Resolution of sister telomere association is required for progression through mitosis

Cohesins keep sister chromatids associated from the time of their replication in S phase until the onset of anaphase. In vertebrate cells, two distinct pathways dissociate cohesins, one acts on chromosome arms and the other on centromeres. Here, we describe a third pathway that acts on telomeres. Knockdown of tankyrase 1, a telomeric poly(ADP-ribose) polymerase caused mitotic arrest. Chromosomes aligned normally on the metaphase plate but were unable to segregate. Sister chromatids separated at centromeres and arms but remained associated at telomeres, apparently through proteinaceous bridges. Thus, telomeres may require a unique tankyrase 1-dependent mechanism for sister chromatid resolution before anaphase.     

大型码头输油臂安全技术管理

从船岸跨接电缆、紧急脱离系统、内外臂失灵及预防措施四个方面对大型码头输油臂的安全技术管理工作进行了分析,指出应从设计、制造、安装、运行维护等方面对大型码头输油臂进行全面的质量管理和安全管理,提出了有针对性的预防措施。     

西藏小麦地方品种“棒型小麦”并列小穗基因的染色体臂定位

 三联小穗小麦 (TriticumaestivumL .concv .tripletum)是一种特殊穗型的普通小麦 ,是混生在西藏小麦地方品种中的一种特殊小麦类型 ,遗传性稳定。它是连接大麦亚族与小麦亚族的例证标本。西藏小麦地方品种“棒型小麦”就是典型的三联小穗小麦 ,有稳定的三联小穗特征。对三联小穗小麦“棒型小麦”并列小穗基因进行染色体臂定位研究 ,发现 :(1)正常穗型与并列小穗相比遗传呈显性。小麦中国春遗传背景中存在抑制并列小穗表达的基因 ;(2 )控制并列小穗的基因定位在 5AL、4BL、6BS、7BL、7DL染色体臂上 ;(3)分枝麦与正常小麦杂交后代出现并列小穗这一现象可能受 5AL和 4BL染色体臂控制。     

Dispelling myths about verification of sea-launched cruise missiles

It is widely believed that an arms control limit on nuclear-armed sea-launched cruise missiles would be nearly impossible to verify. Among the reasons usually given are: these weapons are small, built in nondistinctive industrial facilities, deployed on a variety of ships and submarines, and difficult to distinguish from their conventionally armed counterparts. In this article, it is argued that the covert production and deployment of nuclear-armed sealaunched cruise missiles would not be so straightforward. A specific arms control proposal is described, namely a total ban on nuclear-armed sea-launched cruise missiles. This proposal is used to illustrate how an effective verification scheme might be constructed.     

Technology Creep and the Arms Race: ICBM Problem a Sleeper

In three articles, Science will discuss how the creep of technology affects the arms race. The first two articles will deal with the most important current example: first, how ICBM modernization is giving both sides a destabilizing, first-strike capability, and second, how arms control seems to be dealing inadequately with this pressing problem. The third article will describe other cases of incremental technical improvements affecting arms control, such as antisatellite research and ballistic missile defense research, which are bringing both sides closer to the antiballistic missile capability they forswore in a 1972 treaty.     

Ultrastructure of secretory and high-polymer serum immunoglobulin A of human and rabbit origin

Electron micrographs of immunoglobulins A from human and rabbit colostrum, which were purified on tall agarose columns, revealed Y-shaped molecules (125 by 140 angstroms). The linear dimensions of the arms were 55 to 75 by 25 to 30 angstroms. A molecular model is postulated in which two immunoglobulin A monomers are superimposed on each other in a close-packed state with the secretory piece inserted in the constant region of the alpha-chains. High-polymer (11 or 13S) immunoglobulin A molecules (total span 100 to 110 angstroms) from human serum were composed of four arms (50 to 55 by 20 angstroms) joined at a contrast-rich center.     

金色链霉菌接合转移体系的构建

以金色链霉菌J13基因组DNA为模板,扩增金霉素C6甲基化酶基因ctcF上下游序列作为两端同源交换臂,在两臂之间添加抗性筛选标记neo基因,并在该基因上游加入组成型强启动子ermE*,以强化筛选标记.将该外源DNA序列插入到质粒pSET152,构建重组质粒pFD106.转化大肠杆菌ET12567后,经接合转移导入金色链...     

