Rift Valley Fever: An Economic Assessment of Agricultural and Human Vulnerability

This research focused on the assessment of the U.S. agricultural sector and human vulnerability to a Rift Valley Fever (RVF) outbreak and the implications of a select set of alternative disease control strategies. Livestock impact assessment is done by using an integrated epidemic/economic model to examine the extent of RVF spread in the Southeast Texas livestock population and its consequences plus the outcome of implementing two different control strategies: emergency vaccination and larvicide vector control separately plus when they are used simultaneously. Human impact assessment utilized an inferential procedure, which comprises of a cost of illness calculation to assess the dollar cost of human illnesses and deaths, as well as a Disability Adjusted Life Year calculation to give an estimate of the burden of disease on public health as a whole. Results indicate substantial potential losses to the U.S., where combined livestock and human national costs ranged from $121 million to$2.3 billion.Rift Valley Fever, Outbreak, Welfare, Vaccination, Larvicide., Environmental Economics and Policy, Food Consumption/Nutrition/Food Safety, Food Security and Poverty, Health Economics and Policy,

Quantum corrections for pion correlations involving resonance decays

A method is presented to include quantum corrections into the calculation of two-pion correlations for the case where particles originate from resonance decays. The technique uses classical information regarding the space-time points at which resonances are created. By evaluating a simple thermal model, the method is compared to semiclassical techniques that assume exponential decaying resonances moving along classical trajectories. Significant improvements are noted when the resonance widths are broad as compared to the temperature.Comment: 9 pages, 4 figure

Spatial heterogeneity in ecological models : two case studies

Two models are developed to explore the dynamics associated with spatial heterogeneity. The first model is the expansion of a single cell, fish population model to a landscape of interacting cells. The second model is a tick-borne disease model using a set of differential equations applied to a series of spatial patches. The spatially-explicit landscape fish population model (ALFISH) is a part of the Across Trophic Level System Simulation (ATLSS) project for the freshwater wetlands of the Everglades and Big Cypress Swamp. ALFISH was applied as part of the ATLSS project to Everglades restoration, one of the largest ecological restoration projects in the world. ALFISH has been improved to include new field information as that information became available. The only variable input into ALFISH is the hydrology. Up to 35% of variation in fish populations observed in field data corresponds to the variations predicted by ALFISH. The differential equations underlying the tick-borne disease model designed for the lone star tick (Amblyomma americanum) are analytically evaluated for one patch. The results show that under given criteria for the parameters, the system would be locally stable. For further study, the system is then solved numerically. Patches are identified as either grass or wooded and connected by migration. The disease is endemic in both patches unless some type of control is applied. If a control is applied, the disease is reduced to extremely low levels. If two patches, one grass and one wooded, are linked by migration, applying the control to the wooded patch is effective for controlling the disease while applying it in the grass patch is not. A final simulation using a twelve patch system is run to create results to compare with field data. The results show that the model produced qualitatively similar results to the field data which give reductions of 60% in tick density in the areas with control applied

Optimized Discretization of Sources Imaged in Heavy-Ion Reactions

We develop the new method of optimized discretization for imaging the relative source from two particle correlation functions. In this method, the source resolution depends on the relative particle separation and is adjusted to available data and their errors. We test the method by restoring assumed pp sources and then apply the method to pp and IMF data. In reactions below 100 MeV/nucleon, significant portions of the sources extend to large distances (r > 20 fm). The results from the imaging show the inadequacy of common Gaussian source-parametrizations. We establish a simple relation between the height of the pp correlation function and the source value at short distances, and between the height and the proton freeze-out phase-space density.Comment: 36 pages (inc. 9 figures), RevTeX, uses epsf.sty. Submitted to Phys. Rev.

