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排序方式: 共有132条查询结果,搜索用时 15 毫秒
11.
In this work we study the binding energy of the ground state for a hydrogenic donor impurity in laterally coupled GaAs/Ga1−xAlxAs quantum well wires, considering the simultaneous effects of hydrostatic pressure and applied electric field. We have used a variational method and the effective mass and parabolic band approximations. The low dimensional structure consists of two quantum well wires with rectangular transverse section coupled by a central Ga1−xAlxAs barrier. Our results are reported for several sizes of the structure and we have taken into account variations of the impurity position along the growth direction of the heterostructure. 相似文献
12.
The combined effects of an in-growth direction applied electric field and hydrostatic pressure on the exciton binding energy and photoluminescence energy transitions are reported in this work for triple vertically coupled quantum dots. The calculations have been carried out within the effective mass approximation, and using a variational procedure. The results show that the exciton binding energy and the photoluminescence energy transitions are functions of external probes like the hydrostatic pressure and the applied electric field. 相似文献
13.
M. T. Olguin J. Duque R. Pomés M. E. Villafuerte-Castrejón L. E. Sansores P. Bosch S. Bulbulian 《Journal of Radioanalytical and Nuclear Chemistry》1997,222(1-2):235-237
The present study discusses the incorporation of uranyl ion into Y-zeolite framework. The UO
2
2+
sorption was measured by neutron activation analyses. The Y-zeolite framework distorts in response to the cations present in the structure. Hence, depending on the amount and the location of the exchanged cations, the features of the X-ray diffraction pattern may vary. From the Rietveld analysis of these patterns, the positions occupied by the UO
2
2+
cations in the zeolite network were determined. 相似文献
14.
Water-dispersible sugar-coated iron oxide nanoparticles. An evaluation of their relaxometric and magnetic hyperthermia properties 总被引:1,自引:0,他引:1
Lartigue L Innocenti C Kalaivani T Awwad A Sanchez Duque Mdel M Guari Y Larionova J Guérin C Montero JL Barragan-Montero V Arosio P Lascialfari A Gatteschi D Sangregorio C 《Journal of the American Chemical Society》2011,133(27):10459-10472
Synthesis of functionalized magnetic nanoparticles (NPs) for biomedical applications represents a current challenge. In this paper we present the synthesis and characterization of water-dispersible sugar-coated iron oxide NPs specifically designed as magnetic fluid hyperthermia heat mediators and negative contrast agents for magnetic resonance imaging. In particular, the influence of the inorganic core size was investigated. To this end, iron oxide NPs with average size in the range of 4-35 nm were prepared by thermal decomposition of molecular precursors and then coated with organic ligands bearing a phosphonate group on one side and rhamnose, mannose, or ribose moieties on the other side. In this way a strong anchorage of the organic ligand on the inorganic surface was simply realized by ligand exchange, due to covalent bonding between the Fe(3+) atom and the phosphonate group. These synthesized nanoobjects can be fully dispersed in water forming colloids that are stable over very long periods. Mannose, ribose, and rhamnose were chosen to test the versatility of the method and also because these carbohydrates, in particular rhamnose, which is a substrate of skin lectin, confer targeting properties to the nanosystems. The magnetic, hyperthermal, and relaxometric properties of all the synthesized samples were investigated. Iron oxide NPs of ca. 16-18 nm were found to represent an efficient bifunctional targeting system for theranostic applications, as they have very good transverse relaxivity (three times larger than the best currently available commercial products) and large heat release upon application of radio frequency (RF) electromagnetic radiation with amplitude and frequency close to the human tolerance limit. The results have been rationalized on the basis of the magnetic properties of the investigated samples. 相似文献
15.
16.
