Noncatalytic on water aldol reaction of isatins with cyclic 1,3-diketones at room temperature without the need for subsequent chromatography

Noncatalytic on water aldol transformation of isatins and cyclic 1,3-diketones results in substituted 3-hydroxy-3-(2-hydroxy-6-oxocyclohex-1-en-1-yl)indolin-2-ones in 87–98% yields. Optimized conditions have been found and a mechanistic rationale for the reaction has been deduced. The new efficient and facile process represents a convenient way to compounds with the 3-hydroxyindolin-2-one and 3-hydroxycyclohex-2-en-1-one moieties.     

Heterogeneous Enantioselective Catalysis with Chiral Encoded Mesoporous Pt−Ir Films Supported on Ni Foam

The development of heterogeneous catalysts for asymmetric synthesis is one of the most challenging topics in chemistry, as it allows obtaining enantiomerically pure compounds. Recently, metal layers incorporating molecular chiral cavities, obtained by electroreduction of a metal source in the simultaneous presence of a non-ionic surfactant and asymmetric molecules, have been proposed for a wide range of applications, including enantioselective electroanalysis and electrosynthesis, as well as chiral separation. In contrast to this previous work, solely based on electrochemical phenomena, herein we designed and employed nanostructured chiral encoded Pt−Ir alloys, supported on high surface area nickel foams, as heterogeneous catalysts for the asymmetric hydrogenation of aromatic ketones. Fine-tuning the experimental conditions allows achieving very high enantioselectivity (>80%), combined with improved catalyst stability.     

AunXm(n+m=4,X=Cu，Al，Y)混合小团簇的结构和稳定性研究

采用基于密度泛函理论的B3LYP方法，优化了Au_nX_m(n+m=4,X=Cu，A l，Y)二元混合团簇的稳定结构.计算了稳定结构的平均结合能、电离势、电子亲和势、最高占据轨道能级和最低空轨道能级及二者间的能隙.结合Mulliken集居数分析研究了二元混合团簇稳定存在的规律，得出掺杂可以增强团簇稳定性的结论. 关键词： 混合团簇 结合能 能隙 分子轨道集居数     

A stochastic approach to Wilson loops

Wilson loops exp (i A (x) dx) are investigated in two-dimensional Euclidean space-time. The electromagnetic vector potential A is regarded as a generalized random field given by the stochastic partial differential equation A = F where is a first-order differential operator and F is white noise. We give a rigorous definition of Wilson loops and examine the properties of the N-loop Schwinger functions.     

Leading Coefficients and Extreme Points of Homogeneous Polynomials

Recently, H. Hakopian proved that the squares of a bivariate homogeneous polynomial and of its gradient have, in general, the same set of maximum points on the sphere. A generalization of this result mentioned can be gained by a method O. D. Kellogg used years ago in the estimate of some coefficient functionals. Date received: July 31, 1995. Date revised: May 14, 1996.     

光滑函数集列紧的一个判据

本文讨论紧区间上的C~1光滑函数,用6-网构造法证明了这种函数集合列紧的一个判据,从而使著名的Ascoli-Arzela引理在光滑情形下得到推广,这一结果对讨论光滑动力系统有重要意义。     

圆柱面上微小后向台阶层流绕流场的数值研究

1前言钩体绕流是燃烧、传热领域基本的流动现象，具有流动分离、流态转被、旋涡脱落、涡致振动等复杂特性。降低钩体绕流阻力一直是人们关心的问题。自从Prandtl圆球绊线实验以来，Stuper，Roshko，Zukausks，Achenbach，Klebanoff等［‘一列从不同角度研究了钝体绕流阻力的构成因素及降低钝体绕流阻力的若干方法。一致的观点是：因绕流钝体必然伴随着流动分离，流动阻力可分为与粘性有关的摩擦阻力及与流动分离有关的压差阻力两部分，其中，压差阻力约占总阻力的90N95％，其大小与流动分离点的位置密切相关。若流动分离时边界层内为层流…     

Unexpected deprotection of silyl and THP ethers induced by serious disparity in the quality of Pd/C catalysts and elucidation of the mechanism

Commercial Pd/C catalysts show different catalytic activity toward the deprotection of silyl and THP ethers. The Pd/C purchased from Merck and ACROS exhibits marked tendency to cleave these protective groups unexpectedly without hydrogen conditions although Aldrich's Pd/C (20,569-9) is inactive in the absence of hydrogen. It was proved that the Pd/C disparity toward the deprotection of TES and THP ethers results from residual acids and/or palladium chloride in the production process of Pd/Cs. Although a TES ether cleavage reaction in the absence of hydrogen and a THP ether cleavage reaction in the presence of hydrogen using 10% Pd/C were recently published, we could conclude they were only an acid-catalyzed solvolysis, the acid being released from the catalyst. Hydrogen is essential for the actual 10% Pd/C-catalyzed cleavage of TES ethers and THP ethers which must be stable under the true Pd/C-catalyzed hydrogenation conditions.     

Radiation from a Charge Supported in a Gravitational Field

We examine whether a charge supported statically in a gravitational field radiates, and find the answer to this question to be positive. Based on our earlier results we find that the important condition for the creation of radiation is the existence of a relative acceleration between the charge and its electric field, where such an acceleration causes the curving of the electric field and the creation of a stress force due to this curvature. This stress force is the reaction force, which creates the radiation. Later we find that this condition do exist for a charge supported statically in a gravitational field, where the electric field of the charge falls in the gravitational field, it curves, and the stress force raised in this curved field, creates electromagnetic radiation.