Recursos de colección

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 - Comunicações em Conferências Internacionais

Mostrando recursos 1 - 20 de 40

  1. PDMS anatomical realistic models for hemodynamic studies using rapid prototyping technology

    Queijo, Luís; Lima, R.
    The main purpose of this work is to investigate a simple way of making polydimensiloxane (PDMS) anatomically artery models such as a carotid arteries with and without aneurysm. By using a human carotid computerized tomography (TC) it was possible to develop 3D anatomical models through the application of a rapid prototyping (RP) technique, known as tridimensional printing (TDP). By combining the TDP with a PDMS casting technique we were able to obtain at the end an anatomically transparent model of a human carotid artery made by a silicon elastomer, i.e. PDMS. We believe that this combination is a promising technique...

  2. Surgical training and post-surgery evaluation using rapid prototyped biomodels

    Queijo, Luís; Rocha, João; Pereira, Paulo Miguel; San Juan, Manuel
    The biomedical use of rapid prototyping technologies (RP) had great developments in the last years, especially as supportive tools for tissue growth, direct or supportive technology for implant fabrication or as tool for personalized biomodels production applied to studies, this research will focus on this last type of usage in continuation of previous work developed with RP as an aid of surgery procedures. Biomodels can play an important role as a complementary diagnostic method to medical staff (Queijo et al., 2010). The usage of RP technologies for biomodels production, in Lytic Spondylolisthesis surgical training and as a tool for post-surgery...

  3. Microscale flow dynamics of red blood cells in a circular microchannel

    Lima, R.; Nakamura, M.; Ishikawa, Takuji; Tanaka, S.; Takeda, Motohiro; Imai, Yohsuke; Tsubota, Ken-ichi; Wada, Shigeo; Yamaguchi, Takami
    The blood flow dynamics in microcirculation depends strongly on the motion, deformation and interaction of RBCs within the microvessel. This paper presents the application of a confocal micro-PTV system to track RBCs through a circular polydimethysiloxane (PDMS) microchannel. This technique, consists of a spinning disk confocal microscope, high speed camera and a diode-pumped solid state (DPSS) laser combined with a single particle tracking (SPT) method. By using this system detailed motions of individual RBCs were measured at a microscale level. Our results showed that this technique can provide detailed information about microscale disturbance effects caused by RBCs in flowing blood.

  4. The contour method for residual stress determination applied to an AA6082-T6 friction stir butt weld

    Richter-Trummer, V.; Moreira, P.; Ribeiro, J.E.; Castro, P.T.
    Residual stresses parallel to the welding direction on a cross-section of a 3 mm thick friction stir butt-welded aluminium alloy AA6082-T6 plate were determined using the contour method. This is a destructive relaxation based measurement technique capable of determining the full- eld residual stresses perpendicular to a plane of interest. A wire electro discharge machining cut was performed revealing the plane of interest. The residual stresses present before the straight cut lead to a deformed cutting plane. Then, a coordinate measuring machine was used to acquire the cutting plane shape of both plate halves after the cut. A data reduction scheme...

  5. Use of optical techniques in the assment of the displacement field near the crack tip

    Ribeiro, J.E.; Vaz, M.A.P.; Lopes, H.; Melo, F.J.M.Q. de; Monteiro, Jaime
    A crack tip represents a highly singular stress field existing in a structural component. The evaluation of the associate strain gradient is difficult using experimental discrete methods. An efficient alternative relies on optical methods which are non contact and give continuous information about displacements fields and its derivatives for strain evaluation. This paper describes some experimental methods to fully characterize the displacement field near a crack tip existing in flat plates. Three optical field techniques based on image analysis were used in the present work; respectively ESPI (Electronic speckle pattern interferometry), MI (Moiré Interferometry), and DIC (digital image correlation). These methods...

  6. Red blood cells motion in a glass microchannel

    Pinho, Diana; Pereira, Ana I.; Lima, R.
    The motion of the red blood cells (RBCs) flowing in microvessels and microchannels depend on several effects, such as hematocrit (Hct), geometry, and temperature. According to our knowledge, the effect of the temperature on RBC motion was never investigated at a microscale level. Hence, the aim of the present work is to determine the effect of the temperature on the RBC’s trajectories and to investigate the best approximation of the trajectories through a nonlinear optimization. In vitro human blood was pumped through a 100 mm circular microchannel and by using a confocal micro- PTV system the RBC’s trajectories were measured at different temperatures, i.e., 25◦C...

  7. Flow of physiological fluids in microchannels: the sedimentation effect

    Garcia, Valdemar; Correia, Teresa Montenegro; Dias, Ricardo P.; Lima, R.
    Microfluidic devices are becoming one of the most promising new tools for diagnostic applications and treatment of several chronic diseases. Hence, it is increasingly important to investigate the rheological behaviour of physiological fluids in microchannels. The main purpose of the present experimental work is to investigate the flow of two different physiological fluids frequently used in microfluidic devices. The working fluids were physiological saline (PS) and dextran 40 (Dx40) containing about 6% of sheep red blood cells (RBCs), respectively. The capillaries were placed horizontally on a slide glass and the flow rate of the working fluids was kept constant by using a syringe pump. By means of a camera the images were...

