(+)-安五脂素的分离与结构(英文)

从长梗南五味子中分得一种木脂素新化合物——(+)-安五脂素(1),它在体外对 H~+,K~+-ATP 酶和 P-388细胞有明显抑制作用;对人血清中的 HBsAg 也有弱抑制作用。经与绝对构型已知物(3)对照,证明1的结构为(2R,3S)-1-(3,4-次甲二氧苯基)-2,3-二甲基-4-(4-羟基-3-甲氧苯基)-丁烷。     

Efficient laser performance of Nd:YAG at 946 nm and intracavity frequency doubling with LiJO3, β-BaB2O4, and LiB3O5

3 , β-BaB₂O₄, and LiB₃O₅ yielded a maximum output power of 550 mW at 473 nm with β-BaB₂O₄ as the nonlinear crystal. Received: 15 September 1997     

Nafion~/TiO_2复合膜的质子传导性能研究

0引言Nafion○膜是质子交换膜燃料电池和直接甲醇燃料电池的首选电解质膜。该膜若要成功地应用于燃料电池,还需要解决2个关键问题:降低甲醇渗透率和提高Nafion○膜在高温的质子传导能力(即保水能力)。目前主要靠在Nafion○膜的球状胶束中加入亲水性的无机纳米粒子解决这个问题[1￣9]。无机粒子的加入不仅可以有效地阻隔甲醇分子,而且因其亲水性可增加Nafion○膜在较高温度下的保水能力,使得Nafion○膜在较高温度仍可保持良好的质子导电性。以TiO2作为无机掺杂剂改善Nafion○膜的性能研究已有报道。Watanabe和Uchida等人[2,8]利用Pt的催…     

Fast parallel solvers for symmetric boundary element domain decomposition equations

Summary. The boundary element method (BEM) is of advantage in many applications including far-field computations in magnetostatics and solid mechanics as well as accurate computations of singularities. Since the numerical approximation is essentially reduced to the boundary of the domain under consideration, the mesh generation and handling is simpler than, for example, in a finite element discretization of the domain. In this paper, we discuss fast solution techniques for the linear systems of equations obtained by the BEM (BE-equations) utilizing the non-overlapping domain decomposition (DD). We study parallel algorithms for solving large scale Galerkin BE–equations approximating linear potential problems in plane, bounded domains with piecewise homogeneous material properties. We give an elementary spectral equivalence analysis of the BEM Schur complement that provides the tool for constructing and analysing appropriate preconditioners. Finally, we present numerical results obtained on a massively parallel machine using up to 128 processors, and we sketch further applications to elasticity problems and to the coupling of the finite element method (FEM) with the boundary element method. As shown theoretically and confirmed by the numerical experiments, the methods are of algebraic complexity and of high parallel efficiency, where denotes the usual discretization parameter. Received August 28, 1996 / Revised version received March 10, 1997     

Global identifiability for an inverse problem for the Schrödinger equation in a magnetic field

Partially supported by NSF Grant DMS-9123742     

Revetements du groupe des quantomorphismes de l'oscillateur harmonique

Using Souriau's diffeological structures, we define covering spaces for any diffeomorphisms group. We give an explicit construction of these covering spaces for the cases Diff ($\text{R}$ⁿ) and Quant ($\text{R}$²ⁿ.     

Some formulations coupling finite element and integral equation methods for Helmholtz equation and electromagnetism

Summary. In this paper a study of the coupling between integral equations and finite element methods is presented for two problems of propagation in frequency domain. It is shown that these problems can be viewed as multidomain problems and treated by the mean of the Schur complement technique. The complement coming from the integral equation part is expressed with the integral operators of the scattering theory. This allows to predict the behaviour of the Schur method, either primal or dual, as far as its convergence speed is concerned. Furthermore, the difference of behaviour between electromagnetism and acoustics from this point of view is explained. Received October 21, 1993 / Revised version received February 28, 1994     

On theK-theory of the classifying space of a discrete group

Partially supported by an NSF grant     

Spectral properties of threshold functions

We examine the spectra of boolean functions obtained as the sign of a real polynomial of degreed. A tight lower bound on various norms of the lowerd levels of the function's Fourier transform is established. The result is applied to derive best possible lower bounds on the influences of variables on linear threshold functions. Some conjectures are posed concerning upper and lower bounds on influences of variables in higher order threshold functions.Supported by an Eshkol fellowship, administered by the National Council for Research and Development—Israel Ministry of Science and Development.     

Balancing extensions via Brunn-Minkowski

We give a simple proof, based on the Brunn-Minkowski Theorem, of Theorem. Inany finite poset P not a total order there are elementsx, y such that