553 research outputs found
Nurse led care
What's the difference between medical and nursing care? The answer is not straightforward, but shortages in the medical workforce mean that nurses are increasingly called on to undertake work that was previously done by doctors (such as undertaking surgery,1 prescribing drugs, performing triage in emergency departments), whereas shortages in the nursing workforce mean that healthcare assistants now do many tasks that nurses are trained to do. This fluidity in professional roles and competencies enables the health workforce to respond to need, but are outcomes for patients being improved? Do these benefits come at an additional cost, and if so, are they worth paying for
Linear scaling calculation of band edge states and doped semiconductors
Linear scaling methods provide total energy, but no energy levels and
canonical wavefuctions. From the density matrix computed through the density
matrix purification methods, we propose an order-N (O(N)) method for
calculating both the energies and wavefuctions of band edge states, which are
important for optical properties and chemical reactions. In addition, we also
develop an O(N) algorithm to deal with doped semiconductors based on the O(N)
method for band edge states calculation. We illustrate the O(N) behavior of the
new method by applying it to boron nitride (BN) nanotubes and BN nanotubes with
an adsorbed hydrogen atom. The band gap of various BN nanotubes are
investigated systematicly and the acceptor levels of BN nanotubes with an
isolated adsorbed H atom are computed. Our methods are simple, robust, and
especially suited for the application in self-consistent field electronic
structure theory
Imaging and manipulating electrons in a 1D quantum dot with Coulomb blockade microscopy
Motivated by the recent experiments by the Westervelt group using a mobile
tip to probe the electronic state of quantum dots formed on a segmented
nanowire, we study the shifts in Coulomb blockade peak positions as a function
of the spatial variation of the tip potential, which can be termed "Coulomb
blockade microscopy". We show that if the tip can be brought sufficiently close
to the nanowire, one can distinguish a high density electronic liquid state
from a Wigner crystal state by microscopy with a weak tip potential. In the
opposite limit of a strongly negative tip potential, the potential depletes the
electronic density under it and divides the quantum wire into two partitions.
There the tip can push individual electrons from one partition to the other,
and the Coulomb blockade micrograph can clearly track such transitions. We show
that this phenomenon can be used to qualitatively estimate the relative
importance of the electron interaction compared to one particle potential and
kinetic energies. Finally, we propose that a weak tip Coulomb blockade
micrograph focusing on the transition between electron number N=0 and N=1
states may be used to experimentally map the one-particle potential landscape
produced by impurities and inhomogeneities.Comment: 4 pages 7 figure
Ordered and periodic chaos of the bounded one dimensinal multibarrier potential
Numerical analysis indicates that there exists an unexpected new ordered
chaos for the bounded one-dimensional multibarrier potential. For certain
values of the number of barriers, repeated identical forms (periods) of the
wavepackets result upon passing through the multibarrier potential.Comment: 16 pages, 9 figures, 1 Table. Some former text removed and other
introduce
Local electronic nematicity in the one-band Hubbard model
Nematicity is a well known property of liquid crystals and has been recently
discussed in the context of strongly interacting electrons. An electronic
nematic phase has been seen by many experiments in certain strongly correlated
materials, in particular, in the pseudogap phase generic to many hole-doped
cuprate superconductors. Recent measurements in high superconductors has
shown even if the lattice is perfectly rotationally symmetric, the ground state
can still have strongly nematic local properties. Our study of the
two-dimensional Hubbard model provides strong support of the recent
experimental results on local rotational symmetry breaking. The
variational cluster approach is used here to show the possibility of an
electronic nematic state and the proximity of the underlying symmetry-breaking
ground state within the Hubbard model. We identify this nematic phase in the
overdoped region and show that the local nematicity decreases with increasing
electron filling. Our results also indicate that strong Coulomb interaction may
drive the nematic phase into a phase similar to the stripe structure. The
calculated spin (magnetic) correlation function in momentum space shows the
effects resulting from real-space nematicity
The Optimal Inhomogeneity for Superconductivity: Finite Size Studies
We report the results of exact diagonalization studies of Hubbard models on a
square lattice with periodic boundary conditions and various
degrees and patterns of inhomogeneity, which are represented by inequivalent
hopping integrals and . We focus primarily on two patterns, the
checkerboard and the striped cases, for a large range of values of the on-site
repulsion and doped hole concentration, . We present evidence that
superconductivity is strongest for of order the bandwidth, and intermediate
inhomogeneity, . The maximum value of the ``pair-binding
energy'' we have found with purely repulsive interactions is for the checkerboard Hubbard model with and .
