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Biblioteca Digital do IPB (53.442 recursos)

A Biblioteca Digital do IPB, tem por objectivo divulgar e permitir o livre acesso à produção científica produzida pela comunidade académica, promovendo a integração, partilha e a visibilidade da informação científica e garantindo a preservação da memória intelectual do Instituto Politécnico de Bragança.

DTM - Artigos em Revistas Internacionais

Mostrando recursos 1 - 15 de 15

  1. Human red blood cell behavior under homogeneous extensional flow in a hyperbolic-shaped microchannel

    Yaginuma, Tomoko; Oliveira, Mónica S.N.; Lima, R.; Ishikawa, Takuji; Yamaguchi, Takami
    It is well known that certain pathological conditions result in a decrease of red blood cells (RBCs) deformability and subsequently can significantly alter the blood flow in microcirculation, which may block capillaries and cause ischemia in the tissues. Microfluidic systems able to obtain reliable quantitative measurements of RBC deformability hold the key to understand and diagnose RBC related diseases. In this work, a microfluidic system composed of a microchannel with a hyperbolic-shaped contraction followed by a sudden expansion is presented. We provide a detailed quantitative description of the degree of deformation of human RBCs under a controlled homogeneous extensional flow field....

  2. Measurement of residual stresses with optical techniques

    Ribeiro, J.E.; Monteiro, Jaime; Vaz, M.A.P.; Lopes, H.; Piloto, P.A.G.
    The goal of this work was the development of other experimental techniques to measure residual stresses, as an alternative to the hole-drilling method with strain gauges. The proposed experimental techniques are based on the use of Moiré interferometry and in-plane electronic speckle pattern interferometry (ESPI). Both are field techniques allowing the assessment of in-plane displacements without contact and high resolution. Grating replication techniques were developed to record high-quality diffraction gratings onto the specimen's surfaces. An optical set-up of laser interferometry was developed to generate the master grating (virtual). An in-plane ESPI set-up was also designed and implemented to measure displacements...

  3. Caracterização do campo de deslocamentos em tecidos hiperelásticos

    Ribeiro, J.E.; Martins, Pedro; Monteiro, Jaime; Vaz, M.A.P.; Lopes, H.
    Neste trabalho pretende-se caracterizar, por um lado, o campo de deslocamentos em tecidos hiper-elásticos e, por outro, avaliar a aplicação da técnica de Correlação Digital de Imagem neste tipo de materiais. Para o efeito, implementou-se um ensaio de tracção de um tecido com propriedades mecânicas hiper-elásticas (tecidos da mucosa vaginal humana) e, recorrendo ao equipamento de Correlação Digital de Imagem, Aramis, da GOM, fez-se uma análise global do campo de deslocamentos ocorrido na superfície do provete.

  4. Estudo numérico e experimental do campo de deformações na interface osso-implante

    Ribeiro, J.E.; Lopes, H.; Vaz, M.A.P.; Xavier, José
    As ferramentas numéricas são actualmente utilizadas na simulação do comportamento mecânico de biomateriais. Para uma correcta análise é necessário o conhecimento das propriedades mecânicas destes materiais. As técnicas ópticas de medição de campo sem contacto estão bem adaptadas para a medição do comportamento global da estrutura. Os dados experimentais são utilizados na determinação das propriedades mecânicas e na validação das simulações numéricas. Neste trabalho pretende-se analisar o comportamento do tecido ósseo cortical de bovino na proximidade da interface com um implante metálico e sob a acção de diferentes carregamentos. O osso cortical é um material com uma estrutura altamente porosa, o que impede a medição rigorosa das deformações utilizando...

  5. Pollutant emissions from modern incinerators

    Lima, R.; Bachmann, R.
    Presently, emissions of dioxins are mainly from incinerators, domestic and industrial coal combustion, and traffic. However, the major public concern and research effort are associated with the emissions of organic micropollutants from waste incinerators. Therefore, this paper attempts to give a brief overview on the more recent research and development for the removal of dioxins and heavy metals from flue gas streams. Special attention is devoted to the origin and control of emissions from incinerators. From the study presented it is possible to conclude that flue gas cleaning systems in modern incinerators are very reliable in removing almost all polluting emissions from flue gas streams, however the fly...

