160,704 research outputs found

    Analysis of uniform binary subdivision schemes for curve design

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    The paper analyses the convergence of sequences of control polygons produced by a binary subdivision scheme of the form .0,1,2,...kz,ikj,ifjbm0j1k12ifjam0j1k2if=∈+Σ==++Σ==+ The convergence of the control polygons to a Cu curve is analysed in terms of the convergence to zero of a derived scheme for the differences - . The analysis of the smoothness of the limit curve is reduced to kif the convergence analysis of "differentiated" schemes which correspond to divided differences of {/i ∈Z} with respect to the diadic parameteriz- kif ation = i/2kitk . The inverse process of "integration" provides schemes with limit curves having additional orders of smoothness

    SO_0(1,d+1) Racah coefficients: Type I representations

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    We use AdS/CFT inspired methods to study the Racah coefficients for type I representations of the Lorentz group SO_0(1,d+1) with d>1. For such representations (a multiple of) the Racah coefficient can be represented as an integral of a product of 6 bulk-to-bulk propagators over 4 copies of the hyperbolic space H_{d+1}. To compute the integrals we represent the bulk-to-bulk propagators in terms of bulk-to-boundary ones. The bulk integrals can be computed explicitly, and the boundary integrations are carried out by introducing Feynman parameters. The final result is an integral representation of the Racah coefficient given by 4 Barnes-Mellin type integrals.Comment: 20 pages, 1 figure. v2: Case d=1 corrected, case d>1 clarifie

    Fuzzy de Sitter Space from kappa-Minkowski Space in Matrix Basis

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    We consider the Lie group RκD\mathbb{R}^D_\kappa generated by the Lie algebra of κ\kappa-Minkowski space. Imposing the invariance of the metric under the pull-back of diffeomorphisms induced by right translations in the group, we show that a unique right invariant metric is associated with RκD\mathbb{R}^D_\kappa. This metric coincides with the metric of de Sitter space-time. We analyze the structure of unitary representations of the group RκD\mathbb{R}^D_\kappa relevant for the realization of the non-commutative κ\kappa-Minkowski space by embedding into (2D−1)(2D-1)-dimensional Heisenberg algebra. Using a suitable set of generalized coherent states, we select the particular Hilbert space and realize the non-commutative κ\kappa-Minkowski space as an algebra of the Hilbert-Schmidt operators. We define dequantization map and fuzzy variant of the Laplace-Beltrami operator such that dequantization map relates fuzzy eigenvectors with the eigenfunctions of the Laplace-Beltrami operator on the half of de Sitter space-time.Comment: 21 pages, v3 differs from version published in Fortschritte der Physik by a note and references added and adjuste

    Crossing the Boundary: a study of the nature and extent of racism in local league cricket

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    Since the start of the 1993/4 football season the 'Let's Kick Racism Out of Football’ has had some success in persuading clubs and players to recognise racism in the game and act to counter it. This summer, following our own research (Long et al, 1995) the Rugby Football League and the Commission for Racial Equality launched a 13-point Action Plan for professional clubs to adopt. Within cricket 'Hit Racism for Six' (HR46) was set-up last year to act as a pressure group to stimulate discussion about racism in cricket. Issues of race and racism in sport have recently attracted considerable media attention and stimulated popular debate. Emotion has run high over the articles by Robert Henderson (1995) and Roger Bannister (Connor 1995), the continuing confrontation between Raymond Illingworth and Devon Malcolm, the Botham/Lamb v Khan court case and the trouble on the terraces at Headingley during the summer of 1996. The balance attempted by programmes in the Radio 5 series on ‘Race around the UK’ represented one attempt to encourage a more considered approach, but throughout it has been clear that there is still a shortage of substantive research on race in sport. The Carnegie National Sports Development Centre conducted a study of black and ethnic minorities in cricket in Yorkshire that focused on issues of participation and sports development. Following the success of our rugby league project, Leeds City Council were keen for us to try to explore the more sensitive issues around race and racism. While the study of rugby league had been on the professional game this study of cricket was to be of local league cricket. Within the region this is how most people experience their cricket with some 1,300 teams affiliated to the Yorkshire Cricket Association. To establish views on race and racism we sought responses from: a) the secretaries of local league clubs b) Asian, black and white players in the leagues c) league umpire

    Role of the community matron in advance care planning and ‘do not attempt CPR’ decision-making: a qualitative study

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    The community matron (CM) is often the key worker caring for patients with chronic, life-limiting, long-term conditions, but these patients are not always recognised as palliative cases. This study explored the experiences of CMs with regard to advance care planning (ACP) and ‘do not attempt cardiopulmonary resuscitation’ (DNACPR) decision-making to understand whether or not they felt adequately prepared for this aspect of their role, and why. Qualitative data were generated from six CMs using a broad interpretive phenomenological approach. Face-to-face recorded interviews were analysed using template analysis. The study found that although participants faced complex ethical situations around ACP and DNACPR almost on a daily basis, none had received any formal training despite the emphasis on training in national and local guidelines. Participants often struggled to get their patients accepted on to the Gold Standards Framework. The research found variability and complexity of cases to be the main barriers to clear identification of the palliative phase

    Epitope mapping using mRNA display and a unidirectional nested deletion library

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    In vitro selection targeting an anti-polyhistidine monoclonal antibody was performed using mRNA display with a random, unconstrained 27-mer peptide library. After six rounds of selection, epitope-like peptides were identified that contain two to five consecutive, internal histidines and are biased for arginine residues, without any other identifiable consensus. The epitope was further refined by constructing a high-complexity, unidirectional fragment library from the final selection pool. Selection by mRNA display minimized the dominant peptide from the original selection to a 15-residue functional sequence (peptide Cmin: RHDAGDHHHHHGVRQ; K-D = 38 nM). Other peptides recovered from the fragment library selection revealed a separate consensus motif (ARRXA) C-terminal to the histidine track. Kinetics measurements made by surface plasmon resonance, using purified Fab (antigen-binding fragment) to prevent avidity effects, demonstrate that the selected peptides bind with 10- to 75-fold higher affinities than a hexahistidine peptide. The highest affinity peptides (K-D approximate to 10 nM) encode both a short histidine track and the ARRXA motif, suggesting that the motif and other flanking residues make important contacts adjacent to the core polyhistidine-binding site and can contribute > 2.5 kcal/mol of binding free energy. The fragment library construction methodology described here is applicable to the development of high-complexity protein or cDNA expression libraries for the identification of protein-protein interaction domains
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