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Wall shear stress (WSS) is an important stimulus in vascular remodelling and vascular lesion development. The current methods to assess and predict the risk associated with specific unsteady WSS consider the WSS mean values or the presence of reverse phases described by the oscillatory shear index. Recent evidence has shown that the accuracy of these methods is limited, especially with respect to the venous environment. Unsteady WSS are characterised by several features that may individually affect endothelial cells. Consequently, we assessed the effects of averaged WSS (TAWSS), temporal WSS gradient (TWSSG), maximum WSS (WSS peak) and reverse phase (OSI) by applying different WSS profiles to venous EC in-vitro, using a real-time controlled cone-and-plate cell-shearing device for 24 h. We found that TWSSG and WSS peak affect cell elongation and alignment respectively. We also found that the WSS waveforms with a peak of 1.5 Pa or higher significantly correlate with the induction of a protective phenotype. Cell phenotype induced by these high peak waveforms does not correlate to what is predicted by the hemodynamic indices currently used. The definition of reliable hemodynamic indices can be used to inform the computational models aimed at estimating the hemodynamic effects on vascular remodelling. [ABSTRACT FROM AUTHOR]

The implementation of biodegradable stents has the potential to revolutionize obstructive coronary artery disease treatment. Limitations still currently exist, however, that prevent biodegradable stents from replacing permanent metallic stents in the global market. The ideal combination of stent properties, including sufficient mechanical strength, controlled degradation, and biocompatibility, has yet to be realized. A novel manufacturing process is proposed that utilizes cold gas-dynamic spraying to fabricate a metal structure with significantly reduced grain size. Iron and stainless steel 316L are combined to form a novel amalgamate with enhanced mechanical strength and a controllable degradation rate, due to the resulting microgalvanic reaction. Flat specimens composed of iron and 316L are fabricated in various compositions, and mechanical and degradation tests were conducted. Femto laser techniques are utilized to produce stents composed of 80% Fe and 20% stainless steel 316L. The in vitro degradation behaviour of the stent is investigated using static and dynamic corrosion tests. It is shown that the corrosion rate can be adjusted to desired values, by varying the weight percentage of iron and stainless steel 316L within the amalgamate.

Local mass transfer coefficients and flow patterns were examined in an idealized human aortic bifurcation model. The objectives of this study are to gain further insights on the convective mass transfer process and its possible role in the localization of atherosclerotic lesions. The laser photochromic tracer method provided velocity and wall shear stress estimates in the plane of symmetry of a UV-transparent Plexiglas bifurcation model. Steady flow data were acquired at Reynolds numbers of 500, 600, and 750. A novel copper electrodeposition technique was used to obtain time-averaged convective local mass transfer coefficients in a model identical to that used in the flow experiments. The laminar flow mass transfer data for the trunk of the bifurcation are in good agreement with the analytical Levesque solution. At the bifurcation, higher mass transfer coefficients along the inner wall and lower ones along the outer wall were observed. Further, mass transfer and wall shear stress follow similar patterns both on the inner and outer walls in that StSc 2/3 and C(f)/2 demonstrate analogous behavior. Lower transfer rates of momentum and mass occurred along the outer wall of the branches where lesions tend to develop.