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61.
We employ dynamical mean-field theory to identify the materials properties that optimize T(c) for a generalized double-exchange model. We reach the surprising conclusion that T(c) achieves a maximum when the band angular momentum j equals 3/2 and when the masses in the m(j) = +/- 1/2 and +/-3/2 and subbands are equal. However, we also find that T(c) is significantly reduced as the ratio of the masses decreases from one. Consequently, the search for dilute-magnetic semiconductor materials with high T(c) should proceed on two fronts. In semiconductors with p bands, such as the currently studied Mn-doped Ge and GaAs semiconductors, T(c) may be optimized by tuning the band masses through strain engineering or artificial nanostructures. On the other hand, semiconductors with s or d bands with nearly equal effective masses might prove to have higher T(c)'s than p-band materials with disparate effective masses. 相似文献
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Fishman AI Klimovitskii AE Skvortsov AI Remizov AB 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2004,60(4):843-853
Infrared spectra (4000-250 cm-1) of the liquid, amorphous, crystalline solids and solutions in liquid krypton and Raman spectra (2500-20 cm-1) of the liquid as well as the amorphous and crystalline solids of ethylbenzene and its deuterated analogue-ethylbenzene-d(10) have been recorded. The spectra indicate that in the liquid and amorphous solids a small amount of a second conformer is present, whereas only one conformer remains in the crystalline phases. Assignments of the observed band wave numbers are discussed by comparison with normal mode wave numbers and IR and RS intensities calculated from ab initio 6-31G force fields and optimised geometries for both conformers for two species. All of the normal modes of conformers have been assigned. 相似文献
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Vyacheslav N. Fishman Bruno Linclau Dennis P. Curran Kasi V. Somayajula 《Journal of the American Society for Mass Spectrometry》2001,12(9):1050-1054
A new fluorinated compound mixture has been developed for the calibration of the double focusing mass spectrometer in the mass range of 100–3000 Da in the positive electron ionization (EI) mode. Current calibration standards for EI have either limited mass range [perfluorotributylamine (PFTBA), perfluorokerosene (PFK), s-triazines (TRIS)] or poor peak intensities with significant chemical background in the instrument for several days (perfluoroalkyl phosphazine). The newly synthesized fluorinated silyl alkyl amines mixture is proposed as a reference/calibration standard for EI-MS. This standard produced abundant parent and fragment ions across the entire mass range without any memory effect. 相似文献
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L. Z. Fishman 《Differential Equations》2006,42(6):909-911
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Nigmatullin RR Fishman AI Filippova EA Smith G 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(11-12):2691-2696
A new method, based on the presentation of initial data in the form of probability circles (PC), has been developed for constructing a calibration curve, which shows a monotonic dependence with respect to the given concentration. The centre of the reference probability circle is defined by its mean value and the radius of the circle is calculated as the value of the standard deviation of the sampling considered. The comparative probability circle is defined by the same corresponding parameters but rotated, relative to the initial reference circle, by an angle, which is related to the Pearson's correlation coefficient (PCC). The two parameters of the PCC and the statistical proximity factor (PCF), which defines the positions of the centres of the circles relative to each other, can be chosen as statistical parameters for the construction of the desired calibration curve. Experiments realized with the mixture of two liquids (chloroform serves as the basic matrix) and acetone (serves as an additive) confirm the efficiency of this new analytical method and demonstrate a possible increase sensitivity for the detection of lower concentration limit by approximately one order of magnitude. This new approach, which is free from model assumptions, and having very clear geometrical meaning, can be applied for different types of spectra and has many potential applications in the construction of calibration curves for different additives embedded within different matrices. 相似文献
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The electric response of several isolated rat hearts in a controlled environment was studied experimentally. The correlation dimension D(2) was estimated and was found to be between 4 and 6.5 when the response was nearly periodic. The variation of D(2) with the concentration of calcium was studied and a general trend of its increase with increasing concentration was found. Two types of ventricular fibrillation (VF) were observed, one that corresponds to a stochastic signal where D(2) is unbounded and the other to a low dimensional dynamical system with 3.5=D(2)=4. It was found also that for the heart the correlation dimension is only an approximate concept. A new method for the estimation of D(2), that is suitable for the case when it is only approximate was introduced. A surrogate data method suitable for the analysis of nearly periodic series was implemented. (c) 2000 American Institute of Physics. 相似文献