不对称

Total synthesis of bilobetin and isoginkgetin, natural polyhydroxy biflavones with a Ⅰ-3'/Ⅱ-8 dissymetrical connection, and synthesis of acetyl flavones were investigated in this dissertation.

本论文对天然多羟基不对称连接的双黄酮-白果素、异银杏素的合成以及乙酰基黄酮的合成进行了研究，共包括以下内容

The two-dimensional structural units (such as silicon-oxygen tetrahedral sheet, octahedral sheet), interlayer space are assembled according to the sphere close packing manner, and the close packing layers parallel to {0001}. There are several mechanisms to release the difference in size while the silicon-oxygen tetrahedral sheet and octahedral sheet assemble the TO and TOT-type structural layers. The two types of structural layers with different interlayer space fitted together in six kinds of assembling modes and formed six kinds of crystal layers. The combinatorics analysis of the two-dimensional structural units revealed that there may be 28 kinds of TOT type interstradified minerals in six kinds of polysomatic assembling modes of interatradified structure. The structural layer is symmetrical for octahedron sheet in the structure of interstratified minerals and shows polarity characteristics.

结果表明，不同二维结构单元体（包括硅氧四面体片、八面体片、层间域的构筑基本符合球体紧密堆积原理，紧密堆积层平行{0001}；四面体片与八面体片构筑TO和TOT结构层时采取多种机制消除二者在二维尺寸上的差异；两种模式的结构层与不同类型的层间物组装形成六种组装模式的晶层；并通过二维结构单元体的组合规律的分析，计算出可能存在的28种TOT型间层结构，它们分属于6种间层结构多体性组装模式；间层结构中，结构层对于八面体片是不对称的，并在属性上表现出极性特征；间层矿物的晶层类型可用6种多体性组装模式加以表达。

Preparation of polyvinylidene fluoride asymmetric hollow fiber membranes was studied by introducing small molecular additives, which include nonsolvents (water, ethanol and 1-propanol) and inorganic salt.

制备聚偏氟乙烯的不对称中空纤维膜的研究，通过引入小分子添加剂，其中包括nonsolvents （水，乙醇和1 -丙醇）和无机盐。

According to the complexity of accounting information and the ponderance of disservice, earnings management of listed companies is a great problem for investors, supervisors and auditors in capital market.

由于会计信息的复杂性、信息不对称的不可克服性和舞弊危害的严重性，盈余管理成为困扰证券市场投资者、监管者、审计人员，损害证券市场健康发展的一个大问题。

Addition of metallated terminal alkynes to carbonyls is considered as an effective route for the synthesis of chiral propargyl alcohols and has gained considerable significance in recent years.

末端炔对羰基化合物的不对称加成反应是构建手性炔丙醇的重要方法之一，其产生的光学活性炔丙醇是很多天然产物，精细化学品及药物分子的重要合成砌块。

The asymmetric alkynylation of carbonyls is proved to be one of the most powerful procedures for organic synthetic chemistry,where the formation of one carbon-carbon bond and one chiral center of propargylic alcohol can be achieved in one step,and has attracted organic chemists\' most attentions.Plenty of works have been reported in recent years.

由于催化末端炔对羰基化合物的不对称加成在制备手性炔丙醇的同时，能够构建一个碳碳键和一个手性中心，因而该领域的研究受到了研究者的广泛关注，有大量的研究工作见报道。

And the corresponding chiral tertiary propargylic alcohols were obtained with enantiomeric excesses of up to 86%, which provided a simple, practical and inexpensive method to generate chiral tertiary propargylic alcohols.

经过筛选、测试，发现一β-磺酰胺基醇-钛复合物可在温和条件下，有效促进炔基锌对简单非活化酮的不对称加成，并且得到相应的手性三级炔丙醇，ee值达到了86%。

This thesis mainly focuses on overcoming the substrates limition of the present catalytic systems,low catalytic efficiency,and application in total synthesis.1.Conveniently synthesized sulfonamide alcohol titanium complex has been used to catalyze the asymmetric addtition of methyl propiolate to various aromatic and aliphatic aldehydes with high enantioselectivity.

本论文即针对现有催化体系的底物局限性、催化效率低、应用研究少等展开研究：1、我们将简便合成的磺酰胺基醇配体-钛催化体系应用于催化丙炔酸甲酯对各类芳香醛及脂肪醛的不对称加成取得了理想的结果。

Owing to the transformation from proprietory right to shareholders' right, especially the objective existence of the situation of informational assymmetry, it has threatened the realization of the shareholders' controlling power to the company.

由于所有权向股权的转换，尤其是信息不对称情形的客观存在，股东对公司的支配力弱化，从而危及股东利益的实现。

The recovery of the pseudocubic angle of LSMO resulting from the relaxation of the shear strain introduced by the growth of rhombohedral LSMO on cubic LSAT was suggested to be the origin of the superlattice structure.

不对称的(103)倒易空间图强有力地证明了这面内调制结构源于因菱形的LSMO和立方衬底LSAT之间的角度失配引起的一种剪切应力的弛豫而导致LSMO薄膜中赝立方角的恢复。

Breath, muscle contraction of the buttocks; arch body, as far as possible to hold his head, right leg straight towards the ceiling (peg-leg knee in order to avoid muscle tension).

呼气，收缩臀部肌肉；拱起身体，尽量抬起头来，右腿伸直朝向天花板（膝微屈，以避免肌肉紧张）。

The cost of moving grain food products was unchanged from May, but year over year are up 8%.

粮食产品的运输费用与5月份相比没有变化，但却比去年同期高8％。