NEW YORK, Sept. 12, 2018 /PRNewswire/ -- A new report, released today by the TIAA Institute and the Global Financial Literacy Excellence Center (GFLEC) at the George Washington University School of Business, found there is a financial literacy gap among millennials. The report also found that while most millennials use their smartphones to manage their personal finances, financial technology (fin-tech) does not necessarily improve their personal finance management practices.
The "Millennial Financial Literacy and Fin-Tech Use: Who Knows What in the Digital Era" study utilized the TIAA Institute-GFLEC 2018 Personal Finance Index (P-Fin Index) to examine the personal finance knowledge of millennials. Millennials answered 44 percent of P-Fin Index questions correctly, compared to 50 percent of the US adult population. Moreover, younger millennials (ages 18-27) answered 41 percent of P-Fin Index questions correctly, compared to 47 percent of older millennials (ages 28-37).
Financial literacy among both older and younger millennials is lowest in the areas of comprehending risk and insuring. Understanding insurance, in particular, saw the greatest gap between younger and older millennials. Financial literacy is highest in the area of borrowing and debt management for both younger and older millennials.
The report also examined how millennials use technology to manage their personal finances and the effect of financial technology on financial outcomes. Approximately 80 percent of millennials use their smartphone for transactional purposes like paying bills and depositing checks, and 90 percent use their phones for informational activities like tracking their spending.
While fin-tech offers a convenient way to manage finances, users do not always make savvy financial decisions. Almost 30 percent of millennials who use their smartphone to make mobile payments report overdrawing their checking account, compared with 20 percent who do not make mobile payments. Further, one-quarter of those who track spending with their smartphone report overdrawing their accounts, compared with 20 percent of those who do not track spending via their smartphone.
Fin-tech users benefit from being financially literate; those with high levels of financial literacy are less likely to overdraw their checking accounts.
"The millennial oversample in this year's P-Fin Index sheds a light on the use of mobile technology, and the impact that it has had on an increasingly influential generation," Stephanie Bell-Rose, Head of the TIAA Institute. "As technology continues to develop ways to make our lives easier, it is clear that we cannot exclusively rely on it to guide us through our financial lives. Our research underscores the importance of financial literacy and its complementary relationship with fin-tech in producing good outcomes."
"The low level of financial literacy among millennials speaks of the importance of equipping this large generation with the knowledge and skills that are needed to make financial decisions in the digital era," Annamaria Lusardi, Academic Director at GFLEC and the Denit Trust Chair of Economics and Accountancy at GW. "This study shows that fin-tech users have different needs and characteristics, providing many opportunities for innovation for fin-tech developers."
The P-Fin Index examines financial literacy across eight areas of personal finance in which individuals routinely function. The survey provides a robust indicator of overall personal finance knowledge and understanding. The 2018 survey leveraged a special set of questions to examine millennial fin-tech use and its impact on personal finance.
The report with new insights on financial literacy levels of millennials was authored by Paul Yakoboski, Senior Economist at the TIAA Institute, Annamaria Lusardi, Academic Director at GFLEC, and Andrea Hasler, Assistant Research Professor in Financial Literacy at GW's GFLEC.
Founded in 2011 at the George Washington University School of Business, the Global Financial Literacy Excellence Center (GFLEC) has positioned itself to be the world's leading center for financial literacy research and policy. Through rigorous scholarship and research, wide-reaching education, and global policy services, the Center works with partners in Washington, D.C., throughout the United States, and across the globe to raise the level of financial knowledge. GFLEC builds on more than 20 years of academic research by Professor Annamaria Lusardi, an early contributor to financial literacy as a field of study. The Center collaborates on policy work with key institutions such as the FINRA Investor Education Foundation, the Organization for Economic Cooperation and Development (OECD), and the Italian Financial Education Committee. For more information about GFLEC, visit www.gflec.org.
1 The Lipper Large Fund Award is given to the group with the lowest average decile ranking of three years' Consistent Return for eligible funds over the three-year period ended 11/30/12 (36 fund companies), 11/30/13 (48), 11/30/14 (48), 11/30/15 (37), 11/30/16 (34) and 11/30/17 (34) with at least five equity, five bond, or three mixed-asset portfolios. Note this award pertains to mutual funds within the TIAA-CREF group of mutual funds; other funds distributed by Nuveen Securities were not included. From Thomson Reuters Lipper Awards, © 2018 Thomson Reuters. All rights reserved. Used by permission and protected by the Copyright Laws of the United States. The printing, copying, redistribution, or retransmission of this Content without express written permission is prohibited. Past performance does not guarantee future results. Certain funds have fee waivers in effect. Without such waivers ratings could be lower. For current performance, rankings and prospectuses, please visit the Research and Performance section on TIAA.org. Securities offered through Nuveen, LLC, and TIAA-CREF Individual & Institutional Services, LLC, members FINRA and SIPC.


text:
Сарін () — округ у Швейцарії в кантоні Фрібур.
Адміністративний центр — Фрібур.

Громади

Примітки

Округи кантону Фрібур

redpajama_set_name: RedPajamaWikipedia


Leo Anthony was a top midwestern dirt-track racer of the late 1930s and 1940s. He won three AMA nationals during his 13-year professional racing career, all on Harley-Davidson motorcycles. Anthony was known as a determined and hard-riding competitor on the track, but was said to have been modest and even a bit bashful about his accomplishments.
Anthony was born in Port Huron, Michigan, on December 15, 1916.
The great Joe Petrali was a rider Anthony looked up to as he was coming through the ranks. In an interview, Anthony once called Petrali the greatest dirt track racer of all time.
Entering his first race in 1934, Anthony quickly worked his way through the amateur ranks, racing around the various dirt tracks of the Midwest. By 1937, Anthony had turned pro and promptly went out and finished second to Lester Hillbish at the Springfield (Illinois) Mile.
After World War II, Anthony really hit his stride. His best season was 1947. On May 26, he won the AMA five-mile national for half-mile tracks, that year held in Montgomery, Alabama. A week later, in Richmond, Virginia, he earned a victory in the 10-mile national for half-miles. He went on to earn podium finishes that season at the Springfield (Illinois) and Milwaukee Miles, where he took third and second respectively.
Anthony's final AMA national victory came on June 26, 1948, at the three-mile AMA national held in Spencer, Iowa. He continued to race and was a top contender through 1950.


UPDATE: SEE THE MARCH UPDATE HERE.
CRFB has updated its health care chart, detailing the ten-year costs and savings from the most recent legislation passed by the House and the bill introduced by Senator Reid in the Senate yesterday. To compare the most recent Senate bills with the previous HELP and Finance Committee bills, click here.
View our comparison chart below.
Numbers in billions, with positive numbers representing a reduction in the deficit. Numbers may not add due to rounding.
Sources: Congressional Budget Office, Joint Committee on Taxation, and Authors' Calculations.
#Cost of expanding prescription drug coverage incorporated into savings estimate for reducing payments.
+The CLASS Act makes available government-sponsored long-term care insurance. Because this insurance would have a "vesting period," the provision appears to raise considerable amounts of revenue over the next decade. However, these revenues must ultimately be used to cover the program's costs, and therefore do nt belong in the bill as an offset.


text:
\section{Introduction}

Variable  stars are crucial  astrophysical objects  since they  can be
used  as tracers  of stellar  populations in  the framework  of galaxy
evolution  (\citealt{DEA02,MEA03}).  Moreover, the  comparison between
the observables  predicted by pulsational models  and the observations
themselves supply  an independent  estimate of the  stellar parameters
(\citealt{BEA01,KEA01}).  This implies that stellar pulsations provide
a  way  to  probe  regions   of  the  star  that  would  be  otherwise
unaccessible  to  direct   observations.   Therefore,  variable  stars
provide the unique opportunity  to investigate the plausibility of the
physical  assumptions  adopted  to  construct  both  evolutionary  and
pulsational models (\citealt{BCM02,KW02}).

Nonadiabatic  stellar pulsations are  complicated phenomena,  even for
small amplitudes  and purely radial oscillations, to  which the linear
theory  is applicable.   For large  amplitudes, the  nonlinear effects
become important and the  simplifying assumptions must be treated with
caution. During the last  decades the work on  nonlinear stellar
pulsations  has been  developed  along three  main approaches:  simple
one-zone   models,   the   formalism   of  amplitude   equations   and
hydrodynamical models. Although the  third approach provides the most
detailed and  accurate physical  description of the  outermost stellar
layers  during  the  pulsation cycle,  it  is  also  true that  it  is
difficult to figure  out whether the intrinsic features  of the models
are either a direct consequence of the adopted physical assumptions or
caused by the numerical methods  and the spatial resolution adopted to
discretize the  stellar structure into  a series of  concentric shells
--- see, e.g., \cite{PEA03} and references therein.  It is within
this       framework      where      simple       one-zone      models
(\citealt{B66,STT89,UX93,IFH92,T01}),   and  the   amplitude  equation
formalism  (\citealt{DK84,BK86,IT91,S93}),  play   a  key  role.   The
advantages and drawbacks of  these approaches have already been widely
discussed in the literature  --- see, e.g., \cite{B98}, and references
therein, and  \cite{T01}).  In  particular, one-zone models  have been
introduced  with  the  sole  purpose  of clarifying  the  analysis  by
eliminating possible subtle  uncertainties introduced by the stability
of  numerical  algorithms  and   by  spatial  resolution.   This  was
accomplished  by  considering  the  stellar  envelope  as  a  one-zone
structure: a single,  relatively thin, spherical mass-shell concentric
with   the  stellar   center.   These   models  have   provided  clear
understanding of  the destabilization  mechanisms and of  the possible
consequences  of  couplings  as  well  as  feedbacks  between  several
phenomena  associated  to  stellar  variability  ---  see  \cite{B66},
\cite{UW68}, \cite{STT89}, \cite{UX93}, \cite{IFH92}, and \cite{T01}.

The  simplest one-zone model  that accounts  for the  coupling between
pulsation and  convection was suggested by  \cite{S86}.  Following the
convective  scheme developed  by  \cite{S82a}, he  derived a  one-zone
pulsational model that includes  a time-dependent convective term.  He
computed a set of models  associated to the Cepheid instability strip,
integrating them only for a few dynamical time scales.  The results of
this work  support the  generally accepted view  that convection  is a
damping mechanism, in particular for  models located close to the cool
edge of  the instability  strip.  Although the  pulsationally unstable
region as well  as velocity curves were in  qualitative agreement with
empirical data,  he also found that fully  convective models underwent
vibrational instability for certain values of the parameters.  A
similar  approach   was  also  adopted  by   \cite{UX90,UX93}  and  by
\cite{S93}, but  they did  not discuss in  detail the  pulsational and
dynamical behavior of their models.

In this  work, we present new  results and possible  extensions of the
one-zone model developed  by \cite{S86}, investigating the limit-cycle
behavior (pulsational  instability) and by accounting for  the role of
the turbulent pressure  and of the thickness of  the convective layer.
The paper  is organized as  follows. In \S  2 we present  the one-zone
convective model.   We place special emphasis on  the adopted physical
and  numerical assumptions.   In \S  3 we  thoroughly  investigate the
limit-cycle behavior  of the model  suggested by \cite{S86},  an issue
marginally addressed in the original  paper.  In this section, we also
focus our attention  on the dependence of pulsation  properties on the
shell thickness (\S3.1)  as well as on the  turbulent pressure (\S3.2)
and their  role in  determining the morphology  of light  and velocity
curves.  In \S  4 we discuss the approach  to limit-cycle stability of
completely convective  models and briefly  describe possible empirical
similarities with LPVs.  Finally, in \S6 we summarize our main results
and briefly outline future perspectives.  In appendix A, we discuss in
more detail the physical  assumptions adopted to include the turbulent
pressure in the one-zone model are described.

