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排序方式: 共有75条查询结果,搜索用时 125 毫秒
1.
Claude Lavalle Alain Leborgne Nicolas Spassky Robert E. Prud'homme 《Journal of polymer science. Part A, Polymer chemistry》1987,25(5):1315-1328
β-(trichloromethyl)-β-propiolactone (CCl3-PL), β-(trifluoromethyl,methyl)-β-propiolactone (CF3, Me-PL) and β-(trifluoromethyl,ethyl)-β-propiolactone (CF3,Et-PL) have been obtained by the reaction of ketene with chloral, 1,1,1-trifluoroacetone and 1,1,1-trifluorobutanone, respectively. Chiral catalysis lead to optically active monomers. The enantiomeric excess of the lactones has been measured by 1H-NMR spectroscopy, in the presence of 2,2,2-trifluoro-1-(9-anthryl)ethanol or an europium chiral shift reagent. Polymerizations have been carried out in bulk or in toluene, at 60°C or 80°C, using mainly organometallic initiators. The Polymers become insoluble and crystalline at enantiomeric excesses over 80% for CCl3-PL and 70% for CF3,Me-PL. Melting temperatures were recorded from 238 to 268°C for poly(CCl3-PL) and from 78 to 100°C for poly(CF3,Me-PL), depending upon the molecular weight and the enantiomeric excess. The 13C-NMR specroscopy of poly(CCL3-PL) indicates that the polymerization of the corresponding lactone leads to polymers of increasing degrees of isotacticity with the enantiomeric excess of the monomer. 相似文献
2.
Spassky D. A. Levushkina V. S. Mikhailin V. V. Zadneprovski B. I. Tret’yakova M. S. 《Physics of the Solid State》2013,55(1):150-159
Physics of the Solid State - This paper reports on the results of an investigation into the luminescence properties of yttrium and lutetium borates, as well as the Y0.35Lu0.65BO3 solid solution,... 相似文献
3.
E. N. Voronina L. I. Galanina N. S. Zelenskaya V. M. Lebedev V. N. Mileev L. S. Novikov V. V. Sinolits A. V. Spassky 《Bulletin of the Russian Academy of Sciences: Physics》2009,73(2):197-201
The mechanism of failures of microelectronic elements, caused by ionization of atoms by recoil nuclei and secondary fragments formed at nuclear interactions of cosmic-ray protons and light ions with substance, has been analyzed. Models of nuclear physics are used to calculate the macroscopic failure cross section. 相似文献
4.
V.M. Lebedev A.V. Spassky I.B. Teplov L.N. Fateeva L.Z. Ismail 《Nuclear Physics A》1978,298(2):206-216
The angular distributions of tritons from the (α, t) reaction on 19F, 27Al, 51V and 59Co nuclei corresponding to the (0+) ground states and (2+) excited states in the final nuclei have been measured in the angular range between 15° and 170° at α-particle energies of 25 MeV. For reactions on 27Al and 51V nuclei, the differential excitation functions have also been obtained at different angles of outgoing tritons at Eα from 20 to 25 MeV. The experimental angular distributions are analysed by the DWBA approximation on the assumption of a nucleon stripping mechanism. The analyses of the present results and the data obtained earlier for the (α, t) reaction on the 1 p shell nuclei, A ? 30, reveal that the distinguishing feature of the reaction under study is the presence of backward angle peaks in the reaction cross section, which appear to be associated with exchange processes. For the (α, t) reaction on the heavier nuclei (A > 30), the dominant mechanism is nucleon stripping. 相似文献
5.
