Texture evolution of an extruded dilute Mg-1Sn-1Zn-1Al alloy was thoroughly investigated based on the twinning and dynamic recrystallization(DRX)behavior via hot compression at a strain rate of 10 s^(-1)and temperatur...Texture evolution of an extruded dilute Mg-1Sn-1Zn-1Al alloy was thoroughly investigated based on the twinning and dynamic recrystallization(DRX)behavior via hot compression at a strain rate of 10 s^(-1)and temperature of 225℃.It was found that the types and intensities of the texture are strongly dependent on the fraction of twins and DRX modes as well as regions where sub-grain boundaries(sub-GBs)are intensively accumulated.At the initial stage of deformation,the formation of compression direction(CD)-tilted basal texture was mainly determined by the occurrence of{101^(-)2}extension twins.As the strain increases,the variation in the texture intensity was greatly dominated by the DRX modes but the type of main texture remained unchanged.These findings are of great importance for texture modification of wrought Mg-Sn-based alloys during post-deformation.展开更多
Current research on bone marrow stem cell transplantation and autologous or xenogenic nerve transplantation for peripheral nerve regeneration has mainly focused on the repair of peripher-al nerve defects in rodents. I...Current research on bone marrow stem cell transplantation and autologous or xenogenic nerve transplantation for peripheral nerve regeneration has mainly focused on the repair of peripher-al nerve defects in rodents. In this study, we established a standardized experimental model of radial nerve defects in primates and evaluated the effect of repair on peripheral nerve injury. We repaired 2.5-cm lesions in the radial nerve of rhesus monkeys by transplantation of autografts, acellular allografts, or acellular allografts seeded with autologous bone marrow stem cells. Five months after surgery, regenerated nerve tissue was assessed for function, electrophysiology, and histomorphometry. Postoperative functional recovery was evaluated by the wrist-extension test. Compared with the simple autografts, the acellular allografts and allografts seeded with bone marrow stem cells facilitated remarkable recovery of the wrist-extension functions in the rhesus monkeys. This functional improvement was coupled with radial nerve distal axon growth, a higher percentage of neuron survival, increased nerve fiber density and diameter, increased myelin sheath thickness, and increased nerve conduction velocities and peak amplitudes of compound motor action potentials. Furthermore, the quality of nerve regeneration in the bone marrow stem cells-laden allografts group was comparable to that achieved with autografts. The wrist-extension test is a simple behavioral method for objective quantification of peripheral nerve regeneration.展开更多
The effects of Ti additions(0,0.4,0.6,0.8,1.0,1.2 wt.%)on the microstructure and mechanical properties of as-cast and aging Mg-0.4%Zn-1.0%Zr-1.5%Ca(wt.%)alloys were investigated.The results indicated that minor Ti can...The effects of Ti additions(0,0.4,0.6,0.8,1.0,1.2 wt.%)on the microstructure and mechanical properties of as-cast and aging Mg-0.4%Zn-1.0%Zr-1.5%Ca(wt.%)alloys were investigated.The results indicated that minor Ti can effectively refine grains,while excessive Ti addition resulted in the grain coarsening.When the content of Ti was 0.8 wt.%,the as-cast alloy exhibited the finest grain size of 39μm which contributed to the optimal mechanical properties with Brinell hardness of 57.9 HB,ultimate tensile strength of 145 MPa and elongation of 3.2%.After T6 heat treatment,the continuous net-like Mg_(2)Ca and Mg_(6)Zn_(3)Ca_(2)phases changed to uniform massive T phases(ternary Mg-Zn-Ca phases)and dispersive halo-like precipitates(Mg_(2)Ca and Mg_(6)Zn_(3)Ca_(2)phases).The ultimate tensile strengths of the alloy at room temperature(RT),175℃and 200℃were correspondingly improved to 182 MPa,169 MPa and 141 MPa,respectively.展开更多
基金the Natural Science Foundation of China(51404166 and 51704209)Natural Science Foundation of Shanxi(201801D121088)the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi(2014017 and 201802034).
文摘Texture evolution of an extruded dilute Mg-1Sn-1Zn-1Al alloy was thoroughly investigated based on the twinning and dynamic recrystallization(DRX)behavior via hot compression at a strain rate of 10 s^(-1)and temperature of 225℃.It was found that the types and intensities of the texture are strongly dependent on the fraction of twins and DRX modes as well as regions where sub-grain boundaries(sub-GBs)are intensively accumulated.At the initial stage of deformation,the formation of compression direction(CD)-tilted basal texture was mainly determined by the occurrence of{101^(-)2}extension twins.As the strain increases,the variation in the texture intensity was greatly dominated by the DRX modes but the type of main texture remained unchanged.These findings are of great importance for texture modification of wrought Mg-Sn-based alloys during post-deformation.
基金supported by the National High-Technology Research and Development Program of China(863 Program),No.2006AA02A130the National Natural Science Foundation of China,No.81372041,31070869,30700847
文摘Current research on bone marrow stem cell transplantation and autologous or xenogenic nerve transplantation for peripheral nerve regeneration has mainly focused on the repair of peripher-al nerve defects in rodents. In this study, we established a standardized experimental model of radial nerve defects in primates and evaluated the effect of repair on peripheral nerve injury. We repaired 2.5-cm lesions in the radial nerve of rhesus monkeys by transplantation of autografts, acellular allografts, or acellular allografts seeded with autologous bone marrow stem cells. Five months after surgery, regenerated nerve tissue was assessed for function, electrophysiology, and histomorphometry. Postoperative functional recovery was evaluated by the wrist-extension test. Compared with the simple autografts, the acellular allografts and allografts seeded with bone marrow stem cells facilitated remarkable recovery of the wrist-extension functions in the rhesus monkeys. This functional improvement was coupled with radial nerve distal axon growth, a higher percentage of neuron survival, increased nerve fiber density and diameter, increased myelin sheath thickness, and increased nerve conduction velocities and peak amplitudes of compound motor action potentials. Furthermore, the quality of nerve regeneration in the bone marrow stem cells-laden allografts group was comparable to that achieved with autografts. The wrist-extension test is a simple behavioral method for objective quantification of peripheral nerve regeneration.
基金The authors acknowledge the financial support from the National Science Foundation of China through Grant No.50571073Natural Science Foundation of Shanxi Province through Grant No.2009011028-3.
文摘The effects of Ti additions(0,0.4,0.6,0.8,1.0,1.2 wt.%)on the microstructure and mechanical properties of as-cast and aging Mg-0.4%Zn-1.0%Zr-1.5%Ca(wt.%)alloys were investigated.The results indicated that minor Ti can effectively refine grains,while excessive Ti addition resulted in the grain coarsening.When the content of Ti was 0.8 wt.%,the as-cast alloy exhibited the finest grain size of 39μm which contributed to the optimal mechanical properties with Brinell hardness of 57.9 HB,ultimate tensile strength of 145 MPa and elongation of 3.2%.After T6 heat treatment,the continuous net-like Mg_(2)Ca and Mg_(6)Zn_(3)Ca_(2)phases changed to uniform massive T phases(ternary Mg-Zn-Ca phases)and dispersive halo-like precipitates(Mg_(2)Ca and Mg_(6)Zn_(3)Ca_(2)phases).The ultimate tensile strengths of the alloy at room temperature(RT),175℃and 200℃were correspondingly improved to 182 MPa,169 MPa and 141 MPa,respectively.
