is @xmath364 .
this phase is described by a free - bosonic cft compactified on a circle with radius that depends on the parameter @xmath152 = 2r_circle^2=12k_l= , [ etade ] where @xmath154 is the luttinger liquid parameter . ) and its analogous for the at model ( [ etaat ] ) .
the relation between @xmath38 and @xmath365 and the relation between @xmath154 and @xmath152 are the same for both xxz spin - chain and at model , but the relation between @xmath38 and @xmath152 ( or @xmath154 and @xmath65 ) is different . ]
the sign convention in the hamiltonian ( [ hxxz ] ) is such that the model is ( anti)ferromagnetic for @xmath366 ( @xmath367 ) .
hamiltonian ( [ hxxz ] ) is diagonalizable by means of bethe ansatz .
however , obtaining the spectrum of the reduced density matrix from bethe ansatz is still a major problem and only results for small subsystems are known @xcite . for this reason we exploit variational ttn techniques to obtain the ground state .
here we follow the variational procedure described in detail in ref .
@xcite , where the generic technique ( consisting of assuming a tensor network description of the ground state and minimize the energy variationally improving the tensors one by one as described , i.e. , in ref .
@xcite ) has been specialized and optimized for the case of a ttn .
we exploit translation invariance by using the same tensor at each layer of the ttn .
one could also improve the efficiency further by exploiting the @xmath368 symmetry of the hamiltonian ( [ hxxz ] ) , i.e. the rotations around the @xmath369 axis .
however we did not make use of this symmetry here .
as function of the chord length @xmath240 for different values of @xmath152 .
the dashed curves are fits to the function @xmath370 .
the reported data have been obtained with @xmath67 for @xmath371 and @xmath372 for the other values . ] in this section we report the ttn results for the rnyi entropies in the xxz spin - chain for a single and a double interval . as a main advantage compared to the classical monte carlo simulations performed for the at model , with a single ttn simulation
we obtain the spectrum of the reduced density matrix and hence any rnyi entropy , including von neumann @xmath11 .
oppositely with the monte carlo methods only rnyi entropies @xmath8 of integer order @xmath373 can be obtained and each of them requires an independent simulation .
we first present the ttn results for the single interval .
these have been already obtained with many numerical variational techniques @xcite and are reported here only to test the accuracy of the ttn and to fix units / scales etc . using variational ttn , we find the ground - state of the xxz hamiltonian ( [ hxxz ] ) and from this we extract the spectrum of the reduced density matrix of the single block , as explained in the previous section .
we then numerically obtain @xmath68 .
the maximum size of the chain that we consider is @xmath67 .
the subsystem lengths considered are @xmath374 .
notice that with the ttn method , using a binary tree as we are doing , we can effectively access only subsystems sizes of the form @xmath375 with @xmath167 arbitrary integer , as it should be clear from the previous section .
in particular this limits the calculation to even values of @xmath12 and we can not study the parity effects reported in ref .
@xcite .
we considered different values of the anisotropy parameter @xmath152 , namely @xmath376 .
the ttn becomes less effective for values of @xmath377 .
this can be easily traced back to the smallness of the finite - size gap that in the minimization process causes the algorithm to be stuck in meta - stable states when the system size is large enough .
this drawback could be cured by using larger values of @xmath378 ( and so larger computational cost ) , but as we shall see , the considered values of @xmath152 suffice to draw a very general picture of the entanglement . for the isotropic heisenberg antiferromagnet at @xmath379 we ignore the presence of logarithmic corrections to the scaling @xcite , that have a minimal effect for all our aims . as function of @xmath29 for various sizes of the chain @xmath380 , subsystem lengths @xmath381 , and @xmath382 .
different values of @xmath152 are distinguished by different colors , while different symbols denote different values of @xmath12 .
the arrows denote the ( asymptotically ) increasing subsystem sizes @xmath12 . ] as for the at model , we study the quantity @xmath249 defined by the ratio in eq .
( [ c2l ] ) .
the results are shown in fig .
[ xxzsingle ] for all considered values of @xmath152 .
the scaling corrections are evident , especially for larger values of @xmath152 , as expected @xcite . these corrections for @xmath383 are indeed of the form @xmath252 @xcite ( @xmath154 is defined in eq .
( [ etade ] ) ) .
the dashed lines reported in fig . [ xxzsingle ] are fits to this form for @xmath51 , showing the agreement between ttn data and the fits .
we checked that all the ttn data agree with the ones obtained in ref .
@xcite using density matrix renormalization group .
the agreement is perfect and for this reason we refer to the above paper for a detailed study of @xmath68 for @xmath384 .
we now consider a subsystem made of two parts @xmath357 and @xmath358 of equal length @xmath12 .
we start by studying the quantity @xmath385 for finite chains and extract the universal function @xmath284 by proper extrapolation . since we only consider even @xmath12 , corrections to the scaling are expected to be monotonic in @xmath12 also for @xmath35 , oppositely to the case of arbitrary @xmath12 parity @xcite .
the cft prediction for the function @xmath35 for the xxz chain is eq .
( [ f2 ] ) with @xmath38 given by eq .
( [ etade ] ) . as function of @xmath275 for various @xmath152 .
the dashed lines are fits to the function with the generalized finite-@xmath12 ansatz ( [ ansatz2 ] ) . ] in fig .
[ xxztr_2 ] we report ttn data for @xmath273 ( obtained with the ratio defined in eq .
( [ flat ] ) ) as function of the cross ratio @xmath29 for @xmath386 and subsystem sizes @xmath381 .
the different values of @xmath152 are denoted with different colors , while the different symbols stand for the various @xmath12 .
on the same figure we also show the asymptotic @xmath284 as dashed lines .
it is evident that strong scaling corrections affect the data , as expected .
colored arrows denote the direction of ( asymptotically ) increasing subsystem sizes .
very surprisingly , while for @xmath387 the asymptotic cft result is approached from below , for @xmath388 it is approached from above . moreover , for @xmath388 the behavior of the data is not monotonic .
this contrasts the results obtained for the at model in the previous sections and the ones obtained for the xx and ising spin - chains @xcite . as function of @xmath29 for various sizes of the chain , @xmath389 , and subsystem lengths @xmath381 .
we denote with different symbols the values of @xmath12 and with different colors the various @xmath152 .
the dashed curves are the theoretical results given by eq .
( [ fnv ] ) .
the arrows denote the ( asymptotically ) increasing subsystem sizes @xmath12 . ] in order to shed some light on this unexpected phenomenon , it is worth to look at @xmath390 as functions of @xmath12 for fixed values of @xmath29 . in fig .
[ xxzfits ] we report one of these plots for @xmath281 .
analogous figures are obtained for other values of @xmath29 .
corrections to the scaling are non - monotonic in the range @xmath391 . this phenomenon can be understood if further corrections to the scaling are taken into account .
there are two corrections that can be responsible of this behavior . on the one hand , corrections of the form @xmath392 ( from @xmath393 at @xmath51 ) for any integer @xmath167 are know to be present @xcite , on the other hand usual analytic corrections such as @xmath394 are generically expected to exist for any quantity from general scaling arguments .
thus the most general finite-@xmath12 ansatz has the form f_2^lat(x)=f_2^cft(x)+ + + , [ ansatz2 ] where the first correction is the _ unusual _ one employed also for the ashkin - teller model , and the other two are the ones just discussed .
the effect of subleading corrections is enhanced by the fact the the amplitude functions @xmath270 and @xmath395 or @xmath396 have opposite signs determining the non - monotonic behavior .
unfortunately , for values of @xmath152 for which the effect of subleading corrections is more pronounced ( i.e. @xmath397 ) , we have @xmath398 , making difficult to disentangle corrections with close exponents .
thus , in order to present analyses of a good quality , we ignore the last correction ( i.e. we fix @xmath399 ) .
to check the proposed scenario , we performed the fit of the data in fig .
[ xxzfits ] with the ansatz ( [ ansatz2 ] ) and @xmath399 . the results of the fits are reported in the same figure , showing perfect agreement with the data for all the values of @xmath152 .
we repeated the same analysis for other values of @xmath29 , finding the same quality of fits as for @xmath281 .
however , we can not exclude that corrections of the form @xmath400 have an important role .
now we report the same analysis performed for @xmath402 for the third moment of @xmath10 , i.e. @xmath403 .
again we consider finite - size xxz spin - chains and extract the universal function @xmath404 by finite - size analysis .
the expected cft result is given for general @xmath9 by eq .
( [ fnv ] ) . in fig .
[ xxztr_3 ] we show ttn data for @xmath405 ( obtained from eq .
( [ flat ] ) ) at @xmath389 and subsystem sizes up to @xmath406 .
we also show the theoretical curves given by eq .
( [ fnv ] ) . as for the @xmath51 ,
the asymptotic universal curve is approached from below for @xmath407 , and from above for @xmath408 .
furthermore , the behavior of the numerical data for @xmath409 is non monotonic .
this suggests that the ansatz in eq .
( [ ansatz ] ) is not enough to describe accurately the ttn data and further corrections to the scaling should be included as for @xmath402 . for @xmath401 ,
the leading corrections to the scaling are described by the ansatz ( [ ansatz ] ) , i.e. the leading exponent is @xmath410 .
thus , for the cases when subleading corrections are more important ( i.e. for @xmath411 ) the ordering of the exponents is @xmath412 and so it is reasonable to ignore the analytic correction .
thus we fit ttn data with the function @xmath413 in fig .
[ xxztr_3x05 ] we report ttn data for @xmath414 for @xmath281 and several values of @xmath152 .
the dashed lines are fits with the finite - size ansatz ( [ f3fits ] ) , that perfectly reproduce the data . at fixed @xmath281 as function of @xmath394 for @xmath381 ,
the considered values of @xmath152 are @xmath415 .
the dashed curves are fits with the ansatz ( [ f3fits ] ) ] ttn gives access to the full spectrum of the reduced density matrix of @xmath26 and so to the entanglement entropy @xmath416 as well . in fig .
[ xxzvn ] we report the function @xmath417 defined as f_vn^lat(x)=s_a_1a_2^(1)-s_a_1^(1)-s_a_2^(1)-13(1-x ) , for @xmath152 in the interval @xmath418 $ ] for various @xmath59 up to 128 and subsystem sizes @xmath419 .
we indicate with different symbols different values of @xmath152 , while the colors are for various sizes @xmath12 .
as known from many other investigations on single and double intervals ( quantum ising spin chain , xy model , xxz ) the von neumann entropy does not show oscillations with the parity of the subsystem and the corrections are much smaller , actually negligible from any practical porpouse .
[ xxzvn ] confirms this observation for the two interval entanglement entropy for the xxz spin - chain in a wide range of @xmath152 .
indeed , at fixed value of @xmath152 perfect data collapse is observed even for very small values of @xmath12 . in the interval
@xmath418 $ ] .
we show with different symbols the values of @xmath152 while different colors stand for different @xmath12 and lattice sizes . ] unfortunately , as already stated in the introduction , the cft prediction for @xmath420 is unknown for general @xmath29 because the analytic continuation of @xmath33 to non - integer @xmath9 is not achievable .
however , an expression for the leading term of the small @xmath29 expansion of @xmath420 has been recently extracted @xcite from eq .
( [ s2cft ] ) f_vn(x)=()^ , [ smallx ] where @xmath421 $ ] and @xmath45 is the euler function ( not to be confused with the @xmath45 matrix in eq .
( [ gammadef ] ) ) . in order to check the correctness of this formula , in fig .
[ xxzvn_log ] we report the same data for @xmath420 in a log - log scale to highlight the power - law behavior for small @xmath29 .
we also report the small @xmath29 expected from eq .
( [ smallx ] ) .
for @xmath422 the agreement is good , but it gets worse increasing @xmath152 .
the natural explanation is that the considered values of @xmath29 are not small enough for the asymptotic eq .
( [ smallx ] ) to be valid .
we should then include further terms in the small @xmath29 expansion .
as explained in ref .
@xcite , further coefficients in the expansion for small @xmath29 are difficult to obtain in general . however , there is a term that is very easy to obtain and that ( luckily enough ) is responsible of the previous disagreement . indeed , as shown in ref .
@xcite ( cf .
70 and 71 there ) the function @xmath33 has always ( i.e. independently of @xmath38 ) a simple @xmath423 contribution coming from the denominator in eq .
( [ fnv ] ) , i.e. @xmath424 , that can be easily analytically continued giving f_vn(x)=()^-3+o(x^2 ) . [ smallx2 ] notice that the added term becomes more important when @xmath52 is close to @xmath168 , i.e. in the xxz spin - chain when @xmath152 approaches @xmath168 . in fig .
[ xxzvn_log ] we also report the prediction ( [ smallx2 ] ) as dashed line , that is asymptotically in perfect agreement with the numerical data for all values of @xmath152 . ( the data for different @xmath152 are denoted with different symbols ) in log - log scale .
we used different colors to indicate the different block sizes @xmath12 and lattice sizes @xmath59 .
the continuous lines are the small @xmath29 behavior obtained from ( [ smallx ] ) .
the dashed lines are the small @xmath29 behavior where the @xmath423 term has been added as in eq .
( [ smallx2 ] ) . ]
in this manuscript we provided a number of results for the asymptotic scaling of the rnyi entanglement entropies in strongly interacting lattice models described by cfts with @xmath0 .
schematically our results can be summarized as follows .
* we provided the analytic cft result for the scaling function @xmath35 for @xmath425 in the case of a free boson compactified on an orbifold describing , among the other things , the scaling limit of the ashkin - teller model on the self - dual line .
the final result is given in eq .
( [ atf2 ] ) . *
we developed a cluster monte carlo algorithm for the two - dimensional ashkin - teller model ( generalizing the procedure of caraglio and gliozzi @xcite for the ising model ) that gives the scaling functions of the rnyi entanglement entropy ( for integer @xmath9 ) of the corresponding one - dimensional quantum model . with this algorithm
, we calculated numerically the scaling function @xmath35 of the at model along the self - dual line and we confirm the validity of the cft prediction . in order to obtain a quantitative agreement , the corrections
to scaling induced by the finite length of the blocks are properly taken into account .
* we considered the xxz spin chains by means of a tree tensor network ( ttn ) algorithm .
the low - energy excitations of model are described by a free boson compactified on a circle for which cft predictions are already available both for @xmath51 @xcite and for general integer @xmath9 @xcite .
taking into account the corrections to the scaling , we confirm these predictions ( that resisted until now to quantitative tests ) for @xmath426 .
furthermore , we provide numerical determinations of the scaling function of the von neumann entropy ( cf .
[ xxzvn ] ) for which cft predictions do not exist yet for general @xmath29 . for small @xmath29
we confirm the recent prediction of ref .
@xcite ( cf .
[ xxzvn_log ] ) .
the methods we employed ( classical monte carlo with cluster observables and ttn ) are very general techniques that can be easily adapted to other models of physical interest . on the cft side
, it must be mentioned that a closed form for the functions @xmath33 at integer @xmath9 for a free boson compactified on an orbifold is not yet available , but work in this direction is in progress @xcite .
we thank john cardy , maurizio fagotti , erik tonni , ettore vicari , and guifre vidal for useful discussions .
this work has been partly done when pc was guest of the galileo galilei institute in florence whose hospitality is kindly acknowledged .
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b * 82 * , 012405 ( 2010 ) . | we study the scaling of the rnyi entanglement entropy of two disjoint blocks of critical lattice models described by conformal field theories with central charge @xmath0 .
we provide the analytic conformal field theory result for the second order rnyi entropy for a free boson compactified on an orbifold describing the scaling limit of the ashkin - teller ( at ) model on the self - dual line .
we have checked this prediction in cluster monte carlo simulations of the classical two dimensional at model .
we have also performed extensive numerical simulations of the anisotropic heisenberg quantum spin - chain with tree - tensor network techniques that allowed to obtain the reduced density matrices of disjoint blocks of the spin - chain and to check the correctness of the predictions for rnyi and entanglement entropies from conformal field theory . in order to match these predictions ,
we have extrapolated the numerical results by properly taking into account the corrections induced by the finite length of the blocks to the leading scaling behavior . |
the filling radius of a simple loop @xmath0 in the plane is defined as the largest radius , @xmath1 , of a circle that fits inside @xmath0 , see figure [ 11b ] : @xmath2 , width=302 ] there is a kind of a dual point of view that allows one to generalize this notion in an extremely fruitful way , as shown in @xcite .
namely , we consider the @xmath3-neighborhoods of the loop @xmath0 , denoted @xmath4 , see figure [ 12 ] . ,
width=377 ] as @xmath5 increases , the @xmath3-neighborhood @xmath6 swallows up more and more of the interior of the loop .
the `` last '' point to be swallowed up is precisely the center of a largest inscribed circle .
therefore we can reformulate the above definition by setting @xmath7 given a compact manifold @xmath8 imbedded in , say , euclidean space @xmath9 , we could define the filling radius _ relative _ to the imbedding , by minimizing the size of the neighborhood @xmath10 in which @xmath8 could be homotoped to something smaller dimensional , e.g. , to a lower dimensional polyhedron .
technically it is more convenient to work with a homological definition .
denote by @xmath11 the coefficient ring @xmath12 or @xmath13 , depending on whether or not @xmath8 is oriented . then the fundamental class , denoted @xmath14 $ ] , of a compact @xmath15-dimensional manifold @xmath8 , is a generator of @xmath16 , and we set @xmath17)=0\in h_n(u_\epsilon x ) \right .
\right\},\ ] ] where @xmath18 is the inclusion homomorphism . to define an `` absolute '' filling radius in a situation where
@xmath8 is equipped with a riemannian metric @xmath19 , m. gromov proceeds as follows , cf . .
one exploits an imbedding due to c. kuratowski @xcite ( while the spelling of the author s first name used in @xcite starts with a `` c '' , the correct spelling seems to be kazimierz ) .
one imbeds @xmath8 in the banach space @xmath20 of bounded borel functions on @xmath8 , equipped with the sup norm @xmath21 .
namely , we map a point @xmath22 to the function @xmath23 defined by the formula @xmath24 for all @xmath25 , where @xmath26 is the distance function defined by the metric . by the triangle inequality we have @xmath27 and
therefore the imbedding is strongly isometric , in the precise sense of formula which says that internal distance and ambient distance coincide .
such a strongly isometric imbedding is impossible if the ambient space is a hilbert space , even when @xmath8 is the riemannian circle ( the distance between opposite points must be @xmath28 , not 2 ! ) .
we then set @xmath29 in formula and define @xmath30 exact calculation of the filling radius is discussed in section [ nine ] .
the related invariant called filling volume is defined in section [ four ] .
for the relation between filling radius and systole , see .
the defining text for this material is @xcite , with more details in @xcite .
see also the recent survey @xcite .
the systole , @xmath31 , of a compact non simply connected riemannian manifold @xmath32 is the least length of a noncontractible loop @xmath33 : @xmath34\not= 0\in \pi_1(x)}\operatorname{{\rm length}}(\gamma).\ ] ] this notion of systole is apparently unrelated to the systolic arrays of @xcite .
we will be concerned with comparing this riemannian invariant to the total volume of the metric , as in loewner s inequality . in section [ one ] , we recall the classical loewner inequality , as well as pu s inequality . in section [ four ] , we define an invariant called the filling volume , and state gromov s filling volume ( e.g. , area ) conjecture .
the notion of the successive minima of a lattice in banach space is recalled in section [ five ] .
the results on the precise calculation of filling invariants ( both the filling radius and the filling area ) are reviewed in section [ nine ] .
stable and conformal systoles are defined in section [ six ] . in section
[ seven ] , we recall the definition of the abel - jacobi map to the torus , and present m. gromov s optimal stable systolic inequality for @xmath15-tori .
higher dimensional optimal generalisations of loewner s inequality are discussed in section [ bank ] and section [ ik ] .
thus , in section [ bank ] , we recall j. hebda s inequality combining systoles of dimension and codimension 1 in the case of unit betti number , and present a generalisation to arbitrary betti number .
optimal inequalities combining varieties of 1-systoles appear in section [ ik ] . here
a necessary topological condition is the nonvanishing of the homology class of the lift to the maximal free abelian cover , of the typical fiber of the abel - jacobi map .
the relation of this condition to the generalized casson invariant @xmath35 of @xcite is examined in section [ thirteen ] .
the example of nilmanifolds is discussed in section [ eleven ] , and the general case treated in section [ marin ] .
the hermite constant , denoted @xmath36 , can be defined as the optimal constant in the inequality @xmath37 over the class of all _ flat _ tori @xmath38 , cf .
section [ five ] . here
@xmath36 is asymptotically linear in @xmath15 , cf .
the precise value is known for small @xmath15 , e.g. , @xmath39 ( see lemma [ 217 ] ) , @xmath40 .
it can be shown via the filling invariants that an inequality of type remains valid in the class of _ all _ metrics , but with a nonsharp constant on the order of @xmath41 @xcite .
m. gromov s proof uses inequality as a starting point . around 1949 ,
charles loewner proved the first systolic inequality , cf .
he showed that every riemannian metric @xmath19 on the torus @xmath42 satisfies the inequality @xmath43 while a metric satisfying the boundary case of equality in is necessarily flat , and is homothetic to the quotient of @xmath44 by the lattice spanned by the cube roots of unity .
the following estimate is found in ( * ? ? ?
* corollary 5.2.b ) .
namely , every aspherical compact surface @xmath45 admits a metric ball @xmath46 of radius @xmath47 , which satisfies @xmath48 p. pu s inequality @xcite admits an immediate generalisation via gromov s inequality .
namely , every surface @xmath32 which is not a 2-sphere satisfies the inequality @xmath49 where the boundary case of equality in is attained precisely when , on the one hand , the surface @xmath8 is a real projective plane , and on the other , the metric @xmath19 is of constant gaussian curvature .
consider a compact manifold @xmath50 of dimension @xmath51 with a distance function @xmath26 . here
@xmath26 could be induced by a riemannian metric @xmath19 , but could also be more general .
the notion of the filling volume , @xmath52 , of @xmath50 was introduced in @xcite , where it is shown that when @xmath53 , @xmath54 where @xmath8 is any fixed manifold such that @xmath55 . here
one can even take a cylinder @xmath56 .
the infimum is taken over all complete riemannian metrics @xmath19 on @xmath8 for which the boundary distance function is @xmath57 , i.e. , the length of the shortest path in @xmath8 between boundary points @xmath58 and @xmath59 is @xmath60 . in the case
@xmath61 , the topology of the 2-dimensional filling can affect the infimum , as is shown by example in ( * ? ? ?
* counterexamples 2.2.b ) .
the precise value of the filling volume is not known for any riemannian metric . however , the following values for the canonical metrics on the spheres ( of sectional curvature @xmath62 ) is conjectured in @xcite , immediately after proposition 2.2.a . [ fillsphere ] @xmath63 , where @xmath64 denotes the volume of the unit @xmath65-sphere .
this conjecture is still open in all dimensions .
the case @xmath61 can be broken into separate problems depending on the genus @xmath66 of the filling , cf . .
let @xmath67 . by a _ lattice _
@xmath68 in euclidean space @xmath69 , we mean a discrete subgroup isomorphic to @xmath70 , i.e. , the integer span of a linearly independent set of @xmath71 vectors .
more generally , let @xmath72 be a finite - dimensional banach space , i.e. , a vector space together with a norm @xmath21 .
let @xmath73 be a lattice of maximal rank @xmath74 .
[ mindef ] for each @xmath75 , define the _ @xmath76-th successive minimum _ of the lattice @xmath68 by @xmath77 thus , the first successive minimum , @xmath78 is the least length of a nonzero vector in @xmath68 .
if @xmath79 , then given a pair of vectors @xmath80 in @xmath68 , define the length @xmath81 of @xmath82 by setting @xmath83 .
then the second successive minimum , @xmath84 is the least length of a pair of non - proportional vectors in @xmath68 : @xmath85 , where @xmath82 runs over all linearly independent pairs @xmath86 .
the standard lattice @xmath87 satisfies @xmath88 note that the torus @xmath89 satisfies @xmath90 as it has the unit cube as a fundamental domain . here
the volume of the torus @xmath91 ( also called the covolume of the lattice @xmath68 ) is by definition the volume of a fundamental domain for @xmath68 , e.g. , a parallelepiped spanned by a @xmath12-basis for @xmath68 .
the volume can be calculated as the square root of the determinant of the gram matrix of such a basis . given a finite set @xmath92 in @xmath69
, we define its _ gram matrix _ as the matrix of inner products @xmath93
. then the parallelepiped @xmath94 spanned by the vectors @xmath95 satisfies @xmath96 consider the lattice @xmath97 spanned by @xmath98 and the sixth root of unity @xmath99
. then @xmath100 satisfies @xmath101 .
meanwhile , the torus @xmath102 satisfies @xmath103 .
[ 53 ] the hermite constant @xmath104 is defined in one of the following two equivalent ways : 1 .
@xmath104 is the _ square _ of the maximal first successive minimum , among all lattices of unit covolume ; 2 .
@xmath104 is defined by the formula @xmath105 where the supremum is extended over all lattices @xmath68 in @xmath69 with a euclidean norm @xmath21 . a lattice realizing the supremum is called _
critical_. such a lattice may be thought of as realizing a densest packing in @xmath69 , when we place balls of radius @xmath106 at the points of @xmath68 .
[ 217 ] let @xmath107 .
then we have the following value for the hermite constant : @xmath108 .
the corresponding optimal lattice is homothetic to the @xmath12-span of cube roots of unity in @xmath44 .
consider a lattice @xmath109 . clearly , multiplying @xmath68 by nonzero complex numbers does not change the value of the quotient @xmath110 choose a `` shortest '' vector @xmath111 ,
i.e. , we have @xmath112 . by replacing @xmath68 by the lattice
@xmath113 , we may assume that the complex number @xmath114 is a shortest element in the lattice .
we will denote the new lattice by the same letter @xmath68 , so that now @xmath115
. now complete @xmath62 to a @xmath12-basis @xmath116 , so that @xmath117 thus @xmath118 .
consider the real part @xmath119 .
we can adjust the basis by adding or subtracting a suitable integer to @xmath120 , so as to satisfy the condition @xmath121 thus , the second basis vector @xmath120 may be assumed to lie in the closure of the standard fundamental domain , cf .
@xcite @xmath122 ( for the action of @xmath123 in the upper half - plane of @xmath44 ) .
then the imaginary part satisfies @xmath124 , with equality possible precisely for @xmath125 the proof is concluded by calculating the area of the parallelogram in @xmath44 spanned by @xmath120 and @xmath62 as follows : @xmath126 in dimensions @xmath127 , the hermite constants are harder to compute , but explicit values ( as well as the associated critical lattices ) are known for small dimensions , e.g. , @xmath128 , while in dimension 4 , one has @xmath129 @xcite .
the lattice @xmath130 dual to @xmath68 may be described as follows .
if @xmath68 is the @xmath12-span of vectors @xmath131 , then @xmath130 is the @xmath12-span of a dual basis @xmath132 satisfying @xmath133 the berg - martinet constant , denoted @xmath134 , is defined as follows : @xmath135 where the supremum is extended over all lattices @xmath68 in @xmath69 with its euclidean norm .
a lattice attaining the supremum is called _ dual - critical_. like the hermite constant @xmath104 , the berg - martinet constant @xmath136 is asymptotically linear in @xmath71 .
its value is known in dimensions up to 4 .
[ 22bis ] in dimension 3 , the value of the berg - martinet constant , @xmath137 , is slightly below the hermite constant @xmath138 .
it is attained by the face - centered cubic lattice , which is not isodual @xcite , ( * ? ? ?
* proposition 2.13(iii ) ) , @xcite .
unlike the filling area and volume , the filling radius lends itself somewhat easier to precise calculation .
the following result was proved in @xcite . [ 91 ] let @xmath8 be a length space with distance function @xmath26 .
let @xmath139 be a subset .
let @xmath1 .
assume that the following two conditions are satisfied : 1 .
@xmath140 ; 2 .
@xmath141 for all @xmath22 . then @xmath142 .
let @xmath143 be the riemannian circle .
then @xmath144 more precisely , the neighborhood @xmath145 has the homotopy type of @xmath143 for @xmath146 , and the homotopy type of the sphere @xmath147 when @xmath148 , where @xmath149 .
using the set of vertices of a regular inscribed triangle as our subset @xmath150 in theorem [ 91 ] proves the upper bound .
the lower bound follows from the general inequality @xmath151 valid for an arbitrary essential manifold @xmath8 @xcite .
the more precise result on the homotopy type of the neighborhood was proved in @xcite using a kind of morse theory on the space of subsets of @xmath143 , for which regular odd polygons are the extrema , as discussed below .
let @xmath152 be the @xmath153-th extremal value of the diameter functional on the space of finite subsets of @xmath8 , with the convention that @xmath154 . here
a subset @xmath139 is extremal if small perturbations of size @xmath5 can decrease the diameter of @xmath155 at most quadratically in @xmath3 . for the riemannian circle we have a complete classification of the extrema , namely sets of vertices of odd regular polygons inscribed in the circle
thus , we obtain the following extremal values : @xmath156 for the @xmath15-sphere , the first extremum is the set of vertices of a regular inscribed @xmath157-simplex , but the higher ones are difficult to classify even on @xmath158 @xcite .
the precise calculation of the filling radius is possible in the following cases @xcite . the filling radius of the following two - point homogeneous spaces @xmath8 equals half the first extremal value @xmath159 : 1 .
@xmath160 , where @xmath161 , where @xmath162 denotes the ( constant ) value of sectional curvature ; 2 .
@xmath163 , where @xmath164 ; 3 .
@xmath165 , where @xmath166 , where @xmath162 denotes the maximal value of sectional curvatures .
meanwhile , for @xmath167 we have a strict inequality @xmath168 in general , understanding the homotopy type of neighborhoods of @xmath8 in @xmath169 depends on the study of the extremal values of the diameter functional , which is an interesting open question .
for example , the value of @xmath170 is unknown for @xmath171 , but progress was made in @xcite .
successful calculation of these extrema depends on analyzing certain semialgebraic sets , defined in terms of the distance functions among points , in the cartesian ( or symmetric ) powers of the space .
recently , l. liu @xcite undertook the study of the mapping properties of the filling radius .
we now turn to the related invariant of the filling area .
we report on the recent progress on calculating the optimal ratio @xmath172 of , in the case of hyperelliptic fillings , in the following sense .
we introduce the constant @xmath173 where @xmath174 denotes an orientable filling , of genus @xmath66 , of a riemannian circle @xmath143 , meaning that the inclusion of the boundary @xmath175 is strongly isometric , cf .
formula .
a related invariant appears in the systolic inequality . for simply connected fillings ( i.e. , by a disk @xmath176 ) , we have @xmath177 , by pu s inequality applied to the real projective plane obtained from @xmath178 by identifying pairs of opposite points of the boundary circle .
the case of genus 1 fillings has recently been solved , as well @xcite .
thus , @xmath179 given a filling by an orientable surface @xmath180 of genus @xmath66 , one identifies pairs of antipodal points of the boundary , so to form a nonorientable closed surface @xmath181 .
we construct the orientable double cover @xmath182 with deck transformation @xmath120 .
the pair @xmath183 is thus a real riemann surface of genus @xmath184 , which can be called ovalless since @xmath120 is fixed point free , cf .
@xcite . assuming that @xmath185 is in addition hyperelliptic @xcite
, one can prove that it satisfies a bound equivalent to the formula @xmath186 .
the result follows from a combination of two ingredients . on the one hand ,
one exploits integral geometric comparison with orbifold metrics of constant positive curvature on real surfaces of even positive genus , where the conical singularities correspond to weierstrass points on the hyperelliptic surface . on the other hand
, one exploits an analysis of the combinatorics on unions of closed curves , arising as geodesics of such orbifold metrics .
in a riemannian manifold @xmath32 , we define the volume @xmath187 of a lipschitz @xmath76-simplex @xmath188 to be the integral over the @xmath76-simplex @xmath189 of the `` volume form '' of the pullback @xmath190 .
the stable norm @xmath191 of an element @xmath192 is the infimum of the volumes @xmath193 over all real lipschitz cycles @xmath194 representing @xmath195 .
we define the stable @xmath76-systole of the metric @xmath19 by setting @xmath196 where @xmath21 is the stable norm in homology associated with the metric @xmath19 , while @xmath197 denotes the integral lattice in real homology , and @xmath198 is the first successive minimum , cf . definition [ mindef ] .
the conformally invariant norm @xmath199 in @xmath200 is by definition dual to the conformally invariant @xmath201-norm in de rham cohomology .
the latter norm on @xmath202 is the quotient norm of the corresponding norm on closed one - forms .
thus , given @xmath203 , we set @xmath204 runs over closed one - forms representing @xmath205 .
the conformal 1-systole of @xmath206 is the quantity @xmath207 satisfying @xmath208 on an @xmath15-manifold @xmath32 .
let @xmath8 be a smooth compact manifold with positive first betti number .
we define the jacobi variety @xmath209 of @xmath8 by setting @xmath210 the homotopy class of the _ abel - jacobi map _ can be defined as follows .
consider the abelianisation homomorphism on the fundamental group of @xmath8 , followed by quotienting by torsion .
consider a map @xmath211 associated with the resulting homomorphism .
the composition @xmath212 represents the desired homotopy class . when @xmath8 is equipped with a metric , the abel - jacobi map @xmath213 can be induced by the harmonic one - forms on @xmath8 , originally introduced by a. lichnerowicz @xcite , cf .
more precisely , let @xmath9 be the space of harmonic @xmath214-forms on @xmath8 , with dual @xmath215 canonically identified with @xmath216 . by integrating an integral harmonic @xmath214-form along paths from a basepoint @xmath217
, we obtain a map to @xmath218 . in order to define a map @xmath219 without choosing a basis for cohomology
, we argue as follows .
let @xmath220 be a point in the universal cover @xmath221 of @xmath8 .
thus @xmath220 is represented by a point of @xmath8 together with a path @xmath222 from @xmath223 to it . by integrating along the path @xmath222 ,
we obtain a linear form , @xmath224 , on @xmath9 .
we thus obtain a map @xmath225 , which , furthermore , descends to a map @xmath226 where @xmath227 is the universal free abelian cover . by passing to quotients
, this map descends to the abel - jacobi map .
the abel - jacobi map defined using harmonic forms is unique up to translations of the jacobi torus @xmath209 .
an optimal higher - dimensional generalisation of loewner s inequality is due to m. gromov @xcite ( cf .
* inequality ( 5.14 ) ) ) based on the techniques of d. burago and s. ivanov @xcite .
we give below a slight generalisation of gromov s statement . given a map @xmath228 between closed manifolds of the same dimension
, we denote by @xmath229 , either the algebraic degree of @xmath230 when both manifolds are orientable , or the absolute degree @xcite , otherwise .
we denote by @xmath231 the abel - jacobi map of @xmath8 , cf . ; by @xmath36 , the hermite constant , cf . definition [ 53 ] ; and by @xmath232 , the stable 1-systole of a metric @xmath19 , cf . formula .
[ 11a ] let @xmath233 be a compact manifold of equal dimension and first betti number : @xmath234 .
then every metric @xmath19 on @xmath8 satisfies the following optimal inequality : @xmath235 the boundary case of equality in inequality is attained by flat tori whose group of deck transformations is a critical lattice in @xmath236 .
note that the inequality is nonvacuous in the orientable case , only if the real cuplength of @xmath8 is @xmath15 , i.e. , the abel - jacobi map @xmath231 is of nonzero algebraic degree .
the method of proof is to construct a suitable map @xmath11 from @xmath8 to its jacobi torus , @xmath237 here the torus is endowed with the flat riemannian metric of least volume which dominates the stable norm .
the map @xmath11 has the following properties : 1 .
@xmath11 belongs to the homotopy class of the abel - jacobi map @xmath231 ; 2 .
the derivative of @xmath11 is volume - decreasing at every point .
the existence of such a map @xmath11 follows from the techniques of @xcite , as explained in @xcite .
inequality now follows from the definition of the hermite constant .
this approach was systematized and generalized in @xcite , as explained in section [ ik ] .
the material treated here is in @xcite .
an optimal stable systolic inequality , for @xmath15-manifolds @xmath8 with @xmath238 , is due to j. hebda @xcite : @xmath239 with equality if and only if @xmath32 admits a riemannian submersion with connected minimal fibers onto a circle . here
the systole , @xmath240 , and the stable systole , @xmath241 , coincide in codimension 1 ( i.e. , when @xmath242 ) for orientable manifolds .
thus @xmath243 . in general , the @xmath76-systole is defined by minimizing the @xmath76-dimensional area of _ integral _
@xmath76-cycles which are not nullhomologous .
let @xmath244 be a primitive element in the integer lattice in cohomology , and similarly @xmath245 in homology .
let @xmath246 be the harmonic 1-form for the metric @xmath19 .
then there exists a map @xmath230 to the circle such that @xmath247 using the cauchy - schwartz inequality , we obtain @xmath248 using the coarea formula , cf .
@xcite , @xcite , we obtain @xmath249 since the hypersurface @xmath250 is poincar dual to @xmath251 for every regular value @xmath252 of @xmath230 .
let us normalize the metric to unit total volume to simplify the calculations .
in the case @xmath253 , we have @xmath254 therefore @xmath255 proving hebda s inequality .
an optimal inequality , involving the conformal 1-systole , is proved in @xcite , namely inequality below .
this inequality generalizes simultaneously loewner s inequality , hebda s inequality , the inequality ( * ? ? ?
* corollary 2.3 ) , as well as certain results of g. paternain @xcite .
let @xmath8 be a compact , oriented , @xmath15-dimensional manifold with positive first betti number @xmath256 .
then every metric @xmath19 on @xmath8 satisfies @xmath257 where equality occurs if and only if the following three conditions are satisfied : 1 .
the stable norm in @xmath258 is euclidean ; 2 .
the deck transformations of the jacobi torus form a dual - critical lattice ; 3 .
the abel - jacobi map is a riemannian submersion with connected minimal fibers .
the proof of inequality is similar to the calculation . to conclude the argument , identity
is replaced by the inequality @xmath259 for a pair of minimizing elements @xmath260 note that inequality results from the definition of the berg - martinet s constant @xmath134 combined with the fact that the @xmath261 norm in cohomology is actually a euclidean norm since harmonic forms form a vector space .
a generalisation of gromov s inequality was obtained in @xcite , with a number of further generalisations in @xcite .
the following two theorems were proved in @xcite ( the second one is an immediate corollary of the first one ) .
denote by @xmath262}}\in h_{n - b}(\operatorname{{\overline{x}}};a)$ ] the class of a typical fiber of the map @xmath263 of , where @xmath264 or @xmath13 according as @xmath265 is orientable or not .
following gromov @xcite , denote by @xmath266 the infimum of @xmath267-volumes of cycles representing the class @xmath262}}$ ] .
note that this quantity is a topological invariant only if @xmath268 .
[ 12b ] let @xmath8 be a closed riemannian manifold of dimension @xmath269 .
let @xmath270 , and assume @xmath271 .
then every metric @xmath19 on @xmath8 satisfies the inequality @xmath272 [ 13 ] let @xmath8 be a closed orientable manifold .
let @xmath270 .
assume that @xmath273 , and @xmath262}}\not=0 $ ] .
then every metric @xmath19 on @xmath8 satisfies the following optimal inequality : @xmath274 the main tool in the proof of theorems [ 12b ] and [ 13 ] is a generalisation of the construction of an area - decreasing map in a situation where the dimension is bigger than the betti number . a suitable version of the coarea formula is then applied to this map to conclude the proof .
the paper @xcite contains a number of generalisations of such stable inequalities as well as the study of the boundary case of equality , with conclusions along the closing lines of section [ bank ] . in particular
, the abel - jacobi map is a submersion .
now let @xmath8 be a closed 3-manifold .
let @xmath35 be the extension of the casson - walker invariant defined in @xcite .
the general definition is a bit involved , but in our case the invariant can be expressed in terms of the self - linking number of a typical fiber of the abel - jacobi map , cf . .
we show in section [ thirteen ] that the nonvanishing of the @xmath35 invariant is a sufficient condition for the nonvanishing of the class @xmath262}}$ ] .
the argument runs roughly as follows .
consider the map @xmath275 of .
let @xmath276 .
let @xmath277 and @xmath278 be lifts of the corresponding fibers @xmath279 .
choose a properly imbedded ray @xmath280 joining @xmath71 to infinity while avoiding @xmath281 ( as well as its translates ) , and consider the complete surface @xmath282 with @xmath283 .
furthermore , @xmath284 for all @xmath285 , where @xmath286 denotes the group of deck transformations of the cover @xmath287 .
if @xmath288 is zero - homologous in @xmath265 , choose a compact surface @xmath289 with @xmath290 the linking number @xmath291 in @xmath8 can therefore be computed as the _ algebraic _ intersection @xmath292 where all sums and intersections are algebraic , and the curve @xmath293 is compact by construction .
the details of a rigorous proof are found in section [ marin ] .
therefore we obtain the following immediate corollary of theorem [ 13 ] .
[ 93b ] suppose @xmath8 is a three - manifold such that @xmath294 , with nonvanishing @xmath35-invariant .
then every metric @xmath19 on @xmath8 satisfies the inequality @xmath295 in the boundary case of equality , the manifold must be one of the bundles of example [ 105 ] . analyzing the condition
@xmath262}}\not= 0 $ ] leads to interesting questions about 3-manifolds , see section [ thirteen ] . in dimension 3
, there is a connection between systoles and the lusternik - schnirelmann category , denoted @xmath296 . a new invariant @xmath297 , called _ systolic category _ , is defined in terms of the existence of systolic inequalities of a suitable type @xcite .
it turns out that the two categories coincide in dimension three : @xmath298 .
this and other phenomena relating the two categories are discussed in @xcite . in the case @xmath299 , inequality is related to the filling area conjecture . for simplicity ,
let @xmath300 .
it was proved in @xcite that every metric @xmath19 on @xmath301 satisfies a `` pu times loewner '' inequality @xmath302 where @xmath303 is defined similarly to by allowing all possible topology of fillings .
all the inequalities discussed so far depend on the rather restrictive hypothesis @xmath304 . in the case
@xmath305 it is harder to obtain optimal inequalities , and typically the extremal metrics are not smooth , see @xcite .
recently , progress was achieved toward removing the topological assumption in loewner s inequality ( similarly to the generalisation of pu s inequality ) , which involves the study of surfaces of genus @xmath306 .
namely , all hyperelliptic surfaces satisfy loewner s inequality @xmath307 and in particular @xcite all metrics in genus 2 @xcite .
moreover , all surfaces of genus at least 20 satisfy loewner s inequality , as well @xcite .
[ equation]remarks the results of this section tie in with corollary [ 93b ] .
namely , proposition [ propvoul ] provides a necessary condition so that the invariant @xmath35 does not vanish .
the condition is the nonvanishing of the fiber class in the maximal free abelian cover .
thus the nonvanishing of @xmath35 is a sufficient condition for the inequality to be satisfied . from now on , unless otherwise mentioned , all the manifolds considered are smooth , compact , and oriented .
boundaries are oriented according to the outward normal first convention . in any ( oriented )
@xmath308-manifold @xmath8 , the _ linking number _ of two disjoint closed curves @xmath309 and @xmath26 with null homology classes in @xmath310 is defined as follows .
let @xmath311 be a tubular neighborhood of @xmath309 disjoint from @xmath26 .
there exists a curve @xmath312 in @xmath311 that is homologous to @xmath313 in @xmath311 for some integer @xmath314 , and that bounds a surface @xmath315 transverse to @xmath26 .
then the _ linking number _ of @xmath309 and @xmath26 in @xmath8 is defined as @xmath316 where @xmath317 denotes the algebraic intersection number in @xmath8 .
[ propvoul ] let @xmath8 be a connected closed three - manifold whose first betti number is two .
let @xmath318 and @xmath319 be two surfaces imbedded in @xmath8 whose homology classes generate @xmath320 .
the intersection of @xmath318 and @xmath319 is denoted by @xmath309 .
let @xmath321 be a parallel of @xmath309 in @xmath318 .
let @xmath227 be the maximal free abelian cover of @xmath8 , and let @xmath322 be a lift of @xmath309 in @xmath227 .
if the homology class of @xmath322 vanishes in @xmath323 , then the linking number @xmath324 of @xmath309 and @xmath321 in @xmath8 vanishes , as well .
this proposition will be proved in section [ marin ] as a particular case of a more general result , proposition [ propal ] , as suggested by alexis marin .
the two parallels of @xmath309 in @xmath318 are homotopic to each other in the complement of @xmath309 in @xmath8 and they are also homotopic to the two parallels of @xmath309 in @xmath319 .
we could equivalently define @xmath321 as the parallel of @xmath309 with respect to the framing of @xmath309 induced by @xmath318 or @xmath319 .
by poincar duality , under the assumptions of the proposition , there exists a basis @xmath325 of @xmath310 such that the homology class @xmath326 $ ] of any closed curve @xmath26 of @xmath8 reads @xmath327=\langle d , s_1\rangle_x^{\phantom{i } } a_1 + \langle d , s_2\rangle_x^{\phantom{i } } a_2,\ ] ] cf . .
in particular , we have @xmath328=0 $ ] in @xmath310 .
therefore , the number @xmath329 is well - defined .
in fact , if @xmath35 denotes the extension of the casson invariant defined in @xcite , and if @xmath330 is the cardinality of the torsion part of @xmath331 , then @xmath332 cf . .
thus the linking number does not depend on the choice of the transverse surfaces @xmath318 and @xmath319 whose homology classes generate @xmath320 .
an easy direct proof of this fact is given in @xcite .
let @xmath8 be a connected topological space , and let @xmath333 be a homomorphism .
the _ connected cover @xmath334 of @xmath8 associated to @xmath19 _ is the connected cover of @xmath8 where a loop of @xmath8 lifts homeomorphically if and only if its homotopy class is in the kernel of @xmath19 .
in particular , we have @xmath335 .
the covering group is the image of @xmath19 .
for example , the maximal free abelian cover @xmath265 of @xmath8 is associated with the natural composition @xmath336 since @xmath328=0 $ ] in @xmath310 , the covering map @xmath337 from @xmath227 to @xmath8 maps @xmath322 to @xmath309 , homeomorphically . in particular , @xmath322 is a closed curve .
proposition [ propvoul ] may be illustrated by the following example of the non - trivial circle bundles @xmath338 over the torus . for them
, we shall directly see that * the roles of @xmath309 and @xmath321 can be played by two disjoint fibers @xmath339 and @xmath340 , * @xmath341 does not vanish , and * @xmath342 $ ] . [
105 ] let @xmath343 be the circle bundle over the torus with euler number @xmath344
. denote by @xmath345 and @xmath346 the two @xmath143-factors of the base @xmath347 of @xmath338 .
let @xmath348 be a disk disjoint from the union @xmath349 .
the bundle is trivial both over @xmath176 and over its complement .
thus we have @xmath350 where @xmath351 is a section , and the gluing map reads @xmath352 ( up to signs ) .
let @xmath353 be the fiber .
then @xmath354 \oplus { { \mathbb z}}[s(y ) ] \oplus \frac{{{\mathbb z}}}{|e|{{\mathbb z } } } [ f].\ ] ] the surfaces @xmath318 and @xmath319 of proposition [ propvoul ] may be chosen to be @xmath355 and @xmath356 , since these surfaces are dual to the basis @xmath357 , \left [ s(x ) \right ] \right)\ ] ] of @xmath358 with respect to the algebraic intersection .
then the intersection @xmath359 is precisely the fiber @xmath339 , and its parallel induced by the surfaces is another fiber @xmath340 . in this case , if the loop @xmath360 bounds a section of the bundle over @xmath361 , then the loop @xmath362 bounds a section of the bundle over @xmath176 .
this allows us to see that @xmath363 bounds a surface that is pierced once by @xmath340 , so that the linking number satisfies @xmath364 cf . .
now , let us study the maximal free abelian covering @xmath365 associated with the map @xmath366 \oplus { { \mathbb z}}[s(y)]=g.\ ] ] the free abelian group @xmath286 acts on @xmath367 freely as the covering group .
therefore , @xmath368 becomes a @xmath369$]-module .
the ring @xmath369 $ ] is denoted by @xmath370 and is identified with @xmath371 $ ] by mapping @xmath372 $ ] and @xmath373 $ ] to @xmath374 and @xmath375 , respectively . consider the standard product covering @xmath376 then @xmath367 is obtained from the trivialisation of @xmath337 of over the complement of @xmath176 , @xmath377 by filling in the @xmath378 holes ( with boundaries the lifts of @xmath379 ) by @xmath378 copies of @xmath380 . here
we use the same gluing map as before , @xmath378 times , equivariantly
. then @xmath381 \oplus r [ \overline { \partial d}]}{(t_x -1)r[\overline{f } ] + ( t_y -1 ) r [ \overline { f } ] + r \left ( [ \overline{\partial d } ] \pm e [ \overline { f } ] \right ) } \\ & = \frac{r}{(t_x -1)r + ( t_y -1)r}[\overline{f } ] \\ & = { { \mathbb z}}\left [ \overline{f } \right ] . \end{aligned}\ ] ]
as it will be shown in remark [ rkvoulimpal ] below , proposition [ propvoul ] is a particular case of proposition [ propal ] that has been suggested and proved by alexis marin .
[ propal ] let @xmath8 be a connected closed three - manifold .
let @xmath318 and @xmath319 be two surfaces imbedded in @xmath8 that intersect transversely in @xmath8 along a curve @xmath309 .
let @xmath321 be a parallel of @xmath309 in @xmath318 .
let @xmath382 be the connected cover of @xmath8 associated with the composition @xmath383 & \mapsto & \langle d , s_2\rangle_x \end{array}\ ] ] where the first map is the hurewicz homomorphism , cf . .
let @xmath384 be a lift of @xmath309 in @xmath382 .
if the homology class of @xmath384 vanishes in @xmath385 , then the linking number @xmath329 of @xmath309 and @xmath321 in @xmath8 is well - defined and vanishes .
[ rkvoulimpal ] let @xmath386 be the connected cover of @xmath8 associated with the composition @xmath387 & \mapsto & \left ( \langle d , s_1\rangle_x,\langle d , s_2\rangle_x \right ) \end{array}\ ] ] where the first map is the hurewicz homomorphism . then @xmath386 is a cover of @xmath382 .
suppose the homology class of a lift of @xmath309 in @xmath386 vanishes in @xmath388 .
then its image in @xmath382 under the covering map , that is a lift of @xmath309 in @xmath382 , vanishes , as well .
therefore , assuming that proposition [ propal ] is true , replacing @xmath382 by @xmath386 in its statement yields another true proposition .
in particular , proposition [ propal ] implies proposition [ propvoul ] because in this case the above @xmath386 is precisely the maximal free abelian cover @xmath265 . in proposition [ propal ] that applies to @xmath308-manifolds with arbitrarily large betti numbers , the covering group is the subgroup @xmath389 of @xmath390 that is isomorphic to @xmath391 or @xmath390 .
let @xmath392 be the covering map .
assume that the homology class of @xmath384 vanishes in @xmath385 .
note that this implies that @xmath309 is rationally null - homologous in @xmath8 and that @xmath329 is well - defined .
there exists a surface @xmath393 in @xmath382 whose boundary @xmath394 lies in a small tubular neighborhood @xmath395 of @xmath384 such that * @xmath394 is homologous to @xmath396 $ ] in @xmath395 , for some @xmath314 , * @xmath395 does not meet @xmath397 , * the restriction of @xmath398 to @xmath395 is injective .
then @xmath399 and @xmath400 is the sum over the lifts of @xmath321 of their algebraic intersections with @xmath393 .
we now apply the following lemma [ lem114 ] to complete the proof of proposition [ propal ] .
[ lem114 ] for any lift @xmath401 of @xmath321 , the algebraic intersection of @xmath393 and @xmath401 vanishes .
the proof consists in seeing @xmath402 as the algebraic boundary of the compact oriented intersection of @xmath393 with a noncompact surface @xmath403 that is bounded by @xmath401 and that does not meet @xmath395 .
let us first construct @xmath403 .
consider a tubular neighborhood @xmath404 $ ] of @xmath405 such that@xmath406)$ ] reads @xmath407 $ ] in @xmath404 $ ] ( up to orientations ) .
let @xmath408 be the map to the unit circle in @xmath44 , defined as follows on the subset @xmath404 \subset x$ ] : @xmath409 & \longrightarrow & s^1\\ & ( x , t ) & \mapsto & \exp(i\pi t ) , \end{array}\ ] ] while @xmath410 maps the complement of @xmath404 $ ] in @xmath8 to the point @xmath411 .
note that the map @xmath410 induces the morphism @xmath412 of .
thus the composition @xmath413 induces the trivial map from @xmath414 to @xmath415
. therefore , it factors through the covering @xmath416 yielding a map @xmath417 such that @xmath418 . without loss assume that @xmath419 and that @xmath420.\ ] ] now , any lift @xmath401 of @xmath321 reads @xmath421 for some @xmath422 , and splits @xmath423 as the union of @xmath424 and @xmath425\!-\infty,0 ] \right).\ ] ] one of the non - compact subsurfaces @xmath426 and @xmath427 does not meet @xmath395
this will be our surface @xmath403 .
we may assume that the surface @xmath393 is transverse to @xmath403 .
then these two surfaces intersect along an oriented curve @xmath428 that is oriented so that the triple 1 .
tangent vector @xmath429 to the intersection curve , 2 .
positive normal vector @xmath430 to @xmath393 , 3 .
positive normal vector @xmath431 to @xmath403 is direct .
the curve @xmath428 is a collection of arcs and closed curves properly imbedded in @xmath403 since @xmath403 does not meet @xmath394 .
since the oriented boundary of @xmath428 ( that obviously vanishes in @xmath432 ) represents the algebraic intersection of @xmath433 with @xmath393 , the lemma is proved .
let us be slightly more explicit about this last argument .
a point @xmath220 of the oriented boundary of @xmath428 gets the sign @xmath434 such that the tangent vector @xmath435 of @xmath436 at @xmath220 is oriented as @xmath437 where @xmath438 is the outward normal vector to the curve at @xmath220 .
( in other words , final points of arcs get a positive sign while initial points get a minus sign . ) on the other hand , @xmath438 may be identified to the outward normal of @xmath403 and the triple @xmath439 is direct .
furthermore , @xmath440 may be identified with @xmath441 where @xmath442 is the sign of the intersection of @xmath443 and @xmath393 at @xmath220 .
thus , the triple @xmath444 is direct , too .
this shows that @xmath445 .
then the sum of the @xmath446 vanishes because there are as many initial points of arcs in @xmath447 as there are final points , and that makes the algebraic intersection of @xmath401 and @xmath393 that is the sum of the @xmath442 vanish , too .
this concludes the proof of lemma [ lem114 ] and the proof of the proposition .
note that lemma [ lem114 ] yields the following corollary .
let @xmath8 be a @xmath308-manifold with betti number @xmath448 suppose the lift @xmath68 of a typical fiber of the abel - jacobi map , to an infinite cyclic cover @xmath0 of @xmath8 is rationally zero - homologous .
equip @xmath68 with the framing induced by the abel - jacobi map .
then the self - linking of @xmath449 is zero .
this corollary is obviously not true when @xmath0 is replaced by the compact manifold @xmath8 itself , or by any _
finite _ cyclic cover of @xmath8 .
we are grateful to a. marin for suggesting and proving proposition [ propal ] .
v. bangert , c. croke , s. ivanov , and m. katz , _ filling area conjecture and ovalless real hyperelliptic surfaces _ , geometric and functional analysis ( gafa ) * 15 * ( 2005 ) , no . 3 , 577 - 597 . see ` arxiv : math.dg/0405583 ` r. b. s. brooks , r. f. brown , and h. schirmer , _ the absolute degree and the nielsen root number of compositions and cartesian products of maps _ ,
theory of fixed points and its applications ( so paulo , 1999 ) , topology appl . * 116 * ( 2001 ) , no . 1 , 5 - 27 . , _ systoles and intersystolic inequalities _ , actes de la table ronde de gomtrie diffrentielle ( luminy , 1992 ) , smin . congr . , vol . 1 , soc . math .
france , paris , 1996 , pp .
291 - 362 .
available at the following site : ` www.emis.de/journals/sc/1996/1/ps/smf_sem-cong_1_291-362.ps.gz ` | we investigate the filling area conjecture , optimal systolic inequalities , and the related problem of the nonvanishing of certain linking numbers in 3-manifolds . supported by the israel science foundation ( grants no . 620/00 - 10.0 and 84/03 ) ] supported by cnrs ( umr 5582 ) ] |
dipeptidyl peptidase-4 inhibitors ( gliptins ) are effective drugs in management of type 2 diabetes mellitus ( dm ) .
there are reports implicating them in causing acute pancreatitis , chronic pancreatitis , and pancreatic duct metaplasia ; leading to widespread concern .
although gliptins are increasingly being used in clinical practice , data on incidence of acute pancreatitis with this class of drug is lacking from our country .
we evaluated the extent of this adverse effect in patients on gliptins on our follow - up .
this study was conducted as a prospective , observational study in a tertiary care hospital setting .
patients with type 2 dm receiving one of the gliptins ( sitagliptin , vildagliptin , or saxagliptin ) for at least 1 month during the study period january 2012-june 2013 were included in the study .
equivalent doses of these three gliptins were used interchangeably during the period of the study depending on their availability in the hospital pharmacy .
detailed history regarding gall stone disease , pancreatitis , alcohol abuse , and drug use was obtained .
five of them had history of acute pancreatitis ( all mild ) > 6 months prior to inclusion which had completely resolved with no residual pseudocyst or chronic pancreatitis . during that episode , these patients were not on treatment with gliptins .
in addition to testing fasting and postprandial glycemia ; lipid profile , liver and kidney function test , serum amylase , and ultrasonography ( usg ) of abdomen was done focused at gall stone / sludge , pancreatic morphology , and calcification .
all other tests were done as laid down in relevant guidelines for type 2 dm during follow - up .
patients were explained regarding symptoms of acute pancreatitis ( abdominal pain , nausea , and vomiting ) and asked to report immediately to nearest medical help if it occurred .
acute pancreatitis was diagnosed based on raised serum amylase levels > 3 upper limit of normal ( uln ) with or without ultrasonographic changes in a patients with symptoms suggestive of acute pancreatitis . in asymptomatic patients ,
serum amylase and usg abdomen was performed every 3 months to exclude silent acute / chronic pancreatitis .
patients with history of gall stone disease , chronic pancreatitis , alcohol abuse ( > 10 g daily ) , consuming drugs known to cause pancreatitis ( glucocorticoids , antiretroviral therapy , azathioprine , valproic acid , furosemide , etc . ) , and hypertriglyceridemia ( triglyceride > 1,000 mg / dl ) were excluded .
patients who developed acute pancreatitis were withdrawn from the study , gliptins were discontinued and they were managed on the standard lines for acute pancreatitis based on its severity .
a total of 216 patients with type 2 dm on treatment with one of the gliptins for at least 1 month prior to inclusion in the study were seen during the period of the study .
thirty - one patients were excluded based on the set exclusion criteria ( gallbladder stone / sludge in 15 , alcohol abuse in nine , drug use in five , and triglyceride levels > 1,000 mg / dl in two patients ) . of the remaining 185 patients who were included ,
26 were obese ( body mass index ( bmi ) 25 kg / m ) and 43 overweight ( bmi : 23 - 24.9 kg / m ) .
total follow - up during the study period ( number of monthly visits number of patients ) was 2,464 patient - months ( 205.3 patient - years ) .
total duration of gliptin use varied from 1 month to 4 years in these patients ( median usage 22 months ) . during the study period , one patient ( 0.48 per 100 patient - years ) presented with acute abdomen with raised amylase levels in diagnostic range for acute pancreatitis .
asymptomatic elevation of serum amylase > 3 uln was noted in five patients ( 2.4 per 100 patient years ) , without any sonological evidence of pancreatitis , which resolved within 3 days of withdrawal of gliptins .
as the three available gliptins were used interchangeably by patients during the study period , no particular drug could be implicated in the causation of this adverse effect .
in this observational study , we noted one patient with acute pancreatitis ( an incidence of 0.48 per 100 patient - years ) which was mild and self - limiting on drug withdrawal . during the same period ,
incidence of acute pancreatitis in general population is reported to be around 1.9 per 1,000 patient years and is known to occur at a greater frequency in patients with diabetes ( 5.6 per 1,000 patient years ) .
this risk has been shown to be similar or up to six - folds higher in various observational studies with glucagon - like peptide 1 based therapies .
although drug - induced pancreatitis can occur at any duration of exposure , more than half of gliptin associated acute pancreatitis has been reported to occur in the first month of exposure .
gliptins are also implicated in causing silent chronic pancreatitis , but none was noted in our patients during the period of follow - up .
the limitations of this study are patient self - reporting of symptoms of acute pancreatitis , which often may be mild and ignored by the patient .
alcohol abuse of even less than the exclusion criteria used in this study may cause or contribute to acute pancreatitis .
only usg was used for imaging of the pancreas due to ease of performing and safety although ct scan is a better modality for pancreatic imaging .
amylase levels return to baseline within 48 h of onset of symptoms , hence delayed presentation may have led to a false negative normal amylase .
more patients with asymptomatic hyperamylasemia might have been missed as screening was done quarterly . to the best of our knowledge ,
this is first report of incidence of acute pancreatitis with use of gliptins from india .
larger prospective database with a diabetic and nondiabetic control population is likely to shed more light on this issue .
acute pancreatitis is well known to occur at a greater frequency in patients with type 2 dm .
the heightened risk of this dreaded disease is suspected with the use of gliptins . in this small study with its limitations
, we did not note any greater risk of acute pancreatitis than expected in a cohort of type 2 dm patients
. however , greater watchfulness for this dreaded adverse effect and avoidance of its usage in patients at high risk for pancreatitis is a prudent approach . | there are reports of acute pancreatitis with the use of dipeptidyl peptidase-4 inhibitors ( gliptins ) .
this class of drugs is widely being prescribed for type 2 diabetes mellitus ( dm ) in our country .
we evaluated the incidence of acute pancreatitis with the use of gliptins during the period january 2012-june 2013 .
patients of type 2 dm on treatment with any of the gliptins ( sitagliptin , vildagliptin , or saxagliptin ) for at least 1 month duration were included .
a total of 185 patients were included ( 205.3 patient years of follow - up ) .
five of them had history of acute pancreatitis ( all mild ) > 6 months prior to inclusion with complete resolution and no chronic pancreatitis .
one patient ( 0.48 per 100 patient years ) presented with mild acute pancreatitis which resolved in 8 days .
asymptomatic elevation of serum amylase > 3 upper limit of normal was noted in five patients ( 2.4 per 100 patient years ) , without any sonological evidence of pancreatitis , which resolved on withdrawal of gliptins .
none of the patients with previous history of pancreatitis had a recurrence of pancreatitis . in a group at low risk of acute pancreatitis , incidence of acute pancreatitis is low with the use of gliptins . |
metallic biomaterials , like titanium ( ti ) and its alloys , are widely used in medical applications .
excellent biocompatibility , high strength , and good corrosion resistance [ 1 , 2 ] make titanium alloys a good material for orthopaedic and dental implants .
current applications are , for example , bone screws and nails , parts of artificial heart valves , spinal fusion devices , and total hip replacements . occurring shielding effects ,
bone atrophy , and sequentially implant loosening are disadvantages when young 's modulus of solid implants ( tial6v4 : 114 gpa ) is much higher than the one of human cortical bone ( 1030 gpa ) [ 4 , 5 ] . by reasons of population ageing and increasing popularity of extreme sports as well as costs of implant replacement ( i.e. , revision surgery ) , implant life time has to be increased and optimized .
obviously , materials with mechanical properties closer to the ones of human bone are necessary to develop long lasting implants . here , increasing material porosity was the strategy chosen to decrease its rigidity .
another advantage of porous materials is the possibility of cell ingrowth for further stability of the osseointegrated implant [ 5 , 6 ] . a direct relation between pore size and bone formation
is assumed , since it provides surface and space for cell adhesion and bone ingrowth .
also the pore interconnection ( even below 100 m ) provides the way for cell migration and allows for an efficient in vivo blood vessel formation [ 7 , 8 ] .
several techniques have been developed to produce porous metal ( e.g. , chemical vapour deposition , space holder method , selective laser melting , and direct laser metal sintering ) and even applied to produce porous titanium [ 5 , 12 , 13 ] .
metal injection moulding ( mim ) has the advantages of fast production of rather high amount of complex and net - shaped parts ( i.e. , decreased fabrication costs ) and the potential to tailor material porosities by using different size of metal powder or adjusted sintering temperature . here
, mim technique was successfully applied to produce four kinds of porous tial6v4 specimens ( namely , small , medium ,
the porosity was investigated by means of x - ray tomography ( 3d ) and optical microscopy analysis ( 2d ) .
mechanical properties of each material were investigated via tensile , compression , and resonant ultrasound spectroscopy ( rus ) tests and the obtained results were compared and discussed .
material biocompatibility was tested with two cell lines ( saos-2 , mg-63 ) and also with primary cells ( human bone - derived cells , hbdc ) .
four different samples were obtained using spherical , gas - atomized tial6v4 grade 23 powders of different size with oxygen content in chemical analysis < 0.07% ( tls technik spezialpulver , bitterfeld , germany ) .
samples were named according to the particle diameter employed : small ( < 45 m ) , medium ( 4563 m ) , large ( 125180 m ) , and mix ( 90% 125180 m + 10% < 45 m ) . from each of these materials
three types of specimens were prepared , using mim : ( 1 ) dog - bone - shaped samples for tensile test ( according to iso 2740 ) ; ( 2 ) cylinder - shaped specimens for compression tests ( cut from tensile test specimens ) ; and ( 3 ) disc - shaped samples with a diameter of 10 mm and a height of 2 mm for biological tests . during manufacturing process
each individual compression test sample could be prepared plane - parallel by feeding forward the saw ; cutting at right angle was performed by visual judgement and therefore was not cogent perfect .
anyway , specimens were tested and show even higher strength compared to tensile tests and natural cortical bone ( table 1 ) . for biological tests mirror - polished nonporous
tial6v4 disc - shaped samples with a diameter of 10 mm were employed as reference specimen ( cut from a round bar ( f. w. hempel legierungsmetall gmbh & co. kg , oberhausen , germany ) ) , polished by conventional procedures followed by final manual polishing with a struers oxide polish suspension ( ops ) compound ( struers gmbh , hannover - garbsen , germany ) .
injection moulding , debinding , and sintering .
feedstock production .
gas - atomised spherical tial6v4 alloy powders and binder components ( mainly paraffin and polyethylene derivatives ; merck kgaa , darmstadt , germany , and basell polyolefine gmbh , frankfurt , germany ) were blended for 2 h using a z - blade kneader ( femix misch - und knettechnik gmbh , waiblingen , germany ) .
the feedstock production and powder handling were carried out in a controlled argon atmosphere .
the tensile test samples with an average length of 89.35 0.08 mm were moulded with a maximum injection pressure of 100 mpa at ~130c , thanks to an allrounder 320 s ( arburg gmbh + co kg , loburg , germany ) injection press . specimens for the compression tests were cut from the cylindrical part of tensile test samples with a ratio of 1 : 1.5 ( diameter : height ) .
the disc - shaped specimens were moulded with an mcp 100-ksa injection press ( mcp hek gmbh , lbeck , germany ) with a pressure of 0.45 mpa for small and medium , 0.7 mpa for mix , or 0.8 mpa for large .
temperature of the injector was adjusted to 115c ( small and medium ) or 120c ( mix and large ) . in the green state of the samples ,
the 30 mm disc - shaped specimens were cut into 10 mm discs with the help of a punch .
the chemical debinding of the samples was done for 20 h in hexane ( sigma - aldrich chemie gmbh , munich , germany ) to extract the paraffin in a solvent debinding furnace ( eba 50 , lmi gmbh , aschaffenburg , germany ) .
samples were then transferred to the sintering furnace ( xvac , xerion ofentechnik gmbh , freiberg , germany ) to perform the thermal debinding at 450c and 600c , each 1 h , under argon gas flow .
all specimens were sintered at 1300c for 2 h in a cold - wall furnace with molybdenum shieldings and tungsten heater under a vacuum of 10 mbar ( xvac , xerion ofentechnik gmbh , freiberg , germany ) .
investigation of the pore size distribution , pore diameters , and the materials porosity was determined by material cross sectional microphotographs ( optical microscopy ( om ) ; olympus pmg 3 ; olympus , hamburg , germany ) and further analysed by image analysis software ( analysis pro 5.0 ( olympus soft imaging solutions gmbh , mnster , germany ) and adobe - photoshop cs5 software ( adobe systems incorporated , version 12.0.5x32 ) ) .
first , the 2d pore volume was estimated via photoshop software by calculating the ratio between black ( pore ) and white ( material ) pixels . the second pore volume analysis ( 3d )
was performed using a phoenix nanotom x - ray tube tomography system equipped with a tungsten x - ray source ( ge sensing & inspection technologies gmbh , hrth , germany ) in quadruplicates .
scanning parameters were set to 140 kv source voltage , 45 a ( mix ) and 50 a ( large ) source current , 0.5 mm copper filter , 1000 ms ( large ) and 1250 ms ( mix ) exposure time , and 2304 2304 pixel detector size .
image reconstruction was accomplished using the software datosx reconstruction 1.5 ( ge sensing & inspection technologies gmbh , hrth , germany ) .
the compressed datasets ( 2x binning ) of the specimens mix and large were used in this study .
this was too low to analyse the pore sizes in small and medium . for mix and large the samples ' 3d pore volume was investigated using the software myvgl 2.1 ( volume graphics gmbh , heidelberg , germany ) .
scanning electron microscope ( sem ) measurements were done by an auriga 40 ( carl zeiss , oberkochen , germany ) at 3 kv accelerating voltage with the secondary - electrons detector and 3.5 mm working distance .
conventional leco melt extraction systems ( tc-436ar and cs-444 , leco , mnchengladbach , germany ) were used to determine the level of the interstitial elements oxygen and carbon .
the tensile tests were performed according to the standard test din en iso 6892 - 1 , at room temperature at a strain rate of 1.2 10 s. for the test a servohydraulic structural test machine ( schenck , zwick gmbh & co. kg , ulm , germany ) equipped with a 100 kn load cell was applied to at least 6 samples of each material .
the compression tests ( din 50106 ) were carried out under the same conditions using the same test machine as described for the tensile tests ( n = 6 ) . the determination of the shrinkage ( s(% ) )
was done by comparing the samples length as green part ( l1 ) and after sintering ( l2 ) :
( 1)s(%)=(l1l2l1)100 .
resonant ultrasound spectroscopy ( rus ) tests were carried out in triplicates of each material at room temperature using the resonant frequency damping analyser ( rfda , imce , genk , belgium ) professional according to the test standard astm e 1876 .
the rfda software ( imce , genk , belgium ) calculates the elastic modulus via geometry , density , and frequency damping of the tested material .
saos-2 cells were cultured for 2 days on mix samples as described in section 2.2.1 .
samples were then critical - point - dried before scanning electronic microscope ( sem ) evaluation ( auriga ; carl zeiss , jena , germany ) . in brief , after a glutaraldehyde ( sigma - aldrich chemie gmbh , munich , germany ) fixation step , carriers were stained in osmium tetroxide ( sigma - aldrich chemie gmbh , munich , germany ) prior to an alcoholic dehydration row .
subsequently , samples were critical - point - dried in 2-propanol ( sigma - aldrich chemie gmbh , munich , germany ) to preserve cell morphology by a leica em cpd300 ( leica mikrosysteme vertrieb gmbh , wetzlar , germany ) .
cells on carriers were then visualised by low voltage mode in charge contrast , using the sem inlens detector .
samples were also broken in the middle in order to appreciate cell - sample colonisation along the cross section .
the results are presented as mean values standard deviation ( table 1 , figure 4 ) . for the pore size distribution ( figure 3 )
statistics were performed using the sigmastat software package ( systat software gmbh , erkrath , germany ) . prior to statistical analysis data
standard analysis comparing two treatments ( for mtt assay ; figure 4(a ) ) was performed by using the t - test .
analysis of more than two treatments ( for mtt / dna ; figure 4(b ) ) was done by using the one - way analysis of variance ( anova ; comparison against control group ) .
depending on the data distribution , either a one - way anova or an anova on ranks was performed .
prior to biological tests culture substrates were cleaned by immersing them in 2% hellmanex solution ( hellma , mllheim , germany ) and ultrasonication at room temperature for 20 min .
these steps were repeated by replacing the hellmanex solution with chloroform , then ethanol ( merck , darmstadt , germany ) , optional chloroform / methanol ( 80/20 ) ( merck , darmstadt , germany ) to remove cell debris ( if samples were used before ) , and finally ddh2o ( millipore , billerica , massachusetts , usa ) .
then samples were autoclaved for 20 min at 121c ( systec ve-150 , systec gmbh , wettenberg , germany ) .
hbdc isolation was performed on bone splinters obtained from total hip replacement and approved by the local ethical committee [ 15 , 16 ] .
, cancellous bone pieces of about 5 mm were cut and cultured in dulbecco 's modified eagle medium ( dmem ) glutamax - i ( invitrogen corporation , karlsruhe , germany ) with 10% foetal bovine serum ( fbs , paa laboratories gmbh , linz , austria ) , 1% penicillin , and streptomycin ( invitrogen corporation , karlsruhe , germany ) for about 10 days without medium change . at visibility of outgrowing hbdc ,
human osteosarcoma cell lines saos-2 and mg-63 were obtained from the european collection of cell cultures ( ecacc , salisbury , uk ) .
mg-63 and saos-2 cells were cultured in dmem glutamax - i with 10% fbs and mccoy 's 5 a ( invitrogen corporation , karlsruhe , germany ) with 10% fbs , respectively .
all cells were cultivated at 37c under 5% co2 and 95% humidity controlled atmosphere .
metabolic activity was determined by the cell proliferation kit mtt ( roche diagnostics gmbh , mannheim , germany ) .
the mtt assay is based on the cleavage of the yellow tetrazolium salt mtt ( thiazolyl blue tetrazolium bromide ) into purple formazan by metabolically active cells .
hbdc , saos-2 , or mg-63 cells were seeded on the different porous and mirror - polished ( control ) specimens in a density of 5 10 cells / sample in 50 l medium in beforehand agarose coated 24-well plates .
after 40 min adherence , 1 ml of cell specific medium was added .
the cells were then further cultured for 1 or 3 days before addition of 100 l of mtt solution ( 5 mg / ml mtt in pbs ) . after an incubation period of 4 h
the formed crystals were lysed by adding 1 ml solubilization solution ( 10% sds in 0.01 m hcl ) and incubated overnight in a humidified atmosphere at a temperature of 37c and 5% co2 .
the photometric quantification of the solubilized formazan product was performed using an elisa reader ( tecan sunrise , tecan deutschland gmbh , crailsheim , germany ) at 570 nm with a reference wavelength of 655 nm
.
quantitative analysis of dna . this method , adapted from labarca and paigen , is based on the property of bisbenzimide fluorochrom to bind dna .
samples were washed with phosphate - buffered saline ( pbs ) and immersed in 1 ml papain solution ( 10 mg / ml papain , boehringer mannheim gmbh , mannheim , germany ; 5 l mercaptoethanol in 0.1 m nah2po4 , vwr international gmbh , darmstadt , germany ) at 60c in order to digest the cells .
the crude lysates were then incubated with 100 l of a bisbenzimide solution ( 2 m nacl , 15 mm sodium citrate , and 2 g / ml bisbenzimide ( hoechst 33528 ; serva feinbiochemica gmbh & co. , heidelberg , germany ) for 15 minutes in the dark and subsequently fluorometrically measured ( excitation and emission wavelengths 355 nm and 460 nm , resp . , with a victor3 v. multilabel plate readers , perkin elmer , rodgau - juegesheim , germany ) .
the dna concentrations were then obtained from a standard curve prepared with human genomic dna ( sigma , taufkirchen , germany ) .
pictures of each material taken by sem and optical microscopy are presented in figure 1 .
the 3d pore volume of mix and large ( figure 2 ) obtained via x - ray tomography was found to be 29.2 0.6% and 34.1 0.5% of the complete material volume for mix and large , respectively . in both materials
pore analysis from optical microscopy achieved pore volumes of 5 1% , 11 1% , 33 5% , and 34 1% for small , medium ,
mix , and large , respectively ( see table 1 ) .
the pore diameters were clustered in 25 m steps ( see figure 3 ) .
the calculated complete numbers of pores are 793 , 806 , 127 , and 101 for small , medium , mix , and large , respectively . for the small material nearly 100% of the pores are in the range between 0.1 and 25 m .
90% of medium pore sizes are between 0.1 and 25 m and the remaining ( 10% ) are between 25.1 and 50 m .
. about 55% of the pores are up to 25 m in diameter , nearly 20% between 25.1 and 50 m and from 50.1 to 100 m it is 10% in each step . between 100.1 and 175 m 5% of the pores can be observed in each 25 m cluster .
the maximum for large is up to 25 m with nearly 70% .
mix , such that the ratio is twice decreased between 25.1 and 175 m .
however , large is the only material exhibiting pore diameters of more than 200 m .
tensile tests were performed in order to obtain young 's modulus ( e ) , elongation to fracture ( f ) , ultimate tensile strength ( uts ) , and yield strength ( ys ) for the four materials ( presented in table 1 in normal type ) .
small samples show young 's modulus of about 100 gpa , which is close to bulk material .
the medium material has a little lower value of about 90 gpa , while young 's modulus value decreases extremely for mix and large ( 31 and 18 gpa , resp . ) .
the elongations of small and medium reach up to 13.5% and 5.3% , whereas
small and medium show much higher uts compared to mix and large .
from compression tests , compressibility ( c ) , ultimate compression strength ( ucs ) , and compressive yield strength ( cys ) were obtained from 6 samples of the same materials as mentioned above ; the results are presented in table 1 in bold .
the compressibility for all materials is about 25% except for large which is 14% .
small and medium show uts above 1300 mpa , whereas mix and large are below 700 mpa . the cys of small and medium is higher than 700 mpa and for mix and large it is below 300 mpa . from resonant ultrasound spectroscopy ( rus )
materials small and medium are above 92 gpa , whereas mix and
the sample shrinkage which occurs during the sintering process was examined by the difference in the axial dimension of the dog - bone - shaped
the green part length was detected to be 89.35 0.08 mm for all materials .
after sintering for 2 hours at 1300c , the length of the samples changed differently for each material .
small , medium , mix , and large showed percentage shrinkage of 11.8 0.04% , 10.8 0.05% , 4 0.4% , and 2.9 0.3% , respectively .
the carbon content after the sintering process for all specimens was below 500 g per g. the oxygen content , presented in table 1 with values between 1,500 and 2,000 g per g , is in the common range for this material .
the aforementioned values for oxygen and carbon content are typically observed after the mim processing and do not reduce the ductility of these materials .
mtt assays were carried out with two bone cell lines ( saos-2 and mg-63 ) and with one bone - primary cell type ( human bone - derived cells , hbdc ) for each porous material ( with n = 4 ) to study cell reactions ( i.e. , viability ) either after one day or three days of culture . to have more accurate
cell viability analyses the mtt absorbances were normalized by sample dna content which is directly correlated with the number of adherent cells .
generally , a higher viability with increasing porosity can be observed ( figure 4 ) .
hbdc , saos-2 , and mg-63 viabilities are also enhanced after 3 days of culture ( figure 4(a ) ) .
normalization of the mtt results to the samples dna content after 1 day results in increased values with raised porosity ( figure 4(b ) ) .
investigation of cell ingrowth was performed in a first test by breaking a cell culture disc of material mix and exploring the braking edge via sem for cells . in figure 5 , cells are visible in about 735 m inside the material at an angle of 43.2. pa1 labels the point at the outer surface of the material .
metal injection moulding technology was successfully applied to produce four different porous materials with three different tial6v4 powder grain sizes . after studying their mechanical properties ,
the optical appearance of the freshly produced mim parts as well as metallographic treated specimens is quite homogeneous ( i.e. , pore / metallic part distribution ) .
large , due to a diminished pore volume fraction caused by the addition of the finer granulated powder .
young 's moduli of about 1821 gpa and 3142 gpa for large and mix , respectively , are in a quite close range to that of bone ( 1126 gpa ) [ 23 , 26 ] . furthermore the ultimate tensile strength ( uts ) , yield strength ( ys ) , and elongation values of mix and large are lower than the ones of small and medium ; however , they are as well closer to the ones of bone ( see table 1 ) and possible additional bone ingrowth could further stabilize these materials .
therefore , a medical application of those materials seems to be beneficial to reduce stress - shielding effects observed for nonporous bulk titanium alloy implants [ 4 , 5 , 8 ] , consequently preventing implant loosening .
however , the materials small and medium , made from finer powder grain , result in young 's modulus close to that of bulk tial6v4 and are therefore applicable in the field of conventional implementation . mix and large can be pertinent materials for less load - bearing implant applications such as smaller bone defect corrections .
the specimens for mechanical tests and cell culture tests were both produced with the same process ( mim ) but with different machines .
mechanical tests rely on samples with standardised dimensions , but the dog - bone shaped samples can not be used in cell culture . therefore , it was necessary to use two different machines for sample production . however , the basic raw material ( feedstock ) was the same for all specimens . because the binder powder ratio is chosen in such a way that just the space between the packed powder particles is filled , no significant difference in green density is possible , even if different moulding parameters or machines are applied .
because all the following processing steps ( e.g. , debinding and sintering ) are absolutely the same for all specimens , biological and mechanical test samples reveal the same microstructure and porosity . if at all , only very little and not significant differences are possible .
it is highlighted by simulation that bone ingrowth in material with 50% interconnected porosity and pore sizes about 150300 m will dramatically reduce stress shielding effects .
additionally , quicker and more mature bone formation was obtained using a porous ( 70% porosity with 170 m mean pore size ) rather than a solid structure .
it is pointed out in vivo that material porosity fraction plays a crucial role in tissue ingrowth , highlighting that a 30% porosity provides an excellent tissue ingrowth proofed by an increased calcium concentration within the pores .
accented the pore 's interconnection to be fundamental . with x - ray tomography ( 3d analysis )
pore volumes of 29% and 34% for mix and large , respectively , were shown as well as the interconnected pore network , consisting of just one single pore in these materials , thus fulfilling criteria presented above .
the interconnection between the pores could be proofed by applying the abovementioned software after the tomography data was reconstructed .
a criticism factor could be the tomography resolution of just about 12 m ; this resulted in the distance of the sample between x - ray source and detector in the experimental setup .
anyway , this is an additional unusual method ( 3d ) to the routinely used metallographic method ( 2d ) for pore volume detection and the data shows good compliance ( table 1 ) .
an improvement would be the use of smaller samples during x - ray tomography , but for this study it was considered to be nonessential .
in vitro
it was observed that all tested cell types show higher viability with higher porosity of the sample ( figure 4 ) .
the mtt results ( figure 4(a ) ) of hbdc and mg-63 after one day show similar results , whereas the values for saos-2 on materials control ( co ) and small are decreased .
the viability increased for all tested cell types after 3 days , in case of saos-2 and mg-63 much stronger than for hbdc .
this can be explained by the faster doubling time of the cell lines compared to primary cells ( hbdc ) . to avoid the influence of cell growth rate , the results after 1 day culture were normalized with the dna content on each specimen ( figure 4(b ) ) .
this is suggestive of the highest compliance to this material for hbdc , then saos-2 , and followed by mg-63 .
as mentioned above the volume and interconnectivity of the pore network should be suitable for cell ingrowth .
small and medium exhibit pore diameters ( analysed from 2d optical microscopy pictures ) up to 50 m without interconnected pores .
mix and large on the other hand show pore diameters up to 175 m and for large some pores are even bigger than 200 m ( see figure 3 ) . the highest value for pore diameter is 0.125 m for mix and for large . but in contrast to small and medium , mix and large show pore diameters between 50 and 175 m as well . in large , for example , about 22% of the pores are bigger than 50 m .
the size of hbdc , which are one of the most important cells in osseointegration , is known to be between 20 and 30 m in diameter with a varying cell shape and elongated cell processes when attached .
additionally , it has already been shown that bone ingrowth is possible in materials with a mean pore size of 100300 m .
furthermore the connections between the pores of porous biomaterials are an important pathway between the pores [ 7 , 29 ] and recommended to be at least 2040 m in vitro and 2050 m in vivo for cell penetration . in figure 1
the sem pictures of mix and large already illustrate the open porous structure of these scaffolds .
it was already shown that cells can colonize materials with 200 m pore diameter , and even if the results of this study show a high amount of small pores below 25 m , the ratio of pore volume is mainly influenced by the pores with large volume . additionally , due to the polishing process to obtain the 2d pictures of the materials ,
apparent small pores can be obtained ( i.e. , it depends on at which plane the polishing process is intersecting the pore ( sphere ) : at lower and upper levels , diameters will be smaller ) . furthermore , the numbers of smaller and bigger pores are gradually decreasing and increasing , respectively , for material with increased powder particle sizes .
therefore , cell ingrowth for mix and large is expected and demonstrated in a preliminary test .
cell ingrowth appeared to reach the middle of material mix in cell culture samples ( figure 5 ) .
the recommended pore sizes are a controversy discussed topic and in vivo tests would be great evidence .
the results of this study show that porous tial6v4 processed by mim could be a well - suited net - shaped material for medical application . a material with a completely interconnected pore volume of about 30% and
this could prevent stress shielding in two ways : the mechanical properties are closer to that of bone and the connection with the tissue could take place under the visible surface .
we assume that the porous materials could lead to less revision surgery , but in vivo tests should be the next strategy . | increased durability of permanent tial6v4 implants still remains a requirement for the patient 's well - being .
one way to achieve a better bone - material connection is to enable bone ingrowth into the implant .
therefore , a new porous tial6v4 material was produced via metal injection moulding ( mim ) .
specimens with four different porosities were produced using gas - atomised spherical tial6v4 with different powder particle diameters , namely ,
small
( < 45 m ) , medium ( 4563 m ) , mix ( 90% 125180 m + 10% < 45 m ) , and large ( 125180 m ) .
tensile tests , compression tests , and resonant ultrasound spectroscopy ( rus ) were used to analyse mechanical properties .
these tests revealed an increasing young 's modulus with decreasing porosity ; that is , large and mix exhibit mechanical properties closer to bone than to bulk material . by applying x - ray tomography ( 3d volume ) and optical metallographic methods ( 2d volume and dimensions )
the pores were dissected .
the pore analysis of the mix and large samples showed pore volumes between 29% and 34% , respectively , with pore diameters ranging up to 175 m and even above 200 m for large . material cytotoxicity on bone cell lines (
saos-2 and mg-63 ) and primary cells ( human bone - derived cells , hbdc ) was studied by mtt assays and highlighted an increasing viability with higher porosity . |
Germany's Deutsche Boerse AG, the company that runs the stock exchange in Europe's largest economy, could soon take over the New York Stock Exchange.
Specialist Evan Solomon, left, resumes trading in shares of NYSE Euronext on the floor of the New York Stock Exchange Wednesday, Feb. 9, 2011. Stock market operator NYSE Euronext confirms it's in "advanced... (Associated Press)
Traders work on the floor of the New York Stock Exchange Wednesday, Feb. 9, 2011. Stock market operator NYSE Euronext confirms it's in "advanced discussions" about a potential business combination with... (Associated Press)
Traders work on the floor of the New York Stock Exchange Wednesday, Feb. 9, 2011. Stock market operator NYSE Euronext confirms it's in "advanced discussions" about a potential business combination with... (Associated Press)
NYSE signage adorns the top of trading posts on the floor of the New York Stock Exchange Wednesday, Feb. 9, 2011. Stock market operator NYSE Euronext confirms it's in "advanced discussions" about a potential... (Associated Press)
FILE - In this Feb. 2, 2011 file picture, traders work in the Frankfurt stock exchange , Deutsche Boerse. Stock market operator NYSE Euronext confirms it's in "advance discussions" about a potential... (Associated Press)
Traders gather at the post that handles shares of NYSE Euronext as they wait for trading to resume, on the floor of the New York Stock Exchange, Wednesday, Feb. 9, 2011. Stock market operator NYSE Euronext... (Associated Press)
Traders gather at the post that handles shares of NYSE Euronext as they wait for trading to resume, on the floor of the New York Stock Exchange, Wednesday, Feb. 9, 2011. Stock market operator NYSE Euronext... (Associated Press)
NYSE Euronext Inc., which also operates exchanges in Europe, said Wednesday it is in "advanced discussions" about a possible merger with Deutsche Boerse, owner of the Frankfurt stock exchange.
The new company would have dual headquarters in New York and Frankfurt. The announcement came hours after news of a $2.9 billion merger between the London Stock Exchange and TMX Group Inc., parent company of the Toronto Stock Exchange.
Deutsche Boerse shareholders would hold 59 to 60 percent of the combined company. NYSE Euronext said it expected the two market operators to combine their businesses under a new legal entity incorporated in the Netherlands.
NYSE Euronext's shares jumped 14 percent to close at $38.10 in New York.
The New York Stock Exchange is already the world's largest stock market. But its parent, the $9.9 billion NYSE Euronext, isn't even the largest exchange company in the U.S. That title belongs to the $20 billion CME Group Inc. CME runs the Chicago Mercantile Exchange, where wheat, corn and pork belly futures are traded, as well as a number of other exchanges.
"The real motivation here is really about competing with the CME Group," said Larry Tabb, founder and CEO of the Tabb Group. Increased competition has made stock trading less profitable. So the answer is to get bigger, he said.
But the thought of a German company taking over the NYSE could run into trouble with Congress, Tabb said. "It's going to get interesting," he said.
The NYSE Group, operator of the New York Stock Exchange, bought Euronext for $10.2 billion in 2007. The combined company handles stock and derivative markets in Amsterdam, Brussels, Lisbon and Paris as well as the NYSE Liffe derivatives market.
Deutsche Boerse, whose predecessor was founded in 1585, operates the stock market in Europe's largest economy. It also runs Europe's largest derivative exchange, the Eurex.
Aite Group analyst Simmy Grewal said more mergers may be on the way. Shares in other exchanges jumped on the news. The Nasdaq OMX Group Inc., the IntercontinentalExchange and CBOE Holdings Inc. all gained more than 4 percent. CME Group rose 1 percent.
Deutsche Boerse AG chief executive Reto Francioni would become the new group's chairman, and NYSE's CEO Duncan Niederauer, based in New York, its CEO.
The new company's executive committee would be drawn equally from the current leadership of both companies.
For Deutsche Boerse, the deal would represent a breakthrough in its aim to strengthen its international profile. Deutsche Boerse had been in merger talks with NYSE Euronext three years ago, but no deal was reached.
In 2006, the company tried to buy Euronext NV in a bid to build a pan-European stock exchange, but it eventually gave up, clearing the way for NYSE to merge with Euronext, which then formed the world's first trans-Atlantic stock exchange.
In 2005, a Deutsche Boerse takeover bid for Britain's London Stock Exchange Group PLC did not succeed.
___
Craft reported from New York. Greg Keller contributed from Paris. ||||| (See Corrections and Amplifications item below.)
After 219 years as the citadel of American capitalism, the New York Stock Exchange was near an agreement to be acquired by Deutsche Börse AG in a deal that would create the world's largest financial exchange.
With the parent of the New York Stock Exchange and Germany's Deutsche Borse in advanced talks to merge, Aaron Lucchetti and Dennis Berman look at the likely impact on Wall Street as the financial capital of the world.
If a deal is reached and regulators approve, the combined company would trade more stocks and futures than any rival in the world and more options than any U.S. exchange. The takeover would culminate a decade of tie-ups by exchanges around the world eager to find new sources of growth and catch up with smaller rivals that have been quicker to embrace new and lucrative kinds of trading.
For New York, the move is symbolic of the city's fading dominance on the world stage as other countries are drawing investors directly to their markets. The move also is a recognition that securities trading today goes on at all hours and in all time zones, making the actual bricks and mortar of Wall Street far less important than before.
"New York is going to be important, but it's not the financial center. Capital markets are everywhere now," said Michael LaBranche, CEO of LaBranche & Co, the family-run firm that traded on the floor of the New York Stock Exchange for 87 years before it sold that part of its business to Britain's Barclays Capital in 2010.
Antitrust experts cautioned that the proposed deal could face tough regulatory scrutiny in Europe, as the new behemoth would dominate share and derivatives trading in the European Union—and in Washington, where tempers may rise over a crown jewel of the economy falling into foreign hands.
The exchanges, which are presenting the deal as a merger of equals, said the combination would leave 60% of the company in the hands of Deutsche Börse shareholders, with NYSE Euronext shareholders holding the remaining 40%. The combined company, with a putative market capitalization of some $25 billion as of Wednesday, would be incorporated in the Netherlands and split its headquarters between Frankfurt and New York.
Deutsche Börse Chief Executive Reto Francioni would become chairman, and NYSE Euronext chief Duncan Niederauer would be the new company's CEO under a board drawn equally from both companies.
The proposed all-stock deal is driven by growing competition from purely electronic exchanges, not only in stock trading but also in more-profitable derivative contracts such as options and futures. It lets NYSE and Deutsche Börse fight back against rising competitors such as CME Group Inc. and private exchanges known as "dark pools" run by big securities firms.
A deal would extend NYSE's lead as the largest share-trading venue in the world, adding the Frankfurt Stock Exchange to the New York Stock Exchange and the four European exchanges owned by NYSE.
The new entity would supplant CME Group as the world's largest futures exchange and create the biggest U.S. options group, as measured by contract volume. NYSE Euronext's two options platforms, combined with Deutsche Börse's International Securities Exchange market, amounted to about 40.5% of the U.S. options market last month.
NYSE Euronext and Deutsche Börse are in advanced merger talks, a combination that would create one of the world's largest share- and derivatives-trading platforms. Aaron Lucchetti has details.
Interest over a merger between Singapore and Australia's exchanges has been reignited after Deutsche Börse neared an agreement to buy the NYSE. WSJ's Jake Lee talks to Hong Kong Bureau Chief Peter Stein on possible tie-ups between Asian exchanges.
Global stock listing and U.S. stock trading would be based in New York, people familiar with the situation said. The global derivatives business would be led from Frankfurt, and Paris would host the technology arm and European stock trading.
The merger marks the NYSE's second European deal in just five years. In 2006, the NYSE beat out Deutsche Börse to buy Paris-based Euronext, which boasts exchanges in Amsterdam, Paris and elsewhere.
In 2008 and again in 2009, following their bidding war for Euronext, the German exchange and NYSE discussed a possible merger. But talks foundered because of internal management disputes at Deutsche Börse and disagreements about where a merged company would be based.
The two sides had been planning to announce a deal next week, but put out a statement Wednesday disclosing the talks after word leaked out on a German online financial site, said people familiar with the matter. The companies are in advanced talks, though no terms have been set. Directors will need to sign off on the deal—and a host of regulatory challenges awaits on both sides of the Atlantic.
The plan is likely to trigger an in-depth probe at the European Commission, the executive arm of the EU, said Simon Holmes, partner and head of the EU and Competition department in the London office of international law firm SJ Berwin. "It would be a very complicated deal likely to require a detailed … investigation by the European antitrust regulator," Mr. Holmes said.
The plan drew a cautious, low-key response from American politicians and regulators faced with control of an iconic U.S. institution. The Justice Department, the Securities and Exchange Commission and the U.S. Committee on Foreign Investment all would have a role in signing off on any deal.
Shareholders and those concerned about the Big Board's competitive status applauded the news. NYSE rose 14% to $38.10, while shares of Deutsche Börse were halted in Frankfurt after rising 1.7% to €58.42.
But for those who remember the glory days, when the New York Stock Exchange was the unchallenged center of world finance, there was trouble containing the dismay.
The NYSE "is not the same iconic place that it was in its heyday," said William Higgins, a 74-year-old retired NYSE trader, who still owns about 70,000 shares of the company. He recalls when the NYSE was a private club and traders gained entry by buying a "seat" that entitled them to do business there. "It doesn't mean life won't go on, but to those of us who have been called New Yorkers, to not have that air of sophistication, the sense that 'this is where things get done,' it's sad."
According to lore, New York stock trading can be traced to 1792, when traders signed an agreement under a buttonwood tree on Wall Street. Since then, the exchange has grown into a symbol of American capitalism where thousands of global companies are listed.
For two centuries, trading was face-to-face, conducted between individuals on the exchange floor. When the World Trade Center was attacked in 2001, the exchange unveiled a huge Stars and Stripes on the front of its building, and a symbol of American resilience was born.
Today, the great majority of NYSE trading is done electronically. Actual floor trading tends to be so quiet that some traders began spending time in a lounge where they could watch movies during the day. The lounge was closed after a Wall Street Journal article mentioned it. In Frankfurt, the German exchange voted in November to end face-to-face trading entirely in May of this year.
According to a person familiar with plans, several hundred jobs would likely be cut over time, but most of the cost cutting would be in technology, and fewer than 100 jobs would be cut in New York. Deutsche Börse and NYSE Euronext said a combination could generate €300 million in annualized savings, some 10% of their cost base.
To avoid nationalistic concerns over the name, one idea is to avoid using the word Deutsche or the acronym NYSE, said one person familiar with the plans, who stressed that no decision has been made.
"I wish them luck. I hope they know what they are doing," said veteran stock trader Alan "Ace" Greenberg, a former Bear Stearns Cos. chairman who now is vice-chairman emeritus at J.P. Morgan Chase & Co.
Corrections & Amplifications
The potential purchaseof NYSE Euronext by Deutsche Börse AG could generate €300 million ($408 million) in annual cost savings, the companies said. In addition, the American Stock Exchange was acquired by NYSE Euronext in 2008. An earlier version of this story incorrectly said the cost-savings target was $300 million, and a graphic accompanying the continuation of the article incorrectly said the American Stock Exchange had been acquired by Nasdaq OMX Group
Write to E.S. Browning at [email protected], Jacob Bunge at [email protected] and Aaron Lucchetti at [email protected] | – The raucous cathedral of American capitalism, the New York Stock Exchange, is about to be bought by the Germans. If regulators approve the deal, the acquisition of NYSE Euronext (which owns the NYSE) by Deutsche Börse AG (which owns the Frankfurt stock exchange) would create the world's largest financial exchange. The move is bound to face intense scrutiny from regulators in Europe, where the new operation would dominate trade, and in Washington, where acquisition by a foreign company will pique nationalist sentiment, reports the Wall Street Journal. Deutsche Börse would own 60% of the combined company, estimated to be worth some $25 billion, while NYSE Euronext shareholders would hold 40%. The operation's incorporation papers would be filed in the Netherlands, and its headquarters would be split between New York and Frankfurt. The AP notes that while the NYSE is already the world's largest stock market, NYSE Euronext isn't the largest exchange company in the US. That title belongs to the $20 billion CME Group, which runs the Chicago Mercantile Exchange. "The real motivation here is really about competing with the CME Group," said the head of a financial markets' research and strategic advisory firm. Increased competition has made stock trading less profitable. So the answer is to get bigger, he said. |
You may love your Tesla, but that doesn’t make it any less prone to accidents than other cars. If you want an example, consider that a Tesla driver in Utah recently found that his Model S loaner had parked itself automatically into the back of a trailer.
After analyzing logs, the carmaker told him that he’s the only person to blame for the accident. Apparently, the car’s auto-parking feature was initiated, which is why the car hit the back of the trailer.
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The Summon feature is still in beta and requires human oversight. Tesla advises users to monitor the self-parking feature at all times and intervene to avoid obstacles that could cause accidents.
The driver, Jared Overton, said that he did not activate the Summon feature and that he was near the vehicle for some 20 seconds talking about it with a nearby worker at the business he was visiting. Overton said he parked well behind the trailer, but the car somehow drove itself into it, failing to detect the trailer’s bed.
Overton and the worker discovered the car a few minutes later when exiting the business.
“We were trying to figure out how on earth the vehicle started on its own,” Overton told KSL. “What happened with this kind of rogue vehicle?”
Tesla sent a letter to Overton telling him that it was practically his fault, suggesting he may have invoked the Summon feature and that he may have failed to monitor the car.
“Tesla has reviewed the vehicle’s logs, which show that the incident occurred as a result of the driver not being properly attentive to the vehicle’s surroundings while using the Summon feature or maintaining responsibility for safely controlling the vehicle at all times,” the letter said.
The Summon feature “was initiated by a double-press of the gear selector stalk button, shifting from Drive to Park and requesting Summon activation” Tesla explained. It all happened three seconds after Overton exited the car and closed the door, the letter explained.
The driver disagrees, saying that even if he accidentally started Summon, he would have been able to hear it and stop it.
“Even during that 15, 20-second walk right here, we would have easily heard the impact of the vehicle into the back of the trailer,” Overton said. “They can tell me what they want to tell me with the logs, but it doesn’t change what we know happened here.”
“They’re just assuming that I sat there and watched it happen, and I was OK with that,” Overton said.
A Tesla spokesperson told KSL that the Summon feature is in beta, and each driver has to agree to certain terms and conditions before enabling it. These conditions say that the driver has to be in proximity of the car when using its autonomous features to be able to assume manual control if something goes wrong.
“This feature will park Model S while the driver is outside the vehicle,” the statement said. “Please note that the vehicle may not detect certain obstacles, including those that are very narrow (e.g., bikes), lower than the fascia, or hanging from the ceiling. As such, Summon requires that you continually monitor your vehicle’s movement and surroundings while it is in progress and that you remain prepared to stop the vehicle at any time using your key fob or mobile app or by pressing any door handle. You must maintain control and responsibility for your vehicle when using this feature and should only use it on private property.”
Overton said the statement practically dismissed the experience of two witnesses. “Imagine if a child was right there — I guarantee that they would be responding to this a lot differently,” Overton said. “I will not feel safe with my little boy playing in the garage or the driveway if there’s the potential for a rogue vehicle.” ||||| A Tesla owner in Utah says that he returned to his parked Model S to find that it had crept forward and crashed into the trailer parked ahead of it. The man claims that this all went down without explanation; Tesla refutes that claim, saying that after taking a look at the car's logs, it determined that the Summon feature had been activated, which autonomously calls the car to (or from) the waiting driver without anyone behind the wheel.
The owner says that he was answering questions about the car from a passerby, so it's entirely possible that he opened the app and accidentally activated Summon (for what it's worth, he claims he didn't). But here's the thing: it doesn't matter. Under no circumstances should a production vehicle autonomously collide with a parked vehicle mere feet ahead of it. I think that's common sense, right? Am I saying anything controversial?
As a refresher, here's Tesla's video explaining how Summon works:
A letter to the owner from a regional Tesla service manager obtained by KSL says that "the incident occurred as a result of the driver not being properly attentive to the vehicle's surroundings while using the Summon feature or maintaining responsibility for safely controlling the vehicle at all times." Perhaps! But cars — by virtue of the fact that people of all walks of life and levels of attentiveness use them — are supposed to be far more bulletproof than this by the time they reach production. It's why the FCA just recalled over a million cars with confusing shift levers, because a driver who isn't paying attention could fail to put it in park.
In other words, Summon — and similar features that will inevitably come from other manufacturers — can't rely on an attentive owner to keep the car from smashing into something. It's one of the reasons why Google and a half-dozen automakers are moving more slowly with commercial autonomous deployments. Tesla will be quick to note that Summon is "in beta," but owners are going to use it either way, and unfortunately, we can't always expect them to use good judgement.
We can't be required to be smarter than the software
The notion of safety-critical "beta" software in deployment on commercial vehicles is a relatively new one, and it's something that regulatory agencies aren't equipped to deal with. I suspect that in a decade or two, there will be a well-established framework of tests that systems like Summon will have to pass before being allowed on a production car. But for now, it's the Wild West.
In a statement to KSL, Tesla says that Summon "may not detect certain obstacles, including those that are very narrow (e.g., bikes), lower than the fascia, or hanging from the ceiling." In this incident, the trailer is very high — it only comes as low as the midpoint of the Model S's windshield. But we've seen autonomous vehicles solve much harder problems than this (just watch any of Nvidia's keynotes on computer vision in self-driving cars from the past couple years). And coincidentally, the Model S is equipped with a forward-facing camera mounted at rear view mirror height.
That is to say: "beta" or no, owner liability disclaimer or no, a car capable of autonomously crashing itself into a stationary object in normal operating conditions should never have been sold. Tested, yes — sold, no.
We humans just aren't smart enough to handle something like that.
Update May 11th 3:02PM ET: We saw the letter that Tesla sent to the vehicle's owner, which details what happened. You can read our full story here.
Letting your Tesla drive itself is a bad idea | – The owner of a Tesla Model S says his car went "rogue" while nobody was inside it and drove into a parked trailer. Tesla's response: It was the guy's own fault. Jared Overton of Utah says he parked his Tesla in front of a business, behind a vehicle with a trailer, while running errands in Lindon on April 29, per KSL. He paused briefly outside the car to answer questions from a curious employee of the business, went inside, then came out after a few minutes later to find his car had magically migrated into the trailer, per BGR. “We were trying to figure out how on earth the vehicle started on its own,” says Overton. Tesla looked at the vehicle logs and concluded that Overton had activated the car's "Summon" feature, which it allows it to park without a driver. And the company lays the blame on Overton, not on a software glitch. "The incident occurred as a result of the driver not being properly attentive to the vehicle's surroundings while using the Summon feature or maintaining responsibility for safely controlling the vehicle at all times," Tesla says, adding the Summon feature is in beta and drivers who use it agree to monitor the vehicle. Overton doesn't think he activated the feature, and a post at the Verge raises the possibility that he did so accidentally while answering questions about the car. Even so, "under no circumstances should a production vehicle autonomously collide with a parked vehicle mere feet ahead of it," writes Chris Ziegler. Simply put, he adds, the software needs to be smarter than fallible humans. The damage to the car was a relatively scant $700, but, says Overton, "I will not feel safe with my little boy playing in the garage or the driveway if there's the potential for a rogue vehicle." (A man died when his Tesla went into a pool.) |
.- On Wednesday, a fiery Pope Francis chastised those who spend Mass talking to others, looking at their phone or even taking pictures during papal liturgies, saying these are distractions that take focus away from the “heart of the Church,” which is the Eucharist.
“The Mass is not a show: it is to go to meet the passion and resurrection of the Lord,” the Pope said Nov. 8. “The Lord is here with us, present. Many times we go there, we look at things and chat among ourselves while the priest celebrates the Eucharist... But it is the Lord!”
In particular, Francis condemned the use of cell phones to take photos at papal Masses. At one point during the Mass the priest says, “we lift up our hearts,” he said. “He does not say, ‘We lift up our phones to take photographs!’”
“It’s a bad thing! And I tell you that it gives me so much sadness when I celebrate here in the Piazza or Basilica and I see so many raised cellphones, not just of the faithful, even of some priests and even bishops.”
“But think: when you go to Mass, the Lord is there! And you're distracted. (But) it is the Lord!”
During the general audience, Pope Francis said the Eucharist would be the new focus of his weekly catechesis for the year, because “it is fundamental for us Christians to understand well the value and meaning of the Holy Mass to live more and more fully our relationship with God.”
In the Eucharist we rediscover, through our senses, what is essential, he said. Just as the Apostle Thomas asked to see and touch the wounds of Jesus after his resurrection, we need the same thing: “to see him and touch him to be able to recognize him.”
In this way, the Sacraments meet this very "human need" of ours, he said. And in the Eucharist, in particular, we find a privileged way to meet God and his love.
The Second Vatican Council was inspired by the desire to help Christians understand the beauty of the encounter in the Eucharist even better, he continued. This is why “it was necessary first to implement, with the guidance of the Holy Spirit, an adequate renewal of the liturgy.”
A central theme emphasized at Vatican II was the liturgical formation of the faithful, which Francis said is also the aim of the series of catechesis he began today: to help people “grow in the knowledge of this great gift God has given us in the Eucharist.”
As a side note, Francis asked if people had noticed the chaotic way children make the sign of cross at Mass, moving their hand all over their chest, and asked people to teach children to make the sign of the cross well.
“We need to teach children to do the sign of the cross well,” he said, noting that this is how Mass begins, because just as Mass begins this way, “so life begins, so the day begins.”
Concluding his reflection on the Mass and the Eucharist, Pope Francis said that he hopes that through these brief weekly lessons, everyone will rediscover the beauty "hidden in the Eucharistic celebration, and which, when revealed, gives a full meaning to the life of everyone." ||||| Image copyright Reuters Image caption Many pilgrims try to get pictures of the Pope at his audiences
Pope Francis has chided the Catholic faithful for using their mobile phones during Mass.
He said it made him sad when many phones were held up, and even priests and bishops were taking photos.
The pontiff is not known to have used a mobile phone in public since his election and once asked young people to carry Bibles instead of phones.
However, he is an avid user of social media and regularly allows himself to be snapped with pilgrims for selfies.
He has millions of followers on Twitter.
Speaking at his weekly audience in St Peter's Square in Rome, Pope Francis said that Mass was a time for prayer and not a show.
"At a certain point the priest leading the ceremony says 'lift up our hearts'. He doesn't say 'lift up our mobile phones to take photographs' - it's a very ugly thing," he said.
"It's so sad when I'm celebrating mass here or inside the basilica and I see lots of phones held up - not just by the faithful, but also by priests and bishops! Please!" ||||| (Vatican Radio) Pope Francis on Sunday called on Christians to consult the Bible with the same frequency as they might consult their cellphones for messages.
Listen to the report by Linda Bordoni:
Speaking to the crowds gathered in St. Peter's Square following his weekly Angelus blessing, the Pope urged those present to give the Bible the same place in daily life as cellphones and asked: “What would happen if we turned back when we forget it, if we opened it more times a day, if we read the message of God contained in the Bible the way we read messages on our cellphones?”
The Bible, he explained, contains the Word of God, the most effective tool in fighting evil and keeping us close to God.
Clearly, Francis said, the comparison between the Bible and the cellphone is paradoxical, but it induces us to reflect.
“If we always carried God’s Word in our hearts, no temptation would distance us from the Father, and no obstacle would take us off the path towards good” he said.
He pointed out that in this first Sunday of Lent, the Gospel of Matthew tells of Jesus’s forty days in the desert and of how he was tempted by the devil.
With his temptations, the Pope said, Satan wanted to divert Jesus from the path of obedience and humbleness – because he knew that this was the way to conquer evil – and he wanted him to take the false shortcut towards glory and success.
“But the devil’s poisonous darts are all ‘blocked’ by Jesus with the shield provided by God’s Word” he said, pointing out that Jesus never uses his own words but only God’s Word, and thus, filled with the force of the Holy Spirit, he victoriously crosses the desert.
Pope Francis invited all Christians to follow in Jesus’ footsteps during the forty days of Lent and to confront the spiritual battle against evil with the strength of God’s Word.
“That’s why, he said, it is necessary to become familiar with the Bible: read it often, reflect upon it, assimilate it. The Bible contains the Word of God which is always topical and effective” he said.
Inviting the faithful to carry a pocket-sized Gospel all the time, the Pope concluded with the words: “don’t forget what would happen if we treated the Bible as we treat our cellphone, always with us, always close to us!” | – When the priest says "lift up your hearts" during Mass, you'd better put your cellphone down while you do it. That was Pope Francis' message Wednesday during his weekly address in St. Peter's Square, calling it a "very ugly thing" to see worshippers—even other men of the cloth—with their phones out while he leads services, the BBC reports. "Please! Mass is not a show!" he said, per the Washington Post, with the Catholic News Service tweeting that the pope is "exasperated." Another beef the pontiff brought up: kids not knowing how to do the sign of the cross, instead "moving their hand all over their chest," per the Catholic News Agency. Applause can be heard from the audience in a video of his remarks. Francis has taken on the subject of phones before, telling the faithful earlier this year to swap out their phones for Bibles and warning in last year's apostolic exhortation of the damage to relationships that cellphones can cause. Per CBS New York, locals there mostly agree with the pope's stance, though one churchgoer tries to justify her own phone use. "I have my Bible in my cellphone," she says. "So I'm looking at it, but I'm reading my Bible or finding the Scripture." Not that the pontiff is a total Luddite: The BBC notes his penchant for tweeting and taking selfies with admirers. |
wellens sign , or the lad coronary artery t - wave inversion pattern
( 1 ) , is seen in a subset of patients who often present with chest pain and are found to have specific precordial t - wave changes on ekg .
its incidence is estimated to be about 1015% of acute coronary syndrome ( acs ) . with unstable angina patients ,
however ( excluding bundle branch blocks and old anterior myocardial infarctions [ mis ] ) in the united states , this syndrome is often under - recognized .
the natural course of this pattern is unfavorable , with a high incidence of recurrent symptoms .
it can rapidly progress to an anterior myocardial wall infarction if left untreated , causing catastrophic outcomes due to lesions in the proximal lad artery .
it is vital that physicians are aware of this important prognostic sign and proceed with aggressive management .
wellens sign was first reported in 1982 by de zwaan and wellens , when they noticed the characteristic t - wave changes in a subset of patients with stenosis in the proximal lad artery ( 2 ) .
they observed that this sign was found in about 18% of the 145 patients in their original study published in 1982 ( 3 ) .
they subsequently published a much larger analysis in 1989 , where approximately 87% of the patient population with isolated precordial t - wave inversions in cardiac care units have lad artery stenosis ( of greater than 50% with a mean value of 85% stenosis ) reported during angiography .
biphasic t - waves in v2 and v3type b deep and symmetrical t - wave inversions in v2 and v3ekg without q - waves and no significant st segment elevation , with normal precordial r - wave progression
history of anginal chest painnormal or minimally elevated cardiac enzyme levels ( 1 , 3 , 4).based on these criteria , it is estimated that the positive predictive value of wellens sign is approximately 86% .
cardiac serum markers were often normal or minimally elevated . in a prospective study of patients with wellens syndrome , only 21 of 180 patients ( 12% ) with ekg changes had elevated cardiac enzymes .
therefore , the ekg may be the only indication of an impending extensive anterior wall myocardial infarction in an otherwise asymptomatic patient .
biphasic t - waves in v2 and v3 type b deep and symmetrical t - wave inversions in v2 and v3 ekg without q - waves and no significant st segment elevation , with normal precordial r - wave progression
history of anginal chest pain normal or minimally elevated cardiac enzyme levels ( 1 , 3 , 4 ) .
it is important to remember that the majority of the time , these characteristic ekg findings can be present only during pain - free intervals of patients presenting with intermittent anginal chest pain with critical lad artery stenosis
( 2 , 4 )
the t - wave changes are usually present in leads v2 and v3 .
however , in certain cases , leads v1 and v4 can also be involved . in the study by de zwaan and wellens , they noted that approximately two - thirds of the patients also had these changes in lead v1 and three - fourths of them in lead v4
it is considered a pre - infarction stage of coronary artery disease as the t - wave changes in the syndrome usually occur during a pain - free interval .
however , it is postulated that the changes in the ekg account for reperfusion of the ischemic myocardium due to alleviation of spasm of proximal lad artery ( 5 ) .
the risk factors for wellens syndrome include the traditional risk factors for coronary artery disease such as hypertension , diabetes mellitus , dyslipidemia , obesity , smoking , and family history of premature coronary disease ( 6 ) .
it can be seen in any age group , with the youngest case reported in a 22-year - old man .
( 7 )
wellens syndrome is characterized by a state of impending myocardial infarction even with optimal medical treatment .
acute myocardial infarction , left ventricular dysfunction , and death can ensue if appropriate and prompt interventional catheterization is not performed in a timely fashion ( 8) .
all patients with this syndrome should receive the standard care for acs , including aspirin , nitroglycerin for pain , and beta - blockers if appropriate .
serum ekgs and serum cardiac markers need to be followed . given these patients acuity , inpatient hospital admission is warranted .
it is important to remember that these patients may manifest the signs during pain - free intervals , so repeating serial ekgs is crucial to confirming the diagnosis the primary issue here is recognizing this sign in a timely fashion as patients with wellens syndrome should undergo coronary intervention . performing a stress test with provocative agents is absolutely contraindicated , as it can increase myocardial demand with highly stenotic lesions and induce myocardial infarction and subsequent sudden death ( 6 , 8) .
most patients , when identified early and taken for cardiac catheterization , do well after appropriate intervention .
however , type a wellens sign was appreciated before cardiac intervention , and type b persisted after appropriate percutaneous intervention . weaver et al .
published that persistent st elevation after pci is related to microvascular occlusion and ongoing myocardial damage ( 9 ) .
sakata et al . studied persistent negative t - wave after transmural infarct associated with q - waves .
they demonstrated that patients with persistent t - wave inversion after 12 months have reduced left ventricular function ( 10 ) .
however , we could not find any prognostic significance of persistent t - wave inversion after non - transmural infarction .
wellens syndrome is characterized by t - wave changes in ekg , most often seen during pain - free period in a patient with intermittent angina chest pain .
it carries significant diagnostic and prognostic value because this syndrome represents a pre - infarction stage of coronary artery disease involving proximal lad artery , which can subsequently lead to extensive anterior mi and even death without coronary artery revascularization .
although these patients may initially respond well to medical management , they ultimately fare poorly with a conservative therapy and require revascularization strategies .
therefore , it is crucial for clinicians to recognize ekg features of wellens syndrome in order to take appropriate therapy to reducing mortality and morbidity form impending mi .
the authors have not received any funding or benefits from industry or elsewhere to conduct this study . | wellens syndrome is characterized by t - wave changes in electrocardiogram ( ekg ) during pain - free period in a patient with intermittent angina chest pain .
it carries significant diagnostic and prognostic value because this syndrome represents a pre - infarction stage of coronary artery disease involving proximal left anterior descending ( lad ) artery , which can subsequently lead to extensive anterior myocardial infarctions ( mis ) and even death without coronary angioplasty .
therefore , it is crucial for every physician to recognize ekg features of wellens syndrome in order to take appropriate immediate intervention to reduce mortality and morbidity for mi . here
, we report a case of an overweight man with 35 pack - year of smoking history who presented to easton hospital with intermittent pressing chest pain of 5/6 times within 10 day - period and was found to have type a wellens sign , which was biphasic t - waves in precordial leads v2 and v3 during pain - free period with no cardiac enzymes elevation .
he was given therapeutic lovenox and subsequently underwent coronary angioplasty and had 9599% occlusion in proximal lad artery .
the unique feature of our case was that wellens type b ekg changes were seen after reduction of stenosis with lad artery stent , which was likely explained by the reperfusion of the ischemic myocardium .
therefore , it is important for physicians to recognize ekg features of wellens syndrome in order to take appropriate therapy to reducing mortality and morbidity form impending mi . |
An animal-loving Texas teen committed suicide by cobra.
Grant Thompson, 18, killed himself in July by letting a highly poisonous monocled cobra bite him repeatedly, according to a Travis County Medical Examiner’s autopsy report obtained by KVUE.
The teen, who worked in his family’s pet store, was found inside his SUV parked in front of an Austin Lowe’s with puncture wounds to his arm. The vehicle was filled with caged tarantulas and non-poisonous snakes — but the door to the cobra’s cage was open and the deadly snake was missing.
Thompson had a “history of suicidal ideation” and allowed the toxic serpent to bite him on the left shoulder, the medical examiner said. Shortly before he was found dying, the teen posted an ominous final message to Facebook: “I’m sorry.”
The teen did not recoil and his body showed no signs of struggle with the reptile, the report said.
Grant Thompson killed himself with a cobra, according to an autopsy report. (facebook )
The snake’s venom sent the teen’s body into paralysis and caused respiratory failure, the report said. He died at St. David's Round Rock Medical Center after going into cardiac arrest.
The Texas teen allowed the snake to bite him multiple times, officials said. (Austin Police Department)
The missing cobra sparked panic throughout Austin as animal experts and authorities hunted for the killer creature. After a two-day snake hunt, investigators found it run over by cars a short distance from Thompson’s vehicle.
It’s not clear why the Temple teen was in Austin, which is about 70 miles southwest of his hometown.
Thompson had a lifelong passion for animals and dreamed of breeding exotic pets, his heartbroken mother told the Daily News shortly after his death. The mother-son duo worked at Fish Bowl Pet Express for years.
“Animals were a passion of his,” said Seleese Thompson-Mann, 51. “When he was 4, he got his first big fish tank. We had an animal-themed birthday party. I had a zoo out in Austin bring in animals. From then, he was hooked.”
Thompson-Mann said she was not aware her son, who lived in his own apartment, owned the deadly cobra.
The 18-year-old was found unresponsive in a car parked in an Austin Lowe's parking lot in July. (Fish Bowl Pet Express/via Facebook)
Thompson worked in his family's pet shop and grew up around animals. (Seleese Schraeder Thompson-Mann/via Facebook) He had a slew of pet snake and other animals. (Grant Thompson/via Facebook) Thompson, who worked in his family's pet shop and grew up around animals, had several pet snakes.
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Grant Thompson, age 18 of Temple, died Tuesday July 14, 2015. Services will be held at 10:00 AM Monday, July 20th at First Baptist Church in Temple with Tim Atkinson, Glenn Lackey and Dana Wilhelmsen officiating. Visitation will be 4:00 6:00 PM Sunday at Scanio-Harper Funeral Home.
Grant James Thompson was born in Temple on October 16, 1996. He was raised in Temple and was a member of Immanuel Lutheran Church. He attended school at Kennedy Powell, Bonham Middle School, Temple and Belton High Schools. Grants passion for animals revealed itself at an early age with weekly visits to The Fish Bowl Pet Express, membership to the Cameron Park Zoo, Zoo Camp, building of animal cities with his toys and his constant and ever changing collection of animals.
Grant surrounded himself with living things. He was always eager to share his animals with his friends, family, neighbors, Sunday School class and anyone he could bend an ear to listen, see, touch and share his love of the animals.
Grant had a unique spirit and focused vision of accomplishing his dream to own The Fish Bowl Pet Express. He wanted to be a part of the community and to move in nontraditional directions others often couldnt understand. It wounded his heart to see an animal suffer or be mistreated in any way. Each animal had a place in his circle.
His fourth birthday party was a zoo themed party with an animal program from the Austin Zoo. The spark caught fire. Grant began taking some type of an animal with him every time he left the house. He took an animal to church every Sunday to share with the class or anyone that would take a look at what was in the box he carried with him. He began taking several at one time with him to the Ralph Wilson Youth Club in the summer to the kids attending the summer programs. When his collection started to grow and it was required by his mom that he pay for their premium fruit, nuts, special diets and habitats, he and his mom created Grants Animal Programs in order to generate income to pay for them and to acquire more of the critters he couldnt get enough of owning and sharing.
Because his heart was tender for animals that were hurting and passion for their care and wellbeing, he often rescued and rehabilitated animals and it was always part of his program. He would be asked for advice and he would gladly give it or research options which included seeking advice from his network of other pet stores, vets, breeders and pet owners.
Grants hero was Steve Irwin. He watched The Crocodile Hunter when Animal Planet wasnt the cool thing to do on a Saturday night. When Irwin died he said, What do you do when your hero dies? Grant decided he would carry Steves message of being kind to animals, conserving, educating, and learning how to live on this planet with the gift of animals.
When the opportunity to purchase The Fish Bowl Pet Express presented itself the path was clear. Grants dream was realized with a future designed to include accomplishing his goal of owning the pet store he so deeply loved which included living in the apartment at the store. His vision for The Fish Bowl to be a destination for families will continue to grow, improve, change and thrive in downtown Temple. Volunteer Programs, The Delta Program from Belton High School, Birthday Parties, Ralph Wilson Youth Club, Belton Christian Youth Center, Camp Wildflower, Temple Parks and Leisure Camps, all will continue to be a part of his community.
Grant died surrounded by animals that intrigued and fascinated him. His eyes were donated to help others see the beauty of Gods world. He leaves behind to nurture his legacy his mother, Seleese Thompson-Mann and husband, Mitch of Temple and his father, John Thompson and wife, Sara of Austin, his sister, Faith Thompson of Temple and two step-sisters, Lauren Mann of Austin and Leah Mann of Temple. Also surviving are grandparents, Weldon and Reeneea Schraeder, Phyliss Thompson and Richard Mann all of Temple and Rita McKnight of Magnolia.
His broken hearted family is humbled and thankful for the short time they shared with Grant on this earth and draws strength from knowing we will see Grant in every living thing and feel him with the kindness we show everyone around us. They are blessed and strengthened by the outpouring of love and the peace of the knowledge of how many people Grants life touched. Grants friends and the community are the angels lifting his family to their feet while their wings are having trouble remembering how to fly.
The blessing of memorials can be given in memory of Grant to The Temple Animal Shelter or APAC-Association of a Pet Adoption Center in Temple. Rescuing animals was in Grants heart.
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Close ||||| #austincobra found dead on I-35 (Photo: Tina Shively, KVUE News)
AUSTIN – A Central Texas teenager who died in a SUV earlier this year committed suicide by letting a deadly monocle cobra repeatedly bite him, according to the autopsy report obtained by KVUE’s Tony Plohetski.
The Travis County Medical Examiner’s office report said Grant Thompson, 18, had “several bites” from the cobra on each arm and the bites showed no sign Thompson ever tried to pull away when the snake bit him.
The autopsy report said Thompson, who was right-handed, first allowed the cobra to bite him higher on the left shoulder, which the medical examiner’s office said is consistent with someone right-handed doing so on purpose.
Medical examiners concluded that the bites “appeared to be intentional injection sites” and that Thompson had a “history of suicidal ideation.”
The autopsy showed that cobra venom causes paralysis leading to respiratory failure and death in as little as 30 minutes. Marijuana and amphetamines were also discovered in Thompson’s body.
Thompson, a reptile lover who worked in his family’s pet store in Temple, was found July 14 with his car door open and an empty container that housed the cobra. Police also discovered a viper snake and several tarantulas.
The missing cobra sparked a massive search of the area by animal control experts. The snake was found dead a few days later in an I-35 frontage road.
While the autopsy report answered the question of how he died, other parts of the case remain a mystery including why Thompson was in Austin or why he chose the location where he committed suicide.
Plohetski has reached out to the family multiple times over the past few months, but they have not responded to any interview requests.
For more on the cobra case, click here.
Read or Share this story: http://kvue.tv/1iXWcwg | – Authorities say a young pet-store staffer in Texas committed suicide with help from a cobra. Grant Thompson, 18, was found in cardiac arrest inside his car in a North Austin parking lot on July 14. An autopsy report, obtained by the Austin American-Statesman, shows Thompson suffered "multiple separate bites" on his arms from a monocled cobra. The bites "appeared to be intentional injection sites" as their marks gave no indication that the teen tried to pull away from the snake. The first bite, on Thompson's left shoulder, was consistent with a right-handed person deliberately allowing the bite, according to the report, per KVUE. The report—which notes cobra venom leads to paralysis, respiratory failure, and death within 30 minutes—adds Thompson "had a history of suicidal ideation." Shortly before he died, Thompson had posted a message on Facebook reading, simply, "I'm sorry," per the New York Daily News. Though authorities didn't find the cobra in Thompson's car, which was left with the door open, the snake was discovered dead on a nearby road days later. An empty cage, a viper snake, and numerous tarantulas were also found in the vehicle. Thompson, who worked at a pet store that his mother owns in Temple, lived in an apartment attached to the store; it isn't clear why he was in Austin, which is about 70 miles from his home. "Animals were a passion of his," his mother said, adding he had an animal-themed birthday party at age 4. "From then, he was hooked," she told the Daily News. An obituary said Thompson "died surrounded by animals that intrigued and fascinated him." (This farmer bit a cobra to death.) |
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. ||||| Norfolk Police tell THR that detectives are looking into the livestream after a "shooting incident that sent three people to the hospital with life-threatening injuries Tuesday evening."
A Facebook Live video posted on Tuesday night appears to have captured the shooting of three men in Virginia.
"We are aware of the video and the police are looking into it," Daniel Hudson, the Norfolk Police Department's public information officer, told The Hollywood Reporter.
Reports of the video first surfaced on Twitter from a user who tweeted, "3 boys just got shot on Facebook live in Berkeley smh" at 5:46 p.m. PT, referring to the Berkeley area of Norfolk, Va.
The user included a link to a Facebook Live video posted by T.J. Williams. (Warning: graphic video). In the video, a man who appears to be Williams and another unidentified male driver can be seen in a pulled-over car. Around the 5:30-minute mark, the livestream is interrupted by the sounds of gun shots.
The camera falls to the floor and the remaining clip, which plays for over an hour, captures the sounds of witnesses followed by the first responders attempting to save the men. "Stay with me, stay with me," a man can be heard upon discovering the men. When the responders arrive, a witness can be heard saying the three men have been shot.
Last week, the shooting of Falcon Heights shooting of Philando Castile was captured on Facebook Live by his girlfriend, Diamond Reynolds. A day later, Michael Kevin Bautista live-streamed gunfire from the Dallas attack that left five police officers dead. Following the tragic recordings, Facebook announced new guidelines for live videos with graphic content. Explaining that when it comes to removing graphic real-word events, "context and degree are everything."
On Tuesday night, the Norfolk Police Department released a statement on their website, saying the police were investigating a "shooting incident that sent three people to the hospital with life threatening injuries Tuesday evening."
The statement continues, "At approximately 6:10 p.m., Norfolk dispatchers received a call for gunshots heard in the 900 block of Bainbridge Boulevard. As police responded to the scene, the call was quickly updated to possibly three gunshot victims. Upon arrival, officers located three men inside a vehicle suffering from apparent gunshot wounds.
All three men, ages 27 and 29, were taken to Sentara Norfolk General Hospital with "significant injuries."
The police did not identify the men in the statement.
Hudson told THR that any further updates tonight will posted on the newsflash page, which can be found here. ||||| Skip Ad Ad Loading... x Embed x Share TJ Williams was live streaming on Facebook when he and two other men were gunned down in broad daylight. The camera never stops rolling as first responders arrive to help. WVEC
Police respond after three men were shot while sitting in a car in Norfolk, Va., July 12, 2016. (Photo: WVEC-TV, Norfolk-Hampton, Va.)
NORFOLK, Va. — Three people were injured in a shooting captured on Facebook Live Tuesday evening.
The men were sitting in a car listening to music when they were shot. The phone streaming on Facebook Live fell to the floor of the car and continued recording for about two hours as police arrived and bystanders offered aid.
Police received the 911 call about the shooting a little after 6 p.m. ET in the Norfolk suburb of Berkley.
According to a report by WGNT-TV, neighbors said they heard 10 to 20 gunshots.
It appeared that one of the passengers in the car started a Facebook Live stream just before shots were fired, according to multiple tweets.
Update to shooting on BAINBRIDGE BLVD. 3 men taken to SNGH for treatment. 2 w/ life threatening injuries, 1 w/ non life threatening injuries — Norfolk Police Dept (@NorfolkPD) July 12, 2016
When Norfolk police arrived they found three men with gunshot wounds inside a car.
The three men in their 20s were taken to Sentara Norfolk General Hospital, two with life-threatening injuries and one less seriously injured, police said.
No motive or suspect description has been released.
That's sad, emptied the clip on them & dude was live on Facebook at that. It's really getting outta hand in Norfolk . 😓 — Plugg ‼️ (@_DBrown_10) July 13, 2016
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A shooting that was apparently captured during a Facebook Live video left three men in the hospital — including two with life-threatening injuries, police said.
Video uploaded by Facebook user TJ Willams showed three men sitting in a car listening to music and smoking until gunfire is suddenly heard and the phone is dropped.
About 30 gunshots are audible on the video, which continues with the sound of passers-by calling 911 and comforting the victims.
Police in Norfolk, Virginia, said three men were shot at about 6 p.m. Tuesday in the suburb of Berkley.
“Upon arrival, officers located three men inside a vehicle suffering from apparent gunshot wounds,” the police department said in an update. “All three men, ages 27 and 29, were taken to Sentara Norfolk General Hospital with significant injuries.”
In a later update, police said two of the men had life-threatening injuries.
Update to shooting on BAINBRIDGE BLVD. 3 men taken to SNGH for treatment. 2 w/ life threatening injuries, 1 w/ non life threatening injuries — Norfolk Police Dept (@NorfolkPD) July 12, 2016
The Facebook Live video includes the voices of helpers as they await the arrival of ambulances.
“Stay calm, stay relaxed, don’t go to sleep,” a man says. “Give me your hand. I got you. Stay with me, stay with me. They coming, they coming to get you.”
Police told NBC affiliate WAVY that they were investigating the video in connection with the shooting.
As time passes in the video, the helper asks: “TJ, you good? Stay right there. Keep your eyes open … keep listening to my voice … stay breathing.”
Pictures from the scene showed a parked vehicle with several bullet holes in the windows. ||||| Please enable Javascript to watch this video
NORFOLK, Va. - Police are investigating after three men were shot Tuesday evening during a Facebook Live video.
Officers were called to the 900 block of Bainbridge Blvd. around 6:10 p.m. where they found three men inside a vehicle suffering from apparent gunshot wounds.
The men, all in their late 20s, were taken to Sentara Norfolk General Hospital with life threatening injuries. Two of the men are reportedly doing better while one is still listed as critical, Norfolk Police said Wednesday morning.
Norfolk detectives are aware of the Facebook Live video and are currently investigating. Police confirmed Wednesday morning that the video is of the incident.
The graphic video shows the three men listening to music, a man in the front passenger seat holding the phone. Suddenly, the phone drops to the floor of the car as what sounds like at least 30 gunshots can be heard in the background.
"Call 911," a man can be heard saying. "We need an ambulance, there's three of us shot."
A voice of another man can be heard trying to comfort a victim for about 10 minutes until paramedics arrived. The man repeatedly said, "Stay calm, stay relaxed."
He also said, "Give me your hand, I got you... Stay with me nephew. I got you... It's going to be alright, they are coming to get you."
At one point, the man seemed to address multiple victims, saying, "Everybody keep your eyes open. Keep listening to my voice."
Police have not released any suspect information yet. If you have any information that could help in the investigation, call Crime Line at 1-888-LOCK-U-UP. ||||| Bullet fragment seen on the ground where the three men were shot during Facebook live video. (Photo: Eric Kane, 13News Now)
NORFOLK, Va. (WVEC) -- Police have identified the three men who were hurt in a shooting in Berkley Tuesday that was broadcast live on one of the victim's Facebook pages.
The shooting along Bainbridge Boulevard happened around 6:10 p.m.
Moments before the shooting, T.J. Williams was sitting in a car with two other men listening to music in the live Facebook video.
When the gunfire erupts, Williams drops the phone as pieces of glass fly through the car.
The shots continue for 20 seconds. Neighbors say they heard as many as two dozen rounds.
Several seconds after the gunfire, neighbors are heard coming up to the car to comfort the three men.
"Give me your hand. Stay relaxed. I got you. Stay relaxed," said one person after paramedics were on their way to the scene. "They're coming. They're coming to get you."
The men, ages 27 and 29-years-old, were taken to Sentara Norfolk General Hospital with what police described as significant injuries.
The live Facebook feed continued for more than an hour after the shooting and recorded police as they secured the crime scene.
Detectives have confirmed the video posted to the social outlet is of the actual incident.
All three victims remain hospitalized. Two are in stable condition, but one is suffering from significant injuries.
They have not released a motive or any suspect information.
If you know anything about this shooting call the Crime Line at 1-888-LOCK-U-UP.
6:11 pm. PD investigating a shooting in the 900 blk BAINBRIDGE BLVD. More details to follow @ https://t.co/uAWiYVnlhD — Norfolk Police Dept (@NorfolkPD) July 12, 2016
PHOTOS: Three men injured in Norfolk shooting ||||| A shooting captured on Facebook Live critically wounded three men in Virginia who were apparently ambushed Tuesday night while sitting inside a vehicle and listening to music.
A barrage of at least 30 shots were heard during the attack, which unfolded at around 6 p.m. in the Norfolk suburb of Berkley. The recording uploaded by a T.J. Williams on Facebook continued to record for at least two hours as good Samaritans and paramedics tended to the three victims, who were all in their late 20s.
Norfolk police spokesman Officer Daniel Hudson confirmed that the final Facebook video posted at around 9 p.m. was the same shooting being investigated in the 900 block of Bainbridge Boulevard.
The three men were sitting inside a vehicle that was shot up in the Berkley suburb of Norfolk, Virginia. (WTKR)
The video showed Williams sitting in the passenger seat recording himself singing and smoking with two other men during the evening hangout.
About five minutes into the video, a barrage of gunshots rang out, prompting Williams to drop the phone to the floor. The stream continued to record panicked voices belonging to residents and an apparent family member who heard the gunshots and rushed to call 911 and comfort the shooting victims.
A man with the Facebook profile known as T.J. Williams was one of three men believed shot in a car in Norfolk, Va. (via Facebook)
“Stay relaxed. Don’t go to sleep,” an unidentified man told victims. “Keep your eyes open. Keep listening to my voice. They’re going to get you. It’s going to be OK.”
The man heard assuring the victims then referred to one of the men as “T.J.” as sirens in the distance approached the crime scene and later said, “I love you, nephew.”
The three gunshot victims, including one pictured in WTKR-TV footage, were critically wounded. (WTKR)
The video also captured audio of paramedics treating the men and checking for gunshot wounds before taking them to a local hospital with what cops described as “significant injuries.”
Police did not immediately identify the victims and did not release a suspect description.
A vehicle at the site shooting showed several bullet holes in the window, according to video from WTKR-TV.
Sign up for BREAKING NEWS Emails privacy policy Thanks for subscribing! | – Three men in a car in Norfolk, Va., were ambushed and shot Tuesday evening, and the phone of one of the men streamed the entire incident on Facebook Live, USA Today reports. In the video, a man IDed as TJ Williams is seen hanging out with two other men, listening to music and smoking, when a few minutes into the clip shots start ringing out, continuing for about 20 seconds, WVEC notes; around 30 shots were fired. Williams dropped the phone onto the floor, where it continued recording for more than an hour afterward. Norfolk Police say they found three men, ages 27 and 29, with gunshot wounds, NBC News reports. The police later tweeted that all three men were taken to a local hospital, two with life-threatening injuries. A police rep confirmed the Facebook video was indeed tied to a Bainbridge Boulevard shooting being investigated, per the New York Daily News. A few seconds after the shooting (which can be partly seen in a brief WTKR news clip), a man's voice can be heard saying, "Call the ambulance, please," and soon after that, another man can be heard comforting the victims. "Stay relaxed," he says. "Stay with me. … Keep your eyes open. Keep listening to my voice." Police aren't saying yet if they have a suspect or motive. Per the Hollywood Reporter, following last week's Facebook Live streaming of the aftermath of the shooting of Philando Castile, Facebook updated its guidelines for posting live video, noting that when people share "violent or graphic images of events taking place in the real world … context and degree are everything." Williams' entire video can be viewed here (warning: graphic content). |
primary rhegmatogenous retinal detachment ( rd ) remains an important cause of visual loss ( figure 1 ) .
specifically , all retinal breaks are identified and treated , and vitreous traction is relieved as part of the surgical strategy .
the two most common re - attachment procedures performed today are scleral buckling ( sb ) and pars plana vitrectomy ( ppv ) ( schwartz and flynn 2006 ) .
pneumatic retinopexy ( pr ) is appropriate for selected superior detachments ( tornambe 1997 ) .
laser demarcation ( vrabec and baumal 2000 ) and observation ( brod et al 1995 ) may be considered in rare circumstances .
ppv ( figure 2 ) is growing in popularity for the treatment of primary rd ( spr study group 2003 ) .
the current manuscript will review the published literature on the topic and offer guidelines based on the evidence available today .
successful retinal attachment surgery requires effective treatment of retinal breaks and relief of vitreoretinal traction ( schwartz and mieler 2004 ) .
sb is the most well - established technique , and has the longest published follow - up data ( schwartz et al 2002 ) .
sb has a high single - operation success rate ( sosr ) and is considered for many primary retinal detachments , except cases with very posterior breaks and cases in which placing the buckling elements is too technically difficult , such as eyes with thin sclera , prior strabismus surgery , glaucoma drainage devices , etc .
additional relative contraindications to sb alone ( without ppv ) include giant retinal tear , proliferative vitreoretinopathy ( pvr ) grade c , and significant vitreous opacity or hemorrhage . however , ppv is growing in popularity as a first - line procedure for primary rd , especially in pseudophakic patients ( lois and wong 2003 , spr study group 2003 ) .
perhaps the major benefit of ppv is the potential for an improved view of the retinal periphery , allowing increased identification of retinal breaks .
some authors have advocated the use of transretinal injection of trypan blue ( jackson et al 2007 ) to facilitate intraoperative localization of retinal breaks .
ppv removes vitreous opacities , and allows concomitant cataract surgery or posterior capsulotomy , if necessary to further improve visualization .
ppv allows for more controlled drainage of subretinal fluid , either with perfluorocarbon liquids or internal drainage techniques ( brazitikos et al 2003 ) .
this may achieve complete intraoperative retinal attachment ( particularly important for giant retinal tears ) without the risk of hemorrhage or retinal incarceration inherent in external drainage procedures .
ppv is unlikely to cause significant motility disturbances , and is frequently less painful than sb .
ppv is less likely to cause significant refractive changes than sb in pseudophakic eyes , although some phakic eyes will develop nuclear sclerosis and induced myopia following ppv .
disadvantages and complications may also occur with ppv for primary retinal detachment ( table 1 ) .
ppv increases the risk of new retinal breaks ( al - harthi et al 2005 ) , cataract formation ( ling et al 2005 ) , and intraocular pressure elevation ( lee et al 2004 ) .
if perfluorocarbon liquids are used , they may be retained in the vitreous cavity or subretinal space ( roth et al 2004 ) .
rare complications may include retinal incarceration into a sclerotomy ( stopa and toth 2006 ) , displacement of a laser in situ keratomileusis ( lasik ) flap ( tosi et al 2005 ) , and direct retinal trauma during air - fluid exchange ( yang et al 2006 ) .
ppv is somewhat more technically difficult in phakic patients , because access to the vitreous base is impeded by the crystalline lens .
wide - angle viewing systems and external scleral indentation from a surgical assistant may be helpful ( weichel et al 2006 ) .
perfluorocarbon liquids may be used to stabilize the posterior retina during these maneuvers ( brazitikos et al 2003 ) .
therefore , many surgeons prefer either 23 gauge or 20 gauge vitrectomy instrumentation for this purpose . in addition , concomitant sb or pars plana lensectomy may be considered .
traditional teaching held that ppv for primary retinal detachment had too many disadvantages , but recent published case series have called this concept into question .
ppv without sb was traditionally believed to have a low sosr in patients with inferior breaks .
however , recent series have demonstrated favorable results with ppv for these patients ( sharma et al 2004 ; martinez - castillo , boixadera , et al 2005martinez - castillo , verdugo , et al 2005 ) .
ppv was traditionally believed to require long - acting intraocular gas ( or silicone oil ) tamponade , especially for inferior breaks .
however , recent case series have documented generally favorable results using air tamponade or even aqueous tamponade ( martinez - castillo , boixadera et al 2005 ; martinez - castillo , verdugo et al 2005 ; martinez - castillo et al 2007 ) .
ppv was traditionally believed to require some degree of face - down positioning for inferior breaks , but a recent case series demonstrated favorable outcomes with very limited positioning requirements ( martinez - castillo et al 2007 ) .
an alternative approach to inferior , more complex rds ( large and more posterior tears , advanced proliferative vitreoretinopathy , etc . )
is the use of intermediate - term , heavier - than - water tamponade agents .
some authors have advocated the use of retained intravitreal perfluorocarbon liquids , either alone or in combination with silicone oil , for post - operative internal tamponade ( rofail and lee 2005 ; asensio - sanchez et al 2007 ) . the combination of perflurohexyloctane ( f6h8 ) and silicone oil has been advocated by some authors ( rizzo et al 2006 ) .
heavy silicone oil ( oxane hd , bausch and lomb , toulouse , france ) also has demonstrated some efficacy ( wolf et al 2003 ) .
neither perfluorohexyloctane nor heavy silicone oil is available for routine clinical use in the united states at this time .
the first report of ppv without concomitant sb to treat rd was published in 1985 ( escoffery et al 1985 ) . since that time , numerous case series have been published ( table 3 ) . in general , the outcomes ( sosr and visual acuity ) appear comparable to those achieved with sb for a wide variety of patients .
the poorest outcomes were reported in series which contained patients with chronic detachments and evidence of pvr .
several retrospective series comparing sb , ppv , and/or combined sb / ppv have appeared in the past few years .
these series describe a wide variety of clinical situations and are summarized in table 4 .
the majority of these series found no statistically significant difference in sosr among the various procedures .
similarly , visual results were generally comparable . similarly , an increasing number of prospective clinical trials are being reported , many of which are randomized .
again , the majority of these studies found no statistically significant differences in either sosr or visual results between the two treatment modalities .
one meta - analysis of 29 published studies of pseudophakic rd reported that both ppv and combined ppv / sb were associated with higher sosrs and better visual acuity outcomes than was sb alone ( arya et al 2006 ) .
however , another review of 9 published studies comparing ppv to sb found no statistically significant differences with respect to sosr or visual results ( saw et al 2006 ) .
a recent statistical analysis reported that sb increased the risk of pvr , especially in pseudophakic cases ( rodriguez de la rua et al 2005 ) , which contrasted an earlier report indicating the reverse ( cowley et al 1989 ) . at this time
, there has been no definitive prospective , randomized , controlled clinical trial comparing sb to ppv , and this question remains unresolved ( mcleod 2004 ) .
the scleral buckling versus primary vitrectomy in rhegmatogenous retinal detachment ( spr ) study is a european multicenter , randomized , prospective , controlled clinical trial comparing ppv to sb ( heimann 2001 )
. the spr study may be limited by the fact that a significant proportion of patients in the primary ppv group also received sb .
although ppv was traditionally considered a second - line procedure for rhegmatogenous rd , there is a growing body of evidence that , in certain cases , ppv represents a reasonable primary approach .
however , most of the current literature comes from small case series with limited follow - up and other methodological flaws .
therefore , in the absence of convincing study data , the choice of procedure for any individual patient should be left to the surgeon s best clinical judgment , taking into account various factors such as the number , size , and position of retinal breaks ; the lens status ; the patient s expected ability to cooperate with postoperative positioning requirements ; available operating room equipment and staff ; surgeon preference ; and patient preference . by avoiding a regimented approach and adopting an individualized strategy ,
although some patients will not achieve re - attachment after the initial surgery , a variety of surgical techniques are successful in the vast majority of patients . | pars plana vitrectomy ( ppv ) is growing in popularity for the treatment of primary rhegmatogenous retinal detachment ( rd ) .
ppv achieves favorable anatomic and visual outcomes in a wide variety of patients , especially in pseudophakic rd .
a growing number of clinical series , both retrospective and prospective , have demonstrated generally comparable outcomes comparing ppv and scleral buckling ( sb ) under a variety of circumstances .
the scleral buckling versus primary vitrectomy in rhegmatogenous retinal detachment ( spr ) study is a multicenter , randomized , prospective , controlled clinical trial comparing sb versus ppv .
this study should provide useful guidelines in the future . at this time
, the choice of sb versus ppv should be based on the characteristics of the rd , the patient as a whole , and the experience and preference of the individual retinal surgeon . |
electron has spin as well as charge . the application of the electron spin property opens a fruitful field in the transport of ferromagnetic materials , such as the discovery of gmr and tmr effects @xcite . on the other hand ,
there are growing interests on the mesoscopic normal - metal / superconductor ( n / s ) hybrid system @xcite , in which andreev reflection ( ar ) at n / s interface plays an important role in low bias voltage regime @xcite . in ar process
, an electron incident with energy e and spin @xmath3 picks up another electron with energy -e and spin @xmath5 , both enter s and form a cooper pair , leaving a andreev reflected hole in n side .
one may expect that the interplay of the spin property of ar process and the spin - dependent transport in ferromagnetic materials will add new physics to mesoscopic hybrid systems , and to the future applications of spintronics .
several works have been devoted to this issue . in the pioneering work of
de jong @xmath6 @xmath7 .
