The stress response factor RpoS is required for the natural transformation of Escherichia coli

The natural transformation of Escherichia coli is a novel and recently developed system that has significance for genetic studies and the biological safety of genetic engineering. However, the mechanisms of transformation, including development of competence and DNA uptake, are not thoroughly understood. In this study, we demonstrated the effect of the general stress response regulator RpoS, which has been associated with E. coli transformation, on natural transformation performed in an “open system”. We find that RpoS is required for natural transformation but not to artificial transformation and RpoS mainly affect transformation in the liquid culture prior to plating. In the liquid culture, RpoS over-expression promotes natural transformation in early exponential phase and static incubation accumulates RpoS and promotes transformation to a limited extent. These findings provide detailed understanding of RpoS function on natural transformation.     

当代报纸市民意识管窥

20世纪90年代中期以来,当代报纸在激烈的市场竞争中显示出一种鲜明的市民意识。它们从报纸的读者定位,报纸内容的选择和报道的风格等方面努力向广大市民阶层靠拢。本文对当代报纸市民意识的表征,市民意识兴起的深层原因及市民意识引发的相关思考作了初步的探讨。     

关于多参数局部分歧的一个问题

引进Ｌ０－Ｌ本征值的新概念，讨论了更加一般的非线性方程的分歧问题，并得到有关结果。     

试论《本草纲目》在我国古代中医急救学和外科治疗学方面的贡献

李时珍是举世称颂的中华民族开化史上负有盛名的医药学家和博物学大师。他所著的《本草纲目》内容丰富,今拟从其卷三、卷四百病主治药中,有关我国古代急救医学、外科治疗学方面的贡献,试运用现代医学成就作初步探讨,以期说明祖国医药学在这些方面较之西医早就卓有成就,并为继承和发扬祖国医学在急救学和外科治疗学方面的宝贵经验,实现中医现代化或促进中西医结合尽微薄力量。本文论及的主要内容为:急救医学方面有抢救缢死者的人工呼吸法,抢救溺死者的控水法,抢救冻僵者的胸外心脏温热疗法,抢救蛇伤者使用的结扎法,抢救急性喉梗阻使用的火针及拔发咬指术等。外科治疗学方面有离体器官再植术,肠出纳入术,缝合术、引流术、夹板固定术等。并用现代医学研究成果,初步阐明其用药机理。     

单频散斑光栅膜研测面内位移场

本报道了利用作研制的一种新的光学元件－单频散斑光栅模进行面内位移场测量的方法及原理。     

as和which在关系从句中的异同

“ａｓ”和“ｗｈｉｃｈ”作为关系代词时，可用于两种情况；一般性定语从句和特种定语从句。通过实例证实：“ａｓ”和“Ｗｈｉｃｈ”引出关系从句时，有其相似、相异处，但是不同点多于共同点。     

Mitochondria1 cytochromeb sequences variation of Protura and molecular systematics of Apterygota

Mitochondrial cytochromeb genes of about 450 bp fragments from 3 proturan species, 5 collembolan species and 2 dipluran species have been sequenced. The number of nucleotide substitutions and Kimura 2-parameter distances have also been calculated, and a series of molecular phylogenetic trees reconstructed by using parsimony and distance methods. The proturan, collembolan and dipluran species have evolved monophyletic groups. The results suggest that Protura and Collembola are sister groups, while Diplura is more or less demonstrating a closer phylogenetic relationship to the pterygotan insects. The phylogeny and their systematic position of protura and other groups are also discussed.     

DPSIR model-based evaluation index system for geographic national conditions

Establishing a reasonable evaluation index system is the basis and premise for the scientific evaluation of geographic national conditions. By analyzing the DPSIR model and its correlation and relation with the evaluation index system, the indexes for geographic national conditions were selected from the aspects of resources, ecology, environment, economy, society, etc to build an evaluation index system for geographic national conditions that consists of three hierarchies: index, criterion, and target levels. Furthermore, the index system was analyzed in terms of index integrity, low overlapping of elements, non-existence of isolated indexes, hierarchy of index system, etc., for the purpose of demonstrating that the DPSIR model-based evaluation index system for geographic national conditions meets the principles of index system establishment.