在传统的回归再时效(retrogression and re-aging,RRA)工艺(峰时效)基础上降低预时效或再时效温度,对Fe和Si杂质含量高的超高强Al-Zn-Mg-Cu合金挤压棒材进行RRA处理,通过拉伸性能和疲劳性能测试以及扫描电镜和透射电镜观察,研究RRA工艺...在传统的回归再时效(retrogression and re-aging,RRA)工艺(峰时效)基础上降低预时效或再时效温度,对Fe和Si杂质含量高的超高强Al-Zn-Mg-Cu合金挤压棒材进行RRA处理,通过拉伸性能和疲劳性能测试以及扫描电镜和透射电镜观察,研究RRA工艺对合金力学性能与组织的影响。结果表明:降低预时效或再时效温度都可明显提高该合金的塑性和抗疲劳损伤性能,略微降低合金的抗拉强度。采用峰时效温度(120℃)RRA处理后的合金,晶内的主要析出相为尺寸较大的η′相,不能被位错切割,合金强度较高(674 MPa),但塑性和抗疲劳损伤性能差,伸长率为11.1%,最终应力强度因子幅值ΔK=26.8 MPa·m1/2;降低时效温度可增加析出相中GP区粒子的比例,减小η′相的尺寸,从而提高塑性变形能力以及抗疲劳损伤性能。展开更多
To estimate the antioxidant activities of Peanut polypeptides （PPs） by using a chemiluminescence （CL） method in vitro. The scavenging ability of PPs on superoxide anion, hydroxide radical, and hydrogen peroxide wa...To estimate the antioxidant activities of Peanut polypeptides （PPs） by using a chemiluminescence （CL） method in vitro. The scavenging ability of PPs on superoxide anion, hydroxide radical, and hydrogen peroxide was determined by the Pyrogallol-Luminol system, the CuSO4-Phen-Vc-H2O2 system, and the luminol-H2O2 system, respectively. DNA damage preventing the effect of PPs was determined by the CuSO4-Phen-Vc-H2O2-DNA CL system. The results shows that PPs had good effect on the scavenging ability of superoxide anion （IC50=9.68±0.12 mg/ml）. PPs could scavenge hydroxide radical effectively （the IC50 value was 46.06±0.08 μg/ml）. PPs had a good scavenging ability on hydrogen peroxide, which had a relatively low IC50 value （0.17±0.07 mg/ml）. PPs （the IC50 value was0.72±0.11 mg/ml） were powerful on the DNA damage preventing effect. PPs possesses a good scavenging potency on ROS in different systems, but different results exist in different systems.展开更多
A numerical approach for simulating the seismic performance of steel truss structures, considering damage-induced material softening, is developed based on a ductile damage constitutive model by applying the backward ...A numerical approach for simulating the seismic performance of steel truss structures, considering damage-induced material softening, is developed based on a ductile damage constitutive model by applying the backward Euler explicit algorithm. It is implemented in ABAQUS through a user-defined material subroutine, by which damage evolution could be incorporated into the analysis of seismic performance of steel structures. The case study taken up here is the investigation of a steel connection with a reduced beam section(RBS) and a steel frame with such connections. The material softening effect during the failure process is particularly investigated. The results show that material softening in the vulnerable zone has a significant effect on the distribution of stress and strain fields, as well as on the carrying capacity of the steel connection with RBS. Further, material softening is found to have almost negligible effect on the seismic performance of the steel frame in the early stages of the loading process, but has a large effect when the steel frame is about to fail. These findings offer a practical reference for the assessment of seismic structural failure, and help in understanding the damage mechanism of steel structures under seismic loading.展开更多
OBJECTIVE： To determine the cardioprotective ef- fect of magnesium lithospermate B （MLB） on myo- cardial ischemia/reperfusion （MI/R） injury and to in- vestigate the antioxidant potential in vivo and in vitro. MET...OBJECTIVE： To determine the cardioprotective ef- fect of magnesium lithospermate B （MLB） on myo- cardial ischemia/reperfusion （MI/R） injury and to in- vestigate the antioxidant potential in vivo and in vitro. METHODS： MI/R injury was induced by the occlu- sion of left anterior descending coronary artery for 30 min followed by reperfusion for 3 h in rats. After reperfusion, hearts were harvested to assess infarct size, histopathological damages, the levels of superoxide dismutase （SOD）, catalase （CAT）, glutathione peroxidase （GPx）, reduced glutathione （GSH） and malondialdehyde （MDA）. Blood samples were collected to determine serum levels of creatine kinase-MB （CK-MB）, cardiac troponin （cTnl） and lactate dehydrogenase （LDH）. Furthermore, simulatedischemia/reperfusion （SI/R） injury in vitro was established by oxygen and glucose deprivation （OGD） for 2 h followed by 24-hour recovery period in cardiomyocytes. The activity of LDH in the cultured su- pernatant and the levels of intracellular reactive oxygen species （ROS）, SOD and MDA in cardiomyo- cytes were also measured. Finally, cardiomyocytes apoptosis was determined with flow cytometry. RESULTS： MLB significantly limited infarct size, ameliorated histopathological damages and prevented leakage of CK-MB, cTnl and LDH. Additional- ly, SOD, CAT, GPx and GSH activities were notably increased by MLB, along with the MDA content decreased as compared with the model group in rats. In vitro study, MLB also decreased LDH activity in the cultured supernatant, increased SOD activity in cardiomyocytes, reduced intracellular ROS and MDA levels, and significantly suppressed cardiomyocytes apoptosis. CONCLUSION： MLB possessed remarkably cardioprotective effects on MI/R injury in vivo and in vitro. The protection of MLB may contribute to its antioxidant properties.展开更多
