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11.
Investigations carried out in order to determine traces of 25 elements in tungsten in the lower g/g range are reported on. Atomic absorption spectrometry and plasma atomic emission spectrometry as well as solution photometry and activation analysis were the main techniques used. 相似文献
12.
Marián Kucharík František Šimko Vladimír Danielik Miroslav Boča Roman Vasiljev 《Monatshefte für Chemie / Chemical Monthly》2007,138(12):1211-1215
Summary. The phase diagram of the system Na3AlF6–NaVO3 was determined by means of thermal analysis. The system is a simple binary eutectic one. The eutectic point was estimated
at x(NaVO3) = 0.975 and t
eut = 617°C. The XRD patterns of samples after thermal analysis revealed the presence of cryolite and NaVO3 only supporting the above assumption of a simple eutectic binary system. 相似文献
13.
A method for preconcentration of poorly volatile impurities by continuous thermodesorption of the major component on a TLC
plate is proposed. The method provides multiple (200–500) concentration of the organic impurities present in the initial solution.
A simple device for such concentration is suggested.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2075–2076, October, 1998. 相似文献
14.
A high-performance liquid chromatographic method with evaporative light-scattering detection (ELSD) has been developed for
analysis of spectinomycin and related impurities. Separation of spectinomycin from structurally related impurities was achieved
on a C18 column. The optimized mobile phase was 25 mmol L−1 ammonium acetate (pH 7.5)-methanol, 90:10 (v/v), at a flow rate of 0.6 mL min−1. The temperature of the drift tube of the ELSD was 95°C and the flow rate of carrier gas was 2.2 L min−1. The accuracy, specificity, precision, linearity, sensitivity, and robustness of the method were validated in accordance
with ICH guidelines. In addition to determination of spectinomycin and related impurities, the method is also ideal for determination
of the salts spectinomycin hydrochloride and spectinomycin sulfate. 相似文献
15.
Herbert Spohn 《Journal of statistical physics》1977,17(6):385-412
A single (nonrelativistic, spinless) electron subject to a constant external electric field interacts with impurities located on an infinitely extended lattice by a potential of random strength. The random strength is given by a field of Gaussian random variables. We show the existence of the averaged dynamics and prove that in the weak coupling limit, 0, 2
t= fixed, one obtains the usual transport equation for the velocity distribution.Work supported by a Max Kade Foundation fellowship.On leave of absence of the Fachbereich Physik der Universität München. 相似文献
16.
G. Clouet P. Chaumont P. Corpart 《Journal of polymer science. Part A, Polymer chemistry》1993,31(11):2815-2824
The thermal bulk polymerization of methyl methacrylate (MMA) in a wide range of temperatures has been studied using a dilatometric reactor. It is shown that, irrespective of the care taken to purify the MMA, the evolution of the time-conversion curve can be explained only if we account for the presence of an impurity associated with the monomer acting as a free radical initiator. The activation energy for the decomposition of this impurity has been estimated as 98 kJ/mol. Having accounted for this impurity, the activation energy for the real thermal polymerization of the MMA has been estimated to be 75 kJ/mol. © 1993 John Wiley & Sons, Inc. 相似文献
17.
Magdalena Kurdziel Elżbieta Szczepaniec-Cięciak Barbara Dąbrowska Wojciech Nitek Katarzyna Paliś Edyta Ślusarska 《Journal of solution chemistry》2003,32(7):601-615
The solubilities of solid 2,3-dimethylbutane and cyclopentene in liquid argon at a temperature of 87.3 K and in liquid nitrogen at 77.4 K have been measured by the filtration method. The hydrocarbon contents in solutions were determined using gas chromatography. GC–MS was used to identify impurities in solutes. The experimental value of the mole fraction solubility of solid 2,3-dimethyl-butane in liquid argon at 87.3 K is (8.26 ± 1.60) × 10–6 and (2.77 ± 0.94) × 10–8 in liquid nitrogen at 77.4 K. The experimental value of the mole fraction solubility of solid cyclopentene in liquid argon at 87.3 K is (5.11 ± 0.44) × 10–6 and (4.60 ± 0.76) × 10–8 in liquid nitrogen at 77.4 K. The Preston–Prausnitz method was used for calculation of the solubilities of solid hydrocarbons in liquid argon in the temperature range 84.0–110.0 K and in liquid nitrogen from 64.0 to 90.0 K. The solvent–solute interaction parameters l
12 were also calculated. At 90.0 K liquid argon is a better solvent for investigated solid hydrocarbons than is liquid nitrogen. 相似文献
18.
In spite of Sinai's result that the decay of the velocity autocorrelation function for a random walk on
d
(d=2) can drastically change if local impurities are present, it is shown that local impurities can not abolish weak convergence to the Brownian motion if d2. 相似文献
19.
本文是作者1982年在中国访问时所作的讲演,论述物理学各领域的前沿工作,用许多事例说明计算物理对推动物理理论的重大意义。文中还指出计算物理在其性质、方法及需要等方面不同于和独立于解析的理论物理和实验物理,而成为物理学的第三分支。 相似文献
20.