To understand the quasi-static and dynamic compressive mechanical behavior of two- dimensional SiC fiber-reinforced SiC composites （2D-SiC1/SiC）, their compressive behavior at room temperature was investigated at a ...To understand the quasi-static and dynamic compressive mechanical behavior of two- dimensional SiC fiber-reinforced SiC composites （2D-SiC1/SiC）, their compressive behavior at room temperature was investigated at a strain rate from 10-4 to 104/s, and the fracture surfaces and damage morphology were observed. The results show that the dynamic failure strength of 2D-SiC1/SiC obeys the Weibull distribution, and the Weibull modulus is 5,66. Meanwhile, 2D-SiC1/SiC presents a transition from brittle to tough with a decrease of strain rate, and 2D-SiC1/SiC has a more significant strain rate sensitivity compared to the 2D-C/SiC composites. The failure mode of 2D-SiC1/SiC depends upon the strain rate.展开更多
The creep properties of as-cast Mg-9Al-1Si alloy and Mg-9Al-1Si-1SiC composite were compared.The results show that Mg-9A1-lSi-lSiC composite performs a better creep resistance than that of Mg-9Al-1Si alloy at constant...The creep properties of as-cast Mg-9Al-1Si alloy and Mg-9Al-1Si-1SiC composite were compared.The results show that Mg-9A1-lSi-lSiC composite performs a better creep resistance than that of Mg-9Al-1Si alloy at constant temperature and stress(473 K,70MPa).Besides,the creep behavior of Mg-9Al-1 Si-1SiC composite at various temperature from 448 K to 498 K and under stresses of 70-90 MPa were systematically investigated.The Mg-9Al-1 Si-1SiC composite exhibited a stress exponent from 5.5 to 6.9 and the creep activation energy fell within the range of 86-111 kJ/mol.The results showed that the creep mechanism of Mg-9Al-1Si-1SiC composite was mainly attributed to the effects of secondary phase strengthening mechanism and dislocation climb mechanism.展开更多
The effects of interface shape on stress wave distribution and attenuation were investiga- ted using finite element method （ FEM ）. The simulation results indicate that when the stress wave propagates from SiC ceram...The effects of interface shape on stress wave distribution and attenuation were investiga- ted using finite element method （ FEM ）. The simulation results indicate that when the stress wave propagates from SiC ceramic to A1 alloy, the tensile stress decreases and the attenuation coefficient of the stress wave increases with increasing central angle of the concave interface between SiC and A1. But for the convex interface, the tensile stress increases and attenuation coefficient decreases with increasing central angle. As the stress wave propagates from A1 alloy to SiC ceramic, the atten- uation coefficient of stress wave decreases with increasing the central angle of the concave interface. For the convex interface, the attenuation coefficient increases with increasing central angle.展开更多
Magnetotransport measurements are carried out on the A1GaN/A1N/GaN in an SiC heterostructure, which demon- strates the existence of the high-quality two-dimensional electron gas （2DGE） at the A1N/GaN interface. Whil...Magnetotransport measurements are carried out on the A1GaN/A1N/GaN in an SiC heterostructure, which demon- strates the existence of the high-quality two-dimensional electron gas （2DGE） at the A1N/GaN interface. While the carrier concentration reaches 1.32×10^13 cm^-2 and stays relatively unchanged with the decreasing temperature, the mobility of the 2DEG increases to 1.21 × 10^4 cm2/（V.s） at 2 K. The Shubnikov-de Haas （SdH） oscillations are observed in a magnetic field as low as 2.5 T at 2 K. By the measurements and the analyses of the temperature-dependent SdH oscillations, the effective mass of the 2DEC is determined. The ratio of the transport lifetime to the quantum scattering time is 9 in our sample, indicating that small-angle scattering is predominant.展开更多
