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‣ Investigação do desempenho de diferentes estruturas microporosas tubulares na retenção de bactérias em suspensão por microfiltração tangencial; Investigation of the performance of diferent micro-porous tubular structures in the retention of bacteria emulsion by crossflow microfiltration

Haneda, Renata Natsumi
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 29/03/2006 Português
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Neste trabalho são apresentados resultados experimentais do processo de filtração tangencial de uma suspensão in natura (soro de leite) aplicada na retenção de bactérias do grupo coliforme. No estudo do processo de separação utilizaram-se tubos microporosos de -alumina (Al2O3) e membranas comerciais de tamanho médio de poros no valor de 0,8 e 1,2m. Os tubos microporosos cerâmicos foram sinterizados à temperatura entre 1400 e 1450ºC, os quais foram caracterizados pela técnica de porosimetria por intrusão de mercúrio, constatando o tamanho médio de poros de 0,3 a 0,5µm. Após a sinterização, os tubos cerâmicos foram sujeitos à impregnação com citrato de prata (material bactericida). As membranas comerciais também passaram pelo mesmo processo de impregnação. Com o uso da técnica de microscopia eletrônica de varredura (MEV) foi realizada uma caracterização da morfologia e da composição dos meios microporosos. Ensaios experimentais do processo de microfiltração foram realizados com soro de leite, com o objetivo de estudar a influência de parâmetros fluidodinâmicos tais como: número de Reynolds e pressão transmembrana, além de analisar a retenção da bactéria, Escherichia coli, em regime de escoamento para Reynolds entre 2700 e 32000 e pressões transmembrana entre 1 e 4 bar. O permeado foi analisado seguindo normas da 20ª. Edição dos Métodos Padrões para Análise de Água e Esgoto...

‣ Porous bioactive composites from marine origin based in chitosan and hydroxylapatite particles

Malafaya, P. B.; Reis, R. L.
Fonte: Trans Tech Publications Publicador: Trans Tech Publications
Tipo: Artigo de Revista Científica
Publicado em //2003 Português
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An optimal carrier for bone tissue engineering should be both a controlled release system and a scaffold. In the former role, the carrier must prevent rapid factor clearance and ideally meter out the growth factor in a predictable manner, allowing therapeutic doses to stimulate target cells for the appropriate duration. In the latter role, the material should act as a permissive environment into which bone cells would be attracted to migrate and begin the process of depositing bone matrix. Therefore the direct incorporation of growth factor in porous scaffolds should be a desirable goal. The inclusion of a bioactive ceramic on the scaffold design will confer to the systems a bone bonding behaviour that will guide bone formation. This work reports the development of composite chitosan/HA (from algal origin) porous structures produced by means of freeze-drying processing routes that can be further loaded with a biologically active agent. The developed bioactive 3D structures (completely from marine origin) have potential application as tissue engineering scaffolds and drug delivery systems due to their morphological and bioactive properties.

‣ Similitude criteria for fluid flow in macro-porous materials

Allori, Davide; Bartoli, Gianni; Miguel, Antonio F.
Fonte: Universidade de Évora Publicador: Universidade de Évora
Tipo: Artigo de Revista Científica
Português
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In the present paper, the problem of a suitable modelling of porous elements at the wind tunnel scale is addressed. This works involves an experimental study based on macro-porous materials, performed on perforated plates having holes with different geometry, thickness and sizes. The objective of this paper is double fold. At first, it aims at clarifying the effect of configuration of pores (holes) on fluid flow. Secondly, it aims to present a comprehensive similitude criterion for macro-porous structures based on physical insight.

‣ Simulation and characterization of multi-phase flow and particle transport in porous media

Serrenho, Ana; Aydin, Murat; Miguel, Antonio Ferreira
Fonte: BegellHouse,Inc Publicador: BegellHouse,Inc
Tipo: Artigo de Revista Científica
Português
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473.3844%
The study of multiphase flow through porous structures is of considerable importance in many fields of science and technology. This paper analyzes numerically low and medium Reynold snumber flows in a cavity filled with porous materials and with a stagnant zone. Simulations were carried out with both a single-phase and two-phase flows. The transport of solid particles through the porous structure is also analyzed. This study covers Reynolds numbers ranging from 0.1 to 10 and Peclet numbers ranging from 0.5 to 10^5.

