纳米准晶增强Mg-Zn-Y合金室温具有超高延伸率,具有较广阔的应用前景,需进一步研究其热变形行为,为后续加工提供理论和应用基础。本工作采用半固态+热挤压的复合工艺制备了含有纳米准晶颗粒的Mg-1.92Zn-0.34Y(质量分数,下同)合金,探究本...纳米准晶增强Mg-Zn-Y合金室温具有超高延伸率,具有较广阔的应用前景,需进一步研究其热变形行为,为后续加工提供理论和应用基础。本工作采用半固态+热挤压的复合工艺制备了含有纳米准晶颗粒的Mg-1.92Zn-0.34Y(质量分数,下同)合金,探究本合金在250、300和350℃温度和10^(-3)、10^(-2)和10^(-1)s^(-1)应变速率条件下的高温变形机制,着重研究微量纳米准晶颗粒对Mg-1.92Zn-0.34Y合金热变形行为的影响。结果表明:半固态+热挤压的复合工艺制备了高塑性纳米准晶Mg-1.92Zn-0.34Y合金,其室温下抗拉延伸率为44%±2.6%,抗拉强度为258±2.0 MPa,屈服强度为176±1.6 MPa。通过本构关系获得平均变形激活能达到271.7812 k J/mol,其应力指数为6.7838;Mg-1.92Zn-0.34Y合金具有较好的热塑性,在研究条件下无失稳现象,表明纳米准晶颗粒能够强化其变形能力;最佳热加工区域是:330~350℃,10^(-3)~10^(-2)s^(-1),即高温低应变速率区。展开更多
This prospective study aimed to investigate the associations of untreated cholesterol levels and their longitudinal changes,especially low levels,with all-cause and cause-specific mortality in different populations.Pa...This prospective study aimed to investigate the associations of untreated cholesterol levels and their longitudinal changes,especially low levels,with all-cause and cause-specific mortality in different populations.Participants were drawn from two Chinese cohorts and the UK Biobank,excluding those with lipid-lowering medications,coronary heart disease(CHD),stroke,cancer,clinically diagnosed chronic obstructive pulmonary disease,low body mass index(<18.5 kg·m^(-2))at baseline,and deaths within the first two years to minimize reverse causality.Individual cholesterol changes were assessed in a subset who attended the resurvey after over four years.Mortality data were linked to registries,and risks were estimated using Cox proportional hazards models.A total of 163115 Chinese and 317305 UK adults were included(mean age,49-61 years),with 43%,81%,and 44%males in Dongfeng-Tongji,Kailuan,and UK Biobank cohorts,respectively.During a median follow-up of 9.7-12.9 years,9553 and 15760 deaths were documented in the Chinese cohorts and UK Biobank,respectively.After multivariate adjustments,nonlinear relationships were observed between total cholesterol(TC),low-density lipoprotein cholesterol(LDL-C),and non-high-density lipoprotein cholesterol(non-HDL-C)levels and mortality.In both populations,high cholesterol was primarily associated with CHD mortality,while low cholesterol associated with all-cause and cancer mortality(Pnonlinear≤0.0161).The optimal levels for all-cause mortality risk in Chinese adults(TC:200 mg·dL^(-1);LDL-C:130 mg·dL^(-1);non-HDL-C:155 mg·dL^(-1))were lower than those in the UK Biobank but consistent with guideline recommendation.Additionally,decreasing cholesterol levels over four years were associated with higher all-cause and cancer mortality in the Chinese cohorts(P_(nonlinear)≤0.0100).Participants with low TC,LDL-C,or non-HDL-C levels at both baseline and resurvey experienced elevated all-cause mortality risks in both populations,as did those with low/medium baseline levels and>20%reductions over time in Chinese adults.In conclusion,higher TC,LDL-C,and non-HDL-C levels are associated with elevated CHD mortality.Importantly,low and/or longitudinally decreasing cholesterol levels are robustly associated with increased all-cause and cancer mortality,potentially serving as markers of premature death.Regular cholesterol monitoring,with attention to both high and low levels,is recommended to inform guideline updates and clinical strategies.展开更多
