Exponential Runge-Kutta methods for stiff kinetic equations

We introduce a class of exponential Runge-Kutta integration methods for kinetic equations. The methods are based on a decomposition of the collision operator into an equilibrium and a non equilibrium part and are exact for relaxation operators of BGK type. For Boltzmann type kinetic equations they work uniformly for a wide range of relaxation times and avoid the solution of nonlinear systems of equations even in stiff regimes. We give sufficient conditions in order that such methods are unconditionally asymptotically stable and asymptotic preserving. Such stability properties are essential to guarantee the correct asymptotic behavior for small relaxation times. The methods also offer favorable properties such as nonnegativity of the solution and entropy inequality. For this reason, as we will show, the methods are suitable both for deterministic as well as probabilistic numerical techniques

Indagini briologiche in aree urbane: diversità briofitica dei centri abitati di Erice (Trapani) e Belmonte Mezzagno (Palermo).

Bryologic surveys in urban areas: bryophyte diversity of the population centers of Erice (province of Trapani) and Belmonte Mezzagno ((province of Palermo). The bryophytic flora of the towns of Erice (Trapani) and Belmonte Mezzagno (Palermo) have been studied. The first consists of 53 taxa (42 mosses and 11 liverwort), two of which are new for the province of Trapani, the second of 40 taxa (38 mosses and 2 liverworts), one of which new for the province of Palermo. A comparison between the studied bryofloras and those of other Sicilian urban areas shows that Erice’s bryophytic flora is, given its size, rich in species and families

Analyse du contexte institutionnel de gestion du changement climatique au Sénégal

Les changements et variabilités climatiques représentent des défis majeurs pour la mise en oeuvre des plans et politiques nationaux de développement. Le Sénégal, avec l’appui du programme « Climate Change Agriculture and Food Security » (CCAFS) a formé une Plateforme Multi-acteurs pour faciliter les échanges entre chercheurs et décideurs autours des questions d’adaptation du secteur de l’agriculture et de la Sécurité alimentaire au changement climatique. La présente étude est faite pour comprendre les goulots d’étranglement qui reposent sur la mise en oeuvre effective des politiques de changement climatique. L’étude révèle qu’au niveau national les actions stratégiques semblent tout au plus être définies avec des objectifs cloisonnés qui n'intègrent pas un cadre de référence concerté. L'insuffisance de synergie des différents départements ministériels disperse les efforts de l'Etat en matière de prévision et de planification des changements climatiques dans les stratégies politiques. En plus le déficit en ressources humaines de l’administration publique, notamment dans le secteur agricole après les réformes structurelles des années 90, a engendré un faible accès aux technologies agricoles et aux bonnes pratiques d’adaptation aux changements climatiques. Il a été démontré que la disponibilité de la technologie culturale pour l'adaptation, au moins à court terme, n'est pas un problème, mais c’est plutôt l'accessibilité à ces technologies qui est difficile. Les services d’encadrement et d’appui conseil sont généralement insuffisants en raison de contraintes financières et de compétences. Pour pallier à ces faits, il est nécessaire de mettre l’accent sur : la sensibilisation du monde rural sur les changements climatiques, faciliter l’accès aux formations et services climatiques, surtout dans secteurs de la pêche, de l’agriculture et de l’élevage

Tomografia sísmica da litosfera continental algarvia

RESUMO: O presente estudo de Tomografia é focado na região do Algarve. Para a localização dos eventos e determinação do modelo de velocidades, são utilizadas as ondas P e S. Os dados foram obtidos entre Janeiro/2006 e Julho/2007. As estimativa dos tempos de origem e coordenadas hipocentrais foram calculadas. A relocalização de eventos e inversão linear respeitaram dois passos: 1) determinação do modelo mínimo 1-D e 2) relocalização dos hipocentros e obtenção da estrutura 3-D em termos de velocidades das ondas P. ABSTRACT: The present Tomographic study is focused on Algarve region. For event location and velocity model determination P and S waves were used. Data was collected between January/2006 and July/2007. The estimation of origin times and hipocentral determination were calculated. Relocation of events and linear inversion respected two steps: 1) minimum velocity model determination and 2) hipocentral relocation and 3-D Earth structure determination in terms of P wave velocities

Evidence-based decision making and covid-19: what a posteriori probability distributions speak