Multisubunit SKP1/Cullin1/F-box(SCF)E3 ligases play essential roles in regulating the stability of crucial regulatory factors and controlling growth and development in eukaryotes.Detecting E3 ligase activity in vitro ...Multisubunit SKP1/Cullin1/F-box(SCF)E3 ligases play essential roles in regulating the stability of crucial regulatory factors and controlling growth and development in eukaryotes.Detecting E3 ligase activity in vitro is important forexploring the molecular mechanism of protein ubiquitination.However,in vitro ubiquitination assay systems for multisubunit E3 ligases remain difficult to achieve,especially in plants,mainly owing to difficulties in achieving active components of multisubunit E3 ligases with high purity and characterizing specific E2 and E3 pairs.In this study,we characterized components of the rice ScFDiwARF3(SCFDs)E3 ligase,screened the coordinated E2,and reconstituted active ScFD3 E3 ligase in vitro.We further engineered SCFD3 E3 ligase using a fused SKP1-Cullin1-RBX1(eSCR)protein and found that both the wild-type SCFD3 E3 ligase and the engineered SCFD3 E3 ligase catalyzed ubiquitination of the substrate D53,which is the key transcriptional repressor in strigolactone signaling.Finally,we replaced D3 with other F-box proteins from rice and humans and reconstituted active escF E3 ligases,including escFaID2,escFBxL1s,and escFcDC4 E3 ligases.Our work reconstitutes functional SCF E3 ligases in vitro and generates an engineered system with interchangeable F-box proteins,providing a powerful platform for studying the mechanisms of multisubunit SCF E3 ligases in eukaryotes.展开更多
We have investigated the electronic and structural properties of inorganic nanoribbons （BN, AIN, GaN, SiC, and ZnO） with unpassivated zigzag edges using density functional theory calculations. We find that, in gener...We have investigated the electronic and structural properties of inorganic nanoribbons （BN, AIN, GaN, SiC, and ZnO） with unpassivated zigzag edges using density functional theory calculations. We find that, in general, the unpassivated zigzag edges can lead to spin-splitting of energy bands. More interestingly, the inorganic nanoribbons A1N and SiC with either one or two edges unpassivated are predicted to be half metallic. Possible structural reconstruction at the unpassivated edges and its effect on the electronic properties are investigated. The unpassivated N edge in the BN nanoribbon and P edge in the AlP nanoribbon are energetically less stable than the corresponding reconstructed edge. Hence, edge reconstruction at the two edges may occur at high temperatures. Other unpassivated edges of the inorganic nanoribbons considered in this study are all robust against edge reconstruction.展开更多
基金Funded by the Scientific and Technological Development Project of Yantai(No.2013JH020)
文摘To understand the quasi-static and dynamic compressive mechanical behavior of two- dimensional SiC fiber-reinforced SiC composites （2D-SiC1/SiC）, their compressive behavior at room temperature was investigated at a strain rate from 10-4 to 104/s, and the fracture surfaces and damage morphology were observed. The results show that the dynamic failure strength of 2D-SiC1/SiC obeys the Weibull distribution, and the Weibull modulus is 5,66. Meanwhile, 2D-SiC1/SiC presents a transition from brittle to tough with a decrease of strain rate, and 2D-SiC1/SiC has a more significant strain rate sensitivity compared to the 2D-C/SiC composites. The failure mode of 2D-SiC1/SiC depends upon the strain rate.
基金Shanxi provice scientific facilities and instruments shared service platform of magnesium-based matierals electric impulse aided forming(201805D141005)National Natural Science Foundation of China(51404166,51704209,U1810208)+3 种基金Science and Technology Major Project of Shanxi province(20191102008,20191102007,20181101008)Natural Science Foundation of Shanxi Province(201701D121045)Shanxi Province Science Foundation for Youths(2016021063)The Projects of International Cooperation in Shanxi(201803D421086).
文摘The creep properties of as-cast Mg-9Al-1Si alloy and Mg-9Al-1Si-1SiC composite were compared.The results show that Mg-9A1-lSi-lSiC composite performs a better creep resistance than that of Mg-9Al-1Si alloy at constant temperature and stress(473 K,70MPa).Besides,the creep behavior of Mg-9Al-1 Si-1SiC composite at various temperature from 448 K to 498 K and under stresses of 70-90 MPa were systematically investigated.The Mg-9Al-1 Si-1SiC composite exhibited a stress exponent from 5.5 to 6.9 and the creep activation energy fell within the range of 86-111 kJ/mol.The results showed that the creep mechanism of Mg-9Al-1Si-1SiC composite was mainly attributed to the effects of secondary phase strengthening mechanism and dislocation climb mechanism.
