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31.
IP WaiCheung 《中国科学A辑(英文版)》2008,(12)
AR and bilinear time series models are expressed as time series chain graphical models, based on which, it is shown that the coefficients of AR and bilinear models are the conditional correlation coefficients conditioned on the other components of the time series. Then a graphically based procedure is proposed to test the significance of the coeffcients of AR and bilinear time series. Simulations show that our procedure performs well both in sizes and powers. 相似文献
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33.
Baran N. P. Vorona I. P. Ishchenko S. S. Nosenko V. V. Zatovskii I. V. Gorodilova N. A. Povarchuk V. Yu. 《Physics of the Solid State》2011,53(9):1891-1894
The EPR studies of synthetic hydroxyapatite containing carbonate and nitrate ions exposed to γ-ray and UV irradiations have
been performed. It has been found that γ irradiation leads to the formation of both NO32− and CO2− paramagnetic centers, while the UV irradiation induces only NO32− centers. To explain this fact, the hypothesis has been proposed, according to which in the hydroxyapatites studied, there
coexist complexes consisting of nitrate ions and shallow electron traps that serve as sources of secondary electrons during
UV irradiation. The EPR spectroscopy parameters (g and A) of the detected centers have been determined and compared with similar centers in hydroxyapatite with a different impurity
composition. The study of the thermal stability of the centers has demonstrated that, in the temperature range 20–300°C, the
NO32− centers formed by UV irradiation are more stable than the same centers created by γ-ray irradiation. 相似文献
34.
L. V. Myznikov U. N. Dmitrieva T. V. Artamonova S. V. Vorona N. P. Novoselov Yu. E. Zevatskiy 《Russian Journal of Organic Chemistry》2013,49(5):754-757
Oxidation of 1-substituted 5-arylsulfanyltetrazoles with m-chloroperoxybenzoic acid and NaIO4 in the presence of RuCl3 leads to the formation of the 5-arylsulfonyltetrazoles. The microwave activation significantly accelerates the oxidation with sodium periodate. The phenylsulfonyl group in compounds obtained underwent the nucleophilic substitution when treated with ethanol, phenol, or benzimidazole in acetonitrile in the presence of NaOH. 相似文献
35.
V. Ya. Bratus'' M. Ya. Valakh I. P. Vorona T. T. Petrenko V. A. Yukhimchuk P. L. F. Hemment T. Komoda 《Journal of luminescence》1998,80(1-4):269-273
Thermally grown SiO2 layers on Si substrates implanted with Si+ ions with a dose of 6×1016 cm−2 were studied by the techniques of photoluminescence, electron paramagnetic resonance (EPR), and low-frequency Raman scattering. Distinct oxygen-vacancy associated defects in SiO2 and non-bridging oxygen hole centers were identified by EPR. The luminescence intensity in the 620 nm range was found to correlate with the number of these defects. The low-frequency Raman scattering technique was used to estimate the average size of the Si nanocrystallites formed after the implantation and thermal annealing at T>1100°C, which are responsible for the photoluminescence band with a maximum at 740 nm. The intensity of this band can be significantly enhanced by an additional treatment of the samples in a low-temperature RF plasma. 相似文献
36.
I. P. Vorona S. S. Ishchenko N. P. Baran V. V. Nosenko I. V. Zatovskii A. I. Malyshenko V. Yu. Povarchuk 《Physics of the Solid State》2013,55(12):2543-2548
The effect of preliminary (before irradiation) annealing of synthetic carbonate-containing hydroxyapatite powders on the formation of paramagnetic centers under γ-ray and ultraviolet irradiation has been investigated. Annealing of the samples has been performed in the temperature range from 100 to 700°C. It has been found that electron paramagnetic resonance spectra of radiation-induced defects depend substantially on the annealing temperature. The paramagnetic centers CO 2 ? dominate in the samples annealed to 250°C (γ-ray irradiation) and 500°C (ultraviolet irradiation). In the samples annealed above 400°C, other defects, in particular, the O? and CO 3 3? centers, play a significant role. Annealing at some temperatures leads to an increase in the radiation sensitivity of the material. The observed effects can be associated with the escape of molecular water from the annealed hydroxyapatite samples and with the corresponding transformation of the defect subsystem of the material. 相似文献
37.
