A pair of two-component regulatory genes ecrA1/A2 in S.coelicolor

Two-component genes are kinds of genetic elements involved in regulation of antibiotic production in Streptomyces coelicolor. DNA microarray analysis revealed that ecrA1/A2, which mapped at distant sites from red locus and encode respectively the kinase and regulator, expressed coordinately with genes of Red specific biosynthetic pathway, ecrA1 and ecrA2 gene-disruptive mutants were constructed using homogenotisation by reciprocal double crossover. Fermentation data showed that the undecylprodigiosin (Red) level of production was lower than that of wild-type strain. However, the change of the actinorhodin (Act) production level was not significant compared with wild type. Thus, these experiment results confirmed that the two-component system ecrA 1/A2 was positive regulatory element for red gene cluster.     

熔盐法制备锐钛矿相纳米TiO2

介绍一种新的无机材料粉体的制备方法——熔盐法,以及该方法的部分应用。     

Web Service 系统集成技术在图书联合检索中的应用

分析新兴的Web Service系统集成技术原理,探讨在异构系统中的优势,在.NET平台上实现了跨平台图书信息联合检索的设计模型。     

利用CORBA技术和思想来开展网络远程教学

网络远程教育是一种新兴的教学方式 ,CORBA技术能为我们开发开放的、灵活的、交互的、分布式和实时性的网络远程教学系统提供思想和技术支持。该文首先对CORBA技术及其特点进行了介绍 ,然后探讨了CORBA在网络远程教学系统开发中提供的技术支持和思路     

沸石模型簇与乙烯、氮气和甲烷相互作用的从头算研究

设计不同的超分子计算模型簇Z…X（Z=2TNa（[H3SiOAlH3]-Na^＋），3TNa（[H3SiOAl（H）2OSiH3]^-Na^＋）和4TNa（[H3SiOAl（H）2OSi（H）2OSiH3]^-Na^=），X=C2H4、N2和CH4），模拟计算C2H4、N2和CH4与沸石模型簇的相互作用．在HF／6—31G水平上对Z、X和复合物Z…X进行几何全优化计算得到优化构型，经MP2／6—31G＊电子相关能校正和基组重叠误差（BSSE）校正以获得相互作用能．结果表明，对于一指定X，随Z尺寸增大，复合物Z…X的相互作用能减小；对于一指定Z，复合物Z…X的相互作用能由大到小顺序为Z…C2H4〉Z…N2》Z…CH。．分子间相互作用的能量分解分析显示，静电能在Z…X相互作用能量中占主导地位，电荷转移能在Z…C2H4复合物体系中居第2位，而极化能在Z…M和Z…CH4复合物体系中居第2位。     

多晶VO_2材料的绝缘-金属转变研究

对用粉末冶金(烧结)法制得的多晶VO_2材料进行了X-射线结构分析和R-T曲线的实验研究.结果表明,纯的VO_2多晶材料升温时在338K发生数量级约为10~3倍的绝缘-金属转变,掺杂Cr的VO_2样品转变温度向低温方向偏移。当样品中含有5％以上的V_2O_5或样品淬油时,其R-T曲线将变得平坦.     

对-甲苯磺酸催化合成香料β-萘乙醚

研究了以β-萘酚和乙醇为原料，对甲苯碘酸作催化剂，环己烷作溶, 合成香料β-萘乙醚的新工艺，得出最佳反应条件：M（c10H7O）：M（c2H5OH0＝1：3，回流反应7h，收率为98．7％，产品熔点为35－37℃。     

网络地理信息系统研究与实现

介绍了网络地理信息系统的概念和组成 ,并详细讨论了它的理论研究与实现方法。     

情感和母语对外语教学的影响

影响外语学习最主要的因素是情感和母语。情感是学习的发动机,出现障碍会导致学习的停顿。与母语不同之处因母语的固化而造成外语学习困难。判断外语教学法的优劣在于看它能否有效地克服两个因素引起的学习障碍。     

Minimalist Instruction for Learning to Search the World Wide Web

This study examined the efficacy of minimalist instruction to develop self-regulatory skills involved in Web searching. Two versions of minimalist self-regulatory skill instruction were compared to a control group that was merely taught procedural skills to operate the search engine. Acquired skills were tested on Web search tasks and search tasks in an online library catalogue. Self-regulatory skill instruction was found to increase practice time by 25%. However, it did not enhance search performance on the test tasks. Explanations are advanced for these findings and topics for further research are identified.