The Al and La elements are added to the Sn9Zn alloy to obtain the fusible alloy for the mitigation devices of solid propellant rocket motors. Differential scanning calorimetry(DSC), metallographic analysis,scanning el...The Al and La elements are added to the Sn9Zn alloy to obtain the fusible alloy for the mitigation devices of solid propellant rocket motors. Differential scanning calorimetry(DSC), metallographic analysis,scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS), tensile testing and fracture analysis were used to study the effect of Al and La elements on the microstructure, melting characteristics, and mechanical properties of the Sn9Zn alloy. Whether the fusible diaphragm can effectively relieve pressure was investigated by the hydrostatic pressure at high-temperature test. Experimental results show that the melting point of the Sn9Zn-0.8Al0·2La and Sn9Zn-3Al0·2La fusible alloys can meet the predetermined working temperature of ventilation. The mechanical properties of those are more than 35% higher than that of the Sn9Zn alloy at-50°C-70°C, and the mechanical strength is reduced by 80% at 175°C. It is proven by the hydrostatic pressure at high-temperature test that the fusible diaphragm can relieve pressure effectively and can be used for the design of the mitigation devices of solid propellant rocket motors.展开更多
表观遗传学是构筑完整的遗传学架构的必要内容,是现代遗传学教学的重点和难点之一。为了使学生更好地掌握这方面知识,本文以科学研究中发现的一个具有表观遗传特性的水稻突变体(epigenetic short panicle,esp)为实验材料,设计了一个表...表观遗传学是构筑完整的遗传学架构的必要内容,是现代遗传学教学的重点和难点之一。为了使学生更好地掌握这方面知识,本文以科学研究中发现的一个具有表观遗传特性的水稻突变体(epigenetic short panicle,esp)为实验材料,设计了一个表观遗传学综合性实验。水稻esp突变体植株变矮、穗长缩短、穗型直立且着粒密度增加。突变机理研究表明,DNA甲基化修饰变异引起ESP过量表达是产生突变表型的原因。该实验以突变体表型观测作为切入点,将科学研究与课程教学、课程实验与开放实验深度融合,向学生展现了一个典型表观遗传学研究课题的完整脉络和前沿技术。通过该实验,学生能对表观遗传学有一个更为直观的认识,可深入理解表型与基因型、表观遗传修饰与基因表达之间的关系,有助于培养学生的科学思维和创新能力。展开更多
基金the National Natural Science Foundation of China (Grant No. 11772058)。
文摘The Al and La elements are added to the Sn9Zn alloy to obtain the fusible alloy for the mitigation devices of solid propellant rocket motors. Differential scanning calorimetry(DSC), metallographic analysis,scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS), tensile testing and fracture analysis were used to study the effect of Al and La elements on the microstructure, melting characteristics, and mechanical properties of the Sn9Zn alloy. Whether the fusible diaphragm can effectively relieve pressure was investigated by the hydrostatic pressure at high-temperature test. Experimental results show that the melting point of the Sn9Zn-0.8Al0·2La and Sn9Zn-3Al0·2La fusible alloys can meet the predetermined working temperature of ventilation. The mechanical properties of those are more than 35% higher than that of the Sn9Zn alloy at-50°C-70°C, and the mechanical strength is reduced by 80% at 175°C. It is proven by the hydrostatic pressure at high-temperature test that the fusible diaphragm can relieve pressure effectively and can be used for the design of the mitigation devices of solid propellant rocket motors.
文摘本研究旨在确立兔波氏杆菌外膜囊泡(outer membrane vesicles,OMVs)最佳制备工艺。以兔波氏杆菌毒力较强菌株FX-1为研究对象,筛选出制备OMVs的最优方法,并对培养时间、抗生素添加量及过滤方法进行逐一优化。采用透射电镜(transmission electron microscope,TEM)、扫描电镜(scanning electron microscope,SEM)、纳米颗粒追踪分析(nanoparticle tracking analysis,NTA)等方法分析OMVs的理化性质;采用考马斯亮蓝法(Bradford法)、十二烷基硫酸钠聚丙烯酰胺凝胶电泳(sodium dodecyl sulfate-polyacrylamide gel electrophoresis,SDS-PAGE)及液相色谱-串联质谱法(liquid chromatography-tandem mass spectrometry,LC-MS/MS)检测OMVs的蛋白质含量及组分。试验结果显示,超滤浓缩法是制备兔波氏杆菌OMVs的较适方法,采用该方法的最佳培养时间、头孢氨苄质量浓度和过滤方法分别为18 h、64μg/mL和0.45μm滤膜过滤一次。制得的OMVs呈纳米级球形囊泡,平均直径为127.83 nm±0.68 nm。蛋白质分析结果表明,OMVs上包含多种与兔波氏杆菌毒力和感染机制有关的蛋白质。该制备工艺能够显著提高兔波氏杆菌OMVs的产量,为其工业化生产提供了可能;对其结构和蛋白质成分的分析,为研发新型亚单位疫苗提供了科学依据。
文摘表观遗传学是构筑完整的遗传学架构的必要内容,是现代遗传学教学的重点和难点之一。为了使学生更好地掌握这方面知识,本文以科学研究中发现的一个具有表观遗传特性的水稻突变体(epigenetic short panicle,esp)为实验材料,设计了一个表观遗传学综合性实验。水稻esp突变体植株变矮、穗长缩短、穗型直立且着粒密度增加。突变机理研究表明,DNA甲基化修饰变异引起ESP过量表达是产生突变表型的原因。该实验以突变体表型观测作为切入点,将科学研究与课程教学、课程实验与开放实验深度融合,向学生展现了一个典型表观遗传学研究课题的完整脉络和前沿技术。通过该实验,学生能对表观遗传学有一个更为直观的认识,可深入理解表型与基因型、表观遗传修饰与基因表达之间的关系,有助于培养学生的科学思维和创新能力。
