Dissipative Particle Dynamics with Energy Conservation

The stochastic differential equations for a model of dissipative particle dynamics with both total energy and total momentum conservation in the particle-particle interactions are presented. The corresponding Fokker-Planck equation for the evolution of the probability distribution for the system is deduced together with the corresponding fluctuation-dissipation theorems ensuring that the ab initio chosen equilibrium probability distribution for the relevant variables is a stationary solution. When energy conservation is included, the system can sustain temperature gradients and heat flow can be modeled.Comment: 7 pages, submitted to Europhys. Let

Dissipative Particle Dynamics with energy conservation

Dissipative particle dynamics (DPD) does not conserve energy and this precludes its use in the study of thermal processes in complex fluids. We present here a generalization of DPD that incorporates an internal energy and a temperature variable for each particle. The dissipation induced by the dissipative forces between particles is invested in raising the internal energy of the particles. Thermal conduction occurs by means of (inverse) temperature differences. The model can be viewed as a simplified solver of the fluctuating hydrodynamic equations and opens up the possibility of studying thermal processes in complex fluids with a mesoscopic simulation technique.Comment: 5 page

Economic and Environmental Impacts of Harmful Non-Indigenous Species in Southeast Asia

10.1371/journal.pone.0071255PLoS ONE88-POLN

Conceptual Frameworks and Methods for Advancing Invasion Ecology

Invasion ecology has much advanced since its early beginnings. Nevertheless, explanation, prediction, and management of biological invasions remain difficult. We argue that progress in invasion research can be accelerated by, first, pointing out difficulties this field is currently facing and, second, looking for measures to overcome them. We see basic and applied research in invasion ecology confronted with difficulties arising from (A) societal issues, e.g., disparate perceptions of invasive species; (B) the peculiarity of the invasion process, e.g., its complexity and context dependency; and (C) the scientific methodology, e.g., imprecise hypotheses. To overcome these difficulties, we propose three key measures: (1) a checklist for definitions to encourage explicit definitions; (2) implementation of a hierarchy of hypotheses (HoH), where general hypotheses branch into specific and precisely testable hypotheses; and (3) platforms for improved communication. These measures may significantly increase conceptual clarity and enhance communication, thus advancing invasion ecology

A benefit-cost analysis decision framework for mitigation of disease transmission at the wildlife–livestock interface

The economics of managing disease transmission at the wildlife–livestock interface have received heightened attention as agricultural and natural resource agencies struggle to tackle growing risks to animal health. In the fiscal landscape of increased scrutiny and shrinking budgets, resource managers seek to maximize the benefits and minimize the costs of disease mitigation efforts. To address this issue, a benefit-cost analysis decision framework was developed to help users make informed choices about whether and how to target disease management efforts in wildlife and livestock populations. Within the context of this framework, we examined the conclusions of a benefit-cost analysis conducted for vampire bat (Desmodus rotundus) rabies control in Mexico. The benefit-cost analysis decision framework provides a method that can be used to identify, assemble, and measure the components vital to the biological and economic efficiency of animal disease mitigation efforts. The framework can be applied to commercially-raised and free-ranging species at various levels of management – from detailed intervention strategies to broad programmatic actions. The ability of benefit cost analysis to illustrate the benefits of disease management projects per dollar spent allows for the determination of economic efficiency of alternative management actions. We believe this framework will be useful to the broader natural resource management community to maximize returns on financial and other resources invested in wildlife and livestock disease management programs

Machine Learning Model for Predicting Number of COVID-19 Cases in Countries with Low Number of Tests

Background: The COVID-19 pandemic has presented a series of new challenges to governments and healthcare systems. Testing is one important method for monitoring and controlling the spread of COVID-19. Yet with a serious discrepancy in the resources available between rich and poor countries, not every country is able to employ widespread testing. Methods and Objective: Here, we have developed machine learning models for predicting the prevalence of COVID-19 cases in a country based on multilinear regression and neural network models. The models are trained on data from US states and tested against the reported infections in European countries. The model is based on four features: Number of tests, Population Percentage, Urban Population, and Gini index. Results: The population and the number of tests have the strongest correlation with the number of infections. The model was then tested on data from European countries for which the correlation coefficient between the actual and predicted cases R2 was found to be 0.88 in the multi-linear regression and 0.91 for the neural network model Conclusion: The model predicts that the actual prevalence of COVID-19 infection in countries where the number of tests is less than 10% of their populations is at least 26 times greater than the reported numbers

Comparison of the efficacy of four drug combinations for immobilization of wild pigs

Field immobilization of native or invasive wild pigs (Sus scrofa) is challenging. Drug combinations commonly used often result in unsatisfactory immobilization, poor recovery, and adverse side effects, leading to unsafe handling conditions for both animals and humans. We compared four chemical immobilization combinations, medetomidine–midazolam–butorphanol (MMB), butorphanol–azaperone–medetomidine (BAM™), nalbuphine–medetomidine–azaperone (NalMed-A), and tiletamine– zolazepam–xylazine (TZX), to determine which drug combinations might provide better chemical immobilization of wild pigs. We achieved adequate immobilization with no post-recovery morbidity withMMB. Adequate immobilization was achieved with BAM™; however, we observed post-recovery morbidity. Both MMB and BAM™ produced more optimal results relative to body temperature, recovery, and post-recovery morbidity and mortality compared to TZX. Adequate immobilization was not achieved with NalMed-A. Of the four drug combinations examined, we conclude that MMB performed most optimally for immobilization and recovery of wild pigs

Effects of climate variation on the breeding ecology of Arctic shorebirds

About 50 species of shorebirds breed in the Arctic, where they constitute the most characteristic component of the tundra avifauna. Here, we review the impact of weather and climate on the breeding cycle of shorebirds based on extensive studies conducted across the Arctic. Conditions for breeding shorebirds are highly variable among species, sites and regions, both within and between continents. Weather effects on breeding are most moderate in the Low Arctic of northern Europe and most extreme in the Siberian High Arctic. The decision of whether or not to breed upon arrival on the breeding grounds, the timing of egg-laying and the chick-growth period are most affected by annual variation in weather. In large parts of the Arctic, clutch initiation dates are highly correlated with snowmelt dates and in regions and years where extensive snowmelt occurs before or soon after the arrival of shorebirds, the decision to breed and clutch initiation dates appear to be a function of food availability for laying females. Once incubation is initiated, adult shorebirds appear fairly resilient to variations in temperature with nest abandonment primarily occurring in case of severe weather with new snow covering the ground. Feeding conditions for chicks, a factor highly influenced by weather, affects juvenile production in most regions. Predation has a very strong impact on breeding productivity throughout the Arctic and subarctic, with lemming Dicrostonyx spp. and Lemmus spp. fluctuations strongly influencing predation rates, particularly in the Siberian Arctic. The fate of Arctic shorebirds under projected future climate scenarios is uncertain, but High Arctic species and populations appear particularly at risk. Climatic amelioration may benefit Arctic shorebirds in the short term by increasing both survival and productivity, whereas in the long term habitat changes both on the breeding grounds and in the temperate and tropical non-breeding areas may put them under considerable pressure and may bring some of them near to extinction. Their relatively low genetic diversity, which is thought to be a consequence of survival through past climatically-driven population bottlenecks, may also put them more at risk to anthropogenic-induced climate variation than other avian taxa. &nbsp