@xcite , the transport of a ferromagnet / superconductor ( f / s ) junction was studied by scattering matrix formalism .
the conductance of ar is shown to be strongly affected by the spin polarization of f. the idea was verified by recent experiments in f / s thin film nanocontact @xcite and f / s metallic point contact @xcite . especially , in ref .
@xcite , soulen @xmath6 @xmath7 . successfully determined the spin polarization at the fermi energy for several metals by measuring the differential conductance of f / s metallic point contact .
further calculations @xcite implied that the fermi velocity mismatch between f and s also affects ar conductance of f / s contact , and the conductance may even be enhanced in presence of spin polarization .
in addition to simple f / s junction , f / s contact with s in d - wave symmetry @xcite , f / s nanostructure with giant proximity effect @xcite , and more complicated structures such as fsf double junctions @xcite , sfs double junctions @xcite , s / f superlattices @xcite , ( nf)@xmath8s multilayer structures @xcite were also investigated . in this paper
, we propose an idea that two sources of spin polarized electrons with different orientations are injected into a superconductor , which can be achieved by a three terminal mesoscopic f / s hybrid structure shown in fig.1 . in this system ,
a central quantum dot ( qd ) is coupled via tunnel barriers to two ferromagnetic electrodes ( f@xmath0 and f@xmath1 ) and a superconducting electrode ( s ) ( hereafter , the system is simply referred as to ( f@xmath0,f@xmath1)-qd - s ) .
f@xmath0 and f@xmath1 are assumed to have arbitrary magnetization orientations , spin polarizations , and bias voltages .
the bias voltage of s is set to zero as the ground .
qd is designed to provide a link between f@xmath9 f@xmath1 and s , so that ar can take place through discrete energy states of qd .
consider the special case that f@xmath0 and f@xmath1 are fully polarized , ar only involving f@xmath0 and s or only involving f@xmath1 and s are completely suppressed , while the crossed ar involving f@xmath0 , f@xmath1 , and s depends strongly on the magnetization orientations of f@xmath0 and f@xmath1 , being suppressed if they are in ferromagnetic alignment , enhanced in anti - ferromagnetic alignment . in this paper
, we will derive a current formula by using non - equilibrium green function method , and investigate several special cases to illustrate the properties of ars in this system . during the preparation of this paper , we are aware that in the recent publication of deutscher @xmath6 @xmath7 .
@xcite , a device consisting of two point contacts between two ferromagnetic tips and a superconductor was proposed .
for the two tips with fully but opposite spin polarizations , they suggested that `` mixed '' cooper pair made of electrons coming one from each tip can be injected into the superconductor , leading to unusual properties of such device .
sec.iv of this paper is partially stimulated by their work .
the rest of this paper is organized as follows : in sec.ii , we present the model hamiltonian and derive a general current formula for the hybrid system ( f@xmath10f@xmath1)-qd - s , by non - equilibrium green function method . in sec.iii , we study the zero bias conductance , assuming @xmath11 . the explicit forms of the conductance are presented and numerically studied . in sec.iv , we study the finite bias current with f@xmath0 and f@xmath1 in anti - ferromagnetic alignment , and the fully spin polarized case is discussed in detail .
finally , a brief summary is given in sec.v .
the system under consideration can be described by the following hamiltonian : @xmath12 \;\ ; , \nonumber \\ h_t & = & \sum_{k\sigma } \left [ t_{1\sigma } a_{k\sigma } ^{\dagger } c_\sigma + h.c\right ] + \sum_{k\sigma } \left [ t_{2\sigma } b_{k\sigma } ^{\dagger } c_\sigma + h.c\right ] + \sum_{p\sigma } \left [ t_sd_{p\sigma } ^{\dagger } c_\sigma + h.c\right ] \;\;. \nonumber\end{aligned}\ ] ] @xmath13 and @xmath14 are the hamiltonians of f@xmath0 and f@xmath1 in the mean field approximation , with different magnetization orientations and chemical potentials . the spin bands of f@xmath0 ( f@xmath1 ) are split by @xmath15 ( @xmath16 ) due to the exchange energy
. the magnetization orientation of f@xmath0 is set as z axis , while the orientation of f@xmath1 as z@xmath17 axis which has an angle @xmath18 with respect to z axis .
the operators with the spin - quantization axis z and the operators with the spin - quantization axis z@xmath19 are related by d@xmath20 matrix as @xmath21 @xmath22 describes the quantum dot , in which only one spin degenerate level is considered and the intra - dot interaction is ignored for simplicity .
@xmath23 is the hamiltonian for a bcs superconductor with the chemical potential fixed to zero as the ground .
@xmath24 depicts the tunneling between qd and f@xmath0 , f@xmath1 and s , coupling different parts of the system together . since the current through qd can be expressed in terms of the green functions of qd , we first derive the retarded and distribution green functions by dyson equation and keldysh equation . to include the physics of andreev reflections and the spin flip processes in a unified formulation ,
we introduce a 4@xmath254 matrix representation , in which the green function is defined as @xmath26 let @xmath27 denote the fourier transformed retarded green function of qd , and @xmath27 can be solved by dyson equation : @xmath28 in which @xmath29 is the retarded green function of an isolated qd and @xmath30 is the self - energy due to couplings between qd and leads .
@xmath31 can be easily obtained as : @xmath32 while @xmath33 consists of three parts , @xmath34 @xmath35 is the self - energy from the coupling between qd and f@xmath0 , given by @xmath36 in which @xmath37 and @xmath38 are the spin - dependent coupling strengths defined by @xmath39 , with @xmath40 being the density of states of spin @xmath3 band of f@xmath41 @xmath42 is the self - energy from the coupling between qd and f@xmath1 , given by @xmath43 in which @xmath44 @xmath45 , @xmath46 , @xmath47 and @xmath48 are defined similarly to @xmath49 and @xmath38 .
@xmath50 is the self - energy from by the coupling between qd and s , given by @xmath51 in which @xmath52 , with @xmath53 being the density of states when the superconductor is in normal state , @xmath54 is the modified bcs density of states defined by @xmath55 thus , @xmath27 can be obtained by solving dyson equation , eq.(4 ) .
let @xmath56 denote the fourier transformed distribution green function of qd , and @xmath56 can be obtained by keldysh equation : @xmath57 notice that the advanced green function and self - energy are the hermitian conjugations of the corresponding retarded green function and self - energy . and @xmath58 can be obtained by applying the fluctuation - dissipation theorem to each of @xmath59 , @xmath60 and @xmath61 , @xmath62 in which @xmath63 @xmath64 @xmath65 where @xmath66 , @xmath67 , @xmath68 , @xmath69 and @xmath70 denote @xmath71 , @xmath72 , @xmath73 , @xmath74 and @xmath75 , respectively , in which @xmath75 is the fermi distribution function .
then , the current flowing from f@xmath0 to the qd can be expressed in terms of @xmath76 and @xmath56 as @xmath77 _ { 11 + 33}\;\;,\ ] ] in which we have used the compact notations @xmath78 ^{<}{\bf % \equiv a}^r{\bf b}^{<}{\bf + a}^{<}{\bf b}^a$ ] and @xmath79 _ { 11 + 33}\equiv \left [ \;\;\right ] _ { 11}+\left [ \;\;\right ] _ { 33}$ ] .
after some algebra manipulations , the current can be divided into contributions from four conducting processes : @xmath80 \;\;,\ ] ] in which @xmath81 represents the andreev reflection through f@xmath0-qd - s , @xmath82 represents the crossed andreev reflection through ( f@xmath0,f@xmath83-qd - s , @xmath84 + \\ & & \gamma _ { 1\downarrow } \gamma _ s\tilde{\rho}\left [ \left| g_{31}^r\right| ^2+\left| g_{32}^r\right| ^2+\left| g_{33}^r\right| ^2+\left| g_{34}^r\right| ^2 + 2% % tcimacro{\func{re } } % beginexpansion \mathop{\rm re}% % endexpansion ( -\frac \delta \omega g_{31}^rg_{32}^{r*}+\frac \delta \omega g_{33}^rg_{34}^{r*})\right ] \nonumber\end{aligned}\ ] ] represents the single particle tunneling through f@xmath0-qd - s , and @xmath85 is the ordinary bcs density of states , @xmath86 represents the single - particle tunneling through f@xmath0-qd - f@xmath1 .
similarly , one can obtain the current flowing from f@xmath1 into qd simply by exchange the index 1 and 2 .
the current formula eq.(17 ) is the central result of this work , which can be applied to ferromagnetic electrodes f@xmath0 and f@xmath1 with arbitrary spin polarizations , magnetization orientations and bias voltages . in the following numerical studies ,
we assume that @xmath87 and @xmath88 .
@xmath89 process will vanish because of the factor @xmath90 and the fermi function difference @xmath91 .
@xmath92 process will be ruled out in two special cases : f@xmath0 and f@xmath1 are either equally biased ( section iii ) or fully but oppositely polarized ( section iv ) .
we will concentrate on ar processes @xmath93 ( direct ar through f@xmath0-qd - s ) and @xmath94 ( crossed ar through ( f@xmath95,f@xmath1)-qd - s ) , and investigate several special cases to illustrate the properties of these two ars .
in this section , we study the zero bias conductance by taking @xmath11 . since no bias voltage between f@xmath0 and f@xmath1 , there is no net single - particle current flowing between them . for @xmath88 , the single - particle current from f@xmath0 or f@xmath1 to s is also negligible .
therefore , only ars contribute to the conductance . for simplicity ,
we set @xmath96 and @xmath97 , introduce the spin polarization @xmath98 , and the spin - averaged coupling strength @xmath99 , with @xmath100 @xmath101 for f@xmath0and f@xmath1 respectively .
first consider the simplest case in which @xmath102 , @xmath103 , @xmath104 , @xmath105 , then the three - terminal system ( f@xmath9f@xmath1)-qd - s reduces to a two - terminal system f - qd - s , and the conductance is easily obtained from the current formula as @xmath106 where @xmath107 is the ratio of the two coupling strengths .
analogous to the matching condition of the fermi velocities in f / s contact ( i.e. , @xmath108 here @xmath109 ( i.e. , @xmath110 ) plays the similar role . for @xmath111 ,
the matching condition can never be satisfied , so @xmath112 decreases monotonously with the increase of @xmath113 ( fig.2a)@xmath114 while for @xmath115 , it exists a certain value of @xmath113 , say @xmath116 , satisfying @xmath117 , so @xmath112 first increases with @xmath113 , reaches its maximum value @xmath118 at @xmath119 , then drops to 0 when @xmath113 approaches to 1 ( fig.2b ) .
this result warns us to be careful to deduce the spin polarization of f from ar conductance of f - qd - s .
next , consider the general case of the three terminal system ( f@xmath9f@xmath1)-qd - s .
similar to the composition of polarized light , the total current ( or total conductance ) of f@xmath0 and f@xmath1 are equivalent to that of an effective ferromagnet f. introduce the spin polarization vectors * @xmath120*@xmath95 and * @xmath120*@xmath1 , where * @xmath120*@xmath121 has the magnitude of @xmath122 and the direction of the magnetization direction of f@xmath121 , with @xmath123 .
it is easy to test that these vectors obey the vector composition rule , i.e. , * @xmath120*@xmath124*@xmath125*@xmath126*@xmath120*@xmath1 , in which * @xmath120 * is the spin polarization vector of f. therefore , the effective parameters of f are @xmath127 ^{\frac 12}}{\gamma _ 1+\gamma _ 2}\;\;. \nonumber\end{aligned}\ ] ] as a result , the total conductance of f@xmath0 and f@xmath1 can be obtained as @xmath128 in which @xmath112 has the same form as in eq.(22 ) , @xmath129 is the effective polarization , and @xmath130 is defined by @xmath131 .
then the conductance of f@xmath0 and f@xmath1 can be expressed by the total conductance multiplied by a sharing factor , @xmath132 fig.3 shows the curves of @xmath133 vs @xmath18 ( also can be viewed as @xmath134 vs @xmath135 or @xmath136 vs @xmath18 ) for the symmetric case , in which @xmath137 and @xmath138 . for @xmath139 ,
@xmath133 increases with the increase of @xmath18 or decrease of @xmath113 . for @xmath111 , the curves of @xmath140 vs
@xmath18 is qualitatively the same as those of @xmath139 , but the conductance is lowered and more sensitive to @xmath141 for @xmath115 , the variation is more complicated : if @xmath142 , @xmath133 decreases with the increase of @xmath135 or decrease of @xmath113 ; if @xmath143 , @xmath133 has the maximum @xmath144 at @xmath18 satisfying @xmath145 .
these results are readily understood by the new matching condition @xmath146 with the effective spin polarization @xmath147 .
two points are noteworthy in the above result : ( 1 ) if f@xmath0 and f@xmath1 are regarded as a whole , the effective polarization can be tuned continuously by changing the angle of the mutual orientations , which is impossible for one chosen ferromagnet . ( 2 ) for @xmath148 , the total conductance for the two ferromagnets ins anti - ferromagnetic alignment is larger than that in ferromagnetic alignment , which is completely different from the effect of gmr or tmr . to describe this new effect of magneto - resistance , define the ratio of andreev reflected magnetic resistance ( @xmath149 ) in ( f@xmath9f@xmath1)-qd - s by @xmath150 and the curves of @xmath149 vs @xmath113 for various @xmath151
are shown in fig.4 .
fig.5 shows the curves of @xmath152 vs @xmath18 for an asymmetric case , in which @xmath153 , @xmath154 is arbitrary , and @xmath155 . since f@xmath0 is fully polarized , the conductance of f@xmath0 is sensitive to the spin polarization and orientation of f@xmath1 . for @xmath156 ,
@xmath152 does not depend on @xmath18 ; while for @xmath157 , @xmath152 strongly depends on @xmath18 , with @xmath158 at @xmath159 and @xmath160 at @xmath161 .
we suggest that this effect can be applied to measure the spin polarization of f@xmath1 .
in practice , one may chose a half - metal material as f@xmath0 , the ferromagnetic material to be measured as f@xmath1 , and changing the spin orientation of f@xmath0 by applying an external magnetic field , then the spin polarization of f@xmath1 can be deduced from the weak / strong dependence of @xmath162 on @xmath18 .
now we turn to investigate the non - equilibrium transport of ( f@xmath9f@xmath1)-qd - s . for simplicity
, we only consider the antiparallel orientation of f@xmath95 and f@xmath1 ( i.e. , @xmath161 ) , with finite but small bias voltages ( i.e. , @xmath163 and @xmath164 ) . notice that the self - energy becomes to block - diagonal due to @xmath161 , and the expression of current @xmath165
can be simplified as , @xmath166 \;\ ; , \\
a_{11 } & = & \gamma _
{ 1\downarrow } \gamma _ { 1\uparrow } \left| g_{12}^r\right| ^2+\gamma _
{ 1\uparrow } \gamma _ { 1\downarrow } \left| g_{34}^r\right| ^2\;\ ; , \nonumber \\
a_{12 } & = & \gamma _
{ 2\uparrow } \gamma _ { 1\uparrow } \left| g_{12}^r\right| ^2+\gamma _ { 2\downarrow }
\gamma _ { 1\downarrow } \left| g_{34}^r\right| ^2\;\ ; , \nonumber \\
q_{1s } & = & \gamma _ { 1\uparrow }
\gamma _ s\tilde{\rho}\left [ \left| g_{11}^r\right| ^2+\left| g_{12}^r\right| ^2 + 2% % tcimacro{\func{re } } % beginexpansion \mathop{\rm re}% % endexpansion ( -\frac \delta \omega g_{11}^rg_{12}^{r*})\right ] + \nonumber \\ & & \gamma _ { 1\downarrow } \gamma _ s\tilde{\rho}\left [ \left| g_{33}^r\right| ^2+\left| g_{34}^r\right| ^2 + 2% % tcimacro{\func{re } } % beginexpansion \mathop{\rm re}% % endexpansion ( + \frac \delta \omega g_{33}^rg_{34}^{r*})\right ] \;\ ; , \nonumber \\ q_{12 } & = & \gamma _ { 2\downarrow }
\gamma _ { 1\uparrow } \left| g_{11}^r\right| ^2+\gamma _ { 2\uparrow } \gamma _ { 1\downarrow } \left| g_{33}^r\right| ^2\;\;. \nonumber\end{aligned}\ ] ] at zero temperature and in the low bias regime , the current of @xmath89 process vanishes . further assuming that both f@xmath0 and f@xmath1 are fully polarized , both @xmath92 and @xmath167 process are also forbidden .
only the process of @xmath94 , i.e. , crossed ar involving f@xmath9f@xmath1 and s contributes to the current . @xmath165 and @xmath168 are derived as @xmath169 notice that @xmath170 holds even if @xmath171 and @xmath172 , because @xmath165 is pure spin @xmath173 current and @xmath168 is pure spin @xmath174 current while @xmath175 is required to be non - spin - polarized current by the superconductor . for simplicity , we further assume that @xmath176 ( @xmath177 due to @xmath178 ) and @xmath179 , then the system ( f@xmath9f@xmath1)-qd - s is similar to a special n - qd - s one , in which the two spin bands of n have different chemical potentials controlled by @xmath180 and @xmath181 .
define the transmission probability of crossed ar by @xmath182 , the current can be expressed as @xmath183 notice that @xmath184 is an even function of @xmath185 , the above current formula implies that the sign of @xmath165 or @xmath168 is not determined by @xmath180 or @xmath181 but by @xmath186 .
this is quite unusual because it contains the case that @xmath187 and @xmath188 but @xmath189 ( this unusual property was first addressed in @xcite ) . generally , for a three - terminal system , one may expect that current flows out of the terminal with highest voltage and into the terminal with lowest voltage .
but for the current conducted by crossed ar , the sign of current in each ferromagnetic terminal is linked to the averaged chemical potential of the two , because two ferromagnets cooperate with each other in this process , with total energy balanced .
fig.6 illustrates the conducting process corresponding to the case of @xmath189 with @xmath190 and @xmath191 but @xmath192 .
we ignore the energy structure of qd in fig.6 for simplicity , however , the current @xmath193 depends strongly on the transmission probability of qd .
in fact , @xmath194 is the integral of @xmath184 over the range of @xmath195 .
fig7 shows the surfaces of @xmath196 and corresponding @xmath197 spectrum for three typical cases of @xmath198 and @xmath199 .
in fig.7a , @xmath200 , the spin degenerate level of qd is hybridized to two andreev bound states due to coupling with s , while the coupling with f@xmath0 and f@xmath1 provides the small broadening to these bound states .
@xmath201 has two peaks with the maximum of unity at each of the andreev bound states . correspondingly , the surface of @xmath196 has five steps : the highest step corresponds to @xmath202 covering both of the peaks ; the second step ( including two patches ) corresponds to @xmath202 covering one of the peaks ; the third step ( including three patches ) corresponds to @xmath202 or @xmath203 covering none of the peaks ; the fourth step ( including two patches ) corresponds to @xmath203 covering one of the peaks ; and the lowest step corresponds to @xmath203 covering both of the peaks . in fig.7b , @xmath204 , the andreev bound states
are sufficiently broadened so that the two peaks in @xmath201 merge into one .
the one peak structure of @xmath201 spectrum corresponds to three step pattern in @xmath196 surface . in fig.7c , @xmath205 , the resonant level of qd
is significantly broadened , as a result , @xmath201 is small and flat with tails at @xmath206 .
the structureless @xmath201 spectrum corresponds to a plain in @xmath196 surface , proportional to @xmath207 . in short
, @xmath201 spectrum can be extracted from the measurement of @xmath196 surface .
in this paper , we have investigated the andreev reflection in a ( f@xmath9f@xmath1)-qd - s system . by using the non - equilibrium green function ,
a general current formula is derived , allowing arbitrary spin polarizations , magnetization orientations and bias voltages in f@xmath0 and f@xmath1 .
the formula is applied to several special cases , revealing some interesting properties of this system : ( 1 ) analogous to the fermi velocity mismatch in f / s contact , the zero bias conductance in f - qd - s reaches its maximum @xmath118 if matching condition @xmath208 satisfied .
( 2 ) for total current ( conductance ) of ( f@xmath0,f@xmath1)-qd - s with @xmath209 , the two ferromagnets f@xmath0 and f@xmath1 are equivalent to an effective ferromagnet f , and the effective polarization @xmath129 can be tuned by the angle between the spin orientations of f@xmath0 and f@xmath1 . (
3 ) there is a new effect of magneto - resistance in ( f@xmath0,f@xmath1)-qd - s ( named as @xmath210 ) , in which the conductance for f@xmath0 and f@xmath1 in anti - ferromagnetic alignment is larger than that in ferromagnetic alignment .
base on this effect , a possible way to measure the spin polarization of ferromagnetic material is proposed .
( 4 ) the non - equilibrium transport of this system is quite unusual .
especially , if f@xmath0 and f@xmath1 are fully but opposite polarized , the signs of current through f@xmath0 and f@xmath1 is determined by @xmath207 rather than @xmath180 or @xmath181 .
furthermore , the surface of @xmath211 depends strongly on the ar transmission probability , which can be applied to extract the latter .
finally , we believe that the suggested ( f@xmath212f@xmath1)-qd - s system is accessible of the up - date nano - technology , and we are eager to see relevant experiment on such appealing system .
this project was supported by nsfc under grant no.10074001 .
we would like to thank y. lu and y. f. yang for useful discussions .
one of the authors ( t .- h .
lin ) would also like to thank the support from the visiting scholar foundation of state key laboratory for mesoscopic physics in peking university .
@xmath213 to whom correspondence should be addressed .
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* schematic drawing of the three - terminal system under consideration . f@xmath0 and
f@xmath1 represent two ferromagnetic electrodes with different magnetization orientations and bias voltages , qd is a quantum dot , and s is a superconductor with zero voltage as the ground .
* the zero bias conductance @xmath133 vs @xmath113 for f - qd - s , where @xmath214 is the spin polarization of f. @xmath107 is the ratio of coupling strengths , with @xmath148 for ( a ) and @xmath215 for ( b ) . * the total conductance @xmath133 vs @xmath18 for ( f@xmath9f@xmath1)-qd - s , where @xmath18 is the angle between the orientations of f@xmath0 and f@xmath2 , with @xmath216 , @xmath138 , and @xmath217 . * @xmath149 vs @xmath113 in ( f@xmath9f@xmath1)-qd - s , where @xmath218 @xmath219 , @xmath113 and @xmath151 have the same meaning as in fig.3 . * the conductance @xmath152 vs @xmath18 for different @xmath154 , with @xmath153 and @xmath139 .
@xmath152 has strong / weak dependence on @xmath18 for large / small @xmath154 , which can be applied to measure the spin polarization of f@xmath1 . *
schematic diagram of non - equilibrium transport in ( f@xmath220f@xmath1)-qd - s .
f@xmath0 and f@xmath1 are in anti - ferromagnetic alignment , marked by left- and right- slanted shadows , respectively .
s is marked by crossed shadow , with the energy gap region @xmath221 with respect to the chemical potential ; qd is between the two barriers , and the energy structure is ignored for simplicity .
the diagram illustrates an unusual property of the current conducted by crossed ar involving f@xmath0 , f@xmath1 and s : the signs of @xmath165 or @xmath168 are determined by @xmath222 rather than @xmath223 or @xmath224 . *
the current @xmath193 vs the bias voltages @xmath225 for three typical cases : ( a ) @xmath200 ; ( b ) @xmath226 ; and ( c ) @xmath205 .
the surface of @xmath211 has close relationship to the spectrum @xmath184 , which can be used to extract the latter . | we study the andreev reflection ( ar ) in a three terminal mesoscopic hybrid system , in which two ferromagnets ( f@xmath0 and f@xmath1 ) are coupled to a superconductor ( s ) through a quantum dot ( qd ) . by using non - equilibrium green function
, we derive a general current formula which allows arbitrary spin polarizations , magnetization orientations and bias voltages in f@xmath0 and f@xmath1 .
the formula is applied to study both zero bias conductance and finite bias current .
the current conducted by crossed ar involving f@xmath0 , f@xmath2 and s is particularly unusual , in which an electron with spin @xmath3 incident from one of the ferromagnets picks up another electron with spin @xmath4 from the other one , both enter s and form a cooper pair .
several special cases are investigated to reveal the properties of ar in this system .
pacs numbers : 74.50.+r , 73.40.gk , 75.70.pa |
SECTION 1. SHORT TITLE.
This Act may be cited as the ``Children's Access to Reconstructive
Evaluation & Surgery (CARES) Act of 2007''.
SEC. 2. COVERAGE OF MINOR CHILD'S CONGENITAL OR DEVELOPMENTAL DEFORMITY
OR DISORDER.
(a) Group Health Plans.--
(1) Public health service act amendments.--(A) Subpart 2 of
part A of title XXVII of the Public Health Service Act is
amended by adding at the end the following new section:
``SEC. 2707. STANDARDS RELATING TO BENEFITS FOR MINOR CHILD'S
CONGENITAL OR DEVELOPMENTAL DEFORMITY OR DISORDER.
``(a) Requirements for Reconstructive Surgery.--
``(1) In general.--A group health plan, and a health
insurance issuer offering group health insurance coverage, that
provides coverage for surgical benefits shall provide coverage
for outpatient and inpatient diagnosis and treatment of a minor
child's congenital or developmental deformity, disease, or
injury. A minor child shall include any individual through 21
years of age.
``(2) Requirements.--Any coverage provided under paragraph
(1) shall be subject to pre-authorization or pre-certification
as required by the plan or issuer, and such coverage shall
include any surgical treatment which, in the opinion of the
treating physician, is medically necessary to approximate a
normal appearance.
``(3) Treatment defined.--
``(A) In general.--In this section, the term
`treatment' includes reconstructive surgical procedures
(procedures that are generally performed to improve
function, but may also be performed to approximate a
normal appearance) that are performed on abnormal
structures of the body caused by congenital defects,
developmental abnormalities, trauma, infection, tumors,
or disease, including--
``(i) procedures that do not materially
affect the function of the body part being
treated; and
``(ii) procedures for secondary conditions
and follow-up treatment.
``(B) Exception.--Such term does not include
cosmetic surgery performed to reshape normal structures
of the body to improve appearance or self-esteem.
``(b) Notice.--A group health plan under this part shall comply
with the notice requirement under section 714(b) of the Employee
Retirement Income Security Act of 1974 with respect to the requirements
of this section as if such section applied to such plan.''.
(B) Section 2723(c) of such Act (42 U.S.C. 300gg-23(c)) is
amended by striking ``section 2704'' and inserting ``sections
2704 and 2707''.
(2) ERISA amendments.--(A) Subpart B of part 7 of subtitle
B of title I of the Employee Retirement Income Security Act of
1974 is amended by adding at the end the following new section:
``SEC. 714. STANDARDS RELATING TO BENEFITS FOR MINOR CHILD'S CONGENITAL
OR DEVELOPMENTAL DEFORMITY OR DISORDER.
``(a) Requirements for Reconstructive Surgery.--
``(1) In general.--A group health plan, and a health
insurance issuer offering group health insurance coverage, that
provides coverage for surgical benefits shall provide coverage
for outpatient and inpatient diagnosis and treatment of a minor
child's congenital or developmental deformity, disease, or
injury. A minor child shall include any individual who has not
attained age 22.
``(2) Requirements.--Any coverage provided under paragraph
(1) shall be subject to pre-authorization or pre-certification
as required by the plan or issuer, and such coverage shall
include any surgical treatment which, in the opinion of the
treating physician, is medically necessary to approximate a
normal appearance.
``(3) Treatment defined.--
``(A) In general.--For purposes of this section,
the term `treatment' includes reconstructive surgical
procedures (procedures that are generally performed to
improve function, but may also be performed to
approximate a normal appearance) that are performed on
abnormal structures of the body caused by congenital
defects, developmental abnormalities, trauma,
infection, tumors, or disease, including--
``(i) procedures that do not materially
affect the function of the body part being
treated; and
``(ii) procedures for secondary conditions
and follow-up treatment.
``(B) Exception.--Such term does not include
cosmetic surgery performed to reshape normal structures
of the body to improve appearance or self-esteem.
``(b) Notice Under Group Health Plan.--The imposition of the
requirements of this section shall be treated as a material
modification in the terms of the plan described in the last sentence of
section 102(a), for purposes of assuring notice of such requirements
under the plan; except that the summary description required to be
provided under the fourth sentence of section 104(b)(1) with respect to
such modification shall be provided by not later than 60 days after the
first day of the first plan year in which such requirements apply.''.
(B) Section 731(c) of such Act (29 U.S.C. 1191(c)) is
amended by striking ``section 711'' and inserting ``sections
711 and 714''.
(C) Section 732(a) of such Act (29 U.S.C. 1191a(a)) is
amended by striking ``section 711'' and inserting ``sections
711 and 714''.
(D) The table of contents in section 1 of such Act is
amended by inserting after the item relating to section 713 the
following new item:
``Sec. 714. Standards relating to benefits for minor child's congenital
or developmental deformity or disorder.''.
(3) Internal revenue code amendments.--
(A) In general.--Subchapter B of chapter 100 of the
Internal Revenue Code of 1986 is amended by adding at
the end the following new section:
``SEC. 9813. STANDARDS RELATING TO BENEFITS FOR MINOR CHILD'S
CONGENITAL OR DEVELOPMENTAL DEFORMITY OR DISORDER.
``(a) Requirements for Reconstructive Surgery.--
``(1) In general.--A group health plan, and a health
insurance issuer offering group health insurance coverage, that
provides coverage for surgical benefits shall provide coverage
for outpatient and inpatient diagnosis and treatment of a minor
child's congenital or developmental deformity, disease, or
injury. A minor child shall include any individual who has not
attained age 22.
``(2) Requirements.--Any coverage provided under paragraph
(1) shall be subject to pre-authorization or pre-certification
as required by the plan or issuer, and such coverage shall
include any surgical treatment which, in the opinion of the
treating physician, is medically necessary to approximate a
normal appearance.
``(3) Treatment defined.--
``(A) In general.--For purposes of this section,
the term `treatment' includes reconstructive surgical
procedures (procedures that are generally performed to
improve function, but may also be performed to
approximate a normal appearance) that are performed on
abnormal structures of the body caused by congenital
defects, developmental abnormalities, trauma,
infection, tumors, or disease, including--
``(i) procedures that do not materially
affect the function of the body part being
treated; and
``(ii) procedures for secondary conditions
and follow-up treatment.
``(B) Exception.--Such term does not include
cosmetic surgery performed to reshape normal structures
of the body to improve appearance or self-esteem.''.
(B) Clerical amendment.--The table of sections for
such subchapter is amended by adding at the end the
following new item:
``Sec. 9813. Standards relating to benefits for minor child's
congenital or developmental deformity or
disorder.''.
(b) Individual Health Insurance.--(1) Part B of title XXVII of the
Public Health Service Act is amended by inserting after section 2752
the following new section:
``SEC. 2753. STANDARDS RELATING TO BENEFITS FOR MINOR CHILD'S
CONGENITAL OR DEVELOPMENTAL DEFORMITY OR DISORDER.
``(a) Requirements for Reconstructive Surgery.--
``(1) In general.--A group health plan, and a health
insurance issuer offering group health insurance coverage, that
provides coverage for surgical benefits shall provide coverage
for outpatient and inpatient diagnosis and treatment of a minor
child's congenital or developmental deformity, disease, or
injury. A minor child shall include any individual through 21
years of age.
``(2) Requirements.--Any coverage provided under paragraph
(1) shall be subject to pre-authorization or pre-certification
as required by the plan or issuer, and such coverage shall
include any surgical treatment which, in the opinion of the
treating physician, is medically necessary to approximate a
normal appearance.
``(3) Treatment defined.--
``(A) In general.--In this section, the term
`treatment' includes reconstructive surgical procedures
(procedures that are generally performed to improve
function, but may also be performed to approximate a
normal appearance) that are performed on abnormal
structures of the body caused by congenital defects,
developmental abnormalities, trauma, infection, tumors,
or disease, including--
``(i) procedures that do not materially
affect the function of the body part being
treated; and
``(ii) procedures for secondary conditions
and follow-up treatment.
``(B) Exception.--Such term does not include
cosmetic surgery performed to reshape normal structures
of the body to improve appearance or self-esteem.
``(b) Notice.--A health insurance issuer under this part shall
comply with the notice requirement under section 714(b) of the Employee
Retirement Income Security Act of 1974 with respect to the requirements
referred to in subsection (a) as if such section applied to such issuer
and such issuer were a group health plan.''.
(2) Section 2762(b)(2) of such Act (42 U.S.C. 300gg-62(b)(2)) is
amended by striking ``section 2751'' and inserting ``sections 2751 and
2753''.
(c) Effective Dates.--(1) The amendments made by subsection (a)
shall apply with respect to group health plans for plan years beginning
on or after January 1, 2008.
(2) The amendment made by subsection (b) shall apply with respect
to health insurance coverage offered, sold, issued, renewed, in effect,
or operated in the individual market on or after such date.
(d) Coordinated Regulations.--Section 104(1) of Health Insurance
Portability and Accountability Act of 1996 is amended by striking
``this subtitle (and the amendments made by this subtitle and section
401)'' and inserting ``the provisions of part 7 of subtitle B of title
I of the Employee Retirement Income Security Act of 1974, the
provisions of parts A and C of title XXVII of the Public Health Service
Act, and chapter 100 of the Internal Revenue Code of 1986''. | Children's Access to Reconstructive Evaluation & Surgery (CARES) Act of 2007 - Amends the Public Health Service Act, the Employee Retirement Income Security Act of 1974 (ERISA), and the Internal Revenue Code to require a group health plan, and a health insurance issuer offering group coverage, that cover surgical benefits to also cover outpatient and inpatient diagnosis and treatment of a congenital or developmental deformity, disease, or injury of a minor child (defined as child under the age of 22).
Requires that such coverage: (1) be subject to pre-authorization or pre-certification requirements of the plan or issuer; and (2) include any surgical treatment deemed by the treating physician to be medically necessary to approximate a normal appearance. Defines "treatment" to include reconstructive surgical procedures that are performed on abnormal structures of the body caused by congenital defects, abnormalities, trauma, infection, tumors, or disease, including: (1) procedures that do not materially affect the function of the body part being treated; and (2) procedures for secondary conditions and follow-up treatment. Excludes cosmetic surgery performed to reshape normal structures of the body to improve appearance or self-esteem. |
historically , acute postinfectious glomerulonephritis ( gn ) is caused by staphylococcus epidermidis and s. aureus , with typical findings of diffuse endocapillary proliferation and exudative gn on light microscopy , c3-dominant deposits with or without immunoglobulin ( ig)g codeposition on immunofluorescence , and subepithelial hump - shaped deposits on electron microscopy .
a third pattern was recently described , termed superantigen - related gn or acute postmethicillin - resistant s. aureus ( mrsa ) gn , with the distinguishing feature of iga- or iga - codominant mesangial staining .
most of the causative pathogens of this disease are mrsas , and favorable renal outcomes have been reported after timely administration of antibiotics and adequate immunosuppressant therapy . regarding the emerging importance of mrsa - related iga nephropathy , we present a patient who had an mrsa infection without awareness of early sign of gn , resulting in a devastating renal outcome with crescent formation from iga - dominant postinfectious gn .
a 22-year - old native taiwanese woman was referred for the evaluation of rapidly developing advanced renal failure .
her medical history was unremarkable , and she had no personal or family history of the illness .
a total of 6 months before referral , she had a community - acquired skin infection , initially in the left foot .
subsequently , she developed a skin abscess in the left posterolateral trunk with a pus culture that yielded mrsa .
in addition to 2 weeks of antibiotic treatment with intravenous vancomycin ( 1 g/8 hour ) , an open surgical incision was performed .
she believed that it was related to menstruation and did not receive further medical attention .
then , her serum creatinine ( cr ) level was 1.2 mg / dl ( reference : 0.51.3 mg / dl ) .
she was conscious on admission with a temperature of 35.8c , heart rate of 67 beats / minute , and blood pressure of 156/89 mm hg .
the results of the laboratory tests of her serum were as follows : blood urea nitrogen , 60 mg / dl ( reference : 725 mg / dl ) ; cr , 6.8 mg / dl ; sodium , 137 meq / l ( reference : 133145 meq / l ) ; potassium , 4.5 meq / l ( reference : 3.35.1 meq / l ) ; intact calcium , 4.58 mg / dl ( reference : 3.685.6 mg / dl ) ; phosphate , 4.6 mg / dl ( reference : 2.55 mg / dl ) ; uric acid , 5.6 mg / dl ; total protein , 4.6 g / dl ( reference : 6.08.5 g / dl ) ; albumin , 3.3 g / dl ( reference : 3.55.0 g / dl ) ; and hemoglobin , 9.1 g / dl ( reference : 1214 g / dl ) .
she had low serum levels of c3 ( 38.2 mg / dl ; reference : 79152 mg / dl ) and c4 ( 11.8 mg / dl ; reference : 1638 mg / dl ) .
her immunoglobulin levels were as follows : igg , 418 mg / dl ( reference : 7511560 mg / dl ) ; iga , 135 mg / dl ( reference : 82453 mg / dl ) ; and igm , 32.9 mg / dl ( reference : 46304 mg / dl ) .
serological test results were all negative for antinuclear antibody , anti - dna antibody , antineutrophil cytoplasmic antibody , antiglomerular basement membrane antibody , rheumatoid factor activity , hepatitis b surface antigen , and hepatitis c virus antibody .
urinalysis demonstrated a nephrotic range of proteinuria ( 4166 mg/24 hour , urine volume 1300 ml / day ) , 1630 cells / high - power field , and sterile pyuria .
renal ultrasound demonstrated normal bilateral kidney size ( right kidney , 10 cm ; left kidney , 10.2 cm ) but with increased cortical echogenicity .
a diagnostic renal biopsy was performed because of the unknown cause of her acute renal failure .
light microscopy revealed 9 glomeruli with 6 globally sclerotic glomeruli , 1 segmented sclerotic glomerulus , and 2 glomeruli with fibrocellular crescent formation .
an inflammatory infiltrate of mononuclear cells , diffuse interstitial fibrosis , and tubular atrophy were observed ( fig .
immunofluorescence microscopy demonstrated diffuse global granular - predominant iga staining ( 2 ) with less intense c3 staining ( 1 ) in the mesangium ( fig .
electron microscopy revealed the effacement of podocyte foot processes , segmental expansion of the mesangial matrix , and electron - dense material in the mesangial area .
schiff stain , 600 ) and ( b ) mesangial proliferation with fibrocellular crescent formation ( jones silver stain , 600 ) .
immunofluorescence staining for ( a ) iga scored as 2 + and ( b ) c3 scored as 1 + granular deposition in the mesangium and glomerular capillary loops ( original magnification 600 ) .
electron microscopy demonstrating ( a ) expansion of the mesangial matrix ( original magnification 4000 ) and ( b ) electron - dense deposits in the mesangium ( original magnification 20,000 ) .
according to these clinicopathological correlations , she was further diagnosed with crescentic iga nephropathy secondary to mrsa infection .
she had irreversible renal pathological change ; therefore , plasma exchange and immunosuppressive therapies were not prescribed .
in 1961 , powell first identified staphylococcal infection as the cause of gn . typically , postinfectious gn is dominated by igg , detected using immunofluorescence , and by the presence of immune complex depositions with characteristic humps in the subepithelial areas of glomerular basement membranes .
recently , a new type of iga - dominated postinfectious gn was described that is frequently associated with mrsa infections .
the main clinical characteristics are as follows : insidious onset of rapidly progressive renal failure , hematuria , and proteinuria associated with different types of proliferative gn and varying degrees of crescent formation accompanied by codominant glomerular deposition of iga .
one hypothesis implicates bacterial enterotoxins produced by mrsa as superantigens that lead to t cell activation , release of cytokines , and antibody production , such as iga .
the development of monoclonal antibodies to s. aureus cell envelope antigen proved the existence of marked deposition found in the glomeruli .
subsequently , this disease was detected in patients at an increased frequency than before the use of monoclonal antibodies .
iga - dominant mrsa - gn is often mistaken for idiopathic iga nephropathy because of its similar immunofluorescence pattern .
findings favoring mrsa - gn over iga nephropathy are as follows : hypocomplementemia , intercurrent staphylococcal infection , diffuse endocapillary hypercellularity with prominent neutrophil infiltration detected using light microscopy , and subepithelial humps detected using electron microscopy . however , the characteristic subepithelial hump - shaped deposits are present in only 20% of patients . the hypotheses proposed to explain this feature are as follows : in contrast to igg deposits that are resorbed , iga deposited in poststaphylococcal gn persists even when the disease resolves .
our patient 's characteristics were consistent with the diagnosis of iga - dominant mrsa - gn , according to the findings described above . in our case , a subepithelial hump was absent , which may be due to the delayed finding of gn .
most patients with iga - dominant mrsa - gn experience a fulminant course of acute renal failure , severe proteinuria , and variable hematuria . however , after early eradication of mrsa infection using an antibiotic , there have been reports of renal function recovering in patients .
a separate report revealed the eradication of mrsa infection and restoration of renal function after additional steroid treatment .
however , considering that infection causes this disease , aggressive steroid pulse therapy and immunosuppressant treatment for rapidly progressive crescentic gn is dangerous .
therefore , we suggest controlling the mrsa infection first with adequate antibiotics and then treating it according to the guideline for iga nephropathy . conservative therapy of renin - angiotensin system blockade with blood pressure control was initiated while the proteinuria was 0.5 to 1 g / day .
an add - on steroid therapy was administrated only when persistent proteinuria > 1 g / day and glomerular filtrate rate > 50 ml / minute per 1.73 m was detected after 3 to 6 months of optimized supportive care .
glomerular crescent formation is an uncommon occurrence in this new type of poststaphylococcal gn and complicates the clinical outcome . in total ,
11 patients with this entity have been described in the literature ; 9 were infected with mrsa , and 1 was infected with methicillin - sensitive staphylococcus aureus .
the clinical characteristics of these patients included at least 1 with glomerular crescent formation on renal biopsy . in total ,
all patients recovered partial renal function ; however , 2 died because of infectious complications .
the use of immunosuppressive therapy in this setting is unclear due to limited supporting evidence in literature .
we suggest that immunosuppressant use should be considered when the patient 's renal function deteriorates after well controlling the underlying mrsa infection . in our patient , although her skin infection resolved long before her admission , renal pathology was irreversible due to advanced fibrocellular crescent formation .
therefore , more aggressive treatment was not indicated , and she permanently lost her renal function at a young age .
because the incidence of mrsa infection is increasing , iga crescentic gn due to mrsa may become a significant health issue .
we emphasize the importance of being alert to the signs of gn when examining patients with prior mrsa infection because early intervention can rescue kidney function .
we suggest conducting routine checks of patients urine using a dipstick post - mrsa infection to detect mrsa - related gn without delay .
| abstractmethicillin - resistant staphylococcus aureus ( mrsa ) is an emerging pathogen that infects the skin and soft tissue . however , there are few reports of renal complications from mrsa involving immunoglobulin ( ig)a - dominated rapidly progressive glomerulonephritis ( gn ) .
favorable renal outcomes from iga gn are achieved by administering timely therapy . in the present study
, we describe the case of a healthy young woman suffering from a cutaneous mrsa infection that initially presented with gross hematuria .
six months after eradicating the infection , severe impairment of renal function was noted because of intractable nausea and vomiting .
renal pathology revealed advanced iga nephropathy with fibrocellular crescent formation .
an aggressive treatment plan using immunosuppressants was not adopted because of her irreversible renal pathology , and she was therefore administered maintenance hemodialysis.this instructive case stresses the importance of being aware of the signs of iga nephropathy post - mrsa infection , such as cutaneous lesions that are mostly painless and accompanied by hematuria and mild proteinuria . if the kidney can not be salvaged , it will undergo irreversible damage with devastating consequences . |
SECTION 1. SHORT TITLE.
This Act may be cited as the ``Recalcitrant Cancer Research Act of
2012''.
SEC. 2. SCIENTIFIC FRAMEWORK FOR RECALCITRANT CANCERS.
Subpart 1 of part C of title IV of the Public Health Service Act
(42 U.S.C. 285 et seq.) is amended by adding at the end the following:
``SEC. 417G. SCIENTIFIC FRAMEWORK FOR RECALCITRANT CANCERS.
``(a) Development of Scientific Framework.--
``(1) In general.--For each recalcitrant cancer identified
under subsection (b), the Director of the Institute shall
develop (in accordance with subsection (c)) a scientific
framework for the conduct or support of research on such
cancer.
``(2) Contents.--The scientific framework with respect to a
recalcitrant cancer shall include the following:
``(A) Current status.--
``(i) Review of literature.--A summary of
findings from the current literature in the
areas of--
``(I) the prevention, diagnosis,
and treatment of such cancer;
``(II) the fundamental biologic
processes that regulate such cancer
(including similarities and differences
of such processes from the biological
processes that regulate other cancers);
and
``(III) the epidemiology of such
cancer.
``(ii) Scientific advances.--The
identification of relevant emerging scientific
areas and promising scientific advances in
basic, translational, and clinical science
relating to the areas described in subclauses
(I) and (II) of clause (i).
``(iii) Researchers.--A description of the
availability of qualified individuals to
conduct scientific research in the areas
described in clause (i).
``(iv) Coordinated research initiatives.--
The identification of the types of initiatives
and partnerships for the coordination of
intramural and extramural research of the
Institute in the areas described in clause (i)
with research of the relevant national research
institutes, Federal agencies, and non-Federal
public and private entities in such areas.
``(v) Research resources.--The
identification of public and private resources,
such as patient registries and tissue banks,
that are available to facilitate research
relating to each of the areas described in
clause (i).
``(B) Identification of research questions.--The
identification of research questions relating to basic,
translational, and clinical science in the areas
described in subclauses (I) and (II) of subparagraph
(A)(i) that have not been adequately addressed with
respect to such recalcitrant cancer.
``(C) Recommendations.--Recommendations for
appropriate actions that should be taken to advance
research in the areas described in subparagraph (A)(i)
and to address the research questions identified in
subparagraph (B), as well as for appropriate benchmarks
to measure progress on achieving such actions,
including the following:
``(i) Researchers.--Ensuring adequate
availability of qualified individuals described
in subparagraph (A)(iii).
``(ii) Coordinated research initiatives.--
Promoting and developing initiatives and
partnerships described in subparagraph (A)(iv).
``(iii) Research resources.--Developing
additional public and private resources
described in subparagraph (A)(v) and
strengthening existing resources.
``(3) Timing.--
``(A) Initial development and subsequent update.--
For each recalcitrant cancer identified under
subsection (b)(1), the Director of the Institute
shall--
``(i) develop a scientific framework under
this subsection not later than 18 months after
the date of the enactment of this section; and
``(ii) review and update the scientific
framework not later than 5 years after its
initial development.
``(B) Other updates.--The Director of the Institute
may review and update each scientific framework
developed under this subsection as necessary.
``(4) Public notice.--With respect to each scientific
framework developed under subsection (a), not later than 30
days after the date of completion of the framework, the
Director of the Institute shall--
``(A) submit such framework to the Committee on
Energy and Commerce and Committee on Appropriations of
the House of Representatives, and the Committee on
Health, Education, Labor, and Pensions and Committee on
Appropriations of the Senate; and
``(B) make such framework publically available on
the Internet website of the Department of Health and
Human Services.
``(b) Identification of Recalcitrant Cancer.--
``(1) In general.--Not later than 6 months after the date
of the enactment of this section, the Director of the Institute
shall identify two or more recalcitrant cancers that each--
``(A) have a 5-year relative survival rate of less
than 20 percent; and
``(B) are estimated to cause the death of at least
30,000 individuals in the United States per year.
``(2) Additional cancers.--The Director of the Institute
may, at any time, identify other recalcitrant cancers for
purposes of this section. In identifying a recalcitrant cancer
pursuant to the previous sentence, the Director may consider
additional metrics of progress (such as incidence and mortality
rates) against such type of cancer.
``(c) Working Groups.--For each recalcitrant cancer identified
under subsection (b), the Director of the Institute shall convene a
working group comprised of representatives of appropriate Federal
agencies and other non-Federal entities to provide expertise on, and
assist in developing, a scientific framework under subsection (a). The
Director of the Institute (or the Director's designee) shall
participate in the meetings of each such working group.
``(d) Reporting.--
``(1) Biennial reports.--The Director of NIH shall ensure
that each biennial report under section 403 includes
information on actions undertaken to carry out each scientific
framework developed under subsection (a) with respect to a
recalcitrant cancer, including the following:
``(A) Information on research grants awarded by the
National Institutes of Health for research relating to
such cancer.
``(B) An assessment of the progress made in
improving outcomes (including relative survival rates)
for individuals diagnosed with such cancer.
``(C) An update on activities pertaining to such
cancer under the authority of section 413(b)(7).
``(2) Additional one-time report for certain frameworks.--
For each recalcitrant cancer identified under subsection
(b)(1), the Director of the Institute shall, not later than 6
years after the initial development of a scientific framework
under subsection (a), submit a report to the Congress on the
effectiveness of the framework (including the update required
by subsection (a)(3)(A)(ii)) in improving the prevention,
detection, diagnosis, and treatment of such cancer.
``(e) Recommendations for Exception Funding.--The Director of the
Institute shall consider each relevant scientific framework developed
under subsection (a) when making recommendations for exception funding
for grant applications.
``(f) Definition.--In this section, the term `recalcitrant cancer'
means a cancer for which the five-year relative survival rate is below
50 percent.''. | Recalcitrant Cancer Research Act of 2012 - Amends the Public Health Service Act to require the Director of the National Cancer Institute (NCI) to develop a scientific framework for research on recalcitrant cancers (cancer with a 5-year relative survival rate below 50%), which includes: (1) a review of the status of research, such as a summary of findings, identification of promising scientific advances, a description of the availability of qualified scientific researchers, and the identification of resources available to facilitate research; (2) identification of research questions that have not been adequately addressed; and (3) recommendations for actions to advance research and for appropriate benchmarks to measure progress on achieving such actions. Requires the Director to develop the framework within 18 months and review and update it every 5 years.
Requires the Director to identify within 6 months 2 or more recalcitrant cancers that have a 5-year relative survival rate of less than 20%, and are estimated to cause the death of at least 30,000 individuals in the United States per year. Authorizes the Director to identify additional such cancers and to consider additional metrics of progress (such as incidence and mortality rates) against such cancer.
Requires the Director to convene a working group for each identified cancer to provide expertise on, and assist in developing, a scientific framework under this Act.
Requires the Director to consider each relevant scientific framework developed under this Act when making recommendations for exception funding for grant applications. |
we have previously reported that interleukin-1 ( il-1 ) increases neuronal excitability via the inhibition of large - conductance ca - induced k channels ( bk ) activated by ca influx through both nmda receptors ( nmdars ) and voltage - dependent ca channels ( vdcc ) in the dissociated hippocampal neurons [ 1 , 2 ] .
the inhibitory effect of il-1 on the amplitude of nmda - induced outward currents ( inmda - out ) , which is mediated by bk channel activation , is largely mediated by phosphorylation of p38 mitogen - activated protein kinase ( mapk ) .
it is considered that active p38 mapk directly phosphorylates bk channels to decrease the amplitude of inmda - out . on the other hand
, it has been reported that prostaglandin e2 ( pge2 ) potentiates the amplitude of inmda - out in the dissociated preoptic neurons .
however , the precise intracellular mechanism underlying the effects of pge2 on bk channels activated by ca influx through nmdars still remains to be determined .
pge2 , a major metabolite of arachidonic acid produced by cyclooxygenase pathways , can bind to four e - prostanoid receptor subtypes , ep1 , ep2 , ep3 , and ep4 .
the ep2 and ep4 receptors couple positively to gs to increase camp , whereas the ep3 receptors couple negatively to camp via gi .
in addition , the selective ep2 receptor activation leads to a protection of neurons against nmdar - mediated excitotoxicity and oxygen - glucose deprivation - induced anoxia in the hippocampal neurons [ 57 ] , whereas the genetic deletion of ep2 receptors exacerbates the brain damage after infarction .
at present , it is considered that ep2 receptors induce neuroprotection through the activation of camp - protein kinase a ( pka ) pathway and the subsequent activation of camp - responsive element binding protein ( creb ) , which facilitates the neuronal survival .
in fact , pka inhibitors abrogate the ep2 receptor - mediated neuroprotection . in the present study
, we showed that pge2 enhanced inmda - out through the activation of ep2 receptors in mouse cortical neurons .
the activation of camp / pka signaling pathway was involved in the ep2 receptor agonist - induced potentiation of inmda - out .
furthermore , an ep2 receptor agonist facilitated the recovery from nmda - induced dendritic beading .
all efforts were made to minimize animal suffering and to reduce the number of animals used .
embryonic day 19 mouse pups and 3-week - old male c57bl/6 mice were used for electrophysiology and immunohistochemistry .
the mice were maintained on a 12 hr light / dark cycle ( light on at 8:00 am ) under conditions of 2225c ambient temperature with food and water ad libitum .
kt5720 ( a specific pka inhibitor ) , camp , nmda , and paxilline ( a specific bk channel blocker ) were purchased from sigma .
butaprost ( an ep2 receptor agonist ) and tg6 - 10 - 1 ( an ep2 receptor antagonist ) were purchased from cayman and millipore , respectively .
the concentrations of ep2 agonists / antagonists were determined according to the paper as previously described [ 5 , 10 ] . synthesized selective agonists of ep1 receptor ( ono - di-004 ) ,
ep2 receptor ( ono - ae1 - 259 ) , ep3 receptor ( ono - ae-248 ) , and ep4 receptor ( ono - ae1 - 329 ) were kindly provided from ono pharmaceuticals .
the c57bl/6 mice ( 3 weeks old ) were anesthetized with pentobarbital sodium ( 200 mg / kg i.p . ) and then decapitated .
the cortical slice preparations with a thickness of 375 m were made using a microslicer ( vt1000s ; leica , nussloch , germany ) .
the slices were kept in the incubation medium saturated with 95% o2 - 5% co2 at room temperature ( 2124c ) for 1 hr before mechanical dissociation .
the incubation medium contained ( mm ) 124 nacl , 3 kcl , 1.5 kh2po4 , 24 nahco3 , 2.4 cacl2 , 1 mgcl2 , and 10 glucose .
mechanical dissociation was accomplished using a custom - built vibration device and a fire - polished glass pipette as previously described .
voltage - clamp recordings from mechanically dissociated cortical neurons were carried out using perforated whole - cell patch - clamp technique as previously described .
amphotericin b ( 260 g / ml ) was added to pipette solution ( the pipette solution contained ( mm ) 70 k - methanesulfonate , 10 kcl , and 10 hepes ) .
the external solution contained ( in mm ) 150 nacl , 5 kcl , 2 cacl2 , 10 hepes , and 10 glucose ( ph 7.4 ) .
for the whole - cell recordings , camp or kt 5720 was added to pipette solution .
the holding potential was maintained at 40 mv throughout the voltage - clamp experiments .
cortices were obtained from embryonic day 19 ( e19 ) mouse pups and dissociated with 90 u papain ( worthington biochemical corp . ,
lakewood , nj , usa ) in hank 's balanced salts solution ( hbss ) ( gibco , grand island , ny usa ) containing 10 mm n-[2-hydroxyethyl]piperazine - n-[2-ethanesulfonic acid ] ( hepes ) ( ph 7.5 ) .
cortices were seeded onto polyethyleneimine ( pei ) coated 13 cover glass ( matsunami ) with attachment medium .
attachment medium was minimum essential medium ( mem ) ( gibco ) containing 10% horse serum , 450 mg / ml glucose , 1% penicillin / streptomycin , and 1% sodium pyruvate .
maintenance medium was neurobasal medium containing 2% b-27 ( gibco ) , 1% glutamine , and 1% penicillin / streptomycin .
cortical neurons were used for the experiment on 10 days in vitro ( div ) .
nmda ( 30 m ) was diluted with locke 's solution and applied to cortical neurons on 10 div at 37c for 10 minutes .
locke 's solution contained ( mm ) 154 nacl , 5.6 kcl , 2.3 cacl2 , 1 mgcl2 , 3.6 nahco3 , 5 hepes , and 10 glucose ( ph 7.2 ) .
nmda exposure was terminated by fixation with 4% paraformaldehyde at 4c for 1 hr .
cortical neurons on the 13 cover glass were permeabilized with 0.4% triton x-100 for 1 hr on 24-well plate ( corning ) .
cortical neurons were incubated antimicrotubule associated protein 2 ( map-2 , 1 : 800 , millipore ) overnight at 4c and then incubated with secondary antibody conjugated with alexa 488 ( 1 : 400 , jackson immunoresearch ) at 4c for 2 hr .
images were captured with the c2si confocal laser microscope ( clms , nikon corporation , tokyo , japan ) using 20 ( na : 0.75 ) dry lens and 60 ( na : 1.4 ) oil immersion lens .
bead - forming neuron was defined as the neuron that has at least one beading structure on the dendrite .
bead formation was displayed as a percentage of bead - forming neurons / total neurons in randomly captured images from 20 fields .
statistical analyses of the results were performed with one - way analysis of variance ( anova ) with post hoc dunnett 's or tukey 's test and two - way anova with bonferroni test or unpaired t - test using the graphpad prism software package .
the direct effects of four e - prostanoid receptor agonists on inmda - out were analyzed .
amphotericin b - perforate patch - clamp recordings from acutely dissociated mouse cortical neurons were conducted to minimize the intracellular dialysis , because the activation of bk channels by ca influx through nmdars is the underlying mechanism of inmda - out .
pge2 and selective e - prostanoid receptor agonists were applied 5 min before and during the application of nmda .
nmda ( 30 m ) application for 20 sec at the holding potential of 40 mv elicited inward currents ( inmda - in ) and subsequent outward currents ( inmda - out ) shown in figure 1(a ) , similar to our previous observations .
pge2 ( 110 m ) significantly increased the mean amplitude of inmda - out in a dose dependent manner .
ono - ae1 - 259 ( 110 m ) , an ep2 receptor agonist , was found to mimic the effect of pge2 ( figures 1(a ) and 1(b ) ) .
it was also noted that the increasing effect of an ep2 receptor agonist on the mean amplitude of inmda - out was significantly stronger than that of pge2 ( p < 0.001 , f1 , 40 = 47.28 , two - way anova ; figure 1(b ) ) .
in contrast , ono - ae-248 ( 10 m ) , an ep3 receptor agonist , significantly reduced the amplitude of inmda - out ( p < 0.05 , one - way anova with post hoc dunnett 's test ; figures 1(a ) and 1(b ) ) . on the other hand , ono - di-004 and ono - ae1 - 329 ( 110 m ) , ep1 and ep4 receptors agonists , respectively , showed no significant effects on inmda - out ( figures 1(a ) and 1(b ) ) .
we next ask whether ep2 receptor signaling pathways really can potentiate the amplitude of inmda - out . to address the requirement of increased intracellular camp levels on the amplitude of inmda - out
, we performed intracellular application of camp through the patch pipette . even in the whole - cell configuration , inmda - out at holding potential of 40 mv
the mean amplitude of inmda - out was significantly increased 10 minutes after intracellular perfusion of camp ( 10 m ) ( figures 2(a ) and 2(c ) ) . at the same time , the duration of inmda - out was markedly prolonged ( figure 2(a ) , an arrow ) .
camp - induced increase in the amplitude and duration of inmda - out was completely inhibited by kt5720 , a specific inhibitor of pka ( figures 2(b ) and 2(c ) ) .
we further analyzed the involvement of pka signaling on ep2 receptor agonists - induced potentiation of inmda - out . to address this
, we utilized distinct types of ep2 receptor agonist , ono - ae1 - 259 and butaprost .
an increase in the amplitude of inmda - out by ep2 receptor agonists was significantly inhibited by perfusion of kt5720 through the patch pipette ( figure 3 ) .
these results suggest that ep2 receptor signaling pathway facilitates the amplitude of inmda - out through pka signaling pathway .
we finally examined effects of an ep2 receptor agonist on nmda - induced dendritic beading in the primary cultured mouse cortical neurons , because dendritic beading is an early morphological hallmark of excitotoxic neuronal injury .
dendritic beading leads to disappearance of dendritic spines and neurite breakage , culminating in neuronal death [ 7 , 13 , 14 ] .
immunofluorescent clms images for map2 in the primary cultured cortical neurons showed that the application of nmda ( 30 m ) for 10 min induced the segmental focal swelling ( dendritic beading ) and loss of spines in the dendritic shafts ( figure 4(a ) ) .
butaprost , an ep2 receptor agonist , partially inhibited nmda - induced dendritic beading ( figures 4(c ) and 4(d ) ) .
it is known that nmda - induced dendrite beads disappeared completely 120 min after the elimination of nmda .
thus , it is possible that ep2 receptor agonist - mediated neuroprotection is mainly due to the facilitation of recovery phase of nmda - induced dendritic beading . under the none - treated control condition ,
nmda - induced dendritic beading remained even at 60 min after washout of nmda ( figures 4(e ) and 4(f ) ) .
when butaprost was applied with nmda , dendritic beading was significantly recovered at 60 min after washout of nmda ( figures 4(e ) and 4(f ) ) .
tg6 - 10 - 1 , an ep2 receptor antagonist , significantly inhibited the butaprost - induced facilitation of recovery .
paxilline , a specific bk channel blocker , also significantly abolished butaprost - induced facilitation of recovery ( figures 4(e ) and 4(f ) ) .
therefore , it is conceivable that the activation of bk channels is responsible for an ep2 agonist - induced facilitation of recovery from nmda - induced dendritic beading .
in the present study , an ep2 receptor agonist facilitates nmda - induced outward currents through the activation of bk channels .
furthermore , ep2 receptor agonist - mediated activation of bk channels promotes the recovery phase of nmda - induced dendritic beading .
therefore , the activation of bk channels may be responsible for the neuroprotective role of ep2 receptors against excitotoxicity in cortical neurons .
we observed distinct potency of peg2 and ono - ae-259 - 01 on inmda - out .
ki value of pge2 exhibited 12 nm , whereas that of ono - ae-259 - 01 was 3 nm . from the above observations , a potent effect of ono - ae-259 - 01 compared with pge2 on inmda - out was reasonable .
the affinity of ono - ae-259 - 01 for other types of prostanoid receptors is comparatively low ( ki = 140 nm for prostaglandin d2 receptor , ki > 3.3 10 nm for ep1 receptor , ep3 receptor , ep4 receptor , prostaglandin f receptor , prostacyclin receptor , and thromboxane receptor ) . based on the binding affinity of ono - ae-259 - 01 , the facilitatory effect of ono - ae-259 - 01 on inmda - out is mediated by ep2 receptors . ep2 and
ep4 receptors are involved in the intracellular increase in camp and subsequent activation of pka .
one of the important molecular targets of pka is the transcription factor creb that promotes neuronal survival .
in fact , the protective effects of ep2 and ep4 receptor agonists on neuronal damage associated with ischemia , alzheimer 's disease , and epilepsy were reported [ 5 , 6 , 17 , 18 ] . despite similar downstream signaling pathways of ep2 and ep4 receptors , ep4 receptors agonist had no significant effect on the amplitude of inmda - out , suggesting a relatively low expression level of ep4 receptors in cortical neurons .
these data are consistent with the region specific expression patterns of ep1 and ep4 receptors [ 14 , 19 , 20 ] .
by contrast , ep3 receptors are broadly expressed in the cerebral cortex , hippocampus , and midbrain . in the present study
, we showed opposite effects of ep2 and ep3 receptor agonists on the amplitude of inmda - out and bk currents in the cortical neurons .
distinct responsiveness of ep2 and ep3 receptor agonists to inmda - out may account for the intracellular concentration of camp .
thus , a local distribution pattern of ep receptor subtypes is critical for the functional outcomes of pge2 on neurons .
elevated levels of [ ca]i and the membrane depolarization , which serve as a feedback regulators in neurons , are known to gate the bk channels .
sensitivity of bk channels to the voltage and [ ca]i are modulated by protein phosphorylation of serine / threonine or tyrosine residues within the channels .
generally , pka and pkg - mediated phosphorylation lead to the activation of bk channels , whereas pkc leads to the inhibition of bk channels .
inside - out mode of single channel analyses has revealed that pka makes transition of bk channels from close - state to open - state .
thus , the amplitude of inmda - out might be facilitated by the stimulation of ep2 receptors through the activation of pka .
the source of ca is considered as the endoplasmic reticulum ( er ) or influx of extracellular calcium .
kaufmann et al . proposed that distinct route of ca activates bk channels whose expression patterns are different from soma ( clustered type ) and extrasynaptic site ( scattered type ) .
the ca source of scattered type of bk channels might be the er independent , whereas that of clustered type is internal stores .
intriguingly , thapsigargin and ryanodine had no effect on the glutamate - evoked outward current which are mediated by bk channels .
from these observations , inmda - out caused by nmda - application might be emerging at extrasynaptic site .
beading structure was formed on the dendrite , progressing toward to soma from the tip of dendrite , resulting in the neuronal damage .
the facilitation of recovery phase of dendritic beading by an ep2 receptor agonist was mediated by the bk channels .
therefore , extrasynaptically located bk channels might respond to an ep2 receptor agonist . among the nmda receptors ,
nr2b containing nmda receptors are involved in the excitotoxicity and located in extrasynaptic site .
given the ca source and nmda receptor 's properties , scattered type of bk channels might couple to nr2b .
thus , one of potential molecular targets of ep2 receptor agonist is scattered type of bk channels .
ep2 receptors are widely expressed in both neurons and glia , whereas they exhibit opposite effects in different cells .
in contrast , conditional deletion of ep2 receptors in microglia attenuated inflammation in animal models of parkinson 's disease or alzheimer 's disease [ 32 , 33 ] .
these observations indicate that ep2 receptors in microglia serve as proinflammatory signaling in the chronic neuroinflammation .
zhang et al . reported that the expression level of ep2 mrna was increased in microglia after cellular activation .
in addition , autocrine / paracrine release of pge2 further activates microglia to aggravate neuroinflammation [ 32 , 33 ] .
likewise , il-1 derived from microglia also has an essential role in neuroinflammation [ 3537 ] .
microglia specific gene - ablation of ep2 receptors results in the reduction of il-1 in the hippocampus during neuroinflammatory situation [ 32 , 33 ] . secreted il-1 from microglia eventually causes a loss of feedback inhibition in neurons through the attenuation of bk channel activities [ 1 , 2 ] .
in this way , pge2 and il-1 synergistically worsen the pathology in chronic inflammatory situation . taken together , the role of ep2 receptors on neuroprotection and neurodegeneration is determined by the period after the brain injury .
pge2 enhanced inmda - out through the activation of ep2 receptors in mouse cortical neurons .
the activation of camp / pka pathway is involved in the ep2 receptor agonist - induced potentiation of inmda - out .
furthermore , an ep2 receptor agonist facilitated the recovery from nmda - induced dendritic beading .
these results suggest a novel neuroprotective strategy using ep2 agonists against the acute excitotoxic damage . | prostaglandin e2 ( pge2 ) , a major metabolite of arachidonic acid produced by cyclooxygenase pathways , exerts its bioactive responses by activating four e - prostanoid receptor subtypes , ep1 , ep2 , ep3 , and ep4 .
pge2 enables modulating n - methyl - d - aspartate ( nmda ) receptor - mediated responses .
however , the effect of e - prostanoid receptor agonists on large - conductance ca2 + -activated k+ ( bk ) channels , which are functionally coupled with nmda receptors , remains unclear .
here , we showed that ep2 receptor - mediated signaling pathways increased nmda - induced outward currents ( inmda - out ) , which are associated with the bk channel activation .
patch - clamp recordings from the acutely dissociated mouse cortical neurons revealed that an ep2 receptor agonist activated inmda - out , whereas an ep3 receptor agonist reduced it .
agonists of ep1 or ep4 receptors showed no significant effects on inmda - out .
a direct perfusion of 3,5-cyclic adenosine monophosphate ( camp ) through the patch pipette facilitated inmda - out , which was abolished by the presence of protein kinase a ( pka ) inhibitor .
furthermore , facilitation of inmda - out caused by an ep2 receptor agonist was significantly suppressed by pka inhibitor .
finally , the activation of bk channels through ep2 receptors facilitated the recovery phase of nmda - induced dendritic beading in the primary cultured cortical neurons .
these results suggest that a direct activation of bk channels by ep2 receptor - mediated signaling pathways plays neuroprotective roles in cortical neurons . |
SECTION 1. SHORT TITLE.
This Act may be cited as the ``National Recreational Trails Act of
1994''.
SEC. 2. ELIGIBILITIES.
(a) State Eligibility.--Section 1302(c) of the Intermodal Surface
Transportation Efficiency Act of 1991 (16 U.S.C. 1261(c)) is amended--
(1) by striking ``Act'' each place it appears and inserting
``part'';
(2) in paragraph (2)--
(A) by striking subparagraph (B); and
(B) by redesignating subparagraphs (C) and (D) as
subparagraphs (B) and (C), respectively; and
(3) by adding at the end the following new paragraph:
``(3) Sixth-year provision.--Beginning on the date that is
5 years after the date of enactment of this part, a State shall
be eligible to receive moneys under this part for a fiscal year
only if the State agrees to expend, for the fiscal year, from
non-Federal sources for carrying out projects under this part
an amount equal to 20 percent of the amount received by the
State under this part for the fiscal year.''.
(b) Administrative Costs.--Section 1302(d)(1) of such Act (33
U.S.C. 1261(d)(1)) is amended--
(1) by striking ``(1) Administrative costs.--No more'' and
inserting the following:
``(1) Administrative costs.--
``(A) In general.--No more'';
(2) by striking ``(A) approving'' and inserting the
following:
``(i) approving'';
(3) by striking ``(B) paying'' and inserting the following:
``(ii) paying'';
(4) by striking subparagraph (C) and inserting the
following new clause:
``(iii) contracting for services with other
land management agencies; and'';
(5) by striking ``(D) if'' and inserting the following:
``(iv) if''; and
(6) by adding at the end the following new subparagraph:
``(B) National survey.--Amounts in the Fund may be
used to pay the cost to the Secretary for conducting 1
national survey of nonhighway recreational fuel
consumption by State, for use in making determinations
and estimations pursuant to this part.''.
(c) Environmental Mitigation.--Section 1302(e) of such Act (16
U.S.C. 1261(e)) is amended--
(1) by redesignating paragraphs (5) through (8) as
paragraphs (6) through (9), respectively; and
(2) by inserting after paragraph (4) the following new
paragraph:
``(5) Environmental mitigation.--
``(A) Requirement.--To the extent practicable and
consistent with other requirements of this section, in
complying with paragraph (4), a State shall give
priority to project proposals that provide for the
redesign, reconstruction, nonroutine maintenance, or
relocation of trails in order to mitigate and minimize
the impact to the natural environment.
``(B) Compliance.--The State shall receive guidance
for determining compliance with subparagraph (A) from
the recreational trail advisory board of the State that
meets the requirements of subsection (c)(2)(A).''.
(d) Exclusions.--Section 1302(e)(7) of such Act (16 U.S.C.
1261(e)(7)) (as redesignated by subsection (c)(1)(A)) is further
amended--
(1) by striking ``(7) Small state exclusion.--Any State''
and inserting the following:
``(7) Exclusions.--
``(A) Small state.--Any State''; and
(2) by adding at the end the following new subparagraph:
``(B) Best interest of a state.--A State that
determines based on trail needs identified in the
Statewide Comprehensive Outdoor Recreation Plan of the
State referred to in subsection (b) that it is in the
best interest of the State to be exempt from the
requirements of paragraph (4) may apply to the
Secretary for such an exemption. Before approving or
disapproving an application for such an exemption, the
Secretary shall publish in the Federal Register notice
of receipt of the application and provide an
opportunity for public comment on the application.''.
(e) Return of Moneys Not Expended.--Section 1302(e)(9)(B) of such
Act (16 U.S.C. 1261(e)(9)(B)) (as redesignated by subsection (c)(1)(A))
is further amended--
(1) by inserting ``the State'' before ``may be exempted'';
and
(2) by striking ``and expended or committed'' and all that
follows before the period at the end.
(f) Authorization of Appropriations.--Section 1302 of such Act (16
U.S.C. 1261) is amended--
(1) by redesignating subsection (g) as subsection (h); and
(2) by inserting after subsection (f) the following new
subsection:
``(g) Authorization of Appropriations.--
``(1) In general.--There are authorized to be appropriated
from the Highway Trust Fund (other than the Mass Transit
Account) to carry out this part $6,000,000 for fiscal year
1995.
``(2) Applicability of title 23.--Funds made available
under paragraph (1) shall be available for obligation in the
same manner as funds that were apportioned under chapter 1 of
title 23, United States Code, except that--
``(A) the Federal share of the cost of activities
conducted under this part shall be as provided in this
section;
``(B) the funds shall not be subject to any
obligation limitation other than subsection (d)(3); and
``(C) the funds shall remain available until
expended.
``(3) Treatment.--Funds made available under paragraph (1)
shall be treated as if the funds were part of the Fund for the
purpose of making allocations to the States under subsection
(d).''.
(g) Advisory Committee.--Section 1303(b) of such Act (16 U.S.C.
1262(b)) is amended--
(1) by striking ``11 members'' and inserting ``12
members'';
(2) by redesignating paragraphs (2), (3), and (4) as
paragraphs (3), (4), and (5), respectively; and
(3) by inserting after paragraph (1) the following new
paragraph:
``(2) 1 member appointed by the Secretary representing
individuals with disabilities;''.
(h) Conforming Amendments.--
(1) Section 1302(e) of such Act (16 U.S.C. 1261(e)) is
amended--
(A) in paragraph (4), by striking ``paragraphs (6)
and (8)(B)'' and inserting ``paragraphs (7) and
(9)(B)''; and
(B) in paragraph (6)(A)(i) (as redesignated by
subsection (c)(1)(A)), by striking ``(g)(5)'' and
inserting ``(h)(5)''.
(2) Section 1303(c) of such Act (16 U.S.C. 1262(c)) is
amended by striking ``(b)(2)'' and inserting ``(b)(3)''.
(3) Section 9511(b) of the Internal Revenue Code of 1986 is
amended by striking ``1302(e)(8)'' and inserting
``1302(e)(9)''.
SEC. 3. OFFSETTING RESCISSIONS.
Effective October 1, 1994, each of the following unobligated
balances on September 30, 1994, of funds made available for the
following provisions of law is rescinded:
(1) $65,787.32 made available for section 131(c) of the
Surface Transportation Assistance Act of 1982 (Public Law 97-
424; 96 Stat. 2120).
(2) $3,559,837 made available for section 149(a)(35) of the
Surface Transportation and Uniform Relocation Assistance Act of
1987 (Public Law 100-17; 101 Stat. 187).
(3) $942,249 made available for section 149(a)(66) of such
Act (Public Law 100-17; 101 Stat. 191).
(4) $797,800 made available for section 149(a)(100) of such
Act (Public Law 100-17; 101 Stat. 195).
(5) $376,194.94 made available for section 149(a)(111)(C)
of such Act (Public Law 100-17; 101 Stat. 196).
(6) $258,131.85 made available for section 149(a)(111)(L)
of such Act (Public Law 100-17; 101 Stat. 197). | National Recreational Trails Act of 1994 - Amends the Intermodal Surface Transportation Efficiency Act of 1991 to revise State eligibility requirements with respect to national recreational trails funding to require States to agree to expend a specified amount from non-Federal sources for such trails. Repeals the current requirement that States imposing a tax on nonhighway recreational fuels reserve a reasonable estimation of such tax revenues for recreational trail use.
Allows the use of certain administrative expenditures from the National Recreational Trails Trust Fund for contracting for services with other land management agencies. Limits to one the number of national surveys of non-highway recreational fuel consumption by State that may be paid for out of such Fund.
Requires States, in the mandatory use of specified amounts from such Fund for motorized or non-motorized recreation, to give priority, to the extent practicable, to project proposals that provide for the redesign, reconstruction, maintenance, or relocation of trails in order to mitigate the impact to the natural environment. Authorizes States to apply for exemption from motorized or non-motorized recreation fund use requirements if they have determined, based on trail needs identified in the Statewide Comprehensive Outdoor Recreation Plan, that it is in their best interests to be exempt.
Authorizes appropriations.
Increases from 11 to 12 the number of members of the National Recreational Trails Advisory Committee. Requires such committee to include one member appointed by the Secretary of the Interior representing individuals with disabilities.
Rescinds specified unobligated FY 1994 appropriations. |
leishmaniases are protozoan vector - borne diseases caused by the genus leishmania . based on the clinical features ,
the disease is classified into main three forms of visceral leishmaniasis ( vl ) , cutaneous leishmaniasis ( cl ) , and mucocutaneous leishmaniasis ( mcl ) .
visceral leishmaniasis ( vl ) is caused by l. donovani in the indian subcontinent and eastern africa , l. infantum in mediterranean area and middle east , and l. chagasi in latin america ( 1 ) .
iran is amongst the regions in the world where both cutaneous and visceral forms of the disease are present ( 23 ) .
northwest and southern parts of the country are the main foci of vl while zoonotic cl , caused by l. major , is common in more than 15 provinces and represents about 70% of cutaneous leishmaniasis cases in the country ( 45 ) . moreover , anthroponotic cl caused by l. tropica , is present in several urban foci in the country ( 5 , 6 ) .
the main causative agent of vl in iran is l. infantum and carnivores ( dogs , foxes and jackal ) serve as the reservoirs ( 7 ) .
both l. tropica and l. major which are the causative agents of cutaneous leishmaniasis have been reported from vl patients in iran ( 810 ) . in such cases
l. tropica visceralize and cause systematic illness without obvious cutaneous symptoms . in the persian gulf war , several cases of vl caused by l. tropica were reported in american soldiers ( 11 ) . here
we report a case of vl , caused by l. tropica without any cutaneous symptoms .
we describe a 50-year - old iranian man who had lived in the vl - endemic area in kohgiluyeh and boyer - ahmad province , southwest of iran , presented with a 3-month history of fever and splenomegaly .
results of serological studies were positive and suggestive of vl ; though previous leishmaniasis infection was difficult to rule out .
since vl in iran is mainly among children under 10 years old , the case was rather atypical .
the patient was treated with a 28-day course of intravenous pentavalent antimonial compound sodium stibogluconate with complete resolution of his systemic signs and symptoms .
verbal informed consent was obtained from the patient for publication of this case report . to determine the molecular characteristics of leishmania species isolated from the patient , dna was extracted from the microscopic slides of the spleen biopsy .
briefly , the slides were washed with absolute ethanol and covered with 250 l of lysis buffer ( 50 mm tris , 50 mm nacl , 10 mm edta , ph 7.4 , 1% v / v triton x-100 ) for 12 minutes .
cell lysis was done by incubating the sample with 100 g of proteinase k for 3 h at 56 c .
phenol - chloroform was used to extract the lysate and ethanol was used to precipitate the extracted dna .
the nagt ( n - acetylglucosamine-1-phosphate transferase ) gene of leishmania was pcr - amplified from the extracted genomic , using the primers l1 ( forward ) : ( 5 tca tga ctc ttg gcc tgg tag ) and l4 ( reverse ) : ( 5 ctc tag cgc act tca tcg tag ) .
pcr products were separated by electrophoresis in 1.5% agarose gel and stained with safe stain .
pcr amplification of the nagt gene of leishmania produced fragments of about 1.4 kb , corresponding to leishmania parasite .
the pcr product was sequenced and the sequence was aligned and compared with those of existing sequences related to leishmania in gen - bank .
the sequence analysis demonstrated that the case has 99% identity with those of available sequences of l. tropica in the gen - bank .
alignment of sequence of the current isolate with those of l. tropica existing in the genbank showed just one dna variable site in which nucleotide at position of 106 was single - base substituted .
a phylogenetic tree was constructed , using mega 5 software , and using tamura 3-parameter option ( fig .
intra - species variation within isolate of l. tropica in this study with another isolates of l. tropica amounted to 00.1% ; while , inter - species sequence differences among l. tropica in this study with isolates of l. major and l. infantum was significantly higher , being 1% .
phylogenetic relationship of nagt sequence of l. tropica isolated from vl patient and l. trpoica , l. major and l. infantum from iran , using maximum likelihood method
the nagt ( n - acetylglucosamine-1-phosphate transferase ) gene of leishmania was pcr - amplified from the extracted genomic , using the primers l1 ( forward ) : ( 5 tca tga ctc ttg gcc tgg tag ) and l4 ( reverse ) : ( 5 ctc tag cgc act tca tcg tag ) .
pcr products were separated by electrophoresis in 1.5% agarose gel and stained with safe stain .
pcr amplification of the nagt gene of leishmania produced fragments of about 1.4 kb , corresponding to leishmania parasite .
the pcr product was sequenced and the sequence was aligned and compared with those of existing sequences related to leishmania in gen - bank .
the sequence analysis demonstrated that the case has 99% identity with those of available sequences of l. tropica in the gen - bank .
alignment of sequence of the current isolate with those of l. tropica existing in the genbank showed just one dna variable site in which nucleotide at position of 106 was single - base substituted .
a phylogenetic tree was constructed , using mega 5 software , and using tamura 3-parameter option ( fig .
intra - species variation within isolate of l. tropica in this study with another isolates of l. tropica amounted to 00.1% ; while , inter - species sequence differences among l. tropica in this study with isolates of l. major and l. infantum was significantly higher , being 1% .
phylogenetic relationship of nagt sequence of l. tropica isolated from vl patient and l. trpoica , l. major and l. infantum from iran , using maximum likelihood method
the main causative agent of vl in south of iran , as demonstrated by molecular methods , is l. infantum ( 6 ) .
this is the causative agent of vl in northwest of the country as well ( 2 ) .
however , vl due to l. tropica has been reported in few studies in south and northwest of the country ( 810 ) .
, in southern iran on 64 vl patients revealed that the dominant strain of leishmania in these patients is l. infantum ( 63 out of the 64 cases ) , but l. tropica was also isolated from one of vl patient ( 9 ) . in another study , a case of diffuse cutaneous leishmaniasis ( dcl ) accompanied by visceral leishmaniasis caused by l. tropica was reported from southern iran ( 12 ) .
moreover , two cases of disseminated leishmaniasis due to l. tropica in patients with hiv infection have been reported from iran ( 13 ) .
concurrent mucosal and visceral leishmaniasis due to l. tropica was reported in a puppy from iran ( 8) . moreover ,
vl due to l. tropica was reported in a domestic dog without any cutaneous involvement ( 7 ) .
hajjaran et al . reported a case of canine vl in an 8-yr old dog infected with l. tropica ( 14 ) .
here we described a case of vl with l. tropica in a patients from a vl - endemic areas in southwest of iran .
the main reservoirs of vl in this area are dogs , although infection in cats is present , and the main causative agent of the disease is l. infantum ( 1517 ) .
this is the first case of vl due to l. tropica which has been reported from this area .
molecular characterization of the isolate showed that the case has more than 99% homology with those of l. tropica isolated from the cl patients .
sequence of nagt gene was aligned with those of l. tropica available sequences in the genbank which showed just one dna variable site .
differences in the genotype of the parasite might lead to the type of cutaneous or visceralized forms of leishmaniasis caused by l. tropica . in a study ,
genetic differences of indian strains of l. tropica isolated from human cases of cl with those of indian strains of l. tropica isolated from human cases of vl were evaluated ( 18 ) .
microsatellite analyses of dermatotropic and the viscerotropic strains of l. tropica consigned them to the same main genetic population .
furthermore , it was found that indian strains isolated from human cases of vl fell into the same sub - population but were not genetically identical to the strains of l. tropica isolated from human cases of cl . in our study , intra - species variation within isolate of l. tropica with another isolates of l. tropica was very low while , inter - species sequence differences among the isolates of l. major and l. infantum was meaningfully high .
this should be considered in any measurements which target the control of the disease in the region . | we describe a case of visceral leishmaniasis ( vl ) due to leishmania tropica in a 50-year - old iranian man lived in a vl - endemic area in southwest of iran .
the patient presented with a 3-month history of fever and splenomegaly .
clinical signs and serological findings were suggestive of vl .
spleen biopsy was taken from the patient and intracellular forms of leishmania amastigotes was seen in giemsa stained smears .
the patient was treated with pentavalent antimonial compound with complete resolution of his systemic signs and symptoms .
dna was extracted from the microscopic slides of the spleen biopsy and the nagt ( n - acetylglucosamine-1-phosphate transferase ) gene of leishmania was pcr - amplified .
sequence analysis of the pcr product demonstrated that the case has 99% identity with those of available sequences of l. tropica .
intra - species variation within isolate was 00.1% ; whereas , inter - species differences of the isolate with those of l. major and l. infantum was significantly higher . |
ductal carcinoma - in - situ ( dcis ) of the breast , by definition , does not invade beyond the basement membrane and nodal metastasis is not expected .
however , axillary nodal involvement has been reported in 2% to 13% of dcis [ 1 , 2 ] .
the axillary nodes were seldom evaluated in the past as potential morbidity from full axillary nodal dissection ( alnd ) , where the level i and ii nodes are removed , and even from axillary sampling , outweighed the possibility of finding nodal disease that would change treatment recommendations .
but with the widespread adoption of the simpler and less morbid technique of sentinel lymph node ( sln ) biopsy , there have been efforts to reevaluate the role of nodal evaluation in dcis .
nodal disease is often an indication of microinvasive or invasive foci present within the tumour and is rare in pure dcis tumours , where it may signify the presence of occult microinvasion .
the presence of nodal disease may warrant consideration for more aggressive systemic therapy in view of the potentially higher risk of disease recurrence and systemic metastasis [ 4 , 5 ] .
still , the incidence of nodal metastases is too low to justify sln biopsy in all dcis tumours .
sentinel lymph node biopsy is indicated in the 10% to 20% of dcis tumours in which foci of invasive carcinoma are detected after surgical excision and analysis of the entire lesion [ 6 , 7 ] .
such histological upgrading has become more common now that the preoperative diagnosis of dcis is often made on core biopsy .
most surgeons will include a sln biopsy when performing a mastectomy for dcis since access to the sln lies within the operative field and also because nodal evaluation after a mastectomy often entails alnd as the sln can seldom be successfully identified due to the disruption of lymphatic drainage to the axilla .
on the other hand , with wide local excision ( wle ) , a separate incision in the axilla is required for sln biopsy and even a wle performed in the upper outer quadrant does not interfere with successful sln identification at a later setting . including a sln biopsy with the initial wle may not reduce the reoperation rate as much as with a mastectomy , since up to 20% of these women will need a second surgery because of inadequate surgical margins .
nevertheless , having a sln biopsy done together with the first surgery will undoubtedly save those women in whom a preoperative diagnosis of dcis is upgraded to invasive carcinoma on final histology from a second surgery .
avoiding a second surgery saves time and costs , and more importantly , it reduces psychological stress and facilitates recovery .
completing all necessary surgery in a single setting is particularly important in our society where the need for a second surgery is often perceived as a failure of the initial one . at our institute , since 2006 when sln biopsy was adopted as the standard of care , sln biopsy was included in the initial surgery if it involved a mastectomy .
most surgeons performed wle alone for a preoperative diagnosis of dcis , while some surgeons selectively offered sln biopsy together with the initial wle if the likelihood of histological upgrade to invasive carcinoma was deemed to be high . in this study , we have reviewed our data to evaluate the outcome of sln biopsy performed together with the initial surgery for a preoperative diagnosis of dcis .
in addition , we sought to identify the subgroup of patients who were at risk of a histological upgrade to invasive carcinoma since they would benefit from having sln biopsy performed at the time of the initial surgery .
a retrospective review of 348 consecutive female patients who were diagnosed preoperatively with dcis was performed at our institute over an 8-year period from january 1 , 2001 , to december 31 , 2008 .
patients who did not undergo surgery , either because they had defaulted treatment or because they were deemed medically unfit , were excluded , as were those in whom definite foci of microinvasion had been reported on the biopsy specimen .
biopsy was performed free hand for palpable lesions , and under image guidance , preferably with breast ultrasound , for nonpalpable ones .
ultrasound - guided biopsy was performed by dedicated breast interventional radiologists with a 14-gauge bard needle under local anaesthesia and usually 4 to 6 cores ( average of 5 ) were obtained ; more cores were taken if the target lesion was vague or large .
stereotactic vacuum assisted biopsy was performed with an 11-gauge needle and usually 6 to 12 cores ( average of 10 ) were obtained and immediately imaged to confirm the presence of microcalcifications .
further cores were obtained if the initially visualised microcalcifications were absent in the biopsy specimens .
surgery was performed by a total of 8 specialist breast surgeons during this period . from 2001 to 2005 , sln biopsy was performed selectively , according to surgeon preference and experience .
onwards , sln biopsy was adopted as the standard of care and was routinely performed together with a mastectomy .
sln biopsy was also performed together with the initial wle if microinvasive foci were reported in the biopsy specimen .
some surgeons offered sln biopsy together with the initial wle when features such as high nuclear grade and necrosis were present in the biopsy specimen .
two ml of undiluted patent v blue dye was injected via a subareolar route after induction and 5 minutes of manual massage followed .
the sln was identified as a blue - coloured level i node with blue lymphatic channels leading up to it .
slns were submitted for intraoperative frozen section analysis or for routine histological analysis only according to surgeon preference . the number and size of slns submitted for analysis were recorded and each node was serially sliced at 2 to 3 mm gross intervals . for intraoperative frozen section analysis
, each slice was further sectioned at intervals of 40 m to obtain 3 sections , which are stained in haematoxylin and eosin ( h&e ) and are examined using routine light microscopy .
the entire sln was then formalin - fixed , processed , and paraffin - embedded to obtain permanent sections for final analysis , where additional 1 to 6 levels of each slice of the sln were examined .
the presence or absence of tumour deposits was recorded according to current established cancer reporting guidelines provided by the college american pathologists ( october 2009 ) .
the sln was considered positive when tumour deposits of more than 0.2 mm ( micro- and macrometastasis ) were present and negative when no tumour cells were detected or when only single tumour cells or tumour cell clusters not more than 0.2 mm ( isolated tumour cells ) were present .
molecular tests such as immunohistochemistry and quantitative real - time pcr were not routinely performed for h&e - negative sections , although immunohistochemistry with anticytokeratin antibodies was used in certain instances to verify the presence of metastasis .
whole breast irradiation was recommended for those who underwent wle ; an additional boost to the tumour bed was not routinely administered unless the surgical margins were inadequate and if the patient had refused further surgery .
systemic chemotherapy and targeted therapy were recommended in those with invasive carcinoma according to guidelines .
histological upgrade was defined as the instance where histological analysis of the surgical specimen revealed microinvasive or invasive foci within a tumour which had been preoperatively diagnosed as being dcis .
histological upgrade to invasive carcinoma was correlated with standard clinicopathological parameters , including patient age , clinical presentation , radiological features , pathological tumour size , nuclear grade , necrosis , possible microinvasive foci , and hormone receptor ( oestrogen receptor ( er ) and progesterone receptor ( pr ) status ) .
correlation analyses were performed using either the chi square test or fisher 's exact test where appropriate .
all univariate analyses were performed with graphpad prism version 4 ( graphpad software inc . , san diego , ca ) .
this was performed using the stata package release 8.1 ( stata corporation , 4905 lakeway drive , college station , texas 77845 , usa ) .
a full model was first created to include all potentially important explanatory variables . at each step ,
the variable with the smallest contribution to the model was removed , until a final backward stepwise model was obtained .
a 2-tailed p value test was used in all analyses and a p value of less than 0.05 was considered statistically significant .
one hundred and twenty - eight patients ( 43.5% ) presented with clinical symptoms , 110 with a breast lump and 18 with nipple discharge .
median patient age was 51 years ( ranging from 30 years to 91 years ) .
ethnic distribution reflected that of the general population ( table 1 ) , with chinese women making up the large majority .
dcis was diagnosed on core or vacuum assisted biopsy in 79.3% ( 233 of 294 ) of patients .
a mastectomy was performed in 126 patients ( 42.9% ) and a wle in the remaining 168 patients .
median follow - up was 82.0 months ( ranging from 3.7 to 143.0 months ) .
one hundred and thirty - two patients ( 44.9% ) underwent sln biopsy at the time of the initial surgery , which involved a mastectomy in 70 patients and a wle in the other 62 .
the sln was positive for metastases in 5 patients ( 3.8% ) , all of whom were found to have invasive ductal carcinoma on final histology .
the invasive tumour was classified as t1a in 3 patients ( tumour size ranging from 1 mm to 4 mm ) , as t1c ( tumour size 19 mm ) in 1 and as t2 ( tumour size 25 mm ) in the remaining patient .
micrometastatic deposits ( detected on h&e ) were found in 2 patients , and macrometastases were present in the other 3 .
median age of this group of patients was 51 years ( ranging from 30 years to 63 years ) .
four patients had presented with a clinically palpable breast lump , while the fifth had presented with asymptomatic pleomorphic microcalcifications .
three patients had a suspicious mass detected on mammogram and pleomorphic microcalcifications were detected in the other 2 .
the diagnosis of dcis had been made preoperatively on core or vacuum assisted biopsy in all .
the dcis was classified as high nuclear grade in 3 patients , and necrosis was present in the biopsy specimen in 2 patients .
of the 127 patients in whom the sln was negative for metastases , 43 patients ( 33.9% ) were upgraded to invasive carcinoma on final histological analysis .
half of these ( 23 of 43 ) patients had undergone wle ; and 8 patients required further surgery for inadequate surgical margins . a second surgery was also required in 2 other patients who had undergone mastectomy , both of whom underwent completion alnd after the sln was found to be positive on final histology ( the sln had not been submitted for intraoperative analysis ) .
an upgrade from a preoperative diagnosis of dcis to invasive carcinoma on final histology occurred in 99 of 294 patients ( 33.7% ) .
the invasive component was classified as microinvasion in 28 ( 28.3% ) patients , as t1 disease in 57 ( 57.6% ) patients , as t2 disease in 11 ( 11.1% ) patients , and as t3 disease in 3 ( 3.0% ) patients .
surgery had involved a mastectomy in 52 patients and a wle in the other 47 patients .
the regional axillary nodes had been evaluated during the initial surgery in 52 of these 99 patients , by sln biopsy in 48 patients and by axillary sampling in the other 4 .
histological upgrade occurred more frequently among women who presented with a palpable breast lump ( p < 0.01 , or 2.60 , 95% ci 1.63 to 4.16 ) and who had a mass detected on mammogram ( p < 0.01 , or 2.59 , 95% ci 1.53 to 4.40 ) or on breast ultrasound ( p < 0.01 , or 4.22 , 95% ci 1.36 to 13.07 ) ( table 1 ) .
upgrade was also more likely if the preoperative diagnosis of dcis had been made on biopsy ( p < 0.01 , or 2.76 , 95% ci 1.36 to 5.58 ) , and particularly so if a core biopsy rather than a vacuum assisted biopsy was performed ( p < 0.01 , or 3.77 , 95% ci 1.957.30 ) .
upgrade was also more likely when high nuclear grade or possible microinvasion was reported in the biopsy specimen ( p = 0.03 , or 1.72 , 0.34 to 0.98 and p < 0.01 , or 5.98 , 95% ci 2.70 to 13.25 resp . ) but was not correlated with the presence of necrosis , hormone receptor status , or tumour size ( p > 0.05 ) .
on multivariate analysis , only a mammographically detected mass , a diagnosis made on core or vacuum assisted biopsy , and possible microinvasion in the biopsy specimen were independently correlated with the likelihood of histological upgrade to invasive carcinoma ( p < 0.05 ) ( table 2 ) .
four patients developed axillary nodal recurrence , after a mean interval of 24.9 1.77 months .
two of these patients were upgraded to invasive carcinoma following surgery and had had nodal evaluation , 1 with sln biopsy ( microinvasion found on final histology ) and the other with alnd , after a 4 mm invasive ductal carcinoma was found on final histology .
the axillary nodes were not evaluated in the other 2 patients who were both managed as having pure dcis .
one patient had node - negative microinvasive disease ( t1mic ) and the other was found to have a 45 mm invasive ductal carcinoma , with 2 out of 19 nodes positive for metastasis .
there were 5 deaths during the follow - up period ; 2 patients died from metastatic disease and another 3 died from nonbreast cancer related causes .
detecting nodal metastases in dcis tumours can help identify the small subgroup which may benefit from systemic therapies because of a propensity for disease recurrence and metastasis [ 4 , 5 ] .
but although sln biopsy can be carried out easily and with minimal morbidity , its use in all dcis tumours is difficult to justify given that nodal metastases are so uncommon that it seldom contributes to treatment decision - making [ 3 , 9 ] .
furthermore , some are now exploring whether sln biopsy can be omitted entirely in tumours where the probability of nodal spread is minimal .
existing data can not support this and since nodal status is a major consideration for adjuvant treatment recommendations , sln biopsy is likely to remain the standard of care for all invasive tumours , regardless of tumour size or other tumour characteristics .
nodal disease associated with dcis tumours has been postulated to indicate occult microinvasion present within the primary tumour .
this could possibly explain the occurrence of nodal metastases in reportedly pure dcis tumours and may account for the more aggressive behaviour seen in a small subgroup .
while exact incidence is not known , early studies have reported residual invasive disease in 10 to 20% of mastectomy specimens in women with an initial diagnosis of dcis .
occult microinvasion may have led to nodal recurrence in the 2 patients in our study with dcis . although the axillary nodes had not been evaluated initially , the interval between the nodal recurrence and the surgery favours recurrent disease over inadequately treated residual nodal disease . while it seems reasonable to postulate that women with tumours with occult microinvasion have an increased risk of disease recurrence and metastasis since they would not have received any systemic treatment , there are studies suggesting otherwise [ 11 , 12 ] .
one possible reason is that more than two - thirds of such sln metastases are detected only on immunohistochemistry ( ihc ) and the prognostic significance of such occult metastases is unclear [ 13 , 14 ] .
in contrast to published reports , none of the patients with microinvasion in our study were found to have a positive sln , and this is likely because h&e - negative sections were not routinely subjected to molecular techniques .
nevertheless , microinvasion was associated with disease recurrence in our study and supports the practice of evaluating the regional axillary nodes in the presence of microinvasion .
the finding of nodal involvement will prompt a consideration for systemic therapy particularly when other high - risk factors are present . in our study ,
the sln was positive for tumour metastases in 3.8% of patients , and this was exclusively associated with tumours that were upgraded to invasive carcinoma following histological analysis of the surgical specimen . these support existing evidence that clinically relevant nodal disease and therefore the need for sln biopsy are largely restricted to dcis tumours with microinvasive or invasive foci .
on the other hand , no pure dcis tumour in our study had a positive sln , although this may not reflect the true prevalence of nodal metastases in dcis tumours since less than half of our patients underwent sln biopsy .
nodes were assumed to be negative in the group where the axillary nodes were not assessed , and it was reasonable to assume so since these tumours tended to have more favourable characteristics ; only 27% were of high grade and median size was 9.5 mm , smaller than those where sln biopsy was performed .
but axillary recurrence did develop in 2 cases and does raise the possibility of undiagnosed axillary involvement , particularly in the one instance where nodal disease had recurred in the absence of ipsilateral breast recurrence .
the rate of histological upgrade observed in our study was relatively similar to other published studies where the preoperative diagnosis of dcis was made on core or vacuum assisted biopsy [ 14 , 1621 ] .
core biopsy is the preferred means of preoperative diagnosis in many centres because it is minimally invasive and does not affect analysis of pathological tumour size , a major determinant of adjuvant treatment recommendations .
however , invasive foci may not have been sampled or detected in the core biopsy sample because , unlike with open excisional biopsy where the bulk of the lesion is removed , tissue samples obtained from core biopsies are limited and discontinuous in nature .
this can be overcome by using larger gauge needles and by sampling more cores [ 18 , 21 , 22 ] , and our observation that upgrades were less common following vacuum assisted biopsies where larger 11-gauge needles and a greater number of cores were taken seems to support this .
however , using larger needles and taking more cores potentially increase the risk of procedural complications , even if only marginally , and still will not completely eliminate the possibility of histological upgrade .
since a proportion of tumours will be upgraded to invasive carcinoma as the preoperative diagnosis of dcis is often made on core biopsy , these women will require repeat surgery if sln biopsy was not performed during the initial surgery .
we found histological upgrade to be more likely in women who presented with a palpable lump that corresponded to a mass on breast imaging ( mammogram or breast ultrasound ) .
several others have also found a clinical or mammographic mass to be associated with histological upgrade [ 18 , 19 , 2224 ] . that the size of the lesion should correlate with histological
upgrade is reasonable since sampling error is inherent in the core biopsy technique and small invasive foci are more likely to be missed in larger lesions .
a finding of high - grade dcis in the biopsy specimen was another factor found to correlate with histological upgrade in our study .
this has also been previously reported and is consistent with the frequent progression of high - grade dcis to invasive carcinoma [ 2527 ] . however , since high - grade dcis is often associated with microinvasion , this likely explained why it did not remain significant in the multivariate analysis when microinvasion was included .
nevertheless , high nuclear grade would have identified additional 9 patients ( 9.1% ) with histological upgrade in our study .
comedonecrosis and a young age at diagnosis , reported by others to be also associated with histological upgrade , were not found significant in our study [ 25 , 28 ] . identifying tumours with a high likelihood of histological upgrade will particularly benefit those women undergoing wle .
twenty - eight percent of those who had undergone wle in our study would have needed repeat surgery for sln biopsy if it had not been done together with the initial surgery . of the 23 patients who underwent wle and sln biopsy ,
selective recommendation of sln biopsy together with wle will allow more surgeries to be completed in a single stage and will reduce reoperation rates . predicting histological
upgrade has less of an impact in those undergoing mastectomy since most surgeons will perform sln biopsy at the same time .
this is often because a mastectomy is often offered to those with extensive dcis , in whom the likelihood of histological upgrade is high [ 25 , 29 ] .
this is not necessarily the case in our local context , where many women tend to opt for a mastectomy despite being suitable for wle ( unpublished manuscript ) .
many women , especially those in the older age group , perceive mastectomy as a more complete cure , with a lower risk of recurrence , and are less concerned about postoperative cosmesis .
although many of those undergoing mastectomy have in fact small tumours , we continue to routinely perform sln biopsy together with a mastectomy since there is little added morbidity and since alnd can be avoided if nodal evaluation is required later .
sentinel lymph node involvement is infrequent in women with a preoperative diagnosis of dcis and is almost always associated with histological upgrade to invasive carcinoma . in those opting for wide local excision , findings of a mass on mammogram and possible microinvasion in the core biopsy specimen should prompt a discussion regarding the inclusion of sln biopsy together with the initial surgery . | background .
a proportion of those diagnosed preoperatively with ductal carcinoma - in - situ ( dcis ) will be histologically upgraded to invasive carcinoma .
repeat surgery for sentinel lymph node ( sln ) biopsy will be required if it had not been included with the initial surgery .
we reviewed the outcome of sln biopsy performed with the initial surgery based on a preoperative diagnosis of dcis and aimed to identify patients at risk of histological upgrade .
methods . retrospective review of 294 consecutive female patients diagnosed with dcis was performed at our institute from january 1 , 2001 , to december 31 , 2008 .
results . of the 294 patients ,
132 ( 44.9% ) underwent sln biopsy together with the initial surgery .
the sln was positive for metastases in 5 patients , all of whom had tumours that were histologically upgraded .
histological upgrade also occurred in 43 of the 127 patients ( 33.9% ) in whom the sln was negative for metastases .
on multivariate analysis , histological upgrade was more likely if a mass was detected on mammogram , if the preoperative diagnosis was obtained with core biopsy and if microinvasion was reported in the biopsy .
conclusion .
patients in whom a preoperative diagnosis of dcis is likely to be upgraded to invasive carcinoma will benefit from sln biopsy being performed with the initial surgery . |
since the first simulation
of an enzyme using molecular dynamics
( md ) was reported by mccammon et al . in
1977 , md simulations have evolved to become important tools in rationalizing
the behavior of biomolecules .
the field has grown from that first
10-ps - long simulation of a mere 500 atoms to the point where small
enzymes can be simulated on the microsecond time scale and simulations containing millions of atoms can be considered routine . however , such simulations are numerically very intensive , and using
traditional cpu - centric hardware requires access to large - scale supercomputers
or well - designed clusters with expensive interconnects that are beyond
the reach of many research groups .
numerous attempts have been
made over the years to accelerate classical
md simulations by exploiting alternative hardware technologies .
some
notable examples include atoms by at&t bell laboratories , fastrun by columbia university and brookhaven
national laboratory , mdgrape by riken , and most recently anton by de shaw research llc .
all of these approaches have , however , failed
to make an impact on mainstream research because of their excessive
cost .
additionally , these technologies have been based on custom hardware
and do not form part of what would be considered a standard workstation
specification .
this has made it difficult to experiment with such
technologies , leading to a lack of sustained development or innovation
and ultimately their failure to mature into ubiquitous community - maintained
research tools .
graphics processing units ( gpus ) , on the other
hand , have been
an integral part of personal computers for decades , and a strong demand
from the consumer electronics industry has resulted in significant
sustained industrial investment in the stable , long - term development
of gpu technology .
in addition to low prices for gpus , this has led
to a continuous increase in the computational power and memory bandwidth
of gpus , significantly outstripping the improvements in cpus . as a
consequence
, high - end gpus can be considered standard equipment in
scientific workstations , which means that they either already exist
in many research laboratories or can be purchased easily with new
equipment .
this makes them readily available to researchers and thus
attractive targets for acceleration of many scientific applications
including md simulations . the nature of gpu hardware , however ,
has until recently made their
use in general purpose computing challenging to all but those with
extensive three - dimensional ( 3d ) graphics programming experience .
however , the development of application programming interfaces ( apis )
targeted at general purpose scientific computing has reduced this
complexity substantially such thatgpus are now accepted as serious
tools for the economically efficient acceleration of an extensive
range of scientific problems .
the computational
complexity and fine grained parallelism of md
simulations of macromolecules makes them an ideal candidate for implementation
on gpus . indeed , as we illustrate here for implicit solvent and in
a subsequent paper for explicit solvent
,
the careful implementation of modern md algorithms on gpus can provide
capability , in terms of performance , that exceeds that achieveable
with any current cpu - based supercomputer .
several previous studies
have investigated the use of gpus to accelerate md simulations . for a detailed review of the use of gpus for acceleration of condensed
phase biomolecular md simulations
we
present our high - performance gpu implementation
of implicit solvent generalized born ( gb ) md for the amber and charmm pairwise
additive force fields on cuda - enabled nvidia gpus .
we have implemented
this within the amber pmemd dynamics engine in a manner
that is designed to be as transparent to the user as possible , and
we give an overview of what the code currently supports , as well as
our plans for future developments .
we discuss the specifics by which
we exploit the processing power of gpus , both in serial and using
multiple gpus , and show the performance that can be achieved in comparison
to conventional cpu clusters .
we also discuss our implementation and
validation of three specific precision models that we developed and
their impact on the numerical results of implicit solvent md simulations .
as illustrated
by figure 1 , gpus offer a
tremendous amount of computing power in a compact package .
this , however ,
comes at the cost of reduced flexibility and increased programming
complexity as compared to cpus .
in order to develop software that
runs efficiently on gpus , it is necessary to have a thorough understanding
of the characteristics of the gpu hardware architecture .
a number
of manuscripts have already discussed this in detail in the context
of md .
for this reason , we
provide simply a brief overview of the complexities involved in programming
gpus as they relate to our implementation , focusing on nvidia hardware .
for a more detailed description ,
peak floating - point operations per second ( flop / s ; left )
and memory
bandwidth ( right ) for intel cpus and
nvidia gpus .
a gpu is an example
of a massively parallel stream - processing architecture which uses
the single - instruction multiple data ( simd ) vector processing model .
unlike a regular cpu , which typically operates on one to four threads
in parallel , gpus typically process threads in blocks ( termed warps
within the cuda programming language )
containing between 16 and 64 threads .
these thread blocks logically
map to the underlying hardware , which consists of streaming multiprocessors .
at the time of writing , high - end gpus typically have between 16 and
32 multiprocessors . for example , an nvidia m2090 gpu consists of 16
multiprocessors , each containing 32 cores for a total of 512 cores .
all threads in a single block must execute the same instruction on
the same clock cycle .
this necessarily implies that , for optimum performance ,
codes must be vectorized to match the size of a thread block . branching
must therefore be used with extreme care since if any two threads
in the same warp have to follow different code paths of the branch ,
then threads in the warp will stall while each side of the branch
is executed sequentially .
the memory hierarchy
of gpus has its origins in their graphics lineage , and the high density
of arithmetic units comes at the expense of cache memory and control
units .
all of the cores making up a multiprocessor have a small number
of registers that they can access , a few kilobytes ( 64 kb on an m2090 )
of shared memory [ this can be split into directly accessible memory
and l1 cache ; in the case of an m2090 , it can be split 48/16 kb or
16/48 kb ; in the case of amber , the configuration is switched at runtime
for optimal performance of a given kernel ] which is private to each
multiprocessor and a small amount ( typically 48 kb ) of high - speed
but read - only texture memory .
the majority of the memory ( 6 gb on
an m2090 ) , termed global device memory , is available to all multiprocessors .
while being fast compared to the main memory accessible by cpus , access
to the device memory by gpus is still relatively slow compared to
the local cache memory .
the nature by which the multiprocessors are
connected to this memory also means that there is a significant performance
penalty for nonstride-1 access .
finally , it should be noted that currently the cpu and gpu memories are in different address spaces and this requires careful consideration .
the unique nature of this memory model leads to several considerations
for optimizing gpu performance , including optimizing device memory
access for contiguous data , utilizing the multiprocessor shared memory
to store intermediate results or to reorganize data that would otherwise
require nonstride-1 memory accesses , and using the texture memory
to store read - only information , such as various force field parameters ,
in a fashion that allows very rapid access .
as mentioned
above , the cpu and gpu memories are , at the time of writing , in different
address spaces .
this means it is up to the programmer to ensure that
the memories are synchronized as necessary to avoid race conditions .
however , there is a big performance penalty for such synchronizations
which have to occur via the peripheral component interconnect express
( pcie ) bus , and thus they should be avoided unless absolutely necessary .
the traditional
method for programming scientific algorithms in paralleluses the
message passing interface ( mpi ) in which
each thread runs in a separate address space .
when running gpus in
parallel under an mpi paradigm , additional complexity is introduced
since sending data between two gpus involves copying the data from
the memory of the sending gpu to the cpu memory of the corresponding
mpi thread over the pcie bus , an mpisend by this cpu thread , and corresponding
mpireceive by the receiving cpu thread , which copies the data between
the memories of the cpus , and finally copying the data to the memory
of the receiving gpu .
clearly , this introduces additional considerations
for maximizing parallel performance as compared to traditional cpu
programming . at the time of writing
, there are efforts to streamline
gpu to gpu communication , particularly within a single node but also
for infiniband connections between nodes .
one such approach under
development by nvidia and mellanox is termed gpudirect , which ultimately seeks to unify address spaces
between multiple cpus and gpus . currently , the degree to which this
can be utilized is heavily dependent on the underlying hardware design .
therefore , at present , the added complexity of using the advanced
features of gpudirect , beyond the pinned memory mpi optimizations
offered by gpudirect version 1 , on the large number of possible different
hardware combinations is not worth the effort for a widely used production
code .
early versions
of gpus in nvidia s lineup ( prior to the gt200 model ) only
supported single precision ( sp ) floating point arithmetic .
this was
due to the fact that graphics rendering did not require double precision
( dp ) .
scientific algorithms , however , typically require dp arithmetic
( for a discussion in the context of quantum chemistry , see for example
the work by kniziaet al . ) .
the generation
of gpus at the time of our initial implementation ( 2008 ) supported
dp in hardware , but only at 1/8 the performance of sp . in the latest
generation of cards , at the time of writing , termed the fermi lineup
by nvidia , the dp to sp performance ratio is 1/2 and thus equivalent
to that in cpus .
this , however , only holds for the professional ( termed
tesla ) series of cards .
the significantly cheaper gaming cards ( termed
geforce ) still only support dp at a fraction of the speed of sp .
it
is therefore important to optimize the use of dp such that it is only
used when necessary to maintain numerical accuracy .
early use of gpus
for scientific computing was hampered by the lack of an application
programming interface ( api ) for general purpose calculations .
the
problems to be solved had to be described in terms of a graphics pipeline
employing either opengl or directx , which made the software development
time - consuming and hardware - specific .
the barrier to utilizing gpu
hardware for general purpose computation has since been reduced by
the introduction of gpu programming models such as the brook stream
programming language , opencl , and nvidia s compute unified device architecture
( cuda ) and the availability of corresponding
software development toolkits ( sdks ) .
the amber implementation uses
cuda , which is a relatively simple extension of the standard c programming
language that allows one to code in an inherently parallel fashion
and perform all necessary operations to access and manipulate data
on a gpu device .
realizing the full potential of gpus , however , still
requires considerable effort as indicated above and outlined below
to take advantage of the particular gpu architecture , and not all
algorithms are suitable to achieve good performance on these massively
parallel processors .
the nature of md simulations requires what in computer science
is referred to as strong scaling , that is , reduction of the solution
time with an increasing number of processors for a fixed total problem
size .
this enables access to simulations at longer time scales , which
is required for a proper convergence of results .
this becomes more
important as one moves to larger system sizes since the number of
degrees of freedom increases .
weak scaling , that is , the solution
time with the number of processors for a fixed problem size per processor ,
is only of secondary importance , since this merely enables simulating
larger molecules at currently attainable time scales .
our implementation
therefore has focused on accelerating problem sizes that correspond
to those typically studied by amber users . in the case of gb simulations ,
the initial
driving force in accelerating amber implicit solvent
gb calculations with gpus was to provide the scientific community
with a computational tool that would allow an individual researcher
to obtain performance on a simple desktop workstation equivalent to
that of a small cpu cluster .
such a tool alleviates the costs , both
capital and recurring , involved in purchasing , maintaining , and using
individual research compute clusters . to this end , our goal was that
a single state - of - the - art gpu should provide a performance equivalent
to that of four to six high - end cpu cluster nodes .
such an approach
also removes the need to purchase and maintain expensive interconnects
that are required to achieve scaling even on a modest number of nodes . beyond this initial serial development , which was first released
as an update to amber 10 in august 2009 ,
we have also developed a parallel implementation based on the mpi-2 message passing protocol , released as an update
to amber 11 in october 2010 , that allows
a single job to span multiple gpus .
as shown below , it is possible with this
implementation to achieve a performance improvement that goes beyond
simply making a desktop workstation faster , ultimately providing a
performance capability that surpasses what is achievable on all current
conventional supercomputers . achieving this level of performance required
implementing the entire implicit solvent md algorithm including energy
and force evaluations , restraints , constraints , thermostats , and time
step integration on the gpu .
as described in section 3.2 , cpu to gpu communication only occurs during i / o or to
some extent when data is sent between gpus during parallel runs . while we have designed our gpu implementation to achieve substantial
acceleration of implicit solvent md simulations over that achievable
with amber s cpu implementation , our overriding goal has always
been to maintain the precision of the calculations . to this end
, we
have focused on ensuring that gpu simulations will match cpu simulations .
all approximations made in order to achieve performance on gpu hardware
have been rigorously tested as highlighted in the following sections .
an additional design goal has been to attempt to preserve forward
compatibility of our implementation .
using the cuda programming language
provides this by abstracting the program from the underlying hardware .
the gpu accelerated version of amber can be used on all nvidia cards
that support double precision in hardware , that is , those with hardware
revision 1.3 or 2.0 or higher .
our choice of cuda and nvidia graphics
cards was largely guided by the fact that , at the time we began this
work , opencl was not mature enough to offer the same performance and
stability benefits that cuda did .
a port to opencl is certainly possible ,
and this would support amd hardware .
however , with the public release
of the cuda api by nvidia and the release
of cuda compilers for x86 platforms by pgi , it is possible that an amber implementation will soon be available
on a variety of accelerator hardware .
we
have attempted to make our gpu implementation all - inclusive of the
features available in the pmemd program . at the time of writing ,
the
majority of features applicable to implicit solvent simulations are
available as described below .
support is provided for all gb models
currently implemented within amber as well as the analytical linearized poisson
in addition to constant energy simulations ,
thermostats have been implemented to perform constant temperature
simulations .
this includes all three thermostats available in pmemd ,
that is , the berendsen weak coupling algorithm , the andersen temperature coupling scheme , and the langevin dynamics thermostat .
constraints for hydrogen bond distances use a gpu version
of the standard shake algorithm employed in pmemd ,
and harmonic restraints to a reference structure are supported . to the best of our knowledge
, no gb formalism currently exists that
corrects for the errors introduced by the use of cutoffs for long - range
nonbonded interactions .
the use of cutoffs in gb simulations as implemented
in pmemd does not conserve energy , and their use involves an approximation
with an unknown effect on accuracy .
for this reason , we chose not
to implement van der waals ( vdw ) and electrostatic cutoffs in the
gpu version of this code .
[ cutoffs for the nonbonded interactions
are implemented for explicit solvent simulations with periodic boundary
conditions using the particle mesh ewald ( pme ) method , as described
in a later paper .
a design feature of the gpu code that
goes beyond the cpu implementation is the deterministic nature of
the implementation on a given hardware configuration .
serial cpu calculations
for a given set of input parameters on identical hardware are perfectly
reproducible .
this does not hold for the parallel cpu implementation
since the need to load balance aggressively to achieve good parallel
scaling means that the order of numerical operations is not defined ,
and therefore two simulations started from identical conditions will
always diverge due to rounding differences .
this poses a problem when
transitioning to microsecond or greater simulation time scales since
it can be of advantage to store trajectory information less frequently
than what is optimal in order to conserve available storage space
and produce data files of manageable size .
it is thus not possible
to go back to a given point of the simulation and analyze the trajectory
in finer detail by restarting and sampling more frequently unless
the implementation is deterministic .
the deterministic nature of the
gpu code coupled with machine precision binary restart files ( currently
under development ) makes this mode of simulation possible .
another key feature and a primary design
goal of our gpu acccelerated implementation is that its use is completely
transparent to the user .
as far as the user is concerned , our gpu
implementation is indistinguishable from the cpu implementation , and
using the gpu version of the code is simply a case of switching the
executable name from pmemd to pmemd.cuda or from pmemd.mpi to pmemd.cuda.mpi for the mpi parallelized implementation .
all other items such as
input and output files and regression tests within the code remain
identical . the only difference to be noticed by the user is an increase
of performance .
this guarantees effective uptake of our gpu implementation
by the scientific commmunity because there is no learning curve for
the use of the code , and all tools and scripts that have been developed
for the cpu version of pmemd can be utilized without modifications .
the maximum system size that can be treated
with the gpu implementation is a function of both the gpu hardware
and the md simulation parameters .
in particular , langevin temperature
regulation and the use of larger cutoffs for the effective born radii
calculations increase the memory requirements .
the physical gpu hardware
also affects memory usage since the optimizations used are nonidentical
for different gpu types .
table 1 gives an overview
of the approximate maximum atom counts that can be treated with the
present version of the code .
the dominant sources of gpu memory usage
are the output buffers used for the nonbonded interactions as described
in section 3.2 .
the memory used by those
buffers is proportional to the square of the number of atoms
. currently ,
the atom count limitations imposed by gpu memory usage are roughly
identical in serial and parallel .
all simulations use shake ( amber input ntf=2 ,
ntc=2 ) ; a time step of 2 fs ; the hawkins , cramer , truhlar gb model ( amber input igb=1 ) ; the default cutoff value
of 25 for gb radii ( amber input rgbmax=25 ) ; and temperature
control with the langevin thermostat ( amber input ntt=3 ) , if applicable .
error - correction code ( ecc ) was switched off on the tesla cards . in classical md
, the majority of the computational effort is spent
evaluating the potential energy and gradients , which has to be repeated
each time step . in the case of the amber pairwise
additive force fields , the potential takes the form1where the bond and angle terms are represented
by a simple harmonic expression with force constants bi and ai and equilibrium bond distances / angles ri , eq and i , eq , respectively .
torsional potentials for the dihedral angles
are represented using a truncated fourier expansion in which the individual
terms have a potential vi , n with periodicity n and phase shift
i , n .
the last
two terms are the vdw interaction represented by a lennard - jones potential
with diatomic parameters aij and bij and the
electrostatic interaction between atom - centered point charges qi and qj separated by the distance rij .
the prime on the summation of the
nonbonded interactions indicates that vdw and electrostatic interactions
are only calculated for atoms in different molecules or for atoms
in the same molecule separated by at least three bonds .
those nonbonded
interactions separated by exactly three bonds ( 14 interactions )
are reduced by the application of independent vdw and electrostatic
scale factors , termed scnb and scee in amber , which are dependent
on the specific version of the force field ( 2.0 and 1.2 , respectively ,
for the ff99sb version of the amber force
field ) .
the charmm force field takes
a similar form but includes three additional bonded terms:2the two - body urey
bradley terms account
for angle bending between atoms that are separated by two bonds using
a harmonic potential with force constant ui and equilibrium distance ri , eq .
the improper dihedrals with force
constant ki describe
out - of - plane bending and are used to maintain planarity and prevent
undesired chiral inversions . within the amber force field ,
the third
additional term is a cross term between two sequential protein backbone
dihedral angles , termed cmap .
additionally , the charmm and amber force fields handle 14
nonbonded interactions in a different manner .
the single prime on
the electrostatic summation has the same meaning as described above
for the amber force field with the exception that 14 interactions
are not scaled .
the double prime on the vdw summation implies the
same exclusions as the single prime but the use of different values rijmin and ij for 14 interactions . in the gb implicit solvent model
,
the effect of a surrounding solvent
is described via a continuum electrostatics model that uses a pairwise
descreening approximation and in general also includes a debye hckel
term to account for salt effects at low salt concentrations .
the general
form of the correction to the energy of the solute is given as3where qi and qj are the
atomic partial charges , r is the relative permittivity
of the solvent , and is the debye
the function fijgb interpolates between an effective born radius ri when the distance rij between atoms is short and rij at large distances according
to4the effective born radius ri reflects how deeply buried a charge
is in the low - dielectric medium ( solute ) , and it depends on the intrinsic
radius i of an atom and the relative
positions and intrinsic radii of all other atoms in the solute .
the
models implemented in pmemd differ in the intrinsic radii and the
function that is used to determine the effective born radii .
the remainder of this section discusses key aspects of the gpu
implementation of these equations .
this includes design features to
maximize performance while preserving accuracy as well as addressing
issues of reproducibility which are critical when moving to longer
time scale simulations .
one of the
initial ideas we considered when implementing gpu acceleration for
amber was to write an entirely new code from scratch in a combination
of c++ and cuda .
however , this was quickly dismissed for a number
of reasons . in particular , we wanted to1.keep the maintenance of the amber code
base simple2.minimize
the amount of coding required3.simplify the way in which features
are ported to the gpu4.maintain backward compatibility with
existing input files and regression tests . keep the maintenance of the amber code
base simple minimize
the amount of coding required simplify the way in which features
are ported to the gpu maintain backward compatibility with
existing input files and regression tests .
the approach we ultimately chose was to utilize the
existing fortran code base in pmemd and extend it with calls to specific
cuda kernels for the gpu acceleration with the cuda code protected
with # ifdef cuda preprocessor directives .
a series
of gpu synchronization routines provide an abstract way
to copy relevant data to and from the gpu memory , for example , gpu_upload_vel ( )
and gpu_download_vel ( ) for atomic velocities .
a complete list of synchronization
routines is provided in the supporting information . for performance
, we have implemented the entire md algorithm on
the gpu , which means uploads ( to gpu memory ) are only needed at the
beginning of a run and downloads ( to cpu memory ) are only needed when
i / o is required , for example , downloading the coordinates to write
to the trajectory file .
it remains nevertheless simple to add new
features to the code in a way that will work for both the cpu and
gpu ( see the supporting information for
an example ) . while this limits the performance for the new feature
due to repeated up- and downloads , it does provide a mechanism by
which new features can be easily added and tested with the gpu code
before writing an additional gpu kernel . in order to achieve performance in
parallel on cpus ,
it has always been necessary to include complex
dynamic load balancing algorithms and extensive use of asynchronous
communication within the implementation .
this arises from the fact
that the cpus are expected to perform a number of tasks above and
beyond running the underlying simulation .
for example , the operating
systems run multiple daemons controlling i / o and various other os
related tasks .
in addition , the latency between any two cpus in a
large parallel run can span an order of magnitude or more . as a result
a downside of this is that the order of operations is not well - defined
in the cpu implementation .
this results in rounding differences between
otherwise identical runs . due to the chaotic nature of numerically
integrating newton s equations of motion
, this means that two
initially identical simulations will always decorrelate on time scales
of a few nanoseconds or less .
there is nothing inherently wrong with
this ; the two simulations are just exploring two different regions
of phase space .
as mentioned previously , this does , however , pose
a problem when one starts to routinely run simulations on the microsecond
time scale since it can be necessary to return to a given point in
a simulation and repeat it exactly while saving the output more frequently .
. attempted to address with a bit - wise
reversible integrator based on scaled
integers .
the architectural design of the gpu with many floating
point units controlled by a single instruction unit , and the fact
that the gpu is not required to time slice with os related tasks ,
means that work can be divided between gpu threads and indeed entire
gpus in a predetermined fashion without detrimentally impacting performance .
this can be exploited by careful programming and bookkeeping to ensure
that the order of floating point operations is always predefined at
each given time step .
the gpu implementation of pmemd has been designed
such that any two simulations with identical starting conditions run
on the same gpu model will always be bit - wise identical .
this is extremely
useful for debugging purposes , for example , for detecting shared memory
race conditions , and has also been used to determine that the use
of ecc on gpus has little to no impact on the reliability of amber
simulations . for anderson and langevin
thermostatted simulations ,
it is necessary for the random number generator
( rng ) to also be perfectly deterministic in order for any two initially
identical simulations to be reproducible . to this end
, we use the
parallelized rng that is implemented in the curand library and available
with the cuda toolkits . in amber ,
all of the traditional cpu
codes are written entirely using double precision ( dp ) floating point
arithmetic .
uses single precision ( sp ) floating point numbers
throughout the calculations with the exception of a single double - precision
accumulator in the reduction phase of the force accumulation .
use
of sp in all places within the code , however , can cause substantial
instabilities in the md simulations .
while this error can be
hidden using tightly coupled thermostats , the true effects of such
approximations have not been well characterized .
we distinguish
three different precision models in our gpu implementation in which
the contributions to the nonbonded forces are calculated in single
precision arithmetic , but bonded terms and force accumulation are
in double precision ( spdp ) , or everything is computed and accumulated
in single precision ( spsp ) or double precision ( dpdp ) . the exception
to this is the shake algorithm ( see below ) , which is implemented in
dp for all precision models since it involves calculating relative
differences in distance on the order of 10 .
attempting to use sp for the shake algorithm as implemented leads
to numerically unstable simulations .
the aim in developing our spdp
precision model for the gpu implementation of pmemd was to achieve
numerical stability during md simulations equivalent to that of traditional
dp implementations but with performance as close to the spsp model
as possible .
as highlighted in the subsequent sections , the spdp model
achieves these aims and for this reason is the default precision model
used in the gpu implementation of pmemd , although the other precision
models can be chosen if desired .
our approach to the calculation
of nonbonded interactions is similar to that described in friedrichs
et al .
having been developed at the same
time and with overlapping authors but with several differences and
additional optimizations , including the way in which accumulations
are handled .
the algorithm used for the calculation of the nonbond
forces is identical for all three precision models .
the pairwise interactions
between atoms i and j , which can
schematically be represented by a matrix as in figure 2 , are grouped together into tiles of dimension w w. the evaluation of the nonbond forces
for each tile is dynamically assigned to independent warps across
all of the streaming multiprocessors ( sms ) of a given gpu , which are
each running a sufficient number of threads to bury operational latency .
the reason for doing this is that the gpu schedules work in terms
of warps which effectively perform the same mathematical operation
on w values at once . in the case of nvidia ,
all current
gpus process warps as 32-threads - wide ; in this case , optimum performance
is achieved by making w = 32 .
since the interaction
between two atoms i and j is symmetric ,
only the blue diagonal tiles and the green off - diagonal tiles need
to be considered for the calculation as described below .
unlike the
cpu code , which can just simply loop over atoms i and j , it is crucial to divide up the calculation
on the gpu into as many warp size blocks as possible . however , this
presents a problem when it comes to accumulating the forces for each
atom since the warps can be scheduled for computation in any order .
a nave accumulation of the resulting forces on each
atom can thus lead to race conditions and incorrect results .
the use
of atomic operations within the nonbond routine to avoid this problem ,
however , represents a serial bottleneck that would be unacceptable
in terms of performance .
the approach we use is thus to allocate ( n / w ) + 1 output buffers per atom where n is the total number of atoms and w is
the warp size . in the case of the nonbond force calculation ,
each
output buffer is three double - precision - values - wide for the spdp and
dpdp precision models and three single - precision - values - wide for the
spsp precision model corresponding to the force in the x , y , and z directions of cartesian
coordinate space .
forces calculated within a tile can then be summed
for each atom without fear of overwriting memory effectively providing
a separation in space between tiles . at the conclusion of the force
calculation
, we assign one thread per atom in linear order and cycle
through the output buffers , summing them to obtain the total force
on each atom .
schematic representation of the work - load distribution
for the
calculation of nonbond forces with n atoms .
each
square represents the interactions between two atoms i and j for which the resulting forces need to be
evaluated .
these are grouped together in tiles of size w w that are each assigned to an independent
warp . due to symmetry ,
only the blue diagonal tiles and the green
off - diagonal tiles need to be considered for the calculation . for
details , see the text .
while this approach provides a separation in space
between tiles ,
it is still necessary to deal with race conditions within a tile .
we have to distinguish on - diagonal tiles ( blue ) and off - diagonal tiles
( green ) , see figure 2 .
the on - diagonal tiles
include the interaction of atoms i to i + w 1 with themselves and thus include
the self - interaction from the gb term .
in contrast , off - diagonal tiles
include the interaction of atoms i to i + w 1 with j to j + w 1 , where i j. to avoid race conditions , it is necessary
to handle these two types of tile in different ways . on -
diagonal
tiles store two copies of the coordinates and associated
parameters for each atom , one set in shared memory ( index atom i in figure 2 ) and the second set
in the registers ( index atom j in figure 2 ) .
each thread in the warp then runs linearly through
shared memory ( atom j ) , accumulating only the force
acting on the register atoms i in the corresponding
force output buffer . as illustrated in figure 2 , on the first iteration , the force on atom i resulting
from interacting with itself is obtained and stored in the corresponding
register for i , while simultaneously the force on
atom i + 1 resulting from interacting with atom i is obtained and stored in the register for atom i + 1 . similarly the forces on atoms i +
2 to i + w 1 resulting
from interacting with atom i are obtained and stored
in the corresponding output buffer .
all threads then step to the next
column to obtain the forces on atoms i to i + w 1 due to interactions with
atom i + 1 etc .
this approach does some excessive
computational work since , for any given atom pair ij , the force on atom j is just the negative of the
force on atom i , and thus only the upper or lower
triangle of the tile would have to be considered .
however , this is
far outweighed by the advantage of avoiding race conditions that would
result from several threads updating their force contribution to the
same atom . in the case of off - diagonal tiles , a different approach
is taken
such that the symmetry in the interactions is exploited while avoiding
race conditions .
again , the coordinates and associated parameters
of atoms labeled j to j + w 1 are placed in the registers , while the coordinates
and associated parameters of atoms i to i + w 1 are placed in shared memory .
if
the off - diagonal tiles were handled in the same fashion as the on - diagonal
tiles , on the first iteration , the force on atom j due to interacting with atom i would be calculated
and from this the corresponding force on atom i obtained
by negation . at the same time , the force on atom j + 1 due to interacting with atom i would be calculated
and from this the corresponding force on atom i obtained
by negation .
thus , the forces on atom i due to all
atoms j of the tile would be calculated at the same
time , which would require atomic operations to accumulate correctly .
the solution to this problem that is implemented in amber is to partition
the off - diagonal tiles in time as illustrated in figure 2 . by starting each thread offset by its thread
i d , we avoid
race conditions in the accumulation and eliminate the need for performance
destroying atomic operations . the gb terms are calculated
in an identical fashion to the nonbond terms described above . the
born radii are first calculated within their own kernel and reduced
to per atom radii in an analogous fashion to how the nonbond forces
are handled .
the bonded and 14
terms represent a very small fraction of the computational workload
( typically < 1% of an iteration ) , and thus optimization of their
calculation is not critical for performance compared with , for example ,
the nonbond interactions
. however , efficient calculation on a gpu
still requires some consideration in how these terms are calculated
in order to exploit the massive parallelism within the gpu while avoiding
race conditions and memory overwrites .
our implementation simply creates
a list of the interactions , sorted by type , and then divides up the
bonded and 14 terms across sms on a per interaction basis .
since the resulting forces need to be summed for each atom , there
is the potential for a race condition to occur during this reduction
if two or more gpu threads attempt to accumulate forces for the same
atom at the same time in global memory .
our initial attempts to avoid
this used atomic operations for reduction of the resulting forces
to individual atoms but showed very poor performance .
our solution
to this is to make use of the tile reduction buffers from the nonbond
calculation as described above and then sum these forces in the reduction
step used in the nonbond calculation . at the time of writing ,
these are handled in an identical fashion to the bonded interactions
being calculated as a bond between an atom and a fixed virtual particle
representing the reference structure .
the shake implementation is currently
restricted to hydrogen atoms since this represents > 99% of the
types
of simulation amber users run .
this restriction has the benefit that
each heavy atom and its attached hydrogen atoms can thus be handled
independently .
our approach is to simply spawn a thread for each heavy
atom during the shake calculation .
the use of double precision entirely within
the shake routine provides sufficient precision to handle shake tolerances
on the order of 10 and thus avoids complexities
involved in attempting to implement shake constraints in an internal
coordinate representation as would be required if shake was to be
carried out in single precision .
integration is carried out on the
gpu in a manner analogous to that on the cpu since it is intrinsically
parallel given that each atom can be handled independently .
the integration
is done on the gpu rather than on the cpu to negate the need for expensive
copy operations of the coordinates back and forth between cpu and
gpu . as mentioned above ,
the berendsen and langevin thermostats are applied
in the same way during the coordinate update step , while the anderson
thermostat is implemented as a separate kernel that randomizes the
velocities at regular intervals .
the reason for including the berendsen
and langevin thermostats within the integration kernel is that they
operate on every time step , while the anderson thermostat is typically
called every few hundred time steps . in the case of the langevin thermostat ,
a total of 3n random numbers
are required on each
step , which are extracted from a pool of gpu generated random numbers ,
stored in global memory , which is refilled as needed using the parallel
random number generator implemented within the curand library from
the cuda toolkit .
the same pool is used for the anderson thermostat
as needed . in the interest of performance
and conserving limited gpu resources , the energy is only calculated
alongside the forces when needed .
calculation of the energies causes
a small degree of register spillage to global memory as well as additional
code execution , and since one only periodically needs these values ,
typically only every 1 to 2 ps when writing to the output file , it
is not necessary to calculate these on every iteration .
additionally ,
this is one aspect of the algorithm that is allowed to be nondeterministic
at the level of double - precision round - off error .
we allow this because
the energy values have no effect on the trajectory of the simulation .
however , it was disturbing to observe this in action in the spsp mode
where nondeterminism was initially allowed at the level of single - precision
round - off error .
this was harmless as the forces remained consistent ,
but in the interest of avoiding confusion among end - users , with regression
tests showing differences for repeat runs in spsp mode , all energy
summation was promoted to double - precision where differences in round - off
of the energies are seen only once in approximately 10 printed interactions .
the reasons for this were
to maximize portability of the code and avoid hardware - induced complexities
such as the fact that inter - gpu communication as implemented in cuda
4.0 requires all gpus to be on the same pcie controller .
support for
gpu to gpu copies in different nodes is also not yet sufficiently
mature to be exploited in a widely used software package . for these
reasons ,
the current parallel gpu scaling should be considered as
a lower bound on performance that will likely improve considerably
in subsequent versions of amber running on next generation hardware . unlike the cpu mpi implementation , the gpu mpi implementation is
fully deterministic for a given number of nodes and gpus . at present
,
our gpu implementation performs significant load - balancing between
the sms within each gpu rather than between gpus , which makes it possible
to produce a deterministic implementation . achieving good parallel
scaling on cpu clusters has always required the use of extensive load - balancing
due to the noise introduced from the operating system sharing the
cpu resources on a node .
gpus on the other hand provide significantly
more stable performance , and thus load balancing between gpus is not
as critical . in the current version of the software ( amber v11 ) ,
the gpu parallel
support for gb calculations is implemented by dividing the force calculation
evenly and linearly across all gpus .
for m gpus running
a simulation consisting of n atoms , gpu i calculates all forces for atoms ( i 1 )
n / m + 1 to i n / m .
since gb is a full o(n ) calculation , this introduces
a small degree of redundancy at the gpu level with a worst - case outcome
of doing twice the overall calculation , but usually much less than
this as long as n m. as
currently implemented , there are three stages to the calculation in
parallel , each in need of synchronizing force data across all gpus .
the procedure used consists of three sequential mpi_allgather operations
per iteration to merge born radii , born force , and general force data .
as the hardware evolves and gpus can reliably communicate directly
with each other within a node , we intend to scrap the internode mpi
communication and instead replace it with direct peer to peer copies
between gpus .
to assess both the serial
and parallel performance that can be
achieved with gpu accelerated amber , we ran a series of md simulations
representative of typical research scenarios using the gpu and cpu
implementations on a variety of hardware .
the systems used consisted
of partially folded trpcage ( 304 atoms ) ,
ubiquitin ( 1231 atoms , pdb code 1ubq ) , apo - myoglobin
( 2492 atoms ) , and nucleosome ( 25 095 atoms , pdb code 1kx5 ) . in all three
simulations , the ff99sb version of the
amber force field was used with a time step of 2
fs and bonds to hydrogen atoms constrained using the shake algorithm .
the hawkins , cramer , and truhlar gb model ( amber input igb=1 ) was used with no cutoff applied to the nonbonded
interactions and a cutoff of 15 for the calculation of the
effective gb radii .
the output and trajectory files were written to
every 1000 steps ( 2 ps ) .
the
software base used for all simulations was amber version 11 ,
including patches 115 for ambertools and patches 117
for amber , which were released on august 18 , 2011 .
the executables were built under the redhat enterprise
linux 5 operating system with intel compiler version 11.1.069 , the
intel mkl library version 10.1.1.019 , and the nvidia cuda compiler
version 4.0 .
mvapich2 version 1.5 was used for the parallel runs for
both the cpu and gpu versions of the code .
while the fortran compiler and use
of mkl has little impact on the gpu code performance , this compiler / library
combination gives the best performance for the cpu code and thus forms
a fair basis when assessing the capabilities of the gpu implementation .
both the cpu and gpu simulations were run on machines equipped with
a supermicro x8dtg - df motherboard with dual hex - core intel x5670 processors
clocked at 2.93 ghz and mellanox quadruple data rate ( qdr ) infiniband
interconnects .
each compute node was equipped with one gpu and one
infiniband card , which were each connected to a pcie x16 slot .
error - correction
code ( ecc ) was switched off on the tesla cards , and the 64-bit nvidia
linux driver version 275.21 was used .
additionally , cpu simulations
were run on the xsede trestles supercomputer at the san diego supercomputer
center , whose nodes are equipped with four oct - core amd opteron 6136
processors clocked at 2.4 ghz and also interconnected with qdr infiniband .
the results of the simulation
timings for single gpu runs are summarized in table 2 . for small simulations such as trpcage with 304 atoms where
the gpu s arithmetic hardware
can not be fully utilized , the
serial gpu implementation is approximately twice as fast as a current
state of the art cpu node .
the real advantage of the amber gpu implementation ,
however , becomes apparent for implicit solvent gb simulations of medium
to large systems with 2500 to 25 000 atoms .
for apo - myoglobin
( 2492 atoms ) , the serial gpu version of the code is significantly
faster on a single gpu than a state of the art cpu node .
for nucleosome ,
this performance gap increases dramatically such that a simulation
that takes two weeks on a single desktop machine with one gpu would
take nine months using the same desktop machine without gpu acceleration . for details on the hardware and
software stack ,
the
cpu code requires > 10 atoms
per core , and thus the trpcage simulation was run on 24 cpu cores .
the parallel performance of
the gpu and cpu implementations is compared in table 3 .
a throughput of up to 135.1 ns / day for apo - myoglobin and
up to 3.95 ns / day for nucleosome can be achieved with eight nvidia
m2090 gpus , which is a factor of 4 to 5 faster than the maximum throughput
that can be achieved on a typical supercomputer given that the cpu
scaling plateaus long before it reaches the performance achieved by
the gpu implementation .
even a single gpu is a factor of 2 to 3 faster
than the cpu scaling limit . for details on the hardware and
software stack ,
as mentioned above , the
amber gpu implementation supports three different precision models .
the dpdp model is logically equivalent to the traditional dp approach
used on the cpu .
however , the use of dp on gpus can be more detrimental
to performance than its use on cpus .
therefore , the desire to achieve
high performance prompts for use of sp where possible .
it is critical
though to use sp carefully in order not to detrimentally affect the
accuracy of the md .
for this reason , we designed our hybrid precision
spdp model to achieve performance very close to that achievable with
sp but in a manner that does not impact accuracy . while we recommend
using the spdp precision model , it is instructive to compare the performance
of the different precision models available in the amber gpu implementation .
as shown in table 4 , the single precision ( spsp )
model achieves the highest performance as expected but , as highlighted
in section 5 , at the cost of accuracy . our
hybrid spdp precision model , however , achieves a performance of greater
than 75% of the spsp precision model with accuracy comparable to that
of the full double precision ( dpdp ) model , which is between 4 to 7
times slower . for details on the hardware and
software stack ,
a critical and often overlooked
aspect of any major change to a
widely used scientific software package is a detailed validation of
any and all new approximations made . in the case of the amber gpu
implementation
the first is a detailed testing of the code itself to ensure that
it correctly simulates the existing systems and does not introduce
any new bugs or contain critical logic errors .
this is the key reason
why we implemented a full double precision ( dpdp ) model within the
gpu code .
this precision model matches the cpu code to machine precision
and thus can be used to check that the gpu code is indeed giving the
correct answers .
this allowed us to take the cpu - based regression
tests that we have used for many years to validate an amber installation
and run them using the gpu code and obtain answers to the limits of
machine precision .
more complex , however , is the second category for
validation which is the careful testing of our hybrid ( spdp ) precision
model .
this is significantly more complex since it requires a careful
evaluation of any subtle differences in the dynamics as well as ensemble
properties from converged simulations run in dpdp and spdp precision .
in this section ,
we attempt to extensively validate our spdp model
comparing a number of key observables across all three , dpdp , spdp ,
and spsp , precision models .
the first metric
tested was the effect of the numerical precision model on the force
calculations as compared to a reference precision model , in this case ,
the result from the cpu implementation .
we are using the starting
structures of the test systems described in section 4 above .
the dpdp model matches the reference forces very
closely with maximum deviations not exceeding 10 kcal/(mol ) and rms deviations not exceeding 10 kcal/(mol ) , even for systems as large as nucleosome .
these
deviations are entirely due to the different order of execution of
the floating point operations in the cpu and gpu implementation .
the
dpdp gpu implementation of pmemd will thus generate trajectories of
precision equivalent to the cpu implementation .
the forces obtained
from the spsp model , however , show very large deviations from the
reference values on the order of up to 10 kcal/(mol
) for the largest system studied .
such large deviations introduce
significant numerical noise into the simulations , and it is reasonable
to expect that this may render the results of md simulations questionable .
calculating the force contributions in sp and accumulating them in
dp , however , leads to an improvement of more than 1 order of magnitude
in all cases for the spdp model as compared to the spsp model . in
the following section , we will indeed show that the forces obtained
from the spsp model are not precise enough to conserve energy in biomolecular
md simulations and can lead to instabilities in long time scale md
simulations , while the spdp model is sufficient for this purpose .
one of the most
important gauges for judging the precision of md software is its numerical
stability , which is reflected in its ability to conserve the constants
of motion , in particular the energy . to this end , we have performed
constant energy md simulations of the first three test systems described
in section 4 above .
we collected data for
100 ns ( trpcage ) , 50 ns ( ubiquitin ) , and 20 ns ( apo - myoglobin ) after
an initial equilibration for 1 ns at 300 k using langevin dynamics .
in addition to simulations using a time step of 2 fs with bonds
to hydrogen atoms constrained using the shake algorithm with a relative
geometrical tolerance of 10 , we have run simulations
using time steps of 0.5 and 1.0 fs without constraints .
the
energy drifts along the trajectories are summarized in table 6 , while figure 3 shows a
plot of the total energy for the trajectories of trpcage and ubiquitin
for the different precision models at a time step of 0.5 fs .
the corresponding
plot for apo - myoglobin is very similar to that for ubiquitin and can
be found in the supporting information along
with plots for the larger time steps .
the plots underline that it
is important to validate the precision models for trajectories that
are long enough to uncover numerical instabilities .
while the spsp
model seems to perform reasonably well for a trajectory of 1 ns length ,
in particular for smaller systems like trpcage , it becomes apparent
that the errors introduced lead to unacceptably large energy drifts
in the long term .
apart from the magnitude in the energy drift , the
plots for the other time steps show a similar behavior ( see supporting information ) .
table 6 shows that the spdp model is able to conserve energy to the
same degree as the full double precision model ( dpdp ) and the reference
cpu implementation .
the spsp model , on the other hand , shows energy
drifts that are 1 to 2 orders of magnitude larger and , on the time
scales investigated , leads to completely unphysical results . while
the cpu implementation and the gpu implementations with the full double
precision model ( dpdp ) and mixed precision model ( spdp ) achieve excellent
energy conservation on the order of 10 kt / ns / dof ,
where dof means degree of freedom , for simulations with a time step
of 0.5 fs , the energy drift for the spsp model remains as large as
with a time step of 1.0 fs .
in addition , the energy drift for the
spsp model is not constant and in general increases significantly
along the trajectory as the temperature increases , which eventually
leads to unstable simulations .
total energy ( kcal / mol ) along constant
energy trajectories using
a time step of 0.5 fs without constraints . shown
are results for trpcage
( left ) and ubiquitin ( right ) for different precision models .
the shake algorithm to constrain
bond lengths to hydrogen atoms was used for a time step of 2.0 fs ;
no constraints were used for smaller time steps .
a dash indicates
that the system heated up extremely during the simulation to the point
that it is meaningless to report an energy drift .
an asterisk indicates
that the energy drift increases dramatically for longer time scales . by way of comparison to
other gpu implementations of md ,
the closest published constant energy
gb simulation is that of the repressor ( 1254 atoms ) using
openmm .
simulations of this system at
a time step of 1.0 fs over 1 ns of simulation time without constraints
using the gpu implementation of openmm gave energy drifts of 0.0054
kt / ns / dof ( ati hardware ) ( table
3 of friedrichs et al . ) compared with
our values of 0.000006
kt / ns / dof ( dpdp ) , 0.000030 kt / ns / dof ( spdp ) ,
and 0.000305
kt / ns / dof ( spsp ) for the similarly sized ubiquitin system
( 1231 atoms ) .
it is also interesting to compare the energy conservation
achieved with the amber gpu implementation using the typical simulation
settings that one would use in a production md simulation with those
published for the openmm implementation .
most amber simulations would
use shake constraints and a 2 fs time step with the spdp precision
model , which for ubiquitin gives an absolute energy drift of 0.000165
kt / ns / dof .
this compares extremely favorably with the drift of 0.0060
( nvidia hardware ) and 0.0558 ( ati hardware ) for openmm .
the energy
conservation of the amber gpu implementation looks even better when
one considers that the openmm constraint numbers were obtained with
a smaller time step of 1 fs . on the molecular
level , protein dynamics are at the heart of biological function .
md simulations that are able to accurately describe
protein motions aid in understanding the multitude of functions that
proteins carry out and can be used to interpret and predict experimental
results that are related to its structural and dynamic properties ,
for example , nmr spectroscopic parameters such as spin relaxation or residual dipolar couplings . in order to
scrutinize the reliability of our implementation for protein dynamics ,
we present results of md simulations of ubiquitin with the different
accuracy models of our gpu implementation and compare these to trajectories
obtained with the cpu implementation which serves as a reference .
we focus on root - mean - square deviations ( rmsds ) and root - mean - square
fluctuations ( rmsfs ) of the c backbone carbon atoms
with respect to the crystal structure ( pdb code 1ubq(53,54 ) ) .
the highly flexible end tail of ubiquitin ( residues 71 to 76 )
was excluded from our analysis .
results for the radius of gyration rg of ubiquitin can be found in the supporting information .
although the use
of a thermostat will to some extent cover up numerical noise introduced
by numerical inaccuracies in the implementation , we are analyzing
constant temperature simulations here since typical biomolecular amber
simulations are generally run with some form of temperature control .
in order to obtain statistically meaningful results ,
50 independent
md trajectories each of 100 ns length were generated at 300 k both
for the cpu implementation and for each of the precision models of
the gpu implementation .
the ff99sb force
field was used for all simulations with a time step of 2 fs and bonds
to hydrogen atoms constrained using the shake algorithm with a relative
geometrical tolerance of 10 .
