6,988 research outputs found

    Cardiovascular medication, physical activity and mortality: cross-sectional population study with ongoing mortality follow up

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    Objective: to establish physical activity levels in relation to cardiovascular medication and to examine if physical activity is associated with benefit independently of medication among individuals with no diagnosis of cardiovascular disease (CVD). Design: Cross-sectional surveys in 1998 and 2003 with ongoing mortality follow up. Setting: Household-based interviews in England and Scotland. Participants: Population samples of adults aged 35 and over living in households, respondents of the Scottish Health Survey and the Health Survey for England. Main outcome measure: Moderate to vigorous physical activity (MVPA) levels and CVD mortality. Results: Fifteen percent (N=3,116) of the 20,177 respondents (8,791 men); were prescribed at least one cardiovascular medication. Medicated respondents were less likely than those unmedicated to meet the physical activity recommendations (OR:0.89, 95%CI: 0.81 to 0.99, p=0.028). The mean follow up (±SD) was 6.6 (2.3) years. There were 1,509 any-cause deaths and 427 CVD deaths. Increased physical activity was associated with all-cause and CVD mortality among both unmedicated (all-cause mortality HR for those with ≥150 min/wk of MVPA compared with those who reported no MVPA): 0.58, 95%CI: 0.48 to 0.69, p<0.001) ; CVD mortality: 0.65, 0.46 to 0.91, p=0.036) and medicated respondents (all-cause death: 0.54, 0.40 to 0.72, p<0.001; CVD death: 0.46 (0.27 to 0.78, p=0.008). Conclusions: Although physical activity protects against premature mortality among both medicated and unmedicated adults, cardiovascular medication is linked with lower uptake of health enhancing physical activity. These results highlight the importance of physical activity in the primary prevention of CVD over and above medication

    Quantum phase transitions in the J-J' Heisenberg and XY spin-1/2 antiferromagnets on square lattice: Finite-size scaling analysis

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    We investigate the critical parameters of an order-disorder quantum phase transitions in the spin-1/2 JJJ-J' Heisenberg and XY antiferromagnets on square lattice. Basing on the excitation gaps calculated by exact diagonalization technique for systems up to 32 spins and finite-size scaling analysis we estimate the critical couplings and exponents of the correlation length for both models. Our analysis confirms the universal critical behavior of these quantum phase transitions: They belong to 3D O(3) and 3D O(2) universality classes, respectively.Comment: 7 pages, 3 figure

    A new substrate for sampling deep river macroinvertebrates

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    We compared macroinvertebrate communities colonising multiplate samplers constructed from perspex or tempered hardboard (wood) with an alternative artificial substrate constructed from folded coconut fibre matting (coir) enclosed in nylon netting. Substrates were incubated for 62 days over January to March 2007 at six sites over 240 km along the Waikato River. The three substrates supported similar numbers of invertebrate taxa (27 - 29 taxa), but coir samples contained 71% of total invertebrate numbers from all substrates combined, compared with <17% for each type of multiplate sampler. Coir faunas were heavily dominated by the hydrobiid snail Potamopyrgus (84 % of numbers), and this taxon along with the amphipod Paracalliope comprised 58 - 66 % of invertebrates on both types of multiplate samplers. Analysis of a Bray-Curtis matrix suggested statistically significant differences in percent community composition between coir samplers and each type of multiplate sampler over the late summer study period. Densities per cm3 of Oligochaeta, Mollusca, and "other worms" (Platyhelminthes, Rhabdocoela, Nemertea and Hirudinea combined) were significantly higher in coir samples than one or both of the multiplate samplers. Results suggest coir samplers may provide a useful supplement to multiplate samplers for deep river invertebrate studies by collecting a different range of taxa, including those favouring cover and characteristic of depositional environments

    Series Expansions for Excited States of Quantum Lattice Models

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    We show that by means of connected-graph expansions one can effectively generate exact high-order series expansions which are informative of low-lying excited states for quantum many-body systems defined on a lattice. In particular, the Fourier series coefficients of elementary excitation spectra are directly obtained. The numerical calculations involved are straightforward extensions of those which have already been used to calculate series expansions for ground-state correlations and T=0T=0 susceptibilities in a wide variety of models. As a test, we have reproduced the known elementary excitation spectrum of the transverse-field Ising chain in its disordered phase.Comment: 9 pages, no figures, Revtex 3.0 The revised version corrects the incorrect (and unnecessary) statement in the original that H and H^eff are related by a unitary transformation; in fact they are related by via a similarity transformation. This has no implications for the calculations of spectra, but is important for matrix element

    Spin-wave excitation spectra and spectral weights in square lattice antiferromagnets

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    Using a recently developed method for calculating series expansions of the excitation spectra of quantum lattice models, we obtain the spin-wave spectra for square lattice, S=1/2S=1/2 Heisenberg-Ising antiferromagnets. The calculated spin-wave spectrum for the Heisenberg model is close to but noticeably different from a uniformly renormalized classical (large-SS) spectrum with the renormalization for the spin-wave velocity of approximately 1.181.18. The relative weights of the single-magnon and multi-magnon contributions to neutron scattering spectra are obtained for wavevectors throughout the Brillouin zone.Comment: Two postscript figures, 4 two-column page

    Cold gas in group-dominant elliptical galaxies

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    We present IRAM 30m telescope observations of the CO(1-0) and (2-1) lines in a sample of 11 group-dominant elliptical galaxies selected from the CLoGS nearby groups sample. Our observations confirm the presence of molecular gas in 4 of the 11 galaxies at >4 sigma significance, and combining these with data from the literature we find a detection rate of 43+-14%, comparable to the detection rate for nearby radio galaxies, suggesting that group-dominant ellipticals may be more likely to contain molecular gas than their non-central counterparts. Those group-dominant galaxies which are detected typically contain ~2x10^8 Msol of molecular gas, and although most have low star formation rates (<1 Msol/yr) they have short depletion times, indicating that the gas must be replenished on timescales ~100 Myr. Almost all of the galaxies contain active nuclei, and we note while the data suggest that CO may be more common in the most radio-loud galaxies, the mass of molecular gas required to power the active nuclei through accretion is small compared to the masses observed. We consider possible origin mechanisms for the gas, through cooling of stellar ejecta within the galaxies, group-scale cooling flows, and gas-rich mergers, and find probable examples of each type within our sample, confirming that a variety of processes act to drive the build up of molecular gas in group-dominant ellipticals.Comment: 9 pages, 5 postscript figures, 4 tables, accepted by A&A. Revised throughout in response to referee's comments, including updates to Table 1 and Figure 4, and addition of Figure

    Critical and off-critical studies of the Baxter-Wu model with general toroidal boundary conditions

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    The operator content of the Baxter-Wu model with general toroidal boundary conditions is calculated analytically and numerically. These calculations were done by relating the partition function of the model with the generating function of a site-colouring problem in a hexagonal lattice. Extending the original Bethe-ansatz solution of the related colouring problem we are able to calculate the eigenspectra of both models by solving the associated Bethe-ansatz equations. We have also calculated, by exploring the conformal invariance at the critical point, the mass ratios of the underlying massive theory governing the Baxter-Wu model in the vicinity of its critical point.Comment: 32 pages latex, to appear in J. Phys. A: Math. Ge
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