Post‐traumatic stress disorder and birthweight: methodological challenges

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/89463/1/j.1471-0528.2011.03200.x.pd

Long-range correlations in non-equilibrium systems: Lattice gas automaton approach

In systems removed from equilibrium, intrinsic microscopic fluctuations become correlated over distances comparable to the characteristic macroscopic length over which the external constraint is exerted. In order to investigate this phenomenon, we construct a microscopic model with simple stochastic dynamics using lattice gas automaton rules that satisfy local detailed balance. Because of the simplicity of the automaton dynamics, analytical theory can be developed to describe the space and time evolution of the density fluctuations. The exact equations for the pair correlations are solved explicitly in the hydrodynamic limit. In this limit, we rigorously derive the results obtained phenomenologically by fluctuating hydrodynamics. In particular, the spatial algebraic decay of the equal-time fluctuation correlations predicted by this theory is found to be in excellent agreement with the results of our lattice gas automaton simulations for two different types of boundary conditions. Long-range correlations of the type described here appear generically in dynamical systems that exhibit large scale anisotropy and lack detailed balance.Comment: 23 pages, RevTeX; to appear in Phys. Rev.

Hydrodynamic fluctuations in the Kolmogorov flow: Linear regime

The Landau-Lifshitz fluctuating hydrodynamics is used to study the statistical properties of the linearized Kolmogorov flow. The relative simplicity of this flow allows a detailed analysis of the fluctuation spectrum from near equilibrium regime up to the vicinity of the first convective instability threshold. It is shown that in the long time limit the flow behaves as an incompressible fluid, regardless of the value of the Reynolds number. This is not the case for the short time behavior where the incompressibility assumption leads in general to a wrong form of the static correlation functions, except near the instability threshold. The theoretical predictions are confirmed by numerical simulations of the full nonlinear fluctuating hydrodynamic equations.Comment: 20 pages, 4 figure

Multiple-Point and Multiple-Time Correlations Functions in a Hard-Sphere Fluid

A recent mode coupling theory of higher-order correlation functions is tested on a simple hard-sphere fluid system at intermediate densities. Multi-point and multi-time correlation functions of the densities of conserved variables are calculated in the hydrodynamic limit and compared to results obtained from event-based molecular dynamics simulations. It is demonstrated that the mode coupling theory results are in excellent agreement with the simulation results provided that dissipative couplings are included in the vertices appearing in the theory. In contrast, simplified mode coupling theories in which the densities obey Gaussian statistics neglect important contributions to both the multi-point and multi-time correlation functions on all time scales.Comment: Second one in a sequence of two (in the first, the formalism was developed). 12 pages REVTeX. 5 figures (eps). Submitted to Phys.Rev.

A model for the atomic-scale structure of a dense, nonequilibrium fluid: the homogeneous cooling state of granular fluids

It is shown that the equilibrium Generalized Mean Spherical Model of fluid structure may be extended to nonequilibrium states with equation of state information used in equilibrium replaced by an exact condition on the two-body distribution function. The model is applied to the homogeneous cooling state of granular fluids and upon comparison to molecular dynamics simulations is found to provide an accurate picture of the pair distribution function.Comment: 29 pages, 11 figures Revision corrects formatting of the figure

Scaling, renormalization and statistical conservation laws in the Kraichnan model of turbulent advection

We present a systematic way to compute the scaling exponents of the structure functions of the Kraichnan model of turbulent advection in a series of powers of $\xi$, adimensional coupling constant measuring the degree of roughness of the advecting velocity field. We also investigate the relation between standard and renormalization group improved perturbation theory. The aim is to shed light on the relation between renormalization group methods and the statistical conservation laws of the Kraichnan model, also known as zero modes.Comment: Latex (11pt) 43 pages, 22 figures (Feynman diagrams). The reader interested in the technical details of the calculations presented in the paper may want to visit: http://www.math.helsinki.fi/mathphys/paolo_files/passive_scalar/passcal.htm

Distribution of cytochrome P450 2C, 2E1, 3A4, and 3A5 in human colon mucosa

BACKGROUND: Despite the fact that the alimentary tract is part of the body's first line of defense against orally ingested xenobiotica, little is known about the distribution and expression of cytochrome P450 (CYP) enzymes in human colon. Therefore, expression and protein levels of four representative CYPs (CYP2C(8), CYP2E1, CYP3A4, and CYP3A5) were determined in human colon mucosa biopsies obtained from ascending, descending and sigmoid colon. METHODS: Expression of CYP2C, CYP2E1, CYP3A4, and CYP3A5 mRNA in colon mucosa was determined by RT-PCR. Protein concentration of CYPs was determined using Western blot methods. RESULTS: Extensive interindividual variability was found for the expression of most of the genes. However, expression of CYP2C mRNA levels were significantly higher in the ascending colon than in the sigmoid colon. In contrast, mRNA levels of CYP2E1 and CYP3A5 were significantly lower in the ascending colon in comparison to the descending and sigmoid colon. In sigmoid colon protein levels of CYP2C8 were significantly higher by ~73% than in the descending colon. In contrast, protein concentration of CYP2E1 was significantly lower by ~81% in the sigmoid colon in comparison to the descending colon. CONCLUSION: The current data suggest that the expression of CYP2C, CYP2E1, and CYP3A5 varies in different parts of the colon

