88 research outputs found
Care for children with atopic dermatitis in the Netherlands during the COVID-19 pandemic:Lessons from the first wave and implications for the future
The first wave of the coronavirus disease 2019 (COVID-19) pandemic had an enormous impact on health-care services, including on care provision for children with atopic dermatitis (AD). We investigated the impact of COVID-19 on the care for children with moderate to severe AD at our tertiary outpatient clinic and examined satisfaction with care. We reviewed outpatient records, comparing total number and types of consultations during the first COVID-19 wave (March until July 2020) with the corresponding months of 2019 and 2018. In addition, we conducted a questionnaire-based study investigating the impact of COVID-19 on clinical and psychological symptoms, and satisfaction with care. A total number of 913 consultations (466 individual children) were conducted during the first COVID-19 wave in 2020, while 698 (391 individual children) and 591 consultations (356 individual children) were conducted in 2019 and 2018. The proportion of remote consultations was higher (56.2%) compared to 14.0% in 2019 and 12.7% in 2018. Worsening of AD was reported by 9.7% of caretakers. Overall satisfaction with provided care was high (8.6; interquartile range [IQR] = 7.3–10.0). Caretakers receiving face-to-face consultation were significantly (p = 0.026) more satisfied (9.0; IQR = 8.0–10.0) than caretakers receiving remote consultation (7.9; IQR = 7.0–9.5). The COVID-19 pandemic had an unprecedented impact on care provision for children with AD, particularly on the number of remote consultations. Overall satisfaction with care was high. The impact of COVID-19 on disease severity remained limited. Remote consultations seem to be a useful tool that can be put into practice during the COVID-19 pandemic
Composition Dependence of the Structure and Electronic Properties of Liquid Ga-Se Alloys Studied by Ab Initio Molecular Dynamics Simulation
Ab initio molecular dynamics simulation is used to study the structure and
electronic properties of the liquid Ga-Se system at the three compositions
GaSe, GaSe and GaSe, and of the GaSe and GaSe crystals. The
calculated equilibrium structure of GaSe crystal agrees well with available
experimental data. The neutron-weighted liquid structure factors calculated
from the simulations are in reasonable agreement with recent neutron
diffraction measurements. Simulation results for the partial radial
distribution functions show that the liquid structure is closely related to
that of the crystals. A close similarity between solid and liquid is also found
for the electronic density of states and charge density. The calculated
electronic conductivity decreases strongly with increasing Se content, in
accord with experimental measurements.Comment: REVTeX, 8 pages and 12 uuencoded PostScript figures, submitted to
Phys. Rev. B. corresponding author: [email protected]
Surface Structure of Liquid Metals and the Effect of Capillary Waves: X-ray Studies on Liquid Indium
We report x-ray reflectivity (XR) and small angle off-specular diffuse
scattering (DS) measurements from the surface of liquid Indium close to its
melting point of C. From the XR measurements we extract the surface
structure factor convolved with fluctuations in the height of the liquid
surface. We present a model to describe DS that takes into account the surface
structure factor, thermally excited capillary waves and the experimental
resolution. The experimentally determined DS follows this model with no
adjustable parameters, allowing the surface structure factor to be deconvolved
from the thermally excited height fluctuations. The resulting local electron
density profile displays exponentially decaying surface induced layering
similar to that previously reported for Ga and Hg. We compare the details of
the local electron density profiles of liquid In, which is a nearly free
electron metal, and liquid Ga, which is considerably more covalent and shows
directional bonding in the melt. The oscillatory density profiles have
comparable amplitudes in both metals, but surface layering decays over a length
scale of \AA for In and \AA for Ga. Upon controlled
exposure to oxygen, no oxide monolayer is formed on the liquid In surface,
unlike the passivating film formed on liquid Gallium.Comment: 9 pages, 5 figures; submitted to Phys. Rev.