\section{The one-zone convective model}

In the  classical theoretical  framework of one-zone  models, variable
stars have an equilibrium radius  $R_{\rm 0}$ and an extended shell or
envelope of  variable radius $R$  on top of  a compact core  of radius
$R_{\rm  c}$.   As  detailed  in  \cite{S86}, by  accounting  for  the
equation  of  motion,  the   energy  equation,  and  the  equation  of
convective  transport, the  resultant dynamical  system  describes the
evolution of the convective upper layer and it has the following form:

\begin{eqnarray}       &&\frac{d^2X}{d\tau^2}=HX^{-q}-X^{-2}\nonumber\\
&&\frac{dH}{d\tau}=\zeta       X^{2d}(1-\gamma_{\rm       r}       X^b
H^{s+4}-\gamma_{\rm    c}X^{-c}    U_{\rm    c}^3)\label{eq:dsystem}\\
&&\frac{d  U_{\rm c}}{d\tau}=\zeta_{\rm  c}  (X^{-d}H^{1/2}-U_{\rm c})
\nonumber,
\end{eqnarray}

\noindent  where $X$  and  $H$  are the  radius  and the  nonadiabatic
pressure normalized to their  equilibrium values, while $U_{\rm c}$ is
related to  the convective  velocity and it  is defined as  $U_{\rm c}
\equiv U'/U_{{\rm  ml}_0}$, where $U_{{\rm ml}_0}$  is the equilibrium
mixing-length  convective  velocity.   Moreover,  the  time  variable,
$\tau$,  is normalized  to the  dynamical (free-fall)  time  scale. As
defined in \cite{S86}, the other input parameters of the model are: $q
\equiv m  \Gamma_1-2$, $d\equiv m(\Gamma_1-2)/2$, and  $c \equiv m-2$,
where $\Gamma_1$  is the adiabatic  exponent and $m$ is  the so-called
form factor.  In the  limit of small oscillations (\citealt{S72,S86}),
the form factor is defined as:

\begin{equation}                                           m=\lim_{X\to
1}\frac{\log~[(X^3-\eta^3)/(1-\eta^3)]}{\log(X)}=
\frac{3}{1-\eta^3},\label{eq:m0}
\end{equation}

\noindent with $\eta \equiv R_{\rm  c}/ R_{\rm 0}$.  At the same time,
$b$ is  defined as  $b\equiv 4+m[n-(s+4)(\Gamma_1-1)]$, where  $s$ and
$n$  are the  temperature and  the density  exponents in  the Kramers'
opacity law --- for more details see \cite{B66}.

The main control parameters of the model are $\zeta$, $\zeta _{\rm c}$
and  $\gamma_{\rm c}$,  which  are  defined as  follows:  {\sl i)  the
nonadiabatic  parameter}  ---  $\zeta$   ---  the  ratio  between  the
dynamical  and  the  thermal  time  scale;  {\sl  ii)  the  convective
efficiency} ---  $\zeta_{\rm c}$ ---  the ratio between  the dynamical
time and the convective time scale; {\sl iii) the convective/radiative
splitting}  --- $\gamma_{\rm  c}$ ---  the ratio  between  the initial
convective  luminosity  and the  total  initial  luminosity, that  is,
$\gamma_{\rm  c}   \equiv  L_{{\rm  c}_0}/L_0$,   which  implies  that
$\gamma_{\rm r} = 1-\gamma_{\rm c}$.

The reader interested  in a  detailed discussion  concerning the
convective time scale in the context of one-zone models is referred to
\S  4 of  \cite{S86}.   More quantitative  predictions concerning  the
different  timescales  connected  with  turbulent  energy  across  the
envelope  of  variable  stars   have  been  provided  by  \cite{S82a},
\cite{BMS99} and by \cite{FBK00}.

The values $n=1$  and $s=3$ for the Kramers'  opacity are the standard
ones, while the values  for $\Gamma_1$, $m$, $\gamma_{\rm c}$, $\zeta$
and  $\zeta_{\rm c}$  must  be  treated with  caution.   The value  of
$\Gamma_1=1.1$  adopted  in \cite{S86}  is  a  typical  value for  the
$\gamma$-mechanism  operating   in  the  partial   ionization  regions
(\citealt{C80}).   The  choice  of  a  form factor  $m$  equal  to  10
($\eta=0.888$) ---  considered typical  of Cepheids in  \cite{S86} ---
together with  the values chosen  for the other parameters  assure the
turbulent  stability  and  the   secular  stability  for  $\zeta$  and
$\zeta_{\rm  c}$ in  the range  $[0,10]$  and $\gamma_{\rm  c} \le  1$
(\citealt{S86}).   The  values of  these  parameters were  arbitrarily
chosen  by \cite{S86}  and lead  to the  existence of  a pulsationally
unstable region  (``strip'') for values of $\gamma_{\rm  c} \le 0.45$.
From a  mathematical point  of view,  we refer to  such a  behavior as
having a limit  cycle born through a Hopf  bifurcation.  The stability
analysis in \cite{S86} was hampered by the fact that individual models
were integrated only for a  small number of dynamical time scales.  In
particular, our calculations show that for these cases, no limit-cycle
stability exists.   Note also that \cite{S86} analyzed  only the cases
for $\zeta$ and $\zeta_{\rm c}\le  4$, and that an exhaustive study of
the  dependence of the  limit-cycle behavior  on the  input parameters
remained to be performed.

\begin{figure}[t]
\epsfig{f01.eps}
\caption{Examples  of dynamical behavior  for $\gamma_{\rm
c}=0.4$.    Radius   time   series   for   stable   ---   $(\zeta_{\rm
c},\zeta)=(3,4)$  ---   {\sl  (top)},  limit-cycle   ---  $(\zeta_{\rm
c},\zeta)=(1.5,1.5)$  ---  {\sl (middle)}  and  unstable behavior  ---
$(\zeta_{\rm c},\zeta)=(0.5,0.5)$ --- {\sl (bottom)}. \label{f01}}
\end{figure}

\begin{figure*}[t]
\epsfig{f02.eps}
\caption{The  ($\zeta,\zeta_{\rm  c}$)-plane  for  several
values   of  $\gamma_{\rm   c}$:  $\gamma_{\rm   c}=0.1$   {\sl  (a)};
$\gamma_{\rm  c}=0.2$  {\sl  (b)};  $\gamma_{\rm  c}=0.3$  {\sl  (c)};
$\gamma_{\rm  c}=0.4$  {\sl  (d)};  $\gamma_{\rm  c}=0.5$  {\sl  (e)},
representing  pulsationally   unstable  {\sl  (black)},  pulsationally
stable  {\sl (grey)}  and   vibrationally unstable  behavior {\sl
(white)}}
\label{f02}
\end{figure*}

\begin{figure*}[t]
\epsfig{f03.eps}
\caption{Limit-cycle  characteristics. From top  to bottom
the panels show: the  total luminosity, $L$; the radiative luminosity,
$L_{\rm  r}   \equiv  {L_{\star}}_{\rm  r}/L_0$   and  the  convective
luminosity,  $L_{\rm  c}  \equiv  {L_{\star}}_{\rm  c}/L_0$;  and  the
dimensionless radius,  $X$ and velocity, $V$  variations. The temporal
axis is represented as $\tau -\tau_{\rm lc}$, where $\tau_{\rm lc}$ is
the  time when  the  limit  cycle has  been  reached.  The  parameters
adopted   to  construct   the  individual   cases  were   chosen  from
Fig.~\ref{f02}{\sl b}: {\sl  (a)} Small amplitude: $(\zeta, \zeta_{\rm
c})=(6.5,3)$;   {\sl   (b)}    Bump   Cepheid:   $(\zeta,   \zeta_{\rm
c})=(5.5,3)$;  {\sl  (c)}  Double-peak  Cepheid:  $(\zeta,  \zeta_{\rm
c})=(4,3)$;  {\sl (d)} Steep  bump: $(\zeta,  \zeta_{\rm c})=(1.5,3)$;
{\sl (e)} Pulse-like: $(\zeta, \zeta_{\rm c})=(0.7,3)$.\label{f03}}
\end{figure*}

In  the current  investigation, we  have first  undertaken  a thorough
study  of the  dynamics  in  the $(\zeta,  \zeta_{\rm  c})$ plane  for
$\zeta$ and  $\zeta_{\rm c} \leq 10$  and for different  values of the
convective-radiative   splitting,  $\gamma_{\rm  c}$,   following  the
assumption  of radiative-dominated  energy transport  ($\gamma_{\rm c}
\leq 0.5$).  We  have used the same form factor  ($m=10$) and the same
initial  condition  $(X_0,V_0,H_0,U_{{\rm  c}_0})=  (1.4,0.0,1.0,0.7)$
adopted by  \cite{S86}.  We  have furthermore assumed  that a  case is
pulsationally  unstable (limit-cycle  behavior)  when two  consecutive
maxima  in  radius  variations  differ  by less  than  $10^{-7}$,  and
pulsationally   stable  (damping   oscillations)  when   the  solution
asymptotically approaches the fixed point $(\bar{X}, \bar{V}, \bar{H},
\bar{U_{\rm  c}}) =  (1,0,1,1)$ and  its distance  to the  fixed point
becomes smaller  than $10^{-8}$.  The solution has  been considered to
be  vibrationally unstable when  the rapidly  increasing dimensionless
radius  amplitude  became  larger   than  15.   These  thresholds  are
reasonable values.  Moreover, we have also verified that the resultant
qualitative dynamics  does not depend  on the choice of  these values.
Of course, one could use as well the asymptotic perturbation theory to
compute  the properties  of the  limit cycle.   Nevertheless,  such an
approach  is beyond  the  aims  of the  current  investigation and  we
consider it as  a future line of work.  For  a better understanding of
our  results,  we illustrate  in  Fig.~\ref{f01}  the  three types  of
dynamical behavior we have identified.  The top panel shows an example
of pulsational stability, i.e.,  the initial perturbation decays.  The
bottom  panel  shows  a  vibrationally  unstable  model  (the  initial
perturbation grows), while the middle panel shows the time series of a
case   that   approaches    a   limit-cycle   stability   (pulsational
instability).  Note  that for small  amplitudes ($\tau \leq  100$) the
case plotted in the bottom panel  seems to approach a limit cycle, but
for $\tau  > 200$  it becomes clear  that the amplitudes  are steadily
increasing.  This  finding further strengthens the need  for long time
integrations  to  assess the  type  of  stability  for the  individual
one-zone  models.  As  a final  comment on  the  numerical assumptions
considered  in the  present  work,  it is  worth  mentioning that  the
dynamical  behavior  of  the  system  is independent  of  the  initial
condition, provided that  it belongs to the neighborhood  of the fixed
point  $(\bar{X},  \bar{V},  \bar{H},  \bar{U_{\rm  c}})=  (1,0,1,1)$.
Therefore,   we   did   not   investigate  the   dependence   of   the
characteristics of the time-series on initial conditions.

