Segmented HPGe平面型位置灵敏探测器阵列的γ成像分析；Gamma-ray imaging analysis by using array of segmented planar HPGe detectors

探测器位置分辨能力的高低是实现γ成像的一个重要指标.Segmented HPGe平面型位置灵敏探测器能够很好地给出γ射线与探测器晶体相互作用的作用点位置信息.利用由这种探测器组成的探测器阵列对~(22)Na标准源进行了γ成像实验.结果能够区分出标准源两个不同的摆放位置的细微差别,并与实际情况符合得很好.从而检验了Segmented HPGe平面型位置灵敏探测器的位置分辨能力.

Synthesis of novel ferrocenylphosphine-amidine ligands with central and planar chirality and their diastereomeric effect in Pd-catalyzed asymmetric allylic alkylation

Some novel ferrocenylphosphine-amidine ligands with central and planar chirality were prepared from (R,S-p)-PPFNH2-R 3 and its diastereomer (S,S-p)-PPFNH2 3a. The efficiency and diastereomeric impact of these ferrocenylphosphine-amidine ligands in the palladium-catalyzed asymmetric allylic substitution was examined, and up to 96% e.e. with 98% yield was achieved by the use of ligand (R,S-p)-4a with a methyl group in the amidino moiety. The results also indicated that (R)-central chirality and (S-p)-planar chirality in these ferrocenylphosphine-amidine ligands were matched for the palladium-catalyzed asymmetric allylic alkylation. (C) 2003 Elsevier Ltd. All rights reserved.

Synthesis of novel P-ketimine bidentate ferrocenyl ligands with central and planar chirality and comparsion in the catalytic activity between P-ketimine and P-aldimine

A series of novel ferrocenylphosphine-ketimine ligands 6 were prepared by reaction of (R,S-p)-PPFNH2-R or (S,S-p)-PPFNH2 with a variety of m-substituted acetophenones. A different catalytic activity was observed between ferrocenylphosphine-ketimine ligands and corresponding aldimine ligands. The efficiency and diastereomeric impact of these ferrocenylphosphine-ketimine ligands in Pd-catalyzed asymmetric allylic alkylation were first investigated, and higher enantioselectivity of over 98% e.e. with 95% yield was obtained by the use of ferrocenylphosphine-ketimine ligands. However, in Rh-catalyzed asymmetric hydrosilylation of aryl ketones, only 42% e.e. was obtained by the use of ferrocenylphosphine-ketimine ligands compared to 90% e.e. with the use of aldimine ligands. (C) 2003 Elsevier Ltd. All rights reserved.

Weak epitaxy growth and phase behavior of planar phthalocyanines on p-sexiphenyl monolayer film

We systematically investigated the weak epitaxy growth (WEG) behavior of a series of planar phthalocyanine compounds (MPc), i.e., metal-free phthalocyanine (H2PC), nickel phthalocyanine (NiPc), copper phthalocyanine (CuPc), zinc phthalocyanine (ZnPc), iron phthalocyanine (FePc); cobalt phthalocyanine (CoPc), grown on a p-sexiphenyl (p-6P) monolayer film by selected area electron diffraction (SAED) and atomic force microscopy (AFM). Two types of epitaxial relations, named as incommensurate epitaxy and commensurate epitaxy, were identified between phthalocyanine compounds and the substrate of the p-6P film.

Thiacalix[4]arene-Supported Planar Ln(4) (Ln = Tb-III, Dy-III) Clusters: Toward Luminescent and Magnetic Bifunctional Materials

This paper reports the syntheses, crystal structures, and luminescent and magnetic properties of four tetranuclear Tb-III (1 and 3) and Dy-III (2 and 4) complexes supported by p-phenylthiacalix[4]arene (H(4)PTC4A) and p-tert-butylthiacalix-[4]arene (H(4)TC4A). All four frameworks can be formulated as [Ln(4)(III)(PTC4A/TC4A)(2)(mu(4)-OH)Cl-3(CH3OH)(2)(H2O)(3)], and some methanol and water solvent molecules are occupied in the interstices. The compounds are featured with a sandwichlike unit constructed by two tail-to-tail calixarene molecules and a planar tetragonal (mu(4)-OH)Ln(4) cluster. The photoluminescent analyses suggest that there is an efficient ligand-to-Ln(III) energy transfer for compounds 1-3 and H(4)PTC4A is a more efficient "antenna" than H(4)TC4A.

