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931.
A simple one dimensional diatomic chain model is proposed to explain the reflectivity spectra of TmTe as observed by Wardet al. It is suggested that the system undergoes a structural phase transition of order-disorder type at 4.2 K, where the new phase
assumes an anti-ferroelectric type of arrangement of the atoms. The results, we obtained, agree well qualitatively with the
experimental results. 相似文献
932.
Under the conditions of the Polonovsky reaction, N-(2,7-dimethyl-2,7-octadienyl)-N,N-dimethylamine oxide gives 2,7-dimethyl-2,7-octadienal and N-(2,7-dimethyl-2,7-octadienyl)-N-methylacetamide. Under the same conditions, N-(2,7-dimethyl-2,7-octadienyl)-N,N-dietnylamine oxide dihydrate does not undergo the Polonovsky reaction and gives the rearrangement product, O-(1-isopropenyl-5-methyl-5-hexenyl)-N,N-diethylhydroxylamine, and the hydration product, O-[1-(1-hydroxy-1-methyl)ethyi-5-methyl-5-hexenyl]-N,N-diethylhydroxylamine.The work was accomplished under the financial support of the Russian Fund for the Fundamental Research (93-03-4219).Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1588–1590, September, 1993. 相似文献
933.
The peripheral and ADI hopscotch methods are extended to solve problems in two space dimensions with a mixed derivative term. The method is compared numerically with existing hopscotch methods. 相似文献
934.
H. Henry Lamb Bruce C. Gates Helmut Knzinger 《Angewandte Chemie (International ed. in English)》1988,27(9):1127-1144
Metal carbonyls react on metal oxide surfaces to give a wide range of structures analogous to those of known compounds. The reactions leading to formation of surface-bound metal carbonyls are explained by known molecular organometallic chemistry and the functional group chemistry of the surfaces. The reaction classes include formation of acid-base adducts as the oxygen of a carbonyl group donates an electron pair to a Lewis acidic center; nucleophilic attack at CO ligands by basic surface hydroxyl groups or O2? ions; ion-pair formation by deprotonation of hydrido carbonyls to give carbonylate ions; interaction of bifunctional complexes with surface acid-base pair sites such as [Mg2⊕O2?]; and oxidative addition of surface hydroxyl groups to metal clusters. The reactions of surface-bound organometallic species include redox condensation and cluster formation on basic surfaces (paralleling the reactions in basic solution) as well as oxidation of mononuclear metal complexes and oxidative fragmentation of metal clusters by reaction with surface hydroxyl groups. Most supported metal carbonyls are unstable at high temperatures, but some, including osmium carbonyl cluster anions on the basic MgO surface, are strongly stabilized in the presence of CO and are precursors of catalysts for CO hydrogenation at 550 K. 相似文献
935.
936.
G. E. Boyd 《Journal of solution chemistry》1977,6(2):95-109
Osmotic coefficients for aqueous mixtures of sodium chloride with sodiumpara-ethylbenzenesulfonate NapEBS and lithiumpara-ethylbenzenesulfonate LipEBS with NapEBS obtained by the gravimetric isopiestic vapor pressure comparison method are interpreted with the Scatchard neutral-component and with the Pitzer ion-component equations. Ionic and mean ionic activity coefficients for Na+ and Cl– ions and for NaCl, respectively, were also determined with an electrochemical cell. The ±(NaCl) values at constant unit ionic strength,I=1.00, were compared with those computed from osmotic-coefficient measurements. Strong anion-anion interactions were observed in the NaCl-NapEBS mixtures. 相似文献
937.
ONTHEMIXEDPROBLEMSINANEIASTICPIANEWITHPER1ODICCRACKSZhengKe(郑可)(WuhanUniversity)ONTHEMIXEDPROBLEMSINANEIASTICPIANEWITHPER1ODI... 相似文献
938.
Cd~(2+)与乙二醛-双-(2-羟基缩苯胺)所成配合物在水溶液中极不稳定,立即退色,无法测定其吸光度.本文试验了混合增效分析试剂(Triton X-100+PVA+CTMAB)对此体系的增稳、增敏和增溶作用.在此三种增效分析试剂的协同作用下,使体系可稳定20min以上,表观摩尔吸光系数达1.12×10~4 L.mol~(-1)·Cm~(-1),有可能应用于分析实践.并初步探讨了有关机理. 相似文献
939.
Dry chitosan is an excellent candidate for facilitated transport membranes that can be utilized in industrial applications, such as fuel cell operations and other purification processes. This article is the first to report temperature effects on transport properties of CO2, H2, and N2 in a gas mixture typical of such applications. At a feed pressure of 1.5 atm, CO2 permeabilities increased (0.381–26.1 barrers) at temperatures of 20–150 °C with decreasing CO2/N2 (19.7–4.55) and CO2/H2 (3.14–1.71) separation factors. The pressure effect on solubilities and permeabilities were fitted to the extended dual mode model and its corresponding mixed gas permeation model. The dual mode and transport parameters, the sorption heats and the activation energies of Henry's and Langmuir's regimes and their pre‐exponential parameters were determined. The Langmuir's capacity constants were utilized to estimate chitosan's glass transition temperature (CO2: 172 °C, N2: 175 °C, and H2: 171 °C). The activation energies of diffusion in the Henry's law and Langmuir regimes were dependent on the collision diameter of the gases. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2620–2631, 2007 相似文献
940.
Erwin Lutwak 《Geometriae Dedicata》1997,66(1):119-124
The aim of this note is to strengthen and generalize an inequality of Sangwine–Yager regarding means of various quantities associated with the simplices circumscribing a convex body. 相似文献