2,976 research outputs found
Using information to deliver safer care: a mixed-methods study exploring general practitioners’ information needs in North West London primary care
The National Health Service in England has given increasing priority to improving inter-professional communication, enabling better management of patients with chronic conditions and reducing medical errors through effective use of information. Despite considerable efforts to reduce patient harm through better information usage, medical errors continue to occur, posing a serious threat to patient safety.This study explores the range, quality and sophistication of existing information systems in primary care with the aim to capture what information practitioners need to provide a safe service and identify barriers to its effective use in care pathways.Data were collected through semi-structured interviews with general practitioners from surgeries in North West London and a survey evaluating their experience with information systems in care pathways.Important information is still missing, specifically discharge summaries detailing medication changes and changes in the diagnosis and management of patients, blood results ordered by hospital specialists and findings from clinical investigations. Participants identified numerous barriers, including the communication gap between primary and secondary care, the variable quality and consistency of clinical correspondence and the inadequate technological integration.Despite attempts to improve integration and information flow in care pathways, existing systems provide practitioners with only partial access to information, hindering their ability to take informed decisions. This study offers a framework for understanding what tools should be in place to enable effective use of information in primary care
First principles study of adsorbed Cu_n (n=1-4) microclusters on MgO(100): structural and electronic properties
We present a density functional study of the structural and electronic
properties of small Cu_n (n=1,4) aggregates on defect-free MgO(100). The
calculations employ a slab geometry with periodic boundary conditions,
supercells with up to 76 atoms, and include full relaxation of the surface
layer and of all adsorbed atoms. The preferred adsorption site for a single Cu
adatom is on top of an oxygen atom. The adsorption energy and Cu-O distance are
E_S-A = 0.99 eV and d_S-A = 2.04 Angstroems using the Perdew-Wang gradient
corrected exchange correlation functional. The saddle point for surface
diffusion is at the "hollow" site, with a diffusion barrier of around 0.45 eV.
For the adsorbed copper dimer, two geometries, one parallel and one
perpendicular to the surface, are very close in energy. For the adsorbed Cu_3,
a linear configuration is preferred to the triangular geometry. As for the
tetramer, the most stable adsorbed geometry for Cu_4 is a rhombus. The
adsorption energy per Cu atom decreases with increasing the size of the
cluster, while the Cu-Cu cohesive energy increases, rapidly becoming more
important than the adsorption energy.Comment: Major revision, Latex(2e) document, 23 pages, 11 figures, accepted
for publication in J. of Chem. Phys., paper available at
http://irrmawww.epfl.ch/vm/vm_wor
Local Structure Analysis in Liquid Water
Within the framework of density functional theory, the inclusion of exact
exchange and non-local van der Waals/dispersion (vdW) interactions is crucial
for predicting a microscopic structure of ambient liquid water that
quantitatively agrees with experiment. In this work, we have used the local
structure index (LSI) order parameter to analyze the local structure in such
highly accurate liquid water. At ambient conditions, the LSI
probability distribution, P(), was unimodal with most water molecules
characterized by more disordered high-density-like local environments. With
thermal excitations removed, the resultant bimodal P() in the inherent
potential energy surface (IPES) exhibited a 3:1 ratio between high- and
low-density-like molecules, with the latter forming small connected clusters
amid the predominant population. By considering the spatial correlations and
hydrogen bond network topologies water molecules with the same LSI
identities, we demonstrate that the signatures of the experimentally observed
low- (LDA) and high-density (HDA) amorphous phases of ice are present in the
IPES of ambient liquid water. Analysis of the LSI autocorrelation function
uncovered a persistence time of 4 ps---a finding consistent with the
fact that natural thermal fluctuations are responsible for transitions between
these distinct yet transient local aqueous environments in ambient liquid
water.Comment: 12 pages, 6 figure
Thermal Expansion in Dispersion-Bound Molecular Crystals
We explore how anharmonicity, nuclear quantum effects (NQE), many-body
dispersion interactions, and Pauli repulsion influence thermal properties of
dispersion-bound molecular crystals. Accounting for anharmonicity with
molecular dynamics yields cell parameters accurate to within 2% of
experiment for a set of pyridine-like molecular crystals at finite temperatures
and pressures. From the experimental thermal expansion curve, we find that
pyridine-I has a Debye temperature just above its melting point, indicating
sizable NQE across the entire crystalline range of stability. We find that NQE
lead to a substantial volume increase in pyridine-I (% more than
classical thermal expansion at K) and attribute this to intermolecular
Pauli repulsion promoted by intramolecular quantum fluctuations. When
predicting delicate properties such as the thermal expansivity, we show that
many-body dispersion interactions and sophisticated treatments of Pauli
repulsion are needed in dispersion-bound molecular crystals
Momentum distribution, vibrational dynamics and the potential of mean force in ice
By analyzing the momentum distribution obtained from path integral and phonon
calculations we find that the protons in hexagonal ice experience an
anisotropic quasi-harmonic effective potential with three distinct principal
frequencies that reflect molecular orientation. Due to the importance of
anisotropy, anharmonic features of the environment cannot be extracted from
existing experimental distributions that involve the spherical average. The
full directional distribution is required, and we give a theoretical prediction
for this quantity that could be verified in future experiments. Within the
quasi-harmonic context, anharmonicity in the ground state dynamics of the
proton is substantial and has quantal origin, a finding that impacts the
interpretation of several spectroscopies
Displaced path integral formulation for the momentum distribution of quantum particles
The proton momentum distribution, accessible by deep inelastic neutron
scattering, is a very sensitive probe of the potential of mean force
experienced by the protons in hydrogen-bonded systems. In this work we
introduce a novel estimator for the end to end distribution of the Feynman
paths, i.e. the Fourier transform of the momentum distribution. In this
formulation, free particle and environmental contributions factorize. Moreover,
the environmental contribution has a natural analogy to a free energy surface
in statistical mechanics, facilitating the interpretation of experiments. The
new formulation is not only conceptually but also computationally advantageous.
