An analysis of simultaneous variation in protein structures

The simultaneous substitution of pairs of buried amino acid side chains during divergent evolution has been examined in a set of protein families with known crystal structures. A weak signal is found that shows that amino acid pairs near in space in the folded structure preferentially undergo substitution in a compensatory way. Three different physicochemical types of covariation 'signals' were then examined separately, with consideration given to the evolutionary distance at which different types of compensation occur. Where the compensatory covariation tends towards retaining the combined residue volumes, the signal is significant only at very low evolutionary distances. Where the covariation compensates for changes in the hydrogen bonding, the signal is strongest at intermediate evolutionary distances. Covariations that compensate for charge variations appeared with equal strength at all the evolutionary distances examined. A recipe is suggested for using the weak covariation signal to assemble the predicted secondary structural elements, where the evolutionary distance, covariation type and weighting are considered together with the tertiary structural context (interior or surface) of the residues being examined.      

芳纶橡胶输送带的接头强度研究

针对芳纶橡胶输送带接头强度保持率低的问题,本研究以国内外芳纶橡胶输送带接头方案为基础,采用指型插接方案,系统性地探究了指型长径比、贴胶厚度、织物增强层结构等因素对接头强度的影响。实验证明接头强度随长径比的增大而升高;贴胶厚度在1mm时接头强度达到最大,此后接头强度随贴胶厚度的增加而降低;织物增强层沿经向放置的接头强度提高87%,接头强度保持率达到带体强度的60%。     

节能型活性染料的发展状况

综述了开发节能型活性染料的重要性.重点介绍了适用于冷轧堆染色、小浴比染色和涤/棉一浴法染色用活性染料以及高固色率活性染料的发展状况;通过提高染料的耐碱性、溶解度、染深性以及固着率等方面来达到节能减排的目的.     

CY-61100车床尾座铸造过程仿真优化研究

对CY-61100车床尾座铸件充型及凝固过程进行了数值模拟及优化研究。根据模拟的结果及铸造缺陷预测,改进及优化了尾座浇注系统,在工厂实际浇铸生产应用中取得了良好效果。并由此建立了铸造过程CAE仿真优化技术与传统铸造工艺设计有效结合的先进铸造工艺设计模式。     

中国天然气勘探开发现状及物探技术需求

2000年以来,中国石油天然气集团公司在鄂尔多斯盆地、四川盆地、塔里木盆地、松辽盆地、柴达木盆地、渤海湾盆地等的天然气勘探中不断获得新的发现,初步形成了东部、中部、西部协调发展的合理布局。现阶段面临的问题是如何尽快将资源优势转化为经济优势。目前,我国天然气主要储集层为碎屑岩、碳酸盐岩和火山岩三大岩石类型。碎屑岩储层特征表现为我国中部丘陵地区的低孔、低渗的致密砂岩以及西部复杂高陡构造的孔隙砂岩;碳酸盐岩和火山岩储层普遍埋藏较深,非均质性强,缝洞单元难以刻画。因此,必须采用有针对性的地球物理勘探技术,优先发展碎屑岩气藏检测勘探技术,强化地震岩石物理等基础研究,加快碳酸盐岩、火山岩气藏检测技术攻关。同时开展高密度、多波地震勘探等前沿技术研究,为定量评价和产能建设提供技术保障。     

提高储层预测精度技术思路与对策

采用地质、地震、测井人员协同一体化作业，对地下地质目标进行综合预测与评价，可提高储层预测精度，降低预测结果的多解性。主要方法是针对不同的区块，采用不同的方法和对策，首先从单井储层划分对比入手，建立储层沉积模式，同时对地震数据目的层段进行精细解释，建立地层构造模式，用沉积、构造等地质规律来指导和约束反演；利用测井资料对地震资料进行精细标定，建立各井的单井波阻抗模型，建立井数据和地震数据沟通的桥梁；在严格的测井约束、地质模型约束、层位控制下进行储层反演；充分利用地质、地震反演结果、地震参数提取及分析结果、测井、测试和分析化验等资料对储层预测结果进行综合分析与评价。该方法应用于长庆、大庆、准噶尔等实际区块，取得了较好的效果。     

Kinetic and morphological study of a magnesium ethoxide‐based Ziegler–Natta catalyst for propylene polymerization

