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Efficient approach for the detection and identification of new androgenic metabolites by applying SRM GC‐CI‐MS/MS: a methandienone case study
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Michael Polet Wim Van Gansbeke Peter Van Eenoo Koen Deventer 《Journal of mass spectrometry : JMS》2016,51(7):524-534
Identification of anabolic androgenic steroids (AAS) is a vital issue in doping control and toxicology, and searching for metabolites with longer detection times remains an important task. Recently, a gas chromatography chemical ionization triple quadrupole mass spectrometry (GC‐CI‐MS/MS) method was introduced, and CI, in comparison with electron ionization (EI), proved to be capable of increasing the sensitivity significantly. In addition, correlations between AAS structure and fragmentation behavior could be revealed. This enables the search for previously unknown but expected metabolites by selection of their predicted transitions. The combination of both factors allows the setup of an efficient approach to search for new metabolites. The approach uses selected reaction monitoring which is inherently more sensitive than full scan or precursor ion scan. Additionally, structural information obtained from the structure specific CI fragmentation pattern facilitates metabolite identification. The procedure was demonstrated by a methandienone case study. Its metabolites have been studied extensively in the past, and this allowed an adequate evaluation of the efficiency of the approach. Thirty three metabolites were detected, including all relevant previously discovered metabolites. In our study, the previously reported long‐term metabolite (18‐nor‐17β‐hydroxymethyl,17α‐methyl‐androst‐1,4,13‐trien‐3‐one) could be detected up to 26 days by using GC‐CI‐MS/MS. The study proves the validity of the approach to search for metabolites of new synthetic AAS and new long‐term metabolites of less studied AAS and illustrates the increase in sensitivity by using CI. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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支持矢量机(SVM)是一种新的统计学习方法,其学习原则是使结构风险最小,而非经典学习方法所遵循经验风险最小原则.这使得SVM具有更强的泛化能力.并且,由于SVM求解的是凸二次优化问题,使之能保证所找到的极值解就是全局最优解.本文首次将SVM算法用于乳腺X影像微钙化点自动检测中,对临床实际病例的试用结果表明,同目前常用的基于经验风险最小的人工神经网络(ANN)分类方法相比,SVM具有更高的识别率,值得应用推广. 相似文献
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虚拟化技术在电信灾难恢复计划中的应用研究 总被引:5,自引:3,他引:2
传统的灾难恢复技术由于成本昂贵、配置复杂以及可靠性不高等缺点,影响了电信在灾难恢复领域的发展.本文介绍了如何利用虚拟化技术来解决传统灾难恢复技术应用中的局限性,阐述了虚拟化技术灾难恢复的优势.同时,就虚拟化技术灾难恢复的方案选择、部署与执行展开论述.结合电信业务的开展情况,重点分析虚拟化技术在灾难恢复计划中的应用策略、要点,并给出了一些建议. 相似文献
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M. Herderich E. Richling R. Roscher C. Schneider W. Schwab H. -U. Humpf P. Schreier 《Chromatographia》1997,45(1):127-132
Summary The development of techniques utilizing atmospheric pressure ionization, namely atmospheric pressure chemical ionization (APCI)
and electrospray ionization (ESI), has pioneered the coupling of liquid chromatography (HPLC) with mass spectrometry in recent
years. Both ESI and APCI generate ions from polar and labile biomaterials with remarkable ease and efficiency. In particular,
the use of HPLC with tandem mass spectrometry (MS-MS) opens further dimensions in the field of bioorganic analysis. Thus,
HPLC-MS-MS provides the tools for direct elucidation of the structure and variety of polar natural compounds in complex matrices.
In order to develop efficient and straightforward strategies for the analysis of polar natural products, the potential and
the limitations of these hyphenated analytical techniques are discussed using heterocyclic aromatic amines, fumonisins, acylated
glycoconjugates and regioisomeric fatty acid hydroperoxides as examples.
Presented at the 21st ISC held in Stuttgart, Germany, 15th–20th September, 1996 相似文献
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In quantum information science, it is very important to solve the eigenvalue problem of the Gram matrix for quantum signals. This allows various quantities to be calculated, such as the error probability, mutual information, channel capacity, and the upper and lower bounds of the reliability function. Solving the eigenvalue problem also provides a matrix representation of quantum signals, which is useful for simulating quantum systems. In the case of symmetric signals, analytic solutions to the eigenvalue problem of the Gram matrix have been obtained, and efficient computations are possible. However, for asymmetric signals, there is no analytic solution and universal numerical algorithms that must be used, rendering the computations inefficient. Recently, we have shown that, for asymmetric signals such as amplitude-shift keying coherent-state signals, the Gram matrix eigenvalue problem can be simplified by exploiting its partial symmetry. In this paper, we clarify a method for simplifying the eigenvalue problem of the Gram matrix for quadrature amplitude modulation (QAM) signals, which are extremely important for applications in quantum communication and quantum ciphers. The results presented in this paper are applicable to ordinary QAM signals as well as modified QAM signals, which enhance the security of quantum cryptography. 相似文献
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In an earlier paper (Anal. Chim. Acta 514 (2004) 137) we claimed that the maximal extractability of a metal from soil or sediment for a user-defined extractant, i.e. the chemical availability in that particular extractant, may be biased as a result of inadequate volume to mass (V/m) ratios. Correcting for that artifact using an implementation of the simple linear isotherm model gave good results although we cautioned the general applicability. In this paper we will theoretically derive the limitations of that approach based on the more general assumption that sorption processes are described by a Langmuir isotherm.NIST reference material 8704 was extracted with 1 mol l−1 NaOAc (adjusted to pH 5) to experimentally verify the applicability of the Langmuir isotherm approach and illustrate the deviations obtained for some metals using the linear isotherm approach. Of the seven metals measured (Cr, Co, Ni, Cu, Zn, Cd, and Ba) only for Cr and Cu severe discrepancies between both approaches were found, which could be traced back to non-linear isotherm behaviour. Moreover, the Langmuir isotherm approach showed that the above mentioned extractability artifact is even more serious than earlier assumed applying the linear isotherm approach. 相似文献
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支撑向量机是一种基于统计学理论的新的学习算法,它采用了结构风险最小化原则,能有效地解决过学习问题,具有很强的泛化能力。传统支撑向量机针对两类分类问题,为了深入地分析实际应用中的大规模和多类别的问题,通过对一次性求解法、一对多、一对一、有向无环图方法的原理和实现方法进行分析,从速度和精度两方面对这些方法的优缺点进行了归纳和总结,并通过实验进行了验证和比较。实验结果表明,各种方法可以获得不同的分类器推广能力及训练速度和测试速度,也为今后如何更好地解决支撑向量机多类分类问题指明了方向。 相似文献
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本文提出了基于FPGA嵌入式系统控制开关磁阻电机(SRM)的控制方法,以微处理器软核MicroBlaze作为主控制器,以Xilinx公司提供的通用IP核设计出系统外围设备,用Verilog HDL硬件语言设计出专用的逻辑控制模块,经过CoreConnect片上总线通信链,实现了在一块FPGA芯片上完成了SRM的控制算法策略和外围接口逻辑电路,大大增加的系统的可靠性和性价比。最后以Xilinx公司SPARTAN3E系列的FPGA进行了设计,验证了设计的正确性和可行性。 相似文献