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Koptelov A. A. Milekhin Yu. M. Baranets Yu. N. 《Russian Journal of Applied Chemistry》2009,82(11):2047-2054
Thermal degradation of high-molecular-weight polyethylene is considered from the standpoint of the random break theory. The
quantitative estimations made indicate that the vaporization conditions realized in the experiment exert a decisive effect
on the total conversion rate. The heat of vaporization of macromolecular fragments formed by cleavage of C-C bonds amounts
to approximately a half of the total thermal effect recorded by thermal analysis. The results obtained make it possible to
rationalize some phenomena that were observed experimentally but have not been satisfactorily interpreted previously, and
also to predict the influence of experimental conditions on the course of thermal degradation of polymers. 相似文献
33.
Molchanov A. P. Sipkin D. I. Koptelov Yu. B. Kopf J. Kostikov R. R. 《Russian Journal of Organic Chemistry》2004,40(1):67-78
Thermolysis of 6-aryl-1,5-diazabicyclo[3.1.0]hexanes in the presence of 1,3-dipolarophiles having an unsymmetrically substituted double C=C bond (such as N-arylimides derived from 2-aryl-substituted maleic, citraconic, and itaconic acids, ethyl propynoate, aryl isocyanates, and aryl isothiocyanates) leads to formation of the corresponding 1,3-dipolar cycloaddition products. The reaction is regioselective, and in most cases only one regioisomer is obtained. The addition direction depends on the 1,3-dipolarophile structure, i.e., electronic and steric factors determining the most effective orbital interaction upon approach of the reagent to substrate. 相似文献
34.
Molchanov A. P. Sipkin D. I. Koptelov Yu. B. Kopf J. Kostikov R. R. 《Russian Journal of Organic Chemistry》2003,39(9):1338-1345
Thermolysis of 6-aryl-1,5-diazabicyclo[3.1.0]hexanes in the presence of N-arylmaleimides having a substituent in the ortho position of the aromatic ring leads to predominant formation of the corresponding trans-9-arylperhydropyrazolo[1,2-a]pyrrolo[3,4-c]pyrazole-1,3-diones. 6-Aryl-1,5-diazabicyclo[3.1.0]hexanes react with fumaric acid derivatives in a stereoselective fashion, affording perhydropyrazolo[1,2-a]pyrazoles with a trans,trans configuration. 相似文献
35.
A.A. Semenov C.H. Woo E.A. Koptelov 《Applied Physics A: Materials Science & Processing》2001,73(3):335-340
The random nature of diffusing jumps and cascade occurrence produce stochastic fluctuations of the point-defect fluxes. The
effect of such fluctuations on the kinetics of void growth is investigated in the present paper. It is found that the non-linear
coupling between the stochastic fluctuations and the void sizes may lead to the instability of void evolution within the mean-field
theory, when the sizes of voids and their growth rates are both relatively small. The growth rate of voids becomes dominated
by the stochastic component, causing the smaller voids to shrink away. This effect is investigated in terms of a non-equilibrium
phase transition induced by a purely random stochastic noise. The derived conditions for this non-equilibrium transition are
compared favourably with experimental observations.
Received: 5 June 2000 / Accepted: 9 October 2000 / Published online: 21 March 2001 相似文献
36.
A. A. Alekseev A. A. Bergman A. I. Berlev E. A. Koptelov B. F. Samylin A. M. Trufanov B. I. Fursov V. S. Shorin 《Physics of Atomic Nuclei》2008,71(8):1351-1360
The cross section for 236U fission in the neutron-energy range E n = 0.001–20 keV was measured by using the INR RAS (Institute of Nuclear Research, Russian Academy of Sciences, Moscow) LSDS-100 neutron spectrometer of the lead slowing-down spectrometer type. The resonance fission areas of the resonances at 5.45 eV and 1.28 keV were found, and the fission widths of these resonances were evaluated. The cross section for the 238U(n, f) fission process was measured, and the threshold sensitivity of the LSDS-100 to small values of fission cross sections was estimated. The well-known intermediate structure in the cross section for the neutron-induced subbarrier fission of 236U was confirmed. 相似文献
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38.
Potential of thermal analysis as applied to studying the kinetics of thermal degradation of polymers
A. A. Koptelov I. A. Koptelov A. A. Rogozina E. S. Yushkov 《Russian Journal of Applied Chemistry》2016,89(9):1454-1460
The kinetics of thermal degradation of low-density polyethylene was studied by TGA and DSC at heating rates from 0.5 to 40 deg min–1. Causes of significant discrepancies in the published effective kinetic constants of the overall reaction of thermal degradation of the polymers, determined using different experimental methods and different data treatment procedures, were analyzed. The possibility of using random break model as an alternative approach to describing polymer thermal degradation curves obtained by thermal analysis methods was demonstrated by the example of polyethylene. 相似文献
39.
The thermal opening of the diaziridine ring in 1-methyl-and 1,3,3-trimethyl-1,3,4,8b-tetra-hydro[1,2]diazirino[3,1-a]isoquinolines
in the presence of N-arylmaleimides leads to the predominant or exclusive formation of the trans isomers of the products of
1,3-dipolar cycloaddition. In the absence of dipolarophile, the conversion of the starting diaziridines is incomplete over
the same time period, while the thermolysis products are N-[3,4-dihydro-2(1H)-isoquinolyl]-and N-[3,3-dimethyl-3,4-di-hydro-2(1H)-isoquinolyl]-N-methyleneamines
formed as the result of isomerization of intermediate labile azomethineimines.
Dedicated to the memory of A. A. Potekhin.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 1071–1079, July, 2008. 相似文献
40.
S. P. Kuznetsov I. V. Meshkov R. A. Sadykov V. S. Litvin Yu. A. Lapushkin A. A. Alekseev E. A. Koptelov 《Bulletin of the Lebedev Physics Institute》2013,40(9):245-250
The elements of multifunctional neutron spectrometer designed to simultaneously determine the parameters of atomic and supra-atomic structure and the dynamic parameters of the substance in a condensed state were tested. The neutron spectrum was measured by a direct-beam detector placed in the sample position on a 20-meter sample-source path length. Diffraction patterns of industrial diamond powder were obtained in a wide range of transmitted pulses. The resolutions of back-scattering and high-intensity diffractometers were determined. 相似文献