( amber input igb=5 )
was used with no cutoff applied to the nonbonded interactions and
a cutoff of 15 for the calculation of the effective gb radii .
the output and trajectory files were written to every 1000 steps ( 2
ps ) .
temperature control during production runs was achieved with
the berendsen weak coupling algorithm using a time constant of t =
10.0 ps for the heat bath coupling .
the initial coordinates and velocities
that form the starting point of the 50 trajectories were generated
using the cpu implementation as follows .
after energy minimization
for 2000 steps followed by heating and an initial equilibration for
1 ns at 300 k using langevin dynamics with a collision frequency of
= 1.0 ps , snapshots were extracted at
time intervals of 4 ns from a constant temperature md simulation at
300 k. each of these snapshots was then assigned random velocities
corresponding to a temperature of 10 k followed by heating and equilibration
to 300 k using langevin dynamics for 50 ps and removal of any center
of mass motion that may have been introduced . using the cpu generated
restart files in all cases
guarantees that any numerical differences
observed between the various implementations can be traced back to
the numerical precision of the implementation and is not an artifact
of different initial conditions .
the plot of the rmsd values vs time ( figure 4 ) clearly shows the stability of the md simulations using
the cpu
implementation and the gpu implementation with the full double precision
model ( dpdp ) and the mixed single / double precision model ( spdp ) .
the
value of rg also remains constant throughout
all simulations of ubiquitin using the cpu and gpu dpdp and spdp versions
of the code ( see supporting information ) , indicating that the relative compactness of the protein is maintained .
the rg value stays around 11 to 12 ,
typical for proteins of this size , assuming a spherical conformation , and are in good agreement with the rg reported for other native - state simulations of ubiquitin .
the rmsf values for each residue for the 50
native - state simulations are shown in figure 5 .
the data show an excellent agreement among the cpu implementation
and the gpu implementation using both the dpdp and the spdp precision
model with the majority of the residues remaining within 2 to 3
of their positions in the experimental structure and somewhat larger
fluctuations around residue numbers 33 , 48 , and 63 . on the time scale
investigated , no major structural change is taking place during the
simulation , confirming that the protein remains within a native - state
ensemble .
root - mean - square deviations ( rmsds ) of the c backbone
carbon atoms of ubiquitin ( excluding the flexible tail , residues 7176 )
with respect to the crystal structure for 50 independent trajectories
as obtained with the cpu implementation and the gpu implementation
of pmemd using different precision models .
root - mean - square fluctuations ( rmsfs ) of the c backbone carbon atoms of ubiquitin residues 7176 with respect
to the crystal structure for 50 independent trajectories of 100 ns
length as obtained with the cpu implementation and the gpu implementation
of pmemd using different precision models .
the situation is very different for the spsp precision
model of
the gpu implementation .
while approximately half of the trajectories
show a similar behavior and stability as the trajectories obtained
with the other precision models and the reference cpu implementation
of pmemd , the remaining trajectories experience a very large increase
in the rmsd values ( figure 4 ) and a corresponding
increase in the rmsf values ( figure 5 ) .
the
reason for this behavior is that the numerical noise introduced in
the simulations due to rounding errors can lead to an accumulation
of errors such that ubiquitin starts to unfold .
this is accompanied
by an increase in rg ( see supporting information ) and is also reflected
in the large rmsf values of the residues close to the termini of the
protein .
since it can not be predicted whether a simulation using the
spsp precision model will be stable or not , no judgment can be made
whether the results obtained are meaningful .
the gpu implementation
of pmemd should thus only be used with the dpdp and the spdp precision
models . on the basis of the results shown here , we recommend the use
of the mixed - precison spdp model since the numerical results obtained
are comparable with those obtained with the full double precision
dpdp model but at significantly reduced computational cost .
we presented
a framework for the acceleration of classical molecular
dynamics simulations on graphical processing units within the pmemd
program of the software package amber . in this contribution , we described
the efficient and highly precise implementation of implicit solvent
generalized born molecular dynamics simulations realizing performance
that exceeds that achievable on any current conventional supercomputer .
the implementation supports serial runs on a single nvidia gpu or
parallel runs across multiple gpus using mpi .
performance for moderately
sized systems can exceed 100 ns per day , making microsecond or longer
simulations routine on deskside workstations .
for large systems , the
performance differential between our gpu code and the cpu implementation
increases significantly . a gb simulation of the nucleosome running
on just one nvidia m2090 gpu completes in two weeks what a current
high - end workstation would take nine months to run using cpus .
this
massive performance increase for minimal investment in hardware will
transform the traditional molecular dynamics workflow , providing a
platform for sustained innovation .
the implementation is transparent
to the end user and does not
require any specialized knowledge beyond that required to run the
traditional cpu code .
our gpu implementation supports the majority
of the features provided by the cpu implementation including the amber
and charmm families of biomolecular force fields .
we have developed a
hybrid precision model for floating point arithmetic termed spdp that
provides performance close to full single - precision calculations but
retains energy drifts in constant energy md simulations and structural
properties of proteins for long time scale md simulations equivalent
to what is achievable with full double precision .
energy conservation
with our hybrid spdp model is approximately 1 to 2 orders of magnitude
better than what has been published for other similar gpu implementations
of molecular dynamics .
simulation size is limited by the memory available
on gpu cards , which at the time of writing is at maximum 6 gb corresponding
to approximately 54 000 atoms .
the current cost benefits
of gpus are enticing , and this is driving
both soft- and hardware development at a rapid pace . in a few short
years
, gpu - based md codes have evolved from proof - of - concept prototypes
to the production level amber gpu implementation we described here .
with gpus becoming ubiquitous in workstations and also as accelerators
in high - performance computing ( hpc ) platforms , the impact of our implementation
on the field of molecular dynamics is broad and transformative .
a
gpu accelerated implementation of the particle mesh ewald ( pme ) algorithm
for explicit solvent calculations is also available in amber 11 as
described in another publication .
this ,
along with future support for advanced features including accelerated
md ( amd ) , umbrella sampling , replica exchange md ( remd ) , thermodynamic
integration ( ti ) , polarizable force fields , and constant ph simulations
means the use of gpus is a viable alternative to traditional supercomputers
for classical molecular dynamics simulations . | we present an implementation of generalized born implicit
solvent
all - atom classical molecular dynamics ( md ) within the amber program
package that runs entirely on cuda enabled nvidia graphics processing
units ( gpus ) .
we discuss the algorithms that are used to exploit the
processing power of the gpus and show the performance that can be
achieved in comparison to simulations on conventional cpu clusters .
the implementation supports three different precision models in which
the contributions to the forces are calculated in single precision
floating point arithmetic but accumulated in double precision ( spdp ) ,
or everything is computed in single precision ( spsp ) or double precision
( dpdp ) .
in addition to performance , we have focused on understanding
the implications of the different precision models on the outcome
of implicit solvent md simulations .
we show results for a range of
tests including the accuracy of single point force evaluations and
energy conservation as well as structural properties pertainining
to protein dynamics .
the numerical noise due to rounding errors within
the spsp precision model is sufficiently large to lead to an accumulation
of errors which can result in unphysical trajectories for long time
scale simulations .
we recommend the use of the mixed - precision spdp
model since the numerical results obtained are comparable with those
of the full double precision dpdp model and the reference double precision
cpu implementation but at significantly reduced computational cost .
our implementation provides performance for gb simulations on a single
desktop that is on par with , and in some cases exceeds , that of traditional
supercomputers . |
duodenal involvement is exceptional with only sporadic cases reported in the medline database [ 1 , 2 ] .
this report emphasizes the lack of specific clinical , radiological and endoscopic signs of duodenal tuberculosis and highlights the principal therapeutic modalities .
a 60-year - old patient was admitted to the emergency department with severe abdominal pain and vomiting of one month duration , important weight loss ( 10 kg ) and poor appetite .
he had a history of chronic epigastric pain treated by antiacids and h2 blockers without much relief .
there was no hepatosplenomegaly or palpable mass , but epigastric tenderness was noted at palpation .
biological tests revealed hypochromic anemia with a hemoglobin level of 9.5 g / dl ; laboratory investigations also showed hyponatremia of 130 mmol / l .
upper gastrointestinal endoscopy showed a dilated stomach with food residue and marked narrowing of the first part of duodenum ( fig .
1 ) . exploration of the rest of the duodenum was impossible because of the stenosis .
endoscopic biopsy revealed nonspecific duodenitis . at operation , an important thickening of the entire wall of the first part of the duodenum was found .
it was responsible of an important narrowing of d1 and a dilation of the stomach ( fig .
2 ) . several nodule formations on the serosa , on the peritoneum and tiny ones on the liver surface were observed .
all these operative findings were suggestive of tuberculosis with involvement of duodenum , liver and peritoneum .
biopsy from the mesenteric lymph nodes revealed hyperplasia and tubercles with caseation surrounded by epithelioid cells and some langerhans giant cells .
the following antituberculous treatment was instaured : 2 months of streptomycin , rifampicine , isoniazid and pyrazinamide followed by rifampicine and isoniazid for 9 months .
a 57-year - old male was admitted to our hospital with complaints of vomiting and progressively increasing postprandial epigastric pain of six months duration with significant weight loss ( 20 kg in 6 months ) .
barium examination of the upper gastrointestinal tract revealed stenosis of the third portion of the duodenum associated with a dilated stomach .
abdominal computed tomography ( ct ) scan showed a 3 cm stenosis of d3 and a regular thickening of the duodenum walls ( fig .
peroperatively , a duodenojejunectomy ( d3 , d4 and the first jejunal loop ) was performed .
the second part of the duodenum and the jejunum were anastomosed as a duodenojejunostomy ( end to end ) .
histopathological examination showed an extensive area of caseating necrosis surrounded by epithelioid cells , lymphocytes and giant cells .
the patient was treated with antituberculous chemotherapy for 9 months : streptomycin , rifampicine , isoniazid and pyrazinamide for 2 months followed by rifampicine and isoniazid for 7 months .
3 years subsequently follow - up showed complete recovery from symptoms and 15 kg weight gain .
a 60-year - old patient was admitted to the emergency department with severe abdominal pain and vomiting of one month duration , important weight loss ( 10 kg ) and poor appetite .
he had a history of chronic epigastric pain treated by antiacids and h2 blockers without much relief .
there was no hepatosplenomegaly or palpable mass , but epigastric tenderness was noted at palpation .
biological tests revealed hypochromic anemia with a hemoglobin level of 9.5 g / dl ; laboratory investigations also showed hyponatremia of 130 mmol / l .
upper gastrointestinal endoscopy showed a dilated stomach with food residue and marked narrowing of the first part of duodenum ( fig .
1 ) . exploration of the rest of the duodenum was impossible because of the stenosis .
endoscopic biopsy revealed nonspecific duodenitis . at operation , an important thickening of the entire wall of the first part of the duodenum was found .
it was responsible of an important narrowing of d1 and a dilation of the stomach ( fig .
2 ) . several nodule formations on the serosa , on the peritoneum and tiny ones on the liver surface were observed .
all these operative findings were suggestive of tuberculosis with involvement of duodenum , liver and peritoneum .
biopsy from the mesenteric lymph nodes revealed hyperplasia and tubercles with caseation surrounded by epithelioid cells and some langerhans giant cells .
the following antituberculous treatment was instaured : 2 months of streptomycin , rifampicine , isoniazid and pyrazinamide followed by rifampicine and isoniazid for 9 months .
a 57-year - old male was admitted to our hospital with complaints of vomiting and progressively increasing postprandial epigastric pain of six months duration with significant weight loss ( 20 kg in 6 months ) .
barium examination of the upper gastrointestinal tract revealed stenosis of the third portion of the duodenum associated with a dilated stomach .
abdominal computed tomography ( ct ) scan showed a 3 cm stenosis of d3 and a regular thickening of the duodenum walls ( fig .
peroperatively , a duodenojejunectomy ( d3 , d4 and the first jejunal loop ) was performed .
the second part of the duodenum and the jejunum were anastomosed as a duodenojejunostomy ( end to end ) .
histopathological examination showed an extensive area of caseating necrosis surrounded by epithelioid cells , lymphocytes and giant cells .
the patient was treated with antituberculous chemotherapy for 9 months : streptomycin , rifampicine , isoniazid and pyrazinamide for 2 months followed by rifampicine and isoniazid for 7 months .
3 years subsequently follow - up showed complete recovery from symptoms and 15 kg weight gain .
tuberculosis of the gastrointestinal tract most often affects the ileocecal region [ 3 , 4 ] .
duodenal involvement accounts for only 2.3% of tuberculous enteritis . usually , the intestinal lesions of tuberculosis are associated with other advanced systemic lesions .
this is probably due to the rapid transit time taken by the gastric contents to travel through the duodenum .
the possible routes of infection are directly through mucosa , hematogenous , lymphatic and from adjacent structures in continuity through serosa .
the clinical manifestations of duodenal tuberculosis are varied and nonspecific [ 1 , 5 ] .
the cause of obstruction can be either stricture or external compression with a reported incidence of 59 and 41% , respectively .
our patients presented with features of upper gastrointestinal tract obstruction and had stricture as the cause of obstruction .
the radiological features of duodenal tuberculosis are nonspecific [ 5 , 6 ] . in our cases
these findings are so unspecific that tuberculosis is almost never considered . peptic ulcer disease , neoplasm of the duodenum or pancreas , or crohn 's disease is often suspected on that basis .
tuberculous lymphadenitis can not be distinguished from malignant or other lymphadenopathy according to ct criteria .
submucosal location of the lesion has been cited as a reason for failure of endoscopic biopsies . due to a lack of accurate clinical diagnosis and radiological features ,
patients presenting with diagnostic dilemma or with complications such as a pyloric mass , stenosis , bleeding , or perforation require surgery .
however , the laparoscopic approach can be a very interesting tool to diagnose duodenal tuberculosis by permitting biopsies of lymph nodes or peritoneal granulations .
this can ovoid surgery in many cases because digestive stenosis can be reversible after specific medical treatment .
the discovery of granulomas in a duodenal stricture , in the absence of caseating lesions , and especially when a sinus tract is present , makes it difficult to distinguish duodenal tuberculosis from crohn 's disease , and may delay proper antituberculous treatment and prompt the unfortunate introduction of a corticotherapy .
surgical intervention is indicated in such cases of duodenal tuberculosis because the obstruction occurs as a result of stricture formation [ 4 , 8 ] .
the surgical treatement includes either resection of the affected part or a bypass procedure . in our study , we performed in one case a duodenectomy with a duodenojejunal anastomosis , and in the second case a simple gastrojejunostomy . in these cases ,
both of the two techniques were performed by the same surgeon . even though we had no postoperative complications and the same functional results in both cases , we believe that the bypass should be preferred because it is simpler to realize .
a full course of antitubercular therapy should always complement any operation for duodenal tuberculosis [ 1 , 2 , 3 ] .
duodenal tuberculosis , the rarest form of intestinal tuberculosis , poses great difficulty in diagnosis .
radiologic findings and endoscopic biopsy are nonspecific and surgical intervention is often required to make a diagnosis . | duodenal tuberculosis is a rare clinical entity . the authors report and emphasize the lack of special clinical , radiological and endoscopic signs of duodenal tuberculosis .
the diagnosis is affirmed , at laparotomy , out of the findings of peritoneal granulations or histology of lymphatic nodes .
we report our experience of two cases of duodenal tuberculosis presenting with proximal intestinal obstruction and review the available literature . |
SECTION 1. LAKE PONTCHARTRAIN, LOUISIANA.
(a) Authority of Secretary of the Army.--The project authorized by
section 204 of Flood Control Act of 1965 (Public Law 89-298; 79 Stat.
1077) and modified by section 7012(a)(2) of the Water Resources
Development Act of 2007 (Public Law 110-114; 121 Stat. 1279), the
Emergency Supplemental Appropriations Act for Defense, the Global War
on Terror, and Hurricane Recovery, 2006 (Public Law 109-234; 120 Stat.
454) and Supplemental Appropriations Act, 2008 (Public Law 110-252; 122
Stat. 2350) is further modified to authorize the Secretary of the Army
to construct a pumping station that shall be specifically designed to
evacuate storm water from the area known as Hoey's Basin, as--
(1) generally described in the report entitled ``U.S. Army
Corps of Engineers Individual Environmental Report #5;
Permanent Protection System for the Outfall Canals project on
17th Street, Orleans Avenue, and London Avenue Canals''; and
(2) more specifically described under the ``Pump to the
Mississippi River'' option contained in the report described in
paragraph (1).
(b) Authorized Cost.--The total cost of the project authorized
under subsection (a) shall be $205,000,000.
(c) Federal Share.--The Federal share of the cost of the project
authorized under this Act shall be performed only in accordance with
the Federal cost share provided for under the Emergency Supplemental
Appropriations Act for Defense, the Global War on Terror, and Hurricane
Recovery, 2006 (Public Law 109-234; 120 Stat. 454) and the Supplemental
Appropriations Act, 2008 (Public Law 110-252; 122 Stat. 2350).
(d) Definitions.--In this section:
(1) Project.--The term ``project'' means the project for
permanent pumps and canal modifications authorized by section
204 of Flood Control Act of 1965 (Public Law 89-298; 79 Stat.
1077), modified by section 7012(a)(2) of the Water Resources
Development Act of 2007 (Public Law 110-114; 121 Stat. 1279),
the Emergency Supplemental Appropriations Act for Defense, the
Global War on Terror, and Hurricane Recovery, 2006 (Public Law
109-234; 120 Stat. 454) and the Supplemental Appropriations
Act, 2008 (Public Law 110-252; 122 Stat. 2350); and further
modified by section (a) of this Act.
(2) Project report.--The term ``project report'' means the
report--
(A) submitted by the Secretary to Congress;
(B) dated August 30, 2007; and
(C) provided in response to the requirements
described in section 4303 of the U.S. Troop Readiness,
Veterans' Care, Katrina Recovery, and Iraq
Accountability Appropriations Act, 2007 (Public Law
110-28; 121 Stat. 154) as the basis for complying with
the requirements of--
(i) the project; and
(ii) the modifications to the 17th Street,
Orleans Avenue, and London Avenue canals in and
near the city of New Orleans carried out under
the project.
(3) Secretary.--The term ``Secretary'' means the Secretary
of the Army.
(e) Duties of the Secretary.--
(1) Study; report.--
(A) Study.--Upon enactment of this Act, the
Secretary shall conduct a study under which the
Secretary shall carry out--
(i) an analysis of the residual risks
associated with options 1, 2, and 2a, as
described in the project report; and
(ii) an independent peer review of the
effectiveness of concept designs and
preliminary cost estimates associated with each
option.
(B) Reports.--Not later than 180 days after the
date of enactment of this Act, the Secretary shall
submit to the Committee on Appropriations of the House
of Representatives and the Committee on Appropriations
of the Senate a report that--
(i) contains the results of the study
conducted under subparagraph (A); and
(ii) identifies the option contained in the
project report that--
(I) is more technically
advantageous;
(II) is more effective from an
operational perspective in providing
greater reliability and reducing the
risk of flooding to the New Orleans
area over the long term; and
(III) if implemented, would--
(aa) increase the overall
drainage capacity of the
region;
(bb) reduce local flooding
to the greatest extent
practicable; and
(cc) provide the greatest
system flexibility.
(2) Implementation.--Effective on the date on which the
Secretary submits the report under paragraph (1)(B), the
Secretary shall resume the implementation of the project in
accordance with the option selected by the Secretary under the
report and without regard to the funds available, is directed
under this Act to implement the option contained in the report
that is found to be more technically advantageous and more
effective from an operational perspective in providing greater
reliability and reducing the risk of flooding to the New
Orleans area over the long term. | Modifies the Lake Pontchartrain flood control project, Louisiana, to authorize the Secretary of the Army to construct a pumping station specifically designed to evacuate storm water from the Hoey's Basin area at a specified cost and federal share.
Requires the Secretary to: (1) conduct a study to carry out an analysis of the residual risks associated with specified options described in the project report and an independent peer review of the effectiveness of concept designs and preliminary cost estimates associated with each option; (2) report to specified congressional committees regarding the option that is more technically advantageous and more effective from an operational perspective in providing greater reliability and reducing the risk of flooding to the New Orleans area over the long term and that would increase the overall drainage capacity of the region, reduce local flooding to the greatest extent practicable, and provide the greatest system flexibility; and (3) resume project implementation with that option without regard to the funds available. |
hubble space telescope ( hst ) , faint object camera ( foc ) images for the central regions of the s0/a galaxy ngc 2681 were obtained in four ultraviolet bands in 1993 , in the context of a project aimed at understanding the origin of uv emission from bulge - dominated galaxies . a point - like source which we term _ spike _ for short was evident at its center with a photometric profile being indistinguishable from the psf of the aberrated , pre - costar hst images @xcite . motivated by the related discovery of the variable nature of the uv - bright spike in ngc 4552
, whose flare has been interpreted as an accretion event onto a central supermassive black hole ( bh ) @xcite , we obtained additional foc imaging and faint object spectrograph ( fos ) spectra of the ngc 2681 spike in 1997 , this time with the costar - corrected optics of hst . unlike the case of ngc 4552
, this latter set of hst observations did not reveal any variability of the central spike in ngc 2681 ( not surprising , as we show here that a possible uv flare of the same luminosity as seen in ngc 4552 would have escaped detection in ngc 2681 due to its steeper surface brightness profile ) . in this paper
we demonstrate that for this galaxy convincing evidence for a central bh comes instead from the modeling of the circumnuclear ionised gas kinematics derived from the fos spectrum , properly combined with foc photometry . in so doing
, we find we can also place interesting constraints on origin of the young stellar population in the center of this galaxy . section [ sec : observations ] presents the known information about ngc 2681 and the observations we obtained .
section [ sec : spectroscopy ] presents the spectroscopic observations .
section [ sec : focanalysis ] discusses the analysis of photometric hst data .
section [ sec : nucleus ] derives the physical parameters for the galaxy inner nucleus , including our best estimate for upper limit to the mass of the central bh that resides in this galaxy .
section [ sec : conclusions ] discusses and summarizes our results .
ngc 2681 is a bulge - dominated s0/a galaxy at an estimated distance of 13.3 mpc @xcite , corresponding to a linear scale of @xmath6 pc arcsec@xmath7 and an absolute @xmath8 magnitude @xmath9 @xcite .
the value of the central magnesium index ( mg@xmath10=0.15 ; * ? ? ?
* ; * ? ? ?
* ) is low compared to values typical of spheroids of comparable luminosity .
the iue spectrum of this galaxy @xcite shows that the stellar population in its central region has a ultraviolet spectrum slowly decreasing towards shorter wavelengths , which is interpreted as evidence for a recent ( @xmath5 gyr ) burst of star formation @xcite .
ngc 2681 has two concentric , misaligned bars @xcite as seen in ground based images .
a third inner bar is seen in this galaxy in hst / nicmos images @xcite .
this innermost bar is also seen in our higher resolution foc/96 images .
note that ngc 2681 is viewed almost face - on and thus these structures can not be due to projection effects ( i.e. we can not misinterpret a change of flattening in an axisymmetric structure for a change of ellipticity due to a bar ) . ground based @xmath11 color maps do not show evidence of a ring or a grand design spiral , although two barely visible , small spiral arms exist in the disk .
based on our foc/96 images the , spiral structure pointed out by @xcite appears to extend to within the central few arcsecs of this galaxy .
galactic absorption for this galaxy is @xmath12 @xcite .
ground - based images also reveal a few regions and strong nuclear emission @xcite . @xcite has reported detection of centrally - concentrated emission ( @xmath13 ) via pa @xmath14 imaging using hst / nicmos . on the basis of their spectroscopic optical observations ,
@xcite classify the nucleus of this galaxy as a liner .
fos / red detector spectra of the nucleus of ngc 2681 were obtained in 1997 , using the @xmath15 square aperture ( 0.25-pair ) .
a complete log of fos observations is given in table [ tab : fos_log ] .
analysis of the fos acquisition steps assures us that the nucleus of ngc 2681 was correctly centered in the fos aperture ( with a 0025 accuracy ) .
this is confirmed by the fact that the central flux measured within the fos aperture on our costar - corrected f342w foc/96 image agrees with the flux predicted for that foc filter from the fos g270h spectrum .
foc observations of ngc 2681 include our own 1993 pre - costar and subsequent 1997 costar - corrected , foc/96 images .
a detailed summary of the foc instrumental configurations and exposure times is given in table [ tab : obs_log ] . in this work
we also make use of an archival nicmos image taken on 1997 june 7 with the f160w ( space - based h - band ) , during one of the nic3 `` campaigns '' @xcite .
the scale of this image is 02 pixel@xmath7 and the field of view ( fov ) is @xmath16 .
all of the spectra and images used in this work have been de - archived and recalibrated using the most recent version of the stsci data pipeline and the latest calibration files .
the combined fos nuclear spectrum of ngc 2681 is presented in figure [ fig : fos_complete ] .
clearly recognizable in absorption are the mg ii @xmath172800 , mg i @xmath172852 , and the balmer lines @xmath18 , @xmath19 and @xmath20 , as well as @xmath21 in emission .
strong balmer absorption lines in the spectrum of a galaxy are , of course , indicative of a relatively young stellar component ( 12 gyr ) .
this is consistent with the relative absorption line strengths of mg ii and mg i , which are indicative of a late a - type main sequence for the stars producing this spectrum @xcite , as well as with the interpretation of iue spectrum of this galaxy @xcite .
also prominent are emission lines of the ] @xmath172326 multiplet , [ ] @xmath173727 , [ ] @xmath176300 , [ ] @xmath226548,6584 , and [ ] @xmath226716,6731 .
figure [ fig : continuo ] shows a comparison between the nuclear fos spectrum of ngc 2681 and the spectrum for this galaxy within the @xmath23 iue aperture , both normalized to their respective visual fluxes .
the iue aperture covers an area @xmath24 times larger than the fos aperture we used , and the fos flux contributes @xmath25 of the iue flux .
this can be verified by comparing the uv flux in the fos and iue spectra @xcite . yet
, the two spectra define the same kind of relatively young stellar population within combined errors of the iue spectrum ( 0.25 mag maximum error quoted by burstein et al . ) and the 5% relative error of the fos spectrum as quoted in the latest hst data handbook ( version 3 ) .
the luminosity - weighted average radius within the fos aperture is @xmath26 , while for the iue aperture it is @xmath27 .
the agreement between the iue and fos spectra thus gives strong evidence that little , or no color gradient exists for the stellar population in the center region of ngc 2681 . as a result
, we conclude that whatever redleak does exist for the uv foc images , the lack of a color gradient justifies fitting the same two - dimensional light distribution to all the foc images and the nicmos image ( section [ sec : focanalysis ] ) .
interestingly , both the lack of any perceptible dust lanes seen in the foc images , combined with the lack of a color gradient seen in the iue to fos comparison , strongly suggest that the inner 0.6 kpc of ngc 2681 contains little dust . the emission lines in our spectra have been analyzed by a `` template subtraction '' procedure as in @xcite .
starting from the high s / n spectra of @xcite , we have used a minimization algorithm to construct an emission - line - free template for their ngc 2681 2@xmath284 aperture spectrum .
the best match was obtained using a combination of their spectra of ngc 205 and ngc 4339 .
we use this template to subtract the underlying stellar contribution from the lower s / n 02@xmath2802 fos spectrum .
the upper panel of figure [ fig : modeling ] illustrates the template subtraction from the g650l spectrum ( lacking any reliable emission ) , while the lower panel shows both the template subtraction and the subsequent fit to the prominent emission lines of the template - subtracted fos g780h spectrum .
the emission lines in the continuum - subtracted optical fos spectrum have been modeled using the levenberg - marquardt algorithm @xcite to fit a sum of gaussian components to the observed spectrum .
we adopt the minimum set of free parameters able to generate a satisfactory fit by assuming that all emission lines can be fit by a gaussian profile with the same redshift and the same velocity width within a given grating .
the derived parameters for the emission lines are given in table [ tab : line_modeling ] .
the @xmath29 formal errors of the line parameters are estimated from the covariance matrix .
the ] emission line has also been fit in the g270h spectrum ( table [ tab : line_modeling ] ) by assuming a linear template under the emission feature .
the integrated @xmath30 [ ] flux in our @xmath15 aperture is only a factor @xmath31 smaller than the flux measured by @xcite within a @xmath32 .
given that the ratio of the two apertures is a factor @xmath33 , this small difference in the measured flux shows that the gaseous emission is very centrally concentrated and , in particular , comes mainly from a region not exceeding in size the fos aperture .
figure [ fig : diagnostics ] compares the emission line ratios obtained from our hst spectra of the nuclei of ngc 2681 and ngc 4552 @xcite , to those for seyfert galaxies , liners , and galaxies from @xcite .
note that the [ ] and fluxes were not measured from our g650l fos spectrum , as these lines have low @xmath34 in our data .
rather , for these emission lines , we resort to the @xcite ground - based values
. this choice can not affect the physical classification of ngc 2681 nucleus as most of the flux observed by ho et al
. comes from a region within our hst aperture and what is more the basic discrimination on the agn / non - agn nature of the nucleus comes from our own ( fos ) emission line ratios . as can be seen ,
the nucleus of ngc 2681 is clearly classified as a liner from our fos spectroscopy , in accordance with the ground based classification of @xcite .
we also note with interest that , despite the structural differences of the central regions of the two galaxies , the location of the innermost source of ngc 2681 is surprisingly close to that of the variable spike in ngc 4552 in these spectroscopic diagnostic diagrams .
a rough estimate of the size of the line - emitting region can be obtained from the density as set by the forbidden lines , and by the luminosity @xcite : @xmath35 where @xmath36 is the volume occupied by the emitting gas , @xmath37 is the total luminosity of the h@xmath14 line , @xmath38 is the volume filling factor , @xmath39 is the electron density , @xmath40 @xmath41 s@xmath7 , @xmath42 is the planck constant and @xmath43 the frequency of the h@xmath14 line . adopting @xmath44 from @xcite , a filling factor @xmath45 , a distance @xmath46 mpc @xcite , and spherical geometry ,
we obtain @xmath47 erg s@xmath7 and a size of the emitting region @xmath48 pc ( @xmath49 ) .
this estimate is within the upper limit imposed by the size of our fos aperture ( @xmath50 pc ) .
the latter size would correspond to a much lower filling factor of @xmath51 .
basic ingredients of the dynamical modeling we present later are the availability of a high resolution surface brightness profile of the galaxy , as well as observational support to the adopted hypothesis of a constant stellar mass - to - light ( m / l ) ratio .
we show here that the data provided by the foc and nicmos images do assure both pieces of needed information .
ideally , in order to obtain reliable surface brightness profiles and color gradients , one should correct the foc/96 images for nonlinearity effects in the foc @xcite , deconvolve all images with the psf and , finally , derive the photometric profiles and the corresponding color gradients from the corrected frames . however , in our case this process is numerically very unstable , owing both to the very low signal - to - noise ratio of the foc images and the approximations introduced by the nonlinearity correction which are greatly amplified by the deconvolution process .
the similarity of the available fos and iue spectroscopy ( section [ sec : spectroscopy ] ) strongly suggests a lack of detectable color gradient between @xmath52 and @xmath53 .
moreover , the good agreement between the @xmath54 ( foc / f342w ) and @xmath55 ( nicmos / f160w ) profiles in the radial range 110not affected by dark subtraction , nonlinearity and redleak effects confirms the absence of any significant stellar population gradient in the central regions of this galaxy ( see figures [ fig : nicmos ] , [ fig : foc ] ) . for these reasons we feel permitted to construct a _
unique _ bi - dimensional photometric model of the center of ngc 2681 .
the geometric properties of the model are fixed by imposing a match with the observed isophotes as obtained with the ` ellipse ` iraf task .
the photometric profile is derived as a function of the free parameters given below .
this model is then convolved with the proper psf a normalized mean of both uv and red - leaked psfs constructed by means of tiny tim @xcite and weighted in accordance to a properly chosen energy distribution taking correctly into account of nonlinearity effects ( for foc images alone ; see appendix of * ? ? ?
the resulting model is then simultaneously fit by means of an iterative procedure to all the original images as given by the stsci pipeline ( with the exclusion of the highly nonlinear pixels with @xmath56 in the f342w 1993 image ) .
a very good fit is achieved also for the far uv passbands , ( figure [ fig : foc ] ) , consistent with the lack of color gradients .
however , only @xmath5750% of the detected flux in the three red - leak - affected foc filters ( f175w , f220w and f275w ) is genuinely uv light ( i.e. , falls within the filter fwhm , as one can verify by using their transmission curves and our own fos spectrum ) , thus weakening the importance of this latter outcome , when compared to the evidence quoted above . the perfect match obtained with both the 1993 and 1997 foc observations
also assures that the nucleus of this galaxy has not significantly varied in surface brightness between the two epochs .
however , it is worth mentioning that the foc / f342w profiles of ngc 2681 and ngc 4552 ( figure [ fig : profiles_comparision ] ) show that the surface brightness of ngc 2681 close to the center is higher by @xmath58 mag arcsec@xmath59 than that of ngc 4552 for @xmath60 , before the variable spike starts dominating its luminosity . as a consequence
the central uv surface brightness of ngc 2681 is so high that a uv flare of the luminosity seen in ngc 4552 would have not been detected with observations of the kind discussed here , leaving the ngc 2681 nucleus apparently quiescent for the observer .
we find that a unique double power - law @xcite @xmath61 ^{-\frac{\beta-\gamma}{\alpha}},\ ] ] with parameters @xmath62 , @xmath63 , @xmath64 , @xmath65 can reproduce all of the eight profiles ( see figures [ fig : nicmos ] and [ fig : foc ] ) and also satisfy the constraint that the foc dark countrate ( which is also a free parameter for the foc frames ) remains within plausible ranges @xcite . here
@xmath66 measures the steepness of the inner profile ( @xmath67 for @xmath68 ) , @xmath69 is the steepness of the outer profile ( @xmath70 for @xmath71 ) , @xmath14 is related to the sharpness of the transition and @xmath72 is the scale factor for luminosity .
in the profiles a radius of 0.38 pixel corresponding to the average radius within the central pixel has been assigned to the central value of the surface brightness . due to the small fwhm and the good sampling of the psf in the uv
our foc/96 non - aberrated uv images provide information down to the central @xmath73 pc of ngc 2681 .
the profiles in figures [ fig : nicmos ] and [ fig : foc ] represent the surface brightness in mag arcsec@xmath59 in the stmag magnitude system .
the magnitude zeropoints computed using the synphot package within iraf / stsdas take into account the 1.27@xmath28 higher sensitivity of the foc zoomed mode , relative to the non - zoomed observations @xcite .
it is evident from the profiles from the 1997 foc images ( figure [ fig : foc ] , right panels ) that there is a change of slope of the observed profile around @xmath2 which is _ not _ reproduced by the model .
this radius corresponds to the distance where the nucleus becomes more asymmetric ( see figure [ fig : contours ] ) .
this , in turn , suggests that some substructure could be present .
however , no difference in color or spectral energy distribution is observed for this central feature , thus justifying our choice of resorting to a single component density profile when modeling the dynamics of the central regions .
in order to construct a dynamical model of the innermost regions we need to extract a reliable intrinsic density profile , starting from the observed photometry . to this aim the analytic double power - law photometric profile derived in section [ sec : focanalysis ] is deprojected by means of an abel inversion @xcite , under the assumption of spherical symmetry .
the profile is converted to the v - band using the color @xmath74 mag measured from the nuclear fos spectrum of figure [ fig : fos_complete ] ( the stmag photometric system has the same zero point as that of the v magnitude band ) and applying a foreground extinction @xmath75 @xcite .
the deprojected luminosity density profile in units of @xmath76 pc@xmath77 is presented in figure [ fig : density ] .
the derived density in the central pixel ( @xmath78 ) corresponds to @xmath79 @xmath76 pc@xmath77 .
this is quite a high value for the central luminosity density . for comparison , for a sample of 41 spirals analyzed by @xcite ,
the highest value of the density at 10 pc from the nucleus is a factor @xmath0 lower than the corresponding value we derive for ngc 2681 ( @xmath80 @xmath76 pc@xmath77 ) .
velocity dispersion and rotation curve profiles are not available for ngc 2681 . moreover , as this galaxy contains three concentric bars @xcite , developing a fully three - dimensional model of its mass distribution is problematic , at best .
however , experience has shown that , while detailed observations and general dynamical models are needed to establish the presence of possible bhs in galaxies , a simple isotropic dynamical model gives reasonable order of magnitude estimates of the bh parameters .
a classic example is the @xmath81 bh in m87 inferred by @xcite using spherical isotropic models , an estimate reasonably close to the most recent values ( @xmath82 ) determined by @xcite and @xcite using hst spectra of the gaseous disk surrounding the nucleus of m87 .
a detailed analysis of spherical models with cuspy power - law inner surface density profiles @xmath83 is available from @xcite , @xcite and @xcite .
the dynamics of isotropic power - law cuspy nuclei ( without bh ) are dramatically different , depending on whether @xmath84 or @xmath85 ( @xmath66 being the inner slope of the power - law ) . for the lower @xmath66 case , termed `` weak cusp '' by @xcite , the mean - squared line - of - sight velocity dispersion @xmath86 approaches zero near the center . for the other case ,
termed the `` strong cusp '' regime , the relation @xmath87 diverges near the center ( finite resolution will actually transform these mathematical singularities to finite observable values if @xmath88 ) . in either case , if a bh is present @xmath89 near the center .
thus it is clear that , while with @xmath84 an increase of @xmath86 in the very inner regions ( @xmath90 ) is already an indication of a possible bh , this is not the case when @xmath85 , as is such for ngc 2681 ( @xmath91 ) .
a bh becomes finally undetectable for @xmath92 , when its presence induces the same trend as a simple increase of the m / l stellar ratio .
figure [ fig : dispersion ] shows the kinematical data available for this galaxy : ground based measurements of the _ stellar _ central velocity dispersions of ( * ? ? ?
* @xmath93 within a @xmath94 aperture ) and ( * ? ? ?
* @xmath95 within a 42 diameter aperture ) , and the _ gas _ velocity dispersion of ( * ? ? ?
* @xmath96 within a @xmath97 aperture ) . in figure
[ fig : dispersion ] we also plot our own _ gas _
dispersion fos measurement of @xmath98 within the @xmath15 aperture .
the central @xmath99 is found to increase by a factor of @xmath0 when narrowing the aperture from @xmath1 ( ground ) to @xmath2 ( hst / fos ) . to investigate this further ,
we have computed a simple spherical isotropic model for the stellar kinematics , starting from the double power - law photometric profile @xmath100 determined above , and assuming a constant stellar mass - to - light ratio @xmath101 . with these assumptions
the projected stellar velocity dispersion at a distance @xmath102 from the center can be predicted from the relation ( e. g. * ? ? ?
* ) : @xmath103 the stellar density @xmath104 and the mass within a given radius @xmath105 have been obtained from the deprojected double power - law profile .
@xmath102 is the radial distance on the plane of the sky , while @xmath106 is the radial coordinate measured from the center of the galaxy . in the case
a bh lies at the center of the galaxy we have to substitute the enclosed mass @xmath105 in equation ( [ eq : sigma_p ] ) with the expression @xmath107 $ ] , where @xmath108 is the mass of the bh .
in order to compare the predictions with the observations we calculate the velocity dispersion @xmath109 as measured through a circular aperture of radius @xmath102 _ centered on the galaxy nucleus _ ( seeing and psf effects are not modeled here , since they are smaller than the apertures used ) :
@xmath110 we evaluate this equation for the two cases with and without a central bh . in the former case
we impose that below @xmath111 ( the central resolution of our photometric _ model _ , corresponding to 0.38 foc/96 pixels ) the stellar density profile flattens , becoming constant ( an extreme assumption , which maximizes the possible bh mass ) .
we do this in order to avoid the integral at the numerator in equation ( [ eq : sigma_a ] ) diverging . to compare the models with the data we further assume that the gas behaves as a `` hot '' system , being in distinct clumps in isotropic motion , with a density proportional to the stellar density .
this is appropriate if the gas is produced by the stars themselves , a not unreasonable assumption .
figure [ fig : dispersion ] shows the results of our modelling with the inclusion of a central bh of mass @xmath112 ( solid line ) and without it ( dotted line ) .
it is apparent that a model without a bh can not explain the observations .
however , we stress that , due to the above assumption on the flattening of the central density profile , the value @xmath113 represents a strict _ upper limit _ of the mass of a possible central bh in this galaxy . in this respect
, one should be aware that only measurement of stellar kinematics using long slit stis spectra will permit us to remove the present degeneracy in the modelling of ngc 2681 .
we also note that the ground - based data constrain @xmath114 to be 0.7 and 1.0 for the two above cases , i.e. with and without bh , respectively .
a value @xmath115 is consistent with simple stellar population models of solar metallicity and ages 1 - 2 gyr , for both salpeter and scalo imf @xcite .
the upper limit for the bh mass determined in this paper ( @xmath113 ) is consistent with the recent very tight correlation between the central velocity dispersion @xmath116 and the bh mass as given by @xcite .
the central dispersion @xmath117 ( corrected to @xmath118 ) we observe for this galaxy , corresponds in fact to an expected bh mass of @xmath119 .
we remark that in the above bh mass estimate we have modeled the gas as a `` hot '' system of point masses .
this appears justified from the fact that within an @xmath1 aperture the dispersion observed from the gas and the stars is the same ( see figure [ fig : dispersion ] ) .
the gas motion however may become more ordered closer to the nucleus . as an extreme case , one could even assume that , at hst resolution , the gas lies in a thin disk in circular motion in the combined potential of the bh and the stellar potential . to test this possibility we have tried to explain the observed emission line profile as produced by a thin gaseous disk using the techniques we have developed in @xcite , and subsequently integrating the model spectrum within the fos aperture . using different bh masses and various disk inclinations ,
we have verified that , under the thin disk hypothesis , it becomes impossible to produce an emission line having the width @xmath120 observed with fos without producing a double peaked line profile .
intrinsic dispersion in the gas is thus important and the disk can not be thin .
this assures that the adopted spherical assumption for the geometry gives the correct order of magnitude estimate for the bh mass .
our analysis of the light distribution in the inner 0.6 kpc of ngc 2681 shows that a double power law light profile fits its light distribution both in the nicmos images and in our set of foc/96 uv images .
the good fit of the multiband data obtained with the _ same _ light distribution , coupled to the close similarity of our fos spectrum to the iue spectrum taken with a much larger aperture , argues against the presence of sizable color gradients in the center regions of ngc 2681 .
a remarkable consequence of the steep , innermost profile of ngc 2681 is that it translates when observed in the near - uv into a central surface brightness some 4 mag arcsec@xmath59 higher than that of the recently identified uv - variable spike of ngc 4552 @xcite .
this implies that a uv - bright flare of comparable luminosity as that observed at the center of ngc 4552 would escape detection in the nucleus of ngc 2681 .
the fos spectrum of the central region reveals the presence of broad emission lines . comparison to ground
based spectra shows that the gaseous emission is centrally concentrated , most of it coming from a region inside the central @xmath50 pc of ngc 2681 . on the basis of the observed ratio of the emission lines
, the nucleus of ngc 2681 falls in the region of liners .
this suggests a slow , steady feeding of a central bh .
the presence of the bh is more strongly indicated by the increase of a factor @xmath0 of the gas velocity dispersion , when narrowing the aperture from @xmath1 to @xmath2 .
such an increase can not be accounted for by the stellar potential alone , as derived by deprojecting the observed surface brightness profile .
we also find that the gas in the inner regions of ngc 2681 is not supported by rotation , as in the case of a keplerian disk , but mainly by random motions .
assuming that the gas can be modeled as a `` hot '' system , we derive a firm upper limit to the bh mass of @xmath113 from an isotropic dynamical model .
such an estimate is consistent with the @xmath4 relation of @xcite and @xcite . in this respect ,
ngc 2681 , with a central velocity dispersion of 111 ( corrected to @xmath118 ) and a predicted bh mass @xmath119 , must be regarded as an object of particular interest as it falls in the still poorly populated low-@xmath99 region of the tight @xmath4 relation .
one should be aware , however , that only the knowledge of the _ radial dependence _ of the velocity dispersion ( and not its central value alone , as is our current knowledge for ngc 2681 ) assures the possibility of pinpointing the bh mass in ngc 2681 instead of establishing its upper limit , as we have done here .
to acquire such data requires hst / stis _ slit _ observations
. our dynamical models also indicate a stellar mass to light ratio for the central population of 0.7 - 1 , which is appropriate for a 1 - 2 gyr old , solar metallicity stellar population .
this is fully consistent with previous iue and optical spectroscopy ( namely , the measured mg@xmath10 line strength index ) indicating that the population of this galaxy is dominated by _
stars formed in a fairly - well defined starburst @xmath5 gyr ago @xcite .
finally we remark that a hi survey of ngc 2681 and its associated galaxies would be highly desirable .
such a survey might reveal evidence that ngc 2681 underwent a tidal interaction with another galaxy in the recent past , lending support to the hypothesis of a major merging event affecting what we see in the center of this galaxy today .
on the one hand , ngc 2681 belongs to a galaxy group , an environment in which mergers are particularly favored to occur .
on the other hand , ngc 2681 does not show clear signatures of the recent accretion of a gas - rich dwarf , such as morphological distortions or duplicity of the nucleus .
while the presence of a uniform , dustless , young stellar population in its central 0.6 kpc is puzzling , perhaps we can view ngc 2681 as the older brother of m82 , seen face - on , after the star burst has run its course .
mc is grateful to the european southern observatory for its kind hospitality in the period during which much of the hst data analysis has been completed .
db acknowledges support by nasa / stsci through grants go-03728.01 - 91a and go-06309.01 - 94a .
ccccccr no & 512z@xmath281024 & f175w & 22@xmath2822 & 0.0225 & 1993 nov 5 & 2793 + no & 512z@xmath281024 & f220w & 22@xmath2822 & 0.0225 & 1993 nov 5 & 1077 + no & 512z@xmath281024 & f275w & 22@xmath2822 & 0.0225 & 1993 nov 5 & 597 + no & 512z@xmath281024 & f342w & 22@xmath2822 & 0.0225 & 1993 nov 5 & 417 + yes & 512@xmath28512 & f175w & 7@xmath287 & 0.01435 & 1997 feb 1 & 1134 + yes & 512@xmath28512 & f275w+f1nd & 7@xmath287 & 0.01435 & 1997 feb 1 & 546 + yes & 512@xmath28512 & f342w+f2nd & 7@xmath287 & 0.01435 & 1997 feb 1 & 396 + clccc g270h & ] @xmath172326 & [email protected] & 770@xmath12170 & 390@xmath12130 + g780h & [ ] @xmath176300 & [email protected] & 480@xmath12111 & [email protected] + & [ ] @xmath176548 & [email protected] & & + & [ ] @xmath176584 & [email protected] & & + & & [email protected] & & + & [ ] @xmath176716 & [email protected] & & + & [ ] @xmath176731 & [email protected] & & + | the nucleus of the bulge - dominated , multiply - barred s0/a galaxy ngc 2681 is studied in detail , using high resolution hubble space telescope foc and nicmos imaging and fos spectroscopy .
the ionised gas central velocity dispersion is found to increase by a factor @xmath0 when narrowing the aperture from @xmath1 ( ground ) to @xmath2 ( fos ) .
dynamical modeling of these velocity dispersions suggests that ngc 2681 does host a supermassive black hole ( bh ) for which one can estimate a firm mass upper limit @xmath3 .
this upper limit is consistent with the relation between the central bh mass and velocity dispersion @xmath4 known for other galaxies .
the emission line ratios place the nucleus of ngc 2681 among liners .
it is likely that the emission line region comes from a rather mild , but steady , feeding of gas to the central bh in this galaxy .
the inner stellar population lacks any measurable color gradient ( to a radius of 0.6 kpc ) from the infrared to the ultraviolet , consistently with foc , fos and iue data , all indicating that this system underwent a starburst @xmath5 gyr ago that encompassed its whole interior , down to its very center .
the most likely source of such a widely - distributed starburst is the dumping of tidally - extruded gas from a galaxy neighbor .
if so , then ngc 2681 can be considered as the older brother of m82 , seen face - on as opposed to the edge - on view we have for m82 . |
large data samples of galaxy photometry are now available from the present epoch back to @xmath61 gyr after the big bang .
hundreds of studies have described and analyzed these data in terms of luminosity , mass , and structural evolution , relying on trends between such quantities that assume a considerable uniformity of the growth of stellar populations and , by implication , of dark matter halos .
several considerations , including n - body simulations , the well - populated trend of cosmic sfr density as a function of redshift ( lanzetta , wolfe , & turnshek 1995 , lilly 1996 , pei & fall 1995 , madau & dickenson 2014 ) , and the characterization of the controversially - named ` star formation main sequence ' ( sfms : noeske 2007 ; whitaker 2012)showing a correlation between stellar mass and sfr at every epoch have guided many studies in the crafting of mean evolutionary tracks , whose nature might lend insight into the phenomena driving the evolution of individual galaxies ( e.g. , whitaker 2014 ) .
however , it has been difficult to use such data to go beyond average properties and average evolution , to measuring the star formation histories ( sfhs ) of individual or classes of galaxies .
such data would inform to what degree galaxies follow similar growth histories , offset or scaled in cosmic time , or whether there is genuine diversity in sfhs that is non - conformal .
that is , they could demonstrate whether _ measured _ sfhs fail to conform to scenarios wherein the evolution of scaling relations _
controls _ ( as opposed to _ reflects _ ) galaxy growth ( peng 2010 ; leitner 2012 ; behroozi 2013 ) , by crossing , or not appearing as offset / scaled versions of each other in mass / time .
such data could also determine if the significant scatter in the sfms represents fundamental , long - term diversity in sfhs generating an illusion of uniform growth patterns or only distracting perturbations to physically informative ` average tracks . '
the fundamental problem is that available data , including integrated mass functions over most of cosmic time , are unable to uniquely connect the dots " between one epoch and another : the galaxies at later epochs are not necessarily the decendants of earlier galaxies observed to follow a similar trend .
abramson ( 2016 ) has in particular emphasized the ambiguity of the presently available diagnostics by showing that models in which galaxy growth is conformal over mass , and those that show great diversity of sfhs , are both able to pass the observational tests that present data provide .
the promise of ` average sfhs ' to illucidate important physical processes in galaxy evolution has arguably blinded us to the possibility that more physics will be learned from their diversity than from their sameness .
this ambiguity can be broken by measuring the sfhs of individual galaxies , but this has proven very difficult to do , particularly because from our vantage point in the local universe
stellar populations more than 2 gyr old are essentially indistinguishable from each other .
for this reason ` population - synthesis models ' have been ineffective in describing the buildup of stellar mass even in relatively nearby , well observed galaxies outside the local group , although considerable progress is coming from hst - wfc3 observations , for example , the study of resolved stellar populations in m31 ( dalcanton 2012 ) .
applying the population - synthesis technique at higher redshift would allow a better resolution of the ages of older populations , but spectral observations with sufficient resolution and depth are costly .
one might argue that we already know that sfhs are diverse .
the iconic elliptical galaxy ngc3379 in the leo group likely formed most of its stars before @xmath7 , while common galaxies of the same mass , for example , the milky way and andromeda , have been puttering along for the full age of the universe .
however , the proponents of the conformal " model suggest that both ngc3379 and these starforming spirals are following the same growth history , but that star formation was _ quenched _ in the former by some mechanism that rendered inaccessible the considerable amount of gas still in its vicitiny . some method of forcing long cooling times by heating
the gas is the likely process .
suggested mechanisms include a transition from cold accretion to a hot halo driven by dark matter halo growth ( kere 2005 , dekel and birnboim 2006 ) , heating from an agn or supernovae feedback ( voit 2015b ) , or the transition from low - entropy to high - entropy gas that is unable to cool onto the host galaxy ( voit 2015a ; voit 2015c ) . for galaxies like ngc3379 `
quenching ' could have been rapid
likely a gigayear or less .
but what , then , of galaxies like the milky way and andromeda ? both could have been forming stars consistently at a few for most of a hubble time , or they could have had sfrs of @xmath610 in the first few billion years of their history , falling steadily since @xmath8 to reach their rates of @xmath61 today .
it is clear from recent studies measuring ultraviolet flux and balmer absorption lines ( schawinski 2014 ; dressler & abramson 2015 , vulcani 2015a ) that galaxies traversing the color space between the ` blue cloud ' and ` red sequence ' are mostly doing so over billions of years , not in a @xmath91gyr timescale following an abrupt termination of star formation .
is such a slow decline a ` quenching ? '
has it been triggered by an event , such as an agn or intense feedback from star formation , or is it instead nothing more than a slow exhuastion of gas suitable for star formation ?
rather than
slow quenching , " as it is now being called ( e.g. , barro 2016 ) , perhaps this is just the normal course of galaxy evolution .
both pictures have been valid , given the tools we have used to describe galaxy evolution .
gladders ( 2013 , hereinafter g13 ) developed the fast - clock / slow - clock model by assuming that galaxy sfhs are lognormal in cosmic time .
this work was motivated by two observations : * oemler ( 2013b , hereinafter o13 ) studied distribution functions of specific star formation rates ( ssfrs ) for a sample of galaxies with redshifts @xmath10 and found that an increasing fraction had rising sfrs earlier in this epoch .
the presence of such galaxies , whose abundance increasse steadily from essentially zero today to @xmath620% at @xmath8 , obviates the @xmath11-model , " in which the most aggressive sfh is constant in time ( tinsley 1972 ) * g13 , noted that the evolution of the cosmic sfrd ( the ` madau - lilly ' diagram ) from the present day back to @xmath12 is very well fit by a lognormal in time with two parameters , 0the half - mass time in the production of stellar mass , and @xmath11the width of the lognormal .
g13 adopted this as a parameterization of sfhs of _ individual _ galaxies , and showed an existence proof that the distribution of ssfrs for 2094 present - epoch galaxies , and the cosmic sfrd , could be simulataneously fit by sum of 2094 lognormal sfhs .
moreover , this model described the ssfr distributions at @xmath13 from the _ icbs _ survey ( oemler 2013a ) and ssfr distributions for samples at @xmath14 from data of _ aegis _ survey ( noeske 2007 ) .
this is the model that abramson ( 2015 ) and abramson ( 2015 , 2016 ) have found to be successful in fitting a variety of other data , including mass functions and the sfms ( zero - point , slope , and scatter ) back to @xmath15 , and zero - point and slope back to @xmath16 .
encouraging as these and other results may be , these tests are incapable of distinguishing between conformity and diversity in sfhs . specifically , the work on lognormal sfhs based on the model in g13 demonstrates only that a large set of lognormal sfhs can be constructed that reproduce the available data well .
but , the individual sfhs in this model can not be tagged to specific galaxies : it is only the distribution function of 0 , @xmath11 parameters , not the assignment to individual galaxies , that is robust in this approach . in this paper
we take a next step , presenting what we believe is compelling evidence for sfh diversity , using well - measured though coarse sfrs and mass buildup for over 22,494 galaxies over the epoch @xmath17 from the carnegie - spitzer - imacs ( csi ) survey .
following the recent custom in colloquia of presenting conclusions at the start , we move immediately to a graphic presentation of our principal result on the diversity of sfhs .
the customary discussion of the data and its analysis that compel this result _ follows _ , and this is used to develop a different , more quantitative description of the data based on the mass of ` old ' and ` young ' stellar populations .
the most direct observational test of conformity in galaxy sfhs is to compare their sfrs over a wide range of epochs .
the seds measured in csi survey span from restframe uv to through the near - ir and include low - resolution spectro - photometry that provide exactly this information .
we present in this section a diagram of 240 randomly - selected sfhs from csi survey data that represent what we believe is a decisive test of the conformity versus diversity issue . the csi survey and its methodology is thoroughly described in kelson ( 2014a , hereinafter k14 ) and in greater detail in section 4 than described now .
the subsample of csi we use here is representative : flux - limited from spitzer - irac 3.6@xmath18 imaging over @xmath65.3 square degrees in the swire - xmm - lss field ( see k14 ) .
flux to cover the luminosity peak of common galaxies , the csi survey is closer to mass - limited than comparable studies . ]
additional photometry in the near - ir ( j and k bands ) came from observations with _
( autry 2003 ) , and red - optical to ultraviolet was obtained by reprocessing _ ugriz _
data from the cfht legacy survey .
prism mode ( dressler 2011 ) was used to obtain low - resolution spectra ( _ r _ @xmath19 ) from @xmath20 for @xmath643,000 galaxies in this field .
the present study uses a 22,494 galaxy subsample of these data covering the redshift interval @xmath0 . in k14 stellar population models
were made using maraston ( 2005 ) ; subsequently the data have been reprocessed using the conroy , gunn , & white ( 2009 ) and conroy & gunn ( 2010 ) _ flexible stellar population synthesis _ ( fsps ) models , to take advantage of its improved modeling of the tp - agb .
all stellar mass and sfrs are based on a chabrier ( 2003 ) initial mass function .
k14 parsed the csi sfhs into six age bins , with model seds for each age bin summed in generalized maximum likelihood fits to the observed prism and broadband fluxes simultaneously .
the model sed for each age bin was replicated at four quantized levels of dust attenuation in @xmath21 for a total of 24 stellar population components being non - negatively summed in each fit . allowing each component to have variable dust attenuation
is a crude attempt to allow for variable spatial distribution of dust with respect to the underlying distributions of stars .
more details can be found in section 3 .
each model , described by a _ constant _ sfr over each of the six age bins ( or _ time intervals _ ) can be effectively reduced to mean sfrs on three timescles@xmath22 , @xmath23 , and @xmath4 years : * sfr1 : @xmath24 for gyr ( k14 time interval 1 ) * sfr2 : 1 gyr to 200 myr before ( intervals 2 - 5 ) * sfr3 : 200 myr to ( interval 6 ) where is the age of the universe at the time of observation , and is the duration of the first epoch of star formation ( a parameter of the fit ) , starting at @xmath24 , 1.2 gyr , and potentially lasting until 1 gyr before ( but usually stopping well before this . ) these measurments are largely independent : the oldest population ( sfr1 ) is constrainted by the ir flux , the intermediate age ( sfr2 ) comes from the rest - frame - optical photometry and prism spectrum ( the light from main - sequence a - stars ) , and the present " sfr formation ( sfr3 , averaged over the last 200 myr ) is measured through reframe uv flux below the balmer break . using these measures of stellar mass growth over different periods of a galaxy s lifetime
, we can now look to see the extent to which galaxies uniformly ( conformaly ) rose and fell together , or separately ?
the four panels in figure 1 are plots of log sfr vs. redshift over four ranges of total stellar mass : from log m = 11.012.1 ( upper left ) to log m = 9.010.0 ( lower right ) .
the red , green , and blue points of figure 1 represent the well - measured sfrs for timescales of @xmath3 , and @xmath4 years .
the mass bins are well populated , with 1785 , 8279 , 9062 , and 3385 galaxies , respectively . however ,
for clarity we show only 60 randomly selected galaxies chosen to be evenly spaced in redshift , @xmath25z=0.01 .
( sfrs of 0.1 to 1.0 are detected with low s / n , and sfrs @xmath26 0.1 are essentially non - detections .
for display we have randomly scattered the non - detections in a log distribution from @xmath27 log sfr @xmath28 . , mixing them with the low s / n detections . )
the systematic trends of the sfr measurements is apparent .
the sfhs of the most massive galaxies ( upper left panel ) generally decline , from the high sfrs of stellar populations that are observed at ages of @xmath292 - 6 gyr , to the sfrs of 1 gyr - old and 200 myr - old populations .
not all massive galaxies exhibit steeply declining sfhs : a substantial fraction show gently declining sfrs over a hubble time , perhaps representing more massive , or more vigorously starforming , versions of the milky way ( m101 ?
there are , however , no _ young galaxies _ in this mass range , that is , ` late - bloomers ' whose sfrs rose from the old population to the younger ones .
a move in this direction begins in the second mass bin , log m = 10.511.0 , characteristic of the milky way mass today , where the sfrs typically fall more slowly than for the most massive sample , and there are @xmath65 out of 60 galaxies that are ` young . '
the typical sfhs in the top right panel look about as we speculated ( in section 1 ) for the milky way : an initial period with sfr @xmath6 10 - 20 , declining steadily to perhaps @xmath63 at @xmath30 , headed toward today s level of @xmath61 .
the bottom two panels , on the left , log m = 10.010.5 ( a factor of 2 - 3 below m@xmath31 at @xmath32tomczak 2014 ) and on the right , log m = 9.010.0 , show a large cohort of sfhs that are slowly declining ( m33 ? ) or near - constant ( ngc253 ? ) .
but , here the ` young galaxy ' population has become more obvious : @xmath650% of the population in the log m = 10.010.5 ( lower - left panel ) are young, and these rising sfhs dominate the lower right panel .
because they are remote , some sfrs measured for old stellar populations ( sfr1the red points ) suffer a systematic error relating to how well the sed fit was able to decouple sfr1 from , the timescale over which that mass was produced the two quantities are covariant . repeated measurements ( discussed in section 4 ) indicate that is able to distinguish between old populations and very old populations with limited fidelity . , which is the mass produced in this epoch , is well measured , as we also show in section 4 .
] among the data are very high sfr values ( exceeding 100 ) , the result of improbably short ( less than 1 gyr an artifact of the fitting procedure ) , which biased the sfrs high .
figure 1 would have included a small fraction of these inflated sfrs ; the correction we made ( by redistributing the @xmath33 gyr values between @xmath34 gyr ) lowers only these highest sfrs there is no effect on the sfhs with _ rising _ sfrs , our principal interest . in section 4
we sidestep this covariance problem by switching from sfrs to comparing the ratio of ` old ' and ` young ' stellar mass .
figure 1 shows , then , that a substantial population of galaxies in the lower two panels are genuine cases where no ` old ' star formation ( sfr1 ) has been detected ( in effect , an upper limit @xmath65@xmath35 in ` old ' stellar mass , as we discuss in section 4 ) .
it is this population of ` young galaxies ' that o13 inferred and _ required _ , based on comparisons of ssfr distributions from @xmath36 .
this , then , is the crux of this paper , to show specific cases thousands where in - situ growth after @xmath5 dominates the stellar mass .
these are not simply cases of downsizing , " that is , extended star formation over a hubble time , which could be considered scaled sfh copies of more massive galaxies on a falling sfms a conformal population .
rather , these are galaxies that peak late , or have not peaked at all , and for which star formation lasts a few gyr before fading by the present day .
these are the ` late - bloomers ' of the g13 lognormal sfhs galaxies with long 0 and short @xmath11that are a certain sign of diversity in sfhs ( see figure 10 , discussed in section 5 ) .
there is also evidence from figure 1 that
although sfh diversity as a whole shifts to more extended histories with decreasing mass there is considerable sfh diversity at _ the same stellar mass_. we see this expansive diversity at similar stellar mass as _
fundamental_. in conformal models , the scatter in the sfms is treated as inconsequential . to explore this behavior ,
we define four sfhs representative of the diversity we see in the graphic tracts in figure 1 . in what follows , _
sfr1 , sfr2 , and sfr3 _ are the log@xmath37 values of sfr1 , sfr2 , and sfr3 .
the categories , for illustrative purposes ( not to be taken as _ definitions _ ) are : 1 .
red = old galaxy ( falling sfh ) 2 .
amber = csf ( continuous sfh ) 3 .
green : young galaxy : ( constant or rising sfh ) 4 .
blue = starburst ( or ) purple = starburst figure 2 plots our entire csi sample broken down into these categories . , and the higher - density cluster / supercluster at @xmath38 are familiar features in such diagrams . ]
the trend with mass is unmistakable : from old stellar population dominance ; through continuous star formation ( csf ) over a hubble time ( declining milky way - like , or constant ngc253 , lmc - like ? ) ; to genuinely young galaxies .
an added frosting " of starburst galaxies is found for both the csf and ` young ' galaxy populations ( but rarely for ` old ' galaxies ) .
to quantify this population of young galaxies , we will in the sections to follow shift the emphasis from sfrs to stellar mass buildup . before proceeding , however , we return to the point made through figure 1 , now abundantly on display in figure 2 , that the diversity of sfhs is a strong function of mass .
but , more than this , it is the overlap of these populations , shown by decomposing the left hand multi - color panel into its four components , that is arresting .
` old ' galaxies , those with strongly declining sfrs , cover more than an order - of - magnitude in total stellar mass , limited perhaps only by csi depths and sensitivities , and csf span an order - of - magnitude in stellar mass as well .
the most remarkable fact is that young galaxies , although much less common , are found up to and beyond the mass of the milky way . and
fade by the present epoch , clear examples of the long 0short @xmath11 behavior that can occur in the lognormal picture . ] in other words , even galaxies as massive as the milky way not just low - mass galaxies can follow strikingly different sfhs .
our csi data appear , at a minimum , to confirm the general breakdown of conformity described by abramson ( 2016 ) in their interpretation of sfms scatter as a consequence of the lognormal sfh model . from that conclusion
it is a short step to postulating that galaxies with the same dark - matter - halo mass evolved along very different sfhs , raising questions about the fidelity of the popular practice of abundance matching " ( e.g. conroy & wechsler 2009 ) .
if true , what drives this diversity ?
we are drawn to the notion that such differences are built - in from an early epoch ( as promoted by dressler in his 1980 study of the morphology - density relation ) , perhaps related to the density of the dark matter halo or larger - scale properties of the spectrum of density perturbations in a galaxy s neighborhood .
although this possibility is not compelled by the results of this study , we will explore some aspects of this problem later in the paper .
to this point we have examined sfhs in terms of sfrs in three distinct epochs , acknowledging that a star formation history is the evolution of the star formation rate . however , a more quanitative evaluation using the mass fractions of old and young stars will serve better to understanding what these histories mean in terms of building galaxies , and in the comparison to models .
we invite the reader to continue to appreciate the full implications of diversity in sfhs .
section 3 describes in detail the csi data and how they are analyzed to provide ( independent ) sfrs over timescales of @xmath3 , and @xmath4 years . in section 4
we turn the analysis to the buildup of stellar mass , showing how the ratio of two integrated masses stellar mass produced from z=5 to 1 gyr before observation , and stellar mass produced in the last gigayear , provides a very good tool for searching for the ` late - bloomers ' that o13 ` required . ' while o13 was unable to point to specific galaxies that had rising sfrs after @xmath5 , we _ can _ identify individual galaxies of this population . in section 5
we look for correlations of sfhs related to environment , specifically , signs of a centrals / satellites dichotomy . in section 6
we examine the consistency of the g13 model with csi sfhs in terms of the full range of sfhs we find .
finally , in section 7 we summarize our results on sfh diversity and review the implications for conformal ( plus _ quenching _ ) models .
the defining characteristics of the csi survey were large areal coverage ( 15 sq deg over three widely separated _ swire _ fields ) , galaxy selection via spitzer - irac 3.6@xmath18 flux , and near - ir to optical - ultraviolet photometry and low - resolution spectroscopy from 4500 to 10,000 , corresponding to rest frame 3462 at the @xmath39 lower limit , and 5263 at the @xmath40 upper limit , for the subsample used in this paper . flux measurements at 3.6@xmath18 sample the peak of the energy distribution in seds for typical galaxies at @xmath41 . because of this , the stellar mass completeness limit changes much more slowly with redshift than in previous spectroscopic surveys selected by _
i - band _ or _
r - band _ magnitude , as shown in k14 . over the @xmath0 interval of our subsample ,
this limit changes only by a factor - of-2 , from @xmath42 .
figure 3 of k14 shows that a galaxy of @xmath43 , the present - day mass of the milky way , can be detected to @xmath44 in csi , compared to @xmath45 for primus and deep2 .
it is this combination of depth and volume0.14 gpc@xmath46 for the full survey ( an order - of - magnitude more than deep2 ) that makes csi a powerful tool for galaxy evolution studies .
the csi survey , through its connection to _ swire _ , is a field survey , i.e. , it contains regions of high galaxy density , such as a rich clusters .
there is a substantial population of groups , however , which have been characterized by williams ( 2012 ) and patel ( 2016 ) . as with many astrophysics programs these days , the csi survey is considerably oversized compared to the complexity of the phenomena studied here . for our work on sfhs , it is the quality of the photometric and spectroscopic data and how they enable robust measurements of stellar mass rather than the sample size . ] or areal coverage , that are the strengths of the csi survey .
our subset of the csi sample of galaxies studied in this field reduces to 22,494 galaxies over the redshift range @xmath0 . of course
, the rarest galaxies , with stellar masses of m @xmath47 , and those m @xmath48approximately the 50% completeness limit of the survey are represented by only 1728 and 294 galaxies , respectively , but for the most important middle - territory of this work , sample size does not limit our ability to address the primary question of sfh diversity .
figure 3 shows observational data and model seds for 4 representative galaxies in the survey , including the 6 discrete intervals of star formation ( the basis sets " for fitting stellar population models the sed , described below ) that are used to measure sfrs over timescales of @xmath22 , @xmath23 , and @xmath4 years . each box is a plot of observed wavelength and @xmath49 flux .
the observational data in each box are the 8 bands of photometry ( red boxes ) and the _ imacs _ prism spectrum ( cyan trace ) .
a large part of the data reduction challenge went into intelligently combining ( slit ) spectral data and aperture photometry data and validating the integrity of the combined _ spectro - photometric _ data , as described in detail in section 3 of k14 .
the key step was to use the aperture photometry to anchor and correct imperfect flux calibrations of the prism spectra ( affected by slit losses and differential refraction ) .
the accurately - fluxed prism spectra enable sed - fits to resolved spectral features that constrain the model of stellar populations far more tightly than possible with photometry only , even with a large number of photometric bands .
as described briefly in section 2 , k14 made generalized maximum likelihood fits m - estimator use in most likelihood analyses .
] of these seds , starting with maraston ( 2005 ) stellar libraries ( k14 , section 4 ) .
an sed model to fit these data was made in a three dimensional grid of redshift , metallicity , and ( log of ) the duration of the first epoch of star formation that we have discussed above .
the critical parameters in the model were 6 discrete intervals of constant star formation , starting at @xmath24 for and lasting for gyr , and for five 200 myr intervals beginning 1 gyr before .
each sfr vector " was replicated with 4 levels of dust extinction , with non - negative sums of these able to reproduce the variable dust attenuation of ( most ? ) galaxies .
figure 6 in k14 is a diagram in cartoon form with examples of sfrs in the 6 intervals that characterize normal starforming galaxies , quiescent galaxies , and starburst and post - starburst galaxies .
the four galaxies in figure 3 also show examples of the modeling process .
the middle two of the four small boxes at the top of each figure 3 panel show the star formation and stellar mass growth histories for that galaxy through the sed fitting procedure .
the far left box shows the position of the galaxy in a uvj diagram ( williams 2009 ) .
galaxies in the upper left region are considered passive , while outside they are starforming .
the far right box shows a z - band image of the galaxy from the cfht legacy survey .
it is apparent for these four cases that each derived seds is an excellent match to the broad - band photometry and blue - to - red spectra .
k14 emphasizes that the fine detail contained in the spectra play a particularly important role in constraining redshift to @xmath92% , a better performance than is possible with broad - band photometric data alone .
redshifts of this accuracy are essential for sampling the prism spectra at the proper wavelengths , and vice - versa .
this degree of accuracy in the redshift was also intended as an important feature the csi survey , because it allowed the association of galaxies into groups and clusters .
this environmental component of the survey , which we exploit in section 5 , is something that can not be achieved with redshifts of lower precision .
as was remarked in section 2 , the power of the csi data set with respect to sfhs is bound up in the several stellar evolution timescales inherent in the data .
the k14 analysis recognized this explicitly by adopting six time intervals , over which the sfr was assumed to be constant , as the basis sets " for _ solving _ the sed .
five of the six are fixed time intervals of 200 myr that started 1 gyr before : star formation over this period produces strong variations in the blue - to - visible sed that provide very effective constraints on the model .
the sfr1 interval , starting at z@xmath505 , takes advantage of ( and suffers from ) the immobility of the giant branch in color - magnitude - diagrams for stellar popualtions with ages ranging from 2 gyr to a hubble time .
while it is straightforward to measure the stellar mass producing the light from old populations the product sfr1@xmath51the giant - branch degeneracy makes alone difficult to constrain , and thus sfr1 has a typical error of @xmath650% , a factor - of - two larger than for sfr3 and sfr2 , the combination of the remaining four intervals , as discussed in section 2 .
because of the uncertainty in determining , the k14 analysis allowed the ( constant ) star formation starting at z@xmath505 to continue up to 1 gyr prior to .
however , the constraint on improves if light from main sequence stars makes a significant contribution to the sed . from the vantage point of present - day galaxies
this is never the case , but from a galaxy with a lookback time of 5 gyr
the median for our sample the contribution from dwarf f - stars ( with main - sequence liftetimes of @xmath65 gyr ) can be detected as far back as @xmath522 , the peak epoch of cosmic star formation .
for this reason the csi spectral data have some leverage on _ when _ the stars of the first interval were formed , not just how many .
may not be well constrained , but neither is it unconstrained .
we believe that this is why most values fall in the reasonable range of 2 - 6 gyr , timed to the f - star contribution detected in the blue - to - visible part of the prism spectra .
this would also explain why a there is a small but significant population with @xmath26 1 gyr
such dubious measurements are likely to be the default ` @xmath53 function ' at @xmath24 when there is no measureable signal from an old f - star population ( exacerbated , we think , by the discretation of into small lorarithmic intervals as log approaches zero ) .
examples can be seen in figure 3 in the two middle boxes above each sed .
the left box shows the sfh expressed as constant sfrs in six time intervales , as explained above , and the right box shows the integral of the sfh , e.g. , the buildup of stellar mass .
the galaxies of the top two panels contain only old stars , according to the model .
the case on the left is one of prompt star formation in the first few gyr ( short ) , while for the galaxy on the right the model has settled on a long history of early star formation that continues up to the last gyr before .
no star formation has been detected in any of the final five 200 myr time intervals .
( the integrated mass does not increase in the five colored bins . )
both galaxies fall into the passive " region of the uvj diagram ( williams 2009 ) .
it is not obvious looking at the prism spectra why sed fiting process has extended sfr1 star formation to relatively late times .
this could be a sign of the f - star contribution just discussed , but this effect is expected to be subtle .
we are working on a variation of the d4000 index suitable for such low resolution data in an effort to tease out the subtle markers of such longer - than - intermediate - aged star formation .
in contrast , the galaxies in the two bottom panels appear to have had considerable late - epoch star formation .
the galaxy on the left has accumulated most of its @xmath64 @xmath54 from between 1 and 4 gyr after the big bang . according to the model .
the star formation in the last two interals , starting 400 myr before , add only a little mass ( see the right box ) , but the changes to the sed are dramatic . in particular , the strong upturn in the ultraviolet flux , and the peaks in the sed from [ o ii ] and [ o iii ] emission , are indicative of vigorous star formation in the interval that records the final @xmath55 years .
the galaxy is firmly in the ` starforming ' part of the uvj diagram .
the galaxy on the bottom right is a good example of the principal result of this paper : this massive galaxy of 10@xmath56 is almost entirely composed of young stars , according to the model , which records only a small amount of star formation up to 1 gyr _ before _
, with all the rest in the last gyr .
note also lack of star formation in the final ( 200 myr ) interval , as the absence of an ultraviolet upturn confirms this galaxy is in the ` passive region ' of the uvj diagram .
although the sed looks similar to the passive galaxy directly above it , a closer look at the blue part of the spectrum reveals important differences : the d4000 break and g - band , so prominent in the upper right example of an old galaxy , are not present in the bottom right galaxy .
the spectrum of this galaxy is essentially pure a - stars , the unambiguous signature of a @xmath61 gyr population .
the data just discussed were drawn from a catalog of 33,089 measurements of objects at [email protected] in the xmm field .
this included 4665 repeated observations , and 366 galaxies with three measurements .
from the extensive error analysis described in k14 , a quality parameter r(_s / n _ ) was used to pare the sample to r @xmath26 1.8 ( slightly better than the q@xmath502 rating in a three - tiered system
see k14 , figure 8) for single observations .
multiple observations were combined when r @xmath26 2.5 ( slightly worse than q@xmath502 ) for each measurement .
our final catalog contains 22,494 individual galaxies , where the 27,692 unique objects have been further trimmed by 5198 galaxies below the quality cut .
figure 4 plots the redshift determined for each of the 4666 galaxies with duplicate measurements . from the statistics of the differences in the pairs of measurements , we find @xmath58 for the redshift error per observation . for the median redshift of the sample
@xmath59 this value is in good agreement with the @xmath60 found in the extensive error analysis done by k14 .
as described in section 2 , the sfr in the first @xmath65 gyr is covariant with , the sed model s fit to the duration of star formation that began at z@xmath505 , @xmath61 1.2 gyr . on the other hand , the _ stellar mass _ in this and later epochs
is well constrained by the infrared portion of the sed . to exploit this , and to quantify the diversity of sfhs , we chose to characterize the galaxies simply in terms of ` old ' and ` young ' stellar mass , defining the first as star formation that began at z@xmath505 and lasted typically 26 gyr for this sample , and the second as star formation taking place in the last gyr before .
we then define _
z5fract _ , the integral of the stellar mass produced as : @xmath62 where all sfrs are in gyr@xmath63 . that is , _
z5fract _ is the ratio of old/(old+young ) star formation .
figure 5 shows this result through a histogram of the mass distributions of galaxies with more than 50% ( red ) , and less than 50% ( blue ) , of their mass in an old population . there is a clear mass dependence , analogous to that found for the sfhs in section 2 , in the sense that the fraction of ` young ' galaxies rises to lower mass : at approximately 10@xmath64
there is a 50 - 50 mix of galaxies that formed most of their mass early , and those that formed it late .
this simple parameterization confirms and quantifies the results based on sfrs we presented in section 2 : ( 1 ) there is a diversity of sfhs at all galaxy masses above 10@xmath1 ; and ( 2 ) a significant fraction of galaxies at [email protected] are _ young _ , that is , they formed most of their stellar mass after z@xmath501 . with the 4666 repeated measurements in the csi _ xmm _ sample , as restricted to @xmath0 , it is straightforward to determine how well these two epochs of stellar mass are constrained by the sed fitting process . figure 6 plots derived stellar mass for pairs of measurments of the old and young populations . above 10@xmath1 , the stellar mass within the final gyr ( left ) shows a scatter of 0.28 dex , or a factor of 1.9the increase in scatter at the low - mass end is dominated by the high - redshift part of the sample .
the scatter for the old population above 10@xmath64 shown in the right plot , is only 0.21 dex , or a factor of 1.6 .
the uncertainty increases rapidly below 10@xmath64not surprisingly , it is very difficult to detect @xmath65 of old stars in an intermediate - redshift galaxy .
these expected errors are appropriate uncertainties for the @xmath617,000 individual measurements of the 22,494 galaxies in the sample , with expected improvement for the @xmath65000 multiple measurements that we have co - added . based on the factor - of - two or less uncertainty in the measured masses ,
the result in figure 5 is robust .
a possible concern is the fact that , in the high redshift end of our sample , the csi survey has significant incompleteness for passive " galaxies with masses @xmath63 @xmath51 10@xmath1 .
the worry might be that the ` young galaxy ' phenomenon is exaggerated by a failure to detect an old population in these low mass galaxies .
however , figure 5 shows that the majority of such galaxies found in our study have total masses of 10@xmath64 or greater over most of this redshift range , even the ` old ' mass is reliably detected . for the galaxies with total mass 10@xmath64 , the @xmath261 gyr population is secure , which means that , as _ z5fract _ trends lower , the fraction of mass left for the ` old ' population is small : underestimates of that mass
have no consequence , and overestimates have a small range because masses above 5 @xmath66 should have been detected .
the potentially missing galaxies are the ones that have total masses below 5 @xmath66 with little or no younger population . in summary , while there might be more ` old galaxies ' missing through incompleteness , the ones below 10@xmath64 that we identify as ` young ' ( _ z5fract _ @xmath26 0.5 ) are secure .
lower limits of 10@xmath1 and 10@xmath64 for masses of the young and old stellar populations are sufficient to determine the fraction of old stellar mass for our sample . by comparing 4666 pairs of _
z5fract _ values we find that these have typical errors of 0.33 dex , accurate enough to reliably separate the sample at
_ z5fract _
@xmath50 0.5 .
in section 2 we went from modest numbers of example sfhs in figure 1 to a redshift - mass plot ( figure 2 ) that displayed the entire sample sfhs as discreet classes by colors .
here we do the same , by using points of four colors to display the full range of _ z5fract _ as a proxy for sfhs , over its full range , 0.0 @xmath26 _ z5fract _
@xmath26 1.0 .
figure 7 shows four equal ranges that resemble the sfh categories of figure 2 .
while the sfhs in section 2 were defined by _ ad hoc _ changes in sfr from one epoch to another , the _ z5fract _ values coded into figure 7 record a continuous variation in sfh from galaxies that are exclusively ` old ' to those that are largely , if not completely , ` young . ' as in figure 2 , the most striking thing about the distribution of the red points , @xmath68 ( upper left panel ) is the more - than - an - order - of - magnitude range of mass of this population dominated by old stellar mass .
the ` oldest ' galaxies in our sample are not limited to the most massive ones ; indeed , their frequency of occurrence is roughly mass - independent down to a factor of 30 smaller than the most massive galaxies in the sample .
the falling trend with redshift for the highest masses is due to the decreasing volume of the survey , while the bottom envelope is indicative of the mass incompleteness of the csi sample as a function of redshift , as seen in the modeling of section 6 .
the @xmath68 interval includes _ all traditional sfhs _ , that is , those that were either constant or declining with cosmic time ( discussed further in section 6 ) . for the median redshift of sample , @xmath59 , the time from redshift @xmath24 to 1 gyr before is 6.6 gyr ,
so a constant sfr of any amount will produce @xmath69 .
declining sfhs , such as the inimitable @xmath11-model , will be larger , up to @xmath70 for a passive " galaxy .
this means that , even in this category of the ` oldest ' galaxies , there must be sfhs that had rising sfrs for some time after @xmath24 .
the same can be said for _ all _ the galaxies in the well - populated @xmath71 category ( upper - right panel ) : these may have declining sfhs at , but in order to reach 25% to 50% fractions of young stars in the last gyr before , the old population must also have been rising for as long as several gigayears after @xmath24 .
this in itself ( exclusive of our case for ` younger ' galaxies ) points to a diversity of star formation rise times for galaxies that are dominated by old stellar mass and is inconsistent with the idea of conformal sfhs that all began with the same growth pattern long _ before _ the peak star formation . on the other hand ,
it is natural in the lognormal sfh model , as we discuss in section 6 .
it is notable that this _ amber _ distribution is more steeply falling than the distributions in the other 3 panels .
as we surmise in section 7 , the sfrs for these galaxies peak in the redshift range @xmath72 , so over the @xmath73 epoch of our sample , the total stellar mass ( at ) of galaxies that land in this _ z5fract _ range is falling . once again , however , at every epoch the mass range of such sfhs is wide the points represent galaxies with a substantial range in decline rate .
in contrast , the galaxies with @xmath74 ( bottom left panel
green points ) and @xmath75 ( bottom right panel blue points ) , do not show the relatively steep trend line seen for the _ amber _ galaxies .
the shallow decline of these distribution with mass seems to align with the notion that many of these are galaxies with a longer 0 that are observed closer to the peak sfrs .
however , the most interesting feature of these distributions may be the swell in numbers around @xmath30 , which are sensibly identified as the long 0 , short @xmath11 population postulated by o13 and whose identification was the main motivation for this analysis of the csi data .
it is perhaps the most striking feature of figure 7 that so many of these genuinely young galaxies peak at @xmath30 and rapidly disappear thereafter , to be essentially gone by @xmath76 , at least those with m@xmath77 .
figure 7 is rich in information with respect to sfhs , but a framework is needed to understand the longitudinal nature of the samples in these diagrams . as we show in section 6 , the g13 lognormal sfh provides one such tool .
the influence of local environment on galaxy evolution remains an important yet unresolved issue .
the morphology - density relation was interpreted by dressler ( 1980 ) as the result of very early environment ( to explain the very weak trend of population gradients for such a wide range of present - epoch local density ) that was manifest in the @xmath78 universe but not likely produced by it .
it is of course likely the sfhs and morphology are closely coupled , so the present study can be seen as related to the earlier work .
as has been pointed out widely in recent years , morphology correlates most strongly with galaxy mass ( dressler 2007 ; van den bosch 2008 ) , which suggests that what has been attributed to local environment can be largely reduced to a statement like ` denser environments host galaxies of higher mass than lower density regions . '
while dressler inferred from this that the conditions for making more massive , and therefore early type galaxies , were imprinted at a very early epoch , others have focused on specific processes associated with dark matter halo growth .
van den bosch ( 2003 , 2008 ; see also conroy & wechsler 2009 ) was among the first to develop a now popular picture in which the capture of lower mass satellite " galaxies by higher - mass central galaxies " ( and the stripping of the halos of the former ) is a primary mechanism for shaping sfhs of galaxies and , presumably , their morphologies . while a thorough investigation of the ` centrals and satellites ' paradigm is beyond the scope of this paper , the csi survey s ability to assess the environments of sample galaxies through its spectro - photometric redshift precision of @xmath92% , makes it straightforward to take a first look at how sfhs determined in the manner of this study fit in this picture .
galaxy number densities , and local mass densities , for the 22,494 galaxies of our sample were calculated using projected co - moving circles of 1 , 2 , and 4 mpc .
figure 8 refigures the relationships of figure 7 for samples that include only the @xmath611% of galaxies that reside in the densest environments , corresponding to projected densities of ` m2 ' @xmath79 12 @xmath54 mpc@xmath80 , and ` n2 ' @xmath79 2.7 galaxies mpc@xmath80 .
[ fig : g13d16 ] from one standpoint , showing the data of figure 8 is one way answer questions about the content of previous diagrams in this paper , specifically , whether _ satellites _ and _ centrals _ need to be treated separately , because in this picture many galaxies in dense regions are satellites , while most of the galaxies in sparse regions are centrals. in fact , though , figure 7 and figure 8 are so similar that removing the latter s points from figure 7 would make no discernible change .
it is clear , then , that the analysis we have made showing the diversity of sfhs does not show a strong environmental dependence .
( it is important to qualify , however , that there are no rich clusters of galaxies in the csi xmm region . ) but , a more fundamental point can be made about the way the different _
z5fract _ subsets in figures 7 and 8 are distributed in mass : _ they appear the same_. figure 8 has larger fractions of ` old ' galaxies than the complete sample , 69% and 74% compared to the full sample s 62% .
this is a global average , of course : looking at the dense regions at @xmath81 and @xmath82 , the proportion of `` old '' galaxies is even larger .
this is a natural expression of the stronger clustering of more massive , old galaxies these trace the large scale structure more clearly than previous diagrams .
nevertheless , the distributions in mass for each subset appear indistinguishable even in these densest regions , and even though their proportions are different . in other words
, there are different proportions of sfhs , but when they occur , their properties are the same .
this is a familiar finding for studies of galaxy properties in different environment : for example , the standard morphological types look the same and share the same properties in regions of high and low density , even though the proportions of these types are very different .
our brief treatment of this question is insufficient , but this quick look indicates that it is unlikely that the proposed satellite / central dichotomy plays a major role in shaping sfhs of galaxies in the most common environments from relatively isolated galaxies to groups of 10s of galaxies .
as figures 7 and 8 show , genuinely young galaxies exist over a wide mass range , @xmath83@xmath84 and , though their abundances and masses decrease after @xmath85 , are present at all epochs this study has probed .
the large spreads of masses and times at which young systems are found is the `` smoking gun '' of the kind of sfh diversity that distinguishes the g13 and kelson ( 2014b ) sfh paradigms from more conformal pictures , wherein physical inferences rely on the assumption that galaxies of a given stellar mass can be well described by a common sfh ( plus a quenching event ) .
the data clearly suggest that a substantial amount of astrophysics can not be captured by such approaches .
an examination of the model predictions of g13 for how figure 7 _ should _ look helps us understand these issues .
figure 9 is a reproduction of figure 7 based on the suite of g13 lognormal sfhs .
the points are colored identically in the two figures , which are also based on the same definition of _ z5fract _ ( see section 4 ) .
the shaded regions echo the completeness and volumetric effects evident in the data , although we leave them semi - transparent to show the full range of the model measurements .
as shown in the large ( left ) panel of figure 9 , g13 exhibits all of the qualitative trends seen in the data : there is a broad diversity in sfhs at all stellar masses and epochs , such that that ` young ' galaxies ( _ z5fract _ @xmath86 ) occupy most of the diagram , but also display a tendency to lower masses .
the subpanels in figure 9 ( right ) make the above points slightly more quantitatively . here , we see that g13 shows that the ` youngest ' systems ( _ _ z5fract__@xmath87 ; blue points ) reach @xmath88 , but mainly at the earliest epochs probed : very few of these systems appear above @xmath89 at @xmath39 , just as is seen in the data .
the green points reach to higher masses at slightly later times , on up to the oldest galaxies ( red points ) , which span all masses above @xmath22msun at all epochs .
is the @xmath90 mass limit of the g13 model . ]
such agreement is reassuring : it suggests that the g13 model captures or encodes at least some of the relevant astrophysical processes that more conformal approaches average - out .
however , once we move beyond the above metrics , the g13 model results begin to diverge quantitatively from the data . specifically , in its current form , g13 does not produce the right _ fractions _ of the _
z5fract _ classes : while , at @xmath91the median redshift of the sample the data reveal abundances of 56% , 18% , 10% , and 16% for the red , amber , green , and blue objects , respectively , g13 yields instead 81% , 13% , 3% , and 2% ( @xmath922% ) . yet , this discrepancy is easy to understand : while 1 gyr is a timescale on which spectral features change and thus a natural timescale to use to _ assess _ sfhs it is _ not _ a _ natural _ timescale .
for example , in the kelson ( 2014b ) scheme , sfhs fluctuate on _ all _ timescales with a `` memory '' of a hubble - time .
similarly , in the g13 scheme , sfhs fluctuate on @xmath11-like timescales ranging from 1 to many gyr and are diversified from each other also over hubble - times .
as such , instead of comparing g13 to the csi data by matching measurement definitions , we can compare the two by matching definitions of _ youth_. to do this , we redefine g13 _
z5fract _ as : @xmath93 where @xmath94 gyr is the mean @xmath11 value for the g13 sfhs . here , _
z5fract _ becomes the fraction of mass formed before most sfhs can have changed from a low to high , or high to low state of star formation . with this modification , the g13-predicted abundances for the _
z5fract _ classes moves much closer in - line with what is observed : 63% , 21% , 10% , and 6% ( @xmath923% ) again compared to 56% , 18% , 10% , and 16% in the data
( high - to - low _ z5fract _ ) .
so , what can we learn from this more physically aligned model classification ?
figure 10 ( left ) shows the g13 @xmath95 plane the natural description of galaxies in this model with all sfhs color - coded by their g13 _ z5fract _ ( based on @xmath96 ) at @xmath91 . as anticipated ( see sections 2 and 4 ) , sfh stratification is mainly based on peak - time , demarcated by the blue curved lines : high g13 _
z5fract _ objects have early peaking sfhs ( @xmath97 ) , with peak times moving to later epochs with lower g13 _ _ z5fract__s . indeed , as revealed by a look at the example sfhs for each class shown at _
right _ , the breakdown is nearly exactly as stated in section 4 based on the data : while red sfhs are falling rapidly , amber objects are falling more gently , green objects are being observed near their peak of star formation , and blue ones are still on the rise , peaking sometime between @xmath98 and today . yet
, the subtleties expressed within each class are revealing beyond this .
for example , though the red objects are ` old'and indeed will nearly all be dead by today ( dotted vertical lines in _ right _ panels)many are still actively starforming at the epoch of observation ( dashed vertical lines ) .
this belies a key point : _ galaxies with constant sfhs will fall into the highest g13 _ z5fract _ bin at these epochs .
_ hence , _ old does not mean dead_. ( this point is clarified by noticing that many of the red points lie between the orange curves of constant @xmath99 in figure 10 , left ) . ) furthermore , looking at the amber curves we see that even some systems with high g13 _ z5fracts _ ( @xmath7950% ) can have _ rising _ sfhs ( or relatively late starts ) .
this suggests that the current practice of modeling sfhs not only for high - redshift galaxies , but even intermediate - redshift galaxies with exponentially _ declining _ sfhs can often be a mistake , and serves as a ` yellow flag ' to our intuitions .
such are the effects induced by a two - parameter ( or zero - parameter , in the case of kelson [ 2014b ] ) sfh model . to the extent that those frameworks describe reality which we think is substantial ( gladders 2013 ; kelson 2014b ; abramson 2015 ;
abramson 2016)the above results thus suggest that identifying _
what _ determines a galaxy s location in @xmath95 space or a similar plane to be defined for the kelson model is paramount .
that is , even knowing a galaxy is ` old ' is not enough to pin down its sfh , that is , there is no ` typical ' history , as our discussion of the _ red_ and _ amber _ points highlights .
additional physics could have _ substantially _ influenced not merely perturbed some members of a given class differently than others , and these are perhaps _ the _ critical processes to characterize .
the data in this study can not uniquely reveal such causal mechanisms , but we can combine our discussion of environment in section 4 with the g13 model results to come up with a hypothesis : the fractions of the _
z5fract _ classes change in denser regions ( figure 8) , but not the overall trends ( figure 7 ) .
this suggests a scenario in which late - time environmental effects ( e.g. , stripping , strangulation ) simply do not play a large role .
if they did , the _ z5fract _ patterns in figure 8 would be sensitive to the ( diverse ) infall histories of groups and the subsequent ( chaotic ) existences of galaxies ` post - acquisition . '
that they and a host of structural ( e.g. , allen 2016 ; morishita 2016 ) , and star formation - related properties ( e.g. , peng 2010 ; newman 2014 ; vulcani 2015b)appear _ not _ to be sensitive is evidence that galaxy histories are _ correlated with _
the history of their environment , but not _ causally connected _ to their presence in it at any given time .
that is , most of the interesting physics controlling sfhs must be `` baked - in '' at the _
start _ of halo growth , that is , very early on .
this is the scenario presented by dressler ( 1980 ) . as discussed by abramson ( 2016 ) , because each galaxy is assigned a @xmath95 coordinate at birth in the g13 model , it is _ also _ the scenario that framework naturally describes . in either , galaxies in ( rare ) isolated high - density halos _ can _ have the same early - peaking sfhs as those in denser regions , but because a common initial `` low - frequency '' mode will push the galaxy - scale peaks riding on top of it to collapse earlier , such objects will be significantly biased towards what will become groups and clusters .
environment thus determines a global preference for @xmath100i.e . , low values but does not fundamentally restrict them . in this way , though it need not have been , a scenario in which initial conditions largely determine sfhs is fully consistent with the new measurements presented here .
our principle conclusions are : 1 . coarse sfhs from the csi survey exhibit a diversity of star formation histories that are non - conformal
. that is , they are neither replicas nor appear organized by the behavior of macroscopic / population - level scaling laws .
rather , a two - parameter description , such as a sfr that is lognormal in time with its double timescales of 0 and @xmath11 ( figures 9 and 10)seems to be the minimum required to reproduce the diversity of sfhs , found in our study of the csi survey data , for galaxies log @xmath101 912 and @xmath73 .
our analysis of the csi survey data demonstrates that broad - wavelength coverage and accurate spectro - photometry can constrain the populations of stars formed over ` natural ' timescales of stellar evolution@xmath3 , and @xmath4 years .
sfrs calculated from a sophisticated fitting of spectral energy distributions , based on well understood signatures of stellar populations , are able to discriminate galaxies that formed all their stars early in a few billion years from those that formed stars continuously , and from those that formed most of their stars late after @xmath5 .
we confirm predictions by o13 and modeling by g13 by identifying a substantial population of genuinely young galaxies those that formed most of their stellar mass after @xmath5 and within 1 gyr of the epoch of observation .
we demonstrate through duplicate measurements of galaxy stellar mass that a parameter _ z5fract_the fraction of total stellar mass that was formed in the epoch starting at @xmath24 and lasting @xmath65 gyr is a simple but robust indicator of sfhs .
we quantify the relative proportions of diverse sfhs through _
z5fract _ and show that , at @xmath30 and log m@xmath102 , geniuinely young galaxies those with greater stellar mass made in the final gyr than in the time prior are @xmath650% of the population , and that though they are rare there are young galaxies with masses of the milky way , @xmath103 , and higher .
the different forms of sfhs are functions of total mass , but there is large diversity at any given mass and , conversely , a wide range of mass ( @xmath61.0 dex ) over which a particular sfh can be found . assuming that stellar mass is strongly coupled to dark halo mass , this means that galaxies with the same halo mass at any given epoch can host very different sfhs .
this suggests another parameter , in addition to halo _ mass _ , that controls when star formation begins and how it progresses .
this could be a property of the halo , for example , its density or turn - around time , or of baryonic physics , such as star - formation or black hole growth feedback .
these factors could drive the efficiency " of turning baryonic mass into stars that is offered as an explanation of why the halo mass function and the stellar mass function of galaxies do not ` track . '
our sample is dominated by field " galaxies , which means isolated galaxies or those in moderate mass groups .
the most massive galaxies , and those galaxies most exposed to ` environment effects , ' are not represented in the present study , because the csi survey includes no rich clusters .
that being said , the sfhs we present account for @xmath695% of all galaxies with masses larger than 10@xmath1 .
the conformal approach to sfhs explicitly includes quenching mechanisms " to alter the course of star formation , specifically , to stop it , but only a small fraction of our sample are good candidates for mass quenching " or `` environmental quenching , '' two popular generic concepts .
nevertheless , a very large fraction of our 22,494 galaxy sample have evolved from sfrs of 10 s of early in their lifetime to @xmath91 by the present epoch .
our data therefore suggest that natural processes working on the timescale of a hubble time are able to regulate rising and then falling star formation without discrete , short - timescale quenching events .
the picture that emerges is one of predestined paths for galaxies , perhaps modulated by mergers in their early history , with a `` clock '' and as - yet unidentified intrinsic processes that propel a galaxy_sooner , or later_to a state where halo gas is insufficient , or in a unusuable state , for continued star formation .
these and other data support a picture where sfhs are generally locked - in at an early epoch , determined by specific properties of the environment or the galaxy itself . such built - in trajectories can provide an alternative explanation for supposedly environment - related correlations , like galaxy morphology with local density , or the satellite / central paradigm , as expressions of _ initial conditions_. dark matter halos must play a role in this process , but a simple correlation of sfh and halo mass is clearly incompatible with the diverse histories we present here .
we look to theoretical work to explore halo and/or baryonic properties that are responsible for this manifold variety of sfhs .
the authors thank the scientists and staff of the las campanas observatories for their dedicated and effective support over the many nights of the csi survey . b.v .
acknowledges the support from an australian research council discovery early career re- searcher award ( pd0028506 ) . | we present coarse but robust star formation histories ( sfhs ) derived from spectro - photometric data of the carnegie - spitzer - imacs survey , for 22,494 galaxies at @xmath0 with stellar masses of 10@xmath1 to 10@xmath2 .
our study moves beyond average " sfhs and distribution functions of specific star formation rates ( ssfrs ) to individually measured sfhs for tens of thousands of galaxies . by comparing star formation rates ( sfrs ) with timescales of @xmath3 , and @xmath4 years
, we find a wide _ diversity _ of sfhs : ` old galaxies ' that formed most or all of their stars early ; galaxies that formed stars with declining or constant sfrs over a hubble time , and genuinely ` young galaxies ' that formed most of their stars since @xmath5 .
this sequence is one of decreasing stellar mass , but , remarkably , each type is found over a mass range of a factor of 10 .
conversely , galaxies at any given mass follow a wide range of sfhs , leading us to conclude that : ( 1 ) halo mass does not uniquely determine sfhs ; ( 2 ) there is no ` typical ' evolutionary track ; and ( 3 ) abundance matching " has limitations as a tool for inferring physics .
our observations imply that sfhs are set at an early epoch , and that for most galaxies the decline and cessation of star formation occurs over a hubble - time , without distinct quenching " events .
sfh diversity is inconsistent with models where galaxy mass , at any given epoch , grows simply along relations between sfr and stellar mass , but is consistent with a 2-parameter lognormal form , lending credence to this model from a new and independent perspective . |
Chili's Lifts Permanent Ban on Pam Beesly Halpert
Effective immediately, Chili’s® Grill & Bar has removed the longstanding ban on a Scranton, Pennsylvania woman who allegedly caused a disturbance during a company awards party held at a Chili’s near the Pennsylvania town of Scranton.
The woman, Pam Beesly Halpert, received a prestigious award for having the whitest sneakers in the company.
After thanking her shoes and coworkers, the woman declared, “I feel God in this Chili’s tonight.”
"After reviewing the good conduct of Pam, I have decided to lift the now 11-year ban," said Kelli Valade, President of Chili's. "Pam is an inspiration to many and we welcome her with open arms." ||||| Forgiveness is a cherished virtue.
It's also something that Pam Beesly, former receptionist at Dunder Mifflin from our favorite show The Office, experienced today when restaurant chain Chili's officially forgave her for her uncouth behavior 11 years ago.
It all started when Jenna Fischer, the actress who played Pam, tweeted out this photo.
Should I try to go in? pic.twitter.com/HDpPqzA0by — Jenna Fischer (@jennafischer) February 6, 2017
Fischer is alluding to a scene from Season 2 of The Office, when Pam becomes so drunk at Chili's that she falls out of a chair and is subsequently kicked out of the restaurant. Not only that, but the owner of the restaurant proclaims, "She is not welcome at this restaurant chain ever again."
Well, Fischer's tweet showing her potential reunion with Chili's went around the internet a number of times. When Chili's heard about it, they decided that it was time to give Pam another chance.
BREAKING: Chili’s lifts permanent ban on Pam (@JennaFischer), welcomes her back to any #Chilis restaurant: https://t.co/jw76381O8K — Chili's Grill & Bar (@Chilis) February 7, 2017
The link in the tweet takes you to an actual press release, which states the following:
Effective immediately, Chili’s® Grill & Bar has removed the longstanding ban on a Scranton, Pennsylvania woman who allegedly caused a disturbance during a company awards party held at a Chili’s near the Pennsylvania town of Scranton.
The woman, Pam Beesly Halpert, received a prestigious award for having the whitest sneakers in the company.
After thanking her shoes and coworkers, the woman declared, “I feel God in this Chili’s tonight.”
"After reviewing the good conduct of Pam, I have decided to lift the now 11-year ban," said Kelli Valade, President of Chili's. "Pam is an inspiration to many and we welcome her with open arms."
Classy move, Chili's.
We're sure that Pam Beesly Halpert-Jenna Fischer will seize this opportunity to never misbehave in a Chili's again.
Uh oh. ||||| 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. ||||| Back in 2005 on the beloved TV comedy “The Office,” Pam Halpert née Beesly was permanently banned from Chili’s after getting too drunk during The Dundies award show.
Now it seems Pam has returned to the restaurant chain 11 years later in an apparent attempt to bury the hatchet, and Chili’s was ready to work things out.
Jenna Fischer, the actress who played the soft-spoken but charming secretary, tweeted on Monday a selfie as she stood in front of a Chili’s restaurant with a concerned look on her face.
She asked her fans, “Should I try to go in?”
Should I try to go in? pic.twitter.com/HDpPqzA0by — Jenna Fischer (@jennafischer) February 6, 2017
Fans replied to Fischer’s tweet with nostalgia for the retired show, many of them sharing their favorite Dunder Mifflin moments with a gif.
Lots of people were also quick to remind the actress she was eighty-sixed from the establishment for life.
@jennafischer Be careful. If I remember correctly, they xeroxed your driver's license and you weren't welcome at that chain ever again — Mark Ludwiczak (@MarkLud12) February 6, 2017
Even Chili’s official Twitter account decided to get involved by taking a jab at Pam’s drunken night.
@jennafischer we hope you felt God tonight. — Chili's Grill & Bar (@Chilis) February 7, 2017
The Office
Then something incredible happened.
Brinker International, the company that owns Chili’s, published an official press release Tuesday afternoon officially lifting its “longstanding ban” on “Pam Beesley Halpert.”
“After reviewing the good conduct of Pam, I have decided to lift the now 11-year ban,” Chili’s President Kelli Valade said in an official statement. “Pam is an inspiration to many and we welcome her with open arms.”
BREAKING: Chili’s lifts permanent ban on Pam (@JennaFischer), welcomes her back to any #Chilis restaurant: https://t.co/jw76381O8K — Chili's Grill & Bar (@Chilis) February 7, 2017
Brinker International
Unsurprisingly, die-hard fans of “The Office” went crazy over the unexpected news.
@Chilis @BeccaCanote @jennafischer Finally, we can close this ugly chapter on our history. (I'm going to take whatever victories I can). — Jonathan Strickland (@JonStrickland) February 7, 2017
But based on Fischer’s latest tweets, we’re starting to think Pam hasn’t really learned her lesson.
@johnkrasinski I promise not to fall off the stool next time. — Jenna Fischer (@jennafischer) February 8, 2017 | – Eleven years ago, Pam Beesly felt God in a Chili's. But apparently it's been hell getting back into one. On Monday, actress Jenna Fischer tweeted a photo of herself standing in front of a Chili's, asking if she should "try to go in." Mashable reports Fischer's character on The Office, Pam Beesly, was permanently banned from all Chili's restaurants after getting drunk and falling out of her chair in a 2005 episode. It was a cute tweet. Then things took a turn for the surreal. Apparently having seen the tweet, Chili's parent company, Brinker International, issued a press release, the Huffington Post reports. "Effective immediately, Chili’s Grill & Bar has removed the longstanding ban on a Scranton, Pennsylvania, woman who allegedly caused a disturbance during a company awards party held at a Chili’s," the company states. The president of Chili's goes on to call Pam an "inspiration to many" and says they "welcome her with open arms." Fischer, apparently excited by the prospect of more Chili's margaritas, responded: "OMG! Second drink!!!" |
cercarial dermatitis is a parasitic disease with world - wide distribution , caused by the cercariae of animal schistosomes , if they enter in non - specific host for completion of life cycle .
though , the clinical cases of this disease have been reported from many countries in europe and america , but scattered cases were recorded from southern end of south america ( 1 ) . in india ,
the first report on dermatitis was from mysore ( karnataka state ) among the people who used waste tank for domestic purpose but the cercariae involved were not identified ( 2 ) .
it was experimentally demonstrated that only repeated exposures to cercariae could produce dermatitis in man ( 35 ) . as per views of hoeffler ( 6 ) , cercarial dermatitis is a parasitic disease affecting the skin . a case of schisto - some cercarial dermatitis in man at tiptur in tumkur district in karnataka ( india ) was observed in which both indoplanorbis exustus and lymnaea luteola snails were involved in the transmission of disease in a pond ( 7 ) .
basic ideas about endemic form of cercarial dermatitis ( khujlee ) were emerged in bastar area of madhya pradesh ( india ) where many villages had only one pond which fulfills all their needs ( 8 , 9 ) .
thus the same pond was used by villagers for bathing , washing , even drinking ( except in few where hand pumps are used ) and also for washing and bathing of their domestic animals - mainly cattle .
an outbreak of cercarial dermatitis occurred in a recreational - tourist lake in the quebec city region ( canada ) in the summer ( 10 ) . besides this
, the contributions of some parasitologists ( 1114 ) can be cited who reported that the disease swimmer itch is caused by free - swimming larvae of bird parasites of the family schistosomatidae ( trema - toda ) , which have penetrated through the skin .
earlier in the doon valley , in northern india both the vector snails and pathogens have already been recorded ( 1517 ) but there was no sign of occurrence of cercarial dermatitis . henceforth , the present study is an attempt to provide a way forward towards malaco faunal diversity and distribution of snail borne parasitic diseases especially the cer - carial dermatitis in the chosen area .
survey application on malaco - faunal diversity has been performed from the water bodies of the study areas [ sahaspur and doiwala ] in doon valley in district dehradun in northern india having geographic co - ordinates of 3018 56 n and 78 2 0 e at 652 msl .
snail sampling was done by applying standard methods ( 18 ) and the collected snails were identified using keys and catalogues ( 19 , 20 ) . associated parasites and cercariometry in snails has been worked out by cercarial shedding ( 2123 ) .
a questionnaire having questions in concerned with socio - economic aspects of inhabitants were interviewed and the data was procured .
human involvement at zoonotic level has been worked out in the selected villages in collaboration with health centers and socio - economic aspect of inhabitants of study area .
frequent visits to respective phcs was made for procuring information on skin diseases and confirmation of present results .
simultaneously , a close look to frequently visiting livestock of the study area provided a clue of their potent role in completing the life cycle of the parasites .
the snail diversity revealed the occurrence of 19 species belonging to 8 different families ( table 1 ) .
the collection sites from sahaspur shared all the species while from doiwala , the two species seg - mentina calatha ( benson , 1850 ) and m. nevilli ( brot , 1874 ) were not reported .
for cercariometry , the snails like i. exustus , m. tu - berculata , g. convexiusculus and l. acuminata were found infected with larval trematodes ( fig .
the cercarial diversity comprised four different types viz . , furcocercous , monostome , amphistome and liverfluke / xiphidio cercariae . among the collected snails ,
m. tuberculata have harbored with furcocercous , monostome and am - phistome cercariae whereas l. acuminata and i. ex - ustus released xiphidio and furcocercous cercariae .
the infection was found more in winter than post monsoon , summer and monsoon seasons .
c ) g. convexiusculus d ) l. acuminata malaco - faunal diversity of the study area in doon valley ( uttarakhand ) , india during 2009 to 2010 a survey work on the spread of cercarial dermatitis has been made and some cases of dermatitis have been found . as many as
, 24 villages under 7 blocks were surveyed for social status , occupation and skin infection among the inhabitants during january , 2009 to december , 2010 . among the persons
examined , 0.173% was found with cercar - ial dermatitis ( table 2 and fig .
the localities like khushalpur , dhali - pur , jamanpur and dudhlee in doon valley exhibited a positive correlation .
but in the localities like dhaki , jhajhara , lakhanwala , rampur and nahgal bulandawala the pathogen was existed but no case of dermatitis was recorded .
it has also been observed that in almost all the selected villages the farming was one of the occupations of the residing people .
frequent visits to respective phcs was made for procuring information on skin disease and confirmation of present studies .
it is noted that the physicians at phc s were in the doubtful position whether the skin infection is due to entrance of cercariae or due to allergic reaction of wild variety of grass ( parthenium hysterophorus ) .
cases of cercarial dermatitis ( original ) simultaneously , a close look to frequently visiting livestock of the study area provides a clue of their potent role in completing the life cycle of the parasites . in view of lack of information on skin infection , this needs a comprehensive study on the role of livestock / birds in the zoonotic transmission of the parasites . showing suspected cases of cercarial dermatitis ( c.d . ) in selected areas of doon valley
according to hoeffler ( 6 ) , the cercarial dermatitis is a parasitic disease affecting the skin .
it may be encountered in fresh or salt water and is global in its distribution .
it is a potential economic hazard to persons who work in aquatic environments and to the tourist industry . with regard to occurrence of cercarial
dermatitis the present findings resemble with the contributions of a number of workers ( 7 , 8 , 2428 ) but slightly differ in considering the role of species of snail . in our studies
cercariae of several species of mammalian and avian schistosomes are responsible for causing dermatitis in man , during the act of skin penetration .
these cercariae are unable to propagate and eventually perish . known also as swimmer s itch or paddy field dermatitis
, it could be an occupational hazard for agricultural labourers , washer men and fishermen .
this condition is rampant in rural india , where villagers are largely dependent on water ponds for their domestic and animal needs . on a personal discussion with the village people
there was a case of a young man who collected fresh water fish with bare hands from an irrigation pond .
minutes after collecting the fish , the person experienced itching and erythema on the dorsum of the hands .
soon , a few macules appeared on the hands and 6 - 7 h later these macules developed into papules .
cercarial dermatitis should be considered a potential risk whenever warm - blooded and molluscan hosts share a water resource with man as it is a self - limited , severely itching rash that lasts about one week and may be easily mistaken for insect bites .
more emphasis has been given on ( a ) the temporal occurrence of cercarial dermatitis in humans and ( ii ) the prevalence of animal schisto - some infection in vector snails and the level of cercarial shedding in relation to time of year and water temperature .
ethical issues ( including plagiarism , informed consent , misconduct , data fabrication and/or falsification , double publication and/or submission , redundancy , etc . ) have been completely observed by the authors . | abstractbackgroundcercarial dermatitis also known as swimmers itch ( skin allergies ) is caused by a trematode parasite , schistosoma which has two hosts - an invertebrate ( snail ) and a vertebrate ( livestock , human being ) . although the availability of both vector snails and pathogens at the selected site the doon valley in northern india has already been confirmed but there was a hazy picture of the disease , whether it is due to entrance of cercariae or due to wild variety of grass ( parthenium hysterophorus ) .
the present study is an attempt to provide a way forward towards the vector snails and snail borne diseases in the study area.methodssnail sampling and identification was done by applying standard methods / using keys & catalogues .
associated parasites and cercariometry in snails has been worked out by cercarial shedding .
human involvement at zo - onotic level has been performed in collaboration with health centers and socio- economic aspect of inhabitants of study area.resultsthe snail diversity encountered 19 species including the vector species such as indoplanorbis exustus , gyraulus convexiusculus , melanoides tuberculata and lymnaea acuminata . the cercarial diversity comprised furcocercous , monostome , amphistome and liver fluke / xiphidiocercaria . during the study ( 20092010 ) ,
0.173% was found with cercarial dermatitis among human population in the selected area .
the symptoms of disease recorded were red spots and swellings on effected parts of skin .
frequent visits of livestock to the water body and presence of vector snails provides a clue in completing the life cycle of the parasite of the family schistosomatidae.conclusioncercarial dermatitis has been considered a potential risk at those places where warm blooded and snail s hosts share a link with aquatic bodies with particular emphasis to temperature and time of year . |
the term apoptosis identifies a form of cell death ; the significance of which was suggested by kerr et al . in 1972 .
apoptosis , or programmed cell death ( pcd ) , has been reported initially to occur in multicellular organisms under normal physiological conditions and as a major contributing factor to tissue homeostasis and remodeling . moreover , pcd is the common mechanism by which human tumor cells die , either spontaneously or in response to therapeutic agents or cell mediators such as nitric oxide .
although the first statement was that only nuclei but not cytoplasmic organelles would undergo major modifications , large evidences have being accumulated indicating that all cellular compartments are concerned with the mitochondria being early affected during the pcd process . in the case of kinetoplastids parasites , increasing number of reports have shown that a pcd - like process could occur in these unicellular organisms [ reviewed in ] . however , despite some phenotypic similarities between the apoptosis - like death of kinetoplastids and mammalian nucleated cell pcd , recent elegant approaches have demonstrated that the pathways ( induction / execution ) at the molecular level , at least in the case of leishmania parasites , differ significantly from those of metazoans .
indeed , though dna fragmentation into oligonucleosomes was observed in stationary phase promastigotes and especially in amastigotes of l. major and l. amazonensis , even in the absence of an induction ( stress conditions ) , this process was independent of caspases or lysosomal cathepsin - like enzymes ( i.e. cysteine proteases a and b ) .
although , a recent study has shown that no - induced l. amazonensis amastigotes dna fragmentation could be blocked by proteasome inhibitors such as lactacystin , a lack of inhibition was observed by other investigators , though using another leishmania species ( i.e. l. major ) , and straurosporine as inducer of apoptosis .
taking into account the fact that lactacystin by itself has being shown to be an inducer of apoptosis in some circumstances , the implication of proteasome in leishmania oligonucleosomal dna fragmentation await further investigations .
thus , it is likely that the elucidation of molecular mechanisms leading to the cell death in kinetoplastids parasites would not only help to define the in vivo role of a given gene but may also be useful to identify new target molecules for chemotherapeutic drug development .
many eukaryotic gene products demonstrate remarkable diversity and plasticity of function , a fact that could extend to those involved in protein biosynthesis such as the elongation factor subunits and those involved in the reversible acetylation / deacetylation , a key post - translational modification event , regulating a number of biological processes including gene transcription . among the latter category , the silent information regulator ( sir2 ) family of genes ,
it is the purpose of the present report to review some of our data concerning parasite factors : ef-1 and sir2-related protein , and put them in perspective with points of interest for further studies that will more fully explore the possible involvement of the above mentioned factors in the control or parasite differentiation survival and death .
elongation factors are encoded , in most cases , by housekeeping genes found in eukaryotes and prokaryotes .
although , the protein synthesis seems to be their general function , it appears that they could express a variety of other important and some times surprising biological properties .
elongation factor 1 ( ef-1 ) consists of two functionally distinct parts , ef-1 and ef-1. ef-1 binds aminoacyl - trnas in the acceptor site of 80s ribosome under the hydrolysis of gtp .
ef-1 catalyses the exchange of gdp in the binary complex ef-1 gdp for free gtp .
ef-1 is an exceptionally abundant protein comprising 310% of the soluble proteins in most cells .
although , ef-1 plays a central role in eukaryotic protein biosynthesis , its association with a number of other molecules such as ribonucleoprotein particles , the valyl - trna synthesase , the cytoskeletal matrix , the endoplasmic reticulum and the mitotic apparatus , suggest its involvement in other biological functions .
few years ago , we have characterized the genes encoding the t. cruzi ef-1 subunits ( tcef-1,- and - ) [ reviewed in ] and -. serendipitously , when following the cellular distribution of tcef-1 during the in vitro growth of epimastigotes , as revealed by immunoflorescence using antibodies to tcef-1 , we found its accumulation in the nucleus of ageing parasites showing high levels of binucleated cells indicative of arrest at cytokinesis , and those undergoing apoptosis - like death , therefore suggesting that tcef-1 is capable of cytoplasmic - nuclear shuttling .
these observations are in agreement with previous reports showing ef-1 to be present in the cytoplasm as well as the nucleus of oligodendrocytes .
since the ef-1 is an actin - binding protein and could associate with the microtubular network , it has being suggested that the ef-1 may be associated with the cytoskeletal elements in the nucleus of oligodendrocytes and that the cytoplasmic and the nuclear ef-1 could be functionally distinct entities .
furthermore , recent investigations have shown that changes in the level of ef-1 may be one of pivotal factors regulating the rate of apoptosis .
indeed , an antisense ef-1 provides cells protection against death upon starvation whereas ef-1 overexpression leads to a faster rate of cell death , therefore suggesting that abundance of ef-1 characterize pro - apoptotic cells while low levels is indicative of anti - apoptosis state .
moreover , using a murine erythroleukemic cell line which expresses a temperature - sensitive mutant p53 gene , it has being shown that culturing the cells led to their death by apoptosis .
no significant changes occur in the expression of genes such as bcl-2 , bax , fas and fas - l , instead , mrna display showed that one of the up - regulated genes was ef-1 resulting in microtubule severing ( distortion of cytoskeleton ) , a process which in cooperation with cytochrome c - caspase-3 activation led to cell death .
protein synthesis ef1- has also being shown to be essential for ubiquitin - dependent degradation of certain n - acetylated proteins .
analysis of ef-1 mechanism of action , revealed that it acts along with the 26s protease complex and stimulates degradation of the core nucleosomal histone h2a .
therefore , it make sens to have , under certain circumstances , ef-1 targeted to the nucleus .
although some controversial data concerning the implication of ef-1 in the life span have being reported , it seems that the decrease of ef-1 catalytic activity is a characteristic of senescent cells in agreement with the notion that the loss of enzyme function is a general phenomenon in aging organisms .
therefore , regulation of protein synthesis can be considered as one key homeostatic function common to all cells .
another interesting and unexpected finding relates to the recently reported observations in the case of l. donovani ef-1 .
indeed , this factor was able to be exported from the phagosome and bound to the macrophage scr homology 2 domain containing tyrosine phosphatase-1 ( shp-1 ) leading to its activation .
as a consequence , a down - regulation of macrophage inducible nitric oxide synthase expression in response to interferon- occurred , a process which may contribute to the deactivated phenotype of infected macrophages .
the striking observation was that host cell ef-1 was unable to perform such biological activity .
furthermore , in plants , ef-1 was identified as the activator of the phosphatidylinositol 4-kinase and as an adhesion protein related to vitronectin . therefore , despite high score identity between ef-1 from a wide variety of eukaryotes including mammals , plants and fungi , the presence of slightly different ef-1 genes may account for the generation of proteins with distinct biological properties . in previous studies ,
we have shown for the first time that the t. cruzi ef-1 subunit contains a glutathione s - transferase domain [ reviewed in ] .
independent investigators reported similar observations in the case of a large number of other eukaryotic ef-1 subunits .
although in our initial experiments attempts to detect a gst activity using recombinant t. cruzi ef-1 were unsuccessful perhaps due to the extremely hydrophobic nature of the molecule which precipitate in the absence of detergents , a recent report has demonstrated in rice an ef-1-dependent gst activity after purification of the protein in the presence of 20% glycerol . due to the high association of ef-1 with membrane and cytoskeleton structures
, it has being suggested that ef-1 could direct components of the protein synthesis apparatus towards the three - dimensional cytoplasmic structure of the cell .
we have hypothesized that in addition to this later biological property ef-1 could have other function ( s ) through its gst - like module . to evaluate this concept
, we have used the protozoan parasite t. cruzi as a recipient for a shuttle vector which allows overexpression of ef-1. a strong resistance of transformed organisms to the tricyclic antidepressant drug clomipramine , a lipophilic compound , was observed .
we also found that the parasites had reduced responsiveness to apoptosis stimuli ( unpublished data ) .
the simplest interpretations of these data could be the following : 1-the specific affinity of ef-1 for membranes and tubulin may have induced some distortion at the level of membrane structures rendering them less accessible to the drug , 2-the ef-1 is likely to form a fold very similar to that in the known structures of gsts allowing the conjugation of glutathione with the toxic lipophilic compound . since increased ef-1 production could be seen when the wild - type parasites were cultured in the presence of increasing concentrations of the drug , it is tempting to speculate that ef-1 might be part of a system transmitting external signals towards the protein synthetic machinery providing cells significant protection from apoptotic death . in agreement with this possibility , it is noteworthy that increased transcription of ef-1 in pancreas malignant tissue in comparison with corresponding normal pancreatic tissue has been demonstrated , suggesting that ef-1 could be a useful marker as ras gene in non - familial adenomatous polyposis .
similar findings were reported in the case of adenocarcinomas and adenomas of the colon and in gastric and oesophageal carcinomas , providing preoperative useful information for the prediction of tumor aggression .
there is a rapidly expending interest into the sir2 protein family and the structurally related molecules .
the sir2 gene family members have being cloned from a variety of species ranging from bacteria to man indicating a high degree of conservation throughout evolution [ reviewed in ] . among the mechanism of gene repression transcriptional inactivation or
sir2 was firstly described in budding yeasts to be involved with sir3 and sir4 proteins in transcriptional repression , or silencing , by modulating chromatin structure at mating - type loci ( hml and hmr ) and subtelomeric regions [ reviewed in ] .
the protein encoded by the sir2 gene belongs to a highly conserved family of closely related proteins in both prokaryotic and eukaryotic species named hst proteins ( homologous of sir two ) or sirtuins .
the biological significance of sir2-like proteins diversity is not yet understood and molecular function of sir2p as naddependent deacetylase has recently been explored .
however , the diverse cellular localizations among sir2 homologues nucleus , ( cytoplasm and mitochondria ) and the presence of sir2-like proteins in bacteria suggest that these enzymes have other physiological substrates than histones and thus additional biological functions .
indeed , recent evidence indicates that sir2 proteins are involved in the regulation of p53-dependent apoptotic response via deacetylation of p53 protein .
moreover , mouse msir2 is able to deacetylate tafi68 , a pol i stimulatory factor , repressing pol i transcription in mouse extracts .
few year ago , we have cloned and sequenced a l. major gene encoding a protein bearing domain structure characteristic of sir2 proteins ( lmsir2 ) . the expectation was to find the lmsir2 associated with the nucleus , instead , the protein had a cytoplasmic localization . however , further independent studies revealed the presence of sir2-related proteins in the cytoplasm of different species , and more recently in the mitochondria .
interestingly , l. infantum amastigotes , the vertebrate stage of the parasite , carrying extracopies of lmsir2 or l. infantum sir2 ( lisir2 ) gene , when maintained under normal axenic culture conditions , showed striking increase in the survival due to an inherent resistance to apoptosis - like death , leading to a longer stationary phase of growth .
these observations resemble those reported in the case of c. elegans and yeast [ reviewed in ] . indeed , increased dosage of sir2 gene in these organisms resulted in a their life span extension .
however , no similar effect was observed on the survival of the promastigote forms ( insect stage ) under similar culture conditions as amastigotes . taken into account the fact that promastigote energy source originate mainly from glucose , and the existence of a link between cellular metabolism and sir2 biological properties
, we examined the survival of promastigotes under starvation conditions using glucose as a unique source of energy .
under these experimental conditions , the viability of promastigotes which overexpress sir2 gene increased significantly even in the absence of exogenous added glucose .
in fact caloric restriction in yeast by limiting glucose concentrations leads to a significant extension in the life span of mother cells .
since sir2 is a nicotinamide - adenine dinucleotide ( nad)-dependent deacetylase , it has being proposed that slowing in metabolism would free up the cofactor nad resulting in increase sir2-dependent silencing and therefore longer life span .
thus , our observations reinforce the notion of sir2 protein being coupled to physiological processes which influence gene expression regulation .
although the basic molecular and biological approaches have revealed that leishmania sir2-related gene could modulate the parasite physiology , the question remains to what extent the protein , which has a cytoplasmic localization , could interfere with gene expression processes .
it is noteworthy that overexpression of a yeast cytoplasmic protein homologous to sir2 ( hst2p ) , influences nuclear silencing events , derepressing subtelomeric silencing while increasing repression in the rdna .
the postulated hypothesis was that non - nuclear yeast hst2p can compete for a substrate ligand specifically required for telomeric repression .
the intracellular localization of key regulatory proteins tagged with a short leucine - rich motif ( the nuclear export signal or nes ) is controlled by crm1/exportin1 , which is involved in the export of these proteins from the nucleus [ reviewed in ] .
careful examination of lisir2 sequence revealed that it possesses at its carboxy - terminal region one nes - like motif ( residues 342352 : lx3lxlx3l , where l represents leucine and x any amino acid ) .
therefore , whether leishmania sir2 during very short periods of cell cycle phase , is capable of shuttling between the cytoplasm and nucleus through the nes putative sequence , await further investigations .
although reversible acetylation of histones seems to be key process in the regulation of gene transcription , strong evidence pointed to the critical role of the dynamic of acetylation - deacetylation of non - histone proteins [ reviewed in ] .
in fact , small organic molecules such a spermidine and spermine as free amines contribute to the processes leading to dna condensation , acetylation of these amine groups led to their inactivation .
given that the polyamines are known to be essential factors for the growth of the parasites in their host , it is tempting to speculate that leishmania sir2 , like hst2p , could interact with cellular factor ( s ) necessary for the cell - death machinery responsible for the ultimate destruction of the cell .
the generation of a deficiency state of sir2-related protein by gene targeting should provide a means to assess the implication of this factor in the pathways leading to the prevention of cell death .
the identification and molecular characterization of genes that confer to the parasites true cytoprotection against environmental stress , and those contributing to the " apoptotic " signaling , will shed light on cell death control mechanisms in kinetoplastids . molecular characterization of those genes will allow one to explore the possibility of modulating their function , by generating small inhibiting / activating compounds for chemotherapeutic approaches based on apoptosis manipulation in these organisms .
elongation factors are encoded , in most cases , by housekeeping genes found in eukaryotes and prokaryotes .
although , the protein synthesis seems to be their general function , it appears that they could express a variety of other important and some times surprising biological properties .
elongation factor 1 ( ef-1 ) consists of two functionally distinct parts , ef-1 and ef-1. ef-1 binds aminoacyl - trnas in the acceptor site of 80s ribosome under the hydrolysis of gtp .
ef-1 catalyses the exchange of gdp in the binary complex ef-1 gdp for free gtp .
ef-1 is an exceptionally abundant protein comprising 310% of the soluble proteins in most cells .
although , ef-1 plays a central role in eukaryotic protein biosynthesis , its association with a number of other molecules such as ribonucleoprotein particles , the valyl - trna synthesase , the cytoskeletal matrix , the endoplasmic reticulum and the mitotic apparatus , suggest its involvement in other biological functions .
few years ago , we have characterized the genes encoding the t. cruzi ef-1 subunits ( tcef-1,- and - ) [ reviewed in ] and -. serendipitously , when following the cellular distribution of tcef-1 during the in vitro growth of epimastigotes , as revealed by immunoflorescence using antibodies to tcef-1 , we found its accumulation in the nucleus of ageing parasites showing high levels of binucleated cells indicative of arrest at cytokinesis , and those undergoing apoptosis - like death , therefore suggesting that tcef-1 is capable of cytoplasmic - nuclear shuttling .
these observations are in agreement with previous reports showing ef-1 to be present in the cytoplasm as well as the nucleus of oligodendrocytes .
since the ef-1 is an actin - binding protein and could associate with the microtubular network , it has being suggested that the ef-1 may be associated with the cytoskeletal elements in the nucleus of oligodendrocytes and that the cytoplasmic and the nuclear ef-1 could be functionally distinct entities .
furthermore , recent investigations have shown that changes in the level of ef-1 may be one of pivotal factors regulating the rate of apoptosis .
indeed , an antisense ef-1 provides cells protection against death upon starvation whereas ef-1 overexpression leads to a faster rate of cell death , therefore suggesting that abundance of ef-1 characterize pro - apoptotic cells while low levels is indicative of anti - apoptosis state .
moreover , using a murine erythroleukemic cell line which expresses a temperature - sensitive mutant p53 gene , it has being shown that culturing the cells led to their death by apoptosis .
no significant changes occur in the expression of genes such as bcl-2 , bax , fas and fas - l , instead , mrna display showed that one of the up - regulated genes was ef-1 resulting in microtubule severing ( distortion of cytoskeleton ) , a process which in cooperation with cytochrome c - caspase-3 activation led to cell death .
protein synthesis ef1- has also being shown to be essential for ubiquitin - dependent degradation of certain n - acetylated proteins .
analysis of ef-1 mechanism of action , revealed that it acts along with the 26s protease complex and stimulates degradation of the core nucleosomal histone h2a .
therefore , it make sens to have , under certain circumstances , ef-1 targeted to the nucleus .
although some controversial data concerning the implication of ef-1 in the life span have being reported , it seems that the decrease of ef-1 catalytic activity is a characteristic of senescent cells in agreement with the notion that the loss of enzyme function is a general phenomenon in aging organisms .
therefore , regulation of protein synthesis can be considered as one key homeostatic function common to all cells .
another interesting and unexpected finding relates to the recently reported observations in the case of l. donovani ef-1 .
indeed , this factor was able to be exported from the phagosome and bound to the macrophage scr homology 2 domain containing tyrosine phosphatase-1 ( shp-1 ) leading to its activation .
as a consequence , a down - regulation of macrophage inducible nitric oxide synthase expression in response to interferon- occurred , a process which may contribute to the deactivated phenotype of infected macrophages .
the striking observation was that host cell ef-1 was unable to perform such biological activity .
furthermore , in plants , ef-1 was identified as the activator of the phosphatidylinositol 4-kinase and as an adhesion protein related to vitronectin . therefore , despite high score identity between ef-1 from a wide variety of eukaryotes including mammals , plants and fungi , the presence of slightly different ef-1 genes may account for the generation of proteins with distinct biological properties . in previous studies ,
we have shown for the first time that the t. cruzi ef-1 subunit contains a glutathione s - transferase domain [ reviewed in ] .
independent investigators reported similar observations in the case of a large number of other eukaryotic ef-1 subunits .
although in our initial experiments attempts to detect a gst activity using recombinant t. cruzi ef-1 were unsuccessful perhaps due to the extremely hydrophobic nature of the molecule which precipitate in the absence of detergents , a recent report has demonstrated in rice an ef-1-dependent gst activity after purification of the protein in the presence of 20% glycerol . due to the high association of ef-1 with membrane and cytoskeleton structures
, it has being suggested that ef-1 could direct components of the protein synthesis apparatus towards the three - dimensional cytoplasmic structure of the cell .
we have hypothesized that in addition to this later biological property ef-1 could have other function ( s ) through its gst - like module . to evaluate this concept
, we have used the protozoan parasite t. cruzi as a recipient for a shuttle vector which allows overexpression of ef-1. a strong resistance of transformed organisms to the tricyclic antidepressant drug clomipramine , a lipophilic compound , was observed .
we also found that the parasites had reduced responsiveness to apoptosis stimuli ( unpublished data ) .
the simplest interpretations of these data could be the following : 1-the specific affinity of ef-1 for membranes and tubulin may have induced some distortion at the level of membrane structures rendering them less accessible to the drug , 2-the ef-1 is likely to form a fold very similar to that in the known structures of gsts allowing the conjugation of glutathione with the toxic lipophilic compound . since increased ef-1 production could be seen when the wild - type parasites were cultured in the presence of increasing concentrations of the drug , it is tempting to speculate that ef-1 might be part of a system transmitting external signals towards the protein synthetic machinery providing cells significant protection from apoptotic death . in agreement with this possibility , it is noteworthy that increased transcription of ef-1 in pancreas malignant tissue in comparison with corresponding normal pancreatic tissue has been demonstrated , suggesting that ef-1 could be a useful marker as ras gene in non - familial adenomatous polyposis .
similar findings were reported in the case of adenocarcinomas and adenomas of the colon and in gastric and oesophageal carcinomas , providing preoperative useful information for the prediction of tumor aggression .
there is a rapidly expending interest into the sir2 protein family and the structurally related molecules .
the sir2 gene family members have being cloned from a variety of species ranging from bacteria to man indicating a high degree of conservation throughout evolution [ reviewed in ] . among the mechanism of gene repression transcriptional inactivation or
sir2 was firstly described in budding yeasts to be involved with sir3 and sir4 proteins in transcriptional repression , or silencing , by modulating chromatin structure at mating - type loci ( hml and hmr ) and subtelomeric regions [ reviewed in ] .
the protein encoded by the sir2 gene belongs to a highly conserved family of closely related proteins in both prokaryotic and eukaryotic species named hst proteins ( homologous of sir two ) or sirtuins .
the biological significance of sir2-like proteins diversity is not yet understood and molecular function of sir2p as naddependent deacetylase has recently been explored .
however , the diverse cellular localizations among sir2 homologues nucleus , ( cytoplasm and mitochondria ) and the presence of sir2-like proteins in bacteria suggest that these enzymes have other physiological substrates than histones and thus additional biological functions . indeed , recent evidence indicates that sir2 proteins are involved in the regulation of p53-dependent apoptotic response via deacetylation of p53 protein .
moreover , mouse msir2 is able to deacetylate tafi68 , a pol i stimulatory factor , repressing pol i transcription in mouse extracts .
few year ago , we have cloned and sequenced a l. major gene encoding a protein bearing domain structure characteristic of sir2 proteins ( lmsir2 ) .
the expectation was to find the lmsir2 associated with the nucleus , instead , the protein had a cytoplasmic localization . however , further independent studies revealed the presence of sir2-related proteins in the cytoplasm of different species , and more recently in the mitochondria .
interestingly , l. infantum amastigotes , the vertebrate stage of the parasite , carrying extracopies of lmsir2 or l. infantum sir2 ( lisir2 ) gene , when maintained under normal axenic culture conditions , showed striking increase in the survival due to an inherent resistance to apoptosis - like death , leading to a longer stationary phase of growth .
these observations resemble those reported in the case of c. elegans and yeast [ reviewed in ] . indeed , increased dosage of sir2 gene in these organisms resulted in a their life span extension .
however , no similar effect was observed on the survival of the promastigote forms ( insect stage ) under similar culture conditions as amastigotes . taken into account the fact that promastigote energy source originate mainly from glucose , and the existence of a link between cellular metabolism and sir2 biological properties
, we examined the survival of promastigotes under starvation conditions using glucose as a unique source of energy . under these experimental conditions ,
the viability of promastigotes which overexpress sir2 gene increased significantly even in the absence of exogenous added glucose .
in fact caloric restriction in yeast by limiting glucose concentrations leads to a significant extension in the life span of mother cells .
since sir2 is a nicotinamide - adenine dinucleotide ( nad)-dependent deacetylase , it has being proposed that slowing in metabolism would free up the cofactor nad resulting in increase sir2-dependent silencing and therefore longer life span .
thus , our observations reinforce the notion of sir2 protein being coupled to physiological processes which influence gene expression regulation .
although the basic molecular and biological approaches have revealed that leishmania sir2-related gene could modulate the parasite physiology , the question remains to what extent the protein , which has a cytoplasmic localization , could interfere with gene expression processes .
it is noteworthy that overexpression of a yeast cytoplasmic protein homologous to sir2 ( hst2p ) , influences nuclear silencing events , derepressing subtelomeric silencing while increasing repression in the rdna .
the postulated hypothesis was that non - nuclear yeast hst2p can compete for a substrate ligand specifically required for telomeric repression .
the intracellular localization of key regulatory proteins tagged with a short leucine - rich motif ( the nuclear export signal or nes ) is controlled by crm1/exportin1 , which is involved in the export of these proteins from the nucleus [ reviewed in ] .
careful examination of lisir2 sequence revealed that it possesses at its carboxy - terminal region one nes - like motif ( residues 342352 : lx3lxlx3l , where l represents leucine and x any amino acid ) .
therefore , whether leishmania sir2 during very short periods of cell cycle phase , is capable of shuttling between the cytoplasm and nucleus through the nes putative sequence , await further investigations .
although reversible acetylation of histones seems to be key process in the regulation of gene transcription , strong evidence pointed to the critical role of the dynamic of acetylation - deacetylation of non - histone proteins [ reviewed in ] .
in fact , small organic molecules such a spermidine and spermine as free amines contribute to the processes leading to dna condensation , acetylation of these amine groups led to their inactivation .
given that the polyamines are known to be essential factors for the growth of the parasites in their host , it is tempting to speculate that leishmania sir2 , like hst2p , could interact with cellular factor ( s ) necessary for the cell - death machinery responsible for the ultimate destruction of the cell .
the generation of a deficiency state of sir2-related protein by gene targeting should provide a means to assess the implication of this factor in the pathways leading to the prevention of cell death .
the identification and molecular characterization of genes that confer to the parasites true cytoprotection against environmental stress , and those contributing to the " apoptotic " signaling , will shed light on cell death control mechanisms in kinetoplastids . molecular characterization of those genes will allow one to explore the possibility of modulating their function , by generating small inhibiting / activating compounds for chemotherapeutic approaches based on apoptosis manipulation in these organisms .
| members of the trypanosomatidae family comprises species that are causative of important human diseases such as chagas'disease , leishmaniasis and sleeping sickness .
a wealth of evidence has accumulated that illustrates the ability of these unicellular organisms to undergo , with or without induction ( stress conditions ) , a cell death with some features resembling apoptosis - like phenomenon . however , despite the apparent phenotypic similarities between the apoptosis - like death of kinetoplastids and mammalian nucleated cell programmed cell death ( pcd ) , the pathways seem to differ significantly .
this review analyses some of the current data related to the cell death in trypanosomatids .
special attention is given to members of conserved protein families demonstrating remarkable diversity and plasticity of function [ i.e. elongation factor-1 subunits and ; and the silent information regulator ( sir2)-related gene , showed to be associated with resistance to apoptosis - like death in leishmania ] .
the elucidation of the molecular events which tightly regulated the processes of growth arrest , differentiation and death of trypanosoma cruzi , leishmania spp and african trypanosomes , might allow not only to define a more comprehensive view of the cell death machinery in term of evolutionary origin but may also be useful to identify new target molecules for chemotherapeutic drug development and therapeutic intervention . |
SECTION 1. SHORT TITLE.
