Homogenization results for chemical reactive flows through porous media

This paper deals with the homogenization of a nonlinear problem mod-elllng chemica! reactive flows through periodically perforated domains. The chemical reactions take place on the walls of the porous médium. The effective behavior of these reactive flows is described by a new elliptic boundary-value problem contalning an extra zero-order term which captures the effect of the chemical reactions

Movimiento de descarga de gases en conductos largos: modelizacion y estudio de una ecuacion parabolica doblemente no lineal

Movimiento de descarga de gases en conductos largos: modelizacion y estudio de una ecuacion parabolica doblemente no linea

On the asymptotic behavior of solutions of a damped oscillator under a sublinear friction term: from the exceptional to the generic behaviors

We show that there are two curves of initial data (xo, vo) for which the solutions x(t) of the corresponding Cauchy problem associated to the equation xtt + |xí|a_1 xt + x — 0, where a G (0,1), vanish after a finite time. By using asymptotic and methods and comparison arguments we show that for many other initial data the solutions decay to 0, in an infinite time, as i-"/í1-")

Ars Medicine

Me propusieron hablar sobre las relaciones entre arte y biología. Pensé en mis hijos, uno de ellos pediatra cardiólogo y otro licenciado en artes, para lo cual invertí varios domingos con ellos, y el domingo es sagrado para muchos, significa originariamente dies solis o día del sol, ha terminado siendo el dominicus dies o día del señor, para dedicar a escribir este ensayo en reciprocidad a uno de mis maestros, patólogo Ricardo Pineda Castrejón, mi amor filial teknon y el respeto al lector

Existence and uniqueness of solutions to the Boussinesq system with nonlinear thermal diffusion

The Boussinesq system arises in Fluid Mechanics when motion is governed by density gradients caused by temperature or concentration differences. In the former case, and when thermodynamical coefficients are regarded as temperature dependent, the system consists of the Navier-Stokes equations and the non linear heat equation coupled through the viscosity, bouyancy and convective terms. According to the balance between specific heat and thermal conductivity the diffusion term in the heat equation may lead to a singular or degenerate parabolic equation. In this paper we prove the existence of solutions of the general problem as well as the uniqueness of solutions when the spatial dimension is two

On a quasilinear degenerated system arising in semiconductors theory

A drift-diffusion model for semiconductors with nonlinear diffusion is considered. The model consists of two quasilinear degenerated parabolic equations for the carrier densities and the Poisson equation for the electric potential. We also assume Lipschitz continuous non linearities in the drift and {em generation-recombination terms. Existence of weak solutions is proven by using a regularization technique. Uniqueness of solutions is proven when either the diffusion term $varphi$ is strictly increasing and solutions have spatial derivatives in $L^1(Q_T)$ or when $varphi$ is non decreasing and a suitable entropy condition is fullfilled by the electric potential

First adequately-known quadrupedal sirenian from Eurasia (Eocene, Bay of Biscay, Huesca, northeastern Spain)

Sirenians are the only extant herbivorous mammals fully adapted to an aquatic lifestyle. They originated in Africa during the Paleocene from an undetermined clade of afrotherian mammals, and by the end of the Eocene they were widely distributed across the tropical latitudes. Here we introduce Sobrarbesiren cardieli gen. et sp. nov. It is the first adequately-known quadrupedal sirenian from Eurasia and the oldest record of this clade from western Europe. Fossils have been recovered from the middle Lutetian (SBZ15) site of Castejón de Sobrarbe-41 (Huesca, Spain), and comprise many cranial and postcranial remains, including pelvic girdle and hind limb bones, from at least six sirenian individuals of different ontogenetic stages. Sobrarbesiren shows a suite of characters previously considered synapomorphies of different clades of derived sirenians, such as the presence of the processus retroversus of the squamosal and the pterygoid fossa, combined with ancestral characters such as the presence of an alisphenoid canal, a permanent P5, at least two sacral vertebrae, a primitive pelvis and functional femora and fibulae. Sobrarbesiren is recovered as the sister taxon of Dugongidae and represents a transitional stage of adaptation to aquatic life between the amphibious quadrupedal prorastomids and the aquatic quadrupedal protosirenids

Influence of Polarity and Activation Energy in Microwave-Assisted Organic Synthesis (MAOS)

The aim of this work was to determine the parameters that have decisive roles in microwave-assisted reactions and to develop a model, using computational chemistry, to predict a priori the type of reactions that can be improved under microwaves. For this purpose, a computational study was carried out on a variety of reactions, which have been reported to be improved under microwave irradiation. This comprises six types of reactions. The outcomes obtained in this study indicate that the most influential parameters are activation energy, enthalpy, and the polarity of all the species that participate. In addition to this, in most cases, slower reacting systems observe a much greater improvement under microwave irradiation. Furthermore, for these reactions, the presence of a polar component in the reaction (solvent, reagent, susceptor, etc.) is necessary for strong coupling with the electromagnetic radiation. We also quantified that an activation energy of 20-30 kcal mol-1 and a polarity (µ) between 7-20 D of the species involved in the process is required to obtain significant improvements under microwave irradiation