13,058 research outputs found
A CF3I-based SDD Prototype for Spin-independent Dark Matter Searches
The application of Superheated Droplet Detectors (SDDs) to dark matter
searches has so far been confined to the light nuclei refrigerants C2ClF5 and
C4F10 (SIMPLE and PICASSO, respectively), with a principle sensitivity to
spin-dependent interactions. Given the competitive results of these devices, as
a result of their intrinsic insensitivity to backgrounds, we have developed a
prototype trifluoroiodomethane (CF3I)-loaded SDD with increased sensitivity to
spin-independent interactions as well. A low (0.102 kgd) exposure test
operation of two high concentration, 1 liter devices is described, and the
results compared with leading experiments in both spin-dependent and
-independent sectors. Although competitive in both sectors when the difference
in exposures is accounted for, a problem with fracturing of the detector gel
must be addressed before significantly larger exposures can be envisioned.Comment: revised and updated; accepted Astrop. Phy
Does fire influence the landscape-scale distribution of an invasive mesopredator?
Predation and fire shape the structure and function of ecosystems globally. However, studies exploring interactions between these two processes are rare, especially at large spatial scales. This knowledge gap is significant not only for ecological theory, but also in an applied context, because it limits the ability of landscape managers to predict the outcomes of manipulating fire and predators. We examined the influence of fire on the occurrence of an introduced and widespread mesopredator, the red fox (Vulpes vulpes), in semi-arid Australia. We used two extensive and complimentary datasets collected at two spatial scales. At the landscape-scale, we surveyed red foxes using sand-plots within 28 study landscapes - which incorporated variation in the diversity and proportional extent of fire-age classes - located across a 104 000 km2 study area. At the site-scale, we surveyed red foxes using camera traps at 108 sites stratified along a century-long post-fire chronosequence (0-105 years) within a 6630 km2 study area. Red foxes were widespread both at the landscape and site-scale. Fire did not influence fox distribution at either spatial scale, nor did other environmental variables that we measured. Our results show that red foxes exploit a broad range of environmental conditions within semi-arid Australia. The presence of red foxes throughout much of the landscape is likely to have significant implications for native fauna, particularly in recently burnt habitats where reduced cover may increase prey species\u27 predation risk
Dislocation constriction and cross-slip in Al and Ag: an ab initio study
A novel model based on the Peierls framework of dislocations is developed.
The new theory can deal with a dislocation spreading at more than one slip
planes. As an example, we study dislocation cross-slip and constriction process
of two fcc metals, Al and Ag. The energetic parameters entering the model are
determined from ab initio calculations. We find that the screw dislocation in
Al can cross-slip spontaneously in contrast with that in Ag, which splits into
partials and cannot cross-slip without first being constricted. The dislocation
response to an external stress is examined in detail. We determine dislocation
constriction energy and critical stress for cross-slip, and from the latter, we
estimate the cross-slip energy barrier for the straight screw dislocations
Ensemble density-functional theory for ab-initio molecular dynamics of metals and finite-temperature insulators
A new method is presented for performing first-principles molecular-dynamics
simulations of systems with variable occupancies. We adopt a matrix
representation for the one-particle statistical operator Gamma, to introduce a
``projected'' free energy functional G that depends on the Kohn-Sham orbitals
only and that is invariant under their unitary transformations. The Liouville
equation [ Gamma , H ] = 0 is always satisfied, guaranteeing a very efficient
and stable variational minimization algorithm that can be extended to
non-conventional entropic formulations or fictitious thermal distributions.Comment: 5 pages, two-column style with 2 postscript figures embedded. Uses
REVTEX and epsf macros. Also available at
http://www.physics.rutgers.edu/~dhv/preprints/index.html#nm_meta
VLBI observations of the Crab nebula pulsar
Observations were made at meter wave-lengths using very long base-line interferometry techniques. At 196.5 MHz no resolution of the pulsar are observed; all the pulse shapes observed with the interferometers are similar to single dish profiles, and all the power pulsates. At 111.5 MHz besides the pulsing power there is always a steady component, presumably due to interstellar scattering. The pulsar is slightly resolved at 111.5 MHz with an apparent angular diameter of 0.07 sec ? 0.01 sec. A 50 percent linear polarization of the time-averaged power is noted at 196.5 MHz; at 111.5 MHz, 20 percent of the total time-averaged power is polarized, 35 percent of the pulsing power is polarized, and the steady component is unpolarized
