Bond formation and slow heterogeneous dynamics in adhesive spheres with long--ranged repulsion: Quantitative test of Mode Coupling Theory

A colloidal system of spheres interacting with both a deep and narrow attractive potential and a shallow long-ranged barrier exhibits a prepeak in the static structure factor. This peak can be related to an additional mesoscopic length scale of clusters and/or voids in the system. Simulation studies of this system have revealed that it vitrifies upon increasing the attraction into a gel-like solid at intermediate densities. The dynamics at the mesoscopic length scale corresponding to the prepeak represents the slowest mode in the system. Using mode coupling theory with all input directly taken from simulations, we reveal the mechanism for glassy arrest in the system at 40% packing fraction. The effects of the low-q peak and of polydispersity are considered in detail. We demonstrate that the local formation of physical bonds is the process whose slowing down causes arrest. It remains largely unaffected by the large-scale heterogeneities, and sets the clock for the slow cluster mode. Results from mode-coupling theory without adjustable parameters agree semi-quantitatively with the local density correlators but overestimate the lifetime of the mesoscopic structure (voids).Comment: 10 pages, 8 figure

Local effective dynamics of quantum systems: A generalized approach to work and heat

By computing the local energy expectation values with respect to some local measurement basis we show that for any quantum system there are two fundamentally different contributions: changes in energy that do not alter the local von Neumann entropy and changes that do. We identify the former as work and the latter as heat. Since our derivation makes no assumptions on the system Hamiltonian or its state, the result is valid even for states arbitrarily far from equilibrium. Examples are discussed ranging from the classical limit to purely quantum mechanical scenarios, i.e. where the Hamiltonian and the density operator do not commute.Comment: 5 pages, 1 figure, published versio

ECONOMIC IMPACTS OF MANDATED GRADING AND TESTING TO AVOID A NEGATIVE FOOD SAFETY EVENT: EX ANTE ANALYSIS OF THE FEDERAL MARKETING ORDER FOR PISTACHIOS

The California pistachio industry led an initiative to establish a federal marketing order, which mandates quality standards and an inspection program to assure food safety and consistency in the quality of California pistachios. We develop a stochastic dynamic simulation model of the pistachio market to investigate quantitatively the likely effects of such collective action enforced by government mandates. Simulation results indicate that, across the full range of parameters used in the analysis, the benefit-cost analysis was always favorable to the proposed policy. The measured benefits to producers, the nation, or the world always well exceeded the corresponding measure of costs, typically by many times.Food Consumption/Nutrition/Food Safety,

Demand Enhancement through Food-Safety Regulation: Benefit-Cost Analysis of Collective Action in the California Pistachio Industry

Food safety shocks can threaten the health of consumers, create havoc within an industry and result in severe losses to producers. Governments often attempt to enhance food safety by mandating standards and inspection of food products to supplement the voluntary efforts by private firms. This paper assesses a form of collective action that falls between typical government mandates and purely private action. The California pistachio industry recently established a U.S. federal marketing order. This order sets quality standards and requires inspection and certification, aiming to reduce the likelihood of dangerous or poor quality pistachios being sold to consumers and to provide some quality assurance to consumers. Simulation results indicate that, across the full range of parameters used in the analysis, the benefit-cost analysis was always favorable to the new policy. Continuing work is extending the analysis to account for some particular features of the pistachio industry, to consider alternative policies, and to draw inferences for the application of similar policies to other California specialty crops.Food Safety, Collective Action, Specialty Crops, Government Regulation, Marketing Orders, Pistachios, Food Consumption/Nutrition/Food Safety, Q18, Q13, I18, H4,

Industry-mandated testing to improve food safety: the new US marketing order for pistachios

Food safety shocks can threaten the health of consumers, create havoc within an industry and result in severe losses to producers. Governments often attempt to aid food safety by mandating standards and inspection of food products to supplement the efforts by private firms and industries. This article assesses a form of collective action that falls between typical government mandates and purely private action. The California pistachio industry recently established a U.S. federal marketing order, which sets quality standards and inspection to reduce the likelihood of dangerous or poor quality pistachios. Simulation results indicate that, across the full range of parameters used in the analysis, the benefit-cost analysis was always favorable to the new policy. In the case of California pistachios, collective action is likely to be a helpful tool to ensure a safe product and increase benefits to producers and consumers.food safety, food scare, collective action, marketing orders, pistachios, public good, food regulations, cost-benefit analysis, Agribusiness, Food Consumption/Nutrition/Food Safety,

Critical behavior in an evolutionary Ultimatum Game

Experimental studies have shown the ubiquity of altruistic behavior in human societies. The social structure is a fundamental ingredient to understand the degree of altruism displayed by the members of a society, in contrast to individual-based features, like for example age or gender, which have been shown not to be relevant to determine the level of altruistic behavior. We explore an evolutionary model aiming to delve how altruistic behavior is affected by social structure. We investigate the dynamics of interacting individuals playing the Ultimatum Game with their neighbors given by a social network of interaction. We show that a population self-organizes in a critical state where the degree of altruism depends on the topology characterizing the social structure. In general, individuals offering large shares but in turn accepting large shares, are removed from the population. In heterogeneous social networks, individuals offering intermediate shares are strongly selected in contrast to random homogeneous networks where a broad range of offers, below a critical one, is similarly present in the population.Comment: 13 pages, 7 figure

Economic Consequences of Mandated Grading and Food Safety Assurance: Ex Ante Analysis of the Federal Marketing Order for California Pistachios

Crop Production/Industries, Food Consumption/Nutrition/Food Safety, Marketing,