The evolution of the eutectic structures in the as-cast and homogenized 7X50 aluminum alloys was studied by scanning electron microscopy(SEM), transmission electron microscopy(TEM), energy dispersive spectrometer(EDS)...The evolution of the eutectic structures in the as-cast and homogenized 7X50 aluminum alloys was studied by scanning electron microscopy(SEM), transmission electron microscopy(TEM), energy dispersive spectrometer(EDS), differential scanning calorimetry(DSC), X-ray diffraction(XRD) and tensile test. The results show that the main phases are S(Al2CuMg), T(Al2Mg3Zn3) and Mg Zn2, with a small amount of Al7Cu2 Fe and Al3 Zr in the as-cast 7X50 alloy. The volume fraction of the dendritic-network structure and residual phase decreases gradually during the homogenization. After homogenization at 470 °C for 24 h and then 482 °C for 12 h, the T(Al2Mg3Zn3) phase disappears and minimal S(Al2CuMg) phase remains, while almost no change has happened for Al7Cu2 Fe. There is a strong endothermic peak at 477.8 °C in the DSC curve of as-cast alloy. A new endothermic peak appears at 487.5 °C for the sample homogenized at 470 °C for 1 h. However, this endothermic peak disappears after being homogenized at 482 °C for 24 h. The T(Al2Mg3Zn3) phase cannot be observed by XRD, which is consistent with that T phase is the associated one of S(Al2CuMg) phase and Mg Zn2 phase. The volume fraction of recrystallized grains is substantially less in the plate with pre-homogenization treatment. The strength and fracture toughness of the plate with pre-homogenization treatment are about 15 MPa and 3.3 MPa·m1/2 higher than those of the material with conventional homogenization treatment.展开更多
To construct overexpression lentiviral-based vector carrying rat B7x gene,B7x gene precursor sequences amplified by polymerse chain reaction（PCR） were ligated with pLVTHM to generate pLVTHM-B7x gene expression lenti...To construct overexpression lentiviral-based vector carrying rat B7x gene,B7x gene precursor sequences amplified by polymerse chain reaction（PCR） were ligated with pLVTHM to generate pLVTHM-B7x gene expression lentiviral-based vector.The positive clones were selected to be submitted to DNA sequencing.HEK293T cells were co-transfected with pLVTHM-B7x and two packaging plasmids psPAX2 and pMD2G to produce lentivirus which express B7x gene.The mRNA expression levels of B7x gene and virus titer were detected by real-time PCR in HEK293T cells.The B7x protein levels were detected by Western blot analysis in HEK293T cells.The identification of restriction enzyme digestion and DNA sequencing confirmed that pLVTHM-B7x lentiviral-based vector was successfully constructed.Green fluorescence was observed in HEK293T packaging cells by means of an inverted fluorescence microscope and the virus titer measured was 2×108 TU/mL.It will establish the foundation for studing deeply the biological function of B7x to construct successfully B7x expression lentiviral-based vector.展开更多
基金Project(2011KJZX1-2)supported by the Science and Technology Development Fund of Aluminum Corporation of China
文摘The evolution of the eutectic structures in the as-cast and homogenized 7X50 aluminum alloys was studied by scanning electron microscopy(SEM), transmission electron microscopy(TEM), energy dispersive spectrometer(EDS), differential scanning calorimetry(DSC), X-ray diffraction(XRD) and tensile test. The results show that the main phases are S(Al2CuMg), T(Al2Mg3Zn3) and Mg Zn2, with a small amount of Al7Cu2 Fe and Al3 Zr in the as-cast 7X50 alloy. The volume fraction of the dendritic-network structure and residual phase decreases gradually during the homogenization. After homogenization at 470 °C for 24 h and then 482 °C for 12 h, the T(Al2Mg3Zn3) phase disappears and minimal S(Al2CuMg) phase remains, while almost no change has happened for Al7Cu2 Fe. There is a strong endothermic peak at 477.8 °C in the DSC curve of as-cast alloy. A new endothermic peak appears at 487.5 °C for the sample homogenized at 470 °C for 1 h. However, this endothermic peak disappears after being homogenized at 482 °C for 24 h. The T(Al2Mg3Zn3) phase cannot be observed by XRD, which is consistent with that T phase is the associated one of S(Al2CuMg) phase and Mg Zn2 phase. The volume fraction of recrystallized grains is substantially less in the plate with pre-homogenization treatment. The strength and fracture toughness of the plate with pre-homogenization treatment are about 15 MPa and 3.3 MPa·m1/2 higher than those of the material with conventional homogenization treatment.
基金Supported by the National Natural Science Foundation of China(No.30870354)the Fund of Jilin Provincial Science and Technology Services,China(Nos.20070720,200805120,20090732)the Jilin Provincial Development and Reformation Committee Fund,China(No.2009Y042J12314)
文摘To construct overexpression lentiviral-based vector carrying rat B7x gene,B7x gene precursor sequences amplified by polymerse chain reaction（PCR） were ligated with pLVTHM to generate pLVTHM-B7x gene expression lentiviral-based vector.The positive clones were selected to be submitted to DNA sequencing.HEK293T cells were co-transfected with pLVTHM-B7x and two packaging plasmids psPAX2 and pMD2G to produce lentivirus which express B7x gene.The mRNA expression levels of B7x gene and virus titer were detected by real-time PCR in HEK293T cells.The B7x protein levels were detected by Western blot analysis in HEK293T cells.The identification of restriction enzyme digestion and DNA sequencing confirmed that pLVTHM-B7x lentiviral-based vector was successfully constructed.Green fluorescence was observed in HEK293T packaging cells by means of an inverted fluorescence microscope and the virus titer measured was 2×108 TU/mL.It will establish the foundation for studing deeply the biological function of B7x to construct successfully B7x expression lentiviral-based vector.