Modelling the Effects of Habitat and Hosts on Tick Invasions

Many tick species are invading new areas because of anthropogenic changes in the landscape, shifting climatic variables and increasing populations of suitable host species and tick habitat. However, the relative influences of habitat and hosts in tick dispersal and tick population establishment remain in question. A spatially explicit agent-based model was developed to explore the spatio-temporal dynamics of a generic tick population in the years immediately following the introduction of ticks into a novel environment. The general model was then adapted to investigate a case study of two recent tick species invasions into the Mid-Atlantic United States. The recent simultaneous range expansions of two ixodid tick species, Ixodes affinis and Amblyomma maculatum, provided an opportunity to determine if invasion patterns observed in the field could be replicated in silico on a small scale. The models presented here indicated that for generalist parasites, habitat connectivity is a better indicator than host mobility for spatial and genetic patterns of parasite range expansion. In addition, our results demonstrate the utility of including genetic variables into agent-based models: gene flow functions as a proxy for measuring dispersal, and models can be validated using results from the field

Lambda-proton correlations in relativistic heavy ion collisions

The prospect of using lambda-proton correlations to extract source sizes in relativistic heavy ion collisions is investigated. It is found that the strong interaction induces a large peak in the correlation function that provides more sensitive source size measurements than two-proton correlations under some circumstances. The prospect of using lambda-proton correlations to measure the time lag between lambda and proton emissions is also studied.Comment: 4 pages, 3 figure, revtex style. Two short paragraphs are added at referees' recommendations. Phys. Rev. Lett. in pres

Breakup Density in Spectator Fragmentation

Proton-proton correlations and correlations of protons, deuterons and tritons with alpha particles from spectator decays following 197Au + 197Au collisions at 1000 MeV per nucleon have been measured with two highly efficient detector hodoscopes. The constructed correlation functions, interpreted within the approximation of a simultaneous volume decay, indicate a moderate expansion and low breakup densities, similar to assumptions made in statistical multifragmentation models. PACS numbers: 25.70.Pq, 21.65.+f, 25.70.Mn, 25.75.GzComment: 11 pages, LaTeX with 3 included figures; Also available from http://www-kp3.gsi.de/www/kp3/aladin_publications.htm

Temperatures of Exploding Nuclei

Breakup temperatures in central collisions of 197Au + 197Au at bombarding energies E/A = 50 to 200 MeV were determined with two methods. Isotope temperatures, deduced from double ratios of hydrogen, helium, and lithium isotopic yields, increase monotonically with bombarding energy from 5 MeV to 12 MeV, in qualitative agreement with a scenario of chemical freeze-out after adiabatic expansion. Excited-state temperatures, derived from yield ratios of states in 4He, 5Li, 6Li, and 8Be, are about 5 MeV, independent of the projectile energy, and seem to reflect the internal temperature of fragments at their final separation from the system. PACS numbers: 25.70.Mn, 25.70.Pq, 25.75.-qComment: 10 pages, RevTeX with 4 included figures; Also available from http://www-kp3.gsi.de/www/kp3/aladin_publications.htm

Use of Optimal Control Models to Predict Treatment Time for Managing Tick-Borne Disease

Tick-borne diseases have been on the rise recently, and correspondingly, there is an increased interest in implementing control measures to decrease the risk. Optimal control provides an ideal tool to identify the best method for reducing risk while accounting for the associated costs. Using a previously published model, a variety of frameworks are assessed to identify the key factors influencing mitigation strategies. The level and duration of tick-reducing efforts are key metrics for understanding the successful reduction in tick-borne disease incidence. The results show that the punctuated nature of the tick\u27s life history plays a critical role in reducing risk without the need for a permanent treatment programme. This work suggests that across a variety of optimal control frameworks and objective functionals within a closed environment, similar strategies are created, all suggesting that the tick-borne disease risk can be reduced to near zero without completely eliminating the tick population

Imaging Sources with Fast and Slow Emission Components

We investigate two-proton correlation functions for reactions in which fast dynamical and slow evaporative proton emission are both present. In such cases, the width of the correlation peak provides the most reliable information about the source size of the fast dynamical component. The maximum of the correlation function is sensitive to the relative yields from the slow and fast emission components. Numerically inverting the correlation function allows one to accurately disentangle fast dynamical from slow evaporative emission and extract details of the shape of the two-proton source.Comment: 13 pages, 4 figure