The origin of the brown frogs with 2n=24 chromosomes

Late replication and C-banding analyses of somatic metaphase chromosomes were attempted on three species of brown frogs with 2n=26 chromosomes (Rana japonica, R. tsushimensis andR. temporaria), and three with 2n=24 chromosomes (R. ornativentris, R. dybowskii andR. chensinensis), which are distributed in the Palearctic region. The late replication banding patterns were highly conserved in these species. Four chromosome inversions were demonstrated inR. ornativentris, two inR. dybowskii and two inR. tsushimensis. From a detailed comparison of late replication and C-banding patterns between the 2n=26 and the 2n=24 species, it was found that an end-to-end fusion of two small chromosomes (nos 11 and 13) in an ancestral 2n=26 species may have produced the medium-sized no. 6 chromosome of the 2n=24 species.     

The effect of DDT on DNA replication in the larval salivary gland cells ofDrosophila melanogaster

Summary The inhibitory effect of DDT on the initial stage of the DNA replication process in polytene chromosomes of larval salivary gland cells ofDrosophila melanogaster was investigated and possible mechanisms for the inhibition are discussed.     

医院外设门诊机构与医院内部信息系统之间的数据交换

利用SQL Server复制技术，实现医院外设门诊机构与医院内部信息系统之间的数据交换方法。     

网络数据库系统的实现及安全性技术

随着Internet的应用日益广泛，基于网络的数据库应用系统也越来越普遍，同时人们认识到系统中最重要的不只是各种网络硬件，而是网络中存储的用金钱难以买到业务数据。为了能够有效地利用现有的技术来源增强网络数据库系统的安全性，描述了基于WEB的网络数据库的实现，以及涉及到的安全性问题，即怎样实现系统的安全，为了达到该系统的真正安全性，还提出了一种分层的方法，即实现－安全－复制－恢复的安全管理模式。     

Fluorescence replication banding of frog chromosomes

To identify individual chromosomes of a frog karyotype by their fluorescence banding patterns, chromosomes were stained with actinomycin D and 4,6-diamidino-2-phenylindole (DAPI) after incorporation of BrdU during the late S-phase. The chromosomes of three Rana species which were selected for this study (R. ridibunda, R. lessonae and R. japonica) showed well-defined late replication bands. The fluorescence patterns obtained were the reverse of those produced by a 4Na-EDTA Giemsa-staining technique. Fluorescence patterns of the two water frog species (R. ridibunda and R. lessonae) were similar to each other, except for the different fluorescence of the centromeric heterochromatin, which gave extremely bright signals in R. ridibunda but no signal in R. lessonae. Experiments also showed differences between the fluorescence patterns of R. lessonae chromosome 13 in the Italian and Luxembourgian populations. These results sho w that the fluorescence replication banding using actinomycin D and DAPI is very effective in identifying individual frog chromosomes and detecting their structural changes. Received 7 June 1996; received after revision 23 July 1996; accepted 21 August 1996     

Stimulation of polydnavirus replication by 20-hydroxyecdysone

During oviposition the endoparasitic waspCampoletis sonorensis, introduces a polydnavirus into parasitized insects where viral gene expression is required for endoparasite survival. The polydnavirus is integrated into wasp chromosomal DNA and replicates only in the ovary. Ecdysteroids regulate the developmental expression of many insect genes and may regulate polydnavirus replication. Direct verification of viral replication was performed by dot blot hybridization and by amplifying DNA sequences containing the viral integration site; this junction fragment cannot be amplified from integrated virus. Thoracic ligations and in vitro ecdysteroid treatments of wasp ovaries support the hypothesis that polydnavirus DNA replication is regulated by ecdysteroid during parasite development.     

OceanBase高可用方案

传统关系数据库基于共享存储或者主备同步的方式实现高可用.这些方案要么依赖硬件的高可用,但成本高昂;要么无法同时满足强一致性和高可用性.OceanBase将云计算和数据库两种技术有机地融合起来,实现了基于Paxos协议的高可用方案.该方案构建在普通服务器上,成本低廉,且同时满足强一致性和高可用性.     

基于云平台的电信数据仓库文件备份和分布动态调整算法

Hadoop利用统一的备份机制来确保数据的可用性和容错性.然而对于重要的文件块,只能通过修改配置文件来设置副本数量.通过分析电信业数据仓库文件的访问情况,提出文件备份与存放动态调整算法（BPDA）来提高数据局部性,以减少数据传输带来的I/O和网络消耗,提高查询效率.运用多副本一致性哈希算法,概率采样和竞争力弱化算法,得到每一个文件的最佳备份数和备份位置.实验结果验证了该算法可以提高查询关联效率.     

增加外源基因在植物中复制、转录和翻译的策略

与其他的真核表达系统(例如酵母和昆虫)比较,植物表达系统的主要优越性在于植物细胞具有全能性,能再生植株.这是植物表达系统能够以低廉的成本大规模生产重组蛋白的潜力.但是,由于植物表达系统重组蛋白表达产量低,使植物表达系统在大规模重组蛋白生产中的应用受到很大的影响.蛋白的产量与基因的数量、基凶的转录和翻译水平密切相关.近年来,人们在增加外源基因在植物中复制、转录和翻译作了大量的探讨,使在植物表达重组蛋白产量低的问题得到改善.笔者综述了这方面的研究进展.