703 research outputs found
Evaluation of complex integrated care programmes: the approach in North West London
Background: Several local attempts to introduce integrated care in the English National Health Service have been tried, with limited success. The Northwest London Integrated Care Pilot attempts to improve the quality of care of the elderly and people with diabetes by providing a novel integration process across primary, secondary and social care organisations. It involves predictive risk modelling, care
planning, multidisciplinary management of complex cases and an information technology tool to support information sharing. This paper sets out the evaluation approach adopted to measure its effect.
Study design: We present a mixed methods evaluation methodology. It includes a quantitative approach measuring changes in service utilization, costs, clinical outcomes and quality of care using routine primary and secondary data sources. It also contains a qualitative component, involving observations, interviews and focus groups with patients and professionals, to understand participant experiences
and to understand the pilot within the national policy context. Theory and discussion: This study considers the complexity of evaluating a large, multi-organisational intervention in a changing healthcare economy. We locate the evaluation within the theory of evaluation of complex interventions. We present the specific challenges faced by evaluating an intervention of this sort, and the responses made to mitigate against them.
Conclusions: We hope this broad, dynamic and responsive evaluation will allow us to clarify the contribution of the pilot, and provide a potential model for evaluation of other similar interventions. Because of the priority given to the integrated agenda by governments internationally, the need to develop and improve strong evaluation methodologies remains strikingly important
Dissociative attachment in HCl, DCl, and F2
Resonant scattering models, using nonlocal decay widths, are developed for dissociative attachment of slow electrons to diatomic molecules. Cross sections are obtained for HCl and DCl in several initial rotational and vibrational states, and the dependence of the average attachment cross section upon the rotational and vibrational temperature is examined. For F_2 the cross section for ground state molecules agrees well with experiment above 0.2 eV but shows no zero energy peak. The attachment cross section is higher for vibrationally excited molecules, but the enhancement is much less than that found in H_2 and HCl
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Final report pulsed plasma processing of effluent pollutants and hazardous chemicals
The electrical discharge techniques, called non-thermal, utilize high voltage breakdown of gases using short pulses of one to a few hundred nanoseconds. These short pulses between metal electrodes generate energetic electrons without appreciable thermal heating of the gas. The energetic electrons collide with gas molecules to form radicals. The radicals then react with pollutants to form harmless compounds. Our non-thermal experimental device used a wire in a pipe geometry. The wire was driven by a 40 kilovolt pulse 100 nanoseconds long. Gas was circulated in a loop through the pipe geometry in a closed system. This system permitted the introduction of various gas combinations prior to testing. The recirculated gas was heated to determine the effect on the electrical discharge, and chemical reactions. Additives were introduced to improve the efficiency (defined as energy input per unit molecule destroyed). The efficient was found to be the most important parameter in that the experiments generally required high energy inputs. However, we were able to significantly improve the efficiency of NO removal by the addition of hydrocarbons, nitric oxide has been removed with an energy cost of 15 ev per NO molecule. We believe the hydrocarbon additive serves by recycling the hydroxyl radicals during the oxidation of NO. The implementation of this process will depend largely on how much additives, electrical power consumption, and final NO{sub x} concentration are acceptable for a particular application
An approximate empirical Bayesian method for large-scale linear-Gaussian inverse problems
We study Bayesian inference methods for solving linear inverse problems,
focusing on hierarchical formulations where the prior or the likelihood
function depend on unspecified hyperparameters. In practice, these
hyperparameters are often determined via an empirical Bayesian method that
maximizes the marginal likelihood function, i.e., the probability density of
the data conditional on the hyperparameters. Evaluating the marginal
likelihood, however, is computationally challenging for large-scale problems.
