芳香环状低聚物组分分布与单体结构关系的研究

根据Jacoson-Stockmayer(J-S)环化理论,应用基质辅助激光解吸离子化飞行时间质谱(MAIDL-TOFMS),对一系列芳香环状低聚物组分分布进行分析,研究了芳香环状低聚物的组分分布与单体结构的关系,结果表明,在芳香聚酯、聚膦酸酯及芳香聚醚环状低聚物系列中,Incn与Inn呈良好的线性关系,符合J-S理论分布,在环状聚酯及聚膦酸酯系列中,低聚物的组分分布受双酚单体的中心键角影响,单体的中心键角在100°～120°之间,其中心键角愈小,γ值愈大,而在聚醚系列中,在固定一种单体的前提下,环化物的组分分布受另一单体键角的影响与环状聚酯和聚膦酸酯相一致.     

Structure-activity relationship of Ca2+ channel blockers: A study using conformational analysis and chemometric methods

Summary A structure-activity relationship study has been done on 8 compounds with the activity known as Ca²⁺ channel blockers. Conformational analysis was carried out using a molecular mechanics method. The 3D-QSAR approach was used and the most polar functional groups present in all the molecules were considered. Eight interatomic distances are necessary to define the relative spatial disposition of these relevant molecular fragments. The structure-activity relationship between interatomic distances and biological activity was performed using statistic and chemometric methods. In particular, with Principal Component Analysis, it was possible to reduce the number of interatomic distances: only six of the eight distances are sufficient to describe the system in a useful way. A classification method was iteratively used to select the most probable conformations linked to the biological activity and to build a model able to classify conformations according to their biological behaviour. Cluster analysis on the active selected conformations subsequently allowed the identification of two different geometrical patterns for the active compounds. Finally the validity of the model was verified by correctly predicting the activity of other molecules not used in the construction of the model but possessing known activity.     

不同电场频率对羊柴种子发芽率和幼苗根长的影响

用不同电场强度和不同频率的匀强电场处理羊柴种子5 min,分别测定电场对其发芽率和根系的影响.实验结果表明:羊柴种子受电场作用后能提高种子发芽率.     

高等级公路边坡护坡植被适应性评价体系的研究

以涿廊高速公路为例,利用1999～2010年的年均降水量、年均气温、日照时间、年积温数据和杨树、柳树、紫穗槐、爬山虎、紫花苜蓿的生长条件,基于主成分分析和层次分析法建立高等级公路边坡植被适应性评价模型。结果表明：在一定区域范围内,利用主成份和层次分析法,构建的高等级公路边坡护坡植被适应性评价模型是可行的,并为植被适应性评价探索了一条新方法和途径。     

软件复用技术在基于B/S模式的新闻管理系统中的应用研究

软件复用是在软件开发中避免重复劳动的解决方案.通过软件复用,可以提高软件开发的效率和质量。当前软件构件技术被视为实现成功复用的关键因素之一,本文介绍软件复用的基本概念及关键技术,并结合实际开发中的经验,对基于B/S模式新闻管理系统开发中的软件复用进行了一定的研究。     

线性判别分析与主成分分析及其相关研究评述

线性判别分析（LDA）和主成分分析（PCA）都在各个领域有着重要的作用。他们各自抓住样本在特征空间的不同特征,一般情况下更趋向于使用LDA,因为LDA直接处理类间的分析问题,而PCA则没有突出类的结构。然而实验证明PCA在某些问题上又明显优于LDA。于是,改进或结合使用LDA与PCA成了非常必要的课题。现阶段在这个领域上已经有许多优秀的研究成果,本文简单的介绍了其中几种效果较好的相关分析方法,其中又以混合判别分析（HDA）最优。HDA不仅同时抓住了样本的判别信息和描述信息,使PCA与LDA在各种情况下达到平衡,而且在二维参数空间中提供了一系列的分析方法,更有利于解决小样本问题和高维问题。Boosted HDA的提出通过用迭代的方法改进弱分类器,避免了HDA复杂的参数搜索,并得到一种统一计算HDA的方法。文章将在第三部分引用一些已有的实验结果来验证HDA的优越性。     

