Analysis of EET on Ca increasing the melting point of Mg17Al12 phase

The present investigation showed that the additions of Ca to the alloy AZ91 were mainly dissolved into the Mg17Al12 phase and increased its melting point and thermal stability, which would have great effects on the high- temperature properties of AZ91 alloy. The empirical electron theory (EET) of solid and molecules was used to calculate the valence electron structures (VES) of Mg17Al12 intermetallic compound with and without Ca addition. The results showed that Ca dissolving in Mg17Al12 phase increased the strength of bonds that control the thermal stability of Mg17Al12 phase. Additions of Ca also made the distribution of the valence electrons on the dominant bond network more uniform in the whole unit cell of Mg17Al12. The theoretical conclusions well account for the experimental results.     

PVP对十二烷基甜菜碱/正戊醇/正庚烷O/W型微乳液性质的影响

研究了聚乙烯吡咯烷酮（PVP）存在时，由两性表面活性剂十二烷基甜菜碱（C12BE）/正戊醇（C5OH）/正庚烷（C6H16）和NaCl组成的O/W型微乳液的黏度、Ph、界面张力及形成热效应的变化，结果表明，加入PVP后，微乳液的黏出现电站效应；PH值呈下降趋势，但PVP的分子量不同，PH值下降的幅度不同；PVP的存在，导致微乳液与油相的界面张力稍有升高；微量热测定结果表明，PVP的存在导致微乳液的热效应减少。     

LY12cz铝合金棒料的拉伸实验研究

通过对 LY1 2 cz铝合金棒料在三种应变率下 ( 0 .0 0 1 s-1,60 0 s-1,1 2 0 0 s-1)拉伸力学性能的测试 ,得到各个应变率下完整的应力应变曲线。试验结果表明 ,L Y1 2 cz铝合金板料和棒料的拉伸性能有着很大的区别。棒料和板料相比 ,其屈服应力σs基本不变 ;棒料的强度极限σb比板料的强度极有较大的提高 ;棒料的失稳应变 δb 随着应变率的增加而增大 ;棒料的强性模量较低 ,且棒料的拉伸性能对应变率不敏感 ,基本可看作是应变率无关材料     

西松烯内酯的合成研究——Ⅱ.中间体苏式-7-羟基-3,9,13-三甲基-6-异丙烯基-(2E,8E,12)-十四碳三烯苯硫醚的合成

以香叶醇为原料经过4步反应得到8-溴-3,7-二甲基-(2E,6E)-辛二烯基苯硫醚(7),(7)与(?)牛儿醛在Cr(Ⅱ)作用下立体选择地得到苏式-7-羟基-3,9,13-三甲基-6-异丙烯基-(2E,8E,12)-十四碳三烯苯硫醚.     

LY12铝合金的冰盘抛光纳米加工实验研究

采用冰盘抛光新技术，首次对LY12铝合金材料进行了纳米抛光加工实验研究，给出了实际测量结果。通过分析与实验验证，得出了不同加工参数对冰盘抛光精度带来不同影响的规律。对冰盘抛光纳米加工进行了较为深入的分析与探讨。     

Analysis of components of conserved “backbone sequences”among genomes of Shigella spp. strains

Difference in the genomic compositions of prokaryotes is the basis of the diversity in their biological characters. However, besides their flora-or strain-specific genes,those floras with closer relationship in the evolution also have conserved “backbone sequences”, which reveal the marks of their origin and evolution, and these “backbone sequences”are just the basis of their elementary living abilities and common biological properties. Shigella is very closely related to E. coli in the origin and evolution, and may turn out to belong to the same genus. In this study, a microarray containing E. coli K-12 whole genome and Sf301 specific ORFs is used to investigate the genomic components of four Shigella strains. The results indicate that 16%-22% K-12 ORFs sequences are not detected in the genome of Shigella strains while the genome of Shigella contains at least 2800 conserved ORFs, which compose the common “backbone sequences”.Advanced analysis indicated that the “backbone sequences”are the essential components in maintaining the normal physiological activities of intestinal bacteria. Furthermore,only 20% Sf301-specific ORFs exist in other strains simultaneously, which demonstrate the great genome heterogeneity and the genetic diversity among the strains.     

CD1d and natural T cells: how their properties jump-start the immune system

Cellular and humoral immune mechanisms recruited to defend the host from infectious agents depend upon the early immune events triggered by antigen. The cytokine milieu within which the immune response matures is the most important of many factors that govern the nature of the immune response. Natural T cells, whose function is controlled by CD1d molecules, are an early source of cytokines that can bestow type 1 or type 2 differentiative potential upon helper T lymphocytes. This review attempts to illuminate the glycolipid antigen presentation properties of CD1d, how CD1d controls the function of natural T cells and how CD1d and natural T cells interact to jump start the immune system. CD1d is postulated to function as a sensor, sensing alterations in cellular lipid content by virtue of its affinity for such ligands. The presentation of a neo-self glycolipid, presumably by infectious assault of antigen-presenting cells, activates natural T cells, which promptly release pro-inflammatory and anti-inflammatory cytokines and jumpstart the immune system. Received 10 July 2000; received after revision 16 October 2000, accepted 16 November 2000     

提高超声波测距精度的方法

基于宏晶公司新近推出的STC12C5410单片机,通过利用温度校正、标杆校正、软件校正的方法实现超声波测距精度由厘米级向毫米级跨进的方法。给出了硬件设计电路图及软件的流程图。在电路的实际测试过程中,成功地达到了预期的效果。     

盐生杜氏藻锰超氧化物歧化酶（MnSOD）在大肠杆菌中的功能鉴定

将极端耐盐的盐生杜氏藻(Dunaliella salina)的锰超氧化物歧化酶（DsMnSOD）基因克隆到表达载体pET32a中，并转入SOD缺陷型大肠杆菌菌株K12（SOD-）中，诱导重组蛋白表达，在耐盐、抗辐射和抗寒方面对其功能进行验证.结果显示，导入外源DsMnSOD基因的工程菌，在有氧条件下受到各种胁迫时，生长状况明显优于原菌，其耐受NaCl浓度从8%提高到10%，耐受紫外线（295nm，83μW/cm2）照射时间从45s提高到65s，4℃培养的存活率从10.7%提高19.0%，且SOD的     

CD40L对B淋巴细胞表面分子及分泌IL-12的影响

在体外使用CD40L作用于B淋巴细胞使之活化,通过测定B淋巴细胞表面分子及分泌细胞因子的变化,探讨B淋巴细胞作为抗原递呈细胞在抗肿瘤免疫中的优势,为B淋巴细胞特异性活化细胞毒T淋巴细胞(cytotoxic T lymphocyte,CTL)进而发挥其肿瘤细胞杀伤效应奠定基础.取7名健康成人外周静脉血,经淋巴细胞分离液分离人外周血单个核细胞(PBMC),分为对照组和实验组,实验组培养液中加入加入CD40L和IL-4,共培养21 d.观察B淋巴细胞生长状况,并在第7 d、第14 d和第21 d,用流式细胞仪(FCAS)测定其表面分子CD80、CD86和CD19,在第21 d,使用酶联免疫吸附法(ELISA)测定培养液中的IL-12水平.结果显示,在CD40L的作用下,B淋巴细胞呈克隆样增殖,并高表达表面分子CD80/CD86和CD19,和对照组相比,B淋巴细胞分泌IL-12水平升高(P＜0.05).上述实验结果说明通过CD40L的刺激,B淋巴细胞得到了活化,提示通过该途径活化的B淋巴细胞具备了作为抗原递呈细胞而发挥其抗肿瘤免疫治疗的能力.