Kornerupine: its crystal structure

Three-dimensional analysis of the crystal structure of kornerupine reveals the crystallochemical formula Mg(VI)(2)Mg(VI)AlVI(6)[Si(2)O(7)] [(Al,Si)(2) SiO(10)]O(4)(OH), with four formula units in the structure cell of a = 16.100 (2) A, b = 13.767(2) A, c = 6.735(2) A; space group, Cmcm. The unusual crystal structure includes walls of Al-O edge and corner-sharing octahedra, and chains of alternating Mg-O and Al-O octahedra fused to the walls by further edge-sharing to form dense slabs. These slabs are held together by [Si(2)O(7)] corner-sharing tetrahedral pairs and [(Al,Si)(2)SiO(10)] corner-sharing tetrahedral triplets.     

蛋白质结构的预测及其应用

蛋白质结构的预测是结构基因组学的重要研究内容,本文就蛋白质结构预测的方法和应用进行了综述,介绍了比较建模、折叠识别、从头计算等3种方法及其在结构基因组学研究、药物设计、蛋白质设计中的应用,并且对蛋白质结构预测存在的主要问题进行了讨论,指出了今后蛋白质结构预测研究重点在于优化比对算法和计分函数以及膜蛋白的结构预测.     

树木髓心构造及其美学应用

[目的]研究树木髓心构造及其在美学方面的应用,为树木髓心美学价值探索和开发提供参考.[方法]采用木材解剖技术,分析树木髓心的宏观与微观构造,并对树木髓心进行美学分析和图案创作.[结果]树木髓心横切面大多为圆形,偶有椭圆形、三角形、四棱形、五角星形和花瓣形;树木髓心的纵剖面呈柱状,有空心、实心和分隔3种;树木髓心的微观构造比较简单,都是由初生薄壁细胞构成,细胞形状为大小不等的多边形或椭圆形.[结论]树木髓心组织构造中含有丰富的美学元素,由此可以构建树木髓心美学图案.     

Carbon: a new view of its high-temperature behavior

An increasing body of research indicates that carbon can exist in a number of polymorphic "carbyne" forms. It is proposed that these forms occur because of a shift to triple bonding in the carbon system as temperature increases above 2600 K. It is also proposed that graphite can dissociate into triple-bonded molecules by a simple mechanism.     

Hemoglobin Portland 1: a new human hemoglobin unique in structure

A new hemoglobin (Hb), Portland 1, has been found in a newborn infant having multiple congenital anomalies and complex autosomal chromosomal mosaicism. The new hemoglobin has a unique tetrameric structure (molecular weight, 66,000) composed of two pairs of different types of chains, neither of which is alpha, gamma(2)x(2). The x-chain of Hb Portland 1 may be a new type of hemoglobin chain, but the available evidence suggests that it may be identical with the epsilon chain. We suggest that Hb Portland 1 is an embryonic hemoglobin that persisted until after birth in relatively large amounts in this patient.     

Localization and its absence: a new metallic state for conducting polymers

A widely held view in solid-state physics is that disorder precludes the presence of long-range transport in one dimension. A series of models has been recently proposed that do not conform to this view. The primary model is the random dimer model, in which the site energies for pairs of lattice sites along a linear chain are assigned one of two values at random. This model has a set of conducting states that ultimately allow an initially localized particle to move through the lattice almost ballistically. This model is applicable to the insulator-metal transition in a wide class of conducting polymers, such as polyaniline and heavily doped polyacetylene. Calculations performed on polyaniline demonstrate explicitly that the conducting states of the random dimer model for polyaniline are coincident with recent calculations of the location of the Fermi level in the metallic regime. A random dimer analysis on polyparaphenylene also indicates the presence of a set of conducting states in the vicinity of the band edge. The implications of this model for the metallic state in other polymers, including heavily doped polyacetylene, are discussed.     

一种新的信息系数及应用

给出了一种基于信息理论的广义距离系数.这一新的信息系数较离散增量信息系数有所改进,并可应用于聚类分析.     

