Carbon Fiber-gold/mercury Dual-electrode Detection for Capillary Electrophoresis

Capillary electrophoresis (CE) has become a useful and powerful separation technique and has many applications. Electrochemical detection (ED) has been shown to be one of the most sensitive detection techniques available for use in CE. Dual-electrode detection can expand the applicability of CE-ED1-5, the materials such as gold/mercury1,3, carbon fiber2, Pt4 and Au3,5 have been used for the two electrodes in dual-electrodes. As is well known, the electrochemical response of different c…     

Novel Reaction of Nitroxide with Hantzsch Dihydropyridines

Nitroxides have been found to be the intermediate in the in vivo metabolism of hydroxamic acid, a well-known biological molecule1. Structural modification of some antitumor drugs by introducing nitroxides can lower toxicity remarkably with retention or even increase of the antitumor activity2. Furthermore, the use of nitroxides as spin probes makes it possible to get information regarding the microenvironment of the reaction. 4-Substituted Hantzsch 1,4-dihydropyridines (DHP) are analogs …     

Determination of Amino Acids in Single Human Lymphocytes after On-capillary Derivatization by Capillary Zone Electrophoresis with Electrochemical Detection

Sensitive and selective methods for the detection of amino acids (AAs) in single cells are of increasing importance. Capillary zone electrophoresis (CZE) with electrochemical detection (ED) is suitable for analysis of electroactive contents in single cells. However, most native AAs have no electroactivity. Derivatization with an electroactive tag is an attractive method. An on-capillary derivatization scheme was reported1. Naphtha- lene-2, 3-dicarboxaldehyde (NDA) can react with pri…     

First Total Synthesis of an Analogue of (±)-Hypargenin B

Hypargenin B, a diterpene with the abietane skeleton, was isolated by Ayhan from the root of an endemic species salvia hypargenia and showed antibacterial activity1. In this diterpene, the junction of A/B ring is trans. In order to provide for studying further the relationship between the structure and bioactivities, we develop a novel route whereby the hypargenin B methyl ether 22 could be obtained in good yield. To our knowledge no total synthetic work has been reported on the title com…     

Preliminary Study on Pyrolysis of Polymethylsilsesquioxane by FT—IR and XPS

The term polysilsesquioxanes in this paper refers to all structures with the empiri-cal formulas (RSiO3/2)n where R is hydrogen or any alkyl, alkylene, aryl, arylene, or organo-functional derivatives of alkyl, alkylene, or aryl. Polymethylsilsesquioxane (PMSQ) is characterized by its low weight loss at high temperatures. X-ray photoelectron spectroscopy (XPS) characterization of PMSQ was unavailable from reported literatures. In this study, the pyrolysis was carried out in an inert at…     

Biotransformation of 14-Deacetoxy-13-oxo sinenxan A by Ginkgo Cell Cultures

Sinenxan A, 2a, 5a, 10b,14b-tetraacetoxy-4(20),11-taxadiene, is a taxoid isolated from the callus cultures of Taxus spp. in high yield (ca. 1~2% of dry weight)1,2. The rich resources and its taxane-skeleton vest it valuable potential for the semisynthesis of paclitaxel or other structurally related bioactive compounds, such as 搒econd -generation?taxoid anticancer agents and taxane-based multidrug resistant anticancer agents3-5. Many remarkable studies on its structural modification by chemi…     

Diastereoselective α-Alkylation of β-Amino Esters: Preparation of Novel α-Substituted β-Amino Esters from α-Amino Acids

b-Amino acids and their derivatives have attracted considerable attention in recent years due to their occurrence in biologically active natural products, such as dolastatins 11, cyclohexylnorstatine 22 and taxol 33. bAmino acids also find application in the synthesis of blactams4, piperidines5, indolizidines6. Moreover, the peptides consisting of bamino acids, the so called bpeptides, have been extensively studied recently7. Consequently, considerable efforts have been directed to the synt…     

基于分数阶可停振动系统的周期未知微弱信号检测方法

本文建立了分数阶可停振动系统, 其可停振动状态的改变对周期策动力敏感, 对零均值随机微小扰动不敏感, 这事实上为周期未知微弱信号检测提供了一种新的高效检测方法和判别标准. 与现有的利用混沌系统的大尺度周期状态变化检测周期未知弱信号的方法 需逐一尝试设置不同频率内置信号以便期望与待检周期信号发生共振不同, 利用分数阶可停振动系统的可停振动状态变化检测周期未知微弱信号的方法, 除了同样具有因为状态变化对周期信号的敏感性而能够实现极低检测门限的特点外, 还具有混沌系统信号检测所不具有的优点: 1)无需预先估计待检信号的周期; 2)无需计算系统状态的临界阈值; 3)可停振动状态可由本文设计的指数波动函数可靠地进行判断; 4)通过系统微分阶数的变化, 将检测系统层次化, 从而可得到比整数阶检测系统更低的检测门限, 特别是在色噪声环境下, 通过选取合适的微分阶数, 基于分数阶可停振动系统的微弱周期信号检测法能够大幅度的降低检测门限, 在本文的仿真试验中, 检测门限可达-182 dB. 关键词： 分数阶非线性系统 Duffing振子 弱信号检测     

A Quasi-Interpolation Satisfying Quadratic Polynomial Reproduction with Radial Basis Functions

In this paper,a new quasi-interpolation with radial basis functions which satis- fies quadratic polynomial reproduction is constructed on the infinite set of equally spaced data.A new basis function is constructed by making convolution integral with a constructed spline and a given radial basis function.In particular,for twicely differ- entiable function the proposed method provides better approximation and also takes care of derivatives approximation.     

基于微球透镜的任选区高分辨光学显微成像新方法研究

提出和发展了基于毛细管-微球组合探针的任选区、 高分辨显微成像新方法. 建立了微球显微成像的物理模型, 利用成像理论,推导出微球成像的放大倍率; 采用3.0, 4.4, 5.6, 7.5, 10.0 μm等不同直径的SiO₂微球, 对未经刻录的DVD光盘进行了微球显微成像实验, 可以观察到DVD光盘的微纳米结构被明显放大且对比度显著提高, 与理论计算结果相符合; 采用毛细管微探针操纵微球的方法, 实现了基于微球透镜阵列的样品微纳米结构的高分辨显微成像; 在此基础上, 进一步将毛细管微探针与微球组合, 制备出毛细管-微球组合型探针, 首次实现了基于微球透镜的样品任意区域高分辨显微成像.