Physically consistent simulation of transport of inertial particles in porous media

A new numerical approach is presented for simulating the movement of test particles suspended in an incompressible fluid flowing through a porous matrix. This two-phase particle-laden flow is based on the Navier-Stokes equations for incompressible fluid flow and equations of motion for the individual particles in which Stokes drag is dominant. The Immersed Boundary method is applied to incorporate the geometric complexity of the porous medium. A symmetry-preserving finite volume discretization method in combination with a volume penalization method resolves the flow within the porous material. The new Lagrangian particle tracking is such that for mass-less test particles no (numerical) collision with the coarsely represented porous medium occurs at any spatial resolution

Immersed boundary method predictions of shear stresses for different flow topologies occuring in cerebral aneurysms

A volume-penalizing immersed boundary method is presented that facilitates the computation of incompressible fluid flow in complex flow domains. We apply this method to simulate the flow in cerebral aneurysms, and focus on the accuracy with which the flow field and the corresponding shear stress field are computed. The method is applied to laminar, incompressible flow in curved cylindrical vessels and in a model aneurysm. The time-dependent shear stress distributions over the vessel walls are visualized and interpreted in terms of the flow fields that develop. We compute shear stress levels at two different Reynolds numbers, corresponding to a steady and an unsteady flow. In the latter situation strong fluctuations in the shear stress are observed, that may be connected to raised risk-levels of aneurysm rupture

Diretrizes para implantação de gestão ambiental nas unidades da Embrapa.

Sistema de gestão ambiental - Uma proposta corporativa para a Embrapa; Educação ambiental dos empregados; Gerenciamento de resíduos de laboratórios; Gerenciamento de resíduos de campos experimentais; Gerenciamento de resíduos em geral e otimização do uso da água e energia; Adequação das fazendas experimentais da Embrapa à legislação ambiental. Autores: Edmar das Mercês Penha, CTAA; Juarez Barbosa Tomé Júnior, DPD; Kelly de Oliveira Cohen, CPAC; Maria Augusta Doetzer Rosot, CNPF; Marilice Cordeiro Garrastazú, CNPF; Ricardo de Oliveira Encarnação, DRM; Rodiney de Arruda Mauro, CNPGC; Sandra de Angelis, CNPF; Valéria Sucena Hammes, CNPMA; Yeda Maria Malheiros de Oliveira, CNPF.bitstream/item/32966/1/Livro-Diretrizes.pd

Simulation of impaction filtration of aerosol droplets in porous media

We report on the development of a method to simulate from first principles the particle filtration efficiency of filters that are composed of structured porous media. We assume that the ratio of particle density to the fluid density is high. We concentrate on the motion of the particles in a laminar flow and quantify the role of inertial effects on the filtration of an ensemble of particles. We adopt the Euler-Lagrange approach, distinguishing a flow field in which the motion of a large number of discrete particles is simulated. We associate filtration with the deterministic collision of inertial particles with solid elements of the structured porous medium. To underpin the physical `consistency' of deterministic particle filtration, we investigate to what extent the particle tracking algorithm ensures that mass-less test-particles will not be captured by the structured porous filter at all. This element of the algorithm is essential in order to distinguish physical filtration by inertial effects from unwanted numerical filtration, due to the finite spatial resolution of the gas flow. We consider filtration of particles whose motion is governed by Stokes drag and determine the filtration efficiency in a range of Stokes relaxation times. An exponential decay of the number of particles with time is observed

Estimativas da Biomassa em Carbono do Fitoplâncton Autotrófico da Bacia do Espírito Santo Por Meio do Biovolume e Sua Relação Com Os Valores de Clorofila A