  6. Axisymmetric PDMS (polydimethysiloxane) microchannels for in vitro haemodynamic studies

    Lima, R.; Oliveira, Mónica S.N.; Ishikawa, Takuji; Kaji, H.; Tanaka, S.; Nishizawa, Matsuhiko; Yamaguchi, Takami
    The current microdevices used for biomedical research are often manufactured using microelectromechanical systems (MEMS) technology. Although it is possible to fabricate precise and reproducible rectangular microchannels using soft lithography techniques, this kind of geometry may not reflect the actual physiology of the microcirculation. Here, we present a simple method to fabricate circular PDMS microchannels aiming to mimic in vivo microvascular environment and suitable for state-of-the-art microscale flow visualization techniques, such as confocal uPIV/PTV. By using a confocal uPTV system individual red blood cells (RBCs) were successfully tracked trough a 75 um circular PDMS microchannel. The results show that RBC lateral dispersion increases with the volume fraction of RBCs...

  7. Radial dispersion of red blood cells in blood flowing through glass capillaries: the role of hematocrit and geometry

    Lima, R.; Ishikawa, Takuji; Imai, Yohsuke; Takeda, Motohiro; Wada, Shigeo; Yamaguchi, Takami
    The flow properties of blood in the microcirculation depend strongly on the hematocrit (Hct), microvessel geometry, and cell properties. Previous in vitro studies have measured the radial displacement of red blood cells (RBCs) at concentrated suspensions using conventional microscopes. However, to measure the RBCs motion they used transparent suspensions of ghost red cells, which may have different physical properties than normal RBCs. The present study introduces a new approach (confocal micro-PTV) to measure the motion of labeled RBCs flowing in concentrated suspensions of normal RBCs. The ability of confocal systems to obtain thin infocus planes allowed us to measure the radial position of individual RBCs accurately...

  8. Measurement of individual red blood cell motions under high hematocrit conditions using a confocal micro-PTV system

    Lima, R.; Ishikawa, Takuji; Imai, Yohsuke; Takeda, Motohiro; Wada, Shigeo; Yamaguchi, Takami
    Developments in optical experimental techniques have helped in elucidating how blood flows through microvessels. Although initial developments were encouraging, studies on the flow properties of blood in microcirculation have been limited by several technical factors, such as poor spatial resolution and difficulty obtaining quantitative detailed measurements at such small scales. Recent advances in computing, microscopy, and digital image processing techniques have made it possible to combine a particle tracking velocimetry (PTV) system with a confocal microscope. We document the development of a confocal micro-PTV measurement system for capturing the dynamic flow behavior of red blood cells (RBCs) in concentrated suspensions. Measurements were performed at several depths through...

  9. A particle method for blood flow simulation: application to flowing red blood cells and platelets

    Tsubota, Ken-ichi; Wada, Shigeo; Kamada, H.; Kitagawa, Y.; Lima, R.; Yamaguchi, Takami
    A new computer simulation using a particle method was proposed to analyze the microscopic behavior of blood flow. A simulation region, including plasma, red blood cells (RBCs) and platelets, was modeled by an assembly of discrete particles. The proposed method was applied to the motions and deformations of a single RBC and multiple RBCs, and the thrombogenesis caused by platelet aggregation. It is expected that, combined with a sophisticated large-scale computational technique, the simulation method will be useful for understanding the overall properties of blood flow from blood cellular level (microscopic) to the resulting rheological properties of blood as a mass (macroscopic).

