The cardiovascular diseases(CVD)continue to be the major threat to global public health over the years,while one of the effective methods to treat CVD is stent intervention.Biomedical magnesium(Mg)alloys have great po...The cardiovascular diseases(CVD)continue to be the major threat to global public health over the years,while one of the effective methods to treat CVD is stent intervention.Biomedical magnesium(Mg)alloys have great potential applications in cardiovascular stents benefit from their excellent biodegradability and absorbability.However,excessive degradation rate and the delayed surface endothelialization still limit their further application.In this study,we modified a Mg-Zn-Y-Nd alloy(ZE21B)by preparing MgF_(2) as the corrosion resistance layer,the dopamine polymer film(PDA)as the bonding layer,and hyaluronic acid(HA)loaded astaxanthin(ASTA)as an important layer to directing the cardiovascular cells fate.The electrochemical test results showed that the MgF_(2)/PDA/HA-ASTA coating improved the corrosion resistance of ZE21B.The cytocompatibility experiments also demonstrated that this novel composite coating also selectively promoted endothelial cells proliferation,inhibited hyperproliferation of smooth muscle cells and adhesion of macrophages.Compared with the HAloaded rapamycin(RAPA)coating,our MgF_(2)/PDA/HA-ASTA coating showed better blood compatibility and cytocompatibility,indicating stronger multi-functions for the ZE21B alloy on cardiovascular application.展开更多
Magnesium(Mg)alloys are generally used in light-weight structural applications due to their higher specific strength.However,the usage of these Mg alloys is limited due to their poor formability at room temperature,wh...Magnesium(Mg)alloys are generally used in light-weight structural applications due to their higher specific strength.However,the usage of these Mg alloys is limited due to their poor formability at room temperature,which is attributed to lower count of slip systems associated with the hcp crystal structure.To address these limitations,several new magnesium alloys and also many processing strategies have been developed and reported in the literature.ZE41 Mg is an alloy with significant quantities of zinc(Zn)and rare earth(RE)elements and has emerged as a promising material for aerospace,automotive,electronics,biomedical and many other industries.To make this alloy more competitive and viable,it should possess better mechanical and corrosion properties.Hence,the current paper reviews the effect of bulk mechanical processing on grain refinement,microstructural modification,and corresponding changes in the mechanical behaviour of ZE41Mg alloy.Further,the effect of various surface modification techniques on altering the surface microstructure and surface properties such as wear and corrosion are also briefly summarized and presented.This review also discusses the challenges and the future perspectives in developing high-performing ZE41 Mg alloys.展开更多
Magnesium-based biodegradable metals as cardiovascular stents have shown a lot of excellent performance, which have been used to treat coronary artery diseases. However, the excessive degradation rate, imperfect bioco...Magnesium-based biodegradable metals as cardiovascular stents have shown a lot of excellent performance, which have been used to treat coronary artery diseases. However, the excessive degradation rate, imperfect biocompatibility and delayed re-endothelialization still lead to a considerable challenge for its application. In this work, to overcome these shortcomings, a compound of catalyzing nitric oxide(NO) generation containing copper ions(Cu^(2+)) and hyaluronic acid(HA), an important component of the