Evidence of the validity and accuracy of the Brazilian social attitude of students scale towards politics

Objetivou-se apresentar as evidências de validade e confiabilidade de uma escala brasileira para medir atitudes políticas de estudantes brasileiros de nível superior ante seus comportamentos políticos. O estudo teve uma amostra de abrangência nacional (N = 445), com estudantes brasileiros oriundos de distintos estados. Os resultados indicaram uma estrutura empírica sustentável (teste de Kaiser-Meyer-Olkin - KMO = 0,81), com indicadores psicométricos considerados adequados à mensuração das atitudes políticas. Três fatores empíricos foram identificados: grau de conhecimento sobre política (15 itens, cargas fatoriais entre 0,31 e 0,82, alfa = 0,82, eigenvalue = 5,07 e variância explicada = 18,78 %), afetos relativos à política (7 itens, cargas fatoriais entre 0,41 e 0,58, alfa = 0,72, eigenvalue = 3,17 e variância explicada = 11,73 %) e intenções de comportamento político (2 itens, cargas fatoriais entre 0,70 e 0,72, alfa = 0,80, eigenvalue = 1,8 e variância explicada = 6,8 %). Conclui-se que os resultados fortalecem a estrutura fatorial original da escala e mostram sua utilidade para a identificação de atitudes sociais ante comportamentos políticos.El objetivo de la presente investigación fue presentar las pruebas de confiabilidad y validez de una escala brasileña para medir las actitudes políticas de los estudiantes universitarios brasileños ante su comportamiento político. El estudio contó con una muestra nacional (N = 445) de estudiantes brasileños de diferentes Estados. Los resultados indicaron una estructura empírica sustentable (KMO = .81), con indicadores psicométricos que se consideran adecuados para la medición de las actitudes políticas. Específicamente, se identificaron tres factores empíricos: nivel de conocimiento sobre la política (15 ítems, cargas factoriales entre .31 y .82, alfa = .82, eigenvalue = 5.07 y varianza explicada = 18.78 %), sentimientos acerca de la política (7 ítems, factoriales de .41 y .58, alfa = .72, eigenvalue = 3.17 y varianza explicada = 11.73 °/o) e intenciones del comportamiento político (2 ítems, factoriales de .70 y .72, alfa = .80, eigenvalue = 1.8 y varianza explicada = 6.8 %). Se llegó a la conclusión de que los resultados apoyan la estructura factorial original de la escala y muestran su utilidad en la identificación de las actitudes sociales ante la conducta política.The objective of this study was to present the validity and reliability evidences of a Brazilian scale to measure the political attitudes of Brazilian higher education students regarding their political behavior. The study had a nationwide sample (N = 445), with Brazilian students from different states. The results indicated a sustainable empirical structure (KMO = 0.81), with psychometric indicators considered adequate to the measurement of political attitudes. Three empirical factors were identified: degree of political knowledge (15 items, factorial loads between 0.31 and 0.82, alpha = 0.82, eigenvalue = 5.07 and explained variance = 18.78%), feelings about politics (7 items, factorial loads between 0.41 and 0.58, alpha = 0.72, eigenvalue = 3.17 and explained variance = 11.73%) and intentions of political behavior (2 items, factorial loads between 0, 70 and 0.72, alpha = 0.80, eigenvalue = 1.8 and explained variance = 6.8%). It is concluded that the results strengthen the original factorial structure of the scale and show its utility for the identification of social attitudes regarding political behaviors

Application of Key Events Analysis to Chemical Carcinogens and Noncarcinogens

The existence of thresholds for toxicants is a matter of debate in chemical risk assessment and regulation. Current risk assessment methods are based on the assumption that, in the absence of sufficient data, carcinogenesis does not have a threshold, while noncarcinogenic endpoints are assumed to be thresholded. Advances in our fundamental understanding of the events that underlie toxicity are providing opportunities to address these assumptions about thresholds. A key events dose-response analytic framework was used to evaluate three aspects of toxicity. The first section illustrates how a fundamental understanding of the mode of action for the hepatic toxicity and the hepatocarcinogenicity of chloroform in rodents can replace the assumption of low-dose linearity. The second section describes how advances in our understanding of the molecular aspects of carcinogenesis allow us to consider the critical steps in genotoxic carcinogenesis in a key events framework. The third section deals with the case of endocrine disrupters, where the most significant question regarding thresholds is the possible additivity to an endogenous background of hormonal activity. Each of the examples suggests that current assumptions about thresholds can be refined. Understanding inter-individual variability in the events involved in toxicological effects may enable a true population threshold(s) to be identified

Perception of general and oral health in White and African American adults: assessing the effect of neighborhood socioeconomic conditions 1

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74693/1/j.1600-0528.2004.00177.x.pd