\begin{figure*}[t]
\epsfig{f04.eps}
\caption{The  ($\zeta,\zeta_{\rm  c}$)-plane  for  several
values of $\gamma_{\rm c}$.  Eq.~(\ref{eq:dsystem}) has been used with
$\eta=0.75$: $\gamma_{\rm c}=0.1$ {\sl (a)}; $\gamma_{\rm c}=0.2$ {\sl
(b)}; $\gamma_{\rm c}=0.3$ {\sl  (c)}; $\gamma_{\rm c}=0.4$ {\sl (d)};
$\gamma_{\rm  c}=0.5$ {\sl  (e)}, representing  pulsationally unstable
{\sl   (black)},   pulsationally   stable   {\sl  (grey)}   and
vibrationally unstable behavior {\sl (white)}. \label{f04}}
\end{figure*}

\begin{figure*}[t]
\epsfig{f05.eps}
\caption{The  ($\zeta,\zeta_{\rm  c}$)-plane  for  several
values of $\gamma_{\rm c}$.  Eq.~(\ref{eq:dsystem}) has been used with
$\eta=0.92$: $\gamma_{\rm c}=0.1$ {\sl (a)}; $\gamma_{\rm c}=0.2$ {\sl
(b)}; $\gamma_{\rm c}=0.3$ {\sl  (c)}; $\gamma_{\rm c}=0.4$ {\sl (d)};
$\gamma_{\rm  c}=0.5$ {\sl  (e)}, representing  pulsationally unstable
{\sl   (black)},   pulsationally   stable   {\sl  (grey)}   and
vibrationally unstable behavior {\sl (white)}. \label{f05}}
\end{figure*}

\section{Limit-cycle characteristics}

One-zone models  can be  adopted to  perform only  a qualitative
comparison with pulsation properties of variable stars. Moreover, this
comparison is limited to  observables that one-zone models can account
for.   In particular,  the  shape  of light  and  velocity curves  ---
originally suggested  for RR  Lyrae stars by  \cite{SD86} ---  and the
occurrence of  first overtone pulsators  (\citealt{SGD87}).  The most
interesting  results disclosed  by  our simulations  are presented  in
Fig.~\ref{f02}{\sl a--e}, where the regions of damped oscillations are
shown in grey,  the regions where the radial  displacements approach a
limit cycle  are marked in  black, while vibrationally unstable
cases  are  shown  in  white.    A  glance  at  the  data  plotted  in
Fig.~\ref{f02} discloses that, with the exception of the case in which
$\gamma_{\rm  c}=0.1$,  an  increase  in  $\gamma_{\rm  c}$  causes  a
decrease in  the region of  pulsationally unstable cases and  that for
$\gamma_{\rm c}=0.5$  it vanishes. These findings  support the results
originally  obtained  by \cite{S86}  concerning  the  damping role  of
convection.  In addition to the radius $(X)$ and velocity $(V)$ curves
chosen to be illustrated in  \cite{S86}, we have added the light $(L)$
curve  and  in several  occasions  the  temperature $(T)$  variations,
estimated according to

\begin{eqnarray}                       L                      &\equiv&
\frac{L_{\star}}{L_0}=\frac{{L_{\star}}_{\rm    r}+   {L_{\star}}_{\rm
c}}{L_0}= \gamma_{\rm r} X^bH^{s+4}+ \gamma_{\rm c} X^{-c} U_{\rm c}^3
\\ \frac{T}{T_0} &=& X^{-2 d} H,
\end{eqnarray}

\noindent where  $L_{\star}$ denotes the stellar  luminosity while the
subscripts  ``r'' and  ``c''  refer to  the  radiative and  convective
component,   respectively,    as   they   result    from   \cite{S86}.
Fig.~\ref{f03}  shows the light  curve, $(L)$,  the radius  $(X)$, and
velocity  $(V)$ time  series for  selected cases  that  approach limit
cycle.  Note that to improve the visualization of data plotted in Fig.
~\ref{f03}, we subtracted from  the integration time, $\tau$, the time
interval  spent  by individual  models  to  approach  the limit  cycle
stability.  We  have chosen to illustrate cases  at fixed $\gamma_{\rm
c}$  and $\zeta_{\rm  c}$ values,  and $\zeta$  ranging from  $0.7$ to
$6.5$, being typical examples of the qualitative dynamics encountered.
The  time  series   plotted  in  this  figure  show   that  the  cases
characterized  by  parameters  located   close  to  the  edge  of  the
pulsational  stability region  (grey area  in  Fig.~\ref{f02}) present
small  amplitudes  and  sinusoidal  changes (panel  {\sl  a}).   These
features are quite similar  to the behavior that nonlinear, convective
models show close  to the blue edge of the  instability strip --- see,
e.g., \cite{BCM00}.  On the other hand, models that are located across
the  pulsationally unstable  region (panels  {\sl b,  c}) show  a bump
along  the rising branch  of the  luminosity curve.   Our calculations
reveal  that such  a  feature is  due  to the  sharp  increase in  the
efficiency of  the convective motions,  close to the phase  of minimum
radius.   This  finding  is  also found  in  nonlinear  hydrodynamical
models.

\begin{figure*}[t]
\epsfig{f06.eps}
\caption{The     ($\zeta,\zeta_{\rm     c}$)-plane     for
$\eta=0.888$ and several values of $\gamma_{\rm c}$ when the turbulent
pressure  is included:  $\gamma_{\rm c}=0.1$  {\sl  (a)}; $\gamma_{\rm
c}=0.2$  {\sl  (b)};  $\gamma_{\rm  c}=0.3$  {\sl  (c)};  $\gamma_{\rm
c}=0.4$  {\sl  (d)};  $\gamma_{\rm  c}=0.5$  {\sl  (e)},  representing
limit-cycle {\sl (black)}, stable  {\sl (grey)} and vibrationally
unstable behavior {\sl (white)}. \label{f06}}
\end{figure*}

\begin{figure*}[t]
\epsfig{f07.eps}
\caption{Limit-cycle   characteristics   when  the   turbulent
pressure is introduced. From top  to bottom the panels show: the total
luminosity,   $L$;  the  radiative   luminosity,  $L_{\rm   r}  \equiv
{L_{\star}}_{\rm  r}/L_0$ and  the convective  luminosity,  $L_{\rm c}
\equiv {L_{\star}}_{\rm c}/L_0$; and the radius, $X$ and the velocity,
$V$ variations.  The temporal  axis is represented as $\tau -\tau_{\rm
lc}$, where $\tau_{\rm lc}$ is the time value when the limit cycle has
been  achieved.  The  parameters adopted  to construct  the individual
cases are:  $\eta=0.888$, $\gamma_{\rm c}=0.4$ and  {\sl (a)} $(\zeta,
\zeta_{\rm c})=(4,0.28)$; {\sl  (b)} $(\zeta, \zeta_{\rm c})=(4,0.4)$;
{\sl   (c)}  $(\zeta,  \zeta_{\rm   c})=(4,1)$;  {\sl   (d)}  $(\zeta,
\zeta_{\rm     c})=(4,4)$;    {\sl     (e)}     $(\zeta,    \zeta_{\rm
c})=(4,9)$. \label{f07}}
\end{figure*}

One can notice that for  cases located close to the vibrationally
unstable region,  the bump  becomes very narrow  (panel {\sl  d}) and
pulse-like (panel {\sl e}). This is a behavior that is not observed in
actual  Cepheids and  it  is not  supported  by nonlinear,  convective
models.  This indicates the limit  of the crude physical and numerical
approximations adopted to construct our models.  However, our analysis
suggests that the limit-cycle behavior of these one-zone models in the
pulsationally  unstable region  mimics the  behavior of  the Classical
Cepheids  instability  strip,  as  argued  in the  original  paper  of
\cite{S86}.  Finally, we note that the period of the oscillations
of the  cases plotted in  Fig. 3 is  not unity, even if  the dynamical
timescale was normalized to unity. This strong nonlinear effect on the
period was already  noted by \cite{S86}, and he  suggested that it was
due  to   a  correlation  with  the  pulsation   amplitude  (see  also
\citealt{SD86}).

\subsection{The shell thickness}

In this section,  we present the results concerning  the impact of the
shell thickness on the existence  of a limit-cycle behavior and on its
characteristics.    According   to   classical   physical   arguments,
pulsational  models only account  for the  envelope of  variable stars
(\citealt{C80}).   They include  a damping,  adiabatic region  that is
typically  located on  top of  the  nuclear burning  region (core),  a
transition region,  a driving, nonadiabatic region,  and the outermost
layers (surface).  The  driving region is the envelope  zone where key
elements (hydrogen, helium, metals)  are partially ionized and supply,
via  the  $\kappa$-   and/or  the  $\gamma$-mechanism,  the  pulsation
destabilization.   In  this theoretical  framework,  the  base of  the
envelope in nonlinear, hydrodynamical models is typically located at a
few percents of the total radius (\citealt{PEA03}).

As  far  as  the   one-zone-model  approach  is  concerned,  different
assumptions have  been adopted in  the literature. The  one-zone model
suggested by  \cite{IFH92} for Mira  variables accounts for  a driving
region  (piston  approximation) at  $X\approx  0.2-0.4$, a  transition
region through  which the pressure waves from  the interior propagate,
and a dissipation region that they call mantle. On the other hand, the
one-zone  model  of  \cite{S86}  for  variable stars  in  the  Cepheid
instability strip accounts for  a driving convective region located at
$X\approx  0.85$ on  top of  a damping,  adiabatic region  ({\sl rigid
core}). In  this theoretical framework,  the pulsation destabilization
is provided by  a driving agent ($\Gamma_1 <  4/3$). The two different
assumptions describe the same envelope region if the {\sl rigid core},
assumed by  \cite{S86} is  the outer boundary  of the  damping region.
Therefore,  the  {\sl shell  thickness},  $(1-\eta)$ in  dimensionless
formulation,  is the  radial extent  of the  region located  above the
boundary   between   the   damping   (adiabatic)   and   the   driving
(nonadiabatic) region.

To investigate  the dependence of  the dynamic behavior of  the system
given in Eq.~(\ref{eq:dsystem}) on the shell thickness, we have chosen
two values  of the shell thickness,  one smaller and  the other larger
than the value adopted in \cite{S86}: $\eta=0.75$ and $\eta=0.92$.  We
illustrate in  Fig.~\ref{f04} and Fig.~\ref{f05} the  behaviors in the
($\zeta,\zeta_{\rm c}$)-plane for $\gamma_{\rm  c} \leq 0.5$.  One can
notice that the  increase in the shell thickness  (decrease of $\eta$)
leads  to   the  existence   of  pulsational  instability   for  cases
characterized  by stronger convection  (higher values  of $\gamma_{\rm
c}$). This effect is expected, because a decrease in $\eta$ implies an
increase in the extent of the driving region.  Moreover, we have noted
that for  a fixed  value of $\gamma_{\rm  c}$ and different  values of
$\eta$, the  period distribution of  the cases that approach  a stable
limit cycle peaks at shorter periods as the shell thickness decreases.
This   behavior   is   also   expected,  since   detailed   nonlinear,
hydrodynamical  models  of  RR  Lyrae (\citealt{BS94})  and  classical
Cepheids (\citealt{BMS99}) suggest that  the regions located below the
nodal line supply  a small contribution to the  work integral of first
overtone pulsators.   This supports the suggestion  by \cite{SGD87} to
decrease the shell thickness of one-zone models to mimic the dynamical
behavior of overtone pulsators.

