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排序方式: 共有199条查询结果,搜索用时 15 毫秒
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We show how the quantization of two-dimensional gravity leads to an (Euclidean) quantum space–time where the average geometry is that of constant negative curvature and where the Hartle–Hawking boundary condition arises naturally. 相似文献
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Zusammenfassung 3,5-Dimethylpyrazol bildet in Anwesenheit von Rhodanid mit Kupfer(II) einen gefärbten Komplex, der in Chloroform leicht löslich ist. Diese Reaktion wurde zur photometrischen Bestimmung von 10 bis 100g Cu/5 ml verwendet.
Summary A colored complex, that is readily soluble in chloroform, is formed by copper(II) with 3,5-dimethylpyrazole in the presence of thiocyanate. This reaction was employed for the photometric determination of 10 to 100g Cu/5 ml.
Résumé Le diméthyl-3,5 pyrazol forme avec le cuivre-II en présence de thiocyanate, un complexe coloré, facilement soluble dans le chloroforme. On a utilisé cette réaction pour le dosage photométrique de 10 à 100g Cu/5 ml.相似文献
5.
Alicja Janik Anna Chyra Katarzyna Stadnicka 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(10):o572-o575
The crystal structure of a protected l ‐tyrosine, namely N‐acetyl‐l ‐tyrosine methyl ester monohydrate, C12H15NO4·H2O, was determined at both 293 (2) and 123 (2) K. The structure exhibits a network of O—H...O and N—H...O hydrogen bonds, in which the water molecule plays a crucial role as an acceptor of one and a donor of two hydrogen bonds. Molecules of water and of the protected l ‐tyrosine form hydrogen‐bonded layers perpendicular to [001]. C—H...π interactions are observed in the hydrophobic regions of the structure. The structure is similar to that of N‐acetyl‐l ‐tyrosine ethyl ester monohydrate [Soriano‐García (1993). Acta Cryst. C 49 , 96–97]. 相似文献
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Previously obtained calorimetry results revealed an existance of three solid phases in /Ni(NH3)6/(NO3)2. Neutron quasielastic scattering results, also obtained previously, gave evidence of quick reorientations of NH3 groups around NiN axes in phases I and II. In the Raman profile study now reported we show that the NO?3 groups reorient quickly in phase I, whereas they are fixed in phase II. Connection of NH3 and NO?3 reorientations with entropy of I?II transition is discussed. 相似文献
7.
Radiation formation of polymeric nanogels 总被引:4,自引:0,他引:4
An alternative method of synthesis of polymeric nanogels is proposed, based not on polymerization, but on intramolecular crosslinking of polymer chains, initiated by pulse irradiation in dilute aqueous solutions. Kinetic data show that for many water-soluble polymers irradiation under these conditions result in intramolecular crosslinking. Preliminary product studies on poly(vinyl alcohol) indicate that in fact internally crosslinked macromolecules can be obtained by this technique. 相似文献
8.
X. P. Nguyen J. Krawczyk D. Chruciel J. Chruciel J. A. Janik J. M. Janik 《Liquid crystals》2013,40(6):561-572
Abstract Results of dielectric relaxation, quasielastic neutron scattering, calorimetric D.S.C. and preliminary X-ray measurements on the fifth member, POAOB, of the 4,4'-di-n-alkoxyazoxybenzene homologous series are presented. It has been found that POAOB exhibits two mesophases: a nematic (N) and an intermediate crystalline phase (CI) just below it. From comparison of the dielectric relaxation and quasielastic neutron scattering studies we can conclude that in the nematic phase the molecule as a whole performs rotational diffusion around the long axis (ω ~ 150ps) and at the same time the two moieties perform faster independent reorientations around the N-δ bonds (ω denotes a benzene ring) with δ ~ 5 ps. The intermediate crystal phase is identified as a solid uniaxial rotational phase in which fast molecular reorientations exist. It seems that the fast reorientations observed in the nematic phase to some extent survive to the crystal I phase. A model of molecular arrangements in the crystal I phase is proposed, and it explains the reduction of the dielectric increment observed on passing from the nematic phase to this phase. 相似文献
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Robert T. Paine William F. McNamara Jerzy Fr. Janik Eileen N. Duesler 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2):241-244
Abstract Aspects of the reactivity of metallophosphanes are presented along with the synthesis and structure determinations for new aluminophosphanes. 相似文献