Rapid chiral assembly of rigid DNA building blocks for molecular nanofabrication

Practical components for three-dimensional molecular nanofabrication must be simple to produce, stereopure, rigid, and adaptable. We report a family of DNA tetrahedra, less than 10 nanometers on a side, that can self-assemble in seconds with near-quantitative yield of one diastereomer. They can be connected by programmable DNA linkers. Their triangulated architecture confers structural stability; by compressing a DNA tetrahedron with an atomic force microscope, we have measured the axial compressibility of DNA and observed the buckling of the double helix under high loads.     

Long-range ordered carbon clusters: a crystalline material with amorphous building blocks

Solid-state materials can be categorized by their structures into crystalline (having periodic translation symmetry), amorphous (no periodic and orientational symmetry), and quasi-crystalline (having orientational but not periodic translation symmetry) phases. Hybridization of crystalline and amorphous structures at the atomic level has not been experimentally observed. We report the discovery of a long-range ordered material constructed from units of amorphous carbon clusters that was synthesized by compressing solvated fullerenes. Using x-ray diffraction, Raman spectroscopy, and quantum molecular dynamics simulation, we observed that, although carbon-60 cages were crushed and became amorphous, the solvent molecules remained intact, playing a crucial role in maintaining the long-range periodicity. Once formed, the high-pressure phase is quenchable back to ambient conditions and is ultra-incompressible, with the ability to indent diamond.     

Large clusters of metal ions: the transition from molecular to bulk magnets

Clusters of metal ions are a class of compounds actively investigated for their magnetic properties, which should gradually change from those of simple paramagnets to those of bulk magnets. However, their interest lies in a number of different disciplines: chemistry, which seeks new synthetic strategies to make larger and larger clusters in a controlled manner; physics, which can test the validity of quantum mechanical approaches at the nanometer scale; and biology, which can use them as models of biomineralization of magnetic particles.     

基于GML构建WebGIS的研究

本文简要介绍了地理标记语言GML,研究了基于GML的WebGIS解决方案,随后探讨了J2EE体系结构下实现基于GML的WebGIS技术方案。     

基于作者身份识别的社会网络构建方法研究

E-mail、BBS、Blog等网络用户在注册时往往匿名或提供伪造的个人信息,通过挖掘这些网络用户之间的信息交互,构造的社会网络是不可信的.本文提出1种基于作者身份识别的社会网络构建方法,分析网络信息作者的写作风格,对作者身份的真实性进行判断,以E-mail信息为例,挖掘这种信息用户之间的信息交互,使构建的社会网络更可...     

基于HelixServer的流媒体服务器平台的搭建

流媒体服务器在流式传输上具有Web服务器不可比拟的优势.本文通过笔者的实践,探讨了如何利用流媒体服务器软件HelixServer在局域网内搭建一个流媒体服务器平台,并将其过程加以图示说明.     

高校党建工作改革创新初探

高校党建工作的改革创新,是学校事业科学发展的重要组成部分.高校党组织必须以科学发展观为指导,以改革创新精神推进党建工作,为学校的改革、发展和稳定提供强有力的组织保证和精神动力.     

A molecular shift register based on electron transfer

An electronic shift-register memory at the molecular level is described. The memory elements are based on a chain of electron-transfer molecules and the information is shifted by photoinduced electron-transfer reactions. This device integrates designed electronic molecules onto a very large scale integrated (silicon microelectronic) substrate, providing an example of a "molecular electronic device" that could actually be made. The design requirements for such a device and possible synthetic strategies are discussed. Devices along these lines should have lower energy usage and enhanced storage density.     

基于建筑体形系数的温室屋顶节能分析

体形系数的大小可反映温室能耗的高低,因此求出不同形状的温室屋顶的体形系数,分析温室屋顶体形对体形系数的影响。根据极限体形系数分析不同形状的温室屋顶的节能潜力,确定最佳的节能温室屋顶形状、最佳节能长宽比和最佳节能宽高比,运用计算温室屋顶最佳节能体形的方法,分析各种体形与温室朝向和日辐射得热量的关系,可为温室的节能设计提供科学依据。     

利用RAPD技术对蟠桃品种的分析

为了对蟠桃的品种识别，系统发育及资源保存提供分子生物学依据。本试验利用RAPD技术。采用从200个随机引种中筛选的22个随机引种对13个蟠桃品种的基因组DNA进行扩增，通过扩增位点的谱带的聚类，分析供试蟠桃的系统发育，在相似系数为0.917处可将供试品种划分为5类。并运用特殊谱带，建立了蟠桃品种的识别谱带，并担子同需重点保存的蟠桃种质为玉露蟠桃。五月鲜扁干，苏联蟠桃，嘉庆，扬州124。     

利用转录组测序开发甘蔗SNP分子标记

【目的】利用转录组测序开发甘蔗SNP分子标记,为甘蔗建立一种高效和低成本的分子标记开发方法。【方法】以40个甘蔗栽培品种为试验材料,使用高通量测序平台获得其转录组数据,经质控后将其匹配到参考基因组,然后使用GATK软件检测和过滤SNP分子标记,并使用snpEff对SNP进行注释及统计分析。利用这些SNP分子标记进行系统发生分析、主成分分析和群体结构分析。最后,开发KASP标记并随机验证其有效性。【结果】转录组数据经质控后平均每个样本获得6.5 Gb的序列。通过变异分析和多重过滤筛选后,共获得220397个注释到染色体上的双等位基因SNP位点,平均密度为3 SNP/kb。SNP类型及分布特征分析结果表明,编码区错义突变与沉默突变的比值（N/S）为1.05,转换类型和颠换类型的比值（Ts/Tv）为1.89,杂合SNP占38.66%～49.91%,位于转录本的SNP比例为44.74%。系统发生分析、主成分分析和群体结构分析结果均表明,甘蔗栽培品种遗传来源较为单一,但群体分化较大。开发了11176个KASP分子标记,并随机合成25组KASP引物进行多态性验证,共有23组（92%）引物能检测到扩...     

