Determination of Inhalational Anesthetics in Field and Laboratory by SPME GC/MS

Exposure to inhalational anesthetics in health care workers could lead to several diseases and disorders. This study examined the applicability of solid phase microextraction for sampling and quantification of three inhalational anesthetics including; halothane, isoflurane, and sevoflurane in operating room air. Carboxen-Polydimethylsiloxane in retracted mode was selected and the effects of environmental parameters including temperature, humidity, and air velocity, were studied. There were no significant differences between sampling rates determined at different temperatures and air velocities. On the opposite, relative humidity has a significant effect on sampling rates. Comparison of the results between the developed SPME method and OSHA 103 method on standard test atmosphere and field showed satisfactory agreement.     

Practical capillary gas chromatography—a systematic approach

Capillary gc is now rapidly expanding. Naturally, initiation is most often attempted on the basis of the experience acquired with packed columns. However, such an extrapolation is successful only if a number of essential peculiarities of capillary gc are considered. Based on practical examples this paper discusses six essential details: 1) design and maintenance of the gas flow paths, 2) the greatly increased importance of sampling technique, which should not be confined just to stream splitting, 3) the problems in quantitative analysis arising from small sample size, 4) specific sources of trouble related to small amounts of liquid phase, 5) specific arguments for the choice of the carrier gas, clearly pointing to hydrogen as the ideal carrier and, 6) the different way to approach column production. Figures for all selected examples are given.     

Preconcentration of samples in sandwich tanks for continuous thin-layer chromatography

It is demonstrated that horizontai sandwich tank with two cover plates can be used to preconcentrate sample solutions. Narrow sharply-defined starting zones are obtained just outside the smaller cover plate when the series of spots of the sample solution are applied on the thin layer and predeveloped with a volatile solvent. After evaporation of the solvent, the whole area of the TLC-plate is covered with two plates and developed with a suitable solvent.     

Head space gas chromatography with glass capillaries using an automatic electropneumatic dosing system

Head space GC using a special electropneumatic sampling system works well in combination with glass capillaries. Because a homogenous gas mixture is already present most problems inherent with inlet splitters are thus avoided. In cases where the high vapor pressure of the sample can cause problems with the pressure controlled sampling system, the use of narrow bore glass capillaries provides the necessary inlet pressure. The use of this powerful and convenient analytical tool for water pollution analysis, flavour analysis and the analysis of volatiles in crude oil samples is shown by examples.     

变长度弹性伸缩腿双足机器人动力学与控制

研究了半被动双足机器人的平面稳定行走的控制问题．基于弹簧质点模型，采用拉格朗日方法分别得到双足机器人单支撑阶段与双支撑阶段的动力学方程，对机器人系统的动力学方程求得周期解．应用非线性系统状态反馈线性化理论，在双足机器人的单支撑阶段和双支撑阶段中，通过控制双足机器人的腿长度，实现稳定的周期行走．在理论分析的基础上，对控制算法进行了仿真与研究．结果表明：在周期行走过程中，文中采用的变长度控制算法可以使双足机器人克服外界的干扰，并具有较强的抗干扰性．     

中国普通野生稻线粒体DNA的限制性片段长度多态性

用BamHI／H454、BamHI／pQT2-7-1、EcoRI／B376和EcoRI／pQT12四种酶／探针组合对85份普通野生稻、亚洲栽培稻和橹稻进行了线粒体DNA的限制性片段长度多态性的分析．共检测到16条多态性带，15种表型，组合成14种线粒体DNA变异类型．其中抽稻和粳稻的线粒体DNA已分化，培稻偏粳型，大部分普通野生稻属（或偏）拉型，但江西的东乡普通野生稻类型比较独特．中国普遍野生稻的线粒体DNA与地理分布相关，湖南的江永、茶陵和江西的东乡等不同的群体以地理位置相聚，随地理梯度遗传分化由少到多．     

基于有序抽样样本的参数的极大似然估计的性质

有序抽样是一种新的抽样方法 ,与简单随机抽样方法相比它具有很多很好的性质 .本文讨论了在有序抽样样本下的参数的极大似然估计的性质 .     

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??A single distribution-free (nonparametric) Phase II exponentially weighted moving average (EWMA) chart based on the Cucconi statistic, referred to as the EWMA-Cucconi (EC) chart, is considered here for simultaneously monitoring shifts in the unknown location and scale parameters of a univariate continuous process. A comparison with some other existing nonparametric EWMA charts is presented in terms of the average, the standard deviation and some percentiles of the run length distribution. Numerical results based on Monte Carlo analysis show that the EC chart provides quite a satisfactory performance. The effect of the Phase I (reference) sample size on the IC performance of the EC chart is studied in detail. The application of the EC chart is illustrated by two real data examples.     

Influence of electronic excitations on the thermodynamics of small carbon clusters: the example of C3 +

We illustrate the influence of the thermalization of electrons on the linear-cyclic isomerization of small carbon clusters by model Monte Carlo calculations of C₃ ⁺ at 3500 K. It is shown that the inclusion of the electronic degrees of freedom, in such systems with several low-lying excited states, can significantly change the relative isomer populations and energy distributions, as compared with equivalent electronic ground-state simulations.     

Embedding atom-jellium model for metal surface

To describe metal surfaces efficiently and accurately, an embedding atom-jellium model is proposed. Within density functional theory, we consider a multiscale scheme that combines jellium and atomistic approaches. We use the former to model layers deep inside a metal surface to reduce the computational cost and the later to maintain the accuracy required for chemical bonding. Work functions of Al(111) and Cu(111) surfaces are studied using this model with comparisons to all-atom and pure jellium models. The much closer results of the embedding atom-jellium model to the all-atom results than to the pure jellium results show a good prospect for our approach in large-scale density functional calculations.