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91.
Véronique Pignon Roger Jeannot Emmanuel Sauvard 《International journal of environmental analytical chemistry》2013,93(4):345-366
Abstract The coupling between liquid chromatography and mass spectrometry with an APCI or ESI interface (in positive or negative mode) is used here for multi-residue analyses in natural waters, covering basic and neutral pesticides as well as acid pesticides. The methods developed are applied to drinking and, river waters after the samples are concentrated by liquid-liquid extraction or solid phase extraction on C18 cartridges. Comparisons are made between UV detection and mass spectrometry and between two chromatographic methods for acid substances. The quantitation limits range from 0.01 to 0.1 μg/l according to the substance. 相似文献
92.
《国际化学动力学杂志》2018,50(8):556-567
Experimental and theoretical rate coefficients are determined for the first time for the reaction of 4‐hydroxy‐3‐hexanone (CH3CH2C(O)CH(OH)CH2CH3) with OH radicals as a function of temperature. Experimental studies were carried out using two techniques. Absolute rate coefficients were measured using a cryogenically cooled cell coupled to the pulsed laser photolysis‐laser‐induced fluorescence technique with temperature and pressure ranges of 280‐365 K and 5‐80 Torr, respectively. Relative values of the studied reaction were measured under atmospheric pressure in the range of 298‐354 K by using a simulation chamber coupled to a FT‐IR spectrometer. In addition, the reaction of 4H3H with OH radicals was studied theoretically by using the density functional theory method over the range of 278‐350 K. Results show that H‐atom abstraction occurs more favorably from the C–H bound adjacent to the hydroxyl group with small barrier height. Theoretical rate coefficients are in good agreement with the experimental data. A slight negative temperature dependence was observed in both theoretical and experimental works. Overall, the results are deliberated in terms of structure–reactivity relationship and atmospheric implications. 相似文献
93.
Lee Chuin Chen Md. Matiur Rahman Kenzo Hiraoka 《Journal of mass spectrometry : JMS》2012,47(8):1083-1089
Standard field desorption (FD) ionization is implemented under high vacuum condition. In this paper, non‐vacuum FD is performed under a super‐atmospheric pressure environment using untreated tungsten wires as FD emitter, and the ion source was coupled to a commercial linear ion trap mass spectrometer. The operating pressure of the ion source was 6 bars which was high enough to provide sufficient dielectric strength to the working gas so that the high voltage that was required for FD could be applied to the emitter without occurrence of electrical discharge. Non‐volatile sample deposited on the bare tungsten wire FD emitter was heated by flowing direct current through the emitter. Similar to vacuum FD, the formation of conical protrusion of the liquefied sample layer under the strong electric field was also observed. Using the present ion source, high pressure field‐desorption of polar neutral compounds, organic salts and ionic liquids is demonstrated. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
94.
Nadia Balucani Laura Cartechini Zahra Homayoon Joel M. Bowman 《Molecular physics》2015,113(15-16):2296-2301
Following a recent investigation on the N(2D) + H2O reaction [Homayoon et al., J. Phys. Chem. Lett. 5, 3508 (2014)], we report on an experimental and theoretical study of the isotopologue N(2D) + D2O reaction. Crossed molecular beam (CMB) experiments were conducted at a collision energy of 10.3 kcal mol–1. Quasiclassical trajectory calculations were performed on a recent potential energy surface to derive the centre-of-mass functions necessary to simulate the CMB laboratory distributions. Excellent agreement was found. The importance of the channel leading to HON/DON was confirmed. The inclusion of this channel, in addition to that leading to the isomer HNO/DNO, can affect the models considering the coupling between nitrogen and oxygen chemistry in the upper atmosphere of Titan. 相似文献
95.
96.
