148 research outputs found
Tissue oxygen demand in regulation of the behavior of the cells in the vasculature.
No full textThe control of arteriolar diameters in microvasculature has been in the focus of studies on mechanisms matching oxygen demand and supply at the tissue level. Functionally, important vascular elements include endothelial cells (EC), vascular smooth muscle cells (VSMC) and red blood cells (RBC). Integration of these different cell types into functional units aimed at matching tissue oxygen supply with tissue oxygen demand is only achieved when all these cells can respond to the signals of tissue oxygen demand. Many vasoactive agents that serve as signals of tissue oxygen demand have their receptors on all these types of cells (VSMC, EC, and RBC) implying that there can be a coordinated regulation of their behavior by the tissue oxygen demand. Such functions of RBC as oxygen carrying by hemoglobin (Hb), rheology, and release of vasoactive agents are considered. Several common extra- and intracellular signaling pathways that link tissue oxygen demand with control of VSMC contractility, EC permeability, and RBC functioning are discussed
Static and dynamic analysis of articulated and continuous framed structures by the matrix displacement method
No full textDue to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Not availabl
Efficient disparity vector coding for multi-view 3-D displays
No full textDisparity estimation can be used for eliminating redundancies between different views of an object or a scene recorded by an array of cameras which are arranged both horizontally and vertically. However, estimation of the disparity vectors is a highly time consuming process which takes most of the operation time of the multi-view video coding. Therefore, either the amount of data that is to be processed or the complexity of the coding method needs to be decreased in order to encode the multi-view video in a reasonable time. It is proven that the disparities of a point in the scene photographed by cameras which are spaced equidistantly are equal. Since there is a strong geometrical correlation of the disparity vectors, the disparity vector of a view can for most blocks be derived from the disparity vector of another view or views. A new algorithm is presented that reduces the amount of processing time needed for calculating the disparity vectors of each neighboring view except the principal ones. Different schemes are proposed for 3*3 views and they are applied to several image sequences taken from a camera-array. The experimental results show that the proposed schemes yield better results than the reference scheme while preserving the image quality and the amount of encoded data
Effects of channel surface finish on blood flow in microfluidic devices
No full textThe behaviour of blood flow in relation to microchannel surface roughness has
been investigated. Special attention was focused on the techniques used to
fabricate the microchannels and on the apparent viscosity of the blood as it
flowed through these microchannels. For the experimental comparison of smooth
and rough surface channels, each channel was designed to be 10mm long and
rectangular in cross-section with aspect ratios of â ¥100:1 for channel heights of
50 and 100μm. Polycarbonate was used as the material for the device
construction. The shims, which created the heights of the channels, were made of
polyethylene terephthalate. Surface roughnesses of the channels were varied from
Rz of 60nm to 1.8μm. Whole horse blood and filtered water were used as the test
fluids and differential pressures ranged from 200 to 5000Pa. The defibrinated
horse blood was treated further to prevent coagulation. The results indicate
that a surface roughness above an unknown value lowers the apparent viscosity of
blood dramatically due to boundary effects. Furthermore, the roughness seemed to
influence both water and whole blood almost equally. A set of design rules for
channel fabrication is also presented in accordance with the experiments
performed
A content-adaptive scheme for reduced-complexity, multi-view video coding
No full textDisparity estimation is a highly complex and time consuming process in multi-view video encoders. Since multiple views taken from a 2D camerea array need to be coded at every time instance, the complexity of the encoder plays an important role besides its rate-distortion performance. In previous papers we have introduced a new frame type called D frame that exploits the stron geometrical correspondence between views, thereby reducing the complexity of the encoder. By employing D frames instead of some of the P frames in the prediction structure, significant compexity gain can be achieved if the trhreshold value which is a keystone element to adjust the complexity at the cost of quality and/or bit-rate is selected wisely. In this work, a new adaptive method to calculate the threshold value automatically from existing information during the encoding process is presented. In this method, the threshold values are generated for each block of each D frame to increase the accuracy. The algorithm is applied to several image sets and 20.6% complexity gain is achieved using the automatically generated threshold values without compromising qaulity or bit-rate
Effect of erythrocyte deformability on myocardial hematocrit gradient. Baskurt, O.K.; Edremitlioglu, M.; Temiz, A.
No full text
Prostanoids in the treatment of pulmonary arterial hypertension
No full textProstacyclin, endothelin-1, and nitric oxide pathways are involved in the pathogenesis of pulmonary arterial hypertension. This devastating disease of the pulmonary vasculature is associated with vasoconstriction, thrombosis and proliferation, and this may be partly due to lack of endogenous prostacyclin secondary to prostacyclin synthase downregulation. Prostanoids (prostacycin analogues) are potent vasodilators and possess antiaggregant, antiinflammatory and antiproliferative properties. The first agent to be approved for the treatment of pulmonary arterial hypertension was epoprostenol. In the last decade other prostanoids (treprostinil, iloprost) has been approved for the treatment of pulmonary arterial hypertension. (Anadolu Kardiyol Derg 2010; 10: Suppl 2; 2-8
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