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A complex sedimentary sample from the Monterey Formation (CA, USA) has been submitted to GC-MS analysis followed by mass spectral deconvolution using Automated Mass Spectral Deconvolution and Identification System (AMDIS). Adjusting the parameters of the software allowed for the extraction of the spectrum of an unusual steroidal hydrocarbon coeluting with the major compound of the chromatogram. Following a careful interpretation of the "extracted" mass spectrum, the structure of the unknown has been postulated to be the 4,14-dimethylcholestane (DMC). Possible origins of this rare steroid are briefly discussed. Thus, application of AMDIS appears to be particularly suitable for the GC-MS analysis of natural complex mixtures characterized by a high number of analytes present in low amounts. 相似文献
154.
Let (M,g) be an n-dimensional Riemannian manifold and T2M be its secondorder tangent bundle equipped with a lift metric (g).In this paper,first,the authors construct some Riemannian almost product structures on (T2M,(g)) and present some results concerning these structures.Then,they investigate the curvature properties of (T2M,(g)).Finally,they study the properties of two metric connections with nonvanishing torsion on (T2 M,(g)):The H-lift of the Levi-Civita connection of g to T2 M,and the product conjugate connection defined by the Levi-Civita connection of (g) and an almost product structure. 相似文献
155.
对三种岩石在不同的应力下进行了蠕变实验,对蠕变实验曲线用粘弹模型进行了模型参数的反演,结果认为标准线性体、伯格斯和对数模型都是实验曲线的很好近似.为了进一步了解蠕变实验时间对模型参数的影响,研究了蠕变模型的预测功能.将实验蠕变曲线分成二部分,第一部分用于模型参数的反演,第二部分用于模型预测数据的检验.时间外延所得的模型的预测曲线都明显偏离了实测曲线,伯格斯和对数模型的预测曲线比实测曲线偏高,而标准线性体模型则偏低.根据不同时间的蠕变实验数据的比较和分析,认为实验时间对蠕变模型参数的反演有较为明显的影响,但只要对标准线性体模型作适当修正,引入与时间尺度有关的函数C(t),则该模型的预测能力就有较大的提高. 相似文献
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157.
In this study, proton total reaction cross sections have been investigated for some isotopes such as 12C, 27Al, 9Be, 16O, 181Ta, 197Au, 6Li, and 14N by a proton beam up to 600 MeV. Calculation of the proton total cross sections has been carried out by the analytic expression
formulated by M.A. Alvi by using Coulomb-modified Glauber theory with the Helm model nuclear form factor. The obtained results
have been discussed and compared with the available experimental data and found to be in agreement with each other. 相似文献
158.
Jingjing Chang Maria Vega Caamares Metin Aydin Wilfried Vetter Manfred Schreiner Weiqing Xu John R. Lombardi 《Journal of Raman spectroscopy : JRS》2009,40(11):1557-1563
The normal Raman and surface‐enhanced Raman scattering (SERS) spectra of flavanthrone and indanthrone were obtained at several excitation wavelengths. The spectral assignments were aided by density functional calculations. Since both molecules have very high symmetry (C2h) including a center of inversion, we expect that the modes of u symmetry will be forbidden in the normal Raman spectrum. However, proximity to the surface causes special SERS enhancement of several of the bu modes, along with somewhat weaker enhancement of the au and bg modes. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
159.
A liquid-phase microextraction method for the determination of trihalomethanes (THMs) including chloroform (CHCl3), bromodichloromethane (CHBrCl2), dibromochloromethane (CHBr2Cl) and bromoform (CHBr3) in water samples was developed, with analysis by gas chromatography-electron capture detection (GC-ECD). After the determination of the most suitable solvent and stirring rate for the extraction, several other parameters (solvent drop volume, extraction time and ionic strength of the sample) were optimized using a factorial design to obtain the most relevant variables. The optimized extraction conditions for 5 mL of sample volume in a 10 mL vial were as follows: n-hexane an organic solvent; a solvent drop volume of 2 μL; an extraction time of 5.0 min; a stirring rate of 600 rpm at 25 °C; sample ionic strength of 3 M sodium chloride. The linear range was 1-75 μg L−1 for the studied THMs. The limits of detection (LODs) ranged from 0.23 μg L−1 (for CHBr2Cl) to 0.45 μg L−1 (for CHCl3). Recoveries of THMs from fortified distilled water were over 70% for a fortification level of 15 μg L−1, and relative standard deviations of the recoveries were below 5%. Real samples collected from tap water and well water were successfully analyzed using the proposed method. The recovery of spiked water samples was from 73% to 78% with relative standard deviations below 7%. 相似文献
160.
Let M be an n-dimensional differentiable manifold with an affine connection without torsion and T_1~1(M) its(1, 1)-tensor bundle. In this paper, the authors define a new affine connection on T_1~1(M) called the intermediate lift connection, which lies somewhere between the complete lift connection and horizontal lift connection. Properties of this intermediate lift connection are studied. Finally, they consider an affine connection induced from this intermediate lift connection on a cross-section σ_ξ(M) of T_1~1(M) defined by a(1, 1)-tensor field ξ and present some of its properties. 相似文献