extracellular matrix, were covalently immobilized on a hydrofluoric acid(HF)-pretreated ZE21B alloy via amination layer for improving its corrosion resistance and endothelialization. Specifically,the Cu^(2+) chelated firmly with a cyclen 1,4,7,10-tetraazacyclododecane-N’, N’’, N’’’, N-tetraacetic acid(DOTA) could form a stability of hybrid coating, avoiding the explosion of Cu^(2+). The chelated Cu^(2+) enabled the catalytic generation of NO and promoted the adhesion and proliferation of endothelial cells(ECs) in vascular micro-environment. In this case, the synergistic effect of NO-generation and endothelial glycocalyx molecules of HA lead to efficient ECs promotion and smooth muscle cells(SMCs) inhibition. Meanwhile, the blood compatibility also had achieved a marked improvement. Moreover, the standard electrochemical measurements indicated that the functionalized ZE21B alloy had better anti-corrosion ability. In a conclusion, the dual-functional coating displays a great potential in the field of biodegradable magnesium-based implantable cardiovascular stents.展开更多
新型制冷剂R1234ze(E)(trans-1,3,3,3-tetrafluoropropene)因较低的GWP而被广泛关注,有望在热泵中作为R134a的替代品。本文对R1234ze(E)在内径为8 mm水平管内流动沸腾过程中摩擦压降特性进行实验研究,并在相同实验工况下与R134a进行对...新型制冷剂R1234ze(E)(trans-1,3,3,3-tetrafluoropropene)因较低的GWP而被广泛关注,有望在热泵中作为R134a的替代品。本文对R1234ze(E)在内径为8 mm水平管内流动沸腾过程中摩擦压降特性进行实验研究,并在相同实验工况下与R134a进行对比。实验研究的流动沸腾换热的饱和温度为10℃,热流密度为5.0 k W/m^2和10.0 k W/m^2,质流密度范围为300~500 kg/(m^2·s),并分析质流密度、热流密度对R1234ze(E)和R134a饱和流动沸腾过程中摩擦压降的影响。结果表明,在相同工况下R1234ze(E)的流动沸腾过程的摩擦压降略大于R134a,如质流密度为500 kg/(m^2·s)时,R1234ze(E)的平均摩擦压降值比R134a大8.4%左右。最后,将实验结果同四种摩擦压降经验关联式进行比较分析。展开更多
为了解新型环保工质R1234ze(E)微小通道内的冷凝换热及阻力特性,提出采用VOF(volume of fluid)模型对R1234ze(E)和R134a(Tsat=40℃)在水平微细圆管(Dh=1mm)内的冷凝过程进行数值模拟研究,探讨质量流量、干度以及物性对管内冷凝换热和阻...为了解新型环保工质R1234ze(E)微小通道内的冷凝换热及阻力特性,提出采用VOF(volume of fluid)模型对R1234ze(E)和R134a(Tsat=40℃)在水平微细圆管(Dh=1mm)内的冷凝过程进行数值模拟研究,探讨质量流量、干度以及物性对管内冷凝换热和阻力性能的影响。结果表明,R1234ze(E)和R134a的换热系数和压降都随质量流速和干度的增大而增大。相同情况下,R1234ze(E)换热系数小于R134a,但压降大于R134a。R1234ze(E)的液膜厚度平均要比R134a薄15.7%。当气液两相都为湍流,有效热导率对不同工质在水平圆管内的冷凝换热性能有重要影响。R1234ze(E)在管内的液膜分布特性整体上和R134a相似。现有的关联式对R1234ze(E)的压降都存在一定的低估,平均绝对误差都在30%左右。展开更多
基金For financial support,the authors gratefully acknowledge the National Natural Science Foundation of China(U2004164)the National Key Research and Development Program of China(2018YFC1106703)the Key Projects of the Joint Fund of the National Natural Science Foundation of China(U1804251).
文摘The cardiovascular diseases(CVD)continue to be the major threat to global public health over the years,while one of the effective methods to treat CVD is stent intervention.Biomedical magnesium(Mg)alloys have great potential applications in cardiovascular stents benefit from their excellent biodegradability and absorbability.However,excessive degradation rate and the delayed surface endothelialization still limit their further application.In this study,we modified a Mg-Zn-Y-Nd alloy(ZE21B)by preparing MgF_(2) as the corrosion resistance layer,the dopamine polymer film(PDA)as the bonding layer,and hyaluronic acid(HA)loaded astaxanthin(ASTA)as an important layer to directing the cardiovascular cells fate.The electrochemical test results showed that the MgF_(2)/PDA/HA-ASTA coating improved the corrosion resistance of ZE21B.The cytocompatibility experiments also demonstrated that this novel composite coating also selectively promoted endothelial cells proliferation,inhibited hyperproliferation of smooth muscle cells and adhesion of macrophages.Compared with the HAloaded rapamycin(RAPA)coating,our MgF_(2)/PDA/HA-ASTA coating showed better blood compatibility and cytocompatibility,indicating stronger multi-functions for the ZE21B alloy on cardiovascular application.
