No abstract

Coronary stents are deployed to treat the coronary artery disease (CAD) by reopening stenotic regions in arteries to restore blood flow, but the risk of the in-stent restenosis (ISR) is high after stent implantation. One of the reasons is that stent implantation induces changes in local hemodynamic environment, so it is of vital importance to study the blood flow in stented arteries. Based on regarding the red blood cell (RBC) as a rigid solid particle and regarding the blood (including RBCs and plasma) as particle suspensions, a non-Newtonian particle suspensions model is proposed to simulate the realistic blood flow in this work. It considers the blood's flow pattern and non-Newtonian characteristic, the blood cell-cell interactions, and the additional effects owing to the bi-concave shape and rotation of the RBC. Then, it is compared with other four common hemodynamic models (Newtonian single-phase flow model, Newtonian Eulerian two-phase flow model, non-Newtonian single-phase flow model, non-Newtonian Eulerian two-phase flow model), and the comparison results indicate that the models with the non-Newtonian characteristic are more suitable to describe the realistic blood flow. Afterwards, based on the non-Newtonian particle suspensions model, the local hemodynamic environment in stented arteries is investigated. The result shows that the stent strut protrusion into the flow stream would be likely to produce the flow stagnation zone. And the stent implantation can make the pressure gradient distribution uneven. Besides, the wall shear stress (WSS) of the region adjacent to every stent strut is lower than 0.5 Pa, and along the flow direction, the low-WSS zone near the strut behind is larger than that near the front strut. What's more, in the regions near the struts in the proximal of the stent, the RBC particle stagnation zone is easy to be formed, and the erosion and deposition of RBCs are prone to occur. These hemodynamic analyses illustrate that the risk of ISR is high in the regions adjacent to the struts in the proximal and the distal ends of the stent when compared with struts in other positions of the stent. So the research can provide a suggestion on the stent design, which indicates that the strut structure in these positions of a stent should be optimized further.

No abstract

Regularly faceted copper (Cu) particles ranging from tens of nanometers to submicron were obtained by annealing Cu-Zr films on polyimide and single Si (100) substrates . XRD, TEM, SEM and EDS were used to characterize their microstructural properties . The results show that these particles are pure Cu element and single crystals with [Ill] preferred orientation. Systematical analysis demonstrates that the sizes of Cu particles are closely related to the film composition as well annealingconditions . Specifically, larger Zr contents will suppress the grain growth , and thus lead to smaller Cu particles , while the higher annealing temperature is easier to activate atomic diffusion , and larger particles appear. In addition, the shapes of these Cu particles are also very sensitive to the microstuctural properties of the thin films, the substrates types as well as annealing atmosphere. These aspects will be discussed in detail according to the morphological characteristics and residual stress evolution. This work may provide a new approach to prepare regular metal particles with sizes ranging from tens of nanometers to submicron.