从理论和实验两方面对自由空间光通信中常用的两种调制方式进行性能比较分析,旨在找出一种最适合的调制方法抑制大气湍流。在分析Gamma-Gamma信道下OOK(开关键控)和DPSK(差分相移键控)调制的误码率时,将广义超几何方法引入分析。利用Matlab软件搭建系统,通过实验可知,采取相干及平衡探测的DPSK调制时性能要比基于OOK调制的直接探测高出3.21dB;通过对双管平衡探测和单管探测进行实验,结果表明,双管平衡探测的信噪比优于单管探测,约提高21.6dB。因此,基于DPSK平衡探测的相干通信方案具有可行性和优越性。 相似文献
97.
基于大口径闪烁法和差分到达角起伏法开展了间距为3.95 km近水平路径的大气相干长度测量实验。测量结果表明:在同路径的上下行光传播方向上,闪烁法测量相干长度的相关系数为0.94,而到达角起伏法测量相干长度的相关系数为0.79。路径权重的理论分析揭示了闪烁法对路径中部的湍涡敏感,且路径权重函数关于路径中部呈对称分布;到达角起伏法对接收端附近的湍涡敏感,其路径权重函数从发射端到接收端呈单调递增趋势。因此,实际的长距离光传输实验中,在不能确定路径中湍流强度分布的情况下,采用闪烁法测量路径上的湍流效应更适宜。 相似文献
98.
The MCM‐41 and SiO2 supported TiCl4 and TiCl4/MgCl2 catalysts with different molar ratios of Mg/Ti were synthesized and used for ethylene polymerization under atmospheric pressure. The nanochannels of MCM‐41 serve as nanoscale polymerization reactor and the polyethylene nanofibers were extruded during the reaction. The nanofibers were observed in SEM micrographs of resulting polyethylene. The effect of MgCl2 on catalytic activity and thermal properties of resulting polyethylene is investigated too. In the presence of MgCl2, the catalytic activity increased and more crystalline polyethylene with higher melting points were formed. However, no fibers could be observed in the polyethylene prepared by SiO2 supported catalysts. 相似文献
99.
Raiza Fernández Freddy Galarraga Zully Benzo Gonzalo Márquez M. Gabriela Requiz 《International journal of environmental analytical chemistry》2013,93(3):230-240
Biomonitoring of PAH air pollution using lichens was carried out. Sixteen PAHs were studied in 11 locations along the valley of Caracas (Venezuela). The results of this work indicate that 14 of the 16 analysed PAHs were highly accumulated into the lichen thalli of Pyxine coralligera Malme. PAH levels in the samples revealed that the several volatile PAHs (naphthalene, acenaphtylene, acenaphtene, and fluoranthene) have the highest levels in the majority of the studied locations. The fluoranthene/pyrene and phenantrene/antracene ratios suggested that the major sources of PAHs are anthropogenic, mainly associated with gasoline and diesel combustion (pyrolytic) and unburnt oil derivates (petrogenic). The total PAH concentrations obtained in the present study were in the range of 0.24 to 9.08?µg/g, similar to those reported by other works in European and Asian cities. 相似文献
100.
Bruce M. Allen Paul K. Predecki Maciej Kumosa 《Journal of computational chemistry》2014,35(9):756-764
Three open‐source applications, NanoEngineer‐1, packmol, and mis2lmp are integrated using an open‐source file format to quickly create molecular dynamics (MD) cells for simulation. The three software applications collectively make up the open‐source software (OSS) suite known as MD Studio (MDS). The software is validated through software engineering practices and is verified through simulation of the diglycidyl ether of bisphenol‐a and isophorone diamine (DGEBA/IPD) system. Multiple simulations are run using the MDS software to create MD cells, and the data generated are used to calculate density, bulk modulus, and glass transition temperature of the DGEBA/IPD system. Simulation results compare well with published experimental and numerical results. The MDS software prototype confirms that OSS applications can be analyzed against real‐world research requirements and integrated to create a new capability. © 2014 Wiley Periodicals, Inc. 相似文献