文摘Magnesium(Mg)alloys are generally used in light-weight structural applications due to their higher specific strength.However,the usage of these Mg alloys is limited due to their poor formability at room temperature,which is attributed to lower count of slip systems associated with the hcp crystal structure.To address these limitations,several new magnesium alloys and also many processing strategies have been developed and reported in the literature.ZE41 Mg is an alloy with significant quantities of zinc(Zn)and rare earth(RE)elements and has emerged as a promising material for aerospace,automotive,electronics,biomedical and many other industries.To make this alloy more competitive and viable,it should possess better mechanical and corrosion properties.Hence,the current paper reviews the effect of bulk mechanical processing on grain refinement,microstructural modification,and corresponding changes in the mechanical behaviour of ZE41Mg alloy.Further,the effect of various surface modification techniques on altering the surface microstructure and surface properties such as wear and corrosion are also briefly summarized and presented.This review also discusses the challenges and the future perspectives in developing high-performing ZE41 Mg alloys.
基金supported by the National Key R&D Program of China (grant number 2021YFC2400700)National Natural Science Foundation of China (Nos.51871004 and U1804251)。
文摘Magnesium-based biodegradable metals as cardiovascular stents have shown a lot of excellent performance, which have been used to treat coronary artery diseases. However, the excessive degradation rate, imperfect biocompatibility and delayed re-endothelialization still lead to a considerable challenge for its application. In this work, to overcome these shortcomings, a compound of catalyzing nitric oxide(NO) generation containing copper ions(Cu^(2+)) and hyaluronic acid(HA), an important component of the extracellular matrix, were covalently immobilized on a hydrofluoric acid(HF)-pretreated ZE21B alloy via amination layer for improving its corrosion resistance and endothelialization. Specifically,the Cu^(2+) chelated firmly with a cyclen 1,4,7,10-tetraazacyclododecane-N’, N’’, N’’’, N-tetraacetic acid(DOTA) could form a stability of hybrid coating, avoiding the explosion of Cu^(2+). The chelated Cu^(2+) enabled the catalytic generation of NO and promoted the adhesion and proliferation of endothelial cells(ECs) in vascular micro-environment. In this case, the synergistic effect of NO-generation and endothelial glycocalyx molecules of HA lead to efficient ECs promotion and smooth muscle cells(SMCs) inhibition. Meanwhile, the blood compatibility also had achieved a marked improvement. Moreover, the standard electrochemical measurements indicated that the functionalized ZE21B alloy had better anti-corrosion ability. In a conclusion, the dual-functional coating displays a great potential in the field of biodegradable magnesium-based implantable cardiovascular stents.
文摘新型制冷剂R1234ze(E)(trans-1,3,3,3-tetrafluoropropene)因较低的GWP而被广泛关注,有望在热泵中作为R134a的替代品。本文对R1234ze(E)在内径为8 mm水平管内流动沸腾过程中摩擦压降特性进行实验研究,并在相同实验工况下与R134a进行对比。实验研究的流动沸腾换热的饱和温度为10℃,热流密度为5.0 k W/m^2和10.0 k W/m^2,质流密度范围为300~500 kg/(m^2·s),并分析质流密度、热流密度对R1234ze(E)和R134a饱和流动沸腾过程中摩擦压降的影响。结果表明,在相同工况下R1234ze(E)的流动沸腾过程的摩擦压降略大于R134a,如质流密度为500 kg/(m^2·s)时,R1234ze(E)的平均摩擦压降值比R134a大8.4%左右。最后,将实验结果同四种摩擦压降经验关联式进行比较分析。
文摘为了解新型环保工质R1234ze(E)微小通道内的冷凝换热及阻力特性,提出采用VOF(volume of fluid)模型对R1234ze(E)和R134a(Tsat=40℃)在水平微细圆管(Dh=1mm)内的冷凝过程进行数值模拟研究,探讨质量流量、干度以及物性对管内冷凝换热和阻力性能的影响。结果表明,R1234ze(E)和R134a的换热系数和压降都随质量流速和干度的增大而增大。相同情况下,R1234ze(E)换热系数小于R134a,但压降大于R134a。R1234ze(E)的液膜厚度平均要比R134a薄15.7%。当气液两相都为湍流,有效热导率对不同工质在水平圆管内的冷凝换热性能有重要影响。R1234ze(E)在管内的液膜分布特性整体上和R134a相似。现有的关联式对R1234ze(E)的压降都存在一定的低估,平均绝对误差都在30%左右。
