Probing met repressor-operator recognition in solution.

The three-dimensional crystal structure of the Escherichia coli methionine repressor, MetJ, complexed with a DNA operator fragment is described in an accompanying article. The complex exhibits several novel features of DNA-protein interaction. DNA sequence recognition is achieved largely by hydrogen-bond contacts between the bases and amino-acid side chains located on a beta-ribbon, a mode of recognition previously hypothesized on the basis of modelling of idealized beta-strands and DNA, and mutagenesis of the Salmonella phage P22 repressors Arc and Mnt. The complex comprises a pair of MetJ repressor dimers which bind to adjacent met-box sites on the DNA, and contact each other by means of a pair of antiparallel alpha-helices. Here we assess the importance of these contacts, and also of contacts that would be made between the C-helices of the protein and DNA in a previous model of the complex, by studying mutations aimed at disrupting them. The role of the carboxy-terminal helix face in operator binding was unclear, but we demonstrate that recognition of operator sequences occurs through side chains in the beta-strand motif and that dimer-dimer interactions are required for effective repression.     

正交拉丁矩阵的上下界

引进了一般形式的拉丁矩阵,并讨论了相互正交的拉丁矩阵个数的上下界。     

翅茎香青精油的化学成分

从江西省武功山采集的翅茎香青「Ａｎａｐｈａｌｉｓ ｐｔｅｒｏｃａｕｌａ（Ｆｒａｎｃｄ。ｅｔ Ｓａｖａｔ。）Ｍａｘｉｍ」其精油通过ＧＣ及ＧＣ／ＭＳ分析，共鉴定了３１个化合物，占总量的９０．９１％。其中主要成分为β－丁香烯，含量达４０％以上，为翅茎香青精油的主体成分。油样经轻工业部上海香料研究所评定，认定它与山Ｑｉｕ油的主体成分。油样经轻工业部上海香料研究所评定，认为它与山Ｑｉｕ油的香气相似，可用于调     

改性沥青防水卷材的地下室施工

介绍新型防水材料ＳＢＳ改性沥青柔性油毡的性能、施工工艺、操作方法及保证质量的措施，并提出存在的问题及施工中注意事项。     

铁路主要干线提速有关问题的研究

在对列车提速的必要性、原则和有限目标进行论述的基础上，就列车提速对运输技术设备的要求和运输组织方面的若干问题进行了初步探讨，分析了多速度客货列车混跑时，不同速度配比的组合方案对线路通过能力的影响，为干线提速的方案选定提供了基础     

机载GPS天线的研制

本文论述了作者最近研制的机载ＧＰＳ天线．使天线的波束宽度很宽，满足飞机在上３０°范围内翻滚要求，而能很好的地接收ＧＰＳ导航卫星的信号．实验证明使天线满足设计要求，天线性能是优良的．     

象质评价中光学孔径与波象差的最佳匹配

导出了光学孔径与波象差共同决定成象质量的一些关系式，并从理论和实践两方面找出上述两参数的最佳匹配范围。文中得出的结果与以往传统的象质评价判据有明显的区别。     

炭黑／结晶性含氟树脂合金在自控温加热电缆中应用

选择了结晶性含氟树脂添加改性剂为树脂基体，与炭黑制居复合导电体系。通过这个对体系不同条件下ＰＴＣ特性的研究，对其配方与加工工艺进行优化。并利用扫描电镜，Ｘ射线衍射，ＤＳＣ等分析测试手段，对体系的各种开矿结构进行了研究，阐明了该导电复合体系的形态结构与性能的关系。     

STUDY ON POLYPYRROLE-VISCOSE CONDUCTING FIBER

The conductivity of Polypyrrole-viscose conducting fiber prepared with author's method can be shown up to as high as 2.106x10~(-2) S/cm. The main factors influencing the conductivity are the concentration of FeCl_3 used as dopant and initiator, the treatment time of viscose fiber as base material in FeCl_3 solution, temperature and polymerization time. It is found that the orientation and crystallization degree of viscose fiber keep constant before and after conducting treatment and the mechanical properties of conducting fiber is the same as that of base material. In addition, the distribution of polypyrrole in viscose fiber, and its effect on the conductivity were investigated in details by TEM.