1,589 research outputs found
Preparing medical students for field experiences in low-resource settings: Development and evaluation of a pre-travel trigger video and large group discussion module
Kramers-Kronig Relations For The Dielectric Function And The Static Conductivity Of Coulomb Systems
The mutual influence of singularities of the dielectric permittivity e(q,w)
in a Coulomb system in two limiting cases w tends to zero, q tends to zero, and
opposite q tends to zero, w tends to zero is established. It is shown that the
dielectric permittivity e(q,w) satisfies the Kramers-Kronig relations, which
possesses the singularity due to a finite value of the static conductivity.
This singularity is associated with the long "tails" of the time correlation
functions.Comment: 9 pages, 0 figure
Matter-field theory of the Casimir force
A matter-field theory of the Casimir force is formulated in which the
electromagnetic field and collective modes of dielectric media are treated on
an equal footing. In our theory, the Casimir force is attributed to zero-point
energies of the combined matter-field modes. We analyze why some of the
existing theories favor the interpretation of the Casimir force as originating
from zero-point energies of the electromagnetic field and others from those of
the matter.Comment: 12pages, 1 Postscript figur
Parity-Violating Electron-Deuteron Scattering
The longitudinal asymmetry due to exchange is calculated in
quasi-elastic electron-deuteron scattering at momentum transfers GeV relevant for the SAMPLE experiment. The deuteron and
scattering-state wave functions are obtained from solutions of a Schr\"odinger
equation with the Argonne potential. Electromagnetic and weak neutral
one- and two-nucleon currents are included in the calculation. The two-nucleon
currents of pion range are shown to be identical to those derived in Chiral
Perturbation Theory. The results indicate that two-body contributions to the
asymmetry are small ( 0.2%) around the quasi-elastic peak, but become
relatively more significant ( 3%) in the high-energy wing of the
quasi-elastic peak.Comment: 23 pages, 10 figure
Managing the Socially Marginalized: Attitudes Towards Welfare, Punishment and Race
Welfare and incarceration policies have converged to form a system of governance over socially marginalized groups, particularly racial minorities. In both of these policy areas, rehabilitative and social support objectives have been replaced with a more punitive and restrictive system. The authors examine the convergence in individual-level attitudes concerning welfare and criminal punishment, using national survey data. The authors\u27 analysis indicates a statistically significant relationship between punitive attitudes toward welfare and punishment. Furthermore, accounting for the respondents\u27 racial attitudes explains the bivariate relationship between welfare and punishment. Thus, racial attitudes seemingly link support for punitive approaches to opposition to welfare expenditures. The authors discuss the implications of this study for welfare and crime control policies by way of the conclusion
Sea otter effects on trophic structure of seagrass communities in southeast Alaska
Previous research in southeast Alaska on the effects of sea otters Enhydra lutris in
seagrass Zostera marina communities identified many but not all of the trophic relationships that
were predicted by a sea otter-mediated trophic cascade. To further resolve these trophic connections, we compared biomass, carbon (δ13C) and nitrogen (δ15N) stable isotope (SI), and fatty acid
(FA) data from 16 taxa at 3 sites with high and 3 sites with low sea otter density (8.2 and 0.1 sea
otters km−2, respectively). We found lower crab and clam biomass in the high sea otter region but
did not detect a difference in biomass of other seagrass community taxa or the overall community
isotopic niche space between sea otter regions. Only staghorn sculpin differed in δ13C between
regions, and Fucus, sugar kelp, butter clams, dock shrimp, and shiner perch differed in δ15N. FA
analysis indicated multivariate dissimilarity in 11 of the 15 conspecifics between sea otter regions.
FA analysis found essential FAs, which consumers must obtain from their diet, including 20:5ω3
(EPA) and 22:6ω3 (DHA), were common in discriminating conspecifics between sea otter regions,
suggesting differences in consumer diets. Further FA analysis indicated that many consumers rely
on diverse diets, regardless of sea otter region, potentially buffering these consumers from sea
otter-mediated changes to diet availability. While sea otters are major consumers in this system,
further studies are needed to understand the mechanisms responsible for the differences in biomarkers between regions with and without sea ottersWe thank Tiffany Stephens, Maggie
Shields, Melanie Borup, Ashely Bolwerk, Nicole LaRoche,
Tom Bell, Michael Stekoll and the rest of the Apex Predators, Ecosystems and Community Sustainability (APECS)
team and 26 Earthwatch volunteers for assistance in the
field and laboratory. Special thanks to Reyn Yoshioka,
Natalie Thompson, the Coastal Trophic Ecology Lab, and
Oregon Institute of Marine Biology for their assistance with
fatty acid extractions, Melissa Rhodes-Reese at University of
Alaska Southeast for water nutrient analysis, and Matthew
Rogers and NOAA Auke Bay Laboratories for assistance
with stable isotope analyses. This study was funded by the
National Science Foundation (NSF #1635716, #1600230 to
G.L.E.), through the generous support of Earthwatch, and a
56 NSF Graduate Research Fellowship, a North Pacific Re -
search Board Graduate Student Research Award, an American Fisheries Society Steven Berkeley Marine Conservation
Fellowship, and a Lerner Gray Memorial Fund (to W.W.R).
This study was completed in partial fulfillment of the
requirements for W.W.R.’s PhD at the University of Alaska
Fairbanks and we thank committee members Dr. Franz
Mueter and Dr. Anne Beaudreau for their comments on this
project and the manuscript. Finally, we thank the 3 anonymous reviewers whose comments greatly improved the
manuscript. This study was conducted on the traditional
lands and waters of the Alaska Native Tlingit and Haida
peoples. We are grateful for our access to these spaces and
benefited from conversations and support from the members
of Tribal communities and governments.Ye
ASCR/HEP Exascale Requirements Review Report
This draft report summarizes and details the findings, results, and
recommendations derived from the ASCR/HEP Exascale Requirements Review meeting
held in June, 2015. The main conclusions are as follows. 1) Larger, more
capable computing and data facilities are needed to support HEP science goals
in all three frontiers: Energy, Intensity, and Cosmic. The expected scale of
the demand at the 2025 timescale is at least two orders of magnitude -- and in
some cases greater -- than that available currently. 2) The growth rate of data
produced by simulations is overwhelming the current ability, of both facilities
and researchers, to store and analyze it. Additional resources and new
techniques for data analysis are urgently needed. 3) Data rates and volumes
from HEP experimental facilities are also straining the ability to store and
analyze large and complex data volumes. Appropriately configured
leadership-class facilities can play a transformational role in enabling
scientific discovery from these datasets. 4) A close integration of HPC
simulation and data analysis will aid greatly in interpreting results from HEP
experiments. Such an integration will minimize data movement and facilitate
interdependent workflows. 5) Long-range planning between HEP and ASCR will be
required to meet HEP's research needs. To best use ASCR HPC resources the
experimental HEP program needs a) an established long-term plan for access to
ASCR computational and data resources, b) an ability to map workflows onto HPC
resources, c) the ability for ASCR facilities to accommodate workflows run by
collaborations that can have thousands of individual members, d) to transition
codes to the next-generation HPC platforms that will be available at ASCR
facilities, e) to build up and train a workforce capable of developing and
using simulations and analysis to support HEP scientific research on
next-generation systems.Comment: 77 pages, 13 Figures; draft report, subject to further revisio
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