M. E. Mora-Ramos S. Y. López C. A. Duque 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(3):257-261
The mixing between the Γ and X conduction-band valleys in GaAs-Ga1-xAlxAs quantum wells is investigated by using a
phenomenological model which takes into account the effects of applied hydrostatic pressure. The dependencies of the variationally
calculated
photoluminescence peak-energy transitions on the applied hydrostatic pressure and quantum-well width are presented. A systematic
study of the
Γ-X mixing parameter is also reported. In particular, it is shown that the inclusion of the Γ-X mixing explains the non-linear
behavior in the photoluminescence peak of confined exciton states that has been experimentally observed for pressures above
15 kbar in
GaAs-Ga1-xAlxAs quantum wells. 相似文献
17.
L.A. Valenzuela J.G.S. Duque C.T. Meneses W.C. Nunes M. Knobel 《Journal of Non》2008,354(42-44):4871-4873
We report structural and magnetic properties of fine particles embedded in an amorphous magnetic matrix. As-quenched amorphous Fe73.5Nb3CuSi13.5B9 ribbons (FINEMET) were submitted to the thermal treatments of several times (1 ? t ? 240 min) at 570 °C using a conventional furnace. The analyses of the X-ray diffraction patterns at room temperature reveal that our samples consist of single phase Fe3Si nanocrystals embedded in a residual amorphous phase. Magnetic measurements show that the saturation moment at T = 450 °C increases as a function of annealing time. This behavior is attributed to an increase of the fraction of nanocrystallites in the residual amorphous phase. 相似文献
18.
Duque F. Fabila-Monroy R. Hidalgo-Toscano C. Pérez-Lantero P. 《Acta Mathematica Hungarica》2021,164(1):28-45
Acta Mathematica Hungarica - This paper is devoted to the studying of the weak Orlicz–Lorentz space $$\Lambda_X^{\varphi, \infty}(w)$$ , which can be regarded as an extension of weak Orlicz... 相似文献
19.
Echigo S Hara N Carderon GJ Duque C Fujimoto Y 《Chemical & pharmaceutical bulletin》2006,54(10):1473-1477
The C-24 configuration of (22E,24xi)-24-isopropenyl-22-dehydrocholesterol (1), which was recently isolated from the Colombian Caribbean sponge, Topsentia ophiraphidites, was investigated. Synthesis of the stereodefined (24R)- and (24S)-(22E)-24-isopropenyl-22-dehydrocholesterols (1a, 1b) followed by (1)H- and (13)C-NMR data comparison of these sterols established the (24R)-configuration of 1. In addition, (24R)- and (24S)-24-isopropenylcholesterols (2a and 2b) were also synthesized and their NMR data are provided. The C-24 configurations of the samples of 24-isopropenylcholesterol reported previously are discussed. 相似文献
20.
Optical Absorption in Periodic Graphene Superlattices: Perpendicular Applied Magnetic Field and Temperature Effects 下载免费PDF全文
Melquiades de Dios‐Leyva Michael A. Hernández‐Bertrán Alvaro L. Morales Carlos A. Duque Huynh Vinh Phuc 《Annalen der Physik》2018,530(5)
A detailed study of the magneto‐optical absorption is presented for graphene superlattices (SLs) subjected to a perpendicular magnetic field. For a given temperature, this quantity exhibits a resonant peak structure whose characteristics depend on the magnetic field regime, circular polarization of light and SL barrier height. For the intermediate field regime, we demonstrated that the resonant peak structure of is directly correlated to the partial joint density of states. Specifically, the latter exhibits van Hove‐like singularities and peaks at energies where takes its maximum values. We also investigated the magnetoabsorption in the weak field regime for SLs exhibiting one and extra Dirac points in the absence of the field. It was found that for SLs with only one Dirac point, the absorption spectra consist of resonant peaks satisfying the same circular polarization dependent selection rule as that for pristine graphene, except for one of them. For SLs with extra Dirac points, the resonant peaks arise from transitions between singlet subbands or between doublet subbands and satisfy a circular polarization and peak intensity dependent selection rule. It was also found that the resonant structure of can be observed experimentally at room temperature in clean SLs. 相似文献