Optimal vaccination in a stochastic epidemic model of two non-interacting populations

Developing robust, quantitative methods to optimize resource allocations in response to epidemics has the potential to save lives and minimize health care costs. In this paper, we develop and apply a computationally efficient algorithm that enables us to calculate the complete probability distribution for the final epidemic size in a stochastic Susceptible-Infected-Recovered (SIR) model. Based on these results, we determine the optimal allocations of a limited quantity of vaccine between two non-interacting populations. We compare the stochastic solution to results obtained for the traditional, deterministic SIR model. For intermediate quantities of vaccine, the deterministic model is a poor estimate of the optimal strategy for the more realistic, stochastic case.Comment: 21 pages, 7 figure

Autecological studies of Drosera linearis, a threatened sundew species

The linear-leaf sundew has been extirpated from several stations at the southern edge of Its range. Cedarburg Bog is believed to harbor the largest of the remaining southern colonies of this species. Drosera linearis has a lower reproductive output at Cedarburg Bog than at other sites, and produces fewer seeds per plant than the three sundew species which share its range. The population studied at Cedarburg Bog declined in population size and reproductive output from 1980 to 1982, and revealed characteristics associated with high rates of local extinction. Populations experienced rapid turnover of individuals, and population size was closely coupled to the size of the previous year\u27s seed crop. Sustained flooding in the flarks of the patterned fen further decreased population stability. The species may have persisted at Cedarburg Bog because the patterned fen is sufficiently large to allow the recolonization rate to keep pace with the rate of local extinction

An Analysis of the Changes in the Prevalence of Camallanus Oxycephalus (Nematoda: Camallanidae) in Western Lake Erie

Author Institution: Center for Lake Erie Area Research and The Department of Zoology, Ohio State UniversitySTROMBERG, PAUL C. AND CRITES, JOHN L. An Analysis of the Changes in the Prevalence of Camallanus oxycephalus (Nematoda: Camallanidae) in Western Lake Erie. Ohio J. Sci. 75(1): 1, 1975. Distribution of Camallanus oxycephalus was studied in 16 species of fishes in western Lake Erie during the summer and autumn of 1972. This study was compared to studies done in 1927 and 1957. Analysis of the frequency of infection in these fishes indicates that Camallanus has become more abundant in the lake. This increase has occurred since 1957. The increase in prevalence appears related to changes in plankton, benthos and fish communities of the western basin. The importance of hostparasite contact frequency and its relation to parasite population density and regulation is discussed

Application of multispectral radar and LANDSAT imagery to geologic mapping in death valley

Side-Looking Airborne Radar (SLAR) images, acquired by JPL and Strategic Air Command Systems, and visible and near-infrared LANDSAT imagery were applied to studies of the Quaternary alluvial and evaporite deposits in Death Valley, California. Unprocessed radar imagery revealed considerable variation in microwave backscatter, generally correlated with surface roughness. For Death Valley, LANDSAT imagery is of limited value in discriminating the Quaternary units except for alluvial units distinguishable by presence or absence of desert varnish or evaporite units whose extremely rough surfaces are strongly shadowed. In contrast, radar returns are most strongly dependent on surface roughness, a property more strongly correlated with surficial geology than is surface chemistry

An Open-Sourced Statistical Application for Identifying Complex Toxicological Interactions of Environmental Pollutants

The rising number of chemicals that humans are exposed to on a daily basis, as well as advances in biomonitoring and detection technologies have highlighted the diversity of individual exposure profiles (complex body burdens). To address this, the toxicological sciences have begun to shift away from examining toxic agents or stressors individually to focusing on more complex models with multiple agents or stressors present. Literature on interactions between chemicals is fairly limited in comparison with dose-response studies on individual toxicants, which is largely due to experimental and statistical challenges. Experimental designs capable of identifying these complex interactions are often avoided or not evaluated to their fullest potential because of the difficulty associated with appropriate analysis as well as logistical factors. To assist with statistical analysis of these types of experiments, an online, open-sourced statistical application was created for investigators to use to analyze and interpret potential toxicant interactions in laboratory experimental data using a full-factorial three-way analysis of variance (ANOVA). This model utilizes backward selection on interaction terms to model main effects and interactions

Predator water balance alters intraguild predation in a streamsidefood web

Previous work suggests that animal water balance can influence trophic interactions, with predators increasing their consumption of water-laden prey to meet water demands.But it is unclear how the need for water interacts with the need for energy to drive trophic interactions under shifting conditions. Using manipulative field experiments, we show that water balance influences the effects of top predators on prey with contrasting ratios of water and energy, altering the frequency of intraguild predation. Water-stressed top predators (large spiders) negatively affect water-laden basal prey (crickets), especially male prey with higher water content, whereas alleviation of water limitation causes top predators to switch to negatively affecting energy-rich midlevel predators (small spiders). Thus, the relative water and energy content of multiple prey, combined with the water demand of the top predator, influences trophic interactions in ways that can alter the strength of intraguild predation. These findings underscore the need for integration of multi resource approaches for understanding implications of global change for food webs

Coupling groundwater and riparian vegetation models to assess effects of reservoir releases

Although riparian areas in the arid southwestern United States are critical for maintaining species diversity, their extent and health have been declining since Euro-American settlement. The purpose of this study was to develop a methodology to evaluate the potential for riparian vegetation restoration and groundwater recharge. A numerical groundwater flow model was coupled with a conceptual riparian vegetation model to predict hydrologic conditions favorable to maintaining riparian vegetation downstream of a reservoir. A Geographic Information System(GIS) was used for this one-way coupling. Constant and seasonally varying releases from the dam were simulated using volumes anticipated to be permitted by a regional water supplier. Simulations indicated that seasonally variable releases would produce surface flow 5.4-8.5 km below the dam in a previously dry reach. Using depth to groundwater simulations from the numerical flow model with conceptual models of depths to water necessary for maintenance of riparian vegetation, the GIS analysis predicted a 5- to 6.5-fold increase in the area capable of sustaining riparian vegetation