This Act may be cited as the ``Protecting Workers From Imminent
Dangers Act of 2009''.
SEC. 2. STREAMLINED PROCEDURES TO COUNTERACT IMMINENT DANGERS.
(a) Procedures.--Section 13 of the Occupational Safety and Health
Act of 1970 (29 U.S.C. 662) is amended--
(1) by striking subsections (a), (b), and (c) and inserting
the following:
``(a)(1) If the Secretary determines, on the basis of an inspection
or investigation under this Act, that a condition or practice in a
place of employment is such that an imminent danger to safety or health
exists that could reasonably be expected to cause death or serious
physical harm or permanent impairment of the health or functional
capacity of employees if not corrected immediately or before the
imminence of such danger can be eliminated through the enforcement
procedures otherwise provided by this Act, the Secretary shall inform
the employer and the affected employees and their representative of
such imminent danger and shall request that the condition or practice
be corrected immediately or that employees be immediately removed from
exposure to such danger.
``(2) The Secretary shall not prevent the entry or continued
activity of employees whose presence is necessary to avoid, correct, or
remove such imminent danger or to maintain the capacity of a continuous
process operation to resume normal operations without a complete
cessation of operations or, where a cessation of operations is
necessary, to permit such to be accomplished in a safe and orderly
manner.
``(3) If the employer refuses to comply with the request under
paragraph (1), the Secretary shall immediately issue an order requiring
the employer to cause all persons, except those employees referred to
in paragraph (2), to be withdrawn from, and to be prohibited from
entering, such area until an authorized representative of the Secretary
determines that such imminent danger and the conditions or practices
which caused such imminent danger no longer exist. The issuance of an
order under this subsection shall not preclude the issuance of a
citation under section 9 or the proposing of a penalty under section
17. The fact that an order under paragraph (3) has been issued shall be
noted in any citation issued pursuant to section 9 with respect to the
hazard involved.
``(4) Each finding made and order issued under this section shall
be given promptly to the employer by the person making such finding or
order. All such findings and orders shall be in writing, and shall be
signed by the person making them and shall contain a detailed
description of the conditions or practices which cause and constitute
an imminent danger and a description of the area of the place of
employment from which persons must be withdrawn and prohibited from
entering.
``(5) Any order issued pursuant to subsection (a) may be modified
or terminated by an authorized representative of the Secretary
following consultation with the employer and any representative of the
affected employees. Any order issued under subsection (a) shall remain
in effect until vacated, modified, or terminated by the Secretary, or
modified or vacated by the Commission pursuant to subsection (d).'';
and
(2) by redesignating subsection (d) as subsection (b) and
after such subsection inserting the following:
``(c) No person shall discharge or in any manner discriminate
against any employee because such employee has refused to perform a
duty that has been identified as the source of an imminent danger by
any order issued under subsection (a). The right to refuse to perform
such a duty shall be in addition to any other right to refuse to
perform hazardous work that is afforded to employees by this Act, by
standards or regulations issued pursuant to this Act, by contract, or
by other applicable law.
``(d)(1) Any employer notified of an order under subsection (a) or
any affected employees or representative of affected employees notified
of the issuance, modification, or termination of such an order may
apply to the Commission within 30 days of such notification for
reinstatement, modification or vacation of such order. The Commission
shall forthwith afford an opportunity for a hearing (in accordance with
section 554 of title 5, United States Code, but without regard to
subsection (a)(3) of such section) and thereafter shall issue an order,
based upon findings of fact, vacating, affirming, modifying, or
terminating the Secretary's order. The Commission may not grant
temporary relief from the issuance of any order under subsection (a).
``(2) The Commission shall take whatever action is necessary to
expedite proceedings under this subsection.
``(e) The Secretary may institute a civil action for relief,
including a permanent or temporary injunction, restraining order, or
any other appropriate order in the district court of the United States
for the district in which a place of employment is located or in which
the employer has his principal office, whenever such employer or his
agent violates or fails or refuses to comply with any order or decision
issued under this section.''.
(b) Penalties.--Section 17 of such Act is amended by redesignating
subsections (h) through (l) as subsections (i) through (m),
respectively, and by inserting after subsection (g) the following:
``(h) Any employer who fails to remove all employees from exposure
to a hazard referenced in orders issued under section 13(a) shall be
assessed a civil penalty of not less than $10,000 and not more than
$50,000 for each day during which an employee continues to be exposed
to the hazard, unless the Commission or the district court determines
the condition or practice is not of such nature as to be covered by
section 13(a).''. | Protecting Workers From Imminent Dangers Act of 2009 - Amends the Occupational Safety and Health Act of 1970 to require the Department of Labor to: (1) inform employers and employees and their representatives when a condition or practice in a place of employment is such that an imminent danger to safety or health exists that could reasonably be expected to cause death, serious physical harm, or permanent impairment of the health or functional capacity of employees if not corrected immediately or before the danger can be eliminated through prescribed enforcement procedures; and (2) request that the condition or practice be corrected immediately or that employees be immediately removed from exposure to such danger.
Requires the Department, if an employer refuses to comply with such request, to immediately issue an order requiring the employer to cause all persons to be withdrawn from, and to be prohibited from entering, such area until the Department determines that such imminent danger and the conditions or practices which caused it no longer exist. Declares that such an order shall not preclude issuing a citation or proposing a penalty for a violation under such Act.
Prohibits the Department from preventing: (1) the entry or continued activity of employees whose presence is necessary to avoid, correct, or remove such imminent danger or to maintain the capacity of a continuous process operation to resume normal operations without a complete cessation of operations; and (2) a necessary cessation of operations from being accomplished in a safe and orderly manner.
Prohibits persons from discharging or discriminating against an employee for the refusal to perform a duty that has been identified by an order as the source of an imminent danger.
Sets forth penalties for violations. |
SECTION 1. SHORT TITLE.
This act may be cited as the ``Veterans Appeals Improvement and
Modernization Act of 2009''.
SEC. 2. WAIVER OF REGIONAL OFFICE JURISDICTION OVER INCORPORATION OF
SUPPLEMENTAL EVIDENCE INTO PREVIOUSLY SUBMITTED CLAIMS.
(a) Waiver.--Section 7104 of title 38, United States Code, is
amended by adding at the end the following new subsection:
``(f) If a claimant submits new evidence in support of a case for
which a substantive appeal has been filed, such evidence shall be
submitted to the Board directly and not to a regional office of the
Department, unless the claimant requests that the evidence be reviewed
by the regional office before being submitted to the Board.''.
(b) Effective Date.--Subsection (f) of section 7104 of title 38,
United States Code, as added by subsection (a) of this section, shall
apply with respect to evidence submitted on or after the date that is
90 days after the date of the enactment of this Act.
SEC. 3. MODIFICATION OF JURISDICTION AND FINALITY OF DECISIONS OF THE
COURT OF APPEALS FOR VETERANS CLAIMS.
(a) Modification.--Subsection (a) of section 7252 of title 38,
United States Code, is amended--
(1) by striking the third sentence; and
(2) by adding at the end the following new sentence: ``The
Court shall have power to affirm, modify, reverse, remand, or
vacate and remand a decision of the Board after deciding all
relevant assignments of error raised by an appellant for each
particular claim for benefits. In a case in which the Court
reverses a decision on the merits of a particular claim and
orders an award of benefits, the Court need not decide any
additional assignments of error with respect to that claim.''.
(b) Effective Date.--The amendments made by subsection (a) shall
apply with respect to a decision of the Board of Veterans' Appeals made
on or after the date of the enactment of this Act.
SEC. 4. COMMISSION TO STUDY JUDICIAL REVIEW OF THE DETERMINATION OF
VETERANS' BENEFITS.
(a) Establishment.--There is established a commission to be known
as the ``Veterans Judicial Review Commission'' (in this section
referred to as the ``Commission'').
(b) Duties.--The Commission shall--
(1) evaluate the administrative and judicial appellate
review processes of veterans' and survivors' benefits
determinations; and
(2) make specific recommendations and offer solutions to
improve the accuracy, fairness, transparency, predictability,
timeliness, and finality of such appellate review processes,
including a recommendation as to whether the Court of Appeals
for Veterans Claims should have the authority to hear class
action or associational standing cases.
(c) Membership.--
(1) In general.--The Commission shall be composed of 13
members appointed as follows:
(A) Two individuals appointed by the Speaker of the
House of Representatives.
(B) Two individuals appointed jointly by the
President of the Senate and the President pro tempore.
(C) Two individuals appointed by the minority
leader of the House of Representatives.
(D) Two individuals appointed by the minority
leader of the Senate.
(E) Four individuals appointed by the President.
(F) One individual appointed by the President, by
and with the advice and consent of the Senate, who
shall serve as chairperson.
(2) Qualifications.--Individuals appointed under paragraph
(1) shall--
(A) be specially qualified to serve on the
Commission by virtue of their expert education,
training, or experience associated with veterans'
benefits, judicial review, constitutional law, or other
areas of expertise pertinent to the duties of the
Commission; and
(B) include individuals who--
(i) are current or retired members of the
judiciary;
(ii) are members of the legal or academic
community; or
(iii) represent--
(I) veterans service organizations;
(II) legal service organizations;
or
(III) other affected entities.
(3) Terms.--Each member shall be appointed for the life of
the Commission.
(4) Vacancy.--A vacancy in the Commission shall be filled
in the manner in which the original appointment was made.
(d) Meetings.--
(1) In general.--The Commission shall meet at the call of
the Chairperson or a majority of its members.
(2) Quorum.--A majority of the Commission shall constitute
a quorum but a lesser number may hold hearings.
(e) Pay.--
(1) Rates of pay.--Except as provided in paragraph (2),
members shall serve without pay.
(2) Travel expense.--Each member shall receive travel
expenses, including per diem in lieu of subsistence, in
accordance with applicable provisions under subchapter I of
chapter 57 of title 5, United States Code.
(f) Staff.--
(1) Director.--The Commission shall have a director who
shall be appointed by the Chairperson.
(2) Staff.--Subject to rules prescribed by the Commission,
the Chairperson may appoint additional personnel as the
Chairperson considers appropriate.
(3) Applicability of certain civil service laws.--The
director and staff of the Commission shall be appointed subject
to the provisions of title 5, United States Code, governing
appointments in the competitive service, and shall be paid in
accordance with the provisions of chapter 51 and subchapter III
of chapter 53 of that title relating to classification and
General Schedule pay rates.
(4) Experts and consultants.--Subject to rules prescribed
by the Commission, the Chairperson may procure temporary and
intermittent services under section 3109(b) of title 5, United
States Code.
(5) Staff to federal agencies.--Upon request of the
Chairperson, the head of any Federal department or agency may
detail, on a reimbursable basis, any of the personnel of that
department or agency to the Commission to assist it in carrying
out its duties under this section.
(g) Powers of Commission.--
(1) Hearings and sessions.--The Commission may, for the
purpose of carrying out this Act, hold hearings, sit and act at
times and places, take testimony, and receive evidence as the
Commission considers appropriate. The Commission may administer
oaths or affirmations to witnesses appearing before it.
(2) Powers of members and agents.--Any member or agent of
the Commission may, if authorized by the Commission, take any
action which the Commission is authorized to take by this
section.
(3) Obtaining official data.--The Commission may secure
directly from any department or agency of the United States
information necessary to enable it to carry out this Act. Upon
request of the Chairperson of the Commission, the head of that
department or agency shall furnish that information to the
Commission.
(4) Mails.--The Commission may use the United States mails
in the same manner and under the same conditions as other
departments and agencies of the United States.
(5) Administrative support services.--Upon the request of
the Commission, the Administrator of General Services shall
provide to the Commission, on a reimbursable basis, the
administrative support services necessary for the Commission to
carry out its responsibilities under this Act.
(h) Reports.--
(1) Interim report.--Not later than July 1, 2010, the
Commission shall submit to Congress an interim report of the
evaluation and recommendations made under subsection (b).
(2) Final report.--Not later than December 31, 2010, the
Commission shall submit to Congress a final report on the
activities of the Commission, including--
(A) specific recommendations and solutions proposed
by the Commission under subsection (b), including a
recommendation as to whether the Court of Appeals for
Veterans Claims should have the authority to hear class
action or associational standing cases;
(B) relevant background and statistical information
associated with such recommendations and solutions; and
(C) other information the Commission determines
appropriate.
(i) Termination.--The Commission shall terminate on the date that
is two years after the date on which the Commission submits the final
report pursuant to section (h)(2). | Veterans Appeals Improvement and Modernization Act of 2009 - Provides that if a veteran claimant submits evidence in support of a case for which a substantive appeal has been filed to the Board of Veterans' Appeals, such evidence shall be submitted directly to the Board and not to a regional office of the Department of Veterans Affairs (VA), unless the claimant requests that the evidence first be reviewed by the regional office.
Empowers the Court of Appeals for Veterans Claims to affirm, modify, reverse, remand, or vacate and remand a decision of the Board after deciding all relevant assignments of error raised on appeal. Provides that whenever the Court reverses a decision on the merits of a particular claim and orders an award of benefits, the Court need not decide any additional assignments of error relating to that claim.
Establishes the Veterans Judicial Review Commission to evaluate and make specific decisions to improve the administrative and judicial appellate review processes of veterans' and survivors' benefits determinations. |
Miranda Lambert, left, and Jason Aldean perform "Drowns the Whiskey" at the 52nd annual CMA Awards at Bridgestone Arena on Wednesday, Nov. 14, 2018, in Nashville, Tenn. (Photo by Charles Sykes/Invision/AP) (Associated Press)
Miranda Lambert, left, and Jason Aldean perform "Drowns the Whiskey" at the 52nd annual CMA Awards at Bridgestone Arena on Wednesday, Nov. 14, 2018, in Nashville, Tenn. (Photo by Charles Sykes/Invision/AP) (Associated Press)
Chris Stapleton won the most awards at the 2018 Country Music Association Awards and had the show's best performance, almost capping a perfect night.
That was until Keith Urban surprisingly won the top prize — entertainer of the year — moments before the three-hour show wrapped Wednesday night.
Urban's actress-wife, Nicole Kidman, was in tears as the singer walked onstage to collect the award at the Bridgestone Arena in Nashville, Tennessee.
"Baby girl, I love you so much," he said. "I'm shocked beyond shocked."
Urban last won entertainer of the year in 2005 and also beat out Luke Bryan, Jason Aldean and Kenny Chesney for the prize.
"I wish my dad was alive to see this," the Australian performer said.
Stapleton, however, cleaned house at the CMAs, winning four awards including male vocalist, song and single of the year.
"I want to thank my kids who put up with me being gone quite a bit and not getting to be as a good daddy that I would always like to be," said the father of four and soon to be five since his wife, singer-songwriter Morgane Stapleton, is pregnant.
Stapleton also won the performance of the night: His supergroup featuring Mavis Staples, Maren Morris, Marty Stuart and his wife gave a soulful and powerful performance of "Friendship," a song made famous by Pop Staples, the iconic singer's late father. They then performed "I'll Take You There," jamming onstage along with a choir. They earned a standing ovation from the audience.
When Stapleton won single of the year — where he won as both a performer and producer — earlier in the show, he said he was "thinking about the people in California right now" and he wants to "dedicate this award to them."
He was referring to the 12 people who were killed at a Southern California country music bar last week, who were also honored at the top of the show when Garth Brooks held a moment of silence as the names of the victims were displayed on the screen.
"Tonight let's celebrate their lives. Let the music unite us with love," Brooks said.
The CMAs, which aired on ABC, also took time to honor those affected by the deadly wildfires in California.
"We send our love to you," said Carrie Underwood, also mentioning the "brave firefighters."
Underwood worked triple-duty as co-host, performer and nominee at the CMAs. She was teary-eyed when she won female vocalist of the year.
"Thank you God. I have been blessed with so much in my life," she said. "Thank you family. Thank you country music. Thank you country music family. ...It's all about family around here."
She kept the positive and uplifting theme of the show going when she gave a rousing performance of her song "Love Wins." It features the lyrics, "I believe you and me are sisters and brothers/And I believe we're made to be here for each other."
Kacey Musgraves, the only woman nominated for album of the year, won the prize for "Golden Hour."
"This is really, really crazy timing — 10 years ago today I moved to Nashville. That's so crazy," she said.
"I'm so proud of it," she said of the pop-leaning country album, which was inspired by Sade, the Bee Gees and others. "It's inspired by this beautiful universe, and all of you, and mostly love."
Dan + Shay lost in all four categories they were nominated in but gave an impressive performance of their hit "Tequila." When Brothers Osborne won vocal duo of the year, John Osborne said, "I thought this was going to go to Dan + Shay. Make some noise for those boys."
"I don't know why we keep winning this," John Osborne said when he first walked onstage.
"If this was in Florida there definitely would be a recount," added T.J. Osborne, which earned laughs from the crowd.
Luke Combs, who has the year's most-streamed country music album, sang onstage with a red cup in his hand and won new artist of the year.
"God, I love country music, man," said Combs.
Brooks performed a touching new song dedicated to his wife, Trisha Yearwood, who was teary-eyed and was hearing the song for the first time. Recent Country Hall of Famer Ricky Skaggs performed alongside Brad Paisley and Urban.
Underwood and Paisley returned as CMA hosts for the 11th time this year, telling jokes at the top of the show, which ranged from Lady Gaga and Bradley Cooper's "A Star Is Born" to Underwood's pregnancy.
Underwood seemingly revealed a secret about the child, saying it will be a "Willie" after Paisley repeatedly asked about the sex of the baby. | – Chris Stapleton won the most awards at the 2018 Country Music Association Awards and had the show's best performance, almost capping a perfect night. That was until Keith Urban surprisingly won the top prize—entertainer of the year—moments before the three-hour show wrapped Wednesday night, the AP reports. Urban's wife, Nicole Kidman, was in tears as the singer walked onstage to collect the award at the Bridgestone Arena in Nashville, Tennessee. "Baby girl, I love you so much," he said. "I'm shocked beyond shocked." Urban, who last won entertainer of the year in 2005, also beat out Luke Bryan, Jason Aldean, and Kenny Chesney for the prize. "I wish my dad was alive to see this," the Australian performer said. Stapleton won four awards including male vocalist, song, and single of the year. "I want to thank my kids who put up with me being gone quite a bit and not getting to be as a good daddy that I would always like to be," said the father of four. When Stapleton won single of the year—where he won as both a performer and producer—he said he was "thinking about the people in California" and he wanted to dedicate the award to them. He was referring to the 12 people who were killed at a country music bar last week, who were also honored at the top of the show when Garth Brooks held a moment of silence as the names of the victims were displayed on the screen. "Tonight let's celebrate their lives. Let the music unite us with love," Brooks said. Click for a list of winners. |
“The Daily Show” developed the program over the last three years without publicizing it, but now, because Mr. Stewart is preparing to leave the show, he has taken it into the open, urging other shows to develop their own programs to bring more veterans into the industry.
“This is ready to franchise. Please steal our idea,” Mr. Stewart said in an interview at his Manhattan studio recently. “It isn’t charity. To be good in this business you have to bring in different voices from different places, and we have this wealth of experience that just wasn’t being tapped.”
Photo
Veterans are less likely to struggle to find work after war — their unemployment rate has been lower than the comparable civilian rate for years — but few land in the entertainment industry, according to the industry group Veterans in Film and Television.
Karen Kraft, a board member of the group, which tries to draw more veterans into the industry, said the small number of military veterans in show business was partly because military service supplanted the years of internships and entry-level jobs often required to establish a beachhead in the industry. The phenomenon may also be connected to a cultural divide that has kept quirky, left-leaning Hollywood and the high-and-tight world of the military from connecting.
“Sometimes people want to apologize for being in the military out here; it’s so misunderstood,” Ms. Kraft, a former soldier who became a producer in Los Angeles, said of Hollywood. “It’s a creative industry, and they tend to see military people as a bunch of rule followers.”
Efforts to bring veterans into the field have included workshops by the Writers Guild of America and projects by big-name producers and directors, among them Bruce Cohen and Judd Apatow, that involve young veterans.
Mr. Stewart may at first seem an unexpected bridge for a Hollywood-military divide. For years the host built his audience by playing straight man to the often absurd truths of the global “war on terror,” serving up scathing satire on American involvement in the Middle East in his longstanding segments “Mess o’Potamia” and “Crisis in Israfghyianonanaq.” At the same time, though, he has been an advocate for troops, visiting the wounded at hospitals, visiting Arlington National Cemetery and in 2011 doing a comedy tour of bases in Afghanistan.
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“I knew I had very strong opinions about what we were doing over there, and I wanted to visit the individuals who were part of the effort to gain a perspective on it,” Mr. Stewart said. He added: “Most of all, I realized it was unbelievably hot, nothing but sand. I knew we were nation-building there. I didn’t realize we were nation-building on Mars.”
In 2013, American Corporate Partners, a mentoring nonprofit group, asked Mr. Stewart to take a veteran under his wing and help find that person a job in television, which involved making a few calls.
Photo
“Jon said he wanted to help, but wanted to do more than just drop his name,” said Sid Goodfriend, who runs the program.
Instead, the staff of “The Daily Show” developed an intense five-week immersion program to give veterans a crash course in their business, with behind-the-scenes looks at areas including talent booking and editing.
They put out word to veterans’ groups but did not mention that the boot camp was at “The Daily Show,” an attempt to weed out fans and focus instead on veterans who really wanted to work in the industry.
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“There are well-worn channels into this industry that are closed off to veterans,” Mr. Stewart said. “You get into the television industry generally by going to certain colleges known for having good television programs, getting internships and getting to know people who work in the industry. A lot of veterans never had that opportunity because they were busy at war. This is a way to give them that chance.”
He added that the veterans he had hired had been assets and “way less whiny” than most of his hires.
“The Daily Show” created a program to offer the benefits of an internship — experience and connections — in a form that veterans working full-time jobs could accommodate. Each class of 24 meets once a week in the evening. The program ends with a career fair that has landed a handful of vets jobs in television.
One of them is Justine Cabulong, a former Marine lieutenant who served in Mongolia and Afghanistan and is now a production coordinator at “The Daily Show” — a job that among other things includes a brief comedy routine before the show that warns audience members that if they don’t remain seated and keep their phones turned off, they “will be detained.”
“I feel like the Marines was a good preparation for ‘The Daily Show,’ actually,” she said. “The show is high tempo; it’s pretty chaotic; you have to work together. We might be on the road, not be getting much sleep. But at the same time, it’s not a war zone here. No one is shooting at us. Yes, the printer might have just died, but we can call the printer guy.” ||||| For release 10:00 a.m. (EDT) Thursday, March 22, 2018 USDL-18-0453 Technical information: (202) 691-6378 * [email protected] * www.bls.gov/cps Media contact: (202) 691-5902 * [email protected] EMPLOYMENT SITUATION OF VETERANS -- 2017 The unemployment rate for veterans who served on active duty in the U.S. Armed Forces at any time since September 2001--a group referred to as Gulf War-era II veterans-- edged down to 4.5 percent in 2017, the U.S. Bureau of Labor Statistics reported today. The jobless rate for all veterans declined from 4.3 percent to 3.7 percent in 2017. About 41 percent of Gulf War-era II veterans had a service-connected disability in August 2017, compared with 24 percent of all veterans. This information was obtained from the Current Population Survey (CPS), a monthly sample survey of about 60,000 households that provides data on employment and unemployment in the United States. Data about veterans are collected monthly in the CPS; these monthly data are the source of the 2017 annual averages presented in this news release. In August 2017, a supplement to the CPS collected additional information about veterans on topics such as service-connected disability and veterans' current or past Reserve or National Guard membership. Information from the supplement is also presented in this release. The supplement was co-sponsored by the U.S. Department of Veterans Affairs and by the U.S. Department of Labor's Veterans' Employment and Training Service. For more information, see the Technical Note, which provides definitions of terms used in this release. Highlights from the 2017 data: --The unemployment rate for male veterans (3.6 percent) declined over the year, and the rate for female veterans (4.1 percent) changed little in 2017. The unemployment rate for male veterans was not statistically different from the rate for female veterans. (See table A.) --Among the 370,000 unemployed veterans in 2017, 59 percent were age 25 to 54, 37 percent were age 55 and over, and 4 percent were age 18 to 24. (See table 2A.) --Veterans with a service-connected disability had an unemployment rate of 4.3 percent in August 2017, little different from veterans with no disability (4.5 percent). (See table 7.) --About 1 in 3 employed veterans with a service-connected disability worked in the public sector in August 2017, compared with about 1 in 5 veterans with no disability. (See table 8.) --In 2017, the unemployment rate of veterans varied across the country, ranging from 1.7 percent in Maine and Vermont to 7.3 percent in Rhode Island. (See table 6A.) The Veteran Population In 2017, 20.4 million men and women were veterans, accounting for about 8 percent of the civilian noninstitutional population age 18 and over. About 10 percent of all veterans were women. In the survey, veterans are defined as men and women who have previously served on active duty in the U.S. Armed Forces and who were civilians at the time these data were collected. Veterans are more likely to be men than were nonveterans, and they also tend to be older. In part, this reflects the characteristics of veterans who served during World War II, the Korean War, and the Vietnam era, all of whom are now over 60 years old. Veterans who served during these wartime periods accounted for 39 percent (8.1 million) of the total veteran population in 2017. Thirty-six percent of veterans (7.4 million) served during Gulf War era I (August 1990 to August 2001) or Gulf War era II (September 2001 forward). About a quarter (4.9 million) served outside the designated wartime periods. (See tables 1 and 2A.) Gulf War-era II Veterans In 2017, there were 4.1 million veterans who had served during Gulf War era II (September 2001 forward). Seventeen percent of these veterans were women, compared with about 4 percent of veterans from World War II, the Korean War, and the Vietnam era. Seventy percent of all Gulf War-era II veterans were between the ages of 25 and 44. (See tables 1 and 2A.) Among Gulf War-era II veterans, the unemployment rate for men was not statistically different from the rate for women in 2017. The unemployment rate for men edged down to 4.3 percent in 2017. The rate for women, at 5.5 percent, was essentially unchanged from the prior year. (See table A.) In 2017, the unemployment rate for male Gulf War-era II veterans, at 4.3 percent, was the same as the rate for male nonveterans. Among men age 25 to 34, Gulf War-era II veterans had a higher unemployment rate (6.0 percent) than did nonveterans (4.5 percent). Among men age 45 to 54, however, Gulf War-era II veterans had a lower unemployment rate (1.5 percent) than did nonveterans (3.1 percent). (See table 2B.) Among women, the unemployment rate for Gulf War-era II veterans (5.5 percent) was higher than the rate for nonveterans (4.1 percent) in 2017. By age, unemployment rates for female veterans and nonveterans were similar, with one exception: 25- to 34-year-old female veterans had a rate of 8.0 percent, higher than the rate of 4.5 percent for their nonveteran counterparts. (See table 2C.) Employed Gulf War-era II veterans were about twice as likely to work in the public sector in 2017 as employed nonveterans--27 percent and 13 percent, respectively. Among the employed, 15 percent of Gulf War-era II veterans worked for the federal government, compared with 2 percent of nonveterans. (See table 5.) In August 2017, 47 percent of Gulf War-era II veterans reported serving in Iraq, Afghanistan, or both locations. These veterans had an unemployment rate of 4.4 percent, little different from Gulf War-era II veterans who served elsewhere (4.5 percent). (See table 10.) Gulf War-era I Veterans Of the 3.3 million veterans who served during Gulf War era I (August 1990 to August 2001), the proportion who were women (15 percent in 2017) was similar to that of Gulf War-era II veterans (17 percent). Nearly all (99 percent) Gulf War-era I veterans were age 35 and over in 2017, compared with 54 percent of Gulf War-era II veterans. (See tables 1 and 2A.) In 2017, the unemployment rates for male and female Gulf War-era I veterans were 3.0 percent and 3.4 percent, respectively, lower than the rates for their Gulf War-era II veteran counterparts (4.3 percent and 5.5 percent). The difference in unemployment rates reflects, at least in part, the older age profile of veterans who served during Gulf War era I. Younger people--whether veterans or nonveterans--tend to have higher unemployment rates than older people. (See tables 2B and 2C.) Veterans of Other Service Periods In 2017, 4.9 million veterans had served on active duty during "other service periods," mainly between the Korean War and the Vietnam era and between the Vietnam era and Gulf War era I. All veterans from this period of service were 45 years or older at the time of the survey. Twenty-two percent of these veterans were age 45 to 54 in 2017, another 39 percent were age 55 to 64, and another 39 percent were age 65 and over. (See table 2A.) In 2017, 1 in 10 veterans of other service periods were women. Among veterans of other service periods, the unemployment rate for men (3.2 percent) was little different than the rate for women (2.7 percent). (See table 1.) Veterans with a Service-connected Disability In August 2017, about 4.9 million veterans, or 24 percent of the total, had a service- connected disability. Veterans with a service-connected disability are assigned a disability rating by the U.S. Department of Veterans Affairs or the U.S. Department of Defense. Ratings range from 0 to 100 percent, in increments of 10 percentage points, depending on the severity of the condition. (See table 7.) The unemployment rate for veterans with a service-connected disability was 4.3 percent in August 2017, little different than the rate for veterans with no disability (4.5 percent). The labor force participation rate for veterans with a service-connected disability (48.4 percent) was not statistically different than the rate for veterans with no disability (49.2 percent). Among veterans with a service-connected disability, 28 percent reported a disability rating of less than 30 percent, while another 41 percent had a rating of 60 percent or higher. In August 2017, veterans with a service-connected disability rating of less than 30 percent were much more likely to be in the labor force than those with a rating of 60 percent or higher (53.5 percent and 37.7 percent, respectively). The unemployment rate for veterans with a disability rating of less than 30 percent was 3.3 percent, not statistically different than for those with a disability rating of 60 percent or higher (4.8 percent). Among veterans who served during Gulf War era II, 41 percent (1.7 million) reported a service-connected disability and nearly half of these veterans had a service- connected disability rating of 60 percent or higher. In August 2017, 75.8 percent of all Gulf War era II veterans with a service-connected disability were in the labor force, lower than the 85.5 percent for veterans from this period with no service- connected disability. Among Gulf War-era II veterans, the unemployment rate for those with a service-connected disability was 3.9 percent, not statistically different from those with no disability (4.8 percent). In August 2017, 28 percent (946,000) of veterans who served during Gulf War era I reported a service-connected disability. Their labor force participation rate was lower (65.6 percent) than the rate for veterans from the era who did not have a disability (85.9 percent). The unemployment rate for Gulf War-era I veterans with a service-connected disability (4.3 percent) was not statistically different than that for Gulf War-era I veterans without a service-connected disability (2.8 percent). Among the 1.7 million veterans with a service-connected disability from World War II, the Korean War, and the Vietnam era, 15.4 percent were in the labor force in August 2017, lower than the 23.1 percent of veterans from these periods who did not have a service-connected disability. The unemployment rate of veterans from these wartime periods with a service-connected disability was 3.9 percent, lower than their counterparts with no disability (7.9 percent). Thirteen percent (633,000) of veterans who served during other service periods reported a service-connected disability in August 2017. The labor force participation rate of these veterans (38.6 percent) was lower than their counterparts without a service- connected disability (48.3 percent), while the unemployment rate was not statistically different for veterans with a service-connected disability (6.7 percent) and those with no disability (3.6 percent). Regardless of period of service, many veterans with a service-connected disability worked in the public sector. In August 2017, 33 percent of employed veterans with a disability worked in federal, state, or local government, compared with 19 percent of veterans with no disability and 13 percent of nonveterans. Nineteen percent of employed veterans with a disability worked for the federal government, compared with 7 percent of veterans with no disability and 2 percent of nonveterans. (See table 8.) Reserve and National Guard Membership In August 2017, about one-third of Gulf War-era veterans (August 1990 to present) were current or past members of the Reserve or National Guard. Labor force participation rates were higher for veterans who were current or past members of the Reserve or National Guard (82.4 percent), compared with veterans who were never members (79.4 percent). Among Gulf War-era veterans, those who were current or past members of the Reserve or National Guard had a lower unemployment rate than those who had never been members (2.5 percent and 4.5 percent, respectively). (See table 9.) _____________________________________________________________________________ | | | Adjustments to Veteran Population Estimates | | | |Effective with data for November 2017, estimates for veterans incorporate | |population controls derived from an updated Department of Veterans Affairs | |population model. In accordance with usual practice, BLS did not revise | |estimates for previous years. Information about the updated veteran | |population model is available from the Department of Veterans Affairs at | |www.va.gov/vetdata/docs/Demographics/New_Vetpop_Model/Vetpop16_Overview.pdf. | |_____________________________________________________________________________| ||||| NEW YORK (AP) — Jon Stewart says Aug. 6 will be his last night hosting Comedy Central's "The Daily Show."
FILE - This Nov. 30, 2011 file photo shows television host Jon Stewart during a taping of "The Daily Show with Jon Stewart" in New York. Stewart says Aug. 6, 2015 will be his last night hosting Comedy... (Associated Press)
Stewart set the date in the closing moments of Monday's edition of the parody newscast. With tongue in cheek, he promised to wear a suit for that finale, and to shower beforehand. Then he recanted, saying he would be clad in overalls and skip the shower.
The network said "The Daily Show" will then go on hiatus for the rest of the summer.
Stewart's finale will end a 16-year reign of sharp satire and ample silliness. He first broke the news of his planned departure in February.
His successor will be South African comedian Trevor Noah, a recent addition to the stable of "Daily Show" correspondents. No start date for Noah has been announced.
___
Online:
http://www.cc.com/ | – Jon Stewart's last day on The Daily Show will be Aug. 6, but there may be a few employees sticking around that he's been hiring on the sly: military veterans. In a surprise revelation in the New York Times, Stewart cops to a stealth "boot camp" he's been running for a couple of years to help former service members break into the TV industry and, in some cases, into employment with Stewart's own show. The intensive five-week "crash course" that teaches everything from editing to talent booking meets once a week in the evenings to accommodate veterans with full-time work schedules; the program wraps up with a career fair that has succeeded in placing some students in actual TV jobs. The unemployment rate for veterans in 2014 was 5.3%—7.2% for vets who've been on active duty at any time since 9/11, the Bureau of Labor Statistics notes. But vets drawn to the entertainment industry may have a hard time breaking in since they spent prime learning years with the military instead of in the studio, and because they may be perceived as too rigid for such a "creative industry," a board member of the Veterans in Film and Television industry group tells the Times. The host had been keeping the program on the down-low to keep show superfans out, among other reasons, but now that he's leaving the show, he hopes other TV programs will follow suit. "This is ready to franchise. Please steal our idea," he says, per the Times. Bonus: Stewart tells the Times military hires are "way less whiny" than other workers. |
lung volume measurements are useful for characterizing the severity of respiratory
diseases , evaluating the results of interventions , and determining prognosis .
( , ) patients with restrictive lung disease ( rld ) can
present with reduced tlc , whereas those with chronic obstructive lung disease ( old )
can present with increased tlc ( usually as a result of increased rv ) .
( ) various methods can be used in
order to determine lung volumes , including whole - body plethysmography ( wbp ) , gas
dilution methods , and radiological techniques.(- )
currently , wbp and the multiple - breath helium dilution method are used in pulmonary
function laboratories in order to measure tlc and rv .
any of the abovementioned
methods can be used provided that the equipment and maneuvers are in accordance with
the recommended technical standards .
( , )
however , wbp is considered the gold standard by some researchers .
( ) the single - breath helium dilution ( sbhd ) method is a simpler , cheaper , and more
widely available alternative method for evaluating alveolar volume with equipment
that is less complex than a plethysmograph , having the operational advantage of
being performed in conjunction with dlco determination .
however , because the sbhd
method depends on the air that is mobilized during a single respiratory maneuver , it
can underestimate lung volumes when compared with wbp in patients with a markedly
uneven distribution of ventilation .
( , )
although determination of alveolar volume by the sbhd method for measuring dlco is
used worldwide , the value of this technique in determining lung volumes in patients
with old or rld has yet to be established . in view of the abovementioned considerations ,
the objective of the present study was
to compare lung volumes as measured by the sbhd method with lung volumes as measured
by wbp in individuals with normal lung function , as well as in patients with old or
rld of varying degrees of severity .
in addition , we sought to develop equations to
estimate tlc and rv as measured by wbp ( tlcwbp and rvwbp ,
respectively ) on the basis of tlc and rv as measured by the sbhd method
( tlcsbhd and rvsbhd , respectively ) and adjusted for the
degree of airflow obstruction .
this was a retrospective cross - sectional study involving 142 consecutive patients who
underwent spirometry , static lung volume measurements by wbp , and single - breath
pulmonary diffusing capacity measurements in the pulmonary physiology laboratory of
a referral hospital .
we selected patients with old caused by copd and patients in
whom spirometry results were suggestive of rld .
we excluded patients whose
spirometry results showed mixed obstructive and restrictive lung disease ,
indeterminate lung disease , or old of causes other than copd .
the control group ( n =
27 ) comprised 8 patients ( 6 of whom were smokers ) who had normal spirometry results
and who had undergone wbp and pulmonary diffusing capacity measurements in routine
care , as well as 19 volunteers who were recruited from the community , who were
nonsmokers , who had no respiratory complaints or diseases , who had normal chest
x - rays , and who had undergone the three tests in the same period in order to
determine whether the reference standards used in the laboratory were appropriate .
the ethical and methodological aspects of the study project were approved by the
local research ethics committee .
we collected data regarding age ( years ) , gender , weight ( kg ) , height ( cm ) , body mass
index ( kg / m , and smoking history ( pack - years ) .
all pulmonary function
tests were performed with a masterscreen body spirometer ( jeger , wrzburg , germany )
and were in accordance with the technical recommendations in the brazilian thoracic
association guidelines for pulmonary function testing .
( ) patients underwent spirometry , wbp , and dlco
testing always in the same sequence and at the same time of day .
all tests were
performed before and after the administration of 400 g of albuterol .
we calculated
tlcsbhd by summing the alveolar volume as measured by dlco testing
and the anatomical dead space .
the reference values for spirometry , lung volumes , and dlco were
those described elsewhere.(- ) in order to confirm the diagnosis of copd by spirometry , we used an
fev1/fvc ratio after bronchodilator use 0.70 .
( ) the severity of airflow obstruction was
determined on the basis of fev1 , as recommended by the american thoracic
society .
( ) mild to moderate
old was defined as an fev1 50% of the predicted value ; severe old was
defined as an fev1 of 35 - 49% of the predicted value ; and very severe old
was defined as an fev1 < 35% of the predicted value .
only 5 patients
presented with mild old . therefore , they were evaluated in conjunction with those
who presented with moderate old . for the diagnosis of rld
, we used the following criteria : an fev1/fvc
ratio after bronchodilator use > 0.80 ; reduced vc ( an fvc < 80% of the
predicted value ) ; and reduced tlc ( a tlc < 80% of the predicted value ) . for
data analysis
, we used the median in order to divide the patients with rld into two
groups according to the severity of the disease ( a tlc > 72% of the predicted
value indicating less severe disease and a tlc < 72% of the predicted value
indicating more severe disease ) .
statistical analysis was performed with the statistical analysis system software ,
version 9.1 ( sas institute , cary , nc , usa ) .
for the evaluation of variables with one observation , one - way
anova was performed to determine the differences among the groups . whenever levene 's
test revealed heterogeneity of variance , welch 's anova was performed . for
complementation of results ,
the possible influence of
the covariates gender , age , weight , height , body mass index , and smoking history was
tested by analysis of covariance . for the evaluation of variables for each lung
function method ,
for complementation of significant
effects in relation to the method and group , the tukey - kramer test was performed ( p
< 0.05 ) .
the goodness of fit of the model was tested by analysis of residuals
and determination of normality by the kolmogorov - smirnov test ( p > 0.01 ) , the
anderson - darling test , and the cramr - von mises test ( p > 0.005 ) . in both
models
, we obtained partial or residual pearson correlations , eliminating the effect
of factors in order to determine the association between variables .
bland - altman plots ( ) were used in
order to determine the differences in tlc and rv between the two methods .
we developed
prediction equations to estimate the differences in tlc and rv between the two
methods by means of stepwise multiple linear regression , variables with a value of p
< 0.10 being included in the models .
in the present study , 169 individuals underwent spirometry and lung volume
measurements by wbp and the sbhd method in an open system .
of the 169 individuals ,
27 had normal spirometry results , 93 had old , and 49 had rld .
the patients with old
were stratified as follows : patients with mild to moderate old ( 29 patients ) ;
patients with severe old ( 29 patients ) ; and patients with very severe old ( 35
patients ) .
the patients with rld were stratified as follows : patients with less
severe disease ( 25 patients ) ; and patients with more severe disease ( 24 patients ) .
anthropometric data , duration of smoking , smoking history , and pulmonary function
test results , stratified by lung function status , are presented in table 1 .
table 1 anthropometric characteristics , smoking history , and functional
parameters in 169 individuals stratified by lung function
status .
figure 1 shows mean tlc and rv ( in absolute
values and in percentage of predicted ) . in all groups ,
tlcwbp and
rvwbp values were higher than tlcsbhd and
rvsbhd values ( p < 0.01 ) , the discrepancy between the two
methods being most pronounced in the old group and the difference increasing
progressively as the severity of airflow obstruction increased . a comparison between
the rv / tlc ratio obtained by wbp and the rv / tlc ratio obtained by the sbhd method
provided further evidence of the discrepancy between the two methods . in the
individuals with normal lung function ,
those ratios were 0.36 and 0.29 ,
respectively . in the group of patients with mild to moderate
old , those ratios were
0.53 and 0.38 , respectively ; in the group of patients with severe old , those ratios
were 0.60 and 0.43 , respectively ; and in the group of patients with very severe old ,
those ratios were 0.66 and 0.47 , respectively . in the group of patients with less
severe rld ,
those ratios were 0.44 and 0.32 , respectively , and in the group of
patients with more severe rld , those ratios were 0.45 and 0.39 , respectively .
figure 1 comparison of tlc and rv values as measured by whole - body
plethysmography ( wbp ) with tlc and rv values as measured by the
single - breath helium dilution ( sbhd ) method ( in absolute values and in
percentage of predicted ) in different groups of patients , stratified by
lung function status . in all groups ,
the tlc and rv values obtained by
wbp were higher than those obtained by the sbhd method ( p < 0.01 ) .
old : obstructive lung disease ; mild / mod : mild / moderate ; and rld :
restrictive lung disease .
capital letters represent comparisons of
values obtained by wbp , whereas lower - case letters represent comparisons
of values obtained by the sbhd method . matching letters indicate absence
of statistically significant differences .
two - way anova ( methods and
groups ) ; p < 0.05 .
table 2 shows the differences in tlc and rv
between wbp and the sbhd method ( in absolute values and in percentage of predicted )
in the groups studied . in the groups of patients with rld and normal spirometry
results , the difference in tlc between the two methods ranged from 0.61 l to 0.80 l
( from 10.8% of the predicted value to 13.1% of the predicted value ; p > 0.05 ) .
in addition , the difference in rv between the two methods ranged from 0.52 l to 0.75
l ( from 30.8% of the predicted value to 43.4% of the predicted value ; p >
0.05 ) . in the groups of patients with mild to moderate old and severe old ,
the
difference in tlc between the two methods ranged from 1.58 l to 2.00 l ( from 30.5%
of the predicted value to 38.2% of the predicted value ; p > 0.05 ) , and the
difference in rv between the two methods ranged from 1.46 l to 2.03 l ( from 80.7% of
the predicted value to 99.4% of the predicted value ; p > 0.05 ) .
the group of
patients with very severe old differed from all of the other groups analyzed ,
showing the largest differences between the two methods regarding tlc ( 3.09 l ; 50.4%
of the predicted value ) and rv ( 2.89 l ; 139.5% of the predicted value ) .
table 2 differences between tlc and rv values as measured by whole - body
plethysmography and tlc and rv values as measured by the single - breath
helium dilution method in 169 individuals stratified by lung function
status .
the correlations between fev1/fvc and the differences in tlc and rv values
between the two methods in the individuals with normal spirometry results , in the
patients with old , and in the patients with rld are shown in figure 2 ( panels a , b , and c , respectively ) .
the best
correlations were observed in the group of patients with old ( r = 0.47 for
tlcwbp - sbhd in % of predicted and r = 0.54 for
rvwbp - sbhd in % of predicted ) . when the individuals with normal
spirometry results and the patients with old were analyzed as a whole ,
the
correlation between fev1 in % of predicted and tlcwbp - sbhd in
% of predicted increased to r = 0.61 ( p < 0.0001 ) , as did the correlation
between fev1 in % of predicted and rvwbp - sbhd in % of
predicted ( r = 0.640 ; p < 0.0001 ) .
figure 2 correlations of the difference between tlc as measured by whole - body
plethysmography ( wbp ) and tlc as measured by the single - breath helium
dilution ( sbhd ) method ( left column ) , as well as of the difference
between rv as measured by wbp and rv as measured by the sbhd method
( right column ) , with the fev1/fvc ratio in % in individuals with normal
lung function ( a ) , in patients with obstructive lung disease ( b ) , and in
patients with restrictive lung disease ( c ) .
for the sample as a whole ( n = 169 ) , there was a
moderate positive correlation between tlcwbp and tlcsbhd ( r =
0.71 ; p < 0.001 ) , as well as between rvwbp and rvsbhd ( r
= 0.62 ; p < 0.0001 ) . in the group of individuals with normal spirometry results
and in that of patients with rld , the coefficients of correlation between
tlcwbp and tlcsbhd and between rvwbp and
rvsbhd were , respectively , 0.92 and 0.51 ( p < 0.001 ) , whereas in
the group of patients with old , those correlation coefficients were , respectively ,
0.55 and 0.36 ( p < 0.001 ) .
we used bland - altman plots in order to compare tlcwbp with
tlcsbhd and rvwbp with rvsbhd .
the data are
shown separately for each group , by lung function status , in figure 3 .
the group of patients with rld showed the smallest
difference between the two methods for both variables ; the largest differences were
observed in the patients with old and higher lung volumes .
figure 3 bland - altman plots of the difference between tlc as measured by
whole - body plethysmography ( wbp ) and tlc as measured by the
single - breath helium dilution ( sbhd ) method ( left column ) , as well as of
the difference between rv as measured by wbp and rv as measured by the
sbhd method ( right column ) , in function of the mean of the tlc values
( in l ) obtained by the two methods ( left column ) and of the mean of the
rv values ( in l ) obtained by the two methods ( right column ) in
individuals with normal lung function ( a ) , in patients with obstructive
lung disease ( b ) , and in patients with restrictive lung disease ( c ) .
the
solid line represents the mean , and the dashed lines represent the sd (
1.96 ) .
for the sample as a whole ( n = 169 )
, the difference in tlc values between the two
methods was associated with the fev1/fvc ratio ( r = 0.75 ; p <
0.001 ) , fev1 ( r = 0.51 ; p < 0.001 ) , and dlco ( r = 0.39 ; p <
0.001 ) . likewise , the difference in rv values between the two methods correlated
with the fev1/fvc ratio ( r = 0.75 ; p < 0.0001 ) , fev1 ( r
= 0.53 ; p < 0.0001 ) , and dlco ( r = 0.41 ; p < 0.0001 ) .
there was no
significant correlation between the difference in lung volumes and fvc ( p >
0.05 ) .
for the 93 patients with old , the coefficient of correlation between
tlcwbp and tlcsbhd was 0.57 ( p < 0.001 ) and the
coefficient of correlation between rvwbp and rvsbhd was 0.56
( p < 0.001 ) . in the patients with old , we used a regression equation in order
to predict tlcwbp and rvwbp on the basis of tlcsbhd
and rvsbhd . the fev1/fvc ratio ( % ) , fev1 ( l ) , and
dlco ( ml .
mmhg were included in the models . in the
univariate analysis for tlcwbp - sbhd ,
the adjusted coefficients for
fev1/fvc , fev1 , and dlco were , respectively , r
= 0.32 , r = 0.14 , and r = 0.07 , whereas for
rvwbp - sbhd , the adjusted coefficients for the same variables were ,
respectively , r = 0.30 , r = 0.14 , and r = 0.07 .
in the multivariate analysis , fev1 and dlco lost significance and were
excluded from the models .
the regression equation to predict the difference in tlc
between the two methods in the patients with old was as follows : where y = tlcwbp - sbhd in l and x = fev1/fvc in %
( r = 0.33 ; adjusted r = 0.32 ) .
the regression equation to predict the difference in rv between the two methods was
as follows : where y = rvwbp - sbhd in l and x = fev1/fvc in % ( r
= 0.31 ; adjusted r = 0.30 ) .
we were unable to develop equations for individuals with normal lung function and
those with rld .
our results showed the following : 1 ) tlcwbp and rvwbp values
were higher than tlcsbhd and rvsbhd values , regardless of the
lung function status ; 2 ) the magnitude of the difference in lung volumes between the
two methods was associated with the fev1/fvc ratio , progressively
increasing with the degree of airflow obstruction ; 3 ) lung volumes as measured by
wbp can be estimated on the basis of the values obtained by the sbhd method provided
that the values are corrected for the severity of airflow obstruction .
our study showed that , in the individuals with normal lung function and in those with
rld , the sbhd method underestimated lung volumes when compared with wbp .
comparable
values between the two techniques ( ) or a difference of 0.21 l in tlc in individuals with
normal spirometry results have previously been described .
( ) in another study , when compared with the
multiple - breath helium dilution method , wbp overestimated tlc by 0.47 l or 7.2% in
normal individuals .
( ) in the old patients in the present study , the difference between the lung volumes
obtained by wbp and those obtained by the sbhd method increased or decreased
proportionally to the increase in airflow obstruction and air trapping .
various
studies have compared lung volumes as measured by different methods in patients with
old .
( ) compared
tlc as measured by plethysmography with tlc as measured by chest hrct in patients
with copd and found a difference of 1.12 l ( 17.3% ) between the two .
( ) showed that ,
in patients with copd , wbp systematically overestimates lung volumes in comparison
with the multiple - breath helium dilution method and ct , and that the discrepancy is
most pronounced in individuals with fev1 < 30% of the predicted
value .
in contrast , in 815 males with mild airflow obstruction , the sbhd method
underestimated tlcwbp by 0.75 l. ( ) a difference of up to 1.08
l has been reported
between tlcwbp and tlc as measured by the multiple - breath helium dilution
method .
( , , , )
major discrepancies ( of up to 2.25 l ) have been observed between tlcsbhd
and tlc as measured by the multiple - breath helium dilution method in the presence of
old .
( , ) the different results across studies might be related to the cause of old , the
varying degrees of airflow obstruction , and , in particular , the methods used in
order to measure lung volumes .
in addition to measuring the ventilated volume ,
plethysmography measures areas of air trapping .
conversely , the helium dilution
technique measures only the air that is ventilated . in patients with airflow
obstruction , there are variations in time constants of the respiratory system and in
the distribution of ventilation , and there is early collapse of the airways during
exhalation , which impairs lung emptying and causes air trapping .
these physiological
abnormalities help to explain the difference between the values obtained by wbp and
those obtained by the sbhd method or the multiple - breath helium dilution method in
individuals with old .
( , ) the two helium dilution methods differ in terms of lung volume measurements .
the sbhd
method is a fast and simple technique in which only one ventilatory maneuver is used
( in order to determine dlco ) .
( )
in addition , the sbhd method requires less effort from patients during pulmonary
function testing .
( , , ) in contrast , the multiple - breath helium dilution
method requires a longer test time , allowing a more even distribution of the inhaled
gas so that it is in equilibrium with the alveolar air .
( , ) a comparison between the two techniques showed that they
provide comparable results in individuals without airflow obstruction but show
differences of up to 34% in patients with more severe obstruction .
( , , ) one of the statistical resources that we used in order to compare the findings of wbp
with those of the sbhd method was the linear correlation test .
the test showed a
correlation of 0.92 in the individuals with normal spirometry results or rld and of
0.55 in the patients with old .
a correlation of 0.98 between tlcwbp and
tlcsbhd in 32 normal individuals and of 0.70 between
tlcwbp and tlcsbhd in patients with old had previously
been reported .
( ) however , in our
study , bland - altman plots ( ) were
used for analysis of the lung volumes as measured by the two methods and showed
that , despite a strong correlation between the two in the individuals with normal
spirometry results , there was discordance between the two methods in that group of
patients .
the concordance between the two methods for determining lung volumes was
better in the group of patients with rld , as evidenced by a narrower 95% ci and a
higher concentration of data around the mean .
in contrast , in the group of patients
with old , the difference between the two methods was more pronounced , especially in
the patients with high lung volumes .
the limitations of using linear correlation in
order to evaluate the performance of two methods for measuring the same variable
have previously been described , as have the advantages of using bland - altman plots
in such cases .
( ) the linear regression equations that allow us to estimate tlcwbp and
rvwbp values on the basis of tlcsbhd and rvsbhd
values adjusted for the degree of airflow obstruction constitute an important
contribution of our study .
these equations can be used in patient care in situations
in which only spirometry and pulmonary diffusing capacity testing are available .
although equations for tlc adjusted for the degree of airflow obstruction have
previously been described , ( ) the
gold standard used was the multiple - breath helium dilution technique rather than
wbp .
considering the coefficients of determination for the regression equations
developed in our study , we emphasize that most of the difference between the two
methods remains unexplained .
the number of patients with
mild old in the present study was very small , reflecting the profile of patients
treated at a referral university hospital .
likewise , the number of patients with
severe rld was small , which limited the stratification of rld patients .
in addition ,
rvsbhd was obtained by subtracting fvc from tlcsbhd ; the
use of fvc instead of slow vc possibly contributed to the lower accuracy of the
method , especially in the patients with old .
furthermore , the prediction equations
should be validated in other patient populations in order to increase the external
validity of the study . in conclusion
, our study demonstrated that tlcwbp and rvwbp
values were higher than tlcsbhd and rvsbhd values in normal
individuals and in patients with rld or old .
the discrepancy between the two methods
for measuring lung volumes was most pronounced in the group of patients with old
caused by copd , the magnitude of the difference being directly associated with the
degree of airflow obstruction .
the linear regression equations described in the
present study allow us to adjust tlcsbhd and rvsbhd values for
airflow , predicting the lung volumes as measured by wbp .
therefore , the relatively
simple , faster , and more widely available sbhd method , used in order to determine
pulmonary diffusing capacity , has potential for expanded use .
however , additional
studies are needed in order to validate the equations before they can be used in
clinical practice .
comparar resultados de cpt e vr obtidos pelo mtodo de diluio de hlio em
respirao nica ( dhru ) com aqueles obtidos por pletismografia de corpo
inteiro ( pci ) em indivduos com funo pulmonar normal , portadores de
distrbio ventilatrio obstrutivo ( dvo ) e portadores de distrbio
ventilatrio restritivo ( dvr ) com diferentes nveis de gravidade e elaborar
equaes para estimar cpt e vr por dhru .
estudo transversal retrospectivo com 169 indivduos , dos quais ,
respectivamente , 93 , 49 e 27 apresentavam dvo , dvr e espirometria normal .
a discrepncia
entre os mtodos foi mais acentuada no grupo com dvo e se relacionou com a
gravidade da obstruo ao fluxo areo .
no grupo com dvo , o coeficiente de
correlao da comparao entre os dois mtodos foi de 0,57 e 0,56 para cpt e
vr , respectivamente ( p < 0,001 para ambos ) .
para predizer os valores de
cpt e vr por pci utilizando os respectivos valores por dhru foram utilizadas
equaes de regresso , corrigidas de acordo com os grupos estudados .
somente
foi possvel criar equaes de regresso para predizer as diferenas de cpt
e vr entre os dois mtodos para pacientes com dvo .
essas equaes foram ,
respectivamente , cptpci - dhru em l = 5,264 0,060
vef1/cvf ( r= 0,33 ; r ajustado =
0,32 ) e vrpci - dhru em l = 4,862 0,055 vef1/cvf
( r= 0,31 ; r ajustado = 0,30 ) .
a correo de cpt e vr obtidos por dhru pode melhorar a acurcia desse
mtodo para avaliar os volumes pulmonares em pacientes com dvo .
a mensurao dos volumes pulmonares til para caracterizar a gravidade de
doenas respiratrias , avaliar resultados de intervenes e determinar
prognsticos .
( , ) a cpt pode estar reduzida nas
doenas pulmonares restritivas ou estar aumentada , geralmente custa do aumento
do vr , nos processos obstrutivos crnicos .
( ) diversos mtodos podem ser utilizados para
determinar os volumes pulmonares , como a pletismografia de corpo inteiro ( pci ) ,
a diluio de gases e as tcnicas radiolgicas.(- ) atualmente , tanto a pci como o mtodo de diluio de hlio
por respiraes mltiplas so usados em laboratrios de funo pulmonar para
medir a cpt e o vr .
qualquer um desses mtodos pode ser utilizado , desde que
tanto os equipamentos como as manobras obedeam aos padres tcnicos
recomendados , ( , ) embora a pci seja considerada
o padro ouro por alguns pesquisadores .
( ) uma alternativa mais simples , disponvel e barata para avaliar o volume alveolar ,
que utiliza equipamentos menos complexos em comparao ao pletismgrafo e tem a
vantagem operacional de estar acoplada determinao da dlco a tcnica de
diluio de hlio por respirao nica .
entretanto , esse mtodo , por estar na
dependncia do ar que mobilizado durante uma nica manobra ventilatria , pode
subestimar os valores dos volumes pulmonares em comparao com os da pci em
pacientes com acentuada falta de uniformidade na distribuio da
ventilao .
( , ) embora a determinao do
volume alveolar atravs do mtodo de diluio de hlio por respirao nica para
mensurar a dlco seja mundialmente utilizada , o valor dessa tcnica na
determinao dos volumes pulmonares nos distrbios ventilatrios obstrutivos
( dvo ) ou restritivos ( dvr ) no est estabelecido .
considerando os aspectos acima , o objetivo do presente estudo foi comparar a
medida dos volumes pulmonares obtidos atravs do mtodo de diluio de hlio em
respirao nica com os valores mensurados atravs de pci em indivduos com
funo pulmonar normal , em portadores de dvo e em portadores de dvr com
diferentes nveis de gravidade .
adicionalmente , pretendeu - se , com os resultados
obtidos , elaborar equaes para estimar a cpt e o vr com base na tcnica da
diluio de hlio por respirao nica e sua correo em funo do grau de
obstruo ao fluxo areo .
o presente estudo transversal retrospectivo incluiu 142 pacientes sequenciais que
realizaram espirometria , medidas de volumes pulmonares estticos por pci e
medidas de difuso pulmonar pelo mtodo da respirao nica no laboratrio de
fisiologia pulmonar de um hospital de referncia .
foram selecionados pacientes
com dvo por dpoc e pacientes com espirometria sugestiva de dvr .
foram excludos
pacientes cuja espirometria apresentou distrbio ventilatrio misto ou
indeterminado ou ainda dvo por outras causas que no dpoc .
o grupo controle ( n =
27 ) foi constitudo por 8 pacientes ( 6 desses tabagistas ) com espirometria
normal e que haviam realizado pci e difuso pulmonar na rotina assistencial e
por 19 voluntrios recrutados da comunidade , no tabagistas , sem queixas ou
doenas respiratrias , com radiografia de trax normal e que haviam realizado os
trs exames no mesmo perodo para testar a adequao dos padres de referncia
utilizados no laboratrio .
o projeto foi aprovado pelo comit de tica em
pesquisa da instituio quanto aos seus aspectos ticos e metodolgicos .
de cada paciente foram coletados dados referentes idade ( anos ) , sexo , peso
( kg ) , estatura ( cm ) , ndice de massa corprea ( kg / m ) e carga
tabgica ( anos - mao ) . todos os exames funcionais pulmonares foram realizados com
o equipamento masterscreen body ( jeger , wrzburg , alemanha ) de acordo com as
recomendaes tcnicas preconizadas nas diretrizes de funo pulmonar da
sociedade brasileira de pneumologia e tisiologia .
( ) os pacientes realizaram espirometria , pci e
dlco , sempre na mesma sequncia e no mesmo turno do dia .
todos os testes foram
realizados antes e depois da administrao de 400 g de salbutamol .
a
cpthe foi obtida atravs da soma do volume alveolar medido no
exame de difuso e do espao morto anatmico .
o vrhe foi obtido pela
subtrao da cvf da cpthe . a calibrao dos gases e da cabine
pletismogrfica foi realizada diariamente , antes do incio dos exames .
os
padres de normalidade utilizados para a espirometria , para os volumes
pulmonares e para a dlco foram os descritos previamente.(- ) para confirmar o diagnstico de dpoc pela espirometria foi utilizada a relao
vef1/cvf aps uso de broncodilatador 0,70 .
( ) a classificao da gravidade
da obstruo ao fluxo areo foi realizada pelo vef1 , conforme
recomendao da american thoracic society . ( ) foi considerado dvo leve a
moderado valores de vef1 50% do previsto ; dvo grave , valores de
vef1 entre 35% e 49% do previsto ; e dvo muito grave , valores de
vef1 < 35% do previsto .
como somente 5 pacientes
apresentavam dvo leve , os mesmos foram estudados em conjunto com os pacientes
com dvo moderado .
para o diagnstico de dvr , foram utilizados os seguintes critrios : relao
vef1/cvf aps o uso de broncodilatador > 0,80 , reduo da cv
( cvf < 80% do previsto ) e reduo da cpt ( cpt < 80% do previsto ) .
para
a anlise dos dados , utilizou - se a mediana para separar os pacientes em dois
grupos de acordo com a gravidade da restrio ( cpt > 72% do previsto ,
restrio menos grave ; cpt < 72% do previsto , restrio mais grave ) .
a anlise estatstica foi realizada com o pacote estatstico statistical
analysis system , verso 9.1 ( sas institute , cary , nc , eua )
. os
dados coletados foram expressos em mdia , erro - padro e ic95% .
para a avaliao
das variveis com uma observao , procedeu - se a one - way anova
verificando - se a diferena entre grupos .
quando verificada heterogeneidade de
varincias pelo teste de levene , procedeu - se a anova de welch .
para verificar possveis
influncias das covariveis sexo , idade , peso , estatura , ndice de massa
corprea e carga tabgica , considerou - se o modelo de anlise de covarincia .
para a avaliao das variveis para cada tipo de mtodo de funo pulmonar ,
procedeu - se a anova de modelos mistos . as complementaes de efeitos
significativos
em relao a tipo de mtodo e grupo foram realizadas
utilizando - se o teste de tukey - kramer ( p < 0,05 ) . o estudo de adequao do
modelo foi realizado atravs da anlise dos resduos e da verificao de
normalidade atravs dos testes de kolmogorov - smirnov ( p > 0,01 ) ,
anderson - darling e cramr - von mises ( p > 0,005 ) .
em ambos os modelos , foram
obtidas correlaes parciais ou residuais de pearson , eliminando - se o efeito dos
fatores para verificar a associao entre as variveis .
o mtodo grfico de bland e altman ( ) foi utilizado para comparar diferenas na cpt e no
vr . os limites de concordncia foram calculados como 1,96 dp das diferenas .
equaes de predio para estimar a diferena na cpt e no vr entre os mtodos
foram elaboradas atravs da anlise de regresso linear mltipla
( stepwise ) , sendo as variveis com valor de p < 0,10
consideradas nos modelos .
para todas as anlises , foram utilizados os valores
obtidos aps o uso de broncodilatador .
foram estudados 169 indivduos atravs de espirometria e mensurao de volumes
pulmonares por pci e pelo mtodo de diluio de hlio por respirao nica em
sistema aberto ; desses , 27 indivduos apresentavam espirometria normal , 93
apresentavam dvo , e 49 apresentavam dvr .
os pacientes portadores de dvo foram
estratificados da seguinte forma : portadores de doena leve a moderada , 29
pacientes ; de doena grave , 29 pacientes ; e de doena muito grave , 35 pacientes .
os pacientes com dvr foram estratificados da seguinte maneira : portadores de
distrbio menos grave , 25 pacientes ; e de doena mais grave , 24 pacientes .
antropomtricos , tempo de tabagismo , carga tabgica e resultados dos
testes de funo pulmonar , estratificados de acordo com o diagnstico funcional ,
esto apresentados na tabela 1 .
tabela 1 caractersticas antropomtricas , histria tabgica e parmetros
funcionais de 169 indivduos estratificados de acordo com o
diagnstico funcional pulmonar .
na figura 1 , so mostradas
as mdias dos
valores absolutos e em percentual do previsto da cpt e do vr .
em todos os
grupos , os valores da cpt e do vr mensurados por pci foram superiores aos
medidos pelo mtodo de diluio de hlio ( p < 0,01 ) , sendo a discrepncia
maior no grupo de pacientes com dvo , com aumento progressivo da diferena
medida que havia piora da obstruo ao fluxo areo . a discrepncia entre os dois
mtodos tambm foi observada quando comparadas as relaes vr / cpt obtidas por
pci e pelo mtodo de diluio de hlio por respirao nica .
esses valores foram
de , respectivamente , 0,36 e 0,29 , em indivduos normais ; 0,53 e 0,38 , no grupo
com dvo leve e moderado ; 0,60 e 0,43 , no grupo com dvo grave ; 0,66 e 0,47 , no
grupo com dvo muito grave ; 0,44 e 0,32 , no grupo com dvr menos grave ; e 0,45 , e
0,39 , no grupo com dvr mais grave .
figura 1 comparao das variveis cpt e vr em valores absolutos e em
percentual do previsto medidos pela pletismografia de corpo inteiro
( pci ) e pelo mtodo de diluio do hlio em respirao nica nos
diferentes grupos de pacientes , estratificados de acordo com o
diagnstico funcional pulmonar . em todos os grupos , os valores
obtidos pela pci foram maiores que os valores obtidos pelo mtodo do
hlio ( p < 0,01 ) .
dvo : distrbio ventilatrio obstrutivo ;
lev / mod : leve / moderado ; e dvr : distrbio ventilatrio restritivo .
letras maisculas representam comparaes entre os valores da pci e
letras minsculas entre os do mtodo do hlio .
anova com dois fatores ( mtodos e grupos ) ; p < 0,05 .
na tabela 2 , so mostradas as diferenas
entre a pci e o mtodo de diluio de hlio para a cpt e o vr em valores
absolutos e em percentual do previsto nos grupos estudados . a diferena na cpt
nos grupos de pacientes com dvr ou espirometria normal variou de 0,61 l a 0,80 l
( 10,8% do previsto a 13,1% do previsto ; p > 0,05 ) .
o vr nos mesmos grupos
variou de 0,52 l a 0,75 l ( 30,8% do previsto a 43,4% do previsto ; p >
0,05 ) .
no grupo de pacientes com dvo leve / moderado e grave , a diferena na cpt
entre os dois mtodos variou de 1,58 l a 2,00 l ( 30,5% do previsto a 38,2% do
previsto ; p > 0,05 ) , e a diferena no vr variou de 1,46 l a 2,03 l ( 80,7%
do previsto a 99,4% do previsto ; p > 0,05 ) .
o grupo portador de dvo muito
grave diferiu de todos os outros grupos analisados , apresentando as maiores
diferenas entre os dois mtodos tanto para cpt ( 3,09 l ; 50,4% do previsto )
quanto para vr ( 2,89 l ; 139,5% do previsto ) .
tabela 2 diferenas entre resultados obtidos por pletismografia de corpo
inteiro e mtodo de diluio do hlio por respirao nica para as
variveis cpt e vr em 169 indivduos estratificados de acordo com o
diagnstico funcional pulmonar .
as correlaes entre vef1/cvf e as diferenas nos valores
de cpt e vr
medidos pelos dois mtodos nos pacientes com espirometria normal , com dvo e com
dvr so mostradas na figura 2 ( painis a ,
b e c , respectivamente ) .
as melhores correlaes foram observadas no grupo de
pacientes com dvo ( r = 0,47 para o cptpci - he
num mesmo grupo , a
correlao entre vef1 em % do previsto e cptpci - he em %
do previsto aumentou para r = 0,61 ( p < 0,0001 ) e , entre vef1
em % do previsto e vrpci - he
em % do previsto , a correlao tambm
aumentou ( r = 0,640 ; p < 0,0001 ) .
figura 2 correlaes entre as diferenas mensuradas por pletismografia de
corpo inteiro e pelo mtodo de diluio do hlio em respirao nica
das variveis cpt ( coluna da esquerda ) e vr ( coluna da direita ) em
funo da relao vef1/cvf em % nos grupos de indivduos com padro
ventilatrio normal ( a ) , padro ventilatrio obstrutivo ( b ) e padro
ventilatrio restritivo ( c ) .
a associao entre os valores da cptpci e cpthe foi
estudada atravs do teste de correlao de pearson .
quando considerados todos os
indivduos na anlise ( n = 169 ) , foi observada uma correlao moderada e
positiva entre os valores de cpt ( r = 0,71 ; p < 0,001 ) e vr ( r = 0,62 ; p
<
no grupo com espirometria normal e no
de portadores de dvr , os coeficientes de correlao entre os valores de cpt e vr
mensurados pelas duas tcnicas foram , respectivamente , de 0,92 e 0,51 ( p
<
0,001 ) , enquanto , nos portadores de dvo , esses foram de , respectivamente , 0,55 e
0,36 ( p < 0,001 ) .
adicionalmente , utilizamos o mtodo grfico de bland e altman para comparar os
valores da cpt e do vr mensurados atravs dos dois mtodos
. os dados so
mostrados separadamente por grupos , de acordo com o diagnstico funcional , na
figura 3 . o grupo de portadores de dvr
apresentou a menor diferena entre os mtodos para ambas as variveis ; as
maiores diferenas foram observadas nos pacientes com dvo e volumes pulmonares
maiores .
figura 3 disposies grficas de bland e altman entre as diferenas
mensuradas por pletismografia de corpo inteiro e pelo mtodo de
diluio do hlio em respirao nica das variveis cpt ( coluna da
esquerda ) e vr ( coluna da direita ) em funo da mdia dos valores da
cpt ( coluna da esquerda ) e do vr ( coluna da direita ) , em
l , obtidas
pelos dois mtodos nos grupos de indivduos com padro ventilatrio
normal ( a ) , padro ventilatrio obstrutivo ( b ) e padro ventilatrio
restritivo ( c ) .
a linha contnua indica a mdia dos valores , e as
linhas tracejadas indicam o desvio - padro ( 1,96 ) .
a diferena da cpt mensurada pelos dois mtodos , quando considerada toda a
amostra ( n = 169 ) , se associou com a relao vef1/cvf ( r = 0,75 ; p
< 0,001 ) , vef1 ( r = 0,51 ; p < 0,001 ) e dlco ( r = 0,39 ; p
< 0,001 ) .
do mesmo modo , a diferena do vr entre os dois mtodos se
correlacionou com a relao vef1/cvf ( r = 0,75 ; p < 0,0001 ) ,
vef1 ( r = 0,53 ; p < 0,0001 ) e dlco ( r = 0,41 ; p <
0,0001 ) .
no houve correlao significativa entre a diferena dos volumes
pulmonares e a cvf ( p > 0,05 ) .
o coeficiente de correlao entre os valores
obtidos pelos dois mtodos , quando considerados apenas os 93 pacientes com dvo ,
foi de 0,57 para a cpt ( p < 0,001 ) e de 0,56 para o vr ( p < 0,001 ) .
para predizer a cptpci e o vrpci a partir da
cpthe e do vrhe nos pacientes com dvo , foi utilizada
uma equao de regresso .
foram includos nos modelos a relao
vef1/cvf ( % ) , vef1 ( l ) e dlco ( ml . min .
mmhg .
na anlise univariada para cptpci - he , os
coeficientes ajustados para vef1/cvf , vef1 e dlco foram
de , respectivamente , r= 0,32 , r= 0,14 e r2
= 0,07 , enquanto os coeficientes ajustados para
vrpci - he para as mesmas variveis foram de , respectivamente ,
r= 0,30 , r= 0,14 e r= 0,07 .
na
anlise multivariada , vef1 e dlco perderam a significncia e foram
excludos dos modelos . a equao de
regresso para predizer a diferena da cpt
entre os dois mtodos nos pacientes com dvo foi a seguinte : onde y = cptpci - he em l e x = vef1/cvf em % ( r2
= 0,33 ; r ajustado = 0,32 ) a equao de regresso para predizer
a diferena do vr foi a seguinte : onde y = vrpci - he em l e x = vef1/cvf em % ( r2
= 0,31 ; r ajustado = 0,30 ) .
no foi possvel elaborar uma equao para indivduos normais e para aqueles com
dvr .
nossos resultados demonstraram o seguinte : 1 ) os valores cptpci e
vrpci foram maiores do que cpthe e vrhe ,
independentemente do diagnstico funcional pulmonar ; 2 ) a magnitude da diferena
dos volumes pulmonares obtidos pelos dois mtodos se associou com a relao
vef1/cvf , aumentando progressivamente com o grau de obstruo ao
fluxo areo ; 3 ) os volumes pulmonares medidos por pci podem ser estimados a
partir dos valores obtidos pelo mtodo de diluio do hlio por respirao nica
se realizada a correo para a obstruo ao fluxo areo .
nosso estudo mostrou que o mtodo da diluio do hlio por respirao nica
subestimou os volumes pulmonares em comparao com os da pci em indivduos
normais ou com dvr .
valores comparveis entre as duas tcnicas ( ) ou uma diferena na cpt de
0,21 l em indivduos com espirometria normal foram descritos previamente .
( ) em outro estudo , a pci
superestimou o valor da cpt em relao ao mtodo de diluio do hlio por
respiraes mltiplas em 0,47 l ou 7,2% em indivduos normais .
( ) nos pacientes com dvo , a diferena entre os volumes pulmonares determinados pelos
dois mtodos em nosso estudo variou proporcionalmente com o aumento da obstruo
ao fluxo areo e do aprisionamento areo .
diversos estudos compararam os volumes
pulmonares obtidos por diferentes tcnicas em pacientes com dvo .
( ) compararam a cpt
mensurada por pletismografia e por tcar de trax em portadores de dpoc e
observaram uma diferena de 1,12 l ( 17,3% ) .
( ) demonstraram que ,
em indivduos com dpoc , a pci sistematicamente superestima os volumes pulmonares
em relao ao mtodo de diluio do hlio por respirao mltipla e tc e que a
discrepncia maior nos indivduos com vef1 <
o mtodo de diluio do
hlio por respirao nica subestimou a cpt determinada por pci em 0,75 l. ( ) uma diferena de at 1,08 l
na cpt foi descrita entre pci e a tcnica de diluio do hlio por respirao
mltipla .
( , , , ) discrepncias maiores na cpt de at 2,25 l foram
observadas entre os dois mtodos de diluio do hlio na presena de dvo .
( , ) as disparidades nos resultados dos diferentes estudos podem estar associadas com
a causa do dvo , com os graus variados de obstruo ao fluxo areo e ,
principalmente , com os mtodos usados para medir os volumes pulmonares .
o mtodo
pletismogrfico mede , alm do volume ventilado , reas pulmonares com
aprisionamento de ar .
de forma contrria , a tcnica de diluio do hlio mensura
apenas o ar que ventilado .
nos pacientes com obstruo ao fluxo areo , h
variaes nas constantes de tempo e na distribuio da ventilao , e ocorre
colapso precoce das vias areas na expirao , o que prejudica o esvaziamento
pulmonar e causa aprisionamento areo .
essas anormalidades fisiolgicas ajudam a
explicar a diferena entre os valores obtidos pela pci e pela tcnica de
diluio do hlio por respirao nica ou mltipla em indivduos com dvo .
( , ) os dois mtodos de diluio do hlio apresentam diferenas entre si na estimativa
dos volumes pulmonares . a tcnica por respirao nica uma tcnica simples e
rpida , que utiliza apenas uma manobra ventilatria e que utilizada para
determinar a dlco .
( )
adicionalmente , a tcnica por respirao nica requer menor esforo por parte do
paciente durante a realizao da prova de funo pulmonar .
( , , )
diferentemente , no mtodo da diluio do hlio por respiraes mltiplas , o
tempo do teste maior , permitindo uma distribuio mais adequada do gs inalado
de forma que esse fique em equilbrio com o ar alveolar .
( , ) a comparao entre as duas tcnicas mostrou que as
mesmas fornecem resultados comparveis em indivduos sem obstruo ao fluxo
areo , mas apresentam discrepncia de at 34% nos pacientes com maior grau de
obstruo .
( , , ) um dos recursos estatsticos que usamos para comparar os achados da pci e do
mtodo de diluio do hlio por respirao nica foi o teste de correlao
linear .
esse teste mostrou uma correlao de 0,92 nos indivduos com
espirometria normal ou com padro restritivo e de 0,55 nos pacientes com padro
obstrutivo .
uma correlao de 0,98 entre a cpt obtida pelos dois mtodos em 32
indivduos normais e de 0,70 em pacientes com dvo havia sido relatada
previamente .
( )
entretanto , em nosso estudo , a anlise dos volumes obtidos pelas duas tcnicas
atravs do mtodo grfico de bland e altman ( ) mostrou que , apesar da correlao forte entre as
duas medidas nos indivduos com espirometria normal , houve uma discordncia
entre os dois mtodos nesse grupo de pacientes . a concordncia entre as duas
tcnicas de determinao dos volumes pulmonares foi melhor no grupo de pacientes
com dvr , se traduzindo por um ic95% mais estreito e uma maior concentrao dos
dados em torno da mdia .
contrariamente , no grupo de pacientes com dvo , a
discrepncia tornou - se mais acentuada , principalmente nos pacientes com grandes
volumes pulmonares . as limitaes da correlao linear para avaliar o desempenho
de duas tcnicas que mensuram a mesma varivel foram descritas previamente ,
assim como as vantagens do uso do mtodo grfico de bland e altman nessa
situao .
( ) uma contribuio importante do nosso estudo so as equaes de regresso linear
que permitem estimar os valores de cpt e vr correspondentes ao mtodo
pletismogrfico a partir dos valores obtidos pela tcnica da diluio do hlio
por respirao nica corrigidos para o grau de obstruo ao fluxo areo .
essas
equaes podem ser utilizadas na prtica assistencial em situaes e locais nos
quais somente a espirometria e a difuso pulmonar estejam disponveis .
equaes
semelhantes para a cpt com correo para o grau de obstruo ao fluxo areo
foram descritas anteriormente ( ) ; entretanto , o padro ouro utilizado foi a tcnica de
diluio do hlio por respirao mltipla e no a pci .
ressaltamos que , conforme
os coeficientes de determinao das equaes de regresso obtidas no nosso
estudo , grande parte da diferena entre os mtodos permanece inexplicada .
a nossa
casustica de pacientes com dvo leve foi muito pequena , refletindo o perfil de
pacientes atendidos em um hospital universitrio de referncia .
do mesmo modo ,
no foi possvel incluir um maior nmero de pacientes com dvr grave , o que
limitou a estratificao dos pacientes com doena restritiva .
ainda , o
vrhe foi obtido atravs da subtrao cpthe cvf ; o
uso da cvf , ao invs da cv lenta , pode ter contribudo para uma maior falta de
acurcia no mtodo , especialmente nos pacientes com dvo .
adicionalmente ,
necessrio validar as equaes de predio com outras populaes de pacientes
para aumentar a validade externa do estudo .
em concluso , nosso estudo demonstrou que o mtodo pletismogrfico apresentou
valores maiores tanto para a cpt como para o vr em comparao com o mtodo de
diluio do hlio por respirao nica em indivduos normais e em pacientes com
dvr e dvo . as maiores discrepncias entre os dois mtodos de determinao de
volumes pulmonares foram observadas no grupo de pacientes com dvo por dpoc ,
estando a magnitude da diferena diretamente associada obstruo do fluxo
areo . as equaes de regresso linear descritas no presente estudo permitem que
os valores de cpt e vr , obtidos atravs da tcnica de diluio do hlio por
respirao nica , sejam ajustados para o fluxo areo , predizendo os valores dos
volumes pulmonares que seriam obtidos pela pci .
desse modo , a tcnica
relativamente simples , mais rpida e mais disponvel da diluio do hlio por
respirao nica , empregada no contexto da determinao da capacidade de difuso
pulmonar , tem seu potencial de uso expandido .
entretanto , estudos adicionais so
necessrios para validar as equaes antes que as mesmas sejam utilizadas na
prtica clnica . | objective : to compare tlc and rv values obtained by the single - breath helium dilution
( sbhd ) method with those obtained by whole - body plethysmography ( wbp ) in
patients with normal lung function , patients with obstructive lung disease
( old ) , and patients with restrictive lung disease ( rld ) , varying in
severity , and to devise equations to estimate the sbhd results .
methods : this was a retrospective cross - sectional study involving 169 individuals , of
whom 93 and 49 presented with old and rld , respectively , the remaining 27
having normal lung function . all patients underwent spirometry and lung
volume measurement by both methods . results : tlc and rv were higher by wbp than by sbhd .
the discrepancy between the
methods was more pronounced in the old group , correlating with the severity
of airflow obstruction . in the old group ,
the correlation coefficient of the
comparison between the two methods was 0.57 and 0.56 for tlc and rv ,
respectively ( p < 0.001 for both ) .
we used regression equations ,
adjusted for the groups studied , in order to predict the wbp values of tlc
and rv , using the corresponding sbhd values .
it was possible to create
regression equations to predict differences in tlc and rv between the two
methods only for the old group .
the tlc and rv equations were , respectively ,
tlcwbp - sbhd in l = 5.264 0.060 fev1/fvc
( r2 = 0.33 ; adjusted r2 = 0.32 ) and
rvwbp - sbhd in l = 4.862 0.055 fev1/fvc
( r2 = 0.31 ; adjusted r2 = 0.30 ) .
conclusions : the correction of tlc and rv results obtained by sbhd can improve the
accuracy of this method for assessing lung volumes in patients with old .
however , additional studies are needed in order to validate these equations . |
SECTION 1. SHORT TITLE; AMENDMENT OF 1986 CODE.
(a) Short Title.--This Act may be cited as the ``Rural Renaissance
Act II of 2005''.
(b) Amendment of 1986 Code.--Except as otherwise expressly
provided, whenever in this Act an amendment or repeal is expressed in
terms of an amendment to, or repeal of, a section or other provision,
the reference shall be considered to be made to a section or other
provision of the Internal Revenue Code of 1986.
SEC. 2. CREDIT TO HOLDERS OF RURAL RENAISSANCE BONDS.
(a) In General.--Part IV of subchapter A of chapter 1 (relating to
credits against tax) is amended by adding at the end the following new
subpart:
``Subpart H--Nonrefundable Credit to Holders of Rural Renaissance Bonds
``Sec. 54. Credit to holders of rural renaissance bonds.
``SEC. 54. CREDIT TO HOLDERS OF RURAL RENAISSANCE BONDS.
``(a) Allowance of Credit.--In the case of a taxpayer who holds a
rural renaissance bond on a credit allowance date of such bond, which
occurs during the taxable year, there shall be allowed as a credit
against the tax imposed by this chapter for such taxable year an amount
equal to the sum of the credits determined under subsection (b) with
respect to credit allowance dates during such year on which the
taxpayer holds such bond.
``(b) Amount of Credit.--
``(1) In general.--The amount of the credit determined
under this subsection with respect to any credit allowance date
for a rural renaissance bond is 25 percent of the annual credit
determined with respect to such bond.
``(2) Annual credit.--The annual credit determined with
respect to any rural renaissance bond is the product of--
``(A) the credit rate determined by the Secretary
under paragraph (3) for the day on which such bond was
sold, multiplied by
``(B) the outstanding face amount of the bond.
``(3) Determination.--For purposes of paragraph (2), with
respect to any rural renaissance bond, the Secretary shall
determine daily or caused to be determined daily a credit rate
which shall apply to the first day on which there is a binding,
written contract for the sale or exchange of the bond. The
credit rate for any day is the credit rate which the Secretary
or the Secretary's designee estimates will permit the issuance
of rural renaissance bonds with a specified maturity or
redemption date without discount and without interest cost to
the qualified issuer.
``(4) Credit allowance date.--For purposes of this section,
the term `credit allowance date' means--
``(A) March 15,
``(B) June 15,
``(C) September 15, and
``(D) December 15.
Such term also includes the last day on which the bond is
outstanding.
``(5) Special rule for issuance and redemption.--In the
case of a bond which is issued during the 3-month period ending
on a credit allowance date, the amount of the credit determined
under this subsection with respect to such credit allowance
date shall be a ratable portion of the credit otherwise
determined based on the portion of the 3-month period during
which the bond is outstanding. A similar rule shall apply when
the bond is redeemed or matures.
``(c) Limitation Based on Amount of Tax.--
``(1) In general.--The credit allowed under subsection (a)
for any taxable year shall not exceed the excess of--
``(A) the sum of the regular tax liability (as
defined in section 26(b)) plus the tax imposed by
section 55, over
``(B) the sum of the credits allowable under this
part (other than subpart C thereof, relating to
refundable credits).
``(2) Carryover of unused credit.--If the credit allowable
under subsection (a) exceeds the limitation imposed by
paragraph (1) for such taxable year, such excess shall be
carried to the succeeding taxable year and added to the credit
allowable under subsection (a) for such taxable year.
``(d) Rural Renaissance Bond.--For purposes of this section--
``(1) In general.--The term `rural renaissance bond' means
any bond issued as part of an issue if--
``(A) the bond is issued by a qualified issuer,
``(B) 95 percent or more of the proceeds from the
sale of such issue are to be used for capital
expenditures incurred for 1 or more qualified projects,
``(C) the qualified issuer designates such bond for
purposes of this section and the bond is in registered
form, and
``(D) the issue meets the requirements of
subsections (e) and (g).
``(2) Qualified project; special use rules.--
``(A) In general.--The term `qualified project'
means 1 or more projects described in subparagraph (B)
located in a rural area.
``(B) Projects described.--A project described in
this subparagraph is--
``(i) a water or waste treatment project,
``(ii) an affordable housing project,
``(iii) a community facility project,
including hospitals, fire and police stations,
and nursing and assisted-living facilities,
``(iv) a value-added agriculture or
renewable energy facility project for
agricultural producers or farmer-owned
entities, including any project to promote the
production, processing, or retail sale of
ethanol (including fuel at least 85 percent of
the volume of which consists of ethanol),
biodiesel, animal waste, biomass, raw
commodities, or wind as a fuel,
``(v) a distance learning or telemedicine
project,
``(vi) a rural utility infrastructure
project, including any electric or telephone
system,
``(vii) a project to expand broadband
technology,
``(viii) a rural teleworks project, and
``(ix) any project described in any
preceding clause carried out by the Delta
Regional Authority.
``(C) Special rules.--For purposes of this
paragraph--
``(i) any project described in subparagraph
(B)(iv) for a farmer-owned entity may be
considered a qualified project if such entity
is located in a rural area, or in the case of a
farmer-owned entity the headquarters of which
are located in a nonrural area, if the project
is located in a rural area, and
``(ii) any project for a farmer-owned
entity which is a facility described in
subparagraph (B)(iv) for agricultural producers
may be considered a qualified project
regardless of whether the facility is located
in a rural or nonrural area.
``(3) Special use rules.--
``(A) Refinancing rules.--For purposes of paragraph
(1)(B), a qualified project may be refinanced with
proceeds of a rural renaissance bond only if the
indebtedness being refinanced (including any obligation
directly or indirectly refinanced by such indebtedness)
was originally incurred after the date of the enactment
of this section.
``(B) Treatment of changes in use.--For purposes of
paragraph (1)(B), the proceeds of an issue shall not be
treated as used for a qualified project to the extent
that a borrower takes any action within its control
which causes such proceeds not to be used for a
qualified project. The Secretary shall prescribe
regulations specifying remedial actions that may be
taken (including conditions to taking such remedial
actions) to prevent an action described in the
preceding sentence from causing a bond to fail to be a
rural renaissance bond.
``(e) Maturity Limitations.--
``(1) Duration of term.--A bond shall not be treated as a
rural renaissance bond if such bond is issued as part of an
issue and--
``(A) the average maturity of bonds issued as a
part of such issue, exceeds
``(B) 120 percent of the average reasonable
expected economic life of the facilities being financed
with the proceeds from the sale of such issue.
``(2) Determination of averages.--For purposes of paragraph
(1), the determination of averages of an issue and economic
life of any facility shall be determined in accordance with
section 147(b).
``(3) Ratable principal amortization required.--A bond
shall not be treated as a rural renaissance bond unless it is
part of an issue which provides for an equal amount of
principal to be paid by the qualified issuer during each
calendar year that the issue is outstanding.
``(f) Credit Included in Gross Income.--Gross income includes the
amount of the credit allowed to the taxpayer under this section
(determined without regard to subsection (c)) and the amount so
included shall be treated as interest income.
``(g) Special Rules Relating to Expenditures.--
``(1) In general.--An issue shall be treated as meeting the
requirements of this subsection if--
``(A) at least 95 percent of the proceeds from the
sale of the issue are to be spent for 1 or more
qualified projects within the 5-year period beginning
on the date of issuance of the rural renaissance bond,
``(B) a binding commitment with a third party to
spend at least 10 percent of the proceeds from the sale
of the issue will be incurred within the 6-month period
beginning on the date of issuance of the rural
renaissance bond or, in the case of a rural renaissance
bond, the proceeds of which are to be loaned to 2 or
more borrowers, such binding commitment will be
incurred within the 6-month period beginning on the
date of the loan of such proceeds to a borrower, and
``(C) such projects will be completed with due
diligence and the proceeds from the sale of the issue
will be spent with due diligence.
``(2) Extension of period.--Upon submission of a request
prior to the expiration of the period described in paragraph
(1)(A), the Secretary may extend such period if the qualified
issuer establishes that the failure to satisfy the 5-year
requirement is due to reasonable cause and the related projects
will continue to proceed with due diligence.
``(3) Failure to spend required amount of bond proceeds
within 5 years.--To the extent that less than 95 percent of the
proceeds of such issue are expended within such 5-year period
(and no extension has been obtained under paragraph (2)), the
qualified issuer shall redeem all of the nonqualified bonds on
the earliest call date subsequent to the expiration of the 5-
year period. If such earliest call date is more than 90 days
subsequent to the expiration of the 5-year period, the
qualified issuer shall establish a yield-restricted defeasance
escrow within such 90 days to retire such nonqualified bonds on
the earlier of the date which is 10 years after the issue date
or the first call date. For purposes of this paragraph, the
term `nonqualified bonds' means the portion of the outstanding
bonds in an amount that, if the remaining bonds were issued on
the fifth anniversary of the date of the issuance of the issue,
at least 95 percent of the proceeds of the remaining bonds
would be used to provide qualified projects.
``(h) Special Rules Relating to Arbitrage.--
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``(7) Reporting.--Issuers of rural renaissance bonds shall
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``(A) In general.--For purposes of subsection (a),
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(c) Clerical Amendments.--
(1) The table of subparts for part IV of subchapter A of
chapter 1 is amended by adding at the end the following new
item:
``Subpart H. Nonrefundable credit to holders of rural
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(2) Section 6401(b)(1) is amended by striking ``and G'' and
inserting ``G, and H''.
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(e) Effective Date.--The amendments made by this section shall
apply to bonds issued after the date of the enactment of this Act. | Rural Renaissance Act II of 2005 - Amends the Internal Revenue Code to allow holders of rural renaissance bonds a nonrefundable tax credit of 25 percent of the annual credit amount as determined by the Secretary of the Treasury. Defines "rural renaissance bond" as any bond issued by a nonprofit cooperative lender that is used for capital expenditures for qualified projects in rural areas, including projects for water or waste treatment, affordable housing, community facilities (e.g., hospitals, fire and police stations, nursing facilities, etc.), rural utility infrastructure, broadband technology, and rural teleworks.
Sets forth rules for maturity limitations, arbitrage, and expenditures, including a requirement that 95 percent of the proceeds from the sale of a bond issue be spent on qualified projects within five yeas from the date of a bond issuance. |
the spacetime around an isolated black hole is flat and minkowskian at a large distance where usual quantum mechanics is applicable , while the spacetime closer to the singularity is curved and no satisfactory quantum field theory could be developed as yet .
however , occasionally , it is useful to look into an intermediate situation when a weak perturbation ( due to , say , gravitational , electromagnetic or dirac waves ) originating from infinity scatters from a black hole .
the resulting wave is partially transmitted into the black hole through the horizon and partially scatters off from it to infinity . in the linearized ( ` test field ' )
approximation this problem has been attacked in the past by several authors [ 1 - 4 ] .
these methods are mostly numerical and most of the solutions obtained so far is for particles of integral spin only .
chandrasekhar [ 3 - 4 ] separated the dirac equation in kerr geometry into radial and angular parts .
these works were extended to other spacetimes , such as in kerr - newman geometry [ 5 ] , and around dyon black holes [ 6 ] .
subsequently , chakrabarti [ 7 ] solved the angular part of the dirac equation in kerr geometry and gave the eigenvalues of the equation .
these and the present works mostly concern scattering off tiny black holes and thus changing the incoming solution appreciably into an outgoing solution . scattering effects from larger black holes could be studied by phase shift analysis and these has also been done recently [ 8 ] . in the present paper , we attack a simpler problem to have a ` feel ' for the complete solution when the black hole is non - rotating . in the next section , we present the basic equations . in 3 ,
we classify the parameter space in terms of the physical and unphysical regions and present the method we adopt to solve the equations . in 4 , we present a complete solution . in 5 , we present solutions using a classical method in which the potential is approximated by a series of steps and then compare solutions of these two methods . in 6 , we also compare solutions of various parameters and show how a schwarzschild black hole distinguishes incoming particles of various masses .
finally , in 7 , we draw our conclusions .
following chandrasekhar [ 4 ] , the radial part of the dirac equation is easily reduced into a schrdinger like equation . however , because the spin - spin coupling term is absent in the schwarzschild geometry , the radial equation is much simpler to deal with .
the eigenvalue of the angular equation for spin @xmath0 is trivially obtained as @xmath1 [ 7 , 9 - 10 ] where @xmath2 is the orbital quantum number . in what follows ,
we choose @xmath3 throughout for concreteness .
this eigenvalue turns out to be the separation constant @xmath4 of the original dirac equation [ 4 ] .
here we solve the equation for one possible value of separation constant @xmath4 ( for @xmath5 , @xmath4 is unity ) . in future
we plan to explore the nature of the solutions for other orbital quantum numbers . presently , we need to solve only the following coupled radial equations [ 4 ] : @xmath6 @xmath7 where , @xmath8 @xmath9 @xmath10 here @xmath11 = integer , @xmath12 = frequency of incoming dirac wave , @xmath13 = mass of the black hole , @xmath14 = azimuthal quantum number , @xmath15 = rest mass of the dirac particle ; p indicates particle , @xmath16 = radial wave function for spin up ( down ) particles .
@xmath17 is the complex conjugate operator .
it is to be noted that the dimensionless unit is chosen , so that @xmath18 .
the radial equation here is in coupled form .
we can decouple it and express the equation either in terms of spin up or spin down wave function .
however , it is more convenient to follow chandrasekhar s [ 4 ] approach by which the basis was changed along with the independent variable @xmath19 .
that way , the coupled equation was reduced into two independent one dimensional wave equations since they are easier to solve .
we first define @xmath20 where , @xmath21 , @xmath22 and choose @xmath23 , @xmath24 .
in terms of @xmath25 , the operators take the form : @xmath26 and @xmath27 we choose @xmath28 which yields , @xmath29 and @xmath30 following exactly chandrasekhar s [ 4 ] approach we write @xmath31 \eqno{(5)}\ ] ] and @xmath32 .
\eqno{(6)}\ ] ] finally , a choice of @xmath33 yields @xmath34 . with these definitions ,
the differential equations ( 1 - 2 ) are re - written as @xmath35 and @xmath36 where , @xmath37 , and @xmath38 one important point to note : the transformation of spatial coordinate @xmath19 to @xmath25 ( and @xmath39 ) is taken not only for mathematical simplicity but also for a physical significance . when @xmath19 is chosen as the radial coordinate , the decoupled equations for independent waves show diverging behaviour . however , by transforming those in terms of @xmath25 ( and @xmath39 ) we obtain well behaved functions .
the horizon is shifted from @xmath40 to @xmath41 .
> from the above set of equations , we readily obtain a pair of independent one - dimensional wave - equations , @xmath42 where , @xmath43 @xmath44^{2}}}[\delta^{1 \over 2}(1 + m_p^{2 } r^{2})^{3/2 } \pm \left((r - m)(1 + m_p^{2 } r^{2 } ) + 3m_p^{2 } r \delta\right)]\ ] ] @xmath45^{3}}}[2r(1 + m_p^{2 } r^{2 } ) + 2 m_p^{2 } r^{3 } + m_p ( r - m)/\sigma ] .
\eqno{(11)}\ ] ]
we obtain solutions by employing wkb [ 11 - 12 ] method and then imposing strict boundary conditions on the horizon , so that the reflection coefficient is zero and transmission coefficient is unity at the horizon . after establishing the general solution ,
we present here the solution of eq .
( 9 ) for two sets of parameters as illustrative examples .
it is advisable to choose the parameters in such a way that there is a significant interaction between the particle and the black hole .
this is possible when the compton wavelength of the incoming wave is of the same order as the schwarzschild radius of the black hole , i.e. , @xmath46 here , we are choosing @xmath47 , so @xmath48 again , in the case of schwarzschild geometry , frequency of the incoming particle ( or , wave ) will be of the same order as inverse of time .
so , @xmath49 using the units as before , one can write , @xmath50 in principle , however , one can choose any values of @xmath12 and @xmath15 for a particular black hole and the corresponding solution is possible but we shall concentrate the region of parameter space where the solution is expected to be interesting as pointed out above , namely , region close to @xmath51 . in fig . 1a , we draw this line .
the parameter space is spanned by the frequency @xmath12 and the rest mass of the incoming particle @xmath15 .
it is clear that @xmath52 of total parameter space where @xmath53 is unphysical , and one need not study this region .
rest of the parameter space ( @xmath54 ) is divided into two regions i : @xmath55 and ii : @xmath56 , where @xmath57 is the maximum of the potential . while in region i , the wave is _ locally _ sinusoidal because the wave number @xmath58 is real for the entire range of @xmath59 . in region ii , on the other hand , the wave is decaying in some region when @xmath60 , i.e. , where the wave ` hits ' the potential barrier and in the rest of the region , the wave is propagating
. we shall show solutions in these two regions separately . in region -
i whatever be the physical parameters , energy of the particle is always greater than the potential energy and wkb approximation is generally valid in the whole range ( i.e. @xmath61 ) . in cases of region - ii ,
energy of the particle is always less than the maximum height of potential barrier .
thus , at two points ( where , @xmath62 ) total energy matches with the potential energy and in the neighbour of those two points wkb approximate method is not valid .
they have to be dealt separately . in fig . 1b , we show contours of constant @xmath63max(@xmath64 ) for a given set ( @xmath65 ) of parameters .
the labels show the actual values of @xmath66 .
clearly , except for parameters _ very close _ to the boundary of regions i and ii , wkb approximation is safely valid for any value of @xmath67 .
one has to employ different method ( such as using airy functions , see below ) to find solutions in this region .
in this region , for any set of parameter , energy of the particle is always greater than the corresponding potential energy .
we first re - write equation ( 9 ) as , @xmath68 this is nothing but schrdinger equation corresponding to the total energy of the wave @xmath69 .
this can be solved by regular wkb method [ 11 - 12 ] .
let , @xmath70 @xmath71 here , @xmath58 is the wavenumber of the incoming wave and @xmath72 is the _ eiconal_. the solution of the equation ( 13 ) is , @xmath73 with @xmath74 in this case all along @xmath75 and also @xmath76 , so wkb approximation is generally valid in the whole region .
the quantity @xmath77 falls off rapidly with distance .
thus , wkb is strictly valid at long distance only .
it is clear that a standard wkb solution where @xmath78 and @xmath79 are kept constants throughout should not be accurate , since the physical inner boundary condition on the horizon must be that the reflected component is negligible there . thus wkb approximation requires a slight modification in which the spatial dependence of @xmath80 is allowed . on the other hand , at a large distance , where wkb is strictly valid , @xmath78 and @xmath79 should tend to be constants , and hence their difference is also a constant : @xmath81 here , @xmath82 is determined from the wkb solution at a large distance .
this along with ( 17 ) gives , @xmath83 } \over 2 } .
\eqno{(19)}\ ] ] this spatial variation , strictly valid at large distances only , should not be extendible to the horizon without correcting for the inner boundary condition .
these values are to be shifted by , say , @xmath84 respectively , so that on the horizon one obtains physical @xmath85 and @xmath86 .
we first correct reflection coefficient on the horizon as follows : let @xmath87 be the value of @xmath79 on the horizon ( see , equation ( 19 ) ) , @xmath88 } \over 2}.\ ] ] it is appropriate to use @xmath89 rather than @xmath79 since @xmath90 vanishes at @xmath40 .
incorporating these conditions , the solution ( 16 ) becomes , @xmath91 with the usual normalization condition @xmath92 where , @xmath93 .
here , @xmath94 is to be determined self - consistently by equating the asymptotic behaviour of this reflection coefficient with that obtained using wkb method .
this @xmath94 in turn is used to compute @xmath93 , and therefore the transmission coefficient @xmath86 from eq .
( 21 ) . in this way , normalization of @xmath95 is assured .
normalization factor @xmath96 as @xmath97 and the condition @xmath98 is found to be satisfied whenever @xmath99 is satisfied .
this is the essence of our modification of the wkb . in a true wkb ,
@xmath80 are constants and the normalization is with respect to a ( almost ) constant @xmath58 .
however , we are using it as if wkb is instantaneously valid everywhere .
our method may therefore be called ` instantaneous ' wkb approximation or iwkb for short . using the new notations , the instantaneous values ( i.e. , local values ) of the reflection and transmission coefficients are given by ( see , eq .
20 ) , @xmath100 @xmath101 determination of @xmath102 is done by enforcing @xmath85 obtained from eq .
( 22a ) as the same as that obtained by actual wkb method at infinity . to be concrete , we choose one set of parameters from region i. ( a large number of solutions are compared in 6 below . ) here , total energy of the incoming particle is greater than the potential barrier height for all values of @xmath67 .
we use mass of the black hole , @xmath103 ; mass of the particle , @xmath104 , orbital quantum number , @xmath105 , azimuthal quantum number , @xmath106 , frequency of the incoming wave , @xmath107 .
> from eq .
( 9 ) we observe that there are two wave equations for two potentials @xmath108 and @xmath109 .
the nature of potentials are shown in fig .
it is clear that potentials @xmath110 are well behaved .
they are monotonically decreasing as the particle approaches the black hole , and the total energy chosen in this case ( @xmath69 ) is always higher compared to @xmath110 .
for concreteness , we solve using potential @xmath108 .
similar procedure can be adopted using potential @xmath109 to compute @xmath111 and its form would be @xmath112 note the occurrence of the negative sign in front of the reflected wave .
this is to satisfy the asymptotic property of the wave functions which must conserve the wronskian [ 4 ] . since the coefficients should not change sign between infinity and the horizon ( as that would tantamount to having zero amplitude , i.e. , unphysical , absence of either the forward or the backward component ) the same sign convention
is followed throughout the space .
local values of the reflection and transmission coefficients could also be calculated in the same manner . in the solution ( eq .
@xmath113 and @xmath114 ) , first term represents the incident wave and the second term represents the reflected wave . in fig .
3 we show the nature of @xmath108 ( solid curve ) , @xmath58 ( dashed curve ) and @xmath115 ( short - dashed curve ) .
the difference of @xmath116 and @xmath117 and therefore @xmath58 goes up as the particle approaches the black hole . in fig .
4 , variation of ` local ' reflection and transmission coefficients are shown .
it is observed that as matter comes close to the black hole , the barrier height goes down . as a result , the penetration probability increases resulting in the rise of the transmission coefficients . at the same time
, the reflection coefficient tends to be zero .
it is to be noted , that , strictly speaking , the terms ` reflection ' and ` transmission ' coefficients are traditionally defined with respect to the asymptotic values . the spatial dependence that we show are to be interpreted as the instantaneous values
this is consistent with the spirit of iwkb approximation that we are using .
the behaviour of the solutions with @xmath118 is not very different from what were shown in figs .
( 3 - 4 ) except in a region very close to the black hole horizon where @xmath117 and @xmath118 differs slightly ( see , fig .
2 ) . using the solutions of equations with potential @xmath117 and @xmath118 , the radial wave functions @xmath119 and @xmath120 for spin up and spin down particles respectively of the original dirac equation
are given below ,
@xmath121 @xmath122 @xmath123 @xmath124 here , @xmath125 and @xmath126 . here , we have brought back @xmath58 and @xmath127 so that these may resemble the original solution ( eq .
16 ) using wkb approximation . @xmath128 and @xmath129 are the transmitted and reflected amplitudes respectively for the wave of corresponding potential @xmath118 .
figure 5 shows the resulting wave functions for both the spin @xmath130 and spin @xmath131 particles respectively .
the eiconals used in plotting these functions ( see , eq .
23[a - d ] ) have been calculated by approximating @xmath110 in terms of polynomials ( this was done since @xmath110 as presented in eq .
10 is not directly integrable . ) and using the definition @xmath132 .
note that the amplitude as well as the wavelength remain constants in regions where @xmath58 is also a constant . as discussed before ,
the wave functions are almost sinusoidal close to the horizon and at a very large distance ( albeit with different frequencies ) .
since the net current ( @xmath133 ) is conserved , probability of spin @xmath130 is complimentary to the probability of spin @xmath131 particles respectively .
here we study the second region where for any set of physical parameter total energy of the incoming particle is less than the maximum height of the potential barrier .
thus , the wkb approximation is not valid in the whole range of @xmath67 . in such regions ,
the solutions will be a linear combination of airy functions because the potential is approximately linear in @xmath134 in those intervals . at the junctions one
has to match the solutions with airy functions along with the solution obtained by the wkb method . in the region where the wkb approximation is valid , local values of reflection and transmission coefficients and the wave functions can be calculated easily by following the same method described in case i. in other regions , the equation reduces to @xmath135 where , @xmath136 , @xmath137 is chosen to be positive and @xmath138 is the critical point where the total energy and potential energy are matching .
let @xmath139 and considering region @xmath140 the equation ( 24 ) reduces to @xmath141 by making yet another transformation , @xmath142 we obtain , @xmath143 this is the modified bessel equation .
the solution of this equation is @xmath144 and @xmath145 .
hence , the solution of eq .
( 27 ) will be , @xmath146 .
\eqno{(28)}\ ] ] when @xmath147 the corresponding equation is , @xmath148 which is the bessel equation .
the corresponding solution is @xmath149 , \eqno{(30)}\ ] ] where @xmath150 and @xmath151 are the bessel functions and the modified bessel functions of order @xmath152 respectively .
the airy functions are defined as @xmath153 , \hskip1 cm x > 0 , \eqno{(31)}\ ] ] @xmath154 , \hskip1 cm x < 0 , \eqno{(32)}\ ] ] @xmath155 , \hskip1 cm x > 0 , \eqno{(33)}\ ] ] @xmath156 , \hskip1 cm x < 0 .
\eqno{(34)}\ ] ] in terms of airy functions , the solutions ( 28 ) and ( 30 ) can be written as @xmath157 @xmath158 by matching boundary conditions it is easy to show that the solution corresponding @xmath140 and that corresponding @xmath159 are continuous when @xmath160 and @xmath161 . to have an explicit solution
, we choose the following set of parameters : @xmath103 , @xmath162 , @xmath105 , @xmath106 and @xmath163 . in fig .
6 , we show the nature of @xmath117 and @xmath118 .
however , while solving , we use the equation containing @xmath108 ( eq .
9 ) . unlike the case in the previous section , here
@xmath69 is no longer greater than @xmath110 at all radii . as a result
, @xmath164 may attain negative values in some region . in fig .
7 , nature of @xmath108 ( solid curve ) , parameter @xmath58 ( dashed curve ) and energy @xmath116 ( short - dashed curve ) are shown . here ,
wkb approximation can be applied in regions other than @xmath165 to @xmath166 and @xmath167 to @xmath168 where @xmath58 is close to zero and the condition @xmath169 is not satisfied . in the region @xmath170
to @xmath167 around the turning point @xmath171 the solutions turns out as [ 13 ] @xmath172 similarly , the solution from @xmath166 to @xmath173 i.e. around the turning point @xmath174 can be calculated as [ 13 ] @xmath175 it is to be noted that in the region @xmath176 to @xmath177 , even though the potential energy dominates over the total energy , wkb approximation method is still valid . here
the solution will take the form @xmath178 and @xmath179 .
asymptotic values of the instantaneous reflection and the transmission coefficients ( which are traditionally known as the ` reflection ' and ` transmission ' coefficients respectively ) are obtained from the wkb approximation .
this yields the integral constant @xmath82 as in case i. > from eq .
22(a - b ) local reflection and transmission coefficients are calculated , behaviour of which are shown in fig .
the constants @xmath87 and @xmath102 are calculated as before .
note the decaying nature of the reflection coefficient inside the potential barrier .
in the above sections we presented our semi - analytical solutions by wkb method with an appropriate boundary condition at the horizon . a numerical approach would be to replace the potential @xmath180 by a collection of step function as shown in fig .
, the solid steps approximate the dashed potential for @xmath181 and @xmath182 .
the standard junction conditions of the type , @xmath183 where , @xmath184 + b_{n } exp [ -ik_n{\hat r } _ { * , n}]\ ] ] and @xmath185 where , @xmath186 at each of the @xmath11 steps were used to connect solutions at successive steps .
as before , we use the inner boundary condition , to be @xmath187 at @xmath188 . in reality
, we used as many as 12000 steps to accurately follow the shape of the potential .
smaller step sizes were used whenever @xmath58 varies faster .
9b shows the comparison of the instantaneous reflection coefficients in both the methods .
the solid curve is from the wkb method of previous section and the dotted curve is from the step - potential method as we described here .
the agreement is clearly excellent .
in order to show that the black hole scatters incoming waves of different rest masses ( @xmath15 ) and of different energies ( @xmath69 ) quite differently , we show a collection of solutions in figs .
10(a - d ) . in figs .
10a , we show reflection and transmission coefficients for waves with parameters @xmath189 ( solid ) , @xmath190 ( dotted ) and @xmath191 ( dashed ) respectively with the same @xmath181 . as the energy of the particle rises comparable to the height of the potential ( which is solely dependent on @xmath15 at a large distance )
, the reflection coefficient goes down and the transmission coefficient goes up . in fig .
10b , the real part of the wave @xmath192 , corresponding to these three cases are shown . at @xmath193 ,
the wave pattern is independent of @xmath12 as the phase factor is trivially the same in all the cases .
the dispersal of the wave with frequency is clear .
waves with smaller energy and longer wavelength are scattered with higher amplitude of re(@xmath192 ) as the fraction of the reflected wave goes up when energy is reduced .
this behaviour is valid till @xmath194 since the amplitude of re(@xmath192)= @xmath195 . for @xmath196 , amplitude of re(@xmath192 )
goes down with energy . in fig .
10(c - d ) , solutions are shown with varying the rest mass of the particles while keeping @xmath12 fixed at @xmath197 .
the solid curve , dotted curve and the dashed curves are for @xmath181 , @xmath198 , @xmath199 respectively .
most interesting aspect is that close to the black hole @xmath200 , the reflection and transmission coefficients as well as the nature of the wave are quite independent of the rest mass .
this is understandable , as just outside the horizon , the potential is insensitive to @xmath15 .
however , farther out , amplitude of re(@xmath192 ) goes up as before when @xmath15 is raised as larger fraction of the wave is reflected from the potential ( fig.10c ) .
this interesting behaviour , for the first time shows that one could scatter a mixed wave off a black hole and each of the constituent wave would behave differently as in a prism or a mass spectrograph .
in this paper , we analytically studied scattering of spin - half particles from a schwarzschild black hole .
in particular , we presented the nature of the radial wave functions and the reflection and transmission coefficients .
our main motivation was to give an analytical expression of the solution which could be useful for further study of interactions among hawking radiations , for instance .
we verified that these analytical solutions were indeed correct by explicitly solving the same set of equations numerically using step - potential approach as described in section v. we classified the entire parameter space in terms of the physical and unphysical regions and the physical region was further classified into two regions , depending on whether the particle ` hits ' the potential barrier or not .
we chose one illustrative example in each of the regions .
we emphasize that the most ` interesting ' region to study would be close to @xmath201 .
however we pointed out ( fig .
1b ) that for @xmath202 , wkb solutions can not be trusted , and other methods ( such as those using airy functions ) must be employed .
we used the well known wkb approximation method as well as the step - potential method of quantum mechanics to obtain the spatial dependence of the coefficients of the wave function .
this in turn , allowed us to determine the reflection and transmission coefficients and the nature of wave functions .
the usual wkb method with constant coefficients and ( almost ) constant wave number @xmath58 is successfully applied even when the coefficients and wave number are not constant everywhere .
solution from this ` instantaneous ' wkb ( iwkb for short ) method agrees fully with that obtained from a purely classical numerical method where the potential is replaced by a collection of steps ( simple quantum mechanical approach ) .
the resulting wave forms satisfy the inner and the outer boundary conditions .
our method of obtaining solutions should be valid for any black hole geometry which are asymptotically flat so that radial waves could be used at a large distance . this way we ensure that the analytical solution is closer to the exact solution . in region
ii , in some regions , wkb method can not be applied and hence airy function approach or our step - potential approach could be used . in the literature , reflection and
transmission coefficients are defined at a single point .
these definitions are meaningful only if the potential sharply changes in a small region while studies are made from a large distance from it . in the present case , however , the potential changes over a large distance and we are studying in these regions as well .
although we used the words ` reflection ' and ` transmission ' coefficients , in this paper very loosely , our definitions are very rigorous and well defined .
these quantities are simply the instantaneous values . in our belief
these are more physical .
the problem at hand is very similar to the problem of reflection and transmission of acoustic waves from a strucked string of non - constant density where reflection and transmission occurs at each point . unlike in the case of a kerr black hole ,
the solution of the angular equation around a schwarzschild black hole is independent of the azimuthal or meridional angles [ 5 - 7 ] .
this is expected because of symmetry of the space - time .
however , otherwise , the nature of the reflection and transmission coefficients were found to strongly distinguish solutions of different rest masses and different energies as illustrated in figs .
10(a - d ) .
for instance , when the energy of the wave is increased for a given mass of the particle , reflected component goes down . in regions where @xmath196 , re(@xmath192 ) goes down with energy , but where @xmath194 , re(@xmath192 ) goes up with energy . in any case , the wave scattered off are distinctly different . in a way , therefore , black holes can act as a mass spectrograph ! for instance a mixture of waves should be splitted into its components by the black hole .
our method is quite general and should be used to study outgoing hawking radiations also .
this is beyond the scope of this paper and would be dealt with in future .
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1a : classification of the parameter space in terms of the energy and rest mass of the particles .
the physical region @xmath54 is further classified in terms of whether the particle actually ` hits ' the barrier or not .
1b : contours of constant @xmath66= max@xmath203 are shown to indicate that generally @xmath204 and therefore wkb approximation is valid in most of the physical region .
labels indicate values of @xmath205 .
4 : behaviour of local transmission ( @xmath86 , solid curve ) and reflection ( @xmath85 , dashed curve ) coefficients , as functions of @xmath67 . close to the horizon , transmission is a hundred percent and reflection is almost zero .
fig . 5 : behaviour of ( a ) re@xmath206 , ( b ) im@xmath206 , ( c ) re@xmath207 , ( d ) im@xmath207 , as a function of @xmath67 .
note the complimentary nature wave functions of the spin @xmath130 and spin @xmath131 particles .
this is because the current is conserved .
9b : comparison of variation of instantaneous reflection coefficient @xmath85 with the radial coordinate @xmath59 using analytical wkb method ( solid ) and numerical step - potential method ( dotted ) .
the parameters are @xmath181 and @xmath182 .
10(a - d ) : comparison of ( a ) reflection and transmission coefficients and ( b ) real amplitude of the wave function @xmath192 for @xmath181 and @xmath208 ( solid ) , @xmath190 ( dotted ) and @xmath191 ( dashed ) respectively .
( c - d ) similar quantities for @xmath209 , ( solid ) @xmath198 ( dotted ) and @xmath199 ( dashed ) respectively keeping @xmath182 fixed .
higher reflection component enhances the wave amplitude , thus differentiating the incoming waves very clearly . | separation of the dirac equation in the spacetime around a kerr black hole into radial and angular coordinates was done by chandrasekhar in 1976 . in the present paper
, we solve the radial equations in a schwarzschild geometry semi - analytically using wentzel - kramers - brillouin approximation ( in short wkb ) method . among other things , we present analytical expression of the instantaneous reflection and transmission coefficients and the radial wave functions of the dirac particles .
complete physical parameter space was divided into two parts depending on the height of the potential well and energy of the incoming waves .
we show the general solution for these two regions .
we also solve the equations by a quantum mechanical approach , in which the potential is approximated by a series of steps and found that these two solutions agree .
we compare solutions of different initial parameters and show how the properties of the scattered wave depend on these parameters . 0.5 cm 0.3 cm to appear in classical and quantum gravity |
uncovering the complex mechanisms involved in gene regulation remains to be a major challenge .
while the biochemical processes involved in the expression of a single gene are increasingly well understood , the interplay of whole networks of genes poses additional questions and it is unclear what level of system - specific detail has to be taken into account to describe a gene regulatory network @xcite .
one promising approach to modeling system wide dynamical states of a network is to go to an abstract level of description @xcite which may even include discrete deterministic models such as boolean or threshold networks @xcite .
we here extend a recent model of the yeast cell cycle dynamics that is successfully based on this approach @xcite .
the cell cycle of the budding yeast saccharomyces cerevisiae is a widely studied example of a robust dynamical process @xcite . in @xcite ,
the yeast cell cycle was modeled in the framework of a discrete threshold network . from the data in @xcite , eleven genes that play a key role in the cell cycle process
were identified along with their known ( direct or indirect ) interactions .
the activity of a certain gene is modeled as a two - state system , with values 1 ( active ) or 0 ( inactive ) . using a threshold model of interactions , the biological sequence of activity states in the process
is exactly reproduced .
the authors also find considerable dynamical robustness properties that can be traced to the properties of the basin of attraction of the biological fixed point .
remarkably , these results were obtained using a discrete time model , where each discrete time step @xmath0 is defined by the intervals between activity changes . in the model
, the activity state of every gene is determined solely by the state of its transcription factors at the previous time step .
it is remarkable , that in this case at least , the biochemical stochasticity of gene regulation @xcite can be neglected in the model . in particular ,
as was shown in @xcite , attractors under synchronous dynamics can be unstable if stochasticity is imposed on the transmission times . in this work
, we investigate whether the cell - cycle process is stable under such perturbations .
investigations of dynamical robustness have been discussed in a variety of different biological systems , such as segmentation in the fruit fly @xcite , or two - gene circadian oscillators @xcite .
different conceptions of the word ` robustness ' have been used @xcite .
robustness against mutations means that a specific process can be performed reliably by a system even if some changes to the structure of the system are conducted .
the yeast cell - cycle is remarkably robust in this sense @xcite .
other approaches to assessing robustness in biological networks include local stability and bifurcation analyses @xcite , stability under node state perturbation @xcite and probabilistic boolean networks @xcite . in this work
we will concentrate on the robustness under stochastically varying processing times ( for protein concentration buildup and decay ) as was considered in @xcite
. other models of the yeast cell - cycle include molecular models of major cdk activities in start and finish states @xcite and of s - phase entrance in @xcite . in @xcite
stochastic differential equations have been used to fit time - courses of protein concentration levels in the yeast cell - cycle network .
[ cols="^,^,^,^,^,^,^,^,^,^,^,^,^ " , ] following @xcite , a network of eleven nodes is used to describe the cell cycle process .
they are given in table [ tsequence ] , along with the synchronous sequence of activity states recorded in that work .
using a technique introduced in @xcite we extend that model to include fluctuating transmission delays and to allow for real numbers for protein concentrations levels ( @xmath1 for protein @xmath2 ) .
we keep the characteristics of the description of @xcite , that is the effect of protein @xmath3 on the transcription of protein @xmath2 is determined by a discrete activity state ( ` active ' or ` inactive ' ) of protein @xmath3 . in our continuous description , we set the activity state @xmath4 of a protein to 1 if the concentration is above a certain threshold ( @xmath5 ) , otherwise it is 0 .
the transmission function that determines the transcription or degradation of protein @xmath2 is given by @xmath6 where @xmath7 is the transmission delay time that comprises the time taken by processes such as translation or diffusion that cause the concentration buildup of one protein to not immediately affect other proteins .
the numbers @xmath8 determine the effect that protein @xmath3 has on protein @xmath2 .
an activating interaction is described by @xmath9 , inhibition by @xmath10 . if the presence of protein @xmath3 does not affect expression of protein @xmath2 , @xmath11 . if @xmath12 , the value of @xmath13 depends on whether the node is modeled as a self - degrader .
self - degraders are those nodes that are down - regulated by external processes ( cln3 , cln1,2 , swi5 , cdc20/cdc14 , mcm1/sff ) .
self - degrader nodes will take a value @xmath14 whereas the transmission function of non - self - degraders is left unchanged , i.e. the last time @xmath15 when @xmath16 determines the state at time @xmath0 .
we now describe the time evolution of the system of genes by the following set of delay differential equations @xmath17 for the simple transmission function given above , this equation can be easily solved piecewise ( for every period of constant transmission function ) , leading to charging behavior of the concentration levels @xmath18 , @xmath19).,width=321 ] this has the effect of a low - pass filter , i.e. , a signal has to sustain for a while to affect the discrete activity state . a signal spike , on the other hand , will be filtered out
. concentration buildup in our model is depicted in figure [ fcharging ] . here , the transcription factor of a protein is assumed to be present in the time span @xmath20 to @xmath21 ( upper panel ) .
the production of the protein starts after the delay time ( here @xmath22 ) and the concentration crosses the critical level of @xmath23 at @xmath24 ( central panel ) , switching the activity state to `` on '' ( lower panel ) . in the case of very fast build - up and decay ( @xmath25 in eq .
( [ solution ] ) ) and with the delay time set to one ( @xmath26 ) , we exactly recover the synchronous dynamics of @xcite . thus , our described model is a simple generalization of the synchronous case to allow for a continuous time description .
we now ask the following question : is the original sequence stable under stochastic timing noise ( stochastically varying signal delay times ) or can the noise cause the system to assume different states ? as the sequence from @xcite ( reproduced in table [ tsequence ] ) runs into the stationary @xmath27 fixed point and an external signal is needed to trigger the starting state again , we create a repeating cycle of states ( limit cycle ) by explicitly adding the rule that cln3 production is triggered as soon as the final state in the synchronous sequence is reached
. we will investigate whether this limit cycle is inherently stable or whether it needs the perfect synchronization of the artificial synchronous update . in this context
it is important to note that the stability of the complete cell - cycle system also depends on the behavior of all other proteins involved .
however , the stability of the core genes is most important , as they regulate the other proteins .
only if the regulators perform reliably , the system as a whole can be robust . to compare the time series of our simulations with the discrete time steps of the synchronous case ,
we record a time step whenever the system keeps all its activity states constant for a time span of at least @xmath28 . with every switch of activity states ( say , at time @xmath29 ) we check whether the transcription of any other protein p is affected .
if so , the concentration level of protein p will begin to rise at time @xmath30 where @xmath31 denotes a uniformly distributed random number between @xmath21 and @xmath32 that perturbs the delay times .
our simulation time is not directly related to the actual time intervals of the biological processes involved .
however , we are not so much interested in the specifics of the time course but rather in the properties of stability and for this assessment it is not important how long the actual phases take .
our model captures two principles of real world gene regulatory networks : interactions occur with a characteristic time delay ( denoted by @xmath7 ) ; and we use continuous concentration levels and implement low pass filter behavior due to protein concentration buildup with a characteristic time @xmath33 @xcite .
first , we check if the system reproduces the synchronous sequence under small perturbations of the delay time .
thus we stay in the regime where @xmath32 is significantly smaller than the characteristic protein decay or buildup time @xmath33 . in the main simulation
runs we set @xmath26 , @xmath19 and @xmath34 , but any numbers that fulfill @xmath35 give the same results .
we find that the synchronous sequence of states is reliably reproduced by this stochastic dynamics .
even long simulation runs of @xmath36 can not push the system out of the original attractor .
this means that the biological sequence is absolutely stable against small perturbations . to understand this , we look at the synchronous sequence of states in table [ tsequence ] . in steps
@xmath37 , @xmath38 , @xmath39 , @xmath40 , @xmath41 , @xmath42 ( marked blue in the table ) only a single protein changes its activity state . if all steps were of this kind , fluctuations of the event times would not be able to destroy the attractor at all .
states marked in red denote events where multiples switches happen at the same time . to illustrate this point ,
let s assume two nodes switch their states at times @xmath43 and @xmath44 ( we call this a ` phase lag ' ) .
the system thus assumes an intermediate state in the time span between @xmath43 and @xmath44 .
approximately at time @xmath45 the next switches occur and due to the intermediate state it is possible that proteins switch their states which would normally be constant in this step . because of the charging behavior of the concentration levels , these ` spikes ' will be filtered out . the only way to destroy the attractor is
thus when the phase lags add up in a series of steps .
this can not happen in the yeast cycle , however , due to the states marked in blue color in the table .
when only one protein changes its state in a time step , all divergence of signal times will be reset and the synchrony is restored .
we therefore call these steps ` catcher states ' as they remove phase - lags from the system .
now that we know that small perturbations can not drive the system out of the synchronous attractor , we want to investigate stability under stronger noise . to address this question
, we have to loosen our definition of stability . up to now
, we have requested the system to follow the exact sequence of states of the synchronous dynamics .
it is clear that this strict stability can not be obtained if we increase the noise to be more than half of the transmission delay itself , because two nodes switching at the same synchronous time step can receive switching times that differ by more than @xmath28 .
the intermediate step taken when only one node has switched obviously violates the stability criterion . to assess the stability of the system under strong noise
, we employ a different stability criterion .
we let the system run with the sole constraint that the stationary @xmath27 state will be assumed regularly for a time span of at least @xmath7 .
any fluctuations occurring inbetween two @xmath27 incidences will be tolerated , as long as the system finds its way to the @xmath27 state of the cell cycle in which growth occurs until the cell size signal is triggered .
although this might seem too loose a criterion for robust biological functioning , one has to remember that the cell - cycle process is also backed up by a system of checkpoints that can catch faulty system states .
we investigate here the inherent stability of the system disregarding these checkpoints but at the same time allowing more variability in the sequence . .
black boxes denote active states , white means inactive . on a micro - time level
the effect of fluctuations is visible , but on a larger time scale the dynamics is very stable.,width=321 ] remarkably , with noise of the order of the delay time and largely independent of the filter used , the system reliably stays in the biological attractor .
an example run with @xmath26 , @xmath19 and @xmath46 ran for a time of @xmath47 following the biological attractor sequence ( in the wider sense mentioned above ) .
a typical time span of this run is shown in figure [ stablenoise ] .
this is a surprising result , because in general one expects a system to be able to leave its attractor sequence under such strong noise if a series of multi - switch events ( steps 5 to 8) is involved anywhere during the sequence .
our proposed criterion is not trivially fulfilled : by changes in the sequence of switching events or by delaying one of several events that occur at the same synchronous time step , a new sequence could be triggered .
this could force the system to jump into one of the other six fixed points identified in @xcite without the possibility to return to the biological sequence . in figure [ strongnoise ]
we show an example of a simulation run with extremely strong noise @xmath48 that shows that the system can jump out of the attractor . however , it is also apparent that even under such strong fluctuations the system runs quite regularly until it finally loses its attractor sequence . .
after some repetitions of the biological state sequence the attractor cycle is lost and a fixed point is assumed.,width=321 ] we now quantify the stability of the biological pathway under such strong noise .
how likely is it for the system to lose its biological sequence and to run into a different fixed point ? to address this question , we initialize the system at the start state again and check whether it completes the cycle . again , we use the lose criterion described above , which means we only request the system to reach the start state again . in figure [ errorsvsnoise ]
we show the ratio of erroneous runs of the biological pathway plotted against the noise level @xmath32 . it can be clearly seen that for reasonable noise levels the ratio of sequence runs not ending in a biological fixed point is very small .
in fact , even with unrealistically high noise levels of @xmath49 or more ( which amounts to arbitrary update times ) , only in a quarter of the runs the system jumps out of the biological state sequence .
the by far dominating cause for this ( very small ) instability is the first step ( cf .
table [ tsequence ] ) where both sbf and mbf are activated by cln3 .
if the cln3 concentration is degraded before activating the transcription of either sbf or mbf , the system loses the biological sequence .
if we explicitly force cln3 activity to sustain long enough to make sure that both sbf and mbf are produced , even this small instability vanishes and the system assumes practically complete stability for all reasonable noise levels ( @xmath50 erroneous runs at @xmath51 ) .
this superstability is due to the fact that all proteins keep their activity states for an extended time .
extremely strong noise is therefore needed to delay a single activity switch long enough to significantly perturb the system .
we have tested all results with a wide variety of parameters . with a fixed number for the delay time @xmath7 , only the noise level @xmath32 and the characteristic protein buildup time @xmath33 can be adjusted .
our results are completely robust against changes of @xmath33 , even removing the filter completely or setting it an order of magnitude larger than the delay time does not affect the robustness properties described above .
as we have shown in the previous section , the yeast cell - cycle control network is astonishingly stable against fluctuations of the protein activation and degradation times .
the network and the resulting dynamics exhibit a number of features that cause this stability : as was already discussed in @xcite , the basin of attraction is very large , making it unlikely that an intermediary state belongs to one of the other fixed point basins .
a second remarkable property is that all node states are sustained for at least three ( synchronous ) steps , making the system less dependent on the specifics of the concentration buildup procedure .
third and most important for the observed superstability under noisy transmission times , is the presence of the catcher states which prevent the system from gradually running out of synchrony .
thus , we have seen that without even taking into account the biological checkpoint mechanisms that give additional stability and error - correction features , the system shows a strong inherent robustness against intrinsic fluctuations . in this example of the yeast cell - cycle dynamics , potential mechanisms that provide robustness under biological noise can be observed . a system without an external clock ( or any other external control ) can still run reliably if it has intrinsic features that enforce robustness : catcher states , persistence of states and an attractor landscapes that minimizes the possibilities to escape the biological sequence . to conclude
, we have investigated the stability of the cell - cycle network by extending the model of li et al . to allow asynchronous updating of the activity states of the genes .
we find that the system exhibits robust behavior under noisy transmission times . even without taking into account the checkpoint mechanisms that give additional stability and fallback features ,
the system shows a strong inherent robustness that aids in maintaining reliable functioning .
chen , k .- c . ,
wang , t .- y . , tseng , h .- h . , huang , c .- y .
f. , and kao , c .- y .
a stochastic differential equation model for quantifying transcriptional regulatory network in saccharomyces cerevisiae .
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oscillatory expression of the bhlh factor hes1 regulated by a negative feedback loop .
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lee , t. i. , rinaldi , n. j. , robert , f. , odom , d. t. , bar - joseph , z. , gerber , g. k. , hannett , n. m. , harbison , c. t. , thompson , c. m. , simon , i. , zeitlinger , j. , jennings , e. g. , murray , h. l. , gordon , d. b. , ren , b. , wyrick , j. j. , tagne , j .- b . ,
volkert , t. l. , fraenkel , e. , gifford , d. k. , and young , r. a. ( 2002 ) .
transcriptional regulatory networks in saccharomyces cerevisiae . , 298(5594):799804 .
spellman , p. t. , sherlock , g. , zhang , m. q. , iyer , v. r. , anders , k. , eisen , m. b. , brown , p. o. , d. , b. , and futcher , b. ( 1998 ) .
comprehensive identification of cell cycle - regulated genes of the yeast saccharomyces cerevisiae by microarray hybridization . , 9:32733297 . | gene regulatory dynamics is governed by molecular processes and therefore exhibits an inherent stochasticity . however , for the survival of an organism it is a strict necessity that this intrinsic noise does not prevent robust functioning of the system .
it is still an open question how dynamical stability is achieved in biological systems despite the omnipresent fluctuations . in this paper
we investigate the cell - cycle of the budding yeast saccharomyces cerevisiae as an example of a well - studied organism .
we study a genetic network model of eleven genes that coordinate the cell - cycle dynamics using a modeling framework which generalizes the concept of discrete threshold dynamics . by allowing for fluctuations in the transcription / translation times ,
we introduce noise in the model , accounting for the effects of biochemical stochasticity .
we study the dynamical attractor of the cell cycle and find a remarkable robustness against fluctuations of this kind .
we identify mechanisms that ensure reliability in spite of fluctuations : ` catcher ' states and persistence of activity levels contribute significantly to the stability of the yeast cell cycle despite the inherent stochasticity .
+ _ keywords _ : gene regulatory network ; yeast cell cycle ; boolean models ; computer simulations ; robustness |
gastric cancer ( gc ) is identified to be the second widespread neoplasm around the world ( 1 ) . in spite of advances in surgical treatment and chemotherapy ,
environmental factors such as infection and diet have been considered to play critical roles in gc .
although the genetic supposed to encompass an impressive capacity in gc development , this aspect has not been proved comprehensively ( 3 ) .
moreover , there is an association between infection of h pylori and the possibility of gc occurrence ( 4 , 5 ) in addition ; several studies have demonstrated smoking can be one of the causes of gc ( 6 , 7 ) .
cyclooxygenase ( cox ) known as prostaglandin endoproxide h synthase ( pghs ) and is a rate - limiting enzyme in prostaglandin synthesis .
it converts free arachidonic acid into important prostanoids ( pgs ) and eicosanoids such as prostaglandin h2 ( 8) .
three different isoforms of human cox , cox-1 ,
cox-2 and cox-3 with independent genes and different expression pattern have been reported ( 9 ) .
normally , cox-2 is undetectable in most of tissues but it can be activated by several inducers like cytokines , growth factor , tumor promoters and lipopolysacharides ( lps ) .
some studies reported its stimulation by cigarette smoking leading to carcinogenesis ( 10 , 11 ) .
it is also accounted for inflammatory responses and tumor progression ( 12 ) . over expression of cox-2
is considered to be an indispensable part of tumor development , angiogenesis , metastasis and inhibition of apoptosis ( 13 ) . additionally , the expression of cox-2 is controlled by convoluted signaling pathways such as -catenin signal transduction ( 14 ) .
the involvement of important nuclear proteins like nf-b , cre , pea3 and nf - il-6 in interacting with the cox-2 promoter region is essential for regulating the expression of the gene ( 15 ) .
elevated level of cox-2 has been related to development of many human cancers such as colorectal and breast ( 1618 ) and in particular gastric cancer ( 19 , 20 ) .
the vulnerability to the progression of human cancers like prostate and breast can be as a consequence of genetics variations such as single nucleotide polymorphisms ( snp ) ( 21 , 22 ) . regarding the cox-2 gene , only a few polymorphisms observed in its promoter region appeared to have an efficient impact on the gene transcription ( 23 ) .
nevertheless , the difference in mrna expression level of the gene under the existence of carcinogens among individuals is due to different patterns of snps in the operative regions of the gene ( 24 , 25 ) .
an acknowledged polymorphism in the promoter region of cox-2 gene , featured by a guanine ( g ) to cytosine ( c ) transition at position 765 ( -765 g > c ) performs disruptions in a positive transcription activator , stimulatory protein 1 ( 24 ) .
unfortunately , limited studies have been performed to date to scrutinize cox-2 polymorphisms in different forms of cancer and various diseases ( 2629 ) .
it has been demonstrated that in iranian population , gastric cancer incidence is high and the rate of this disease have increased about two fold when compared with the data of 40 years ago ( 30 ) .
this study was performed to investigate the influence of age and gender on association between -765 g > c cox-2 genetic polymorphism and the development of gastric adenocarcinoma among iranian samples .
this study was executed between two groups of healthy people with no clinical presentation of cancer including 91 subjects and individuals with evident gastric adenocarcinomas ( n=91 ) .
blood samples were stored in a -20 c freezer . using a standard salting - out protocol
optical density ( od ) and concentration was measured using nanophotometer at 260 and 280 nm .
a 157 bp dna segment was amplified using the following primers : forward 5-attctggcctcgccgcttc-3 and reverse 5-ctccttgtttcttggaaagagacg-3. pcr reactions were carried out using 10 l of prime taq premix ( 2x ) ( genet bio , korea ) , 0.7 l of each forward and reverse primers , 0.5 l genomic dna and 8.1 l ddh2o in a total volume of 20 l under following thermal conditions : 94 c for 5 min intended for the initial denaturation , 94 c ( 1 min ) for denaturation , 59 c ( 1 min ) for annealing and 72 c ( 1 min ) for extension repeating 35 cycles ( master cycler gradient eppendorf , usa ) .
9 l pcr reaction products were subjected to 0.7 l bsh1236i restriction endonuclease ( fermentas , vilnius , lithuania ) , 2 l of r buffer and 2.3 l of ddh2o for 11 h at 37 c. 3% agarose gel was utilized for electrophoresis and then dna fragments were separated based on their specific length . in all samples ,
c cox-2 polymorphism , the wild - type homozygous -765gg was cut into fragments of 134 bp and 23 bp , however the uncut homozygous -765 cc was 157 bp .
the presence of all the three fragments ( 157 , 134 and 23 bp ) showed a heterozygous -765 gc . the 23 bp fragment was not identified in the agarose gel due to primer - dimer band .
pcr - rflp analysis of -765 g > c cox-2 polymorphism ; lane 1 : 20 bp dna ladder ; lane 2 : pcr product ( undigested ) ; lane 3 : homozygous -765 cc genotype ; lanes 4 , 6 : homozygous -765 gg genotype ; lane5 : heterozygous-765 gc genotype . in this study ,
overall , 91 gastric adenocarcinoma patients ( 44 female and 47 male , mean age : 60.515.1 ) and 91 control normal ( 47 female and 44 male , mean age : 36.112.5 ) were enrolled .
mean standard deviation age of case and control groups there was a statistically significant difference between increasing of age and gastric adenocarcinoma risk ( odds ratio=1.12 , 95% ci=1.08 - 1.16 ; p < 0.001 ) .
the frequency of the -765 > cc , gc and gg genotypes were 4.4% , 61.5% and 34% in controls and 4.4% , 68.1% and 27.5% in gastric adenocarcinoma patients respectively .
however , differences were considered significant ( p=0.04 ) for female patients with c carrier genotypes ( sum : gc and cc ) and gastric adenocarcinoma when compared with male patients ( p=0.65 ) and control groups ( p=0.65 ) .
based on the present results , we found that age and gender are important factors which are involved on association between -765 g > c cox-2 genetic polymorphism and gastric adenocarcinoma risk .
although cox-1 is constitutively expressed , cox-2 expression is associated with various pathophysiological conditions , including inflammatory diseases and different cancers such as adenocarcinoma tissues and gastric precancerous ( 31 , 32 ) . molecular mechanisms and other pathways that are responsible for over expression of cox-2 protein has not elucidate completely .
the current consensus is that both transcriptional and post - transcriptional events are important ( 33 ) .
many studies suggest an important role of cox-2 in the carcinogenesis pathway including in the inhibition of apoptosis , tumor growth , angiogenesis , invasion and metastasis ( 34 ) .
one of the most important polymorphism in cox-2 gene consisted on g / c transversion 765 nucleotides upstream from the transcription start ( 35 ) . for these reasons
previously pereira et al have investigated the influence of the cox2 -765 g > c polymorphism on gastric cancers ( 36 , 37 ) .
they have reported not only a nearly 3-fold increased risk of progression from gastric lesions into gastric cancer , but also described an associated between c - allele and gastric cancers .
demonstrated that cox2- 765 g allele promoter polymorphism is associated with most kinds of gastric cancers ( 34 ) . in the present study
, we investigated the presence of this nucleotide variant and recognized allelic frequencies of g-765c in the iranians for the first time , similar to those formerly reported in other studies ( 5 , 23 , 32 ) .
we found no statistically significant between the presence of cc , gc and cc genotypes 765 g > c polymorphisms and risk of gastric cancer .
however , we observed a border line statistically significant ( p=0.043 ) for female subjects with c- carrier genotypes when compared with male subjects ( p=0.645 ) and control groups ( p=0.653 ) .
these results appear that gender may be a risk factor for the development of gastric adenocarcinoma related to cox-2 polymorphism in iranian samples .
although the frequency of gc genotype is much higher than other similar published studies ( 5 , 26 , 34 ) , the frequency of gg ( 27.5% ) and c - carrier ( 72.5% ) genotypes are similar to indian population ( 5 ) . thus , it can be concluded that cox2 -765g / c polymorphism perhaps play a similar role in susceptibility to gastric cancer between asian populations .
we found that , age factor can be excessively marker for gc because we observe a statistically significant difference between increasing of age and gc risk ( or=1.125 , 95ci=1.089 - 1.162 ) .
in general , cox2 -765g / c polymorphisms possibly play a role in cancer development under specific situation or in specific populations .
finally , we conclude that age and gender are important factors which can be involved on association between -765 g > c cox-2 genetic polymorphism and gastric adenocarcinoma risk in iranian samples . | aimthe purpose of this study was to investigate the possible influence of age and gender on association between -765 g > c cox-2 genetic polymorphism and gastric adenocarcinoma risk in iranian patients.backgroundthe promoter polymorphism of cox-2 gene -765 g > c has been described to play an important role in many cancers such as gastric cancer.patients and methodswe carried out single - nucleotide polymorphism analysis in iranian samples including 91 patients and 91 control normal using pcr- rflp technique.resultsstatistical analysis revealed no significant association between gg , gc and cc genotypes and risk of gastric adenocarcinoma
. however differences were considered significant ( p=0.043 ) for female subjects with c carrier genotypes ( gc and cc ) and gastric adenocarcinoma when compared with male patients ( p=0.645 ) and control groups ( p=0.653 ) .
also , there was a statistically significant difference between increasing of age and susceptibility for gastric adenocarcinoma ( odd ratio=1.125 , 95% ci=1.089 - 1.162).conclusionthese results suggested that iranian c carrier females can be more susceptible for gastric adenocarcinoma in comparison with control group . also increasing of age should be considered as a risk factor for this disease . |
the full oxidation of one glucose molecule ( oxidative phosphorylation ) within a cell in the presence of oxygen produces 38 molecules of adenosine - three - phosphate ( atp ) , which in turn represents the essential cellular fuel ( figure 1.a ) .
the first step ( glycolysis , occurring in cytoplasm ) of glucose cellular respiration produces only 2 atp molecules and ends up with production of two molecules of pyruvic acid .
if a given cell has access to oxygen , the pyruvic acid will be converted to acetyl - coenzyme a , which enters the krebs cycle ( citric acid cycle , occurring within mitochondria ) followed by the electron transport chain process ( occurring on the inner mitochondrial membrane ) that creates most of the atp molecules .
it is the very last step within electron transport chain that needs oxygen to collect the terminal electron from the last cytochrome ( cyt a3 ) and become a nascent o to pick up 2 h and create one of the byproducts of aerobic cellular respiration - a water molecule . on the other hand ,
if the cells reside under hypoxic conditions , the pyruvic acid is not converted into acetyl - coenzyme a , but into a lactic acid - the process termed anaerobic cellular respiration ( lactic acid cycle ) . in the latter case , the net energy balance is only two atp molecules making the anaerobic glucose metabolism energetically highly inefficient process . while the lack of oxygen at the cellular level can occur at times of excessive physical activity ( resulting in subsequent muscle pain ) , it also represents a hallmark of highly invasive and fast - growing cancers [ ] . as the cancer cells multiply
, their fast multiplication rate outgrows the angiogenesis so much so that while the glucose access to fast - growing cells could be sufficient the lack of blood vessels disrupts the level of oxygen needed for the full glucose oxidation .
such a microscopic picture defines one of the fundamental properties of the cancer microenvironment that forces malignant cells to metabolize glucose through the lactic acid cycle .
looking at chemical equations between aerobic and anaerobic glucose metabolism ( figure 1 ) one may conclude that cancer cells ( as well as healthy ones ) under hypoxic condition would need 19 times higher uptake of glucose to maintain the same metabolic level as well - oxygenated cells .
this would , in turn , mean that the appropriate quantitative analysis of fdg - based pet images could help in pinpointing hypoxic segments ( by abundance only [ ] ) of the tumor by solely looking into very high uptake values , which would eventually be some 20 times greater than in well - oxygenated cancer cells .
however , the isolation of the hypoxic target volumes is far from being that simple .
apart from the fact that acute hypoxia in tumors develop as soon as one moves few hundred microns from the blood vessels , yet another important fact prevents fdg being an ideal hypoxia marker - the warburg effect .
recently , interest in tumor metabolism has been revived partly as a result of the widespread clinical application of pet using fdg .
fdg - based pet imaging has confirmed that most primary and metastatic cancers show a significant increase in the glucose uptake when compared to normal tissues .
glycolysis involves the conversion of glucose to pyruvate and then to lactic acid , the waste product . in non - cancerous cells ,
mitochondria oxidize pyruvate to carbon dioxide and water in the presence of oxygen ( figure 2.a ) , and the glycolytic reaction is inhibited ( pasteur effect [ ] ) .
conversion of glucose to lactic acid , even in the presence of oxygen is known as aerobic glycolysis ( figure 2.b ) or the warburg effect [ , ] . in one of his seminal papers [ ]
the second phase of cancer formation represents a long struggle for existence by the injured cells to maintain their structure , in which a part of the cells die from lack of energy while another part succeeds in replacing the irretrievably lost respiration energy by fermentation energy ( from lactic acid cycle ) .
warburg 's initial hypothesis that cancer results from impaired mitochondrial metabolism has been shown to be incorrect , but the observation of augmented glycolysis in tumors , even in the presence of oxygen , has been continually proven [ ] . while cancer cells do carry oxidative phosphorylation , the majority of glucose molecules taken by cancer cells ( 66% ) are metabolized through fermentation [ ] , a process that is ten times faster than full glucose oxidation .
in addition to being energetically highly inefficient process glycolysis ( either anaerobic or aerobic ) , with its metabolic products ( such as hydrogen ions ) , cause constant acidification of the extracellular space , which might result in increased local toxicity [ , ]
. nevertheless , despite these drawbacks , cancer cells consistently progress towards the wasteful and potentially toxic glycolytic phenotype .
gatenby and gillies [ ] proposed that the consistent expression of up - regulated glycolysis is not accidental but represents a solution to the environmental growth constraints during tumor development .
they suggest that increased glycolysis is an essential component of the malignant phenotype and , therefore , a hallmark of invasive cancers .
transport enzymes of the glut and hexokinase families are up - regulated in tumor cells expressing the glycolytic phenotype , and the level of glut-1 glucose transporter expression has been shown to correlate with [ 18f ] fdg uptake in non - small cell lung cancer , for example [ ] .
gatenby and gillies 11 describe the concept of carcinogenesis as a process that occurs by cellular evolution implying that common characteristics of malignant phenotypes , such as upregulation of glycolysis , are the result of active selection processes .
they further argue that upregulation of glycolysis is likely to be an adjustment to hypoxia developing as pre - malignant tissue grows gradually further away from their blood supply .
also , an augmented acid production from glycolysis upregulation leads to microenvironmental acidosis and requires further adjustments through somatic evolution to phenotypes resistant to acid - induced toxicity .
finally , they conclude that cell populations that emerge from this evolutionary sequence have a compelling growth advantage , as they alter their environment through increased glycolysis in a way that is toxic to other phenotypes , but harmless to themselves . to further support the attempt by gatenby and gillies 11 in explaining the cause of warburg effect in aggressive tumors as a response to harsh environmental conditions
know a priori they will encounter severe conditions in the future . consequently , they
decide to switch their glucose metabolism to highly inefficient but the only possible ( and highly toxic ) metabolic pathway . to make their explanation more sounded ,
gatenby and gillies 11 speculate that : intuitively , it would seem that the darwinian forces prevailing during the somatic evolution of invasive cancers would select against a metabolic phenotype that is more than an order of magnitude less efficient than its competitors and that is environmentally poisonous . in other words , the accepted tenet of survival of the fittest would seem to generally favour populations with more efficient and sophisticated substrate metabolism .
consequently , they suggest that glycolytic phenotype in cancers is directly governed by the evolutive mechanisms , over the relatively short time frame during which tumors develop .
figure 3 illustrates the very point within a cellular glucose metabolism where the fate of the pyruvic acid is decided . in the presence of oxygen
, the pyruvic acid will be converted into acetyl group and attached to coenzyme a , a process mediated by the so - called pyruvate dehydrogenase complex ( pdc ) .
the complex consists of three enzymes : pyruvate dehydrogenase , dihydrolipoyl transacetylase , and dihydrolipoyl dehydrogenase . on the other hand , conversion of pyruvic acid to lactic acid requires one enzyme only - lactate dehydrogenase ( ldha ) . from the cellular kinetics point of view
, one may ask a simple question : what is the probability that something goes wrong with either of the two possible metabolic pathways depicted in figure 3 ?
synthesis of three enzymes , needed to provide conversion of pyruvic acid to acetyl coenzyme a , even in the presence of oxygen will be ( notably three times ) more prone to the errors than a transcription of only one ( competing ) enzyme .
it was reported that many human cancers have higher ldha levels than normal tissues [ ] , but the correlation between oncogenes and glycolysis was poorly understood .
the question could be then raised whether the warburg effect is only a consequence , or could it be at the root of the very cause of carcinogenesis ?
a new hypothesis could be staged that the switch from aerobic cellular respiration to aerobic glycolysis leads to carcinogenesis , and the cell begins to develop the cancerous phenotype [ , ] at the point where the fate of pyruvic acid is decided .
such a switch could be governed by the lack of complete pdc ( at least one of the enzymes is missing ) .
while at this very moment the question whether warburg effect is a hen , or an egg remains at the level of pure hypothesis , several clinical observations might be called upon to support such proposition indirectly . while there is no apparent relation between type 1 diabetes mellitus patients and incidence of cancer to this date [ ] ,
several publications argue that there could be a lower cancer rate in patients with insulin - dependent diabetes . in 2003 , zendehdel et al .