Moreover, for near optimal values, our results are insensitive to changes in
boundary conditions, suggesting that the correlation length is sufficiently
short that finite size effects are already unimportant.Comment: 8 pages, 9 figures; minor revisions; more references adde
Theory of momentum resolved tunneling into a short quantum wire
Motivated by recent tunneling experiments in the parallel wire geometry, we
calculate results for momentum resolved tunneling into a short one-dimensional
wire, containing a small number of electrons. We derive some general theorems
about the momentum dependence, and we carry out exact calculations for up to
N=4 electrons in the final state, for a system with screened Coulomb
interactions that models the situation of the experiments. We also investigate
the limit of large using a Luttinger-liquid type analysis. We consider the
low-density regime, where the system is close to the Wigner crystal limit, and
where the energy scale for spin excitations can be much lower than for charge
excitations, and we consider temperatures intermediate between the relevant
spin energies and charge excitations, as well as temperatures below both energy
scales.Comment: 19 pages, 13 figures, clarified text in a few points, added 1 figure,
updated reference
What's the evidence that NICE guidance has been implemented? Results from a national evaluation using time series analysis, audit of patients' notes, and interviews
OBJECTIVES: To assess the extent and pattern of implementation of guidance issued by the National Institute for Clinical Excellence (NICE). DESIGN: Interrupted time series analysis, review of case notes, survey, and interviews. SETTING: Acute and primary care trusts in England and Wales. PARTICIPANTS: All primary care prescribing, hospital pharmacies; a random sample of 20 acute trusts, 17 mental health trusts, and 21 primary care trusts; and senior clinicians and managers from five acute trusts. MAIN OUTCOME MEASURES: Rates of prescribing and use of procedures and medical devices relative to evidence based guidance. RESULTS: 6308 usable patient audit forms were returned. Implementation of NICE guidance varied by trust and by topic. Prescribing of some taxanes for cancer (P <0.002) and orlistat for obesity (P <0.001) significantly increased in line with guidance. Prescribing of drugs for Alzheimer’s disease and prophylactic extraction of wisdom teeth showed trends consistent with, but not obviously a consequence of, the guidance. Prescribing practice often did not accord with the details of the guidance. No change was apparent in the use of hearing aids, hip prostheses, implantable cardioverter defibrillators, laparoscopic hernia repair, and laparoscopic colorectal cancer surgery after NICE guidance had been issued. CONCLUSIONS: Implementation of NICE guidance has been variable. Guidance seems more likely to be adopted when there is strong professional support, a stable and convincing evidence base, and no increased or unfunded costs, in organisations that have established good systems for tracking guidance implementation and where the professionals involved are not isolated. Guidance needs to be clear and reflect the clinical context
Fluctuations of the correlation dimension at metal-insulator transitions
We investigate numerically the inverse participation ratio, , of the 3D
Anderson model and of the power-law random banded matrix (PRBM) model at
criticality. We found that the variance of scales with system size
as , being the
correlation dimension and the system dimension. Therefore the concept of a
correlation dimension is well defined in the two models considered. The 3D
Anderson transition and the PRBM transition for (see the text for the
definition of ) are fairly similar with respect to all critical magnitudes
studied.Comment: RevTex, 5 pages, 4 eps figures, to be published in Phys. Rev. Let
Iterative methods for solving Ax = b GMRES/FOM versus QMR/BiCG
We study the convergence of GMRES/FOM and QMR/BiCG methods for solving
nonsymmetric Az = b. We prove that given the results of a BiCG
computation on Az = b, we can obtain a matrix B with the same eigenvalues
as A and a vector c such that the residual norms generated by a FOM
computation on Bz = c are identical to those generated by the BiCG
computations. Using a unitary equivalence for each of these methods, we
obtain test problems where we can easily vary certain spectral properties
of the matrices. We use these test problems to study the effects of
nonnormality on the convergence of GMRES and QMR, to study the effects of
eigenvalue outliers on the convergence of QMR, and to compare the
convergence of restarted GMRES and QMR across a family of normal and
nonnormal problems. Our GMRES tests on nonnormal test matrices indicate
that nonnormality can have unexpected effects upon the residual norm
convergence, giving misleading indications of superior convergence when
the error norms for GMRES are not significantly different from those for
QMR. Our QMR tests indicate that the convergence of the QMR residual and
error norms is infLuenced predominantly by small and large eigenvalue
outliers and by the character, real, complex, or nearly real, of the
outliers and the other eigenvalues. In our comparison tests QMR
outperformed GMRES(10) and GMRES(20) on both the normal and nonnormal
test matrices.
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(Also cross-referenced as UMIACS-TR-96-2
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