140 research outputs found
Bandgap and effective mass of epitaxial cadmium oxide
The bandgap and band-edge effective mass of single crystal cadmium oxide, epitaxially grown by metal-organic vapor-phase epitaxy, are determined from infrared reflectivity, ultraviolet/visible absorption, and Hall effect measurements. Analysis and simulation of the optical data, including effects of band nonparabolicity, Moss-Burstein band filling and bandgap renormalization, reveal room temperature bandgap and band-edge effective mass values of 2.16±0.02 eV and 0.21±0.01m0 respectively
Isospin-0 s-wave scattering length from twisted mass lattice QCD
We present results for the isospin-0 s-wave scattering length
calculated with Osterwalder-Seiler valence quarks on Wilson twisted mass gauge
configurations. We use three ensembles with unitary (valence) pion
mass at its physical value (250MeV), at 240MeV (320MeV) and
at 330MeV (400MeV), respectively. By using the stochastic Laplacian
Heaviside quark smearing method, all quark propagation diagrams contributing to
the isospin-0 correlation function are computed with sufficient
precision. The chiral extrapolation is performed to obtain the scattering
length at the physical pion mass. Our result agrees reasonably well with various experimental measurements and
theoretical predictions. Since we only use one lattice spacing, certain
systematics uncertainties, especially those arising from unitary breaking, are
not controlled in our result.Comment: 21 pages, 5 figures, 6 table
Complete flavor decomposition of the spin and momentum fraction of the proton using lattice QCD simulations at physical pion mass
We evaluate the gluon and quark contributions to the spin of the proton using
an ensemble of gauge configuration generated at physical pion mass. We compute
all valence and sea quark contributions to high accuracy. We perform a
non-perturbative renormalization for both quark and gluon matrix elements. We
find that the contribution of the up, down, strange and charm quarks to the
proton intrinsic spin is
and to the total spin
. The gluon contribution to the spin is
yielding confirming the spin sum. The
momentum fraction carried by quarks in the proton is found to be
and by gluons , the sum of which gives confirming the
momentum sum rule. All scale and scheme dependent quantities are given in the
scheme at 2 GeV
Optical Absorption of an Interacting Many-Polaron Gas
The optical absorption of a many (continuum) polaron gas is derived in the
framework of a variational approach at zero temperature and weak or
intermediate electron-phonon coupling strength. We derive a compact formula for
the optical conductivity of the many-polaron system taking into account
many-body effects in the electron or hole system. Within the method presented
here, these effects are contained completely in the dynamical structure factor
of the electron or hole system. This allows to build on well-established
studies of the interacting electron gas. Based on this approach a novel feature
in the absorption spectrum of the many-polaron gas, related to the emission of
a plasmon together with a phonon, is identified. As an application and
illustration of the technique, we compare the theoretical many-polaron optical
absorption spectrum as derived in the present work with the `d-band' absorption
feature in NdCuO. Similarities are shown between the theoretically
and the experimentally derived first frequency moment of the optical absorption
of a family of differently doped NdCeCuO materials.Comment: 24 pages, 5 figures; revised and expanded versio
Isospin-0 ππ scattering from twisted mass lattice QCD
We present results for the isospin-0 s-wave scattering length
calculated in twisted mass lattice QCD. We use three ensembles with
unitary pion mass at its physical value, 240~MeV and 330~MeV respectively. We
also use a large set of ensembles with unitary pion masses
varying in the range of 230~MeV - 510~MeV at three different values of the
lattice spacing. A mixed action approach with the Osterwalder-Seiler action in
the valence sector is adopted to circumvent the complications arising from
isospin symmetry breaking of the twisted mass quark action. Due to the
relatively large lattice artefacts in the ensembles, we do not
present the scattering lengths for these ensembles. Instead, taking the
advantage of the many different pion masses of these ensembles, we
qualitatively discuss the pion mass dependence of the scattering properties of
this channel based on the results from the ensembles. The
scattering length is computed for the ensembles and the chiral
extrapolation is performed. At the physical pion mass, our result agrees reasonably well with various
experimental measurements and theoretical predictions
Effective treatment of severe thermodysregulation by oral retinoids in a patient with recessive congenital lamellar ichthyosis
Ichthyoses are a heterogenous group of keratinization disorders, which are often associated with hypohidrosis. We report a 42-year-old man with generalized thick brownish scales and severe thermodysregulation leading to heat intolerance. Based on clinical, histological and genetic findings, autosomal recessive lamellar ichthyosis (ultrastructural electron microscopy type III) was diagnosed. Severe generalized hypohidrosis both at rest and after physical exercise (bicycle ergometer) was documented. Oral treatment with retinoids not only markedly improved the skin condition but also restarted the ability of the patient to thermoregulate by perspiration. The normalization of sweat-gland function was confirmed by gravimetrically measuring sweat rates before and after retinoid treatment. This report shows that retinoid therapy can markedly improve the quality of life in patients with generalized lamellar ichthyosis by reconstitution of perspiration
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