Muchimangins E and F: novel diphenylmethyl-substituted xanthones from Securidaca longepedunculata

Two new highly oxygenated xanthones, named muchimangins E (1) and F (2), have been isolated from the root of Securidaca longepedunculata (Polygalaceae). Their structures were elucidated by the analyses of spectral data to be a novel xanthone with a diphenylmethyl substituent at C-2. Moreover, the structures of muchimangins B (4) and C (5) were revised by careful analysis of the spectral data and by comparing their NMR data with those of 1 and 2, to be xanthones with the diphenylmethyl substituent at C-2, not at C-4 reported previously.     

基于循环修正思路的低碳经济评价模型研究——以秦皇岛市低碳经济评价为例

根据科学发展观的内涵筛选指标建立低碳经济评价指标体系;通过层次分析法、标准离差、熵权法等赋权方法进行赋权,并以秦皇岛市的低碳经济为例进行评价,确定秦皇岛低碳经济评价结果排序.根据循环修正思路对不同赋权方法的评价结果排序进行修正,确定一致性排序,得到秦皇岛市低碳经济评价结果.研究结果表明:秦皇岛市低碳经济发展水平逐年提高;影响秦皇岛市低碳经济发展的主要指标有污水处理率,GDP,人均GDP,人均GDP增长速度,危险废物,生活垃圾无害化处理率,万元GDP能耗等.     

内蒙古小网蝽外生殖器特征及国内新纪录(半翅目;异翅亚目;网蝽科)

作者重新整理了内蒙古小网蝽属昆虫标本,并对雄虫外生殖器及雌虫第一生殖肢进行了解剖观察。在此基础上,对内蒙古小网蝽作了修订,简要描述了两性外生殖器的主要特征,并记述了2中国新纪录种:黑腿小网蝽Agramma femorale Thomson,1871,淡须小网蝽A. abruptifrons Golub, 1989。     

Revising Space Groups from Simulated SHELXfcf Structure Factors. More Examples of Incorrect Space Groups, an Example of a Chemically-Incorrect Structure and the Special Case of Pgl to PRevisions

1 INTRODUCTION Although the incorrect assignment of the space groups of crystal structures has been addressed in a number of reports, instances of crystal structures refined in incorrect symmetry turn up even in the recent literature[1～4]. A simple method of space group revision makes use of the published atomic coordinates and temperature factors to simulate the diffraction intensities; the structure is then 搒olved?in the correct space group from the simulated hkl-F2 data[5] and an O…     

Revised structures of Arillatanosides A–C from Polygala arillata

Arillatanosides A–C are three triterpenoid saponins from Polygala arillata Buch–Ham that have been reported previously, but with partially incorrect structures. Further investigation of their NMR data led to the conclusion that the terminal α‐L ‐arabinopyranosyl unit originally proposed for Arillatanosides A–C ( I – III ) is actually a β‐D ‐xylopyranosyl unit. Thus, the correct structures of Arillatanosides A–C are represented by 1 – 3 . Complete NMR assignments of Arillatanosides A–C ( 1 – 3 ) and the related polygalasaponin XXXV ( 4 ) were achieved using modern 2D NMR techniques, such as DQF H–H COSY, HMQC, HMBC, TOCSY, 2D HMQC–TOCSY. Copyright © 2002 John Wiley & Sons, Ltd.     

Structure of zamamistatin—a correction

The structure of zamamistatin, an antibacterial dibromotyrosine derivative, has been revised. Its structure was not exo- or endo-type dimer 1 or 2 which were described previously, but was identical to a dibromophenylpyruvic acid derivative, aeroplysinin-1 (3).     

应用HPLC色谱技术进行柃属植物化学分类学研究

利用高效液相色谱(HPLC)技术对24种1变种柃属植物28份样品的化学成分进行检测,并以各样品中色谱峰的相对保留时间对柃属植物的特征化学成分进行标记,最终统计到23个特征色谱峰用于化学分类研究。结果显示,柃属植物色谱峰在种内稳定出现,在种间则呈现多样性,可用于物种的鉴别。为进一步探讨种间亲缘关系及部分种的具体分类学地位,研究同时还采用UPGMA法和NJ法对色谱峰进行聚类分析,并根据两种聚类树型图讨论了化学成分的分类学意义。研究结果表明HPLC色谱技术具有快捷性、直观性和重现好的特点,可作为一种理想的标记用于柃属植物的分类鉴定。此外,本研究还能为柃属进一步的资源利用研究提供重要的参考。     

基于邻域粗糙集的网络入侵分类诊断组合模型研究

网络入侵诊断直接影响网络正常运行和安全.针对入侵类型复杂,现有分类诊断模型精度有限的问题,提出一种基于邻域粗糙集的网络入侵分类诊断优化模型.首先,运用邻域粗糙集对网络入侵数据进行条件属性的约简,确定关键属性,然后将其作为训练输入构建相关向量机分类诊断模型,并同时运用遗传算法进行超参数优化,提高模型诊断精度和速度.通过KDDCup99数据集对优化模型性能进行检验,结果表明,组合预测方法精确度高于支持向量机、相关向量机和BP神经网络.组合模型诊断精度高、速度快,具有优异的综合性能.     

Concise,enantioselective total syntheses of both the proposed and revised structures of (-)-versiquinazoline H

The enantioselective total synthesis of the putative structure of versiquinazoline H and three diastereomers has been achieved,which allowed the revision of the stereochemistry of this natural product.This six-step total synthesis relied on the evolution of the strategy that we previously developed,which features a DMDO-triggered tandem reaction.The modification of the lactamization step resulted in a significant improvement of yield that ensured the efficient total synthesis.     

CVE漏洞分类框架下的SVM学习模型构建

在CVE漏洞分类框架中,构建了基于支持向量机的学习模型,实现了根据不同的分类特征对CVE进行分类.