14,238 research outputs found
Changing habitat associations of a thermally constrained species, the silver-spotted skipper butterfly, in response to climate warming
Experimental study of the turbulent boundary layer in acceleration-skewed oscillatory flow
Peer reviewedPublisher PD
FFT for the APE Parallel Computer
We present a parallel FFT algorithm for SIMD systems following the `Transpose
Algorithm' approach. The method is based on the assignment of the data field
onto a 1-dimensional ring of systolic cells. The systolic array can be
universally mapped onto any parallel system. In particular for systems with
next-neighbour connectivity our method has the potential to improve the
efficiency of matrix transposition by use of hyper-systolic communication. We
have realized a scalable parallel FFT on the APE100/Quadrics massively parallel
computer, where our implementation is part of a 2-dimensional hydrodynamics
code for turbulence studies. A possible generalization to 4-dimensional FFT is
presented, having in mind QCD applications.Comment: 17 pages, 13 figures, figures include
Gambling Harm as a Global Public Health Concern: A Mixed Method Investigation of Trends in Wales
Background: Recent research evidence has suggested that gambling is a public health concern. A number of studies report the association between gambling activity and increased instances of various other harms, including substance misuse and psychological disorders. In parallel to alcohol misuse, it is also becoming clear that gambling related harm is more of a continuum of harm, as opposed to traditionally accepted categorisations of gambling behavior: safe and responsible or “problem” and harmful. Previous effective treatment models for alcohol misuse have considered a public health approach to develop interventions. As such, the current research seeks to use a public health approach to both investigate the extent of gambling harm across Wales, and to identify upstream predictors of harm to inform future interventions. /
Method: A triangulation of data collection methods was utilized across Wales, UK. Two hundred and forty-eight participants completed a quantitative survey relating to gambling behavior and related harm, which included the Problem Severity Gambling Index, the Gambling Commission measure of frequency, The Gambling Motives Questionnaire and the Fast Alcohol Screening tool. Ninety-eight of these participants completed a qualitative subsection. Structured interviews were conducted with 20 individuals from 11 service providers. Semi-structured interviews were conducted for the five case studies of individuals who had previously sought help for gambling. The geographical density and distribution of Licensed Gambling Outlets was also mapped in local areas. /
Results: The findings provide further evidence of a continuum of gambling related harm. Twenty seven percent of survey participants demonstrate some indicators of risk of gambling harm. Social, cultural and environmental contexts play a role in initiation and maintenance of gambling behavior and the subsequent related harm. Accounts from individuals corroborated the quantitative findings. /
Conclusions: Findings from this Welsh sample are in line with and add support to the growing international research evidence that gambling harms are a universal issue that cross cultures. It is clear that action is needed by legislators at a policy level and that broadening the focus of intervention to a public health level is necessary to develop effective strategies for harm reduction
Impact of magnetic activity on inferred stellar properties of main-sequence Sun-like stars
The oscillation frequencies observed in Sun-like stars are susceptible to being shifted by magnetic activity effects. The measured shifts depend on a complex relationship involving the mode type, the field strength, and spatial distribution of activity, as well as the inclination angle of the star. Evidence of these shifts is also present in frequency separation ratios that are often used when inferring global properties of stars in order to avoid surface effects. However, one assumption when using frequency ratios for this purpose is that there are no near-surface perturbations that are non-spherically symmetric. In this work, we studied the impact on inferred stellar properties when using frequency ratios that are influenced by non-homogeneous activity distributions. We generate several sets of artificial oscillation frequencies with various amounts of shift and determine stellar properties using two separate pipelines. We find that for asteroseismic observations of Sun-like targets we can expect magnetic activity to affect mode frequencies that will bias the results from stellar modelling analysis. Although for most stellar properties this offset should be small, typically less than 0.5 per cent in mass, estimates of age and central hydrogen content can have an error of up to 5 per cent and 3 per cent, respectively. We expect a larger frequency shift and therefore larger bias for more active stars. We also warn that for stars with very high or low inclination angles, the response of modes to activity is more easily observable in the separation ratios and hence will incur a larger bias
Spatially resolved spectroscopy of Coma cluster early -- type galaxies: III. The stellar population gradients
We derive central values and logarithmic gradients for the Hbeta, Mg and Fe
indices of 35 early-type galaxies in the Coma cluster. We find that pure
elliptical galaxies have on average slightly higher velocity dispersions, lower
Hbeta, and higher metallic line-strengths than galaxies with disks (S0). The
gradients strongly correlate with the gradients of sigma, but only weakly with
the central index values and galaxy velocity dispersion. Using stellar
population models with variable element abundance ratios from Thomas, Maraston
& Bender (2003a) we derive average ages, metallicities and [alpha/Fe] ratios in
the center and at the effective radius. We find that the [alpha/Fe] ratio
correlates with velocity dispersion and drives 30% of the Mg-sigma relation,
the remaining 70% being caused by metallicity variations. We derive negative
metallicity gradients (-0.16 dex per decade) that are significantly flatter
than what is expected from gaseous monolithic collapse models, pointing to the
importance of mergers in the galaxy formation history. The gradients in age are
negligible, implying that no significant residual star formation has occurred
either in the center or in the outer parts of the galaxies, and that the
stellar populations at different radii must have formed at a common epoch. For
the first time we derive the gradients of the [alpha/Fe] ratio and find them
very small on the mean. Hence, [alpha/Fe] enhancement is not restricted to
galaxy centers but it is a global phenomenon. Our results imply that the
Mg-sigma local relation inside a galaxy, unlike the global Mg-sigma relation,
must be primarily driven by metallicity variations alone.Comment: 19 pages, 8 figures, Accepted for publication in A&
Atmospheric extinction coefficients in the band for several major international observatories: Results from the BiSON telescopes, 1984 to 2016
Over 30 years of solar data have been acquired by the Birmingham Solar
Oscillations Network (BiSON), an international network of telescopes used to
study oscillations of the Sun. Five of the six BiSON telescopes are located at
major observatories. The observational sites are, in order of increasing
longitude: Mount Wilson (Hale) Observatory (MWO), California, USA; Las Campanas
Observatory (LCO), Chile; Observatorio del Teide, Iza\~{n}a, Tenerife, Canary
Islands; the South African Astronomical Observatory (SAAO), Sutherland, South
Africa; Carnarvon, Western Australia; and the Paul Wild Observatory, Narrabri,
New South Wales, Australia. The BiSON data may be used to measure atmospheric
extinction coefficients in the band (approximately 700-900 nm),
and presented here are the derived atmospheric extinction coefficients from
each site over the years 1984 to 2016.Comment: 15 pages, 10 figures, 4 tables. Accepted by Astronomical Journal:
2017 July 2
Two scenarios for avalanche dynamics in inclined granular layers
We report experimental measurements of avalanche behavior of thin granular
layers on an inclined plane for low volume flow rate. The dynamical properties
of avalanches were quantitatively and qualitatively different for smooth glass
beads compared to irregular granular materials such as sand. Two scenarios for
granular avalanches on an incline are identified and a theoretical explanation
for these different scenarios is developed based on a depth-averaged approach
that takes into account the differing rheologies of the granular materials.Comment: 4 pages, 4 figures, accepted to Phys. Rev. Let
- …