3,089 research outputs found
Extending canonical Monte Carlo methods II
Previously, we have presented a methodology to extend canonical Monte Carlo
methods inspired on a suitable extension of the canonical fluctuation relation
compatible with negative heat capacities .
Now, we improve this methodology by introducing a better treatment of finite
size effects affecting the precision of a direct determination of the
microcanonical caloric curve , as well as
a better implementation of MC schemes. We shall show that despite the
modifications considered, the extended canonical MC methods possibility an
impressive overcome of the so-called \textit{super-critical slowing down}
observed close to the region of a temperature driven first-order phase
transition. In this case, the dependence of the decorrelation time with
the system size is reduced from an exponential growth to a weak power-law
behavior , which is shown in the particular case of
the 2D seven-state Potts model where the exponent .Comment: Version submitted to JSTA
Equilibrium fluctuation theorems compatible with anomalous response
Previously, we have derived a generalization of the canonical fluctuation
relation between heat capacity and energy fluctuations , which is able to describe the existence of macrostates with negative
heat capacities . In this work, we extend our previous results for an
equilibrium situation with several control parameters to account for the
existence of states with anomalous values in other response functions. Our
analysis leads to the derivation of three different equilibrium fluctuation
theorems: the \textit{fundamental and the complementary fluctuation theorems},
which represent the generalization of two fluctuation identities already
obtained in previous works, and the \textit{associated fluctuation theorem}, a
result that has no counterpart in the framework of Boltzmann-Gibbs
distributions. These results are applied to study the anomalous susceptibility
of a ferromagnetic system, in particular, the case of 2D Ising model.Comment: Extended version of the paper published in JSTA
IDENTIFYING RISK FACTORS ASSOCIATED WITH CARDIOVASCULAR DISEASE RISK IN LESBIANS
Cardiovascular disease (CVD) is the leading cause of female deaths in the United States (1). While women, in general, are at risk for CVD, current research indicates that sexual minority women (i.e. lesbians and bisexual women [SMW]) may be at greater risk for CVD than heterosexual women. This heightened risk potentially stems from an increased prevalence of traditional CVD risk factors in SMW, creating health disparities between SMW and their heterosexual counterparts (2). Further research into this high-risk population is needed, in order to minimize these disparities.
The purpose of this study was to establish differences in the prevalence of modifiable CVD risk factors among lesbians and heterosexual women and compare their risks for coronary heart disease. This study also sought to identify best practices for obtaining higher rates of sexual orientation (SO) disclosure in questionnaire settings.
Data collected through the Houston HeartReach Registry from 2013-2017 was used for the creation of a lesbian cohort. A cohort of heterosexual women was aggregated from the 2015-2016 National Health and Nutrition Examination Surveys. Both cohorts contained information on sociodemographic data and traditional CVD risk factors. A 10-year risk score for developing coronary heart disease was calculated for all women and compared by SO. Differences in the prevalence of traditional cardiovascular disease risk factors were also examined by SO.
Lesbians were more likely to be current or ever smokers, to be depressed or have hypertension, to have an education level past high school, and to earn less income than their heterosexual counterparts. On average, lesbian participants had a 0.60% (95% confidence interval [CI] = -0.25%, 1.44%) greater chance of developing coronary heart disease over the next ten years than their heterosexual counterparts, but this difference was not significant (p = 0.167). Neither income, glucose, family history of cardiovascular disease, or depression accounted for this difference, but education and body mass index (BMI) partially intensified this difference. Lesbians have an increased prevalence of various CVD risk factors compared to their heterosexual counterparts, but future research is needed to fully understand the causes of these increased risk factors and their effect on CVD risk. With lesbians comprising a uniquely high-risk subgroup for CVD, attention must be paid to their CVD risk profile. The identification of CVD risk factors unique to and/or heightened in lesbians will allow for more targeted interventions that can lead to a reduction in disparities of CVD risk for lesbians and reduce the morbidity of CVD in women overall. A literature review of PubMed, conducted as a part of this thesis, indicates that future epidemiologic studies working with SMW should create an LGBT-welcoming environment, use accepting and inclusive language, and demonstrate a knowledge of lesbian-specific health at recruiting events and in questionnaires, in order to facilitate SO disclosure and increase the likelihood of successful recruitment
Understanding critical behavior in the framework of the extended equilibrium fluctuation theorem
Recently (arXiv:0910.2870), we have derived a fluctuation theorem for systems
in thermodynamic equilibrium compatible with anomalous response functions, e.g.
