Synthesis and structure revision of litseaone A

Litseaone A, isolated from the stem barks of Litsea rubescens and Litsea pedunculata, is a chalcone derivative with a novel spiro-epoxide moiety. The structural revision of litseaone A was achieved by the racemic synthesis of the proposed structure and the asymmetric synthesis of the revised structure. The major tautomeric structure of litseaone A and the relative stereochemistry at the epoxide carbon center were also clarified.     

CoLab: A hybrid knowledge representation and compilation laboratory

Knowledge bases for real-world domains such as mechanical engineering require expressive and efficient representation and processing tools. We pursue a declarative-compilative approach to knowledge engineering.While Horn logic (as implemented in PROLOG) is well-suited for representing relational clauses, other kinds of declarative knowledge call for hybrid extensions: functional dependencies and higher-order knowledge should be modeled directly. Forward (bottom-up) reasoning should be integrated with backward (top-down) reasoning. Constraint propagation should be used wherever possible instead of search-intensive resolution. Taxonomic knowledge should be classified into an intuitive subsumption hierarchy.Our LISP-based tools provide directtranslators of these declarative representations into abstract machines such as an extended Warren Abstract Machine (WAM) and specialized inference engines that are interfaced to each other. More importantly, we provide source-to-sourcetransformers between various knowledge types, both for user convenience and machine efficiency.These formalisms with their translators and transformers have been developed as part of CoLab, acompilationlaboratory for studying what we call, respectively, vertical and horizontal compilation of knowledge, as well as for exploring the synergeticcolaboration of the knowledge representation formalisms.A case study in the realm of mechanical engineering has been an important driving force behind the development of CoLab. It will be used as the source of examples throughout the paper when discussing the enhanced formalisms, the hybrid representation architecture, and the compilers.Supported by BMFT Research Project ARC-TEC (grant ITW 8902 C4)     

Total synthesis of stevastelins B3 and C3: structure confirmation of stevastelin B3 and revision of stevastelin C3

The total synthesis of stevastelin B3, stevastelin C3 and 5-deoxy derivative of stevastelin C3, novel 13-membered cyclic depsipeptides, is described. This study unambiguously confirmed the proposed absolute structure of stevastelin B3, and revealed that the structure of stevastelin C3 is incorrect. The correct structure of stevastelin C3 was established by the total synthesis to be 5-deoxy derivative of the proposed structure.     

“比较法”因素修正系数分析、判断及其应用

房地产估价实务中，“比较法”因具有较好的实用性和适用性而被普遍采用，但由于因素修正所带有的主观性和不确定性，必影响到评估结果的准确性，该文为提高评估结果的准确性，从技术上对因素修正系数做出分析，判断，最后给出一个应用实例。     

协同标签系统的应用研究

协同标签系统在帮助用户管理标签的同时,也为用户的导航和检索提供了便利.本文在分析了协同标签系统现状的基础上,提出了一种建立分类标签树的算法,将混乱的标签进行整理,转换成为有序的、层次的、分类的标签树,使标签提供的信息能被用于检索、导航,使用户更好的协同组织管理和利用网上资源,最后对算法进行了测试.     

多道脉冲幅度分析器死时间问题探讨

核分析能谱测量要用多道脉冲幅度分析器 ,这种分析器进行模数转换时需要一定的时间 ,使分析器产生漏计数。因而在相同测量时间内 ,对放射性强弱不同的样品进行测量时 ,漏计情况不同 ,造成相对测量条件不同 ,给测量分析带来误差。因此 ,为确保相对测量条件完全一致 ,测量结果更加可靠 ,必须对死时间进行修正     

Synthesis and structure revision of tyroscherin, and bioactivities of its stereoisomers against IGF-1-dependent tumor cells

Synthesis of the proposed structure of tyroscherin, a growth inhibitor of IGF-1-dependent cancer cells, was succeeded by one-pot Julia coupling. However, spectral data of the synthetic compound were not identical with those of natural tyroscherin. The stereochemistry of tyroscherin is revised to be 2S,3R,8R,10R by syntheses of stereoisomers. Synthetic tyroscherin showed more potent activity than its stereoisomers against IGF-1-dependent cancer cells.     

新中文命名规则下的最新中国苦苣苔科植物名录

中国苦苣苔科植物的物种数量在过去的十余年内出现了令人惊讶的飞速增长,同时自2011年以来属一级水平上的大范围修订使得我国苦苣苔科植物物种系统位置的变动频繁而巨大,导致中文文献中使用的学名和对应的中文名称出现了相当程度上的混乱。本文整理了自专著《中国植物志·第69卷》《Flora of China:Vol. 18》《中国苦苣苔科植物》《华南苦苣苔科植物》和前一阶段归纳的我国苦苣苔科植物生物多样性文献付梓和发表以来,正式报道的所有中国苦苣苔科植物新分类群,提供了物种修订前后的新旧物种名的对照,为部分发表时未指定中文名称的新分类群新拟了中文名,对出现了混淆的物种中文名进行了梳理,以期为国内研究者更好地引用和使用我国苦苣苔科植物的中文名称奠定基础。截止2019年1月,我国已经正式报道和合格发表的苦苣苔科植物物种数已经有719种(含种下等级)。在新命名规则背景下梳理的中国苦苣苔科植物名录将在中国苦苣苔科植物保育中心(GCCC)的网站(http://gccc.gxib.cn)上实时更新。     

内蒙古花忍属植物的分类校正及区系地理分布

确认了花Ｒｅｎ属在内蒙古仅有Ｐ．ｃｏｅｒｕｌｅｕｍ Ｌ和Ｐ．ｖｉｌｌｏｓｕｍ Ｒｕｄ．ｅｘ．Ｇｅｒｏｇｉ．两种，确定了其植物区系地理成分，前者为泛北极种，后者为中西伯利亚南部种。     

浅析爱伦·坡作品中的“二性人”现象

爱论·坡是一位美国十九世纪浪漫主义文学家。本文试图通过分析他创造的二性人形象 ,说明必须由一个能用新的眼光回头看 ,以新的批评的角度回头看的人来发现故事中的“第二个故事”。坡的这种需要“回头看”来解决问题的方法 ,就是二性人的思想