  8. Flow behaviour of labeled red blood cells in microchannels : a confocal micro-PTV assessment

    Lima, R.
    The development of optical experimental techniques has contributed to obtain explanations on the blood flow behaviour through microvessels. Although the past results have been valuable, detailed studies on the flow properties of blood in the microcirculation have been limited by several technical factors such as poor spatial resolution and difficulty to obtain quantitative detailed measurements at such small scales. In recent years, due to advances in computers, optics, and digital image processing techniques, it has become possible to combine particle tracking methods with confocal microscopes. As a result, this combination has greatly increased the resolution of the conventional PIV systems and consequently provided additional detailed description on the blood cells motion not...

  9. Mixing of red blood cells in a micro-channel flow under high hematocrit conditions

    Ishikawa, Takuji; Lima, R.; Fujiwara, Hiroki; Imai, Yohsuke; Matsuki, Noriaki; Yamaguchi, Takami

  10. Dispersion of red blood cells in microchannels : a confocal micro-PTV assessment

    Lima, R.; Ishikawa, Takuji; Imai, Yohsuke; Fujiwara, Hiroki; Takeda, Motohiro; Matsuki, Noriaki; Wada, Shigeo; Yamaguchi, Takami
    Blood in large arteries may be treated as a homogenous fluid from a macroscopic prospective. However, in reality blood is a suspension of deformable cells in viscous fluid plasma. In microcirculation, which comprises the smallest arteries and veins, the flow behavior of individual blood cells and their interactions provide the microrheological basis of flow properties of blood at a macroscopic level. Hence, in microcirculation it is fundamental to study the flow behavior of blood at cellular level. Several studies on both individual and concentrated RBCs have already been performed in the past. However, all studies used conventional microscopes and also ghost cells to obtain visible trace RBCs through the microchannel. The...

  11. Measurement of erythrocyte motions in microchannels by using a confocal micro-PTV system

    Lima, R.; Ishikawa, Takuji; Takeda, Motohiro; Tanaka, S.; Imai, Yohsuke; Tsubota, Ken-ichi; Wada, Shigeo; Yamaguchi, Takami
    Detailed knowledge on the motion of individual red blood cells (RBCs) flowing in microchannels is essential to provide a better understanding on the blood rheological properties and disorders in microvessels. Several studies on both individual and concentrated RBCs have already been performed in the past. However, all studies used conventional microscopes and also ghost cells to obtain visible trace RBCs through the microchannel. Recently, considerable progress in the development of confocal microscopy and consequent advantages of this microscope over the conventional microscopes have led to a new technique known as confocal micro-PIV. This technique combines the conventional PIV system with a spinning disk confocal microscope (SDCM). Due to its outstanding spatial...

  12. Determination of blood cells motions and interactions by a confocal micro-PIV system

    Lima, R.; Ishikawa, Takuji; Imai, Yohsuke; Takeda, Motohiro; Wada, Shigeo; Yamaguchi, Takami
    The development of optical experimental techniques has contributed to obtain explanations on the way the blood flows through microvessels. Although the past results have been encouraging, detailed studies on the flow properties of blood in the microcirculation has been limited by several technical factors such as poor spatial resolution and difficulty to obtain quantitative detailed measurements at such small scales. In recent years, due to advances in computers, confocal microscopy, and digital image processing techniques, it has become possible to combine a micro-particle tracking velocimetry (PTV) system with a confocal microscope. The present study shows for the first time confocal micro-PTV measurements of the dynamic flow behaviour of red blood cells (RBCs) in concentrated suspensions. The measurements...

  13. The role of the hematocrit on the radial dispersion of red blood cells in glass capillaries

    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, they have used transparent suspensions of ghost red cells, which may have different physical properties than normal RBCs. In this study, we have used a new approach (confocal micro-PTV) to obtain direct and quantitative detailed descriptions of the flow behaviour of RBCs in concentrated suspensions of normal RBCs. The experiments were performed in 100 mm glass capillaries at Reynolds numbers (Re) of 0.005 and Hcts from 3 to 35%. Emphasis was devoted to the radial...

  14. Tracking red blood cells in a circular PDMS microchannel using a confocal micro-PIV system

    Lima, R.; Ishikawa, Takuji; Tanaka, S.; Takeda, Motohiro; Imai, Yohsuke; Tsubota, Ken-ichi; Wada, Shigeo; Yamaguchi, Takami
    The blood flow in microcirculation is characterized mainly by the flow of red blood cells (RBCs), which may be normal or pathological. This paper presents the application of a confocal micro-P1V system lo track RBCs through a circular polydimelhysiloxane (PDMS) microchannel. This technique, consists o!’ a spinning disk confocal microscope, high speed camera and a diode-pumped solid stale (DPSS) laser combined with a single particle tracking (SPT) software (Mtracki). To show the ability of this system detailed motions o!’ individual RBCs were measured at different haematocrits (Hct): 3%, 14% and 37%. Our results show clearly that this technique can provide...

