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141.
S. V. Stovbun S. M. Lomakin A. I. Shchegolikhin A. A. Skoblin V. P. Mel’nikov 《Russian Journal of Physical Chemistry B, Focus on Physics》2018,12(1):36-45
Thermogravimetry is used to study the thermodestruction of nitrocellulose (NC) with various nitrogen contents at various heating rates. At high degrees of nitration and high heating rates of the sample, the reaction occurs in an explosion mode with a threshold of its weight loss depending on the temperature. To explain this behavior, it is assumed that the nitration of cellulose gives rise to structural stresses, which weaken the covalent bonds in it by ~37 kJ/mol (at a nitrogen content of ~13%). This process apparently involves two different mechanisms of weight loss during heating: (a) conventional thermal destruction of NC macromolecules through the rupture of covalent bonds (with k0 = 1013 s?1, E = 150.2 kJ/mol, and n = 1) at heating rates of up to 10 K/min and nitrogen content in NC of up to 9%; (b) Zhurkov’s thermofluctuational mechanism of the destruction of strained macromolecules, characterized by a sharp (threshold) dependence of the weight loss on the heating rate, which is operative at heating rates above ~4 K/min and high (>13%) nitrogen contents and at 20 K/min and a low (~9%) nitrogen content. Under conditions of rapid heating, ~10–20 K/min, the work done by stressed states to overcome the potential barrier to the rupture of covalent bonds causes an increase in the decomposition rate by a factor of 2000. The observed threshold pattern of weight loss during the thermodestruction of NC explains the long-known critical dependence of the properties of NC used to manufacture propellants on small changes in the nitrogen content. 相似文献
142.
Vladimir V. Rybakov Mehmet Terziler Vitaliy Remazki 《Mathematical Logic Quarterly》2000,46(2):207-218
We study the problem of finding a basis for all rules admissible in the intuitionistic propositional logic IPC. The main result is Theorem 3.1 which gives a basis consisting of all rules in semi‐reduced form satisfying certain specific additional requirements. Using developed technique we also find a basis for rules admissible in the logic of excluded middle law KC. 相似文献
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144.
Effects of fatty acyl chain length,double‐bond number and matrix on phosphatidylcholine responses in matrix‐assisted laser desorption/ionization on an Orbitrap mass spectrometer
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Vitaliy Chagovets Miroslav Lísa Michal Holčapek 《Rapid communications in mass spectrometry : RCM》2015,29(24):2374-2384
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The influence of a nonuniform field of internal stresses and the generation of a dislocation loop by a Frank-Read source operating under the action of an alternating load is investigated by computer simulation. It is shown that the field of a tilt boundary affects every stage of development of a dislocation loop until its closure. The influence of the boundary field is determined by the ratio between the length of the source and the space scale of the field nonuniformities. It is established that not only the value of the dynamic yield point but also the form of its dependence on the ultrasonic frequency can vary in an internal stress field.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 35–39, February, 1985. 相似文献
147.
Vitaliy Gerasimov Vladimir Mitsa Yuriy Babinets 《Fresenius' Journal of Analytical Chemistry》1996,355(3-4):404-405
The depth dependence of Raman spectra of a-GeS2-type films having a different optical thickness (/4 and /2) and their refractive index profile have been investigated. The model of a layered-inhomogeneous structure of films has been proposed. There have been distinguished three regions: near-surface region (up to 50 Å), central part and transition film-substrate region (up to 300 Å). 相似文献
148.
The depth dependence of Raman spectra of a-GeS(2)-type films having a different optical thickness (lambda/4 and lambda/2) and their refractive index profile have been investigated. The model of a layered-inhomogeneous structure of films has been proposed. There have been distinguished three regions: near-surface region (up to 50 A), central part and transition film-substrate region (up to 300 A). 相似文献
149.
Nesterenko V Putt KS Hergenrother PJ 《Journal of the American Chemical Society》2003,125(48):14672-14673
The selective induction of death in cancer cells is a major challenge in modern medicine. In this communication we describe the synthesis of an 88-membered combinatorial library, and the subsequent evaluation of these compounds for their ability to selectively induce apoptosis in cancerous cells. A compound was identified from the library that induces apoptosis in U-937 and HL-60 cell lines. This compound is a remarkably selective pro-apoptotic agent for these cancer cell lines, as it does not induce significant death in noncancerous white blood cells, even at concentrations as high as 1000 muM. 相似文献
150.