Thermally activated barrier crossing and stochastic resonance of a flexible polymer chain in a piecewise linear bistable potential

We study the stochastic resonance (SR) of a flexible polymer chain crossing over a piecewise linear bistable potential. The dependence of signal to noise ratio $SNR$ on noise intensity $D$, coupling constant $k$ and polymer length $N$ is studied via two state approximation. We find that the response of signal to the background noise strength is significant at optimum values of $D_{opt}$, $k_{opt}$ and $N_{opt}$ which suggests novel means of manipulating proteins or vesicles. Furthermore, the thermally activated barrier crossing rate $r_{k}$ for the flexible polymer chain is studied. We find that the crossing rate $r_{k}$ exhibits an optimal value at an optimal coupling constant $k_{opt}$; $k_{opt}$ decreases with $N$. As the chain length $N$ increases, the escape rate for the center of mass $r_{k}$ monotonously decreases. On the other hand, the crossing rate for the portion of polymer segment $r_s$ increases and saturates to a constant rate as $N$ steps up.Comment: 16 pages, 9 figure

Energetics of a simple microscopic heat engine

We model a microscopic heat engine as a particle hopping on a one-dimensional lattice in a periodic sawtooth potential, with or without load, assisted by the thermal kicks it gets from alternately placed hot and cold thermal baths. We find analytic expressions for current and rate of heat flow when the engine operates at steady state. Three regions are identified where the model acts either as a heat engine or as a refrigerator or as neither of the two. At quasistatic limit both efficiency of the engine and coefficient of performance of the refrigerator go to that for Carnot engine and Carnot refrigerator, respectively. We investigate efficiency of the engine at two operating conditions (at maximum power and at optimum value with respect to energy and time) and compare them with those of the endoreversible and Carnot engines.Comment: 6 pages and 8 figure

Disparities in Access to Health Insurance and Workers’ Compensation Benefit between Non-Contingent and Contingent Farm Workers in U.S. Agriculture

The share of contingent employment has increased significantly in the last two decades. Not much is known about the impact of this shift on disparities in access to health insurance and other benefits. I examined disparities in access to any type of health insurance, employer-sponsored health insurance and workers’ compensation (WC) benefits between contingent and non-contingent workers in U.S. agriculture. I used the National Agricultural Workers Survey and the extended Oaxaca-Blinder decomposition technique to estimate disparities. Contingent employment could be a barrier to access of health insurance and WC benefit, which in turn could contribute to health inequalities in the long-run

Supermarket purchases and the dietary patterns of households in Guatemala:

"Very limited empirical analyses are done on evaluating how changes in the retail environment affect diet and health status of consumers, especially in developing countries. The major objective of this study is to shed some light on some of these neglected but crucial issues. The study examines the impact of supermarket purchases on dietary practices (defined as the calorie share of different food groups) of Guatemalan households using the 2000 Guatemalan household survey. I use an instrumental variable method to take into account the potential endogeneity of the supermarket-purchase variable in the calorie share equations.... The results of the study reveal that supermarket purchases increase the share that highly and partially processed food items, such as pastries, cookies, crackers, chocolate, ice cream, and so forth, make of total calories, at the expense of staple food items such as corn and beans. Since most processed foods contain disproportionately high amounts of added fat, sugar, and salt, and since supermarkets are expanding rapidly, different policy measures should be developed to ensure that supermarkets have a "healthier" impact on diets." from Authors' AbstractSupermarkets, Health and nutrition, Calorie share, Diet quality, Staple foods, Household behavior, Processed foods, Energy dense foods, Energy dilute foods, Instrumental variable method,

Exploring the operation of a tiny heat engine

We model a tiny heat engine as a Brownian particle that moves in a viscous medium in a sawtooth potential (with or without load) assisted by $\it {alternately}$ placed hot and cold heat baths along its path. We find closed form expression for the steady state current as a function of the model parameters. This enables us to deal with the energetics of the model and evaluate either its efficiency or its coefficient of performance depending upon whether the model functions either as a heat engine or as a refrigerator, respectively. We also study the way current changes with changes in parameters of interest. When we plot the phase diagrams showing the way the model operates, we not only find regions where it functions as a heat engine and as a refrigerator but we also identify a region where the model functions as neither of the two.Comment: 8 pages and 13 figure