The hardening curve for sheet metal can be determined from the load-displacement curve of tensile specimen with rectangular cross-section. Therefore,uniaxial compression test on cylinder specimen made from laminated s...The hardening curve for sheet metal can be determined from the load-displacement curve of tensile specimen with rectangular cross-section. Therefore,uniaxial compression test on cylinder specimen made from laminated sample is put forward. Considering the influence of anisotropy on hardening properties and the stress state in popular forming process,plane strain compression test on cubic specimen made from laminated sample was advanced. Results show that the deformation range of hardening curves obtained from the presented methods is wide,which meets the need for the application in sheet metal forming processes. In view of the characteristics of methods presented in the paper and the stress strain state of various forming processes,the adaptability of the two methods presented in this paper is given.展开更多
The stent was a major breakthrough in the treatment of atherosclerotic vascular disease. The permanent vascular implant of a stent, however, changes the intra-stent blood flow hemodynamics. There is a growing consensu...The stent was a major breakthrough in the treatment of atherosclerotic vascular disease. The permanent vascular implant of a stent, however, changes the intra-stent blood flow hemodynamics. There is a growing consensus that the stent implant may change the artery wall shear stress distribution and hence lead to the restenosis process. Computational fluid dynamics （CFD） has been widely used to analyze hemodynamics in stented arteries. In this paper, two CFD models （the axisymmetric model and the 3-D stent model） were developed to investigate the effects of strut geometry and blood rheology on the intra-stent hemodynamics. The velocity profile, flow recirculation, and wall shear stress distribution of various stent strut geometries were studied. Results show strong correlations between the intra-stent hemodynamics and strut geometry. The intra-stent blood flow is very sensitive to the strut height and fillet size. A round strut with a large fillet size shows 36% and 34% reductions in key parameters evaluating the restenosis risk for the axisymmetric model and the 3-D stent model, respectively. This suggests that electrochemical polishing, a surface-improving process during stent manufacturing, strongly influences the hemodynamic behavior in stented arteries and should be controlled precisely in order to achieve the best clinical outcome. Rheological effects on the wall shear stress are minor in both axisymmetric and 3-D stent models for the vessel diameter of 4 mm, with Newtonian flow simulation tending to give more conservative estimates ofrestenosis risk. Therefore, it is reasonable to simulate the blood flow as a Newtonian flow in stented arteries using the simpler axisymmetric model. These findings will provide great insights for stent design optimization for potential restenosis improvement.展开更多
Complement component 5a(C5a)is a 74 amino acid glycoprotein and an important proinflammatory mediator that is cleaved enzymatically from its precursor,C5,on activation of the complement cascade.C5a is quickly metaboli...Complement component 5a(C5a)is a 74 amino acid glycoprotein and an important proinflammatory mediator that is cleaved enzymatically from its precursor,C5,on activation of the complement cascade.C5a is quickly metabolised by carboxypeptidases,forming the less-potent C5a desArg.C5a and C5a desArg interact with their receptors(C5aR and C5L2),which results in a number of effects which are essential to the immune response.C5a has a broad range of biological effects throughout the human body because the widespread expression of C5a receptors throughout the human organs enables C5a and C5a desArg to elicit a broad range of biological effects.Recently,accumulating evidence in humans and experimental animal models shows that the C5a-C5aR axis is involved in the development of atherosclerosis lesions.The absence or blockade of C5aRs greatly reduces the formation of atherosclerotic lesions or wire-injury-induced neointima formation in atherosclerosis-prone mice.Serum C5a level was related to the major adverse cardiovascular events in patients with advanced atherosclerosis and those with drug-eluting stent implantation.Thus,the C5a-C5aR axis may be a significant pathogenic driver of arteriosclerotic vascular disease,making C5a-C5aR inhibition an attractive therapeutic strategy.展开更多
文摘The hardening curve for sheet metal can be determined from the load-displacement curve of tensile specimen with rectangular cross-section. Therefore,uniaxial compression test on cylinder specimen made from laminated sample is put forward. Considering the influence of anisotropy on hardening properties and the stress state in popular forming process,plane strain compression test on cubic specimen made from laminated sample was advanced. Results show that the deformation range of hardening curves obtained from the presented methods is wide,which meets the need for the application in sheet metal forming processes. In view of the characteristics of methods presented in the paper and the stress strain state of various forming processes,the adaptability of the two methods presented in this paper is given.
文摘The stent was a major breakthrough in the treatment of atherosclerotic vascular disease. The permanent vascular implant of a stent, however, changes the intra-stent blood flow hemodynamics. There is a growing consensus that the stent implant may change the artery wall shear stress distribution and hence lead to the restenosis process. Computational fluid dynamics （CFD） has been widely used to analyze hemodynamics in stented arteries. In this paper, two CFD models （the axisymmetric model and the 3-D stent model） were developed to investigate the effects of strut geometry and blood rheology on the intra-stent hemodynamics. The velocity profile, flow recirculation, and wall shear stress distribution of various stent strut geometries were studied. Results show strong correlations between the intra-stent hemodynamics and strut geometry. The intra-stent blood flow is very sensitive to the strut height and fillet size. A round strut with a large fillet size shows 36% and 34% reductions in key parameters evaluating the restenosis risk for the axisymmetric model and the 3-D stent model, respectively. This suggests that electrochemical polishing, a surface-improving process during stent manufacturing, strongly influences the hemodynamic behavior in stented arteries and should be controlled precisely in order to achieve the best clinical outcome. Rheological effects on the wall shear stress are minor in both axisymmetric and 3-D stent models for the vessel diameter of 4 mm, with Newtonian flow simulation tending to give more conservative estimates ofrestenosis risk. Therefore, it is reasonable to simulate the blood flow as a Newtonian flow in stented arteries using the simpler axisymmetric model. These findings will provide great insights for stent design optimization for potential restenosis improvement.
基金supported by the National Natural Science Foundation of China(81000125,81000127)Specialized Research Fund for the Doctoral Program of Higher Education(20100131120057)Promotive Research Fund for Young and Middle-aged Scientisits of Shandong Province(BS2012YY017)
文摘Complement component 5a(C5a)is a 74 amino acid glycoprotein and an important proinflammatory mediator that is cleaved enzymatically from its precursor,C5,on activation of the complement cascade.C5a is quickly metabolised by carboxypeptidases,forming the less-potent C5a desArg.C5a and C5a desArg interact with their receptors(C5aR and C5L2),which results in a number of effects which are essential to the immune response.C5a has a broad range of biological effects throughout the human body because the widespread expression of C5a receptors throughout the human organs enables C5a and C5a desArg to elicit a broad range of biological effects.Recently,accumulating evidence in humans and experimental animal models shows that the C5a-C5aR axis is involved in the development of atherosclerosis lesions.The absence or blockade of C5aRs greatly reduces the formation of atherosclerotic lesions or wire-injury-induced neointima formation in atherosclerosis-prone mice.Serum C5a level was related to the major adverse cardiovascular events in patients with advanced atherosclerosis and those with drug-eluting stent implantation.Thus,the C5a-C5aR axis may be a significant pathogenic driver of arteriosclerotic vascular disease,making C5a-C5aR inhibition an attractive therapeutic strategy.
