Studies of Coprostanol (5β-Cholestan-3β-ol) in Environmental Samples by Tandem Mass Spectrometry

Cholesterol, coprostanol, dihydrocholesterol, and epicoprostanol are the principal fecal sterols found in animal feces. Coprostanol, a sterol formed exclusively in the gut of man and higher mammals, has been recognized as a good indicator of pollution of water resources by sewage discharges. Because of structural similarities, complete resolution of chromatographic peaks presents a difficult task, especially for coprostanol and its epimers. In this paper, separation of coprostanol and epicoprostanol after conversion to their corresponding trimethylsilyl derivatives is described. Confirmation of the identity of coprostanol is achieved by tandem mass spectrometry. Interfering compounds can be eliminated by virtue of their different retention times or their mass spectra.     

Soft X-ray bands of highly ionized tungsten,gold and lead emitted by the TEXT tokamak plasma

Spectra of highly ionized tungsten, gold and lead emitted from the TEXT tokamak have been recorded in the 20–70 Å range by means of a grazing incidence, time-resolving spectrograph. The narrow and bright emission bands centered around 40, 45 and 50 Å in Pb, Au and W respectively, and bands of lesser intensities at lower wavelenghts, are emitted by a very large number of superimposed lines originating from transitions of the type 4d¹⁰4fⁿ−4d⁹4fⁿ⁺¹, 4d¹⁰4fⁿ−4d⁹4fⁿ5p and 4fⁿ−4fⁿ⁻¹5l (l=d, g). The isoelectronic analysis shows that at the electron temperatures prevailing in the present experiment, T_e≈800 eV, there are no contributions to the bands from ions having a 4p⁶4dⁿ ground state. This, together with the experimental measurement of the electron temperature profile, indicates that the heavy ion impurity distribution in the tokamak plasma is very close to ionization equilibrium.     

Evaluation du fe3+ dans les spinelles pour l'obtention de la fugacité d'oxygène des nodules ultrabasiques

The analysis by electron microprobe allows the evaluation of the quantity of Fe³⁺ in spinels with considerable errors. The use of a correction equation which is based on a the calibration of analyses with an electron microprobe in relation to those carried out with Mössbauer spectroscopy gives more precise evaluations of Fe³⁺. In fact, it allows a calculation of the oxygen fugacity in peridotitic xenoliths. The obtained results show that peridotites of the French Central Massif crystallised under oxygen fugacities which were higher than those of the Moroccan AntiAtlas.     

黄土边坡剥落病害的发育特征及其发育程度评价

黄土边坡剥落病害影响黄土边坡的坡面稳定及环保美观。以黄延高速公路黄土路堑边坡剥落病害为背景,采用现场调查结合理论分析的方法,研究了黄土边坡剥落病害的发育特征; 将发育特征与可拓工程方法相结合,实现了黄土边坡剥落病害发育程度的评价。研究结果表明:(1)黄土中节理裂隙分布密度大于6条 ·m^-1 时,极易发生剥落,小于2条 ·m^-1 时,基本不发生剥落。黏粒含量大于15%时,剥落病害越易发生,小于5%时,不易发生剥落。黄土边坡开挖量越大、剥落产生的厚度越大。黄土边坡坡体节理裂隙促使剥落病害的发生。当黄土边坡单级坡高大于10m、坡度大于60°时,容易出现重力型剥落病害; 而单极坡高小于4m、坡度小于50°时,边坡坡面很少出现剥落病害。(2)针对影响黄土边坡剥落病害发育因素的复杂性和模糊性,重视实践中的经验,将可拓工程方法与黄土边坡剥落发育程度评价相结合,提出了黄土边坡剥落发育程度的物元关联函数及物元关联度的计算方法。建立了适合可拓学理论的黄土边坡剥落发育程度的分类标准,实现了定性与定量评价结合。     

因子分析在X射线荧光光谱重叠谱峰识别中的应用

用渐进因子分析（ＥＦＡ）方法处理合金样品的Ｘ射线荧光扫描谱数据,按照数学原理选取扫描步长,根据ＸＲＦ特性选择合适的训练集建立数学模型,可以准确判断谱峰重叠,该方法在合理取点和组分含量相当的情况下有良好的识别能力。     

Infrared remote sensing of planetary atmospheres

Infrared remote sensing is a powerful tool for studying the chemical composition and the thermal structure of planetary atmospheres. Infrared spectra, in particular, are used to derive molecular abundances and to infer elemental and isotopic ratios, which allow to constrain theoretical models of the formation and early evolution of the solar system, as well as the history of planetary atmospheres. Infrared imaging and spectroscopy have been performed from the ground but also from space planetary missions (Mariner 9 on Mars, Voyager on the giant planets, Galileo on Jupiter), and from the ISO Earth-orbiting infrared satellite. In the forthcoming decade, the Cassini mission will explore the Saturn system. Planetary exploration from Earth orbit will be performed by the FIRST and NGST space observatories.     

Crystal structure of Pb3O2(OH)Br,a Br-analogue of damaraite

The crystal structure of Pb₃O₂(OH)Br (orthorhombic, Pmc2₁, a=5.8447(8), b=7.0715(10), c=15.309(2) Å, V=632.75(15) Å³) has been solved by direct methods and refined to R₁=0.046 (wR=0.077). The structure is based on [O₂Pb₃] chains of edge-sharing OPb₄ oxocentered tetrahedra that extend parallel to the a axis and occur in two orientations inclined to each other by ∼50°. The [O₂Pb₃] chains are linked through OH(3) groups to form an [Pb₃O₂](OH) sheet that is parallel to (010). Additional OH(4) groups are attached to the [O₂Pb₃] chains. The OH groups form two short (OH)Pb bonds that results in (OH)Pb₂ dimers.     

Application of Alternative K-Nearest Neighbor method to Classification of Alloy Samples

Pattern Recognition is one of main methods that can resolve structure of chemistry and classification of compounds. In chemistry, K-Nearest Neighbor method (KNN) is mostly used for recognition of compounds that are not classified by a linear method. ALKNN (Alternative KNN) is an improvement of KNN. The method is based on the classification rules which are produced by using standards and knowledge. The unknown samples are,then, classified with the aid of the rules.