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81.
We prove that any affine, resp. polarized projective, spherical variety admits a flat degeneration to an affine, resp. polarized
projective, toric variety. Motivated by mirror symmetry, we give conditions for the limit toric variety to be a Gorenstein
Fano, and provide many examples. We also provide an explanation for the limits as boundary points of the moduli space of stable
pairs whose existence is predicted by the Minimal Model Program. 相似文献
82.
Ekaterina A. Shilova Valery P. Perevalov Corinne Moustrou 《Tetrahedron letters》2008,49(21):3453-3457
The novel photochromic [2]rotaxane based on chromene molecule introduced into a crown-containing macrocyclic receptor was synthesized. The photochemical properties of rotaxane could be modified by the complexation of the crown ether moiety. 相似文献
83.
Valery Marenich 《Transactions of the American Mathematical Society》2000,352(10):4451-4468
We prove that a convergence in the Gromov-Hausdorff distance of manifolds with minimal radial curvature bounded from below by 1 to the standard sphere is equivalent to a volume convergence.
84.
P. Yu. Teslenko A. G. Razumnaya V. O. Ponomarenko A. G. Rudskaya A. V. Nazarenko A. S. Anokhin M. V. Avramenko D. I. Levshov M. F. Kupriyanov Yu. I. Yuzyuk 《Physics of the Solid State》2014,56(9):1866-1871
The structures and the dynamic characteristics of the lattices of two compositions of solid solutions of multiferroic BiFeO3 with ferroelectric KNbO3 and antiferroelctric NaNbO3, namely, (1 ? x)BiFeO3-xKNbO3 and (1 ? x)BiFeO3-xNaNbO3, have been studied using X-ray powder diffraction and Raman spectroscopy. For these systems with x = 0.3, 0.5, and 0.7, the symmetry and unit cell parameters at room temperature have been determined. An analysis of the vibrational spectra has revealed sequences of rotational distortions with variations in the concentrations of components. 相似文献
85.
Ivan V. Tikhonov Vasily D. Sen' Leonid I. Borodin Evgeny M. Pliss Valery A. Golubev Alexander I. Rusakov 《Journal of Physical Organic Chemistry》2014,27(2):114-120
Acid‐catalyzed disproportionation of cyclic nitroxyl radicals R2NO? includes the half‐reactions of their oxidation to oxoammonium cations R2NO+ and reduction to hydroxylamines R2NOH. For many nitroxyl radicals, this reaction is characterized by its ~100% reversibility. Quantitative characteristics of acid–base and redox properties of the whole redox triad may be obtained from research of kinetics and equilibrium of this reaction. Here, we have examined the kinetics for the disproportionation of twenty piperidine‐, pyrroline‐, pyrrolidine‐, and imidazoline nitroxyl radicals in aqueous H2SO4, and interpreted it in terms of the excess acidity function X. The rate‐limiting step of this reaction is R2NO? oxidation by its protonated counterpart R2NOH+?. Kinetic stability of R2NO? in acidic media depends on the basicity of nitroxyl group. This basicity is influenced predominantly by protonation of another, more basic group in radical structure, and its proximity to nitroxyl group. The discovered estimates of pK values for radical cations R2NOH+? (from ?5.8 to ?12.0) indicate a very low basicity of nitroxyl groups in all commonly used R2NO?. For the first time, a linear correlation is obtained between the one‐electron reduction potentials of oxoammonium cations and the basicity of nitroxyl groups of related radicals. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
86.
Valery E. Lyubovitskij Thomas Gutsche Ivan Schmidt Alfredo Vega 《Few-Body Systems》2014,55(5-7):447-453
We discuss baryon structure in a soft-wall anti-de Sitter/quantum chromodynamics model. From unified point of view we describe nucleon form factors and the electroproduction of the N(1440) Roper resonance. The Roper resonance is identified as the first radially excited state of the nucleon. The obtained results for helicity amplitudes of the Roper electroproduction are in good agreement with the recent results of the CLAS Collaboration at JLab. 相似文献
87.
The interaction of solid supported liquid films of lipids with levomepromazine is investigated in the present work by voltammetry. It is shown that the levomepromazine penetrates into the films, which results in a readily detectable change of the film permeability to electroactive species. In this respect, possibilities for the employment of supported lipid films as model systems in the research of biomembrane active compounds are briefly discussed. 相似文献
88.
The reconstructive phase transition from the ilmenite-like CdTiO3 modification to the perovskite modification is investigated thoroughly. It is revealed that the reconstructive transition is determined by size effects, results in the formation of the closest packing of the ilmenite CdTiO3 structure, and is irreversible with a decrease in temperature. The perovskite CdTiO3 modification undergoes displacive structural phase transitions at temperatures of 110, 220, and 380°C. The first displacive phase transition is isostructural, whereas the second and third transitions are associated with rotations of oxygen octahedra. 相似文献
89.
The paper is concerned with the finite-element analysis of natural vibrations and hydroelastic stability of two parallel plates interacting with liquid. The influence of the fluid layer thickness on the eigenfrequencies, vibration modes and hydroelastic stability boundary are estimated based on the results of numerical solution of some example problems. The numerical investigation substantiates the existence of various instability modes, the onset of which depends on the combinations of kinematic boundary conditions specified at the plate ends. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
90.
On the basis of some works on persistent centers and weakly persistent centers, in this paper we discuss a generalized version of persistent center and weakly persistent center for complex planar differential systems, in which conjugacy of variables may not be required. We give some complex systems which have a persistent center or weakly persistent center at the origin. Then, we find all conditions of persistent center for cubic systems and all conditions of weakly persistent center for complex cubic Lotka–Volterra system. Relations between complex systems and real ones are given concerning persistent centers and weakly persistent centers. 相似文献