3,224 research outputs found
The thermal conductivity reduction in HgTe/CdTe superlattices
The techniques used previously to calculate the three-fold thermal
conductivity reduction due to phonon dispersion in GaAs/AlAs superlattices
(SLs) are applied to HgTe/CdTe SLs. The reduction factor is approximately the
same, indicating that this SL may be applicable both as a photodetector and a
thermoelectric cooler.Comment: 5 pages, 2 figures; to be published in Journal of Applied Physic
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Cervical cancer in Tanzania: A systematic review of current challenges in six domains.
Cervical cancer is the most common cancer in Tanzania. After excluding human immunodeficiency virus, lower respiratory infections, malaria, diarrheal diseases, and tuberculosis, cervical cancer kills more women than any other form of illness in the country. Unfortunately, Tanzania has a low doctor-to-patient ratio (1:50,000) and nearly 7000 women die each year from this disease. The clinical problem is further magnified by the country\u27s lack of resources and prevailing poverty, sporadic cervical cancer screening, prevalence of high-risk oncogenic human papillomavirus subtypes, and relatively high rates of human immunodeficiency virus co-infection. In recent years, addressing the cervical cancer problem has become a priority for the Tanzanian government. In this systematic review of 39 peer-reviewed publications that appeared in the PubMed/MEDLINE (NCBI) database from 2013 to 2018, we synthesize the growing body of literature to capture current trends in Tanzania\u27s evolving cervical cancer landscape. Six domains were identified, including risk factors, primary prevention, barriers to screening, treatment, healthcare worker education, and sustainability. In addition to traditional risk factors associated with sexual behavior, acetowhite changes observed during visual inspection of the cervix with acetic acid, lower education, rural setting, and HIV positivity also have a noteworthy clinical impact
Quantum simulations of the superfluid-insulator transition for two-dimensional, disordered, hard-core bosons
We introduce two novel quantum Monte Carlo methods and employ them to study
the superfluid-insulator transition in a two-dimensional system of hard-core
bosons. One of the methods is appropriate for zero temperature and is based
upon Green's function Monte Carlo; the other is a finite-temperature world-line
cluster algorithm. In each case we find that the dynamical exponent is
consistent with the theoretical prediction of by Fisher and co-workers.Comment: Revtex, 10 pages, 3 figures (postscript files attached at end,
separated by %%%%%% Fig # %%%%%, where # is 1-3). LA-UR-94-270
Center of mass and relative motion in time dependent density functional theory
It is shown that the exchange-correlation part of the action functional
in time-dependent density functional theory , where
is the time-dependent density, is invariant under the
transformation to an accelerated frame of reference , where is an arbitrary
function of time. This invariance implies that the exchange-correlation
potential in the Kohn-Sham equation transforms in the following manner:
. Some of the
approximate formulas that have been proposed for satisfy this exact
transformation property, others do not. Those which transform in the correct
manner automatically satisfy the ``harmonic potential theorem", i.e. the
separation of the center of mass motion for a system of interacting particles
in the presence of a harmonic external potential. A general method to generate
functionals which possess the correct symmetry is proposed
Anisotropic two-dimensional Heisenberg model by Schwinger-boson Gutzwiller projected method
Two-dimensional Heisenberg model with anisotropic couplings in the and
directions () is considered. The model is first solved in the
Schwinger-boson mean-field approximation. Then the solution is Gutzwiller
projected to satisfy the local constraint that there is only one boson at each
site. The energy and spin-spin correlation of the obtained wavefunction are
calculated for systems with up to sites by means of the
variational Monte Carlo simulation. It is shown that the antiferromagnetic
long-range order remains down to the one-dimensional limit.Comment: 15 pages RevTex3.0, 4 figures, available upon request, GWRVB8-9
Effect of inter-wall surface roughness correlations on optical spectra of quantum well excitons
We show that the correlation between morphological fluctuations of two
interfaces confining a quantum well strongly suppresses a contribution of
interface disorder to inhomogeneous line width of excitons. We also demonstrate
that only taking into account these correlations one can explain all the
variety of experimental data on the dependence of the line width upon thickness
of the quantum well.Comment: 13 pages, 8 figures, Revtex4, submitted to PR
Initial Hubble Diagram Results from the Nearby Supernova Factory
The use of Type Ia supernovae as distance indicators led to the discovery of
the accelerating expansion of the universe a decade ago. Now that large second
generation surveys have significantly increased the size and quality of the
high-redshift sample, the cosmological constraints are limited by the currently
available sample of ~50 cosmologically useful nearby supernovae. The Nearby
Supernova Factory addresses this problem by discovering nearby supernovae and
observing their spectrophotometric time development. Our data sample includes
over 2400 spectra from spectral timeseries of 185 supernovae. This talk
presents results from a portion of this sample including a Hubble diagram
(relative distance vs. redshift) and a description of some analyses using this
rich dataset.Comment: Short version of proceedings for ICHEP08, Philadelphia PA, July 2008;
see v1 for full-length versio
Non-circular semiconductor nanorings of type I and II: Emission kinetics in the exciton Aharonov-Bohm effect
Transition energies and oscillator strengths of excitons in dependence on
magnetic field are investigated in type I and II semiconductor nanorings. A
slight deviation from circular (concentric) shape of the type II nanoring gives
a better observability of the Aharonov-Bohm oscillations since the ground state
is always optically active. Kinetic equations for the exciton occupation are
solved with acoustic phonon scattering as the major relaxation process, and
absorption and luminescence spectra are calculated showing deviations from
equilibrium. The presence of a non-radiative exciton decay leads to a quenching
of the integrated photoluminescence with magnetic field.Comment: The first version submitted to Phys. Rev. B on April 16, 2007.
Revised (this) version on July 31, 200
Time-dependent density functional theory beyond the adiabatic local density approximation
In the current density functional theory of linear and nonlinear
time-dependent phenomena, the treatment of exchange and correlation beyond the
level of the adiabatic local density approximation is shown to lead to the
appearance of viscoelastic stresses in the electron fluid. Complex and
frequency-dependent viscosity/elasticity coefficients are microscopically
derived and expressed in terms of properties of the homogeneous electron gas.
As a first consequence of this formalism, we provide an explicit formula for
the linewidths of collective excitations in electronic systems.Comment: RevTeX, 4 page
Correction to: Evaluation of different deployment strategies for larviciding to control malaria: a simulation study
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