the existence of states with \textit{negative heat capacities} . In this
work, we show that the present approach of the fluctuation theory introduces
new insights in the understanding of \textit{critical phenomena}. Specifically,
the new theorem predicts that the environmental influence can radically affect
critical behavior of systems, e.g. to provoke a suppression of the divergence
of correlation length and some of its associated phenomena as spontaneous
symmetry breaking. Our analysis reveals that while response functions and state
equations are \emph{intrinsic properties} for a given system, critical
behaviors are always \emph{relative phenomena}, that is, their existence
crucially depend on the underlying environmental influence
Geometrical aspects and connections of the energy-temperature fluctuation relation
Recently, we have derived a generalization of the known canonical fluctuation
relation between heat capacity and
energy fluctuations, which can account for the existence of macrostates with
negative heat capacities . In this work, we presented a panoramic overview
of direct implications and connections of this fluctuation theorem with other
developments of statistical mechanics, such as the extension of canonical Monte
Carlo methods, the geometric formulations of fluctuation theory and the
relevance of a geometric extension of the Gibbs canonical ensemble that has
been recently proposed in the literature.Comment: Version accepted for publication in J. Phys. A: Math and The
Photo-ionization of planetary winds: case study HD209458b
Close-in hot Jupiters are exposed to a tremendous photon flux that ionizes
the neutral escaping material from the planet leaving an observable imprint
that makes them an interesting laboratory for testing theoretical models. In
this work we present 3D hydrodynamic simulations with radiation transfer
calculations of a close-in exoplanet in a blow-off state. We calculate the
Ly- absorption and compare it with observations of HD 209458b an
previous simplified model results.Our results show that the hydrodynamic
interaction together with a proper calculation of the photoionization proccess
are able to reproduce the main features of the observed Ly- absorption,
in particular at the blue-shifted wings of the line. We found that the ionizing
stellar flux produce an almost linear effect on the amount of absorption in the
wake. Varying the planetary mass loss rate and the radiation flux, we were able
to reproduce the absorption observed at .Comment: 9 pages, 6 figure
A unified framework based on the binding polynomial for characterizing biological systems by isothermal titration calorimetry
Isothermal titration calorimetry (ITC) has become the gold-standard technique for studying binding processes due to its high precision and sensitivity, as well as its capability for the simultaneous determination of the association equilibrium constant, the binding enthalpy and the binding stoichiometry. The current widespread use of ITC for biological systems has been facilitated by technical advances and the availability of commercial calorimeters. However, the complexity of data analysis for non-standard models is one of the most significant drawbacks in ITC. Many models for studying macromolecular interactions can be found in the literature, but it looks like each biological system requires specific modeling and data analysis approaches. The aim of this article is to solve this lack of unity and provide a unified methodological framework for studying binding interactions by ITC that can be applied to any experimental system. The apparent complexity of this methodology, based on the binding polynomial, is overcome by its easy generalization to complex systems
Fluctuation geometry: A counterpart approach of inference geometry
Starting from an axiomatic perspective, \emph{fluctuation geometry} is
developed as a counterpart approach of inference geometry. This approach is
inspired on the existence of a notable analogy between the general theorems of
\emph{inference theory} and the the \emph{general fluctuation theorems}
associated with a parametric family of distribution functions
, which describes the behavior of a set of
\emph{continuous stochastic variables} driven by a set of control parameters
. In this approach, statistical properties are rephrased as purely
geometric notions derived from the \emph{Riemannian structure} on the manifold
of stochastic variables . Consequently, this theory
arises as an alternative framework for applying the powerful methods of
differential geometry for the statistical analysis. Fluctuation geometry has
direct implications on statistics and physics. This geometric approach inspires
a Riemannian reformulation of Einstein fluctuation theory as well as a
geometric redefinition of the information entropy for a continuous
distribution.Comment: Version submitted to J. Phys. A. 26 pages + 2 eps figure
Constraining the History of the Sagittarius Dwarf Galaxy Using Observations of its Tidal Debris
We present a comparison of semi-analytic models of the phase-space structure
of tidal debris with observations of stars associated with the Sagittarius
dwarf galaxy (Sgr). We find that many features in the data can be explained by
these models. The properties of stars 10-15 degrees away from the center of Sgr
--- in particular, the orientation of material perpendicular to Sgr's orbit
(c.f. Alard 1996) and the kink in the velocity gradient (Ibata et al 1997) ---
are consistent with those expected for unbound material stripped during the
most recent pericentric passage ~50 Myrs ago. The break in the slope of the
surface density seen by Mateo, Olszewski & Morrison (1998) at ~ b=-35 can be
understood as marking the end of this material. However, the detections beyond
this point are unlikely to represent debris in a trailing streamer, torn from
Sgr during the immediately preceding passage ~0.7 Gyrs ago, but are more
plausibly explained by a leading streamer of material that was lost more that 1
Gyr ago and has wrapped all the way around the Galaxy. The observations
reported in Majewski et al (1999) also support this hypothesis. We determine
debris models with these properties on orbits that are consistent with the
currently known positions and velocities of Sgr in Galactic potentials with
halo components that have circular velocities v_circ=140-200 km/s. The best
match to the data is obtained in models where Sgr currently has a mass of ~10^9
M_sun and has orbited the Galaxy for at least the last 1 Gyr, during which time
it has reduced its mass by a factor of 2-3, or luminosity by an amount
equivalent to ~10% of the total luminosity of the Galactic halo. These numbers
suggest that Sgr is rapidly disrupting and unlikely to survive beyond a few
more pericentric passages.Comment: 19 pages, 5 figures, accepted to Astronomical Journa
Disaster Resilience Education and Research Roadmap for Europe 2030 : ANDROID Report
A disaster resilience education and research roadmap for Europe 2030 has been launched. This roadmap represents an important output of the ANDROID disaster resilience network, bringing together existing literature in the field, as well as the results of various analysis and study projects undertaken by project partners.The roadmap sets out five key challenges and opportunities in moving from 2015 to 2030 and aimed at addressing the challenges of the recently announced Sendai Framework for Disaster Risk Reduction 2015-2030. This roadmap was developed as part of the ANDROID Disaster Resilience Network, led by Professor Richard Haigh of the Global Disaster Resilience Centre (www.hud.ac.uk/gdrc ) at the School of Art, Design and Architecture at the University of Huddersfield, UK. The ANDROID consortium of applied, human, social and natural scientists, supported by international organisations and a stakeholder board, worked together to map the field in disaster resilience education, pool their results and findings, develop interdisciplinary explanations, develop capacity, move forward innovative education agendas, discuss methods, and inform policy development. Further information on ANDROID Disaster Resilience network is available at: http://www.disaster-resilience.netAn ANDROID Disaster Resilience Network ReportANDROI
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