190 research outputs found
Overview of the labour market [January 2001]
The most recent labour market data indicates continued employment growth. The number of unfilled vacancies appears to be rising apace indicating that as the number of unemployed continues to fall, employers are finding it increasingly difficult to recruit staff. The rise in the level of those economically active (and a corresponding fall in economic inactivity) is reassuring. This suggests that both government policy and opportunity has spurred people into the labour market who othewise might not have taken part. Rising wage levels and further vacancy information will indicate whether this injection into the labour market is sufficient to prevent any labour shortages, thus enabling the current run of growth to continue
Gamma-Ray Background from Structure Formation in the Intergalactic Medium
The universe is filled with a diffuse and isotropic extragalactic background
of gamma-ray radiation, containing roughly equal energy flux per decade in
photon energy between 3 MeV-100 GeV. The origin of this background is one of
the unsolved puzzles in cosmology. Less than a quarter of the gamma-ray flux
can be attributed to unresolved discrete sources, but the remainder appears to
constitute a truly diffuse background whose origin has hitherto been
mysterious. Here we show that the shock waves induced by gravity during the
formation of large-scale structure in the intergalactic medium, produce a
population of highly-relativistic electrons with a maximum Lorentz factor above
10^7. These electrons scatter a small fraction of the microwave background
photons in the present-day universe up to gamma-ray energies, thereby providing
the gamma-ray background. The predicted diffuse flux agrees with the observed
background over more than four decades in photon energy, and implies a mean
cosmological density of baryons which is consistent with Big-Bang
nucleosynthesis.Comment: 7 pages, 1 figure. Accepted for publication in Nature. (Press embargo
until published.
Toward High-Precision Measures of Large-Scale Structure
I review some results of estimation of the power spectrum of density
fluctuations from galaxy redshift surveys and discuss advances that may be
possible with the Sloan Digital Sky Survey. I then examine the realities of
power spectrum estimation in the presence of Galactic extinction, photometric
errors, galaxy evolution, clustering evolution, and uncertainty about the
background cosmology.Comment: 24 pages, including 11 postscript figures. Uses crckapb.sty (included
in submission). To appear in ``Ringberg Workshop on Large-Scale Structure,''
ed D. Hamilton (Kluwer, Amsterdam), p. 39
Mycobacterial infections in a large Virginia hospital, 2001-2009
<p>Abstract</p> <p>Background</p> <p>In areas where both tuberculosis (TB) and nontuberculous mycobacteria (NTM) are prevalent, descriptive studies of the clinical features of individual mycobacteria are needed to inform clinical triage.</p> <p>Methods</p> <p>We queried the University of Virginia Clinical Data Repository for all mycobacterial infections from 2001-2009.</p> <p>Results</p> <p>Of 494 mycobacterial infections in 467 patients there were 22 species. Patients with pulmonary Tb were more likely to be reported as immigrants (p < 0.001) and less likely to have a predisposing risk factor for NTM (pre-existing lung disease or host predisposition; p = 0.002). Review of chest CT scans revealed that TB infection was more likely to exhibit cavities and pleural effusion than NTM infection (p < 0.05). Among NTM infections <it>M. kansasii</it>, <it>M. xenopi</it>, and <it>M. fortuitum </it>were more likely than MAC to have cavities. There were at least 83 patients that met criteria for NTM lung disease and these were caused by 9 species. <it>M. abscessus </it>infection was associated with cystic fibrosis and <it>M. xenopi </it>infection was associated with male gender.</p> <p>Conclusions</p> <p>In our center mycobacterial infections were common and of diverse species. Immigrant status, cavities, and effusion were associated with TB vs. NTM.</p
The Cosmological Constant
This is a review of the physics and cosmology of the cosmological constant.
Focusing on recent developments, I present a pedagogical overview of cosmology
in the presence of a cosmological constant, observational constraints on its
magnitude, and the physics of a small (and potentially nonzero) vacuum energy.Comment: 50 pages. Submitted to Living Reviews in Relativity
(http://www.livingreviews.org/), December 199
Ecological implications of a flower size/number trade-off in tropical forest trees
Peer reviewedPublisher PD
Association of waterpipe smoking and road traffic crashes
<p>Abstract</p> <p>Background</p> <p>The purpose of this research was to examine whether waterpipe smokers experience increased risk of motor vehicle crashes.</p> <p>Methods</p> <p>In a telephone survey, a random sample of Iranian drivers were asked to report their age, gender, vehicle age, whether their vehicles were equipped with anti-lock braking system (ABS), average daily drive time (DDT), whether they smoked cigarette or waterpipe, whether they had diabetes mellitus (DM), number of traffic crashes during the last calendar year and whether the crash involved a pedestrian or another vehicle.</p> <p>Results</p> <p>A total of 2070 motor vehicle owners with the mean age of 41.6 ± 11.45 were interviewed. The annual incidence of Road Traffic Crashes (RTC) was 14.9%; 14.0% involved a collision/s with other vehicles and 0.9% with pedestrians. There was an association between the RTC and male gender, DDT, being a cigarette smoker, being a waterpipe smoker and DM in univariable analysis. The association between RTC and being a waterpipe smoker and also cigarette smoker was significant in multivariable analysis after adjustment for DDT.</p> <p>Conclusions</p> <p>Being waterpipe and/or cigarette smoker and DDT were the independent predictors of the number of traffic crashes in Poisson regression model. If the increased risk of RTC among waterpipe or cigarette smokers is seen in other studies, it would be beneficial to promote tobacco cessation and control strategies through injury prevention initiatives.</p
On the Existence of Undistorted Progressive Waves (UPWs) of Arbitrary Speeds in Nature
We present the theory, the experimental evidence, and fundamental physical
consequences concerning the existence of families of undistorted progressive
waves (UPWs) of arbitrary speeds , which are solutions of the
homogeneous wave equation, Maxwell equations, and Dirac and Weyl equations.Comment: 77 pages, Latex article, with figures. Includes corrections to the
published versio
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