N-方酰麻黄碱配体的合成及催化前手性芳酮的不对称还原反应

方酸与醇反应成方酸二酯,后者与天然麻黄碱反应得到N-方酰麻黄碱或N-方酰双麻黄碱。单N-方酰麻黄碱与脂肪胺及硫氢化钠等反应合成了C-3位含氮和含硫的系列配体。首次将这些方酰麻黄碱配体经原位制备手性恶唑硼烷催化前手性芳酮及二酮的不对称还原反应,得到化学产率和e.e.值分别为85%-98%和52.5%-87.4%的手性仲醇。新化合物的结构已IR,^1H NMR,MS和元素分析所证实,化合物4b的晶体结构用X射线射确认。     

Asymmetric Catalytic Hydrogenation Using Rhodium Diphosphinites Derived From D-glucose and D-mannitol

Duringpastthreedecades,manyreportshaveappeareddescribingtheuseofchira1ligands-transitionmetalcomplexesforasymmetrichydrogenationreactionl.Amongthechiralligands,chiralbis(phospines),l,2-bis(aminophospines)andbis(phosphinites)'arewe1lknownforrhodium(I)complexes.Duetotheireasyaccessibilityfrompracticalviewpoint,diphosphiniteligandshavebeenreportedtillrecently'.Chanetal3a,candZhangelal3bobservethatincreasingligandrigidityisthekeyforthedevelopmentofhighlyenantioselectivereactions.Aschiralblock,car…     

接触角及其在表面化学研究中的应用

润湿是一种流体取代界面上另一种流体的界面现象,通常是指液体从固体表面取代气体的过程。如在干净玻璃板上加水,排走表面上的空气形成薄的水膜,即为铺展润湿,简称铺展,此过程的特点是原固气界面消失,气液界面扩大,并形成新的固液界面。将固体完全浸渍于液体中,固气界面消失,气液界面不变,形成新的固液界面,此过程为现润湿（浸湿）。液体与固体接触,气液和固气界面减小,形成固液界面的过程为沾湿。润湿过程涉及固体和液     

用接触电池原理处理含铬电镀废水

利用焦炭和铁屑在酸性含铬溶液中形成接触电池,使六价铬转化为三价铬,再在碱性液中把三价铬沉淀析出的方法,采用简单的设施对电镀厂含铬废水进行处理,以较少的投入达到国家废水排放标准。     

激光光栅显微图像检测技术及其应用

介绍一种可以用来测量曲面试件表面应分量（εｚ,εθ,εｚθ）的激光光栅显微图像检测技术（ＩＧＭ）,它能实现从小应变到大应变全过程的高精度定量测量。我们将这一技术成功地应用在铁基形状记忆合金（ＦＳＭＡ）管接头的结构设计中,在这项研究中,首先在管接头结构表面制作了变形的载体－位相型干涉光栅,由结构表面产生的衍射光通宵我学系统后形成新的干涉光栅,我们利用数字图像系统接收了逆相变前后各自的干涉图像,采用带     

A contact searching algorithm for contact-impact problems

A new contact searching algorithm for contact-impact systems is proposed in this paper. In terms of the cell structure and the linked-list, this algorithm solves the problem of sorting and searching contacts in three dimensions by transforming it to a retrieving process from two one-dimensional arrays, and binary searching is no longer required. Using this algorithm, the cost of contact searching is reduced to the order ofO(N) instead ofO(Nlog₂ N) for traditional ones, whereN is the node number in the system. Moreover, this algorithm can handle contact systems with arbitrary mesh layouts. Due to the simplicity of this algorithm it can be easily implemented in a dynamic explicit finite element program. Our numerical experimental result shows that this algorithm is reliable and efficient for contact searching of three dimensional systems. The project supported by the National Natural Science Foundation of China (59875045), and the State Key Laboratory of Automobile Safety and Energy Saving (K9705)     

三维接触问题的非光滑算法

给出了一种非光滑算法直接用于求解三维摩擦接触问题的不可微非线性互补模型,不再对模型进行光滑化处理,使算法更加简单。文中对非光滑算法的收敛性给出了严格的数学证明,数值实验表明该算法列式简单,但与光滑化算法同样有效。     

Communication, credible improvements and the core of an economy with asymmetric information

We analyze an economy with asymmetric information and endogenize the possibilities for information transmission between members of a coalition. We then define a concept of the Core that takes into account these communication possibilities. The internal consistency of the improvements is considered and an Internally Consistent Core, which requires credibility from the improvements is introduced. Received: September 1998/revised version: June 1999     

Influence of the transport direction on gas permeation in two-layer ceramic membranes

Experimental and theoretical results of studying gas permeation through porous membranes are presented. In order to mimic an asymmetric membrane two porous ceramic disks with different pore radii were arranged in series. Besides the possibility to perform conventional permeation measurements, the applied experimental setup permits the determination of the pressure at the interface between the two discs. To predict the performance of the asymmetric structure, in preliminary experiments structure parameters were determined for both membranes separately. For the same total pressure difference across the two-disk arrangement, different interlayer pressures and fluxes were predicted and detected experimentally depending on the flow direction.     

有机锡化合物在天然产物合成中的应用

综述了有机锡化合物在不同对称合成天然产物中的应用。有机锡化合物应用于天然产物的不对称合成,反应条件温和、活性高,有很高的立体选择性和区域选择性,有广阔的应用前景。