6,208 research outputs found

    Should we be giving enhanced vitamin D intakes to all?

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    Canadian national sport organisations’ use of the web for relationship marketing in promoting sport participation

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    Sport participation development requires a systematic process which involves knowledge creation, dissemination and interactions between National Sport Organisations, participants, clubs and associations as well as other agencies. Using a relationship marketing approach (Grönroos, 1997, Gummesson, 2002, Olkkonen, 1999), this paper addressed the question ‘How do Canadian NSOs use the Web, in terms of functionality and services offered, to create and maintain relationships with sport participants and their sport delivery partners?’ Ten Canadian NSOs’ websites were examined: functionality was analysed using Burgess and Cooper’s (2000) eMICA model, while NSOs’ utilisation of the Internet to establish and maintain relationships with sport participants was analysed using Wang, Head and Archer’s (2000) relationship-building process model for the Web. It was found that Canadian NSOs were receptive to the use of the Web, but their information-gathering and dissemination activities, which make-up the relationship-building process, appear sparse, and in some cases are lagging behind the voluntary sector in the country

    From Skew-Cyclic Codes to Asymmetric Quantum Codes

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    We introduce an additive but not F4\mathbb{F}_4-linear map SS from F4n\mathbb{F}_4^{n} to F42n\mathbb{F}_4^{2n} and exhibit some of its interesting structural properties. If CC is a linear [n,k,d]4[n,k,d]_4-code, then S(C)S(C) is an additive (2n,22k,2d)4(2n,2^{2k},2d)_4-code. If CC is an additive cyclic code then S(C)S(C) is an additive quasi-cyclic code of index 22. Moreover, if CC is a module θ\theta-cyclic code, a recently introduced type of code which will be explained below, then S(C)S(C) is equivalent to an additive cyclic code if nn is odd and to an additive quasi-cyclic code of index 22 if nn is even. Given any (n,M,d)4(n,M,d)_4-code CC, the code S(C)S(C) is self-orthogonal under the trace Hermitian inner product. Since the mapping SS preserves nestedness, it can be used as a tool in constructing additive asymmetric quantum codes.Comment: 16 pages, 3 tables, submitted to Advances in Mathematics of Communication

    Continuous cardiac autonomic and haemodynamic responses to isometric exercise in females

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    Purpose: Hypertension is associated with impaired haemodynamic control mechanisms and autonomic dysfunction. Isometric exercise (IE) interventions have been shown to improve autonomic modulation and reduce blood pressure (BP) in predominantly male participants. The physiological responses to IE are under explored in female populations; therefore, this study investigated the continuous cardiac autonomic and haemodynamic response to a single bout of IE in a large female population. Methods: Forty physically inactive females performed a single, individually prescribed isometric wall squat training session. Total power spectral density of heart rate variability (HRV) and associated low frequency (LF) and high-frequency (HF) power spectral components, were recorded in absolute (ms2) and normalised units (nu) pre, during and post an IE session. Heart rate (HR) was recorded via electrocardiography and baroreceptor reflex sensitivity (BRS) via the sequence method. Continuous blood pressure was recorded via the vascular unloading technique and stroke volume via impedance cardiography. Total peripheral resistance (TPR) was calculated according to Ohm’s Law. Results: During IE, there were significant reductions in HRV (p<0.001) and BRS (p<0.001), and significant increases in heart rate (p<0.001), systolic, mean and diastolic BP (p<0.001 for all). In recovery following the IE session, cardiac autonomic parameters returned to baseline (p=0.974); however, total peripheral vascular resistance significantly reduced below baseline (p<0.001). This peripheral vascular response was associated with significant reductions in systolic (-17.3±16.5 mmHg, p<0.001), mean (-18.8±17.4 mmHg, p<0.001) and diastolic BP (-17.3±16.2 mmHg, p<0.001), below baseline. Conclusion: A single IE session is associated with improved haemodynamic cardiovascular responses in females. Cardiac autonomic responses return to baseline values, which suggests alternative mechanisms are responsible for the post exercise haemodynamic improvements in females. Future mechanistic research is required to investigate the acute and chronic effects of IE in female populations with different resting BP profiles

    Amp\`ere-Class Pulsed Field Emission from Carbon-Nanotube Cathodes in a Radiofrequency Resonator

