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1.
Unexpected benzimidazole ring formation from a quinoneimide species in the presence of ammonium acetate as supporting electrolyte used in the coupling of electrochemistry with mass spectrometry 下载免费PDF全文
2.
3.
The thermotropic liquid-crystalline phase behaviour of a homologous set of bis[N-[[4-[4-(alkoxy)benzoyloxy]2-hydroxyphenyl]methylene]alkanamino] copper(II) complexes is examined. New data are reported and taken into account in addition to those previously reported in this Journal. The influence of alkoxy and alkanamine groups on the nature and stability of the mesophase is underlined. As a general trend, with some notable exception, smectic (C type) mesomorphism is favoured by longer alkoxy and alkanamine chains. Data concerning some Pd(II) and Ni(II) homologous complexes are also reported. The mesophase stability (nematic phase) is higher for palladium and nickel complexes than for the copper containing homologues. 相似文献
4.
Demetrio Pitea Laura Bonati Elena Collina Ugo Cosentino Marina Lasagni Giorgio Moro Roberto Todeschini 《Fresenius' Journal of Analytical Chemistry》1994,348(1-2):111-120
Summary The role of multivariate analysis methods in evaluating, rationalizing, and working out complex environmental problems is discussed. The discussion is organized in two sections; a literature analysis of the application of chemometric methods to PCDD/PCDF data interpretation and source correlation and a review of the role of chemometric methods in analysing the results obtained by the Authors studying PCDD/PCDF formation and destruction mechanisms in MSW combustion processes. 相似文献
5.
Ugo Gianazza Vincenzo Vespri 《NoDEA : Nonlinear Differential Equations and Applications》1997,4(3):305-324
We consider the generation of analytic semigroups by degenerate elliptic operators satisfying a uniform H?rmander condition
under homogeneous Dirichlet boundary conditions.
Received January 12, 1996 相似文献
6.
The effect of gamma irradiation in air is investigated on four thermoplastic polyesters (PET, PBT, PEN, PCT-co-ET) in films containing aromatic rings, in order to evaluate the influence of aromatic density and the role of oxygen on radiation resistance. Physical-chemical-nuclear analyses were used to this purpose. EPR measurements were carried out to detect radical stability against oxygen permeation. Viscometric investigations reported a very similar trend for all the investigated polyesters: a chain break effect that decreases at the highest doses. FT-IR analyses focused on the formation of oxidized species. Positron annihilation spectra pointed out a decrease of the intensity of ortho-positronium formation, while its lifetime remains unchanged with radiation dose. 相似文献
7.
Franco Piacenti Mario Bianchi Piero Frediani Ugo Matteoli 《Journal of organometallic chemistry》1975,87(3):C54-C55
Both normal and secondary alkylcobalt carbonyls are shown not to undergo isomerization under catalytic “oxo” conditions, and the relevance of this obervation for the mechanism of the “oxo” reaction is discussed. 相似文献
8.
Treatment of 2,3-diketo-cholestane (1) with thallium triacetate in acetic acid afforded mainly 3α-carbomethoxy-A-nor-5α-cholestan-2-one (2). Under similar conditions, the 3,4-diketo steroids (3 and 4) underwent extensive rearrangement affording spiro-lactones (9 and 10), in low yields. The structural assignment of the spiro-cholestane derivative was supported by crystallographic X-ray analysis. This product was the result of A and B-ring contractions followed by acid-catalysed cyclization of an unsaturated carboxy intermediate. 相似文献
9.
Tessore F Roberto D Ugo R Pizzotti M Quici S Cavazzini M Bruni S De Angelis F 《Inorganic chemistry》2005,44(24):8967-8978
Coordination of 4'-(C6H4-p-X)-2,2':6',2'-terpyridines [X = NO2, NBu2, (E)-CH=CH-C6H4-p-NBu2, (E,E)-(CH=CH)2-C6H4-p-NMe2] to Zn(II), Ru(III), and Ir(III) metal centers induces a significant enhancement of the absolute value of the second-order nonlinear optical (NLO) response of the terpyridine, measured by means of both electric field induced second harmonic generation and solvatochromic methods. By varying the nature of the metal center, the enhanced second-order NLO response shifts from positive to negative. Such a shift is controlled by electronic charge-transfer transitions, such as metal-to-ligand or ligand-to-metal transitions, in addition to the intraligand charge transfer. The enhancement generated by coordination is also controlled by the chelation effect and by fine-tuning of the ancillary ligands. 相似文献
10.
The cyclic voltammetric technique is used to study hydrogen-bond formation in some polar organic solvents (S) of electroanalytical interest (1,2-dimethoxy, tetrahydrofuran, dimethylformamide, dimethyl sulphoxide and pyridine). The cathodic shift of the proton reduction caused by stepwise addition of the solvent investigated to a solution of anhydrous perchloric acid in acetonitrile is utilized. The theoretical treatment applied produced evidence that HS+ and HS+2 are the only acidic species involved, so that the relevant formation constants can be evaluated. The data obtained mostly compare well with those available in the literature. The features that condition the tendency to hydrogen-bonding and the effect of hydrogen bonding on solvent basicity are discussed. 相似文献