Both clinical and post mortem studies indicatethat,in humans,the carotid sinus of the carotid artery bifur-cation is one of the favored sites for the genesis and develop-ment of atherosclerotic lesions.Hemodynamic factors havebeen suggested to be important in atherogenesis.Tounderstand the correlation between atherogenesis and fluiddynamics in the carotid sinus,the blood flow in artery wassimulated numerically.In those studies,the property of bloodwas treated as an incompressible,Newtonian fluid.In fact,however,the blood is a complicated non-Newtonian fluidwith shear thinning and viscoelastic properties,especiallywhen the shear rate is low.A variety of non-Newtonian mod-els have been applied in the numerical studies.Among them,the Casson equation was widely used.However,the Cas-son equation agrees well only when the shear rate is lessthan 10s^(-1).The flow field of the carotid bifurcation usuallycovers a wide range of shear rate.We therefore believe thatit may not be sufficient to describe the property of bloodonly using the Casson equation in the whole flow field ofthe carotid bifurcation.In the present study,three differentblood constitutive models,namely,the Newtonian,the Cas-son and the hybrid fluid constitutive models were used in theflow simulation of the human carotid bifurcation.The resultswere compared among the three models.The results showedthat the Newtonian model and the hybrid model had very similar distributions of the axial velocity,secondary flow andwall shear stress,but the Casson model resulted in significantdifferences in these distributions from the other two mod-els.This study suggests that it is not appropriate to only usethe Casson equation to simulate the whole flow field of thecarotid bifurcation,and on the other hand,Newtonian fluidis a good approximation to blood for flow simulations in thecarotid artery bifurcation.
Yubo FanWentao JiangYuanwen ZouJinchuan LiJunkai ChenXiaoyan Deng
Osteoblasts were cultured on porous scaffolds of poly(L-lactide-co-glycolide) (PLGA) and PLGA/β-tricalcium phosphate (β-TCP) to evaluate their cytocompatibility.The proliferation of the cells on both scaffolds was examined before and after in vitro degradation for 4,8 and 12 weeks under static (shaking water bath) and dynamic (cyclic loading) conditions.Results indicate that porous PLGA and PLGA/β-TCP scaffolds have good biocompatibility and can be used as effective templates for guiding the growth of osteoblasts.The degradation of the scaffolds affects the proliferation of osteoblasts and the cell viability decreased with the degradation time.
YANG YanFangTANG GongWenZHAO YunHuiZHANG YangLI XiuLanYUAN XiaoYan
