Percutaneous coronary intervention (PCI) has become the primary treatment for patients with coronary heart disease because of its minimally invasive nature and high efficiency. Anatomical studies have shown that most coronary vessels gradually shrink, and the vessels gradually become thinner from the proximal to the distal end. In this paper, the effects of different stent expansion methods on the mechanical and hemodynamic behaviors of coronary vessels and stents were studied. To perform a structural-mechanical analysis of stent implantation, the coronary vessels with branching vessels and the coronary vessels with large bending curvature are selected. The two characteristic structures are implanted in equal diameter expansion mode and conical expansion mode, and the stress and mechanical behaviors of the coronary vessels and stents are analyzed. The results of the structural-mechanical analysis showed that the mechanical behaviors and fatigue performance of the cobalt-chromium alloy stent were good, and the different expansion modes of the stent had little effect on the fatigue performance of the stent. However, the equal diameter expansion mode increased distal coronary artery stress and the risk of vascular injury. The computational fluid dynamics analysis results showed that different stent expansion methods had varied effects on coronary vessel hemodynamics and that the wall shear stress distribution of conical stent expansion is more uniform compared with equal diameter expansion. Additionally, the vortex phenomenon is not apparent, the blood flow velocity is slightly increased, the hydrodynamic environment is more reasonable, and the risk of coronary artery injury is reduced.
中国西藏植物多样性较为丰富,尽管已经进行了多次的植物多样性调查,但仍存在较严重的不均衡现象,部分地区和类群存在采集不足,甚至空白。我们针对西藏日喀则植物多样性调查薄弱区域开展调查,发现一个未记录的绿绒蒿属(Meconopsis Viguier)植物,采集了标本和种子。经查阅《西藏植物志》《中国植物志》、Flora of China、Flora of Nepal鉴定为尼东绿绒蒿(M. dhwojii G. Taylor ex Hay)。该文植物新资料报道如下:(1)尼东绿绒蒿形态描述及其彩色图片。(2)该植物种子微形态、与近似种间的形态差异。新发现丰富了中国绿绒蒿属植物多样性,对研究西藏乃至中国绿绒蒿属植物具有一定的生物地理学意义和潜在的园艺价值。绿绒蒿属分类须加强野外调研,多技术手段开展研究。 相似文献