Nitrile Rubber Reactor Operation Troubleshooting with Principal Component Analysis

Principal Component Analysis (PCA) is employed as a tool in order to demonstrate yet another application of the technique, and, most importantly, to show that results from the statistical multivariate technique do make physico-chemical sense. The operation of a typical emulsion copolymerization of acrylonitrile and butadiene (nitrile butadiene rubber, NBR) is used as an example of process troubleshooting. In more general terms, a statistical tool is used to aid process data analysis and process operation (recipe, product property) troubleshooting.

The goal is to produce consistent Mooney Viscosity (MV) among different batches. The observation is that varying induction times lead to Mooney Viscosity inconsistencies. Firstly, we show results from the application of PCA to process data. Secondly, we deal with an even more important (and often ignored) question by examining whether the trends indicated by PCA make process sense.     

Membrane lipids are both the substrates and a mechanistically responsive environment of TMEM16 scramblase proteins

Recent discoveries about functional mechanisms of proteins in the TMEM16 family of phospholipid scramblases have illuminated the dual role of the membrane as both the substrate and a mechanistically responsive environment in the wide range of physiological processes and genetic disorders in which they are implicated. This is highlighted in the review of recent findings from our collaborative investigations of molecular mechanisms of TMEM16 scramblases that emerged from iterative functional, structural, and computational experimentation. In the context of this review, we present new MD simulations and trajectory analyses motivated by the fact that new structural information about the TMEM16 scramblases is emerging from cryo-EM determinations in lipid nanodiscs. Because the functional environment of these proteins in in vivo and in in vitro is closer to flat membranes, we studied comparatively the responses of the membrane to the TMEM16 proteins in flat membranes and nanodiscs. We find that bilayer shapes in the nanodiscs are very different from those observed in the flat membrane systems, but the function-related slanting of the membrane observed at the nhTMEM16 boundary with the protein is similar in the nanodiscs and in the flat bilayers. This changes, however, in the bilayer composed of longer-tail lipids, which is thicker near the phospholipid translocation pathway, which may reflect an enhanced tendency of the long tails to penetrate the pathway and create, as shown previously, a nonconductive environment. These findings support the correspondence between the mechanistic involvement of the lipid environment in the flat membranes, and the nanodiscs. © 2019 Wiley Periodicals, Inc.     

中国岩黄耆属(Hedysarum L.)植物区系生态地理分布

依据种的现代分布、替代关系、地质历史、古气候和化石资料,探讨了中国岩黄耆属植物区系的发生、演变及形成机制.结果表明:岩黄耆属可能是由古地中海旱生植物区系中一类中生的原始灌木类群,在晚始新世到早渐新世或比这个时期稍晚一些,经过第三纪以来的环境分异变化,逐渐形成适应高寒山地生长的扁荚组种类和适应干旱环境生长的多茎组、短茎组种类,短茎组种类是多茎组对干旱强化进一步适应的结果,与此同时,原始的灌木类群自身也在继续演化,形成适应荒漠半荒漠生长的种类.这种演化过程揭示出生存环境中水热条件的剧烈变化是植物演化的主要动力.     

基于FPGA的IP仿真验证平台

IP（集成电路知识产权芯核）的仿真和硬件验证是IP开发中不可缺少的环节．文中基于FPGA（现场可编程门阵列）开发了一个IP仿真验证平台,并使用PCI（外部设备互连）总线来测试IP．用户只要将自已设计的IP插入所开发的仿真验证平台,就可以方便地对IP进行测试．文中还对所设计的平台进行了软件仿真,以验证其功能,并在载有Xilinx Spartan-3 600E FPGA的PCI插卡上进行上板调试．结果表明,所建立的基于FPGA的IP仿真验证平台可以对IP进行有效的仿真和验证,并具有良好的稳定性和实用价值．