  15. Blood cell motions and interactions in microchannels

    Lima, R.; Ishikawa, Takuji; Fujiwara, Hiroki; Takeda, Motohiro; Imai, Yohsuke; Tsubota, Ken-ichi; Wada, Shigeo; Yamaguchi, Takami
    Detailed knowledge on the motions and interactions of individual blood cells flowing in microchannels is essential to provide a better understanding on the blood rheological properties and disorders in microvessels. This paper presents the ability of a confocal micro-PTV system to track red blood cells (RBCs) through a 100 μm circular glass microchannel. The technique consists of a spinning disk confocal microscope, high speed camera and a diode-pumped solid state (DPSS) laser combined with a single particle tracking (SPT) software (MtrackJ). Detailed measurements on the motions of RBCs were measured at different haematocrits (Hct). Our results show clearly that this technique can provide detailed information about microscale disturbance...

  16. Velocity measurements of physiological flows in microchannels using a confocal micro-PIV system

    Lima, R.; Wada, Shigeo; Tsubota, Ken-ichi; Yamaguchi, Takami
    The detail measurements of velocity profiles of in vitro blood flow in micorchannels are fundamental for a better understanding on the biomechanics of the microcirculation. Despite the high amount of research in microcirculation, there is not yet any detailed experimental information about flow velocity profiles, RBCs deformability and aggregation in microvessels (diameter in the order of 100μm or less). These lack of knowledge is mainly due to the absence of adequate techniques to measure and quantitatively evaluate fluid mechanical effects at a microscopic level [1, 2]. During the years the most research work in this area has focused in experimental studies using techniques such as laser Doppler anemometry (LDA) or conventional particle...

  17. Confocal micro-PIV measurements of blood flow in microchannels

    Lima, R.; Wada, Shigeo; Tsubota, Ken-ichi; Yamaguchi, Takami
    The detail measurements of velocity profiles of blood flow in microchannels are fundamental for a better understanding on the biomechanics of the microcirculation. It is therefore very important to obtain measurements with high accuracy and spatial resolution of the influence of the blood cells on the plasma flow behaviour. This paper presents and compares measurements of in vitro blood with different hematocrits within a square microchannel obtained by a confocal particle image velocimetry (PIV) system. This emerging technology by combining the conventional PIV system with a spinning confocal microscope has the ability to obtain not only high spatial resolution images but also three-dimensional (3D) optical sectioning velocity measurements. Velocity measurements...

  18. Velocity measurements of blood flow in a rectangular PDMS microchannel assessed by confocal micro-PIV system

    Lima, R.; Wada, Shigeo; Tanaka, S.; Takeda, Motohiro; Tsubota, Ken-ichi; Ishikawa, Takuji; Yamaguchi, Takami
    This paper examines the ability to measure the velocity of both physiological saline (PS) and in vitro blood in a rectangular polydimethysiloxane (PDMS) microchannel by means of the confocal micro-PIV system. The PDMS microchannel, was fabricated by conventional soft lithography, had a microchannel near to a perfect rectangular shape (300μm wide, 45μm deep) and was optically transparent, which is suitable to measure both PS and in vitro blood using the confocal system. By using this latter combination, the measurements of trace particles seeded in the flow were performed for both fluids at a constant flow rate (Re=0.021). Generally, all the velocity profiles were found to be markedly blunt in the central region...

  19. Rapid prototyping of 3D anatomical models to hemodynamic studies

    Freitas, Vania; Queijo, Luís; Lima, R.
    The purpose of this work is mainly to manufacture several anatomical models in a polymeric material – polydimensiloxane (PDMS) to study the blood flow through a carotid artery bifurcation. Over the last few decades, research has been shown that the geometry of the carotid artery is closely related to the development of serious cardiovascular diseases. Hence, there is a considerable interest in the development of in vitro experimental techniques able to obtain accurate measurements of the blood flow behavior through a realistic carotid artery. In this study we decide to apply rapid prototyping (RP) technologies combined with a PDMS casting technique in order to fabricate an anatomically...

  20. Analysis of velocity profiles of blood flow in microchannels using confocal micro-PIV and particle method

    Lima, R.; Wada, Shigeo; Tsubota, Ken-ichi; Yamaguchi, Takami
    The combination of computational and experimental investigations provides an excellent approach to understand complex phenomena involved at a microscopic level. This paper emphasizes a new experimental technique capable to quantify the flow patterns inside microchannels with high spatial and temporal resolution. This technique, known as confocal micro-PIV, consists of a spinning disk confocal microscope, high speed camera and a diodepumped solid state (DPSS) laser. Velocity profiles of physiological fluids were measured within different microchannels. The measured results agree reasonably well with the predicted analytical values. This new PIV system is a very promising technique to confirm the validity of the data obtained by numerical simulations, such as the...

Aviso de cookies: Usamos cookies propias y de terceros para mejorar nuestros servicios, para análisis estadístico y para mostrarle publicidad. Si continua navegando consideramos que acepta su uso en los términos establecidos en la Política de cookies.