For high corrosion resistance and extensively modified biodegradable Mg-based alloys and composites for bone implants,a new Mgbased matrix model prepared by powder metallurgy is discussed and developed.In this researc...For high corrosion resistance and extensively modified biodegradable Mg-based alloys and composites for bone implants,a new Mgbased matrix model prepared by powder metallurgy is discussed and developed.In this research,Mg-5 wt.%Zn alloys were selected as a case.And they were impacted by hot extrusion and aging treatments to construct microstructure with different characteristics.Their selfforming corrosion product layer in Ringer’s solution,biodegradable behavior and corrosion mechanism were minutely investigated by in vitro degradation,electrochemical corrosion and cytocompatibility.The results demonstrated the extruded Mg-5 wt.%Zn alloy aged for 96 h showed high corrosion resistance,good biocompatibility for L929 and excellent ability of maintaining sample integrity during the immersion.Significantly,the alloy showed fine-grain microstructure and uniform distributed hundred nano-sized second phases,which promoted the formation of the uniform and smooth corrosion product layer at the beginning of immersion.The corrosion product layer was more stable in chloride containing aqueous solution and could be directly formed and repaired quickly,which effectively protected the matrix from further corrosion.In addition,an ideal model of Mg-based matrix for bone tissue engineering was tried to presume and propose by discussing the causal relationship between microstructure and bio-corrosion process.展开更多
Background During mammalian pre-implantation embryonic development(PED),the process of maternal-to-zygote transition(MZT)is well orchestrated by epigenetic modification and gene sequential expression,and it is related...Background During mammalian pre-implantation embryonic development(PED),the process of maternal-to-zygote transition(MZT)is well orchestrated by epigenetic modification and gene sequential expression,and it is related to the embryonic genome activation(EGA).During MZT,the embryos are sensitive to the environment and easy to arrest at this stage in vitro.However,the timing and regulation mechanism of EGA in buffaloes remain obscure.Results Buffalo pre-implantation embryos were subjected to trace cell based RNA-seq and whole-genome bisulfite sequencing(WGBS)to draw landscapes of transcription and DNA-methylation.Four typical developmental steps were classified during buffalo PED.Buffalo major EGA was identified at the 16-cell stage by the comprehensive analy-sis of gene expression and DNA methylation dynamics.By weighted gene co-expression network analysis,stage-spe-cific modules were identified during buffalo maternal-to-zygotic transition,and key signaling pathways and biological process events were further revealed.Programmed and continuous activation of these pathways was necessary for success of buffalo EGA.In addition,the hub gene,CDK1,was identified to play a critical role in buffalo EGA.Conclusions Our study provides a landscape of transcription and DNA methylation in buffalo PED and reveals deeply the molecular mechanism of the buffalo EGA and genetic programming during buffalo MZT.It will lay a foundation for improving the in vitro development of buffalo embryos.展开更多
Precipitation-strengthened medium/high-entropy alloys(MEAs/HEAs)have great potential for high-temperature applications.In this study,we designed a novel Ni_(45.9)Fe_(23)Cr_(23)V_(4)Nb_(3)Mo_(1)B_(0.1)(at.%)MEA alloy,h...Precipitation-strengthened medium/high-entropy alloys(MEAs/HEAs)have great potential for high-temperature applications.In this study,we designed a novel Ni_(45.9)Fe_(23)Cr_(23)V_(4)Nb_(3)Mo_(1)B_(0.1)(at.%)MEA alloy,hardened by the D0_(22)(Ni,Fe,Cr)_(3)(Nb,V)-type nanoprecipitates,with an excellent strength-ductility com-bination from room to elevated temperatures.Specifically,the tensile strengths,at 700 and 800℃,could be maintained as high as 845 and 589 MPa,respectively;meanwhile,elongations at all testing temper-atures exceeded 25%without any intermediate-temperature embrittlement.The temperature-dependent deformation mechanisms were unraveled using multi-scale characterizations,which involved profound slip planarities,such as stacking fault(SF)networks and deformation twins(DTs).Furthermore,the crit-ical resolved shear stress(CRSS)to initiate SFs in both face-centered cubic(FCC)and D0_(22)phases was evaluated,and the possible reasons for the origin of anomalous DTs at 800℃were discussed in de-tail.The main findings demonstrate that the shearable D0_(22)nanoparticles can provide the FCC matrix with considerable dislocation storage capacity,reinforcing strain hardening at ambient and intermedi-ate temperatures.This work provides fundamental insights into the controllable design and deformation mechanisms of high-performance D0_(22)-strengthened MEAs/HEAs.展开更多
基金The authors acknowledge the Project(81472058)sup-ported by the National Natural Science Foundation of Chinathe financial support of the 2015 ShanDong province project of outstanding subject talent group.the project(LSD-KB1806)+2 种基金supported by the foundation of National Key labo-ratory of Shock Wave and Detonation Physics and the project(11802284)supported by the National Natural Science Foun-dation of China.The project(2017GK2120)supported by the Key Research and Development Program of Hunan Province and the Natural Science Foundation of Hunan Province of China(2018JJ2506).
