Influence of reaction heat on time dependent processes in a chemically reacting binary mixture

In this paper we study time dependent problems, like the propagation of sound waves or the behavior of small local wave disturbances induced by spontaneous internal fluctuations, in a binary mixture undergoing a chemical reaction of type A+A= B+B. The study is developed at the hydrodynamic Euler level, in a chemical regime of fast reactive process in which the chemical reaction is close to its final equilibrium state. The hydrodynamic state of the mixture is described by the balance equations for the mass densities of both constituents A and B, together with the conservation laws for the momentum and total energy of the mixture. The progress of the chemical reaction is specified by an Arrhenius-type reaction rate which defines the net balance between production and consumption of each constituent. Assuming that the considered time dependent problems induce weak macroscopic deviations, the hydrodynamic equations are linearized through a normal mode expansion of the state variables around the equilibrium state. From the dispersion relation of the normal modes, we determine the free and forced phase velocities as well as the attenuation coefficients of the waves. We show that the dispersion and absorption of these waves depend explicitly on the heat of the chemical reaction, the concentrations of the constituents and the activation energy through the exponential factor of Arrhenius law.Fundação para a Ciência e a Tecnologia, Brazilian Research Council (CNPq

Spectral distribution of scattered light from a chemical relaxation system

The aim of this work is to describe the light scattering spectra of a quaternary reacting gas mixture from the macroscopic field equations derived from the kinetic BGK-type model proposed by the authors in a previous paper. The study is developed in a hydrodynamic regime for which the system of the field equations of constituent number densities, momentum and temperature of the mixture is closed by the constitutive equations for rate of reaction, diffusion velocities, pressure tensor and heat flux vector. The spontaneous Rayleigh-Brillouin scattering is calculated from the constituent density perturbations of the linearized field equations, and its line shape is drawn for two different mixtures of the Hydrogen-Chlorine system showing the induced chemical reaction effect.Brazilian Research Council (CNPq)Universidade do Minho. Centro de Matemática(CMat)Fundação para a Ciência e a Tecnologia (FCT) - FCT-PTDC/MAT/68615/2006Italian National Project GNFM 2009/1

A kinetic model for chemical reactions without barriers : transport coefficients and eigenmodes

The kinetic model of the Boltzmann equation proposed in the work of Kremer and Soares 2009 for a binary mixture undergoing chemical reactions of symmetric type which occur without activation energy is revisited here, with the aim of investigating in detail the transport properties of the reactive mixture and the influence of the reaction process on the transport coefficients. Accordingly, the non-equilibrium solution of the Boltzmann equation is determined through an expansion in Sonine polynomials up to the first order, using the Chapman-Enskog method, in a chemical regime for which the reaction process is close to its final equilibrium state. The non-equilibrium deviations are explicitly calculated for what concerns the thermal-diffusion ratio and coefficients of shear viscosity, diffusion and thermal conductivity. The theoretical and formal analysis developed in the present paper is complemented with some numerical simulations performed for different concentrations of reactants and products of the reaction as well as for both exothermic and endothermic chemical processes. The results reveal that chemical reactions without energy barrier can induce an appreciable influence on the transport properties of the mixture. Oppositely to the case of reactions with activation energy, the coefficients of shear viscosity and thermal conductivity become larger than those of an inert mixture when the reactions are exothermic. An application of the non-barrier model and its detailed transport picture is included in this paper, in order to investigate the dynamics of the local perturbations on the constituent number densities, and velocity and temperature of the whole mixture, induced by spontaneous internal fluctuations. It is shown that for the longitudinal disturbances there exist two hydrodynamic sound modes, one purely diffusive hydrodynamic mode and one kinetic mode.This paper is partially supported by the Brazilian Research Council (CNPq), by Minho University Mathematics Centre (CMAT-FCT) and by Project FCT-PTDC/MAT/68615/2006

Conservação e melhoramento dos recursos genéticos animais da Amazônia Brasileira.

