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991.
Zhang L Cradlebaugh J Litwinienko G Smart BE Ingold KU Dolbier Jr WR 《Organic & biomolecular chemistry》2004,2(5):689-694
A combination of laser flash photolysis and competitive kinetic methods have been used to measure the absolute bimolecular rate constants for hydrogen atom abstraction in water from a variety of organic substrates including alcohols, ethers, and carboxylic acids by the perfluoroalkyl radical, *CF(2)CF(2)OCF(2)CF(2)SO(3)(-) Na(+). Comparison, where possible, of these rate constants with those previously measured for analogous reactions in the non-polar organic solvent, 1,3-bis(trifluoromethyl)benzene (J. Am. Chem. Soc, 1999, 121, 7335) show that the alcohols react 2-5 times more rapidly in the water solvent and that the ethers react at the same rate in both solvents. A transition state for hydrogen abstraction that is more reminiscent of an "intimate ion pair" than a "solvent separated ion pair" is invoked to explain these modest solvent effects. 相似文献
992.
A mathematical framework for translational Brownian motion on hypersurfaces is presented, using an imbedding of the surface and Ito diffusions in the ambient space. This includes a survey of Ito calculus and differential geometry. Computational methods for time correlation functions relevant to spin relaxation studies on curved interfaces are given, and explicit calculations of time correlation functions and order parameters for a Rippled surface are presented. 相似文献
993.
D. T. Asil'bekova S. D. Gusakova A. U. Umarov F. N. Suleimanova D. N. Alavutdinov 《Chemistry of Natural Compounds》1981,16(6):550-553
The presowing irradiation of cotton seeds with pulses of concentrated light (PCL) causes a change in a number of indices of the oil. When the seeds are stored, oxidative processes in them are intensified. In the oil of the harvested seeds some indices are restored.Institute of the Chemistry of Plant Substances of the Academy of Sciences of the Uzbek SSR, Tashkent, and S. V. Starodubtsev Institute of Technical Physics of the Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 777–780, November–December, 1980. 相似文献
994.
Toluene diluted in argon subjected to continuous argon discharge radiation during condensation at 21 K revealed absorptions at 310.5 and 449.6 nm due to benzyl radical, and 317 nm due to a C77H9 radical. A photosensitive 430 nm band, in agreement with photodissociation spectra of the toluene parent cation, is assigned to this species. 相似文献
995.
Summary The structure of the heterobinuclear complex of Ni2+ and [U022]2+ with the tetraanionic ligand derived from the condensation of 1,2-diaminoethane with o-acetoacetylphenol has been determined from diffractometer data and refined to R = 7.2%. The crystals are monoclinic, P21 /a, with = 20.65(2), b = 8.58(1), c = 14.68(2) Å and = 97.78(5); Z = 4. The ligand employed has two different coordination sets of atoms, N2O2 and O2O2, two oxygen atoms being common to both donor sets. In the complex the nickel ion, which is four coordinate but not square planar, is retained in the inner N2O2 chamber, whilst the uranyl ion is incorporated in the outer O2O2 chamber. A molecule of solvent is retained to preserve the preferred seven coordination of uranium. 相似文献
996.
A method for the determination of the dynamic surface tension of surfactant solutions is presented which allows to cover adsorption times down to 10 seconds. This method is based on the determination of the pressure inside two communicating bubbles. There is no deformation of the solution/air interface during the experimental procedure. Hence, in evaluating the kinetic data no surface area enlargement has to be taken into account. An automatically operating procedure should allow to cover adsorption times down to approximately one second and should improve the measuring accuracy substantially. Experimental investigations with aqueous n-decanoic acid solutions using the method proposed provided evidence that decanoic acid is adsorbed by a diffusioncontrolled mechanism. 相似文献
997.
The results of a differential scanning calorimetric study of the transitions involving the various polymorphs of Na2SO4 are described. They are discussed in the light of their crystal structures and also in conjunction with more recently published data regarding these transitions.
Zusammenfassung Die Ergebnisse einer mit Differentialabtastkalorimetrie durchgeführten Untersuchung der Übergänge verschiedener Polymorphe von Na2SO4 werden beschrieben. Sie werden im Hinblick ihrer Kristallstrukturen und im Zusammenhang mit verschiedenen unlängst veröffentlichten Daten bezüglich dieser Übergänge diskutiert.
Résumé On décrit les résultats de l'étude, effectuée par analyse calorimétrique différentielle, des transitions mettant en jeu les diverses formes polymorphes de Na2SO4. Les résultats sont discutés en tenant compte des données récemment publiées sur ces transitions.
. , .相似文献
998.
Polymer films containing a sodium or potassium ion-selective exchanger were coated onto platinum wire and incorporated into a potentiometric arrangement. Comparative results obtained by utilizing different measuring devices, one a conventional pH-meter and the other a field-effect transistor (FET) in series with an electrometer, are discussed. The linear range of either system is comparable with that of other electrochemical techniques. Possible applications of such a device are described. 相似文献
999.
Lipid membranes composed of phosphatidyl choline and cholesterol were interfaced to polyacrylamine hydrogen by Langmuir—Blodgett thin-film deposition. The extent of lipid adsorption to the gel surface was critically dependent on the hydration of the polymer as determined by contact angle measurements. Some electrochemical transducers incorporating the deposited membrane/gel structure responded positively to phloretin and valinomycin. Limitations to the construction of this device are discussed. 相似文献
1000.
Mixed gels of starch and bentonite are investigated in the interval 0.056–0.089 of total solids/water ratio and 0-100% starch in the solids. The bentonite was a sodium calcium bentonite with a Na/Ca ratio of 1.76. In water it forms gels consisting of a network of band-type structures. Starch forms gels through hydrogen bonds between granules and/or amylose and amylopectin present on the external surfaces of granules and/or in fully stretched form. Mixed gels of bentonite and starch were obtained by adding corn starch granules to the already formed bentonite gels and heating the mixture above the Kofler gelatinization temperature. Amylose and amylopectin were adsorbed on strands of band-type structures of mont-morillonite lamellae. Starch gellation, e.g. diffusion of amylose out of the granule, was facilitated in the presence of bentonite. On the other hand, the presence of starch favored delamination of the montmorillonite particle into thinner lamellae. Maximum gelatinization and polymer adsorption were observed for gels with 20% starch and 80% bentonite. Montmorillonite networks formed the continuous phase for 0-80% starch. At higher starch concentrations, montmorillonite flakes were dispersed within the polymer network. Increase in the water content of the gels caused segregation of the bentonite and starch. 相似文献