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21.
The superconducting transition temperatureT c of a two band superconductor in the presence of magnetic and nonmagnetic impurities as well as exchange fields is calculated using a new (8 × 8)-matrix formalism for the electron Green's function. In particular we investigate the influence of spin correlations onT c near a magnetic phase transition. It is shown that in the strong interband phonon coupling limit the system behaves essentially as a one band superconductor. In the weak coupling limit we find typical deviations from one band theories. 相似文献
22.
P. Schramel und B. -J. Klose 《Fresenius' Journal of Analytical Chemistry》1981,307(1):26-30
Zusammenfassung Die Anwendung der ICP-Emissionsspektralanalyse für die direkte Bestimmung von Cu, Fe, Zn, Ca, Mg und Na in menschlichem und tierischem Blutserum wird beschrieben. Aufgrund der hohen Anregungstemperatur in einem Plasma treten dabei die von der konventionellen Atomabsorptionsspektroskopie her bekannten chemischen Interferenzen nicht auf, so daß mit geringen Probenmengen (max. 1 ml Serum für den Nachweis dieser 6 Elemente) ein sehr empfindlicher und sehr gut reproduzierbarer Nachweis möglich ist.
Direct determination of Cu, Fe, Zn, Ca, Mg, and Na in serum by means of ICP-emission spectrometry
Summary The application of ICP-emission spectroscopy for the determination of Cu, Fe, Zn, Ca, Mg and Na in human and animal serum is described. Due to the very high excitation temperature in a plasma the well known chemical interferences in atomic absorption spectroscopy do not appear in this technique. It is possible to carry out very sensitive and very well reproducible measurements on very small amounts of the sample (the total sample consumption for the determination of the above mentioned six elements is less than 1 ml).相似文献
23.
Gisbert Depke Walter Klose Helmut Schwarz Wolfgang Blum Wilhelm J. Richter 《Journal of mass spectrometry : JMS》1983,18(12):568-571
Unimolecular hydroxyl (OD˙) loss from regio- and stereo-specifically labelled o-nitrostyrenes 1a, 1c and 1d results in the formation of an ion which upon collisional activation gives identical mass spectra. Suggestions are made which aim at explaining: (i) the loss of stereochemical integrity of the diastereotopic methylene hydrogens in the course of hydroxyl elimination; and (ii) to account for the collision induced losses of CO and HNC from the [M—hydroxyl]+ ion. 相似文献
24.
25.
An iteration procedure allows to find an equation for the critical temperatureT c of superconductors starting from the linearized Eliashberg equations without using any cutoff parameters or a Coulomb pseudopotential. Explicit calculation ofT c for a simple model leads to Morel, Anderson and McMillan's1,2 expression thereby allowing for a physical interpretation of the commonly used approximation for the Coulombpseudopotential. 相似文献
26.
27.
Jörg Wolfram Anselm Fischer Andreas Brenig Dr. Daniel Klose Prof. Dr. Jeroen Anton van Bokhoven Dr. Vitaly L. Sushkevich Prof. Dr. Gunnar Jeschke 《Angewandte Chemie (International ed. in English)》2023,62(34):e202303574
Cu-exchanged mordenite (MOR) is a promising material for partial CH4 oxidation. The structural diversity of Cu species within MOR makes it difficult to identify the active Cu sites and to determine their redox and kinetic properties. In this study, the Cu speciation in Cu-MOR materials with different Cu loadings has been determined using operando electron paramagnetic resonance (EPR) and operando ultraviolet-visible (UV/Vis) spectroscopy as well as in situ photoluminescence (PL) and Fourier-transform infrared (FTIR) spectroscopy. A novel pathway for CH4 oxidation involving paired [CuOH]+ and bare Cu2+ species has been identified. The reduction of bare Cu2+ ions facilitated by adjacent [CuOH]+ demonstrates that the frequently reported assumption of redox-inert Cu2+ centers does not generally apply. The measured site-specific reaction kinetics show that dimeric Cu species exhibit a faster reaction rate and a higher apparent activation energy than monomeric Cu2+ active sites highlighting their difference in the CH4 oxidation potential. 相似文献
28.
The literature knows semi-Lagrangian relaxation as a particular way of applying Lagrangian relaxation to certain linear mixed integer programs such that no duality gap results. The resulting Lagrangian subproblem usually can substantially be reduced in size. The method may thus be more efficient in finding an optimal solution to a mixed integer program than a “solver” applied to the initial MIP formulation, provided that “small” optimal multiplier values can be found in a few iterations. Recently, a simplification of the semi-Lagrangian relaxation scheme has been suggested in the literature. This “simplified” approach is actually to apply ordinary Lagrangian relaxation to a reformulated problem and still does not show a duality gap, but the Lagrangian dual reduces to a one-dimensional optimization problem. The expense of this simplification is, however, that the Lagrangian subproblem usually can not be reduced to the same extent as in the case of ordinary semi-Lagrangian relaxation. Hence, an effective method for optimizing the Lagrangian dual function is of utmost importance for obtaining a computational advantage from the simplified Lagrangian dual function. In this paper, we suggest a new dual ascent method for optimizing both the semi-Lagrangian dual function as well as its simplified form for the case of a generic discrete facility location problem and apply the method to the uncapacitated facility location problem. Our computational results show that the method generally only requires a very few iterations for computing optimal multipliers. Moreover, we give an interesting economic interpretation of the semi-Lagrangian multiplier(s). 相似文献
29.
Synthesis of Phosphido Chalcogenido Bridged Dirhenium Complexes of the Type Re2(μ‐PCy2)(μ‐ER)(CO)8 (E = S, Se, Te; R = org. Residue) The reaction of Re2(μ‐Br)(μ‐PCy2)(CO)8 with nucleophiles MER (M = Na, Li; E = S, Se, Te; R = org. residue) gives via substitution of the bromido bridge phosphido chalcogenido bridged dirhenium complexes of the general formula Re2(μ‐PCy2)(μ‐ER)(CO)8. The new compounds were characterized by IR, 1H and 13C NMR spectroscopic data and by elemental analyses. In addition the molecular structures for E = S, Se, Te and R = Ph as well as for E = S and R = H, n‐Bu, 2‐pyridyl have been established by single crystal X‐ray analysis. 13C NMR spectra of Re2(μ‐PCy2)(μ‐EPh)(CO)8 (E = S, Se, Te) prove that the sulfur and selenium compounds are at room temperature dynamic molecules due to inversion of the pyramidal chalcogenido bridge. The tellurium compound, however, is rigid on the time scale of 13C NMR spectroscopy. Eventually the reactivity of the SH function of the novel complex Re2(μ‐PCy2)(μ‐SH)(CO)8 was investigated by reaction with Re2(CO)8(MeCN)2. In toluene at 90 °C the novel spirocyclic complex Re2(μ‐PCy2)(CO)8(μ4‐S)Re2(μ‐H)(CO)8 was formed by SH oxidative addition. 相似文献