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61.
A multiply charged ion source based on E.C.R. heating is described and abundances for xenon ions up to Xe13+ are given. 相似文献
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A. A. Geller A. G. Yereshchenko Zh. A. Zgibneva M. V. Polovnikova 《Journal of polymer science. Part A, Polymer chemistry》1974,12(10):2327-2335
The kinetic and thermodynamic specific features of the process of heterogeneous alkaline saponification of the copolymer of acrylonitrile (92.2%), methyl acrylate (6.3%), and sodium monoithaconate (1.5%) were investigated. Chemical and infrared spectroscopic methods reveal that the saponification of the nitrile groups of copolymer of acrylonitrile proceeds faster to yield amide groups and then slower to yield carboxylate groups. The order of both stages of the process with respect to the accumulation of the respective groups was evaluated. The dependence of the rate of saponification on the packing density of the structural units was demonstrated. With increasing conversion, the fiber structure becomes looser, as demonstrated by density and sorption investigations. If acrylonitrile copolymer is treated with alkali, the carboxylate groups in the polymer substrate accumulate as a result of saponification of the ester groups of the copolymer, while the nitrile groups are predominantly transformed into the amide groups. If the degree of conversion (with respect to the CN groups) is higher than 62.7%, the copolymer abruptly suffers a marked change in its mechanical properties and gradually dissolves. The products of partial saponification of copolymer were investigated by thermomechanical methods and DTA. The polycyclization of the polymer substrate was found to proceed at a temperatures which decreases as the content of the amide groups increases. 相似文献
64.
Chemistry of singlet oxygen. XVIII. Rates of reaction and quenching of alpha-tocopherol and singlet oxygen 总被引:4,自引:0,他引:4
Abstract —α-Tocopherol scavenges singlet oxygen (produced by methylene blue photosensitization in methanol) by a combination of chemical reaction (4.6 times 107M-1s-1) and quenching (6.2 times 108M-1 s-1). The total rate of scavenging (6.7 times 108 M-1s-1) makes it an effective protective agent against photooxidation mediated by singlet oxygen. 相似文献
65.
Geller AM Stedile FC Peralba Mdo C Pizzolato TM Dos Santos JH 《Journal of colloid and interface science》2005,288(1):45-54
Silica (350 m(2) g(-1)) was chemically modified with Cp2ZrCl2 and (nBuCp)2ZrCl2 by grafting. Hybrid silica bearing surface indene groups was synthesized by the sol-gel method, followed by metallation with ZrCl(4)2THF. The resulting phases were characterized by Rutherford backscattering spectrometry (RBS), 13C and 29Si magic angle spin nuclear magnetic resonance, X-ray photoelectron spectroscopy, and diffuse reflectance infrared Fourier transform spectroscopy. According to RBS measurements, metal content was 0.2- to 0.3-wt% Zr/SiO2 for the grafted systems and 4.5-wt% Zr/SiO2 for the phase prepared by the sol-gel method. The solid phases were evaluated for the adsorption/preconcentration of lindane and heptachlor epoxide from aqueous solution. For comparative reasons, the commercial LC-18 phase was also evaluated. Analyte concentration was monitored by gas chromatography electron capture detection. For the grafted phases, the coordination sphere around the metal center seems not to influence the adsorption/desorption properties of these phases vis-a-vis the studied analytes. In the case of the phases prepared by the sol-gel method, recovery results were comparable to those observed for LC-18. Experiments using ZrO2 and ZrO2/SiO2 phases led to lower recovery results. 相似文献
66.
William Geller Zhenhua Zhang 《Proceedings of the American Mathematical Society》1998,126(12):3709-3713
The entropy of a permutation is the least topological entropy of any continuous interval map having an invariant set which is shuffled according to the permutation. For each , we identify the maximal entropy permutations of size .
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Laser Physics - Low intensity continuous wave and pulsed emission modes laser is used in treating many diseases and the resulting biostimulative effect on tissues has been described, yet the... 相似文献
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N. M. Geller A. G. Ivanov L. B. Nadezhdina V. V. Shamanin L. A. Shibaev A. V. Gribanov 《Russian Journal of Applied Chemistry》2008,81(8):1398-1402
New silicon-containing poly(salicylidene azomethines) were prepared by polycondensation of di-or tetrasalicylidene derivatives of aromatic di- or tetraamines. The spectral data suggest the occurrence of noncovalent transannular donor-acceptor interaction N→Si providing “nonclassical” conjugation. 相似文献