Background: In the absence of any pharmaceutical interventions, the management of the COVID-19 pandemic is based on public health measures. The present study fosters evidence-based decision making by estimating various “a posteriori probability distributions" from COVID-19 patients.  Methods: In this retrospective observational study, 987 RT-PCR positive COVID-19 patients from SMS Medical College, Jaipur, India, were enrolled after approval of the institutional ethics committee. The data regarding age, gender, and outcome were collected. The univariate and bivariate distributions of COVID-19 cases with respect to age, gender, and outcome were estimated. The age distribution of COVID-19 cases was compared with the general population's age distribution using the goodness of fit c2 test. The independence of attributes in bivariate distributions was evaluated using the chi-square test for independence. Results: The age group ‘25-29’ has shown highest probability of COVID-19 cases (P [25-29] = 0.14, 95% CI: 0.12- 0.16). The men (P [Male] = 0.62, 95%CI: 0.59-0.65) were dominant sufferers. The most common outcome was recovery (P [Recovered] = 0.79, 95%CI: 0.76-0.81) followed by admitted cases (P [Active]= 0.13, 95%CI: 0.11-0.15) and death (P [Death] = 0.08, 95%CI: 0.06-0.10). The age distribution of COVID-19 cases differs significantly from the age distribution of the general population (c2  =399.04, P < 0.001). The bivariate distribution of COVID-19 across age and outcome was not independent (c2 =106.21, df = 32, P < 0.001). Conclusion: The knowledge of disease frequency patterns helps in the optimum allocation of limited resources and manpower. The study provides information to various epidemiological models for further analysis

Evidence-based decision making and covid-19: what a posteriori probability distributions speak

Background: In the absence of any pharmaceutical interventions, the management of the COVID-19 pandemic is based on public health measures. The present study fosters evidence-based decision making by estimating various “a posteriori probability distributions" from COVID-19 patients.  Methods: In this retrospective observational study, 987 RT-PCR positive COVID-19 patients from SMS Medical College, Jaipur, India, were enrolled after approval of the institutional ethics committee. The data regarding age, gender, and outcome were collected. The univariate and bivariate distributions of COVID-19 cases with respect to age, gender, and outcome were estimated. The age distribution of COVID-19 cases was compared with the general population's age distribution using the goodness of fit c2 test. The independence of attributes in bivariate distributions was evaluated using the chi-square test for independence. Results: The age group ‘25-29’ has shown highest probability of COVID-19 cases (P [25-29] = 0.14, 95% CI: 0.12- 0.16). The men (P [Male] = 0.62, 95%CI: 0.59-0.65) were dominant sufferers. The most common outcome was recovery (P [Recovered] = 0.79, 95%CI: 0.76-0.81) followed by admitted cases (P [Active]= 0.13, 95%CI: 0.11-0.15) and death (P [Death] = 0.08, 95%CI: 0.06-0.10). The age distribution of COVID-19 cases differs significantly from the age distribution of the general population (c2  =399.04, P < 0.001). The bivariate distribution of COVID-19 across age and outcome was not independent (c2 =106.21, df = 32, P < 0.001). Conclusion: The knowledge of disease frequency patterns helps in the optimum allocation of limited resources and manpower. The study provides information to various epidemiological models for further analysis

A comparison of three data-poor stock assessment methods for the pink spiny lobster fishery in Mauritania

Several data-poor stock assessment methods have recently been proposed and applied to data-poor fisheries around the world. The Mauritanian pink spiny lobster fishery has a long history of boom and bust dynamics, with large landings, stock collapse, and years-long fishery closures, all happening several times. In this study, we have used catch, fishing efforts, and length-frequency data (LFD) obtained from the fishery in its most recent period of activity, 2015–2019, and historical annual catch records starting in 2006 to fit three data-poor stock assessment methods. These were the length-based Bayesian (LBB) method, which uses LFD exclusively, the Catch-only MSY (CMSY) method, using annual catch data and assumptions about stock resilience, and generalised depletion models in the R package CatDyn combined with Pella-Tomlinson biomass dynamics in a hierarchical inference framework. All threemethods presented the stock as overfished. The LBB method produced results that were very pessimistic about stock status but whose reliability was affected by non-constant recruitment. The CMSY method and the hierarchical combination of depletion and Pella-Tomlinson biomass dynamics produced more comparable results, such as similar sustainable harvest rates, but both were affected by large statistical uncertainty. Pella-Tomlinson dynamics in particular demonstrated stock experiencing wide fluctuations in abundance. In spite of uncertain estimates, a clear understanding of the status of the stock as overfished and in need of a biomass rebuilding program emerged as management-useful guidance to steer exploitation of this economically significant resource into sustainability.info:eu-repo/semantics/publishedVersio