11,123 research outputs found
Panic on the streets of London
The terrorist attacks of 7 July 2005 resulted in a very large redeployment of police officers to central London boroughs. New research by Mirko Draca, Stephen Machin and Robert Witt looks at the impact of this increased security presence on criminal activity in the weeks and months after the bomb blasts
Using HCMM Thermal Data to Improve Classification of MSS Data
Spectral overlap between urban and rural land use/land cover categories can lead to unacceptable map accuracy levels in the classification of LANDSAT multispectral scanner (MSS) data. The four MSS bands used alone are not always adequate to distinguish among various land uses and cover types having similar spectral responses. The use of thermal data from the Heat Capacity Mapping Mission (HCMM) satellite as a means of improving MSS land cover classification accuracies for urban versus rural categories was investigated. The approaches used to integrate the HCMM data are described
Magnification relations in gravitational lensing via multidimensional residue integrals
We investigate the so-called magnification relations of gravitational lensing
models. We show that multidimensional residue integrals provide a simple
explanation for the existence of these relations, and an effective method of
computation. We illustrate the method with several examples, thereby deriving
new magnification relations for galaxy lens models and microlensing (point mass
lensing).Comment: 16 pages, uses revtex4, submitted to Journal of Mathematical Physic
Preparation of homogeneous vitreous materials for electronic and optical devices
Vitreous material builds up as series of solidified layers on inside walls of sealed quartz ampoule containing molten constituents of material, and forms well defined shapes to close dimensional tolerances. Ampoules are made of material which does not react with melt and has lower thermal expansion coefficient than solidified layer
Quasiconformality and mass
We identify universal quasiconformal (walking) behaviour in non-Abelian gauge
field theories based on the mass-dependent all-order beta-function introduced
in arXiv:0908.1364. We find different types of walking behaviour in the
presence of (partially) massive species. We employ our findings to the
construction of candidate theories for dynamical electroweak symmetry breaking
by walking technicolour.Comment: 16 pages, 8 figures
Probability of Detecting a Planetary Companion during a Microlensing Event
The probability of detecting a planetary companion of a lensing star during a
microlensing event toward the Galactic center, averaged over all relevant event
and galactic parameters, when the planet-star mass ratio has a
maximum exceeding 10% at an orbit semimajor axis near 1.5 AU for a uniform
distribution of impact parameters. The maximum probability is raised to more
than 20% for a distribution of source-lens impact parameters that is determined
by the efficiency of event detection. The averaging procedures are carefully
defined, and they determinine the dependence of the detection probabilities on
several properties of the Galaxy. The probabilities scale approximately as
. A planet is assumed detectable if the perturbation of the single
lens light curve exceeds for at least 20 consecutive photometric
points sometime during the event. Two meter telescopes with 60 second
integrations in I-band with high time resolution photometry throughout the
duration of an ongoing event are assumed. The probabilities are derived as a
function of , where they remain significant for AU. Dependence of
the detection probabilities on the lens mass function, luminosity function of
the source stars as modified by extinction, distribution of source-lens impact
parameters, and the line of sight to the source are also determined, and the
probabilities are averaged over the distribution of the projected planet
position, the lens mass function, the distribution of impact parameters, the
lens and source distances as weighted by their distributions along the line of
sight and over the -band apparent luminosity function of the sources. The
extraction of the probabilility as a function of for a particular from
empirical data is indicated.Comment: 32 pages, 20 figures, In Press, ApJ, Latex format with aas2pp4 forma
Gravitational Lenses With More Than Four Images: I. Classification of Caustics
We study the problem of gravitational lensing by an isothermal elliptical
density galaxy in the presence of a tidal perturbation. When the perturbation
is fairly strong and oriented near the galaxy's minor axis, the lens can
produce image configurations with six or even eight highly magnified images
lying approximately on a circle. We classify the caustic structures in the
model and identify the range of models that can produce such lenses. Sextuple
and octuple lenses are likely to be rare because they require special lens
configurations, but a full calculation of the likelihood will have to include
both the existence of lenses with multiple lens galaxies and the strong
magnification bias that affects sextuple and octuple lenses. At optical
wavelengths these lenses would probably appear as partial or complete Einstein
rings, but at radio wavelengths the individual images could probably be
resolved.Comment: 30 pages, including 12 postscript figures; accepted for publication
in Ap
Extended Source Diffraction Effects Near Gravitational Lens Fold Caustics
Calculations are presented detailing the gravitational lens diffraction due
to the steep brightness gradient of the limb of a stellar source. The lensing
case studied is the fold caustic crossing. The limb diffraction signal greatly
exceeds that due to the disk as a whole and should be detectable for white
dwarf sources in our Galaxy and it's satellites with existing telescopes.
Detection of this diffraction signal would provide an additional mathematical
constraint, reducing the degeneracy among models of the lensing geometry. The
diffraction pattern provides pico-arcsecond resolution of the limb profile.Comment: 19 pages including 17 figures, Accepted for publication in ApJ, Minor
conceptual change from previous versio
Injuries Among Security and Law Enforcement Personnel in the Private Versus Public Sectors
Background and Objectives: Data collected through workersâ compensation may be useful for occupational injury surveillance. This study examined whether differences existed between the public and private sectors of the security and law enforcement industry in Kentucky.
Methods: Using a cross-Ââsectional design, workersâ compensation data from the Kentucky Department of Workersâ Claims was analyzed to evaluate differences in demographic and injury characteristics, as well as award outcomes, stratified by industry sector. The dataset included all workersâ compensation first reports of injury and claims filed by security and law enforcement personnel in Kentucky from 2005 to 2015. Statistical analyzes included chi-Ââsquare and logistic regression.
Results: When adjusting for gender, age, nature of injury, cause of injury, and body part injured, the estimated odds that a first report resulted in an adjudicated award was observed to be 1.334 times larger [95% CI: (1.069, 1.666), (p=0.011)] in the private sector, compared to the public sector.
Conclusion: A statistically significant difference in the estimated, adjusted odds of a first report of injury resulting in an adjudicated award was observed between public and private sector law enforcement. Further studies are necessary to better understand contributing factors to the variation observed between the industry sectors
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