‣ Some features of flow and particle transport in porous structures

Aydin, M; Balik, G; Miguel, A. F.; Reis, A
Fonte: SVJME Publicador: SVJME
Tipo: Artigo de Revista Científica
Português
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There has been a growing interest in the study of porous and complex flow structures due to its impact in technology. This concerns not only environmental but also diagnostic and therapeutic exposure in medical research. Physics of flow within porous structures is especially important to model transport and deposition of viruses, pollutants and drugs deep in these structures. In this work we analyze numerically low and medium Reynolds number flows in axisymmetric cylindrical duct surrounded by a torus. We also consider three different particle sizes (0.02, 0.1 and 20 micron) for possible physiological and environmental applications.

‣ Computational investigation of particle losses in random porous structures

Serrenho, A.; Miguel, A. F.; Reis, A.H.
Fonte: European Aerosol Conference Publicador: European Aerosol Conference
Tipo: Artigo de Revista Científica
Português
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This work studies the influence of random porous structures with different porosities on mixing of aerosol particle streams with clean gas streams. Two key quantities were used to characterize the process: particle losses (deposition) within the porous structure and residence time distribution of the particles.

‣ Particle transport and deposition in porous structures: effects of particle properties, porosity and Reynolds number

Kruz, S.; Pinela, J; Reis, A. H.; Miguel, A. F.; Aydin, M.
Fonte: Pacific Center of Thermal-Fluids Engineering Publicador: Pacific Center of Thermal-Fluids Engineering
Tipo: Artigo de Revista Científica
Português
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573.7908%
Since experiments are expensive and often difficult to perform reliable computational fluid dynamics (CFD) models save time and money when applied to transport and deposition of aerosol particles. In this work, we simulate particle transport and deposition in porous structures with different porosity. The resulting air-flow patterns as well as particle transport and deposition are analyzed for different inlet flows and particle with different properties (i.e., density and diameter). We compute particle trajectories and the deposition for different conditions. In addition, the loss of permeability due to deposition is evaluated.

‣ Some features of flow and particle transport in porous structures

Aydin, M.; Balik, G.; Miguel, A. F.; Reis, A. H.
Fonte: ASME - ZSIS Publicador: ASME - ZSIS
Tipo: Artigo de Revista Científica
Português
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684.7402%
There has been a growing interest in the study of porous and complex flow structures due to its impact in technology. This concerns not only environmental but also diagnostic and therapeutic exposure in medical research. Physics of flow within porous structures is especially important to model transport and deposition of viruses, pollutants and drugs deep in these structures. In this work we analyze numerically low and medium Reynolds number flows in axisymmetric cylindrical duct surrounded by a torus. We also consider different particle sizes for possible physiological and environmental applications.

‣ Simulation and Characterization of Multi‐Phase Flow and Particle Transport in Porous Media

Serrenho, A.; Aydin, M.; Miguel, A. F.
Fonte: 5th International Conference on Diffusion in Solids and Liquids Publicador: 5th International Conference on Diffusion in Solids and Liquids
Tipo: Aula
Português
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480.12367%
The study of multi‐phase flow through porous structures is of considerable importance in many fields of science and technology. Examples include fields such as biotechnology, environmental sciences, engineering, etc. The study of these flow structures will help to understand more about filters, oil recovery, and even lab‐on‐chip applications. This paper analyzes numerically low and medium Reynolds number flows in a porous structure with a stagnant zone. Simulations were carried out with a single‐liquid phase and two‐liquid phases flow. We analyze also solid particle transport and deposition within the porous structure influenced by particle dimension.

‣ Fluid flow through macro-porous materials: friction coefficient and wind tunnel similitude criteria

Allori, D.; Bartoli, G.; Miguel, A. F.
Fonte: Begell House Inc Publicador: Begell House Inc
Tipo: Artigo de Revista Científica
Português
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470.82688%
This work reports the study of airflow fluid through macro-porous materials. Several perforated plates having holes with different geometry, thickness and size were tested in a wind tunnel. The objective of this paper is double fold. At first, it aims at clarifying the effect of configuration of pores (holes) on fluid flow. Friction resistance and drag coefficients are obtained. Secondly, it has the purpose to present a comprehensive similitude criterion for macro-porous structures based on physical insight.