Single-crystalline films of Ce-doped YAG and LuAG phosphors: advantages over bulk crystals analogues 总被引:1,自引:0,他引:1
Yu. Zorenko V. Gorbenko A. Voloshinovskii V. Mikhailin D. Spassky 《Journal of luminescence》2005,114(2):85-94
Luminescent properties of phosphors based on single-crystalline films (SCF) of Y3Al5O12:Ce (YAG:Ce) and Lu3Al5O12:Ce (LuAG:Ce) garnet have been analyzed in comparison with single-crystal (SC) analogues. It has been shown that the main peculiarity of luminescent properties of YAG:Ce and LuAG:Ce SCF as compared to SC is determined by the extremely low concentration of YAl3+ and LuAl3+ antisite defects (AD) in SCF. The advantages of phosphors based on YAG:Ce and LuAG:Ce SCF are caused by the absence in these SCF the additional channels for dissipation of excitation energy connected with AD and vacancy-type defects. 相似文献
6.
L. I. Galanina N. S. Zelenskaya I. A. Konyukhova V. M. Lebedev N. V. Orlova A. V. Spassky S. V. Artemov 《Bulletin of the Russian Academy of Sciences: Physics》2011,75(4):552-557
The results from measuring the angular dependence of differential α-scattering cross sections on 24Mg with final nucleus formation in the ground and three lower excited states are presented, along with the double differential
24Mg(α, αγ)24Mg(2+, 1.369 MeV) reaction cross sections at E
α = 30.3 MeV. The spin-tensor components of the density matrix of the 24Mg nucleus in the 2+(1.369 MeV) state are reconstructed and its orientation characteristics are determined. The experimental results are compared
to theoretical results under the assumption of collective excitation and mechanisms for compound nucleus formation. 相似文献
7.
8.
The angular distributions of deuterons from the 6Li(α, d)8Be reaction corresponding to the 0+ ground state and the 2.9 MeV (2+) state in8Be have been measured at Eα = 17.3, 23.3 and 25.1 MeV. The excitation functions for this reaction have been measured at seven emission angles in the region from 12 up to 25 MeV. The experimental angular distributions are compared with theoretical predictions obtained using DWBA stripping calculations and the plane wave approximation (PWA) for various direct processes. It is shown that the experimental angular distributions can be described throughout the angular region using the simple mechanisms associated with the break-up of the 6Li target nuc clusters and heavy-particle stripping. The interference of these processes is taken into account. 相似文献
9.
L. I. Galanina N. S. Zelenskaya I. A. Konyukhova V. M. Lebedev N. V. Orlova A. V. Spassky 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(4):447-452
Double differential cross sections of the 13C(d, αγ)11B(5/2−, 4.445 MeV) reaction were measured at E
d = 15.3 MeV. Angular dependences of the even components of density matrix spin tensors, magnetic sublevel populations, and
components of multipole moment orientation tensors of the 11B nucleus in this state were obtained. Experimental results were compared with theoretical data calculated under the assumption
of different reaction mechanisms: deuteron pickup, heavy particle stripping, two-step mechanism of sequential cluster transfer,
and compound nucleus formation. 相似文献
10.
D. Spassky V. Mikhailin M. Nazarov M.N. Ahmad-Fauzi A. Zhbanov 《Journal of luminescence》2012,132(10):2753-2762
The processes of the excitation energy transfer to the emission centers have been investigated for calcium tungstate crystals taking into account features of the electronic structure of valence band and conduction band. The calculations of the electronic structure of host lattice CaWO4 were performed in the framework of density functional theory. The underestimation of the bandgap value in the calculations has been corrected according to the experimental data. Luminescence of two samples grown using Czochralski (cz) and hydrothermal (ht) techniques were studied. Intrinsic emission band related to excitons, self-trapped on WO4 complexes has been observed for the both samples while the additional low-energy emission band related to the defects of crystal structure has been observed only for (ht) sample indicating the enhanced concentration of the defects in the sample. It was shown that the features of the conduction band electronic structure are reproduced in the excitation spectrum of intrinsic luminescence only for the (ht) sample while for (cz) sample the correlation is absent. The enhanced role of the competitive channels in the process of excitation energy transfer to intrinsic emission centers in (ht) sample is responsible for the observed difference. 相似文献