波段三维ESR成像系统的研制（Ⅴ）——灵敏度与分辨率实验及系统总性能指标

实验确定了自行研制的L波段三维电子自旋共振成像（3D-ESRI）系统的检测灵敏度及成像分辨率指标. 用Tempo水溶液模型测量灵敏度结果表明： 样品体积为10 mm, 高30 mm，测量浓度1×10^-4 mol/L水溶液的信噪比为S/N=4∶1；加梯度磁场后，样品浓度需>5×10^-4 mol/L，样品体积为19 mm, 高30 mm时，获得的投影谱的信噪比可满足图像重建的需要. 用DPPH固体样品确定的成像分辨率结果<1 mm. 文中还对ESRI系统的
各项总体性能做了归纳总结.     

非均匀网格时域伪谱算法在超宽带技术中的应用

 与传统时域有限差分算法相比，采用以伪谱方法离散Maxwell微分方程为基础的时域伪谱(PSTD)算法计算大的电尺度电磁场时域问题，将大大提高计算效率，降低内存需求。为了拓宽PSTD算法的应用，近年来，基于网格插值方法的非均匀时域伪谱算法得到了发展。研究的重点是算法中非均匀网格技术的实现及其在时域瞬态脉冲电磁场模拟和高功率超宽带脉冲技术方面的应用。以高斯脉冲为激励源，用该算法计算了多层介质的反射和透射，并通过超宽带脉冲穿墙实验对这一方法的应用进行了验证。模拟和实验结果具有较好的一致性。     

含氮类金刚石薄膜的紫外辐照研究

 用射频等离子体方法在玻璃基底上制备的类金刚石（DLC）薄膜，采用离子注入法掺氮，并对掺氮DLC薄膜紫外（UV）辐照前后的性能变化进行了研究。研究结果表明：随氮离子注入剂量及UV辐照时间的增加，位于2 930cm^-1附近的SP ³C-H吸收峰明显变小，而位于1 580cm^-1附近的SP2C-H吸收峰则明显增强，薄膜的电阻率明显呈下降趋势；随UV辐照时间的增加，位于1 078cm^-1附近的Si-O-Si键数量及位于786cm^-1附近的Si-C键数量明显增加。即氮离子注入和UV辐照明显改变了DLC薄膜的结构与特性。     

一种新的永久周期磁铁聚焦的高功率宽带放大器

 提出了一种新的高功率宽带放大器，它由速调管和自由电子脉塞组成，用永久周期磁铁聚焦。研究了这种器件的电子束聚焦、群聚和辐射。在速调管提供一阶调制系数为30%，波导管的半径1.51cm，摇摆器的磁场振幅0.16T，周期7.92cm，电子束的电压490kV，电流50A和半径0.368cm的条件下，预估这种器件的辐射波频率为11.4GHz，输出辐射功率为18MW，输出辐射带宽为44%。     

PURIFICATION OF L-METHIONINE AND N-ACETYL-D-METHIONINE FROM THE MIXTURE OF ENZYMATICALLY DEACYLATED N-ACETYL-DL-METHIONINE

1. INTRODUCTION Methionine, namely 2-amido-4-thiomethyl butyric acid with a structure of CH3SCH2CH2CHCOOH, is one of the essential amino acids and has two natural enantionmers, D and L-methionine. The mixture of L- and D-isomers can be used as analeptics or nutritive additives to maintain the equilibrium of amino acids of feed [1,2]. L-methionine can release active methyl and accelerate the synthesis of choline, which further speeds up the conversion of the lipid accumulated in liv…     

InCl3·4H2O Promoted Green Preparation of Xanthenedione Derivatives in Ionic Liquids

Xanthenediones derivatives have attracted considerable interests in recent times because they constitute a structural unit in a number of natural products1 and have been used as versatile synthons due to the inherent reactivity of the inbuilt pyran ring2. The conventional syntheses of xanthenediones were acid or base catalyzed condensation of appropriate active methylene carbonyl compounds with aldehydes3. However, many of these procedures involved longer reaction times,low yields and side reactions of aldehydes. In recent years, room temperature ionic liquids (RTILs) have been used as novel green reaction media4. Considering that InCl3 is an efficient Lewis acid catalyst used in promoting many organic reactions, especially in several condensation processes, we herein wish to report a very simple and green method for the preparation of poly-hydrogenated xanthenediones through InCl3·4H2O promoted cascade reaction of aldehydes and 5,5-dimethyl-l,3-cyclohexanedione in ionic liquid,1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]). The preparative process presented here is operationally simple, environmentally benign and has the advantage of enhanced atom utilization. Furthermore, the solvent and the catalyst used can be recovered easily and reused efficiently.     

Synthesis of New 13-O-Acylavermectin Bl Aglycones

Six new 13-O-acylavermectin Bl aglycones(3-8) were synthesized from avermectin B1 aglycone and their bioactivities were evaluated against Spodoptera exigua, Spodoptera eridania, Tetranychus urticae and Aphis fabae.     

Optimization of Mass Transfer Processes in the Zone of the Air Electrode of a Fuel Cell with a Solid Polymer Electrolyte

A two-dimensional mathematical model for the transport of reactants in a fuel cell with a solid polymer electrolyte is developed. The model is used for analyzing spatial distributions of the concentration of reactants and current density over the cell. The effect of the catalytic-layer activity, reactant speed, bipolar-plate geometry, thickness and porosity of current collector and/or gas-diffusion sublayer, and the reaction mixture composition on the fuel cell efficiency is estimated theoretically and experimentally.     

On the Existence of Solutions to Vector Quasivariational Inequalities and Quasicomplementarity Problems with Applications Break to Traffic Network Equilibria

For vector quasivariational inequalities involving multifunctions in topological vector spaces, an existence result is obtained without a monotonicity assumption and with a convergence assumption weaker than semicontinuity. A new type of quasivariational inequality is proposed. Applications to quasicomplementarity problems and traffic network equilibria are considered. In particular, definitions of weak and strong Wardrop equilibria are introduced for the case of multivalued cost functions.     

Elliptic and parabolic problems in unbounded domains

We consider elliptic and parabolic problems in unbounded domains. We give general existence and regularity results in Besov spaces and semi‐explicit representation formulas via operator‐valued fundamental solutions which turn out to be a powerful tool to derive a series of qualitative results about the solutions. We give a sample of possible applications including asymptotic behavior in the large, singular perturbations, exact boundary conditions on artificial boundaries and validity of maximum principles. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)