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1.
Under idealized conditions, electroconvection in a nematic liquid crystal sets in at a well-defined threshold of the driving ac voltage. Fluctuating convection rolls of a small amplitude below that threshold have been observed recently. The measurement of the amplitude of these fluctuations is described in detail in this paper. It is based on averaging the light intensity signals using the structure function and a quantitative analysis of the light deflection. 相似文献
2.
Richard P. Kent IV 《Geometriae Dedicata》2004,106(1):145-159
We answer a question of J. Anderson's by producing infinitely many commensurability classes of fibered hyperbolic 3-manifolds whose fundamental groups contain subgroups that are locally free and not free. These manifolds are obtained by performing 0–surgery on a collection of knots with the same properties. 相似文献
3.
The subject of this paper is a characterization of the -definable set functions of Kripke-Platek set theory with infinity and a uniform version of axiom of choice: . This class of functions is shown to coincide with the collection of set functionals of type 1 primitive recursive in a
given choice functional and . This goal is achieved by a G?del Dialectica-style functional interpretation of and a computability proof for the involved functionals.
Received October 9, 1996 相似文献
4.
Anionie Nickel Pseudohalide Complexes of the Types [Ni{N(CN)2}3]? and [Ni{N(CN)2}2(NCS)2]2? The preparation of a new type of anionic pseudohalide complexes of nickel [Ni{N(CN)2}3]? and of mixed thiocyanate-dicyanamide complexes [Ni{N(CN)2}2(NCS)2]2? is reported. The structures of the complexes are discussed on the basis of IR- and magnetic measurements. The new compounds are representing polymer octahedral complexes with a bridging function of the dicyanamide ligands. 相似文献
5.
6.
Beller M Thiel OR Trauthwein H Hartung CG 《Chemistry (Weinheim an der Bergstrasse, Germany)》2000,6(14):2513-2522
A new catalytic amination of aromatic olefins with anilines is presented. In a domino reaction, substituted quinoline derivatives are obtained in the presence of cationic rhodium complexes, such as [Rh(cod)2]BF4, and PPh3. Ethylbenzene is formed as a by-product in this new oxidative reaction. The first transition metal catalyzed anti-Markovnikov hydroamination of styrene with anilines occurs as a side reaction. Mechanistic investigations strongly support the regioselective oxidative amination of styrene as the key reaction step. 相似文献
7.
Heavy Metal Chelates of α-Cyano-β-amino-dithioacrylates The inner metal chelates of PdII, NiII, CoIII, and AgI with α-cyano-β-amino-dithioacrylates have been prepared. The coordination of the dithioester group and the amine nitrogen (S/N-coordination) has been proved by the chemical shift of the S2p and N1s electron binding energies in the ESCA spectra. 相似文献
8.
Egon Fanghnel Hagen Bartossek Ute Baumeister Matthias Biedermann Helmut Hartung 《Journal of heterocyclic chemistry》1998,35(6):1449-1454
The first synthesis of substituted 2,2-dioxo-1-phenyl-1H-thieno[3,4-c][1,2]thiazines 2 and some of their reactions are achieved. Compounds 2 were prepared from the 3,5-dimethyl-1,1-dioxo-1,2-thiazine-4-carbaldehydes 1 by reaction with sulfur and triethyl amine in dimethylformamide under mild conditions. They were characterized spectroscopically and by X-ray structure analysis. The formylation, chlorination and oxidation of 2 are reported. 相似文献
9.
10.
E. Hartung K. Heide R. Naumann K. H. Jost W. Hilmer 《Journal of Thermal Analysis and Calorimetry》1983,26(2):277-284
In spite of numerous investigations the literature data on the thermal decomposition of borax are contradictory. On the basis of thermal, X-ray, gas analytical and optical investigations this fact can be attributed to the complex decomposition mechanism. After the release of about 8 mole water the reaction product is an X-ray amorphous phase, having the thermal behaviour of glass. From this glass sodium diborate (Na2O.2B2O3) crystallizes between 500–600? with further mass loss. Sodium diborate decomposes from about 700? incongruently yielding NaBO2 vapor and B2O3 glass phase. After evaporation of NaBO2 is completed the rate of evaporation of B2O3 increases considerably. 相似文献