Sequence and analysis of chromosome 2 of the plant Arabidopsis thaliana

Arabidopsis thaliana (Arabidopsis) is unique among plant model organisms in having a small genome (130-140 Mb), excellent physical and genetic maps, and little repetitive DNA. Here we report the sequence of chromosome 2 from the Columbia ecotype in two gap-free assemblies (contigs) of 3.6 and 16 megabases (Mb). The latter represents the longest published stretch of uninterrupted DNA sequence assembled from any organism to date. Chromosome 2 represents 15% of the genome and encodes 4,037 genes, 49% of which have no predicted function. Roughly 250 tandem gene duplications were found in addition to large-scale duplications of about 0.5 and 4.5 Mb between chromosomes 2 and 1 and between chromosomes 2 and 4, respectively. Sequencing of nearly 2 Mb within the genetically defined centromere revealed a low density of recognizable genes, and a high density and diverse range of vestigial and presumably inactive mobile elements. More unexpected is what appears to be a recent insertion of a continuous stretch of 75% of the mitochondrial genome into chromosome 2.     

再生水中亚硝酸盐对余氯衰减的影响及其控制

根据华北地区某再生水厂的实际水质特点,通过实验比较了加氯消毒后水中TOC、NO2-对余氯消耗的影响;使用平行一级反应模型分析实验结果,发现折点氯化后亚硝酸盐耗氯反应的速率常数显著高于有机物耗氯反应,亚硝酸盐成为再生水中重要耗氯物质．为稳定再生水中余氯浓度,提出了2个方案：再生水中加氨或调节pH值,分别进行了模型拟合和实验效果分析．通过对比加氨和调pH值方案的余氯成分和所需药剂投量,得出调节水体至弱碱性（pH值为8．3）是更好的途径．本研究对再生水厂消毒工艺的设计、运行具有一定的借鉴意义,对保证再生水水质安全具有较高的实用价值．     

光系统Ⅱ核心天线蛋白CP43和CP47的圆二色和磁圆二色性研究

从菠菜中分离提纯了光系统Ⅱ核心天线复合物ＣＰ４７,利用吸收光谱、圆二色（ＣＤ）光谱和磁圆二色（ＭＣＤ）光谱对二者色素结合状态进行了研究。对ＣＰ４３和ＣＰ４７上色素结合状态的不同进行了讨论。ＭＣＤ光谱是一种高灵敏度的检测色素的光谱手段,适宜于对光合作用中色素－蛋白复合物的研究。     

Structural Optimization of Damping Groove Based on Valve Plate Dynamic Cavitation Response Model

To reduce cavitation occurring on valve plate of piston pump,an optimization design method was introduced to quantitively analyze the accurate relationship between structural jet groove parameters and cavitation. Using the computational fluid dynamics（ CFD） method,the absorbing and discharging processes in piston pump were simulated dynamically. The damping groove＇s structure effects on both jet angle and pressure shock were analyzed visually with a series of different parametrical grooves. By establishing parametrical damping groove model,the piston pumps＇ dynamic analysis was integrated with CFD analysis,experimental design and approximation model, etc. The mathematical model of plunger pressure during oil back period,jet angle and structural parameters of damping groove were established in the form of second-order response surface method（ RSM） model. The damping groove structure of valve plate was optimized on the basis of the RSM model. Test data shows that the anti-cavitation performance of optimized valve plate was obviously improved. And this method provides theoretical foundation for the structure design of damping groove.     

第三纪火山沉积硼矿与火山岩关系研究

第三纪火山沉积硼矿的物源与同时代的火山岩有密切联系,火山岩与岩浆活动也有遗传关系。硼富集的两种方式:洋壳经过水下蚀变导致硼富集以及深海沉积物从海水吸附硼,俯冲带内蚀变洋壳和深海沉积物在脱水过程中释放的富硼流体。富硼流体通过岩浆作用融入岩石圈地幔,最后形成富硼火山岩。富硼火山岩通过风化、热液淋滤出硼通过流水、热液(泉)搬入盆地,形成火山沉积硼矿。     

4—芳基—2,6—二苯吡喃高氯酸盐的合成方法

介绍了合成４－芳基－２，６－二苯吡喃高氯酸盐及转化为吡啶和取代吡啶化合物的方法。     

浅析施工现场管理安全生产保证体系

为保证施工生产的人身安全、设备安全、结构安全、财产安全和适宜的施工环境,本文依据作者的施工经验,对施工现场的安全管理生产工作进行了详细的阐述,以供参考。     

泡沫混凝土减震层对隧道地震响应影响分析

应用有限差分软件FLAC^{3D对泡沫混凝土减震层对花岗岩隧道地震响应的影响规律进行分析. 综合考虑围岩位移、塑性区范围、应力场分布、应变增量等指标,得出增设泡沫混凝土减震层可以大幅降低围岩最大主应力以及衬砌结构的内力,有利于围岩的稳定.其次分析了减震层各物理力学参数对花岗岩隧道地震响应的具体影响,得出增加减震层变形模量或粘聚力可以大幅降低衬砌结构中的内力;而减震层的内摩擦角及泊松比的改变对减震层的减震效果影响较小.}     

Snake venom thrombin-like enzymes: from reptilase to now

The snake venom thrombin-like enzymes (SVTLEs) comprise a number of serine proteases functionally and structurally related to thrombin. Until recently, only nine complete sequences of this subgroup of the serine protease family were known. Over the past 5 years, the primary structure of several SVTLEs has been characterized, and now this family includes several members. Of particular interest is their possible use in pathologies such as thrombosis. The aim of the present review is to summarize the state of the art concerning the evolutionary, structural and biological features of the SVTLEs.Received 16 August 2003; received after revision 26 September 2003; accepted 1 October 2003     

迎面会车二维气动仿真模拟研究

应用计算流体力学(CFD)中的动网格技术,模拟由于流域边界运动引起的模型运动状态随某一变量变化的流动情况,结合新版公路工程建设标准,对在一级公路和三级公路上的迎面会车过程进行瞬态气动特性仿真研究,根据仿真结果分析速度和间距对汽车稳定性的影响.结果表明:不同间距、不同速度的会车侧向力呈现不稳定波动的变化曲线,并伴有极值出现,侧向力负向最大值出现在两车头平齐时,正向最大值出现在两车身平行时.此仿真结论与在道路行驶过程中的真实会车情况相吻合,可为道路建设和行车安全提供参考.