1,360 research outputs found
Energy levels and far-infrared spectroscopy for two electrons in a semiconductor nanoring
The effects of electron-electron interaction of a two-electron nanoring on
the energy levels and far-infrared (FIR) spectroscopy have been investigated
based on a model calculation which is performed within the exactly numerical
diagonalization. It is found that the interaction changes the energy spectra
dramatically, and also shows significant influence on the FIR spectroscopy. The
crossings between the lowest spin-singlet and triplet states induced by the
coulomb interaction are clearly revealed. Our results are related to the
experiment recently carried out by A. Lorke et al. [Phys. Rev. Lett. 84, 2223
(2000)].Comment: 17 pages, 6 figures, revised and accepted by Phys. Rev. B (Dec. 15
A possible cooling effect in high temperature superconductors
We show that an adiabatic increase of the supercurrent along a superconductor
with lines of nodes of the order parameter on the Fermi surface can result in a
cooling effect. The maximum cooling occurs if the supercurrent increases up to
its critical value. The effect can also be observed in a mixed state of a bulk
sample. An estimate of the energy dissipation shows that substantial cooling
can be performed during a reasonable time even in the microkelvin regime.Comment: 5 pages, to appear in Phys. Rev.
Electron locking in semiconductor superlattices
We describe a novel state of electrons and phonons arising in semiconductor
superlattices (SSL) due to strong electron-phonon interactions. These states
are characterized by a localization of phonons and a self-trapping or locking
of electrons in one or several quantum wells due to an additional,
deformational potential arising around these locking wells in SSL. The effect
is enhanced in a longitudinal magnetic field.
Using the tight-binding and adiabatic approximations the whole energy
spectrum of the self-trapped states is found and accurate, analytic expressions
are included for strong electron-phonon coupling. Finally, we discuss possible
experiments which may detect these predicted self-trapped states.Comment: 8 pages, 2 figures. Please note that the published article has the
title 'Electron locking in layered structures by a longitudinal magnetic
field
Inelastic light scattering and the excited states of many-electron quantum dots
A consistent calculation of resonant inelastic (Raman) scattering amplitudes
for relatively large quantum dots, which takes account of valence-band mixing,
discrete character of the spectrum in intermediate and final states, and
interference effects, is presented. Raman peaks in charge and spin channels are
compared with multipole strengths and with the density of energy levels in
final states. A qualitative comparison with the available experimental results
is given.Comment: 5 pages, accepted in J. Phys.: Condens. Matte
Localized magnetoplasmon modes arising from broken translational symmetry in semiconductor superlattices
The electromagnetic propagator associated with the localized collective
magnetoplasmon excitations in a semiconductor superlattice with broken
translational symmetry, is calculated analytically within linear response
theory. We discuss the properties of these collective excitations in both
radiative and non-radiative regimes of the electromagnetic spectra. We find
that low frequency retarded modes arise when the surface density of carriers at
the symmetry breaking layer is lower than the density at the remaining layers.
Otherwise a doublet of localized, high-frequency magnetoplasmon-like modes
occurs.Comment: Revtex file + separate pdf figure
Magnetoplasmon excitations in an array of periodically modulated quantum wires
Motivated by the recent experiment of Hochgraefe et al., we have investigated
the magnetoplasmon excitations in a periodic array of quantum wires with a
periodic modulation along the wire direction. The equilibrium and dynamic
properties of the system are treated self-consistently within the
Thomas-Fermi-Dirac-von Weizsaecker approximation. A calculation of the
dynamical response of the system to a far-infrared radiation field reveals a
resonant anticrossing between the Kohn mode and a finite-wavevector
longitudinal excitation which is induced by the density modulation along the
wires. Our theoretical calculations are found to be in excellent agreement with
experiment.Comment: 9 pages, 8 figure
Theoretical calculations of the primary defects induced by pions and protons in SiC
In the present work, the bulk degradation of SiC in hadron (pion and proton)
fields, in the energy range between 100 MeV and 10 GeV, is characterised
theoretically by means of the concentration of primary defects per unit
fluence. The results are compared to the similar ones corresponding to diamond,
silicon and GaAs.Comment: 9 pages, 2 figures, in press to Nuclear Instruments and Methods in
Physics Research A v2 - modified title, and major revision
Structure and optical properties of silicon layers with GaSb nanocrystals created by ion-beam synthesis
We have studied the ion-beam synthesis of GaSb nanocrystals in Si by high-fluence implantation of Sb and Ga ions followed by thermal annealing. RBS, TEM/TED, RS, and photoluminescence (PL) were employed to characterize the implanted layers. It was found that the nanocrystals size increases from 5 to 60 nm in the samples annealed at 900 8Cup to 20–90 nm in the samples annealed at 1100 8C. An existence of significant mechanical stresses within implanted layers has been detected. The stress values have been calculated from the shift of the Si first order Raman band. For the samples annealed at 900 8C a broad band in the spectral region of about
0.75–1.05 eV is detected in the PL spectra. The nature of this PL band is discussed
Recommended from our members
Application of multiplexed ion mobility spectrometry towards the identification of host protein signatures of treatment effect in pulmonary tuberculosis.
RationaleThe monitoring of TB treatments in clinical practice and clinical trials relies on traditional sputum-based culture status indicators at specific time points. Accurate, predictive, blood-based protein markers would provide a simpler and more informative view of patient health and response to treatment.ObjectiveWe utilized sensitive, high throughput multiplexed ion mobility-mass spectrometry (IM-MS) to characterize the serum proteome of TB patients at the start of and at 8 weeks of rifamycin-based treatment. We sought to identify treatment specific signatures within patients as well as correlate the proteome signatures to various clinical markers of treatment efficacy.MethodsSerum samples were collected from 289 subjects enrolled in CDC TB Trials Consortium Study 29 at time of enrollment and at the end of the intensive phase (after 40 doses of TB treatment). Serum proteins were immunoaffinity-depleted of high abundant components, digested to peptides and analyzed for data acquisition utilizing a unique liquid chromatography IM-MS platform (LC-IM-MS). Linear mixed models were utilized to identify serum protein changes in the host response to antibiotic treatment as well as correlations with culture status end points.ResultsA total of 10,137 peptides corresponding to 872 proteins were identified, quantified, and used for statistical analysis across the longitudinal patient cohort. In response to TB treatment, 244 proteins were significantly altered. Pathway/network comparisons helped visualize the interconnected proteins, identifying up regulated (lipid transport, coagulation cascade, endopeptidase activity) and down regulated (acute phase) processes and pathways in addition to other cross regulated networks (inflammation, cell adhesion, extracellular matrix). Detection of possible lung injury serum proteins such as HPSE, significantly downregulated upon treatment. Analyses of microbiologic data over time identified a core set of serum proteins (TTHY, AFAM, CRP, RET4, SAA1, PGRP2) which change in response to treatment and also strongly correlate with culture status. A similar set of proteins at baseline were found to be predictive of week 6 and 8 culture status.ConclusionA comprehensive host serum protein dataset reflective of TB treatment effect is defined. A repeating set of serum proteins (TTHY, AFAM, CRP, RET4, SAA1, PGRP2, among others) were found to change significantly in response to treatment, to strongly correlate with culture status, and at baseline to be predictive of future culture conversion. If validated in cohorts with long term follow-up to capture failure and relapse of TB, these protein markers could be developed for monitoring of treatment in clinical trials and in patient care
- …