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991.
G. S. Krinchik E. E. Chepurova I. M. Kuznetsova N. V. Pronina 《Russian Physics Journal》1989,32(11):871-874
We present results of magnetooptical investigations of bismuth-containing ferrite-garnet films with the easy axis of magnetization parallel to the specimen surface. Measurements were conducted for incident light with energies in the range 1.5–3.2 eV for transverse [equatorial Kerr effect (EKE)] and for longitudinal [meridional intensity effect (MIE)] magnetizations of thin-layer specimens. It is shown that the EKE differs from zero when the films are opaque, and it is established that the EKE peak in the region 2.8 eV increases with increasing bismuth concentration. For longitudinal magnetization, conditions for observing magnetooptical interference were realized. The experimental curves agree well with the theoretical ones.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 10–14, November, 1989. 相似文献
992.
N. B. Brandt Zh. T. Ismailov V. A. Kul'bachinskii S. A. Lapin S. M. Chudinov 《Russian Physics Journal》1989,32(11):889-898
A new method is proposed for determining the magnetic characteristics (magnitude and sign of the exchange interaction energy and the average size of clusters of magnetic ions) of dilute solid solutions of semimagnetic semiconductors at low temperatures based on oscillation measurements. The method makes it possible to find the magnetic characteristics of the indicated systems at temperatures between the point of the transition into the spin glass state and the temperature corresponding to the characteristic binding energy of magnetic atoms in clusters, for which standard methods based on the measurement of the magnetic susceptibility are not effective. The method is used to study the character of the exchange interaction in the system of solid solutions Hg1–xMnxSe as a function of their composition as well as under conditions of hydrostatic compression. To this end the oscillations of the magnetoresistance (Shubnikov-de Haas (SH) effect) in single-crystalline samples of Hg1–xMnxSe in the region of compositions 0.001 x 0.23 in magnetic fields H up to 65 kOe at temperatures T = (0.4–20) K and pressures up to 16 kbar were studied.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 29–39, November, 1989. 相似文献
993.
Effect of methanol dilution on H-ZSM-5 zeolite deactivation in the process of light olefin formation
A. .A. Cichowlas P. T. Wierzchowski L. W. Zatorski 《Reaction Kinetics and Catalysis Letters》1986,32(2):341-346
Conversion of methanol in the presence of H2O, O2, H2, CO, CO2 and He was studied at 733 K on H-ZSM-5 zeolite. The effect of diluent on the selectivity to light olefins and resistance to coking of H-ZSM-5 were observed. Among the diluents studied only water exerts a promoting effect on prolonged activity of the catalyst. Some explanations of the deactivation process are given.
H2O, O2, H2, CO, CO2 He H-ZSM-5 733K. H-ZSM-5. . .相似文献
994.
Quantum dynamics of H2 formation on a graphite surface through the Langmuir Hinshelwood mechanism 总被引:1,自引:0,他引:1
We have studied the formation of the H2 molecule on a graphite surface, when both H atoms are initially physisorbed. The graphite surface is assumed to be planar, and a model potential is obtained in a semiempirical way to reproduce the experimental properties of H physisorption on graphite. The reaction probability has been computed in the case when the angular momentum of the relative H-H motion lies parallel to the surface plane. Three-dimensional wave packet calculations have been performed for collision energies ranging from 2 to 50 meV. It is shown that the reaction occurs with a significant probability and produces the H2 molecule with a considerable amount of vibrationnal energy. A simple mechanical model is presented, where desorption of the nascent H2 molecule results from two successive binary elastic collisions. 相似文献
995.
