4,500 research outputs found
Universality of Load Balancing Schemes on Diffusion Scale
We consider a system of parallel queues with identical exponential
service rates and a single dispatcher where tasks arrive as a Poisson process.
When a task arrives, the dispatcher always assigns it to an idle server, if
there is any, and to a server with the shortest queue among randomly
selected servers otherwise . This load balancing scheme
subsumes the so-called Join-the-Idle Queue (JIQ) policy and the
celebrated Join-the-Shortest Queue (JSQ) policy as two crucial
special cases. We develop a stochastic coupling construction to obtain the
diffusion limit of the queue process in the Halfin-Whitt heavy-traffic regime,
and establish that it does not depend on the value of , implying that
assigning tasks to idle servers is sufficient for diffusion level optimality
Investigation of the New Local Group Galaxy VV 124
We present the results of our stellar photometry and spectroscopy for the new
Local Group galaxy VV 124 (UGC 4879) obtained with the 6-m BTA telescope. The
presence of a few bright supergiants in the galaxy indicates that the current
star formation process is weak. The apparent distribution of stars with
different ages in VV 124 does not differ from the analogous distributions of
stars in irregular galaxies, but the ratio of the numbers of young and old
stars indicates that VV 124 belongs to the rare Irr/Sph type of galaxies. The
old stars (red giants) form the most extended structure, a thick disk with an
exponential decrease in the star number density to the edge. Definitely, the
young population unresolvable in images makes a great contribution to the
background emission from the central galactic regions. The presence of young
stars is also confirmed by the [O III] emission line visible in the spectra
that belongs to extensive diffuse galactic regions. The mean radial velocity of
several components (two bright supergiants, the unresolvable stellar
population, and the diffuse gas) is v_h = -70+/-15 km/s and the velocity with
which VV 124 falls into the Local Group is v_LG = -12+/-15 km/s. We confirm the
distance to the galaxy D = 1.1+/-0.1 Mpc and the metallicity of red giants
([Fe/H] = -1.37) found by Kopylov et al. (2008).VV 124 is located on the
periphery of the Local Group approximately at the same distance from M 31 and
our Galaxy and is isolated from other galaxies. The galaxy LeoA nearest to it
is 0.5 Mpc away.Comment: 10 pages, 8 figures. Accepted for publication in Astronomy Letters
(2010, Vol. 36, No. 5, pp. 309-318
HI and OH absorption in the lensing galaxy of MG J0414+0534
We report the detection of \HI 21-cm absorption in the early-type
lensing galaxy towards MG J0414+0534 with the Green Bank Telescope. The
absorption, with total , is resolved into two strong components, probably due to the two
strongest lens components, which are separated by 0.4\arcsec. Unlike the other
three lenses which have been detected in \HI, J0414+0534 does not exhibit
strong OH absorption, giving a OH/\HI column density ratio of N_{\rm
OH}/N_{\rm HI}\lapp10^{-6} (for K, K and
). This underabundance of molecular gas may indicate
that the extreme optical--near-IR colour () along the line-of-sight
is not due to the lens. We therefore suggest that despite the strong upper
limits on molecular absorption at the quasar redshift, as traced by millimetre
lines, the extinction occurs primarily in the quasar host galaxy.Comment: Accepted by MNRAS Letters, 5 (and a bit) pages, 5 figure
Near-field radiative heat transfer between macroscopic planar surfaces
Near-field radiative heat transfer allows heat to propagate across a small
vacuum gap in quantities that are several orders of magnitude greater then the
heat transfer by far-field, blackbody radiation. Although heat transfer via
near-field effects has been discussed for many years, experimental verification
of this theory has been very limited. We have measured the heat transfer
between two macroscopic sapphire plates, finding an increase in agreement with
expectations from theory. These experiments, conducted near 300 K, have
measured the heat transfer as a function of separation over mm to m and as
a function of temperature differences between 2.5 and 30 K. The experiments
demonstrate that evanescence can be put to work to transfer heat from an object
without actually touching it
Economic evaluation of physical activity interventions for type 2 diabetes management: a systematic review
Background: Economic evaluation of physical activity interventions has become an important area for policymaking considering the high costs attributable to physical inactivity. However, the evidence for such interventions targeting type 2 diabetes control is scarce. Therefore, the present study aimed to synthesize economic evaluation studies of physical activity interventions for type 2 diabetes management. Methods: A systematic review was conducted using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 statement (PROSPERO reference number CRD42021231021). An electronic search was performed in PubMed, Web of Science, Cochrane Library and NHS Economic Evaluation Database. Studies were eligible if they included: adults with type 2 diabetes; any physical activity intervention in the community settings; an experimental or quasi-experimental design; and a parameter of economic evaluation [cost analysis of interventions, cost-effectiveness analysis (including cost-utility analysis) and cost-benefit analysis] as an outcome. Results: Ten studies were included in this review: seven were randomized controlled trials and three were quasi-experimental studies. All studies included direct costs, and four also included indirect costs. Four studies demonstrated that physical activity interventions were cost-saving, six studies showed cost-effectiveness, and two studies reported cost-utility. The estimates varied considerably across the studies with different analytical and methodological approaches. Conclusion: Overall, this systematic review found that physical activity interventions are a worth investment for type 2 diabetes management. However, comparability across interventions was limited due to heterogeneity in interventions type, design and delivery, which may explain the differences in the economic measures. © 2022 The Author(s). Published by Oxford University Press on behalf of the European Public Health Association.This work was funded by the Portuguese Foundation for Science and Technology within the scope of projects UIDB/04750/2020 and LA/P/0064/2020. Ana Barbosa was supported by the Portuguese Foundation for Science and Technology, grant number SFRH/BD/136702/2018
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