Cerebral aneurysms develop near bifurcation apices, where complex hemodynamics occur: Flow impinges on the apex, accelerates into branches, then slows again distally, creating high wall shear stress (WSS) and positive and negative spatial gradients in WSS (WSSG). Endothelial responses to these kinds of high WSS hemodynamic environments are not well characterized. We examined endothelial cells (ECs) under elevated WSS and positive and negative WSSG using a flow chamber with constant-height channels to create regions of uniform WSS and converging and diverging channels to create positive and negative WSSG, respectively. Cultured bovine aortic ECs were subjected to 3.5 and 28.4 Pa with and without WSSG for 24 and 36 h. High WSS inhibited EC alignment to flow, increased EC proliferation assessed by bromodeoxyuridine incorporation, and increased apoptosis determined by terminal deoxynu-cleotidyl transferase dUTP-mediated nick-end labeling. These responses to high WSS were either accentuated or ameliorated by WSSG: Positive WSSG (+980 Pa/m) inhibited alignment and stimulated proliferation and apoptosis, whereas negative WSSG (−1120 Pa/m) promoted alignment and suppressed proliferation and apoptosis. These results demonstrate that ECs discriminate between positive and negative WSSG under high WSS conditions. EC responses to positive WSSG may contribute to pathogenic remodeling that occurs at bifurcations preceding aneurysm formation.

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NiCrFeSiBC/Cr 3 C 2 composite coatings were developed on to GrA1 boiler steel by high velocity oxy fuel spray process. The aim was to develop the novel composite coating by finding optimum concentration of Cr 3 C 2 in NiCrFeSiBC matrix, which further possesses the superior solid particle erosion resistance. The mechanical and microstructural properties of the developed coatings were critically examined. The as sprayed coatings were characterised by X-ray diffraction, SEM/ energy dispersive spectroscopy analyses. The coatings exhibited characteristic splat-like morphology with the presence of micropores, unmelted and semimelted particles and inclusions. The adhesion strength of the developed coatings was also determined. The physical properties like surface roughness, porosity and microhardness of the as sprayed coatings have also been reported. The blending resulted into the formation of composite-like coatings where, the Cr 3 C 2 phase was nearly uniformly distributed into the NiCrFeSiBC matrix. The results have been discussed with respect to the existing literature.