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291.
V. B. Rybakov E. V. Babaev K. Yu. Pasichnichenko E. J. Sonneveld 《Crystallography Reports》2002,47(1):69-74
The structure of 3-(isonicotinoyl)-2-oxooxazolo[3,2-a]pyridine, C13H8N2O3, (I) is determined by X-ray powder diffraction analysis. Crystals I are orthorhombic, a = 16.610(2) Å, b = 3.853(1) Å, c = 16.431(2) Å, Z = 4, and space group Pna21. The structure is solved by the grid search procedure and refined by the Reitveld method (Rp = 0.086, Rwp = 0.115, Re = 0.030, and χ2 = 11.138). The structure of the product of hydrolysis of compound I, C12H10N2O2, (II) is determined by the single-crystal X-ray diffraction technique. Crystals II are orthorhombic, a = 8.755(4) Å, b = 10.526(17) Å, c = 23.088(6) Å, Z = 8, and space group Pc21b. The structure is solved by the direct method and refined by the full-matrix least-squares procedure to R = 0.0464. A fragment of two fused heterocycles in I is planar. The dihedral angle between the plane of the pyridine ring in the isonicotinoyl fragment and the plane of the bicyclic system is 51.2(2)°. Both exocyclic CO groups that are adjacent to the five-membered fragment contain double bonds. The structures of two crystallographically independent molecules II are almost identical to each other, and the isonicotinoyl fragment is nearly perpendicular to the plane of the pyridone fragment [84.3(1)° and 87.0(1)°]. 相似文献
292.
O. S. Mazina V. B. Rybakov S. I. Troyanov E. V. Babaev L. A. Aslanov 《Crystallography Reports》2005,50(1):61-71
The structures of five compounds are studied using single-crystal X-ray diffraction: 2-oxo-2,5,6,7-tetrahydro-1H-cyclopenta[b]pyridine-3-carbonitrile [a = 15.641(8) Å, b = 9.373(5) Å, c = 7.387(4) Å, β = 92.91(5)°, Z = 4, space group P21/c]; 1-[2-(4-chlorophenyl)-2-oxoethyl]-2-oxo-2,5,6,7-tetrahydro-1H-cyclopenta[b]pyridine-3-carbonitrile [a = 4.728(4) Å, b = 28.035(11) Å, c = 11.184(3) Å, Z = 4, space group P212121]; 2-[2-(4-chlorophenyl)-2-oxoethoxy]-6,7-dihydro-5H-cyclopenta[b]pyridine-3-carbonitrile [a = 10.1202(13) Å, b = 11.2484(18) Å, c = 13.4323(19) Å, β = 102.05(1)°, Z = 4, space group P21/c]; 2-(4-chlorophenyl)-3a, 6,7,8-tetrahydrocyclopenta[e][1.3]oxazolo[3.2-a]pyridine-4-carboxamide perchlorate [a = 7.702(2) Å, b = 9.599(3) Å, c = 23.798(5) Å, β = 93.44(2)°, Z = 4, space group P21/c]; and (3-amino-6,7-dihydro-5H-cyclopenta[b]furo[3.2-e]pyridin-2-yl)(4-chlorophenyl)methanone [a = 7.3273(2) Å, b = 13.390(3) Å, c = 28.792(8) Å, Z = 8, space group Pbca]. The structures are solved using direct methods and refined by the full-matrix least-squares procedure in the anisotropic approximation to R = 0.0580, 0.0724, 0.0469, 0.0477, and 0.0418, respectively. 相似文献
293.
294.
Y. P. Rybakov G. N. Shikin Y. A. Popov Bijan Saha 《International Journal of Theoretical Physics》2011,50(11):3421-3431
The important role of scalar field in cosmology was noticed by a number of authors. Due to the fact that the scalar field
possesses zero spin, it was basically considered in isotropic cosmological models. If considered in an anisotropic model,
the linear scalar field does not lead to isotropization of expansion process. One needs to introduce scalar field with nonlinear
potential for the isotropization process to take place. In this paper the general form of scalar field potentials leading
to the asymptotic isotropization in case of Bianchi type-I cosmological model, and inflationary regime in case of isotropic
space-time is obtained. In doing so we solved both direct and inverse problem, where by direct problem we mean to find metric
functions and scalar field for the given potential, whereas, the inverse problem means to find the potential and scalar field
for the given metric function. The scalar field potentials leading to the inflation and isotropization were found both for
harmonic and proper synchronic time. 相似文献
295.
