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11.
12.
M. Contineanu O. Constantinescu M. Ciureanu 《Journal of Radioanalytical and Nuclear Chemistry》1987,117(2):81-90
Electron spin resonance spectra of free radicals formed in the radiolysis of benzen-2,1-diazoquinone-4-sulphonic acid in polycrystalline form have been recorded. Two different radical species were found; the first one was stable at 77 K, whereas the second one was formed at higher temperatures. The thermal stability of the latter was investigated in the 20–100 °C temperature range, and the kinetic parameters for the decomposition process were determined. An appropriate mechanism of radiolysis was proposed. 相似文献
13.
Gas chromatography-mass spectrometry of carbonyl compounds in cigarette mainstream smoke after derivatization with 2,4-dinitrophenylhydrazine 总被引:3,自引:0,他引:3
An improved gas chromatography-mass spectrometry (GC-MS) method was described for the analysis of carbonyl compounds in cigarette mainstream smoke (CMS) after 2,4-dinitrophenylhydrazine (DNPH) derivatization. Besides formaldehyde, acetaldehyde, acetone, acrolein, propionaldehyde, methyl ethyl ketone, butyraldehyde, and crotonaldehyde that are routinely analyzed in cigarette smoke, this technique separates and allows the analysis of several C4, C5 and C6 isomeric carbonyl compounds. Differentiation could be made between the linear and branched carbon chain components. In cigarette smoke, the branched chain carbonyls are found at higher level than the linear chain carbonyls. Also, several trace carbonyl compounds such as methoxyacetaldehyde were found for the first time in cigarette smoke. For the analysis, cigarette smoke was collected using DNPH-treated pads, which is a simpler procedure compared to conventional impinger collection. Thermal decomposition of DNPH-carbonyl compounds was minimized by the optimization of the GC conditions. The linear range of the method was significantly improved by using a standard mixture of DNPH-carbonyl compounds instead of individual compounds for calibration. The minimum detectable quantity for the carbonyls ranged from 1.4 to 5.6 microg/cigarette. 相似文献
14.
Z. Szeglowski L. I. Guseva Dinh Thi Lien V. P. Domanov B. Kubica G. S. Tikhomirowa O. Constantinescu M. Constantinescu A. B. Yakushev 《Journal of Radioanalytical and Nuclear Chemistry》1998,228(1-2):145-150
The short-lived isotopes of W and their descendants have been separated from nuclear reaction products arising in the bombardment of samarium target with24Mg ions at the U-400 cyclotron of JINR-Dubna. Chemical separations were performed using previously elaborated fast and continuous ion exchange. In similar way products of235U fission, obtained at the microtron MT-25 during irradiation of235U target with photoneutrons were separated. 相似文献
15.
B. Constantinescu D. Galeriu E. A. Ivanov G. Pascovici D. Plostinaru 《Journal of Radioanalytical and Nuclear Chemistry》1988,128(1):15-21
Various samples from the south-east region of Roumania/greens, fodder, cheese/were analyzed for131I,134Cs and137Cs concentrations in May and July 1986 by -ray spectrometry. The concentrations are reported in nCi. kg–1 wet weight. For greens, a considerable decrease was observed for131I/to 3.0–7.0 nCi. kg–1/,134Cs/to 0.5–2.0 nCi.kg–1/ and137Cs /to 1.0–4.0 nCi. kg–1/ from the first half /5–15 May/ till the end of May 1986. For cheese, maximum values were measured between 5 and 15 May /sheep cottage cheese: 500–800 nCi.kg–1 for131I, 25–50 nCi. kg–1 for134Cs, 40–80 nCi. kg–1 for137Cs/; at the beginning of July a considerable decrease /to 5–10 nCi. kg–1 for131I, 1.2–2.0 nCi.kg–1 for134Cs, 2.2–3.0 nCi. kg–1 for137Cs/ was observed. In autumn 1986 a small increase up to 2.0–3.0 nCi. kg–1 for134Cs and 3.4–5.0 nCi. kg–1 for137Cs /in November/ was reported. The population's internal possible contamination was strongly limited by the authorities' severe control of the food-stuff. 相似文献
16.
