19,143 research outputs found

    From ‘other’ to involved: User involvement in research: An emerging paradigm

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    This article has been made available through the Brunel Open Access Publishing Fund. Copyright @ 2013 The Author(s). This is an Open Access article. Non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly attributed, cited, and is not altered, transformed, or built upon in any way, is permitted. The moral rights of the named author(s) have been asserted.This article explores the issue of ‘othering’ service users and the role that involving them, particularly in social policy and social work research may play in reducing this. It takes, as its starting point, the concept of ‘social exclusion’, which has developed in Europe and the marginal role that those who have been included in this construct have played in its development and the damaging effects this may have. The article explores service user involvement in research and is itself written from a service user perspective. It pays particular attention to the ideological, practical, theoretical, ethical and methodological issues that such user involvement may raise for research. It examines problems that both research and user involvement may give rise to and also considers developments internationally to involve service users/subjects of research, highlighting some of the possible implications and gains of engaging service user knowledge in research and the need for this to be evaluated

    Four-quark state in QCD

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    The spectra of some 0++ four-quark states, which are composed of \bar qq pairs, are calculated in QCD. The light four-quark states are calculated using the traditional sum rules while four-quark states containing one heavy quark are computed in HQET. For constructing the interpolating currents, different couplings of the color and spin inside the \bar qq pair are taken into account. It is found that the spin and color combination has little effect on the mass of the four-quark states.Comment: 10 pages, 4 ps figures, Late

    Hybrid Decays

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    The heavy quark expansion of Quantum Chromodynamics and the strong coupling flux tube picture of nonperturbative glue are employed to develop the phenomenology of hybrid meson decays. The decay mechanism explicitly couples gluonic degrees of freedom to the pair produced quarks and hence does not obey the well known, but model-dependent, selection rule which states that hybrids do not decay to pairs of L=0 mesons. However, the nonperturbative nature of gluonic excitations in the flux tube picture leads to a new selection rule: light hybrids do not decay to pairs of identical mesons. New features of the model are highlighted and partial widths are presented for several low lying hybrid states.Comment: 13 pages, 1 table, revte

    Anderson impurity model at finite Coulomb interaction U: generalized Non-crossing Approximation

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    We present an extension of the non-crossing approximation (NCA), which is widely used to calculate properties of Anderson impurity models in the limit of infinite Coulomb repulsion U→∞U\to\infty, to the case of finite UU. A self-consistent conserving pseudo-particle representation is derived by symmetrizing the usual NCA diagrams with respect to empty and doubly occupied local states. This requires an infinite summation of skeleton diagrams in the generating functional thus defining the ``Symmetrized finite-U NCA'' (SUNCA). We show that within SUNCA the low energy scale TKT_K (Kondo temperature) is correctly obtained, in contrast to other simpler approximations discussed in the literature.Comment: 7 pages, 6 figure

    Bi-layer splitting in overdoped high TcT_{c} cuprates

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    Recent angle-resolved photoemission data for overdoped Bi2212 are explained. Of the peak-dip-hump structure, the peak corresponds the q⃗=0\vec q =0 component of a hole condensate which appears at TcT_c. The fluctuating part of this same condensate produces the hump. The bilayer splitting is large enough to produce a bonding hole and an electron antibonding quasiparticle Fermi surface. Smaller bilayer splittings observed in some experiments reflect the interaction of the peak structure with quasiparticle states near, but not at, the Fermi surface.Comment: 4 pages with 2 figures - published versio

    Spin Excitations and Sum Rules in the Heisenberg Antiferromagnet

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    Various bounds for the energy of collective excitations in the Heisenberg antiferromagnet are presented and discussed using the formalism of sum rules. We show that the Feynman approximation significantly overestimates (by about 30\% in the S=12S={1\over2} square lattice) the spin velocity due to the non negligible contribution of multi magnons to the energy weighted sum rule. We also discuss a different, Goldstone type bound depending explicitly on the order parameter (staggered magnetization). This bound is shown to be proportional to the dispersion of classical spin wave theory with a q-independent normalization factor. Rigorous bounds for the excitation energies in the anisotropic Heisenberg model are also presented.Comment: 26 pages, Plain TeX including 1 PostScript figure, UTF-307-10/9

    Numerical Renormalization Group Study of Pseudo-Fermion and Slave-Boson Spectral Functions in the Single Impurity Anderson Model

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    We use the numerical renormalization group to calculate the auxiliary spectral functions of the U=∞U=\infty Anderson impurity model. The slave--boson and pseudo--fermion spectral functions diverge at the threshold with exponents αb\alpha_{b} and αf\alpha_{f} given in terms of the conduction electron phase shifts by the X--ray photoemission and the X--ray absorption exponents respectively. The exact exponents obtained here depend on the impurity occupation number, in contrast to the NCA results. Vertex corrections in the convolution formulae for physical Green's functions are singular at the threshold and may not be neglected in the Fermi liquid regime.Comment: 12 pages, RevTeX 3.0, 2 PS figures appende

    T-Lymphocyte subpopulation in tuberculosis

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    Tuberculosis is associated with both qualitative and quantitative defects in the cell mediated immune response. The changes that occur in the lymphocyte profile in blood in children with tuberculosis are not well understood. Design: Prospective study. Setting: Referral hospitals. Methods: Lymphocyte subpopulations were determined by flow cytometry in 17 healthy tuberculin positive children, in 22 children with newly diagnosed pulmonary tuberculosis and in 8 of these children after antituberculosis therapy, Results: Absolute numbers and percentages of CD3+ and CD4+ T cells were reduced in children with tuberculosis, compared to controls. CD4+ counts increased significantly following antituberculosis treatment, compared to baseline values. In contrast, the proportion of T cells expressing the gd T cell receptor was similar in tuberculosis patients and controts. Conclusion: Children with tuberculosis have a systemic decrease in the proportion and number of CD3+ and CD4+ T cells which reverses during therapy

    Exact Critical Exponents for Pseudo-Particles in the Kondo Problem

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    Exact critical exponents of the Green functions for pseudo-fermions and slave bosons in the SU(NN) Anderson model with U→∞U\rightarrow\infty are obtained by using the Bethe ansatz solution and boundary conformal field theory. They are evaluated exactly for mixed valence systems and Kondo systems with crystalline fields. The results agree with the prediction of Menge and M\"uller-Hartmann, which coincide with those of the X-ray problem. Some implication of our results in one-dimensional chiral systems is also discussed.Comment: 9 pages, no figure

    No meditation-related changes in the auditory N1 during first-time meditation

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    Recent studies link meditation expertise with enhanced low-level attention, measured through auditory event-related potentials (ERPs). In this study, we tested the reliability and validity of a recent finding that the N1 ERP in first-time meditators is smaller during meditation than non-meditation – an effect not present in long-term meditators. In the first experiment, we replicated the finding in first-time meditators. In two subsequent experiments, we discovered that this finding was not due to stimulus-related instructions, but was explained by an effect of the order of conditions. Extended exposure to the same tones has been linked with N1 decrement in other studies, and may explain N1 decrement across our two conditions. We give examples of existing meditation and ERP studies that may include similar condition order effects. The role of condition order among first-time meditators in this study indicates the importance of counterbalancing meditation and non-mediation conditions in meditation studies that use event-related potentials
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