BACKGROUND: Kinetic and morphological aspects of slurry propylene polymerization using a MgCl₂‐supported Ziegler–Natta catalyst synthesized from a Mg(OEt)₂ precursor are investigated in comparison with a ball‐milled Ziegler–Natta catalyst. RESULTS: The two types of catalyst show completely different polymerization profiles: mild activation and long‐standing activity with good replication of the catalyst particles for the Mg(OEt)₂‐based catalyst, and rapid activation and deactivation with severe fragmentation of the catalyst particles for the ball‐milled catalyst. The observed differences are discussed in relation to spatial distribution of TiCl₄ on the outermost part and inside of the catalyst particles. CONCLUSION: The Mg(OEt)₂‐based Ziegler–Natta catalyst is believed to show highly stable polymerization activity and good replication because of the uniform titanium distribution all over the catalyst particles. Copyright © 2008 Society of Chemical Industry     

北京妫水河湿地植物多样性调查与评价研究

为探究北方缺水地区湿地植物物种多样性变化,选取北京市延庆区妫水河为研究区,采用物种丰富度(R),Shannon-Wiener指数(H),Simpson指数(D)和Peilou均匀度指数(J)作为植物群落多样性指标,使用方差法和典型对应分析(CCA)对不同河段和区域间湿地植物物种分布与环境因子之间的响应关系进行研究。研究结果表明:研究区现有湿地植物93种,隶属于44科76属,优势科有菊科(Asteraceae)、禾本科(Poaceae)、豆科(Fabaceae)和莎草科(Cyperaceae); 93种植物的Shannon-Wiener指数(H)小于3,Simpson指数(D)和Peilou均匀度指数(J)介于0. 5～0. 75之间,物种数量总体不多,但分布较均匀,处于中等水平;对湿地植物群落形成及生长影响较大的水质因子依次为全氮(TN)、p H和化学需氧量(COD)。     

Institutional Capacity Building within the Water Resources Sector of Developing Countries

Abstract

Part 1 of this paper analyzes the concepts of institutional capacity building and of integrated water resources management, on the basis of recent publications. The authors, building on the work of others, combine this into a conceptual framework for institutional capacity building in the water resources sector. A matrix approach is developed that allows the analysis of project activities, projects and possibly even complete sector programs. At the same time various aspects of process orientation of projects and programs are distinguished and described. The result is a set of analysis tools specifically oriented towards the evaluation of institutional capacity building projects and programs in the water resources sector. Part 2 presents a number of case studies and shows the application of the set of analysis tools. The same set of tools can also be used for the design of such projects or programs, but this is not covered in the present papers.     

Root growth and phosphorus and potassium uptake by two corn genotypes in the field

In a field study P and K uptake by two corn (Zea mays L.) genotypes which differed in root growth was investigated. The effect of differences in root growth on P and K uptake was assessed using a mechanistic-mathematical model which describes nutrient uptake by growing plant roots in soil. Nitrogen was applied at 0 and 227 kg ha^–1 to Pioneer 3732 and B73xMo17 corn grown on Raub silt loam (fine-silty, mixed, mesic Aquic Argiudoll) and at 227 kg N ha^–1 to these two genotypes on Chalmers silt loam (finesilty, mixed, mesic, Typic Haplaquoll). Root growth and P and K uptake by the two corn genotypes was measured 31, 47, 75 and 91 d after planting on the Raub and 31, 47, 61 and 75 d after planting on the Chalmers soil.Root growth and P and K uptake by B73xMo17 was greater than that of Pioneer 3732 on N-fertilized Raub soil. On Chalmers soil the difference in root growth between the two genotypes resulted in an increase in K but not P uptake. The higher soil P level of the Chalmers appears to have offset possible differences in P uptake due to root size. There were no differences between the two genotypes in either the percentage of roots with root hairs, or the density or length of root hairs. Phosphorus and K uptake calculated with the simulation models for both corn genotypes on both soils over each of three growth periods agreed with observed P (Y = 0.68X + 1.71; r = 0.944^**) and K (Y = 0.88X + 15.52; r = 0.928^**) uptake. Differences in P and K uptake between B73xMo17 and Pioneer 3732 resulted primarily from the difference in root growth in the topsoil. A high correlation was found between root surface area and P (r = 0.893^**) and K (r = 0.928^**) uptake by both corn genotypes on both the soils.Journal paper No. 10,316 Purdue Univ. Agric. Exp. Stn., W. Lafayette, In 47906. Contribution from the Dep. of Agron. This paper was supported in part by a grant from the Tennessee Valley Authority.