Influence of γ' precipitate on deformation and fracture during creep in PM nickel-based superalloy

FGH96 is a powder metallurgy nickel based superally used for turbine disk of aero-engines. In the present study FGH96 alloy with four different γ' precipitate microstructures were produced via solution heat-treatment with different cooling rates, and the maximum cooling rate reached 400°C/min which was a super cooling rate for Nickel-based superalloy. The creep tests were conducted for PM FGH96 alloy under the testing condition of 704°C and 690 MPa. The relationship between the creep properties and the distribution of γ' precipitate was established. The creep mechanism was analyzed by using TEM and ACTEM, and the dislocation movement was studied at the atomic scale. The creep strain rate was calculated through a physically based crystal slip model established based on crystal plasticity. The calculated results were consistent with the test ones, illustrating the validity of the model. The fracture mechanism was also investigated, and the results showed that the creep cracks generated on the surface due to the oxidation. It was observed that the cracks propagated in different ways depending on the different average diameters of γ' precipitate. With the decrease of the average γ' precipitate size,the critical shearing stress increased and the resistance of the dislocation slipping increased. The fracture mechanism for the primary stage transformed from intragranular to intergranular due to the change of dislocation slipping.     

中国北方汉族人群PPAR6基因C／T多态研究

为研究中国汉族群体PPARδ基因C294T酶切位点的遗传多态性以及该位点的具体多态形式,采用PCR-RFLP技术对329例无血缘关系的健康中国北方汉族人的染色体进行检测．用卡方检验对所得等位基因频率、基因型频率进行分析,实验结果与其他种族进行比较．结果显示C294T位点存在多态性,等位基因频率rc=25．9％,rT=74．1％;基因型频率rc/c=6．1％,rc/T=39．8％,rT／T=54．1％;经卡方检验符合Hardy-Weinberg遗传平衡定律;认为中国汉族群体PPARδ基因C294T酶切位点也具有遗传多态性．其基因型频率和等位基因频率在男女间没有显著性差异,与德国人群有显著性差异;与瑞典人群相比有极显著差异,而与韩国人相比没有显著性差异．     

大鼠再生肝8种细胞的PPARγ信号通路相关基因转录谱预示脂类代谢活动

为了解大鼠肝再生中肝细胞、胆管上皮细胞、卵圆细胞、星形细胞、窦内皮细胞、库普弗细胞、陷窝细胞、树突状细胞等8种肝脏细胞的PPARγ信号通路相关基因转录谱及其预示的脂类代谢活动,按本卷2期张丽君[1]等方法分离大鼠再生肝8种细胞,检测它们的PPARγ信号通路基因表达谱,分析其预示的生理活动.结果表明,41个PPARγ信号通路相关基因在大鼠肝再生中发生了有意义的表达变化,其中上调、下调和上/下调的基因为9、9、23个,呈现15种表达相关性.相应细胞的基因数为10、6和1,10、12和2,7、7和0,16、8和3,18、7和1,10、6和1,11、20和0,13、9和4.它们的转录谱预示,胆管上皮细胞和星形细胞的脂肪合成、星形细胞和树突状细胞的胆固醇代谢、8种肝脏细胞的脂肪酸运输和脂肪细胞分化、星形细胞、窦内皮细胞和树突状细胞的脂肪酸氧化和糖异生、胆管上皮细胞和树突状细胞的能量代谢增强.上述结果表明,PPARγ信号通路与大鼠肝再生密切相关.     

非精确Newton法的半局部收敛性

通过引入中心γ0-条件及γ-条件,研究了非精确Newton法的半局部收敛性问题,得到了更优的半局部收敛性分析及更精确的误差估计.     

抗病毒中药复方制剂对雏鸡IFN-γ水平影响的研究

为了探讨抗病毒中药复方制剂的抗病毒作用机理和为临床合理用药提供实验依据,采用水萃取法制备抗病毒中药复方浸膏制剂,将实验动物随机分为阴性对照组、阳性对照组、低剂量中药组、中剂量中药组和高剂量中药组,在免疫接种NDV-Lasota株灭活疫苗的基础之上,以IFN-γ(干扰素γ)为检测指标,研究中药复方制剂对雏鸡血清IFN-γ水平的影响.实验结果表明:抗病毒中药复方制剂具有诱导实验雏鸡在免疫应答过程中IFN-γ产生的作用,诱导作用可能与中药剂量及机体的免疫状态有关.     

γ-丁内酯的生产方法及其应用综述

简要介绍了γ-丁内酯的性质和用途,总结了γ-丁内酯合成技术的国内外进展情况及其主要应用领域,分析了我国γ-丁内酯的市场需求情况。     

苯基三乙氧基硅烷与氨丙基三乙氧基硅烷的水解共缩聚

研究了苯基三乙氧基硅烷与氨丙基三乙氧基硅烷在甲苯/水/盐酸、四氢呋喃/水/盐酸、乙醇/水/氨、十二烷基硫酸钠/水/四甲基氢氧化铵四个较典型体系中的水解共缩聚,通过界面聚合、溶液聚合、分散聚合、乳液聚合分别得到了树脂状、粒径200nm微球、粒径3μm微球和乳液状的聚氨丙基/苯基倍半硅氧烷,采用元素分析、红外光谱、核磁共振等对各产物的组成、结构、性能等进行了对比分析。结果表明酸催化体系共聚物为溶解性良好的低交联链状结构,乙氧基水解完全,而存在碱催化的体系产物交联度高,溶解性较差,结构中残留未水解的乙氧基; 溶剂的极性对共聚物的溶解、析出、粒子的形成影响较大。     

不对称合成γ-酮酯

手性醇衍生的γ-重氮苯乙酸酯与N(-苯乙烯基)-吗啉在铜盐催化下的反应,能够以高度的化学产率制备手性的4-氧代-2,4-二苯基-丁酸酯,产物中两种非对映异构体的比例达到2∶1.