Facing nuclear reality

Nuclear weapons that are safe and secure, reliable, survivable, and effective will be a critical element of this nation's deterrent for the foreseeable future. The existence of these weapons reflects the tension that exists between the United States and the Soviet Union. Nuclear test bans will not reduce or eliminate nuclear weapons or this tension. Imprudent nuclear test bans, however, could impair the viability of this vital element of U.S. security. New, more restrictive test limitations would not enhance our national security. They do not address the two most important issues-namely, major reductions in strategic and conventional forces of both the Soviet Union and the United States, and a widespread lessening of tension between our two countries. In fact, it is conceivable that the diversion of political attention from arms reduction efforts and the distrust generated by test-ban verification problems could actually increase tensions between the two countries. We believe that more restrictive test limitations or a nuclear test ban should be considered only as part of an integrated and comprehensive approach to arms control. We must reduce the numbers of the most destabilizing weapons and the overall size of the strategic arsenals through negotiations. A restrictive test ban may be a proper last step in our quest for nuclear arms control and a stable peace, but it would, in our opinion, be an imprudent first step. Further test limitations will be consistent with increased stability and decreased tension between the United States and the Soviet Union only if they are instituted after major stabilizing reductions are made in the strategic nuclear and conventional forces of both countries.     

近交对中间球海胆受精率、孵化率和幼体发育的影响

通过构建不同近交水平的海胆群组,即半同胞近交组(H组,F=0.125)、全同胞近交组(F组,F=0.25)和对照组(C组,F=0),研究了近交对中间球海胆Strongylocentrotus intermedius受精、孵化和幼体发育阶段的影响。结果表明:近交对海胆的受精率、孵化率和四腕幼体的畸形率均无显著影响(P>0.05);不同近交水平的四腕、六腕和八腕幼体体长均表现为H组>C组>F组,体宽表现为无规律性;六腕幼体的胃长和胃宽均为F组>C组>H组,八腕幼体的胃长和胃宽均为C组>H组>F组。研究表明,一定近交水平(F=0.25)的中间球海胆的受精、孵化,以及变态前幼体的体长、体宽均没有出现明显的近交衰退,但幼体胃长和胃宽的近交衰退现象比较明显。     

家兔核仁组成区的银染多态性及其与品种间血缘关系的研究

对青紫蓝兔、加利福尼亚兔、大耳白兔、新西兰白兔,德系安哥拉兔等5个家兔品种。采用外周血淋巴细胞培养技术制备早中期染色体。并利用Ag-As、Ag-Ⅰ及1-stcp等3种方法进行Ag-NORs数目和频率分布的研究,分析各品种间亲缘关系。结果表明:本实验中制备的染色体其长度较长,可以被准确编号,并通过G-带分析支持了上述结论。在3种银染方法中,以1-step法最为满意。家兔的Ag-NORs定位于第13、16、20号染色体短臂和第21号染色体长臂端部。家兔Ag-NORs在细胞间、个体间、品种间均有差异,上述品种的Ag-NORs均数分别为3.27、2.97、3.53、2.93、2.67,品种间差异显著大于品种内个体间差异,说明Ag-NORs具有品种特征。并且以Ag-NORs的数目和频率分布进行聚类分析结果表明,新西兰白兔、青紫蓝兔、加利福尼亚兔、德系安哥拉兔为一个类群,而大耳白兔为另一个类群。证实Ag-NORs作为遗传指标,具有品种特征,可用于研究家兔各品种间的亲缘关系。     

Microfossils in conophyton from the soviet union and their bearing on precambrian biostratigraphy

Silicified specimens of the Vendian (late Precambrian) "index fossil" Conophyton gaubitza from South Kazakstan contain a diverse assemblage of well-preserved cyanophytic and apparently eukaryotic algae, the first stromatolitic microbiota to be reported from the Soviet Union. Unlike the stromatolites in which they occur, the microorganisms that apparently built this form of Conophyton did not become extinct at the end of the Precambrian.     

Visual and "phonetic" coding of movement: evidence from american sign language

Hearing subjects unfamiliar with American Sign Language and deaf native signers made triadic comparisons of movements of the hands and arms isolated from American Sign Language. Clustering and scaling of subjects' judgments revealed different psychological representations of movement form for deaf and hearing observerd. Linguistically relevant dimensions acquired modified salience for users ofa visual-gestural language. The data indicate that the modification of natural perceptual categories after language acquisition is not bound to a particular transmission modality, but rather can be a more general consequence of acquiring a formal linguistic system.     

海洋酸化和升温对中间球海胆幼虫发育和生长的影响

为了研究海洋酸化和气候变暖对海洋生物的联合作用,按照文献[4]和[7]中对海洋环境变化的预测趋势,设置了3组海水,即对照组(pH为7.93～7.99,水温T为18℃)、试验组E3(在对照组基础上pH减小0.3,T升高3℃)、试验组E6(在对照组基础上pH减小0.6,T升高6℃),在此条件下对中间球海胆Strongylocentrotus intermedius幼虫的发育及生长情况进行了研究。结果表明:酸化及升温海水对海胆孵化率没有显著影响;E3组海胆与对照组发育进程一致,而E6组则较慢;E3和E6组海胆分别存活了18 d和12 d,分别发育至八腕幼虫和四腕幼虫阶段,可见试验海水环境严重影响海胆幼虫的存活;E3组海胆幼虫的生长在受精后的前10 d与对照组差异不显著(P>0.05),之后显著低于对照组(P<0.05),而E6组海胆幼虫的生长在整个试验阶段均显著低于对照组(P<0.05);将骨针长度分解为口后腕骨针长度和躯干部骨针长度,各组海胆的生长差异主要表现在口后腕骨针长度上;试验组长腕幼虫畸形均不同程度地表现为腕短小、萎缩、腕骨针折断、骨针弯曲变形等。研究表明,中间球海胆对海洋酸化和气候变暖的海洋环境非常敏感,如果按照预测趋势,海洋环境变化将会对该海胆产生严重的负面影响。     