[ ] published results on cancer incidence in patients with type 1 ( insulin - dependent ) diabetes mellitus on a cohort of 29 187 patients , followed over a period of 30 years , during which they observed 355 incidences of cancer .
such a low frequency ( 1% over 30 years , or 0.04% per year ) appears negligible when compared to 1.66 million cases of new cancer cases per year in the us ( 0.52% per year [ ] ) .
[ ] reported on the lower incidence of cancer death mortality in diabetic patients ( 6.7% , both type 1 and 2 ) when compared to non - diabetic patients ( 13.4% ) using a cohort of 39 811 patients with the end - stage renal disease .
it might be argued that cells in diabetic patients ( generally deprived of normal glucose uptake due to lacking insulin ) become trained ( to use rhetoric by blagosklonny [ ] ) by the microenvironment and well prepared as soon as glucose becomes available .
once the glucose is phosphorylated by hexokinase and enters the glucose oxidation process , the cell is prepared not to waste the opportunity and gets the maximum out of the relatively scars glucose supplies .
one could further argue that diabetic patient cells are making sure that the synthesis of the pdc is up and running flawlessly , to avoid wasteful pathway of cellular glucose metabolism . on the other hand , despite a relatively small amount of data published it appears that the incidence of cancer is also correlated with the increased intake of carbohydrates [ , , ] .
one may argue that normal cells , exposed to increased supply of glucose would quickly switch towards the energetically inefficient pathway ( lactic acid cycle ) of burning glucose even in the presence of oxygen ( warburg effect ) since the source of energy ( glucose - atp ) are virtually inexhaustible .
in addition , the atp production via fermentation is much faster ( as mentioned above ) , albeit highly ineficient , when compared to full oxydation .
it is also of note that contrary to type 1 ( insulin - dependent ) , patients with type 2 diabetes mellitus have higher probability for cancer incidence [ ] .
yet another detail deserves attention : type 1 diabetes is commonly regarded as a juvenile - onset diabetes as it often begins in childhood while the type 2 diabetes was considered an adult - onset diabetes .
however , type 2 diabetes is becoming increasingly common in children [ ] who are more obese or overweight that could be correlated with carbohydrates rich diets . finally
, the possible triggering of carcinogenesis by aerobic glycolysis , accompanied by increased glucose uptake , can be further supported by studies demonstrating increased glucose uptake observed to coincide with the transition from premalignant lesions to invasive cancer [ , ] .
unlike warburg 's initial hypothesis that cancer cells metabolize glucose through aerobic glycolysis due to impaired mitochondrial function a new hypothesis was presented that the normal cell becomes cancerous at the point when it switches its glucose metabolism from oxidative phosphorylation to aerobic glycolysis . the new hypothesis that warburg effect corresponds to the very beginning of carcinogenesis
such failure could be mediated by one ( or multiple ) of the well - known carcinogenic factors in synergy with an excessive supply of glucose in carbohydrates rich diets .
the new hypothesis revolves around a point within cellular glucose oxidation at which the fate of pyruvic acid is decided .
several observations have been presented to support such hypothesis : lower incidence of cancer in insulin - dependent type 1 diabetes mellitus patients ; increased cancer incidence in societies consuming high quantities of carbohydrates ; and the increased probability of synthesis failure of the pyruvate dehydrogenase complex consisting of three enzymes when compared to the synthesis of a single lactate dehydrogenase enzyme .
contemporary agreement in explaining why tumor cells opt for aerobic glycolysis ( warburg effect ) that is far less efficient than oxidative phosphorylation at producing atp , is that it represents evolutionary adaptation to harsh microenvironmental conditions by using the carbon chains ( from the lactic acid ) as building blocks for synthesis of biomolecules ( nucleic acids , proteins , and lipids ) , which are essential for cell proliferation .
however , even the acceptance of the aerobic glycolysis being a more adequate glucose metabolism pathway for cancer cells , the question of a hen or an egg remains : is the warburg effect just a consequence , or could it be the very cause of carcinogenesis ( figure 4 ) ? | ever since its discovery ( 1924 ) the warburg effect ( aerobic glycolysis ) remains an unresolved puzzle : why the aggressive cancer cells prefer to use the energetically highly inefficient method of burning the glucose at the cellular level ? while in the course of the last 90 years several hypotheses have been suggested , to this date there is no clear explanation of this rather unusual effect .
even though it is commonly assumed that warburg effect is a consequence of carcinogenesis , yet another hypothesis could be brought up that the cellular switch to aerobic glycolysis may represent the very point in time when a normal cell becomes cancerous .
furthermore , this switch may happen at the point where the fate of pyruvic acid is determined , caused by the inadequate supply of enzymes that promote citric as opposed to lactic acid cycle .
currently , few clinical observations , like low cancer incidence in type 1 diabetes mellitus and increased cancer incidence in people on high carbohydrate diets might be called upon to support such hypothesis . |
actually , any quantum system interacting with the environment ( the bath ) can not be isolated from the environment completely .
@xcite in quantum information and quantum computation , @xcite the decay process of quantum system induced by quantum fluctuations of the bath is very important for the qubit . in quantum optics ,
@xcite the jaynes - cummings model has been one of the most important models , @xcite which describes the light - matter interaction of a two - level atom and a single mode of the quantized electromagnetic field .
@xcite among these light - matter interaction issues , @xcite the revivals and collapses of the atomic population inversion ( also named rabi oscillation ) has been studied in the literatures .
@xcite decay of rabi oscillation has also been used as a tool to characterize the decoherence in superconducting qubits ( charge qubit , phase qubit and flux qubit ) .
@xcite recently , in circuit qed system , @xcite the researchers have performed spectroscopic measurements of a superconducting qubit dispersively coupled to a nonlinear resonator driven by a pump microwave field .
@xcite also in nanomechanical qed system , the integration of josephson junction qubit and nanomechanical resonators are attracting considerable attentions .
@xcite the dynamics of all these qubit - resonator systems could be described by the jaynes - cummings hamiltonian .
when intrinsic nonlinearity of nanomechanical resonator @xcite is considered in the coupled qubit - resonator system , superconducting qubit can be used to probe quantum fluctuations of nonlinear resonator . @xcite and
the nonlinearity can be used to create nonclassical states in mechanical systems @xcite and selectively address the nanomechanical qubit transitions in quantum information processing .
@xcite in previous studies , @xcite master equation approach has been used to deal with the issues in open quantum system . in this paper ,
considering the influence of the environment on this nanomechanical qed system , we can use microscopic master equation approach @xcite to solve time evolution of the density operator for the qubit - resonator system and study the temporal behavior of rabi oscillation .
the paper is structured as follows . in sec.ii ,
a nonlinear jaynes - cummings model @xcite is used to describe the dynamics of the coupled qubit - nanomechanical resonator system . in sec.iii , using microscopic master equation approach , we solve time evolution of density operator for the qubit - resonator system . the probability on excited state of the qubit is calculated to show the temporal process of rabi oscillation .
finally , the results are summarized .
in nanomechanical qed system , we can use a jaynes - cummings type hamiltonian to describes the dynamics of the qubit - resonator system consisting of a charge qubit and a nanomechanical resonator system , @xmath0 considering the nonlinearity of nanomechanical resonator , the hamiltonian for this qubit - resonator system writes @xcite @xmath1 here the rotating - wave approximation ( @xmath2 ) and @xmath3 is adopted .
corresponding to charge qubit and nanomechanical resonator , the lowering ( raising ) operator @xmath4 ( @xmath5 ) and the annihilation ( creation ) operator @xmath6 ( @xmath7 ) satisfy the commutation relation @xmath8=\sigma_{z}$ ] and @xmath9=1 $ ] .
the hamiltonian in eq .
( [ nonlinear jc ham ] ) describes the dynamics of a nonlinear jaynes - cummings model , @xcite and a quartic potential @xmath10 @xcite gives nonlinear part @xmath11 which leads to the phonon - phonon interaction in nanomechanical qed systems .
the @xmath12 is the coupling constant and the @xmath13 is the nonlinearity parameter ( @xmath14 ) . solving the hamiltonian @xmath15 , we get the ground state @xmath16 with energy @xmath17 and excited state doublets @xmath18 for @xmath19 with energy @xmath20 some parameters are defined , i.e. , @xmath21 and @xmath22 . with the loss of nanomechanical resonator , the total hamiltonian @xmath23 consists of three parts , i.e. , the system part @xmath15 , the interaction part @xmath24 and the bath part @xmath25 where @xmath26 and @xmath27 are bosonic annihilation and creation operators for the bath oscillators for the mode frequency @xmath28 ( @xmath29 ) . in this paper , we adopt microscopic master equation approach @xcite to solve time evolution of density operator ( @xmath30 ) for the qubit - resonator system , our master equation is @xmath31 where @xmath32 is a time - independent linear superoperator . using the microscopic master equation approach , @xcite
we obtain the eigen - equations @xmath33 the @xmath34 is a set of eigenoperators due to the superoperator @xmath32 with the eigenvalue @xmath35 for the index @xmath36 . given initial state of the qubit - resonator system , the initial reduced density operator @xmath37 is expanded in terms of @xmath38 , @xmath39 where the @xmath40s are time - independent coefficients .
the results in ref.@xcite tell us that time evolution of reduced density operator @xmath30 will be @xmath41 now only one excitation is interested , our truncated basis @xmath42 consists of the three lowest eigenstates due to the hamiltonian @xmath15 , now we can rewrite the master equation in eq .
( [ master equation-1 ] ) , @xmath43+\mathcal{l}_{+}\rho+\mathcal{l}_{-}\rho.\label{master equation}\ ] ] here the non - unitary parts of dissipative dynamics are described by @xmath44 and @xmath45 , @xmath46 the superoperator @xmath47describe the transitions between the higher excited state @xmath48 and the ground state @xmath49 induced by the environment . the corresponding decay rate @xmath50 ( @xmath51 ) describes the transition from the excited state @xmath52 ( @xmath53 ) to the ground state @xmath49 , these transitions are induced by the interaction between the system and the environment . with respect to the system hamiltonian @xmath15 in eq .
( [ nonlinear jc ham ] ) , the eigenoperators @xmath38s are obtained , @xmath54 the corresponding eigenvalues @xmath55s ( for @xmath56 ) are @xmath57 @xmath58 and @xmath59
in traditional cavity qed theory , @xcite the rabi oscillation means that there exists energy exchange of one photon between a two - level atom and a single mode quantized field in cavity .
considering the nonlinearity of nanomechanical resonator , we study the decay process of rabi oscillation in the nonlinear jaynes - cummings model described by the hamiltonian in eq .
( [ nonlinear jc ham ] ) . given the initial state of the qubit - resonator system @xmath60 , it means that the qubit is in excited state @xmath61 and the resonator is in vacuum state @xmath62 .
thus , the initial reduced density operator reads @xmath63 expanding @xmath37 into some eigenoperators @xmath38s , we obtain a set of coefficients @xmath40s , @xmath64 @xmath65 and @xmath66 according to eq.([time rho ] ) , the time evolution of density operator for the qubit - resonator system is calculated as @xmath67 here the probability of the qubit in the excited ( upper ) state @xmath68 is @xmath69^{2}\nonumber \\ & & + \sin^{2}\theta e^{-\frac{\gamma_{1+}+\gamma_{1-}}{4}t}\cos^{2}\left(\omega t\right).\label{probability of excited state}\end{aligned}\ ] ] it characterizes the temporal behavior of rabi oscillation in the qubit - resonator system , decay process of rabi oscillation owns the periodic structure of time oscillating . the nanomechanical resonator is assumed to be an ideal resonator ( @xmath70 ) , and ignoring the difference of decay rates ( @xmath71 ) , then the probability @xmath72 becomes @xmath73 it describes the well known rabi oscillation in jaynes - cummings model.@xcite comparing the results in eq .
( [ probability of excited state ] ) with eq .
( [ probability at excited state in rabi ] ) , we find that nonlinearity parameter @xmath13 and decay rates @xmath74 modify the periodic structure of time oscillating in rabi oscillation . to further clarify the dependence of nonlinearity parameter and decay rates on the probability @xmath72 clearly
, some figures are plotted with parameters @xmath75 . here ,
we take the frequency @xmath76 as the unit for all these parameters . in fig.@xmath77 , the probability @xmath72 versus time @xmath78 is plotted with parameters @xmath70 and @xmath79 .
figure 1 shows the well known rabi oscillation , it verifies the results in eq .
( [ probability at excited state in rabi ] ) . and
@xmath80.,title="fig:",width=302][rabi in jc model ] vs the time @xmath78 , where the excite states ( @xmath81 and @xmath82 ) own the different decay rate ( @xmath83 and @xmath84 ) and @xmath70.04.,title="fig:",width=302][different decay rate and nonlinearity ] in fig.@xmath85 , the probability @xmath72 versus time @xmath78 is plotted with parameters @xmath86 , @xmath84 and @xmath83 .
figure 2 shows that nonlinearity parameter @xmath13 and decay rates ( @xmath74 ) modify the periodic structure of time oscillating in rabi oscillation , which is obviously different from figure 1 .
based on those results in eq .
( [ probability of excited state],[probability at excited state in rabi ] ) , we find that nonlinearity parameter @xmath13 slows down the time - oscillating period of rabi oscillation @xmath87 . in the following , we will study how nonlinearity parameter @xmath13 and decay rates ( @xmath74 ) affect the temporal behavior in rabi oscillation solely .
firstly , assuming the same decay rates @xmath88 and nonlinearity parameter @xmath89 , the probability in eq .
( [ probability of excited state ] ) becomes @xmath90 the dependence of the probability @xmath72 on nonlinearity parameter @xmath13 is plotted in fig.@xmath91 .
when @xmath92 , the minimum of the probability @xmath93 decays exponentially , which is different from the well known rabi oscillation in fig.@xmath77 . secondly , assuming no nonlinearity @xmath70 and different decay rates ( @xmath74 ) , the probability in eq .
( [ probability of excited state ] ) becomes @xmath94 the dependence of the probability @xmath72 on different decay rates is plotted in fig.@xmath95 .
when @xmath96 , the minimum of the probability @xmath97 shows that the difference of decay rates between @xmath98 and @xmath99 does not affect the short - time behavior and long - time behavior of rabi oscillation obviously , which is seen in fig.@xmath95 .
vs the time @xmath78 , where the excite states ( @xmath81 and @xmath82 ) own the same decay rate ( @xmath100 ) and nonlinearity parameter @xmath86.,title="fig:",width=302][nonlinearity fig1 ] vs the time @xmath78 , the excite states ( @xmath81 and @xmath82 ) of the qubit - resonator system own the different decay rate ( @xmath83 and @xmath84 ) and nonlinearity parameter @xmath70.,title="fig:",width=302][pure jc with microscopic master ] analytically , we can study the short - time behavior of rabi oscillation , then the probability @xmath101 becomes @xmath102t\right\ } .\label{short - time probability}\ ] ] ignoring the nonlinearity of nanomechanical resonator or the difference of decay rates , i.e. , @xmath70 or @xmath103 , the probability @xmath101 becomes @xmath104 according to the results in eq .
( [ short - time probability ] ) and eq .
( [ short - time decay rate ] ) , we find that both nonlinearity parameter @xmath13 and the difference of decay rates ( @xmath74 ) affect dominate the short - time behavior of rabi oscillation jointly .
also , these two factors speed up the decay of rabi oscillation in short - time limit .
in summary , we have studied the dynamics of the nanomechanical qed system consisting of a charge qubit and a nanomechanical resonator .
the temporal behavior of rabi oscillations is analytically studied while the intrinsic nonlinearity of nanomechanical resonator is considered . with the loss of nanomechanical resonator
, microscopic master equation approach is used to calculate the excited - state probability of charge qubit in this nonlinear jaynes - cummings model .
these results show that nonlinearity parameter and decay rates can affect time - oscillating and decaying of rabi oscillation solely or jointly . | in nanomechanical qed system , consisting of a charge qubit and a nanomechanical resonator with intrinsic nonlinearity , we study the temporal behavior of rabi oscillation in the nonlinear jaynes - cummings model . using microscopic master equation approach ,
we solve time evolution of the density operator describing this model .
also , the probability of excited state of charge qubit is calculated .
these analytic calculations show how nonlinearity parameter and decay rates of two different excited states of the qubit - resonator system affect time - oscillating and decaying of rabi oscillation . |
in the study of interconnection and communication networks , the theory of digraphs plays a key role because , in many cases , the links between nodes are unidirectional . in this theory , there are three concepts that have shown to be very fruitful to construct good and efficient networks .
namely , those of quotient digraphs , voltage digraphs and ( partial ) line digraphs . roughly speaking ,
quotient digraphs allow us to obtain a simplified or ` condensed ' version of a bigger digraph , while the voltage and line digraph techniques do the converse by ` expanding ' a smaller digraph . from this point of view , it is natural that the three techniques have close relationships . in this paper
we explore some of such interrelations by introducing a general construction that we call expanded digraphs .
these digraphs are obtained from a base graph whose vertices become vertex sets in the new graph , and the adjacencies are defined from a set of mappings .
a special case is obtained when such mappings are defined within a group , so obtaining the lifted graphs of base graphs with assigned voltages ( elements of the group ) on its arcs . in this context , we show that de bruijn and kautz digraphs can be defined as lifted digraphs of smaller de bruijn digraphs .
moreover , it is proved that , under some sufficient conditions , the lift of a base graph that is a line digraph is again a line digraph . in the more general case of nonrestricted maps
, we consider the quotient digraphs , and the equivalent constructions of vertex - split digraphs and partial line digraphs . here
, it turns out that the line digraph and quotient operations commute .
finally , it is proved that the techniques of vertex - splitting and partial line digraph are equivalent , and some consequences are derived .
let us first recall some basic terminology and notation concerning digraphs
. for the concepts and/or results not presented here , we refer the reader to some of the basic textbooks on the subject ; see , for instance , chartrand and lesniak @xcite or diestel @xcite . through this paper , @xmath0 denotes a digraph , with vertex set @xmath1 and arc set @xmath2 . an arc from vertex @xmath3 to vertex @xmath4
is denoted by either @xmath5 , @xmath6 , or @xmath7 .
we allow _ loops _ ( that is , arcs from a vertex to itself ) , and _
multiple arcs_. the set of vertices adjacent to and from @xmath8 is denoted by @xmath9 and @xmath10 , respectively .
such vertices are referred to as _ in - neighbors _ and _ out - neighbors _ of @xmath4 , respectively .
moreover , @xmath11 and @xmath12 are the _ in - degree _ and _ out - degree _ of vertex @xmath4 , and @xmath13 is _ @xmath14-regular _ when @xmath15 for any @xmath8 .
expanded digraphs are , in fact , a type of compounding that consists of connecting together several copies of a ( di)graph by setting some ( directed ) edges between any two copies .
let @xmath0 be a ( base ) digraph on @xmath16 vertices .
as said before , we allow loops and multiple arcs .
assume that each vertex @xmath8 has assigned a vertex set @xmath17 , and each arc @xmath18 has assigned a mapping @xmath19 .
let @xmath20 .
the _ expanded digraph _
@xmath21 of @xmath13 with respect to @xmath22 has vertex set @xmath23 , and there is an arc from @xmath24 to @xmath25 whenever @xmath26 and @xmath27 .
some important particular cases of this construction are obtained when the mappings in @xmath22 are defined from a group : * * cayley digraphs*. let @xmath28 be a group with generating set @xmath29 having @xmath30 elements . if @xmath13 is a singleton with assigned vertex set @xmath28 , @xmath30 loops , and each loop @xmath31 has the mapping @xmath32 , with @xmath33 , then the expanded digraph @xmath21 is the _ cayley digraph _ @xmath34 . *
* coset digraphs*. let @xmath28 be a group with generating set @xmath29 having @xmath30 elements and with subgroup @xmath35 .
if @xmath13 is a singleton with assigned vertex set @xmath36 , @xmath30 loops , and each loop @xmath31 has the mapping @xmath37 , with @xmath33 , then the expanded digraph @xmath21 corresponds to the _ coset digraph _ @xmath38 .
two natural generalizations of these concepts are the following ( as far as we know , the second one is a new proposal ) : * * lifted ( of voltage ) digraphs * or * expanded cayley digraphs*. let @xmath28 be a group with generating set @xmath29 having @xmath30 elements .
if each vertex of @xmath13 is assigned to the vertex set @xmath28 , and each arc @xmath31 has the mapping @xmath39 , with @xmath33 , then the expanded digraph @xmath21 is the so - called _ lifted digraph _
( or simply _ lift _ ) @xmath40 ( see section [ sec : voltage ] ) . * * expanded coset digraphs*. let @xmath28 be a group with generating set @xmath29 having @xmath30 elements and with subgroup @xmath35 .
if each vertex of @xmath13 is assigned to the vertex set @xmath36 , and each arc @xmath31 has the mapping @xmath37 , with @xmath33 , then we refer to the corresponding expanded digraph @xmath21 as the _ expanded coset digraph _ @xmath40 .
when a group is involved in the setting of the mappings , the symmetry of the obtained constructions yield digraphs with large automorphism groups . to our knowledge ,
one of the first papers where voltage ( undirected ) graphs were used for construction of dense graphs was that of alegre , fiol and yebra @xcite , but without using the name of ` voltage graphs ' .
this name was coined previously by gross @xcite . for more information ,
see gross and tucker @xcite , baskoro , brankovi , miller , plesnk , ryan and ir @xcite , and miller and ir @xcite .
let @xmath13 be a digraph with vertex set @xmath41 and arc set @xmath42 .
then , given a group @xmath28 with generating set @xmath29 , a voltage assignment of @xmath13 is a mapping @xmath43 .
the lift @xmath44 is the digraph with vertex set @xmath45 and arc set @xmath46 , where there is an arc from vertex @xmath47 to vertex @xmath48 if and only if @xmath49 and @xmath50 . such an arc is denoted by @xmath51 .
recall that the _ de bruijn digraph _ @xmath52 has vertices @xmath53 , where @xmath54 for @xmath55 , and adjacencies @xmath56 in contrast with that , the _ kautz digraph _ @xmath57 has vertices @xmath53 , where @xmath58 , @xmath59 for @xmath60 , and adjacencies : @xmath61 now , if we consider the mapping @xmath62 two alternative definitions are the following : the de bruijn digraph @xmath52 has vertices @xmath63 , where @xmath64 , and adjacencies : @xmath65 similarly , the kautz digraph @xmath57 has vertices @xmath66 , where @xmath67 , @xmath68 , and adjacencies : @xmath69 notice that the mapping @xmath70 where @xmath71 , is a homomorphism from the kautz digraph @xmath57 to the de bruijn digraph @xmath72 .
also , note the inverse mapping @xmath73 now we show that both de bruijn and kautz digraphs can be seen as lifts of smaller de bruijn digraphs with appropriate voltage assignments .
[ lemmadb ] the equality @xmath74 holds with @xmath75 the vertices of the arc @xmath76 in @xmath52 , with voltage @xmath77 , give rise to the vertex subsets @xmath78 and @xmath79 in @xmath80 .
moreover , the elements of @xmath81 can be written as @xmath82 and @xmath83 thus , if we define the mapping @xmath84 in such a way that @xmath85 , we get the adjacencies @xmath86 with @xmath87 , which correspond to those of the de bruijn digraph @xmath88 , as claimed . as an example , figure [ voltage - debruijn - dibuix ] shows how to obtain @xmath89 as a lifted digraph of @xmath90 . as a lifted digraph of the base digraph @xmath90.,width=529 ]
-14 cm similarly , the following result shows that kautz digraphs can be seen as lifted digraphs of de bruijn digraphs .
the equality @xmath91 holds with @xmath92 where @xmath93 .
the proof is similar to that of proposition [ lemmadb ] .
indeed , the vertices of the arc @xmath76 in @xmath52 , with @xmath93 and voltage @xmath77 , give rise to the vertex subsets @xmath94 and @xmath95 in @xmath96 .
moreover , the elements of @xmath97 can be written as @xmath98 and @xmath99 thus , if we define the mapping @xmath100 in such a way that @xmath85 , we get the adjacencies @xmath86 with @xmath101 , which correspond to those of the kautz digraph @xmath102 .
this completes the proof . by way of example , in figure [ k(2,3)voltage - dibuix ] we show how @xmath103 can be seen as a lifted digraph of @xmath90 . as a lifted digraph of the base digraph @xmath90.,width=529 ] -13.5 cm
in the more general context of nonrestricted maps , we now consider the quotient digraphs , and the equivalent constructions of vertex - split digraphs and partial line digraphs .
let @xmath0 be a digraph with @xmath16 vertices .
a partition @xmath104 of its vertex set @xmath105 , for @xmath106 , is called _ regular _ if the number @xmath107 of arcs from a vertex @xmath108 to vertices in @xmath109 only depends on @xmath110 and @xmath111 .
the numbers @xmath107 are usually called _ intersection parameters _ of the partition .
the _ quotient digraph _ of @xmath13 with respect to @xmath104 , denoted by @xmath112 , has vertices the subsets @xmath113 , for @xmath114 , and @xmath107 parallel arcs from vertex @xmath113 to vertex @xmath109 . in the _ line digraph _ @xmath115 of a digraph @xmath13
, each vertex represents an arc of @xmath13 , that is , @xmath116 , and a vertex @xmath6 is adjacent to a vertex @xmath117 when the arc @xmath5 is adjacent to the arc @xmath118 : @xmath119 .
line digraphs have shown to be very interesting structures in the study of dense digraphs ( that is , digraphs with a large number of vertices for given degree and diameter ) . moreover ,
it is know that the iteration of the line digraph technique yields digraphs with maximum connectivity . for more details ,
see , for instance the papers by fiol , yebra , and alegre @xcite , and fbrega and fiol @xcite .
furthermore , by the heuchenne s condition @xcite , a digraph @xmath13 is a line digraph if and only if , for every pair of vertices @xmath3 and @xmath4 , either @xmath120 or @xmath121
. let @xmath124 be a regular partition of @xmath13 with intersection parameters @xmath107 .
then , consider the induced partition of its arcs ( or vertices of @xmath115 ) @xmath125 with sets @xmath126 . this partition is also regular since , from the definition of line digraph , the number of arcs from a vertex @xmath127 to any vertex @xmath128 is @xmath129 . to prove the digraph isomorphism ,
assume that @xmath130 has the arc @xmath131 .
this means that in @xmath13 there is the path @xmath132 , where @xmath133 , @xmath134 and @xmath135 . but
@xmath127 and @xmath136 so that , in @xmath137 , there is the arc @xmath138 and this concludes the proof .
[ prop : lift - is - a - ld ] let @xmath139 be a digraph endowed with a voltage assignment @xmath140 . if @xmath13 is a line digraph , and for every pair of vertices @xmath3 and @xmath4 with common out - neighbor sets @xmath141 , we have @xmath142 then , the lifted digraph @xmath40 is again a line digraph .
it suffices to prove that @xmath40 satisfies heuchenne s condition . with this aim ,
let @xmath143 , so that in @xmath40 the vertex @xmath47 is adjacent to the vertices @xmath144 and @xmath145 .
now , if there is a vertex @xmath8 such that @xmath146 , we also have @xmath147 ( because @xmath13 is a line digraph ) .
but the former implies that vertex @xmath48 , where @xmath148 is adjacent to vertex @xmath149 moreover , from ( [ line - condition ] ) interchanging @xmath110 and @xmath111 , we get that @xmath150 .
let us now consider what we call _ the vertex - splitting method _ to `` blow up '' a digraph . given a digraph @xmath139 on @xmath16 vertices and @xmath152 arcs , the vertex - split digraph @xmath153 , where @xmath154 is constructed as follows .
every vertex @xmath8 is split into @xmath155 vertices @xmath156 , where @xmath157 .
thus the order of @xmath153 is @xmath158 satisfying @xmath154 .
moreover , for each arc @xmath159 , we choose any vertex , say @xmath160 , with @xmath161 , and set the arcs @xmath162 for every @xmath163 .
we proceed in this way with all the arcs of @xmath13 , with the condition that , in the end , all vertices of @xmath153 must have nonzero indegree .
( notice that this is always possible , as @xmath164 for every @xmath165 . )
the above method is shown to be equivalent to the partial line digraph technique , that was proposed by fiol and llad in @xcite , which is as follows . given the digraph @xmath166 as above , let @xmath167 a subset of @xmath168 arcs satisfying @xmath169 , so that @xmath170 . then in the _ partial line digraph _ of @xmath13 , denoted by @xmath171 , each vertex represents an arc of @xmath172 , and a vertex @xmath6 is adjacent to the vertices @xmath173 for each @xmath174 , where let the partial line digraph @xmath180 be constructed from the arc set @xmath172 .
then , in constructing @xmath153 , every vertex @xmath4 of @xmath13 is split into the vertices @xmath181 if and only if @xmath182 for every @xmath183 . now , for every @xmath8 , assume that @xmath184 . then ,
in @xmath153 we have @xmath185 for some @xmath186 . assuming that @xmath159
, we have to consider two cases : * if @xmath176 , then in @xmath153 we choose every vertex @xmath187 , for @xmath188 , to be adjacent to the vertex @xmath189 . * otherwise , in @xmath180 we choose the vertex @xmath6 to be adjacent to the vertex @xmath173 , where @xmath190 ( for the chosen vertex @xmath191 in @xmath153 ) .
let @xmath13 be a digraph different from a cycle , with diameter @xmath194 and mean distance @xmath195 .
then , the diameter @xmath196 and mean distance @xmath197 of the vertex - split digraph @xmath153 , with @xmath198 , satisfy : @xmath199 * acknowledgments .
* this research is supported by the _ ministerio de ciencia e innovacin _ , spain , and the _
european regional development fund _ under project
mtm2014 - 60127-p , and the _ catalan research council _ under project 2014sgr1147 ( c. d. and m. a. f. ) . | in this note we present a general approach to construct large digraphs from small ones .
these are called expanded digraphs , and , as particular cases , we show the close relationship between lifted digraphs of voltage digraphs and line digraphs , which are two known ways to obtain dense digraphs . in the same context , we show the equivalence between the vertex - splitting and partial line digraph techniques . then , we give a sufficient condition for a lifted digraph of a base line digraph to be again a line digraph .
some of the results are illustrated with two well - known families of digraphs .
namely , the de bruijn and kautz digraphs , where it is shown that both families can be seen as lifts of smaller de bruijn digraphs with appropriate voltage assignments .
_ keyword : _ digraph , adjacency matrix , regular partition , quotient digraph , voltage digraphs , lifted digraph , partial line digraphs , vertex - split digraphs .
_ mathematics subject classifications : _ 05c20 , 05c50 , 15a18 . |
it may occur when a person is suffering from extreme stress , for example , facing his or her own death .
it is believed to be a systemic disease , e.g. , it has been associated with vicarious menstruation , a condition in which bleeding occurs from a surface other than the mucous membrane of the uterine cavity at a time when normal menstruation should take place .
hematohidrosis can also occur in the settings of excessive exertion , psychogenic and other unknown factors .
it has also been reported in an 8-year - old child just as in this case without any specific pathology .
one such school of thought says that there are multiple blood vessels around the sweat glands arranged in a net like form .
the blood at this point goes into the sweat glands which push the blood to the surface and manifests as droplets of blood mixed with sweat .
the term hematofolliculohidrosis was proposed because it appeared along with sweat - like fluid and the blood exuded via the follicular canals .
hereby , we report a case of 13-year - old boy with history of spontaneous bleeding from skin and mucous membranes since january 2007 . he bled daily , more so during school hours of 9 - 11 am and this lasted for around 1 minute .
it recurred after 5 minutes and the patient bled continuously or intermittently followed by spontaneous cessation .
there was no past history or family history of bleeding tendencies , nor of any systemic diseases .
there was no evidence of any trauma , purpura , scratch marks or any sign suggestive of bleeding . on examination , there was oozing of blood stained fluid from face [ figure 1 ] , arm [ figure 2 ] and trunk . on mopping , it disappeared immediately leaving behind no signs of trauma , nor any disease only to appear again within few seconds .
patient was referred to ent department for history of bleeding from external ear . sweating blood from face sweating blood from arms
he was investigated for complete blood count , urine routine , liver function tests and renal function tests which were all normal .
bleeding time was 2.15 min [ normal range ( n)- 2 - 7 min ] , clotting time was 6 min ( n- 5 - 10 min ) , prothrombin time 15.1 ( control- 15.6 sec ) , activated partial thromboplastin- 31.8 sec ( control- 32.0 sec ) , platelet count was 3.3 lakhs ( n- 1.5 - 4.5 lakhs / cu.mm ) and -feto protein levels were 1.0 iu / ml ( n- 0 - 8 iu / ml ) .
computed tomography ( ct ) , intracranial and neck angiography and magnetic resonance imaging of brain were normal .
diagnosis of hematohidrosis was made clinically , and confirmed by benzidine test in which hemoglobin in blood reacts with hydrogen peroxide liberating oxygen , which then reacts with organic reagent producing a green to blue - colored compound .
he was given alprazolam ( 0.25 mg ) once daily for 10 days , which was then stopped .
the patient then decided to opt for alternative medicinal system along with breathing exercises and reported no recurrence until he was on that treatment .
hematohidrosis also known as hematidrosis , hemidrosis and hematidrosis , is a condition in which capillary blood vessels that feed the sweat glands rupture , causing them to exude blood , and occurs under conditions of extreme physical or emotional stress .
one author proposed the term " hematofolliculohidrosis " because it appeared along with sweat - like fluid and blood exudes via the follicular canals .
various causative factors , like it being component of systemic disease , vicarious menstruation , excessive exertion , psychogenic , psychogenic purpura and unknown causes have been suggested . acute fear and intense mental contemplation are the most frequent causes , as reported in six cases in men condemned to execution , a case occurring during the london blitz , a case involving fear of being raped , a case of fear of a storm while sailing , etc . in another indian case report , the probable cause for hematohidrosis was chronic stress , as the other causes were ruled out by detailed investigations .
psychogenic purpura is supposed to be caused by hypersensitivity to the patients own blood or autoerythrocyte sensitization and is characterized by repeated crops of ecchymoses , gastrointestinal bleedings and hematuria .
another type of bleeding through skin is psychogenic stigmata ; a term used to signify areas of scars , open wounds or bleeding through the unbroken skin .
the clinical findings of this type are a slight elevation of skin before prolonged oozing of blood , a pea - sized bluish discoloration on patient 's palm and erysipelas - like lesions . in another study , a patient developed bleeding from her old scars whenever she had severe anxiety .
the severe mental anxiety activates the sympathetic nervous system to invoke the stress - fight or flight reaction to such a degree as to cause hemorrhage of the vessels supplying the sweat glands into the ducts of the sweat glands .
effect on the body is weakness and mild to moderate dehydration from the severe anxiety and both blood and sweat loss .
it has recently been proposed that there may be some defects in the dermis causing stromal weakness .
these defects will communicate with vascular spaces in the dermis and they will eventually dilate and enlarge as blood - filled spaces when the blood comes in .
after that , they will exude the blood out by either via follicular canals or directly on to the skin surface and this will occur whenever the positive pressure inside is enough . later they will collapse leaving no scar .
this phenomenon acts like a balloon , waxes and wanes and thus explains why these bleeding episodes are sometimes intermittent and self - limiting .
immediate biopsy is important because a biopsy done after these spaces collapse will not help in identifying them .
we are unable to comment on the efficacy of the alternate medicinal systems . as the patient was on multiple therapies . | hematohidrosis is a rare clinical condition of sweating blood .
a 13-year - old boy was presented to the department of dermatology with a history of spontaneous bleeding from skin since january 2007 . during examination
, it disappeared as soon as it was mopped leaving behind no sign of trauma only to reappear within a few seconds .
this confirms that it was sweating of blood and not bleeding .
bleeding time , clotting time and prothrombin time was normal .
patient was diagnosed with hematohidrosis clinically by exclusion , confirmed by benzidine test , biochemical and microscopic examination of fluid . at present
, no treatment is available for this condition .
etiology is unknown till date .
stress may be a precipitating factor . |
the experimental data for @xmath25 are presented in figure [ fig2 ] ( colored dots ) , in the complex plane .
the color code gives an insight of the driving frequency @xmath0 .
globally , we observe that @xmath25 draws a spiral in the complex plane . for @xmath26
ghz , we observe that @xmath27 , reflecting the fact that the current injected in the outer channel remains in this channel ( @xmath28 ) . at low frequencies ( @xmath29 ghz )
, @xmath25 is mainly imaginary , as expected for a capacitive coupling between the two edge states . as frequency increases , @xmath25 winds around , reaching a maximum @xmath30 for @xmath31 ghz , meaning that 75% of the charge density wave has been transferred to the inner channel . for increasing @xmath0
, @xmath25 continues to spiral , decreasing to @xmath32 , then increasing again above 9 ghz ( for clarity , the corresponding data are not shown on fig.2 but the modulus and phase of @xmath25 in the range 9 ghz @xmath33 11 ghz are shown on fig.[fig3bis ] ) .
this behavior demonstrates coherent oscillations of the charge density wave from one edge to the other as the driving frequency @xmath0 is varied .
these oscillations can be understood in a simple manner .
taking here as eigenmodes ( this assumption is discussed later ) the symmetric charge mode @xmath34 and the antisymmetric neutral mode @xmath35 , the current @xmath36 can be decomposed in the eigenbasis as @xmath37 , where @xmath38 are the coordinates in the eigenbasis , @xmath39 .
their propagation reduces to a phase factor @xmath40 , where @xmath41 are the phase velocities of respectively the charge and neutral modes , with : @xmath42 where we have assumed in eq.([s21velocity ] ) that the charge mode propagates much faster than the neutral mode , @xmath43 , such that @xmath44 .
the term @xmath45 in eq.([s21velocity ] ) shows that the oscillation stems from the progressive phase shift between the charge and neutral components of the emp propagating at different velocities . in the complex plane
, @xmath25 should describe a circle of radius 1/2 centered at @xmath46 , with angle @xmath47 when the frequency is varied . at low frequency , the propagation length @xmath17 is much smaller than the wavelength of the neutral mode @xmath48 and propagation effects can be neglected .
one then recovers the well - established@xcite rc - circuit limit where @xmath25 starts from @xmath49 and @xmath50 for @xmath51 , with @xmath52 .
@xmath53 can be expressed in term of discrete elements @xmath54 and
@xmath55 , @xmath56 ( see methods ) .
@xmath55 is the electrochemical capacitance given by the series association of a quantum capacitance @xmath57 for each channel ( where @xmath58 is the velocity in the edge channels in the absence of inter or intra edge channel interactions ) and the geometrical capacitance between channels @xmath59 .
the resistor is @xmath60 , the series combination of a charge relaxation resistance @xmath61 for each channel .
this corresponds to the low frequency velocity @xmath62 . at higher frequencies ,
the propagation length becomes comparable with the wavelength of the neutral mode and propagation effects can not be ignored . using eq.([s21velocity ] ) , the trajectory followed by @xmath25 in the complex plane then gives a direct access to the neutral mode velocity @xmath63 or , in an equivalent way , to the @xmath11 dependence of the wave vector @xmath64 ( the dispersion relation ) related to the phase velocity by @xmath65 .
one can see on fig.[fig2 ] that when the frequency is increased , @xmath25 follows the expected circle for @xmath66 ghz ( eq.([s21velocity ] ) is plotted in black line ) .
however , for frequency ranging from 4 to 9 ghz , data points deviate from the expected circle and the experimental curve seems to spiral down towards a state where the charge density wave is evenly distributed between both channels with @xmath67 .
this can be understood as a dissipation of the emp during propagation and can be accounted for by introducing an imaginary part in the wave vector @xmath64 .
these considerations bring to light the remarkable robustness of the nyquist diagram presented on fig.[fig2 ] .
separation between the charge and neutral mode show up in the inter - edge oscillations revealed by the winding of @xmath25 around the point @xmath68 , which corresponds to an equal repartition of the emp .
this feature , clearly visible on fig.[fig2 ] in spite of dissipation , does not depend on the details of the interaction .
the interaction characteristics are encoded in the dispersion relation @xmath64 or equivalently in the @xmath11-dependence of the phase @xmath69 . to depict interactions ,
the most frequently used approach is a zero - range model@xcite .
it has no characteristic length , so that the velocity @xmath70 is frequency independent : @xmath71 . since @xmath70 is frequency
independent , @xmath72 draws a circle with a linear @xmath11-dependence of the phase @xmath73 .
any deviation from this linear dependence reflects the existence of a finite range in the interactions which can be unveiled through a careful study of the frequency dependence of @xmath25 .
fig.[fig3 ] presents our measurements of the dispersion relation @xmath64 where the complex value of @xmath74 is extracted from eq.([s21velocity ] ) .
as already mentioned , the existence of an imaginary part @xmath75 in the wave vector @xmath74 signals the presence of dissipation .
two non - dispersive regimes are observed : at low frequency , @xmath76 , with @xmath77 m.s@xmath78 .
this regime of constant velocity with respect to frequency is consistent with a short range description of interactions in the low frequency limit .
however , for @xmath79 ghz , a second linear dispersion relation regime appears @xmath80 , with @xmath81 m.s@xmath78 .
we attribute this decrease of @xmath70 to the finite range of interactions . to go beyond this qualitative discussion
, we now rely on a quantitative comparison between our experimental data for @xmath25 and various models of intra - edge and inter - edge interaction . in figure [ fig3bis ] ,
experimental data for @xmath82 and @xmath83 are presented as a function of driving frequency @xmath0 . at low frequency , the rc - circuit behavior is recovered and the agreement with the experimental data is good in the range 0.73 ghz , with a value of @xmath84 ps extracted from the low - frequency regime of the dispersion relation .
however , this rc - circuit model ( green small dashes ) does not predict oscillations . the zero - range interaction model , obtained by locally coupling the electrostatic potential of the edges to the charge densities ( see methods and fig.[fig5 ] ) for which the velocity is frequency independent , @xmath85 is plotted in dashed red line . as already discussed
, it does predict the oscillations , but fails to describe accurately the regime of high frequencies ( 3 to 11 ghz ) .
once @xmath53 , which prescribes the low frequency behavior , is fixed , no other parameter is to be fixed for the zero range model . to capture these features ,
an heuristic long range model has been developed ( see methods and fig.[fig5 ] ) based on a discrete element description @xcite .
an effective range on the order of the propagation length @xmath17 is introduced by assuming that the electrostatic potentials of each edge state are constant over @xmath17 , and by coupling these potentials to the total charges in the channels via a capacitance @xmath59 .
this long range model depends on two timescales @xmath86 and @xmath87 such that the velocity @xmath88 becomes frequency dependent , @xmath89 ( with @xmath90 ) and @xmath91 .
an intrinsic dissipation inside each edge channel that accounts for the damping of the charge oscillations is introduced through the parameter @xmath92 .
we choose the following @xmath11 dependence , @xmath93 , which is still compatible with a discrete circuit elements description at low frequency .
dissipation modifies the value of the resistance in the rc circuit description : a resistor of @xmath94 is added in series with the charge relaxation resistor @xmath61 . putting first @xmath95 ( no dissipation ) , this long - range interaction model captures already both the low - frequency behavior and the period of oscillation ( see the blue dash - dotted curve on fig.[fig3bis ] ) from which we extract @xmath96 ps ( which implies @xmath97 ps since we have set @xmath98 ps ) . a good agreement with experimental data including dissipation
can then be obtained using @xmath99 ps ( black curve on fig .
[ fig3bis ] ) .
note that the value of @xmath100 extracted from our data is rather small , @xmath101 such that the low - frequency regime is not strongly affected . from the evaluated value of @xmath102 , we also deduce @xmath103 m.s@xmath78 , consistently with the velocity @xmath104 m.s@xmath78 extracted from the dispersion relation .
these values are compatible with the assumption @xmath105 estimating the charge velocity from experiments performed with similar samples@xcite . in ref .
indeed find a charge velocity of a few @xmath106 m.s@xmath78 at filling factor @xmath3 for an ungated two dimensional electron gas .
their sample characteristics are close to ours , it is made from a gallium arsenide heterostructure , the electron gas has a density of @xmath107 and mobility @xmath108 ( close to our values , see methods ) and the sample edges are defined by chemical etching ( as ours ) .
simulations of the dispersion relation with the same parameters are also presented in fig.[fig3 ] .
the overall behavior of re(@xmath74 ) is well - rendered : though not as abrupt , the change in the velocities is as expected described by the long - range interaction . in the meantime , im(@xmath74 ) is also correctly depicted with our choice of dissipation for the emp : @xmath109 . throughout the paper ,
the case of symmetric edge channels has been considered which naturally leads to the existence of pure charged and neutral eigenmodes . as there is no reason for both edge channels to have identical propagation properties
, one should consider in full generality the decomposition @xmath110 , where the eigenmodes @xmath111 and @xmath112 are parametrized by the angle @xmath113 : @xmath114 the case @xmath115 corresponds to completely independent channels while @xmath116 corresponds to the strong coupling case where the eigenmodes are the charged ( @xmath117 ) and neutral ( @xmath118 ) modes .
as already discussed , the latter situation occurs in the case of identical edge channels but can also occur for non - identical channels as long as the interchannel interaction is strong enough ( see methods ) .
any other intermediate case corresponds to partially charged eigenmodes for which one can define the ratio @xmath119 of the total charge carried by modes @xmath120 and @xmath121 from the expression of the eigenmodes , eq.([eigenvecs ] ) : @xmath122 . for @xmath123 ,
the contribution of the antisymmetric mode to the current is 0 , reflecting its neutrality . in this general case ,
the expressions for @xmath72 and @xmath124 , and thus for the measured quantity @xmath25 , differ from eqs .
( [ srho ] ) , ( [ sn ] ) , ( [ s21velocity ] ) : @xmath125 eq.([s21theta ] ) , shows that @xmath72 describes coherent oscillations from channel 1 to channel 2 , whose amplitude are given by the factor @xmath126 .
this amplitudes only reaches unity at strong coupling @xmath123 , the only regime where a complete charge transfer from one channel to the other can be achieved .
@xmath127 is also affected and oscillates ( either with frequency @xmath0 or length @xmath17 ) reflecting the fact that in this general case , the charge mode @xmath128 is no longer an eigenmode such that the total current @xmath129 oscillates instead of simply accumulating a phase . as a result , @xmath25 still follows a circle in the complex plane but with a @xmath113 dependent radius and center . from these general expressions and the comparison with our experimental data
, one can assess that the eigenmodes are indeed the charge and neutral ones , within an accuracy of @xmath130 for the charge ratio between the eigenmodes .
the first argument comes from the low frequency behavior of @xmath25 where dissipation can be safely neglected .
both the modulus @xmath82 and the phase @xmath83 follow a linear @xmath11 dependence but with two different @xmath113 dependent slopes , @xmath131 , @xmath132 . by measuring the ratio of these slopes
, one can directly measure the angle @xmath113 .
remarkably , in the strong coupling case , @xmath133 , data points for @xmath82 and @xmath134 should follow the exact same frequency dependence in the low frequency regime . data points in the low frequency @xmath135 ghz range are plotted on fig.[fig6 ] , with their linear fits . a linear fit for @xmath82 ( in the @xmath136 ghz range , as @xmath82 approaches its maximum for @xmath137 ghz ) is presented in black plain line , yielding @xmath138 .
similarly , @xmath134 is fitted in red line in the range @xmath139 ghz range , with @xmath140 .
data below 1.2 ghz are not used in the fitting procedure due to their dispersion , as , at low frequency , @xmath83 is obtained from the ratio between two small currents .
the slope of @xmath82 , that is , the value of @xmath141 for small @xmath11 , is determined with a 10% accuracy .
it thus defines two bounds ( dashed blue lines ) that correspond to the slopes of @xmath134 for @xmath142 ( upper bound ) @xmath143 ( lower bound ) .
these extremum values of the angle @xmath113 correspond to a charge ratio @xmath144 .
our data points for @xmath134 fall between these bounds which assesses the neutrality of the slow mode with a 10% accuracy .
the second argument comes from the study of the full trajectory of @xmath25 in the complex plane . from the amplitude of the oscillations of the emp from one edge to the other ,
a lower bound for @xmath113 can be obtained , @xmath145 corresponding to @xmath146 .
this lower bound is obtained by assuming that the amplitude of the oscillation is only limited by the value of @xmath113 and neglects fully the dissipation .
taking into account dissipation , the full trajectory and in particular the position of the center of the spiral described by @xmath25 confirm @xmath147 with the same accuracy of @xmath148 as in the low frequency regime .
we have directly observed the collective excitations of two coupled chiral edge channels at filling factor 2 and demonstrated that it consisted in an antisymmetric neutral mode and a symmetric mode carrying the charge . by creating selectively a charge density wave at frequency @xmath0 in the outer edge and measuring the current transferred to the inner one , we have observed oscillations as a function of frequency that reflect the phase shift between the charge and neutral modes .
the minima of these oscillations correspond to integer values of the ratio @xmath149 between the propagation length and the wavelength of the neutral mode . from these measurements ,
we have deduced the dissipation and dispersion relation of the neutral mode , @xmath150 . we have observed two non - dispersive regimes , corresponding to a phase velocity @xmath77 m.s@xmath78 at low frequency and @xmath81 m.s@xmath78 at high frequency .
comparing our results with various models of inter - edge interactions , our results show that edge channel propagation differs from the ideal luttinger limit of dissipationless propagation with short range interaction , but rather agrees with a model of dissipative channels coupled through a long range interaction .
dissipation could be caused by the internal structure of compressible edges leading to a coupling of emp to acoustic modes @xcite but a non ambiguous diagnosis will require further investigation .
the sample is realized in a standard gaas / ga(al)as two dimensional electron gas located 100 nm below the surface , of density @xmath151 and mobility @xmath152 .
the sample is then patterned using e - beam lithography and chemical etching of the heterojunction , and by deposition of metallic gates at the surface .
the electron gas is contacted using gold / germanium ohmic contacts schematically represented as white squares on fig.[fig1](a ) .
the sample is placed in a strong magnetic field @xmath153 t so as to reach a filling factor @xmath3 in the bulk ( see fig.[fig1 ] ( a ) ) .
a driven mesoscopic capacitor ( described in references @xcite ) is used to selectively inject current in the outer edge channel ( labeled 1 ) .
the mesoscopic capacitor comprises a small portion of the electron gas ( of submicronic size ) , called a quantum dot , capacitively coupled to a metallic top gate , see fig.[fig1 ] ( a ) .
a quantum point contact is used to fully transmit the outer edge channel ( 1 ) inside the dot while the inner channel ( 2 ) is fully reflected .
a sine drive of frequency @xmath154 is applied on the metallic top gate deposited on top of the dot , so that an emp of frequency @xmath0 is capacitively induced in the outer channel , carrying a current @xmath155 .
the propagation takes place on a length @xmath156 m , during which channels are interacting .
the emp then reaches a quantum point contact ( qpc ) , that allows to reflect or transmit selectively each edge channel .
the reflected ac current flows toward ohmic contact a , situated at distance @xmath157 m from the qpc , and where the total current is measured .
note that the propagation after the qpc , on length @xmath158 , is irrelevant in the analysis of the data : according to eq.([srho ] ) , measuring the total reflected current in ohmic contact a is equivalent , up to a phase factor @xmath159 , to measuring the total current flowing right after the qpc .
the current is measured using a wideband room temperature homodyne detection .
a set of microwave filters and room - temperature low noise amplifiers enables a proper measurement in the 0.7 to 11 ghz range .
note that @xmath25 does not depend on the total gain of the amplifying detection scheme which varies considerably in the studied frequency range .
each reported data point results from a simple averaging protocol , and the statistical analysis is in good agreement with the observed dispersion of the experimental data . at low frequency ( below 1 ghz ) , the quality of our measurements is limited by the bandwidth of our filters and amplifiers . at high frequency ( above 10 ghz ) , it is limited for the same reason , combined with increased attenuation of the output rf coaxial cables .
experiments were performed in a dilution fridge of base temperature 50 mk . by performing coulomb thermometry on the mesoscopic capacitor@xcite , we have calibrated the electronic temperature to @xmath160 mk . in the integer quantum hall regime , edge magnetoplasmons in channel 1 ( outer ) and
2 ( inner ) are described by a chiral bosonic field @xmath161 ( @xmath162 ) . in this approach
, the two edge channels are bosonized in the spirit of wen s description of quantum hall edges as chiral luttinger liquids @xcite .
the current in channel @xmath163 is then determined by @xmath164 , while the charge density is @xmath165 .
both are related via the current conservation equation . in
fourier space , the motion of the chiral field @xmath166 along the edge obeys : @xmath167 where @xmath168 is the velocity of edge channel @xmath163 in the absence of interactions and @xmath169 the potential in edge channel @xmath163 .
the term @xmath92 models an intrinsic dissipation inside the edge states that accounts for the damping of the charge oscillations .
eq.([eqphi ] ) can be rewritten as a function of the current in edge channel @xmath163 : @xmath170 first , let us consider the non - damped case @xmath171 .
the short range description of the interaction can be obtained by coupling locally the charge densities @xmath172 to the local electrostatic potential @xmath173 via distributed capacitances @xmath174 ( see fig.[fig5 ] ) : @xmath175 where @xmath176 accounts for the coupling between channels whereas @xmath177 describes intra - channel interactions in edge channel @xmath163 .
these coupled equations are solved when working in the eigenbasis @xmath178 that diagonalizes the velocity matrix , @xmath179 . in the absence of inter - channel interaction , @xmath180 ,
the channels are not coupled ( @xmath181 ) but the velocities are renormalized by intra - channel interactions : @xmath182 . in the presence of inter - channel interactions ( @xmath183 ) , new eigenmodes denoted by @xmath121 and @xmath120 and defined by eqs.([eigenvecs ] ) to ( [ eigenphase ] ) with @xmath184 appear .
the velocities @xmath185 and coupling angle @xmath113 are expressed as functions of the velocity matrix elements by : @xmath186 \end{aligned}\ ] ] as a consequence of the zero range of the interaction , the velocities @xmath185 are @xmath11-independent . note that the domain @xmath187 corresponds the expected situation where , in the absence of inter channel interaction , the outer edge channel velocity is greater than the inner one , @xmath188 .
the scattering matrix describing the coupled propagation can then be straightforwardly calculated , yielding eqs.([s21theta ] ) , ( [ ssumtheta ] ) , ( [ rtheta ] ) .
the charge ( @xmath189 ) and neutral ( @xmath190 ) eigenmodes are recovered for @xmath191 , which always occurs for identical edge channels , @xmath192 but also for strong enough inter - channel interaction , @xmath193 . as demonstrated above , this limit corresponds to the experimental situation . in this case
, the velocity becomes @xmath194 , with @xmath195 and @xmath196 .
the case @xmath197 corresponds to total influence between edge channels , @xmath198 and such that @xmath199 . at low enough frequency
, this short range model should describe correctly the coupling between channels . as discussed in the paper
, this corresponds to the rc circuit description , @xmath200 , @xmath201 where @xmath202 is the total geometrical capacitance and @xmath203 the total quantum capacitance . at higher frequencies ,
a way to account for long range interaction is to assume that the potentials @xmath169 are uniform in the whole edge channel @xmath163 , and related to the total charges in the 1d wires : @xmath204 with @xmath205 ( see fig.[fig5 ] ) . in this description ,
the effective interaction range is given by the co - propagating length @xmath17 itself .
the same calculations can be performed to calculate @xmath72 and @xmath25 in full generality ( even for @xmath206 as detailed below ) . from now on
, we assume that @xmath123 as demonstrated in this article .
taking into account the damping in this model ( @xmath206 ) , we now obtain : @xmath207 for @xmath171 , @xmath72 also draws a circle of radius 1/2 centered on ( 1/2,0 ) in the complex plane , but in contrast to the short range case , the @xmath11-dependence of the phase deviates from the linear law @xmath208 , which shows that the velocity @xmath88 becomes frequency dependent .
this frequency dependence is related to the two timescales @xmath209 and @xmath102 introduced by the model . at low frequencies
one recovers the rc circuit description with @xmath90 . for @xmath210 and choosing @xmath93 ,
as mentioned above , the rc - circuit description is modified : a resistor of @xmath94 is added in series with the charge relaxation resistor @xmath61 .
10 o.m .
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we gratefully acknowledge c. glattli , c. grenier , u. gennser , f. pierre , i.p .
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this work is supported by the anr grant 1shot , anr-2010-blanc-0412 .
are depicted in blue . a mesoscopic capacitor used as the source
is capacitively coupled to the outer channel only , and the emp is generated by a sine drive of variable frequency @xmath154 .
the source is placed @xmath211 m before a quantum point contact whose reflection can be varied so as to enable selective readout of the current in both edge states . the figure shows the setup in configuration 1 when channel 2 only is reflected .
( b ) ratio @xmath25 for @xmath212 mhz ( black dots ) and 5500 mhz ( red squares ) in the complex plane .
the principle of measurement is illustrated : @xmath25 is calculated from the ratio of the total current measured in configuration 2 and the current in the inner channel ( configuration 1 ) .
the grey arrow is the complex vector representing @xmath25 in the complex plane .
( inset ) dc measurement of the conductance of the qpc , as a function of the gate voltage @xmath213 , illustrating configuration 1 and 2 .
, scaledwidth=100.0% ] in the complex plane .
the color code indicates the frequency @xmath0 of the excited emp .
experimental data ( colored dots ) are compared with simulations .
the grey dashes show a simulation of both short and long range model , without relaxation .
colored hollow circles present a simulation of the long range model with relaxation , for parameters @xmath98 ps , @xmath214 ps ( such that @xmath215 ps ) , and @xmath216 ps . , scaledwidth=90.0% ] .
@xmath217 exhibits two non - dispersive regimes : at low frequency ( @xmath218 ghz ) , @xmath219 m.s@xmath78 , whereas at high frequency ( @xmath220 ghz ) , @xmath221 m.s@xmath78 .
@xmath222 indicates damping .
simulations ( in black and red line ) are proposed with parameters @xmath98 ps , @xmath214 ps ( @xmath215 ps ) , and @xmath216 ps.,scaledwidth=70.0% ] and @xmath223 as a function of drive frequency @xmath0 .
experimental data ( black circles ) are compared with rc - circuit ( green small dashes ) , short range model ( red dashes ) , long range model without damping ( blue dash - dotted line ) , long range model with relaxation ( black plain line ) .
parameters used are @xmath98 ps , @xmath214 ps ( @xmath215 ps ) , and @xmath216 ps.,scaledwidth=70.0% ] are locally coupled to the electrostatic potential @xmath224 by the capacitance matrix per unit length , @xmath175 . for the long range model ( b ) ,
the potential in each edge @xmath225 is supposed to be uniform and coupled to the total charges @xmath226 by the capacitance matrix @xmath204,scaledwidth=80.0% ] and @xmath227 are presented respectively in black and red circles , and fitted with linear functions ( black and red lines ) .
the slope of @xmath82 is obtained with a @xmath228 accuracy , defining two bounds drawn in blue dashes associated to @xmath229 for @xmath230 and @xmath231 .
data points fall between these bounds confirming @xmath130 .
, scaledwidth=80.0% ] | coulomb interactions have a major role in one - dimensional electronic transport .
they modify the nature of the elementary excitations from landau quasiparticles in higher dimensions to collective excitations in one dimension . here
we report the direct observation of the collective neutral and charge modes of the two chiral co - propagating edge channels of opposite spins of the quantum hall effect at filling factor 2 . generating a charge density wave at frequency @xmath0 in the outer channel
, we measure the current induced by inter - channel coulomb interaction in the inner channel after a 3-mm propagation length .
varying the driving frequency from @xmath1 to @xmath2 ghz , we observe damped oscillations in the induced current that result from the phase shift between the fast charge and slow neutral eigenmodes .
we measure the dispersion relation and dissipation of the neutral mode from which we deduce quantitative information on the interaction range and parameters .
most studies of collective excitations in one dimensional systems performed so far have focused on non - chiral quantum wires @xcite . in these systems ,
the collective excitations carrying the charge and the spin propagate at different velocities leading to the separation of the charge and spin degrees of freedom .
this spin - charge separation has been probed by measuring the tunneling spectroscopy of individual electrons between a pair of one dimensional wires @xcite , or alternatively , between a wire and a two dimensional electron gas @xcite .
however , a direct observation of the collective modes is experimentally challenging as the relevant energy scales are too high for usual low frequency measurements .
the edge channels of the quantum hall effect provide another implementation of one dimensional transport , where propagation is chiral and ballistic over large distances .
these specificities have inspired several experiments that aim at reproducing , in solid state , optical setups where light beams are replaced by electron beams@xcite .
one major difference between electrons and photons comes from interaction effects , which are amplified in the one dimensional geometry and should enrich electron optics compared to its photonic counterpart .
of particular interest is the case of filling factor @xmath3 where transport along the sample edge occurs through two copropagating edge channels of opposite spins . due to coulomb interaction , the two edge states are coupled and new propagating eigenmodes , with different velocities , appear@xcite , similarly to the physics arising in 1d wires .
consequently , considering edge channels with the same propagation characteristics ( but different spins ) , and denoting @xmath4 the current components in edge channels @xmath5 and @xmath3 at position @xmath6 and time @xmath7 , a current @xmath8 in channel @xmath5 decomposes in the symmetric fast charge mode @xmath9 and the antisymmetric slow neutral mode @xmath10 ( also called dipolar mode ) . as these two modes propagate at different velocities ,
the current initially injected in channel 1 separates into the charge and the neutral modes of the two coupled edges .
this mechanism is at the heart of the decoherence@xcite and relaxation@xcite of electronic excitations propagating in these systems . as such
, it has been probed through mach - zehnder interferometry@xcite or spectroscopy of edge channels @xcite .
this situation bears strong analogies with the spin - charge separation of conventional 1d wires except that the two spin species are carried by two separated edge channels .
the direct observation of the neutral and charge eigenmodes is thus particularly favorable in the filling factor 2 case as , contrary to a conventional wire , each spin channel can be individually addressed due to their spatial separation .
still , the observation remains challenging as transport properties remain unaffected up to ghz frequencies , where the wavelength of the eigenmodes becomes comparable with the propagation length of a few microns .
many experimental works have studied charge transport in quantum hall edge channels and interaction effects between copropagating and counterpropagating edge channels either in time @xcite or in frequency @xcite domains . however , none directly addressed the separation in charge and neutral modes as the individual control of edge channels was missing . in this work , by addressing edge channels individually ,
we provide a direct observation of the neutral - charge eigenmodes . using a driven mesoscopic capacitor ( fig.[fig1 ] ( a ) , see methods for details ) , a sinusoidal charge density wave , or edge magnetoplasmon ( emp ) is induced at pulsation @xmath11 and position @xmath12 in channel 1 , thus creating a current @xmath13 ( with @xmath14 ) .
as initially introduced in the context of a non chiral one dimensional wire @xcite and later developed for chiral edge channels @xcite at filling factor @xmath3 , coulomb interaction during propagation can be described as the scattering of the charge density waves . for the case of filling factor @xmath3 of interest here , scattering properties of emps
are encoded in the @xmath15 scattering matrix @xmath16 that relates the amplitudes of the output emp in channels 1 and 2 after propagation length @xmath17 to the amplitudes of the input emp at @xmath12 .
after an interaction length @xmath18 m , both edge channels reach a quantum point contact ( qpc ) which is used to transmit or reflect channels 1 and 2 .
figure [ fig1](b ) presents the principle of measurement for two typical sets of data ( for @xmath19 and 5.5 ghz ) . in configuration
@xmath5 , channel 1 is transmitted and channel @xmath3 is reflected .
the current in channel 2 resulting from the interaction , denoted @xmath20 , can then be measured in ohmic contact @xmath21 , with @xmath22 . when the qpc is closed ( configuration 2 ) , both channels are reflected so that the total collected current in @xmath21 is @xmath23
. consequently , the ratio of the currents collected in these two configurations yields the complex quantity @xmath24 , which encodes the effect of coulomb interaction on the propagation along the edge states . |
Dr. Philip Nitschke considers himself the Elon Musk of assisted suicide—and his latest death machine, the Sarco, is his Tesla.
Newsweek spoke with the 70-year-old doctor immediately after the state of Victoria in Australia, his home country, voted this week to legalize euthanasia. Many are billing this as the first law of this nature Down Under, though Nitschke performed his first assisted death in 1996, during a brief period of legality in the country’s Northern Territory.
As a young medical school graduate, Nitschke found himself drawn to the world of euthanasia and the work of Dr. Jack Kevorkian, the most famous euthanasia proponent in the United States. Inspired by Kevorkian's death machine, Nitschke set out to create an updated version that he called “the Deliverance.” The machine was rudimentary, comprising only a laptop hooked to an IV system, but it worked. A computer program would confirm a patient's intent to die and then trigger a lethal injection of barbiturates. It successfully ended four lives before Australia repealed the bill that legalized euthanasia in 1997.
But ending legal euthanasia “didn’t stop people from coming to me saying that they wanted to die,” said Nitschke. “I’ve spent the last 20 years fighting for the legislation that just passed.”
Nitschke has aided in hundreds of what he calls “rational suicides.” In 1997, he founded Exit International, a nonprofit that advocates for the legalization of euthanasia, and in 2006, he published the Peaceful Pill Handbook, which instructs on the most painless and efficient ways to commit suicide.
Sarco
All the while, Nitschke continued to innovate his death devices. He created an “exit bag,” a bizzaro breathing mask with carbon monoxide replacing oxygen. The bag was highly effective but not very appealing, Nitschke said, citing the “plastic bag factor”: People don’t want to leave the world in such an aesthetically displeasing way.
His latest machine, the Sarco, is the answer to that problem. The Sarco is sleek—and, Nitschke stresses, luxurious. It resembles a spaceship and is intended to convince its user that he or she is journeying to the great beyond. Its base contains canisters of liquid nitrogen and a removable capsule compartment that can be repurposed as a casket. The whole operation will be open-source and could theoretically be 3-D-printed anywhere in the world. It is, in short, the Model S of death machines.
Here’s how it works: Potential users fill out an online test of mental fitness, and if they pass, they receive an access code that works for 24 hours. After the code is entered and an additional confirmation is given, the Sarco capsule will fill up with liquid nitrogen to bring the oxygen level down to about 5 percent. Within one minute the user passes out, and a few minutes later, death comes.
Nitschke vowed that a Sarco death was relatively painless—there is no asphyxiation and the user breathes easily, he said, comparing it to an airplane cabin depressurizing. The model is scheduled to become widely available next year, and Nitschke was already in talks with some suicide clinics in Switzerland to license the machine.
Fighting to die
In the past 20 years, the right to physician-assisted suicide has been legalized in Washington, California, Vermont, Oregon and a several European countries. Nitschke believes the change in attitude stemmed from the aging Baby Boomer generation. “I’ve seen a marked difference between generations,” he said. “Boomers want to be in control of their own deaths. They don’t like the idea of someone patting them on the head and telling them what to do.”
Reuters
But each state and country has its own nuanced set of rules around medical aid in dying, while Nitschke believes the right to die is a human right, not a medical or legal privilege. No one should be subject to rules about whether or not a person is sick enough to choose to die, he said.
It is the “right of a rational adult to have a peaceful death," he said. "Every person over the age of 70 should be able to die.”
Of course, not everyone agrees with Nitschke. “I think it’s bad medicine, ethics, and bad public policy,” Dr. Daniel Sulmasy, a Georgetown professor of biomedical ethics, told Newsweek. “It converts killing into a form of healing and doesn’t acknowledge that we can now do more for symptoms through palliative than ever before.” Palliative care focuses on improving the quality of lives for people fighting deadly illnesses, rather than ending those lives.
Sulmasy believes assisted suicide violates the bedrock of all ethical thinking, which is that people have value simply by being human beings. He argued that assisted suicide sent a message to disabled and dying people that society believed they should choose death if they became too much of a burden.
He worried about the contagious effect suicide often has, pointing to the rash of suicides that occurred after Derek Humphry published Final Exit, a book that detailed aspects of planning and carrying out suicide. After the book was published in 1991, the number of suicides by asphyxiation in New York City rose by 313 percent that year. Sulmasy also pointed out that in Holland, nearly 5 percent of all deaths are due to euthanasia or assisted suicide.
Doctors can ethically help patients find the ultimate relief in their final days, ethically, through a process called the rule of double effect, Sulmasy said. The rule says that if a patient agrees to the risks, an attending physician is allowed to keep increasing the dosage of pain medication until pain is completely under control, which may mean administering enough to render the patient unconscious or kill them.
Nitschke argued that palliative care wasn't for everybody. People in good health had approached him simply because they felt that they’d had a good life and were ready to go, he said. He believes they have just as much a right to death as anyone else.
Now a septuagenarian himself, the death doctor is coming to terms with his own mortality. And his invention might be his solution.
“I’ve thought about it a lot lately,” he said. “I am attracted to the idea of the Sarco, and if I find myself in a situation where I need to use, it I will.” ||||| Euthanasia advocate displays ‘Sarco’, a pod that fills with nitrogen, which he hopes will one day be available as a 3D-printable device
A controversial suicide pod that enables its occupant to kill themselves at the press of a button went on display at an Amsterdam funeral show on Saturday.
The ban on assisted death ignores the reality of illnesses like dementia | Polly Toynbee Read more
Called the “Sarco”, short for sarcophagus, the 3D-printed machine invented by Australian euthanasia activist Philip Nitschke and Dutch designer Alexander Bannink comes with a detachable coffin, mounted on a stand that contains a nitrogen canister.
“The person who wants to die presses the button and the capsule is filled with nitrogen. He or she will feel a bit dizzy but will then rapidly lose consciousness and die,” said Nitschke. The Sarco was a device “to provide people with a death when they wish to die,” Nitschke said.
The inventors put a model of the device on display, together with a set of virtual reality glasses to give visitors a true-to-life experience of what it would be like to sit in the pod, before ultimately pressing the button.
Nitschke said he aimed to build the first fully functioning pod before the end of the year.
After that, the design will be put online as an open-source document for people to download. “That means that anybody who wants to build the machine can download the plans and 3D-print their own device,” Nitschke said.
Facebook Twitter Pinterest Dutch designer Alexander Bannink explains how the “Sarco” euthanasia pod works to a man via virtual reality goggles. Photograph: Jasper Juinen/AFP/Getty Images
Asked about the controversy surrounding euthanasia and legal hurdles, Nitschke said: “In many countries suicide is not against the law, only assisting a person to commit suicide is. This is a situation where one person chooses to press a button ... rather than for instance standing in front of a train.
“I believe it’s a fundamental human right [to choose when to die]. It’s not just some medical privilege for the very sick. If you’ve got the precious gift of life, you should be able to give that gift away at the time of your choosing,” Nitschke said.
Thousands of visitors flocked to the annual Amsterdam funeral fair at the city’s famous Westerkerk, where all the latest trends in death, such as biodegradable coffins and a hot-rod funeral hearse were on display.
But the Sarco drew large crowds, many curious to try out the device’s chair and virtual reality glasses. iet Verstraaten, 52, from the eastern Dutch city of Venray, said: “It was really an experience and a strange thing to see. But very pretty and calm. You see the moon, you see the sea. It’s very calm.”
Others, however, were not impressed. Rob Bruntink, 52, said: “Well, I think it’s quite silly. It’s stupid. I don’t get it. I’m not interested in a real ‘Sarco’. No.”
• In the UK the Samaritans can be contacted on 116 123. In the US, the National Suicide Prevention Lifeline is 1-800-273-8255. In Australia, the crisis support service Lifeline is 13 11 14. Other international suicide helplines can be found at www.befrienders.org. | – Visitors at an Amsterdam funeral show Saturday were able to don virtual reality glasses and see their own suicide by nitrogen gas—all to imagine a new way of dying, the Guardian reports. Inventors Alexander Bannink and Philip Nitschke were there to show off a model of their "Sarco," a 3D-printed euthanasia pod replete with detachable coffin, and VR glasses to imagine using it. "The person who wants to die presses the button and the capsule is filled with nitrogen," says Nitschke, an Australian euthanasia activist. "He or she will feel a bit dizzy but will then rapidly lose consciousness and die." He says the goal is "to provide people with a death when they wish to die." The Sarco (short for sarcophagus) is another step in Nitschke's long journey to make suicide widely available, Newsweek reports. His earlier devices include a laptop-connected IV system that dispensed lethal barbituates into the bloodstream (it was used four times in Australia when euthanasia was briefly legal there) and the "exit bag" breathing mask that released carbon monoxide (it never caught on). With the Sarco, users who pass an online mental-health test could fill the capsule with liquid nitrogen and lower the oxygen level to roughly 5% for a peaceful death. Due out later this year, the device comes at a time when euthanasia is legal in some US states and European countries and suicide is legal in many countries, Stuff (NZ) notes. A critic says the Sarco is unethical and overlooks advances in palliative care, but Nitschke considers suicide a basic right for people healthy or ill. It's the "right of a rational adult to have a peaceful death," he says. "Every person over the age of 70 should be able to die." (One couple died in double euthanasia after 65 years of marriage.) |
changing childbirth , published in 1993 ( department of health , 1993 ) , represented a watershed in maternity care in england . prior to this , women had little say in their care , which tended to be highly medicalised and treated as normal only in hindsight ( mcintosh and hunter , 2014 ) . changing childbirth and the maternity services report of the previous year
, the winterton report ( department of health , 1992 ) , enshrined the concept of woman - centred care , reversed official policy that hospital was always the safest place to give birth , and highlighted the importance of humanised , responsive care and the three
the aims of changing childbirth have been only partially achieved , due to some extent to resource constraints .
in addition , the rising birth rate , higher maternal age at first birth , increasingly complex health and social care needs of the childbearing population and increasing rates of medical intervention have put maternity services under considerable , and continuing , pressure . the evidence base has improved over the years which has , in turn , influenced priorities and increased the number of guidelines for good practice .
policy documents subsequent to changing childbirth , including the national service framework for children , young people and maternity services ( department of health , 2004 ) , maternity matters ( department of health , 2007 ) , midwifery 2020 ( chief nursing officers of england northern ireland scotland and wales , 2010 ) , the annual report of the chief medical officer in england ( chief medical officer , 2015 ) , and the national maternity review ( nhs england , 2016 ) have continued to put woman - centred care at the heart of policy .
government policy now favours choice for all women in the manner of their maternity care and there is an ever - increasing focus on continuity of care and carer , satisfaction , and quality of care as perceived by the women using the maternity services .
surveys of women 's experiences of care , including the audit commission review of 1995 ( audit commission , 1997 , garcia , 1998 ) and the later healthcare commission and care quality commission ( cqc ) surveys ( care quality commission , 2010 , care quality commission , 2013 , care quality commission , 2015 , healthcare commission , 2007 ) have highlighted national variations and inform the department of health 's strategy for monitoring progress in these areas . throughout this period
there have been significant changes to the structure of british society which are relevant to maternity services .
these include the increasing number of women from black and minority ethnic ( bme ) groups , and women born outside the uk , many with limited english ( office for national statistics , 2015 ) .
also , over this time period women 's partners have become increasingly engaged in pregnancy , childbirth and childcare ( o'brien and shemilt , 2003 ) with implications for women 's expectations , experience and satisfaction with maternity services and affecting their transition to parenthood more broadly .
similar changes have been observed in other developed countries ( chote et al . , 2011 , small et al . , 1999
there have been changes to obstetric clinical practice over this time period , most notable the increase in rates of caesarean delivery from 12.4% in 1990 - 91 to 26.5% in 2014 - 15 in england ( health and social care information fcentre , 2015 ) . alongside this , rates of episiotomy have declined from 24.0% to 15.2% , and the proportion of births managed by an obstetrician has increased from 24.5 to 38.9% ( health and social care information centre , 2015 ) .
however , partly in response to the findings of the birthplace study ( birthplace in england collaborative group et al . , 2011 ) , the number of midwife - led birth centres ( both freestanding and alongside ) has increased ( national audit office , 2013 ) . throughout this period , surveys of women 's views of their care have been undertaken but no studies have examined how women 's views have changed over time . the aim of this study was to assess these changes within the context of a changing service in england .
the surveys were approved by trent multi - centre research ethics committee ( 06/mrec/16 ) and by the yorkshire & the humber
surveys of women 's views of maternity care have been conducted by , or in association with , the national perinatal epidemiology unit in 1995 , 2006 , 2010 and in 2014 ( garcia , 1998 , redshaw and heikkila , 2010 , redshaw and henderson , 2015 , redshaw et al . , 2006 ) .
the office for national statistics ( ons ) randomly selected women from birth registrations within a specified time period ( see table 1 ) after exclusion of women aged less than 16 years and those whose infant had died .
women were sent a self - completion postal questionnaire , with freepost return , at approximately three months postpartum which asked about their experience of care during pregnancy , labour and birth , and about the postpartum period , as well as sociodemographic details .
the questionnaire sent in 1995 had no reminders but the other three used a tailored reminder system such that up to three reminders were sent to women who had not responded .
all the surveys gave women the option of completing questionnaires by telephone interview , using an interpreter if necessary .
the 2010 and 2014 questionnaires also included an option to complete it online . in this study women 's responses to questions about their care and their perceptions of care are compared over the 19 year period covered by the surveys .
where there were differences in the wording of the questions in the different questionnaires this is noted .
descriptive statistics are presented ; odds ratios and 95% confidence intervals were calculated adjusting for parity , ethnicity , age and level of education .
table 1 gives details of the number of women sampled , the usable response rates , and the sociodemographic characteristics of respondents .
response rates declined over the period 1995 to 2014 from 67% to 48% . in all years there was significant under - representation of women who were young , ethnic minority , and either economically inactive or living in a deprived area ( garcia , 1998 , redshaw and heikkila , 2010 , redshaw and henderson , 2015 , redshaw et al . , 2006 ) .
it is clear from table 1 that the women responding to the surveys came increasingly from older groups and those who were primiparous , although the ethnic diversity of the respondents increased in line with that seen in the general population .
they did not differ from other women except that they were significantly more likely to live in the london area and to be born outside the uk .
table 2 , table 3 , table 4 show the proportions of women who received various components of antenatal , intrapartum and postnatal care , their views of their care , and odds ratios of change over time with 1995 as the reference year ( or 2006 if no data were available for 1995 ) adjusted for maternal age , parity , low level of education and ethnicity .
almost all results were highly statistically significant due partly to the size of the combined dataset . to ease interpretation and focus on the actual differences ,
a steadily increasing proportion of women had their first contact with a healthcare professional before 10 weeks of pregnancy ( table 2 ) .
similarly , the offer and uptake of down 's screening also increased steadily although the manner of screening changed from blood tests ( the triple test ) to combined nuchal screening .
the proportion of women who reported receiving explanations about down 's screening increased from 89% in 2006 to 95% in 2014 . similarly for dating and anomaly scans , increasing proportions of women reported receiving explanations and having the scans ( table 2 ) .
dating and anomaly scans are now carried out for the vast majority of women and the total number of pregnancy ultrasound scans has increased over the period . between 1995 and 2014
the proportion of women having four or more scans during their pregnancy nearly doubled from 23% to 44% .
questions about antenatal education were not asked in the 1995 survey , but in 2006 71% of women ( 88% of primiparous women ) were offered classes and 37% attended ( 61% of primiparous women ) , compared to 65% offered and 31% attended in 2014 .
women were increasingly aware of the option of a home birth although this may not have been a realistic option for all women .
overall , women were satisfied with their care with no significant variation across the years , and reported that both midwives and doctors treated them with respect . the wording of the questions about respect changed in 2014 from agreeing or disagreeing that they were shown respect , to indicating that respect was shown always , sometimes , or not at all. changes over time in care during labour and birth are shown in table 3 .
medical induction of labour ( defined here as having a gel , pessary or drip to start labour ) declined from 29% to 25% .
women increasingly reported having a choice regarding induction of labour , especially between 1995 and 2006 , and more women reported being able to move around in labour to find a comfortable position , deliver on a mat on the floor , or in water , and have an upright position ( standing , squatting or kneeling ) for birth .
fewer women reported being left alone and worried during labour or shortly after the birth and the woman 's partner was present for labour in the vast majority of cases . however ,
fewer of the midwives were known to the woman beforehand , and a greater number of midwives were involved in labour care .
almost all women reported being shown respect during labour and childbirth and were satisfied with their care with no significant change over time .
the proportion of women with a length of stay of three days or more declined from 47% in 1995 to 29% in 2014 . despite this
, the proportion of women who considered their length of stay too short remained a constant 1213% .
concurrent with the decline in postnatal length of stay , the number of home visits by community midwives has also fallen .
the proportion of women who received three or more home visits fell from 91% in 2006 to 62% in 2014 , a declining proportion of women reported having met at least some of the midwives before , there was a substantial increase in the proportion who would have liked more visits , and between a third and half of women reported not receiving enough help with their infant 's crying or settling their infant .
however , an increasing proportion of women also reported that their last visit was at more than 14 days and these later visits tended to be targeted at women who had delivered by caesarean section and those reporting greater postnatal morbidity including mental health problems ( data not shown ) .
an increasing proportion of women reported receiving consistent advice , practical help and active support and encouragement from staff with infant feeding . overall satisfaction with
postnatal care remained fairly constant over the period at around 80% , although lower than that for antenatal and intrapartum care at around 87% .
a steadily increasing proportion of women had their first contact with a healthcare professional before 10 weeks of pregnancy ( table 2 ) .
similarly , the offer and uptake of down 's screening also increased steadily although the manner of screening changed from blood tests ( the triple test ) to combined nuchal screening .
the proportion of women who reported receiving explanations about down 's screening increased from 89% in 2006 to 95% in 2014 . similarly for dating and anomaly scans , increasing proportions of women reported receiving explanations and having the scans ( table 2 ) . dating and anomaly scans
are now carried out for the vast majority of women and the total number of pregnancy ultrasound scans has increased over the period . between 1995 and 2014
the proportion of women having four or more scans during their pregnancy nearly doubled from 23% to 44% .
questions about antenatal education were not asked in the 1995 survey , but in 2006 71% of women ( 88% of primiparous women ) were offered classes and 37% attended ( 61% of primiparous women ) , compared to 65% offered and 31% attended in 2014 .
women were increasingly aware of the option of a home birth although this may not have been a realistic option for all women .
overall , women were satisfied with their care with no significant variation across the years , and reported that both midwives and doctors treated them with respect .
the wording of the questions about respect changed in 2014 from agreeing or disagreeing that they were shown respect , to indicating that respect was shown
changes over time in care during labour and birth are shown in table 3 . some interventions in labour appear to be declining .
medical induction of labour ( defined here as having a gel , pessary or drip to start labour ) declined from 29% to 25% .
women increasingly reported having a choice regarding induction of labour , especially between 1995 and 2006 , and more women reported being able to move around in labour to find a comfortable position , deliver on a mat on the floor , or in water , and have an upright position ( standing , squatting or kneeling ) for birth .
fewer women reported being left alone and worried during labour or shortly after the birth and the woman 's partner was present for labour in the vast majority of cases . however ,
fewer of the midwives were known to the woman beforehand , and a greater number of midwives were involved in labour care .
almost all women reported being shown respect during labour and childbirth and were satisfied with their care with no significant change over time .
the proportion of women with a length of stay of three days or more declined from 47% in 1995 to 29% in 2014 . despite this
, the proportion of women who considered their length of stay too short remained a constant 1213% .
concurrent with the decline in postnatal length of stay , the number of home visits by community midwives has also fallen .
the proportion of women who received three or more home visits fell from 91% in 2006 to 62% in 2014 , a declining proportion of women reported having met at least some of the midwives before , there was a substantial increase in the proportion who would have liked more visits , and between a third and half of women reported not receiving enough help with their infant 's crying or settling their infant .
however , an increasing proportion of women also reported that their last visit was at more than 14 days and these later visits tended to be targeted at women who had delivered by caesarean section and those reporting greater postnatal morbidity including mental health problems ( data not shown ) .
an increasing proportion of women reported receiving consistent advice , practical help and active support and encouragement from staff with infant feeding .
overall satisfaction with postnatal care remained fairly constant over the period at around 80% , although lower than that for antenatal and intrapartum care at around 87% .
this study found many positive changes in maternity care provision over the years 1995 to 2014 including earlier initiation of antenatal care , women being able to move around in labour to find a comfortable position , giving birth in an upright position , not necessarily on a bed , and increased flexibility in provision of postnatal care .
earlier initiation of care is a reflection of the technology which now allows women to identify their pregnancy from the first day of a missed period ( nhs choices , 2015a ) .
this is important as currently the window of opportunity for combined nuchal testing for down 's syndrome is only 10 to 14 weeks gestation although other tests are available beyond this ( nhs choices , 2015b ) . the increase in number of ultrasound scans is likely to relate to the increasing sophistication of ultrasound equipment , increasing maternal morbidity , as well as women 's preferences and expectations ( garcia et al . , 2002 , mace et al . , 2012
. however , despite these positive changes , there has also been a reduction in continuity of carer , both during labour and in the postnatal period , which may have implications for the course of labour ( hodnett et al . ,
continuity of carer based on mutual trust and respect has been highlighted in the recent national maternity review as a particularly important component of care ( nhs england , 2016 ) .
women also reported significantly less hospital and community postnatal care provision now than in the past , as has been commented on elsewhere ( scrivens and summers , 2001 ) .
although there was no significant change over time in women indicating that they would have liked to stay in hospital longer , a greater proportion of women would have liked more home visits from the midwife , and between a third and half of women indicated that they did not receive enough help with settling their infant or the infant 's crying .
the pattern of postnatal care appears to be changing with more care provided in clinics or drop - in centres and less in the woman 's home , and the healthcare provider may be a maternity care assistant rather than a midwife . despite these problems with postnatal care , increasing proportions of women
reported that they received consistent advice and support with infant feeding reflecting the work that has been put into this aspect of care ( perez - escamilla et al .
, 2016).overall , the vast majority of women said that staff treated them with respect , although less so in the postnatal period compared to antenatal and intrapartum care , and overall , women indicated consistently high satisfaction with their care .
particular strengths of this study include the large numbers of women who responded to the questionnaires and the fact that the questions were broadly the same over the different surveys allowing for fair comparison .
the principle limitation is the response rate which declined over the years from 67% to 48% with younger , unmarried women , those living in deprived areas , and women born outside the uk being less likely to respond .
however , there were still appreciable numbers of women in all these groups and their views are represented .
declining response rates have also been reported in other similar surveys ( care quality commission , 2010 , care quality commission , 2013 , care quality commission , 2015 , healthcare commission , 2007 ) .
a further possible limitation is that women may be unclear about some aspects of their care , however , in the main the evidence suggests that women remember the salient events of pregnancy and childbirth well ( bat - erdene et al .
particular strengths of this study include the large numbers of women who responded to the questionnaires and the fact that the questions were broadly the same over the different surveys allowing for fair comparison .
the principle limitation is the response rate which declined over the years from 67% to 48% with younger , unmarried women , those living in deprived areas , and women born outside the uk being less likely to respond .
however , there were still appreciable numbers of women in all these groups and their views are represented .
declining response rates have also been reported in other similar surveys ( care quality commission , 2010 , care quality commission , 2013 , care quality commission , 2015 , healthcare commission , 2007 ) .
a further possible limitation is that women may be unclear about some aspects of their care , however , in the main the evidence suggests that women remember the salient events of pregnancy and childbirth well ( bat - erdene et al . , 2013 , quigley et al . , 2007 ) .
women 's perceptions of their care in pregnancy , labour and birth , and the postnatal period were generally very positive .
many aspects of the planning and provision of care have improved considerably since 1995 , such as the developmental of flexible , but targeted care pathways , improved information and explanations relating to antenatal screening , options regarding place of birth , and choice regarding induction of labour .
healthcare professionals are reported to be respectful and overall satisfaction is high . however , some components of care have been reduced , such as access to antenatal education , length of postnatal hospital stay , and number of postnatal home visits . whereas women were apparently unconcerned by a shorter length of hospital stay , an increasing proportion of women , almost a quarter in 2014 , indicated that they would have liked to see a health professional more after hospital discharge and that they needed more help and support .
recognition of the importance of the transition to parenthood and the early months of parenting would suggest that this is an area where improvements could be made .
the datasets supporting the conclusions of this article are currently undergoing further analysis and will be made publically available in due course .
mr conceived the idea , jh did the analyses and drafted the manuscript , both authors revised the manuscript .
| backgroundthere have been changes in maternity care policy over the last 20 years and women 's experience , continuity and satisfaction with care have become more prominent .
however there has been no research examining changes over time in women 's reported experience.methodsthis study used secondary analysis of data collected in four postal surveys of maternity care experiences in 1995 , 2006 , 2010 and 2014 . in each case
women who had delivered in a specified time period in england were randomly sampled and sent a questionnaire three months after the birth .
women were excluded if they were aged less than 16 years or their infant had died .
the majority of questions were comparable over the different surveys .
descriptive statistics and adjusted odds ratios are presented.findingsin the antenatal period , an increasing proportion of women had early first contact with a healthcare professional , screening for down 's syndrome , both dating and anomaly scans and the total number of ultrasound scans increased over the period .
the proportion of women given explanations about screening and choice regarding interventions during labour and birth both appear to have increased . in the postnatal period ,
length of hospital stay declined over time but the proportion of women who considered their length of stay too short remained constant .
the number of postnatal home visits also declined and there was a substantial increase in the proportion of women who would have liked more visits .
overall satisfaction with care remained high especially for care during pregnancy , labour and birth.conclusionsdespite fewer antenatal checks , shorter hospital stays and fewer postnatal home visits , women were generally very positive about their care in pregnancy , labour and birth , and the postnatal period .
maternity care has changed in many respects , with earlier contact with health professionals , more scans and more information
. however , reduced continuity of care and a need for support in the early weeks with a new infant was expressed by many women and are issues that may be contributing to some of the dissatisfaction expressed . |
Rudy Giuliani on Sunday argued that President Trump Donald John TrumpTrump praised White House defender who was fired for sexual harassment: report Cohen's father said he didn’t survive Holocaust to have his name 'sullied' by Trump: report NYT: Trump after Cohen plea mused, 'How did we end up here?' MORE could get caught in a perjury trap if he agrees to an interview with special counsel Robert Mueller Robert Swan MuellerSasse: US should applaud choice of Mueller to lead Russia probe MORE, saying "truth isn't truth."
Giuliani, who is Trump's personal lawyer in the Russia investigation, sought to explain the reason for the drawn-out negotiations between Trump's legal team and Mueller's team over a potential interview.
"I’m not going to be rushed into having him testify so he gets trapped into perjury," Giuliani said on NBC's "Meet the Press."
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"And when you tell me that he should testify because he’s going to tell the truth and he shouldn’t worry, well that’s so silly because that’s somebody’s version of the truth, not the truth," Giuliani said.
"Truth is truth,” anchor Chuck Todd responded.
"No it isn’t," Giuliani said. "Truth isn’t truth."
"Mr. Mayor … this is going to become a bad meme," Todd interjected.
Giuliani went on to say he is skeptical of having Trump speak with Mueller because the special counsel may believe former FBI Director James Comey James Brien ComeyFlake backs effort to rein in Trump on security clearances Graham: Pardoning Manafort would be ‘bridge too far’ Brennan would face long odds in challenging Trump decision MORE or another witness's account of events if it contradicts the president.
"We have a credibility gap between the two of them," Giuliani said. "You’ve got to select one or the other."
WATCH: Rudy Giuliani tells @chucktodd that he doesn’t want President Trump to be caught in a perjury trap by speaking with Special Counsel Robert Mueller. #MTP #IfItsSunday
Giuliani: “Truth isn’t truth" pic.twitter.com/SChZbfgAOX — Meet the Press (@MeetThePress) August 19, 2018
Trump's legal team and Mueller's team have been locked in a months-long back and forth over a potential interview with the president. Trump has maintained he'd like to speak with investigators, but his lawyers have voiced concerns he could perjure himself.
Giuliani earlier this month rejected Mueller's latest offer for interview terms, which included limiting questions about potential obstruction of justice.
Trump has repeatedly called Mueller’s investigation a “witch hunt” and a “hoax.” He has in recent days accused Mueller of a conflict of interest, though he has not elaborated.
The president on Sunday once again lashed out at Mueller, saying he should investigate Hillary Clinton Hillary Diane Rodham ClintonCohen’s lawyer on Trump Tower meeting: Cohen was ‘present at a discussion with' Trump and Trump Jr. Lawyer: Cohen witnessed Trump's 'awareness' of hacked Dem emails before they were released Election Countdown: Trump plans ambitious travel schedule for midterms | Republicans blast strategy for keeping House | Poll shows Menendez race tightening | Cook Report shifts Duncan Hunter's seat after indictment MORE, and that he makes Sen. Joseph McCarthy (R-Wis.) of the 1950s "look like a baby." ||||| "Bad lawyering" from President Trump's previous attorneys explains recent reports that White House counsel Don McGahn had spoken at length with Special Counsel Robert Mueller's team, former New Jersey Gov. Chris Christie said Sunday.
Fox News confirmed Saturday that McGahn had met several times with federal investigators, amid a New York Times report that the sit-downs totaled more than 30 hours over nine months.
Christie specifically called out former Trump attorneys Ty Cobb and John Dowd for failing to invoke executive privilege and initially cooperating with investigators, which he said had forced McGahn's hand and exposed the president to legal jeopardy.
"This shows what a C-level legal team the president had, in Ty Cobb and John Dowd," Christie said on ABC's "This Week."
Cobb and Dowd had broadly pursued a strategy of cooperation with the special counsel's probe, saying the administration had nothing to hide. But, Christie charged, once Cobb and Dowd waived the president's legal privilege that shielded him from investigators' document requests, they effectively prevented the president's future lawyers from legally using that privilege in the future.
"You never waive that. Absolutely not," Christie added, referring to the executive and attorney-client privileges which could have barred investigators significant access to Trump administration officials and documents. "And it put Don McGhan in an impossible position. Once you waive that privilege and you turn over all those documents, Don McGahn has no choice then but to go in and answer everything, answer every question they can ask him.
"That wasn't in the president's interest," Christie continued. "If he had gotten good legal advice at the time, he would've done something else. It's bad legal advice, bad lawyering, and this is the result of it."
Meanwhile, Alan Dershowitz told "Fox & Friends" on Sunday that McGahn probably did not have attorney-client privilege with Trump, because he represents the White House, not the president himself. But on the executive privilege issue, Dershowitz said Cobb and Dowd had made a "tough call," but a reasonable one that simply did not work out.
TRUMP ATTY RUDY GIULIANI: MUELLER DOES NOT HAVE A 'LEGITIMATE' INVESTIGATION
A source reached by Fox News played down the Times article, saying that there didn’t seem to be anything revelatory in the report’s information and adding that it was already known that Trump had instructed McGahn to cooperate with Mueller’s team.
Trump himself on Sunday tweeted that McGahn isn't "a John Dean type 'RAT,'" referring to the Watergate-era White House attorney who turned on Richard Nixon. And John Dowd, Trump’s former lead outside attorney, told Fox News that “Don McGahn was a very strong witness for the president.”
The Times report comes amid pressure from Rudy Giuliani, Trump’s personal attorney, for Mueller to conclude the monthslong investigation.
Speaking on Fox News' "Sunday Morning Futures," Giuliani pressed for Mueller to wrap up the probe and said McGahn couldn't have revealed any significantly damaging information about Trump -- because that would imply he was complicit in wrongdoing.
"The New York Times uses very, very deftly the idea that he cooperated extensively -- well, sure he did," Giuliani said. "It's a complicated thing. But we are confident that he said nothing wrong about the president, and we're confident because the man [McGahn] is a man of integrity, and he would have resigned if something like that would have happened."
Giuliani turned to ex-CIA Director John Brennan, whose security clearance was revoked by President Trump last week. Brennan, who has accused Trump of "treason," on Sunday floated the idea of suing Trump for the move -- and Giuliani said he'd love to see him try.
"Well, then we take his deposition right away," Giuliani said. "I’d volunteer to do that case for the president. I'd love to have Brennan under oath. ... We'll find out about Brennan, and we'll find out what a terrible job he did -- going back to being the head of mission when the Khobar Towers were bombed and our Marines were killed, or we can see what he did or said about Benghazi.”
The White House has accused Brennan of misleading Congress about CIA spying in the Senate, as well as improperly politicizing his security clearance.
Speaking separately on NBC's "Meet the Press" Sunday, Giuliani attracted criticism online for telling host Chuck Todd that "truth isn't truth," as part of his argument that federal investigators can sometimes catch witnesses in so-called "perjury traps" even when they are telling the truth, as long as they can find other witnesses who dispute their claims.
Todd responded: "This is going to become a bad meme."
Fox News' Elizabeth Zwirz contributed to this report. | – There's a reason President Trump hasn't sat down yet for an interview with Robert Mueller, says Rudy Giuliani—and it's all about "truth." The president's personal lawyer in the Russia probe dueled with anchor Chuck Todd over a clear definition of the word Sunday on Meet the Press, the Hill reports. "I'm not going to be rushed into having him testify so he gets trapped into perjury," says Giuliani. "And when you tell me that he should testify because he's going to tell the truth and he shouldn't worry, well that’s so silly because that’s somebody’s version of the truth, not the truth." Says Todd: "Truth is truth." Giuliani: "No it isn't. Truth isn't truth." Todd: "Mr Mayor ... this is going to become a bad meme." For more around the dial: Executive privilege: "You never waive that. Absolutely not," says former New Jersey Gov. Chris Christie on ABC's This Week of Trump's not invoking executive or attorney-client privilege in the Russia probe, per Fox News. "And it put [White House counsel] Don McGhan in an impossible position. Once you waive that privilege and you turn over all those documents, Don McGahn has no choice then but to go in and answer everything, answer every question they can ask him." |
Clint Eastwood will direct the upcoming "Sully" Sullenberger biopic. (Photo: Alberto E. Rodriguez, Getty Images for CinemaCon)
There's no slowing Clint Eastwood down.
The actor/director has handpicked his next project, and like American Sniper, it's stocked with Americana and bravery — and torn straight from the headlines.
Fresh off Sniper's success, The Hollywood Reporter reports, Eastwood will direct a biopic of Capt. Chesley "Sully" Sullenberger and the dramatic tale of how the veteran pilot ditched U.S. Airways Flight 1549 in a splash landing on the Hudson River in January 2009, saving everyone on board.
The jet lost both engines from goose strikes just after taking off from LaGuardia in New York. Sullenberger's expert emergency landing quickly became dubbed as the "Miracle on the Hudson."
"I am very glad my story is in the hands of gifted storyteller and filmmaker Clint Eastwood, and veteran producers Allyn Stewart and Frank Marshall. The project could not have found a better home than Warner Bros. Pictures. This is truly a dream team," Sullenberger said in a statement.
Released in December, Sniper grossed over half-a-billion dollars worldwide, officially becoming the most successful war-themed film of all time.
(Photo: Frank Franklin II, AP)
Read or Share this story: http://usat.ly/1M2dVf1 ||||| Sullenberger became a national hero after ditching U.S. Airways Flight 1549 in the Hudson River.
Clint Eastwood is tackling another real-life hero: Capt. Chesley "Sully" Sullenberger.
The prolific director's next film will be the story of Sullenberger's life and the dramatic tale of how the veteran pilot ditched U.S. Airways Flight 1549 in the Hudson River in January 2009, saving everyone on board. Eastwood, 85, will make the movie for Warner Bros., his longtime home studio, and is set to start shooting this fall (there's no word yet on who will play the heroic pilot).
"I am very glad my story is in the hands of gifted storyteller and filmmaker Clint Eastwood, and veteran producers Allyn Stewart and Frank Marshall. The project could not have found a better home than Warner Bros. Pictures. This is truly a dream team," Sullenberger, 64, said in a statement.
In addition to directing, Eastwood and Tim Moore will produce the "Miracle on the Hudson" via their Malpaso Productions, alongside Marshall and Stewart of Flashlight Films. Marshall and Stewart optioned the rights to Sullenberger's life story and memoir, Highest Duty: My Search for What Really Matters, in 2010, but it wasn't until now that the project landed at a Hollywood studio. (Harrison Ford, an aviation enthusiast and pilot, first introduced Sullenberger to Marshall.)
All of Hollywood had been waiting to see what Eastwood would direct following his global blockbuster American Sniper, also from Warners. Released in December, Sniper grossed north of $543 million globally to become the most successful war-themed film of all time. The biopic, starring Bradley Cooper as the late Navy SEAL Chris Kyle, is also Eastwood's most successful directing outing.
Eastwood's involvement is a huge boost for the Sullenberger project. Todd Komarnicki is writing the adapted script, drawing from Sullenberger's life and memoir. Sullenberger co-wrote his memoir with Jeffrey Zaslow, who died in a car crash in 2012. The announcement was made by Greg Silverman, Warner Bros.' president of creative development and worldwide production.
Said Silverman in a statement: "Simply put, Clint Eastwood is at the top of his game, not to mention a global treasure. On the heels of his extraordinary work in American Sniper, it is tremendously exciting to see him explore the life of another captivating true-life hero. It is also great to be collaborating with Frank Marshall and Allyn Stewart to produce this compelling script by Todd Komarnicki."
Sullenberger and his crew had just taken off from LaGuardia Airport when both engines were knocked out by a flock of Canada geese. The veteran pilot quickly realized there was no time to return to LaGuardia, or reach another airport, so he made the decision to attempt a water landing on the Hudson. The plan worked, and all 155 people on board survived. He instantaneously achieved hero status, and was dubbed "Captain Cool" by then-New York City mayor Michael Bloomberg.
Eastwood had been mulling directing Fox's untitled Richard Jewell biopic, but a deal to bring Warners aboard as a partner failed to materialize. The movie stars Jonah Hill as the heroic security guard who helped save numerous lives during the bombing at the 1996 Summer Olympics in Atlanta. Eastwood also decided against directing a remake of A Star is Born. | – Clint Eastwood has picked his next project as a director—the story of how Capt. Chesley "Sully" Sullenberger landed his US Airways plane safely in the Hudson River in 2009, reports the Hollywood Reporter. The 85-year-old Eastwood is coming off American Sniper, which grossed more than a half-billion dollars to become the most successful movie with a war theme ever, notes USA Today. No word yet on when Miracle on the Hudson will be out, or who will play Sully, but shooting begins in the fall. |
stochastic resonance ( sr ) has attracted considerable attention of many researchers during the last quarter century @xcite . at first sr
was proposed to explain the observed periodicities in global climate dynamics @xcite .
sr occurs when the signal - to - noise ratio ( snr ) for the response of a single nonlinear system to a subthreshold sinusoidal input signal has its maximum at a nonzero noise strength @xmath0 . as well - known , the sr effect is understood as enhancement of the system input to a subthreshold input signal by addition of noise .
there are many studies on sr for a single element .
for example gammaitoni _
_ showed with snr that a subthreshold sinusoidal signal to a single threshold element is optimally transduced by appropriate additive noise @xcite .
collins _ et al . _ also reported that a single neuron can optimally transmit a slowly varying subthreshold aperiodic signal with the aid of appropriate additive noise @xcite .
they proposed the power norm @xmath1 and the normalized power norm @xmath2 in order to measure a correlation between the input signal and the output signal and showed that both @xmath1 and @xmath2 monmonotonically vary with increasing the noise strength .
it is known as _ aperiodic stochastic resonance _ ( asr ) .
many researchers have both experimentally and numerically studied the symmetrical stochastic resonator such as the schmitt trigger @xcite . in recent years
, the central attention of sr seems to move to a network of the stochastic resonators , instead of a single stochastic resonator , such as the global coupled networks and linear chains @xcite . in more recent years a parallel array of nonlinear elements gathers a lot of attention , where the parallel array means that the nonlinear elements are connected in parallel and convergent on a summing center @xcite .
recently stocks studied the parallel array of the nonlinear devices and reported that the suprathreshold stochastic resonance ( ssr ) can be observed on these array motivated by applications to signal processing @xcite . also from the standpoint of neurophysiology collins _
et al . _ and chialvo _ et al .
_ studied an parallel array of noisy neurons can exhibit asr for slowly varying signal @xcite .
consequently it is important to consider the parallel array in both signal processing and neurophysiology .
the main focus of the article is to find an optimal threshold to transmit an arbitrary signal on the parallel array of the bithreshold elements .
according to the assumption that the amplitude of the input signal is smaller than the standard deviation of the noises we derive an analytical approximation of the normalized power norm .
under this assumption it is not necessary to distinguish between subthreshold and suprathreshold .
furthermore we apply the linear response theory to the system that we consider in the article .
the fundamental idea is the noise - induced linearization , which is an effect that an ensemble average of output from a nonlinear system is linearized due to noise @xcite . from the theoretical approximation of the normalized power norm
we show that there exists the optimal threshold to maximize it .
in fact stocks and mannella numerically showed that for a summing network of fitzhugh - nagumo equations adjusting the threshold to maximize information transmission does not remove sr effects .
they pointed out that there is a optimal threshold to maximize the mutual information @xcite .
our result is consistent with their indication .
the article is organized as follows . in sec .
[ sec : model ] we show the array of bithreshold units .
it is well - known that schmitt trigger is a prototype of bithreshold devices @xcite . in sec .
[ sec : theory ] we theoretically derive an approximation of the normalized power norm under the assumption that the norm of the input signal is smaller than the additive noise . utilizing the approximation we find an optimal threshold where the normalized power norm is maximized . in sec .
[ sec : simulation ] we perform numerical simulations for the model and show that the threshold value at the maximum normalized power norm depends on the variance of the additive noises .
[ sec : conclusion ] is devoted to concluding remarks .
figure [ fig : n - array ] displays noisy bithreshold elements connected in parallel and convergent on a summing center .
@xmath3 , which is sampled with a sampling period @xmath4 , namely , @xmath5 ( @xmath6 ) , represents a weak aperiodic signal fluctuating around 0 with @xmath7 and @xmath8 denoting the input to and output from the @xmath9th subsystem , respectively .
the input to the bithreshold element is transmitted over noisy channel .
hence the input to the subsystem is expressed as @xmath10 where @xmath11 ( @xmath12 ) is independently sampled from the gaussian distribution , @xmath13 where @xmath14 are the variance of @xmath11 .
each bithreshold element is symmetric and has three output values .
it is formalized by @xmath15 where @xmath16 are threshold values .
the system output through the summing center @xmath17 is defined as , @xmath18 where @xmath19 is the number of the subsystems . without noises , each input
@xmath7 can not cross the threshold value , leading to the system output @xmath20 . with noises having an appropriate variance
, @xmath7 can cross the threshold value .
we consider the @xmath9th bithreshold subsystem .
let @xmath21 , @xmath22 and @xmath23 be probabilities that @xmath8 takes @xmath24 , @xmath25 and @xmath26 , respectively . for an arbitrary input signal @xmath3 these probabilities are given by , @xmath27 where @xmath28 is the complementary error function , which is defined as , @xmath29 for simplicity we set @xmath30 and @xmath31 for all the subsystems . from eqs .
( [ eq : probability1 ] ) , ( [ eq : probability2 ] ) and ( [ eq : probability3 ] ) we introduce @xmath32 and @xmath33 .
the input signal is subthreshold when @xmath34 and suprathreshold when @xmath35 . from eqs .
( [ eq : system - output ] ) , ( [ eq : probability1 ] ) , ( [ eq : probability2 ] ) and ( [ eq : probability3 ] ) the ensemble average of @xmath17 is calculated as @xmath36 taylor expansion of eq .
( [ eq : ensemble ] ) around @xmath37 yields @xmath38 where @xmath39 represents the first order coefficient , which is given by @xmath40 thus eq .
( [ eq : linearization ] ) shows that @xmath41 is a linear function of the input signal @xmath42 for latexmath:[$\langle the norm of the input signal , measured by the average of the amplitude of the signal .
we call @xmath39 in eq .
( [ eq : linearization ] ) `` gain '' . now
in order to measure correlation between the input signal @xmath3 and the output signal @xmath17 we introduce the normalized power norm @xcite @xmath44^{1/2}[\overline{(y_n(t_j ) - \overline{y_n(t_j)})^2}]^{1/2 } } , \label{eq : def - c1}\ ] ] where @xmath1 is defined as @xmath45 with the overbar denoting an average over time , @xmath46 maximizing @xmath2 corresponds to maximizing the coherence between @xmath3 and @xmath17 , namely , it is equivalent to maximizing information transmission through the devices in fig . [
fig : n - array ] .
at first we discuss the numerator of eq .
( [ eq : def - c1 ] ) . for large @xmath19 @xmath17 asymptotically tends to @xmath47 according to the law of large number . from eq .
( [ eq : linearization ] ) the power norm @xmath1 is calculated as , @xmath48 where @xmath49 is define as @xmath50 , namely , the power norm is proportional to the gain @xmath39 for a given input signal .
next we consider the denominator of eq .
( [ eq : def - c1 ] ) . for the purpose
we introduce @xmath51 we have @xmath52 and @xmath53 ^ 2 \rangle \\ \nonumber & = & \langle y_n^2(t_j ) \rangle - \langle y_n(t_j ) \rangle^2 \\ & = & \frac{1}{n}\bigl\{p_+(t_j)+p_-(t_j ) - \bigl(p_+(t_j)-p_-(t_j)\bigr)^2 \bigr\}. \label{eq : delta}\end{aligned}\ ] ] @xmath17 is distributed around the ensemble average @xmath41 , and @xmath54 is of order of @xmath55 . substituting eqs .
( [ eq : probability1 ] ) , ( [ eq : probability2 ] ) and ( [ eq : probability3 ] ) into eq .
( [ eq : delta ] ) yields @xmath56 expanding the variance @xmath57 around @xmath37 we have @xmath58 the first term of eq .
( [ eq : delta ] ) results from a fluctuation of the output signal @xmath17 without the input signal .
now we consider @xmath59 , calculated as follows @xcite .
we have @xmath60 . since we consider a zero - mean input signal @xmath61 . from @xmath62
we have @xmath63 where we use @xmath64 , which is proven by employing an ergodic assumption . hence from eqs .
( [ eq : power - norm ] ) and ( [ eq : overbar - yn2 ] ) @xmath2 is expressed by @xmath65 where @xmath66 denotes the ratio between @xmath67 and the variance @xmath68 : @xmath69 this statistical measure , which is dimensionless and independent of scale , is the squared reciprocal of the coefficient of variation .
high @xmath66 indicates low variability of the output signal . if @xmath41 is approximated by the first term of eq .
( [ eq : linearization ] ) , and @xmath68 the first term of eq .
( [ eq : delta ] ) , we obtain @xmath70 where @xmath71 . from eq .
( [ eq : c1 ] ) it is clear that @xmath2 is maximized when @xmath66 is maximize .
moreover from eq .
( [ eq : c1 ] ) it is easily confirmed that @xmath66 is maximized at @xmath72 , so that @xmath73 is the optimal threshold . in order to infer the input signal @xmath3 from the output signal @xmath17
it is necessary that @xmath41 is sufficiently larger than the fluctuation of @xmath17 .
if we impose the condition @xmath74 , i.e. , @xmath75 we have @xmath76 this inequality assures that we can infer the input signal @xmath3 from @xmath77 for @xmath78 .
figure [ fig : c1 ] displays the normalized power norm @xmath2 drawn as a function of @xmath79 at fixed @xmath80 from direct numerical simulations of the array of the bithreshold elements at @xmath81 .
the input signal is given by @xmath82 at @xmath83 and @xmath84 , where @xmath80 is given by @xmath85 .
the points are obtained from the numerical simulations for various @xmath79 at @xmath86 , @xmath87 and @xmath88 , respectively .
the curves represent eq .
( [ eq : c1 ] ) at the same parameters as the numerical simulations .
it is found that the results from the numerical simulations is well fitted by the theoretical relation for @xmath89 and @xmath88 .
@xmath2 has it maximum at @xmath90 .
however for @xmath86 it differs from the theoretical equation .
the reason is because the output signal @xmath17 is not well approximated by the linear response of the input signal @xmath3 due to the limit of applying the linear response theory .
this disagreement is originated from difference between the nonlinear response of the system and the linear response assumed in sec .
[ sec : theory ] .
we demonstrate the output signal @xmath17 for various @xmath91 , @xmath92 and @xmath93 as shown in fig .
[ fig : output ] .
the output signal @xmath17 is similar to the input signal @xmath3 in the order for @xmath79 shown . in this demonstration
the input signal is given by a periodic signal .
naturally the theoretical equation of @xmath2 which we obtained is applicable to any input signal ( of course an aperiodic signal ) satisfied with @xmath94 .
specifically when the input signal is satisfied with eq .
( [ eq : low ] ) the output signal gives a good approximation of the input signal at @xmath95 .
we have investigated the parallel array of bithreshold elements both theoretically and numerically .
we give an analytical approximation of the normalized power norm @xmath2 under the assumption that the norm of the input signal @xmath3 is smaller than the standard deviation of the additive noises without distinguishing between subthreshold input and suprathreshold input .
we confirmed that the theoretical approximation of @xmath2 is consistent with the results obtained from the direct numerical simulations of the array of the bithreshold elements when the norm of the input signal is smaller than the standard deviation of the additive noises . while for the larger norm than the standard deviation the difference between the approximation and the numerical results appears .
this disagreement is originated from the nonlinear response of the system .
we demonstrated that the output signal gives a good approximation of the input signal at an appropriate threshold .
we clarify that the optimal threshold , where the normalized power norm has a maximum value , is given by 0.63 times the standard deviation of the noises .
our study may be applied to a sophisticated array of amplifiers .
moreover the result shows that a collection of simple bithreshold sensors can detect a weak signal under an independently noisy environment .
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a * 193 * , 61 ( 1994 ) . | we consider the problem of optimizing signal transmission through multi - channel noisy devices .
we investigate an array of bithreshold noisy devices which are connected in parallel and convergent on a summing center . utilizing the concept of noise - induced linearization we derive an analytical approximation of the normalized power norm and clarify the relation between the optimum threshold and the standard deviation of noises .
we show that the optimum threshold value is 0.63 times the standard deviation of the noises .
this relation is applicable to both subthreshold and suprathreshold inputs . |
we obtained written informed consent from all patients who participated in the study or their legal guardians .
the study population was composed of patients who came to hospitals or clinics in yucatan during august october 2015 with chikungunya - like illness .
these patients were referred to the hematology laboratory at the hideyo noguchi research center ( merida , yucatan , mexico ) . a patient was considered to have chikungunya - like illness if he or she had fever and arthralgia .
travel history of each study participant was recorded , and any patient who had traveled outside yucatan in the past 30 days before disease onset was excluded from the study .
blood was collected from the cephalic vein of each patient , dispensed into a vacutainer tube ( bd diagnostics , franklin lakes , nj , usa ) , and centrifuged .
resting mosquitoes were collected from the homes of each study participant by using centers for disease control and prevention ( atlanta , ga , usa ) backpack - mounted aspirators .
each house was examined once , and collections were made between 9:00 am and noon .
all rooms were inspected , particularly dark areas ( i.e. , underneath furniture , in closets , and in curtains ) .
backyards were also searched , particularly shaded areas ( i.e. , pet homes , tool sheds , and underneath vegetation ) .
mosquitoes were transported alive to the laboratory and identified on chill tables by using morphologic characteristics ( 7 ) .
female mosquitoes were sorted into pools of < 10 and homogenized in phosphate - buffered saline ( ph 7.2 ) by using a mortar and pestle .
an aliquot of each serum sample and mosquito homogenate was filtered and inoculated onto subconfluent monolayers of ae .
second and third blind passages were performed in c6/36 and african green monkey kidney ( vero ) cells , respectively .
vero cells were incubated for 37 days at 37c in an atmosphere of 5% co2 .
cells were scraped from flasks after each passage and centrifuged at 10,000 g for 10 min at 4c .
cell pellets were resuspended in trizol ( invitrogen , carlsbad , ca , usa ) , and total rna was extracted following the manufacturer s instructions .
we analyzed total rna by using reverse transcription pcr ( rt - pcr ) and chikv - specific primers for a 107-nt region of the nonstructural protein 1 gene ( primer sequences available upon request from the authors ) and dengue virus ( denv)specific primers for a 511-nt region of the capsid membrane genes of all 4 serotypes ( 8) . if denv rna was detected , we performed a semi - nested rt - pcr with serotype - specific primers . if chikv rna was detected , we amplified a 3,744-nt region that spans the structural protein genes ( capsid - e3-e2 - 6k - e1 ) ( e , envelope ; 6k , membrane - associated peptide ) as 2 overlapping fragments ( primer sequences available upon request from the authors ) .
complementary dnas were generated by using superscript iii reverse transcriptase ( invitrogen ) , and pcrs were performed by using taq polymerase ( invitrogen ) .
rt - pcr products were purified by using the purelink gel extraction kit ( invitrogen ) and sequenced by using a 3730x1 dna sequencer ( applied biosystems , foster city , ca , usa ) .
denv was readily detected in cultured cells after the first blind passage , but its ability to replicate decreased after subsequent passages , presumably because chikv outcompeted this slower - replicating flavivirus .
the most common symptoms in patients infected with only chikv , in addition to fever , during the first 3 days of disease onset were arthralgia ( 100% ) , myalgia ( 100% ) , asthenia ( 90.9% ) , and rash ( 45.5% ) ( table ) .
symptoms of the co - infected patient ( a 31-year - old woman ) included headache , myalgia , and rash .
age range of patients infected with only chikv was 959 years ( mean age 31 years ) .
we collected a total of 237 female mosquitoes , and all were identified as ae .
one pool contained mosquitoes collected in the living room of a 53-year - old patient who had a confirmed chikv infection .
the capsid - e3-e2 - 6k - e1 region of each chikv isolate was sequenced and submitted to genbank under accession nos .
pairwise alignments of the nucleotide and deduced amino acid sequences were performed by using clustal omega ( http://www.ebi.ac.uk/tools/
analysis showed that nucleotide sequences had 99.41%99.97% identity and amino acid sequences 99.44%100% identity with each other .
ku295121 ) was aligned with all other chikv sequences in genbank and shown to have highest identity ( 99.52% ) with the corresponding gene region of chikv isolates from panama and el salvador , followed by an identity of 99.49% with isolates from chiapas , mexico ; guatemala ; puerto rico ; guyana ; and elsewhere in the western hemisphere .
analysis of deduced amino acid sequences showed that mutations associated with increased infectivity of ae .
albopictus mosquitoes ( e1-a226v and e2-l210q ) ( 9,10 ) were not present in genomes of any isolates .
complete structural gene sequences of 60 chikv isolates , including the 14 isolates from yucatan , were aligned by using muscle ( 11 ) , and phylogenetic trees were constructed by using the neighbor - joining algorithm as implemented in phylip ( 12 ) ( figure ) .
we observed 4 lineages , asian , east / central / south african , indian ocean , and west african lineages , which was consistent with results of previous studies ( 1,5 ) .
chikv isolates from yucatan belonged to the asian lineage and shared a close phylogenetic relationship with other isolates from the western hemisphere ( figure ) .
analysis was based on a 3,744-nt structural gene region ( capsid - e3-e2 - 6k - e1 ) of 63 chikv isolates , including the 14 isolates from yucatan .
sequences were aligned by using muscle ( 11 ) , and the tree was constructed by using the neighbor - joining algorithm as implemented in phylip ( 12 ) and using ete3 ( environment for tree exploration 3 ) ( 13 ) .
bootstrap values were generated by using 1,000 repetitions and normalized on a scale of 01 .
6k , membrane - associated peptide ; e , envelope ; ecsa , east / central / south african lineage ; iol , indian ocean lineage .
aegypti mosquitoes in yucatan , mexico , which provided additional evidence that this virus is spreading throughout the americas at an alarming rate
. concurrent isolation of chikv and denv from a patient in this study and patients in previous studies ( 14,15 ) underscores the need for differential diagnosis in areas where these viruses co - circulate . | chikungunya virus ( chikv ) was isolated from 12 febrile humans in yucatan , mexico , in 2015 .
one patient was co - infected with dengue virus type 1 .
two additional chikv isolates were obtained from aedes aegypti mosquitoes collected in the homes of patients .
phylogenetic analysis showed that the chikv isolates belong to the asian lineage . |
link discovery frameworks are of utmost importance during the creation of linked data @xcite .
this is due to their being the key towards the implementation of the fourth linked data principle , i.e. , the provision of links between datasets .
two main challenges need to be addressed by link discovery frameworks @xcite .
first , they need to address the _ accuracy challenge _ ,
i.e. , they need to generate correct links .
a plethora of approaches have been developed for this purpose and contain algorithms ranging from genetic programming to probabilistic models .
in addition to addressing the need for accurate links , link discovery frameworks need to address the _ challenge of time efficiency_. this challenge comes about because of the mere size of knowledge bases that need to be linked . in particular ,
large knowledge bases such as linkedtcga @xcite contain more than 20 billion triples .
one of the approaches to improving the scalability of link discovery frameworks is to use planning algorithms in a manner akin ( but not equivalent to ) their use in databases @xcite . in general , planners rely on cost functions to estimate the runtime of particular portions of link specifications .
so far , it has been assumed that this cost function is linear in the parameters of the planning , i.e. , in the size of the datasets and the similarity threshold .
however , this assumption has never been verified . in this paper , we address exactly this research gap and _ study how well other models for runtime approximation perform_. in particular , we study linear , exponential and mixed models for runtime estimation .
the contributions of this paper are thus as follows : * we present three different models for runtime approximation in planning for link discovery .
* we compare these models on six different datasets and study how well they can approximate runtimes of specifications as well as with respect to how well they generalize across datasets . *
we integrate the models with the helios planner for link discovery as described in @xcite and compare their performance using 400 specifications .
the rest of the paper is structured as follows : in section [ sec : preliminaries ] , we present the concept and notations necessary to understand this work . the subsequent section , section [ sec : approach ] , presents the runtime approximation problem and how it can be addressed by different models .
we then delve into a thorough evaluation of these models in section [ sec : evaluation ] and compare the expected runtimes generated by the models at hand with the real runtimes of the link discovery framework .
we also study the transferability of the results we achieve and their performance when planning whole link specifications .
finally , we recapitulate our results and conclude .
in this section , we present the necessary concepts and notations to understand the rest of the paper .
we begin by giving a description of a knowledge base @xmath0 and link discovery ( ld ) , we continue by providing a formal definition of a link specification ( ls ) and its semantics and we finish our preliminary section with an explanatory presentation of a plan , its components and its relation to a ls .
[ [ knowledge - base . ] ] knowledge base .
+ + + + + + + + + + + + + + + a knowledge base @xmath0 is a set of triples @xmath1 , where @xmath2 is the set of all rdf resources , @xmath3 is the set of all rdf properties , @xmath4 is the set of all rdf blank nodes and @xmath5 is the set of all literals .
[ [ link - discovery . ] ] link discovery .
+ + + + + + + + + + + + + + + given two ( not necessarily distinct ) sets of rdf resources @xmath6 and @xmath7 and a relation @xmath8 ( e.g , ` directorof ` , ` owl : sameas ` ) , the main goal of ld is to discover the set ( _ mapping _ ) @xmath9 .
given that this task can be very tedious ( especially when @xmath6 and @xmath7 are large ) , ld frameworks are commonly used to achieve this computation .
[ [ link - specification . ] ] link specification .
+ + + + + + + + + + + + + + + + + + + declarative ld frameworks use link specifications ( lss ) to describe the conditions for which @xmath10 holds for a pair @xmath11 .
a ls consists of two basic components : * _ similarity measures _ which allow the comparison of property values of resources found in the input data sets @xmath6 and @xmath7 .
we define an _ atomic similarity measure _ @xmath12 as a function @xmath13 $ ] .
we write @xmath14 to signify the similarity of @xmath15 and @xmath16 w.r.t .
their properties @xmath17 resp . @xmath18 . *
_ operators _ @xmath19 that allow the combination of two _
similarity measures_. an atomic ls consists of one similarity measure and has the form @xmath20 where @xmath21 $ ] .
a complex ls @xmath22 consists of two ls , @xmath23 and @xmath24 .
we call @xmath23 the _ left sub - specification _ and @xmath24 the _ right sub - specification _ of @xmath25 .
we denote the semantics ( i.e. , the results of a ls for given sets of resources @xmath6 and @xmath7 ) of a ls @xmath25 as @xmath26}$ ] and call it a mapping .
we begin by assuming the natural semantics of the combinations of measures .
filters are pairs @xmath27 , where ( 1 ) @xmath28 is either empty ( denoted @xmath29 ) or a combination of similarity measures by means of specification operators and ( 2 ) @xmath30 is a threshold .
note that an atomic specification can be regarded as a filter @xmath31 with @xmath32 = s \times t$ ] .
we will thus use the same graphical representation for filters and atomic specifications .
we call @xmath27 the _ filter of @xmath25 _ and denote it with @xmath33 . for our example @xmath25 in fig .
[ fig : specexample ] , @xmath34 .
we denote the _ operator of a ls _ @xmath25 with @xmath35 . for @xmath36 , @xmath37 .
the operator of the ls shown in our example is @xmath38 .
the semantics of lss are then as shown in table [ tab : semantics ] .
[ [ execution - plan . ] ] execution plan .
+ + + + + + + + + + + + + + + to compute the mapping @xmath26}$ ] ( which corresponds to the output of @xmath25 for a given pair ( @xmath39 ) ) , ld frameworks implement ( at least partly ) a generic architecture consisting of a rewriter ( optional ) , a planner ( optional ) and an execution engine ( necessary ) .
the _ rewriter _ performs algebraic operations to transform the input ls @xmath25 into a ls @xmath40 ( with @xmath26 } = { [ [ l]]}'$ ] ) that is potentially faster to execute .
the most common planner is the _ canonical planner _ ( dubbed canonical ) , which simply traverses @xmath25 in post - order and has its results computed in that order by the execution engine . for the ls shown in fig .
[ fig : specexample ] , the execution plan returned by canonicalwould thus foresee to first compute the mapping @xmath41 $ ] of pairs of resources whose property ` title ` has a cosine similarity greater or equal to @xmath42 .
the computation of @xmath43 $ ] would follow .
step 3 would be to compute @xmath44 while abiding by the semantics described in table [ tab : semantics ] .
step 4 would be to obtain @xmath45 by filtering the results and keeping only the pairs that have a similarity above 0.5 .
step 5 would be @xmath46 $ ] and step 6 would be to compute @xmath47 . finally , step 7 would be to filter out the pairs of links in @xmath48 that have a similarity less than 0.8 . given that there is a 1 - 1 correspondence between ls and the plan generated by the canonical planner , we will reuse the representation of ls devised above for plans .
the sequence of steps for such a plan is then to be understood as the sequence of steps that would be derived by canonicalfor the ls displayed .
.semantics of link specifications [ cols="^,<",options="header " , ] ( filter1)[]@xmath49 ; ( intersection ) [ right = of filter1,xshift=0.8 cm ] @xmath38 edge [ - > ] ( filter1 ) ; ( label3)[right = of intersection.west,anchor=west,xshift=2.2cm ] @xmath50 edge [ - > ] ( intersection ) ; ( filter2)[below = of intersection]@xmath51edge [ - > ] ( intersection ) ; ( intersection2)[right = of filter2.west,xshift=.8cm ] @xmath52 edge [ - > ] ( filter2 ) ; ( label2)[right = of intersection2.west,xshift=.4cm ] @xmath53edge [ - > ] ( intersection2 ) ; ( label1)[below = of label2.west,anchor=west]@xmath54edge [ - > ] ( intersection2 ) ;
in general , planners aims to estimate the cost of the leaves of a plan , i.e. , the runtime of atomic link specifications .
so far , linear models @xcite have been used for this purpose but the appropriateness of other models has never been evaluated .
hence , in this work , we compare non - linear models with linear models to approximate the runtime of of atomic link specifications . like in previous works
, we follow a _ sampling - based approach_. first , given a particular similarity measure @xmath55 ( e.g. , levenshtein ) and an implementation of the said measure ( e.g. , _ ed - join _
@xcite ) , we begin by collecting sample of runtimes for a given measure with varying values of @xmath56 , @xmath57 and @xmath58 . and @xmath7 but found that they do not affect the models we considered .
an exploration of other parameters remains future work .
] these samples can be regarded as the output of a function that can predict the runtime of the implementation of @xmath55 for which we were given samples .
the major question that is to be answered is hence _
what is the shape of the runtime evaluation function _ ?
we tried fitting functions of different shapes to the previously measured runtimes in order to compare their performance when planning the execution of link specifications .
formally , these functions are mappings @xmath59 \mapsto \mathbb{r}$ ] , whose value at @xmath60 is an approximation of the runtime for the link specification with these parameters .
if @xmath61 are the measured runtimes for the parameters @xmath62 , @xmath63 and @xmath64 , then we constrain the mapping @xmath65 to be a local minimum of the l2-loss : @xmath66 writing @xmath67 . within this paper
, we consider the following parametrized families of functions : @xmath68 the parameters are then determined by @xmath69 for some local minimum . in the case of @xmath70 and @xmath71
this problem is linear in nature and we solved it using the pseudo - inverse of the associated vandermonde matrix .
for @xmath72 we used the levenberg - marquardt algorithm @xcite for nonlinear least squares problems , using @xmath73 as initial guess for all parameters .
we chose @xmath70 as the baseline linear fit .
@xmath71 is the standard log - linear fit , except for the @xmath74 term .
we included this term during a grid search for polynomials to perform a log - polynomial fit .
higher orders of @xmath56 or @xmath57 or @xmath58 did not contribute to a better fit .
@xmath72 can be interpreted as an interpolation of @xmath70 and @xmath71 with a constant offset @xmath75 . to exemplify our approach for @xmath71 , assume we have measured @xmath76 @xmath77 and @xmath78 . inserting into eq .
( 1 ) and taking the logarithm , one arrives at the optimization problem @xmath79 the solution to this least squares problem also is the unique solution of its normal equations : @xmath80 @xmath81 by multiplying and inverting matrices , we arrive at the linear equation @xmath82 where @xmath83 denotes the moore - penrose pseudo inverse of @xmath84 @xcite . multiplying the matrices , we arrive at @xmath85
thus we have found the coefficients of the fit function .
we evaluated the three runtime estimation models using six data sets .
the first three are the benchmark data sets for ld dubbed amazon - google products , dblp - acm and dblp - scholar described in @xcite .
we also created two larger additional data sets ( movies and villages , see table [ tab : datasetsproperties ] ) from the data sets dbpedia , linkedgeodata and linkedmdb .
the sixth dataset was the set of all english labels from dbpedia 2014 .
table [ tab : datasetsproperties ] describes the characteristics of the datasets and presents the properties used when linking the retrieved resources for the first four datasets .
the mapping properties were provided to the link discovery algorithms underlying our results .
each of our experiments consisted of two phases : during the _ training _ phase , we trained each of the models independently . for each model , we computed the set of coefficients for each of the approximation models that minimized the root mean squared error ( rmse ) on the training data provided .
the aim of the subsequent _ test _ phase was to evaluate the accuracy of the runtime estimation provided by each model and the performance of the currently best ld planner , helios@xcite , when it relied of each of the three models for runtime approximations . throughout our experiments
, we used the algorithms _ ed - join _
@xcite ( which implements the levenshtein string distance ) and _ ppjoin+ _ @xcite ( which implements the jaccard , overlap , cosine and trigrams string similarity measures ) to execute atomics specifications . as thresholds @xmath58 we used random values between @xmath86 and @xmath73 .
the aim of our evaluation was to answer the following set of questions regarding the performance of the three models _ exp _ , _ linear _ and _ mixed _ : * @xmath87 : how do our models fit each class separately ? to answer this question , we began by splitting the source and target data of each of our datasets into two non - overlapping parts of equal size .
we used the first half of each source and each target for training and the second half for testing . * * _ training _
: we trained the three models on each dataset . for each model , dataset and mapper ,
we a ) selected 15 source and 15 target random samples of random sizes from the first half of a dataset ( amazon - google products , dblp - acm , dblp - scholar , movies and villages ) and b ) compared each source sample with each target sample 3 times .
note that we used the same samples across all models for the sake of fairness .
overall , we ran 675 training experiments to train each model on each dataset . * * _ testing _ : to test the accuracy of each model , we ran the corresponding algorithm ( _ ed - join _ and _ ppjoin+ _ ) with a random threshold between @xmath86 and @xmath73 and recorded the real runtime of the approach and the runtimes predicted by our three models .
each approach was executed 100 times against the whole of the second half of the same dataset .
* @xmath88 : how do our models generalize across classes , i.e. , can a model trained on data from one class be used to predict runtimes accurately on another class ? * * _ training _ : we trained each model in the same manner as for @xmath87 on exactly the same five datasets with the sole difference that the samples were selected randomly from the whole dataset . *
* _ testing _ : like in the previous series of experiments , we ran _ ed - join _ and _ ppjoin+ _ with a random threshold between @xmath86 and @xmath73 .
each of the algorithms was executed 100 times against the remaining four datasets .
* @xmath89 : how do our models perform when trained on a large dataset ? * * _ training _
: we trained in the same fashion as to answer @xmath87 with the sole differences that ( 1 ) we used 15 source and 15 target random samples of various sizes between @xmath90 and @xmath91 from ( 2 ) the english labels of dbpedia to train our model . * * _ testing _ : we learned 100 lss for the amazon - gp , dblp - acm , movies and villages datasets using the unsupervised version of the eagle algorithm @xcite .
we chose this algorithm because it was shown to generate meaningful specifications that return high - quality links in previous works .
for each dataset , we ran the set of 100 specifications learned by eagle on the given dataset by using each of the models during the execution in combination with the helios planning algorithm @xcite , which was shown to outperforms the canonical planner w.r.t .
runtime while producing exactly the same results . throughout our experiments
, we configured eagleby setting the number of generations and population size to 20 , mutation and crossover rates were set to 0.6 .
all experiments for all implementations were carried out on the same 20-core linux server running _ openjdk _ 64-bit server @xmath92 on ubuntu 14.04.4 lts on intel(r ) xeon(r ) cpu e5 - 2650 v3 processors clocked at 2.30ghz .
train _ experiment and each _ test _ experiment for @xmath89 was repeated three times . as evaluation measure , we computed root mean square error ( _ rmse _ ) between the _ expected _ runtime and the average _ execution _ runtime required to run each ls .
we report all three numbers for each model and dataset .
to address @xmath87 , we evaluated the performance of our models when trained and tested on the same class .
we present the results of this series of experiments in table [ tab : exp1 ] . for _ ppjoin+ _
( in particular the _ trigrams _ measure ) , the _ mixed _ model achieved the lowest error when tested upon amazon - gp and dblp - scholar , whereas the _ linear _ model was able to approximate the expected runtime with higher accuracy on the movies and villages datasets . on average , _ linear _ model was able to achieve a lower _ rmse _ compared to the other two models .
for the _ ed - join _ , the _ mixed _ model outperformed _ linear _ and _ exp _ in the majority of datasets ( dblp - scholar , movies and villages ) and obtained the lowest _ rmse _ on average .
as we observe in table [ tab : exp1 ] , for both measures , the _ exp _ model retrieved the highest error on average and is thus the model less suitable for runtime approximations .
especially , for the _ ed - join _ , _ exp _ had the worst performance in four out of the five datasets and retrieved the highest _ rmse _ among the different test datasets for villages .
this clearly answers our first questions : the _ linear _ and _ mixed _ approximation models are able achieve the smallest error when trained on the class on which they are tested .
to continue with @xmath88 , we conducted a set of experiments in order to observe how well each model could generalize among the different classes included in our evaluation data .
tables [ tab : exp2acm ] , [ tab : exp2amazon ] , [ tab : exp2scholar ] , [ tab : exp2movies ] and [ tab : exp2villages ] present the results of training on one dataset and testing the resulting models on the set of the remaining classes .
the highest _ rmse _ error was achieved when both measures were tested using the _ exp _ model in all datasets but villages .
however , table [ tab : exp2villages ] shows that the fitting error when trained on villages is relatively low among all three models .
additionally , we observe that the _ exp _ model s _ rmse _ increased exponentially as the quantity of the training data decreased , which constitutes this model as inadequate and unreliable for runtime approximations . by observing tables [ tab : exp2acm ] and [ tab : exp2scholar ]
, we see that the _ rmse _ of the _ exp _ model increased by 38 orders of magnitude for _ ed - join_. for both measures , the _ linear _ model outperformed the other two models on average when trained on the amazon - gp , dblp - acm and dblp - scholar datasets and achieved the lowest _ rmse _ when trained on movies for _ ed - join _ compared to _ exp _ and _ mixed_. both _ linear _ and _ mixed _ achieved minuscule approximation errors compared to _ exp _ , but _
linear _ was able to produce at least 35% less _ rmse _ compared to _
mixed_. therefore , we can answer @xmath88 by stating that the _ linear _ model is the most suitable and sufficient model that can generalize among different classes . for our last question ,
we tested the performance of the different models when trained on a bigger and more diverse dataset .
table [ tab : exp3 ] shows the results of our evaluation , where each model was trained on dbpedia english labels and tested on the the four evaluation datasets .
the _ linear _ model error was 1 order of magnitude less than the _ rmse _ obtained by _ exp _ and 3 orders of magnitude less compared to the _ mixed _ error . in all four datasets , the
model produced the highest _
rmse_. for the villages dataset , the _ mixed _
model s error was 1916 and 214 times higher compared to _ linear _ and _ exp _ resp .
[ fig : exp ] and [ fig : linear ] present the plans produces by heliosfor the ls ` minus(and(levenshtein(x.description , y.description)|0.5045,trigrams ( x.title , y.name)|0.4871)|0.2925,or(levenshtein(x.description,y.descri ption)|0.5045,trigrams(x.title , y.name)|0.4871)| 0.2925)>=0.2925 ` of the amazon - gp dataset , if the planner used the _ exp _ model and the _ linear _ or the _ mixed _ model resp .
for the child ls ` and(levenshtein(x.description , y.descri ption)|0.5045,trigrams(x.title , y.name)|0.4871)|0.2925 ` , the _ linear _ and the _ mixed _ model chose to execute only ` trigrams(x.title , y.name)|0.4871 ) ` and use the other child as a filter .
moreover , the plan retrieved by using the _ exp _ model for runtime approximations aims to execute both children lss , which results into an overhead in the execution of the ls .
it is obvious that the _ linear _ model achieved by far the lowest _ rmse _ on average compared to the other two models , which concludes the answer to @xmath89 .
