Investigation of capillary micro-packed columns composed of two segments packed with a sorbent of different particle size

Summary For the first time gas chromatographic characteristics of fused-silica capillary micro-packed columns consisting of two segments (i.e., serial columns) and packed with two different particle size fractions of the same sorbent have been investigated. The height equivalent to a theoretical plate (HETP) and the specific separation number vs. carrier gas velocity dependence has been studied. The expediency of empolying serial columns in which the segment containing the finer sorbent fraction is located near the column outlet has been theoretically and practically expalined. Serial columns with such an arrangement of the two segments show a better performance from the view point of efficiency and mass transfer coefficient.     

串口数据丢帧引起的雷达测试故障原因分析

为解决某雷达高度表试验过程中发生的动作高度测试异常故障,采用故障树分析法对雷达高度表和测试设备进行故障排查。经检测发现,测试设备上位机的串口通信卡接收下位机的数据中有几十帧数据帧出现CRC校验位错误,被应用程序丢弃。原因是下位机发出的数据信号存在一定程度的畸变,上位机串口通信卡的串口控制器芯片OX16PCI694适应性不足导致数据读取出错。而应用程序在健壮性设计上也存在缺陷,以数据帧数来计算时间及雷达动作高度,但丢弃数据帧时未作相应处理。采用兼容性好的串口控制器芯片16C554重新设计通信卡,在上位机与下位机通信协议中增加数据的帧序号。经试验验证故障定位正确,解决措施有效。     

《六合丛谈》传播的近代化学及其述评

《六合丛谈》(1857-1858年)是近代上海第1份综合性中文杂志,对近代科学的传播具有重要影响。在《六合丛谈》中,“化学”一词首见于正式出版物,并传入日本。对《六合丛谈》中涉及的化学内容包括“化学”名词、元素种类、化学反应、金属提取、物质组成、质量守恒等进行研究,阐明其传播“化学”的意义及作用。     

Serial dependence in ARCH-models as measured by tail dependence coefficients

Serial dependence in non-linear time series cannot always be reliably quantified using linear autocorrelation. We do a detailed study of serial dependence in an ARCH(1) process from the point of view of the lower tail dependence coefficient and certain generalisations thereof. Our results are relevant for estimating probabilities of consecutive value-at-risk violations in GARCH models.      

Serial displacement chromatofocusing and its applications in multidimensional chromatography and gel electrophoresis: II. Experimental results

Part I of this study investigated the theory and basic characteristics of “serial displacement chromatofocusing” (SDC). In Part II of this study, SDC is applied to two prototype applications which have potential uses in proteomics and related areas involving the analysis of complex analyte mixtures. In the first application, SDC was used as a prefractionation method prior to two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) to separate a human prostate cancer cell lysate. It was observed that the resolution achieved in narrow-pI-range 2D-PAGE was improved when using SDC prefractionation, so that SDC may be useful as a low-cost, high-speed, and highly scalable alternative to electrophoretic prefractionation methods for 2D-PAGE. The second application involves the use of SDC as the first dimension, and reversed-phase chromatography as the second dimension, to produce a novel, fully automated, two-dimensional high-performance liquid chromatography technique. The method was shown to have performance advantages over one-dimensional reversed-phase chromatography for peptide separations.     

Serial displacement chromatofocusing and its applications in multidimensional chromatography and gel electrophoresis: I. Theory and general considerations

The technique of “serial displacement chromatofocusing” (SDC) is investigated both theoretically and experimentally with model mixtures of proteins and peptides. The method employs a multistep, retained pH gradient formed using adsorbed buffering species to produce a series of discrete effluent fractions. Each of these fractions may contain several displaced protein bands under conditions of sufficient mass overloading, so that several displacement trains of adjoined bands can be produced in a single chromatographic run. Numerical simulations and experimental results showed selective concentration effects for minor components in a fraction when the feed amount was sufficient large. A computer-aided design method was developed to facilitate the use of the method and was applied to both anion- and cation-exchange column packings. Good agreement was achieved between the designed pH gradients and experimental results. The characteristics of SDC were also explored in terms of its loading capacity, scalability, repeatability, recovery, and differentiation of proteins between their true and apparent isoelectric point values.     

A note on the serial dictatorship with project closures

In this paper, we consider the problem of assigning agents having preferences to projects with capacities and lower quotas. For this problem, Monte and Tumennasan proposed a strategy-proof and Pareto efficient mechanism, called the serial dictatorship with project closures. In this paper, we show that the serial dictatorship with project closures can be extended to a more general setting.     

Temporal variations of serial correlations of trading volume in the US stock market

Serial correlations in the trading volume of the US stock market are investigated in this paper. The use of the detrended fluctuation analysis implemented within a rolling window indicated that, for the period 1929–2011, the strength of correlations exhibits important temporal variations with a trend shift by the 1990s, and 4-year and 21-year cycles. These empirical findings are compared to those obtained for mature international stock markets (FTSE-100 and Nikkei) and discussed in terms of potential economic and financial implications.     

Quadratic forms in skew normal variates

In this paper first a characterization of the multivariate skew normal distribution is given. Then the joint moment generating functions of two quadratic forms, and a linear compound and a quadratic form in skew normal variates, have been derived and conditions for their independence are given. Distribution of the ratios of quadratic forms in skew normal variates has also been studied.