3,430 research outputs found
Winning the Un-Winnable in Afghanistan? Counterinsurgency and Ethnic Strife
After pursuing military actions in both Iraq and Afghanistan, the United States adopted a counterinsurgency policy to properly address these conflicts. After implementing this new strategy, it appears that the United States has been able to succeed against the insurgency, while losing more and more ground in Afghanistan. Upon examination, it was determined that the ethnic fractionalization in Afghanistan presented a unique challenge to the counterinsurgency effort that had not been present in Iraq.
The effects of this ethnic fractionalization were then analyzed on local counterinsurgency tactics and the overall nation building strategy in Afghanistan. Local counterinsurgency tactics had largely not been tailored to work in Afghanistan\u27s multi-ethnic climate. The nation building strategy that has been pursued in Afghanistan has not been successful in uniting the country under the power of the central Afghan government. A more proficient implementation of local counterinsurgency and more effective governmental institutions are important to bringing Afghanistan\u27s fractured ethnicities together into one nation and ending the ongoing insurgency
A Survey of Merger Remnants II: The Emerging Kinematic and Photometric Correlations
This paper is the second in a series exploring the properties of 51 {\it
optically} selected, single-nuclei merger remnants. Spectroscopic data have
been obtained for a sub-sample of 38 mergers and combined with previously
obtained infrared photometry to test whether mergers exhibit the same
correlations as elliptical galaxies among parameters such as stellar luminosity
and distribution, central stellar velocity dispersion (), and
metallicity. Paramount to the study is to test whether mergers lie on the
Fundamental Plane. Measurements of have been made using the
Ca triplet absorption line at 8500 {\AA} for all 38 mergers in the sub-sample.
Additional measurements of were made for two of the mergers
in the sub-sample using the CO absorption line at 2.29 \micron. The results
indicate that mergers show a strong correlation among the parameters of the
Fundamental Plane but fail to show a strong correlation between
and metallicity (Mg). In contrast to earlier studies,
the of the mergers are consistent with objects which lie
somewhere between intermediate-mass and luminous giant elliptical galaxies.
However, the discrepancies with earlier studies appears to correlate with
whether the Ca triplet or CO absorption lines are used to derive
, with the latter almost always producing smaller values.
Finally, the photometric and kinematic data are used to demonstrate for the
first time that the central phase-space density of mergers are equivalent to
elliptical galaxies. This resolves a long-standing criticism of the merger
hypothesis.Comment: Accepted Astronomical Journal (to appear in January 2006
Toroidal metrics: gravitational solenoids and static shells
In electromagnetism a current along a wire tightly wound on a torus makes a
solenoid whose magnetic field is confined within the torus. In Einstein's
gravity we give a corresponding solution in which a current of matter moves up
on the inside of a toroidal shell and down on the outside, rolling around the
torus by the short way. The metric is static outside the torus but stationary
inside with the gravomagnetic field confined inside the torus, running around
it by the long way. This exact solution of Einstein's equations is found by
fitting Bonnor's solution for the metric of a light beam, which gives the
required toroidal gravomagnetic field inside the torus, to the general Weyl
static external metric in toroidal coordinates, which we develop. We deduce the
matter tensor on the torus and find when it obeys the energy conditions. We
also give the equipotential shells that generate the simple Bach-Weyl metric
externally and find which shells obey the energy conditions.Comment: To appear in Class. Quantum Gra
Botulism Type E Outbreak Associated with Eating a Beached Whale, Alaska
We report an outbreak of botulism that occurred in July 2002 in a group of 12 Alaskan Yu'pik Eskimos who ate blubber and skin from a beached beluga whale. Botulism death rates among Alaska Natives have declined in the last 20 years, yet incidence has increased
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Identification and control of subglacial water networks under Dome A, Antarctica
Subglacial water in continental Antarctica forms by melting of basal ice due to geothermal or frictional heating. Subglacial networks transport the water from melting areas and can facilitate sliding by the ice sheet over its bed. Subglacial water flow is driven mainly by gradients in overburden pressure and bed elevation. We identify small (median 850 m) water bodies within the Gamburtsev Subglacial Mountains in East Antarctica organized into long (20–103 km) coherent drainage networks using a dense (5 km) grid of airborne radar data. The individual water bodies are smaller on average than the water bodies contained in existing inventories of Antarctic subglacial water and most are smaller than the mean ice thickness of 2.5 km, reflecting a focusing of basal water by rugged topography. The water system in the Gamburtsev Subglacial Mountains reoccupies a system of alpine overdeepenings created by valley glaciers in the early growth phase of the East Antarctic Ice Sheet. The networks follow valley floors either uphill or downhill depending on the gradient of the ice sheet surface. In cases where the networks follow valley floors uphill they terminate in or near plumes of freeze-on ice, indicating source to sink transport within the basal hydrologic system. Because the ice surface determines drainage direction within the bed-constrained network, the system is bed-routed but surface-directed. Along-flow variability in the structure of the freeze-on plumes suggests variability in the networks on long (10s of ka) timescales, possibly indicating changes in the basal thermal state