We illustrate the method with applications to an empirical water model,
ab-initio ice, and one dimensional model systems
Inverse design of disordered stealthy hyperuniform spin chains
Positioned between crystalline solids and liquids, disordered many-particle
systems which are stealthy and hyperuniform represent new states of matter that
are endowed with novel physical and thermodynamic properties. Such stealthy and
hyperuniform states are unique in that they are transparent to radiation for a
range of wavenumbers around the origin. In this work, we employ recently
developed inverse statistical-mechanical methods, which seek to obtain the
optimal set of interactions that will spontaneously produce a targeted
structure or configuration as a unique ground state, to investigate the
spin-spin interaction potentials required to stabilize disordered stealthy
hyperuniform one-dimensional (1D) Ising-like spin chains. By performing an
exhaustive search over the spin configurations that can be enumerated on
periodic 1D integer lattices containing sites, we were able
to identify and structurally characterize \textit{all} stealthy hyperuniform
spin chains in this range of system sizes. Within this pool of stealthy
hyperuniform spin configurations, we then utilized such inverse optimization
techniques to demonstrate that stealthy hyperuniform spin chains can be
realized as either unique or degenerate disordered ground states of radial
long-ranged (relative to the spin chain length) spin-spin interactions. Such
exotic ground states are distinctly different from spin glasses in both their
inherent structural properties and the nature of the spin-spin interactions
required to stabilize them. As such, the implications and significance of the
existence of such disordered stealthy hyperuniform ground state spin systems
warrants further study, including whether their bulk physical properties and
excited states, like their many-particle system counterparts, are singularly
remarkable, and can be experimentally realized.Comment: 11 pages, 9 figure
Optical study of the anisotropic erbium spin flip-flop dynamics
We investigate the erbium flip-flop dynamics as a limiting factor of the
electron spin lifetime and more generally as an indirect source of decoherence
in rare-earth doped insulators. Despite the random isotropic arrangement of
dopants in the host crystal, the dipolar interaction strongly depends on the
magnetic field orientation following the strong anisotropy of the -factor.
In Er:YSiO, we observe by transient optical spectroscopy a three
orders of magnitude variation of the erbium flip-flop rate (10ppm dopant
concentration). The measurements in two different samples, with 10ppm and 50ppm
concentrations, are well-supported by our analytic modeling of the dipolar
coupling between identical spins with an anisotropic -tensor. The model can
be applied to other rare-earth doped materials. We extrapolate the calculation
to Er:CaWO, Er:LiNbO and Nd:YSiO at
different concentrations
Electronic Properties of Molecules and Surfaces with a Self\uad-Consistent Interatomic van der Waals Density Functional.
How strong is the effect of van der Waals (vdW) interactions on the electronic properties of molecules
and extended systems? To answer this question, we derived a fully self-consistent implementation of the
density-dependent interatomic vdW functional of Tkatchenko and Scheffler [Phys. Rev. Lett. 102, 073005
(2009)]. Not surprisingly, vdW self-consistency leads to tiny modifications of the structure, stability, and
electronic properties of molecular dimers and crystals. However, unexpectedly large effects were found in
the binding energies, distances, and electrostatic moments of highly polarizable alkali-metal dimers. Most
importantly, vdW interactions induced complex and sizable electronic charge redistribution in the vicinity
of metallic surfaces and at organic-metal interfaces. As a result, a substantial influence on the computed
work functions was found, revealing a nontrivial connection between electrostatics and long-range electron
correlation effects
Hybrid Superconductor-Quantum Point Contact Devices using InSb Nanowires
Proposals for studying topological superconductivity and Majorana bound
states in nanowires proximity coupled to superconductors require that transport
in the nanowire is ballistic. Previous work on hybrid nanowire-superconductor
systems has shown evidence for Majorana bound states, but these experiments
were also marked by disorder, which disrupts ballistic transport. In this
letter, we demonstrate ballistic transport in InSb nanowires interfaced
directly with superconducting Al by observing quantized conductance at
zero-magnetic field. Additionally, we demonstrate that the nanowire is
proximity coupled to the superconducting contacts by observing Andreev
reflection. These results are important steps for robustly establishing
topological superconductivity in InSb nanowires
- …