\subsection{The turbulent pressure}

Convection affects pulsation  through three factors, namely convective
energy  transfer  (thermodynamic  coupling), turbulent  pressure,  and
turbulent  viscosity  (dynamic  coupling).   The effect  of  turbulent
viscosity  is to  convert the  kinetic energy  of radial  motions into
thermal energy by means of  a turbulent cascade of smaller and smaller
turbulent eddies.  This  means that the turbulent viscosity  is a pure
damping factor (\citealt{S82a,XDC98a,YKB98}).  The role that turbulent
pressure   plays  in  driving   or  damping   the  pulsation   is  not
straightforward, since the contributions of gas and turbulent pressure
can not  be easily  separated. Linear (\citealt{YKB98})  and nonlinear
(\citealt{BMS99}) convective models of Classical Cepheids suggest that
the work  done by turbulent  pressure attains both  positive (driving)
and   negative  (damping)   values   in  different   regions  of   the
envelope. Linear  and nonlinear, convective LPV  models constructed by
\cite{OC86} and  by \cite{CO93} indicate that turbulent  pressure is a
driving mechanism,  whereas more recent  calculations by \cite{XDC98a}
support the evidence that it is a damping mechanism.

The turbulent pressure, $P_{\rm t}$,  was not included in the original
one-zone model by \cite{S86}, but it was shortly mentioned as being

\begin{equation} \frac{P_{\rm t}}{P_{\rm t_0}}=X^{-m}U_{\rm c}^2,
\label{eq:turbulence}
\end{equation}

\noindent where the zero  subscript denotes its equilibrium value.  In
this section, we  present the results obtained by  the introduction of
the  turbulent   pressure.   The  reader  interested   in  a  detailed
description  of  the  physical  assumptions  adopted  to  include  the
turbulent  pressure  term  in  Eq.~(\ref{eq:dsystem}) is  referred  to
Appendix A. The new dynamic system becomes now:

\begin{eqnarray}                  \frac{d^2X}{d\tau^2}&=&(1-\alpha_{\rm
p})X^{-q}h+\alpha_{\rm    p}X^{-c}    U_{\rm    c}^2-X^{-2}\nonumber\\
\frac{dH}{d\tau}&=&-m~\frac{\alpha_{\rm p}(\Gamma_3-1)}{1- \alpha_{\rm
p}}~X^{2d-1}~\frac{dX}{d\tau}~U_{\rm    c}^2~-\nonumber\\    &-&~\zeta
X^{2d}~(\gamma_{\rm  r}X^b  h^{s+4}+(1-\gamma_{\rm  r}) X^{-c}  U_{\rm
c}^3-1) \label{eq:dsystemtp}\\ \frac{d U_{\rm c}}{d\tau}&=& \zeta_{\rm
c}(X^{-d}H^{1/2}-U_{\rm c}) \nonumber,
\end{eqnarray}

We  have undertaken  a parametric  study in  order to  investigate the
influence of  the turbulent  pressure on the  overall dynamics  of the
system  and implicitly  on the  existence  of limit  cycles. For  this
purpose, we have chosen the same initial condition as in \S 2, that is
$(X_0, V_0, H_0, U_{{\rm c}_0})=(1.4,  0.0, 1.0, 0.7)$, which led to a
value  of $\alpha_{\rm p}  \approx 0.4$.   The results  concerning the
plane $(\zeta,\zeta_{\rm  c})$ are shown in  Fig.~\ref{f06}, using the
color  code from  Fig.~\ref{f02}.   The regions  characterized by  the
existence of limit cycles for $\gamma_{\rm c} < 0.5$ are more extended
than in the  case without turbulent pressure, as  expected because the
additional pressure adds to the driving mechanism.

We have also investigated the  light and velocity curves for the cases
characterized by limit-cycle behavior.  From the hydrodynamical models
as  well as  from plain  physical arguments  on the  existence  of the
Cepheid  instability  strip,  it  is  expected that  by  crossing  the
instability strip from the blue  to the red edge, the period increases
and the amplitude of the  oscillations quickly reaches its maximum and
then slowly decreases.  In order  to obtain a similar evolution of the
amplitude  from this one-zone  model, the  limit-cycle region  must be
bounded in  the $(\zeta,\zeta_{\rm c})$-plane  by pulsationally stable
regions both  to the left (low  values of $\zeta_{\rm c}$)  and to the
right (high values of $\zeta_{\rm c}$).  If bounded by a vibrationally
unstable region,  the oscillations which result  from using parameters
close to this  boundary are pulse-like and the  amplitude is large, as
in  Fig.~\ref{f03}{\sl  e}.  One  can  notice  that  for the  case  of
zero-turbulence  pressure, the  limit-cycle region  is bounded  to the
left  by  the  vibrationally  unstable  behavior and  thus  the  above
condition  is not satisfied.   However, with  the introduction  of the
turbulent  pressure, there  exists a  case for  which  the limit-cycle
region  is bounded in  the $(\zeta,\zeta_{\rm  c})$-plane both  to the
left  and   to  the  right   by  the  pulsationally   stable  behavior
(Fig.~\ref{f06}{\sl d}).  For this  case, we present in Fig.~\ref{f07}
the types of light and velocity curves obtained in the transition from
the hot (blue, low $\zeta_{\rm c}$) to the cool (red, high $\zeta_{\rm
c}$) edge, at constant $\zeta$.  One can notice that the amplitude has
a  peak  toward the  center  of the  limit-cycle  region  and then  it
decreases.   Moreover  and  even  more importantly,  data  plotted  in
Fig.~\ref{f07}  disclose   that  one-zone  models   that  account  for
turbulent pressure  do not  present, in this  region of  the parameter
space,  the spurious  secondary  peak along  the  rising branch.   The
morphology of light and velocity  curves plotted in this figure are in
qualitative  agreement   with  actual  classical   Cepheids  and  with
nonlinear, convective models.

\section{The red variables}

\begin{figure}[b]
\epsfig{f08.eps}
\caption{The ($\zeta,\zeta_{\rm  c}$)-plane for the completely
convective  shell  illustrated in  the  spirit  of Fig.\ref{f02}  for:
$\gamma_{\rm  c}=1.0$,  $\eta=0.888$   and  {\sl  (a)}:  no  turbulent
pressure, and  {\sl (b)}: turbulent pressure included;  {\sl (c)} Time
series for the luminosity $L$, radius $X$, velocity $V$, pressure $H$,
convective velocity $U_{\rm c}$ and temperature $T$ for a Cepheid-like
(solid line: $\gamma_{\rm c}=0.2$, $\zeta_{\rm c}=1.2$, $\zeta=8$) and
a   LPV-like  variable  star   (dashed  line:   $\gamma_{\rm  c}=1.0$,
$\zeta_{\rm c}=9$,  $\zeta=7.5$), the  latter case was  extracted from
panel {\sl(a)}. \label{f08}}
\end{figure}

\cite{S86}  remarked a  paradox of  the present  one-zone  model: {\sl
although  the  convection tends  to  stabilize  the  pulsation in  the
majority of cases, the completely convective case shows instability in
every criterion}.  We have verified that indeed the present model with
fully   convective  ($\gamma_{\rm   c}=1$)  thick   shell   ($m<8$  or
$\eta<0.85$)  presents   vibrational  instability  for   any  $\zeta$,
$\zeta_{\rm c}  \leq 10$. However,  for a thin shell,  our simulations
revealed that  while no limit-cycle  regions exist for the  cases with
$0.5  \mathrel{\rlap{\lower4pt\hbox{\hskip1pt$\sim$} \gamma_c  < 1.0$  and $\zeta,  \zeta_{\rm c}  \in [0,10]$,
limit-cycle  models exist  for the  case of  fully  convective shells.
Fig.~\ref{f08}{\sl  a}  shows  the ($\zeta,\zeta_{\rm  c}$)-plane  for
$\gamma_{\rm  c}=1.0$, $\eta=0.888$  and  without turbulent  pressure.
Although the  current analysis relies on simple  one-zone models, this
is a  very interesting  finding and we  are tempted to  attribute this
region of the plane $(\zeta,  \zeta_{\rm c})$ to the instability strip
of LPVs --- variable red  giants and supergiants --- which are thought
to  be significantly  nonadiabatic  and highly  convective.  There  is
general  agreement   within  the  astrophysical   community  that  the
intrinsic  reason for the  existence of  the red  edge of  the Cepheid
instability  strip is  the damping  produced by  convection.  However,
theoretical and empirical evidence  suggest that convection might also
be  a destabilizing mechanism  in the  cool region  of the  HR diagram
(\citealt{FW82,EG96,XDC98a,Wood00,CDKM01,DEA01,KB03,IEA04}).  When the
convective time  scale is  much longer than  the dynamical  time scale
($\zeta_{\rm c} \ll 1$), the  effect of convection is stabilizing, but
when the  convective time scale is  much shorter, the  reverse is true
(\citealt{G67}).  Thus, it may  provide an important driving mechanism
in  red   giants  and  supergiants.   More   exactly,  the  convective
luminosity  in the ionization  regions of  red pulsating  variables is
expected  to exceed  99\% of  the  total luminosity,  as mentioned  by
\cite{XDC98a}.   They identify  a Mira  instability strip  outside the
Cepheid  instability strip  when  pulsation-convection interaction  is
taken into account.

To investigate the  effect of the turbulent pressure in  the case of a
completely   convective    shell,   we   have    identified   in   the
($\zeta,\zeta_{\rm c}$)-plane the regions characterized by limit-cycle
behavior.  We  illustrate the  results in Fig.~\ref{f08}{\sl  b}.  The
region  of limit cycles  for the  completely convective  case persists
when the turbulent pressure is introduced.  Compared to the cases with
no turbulent  pressure, this  region shifts to  smaller values  of the
convective efficiency, $\zeta_{\rm c}$.  This shift is due to the fact
that  the  minimal  perturbation   strength  necessary  to  drive  the
pulsational  instability  is  achieved  at weaker  convective  driving
(smaller $\zeta_{\rm c}$), as the  rest of the driving is now provided
by the turbulent pressure.

\begin{figure}[t]
\epsfig{f09.eps}
\caption{Variation  of  the  luminosity ($L$),  radius  ($X$),
velocity ($V$), pressure ($H$), convective velocity ($U_{\rm c}$), for
the   case  of  completely   convective  shell   close  to   the  {\bf
vibrationally  unstable} edge  ($\zeta_{\rm c}=8.7$;  $\zeta=9$).  The
case of zero-turbulent pressure was considered. \label{f09}}
\end{figure}

Before  verifying  that  convection  is  the  driving  agent  for  the
completely  convective  shell,   we  briefly  describe  the  pulsation
characteristics  of the  models constructed  by  adopting $\gamma_{\rm
c}=1.0$ and  compare them with the previously  discussed limit cycles.
For comparative purposes, Fig.~\ref{f08}{\sl  c} shows the time series
of  a  ``Cepheid'' ($\gamma_{\rm  c}<0.5$),  and  of  a ``LPV''  model
($\gamma_{\rm  c}=1.0$). The  increase  both in  period and  amplitude
observed  in this  figure when  passing from  a ``Cepheid''-like  to a
``LPV''-like supports the previous working hypothesis. In this context
it  is  worth  mentioning  that ``Cepheid''-like  pulsators  show  the
well-known phase-lag  between the light  and the velocity  curve.  The
pulsation behavior of the ``LPV''-like  model needs to be discussed in
more detail. The data plotted in  the top and in the bottom panel show
a very small phase lag  between the light and the temperature changes.
This evidence  appears to be supported by  infrared spectroscopic data
(\citealt{HHR82,HSH84})  of pulsating  Asymptotic  Giant Branch  (AGB)
stars.  However, the maximum in the light curve takes place before the
minimum  in  the  velocity  curve.   This  finding  is  at  odds  with
observational  data  for Mira  and  Semiregular  Variables, since  the
minimum    velocity   is    not   correlated    with    light   maxima
(\citealt{HHR82,LKH00,LH02}).   Nevertheless,  the comparison  between
theory  and  observations  is  hampered  by  the  occurrence  of  long
secondary  periods  (\citealt{HLJF02,WOK04}),  and  indeed  in  a  few
objects the minimum  in the velocity curve takes  place later than the
maximum in the velocity  curve --- $\chi$~Oph, R~Leo (\citealt{HSH84})
and S~Lep  (\citealt{WOK04}).  In passing  we would also like  to draw
the attention  on the correlation between light  maxima and convective
velocity, since the maximum takes  place just before maximum light. We
are not aware of macroturbulent velocity measurements in LPVs, and new
observations would be very useful to constrain the plausibility of the
physical assumptions adopted in simple one-zone convective models.