A tunnel in the large ribosomal subunit revealed by three-dimensional image reconstruction

A better understanding of the molecular mechanism of protein biosynthesis depends on the availability of a reliable model for the ribosome particle. The application of a diffraction technique, namely, three-dimensional image reconstruction from two-dimensional sheets of the large ribosomal subunits of Bacillus stearothermophilus at a resolution of 30 angstroms is described. The resulting three-dimensional model shows at least four projecting arms, arranged radially near the presumed interface with the 30S subunit. The projecting arms are positioned around a cleft, which turns into a tunnel with a length of 100 to 120 angstroms and a diameter of up to 25 angstroms. This tunnel spans the particle and may provide the path taken by the nascent polypeptide chain.     

江西野葛的核型分析

以江西野葛为材料，进行染色体核型分析，结果显示：野葛染色体数2n=22，核型公式K(2n)=22=20m(5sat) 2sm(1sat)，2、3、5、7、11号染色体的短臂和8号染色体的长臂各具一随体，属2B核型。从野葛核型不对称和核型类型看，野葛在葛属植物中具有明显较高级的进化地位。     

厦门城市“干岛效应”研究

利用厦门市2个气象观测台站的相对湿度观测资料和通过温度及水汽压观测资料计算绝对湿度,对厦门市相对湿度和绝对湿度的年、季、月变化特征进行全面分析,进行城市＂干岛效应＂研究。结果表明,①由于厦门地区独特的地理环境,市区城区和郊区城区的空气湿度有着不一样的变化规律,20世纪市区城区并没有明显的＂干岛效应＂;②20世纪90年代以前年平均空气湿度变化趋势并不明显,从90年代初起,厦门的郊区城区空气湿度开始明显减小,两站分别在1993年和2004年出现变干的突变,21世纪初开始,厦门市区城区和郊区城区都明显变干;③从季节变化来看,季平均相对湿度,同安站各季节都呈减小趋势,厦门站没有明显变化;而季平均绝对湿度,同安站主要是春夏季呈明显减小趋势,秋冬季变化不明显,厦门站主要是夏季呈明显减小趋势,其余季节变化不明显;④从各时次的空气湿度气候变化来看,同安站在4个时次都呈明显变小趋势,相对湿度以20：00和08：00变小趋势最明显,绝对湿度以14：00变小趋势最明显;厦门站只在14：00相对湿度明显变小,绝对湿度在02：00和20：00变小明显。     

Ten-armed fossil cephalopod from the Pennsylvanian of Illinois

Jeletzkya douglassae Johnson and Richardson is described as the oldest known representative of an extant squid group. The species is known from a single specimen from the Middle Pennsylvanian of Illinois. This very unusual fossil consists of the complete tentacular crown and a fragile shell. The arms bear hooks in double rows.     

Star formation in irregular galaxies

Irregular galaxies can be viewed as laboratories for studying the processes of star formation. This class of galaxy, unlike the more familiar spiral galaxies, forms stars without spiral arms and does so from a chemically less-evolved interstellar medium. In this article the problems associated with star formation in irregular galaxies are outlined and their relevance to our understanding of star formaton as a general astrophysical process is discussed.     

基于SolidWorks与有限元理论联合采伐机机械臂的设计方法

应用SolidWorks软件实现联合采伐机在计算机平台下的虚拟设计,结合有限元理论对机械臂建立有限元分析模型,得到了机械臂的应力分布,并依据应力分析结果做出结构设计优化;探讨了一种该型机械臂的虚拟设计方法,以确定其结构设计的可靠性,缩短了产品的开发周期和减少研发费用,并成功地应用于制造和检测。     

新疆野生黑麦(Secale cereale)的Giemsa C-带

利用BSG显带技术,将新疆野生黑麦的Giemsa C-带与其他作者的研究结果进行了比较,从而确定了黑麦C-带的基本带型为全部染色体(除随体染色体外)短臂上显末端带,随体染色体显核仁缢痕带。为此,从带型上可判断出野生黑麦与栽培黑麦之间亲缘关系密切。为栽培黑麦起源于野生黑麦提供了直接的细胞学证据。从分析比较中也看出,黑麦C-带带型的异染色质多态性现象明显存在。而野生黑麦的杂合性现象也较明显。这可能与野生黑麦本身的遗传性有关。