美国推迟部署NMD

“我已经决定暂不授权部署国家导弹防御系统”——比尔·克林顿2000年9月1日,美国总统克林顿在华盛顿的乔治敦大学发表演讲,宣布推迟部署国家导弹防御系统(NMD),将决定 NMD 的“生死牌”传给美国的下一位总统。     

危险的三步曲——1999年度美国向国际安全叫板

三个举动 1999年度,美国在核裁军和军控领域先后采取了三个令世人瞩目的行动——决定部署国家导弹防御系统(NMD)、要求修改“反导条约”和拒绝批准“核禁试条约”。事情的大体经过是:年初,美国国防部提出发展导弹防御系统计划,这一计划从概念上讲是里根总统时期的“星球大战计划”的替代物。它由两个部分组成:一个是国家导弹防御系统(简称NMD),另一个是战区导弹防御系统(简称TMD)。同年3月,美国国会率先通过部署国家导弹防御系统法案,这一法案随后经克林顿总统批准,决定于2005年在美国本土两个     

时事点评

布什：求连任NMD出台，苦心2002年12月17日，布什总统通过白宫发言人宣布，美国将于2004年正式部署国家导弹防御系统（NMD），这个自克林顿时期就争议不断的导弹计划终于付诸实施。然而就在六天前的同月11日，第八次NMD导弹拦截试验刚刚以失败告终。面临着山雨欲来的对伊形势和扑朔迷离的朝核危机，布什选在此时将技术上远未成熟的导弹防御系统推上“生产线”，令人颇为费解。“采取一切必要的措施保护美国不受大规模杀伤性武器的攻击”虽然是冠冕堂皇的理由，但NMD匆匆上马却并非如此简单，恐怕其“政治意义”要远大于其“军事意义”…     

美国NMD“砸锅”了

美国国防部前不久进行的耗资1亿美元的国家导弹防御系统(NMD)第三次拦截试验又“砸锅”了。拦截导弹作为五角大楼正在研制开发的国家导弹防御系统中的关键组成部分表现不佳,不仅没有在太平洋上空命中“来袭”弹头,甚至根本就没有“试图”将其击中。     

中国构筑导弹防御网

1999年似乎是一个“TMD热”年。美国、日本借口防止潜在敌人实施导弹攻击,紧锣密鼓地搞所谓“国家导弹防御系统”(NMD)和“战区导弹防御系统”(TMD),并有意将台湾纳入TMD。美国的西欧盟友也提出了“全球反导弹系统”和研制反战术弹道导弹的ATBM计划。本来就不太平的世界为此闹得更加沸沸扬扬。     

"NMD"能否成为美国的护身符

7月15日,美国军方进行的国家导弹防御计划(NMD)第4次导弹拦截试验获得成功。据有关资料介绍,美国的导弹防御系统主要由红外探测系统、改进型预警雷达、X波段相控阵雷达、拦截导弹及其阵地、作战管理与指挥控制通信系统5大部分组成。其作用是及时发现和正确识别来袭目标,对目标进行跟踪并迅速作出决策和有效地实施拦截。此次试验所用的靶标是携带模拟弹头的民兵2洲际弹道导弹。这种导弹     

敲响国际核裁军的警钟——外交部军控司沙祖康司长访谈录

10月2日,美国国防部宣布,用于“国家导弹防御系统”(NMD)的导弹拦截试验获得成功;10月13日,美国参议院否决了批准《全面禁止核试验条约》(CTBT)的决议案。接着,美国又向俄罗斯施压,试图迫其同意修改美苏两国于1972年签署的《反弹道导弹条约》(ABM),并威胁说,若     

NMD——美国的战略败笔

铁了心以实力求霸权最近几个月来 P 的形势发展,本来已使人们不断地担忧,而布什5月1日在美国国防大学的讲话,直接了当地宣布将突破美苏1972年《反弹道导弹条约》,建立国家导弹防御系统(NMD)。人们的担忧和判断终于被证实:布什政府在部署 NMD 问题上已经铁了心,剩下来的只不过是何时部署,以及部署多大规模之类的问题而已。     

时事点评

随着美国研发国家导弹防御系统第三次导弹拦截试验在太平洋上空失败,美国防部在世人面前重重地丢了回脸,克林顿部署 NMD 计划更将举棋不定。俄罗斯总统普京发表上任后的第一篇国情咨文,招招击中肯綮,加强联邦中央权力,建设负责任的政党体制,引进现代政企关系改革,建立真正自由、公正的新闻媒体,成为其鲜明的施政重点。墨西哥革命制度党执     

珍海拾贝

国家导弹防御系统(NMD)世界贸易组织(wr0)联合国教科文组织(uNES(:0)世界知识产权组织(WIPO)世界卫生组织(WHO)国际人类基因组织(HOGO)联合国难民署(LJNHCR)国际标准化组织(ISO)国内生产总值(GDP)国民生产总值(GNP)口蹄疫(FMD)艾滋病(AIS)氟利昂(CFC)生物化学战(CBW)珍海拾贝@范丽琴     

重组慢病毒介导的NMD途径因子UPF1和SMG1可诱导干扰细胞株的构建

无义介导的mRNA降解途径是一个比较完善的异常mRNA的降解机制,结合在外显子拼接复合体上的多种蛋白决定NMD途径对异常转录物的识别和降解的启动,其中UPF1和SMG1发挥主要功能.UPF1是一个RNA解旋酶和RNA依赖的ATP酶;而SMG1具有磷脂酰肌醇激酶活性,负责UPF1的磷酸化.本研究构建了含有UPF1和SMG-1基因发夹结构的诱导开关基因表达干扰质粒.利用慢病毒介导转化哺乳动物细胞HEK293T细胞得到重组病毒,经鉴定后感染细胞AD_293,目的基因在细胞中得以高效表达.通过继代培养和单克隆化,得到强力霉素诱导干扰UPF1和SMG-1表达的稳定细胞株.     