文摘在传统的回归再时效(retrogression and re-aging,RRA)工艺(峰时效)基础上降低预时效或再时效温度,对Fe和Si杂质含量高的超高强Al-Zn-Mg-Cu合金挤压棒材进行RRA处理,通过拉伸性能和疲劳性能测试以及扫描电镜和透射电镜观察,研究RRA工艺对合金力学性能与组织的影响。结果表明:降低预时效或再时效温度都可明显提高该合金的塑性和抗疲劳损伤性能,略微降低合金的抗拉强度。采用峰时效温度(120℃)RRA处理后的合金,晶内的主要析出相为尺寸较大的η′相,不能被位错切割,合金强度较高(674 MPa),但塑性和抗疲劳损伤性能差,伸长率为11.1%,最终应力强度因子幅值ΔK=26.8 MPa·m1/2;降低时效温度可增加析出相中GP区粒子的比例,减小η′相的尺寸,从而提高塑性变形能力以及抗疲劳损伤性能。
文摘To estimate the antioxidant activities of Peanut polypeptides （PPs） by using a chemiluminescence （CL） method in vitro. The scavenging ability of PPs on superoxide anion, hydroxide radical, and hydrogen peroxide was determined by the Pyrogallol-Luminol system, the CuSO4-Phen-Vc-H2O2 system, and the luminol-H2O2 system, respectively. DNA damage preventing the effect of PPs was determined by the CuSO4-Phen-Vc-H2O2-DNA CL system. The results shows that PPs had good effect on the scavenging ability of superoxide anion （IC50=9.68±0.12 mg/ml）. PPs could scavenge hydroxide radical effectively （the IC50 value was 46.06±0.08 μg/ml）. PPs had a good scavenging ability on hydrogen peroxide, which had a relatively low IC50 value （0.17±0.07 mg/ml）. PPs （the IC50 value was0.72±0.11 mg/ml） were powerful on the DNA damage preventing effect. PPs possesses a good scavenging potency on ROS in different systems, but different results exist in different systems.
文摘A numerical approach for simulating the seismic performance of steel truss structures, considering damage-induced material softening, is developed based on a ductile damage constitutive model by applying the backward Euler explicit algorithm. It is implemented in ABAQUS through a user-defined material subroutine, by which damage evolution could be incorporated into the analysis of seismic performance of steel structures. The case study taken up here is the investigation of a steel connection with a reduced beam section(RBS) and a steel frame with such connections. The material softening effect during the failure process is particularly investigated. The results show that material softening in the vulnerable zone has a significant effect on the distribution of stress and strain fields, as well as on the carrying capacity of the steel connection with RBS. Further, material softening is found to have almost negligible effect on the seismic performance of the steel frame in the early stages of the loading process, but has a large effect when the steel frame is about to fail. These findings offer a practical reference for the assessment of seismic structural failure, and help in understanding the damage mechanism of steel structures under seismic loading.
基金Supported by the National Natural Science Foundation of China (No. 81173514,No.81001673)the Xijing Research Boosting Program (No. XJZT10D02)the Excellent Civil Service Training Fund of Fourth Military Medical University(No. 4138C4IDK6)
文摘OBJECTIVE： To determine the cardioprotective ef- fect of magnesium lithospermate B （MLB） on myo- cardial ischemia/reperfusion （MI/R） injury and to in- vestigate the antioxidant potential in vivo and in vitro. METHODS： MI/R injury was induced by the occlu- sion of left anterior descending coronary artery for 30 min followed by reperfusion for 3 h in rats. After reperfusion, hearts were harvested to assess infarct size, histopathological damages, the levels of superoxide dismutase （SOD）, catalase （CAT）, glutathione peroxidase （GPx）, reduced glutathione （GSH） and malondialdehyde （MDA）. Blood samples were collected to determine serum levels of creatine kinase-MB （CK-MB）, cardiac troponin （cTnl） and lactate dehydrogenase （LDH）. Furthermore, simulatedischemia/reperfusion （SI/R） injury in vitro was established by oxygen and glucose deprivation （OGD） for 2 h followed by 24-hour recovery period in cardiomyocytes. The activity of LDH in the cultured su- pernatant and the levels of intracellular reactive oxygen species （ROS）, SOD and MDA in cardiomyo- cytes were also measured. Finally, cardiomyocytes apoptosis was determined with flow cytometry. RESULTS： MLB significantly limited infarct size, ameliorated histopathological damages and prevented leakage of CK-MB, cTnl and LDH. Additional- ly, SOD, CAT, GPx and GSH activities were notably increased by MLB, along with the MDA content decreased as compared with the model group in rats. In vitro study, MLB also decreased LDH activity in the cultured supernatant, increased SOD activity in cardiomyocytes, reduced intracellular ROS and MDA levels, and significantly suppressed cardiomyocytes apoptosis. CONCLUSION： MLB possessed remarkably cardioprotective effects on MI/R injury in vivo and in vitro. The protection of MLB may contribute to its antioxidant properties.