文摘纳米准晶增强Mg-Zn-Y合金室温具有超高延伸率,具有较广阔的应用前景,需进一步研究其热变形行为,为后续加工提供理论和应用基础。本工作采用半固态+热挤压的复合工艺制备了含有纳米准晶颗粒的Mg-1.92Zn-0.34Y(质量分数,下同)合金,探究本合金在250、300和350℃温度和10^(-3)、10^(-2)和10^(-1)s^(-1)应变速率条件下的高温变形机制,着重研究微量纳米准晶颗粒对Mg-1.92Zn-0.34Y合金热变形行为的影响。结果表明:半固态+热挤压的复合工艺制备了高塑性纳米准晶Mg-1.92Zn-0.34Y合金,其室温下抗拉延伸率为44%±2.6%,抗拉强度为258±2.0 MPa,屈服强度为176±1.6 MPa。通过本构关系获得平均变形激活能达到271.7812 k J/mol,其应力指数为6.7838;Mg-1.92Zn-0.34Y合金具有较好的热塑性,在研究条件下无失稳现象,表明纳米准晶颗粒能够强化其变形能力;最佳热加工区域是:330~350℃,10^(-3)~10^(-2)s^(-1),即高温低应变速率区。
基金supported by the National Natural Science Foundation of China(82021005,82192903,81930092)the Chief Scientist Research Project of Hubei Shizhen Laboratory(HSL2024SX0003)+1 种基金the Fundamental Research Funds for the Central Universities(2019kfyXMBZ015)the 111 Project and the Program for Changjiang Scholars and Innovative Research Team in University.
文摘This prospective study aimed to investigate the associations of untreated cholesterol levels and their longitudinal changes,especially low levels,with all-cause and cause-specific mortality in different populations.Participants were drawn from two Chinese cohorts and the UK Biobank,excluding those with lipid-lowering medications,coronary heart disease(CHD),stroke,cancer,clinically diagnosed chronic obstructive pulmonary disease,low body mass index(<18.5 kg·m^(-2))at baseline,and deaths within the first two years to minimize reverse causality.Individual cholesterol changes were assessed in a subset who attended the resurvey after over four years.Mortality data were linked to registries,and risks were estimated using Cox proportional hazards models.A total of 163115 Chinese and 317305 UK adults were included(mean age,49-61 years),with 43%,81%,and 44%males in Dongfeng-Tongji,Kailuan,and UK Biobank cohorts,respectively.During a median follow-up of 9.7-12.9 years,9553 and 15760 deaths were documented in the Chinese cohorts and UK Biobank,respectively.After multivariate adjustments,nonlinear relationships were observed between total cholesterol(TC),low-density lipoprotein cholesterol(LDL-C),and non-high-density lipoprotein cholesterol(non-HDL-C)levels and mortality.In both populations,high cholesterol was primarily associated with CHD mortality,while low cholesterol associated with all-cause and cancer mortality(Pnonlinear≤0.0161).The optimal levels for all-cause mortality risk in Chinese adults(TC:200 mg·dL^(-1);LDL-C:130 mg·dL^(-1);non-HDL-C:155 mg·dL^(-1))were lower than those in the UK Biobank but consistent with guideline recommendation.Additionally,decreasing cholesterol levels over four years were associated with higher all-cause and cancer mortality in the Chinese cohorts(P_(nonlinear)≤0.0100).Participants with low TC,LDL-C,or non-HDL-C levels at both baseline and resurvey experienced elevated all-cause mortality risks in both populations,as did those with low/medium baseline levels and>20%reductions over time in Chinese adults.In conclusion,higher TC,LDL-C,and non-HDL-C levels are associated with elevated CHD mortality.Importantly,low and/or longitudinally decreasing cholesterol levels are robustly associated with increased all-cause and cancer mortality,potentially serving as markers of premature death.Regular cholesterol monitoring,with attention to both high and low levels,is recommended to inform guideline updates and clinical strategies.
