A Pair of Dimeric Stilbene Epimers from Gnetum Montanum

GnetummontanumofgnetaceaisdistributedinsouthernChina.AsaChinesefOlkmedicine,itslianasareusedtotreatbronchitisandarthritis'.Previousinvestigationofthisspeciesledtotheisolationofsomealkaloidsanddibenzyletherde,i.ati.es2.lnourstudies,tenknowncomponentsincludingresveratrol,isohapontigenin,daucosterol,6-sitosterol,stearicacid,gnetifolinE,gnetol,isorhapontigenin-3-O-6-glucopyra(-)E-viniferinandgnetifolinCwereisolatedfromthesameresource.Atthesametime,apairoftraceepimerswereobtained.Thisisthefirste…     

三种群食物链交错扩散模型的整体

本文应用能量估计方法和Gagliardo-Nirenberg型不等式证明了一类强耦合反应扩散系统整体解的存在性和一致有界性，该系统是带自扩散和交错扩散项的三种群Lotka-Volterra食物链模型．通过构造Lyapunov函数给出了该模型正平衡点全局渐近稳定的充分条件．     

Controlled/living polymerization of 2‐(diethylamino)ethyl methacrylate and its block copolymer with tert‐butyl methacrylate by atom transfer radical polymerization

Polymerization of 2‐(diethylamino)ethyl methacrylate (DEAEMA) via homogeneous atom transfer radical polymerization under various reaction conditions is described. The effects of the initiators and solvents were examined. With 1,1,4,7,10,10‐hexamethyl triethylenetetramine/copper(I) chloride/p‐toluenesulfonyl chloride as the ligand/catalyst/initiator system in methanol, poly(DEAEMA) with a polydispersity index as low as 1.07 was synthesized. Kinetic studies demonstrated the polymerization was very well controlled and exhibited the living characteristic of the process. Well‐defined block copolymers of DEAEMA and tert‐butyl methacrylate (tBMA) were successfully synthesized. The copolymers could be synthesized with equally good results by starting with either p(DEAEMA) or p(tBMA) as the macroinitiators. However, only the macroinitiators terminated with chlorine should be used. The corresponding macroinitiators with bromine as a transferable group did not yield well‐defined copolymers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2688–2695, 2003     

On the existence of positive solutions for a class of singular boundary value problems

In this paper, by the use of a fixed point theorem, many new necessary and sufficient conditions for the existence of positive solutions in C[0,1]∩C¹[0,1]∩C²(0,1) or C[0,1]∩C²(0,1) are presented for singular superlinear and sublinear second-order boundary value problems. Singularities at t=0, t=1 will be discussed.     

Hydrogen indium vacancy complex VInH4 in n-type InP studied by positron-lifetime

Positron-lifetime experiments have been carried out on two undoped n-type liquid encapsulated Czochralski (LEC)-grown InP samples with different stoichiometric compositions in the temperature range 10-300 K. For temperatures below 120 K for P-rich InP and 100 K for In-rich InP, the positron average lifetime began to increase rapidly and then leveled off, which was associated with the charge state change of hydrogen indium vacancy complexes from (V_InH₄)⁺ to (V_InH₄)⁰. This phenomenon was more obvious in P-rich samples that have a higher concentration of V_InH₄. The transformation temperature of approximately 120 K suggests that the complex V_InH₄ is a donor defect and that the ionization energy is about 0.01 eV. The ionization of neutral V_InH₄ accounted for the decrease of the positron average lifetime when the sample was illuminated with a photon energy of 1.32 eV at 70 K. These results provide evidence for hydrogen complex defects in undoped LEC InP.     

管理系统的最经济控制问题

依据最经济控制问题的概念及其对无确定性数学模型系统分析存在的局限性，对现代管理系统最经济控制问题，提出了在满足系统基本要求前提下。实现控制功能及品质与控制成本比最佳或最划算的模型定义，并对管理系统的可靠性、ABC管理法、WSR方法论等方面的可靠性成本、运行成本和最佳收益等最经济控制问题进行了研究．     

核内核子－核子非弹散射截面（Ⅰ）

在与平均场、核内核子－核子弹性散射截面以及输运方程相统一的理论框架内推导了核内核子－核子非弹散射截面的解析表达式．其数值结果能很好地重现自由非弹截面的实验值，所计算的有效非弹截面与Ｄｉｒａｃ－Ｂｒｕｅｃｋｎｅｒ的计算结果相一致．     

非公有制经济参与西部大开发若干问题的研究

我国经济发展机制的重要变化是非公有制经济迅速成长壮大,并以其特有的活力与生机成为经济发展的新的增长空间。注重和加强非公有制经济参与西部大开发的问题研究,对促进以国有经济为主导的西部地区经济高速发展,具有重要的理论意义和实际意义,并能为政府关于区域和西部开发的发展战略提供参考依据。     

A Mössbauer spectroscopic study of an industrial catalyst for dehydrogenation of etylbenzene to styrene

Iron oxide catalyst with spinel structure used for dehydrogenation of ethylbenzene is one kind of important catalyst in petrochemical industry. In this work several series of industrial catalyst were prepared with different components and different manufacturing processes. Mössbauer Spectroscopy has been used to determine the optimal components and the better manufacturing process for spinel structure formation. The results may prove useful for producing the industrial dehydrogenation catalyst with better catalytic property.     

中国入世对政府的影响及政府应对问题

中国成功入世后，各行各业和各市场主体都面临新的机遇和挑战，以及自我适应和应对的问题。相对而言，政府受到的影响是首要的、最为全面而深远的，政府率先入世既十分必要又相当紧迫。政府要实现真正意义上的入世，关键是要转变公务员队伍观念，提高公务员队伍的整体综合素质，转变政府职能，转变行政方式，实现依法行政。