文摘For high corrosion resistance and extensively modified biodegradable Mg-based alloys and composites for bone implants,a new Mgbased matrix model prepared by powder metallurgy is discussed and developed.In this research,Mg-5 wt.%Zn alloys were selected as a case.And they were impacted by hot extrusion and aging treatments to construct microstructure with different characteristics.Their selfforming corrosion product layer in Ringer’s solution,biodegradable behavior and corrosion mechanism were minutely investigated by in vitro degradation,electrochemical corrosion and cytocompatibility.The results demonstrated the extruded Mg-5 wt.%Zn alloy aged for 96 h showed high corrosion resistance,good biocompatibility for L929 and excellent ability of maintaining sample integrity during the immersion.Significantly,the alloy showed fine-grain microstructure and uniform distributed hundred nano-sized second phases,which promoted the formation of the uniform and smooth corrosion product layer at the beginning of immersion.The corrosion product layer was more stable in chloride containing aqueous solution and could be directly formed and repaired quickly,which effectively protected the matrix from further corrosion.In addition,an ideal model of Mg-based matrix for bone tissue engineering was tried to presume and propose by discussing the causal relationship between microstructure and bio-corrosion process.
基金funded by the National Natural Science Foundation of China (31972996 and 32160790)Guangxi Bagui Scholar ProgramGuangxi Innovation-Driven Development Project (AA17204051)
文摘Background During mammalian pre-implantation embryonic development(PED),the process of maternal-to-zygote transition(MZT)is well orchestrated by epigenetic modification and gene sequential expression,and it is related to the embryonic genome activation(EGA).During MZT,the embryos are sensitive to the environment and easy to arrest at this stage in vitro.However,the timing and regulation mechanism of EGA in buffaloes remain obscure.Results Buffalo pre-implantation embryos were subjected to trace cell based RNA-seq and whole-genome bisulfite sequencing(WGBS)to draw landscapes of transcription and DNA-methylation.Four typical developmental steps were classified during buffalo PED.Buffalo major EGA was identified at the 16-cell stage by the comprehensive analy-sis of gene expression and DNA methylation dynamics.By weighted gene co-expression network analysis,stage-spe-cific modules were identified during buffalo maternal-to-zygotic transition,and key signaling pathways and biological process events were further revealed.Programmed and continuous activation of these pathways was necessary for success of buffalo EGA.In addition,the hub gene,CDK1,was identified to play a critical role in buffalo EGA.Conclusions Our study provides a landscape of transcription and DNA methylation in buffalo PED and reveals deeply the molecular mechanism of the buffalo EGA and genetic programming during buffalo MZT.It will lay a foundation for improving the in vitro development of buffalo embryos.
基金the City University of Hong Kong acknowl-edge the financial support from the Shenzhen Science and Tech-nology Program(Grant No.SGDX20210823104002016)the Hong Kong Research Grant Council(RGC)(Grant Nos.CityU 21205621 and C1020-21G)the National Natural Science Foundation of China(Grant No.52301174).
文摘Precipitation-strengthened medium/high-entropy alloys(MEAs/HEAs)have great potential for high-temperature applications.In this study,we designed a novel Ni_(45.9)Fe_(23)Cr_(23)V_(4)Nb_(3)Mo_(1)B_(0.1)(at.%)MEA alloy,hardened by the D0_(22)(Ni,Fe,Cr)_(3)(Nb,V)-type nanoprecipitates,with an excellent strength-ductility com-bination from room to elevated temperatures.Specifically,the tensile strengths,at 700 and 800℃,could be maintained as high as 845 and 589 MPa,respectively;meanwhile,elongations at all testing temper-atures exceeded 25%without any intermediate-temperature embrittlement.The temperature-dependent deformation mechanisms were unraveled using multi-scale characterizations,which involved profound slip planarities,such as stacking fault(SF)networks and deformation twins(DTs).Furthermore,the crit-ical resolved shear stress(CRSS)to initiate SFs in both face-centered cubic(FCC)and D0_(22)phases was evaluated,and the possible reasons for the origin of anomalous DTs at 800℃were discussed in de-tail.The main findings demonstrate that the shearable D0_(22)nanoparticles can provide the FCC matrix with considerable dislocation storage capacity,reinforcing strain hardening at ambient and intermedi-ate temperatures.This work provides fundamental insights into the controllable design and deformation mechanisms of high-performance D0_(22)-strengthened MEAs/HEAs.