For completeness, we illustrate in Fig.~\ref{f09} the time behavior of
a  model  located close  to  the  vibrational  instability edge  after
approaching to limit-cycle stability.  This example is generic for all
the  cases  with  or  without  the turbulent  pressure  close  to  the
vibrational-instability edge for  the completely convective shell. The
data  plotted  in this  figure  show  a  well-defined bump  along  the
decreasing  branch  of  the  light  curve.   This  bump  becomes  more
pronounced as the values of the parameters $\zeta$ and $\zeta_{\rm c}$
approach  the  vibrational-instability edge,  while  the  peak of  the
luminosity  becomes  a pulse-like  feature.   The  occurrence of  such
secondary features  is quite typical  along the light curves  of Miras
(\citealt{WOK04}).  Moreover, the occurrence of the luminosity maximum
appears  strongly  correlated with  the  variation  of the  convective
velocity ($U_{\rm c}$), while the bump  is in phase with the change of
the radial velocity ($V$).

Similar to the limit cycles for the weakly convective cases associated
to  the Classical  Cepheids,  it is  highly  speculative to  attribute
specific  values of  the  parameters $\zeta$  and  $\zeta_{\rm c}$  to
different  types  of  LPVs.   A  more detailed  investigation  of  the
parameter space  is mandatory to pinpoint the  pulsation properties of
completely convective one-zone models  that mimic an ``RGB''-like or a
``Mira''-like behavior.

\subsection{The $\gamma$-mechanism}

\begin{figure}[b]
\epsfig{f10.eps}
\caption{The   ($\zeta,\zeta_{\rm   c}$)-plane   for  the   completely
convective shell ($\gamma_{\rm c}=1.0$) and different values of $\eta$
and $\Gamma_1$  giving birth to  several behaviors: limit  cycle ({\sl
filled  circles}),   pulsational  stability  ({\sl   dots})  and  {\bf
vibrational   instability}   ({\sl   white   regions}).    {\sl   (a)}
$\eta=0.92$,  $\Gamma_1=1.1$; {\sl (b)}  $\eta=0.888$, $\Gamma_1=1.1$;
{\sl  (c)}  $\eta=0.888$,   $\Gamma_1=1.2$;  {\sl  (d)}  $\eta=0.888$,
$\Gamma_1=1.3$. Eq.~(\ref{eq:dsystem}) has been used. \label{f10}}
\end{figure}

As  a  natural  further  step   into  clarifying  the  origin  of  the
pulsationally unstable  cases for the completely  convective shell, we
have investigated  the role of the adiabatic  exponent, $\Gamma_1$, as
driving  agent. From the  mathematical perspective  of the  model, the
question resides  into establishing the relative effect  on the system
dynamics of  the parameter $\gamma_{\rm c}$,  on one hand,  and of the
parameter $\Gamma_1$, on the other hand, included in the definition of
the    parameters    $q   \equiv    m    \Gamma_1-2$   and    $d\equiv
m(\Gamma_1-2)/2$. The  case of completely  convective shell translates
for   this   one-zone   model    into   the   disappearance   of   the
$\kappa$-mechanism,  with  the  driving  being supplied  only  by  the
$\gamma$-mechanism.   To test whether  the pulsational  instability of
our  convective  models is  due  to  the  $\gamma$-mechanism or  to  a
convection-induced driving mechanism, we  studied the evolution of the
limit-cycle region in  the ($\zeta,\zeta_{\rm c}$)-plane as $\Gamma_1$
is  varied.   The  results  obtained   so  far  have  used  the  value
$\Gamma_1=1.1$ as the one  employed by \cite{S86}.  We conjecture that
if the obtained cases of  self-sustained oscillations are a product of
convection-induced  driving,  then  the  $\gamma$-mechanism  has  very
little, if any, influence  on their properties.  Fig.~\ref{f10}{\sl a}
and {\sl b} display two cases of different shell thickness concluding,
as  in  $\S3.1$,  that  a  thicker  shell implies  a  wider  range  of
parameters  leading  to  pulsational  instability. In  the  completely
convective  case, this  increase  causes a  shift  of the  limit-cycle
region to lower $\zeta_{\rm c}$.   The same shift occurs by increasing
the $\Gamma_1$ value at constant  shell thickness, or, in other words,
by    decreasing   the    efficiency    of   the    $\gamma$-mechanism
(Fig.~\ref{f10}{\sl b,c,d}).  This means that convection and turbulent
pressure are driving mechanisms for fully convective models, since the
region where  these models display a limit  cycle stability marginally
depends  on the adopted  $\Gamma_1$ value.  This finding  supports the
theoretical  predictions  by   \cite{XDC98a}  concerning  the  driving
provided by the coupling between pulsation and convection, but we also
find that turbulent pressure is a destabilizing mechanism instead of a
damping factor for pulsation.  However, current models assume that the
physical  properties of  the  driving  region can  be  described by  a
Kramers' opacity law and by a very crude equation of state. Therefore,
there is  no guarantee  that current models  properly account  for the
thermodynamical  and  dynamical properties  of  the different  partial
ionization zones in low density envelope regions.

\section{Conclusions}

In  this paper  we have  thoroughly analyzed  the  one-zone convective
model introduced  by \cite{S86}.  The model  appears in the  form of a
system of  4 ordinary differential  equations where the  variables are
the radius of the shell, the velocity, the pressure and the convective
velocity.   The  nonadiabaticity  resides  in the  pressure  which  is
considered as  a nonadiabatic  perturbation of the  reference pressure
and, thus, can be considered as a nonadiabatic variable of the system.
The  model accounts for  the self-excited  oscillations by  adopting a
value  for the adiabatic  exponent, $\Gamma_1$,  close to  unity.  The
main parameters  of the  system are the  fraction $\gamma_{\rm  c}$ of
convective luminosity  with respect to  the total luminosity,  and the
time-scales ratios,  $\zeta$ and $\zeta_{\rm c}$, which  are a measure
of  the dynamical  time scale  to the  thermal time  scale and  to the
convective time  scale, respectively.  We  have extended the  model by
considering explicitly the role of the turbulent pressure and the case
of completely convective shell.

The one-zone models constructed by \cite{S86} were integrated only for
a  few   dynamical  time  scales  and,  therefore,   the  approach  to
limit-cycle stability remained still  to be investigated.  To properly
identify the region  of the parameter space which  shows a limit-cycle
behavior  (pulsational  instability), we  have  selected a  parametric
space given by $\gamma_{\rm c}  \in [0,1)$, $\zeta$ and $\zeta_{\rm c}
\in [0,10]$.  Our parametric study revealed well-defined regions where
limit cycles exist, born through  the Hopf bifurcation.  For a typical
shell thickness of 11\%,  pulsational instability was encountered only
for  the radiation-dominated cases  ($\gamma_{\rm c}<0.5$),  while the
increase in the  shell thickness displaces this limit  to upper values
of $\gamma_{\rm c}$.  The existence of these upper values supports the
work  by  \cite{S86}  and  further  strengthens  the  role  played  by
convection as a damping mechanism.   Moreover, we found that the shell
thickness  is,  as expected,  positively  correlated  with the  period
distribution of  pulsationally unstable cases.   Interestingly enough,
models constructed by adopting thick and thin shells obey different PL
relations that  mimic the behavior  of fundamental and  first overtone
Cepheids.

Additionally, we have undertaken a parametric study to investigate the
influence of  the turbulent  pressure on the  overall dynamics  of the
system and implicitly on the existence of limit cycles.  The turbulent
pressure appears  to be a driving  mechanism as the  regions where the
models  approach a limit-cycle  stability are  more extended  than for
models that do  not account for the turbulent  pressure.  Moreover and
even more importantly,  we find that one-zone models  that account for
turbulent pressure do not show a spurious peak along the rising branch
of light curves.  The inclusion of  this term is also supported by the
occurrence  in the  ($\zeta,\zeta_{\rm c}$)-plane  of  a pulsationally
unstable  region  bounded  to  the  left  and  to  the  right  by  two
pulsationally stable regions, as expected from physical considerations
and hydrodynamical models. Moreover, the models located in this region
display a morphology of the  light curves and the velocity time series
quite similar to those  of nonlinear, hydrodynamical models and actual
Cepheids.

As  a  natural  continuation  of  the  work  by  \cite{S86},  we  have
investigated the  vibrational and pulsational  stability of completely
convective models.  Our predictions  disclose a well-defined region of
the  parameter space  where these  red models  approach  a limit-cycle
stability. The turbulent pressure appears to be a driving mechanism, a
finding  that  supports  the   results  original  brought  forward  by
\cite{OC86} and \cite{CO93} on the  basis of both linear and nonlinear
LPV models, but  at odds with predictions based  on linear, convective
models provided  by \cite{XDC98a}.   We computed several  sequences of
models by adopting  different values of the adiabatic  exponent and of
the shell  thickness.  We found  in agreement with  \cite{XDC98a} that
the  coupling between  pulsation and  convection is  the  key physical
mechanism  that  drives  the  pulsation instability  in  these  simple
structures.   We have  also  performed a  qualitative comparison  with
empirical properties  of LPVs.  We  have found some  similarities, but
only one feature partially agrees  with empirical data: the maximum in
the light  curve is  not correlated with  the minimum in  the velocity
curve.  However, the comparison with observations might be hampered by
the  occurrence  of long  secondary  periods.   We  are not  aware  of
detailed measurements  of macroturbulent velocity  along the pulsation
cycle  of LPVs, however  our models  suggest that  the maximum  in the
light  curve takes  place soon  after  the maximum  in the  convective
velocity.