‣ Development of biocompatible and “smart” porous structures using CO2-assisted processes

Temtem, Márcio Milton Nunes
Fonte: FCT - UNL Publicador: FCT - UNL
Tipo: Tese de Doutorado
Publicado em //2009 Português
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Dissertação apresentada para a obtenção do grau de Doutor em Engenharia Química, especialidade Engenharia da Reacção Química, pela Universidade Nova de Lisboa, Faculdade de Ciências e Tecnologia; Over the past three decades the use of supercritical carbon dioxide (scCO2) has received much attention as a green alternative in the synthesis and processing of polymers. The scope of this thesis is the development of biocompatible and “smart” porous structures using CO2-assisted processes. This thesis is organized in four main chapters. The first one reviews and highlights some potentialities of supercritical fluid technology and the following ones compile the experimental work developed. The work is divided in three main parts: in the first part (2nd chapter) a CO2-assisted phase inversion method was developed in order to prepare porous structures, namely membranes. In the second part (3rd chapter) the focus was the synthesis of “smart” polymers,especially thermo and pH sensitive polymers. Finally, these two areas were combined (4th chapter) for the preparation of “smart” porous structures. The common guide line was the preparation or processing of biodegradable and/or biocompatible materials with special emphasis on the preparation of porous matrices...

‣ Manufacturing of metallic porous structures to be used in capillary pumping systems

Reimbrecht,Eduardo Gonçalves; Bazzo,Edson; Almeida,Luis Henrique Seabra; Silva,Henrique Cislagui; Binder,Cristiano; Muzart,Joel Louis Rene
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2003 Português
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Sintered metallic porous structures have an application as capillary structures in two-phase heat transfer loops. In this work the manufacturing procedure of tubular porous structures for capillary pump application is discussed. The application of porous structures on capillary pumping systems requires porosity higher than 40% and pore size diameter lower than 20 µm. Carbonyl nickel powder with particle diameter between 3 and 7 µm and stainless steel AISI316L powder with particle diameter between 1 and 22 µm were used as raw material. Sintering under hydrogen atmosphere was performed both in a resistive furnace and in a plasma reactor. Temperature and time were the modified parameters to obtain suitable porosity and roundness on the samples. The porosity was measured using the Arquimedes Principle (MPIF-42), the roundness was evaluated using a simplified measurement technique of the sample diameter and the pore size distribution was determined by image analysis techniques. Images obtained by Scanning Electronic Microscopy were employed on the image analysis. The sintering parameters selected to manufacture nickel samples were 700 °C and 30 min resulting in a porosity of about 44%. The sintering parameters selected to manufacture stainless steel samples were 1000 °C and 30 min resulting in a porosity of about 40%.

‣ Polymer-Lipid Microbubbles for Biosensing and the Formation of Porous Structures

Hettiarachchi, Kanaka; Lee, Abraham P.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Português
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Polymer-lipid microbubbles (PLBs) are generated by microfluidic flow-focusing devices to form a new class of long-lasting hybrid particles. The specific PLB construct developed is an elastic gas-filled microsphere with a polydimethylsiloxane (PDMS) shell containing phospholipids conjugated to functionalized polyethyleneglycol (PEG). Digital “droplet-based” microfluidics technology enables control of particle composition, size, and polydispersity (σ < 10%). Use of PDMS as a shell component improves the functionality and stability (lifetime > 6 months) of the hybrid particles due to the thermally maneuverable solidification process. With a gas core, they serve as a template material for creating three-dimensional porous structures and surfaces, requiring no cumbersome post-processing removal steps. By adding biotinylated PEG-lipid derivatives that offer targeting capabilities, we demonstrate the immobilization of fluorescent IgG antibodies on stationary PDMS-lipid microbubbles through biotinavidin interactions and on-chip trapping for immunoassays. A PDMS-lipid composition offers several advantages such as biocompatibility and biodegradability for future in-vivo use as porous engineered scaffolds, packing materials, or delivery (i.e. therapeutic) agents with cell targeting capability.

