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71.
72.
The cutoff frequency f_(max) of radiation from earthquakes is one of the important parameters for studying the source process. By theoretical analysis and numerical experiments on acceleration Fourier spectrum it is suggested that f_(max) mainly depends on the lower values of slip rise time. This result can be used to explain the observational fact that the greater the earthquake magnitude, the smaller the value of f_(max). 相似文献
73.
Anna B. DenisovaVyacheslav Ya. Sosnovskikh Wim Dehaen Suzanne ToppetLuc Van Meervelt Vasiliy A. Bakulev 《Journal of fluorine chemistry》2002,115(2):183-192
Reaction of 2-hydrazinothiazoles 1 with 1-thienyl- and 1-furyl-1,3-butanediones 2a,b in methanol in the presence of hydrochloric acid mainly leads to a mixture of pyrazoles 3 and pyrazolines 4 or pyrazoles 3 and 5 in strong acidic conditions. Isomeric hydrazones 6 and pyrazolines 4 were formed and isolated in these reactions in the absence of hydrochloric acid. It has been shown that the regioselectivity in the reaction of diketones 2 with hydrazine 1 is governed by both the concentration of acid and the nature of substituents in the 1,3-diketones 2. Cyclization of hydrazones 6 is shown to occur under milder conditions than dehydration for pyrazolines 4. The new heterocyclic compounds were prepared and fully characterized by NMR spectra and by X-ray analysis for 3c. 相似文献
74.
75.
One hundred and forty-seven species of spores and pollen referred to 77 genera found in the crudeoil samples taken from four petroliferous provinces of the Tarim Basin of Xinjiang Provincehave been studied in this paper. By means of these spore and pollen fossils, the geological ages anddistribution of the petroleum source rocks of the basin are judged. Also, the principles and methodsto judge the petroleum source of a petroleum province by spore/pollen and other microfossils in crudeoils are explained. 相似文献
76.
在仔细研辉光放电光源工作过程的基础上,在国内首先设计、制成了HGZ-Ⅱ型自动辉光放电光源。该光源除换样品外,实现了抽空、进气、对光、预燃、曝光、充气、复位等摄谱全过程的自动控制。有水压、真空度、短路保护措施和醒铃线路。设计合理,性能良好,操作简便,工作安全,可靠。程控部分的编排包括顺序控制。时序控制和条件控制。由于使用了通用执行元、器件,降低了成本,提高了耐用性。为满足表层,逐层分析的需要,还专门设计了计数电路。供电源实现了高压直流供电和脉冲供电。该光源可应用于合金中主成分和少量杂质分析及金属、合金表层,逐层成分分析。 相似文献
77.
J. Canosa 《The Journal of chemical thermodynamics》2003,35(12):2021-2031
Density, refractive index and speed of sound at T=298.15 K and atmospheric pressure have been measured over the entire composition range for (dimethyl carbonate (DMC) + methanol + ethanol) and (DMC + methanol + 1-propanol). Excess molar volumes, changes of refractive index on mixing and deviations in isentropic compressibility for the above systems have been calculated. The calculated quantities are further fitted to the Cibulka equation to estimate the ternary fitting parameters. Standard deviations from the regression lines are shown. 相似文献
78.
The current status of plasma source-mass spectrometry (PS-MS) is reviewed. An overview of interference effects that exist, alternative plasma sources available, and mass spectrometer interface studies is provided. A discussion of current and future development areas in plasma source mass spectrometry is also included. 相似文献
79.
Marcos Mandaji Tiago Buckup Rafael Rech Ricardo Rego Bordalo Correia Tarso Ledur Kist 《Talanta》2007,71(5):1998-2002
The performance of fluorescence detectors in capillary electrophoresis is maximized when the excitation light intensity is modulated in time with optimal frequencies. This is especially true when photomultiplier tubes are used to detect the fluorescent light. The photomultiplier tube amplified raw output signal can in principle be captured directly by a personal computer sound card (PCSC) and processed by a lock-in emulated by software. This possibility is demonstrated in the present work and the performance of this new setup is compared with a traditional data acquisition system. The results obtained with this “PCSC and lock-in emulated by software” were of the same quality or even better compared to that obtained by conventional time integrators (Boxcars) and data acquisition boards. With PCSC the limits of detection (LOD) found for both naphthalene-2,3-dicarboxaldehyde-derivatized tyrosine and alanine were 3.3 and 3.5 fmol (injection of 5 nL of samples at 0.66 and 0.70 μmol/L), respectively. This is at least three times better compared to conventional systems when light emitting diodes (LEDs) are used as the excitation source in fluorescence detectors. The PCSC linear response range was also larger compared to conventional data acquisition boards. This scheme showed to be a practical and convenient alternative of data acquisition and signal processing for detection systems used in capillary electrophoresis. 相似文献
80.
The molecular characterization of unknown naturally presented major histocompatibility complex (MHC) class II glycopeptides carrying complex glycans has so far not been achieved, reflecting the different fragmentation characteristics of sugars and peptides in mass spectrometric analysis. Human leukocyte antigen (HLA)-DR-bound peptides were isolated by affinity purification, separated via high performance liquid chromatography and analyzed by matrix-assisted laser desorption/ionization and electrospray ionization mass spectrometry. We were able to identify two naturally processed MHC class II ligands, CD53(122-136) and CD53(121-136), carrying complex N-linked glycan side chains by a combination of in-source and collision-induced fragmentation on a quadrupole time-of-flight tandem mass spectrometer. 相似文献