Two isoperimetric inequalities for the Sobolev constant
In this note we prove two isoperimetric inequalities for the sharp constant
in the Sobolev embedding and its associated extremal function. The first such
inequality is a variation on the classical Schwarz Lemma from complex analysis,
similar to recent inequalities of Burckel, Marshall, Minda, Poggi-Corradini,
and Ransford, while the second generalises an isoperimetric inequality for the
first eigenfunction of the Laplacian due to Payne and Rayner.Comment: 11 page
Operation of Faddeev-Kernel in Configuration Space
We present a practical method to solve Faddeev three-body equations at
energies above three-body breakup threshold as integral equations in coordinate
space. This is an extension of previously used method for bound states and
scattering states below three-body breakup threshold energy. We show that
breakup components in three-body reactions produce long-range effects on
Faddeev integral kernels in coordinate space, and propose numerical procedures
to treat these effects. Using these techniques, we solve Faddeev equations for
neutron-deuteron scattering to compare with benchmark solutions.Comment: 20 pages, 8 figures, to be published in Few-Body System
A Product Formula for the Normalized Volume of Free Sums of Lattice Polytopes
The free sum is a basic geometric operation among convex polytopes. This note
focuses on the relationship between the normalized volume of the free sum and
that of the summands. In particular, we show that the normalized volume of the
free sum of full dimensional polytopes is precisely the product of the
normalized volumes of the summands.Comment: Published in the proceedings of 2017 Southern Regional Algebra
Conferenc
Evaluation of the palatability and toxicity of candidate baits and toxicants for mongooses (\u3ci\u3eHerpestes auropunctatus\u3c/i\u3e)
The small Indian mongoose (Herpestes auropunctatus) is an invasive pest species responsible for damage to native avian, reptile, and amphibian species on Hawaii, Croatia, Mauritius, and several Caribbean Islands, among other regions.Mongoose control has been pursued through a variety of means, with varying success. One toxicant, diphacinone, has been shown to be effective in mongooses and is co-labeled in a rodenticide bait for mongoose control in Hawaii; however, preliminary observations indicate low performance as a mongoose toxicant due likely to poor consumption. We evaluated the efficacy and palatability of 10 commercial rodenticide baits, technical diphacinone powder, and two alternative acute toxicants against mongooses in laboratory feeding trials. We observed poor acceptance and subsequent low overall mortality, of the hard grain-based pellets or block formulations typical of most of the commercial rodenticide baits. The exception was Tomcat® bait blocks containing 0.1% bromethalin, an acute neurotoxin, which achieved up to 100% mortality. Mortality among all other commercial rodenticide formulations ranged from 10 to 50%. Three-day feedings of 0.005% technical diphacinone formulated in fresh minced chicken achieved 100% mortality. One-day feedings of para-aminopropiophenone (PAPP), a chemical that reduces the oxygen-carrying capacity of the blood, achieved 100% mortality at concentrations of 0.10 to 0.15%. Bait acceptance of two sodium nitrite formulations (similar toxic mode of action as PAPP) was relatively poor, and mortality averaged 20%. In general, commercially produced rodenticide baits were not preferred by mongooses and had lower mortality rates compared to freshly prepared meat bait formulations. More palatable baits had higher consumption and achieved higher mortality rates. The diphacinone bait registered for rat and mongoose control in Hawaii achieved 20% mortality and was less effective than some of the other commercial or candidate fresh bait products evaluated in this study
WATER REPELLENT RENDERINGS FOR THE DAMP-PROOFING OF MONUMENTS
The global transitional justice tool kit—involving the use of criminal prosecutions, amnesties, and other mechanisms to address past human rights abuse—has become a primary means for thwarting future human rights violations and consolidating democracy. Nevertheless, evidence on the consequences of transitional justice remains mixed and amenable to contradictory interpretations. Existing studies fail to adequately address issues of selection, the difference between short- and long-term effects of transitional justice mechanisms, and qualitative and quantitative differences in state practices. This article uses a new database of transitional justice mechanisms to address these concerns and test propositions from realist, constructivist, and holistic approaches to this set of policy issues. We find, among other things, that prosecutions increase physical integrity protections, while amnesties increase the protection of civil and political rights. Our analysis suggests that different transnational justice policies each play a potentially positive, but distinct, role in new democracies and in decreasing violations of human rights
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