‣ In Situ Porous Structures: A Unique Polymer Erosion Mechanism in Biodegradable Dipeptide-based Polyphosphazene and Polyester Blends Producing Matrices for Regenerative Engineering

Deng, Meng; Nair, Lakshmi S.; Nukavarapu, Syam P.; Kumbar, Sangamesh G.; Jiang, Tao; Weikel, Arlin L.; Krogman, Nicholas R.; Allcock, Harry R.; Laurencin, Cato T.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 09/09/2010 Português
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Synthetic biodegradable polymers serve as temporary substrates that accommodate cell infiltration and tissue in-growth in regenerative medicine. To allow tissue in-growth and nutrient transport, traditional three-dimensional (3D) scaffolds must be prefabricated with an interconnected porous structure. Here we demonstrated for the first time a unique polymer erosion process through which polymer matrices evolve from a solid coherent film to an assemblage of microspheres with an interconnected 3D porous structure. This polymer system was developed on the highly versatile platform of polyphosphazene-polyester blends. Co-substituting a polyphosphazene backbone with both hydrophilic glycylglycine dipeptide and hydrophobic 4-phenylphenoxy group generated a polymer with strong hydrogen bonding capacity. Rapid hydrolysis of the polyester component permitted the formation of 3D void space filled with self-assembled polyphosphazene spheres. Characterization of such self-assembled porous structures revealed macropores (10-100 μm) between spheres as well as micro- and nanopores on the sphere surface. A similar degradation pattern was confirmed in vivo using a rat subcutaneous implantation model. 12 weeks of implantation resulted in an interconnected porous structure with 82-87% porosity. Cell infiltration and collagen tissue in-growth between microspheres observed by histology confirmed the formation of an in situ 3D interconnected porous structure. It was determined that the in situ porous structure resulted from unique hydrogen bonding in the blend promoting a three-stage degradation mechanism. The robust tissue in-growth of this dynamic pore forming scaffold attests to the utility of this system as a new strategy in regenerative medicine for developing solid matrices that balance degradation with tissue formation.

‣ Estudo da microestrutura e propriedades mecânicas de estruturas porosas de Ti-6Al-4V produzidas por sinterização seletiva a laser; Study of microstructure and mechanical properties of Ti-6Al-4V porous parts produced by selective laser sintering

Edwin Sallica Leva
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 04/07/2012 Português
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Peças fabricadas em titânio com estrutura porosa apresentam vantagens como material para implantes basicamente pela redução do módulo de elasticidade, o que aproxima sua rigidez à de tecidos ósseos, tornando-as mais adequadas á sua função. Neste trabalho apresenta-se um estudo da microestrutura e propriedades mecânicas de peças porosas de Ti-6Al-4V fabricadas por sinterização seletiva a laser, que é uma das técnicas de prototipagem rápida, que consolida, camada a camada, peças com geometria complexa a partir de pó. As estruturas porosas foram modeladas em programa CAD e fabricadas em um equipamento EOSINT M 270. Os modelos computacionais têm forma cúbica com 15 mm de aresta e possuem arquitetura interna de poros interconectados também de forma cúbica. A porcentagem de porosidade foi variada na faixa de 61 a 76%, mudando-se o número e o tamanho dos poros e a espessura das paredes internas. Pó atomizado da liga Ti-6Al-4V foi utilizado como matéria-prima. Utilizaram-se dois níveis de energia fornecida, variando-se alguns parâmetros do processo, como a velocidade de varredura do feixe de laser, a potência do laser e distância entre linhas de sinterização. As amostras sinterizadas foram caracterizadas por microscopia óptica e eletrônica de varredura...

‣ Compaction through Buckling in 2D Periodic, Soft and Porous Structures: Effect of Pore Shape

Overvelde, Johannes Tesse Bastiaan; Shan, Sicong; Bertoldi, Katia
Fonte: Wiley Blackwell Publicador: Wiley Blackwell
Tipo: Artigo de Revista Científica
Português
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Soft cellular structures that comprise a solid matrix with a square array of holes open avenues for the design of novel soft and foldable structures. Our results demonstrate that by simply changing the shape of the holes the response of porous structure can be easily tuned and soft structures with optimal compaction can be designed.; Engineering and Applied Sciences

‣ Heat Removal from Bipolar Transistor by Loop Heat Pipe with Nickel and Copper Porous Structures