Current one-zone  models account  for the coupling  between convection
and  pulsation  and  for  turbulent  pressure.   We  investigated  the
sensitivity to free parameters and to the physical assumptions adopted
to construct the  models. However, the treatment and  the inclusion of
these physical  ingredients rely on crude  physical approximations.  A
more detailed  investigation is required before we  can assess whether
our current  theoretical framework  might mimic the  complex pulsation
behavior  of  LPVs  and  this   implies  the  use  of  the  asymptotic
perturbation  theory to  compute  analytically the  properties of  the
limit cycle.

The pulsational behavior  disclosed by  these simple  models for
fully convective  models will be  addressed in a forthcoming  paper on
the basis of nonlinear,  hydrodynamical models (Munteanu et al.  2005,
in preparation).

\acknowledgments It  is a  pleasure to thank  P.  Wood for  a detailed
reading  of a  draft of  this manuscript  and for  several suggestions
concerning the comparison between  theory and observations.  This work
has been  partially supported by the  MCYT grant AYA2002-04094-C03-01,
by the European Union FEDER funds, and by the CIRIT.  One of us, G.B.,
acknowledges  for partial  support INAF  within the  framework  of the
project:  ``The  Large  Magellanic  Cloud  a  laboratory  for  stellar
astrophysics``,  and PRIN~2003  within the  framework of  the project:
``Continuity      and       Discontinuity      in      the      Galaxy
Formation``. A.M. acknowledges a  scholarship of UPC which allowed her
to conclude the present work.

\begin{appendix}

\section{The turbulent pressure}

In order to  include the turbulent pressure and  its associated energy
terms in the present one-zone  model, one must start from the equation
of momentum and energy conservation for the treatment of convection of
\cite{S82a}:

\begin{eqnarray}
&&\frac{D\langle\mbox{\boldmath$u$}\rangle}{Dt}~=~-\frac{1}{\rho}~
\nabla(P+P_{\rm t})-\nabla\Phi\label{eq:momenteq}\\
&&\frac{D}{Dt}~(E+E_{\rm t})+(P+P_{\rm t})~\frac{DV}{Dt}~=~
-\frac{1}{\rho}\nabla\cdot(F_{\rm r}+F_{\rm c}+F_{\rm t}).
\label{eq:energy}
\end{eqnarray}

\noindent  Here as  well  as throughout  our  work, we  have used  the
notations employed in the original investigations. In \cite{S82a}, any
quantity was written  as $x=\langle x \rangle +  x'$, where $\langle x
\rangle$ was  the mean  quantity and $x'$,  the fluctuating  part.  In
Eq.~(\ref{eq:energy}),   $D/Dt=(\partial   /\partial   t   +   \langle
\mbox{\boldmath$u$}  \rangle  \cdot \nabla)$  is  the Lagrangian  time
derivative with $u$ being the convective velocity, $E$ is the specific
internal energy, $V\equiv  1/\rho$ is the specific volume,  $P$ is the
thermodynamic pressure and

\begin{eqnarray}
&& E_{\rm t}\equiv\frac{1}{2}\langle(u')^2\rangle,\\
&& P_{\rm t}\equiv\rho\langle(u')^2\rangle,\\
&& F_{\rm c}\equiv\rho C_{\rm p}\langle(u'T')\rangle,\\
&& F_{\rm t}\equiv\frac{1}{2}\langle(\mbox{\boldmath$u'$})^2
\mbox{\boldmath$u$}
\rangle \label{eq:Ft}
\end{eqnarray}

\noindent   represent,  respectively,   the  convective   energy,  the
turbulent pressure,  the convective  and turbulent kinetic  fluxes, as
they are defined  in \cite{S82a}.  These equations must  be adapted to
the one-zone model.  The momentum equation translates into

\begin{equation}
\frac{d^2 X}{d\tau^2}=(1-\alpha_{\rm p})X^{-q}h+\alpha_{\rm p}X^{-c}
U_{\rm c}^2-X^{-2},
\label{eq:momentum}
\end{equation}

\noindent  where  Eq.~(\ref{eq:turbulence})  has  been  used  and  the
parameters are $q\equiv m\Gamma_1-2$, $c\equiv m-2$ and

\begin{equation}
\alpha_{\rm p}\equiv\frac{P_{{\rm t}_0}}{P_0+P_{{\rm t}_0}}
=\frac{X_0^{-m}U_{{\rm c}_0}^2}{X_0^{-m\Gamma_1} h_0+X_0^{-m} U_{{\rm
c}_0}^2}~.
\label{eq:ap}
\end{equation}

\noindent To ease the calculation,  the energy equation can be divided
into

\begin{eqnarray}
\frac{\partial(L_{\rm r}+L_{\rm c})}{\partial m}&=& \frac{\Gamma_1
P}{\rho^2(\Gamma_3-1)}~\frac{\partial\rho}{\partial t}-
\frac{1}{\rho(\Gamma_3-1)}~\frac{\partial P}{\partial t}
\label{eq:LrLc} \\
\frac{\partial L_{\rm t}}{\partial m}&=& \frac{P_{\rm
t}}{\rho^2}~\frac{\partial\rho}{\partial t} -\frac{\partial E_{\rm
t}}{\partial t} .
\label{eq:Lt}
\end{eqnarray}

\noindent  In  the  determination  of  the  convective  and  turbulent
luminosities, one  can use the  conservative choice of $L_{\rm  c}$ of
Eq.~(27) of  \cite{S86} and Eq.~(\ref{eq:Ft}).   The calculations lead
to an  expression for  $L_{\rm t}$ identical  to that of  $L_{\rm c}$,
that  is  $L_{\rm  t}=X^{-c}  U_{\rm c}^3$,  while  $E_{\rm  t}=U_{\rm
c}^2/2$.  Using  Eqs.~(\ref{eq:LrLc}--\ref{eq:Lt}),  one can  get  the
final  equation  of  energy   conservation  taking  into  account  the
turbulence:

\begin{eqnarray}
\frac{dh}{d\tau}=&-&m~\frac{\alpha_{\rm p}(\Gamma_3-1)}{1-\alpha_{\rm
p}}X^{2d-1}~\frac{dX}{d\tau}~U_{\rm c}^2~-~\frac{\rho_0(\Gamma_3-1)}
{P_0}~\zeta_{\rm c}~(X^d h^{1/2}U_{\rm c}-\nonumber\\
&-&X^{2d}U_{\rm c}^2)~-~\zeta X^{2d}~(\gamma_{\rm r} X^b h^{s+4}
+(1-\gamma_{\rm  r}) X^{-c} U_{\rm c}^3 -1) ,
\label{eq:energyeq}
\end{eqnarray}

\noindent where  $d \equiv m (\Gamma_1  -1) / 2$ and  $ \gamma_{\rm r}
\equiv  L_{{\rm  r}_0}  /  L_0$.    All  the  other  symbols  used  in
Eq.~(\ref{eq:energyeq})  have their usual  meaning.  The  equation for
the convective velocity coincides with the zero-turbulence case as the
approximation  made for  its recovery  uses  of the  temperature as  a
function of the thermodynamic pressure  only. In the case in which the
turbulent energy, $E_{\rm  t}$, is neglected in Eq.~(\ref{eq:energy}),
Eq.~(\ref{eq:energyeq}) becomes

\begin{eqnarray}
\frac{dh}{d\tau}=&-&m~\frac{\alpha_{\rm p}(\Gamma_3-1)}{1-\alpha_{\rm
p}}~X^{2d-1}~\frac{dX}{d\tau}~U_{\rm c}^2~-\nonumber\\
&-&~\zeta X^{2d}~(\gamma_{\rm r}X^b h^{s+4}+(1-\gamma_{\rm  r})X^{-c}
U_{\rm c}^3 -1).
\label{eq:energysimple}
\end{eqnarray}

Thus,  to a first  approximation, the  one-zone convective  model with
turbulent  pressure  is   described  by  Eqs.~(\ref{eq:momentum})  and
(\ref{eq:energysimple}),    while   for   the    convective   velocity
Eq.~(\ref{eq:dsystem}) remains valid.

\end{appendix}

redpajama_set_name: RedPajamaArXiv


text:
Home > 'What Spam is to a pig'
Now up on our homepage is Andrew J. Bacevich's commentary [1] on the Obama administration's 2015 National Security Strategy [2] (NSS), which was delivered to Congress on February 6. Bacevich isn't impressed:
Can there be a more thankless task than assembling such texts? Paying homage to clichés ancient and contemporary; nodding to every constituency, large or small, lest anyone feel slighted; claiming to know history's very purposes, while taking care to package such claims in bland (and therefore incontrovertible) generalities; inserting anticipatory rebuttals to the inevitable sniping of partisan critics: These number among the essential elements. Satisfying them necessarily results in a product that is to expository prose what Spam is to a pig: highly processed and short on nutrition.
Bacevich digs through the Spam to uncover the document's underlying logic, which is as evident in its omissions as in its "highly processed" rhetoric. He is especially hard on the NSS's flourishes of self-congratulation:
As measured by "might, technology, and geostrategic reach," U.S. military forces are "unrivaled in human history." More accurately: While the United States undoubtedly possesses enormous military power, it has yet to figure out how to translate armed might into politically purposeful outcomes achieved at reasonable cost. Time and again, vast expenditures of lives, treasure, and political capital yield results other than those intended.
The United States is "embracing constraints on our use of new technologies like drones." A bit of a stretch, that. More accurately: Through its shadowy campaign of targeted assassination, the Obama administration is erasing long-established conceptions of sovereignty while removing constraints on the use of force. Something of a novelty when inaugurated by George W. Bush, drone strikes have now become routine—about as newsworthy as traffic accidents. In effect, Washington claims the prerogative of converting lesser countries like Yemen or Somalia into free-fire zones. What these precedent-setting actions imply for the future is anybody's guess. One thing seems likely: As drones proliferate with astonishing speed, others are likely to avail themselves of the same prerogative.
Bacevich's response to the NSS has much in common with Jackson Lears's review [3] of Hillary Clinton's Hard Choices in the London Review of Books. (The review's title, "We came, we saw, he died," is Clinton's verbatim response to the news that Gaddafi had been killed.) Both Bacevich and Lears are skeptical of the neoliberal assumptions behind the Obama administration's foreign policy, assumptions that Obama and Clinton share. But, in Lears's view, Clinton's version of these assumptions is slightly less nuanced and slightly more hawkish than Obama's. Both Obama and Clinton lean heavily on the idea of American exceptionalism, which can be used to justify our double standards and plaster over the wounds we've inflicted—on others and ourselves—by waging foolish wars. Obama at least has the decency and sophistication to express reservations about this idea, even if these reservations have had too little effect on his policies. Clinton, by contrast, is an enthusiast. She, too, may have some of Obama's reservations; if so, she's keeping them to herself. Her book is full of rah-rah boilerplate about America's obligations as the world's midwife of Progress. In her capacity as Secretary of State, Clinton was eager to warn foreign leaders that they had better become more like us or prepare to be buried by history. As Lears writes:
Clinton's outlook epitomises the bipartisan wisdom of the Washington foreign policy establishment, which claims to offer a pragmatic centrist alternative to the extremes of right and left. Yet the centrists turn out to be at least as ideologically driven as the zealots they deplore. The core of their ideology is the belief that the US has a uniquely necessary role to play in leading the world towards an inevitably democratic (and implicitly capitalist) future. The process is foreordained but can be helped along through neoliberal policy choices. This muddle of determinism and freedom is a secular residue of providentialist teleology, held with as much religious fervour and as little regard for contrary evidence as other dogmatic faiths derided by self-styled liberal pragmatists.
Only a secular providentialist could ask what it means 'to be on the right side of history'. Clinton poses this question as if it were a guide to policy. The notion that history has a discernible direction, and that nations must align themselves with it, is a relic of the grand historical narratives of the 19th and 20th centuries. Such views are no longer held by serious historians but continue to animate the pundits and politicians in Washington. Clinton often appeals to teleology in Hard Choices: she repeatedly recalls a speech she gave in Qatar, just before the uprising in Tahrir Square, when she told the assembled Arab leaders that they must adopt political and economic reforms or their entire region would continue 'sinking into the sand' – the Ozymandian fate of autocrats in an irresistibly democratic age.
Source URL: https://www.commonwealmagazine.org/what-spam-pig
[1] https://www.commonwealmagazine.org/soft-thinking-hard-problems
[2] http://www.whitehouse.gov/sites/default/files/docs/2015_national_security_strategy.pdf
[3] http://www.lrb.co.uk/v37/n03/jackson-lears/we-came-we-saw-he-died
[6] http://www.facebook.com/sharer/sharer.php?u=https://www.commonwealmagazine.org/what-spam-pig
[7] https://twitter.com/intent/tweet?url=https://www.commonwealmagazine.org/what-spam-pig

