The mechanical properties of as-extruded AZ80 magnesium alloy at temperatures of 450-525℃ and strain rates of 3.0 s^(−1)and 0.15 s^(−1)were investigated by tensile tests.Zero ductility of alloy appeared at 500℃ with...The mechanical properties of as-extruded AZ80 magnesium alloy at temperatures of 450-525℃ and strain rates of 3.0 s^(−1)and 0.15 s^(−1)were investigated by tensile tests.Zero ductility of alloy appeared at 500℃ with a strain rate of 0.15 s^(−1),while the zero strength and zero ductility of the alloy were obtained nearly simultaneously at 525℃ with a strain rate of 3.0 s^(−1).The results indicated that the lower strain rate accelerated the arrival of zero ductility.As the temperature increased,the failure mode of the alloy developed from trans-granular fracture to cleavage fracture and then to inter-granular fracture with the feature of sugar-like grains and fusion traces.The existence of the low-melting composite ofβ-Mg_(17)Al_(12) and Al_(8)Mn_(5) particles segregated near the Mg_(17)Al_(12) phase along grain boundaries were demonstrated to be the reason for the brittle fracturing of the AZ80 alloy at high temperatures.Furthermore,microstructural evolution at temperatures approaching the solidus temperature was discussed to clarify magnesium alloy’s high temperature deformation mechanism.展开更多
Lobophorins(LOBs)belong to a large family of spirotetronate antibiotics with antibacterial and antitumor activities.In this study,we demonstrated the function of LobP1,a P450 monooxygenase encoded in the LOB biosynthe...Lobophorins(LOBs)belong to a large family of spirotetronate antibiotics with antibacterial and antitumor activities.In this study,we demonstrated the function of LobP1,a P450 monooxygenase encoded in the LOB biosynthetic gene cluster,by in vivo deletion and in vitro biochemical assays.The disruption of lobP1 led to the isolation of three new LOBs derivatives(3-5)and three known ones(6-8)without the hydroxyl group at C-32.LobP1 was shown to have relatively broad substrate scope.Determining the kinetic parameters of LobP1 towards different substrates revealed that LobP1 preferred substrate with a nitrosugar.The new LOBs 3-5 displayed significant antibacterial activities against Bacillus subtilis and Micrococcus luteus with MIC values of 0.125 to 1μg·mL^(-1),and the major product LOB E(6)from the∆lobP1 mutant showed moderate cytotoxic activities against several cancer cell lines.展开更多
基金financially supported by the National Natural Science Foundation of China (Nos. U1910213, 52001037, and U207601)the Chongqing Science and Technology Commission, China (Nos. cstc2020jcyj-msxmX0184 and cstc2019jscx-mbdx X0031)+2 种基金the University Innovation Research Group of Chongqing, China (No. CXQT20023)the Qinghai Scientific and Technological Plan Projects, China (No. 2018-GX-A1)the Scientific Research Foundation of Chongqing University of Technology, China
文摘The mechanical properties of as-extruded AZ80 magnesium alloy at temperatures of 450-525℃ and strain rates of 3.0 s^(−1)and 0.15 s^(−1)were investigated by tensile tests.Zero ductility of alloy appeared at 500℃ with a strain rate of 0.15 s^(−1),while the zero strength and zero ductility of the alloy were obtained nearly simultaneously at 525℃ with a strain rate of 3.0 s^(−1).The results indicated that the lower strain rate accelerated the arrival of zero ductility.As the temperature increased,the failure mode of the alloy developed from trans-granular fracture to cleavage fracture and then to inter-granular fracture with the feature of sugar-like grains and fusion traces.The existence of the low-melting composite ofβ-Mg_(17)Al_(12) and Al_(8)Mn_(5) particles segregated near the Mg_(17)Al_(12) phase along grain boundaries were demonstrated to be the reason for the brittle fracturing of the AZ80 alloy at high temperatures.Furthermore,microstructural evolution at temperatures approaching the solidus temperature was discussed to clarify magnesium alloy’s high temperature deformation mechanism.
基金supported in part by the National Natural Science Foundation of China(22193072 and 32100045)the Key Science and Technology Project of Hainan Province(ZDKJ202018)+4 种基金MOST(2018YFA0901903)K.C.WongEducationnFoundation(GJTD-2020-12)the Guangdong Provincial Special Fund for Marine Economic Development Project(GDNRC[2021]48)the Science and Technology Planning Project of Guangzhou(202102020471)Rising Star Foundation of the South China Sea Institute of Oceanology(NHXX2018SW0201)。
文摘Lobophorins(LOBs)belong to a large family of spirotetronate antibiotics with antibacterial and antitumor activities.In this study,we demonstrated the function of LobP1,a P450 monooxygenase encoded in the LOB biosynthetic gene cluster,by in vivo deletion and in vitro biochemical assays.The disruption of lobP1 led to the isolation of three new LOBs derivatives(3-5)and three known ones(6-8)without the hydroxyl group at C-32.LobP1 was shown to have relatively broad substrate scope.Determining the kinetic parameters of LobP1 towards different substrates revealed that LobP1 preferred substrate with a nitrosugar.The new LOBs 3-5 displayed significant antibacterial activities against Bacillus subtilis and Micrococcus luteus with MIC values of 0.125 to 1μg·mL^(-1),and the major product LOB E(6)from the∆lobP1 mutant showed moderate cytotoxic activities against several cancer cell lines.