Translational control of intron splicing in eukaryotes

Most eukaryotic genes are interrupted by non-coding introns that must be accurately removed from pre-messenger RNAs to produce translatable mRNAs. Splicing is guided locally by short conserved sequences, but genes typically contain many potential splice sites, and the mechanisms specifying the correct sites remain poorly understood. In most organisms, short introns recognized by the intron definition mechanism cannot be efficiently predicted solely on the basis of sequence motifs. In multicellular eukaryotes, long introns are recognized through exon definition and most genes produce multiple mRNA variants through alternative splicing. The nonsense-mediated mRNA decay (NMD) pathway may further shape the observed sets of variants by selectively degrading those containing premature termination codons, which are frequently produced in mammals. Here we show that the tiny introns of the ciliate Paramecium tetraurelia are under strong selective pressure to cause premature termination of mRNA translation in the event of intron retention, and that the same bias is observed among the short introns of plants, fungi and animals. By knocking down the two P. tetraurelia genes encoding UPF1, a protein that is crucial in NMD, we show that the intrinsic efficiency of splicing varies widely among introns and that NMD activity can significantly reduce the fraction of unspliced mRNAs. The results suggest that, independently of alternative splicing, species with large intron numbers universally rely on NMD to compensate for suboptimal splicing efficiency and accuracy.     

改性锰矿对废水中苯酚的去除及机理研究

采用水合肼法对天然锰矿(NMD)进行改性,比较其改性前后对苯酚的吸附性能,考察了苯酚初始浓度、pH值、温度等工艺条件对苯酚吸附去除率的影响,并探讨了改性机理.结果表明,改性锰矿(AMD)对废水中苯酚的吸附性能优于NMD,在适宜条件下,去除率可达71.7%;低pH值有利于吸附,其吸附模式符合Langmuir吸附.通过TEM图、吸附-脱附等温线I、R对AMD进行了表征,结果表明AMD比表面积大,表面羟基丰富,适于做水处理材料.     

空间目标的热效应研究

为了防止NM D系统基于目标的热效应,从众多的气球中识别真正的目标,文章对目标的热效应作了初步的研究,并提出了一些相应的预防措施.     

An eIF4AIII-containing complex required for mRNA localization and nonsense-mediated mRNA decay

The specification of both the germ line and abdomen in Drosophila depends on the localization of oskar messenger RNA to the posterior of the oocyte. This localization requires several trans-acting factors, including Barentsz and the Mago-Y14 heterodimer, which assemble with oskar mRNA into ribonucleoprotein particles (RNPs) and localize with it at the posterior pole. Although Barentsz localization in the germ line depends on Mago-Y14, no direct interaction between these proteins has been detected. Here, we demonstrate that the translation initiation factor eIF4AIII interacts with Barentsz and is a component of the oskar messenger RNP localization complex. Moreover, eIF4AIII interacts with Mago-Y14 and thus provides a molecular link between Barentsz and the heterodimer. The mammalian Mago (also known as Magoh)-Y14 heterodimer is a component of the exon junction complex. The exon junction complex is deposited on spliced mRNAs and functions in nonsense-mediated mRNA decay (NMD), a surveillance mechanism that degrades mRNAs with premature translation-termination codons. We show that both Barentsz and eIF4AIII are essential for NMD in human cells. Thus, we have identified eIF4AIII and Barentsz as components of a conserved protein complex that is essential for mRNA localization in flies and NMD in mammals.     

A faux 3'-UTR promotes aberrant termination and triggers nonsense-mediated mRNA decay

Nonsense-mediated messenger RNA decay (NMD) is triggered by premature translation termination, but the features distinguishing premature from normal termination are unknown. One model for NMD suggests that decay-inducing factors bound to mRNAs during early processing events are routinely removed by elongating ribosomes but remain associated with mRNAs when termination is premature, triggering rapid turnover. Recent experiments challenge this notion and suggest a model that posits that mRNA decay is activated by the intrinsically aberrant nature of premature termination. Here we use a primer extension inhibition (toeprinting) assay to delineate ribosome positioning and find that premature translation termination in yeast extracts is indeed aberrant. Ribosomes encountering premature UAA or UGA codons in the CAN1 mRNA fail to release and, instead, migrate to upstream AUGs. This anomaly depends on prior nonsense codon recognition and is eliminated in extracts derived from cells lacking the principal NMD factor, Upf1p, or by flanking the nonsense codon with a normal 3'-untranslated region (UTR). Tethered poly(A)-binding protein (Pab1p), used as a mimic of a normal 3'-UTR, recruits the termination factor Sup35p (eRF3) and stabilizes nonsense-containing mRNAs. These findings indicate that efficient termination and mRNA stability are dependent on a properly configured 3'-UTR.     

基于字典统计耦合归一化多重距离的图像检索算法

针对当前彩色图像检索技术容易受到色彩干扰,鲁棒性不强等不足,提出了一种字典统计耦合归一化多重距离的彩色图像检索算法.首先,将图像量化并转换成一维信号;然后,引入字典统计,将一维信号进行字典编码,并计算编码后的图像多样值;在归一化字典距离的基础上,嵌入字典编码图像的多样值,从而定义了归一化多重距离(NMD)的相似度量准则,利用NMD对查询图像与数据库图像的多样值进行比较与识别,搜索出与查询图像具有相同特征的最相似图像,完成目标检索.在COREL数据库的实验结果表明:相对于当前常用的检索技术,该检索算法具有更高的查准率和查全率,可对彩色图像完成精确检索,有效减低了色彩对检索性能的干扰.