基金Supported by the National Basic Research Program of China("973" Program)(613135)
文摘The effects of interface shape on stress wave distribution and attenuation were investiga- ted using finite element method （ FEM ）. The simulation results indicate that when the stress wave propagates from SiC ceramic to A1 alloy, the tensile stress decreases and the attenuation coefficient of the stress wave increases with increasing central angle of the concave interface between SiC and A1. But for the convex interface, the tensile stress increases and attenuation coefficient decreases with increasing central angle. As the stress wave propagates from A1 alloy to SiC ceramic, the atten- uation coefficient of stress wave decreases with increasing the central angle of the concave interface. For the convex interface, the attenuation coefficient increases with increasing central angle.
基金Project supported by the National Basic Research Program of China (Grant No.2011CB309606)
文摘Magnetotransport measurements are carried out on the A1GaN/A1N/GaN in an SiC heterostructure, which demon- strates the existence of the high-quality two-dimensional electron gas （2DGE） at the A1N/GaN interface. While the carrier concentration reaches 1.32×10^13 cm^-2 and stays relatively unchanged with the decreasing temperature, the mobility of the 2DEG increases to 1.21 × 10^4 cm2/（V.s） at 2 K. The Shubnikov-de Haas （SdH） oscillations are observed in a magnetic field as low as 2.5 T at 2 K. By the measurements and the analyses of the temperature-dependent SdH oscillations, the effective mass of the 2DEC is determined. The ratio of the transport lifetime to the quantum scattering time is 9 in our sample, indicating that small-angle scattering is predominant.
基金The research was supported by grants from the National Natural Science Foundation of China(32133012,31788103,32100268,and 31900244)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(2019099).
文摘Multisubunit SKP1/Cullin1/F-box(SCF)E3 ligases play essential roles in regulating the stability of crucial regulatory factors and controlling growth and development in eukaryotes.Detecting E3 ligase activity in vitro is important forexploring the molecular mechanism of protein ubiquitination.However,in vitro ubiquitination assay systems for multisubunit E3 ligases remain difficult to achieve,especially in plants,mainly owing to difficulties in achieving active components of multisubunit E3 ligases with high purity and characterizing specific E2 and E3 pairs.In this study,we characterized components of the rice ScFDiwARF3(SCFDs)E3 ligase,screened the coordinated E2,and reconstituted active ScFD3 E3 ligase in vitro.We further engineered SCFD3 E3 ligase using a fused SKP1-Cullin1-RBX1(eSCR)protein and found that both the wild-type SCFD3 E3 ligase and the engineered SCFD3 E3 ligase catalyzed ubiquitination of the substrate D53,which is the key transcriptional repressor in strigolactone signaling.Finally,we replaced D3 with other F-box proteins from rice and humans and reconstituted active escF E3 ligases,including escFaID2,escFBxL1s,and escFcDC4 E3 ligases.Our work reconstitutes functional SCF E3 ligases in vitro and generates an engineered system with interchangeable F-box proteins,providing a powerful platform for studying the mechanisms of multisubunit SCF E3 ligases in eukaryotes.
文摘We have investigated the electronic and structural properties of inorganic nanoribbons （BN, AIN, GaN, SiC, and ZnO） with unpassivated zigzag edges using density functional theory calculations. We find that, in general, the unpassivated zigzag edges can lead to spin-splitting of energy bands. More interestingly, the inorganic nanoribbons A1N and SiC with either one or two edges unpassivated are predicted to be half metallic. Possible structural reconstruction at the unpassivated edges and its effect on the electronic properties are investigated. The unpassivated N edge in the BN nanoribbon and P edge in the AlP nanoribbon are energetically less stable than the corresponding reconstructed edge. Hence, edge reconstruction at the two edges may occur at high temperatures. Other unpassivated edges of the inorganic nanoribbons considered in this study are all robust against edge reconstruction.
