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941.
942.
M. S. Batista M. A. Morales E. Baggio-Saitovich E. A. Urquieta-González 《Hyperfine Interactions》2001,134(1):161-166
The Fe species present in Fe/ZSM-5 catalysts prepared by ionic exchange in aqueous solution or in the solid state are investigated. The samples were characterized by XRD, EPR, Mössbauer Spectroscopy (MOS-S) and chemical analysis. XRD showed that the peak intensity decreased with the increase in Fe content in the samples. EPR and MOS-S showed that the Fe atoms in all the activated samples appear as Fe+3, independently of the method used in the catalyst preparation. The MOS-S data also showed that Fe/ZSM-5, prepared by ion exchange in the solid state presented lower hematite content and more Fe species in charge-compensation sites, the responsible for the catalytic activity, as confirmed by the behavior in the propane oxidation. 相似文献
943.
A novel organic electron acceptor, N,N′-dipyrimidinyl-3,4,9,10-perylene-tetracarboxylic diimide (DMP), was designed and synthesized. The molecular structure was
characterized by FTIR spectrum and elemental analysis. By cyclic voltammetry measurements, DMP was found to possess a lower
LUMO energy level than N,N′-diphenyl-3,4,9,10-perylene-tetracarboxylic diimide due to the stronger electron-withdrawing pyrimidinyl group than the phenyl
group. Fluorescence quenching is observed in a dual-layer film consisting of a DMP layer and a C60 layer and was attributed to the charge transfer at the interface due to the energy level offset between DMP and C60.
Supported by the National Natural Science Foundation of China (Grant Nos. 50433020, 50520150165 & 50403022) 相似文献
944.
In this paper, using the exit-time statistic, we study the structure of the price variations for the high-frequency data set of the bid–ask Deutschemark/US dollar exchange rate quotes registered by the inter-bank Reuters network over the period October 1, 1992 to September 30, 1993. Having rejected random-walk models for the returns, we propose a Markovian model which reproduce the available information of the financial series. Besides the usual correlation analysis we have verified the validity of this model by means of other tools all inspired by information theory. These techniques are not only severe tests of the approximation but also evidence of some aspects of the data series which have a clear financial relevance. 相似文献
945.
S. P. Gromov E. N. Ushakov A. I. Vedernikov L. G. Kuz’mina M. V. Alfimov 《Theoretical and Experimental Chemistry》2009,45(1):3-11
A universal approach to the molecular design of light-sensitive nanodimensional systems with specific characteristics was
developed on the basis of unsaturated and macrocyclic compounds. It was possible to construct various nanodimensional systems
within the scope of a single class of compound using a limited number of components. The use of photostructural transformations
to control complex formation and mechanical movements in molecular devices and machines is discussed.
Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 45, No. 1, pp. 1–7, January-February, 2009. 相似文献
946.
S. Delaborde H.-R. Loosli M. Ponelle R. Griesser G. Maurer 《Journal of separation science》1987,10(2):71-76
890 ml of urine of rats treated with [14C] 205–734 was desalted over an Amberlite XAD-2 adsorption column. The methanol extract dissolved in 10 ml methanol was injected onto an anion exchange column (Nucleosil 10 SB 250 × 16 mm i.d.) equilibrated in methanol. A gradient of decreasing methanol proportion versus a 0.2 M ammonium hydrogen carbonate buffer eluted a pure glucuronide of 205–734. Its structure was established by NMR, MS, UV, and IR analyses. This procedure is simple, rapid, and very selective for the compound of interest. 相似文献
947.
本文给出了强流相对论性电子束(IREB)在低压中性气体中传输特性的理论和实验研究结果。660kV,40kA,脉宽100ns的电子束注入充有H_2,N_2的漂移管,稳定的传输气压范围在(0.7-6.7)×10~2Pa间,传输效率可达80%以上;极低气压时(P≈13.3Pa)由于空间电荷效应,束电子被虚阴极阻滞并径向发散,不能有效传输;而较高气压时,束电子除受自身电磁场作用及库仑碰撞散射外,等离子体不稳定性使束流传输效率明显降低。用蒙特·卡洛法及数值解析法对电荷中和、电流中和过程进行了模拟计算并解释了实验结果。 相似文献
948.
A procedure for the colorimetric assay of praziquantel has been developed. The method is based on the formation of charge-transfer
complexes with p-chloranil (I), dichloronitrophenol (II), 2,3-dichloro-5,6 dicyano-p-benzoquinone (III), 7,7,8,8-tetracyanoquinodimethane
(IV) and tetracyanoethylene (V) as π-acceptors to give highly coloured species. The coloured products are measured spectrophotometrically
at 550, 425, 460, 844 and 393 nm for I, II, III, IV and V, respectively. Optimization of the different reaction conditions
is described. The colour system obeyed Beer’s law in non-aqueous media in the concentration range 2.0–48 μg ml−1. It was stable for at least 4.0 h. The detection limit was found to be 0.6 μg ml−1. Applications of the procedure to the analysis of various pharmaceutical samples gave reproducible and accurate results.
Further, the validity of the procedure was confirmed by applying the standard addition technique. The total average recovery
was 100.2%.
Received June 10, 2000. Revision December 23, 2000. 相似文献
949.
950.
Wayne E. Steinmetz 《Magnetic resonance in chemistry : MRC》2010,48(7):565-570
Granatin B, a complex ellagitannin extracted from pomegranate fruit, has two equilibrating isomers, form a and form b. A full ensemble of proton and carbon‐13 NMR methods over a wide range of temperature enabled a complete assignment of the more abundant isomer and showed it to be form b. This result is based on the NMR data for granatin alone and agrees with the previous determinations which were based on a combination of chemical methods and a partial assignment of the NMR spectra. The new NMR spectra also yield exchange rates for the hydroxyl protons as a function of temperature. A molecular model involving hydrogen bonding provides an explanation for the exchange data. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献