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81.
Carbon K‐edge X‐ray spectroscopy has been applied to the study of a wide range of organic samples, from polymers and coals to interstellar dust particles. Identification of carbonaceous materials within these samples is accomplished by the pattern of resonances in the 280–320 eV energy region. Carbonate minerals are often encountered in the study of natural samples, and have been identified by a distinctive resonance at 290.3 eV. Here C K‐edge and Ca L‐edge spectra from a range of carbonate minerals are presented. Although all carbonates exhibit a sharp 290 eV resonance, both the precise position of this resonance and the positions of other resonances vary among minerals. The relative strengths of the different carbonate resonances also vary with crystal orientation to the linearly polarized X‐ray beam. Intriguingly, several carbonate minerals also exhibit a strong 288.6 eV resonance, consistent with the position of a carbonyl resonance rather than carbonate. Calcite and aragonite, although indistinguishable spectrally at the C K‐edge, exhibited significantly different spectra at the Ca L‐edge. The distinctive spectral fingerprints of carbonates provide an identification tool, allowing for the examination of such processes as carbon sequestration in minerals, Mn substitution in marine calcium carbonates (dolomitization) and serpentinization of basalts. 相似文献
82.
Bhagwat PrasadAmit Garg Hardik TakwaniSaranjit Singh 《Trends in analytical chemistry : TRAC》2011,30(2):360-387
Metabolite identification (Met ID) is important during the early stages of drug discovery and development, as the metabolic products may be pharmacologically active or toxic in nature. Liquid chromatography-mass spectrometry (LC-MS) has a towering role in metabolism research.This review discusses current approaches and recent advances in using LC-MS for Met ID. We critically assess and compare various mass spectrometers, highlighting their strengths and limitations. Citing appropriate examples, we cover recent LC and ion sources, isotopic-pattern matching, hydrogen/deuterium-exchange MS, data dependent analyses, MSE, mass defect filter, 2D and 3D approaches for the elucidation of molecular formula, polarity switching, and background-subtraction and noise-reduction algorithms. A flow chart outlines a comprehensive strategy for Met ID, including a focus on reactive metabolites. 相似文献
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Danilo Di Genova Daniele Morgavi Kai‐Uwe Hess Daniel R. Neuville Nikita Borovkov Diego Perugini Donald B. Dingwell 《Journal of Raman spectroscopy : JRS》2015,46(12):1235-1244
The effect of chemical composition on the Raman spectra of a series of natural calcalkaline silicate glasses has been quantified by performing electron microprobe analyses and obtaining Raman spectra on glassy filaments (~450 µm) derived from a magma mingling experiment. The results provide a robust compositionally‐dependent database for the Raman spectra of natural silicate glasses along the calcalkaline series. An empirical model based on both the acquired Raman spectra and an ideal mixing equation between calcalkaline basaltic and rhyolitic end‐members is constructed enabling the estimation of the chemical composition and degree of polymerization of silicate glasses using Raman spectra. The model is relatively insensitive to acquisition conditions and has been validated using the MPI‐DING geochemical standard glasses 1 as well as further samples. The methods and model developed here offer several advantages compared with other analytical and spectroscopic methods such as infrared spectroscopy, X‐ray fluorescence spectroscopy, electron and ion microprobe analyses, inasmuch as Raman spectroscopy can be performed with a high spatial resolution (1 µm2) without the need for any sample preparation as a nondestructive technique. This study represents an advance in efforts to provide the first database of Raman spectra for natural silicate glasses and yields a new approach for the treatment of Raman spectra, which allows us to extract approximate information about the chemical composition of natural silicate glasses using Raman spectroscopy. We anticipate its application in handheld in situ terrestrial field studies of silicate glasses under extreme conditions (e.g. extraterrestrial and submarine environments). © 2015 The Authors Journal of Raman Spectroscopy Published by John Wiley & Sons Ltd 相似文献
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Probing the Anticancer Mechanism of (−)‐Ainsliatrimer A through Diverted Total Synthesis and Bioorthogonal Ligation 下载免费PDF全文
Dr. Chao Li Ting Dong Qiang Li Prof. Dr. Xiaoguang Lei 《Angewandte Chemie (International ed. in English)》2014,53(45):12111-12115
Herein, we report an efficient approach for exploring the novel anticancer mechanism of (?)‐ainsliatrimer A, a structurally complex and unique trimeric sesquiterpenoid, through a combined strategy of diverted total synthesis (DTS) and bioorthogonal ligation (TQ ligation), which allowed us to visualize the subcellular localization of this natural product in live cells. Further biochemical studies facilitated by pretarget imaging revealed that PPARγ, a nucleus receptor, was a functional cellular target of ainsliatrimer A. We also confirmed that the anticancer activity of ainsliatrimer A was caused by the activation of PPARγ. 相似文献
87.
Ultra‐performance liquid chromatography coupled with electrospray ionization/quadrupole time‐of‐flight mass spectrometry for the rapid analysis of constituents in the traditional Chinese medical formula Danggui San 下载免费PDF全文
In this work, ultra‐performance LC with ESI quadrupole TOF‐MS (UPLC–ESI‐Q‐TOF‐MS) and automated MetaboLynx analysis was used to rapidly separate and identify the chemical constituents of Danggui San, a traditional Chinese medical formula. The analysis was performed on a Waters UPLC BEH C18 column using a gradient elution system. A hyphenated ESI and Q‐TOF analyzer was used for the determination of the accurate mass of the protonated or deprotonated molecule and fragment ions in both positive and negative modes. Based on retention times, accurate mass, and the mass spectrometric fragmentation characteristics, a total of 47 compounds distributed over the chemical groups of phthalides, flavonoids, monoterpene glycosides, sesquiterpenoids, phenolics, and alkaloids, were simultaneously separated within 18 min and identified or tentatively elucidated in Danggui San for the first time. UPLC–ESI‐Q‐TOF‐MS analysis revealed the complexity of the chemical composition of this formula. The method developed is rapid, accurate, reliable, and highly sensitive to characterize the chemical constituents of Danggui San. 相似文献
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协同知识创新是企业降低创新成本,提高创新能力的重要手段.由于企业知识创新具有高度的不确定性和不可预测性,因此,有效地利用企业协同优势,有针对性地降低协同知识创新的风险,是协同知识创新活动得以顺利开展的重要条件.影响协同知识创新的内外因素有很多,利用粗糙集理论对这些因素进行简约,消除冗余因素,得到在协同知识创新中的核心因素;确定约简集因素权重,判断协同知识创新的风险程度,为协同知识创新的决策提供依据. 相似文献
90.
基于语言评价信息的知识资本要素识别方法 总被引:1,自引:0,他引:1
知识资本是组织创造价值和获取竞争优势的关键资源, 其要素通常具有复杂的关联性, 如何识别知识资本的核心要素、原因要素和结果要素,对于组织进行知识资本管理具有重要意义.本文在构建了知识资本要素识别体系的基础上,借鉴决策试验和评价实验室报告的思想提出了一种基于语言评价信息的知识资本要素识别方法,通过处理和集结专家针对知识资本要素关联给出的语言评价信息,对知识资本要素进行排序与归类.最后通过一个实例分析说明了该方法的应用, 并说明了如何根据识别结果制定相应的策略以便进行知识资本的投资和控制. 相似文献