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94.
Guowang Chen 《偏微分方程(英文版)》2003,16(1):49-61
In the paper, the existence and uniqueness of the generalized global solution and the classical global solution of the initial boundary value problems for the nonlinear hyperbolic equation u_{tt} + k_1u_{xxxx} + k_2u_{xxxxt} + g(u_{xx})_{xx} = f(x, t) are proved by Galerkin method and the sufficient conditions of blow-up of solution in finite time are given. 相似文献
95.
Summary Modified nucleosides derived predominantly from transfer ribonucleic acid (tRNA) have been studied as possible tumor markers.
In this paper a reversed-phase high-performance liquid chromatographic (RP-HPLC) method has been applied to study 15 normal
and modified nucleosides in serum. The nucleoside levels in normal human serum were established, and the concentrations of
15 nucleosides in serum from 19 cancer patients were determined. It was found that the concentrations of modified nucleosides
were significantly higher in patient sera. Based on 15 nucleoside concentrations in serum, factor analysis could classify
correctly 90% of cancer patients from the normal humans. Further work showed that urine was slightly better than serum when
determining nucleosides as biological marker candidates. More work is ongoing to determine the clinical usefulness of modified
nucleosides as tumor markers. 相似文献
96.
茶叶中的化学成分是构成其风味特征的物质基础。本研究建立了基于气相色谱-质谱联用和液相色谱-质谱联用的非靶向代谢组学方法。完成预处理及分析条件优化后,使用标准样品考察方法的线性、回收率及重复性,结果表明方法整体稳定且结果可靠。将该方法用于绿茶、乌龙茶和红茶中化学成分的分析。通过超声辅助溶剂提取及气相色谱-质谱联用分析共获得1812个特征峰,而使用加热溶剂提取及液相色谱-质谱联用分析可获得2608个特征峰。结合保留规律及质谱数据库,共定性173种化合物(109种随后经标准样品验证),其中只有9种化合物在上述两类分析中被同时检出,表明方法互补性良好。3类茶叶数据的偏最小二乘判别分析结果表明,三者间存在显著差异。结合模型的变量重要因子(VIP)与非参数检验共筛选出90种化合物,其中包含儿茶素、氨基酸、糖、有机酸和黄酮苷类等众多与茶叶滋味密切相关的化学成分。 相似文献
97.
Metabolomics study of cured tobacco using liquid chromatography with mass spectrometry: Method development and its application in investigating the chemical differences of tobacco from three growing regions 总被引:1,自引:0,他引:1
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Lili Li Chunxia Zhao Yuwei Chang Xin Lu Junjie Zhang Yanni Zhao Jieyu Zhao Guowang Xu 《Journal of separation science》2014,37(9-10):1067-1074
Cured tobacco is an important plant material. Component studies are a big challenge for its significantly diverse chemical properties and vastly different concentrations. In this work, liquid chromatography with quadrupole time‐of‐flight mass spectrometry was used to perform a metabolomics study of cured tobacco owing to its efficient separation and detection of semipolar metabolites. A solvent of methanol/water (8:2, v/v) and 30 min of ultrasound time were found to be optimal to perform extraction. 95, 92, and 93% of metabolite features had within 20% of coefficient of variation for repeatability, intraday and interday precision analysis, respectively, indicating a good stability of the method developed. 113 metabolites were identified in cured tobacco based on accurate mass, retention time, and MS/MS fragments. The developed method was applied to a metabolomics study of cured tobacco from three growing regions. Forty three metabolites were found to be contributed to the classification. It is shown that the developed method can be applied to metabolomics analysis of plant materials. 相似文献
98.
In this paper, the asymptotic behavior of the solution to the initial–boundary value problem for a nonlinear evolution equation of fourth order is studied. The sufficient conditions for blow-up of the solutions to the initial–boundary value problems for Eq. (1) are given. 相似文献
equation(1)
utt−a1uxx−a2uxxt−a3uxxtt=φ(ux)x
99.
Simultaneous determination of non-volatile, semi-volatile, and volatile organic acids in tobacco by SIM-Scan mode GC-MS 总被引:1,自引:0,他引:1
A method for simultaneous determination of seven nonvolatile organic acids (NVOAs), five semivolatile organic acids (SVOAs), and twelve volatile organic acids (VOAs) in tobacco by synchronous SIM (Selected Ion Monitoring)-scan mode GC-MS was developed. The collection of NVOAs and SVOAs data was performed in full-scan mode, and that of VOAs data was carried out with SIM. Recoveries of NVOAs and SVOAs varied from 90.0 to 103.0%, and RSDs were less than 4.0%; recoveries of VOAs ranged from 89.5 to 99.3%, and their RSDs were less than 3.0%. Twelve tobacco samples were analyzed by the described method, and the results show that the method is applicable for the simultaneous determination of VOAs, NVOAs, and SVOAs in tobacco. 相似文献
100.
In the present study, we developed a novel online hydrophilic interaction chromatography (HILIC)-RPLC separation system for simultaneous separation of both hydrophilic and hydrophobic solutes in a complex sample with one injection. A HILIC Si column and a C18 column were hyphenated with an interface including two electronic 2-position valves, a solvent pump, and a solute transfer column. By using column-switching technique, the nonretained hydrophobic solutes were eluted out of the HILIC column and transferred into the C18 column to perform further separation. The hydrophilic solutes were separated on the HILIC column at the same time. One detector was equipped for each column to record the individual chromatograms. By separating a standard mixture and a traditional Chinese medicine (TCM) extract, the developed HILIC-RPLC system demonstrates its potential for "entire-components" separation of complex samples with improved peak capacity and throughput compared with the common single-column LC. 相似文献