农业结构调整的风险及其防范措施

阐述了农业结构调整的三大风险，提出了采用农业保险、落实保护政策、规范市场行为、普及科学技术等风险防范措施。     

一种新的混沌激振器及其动力学特性

在分析已有混沌发生机构的基础上,结合混沌中的倍周期分叉现象,设计了一种新的混沌激振器。该激振器由2个偏心轮构成,2个偏心轮之间的约束由传统的光滑铰链改为沿圆形轨道滑动,从而使系统产生倍周期现象的条件大幅度放宽。建立了该混沌激振器的动力学模型,通过仿真试验分析其动力学特性。结果表明,较普遍应用的三连杆混沌激振器,该混沌激振器具有更强的混沌特性和更为宽松的参数选择,因而具有更大的使用范围。     

高粱新品种引进及产业化开发

介绍了浙江省诸暨市引进高粱新品种湘两优糯粱1号的成功经验.该品种引进当地种植,不仅能增产增收,而且带动了当地的农业龙头企业的发展,走出了一条高粱生产、酿酒一条龙的产业化开发之路.     

The predicted structure of immunoglobulin D1.3 and its comparison with the crystal structure

Predictions of the structures of the antigen-binding domains of an antibody, recorded before its experimental structure determination and tested subsequently, were based on comparative analysis of known antibody structures or on conformational energy calculations. The framework, the relative positions of the hypervariable regions, and the folds of four of the hypervariable loops were predicted correctly. This portion includes all residues in contact with the antigen, in this case hen egg white lysozyme, implying that the main chain conformation of the antibody combining site does not change upon ligation. The conformations of three residues in each of the other two hypervariable loops are different in the predicted models and the experimental structure.     

调整品种结构,加快甘蔗良种推广应用

分析云南甘蔗品种现状 ,合理调整品种结构 ,坚持自育与引进相结合的原则 ,建立甘蔗良种育、繁、推一体化 ,加快甘蔗良种的推广应用 ,是降低甘蔗和制糖生产成本 ,增强蔗糖业竞争能力的有效措施     

A new tax on gasoline: estimating its effect on consumption

Based on extrapolation of a recent estimate of the elasticity of demand for gasoline, it is concluded that a tax of 5 cents per gallon per year over the period 1979 to 1988 can be expected to produce significant reductions in gasoline consumption, contrary to widely expressed opinions.     

Methane in lake kivu: new data bearing on its origin

Lake Kivu, an African rift lake, contains about 50 cubic kilometers of methane (at standard temperature and pressure) in its deep water. Data resulting from two recent expeditions to the lake and a reevaluation of earlier data suggest that most of the methane was formed by bacteria from abiogenetic carbon dioxide and hydrogen, rather than being of volcanic origin or having formed from decomposing organic matter.     

适应新形势,构建新蓝图,实现新目标--全国农业教育发展"十五"计划纲要

随着高等教育体制改革和机构改革的逐步深化 ,农业部作为行业部门对农业教育管理的重点将逐步转移到农民职业技术教育、农业职业教育和农业继续教育 ,同时仍要积极支持高等农业教育的发展。根据工作重点的转移 ,面对新时期农业和农村经济的发展 ,社会主义市场经济体制的逐步建立和加入WTO带来的机遇与挑战 ,农业教育必须主动适应新形势。为此 ,农业部组织制订了《全国农业教育发展“十五”计划纲要》 ,以加强对农业教育改革和发展的指导 ,促进“科教兴农”战略的贯彻落实 ,确保新时期农业和农村发展目标的实现。     

“莎彤”番茄新品种及栽培技术

“莎彤”是青岛市农业科学研究院新育成的适合保护地、露地栽培的中熟番茄一代杂交种,其母本是自交系S以2-4,1996年由以色列引入品种R-144中分离10代得到,具有早熟、抗裂、耐贮藏、果实圆整、果色红、耐低温的特点;父本是S21,1999年由美国引入试材分离9代所得,具有抗病毒病、高