redpajama_set_name: RedPajamaCommonCrawl


Where can I learn more about the issues addressed by the Teach-in?
Bowdoin library staff members have compiled an amazing list of resources for the Teach-in.
There you will find multiple links to information about energy; food & agriculture; gender; healthcare; income; policing & judicial system; race & ethnicity; social justice; and voting & democracy.
Teach in volunteers also assembled a Fact Sheet for the Teach-in Day. It is linked here.
Where can I say what I really think about the Teach-in?
The organizers are collecting feedback through a Google Survey here.
The Center for the Common Good is also sponsoring a debriefing on Friday, October 2, 12:30 pm, Daggett Lounge: Join the community for Next Steps: Learn, Connect, Move Forward, an opportunity to share knowledge gained from the teach in, reflect, explore your personal passions, and help determine next steps.
I want to Tweet the Teach-in! How do I get started?
#BowdoinTeachIn is ready for you. As part of our campus conversation, data experts from the Digital and Computational Media Studies Program will gather data from this hashtag to map our connections and excitement!
If you need help getting started in the world of hashtags, Chelsea Doyle, Bowdoin's Digital Community Manager has provided some basic instructions for you here.
I'm confused by the registration system. Do I have to register to attend events?
Registration is recommended for just 17 of the more than 35 events on October 1. These include smaller open classes designed just for today with small group discussion or creative activities and some larger open classes that are part of a semester course with limited space for additional participants.
There is no reservation for large forum events, scheduled in larger lecture spaces. Seating at these events will be based on room capacity. With so many parallel events, the organizers are confident that there will be opportunities for the whole campus to explore and enjoy the Teach-in.
Links to the registration tool are found on the detailed schedule and the open class registration page.
The Teach-in will be Thursday, October 1, 2015, from 10:00 a.m. – 5:00 p.m.
Why are we holding the Teach-in?
As members of an educational community, students, staff, and faculty at Bowdoin are committed to teaching and learning about the likely consequences of our current actions and about alternatives.
The dual threats of systemic inequity and climate destabilization are linked in both cause and effect. We all agree they are serious problems, yet meaningful and productive conversations about them can be very difficult.
Some faculty and staff have specific scholarly understandings and longstanding engagements with these topics. We eagerly welcome that expertise and many of us can learn from our resident experts. However, as educated people we are all capable of making useful sense of the world, of asking pointed questions, of making connections between apparently unrelated things, of knowing and admitting the limits of our competence, and of conducting civil and reasoned dialogue across deep divides.
The organizers of the Teach-in encourage you to contribute to the dialogue both by sharing your knowledge and by modeling respectful public conversation.
I'm a faculty member. What is 'participation' in the teach-in?
Encourage your students to attend as much of the event as possible.
Attend as much of the event yourself as possible. Sign up for events here (after September 15).
Incorporate material relevant to the teach-in into your Oct. 1 class.
Incorporate relevant material and move your class to one of the Teach-in time slots. See the schedule here Contact the organizers about room reservations promptly, so we can help find an appropriate space.
Consider redirecting your students' learning to the Teach-in. The schedule will be full of interesting interdisciplinary presentations with broad relevance.
Put together an open class, ideally team-taught, on some aspect of the teach-in topic. Here are examples. If you need ideas, we have them!
Participate in a panel discussion. Here are some that are already planned.
Plan a reading, short performance or presentation for the Arts Stage.
The wider ranging your politics and positions on the Teach-in topics, the better. We only ask that your contribution explicitly address the connections between racism, climate change and social justice.
I'm a student. How can I participate?
Attend as much of the event as possible. Sign up here (after September 15).
Spread the word to your friends, clubs or anyone else and/or help with postering and other advertising.
Staff a table with information about campus programs and Intersectional opportunities at the Expo.
Put together an open team-taught class (in consultation with the organizers), on some aspect of the Teach-in topics. Here are examples. If you need ideas, we have them!
Become a volunteer organizer and get involved in planning discussions by emailing the organizers.
Encourage your professors to be involved in the event by redirecting their classes to the Teach-in, incorporating relevant material in regular classes, putting together an open class or participating in a panel discussion.
I'm a staff member. How can I participate?
College operations will run as usual. Recognizing this, employees interested in attending will need to work with their supervisor to coordinate schedules and determine an appropriate amount of release time to ensure that offices can remain open.
All employees are encouraged to take advantage of the opportunities for teaching, learning and dialogue provided by the Teach-in. The more people engaging with the topics, the more valuable it will be for all participants.
Let the organizers know about your interest and relevant expertise. We are very interested in staff participation in panel discussions, directing open classes, or facilitating discussion.
If you are a supervisor, encourage participation by your staff as much as possible.
Put together an open team-taught class (in consultation with the organizers), on some aspect of the Teach-in topics. Here are some guidelines. If you need ideas, we have them!
Here is the current list of planned open classes and panels. Consider participating as a panelist or audience member, but also suggest themes of interest that we may have missed.
I want to design an Open Class or Panel Discussion. What should I consider?
Faculty, students and staff have met many times since last December. This summer, working groups have distilled the content of these meetings and chosen four overarching intersectional themes for the day: Power, Resources, Communities and Equity.
We are aiming for panels and open classes that will consider these themes from a variety of perspectives and disciplinary approaches. We intend to have each panel include a fair combination of presentations addressing the effects of climate change and issues of environmental justice side by side with research, artistic and cultural production about the effects of injustice based on race and racialization, gender and sexuality, and socioeconomic hierarchies. We acknowledge and welcome the specificity of your area of expertise, and don't expect you to touch on every element of this equation. However, efforts to think of intersections are encouraged at individual presentations, and expected from people co-teaching classes and chairing panels. The combination of local, national and transnational approaches to each of these matters should also be stressed.
I heard classes are cancelled. Do students have to go to regularly scheduled Thursday classes on October 1?
When the faculty voted in favor of a day "dedicated to to a campus-wide teach-in on racial and social justice, climate change, and their intersections" they did not vote to cancel classes across the board. Some Professors will be redirecting their classes to Teach-In events, others plan to incorporate Intersections themes in their scheduled classes and/or open their classes to Teach-In participants, and some may choose to meet their regular classes. Students should check with their Professors about class plans for the day.
What is the sponsoring group, IP3?
Intersections: People, Planet, and Power (IP3) is a group of Bowdoin community members committed to reframing the discussion surrounding injustice from a divided conversation to an integrated and holistic one. Across the globe, from Ferguson to the People's Climate March, from the water wars of Bolivia and Detroit to the fight against discrimination right here on campus, people are standing up to resist injustice. The accelerating climate disaster, which threatens to destabilize all aspects of civilization within the next century, intensifies these conflicts and creates a new urgency for collaboration and unified action.
IP3 aims to bring together traditionally separated social movements, such as climate justice and social justice, in order to facilitate a multi-faceted approach to understanding and addressing injustice on all levels. We will host campus events that will serve as platforms fostering inclusive community discussion and education, and work together to design and take actions promoting a just and sustainable future for all. We will also work with existing organizations on campus to highlight their intersections and support them in developing alliances around issues of justice. We are committed to improving humanity's relationship with both our natural and our social environments as an acknowledgement of our responsibility to the Common Good.


text:
Frame.io Makes its Debut on the iPad
Frame.io for iPad transforms and enhances the mobile workflow
(New York, NY--December 10, 2019) Frame.io, the world's leading video review and collaboration platform, announced today the arrival of Frame.io for iPad. Frame.io for iPad follows the success of the company's 2016 Apple Design Award-winning iOS app, and, like its smaller sibling, allows users to stay up to date with what's happening on set or in the edit suite while on the move. Frame.io for iPad is another step toward realizing a fully, globally distributed video workflow, giving creators and collaborators the ability to review or approve work in progress from anywhere in the world.
Apple's high quality iPad screen lets users view true-to-life color, while making the mobile experience more flexible and delightful. There are times when watching dailies, evaluating VFX shots, or getting a better sense of composition and color benefits from a larger display than a smartphone can offer - that's where Frame.io for iPad comes into play.
Learn more about Frame.io's fully connected suite of apps: http://www.frame.io/apps
Frame.io was designed to streamline the collaborative video review process, and the platform continues to evolve to meet ever-changing industry needs and the demands of its users. Frame.io for iPad comes equipped with features that elevate the mobile workflow, as well as enhance the functionality of the edit suite with powerful features including:
Split view for side-by-side app viewing
Split view lets users keep Frame.io in view on one side of the iPad screen while using apps like Final Draft, Slack, or FaceTime on the other. View scripts, chat with team members, track assets—and so much more.
Draw detailed annotations with Apple Pencil
Leave detailed drawings and annotations on work using Apple Pencil. Fine-tune stills or moving images, create illustrations, or work in Photoshop and import assets into Frame.io right on the iPad. Using the Apple Pencil makes it simple to leave notes as easily as writing on paper—except that it flows directly into the project.
Frame.io for iPad arrives just a few weeks after Frame.io announced a $50M round of Series C funding and the appointment of Michael Cioni as Global SVP of Innovation, all key factors as Frame.io plans for exciting developments to come in 2020.
About Frame.io
Frame.io is the world's leading cloud-based video collaboration platform, designed to streamline the video creation process by centralizing all media assets—and all feedback—in one secure place that's easily accessible from anywhere in the world. Frame.io integrates with most major professional video tools, acting as the connective tissue of the entire video ecosystem, no matter the scale. Conceived and designed by video creators, the UI is intuitive and simple for both highly technical professionals and less-technical clients to use with little (or no) training. The world's leading creators and innovators trust Frame.io every day to help power their video workflows, including Turner Broadcasting, Disney, NASA, Snapchat, BBC, BuzzFeed, TED, Adobe, Udemy, Google, Fox Sports, Media Monks, Ogilvy and VICE Media.
Frame.io's purpose is to allow all the contributors and participants in the video creation process to collaborate as if they're all in the same room, no matter their physical location, accelerating workflows and eliminating obstacles to creativity. From script or storyboard to dailies to delivery, Frame.io redefines the modern video workflow.
Frame.io is backed by industry heavyweights including Accel, FirstMark Capital, SignalFire, Shasta Ventures and Insight Partners. To learn more please visit http://frame.io. Watch: What is Frame.io?


