Maxwell-Stefan diffusion asymptotic for gas mixtures in non-isothermal setting

A mathematical model is proposed where the classical Maxwell-Stefan diffusion model for gas mixtures is coupled to an advection-type equation for the temperature of the physical system. This coupled system is derived from first principles in the sense that the starting point of our analysis is a system of Boltzmann equations for gaseous mixtures. We perform an asymptotic analysis on the Boltzmann model under diffuse scaling to arrive at the proposed coupled system.Comment: 14 page

The nonlinear diffusion limit for generalized Carleman models: the initial-boundary value problem

Consider the initial-boundary value problem for the 2-speed Carleman model of the Boltzmann equation of the kinetic theory of gases set in some bounded interval with boundary conditions prescribing the density of particles entering the interval. Under the usual parabolic scaling, a nonlinear diffusion limit is established for this problem. In fact, the techniques presented here allow treating generalizations of the Carleman system where the collision frequency is proportional to some power of the macroscopic density, with exponent in [-1,1]

Existence and uniqueness analysis of a non-isothermal cross-diffusion system of Maxwell-Stefan type

In this article we prove local-in-time existence and uniqueness of solution to a non-isothermal cross-diffusion system with Maxwell-Stefan structure.Comment: 6 page

Cellular mechanisms of arrhythmias: from rate-dependent APD variations to heterocellular coupling

It is well established that a variety of pathological conditions induces structural and electrical remodeling of the heart which can lead to heart failure and cardiac arrhythmias. Clinically, structural remodeling is characterized by changes in the shape, size and function of the heart. These changes are based on diverse and complex cellular reactions to injury and involve both cardiomyocytes and non-cardiomyocytes. Histopathologically, remodeling typically involves cardiomyocyte hypertrophy, activation and proliferation of fibroblast, increased extracellular matrix deposition and cell death. Functionally, structural remodeling induces mechanical dysfunction and is accompanied by an increased likelihood of occurrence of life-threatening cardiac arrhythmias (Adamson et al., 2005). The electrical remodeling is usually defined as changes related to ion channels, transporters, passive electrical properties, redistribution of the gap junctions and it involves disturbances of the initiation, conduction, and coordination of the electrical stimulus in the heart. An increase in temporal variability of repolarization has been found in different pathologies to follow the electrical remodeling of the heart. In the first part of my work I have studied heterocellular electrotonic interactions between myofibroblasts and cardiomyocytes, whereas in the second part I have focused on temporal variability of ventricular cardiomyocytes repolarization. In the appendix I have studied the mechanisms of a way to electrically elicit action potentials in single cells: “the anode break excitation”

Diagnóstico da conservação das tartarugas marinhas em ambiente escolar

Mestrado em Biologia Aplicada - Ecologia, Biodiversidade e Gestão de EcossistemasDevido à exploração dos recursos naturais pelo homem, espécies de animais e plantas sofrem a ameaça de extinção. O impacto humano sobre os habitats das tartarugas marinhas é reconhecido há décadas, sendo que todas as espécies estão catalogadas como “vulneráveis” ou “em perigo”. Uma das formas de sensibilizar a sociedade sobre a sua importância e riscos é através da informação sobre essas questões. A Educação Ambiental surgiu na década de 60 e na Conferência de Estocolmo foi apontada como uma das estratégias para a solução dos problemas ambientais e para a educação dos indivíduos. Para que a educação seja efetiva, é necessário que o professor relacione os conteúdos aprendidos com o cotidiano dos alunos, para que os mesmos pensem as suas atitudes junto aos problemas ambientais. Este trabalho tem por objetivo identificar e caracterizar através da utilização de inquéritos, a percepção dos alunos de duas escolas em Aveiro, quanto aos conceitos ambientais focando a Conservação das Tartarugas Marinhas. Com base no levantamento da percepção dos alunos, foi possível identificar a necessidade de sensibilizá-los sobre as questões ambientais, principalmente na conservação de animais marinhos, pois a maioria não possui conhecimento da importância de sua preservação. Os inquéritos aplicados foram considerados uma boa ferramenta na avaliação para diagnosticar a percepção ambiental dos alunos. Resultados obtidos no inquérito experimental mostram que em relação ao conhecimento sobre o meio ambiente alunos do 1º Ciclo obtivem um maior conhecimento sobre o assunto do que alunos do 3º Ciclo (inquérito inicial e final), entretanto no inquérito de controle alunos do 1º e 3º Ciclos obtiveram o mesmo nível de conhecimento sobre o mesmo tema. Em relação ao conhecimento sobre a biologia das tartarugas marinhas alunos do 1º e 3º Ciclos tanto no inquéritos experimetal e controle obtiveram o mesmo nível de conhecimento no inquérito inicial e um aumento significativo no inquérito final.Due to mankind’s exploitation of natural resources, animal and plant species face the threat of extinction. Human impact on sea turtle’s natural habitats has been acknowledged for decades, with all species listed as "vulnerable" or "endangered". A way to make society aware of the importance and the risks is through the spread of information on these issues. Environmental education emerged in the 60’s, and in the “Stockholm Conference”, it was named one of the strategies for solving environmental problems and to educate people. For education to be effective, it is imperative that teachers relate the content learned in the classroom to the students’ daily lives so that they can apply what they learn to real environmental issues. This research aims to identify and illustrate the awareness of students through the use of surveys, with a focus on environmental concepts regarding the Conservation of Sea Turtle from two schools in Aveiro. Based on the survey results on the students’ awareness, it was possible to identify the need to familiarize them on environmental issues, especially in the conservation of sea animals, as most student do not have knowledge of the importance of its preservation. The surveys used were considered a good tool in the assessment to diagnose students' environmental awareness. Results obtained in the survey experiment show that concerning the knowledge about the environment, students from the 1st cycle got a better understanding of the subject than students in the 3rd cycle (the original and final). However, in the survey control students of the 1st and 3rd cycles achieved the same level of knowledge on the same topic. Concerning the knowledge about the biology of sea turtles, students from the 1st and 3rd cycles in both surveys (experimental and control surveys) achieved the same level of knowledge in the original survey and a significant increase in the final survey

Opinion dynamics: kinetic modelling with mass media, application to the Scottish independence referendum

International audienceWe consider a kinetic model describing some mechanisms of opinion formation in the framework of referendums, by allowing that the individuals, who can interact between themselves and modify their opinion by means of spontaneous self-thinking, are moreover under the influence of mass media. After proving the main properties of the model, such as existence of solutions and conservation properties, we study, at the numerical level, both the transient and the asymptotic regimes. In particular, we point out that a plurality of media, with different orien-tations, is a key ingredient to allow pluralism and prevent consensus. The forecasts of the model are compared to some polls related to the Scottish independence referendum of 2014

Long time simulation of a beam in a periodic focusing channel via a two-scale PIC-method

We study the two-scale asymptotics for a charged beam under the action of a rapidly oscillating external electric field. After proving the convergence to the correct asymptotic state, we develop a numerical method for solving the limit model involving two time scales and validate its efficiency for the simulation of long time beam evolution

THE ROSSELAND LIMIT FOR RADIATIVE TRANSFER IN GRAY MATTER

This paper establishes the Rosseland approximation of the radiative transfer equations in a gray atmosphere, i.e. assuming that the opacity is independent of the radiation frequency