1,736 research outputs found
Magnetophonon resonance in photoluminescence excitation spectra of magnetoexcitons in GaAs/Al0.3Ga0.7As superlattice
Strong increase in the intensity of the peaks of excited magneto-exciton (ME)
states in the photoluminescence excitation (PLE) spectra recorded for the
ground heavy-hole magneto-excitons (of the 1sHH type) has been found in a
GaAs/AlGaAs superlattice in strong magnetic field B applied normal to the
sample layers. While varying B the intensities of the PLE peaks have been
measured as functions of energy separation between excited ME peaks
and the ground state of the system. The resonance profiles have been found to
have maxima at close to the energy of the GaAs LO-phonon.
However, the value of depends on quantum numbers of the
excited ME state. The revealed very low quantum efficiency of the investigated
sample allows us to ascribe the observed resonance to the enhancement of the
non-radiative magneto-exciton relaxation rate arising due to LO-phonon
emission. The presented theoretical model, being in a good agreement with
experimental observations, provides a method to extract 1sHH magneto-exciton
``in-plane" dispersion from the dependence of on the
excited ME state quantum numbers.Comment: 9 pages, 6 figure
Analysis of coupled heat and moisture transfer in masonry structures
Evaluation of effective or macroscopic coefficients of thermal conductivity
under coupled heat and moisture transfer is presented. The paper first gives a
detailed summary on the solution of a simple steady state heat conduction
problem with an emphasis on various types of boundary conditions applied to the
representative volume element -- a periodic unit cell. Since the results
essentially suggest no superiority of any type of boundary conditions, the
paper proceeds with the coupled nonlinear heat and moisture problem subjecting
the selected representative volume element to the prescribed macroscopically
uniform heat flux. This allows for a direct use of the academic or commercially
available codes. Here, the presented results are derived with the help of the
SIFEL (SIimple Finite Elements) system.Comment: 23 pages, 11 figure
Radiolabeling an Electronic Cigarette Aerosol Using Technetium Carbon Ultrafine Particles
Background: Electronic cigarettes (ECIGs) are widely used, but their health effects are not well known. ECIG exposure is difficult to quantify, and a direct measurement of deposition would be beneficial to in vivo and in vitro toxicity studies. The aim of this study was to demonstrate effective radiolabeling of an ECIG. Methods: A technetium-99m-labeled carbon ultrafine (TCU) aerosol was generated and introduced to a fourth-generation ECIG before nucleation and aerosol formation. The aerosolized e-liquid was a commercially available strawberry flavor containing 1.2% nicotine in a 55% propylene glycol and 45% vegetable glycerine base. An ECIG power setting of 100 W was selected. Mass and radioactivity were measured on each stage within a Sierra Cascade Impactor at 14 L/min to verify the labeling technique using the calculated aerodynamic diameters. A strong positive correlation (R 2 > 0.95) between the percent activity and percent mass deposition on each stage provides a reliable validation of colocation. Results: Unlabeled ECIG aerosol from the chosen e-liquid produced a mass median aerodynamic diameter (MMAD) of 0.85 ÎĽm. An ECIG labeled with TCU produced an aerosol with an activity median aerodynamic diameter of 0.84 ÎĽm and an MMAD of 0.84 ÎĽm. The relative mass versus radioactivity on each plate was highly correlated (average R 2 = 0.973, p < 0.001). Conclusion: A TCU radiolabel was generated and shown to associate with the mass of an aerosol produced by a typical commercially available ECIG. Thus, the radioactivity of the deposited aerosol may be used to determine ECIG aerosol deposition for the future in vivo and in vitro dosimetry studies of the third- and fourth-generation ECIGs
Magneto infra-red absorption in high electronic density GaAs quantum wells
Magneto infra-red absorption measurements have been performed in a highly
doped GaAs quantum well which has been lifted off and bonded to a silicon
substrate, in order to study the resonant polaron interaction. It is found that
the pinning of the cyclotron energy occurs at an energy close to that of the
transverse optical phonon of GaAs. This unexpected result is explained by a
model taking into account the full dielectric constant of the quantum well.Comment: 4 pages, 4 figures, to be published in Phys. Rev. Let
Invariant Sets and Explicit Solutions to a Third-Order Model for the Shearless Stratified Turbulent Flow
We study dynamics of the shearless stratified turbulent flows. Using the
method of differential constraints we find a class of explicit solutions to the
problem under consideration and establish that the differential constraint
obtained coincides with the well-known Zeman--Lumley model for stratified
flows.Comment: arxiv version is already officia
Minimal Model for Sand Dunes
We propose a minimal model for aeolian sand dunes. It combines an analytical
description of the turbulent wind velocity field above the dune with a
continuum saltation model that allows for saturation transients in the sand
flux. The model provides a qualitative understanding of important features of
real dunes, such as their longitudinal shape and aspect ratio, the formation of
a slip face, the breaking of scale invariance, and the existence of a minimum
dune size.Comment: 4 pages, 4 figures, replaced with publishd versio
Electron-impact excitation of the (5d106s)2S1/2-(5d106p)2P1/2,3/2 resonance transitions in gold atoms
Results from a joint experimental and theoretical investigation of electron-impact excitation of the (5 d10 6s) S2 1/2 → (5 d10 6p) P2 1/2,3/2 resonance transitions in gold atoms are presented. The calculations were performed using three fully relativi
The Phenotypic Spectrum of 47 Czech Patients with Single, Large-Scale Mitochondrial DNA Deletions
BACKGROUND:
In this retrospective study, we analysed clinical, biochemical and molecular genetic data of 47 Czech patients with Single, Large-Scale Mitochondrial DNA Deletions (SLSMD).
METHODS:
The diagnosis was based on the long-range PCR (LX-PCR) screening of mtDNA isolated from muscle biopsy in 15 patients, and from the buccal swab, urinary epithelial cells and blood in 32 patients.
RESULTS:
A total of 57% patients manifested before the age of 16. We did not find any significant difference between paediatric and adult manifestation in either the proportion of patients that would develop extraocular symptoms, or the timespan of its progression. The survival rate in patients with Pearson Syndrome reached 60%. Altogether, five patients manifested with atypical phenotype not fulfilling the latest criteria for SLSMD. No correlation was found between the disease severity and all heteroplasmy levels, lengths of the deletion and respiratory chain activities in muscle.
CONCLUSIONS:
Paediatric manifestation of Progressive External Ophthalmoplegia (PEO) is not associated with a higher risk of multisystemic involvement. Contrary to PEO and Kearns-Sayre Syndrome Spectrum, Pearson Syndrome still contributes to a significant childhood mortality. SLSMD should be considered even in cases with atypical presentation. To successfully identify carriers of SLSMD, a repeated combined analysis of buccal swab and urinary epithelial cells is neede
Generated heat by different targets irradiated by 660 MeV protons
246-254Calorimetric experiments have been performed to analyze different thick targets of natU, C, Pb material, irradiated by 660 MeV protons at the Phasotron accelerator facility, Joint Institute for Nuclear Research (JINR) in Dubna, Russia. The method of online temperature measurement has been compared with MCNPXÂ 2.7.0 simulation and selected with Ansys Transient Thermal Simulation to compare measured temperature with the simulated one. Thermocouples type T and E have been used as a temperature probe. Many different positions have been measured for each target. Temperature results are following very well the processes inside of the cylinders. Changes of heat deposition caused by drops of the proton beam intensity are displayed very well as a jagged line shown in almost every chart. Accurate temperature changing measurement is a very modest variation of how to observe inner macroscopic behavior online
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