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    Pulsed field emission from cold carbon-nanotube cathodes placed in a radiofrequency resonant cavity was observed. The cathodes were located on the backplate of a conventional 1+121+\frac{1}{2}-cell resonant cavity operating at 1.3-GHz and resulted in the production of bunch train with maximum average current close to 0.7 Amp\`ere. The measured Fowler-Nordheim characteristic, transverse emittance, and pulse duration are presented and, when possible, compared to numerical simulations. The implications of our results to high-average-current electron sources are briefly discussed.Comment: 5 pages, 6 figures; submitted to Applied Physics Letter

    The crystal structure of superoxide dismutase from Plasmodium falciparum

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    Background: Superoxide dismutases (SODs) are important enzymes in defence against oxidative stress. In Plasmodium falciparum, they may be expected to have special significance since part of the parasite life cycle is spent in red blood cells where the formation of reactive oxygen species is likely to be promoted by the products of haemoglobin breakdown. Thus, inhibitors of P. falciparum SODs have potential as anti-malarial compounds. As a step towards their development we have determined the crystal structure of the parasite's cytosolic iron superoxide dismutase. Results: The cytosolic iron superoxide dismutase from P. falciparum (PfFeSOD) has been overexpressed in E. coli in a catalytically active form. Its crystal structure has been solved by molecular replacement and refined against data extending to 2.5 angstrom resolution. The structure reveals a two-domain organisation and an iron centre in which the metal is coordinated by three histidines, an aspartate and a solvent molecule. Consistent with ultracentrifugation analysis the enzyme is a dimer in which a hydrogen bonding lattice links the two active centres. Conclusion: The tertiary structure of PfFeSOD is very similar to those of a number of other iron-and manganese-dependent superoxide dismutases, moreover the active site residues are conserved suggesting a common mechanism of action. Comparison of the dimer interfaces of PfFeSOD with the human manganese-dependent superoxide dismutase reveals a number of differences, which may underpin the design of parasite-selective superoxide dismutase inhibitors

    Introducing the Dark Energy Universe Simulation Series (DEUSS)

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    In this "Invisible Universe" proceedings, we introduce the Dark Energy Universe Simulation Series (DEUSS) which aim at investigating the imprints of realistic dark energy models on cosmic structure formation. It represents the largest dynamical dark energy simulation suite to date in term of spatial dynamics. We first present the 3 realistic dark energy models (calibrated on latest SNIa and CMB data): LambdaCDM, quintessence with Ratra-Peebles potential, and quintessence with Sugra potential. We then isolate various contributions for non-linear matter power spectra from a series of pre-DEUSS high-resolution simulations (130 million particles). Finally, we introduce DEUSS which consist in 9 Grand Challenge runs with 1 billion particles each thus probing scales from 4 Gpc down to 3 kpc at z=0. Our goal is to make these simulations available to the community through the "Dark Energy Universe Virtual Observatory" (DEUVO), and the "Dark Energy Universe Simulations" (DEUS) consortium.Comment: 6 pages, 3 figures, to appear in the AIP proceedings of the 'Invisible Universe International Conference', UNESCO-Paris, June 29-July 3, 200

    On the Asymptotic Stability of De-Sitter Spacetime: a non-linear perturbative approach

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    We derive evolution and constraint equations for second order perturbations of flat dust homogeneous and isotropic solutions to the Einstein field equations using all scalar, vector and tensor perturbation modes. We show that the perturbations decay asymptotically in time and that the solutions converge to the De-Sitter solution. By induction, this result is valid for perturbations of arbitrary order. This is in agreement with the cosmic no-hair conjecture of Gibbons and Hawking.Comment: 11 pages, 2 figure

    Possible Localized Modes in the Uniform Quantum Heisenberg Chains of Sr2CuO3

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    A model of mobile-bond defects is tentatively proposed to analyze the "anomalies" observed on the NMR spectrum of the quantum Heisenberg chains of Sr2CuO3. A bond-defect is a local change in the exchange coupling. It results in a local alternating magnetization (LAM), which when the defect moves, creates a flipping process of the local field seen by each nuclear spin. At low temperature, when the overlap of the LAM becomes large, the defects form a periodic structure, which extends over almost all the chains. In that regime, the density of bond-defects decreases linearly with T.Comment: 4 pages + 3 figures. To appear in Physical Review
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