Nemec, Patrik; Smitka, Martin; Malcho, Milan
Fonte: Hindawi Publishing Corporation Publicador: Hindawi Publishing Corporation
Tipo: Artigo de Revista Científica
Português
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Loop heat pipes (LHPs) are used in many branches of industry, mainly for cooling of electrical elements and systems. The loop heat pipe is a vapour-liquid phase-change device that transfers heat from evaporator to condenser. One of the most important parts of the LHP is the porous wick structure. The wick structure provides capillary force to circulate the working fluid. To achieve good thermal performance of LHP, capillary wicks with high permeability and porosity and fine pore radius are expected. The aim of this work was to develop porous structures from copper and nickel powder with different grain sizes. For experiment copper powder with grain size of 50 and 100 μm and nickel powder with grain size of 10 and 25 μm were used. Analysis of these porous structures and LHP design are described in the paper. And the measurements' influences of porous structures in LHP on heat removal from the insulated gate bipolar transistor (IGBT) have been made.

‣ Porous crystal structures obtained from directionally solidified eutectic precursors

Larrea, A.; Orera, V. M.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artículo Formato: 10752 bytes; application/octet-stream
Português
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7 figures, 2 figures.; Interconnecting cage-like porous structures of several halide compounds were prepared by the selective leaching of one eutectic phase method. The binary eutectic precursors were prepared by directional solidification using the Bridgman crystal growth technique. Porous NaMgF3 (40% pore volume), CaF2 (57% pore volume) and BaF2 (43% pore volume) crystals were obtained after water leaching the NaF component of the directionally solidified NaF/NaMgF3, NaF/CaF2 and NaF/BaF2 eutectics with the appropriate entangled microstructure. The growth conditions for eutectic-coupled growth and the morphology of the eutectics have been determined. In the coupled growth regime, the size of the eutectic phases “λ” is fairly uniform and varies with the eutectic growth rate “v” as λ2v=constant, which allows us to control the pore size within the 0.5–10 μm range. The simplicity and versatility of the eutectic growth also allows us to fabricate highly aligned porous structures at relatively high production rates.; The authors are indebted to Ruben Gotor of the University of Zaragoza for his help during the crystal growth. The results were obtained under projects financed by the Spanish Government MAT2003-1182 and MAT2003-6085.; Peer reviewed

‣ Preparation and characterization of porous blocks of synthetic hydroxyapatite

Peón,E.; Fuentes,G.; Delgado,J. A.; Morejon,L.; Almirall,A.; García,R.
Fonte: Latin American applied research Publicador: Latin American applied research
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/10/2004 Português
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Porous structures were conformed by pressing and heating of hydroxyapatite powders. Samples were obtained in the form of blocks with 47 % porosity. An interval of pore sizes interconnected among 50-120 mm was obtained. The diametrile tensile stress of evaluated samples oscillated between 4 and 21 MPa, according to what has been reported for porous ceramics. The diffraction studies of x-ray of heated samples indicated an increase of hydroxyapatite crystallinity. The microstructure was studied by scanning electronic microscopy. Statistical techniques were employed to determine the certainty of the answer.

‣ The influence of the glycerin concentration on the porous structure of ferritic stainless steel obtained by anodization

Bervian,Alexander; Ludwig,Gustavo Alberto; Raquel Kunst,Sandra; Rossa Beltrami,Lílian Vanessa; Dewes Moura,Angela Beatrice; Malfatti,Célia de Fraga; Trindade Oliveira,Claudia
Fonte: DYNA Publicador: DYNA
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2015 Português
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Anodizing of ferritic stainless steel has been used for decoration purposes to obtain a barrier effect. The most commonly used electrolyte for this process is INCO (5M H2SO4 + 2,5M CrO3). INCO electrolyte with glycerin addition induces the formation of ordered porous structures, because glycerin reduces the electrolyte conductivity. Ferritic stainless steel was anodized in electrolyte composed by 2M H2SO4 with glycerin addition in different concentrations, without chromium oxide addition. It was observed that the addition of 90 v/v% glycerin promoted a reduction in the electrolyte conductivity, which caused an increase in the anodizing potential. The glycerin addition to the electrolyte diminished the oxide dissolution in the electrolytic solution, promoting the formation of an oxide with an ordered porous structure.