The Physics of High-Field Superconductors: New materials, used in lossless magnets at low temperatures, challenge scientific understanding

The recent burst of effort in the area of high-field superconductors has led to the construction of 70,000-oersted coils and the expectation that 100,000-oersted fields will be attained in the near future. The general theory suggests that fields above 300,000 oersteds are conceivable and that current densities of millions of amperes per square centimeter may be attained. Theory and experiment suggest that the upper critical field of materials such as Nb(3)Sn and Nb(.75)Zr(.25) is determined by their tendency to form a mixed state, and that a crucial question concerning their other properties is that of the interaction of this mixed state with imperfections. Lastly, it is possible to make a synthetic high-field superconductor by mechanically subdividing an ideal superconductor.     

The structure of the c60 molecule: x-ray crystal structure determination of a twin at 110 k

Single-crystal x-ray diffraction methods were used to determine the crystal and molecular structure of C(60) buckminsterfullerene. At 110 kelvin C(60) is cubic, apparent Laue symmetry m3m, but it exhibits noncrystallographic systematic extinctions indicative of a twin in which I(hkl) and I(khl) are superimposed. In fact, C(60) crystallizes with four molecules in space group [See equation in the PDF file] of the cubic system (Laue symmetry m3) with lattice constant a = 14.052(5) angstroms (A) at 110 kelvin. The twin components are equal. A given component, which has crystallographically imposed symmetry [See equation in the PDF file] displays an ordered structure of a truncated icosahedron. The five independent C=C bonds that join C(6) rings average 1.355(9) A; the ten independent C-C bonds that join C(6) and C(5) rings average 1.467(21) A. The mean atom-to-atom diameter of the C(60) molecule is 7.065(3) A. The molecules are very tightly packed in the crystal structure, with intermolecular C...C distances as short as 3.131(7) A.     

基于多基因的分子分类技术在库蠓鉴定中的应用

以采自我国14个省(自治区)的77种库蠓标本为研究对象,测定分析库蠓的线粒体COⅠ、Cyt b、16S rDNA及核糖体ITS1-ITS2基因序列,并构建系统发育树.多基因聚类分析显示:77种库蠓分别隶属于屋室亚属、带纹亚属、库蠓亚属、二囊亚属、血色亚属、三囊亚属和单囊亚属,该结果与形态学鉴定结果基本吻合,表明基于多基因的分子分类技术可用于库蠓的种类鉴定.     

分子生物学技术应用于木材识别的研究进展

木材识别技术的进步对于木材科学的发展及保护森林资源意义重大。随着木材DNA提取方法的不断突破,分子生物学技术开始应用于木材及木制品的材种鉴定及来源地识别,这对于阻止木材的非法砍伐及贸易具有重要意义。对近年来研究者在木材分子识别技术领域取得的进展进行了概述,介绍了木材DNA提取常用的方法、存在的困难、改良的措施及不同提取方法获得的DNA质量;在木材树种鉴定方面,主要介绍了微卫星、单核苷酸多态性和DNA条形码技术的应用进展;列举了分子生物学技术在木材来源地的鉴定中的成功案例;最后,分析了木材分子识别技术仍存在的问题,并对其发展及应用前景进行了展望。参43     

Reversible molecular adsorption based on multiple-point interaction by shrinkable gels

A general approach is presented for creating polymer gels that can recognize and capture a target molecule by multiple-point interaction and that can reversibly change their affinity to the target by more than one order of magnitude. The polymers consist of majority monomers that make the gel reversibly swell and shrink and minority monomers that constitute multiple-point adsorption centers for the target molecule. Multiple-point interaction is experimentally proven by power laws found between the affinity and the concentration of the adsorbing monomers within the gels.     

基于林业局(场)级森林资源数据建库技术及标准化的研究

该文主要研究了林业局 (场 )级森林资源数据库建设过程中所涉及到的数据采集方法的标准化和规范化、数据入库流程、功能设计、实现方法等     

基于ISSR的野生桑树桑黄菌株遗传多样性分析

为保护开发野生桑树桑黄种质资源,对17个不同来源的野生桑树桑黄菌株开展种内遗传多样性分析,利用简单重复序列间扩增(ISSR)分子标记技术对桑黄菌株DNA进行扩增,分析扩增条带,利用NTSYS软件构建亲缘关系UPGMA聚类图。结果表明:16条ISSR引物中,有10条ISSR引物多态性丰富,条带清晰;10条引物共检测到904个位点,其中,多态性位点717个,多态性百分比79.3%。在DNA指纹图谱中,引物P5、P812扩增条带多态性最高。NTSYS-PC2.10e软件分析表明,17个桑树桑黄遗传相似系数为0.57~0.99。UPGMA聚类分析结果显示,在遗传相似系数(GS)约0.65处,可将17个桑树桑黄划分为2大类群: S4,S23,S26为一大类群,其余为一大类群。综上可知,桑树桑黄种质资源具有丰富的遗传多样性,ISSR分子标记可有效区分不同桑树桑黄菌株。