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121.
122.
A. Cruz Orea I. Delgadillo H. Vargas J.L. Pichardo J.J. Alvarado-Gil L.C.M. Miranda 《Solid State Communications》1996,100(12):855-859
The photoacoustic technique is used in semiconductor two-layer systems for the determination of thermal properties and thermal expansion coefficient. The two-layer systems studied were amorphous silicon-glass and Al0.2Ga0.8As---GaAs. Our results show that the proposed method is a reliable technique for the characterization of other semiconductor two-layers systems. 相似文献
123.
J. M. Garcia O. Sanchez P. Segovia J. E. Ortega J. Alvarez A. L. Vazquez de Parga R. Miranda 《Applied Physics A: Materials Science & Processing》1995,61(6):609-613
We observe the partial confinement of the twodimensional electron gas of ans-p-like surface state by the regular step distribution of several vicinal Cu(111) surfaces. The spatial distribution of the surface state is visualized by scanning tunneling microscopy. Local tunneling spectroscopy reveals a shift of the maximum of the density of states of the surface state towards the Fermi level, which correlates with the size of the terraces. The average shift is also measured by angle-resolved photoemission and found to be consistent with a one-dimensional Kronig-Penney model. 相似文献
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125.
A. I. Belogorokhov I. A. Belogorokhov M. I. Vasilevskiĭ S. A. Gavrilov R. P. Miranda Th. Dittrich D. R. Khokhlov 《JETP Letters》2006,84(3):124-126
Based on the results of experimental studies, it is shown that, when the effect of size quantization on the vibratory properties of CdS nanocrystals is insignificant, the absorption spectra of nanocomposites containing CdS quantum wires and quantum dots exhibit not only the peak associated with the transverse optical phonons but also two other pronounced peaks associated with electrostatic vibration modes. When the size of nanocrystals is so small that the effect of size quantization cannot be neglected, the structure of the reflection and transmission spectra becomes much more complicated because of the contribution of the mixed longitudinal-transverse phonon modes. 相似文献
126.
Carlo Bertoluzza Pedro Miranda Pedro Gil 《International Journal of Approximate Reasoning》2005,40(3):127-146
In this paper we propose a generalization of the concept of the local property for divergence measures. These new measures will be called g-local divergence measures, and we study some of their properties. Once this family is defined, a characterization based on Ling’s theorem is given. From this result, we obtain the general form of g-local divergence measures as a function of the divergence in each element of the reference set; this study is divided in three parts according to the cardinality of the reference set: finite, infinite countable or non-countable. Finally, we study the problem of componible divergence measures as a dual concept of g-local divergence measures. 相似文献
127.
128.
We investigate the leakage current in ultrathin (sub-5 nm) La2O3 dielectric films deposited on n-Si (1 0 0) substrates by electron-beam evaporation and annealed in situ in ultra-high vacuum conditions. We show that simple tunneling models both for the direct and Fowler-Nordheim conduction regimes can accurately reproduce the measured current-voltage characteristics over a wide voltage range. In the latter regime, it is shown the importance of considering the series resistance effect to account for the shape of the characteristics. We propose a method to obtain the series resistance’s value based on the linearization of the Fowler-Nordheim plot. Some experimental features in combination with an exploratory analysis of the fitting parameters seem to indicate that the current flow through the structure is mostly localized, which is attributed to the existence of thickness non-uniformities in the oxide layer. In addition, we show that the application of electrical stress creates traps or defects within the insulator that leads to a progressive increase of the leakage current and to a change of the dominant conduction mechanism at the lowest biases. 相似文献
129.
Raquel S. Amim Marcelo R.L. Oliveira Genivaldo J. Perptuo Jan Janczak Liany D.L. Miranda Mayura M.M. Rubinger 《Polyhedron》2008,27(7):1891-1897
The reaction of 4-iodobenzenesulfonamide or 4-fluorobenzenesulfonamide with CS2 and KOH in dimethylformamide yielded the potassium N-R-sulfonyldithiocarbimates, K2(RSO2NCS2) [R = 4-IC6H4 (1) and 4-FC6H4 (2)]. These salts reacted with K2[PtCl4] in water/methanol to yield complex anions bis(N-R-sulfonyldithiocarbimato)platinate(II), which were isolated as their tetrabutylammonium salts, (Bu4N)2[Pt(RSO2NCS2)2] [R = 4-IC6H4 (3) and 4-FC6H4 (4)]. The structures of 2–4 were determined by X-ray crystallography. The Pt2+ in both complexes 3 and 4 lies at the inversion centre and the PtS4 moiety has a distorted square-planar configuration. The compounds were also characterized by IR, 1H NMR and 13C NMR spectroscopies, and elemental analyses. The molar conductance data are consistent with the fact that 3 and 4 are dianionic complexes. 相似文献
130.
Simultaneous quantification of zidovudine and its glucuronide in serum by high-performance liquid chromatography 总被引:12,自引:0,他引:12
A sensitive high-performance liquid chromatography (HPLC) assay has been developed to simultaneously determine levels of the anti human immunodeficiency virus agent, zidovudine (AZT), and its major metabolite (the 5'-O-glucuronide) in serum. Samples were first mixed with an internal standard (a stereoisomer of AZT), then prepared for analysis using solid-phase extraction columns and chromatographed using a reversed-phase analytical column. Isocratic elution with a mobile phase of 15% acetonitrile, buffered to pH 2.70 with ammonium phosphate, gave good resolution of the three analytes and endogenous serum components. The HPLC analysis time required per sample was 34 min and analyte recoveries were reproducibly high (greater than 93%). Replicate analyses of prepared standards gave satisfactory precision and accuracy, with coefficients of variation less than 15% and deviations from expected concentrations less than 10%. 相似文献