( filter)[]@xmath93 ; ( minus)[right = of filter , xshift=0.7cm]@xmath94 edge [ - > ] ( filter ) ; ( filter1)[above = of minus.west,xshift=2.6cm ] @xmath93 edge [ - > ] ( minus ) ; ( intersection)[right = of filter1,xshift=0.7cm , yshift=0.8cm]@xmath52 edge [ - > ] ( filter1 ) ; ( label1)[above = of intersection.west,xshift=3.8cm]@xmath95 edge [ - > ] ( intersection ) ; ( label2)[below = of intersection.west,xshift=3.8cm]@xmath96 edge [ - > ] ( intersection ) ; ( filter2)[below = of minus.east,xshift=1.9cm ] @xmath93 edge [ - > ] ( minus ) ; ( union)[right = of filter2,xshift=0.7cm , yshift=-0.8cm]@xmath38 edge [ - > ] ( filter2 ) ; ( label3)[above = of union.west,xshift=3.8cm]@xmath95 edge [ - > ] ( union ) ; ( label4)[below = of union.west,xshift=3.8cm]@xmath96 edge [ - > ] ( union ) ; ( filter0)[]@xmath93 ; ( minus)[below = of filter0,]@xmath94 edge [ - > ] ( filter ) ; ( filter)[below = of minus]@xmath93 edge [ - > ] ( minus ) ; ( filterintersection)[below = of filter]@xmath96 edge [ - > ] ( filter ) ; ( filter1)[below = of filterintersection ] @xmath95 edge [ - > ] ( filterintersection ) ; ( filter2)[right = of minus.east ] @xmath93 edge [ - > ] ( minus ) ; ( union)[right = of filter2,xshift=0.7cm]@xmath38 edge [ - > ] ( filter2 ) ; ( label3)[above = of union.west,xshift=0.3cm]@xmath95 edge [ - > ] ( union ) ; ( label4)[below = of union.west,xshift=1.6cm,yshift=0.3cm]@xmath96 edge [ - > ] ( union ) ;
the task of efficient query execution in database systems is similar to the task of execution optimization using runtime approximations in ld frameworks .
efficient and scalable data management has been of central importance in database systems @xcite . over the past few years
, there has been an extensive work on query optimization in databases that is based on statistical information about relations and intermediate results @xcite . the author of @xcite
gives an analytic overview regarding the procedure of query optimization and the different approaches used at each step of the process .
a novel approach in this field was presented by @xcite , in which the proposed approach introduced the concept of parametric query optimization . in this work
, the authors provided the necessary formalization of the aforementioned concept and conducted a set of experiments using the buffer size as parameter . in order to minimize the total cost of generating all possible alternative execution plans
, they used a set of randomized algorithms . on a similar manner ,
the authors of @xcite introduced the idea of multi - objective parametric query optimization ( mpq ) , where the cost of plan is associated with multiple cost functions and each cost function is associated with various parameters .
their experimental results showed however that the mpq method performs an exhaustive search of the solution space which addresses this approach computationally inefficient .
another set of approaches in the field of query optimization have focused on creating dynamic execution plans .
dynamic planning is based on the idea that the execution engine of a framework knows more than the planner itself .
therefore , information generated by the execution engine is used to re - evaluate the plans generated by the optimizer .
there has been a vast amount of approaches towards dynamic query optimization such as query scrambling for initial delays @xcite , dynamic planning in compile - time @xcite , adaptive query operators @xcite and re - ordering of operators @xcite .
moreover , the problem addressed in this work focus on identifying scalable and time - efficient solutions towards ld .
a large number of frameworks were developed to assist this issue , such as silk @xcite , limes@xcite , knofuss @xcite and zhishi.links @xcite .
silk and knofuss implement blocking approaches in order to achieve efficient linking between resources .
silk framework incorporates a rough index pre - match , whereas knofuss blocking technique is highly influenced from databases systems techniques . to this end , the only ld framework that provides both theoretical and practical guarantees towards scalable and accurate ld is limes .
as we mentioned throughout this work , limesexecution strategy incorporates the heliosplanner @xcite which is ( to the best of our knowledge ) the first execution optimizer in ld .
heliosis able to provide accurate runtime approximations , which we have extended in this work , and is able to find the least costly execution plan for a ls , consuming a minute portion of the overall execution runtime .
in this paper , we studied approximation functions that allow predicting the runtime of link specifications .
we showed that on average , linear models are indeed the approach to chose to this end as they seem to overfit the least .
still , mixed models also perform in a satisfactory manner .
exponential models either fit very well or not at all and are thus not to be used . in future work , we will study further models for the evaluation of runtime and improve upon existing planning mechanisms for the declarative ld . in particular , we will consider other features when approximation runtimes , e.g. , the distribution of characters in the strings to compare . | time - efficient link discovery is of central importance to implement the vision of the semantic web .
some of the most rapid link discovery approaches rely internally on planning to execute link specifications . in newer works ,
linear models have been used to estimate the runtime the fastest planners .
however , no other category of models has been studied for this purpose so far . in this paper
, we study non - linear runtime estimation functions for runtime estimation .
in particular , we study exponential and mixed models for the estimation of the runtimes of planners . to this end
, we evaluate three different models for runtime on six datasets using 400 link specifications .
we show that exponential and mixed models achieve better fits when trained but are only to be preferred in some cases .
our evaluation also shows that the use of better runtime approximation models has a positive impact on the overall execution of link specifications . |
SECTION 1. AUTHORITY TO MAKE ENTIRE ACTIVE CAPACITY OF FONTENELLE
RESERVOIR AVAILABLE FOR USE.
(a) In General.--The Secretary of the Interior, in cooperation with
the State of Wyoming, may amend the Definite Plan Report for the
Seedskadee Project authorized under the first section of the Act of
April 11, 1956 (commonly known as the ``Colorado River Storage Project
Act'' (43 U.S.C. 620)) to provide for the study, design, planning, and
construction activities that will enable the use of all active storage
capacity (as may be defined or limited by legal, hydrologic,
structural, engineering, economic, and environmental considerations) of
Fontenelle Dam and Reservoir, including the placement of sufficient
riprap on the upstream face of Fontenelle Dam to allow the active
storage capacity of Fontenelle Reservoir to be used for those purposes
for which the Seedskadee Project was authorized.
(b) Cooperative Agreements.--
(1) In general.--The Secretary of the Interior may enter
into any contract, grant, cooperative agreement, or other
agreement that is necessary to carry out subsection (a).
(2) State of wyoming.--
(A) In general.--The Secretary of the Interior
shall enter into a cooperative agreement with the State
of Wyoming to work in cooperation and collaboratively
with the State of Wyoming for planning, design, related
preconstruction activities, and construction of any
modification of the Fontenelle Dam under subsection
(a).
(B) Requirements.--The cooperative agreement under
subparagraph (A) shall, at a minimum, specify the
responsibilities of the Secretary of the Interior and
the State of Wyoming with respect to--
(i) completing the planning and final
design of the modification of the Fontenelle
Dam under subsection (a);
(ii) any environmental and cultural
resource compliance activities required for the
modification of the Fontenelle Dam under
subsection (a) including compliance with--
(I) the National Environmental
Policy Act of 1969 (42 U.S.C. 4321 et
seq.);
(II) the Endangered Species Act of
1973 (16 U.S.C. 1531 et seq.); and
(III) subdivision 2 of division A
of subtitle III of title 54, United
States Code; and
(iii) the construction of the modification
of the Fontenelle Dam under subsection (a).
(c) Funding by State of Wyoming.--Pursuant to the Act of March 4,
1921 (41 Stat. 1404, chapter 161; 43 U.S.C. 395), and as a condition of
providing any additional storage under subsection (a), the State of
Wyoming shall provide to the Secretary of the Interior funds for any
work carried out under subsection (a).
(d) Other Contracting Authority.--
(1) In general.--The Secretary of the Interior may enter
into contracts with the State of Wyoming, on such terms and
conditions as the Secretary of the Interior and the State of
Wyoming may agree, for division of any additional active
capacity made available under subsection (a).
(2) Terms and conditions.--Unless otherwise agreed to by
the Secretary of the Interior and the State of Wyoming, a
contract entered into under paragraph (1) shall be subject to
the terms and conditions of Bureau of Reclamation Contract No.
14-06-400-2474 and Bureau of Reclamation Contract No. 14-06-
400-6193.
SEC. 2. SAVINGS PROVISIONS.
Unless expressly provided in this Act, nothing in this Act
modifies, conflicts with, preempts, or otherwise affects--
(1) the Act of December 31, 1928 (43 U.S.C. 617 et seq.)
(commonly known as the ``Boulder Canyon Project Act'');
(2) the Colorado River Compact of 1922, as approved by the
Presidential Proclamation of June 25, 1929 (46 Stat. 3000);
(3) the Act of July 19, 1940 (43 U.S.C. 618 et seq.)
(commonly known as the ``Boulder Canyon Project Adjustment
Act'');
(4) the Treaty between the United States of America and
Mexico relating to the utilization of waters of the Colorado
and Tijuana Rivers and of the Rio Grande, and supplementary
protocol signed November 14, 1944, signed at Washington
February 3, 1944 (59 Stat. 1219);
(5) the Upper Colorado River Basin Compact as consented to
by the Act of April 6, 1949 (63 Stat. 31);
(6) the Act of April 11, 1956 (commonly known as the
``Colorado River Storage Project Act'') (43 U.S.C. 620 et
seq.);
(7) the Colorado River Basin Project Act (Public Law 90-
537; 82 Stat. 885); or
(8) any State of Wyoming or other State water law.
Passed the House of Representatives July 5, 2016.
Attest:
KAREN L. HAAS,
Clerk. | (This measure has not been amended since it was reported to the House on March 14, 2016. (Sec. 1) This bill authorizes the Department of the Interior, in cooperation with the state of Wyoming, to amend the Definite Plan Report for the Seedskadee Project authorized under the Colorado River Storage Project Act to provide for the study, design, planning, and construction activities that will enable the use of all active storage capacity of Fontenelle Dam and Reservoir, including the placement of sufficient riprap on the upstream face of the Dam to allow such storage capacity to be used for authorized Project purposes. Interior may enter into: (1) any contract, grant, cooperative agreement, or other agreement that is necessary to carry out this Act; and (2) contracts with Wyoming for division of any additional active capacity made available under this Act. Interior shall enter into a cooperative agreement with Wyoming for planning, design, related preconstruction activities, and construction of any modification of the Fontenelle Dam under this Act, which shall specify the responsibilities of Interior and Wyoming regarding: (1) completing the planning and final design of such modification, (2) any environmental and cultural resource compliance activities required for such modification, and (3) the construction of such modification. As a condition of providing additional storage, Wyoming shall provide to Interior funds for any work carried out to do so. |
SECTION 1. SHORT TITLE.
This Act may be cited as the ``Fall River Water Users District
Rural Water System Act of 1996''.
SEC. 2. FINDINGS AND PURPOSES.
(a) Findings.--The Congress finds that--
(1) there are insufficient water supplies of reasonable
quality available to the members of the Fall River Water Users
District Rural Water System located in Fall River County, South
Dakota, and the water supplies that are available are of poor
quality and do not meet the minimum health and safety
standards, thereby posing a threat to public health and safety;
(2) past cycles of severe drought in the southeastern area
of Fall River county have left local residents without a
satisfactory water supply and during 1990, many home owners and
ranchers were forced to haul water to sustain their water
needs;
(3) most members of the Fall River Water Users District are
forced to either haul bottled water for human consumption or
use distillers due to the poor quality of water supplies
available;
(4) the Fall River Water Users District Rural Water System
has been recognized by the State of South Dakota; and
(5) the best available, reliable, and safe rural and
municipal water supply to serve the needs of the Fall River
Water Users District Rural Water System members consists of a
Madison Aquifer well, 3 separate water storage reservoirs, 3
pumping stations, and approximately 200 miles of pipeline.
(b) Purposes.--The Congress declares that the purposes of sections
1 through 13 are to--
(1) ensure a safe and adequate municipal, rural, and
industrial water supply for the members of the Fall River Water
Users District Rural Water System in Fall River County, South
Dakota;
(2) assist the citizens of the Fall River Water Users
District to develop safe and adequate municipal, rural, and
industrial water supplies; and
(3) promote the implementation of water conservation
programs by the Fall River Water Users District Rural Water
System.
SEC. 3. DEFINITIONS.
As used in this Act (unless the context clearly requires
otherwise):
(1) Engineering report.--The term ``engineering report''
means the study entitled ``Supplemental Preliminary Engineering
Report for Fall River Water Users District'' in August 1995.
(2) Project construction budget.--The term ``project
construction budget'' means the description of the total amount
of funds that are needed for the construction of the water
supply system, as contained in the feasibility study.
(3) Pumping and incidental operational requirements.--The
term ``pumping and incidental operational requirements'' means
all power requirements that are incidental to the operation of
intake facilities, pumping stations, water treatment
facilities, cooling facilities, reservoirs, and pipelines up to
the point of delivery of water by the Fall River Water Users
District Rural Water System to each entity that distributes
water at retail to individual users.
(4) Secretary.--The term ``Secretary'' means the Secretary
of the Interior.
(5) Water supply system.--The term ``water supply system''
means the Fall River Water Users District Rural Water System
that is established and operated substantially in accordance
with the feasibility study.
SEC. 4. FEDERAL ASSISTANCE FOR THE WATER SUPPLY SYSTEM.
(a) In General.--The Secretary is authorized to make grants to the
Fall River Water Users District Rural Water System, a nonprofit
corporation, for the planning and construction of the water supply
system.
(b) Service Area.--The water supply system shall provide for safe
and adequate municipal, rural, and industrial water supplies,
mitigation of wetlands areas; and water conservation within the
boundaries of the Fall River Water Users District, described as
follows: bounded on the north by the Angostura Reservoir, the Cheyenne
River, and the Fall River/Custer County line, bounded on the east by
the Fall River/Shannon County line, bounded on the south by the South
Dakota/Nebraska State line, and bounded on the west by the previously
established Igloo-Provo Water Project District.
(c) Amount of Grants.--Grants made available under subsection (a)
to the Fall River Water Users District Rural Water System shall not
exceed the amount authorized under section 10.
(d) Limitation on Availability of Construction Funds.--The
Secretary shall not obligate funds for the construction of the water
supply system until--
(1) the requirements of the National Environmental Policy
Act of 1969 (42 U.S.C. 4321 et seq.) have been met;
(2) a final engineering report has been prepared and
submitted to the Congress for a period of not less than 90 days
before the commencement of construction of the system; and
(3) a water conservation program has been developed and
implemented.
SEC. 5. WATER CONSERVATION.
(a) Purpose.--The water conservation program required under this
section shall be designed to ensure that users of water from the water
supply system will use the best practicable technology and management
techniques to conserve water use.
(b) Description.--The water conservation programs shall include--
(1) low consumption performance standards for all newly
installed plumbing fixtures;
(2) leak detection and repair programs;
(3) rate structures that do not include declining block
rate schedules for municipal households and special water users
(as defined in the feasibility study);
(4) public education programs; and
(5) coordinated operation between the Fall River Water
Users District Rural Water System and any preexisting water
supply facilities within its service area.
(c) Review and Revision.--The programs described in subsection (b)
shall contain provisions for periodic review and revision, in
cooperation with the Secretary.
SEC. 6. MITIGATION OF FISH AND WILDLIFE LOSSES.
Mitigation of fish and wildlife losses incurred as a result of the
construction and operation of the Fall River Water Users District Rural
Water System shall be on an acre-for-acre basis, based on ecological
equivalency, concurrent with project construction, as provided in the
feasibility study.
SEC. 7. USE OF PICK-SLOAN POWER.
(a) In General.--From power designated for future irrigation and
drainage pumping for the Pick-Sloan Missouri River Basin Program, the
Western Area Power Administration shall make available the capacity and
energy required to meet the pumping and incidental operational
requirements of the water supply system during the period beginning May
1, and ending October 31, of each year.
(b) Conditions.--The capacity and energy described in subsection
(a) shall be made available on the following conditions:
(1) The water supply system shall be operated on a not-for-
profit basis.
(2) The water supply system shall contract to purchase its
entire electric service requirements, including the capacity
and energy made available under subsection (a), from a
qualified preference power supplier that itself purchases power
from the Western Area Power Administration.
(3) The rate schedule applicable to the capacity and energy
made available under subsection (a) shall be the firm power
rate schedule of the Pick-Sloan Eastern Division of the Western
Area Power Administration in effect when the power is delivered
by the Administration.
(4) It shall be agreed by contract among--
(A) the Western Area Power Administration;
(B) the power supplier with which the water supply
system contracts under paragraph (2);
(C) the power supplier of the entity described in
subparagraph (B); and
(D) the Fall River Water Users District,
that in the case of the capacity and energy made available
under subsection (a), the benefit of the rate schedule
described in paragraph (3) shall be passed through to the water
supply system, except that the power supplier of the water
supply system shall not be precluded from including, in the
charges of the supplier to the water system for the electric
service, the other usual and customary charges of the supplier.
SEC. 8. NO LIMITATION ON WATER PROJECTS IN STATE.
This Act shall not limit the authorization for water projects in
South Dakota and under law in effect on or after the date of enactment
of this Act.
SEC. 9. WATER RIGHTS.
Nothing in this Act--
(1) invalidates or preempts State water law or an
interstate compact governing water;
(2) alters the rights of any State to any appropriated
share of the waters of any body of surface or ground water,
whether determined by past or future interstate compacts or by
past or future legislative or final judicial allocations;
(3) preempts or modifies any Federal or State law, or
interstate compact, dealing with water quality or disposal; or
(4) confers on any non-Federal entity the ability to
exercise any Federal right to the waters of any stream or to
any ground water resource.
SEC. 10. FEDERAL COST SHARE.
The Secretary is authorized to provide funds equal to 80 percent
of--
(1) the amount allocated in the total project construction
budget for the planning and construction of the water supply
system under section 4; and
(2) such sums as are necessary to defray increases in
development costs reflected in appropriate engineering cost
indices after August 1, 1995.
SEC. 11. NON-FEDERAL COST SHARE.
The non-Federal share of the costs allocated to the water supply
system shall be 20 percent of--
(1) the amount allocated in the total project construction
budget for the planning and construction of the water supply
system under section 4; and
(2) such sums as are necessary to defray increases in
development costs reflected in appropriate engineering cost
indices after August 1, 1995.
SEC. 12. BUREAU OF RECLAMATION AUTHORIZATION.
(a) Authorization.--The Secretary is authorized to allow the Bureau
of Reclamation to provide construction oversight to the water supply
system for those areas of the water supply system that are described in
section 4(b).
(b) Project Oversight Administration.--The amount of funds used by
the Bureau of Reclamation for planning and construction of the water
supply system may not exceed an amount equal to 3 percent of the amount
provided in the total project construction budget for the portion of
the projects to be constructed in Fall River County, South Dakota.
SEC. 13. AUTHORIZATION OF APPROPRIATIONS.
There are authorized to be appropriated $3,600,000 for the planning
and construction of the water system under section 4, plus such sums as
are necessary to defray increases in development costs reflected in
appropriate engineering cost indices after August 1, 1995. | Fall River Water Users District Rural Water System Act of 1996 - Authorizes the Secretary of the Interior to make grants for the construction and operation of the Fall River Water Users District Rural Water System, Inc. Prohibits the obligation of System construction funds until: (1) Federal environmental compliance requirements have been met; (2) a final System engineering report has been prepared and submitted to the Congress for at least a 90-day period; and (3) a water conservation program has been developed and implemented.
Requires the water conservation program to be designed to ensure that System water users will use the best practicable technology and management techniques to conserve water use.
Requires the mitigation of fish and wildlife losses during System construction and operation.
Directs the Western Area Power Administration to make available, from power produced under the Pick-Sloan Missouri River Basin Program, the capacity and energy required to meet the pumping and incidental operational requirements of the System from May 1 to October 31 of each year. Provides power use conditions.
States that this Act does not limit: (1) the authorization for water projects in South Dakota under any law; or (2) current water rights.
Provides the Federal share (80 percent) of System costs.
Authorizes the Secretary to allow the Bureau of Reclamation to provide construction oversight to a specified service area within the System, limiting oversight costs.
Authorizes appropriations. |
SECTION 1. SHORT TITLE.
This Act may be cited as the ``Traumatic Brain Injury Act
Amendments of 2000''.
SEC. 2. FINDINGS AND PURPOSES.
(a) Findings.--Congress makes the following findings:
(1) Traumatic brain injury is among the nation's most
significant public health concerns. It is the leading cause of
death and disability in young Americans.
(2) 1,500,000 traumatic brain injuries occur each year.
1,000,000 of those injuries are serious enough to require
treatment in hospital emergency departments. An estimated
5,300,000 Americans live with a disability as a result of brain
injury. The annual cost to society is estimated conservatively
at $38,700,000,000.
(3) Traumatic brain injury often results in significant
impairment of an individual's physical, cognitive, and
psychosocial functioning requiring access to an array of health
care, education, social services and long-term supports from
acute care to rehabilitation to community re-entry and
participation.
(b) Purposes.--In is the purpose of this Act to--
(1) require the Secretary of Health and Human Services,
working in cooperation with other Federal agencies, to study
and monitor the incidence and prevalence of traumatic brain
injury and conduct national education activities to increase
awareness of the causes and consequences of traumatic brain
injury;
(2) require the Secretary of Health and Human Services to
cause to be identified best practices in diagnosis, emergent
care, special education, and rehabilitation with the ultimate
goal of independent functioning within the community;
(3) require the Secretary of Health and Human Services to
encourage States to build capacity and enhance community based
service delivery systems to provide adequate, appropriate, and
accessible services to individuals with traumatic brain injury
and their families; and
(4) require the Secretary of Health and Human Services to
conduct basic and applied research regarding traumatic brain
injury, including diagnosis, treatment, and rehabilitation.
SEC. 3. PROGRAMS OF CENTERS FOR DISEASE CONTROL AND PREVENTION.
Section 393A(b) of the Public Health Service Act (42 U.S.C. 280b-
1b(b)) is amended--
(1) in paragraph (1), by striking ``and'' at the end;
(2) in paragraph (2), by striking the period and inserting
``; and''; and
(3) by adding at the end the following:
``(3) the implementation of a national education and
awareness campaign in conjunction with Healthy People 2010,
including--
``(A) national dissemination and distribution of
incidence and prevalence findings;
``(B) national dissemination of information
relating to traumatic brain injury and the sequelae of
secondary conditions arising from traumatic brain
injury upon discharge from hospitals and trauma
centers; and
``(C) the provision of information in primary care
settings, including emergency rooms and trauma centers,
concerning the availability of State level services and
resources.''.
SEC. 4. STUDY AND MONITOR INCIDENCE AND PREVALENCE.
Section 4 of Public Law 104-166 (42 U.S.C. 300d-61 note) is
amended--
(1) in subsection (a)(1)(A)--
(A) by striking clause (i) and inserting the
following:
``(i) determine--
``(I) the incidence and prevalence
of traumatic brain injury in all age
groups in the general population of the
United States, including institutional setting; and
``(II) appropriate methodological
strategies to obtain data on the
incidence and prevalence of mild
traumatic brain injury and report to
Congress on such strategies within 18
months of the date of enactment of the
Traumatic Brain Injury Act Amendments
of 2000; and''; and
(B) in clause (ii), by striking ``, if the
Secretary determines that such a system is
appropriate'';
(2) in subsection (a)(1)(B)(i), by inserting ``, including
return to work or school and optimal community participation,''
after ``functioning''; and
(3) in subsection (d), to read as follows:
``(d) Authorization of Appropriations.--There is authorized to be
appropriated to carry out this section, such sums as may be necessary
for each of the fiscal years 2001 through 2005.''.
SEC. 5. PROGRAMS OF THE NATIONAL INSTITUTES OF HEALTH.
(a) Interagency Program.--Section 1261(d)(4) of the Public Health
Service Act (42 U.S.C. 300d-61(d)(4)) is amended--
(1) in subparagraph (A), by striking ``degree of injury''
and inserting ``degree of brain injury'';
(2) in subparagraph (B), by striking ``acute injury'' and
inserting ``acute brain injury''; and
(3) in subparagraph (D), by striking ``injury treatment''
and inserting ``brain injury treatment''.
(b) Research on Cognitive Disorders Arising From Traumatic Brain
Injury.--Section 1261(d)(4) of the Public Health Service Act (42 U.S.C.
300d-61(d)(4)) is amended--
(1) in subparagraph (C), by striking ``and'' after the
semicolon at the end;
(2) in subparagraph (D), by striking the period at the end
and inserting ``; and''; and
(3) by adding at the end the following:
``(E) carrying out subparagraphs (A) through (D)
with respect to cognitive disorders and the
neurobehavioral consequences arising from traumatic
brain injury, including the development, modification,
and evaluation of therapies and programs of
rehabilitation toward restoring normal capabilities to
read, comprehend, speak, reason, and deduce.''.
(c) Authorization of Appropriations.--Section 1261 of the Public
Health Service Act (42 U.S.C. 300d-61) is amended by adding at the end
the following:
``(i) Authorization of Appropriations.--There is authorized to be
appropriated to carry out this section, such sums as may be necessary
for each of the fiscal years 2001 through 2005.''.
SEC. 6. PROGRAMS OF HEALTH RESOURCES AND SERVICES ADMINISTRATION.
Section 1252 of the Public Health Service Act (42 U.S.C. 300d-52)
is amended--
(1) in the section heading by striking ``demonstration'';
(2) in subsection (a), by striking ``demonstration'';
(3) in subsection (b)(3)--
(A) in subparagraph (A)(iv), by striking
``representing traumatic brain injury survivors'' and
inserting ``representing individuals with traumatic
brain injury''; and
(B) in subparagraph (B), by striking ``who are
survivors of'' and inserting ``with'';
(4) in subsection (c)--
(A) in paragraph (1), by striking ``in cash'' and
inserting ``in cash (or with respect to the second and
each subsequent year for which matching funds are
required, in-kind)''; and
(B) by adding at the end the following:
``(3) Effective date.--The requirements of this subsection
shall apply with respect to a State for grant years beginning
after the first year in which the State receives a grant under
this section.'';
(5) by redesignating subsections (e) through (h) as
subsections (g) through (j), respectively;
(6) by inserting after subsection (d), the following:
``(e) Continuation of Previously Awarded Demonstration Projects.--A
State that received a grant under this section prior to the date of
enactment of the Traumatic Brain Injury Act Amendments of 2000 may
compete for new project grants under this section after such date of
enactment.
``(f) Use of State Grants.--
``(1) Community services and supports.--A State shall use
amounts received under a grant under this section to, directly
or through grants or contracts with nonprofit entities--
``(A) develop, change, or enhance community based
service delivery systems that include timely access to
an array of comprehensive services and supports that
promote full community participation by individuals
with brain injury and their families;
``(B) reflect local consumer or family driven
values;
``(C) address the needs of individuals of all ages;
``(D) provide outreach and services to underserved
and inappropriately served individuals, such as
individuals in institutional settings, individuals with
low socioeconomic resources, individuals in rural
communities, and individuals in culturally and
linguistically diverse communities;
``(E) provide grants to nonprofit entities for
consumer or family service access training, consumer
support, peer mentoring, and parent to parent programs;
``(F) provide individual and family service
coordination or case management systems; and
``(G) support other needs identified by a State
plan that is supported by its advisory council and that
reflects local consumer or family driven values.
``(2) Best practices.--
``(A) In general.--State services and supports
provided under a grant under this section shall reflect
the best practices in the field of traumatic brain
injury, and shall be supported by quality assurance
measures as well as the appropriate standard of health
care and integrated community supports.
``(B) Demonstration by state agency.--The State
agency responsible for administering amounts receive
under a grant under this section shall demonstrate or
obtain expertise and knowledge of traumatic brain
injury and the unique needs associated with traumatic
brain injury.
``(3) State capacity building.--A State may use amounts
received under a grant under this section to leverage State
resources to--
``(A) educate consumers and families;
``(B) train professionals in public and private
sector financing (such as third party payers, State
agencies, community-based providers, schools, and
educators);
``(C) develop or improve case management or service
coordination systems;
``(D) develop best practices in areas such as
family or consumer support, return to work, housing or
supportive living, personal assistance services,
assistive technology, substance abuse, behavioral
health services, and traumatic brain injury treatment
and rehabilitation;
``(E) tailor existing State systems to provide
accommodation to the needs of individuals with brain
injury (including systems administered by the State
departments responsible for health, mental health,
labor, education, mental retardation or developmental
disabilities, transportation, housing, and correctional
systems); and
``(F) improve data sets coordinated across systems
and other needs identified by a State plan supported by
its advisory council.'';
(7) in subsection (g) (as so redesignated), by striking
``agencies of the Public Health Service'' and inserting
``Federal agencies'';
(8) in subsection (j) (as so redesignated), to read as
follows:
``(j) Authorization of Appropriations.--For the purpose of carrying
out this section, there is authorized to be appropriated--
``(1) $7,000,000 for fiscal year 2001;
``(2) $9,000,000 for fiscal year 2002;
``(3) $7,500,000 for fiscal year 2003;
``(4) $6,500,000 for fiscal year 2004; and
``(5) $6,000,000 for fiscal year 2005.''; and
(9) by adding at the end the following:
``(k) State.--In this section, the term `State' includes
territories of the United States.''. | Requires certain programs of the National Institutes of Health to include research on brain injury, its treatment, and nuerobehavioral consequences of such injury.
Authorizes the Secretary to make grants to States to carry out projects (currently, demonstration projects) to improve access to health and other services regarding traumatic brain injury. Allows such grant funds to be used: (1) for community services and support for those with such injuries and their families; and (2) to build a State's capacity to address and treat such injuries. Requires such services and support to reflect best practices in the field of traumatic brain injury and to be supported by quality assurance measures. |
the bipolar homunculus nebula surrounding @xmath0 carinae offers an unusually well - constrained laboratory to study a wide array of physical processes in the interstellar medium .
the distance , size , shape , orientation , and structure of the nebula are all known ( smith 2006 ; davidson et al .
2001 ) , as are its expansion velocity and age ( morse et al . 2001 ; currie & dowling 1999 ; smith & gehrz 1998 ) .
ionized ejecta outside the homunculus indicate nitrogen - rich gas ( davidson et al . 1986
; dufour et al . 1997 ; smith & morse 2004 ) , and the recent detection of ammonia in the homunculus suggests that it too is n - rich ( smith et al .
the homunculus itself is mostly neutral , since the star s dense wind extinguishes nearly all of the lyman continuum produced by the system .
this means that familiar temperature and density diagnostics of low - density ionized gas in h ii regions ( e.g. , osterbrock & ferland 2006 ) can not be used here . at uv
/ visual wavelengths the homunculus is seen mainly in reflection . the dust that absorbs and scatters this light acts as a calorimeter by re - emitting the absorbed luminosity in the infrared ( ir ) , providing us with a practical and accurate measure of the bolometric luminosity of the central source ( e.g. , smith et al.2003b ; cox et al . 1995 ; hackwell et al . 1986 ; davidson 1971 ; pagel 1969 ; westphal & neugebauer 1969 ) . despite these constraints
, @xmath0 car s nebula is such a bright and complex object that it leaves no shortage of observational puzzles .
these can sometimes make it difficult to see the trees for the forest .
relevant physical conditions in the homunculus nebula can be constrained if we understand the origin of the distinct double - shell structure in the walls of the nebula .
these layers manifest themselves in three independent ways that have been clearly observed .
first , high resolution thermal - ir images reveal a stratification in the dust color temperature , with a thin outer shell at @xmath9140 k , and a warmer , thicker inner zone with a color temperature of @xmath9200 k ( smith et al .
second , near - ir spectra show an outer skin of h@xmath1 , and an inner shell in tracers of dense , low - ionization atomic gas like collisionally - excited lines of [ fe ii ] ( smith 2006 , 2002a ) .
these two layers are segregated from one another .
third , the two distinct shells can be seen at different radial velocities in uv absorption profiles along our line - of - sight to the star ( gull et al .
2006 , 2005 ; nielsen et al .
the outer molecular layer is also detected in uv absorption lines of ch and oh ( verner et al .
2005 ) , and the inner layer is also seen in visual - wavelength emission lines like [ ni ii ] and [ fe ii ] , plus faint emission of h@xmath10 and [ n ii ] ( davidson et al.2001 ; hillier & allen 1992 ; allen & hillier 1993 ; smith et al.2003a ) .
a detailed account of this structure was given recently in paper i ( smith 2006 ) .
it is this pronounced double - shell structure that we aim to reproduce in the model presented here .
we are particularly interested in the physical conditions that allow h@xmath1 to form and survive in such a thin layer .
so far , @xmath0 carinae is the only luminous blue variable ( lbv ) known to be surrounded by molecular gas in its own ejecta , while nearly all lbv nebulae exhibit bright near - ir emission of [ fe ii ] ( smith 2002b ; smith & hartigan 2006 ) .
the h@xmath1 is probably a consequence of the extreme youth and high density of the nebula .
new observations presented in paper i , obtained with the phoenix spectrograph on the gemini south telescope , have shown the h@xmath1 layer to be surprisingly thin ( only a few per cent of the radius ) and uniformly so , despite the fact that it traces a wide range of different radii at various latitudes in the bipolar nebula .
this hints that the near - ir h@xmath1 emission arises at the inside surface of an optically - thick shell , which absorbs the remainder of whatever fuv radiation penetrates the inner [ fe ii]-emitting zone .
by varying the density in this outer shell , we can test what physical density permits h@xmath1 to survive .
this density constraint , in turn , provides an independent measure of the mass of the homunculus because the geometric thickness of the shell is known .
the total mass is thought to be at least 12 m@xmath8 derived from ir dust observations ( smith et al .
car s grains may have unusual composition ( chesneau et al .
here we are fine - tuning an earlier uniform - density shell model for the physical conditions in the homunculus ( ferland et al .
2005 ) in order to account for the observed thin structure of the h@xmath1 layer .
we simulate the conditions within the nebula using the development version of cloudy , last described by ferland et al .
the incident stellar continuum is represented by an interpolated 20,000 k costar atmosphere with a total luminosity of 5@xmath310@xmath11 . to account for the hard x - rays from the colliding wind binary system , we add a high - energy component corresponding to a 3@xmath310@xmath12 k blackbody with a luminosity of 30 @xmath13 ( e.g. , corcoran et al . 2001 ) .
the lack of a prominent h ii region shows that few hydrogen - ionizing photons strike the inner edge of the nebula , most likely due to absorption by the stellar wind .
therefore , we extinguish the net continuum by photoelectric absorption from a neutral hydrogen layer of 10@xmath14 @xmath15 to account for this . some high - energy photons are transmitted and they help drive the chemistry .
we also include the galactic background cosmic ray ionization rate , although the actual ionization rate may be higher if radiative nuclei are present .
cosmic rays have effects that are similar to x - rays , providing ionization that helps drive the chemistry .
we adopt solar gas phase abundances except for the following : he / h=0.4 , [ c / h]=4.4 , [ n / h]=2.82 , and [ o / h]=4.12 . the gas : dust mass ratio was set to the normal ism value of 100 , and we adopted silicate grains rather than graphitic grains because the 2175 absorption feature is absent in observations ( e.g. , hillier et al .
2006 ) and the 10 @xmath16 silicate emission feature is strong ( see , however , chesneau et al .
2005 ) .
we chose the nebular geometry to be a thick shell separated into two radial zones , where the concentric shells are permitted to have different densities .
table 1 gives our adopted geometric and physical properties of the double - shell structure .
the inner shell ( zone 1 ) has lower density and is geometrically thicker , corresponding to the gas traced by infrared [ fe ii ] lines and warm @xmath9200 k dust .
the outer shell ( zone 2 ) is very thin , and corresponds to the material traced by h@xmath1 emission and cooler @xmath9140 k dust .
the outer edge of the inner shell is directly in contact with the inner surface of the outer shell .
we calculated the physical conditions in these two zones separately in cloudy , using the _ transmitted _ continuum at the outside of zone 1 as the _ incident _ continuum for zone 2 .
although the shells were calculated using spherical symmetry in cloudy , they are meant to approximate the observed properties of the nebula roughly along our sight line through the polar region of the bipolar lobes .
the equatorial region of the nebula with much smaller radii was modeled separately ( see below ) .
the inner and outer radii for the two zones were taken directly from observations ( paper i ) and are not free parameters .
our goal is to investigate the densities in these two zones , to answer the following questions : 1 ) what is the density in zone 1 that is consistent with the observed @xmath17 value of @xmath1810@xmath19 @xmath5 ( smith 2002a ) and permits significant fuv radiation to fully penetrate the shell , causing iron to remain as fe@xmath6 throughout ?
2 ) what is the minimum density in zone 2 that allows hydrogen to become predominantly molecular , and iron to recombine to fe@xmath7 ?
the most important free parameters here are therefore the value of @xmath20 chosen for each zone , but other factors like the gas : dust mass ratio and the filling factor play roles as well
. the main determining factor in whether or not h@xmath1 can survive in zone 2 is the attenuation of fuv radiation in the lyman and werner bands by the total column density of gas and dust in both zones . based on spatially - resolved infrared [ fe ii ] spectra ( paper i ) we adopt a volume filling factor of 0.5 in zone 1 . from similar h@xmath1 spectra and the size scales of structures seen in _ hst
_ images ( morse et al .
1998 ) we adopt a filling factor of 0.9 for the thin outer shell in zone 2 .
a fraction of 0.9 also matches the fraction of the total stellar luminosity absorbed by dust grains that is reemitted in the ir , while @xmath910% of the starlight escapes at near - uv and visual wavelengths .
finally , we note that we have ignored the possible influence of the little homunculus ( ishibashi et al .
this inner nebula has a much lower mass a few percent of the homunculus ( smith 2005 ) and is apparently clumpy on large scales , allowing both radiation and wind to leak through .
thus , its influence should be minimal , absorbing whatever small amount of lyman continuum radiation may escape the dense stellar wind , causing strong variability in the radio continuum ( duncan et al .
figure 1 shows the results of a cloudy calculation matched to observations of the polar lobes of the homunculus roughly along our line - of - sight ( paper i ) .
the transition between zones 1 and 2 is sudden at a depth of a little more than 7@xmath310@xmath21 cm , showing a thick inner zone traced by [ fe ii ] and a very thin outer shell seen in h@xmath1 emission . in order to reproduce this sharp transition ,
the simulation required a strong density increase of a factor of 1530 from zone 1 to 2 . throughout zone 1 , hydrogen remains fully atomic , while fe is singly ionized ( representative values about halfway through zone 1 give an h@xmath1 fraction of 5@xmath310@xmath22 and a neutral fe fraction of 2@xmath310@xmath23 ) .
the electron density from infrared [ fe ii ] line ratios in zone 1 is n@xmath2410@xmath19 @xmath5 ( smith 2002a ) . to match this constraint ,
the hydrogen density in zone 1 was set to 10@xmath25 @xmath5 , since n@xmath26/n@xmath27 was only about 3% at this distance from the star .
only 12% of the hydrogen was ionized at the innermost edge of zone 1 , probably through balmer continuum ionization from the 2s level .
this may account for the faint h@xmath10 emission there ( smith et al .
2003a ; davidson et al .
2001 ) , as well as faint radio continuum ( duncan et al .
1997 ) . in both zone 1 and 2 ,
heating of the gas was dominated ( @xmath2890% ) by grain - gas photoelectric heating , whereas direct heating by line absorption was minimal . to investigate the formation of h@xmath1 and the recombination of fe in zone 2 we considered several different values for the hydrogen density , and discuss a few representative values here :
n@xmath27=10@xmath29 , 10@xmath30 , 10@xmath31 , 10@xmath32 , and 10@xmath4 @xmath5 .
table 1 lists the properties in zone 2 at these various densities , and figure 2 gives a detailed view of the transition to molecular gas for each of these adopted densities .
with n@xmath27=10@xmath29 @xmath5 , we found that h@xmath1 did not form at all , with h remaining fully atomic and fe remaining singly ionized throughout zone 2 . when the density was raised to 2@xmath310@xmath29 @xmath5
, h@xmath1 did begin to form at the outer edge of zone 2 ; the molecular fraction reached a maximum of about 40% at the outermost edge ( fig . 2 ) .
however , fe remained singly ionized throughout zone 2 at this density .
this is not in agreement with observations , since fe i absorption is seen from zone 2 in uv spectra ( nielsen et al .
2005 ) , so the density must be higher than 2@xmath310@xmath29 @xmath5 . at a density of 3@xmath310@xmath29 @xmath5 , hydrogen became 99% molecular at the outer edge of the shell ( fig .
2 ) , but fe@xmath6 still did not recombine to fe@xmath33 .
observations suggest that h@xmath1 should form and the recombination of fe should occur _ early _ in zone 2 , especially at the remote polar regions where the radiation field is weaker than at other latitudes .
this condition is met only for higher hydrogen densities around 10@xmath32 to 10@xmath4 @xmath5 ( fig . 2 ) .
at a depth of only about 10@xmath34 cm into zone 2 ( 1020% of the way through the layer ) , the h@xmath1 fraction begins to rise sharply .
this is because its destruction rate collapses as uv radiation in the lyman and werner bands becomes optically thick and is extinguished by the much higher column density of gas and dust encountered here .
once molecules begin to form , the transition is rapid .
hydrogen remains fully molecular throughout the rest of zone 2 , while fe@xmath6 does finally recombine .
the fe@xmath6/fe@xmath7 transition occurs at a slightly larger depth than the atomic / molecular hydrogen transition , because fe@xmath7 can still be ionized by balmer continuum photons with wavelengths longer than the lyman - werner bands .
the hydrogen density is probably not much above 10@xmath4 @xmath5 , because then the h@xmath1 shell would be thicker than observed , and the extinction to the star would be unreasonably high .
the bottom panel of figure 1 shows the dust temperature for various grain radii at a range of depths through the shell . in zone 1 , we see that only the largest grains with radii @xmath350.2 @xmath16 can match the observed dust color temperatures .
the transition to higher densities at the beginning of zone 2 is accompanied by a sharp drop in the grain temperature , as observed in mid - ir images ( smith et all.2003b ) .
this sharp drop to lower grain temperatures only occurred for the highest - density models with n@xmath27=10@xmath32 to 10@xmath36 @xmath5 in zone 2 .
the grain temperature in zone 2 appears to be independent of grain size .
this is perhaps because much of the short - wavelength fuv radiation has been extinguished and the grains are heated predominantly by radiation at near - uv , visual , and ir wavelengths instead , where the absorption efficiency is less sensitive to grain size ( e.g. , draine 2003 ) . in this case
, grain - gas photoelectric heating will drop as well .
in fact , we see that the grain temperature eventually drops to within 20 k of the equilibrium blackbody temperature t@xmath37 ( dashed line ) , independent of grain radius .
the fact that the temperature in zone 2 is nearly independent of grain size is interesting , because it contradicts long - held conventional wisdom .
the observed near - blackbody color temperature has often been taken as an indication that the grains have radii of 12 @xmath16 ( smith et al . 2003b , 1998 ; polomski et al .
1999 ; hackwell et al . 1986
; mitchel et al . 1983 ) .
however , figure 1 indicates that grains this large may not be necessary to explain the grain temperature in zone 2 after all ( although some large grains are still needed for the nearly gray extinction ; rodgers 1971 ; hillier 2006 ; whitelock et al .
in particular , a population that includes _ both _ large and small grains is evidently allowed in zone 2 .
the visual extinction through zone 1 is only @xmath91 mag , compared to about 4.59 magnitudes for zone 2 ( table 1 ) .
thus , the thin outer h@xmath1 shell dominates the visual extinction , the total infrared luminosity , and also the scattered light seen in visual - wavelength images and hard x - rays ( corcoran et al .
this is why model shapes for the homunculus derived from [ fe ii ] or [ ni ii ] emission from zone 1 ( davidson et al .
2001 ; allen & hillier 1991 ) are too small compared to images , whereas model shapes derived from h@xmath1 emission have the correct apparent size ( paper i ) .
the stellar continuum that illuminates the nebula is strongly reprocessed by the inner region before it reaches the denser outer zone .
figure 3 shows the stellar continuum ( the smoother dotted line ) that is incident upon the inner nebula .
the gray solid line with many spectral emission features is the net emission that emerges from the inner region and goes on to irradiate the molecular gas in zone 2 .
this continuum is a combination of the attenuated incident continuum plus reprocessed emission from the inner nebula .
the uv continuum has been heavily absorbed by dust within the inner region .
thermal dust emission dominates the infrared continuum , and the dust is warm enough for the 10 @xmath16 silicate feature to come into emission .
many emission lines , mainly atomic and singly ionized species , are formed in the inner region .
the major effect of this reprocessed continuum will be upon dust in the outer nebula .
much of the incident uv continuum has been converted into thermal - ir emission already .
the uv is the most effective in photoelectrically heating gas , so the outer nebula is cooler as a result of the absence of this light , as noted earlier .
the very strong infrared continuum heats the outer nebula indirectly , by first heating the dust , which then shares its energy with the gas as the result of gas - dust collisions .
the emergent spectrum from zone 2 with @xmath20=10@xmath32 @xmath5 is shown with the solid black line in figure 3 .
as expected , the thermal - ir continuum is shifted toward longer wavelengths because of the cooler dust , and the uv / visual light is more severely attenuated than for zone 1 .
interestingly , when we compare the spectrum from zone 1 alone to the emergent spectrum from zone 2 ( which includes the emergent spectrum of zone 1 that passes through zone 2 ) , we see that the 10 @xmath16 silicate feature has a different shape the silicate profile from zone 2 is somewhat muffled , indicating that the emission is beginning to turn optically thick .
in fact , when the density is increased to @xmath20=10@xmath4 @xmath5 in zone 2 ( dashed gray line ) the silicate feature turns clearly to self - absorption .
this trend in the silicate profile shape has two important implications .
first , when the emission begins to turn optically thick , the silicate profile appears wider and flatter , and the peak moves toward longer wavelengths .
this effect will modify the required contribution from other grain species like corrundum ( see chesneau et al .
second , the strong silicate feature observed in @xmath0 car s mid - ir spectrum may indicate that densities of @xmath20=10@xmath4 @xmath5 are too high ( although the effects of clumping are an issue ) . if densities near our lower bound @xmath20=10@xmath32 @xmath5 are preffered , then a total mass of the homunculus near 16 m@xmath8 is favored over a much larger value of @xmath930 m@xmath8 ( see 5.1 ) .
this is , perhaps , a relief .
high spatial resolution spectroscopy of the silicate profile in the homunculus could provide a powerful and independent constraint on the density and total mass of the nebula .
near - infrared h@xmath1 emission is seen at all latitudes in the homunculus ( paper i ) , even though the distance from the star changes by an order of magnitude . in the side walls of the polar lobes at mid - latitudes ,
the oblique incident angle of the radiation ( i.e. `` seasons '' ) will mitigate the stronger radiation field at closer radii to the central star , but this geometric advantage disappears for the molecular gas at the pinched - waist of the nebula .
thus , we also investigate the physical conditions in the equatorial plane of the homunculus , where h@xmath1 is seen nearest to the star .
the equatorial model was identical to the polar lobe / line - of - sight model , except that the radii and thicknesses of zones 1 and 2 were adjusted to match observations ( paper i ) , and the density in zone 1 was increased .
the equatorial model is summarized in table 2 .
figure 4 shows the results of a cloudy calculation matched to observations of the radial stratification in the equatorial plane of the homunculus ( paper i ) .
the inner radius is set approximately equal to the distance between the star and the weigelt knots , which is 0@xmath382 to 0@xmath383 ( smith et al . 2004 ; dorland et al .
2004 ) , or roughly 10@xmath21 cm if we correct for the 41 inclination angle ( paper i ; davidson et al .
2001 ) . in order to match observed electron densities of @xmath3910@xmath29 @xmath5 in the weigelt knots and other bright equatorial ejecta ( smith 2002 ; hamann et al . 1999 , 1994 ; davidson et al .
1995 ) , the simulations required a hydrogen density of about n@xmath27=2@xmath310@xmath29 @xmath5 or more .
to 10@xmath40 @xmath5 ( hamann et al .
] this was also the highest density that allowed h to remain predominantly atomic and fe to remain as fe@xmath6 throughout zone 1 .
even though the material is much closer to the star and feels a much stronger radiation field than in the polar model , @xmath210@xmath4 @xmath5 in zone 2 was still sufficient to allow a sharp transition to molecular hydrogen and neutral fe . unlike the polar model
, the inner edge of zone 1 experienced a more substantial h@xmath6 fraction of @xmath975% , while @xmath920% of the iron was ionized to fe@xmath41 .
this ionization occurs despite the fact that , aside from hard x - rays ( corcoran et al .
2001 ) , we did not include radiation from a hot companion star in our calculation . throughout most of zone 1 ,
the typical molecular hydrogen fraction was of order 10@xmath42 , while the neutral fe fraction was typically 10@xmath23 .
the bottom panel of figure 4 shows the dust temperature for grains in the equatorial model . in zone 1
, the predicted dust temperatures greatly exceed observational constraints on the color temperature for most grain sizes .
the hottest extended dust in the core of the homunculus ( associated with the weigelt knots and more distant ejecta ) is about 550 k ( smith et al .
2003b ; chesneau et al .
this is marginally consistent with @xmath43=0.2 @xmath16 grains within observational uncertainty , but the observed tempertures would be more consistent with significantly larger grains .
the transition to lower dust temperature at the boundary between zones 1 and 2 is not as stark as in the polar model , but like the polar model , the grain temperature in zone 2 drops and becomes insensitive to grain size ( fig . 4 ) . here
it fully reaches temperatures as low as the equilibrium blackbody temperature t@xmath37 .
figure 5 shows the incident ( dotted ) and transmitted energy distributions for the equatorial model .
the transmitted radiation is that which escapes from the outer boundary of zone 2 .
this emission at the equator is of particular interest , as it illuminates material in the equatorial skirt at larger radii .
some of that equatorial gas has pecular spectral properties , like the so - called `` strontium filament '' ( hartman et al .
2004 ; zethson et al . 2001 ; bautista et al . 2006 , 2002 ) , the very bright and possibly fluorescent [ ni ii ] @xmath447379 emission ( davidson et al . 2001 ) , and he i @xmath4410830 emission ( smith 2002 ) . in figure 5
we see that radiation shortward of 2000 is severely attenuated , while near - uv radiation beyond this limit remains strong .
our most important observational constraint on the density in the polar lobes is that molecular hydrogen is able to survive and fe becomes neutral , even though they are within only 0.1 pc of the most luminous hot supergiant in our galaxy .
furthermore , both of these conditions should be met in the polar model of zone 2 with some room to spare , since h@xmath1 emission is seen to be fairly uniform at all latitudes , including lower latitudes closer to the equator ( and closer to the star ) where the radiation field is stronger .
as we have discussed above , these constraints are only met for high densities of n@xmath27=10@xmath45 @xmath5 in zone 2 . from the thermal - ir spectral energy distribution and conservative assumptions , smith
( 2003b ) derived a lower limit to the total mass of the homunculus of about 12.5 m@xmath8 ( about 11 m@xmath8 in the cool 140 k shell , and 1.5 m@xmath8 in the warmer inner shell ) .
if this mass of cool dust were spread evenly over the volume of the h@xmath1 shell inferred observationally , the density would be at least n@xmath27=10@xmath31 @xmath5 in zone 2 ( paper i ) .
however , our cloudy calculations show that even higher densities are likely , as noted above .
these higher average densities distributed over the same volume would imply a total gas mass for the homunculus in the range of roughly 1535 m@xmath8 .
thus , our study confirms the large mass of the homunculus deduced from ir observations of dust , but uses an independent method sensitive to the gas density .
it also confirms that previous ir estimates were indeed lower limits to the total mass .
we also find that 35 m@xmath8 is an upper limit to the mass , since for densities much higher than 10@xmath4 @xmath5 , the transition to molecular gas would occur earlier and the h@xmath1 shell would be thicker than observed .
caveats : although our mass estimate is sensitive to the gas density , it is not completely independent of the gas : dust ratio , since dust helps attenuate the uv radiation in the lyman - werner bands that destroys h@xmath1 , and grains act as a catalyst by providing a surface for h@xmath1 formation .
however , like mass estimates from thermal - ir dust emission , these are probably underestimates if they are wrong .
our cloudy calculations were tuned to match the observed structure in ir lines of h@xmath1 and [ fe ii ] , but they naturally reproduce the bimodal stratification of the observed dust color temperature as well .
high - resolution thermal - ir images show a thick inner shell at @xmath9200 k and a thin outer shell at @xmath9140 k ( smith et al .
2003b ) , where the cooler dust color temperatures are coincident with the outer h@xmath1 shell .
this is clearly reproduced in our model ( fig . 1 ) .
our earlier simulations with cloudy used a uniform density of 10@xmath29 @xmath5 throughout a thick shell ( ferland et al .
2005 ) and were able to reproduce a transition from h to h@xmath1 and fe@xmath6 to fe@xmath7 at some point within the shell , _ but in that model a sharp drop in dust temperture did not occur at the same position as the onset of h@xmath1_. instead , in the constant - density thick - shell model , the dust temperature began to drop immediately at the inner radius of the shell and continued smoothly thereafter .
therefore , the observed sharp transition from a geometrically thick zone of @xmath9200 k to a very thin layer of @xmath9140 k dust coincident with the onset of the thin h@xmath1 shell ( fig
. 1 ) gives a robust and independent confirmation that a sharp density contrast between the two zones is indeed required . because of the strong density increase of a factor of 15 - 30 from zone 1 to zone 2
, the model also successfully reproduced the relative contributions to the total mass observed in each component .
fits to the ir spectral energy distribution ( smith et al .
2003b ) show that the 200 k dust in the inner shell only contains about 10% of the total mass in the nebula , while the rest of the mass resides in the thin outer shell at 140 k. because the outer shell is so thin , it must be much denser in order to have a higher total mass .
the relative masses for the inner ( @xmath91 m@xmath8 ) and outer ( 16 - 33 m@xmath8 ) shells in table 1 agree with these observational constraints . by stark contrast
, a uniform - density thick shell would have much more mass in the [ fe ii ] zone .
interestingly , the radial behavior of the dust temperature brings into question long - held notions about the grain properties .
several authors have noted that the low dust color temperatures at thermal - ir wavelengths are close to the equilibrium blackbody temperatures at those radii , suggesting large grain sizes above @xmath461 @xmath16 ( mitchell et al .
1983 ; mitchell & robinson 1986 ; hackwell et al.1986 ; robinson et al .
1987 ; apruzese 1975 ; smith et al . 1998 , 2003b ; polomski et al .
silicate emission feature , but chesneau et al .
( 2005 ) , mitchell & robinson ( 1978 ) , and hyland et al .
( 1979 ) have suggested that this may be due to a partial contribution from other grain emission features like corrundum .
] in contrast , we find that the dust temperature in the outer layer is _ independent of grain size _ ( figs . 1 and 4 ) , and approaches the equilibrium blackbody temperature even for small grains .
the material becomes optically thick and severely attenuates the uv radiation , leaving the burden of energy balance to heating by longer wavelength radiation . at longer wavelengths
, the difference between absorption efficiency and the thermal - ir emissivity is smaller , allowing small and large grains to maintain similar temperatures .
the dust temperature never gets below the equilibrium blackbody temperature in our calculations .
therefore , the very low dust temperature of 110 k that morris et al .
( 1999 ) deduced from fits to the far - ir spectral energy distribution is probably too low , especially at the small radii in the equator suggested by those authors .
although the temperature is apparently independent of grain size in zone 2 , very small grains are not permitted in zone 1 because corresponding high temperatures are not seen there .
the color temperature in zone 1 is about @xmath9200 k , which would be consistent with grains of radius @xmath350.2 @xmath16 .
thus , our calculations relax but do not eliminate the constraints on large grain size posed by the low observed dust temperatures in the homunculus . allowing the presence of somewhat smaller grains may be relevant to the high degree of polarization ( thackeray 1961 ; visvanathan 1967 ; warren - smith et al . 1979 ; meaburn et al . 1987 ; 1993 ;
walsh & ageorges 2000 ) and the unusual scattering properties of the homunculus seen in high - resolution polarization imaging ( schulte - ladbeck et al .
1999 ) .
an accurate model for zone 1 determines the radiation field that penetrates it to illuminate the outer h@xmath1 shell ( fig .
3 ) , but the inner shell is interesting in its own right because of the physical conditions that give rise to the extraordinarily bright infrared [ fe ii ] emission seen there ( paper i ) .
these bright infrared [ fe ii ] emission lines are a common feature of other lbv nebulae ( smith 2002b ; smith & hartigan 2006 ) , which is in contrast to the outer h@xmath1 shell that seems to make @xmath0 car unique among hot luminous stars . to investigate this bright [ fe ii ] emission in detail
, we ran cloudy using the more sophisticated large fe atom .
this predicts the strength of numerous fe lines , including the distinct [ fe ii ] ( @xmath47 ) and ( @xmath48 ) transitions in the 12 @xmath16 region .
for example , with solar fe abundance , our cloudy model for zone 1 predicts a total luminosity for [ fe ii ] @xmath4416435 of about 65 l@xmath8 . this line has been observed extensively in @xmath0 car in both moderate and high resolution spectra ( smith 2002a ; paper i ) , and exhibits an average brightness in the polar lobes of about 2@xmath310@xmath49 ergs s@xmath50 @xmath15 arcsec@xmath51 ( although the local value is highly spatially dependent ) .
integrating this over the roughly 140 - 150 arcsec@xmath52 projected area of the homunculus would indicate a total flux in this line of 3@xmath310@xmath22 ergs s@xmath50 @xmath15 ( excluding the bright [ fe ii ] contribution from the little homunculus ; smith 2005 ) .
this corresponds to a total observed [ fe ii ] @xmath4416435 luminosity of about 4050 l@xmath8 .
the agreement between our model s predicted luminosity of 65 l@xmath8 and the observed value of @xmath945 l@xmath8 in this same line is remarkable , considering that the bipolar homunculus has a somewhat smaller projected area on the sky than the equivalent - radius spherical shell in cloudy .
this match indicates that the gas - phase fe abundance is indeed roughly solar in zone 1 .
a solar gas - phase fe abundance here is actually quite astonishing . in dusty regions of the ism ,
the abundance of fe is normally depleted by two orders of magnitude due to the formation of fe - bearing grains ( e.g. , shields 1970 ) .
we do nt expect the overall dust - to - gas ratio in zone 1 to be unusually low , since the mass inferred for the gas from the observed electron density agrees with the mass measured from the 200 k dust component that occupies the same region ( uncertainties of a factor of 2 are likely , but not factors of 100 ) .
therefore , some process has selectively destroyed fe - bearing grains _ without _ destroying the remaining grain population , or some mechanism has specifically inhibited the formation of fe - bearing grains .
shock speeds @xmath2880 km
s@xmath50 can destroy iron grains and release the corresponding atomic fe into the gas phase .
while we see no spectroscopic evidence for such fast shocks in the polar lobes today , shocks of this speed may have been active earlier in the life of the homunculus .
if such shocks destroyed the fe - bearing grains early - on , they may have been released into an environment where the density was too low to reform the grains , locking fe in the gas phase .
alternatively , the ejecta in the homunculus are c- and o - poor , and n - rich .
the low oxygen abundance may have inhibited the formation of iron oxides , which can be an important repository for storing fe in the solid phase of the ism . in the absence of c , o , and fe
, grains might form preferentially with al , mg , or ca instead . interestingly
, mid - ir spectroscopy of the homunculus strongly suggests the presence of al - bearing grains like corrundum ( mitchell & robinson 1978 ; hyland et al .
1979 ; chesneau et al .
we also know that fe is present in the gas phase in the outer h@xmath1 shell , since fe@xmath7 is seen in absorption there in uv spectra ( gull et al . 2005 ; nielsen et al.2005 ) .
the existence of a region of the ism with a high dust content and where fe is predominantly in the gas phase has important ramifications beyond the study of @xmath0 carinae , and will be discussed elsewhere .
we have shown that the observed double - shell structure of the homunculus requires a strong density jump in the walls of the nebula .
the observed transition from atomic to molecular gas ( paper i ) and the corresponding drop in dust temperature ( smith et al .
2003b ) result when fuv radiation propagating through the low - density inner zone suddenly encounters the high densities in the thin outer shell .
the absorption of this uv radiation in the lyman - werner bands by gas and dust in the dense outer shell regulates the destruction rate of h@xmath1 , allowing the h@xmath1 to survive .
the required density contrast between these two zones is a factor of roughly 1530 .
while our cloudy calculations explain how the observed properties of the double - shell structure result from a strong density stratification , they do not explain the origin of the density structure itself .
since the homunculus appears to be expanding ballistically ( smith & gehrz 1998 ) and because the current stellar wind is too weak to shape the massive nebula , it is likely that this density structure was determined early . the observed
stratification is reminiscent of the layered structure seen in cooling zones behind shock fronts ; although this is unlikely to be occuring at the present time ( paper i ) , the observed density structure may be frozen - in to the ejecta from shocks that occurred during the event itself as the dense material cooled .
as noted in the previous section , shocks present during an earlier epoch would also be interesting from the point of view of the gas - phase fe abundance .
the rapid cooling of this dense layer may have triggered severe thermal instabilities , which in turn , could explain the currently - observed clumping and fragmentation seen in images of the homunculus ( morse et al .
1998 ) . alternatively
, the low - density inner zone may result from a photoevaporative flow off the inside face of the much denser outer h@xmath1 shell , as is commonly seen in photodissociation regions at the surfaces of giant molecular clouds .
finally , an obvious possibility is that the two shells simply result from separate ejection events during the @xmath920 yr timespan of the great eruption . we know that this is at least plausible from the existence of the outer ejecta , the homunculus , and the little homunculus , indicating that @xmath0 car has suffered multiple mass ejections ( walborn 1976 ; walborn et al .
1978 ; ishibashi et al . 2003 ; smith 2005 ) .
our models that reproduce the fundamental observed structure have constrained the most basic physical properties of the homunculus : namely , its density and temperature .
these will allow further refinements to models trying to understand emission line spectra , unusual grain properties , molecular chemistry , abundances , and radiative transfer models of the appearance of @xmath0 car s nebula in images . the physical explanation for this distinct double - shell structure may have wider applications as well , especially to objects like planetary nebulae .
for example , the bipolar nebula m2 - 9 has a similar and pronounced double - shell structure , with a thin outer h@xmath1 shell and an inner [ fe ii ] shell ( smith et al .
2005 ; hora & latter 1994 ) . the uv radiation field of m2 - 9 is known to be highly asymmteric and time variable because of a central binary system ( e.g. , doyle et al .
2000 ) , so it is likely that a density jump controls the shape of the h@xmath1 lobes , as in @xmath0 car . our cloudy models for @xmath0 car would then suggest that the transition from atomic to molecular gas in such pne would be accompanied by a similar sharp drop in observed dust color temperature at mid - ir wavelengths , possibly insensitive to grain size as well . since @xmath0 car is the only lbv nebula known to have a dense h@xmath1 shell , we must ask if this is a truly unique property of @xmath0 car itself , or if it is simply a consequence of @xmath0 car being observed at a special time so soon after its mass ejection ; the homunculus is also the _ youngest _ lbv nebula . we expect that in the decades immediately following the outburst , the ejecta around @xmath0 car were extremely dense and self - shielding , permitting the formation of not only dust , but also h@xmath1 and even more complex polyatomic molecules like ammonia ( smith et al .
the physical conditions in this early high - density epoch are of great interest .
this material has since been expanding and thinning , as the observed extinction drops and the star brightens ( whitelock et al .
1983 ; davidson et al .
1999 ; smith et al .
2000 ) .
due to the high mass of the homunculus and its relatively empty surroundings , the shell will continue to expand quasi - ballistically .
thus , the hydrogen density will drop as @xmath53 , and because of ballistic motion , roughly as @xmath54 as well . in another couple
hundred years , the density in the nebula will drop below the threshold at which h@xmath1 can survive ( this may happen even sooner , since @xmath0 car resides in a giant h ii region with a strong ambient uv field ) .
eventually , the homunculus will become an atomic shell resembling the massive shells seen around other lbvs and lbv candidates , like the more evolved nebulae around the pistol star ( figer et al .
1999 ) , ag car ( voors et al .
2000 ) , and p cygni ( smith & hartigan 2006 ) . at these later stages ,
the homunculus may even overtake and mix with more distant outer ejecta ( walborn 1976 ) , appearing as a single ring - like lbv nebula , thereby erasing the details of its eruptive history .
we have modeled the basic double - shell structure in the homunculus , as traced most vividly by near - ir emisison from [ fe ii ] and h@xmath1 ( paper i ) .
our aim was to constrain the density which permits the survival of h@xmath55 , and thus , to provide an independent constraint on the mass of the homunculus and the physical conditions in the nebula .
the main observational constraints on our cloudy models were the geometric thickness of each zone , the electron density in the inner [ fe ii ] zone , and the survival of both h@xmath1 and fe@xmath7 in the thin outer zone .
our primary conclusions are as follows : \3 .
the relative mass of gas in the two zones closely matches that derived for warm and cool dust components in the same two zones ( smith et al .
this suggests that previous assumptions of a normal gas : dust mass ratio of 100 are not wildly in error .
we predict a sharp drop in the dust temperature between the inner and outer zones of the double shell , as observed ( smith et al .
the temperature in the outer zone approache the equilibrium blackbody temperature independent of grain size , due to shielding of uv radiation .
this relaxes constraints on the unusually large grains inferred from observed dust temperatures .
even though dust formation was efficient in the ejecta of @xmath0 car , we find that the gas phase fe abundance is still roughly solar .
one normally expects fe to depleted by two orders of magnitude in dusty environments .
this has occurred despite the severe depletion of c and o in the ejecta .
n.s . was supported by nasa through grant hf-01166.01a from the space telescope science institute , which is operated by the association of universities for research in astronomy , inc .
, under nasa contract nas5 - 26555 .
research into the physical processes in the ism by g.j.f . is supported by nsf ( ast0307720 ) and nasa ( nag5 - 12020 ) .
log r@xmath56 & cm & 17.255 & 17.398 & 17.398 & 17.398 & 17.398 & 17.398 + log r@xmath57 & cm & 17.398 & 17.415 & 17.415 & 17.415 & 17.415 & 17.415 + log @xmath58r & cm & 16.845 & 16.0 & 16.0 & 16.0 & 16.0 & 16.0 + log n@xmath27 & @xmath5 & 5.5 & 7.0 & 6.7 & 6.5 & 6.3 & 6.0 + log n@xmath59 & @xmath15 & 22.35 & 23.0 & 22.7 & 22.5 & 22.3 & 22.0 + m@xmath60 & m@xmath8 & 1 & 33 & 16 & 11 & 7.5 & 3.7 + filling factor & & 0.5 & 0.9 & 0.9 & 0.9 & 0.9 & 0.9 + log n@xmath26 & @xmath5 & 3.7 & 4.5 & 4.35 & 4.26 & 4.2 & 4.0 + t@xmath61 & k & 170 & 118 & 142 & 169 & 190 & 191 + fe@xmath6/fe & & 1.0 & 2(-4 ) & 0.97 & 1.0 & 1.0 & 1.0 + n(h@xmath6)/n@xmath27 & & 0.016 & 2(-12 ) & 2(-3 ) & 3(-3 ) & 3(-3 ) & 1(-4 ) + max 2n(h@xmath1)/n@xmath27 & & 5(-10 ) & 1.0 & 1.0 & 0.99 & 0.42 & 2(-4 ) + d 2n(h@xmath1)/n@xmath27=0.5 & ... & ... & 0.15 & 0.36 & 0.61 & ... & ... + d 2n(h@xmath1)/n@xmath27=0.99 & ... & ... & 0.41 & 0.88 & ... & ... & ... + @xmath62 & mag & 1.1 & 8.9 & 4.5 & 2.8 & 1.8 & 0.9 + log r@xmath56 & cm & 16.0 & 16.498 + log r@xmath57 & cm & 16.498 & 16.618 + log @xmath58r & cm & 16.332 & 16.0 + log n@xmath27 & @xmath5 & 6.3 & 7.0 + log n@xmath59 & @xmath15 & 22.63 & 23.0 + filling factor & & 0.5 & 0.9 + | we present models that reproduce the observed double - shell structure of the homunculus nebula around @xmath0 carinae , including the stratification of infrared h@xmath1 and [ fe ii ] emission seen in data obtained with the phoenix spectrograph on gemini south , as well as the corresponding stratified grain temperature seen in thermal - infrared data .
tuning the model to match the observed shell thickness allows us to determine the threshold density which permits survival of h@xmath1 .
an average density of @xmath2(0.51)@xmath310@xmath4 @xmath5 in the outer zone is required to allow h@xmath1 to exist at all latitudes in the nebula , and for fe@xmath6 to recombine to fe@xmath7 .
this gives independent confirmation of the very large mass of the homunculus , indicating a total of roughly 1535 m@xmath8 ( although we note reasons why the lower end of this range is favored ) . at the interface between the atomic and molecular zones , we predict a sharp drop in the dust temperature , in agreement with the bimodal dust color temperatures observed in the two zones . in the outer molecular shell
, the dust temperature drops to nearly the blackbody temperature , and becomes independent of grain size because of self - shielding at shorter uv wavelengths and increased heating at longer wavelengths .
this relaxes constraints on large grain sizes suggested by near - blackbody color temperatures .
finally , from the strength of infrared [ fe ii ] emission in the inner shell we find that the gas - phase fe abundance is roughly solar .
this is astonishing in such a dusty object , where one normally expects gaseous iron to be depleted by two orders of magnitude . |
paediatric emergency departments ( eds ) frequently become congested with non - urgent patients , resulting in patients with high acuity conditions ( such as altered consciousness , respiratory distress or haemodynamic compromise ) experiencing delays in receiving appropriate management .
the goal of paediatric ed triage is to prioritise patients rapidly and accurately based on acuity so that any critical medical needs can be met in a timely manner .
effective triage ensures that all ed patients are managed safely and assessed accurately according to their presenting condition . in taiwan
the department of health and national health insurance ( nhi ) first mandated the use of the taiwan paediatric triage system ( ped - tts ) in 1998 .
the ped - tts is a four - level triage system that classifies patients according to their vital signs and chief complaints / conditions .
the four - level ped - tts does not include trauma complaints or other common presentations such as ophthalmic , otorhinolaryngological or dental complaints , nor does it include a pain scale .
no validity studies were undertaken to evaluate the efficacy of ped - tts . with the growing demand for the use of paediatric eds ,
an accurate paediatric triage scale is needed to support the provision of quality care being pursued by the specialty of paediatric emergency medicine .
studies have also raised issues concerning the validity and reliability of paediatric triage in general.16 this may be related to inadequate triage training or insufficient standardisation of triage processes.7 two review articles have suggested that the use of a valid and reliable five - level triage system can improve ed operations.8
9 furthermore , less structured triage systems are considered inadequate because they do not provide sufficient discrimination to stratify patients appropriately by acuity in high volume and overcrowded eds.8 to address this , a new five - level paediatric triage and acuity system ( ped - ttas ) was developed in parallel with the establishment of the five - level adult ttas system by the ttas national working group ( nwg ) in taiwan.10
11 these were adapted from the adult and paediatric canadian triage and acuity scales.12
13 the new ped - ttas criteria and chief complaint list was developed by an 11-member emergency medicine expert panel ( seven members from the taiwan society of emergency medicine and four from the taiwan association of critical care nurses ) that formed the ttas nwg , using the paediatric canadian emergency triage and acuity scale ( paed - ctas ) and a literature review .
guidelines were adapted and modified by consensus whenever required to be pertinent to ed conditions in taiwan .
the content validity index for approved ped - ttas changes was between 0.8 and 1.0 .
the ped - ttas retains most of the features of the paed - ctas but includes some major modifications .
the ped - ttas has shorter reassessment time intervals for acuity levels 1 , 2 , 3 , 4 and 5 ( 0 , 10 , 30 , 60 and 120 min , respectively ) and classifies chief complaints into two categories ( non - trauma and trauma ) .
the non - trauma category is similar to the paed - ctas and includes12 categories with 74 chief complaints .
the chief complaints in the trauma category are grouped by anatomical region and include15 categories with 47 chief complaints .
patients meeting explicit threshold levels for haemodynamic instability ( appendix a ) are considered as acuity level 1 in the ped - ttas .
pain scale revisions include the deletion of chronic pain to accommodate cultural expectations in taiwan .
an electronic clinical decision ped - ttas support tool ( eped - ttas ) was introduced during implementation to assist triage nurses to accurately apply the paediatric triage in taiwan .
the evaluation of the two triage systems is important as crowding in the ed continues to impose a heavy burden on emergency care providers in taiwan .
comparison of the characteristics of the four - level paediatric taiwan triage system and the five - level paediatric triage and acuity system the purpose of this study was to examine the effectiveness of the five - level ped - ttas by comparing its reliability in patient prioritisation and resource utilisation with the previous four - level ped - tts in non - trauma paediatric ed patients .
this is a retrospective study using an administrative database from the hospital information system in the largest university - affiliated medical centre in taiwan .
the ped - tts was applied to ed patients from 1998 until 2009 ( the transition year ) .
the 2009 data were not used due to contamination related to changeover preparation and triage nurse training prior to implementing the new triage system . to account for this , the comparison of the two triage systems was made between the 2008 and 2010 data .
only data from non - trauma paediatric patients ( aged < 18 years ) were used because the four - level triage system did not include trauma complaints or discriminator criteria for trauma patient triage level assignment .
patient demographics , chief complaints , clinical outcomes and medical resource utilisation were extracted from the ed for validity analyses .
the clinical outcomes included : discharged from ed , admission to a general ward , admission to paediatric intensive care unit and death .
medical resource utilisation was defined as medical costs incurred in the ed including nurse and physician fees , cost of medications and diagnostics , and medical materials .
we used a computerised version of the ped - ttas ( eped - ttas ) , which was designed to assist triage nurses in decision - making at the point of care .
the eped - ttas application was developed in strict compliance with the ped - ttas standards and provided the nurse with rapid access to the standardised complaints list .
content validity of the ped - ttas and eped - ttas was assessed and was shown to be comparable .
after entry of the vital signs , the system automatically prompted the nurse to assign the appropriate triage level if the vital signs were abnormal or provided any other complaint - specific modifiers for patients with normal vital signs .
data are summarised using descriptive statistics where numerical variables are presented as medians and iqr and categorical variables are expressed as frequency and percentage
multiple regression models adjusting for age , gender and chief complaint were used to compare differences and trends regarding hospitalisation ( multiple logistic regression ) and ed medical costs ( multiple linear regression ) among levels of triage and acuity .
all data were analysed using sas v.9.12 ( sas , cary , north carolina , usa )
this is a retrospective study using an administrative database from the hospital information system in the largest university - affiliated medical centre in taiwan .
the ped - tts was applied to ed patients from 1998 until 2009 ( the transition year ) .
the 2009 data were not used due to contamination related to changeover preparation and triage nurse training prior to implementing the new triage system . to account for this , the comparison of the two triage systems was made between the 2008 and 2010 data .
only data from non - trauma paediatric patients ( aged < 18 years ) were used because the four - level triage system did not include trauma complaints or discriminator criteria for trauma patient triage level assignment .
patient demographics , chief complaints , clinical outcomes and medical resource utilisation were extracted from the ed for validity analyses .
the clinical outcomes included : discharged from ed , admission to a general ward , admission to paediatric intensive care unit and death .
medical resource utilisation was defined as medical costs incurred in the ed including nurse and physician fees , cost of medications and diagnostics , and medical materials .
we used a computerised version of the ped - ttas ( eped - ttas ) , which was designed to assist triage nurses in decision - making at the point of care .
the eped - ttas application was developed in strict compliance with the ped - ttas standards and provided the nurse with rapid access to the standardised complaints list .
content validity of the ped - ttas and eped - ttas was assessed and was shown to be comparable .
after entry of the vital signs , the system automatically prompted the nurse to assign the appropriate triage level if the vital signs were abnormal or provided any other complaint - specific modifiers for patients with normal vital signs .
data are summarised using descriptive statistics where numerical variables are presented as medians and iqr and categorical variables are expressed as frequency and percentage .
multiple regression models adjusting for age , gender and chief complaint were used to compare differences and trends regarding hospitalisation ( multiple logistic regression ) and ed medical costs ( multiple linear regression ) among levels of triage and acuity .
all data were analysed using sas v.9.12 ( sas , cary , north carolina , usa ) .
a total of 85 536 non - trauma paediatric emergency visits were identified during the study period ; 662 cases ( 0.77% ) were excluded due to incomplete information ( 351 from 2008 and 311 from 2010 ) , leaving a total of 84 874 patient records for inclusion in the analysis . of these ,
42 346 patients treated in 2008 were triaged using the four - level ped - tts and 42 528 patients presenting in 2010 were triaged using the five - level ped - ttas .
there were no age or gender differences between the 2008 and 2010 paediatric presentations to the ed .
presentation volumes were the same by shift across both study periods and the overall admission rates were almost identical ( 22.91% in 2008 and 22.06% in 2010 ) and the median ed length of stay was 84 min ( iqr 38192 ) and 85 min ( iqr 38178 ) , respectively .
the median ed cost was found to have increased from 1552 nt dollars ( iqr 11712945 ) to 1627 nt dollars ( iqr 12103031 ) over the two study periods ( p<0.001 ) .
the distribution of the top 15 chief complaints was highly consistent across the study periods ( table 2 ) .
comparisons of patient demographics , triage acuity and ed process data between the two study groups * patients treated in 2008 .
the top 15 chief complaints were identified and arranged in descending order of frequency from the 2010 patient presentations and the frequency was then compared with the 2008 presentations .
ed , emergency department ; los , length of stay ; picu , paediatric intensive care unit ; urti , upper respiratory tract infection .
there were 28.14% and 20.91% triaged as levels 1 and 2 , respectively , using the four - level ped - tts compared with 13.94% and 9.40% using the five - level ped - ttas , with nearly half of the patients ( 49.71% ) assigned acuity level 3 . using the four - level ped - tts ,
admission rates were 26.09% for level 1 , 28.77% for level 2 , 20.09% for level 3 and 14.63% for level 4 . using the five - level ped - ttas , admission rates were 27.83% , 36.39% , 21.86% , 15.56% and 8.94% , respectively , for triage levels 1 , 2 , 3 , 4 and 5 .
the linear trend between decreasing acuity ( from levels 1 to 4 or levels 1 to 5 ) and admission rate was calculated as 0.85 ( 95% ci 0.83 to 0.87 ) and 0.78 ( 95% ci 0.77 to 0.80 ) for the four - level ped - tts and five - level ped - ttas , respectively .
a statistically significant difference was observed , showing a higher strength of association between a lower admission rate and lower acuity using the five - level ped - ttas after adjusting for age , gender and chief complaint using multiple logistic regression models ( table 3 ) .
comparison of effectiveness between the two triage systems * dependent variable : hospitalization ( y / n ) ; performed with multiple logistic regression analysis adjusted by age , sex and chief complaints .
dependent variable : ln(ed expenses ) ; performed with multiple linear regression analysis adjusted by age , sex and chief complaints .
ed , emergency department ; ped - tts , paediatric taiwan triage system ; ped - ttas , paediatric triage and acuity system . a similar linear trend for decreasing medical costs with decreasing triage acuity
the linear trend was calculated as 0.15 ( 95% ci 0.15 to 0.14 ) for the four - level ped - tts and 0.17 ( 95% ci 0.18 to 0.17 ) for the five - level ped - ttas .
a statistically significant difference was observed based on the decreasing ed medical costs using both triage systems , but a higher strength of association was found with the five - level ped - ttas after adjusting for age , gender and chief complaint using multiple linear regression models ( table 3 ) .
a total of 85 536 non - trauma paediatric emergency visits were identified during the study period ; 662 cases ( 0.77% ) were excluded due to incomplete information ( 351 from 2008 and 311 from 2010 ) , leaving a total of 84 874 patient records for inclusion in the analysis . of these ,
42 346 patients treated in 2008 were triaged using the four - level ped - tts and 42 528 patients presenting in 2010 were triaged using the five - level ped - ttas .
there were no age or gender differences between the 2008 and 2010 paediatric presentations to the ed .
presentation volumes were the same by shift across both study periods and the overall admission rates were almost identical ( 22.91% in 2008 and 22.06% in 2010 ) and the median ed length of stay was 84 min ( iqr 38192 ) and 85 min ( iqr 38178 ) , respectively .
the median ed cost was found to have increased from 1552 nt dollars ( iqr 11712945 ) to 1627 nt dollars ( iqr 12103031 ) over the two study periods ( p<0.001 ) .
the distribution of the top 15 chief complaints was highly consistent across the study periods ( table 2 ) .
comparisons of patient demographics , triage acuity and ed process data between the two study groups * patients treated in 2008 .
the top 15 chief complaints were identified and arranged in descending order of frequency from the 2010 patient presentations and the frequency was then compared with the 2008 presentations .
ed , emergency department ; los , length of stay ; picu , paediatric intensive care unit ; urti , upper respiratory tract infection .
the distribution by acuity level for each triage system is shown in table 2 . there were 28.14% and 20.91% triaged as levels 1 and 2 , respectively , using the four - level ped - tts compared with 13.94% and 9.40% using the five - level ped - ttas , with nearly half of the patients ( 49.71% ) assigned acuity level 3 . using the four - level ped - tts , admission rates were 26.09% for level 1 , 28.77% for level 2 , 20.09% for level 3 and 14.63% for level 4 . using the five - level ped - ttas , admission rates were 27.83% , 36.39% , 21.86% , 15.56% and 8.94% , respectively , for triage levels 1 , 2 , 3 , 4 and 5 .
the linear trend between decreasing acuity ( from levels 1 to 4 or levels 1 to 5 ) and admission rate was calculated as 0.85 ( 95% ci 0.83 to 0.87 ) and 0.78 ( 95% ci 0.77 to 0.80 ) for the four - level ped - tts and five - level ped - ttas , respectively .
a statistically significant difference was observed , showing a higher strength of association between a lower admission rate and lower acuity using the five - level ped - ttas after adjusting for age , gender and chief complaint using multiple logistic regression models ( table 3 ) .
comparison of effectiveness between the two triage systems * dependent variable : hospitalization ( y / n ) ; performed with multiple logistic regression analysis adjusted by age , sex and chief complaints .
dependent variable : ln(ed expenses ) ; performed with multiple linear regression analysis adjusted by age , sex and chief complaints .
ed , emergency department ; ped - tts , paediatric taiwan triage system ; ped - ttas , paediatric triage and acuity system . a similar linear trend for decreasing medical costs with decreasing triage acuity
the linear trend was calculated as 0.15 ( 95% ci 0.15 to 0.14 ) for the four - level ped - tts and 0.17 ( 95% ci 0.18 to 0.17 ) for the five - level ped - ttas .
a statistically significant difference was observed based on the decreasing ed medical costs using both triage systems , but a higher strength of association was found with the five - level ped - ttas after adjusting for age , gender and chief complaint using multiple linear regression models ( table 3 ) .
the distribution by acuity level for each triage system is shown in table 2 . there were 28.14% and 20.91% triaged as levels 1 and 2 , respectively , using the four - level ped - tts compared with 13.94% and 9.40% using the five - level ped - ttas , with nearly half of the patients ( 49.71% ) assigned acuity level 3 .
using the four - level ped - tts , admission rates were 26.09% for level 1 , 28.77% for level 2 , 20.09% for level 3 and 14.63% for level 4 . using the five - level ped - ttas , admission rates were 27.83% , 36.39% , 21.86% , 15.56% and 8.94% , respectively , for triage levels 1 , 2 , 3 , 4 and 5 .
the linear trend between decreasing acuity ( from levels 1 to 4 or levels 1 to 5 ) and admission rate was calculated as 0.85 ( 95% ci 0.83 to 0.87 ) and 0.78 ( 95% ci 0.77 to 0.80 ) for the four - level ped - tts and five - level ped - ttas , respectively .
a statistically significant difference was observed , showing a higher strength of association between a lower admission rate and lower acuity using the five - level ped - ttas after adjusting for age , gender and chief complaint using multiple logistic regression models ( table 3 ) .
comparison of effectiveness between the two triage systems * dependent variable : hospitalization ( y / n ) ; performed with multiple logistic regression analysis adjusted by age , sex and chief complaints .
dependent variable : ln(ed expenses ) ; performed with multiple linear regression analysis adjusted by age , sex and chief complaints .
ed , emergency department ; ped - tts , paediatric taiwan triage system ; ped - ttas , paediatric triage and acuity system .
a similar linear trend for decreasing medical costs with decreasing triage acuity was seen for both systems .
the linear trend was calculated as 0.15 ( 95% ci 0.15 to 0.14 ) for the four - level ped - tts and 0.17 ( 95% ci 0.18 to 0.17 ) for the five - level ped - ttas .
a statistically significant difference was observed based on the decreasing ed medical costs using both triage systems , but a higher strength of association was found with the five - level ped - ttas after adjusting for age , gender and chief complaint using multiple linear regression models ( table 3 ) .
the ctas was developed in the late 1990s by the canadian association of emergency physicians and national emergency nurses affiliation.14 in 2001 the paediatric ctas was first published15 and then revised in 2008,12 designed to support programming into a clinical information system , allowing triage to become more simplified and standardised for better reliability .
studies have shown paed - ctas to have moderate to good reliability and validity.9
1620 the ped - ttas was developed from the paed - ctas , and our study has shown that the five - level ped - ttas exhibits better discrimination than the four - level ped - tts . the triage criteria ( modifiers ) in the five - level ped - ttas are more consistent in physiological and risk identifying clinical descriptors than those found in the four - level ped - tts , which may explain why nearly half the children were classified as having life - threatening or emergency conditions ( levels 1 and 2 ) with the ped - tts compared with only 23.3% using the five - level ped - ttas .
the five - level ped - ttas was better able to discriminate between high , intermediate and low acuity patients and to identify patients who were more seriously ill and needing prompt treatment , thus improving patient safety .
being able to assign an accurate triage acuity score reliably enables the prediction of patient volumes stratified by presentation type and severity .
the five - level ped - ttas better supports the optimal use of patient placement and nurse and physician utilisation to deliver the most appropriate care to each patient group within the constraints of available resources .
the validation of a triage system requires that it is consistent with medical needs and also leads to a predictable outcome including morbidity , mortality , resource utilisation and cost.4
10
17
21
22 our study demonstrated that triaging patients with the five - level ped - ttas led to greater discrimination in terms of measured outcomes such as total ed expenses and admission rates than the four - level ped - tts . using multiple regression analysis , the five - level ped - ttas performed better than the previous four - level ped - tts ( table 3 ) .
similar differentiation between the two triage systems for adult patients in the ed was well demonstrated in our previous study.11 the admission rate in this study was 22.122.9% , which is higher than previously reported paediatric ed admission rates of 3.017.0%.2326 the higher admission rate in our study might be due to the implementation of nhi which covers the hospital cost.27
28 in previous studies examining the correlation between ctas acuity and admission rate , ma et al reported hospitalisation rates of 45% , 15% , 2.5% and 0% for ctas levels 12 , 3 , 4 and 5 , respectively,29 while two other studies reported rates of 63100% , 2437% , 1214% , 24% and 02% for levels 15 , respectively.19
21 comparing our study results with those of others,19 we note that the percentage of patients in ped - ttas level 1 was more closely associated with a relatively low admission rate , suggesting that our patients were over - triaged .
upon further analysis , we determined that the absolute vital sign values set for the ped - ttas level 1 modifiers were over - sensitive .
other studies have also reported that over - reliance on vital sign values identifies many patients who do not have serious conditions.30
31 during the development of ped - ttas , the ttas nwg decided to remove all the vital sign values used in the previous four - level system except for the level 1 vital sign values , not wanting to miss potential life - threatening conditions in patients who did not appear to be acutely ill .
this is at variance with the paed - ctas which provides nurses with tables of age - based vital signs and then uses the number of sds from normal to support ctas acuity selection.12 the ttas nwg mandated vital signs to be recorded on all paediatric patients during their emergency visit . for patients identified as acuity levels 1 or 2 based on the critical first appearance , vital signs are measured during treatment . for patients assessed as levels 35 ,
vital signs are required as part of the triage process to confirm their ped - ttas score in order to determine whether it is safe for them to wait for treatment .
vital sign criteria were established according to the following age groups : 03 months , > 3 months to 3 years and > 3 years .
a review of our study groups showed that 84% of the ped - ttas level 1 patients were aged 3 months to 6 years .
given the stressful and chaotic environment of the ed , we postulate that a number of patients initially identified as acuity levels 35 had abnormal vital signs due to environmental or personal stress and were therefore assigned a level 1 score , resulting in an over - triaged group of patients .
we did not review each patient 's individual vital sign data and subject them to analysis , but we propose to do this as part of a future study .
reference standard measure of triage scale validity so , like other authors , we relied on a series of surrogate markers.22
32 the relationship between patient acuity level and outcome depends on surrogate outcome markers and the impact of confounding factors such as patient type and complexity , patient volumes , rate and surges of patient presentation and efficiency of care provided.32 however , if triage acuity is consistently applied , site - based year on year comparisons are very helpful to look for changes of case mix changes , patient safety , system and efficiencies , resource utilisation and patient outcomes derived from acuity changes .
while ped - tts had been used since 2008 , there has been no standardised educational programme for nurses or an electronic decision support tool .
the implementation of the new triage system ped - ttas , supported by an electronic decision support tool , was successfully used in a series of educational training initiatives .
prior to the formal implementation of the new ped - ttas system , all triage nurses were required to attend a 2 h education programme including 20 written triage scenarios as part of the training .
furthermore , the hospital information systems , ed charts and ed patient tracking systems were updated to reflect the new triage scale .
the complaint - orientated triage structure adapted from ctas facilitated the development of a highly functional electronic clinical decision support system assisting both education and triage at the point of care .
previous research has shown that an electronic triage tool is easy to learn , even by users unfamiliar with computers , and is readily accepted by triage nurses.33 this study has a number of limitations .
( 1 ) it is a single - site retrospective study which may limit the generalisability .
( 2 ) although the intervention is unlikely to have an effect as this is a retrospective study using an administrative database , the fact that the comparisons involved a healthcare environment that may have experienced other changes during the 2-year period should be taken into consideration . ( 3 ) the study cohorts did not include trauma cases because trauma triage criteria were not well - defined in the previous four - level ped - tts , so the results of this study are only applicable to non - trauma paediatric ed patients .
the five - level ped - ttas has significantly better predictability than the previous four - level ped - tts with regard to utilisation of medical resources .
it is anticipated that an efficient emergency care system is required when medical resources are scarce under prospective payment systems such as the global budget system in taiwan . however , triage tools are expected to have high sensitivity in discriminating emergency conditions in terms of risk management in paediatric care .
the cautious use of vital signs in different paediatric age groups is a critical issue for future designs of paediatric triage systems .
revisions of paediatric triage systems should include specific chief complaints while considering factors leading to over - triage as well as appropriate use of vital signs or age factors .
( 1 ) it is a single - site retrospective study which may limit the generalisability .
( 2 ) although the intervention is unlikely to have an effect as this is a retrospective study using an administrative database , the fact that the comparisons involved a healthcare environment that may have experienced other changes during the 2-year period should be taken into consideration .
( 3 ) the study cohorts did not include trauma cases because trauma triage criteria were not well - defined in the previous four - level ped - tts , so the results of this study are only applicable to non - trauma paediatric ed patients .
the five - level ped - ttas has significantly better predictability than the previous four - level ped - tts with regard to utilisation of medical resources .
it is anticipated that an efficient emergency care system is required when medical resources are scarce under prospective payment systems such as the global budget system in taiwan . however , triage tools are expected to have high sensitivity in discriminating emergency conditions in terms of risk management in paediatric care .
the cautious use of vital signs in different paediatric age groups is a critical issue for future designs of paediatric triage systems .
revisions of paediatric triage systems should include specific chief complaints while considering factors leading to over - triage as well as appropriate use of vital signs or age factors .
| objectivesto examine the effectiveness of a five - level paediatric triage and acuity system ( ped - ttas ) by comparing the reliability of patient prioritisation and resource utilisation with the four - level paediatric taiwan triage system ( ped - tts ) among non - trauma paediatric patients in the emergency department ( ed).methodsthe study design used was a retrospective longitudinal analysis based on medical chart review and a computer database .
except for a shorter list of complaints and some abnormal vital sign criteria modifications , the structure and triage process for applying ped - ttas was similar to that of the paediatric canadian emergency triage and acuity scale .
non - trauma paediatric patients presenting to the ed were triaged by well - trained triage nurses using the four - level ped - tts in 2008 and five - level ped - ttas in 2010 .
hospitalisation rates and medical resource utilisation were analysed by acuity levels between the contrasting study groups.resultsthere was a significant difference in patient prioritisation between the four - level ped - tts and five - level ped - ttas .
improved differentiation was observed with the five - level ped - ttas in predicting hospitalisation rates and medical costs.conclusionsthe five - level ped - ttas is better able to discriminate paediatric patients by triage acuity in the ed and is also more precise in predicting resource utilisation . the introduction of a more accurate acuity and triage system for use in paediatric emergency care should provide greater patient safety and more timely utilisation of appropriate ed resources . |
the polycystic ovary syndrome ( pcos ) is a common endocrinopathy affecting at least 510% of women in childbearing years .
it is classically characterized by hyperandrogenism , chronic anovulation , and polycystic ovarian morphology in ultrasonography .
although the underlying pathophysiological mechanisms of pcos remain unclear , insulin resistance ( ir ) intrinsic to the syndrome appears to play a central role in its development .
presence of ir in pcos is partially explained by obesity , but it is also found in lean women with pcos . given the significant metabolic burden of ir seen in women with pcos , affected women may have an increased risk of type 2 diabetes mellitus , cardiovascular disease [ 4 , 5 ] , and also nonalcoholic fatty liver disease ( nafld ) [ 611 ] .
nafld is the most common form of liver disease , with a prevalence of 533% in the general population .
simple steatosis hepatis ( sh ) , the most common form of nafld , typically follows a benign clinical course .
however , the progressive form , nonalcoholic steatohepatitis ( nash ) , is a potentially serious condition resulting in progression to cirrhosis in 25% of these patients , including the long - term complications of portal hypertension , liver failure , and hepatocellular carcinoma [ 12 , 13 ] .
although still serving as the gold standard for differentiating between sh and nash , liver biopsy can result in various complications due to its invasive character .
hepatocyte apoptosis plays an important role in liver injury and disease progression in nash and various other liver diseases [ 1923 ] .
indeed , hepatocyte cell death by apoptosis is typically enhanced in nash but absent in sh .
in fact , feldstein and colleagues [ 25 , 26 ] have reported that cell death index can replace liver biopsy to diagnose nash in a cohort of patients with various types of liver disease .
induction of apoptosis by such events as accumulation of free fatty acids in the liver cells activates effector caspases that cleave a host of intracellular substrates including cytokeratin 18 ( ck18 ) , a member of the intermediate filament family of cytoskeletal proteins .
caspase-3-dependent cleavage of ck18 at asp396 exposes a neoepitope , m30 , which reflects hepatic apoptosis .
recently , it has been shown that the plasma - borne caspase - generated ck18 fragments independently predict nash in multivariate analysis [ 25 , 26 ] . although not assessed in routine clinical practice , the american college of gastroenterology and the american gastroenterological association regard ck18 as a promising biomarker for identifying steatohepatitis .
pcos is highly associated with nafld diagnosed by aspartate aminotransferase ( ast ) elevation and/or ultrasound [ 68 ] .
furthermore , in a small number of patients with pcos and persistently elevated liver enzymes , liver biopsy revealed nash with advanced fibrosis .
conversely , 10 of 14 ( 71% ) female patients in childbearing years with histologically diagnosed nafld also had revealed pcos , indicating a close relationship between these two entities .
using ck18 fragments as a surrogate parameter of apoptotic cell death , we could demonstrate a high risk for nash in pcos with up to a quarter of patients with pcos fulfilling the criteria for serologic nash previously .
as ir plays a key role in the pathophysiology of pcos , insulin sensitizing agents are widely studied and used in the treatment of pcos , with metformin ( mf ) as the most commonly used pharmacological agent .
mf acts as an insulin sensitizing agent resulting in a reduction of hepatic glucose secretion and increase of peripheral glucose utilization with positive effects on ir , body weight , and menstrual cycling in pcos . improving insulin sensitivity by mf may positively influence the development of nash , for example , by suppressing acetyl - coa carboxylase activity and accumulation of adenosine monophosphate in hepatocytes resulting in inhibition of mitochondrial fatty acid oxidation and blocking glucagon - dependent glucose output from hepatocytes [ 31 , 32 ] .
some studies report a beneficial effect of mf on liver function with improvement of liver enzymes or even improvement of tissue steatosis or inflammation in nafld and/or nash [ 3338 ] . though there is also conflicting data [ 3942 ] , two studies demonstrated improvement of liver enzymes in patients with pcos under mf treatment , indicating that mf positively influences liver function [ 43 , 44 ] .
pcos is a frequent endocrinopathy and includes a high percentage of young women , who are potentially at high risk for serious liver disease , and ir plays a key role in the pathophysiology of both entities , pcos and nafld .
we hypothesize that a six - month therapy with mf positively influences serologic defined nash by improving ir in patients with pcos .
consecutive patients with newly diagnosed , currently untreated pcos with and without ir ( n = 89 ) were retrospectively recruited at the outpatient clinic of the department of endocrinology and division of laboratory research , university of duisburg - essen , germany .
pcos was defined according to the rotterdam criteria ; therefore , diagnosis of pcos was established if two or more of the criteria , hyperandrogenism , chronic anovulation , or polycystic ovaries , were fulfilled and other pituitary , adrenal , or ovarian diseases could be excluded .
participants were carefully characterized with regard to medical history and clinical and sociodemographic variables using questionnaires , interview , and physical examination , as previously described in detail .
free androgen index ( fai ) was calculated as total testosterone ( nmol / liter ) 100/shbg ( nmol / liter ) .
ir was defined as elevation of homeostasis model assessment of ir ( homa - ir > 2.5 ) [ 4547 ] . homa
- ir > 2.5 was also suggested as cut - off to discriminate between patients with biopsy proven nafld or patients with nafld diagnosed by ultrasound and elevated liver enzymes with a specificity of 94% and a sensitivity of 74%
. metabolic syndrome ( mbs ) was defined according to ncep / atp guidelines when 3 of the 5 following criteria were fulfilled : ( 1 ) waist circumference > 88 cm , ( 2 ) triglycerides 150 mg / dl , ( 3 ) hdl - cholesterol < 50 mg / dl , ( 4 ) blood pressure 130/85 mmhg , and ( 5 ) fasting glucose 110 mg / dl . liver injury implicating fatty liver ( lifl ) has been defined as elevation of aspartate aminotransferase ( ast ) or alanine aminotransferase ( alt ) above the upper normal range ( ast or alt > 30
u / l ) in the absence of relevant alcohol consumption or known chronic liver disease .
bard - score ( bmi , ast / alt - ratio , diabetes mellitus score ) was calculated to evaluate risk for advanced fibrosis , .
as diabetes mellitus represented an exclusion criterion , possible reached maximum points in bard - score were 3 ( if bmi 28 kg / m : 1 point and if ast / alt - ratio 0.8 : 2 points ; presence of diabetes mellitus : 1 point and as no patient had diabetes : always 0 points ) .
m30 was used as serum surrogate parameter of nash and levels 395 u / liter were defined as serologic defined nash ( snash ) .
alcohol consumption greater than 20 g / d and other previously known or newly detected secondary reasons of liver diseases such as viral hepatitis , hemochromatosis , wilson 's disease , autoimmune diseases , and hepatotoxic drugs represented an exclusion criterion .
patients were evaluated at baseline and following treatment with mf in a weight - adapted dose for six months ( body weight
< 60 kg : 1000 mg , 60100 kg : 1700 mg , and > 100 kg or bmi 30 kg / m : 2000 mg daily ) .
they were divided into two groups according to presence or absence of ir defined by homa - ir > 2.5 .
fifty - three patients with ir ( pcos - ir ) were compared to a control group of 36 patients without ir ( pcos - c ) . according to therapy success defined by homa - ir normalization after metformin treatment
, the pcos - ir group was subdivided into a group with persistent ir ( pcos - pir ) and a group with dissolved ir ( pcos - exir ) ( see figure 1 ) .
secondary outcome parameters included testosterone levels , bmi , parameters of ir , lipid status , liver enzymes , and apoptotic marker m30 as well as prevalence of mbs .
automated chemiluminescence immunoassay systems were used for the determination of lh , fsh , tsh , testosterone , estradiol , cortisol , free t4 , prolactin , blood glucose , ast , alt ( advia centaur ; siemens , eschborn , germany ) , acth , dehydroepiandrosterone sulfate , androstenedione , shbg , insulin , and igf ( immulite 2000 , siemens ) .
measurement of blood glucose was performed by photometric determination ( advia 2400 , siemens ) .
intra- and interassay variation were less than 5% , respectively , and 8% for all measured variables .
17-hydroxyprogesterone was measured by the biosource 17-oh - ria - ct kit ( biosource international , camarillo , ca ) provided by ibl hamburg ( ibl , gesellschaft fr immunchemie und immunbiologie , hamburg , germany ) .
sera were collected upon admission and stored within 2 h at 20c until testing .
ck18 fragments were assessed by monoclonal antibody m30 using the m30-apoptosense elisa kit ( peviva , bromma , sweden ) as previously described .
patients who were insulin sensitive at baseline ( pcos - c ) and patients with ir at baseline were compared using independent samples t - tests or chi-tests.for all subsequent analyses , patients with ir were subdivided into patients with insulin resistance after treatment ( pcos - pir ) and initially insulin resistant patients whose ir dissolved after treatment ( pcos - exir ) . to evaluate treatment effects , repeated measures analyses of variance ( anova ) were computed with the main factors group ( pcos - c , pcos - pir , and pcos - exir ) and time ( baseline , after 6-month mf treatment ) . in case of significant anova treatment ( time ) or treatment group interaction effects ,
post hoc comparisons of means with bonferroni corrections were calculated using paired t - tests within pcos groups . for nonparametric parameters ( i.e. , bard - score ) ,
wilcoxon tests were computed.to additionally explore differences in treatment effects between pcos groups , delta scores ( i.e. , percent changes from baseline to six - month mf treatment ) were computed for dichotomous variables ( mbs , lifl , and snash prevalence ) , and patient groups were compared using chi-tests.to exclude that treatment effects ( or differences in treatment effects between pcos groups ) were attributable to body weight reduction , all anova analyses were repeated with delta body weight as covariate .
since body weight reduction did not affect any result , these data are not presented.all results are shown as mean standard deviation unless otherwise indicated .
patients who were insulin sensitive at baseline ( pcos - c ) and patients with ir at baseline were compared using independent samples t - tests or chi-tests .
for all subsequent analyses , patients with ir were subdivided into patients with insulin resistance after treatment ( pcos - pir ) and initially insulin resistant patients whose ir dissolved after treatment ( pcos - exir ) . to evaluate treatment effects , repeated measures analyses of variance ( anova )
were computed with the main factors group ( pcos - c , pcos - pir , and pcos - exir ) and time ( baseline , after 6-month mf treatment ) . in case of significant anova treatment ( time ) or treatment group interaction effects ,
post hoc comparisons of means with bonferroni corrections were calculated using paired t - tests within pcos groups . for nonparametric parameters ( i.e. , bard - score ) ,
wilcoxon tests were computed . to additionally explore differences in treatment effects between pcos groups , delta scores ( i.e.
, percent changes from baseline to six - month mf treatment ) were computed for dichotomous variables ( mbs , lifl , and snash prevalence ) , and patient groups were compared using chi-tests . to exclude that treatment effects ( or differences in treatment effects between pcos groups )
were attributable to body weight reduction , all anova analyses were repeated with delta body weight as covariate .
since body weight reduction did not affect any result , these data are not presented .
the majority of patients presented with ir at the beginning of mf therapy ( 53/89 , 59.6% ) .
testosterone concentration was similar in both groups , but fai levels were significantly higher in insulin resistant patients .
furthermore , patients with ir presented with an adverse metabolic profile with significantly higher bmi , body weight , and triglycerides and lower hdl and therefore fulfilled 12-fold more often the criteria for mbs .
liver enzymes , bard - score , and m30 as well as prevalence of lifl and snash were similar in both groups .
regarding the whole cohort , prevalence of ir significantly declined after six - month metformin therapy ( 59.6% versus 33.7% , p < 0.001 ) . in detail , normalization of ir was achieved in 47.2% ( 25/53 , pcos - exir ) of cases , while two of 36 patients developed ir during the treatment period ( 5.6% ) and 38.2% patients remained insulin sensitive ( 34/89 ) and 31.5% remained insulin resistant ( 28/89 , pcos - pir ) , respectively .
pcos - exir and pcos - pir showed significantly greater improvements in homa - ir ( f = 8.5 , p < 0.001 , interaction effect ) and fasting insulin ( f = 9.0 , p < 0.001 , interaction effect ) than the pcos - c group .
furthermore , pcos - exir patients showed an improvement of auci ( for post hoc comparisons , see table 2 ) . a significant loss in body weight ( 6 kg ) and bmi ( 2.2 kg / m ) was observed only in pcos - exir patients ( body weight : f = 6.3 , p <
0.01 ; bmi : f = 6.3 , p < 0.01 , interaction effects ; for post hoc comparisons , see table 2 ) . mf treatment led to a slight but significant increase in hdl - cholesterol ( f = 4.5 , p < 0.05 ) , while no significant changes in cholesterol , ldl - cholesterol and triglycerides could be demonstrated in all patients ( table 2 ) . both pcos - exir and pcos - pir groups showed significantly greater reductions in mbs prevalence ( delta mbs ) compared to pcos - c ( chi = 43.0 , p < 0.001 ; figure 2 ) . whereas pcos - c and pcos - exir groups showed improvement of liver enzymes ( i.e. , a significant reduction of alt ) , alt concentration increased in pcos - pir patients ( f = 7.6 , p < 0.001 , interaction effect ; table 2 ) . in comparison to pcos - pir patients , decreases in lifl prevalence were significantly greater in pcos - c and pcos - exir patients ( chi = 29.5 , p < 0.001 ; figure 2 ) .
ast / alt - ratio , bard - score , m30 levels , and snash prevalence did not change significantly under treatment .
patients with pir showed a nominal increase in levels of liver enzymes and lifl prevalence and in m30 levels and snash prevalence .
however , the magnitude of changes in these parameters ( i.e. , delta values ) did not differ significantly between pcos groups ( figure 2 ) . to exclude an effect of mf - induced body weight reduction on any other outcome parameter ( excluding bmi ) , anova was additionally performed with change of body weight as covariate .
in the presented study , we describe the effect of mf not only on liver enzymes but also on hepatic apoptotic markers as serologic parameter for nash in pcos .
this study demonstrates that mf has a positive effect on liver enzymes in patients with pcos , who were insulin sensitive , and in those reaching insulin sensitivity under mf .
however , even in the presence of treatment response for ir , this was not accompanied by improvement of apoptotic markers or snash prevalence . in contrast , patients with pcos who did not demonstrate improvement in insulin sensitivity with mf treatment demonstrated worsening of liver enzymes with a nominal increase in apoptotic cell death marker m30 .
a positive influence on liver enzymes by mf in pcos has been described by two study groups . in an italian study cohort ,
not only a high prevalence of nafld with 58% , but also a decrease in liver enzymes by mf in hyperinsulinemic , overweight patients with pcos could be demonstrated .
found a decrease of alt levels in obese women with pcos treated with mf which was associated with body weight improvement .
this is in line with some small studies in patients with biopsy proven nafld and/or nash , which also showed improvement of liver function under mf therapy [ 3337 ] .
our study shows that , in insulin resistant patients , the positive effect of mf on liver function seems to be limited to those who are able to achieve insulin sensitivity .
furthermore , improvement of lifl by mf can also be demonstrated in patients who are insulin sensitive . concerning the influence of mf on nash , studies including patients with biopsy proven nafld and/or nash show divergent results in regard to the effect of mf on histological indices .
an italian study examining the effect of mf versus vitamin e and versus diet in nondiabetic nafld showed a decrease of liver fat , necroinflammation , and fibrosis in some patients who were treated with mf and underwent liver rebiopsy .
however , in this study , no biopsy was undertaken in patients of the other therapy regimes due to concerns of the local ethical committee . in a turkish study ,
patients with biopsy proven nash were treated with therapeutic lifestyle changes alone or in combination with insulin sensitizers ( mf or rosiglitazone ) .
treatment with insulin sensitizers led to significant improvement of nash activity score , while grade of fibrosis did not change . in a small , long - term mf treatment study of nafld patients over one year , nair et al . observed only a transient improvement of liver enzymes and a modest beneficial effect with improvement of histologically assessed steatosis in 33% and of inflammation and fibrosis in 20% and 10% of cases , respectively .
could not demonstrate a significant effect on histopathological findings of liver rebiopsy in mf / diet - treated nash - patients , although patients in the mf regime showed significantly greater weight loss and improvement of ir and liver function than the patients undergoing diet alone .
two placebo controlled intervention studies in nafld or nash - patients , respectively , one with higher and one with lower mf than usually used ( 3000 mg and 500 mg / d ) , did not show a positive effect of mf on liver histology [ 41 , 42 ] .
unchanging levels of m30 and unchanged prevalence of snash in our study possibly support the missing effect of mf seen in these studies with histological nafld assessment , though , considering that patients with persistent ir exhibited an increase of liver enzymes and apoptotic markers , the unchanged apoptosis marker in association with lower liver enzymes could also be interpreted as stabilization of hepatic damage .
in contrast , patients who fail to normalize ir might be at greater risk for progression of nafld as suggested by increasing serum apoptosis markers and liver enzymes .
however , the mentioned changes in m30 levels in the pcos - pir group did not reach statistical significance and patient number with snash in our groups is low .
another explanation might be a longer duration needed for nafld or nash to get cleared .
taken together , ir alone might not be accountable for development of nafld and the impact of mf on nafld seems limited or might require a longer observation time to be fully understood .
another finding of this study was that patients with pcos who failed to achieve normalization of homa - ir were significantly more obese than the other two groups .
loomba and colleagues reported in their subanalysis of histological responders versus nonresponders that histological response under mf treatment in nash patients was associated with loss of body weight of at least 5 kg and that none of the patients with a bmi > 40 kg / m at baseline reached histological response to mf therapy .
patients with pcos who are severely obese and/or insulin resistant without response to mf should possibly be monitored more closely as they are potentially at higher risk for progression of nafld from simple steatosis towards nash .
the examined study population is quite small and we performed this analysis as an observational study .
patients with pcos without ir represented a control population assuming that in these patients mf will not influence hepatic markers . though no randomized trial with a placebo group was performed , we can not exclude that observed results are a time effect . despite these limitations , this study shows preliminary data about the effect of mf on hepatic injury and apoptosis in a cohort of patients with pcos . in summary , we found a significant improvement of liver enzymes in subgroups of patients with pcos without change in hepatic apoptotic markers . whether the latter means
a missing effect of mf on nafld or can be interpreted as prevention of progression is unclear .
further studies are needed to elucidate nafld in the context of pcos and its potential therapeutic options .
studies evaluating the therapeutic effect of insulin sensitizing agents like mf on nafld should possibly take the patients ' response regarding insulin resistance into account . | objective . polycystic ovary syndrome ( pcos ) is associated with obesity and insulin resistance ( ir ) , key features of nonalcoholic steatohepatitis ( nash ) .
cytokeratin 18 fragments ( m30 ) have been established as a serum marker for nash .
the insulin sensitizer metformin improves hepatic ir .
this study evaluates the influence of mf on serologic nash ( snash ) in patients with pcos .
patients and methods . in 89 patients , metabolic parameters , liver injury indicating fatty liver ( lifl ) , and m30 were assessed at baseline and after metformin treatment .
patients with initial ir were subdivided into dissolved ( pcos - exir ) and persistent ir ( pcos - pir ) after treatment and compared to an initially insulin sensitive pcos group ( pcos - c ) .
results .
improvement of lifl prevalence could be seen in pcos - c and pcos - exir compared to pcos - pir ( 19.4 , resp .
, 12.0% versus 7.2% , chi2 = 29.5 , p < 0.001 ) without change in snash prevalence . in pcos - pir ,
alt levels increased significantly accompanied by a nominal , nonsignificant m30 increase .
conclusions .
metformin improves lifl in subgroups of patients with pcos without influencing snash .
this could either indicate a missing effect of metformin on nafld or slowed disease progression .
further studies are needed to elucidate nafld in the context of pcos and potential therapeutic options . |
SECTION 1. SHORT TITLE.
This Act may be cited as the ``Great Cats and Rare Canids Act of
2009''.
SEC. 2. PURPOSES.
The purposes of this Act are to provide financial resources and to
foster international cooperation--
(1) to restore and perpetuate healthy populations of rare
felids and rare canids in the wild; and
(2) to assist in the conservation of rare felid and rare
canid populations worldwide.
SEC. 3. DEFINITIONS.
In this Act:
(1) CITES.--The term ``CITES'' means the Convention on
International Trade in Endangered Species of Wild Fauna and
Flora, done at Washington March 3, 1973 (27 UST 1087; TIAS
8249), including appendices to that convention.
(2) Conservation.--
(A) In general.--The term ``conservation'' means
the methods and procedures necessary to bring a species
of rare felid or rare canid to the point at which there
are sufficient populations in the wild to ensure the
long-term viability of the species.
(B) Inclusions.--The term ``conservation'' includes
all activities associated with protection and
management of a rare felid or rare canid population,
including--
(i) maintenance, management, protection,
and restoration of rare felid or rare canid
habitat;
(ii) research and monitoring;
(iii) law enforcement;
(iv) community outreach and education;
(v) conflict resolution initiatives; and
(vi) strengthening the capacity of local
communities, governmental agencies,
nongovernmental organizations, and other
institutions to implement conservation
programs.
(3) Fund.--The term ``Fund'' means the Great Cats and Rare
Canids Conservation Fund established by section 4(a).
(4) IUCN red list.--The term ``IUCN Red List'' means the
Red List of Threatened Species Maintained by the World
Conservation Union.
(5) Rare canid.--
(A) In general.--The term ``rare canid'' means any
of the canid species dhole (Cuon alpinus), gray wolf
(Canis lupus), Ethiopian wolf (Canis simensis), bush
dog (Speothos venaticus), African wild dog (Lycaon
pictus), maned wolf (Chrysocyon brachyurus), and
Darwin's fox (Pseudalopex fulvipes) (including any
subspecies or population of such a species).
(B) Exclusions.--The term ``rare canid'' does not
include any subspecies or population that is native to
the area comprised of the United States and Canada or
the European Union.
(6) Rare felid.--
(A) In general.--The term ``rare felid'' means any
of the felid species lion (Panthera leo), leopard
(Panthera pardus), jaguar (Panthera onca), snow leopard
(Uncia uncia), clouded leopard (Neofelis nebulosa),
cheetah (Acinonyx jubatus), Iberian lynx (Lynx
pardina), and Borneo bay cat (Catopuma badia)
(including any subspecies or population of such a
species).
(B) Exclusions.--The term ``rare felid'' does not
include--
(i) any species, subspecies, or population
that is native to the United States; or
(ii) any tiger (Panthera tigris).
(7) Secretary.--The term ``Secretary'' means the Secretary
of the Interior.
SEC. 4. GREAT CATS AND RARE CANIDS CONSERVATION FUND.
(a) Establishment.--There is established in the multinational
species conservation fund established under the heading ``multinational
species conservation fund'' of title I of the Department of the
Interior and Related Agencies Appropriations Act, 1999 (16 U.S.C.
4246), a separate account to be known as the ``Great Cats and Rare
Canids Conservation Fund'', consisting of--
(1) amounts transferred to the Secretary of the Treasury
for deposit in the account under subsection (c); and
(2) amounts appropriated to the account under section 7.
(b) Expenditures From Fund.--
(1) In general.--Subject to paragraph (2), on request by
the Secretary, the Secretary of the Treasury shall transfer
from the Fund to the Secretary, without further appropriation,
such amounts as the Secretary determines to be necessary to
provide assistance under section 5.
(2) Administrative expenses.--Of the amounts in the Fund
available for each fiscal year, the Secretary may use to pay
the administrative expenses of carrying out this Act not more
than the greater of--
(A) 3 percent; and
(B) $100,000.
(c) Acceptance and Use of Donations.--
(1) In general.--The Secretary may--
(A) accept and use donations to provide assistance
under section 5; and
(B) publish on the Internet website and in
publications of the Department of the Interior a notice
that the Secretary is authorized to accept and use such
donations.
(2) Use.--Amounts received by the Secretary in the form of
donations shall be transferred to the Secretary of the Treasury
for deposit in the Fund.
SEC. 5. FINANCIAL ASSISTANCE.
(a) In General.--Subject to the availability of funds and in
consultation with other appropriate Federal officials, the Secretary
shall use amounts in the Fund to provide financial assistance for
projects for the conservation of rare felid and rare canids for which
project proposals are approved by the Secretary in accordance with this
section.
(b) Project Proposals.--
(1) Eligible applicants.--A proposal for a project for the
conservation of rare felid and canids may be submitted to the
Secretary by--
(A) any wildlife management authority of a country
that has within its boundaries any part of the range of
a rare felid or rare canid species, respectively; and
(B) any person or group with the demonstrated
expertise required for conservation in the wild of rare
felids or rare canids, respectively.
(2) Project proposals.--To be eligible for financial
assistance for a project under this Act, an applicant shall
submit to the Secretary a project proposal that includes--
(A) a concise statement of the purposes of the
project;
(B) the name of the individual responsible for
conducting the project;
(C) a description of the qualifications of the
individuals who will conduct the project;
(D) a concise description of--
(i) methods for project implementation and
outcome assessment;
(ii) staffing for the project;
(iii) the logistics of the project; and
(iv) community involvement in the project;
(E) an estimate of funds and time required to
complete the project;
(F) evidence of support for the project by
appropriate governmental entities of the countries in
which the project will be conducted, if the Secretary
determines that such support is required for the
success of the project;
(G) information regarding the source and amount of
matching funding available for the project; and
(H) any other information that the Secretary
considers to be necessary for evaluating the
eligibility of the project for funding under this Act.
(c) Project Review and Approval.--
(1) In general.--The Secretary shall--
(A) not later than 30 days after receiving a
project proposal, provide a copy of the proposal to the
appropriate Federal officials; and
(B) review each project proposal in a timely manner
to determine whether the proposal meets the criteria
specified in subsection (d).
(2) Consultation; approval or disapproval.--Not later than
180 days after receiving a project proposal, and subject to the
availability of funds, the Secretary, after consulting with
other appropriate Federal officials, shall--
(A) ensure the proposal contains assurances that
the project will be implemented in consultation with
relevant wildlife management authorities and other
appropriate government officials with jurisdiction over
the resources addressed by the project;
(B) approve or disapprove the proposal; and
(C) provide written notification of the approval or
disapproval to--
(i) the individual or entity that submitted
the proposal;
(ii) other appropriate Federal officials;
and
(iii) each country within the borders of
which the project will take place.
(d) Criteria for Approval.--The Secretary may approve a project
proposal under this section if the project will contribute to
conservation of rare felids or rare canids in the wild by assisting
efforts--
(1) to implement conservation programs;
(2) to address the conflicts between humans and rare felids
or rare canids, respectively, that arise from competition for
the same habitat or resources;
(3) to enhance compliance with CITES, the Endangered
Species Act of 1973 (16 U.S.C. 1531 et seq.), and other
applicable laws that--
(A) prohibit or regulate the taking or trade of
rare felids and rare canids; or
(B) regulate the use and management of rare felid
and rare canid habitat;
(4) to develop sound scientific information on, or methods
for monitoring--
(A) the condition and health of rare felid or rare
canid habitat;
(B) rare felid or rare canid population numbers and
trends; and
(C) the ecological characteristics and requirements
of populations of rare felids or rare canids for which
there are little or no data;
(5) to promote cooperative projects among government
entities, affected local communities, nongovernmental
organizations, and other persons in the private sector; or
(6) to ensure that funds will not be appropriated for the
purchase or lease of land to be used as suitable habitat for
felids or canids.
(e) Project Sustainability.--In approving project proposals under
this section, the Secretary shall give preference to conservation
projects that are designed to ensure effective, long-term conservation
of rare felids and rare canids and their habitats.
(f) Matching Funds.--In determining whether to approve project
proposals under this section, the Secretary shall give preference to
projects any portion of the costs of which will be provided with
matching funds.
(g) Project Reporting.--
(1) In general.--Each individual or entity that receives
assistance under this section for a project shall submit to the
Secretary periodic reports (at such intervals as the Secretary
considers necessary) that include all information that the
Secretary, after consultation with other appropriate government
officials, determines to be necessary to evaluate the progress
and success of the project for the purposes of ensuring
positive results, assessing problems, and fostering
improvements.
(2) Availability to public.--Reports under paragraph (1),
and any other documents relating to projects for which
financial assistance is provided under this Act, shall be made
available to the public.
(h) Limitations.--
(1) Use for captive breeding or display.--Amounts provided
as a grant under this Act--
(A) may not be used for captive breeding or display
of rare felids and rare canids, other than captive
breeding for release into the wild; and
(B) may be used for captive breeding of a species
for release into the wild only if no other conservation
method for the species is biologically feasible.
(2) Ineligible countries.--Amounts provided as a grant
under this Act may not be expended on any project in a country
the government of which has repeatedly provided support for
acts of international terrorism, as determined by the Secretary
of State pursuant to--
(A) section 6(j)(1)(A) of the Export Administration
Act of 1979 (50 U.S.C. App. 2405(j)(1)(A)) (or any
successor to that Act);
(B) section 40(d) of the Arms Export Control Act
(22 U.S.C. 2780(d)); or
(C) section 620A(a) of the Foreign Assistance Act
of 1961 (22 U.S.C. 2371(a)).
(i) Advisory Group.--
(1) In general.--To assist in carrying out this Act, the
Secretary may establish an advisory group, consisting of
individuals representing public and private organizations
actively involved in the conservation of felids and canids.
(2) Public participation.--
(A) Meetings.--The advisory group shall--
(i) ensure that each meeting of the
advisory group is open to the public; and
(ii) provide, at each meeting, an
opportunity for interested individuals to
present oral or written statements concerning
items on the agenda.
(B) Notice.--The Secretary shall provide to the
public timely notice of each meeting of the advisory
group, including the meeting agenda.
(C) Minutes.--The minutes of each meeting of the
advisory group shall be--
(i) kept by the Secretary; and
(ii) made available to the public.
(3) Nonapplicability of federal advisory committee act.--
The Federal Advisory Committee Act (5 U.S.C. App.) shall not
apply to the advisory group.
SEC. 6. STUDY OF CONSERVATION STATUS OF FELID AND CANID SPECIES.
(a) In General.--Not later than 90 days after the date of enactment
of this Act, the Secretary shall initiate a study of felid and canid
species listed under the IUCN Red List that are not rare canids or rare
felids, respectively, to determine--
(1) the conservation status of each such species in the
wild, including identification of any such species that are
critically endangered or endangered; and
(2) whether any such species that should be made eligible
for assistance under this Act.
(b) Report.--Not later than 2 years after date of enactment of this
Act, the Secretary shall submit to Congress a report describing the
determinations made in the study, including recommendations of
additional felid species and canid species that should be made eligible
for assistance under this Act.
SEC. 7. AUTHORIZATION OF APPROPRIATIONS.
There are authorized to be appropriated--
(1) to the Fund, $5,000,000 for each of fiscal years 2010
through 2014 to carry out this Act, other than section 6; and
(2) such sums as are necessary to carry out section 6. | Great Cats and Rare Canids Act of 2009 - (Sec. 4) Establishes the Great Cats and Rare Canids Conservation Fund as a separate account of the Multinational Species Conservation Fund.
(Sec. 5) Directs the Secretary of the Interior to use Fund amounts to provide assistance for projects for the conservation of rare felids and rare canids. Sets forth provisions governing project proposals, review, and approval.
Defines "rare canid" to mean any of the canid species dhole, gray wolf, Ethiopian wolf, bush dog, African wild dog, maned wolf, and Darwin's fox, including any subspecies of such a species and excluding any subspecies or population that is native to the area comprised of the United States and Canada or the European Union.
Defines "rare felid" to mean any of the felid species lion, leopard, jaguar, snow leopard, clouded leopard, cheetah, Iberian lynx, and Borneo bay cat, including any subspecies of such a species and excluding any species, subspecies, or population that is native to the United States and any tiger.
Prohibits: (1) the use of assistance under this Act for captive breeding or display purposes, other than captive breeding for release into the wild where no other conservation method for the species is biologically feasible; or (2) the expenditure of such assistance for any project in a country the government of which has repeatedly provided support for acts of international terrorism.
Authorizes the Secretary to establish an advisory group to assist in carrying out this Act, which shall provide for public participation.
(Sec. 6) Requires the Secretary to initiate and report to Congress on a study of felid and canid species listed under the Red List of Threatened Species Maintained by the World Conservation Union that are not rare canids or rare felids (as defined in this Act), to determine: (1) the conservation status of each such species in the wild, including identification of those that are critically endangered or endangered; and (2) whether any such species should be made eligible for project assistance.
(Sec. 7) Authorizes appropriations. |
stroke is one of the leading causes of death and physical disability among adults , with one - quarter to half of stroke survivors being left with complete or partial dependence on others .
stem cell therapy is an emerging paradigm in the field of stroke treatment , and is considered a potential regenerative strategy for patients with neurologic deficits .
studies involving animal models of ischemic stroke have shown that stem cells transplanted into the brain can lead to functional improvement.1 various cell types have been used to improve function and the recovery after stroke , including embryonic stem cells ( escs ) , immortalized pluripotent stem cells ( ipscs ) , neural stem / progenitor cells ( nscs ) , and nonneuronal adult stem cells such as mesenchymal stem cells ( mscs ) and bone marrow mononuclear cells ( mncs ) .
most clinical trials involving patients with stroke have used adult stem cells , such as mscs , mncs , and nscs .
the international cellular medicine society classifies culture - expanded autologous mscs as a clinical cell line , unlike escs , ipscs , and genetically modified stem cells .
mscs can migrate to injured brain regions ( tropism ) and self - renew , reportedly without inducing carcinogenesis .
this review presents the status of the current understanding regarding adult stem cells and the results from clinical trials .
the most recent advances in preclinical studies are discussed , and ongoing clinical studies of adult stem cell therapy in the field of stroke are described .
stem cells aid stroke recovery via various mechanisms of action depending on the specific cell type used .
transplanted escs , ipscs , and nscs can replace the missing brain cells in the infarcted area , while nonneuronal adult stem cells , such as mscs and mncs , provide trophic support to enhance self - repair systems such as endogenous neurogenesis .
most preclinical studies of stem cell therapy for stroke have emphasized the need to enhance self - repair systems rather than to replace lost cells , regardless of the type of cells used ( msc and ipsc ) . a recent study found that although ipsc - derived nscs induced neurogenesis , they enhanced endogenous neurogenesis via trophic support , in a manner similar to adult nonneuronal stem cells ( e.g. , mscs ) , rather than by cell replacement with exogenous ipsc - derived nscs.2 in addition , there are hurdles associated with using cell replacement to restore neuronal function after stroke .
true neuronal substitution requires specific anatomic and functional profiles , such as the need for biode - gradable scaffolds ( longitudinal channel - like structures for axonal connections ) and topologic transplantation of different types of stem - cell - derived neurons ( cortical neurons , interneurons , and oligodendrocytes).3 the above - described features mean that adult stem cells such as mscs may be a good choice for stroke therapy because they secrete a variety of bioactive substances - including trophic factors - into the injured brain , which may be associated with enhanced neurogenesis , angiogenesis , and synaptogenesis.4567 besides trophic factors , mscs release extra - cellular vesicles to deliver functional proteins and micrornas to nscs or neuronal cells.8 in addition , mscs exert their actions by attenuating inflammation,910 reducting scar thickness ( which may interfere with the recovery process),11 enhancing autophagy,12 and normalizing microenvironmental / metabolic profiles13 in various brain diseases .
preclinical studies have found that most injected stem cells disappear within a few weeks , which makes it unlikely that the transplanted stem cells were functionally integrated into the brain.1415 however , it was also reported that subpopulations of mscs ( e.g. , multilineage differentiating stress - enduring cells ) were able to differentiate into neuronal cells , and were integrated into the peri - infarcted cortex and acted as tissue repair cells.16 thus , mscs are thought to play multiple roles ( fig .
the number of studies of stem cells in stroke has increased markedly recently ( fig .
2 ) . with current advances in the understanding of the effects of introducing stem cells and their mechanisms of action ,
several clinical trials of stem cell therapy have been conducted in patients with stroke since 2005 , including studies using mscs,17181920 mncs,212223242526 and nscs ( table 1).2728 for stem cell therapy to be useful in augmenting the recovery after stroke , it needs to be safe and effective , applicable to a broad spectrum of patients with stroke , and cost - effective.29 most clinical trials using various types of stem cell have demonstrated that stem cell therapy following stroke is both feasible and safe , and may improve recovery .
however , these trials varied in terms of the patient characteristics , cell therapy timing , dose and type of cells delivered , and mode of treatment .
in addition , many factors that could be critical to the transplantation success , including the location and the extent of lesions , were not adequately considered . moreover ,
the assessments of functional improvement , adverse effects , and pretreatment screening tests for safety have varied greatly among the studies .
none of the studies aimed to determine the efficacy of msc therapy in patients with stroke .
all of the studies aimed to assess the feasibility and safety of stem cell treatments , and most were small series and did not include a control group .
while stem cells appeared to be of some benefit in several studies , there was significant bias in subsequent studies ( fig .
3 ) . a recent multicenter randomized controlled clinical trial ( rct ) of intravenous infusion of autologous bone marrow mncs failed to show any effectiveness.26 presently , rigorous reasoning is required to replicate experimental results in patients with stroke .
the stem cell therapies as an emerging paradigm in stroke ( steps ) committee recently suggested guidelines for bridging the gap between basic and clinical studies,30 early stage clinical trials,31 and phase ii / iii trials32 of stem cell therapies in stroke . according to these recommendations
after randomization , experimental procedures may not be blinded , because applying stereotaxic sham surgery or bone marrow sham aspiration to control patients may increase the risk of adverse effects .
patient selection and a cell dose that is equivalent to that used in animal studies should be used .
patients with stroke in the middle cerebral artery territory ( or anterior circulation ) and those with moderately severe neurologic disabilities could be ideal candidates .
the mode of application of stem cells may significantly influence the number of cells delivered to target regions , as well as the incidence of adverse effects .
for example , one study demonstrated that intra - arterial transplantations resulted in superior delivery of stem cells in the ischemic brain compared to intravenous infusions,33 but this may cause arterial occlusion , resulting in stroke.3334 there have been relatively few studies directly comparing the efficacy of intravenous and intra - arterial delivery of mscs.35 the mode of treatment should be based on the severity and location of lesions , and the timing of application .
in addition to the clinical outcomes measured , laboratory and neuroimaging findings should be used as surrogate markers of efficacy .
advanced technologies such as multimodal magnetic resonance imaging ( mri ; e.g. , resting - state functional mri or diffusion - tensor imaging ) can be used to monitor the response to restorative therapy.3637 finally , patients should be followed for more than 90 days .
long - term monitoring ( > 6 months ) is likely to be unnecessary because autologous mscs are a clinical cell line and die within days or weeks of administration.31
among the various adult stem cells , mscs have been most commonly used in the clinical trials for patients with stroke .
for example , mscs can be isolated from various tissues , such as umbilical cord , endometrial polyps , menses blood , adipose tissue , and bone marrow.38 while a long culture period is required to obtain sufficient stem cells from the patient 's own bone marrow , allogeneic msc therapy can form the basis of ' off - the - shelf ' products .
in addition , mscs are heterogeneous with respect to their developmental potential and trophic supports .
the use of functionally distinct subpopulations of mscs was found to improve their effects.39 finally , presenting appropriate stimuli to cells may promote a transient adaptive response ( preconditioning ) so that injury resulting from subsequent exposure to a harmful stimulus is reduced .
anoxic preconditioning of stem cells has been tested for the promotion of cell survival after transplantation in ischemic disease conditions.4041 it is interesting that earlier clinical trials ( i.e. , performed during 2005 - 2010 ) used autologous nave mscs , whereas several recent trials performed since 2011 have examined allogeneic or manipulated mscs , including by isolating functional subpopulations or the preconditioning of stem cells ( fig .
, we were aware of at least 15 active clinical trials using adult stem cells to treat ischemic stroke ( http://clinicaltrials.gov ) ( supplementary table 1 in the online - only data supplement ) .
it should be noted that seven of these trials were rcts that aimed to determine the efficacy of msc therapy , five tested the efficacy and safety of allogeneic mscs in patients with stroke , and four studies used manipulated ( conditioned or selected ) mscs . in the stem cell application research and trials in neurology-2 ( starting-2 ) trial , we are incorporating ischemic preconditioning using ischemic serum , blood - brain - barrier manipulation , and strict selection of candidates in order to improve the therapeutic effects and safety of mscs.42
it is too early to conclude whether msc therapy can improve functional outcomes in patients with stroke .
a recent meta - analysis in the field of cardiology concluded that transplanting adult bone marrow cells improved left ventricular function , infarct size , and remodeling in patients with ischemic heart disease compared with standard therapies .
this conclusion was reached after analyzing data from 50 studies ( involving 2,625 patients ) , in which patients received echocardiographic evaluations and long - term follow - up.43 in the field of hematology , a developmental history of 60 years was required to develop the first successful stem cell therapy- the transplantation of hematopoietic stem cells .
this suggests that development of a dramatically new therapy will require patience and constant dialogue between basic scientists and the physicians performing the clinical trials.44 more evidence from rcts is needed .
further advances at both the bench and bedside would advance the understanding of the basic mechanisms underlying stem cell therapy as well as improve the therapeutic efficacy and safety of applying stem cells to patients with stroke .
| stem cell therapy is considered a potential regenerative strategy for patients with neurologic deficits .
studies involving animal models of ischemic stroke have shown that stem cells transplanted into the brain can lead to functional improvement . with current advances in the understanding regarding the effects of introducing stem cells and their mechanisms of action , several clinical trials of stem cell therapy have been conducted in patients with stroke since 2005 , including studies using mesenchymal stem cells , bone marrow mononuclear cells , and neural stem / progenitor cells .
in addition , several clinical trials of the use of adult stem cells to treat ischemic stroke are ongoing .
this review presents the status of our understanding of adult stem cells and results from clinical trials , and introduces ongoing clinical studies of adult stem cell therapy in the field of stroke . |
full heusler alloys ( fha ) have drawn considerable attention of the researchers as some of them show shape memory alloy property . in this family
, ni@xmath0mnga is the most studied prototype ferromagnetic shape memory alloy .
it is reported that ni@xmath0mnga shows large magnetic field induced strain ( mfis ) as well as magnetoresistance effect ( mre ) , which makes ni@xmath0mnga a potential material to be used as sensors , actuators etc.@xcite however , the basic drawbacks of this material in terms of technological application are its brittleness and the low martensite transition temperature ( t@xmath1 which is 210 k)@xcite , because from the application point of view , it is mandatory that t@xmath1 should be above room temperature . in the literature ,
it is reported that , for this type of fha systems , the t@xmath1 , curie temperature ( t@xmath2 ) as well as the inherent crystalline brittleness ( icb ) are highly dependent on the composition .
hence , there is a vast amount of work searching for new heusler alloys with improved properties , which include low icb , as well as t@xmath1 and t@xmath2 above room teperature .
this is important from the point of view of technological application , for example , as actuators , sensors etc.@xcite there are also some shape memory alloys found in the literature which are termed as high temperature shape memory alloys ( htsma ) , whose martensite transition temperature is above about 120@xmath3c ( i.e. 393 k ) and they find their application in engines of automobiles , turbines , airplanes etc.@xcite there is another class of fhas which is seen to be half metallic in nature.@xcite in this kind of heusler alloys , density of states of either the majority or the minority spin vanishes at the fermi level and these materials have potential application as spintronic devices .
generally , many of the co - based heusler alloys exhibit this behaviour , like , co@xmath0crga , co@xmath0mnga , co@xmath0mnsn.@xcite however , some metallic co - based materials , like , co@xmath0nbsn , co@xmath0niga are found to exhibit shape memory alloy property.@xcite hence , it may be worth probing if there are co - based heusler alloys which show both the properties i.e. shape memory property as well as high spin polarization at the fermi level .
one such material , co@xmath0moga , has recently been predicted by us.@xcite currently , co@xmath0niga and related alloys have gained interest among the researchers .
some of these have been studied in detail theoretically@xcite as well as have already been prepared experimentally.@xcite interestingly , co@xmath0niga shows the shape memory alloy property as well as it possesses different ( inverse heusler alloy ) structure compared to many of the co - based systems , which are known to exhibit half - metallicity and have the conventional heusler alloy structure in their ground state .
it is to be further noted that , the co - based materials possess reasonably high curie temperature .
all these above - mentioned findings in the literature have motivated us to probe the co@xmath0niga - derived heusler alloy systems .
it is to be further noted that , in a very recent work@xcite it has been shown that , substitution of ni by pt in case of ni@xmath0mnga reduces the inherent crystalline brittleness as well as it makes the tetragonal state more stable compared to its cubic phase . besides that , mario et al have observed an enhancement of t@xmath2 in case of co doping in the pt based systems.@xcite so , studying the literature@xcite , we can expect that , the effect of replacement of ni by pt on various physical properties of co@xmath0niga may turn out to be interesting both from fundamental as well as application points of view .
furthermore , number of valence electrons of the system has been shown to play an important role in determining the properties of these alloy systems . in this work ,
therefore , we have discussed the changes in the magnetic , electronic as well as mechanical properties of x@xmath0ptga as x is varied and the number of valence electrons of the x element , which is a first row transition metal atom ( tm ) , changes systematically ( x being cr , mn , fe , co ) . among these materials
mn@xmath0ptga is already experimentally prepared and theoretically studied.@xcite it shows an inverse heusler alloy structure and possesses a ferrimagnetic configuration as is the case for mn@xmath0niga.@xcite we compare our calculated results with the data in the literature , wherever available . in what follows , first , we give a brief account of the method we used and then we present the results and discussion . in the end ,
the results of this work are summarized and conclusions are drawn .
the geometry optimization of all the materials have been carried out using vienna ab initio simulation package ( vasp)@xcite where the projector augmented wave method ( paw)@xcite is implemented .
for the exchange - correlation functional , generalized gradient approximation has been used over local density approximation.@xcite we have used the energy cut - off for plane wave expansion of 500 ev . the calculations of energies have been performed with a @xmath4 mesh of 15@xmath515@xmath515 for the cubic case and for the tetragonal phase also we have used similar kind of @xmath4 mesh .
all the calculations have been carried out with the energy and the force tolerance were 10 @xmath6ev and 10 mev / , respectively . for cubic crystals
there are three independent elastic constants namely @xmath7 , @xmath8 and @xmath9 . to find these three independent constants we have applied three different kind of strains on the geometrically optimized cubic structure of the respective systems using vasp code .
these strains are ( @xmath10 , @xmath10 , @xmath10 , 0 , 0 , 0)(@xmath11 ) , ( 0 , 0 , @xmath10@xmath12/(1- @xmath10@xmath12 ) , 0 , @xmath10)(@xmath13 ) and ( @xmath10 , @xmath10 , ( 1+@xmath10)@xmath14 - 1 , 0 , 0 , 0)(@xmath15 ) . the applied strain should be as small as possible ; in our case we have applied strain varying from 0.02 to -0.02 in steps of 0.005 .
it is well known that , all - electron calculations are more reliable for the prediction of magnetic properties particularly for the systems containing first row transition elements .
hence , we have carried out all electron spin polarized relativistic calculations on the optimized geometry for all the systems using full potential linearised augmented plane wave method ( fplapw).@xcite for exchange - correlation functional , generalized gradient approximation ( gga)@xcite over local density approximation is used .
an energy cut - off for plane wave expansion was used of about 16 ry ( @xmath16@xmath17 = 9.5 ) .
the cut - off for charge density was g@xmath18=14 .
the number of @xmath4 points in the self - consistent - field calculation is 8000 ( 256 ) in the cubic case , whereas for the tetragonal case the number is 8000 ( 635 ) in the reducible ( irreducible ) brillouin zone ( bz ) . to get detailed insight about the magnetic interaction between the constituent atoms ,
we have used spin - polarized - relativistic korringa - kohn - rostoker method ( sprkkr ) as implemented in sprkkr package@xcite , which provides the heisenberg exchange coupling constants ( j@xmath19 ) . from j@xmath19
we have calculated t@xmath2 following the approach of liechtenstein et al.@xcite the scf calculations have been carried out with the local density approximation as the exchange - correlation potential and a @xmath4 mesh of 21@xmath521@xmath521 in the bz were used and further an angular expansion upto @xmath20 was considered for each atom .
_ geometry optimization _ - fhas in the cubic phases crystallize in two types of crystal structures , namely , conventional heusler alloy structure and inverse heusler alloy structure . in case of fha
there are four fcc sublattices centered at ( 0.25 , 0.25 , 0.25 ) , ( 0.75 , 0.75 , 0.75 ) , ( 0.50 , 0.50 , 0.50 ) , ( 0.00 , 0.00 , 0.00 ) , which we label as a , b , c and d sublattices , respectively . in case of a conventional heusler alloy structure ( with a formula x@xmath0yz ) ,
the x atom occupies the a and b sublattices , the y atom occupies the c sublattice and d sublattice is occupied by the z atom .
this x@xmath0yz structure shows a fm@xmath21 m ( number 225 ) space group . on the other hand , in case of inverse heusler alloy structure ( with a formula xyxz ) , x atom occupies the a and c sublattices and they are termed as x2 and x1 , respectively , y atom occupies the b sublattice whereas the z atom occupies the d sublattice .
this xyxz structure assumes a f@xmath223 m ( number 216 ) space group .
full geometry optimization has been carried out for both the possibilities for all the materials .
table 1 .
comparison of formation energies between inverse and conventional heusler alloy structure with different magnetic configurations .
lattice parameters after geometry optimization are also reported.ref . ] [ cols="^,^,^,^,^,^",options="header " , ] cauchy pressure ( @xmath23 ) is defined as the difference between @xmath8 and @xmath9 .
the value of @xmath23 indicates the nature of bonding in a system.@xcite for all the systems studied here @xmath23 is found to be positive .
pugh phenomenologically related the ratio between shear modulus and bulk modulus ( @xmath24/@xmath25 ) to the inherent crystalline brittleness of a material.@xcite in the estimation of shear modulus we have followed the formalism given by voigt@xcite(@xmath26 ) over given by reuss@xcite(@xmath27 ) .
this is because @xmath27 is largely underestimated for the materials which show softening of @xmath28 ; the reason behind this has been discussed in detail in our previous work.@xcite if the ratio ( @xmath24/@xmath25 ) is greater than @xmath290.57 , the corresponding crystalline material is supposed to be inherently brittle .
according to our calculations , co@xmath0ptga is predicted to possess the lowest inherent crystalline brittleness .
the upper panel of figure 8 shows an inverse linear relationship between @xmath23 and @xmath24/@xmath25 (= @xmath26/@xmath25 ) . this inverse linear relationship between these two parameters
is already reported in literature for a large number of systems.@xcite figure 8 ( a ) suggests that the icb of co@xmath0ptga is quite low with respect to that of ni@xmath0mnga .
the bottom panel of figure 8 shows the variation of @xmath24/@xmath25 as a function of atomic number ( z ) of the x atom of x@xmath0ptga ( x = cr , mn , fe , co ) .
it is to be noted that the value of @xmath24/@xmath25 is lowest for z = 27 , i.e. for co@xmath0ptga . in literature@xcite
it has been mentioned that the materials with lower value of @xmath24 are likely to undergo shear deformation and become more prone to ductility instead of brittle fracture when strain is applied which leads to a higher inherent crystalline brittleness .
versus @xmath26/@xmath25 plot : a linear fitting has been done , which shows an inverse linear relationship between them .
ni@xmath0mnga is used as a reference material .
( b ) @xmath24/@xmath25 versus @xmath30 plot .
@xmath30 is the atomic number of the x atom.,width=264,height=340 ] _ high melting temperature of the studied systems _ - for high temperature application of a material , it is mandatory to have very high melting temperatures .
al.@xcite have correlated the elastic constant @xmath7 of the cubic metallic as well as interametallic systems with the melting temperature by the following empirical relationship : @xmath31 calculated @xmath32@xmath33 values for all the systems ( table 4 ) are predicted to be sufficiently high for a possible application as sma even at high temperature , specifically for co@xmath0ptga , which is predicted to possess @xmath34 ( around 886 k ) well above the room temperature .
from first - principles calculations , we study the electronic and magnetic properties of x@xmath0ptga ( x being cr , mn , fe , co ) heusler alloys .
we predict a few new materials with pt being an essential ingredient . by comparing the energies of various types of magnetic configurations
, we predict that cr@xmath0ptga and mn@xmath0ptga possess a ferrimagnetic configuration , whereas , fe@xmath0ptga and co@xmath0ptga possess a long - range ferromagneic ordering in their respective ground states .
analysing the electronic , magnetic and mechanical properties of all these materials , we predict that , co@xmath0ptga , cr@xmath0ptga and fe@xmath0ptga are found to be three new full heusler alloy systems , which are likely to show the martensite transition . among these
co@xmath0ptga is likely to possess the highest spin polarization at the fermi level for both the cubic and tetragonal phases .
it also exhibits the lowest inherent crystalline brittleness as well as the highest martensite transition ( @xmath34 ) , melting temperature ( @xmath35 ) and curie temperature ( @xmath36 ) ; all of these well above the room temperature .
authors thank p. d. gupta and p. a. naik for encouragement throughout the work .
authors thank s. r. barman and c. kamal for useful discussion and computer centre , rrcat for technical support .
tr thanks hbni , rrcat for financial support .