Este trabalho estudou a estimativa da biomassa em carbono do fitoplâncton autotrófico baseado no método do biovolume e sua relação com a clorofila a. Foram realizadas duas campanhas oceanográficas, uma no inverno (julho a agosto de 2013) e outra no verão (março a abril de 2014). Foram amostrados quatro transectos ao longo da costa do estado do Espírito Santo, as estações amostradas dentro de cada transecto foram organizados em oito isóbatas, as amostras foram coletadas em duas profundidades, tanto na região da plataforma continental como no talude. As amostras de plâncton foram coletadas utilizando-se a garrafa de Niskin, em seguida foram preservadas com formalina 0,4% e submetidas a sucessivos processos de sedimentação. Foram feitas contagem dos organismos em microscópio invertido com base no método de campos aleatórios, concomitante às contagens dos organismos, foram efetuadas as análises morfométricas para a avaliação do volume celular, que foram feitas de acordo com a forma geométrica que a alga se assemelhava. Para estimar a biomassa em carbono (pgC. cél-1) aplicou-se diferentes tipos de conversão do biovolume para biomassa em carbono. Os dados de clorofila a desta pesquisa pertencem ao Projeto AMBES e foram obtidos do Banco de Dados de Ambientes Costeiros e Oceânicos. Foram analisados a biomassa em carbono de 332 táxons no inverno e 304 no verão, os táxons incluíram representantes das Classes Bacillariophyceae, Coccolithophyceae, Coscinodiscophyceae, Cyanophyceae, Dinophyceae, Fragilariophyceae, entre outras Classes. A relação entre biomassa em carbono e biovolume mostrou ser significativa, entre os períodos, entre as profundidades e entre as regiões. A Classe Cyanophyceae apresentou baixo número de espécie, entretanto, apresentou um dos maiores valores em biomassa em carbono, representado principalmente pela cianobactéria do Gênero Trichodesmium. Na região da plataforma continental, Coscinodiscophyceae e Cyanophyceae mostraram em termos de biomassa os valores mais elevados, na região do talude e da subsuperfície as Classes de Cyanophyceae e Coccolithophyceae e na segunda profundidade foram Coscinodiscophyceae e Bacillariophyceae. Foi possível observar uma variação espacial e temporal da biomassa em carbono, os maiores valores de biomassa de carbono foram encontrados no verão, subsuperfície e plataforma continental. 8 A relação entre biomassa em carbono e clorofila a mostrou-se significativa, mas baixa. Foi possível observar relações significativas entre estes dois métodos de estimativa de biomassa, no entanto, com baixos valores de coeficiente de correlação, no inverno (0,36; r2:0,10), na plataforma continental no inverno (0,40; r2:0,22) e no talude no verão (0,57; r2:0,32). A grande diversidade de técnicas para estimar a biomassa do fitoplâncton, oferece uma grande variedade no grau de precisão dos dados, e as combinações de técnicas de estimava de biomassa podem ser a melhor proposta para evitar as limitações dos diferentes métodos. Estimativas da biomassa em carbono por meio do método do biovolume tem se mostrado eficiente é importantíssimo para estudos fisiológicos e ecológicos nos ambientes marinhos. Palavra-chave: Carbono orgânico. Espírito Santo. Fitoplâncton marinho. Relação de métodos. Variação espacial e temporal

An immersed boundary method for computing heat and fluid flow in porous media

A volume-penalizing immersed boundary (IB) method is presented that facilitates the computation of fluid flow in complex porous media. The computational domain is composed of a uniform Cartesian grid, and solid bodies are approximated on this grid using a series of grid cells (i.e., a ''staircase'' approximation). Solid bodies are distinguished from fluid regions using a binary phase-indicator function: Taking the value of ''1'' in the solid parts of the domain and ''0'' in the fluid parts. The effect of solid bodies on the flow is modeled using a source term in the momentum equations. The source term is active only within solid parts of the domain, and enforces the no-slip boundary condition. Fluid regions are governed by the incompressible Navier-Stokes equations. An extension of the IB method is proposed to tackle coupled fluid-solid heat transfer. The extended IB method is validated for Poiseuille flow, which allows for a direct comparison of the numerical results against a closed analytical solution. We subsequently apply the extended IB method to flow in a structured porous medium and focus on bulk properties such as the gradient of the average pressure and the Nusselt number. Reliable qualitative results were obtained with 16-32 grid points per singly-connected fluid region

Proteomic analysis of cytosolic proteins associated with petite mutations in Candida glabrata

The incidence of superficial or deep-seated infections due to Candida glabrata has increased markedly, probably because of the low intrinsic susceptibility of this microorganism to azole antifungals and its relatively high propensity to acquire azole resistance. To determine changes in the C. glabrata proteome associated with petite mutations, cytosolic extracts from an azole-resistant petite mutant of C. glabrata induced by exposure to ethidium bromide, and from its azole-susceptible parent isolate were compared by two-dimensional polyacrylamide gel electrophoresis. Proteins of interest were identified by peptide mass fingerprinting or sequence tagging using a matrix-assisted laser desorption/ionization tandem time-of-flight mass spectrometer. Tryptic peptides from a total of 160 Coomassie-positive spots were analyzed for each strain. Sixty-five different proteins were identified in the cytosolic extracts of the parent strain and 58 in the petite mutant. Among the proteins identified, 10 were higher in the mutant strain, whereas 23 were lower compared to the parent strain. The results revealed a significant decrease in the enzymes associated with the metabolic rate of mutant cells such as aconitase, transaldolase, and pyruvate kinase, and changes in the levels of specific heat shock proteins. Moreover, transketolase, aconitase and catalase activity measurements decreased significantly in the ethidium bromide-induced petite mutant. These data may be useful for designing experiments to obtain a better understanding of the nuclear response to impairment of mitochondrial function associated with this mutation in C. glabrata