一般n阶特征量泛函的Euler-Lagrange方程及与定量因果原理、相对性原理和广义牛顿三定律的统一

本文获得了有各种相互作用的一般n阶特征量泛函,其耦合系数反映了不同特征量泛函之间的耦合强度.依据定量因果原理,导出了一般n阶特征量泛函的变分原理,获得了一般n阶特征量泛函的Euler-Lagrange方程,它的不同系数可拟合不同的物理现实,如从线性到任意n阶非线性物理系统,使复杂难解的任意n阶非线性物理系统变得具体可解.并获得了该对称变换下不变的m个的守恒量,以及它们之间的关系和统一描述.依据定量因果原理导出了相对性原理,证明了绝对加速参考系、牵连参考系和相对参考系的力都有来自加速度和质量变化的贡献.利用定量因果原理自然导出了广义牛顿第一定律和广义牛顿第二定律,而且还导出了一个新定律,即广义牛顿第三定律,亦即平移不变性系统合力为零定理.进而将研究结论应用于对银河系的修正引力势、分子势、夸克禁闭势等,且其结果与物理实验一致.     

On relative stability of linear stationary feedback control systems with time delay

A method is presented whereby the absolute and relative stabilityof linear control systems containing transport lag can be determined.As a result feedback systems with variable time delay and loopgain, may be investigated in straightforward manner.     

Quantitative evaluation of chromatographic analysis of complex mixtures by establishing limits of determination

A method is presented for the calculation of limits of determination in the chromatography of complex samples. This limit, DLS^w_e, is defined as the minimum concentration (μg g^?1) of the compound in the original sample that should be present in an extract taken at random from a well-defined set of extracts, so as to give a probability w that the result will have a relative error smaller than e. The interference caused by other components of the samples is taken into account. This limit of determination was calculated for the determination of quercetin and caffeic acid in European plant extracts by reversed-phase h.p.l.c. with u.v./visible detection. These determination limits were calculated as a function of the detector wavelength (250–400 nm) with a minicomputer. One of the main parameters used in these calcualtions for optimizing wavelengths of measurement in the chromatography of complex mixtures is a peak density function for the whole chromatogram.     

Convection/diffusion- and diffusion-controlled rapid-scan voltammetry in liquid chromatographic systems with a large-volume wall-jet detector

On-line voltammetric measurements under liquid chromatographic (LC) conditions yield voltammograms which are either purely diffusion- or purely convection/diffusion-controlled, or a combination of both. The dependence of this behaviour on flow-rate, scan-rate and electrode diameter is investigated for a large-volume wall-jet detector. It is shown that for 4 V s^?1 scan-rates at 1 ml min^?1 flow-rates (conventional LC conditions), S-shaped (convection/diffusion-controlled) voltammograms can be obtained with macro-electrodes (? 1 mm diameter). Distortion of voltammogram shape by the cell time constant is discussed for macro-electrodes. The behaviour of the cell in microbore and micro-LC applications is demonstrated. The advantage of being able to change from convection/diffusion-controlled to diffusion-controlled behaviour is discussed.     

Determination of electroinactive organic acids with LC and amperometric detection, using a PPy coated electrode

This paper reports on the amperometric detection of electroinactive sulfonic acids, organic acids and phosphate esters subsequent to chromatographic separation. The working electrode consisted of a 3 mm diameter glassy carbon electrode, coated with electrochemically deposited polypyrrole. The electrode was placed in a large volume wall jet cell, and a potential of +750 mV versus SCE was applied. The electroinactive analytes were detected as they induce a current, which originates from their effect on the doping of the polypyrrole coating. This allows sensitive detection of electrochemically inactive organic acids. Detection limits for sulfonic acids in LC with 4.6-mm ID columns (1 ml min(-1) flow rate) were 3 ng. The electrode had a linear response in the 1x10(-6) to 1x10(-3) M concentration range. The response time of the electrode was 3.6 s in a FIA set up. Peak heights are quasi independent on the flow rate, indicating that the phenomenon is not controlled by mass transfer in the diffusion layer. The electrode activity decreases to 50% after 24 h of continuous use. The electrode can be partly reactivated after application of a potential of -300 mV (versus SCE) for 1 h.     

Potentiometric detection of organic acids in liquid chromatography using conducting oligomer electrodes

A conducting oligomer electrode was used for the potentiometric detection of organic acids in reversed phase liquid chromatography (LC). The conducting material consisted of a mixture of a phenylene vinylene trimer with a polycarbonate host polymer and iodine. A glassy carbon electrode was coated with this material by evaporation from a chloroform solution. A theoretical model was given to describe the observed potentiometric responses. The analysis conditions were optimized to obtain both efficient separations, and sensitive potentiometric responses. Detection limits in the nanogram level were attained when a 1 mM phosphoric acid solution was used as the eluent, which were comparable to the values obtained with low-wavelength UV detection. Calibration curves showed a logarithmic dependence on an injected amount for amounts higher than 5 nmol, and a linear dependence for injected amounts below this value. The response times of the electrode were smaller than 1 s at typical LC flow-rates. The reproducibility for consecutive injections was 5%.     

Observation of quantum coherence in mesoscopic molecular magnets

By applying a transverse magnetic field B( perpendicular) of sufficient strength to the uniaxial molecular magnets Fe8 and Mn12, the tunneling splitting Delta(t) of their S = +/-10 magnetic ground states can be made large compared to perturbations such as hyperfine and dipolar interactions. We present evidence for such a Delta(t) from magnetic specific heat data below 1 K that is consistent with coherent quantum mechanical tunneling in a "mesoscopic" system under such conditions.