Muitas espécies animais da Amazônia estão ameaçadas de extinção ou sofrem forte pressão de descaracterização. Isto ocorre com eqüinos como o cavalo Marajoara e Puruca (Equus caballus), búfalos como o Tipo Baía e a raça Carabao do Brasil (Bubalus bubalis) e com espécies nativas, como o Muçuã (Kinosternon scorpioides). A Amazônia é uma das áreas mais predadas do planeta e a devastação que vem ocorrendo, ainda hoje, contribuí para o empobrecimento da biodiversidade, além de interferir na adaptabilidade, desempenho e sobrevivência das espécies introduzidas. No permeio de espécies amazônicas importantes como o peixe-boi, o pirarucu, os jacarés, araras diversas ou de um inseto, que nem foi catalogado pelo homem, há animais de interesse zootécnico que podem desaparecer. Os eqüinos e os búfalos fazem parte dos recursos zoogenéticos do Brasil, na Rede Nacional de Recursos Genéticos - RENARGEN, coordenada pela Embrapa CENARGEN, juntamente com inúmeras raças naturafízadas que compõem o universo da pecuária brasileira, que é a mais diversificada de fado O planeta. Nesse contexto há peculiaridades genéticas importantes, como: o único mini cavalo do Brasil, o Puruca, com características tão próprias e importantes que o fazem enfrentar as adversidade climáticas e geográficas da maior ilha flúvio-marinha do mundo, o Marajó, que abriga em contexto semelhante um dos cavalos brasileiros mais importantes, o Marajoara, não só pela rusticidade, inteligência no adestramento, força e resistência natural, como pela importâncía genética, pois deve ter grande participação na origem de outros importantes grupamentos de eqüinos da região, ou seja: os cavalos Baixadeiro (Baixada maranhense) e o Lavradeiro (dos campos de Roraima), além do Varzeiro, que domina grande parte das áreas de várzeas de Itacoatiara (Amazonas) até Prainha (Pará); dentre os búfalos há um tipo que não é reconhecido como raça, o Baio, e outro que, apesar de constituir uma raça, ainda hoje presente em todo o Sudeste asiático (o Swamp buftalo), adquiriu características próprias das condições brasileiras. Ambos fazem parte do conjunto de raças naturalizadas em conservação no nosso País. Vale ressaltar que não há, em todo o Brasil, 300 animais Baios ou 500 Carabaos, enquadrando-se na classificação da FAO, como grupos em alto risco de extinção. Existe, ainda, uma tartaruguinha característica das áreas de campo, importante para a gastronomia regional que, se conhecida, pode adquirir também grande importância como animal ornamental. Estas foram as principais razões para a criação e implantação, pela Embrapa Amazônia Oriental, do Banco de Germoplasma Animal da Amazônia Oriental - BAGAM, em 1997, destinado à conservação "on ierm" de espécies animais da Amazônia de valor socioeconômico e biológico, que apresentam risco de extinção e/ou descerectetizeçêo. Com tais ações espera-se manter as populações ameaçadas num patamar seguro de conservação, municiando a comunidade científica e a classe produtora com informações sobre os genes mais produtivos, além de assegurar a manutenção da variabilidade genética, bem como estudar a biologia das espécies, possibilitando novos estudos e descobertas.ZOOTEC

The extravasation of contrast as a predictor of cerebral hemorrhagic contusion expansion, poor neurological outcome and mortality after traumatic brain injury: A systematic review and meta-analysis.

BACKGROUND: The active extravasation of contrast on CT angiography (CTA) in primary intracerebral hemorrhages (ICH) is recognized as a predictive factor for ICH expansion, unfavorable outcomes and mortality. However, few studies have been conducted on the setting of traumatic brain injury (TBI). PURPOSE: To perform a literature systematic review and meta-analysis of the association of contrast extravasation on cerebral hemorrhagic contusion expansion, neurological outcomes and mortality. DATA SOURCES: The PubMed, Cochrane Library, Medline, Scielo, VHL and IBECS databases up to September 21, 2019, were searched for eligible studies. STUDY SELECTION: A total of 505 individual titles and abstracts were identified and screened. A total of 36 were selected for full text analysis, out of which 4 fulfilled all inclusion and exclusion criteria. DATA ANALYSIS: All 4 studies yielded point estimates suggestive of higher risk for hematoma expansion with contrast extravasation and the summary RR was 5.75 (95%CI 2.74-10.47, p<0.001). Contrast extravasation was also associated with worse neurological outcomes (RR 3.25, 95%CI 2.24-4.73, p<0.001) and higher mortality (RR 2.77, 95%CI 1.03-7.47, p = 0.04). DATA SYNTHESIS: This study is a Systematic Review and Meta-Analysis revealed the extravasation of contrast is a useful imaging sign to predict hematoma expansion, worse neurological outcomes and higher mortality. LIMITATIONS: Only four articles were selected. CONCLUSIONS: The extravasation of contrast in the setting of TBI is a useful imaging sign to predict hematoma expansion, worse neurological outcomes and higher mortality

Avaliação da condutividade hidráulica saturada utilizando dois métodos de laboratório numa toposseqüência de solos amazônicos com diferentes coberturas vegetais.

O objetivo desse trabalho foi avaliar dois métodos de laboratório para a determinação da condutividade hidráulica do solo saturada (Ko) conhecidos como Permeâmetro de carga constante (CC) e Permeâmetro de carga decrescente (CD), com o intuito de verificar sua aplicabilidade e variabilidade em solos amazônicos