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, h. l. marcus , scr . metall . * 18 * , 951 ( 1984 ) . | using first - principles calculations based on density functional theory , we probe the electronic and magnetic properties of x@xmath0ptga ( x being cr , mn , fe , co ) heusler alloys .
our calculations predict that all these systems possess inverse heusler alloy structure in their respective ground states .
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SECTION 1. SHORT TITLE.
This Act may be cited as the ``Iran Terror Finance Transparency
Act''.
SEC. 2. CERTIFICATION REQUIREMENT FOR REMOVAL OF FOREIGN FINANCIAL
INSTITUTIONS, INCLUDING IRANIAN FINANCIAL INSTITUTIONS,
FROM THE LIST OF SPECIALLY DESIGNATED NATIONALS AND
BLOCKED PERSONS.
(a) In General.--On or after July 19, 2015, the President may not
remove a foreign financial institution, including an Iranian financial
institution, described in subsection (b) from the list of specially
designated nationals and blocked persons maintained by the Office of
Foreign Asset Control of the Department of the Treasury unless and
until the President submits to the appropriate congressional committees
a certification described in subsection (c) with respect to the foreign
financial institution.
(b) Covered Institutions.--A foreign financial institution,
including an Iranian financial institution, described in this
subsection is a foreign financial institution listed in Attachment 3 or
Attachment 4 to Annex II of the Joint Comprehensive Plan of Action.
(c) Certification.--The President may remove a foreign financial
institution, including an Iranian financial institution, described in
subsection (b) from the list of specially designated nationals and
blocked persons maintained by the Office of Foreign Asset Control of
the Department of the Treasury if the President submits to the
appropriate congressional committees a certification that the foreign
financial institution--
(1) has not knowingly, directly or indirectly, facilitated
a significant transaction or transactions or provided
significant financial services for or on behalf of--
(A) Iran's Revolutionary Guard Corps or any of its
agents or affiliates whose property or interests in
property are blocked pursuant to the International
Emergency Economic Powers Act (50 U.S.C. 1701 et seq.);
(B) a foreign terrorist organization for or on
behalf of a person whose property or interests in
property have been blocked pursuant to Executive Order
No. 13224 (66 Fed. Reg. 49079; relating to blocking
property and prohibiting transactions with persons who
commit, threaten to commit, or support terrorism); and
(C) a person whose property or interests in
property are blocked pursuant to the International
Emergency Economic Powers Act in connection with Iran's
proliferation of weapons of mass destruction or
delivery systems for weapons of mass destruction, or to
further Iran's development of ballistic missiles and
destabilizing types and amounts of conventional
weapons; and
(2) no longer knowingly engages in illicit or deceptive
financial transactions or other activities.
(d) Form.--A certification described in subsection (c) shall be
submitted in unclassified form, but may contain a classified annex.
(e) Definitions.--In this section:
(1) Foreign financial institution.--The term ``foreign
financial institution'' has the meaning given such term in
section 1010.605 of title 31, Code of Federal Regulations.
(2) Foreign terrorist organization.--The term ``foreign
terrorist organization'' means any organization designated by
the Secretary of State as a foreign terrorist organization in
accordance with section 219(a) of the Immigration and
Nationality Act (8 U.S.C. 1189(a)).
(3) Iranian financial institution.--The term ``Iranian
financial institution'' has the meaning given the term in
section 104A(d)(3) of the Comprehensive Iran Sanctions,
Accountability, and Divestment Act of 2010 (22 U.S.C.
8513b(d)(3)).
SEC. 3. CERTIFICATION REQUIREMENT FOR REMOVAL OF CERTAIN FOREIGN
PERSONS FROM THE LIST OF SPECIALLY DESIGNATED NATIONALS
AND BLOCKED PERSONS.
(a) In General.--On or after July 19, 2015, the President may not
remove a foreign person described in subsection (b) from the list of
specially designated nationals and blocked persons maintained by the
Office of Foreign Asset Control of the Department of the Treasury until
the President submits to the appropriate congressional committees a
certification described in subsection (c) with respect to the foreign
person.
(b) Covered Persons and Entities.--A foreign person described in
this subsection is a foreign person listed in Attachment 3 or
Attachment 4 to Annex II of the Joint Comprehensive Plan of Action.
(c) Certification.--The President may remove a foreign person
described in subsection (b) from the list of specially designated
nationals and blocked persons maintained by the Office of Foreign Asset
Control of the Department of the Treasury if the President submits to
the appropriate congressional committees a certification that the
foreign person--
(1) has not knowingly assisted in, sponsored, or provided
financial, material, or technological support for, or financial
or other services to or in support of terrorism or a terrorist
organization; and
(2) has not knowingly engaged in significant activities or
transactions that have materially contributed to the Government
of Iran's proliferation of weapons of mass destruction or their
means of delivery (including missiles capable of delivering
such weapons), including any efforts to manufacture, acquire,
possess, develop, transport, transfer, or use such item.
(d) Form.--A certification described in subsection (c) shall be
submitted in unclassified form, but may contain a classified annex.
(e) Definitions.--In this section:
(1) Foreign person.--The term ``foreign person''--
(A) means--
(i) an individual who is not a United
States person;
(ii) a corporation, partnership, or other
nongovernmental entity which is not a United
States person; or
(iii) any representative, agent or
instrumentality of, or an individual working on
behalf of a foreign government; but
(B) does not include a foreign financial
institution, including an Iranian financial
institution, described in section 2(b).
(2) United states person.--The term ``United States
person'' means--
(A) a United States citizen or an alien lawfully
admitted for permanent residence to the United States;
or
(B) an entity organized under the laws of the
United States or of any jurisdiction within the United
States, including a foreign branch of such an entity.
SEC. 4. CERTIFICATION REQUIREMENT FOR REMOVAL OF DESIGNATION OF IRAN AS
A JURISDICTION OF PRIMARY MONEY LAUNDERING CONCERN.
(a) In General.--The President may not remove the designation of
Iran as a jurisdiction of primary money laundering concern pursuant to
section 5318A of title 31, United States Code, unless the President
submits to the appropriate congressional committees a certification
described in subsection (b) with respect to Iran.
(b) Certification.--The President may remove the designation of
Iran as a jurisdiction of primary money laundering concern if the
President submits to the appropriate congressional committees a
certification that the Government of Iran is no longer engaged in
support for terrorism, pursuit of weapons of mass destruction, and any
illicit and deceptive financial activities.
(c) Form.--The certification described in subsection (b) shall be
submitted in unclassified form, but may contain a classified annex.
(d) Definition.--In this section, the term ``appropriate
congressional committees'' means--
(1) the Committee on Foreign Affairs and the Committee on
Financial Services of the House of Representatives; and
(2) the Committee on Banking, Housing, and Urban Affairs of
the Senate.
SEC. 5. APPLICABILITY OF CONGRESSIONAL REVIEW OF CERTAIN AGENCY
RULEMAKING RELATING TO IRAN.
(a) In General.--Notwithstanding any other provision of law, any
rule to amend or otherwise alter a covered regulatory provision as
defined in subsection (c) that is published on or after the date of the
enactment of this Act shall be deemed to be a rule or major rule (as
the case may be) for purposes of chapter 8 of title 5, United States
Code, and shall be subject to all applicable requirements of chapter 8
of title 5, United States Code.
(b) Quarterly Reports.--Not later than 60 days after the date of
the enactment of this Act, and every 90 days thereafter, the head of
the applicable department or agency of the Federal Government shall
submit to the appropriate congressional committees a report on the
operation of the licensing system under each covered regulatory
provision as defined in subsection (c) for the preceding 2-year period,
including--
(1) the number and types of licenses applied for;
(2) the number and types of licenses approved;
(3) a summary of each license approved;
(4) a summary of transactions conducted pursuant to a
general license;
(5) the average amount of time elapsed from the date of
filing of a license application until the date of its approval;
(6) the extent to which the licensing procedures were
effectively implemented; and
(7) a description of comments received from interested
parties about the extent to which the licensing procedures were
effective, after the applicable department or agency holds a
public 30-day comment period.
(c) Definition.--In this section, the term ``covered regulatory
provision'' means any provision of part 535, 560, 561, or 1060 of title
31, Code of Federal Regulations, as such part was in effect on June 1,
2015.
SEC. 6. PROHIBITIONS AND CONDITIONS WITH RESPECT TO CERTAIN ACCOUNTS
HELD BY FOREIGN FINANCIAL INSTITUTIONS.
Section 104(c)(2)(A)(ii) of the Comprehensive Iran Sanctions,
Accountability, and Divestment Act of 2010 (22 U.S.C.
8513(c)(2)(A)(ii)) is amended by adding at the end before the semicolon
the following: ``, including Hezbollah, Hamas, the Palestinian Islamic
Jihad, and any affiliates or successors thereof''.
SEC. 7. DEFINITIONS.
In this Act:
(1) Appropriate congressional committees.--The term
``appropriate congressional committees'' has the meaning given
the term in section 14(2) of the Iran Sanctions Act of 1996
(Public Law 104-172; 50 U.S.C. 1701 note).
(2) Joint comprehensive plan of action.--The term ``Joint
Comprehensive Plan of Action'' means the Joint Comprehensive
Plan of Action, signed at Vienna July 14, 2015, by Iran and by
the People's Republic of China, France, Germany, the Russian
Federation, the United Kingdom and the United States, with the
High Representative of the European Union for Foreign Affairs
and Security Policy, and all implementing materials and
agreements related to the Joint Comprehensive Plan of Action,
and transmitted by the President to Congress on July 19, 2015,
pursuant to section 135(a) of the Atomic Energy Act of 1954, as
amended by the Iran Nuclear Agreement Review Act of 2015
(Public Law 114-17; 129 Stat. 201).
Passed the House of Representatives February 2, 2016.
Attest:
KAREN L. HAAS,
Clerk. | . Iran Terror Finance Transparency Act (Sec. 2) This bill prohibits the President from removing certain foreign financial institutions, including an Iranian financial institution, from the list of designated nationals and blocked persons maintained by the Department of the Treasury's Office of Foreign Asset Control until the President makes two certifications to Congress, the first of which is that the institution has not knowingly facilitated a significant transaction or transactions or provided significant financial services for or on behalf of: Iran's Revolutionary Guard Corps or any of its agents or affiliates whose property or property interests are blocked pursuant to the International Emergency Economic Powers Act (IEEPA), a foreign terrorist organization for or on behalf of a person whose property or property interests have been blocked pursuant to Executive Order 13224, and a person whose property or property interests are blocked pursuant to the IEEPA in connection with Iran's proliferation of weapons of mass destruction. The second certification shall be that the institution no longer knowingly engages in illicit or deceptive financial transactions or other activities. (Sec. 3) On or after July 19, 2015,the President may not remove specified foreign persons from the list of designated nationals and blocked persons maintained by the Office of Foreign Asset Control until the President certifies to Congress that the person has not knowingly: assisted in or provided financial, material, or technological support for terrorism or a terrorist organization; and engaged in significant activities or transactions that have materially contributed to Iran's proliferation of weapons of mass destruction or their means of delivery. (Sec. 4) The President may not remove Iran's designation as a jurisdiction of primary money laundering concern unless the President certifies to Congress that Iran is no longer engaged in support for terrorism, pursuit of weapons of mass destruction, and any illicit and deceptive financial activities. (Sec. 5) Any rule to amend or otherwise alter a covered regulatory provision regarding sanctions on Iran shall be subject to congressional review requirements. Applicable federal departments or agencies shall report to Congress on the operation of the licensing system under each covered regulatory provision for the preceding two-year period, including: the number and types of licenses applied for, and the number and types approved; a summary of each license approved; a summary of transactions conducted pursuant to a general license; the average amount of time from the date of filing for a license until the date of approval; and the extent to which the licensing procedures were effectively implemented. (Sec. 6) The Comprehensive Iran Sanctions, Accountability, and Divestment Act of 2010 is amended to prohibit or impose strict conditions on the opening or maintaining in the United States of a correspondent account or a payable-through account by a foreign financial institution that facilitates Iran's support for Hezbollah, Hamas, the Palestinian Islamic Jihad, and any affiliates or successors. (Sec. 7) Defines "Joint Comprehensive Plan of Action" as the Joint Comprehensive Plan of Action, signed at Vienna July 14, 2015, by Iran and by China, France, Germany, the Russian Federation, the United Kingdom and the United States, with the High Representative of the European Union for Foreign Affairs and Security Policy, and all related implementing materials and agreements, and transmitted by the President to Congress on July 19, 2015, pursuant to section 135(a) of the Atomic Energy Act of 1954, as amended by the Iran Nuclear Agreement Review Act of 2015. |
we often find ourselves in environments where we need to keep track of objects moving around us while we ourselves are also in motion , such as when we drive in traffic , play team sports , or walk down a crowded sidewalk .
these common situations can be challenging tracking moving objects and navigating through space are both demanding tasks .
we use attention and memory to keep tabs on the changing locations of objects of interest as they move , a process known as object tracking ( cavanagh and alvarez , 2005 ; allen et al . , 2006 ;
object tracking has a limited capacity that can be measured as the number of targets that can be tracked in a given set of conditions ( pylyshyn and storm , 1988 ; scholl et al . , 2001 ;
as we move , we update a representation of our own changing location in space , a process known as spatial updating .
although spatial updating tends to occur obligatorily ( rieser , 1989 ; farrell and robertson , 1998 ; farrell and thomson , 1998 ; may and klatzky , 2000 ) , it requires cognitive resources ( amorim et al . , 1997 ) and also appears to be limited in capacity ( wang et al . , 2006 ; wang , 2007 ) .
research describing the limitations of these processes provides a better understanding of how people function in complex environments .
much previous research has investigated the properties of object tracking and spatial updating abilities , but there are few details about how these processes interact .
recently , we have found that these two processes tap common spatial resources ( thomas and seiffert , 2010 ) .
our experiments demonstrated that when observers moved around an area in which they were tracking three targets moving amidst identical distractors , their object tracking performance suffered compared to when they remained in one location .
self - motion impaired object tracking both when observers walked around the tracking area and when they were pushed along the same path in a wheelchair .
this impairment occurred both in an immersive virtual environment and a real - world analog and was robust even when observers did not receive visual feedback about their own movements .
however , we also found that self - motion did not interfere when observers moved while performing a difficult feature - tracking task that did not involve changes to target locations . taken together
, these experiments strongly suggest that self - motion impairs object tracking performance because both rely on a process of updating spatial representations over time .
our previous findings suggest spatial updating and object location tracking processes interfere with one another , indicating that they rely on common spatial resources .
if object tracking and spatial updating require common resources , then perhaps we can understand one process in terms of the other how these resources are shared and allocated across the two tasks .
as our first step in achieving this goal , we asked how spatial updating could be assessed in terms of object tracking capacity .
quantifying attributes of cognitive function provides insights into the underlying structure of information processing and the relationship between different functions .
for example , working memory was originally quantified as containing about seven objects ( miller , 1956 ) , but this value was later revised to about four objects when the strategies and components of memory were better understood ( see baddeley , 1992 ; cowan , 2001 ) . quantifying the capacity of working memory has benefited understanding of its nature in terms of representational structure of features , neural substrates , and development ( vogel et al . , 2001 ;
ross - sheehy et al . , 2003 ; alvarez and cavanagh , 2004 ; todd and marois , 2004 ; xu and chun , 2006 ; jiang et al . , 2008 ; oakes et al . , 2010 ) .
for the current study , the goal was to understand the relationship between self - motion and object tracking .
quantification of the effect of self - motion in terms of object tracking will allow us to determine whether it makes sense to interpret the interference between the two tasks in terms of a single process , such as a mechanism for tracking changes in spatial location .
when an observer needs to move through her environment while simultaneously keeping track of the things moving around her , does a location tracking mechanism treat the self as just another moving item to track ?
alternatively , is spatial updating of self - position calculated in a more efficient or even more costly manner ? in the current experiment , we set out to quantify the load of self - motion on tracking capacity .
to measure the cost of self - motion on object tracking , we asked participants to keep track of a subset of identical moving balls while walking in an immersive virtual environment .
participants either walked around the area in which the balls moved or walked in place maintaining a constant location as in previous work ( thomas and seiffert , 2010 ) . in the current study
, we systematically varied the number of targets participants tracked in order to derive estimates of participants tracking capacity that is , how many moving objects they could successfully individuate and maintain over time . by
measuring tracking capacity both while participants walked around and walked in place , we quantified the cost of self - motion in terms of the number of objects tracked .
the research was approved by the vanderbilt university institutional review board and conformed to the ethical standards for conducting research established by the american psychological association .
participants viewed the virtual environment on an nvisor sx head mounted display ( hmd ; nvis , reston , va , usa ) , which presented stereoscopic images in a 60 diagonal field of view at a refresh rate of 60 hz using vizard software ( worldviz , santa barbara , ca , usa ) rendered graphics .
a three - axis orientation sensor ( inertiacube2 ; intersense , bedford , ma , usa ) tracked head orientation and an optical tracking system ( pptx4 ; worldviz , santa barbara , ca , usa ) tracked head position .
the graphics displayed in the hmd were updated based on head position and orientation , leading participants physical movements to translate into visual movements within the virtual world .
participants saw a virtual world inside the hmd consisting of blue sky and a green ground plane .
they stood approximately 4 ft from the center of a rendered 2.7 2.7 ft black outlined box on the ground plane .
inside this box were 10 red balls that subtended approximately 1.3 of visual angle when viewed in the center of the box .
each ball appeared stationary in a random starting location along its predefined path for 500 ms .
one , two , three , four , or five of these balls were designated as targets , changing color from red to blue for 1700 ms before returning to red .
all of the balls then moved in circular paths around the center of the box , with the radius of each path ranging randomly in 0.09 ft steps from approximately 0.2 to 1.3 ft , the speed of each dot ranging randomly in 1 deg steps from approximately 2 to 25 deg / s .
at these radii and speeds , the slowest balls tended to move about a quarter of a full circle during a trial , while the fastest balls tended to move around their circular paths up to three times .
although the circles were often very close together , making it difficult to distinguish whether an individual ball was moving along a path with a radius greater or less than its neighbors , to prevent participants from encoding ball position based on radius without regard for the balls motion , the two innermost and two outermost balls were never designated as targets .
after 4 s of movement , the balls stopped moving and one ball changed color from red to blue .
if they thought that the probed blue ball was the same as one of the targets and no otherwise .
for half of trials , the cued ball was a target ; for the other half of trials it was a distractor .
while engaged in the tracking task , participants could move in two different ways . in the move condition , participants walked an arc 90 around the box , moving a quarter circle from the center of one side of the box to an adjacent side . while walking , participants remained oriented so that their bodies faced the direction in which they moved and their heads remained turned toward the box .
participants initiated this walk at the same time that the tracking balls began to move and completed the walk when the balls stopped . to ensure that participants walked appropriately , an experimenter guided them by holding one end of a 4-ft stick while the participant held the other end . in the stay condition , on the other hand , participants simply walked in place , replacing their feet in the same location that they picked them up . while walking in place , participants were oriented identically to the move condition but maintaining a constant position . at the end of each trial in which participants changed location , they turned 180 so that they could move in the opposite direction along the same arc on the next move trial . at the beginning of a session
, participants spent a few minutes observing the testing area without the hmd as they provided consent and listened to instructions .
participants then had the opportunity to look around the virtual environment with the hmd before performing eight practice trials in which they tracked one or two targets .
they then performed four blocks of 60 trials each in which number of targets ( 15 ) , movement condition ( move or stay ) , and probe identity ( target or distractor ) were randomly intermixed .
before each trial began , an experimenter announced whether the trial was in the move or stay condition .
the research was approved by the vanderbilt university institutional review board and conformed to the ethical standards for conducting research established by the american psychological association .
participants viewed the virtual environment on an nvisor sx head mounted display ( hmd ; nvis , reston , va , usa ) , which presented stereoscopic images in a 60 diagonal field of view at a refresh rate of 60 hz using vizard software ( worldviz , santa barbara , ca , usa ) rendered graphics .
a three - axis orientation sensor ( inertiacube2 ; intersense , bedford , ma , usa ) tracked head orientation and an optical tracking system ( pptx4 ; worldviz , santa barbara , ca , usa ) tracked head position .
the graphics displayed in the hmd were updated based on head position and orientation , leading participants physical movements to translate into visual movements within the virtual world .
participants saw a virtual world inside the hmd consisting of blue sky and a green ground plane .
they stood approximately 4 ft from the center of a rendered 2.7 2.7 ft black outlined box on the ground plane .
inside this box were 10 red balls that subtended approximately 1.3 of visual angle when viewed in the center of the box .
participants performed a multiple object tracking task . at the start of each trial , each ball appeared stationary in a random starting location along its predefined path for 500 ms .
one , two , three , four , or five of these balls were designated as targets , changing color from red to blue for 1700 ms before returning to red .
all of the balls then moved in circular paths around the center of the box , with the radius of each path ranging randomly in 0.09 ft steps from approximately 0.2 to 1.3 ft , the speed of each dot ranging randomly in 1 deg steps from approximately 2 to 25 deg / s . at these radii and speeds
, the slowest balls tended to move about a quarter of a full circle during a trial , while the fastest balls tended to move around their circular paths up to three times .
although the circles were often very close together , making it difficult to distinguish whether an individual ball was moving along a path with a radius greater or less than its neighbors , to prevent participants from encoding ball position based on radius without regard for the balls motion , the two innermost and two outermost balls were never designated as targets .
after 4 s of movement , the balls stopped moving and one ball changed color from red to blue .
if they thought that the probed blue ball was the same as one of the targets and no otherwise .
for half of trials , the cued ball was a target ; for the other half of trials it was a distractor .
while engaged in the tracking task , participants could move in two different ways . in the move condition , participants walked an arc 90 around the box , moving a quarter circle from the center of one side of the box to an adjacent side . while walking , participants remained oriented so that their bodies faced the direction in which they moved and their heads remained turned toward the box .
participants initiated this walk at the same time that the tracking balls began to move and completed the walk when the balls stopped . to ensure that participants walked appropriately , an experimenter guided them by holding one end of a 4-ft stick while the participant held the other end . in the stay condition , on the other hand , participants simply walked in place , replacing their feet in the same location that they picked them up . while walking in place
, participants were oriented identically to the move condition but maintaining a constant position . at the end of each trial in which participants changed location , they turned 180 so that they could move in the opposite direction along the same arc on the next move trial . at the beginning of a session
, participants spent a few minutes observing the testing area without the hmd as they provided consent and listened to instructions .
participants then had the opportunity to look around the virtual environment with the hmd before performing eight practice trials in which they tracked one or two targets .
they then performed four blocks of 60 trials each in which number of targets ( 15 ) , movement condition ( move or stay ) , and probe identity ( target or distractor ) were randomly intermixed .
before each trial began , an experimenter announced whether the trial was in the move or stay condition .
participants made more tracking errors as tracking load increased from one to five balls and made more errors in the move condition than in the stay condition ( figure 1 ) .
a 5 2 anova confirmed these effects , showing significant main effects of number of targets [ f(4 , 52 ) = 39.37 , mse = 56.04 , p < 0.001 ] and self - motion [ f(1,13 ) = 46.14 , mse = 22.76 , p < 0.001 ] .
the interaction between number of targets and self - motion approached significance [ f(4,52 ) = 2.43 , mse = 45.43 , p < 0.06 ] . planned pairwise comparisons showed that this marginal interaction was driven by a lack of difference between tracking performance in the move versus stay conditions under low tracking load [ t(13 ) = 0.99 , p > 0.3 for the one - target case and t(13 ) = 1.39 , p > 0.1 for the two - target case ] but significantly better tracking in the stay condition under higher tracking load [ t(13 ) = 3.43 , p < 0.01 for tracking three targets , t(13 ) = 2.35 , p < 0.04 for tracking four targets , and
t(13 ) = 2.75 , p < 0.02 for tracking five targets ] .
this pattern of results replicates and extends our previous findings , showing that self - motion impairs object tracking when tracking load is sufficiently high ( thomas and seiffert , 2010 ) .
mean percentage correct in the tracking task . to determine whether results indicate differences in sensitivity or report bias , we conducted the same analyses as reported above on d and beta ratio values ( macmillan and creelman , 2005 ) .
a 5 2 anova on d values showed significant effects of number of targets [ f(4,52 ) = 43.98 , partial = 0.772 , p < 0.001 ] and self - motion [ f(1,13 ) = 43.71 , partial = 0.771 , p < 0.001 ] .
the interaction between number of targets and self - motion approached significance [ f(4,52 ) = 2.43 , partial = 0.158 , p < 0.06 ] . planned pairwise comparisons on d values showed that this marginal interaction was driven by a lack of difference between tracking performance in the move versus stay conditions under low tracking load [ t(13 ) = 1.05 , p > 0.30 for the one - target case and t(13 ) = 1.41 , p > 0.10 for the two - target case ] but significantly better tracking in the stay condition under higher tracking load [ t(13 ) = 3.39 , p < 0.005 for tracking three targets , and t(13 ) = 2.92 ,
p < 0.02 for tracking five targets ; for four targets results were marginal , t(13 ) = 2.12 , p < 0.06 ] .
a 5 2 anova on beta ratio values showed a marginal main effect of number of targets [ f(4,52 ) = 2.24 , partial = 0.147 , p < 0.08 ] and no effect of self - motion [ f(1,13 ) = 2.14 , partial = 0.141 , p > 0.10 ] and no interaction [ f(4,52 ) < 1 ] .
taken together , this pattern of results replicates results reported as percent correct and shows that self - motion impairs tracking sensitivity and not bias ( thomas and seiffert , 2010 ) . at first glance , the averaged data are suggestive about the quantitative cost of self - motion in terms of number of objects tracked .
when participants tracked three balls while moving , their performance was similar to when they tracked four balls while stationary [ green dashed line in figure 1 ; t(13 ) = 0.32 , p > 0.75 ] .
similarly , performance tracking four balls while moving was equivalent to tracking five balls while stationary [ blue dashed line in figure 1 ; t(13 ) = 0.54 , p > 0.59 ] .
in other words , the cost of adding one more target appears similar to the cost of self - motion ; the decrement in performance from adding one more target in the stay condition was similar to the decrement in performance associated with moving .
overall participants average percent correct suggests that the cost of self - motion is about one object . to quantify the cost of self - motion on tracking in terms of the number of objects , we estimated tracking capacity for each individual participant in both stay and move conditions .
we evaluated performance in terms of the effective number of targets tracked by calculating cowan
pashler s k ( pashler , 1988 ; cowan , 2001 ) with : where k = estimated number of balls tracked , h = proportion of accurate yes responses ( hits ) , cr = proportion of accurate no responses ( correct rejections ) , and n = number of target balls .
k values are a performance measure similar to percent correct , but given in terms of the number of objects that are effectively tracked ( as in scholl et al . , 2001 ) .
for example , when there were three targets , if a participant had a hit rate of 0.8333 and a correct rejection rate of 0.8333 , then the k value of 1.999 would indicate that participant was able to effectively track about two of the three targets on average .
for each participant , we calculated k for each level of the factor that varied the number of targets , separately for the move and stay conditions .
this allowed us to compare the asymptotes of the k curves as an estimate of the overall capacity costs of self - motion during tracking .
tracking capacity ( c ) for each individual was estimated by fitting the k values with an elbow curve that assumed perfect tracking performance for conditions with fewer targets than c and performance capped at c for conditions with more targets than c. the value of c that provided the least squared error from the data was taken as the estimated tracking capacity .
this estimation of tracking capacity does not correct for guessing , nor consider the benefit to performance from known distractors ( hulleman , 2005 ) .
however , we assume that any such correction would be the same for move and stay conditions because we manipulated self - motion independently of the tracking task . while the absolute values of capacity may be overestimated here
, we assume the relationship between the capacity for move and stay conditions would not be affected by such analyses . as such
, we use this analysis to quantify the cost of self - motion in terms of the effective number of targets tracked .
capacity estimates under both the move and stay conditions for each participant agreed with the estimates from the overall average .
all but one participant had a smaller capacity in the move condition than the stay condition ( figure 2 , points relative to blue line ) , showing the reliability of the effect of self - motion on tracking performance across participants .
interestingly , 9 out of the 13 participants showing a cost had a difference between capacities for stay versus move conditions that was less than one ( figure 2 , points relative to the red line ) . calculating difference scores subtracting the tracking capacity for the move condition from the tracking capacity for the stay condition revealed a self - motion cost that , averaged across participants , was 0.8 objects ( se = 0.2 ) .
this estimate for the cost of self - motion was reliably greater than zero [ t(13 ) = 4.6 , p < 0.0005 ] , but not reliably different from one [ t(13 ) < 1 , ns ] . taken together , these analyses suggest that most individual participants experienced a cost of self - motion of about one object .
estimates of tracking capacity ( c ) for each participant in the move and stay conditions .
the blue line shows the perfect one - to - one relationship that would occur if tracking capacity was unaffected by self - motion .
the red line shows a perfect cost of one object due to self - motion .
we often find ourselves in situations where we must move through the environment while simultaneously keeping track of other objects moving around us .
the results of the current study show that self - motion hampers tracking performance at a cost that is about the same as adding one more target object . replicating and extending our previous work ( thomas and seiffert , 2010 )
, we found that when participants were only required to track one or two objects , self - motion did not substantially interfere with this task .
however , when participants attempted to keep track of three , four , or five objects , there was a significant cost of self - motion on tracking performance .
more specifically , we found that participants capacity data in move versus stay conditions were best described by fitting curves that differed in their asymptotes by 0.8 .
these results are in line with the idea that the spatial updating associated with self - motion draws upon resources that are also tapped in keeping track of multiple moving objects .
we can not help but update a representation of our own changing location in space as we move ( e.g. , farrell and robertson , 1998 ; may and klatzky , 2000 ) , but we do so at the expense of updating other objects changing locations as they move .
moreover , results from the majority of participants showed that keeping track of one s own location in space may be slightly less costly than tracking another object . in other words ,
when an observer moves while trying to keep track of other moving objects , self - motion imposes an additional load on the tracking mechanism of a bit less than one additional external object .
the results of the current study provide the first estimate of the actual cost of self - motion on object tracking .
quantification of the effect of self - motion in terms of object tracking allows us to interpret the interference between the two tasks in terms of a single process .
the observation that self - motion produces a cost to tracking performance that is very similar to adding one more target object seems to suggest that people mentally update a representation of their own location in space with the same process they use to update representations of moving objects .
a mechanism that tracks the location of the self and objects could use a single spatial representation , such as an allocentric map of the room , or affect multiple representations in a similar way , such as updating egocentric coordinates of objects and a representation of the self in the room . in our experiment
, we attempted to match the speed and trajectories of both observers and the targets ; participants walked along a curved path that was similar to the circular paths of the moving balls .
our results therefore speak to situations in which an observer s location changes in a very similar manner to tracking target locations .
it is possible that in situations where an observer moves more quickly or along a more complicated trajectory , self - motion may reduce object tracking capacity to an even greater extent .
in addition , our evidence does not allow for strong conclusions about the nature of the limitation in cognitive processing driving these effects .
the concept of capacity as depicted here could be taken to suggest that the mind has slots for attending to and remembering a set number of objects ( miller , 1956 ; cowan , 2001 ; awh et al .
however , results are equally compatible with a more complex model of cognitive processing in which limits of performance are due to other factors , such as sampling rate , interference , or optimization of representation integrity ( davossa et al . , 2006 ;
kazanovich and borisyuk , 2006 ; ma and huang , 2009 ; vul et al . ,
whatever the model , the results demonstrate that the cost of self - motion is approximately the same as the cost of tracking another object , suggesting that similar processing may occur for updating the memory of the location of the self and the location of objects . in conclusion
, we find that adding self - motion to a multiple object tracking task costs a little less than adding one additional target , at least in cases where self - motion mirrors target motion such as driving in traffic , playing team sports , or walking down a crowded sidewalk .
both spatial updating and object tracking call upon a common mechanism that keeps track of the changing locations of items
this mechanism may process information about self - location somewhat more efficiently than information about other objects .
after all , we have more experience keeping track of where we are than we do for any external objects and before we can act effectively on our environment , we must first have a representation of where we are within it .
the authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest . | perhaps walking and chewing gum is effortless , but walking and tracking moving objects is not .
multiple object tracking is impaired by walking from one location to another , suggesting that updating location of the self puts demands on object tracking processes . here
, we quantified the cost of self - motion in terms of the tracking load .
participants in a virtual environment tracked a variable number of targets ( 15 ) among distractors while either staying in one place or moving along a path that was similar to the objects motion . at the end of each trial
, participants decided whether a probed dot was a target or distractor .
as in our previous work , self - motion significantly impaired performance in tracking multiple targets .
quantifying tracking capacity for each individual under move versus stay conditions further revealed that self - motion during tracking produced a cost to capacity of about 0.8 ( 0.2 ) objects . tracking
your own motion is worth about one object , suggesting that updating the location of the self is similar , but perhaps slightly easier , than updating locations of objects . |
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. ||||| A Texas family is suffering after a car crash left two siblings dead and sent the parents to the hospital. The family was on their way home from a Christmas lights tour when they were struck from behind by another car. VPC
Alexander Trejo and Gabrielle Estelle were killed in a wreck after a Christmas light outing with family. (Photo: WFAA)
HALTOM CITY, Texas — Just days before Christmas, a North Texas family is having to plan funerals for a brother and sister killed in a car wreck after looking at Christmas lights.
Alexander Trejo and Gabrielle Estelle of Haltom City died Monday night.
But now strangers are helping the family heal.
The Estelle family was together and on their way home after taking the driving tour of Christmas lights at the Texas Motor Speedway.
Nora Morales says her sister and husband and their three kids "were doing their normal thing."
"In their car singing Christmas carols," Morales said. "My sister said within seconds everything turned to chaos."
Fort Worth police say a Ford Explorer struck the back of their car on Interstate 35W near Heritage Trace Parkway.
Alex, 23, and Gabbi, 19, died at the scene.
Their 17-year-old brother, Zach, survived. Their parents also survived, but both were hospitalized.
Michelle Flores, who works with their mother Dee Estelle, and her co-workers are turning their grief into action, setting up a GoFundMe page, which has raised more than $8,000 as of Wednesday night.
"If we can't do anything else, we can at least help them financially because they have a long road ahead of them," Flores said.
Fort Worth police said the traffic investigation unit is still working on a final crash report. But right now, the driver of the SUV doesn't face any criminal charges.
Follow David Goins on Twitter: @dgoins
Read or Share this story: http://usat.ly/1OoTQWa | – A Texas family's ride to view a Christmas lights display ended in tragedy Monday night when their car was rear-ended, killing the two oldest kids, WFAA reports. The Haltom City mom and dad and their three children had just completed a drive-through of the Christmas lights extravaganza at Texas Motor Speedway and were on their way home "in their car singing Christmas carols," the deceased's aunt tells the station. "My sister said within seconds everything turned to chaos." That chaos came in the form of a Ford Explorer that smashed into the back of the family's car, killing 23-year-old Alexander Trejo and his 19-year-old sister, Gabrielle Estelle. The local medical examiner says the two victims, who had to be pulled from their Ford Fusion, died of blunt force trauma, per the Star-Telegram. "We were laughing, giggling, singing Christmas songs, and then the next thing I know is I blacked out," 17-year-old Zachary, the sole surviving sibling, tells Fox 4 News. Zachary's parents were both hospitalized after the accident with injuries that were said to be non-life-threatening, per a GoFundMe page set up by the mom's co-workers. Fort Worth police are still trying to figure out what caused the Ford Explorer to plow into the family's car, WFAA reports; as of now, the driver of the SUV isn't facing any criminal charges. Meanwhile, family and friends held a tribute Wednesday night for Alexander, who had a love of music, and Gabrielle, said to be an aspiring photographer, Fox 4 News notes. The GoFundMe page has so far raised more than $9,000 for the family's hospital and funeral expenses. |
the search - enhanced instantaneous frequency detection ( seifd ) algorithm uses genetic algorithm ( ga ) @xcite to identify the characteristics of sinusoidal components ( see fig .
[ fig : sinudoidal - component ] ) within a nonlinear non - stationary time series data .
the time - series data is modeled as a superposition of these components , each exist within a unique time range .
it is represented as below .
@xmath0 where , @xmath1 is the index of each sinusoidal component ; @xmath2 is its amplitude ; @xmath3 , is its frequency ; and @xmath4 is its phase .
the parameters which define each of the components are encoded as a solution string consisting binary values . during implementation ,
the ga attempts to find their value by simulating it as a solution improvement process modeled as a series of genetic evolutions . because the problem is non - stationary , each of the sinusoidal components possesses unique start and end time ( denoted respectively as @xmath5 and @xmath6 ) .
they are as well encoded in the solution string . in this way , the solver attempts to decompose the time - series data into its consituting sinusoidal components in order to reveal the instantaneous frequencies of the time - series data .
the sinusoidal parameters are encoded as a string of binary values .
the length of the binary string is determined based on the sum of the bit counts carried by each of the parameters computed with their respective lower and upper bound , as well as the step size of increment .
the bit count for each of the parameters is computed as below .
@xmath7 + 1\ ] ] where , bit(@xmath8 ) is the bit count of parameter @xmath8 ; @xmath9 and @xmath10 respectively are the upper bound and lower bound of parameter @xmath8 ; and @xmath11 is the step size of each increment of parameter @xmath8 in the solution .
the solution string is organized as shown in fig .
[ fig : sample - solution - string ] .
the real value of each of the parameters can be decoded from the solution string using the following equation .
@xmath12\ ] ] where , @xmath13 is the length of bits in the solution string representing the value of @xmath8 .
the solution string is regarded as a chromosome ( fig .
[ fig : chromosome ] ) in the simulated genetic evolution process . in the initial stage , ga generates a group ( a population ) of random chromosomes of varying quality computed with the following fitness function .
@xmath14\ ] ] where the @xmath15 is the raw time - series data .
the fitness function describes the environment ( the solution space ) in which the chromosomes evolve .
the implementation should achive continuous improvement ( lower fitness function in every subsequent generation ) until the fitness score converged at a targeted fitness score
. the targeted fitness score of @xmath16 is 0 .
then , ga selects some chromosomes possessing good fitness score for creating new offsprings in the subsequent repetitions . in the process ,
the algorithm identify and retain good alleles that lead to the yielding of better fitness scores .
meanwhile , it modifies the inferior allele values using simulated biological crossover and mutation processes .
the operation is repeated until the termination criterion is finally met .
compare to fourier transforms , the method adaptively identifies the start and end of such sinusoidal components ( within the time horizon of the data ) , as well as their exact instantaneous attributes . among others , its performance is not constrained by : i. ) the need to ensure the completion of at least one oscillation cycle in all of the sinusoidal components ; and ii . )
the existence of discontinuity within the data .
the result fulfills the following generalized fourier representation @xcite : @xmath17 the identification of the quantity of sinusoidal components at every time step , @xmath18 can be solved as a combinatorial optimization ( co ) problem ( the ga is a well - known approach for solving co problems ( i.e. , @xcite ) ) . to do so
, the method could be implemented as below : 1 .
establish a list of repeatable combination , @xmath19 of length @xmath20 , which consist of a list of integer , @xmath21 ; where @xmath20 is the length of the data , @xmath22 is an integer representing the maximum quantity of sinusoidal components in the data .
2 . implement ga to determine the value of components in @xmath19 , @xmath23 .
3 . determine the @xmath24 and @xmath25 for each of the sinusoidal component based on @xmath19 , and identify their configurations .
improve @xmath19 until convergence is achieved .
the method is tested on a time series data shown in fig . [
fig : sample - data ] .
the algorithm is codified using the python programming language .
the iteration - best value of @xmath2 , @xmath3 , and @xmath4 found by the ga is shown in fig . [
fig : convergence ] .
the changes in the parameter values which leads to the convergence of @xmath16 is clearly seen in the figure .
the final results obtained in the implementation is shown in fig .
[ fig : result ] .
a. l. corcoran and r. l. wainwright , `` using libga to develop genetic algorithms for solving combinatorial optimization problems , '' in _ the application handbook of genetic algorithms_,1995 , pp . 143172 . n. e. huang , z. shen , s. r. long , m. c. wu , h. h. shih , q. zheng , n. yen , c. c. tung , and h. h. liu , `` the empirical mode decomposition and the hilbert spectrum for nonlinear and non - stationary time series analysis , '' _ proceedings : mathematical , physical and engineering sciences _ , vol .
1971 , pp .
903995 , 1998 . | this paper presents a method developed for finding sinusoidal components within a nonlinear non - stationary time - series data using genetic algorithm ( ga ) ( a global optimization technique ) .
it is called search - enhanced instantaneous frequency detection ( seifd ) algorithm .
the ga adaptively define the configuration of the components by simulating the solution finding process as a series of genetic evolutions . the start - time , end - time , frequency , and phase of each of these components
are identified once convergence in the implementation is achieved .
adaptive data analysis ; instantaneous frequency ; global optimizations ; genetic algorithms . |
the young s double - slit interference experiment is one of the powerful ways to exhibit the nature of optical field , both classical and nonclassical coherence effects . in the recent years , an interesting subject is devoted to the study of two - photon double - slit interference in the process of spontaneous parametric down - conversion ( spdc).@xcite-@xcite since in this process a pair of converted beams created by a pump beam is in entanglement , the two - photon double - slit interference may show some peculiar phenomena such as the quantum sub - wavelength lithography and the ghost interference . for the former , both signal and idler beams are set together to pass through a double - slit,@xcite,@xcite,@xcite-@xcite,@xcite,@xcite and for the latter , the double - slit is placed on the path for only one beam.@xcite-@xcite,@xcite,@xcite , gigi the original idea of the quantum lithography comes from the reduction of de broglie wavelength for combining two massive particles . in optical system ,
the sub - wavelength interference occurs for a biphoton state.yama in addition to the two - photon double - slit interference , the quantum lithography can be carried out in a mach - zehnder interferometer.@xcite-@xcite due to the fact that this effect can overcome the rayleigh diffraction limit , it may have prospective application in photo - lithography technology . in most of the theoretical analyses ,
the sub - wavelength interference is explained by a two - photon entangled state which can be acquired in the spdc with very low gain . nevertheless , it is the obstacle in practical application due to the lower power .
therefore , the exploration of these quantum effects in macroscopic regime makes sense.@xcite,@xcite in this paper , we study one - photon and two - photon double - slit interferences in both spontaneous and stimulated parametric down - conversions .
we focus on the case in which a double - slit is inserted on the paths for both signal and idler beams .
we find that the sub - wavelength lithography can occur at very high gain of spdc with substantial visibility .
the discussion covers both type i and type ii crystals which exhibit different behaviors in two - photon interference . in the stimulated process
, the amplified beam can not perform quantum lithography but create rich interference patterns .
the paper is organized as follows : in sec .
ii we briefly review double - slit interferences for a coherent state and a two - photon state . in sec .
iii we cite several formula as review of the optical parametric down - conversion process .
we analyze two - photon double - slit interference in secs .
iv and v for the spontaneous and stimulated processes , respectively .
the final section vi is the conclusion and discussion .
we consider the scheme of young s double - slit experiment as shown in fig .
1 . the double - slit function is defined by @xmath0where @xmath1 is the distance between the centers of two slits and @xmath2 is the width of each slit . in fig .
1 , both the double - slit and the detection screen are placed at the two focus planes of a lens . by ignoring the thickness of the double - slit , the transverse envelope operators of the input field @xmath3 and
the output field @xmath4 of the double - slit are related as @xmath5e_{vac}(x , t)\text { , } \label{2}\]]where the vacuum field operator @xmath6 is introduced for the sake of @xmath4 satisfying the bosonic commutation relation . since the vacuum field has no contribution to the normal - order correlation , it can be neglected in the calculations below . in the paraxial approximation , the field @xmath7 in the detection plane @xmath8
is expressed by the fourier transform of the lens @xmath9dx^{\prime } .
\label{3}\]]by substituting eq .
( [ 2 ] ) into eq . ( [ 3 ] ) , one obtains @xmath10dqd\omega \text { , } \label{4}\]]where @xmath11is the fourier transform of the double - slit function @xmath12 , and @xmath13 is the fourier transform of @xmath14 for both the spatial and temporal variables .
first , we consider the input field to be a stationary , monochromatic plane wave in a coherent state @xmath15where @xmath16 is a constant .
it has@xmath17 in the detection plane , the first - order correlation is calculated as@xmath18hence , the intensity distribution in the detection plane is written as @xmath19where @xmath20 and @xmath21 . note that @xmath22 is a real function .
equation ( [ 8 ] ) represents an interference fringe with the interval @xmath23 in the range @xmath24 , as shown in fig .
similarly , the second - order correlation function can be obtained as @xmath25according to the theory of field coherence , the separability of spatial variables in the first - order and the second - order correlation functions verifies the perfect coherence of the field .
since the field operators at different positions are commutable , the second - order correlation of the field is in fact the spatial intensity correlation and it can be observed by a coincidence measurement as shown in fig .
the spatial patterns related to @xmath26 and @xmath27 are called the one - photon and the two - photon interferences , respectively . according to eq . ( [ 9 ] ) , in the coincidence measurement , if we scan one detector by fixing another , the same interference fringe as the one - photon interference can be observed .
now , we introduce two other ways of observations for the two - photon double - slit interference .
one is the spatial intensity - correlation measurement by scanning two detectors synchronously at a pair of symmetric positions , @xmath28 .
the other one is the two - photon intensity measurement by using a two - photon detector which generates an photo - electron by absorbing two photons . applying these two observations to eq .
( [ 9 ] ) , one has@xmath29 in fig .
2 , we plot @xmath30 ( @xmath31 ) in comparison with @xmath32 for the coherent beam .
it shows that the two interference patterns are alike .
the above discussion on the coherent state is analogous to the classical field .
then , we consider a two - photon state as input , which is the quantum state without classical analogue .
a general two - photon state can be written as@xmath33where @xmath34 and @xmath35 are the creation operators for @xmath36 and @xmath37 photons which are assumed to be distinguishable . @xmath38 and @xmath39 are the transverse wave - vectors .
when the input field is stationary , eq . ( [ 4 ] ) can be simplified as@xmath40by using eq .
( [ t2 ] ) , the first - order correlation functions for @xmath36-photon and @xmath37-photon in the detection plane are obtained as [ t3 ] @xmath41respectively . for two fields case ,
the second - order correlation function is defined by @xmath42 which describes the coincidence probability of @xmath36-photon at position @xmath43 and @xmath37-photon at position @xmath44 . in the case of @xmath45
, it describes a two - photon intensity distribution .
first , for the two - photon state ( [ t1 ] ) , we calculate the two - photon wavepacket in the detection plane@xmath46then the second - order correlation is obtained as@xmath47 we discuss two extreme cases : two photons are independent and perfectly entangled in the transverse wave - vector . in the unentangled case , @xmath48@xmath49 , the first- and second - order correlations are written as [ t7 ] @xmath50equations ( [ t7 ] ) show two separabilities .
the one is the separability of positions in both the first- and second - order correlation functions .
the other is that the second - order correlation is factorized to two one - photon intensity distribution .
that is , the two - photon interference consists of two individual one - photon interferences , verifying the dirac s statement : `` each photon interferes only with itself .
interference between two different photons never occurs . ''
however , these features mean the perfect first- and second - order coherencies for the two independent photons . in the opposite extreme ,
the perfect entanglement in wavevector , @xmath51 , is hold in state ( [ t1 ] ) . for simplicity , we assume @xmath52 , and the first- and second - order correlations are written as [ t8 ] @xmath53 , \label{t8a } \\
g^{(2)}(x_{1},x_{2 } ) & = & \left\vert \frac{k}{2\pi f}\int dq\widetilde{t}(% \frac{kx_{2}}{f}+q)\widetilde{t}(\frac{kx_{1}}{f}-q)\right\vert ^{2}=\frac{% k^{2}}{2\pi f^{2}}\widetilde{t}^{2}[\frac{k}{f}(x_{1}+x_{2 } ) ] , \label{t8b}\end{aligned}\]]where we use the integrals @xmath54 , \notag\end{aligned}\ ] ] and@xmath55 .
\label{t10}\]]note that @xmath56 . equations ( [ t8 ] ) show that for the wavevector - entangled two - photon state the first- and second - order correlation functions in double - slit interference have position - correlation which results in decoherence . in the measurement , letting @xmath57 in eq .
( [ t8 ] ) , one obtains [ t11 ] @xmath58 , \label{t11a } \\
g^{(2)}(x , x ) & = & \frac{k^{2}}{2\pi f^{2}}\widetilde{t}^{2}[\frac{k}{f}(2x ) ] .
\label{t11b}\end{aligned}\]]therefore , the one - photon double - slit interference disappears completely and the two - photon double - slit interference shows a sub - wavelength property
since it has @xmath59\cos ^{2}[\frac{\pi dx}{(\lambda /2)f } ] . \label{31}\ ] ] the fringe is the same as the ordinary double - slit interference with the half of the wavelength .
the above analysis explains the complementarity of coherence and entanglement.@xcite,@xcite,@xcite we emphasize that the discussion is also true for the case when @xmath36 and @xmath37 photons can be indistinguishable .
in the optical parametric down - conversion , in which a plane - wave pump field of frequency @xmath60 activates a @xmath61 nonlinear crystal , the basic unitary transformation is described by@xcite , @xcite-@xcite @xmath62where @xmath63 and @xmath64 are the output and input field operators , respectively .
@xmath65 is the transverse wavevector and @xmath66 is the frequency deviation from the carrier frequency .
the transfer coefficients @xmath67 and @xmath68 are given by@xcite @xmath69 , \label{14}\]]@xmath70@xmath71 , \label{16}\]]@xmath72where @xmath73l_{c}/2},\qquad ( m\neq n = s , i ) , \label{18}\]]@xmath74@xmath75l_{c } , \label{20}\]]@xmath76@xmath77 is the coupling strength and @xmath78 is the length of crystal .
@xmath79 is the collinear phase mismatching of the central frequency components which correspond to the wave - numbers @xmath80 ( @xmath81 ) . for simplicity , we assume that two down - converted beams have the degenerate carrier frequency @xmath82 . hence , eq . ( [ 20 ] ) can be reduced to an even function of both @xmath65 and @xmath66@xmath83where @xmath84 and @xmath85 are defined as the frequency and spatial - frequency bandwidths , respectively .
equations ( [ 11])-([20p ] ) describe the spdc process of type ii crystal but also can be applicable to type i crystal . for the former , two converted beams
are orthogonally polarized , whereas for the latter , they are degenerate in both polarization and frequency but spatially separated .
therefore , eq . ( [ 11 ] ) can describe type i crystal by omitting the subscripts . as a matter of fact , under the assumption of the carrier frequency degeneracy , eqs .
( [ 14 ] ) and ( [ 15 ] ) are the same as eqs .
( [ 16 ] ) and ( [ 17 ] ) .
in fig . 1 , the two down - converted beams generated from the crystal illuminate a double - slit and then are detected in the focus plane of the lens .
we designate @xmath86 , @xmath87,@xmath88 , @xmath89 the slowly varying field operators for the input surface @xmath90 and the output surface @xmath91 of the crystal and the output plane of the double - slit @xmath92 and the detection plane @xmath93 , respectively . substituting eq .
( [ 11 ] ) into eq .
( [ 4 ] ) , we may calculate the first- and the second - order correlations for the field in the detection plane @xmath94 .
in this section , we consider the case of the spontaneous parametric down - conversion in which the input fields are in the vacuum state .
the first - order correlations for two beams are obtained to be @xmath95@xmath96 illustrates the intensity distribution for beam @xmath97 in the detection plane .
then we consider the second - order correlation function defined by eq .
( [ t4 ] ) , which now describes the intensity correlation between the signal beam at position @xmath43 and the idler beam at position @xmath98 . in the case of @xmath45
, it describes a two - photon intensity distribution . for type ii crystal
, the two - photon intensity distribution can be measured experimentally by the scheme shown in fig .
1b in which the coincidence measurement of two orthogonally polarized photons is performed at the same position @xmath45 . however , for type i crystal , the subscripts @xmath36 and @xmath37 should be omitted in eq .
( [ t4 ] ) .
if there is a two - photon detector available , one may observe the two - photon intensity distribution at position @xmath45 . alternatively , a realistic detective scheme for type i crystal is shown in fig .
1a in which the intensity correlation is measured by two one - photon detectors at the different positions @xmath44 and @xmath43 . for the vacuum state set in eq .
( [ t4 ] ) , by using eqs .
( [ 4 ] ) and ( 11 ) , the second - order correlation is calculated as @xmath99where @xmath100 is 1 for type i and 0 for type ii crystal .
@xmath101 is given by eq .
( [ 22 ] ) , and @xmath102 equation ( [ g2 ] ) shows that the second - order correlation is related to the first - order correlation . in eq .
( [ g2 ] ) , the first term , which is separable in term of both polarization and position , describes the part of two - photon interference contributed by two individual single - photon double - slit processes .
however , the second and the third terms describe two - photon interference effect related to photon entanglement .
the difference between the two types of crystals is devoted by the third term , that is , the first - order correlation @xmath103 .
we note that , since @xmath104 $ ] , it has @xmath105 , and hence @xmath106 .
this result is obvious because exchange of the indices @xmath37 and @xmath36 makes no difference physically .
moreover , due to eq .
( [ 20p ] ) , @xmath107 is the even function of @xmath65 and @xmath66 under the assumption of the frequency degeneracy so that @xmath108 .
therefore , two first - order correlation functions for the signal and the idler beams are equal in type ii crystal , i.e. @xmath109 . nevertheless , we keep the subscripts in eq .
( [ g2 ] ) for a general description of type ii crystal in case the two converted beams have different carrier frequencies . in order to obtain the analytical result for the integrals , we discuss two bandwidth limits of spdc process : the broad and the narrow bandwidths . in the broadband limit
, @xmath110 , @xmath67 and @xmath111 are much flatter in comparison with @xmath112 and one can set @xmath113 and @xmath114 in the integrals . by taking into account eqs .
( [ t9 ] ) and ( [ t10 ] ) , eqs .
( [ 22 ] ) and ( [ 25 ] ) can be rewritten as @xmath115,\text{\qquad } ( m = s , i ) , \label{27a}\ ] ] and [ 27 ] @xmath116,\text{% \qquad } ( m\neq n = s , i ) , \label{27b}\]]respectively , where we define @xmath117 and @xmath118 . in the broadband limit , which exhibits the maximum entanglement in transverse wavevector for two converted beam ,
we see again the position - correlation in the correlation functions .
the first - order correlation eq .
( [ 27a ] ) shows the same position - correlation as eq .
( t8a ) for the two - photon state with the maximum wavevector - entanglement .
this makes the one - photon intensity distribution in the detection plane @xmath8 homogeneous , @xmath119 , so that the one - photon double - slit interference disappears completely . in this limit , the second - order correlation ( [ g2 ] ) is obtained to be @xmath120\right\ } + \left\vert \xi _ { is}\right\vert ^{2}\widetilde{t}^{2}[\frac{k}{f}(x_{1}+x_{2 } ) ] .
\label{28}\ ] ] the first term in \ { } comes from two individual single - photon double - slit processes which are now homogeneous . the second term in \ { } and the last term manifest explicitly the position - corrlation .
if we fix one detector at a position and scan another in the coincidence measurement , the interference fringe observed is the same as the single - photon one .
to show the position correlation in the two - photon interference , we discuss two special observations , that is , @xmath45 and @xmath28 .
equation ( 28 ) is reduced to@xmath121and@xmath122the former exhibits a two - photon intensity distribution and the latter exhibits the intensity correlation at a pair of symmetric positions . both eqs .
( [ 29 ] ) and ( [ 30 ] ) include a term @xmath123 which characterizes a sub - wavelength interference pattern by the factor of @xmath124 in comparison with the ordinary interference shown by eq .
( [ 8 ] ) .
obviously , due to eq .
( [ 29 ] ) , the sub - wavelength interference for the two - photon intensity distribution can occur in both type i and type ii crystals . however , eq . (
[ 30 ] ) shows that , for type i crystal , when a pair of single - photon detectors are placed at a pair of symmetric positions and moved synchronously in the opposite direction , the sub - wavelength interference can be also observed .
but this effect never happens in type ii crystal . according to eqs .
( [ 29 ] ) and ( [ 30 ] ) , the visibilities of fringes designated by @xmath125 and @xmath126 are calculated to be @xmath127and @xmath128respectively , where @xmath129 .
note that @xmath130 makes sense only for type i crystal , for which @xmath131 .
as the parameter @xmath132 is increased from a very small quantity , @xmath133 decreases monotonously from unity and @xmath134 increases from zero up to 1/3 . since the parameter @xmath132 is related to the coupling strength @xmath77 of spdc , we plot the visibilities as functions of @xmath77 in figs .
3 , in which @xmath133s for type ii and type i crystals are indicated by the solid and dashed lines , respectively , and @xmath130 for type i crystal is indicated by the dotted line . in a weak coupling of spdc , which may generate approximately a two - photon entangled state , the visibilities @xmath133 for both type i and ii crystals reach perfectness . the sub - wavelength interference in the weak spdc has been observed experimentally.@xcite,@xcite,@xcite , eda the important fact is that , in figs .
3 , the sub - wavelength interference can still exist , with a substantial visibility , even in very high gain of spdc , in which the beams contain a large amount of photons . on the other hand , in the strong coupling of type i crystal
, the sub - wavelength interference can occur in the joint - intensity measurement at a pair of symmetric positions .
equations ( [ 32 ] ) and ( [ 33 ] ) show that , for type i crystal , two observations of sub - wavelength interferences compete for visibility . when @xmath133 reaches the perfectness , @xmath130 vanishes .
however , in the very high gain of spdc of type i , two visibilities are the same as 25% . in the opposite limit , we assume that the spdc has a very narrow bandwidth @xmath135 .
extremely , letting @xmath136 , the transfer coefficient @xmath137 ( @xmath138,@xmath37 ) tends to the delta function @xmath139equations ( [ 22 ] ) and ( [ 25 ] ) are respectively written as@xmath140and@xmath141 in this limit , the position - correlation disappears completely .
the second - order correlation is then @xmath142\widetilde{t}^{2}(\frac{kx_{1}}{f})\widetilde{t}^{2}(\frac{kx_{2}% } { f } ) .
\label{37}\]]therefore , the one - photon intensity distribution @xmath143 and the second - order correlation @xmath144 in the plane @xmath93 are the same as the case for the coherent state . in the narrow bandwidth limit , since each converted beam is monochromatic , the one - photon double - slit interference occurs with the perfect visibility . on the other hand ,
two monochromatic converted beams have no more correlation in the transverse wavevector so that the position - correlation degrades completely in the two - photon interference .
we plot the two - photon interference patterns by varying the bandwidth of spdc process @xmath85 in figs .
4 , in which figs . 4a and 4b ( 4c and 4d ) are for type i ( type ii ) crystal . in figs . 4a and 4c , a low gain of spdc , @xmath145 ( with the amplification rate 1.5 )
is taken in two - photon intensity measurement so that the sub - wavelength interferences with a better visibility are achieved when the normalized bandwidth @xmath146 is increased .
two sets of patterns are very similar with exception of tiny higher intensity for type i crystal .
figures 4b and 4d show the interference patterns for the joint - intensity measurement of two one - photon detectors at a pair symmetric positions .
the sub - wavelength interferences can be observed only for type i crystal when the gain of spdc is higher , for instance , @xmath147 ( with the amplification rate 10 ) is taken in the figures . though the visibilities are lower , the intensities of the patterns are getting much higher .
this also happens in the case of two - photon intensity measurement .
the three plots of figs .
4a-4c show that the bandwidth of spdc governs two - photon sub - wavelength interference . for a very small bandwidth of spdc ,
the two converted beams are de - entangled in transverse wavevector so that the nonclassical sub - wavelength interference disappears .
in the stimulated optical parametric process , a signal beam is injected into the nonlinear crystal and is then amplified .
the nonlinear crystal becomes an optical parametric amplifier ( opa ) .
we assume inputting a stable plane - wave beam in a coherent state@xmath148where @xmath149 designates the transverse wavevector of the input beam deviated from the normal incidence . for type ii crystal ,
we set the input beam as the signal which can be identified by the polarization , while the idler beam is in the vacuum state . for type i crystal , the subscript @xmath36 in the input beam ( [ 38 ] )
is omitted .
considering the input beam describing by eq .
( [ 38 ] ) instead of the vacuum state , we calculate the first - order correlation in the plane @xmath93@xmath150where [ 40 ] @xmath151for type ii crystal , and @xmath152 \label{41}\ ] ] for type i crystal .
@xmath153 has been defined by eq .
( [ 22 ] ) . in eq .
( [ 39 ] ) , the first and the second terms show contributions coming from the stimulated and the spontaneous processes , respectively , and they are independent in the one - photon interference pattern .
obviously , the stimulated part shows the first - order coherence due to the separability of the spatial variables .
nevertheless , for the input beam is enough strong , the spontaneous process can be neglected . @xmath154 and the other for the idler beam with the amplification rate @xmath155.@xcite according to eqs .
( [ 40 ] ) , these two patterns are the same as the ordinary fringe ( see eq .
( [ 8 ] ) ) and can be identified by the polarization and separated in space when the input beam is well tilted in incidence . however , for type i crystal , the one - photon interference pattern is written as@xmath156\}. \label{42}\end{aligned}\]]the first and second terms illustrate the two interference patterns created by two stimulated beams , i.e. the signal beam with the transverse wavevector @xmath149 and the idler beam with the transverse wavevector @xmath157 .
the third term shows an additional coherent superposition of the two interferences of the converted beams . in result
, the interference pattern can be different from the ordinary one due to the `` interference term '' in the square brackets of eq .
( [ 42 ] ) . only for the normal incidence , @xmath158 ,
the interference pattern is the same as the ordinary one .
figures 5a and 5b show the density patterns of the one - photon interference by varying the transverse wavevector of the input beam for type i and type ii crystals , respectively . in fig .
5a , the fringes alternate between onset and offset when the transverse wavevector @xmath149 of the input field is increased until the two fringes are well apart .
the offset is due to the destructive interference of two indistinguishable stimulated beams when they are folded .
however , for type ii crystal , we put two interference patterns for the signal and idler beams together in fig .
5b , in which the right part is for the signal field , and is stronger than the left part ( idler ) .
this corresponds to the measurement when the detection is insensitive to the polarizations .
different from type i crystal , when the transverse wavevector @xmath149 of the input field is increased , the bright and dark spots of the patterns exchange alternatively until the two fringes are apart .
this feature comes from the incoherent superposition of the two patterns for the signal and idler beams .
we go through a long derivation , using the unitary transformation ( [ 11 ] ) and the bosonic commutation relation , and obtain the second - order correlation function @xmath159[\left\vert w_{s}(x_{2},q)\right\vert ^{2}+m_{s}(x_{2},x_{2 } ) ] \label{43 } \\ & + [ w_{i}(x_{1},q)w_{s}(x_{2},q)n_{is}^{\ast } ( x_{1},x_{2})+\text{c.c.}% ] + \left\vert n_{is}(x_{1},x_{2})\right\vert ^{2 } \notag \\ & + \delta _ { is}\{[w^{\star } ( x_{1},q)w(x_{2},q)m(x_{1},x_{2})+\text{c.c.}% ] + \left\vert m(x_{1},x_{2})\right\vert ^{2}\}. \notag\end{aligned}\]]again , eq .
( [ 43 ] ) can describe two types of crystals . for type i crystal ,
the subscripts @xmath37 and @xmath36 are omitted and @xmath160 , whereas for type ii crystal @xmath161 .
similar to eq .
( [ g2 ] ) , the first term is the product of the two one - photon interferences for the converted beams . the second and the fourth terms exhibit the coupling of the interferences between the stimulated and spontaneous processes .
this result is similar to the discussion of the image amplification in the optical parametric amplification in which @xmath162 describes an amplified image.wkg we note that the interferences coming from the stimulated process are uncorrected in positions .
this reflects that the stimulated process does not includes the entanglement in transverse wavevectors for the two converted beams .
therefore , the quantum lithography can not be achieved in the stimulated parametric amplification by input a coherent beam . in figs .
6 , we plot the density patterns of the two - photon interferences by varying the input direction of the signal field .
figures 6a and 6b show patterns of @xmath163 and @xmath126 for type i crystal , respectively .
these two patterns are similar to the one - photon interference case with the exception of that the sub - wavelength fringe coming from the spontaneous process appears in the central part . in fig .
6a , the fringe of the signal part ( the right side ) is stronger than the idler part ( the left side ) , whereas in fig .
6b , the pattern is mirror - symmetry since exchange of two detectors at a pair of symmetric positions makes no difference .
however , figs . 6c and 6d show patterns of @xmath125 and @xmath126 for type ii crystal , respectively .
correspondingly , fig .
6c is similar to the one - photon interference case with the exception of that of the spontaneous contribution . in fig .
6d , we define @xmath164 as the transverse position for the detector sensitive to the polarization of the signal beam , so that it is comparable to the one - photon case for the signal beam ( the right part in fig .
furthermore , in fig .
6d , the spontaneous process contributes a homogeneous background instead of a sub - wavelength fringe in fig .
if two detectors in the joint - intensity measurement are polarization - insensitive , one observes a symmetric patterns which is the mirror - symmetry of fig . 6d .
in summary , we formulate the first- and second - order correlation functions in the young s double - slit interference for both spontaneous and stimulated parametric down - conversions .
the results reveal the relations between the first- and second - order correlations , and hence it can explain the complementarity of coherence and entanglement .
we show that the nonclassical sub - wavelength two - photon interference can occur macroscopically in a general spontaneous parametric process . for a high gain of spdc ,
in which the converted beams contain a huge number of photons , the sub - wavelength interference pattern is intensive with a substantial visibility .
this makes the quantum lithography technology in practicability .
moreover , we find an alternative way to observe the sub - wavelength interference for only type i crystal , in which a joint - intensity measurement is performed by a pair of one - photon detectors placed at the symmetric positions .
the advantage of this method is that the quantum lithography in type i of spdc can be performed by two one - photon detectors instead of a two - photon detector which could be unavailable .
since , this effect occurs only in a higher gain of spdc , it reflects macroscopically quantum nature for the entangled beams containing a huge number of photons .
the two ways of observations compete for the visibility , so that at the low gain of spdc of type i the interference of the first observation reaches perfectness while the second observation disappears . in the stimulated process , the one - photon and two - photon interference patterns generated by a pair of stimulated down - converted beams are alike . for type i crystal , since two converted beams are polarization - indistinguishable
, the coherent superposition of two converted beams causes a secondary interference which may fade the fringe when two beams are not well apart .
however , this effect does not exist for type ii crystal because of the distinguishability in polarization for the two stimulated beams .
this research was supported by the national program of fundamental research no .
2001cb309310 and the national natural science foundation of china , project nos . 10074008 , 60278021 and 10174007 .
e. j. s. fonseca , p. h. s. ribeiro , s. pdua , and c. h. monken , phys .
a * 60 * , 1530 ( 1999 ) ; e. j. s. fonseca , z. paulini , p. nussenzveig , c. h. monken , and s. pdua , phys .
a * 63 * , 043819 ( 2001 ) fig .
1 . schemes of young s double - slit interference with a convex lens : ( a ) a one - photon ( two - photon ) detector measures one - photon ( two - photon ) intensity distribution ; two one - photon detectors measure joint - intensity distribution at a pair of symmetric positions .
( b ) for type ii crystal , two - photon intensity distribution is measured by a polarizing beamsplitter ( pbs ) and two one - photon detectors .
visibilities versus the gain of spdc for different collinear phase - mismatching ( a ) @xmath165 ; ( b ) @xmath166 ; and ( c ) @xmath167 .
solid and dashed lines designate @xmath133 for type ii and type i crystals , respectively ; dotted line designates @xmath134 for type i crystal .
two - photon interference patterns versus the normalized bandwidth of spdc @xmath146 : ( a ) @xmath168 for type i crystal ; ( b ) @xmath169 for type i crystal ; ( c ) @xmath168 for type ii crystal ; and ( d ) @xmath170 for type ii crystal , where @xmath171 is the normalized transverse position in the detection plane .
the gains are set as @xmath145 in ( a ) and ( c ) , and @xmath172 in ( b ) and ( d ) .
the other parameters in figs .
4 - 6 are taken as the phase matching @xmath166 , the ratio @xmath173 , and @xmath174 for an arbitrary unit of the correlation functions .
5 . stimulated one - photon interference patterns by varying the normalized transverse wavevector of the input field @xmath175 for ( a ) type i crystal and ( b ) type ii crystal .
the normalized bandwidth and the input intensity are taken as @xmath176 and @xmath177 , respectively .
6 . stimulated two - photon interference patterns by varying the normalized transverse wavevector of the input field @xmath175 : ( a ) @xmath163 for type i crystal ; ( b ) @xmath126 for type i crystal
; ( c ) @xmath125 for type ii crystal ; and ( d ) @xmath126 for type ii crystal . the normalized bandwidth and the input intensity are the same as in fig . | we theoretically discuss one - photon and two - photon double - slit interferences for spontaneous and stimulated parametric down - conversions .
we show that the two - photon sub - wavelength interference can exist in a general spontaneous parametric down - conversion ( spdc ) for both type i and type ii crystals .
we propose an alternative way to observe sub - wavelength interference by a joint - intensity measurement which occurs for only type i crystal in a higher gain of spdc .
when a signal beam injects into the crystal , it may create two interference patterns by two stimulated down - converted beams , showing no sub - wavelength interference effect . |
SECTION 1. SHORT TITLE.
This Act may be cited as the ``Hunting Heritage Protection Act''.
SEC. 2. FINDINGS.
Congress finds that--
(1) recreational hunting is an important and traditional
recreational activity in which 13,000,000 people in the United
States 16 years of age and older participate;
(2) hunters have been and continue to be among the foremost
supporters of sound wildlife management and conservation
practices in the United States;
(3) persons who hunt and organizations relating to hunting
provide direct assistance to wildlife managers and enforcement
officers of the Federal Government and State and local
governments;
(4) purchases of hunting licenses, permits, and stamps and
excise taxes on goods used by hunters have generated billions
of dollars for wildlife conservation, research, and management;
(5) recreational hunting is an essential component of
effective wildlife management by--
(A) reducing conflicts between people and wildlife;
and
(B) providing incentives for the conservation of--
(i) wildlife; and
(ii) habitats and ecosystems on which
wildlife depend;
(6) each State has established at least 1 agency staffed by
professionally trained wildlife management personnel that has
legal authority to manage the wildlife in the State; and
(7) recreational hunting is an environmentally acceptable
activity that occurs and can be provided for on Federal public
land without adverse effects on other uses of the land.
SEC. 3. DEFINITIONS.
In this Act:
(1) Agency head.--The term ``agency head'' means the head
of any Federal agency that has authority to manage a natural
resource or Federal public land on which a natural resource
depends.
(2) Federal public land.--
(A) In general.--The term ``Federal public land''
means any land or water that is--
(i) publicly accessible;
(ii) owned by the United States; and
(iii) managed by an executive agency for
purposes that include the conservation of
natural resources.
(B) Exclusion.--The term ``Federal public land''
does not include any land held in trust for the benefit
of an Indian tribe or member of an Indian tribe.
(3) Hunting.--The term ``hunting'' means the lawful--
(A) pursuit, trapping, shooting, capture,
collection, or killing of wildlife; or
(B) attempt to pursue, trap, shoot, capture,
collect, or kill wildlife.
SEC. 4. RECREATIONAL HUNTING.
(a) In General.--Subject to valid existing rights, Federal public
land shall be open to access and use for recreational hunting except as
limited by--
(1) the agency head with jurisdiction over the Federal
public land--
(A) for reasons of national security;
(B) for reasons of public safety; or
(C) for any other reasons for closure authorized by
applicable Federal law; and
(2) any law (including regulations) of the State in which
the Federal public land is located that is applicable to
recreational hunting.
(b) Management.--Consistent with subsection (a), each agency head
shall manage Federal public land under the jurisdiction of the agency
head--
(1) in a manner that supports, promotes, and enhances
recreational hunting opportunities;
(2) to the extent authorized under State law (including
regulations); and
(3) in accordance with applicable Federal law (including
regulations).
(c) No Net Loss.--
(1) In general.--Federal public land management decisions
and actions should, to the maximum extent practicable, result
in no net loss of land area available for hunting opportunities
on Federal public land.
(2) Annual report.--Not later than October 1 of each year,
each agency head with authority to manage Federal public land
on which recreational hunting occurs shall submit to the
Committee on Resources of the House of Representatives and the
Committee on Energy and Natural Resources of the Senate a
report that describes--
(A)(i) any Federal public land administered by the
agency head that was closed to recreational hunting at
any time during the preceding year; and
(ii) the reason for the closure; and
(B) areas administered by the agency head that were
opened to recreational hunting to compensate for the
closure of the areas described in subparagraph (A)(i).
(3) Closures of 5,000 or more acres.--The withdrawal,
change of classification, or change of management status that
effectively closes 5,000 or more acres of Federal public land
to access or use for recreational hunting shall take effect
only if, before the date of withdrawal or change, the agency
head that has jurisdiction over the Federal public land submits
to the Committee on Resources of the House of Representatives
and the Committee on Energy and Natural Resources of the Senate
written notice of the withdrawal or change.
(d) Areas Not Affected.--Nothing in this Act compels the opening to
recreational hunting of national parks or national monuments under the
jurisdiction of the Secretary of the Interior.
(e) No Priority.--Nothing in this Act requires a Federal agency to
give preference to hunting over other uses of Federal public land or
over land or water management priorities established by Federal law.
(f) Authority of the States.--
(1) Savings.--Nothing in this Act affects the authority,
jurisdiction, or responsibility of a State to manage, control,
or regulate fish and wildlife under State law (including
regulations) on land or water in the State, including Federal
public land.
(2) Federal licenses.--Nothing in this Act authorizes an
agency head to require a license or permit to hunt, fish, or
trap on land or water in a State, including on Federal public
land in the State.
(3) State right of action.--
(A) In general.--Any State aggrieved by the failure
of an agency head or employee to comply with this Act
may bring a civil action in the United States District
Court for the district in which the failure occurs for
a permanent injunction.
(B) Preliminary injunction.--If the district court
determines, based on the facts, that a preliminary
injunction is appropriate, the district court may grant
a preliminary injunction.
(C) Court costs.--If the district court issues an
injunction under this paragraph or otherwise finds in
favor of the State, the district court shall award to
the State any reasonable costs of bringing the civil
action (including an attorney's fee). | Hunting Heritage Protection Act - Requires that Federal public lands be open to access and use for recreational hunting except: (1) as limited by the Federal agency with responsibility for such lands for national security or public safety reasons, or for reasons authorized in applicable Federal statutes as reasons for closure; and (2) as such hunting is limited by the State in which such lands are located.Directs the head of each Federal agency with authority to manage a natural resource or public lands on which such a resource depends to exercise that authority in a manner so as to support, promote, and enhance recreational hunting opportunities.Declares that Federal land management decisions and actions should result in no net loss of land area available for hunting opportunities on Federal public lands.Requires the heads of Federal agencies with authority to manage Federal public lands on which recreational hunting occurs to report annually to specified congressional committees on areas administered that have been closed during the previous year to recreational hunting and reasons for such closures and on areas that were open to such hunting to compensate for closed areas.Prohibits a withdrawal, change of classification, or change of management status, that effectively closes 5,000 or more acres of Federal public land for use for recreational hunting, from occurring unless the head of the Federal agency with authority to manage the land has submitted written notice of the action to both Houses of Congress.Grants States the right to file civil actions in district courts in cases where Federal agencies fail to comply with State authority to manage or regulate fish and wildlife. |
the biomedical community has established the standards of good clinical practice as the cornerstone of medical research on humans .
what are the standards for studying practices that overtly and intention ally fall short of good practice and are clearly discriminatory against the aged ?
i find four ethical problems in the study on ventilated patients outside the intensive care unit ( icu ) .
had this been an interventional study , omission of informed consent would have been unthinkable .
but , unfortunately , in that hospital , and in many others , these patients would have been sent anyway to a medical floor . in some other countries
, they would not have been ventilated at all unless an icu bed was secured for them in advance .
the fundamental difference between the icu and a regular hospital floor lies in the capacity to monitor and to react .
is it not likely that when an icu person collects all sorts of data on the participants , issues come to attention - such as wrong ventilator settings , a need for a different drug , and so forth ?
intervention is incompatible with the methodology of the study ; non - intervention is grossly immoral .
moreover , since icu beds might become available and patients might deteriorate , ventilated patients who can not be admitted to the icu on the day of hospitalization deserve reassessment for admittance later on . interestingly , no study patient was transferred from the medical floor to the icu .
a third problem is related to the fact that in israel , as well as in many other places , the decision of whether to admit a patient to the icu is solely in the hands of icu doctors .
it follows that this research was conducted in order to evaluate the safety of gatekeeping by the very people who serve as the sole gatekeepers .
i wish the ethics committee of soroka hospital had set some provisory guidelines for triage and for care of ventilated patients in the medical floors prior to that hospital 's institutional review board 's endorsement of this non - interventional study .
the authors themselves testify to their deviation from established ethical norms : the recommendation that ' chronological age per se is not a relevant criterion for hospitalization in an icu ' was not substantiated in the present study population .
what the authors actually say is that the icu team in their hospital violates professional ethical guidelines protecting a vulnerable population , without any sort of reflection or policy endorsement .
a study conducted in the united kingdom found that 12% of icu patients could be cared for in a regular ward and 53% of ward patients were better suited for icu care .
healthcare expenditure , which is an explicit concern in the article , did not correlate with availability and accessibility of intensive care services .
a meta - analysis of numerous clinical publications from all over the world has found age to be a factor in the triage of patients for critical care .
the number of icu beds per capita varies substantially from one place to another , and a low bed / population ratio correlates with increased inhospital mortality overall .
perhaps ageism rears its head when the ratio of icu beds to population is low , as is the case in israel .
deliberate rationing of scarce health resources on the basis of age is highly controversial . like any other form of rationing
, it depends on open deliberation for justification and legitimization , and not on inconclusive evidence and a motivation to save money .
a serious confounding factor in the whole discourse on the allocation of intensive care is lack of clarity regarding the prognosis of ventilated patients .
for some , icu care is plainly futile - but legal and psychosocial issues do not allow doctors to disconnect .
a second group of patients is also sent to the regular floor , however , not because they do not need intensive care but because the person responsible for the icu does not have a bed for them . in the absence of conceptual differentiation of patients who need icu care from those for whom
such care is futile , little may be said about the overall outcome in terms of mortality .
those who are accustomed to seeing ventilated patients on the medical floors are not surprised to learn that more than one - quarter of them survived despite non - icu standards of care .
doctors who avoid intubation of patients that have no chance of entry into the icu may reconsider this policy . in my eyes , this is the most important lesson to take from this publication .
my second take - home message is that ageism is still prevalent in healthcare and clinical research .
policy - makers should deliberate more openly the role of age in distributive justice in healthcare , while boosting awareness of existing ethical guidelines and of every doctor 's commitment to protect the vulnerable .
| four ethical issues loom over the study by lieberman and colleagues - the absence of informed consent , the study being non - interventional in situations that typically call for life - saving interventions , the bias involved in doctors that study their own problematic practice and monopoly over intensive care unit triage , and ageism .
we learn that the israeli doctors in this study never make no - treatment decisions regarding patients in need of mechanical ventilation .
they are complicit with botched standards of care for these patients , however , accepting without much doubt an ethos of scarce resources and poor managerial habits .
the main two practical lessons to be taken from this study are that , for patients in need of mechanical ventilation , compromised care is better than a policy of intubation only when the intensive care unit is available , and that vigorous efforts are needed in order to extirpate ageism . |
This week Netflix surprised everyone with the news that a new eight-episode series, The OA, will premiere on Friday. Like summer megahit Stranger Things, the intriguing new show about a 20-something woman looks to combine elements of science fiction, mystery and horror. It’s also notable that the trailer dropped just a few days before The OA premieres, a show of faith that this new offering doesn’t need much hype to hook audiences. Netflix didn’t release much information about the premise, but here’s what we know so far.
What it’s about:
The story centers on a woman who may or may not have it together: Prairie Johnson (Brit Marling) who returns to her family seven years after she disappeared without explanation. Twist #1: when she went missing as a kid, she was blind, and now she can see. In the trailer, Prairie plays a low-key game of “what happened to me for the last seven years?” If Prairie experienced severe trauma (or even resurrection) related to her disappearance, she couldn’t see it, but she can recall people through touch. The series asks the audience to buy into the “unknown,” and Netflix describes it as a “powerful, mind-bending tale about identity, human connection and the borders between life and death.”
Who’s involved:
The creators are the team behind the 2013 thriller The East: Brit Marling, who stars, and Zal Batmanglij, who directs all eight episodes. And you’ve probably seen Marling’s co-stars before: Emory Cohen (Tony Fiorello in Brooklyn), Scott Wilson (Hershel Greene in The Walking Dead) and Jason Isaacs (Lucius Malfoy in the Harry Potter movies.)
What it’s like:
From what we can tell from the vibes of the trailer, this may be a strong contender to fill the gaping Stranger Things hole in your heart until the second season premieres in 2017. As Prairie’s recovers her memory, she seems to access some very supernatural experiences including that time she had a confused walkabout on a terrain that looks a lot like a video game. Like many stories about young female “science experiments” before her (Stranger Things and Firestarter anyone?) Prairie’s a small town girl participating in psychological experiments at an unethical lab, but there’s no telling how familiar it will be just yet. As far as mysteries about missing people go, it seems less horror-like than True Detective’s first season.
It might also scratch the Westworld itch before that show returns in 2018. As detectives question Prairie about her disappearance, she seems to flash back to memories that will give everyone some clarity on what happened to her. Dolores much? So if hopping on a rollercoaster “who am I?” ride is your thing, then this might be your show.
More cryptic hints from Netflix:
All ideal icebreakers for holiday parties.
Everyone will know more on Friday. Watch the full trailer above. ||||| The trailer looks spookily familiar
Today we’re all watching a new trailer for The OA, a sci-fi drama and psychological thriller that drops on Netflix this Friday – and might just become a whirlwind success.
The synopsis (from what we can gather from the trailer)
A young woman (Prairie Johnson, played by Brit Marling) goes missing and returns to her family seven years later. At first she doesn’t recognise them. It is revealed that when she went missing she was blind; she has now miraculously gained her sight, but can only recognise her parents from touch memory.
She then begins to talk about what happened when she went missing. “I didn’t disappear. I was present for all of it,” she says. The trailer cuts through clips of Prairie going through scientific experiments, slipping off the edge of a boat into the sea, running through the woods, and being spied upon through a door, revealing strange red and orange markings on her back. She rides on the back of a bicycle as the video cuts to a lorry falling from a viaduct. Cue lots of crescendo, running, blood falling backwards and, finally, the woman standing in a glass box in a house. It’s creepy as hell, and looks pretty incredible.
The new Stranger Things? The sequel to Stranger Things?
It’s very Stranger Things, but there’s no kid in sight. Take the scientific experimentation for example:
Very reminiscent of Eleven’s sensory deprivation tank.
And the bike riding. And van crashing.
Familiar?
This video is taken from The OA Instagram page.
Dreams don't give you nosebleeds. A video posted by The OA (@the_oa) on Dec 9, 2016 at 11:31am PST
Quite Eleven-like, don’t you think?
Still
They’ve done several collage images, taking individual Instagram squares to create a larger image. And one of those images? UPSIDE DOWN.
The OA/Instagram
And if this doesn’t give you Stranger Things feels, I don’t know what will.
The OA/Instagram
Could The OA and Stranger Things be part of the same universe? Is Prairie Johnson an adult Eleven, or another one of Papa’s experiments from the Hawkins National Laboratory? Or is The OA just piggybacking on the Netflix success of July’s spooky thriller? Either way, it’s rather exciting.
READ: Stranger Things Season 2: Everything you need to know ||||| Here’s a concept: A medical mystery of a girl is seen hooked up to wires in a secretive research facility that appears to conduct high-tech mind-based experiments. The scene is contrasted by images of her running through woods and bleeding from the nose.
The character in question is Prairie Johnson in Netflix’s upcoming series “The OA” ― but she’s giving us serious Eleven from “Stranger Things” vibes. (Minus the whole ‘80s thing.) Netflix announced by surprise on Monday that all eight episodes of the drama series are set for release Friday.
Trust the unknown. All chapters of Netflix Original Series #theOA launch this Friday. pic.twitter.com/hTNiEPbdp9 — The OA (@The_OA) December 12, 2016
Although the streaming service produces a lot of new original content on the regular, we usually know what’s coming out when. In this case, there’s almost no information about “The OA” on Netflix ― and only some creepy hints on Twitter.
Have you seen death? — Netflix US (@netflix) December 12, 2016
Have you seen darkness? — Netflix US (@netflix) December 12, 2016
Have you seen the light? — Netflix US (@netflix) December 12, 2016
The series comes from creators Brit Marling and Zal Batmanglij, who partnered up on a environmental-themed thriller, “The East,” which premiered at Sundance in 2013.
Its trailer reveals little, but sets itself apart from “Stranger Things” with somber violin music and scenes bathed in muted tones. Marling stars as Prairie, who went missing for seven years as a girl and returned as an adult with her blindness mysteriously cured. After returning home to some intense public attention, a team of men questions Prairie about her disappearance, and she undergoes some kind of memory recovery therapy. In flashes, she’s also shown running through woods and fields, jumping off a bridge, and uncovering odd markings on her back. There’s a gun, blood, and an accident on a bridge.
Also appearing are Emory Cohen (Tony Fiorello in “Brooklyn”), Scott Wilson (Herschel Greene in “The Walking Dead”), Jason Isaacs (Lucius Malfoy in “Harry Potter”) and Phyllis Smith (Phyllis Vance in “The Office”).
So: What’s “The OA” about? We’re still not quite sure. Social media pages for the series offer only the most cryptic of hints.
On Instagram, images showing pills and people hooked up to machines are peppered with messages reading “This is a dream but you’re wide awake,” “I liked it better when you were blind,” “How do we fight the cold?” and “Which way is up?” | – Netflix is letting everyone unwrap an early Christmas present on Friday: an eight-episode series that has remained a virtual mystery. Time notes The OA—starring Brit Marling as a young woman who comes back to her family after vanishing seven years earlier—looks like it's going to meld "science fiction, mystery, and horror," but beyond that basic plot point, not much else is known about the show. The magazine says it may "scratch the itch" of fans of Stranger Things and Westworld while those shows are on break. Netflix's sparse description labels it a "powerful, mind-bending tale about identity, human connection, and the borders between life and death." More reaction from online: The Huffington Post tries to cull clues from social media, including Netflix's US Twitter account—cryptic tweets such as "Have you seen death?" are among the possible tells—the show's Facebook page, and the series' Instagram photos, which so far reveal a woman with a bloody nose, people hooked up to intricate-looking machinery, and messages like "Who did this to you?," among others. NME takes the Stranger Things comparison further, wondering if The OA is "part of the same universe" and comparing some of the new show's imagery to that of the former—even speculating that Marling's character could be an adult Eleven. Vanity Fair details the show's major players, including Marling and director Zal Batmanglij, who worked together on the movies The East and The Sound of My Voice. The show's Netflix page also mentions appearances from Jason Isaacs (Lucius Malfoy in the Harry Potter movies) and Brooklyn's Emory Cohen. The series' official trailer, which Time notes was released just this week as "a show of faith that this new offering doesn't need much hype to hook audiences." (Feel like watching or rewatching Stranger Things? You can now do that offline.) |
the cosmological principle requires that the universe be spatially homogeneous and isotropic in average on scales larger than the size of any structure @xcite .
observations show that the greatest structures ( filaments , voids , superclusters , ... ) have sizes around 400 mpc @xcite .
hence , at redshifts @xmath0 the matter distribution in the universe is anisotropic and inhomogeneous .
there are further supports ( both observational @xcite and theoretical @xcite ones ) that such structures exist also at redshift @xmath1 .
if the structures with sizes @xmath2 mpc are not distributed isotropically at @xmath3 , then some structures should exist even with sizes @xmath4 gpc . in other words , if this is the case , then the scale - where the averaging should be done - should be at least of order @xmath5 . in this case
the fulfilement of the cosmological principle would be in doubt .
the angular distribution of the gamma - ray bursts ( grbs ) allows to test this principle too , because - if this principle holds - grbs should be distributed isotropically on the sky , if they are dominantly at @xmath6 . for this test
it is convenient that grbs are well seen in the gamma - band also in the galactic plane . at the last years the authors provided several different tests probing the intrinsic isotropy in the angular sky - distribution of grbs collected in batse catalog ( for the survey and for further details
see @xcite ) . shortly summarizing the results of these studies
one may conclude : a.
the long subgroup ( @xmath7 ) seems to be distributed isotropically ; b. the intermediate subgroup ( @xmath8 ) is distributed anisotropically on the @xmath9% significance level ; c. for the short subgroup ( @xmath10 ) the assumption of isotropy is rejected only on the @xmath11% significance level ; d. the long and the short subclasses , respectively , are distributed differently on the @xmath12% significance level .
( about the definition of subclasses and other relevant topics see , e.g. , @xcite ; @xmath13 is the duration of a grb , during which time the @xmath14% of the radiated energy is received . )
because mainly the situation concerning the short grbs was unclear , we provided a new more powerful testing of the isotropy on the batse data .
we used three methods .
( the detailed description of these three methods with references is given in @xcite . )
the first one is the method called * voronoi tesselation ( vt)*. the voronoi diagram - also known as dirichlet tesselation or thiessen polygons - is a fundamental structure in computational geometry . generally , this diagram provides a partition of a point pattern ( `` point field '' , also `` point process '' ) according to its spatial structure , which can be used for analyzing the underlying point process .
the points on sphere may be distributed completely randomly or non - randomly ; the non - random distribution may have different characters ( clustering , filaments , etc . ) .
the second method is called * minimal spanning tree ( mst)*. contrary to vt , this method considers the distances ( edges ) among the points ( vertices ) .
clearly , there are @xmath15 distances among @xmath16 points .
a spanning tree is a system of lines connecting all the points without any loops .
the mst is a system of connecting lines , where the sum of the lengths is minimal among all the possible connections between the points . in our study
the spherical version of msf was used .
the @xmath17 separate connecting lines ( edges ) together define the minimal spanning tree .
the statistics of the lengths and the @xmath18 angles between the edges at the vertices can be used for testing the randomness of the point pattern
. the third method uses the * multifractal spectrum ( ms)*. the idea here is the following : let denote @xmath19 the probability for finding a point in an area of @xmath20 radius . if @xmath19 scales as @xmath21 ( i.e. @xmath22 ) , then @xmath23 is called the local fractal dimension ( e.g. @xmath24 for a completely random process on the plane ) . in the case of a monofractal @xmath23
is independent on the position .
a multifractal ( mfr ) on a point process can be defined as unification of the subsets of different ( fractal ) dimensions .
one usually denotes with @xmath25 the fractal dimension of the subset of points at which the local fractal dimension is in the interval of @xmath26 .
the contribution of these subsets to the whole pattern is not necessarily equally weighted , practically it depends on the relative abundances of subsets . the @xmath25 functional relationship between the fractal dimension of subsets and the corresponding local fractal dimension
is called the mfr or hausdorff spectrum .
the randomness of the point field on the sphere can be tested with respect to different criteria . since different non - random behaviors are sensitive for different types of criteria of non - randomness , it is not necessary that all possible tests using different measures reject the assumption of randomness .
we defined several test - variables which are sensitive to different stochastic properties of the underlying point pattern .
for vt any of the four quantities characterizing the voronoi cell - i.e. the area , the perimeter , the number of vertices , and the inner angles - can be used as test - variables or even some of their combinations , too .
we used three quantities obtained for mst : variance of the mst edge - length ( @xmath27 ) ; mean mst edge - length ( @xmath28 ) ; and the mean angle between edges ( @xmath18 ) . for the multifractal spectrum
the only used variable is the @xmath25 multifractal spectrum , which is a sensitive tool for testing the non - randomness of a point pattern .
together we had 13 variables , not being independent .
the significance levels were calculated by monte carlo simulations .
we divided the batse s grbs into three groups : @xmath29 ( @xmath30 ) , @xmath31 ( @xmath32 ) and @xmath33 ( @xmath34 ) . to avoid the problems with the changing detection threshold we omitted the grbs having a peak flux @xmath35 .
the bursts may emerge at very different distances in the line of sight and it may happen that the stochastic structure of the angular distribution depends on it .
therefore , we also made tests on the bursts with @xmath36 in the short and long population , separately .
all this means that we studied five samples : `` short1 '' with @xmath37 s and @xmath38 containing 261 grbs ; `` short2 '' with @xmath37 s and @xmath39 containing 406 grbs ; `` intermediate '' with @xmath40 and @xmath39 containing 253 grbs ; `` long1 '' with @xmath41 s and @xmath38 containing 676 grbs ; and `` long2 '' with @xmath42 s and @xmath39 containing 966 grbs .
vt of the short1 sample in galactical coordinates is shown on the figure .
* both the short1 and the short2 samples deviate significantly on the 99.90% and 99.98% significance levels from the full randomness . also the intermediate sample gave a significant deviation ( 98.51% ) from the full randomness in accordance with the earlier study @xcite .
the long samples remained random . *
the subgroups of grbs , detected by batse , show different sky distribution : both the short and intermediate ones are distributed anisotropically on a high significance level ; the long ones seem to be distributed isotropically .
the situation concerning the intermediate ones is unclear ( is it a physically different subgroup or not ? ) , but there is no doubt that the short and long ones are different phenomena . because the short ones are distributed anisotropically ( in addition - on large angular scales @xcite ) , * up to the redshifts - where the short ones dominate - the cosmological principle hardly can be fulfilled . *
the directly measured redshifts of the short grbs - detected by swift @xcite - suggest that just this happens up to @xmath1 ( see table 1 of @xcite ) .
it is not sure that the short grbs detected by batse , and the short grbs detected by swift together with measured redshifts are at the same redshift range .
but , even keeping in mind this eventuality , it is well possible * that the validity of the cosmological principle is in doubt at @xmath3 .
a support for this point of view was given by @xcite .
* note here that a similar sceptical points of view about the validity of the cosmological principle were claimed , too , from the studies of fully different topics @xcite .
this research was supported from otka grants t048870 and t077795 , by a gauk grant no.46307 , by the research program msm0021620860 of the ministry of education of the czech republic ( a.m. ) , and by a polnyi grant kfkt-2006 - 01 - 00012 ( p.v . ) . | after the discovery of the anisotropy in the sky - distribution of intermediate gamma - ray bursts recently also the distribution of the short gamma - ray bursts is proven to be anisotropic . the impact of these behaviors on the validity of the cosmological principle is shortly discussed .
address = charles university , prague , czech republic , [email protected] , address = konkoly observatory , budapest , hungary , [email protected] , address = etvs university , budapest , hungary , [email protected] , address = etvs university , budapest , hungary , [email protected] , |
takayasu arteritis ( ta ) , also known as aortoarteritis and pulseless disease , is a rare condition .
it is a form of granulomatous arteritis , which affects large- and medium - sized arteries , primarily the aorta and its large branches as well as proximal portions of pulmonary , coronary , and renal arteries .
initially , there are mononuclear cell infiltrations in the adventitia and granulomas with langerhans cells in the media , followed by disruption of the elastin layer and subsequent massive medial and intimal fibrosis
. these lesions result in segmental stenosis , occlusion , dilatation , and aneurysmal formation in the affected vessels .
ta is predominantly a disease of young adults in the second and third decades of life , but it has also been reported in childhood and in adults older than 40 years [ 20 , 28 , 44 ] .
the youngest patient described was 6 months old , and the oldest one was 75 years .
females are more likely to be affected than males . in adults approximately 80% of patients with ta
are women , although the female - to - male ratio varied from 9:1 in reports from japan , 6.9:1 in mexico to 1.2:1 in israel . in the pediatric population ,
a series of studies of ta in childhood from india and south africa report a 2:1 female - to - male ratio [ 16 , 46 ] .
although the disease has a worldwide distribution , the incidence is considered to be substantially greater in regions such as india and east asia than europe or north america . unfortunately , there are no worthwhile epidemiological studies from these supposedly high incidence countries to support this assertion . according to the published reports ,
the worldwide incidence of ta is estimated at 2.6 cases per million population per year .
the incidence of ta is estimated to be 2.6 persons per million population per year in minnesota olmsted county . however , the applicability of this number to the diverse population of the usa as a whole is uncertain .
the incidence in europe overall is reported at one case per million persons per year . in sweden
, the annual incidence is 1.2 per million , whereas in the united kingdom it is 0.15 case per million per year .
kerr et al . included about 30% of pediatric patients in their study and reported an incidence in all ages of 2.6 per million .
although patients with takayasu arteritis may present with numerous clinical manifestations , arterial hypertension is the most common feature of the disease in both adults and children [ 10 , 16 , 17 , 24 , 46 ] .
a 16-year - old caucasian girl was referred to our hospital due to elevated arterial blood pressure , which was detected by chance . upon admission ,
her body weight and height were 49 kg ( the10th percentile ) and 161 cm ( the 25th percentile ) , respectively , with a bmi of 18/kg / m .
however , weakness and fatigability of the upper left extremity were disclosed by a detailed history .
in addition , we found out that 2 years earlier , difficulties in measurement of blood pressure on her left arm had occurred .
her family history was unremarkable . on physical examination , there was no evidence of heart failure .
vascular bruits over the interscapular and right supra- and the subclavian areas were heard on auscultation .
the muscles of the upper left extremity were slightly atrophic , and their tone was decreased .
the pulse of the left external carotid artery and that of the left radial artery was absent .
the femoral pulses were present and equal . on admission , a significantly elevated systolic blood pressure 192/77 mmhg on the right arm was observed ( systolic blood pressure above 95th percentile for patient s age , gender , and height , and normal diastolic blood pressure ) , whereas the measurement of blood pressure on the left arm was difficult but was about 90/52 mmhg .
the blood pressure on right and left legs was 137/74 and 134/70 mmhg , respectively .
laboratory findings showed an elevated erythrocyte sedimentation rate ( esr ) of 46 mm / h ( normal value < 20 mm/1 h ) and serum c - reactive protein level of 1.13 mg / dl ( normal value < 0.5 mg / dl ) .
the rest of the laboratory investigations , including serum creatinine , electrolytes , autoantibodies , and urinalysis , were normal , as well as the ecg and chest x - ray .
on echocardiography , except for small mitral valve regurgitation , intracardiac anatomy abnormalities were not observed .
the left ventricular walls were not hypertrophied , the left ventricular internal diastolic dimension was 47.5 mm and remained within the normal range for the patients age and weight ( 37.554.7 mm ) .
dilatation of the ascending aorta and stenosis of the descending aorta were visible but without a significant poststenotic increase in blood flow velocity .
no prograde blood flow was observed in the left common carotid and in the left subclavian arteries .
1 and 2 ) showed a thickened thoracic aortic wall ( 2.74.5 mm ) and narrowing of its lumen .
the aortic measurements and z score date , according to kaiser et al . , were performed as presented in table 1 . on the basis of clinical manifestations and angiographic abnormalities ,
1spiral computed tomography angiography examination , cross - section slices presenting circumferential thickening of aortic wall . a level of aao and dao with slightly thickened wall of proximal section of pulmonary trunk ; b level of aortic arch with nonenhanced l ita ; c proximal sections of aortic arch branches with occluded l cca and l sca ; d widening of r va , lack of opacification of l va and l cca ( marked with arrows ) .
aao ascending aorta , aa aortic arch , dao descending aorta , bct brachiocephalic trunk , cca common carotid artery ( l left , r right ) , sca subclavian artery ( l left , r right ) , va vertebral artery ( l left , r right ) , ita internal thoracic artery ( l left , r right ) , pt pulmonary trunkfig . 2scta examination
thickened aortic wall with slightly narrowed lumen of dao ; b volumetric reconstruction view of branches of aortic arch with occluded l cca and l sca marked with arrowstable 1the results of scta examinationsites of measurementdiameter ( mm)z score ascending aorta293.87 first transverse segment20 second transverse segment19 the isthmic region141.87 the minimal diameter of the descending aorta84.77 ( below 3 percentile)abnormalities smooth external outline of the aorta , irregular internal outline , and laminar calcification in the ascending aorta wall thickened walls of brachiocephalic trunk , right common carotid artery proximal portion ( about 7 cm in length ) , and right subclavian artery proximal portion ( about 1 cm in length ) with narrowed lumina complete occlusion of the left common carotid artery and the left subclavian artery collateral circulation on the thoracic wall and parathyroid vessels slight thickening of the pulmonary trunk wall normal abdominal aorta and renal arteriesmeasurements and observed abnormalities spiral computed tomography angiography examination , cross - section slices presenting circumferential thickening of aortic wall .
a level of aao and dao with slightly thickened wall of proximal section of pulmonary trunk ; b level of aortic arch with nonenhanced l ita ; c proximal sections of aortic arch branches with occluded l cca and l sca ; d widening of r va , lack of opacification of l va and l cca ( marked with arrows ) .
aao ascending aorta , aa aortic arch , dao descending aorta , bct brachiocephalic trunk , cca common carotid artery ( l left , r right ) , sca subclavian artery ( l left , r right ) , va vertebral artery ( l left , r right ) , ita internal thoracic artery ( l left , r right ) , pt pulmonary trunk scta examination
thickened aortic wall with slightly narrowed lumen of dao ; b volumetric reconstruction view of branches of aortic arch with occluded l cca and l sca marked with arrows the results of scta examination measurements and observed abnormalities treatment with prednisone in the initial dose of 60 mg / day ( 1.3 mg / kg ) was introduced together with given orally methotrexate in a dose of 20 mg / m / week .
hypertension was treated using three medications namely : amlodipine ( 10 mg / day ) , hydrochlorothiazide ( 12.5 mg twice a day ) , and carvedilol ( 6.25 mg twice a day ) .
after 3 months , the dose of prednisone was gradually tapered to 10 mg / day .
initially the hypertension was not well controlled , so the option of stenting of the descending thoracic aorta had also been considered .
but due to the fact that nonspecific markers of inflammation were elevated and this girl had never been treated before , she was qualified for continued medical treatment . at present , under treatment , her blood pressure on the right arm varies between 123/70 and 140/96 mmhg and there is no pressure difference between her right arm and legs . in laboratory tests ,
c - reactive protein is only slightly elevated 0.67 mg / dl , esr is 17 mm / h .
moreover , an scta examination after a couple of months revealed a similar range of inflammatory changes within the aorta but the thickness of the infiltration had been reduced .
the patient is currently under a long - term clinical surveillance by a cardiologist , rheumatologist , nephrologist , and psychologist .
although our knowledge of ta has considerably improved over the last decade , the etiology and pathogenesis of this disease still remain controversial .
several etiologic factors have been proposed , including spirochetes , mycobacterium tuberculosis , streptococci , circulating antibodies due to an autoimmune process , and genetic aspects .
one hypothesis states that an antigen deposited in vascular walls activates cd4 + t cells , followed by the release of cytokines chemotactic for monocytes .
these monocytes are transformed into macrophages that mediate endothelial damage and granuloma formation in the vessel wall .
human studies , suggesting endothelial cell activation , have demonstrated increased expression of intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 in patients with ta .
antimonocyte antibodies and anti - endothelial cell antibodies are present in patients with ta and correlate with disease activity .
genetic susceptibility to ta has been extensively studied . a significant association with hla b-52 and dr-2
was demonstrated in japanese patients , but this finding was not confirmed in the western countries [ 28 , 39 ] . rarely has ta also been associated with other autoimmune diseases such as glomerulonephritis , systemic lupus erythematosus , juvenile idiopathic arthritis , anterior uveitis , sarcoidosis , seronegative spondyloarthropathy , crohn s disease , wegener s granulomatosis , sweet syndrome , and ulcerative colitis , which may indicate immune mechanisms in the pathogenesis [ 1 , 6 , 9 , 18 , 33 , 34 , 40 , 43 , 51 ] .
considering arterial lesion location , on the basis of angiographic findings , ta is divided into six types ( table 2).table 2angiography - based categoriestypethe vessels involvedtype ibranches of the aortic archtype iiaascending aorta , aortic arch , and its branchestype iibtype iia region and thoracic descending aortatype iiithoracic descending aorta , abdominal aorta , and/or renal arteriestype ivabdominal aorta and/or renal arteriestype ventire aorta and its branches angiography - based categories there are some differences in the sites affected by inflammatory process among different ethnic groups .
japanese patients with ta have a higher incidence of aortic arch involvement , whereas in patients from korea , india , and western countries , the abdominal aorta and renal arteries are most frequently affected .
the clinical course of the disease is divided into an early active inflammatory phase and late chronic phase .
the active phase lasts for weeks to months and may have a remitting and relapsing course .
it is characterized by systemic disease with symptoms of fever , general malaise , night sweats , loss of appetite , weight loss , headaches , dizziness , arthralgia , skin rashes , etc .
the acute phase does not occur in all patients , but constitutional symptoms are often seen in children with ta .
it should be highlighted that the correct diagnosis of ta is seldom made in the early phase .
evidence of vessel inflammation such as tenderness along arteries , bruits , and aneurysm may point to the diagnosis of ta .
the late chronic phase is the result of arterial stenosis and/or occlusion and ischemia of organs .
its clinical manifestations are varied and related to the location of arterial lesions [ 28 , 39 ] , as presented in table 3.table 3clinical features of takayasu arteritis related to ischemiathe vessels involvedclinical features1 .
aortic branchesmalaise , decreased or absent pulse of upper extremities , dysfunction of upper extremities , headaches , dizziness , vision and orientation disturbances , syncope [ 25 , 48]2 .
aortic archcongestive heart failure , aortic valve insufficiency , arterial hypertension [ 13 , 14 , 29]3 . coronary arteriesischemic heart disease , myocardial infarction [ 4 , 11]4 .
abdominal aorta or celiac trunkischemia of the stomach and intestines , abdominal pain , nausea , vomiting 6 .
renal arteriesarterial hypertension , chronic renal failure [ 5 , 7 , 15 ] clinical features of takayasu arteritis related to ischemia it should be remembered that , although ta has been described in patients of all races , reports of caucasian patients in europe are infrequent .
therefore , key data concerning the condition , both in adults and in children , come from experience in asian as well as south african and south american countries . at present
, ta in children is diagnosed on the basis of the criteria proposed by european league against rheumatism
pediatric rheumatology international trials organization pediatric rheumatology european society , ankara 2008 , presented in table 4.table 4the diagnostic criteria for takayasu arteritis in childrenthe mandatory criterion the presence of an angiographic abnormality , i.e. , aneurysm / dilatation , narrowing , occlusion or thickened arterial wall not due to fibromuscular dysplasia and shown by conventional angiography , spiral computed tomography angiography or mra of the aorta or its main branches and pulmonary arteriesin addition to the mandatory criterion , at least one of the five following criteria must be met : pulse deficit ( lost , decreased , unequal ) or claudication ( focal muscle pain induced by physical activity ) discrepancy of four limb systolic blood pressure > 10 mmhg difference in any limb audible vascular bruits or palpable thrills over large arteries arterial hypertension ( systolic and/or diastolic blood pressure greater than 95th centile for patient s age , gender , and height ) elevation of acute phase reactant ( erythrocyte sedimentation rate > 20 mm per first hour or serum c - reactive protein of any value above normal according to the local laboratory ) the diagnostic criteria for takayasu arteritis in children in our patient , all the above - mentioned criteria were met . on the basis of the scta examination , ta of type iib , with pulmonary trunk involvement , was recognized . in our patient case ,
the onset of her disease was undetectable , and severe systolic arterial hypertension , which was revealed accidentally , was the predominant clinical manifestation .
pathogenesis of arterial hypertension due to ta is complex , multifactorial , and not fully understood . at present , it is thought to be the result of three mechanisms : ( a ) mechanical , in which hypertension proximal to narrowed aorta(atypical coarctation ) is due to high resistance to cardiac output imposed by narrowing ; ( b ) neural , in which hypertension proximal to narrowed aorta results from aortic arch baroreceptors readjustment and this allows to ensure adequate blood supply to organs distal to narrowed aorta ; and ( c ) hormonal , in which hypertension is caused by renal hypoperfusion due to stenotic lesions of one or both renal arteries or aorta alone [ 12 , 39 ] . a decrease in elasticity of arterial walls observed in ta may also contribute to the elevation of the blood pressure . in our patient
, systolic arterial hypertension seemed to result from narrowing of thoracic aorta , renal ischemia , and probably aortic arch baroreceptors hyposensitivity .
it should be emphasized that in ta , blood pressure may be over- or underestimated because alternation in wave pulse propagation occurs when cephalad arteries of the aortic arch and both subclavian arteries are affected .
the clinical spectrum at presentation of children with takayasu arteritis differs from that of adults . however , hypertension is the most common sign in both groups .
the clinical studies in three large series of pediatric cases from mexico , india , and south africa have revealed that systemic symptoms are seen in a high proportion of children with ta .
the usual presenting symptoms are due to hypertension , heart failure , or a neurological event .
claudication , bruit , and a missing pulse in an asymptomatic child are uncommon presentations , although those symptoms were present in our patient and they were crucial for establishing the diagnosis .
while the intra - arterial angiography still remains the standard for diagnosis and evaluation of takayasu arteritis , it has been largely replaced by computed tomography angiography or magnetic resonance angiography ( mra ) .
these techniques , in addition to visualizing the arterial lumen , may provide valuable information about inflammation in the arterial wall and periarterial structures .
this might facilitate the diagnosis of ta at an early stage , in which arterial wall thickening is present and the lumen diameter is preserved [ 3 , 42 ] .
the other investigative modalities , such as gallium-67 radionuclide scanning and positron emission tomography utilizing 18f - fdg , are currently in vogue when evaluating such patients [ 8 , 31 ] , although they are not widely available yet .
it should be emphasized that despite the significant advance in noninvasive imaging modalities over past decade , detailed medical history and thorough physical examination still remain important for clinical diagnosis .
treatment of ta is based on the use of immunosuppressants such as prednisone and/or methotrexate to decrease or eliminate inflammatory activity .
alternative therapies such as azathioprine , cyclophosphamide , mycophenolate mofetil , and tacrolimus hydrate are also used in ta , especially for corticosteroid - resistant disease [ 8 , 20 , 28 , 39 ] .
hypertension should be treated aggressively often with multidrug regimen , but pediatricians should be warned against ace inhibitors until renal artery stenosis has been excluded . in the presence of symptomatic stenotic or occlusive lesions ,
endovascular revascularization procedures like bypass grafts , patch angioplasty , endarterectomy , percutaneous transluminal angioplasty , or stent placement should be taken into consideration [ 15 , 49 , 50 ] .
the status of such treatment is controversial in the literature . despite providing short - term benefit , endovascular revascularization procedures
published results suggest that these procedures should be undertaken with great care and be reserved for specific indications .
both , surgical and endovascular , treatments become risky and achieve poorer outcomes , if they are undertaken during a period of inflammatory activity [ 31 , 36 , 47 ] .
the 5-year survival rate in adults is as high as 94% . the mortality rate in children ,
increasing knowledge of the pathogenesis of takayasu arteritis might eventually lead to novel - targeted therapies , such as antitumor necrosis factor agents .
although early diagnosis holds the key to improved outcome , a novel biological approach to treatment might prove more effective and be potentially less toxic than the immunosuppressive regiments used at present [ 31 , 38 ] . | we report a 16-year - old girl in whom takayasu arteritis ( ta ) was manifested mainly by severe arterial hypertension on her right arm , which was detected during a routine examination at school .
her systolic blood pressure on the right arm was significantly higher than that on the left one .
there was also a pressure difference between the right arm and legs .
the pulse of the left external carotid artery and that of the left radial artery was absent .
vascular bruits over interscapular and right supra- and subclavian areas were heard on auscultation .
the diagnosis of ta was confirmed by a spiral computed tomography angiography , which showed a thickened thoracic aortic wall and narrowing of its lumen .
in addition , complete occlusion of the left common carotid artery and the left subclavian artery was observed .
conclusion : the rarity of the disorder and the heterogeneous nature of its clinical manifestation predispose to a late diagnosis and delayed treatment .
our report highlights the fact that the condition can and does occur in a pediatric population in europe and hence must be considered in patients presenting with suggestive symptoms and signs , especially in young patients with unexplained hypertension . clinical suspicion and proper imaging
are crucial for the correct diagnosis and management of patients with ta .
a brief review of literature completes this report . |
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Zuma Press Madonna is one of the most controversial musicians of all times. ||||| It’s not surprising that “Carol” was locked away in Hollywood’s development closet for 15 years. Based on Patricia Highsmith’s scandalous 1952 novel “The Price of Salt,” Todd Haynes’ latest movie is a double whammy by industry standards: it’s headlined by two women, who fall in love with each other.
The film, which stars Cate Blanchett and Rooney Mara, and premieres at the Cannes Film Festival on May 17, arrives at a pivotal, yet paradoxical, time for female-driven stories. There has been a string of hits this year that celebrate female empowerment — from “Insurgent” and “Fifty Shades of Grey” to “Cinderella,” and the upcoming “Trainwreck,” “Spy” and the final installment of “The Hunger Games.” That said, gender inequality both in front of and behind the camera is a hot-button issue in the global entertainment business.
As one of cinema’s most prominent stars, Blanchett, whose recent roles include the evil stepmother in “Cinderella,” doesn’t want Hollywood to wait for Prince Charming to save the day. “We have to push forward,” says the 45-year-old Australian actress, who believes successful women are finally starting to nurture projects for females. “What industry has parity pay for women? None. Why would we expect this industry to be any different?” She says the dominance of male stories on the bigscreen is bad business. “It’s not serving the audience,” she explains. “People want to see good films. We should have equal access to the multiplexes.”
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On a recent afternoon in Manhattan, lounging outside the Crosby Street Hotel with her hair in a ponytail and a shawl draped over her shoulders, Blanchett says she wasn’t convinced that “Carol” would ever make it to theaters. “It was so hard,” she recalls. “Midrange films with women at the center are tricky to finance. There are a lot of people laboring under the misapprehension that people don’t want to see them, which isn’t true.” And while the franchise-obsessed movie industry covets young male audiences above all else, it can no longer ignore female moviegoers — who account for at least half of ticket sales each year.
Blanchett believes there is some hope. “I think there’s been a critical mass of women who have reached a certain place in the industry,” she says, citing Meryl Streep, Reese Witherspoon and Nicole Kidman, as well as producer Allison Shearmur, who made the Disney fairy tale about a magical glass slipper a reality. “I want it to not be discussed anymore,” Blanchett notes. “But it needs to be discussed.”
Blanchett was delighted when she received a call in 2013 from her old pal Haynes (“I’m Not There”), telling her he wanted to make “Carol,” after a series of directors had dropped out. The drama centers on a charismatic New Yorker (Blanchett) who embarks on a passionate love affair with a younger department store clerk, Therese (Mara).
The indie production, which was financed by Film4 and Goldcrest Films, and was filmed in a Cincinnati outfitted to look like 1950s New York, wrapped in only 35 days in April 2014. “We shot in these old homes that felt like tombs,” Blanchett says. “The atmosphere of the city really added to the atmosphere of the film.” But after various cuts were shown to test audiences, the movie (scheduled for a late 2015 release from the Weinstein Co.) went into hibernation.
If “Carol” works, it could earn Blanchett a seventh Oscar nomination (she’s already won two Academy Awards, for 2004’s “The Aviator” and 2013’s “Blue Jasmine”). But if it stumbles, it may be perceived as yet another example of the curse of the gay love story.
When Highsmith first published “The Price of Salt,” she used a pseudonym to protect herself from public outcry. These are very different times, but Hollywood still hasn’t caught up. “Brokeback Mountain” debuted 10 years ago, and there have been few breakthrough gay romances since. Even the past summer’s enthusiastically reviewed “Love Is Strange,” starring Alfred Molina and John Lithgow as a couple, eked out only $2.3 million at the domestic box office.
Haynes, who directed Dennis Quaid’s closeted husband character in “Far From Heaven,” says the focus on gay stories has shifted more to TV. “In some ways, the event of a gay love story is less surprising every day,” Haynes says. “But I think love stories are hard to pull off, period. They require external forces that keep the lovers apart.” Elizabeth Karlsen, who produced “Carol,” adds: “I hope it’s a film for everyone. And certainly when we’ve screened it, we’ve found young and old, male and female, straight and gay, have all responded.”
Blanchett was a celebrated Australian stage actress before she was cast in Shekhar Kapur’s 1998 drama “Elizabeth.” Kapur recalls interest from a variety of A-list actresses — including Gwyneth Paltrow and Kidman — in playing the virgin queen, but from the moment he saw a clip of Blanchett, he knew she was fated to assume the throne. “Cate Blanchett was destined to break upon the international screen, and I was her conduit,” Kapur says. He recalls how a young Blanchett would beat herself up after takes, saying that she hadn’t quite landed a scene.
That trait evidently still persists some 50 movies later. “There are days when she’s frustrated by her own work,” Haynes says. “We don’t know what she talking about, but she’ll say, ‘I need to take an acting pill today. It’s not working.’ ” Blanchett doesn’t like to talk about her how she prepares for a role. “Do I have a process?” she asks. “I don’t know. There are certainly things perhaps that I don’t want to identify.”
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Until recently, she ran the Sydney Theatre Company in Australia with her husband, Andrew Upton, and she’d criss-cross between stage and screen roles such as “The Monuments Men,” “The Curious Case of Benjamin Button,” and the “Hobbit” and “Lord of the Rings” trilogies, in which she portrayed the elf Galadriel.
When asked if this is her first turn as a lesbian, Blanchett curls her lips into a smile. “On film — or in real life?” she asks coyly. Pressed for details about whether she’s had past relationships with women, she responds: “Yes. Many times,” but doesn’t elaborate. Like Carol, who never “comes out” as a lesbian, Blanchett doesn’t necessarily rely on labels for sexual orientation. “I never thought about it,” she says of how she envisioned the character. “I don’t think Carol thought about it.” The actress studied the era by picking up banned erotic novels. “I read a lot of girl-on-girl books from the period,” she says.
The other book on Blanchett’s shelf was “The Private Life: Why We Remain in the Dark,” by psychoanalyst Josh Cohen, which she found relevant on many levels. She describes Carol as “unknowable,” but she could just as easily be talking about herself. Unlike many celebrities today, she treasures her privacy.
For example, she says she’ll never join Twitter. “I think I’d end up in rehab,” she jokes. “That stuff is addictive.” She doesn’t Google herself either. She finds out she’s made headlines when she walks her kids to school and the crossing guard tells her, “What they said about you — that was terrible!” Blanchett realizes we live in a society of snoops. “We need to get into people’s private lives now,” she says. “If they are hiding something, they are dishonest.”
She eventually offers some details about how she unlocked her latest character. Blanchett turned to the film’s costume designer, Sandy Powell, for help. “We asked, ‘What is the most erotic part of the body?’” Blanchett says. “We kept saying that wrists are really erotic. The neck. The ankles. The way Highsmith writes, she’s got this exquisite observation of detail that most people would miss, but a lover’s eye never would. We talked a lot about erogenous zones.”
One of the most memorable scenes in the novel takes place in a hotel room, when the women consummate their love for the first time. The scene appears in the film too, though it isn’t overtly racy. “It’s not ‘Blue Is the Warmest Color,’ ” Blanchett says. “That’s not the ambition of the film.”
Screenwriter Phyllis Nagy had always been a Highsmith fan. As a researcher at the New York Times Magazine in the late ’80s, she finally met her literary idol when Highsmith was commissioned to write a walking tour of Brooklyn’s Green-Wood Cemetery, and Nagy tagged along. The two struck up a friendship through letters and occasional visits — Highsmith would write to her from Switzerland, where she spent her final years. She even suggested Nagy make one of her books into a movie, a daunting proposition, because Highsmith loathed all adaptations of her work, including the 1951 Hitchcock classic “Strangers on a Train.” (She died in 1995, four years before the release of “The Talented Mr. Ripley,” in which Blanchett co-stars and first discovered Highsmith.)
Around 2000, a producer from Film4 had acquired the rights to “Carol,” and asked Nagy to work on an adaptation. The writer had a distinct take. “To me, Carol was very much like Grace Kelly in ‘Rear Window,’ ” she says. “There’s a sexuality beneath the cool.” She cranked out a first draft in 10 weeks, and spent the next decade working on roughly 10 revisions. “People came and went,” Nagy says. “Various directors were attached and unattached,” including Kenneth Branagh and John Maybury.
The rights eventually lapsed, and returned to the Highsmith estate. That’s when producer Karlsen at Number 9 Films decided to chase after them. The pursuit took her all the way to Zurich, where she had to arrange for an in-person meeting with publishing house Diogenes to make her case that she’d actually get the movie finished. “It’s not a coincidence that I’m a female producer,” Karlsen says. “I have three daughters, and that puts me in tune with the paucity of great female roles. It’s almost by osmosis that you’re drawn to them.”
Steven Chee for Variety
The “Carol” team underwent one more round of musical chairs before the cameras rolled. Blanchett was always interested in starring, and director John Crowley (“Brooklyn”) boarded the project, and tried to lure Mara to play Therese, but she had just completed “The Girl With the Dragon Tattoo” and passed.
“I didn’t think I could play the part,” Mara says. “So I turned it down, which is insane to me now, because working with Cate has always been a dream.”
Then Crowley had to bail due to scheduling, and producer Christine Vachon suggested Haynes, who was available. “I felt there was something exciting about the festering interiority of a person falling in love,” says the director, who shot the movie in 16mm (the look was inspired by the photography of Vivian Maier).
Haynes and Blanchett were glad to be reunited, and Mia Wasikowska was cast as Therese, but she too had to drop out due to a conflict. Haynes went back to Mara, who agreed to take the part this time. With all the near misses, Nagy believes Haynes was always meant to direct “Carol.” “Happily, we saved the best for last,” she says.
Blanchett is no stranger to Cannes. She first attended the festival in 1997, as an up-and-coming actress who used her connections to land a ticket to the premiere of Ang Lee’s “The Ice Storm.” She returned in 1999, with “An Ideal Husband,” in which she played Lady Gertrude Chiltern. “It was like night and day, walking down the Croisette on star Rupert Everett’s arm,” Blanchett recalls. “I was laughing so hard, because only two years earlier, I’d been on the other side of the barricades.”
Other trips to the festival would follow, for films including 2006’s “Babel.” But it was 2008’s out-of-competition screening for “Indiana Jones and the Kingdom of the Crystal Skull,” in which she plays a villainous Soviet agent opposite Harrison Ford, that drew the biggest crowds. “I’d never seen so many people,” she marvels. “It was like Harrison was the pope.” Last year, she returned with “How to Train Your Dragon 2,” for which she voiced Valka, Hiccup’s mom.
Though she is considered one of the greatest modern screen actresses, Blanchett doesn’t like to watch herself in movies. “I never think I have it,” she says. “Maybe that’s why I keep working.” She’ll often calm herself by imagining that nobody will ever see the movie she’s making, but that didn’t work when she boarded “The Aviator” as Katharine Hepburn, given the high profiles of director Martin Scorsese and co-star Leonardo DiCaprio. She had a ball on set, but when she saw the finished film, she wasn’t satisfied with her performance. “I was filled with disappointment and regret,” admits the actress, who has starred in plays such as “A Streetcar Named Desire,” “Hedda Gabler” and Chekhov’s “Uncle Vanya.” “That’s what I love about theater — you can try to improve what happened the night before.”
The Blanchett-Uptons are planning to move soon from Sydney to either New York or San Francisco. But first, she is in Manhattan for a quick visit before Cannes to reshoot a scene for “Truth,” about Dan Rather’s last days at CBS, in which she stars with Robert Redford. She’s also completed back-to-back Terrence Malick projects, filming for four days on “Knight of Cups,” and then two weeks on “Weightless,” a film for which she had to pseudo-improvise. “Terry would write reams and reams of poetry, and he’d give it to you in the morning,” says Blanchett, who told the director she couldn’t memorize all those lines that quickly. So he’d read her the dialogue in an earpiece. “You’d say what you heard or misheard,” Blanchett says.
She hasn’t seen either of those films, but Haynes showed her an early cut of “Carol” last August. “The visuals surprised even me,” Blanchett says. “I somehow was expecting something more familiar.” If Carol lived today, she couldn’t see her marching in a gay pride parade. “Her sexuality isn’t politicized,” Blanchett says. “I think there are a lot of people that exist like that who don’t feel the need to shout things from the rafters.” She says the movie captures the spirit of Highsmith’s prose. “Her stories, her characters, the texture that she writes are so slippery,” Blanchett says. “It was no surprise to me that it was a tricky thing to get made.” | – In Carol, debuting at Cannes Sunday, Cate Blanchett plays a woman who gets romantically involved with another woman. In an extensive Variety interview about the film, asked whether this is Blanchett's "first turn as a lesbian," the actress replied, "On film—or in real life?" But don't expect to get details out of her: Asked, then, if she'd "had past relationships with women," all Blanchett said was, "Yes. Many times." And, who knows, she may not even refer to those relationships as "lesbian" ones—her character never comes out as a lesbian, and Blanchett says she "never thought about" labels and doesn't think the character did, either. (Click through for 30 stars who've identified as bisexual.) |
cinacalcet hydrochloride is a new class of drugs for the treatment of severe secondary hyperparathyroidism in haemodialysis patients .
it has also been reported that successful suppression of parathyroid hormone ( pth ) levels results in a decrease in serum markers for bone formation . here , we report a case of a dialysis patient presenting with severe hyperparathyroidism , who was treated with cinacalcet hydrochloride . without significant suppression or further increases in pth levels , marked and progressive increases in serum markers for bone formation were observed .
bone histology did not support the development of hungry bone syndrome , as was presumed in previous cases .
a 59-year - old female with diabetic nephropathy was referred to our hospital for bone pain .
she had severe hyperparathyroidism ( whole pth level , 904 pg / ml ; normal , 939 pg / ml ) with a single enlarged parathyroid gland ( 16 mm 15 mm 19 mm ) .
although intensive intravenous vitamin d receptor activator ( vdra ) treatments were performed several years ago , secondary hyperparathyroidism progressed .
although 22-oxacalcitriol ( oct ) was administered at a dose of 2.5 g twice a month since january 2007 , oct was stopped in august 2007 .
because of the progression of secondary hyperparathyroidism , oct was started again at a dose of 10 g once a week since october 2007 .
although calcium carbonate was administered at a dose of 1.5 g / day , no phosphate binder was administered since january 2007 .
while planning a surgical parathyroidectomy that was scheduled to be conducted in the near future , cinacalcet hydrochloride was started at a dose of 25 mg / day and was finally increased to 75 mg / day .
cinacalcet hydrochloride therapy induced a mild decrease in the patient 's serum calcium and phosphate levels .
pth levels also decreased slightly , whereas serum alkaline phosphatase ( alp ) levels ( normal : 109321
iu / l ) increased significantly and progressively after the start of cinacalcet treatment , as shown in figure 1 .
serum bone - specific alkaline phosphatase ( bap ) levels also significantly increased from 295 u / l to 995 u / l ( normal : 9.635.4
there was no difference in bone scintigraphies obtained before and after 3 months of initiating cinacalcet therapy .
on the other hand , serum bone resorption marker type i collagen cross - linked n - telopeptide ( ntx ) levels were significantly high ( 1058.4 nmol
. change of serum alp , pth , calcium and phosphate levels before and after the administration of cinacalcet hydrochloride .
four glands were removed and the smallest gland that weighed 100 mg was autotransplanted into the forearm . during the operation ,
an iliac bone biopsy was performed before removing the parathyroid tissue to identify the cause of elevation of serum alp and bap levels . the bone biopsy specimen demonstrated osteitis fibrosa ( fibrosis volume / tissue volume 21.4% ) and defective mineralization ( osteoid volume / bone volume 29.1% ) ( figure 2a ) . with regard to bone formation parameters ,
osteoblast surface / bone surface ( bs ) increased ( 25.3% ) . the bone formation rate ( bfr)/bs also increased to 0.094 m / m / year ( normal : 0.015 0.008 m / m/ year ) .
multinucleated osteoclasts resorbing mineralized bone were observed , in contrast to the mechanisms observed in hungry bone syndrome after parathyroidectomy ( figure 2b ) .
( villanueva goldner stain , 40 ) ( b ) multinucleated osteoclasts ( arrows ) resorbing mineralized bone .
serum alp levels decreased slowly and returned to a normal range at 6 months after parathyroidectomy . at that time , serum calcium levels were 8.5 mg / dl , serum phosphate levels were 3.8 mg / dl and serum whole pth levels were 25.1 pg / ml .
cinacalcet hydrochloride reduces serum pth levels by direct action in the parathyroid calcium - sensing receptor , therefore decreasing bone formation markers in haemodialysis patients .
nevertheless , in a recent report of a clinical trial , it has been shown that serum bap levels increase early after the start of cinacalcet treatment .
this temporary increase of bap was assumed to be a result of hungry bone syndrome without a bone biopsy .
although the development of hungry bone syndrome by cinacalcet was previously reported in two reports , the authors failed to describe the changes in bone formation markers after the administration of cinacalcet .
typical hungry bone syndrome develops after surgical parathyroidectomy and is characterized by hypocalcaemia and a temporary increase in bone formation .
bone histology of this particular case did not support the development of hungry bone syndrome seen after parathyroidectomy . in the present case ,
neither the progression of hyperparathyroidism nor the sudden decrease of pth level , as in spontaneous infarction , was observed during cinacalcet treatment .
we could not find any evidence of bone fracture by x - ray or in changes of bone scintigraphies .
although we could not completely rule out the possibility of microfractures , we hypothesized that bone formation is possibly enhanced as a result of cinacalcet treatment by unknown mechanisms .
we failed to demonstrate the pathomechanism of a bone biopsy clearly because the bone biopsy specimen was taken only at the end of the cinacalcet treatment and not prior to treatment .
therefore , cinacalcet induces daily fluctuation of serum pth levels , which differs from vdra treatments .
as previously reported , pth ( 134 ) has different effects on bone mass when administrated by intermittent injections or by continuous infusion .
furthermore , it has been suggested that intermittent decreases in serum pth levels by oral administration of calcimimetics have an anabolic - like effect on the bones , whereas continuous suppression of pth by calcimimetics infusion does not have a similar effect .
therefore , we conclude that daily fluctuations of pth , as induced by cinacalcet treatment , may have promoted bone formation .
it has been shown that high extracellular ionized calcium concentration stimulation induces mitogenic action of osteoblasts via calcium - sensing receptors . however , the calcium - sensing receptor in osteoblasts may be different from parathyroid .
therefore , further studies will be necessary to clarify whether cinacalcet has direct effects on osteoblasts .
hypovitaminosis d probably induced defective mineralization because serum vitamin d levels at bone biopsy were low [ 1,25(oh)2d3 level , 5.6 pg / ml ; normal , 2060 pg / ml : 25(oh)d3 level , 21 ng / ml ; normal , 741 ng / ml ] . however , since hypovitaminosis d may be recognized before the start of cinacalcet treatment , the significance of hypovitaminosis d for bone formation markers in this case is unclear . in summary , we have reported a case with a marked increase of serum markers for bone formation due to cinacalcet treatment . the mechanism responsible for bone formation was distinct for hungry bone syndrome . | a 59-year - old female who was on dialysis due to diabetic nephropathy was referred to our hospital for severe hyperparathyroidism refractory to intravenous vitamin d receptor activator treatment . with subsequent cinacalcet hydrochloride treatment ,
parathyroid hormone ( pth ) levels were only slightly suppressed . however , progressive increases were observed in serum alkaline phosphatase ( alp ) and bone - specific alkaline phosphatase ( bap ) levels with mild hypocalcaemia .
a bone biopsy , obtained immediately before surgical parathyroidectomy after 3 months of cinacalcet treatment , revealed no disappearance of osteoclasts .
these data suggest that cinacalcet hydrochloride treatment may induce a marked promotion of bone formation by mechanisms distinct from hungry bone syndrome that usually develops after parathyroidectomy . |
there is a long history to chiral symmetry breaking .
it began with cvc and the goldberger - treiman relation @xcite , and proceeded through the ground - breaking work of gell - mann and l ' evy who invented pcac and the linear and non - linear @xmath0 models @xcite .
their lagrangian began from chiral symmetry in the sense that both @xmath5 and @xmath0 fields appear on an equal footing , but the symmetry between them is spontaneously broken by introducing a negative @xmath6 term .
adler @xcite showed that in both @xmath7 and @xmath8 systems there is a zero at the unphysical point @xmath9 midway between the thresholds of @xmath10 and @xmath11 channels .
` soft ' pion theory , current algebra and qcd led to the standard model . with the idea that ` bare ' quarks are almost massless , gasser and leutwyler introduced chiral perturbation theory as a systematic method of expanding amplitudes in the domain where pion masses and momenta are small @xcite . the s - wave elastic scattering amplitude may be written @xmath12 where @xmath13 is the usual phase space factor .
the numerator @xmath14 is real and describes ` driving forces ' from the left - hand cut .
unitarity is accomodated by means of the @xmath15-matrix .
the adler zero in the @xmath8 amplitude makes the s - wave unusual .
when one projects out the s - wave from the full amplitude , there is a zero at @xmath16 .
the amplitude near the @xmath8 threshold rises nearly linearly .
the simplest acceptable form is @xcite @xmath17,\ ] ] where @xmath18 , @xmath19 and @xmath20 are constants ; the exponential makes @xmath21 as @xmath22 but introduces non - linearity in a controlled way . above the @xmath4 threshold @xmath23.\ ] ] a similar approach has been used by pelaez , oset and oller @xcite @xcite in a series of papers building chiral symmetry breaking into fits to data . during the era 1975 to 1995 , many theorists fitted the @xmath8 s - wave in ways similar to this and found a pole with mass roughly 500 mev and a large width @xmath24 500 mev . in elastic scattering ,
the adler zero in the numerator makes the amplitude small near the @xmath8 threshold .
however , in a production process , the numerator need not contain the adler zero , and is in fact consistent within rather small errors with a constant .
the @xmath0 pole appeared clearly in e791 data on @xmath25 @xcite and bes data on @xmath26 @xcite .
both sets of data show a conspicuous peak visible by eye at @xmath27 mev .
1 shows the dalitz plot and mass projections for bes data .
there are conspicuous diagonal bands due to the @xmath0 and @xmath28 and vertical / horizontal bands due to @xmath29 .
the @xmath8 mass projection is shown in ( b ) and the @xmath0 component in ( d ) .
those data may be fitted simultaneously with elastic scattering data ; bes found a pole at @xmath30 mev .
[ htb ] -12 mm -51.5 mm since 2004 , couplings to @xmath4 and @xmath31 have been determined by fitting ( a ) all available data on @xmath32 and @xmath31 , ( b ) kloe and novosibirsk data on @xmath33 @xcite .
all these data agree on a substantial coupling of @xmath0 to @xmath4 .
a further refinement is to include in the breit - wigner denominator a dispersive correction @xmath34 ( discussed below ) .
the @xmath0 pole moves to @xmath35 mev .
there was some debate whether the peak could be due to interference with a ` background ' .
however , bes data give a phase variation with @xmath10 consistent with elastic scattering and hence a simple pole @xcite . secondly
, caprini et al . calculated a prediction from the roy equations and driving forces on the left - hand cut @xcite .
the great merit of this calculation is that it maps out the magnitude and phase of the s - wave amplitude over the whole of the low mass region of the complex @xmath10-plane , including the sub - threshold region inaccessible to experiment .
this leaves no possible doubt of the existence of the pole and gives a pole position @xmath36 mev .
however , the result for @xmath37 does not reproduce accurately the upper side of the @xmath0 peak in bes data .
a combined fit to their predictions and bes data using @xmath38 instead of @xmath18 in eq .
( 2 ) gives @xmath39 mev without departing from their predicted phases by more than @xmath40 @xcite .
understanding the @xmath0 pole requires some gymnastics in complex variables .
it lies at @xmath41 gev@xmath42 , not too far above the @xmath8 threshold but far into the complex plane .
the phase shift is @xmath43 just above the pole .
but on the real @xmath10-axis where experiments are done , the phase shift must go to 0 at the @xmath8 threshold .
there is therefore a strong variation of the phase as one moves into the complex plane .
this arises directly from the cauchy - riemann equations : the adler zero gives a real part of the amplitude rising nearly linearly with @xmath10 at low mass , and there must be a corresponding variation of the imaginary part of the amplitude with @xmath44 . roughly speaking , the pole would give rise to a phase shift approaching @xmath45 at 1 gev , but the effect of unitarity is to distort the phase observed on the real @xmath10-axis to @xmath43 at 1 gev .
for the @xmath1 , the effect is even larger .
the @xmath1 pole lies almost below the @xmath46 threshold and is very broad .
the consequence is that the phase shift measured on the real @xmath10 axis only reaches @xmath47 at 1400 mev / c . at the hadron95 conference ,
mike scadron asked me if there could be a @xmath1 resonance below 1 gev . at the time , the only reply which could be given was that it must be very broad if it exists at all .
later , zheng and collaborators @xcite showed that including the adler zero in the fit to lass phase shifts for @xmath46 elastic scattering and including the effects of unitarity and analyticity demands a pole at @xmath48 mev , @xmath49 mev .
descotes - genon and moussallam obtained a pole at @xmath50 mev , @xmath51 mev @xcite using the roy equations .
a low mass peak appears in e791 data on @xmath52 @xcite and bes data on @xmath53 @xcite .
experimentalists have been bewildered by the strange behaviour of the @xmath46 phase shift and have undertaken the task of determining the magnitude and phase of the @xmath54-wave amplitude in bins of mass up to 1700 mev / c @xcite .
it turns out that these e791 results , the bes data and lass phase shifts may all be fitted simultaneously @xcite with @xmath55 mev .
this result is rather higher in mass than the prediction from the roy equations , but again much of the discrepancy can be traced to the effect of the strong @xmath56 threshold , which was not included in the treatment of the roy equations .
the way the fit to data goes is as follows .
the lass data @xcite play a strong role in determining the phase of the amplitude .
the bes data determine the parameters of the strong @xmath57 observed there - considerably stronger than in lass or e791 data .
the e791 data determine the magnitude of the amplitude , which turns out to be accurately consistent with the phase variation when the numerator of the production amplitude is taken to be constant .
this is a clear example how one can improve the precision of the analysis by fitting several sets of data simultaneously .
currently , the belle , babar and cleo c collaborations make fits without the adler zero .
fits including it are urgently needed to reduce the confusion .
are they claiming their results demonstrate that chiral symmetry is not broken in the @xmath46 sector ?
that seems unlikely in view of the fact that the adler zero is very well established in the heavier @xmath7 sector .
the whole question of how resonances can be attracted to thresholds is discussed in a full length article @xcite and will be recapitulated here . in the breit - wigner denominator of a resonance , there must be dispersive terms in the real part @xmath58 in fact , the terms @xmath59 of eq .
( 3 ) arise from the pole at @xmath60 in eq .
2 shows @xmath61 and @xmath62 near the @xmath4 threshold , using a form factor @xmath63 , where @xmath64 is centre of mass @xmath4 momentum in gev / c .
there is a cusp in @xmath61 at the threshold .
it is positive definite at the theshold , signifying additional attraction there .
-8 mm -6 mm if the cusp is superimposed on attraction from another source , for example meson exchanges , a resonance can be generated by the peak in @xmath61 .
the locking of @xmath2 and @xmath3 to the @xmath4 threshold is explained naturally by this cusp mechanism . near threshold
, the wave function of the resonance has a long tail , like the deuteron .
this tail is purely mesonic ; contributions from coloured quarks are confined in the resonance at short range or in the decay mesons .
confined quarks have kinetic energy @xmath65 ; here @xmath64 and @xmath66 are quark momentum and effective mass and @xmath67 is the wave function . to create a bound state , extra potential energy
must compensate the kinetic energy of the confined particles .
this again pulls the resonance towards the threshold .
t " ornqvist provides a formula allowing an estimate of the meson - meson component @xcite ; for the @xmath3 it is at least @xmath68 and for @xmath2 at least @xmath69 .
other examples of resonances appearing at sharp thresholds are known : @xmath70 at the @xmath71 threshold , @xmath57 at the @xmath72 threshold , @xmath73 at the @xmath74 threshold , and @xmath75 at the @xmath76 threshold .
the nonet of @xmath0 , @xmath1 , @xmath2 and @xmath3 may be understood quantitatively in terms of meson exchanges , witness the calculations from the roy equations by caprini et al . and
descotes - genon et al .
janssen et al . have shown that the @xmath3 may be fitted well in terms of @xmath77 and @xmath13 exchanges in @xmath11 and @xmath78 channels @xcite .
however , most mesons and baryons are explained as quark - model states .
there has been much debate about ` molecules ' and multi - quark states , e.g. @xmath79 .
one of the mysteries of the quark model is how confined states penetrate the confining potential and turn into mesons .
how , for example , does the @xmath13 ` know ' to have the right width to create the @xmath0 pole via the roy equations ?
my suggestion is that the confining potential arises as a cooperative effect between qcd at short range ( coloured quarks and gluons ) and meson exchanges at long range .
meson exchanges are certainly present , witness the peaks observed at small @xmath78 and @xmath11 . if both qcd and meson exchanges contribute , the well known eigenvalue equation is @xmath80 where @xmath81 and @xmath82 describe isolated @xmath83 and meson - meson configurations and @xmath84 describes mixing .
this mixing pushes the eigenstate down in mass .
this is the well known variational principle which minimises the eigenvalue when states mix .
it is closely analogous to formation of a covalent bond in chemistry .
van beveren and rupp @xcite have proposed a similar idea .
they adopt a transition potential which couples states confined in a harmonic oscillator potential to outgoing waves ; they match the logarithmic derivative at a @xmath85 function transition radius @xmath86 fm , though they mention the possibility of a gradual transition with a @xmath87 dependence on radius .
the @xmath0 , @xmath1 , @xmath2 and @xmath3 emerge from the continuum when the coupling constant to confined states increases .
the simplicity of their model makes it easy to follow the movement of poles as this coupling constant is varied .
they illustrated results for the @xmath1 and @xmath88 poles .
the dependence of the @xmath0 , @xmath1 , @xmath2 and @xmath3 poles on the coupling constant is tabulated in ref .
the model reproduces well the amplitudes for all these states using a universal coupling constant and su3 clebsch - gordan coefficients .
the @xmath89 does not appear at the @xmath90 threshold because of its associated adler zero . if the coupling constant is increased by a factor 2.5 , the @xmath0 , @xmath1 and @xmath89 all become bound states .
there has been great enthusiasm for explaining states observed in charmonium physics as 4-quark states . however , valcarce et al .
@xcite find from a detailed model calculation that such states always appear higher in mass than @xmath91 configurations with the same quantum numbers , unless attractive interactions arise between diquarks . at short range
, coloured combinations could contribute to a lowering of the energy of the @xmath92 eigenstate .
however , the long - range tail of such an eigenstate is uncoloured , taking us back to a meson - meson configuration .
molecular states certainly exist as nuclei .
the nucleon - nucleon interaction is a classic example of meson exchanges .
there is a repulsive core due to the pauli principle pushing identical quarks apart .
oset , oller and collaborators find that they can account for many resonances from a chiral lagrangian @xcite @xcite .
this is essentially a meson - meson interaction with chiral symmetry breaking built in .
they also include short - range @xmath93 interactions .
however , the short - range interactions need to be tuned to reproduce accurately the masses , widths and branching ratios of @xmath94 , @xmath95 , @xmath96 and @xmath97 . in the @xmath7 system ,
donnachie and hamilton showed in 1965 that meson exchanges are attractive for quantum numbers where there are prominent resonances : @xmath98 , @xmath99 , @xmath100 , @xmath101 , etc . @xcite .
ochs has waged a long campaign claiming that cern - munich ( cm ) data @xcite are better than the sum total of all other data and disprove the existence of @xmath102 .
this is not true .
cm data give an excellent determination of @xmath8 phase shifts @xmath85 from 610 mev to the @xmath4 threshold ( 990 mev ) .
however , above this there are strong correlations between @xmath85 and elasticity parameters @xmath103 ; consequently , errors on both become large .
these are illustrated in figs .
4 and 6 of au , morgan and pennington @xcite and in fig . 1 of kaminski , pelaez and yndurain @xcite ; errors for @xmath103 are very large because of lack of data determining accurately the absolute magnitudes of @xmath32 , @xmath31 and particularly the dominant channel @xmath104 .
it is easy to check these errors directly from errors on cm moments . for every bin ,
four algebraic solutions emerge .
there is some constraint on the @xmath8 d - wave from the line - shape of @xmath28 .
however , there is a substantial contribution from @xmath70 , ignored by ochs .
it couples strongly to @xmath105 @xcite ; the sub - threshold continuation of this channel is poorly known , as is its coupling to @xmath106 .
consequently , there is large uncertainty in the d - wave contribution to moments @xmath107 , @xmath108 and @xmath109 .
also the @xmath110 and @xmath111 can not be identified in cm data , leading to further poorly identified contributions to @xmath108 , @xmath112 and @xmath109 .
all these systematic uncertainties accumulate in @xmath109 , which determines the s - wave intensity ; it can be fitted very flexibly .