First principles simulations of liquid Fe-S under Earth's core conditions
First principles electronic structure calculations, based upon density
functional theory within the generalized gradient approximation and ultra-soft
Vanderbilt pseudopotentials, have been used to simulate a liquid alloy of iron
and sulfur at Earth's core conditions. We have used a sulfur concentration of
wt, in line with the maximum recent estimates of the sulfur
abundance in the Earth's outer core. The analysis of the structural, dynamical
and electronic structure properties has been used to report on the effect of
the sulfur impurities on the behavior of the liquid. Although pure sulfur is
known to form chains in the liquid phase, we have not found any tendency
towards polymerization in our liquid simulation. Rather, a net S-S repulsion is
evident, and we propose an explanation for this effect in terms of the
electronic structure. The inspection of the dynamical properties of the system
suggests that the sulfur impurities have a negligible effect on the viscosity
of Earth's liquid core.Comment: 24 pages (including 8 figures
The Structure, Dynamics and Electronic Structure of Liquid Ag-Se Alloys Investigated by Ab Initio Simulation
Ab initio molecular-dynamics simulations have been used to investigate the
structure, dynamics and electronic properties of the liquid alloy Ag(1-x)Se(x)
at 1350 K and at the three compositions x=0.33, 0.42 and 0.65. The calculations
are based on density-functional theory in the local density approximation and
on the pseudopotential plane-wave method. The reliability of the simulations is
confirmed by detailed comparisons with very recent neutron diffraction results
for the partial structure factors and radial distribution functions (RDF) of
the stoichiometric liquid Ag2Se. The simulations show a dramatic change of the
Se-Se RDF with increasing Se content. This change is due to the formation of Se
clusters bound by covalent bonds, the Se-Se bond length being almost the same
as in pure c-Se and l-Se. The clusters are predominantly chain-like, but for
higher x a large fraction of 3-fold coordinated Se atoms is also found. It is
shown that the equilibrium fractions of Se present as isolated atoms and in
clusters can be understood on a simple charge-balance model based on an ionic
interpretation. The Ag and Se diffusion coefficients both increase with Se
content, in spite of the Se clustering. An analysis of the Se-Se bond dynamics
reveals surprisingly short bond lifetimes of less than 1 ps. The changes in the
density of states with composition arise directly from the formation of Se-Se
covalent bonds. Results for the electronic conductivity obtained using the
Kubo-Greenwood approximation are in adequate agreement with experiment for
l-Ag2Se, but not for the high Se contents. Possible reasons for this are
discussed.Comment: 14 pages, Revtex, 14 Postscript figures embedded in the tex
A Coupled Map Lattice model for geomagnetic polarity reversals that exhibits realistic scaling
Iron under Earth's core conditions: Liquid-state thermodynamics and high-pressure melting curve
{\em Ab initio} techniques based on density functional theory in the
projector-augmented-wave implementation are used to calculate the free energy
and a range of other thermodynamic properties of liquid iron at high pressures
and temperatures relevant to the Earth's core. The {\em ab initio} free energy
is obtained by using thermodynamic integration to calculate the change of free
energy on going from a simple reference system to the {\em ab initio} system,
with thermal averages computed by {\em ab initio} molecular dynamics
simulation. The reference system consists of the inverse-power pair-potential
model used in previous work. The liquid-state free energy is combined with the
free energy of hexagonal close packed Fe calculated earlier using identical
{\em ab initio} techniques to obtain the melting curve and volume and entropy
of melting. Comparisons of the calculated melting properties with experimental
measurement and with other recent {\em ab initio} predictions are presented.
Experiment-theory comparisons are also presented for the pressures at which the
solid and liquid Hugoniot curves cross the melting line, and the sound speed
and Gr\"{u}neisen parameter along the Hugoniot. Additional comparisons are made
with a commonly used equation of state for high-pressure/high-temperature Fe
based on experimental data.Comment: 16 pages including 6 figures and 5 table
Nonquasiparticle states in half-metallic ferromagnets
Anomalous magnetic and electronic properties of the half-metallic
ferromagnets (HMF) have been discussed. The general conception of the HMF
electronic structure which take into account the most important correlation
effects from electron-magnon interactions, in particular, the spin-polaron
effects, is presented. Special attention is paid to the so called
non-quasiparticle (NQP) or incoherent states which are present in the gap near
the Fermi level and can give considerable contributions to thermodynamic and
transport properties. Prospects of experimental observation of the NQP states
in core-level spectroscopy is discussed. Special features of transport
properties of the HMF which are connected with the absence of one-magnon
spin-flip scattering processes are investigated. The temperature and magnetic
field dependences of resistivity in various regimes are calculated. It is shown
that the NQP states can give a dominate contribution to the temperature
dependence of the impurity-induced resistivity and in the tunnel junction
conductivity. First principle calculations of the NQP-states for the prototype
half-metallic material NiMnSb within the local-density approximation plus
dynamical mean field theory (LDA+DMFT) are presented.Comment: 27 pages, 9 figures, Proceedings of Berlin/Wandlitz workshop 2004;
Local-Moment Ferromagnets. Unique Properties for Moder Applications, ed. M.
Donath, W.Nolting, Springer, Berlin, 200
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