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71.
The characteristic length scales for the transport in disordered metals are discussed. Based on a phenomenological model of phase randomising scattering processes, the influence of the phase coherence length on the conductance of ballistic systems is studied. It is argued that the frequency dependence of the conductance of quasi-one dimensional systems can be used in order to determine not only the statistical average but the whole distribution function of the phase coherence length. Various cases of distributions, the -function, the exponential, and the Gamma distribution, are discussed. It is shown that due to quantum coherence effects deviations from the classical (Drude) behavior of the conductance exist. For independent scattering processes the probability distribution function is given by the Poisson distribution function. In this case an expression for the conductance can be derived which contains the ballistic transport, and the result for the exponential distribution. 相似文献
72.
J. Požela A. Namajūnas A. Tamaševičius J. Ulbikas 《Applied Physics A: Materials Science & Processing》1989,48(2):181-188
A method for quantitative characterization of chaotic dynamical systems is discussed. An electronic instrument for determining the number of independent variablesk
*, involved in the motion, is described. It allows one to obtain these in real time from a single observable. The suggested technique has been applied to quantification of strange attractors underlying chaotic instabilities in semi-insulating GaAsCr, and n-Ge, irradiated with high energy electrons. In n-Ge, for instance, the measured numbersk
* range from 2 to 4 depending on control parameters. These measurements reveal the highly deterministic nature of the observed chaotic oscillations. The physical mechanisms responsible for the current instabilities and chaotic behaviour are discussed. 相似文献
73.
Vukadin M. Leovac Goran A. Bogdanović Valerija I. Češljević Ljiljana S. Jovanović Sladjana B. Novaković Ljiljana S. Vojinović-Ješić 《Structural chemistry》2007,18(1):113-119
The ligand, salicylaldehyde Girard-T hydrazonium chloride, [H2SalGT]Cl (1), and two complexes [Cu(HSalGT)X2]·H2O (X = Br(2); Cl(3)) were synthesized and their crystal structures were determined by single-crystal X-ray analysis. In the two isostructural
complexes, the Cu(II) is located in a square-pyramidal environment, with the chelating ligand and one halogen atom in the
basal plane and the second halogen in the apical position. The most apparent structural difference between the 1 and its complexes 2 and 3 is the orientation of the N(CH3)3 group: in 1, it is practically coplanar to the rest of the molecule, while in 2 and 3 it is oriented to the side of the axially bonded halogen, which can be explained by the C–H…X intramolecular interactions.
The compounds were characterized by elemental analysis, molar conductivity, magnetic susceptibility and electronic absorption
spectra. 相似文献
74.
Zusammenfassung Die Jodidoxydation durch Cu(II) wird in Anwesenheit von Ammoniak, Natriumtartrat, citrat oder -oxalat infolge Komplexbildung verhindert. Daher kann man z. B. Quecksüber(II) in Anwesenheit der genannten Komplexbildner mit Kaliumjodid maskieren und Kupfer(II) durch direkte Titration mit ÄDTA gegen Murexid, Brenzcatechinviolett, Chromazurol S, PAN oder PAR als Indikator bestimmen.
Masking with potassium iodide in direct titrations of copper(II) with ethylenediamine tetraacetic acid
Summary The formation of a complex prevents the iodide oxidation by Cu(II) in the presence of ammonia, sodium tartrate, citrate, or oxalate. Hence mercury(II) for instance, can be masked against potassium iodide in the presence of these complex formers, and Cu(II) can be determined by direct titration with EDTA in the presence of murexide, pyrocatechol violet, chromazurol, PAN or PAR as indicator.相似文献
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The phase analysis of cryolite (Na3AlF6) and sodium metasilicate (Na2SiO3) was performed by thermal analysis. The eutectic system with a region of two immiscible substances at a concentration of Na2SiO3 between 42.8 and 46.3 mol‐% was identified and the eutectic temperature determined to (886±2) °C. Based on the results of mass‐loss measurements, it was assumed that the introduced Na2SiO3 reacts with Na3AlF6 due to the formation of some nonvolatile stable compounds. The stable reaction products were identified by X‐ray diffraction analysis and IR spectroscopy of the spontaneously cooled samples, which established the formation of NaF and stable amorphous aluminosilicate compounds. 相似文献