Dan Donescu Liana Fusulan Stela Lungoci Sever Serban Cristian Peteu 《Journal of Dispersion Science and Technology》2013,34(5):647-653
ABSTRACT The modification of decomposition rate of the potassium persulfate initiator during the synthesis of “two-stage latexes” polystyrene-ethyl acrylate (EtA) of butyl acrylale (BuA) and of 2-ethylhexyl acrylate (EHA) is studied. This rate is minimum for BuA and maximum for EHA, in good agreement with the value of solubility parameters. The appearance of poryacrvlaf.es determines the existence of water bonded to the polar polymer. The amount of water bonded increases in the sequence PEtA?PBuA?PEHA, function of the modification of the diameters of the particles resulted from the latexes obtained. 相似文献
17.
Guo Chang Zhuo Xiaoyang Constantinescu Corina Pamen Olivier Menoukeu 《Methodology and Computing in Applied Probability》2018,20(4):1477-1502
Methodology and Computing in Applied Probability - In this paper, we pursue the optimal reinsurance-investment strategy of an insurer who can invest in both domestic and foreign markets. We assume... 相似文献
18.
A significant amount of work has been previously dedicated to the understanding of methylene selectivity parameter. The conventional theory applied for this understanding was mostly based on the assumption that the difference in the Gibbs free energy of transfer from the mobile phase to the stationary phase is a constant for any two compounds in a homologous series that differ by a CH2 group. In the present study, it is shown based on solvophobic theory that this assumption is indeed correct, but it provides a theoretical justification for it. Exemplification of the results of theory was obtained using the values for methylene selectivity (α(CH2)) measured experimentally for seven different C18 chromatographic columns including two core–shell columns and using water and either methanol or acetonitrile as an organic component. Four different homologous series of compounds were used for evaluation. The study proved the theoretical prediction that the values for α(CH2) obtained using different homologous series of compounds are only slightly different from those obtained using the toluene–butylbenzene series. Even using different homologous series, the same type of information regarding the columns comparison, and the changes in log α(CH2) with the solvent composition was obtained. 相似文献
19.
C. Constantinescu E. Morîntale Ana Emandi Maria Dinescu P. Rotaru 《Journal of Thermal Analysis and Calorimetry》2011,104(2):707-716
A newly synthesized copper-complex exhibiting nonlinear optical properties, crystalline nature, and generating interest as
a material for non-linear optical applications was investigated. As thermal stability studies are indispensable before attempting
any laser-assisted processing experiments, the thermal behavior of 2,2′-dihydroxy azobenzene with Cu2+ cations that are found to organize themselves as non-central symmetric crystallites, was investigated. The thin films were
deposited on silicon substrates by matrix-assisted pulsed laser evaporation using a Nd:YAG laser working at 266 and 355 nm.
Thermal analysis of the bulk compound indicates a higher thermal stability in argon flow when compared to the air atmosphere;
as well, since, the adhesion of the compound onto the substrate enhances the bonding, the thermal stability of the Cu complex
increases. Fourier transform infrared spectroscopy, atomic force microscopy, scanning electron microscopy, spectroscopic ellipsometry,
and ultraviolet–visible spectroscopy investigations were also performed. 相似文献
20.
The local electric properties at K and Zn sites in the normal, incommensurate and commensurate phases of K2ZnCl4, as derived from a numerical computation of the lattice contributions to the electric potential V(r), electric field intensityE(r) and electric field gradient tensorV αβ(r) are reported. The numerical data obtained at each cationic position were correlated with the experimental39K NMR, Cu2+ and Mn2+ EPR and57Fe Mössbauer results in pure and doped K2ZnCl4. A proportionality between crystal field and zero-field splitting was taken into account for Mn2+, whereas for K+, Cu2+ and Fe3+ ions the electric field gradient is directly related to the crystal field parameter. By this comparison, on computations done in the ionic fractional charge and relaxed lattice approximations, the insertion of probe-species of iron, copper and manganese ions on off-center Zn sites is proposed. The39K electric field gradient tensor calculations in the incommensurate phase fit well with the NMR data reported recently. 相似文献