In this work, we present a method to approximately evaluate marginal likelihood
functions, based on a low-rank approximation of the update from the prior
covariance to the posterior covariance. We show that this approximation is
optimal in a minimax sense. Moreover, we provide an efficient algorithm to
implement the proposed method, based on a combination of the randomized SVD and
a spectral approximation method to compute square roots of the prior covariance
matrix. Several numerical examples demonstrate good performance of the proposed
method
Anisotropic fragmentation in low-energy dissociative recombination
On a dense energy grid reaching up to 75 meV electron collision energy the
fragmentation angle and the kinetic energy release of neutral dissociative
recombination fragments have been studied in a twin merged beam experiment. The
anisotropy described by Legendre polynomials and the extracted rotational state
contributions were found to vary on a likewise narrow energy scale as the
rotationally averaged rate coefficient. For the first time angular dependences
higher than 2 order could be deduced. Moreover, a slight anisotropy at
zero collision energy was observed which is caused by the flattened velocity
distribution of the electron beam.Comment: 8 pages, 4 figures; The Article will be published in the proceedings
of DR 2007, a symposium on Dissociative Recombination held in Ameland, The
Netherlands (18.-23. July 2008); Reference 19 has been published meanwhile in
S. Novotny, PRL 100, 193201 (2008
Finite element analysis predicts Ca 2+ microdomains within tubular-sarcoplasmic reticular junctions of amphibian skeletal muscle
Abstract: A finite element analysis modelled diffusional generation of steady-state Ca2+ microdomains within skeletal muscle transverse (T)-tubular-sarcoplasmic reticular (SR) junctions, sites of ryanodine receptor (RyR)-mediated SR Ca2+ release. It used established quantifications of sarcomere and T-SR anatomy (radial diameter d=220nm; axial distance w=12nm). Its boundary SR Ca2+ influx densities,Jinflux, reflected step impositions of influxes, Φinflux=Jinfluxπd24, deduced from previously measured Ca2+ signals following muscle fibre depolarization. Predicted steady-state T-SR junctional edge [Ca2+], [Ca2+]edge, matched reported corresponding experimental cytosolic [Ca2+] elevations given diffusional boundary effluxΦefflux=D[Ca2+]edgeλ(πdw), established cytosolic Ca2+ diffusion coefficients (D=4×107nm2/s) and exit length λ=9.2nm. Dependences of predicted [Ca2+]edge upon Jinflux then matched those of experimental [Ca2+] upon Ca2+ release through their entire test voltage range. The resulting model consistently predicted elevated steady-state T-SR junctional ~ µM-[Ca2+] elevations radially declining from maxima at the T-SR junction centre along the entire axial T-SR distance. These [Ca2+] heterogeneities persisted through 104- and fivefold, variations in D and w around, and fivefold reductions in d below, control values, and through reported resting muscle cytosolic [Ca2+] values, whilst preserving the flux conservation (Φinflux=Φefflux) condition, Ca2+edge=λdJinflux4Dw. Skeletal muscle thus potentially forms physiologically significant ~ µM-[Ca2+] T-SR microdomains that could regulate cytosolic and membrane signalling molecules including calmodulin and RyR, These findings directly fulfil recent experimental predictions invoking such Ca2+ microdomains in observed regulatory effects upon Na+ channel function, in a mechanism potentially occurring in similar restricted intracellular spaces in other cell types
Optimally shaped terahertz pulses for phase retrieval in a Rydberg atom data register
We employ Optimal Control Theory to discover an efficient information
retrieval algorithm that can be performed on a Rydberg atom data register using
a shaped terahertz pulse. The register is a Rydberg wave packet with one
consituent orbital phase-reversed from the others (the ``marked bit''). The
terahertz pulse that performs the decoding algorithm does so by by driving
electron probability density into the marked orbital. Its shape is calculated
by modifying the target of an optimal control problem so that it represents the
direct product of all correct solutions to the algorithm.Comment: 6 pages, 3 figure
On the Influence of Pulse Shapes on Ionization Probability
We investigate analytical expressions for the upper and lower bounds for the
ionization probability through ultra-intense shortly pulsed laser radiation. We
take several different pulse shapes into account, including in particular those
with a smooth adiabatic turn-on and turn-off. For all situations for which our
bounds are applicable we do not find any evidence for bound-state
stabilization.Comment: 21 pages LateX, 10 figure
The orbit structure of Dynkin curves
Let G be a simple algebraic group over an algebraically closed field k;
assume that Char k is zero or good for G. Let \cB be the variety of Borel
subgroups of G and let e in Lie G be nilpotent. There is a natural action of
the centralizer C_G(e) of e in G on the Springer fibre \cB_e = {B' in \cB | e
in Lie B'} associated to e. In this paper we consider the case, where e lies in
the subregular nilpotent orbit; in this case \cB_e is a Dynkin curve. We give a
complete description of the C_G(e)-orbits in \cB_e. In particular, we classify
the irreducible components of \cB_e on which C_G(e) acts with finitely many
orbits. In an application we obtain a classification of all subregular orbital
varieties admitting a finite number of B-orbits for B a fixed Borel subgroup of
G.Comment: 12 pages, to appear in Math
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