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21.
22.
A. V. Zakharov 《Russian Physics Journal》1987,30(12):1015-1019
The general solution of Einstein's equations with the energy-momentum tensor of an ideal dust in the plane-symmetric case is used to obtain the generalization of the solutions for scalar perturbations in a spatial-plane Friedman universe. It is shown that, in order for plane accumulations of matter with a density much greater than the mean density of the matter in the Universe to exist in the Universe at the present time, perturbations of the density are necessary at the time of recombination, (/)p 10–4.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 20–24, December, 1987. 相似文献
23.
V. P. Zvolinskii P. I. Zakharov V. K. Shevtsov A. V. Varlamov V. G. Pleshakov G. A. Vasil'ev N. S. Prostakov 《Chemistry of Heterocyclic Compounds》1978,14(2):200-203
The dissociative ionization of 4-azafluorene and its methyl and phenyl derivatives was investigated. The relative intensity of the [M — CH3]+ ion peak depends on the position of the CH3 group in the 4-azafluorene ring. It was established that the loss of an RCN particle (R=H, CH3, and C6H5) for unsubstituted 4-azafluorene takes place from the M+ and [M — H]+ ion, exclusively from the [M — H]+ ion for the methyl-substituted compounds, and from the [M — H]+ and [H — 2H]+ fragments for the phenyl-substituted derivatives. Randomization of the deuterium ions in the 9,9-d2-4-azafluorene molecular ion was observed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 246–250, February, 1978. 相似文献
24.
N. S. Prostakov A. V. Varlamov B. N. Anisimov N. M. Mikhailova G. A. Vasil'ev P. I. Zakharov M. A. Galiullin 《Chemistry of Heterocyclic Compounds》1978,14(9):997-1003
A number of tertiary aza-9-fluorenols were obtained from 4- and 2-azafluofenones and were subjected to dehydration in order to synthesize the previously unknown 9-methyleneazafluorenes. The corresponding 9-methyleneazafluorenes and their polymers were obtained simultaneously in relatively stable form from both pyridine-ring-substituted and -unsubstituted 4-aza-9-fluorenols and from 1,3-diphenyl-2-aza-9-fluorenol. On the basis of an analysis of the mass spectrum of the polymer obtained from 9-methylene-4-azafluorene it was concluded that it is evidently isolated in the form of two dimers — dispiro [bis (4-aza-9-fluorene)-1, 3-cyclobutane] and the analogous product of dispiro addition with a 1,2-substituted cyclobutane ring. Condensation of the corresponding azafluorenes with benzaldehyde gave their 9-benzylidene derivatives in the form of geometrical isomers, the structures of which were established on the basis of the PMR spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1234–1240, September, 1978. 相似文献
25.
V. A. Zamureenko N. A. Klyuev B. V. Bocharov V. S. Kabanov A. M. Zakharov 《Chemistry of Natural Compounds》1990,25(5):549-551
The composition of the essential oil of wild bergamot bee balm introduced into the Krasnodarsk Krai has been analyzed by chromatomass spectrometry. The essential oil contains 34 components of which the main ones are -pinene (3.5%), -pinene (2.9%), -terpinene (1.7%), p-cymene (32.5), an aliphatic aldehyde (6.3%), sabinene hydrate (1.9%), -caryophyllene (1.1%), the methyl ether of carvacrol (5.5%), citronellyl acetate (1.6%), thymol (12.6%), and carvacrol (24.0%). The compounds were identified on the basis of their mass-spectrometric characteristics and arithmetical retention indices.A. N. Severtsov Institute of Animal Evolutionary Morphology and Ecology, Academy of Sciences of the USSR, Moscow. All-Union Scientific-Research Institute of Drugs, Moscow. Translated from Khimiya Prirodnykh Soedinenii, Vol. 5, pp. 646–649, September–October, 1989. 相似文献
26.
