The Influence of Electrostatic Truncation on Simulations of Polarizable Systems

Different schemes for the treatment of long-ranged electrostatic interactions will be examined for water simulations using the polarizable fluctuating charge potential. Several different methods are compared, including Ewald sums, potential shifting, spherical truncation and reaction field corrections. For liquid water, properties such as the energy, pressure, dynamics and structure are more sensitive to the treatment of the long-ranged interactions with polarizable than with non-polarizable potentials.Comment: 4 figures, 13 pages, to be published in the Proceedings from the Workshop on Treatment of Electrostatic Interactions in Computer Simulations of Condensed Mediaof Con

Ion clustering in aqueous salt solutions near the liquid/vapor interface

Molecular dynamics simulations of aqueous NaCl, KCl, NaI, and KI solutions are used to study the effects of salts on the properties of the liquid/vapor interface. The simulations use the models which include both charge transfer and polarization effects. Pairing and the formation of larger ion clusters occurs both in the bulk and surface region, with a decreased tendency to form larger clusters near the interface. An analysis of the roughness of the surface reveals that the chloride salts, which have less tendency to be near the surface, have a roughness that is less than pure water, while the iodide salts, which have a greater surface affinity, have a larger roughness. This suggests that ions away from the surface and ions near the surface affect the interface in opposite ways.Comment: 10 pages, 5 figure

Mammals of Southwestern Arkansas Part II. Rodents

This study investigated the composition and habitat affinities of the mammalian fauna of southwestern Arkansas. The study area was comprised of the 21 counties located south and/or west of and including Pulaski County. The previously existing data set pertaining to the mammals of Arkansas was notably incomplete and this study area in particular, was poorly known mammalogically. Specimens were collected by standard trapping and salvage methods throughout the study area. The mammals considered during this study were limited to those species meeting a set of criteria designed to eliminate species that had been introduced or artificially maintained. This study has accumulated records of 25 species of rodents; over 1500 specimens have been recorded; and a total of 95 new county records have been documented

The Groucho Effect of Uncertain Standards

Consumers are rarely sure of the exact standard that product labels and other certificates of quality represent. We show that any such uncertainty creates a “Groucho effect” in which seeing that a product has a label leads consumers to infer that the standard for the label itself is not very demanding. Label adoption is therefore always less likely to be an equilibrium than without uncertainty over the standard, and if it is an equilibrium it is always less informative than without such uncertainty. The Groucho effect leads to an information externality so better firms are reluctant to adopt labels if worse firms adopt them. Applying the model to eco-labels, we find that industry groups, governments, and NGOs can increase label adoption by publicizing labeling criteria, by encouraging consumers to expect label adoption when there are multiple equilibria, and by setting high standards that are less likely to be devalued by low quality firms.Eco-labels, disclosure, certification, persuasion, standards