Yu. A. Yuzhelevskii E. G. Kagan V. N. Frolov A. L. Klebanskii 《Chemistry of Heterocyclic Compounds》1970,4(1):24-28
The influence of the number of 3, 3, 3-trifluoropropyl(methyl)siloxane links (/) in the cyclotetrasiloxanes mD4-m, where D represents the dimethylsiloxane link and m=0–4, on the rearrangement of these compounds in acetone solution under the action of sodium siloxanolate has been studied. The rearrangement takes place with the formation of a linear polysiloxane the degradation of which yields, in addition to the initial ring, cyclosiloxanes with a different structure. The rate of rearrangement of mD4-m and of the formation of a linear polysiloxane rises with an increase in m from 0 to 3. The equilibrium concentration of the linear polysiloxane formed from mD4-m is inversely proportional to m. Results have been obtained on the kinetics of the formation of the cyclosiloxanes mDn, where m=0–5, n=0–5, and m+n=3–6, in the rearrangement of the rings D3, 2D2, 3D, and 4. The reactivity of the siloxane links rises in the sequence (CH3)2Si-O-Si(CH3)2 < (CF3CH2CH2)-(CH3) Si-O-Si(CH3)2 <(CF3CH2CH2) (CH3)Si-O-Si(CH3) (CH2CH2CF3) . Because of the negative inductive effect transferred through the siloxane links, the 3, 3, 3-trifluoropropyl groups strongly activate the siloxane ring with respect to nucleophiiic reagents.For part I, see [3]. 相似文献
996.
Commercial grade 2-butyne-1,4-diol has been used in electroplating for several years. In laboratory experiments, its presence in the electrolyte increases the current efficiency of zinc electro-winning. Its chemical behaviour in solution is not well known. The present paper indicates that the brownish technical grade 2-butyne-1,4-diol contains the monomer, the dimer and some trimer. Pure monomeric 2-butyne-1,4-diol is a white solid obtained by evaporation of the technical grade product. The monomer is slowly transformed into dimer and possibly into a trimer when dissolved in water. Various analytical techniques were used in the study of this system. Factor analysis with column cross-validation was applied to chromatographic data to help in the resolution of the system. 相似文献
997.
Deprotection of cyclic acetals and oxidative desilylation of trimethylsilyl ethers into the corresponding carbonyl compounds with -picolinium chlorochromate (-PCC) under nonaqueous conditions at room temperature is described. Oxidation of aldehydes to carboxylic acids was not observed in any case. 相似文献
998.
N. S. Prostakov N. M. Mikhailova Yu. M. Talanov 《Chemistry of Heterocyclic Compounds》1970,6(10):1266-1268
The position of the pyridine ring is arylated by reaction of 2,5-dimethyl-4-phenylpyridine with phenyllithium and p-tolyllithium. Destructive oxidation of the diaryl-substituted pyridines primarily affects the pyridine ring.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1359–1361, October, 1970. 相似文献
999.
M. G. Voronkov N. N. Vlasova S. A. Bolshakova S. V. Kirpichenko 《Journal of organometallic chemistry》1980,190(4):335-341
The hydrosilylation of mono- and di-alkenyl sulphides of the type RS(CH2)nCH=CH2 (R = C2H5, CH2=CH, CH2=CHCH2, C3H7, n = 0, 1 and 4) by triethyl- and triethoxy-silane, catalyzed by H2PtCl6·6 H2O, (Ph3P)3RhCl and (PhCN)2PdCl2·Ph3P, has been studied. The addition of hydrosilane to the double bond of alkenyl sulphide leads to a mixture of two isomeric monoadducts. The hydrosilane can cleave the C---S bond of the initial sulphides giving the corresponding derivatives of thiosilanes, X3SiS(CH2)nCH=CH2 (X = C2H5, C2H5O). Hydrosilylation of alkenyl sulphides is accompanied by some side reactions such as dehydrocondensation, reduction and polymerization. The effect of the catalyst nature, the structure of hydrosilane and alkenyl sulphide on the reaction route has been investigated. 相似文献
1000.
Enthalpies of solution have been measured from 5 to 85°C for aqueous tetraethyl- and tetrapropylammonium bromides, and the integral heat method is employed to evaluate
for these electrolytes over a wide temperature range. Data taken from the literature have been used to evaluate
for aqueous Bu4NBr over a similar temperature range. These data, along with similar data for Me4NBr, previously reported, have been used to evaluate absolute ionic heat capacities. While the absolute values agree only qualitatively with two other methods of division, the temperature dependences of the three methods essentially agree up to 65°C. Heat capacities due to structural effects on the solvent, obtained by subtracting the inherent heat capacities of the ions, are extraordinarily positive for all four tetraalkylammonium ions and have negative temperature coefficients, indicating that all four ions, including the tetramethylammonium ion, are structure-making ions. 相似文献