Crich D Mataka J Zakharov LN Rheingold AL Wink DJ 《Journal of the American Chemical Society》2002,124(21):6028-6036
A series of four S-allyl D-thiopyranosides, alpha- and beta-manno and xylo, were oxidized with MCPBA at low temperature to give seven of the eight possible sulfoxides, whose configuration at sulfur was determined either directly by X-ray crystallography or by correlation with closely related structures. For the axial thioglycosides oxidation leads very predominantly to the (R)(S)-diastereomer in the xylo series and exclusively so in the manno series; the configuration at C2 is of little importance in determining the stereoselectivity of oxidation of axial thioglycopyranosides. In the equatorial series the configuration at C2 has a significant effect on the outcome of the reaction as, although both series favored the (S)(S)-sulfoxide, selectivity was significantly higher in the case of the beta-mannoside than of the beta-xyloside. The two alpha-xylo sulfoxides have different conformations of the pyranoside ring with the (R)(S)-isomer adopting the (1)C(4) chair and the (S)(S)-diastereomer the (4)C(1). Each pair of diastereomeric sulfoxides was thermally equilibrated in C(6)D(6) and in CD(3)OD. In the mannose series the kinetic isomers are also thermodynamically preferred. In the xylose series, on the other hand, the nature of the thermodynamic isomer in both the alpha- and beta-anomers is a function of solvent with a switch observed on going from C(6)D(6) to CD(3)OD. The results are rationalized in terms of the exo-anomeric effect, steric shielding provided by H3 and H5 in the axial series, the interaction of the C2-O2 and sulfoxide dipoles, and increased steric interactions on hydrogen bonding of the sulfoxides to CD(3)OD. 相似文献
27.
I. I. Zakharov O. V. Voroshina A. N. Startsev 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2006,80(7):1083-1087
The density functional theory (DFT) with the B3P86 hybrid exchange-correlation functional was used to calculate the molecular and electronic structure of the Mo12S24 macromolecule as a single MoS2 layered structure slab. Calculations with geometry optimization are indicative of insignificant relaxation of the coordinatively unsaturated Mo and S atoms, which corresponds with the literature DFT data on the MoS2 single slab obtained with periodic boundary conditions. The calculated forbidden band width (0.85–0.98 eV) is comparable with its experimental value (1.30 eV) and the results of DFT calculations of MoS2 with periodic boundary conditions (0.89 eV). An analysis of the electronic state of the surface Mo centers in the Mo12S24 macromolecule showed that these centers were reduced to a greater degree than the Mo(IV) atoms in the bulk. The adsorption complex between the Mo12S24 macromolecule and six H2S molecules was calculated to characterize the adsorption ability of the coordinatively unsaturated Mo centers. The structure and energy characteristics of the adsorption complex corresponded to weak donor-acceptor interaction between the π lone pair of H2S and the surface (reduced) Mo centers. The suggestion was made that the active center of the catalytic cycle of thiophene hydrodesulfurization should induce the oxidative addition of H2 followed by the occlusion of hydrogen into the MoS2 matrix. 相似文献
28.
A. V. Gavrilov A. A. Druzhinin K. I. Zakharov V. A. Ishutin S. A. Nemkov I. A. Pushkin 《Journal of Analytical Chemistry》2005,60(11):1029-1034
It was found that alkaline solutions of luminol exhibit chemiluminescence in the presence of p-nitrobenzaldehyde (p-NBA), hemin, and cyanide ions. Air oxygen dissolved in the solutions is an essential component of the process. The kinetics of luminol chemiluminescence in the presence of p-NBA, hemin, and cyanide ions indicates the catalytic nature of the process. A scheme was proposed for the series of reactions resulting in chemiluminescence and generated by superoxide radicals formed in the p-NBA-catalyzed reaction between hemin-activated air oxygen and hydrated p-NBA species. A procedure was developed with a determination limit of (1.0 ± 0.3) × 10?7 mg/mL (n = 5, P = 0.95) for cyanide ions. 相似文献
29.
In conclusion, let us note the principal results of the calculation.
Institute of Catalysis, Siberian Branch, Russian Academy of Sciences. Translated from Zhurnal Strukturnoi Khimii, Vol. 33, No. 2, pp. 35–41, March-April, 1992. 相似文献
1. | On a clean Ni(100) surface, only molecular adsorption of water is realized. Partial dissociation of H2O is thermodynamically allowed process; however, dissociation of water is impossible because of kinetic limitations. |
2. | Modification of the nickel surface by oxygen stabilizes the donor-acceptor pair (H2O/O) on the surface and removes the kinetic limitation in decomposition of water, through a substantial reduction of the activation energy of dissociation. |
3. | The promoting role of oxygen is manifested in an increase in the nonuniformity of electron density on the nickel surface in the vicinity of the [Ni]–OH2 bond, which makes it possible to open up a new channel of the reaction in which a high degree of energy compensation in the water dissociation reaction is possible. |
30.