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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.
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
14.
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
15.
A recently proposed perturbational approach to the electron correlation cusp problem 1 is tested in the context of three spherically symmetrical two‐electron systems: helium atom, hydride anion, and a solvable model system. The interelectronic interaction is partitioned into long‐ and short‐range components. The long‐range interaction, lacking the singularities responsible for the electron correlation cusp, is included in the reference Hamiltonian. Accelerated convergence of orbital‐based methods for this smooth reference Hamiltonian is shown by a detailed partial wave analysis. Contracted orbital basis sets constructed from atomic natural orbitals are shown to be significantly better for the new Hamiltonian than standard basis sets of the same size. The short‐range component becomes the perturbation. The low‐order perturbation equations are solved variationally using basis sets of correlated Gaussian geminals. Variational energies and low‐order perturbation wave functions for the model system are shown to be in excellent agreement with highly accurate numerical solutions for that system. Approximations of the reference wave functions, described by fewer basis functions, are tested for use in the perturbation equations and shown to provide significant computational advantages with tolerable loss of accuracy. Lower bounds for the radius of convergence of the resulting perturbation expansions are estimated. The proposed method is capable of achieving sub‐μHartree accuracy for all systems considered here. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003 相似文献
16.
Laura Pop Pierrik Lassalas László Csaba Bencze Monica Ioana Toşa Botond Nagy Florin Dan Irimie Christophe Hoarau 《Tetrahedron: Asymmetry》2012,23(6-7):474-481
Stereoselective preparative enzymatic acylation and hydrolysis/methanolysis of various C-substituted rac-thiazol-2-yl-methanols were achieved for the preparation of enantiopure or enantiomerically enriched, naturally occurring 2-hydroxymethylthiazoles. The absolute configurations of the resulting secondary alcohols were determined by a detailed 1H NMR study of Mosher’s derivatives. 相似文献
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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
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Ioana Konz Beatriz Fernández M. Luisa Fernández Rosario Pereiro Héctor González Lydia Álvarez Miguel Coca-Prados Alfredo Sanz-Medel 《Analytical and bioanalytical chemistry》2013,405(10):3091-3096
Laser ablation coupled to inductively coupled plasma mass spectrometry has been developed for the elemental imaging of Mg, Fe and Cu distribution in histological tissue sections of fixed eyes, embedded in paraffin, from human donors (cadavers). This work presents the development of a novel internal standard correction methodology based on the deposition of a homogeneous thin gold film on the tissue surface and the use of the 197Au+ signal as internal standard. Sample preparation (tissue section thickness) and laser conditions were carefully optimized, and internal normalisation using 197Au+ was compared with 13C+ correction for imaging applications. 24Mg+, 56Fe+ and 63Cu+ distributions were investigated in histological sections of the anterior segment of the eye (including the iris, ciliary body, cornea and trabecular meshwork) and were shown to be heterogeneously distributed along those tissue structures. Reproducibility was assessed by imaging different human eye sections from the same donor and from ten different eyes from adult normal donors, which showed that similar spatial maps were obtained and therefore demonstrate the analytical potential of using 197Au+ as internal standard. The proposed analytical approach could offer a robust tool with great practical interest for clinical studies, e.g. to investigate trace element distribution of metals and their alterations in ocular diseases. Figure
Development of a new internal standard correction methodology for qualitative elemental imaging by LA-ICP-MS 相似文献