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931.
M. Schnitzer C. Tarnocai P. Schuppli R. Hempfling R. Müller H.-R. Schulten 《Fresenius' Journal of Analytical Chemistry》1990,337(8):882-884
Summary The analytical potential of the combination of solid state NMR and soft ionization mass spectrometry for direct investigations of complex organic matter in soils without chemical pretreatment is demonstrated. The results show that the Oh horizon of a Gleysolic paleosol (±45 Ma) from the Canadian Arctic consists mainly of components of cuticular waxes which include 10-nonacosanol, C15–C36 n-fatty acids, C44–C75 n-alkyl monoesters and C60–C76 diesters. It is likely that these waxes originated from the coniferous and deciduous vegetation which dominated this area when these soils were formed and that the climate was warm and moist. 相似文献
932.
U. Baltaev M. B. Gorovits Ya. V. Rashkes N. K. Abubakirov 《Chemistry of Natural Compounds》1979,14(4):393-395
Summary A new phytoecdysone has been isolated from the flower heads ofRhaponticum integrifolium, and for it the structure of 24(28)-dehydromakisterone A has been established.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 463–465, July–August, 1978. 相似文献
933.
A. T. Shakhtakhtinskaya Z. M. Mamedova Sh. F. Mutallibova S. Z. Alieva R. G. Mardzhanova 《Reaction Kinetics and Catalysis Letters》1989,39(1):137-140
Acidity of catalyst surfaces of different nature such as -Al2O3, natural zeolite-clinoptilolite, and synthetic zeolite zeokar by adsorption of ammonia over a wide temperature range has been studied. Ammonia is adsorbed on the catalysts with different strengths, as evidenced by the presence of different types of acid sites.
(-Al2O3, - , () . , , .相似文献
934.
Norbert Kuhn Stefan Stubenrauch
Roland Boese
Dieter Bl ser 《Journal of organometallic chemistry》1992,440(3):289-296The azacyclopentadienyl compounds (2,5-C4tBu2RHN)MCl3 (M = Ti, Zr, Hf; R = H, SiMe3) have been prepared as stable solids from the lithiated pyrroles and MCl4. The π-coordination of the azacyclopentadienyl ligands, as suggested from 13 C NMR data, has been confirmed for (2,5-C4tBu2H2N)TiCl3 by an X-ray diffraction study. 相似文献
935.
N. E. Bogdanchikova M. N. Dulin E. I. Vasilevskaya A. V. Kalinkin 《Reaction Kinetics and Catalysis Letters》1992,48(2):475-481
Silver clusters having unusual optical and chemical properties and characterized by a band at 320–330 nm, are shown to be stabilized by solid matrices of various chemical nature.
, , 320–330 , .相似文献
936.
Summary A method for the determination of trace amounts of molybdenum in fresh water and seawater samples by sequential ICP-AES with microsampling technique after cobalt-dithiocarbamate coprecipitation was developed. The precipitate was dissolved in 100 l of diluted nitric acid (1:2), and the solution obtained was then introduced into an ICP via a concentric nebulizer. By use of 1.7 ml sample, a preconcentration factor of 17 was achieved. Different factors including integration time, sample volume, pumping rate as well as coprecipitation conditions such as pH of the solution, amounts of reagents, standing time for the precipitate and matrix effects were examined and optimized in detail. Under selected conditions the detection limit of the method for Mo is 0.52 g/l using 1.7 ml sample. The procedure was applied to the analysis of water samples (artificial water and open ocean seawater reference material) with quantitative recovery. The analytical results were in good agreement with the certified value. The method is sensitive, simple, accurate and effective, also in the presence of interfering salts and can be applied to small sample volumes.On leave from the Department of Chemistry, Wuhan University, Wuhan, 430072 China 相似文献
937.
K. Bächmann J. Hauptmann J. Polzer P. Schütz 《Fresenius' Journal of Analytical Chemistry》1992,342(10):809-812
Summary In this study three methods for the determination of peroxy compounds with HPLC are presented. The applicability of these methods with respect to atmospheric chemistry is discussed. In rain samples 1-hydroxy hydroperoxides are determined with a detection limit of 0.058 mol/l. Alkyl hydroperoxides are determined in a mixture of hydrocarbon, hydrogen peroxide and air which has been irradiated with light before analysis. A new method for the detection of peroxides in such photolysis mixtures by GC/MS is presented. 相似文献
938.
E. L. Zapadinskii V. V. Korolev N. M. Bazhin V. A. Tolkachev 《Reaction Kinetics and Catalysis Letters》1988,37(2):477-479
The effect of n-butanol glass annealing on the oxidation kinetics of radicals and phenanthrene phosphorescence quenching by oxygen at T=90 K has been studied. It has been established that the influence of matrix annealing is due to the migration retardation of oxygen molecules.
- 90 . .相似文献
939.
A. V. Neimark V. B. Fenelonov L. I. Heifets 《Reaction Kinetics and Catalysis Letters》1976,5(1):67-72
The distribution of the precipitated active component has been analyzed using the concepts of moisture transfer mechanism for the evaporation of porous materials. Formulas are proposed for the low-dispersity phase, depending on the precipitation parameter. The calculations performed using a statistical porous environment model are in reasonable agreement with the experimental data.
- . . , , .相似文献
940.
B. V. Derjaguin N. A. Krotova V. V. Karassev Y. M. Kirillova I. N. Aleinikova 《Progress in Surface Science》1994,45(1-4):95-104
Upon tearing off polymer films from metals and glasses phenomena are observed which testify to the apparition of high differences of potentials between the interfaces formed. In particular, if the film is stripped under vacuum, electron emission is observed with electron velocities of the order of kilovolts. These phenomena are due to division upon stripping of the double electric layer, formed upon close contact between the polymer and the substrate, and to retardation of its discharge. The same retardation of the discharge of the double layer may explain quantitatively both the high value of the work spent on tearing off the film, the dependence of the latter on the speed of stripping and on the pressure of surrounding gas. Similar phenomena were found to take place during the destruction of many crystalline (but not amorphous) solids and are explained by the formation and division of an alternating-sign double layer of mosaic structure. 相似文献