3 shows my fit to cm moments using fully analytic functions ( a major constraint ) .
some mixing is required ( and expected ) between @xmath102 , @xmath0 and @xmath95 , which overlap strongly .
mixing induces a phase rotation of the @xmath102 , see @xcite .
[ htb ] -12 mm -8 mm the problem in identifying @xmath102 is that its @xmath113 decay is obscured in many sets of data by @xmath28 .
however , it produces a clearly visible peak in @xmath114 at rest ; this peak can not be due to @xmath28 which has a branching fraction to @xmath31 of only 0.4% .
it is also visible as a peak in bes data for @xmath115 @xcite , where angular correlations between production and decay of the @xmath116 separate @xmath117 and @xmath118 cleanly .
it was first observed in 3 sets of data on @xmath32 from anl and bnl @xcite @xcite @xcite .
its parameters are best determined by crystal barrel data on @xmath119 at rest in liquid and gaseous hydrogen ; these data separate @xmath120 and @xmath121 annihilation , which give independent determinations of mass and width agreeing within @xmath122 and @xmath123 mev respectively .
crystal barrel data on charge combinations of @xmath124 give consistent parameters with all other data @xcite .
the resonance mass is @xmath125 mev with a full - width at half maximum of @xmath126 mev .
however , the rapid opening of the @xmath104 threshold moves the peak in @xmath104 higher by @xmath127 mev because of phase space .
the opening of the @xmath104 channel was not taken into account in most analyses , leading to confusion and inflated errors .
the @xmath102 was observed by gasparo @xcite and then by crystal barrel , obelix and wa102 in many sets of @xmath104 data @xcite .
when one allows for @xmath104 phase space and the associated dispersive effect , all observations where both @xmath128 and @xmath95 have been fitted are close to consistency within errors .
with the @xmath102 , @xmath95 and @xmath96 well established , there is one state too many to fit as @xmath129 and @xmath130 .
the glueball predicted in this mass range by lattice gauge calculations mixes with the @xmath93 states .
the @xmath96 decays almost purely to @xmath4 , with a possible small @xmath31 decay .
the @xmath95 behaves as an octet state with @xmath131 and @xmath132 .
an intriguing result is the sharp @xmath133 signal reported by the bes collaboration @xcite , peaking at 1812 mev , just above the @xmath134 threshold at 1801 mev .
a purely threshold effect should peak much higher .
it is therefore probably due to @xmath97 , a resonance clearly separated from @xmath96 in bes data on @xmath135 @xcite , @xmath136 @xcite , @xmath137 and @xmath138 @xcite .
there is a strong @xmath96 peak in @xmath139 data , but nothing in @xmath136 despite large statistics .
conversely , the @xmath97 appears clearly in @xmath140 , but not in @xmath138 .
there is a factor 22 difference in decay branching ratios to @xmath8 and @xmath4 , requiring separate @xmath96 and @xmath97 .
the @xmath97 was first observed in @xmath141 @xcite @xcite .
it makes a natural radial excitation of @xmath102 . the @xmath134 decay can arise naturally from a glueball component in @xmath97 @xcite
a glueball is a flavour singlet with flavour content @xmath142 [ the @xmath130 component might be enhanced with respect to @xmath143 by a factor @xmath144 . ]
the component @xmath145 can make @xmath146 or @xmath147 or a linear combination .
bes i data on @xmath148 show that the @xmath149 channel contains no significant @xmath150 signal @xcite . a signal with the same magnitude as that of @xmath151 would be conspicuous near 1800 mev .
its absence may be qualitatively explained by the larger phase space for @xmath152 in @xmath4 decays than in @xmath153 .
in fitting @xmath0 and @xmath1 , it is essential to include the adler zero explicitly into the breit - wigner denominator - or demonstrate that such a fit is unacceptably bad .
the adler zero needs to be included also into the @xmath57
. it would be good if competing experimental groups would join forces , like lep groups , to try and achieve an optimum compromise between different sets of data and iron out inconsistencies .
experience is that different sets of data illuminate different aspects required for an optimum fit .
the @xmath0 , @xmath1 , @xmath2 and @xmath3 fit naturally according to meson exchanges .
why look further ?
the cusp at the @xmath4 threshold plays an essential role in locking @xmath89 and @xmath154 to this threshold .
the cusp mechanism can attract a resonance over a surprisingly large mass interval of @xmath155 mev . at the threshold
, zero point energy is minimised by the long - range tail of the wave function . mixing between quark configurations and meson - meson states minimises the energy of the linear combination in a way analogous to the formation of a covalent bond in chemistry .
this idea is similar to the idea of duality between resonances and particle exchanges .
i wish to thank prof .
g. rupp and prof .
e. van beveren for extensive discussions and for their efforts in organising a workshop on scalar mesons to mark the 70th birthday of mike scadron .
i am very grateful to mike scadron for illuminating the role of pcac and the linear @xmath0 model on many occasions . | the formulae needed to parametrise @xmath0 , @xmath1 , @xmath2 and @xmath3 are reviewed . for @xmath0 and @xmath1 , the adler zero due to chiral symmetry breaking plays a crucial role .
the @xmath3 and @xmath2 are locked to the @xmath4 threshold by a cusp mechanism which leads to a sharp peak in attraction at the threshold .
this mechanism may play a wider role .
a novel suggestion is that the confinement potential involves a cooperative effect between qcd effects ( coloured quarks and gluons ) and conventional meson exchanges .
pacs numbers : 13.25.gv , 13.25.hw , 14.40.gx .
14.40.nd * review of scalar mesons * |
CLOSE Marlins ace Jose Fernandez has died in boating accident at the age of 24. USA TODAY Sports
Miami Marlins starting pitcher Jose Fernandez was 24 years old. (Photo: Eric Hartline, USA TODAY Sports)
MIAMI — A boat carrying Jose Fernandez was traveling at a significant speed when it struck rocks as it approached a channel near the port of Miami, resulting in the death of the Miami Marlins pitcher and two close friends early Sunday morning, officials in Florida said.
Fernandez was killed as a result of the impact of the crash, and did not drown, Lorenzo Veloz, an official with the Florida Wildlife Commission, confirmed to USA TODAY Sports.
Fernandez, 24, was not driving the boat when it struck a jetty near Government Cut, a channel that provides boats direct ocean access from Miami Beach. Veloz said the three victims were between 24 and 27 years old. They were not identified pending notification of family members.
Veloz said alcohol is not believed to be a factor in the crash and no illicit drugs were found at the scene. Toxicology results will not be available until autopsies are performed
Veloz said Fernandez and his friends made frequent trips on the boat, and that he saw other Marlins players on the boat on occasions he stopped it for safety checks.
The scene of the boat accident. (Photo: Courtesy Miami Dade Fire Rescue)
“Jose was never known to drive it,” Veloz said.
He said the 32-foot Sea Vee Center Console fishing vessel was owned by one of the other men killed in the crash. Those boats can reach speeds between 55 and 65 mph depending on the size of the engine, according to the SeaVee Boats web site.
Their boat was traveling southbound toward Government Cut when it struck the north end of the jetty at, Veloz said, “what appeared to be full speed.” The boat suffered severe damage on the bottom.
“The vessel hit the rocks and capsized,” Veloz said. “It does appear speed was involved due to the impact and severity of it.”
Debris from the boat was spotted and reported to the Coast Guard shortly after 3 a.m., said Megan Dean, a Coast Guard commander in Miami. Eight divers from Miami Fire and Rescue were deployed shortly before 4 a.m. and soon recovered three bodies. Veloz said they are certain there are no other victims.
It is unclear at what time the crash occurred, though the Marlins' game against the Atlanta Braves on Saturday night did not end until 10:30 p.m.
Veloz said none of the men were wearing life jackets, although it appears that might not have aided in their rescue.
“The jetty is rocks, it’s not very visible,” Veloz said. “But we are aware that vessel has traveled several times through the area. Sometimes, at night, you deviate.”
Contributing: Gabe Lacques ||||| Rob Foldy/Getty Images
José Fernández, the 24-year-old Miami Marlins pitcher who died this weekend in a boating accident off the coast of Florida, was imprisoned in Cuba as a teenager for trying to escape the island. He finally managed to defect at age 15, but only after saving his mother Maritza from drowning. Just five years later, he won the 2013 National League Rookie of the Year Award and finished third in the voting for the Cy Young.
Though he started only 76 games in his career, Fernández had the potential to be a Hall of Famer. This season, just his second full one in the big leagues—he missed parts of 2014 and 2015 due to a torn elbow ligament and his subsequent recovery from Tommy John surgery—he averaged an incredible 12.5 strikeouts per 9 innings, the fifth-best mark in history for a starting pitcher. But Fernández also had the potential to change a sport that desperately needs changing. The Marlins starter loved the competition and camaraderie of baseball, and he loved striking fools out. From the moment he made his debut for the Marlins, he ignored the fusty expectation that players—often young, Latino players—dial back their exuberance lest they annoy their tight-assed opponents. At age 24, he’d already started to modernize the game’s old-fashioned codes and what it meant to “play the game the right way.”
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Fernández defied those codes during his rookie year. The then 21-year-old hit his first major-league home run on Sept. 11, 2013, though “hit his first major-league home run” doesn’t do this shot justice. Fernández crushed the ball, and he was justifiably thrilled, dropping his bat and watching his shot arc over the left-field fence before commencing a slow trot around the bases.
When Fernández reached home plate, Atlanta Braves catcher Brian McCann started lecturing him, whereupon the benches cleared, and both teams pretended to want to fight each other. “I just told him you can’t do that,” McCann said later. “You can get someone hurt. It was just something that didn’t need to happen.” Braves third baseman Chris Johnson added, “The kid is a good pitcher. He’s got some other stuff going on, too, that upsets people sometimes. There were some guys in the dugout who weren’t too happy with the smiling after getting people out and all of that kind of stuff.”
Fernández did not try to defend his actions. “I feel I don’t deserve to be here, because this isn’t high school no more,” he said. “This is a professional game, and we should be professional players. I think that never should happen. I’m embarrassed, and hopefully that will never happen again.”
A Slate Plus Special Feature: The Best Moments From Hang Up and Listen History, According to You Revisiting the show’s most noteworthy afterballs from the vault. Listen to this special Slate Plus bonus segment by joining - your first two weeks are free.
Veterans lecturing rookies on how to behave is as much a part of baseball’s folkways as players scratching their crotches. These lectures are typically focused on ensuring the game is as much of a joyless slog as possible, and that lesson is enforced via threats of retaliatory violence. If you stop and stare because you’re happy about hitting the ball very far, then someone will throw a 95 mile per hour fastball at your head. If you smile at people after striking them out, then … someone will throw a 95 mile per hour fastball at your head. (Baseball players’ revenge plots are not very creative.)
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Last October, the Toronto Blue Jays’ José Bautista threatened to rip the game apart by launching his bat into orbit—a spontaneous reaction after hitting one of the most dramatic home runs in playoff history.
Bautista’s spectacular bat flip, Hall of Fame pitcher Goose Gossage later explained, represented everything wrong with the sport he’d once loved. “Bautista is a fucking disgrace to the game,” Gossage said in an interview with ESPN. “He’s embarrassing to all the Latin players, whoever played before him.” Gossage made the subtext of the sport’s on-field policing explicit: White players born in the United States don’t think their Latino counterparts conform to the sport’s behavioral norms.
As Jay Caspian Kang noted in a New York Times Magazine story headlined “The Unbearable Whiteness of Baseball,” baseball’s demographics have shifted multiple times since Jackie Robinson broke the game’s color line in 1947. That season, 98.3 percent of players were white, 0.9 percent were black Americans, and 0.7 percent were Latino. By 1975, 71.3 percent of major leaguers were white, 18.5 percent were black Americans, and 10.2 percent were Latino. At the start of the 2015 season, white players represented 58.8 percent of all major leaguers and 8.3 percent were black, while the sport’s Latino minority had grown to 29.3 percent of all major-league players.
Back in November, the bat-flipping Bautista argued in a piece that appeared under his byline in the Players’ Tribune that Latin players can make baseball great again if the sport’s powers that be allow them to be themselves. “Baseball is a metaphor for America,” the Players’ Tribune article said. “It’s a giant melting pot made up of people from all over the world and all walks of life. How can you expect everybody to be exactly the same? Act exactly the same? More importantly, why would you want them to?”
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I disagree with the Blue Jays slugger. It would be perfectly fine if every baseball player acted the same way on the field, so long as they all chose to act like José Bautista and José Fernández.
In 2013, a month before the Braves got mad at him for hitting a home run, Fernández snared a liner hit by the Rockies’ Troy Tulowizki. The subsequent byplay between the two All-Stars was joyful and human, and a reminder that intense competition doesn’t have to be unsmiling competition.
One of the best Jose Fernandez moments. Rest in Power. You'll never be forgotten. 🙏🏻
pic.twitter.com/P5Lvi1v0kj — E (@esheikh_) September 25, 2016
The next spring, the Rockies’ Carlos González hit a massive home run off Fernández and loitered around the plate to admire his achievement. Fernández didn’t pout or act aggrieved. He grinned, broadly.
González “was just acting like a really good baseball player who was excited about crushing a massive home run against another really good baseball player, and Fernández understood that,” Deadspin’s Tom Ley wrote the next day. “Together they helped make a baseball game something that baseball games increasingly struggle to be: fun.”
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In the end, Fernández failed to live up to the terms of his 2013 apology—his admonition to himself that “this isn’t high school no more”—and thank goodness for that. Goose Gossage, who was born in 1951, is not the face of the modern game. Neither is crusty 32-year-old catcher Brian McCann. Fernández, smiling after he gave up a home run—that is the look everyone in baseball should aspire to emulate.
The sport’s young stars seem to understand that. In an ESPN the Magazine profile earlier this year, reigning MVP Bryce Harper said that Fernández represented a new image for a sport that truly needed one:
[Baseball is] a tired sport, because you can’t express yourself. You can’t do what people in other sports do. I’m not saying baseball is, you know, boring or anything like that, but it’s the excitement of the young guys who are coming into the game now who have flair. …
José Fernández is a great example. José Fernández will strike you out and stare you down into the dugout and pump his fist. And if you hit a homer and pimp it? He doesn't care. Because you got him. That’s part of the game. It’s not the old feeling—hoorah ... if you pimp a homer, I’m going to hit you right in the teeth. …
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Fernández could himself be susceptible to upholding baseball’s old codes. Just this month, he plunked Nick Markakis with a fastball a couple of innings after the Braves outfielder hit a two-run homer. Later in the game, Atlanta’s José Ramirez threw a pitch over Fernández’s head, leading both benches to clear.
But far more often than not, Fernández played with a kind of generosity of spirit that’s rare at any level of any sport. To understand what Fernández represented, watch this sequence in which he swings and misses at a breaking pitch from the Dodgers’ Kenta Maeda.
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The death of Marlins pitcher Jose Fernandez sent shockwaves through the Cuban community in Florida. (Photo: Steve Mitchell, USA TODAY Sports)
MIAMI -- When Raul Mas heard the news that Miami Marlins pitcher Jose Fernandez died in a boating accident, his first call was to his father.
Mas, a Cuban-American worker for Miami-Dade County, said Fernandez meant so much more to his family than any other athlete. As a Cuban, Fernandez made people in this Cuban community feel as if one of their own was on the mound.
"He was one of us," said Mas, 29. "My father is 45 years older than me, so baseball is our bond. And Jose was all we talked about -- a certain game, a certain pitch. We'd only go to games where he pitched.
"I'm really hurting right now. So is he."
News of Fernandez's death passed through South Florida on Sunday in a way akin to a relative's passing. Text messages and phone calls crisscrossed the region from Little Havana to the Cuban enclave of Hialeah.
Up in Fort Lauderdale, Logan Zuckerman was woken by his father who broke the news. That led Zuckerman, a 23-year-old University of Florida student, to wear his Marlins jersey to the Miami Dolphins game on Sunday.
Like others on Sunday, Zuckerman rattled off a series of moments he remembered of Fernandez's short but meteoric career.
"June 5, it was a Sunday, 'Bark in the Park,' so I brought my dog. He threw seven shutout innings against the Mets and struck out something like 13, 14, 15 people," Zuckerman said. Fernandez struck out 14 that day in the 1-0 win.
But it was Fernandez's background that is leaving so many people crestfallen. Everyone in Miami knows the story of his escape from Cuba on a boat, jumping in the water to save his drowning mother. They remember the moment Marlins executives surprised him by flying his grandmother to Miami from Cuba. They recognize Fernandez's mother and grandmother cheering from their usual seats at Marlins Park, reminding them of their own families.
"It was perfect," said Joe Naya, 53, whose parents are both Cuban. "I was so proud of him. I didn't know him, but I was proud. One of your own was up there."
Gov. Rick Scott tweeted about Fernanedez, and Miami mayor Tomas Regalado, who was born in Havana, released a statement: "I was honored to give the key to the City to Marlins pitcher Jose Fernandez as a rising star and proud son of Miami. My condolences to his family and to the Miami Marlins. His death is a huge loss for our community."
Otto Fernandez, no relation, could barely conjure up the words to describe how he felt. The 40-year-old information technology specialist left Cuba in the 1980s during the Mariel Boatlift, crossing the same waters that the future All Star did as a teen. Both grew up in the same kind of Cuban exile community. And on Sunday, Fernandez said all he could do was take solace in the fact that he had the privilege to watch the young Cuban for as long as he did.
"He's going to be a legend," he said.
PHOTOS: A LOOK AT THE CAREER OF JOSE FERNANDEZ ||||| The Miami Marlins held an emotional press conference early this afternoon on news of the death of star pitcher Jose Fernandez in a boating accident.
Don Mattingly, the team's manager, wept as he spoke of the joy with which Fernandez played the game of baseball.
"I see such a little boy in him --," Mattingly said, pausing to compose himself. "The way he played. It was just joy with him, when he played. When you watch little kids play Little League, that's the joy that Jose had when he was playing."
Team president David Samson, fighting back tears, spoke of how the Fernandez, who emigrated from Cuban, was a beloved figure in Miami who was intimately involved with the community.
Veteran third-baseman Martin Prado spoke on behalf of the team's players, describing Fernandez as a fierce competitor on the baseball diamond.
"Just to see him go up there every time," Prado said. "He didn't care who he faced or who we were playing."He placed an emphasis on his battle to play American baseball, coming from Cuba. A 2013 story in Grantland described the perilous journey he took to reach American shores.
Fernandez, widely considered to be among the best pitchers in Major League Baseball, was killed when a boat that had apparently been speeding crashed into a jetty outside Miami Harbor, authorities said.
Patrick Farrell/Miami Herald via AP
Fernandez was one of three males killed, authorities said. Two were found in the 32-foot boat and one in the water, the Miami-Dade County Sheriff Lorenzo Velos said at a press conference Sunday morning. None of the three were wearing life vests, Velos said.
The other victims appear to be friends of the pitcher and were not teammates, the sheriff said, adding that Fernandez was not the boat's owner and had not been driving it. He said the boat's owner has been stopped before for safety violations.
The sheriff said there was no obvious indication that alcohol or drugs were involved in the accident but that autopsies could help to determine that.
Florida Fish and Wildlife Capt. Meagan Dean said the wrecked boat was discovered early morning Sunday on a routine search of the area.
The Marlins announced that Sunday's game against the Atlanta Braves has been canceled as a result of the sudden death of one of the team's stars.
Fernandez, just 24 years old at the time of his death, amassed several eye-popping seasons in his short career on the professional baseball diamond, winning the National League Rookie of the Year award in 2013.
He had a career earned-run average of just 2.58 over four seasons. He led baseball this season in strikeouts per nine innings with 12.49 among starting pitchers.
WPLG
He was particularly dominant while playing at home in Miami's Marlins Park, becoming the first pitcher in the modern era to win his first 17 career home decisions. He eventually went on to go 24-1 in his first 25 home decisions.
Born in Santa Clara, Cuba, Fernandez defected to America in 2008 and became one of the most prominent faces among a wave of Cuban stars breaking into professional baseball at that time.
Fernandez posted a photo on Instagram of his pregnant girlfriend, Carla Mendoza, last week. The team mentioned during the press conference that she is expecting his daughter.
This is a breaking story. Please check back here for updates. ||||| Before José Fernández was a star pitcher for the Miami Marlins, he shined on his high school playing field.
On Sunday — following news of Fernández's tragic death — the Florida High School Athletic Association posted a nostalgic throwback picture to honor the athlete.
This is just one of many tributes to the late athlete, who died at age 24 in a boating accident.
His high school district also tweeted following the news. ||||| Mike Downey is a former Los Angeles Times and Chicago Tribune columnist and a frequent contributor to CNN. The views expressed in this commentary are his.
(CNN) The "old-timers" were the ones Major League Baseball's players and fans expected to be saying goodbye to in this, the 2016 schedule's final week before the playoffs — David Ortiz, the 40-year-old slugger of the Boston Red Sox; and 88-year-old Vin Scully, the voice of the Los Angeles Dodgers; and oh, how wonderful both are still with us to do what they do, and oh, how much we wish neither needed to leave.
Instead, it is one of the sport's youngest, brightest, happiest, heartiest stars everybody is saying goodbye to — Jose Fernandez, just 24, a phenomenally good pitcher for the Miami Marlins with a sky's-the-limit future, found dead from a boating accident Sunday morning in South Florida, a short boat ride from his native Cuba.
Shock waves vibrated through baseball, and many immediately took to Twitter to express their grief:
Yasiel Puig of the Los Angeles Dodgers, his fellow Cuban: "Hermano, wherever you are, you know how much I loved you."
On and on, one by one, the people who populate the baseball world found themselves unable to concentrate on the upcoming World Series or which players might end up playing in it. Members of the Marlins, disappointed by the increasing likelihood that they will miss the playoffs , didn't understand what true pain felt like until they woke Sunday to the news that Jose Fernandez was gone.
What a gem on and off the diamond he was. His pitching dazzled everyone. His personality tickled everyone. He was fun and funny and self-confident to the max. In 2012, he was still a beginner, dividing his time between the Greensboro (N.C.) Grasshoppers and the Jupiter (FL) Hammerheads of the minor leagues. By 2013, he was already not just in the Major Leagues but a member of the All-Star team and the National League's Rookie of the Year.
He put on a show wherever he'd go: 13 strikeouts against the Pittsburgh Pirates, 14 against the Cleveland Indians, mowing them down. Fernandez was a mere 21 years old at that point, yet already phrases like "future Hall of Famer" were being tossed around by people who had seen quite a few pitchers in their day. Veterans marveled at his poise. Broadcasters sang his praises.
"Watching him, he played with an unbridled joy," another of the Dodgers' longtime voices, Charley Steiner, recalled Sunday morning for CNN after hearing the news. "He exuded a confidence that bordered on cocky, but that is what set him apart. His career path seemed infinite."
The bodies of Fernandez and two other men were discovered by the Coast Guard at approximately 3 a.m. off the shore of Miami Beach, where their 32-foot vessel had capsized. Two of the victims were found beneath the boat, the third in the water nearby.
Fernandez was scheduled to make his next start Monday for the Marlins, who trail in the National League's wild-card race but still had a mathematical possibility of making it to the October playoffs. He was having yet another outstanding season with a record of 16-8. Whenever anyone made a list of baseball's most skilled young stars, Fernandez's name always came up.
To have him struck down in his prime — no, ahead of his prime — is a loss like few in baseball have experienced. Some of the Los Angeles Angels had this same sick feeling in the pits of their stomachs on April 9, 2009, when their young teammate Nick Adenhart , another pitcher of endless promise, was killed in a California car crash. The sudden death of Fernandez caused a similar jolt.
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"Absolutely devastated," tweeted the Angels' star outfielder Mike Trout after hearing the news from Miami.
Marlin team officials and players gathered together to speak of their loss, bringing one of Fernandez's jerseys with them to a press conference. Sunday's scheduled game against the Atlanta Braves was called off. Teammates must press on in the days ahead, but no sleeve patch with a fallen comrade's initials or uniform number can sufficiently fill the void.
"I don't know how you ever get over it," New York Yankees manager Joe Girardi said.
The Marlins had been a franchise known to deal away many of its top players in years past, sometimes to save money, sometimes simply on a team executive's whim. That's why other teams came calling before MLB's trade deadline this summer — Jose Fernandez was a guy everybody else wanted on their side, rather than someone throwing fiery fastballs past their own batters.
This time, however, the Marlins turned away all potential suitors, all kinds of offers, thanks but no thanks. They had every intention of hanging onto this player for as long as they could, because this was one of those once-in-a-lifetime prospects you didn't part with, no matter what.
Rob Manfred, baseball's commissioner, called Fernandez "one of our game's great young stars."
The hard truth: He will get no older, leaving us to forever wonder how much greater he was going to be. | – As mourning continues for the tragic death of Miami Marlins pitcher Jose Fernandez, investigators are starting to unravel the circumstances behind his passing early Sunday morning. Lorenzo Veloz, a spokesman with the Florida Fish and Wildlife Conservation Commission, tells USA Today Sports that the 32-foot boat Fernandez was on appeared to be traveling at "full speed" when it slammed into a jetty off of Miami, that alcohol and drugs aren't believed to be factors in the crash (though toxicology reports are still pending), and that the 24-year-old died from the impact of the crash, not from drowning. Veloz says he had stopped the boat, owned by one of the other two men who died in the accident, before for safety checks, and while Fernandez was a frequent passenger, along with other Marlins players, "Jose was never known to drive it." More from around the web on Fernandez's untimely death: Josh Levin pens a poignant tribute for Slate on Fernandez, "the future of baseball" who "changed what it meant to play the game the right way." Mike Downey, meanwhile, calls Fernandez "one of baseball's brightest stars" for CNN. USA Today explores how Fernandez's death has devastated Florida's Cuban community. Don Mattingly, manager of the Marlins, wept at a press conference Sunday afternoon, per ABC News, comparing Fernandez's joy of playing to that of unjaded Little Leaguers. Along those lines, Mashable points out a "victorious photo" from Fernandez's high school days posted on Facebook by the Florida High School Athletic Association—an image that shows Fernandez basking in that pure love of the game. ESPN's Dave Szymborski tweeted out "what remains my favorite Jose Fernandez GIF," which has already been retweeted more than 8,000 times. It's pretty amazing—and smile-inducing. |
non - separability in classical light fields has been studied recently in the context of quantum information and entanglement@xcite .
this non - separability is analogous to intra - system entanglement involving different degrees of freedom of a light beam .
however , the term `` classical entanglement '' has received some serious criticism recently @xcite .
the non - separability can exist in between continuous or discrete variables , for which the classical light beams are shown to violate the corresponding form of the bell s inequality @xcite .
one can construct classical equivalent of many exotic quantum states using polarization and spatial modes of light .
these non separable states are used to mimic many quantum protocols @xcite .
apart from the basic interest of demonstrating quantum protocols using classical light beams , they find applications in various fields@xcite .
these non - separable states are shown to be robust under scattering and used to show the phase recovery of a beam after scattering @xcite .
when light fields undergo a cyclic polarization evolution , they acquire a geometric phase which is known as pancharatnam phase @xcite .
the phase acquired by the light depends on the path taken by the polarization state upon its evolution on the poincar sphere .
the geometric phase is generalized to any quantum system under cyclic evolution by a time dependent hamiltonian and called as the berry phase@xcite .
entangled states , when generated experimentally , may possess a relative phase due to the phase delays in the generating process .
one can nullify this relative phase by introducing a geometric phase in one of the subsystem .
in such cases , we need to see the bell violation , as a measure of entanglement , to optimize the state corresponding to different relative phases . the effect of berry phase in entangled systems and their violation of bell s inequality were studied for spin-@xmath0 particles@xcite .
the measurement in two degrees of freedom of non - separable state , be it classical or quantum , is very important for various protocols .
any relative phase will change the measurement outcome which will affect the efficiency of the protocol .
thus optimizing the measurements in two degrees of freedom , when the state acquires a relative phase is very important for efficient implementation of such protocols . here
, we introduce pancharatnam geometric phase to the non - separable state in a controlled way and show that a proper selection of measurement basis can make the bell measurement phase independent . in this article
, we generate a classical non - separable bell - like state of polarization and orbital angular momentum ( oam ) of light using a polarizing sagnac interferometer .
we demonstrate the presence of non - separability by the violation of bell s inequality for the generated state .
next , we study the effect of pancharatnam phase introduced by the polarization subsystem , through its cyclic evolution on the poincar sphere , on the violation of bell s inequality . the maximum violation @xmath1 varies sinusoidally according to the pancharatnam phase when maximized over the set of linear bases .
we experimentally show that the bell parameter can obtain its maximum value of @xmath2 irrespective of the pancharatnam phase if we introduce a corresponding relative phase in the projecting basis .
we also investigate the effect of pancharatnam phase on the spatially varying polarization structure of these non - separable beams .
the result give insight to the measurement optimization of bell chsh inequality for a non - separable state under different relative phase . in section [ sc.2
] , we give a theoretical background for the problem .
we are using dirac notation for the representation of states .
however it is to be noted that the state correspond to classical electromagnetic fields and also we have omitted the normalization by total intensity for the convenience of representation . in section [ sc.3 ] we describe the experimental details for the generation , evolution and measurement of the non - separable state of light .
we also give the holograms for the oam measurements .
the results and discussion are given in section [ sc.4 ] .
along with the projective measurement results , we give the stokes polarimetric images of the beam for different pancharatnam phase which can give a physical explanation for the variation of @xmath1 and the bases adjustments .
we finally conclude in section [ sc.5 ] .
we start with a maximally non - separable bell - like state of polarization and oam that can be written as @xmath3 where @xmath4 and @xmath5 are basis vectors for 2d complex vector spaces of polarization and oam .
we define the set of linear bases corresponding to polarization and oam as @xmath6 these bases are represented geometrically as blue circles on the poincar sphere of polarization and that of oam as given in fig .
the bell - chsh inequality is defined as @xmath7 where @xmath8 @xmath9 is the probability amplitude of a state for being in @xmath10 .
projecting the state given in eq . [ 1 ] to a general state @xmath10 in the linear bases of polarization and oam we get @xmath11 using above expression in eq .
[ 4 ] , one can obtain @xmath12 at @xmath13 .
note that the maximization is done over states in the linear bases of polarization and oam by changing @xmath14 and @xmath15 respectively . and @xmath16 are oam states corresponding to the topological charge + 2 and -2 respectively .
also @xmath17 and @xmath18 . ]
now , consider a cyclic evolution of polarization for the state given in eq .
[ 1 ] which can be done by action of half wave plate ( h ) oriented at @xmath19 with the horizontal , quarter wave plate ( q ) oriented at @xmath20 and another half wave plate at @xmath21 . here ,
the two orthogonal polarization states evolve as @xmath22 and @xmath23 .
thus the state becomes @xmath24 where @xmath25 .
the joint measurement probability becomes @xmath26 which is a function of @xmath27 also .
thus the @xmath1 will also be a function of @xmath27 along with @xmath28 and @xmath29 .
changing @xmath27 will affect the angles corresponding @xmath1 and its value .
for @xmath1 with @xmath30 , @xmath15 and @xmath29 are varied as @xmath31 the @xmath1 varies periodically with the relative phase @xmath27 . to get back the maximum bell violation , one need to use different bases for the maximization of the bell parameter .
we redefine the oam projecting state as @xmath32 that gives @xmath33 one can obtain the same by introducing a relative phase in polarization state @xmath34 too . now
the bell - chsh parameter @xmath1 is independent of the relative phase @xmath27 .
the different oam measurement bases for different @xmath27 are given in fig .
[ fg.2 ] .
next we check the bell - chsh parameter by projecting the state @xmath35 in circular basis of polarization and oam .
the states are given as @xmath36 these measurement bases are given as red circles in fig.[fg.1 ] .
measuring the state @xmath37 will result the same outcome as given in eq . [ 2 ] .
now the joint detection probability for the projection of the state @xmath35 to state @xmath10 is given as @xmath38 thus with @xmath39 and @xmath40 we can obtain the bell - chsh parameter as @xmath2 .
the experimental set up used to generate the non - separable state and to study its properties is shown in fig .
we have used a diode pumped solid state green laser ( verdi 10 ) with vertical polarization for our study .
the laser beam passes through a half wave plate oriented at @xmath41 with the horizontal that changes the polarization from vertical to diagonal .
then it passes through a polarizing sagnac interferometer containing a spiral phase plate ( spp ) to generate a light beam with non - separable polarization and oam .
two orthogonally polarized ( h and v ) counter propagating gaussian beams are converted into optical vortices of orders @xmath42 ( for h ) and @xmath43 ( for v ) by the spp designed for order @xmath44 .
these orthogonally polarized and oppositely charged vortices superpose at the same pbs to form the non - separable state . for the measurements of oam states in linear bases ] for the polarization evolution
we have introduced a simon - mukunda ( sm ) gadget @xcite , a combination of two quarter wave plates ( q ) and a half wave plate ( h ) in q - h - q order . a quarter wave plate with fast axis oriented at @xmath21 with the horizontal convert the horizontal and vertical polarizations into right and left circular polarizations respectively .
now a half wave plate will convert right circular polarization to left circular polarization and vice - versa .
the second quarter wave plate at @xmath21 will convert the circular polarization to the initial linear polarization state .
but the evolution on the poincar sphere takes different path according to the fast axis orientation angle ( @xmath45 ) of the half wave plate . the polarization evolution is also given in fig .
[ fg.3 ] . as given in eq.[9 ] and @xmath46 ] the measurement in polarization
is done by a quarter wave plate ( at 0 or 45 for linear and circular projections ) , half wave plate ( at @xmath47 ) and a polarizer oriented at @xmath48 . for oam measurements we use a spatial light modulator ( slm ) along with a single mode fiber and a photo multiplier tube for the detection .
the holograms of the slm is made in such a way that it converts the particular oam state @xmath49 into gaussian which is coupled to the single mode fiber ( smf ) .
the holograms for projection in liner oam bases for different value of @xmath15 are given in fig .
the hologram for @xmath50 in circular bases is equivalent to the linear basis hologram corresponding to @xmath51 given in fig .
[ fg.4 ] . for other values of @xmath15 ,
the hologram is rotated at an angle @xmath52 .
[ fg.4a ] gives the holograms for the optimized measurement of bell parameter as given in eq.[9 ] with @xmath53 and for different @xmath15 . to study the spatially varying polarization structure and its evolution with the introduced geometric phase , we have carried out the stokes polarimetric imaging of the beam . for this
we image the beam after the polarizer ( p ) using a ccd camera for the projection to three sets of orthogonal polarization states .
spatially varying stokes parameters are measured from the images corresponding to different polarization projections .
measurements on a light beam with non - separable state of polarization and oam give raise to contexual results .
the measurements are similar to two photon correlation experiments in entangled photon pairs . instead of measuring one quantity , say polarization , of two spatially separated photons , here we are performing a measurement in two independent degrees of freedom , namely polarization and oam , of the same beam .
the measurement in polarization affects the measurement outcome in oam .
we measure the power coupled to the single mode fibre after the polarization projection by the wave plates and the polarizer and oam projection by the slm .
we vary the @xmath14 by changing hwp orientation for different values of oam projection angle @xmath15 .
the curves for the state given in eq .
[ 1 ] , are given in fig .
[ fg.5].the theoretical curves which follow the eq .
[ 2 ] are also given for comparison . .
measurements are done in linear bases ] . ] to find the optimum angles for the maximum violation of bell - chsh inequality , we vary the projecting angle from @xmath48 to @xmath54 fixing @xmath55 and @xmath56 . for the generated non - separable state ,
we have carried out the measurements in linear ( black squares ) and circular bases ( red circles ) and the results are given in fig .
theoretically expected curve is also given in comparison .
with @xmath57 we obtain @xmath58 corresponding to @xmath59 when measured in linear bases .
measurement in circular bases with the angles mentioned yields a value of @xmath60 .
the violation of bell - chsh inequality indicates the presence of non - separability of polarization and oam present in the beam .
this accounts for the contexuality in measuring these two properties of light .
the result of oam measurement depends on the polarization measurement settings .
the imperfections in the linear bases projection of oam using slm and single mode fiber results in the lesser violation of bell chsh inequality . when projecting the input oam state ( after the polarization projections ) by the holograms given in fig .
[ fg.4 ] , the center of the gaussian mode at the fiber coupler slightly get shifted for different projections which affects the coupling to the single mode fiber . in the case of projections to circular bases , the centers of the projected gaussian mode are comparatively stable due to the circular symmetry of the different holograms . with the relative phase when maximized over the linear bases ] by introducing phase compensation in linear bases ( black squares ) and changing @xmath15 in circular bases ]
we have changed the relative phase @xmath27 using the sm gadget and obtained @xmath1 using conditions given in eq . [ 8 ] .
experimental curve for the @xmath1 with the phase @xmath27 is given in fig.[fg.7 ] . at @xmath61
the value of @xmath1 drops to zero , and there is no violation of bell inequality .
however , the state given in eq .
[ 6 ] is always maximally non - separable/ entangled as the other entanglement measures like concurrence or von - newman entropy are independent of @xmath27 .
we have carried out the bell parameter measurement with the introduction of relative phase in @xmath49 to transform it to @xmath49 as given in eq .
the @xmath27 independent values of @xmath1 for these measurements are given in fig .
we also measure in circular basis for which projecting states are described by eq .
[ 11 ] . ] with the change in measurement angles as mentioned above bell - chsh parameter is found to be constant with the relative phase @xmath27 .
the results are given in fig .
here we do nt have to change the measurement basis , as we have done in the linear case , to maximize @xmath62 .
so , when projecting in circular basis , one can easily compensate the effect of pancharatnam phase in the bell - chsh inequality measurement .
we have analyzed the spatially varying polarization structure with the cyclic polarization evolution .
the results are given in fig .
the magenta and cyan circles show right and left circular polarizations .
two black lines are drawn corresponding to the diagonal polarization .
it is found that the total polarization structure rotates with the relative phase introduced .
we also give the images corresponding to different polarization projections for different @xmath27 .
one can see that the images corresponding to diagonal and anti - diagonal projections are rotated with the relative phase @xmath27 .
however , it does nt affect the mode structure corresponding to horizontal or vertical projection .
for the projection in any other linear state , the mode rotates with the relative phase .
thus a hologram that is supposed to convert the diagonal oam state @xmath63 to gaussian , will not effectively convert the state @xmath64 . by introducing a phase in the oam projecting bases as given in eq . [ 9 ] , which gives a rotation for the hologram corresponding to the projection onto @xmath15 other than @xmath65 , one can compensate this effect and achieve the maximum violation of bell chsh inequality as given in fig .
the optimized holograms are given in fig .
[ fg.4a ] for @xmath66 .
in conclusion , we have studied the effect of pancharatnam geometric phase in a non - separable state of polarization and oam .
the non - separability is confirmed by the violation of bell - chsh inequality .
the geometric phase introduced in the polarization subsystem induces a relative phase in the bell like state of oam and polarization .
the maximum value of the bell parameter @xmath1 , maximized over the measurement angles , varies sinusoidally according to the relative phase .
we obtain a constant @xmath1 for different geometric phase by introducing a relative phase in the projected oam state .
we also show that the bell chsh inequality measurement in circular bases can remove the phase dependence of the @xmath1 by shifting the measurement angle .
we have analyzed the polarization structure of the non - separable state for different pancharatnam phases which gives a rotation to it .
this physically explain the effect of pancharatnam phase in the joint measurement of polarization and oam .
authors like to acknowledge prof .
partha ghose , srfti , kolkatta for the fruitful discussions .
also we would like to acknowledge dr .
vijay kumar , pdf , physical research laboratory for the polarization stokes images .
10 priyanka chowdhury , a. s. majumdar , and g. s. agarwal .
nonlocal continuous - variable correlations and violation of bell s inequality for light beams with topological singularities .
, 88:013830 , jul 2013 .
ebrahim karimi , jonathan leach , sergei slussarenko , bruno piccirillo , lorenzo marrucci , lixiang chen , weilong she , sonja franke - arnold , miles j. padgett , and enrico santamato .
spin - orbit hybrid entanglement of photons and quantum contextuality .
, 82:022115 , aug 2010 .
benjamin perez - garcia , melanie mclaren , sandeep k. goyal , raul i. hernandez - aranda , andrew forbes , and thomas konrad .
quantum computation with classical light : implementation of the deutsch jozsa algorithm .
, 380(2223):1925 1931 , 2016 .
vincenzo dambrosio , nicol spagnolo , lorenzo del re , sergei slussarenko , ying li , leong chuan kwek , lorenzo marrucci , stephen p. walborn , leandro aolita , and fabio sciarrino .
photonic polarization gears for ultra - sensitive angular measurements . , 4:022115 , sep 2013 .
giovanni milione , thien an nguyen , jonathan leach , daniel a nolan , and robert r alfano .
using the nonseparability of vector beams to encode information for optical communication .
, 40(21):48874890 , 2015 .
s. sponar , j. klepp , r. loidl , s. filipp , k. durstberger - rennhofer , r. a. bertlmann , g. badurek , h. rauch , and y. hasegawa .
geometric phase in entangled systems : a single - neutron interferometer experiment .
, 81:042113 , apr 2010 .
salla gangi reddy , shashi prabhakar , a. aadhi , ashok kumar , megh shah , r. p. singh , and r. simon . measuring the mueller matrix of an arbitrary optical element with a universal su(2 ) polarization gadget .
, 31(3):610615 , mar 2014 . | we generate the non - separable state of polarization and orbital angular momentum ( oam ) using a laser beam .
the generated state undergoes a cyclic polarization evolution which introduces a pancharatnam geometric phase to the polarization state and in turn a relative phase in the non - separable state .
we experimentally study the violation of bell - chsh inequality for different pancharatnam phases introduced by various cyclic polarization evolutions with linear and circular states as measurement bases . while measuring in linear bases , the bell - chsh parameter oscillates with pancharatnam phase .
one can overcome this dependence by introducing a relative phase in one of the projecting state .
however for measurement in circular bases , the pancharatnam phase does not affect the bell - chsh violation .
_ keywords _ : orbital angular momentum , non - separable states , pancharatnam phase |
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. ||||| Wesley, a 7-month-old giraffe, died after an apparent spinal injury
The giraffe got his head stuck between two posts and panicked
A decision was made to euthanize him after he lost ability to stand and condition worsened ||||| Follow CBSMIAMI.COM: Facebook | Twitter
MIAMI (CBSMiami) — One of Zoo Miami’s very own has passed away following what they are calling a freak accident.
A young male giraffe named “Wesley,” born last May at the zoo, had to be euthanized on Tuesday after he had lodged his head between two posts.
“He lowered his neck and wedged his head and panicked and as he panicked, he pulled his neck and obviously caused some traumatic injury to his spinal cord and neck,” said Ron Magill of Zoo Miami told CBS4’s Ted Scouten.
It all happened while another giraffe was undergoing a procedure. Wesley had returned to the holding area and apparently tried to see what was happening to the giraffe.
The staff was able to dislodge him within a few minutes, officials said, but by that time, it was too late to prevent significant damage.
“They tried for several hours with different types of medications, different types of supportive therapy, but it was a consistent and dramatic decline and eventually a very difficult decision had to be made to euthanize him,” said Magill.
The injury prevented him from being able to stand and maintain equilibrium.
If a giraffe can’t stand up, it can’t survive, Magill told Scouten.
“He was falling over. They went as far as to use a sling to try to get him up to support him with a sling to maintain his weight and it got progressively worse. It was just horrific,” said Magill.
A necropsy will be performed Wednesday to find out the extent of the injury.
Wesley was the 48th giraffe born at the zoo. As for the accident, it’s the first of its kind in the zoo’s history.
Zoo staff said they are making modifications around the zoo to prevent an accident like this from happening again.
“Since then, we had a welder come out. We’ve closed every possible gap. We’ve blanketed the entire zoo to make sure something like that cannot happen in a similar way,” said Magill. | – Staff at Zoo Miami are mourning the loss of a juvenile giraffe that had to be put down Tuesday after the 7-month-old got his head stuck in a fence. Wesley the giraffe poked his head into a 10-inch gap in a chain link fence on Tuesday, toward where another giraffe was having a routine exam, but panicked when he couldn't get it out again, zoo rep Ron Magill tells the Miami Herald. As Wesley tried to pull his head out, he lost his footing, causing serious injury to his neck. Zoo staff freed the giraffe's head in minutes, but Wesley couldn't stand, even with the help of a sling. Zoo staff "tried for several hours with different types of medications, different types of supportive therapy," Magill tells CBS Miami. But "it became painfully obvious that he'd done a traumatic injury, probably to his spinal cord." "I've been here for 36 years; we've never had an incident like this," Magill adds. "It was just horrific." Staff have since blocked the hole in the fence and sealed similar openings elsewhere in the zoo so such an accident "won't happen again," Magill says. Similarly, a baby giraffe died at a California zoo in October after running into a metal wire barrier, per the Fresno Bee. |
in the recent papers @xcite , @xcite the dilepton ( dimuon and dielectron ) production at the lhc was studied in the framework of the _ rssc model _
( randall - sundrum - like model with the small curvature ) @xcite-@xcite .
the classical action of the model is @xmath0 where @xmath1 is the 5-dimensional metric , with @xmath2 , @xmath3 , and @xmath4 is the 5-th dimension coordinate of the size @xmath5 .
the quantities @xmath6 are induced metrics on the branes , @xmath7 and @xmath8 are brane lagrangians , @xmath9 , @xmath10 . as in the original rs model @xcite ,
the periodicity @xmath11 is imposed and the points @xmath12 and @xmath13 are identified .
thus , we get the orbifold @xmath14 .
there are two 3d branes located at the fixed points @xmath15 ( plank brane ) and @xmath16 ( tev brane ) .
the sm fields are constrained to the tev brane , while the gravity propagates in all spatial dimensions . in order to solve einstein - hilbert s equations which follow from the action ( [ kisselev : action ] ) , it is assumed that the background metric respects 4-dimensional poincare invariance @xmath17 thus , the 5-dimensional metric tensor has the form @xmath18 where @xmath19 and @xmath20 is the minkowski tensor @xmath21 .
the background metric was found to be @xcite @xmath22 with the fine tuning @xmath23 ^ 2 \ ; , \nonumber \\
\lambda_1 & = & - \lambda_2 = 12 \bar{m}_5 ^ 3 \kappa \;.\end{aligned}\ ] ]
the quantity @xmath24 defines the curvature of the 5-dimensional space - time . in the rssc model
the hierarchy relation looks like @xmath25 where @xmath26 is the reduced planck scale , and @xmath27 is the _ reduced _ fundamental gravity scale .
@xmath27 is related to the 5-dimensional planck scale as @xmath28 the masses of the kaluza - klein ( kk ) graviton excitations @xmath29 are proportional to @xmath24 , @xmath30 the interaction lagrangian of gravitons is given by @xcite , @xcite @xmath31 where @xmath32 is the energy - momentum tensor of the sm fields on the tev brane , and @xmath33 note that in the rssc model the mass spectrum ( [ kisselev : graviton_masses ] ) and experimental signature are similar to those in the add model with one flat extra dimension @xcite .
let us remember that the original rs model predicts heavy graviton resonances .
in the framework of the rssc model @xcite , @xcite , gravity effects can be searched for in the dilepton production ( @xmath34 ) , @xmath35 in particular , the @xmath36-distribution of the final leptons in the process ( [ kisselev : process ] ) is given by the formula @xmath37 here @xmath38 is the distribution of the parton of the type @xmath39 in momentum fraction @xmath40 inside the proton taken at the scale @xmath41 .
@xmath42 is the differential cross section of the subprocess @xmath43 . in eq .
( [ kisselev : cross_sec ] ) two dimensionless variables are introduced @xmath44 where @xmath45 is the momentum fraction of the parton @xmath46 inside the proton .
the contribution of the virtual gravitons to lepton pair production comes from the quark - antiquark annihilation and gluon - gluon fusion , @xmath47 where @xmath48 and @xmath49 are mandelstam variables of the subprocess .
the sum @xmath50 is the invariant part of the partonic matrix elements , with @xmath51 being total width of the graviton with the kk number @xmath52 and mass @xmath53 @xcite @xmath54 note that the function @xmath55 is universal for all processes mediated by @xmath56-channel virtual gravitons . in papers
@xcite , @xcite contributions from @xmath56-channel gravitons to the @xmath36-distributions of the final leptons were calculated in the rssc model by using eqs .
( [ kisselev : cross_sec])- ( [ kisselev : parameters ] ) .
the calculations were made for different values of 5-dimensional planck scale @xmath27 .
the mstw 2008 nnlo parton distributions @xcite were used .
the pdf scale @xmath41 was taken to be equal to the invariant mass of the lepton pair , @xmath60 . in fig .
[ kisselev : fig:1 ] the gravity cross sections for the dimuon production at the lhc are presented .
the gravity mediated contributions to the cross sections do not include the sm contribution .
[ kisselev : fig:2 ] demonstrates that an ignorance of the graviton widths would be a rough approximation since it results in very large suppression of the gravity contributions .
the @xmath36-distributions for the dielectron production are shown in fig .
[ kisselev : fig:3 ] and fig .
[ kisselev : fig:4 ] , for @xmath62 tev and @xmath63 tev , respectively .
let @xmath64(@xmath65 ) be a number of signal ( background ) dilepton events with @xmath66 , @xmath67 then one can define the statistical significance @xmath68 and require a @xmath69 effect . in fig .
[ kisselev : fig:5 ] the statistical significance is shown for @xmath70 tev as a function of the transverse momentum cut @xmath71 and reduced 5-dimensional planck scale @xmath27 .
[ kisselev : fig:6 ] represents the statistical significance for the dimuon events at @xmath72 tev .
the statistical significances for the dielectron events are shown in fig .
[ kisselev : fig:7 ] and fig .
[ kisselev : fig:8 ] . as a result ,
lhc discovery limits on the 5-dimensional planck scale @xmath75 were obtained .
in particular , for the ( 7 + 8 ) tev lhc with the integrated luminosity ( 5 + 20 ) fb@xmath76 the search limit in the dielectron production is equal to @xcite @xmath77 for the 13 tev dielectron events with the integrated luminosity 30 fb@xmath76 the search limit was found to be @xcite @xmath78 11 a.v .
kisselev , jhep * 04 * , 025 ( 2013 ) [ arxiv:1210.3238 ] .
kisselev , arxiv:1306.5402 .
g. f. giudice , t. plehn and a. strumia , nucl .
* b 706 * , 455 ( 2005 ) [ hep - ph/0408320 ] .
kisselev and v.a .
petrov , phys . rev . *
d 71 * , 124032 ( 2005 ) [ hep - ph/0504203 ] .
kisselev , phys . rev . *
d 73 * , 024007 ( 2006 ) [ hep - th/0507145 ] .
l. randall and r. sundrum , phys .
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n. arkani - hamed , s. dimopoulos and g. dvali , phys .
* b 429 * , 263 ( 1998 ) [ hep - ph/9803315 ] ; i. antoniadis , n. arkani - hamed , s. dimopoulos and g. dvali , phys . lett . * b 436 * , 257 ( 1998 ) [ hep - ph/9804398 ] ; n. arkani - hamed , s. dimopoulos and g. dvali , phys .
d 59 * , 086004 ( 1999 ) [ hep - ph/9807344 ] .
martin , w.j .
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j. c * 63 * , 189 ( 2009 ) [ arxiv:0901.0002 ] .
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* b 711 * , 15 ( 2012 ) [ arxiv:1202.3827 ] . | the brief review of the recent results obtained in the randall - sundrum scenario with the small curvature of the five - dimensional space - time is presented . |
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Given his history, you wouldn't think Chris Brown would want to associate himself with violence and destruction.
But Breezy clearly likes courting controversy: On Halloween, the 23-year-old R&B star and his pals dressed up with beards, turbans and fake guns—seemingly trying to look like stereotypical Arab terrorists—as they swung by Rihanna's Halloween bash at Greystone Manor in West Hollywood.
"Ain't nobody F--king wit my clique!!! #ohb," Chris tweeted, linking to an Instagram shot of himself and four pals posing threateningly for the camera.
In the picture, Brown holds a large (presumably) fake assault rifle in the air, surrounded by his crew draped in fake ammo.
Although Brown himself provided no commentary on his questionable costume, Mama Breezy was quick to weigh in on Twitter.
"HALLOWEEN IS FOR FUN NOTHING MORE THAN JUST FUN," Joyce Hawkins wrote. "GET A LIFE PLEASE."
OK, Mom. We still think Chris might've been safer with a less threatening ensemble. There's always next year.
(Originally published on Nov. 1, 2012 at 6:15 a.m. PT)
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||||| PICTURES: LeAnn Rimes Dresses as "Sandy" From Grease Days After Superstorm
Sexy or insensitive?
On Wednesday,LeAnn Rimes shared her 2012 Halloween getup to her 300,000-plus Twitter followers. Her choice? Sandy.
PHOTOS: Best and worst Halloween 2012 costumes in Hollywood
The country singer, 30, channeled Olivia Newton-John's character from Grease -- as she appears transformed at the very end of the beloved 1978 musical film, sexed-up in tight spandex, luscious curls and platform wedges. Her husband Eddie Cibrian was Danny, Sandy's bad-boy love from the T-Birds, whom she strives to impress with a more mature, edgy look.
"Danny and Sandy #Halloween," Rimes explained beneath a pic in which she leans in for a kiss from Cibrian, 38, with a pompadour wig, black t-shirt and jeans.
Credit: twitter.com
PHOTOS: LeAnn's skimpiest bikinis ever
It's a surprising choice of costume, given that another Sandy, Superstorm Sandy, wreaked major havoc in NYC, New Jersey and surrounding areas just days ago, with over 50 people confirmed dead, widespread power outages, a transit shutdown and extensive damage throughout the region.
In another pic, Rimes and Cibrian posed with Mason, 9, and Jake, 5, his sons with ex-wife Brandi Glanville. "Family of the Grease days, Indiana Jones and a tribute to our navy seals," Rimes said.
The Grammy winner is on the comeback trail after checking herself in a rehab center in August for anxiety.
PHOTOS: LeAnn and Eddie's romance
"I feel like I am starting over even though I've had all these years behind me," Rimes recently told Katie Couric. "How many people get to [start] over again in this day and age?"
Adds Rimes, "People look at you and go, 'Why are you struggling?' No one can quite understand why you hurt so badly." | – Chris Brown, that bastion of good judgement, is once again courting controversy. The singer attended a Halloween party thrown by Rihanna, but the latest Brown-Rihanna meeting isn't what has fans peeved—it's his costume choice. E! reports that Brown and four friends went as a posse of Arab-style terrorists, complete with beards, turbans, and weapons, as evidenced by an Instagram shot and Brown's accompanying tweet: "Ain't nobody F--king wit my clique!!! #ohb." Sure, it's just a costume, but "given his history, you wouldn't think Chris Brown would want to associate himself with violence and destruction," writes Rebecca Macatee. Meanwhile, Leann Rimes stirred up her own batch of controversy by dressing as Sandy from Grease—days after the storm of the same name. US Weekly has pictures. Hubby Eddie Cibrian got his Danny on to complete the effect. |
As big as a car and as well-equipped as a laboratory, NASA's newest Mars rover blows away its predecessors in size and skill.
In this 2011 artist's rendering provided by NASA/JPL-Caltech, a "sky crane" lowers the Mars Science Laboratory Curiosity rover onto the surface of Mars. The mobile robot is designed to investigate Mars'... (Associated Press)
In this 2011 artist's rendering provided by NASA/JPL-Caltech, the Mars Science Laboratory Curiosity rover examines a rock on Mars with a set of tools at the end of its arm, which extends about 2 meters... (Associated Press)
Nicknamed Curiosity and scheduled for launch on Saturday, the rover has a 7-foot arm tipped with a jackhammer and a laser to break through the Martian red rock. What really makes it stand out: It can analyze rocks and soil with unprecedented accuracy.
"This is a Mars scientist's dream machine," said NASA Jet Propulsion Laboratory's Ashwin Vasavada, the deputy project scientist.
Once on the red planet, Curiosity will be on the lookout for organic, carbon-containing compounds. While the rover can't actually detect the presence of living organisms, scientists hope to learn from the $2.5 billion, nuclear-powered mission whether Mars has _ or ever had _ what it takes to nurture microbial life.
Curiosity will be "the largest and most complex piece of equipment ever placed on the surface of another planet," said Doug McCuistion, director of NASA's Mars exploration program.
Ten feet long, 9 feet wide and 7 feet tall at its mast, Curiosity is about twice the size of previous rovers Spirit and Opportunity, weighs 1 ton and is loaded with 10 science instruments. Its formal name: Mars Science Laboratory, or MSL.
In a spacecraft first, Curiosity will be lowered to Mars' surface via a jet pack and a tether system similar to the sky cranes used by helicopters to insert heavy equipment in inaccessible spots on Earth. No bouncing air bags like those used for the Mars Pathfinder lander and rover in 1997 and for Spirit and Opportunity in 2004 _ Curiosity is too heavy for that.
It is the kind of precision landing that officials said will benefit future human explorers on Mars.
The rover is scheduled to arrive at the mineral-rich Gale Crater next August, 8 1/2 months after embarking on the 354-million-mile voyage aboard an Atlas V rocket.
It's a treacherous journey to Mars, and the road is littered with failures. In all, more than three dozen missions have aimed over the decades at the most Earth-like planet known, and fewer than half have succeeded. Of this flotilla, only one lander is still working on the dry, barren, cold surface _ Opportunity _ and only three craft still are observing the planet from orbit.
In fact, Russia's latest Mars probe remains stuck in orbit around Earth two weeks after its botched launch. NASA has had better luck at Mars, although it has lost a few spacecraft there.
"Mars is difficult, and so many things have to go right for a mission to work," said Michael Meyer, lead scientist for NASA's Mars exploration program.
Curiosity is the capstone of what NASA calls the year of the solar system. A spacecraft is en route to Jupiter after lifting off last August from Cape Canaveral, and twin lunar probes launched in September will arrive at the moon New Year's weekend.
A huge crowd _ 13,500 invited guests _ is expected for Curiosity's Thanksgiving weekend send-off.
There will be more anxiety than usual over the launch. Curiosity holds 10.6 pounds of plutonium, more than enough to power the rover on the Martian surface for two years. A nuclear generator won out over solar energy because it allows for a bigger workload and more flexibility. The plutonium is encased in several protective layers in case of a launch accident.
Once safely down on Mars, the rover will survey the landscape with high-definition and laser cameras mounted like eyes atop its mast. The laser will aim at soil and rocks as far as 23 feet away to gauge their chemical composition.
The rover also has a weather station for updates on Martian temperature, humidity and wind, as well as a radiation detector that will be especially useful for planning human expeditions.
Despite all its fancy upgrades, Curiosity will go no faster than the one-tenth-mile-per-hour logged by past Martian rovers. But it is expected to venture more than 12 miles during its two-year mission. If it's still working after that, it will keep on trucking, possibly all the way up the crater's 3-mile peak.
This mountain is composed of geologic layers similar to what one might find in the Grand Canyon, said project scientist John Grotzinger, a geologist at the California Institute of Technology.
"Our rover is going to be like John Wesley Powell going down the Grand Canyon," Grotzinger said, referring to the 19th-century explorer who led an expedition down the Colorado River.
The next logical step in Mars exploration, said Cornell University's Steve Squyres, who led the science team for Spirit and Opportunity, would be a robotic mission to deliver Mars samples to Earth for analysis. NASA hopes to pull that off later this decade, but the project is on Congress' chopping block.
Squyres warned that without such missions, U.S. leadership in science won't just be challenged _ "it's going to go away."
___
Online:
NASA: http://marsprogram.jpl.nasa.gov/msl/ ||||| The rover is to be powered by nuclear generator (not shown in this drawing) permitting the Mars machinery a long range ability to explore science targets.
NASA's new state-of-the-art Mars rover, which is slated to launch into space on Saturday (Nov. 26), will investigate whether the Martian environment is — or ever was — habitable. While the ambitious mission is expected to help researchers understand the Red Planet better than ever before, it is also a key stepping stone in the wider search for alien life in the universe, scientists said.
The Mars Science Laboratory (MSL), or Curiosity rover, is equipped with a suite of instruments that will allow scientists to study features on the Martian surface and the surrounding environment to piece together clues of the planet's potential habitability.
"We have to remember that any life that exists somewhere else will be a function of that environment," Pamela Conrad, deputy principal investigator for the Mars Science Laboratory, said in a news briefing today (Nov. 22). "Mars Science Laboratory is off to study that environment. Hopefully we'll walk away with a lot more information about what environments look like on the surface of Mars. I like to say it's extraterrestrial real estate appraisal."
Curiosity is carrying 10 instruments that will allow it to dig, drill and analyze rock samples. The vehicle also has the ability to fire a laser at rocks, creating a cloud of plasma that can be scanned to reveal its chemical makeup.
As the rover rolls along the surface of Mars, it will also be able to sniff the air to help scientists paint a clearer picture of the Martian environment, Conrad said.
A schematic showing the 10 science instruments aboard NASA's Mars rover Curiosity. Credit: NASA/JPL
The Mars Science Laboratory is not a life detection mission, but by understanding the chemical environment of Mars, and by searching for signs of habitability in the planet's geological history, researchers can gain additional insight into whether and how microbial life could exist on the Red Planet. [7 Biggest Mysteries of Mars]
But, like any mission of exploration, it's impossible to say in advance what discoveries will be made.
"Do we anticipate that we'll learn a lot about Mars? Absolutely," Conrad said. "Do we know specifically what that will be? We have no clue."
Still, the car-size Curiosity rover should help clarify whether or not Mars ever hosted life. In addition, the mission is also an important stepping stone for other searches for alien life.
"The game is afoot, the search is on and MSL is taking a very important step and part of it is developing a strategy for narrowing that search," Mary Voytek, director of NASA's astrobiology program, said.
Ultimately, scientists said the search for life elsewhere in the universe is of fundamental importance to humankind.
"It'sthe argument that is made for exploration anywhere," said Catharine Conley, a planetary protection officer at NASA. "We don't know what we're going to find, but if we don't go there, we're not going to find it."
You can follow SPACE.com staff writer Denise Chow on Twitter @denisechow. Follow SPACE.com for the latest in space science and exploration news on Twitter @Spacedotcom and on Facebook. | – It’s “a Mars scientist's dream machine”: NASA is getting ready to launch its largest-ever Mars rover on Saturday. It’s not just big—it’s “the largest and most complex piece of equipment ever placed on the surface of another planet,” the agency’s Mars boss tells the AP. Curiosity, as the 7-foot-high rover is called, is equipped with a jackhammer and laser arm to break through rocks as it probes Martian soil. The $2.5 billion machine will attempt to figure out whether Mars has ever been capable of sustaining life. Scientists have found evidence of methane on the planet, and they’re wondering how it got there, the New York Times reports. “I like to say it's extraterrestrial real estate appraisal,” an expert tells Space.com. Officially called the Mars Science Laboratory, the rover will be lowered to the planet’s surface using a crane-like system similar to what may be used in the future to land humans on the Red Planet. Of course, no aliens have been discovered yet, the White House says. |
most solar system bodies are depleted in nitrogen relative to the sun and the ism .
@xcite compare the cno abundances in various solar system bodies relative to silicon .
comets halley and hale - bopp , which likely formed in the outer disk ( @xmath4 au ) , where there is thought to be less chemical reprocessing , are depleted in nitrogen by less than an order of magnitude with respect to solar values .
in contrast the nitrogen content of meteorites is between one and three orders of magnitude below the amount of nitrogen that was available , as traced by the sun @xcite .
in fact , comets and meteorites exhibit greater depletion in nitrogen than in other volatiles such as oxygen and carbon @xcite . in this context
the earth is extremely depleted in nitrogen with an abundance ratio more than five orders of magnitude below the solar abundance .
most of the known nitrogen resides in the atmosphere in the form of , however , it is possible that much of earth s nitrogen was locked in its interior @xcite
. the @xmath5 ratio of the terrestrial surface , which includes the atmosphere and oceans , as well as the crust , agrees with that of chondrites , suggesting that both the earth s surface and meteorites obtained their nitrogen from the same reservoir @xcite .
it remains unclear what the dominant nitrogen - bearing species was upon delivery to the young earth , whether it was carried by organics in meteorites , from the solar nebular gas , or /organics in cometary bodies @xcite .
the cronian satellites titan and enceladus both show evidence of rich atmospheres @xcite .
isotopic abundances in titan s atmosphere were measured by the huygens probe and the low @xmath6ar/@xmath7n ratio along with the absence of detectable of @xmath8ar , kr and xe provides circumstantial evidence that titan first received its nitrogen in a less volatile form , such as @xcite .
the nitrogen could later be converted to the more volatile , possibly by impacts during the period of late heavy bombardment @xcite . which nitrogen - bearing molecules end up in solar system bodies depends on the chemical composition of the protoplanetary disk at the time of planetesimal formation . in this paper
we show that the dominant bearer of nitrogen is highly dependent on initial chemical abundances .
there continues to be some uncertainty in regards to the nitrogen partitioning in dense molecular pre - stellar cores , which represent the initial conditions .
this uncertainty stems from the difficulty of detecting many of the most probable nitrogen reservoirs : n , , and nitrogen - bearing ices .
n and are not directly observable in the dense ism . instead
their abundances must be inferred from observations of trace molecules such as n@xmath1h@xmath2 , which is a reaction product of .
ice abundances are derived from absorption features . however , the measured ice abundances are uncertain due to the blending of particular absorption features with those of water and silicates @xcite .
spectroscopic observations of ices toward low - mass young stellar objects as part of the spitzer `` cores to disks '' program find that on average 10% of the total nitrogen is contained in known ices , primarily , nh@xmath9 , and xcn ( ocn@xmath10 ) , though in some sources the percentage is as high as 34% @xcite .
the remaining nitrogen is posited to reside in the gas phase as either atomic n or .
@xcite estimate abundances in multiple dense molecular cores using observations of @xmath1h@xmath2 .
they find an average fractional abundance of 4@xmath11 with respect to , or @xmath12 of the total nitrogen reservoir assuming solar abundances @xcite .
@xcite find the gas phase nitrogen to be primarily in atomic as opposed to molecular nitrogen for the prestellar core b68 , though based on their models the main nitrogen - bearing species is ice .
similarly , @xcite conclude that 45% of the total elemental nitrogen in dense clouds is in the form of ices on grains , though the abundances they predict are larger than those observed .
le gal et al .
( 2014 ) modeled the gas phase nitrogen chemistry in dark clouds . starting with nitrogen all in gas phase
n they find that once a steady state is reached the dense core contains equal abundances of n and with a small fraction of the initial nitrogen in other species .
has long been a tracer of dense cores ( e.g. * ? ? ?
* ) . using detections of inverse transitions toward five starless cores , @xcite calculated gas abundances ranging @xmath13 to @xmath14 with respect to .
gas has also been observed in absorption several thousand au from the class 0 protostar iras 16293 - 2422 with an abundance relative to of @xmath15 @xcite .
finally , @xcite find that the steady state abundances of nitrogen hydrides in their chemical model were in good agreement with those observed toward iras 16293 - 2422 . in sum , in prestellar cores ,
gas phase is clearly not a major nitrogen reservoir , however as discussed earlier there is a significant amount of potentially present in the ices . @xcite
modeled the chemical evolution of a collapsing protostar from a pre - stellar core to a disk , finding that the disk begins with most of the nitrogen in gas phase with minor contributions from n , , and no . despite detections in these earlier stages of star formation
there are currently no published detections of gas in protoplanetary disks , though upper limits exist for several t tauri stars in the near - infrared @xcite .
however , both cn and hcn have been detected in multiple protoplanetary disks ( e.g. * ? ? ?
* ; * ? ? ?
* ) and resolved @xmath1h@xmath2 emission is seen in the t tauri system tw hya @xcite while unresolved emission is seen toward several more systems @xcite .
thus a variety of potential initial distributions of the total nitrogen reservoir could be provided to the forming disk .
it is possible that a substantial fraction of the nitrogen could be in the form of n gas , gas , or ices . alternatively ,
if the source is warm enough during collapse , a significant amount of could be provided to the disk as gas . in this paper
we perform simulations of the disk chemistry in which we make four different initial abundance assumptions : ( 1 ) most of the nitrogen is in atomic form ; ( 2 ) most of the nitrogen arrives in the disk in molecular form ; ( 3 ) the nitrogen arrives as ice ; ( 4 ) most of the nitrogen arrives as gas .
we use the disk chemistry model of @xcite to explore the effects of different initial abundances .
we first set the physical structure of the disk , including temperature , density , and dust properties .
next we perform uv and x - ray radiative transfer , assuming all radiation is from the central star .
the model then calculates chemical abundances based on a network of 5903 chemical reactions and specified initial abundances .
the specifics of the model are discussed in greater detail below .
we use the two - dimensional , azimuthally symmetric disk physical structure adopted by @xcite .
this model is designed to represent a ` typical ' t - tauri disk based on the transition disk observations presented by @xcite . the density structure is fixed and of the form : @xmath16 here @xmath17 and @xmath18 are the characteristic surface density and radius , taken to be 3.1 g @xmath19 and 135 au respectively .
the disk is a settled disk , @xmath20=0.1 , where @xmath20 is the dust - to - gas mass ratio of dust grains in the upper disk relative to the standard value of 0.01 @xcite .
smaller @xmath20 values indicate less dust in the upper disk and more dust in the midplane .
two types of dust are included : small , micron size grains and larger millimeter size grains .
the grain distribution is given by : @xmath21},\ ] ] @xmath22},\ ] ] and @xmath23 the height profile given by equation ( 4 ) is applied to both the small dust grains and the gas , with a characteristic scale height of @xmath24 = 12 au and @xmath25 = 0.3 .
the scale height for the large grains is smaller by a factor of @xmath26 .
85% of the total dust mass is in the large grains such that @xmath27 = 0.85 .
the dust density and temperature distributions are shown in figure [ physicalproperties ] .
the fuv field from the central star , including ly@xmath28 radiation , and the stellar x - ray field were generated using a monte carlo radiative transfer and scattering model as described by @xcite .
we adopt the fuv spectrum to be that measured for tw hya @xcite .
we assume a thermal x - ray spectrum between 1 and 10 kev with an integrated x - ray luminosity of erg s@xmath29 , which is typical for a t tauri star @xcite .
we then compute the x - ray attenuation using the cross - sections of @xcite .
ly@xmath28 radiation contains @xmath30 of the total fuv flux @xcite .
additionally several species have photodissocation cross sections close to ly@xmath28 . for these reasons ,
ly@xmath28 radiation can not be ignored , as is the case for the weaker uv emission lines @xcite .
in addition to scattering off dust grains , ly@xmath28 photons will first isotropically scatter off of hydrogen atoms on the top of the disk surface .
this layer scatters a fraction of the ly@xmath28 radiation more directly towards the midplane , allowing the ly@xmath28 radiation greater penetrating power than the whole of the fuv continuum and lines beyond ly@xmath28 @xcite .
we use the chemical model of @xcite , which is based on the gas - phase reaction network of the ohio state university astrophysical chemistry group @xcite and modified to include the updated reaction rates of @xcite .
this network does not include the expansions for reactions at high temperatures from @xcite .
thus the predictions for the inner edge of the disk may change . however , in this paper we focus on the abundances of molecules with high volatility at radii beyond a few au .
the chemical code is run at 74 radii with each radius broken into 45 vertical zones .
the grid spacing is logarithmic in radius and linear in angle . the chemistry in each vertical zone is run independently , except for the considerations needed for self - shielding , which is treated vertically , with no mixing between zones .
a pseudo two - dimensional result is obtained by running the model for many radii .
the model includes photodesorption , photodissociation , freeze out , grain surface reactions , gas phase ion and electron reactions , and cosmic ray and stellar x - ray ionization as well as self - shielding of and co. cosmic rays are assumed to strike the disk vertically with an unshielded ionization rate of @xmath31 s@xmath29 .
the photodissociation rates depend on the strength of the radiation field at a given point in the disk and the molecule s cross section .
grain surface reactions are limited to the formation of , h@xmath32o , , and ch@xmath33 via successive hydrogenation .
the self - shielding and grain surface reactions are time dependent and the chemistry is run for 3 myr .
we present the results from four chemical models , each with different initial conditions as listed in table 1 .
model n uses the initial abundances of @xcite , with most nitrogen originating in atomic form .
none of the initial nitrogen is in ices .
most of the oxygen is provided as either co , @xmath34 , or water ice , @xmath35 , with a small fraction of the oxygen in other gas phase species .
these values are for the model molecular cloud of @xcite , which is in good agreement with observed molecular abundances in cores ( e.g. * ? ? ?
* ) . in model ( gr )
most of the nitrogen is in ice and there is initially no atomic nitrogen .
this is a simplification of the @xcite and @xcite models which predict large ice abundances .
model differs from model ( gr ) in that it starts with in the gas phase .
this model is only viable if the collapse of the initial molecular cloud liberates from grains .
finally , model starts with the nitrogen primarily in .
as discussed above , gas phase n and are not directly observable , making it difficult to observationally determine the relative gas phase abundances .
model , when compared to model n , allows us to determine whether the partitioning between n and has an observable effect on the chemistry at later stages .
we emphasize that the variations in the initial conditions of our models do not represent the most likely nitrogen distribution in the disk .
rather , they are extreme examples meant to illustrate the effect the initial nitrogen distribution has on the chemistry at later stages .
the following results are for a chemical time of @xmath361 myr unless otherwise stated .
the abundances of the major nitrogen species are shown for a cross section of the disk in figures [ standardcontours1 ] and [ standardcontours2 ] . in the cold midplane ( @xmath37 ) the thermal desorption rates are low , allowing many species to freeze out onto ices . above the midplane
the ices have evaporated and the chemistry is able to process n into as well as ice .
this region corresponds to the ` warm molecular layer ' @xcite . at
@xmath38 = 200 au the warm molecular layer extends vertically from @xmath39 @xmath40 60 au . in the upper ,
photon dominated region of the disk molecules are destroyed quickly and atomic nitrogen dominates .
figure [ zcut ] shows the vertical structure of nitrogen carriers at a radius of 200 au .
this far from the central star , ice is only abundant close to the midplane where the gas temperature is low , @xmath41 20 k , and molecules are shielded from radiation from the central star .
however , the midplane is dominated by ice .
the majority of the ice in the midplane is formed on the grains , rather than resulting from freeze out of gas .
closer to the star ice evaporates and hcn ice , which has a higher binding energy , is present in greater abundance ( see figure [ snow ] ) . inside @xmath38 = 200 au
chemical processing converts the n gas into in the midplane . at the disk surface n
is also able to form , cn , and hcn gas . for @xmath42 10
au these molecules are able to remain in the gas phase in the surface layers , while for @xmath43 10 au they adsorb onto dust grains .
the highest concentration of and ice in the disk is in the range @xmath44 20 au except in the outer disk , where ice remains highly abundant at @xmath44 50 au ( figure [ standardcontours1 ] ) .
in addition to forming on grains , is the end result of a series of ion - neutral reactions and forms quickly in these regions . due to its high binding energy , ice acts as a sink , leaving little in the gas phase .
however , near the midplane there is a residual abundance of and .
cosmic ray desorption prevents from completely adsorbing onto grains . instead , remains active in the gas phase chemistry , allowing the continued formation of .
this chemistry is sensitive to the binding energies of molecules such as on grains and to the presence / absence of ionizing photons .
however , these binding energies are often uncertain and the presence of cosmic rays in the midplane has been called into question @xcite .
this uncertainty will be discussed in more detail in section 3.3 .
cn and hcn gas phase abundances are low in the cold midplane region ( figure [ standardcontours2 ] ) .
these molecules are formed via gas phase reactions and only exist in abundance in the warm molecular layer . after forming , cn and hcn quickly adsorb onto dust grains .
thus cn and hcn ices also exist in the molecular layer . at @xmath38 = 200 au , hcn ice becomes the dominant form of nitrogen at heights between 10 and 30 au ( figure [ zcut ] ) . because much of the cn goes into forming hcn and before it can freeze out
, a similar peak is not observed in cn ice . for @xmath43 100 au
, @xmath1h@xmath2 traces the midplane ( figure [ standardcontours2 ] ) . inside 100 au ,
@xmath1h@xmath2 is destroyed via gas phase reactions with co , which does not exist in abundance in the midplane for @xmath43 100 au .
no , a precursor molecule to , is most abundant in the surface layers ( @xmath45 au at @xmath46 au ) , where the main formation and destruction mechanisms are : @xmath47 and @xmath48 in the surface layers oh is slightly more abundant than no , allowing the creation of no to outpace its destruction .
figure [ snow ] illustrates the snow lines for nitrogen - bearing species in the midplane . at a radius of 100 au in the midplane , and n have evaporation temperatures of 14.8 k and 15 k respectively .
these temperatures were calculated using eqn . 5 from @xcite and the binding energies in table 1 .
in comparison , the evaporation temperatures of hcn and are 38 k and 57 k. while it is fairly easy to free n and from grains in the midplane , hcn and remain locked in ices outside of 17 au and 5 au respectively .
this range of evaporation temperatures results in a series of sublimation fronts .
the dearth of ices at small radii does not correspond with an increase in the gas phase abundance of the same species . instead ,
inside 150 au the majority of the nitrogen makes its way into via chemical processing .
this process is discussed in more detail in section 3.1.3 . early in the chemical evolution of the disk , most of the hcn gas in the midplane either freezes out onto grains or is destroyed via gas phase reactions with ions .
because of its high binding energy , it remains on grains for radii greater than 17 au .
the same process occurs for the and cn gas , resulting in a substantial fraction of the total nitrogen locked in hcn and ices in the midplane beyond 17 au .
the resulting reservoir of moderately volatile ices could be used to form more complex molecules , thus changing the picture presented above . and
hcn are both needed to form aminomethanol , a precursor to glycine , in ices via strecker synthesis @xcite . the same ices are also capable of forming hydroxyacetonitrile .
in addition hydrogenation of hcn can result in the formation of methylamine on grain surfaces @xcite .
ices in the presence of uv radiation have been shown to form more complex molecules ( e.g. * ? ? ?
for example , irradiation of ice at 10 k can lead to the formation of nh@xmath1 and n@xmath1h@xmath33 while becomes n@xmath0 @xcite . especially in the warm molecular layer , which is more transparent to uv photons that the midplane , the abundance of , , and hcn ices could decreases , corresponding to an increase in more complex species .
turbulent mixing would likely transport ices from the midplane to the warmer upper regions of the disk , where desorption would remove the molecules from grains @xcite .
once in the gas phase molecules such as would be dissociated , with the nitrogen eventually going into either or n depending on the local disk temperature .
additionaly , planetesimal drift and advection would bring ice coated grains to smaller radii @xcite . there
they would evaporate , likely contributing to the gas phase abundance . to explore time dependent behavior throughout the disk the abundances
are collapsed to radial column density plots by integrating over the vertical direction ( figure [ standardtime ] ) .
these plots provides the most complete information at a given stage in addition to allowing easy examination of the time evolution of the chemistry . at early stages , atomic
n , where the majority of the nitrogen initially resides , and dominate
. there is a general evolution of n becoming on fairly short time scales via gas phase reactions with cn and no .
these are both two step reactions : @xmath49 @xmath50 and @xmath47 @xmath51 though other reactions can also create cn and no .
the c and o are released when co reacts with he@xmath52 @xcite . beyond 50
au these reactions primarily take place in the warm molecular layer . inside 50
au the same reactions place a majority of the initial n into early on . at @xmath53
= 8.9@xmath54 years in our model the n gas column density still surpasses that of beyond @xmath38 = 200 au .
inside of 200 au the presence of gas phase co allows for more o to be present in the midplane .
some of this o goes into oh , leading to the formation of as discussed previously .
the evaporation timescale increases with temperature , so as time passes larger radii begin to be affected by evaporation .
for n the evaporation timescale in the midplane at 180 au is @xmath55 years .
this , in conjunction with the formation of on grains , destroys the n snow line at late stages .
once it freezes out onto grains , n ice is quickly converted to ice . over time
this depletes the n ice reservoir .
more of the nitrogen becomes locked in and hcn ices , with hcn ices becoming the dominant nitrogen - bearing species between 60 au and 170 au for late stages .
closer to the central star hcn is more likely to be photo - dissociated before it can freeze out onto the grains . as more of the total nitrogen becomes trapped in ices the abundances of the molecules needed to form , such as nh@xmath9 , drop and the formation rate of gas phase slows
this is also true for the precursors of hcn .
thus there is little change in ice and hcn ice abundances at late stages . in model ( gr ) the initial gas phase atomic
n has been replaced with ice .
radiation from the central star is unable to liberate the except at radii less than @xmath36 5 au and ice remains the dominant bearer of nitrogen for all times considered in our model ( figure [ nh3grcontours1 ] ) .
abundances of the remaining molecules are much lower than those in model n since most of the nitrogen remains in ice and does not participate in the chemistry ( figures [ nh3grcontours2 ] and [ nh3grstandard ] ) . model places the majority of the initial nitrogen in gas . at late stages
the nitrogen partitioning is very similar to that in model ( gr ) , though there are several key differences ( figures [ nh3contours1]-[nh3standard ] ) .
becomes trapped on grains in the warm molecular layer and the midplane early on . before freezing out
some of the gas phase is able to react with other molecules . because of this there is more gas , as well as hcn ice and cn ice , in model than in model ( gr ) .
the formation of additional depletes the no , such that model has slightly lower no abundances than those seen in model ( gr ) . in the midplane
the larger abundance also leads to the creation of more @xmath1h@xmath2 beyond 300 au when compared to model ( gr ) . in the surface layers
gas does not freeze out as quickly as it does closer to the midplane .
gas phase reactions are able to remove a larger fraction of the nitrogen from , most of which becomes n and gas .
model , where most of the nitrogen is initially in gas phase , results in a nitrogen partitioning very similar to that of model n ( figures [ n2contours1 ] - [ n2standard ] ) .
that the differences are so subtle indicates that the disk is able to efficiently transfer n to , assuming there is no substantial processing of n on grains limiting the availability of atomic n in the gas .
together , model n and model illustrate that if the nitrogen is delivered to the disk primarily as either atomic or molecular nitrogen , the disk will likely be able to produce significant amounts of gas via the reactions discussed previously .
much of the chemistry explored in this work depends on the amount of nitrogen available for gas phase reactions . in other words
, it depends on the desorption rates , which are extremely sensitive to the binding energies used .
the residual midplane abundance of in figure [ standardcontours1 ] is present because the evaporation temperature of is low enough to allow gas phase to exist in the midplane . in the absence of chemical processing the gas to ice ratio
is set by balancing freeze out with thermal and cosmic ray desorption : @xmath56 where @xmath57 is the number density of species x , @xmath58 is the vibrational frequency of bound to the grain , @xmath59 k is the binding energy of @xcite , @xmath60 k is the dust temperature at @xmath61 au in the midplane , @xmath62 s@xmath29 is the cosmic ray desorption rate , @xmath63 is the collisional cross section of a 0.1 micron dust grain , @xmath64 is the sound speed , and @xmath65 is the sticking coefficient , assumed to be 1 . at a radius of 100 au in the midplane
this gives @xmath66 .
the actual ratio for model n is @xmath67 , indicating that chemical processing and gas phase formation have a non - negligible effect on the ratio .
unfortunately it is not clear what assumptions should be made when determining binding energies experimentally .
the binding energy depends both on the species being bound to the grain and the composition of the grain s surface .
commonly used surfaces include co , h@xmath32o , silicates @xcite , and more recently co@xmath32 @xcite .
the binding energies of molecules on ices can be calculated or measured in the lab . in model
n the binding energy of is 790 k ( corresponding to an evaporation temperature of @xmath68 k in the midplane at 100 au ) and the binding energy of co is 855 k ( @xmath69 k ) , as determined by @xcite .
these binding energies assume an and co coated grain surface respectively and are appropriate for dust temperatures near 17 k. figures [ hbcontours1 ] and [ hbcontours2 ] show the resulting chemical abundances when the binding energies for co and are both changed to 1110 k ( @xmath70 k ) , as is appropriate for co@xmath32 coated grains and dust temperatures between 25 k and 50 k @xcite .
changing just these two binding energies has a noticeable effect on the chemical abundances ( figures [ hbcontours1 ] and [ hbcontours2 ] ) .
the residual gas near the midplane is gone , in addition to the lower abundances of n and gas in the warm molecular layer .
the abundances of most nitrogen - bearing ices has decreased .
however , much of the nitrogen in gas in figure [ standardcontours1 ] is now trapped in ice , particularly in the outer disk . with less gas phase available , the amount of gas inside of 200 au has also dropped .
the total amount of @xmath1h@xmath2 in the outer disk does not change , though it is less concentrated in the midplane and more abundant in the warm molecular layer compared to model n. the outer disk contains more no in the high binding energy model . with less
n in the gas phase to react with , no is not destroyed as quickly .
the differences in @xmath1h@xmath2 and no are particularly interesting , as these molecules are potentially observable .
many of the dominant nitrogen - bearing species , such as n , , and all ices , are not directly observable .
instead indirect methods are needed to infer their presence .
as discussed previously the existence of no and @xmath1h@xmath2 in the midplane depends on the amount of gas present . in this section
we discuss the feasibility of using no and @xmath1h@xmath2 to determine the dominant nitrogen reservoir .
we assume a disk at a distance of 140 pc inclined at an angle of 6@xmath71 .
emission from the @xmath1h@xmath2 j=4 - 3 transition , 372.67251 ghz , and no ( @xmath72 ) transition , 350.68949 ghz , are calculated using lime , a non - lte line radiation transfer code @xcite .
the @xmath1h@xmath2 transition was chosen based on the @xmath1h@xmath2 j=4 - 3 observations made by @xcite .
the no transition is the most readily observable transition based on radex calculations @xcite figure [ nnhp32 ] shows the strength of the @xmath1h@xmath2 ( 4 - 3 ) line for our four models relative to the strongest line , while figure [ nnhprad ] shows the average emission as a function of radius .
we choose to focus on the relative line strengths because the absolute line strength is highly dependent on the physical model used .
the strongest emission is seen in model n in the inner 25 au of the disk due to a temporary increase in the local @xmath1h@xmath2 abundance .
this is a time dependent effect that is also seen in the other models at slightly different times . as such
it should not be used as a way to differentiate between the models .
the cause is time dependent destruction of reactive molecules with @xmath1h@xmath2 .
these molecules , such as co and ch@xmath33 , are depleted in local layers via ionization effects @xcite . beyond @xmath38 = 25 au
the strongest emission is in model . at early times
there is less atomic nitrogen available to form on grains in model compared to model n and a larger fraction of the hydrogen goes into the hydrogenation of carbon on grains . with more carbon in ch@xmath32
there is less co available to destroy @xmath1h@xmath2 , leading to the stronger @xmath1h@xmath2 emission in model beyond @xmath73 au . between @xmath38 = 40 au and @xmath38 = 170 au
the emission in model n and model is comparable .
the remaining models , model and model ( gr ) , show weaker @xmath1h@xmath2 emission overall . while the emission in model and model ( gr ) is identical inside of @xmath38 = 150 au , in the outer disk the amount of @xmath1h@xmath2 in model increases due to the increased presence of while the abundance in model ( gr ) remains low .
this leads to overall weaker emission in model ( gr ) .
the strongest @xmath1h@xmath2 j=4 - 3 emission in models n and originates between @xmath38 = 100 au and @xmath38 = 300 au in the midplane ( figure [ nnhprad ] ) , resulting in a ring of strong @xmath1h@xmath2 emission , similar to that seen in tw hya @xcite . in models and ( gr ) a similar , though weaker , ring structure is seen beyond @xmath38 = 300 au . figure [ snowother ] illustrates the midplane abundances in models , ( gr ) , and . together with figure [ snow ] they illustrate the gas phase abundance in the @xmath1h@xmath2 emission region . in model n and model , the models with the strongest emission lines , at @xmath38 = 150 au in the midplane , @xmath74 and @xmath75 . in comparison , for model and model ( gr ) , @xmath76 and @xmath77 .
when the gas phase abundance drops below @xmath75 , @xmath1h@xmath2 is no longer present .
thus , the strength of the @xmath1h@xmath2 line can be used as a proxy for the midplane abundance between 100 and 300 au for an assumed ionization rate and disk structure .
this is entirely consistent with earlier work attempting to determine the abundance from @xmath1h@xmath2 in dense cores @xcite .
@xmath1h@xmath2 has been observed in several disks @xcite .
our models suggest that for @xmath1h@xmath2 to be strongly emissive there must be a significant gas phase abundance .
it is likely that the mere detection of the @xmath1h@xmath2 ( 4 - 3 ) line at the level @xmath36 jy at 54 pc , e.g. @xcite , implies @xmath3 .
the distribution of no shows some variance between our models . for all of our models
it is present in the surface layers .
however , in model ( gr ) and model it is also abundant in the warm molecular layer .
model n , model ( gr ) and model all show a high no abundance near the midplane beyond @xmath38 = 300 au .
no emission in strongest in model ( gr ) , which has the lowest volatile nitrogen abundances .
thus , detecting no could indicate a depleted volatile nitrogen reservoir , especially if the @xmath1h@xmath2 emission from the source is weak .
unfortunately , because no has an uneven number of electrons ( @xmath78 ground electronic state ) , strong rotational transitions are replaced by a multitude of weaker lines split by @xmath79 doubling and hyperfine structure that is due to the non - zero spin of the nitrogen atom @xcite . as a result , detecting no is extremely difficult .
currently there are no no detections towards protoplanetary disks , though circumstellar no has been detected toward the embedded protostar ngc 1333-iras 4a @xcite and it has been detected in the dense ism @xcite . however , our models predict the no ( @xmath80 ) transition ( 350.68949 ghz ) to be on the order of several hundred mjy for a disk 140 pc away ( figure [ no ] ) .
the strongest emission is in model ( gr ) , with a flux of 437 mjy . for the full alma array
4.6 minutes of integration time would be required to detect the strongest of our simulated no ( @xmath80 ) lines with a 1.4 beam at the 10 sigma level assuming a spectral resolution of 0.3 km / s .
we again note that our models are descriptive of general effects rather than predictive of the overall flux ; however , this flux level suggests that no may be detectable in some systems .
@xmath1h@xmath2 is used as a tracer of the co snow line , since gas phase co destroys @xmath1h@xmath2@xcite .
our models support this interpretation ( figures [ snow ] and [ snowother ] ) .
the decrease in the @xmath1h@xmath2 abundance between @xmath46 au and @xmath61 au in models n and corresponds with an increase in the co gas phase abundance . in models nh3 and nh3(gr ) the midplane @xmath1h@xmath2 abundance is much lower .
while there is still an increase in the midplane abundance between @xmath81 au and @xmath61 au in these models , the mere presence of strong @xmath1h@xmath2 emission at the co snow line suggests that is the main nitrogen reservoir .
cn and hcn are widely detected in protoplanetary disks ( e.g. * ? ? ?
figure [ cnhcn ] shows the column density ratio of cn to hcn for our four models . in model
the ratio is much larger than in the other models inside of 5 au due to a decrease in the cn column density . beyond 100
au the column density of hcn in model ( gr ) falls off , resulting in a higher cn / hcn ratio compared to the other models .
the ratio of the simulated cn ( @xmath82 ) and hcn ( 3 - 2 ) line strength is 0.5 for model n. in comparison for most disks with detected cn and hcn emission the ratio is between 1 and 3 @xcite .
our simulated hcn line emission is too strong .
this could be due to the specific dust structure used in this model , underestimating the highly uncertain hcn binding energy , or a missing hcn processing mechanism ( see discussion in * ? ? ?
comets are thought to be indicative of the abundances in the young solar nebula @xcite .
figure [ comets ] shows how the and ice abundances in the midplane compare to the observed abundances in comets .
the figure shows the inner 50 au of the disk , where comets are thought to have formed in the solar system @xcite .
the cometary value is an upper limit for comet halley @xcite .
the shows the range of values detected in comet hale - bopp , comet halley , and comet hyakutake @xcite .
the ice abundance relative to water is below the upper limit for comet halley in all of our models , with model
n having the highest to water ratio . though our models are not meant to be analogs for the solar nebula , model n reproduces the ammonia to water ratio observed in comets , while model is at the upper limit of the observed range .
this suggests either that is processed into more refractory like material , such as part of chon dust grains ( e.g. * ? ? ? * ) or ice is not as easily incorporated into ices as the models predict . in this case , at face value , these models suggest n was delivered either as n or .
we have presented four models for the initial nitrogen abundances in protoplanetary disks .
models in which the majority of the initial nitrogen is in gas phase atomic n predict that n , , and ice are the dominant nitrogen - bearing species at late stages , with a significant fraction of the nitrogen also in hcn ice .
when the initial nitrogen is instead placed in gas the differences are difficult to differentiate observationally , indicating that the disk is able to convert gas phase n to efficiently .
when the nitrogen starts as , either in the gas phase or frozen onto grains , the majority of the n remains in ice .
n best matches the to h@xmath32o ratio in comets , suggesting that n was delivered to the solar nebula in a highly volatile form rather than , for example , in ices . the presence or absence of @xmath1h@xmath2 in the midplane beyond the co snow line indicates whether nitrogen is dominated by in the midplane , with the presence of @xmath1h@xmath2 correlating with the presence of gas and inversely correlating with the presence of ice .
@xmath1h@xmath2 traces the snow line in all four models , though the emission is stronger for models n and .
thus the detection of strong @xmath1h@xmath2 emission with a ring - like distribution suggests a disk with a high abundance .
in addition , @xmath1h@xmath2 emission can be used to determine the gas phase abundance in the midplane .
future sensitive observations of no and @xmath1h@xmath2 combined with disk chemical models will allow us to disentangle the nitrogen history of protoplanetary disks .
this work was supported by funding from the national science foundation grant ast-1008800 and ast-1344133 ( inspire ) .
llllll [ abundances ] n & 800 & 2.250 & 0 & 0 & 0 + & 790 & 1.000 & 1.000 & 1.000 & 1.225 + cn & 1600 & 6.000 & 6.000 & 6.000 & 6.000 + hcn & 2050 & 2.000 & 2.000 & 2.000 & 2.000 + & 3080 & 8.000 & 8.000 &
2.258 & 0 + ( gr ) & & 0 & 2.250 & 0 & 0 + | the dominant form of nitrogen provided to most solar system bodies is currently unknown , though available measurements show that the detected nitrogen in solar system rocks and ices is depleted with respect to solar abundances and the interstellar medium .
we use a detailed chemical / physical model of the chemical evolution of a protoplanetary disk to explore the evolution and abundance of nitrogen - bearing molecules . based on this model
we analyze how initial chemical abundances , provided as either gas or ice during the early stages of disk formation , influence which species become the dominant nitrogen bearers at later stages .
we find that a disk with the majority of its initial nitrogen in either atomic or molecular nitrogen is later dominated by atomic and molecular nitrogen as well as and hcn ices , where the dominant species varies with disk radius . when nitrogen is initially in gaseous ammonia , it later becomes trapped in ammonia ice except in the outer disk where atomic nitrogen dominates . for a disk with the initial nitrogen in the form of ammonia ice
the nitrogen remains trapped in the ice as nh@xmath0 at later stages .
the model in which most of the initial nitrogen is placed in atomic
n best matches the ammonia abundances observed in comets .
furthermore the initial state of nitrogen influences the abundance of @xmath1h@xmath2 , which has been detected in protoplanetary disks .
strong @xmath1h@xmath2 emission is found to be indicative of an abundance greater than @xmath3 , in addition to tracing the co snow line .
our models also indicate that no is potentially detectable , with lower n gas abundances leading to higher no abundances . |
a 61-year - old white woman with aquaporin-4 immunoglobulin ( ig ) g antibody seropositive nmo had 10 clinical relapses in the first 4 years of her disease despite treatment with iv pulse cyclophosphamide , chronic glucocorticoids ( up to 60 mg / day prednisone ) , mycophenolate mofetil ( up to 3,000 mg / day ) , rituximab ( 2,000 mg iv , divided doses ) , and multiple courses of pulsed high - dose glucocorticoids and plasma exchange for acute flares .
relapses included 8 episodes of myelitis , one episode of intractable hiccups , and one episode of postchiasmal visual pathway injury .
functional recovery was poor , and her expanded disability status scale score ranged from 7.5 to 8.0 ( severely paraparetic , essentially restricted to a wheelchair much of the day , preserved cognition ) .
alemtuzumab 12 mg iv 5 days ( total dose 60 mg ) was administered .
prednisone was tapered from 20 mg / day to 10 mg / day over the next year .
fifteen months after her initial infusion , she was retreated with alemtuzumab 12 mg iv 3 days ( total dose 36 mg ) and oral prednisone was discontinued the following month .
for the first 19 months after the initial alemtuzumab infusion , she did not experience any discrete clinical relapses or have evidence of abnormally enhancing lesions on brain or spinal cord mri .
however , she did experience insidiously progressive nausea and vomiting that became intractable , resulting in 27 kg of weight loss in the final year of life .
she also developed insidiously progressive bilateral vision loss : jaeger 1 od and j2 os ( 20/25 and 20/30 snellen equivalent respectively ) to j2 od and j3 os ( 20/30 and 20/40 snellen equivalent respectively ) at 15 months post - alemtuzumab and j4 ( 20/50 snellen equivalent ) by 17 months .
she remained seropositive for aquaporin-4 igg . prior to receiving alemtuzumab , while on other immunosuppressive therapies , she had multiple urinary tract infections , one episode of urosepsis requiring hospitalization , herpes zoster ophthalmicus , a deep venous thrombosis in the leg , hematomas following plasma exchange , and a broken femur after falling from her wheelchair .
following alemtuzumab treatment , her course was complicated by clostridium difficile colitis ( 2 months after the initial alemtuzumab infusion ) and recurrent urosepsis ( 16 and 20 months after the first cycle of alemtuzumab ) .
enteral feeding was initiated 20 months after the initial alemtuzumab infusion for refractory nausea and appetite loss . the patient and her family requested transition to comfort care , and she died at home .
gross neuropathologic evaluation of the spinal cord revealed severe destruction at the thoracic and upper lumbosacral levels such that the normal gray white junction and the delineation of dorsal , lateral , and anterior columns were completely effaced .
the optic nerves showed gray - tan discoloration on cross sections , with the left more prominent than the right .
in addition , there were numerous areas of demyelination where gray , gelatinous lesions appeared to involve the periventricular white matter , middle cerebellar peduncles , cerebellar white matter , and brainstem .
foci suspicious for demyelination were noted in the area postrema of the medulla oblongata and the pontine tegmentum .
coronal sections of the cerebrum showed a 0.5 cm diameter brown - tan cavitary lesion in the periventricular white matter at the anterior horn of the left lateral ventricle extending into the genu of the corpus callosum .
another soft cavitary lesion was found in the periventricular white matter of the posterior horn of the right lateral ventricle .
microscopic examination showed a range of acute , subacute , and chronic demyelinating lesions in the aforementioned areas in the gross examination .
one of the most extensively involved areas ( figure 1 ) extended from the pons into the right middle cerebral peduncle and cerebellar white matter and correlated clinically with the mri t2/fluid - attenuated inversion recovery abnormality shown in figure 2 .
all foci of demyelination demonstrated marked loss of myelin on luxol fast blue periodic acid - schiff stain and infiltration by cd68-positive macrophages .
the actively demyelinating lesions showed dense macrophage infiltrates , whereas the subacute to chronic lesions showed cavity formation and relatively fewer macrophages . in all of the lesions
there was a loss of the normal volume of oligodendroglia and a relative paucity of mature lymphocytes and neutrophils .
the spinal cord showed extensive demyelination in the thoracic segment and peripheral demyelination at the cervical level ( figure 3 ) .
there was no evidence of progressive multifocal leukoencephalopathy on autopsy . the gray discoloration and softening noted in the right cerebellar peduncle ( arrow , a ) corresponds to an area of pallor on neuropathologic examination ( b , hematoxylin & eosin , 100 ) .
the pale area is infiltrated by numerous macrophages ( c , cd68 , 100 ) and shows marked myelin loss ( d , luxol fast blue periodic acid - schiff , 100 ) .
immunohistochemistry for lymphocyte markers cd4 and cd20 shows no evidence of an adaptive immune response ( e and f , cd20/cd4 , 100 ) . brain mri ( a c ) shows interval progression of white matter lesions involving the pontine tegmentum ( thin arrow in a and b ) , right cerebellum ( arrowhead in a and b ) , and periventricular ( wide arrows in c ) .
there was no abnormal contrast enhancement in the first 3 studies shown ; no contrast was administered for the last mri .
mri thoracic spine ( d ) at month 12 after alemtuzumab administration shows multiple t2 parenchymal hyperintensities and prominent myelomalacia .
there was no abnormal contrast enhancement ( not shown ) . flair = fluid - attenuated inversion recovery .
a cross - section of the cervical spinal cord shows similar areas of pallor on microscopic examination ( a , hematoxylin & eosin , 20 ) .
high - magnification examination of the boxed area from panel a shows macrophage infiltration ( b , cd68 , 100 ) and loss of myelin staining ( c , luxol fast blue periodic acid - schiff , 100 ) .
there is also a marked increase in staining for glial fibrillary acidic protein ( gfap ) , corresponding to reactive astrogliosis ( d , gfap , 100 ) .
a portion of the optic nerve ( a , hematoxylin & eosin , 200 ) shows some myelin loss ( b , luxol fast blue periodic acid - schiff , 200 ) and striking macrophage infiltration ( c , cd68 , 200 ) .
we recognize that nmo can be a difficult disease to treat and that some patients do not respond to immune suppression .
we believe that this case is noteworthy because following alemtuzumab treatment there appeared to be ongoing innate immune activation associated with tissue destruction .
we interpret the cessation of clinical relapses , absence of contrast - enhancing lesions on mri , and scarcity of lymphocytes at autopsy to be indicative of suppression of adaptive immunity as a consequence of alemtuzumab treatment .
in contrast , extensive mononuclear cell infiltrates on neuropathology correlated with new , enlarging , nonenhancing lesions on t2-weighted mri . the neuroanatomical areas of cns involvement on imaging and neuropathology corresponded to the patient 's progressive neurologic impairments .
we believe that there is a possible relationship between these observations and alemtuzumab 's presumed mechanism that primarily targets adaptive immune function .
we speculate that an underlying disease process involving the innate immune system causing massive monocytic infiltration and tissue destruction occurred .
this observation may be relevant to ms as well as nmo and might explain why in secondary progressive ms alemtuzumab did not seem to inhibit disability progression despite a dramatic decline in contrast - enhancing lesions .
mononuclear inflammation is a prominent histologic feature of progressive ms , particularly foamy macrophages in periplaque white matter , subpial mononuclear inflammatory infiltrates associated with cortical demyelination , and widespread microglial activation . in progressive
ms , t - cell infiltration typically is also present in normal - appearing white matter associated with diffuse axonal injury and in perivascular cuffs .
it is possible that alemtuzumab treatment contributed to worsening in this patient , possibly through triggering monocyte activation ; however , alemtuzumab treatment does not appear to precipitate worsening in most patients with relapsing or progressive ms .
therefore , if alemtuzumab somehow contributed to the decline in this patient , this effect may be patient- or disease - specific .
it is also important to note that our patient was already severely disabled at the time of alemtuzumab treatment .
nmo can be an exceedingly difficult disease to treat , with some patients succumbing to their illness despite empiric use of immune suppressants .
we believe that this case illustrates that progressive worsening in nmo can occur in the absence of clinical relapses or contrast - enhancing lesion activity on mri as a consequence of tissue injury associated with monocytic infiltration .
dr . gelfand : drafting the manuscript , study concept , analysis / interpretation of data , acquisition of data .
cotter : revising the manuscript for important intellectual content , analysis / interpretation of data , acquisition of data .
huang : revising the manuscript for important intellectual content , analysis / interpretation of data , acquisition of data .
cree : revising the manuscript for important intellectual content , study concept / design , analysis / interpretation of data , acquisition of data , study supervision .
research reported in this publication was supported by the national center for advancing translational sciences of the nih under award number kl2tr000143 and american academy of neurology clinical research training fellowship ( j.m.g . ) .
its contents are solely the responsibility of the authors and do not necessarily represent the official views of the nih .
gelfand has received research support from the national center for advancing translational sciences of the nih and he and his spouse have received compensation for expert witness medical - legal consulting .
huang is an associate editor for the journal of neuroscience and is on the editorial board for brain pathology .
cree is an editor for annals of neurology ; is a consultant for abbvie , biogen idec , emd serono , genzyme , novartis , sanofi aventis , and teva neurosciences ; has received research support from acorda , avanir , biogen idec , emd serono , hoffman la roche , and novartis ; and has been an expert consultant for biogen idec . | objectives : to describe the clinical course and neuropathology at autopsy of a patient with neuromyelitis optica ( nmo ) treated with alemtuzumab.methods:case report.results:a 61-year - old woman with aquaporin-4 immunoglobulin g antibody seropositive nmo had 10 clinical relapses in 4 years despite treatment with multiple immunosuppressive therapies .
alemtuzumab was administered and was redosed 15 months later . for the first 19 months after the initial alemtuzumab infusion , the patient did not experience discrete clinical relapses or have evidence of abnormally enhancing lesions on brain or spinal cord mri . however , she experienced insidiously progressive nausea , vomiting , and vision loss , and her brain mri revealed marked extension of cortical , subcortical , and brainstem t2/fluid - attenuated inversion recovery ( flair ) hyperintensities .
she died 20 months after the initial alemtuzumab infusion .
acute , subacute , and chronic demyelinating lesions were found at autopsy .
many of the lesions showed marked macrophage infiltration with a paucity of lymphocytes.conclusions:following alemtuzumab treatment , there appeared to be ongoing innate immune activation associated with tissue destruction that correlated with nonenhancing t2/flair hyperintensities on mri .
we interpret the cessation of clinical relapses , absence of contrast - enhancing lesions , and scarcity of lymphocytes at autopsy to be indicative of suppression of adaptive immunity by alemtuzumab .
this case illustrates that progressive worsening in nmo can occur as a consequence of tissue injury associated with monocytic infiltration
. this observation may be relevant to multiple sclerosis ( ms ) as well as nmo and might explain why in previous studies of secondary progressive ms alemtuzumab did not seem to inhibit disability progression despite a dramatic decline in contrast - enhancing lesions . |
MINNEAPOLIS (WCCO) – A Minnesota Air National Guardsman is being hailed as a hero for helping pull a man who was trapped out of a burning car just moments before it became fully engulfed in flames.
The Minnesota State Patrol said the incident happened at about 6:40 p.m. on I-35W and County Road D. A motorist, identified as Robert Renning, was heading southbound when he noticed a vehicle on fire nearby. He was able to get the driver, Michael Johannes’, attention and both vehicles pulled over.
“I could see the flames coming out from underneath the car on the way back,” Renning said.
By the time Renning waved him down, Johannes had smelled something odd.
Both Johannes and Renning pulled over.
But once on the shoulder the SUV automatically locked, trapping Johannes inside.
“I put it in park and that’s when I couldn’t get out,” Johannes said.
The SUV’s doors had automatically locked. Johannes could not open them.
“The flames were starting to kick out around the bottom a little bit. Starting to smoke. The interior of the car was completely filled in smoke. You couldn’t see who or what was inside,” Renning said.
The State Patrol said Renning immediately ran to the car and was able to get a car door open by bending it in half and shattering the glass.
Renning tried the car doors but they wouldn’t open. Then he saw Johannes trying to kick out the passenger side window. Renning said he knew he had to do something.
The State Patrol said Renning immediately ran to the car and was able to get a car door open by bending it in half and shattering the glass.
“I grabbed the top of the door frame and pulled until the glass shattered,” Renning said.
He then pulled Johannes to safety.
“It had to have been adrenaline. I don’t know how I did it. I truly don’t,” Renning said.
The charred frame of the car shows where Renning bent the frame with his bare hands.
Authorities said Renning was not hurt during the rescue. Johannes suffered minor smoke inhalation and a couple of minor cuts after being pulled through the shattered glass.
Renning says he is not a hero.
“I didn’t do anything anyone else wouldn’t have done at the time. It was all timing,” he said.
But that’s not the way the Johannes see it.
“I am eternally grateful for myself and my husband and my daughter that we can still be here as a family so thank you Bob,” Johannes’ wife, Lisa, said.
Michael Johannes and Robert Renning have talked by phone and Johannes says he repeatedly thanked him.
Renning says that is all that he wants, but Johannes says he also plans to take him out for a beer.
The State Patrol will be nominating Renning for a Good Samaritan award.
“He did an extraordinary deed, bending a locked car door in half of a burning car to extricate a trapped person,” said State Trooper Zachary Hill, who responded to the scene. “I feel this man deserves any and all commendation for his extraordinary life-saving measure that kept another from burning alive.”
Johannes had just purchased the 2006 Chevy Trailblazer the week before.
WCCO checked and that GM model had been the subject of two fire related calls.
GM did not return our phone call. ||||| Bob Renning, 52, of Woodbury got Michael Johannes of Minneapolis out of Johannes' burning car June 29, 2014. Both were traveling south on Interstate-35W near County Road D in New Brighton when Renning noticed Johannes' car was on fire. (Courtesy of Minnesota State Patrol)
As flames licked up from beneath an SUV and smoke filled its interior, Bob Renning pried open its door to let the driver escape.
Renning credits "pure adrenaline" for giving him the strength to bend the door until the window shattered Sunday evening along Interstate 35W in New Brighton.
Renning, 52, of Woodbury said he could hear Michael Johannes, 51, of Minneapolis trying to escape through the passenger side door as the 2006 Chevy Trailblazer filled with smoke.
"He was kicking and beating the window trying to break it open from the inside," Renning said. "I knew I didn't have a lot of time."
Renning was southbound on I-35W near County Road D when he saw in his mirrors flames shooting out from beneath an SUV six or seven car-lengths behind him.
Johannes, who just bought the Trailblazer last week, said he knew he was in trouble when his brakes started to fail out and the vehicle began filling up with smoke as he drove down the freeway at 65 mph.
Renning said he slowed down to get Johannes' attention, though both pulled over about the same time, with Renning stopping about 250 feet in front of the burning vehicle.
Renning told his girlfriend, who was in the car with him, to call 911, and he bolted toward the flames.
Meanwhile, Johannes was locked inside his SUV that was quickly filling up with smoke. On Monday, he said the SUV's electrical malfunction had caused it to lock.
Since flames had begun to engulf the driver's side, he scrambled to the passenger side, kicking at the window.
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Luckily, Renning was there.
Grabbing the top of the door frame and leveraging his body against it, Renning pulled until the glass shattered.
"It was just chaos," Johannes said. "I just dove toward the light (coming in) through the window. I'm a pretty big guy and (Renning) just pulled me out."
Johannes successfully climbed out of the burning SUV, and both men moved a safe distance away. Renning said police and rescue crews quickly arrived.
"(Renning) did an extraordinary deed, bending a locked car door in half ... to extricate a trapped person," Minnesota State Patrol trooper Zachary Hill, who was at the scene, said in a statement. "I feel this man deserves any and all commendation for his extraordinary life-saving measure that kept another from burning alive."
Renning, a member of the Air National Guard, said he had "no clue" where his strength came from.
"I'm sure it was pure adrenaline," he said, adding that he left the scene unscathed.
Johannes, his wife and their 7-year-old daughter were at his wife's parents' house in Chisago County for the weekend. On Sunday night, he left his daughter with his in-laws, he said, and was driving home to be at work Monday morning at 3M, where he works in the abrasives division. His wife was already home when his vehicle caught fire.
After rescue crews left the scene and he was treated for minor smoke inhalation, cuts and scrapes, Johannes and his wife went back to his in-laws, where he said he gave his daughter a big hug.
Sunday's incident marks Johannes' second totaled vehicle in two weeks. He said that a week before he bought the Trailblazer, someone had crashed into his former vehicle, which was parked in front of his house.
"We're going to take our time in selecting our next vehicle," Johannes said.
Raya Zimmerman can be reached at 651-228-5524. Follow her at Twitter.com/RayaZimmerman.
| – A Minnesota man demonstrated superhuman strength at exactly the right time Sunday. Air National Guardsman Robert Renning, 52, was driving along the interstate around New Brighton when he saw flames underneath an SUV about six car-lengths behind him, reports Twin Cities Pioneer Press. He slowed to get driver Michael Johannes' attention—Johannes’ brakes had started to fail as he drove 65mph, and he had just started to smell something odd as Renning flagged him down—but both drivers were able to pull over to the side of the road. Then an electrical malfunction caused the Chevy Trailblazer's doors to lock and trap Johannes inside, and that was when Renning’s adrenaline kicked in. "The interior of the car was completely filled in smoke. You couldn’t see who or what was inside," Renning tells WCCO. After asking his girlfriend to call 911, he ran toward the SUV as Johannes tried to kick out the passenger side window. Renning "grabbed the top of the door frame and pulled until the glass shattered," he says, then pulled Johannes out. Renning was unharmed and Johannes suffered only minor cuts and smoke inhalation. For his trouble, Renning was nominated for a Good Samaritan Award by the state police and will also be rewarded with a beer, courtesy of Johannes. Johannes’ previous car had been totaled two weeks before, and he'd just purchased the used 2006 SUV. "We're going to take our time in selecting our next vehicle," he notes. It's not clear what caused the Trailblazer to catch on fire, but WCCO says that model has been the subject of two fire-related recalls. |
Image copyright Thinkstock
Nearly one in 10 British women finds sex painful, according to a big study.
The survey of nearly 7,000 sexually active women aged 16 to 74, in BJOG: An International Journal of Obstetrics and Gynaecology, suggests this medical problem - called dyspareunia - is common and affects women of all ages.
Women in their late 50s and early 60s are most likely to be affected, followed by women aged 16-24.
Doctors say there are treatments that can help if women seek advice.
But many still find the subject embarrassing and taboo, the survey results show.
Painful sex was strongly linked to other sexual problems, including vaginal dryness, feeling anxious during sex, and lack of enjoyment of sex.
However, there can be lots of different physical, psychological and emotional factors causing painful sex, which can be complex to treat.
Some women said they avoided intercourse because they were so afraid of the pain.
Image copyright Science Photo Library Image caption Karen's problems meant she started dreading smear tests too
'It hurt so much'
Karen (not her real name) is 62 and from Greater London. She said her problems began around the age of 40.
"I felt that my sex drive dipped quite considerably, arousal seemed to take longer, and, despite an understanding husband, I started to dread him making approaches.
"It's like any muscle group I guess, the less you use it the worse it gets."
Karen tried using lubricant but still encountered problems.
"It became like a vicious cycle. You worry and get tense and that only makes it worse."
Karen developed another complication called vaginismus - involuntary tightening of the muscles around the vagina whenever penetration is attempted.
"It wasn't just in bed. It happened when I needed smear tests too. I would be crawling up the bed away from the nurse because it hurt so much."
Karen spoke to her doctor who recommended she try oestrogen creams and pessaries for the dryness and dilators to help with the involuntary tightening.
"Women need to know that there is help out there for these kinds of problems, especially as we are all living longer.
"You shouldn't have to be writing off your sex life in your 50s.
"Many women don't like to talk about it. We share all the gore of childbirth, yet women of my generation don't tend to talk openly about sex and the menopause. We should."
The national survey of sexual attitudes and lifestyles was carried out by the London School of Hygiene and Tropical Medicine (LSHTM), University College London and NatCen Social Research.
Of those who reported painful sex (7.5%), a quarter had experienced symptoms frequently or every time they had had intercourse in the last six months or more.
Around a third of these women said they were dissatisfied with their sex life, compared with one tenth of the women who didn't report painful sex.
Lead researcher, Dr Kirstin Mitchell, from LSHTM and the University of Glasgow, the said there could be a whole range of reasons for dyspareunia.
Lack of enjoyment
"In younger women, it might be that they are starting out in their sexual lives and they are going along with things that their partner wants but they are not particularly aroused by.
"Or they might be feeling tense because they are new to sex and they are not feeling 100% comfortable with their partner."
Image copyright Thinkstock Image caption Lubricants can help with vaginal dryness, but persistent pain should be checked by a GP or sexual health clinic
Painful sex might be caused by other health problems, such as sexually transmitted infections, endometriosis and fibroids, which should be diagnosed and treated.
Women around the age of the menopause can find sex painful because of vaginal dryness.
Dr Mitchell says it's not just older women who can feel embarrassed talking about painful sex, even though the condition is common.
Other research, involving about 200 university students in Canada, suggests up to half of young women find their first experience of intercourse painful.
Seek advice
Dr Mitchell says sex education should do more to better prepare young people.
"Often sex education is about STIs and pregnancy, but it should also prepare people to think about what makes sex enjoyable and how to communicate what they like and dislike in a trusting and respectful relationship."
If you have pain during or after sex, you should get advice from your GP or a sexual health clinic.
If there is an emotional reason or anxiety that is causing problems, a counsellor or sex therapist may be able to help - and your GP or sexual health clinic can refer you to one. ||||| Almost one in ten women experience pain when they have sex, a new study has found.
The survey of almost 7,000 British women, published in the British Journal of Obstetrics and Gynaecology found that 7.5 per cent of sexually active women between the ages of 16 and 74 reported painful sex lasting three months or more over the past year. A quarter of those women reported “morbid” painful sex occurring very often or always for six months.
The age groups who were most likely to be affected by the issue were women between the ages of 55 and 64, followed by younger women between the ages of 16 and 24.
The authors concluded that “painful sex is reported by a sizeable minority of women in Britain” and recommended health professionals look to holistic treatment which could take into account the context of the symptoms.
Love and sex news: in pictures
+ show all Love and sex news: in pictures
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2/23 What men think about make-up According to a new survey from YouGov, 63 per cent of men believe that the main reason women wear makeup is to trick people into thinking they’re more attractive than they really are Getty Images/iStockphoto
3/23 The best way to feel better after a breakup Just like taking a placebo medicine has at times proven to be effective for pain treatment, placebo pretending to be okay can also be helpful after a break-up according to researchers from the University of Colorado Getty Images/iStockphoto
4/23 Book readers make the best lovers The dating site eHarmony found that listing reading as a hobby on your dating profile is a winning move that makes you more appealing to the opposite sex. Data revealed that men who list it as an interest receive 19 per cent more messages, and women three per cent more Getty Images/iStockphoto
5/23 Couples can improve their wellbeing by giving each other a massage New research found that when people, who were novices when it came to massages, gave their partners one it improved their physical and emotional wellbeing. The satisfaction levels were the same whether the partner was giving or receiving the massage with 91 per cent of the couples studied saying they would recommend mutual massages to their friends Getty Images/iStockphoto
6/23 Top strain on relationships in the UK revealed Finding a partner who has similar attitudes to you, when it comes to money, could be more likely to guarantee you a successful, harmonious relationship. The main strain on UK relationships is money worries, according to new research, and the key to avoiding money ruining a relationship is to align how you deal with your finances. Concerns about finances make up 26 per cent of relationship difficulties, according to new research from relationship charities Relate, Relationships Scotland and Marriage Care who surveyed over 5,000 people in the UK Getty Images/iStockphoto
7/23 Cheaters are likely to be unfaithful to their partners multiple times Research by UCL suggests why serial cheaters repeatedly lie to their partners and commit adultery. According to the study, it’s because with every lie a person tells, they feel less bad about doing so afterwards Getty Images/iStockphoto
8/23 Timetable of Love A new study has revealed that Sunday at 9am is the most popular time of the week for Brits to get busy in the bedroom. Our weekends tend to be a lot sexier than our weekdays, with three of the top five most common times for sex falling on a Saturday, at 11.30am, 10.30pm and 11.30pm Getty Images/iStockphoto
9/23 Spain appoints 'sex tsar' Spain has appointed a ‘sex tsar’ to encourage the declining population to ramp up procreation in a bid to reverse a dip in the birth rate. The country reported a higher number of deaths than births for the first time last year, prompting the government to take action
10/23 How to spot when your partner is hiding their true feelings How often do you and your partner actually spot when one of you is hiding your emotions? According to a new study, it’s probably not as frequently as you think. New research suggests that people miss cues that their partner may be suppressing negative feelings because we see our other-halves in a more positive light Getty Images/iStockphoto
11/23 Online dating risk A new report by the National Fraud Intelligence Bureau has found that last year, singles were conned out of £39 million by fraudsters they’d met on dating sites and apps. Con artists are increasingly creating fake online profiles and tricking people on dating sites into handing over often large sums of money. Getty Images/iStockphoto
12/23 Singletons judge potential partners on their phones, says new study A new study has found that women are 92 per cent more likely than men to judge a potential partner negatively for having an older phone model. Getty Images/iStockphoto
13/23 Mother's blood pressure before conception could influence sex of child, study suggests Pregnant woman measures the blood pressure with automatic sphygmomanometer. Getty Images/iStockphoto
14/23 Sainsbury’s sells same sex valentine’s day cards for first time For the first time, Sainsbury’s is selling a range of Valentine’s Day cards that represent same-sex couples. The simple designs feature illustrations of a woman and a woman, and a man and a man, with the caption ‘You + Me.’
15/23 Couples oversharing on social media do so to mask relationship insecurities, expert suggests Couple sitting on couch with their phones in their hand Getty Images/iStockphoto
16/23 Injection of ‘romantic’ hormone could help treat psychosexual problems Getty Images/iStockphoto
17/23 One in ten British women experience pain during Getty Images/iStockphoto
18/23 Watching porn does not cause negative attitudes to women The average porn user may have more egalitarian views towards women than non-users, a contentious new study has suggested. Researchers at Western University in Canada have even argued that many pornography fans might be “useful allies” in women’s struggles for equality in the workplace and in public office. They reported in the Journal of Sex Research that the 23 per cent of people who said they had watched an “X-rated” film during the previous year were no more or less likely to identify as feminists than those who did not watch porn. Getty
19/23 Erectile dysfunction 'linked to risk of early death' Men who suffer from erectile dysfunction (ED) are 70 per cent more likely to die early, a new study has found. US scientists believe that the disorder may be linked to poor cardiovascular health, and suggested that men with ED should be screened for health issues that could cut their lives short Rex Features
20/23 The characteristics of men who pay for sex Men who pay for sex share similar traits to rapists and sex offenders, according to new research. A study from University of California, Los Angeles (UCLA), claims that men who have sex with female sex workers feel less empathy for them than men who do not buy sex. Part of this reason is due to the fact that they view them as "intrinsically different from other women,” according to the authors. Getty Images
21/23 Heartbreak can actually change the rhythm of your heart Losing a loved one really can break your heart, research suggests, although not for ever. People who lose a partner are at an increased risk of developing an irregular heartbeat for the next 12 months, scientists found. The risk seems to be greatest among the under 60s and when the loss of the partner was least expected Getty
22/23 'Weird' sexual fetishes are actually very normal A number of sexual fetishes considered anomalous in psychiatry are actually common in the general population, a study has found. According to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), sexual interests fall into two categories: normal (normophilic) and anomalous (paraphilic). Researchers asked 1,040 Quebec residents, representative of the general population, about their experiences of sexual behaviour considered abnormal by the DSM-5. The study, published in The Journal of Sex Research, found that of the eight types of anomalous behaviour listed in the DSM-5, four were found to be neither rare or unusual among the experiences and desires reported by men and women
23/23 A new dating show for Trump supporters Across the pond, there’s a new TV dating show in the pipeline: one inspired by President Donald Trump. The dating site - whose tagline is ‘Making dating great again’ - launched in May 2016 and now has over 37,500 active users Getty Images
Of the many women who reported painful sex, links were found with other issues around sexual health and wellbeing:
Lack of enjoyment in sex: 62 per cent of women who reported painful sex said they lacked interest in having sex and 40 per cent said they lacked enjoyment. Almost a quarter said they experienced no excitement or arousal during sex too.
Vaginal dryness: 45 per cent of women who reported painful sex said they had an uncomfortably dry vagina compared to 10 per cent of women who did not report painful sex but experienced the same condition.
Mental health: Links were found between the women experiencing pain during sex and mental health issues. A fifth of women who had painful sex said they felt anxious during sex, compared to only 4 per cent of women who had no pain. Additionally, 11 per cent of women who reported painful sex said they were experiencing depression.
Poor health: Physical health was also an issue when it came to women who experienced pain, 13 per cent reported their physical health status to be bad or very bad and 11 per cent said they suffered more than two chronic conditions.
Sexually transmitted infections: Of the women who experienced painful sex, 13 per cent had reported having an STI over the past five years.
Emotional connection: 13 per cent of women experiencing pain during sex said they did not feel emotionally close to their partner during sex. Eight per cent of women who had pain also said they found it difficult to talk about sex with their partner.
History of sexual abuse: 14 per cent of women who had sex said they had experienced ‘non-volitional sex’. Researchers noted they found a link with sex against one’s will after the age of 13, “suggesting that non-volitional sex in adolescence and adulthood is also important”.
Menopause: Almost ten per cent were menopausal.
Just under a third of women who reported painful sex said they were dissatisfied with their sex life compared with 10 per cent of women who said the same but did not experience pain. Almost half (44.9 per cent) of women who had experienced painful sex were also more likely to have avoided sex over the past year. The study found no link between the amount of times women had sex and those who reported pain.
The study found no relationship between general happiness in the relationship and sex but strong associations with sexual aspects of the relationship including different levels of interest in sex, the lack of an emotional connection and not sharing the same sexual likes and dislikes.
The researchers suggested that health professionals should take into account the woman’s history and relationship context if a patient reports painful sex.
Co-author Dr Kirstin Mitchell from the University of Glasgow told The Independent there is a tendency of health professionals to “just focus on the presentation of pain and find an underlying cause”, while sometimes health reasons like endometriosis or STIs will be a reason for painful sex, when this is not the case health professionals should delve further.
“Sometimes women may want to discuss the impact on their relationship, how it’s causing them anxiety, what they can do within the relationship to improve it, for example couples being assisted on having enjoyable sexual activity without doing what causes the pain that could bring relief to the patient. So it is important for health professionals to be aware of the context,” she said.
She also noted that they found a low proportion of women affected by the issue sought help, which could be because they are not sure where to go, how their doctor could help them or they think they have found some sort of solution like having less sex or abstaining. Dr Mitchell also suggested “embarrassment” could be a reason.
For the younger group of women who reported the second highest levels of pain during sex, Dr Mitchell suggested this could be weaved into sex education, particularly around the issues of young women feeling like they can tell their partner what they like or do not like or reach a point where they feel comfortable discussing if they experience pain with their sex
“In terms of prevention, this could be addressed in sex education in school , for example the importance of being able to talk about what you like and don’t like, for young women not to go into their sex lives feeling that painful sex is something they have to accept. Younger age groups could also have difficulties becoming aroused or they feel anxious which could be a sign they are not ready or are in a relationship where they do not yet feel comfortable or trusting – all of these issues could be addressed in sex education.
“Of course, with younger age groups, some of it may be due to experimental . You learn what you like and dislike as you get older and older people have had time to figure out what they want.” | – A new study out of Britain reveals that pain during sex afflicts a surprising number of women. The survey of nearly 7,000 sexually active women found that one in 10 reported some type of pain during intercourse, the BBC reports. Writing in BJOG: An International Journal of Obstetrics and Gynaecology, the authors note that painful sex (dyspareunia) is a neglected, often chronic problem that afflicts women around the world. The latest sampling of women aged 16 to 74 found that women in their late 50s and 60s were most affected, though younger women were not spared. Pain during sex can be caused by vaginal dryness, particularly post-menopause, but can have more serious roots in untreated conditions such as STDs, endometriosis, and fibroids. Emotional causes such as anxiety can also play a role. "You worry and get tense and that only makes it worse," says one middle-aged woman of the "vicious cycle." After her sex drive dipped, she experienced vaginismus, involuntary tightening of the vaginal muscles during penetration. One quarter of the women who reported painful sex said it happened often or all the time in the past six months. About 33% said they were unhappy with their sex life. Lead author Dr. Kirstin Mitchell says embarrassment prevents many women from seeking help, including young women new to sex who may be ill at ease. Given that women aged 16-24 came in second in the survey, she urged better sex education in school—"for example the importance of being able to talk about what you like and don’t like," per the Independent. (This ignored disease afflicts 176 million women worldwide.) |
coronary arterial fistulas are rare cardiac anomalies that create new pathways of blood flow between coronary vessels and thoracic vasculature or chambers of the heart .
although generally asymptomatic , patients can develop complications of thrombosis , congestive heart failure , rupture , endocarditis , and arrhythmias . here , we describe a patient with acute decompensated heart failure and transient left bundle branch block ( lbbb ) , found to have an underlying left anterior descending ( lad- ) to - pulmonary artery ( pa ) fistula .
this case illustrates the potential of coronary fistulas to induce a clinical presentation of cardiac ischemia via a coronary steal mechanism .
a 64-year - old man with a history of congestive heart failure and stage iv chronic kidney disease secondary to uncontrolled hypertension and diabetes mellitus presented with three days of orthopnea and one night of intermittent left shoulder pain radiating to the back .
physical examination revealed a heart rate of 99 beats per minute and blood pressure of 149/71 mm hg with an oxygen saturation of 94% on 4 liters of oxygen .
laboratory analyses were significant for a hematocrit of 24% and creatinine of 3.8 mg / dl .
twelve - lead electrocardiography ( ecg ) revealed sinus rhythm at 94 beats per minute and a new lbbb .
an acute myocardial infarction was suspected and the patient was taken for emergent cardiac catheterization , which showed stenosis of up to 40% of the mid - lad coronary artery and mild disease in other vessels .
in addition , a fistula was identified connecting the lad to the distal main pa ( figures 1(a ) and 1(b ) ) .
transthoracic echocardiography demonstrated moderate global systolic dysfunction with a left ventricular ejection fraction of 40% as well as a moderate - sized pericardial effusion without echocardiographic evidence of increased intrapericardial pressure .
a regadenoson nuclear perfusion stress imaging study performed after 4 days of diuresis and a blood transfusion was negative for inducible ischemia .
furthermore , an ecg on the day of the stress imaging study showed resolution of the lbbb , and one week later the patient 's ecg showed recovery to near normal left ventricular ejection fraction and decrease in size of the pericardial effusion .
we hypothesized that the small lad - pa fistula was not the sole cause of heart failure symptoms but was a contributor to the patient 's clinical presentation and ecg findings .
the small fistula in this case steals from the lad - supplied myocardium , including the left bundle . by itself , the fistula was not sufficient to manifest clinically .
however , in the setting of increased oxygen demand and decreased oxygen supply during the heart failure exacerbation , this coronary steal likely decreased the total oxygen supply in the lad territory enough to cause additional transient ischemia and lbbb .
since he was previously asymptomatic without objective evidence of ischemia in the absence of myocardial oxygen supply and demand mismatch , we elected to continue close observation rather than closure of the fistula .
coronary arterial fistulas are rare communications between coronary vasculature and thoracic vessels or cardiac chambers .
the most frequent sites of drainage include the ventricles , pulmonary arteries , the coronary sinus , the superior vena cava , or the pulmonary veins . of the different types of fistulas , 42% originate from the left coronary tree and 17% drain into the pulmonary artery .
fistulas are generally congenital in origin , but they can also arise from cardiac trauma , chest irradiation , cardiac surgery , coronary angioplasty , and endomyocardial biopsy . while fistulas are usually asymptomatic , their natural history can be variable . adult patients who develop symptoms often do so in the 5th or 6th decade [ 1 , 2 ] .
common clinical presentations include dyspnea , congestive heart failure , angina , aneurysm , or myocardial infarction . whether or not a patient will develop symptoms is determined by the degree of fistula - induced volume overload , as well as the severity of left - to - right shunting secondary to fistula size and location .
transesophageal echocardiogram may be useful in delineating the origin , course , and drainage of a fistula .
therefore , in the presence of large shunts or even in asymptomatic patients , surgical or transcatheter ligation may be considered to prevent long - term sequelae such as steal , spontaneous rupture , heart failure , or myocardial ischemia [ 6 , 7 ] .
transcatheter closure is first - line therapy in suitable anatomic cases due to lower cost , shorter recovery time , and reduced hospital stay .
although coronary steal may have contributed to ischemia of the left bundle as evidenced by subsequent ecg findings , we can not exclude a rate - related bundle branch block .
however , this is less likely since an ecg tracing 5 months earlier , at the same heart rate , revealed a normal qrs duration as did subsequent ecg tracings at similar heart rates .
a right heart catheterization was not performed to assess filling pressures or to calculate a shunt fraction . even without direct measures of these pressures , it was still evident that the patient was in congestive heart failure by history and physical exam findings .
he improved significantly with diuresis , suggesting elevated filling pressures also contributed to the supply - demand mismatch .
the left ventricular systolic function may have also appeared decreased at presentation because of the septal motion abnormality from the lbbb .
our patient , who presented with orthopnea , shoulder pain , and a new lbbb , illustrates that even a small coronary fistula may
steal enough blood flow to mimic the symptoms of an acute myocardial infarction in the setting of a transient oxygen supply - demand mismatch .
a coronary fistula , therefore , may not be the sole culprit lesion or an innocent bystander , but an accomplice in causing signs and symptoms of acute heart failure .
the authors have no disclosures or financial conflicts of interest relevant to this paper to report . | coronary arterial fistulas are rare communications between vessels or chambers of the heart .
although cardiac symptoms associated with fistulas are well described , fistulas are seldom considered in the differential diagnosis of acute myocardial ischemia .
we describe the case of a 64-year - old man who presented with left shoulder pain , signs of heart failure , and a new left bundle branch block ( lbbb ) .
cardiac catheterization revealed a small left anterior descending ( lad)-to - pulmonary artery ( pa ) fistula .
diuresis led to subjective improvement of the patient 's symptoms and within several days the lbbb resolved .
we hypothesize that the coronary fistula in this patient contributed to transient ischemia of the lad territory through a coronary steal mechanism .
we elected to observe rather than repair the fistula , as his symptoms and ecg changes resolved with treatment of his heart failure . |
crack fronts propagating along a weak plane of a disordered material provide an ideal experimental system for studying phenomena such as the depinning transition , the associated avalanche dynamics and roughness of the crack front .
experimentally , by studying systems such as sintered plexiglas plates @xcite and paper sheets @xcite , it has been established that a slowly driven planar crack front propagates in a sequence of avalanches , with a power law size distribution . in the case of the plexiglas experiments the crack fronts
have been observed to be rough @xcite .
as is often the case when studying similar phenomena typically exhibiting some degree of universality , it is expected that the statistical properties of the planar crack fronts can be theoretically described with a simplified model , which here is given by the long - range elastic string @xcite .
such a model has successfully reproduced the statistics of avalanches of crack front propagation @xcite , and in particular the local clusters such avalanches are broken into due to the long range elastic interactions between different segments of the crack front @xcite .
early experiments @xcite found a roughness exponent significantly larger than that predicted by the crack line model @xcite , but a more recent study has shown that the theoretically predicted value of the roughness exponent is recovered if large enough length scales are considered @xcite .
moreover , the short length scale regime has been found to exhibit multiscaling @xcite . in this paper
we consider the long range elastic string driven in a random potential with a tunable disorder correlation length , in order to clarify the origin and nature of the different scaling regimes of the crack front roughness .
the main benefit of our model as compared to previous studies of the crack line model is that the disorder correlation length @xmath0 can be chosen to be larger than the crack line segment length , thus making it possible to study also the regime below @xmath0 .
it is demonstrated that the problem includes two relevant length scales , the disorder correlation length @xmath0 and the larkin length @xmath1 @xcite . by considering different sets of parameters of the model , the relative magnitudes of these two length scales can be tuned . for strong enough disorder ( or equivalently soft enough lines ) , multiscaling of the crack front is observed for scales below @xmath0 .
asymptotically , for length scales exceeding both @xmath0 and @xmath1 , we recover the well known roughness exponent @xmath2 of the long - range elastic string @xcite .
an intermediate regime characterized by the larkin exponent @xmath4 is observed above @xmath0 and below @xmath1 , if @xmath5 .
the paper is organized as follows : in the next section , the details of the numerical model are presented . in section [ sec3 ]
we present a theoretical description of the expected scaling regimes of the front roughness , while section [ sec4 ] includes detailed numerical results from simulations of the crack line model .
section [ sec5 ] finishes the paper with conclusions and discussion .
the model of a propagating planar crack front considered here is represented by a vector of single - valued integer heights @xmath6 , @xmath7 , with @xmath8 the system size @xcite .
crack propagation is driven by the local stress intensity factor ( sif ) @xmath9 , representing the asymptotic prefactor of the @xmath10 divergence if the stress field near the crack tip .
@xmath9 is taken to be of the form @xmath11 . here
@xmath12 is the first - order variation of the stress intensity factor due to first - order perturbation of the front position @xcite , with @xmath13 the front segment spacing and @xmath14 tunes the strength of the long - range elastic interactions . for periodic boundary conditions along the crack front as considered here , this becomes @xcite @xmath15 @xmath16 is a time - independent disorder field with correlations @xmath17 where @xmath18 and @xmath19 for @xmath20 and @xmath21 for @xmath22 . in practice
, such a disorder field can be prepared by assigning uncorrelated random numbers from a distribution to a subset of lattice sites forming a square grid with a spacing of @xmath0 , and filling the rest of the lattice sites by using an appropriate interpolation algorithm . here , we use a uniform distribution from -1 to 0 , and bilinear interpolation to obtain a smooth disorder field , see fig .
[ fig : fronts ] for examples .
@xmath23 is the contribution of the external load .
the dynamics is defined in discrete time by setting @xmath24 where @xmath25 is the local velocity of the front element @xmath26 , and @xmath27 is the heaviside step function .
parallel dynamics is assumed , such that during a single time step , all the front elements with @xmath28 are advanced by a unit step , @xmath29 .
the local forces are then recomputed for each element , and the process is repeated until @xmath30 for all @xmath26 and the avalanche stops .
the applied load is then increased so that exactly one front element becomes unstable ( i.e. @xmath28 ) , and a new avalanche is initiated . as the crack front advances , the applied sif @xmath23 decreases at a rate proportional to the instantaneous average velocity @xmath31 of the front , with a proportionality constant @xmath32 .
such a protocol leads to a cut - off for the avalanche size distribution scaling with @xmath32 @xcite , and corresponds to quasistatic driving , which has the advantage that observables such as the avalanche sizes can be defined without the need to apply ( a possibly ambiguous ) non - zero threshold .
notice that while the discretized dynamics we employ here neglects the fact that the local velocity of the crack front should be proportional to the local sif , this simplification is well known to have no influence on the scaling behaviour we study here .
as the planar crack front advances along the weak plane , it will roughen due to disorder . such disorder , originating from the fluctuations of the local toughness of the weak plane , is characterized by a fluctuation amplitude @xmath33 and a correlation length @xmath0 .
the crack front morphology can be characterized by considering the structure functions @xcite @xmath34 if the front fluctuations follow gaussian statistics , the structure functions with different @xmath35 can be collapsed by normalizing the @xmath36 s with the gaussian factors @xcite @xmath37^{1/k}.\ ] ] close to the depinning transition ( i.e. when a slow enough external drive is applied ) , we expect the roughness of the front to be controlled by two length scales , @xmath0 and the larkin length @xmath38 @xcite . in the following
, we will consider the different regimes separately .
for small enough @xmath14 ( or equivalently , large enough @xmath33 ) , the disorder is strong enough to substantially deform the front locally , which may lead to steep slopes ( and possibly even overhangs in experiments and in models which would allow them to be formed ) of the crack front , and thus to multiscaling of the front roughness , or @xmath35-dependent scaling of the structure functions @xmath39 . in the spirit of the idea of strong pinning ( individual `` pinning centers '' , or correlated fluctuations of the random potential ,
are strong enough to substantially deform the front ) , we expect such large deformations and steep slopes of the crack front to take place up to a lateral length scale proportional to the disorder scale @xmath0 .
this regime corresponds to a small larkin length as compared to the scale of the toughness fluctuations , @xmath40 .
thus , we expect to observe multiscaling for scales below @xmath0 , and the asymptotic scaling characterized by the unique roughness exponent @xmath2 for scales larger than @xmath0 . by tuning @xmath14 within this regime , the amplitude of the local deformations and thus the strength of the multiscaling can be changed . in the opposite limit , where @xmath41 , the toughness fluctuations are weak and no significant deformation of the crack front takes place for lateral scales of the order of @xmath0 .
instead , the front remains essentially undeformed for lateral scales below @xmath1 , and the potential energy fluctuations follow poissonian statistics .
this leads to front roughness characterized by the larkin exponent @xmath42 for scales above @xmath0 and below @xmath1 . for scales above @xmath1 the toughness fluctuations become effective and the asymptotic roughness exponent @xmath2 is expected .
we simulate the crack line model in a system of linear size @xmath43 , by considering different disorder correlation lengths ( @xmath44 and @xmath45 ) and values of the crack front stiffness ( @xmath46 and @xmath47 ) .
the value @xmath48 is used for the parameter controlling the avalanche cut - off scale .
[ fig : fronts ] shows examples of the crack front profiles for different @xmath0 and @xmath14 .
also the toughness fluctuations are shown , with dark ( light ) blue corresponding to regions with low ( high ) local toughness . in the spirit of the discussion of the previous section , we consider the scaling form @xmath49 to account for the effect of varying @xmath0 for fixed @xmath14 . here
, @xmath50 is expected to scale as @xmath51 for @xmath52 and @xmath40 , and @xmath53 for @xmath41 .
[ fig : roughness ] shows the rescaled @xmath39 functions for three different values of @xmath14 . for @xmath54 , the data collapse nicely , verifying the scaling form , eq .
( [ eq : collapse ] ) , and the gaussian nature of the large scale front roughness . also the different scaling regimes as given by eqs .
( [ eq : fx11 ] ) , ( [ eq : fx12 ] ) and ( [ eq : fx22 ] ) are clearly visible , with @xmath2 and @xmath4 .
notice also that no multiscaling is observed , as long as only scales above @xmath0 are considered . for @xmath55 and small @xmath14
, the data displays multiscaling , a signature of a deviation from the gaussian statistics .
the strength of this multiscaling depends on @xmath14 .
this indicates that the multiscaling regime may not be universal : different parameters of the model could correspond to different effective exponents within this regime . for large enough @xmath14
, the @xmath55 regime is characterized by a linear dependence of @xmath39 on @xmath56 , or @xmath57 with @xmath58 , and essentially no multiscaling is observed : the small deviation from linear behaviour for the smallest values of @xmath56 in the bottom panel of fig .
[ fig : roughness ] is due to the discrete nature of the model .
in this paper we have studied the roughness of a planar crack front driven in a disordered medium , by considering the standard crack line model , with the additional ingredient of using toughness fluctuations with a characteristic scale @xmath0 which may be tuned .
such a simple approach has made it possible to identify the relevant length scales of the problem , and to propose an explanation of the experimental results regarding the crack front roughness .
based on our results , we think that the experiments reported in ref .
@xcite correspond to the " strong pinning
regime , where the toughness fluctuations cause substantial local deformations of the crack front , visible as multiscaling for short length scales .
we expect the cross - over scale separating this multiscaling regime from the asymptotic scaling regime characterized by the roughness exponent @xmath59 to be proportional to the disorder scale @xmath0 . indeed , in the experiments reported in ref .
@xcite , the cross - over scale is shifted towards larger values when the diameter of the beads used for the sand blasting process to prepare the experimental samples is increased .
moreover , the spatial resolution of the experiment is clearly high enough to observe features of the crack front also below scales corresponding to the diameter of the beads @xcite .
however , it is not clear how the statistical properties of the toughness fluctuations depend on the preparation procedure of the samples , making it difficult to make a precise comparison between theory and experiment .
future directions of research related to the present topic would include to develop an experimental setup in which the toughness fluctuations could be controlled , and thus the effect of their statistical properties could be tested properly . regarding the theoretical side , it could be useful to develop a model in which a more accurate expression for the long range interaction kernel would be used , accurately describing interactions between segments of a crack front of an arbitrary shape @xcite . such a more realistic line model for the crack front could also include the possibility to form overhangs .
however , we think that the picture regarding the different scaling regimes and the cross - over scales separating them presented in this paper would hold also in that case .
stephane santucci is thanked for interesting discussions .
ll acknowledges the financial support from the academy of finland .
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solids _ * 38 * 443 | we consider numerically the roughness of a planar crack front within the long - range elastic string model , with a tunable disorder correlation length @xmath0 .
the problem is shown to have two important length scales , @xmath0 and the larkin length @xmath1 .
multiscaling of the crack front is observed for scales below @xmath0 , provided that the disorder is strong enough .
the asymptotic scaling with a roughness exponent @xmath2 is recovered for scales larger than both @xmath0 and @xmath1 . if @xmath3 , these regimes are separated by a third regime characterized by the larkin exponent @xmath4 .
we discuss the experimental implications of our results . |