  10. Red blood cell motions in high-hematocrit blood flowing through a stenosed microchannel

    Fujiwara, Hiroki; Ishikawa, Takuji; Lima, R.; Matsuki, Noriaki; Imai, Yohsuke; Kaji, H.; Nishizawa, Matsuhiko; Yamaguchi, Takami
    We investigated the behaviour of red blood cells (RBCs) in a micro-channel with stenosis by using a confocal micro-PIV system. We could successfully measure individual trajectories of RBCs in a concentrated suspension up to 20% hematocrit (Hct). The results show that the trajectories of healthy RBCs become asymmetric before and after the stenosis, though trajectories of tracer particles in pure water are almost symmetric. The asymmetry is larger in a 10% Hct case than in a 20% Hct case. We also investigated the effect of deformability of RBCs on the trajectories by hardening RBCs by glutarardehyde treatment. The results indicate that...

  11. Blackburn meadows wastewater treatment works

    Lima, R.; Bachmann, R.
    Blackbum Meadows wastewater treatment works is situated in Sheffield, the fourth largest city in England, in the county of South Yorkshire. This treatment plant has a fluidized bed incinerator in order to treat and dispose the sludge. This paper gives a brief overview of the various stages and processes involved in effluent treatment at Blackbum Meadows and assesses the sludge disposal operation.

  12. An effective thermal technology for the detoxification of the MSW fly ash

    Lima, R.; Saloca, M.
    The increasing public concern of potential health problems, due to improper waste disposal practices as well as the introduction of landfill taxes, have induced the practice of incineration. Presently, all UK incinerators have to meet very strict emission levels. In this way, the generated fly ash residues have to be managed very carefully as they are enriched with toxic organic micropollutants and heavy metals. The aim of the present work is to describe a novel thermal technology, known as the ash detoxification process, that has shown success not only in the destruction of its toxic organic components, but also in the fixation of...

  13. In vitro confocal micro-PIV measurements of blood flow in a square microchannel: the effect of the haematocrit on instantaneous velocity profiles

    Lima, R.; Wada, Shigeo; Takeda, Motohiro; Tsubota, Ken-ichi; Yamaguchi, Takami
    A confocal microparticle image velocimetry (micro-PIV) system was used to obtain detailed information on the velocity profiles for the flow of pure water (PW) and in vitro blood (haematocrit up to 17%) in a 100-μm-square microchannel. All the measurements were made in the middle plane of the microchannel at a constant flow rate and low Reynolds number (Re=0.025). The averaged ensemble velocity profiles were found to be markedly parabolic for all the working fluids studied. When comparing the instantaneous velocity profiles of the three fluids, our results indicated that the profile shape depended on the haematocrit. Our confocal micro-PIV measurements...

  14. In vitro blood flow in a rectangular PDMS microchannel: experimental observations using a confocal micro-PIV system

    Lima, R.; Wada, Shigeo; Tanaka, S.; Takeda, Motohiro; Ishikawa, Takuji; Tsubota, Ken-ichi; Imai, Yohsuke; Yamaguchi, Takami
    Progress in microfabricated technologies has attracted the attention of researchers in several areas, including microcirculation. Microfluidic devices are expected to provide powerful tools not only to better understand the biophysical behavior of blood flow in microvessels, but also for disease diagnosis. Such microfluidic devices for biomedical applications must be compatible with state-of-the-art flow measuring techniques, such as confocal microparticle image velocimetry (PIV). This confocal system has the ability to not only quantify flow patterns inside microchannels with high spatial and temporal resolution, but can also be used to obtain velocity measurements for several optically sectioned images along the depth of...

  15. Confocal micro-PIV measurements of three-dimensional profiles of cell suspension flow in a square microchannel

    Lima, R.; Wada, Shigeo; Tsubota, Ken-ichi; Yamaguchi, Takami
    A detailed measurement of the blood flow velocity profile in microchannels in vitro is fundamental to better understand the biomechanics of microcirculation. Therefore it is very important to determine the influence of suspended blood cells on the flow behaviour with high accuracy and spatial resolution. We measured the flow of blood cells suspended in a physiological fluid within a square microchannel using a confocal particle image velocimetry (PIV) system and compared it to pure water. This emerging technology combines a conventional PIV system with a spinning confocal microscope and has the ability to obtain high-resolution images and three-dimensional (3D) optical...

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