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Number of Pages: 4Integrative BiologyGeological Science

Preliminary Results on the Structure and Functioning of a Taiga Watershed

Comprehensive research in ecosystem functioning may logically be undertaken in the conceptual and physical context of complete drainage basins (watersheds or catchments). The watershed forms a fundamental, cohesive landscape unit in terms of water movement following initial receipt of precipitation. Water itself is a fundamental agent in energy flux, nutrient transport, and in plant and animal life. The Caribou-Poker Creeks Research Watershed is an interagency endeavor aimed at understanding hydrologic and, ultimately, ecological functioning in the subarctic taiga, the discontinuous permafrost uplands of central Alaska. Initial work includes acquisition and analysis of data on soils, vegetation, local climate, hydrology, and stream quality. Information acquired in the research watershed is summarized here, and implications for future data acquisition and research are considered

The Effect of Fluctuations on the Helium-Ionizing Background

Interpretation of He II Ly{\alpha} absorption spectra after the epoch of He II reionization requires knowledge of the He II ionizing background. While past work has modelled the evolution of the average background, the standard cosmological radiative transfer technique assumes a uniform radiation field despite the discrete nature of the (rare) bright quasars that dominate the background. We implement a cosmological radiative transfer model that includes the most recent constraints on the ionizing spectra and luminosity function of quasars and the distribution of IGM absorbers. We also estimate, for the first time, the effects of fluctuations on the evolving continuum opacity in two ways: by incorporating the complete distribution of ionizing background amplitudes into the standard approach, and by explicitly treating the quasars as discrete -- but isolated -- sources. Our model results in a He II ionization rate that evolves steeply with redshift, increasing by a factor ~2 from z=3.0 to z=2.5. This causes rapid evolution in the mean He II Ly{\alpha} optical depth -- as recently observed -- without appealing to the reionization of He II. The observed behaviour could instead result from rapid evolution in the mean free path of ionizing photons as the helium in higher H I column density absorbers becomes fully ionized.Comment: 14 pages, 9 figures. Accepted by MNRAS; significantly modified from previous versio

ECONOMIC BURDEN OF SALMONELLA INFECTIONS IN THE UNITED STATES

The aim of this study is to evaluate medical expenditures and lost productivity associated with burden of Salmonella infections. We used laboratory confirmed number of Salmonella cases and corresponding multipliers to estimate the burden of illness using the method adopted by Foodborne Diseases Active Surveillance Network (FoodNet) at Centers for Disease Control and Prevention (CDC). The medical costs estimates are retrospective analysis of reimbursement records from MarketScan data. We identified patients with a diagnosis of salmonellosis using ICD-9 CM codes from the MarketScan 1993-2001 databases. Productivity loss from the nonfatal cases of Salmonella was calculated using the distributions of lost workdays and household services due to the illness. Statistical value of life approach was used to estimate the costs due to premature deaths. We also compared the costs for the gastrointestinal salmonellosis to the cost for the invasive salmonellosis. Confidence intervals around the cost estimates were calculated using a Monte Carlo simulation technique. Estimated average economic burden due to Salmonella was $210 per outpatient,$5,797 per inpatient with gastrointestinal infection, $16,441 per impatient with invasive infection and$4.63 million per premature death. Total economic buren due to Salmonella in the United States was estimated at $2.8 billion (95$1.6 to $5.3 billion) annually, which is approximately$2,472 per case of Salmonella infection. The cost estimate is largely driven by the number of premature deaths followed by average cost of hospitalization. Defining the risk factors for fatal outcomes may help target treatment and preventive strategies.Food Consumption/Nutrition/Food Safety,