Galaxy Zoo: dust lane early-type galaxies are tracers of recent, gas-rich minor mergers
We present the second of two papers concerning the origin and evolution of
local early-type galaxies exhibiting dust features. We use optical and radio
data to examine the nature of active galactic nucleus (AGN) activity in these
objects, and compare these with a carefully constructed control sample. We find
that dust lane early-type galaxies are much more likely to host emission-line
AGN than the control sample galaxies. Moreover, there is a strong correlation
between radio and emission-line AGN activity in dust lane early-types, but not
the control sample. Dust lane early-type galaxies show the same distribution of
AGN properties in rich and poor environments, suggesting a similar triggering
mechanism. By contrast, this is not the case for early-types with no dust
features. These findings strongly suggest that dust lane early-type galaxies
are starburst systems formed in gas-rich mergers. Further evidence in support
of this scenario is provided by enhanced star formation and black hole
accretion rates in these objects. Dust lane early-types therefore represent an
evolutionary stage between starbursting and quiescent galaxies. In these
objects, the AGN has already been triggered but has not as yet completely
destroyed the gas reservoir required for star formation.Comment: 11 pages, 18 figures, 4 tables, MNRAS (Accepted for publication- 2012
January 19
Recommendations for dealing with waste contaminated with Ebola virus: a Hazard Analysis of Critical Control Points approach
Objective To assess, within communities experiencing Ebola virus outbreaks, the risks associated with the disposal of human waste and to generate recommendations for mitigating such risks. Methods A team with expertise in the Hazard Analysis of Critical Control Points framework identified waste products from the care of individuals with Ebola virus disease and constructed, tested and confirmed flow diagrams showing the creation of such products. After listing potential hazards associated with each step in each flow diagram, the team conducted a hazard analysis, determined critical control points and made recommendations to mitigate the transmission risks at each control point. Findings The collection, transportation, cleaning and shared use of blood-soiled fomites and the shared use of latrines contaminated with blood or bloodied faeces appeared to be associated with particularly high levels of risk of Ebola virus transmission. More moderate levels of risk were associated with the collection and transportation of material contaminated with bodily fluids other than blood, shared use of latrines soiled with such fluids, the cleaning and shared use of fomites soiled with such fluids, and the contamination of the environment during the collection and transportation of blood-contaminated waste. Conclusion The risk of the waste-related transmission of Ebola virus could be reduced by the use of full personal protective equipment, appropriate hand hygiene and an appropriate disinfectant after careful cleaning. Use of the Hazard Analysis of Critical Control Points framework could facilitate rapid responses to outbreaks of emerging infectious disease
Relativistic conservation laws and integral constraints for large cosmological perturbations
For every mapping of a perturbed spacetime onto a background and with any
vector field we construct a conserved covariant vector density ,
which is the divergence of a covariant antisymmetric tensor density, a
"superpotential". is linear in the energy-momentum tensor
perturbations of matter, which may be large; does not contain the
second order derivatives of the perturbed metric. The superpotential is
identically zero when perturbations are absent.
By integrating conserved vectors over a part \Si of a hypersurface of
the background, which spans a two-surface \di\Si, we obtain integral
relations between, on the one hand, initial data of the perturbed metric
components and the energy-momentum perturbations on \Si and, on the other
hand, the boundary values on \di\Si. We show that there are as many such
integral relations as there are different mappings, 's, \Si's and
\di\Si's. For given boundary values on \di\Si, the integral relations may
be interpreted as integral constraints (e.g., those of Traschen) on local
initial data including the energy-momentum perturbations. Conservation laws
expressed in terms of Killing fields \Bar\xi of the background become
"physical" conservation laws.
In cosmology, to each mapping of the time axis of a Robertson-Walker space on
a de Sitter space with the same spatial topology there correspond ten
conservation laws. The conformal mapping leads to a straightforward
generalization of conservation laws in flat spacetimes. Other mappings are also
considered. ...Comment: This paper, published 7 years ago, was found useful by some
researchers but originally was not put on the gr-qc website. Now it has been
retyped with very minor changes: few wordings have been modified and several
misprints occurring in the printed version correcte
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