4,583 research outputs found

    Liberating the NHS; commissioning, outsourcing and a new politics debate

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    In the short months following the result of the UK 2010 General election, a new Government White Paper has been released entitled: Equity and Excellence: Liberating the NHS (Department of Health (DH), 2010a). It strives to distance itself from previous health-care proposals (DH, 2009), yet if the initiatives of this latest paper are combined against previous initiatives, also using high impact declarative terms, such as competition and choice, it is clear that little has changed and more important principles than saving money are at risk

    Cosmic String Power Spectrum, Bispectrum and Trispectrum

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    We use analytic calculations of the post-recombination gravitational effects of cosmic strings to estimate the resulting CMB power spectrum, bispectrum and trispectrum. We place a particular emphasis on multipole regimes relevant for forthcoming CMB experiments, notably the Planck satellite. These calculations use a flat sky approximation, generalising previous work by integrating string contributions from last scattering to the present day, finding the dominant contributions to the correlators for multipoles l > 50. We find a well-behaved shape for the string bispectrum (without divergences) which is easily distinguishable from the inflationary bispectra which possess significant acoustic peaks. We estimate that the nonlinearity parameter characterising the bispectrum is approximately f_NL \sim -20 (given present string constraints from the CMB power spectrum. We also apply these unequal time correlator methods to calculate the trispectrum for parrallelogram configurations, again valid over a large range of angular scales relevant for WMAP and Planck, as well as on very small angular scales. We find that, unlike the bispectrum which is suppressed by symmetry considerations, the trispectrum for cosmic strings is large. Our current estimate for the trispectrum parameter is tau_NL \sim 10^5, which may provide one of the strongest constraints on the string model as estimators for the trispectrum are developed

    A critical commentary on management science in relation to reforms following institutional National Health Service failures

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    Aim(s): A discussion paper on the United Kingdom (UK) National Health Service (NHS) market reforms. Background: NHS market reforms reliance on management science methods introduced a fundamental shift in measuring care for commissioning purposes rather than what actually counts such as putting patients first, maintaining a generosity of purpose and social philosophy. Evaluation: A number of key reports are discussed in relation to NHS market reforms and management science. Key issues: NHS market reforms were influenced through a close alliance between policy makers, the department of health, free market think tanks and management consultancies. The timing of reforms coincided with reports on NHS failings and the evolution of measurement methods to focus on finance. Conclusions: The balance in favour of measurement practises is of concern. Management science methods are criticised in the Francis report yet promoted as the solution to some of the key findings; why may be explained by the close alliance. Implications for Nursing Management: A return to principles of management involving consensus, trust, involvement in which a shared vision and a can do, hands on approach to management would be valued in the drive to promote quality care and use management science methods to this end

    General CMB and Primordial Trispectrum Estimation

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    We present trispectrum estimation methods which can be applied to general non-separable primordial and CMB trispectra. We present a general optimal estimator for the connected part of the trispectrum, for which we derive a quadratic term to incorporate the effects of inhomogeneous noise and masking. We describe a general algorithm for creating simulated maps with given arbitrary (and independent) power spectra, bispectra and trispectra. We propose a universal definition of the trispectrum parameter TNLT_{NL}, so that the integrated bispectrum on the observational domain can be consistently compared between theoretical models. We define a shape function for the primordial trispectrum, together with a shape correlator and a useful parametrisation for visualizing the trispectrum. We derive separable analytic CMB solutions in the large-angle limit for constant and local models. We present separable mode decompositions which can be used to describe any primordial or CMB bispectra on their respective wavenumber or multipole domains. By extracting coefficients of these separable basis functions from an observational map, we are able to present an efficient estimator for any given theoretical model with a nonseparable trispectrum. The estimator has two manifestations, comparing the theoretical and observed coefficients at either primordial or late times. These mode decomposition methods are numerically tractable with order l5l^5 operations for the CMB estimator and approximately order l6l^6 for the general primordial estimator (reducing to order l3l^3 in both cases for a special class of models). We also demonstrate how the trispectrum can be reconstructed from observational maps using these methods.Comment: 38 pages, 9 figures. In v2 Figures 4-7 are altered slightly and some extra references are included in the bibliography. v3 matches version submitted to journal. Includes discussion of special case

    Rapid Separable Analysis of Higher Order Correlators in Large Scale Structure

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    We present an efficient separable approach to the estimation and reconstruction of the bispectrum and the trispectrum from observational (or simulated) large scale structure data. This is developed from general CMB (poly-)spectra methods which exploit the fact that the bispectrum and trispectrum in the literature can be represented by a separable mode expansion which converges rapidly (with nmax=O(30)n_\textrm{max}={\cal{O}}(30) terms). With an effective grid resolution lmaxl_\textrm{max} (number of particles/grid points N=lmax3N=l_\textrm{max}^3), we present a bispectrum estimator which requires only O(nmax×lmax3){\cal O}(n_\textrm{max} \times l_\textrm{max}^3) operations, along with a corresponding method for direct bispectrum reconstruction. This method is extended to the trispectrum revealing an estimator which requires only O(nmax4/3×lmax3){\cal O}(n_\textrm{max}^{4/3} \times l_\textrm{max}^3) operations. The complexity in calculating the trispectrum in this method is now involved in the original decomposition and orthogonalisation process which need only be performed once for each model. However, for non-diagonal trispectra these processes present little extra difficulty and may be performed in O(lmax4){\cal O}(l_\textrm{max}^4) operations. A discussion of how the methodology may be applied to the quadspectrum is also given. An efficient algorithm for the generation of arbitrary nonGaussian initial conditions for use in N-body codes using this separable approach is described. This prescription allows for the production of nonGaussian initial conditions for arbitrary bispectra and trispectra. A brief outline of the key issues involved in parameter estimation, particularly in the non-linear regime, is also given

    Universal Non-Gaussian Initial Conditions for N-body Simulations

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    In this paper we present the implementation of an efficient formalism for the generation of arbitrary non-Gaussian initial conditions for use in N-body simulations. The methodology involves the use of a separable modal approach for decomposing a primordial bispectrum or trispectrum. This approach allows for the far more efficient generation of the non-Gaussian initial conditions already described in the literature, as well as the generation for the first time of non-separable bispectra and the special class of diagonal-free trispectra. The modal approach also allows for the reconstruction of the spectra from given realisations, a fact which is exploited to provide an accurate consistency check of the simulations.Comment: 7 pages, 3 figure

    Microscopic Surface Structure of Liquid Alkali Metals

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    We report an x-ray scattering study of the microscopic structure of the surface of a liquid alkali metal. The bulk liquid structure factor of the eutectic K67Na33 alloy is characteristic of an ideal mixture, and so shares the properties of an elemental liquid alkali metal. Analysis of off-specular diffuse scattering and specular x-ray reflectivity shows that the surface roughness of the K-Na alloy follows simple capillary wave behavior with a surface structure factor indicative of surface induced layering. Comparison of thelow-angle tail of the K67Na33 surface structure factor with the one measured for liquid Ga and In previously suggests that layering is less pronounced in alkali metals. Controlled exposure of the liquid to H2 and O2 gas does not affect the surface structure, indicating that oxide and hydride are not stable at the liquid surface under these experimental conditions.Comment: 12 pages, 3 figures, published in Phys. Rev.
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