Trends in Americans food-related time use: 1975-2006

Journal ArticleObjective: To describe how the time spent in food-related activities by Americans has changed over the past 30 years. Design: Data from four national time diary surveys, spanning 1975-2006, are used to construct estimates of trends in American adults' time spent in food-related activities. Multivariate Tobits assess how food-related activities have changed over time controlling for sociodemographic and economic covariates. Results: Both bivariate and multivariate estimates reveal that between 1975 and 2006, American women's time spent in food preparation declined substantially, whereas the time spent in these activities by American men changed very little. On the contrary, grocery shopping time increased modestly for both men and women. The primary eating time (i.e. time when eating/drinking was the respondent's main focus) declined for both men and women over this historical period, and the composition of this time changed with less primary eating time being done alone. Concurrently, secondary eating time (i.e. time when something else had the respondent's primary attention, but eating/drinking simultaneously occurred) rose precipitously for both women and men between 1975 and 1998. Conclusions: The total time spent in eating (i.e. primary plus secondary eating time) has increased over the past 30 years, and the composition of this time has shifted from situations in which energy intake can be easily monitored to those in which energy intake may be more difficult to gauge. Less time is also being spent in food preparation and clean-up activities. Future research should explore possible links between these trends and Americans' growing obesity risk

Time use choices and healthy body weight: A multivariate analysis of data from the American Time use Survey

<p>Abstract</p> <p>Background</p> <p>We examine the relationship between time use choices and healthy body weight as measured by survey respondents' body mass index (BMI). Using data from the 2006 and 2007 American Time Use Surveys, we expand upon earlier research by including more detailed measures of time spent eating as well as measures of physical activity time and sedentary time. We also estimate three alternative models that relate time use to BMI.</p> <p>Results</p> <p>Our results suggest that time use and BMI are simultaneously determined. The preferred empirical model reveals evidence of an inverse relationship between time spent eating and BMI for women and men. In contrast, time spent drinking beverages while simultaneously doing other things and time spent watching television/videos are positively linked to BMI. For women only, time spent in food preparation and clean-up is inversely related to BMI while for men only, time spent sleeping is inversely related to BMI. Models that include grocery prices, opportunity costs of time, and nonwage income reveal that as these economic variables increase, BMI declines.</p> <p>Conclusions</p> <p>In this large, nationally representative data set, our analyses that correct for time use endogeneity reveal that the Americans' time use decisions have implications for their BMI. The analyses suggest that both eating time and context (i.e., while doing other tasks simultaneously) matters as does time spent in food preparation, and time spent in sedentary activities. Reduced form models suggest that shifts in grocery prices, opportunity costs of time, and nonwage income may be contributing to alterations in time use patterns and food choices that have implications for BMI.</p

Hydrodynamic and Brownian Fluctuations in Sedimenting Suspensions

We use a mesoscopic computer simulation method to study the interplay between hydrodynamic and Brownian fluctuations during steady-state sedimentation of hard sphere particles for Peclet numbers (Pe) ranging from 0.1 to 15. Even when the hydrodynamic interactions are an order of magnitude weaker than Brownian forces, they still induce backflow effects that dominate the reduction of the average sedimentation velocity with increasing particle packing fraction. Velocity fluctuations, on the other hand, begin to show nonequilibrium hydrodynamic character for Pe > 1Comment: 4 pages 4 figures, RevTex, to appear in Phys. Rev. Lett. New version with some minor correction

A Numerical Model for Brownian Particles Fluctuating in Incompressible Fluids

We present a numerical method that consistently implements thermal fluctuations and hydrodynamic interactions to the motion of Brownian particles dispersed in incompressible host fluids. In this method, the thermal fluctuations are introduced as random forces acting on the Brownian particles. The hydrodynamic interactions are introduced by directly resolving the fluid motions with the particle motion as a boundary condition to be satisfied. The validity of the method has been examined carefully by comparing the present numerical results with the fluctuation-dissipation theorem whose analytical form is known for dispersions of a single spherical particle. Simulations are then performed for more complicated systems, such as a dispersion composed of many spherical particles and a single polymeric chain in a solvent.Comment: 6 pages, 8 figure

The MOSDEF Survey: The Metallicity Dependence of X-Ray Binary Populations at z ∼ 2

Population synthesis models predict that high-mass X-ray binary (HMXB) populations produced in low-metallicity environments should be more X-ray luminous, a trend supported by studies of nearby galaxies. This trend may be responsible for the observed increase of the X-ray luminosity (L X) per star formation rate (SFR) with redshift due to the decrease of metallicity (Z) at fixed stellar mass as a function of redshift. To test this hypothesis, we use a sample of 79 z ∼ 2 star-forming galaxies with oxygen abundance measurements from the MOSDEF survey, which obtained rest-frame optical spectra for ∼1500 galaxies in the CANDELS fields at 1.37 &lt; z &lt; 3.80. Using Chandra data from the Chandra AEGIS-X Deep, Chandra Deep Field North, and Chandra Deep Field South surveys, we stack the X-ray data at the galaxy locations in bins of redshift and Z because the galaxies are too faint to be individually detected. In agreement with previous studies, the average L X/SFR of our z ∼ 2 galaxy sample is enhanced by ≈0.4-0.8 dex relative to local HMXB L X-SFR scaling relations. Splitting our sample by Z, we find that L X/SFR and Z are anticorrelated with 97% confidence. This observed Z dependence for HMXB-dominated galaxies is consistent with both the local L X-SFR-Z relation and a subset of population synthesis models. Although the statistical significance of the observed trends is weak owing to the low X-ray statistics, these results constitute the first direct evidence connecting the redshift evolution of L X/SFR and the Z dependence of HMXBs

Religious Styles Predict Interreligious Prejudice: A Study of German Adolescents with the Religious Schema Scale

Streib H, Klein C. Religious Styles Predict Interreligious Prejudice: A Study of German Adolescents with the Religious Schema Scale. International Journal for the Psychology of Religion. 2014;24(2):151-163.Based on a sample of 340 German adolescents age 12 to 25, this article presents an analysis of the effects of religion on two instances of interreligious prejudice: anti-Islamic and anti-Semitic prejudice. Reflecting the emergent interest in implementing a perspective of religious maturity and religious development into research on religion and prejudice, the present study has included the Religious Schema Scale (RSS) which, with its three subscales, Truth of Texts & Teachings (ttt), Fairness, Tolerance & Rational Choice (ftr), and Xenosophia/Interreligious Dialog (xenos), differentiates religious styles. Regression analyses indicate the superior explanatory power of the RSS in comparison to other measures of religiosity. The RSS subscale ttt relates to and predicts anti-Islamic and anti-Semitic prejudice, whereas ftr and xenos relate to and predict disagreement with interreligious prejudice. Results of an analysis of variance using high agreement on ttt, ftr, and xenos for group construction indicate a decrease in interreligious prejudice in relation to religious development

Physical activity during the transition from adolescence to adulthood

Background: We examine how age, life course roles, and contextual variables relate to both the composition and the overall level of physical activity in late adolescence and early adulthood. Methods: Data on respondents age 15 to 29 y in the 2003 American Time Use Survey are used to estimate multivariate logistic regressions that assess what factors are associated with meeting the recommended level of physical activity. Results: The proportion of respondents who do 30 min or more of team sports declines over the 15 to 29 y age range even after controlling for life course and contextual covariates. Parenthood, employment status, and school enrollment have selective effects on the odds of meeting physical activity recommendations. Conclusions: Given the declines in team sports activities, schools and public health officials should consider the potential benefits of promoting other options such as cardiovascular activities, strength training activities, and/or active transportation