Yu. P. Rybakov 《Physics of Atomic Nuclei》2011,74(7):1073-1076
The generalization of the Mie electrodynamics within the scope of the effective 8-spinor field model is suggested, with the
Lagrangian including Higgs-like potential and higher degrees of the invariant A
μ
A
μ. Using special Brioschi 8-spinor identity, we show that the model includes the Skyrme and the Faddeev models as particular
cases. We investigate the large-distance asymptotic of static solutions and estimate the electromagnetic contribution to the
energy of the localized charged configuration. 相似文献
296.
Yu. P. Rybakov 《Physics of Particles and Nuclei》2010,41(1):101-107
The review is devoted to cosmic chiral vortices (strings) and their possible role in the evolution of the early Universe.
An exact cylindrically-symmetric solution to Einstein equations was obtained within the SU(2) sigma model for a configuration with a topological charge of the degree type. The linearized stability of the solution
with respect to radial perturbations is proven by Lyapunov’s direct method. The metric found corresponds to the conical type
with an angular deficiency proportional to the topological charge or the linear mass density of the vortex. The ray deflection
angle close to the angular deficiency (the gravitational lens effect) was determined by direct integration of geodesic equations
for the light ray orthogonal to the vortex. A gauge generalization of the model was considered involving the axially symmetric
Yang-Mills field. In the approximation of the large topological charge, a solution with proper longitudinal magnetic field
was obtained and the effect of a decrease in the vortex energy was found. The effect of closing the string was also considered
in the approximation of the large closure radius. To this end, the toroidal moment of a closed string was calculated and an
energy correction caused by the Skyrme term. 相似文献
297.
Yu. V. Bykov S. V. Egorov A. G. Eremeev I. V. Plotnikov K. I. Rybakov A. A. Sorokin V. V. Kholoptsev 《Technical Physics》2018,63(3):391-397
We report on the results of the analysis of the effect of flash sintering, which is observed upon heating compacted powder materials by high-intensity microwave radiation. Ceramic samples of Y2O3, MgAl2O4, and Yb: (LaO)2O3 were sintered to a density exceeding 98–99% of the theoretical value during 0.5–5 min without isothermal hold. The specific microwave power absorbed volumetrically in the samples was 20–400 W/cm3. Based on the analysis of the experimental data (microwave radiation power and heating and cooling rates) and of the microstructure of the obtained materials, we propose a mechanism of flash sintering based on the evolution of the thermal instability and softening (melting) of the grain boundaries. The proposed mechanism also explains the flash sintering effect observed when a dc or a low-frequency ac voltage is applied to the samples. The microwave heating makes it possible to implement flash sintering without using electrodes for supplying energy to the articles being sintered. 相似文献
298.
Dmitry A. Vasilenko Kirill S. Sadovnikov Kseniya N. Sedenkova Dmitry S. Karlov Eugene V. Radchenko Yuri K. Grishin Victor B. Rybakov Tamara S. Kuznetsova Vladimir L. Zamoyski Vladimir V. Grigoriev Vladimir A. Palyulin Elena B. Averina 《Molecules (Basel, Switzerland)》2021,26(21)
A convenient synthetic approach to novel functionalized bis(isoxazoles), the promising bivalent ligands of the AMPA receptor, was elaborated. It was based on the heterocyclization reactions of readily available electrophilic alkenes with the tetranitromethane-triethylamine complex. The structural diversity of the synthesized compounds was demonstrated. In the electrophysiological experiments using the patch clamp technique on Purkinje neurons, the compound 1,4-phenylenedi(methylene)bis(5-aminoisoxazole-3-carboxylate) was shown to be highly potent positive modulator of the AMPA receptor, potentiating kainate-induced currents up to 70% at 10−11 M. 相似文献
299.