M. Vorona I. Potorochina G. Veinberg S. Belyakov I. Shestakova I. Kanepe E. Lukevics 《Chemistry of Heterocyclic Compounds》2009,45(12):1532-1538
The sulfoxide of 6Z-[2-(methoxyimino)propylidene]penicillanic acid tert-butyl ester and the sulfones of 6Z-[2-(hydroxyimino-, methoxyimino-, benzyloxyimino-, 2-bromo- and 4-bromobenzyloxyimino)-propylidene]penicillanic acid in the
syn and anti forms have been synthesized by the condensation of the sulfoxide and sulfone of 6Z-acetylmethylenepenicillanic acid tert-butyl ester with hydroxylamine, methoxyamine, benzyloxyamine, 2-bromo- and 4-bromobenzyloxyamines. The syn and anti isomers
of 3Z-(2-methoxyiminopropylidene)-4R-(benzothiazolyl-2-dithio)-2-oxoazetidinyl-1R-(2-propenyl)acetic acid tert-butyl ester were obtained by opening of the thiazolidine ring in 6Z-[2-(methoxy-imino)propylidene]-1-oxopenicillanic acid tert-butyl ester with 2-mercaptobenzothiazole. The 3Z-(2-methoxyiminopropylidene)-4R-(methylsulfonyl)-2-oxoazetidinyl-1-(2-propylidene)acetic acid tert-butyl ester was synthesized by the interaction of 1,8-diazobicyclo[5.4.0]undec-7-ene and methyl iodide with 6Z-[2-(methoxyimino)propylidene]-1,1-dioxopenicillanic acid tert-butyl ester. A dependence of the cytotoxic effect in relation to cancer and normal cells in vitro on the structure of the
substituent in position 6 and the syn and anti isomerism of the oxyimino group was established for the synthesized compounds. 相似文献
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39.
G. Veinberg K. Dikovskaya M. Vorona I. Turovskis I. Shestakova I. Kanepe E. Lukevics 《Chemistry of Heterocyclic Compounds》2005,41(1):93-97
New derivatives of 2-oxo-1-azetidinylacetamide have been synthesized by the four-component condensation of -amino acids with aldehydes and isonitriles. Study of their cytotoxic activity in vitro revealed a cytotoxic effect of individual compounds in relation to cancer cells of human fibrosarcoma, mouse hepatoma, and mouse neuroblastoma. 相似文献
40.
Ivan V. Ogorodnyk Igor V. Zatovsky Nikolay S. Slobodyanik Igor P. Vorona 《Journal of solid state chemistry》2007,180(10):2838-2844
Two new mixed valence manganese-containing orthophosphates with a langbeinite structure have been obtained from the complex fluoride-phosphate melts using the high-temperature flux technique. MIVF4 and K2MIVF6 (MIV—Zr, Hf) were used as fluoride and polyvalent metal precursors. Obtained langbeinites were investigated using a single-crystal X-ray diffraction, FTIR-, UV-VIS- and electron paramagnetic resonance (EPR)-spectroscopy. Both compounds crystallize in a cubic system (sp. gr. P213) with cell parameters a=10.2106(12) and 10.1896(9) Å for K1.96Mn0.57Zr1.43(PO4)3 and K1.93Mn0.53Hf1.47(PO4)3, respectively. The rigid langbeinite-like framework is built up from the isolated [MO6] octahedra and [PO4] tetrahedra interlinked via oxygen vertices. Potassium cations occupy positions in the large closed cavities of the framework. Statistical distribution of manganese and tetravalent metal over two crystallographic positions in octahedral oxygen environment can be observed. The presence of the mixed valence manganese in the reported phosphates was confirmed using UV-VIS and EPR-spectroscopy. 相似文献