Weak solutions for a hyperbolic system with unilateral constraint and mass loss

We consider isentropic gas dynamics equations with unilateral constraint on the density and mass loss. The γ and pressureless pressure laws are considered. We propose an entropy weak formulation of the system that incorporates the constraint and Lagrange multiplier, for which we prove weak stability and existence of solutions. The nonzero pressure model is approximated by a kinetic BGK relaxation model, while the pressureless model is approximated by a sticky-blocks dynamics with mass loss.     

Spectroscopic Studies of 1-Aryl-2,2-Dichlorocyclopropanes

Seventeen 1-aryl-2,2-dichlorocyclopropanes were examined by using IR, ¹³C NMR, and mass spectrometry. The data obtained from IR and ¹³C NMR spectra indicate that the bond strength of carbon-chlorine on the cyclopropane ring and the electron density of that carbon depend on the substituent. The mass fragmentation patterns of compounds in this series resemble those of the dibromo analogues. The fragmentation mechanism is proposed to involve the formation of indenium ion through an electrocyclization.     

Policies for biodefense revisited: The prioritized vaccination process for smallpox

Handling bioterror events that involve contagious agents is a major concern for authorities and a cause for debate among policymakers about the best response policy. At the core of this debate stands the question which of the two post-event policies to adopt: mass vaccination or trace (also called ring or targeted) vaccination. We present a new dynamic epidemic-intervention model that captures key features of the situation and generalizes some previous assumptions regarding the probability distributions of inter-temporal parameters. It is shown that a mixture of mass and trace vaccination policies—the prioritized vaccination policy—is more effective than either of the two aforementioned policies.     

负关联噪声驱动下单模激光的定态分析

研究了负关联的加法和乘法高斯白噪声驱动下单模激光损失模型的定态情况。文中推导了负关联情况下，定态时的激光场幅的几率分布，光强的平均值，光强的协方差以及光强的偏斜率。并和文献〔１，２〕中正关联时的定态分析作了比较，发现了有意义的新现象。     

Identification of chlorinated sulfur compounds in pulp mill effluents by GC-MS and GC-AED

Summary Three chlorinated dimethyl sulfones and five chlorinated thiophenes have been identified in the alkaline extraction liquor from a bleach plant by gas chromatography with atomic emission detection (GC-AED) and with mass spectrometry (GC-MS). The information on elemental content obtained by GC-AED enabled a rapid screening of the sulfur compounds and provided important structural information complementary to the mass spectral data. Quantitation was accomplished by GC-AED based on universal calibration.     

线圈型全光纤偏振器的研究

本文采用等效电流法对线圈型全光纤偏振器进行了分析计算.对应于保偏光纤中两正交传输基模的消光比,提出了一种分析保偏光纤弯曲损耗的新方法,这种方法基于将保偏光纤两个不同偏振模式分别等效为两个普通圆光纤的基模,等效参数通过测量不同偏振模式的模场半径来确定.实验证明这种理论计算方法与实验结果一致.最终,我们研制出的线圈型光纤偏振器在1.31μm工作波长下,实测消光比达30dB以上,工作偏振模式插入损耗≤3dB.     

On sequential procedures for the point estimation of the mean of a normal population

The sequential procedures developed by Starr (1966, Ann. Math. Statist., 37, 1173–1185) for estimating the mean of a normal population are further analyzed. Asymptotic properties of the regret and first two moments of the stopping rules are studied and second-order approximations are derived.     

血液净化用吸附剂脱附过程的数学模型研究

对已吸附了低密度脂蛋白（ＬＤＬ）及极低密度脂蛋白（ＶＬＤＬ）达到饱和程度的吸附柱，用１ｍｏｌ／Ｌ的生理盐水进行脱附，采用修正Ｌａｎｇｍｕｉｒ吸附式建立了连续脱附过程的数学模型，计算结果与实验测定值吻合，表明该数学模型适用于描述类似于ＬＤＬ及ＶＬＤＬ这类蛋白质大分子的脱附过程。     

Accuracy and long-term reproducibility of lead isotopic measurements by multiple-collector inductively coupled plasma mass spectrometry using an external method for correction of mass discrimination

The precision of isotopic measurements of Pb by thermal ionization mass spectrometry (TIMS) is limited by the fact that this element does not possess an invariant isotope ratio that can be used for the correction of mass fractionation by internal normalization. Multiple-collector inductively coupled plasma mass spectrometry (MC-ICPMS) can overcome this limitation, because with plasma ionization, elements with overlapping mass ranges are thought to display identical mass discrimination. With respect to Pb, this can be exploited by the addition of Tl to the sample solutions; the mass discrimination factor obtained for Tl can then be used for the correction of the measured Pb isotope ratios. In this article we present the results of a detailed study that investigates the accuracy and precision of such an external correction technique for mass discrimination based upon the results of multiple analyses of a mixed standard solution of NIST SRM-981 Pb and SRM-997 Tl. Our data indicate that normalization of the Pb isotope ratios to the certified isotopic composition of SRM-997 Tl produces Pb isotopic results that are significantly lower than recently published reference values by TIMS. This systematic offset can be eliminated by renormalization of the Pb data to a different Tl isotopic composition to obtain an empirically determined mass discrimination factor for Pb that generates accurate results. It is furthermore shown that a linear law is least suited for the correction of mass discrimination, whereas a power or exponential law function provide significantly more accurate and precise results. In detail, it appears that a power law may provide the most appropriate correction procedure, because the corrected Pb isotope ratios display less residual correlations with mass discrimination compared to the exponentially corrected data. Using an exponential or power law correction our results, obtained over a period of over seven months, display a precision (2σ) of better than 60 parts per million (ppm) for ²⁰⁸Pb/²⁰⁶Pb and ²⁰⁷Pb/²⁰⁶Pb and of better than 350 ppm for ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb/²⁰⁴Pb, and ²⁰⁸Pb/²⁰⁴Pb. This represents a significant improvement compared to conventional TIMS techniques and demonstrates the potential of MC-ICPMS for routine, high-precision measurements of Pb isotopic compositions.     

Multiphoton-Ionization-Mass Spectrometry (MUPI-MS) [New Analytical Methods (34)]

Mass spectrometry is one of the most important analytical tools in chemistry, biology, medicine and related areas. During the past 30 years, methods have been developed, both for the qualitative as well as the quantitative analysis of a wide variety of substances. The introduction of lasers into chemistry has also profited mass spectrometry, since its nonlinear properties and its tunability open up fundamentally new frontiers. Multiphoton ionization mass spectrometry combines UV-spectroscopy and mass spectrometry, thus providing a two-dimensional method that enables substance-specific and even state-specific analyses. This progress report presents the fundamentals and possibilities of MUPI mass spectrometry and discusses investigations on amino acids, peptides, chlorophylls and sugars. For each substance, multiphoton ionization can be tuned in such a way that only the molecular ion is formed. An increase of laser intensity induces substance-specific fragmentations of the molecule, thus contributing to a quick and easy identification of the substance.