Electrochemical preparation of silver nanostructure on the planar surface for application in metal-enhanced fluorescence

We introduce a fast and simple method, named the potentiostatic electrodeposition technique, to deposit metal particles on the planar surface for application in metal-enhanced fluorescence. The as-prepared metallic surfaces were comprised of silver nanostructures and displayed a relatively homogeneous morphology. Atomic force microscopy and UV-visible absorption spectroscopy were used to characterize the growth process of the silver nanostructures on the indium tin oxide (ITO) surfaces. A typical 20-fold enhancement in the intensity of a nearby fluorophore, [Ru(bpy)(3)](2+), could be achieved on the silvered surfaces. In addition, the photostability of [Ru(bpy)(3)](2+) was found to be greatly increased due to the modification of the radiative decay rate of the fluorophore. It is expected that this electrochemical approach to fabricating nanostructured metallic surfaces can be further utilized in enhanced fluorescence-based applications.

Investigation on the Voltammetric Behaviors in Planar Bilayer Lipid Membranes

In the TCNQ-modified BLM, the voltammetric response is different due to the different methods used to prepare the membrane forming solution. The direct and indirect dissolved methods result in irreversible and reversible responses respectively. These results can be explained by the different styles of the orientation of TCNQ in the membrane. The reversible response is controlled by the diffusion of electroactive species in the interior of the membrane. When MB is used to modify the BLM, very complex voltammograms are obtained. The intersection of the voltammetric curves can be regarded to be owing to the appearance of new phase in the membrane caused by MB. But it disappears at lower scan rate. Peak current increases with decreasing scan rate. This indicates that the resistance of the membrane at lower scan rate is lower than that at higher scan rate. Asymmetric curve of MB incorporated BLM is ascribed to the different rates of redox reaction at the two membrane/solution interfaces.

THEORY OF STEADY-STATE CURRENT AT MULTIPLE MICROCYLINDER ELECTRODES COUPLED WITH A PARALLEL PLANAR ELECTRODE

A novel device of multiple cylinder microelectrodes coupled with a parallel planar electrode was proposed. The feedback diffusion current at this device was studied using bilinear transformation of coordinates in the diffusion space, where lines of mass flux and equiconcentration are represented by orthogonal circular functions. The derived expression for the steady-state current shows that as the gap between cylindrical microelectrodes and planar electrode diminishes, greatly enhanced currents can be obtained with high signal-to-noise ratio. Other important geometrical parameters such as distance between adjacent microcylinders, cylinder radius, and number of microcylinders were also discussed in detail.

一种7DOF冗余手臂构形的运动学与动力学特性研究

冗余度机构具有高度的灵活性和避障能力,利用冗余自由度可以改善仿人机器人手臂的运动性能。以实现人体手臂的运动特性和操作灵活性为目标,研制了一种7DOF冗余仿人机器人手臂,根据冗余手臂的机构学特点,研究了手臂的运动学和动力学性能,并在工作空间、肘部关节的自运动能力以及手臂自重引起的关节重力矩等方面与其它两种典型的冗余手臂构形进行了比较分析。

基于超冗余度机械臂动力学的时间最优轨迹规划

基于超冗余度机械臂的动力学方程 ,提出了一种超冗余度机械臂同时受速度和力矩约束的时间最优轨迹规划方法 .它首先采用 B样条曲线拟合无碰撞离散路径 ,得到由伪位移参数 s表示的超冗余度机械臂连续、光滑运动路径 ,然后对动力学方程和约束方程进行数学变换 ,得到由 s表示的动力学方程和约束方程 ,最后以 s和伪速度 s· 分别作为动态规划的阶段变量和状态变量 ,对超冗余度机械臂进行时间最优轨迹规划 .仿真结果表明 ,所给出的时间最优轨迹规划算法是正确的 ,所采取的解决方法是可行的