Prelude: This figure here was a gift from my good buddy Caked-Up, who also said that I should be able to just "sneeze out" a review for this little guy, whatever that means exactly. So, thank you Caked-Up, but this review will not contain snot, just so you know.
Robot Mode: Brawn, the G1 toy, and Brawn, the cartoon character were a closer match than was the case for quite a few other G1 characters, but there were still noticeable differences. The Titans Return figure here is clearly cartoon Brawn, very faithfully depicting the small powerhouse we saw on the screens. The look is pretty much perfect and articulation is quite good for this figure thanks to ball joints.
The only downside for me is that Brawn doesn't come with a gun. Instead his sole accessory is a plate that he can attach to his arm as a kind of shield. With some imagination it can double as a sort of gun, I guess. If you don't want to use it, he can store it on his lower back. Bottom line, this robot mode here is Brawn, period. Very nicely done, no complaints except for the lack of a gun.
Alternate Mode: Like in days of yore Brawn transforms into a green jeep of undetermined model. The resulting vehicle looks pretty good and is as detailed as you can possibly expect at this size. The panel he used as a shield in robot mode now forms the rear part of the roof, but the sculpting is such that even without it the car doesn't look incomplete. So if you happen to lose this small extra part, it's not the end of the world.
Like many Legends-sized TFs from the Titan Return line Brawn features a cockpit where a Titan Master figure can ride inside the car (Titan Master Brawn could thus ride inside Legends Brawn if you wish). The car also has a 5mm hole on top to plug in weapons, once again highlighting the fact that Brawn doesn't have a gun, sadly. Overall, though, a good vehicle mode that is very Brawn, pure and simple. No complaints.
Remarks: Brawn was one of the more prominent members of the Autobot crew during season 1 and early season 2 of the original Transformers cartoon. Sure, he was a stereotype, the tough little guy who regularly beats up bigger and badder bots, but it worked. Brawn successfully tangled with lots of opponents much bigger than himself. In the three-part episode "Ultimate Doom", for example, he took out three nameless Seekers and Soundwave in a manner of seconds, then holding his own against Shockwave until help arrived in the form of Skyfire. Sadly Brawn was the first casualty of the infamous shuttle slaughter scene in the 1986 Transformers movie, dying from a single blast to the shoulder. How the mighty had fallen.
For all that he appeared in lots of episodes, toy-wise Brawn hasn't exactly been prominent. Apart from the original toy back in 1984 we haven't seen a whole lot of him. A Universe Legends figure in 2009 and some repaints of other figures to keep the name in use, that was pretty much it. But Titans Return gives us not just one, but two Brawns. This one here and a Titan Master that can become a Brawn-head for any other figure.
This particular figure here is Brawn as if he stepped right off the TV screen, really. I wish they had given him a gun, but that's pretty much the extent of my complaints. Otherwise a fun little figure of one of my favorite characters from the early days of the Transformers. Nicely done.


Weston professionals attended the Battelle Conference on Remediation of Chlorinated and Recalcitrant Compounds in Palm Springs in April 2018. Five Weston remediation professionals with various technical backgrounds participated at this major event to benchmark progress in addressing these compounds across the marketplace.
Our team comprised Fred Symmes (Technical Director – Engineering), Kathleen Soukup (Senior Project Manager), Ryan Wahl (Senior Project Scientist and Vapor Intrusion Technical Leader), Justin Warrington (Project Engineer) and Jason Shirer (Client Service Manager) attended to maintain and further Weston's over 60-year track record of providing cutting-edge solutions to solve complex environmental and infrastructure challenges. Hot topics included Vapor Intrusion evaluation methods, Poly- and Perfluoroalkyl Substances (PFAS) precursors, Electrokinetically-Based Remediation, Thermal Remediation technologies, and more described below.
– Multiple Lines Of Evidence (MLE) – USEPA presented on this topic and communicated that regulatory agencies continue to change and push MLE for vapor intrusion (VI) evaluation to avoid false negatives/positives. However, when using MLE, no single investigation result is considered definitive. According to USEPA, data collection should be based off different factors identified that influence the preferential pathway to streamline efforts for efficiency. Multiple datasets and investigation results are evaluated collectively to determine whether there is VI pathway or not. Acquiring data from MLE forces investigators to cross check and confirm their findings with other scientific methods.
– Value Of Building Differential Pressure Measurement – The pressure difference between a building and the subsurface has a major impact in controlling the direction of airflow through the building foundation. A small positive pressure can effectively suppress VI just as a small negative pressure can initiate VI. This is why it is critical to measure building differential pressure during indoor air sampling events. When the building differential pressure is positive, there is a good chance that volatile organic compounds (VOCs) detected in indoor air samples are not from the subsurface. Understanding building differential pressure will serve as a solid line of evidence. Building differential pressure in many cases can be manipulated by using the heating ventilation and air conditioning system. A controlled negative differential pressure environment is one way to identify near worst-case scenario conditions for VI of VOCs to indoor air.
Weston has Communities of Practice that connect employees across the company, so we can grow our technical excellence by sharing best practices and resources. Employees gain exposure from projects throughout the company and share knowledge with others working through similar technical challenges. These Communities of Practice provide the platform of communication needed to deliver the Vapor Intrusion takeaways described above.
– While USEPA has not set an MCL for any PFAS at this time, they have set a Lifetime Health Advisory (LHA) of 70 nanograms per liters for (Perfluorooctanoic Acid) PFOA and (Perfluorooctyl Sulfonate) PFOS, individually or combined. However, the total PFAS suspect list includes some 1,500 compounds and most sites have 10-100 PFAS compounds – not just PFOA and PFOS. There are many precursor compounds that can be transformed into PFAS. One presenter triggered a series of questions. Should we be looking at precursors even though they are not regulated? Should we look at those that can turn into PFOA and PFOS? How can we evaluate what conditions (subsurface or applied treatment technologies) can transform precursors into "undesirable" PFAS. An example was used by the presenter. Oxidation processes in wastewater treatment plants could be inadvertently transforming precursors into PFAS. It was presented that testing the influent and effluent water could be important in some situations. While running tests like a Total Oxidizable Precursor assay may provide additional data, it was not clear what the results mean, especially those compounds other than PFOA and PFOS? Advances in lab technologies allow us to see more precursors and PFAS compounds, but there is a lag with the toxicology and risk assessment of PFAS.
Weston monitors closely the progress being made in addressing PFAS. Weston works closely with the laboratories to determine the best analytical method and compound list for sites based on their geographic location and known contaminants of concern. As a recognized leader in addressing PFAS in the environment we have established strong working relationships with clients, regulators, stakeholders, and laboratories making us a trusted provider when evaluating PFAS at sites.
– EK-based remediation involves the application of low density direct current (DC) to the subsurface. An electric field is created by inserting electrodes in the contaminated site and passing low density DC making the contaminant particles mobile in the soil media. The contaminants get transported towards the electrodes, and they are pumped out. EK remediation is particularly useful in soils with low permeability (clay or till) and heterogeneous environments (mixtures of sand and clay) where other common remediation technologies may only partially treat the site. EK remediation can also be integrated with other technologies. For example, a routine In-Situ Chemical Oxidation (ISCO) application in a heterogeneous subsurface of sand with clay layers may quickly reduce contaminants within the sand layers, only to leave behind contaminants in the clay that will leach back into the groundwater. An electric field can be applied to move the oxidant into the clay layer for more successful treatment.
Weston is well positioned to successfully implement EK-based remediation in the field. Our project team of scientists and engineers have been highly successful with in situ remediation, including ISCO treatments and thermal remediation techniques. Using EK to move contaminants or enhance amendment delivery to complete treatment of low permeability areas could be the finishing step at complex sites, and Weston has the resources to make it happen.
– Making The Right Choice Between Remediation Options – Thermal remediation is a proven supplementary technology that can be added to a treatment train to further remediate a site. Thermal can enhance bioremediation, in-situ chemical oxidation and some pump and treat applications. Although it can be more costly than other technologies, there is a certainty to its effectiveness for destruction of VOCs and non-aqueous phase liquid (NAPL) sources. There are primarily three types of thermal remediation used today including conductive heating, steam, and electrical resistance heating (ERH). A comprehensive Conceptual Site Model will determine the most effective, cost efficient technology: a type of thermal remediation; a non-thermal remediation; or combination of multiple technologies in a treatment train.
– O&M Costs Are An Important Consideration In Choosing System – 90% of volatile contaminants are contained in vapor phase while 10% are liquid phase. Supplementing an existing soil vapor extraction (SVE) system with ERH and steam will volatilize and mobilize contaminants that may not have been effectively removed using the existing system. When choosing a technology, consider operations, and specifically, maintenance costs on running the system instead of the upfront cost. Long lead times on expensive components or difficult to repair equipment can quickly become more expensive than the upfront cost of a simpler but more costly solution.
– Bench & Pilot Scale Studies: Worthwhile Tools – Bench scale studies will provide breakdown products of contaminants at various temperatures allowing a contractor to dial in a temperature for which to run a pilot scale operation. A pilot scale study will provide information as to the proper well spacing for a larger scale thermal remediation. Evidence continues to support bioremediation being enhanced by an increase in soil temperature. Coupled with vapor and liquid extraction and treatment with granular activated carbon, thermal enhanced bioremediation remains an effective means of removing VOCs from a contaminated site.
Weston has been successful in developing solutions and working with others to remediate complex sites utilizing ISCO, pump and treat systems, bioremediation, SVE systems, and other technologies either as standalone or part of integrated treatment trains. Weston has demonstrated capability in developing bench and pilot scale studies to provide an authentic model to determine whether or not a component of a treatment train solves our clients' remediation needs. Weston is well positioned to evaluate a given site and team with a thermal contractor to provide thermal remediation as another means to remediate complex sites where a single technology is insufficient to meet clean-up criteria.


Several legal professionals gave the Observer their views on the judge races.
Updated Aug. 23 to correct information about Steven Burk. He practices in DeLand, not Deltona. Also, he has not refused drug tests in the past; rather, he has not even been asked to submit to drug tests. He revealed to the Volusia Bar his marijuana use in the spirit of full disclosure.
Of all the names on the ballot in this Primary, the candidates for judge might make the biggest impact in our community if elected. And yet, they are the candidates about whom voters often know the least. To help our readers, the Observer consulted with several legal professionals about the candidates so that we could offer our own recommendations.
Incumbent Dawn Fields received the lowest ratings of the eight Volusia County judges in a survey of Volusia Bar attorneys. That is concerning. Is it enough to vote her out of office?
The challenger is Steven Burk, a DeLand attorney who has argued 10 jury trials in the past 10 years. That's not a lot. Most of the legal professionals consulted by the Observer agreed that jury trial experience is an important test of a potential judge.
Moreover, Burk revealed in his judicial election questionnaire, submitted to the Volusia Bar, that he had used marijuana to deal with pain after surgeries. While that may not bother many voters, it does raise an important question: Should an attorney who willingly justifies breaking the law be entrusted with the role of upholding and respecting the law? We say no.
Of the three candidates running for this open seat, Sebrina Slack and Ryan Will both earned high marks from the legal professionals consulted. Both would make good judges.


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