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921.
Bernard Gillot Jean François Ferriot Abel Rousset 《Journal of Physics and Chemistry of Solids》1976,37(9):857-862
The magnetites substituted for aluminium and chromium show a high conductivity decrease as well as a change in the conduction type under vacuum when passing from the inverse to the normal spinel during substitution. This type of conduction is confirmed by the study of oxygen chemisorption at temperatures close to room temperature. At higher temperatures, volume oxidation is accompanied by a sharp change in conductivity, which differs depending on whether the spinel is inverse or normal. 相似文献
922.
Jean Devillers Jean Roussel Jacques Navech Ramon Burgada 《Magnetic resonance in chemistry : MRC》1973,5(11):511-514
The PMR spectra of the title 1,3,2-oxazaphospholane derivatives present an ABKLX pattern. The subspectral analysis of such a system shows that there are eight solutions. INDOR experiments permit the establishment of the energy diagram and the selection of the correct solution. 相似文献
923.
Using Fourier transform infrared spectroscopy, the ethene yield from the reaction of C2H5 radicals with O2 has been determined to be 1.50 ± 0.09%, 0.85 ± 0.11%, and <0.1% at total pressures of 25, 50, and 700 torr, respectively. Additionally, the rate constant of the reaction of C2H5 radicals with molecular chlorine was measured relative to that with molecular oxygen. (1) A ratio k6/k7 = 1.99 ± 0.14 was measured at 700 torr total pressure which, together with the literature value of k7 = 4.4 × 10?12 cm3 molecule?1s?1, yields k6 = (8.8 ± 0.6) × 10?12 cm3 molecule?1s?1. Quoted errors represent 2σ. These results are discussed with respect to previous kinetic and mechanistic studies of C2H5 radicals. 相似文献
924.
We calculate the production of narrow resonances with even charge conjugation in e+e? annihilation in the quarkonium and vectordominance models. We give unitarity bounds for in terms of and . The electromagnetic production dominates through the neutral current at low energies independent of details of the model. For masses above 10 GeV the situation is reversed. 相似文献
925.
H. C. Beachell Jean C. Peterson Buck 《Journal of polymer science. Part A, Polymer chemistry》1969,7(7):1873-1879
A high molecular weight linear polyurethane was prepared by the polyaddition of equimolar amounts of ethylene glycol and methylene bis(4-phenyl isocyanate). Varying amounts of the labile carbamate protons of the polyurethane backbone were substituted by a number of groups of varying length and composition. The resultant grafted or nitrogen-substituted polyurethanes were then studied viscometrically in both polymer solvent and in a polymer solvent—nonsolvent mixture. The configuration of the nitrogen-substituted polyurethane was found to be dependent upon the number and length of pendent branches. 相似文献
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929.
G. Cosme A. Courau B. Dudelzak B. Grelaud B. Jean Marie S. Jullian D. Lalanne F. Laplanche G. Parrour R. Riskalla Ph. Roy G. Szklarz 《Physics letters. [Part B]》1976,63(3):349-351
The production of multipion events by e+e? annihilation has been measured at centre of mass energies 915,990 and 1076 MeV. Both channels e+e?→π+π?πo and e+e?→π+π?π+π? have been analysed. An energy threshold effect analysed. An energy threshold effect around 919 MeV (mω + mπo) has been evidenced for the π+π?πoπo channel and the cross section is consistent with the quasi two-body process e+e?→ωπo. The cross section for π+π?π+π? is lower by an order of magnitude and increases with the energy. 相似文献
930.
Alain Gaudemer Franois Nief Rene Pontikis Jean Zylber 《Magnetic resonance in chemistry : MRC》1977,10(1):135-145
Conformational analysis using 1H n.m.r. data (δ, 3J and NOE) has been carried out on several derivatives of 2′,3′,-O-isopropylideneadenosine bearing various substituents at positions C-5′, C-8 and N-6. Conformational modifications are assigned to specific interactions between the sugar and purine moieties and also to solvent effects. 相似文献