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Micro-PIV Measurement of Abnormal Cardiac Outflow in a Hypothermic Chicken Embryo
Eunseop Yeom(염은섭),Kweon-Ho Nam(남권호),Hojin Ha(하호진),Sang-Joon Lee(이상준) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
Blood in the outflow tract (OFT) of a chicken embryonic heart exhibits highly variable flow pattern depending on the change of heart shape during the variation of developmental stages and variation of environmental conditions. In this study, the pulsatile blood flow in the OFT of a chicken embryonic heart was investigated experimentally using a micro PIV technique. Microscopic images were consecutively captured from a chicken embryo at HH stage 17 (2.5 days of incubation) and stored for PIV analysis. Red blood cells (RBCs) were directly used as flow tracers. When the heart is exposed to room temperature, reflux occurs during the diastole. This results from the inharmonic heart movement under hypothermic condition and the undeveloped heart valve at this developmental stage. The peak velocity and heart rate are lower than those of normal embryonic heart. The comparative study on the blood flows in the OFT of a chicken embryonic heart for both normal and abnormal conditions would be helpful to understand the corresponding hemodynamic characteristics and develop a valveless biomimetic pump system.
Different adhesion behaviors of platelets depending on shear stress around stenotic channels
Springer-Verlag 2018 JOURNAL OF VISUALIZATION Vol.21 No.1
<P>Platelet adhesion, activation, and aggregation play important roles in pathological thrombosis and the progression of atherosclerosis. In our previous study, it was observed that the probability of platelet adhesion increased under high-hematocrit conditions. The present study aimed to investigate how the interactions between hemodynamic properties and platelet adhesion around stenosed channels varied according to the hematocrit level. After passing through the narrow stenotic channels with different stenotic widths (100, 50, and 10 mu m), the platelets were activated, and then these platelets were adhered on the downstream of the stenosis. Flow information, such as the velocity field and shear rate around the stenotic channels, was estimated by using particle image velocimetry (PIV) measurements and simulations. By using a Y-shaped device, the viscosity variations according to the shear rate could be measured for samples with different hematocrit levels (0, 30, and 50%). Based on the estimated flow and viscosity information, the distribution of shear stress around the stenotic channels was estimated. Due to the high shear stress in the 10-mu m-wide stenosis, significant adhesion of platelets with a 3D circulating motion was observed at the posterior end of the stenosis. In the 50-mu m-wide stenosis, the degree of platelet adhesion varied according to the hematocrit levels; the area of the adhered platelets increased as the hematocrit of the sample increased. Thus, in relatively high-viscosity conditions, frequent particle collision can contribute to the promotion of platelet activation and adhesion, even when the shear rate is relatively low. This study provides a better understanding of the effect of the hematocrit level on the adhesion of platelets after they pass through a stenosis.</P>