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81.
Kolesnikova Inna Nikolaevna Kuznetsov Vladimir Vladimirovich Goloveshkin Alexander Sergeevich Chegodaev Nikolai Andreevich Makhova Nina Nikolaevna Shishkov Igor Fedorovich 《Structural chemistry》2021,32(6):2303-2312
Structural Chemistry - A new diaziridine derivative with two bicyclic diaziridine-containing moieties in one molecule,... 相似文献
82.
D. M. Kheiker M. V. Kovalchuk Yu. N. Shilin V. A. Shishkov S. N. Sulyanov P. V. Dorovatovskiĭ A. A. Rusakov 《Crystallography Reports》2007,52(2):358-364
Design modifications made in the initial project of the Belok station in the Sibir-2 storage ring and the alignment and calibration methods are considered. The main operating parameters of the station are reported. Protein single crystals in a capillary at T = 293 K and without a capillary at T = 95 K, powders (angular resolution Δ2? = 0.04°), and nanocrystalline Na and Cl2 precipitates (sizes, shape, and orientation) in electron-irradiated NaCl crystals have been investigated. The problem of focusing of a short-wavelength synchrotron radiation beam with sagittal bending of the second crystal in the double-crystal monochromator at a limited source-to-sample distance is solved in the Belok project. 相似文献
83.
84.
In an unbounded noncylindrical domain G we consider classical solutions of general second order linear parabolic equations satisfying a Dirichlet boundary condition on the parabolic part of the boundary of G. On the basis of the maximum principle we single out classes of uniqueness of such solutions depending on the geometry of the domain G which are analogs of the classes of A. N. Tikhonov and S. Täcklind.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 42, No. 7, pp. 924–930, July, 1990. 相似文献
85.
Denis N. Ksenafontov Natalia F. Moiseeva Anatoliy N. Rykov Igor F. Shishkov Heinz Oberhammer 《Structural chemistry》2013,24(1):171-179
The gas-phase structure and conformational properties of carphedon (C12H14N2O2, phenylpiracetam, 2-oxo-4-phenyl-1-pyrrolidineacetamide) have been determined by gas electron diffraction (GED) and quantum chemical calculations (B3LYP and MP2 with 6-31G and cc-pVDZ basis sets). Since quantum chemical calculations demonstrate that the orientation of the acetamide group is fixed by a strong intramolecular N–H(amide)···O(pyrrolidone) hydrogen bond, the number of possible conformers is reduced considerably. Depending on the conformation of the pyrrolidine ring, envelope with out-of-plane C4 atom and acetamide group on the same side of the plane (“+”) or envelope with C4 and acetamide group on opposite sides (“?”), and on the orientation of the phenyl ring, axial (Ax), or equatorial (Eq), four relevant conformations, Ax?, Ax+, Eq?, and Eq+, exist. According to both quantum chemical methods (B3LYP and MP2 with cc-pVDZ basis sets) these four conformers differ by less than 2 kcal/mol in free energies. However, the two methods predict different relative free energies. The GED data were analyzed with different models. With a single-conformer model the best fit of the experimental GED intensities (agreement factor R f = 4 %) is obtained with the Ax+ conformer. Using a two-conformer model the fit improves considerable for a 50(11):50(11) mixture of Ax? and Eq+ conformers (R f = 2.7 %). No further improvement is obtained with a three-conformer model and large uncertainties for relative contributions occur. The geometric parameters of gaseous carphedon are compared with those in the crystal phase, where two molecules are connected by two intermolecular N–H···O hydrogen bonds, and with gas-phase values of piracetam. 相似文献
86.
Dorofeeva Olga V. Marochkin Ilya I. Karasev Nikolai M. Shishkov Igor F. Oberhammer Heinz 《Structural chemistry》2011,22(2):419-425
Structural Chemistry - B3LYP and MP2(Full) calculations with large basis sets predict the planar equilibrium structure of barbituric acid and reveal large amplitude ring puckering motion which is... 相似文献
87.
Mathematical Notes - Singular blow-up regimes are studied for a wide class of second-order quasilinear parabolic equations. Energy methods are used to obtain exact (in a certain sense) estimates of... 相似文献
88.
The rate constants of the decay of carbocation generated in the photolysis of 2,2,4,6-tetramethyl-1,2-dihydroquinoline and the composition of reaction products were studied as a function of solvent composition in the mixtures H2O–ROH and MeOH–ROH (R = Et, n-Pr, and i-Pr). The rate constants of carbocation decay in alcohols are more than 20 times higher than the corresponding rate constants in water. As follows from the composition of the products obtained in the photolysis in the alcohol–water mixtures, MeOH is only 1.4 times more reactive than water, and EtOH and n-PrOH are even less active than water. The inconsistency in the product composition in the mixtures and the values of the observed rate constants in these solvents was explained by the two-step mechanism of the reaction: the reversible formation of an adduct of the carbocation with the solvent components and subsequent proton transfer to the solvent to form the final product, with the first step determining the product composition and the second step determining the rate of carbocation decay. The relative rate constants of alcohols and water were determined for the two steps. The preferred solvation of the carbocation with water also contributes significantly to the reaction kinetics and the product composition in the water–alcohol solutions. 相似文献
89.
D. M. Kheiker V. A. Shishkov Yu. N. Shilin A. A. Rusakov P. V. Dorovatovski N. V. Zhavoronkov 《Crystallography Reports》2007,52(4):740-742
A new crystal monochromator is designed and tested. The crystal monochromator allows for the use of a large curvature of the sagittal bending and makes it possible to focus synchrotron radiation at a short wavelength and a limited distance from the synchrotron radiation source to the sample. 相似文献
90.
E. N. Il’icheva A. V. Klushina N. B. Shirokova N. N. Ustanov A. G. Shishkov 《Technical Physics》1997,42(6):615-618
An experimental study is made of the effect of an in-plane field H
p
of various orientations on the domain structure and shape of the hysteresis loops of epitaxial iron garnet films with the
(210) orientation. The characteristic of the magnetization reversal process (in fields somewhat lower than the anisotropy
field) is taken to be the critical fields H
p1, H
p2, and H
p3, for which the magnetization reversal processes is interrupted at distinct stages. A method is proposed for constructing
the phase diagram of the magnetic states of films, using measurements of the critical fields H
p
for different amplitudes of the magnetization reversal field H
z
. Two directions in the plane of the film are determined with an accuracy of a fraction of a degree from the hysteresis loops,
where in the corresponding field Hp the transition from a single-domain state to a multidomain state occurs as a second-order phase transition. The characteristic
changes in the shape of the hysteresis loop are consistent with the features in the reorganization of the domain structure
of the (210) film. The preferential orientations of the stripe domain structure of the samples are determined relative to
the crystal axes as determined by x-ray methods.
Zh. Tekh. Fiz. 67, 32–35 (June 1997)
Deceased 相似文献