4,235 research outputs found
Performance of alkaline battery cells used in emergency locator transmitters
The characteristics of battery power supplies for emergency locator transmitters (ELT's) were investigated by testing alkaline zinc/manganese dioxide cells of the type typically used in ELT's. Cells from four manufacturers were tested. The cells were subjected to simulated environmental and load conditions representative of those required for survival and operation. Battery cell characteristics that may contribute to ELT malfunctions and limitations were evaluated. Experimental results from the battery cell study are discussed, and an evaluation of ELT performance while operating under a representative worst-case environmental condition is presented
Binary Population and Spectral Synthesis Version 2.1: construction, observational verification and new results
The Binary Population and Spectral Synthesis (BPASS) suite of binary stellar
evolution models and synthetic stellar populations provides a framework for the
physically motivated analysis of both the integrated light from distant stellar
populations and the detailed properties of those nearby. We present a new
version 2.1 data release of these models, detailing the methodology by which
BPASS incorporates binary mass transfer and its effect on stellar evolution
pathways, as well as the construction of simple stellar populations. We
demonstrate key tests of the latest BPASS model suite demonstrating its ability
to reproduce the colours and derived properties of resolved stellar
populations, including well- constrained eclipsing binaries. We consider
observational constraints on the ratio of massive star types and the
distribution of stellar remnant masses. We describe the identification of
supernova progenitors in our models, and demonstrate a good agreement to the
properties of observed progenitors. We also test our models against photometric
and spectroscopic observations of unresolved stellar populations, both in the
local and distant Universe, finding that binary models provide a
self-consistent explanation for observed galaxy properties across a broad
redshift range. Finally, we carefully describe the limitations of our models,
and areas where we expect to see significant improvement in future versions.Comment: 69 pages, 45 figures. Accepted for publication in PASA. Accompanied
by a full, documented data release at http://bpass.auckland.ac.nz and
http://warwick.ac.uk/bpas
Genomic comparison of diverse Salmonella serovars isolated from swine.
Food animals act as a reservoir for many foodborne pathogens. Salmonella enterica is one of the leading pathogens that cause food borne illness in a broad host range including animals and humans. They can also be associated with a single host species or a subset of hosts, due to genetic factors associated with colonization and infection. Adult swine are often asymptomatic carriers of a broad range of Salmonella servoars and can act as an important reservoir of infections for humans. In order to understand the genetic variations among different Salmonella serovars, Whole Genome Sequences (WGS) of fourteen Salmonella serovars from swine products were analyzed. More than 75% of the genes were part of the core genome in each isolate and the higher fraction of gene assign to different functional categories in dispensable genes indicated that these genes acquired for better adaptability and diversity. High concordance (97%) was detected between phenotypically confirmed antibiotic resistances and identified antibiotic resistance genes from WGS. The resistance determinants were mainly located on mobile genetic elements (MGE) on plasmids or integrated into the chromosome. Most of known and putative virulence genes were part of the core genome, but a small fraction were detected on MGE. Predicted integrated phage were highly diverse and many harbored virulence, metal resistance, or antibiotic resistance genes. CRISPR (Clustered regularly interspaced short palindromic repeats) patterns revealed the common ancestry or infection history among Salmonella serovars. Overall genomic analysis revealed a great deal of diversity among Salmonella serovars due to acquired genes that enable them to thrive and survive during infection
Ground State Correlations in 16O and 40Ca
We study the ground state properties of doubly closed shell nuclei O
and Ca in the framework of Correlated Basis Function theory using state
dependent correlations, with central and tensor components. The realistic
Argonne and two-nucleon potentials and three-nucleon
potentials of the Urbana class have been adopted. By means of the Fermi
Hypernetted Chain integral equations, in conjunction with the Single Operator
Chain approximation, we evaluate the ground state energy, one- and two-body
densities and electromagnetic and spin static responses for both nuclei. In
O we compare our results with the available Monte Carlo and Coupled
Cluster ones and find a satisfying agreement. As in the nuclear matter case
with similar interactions and wave functions, the nuclei result under-bound by
2--3 MeV/A.Comment: 33 RevTeX pages + 8 figures, to appear in Phys.Rev.
Assessment of the Effect of the Oral Iron Chelator Deferiprone on Asymptomatic Plasmodium Falciparum Parasitemia in Humans
While the parenteral iron-chelating agent desferrioxamine B has anti- malarial activity in humans, the usefulness of an orally active chelator for this indication has not been investigated previously in vivo. We conducted a prospective, double-blind, placebo-controlled, cross-over trial of deferiprone (L1; CP20; 1,2-dimethyl-3-hydroxypyridin-4-one) in 25 adult Zambians with asymptomatic Plasmodium falciparum parasitemia. Deferiprone was administered daily for three or four days in divided doses of 75 or 100 mg/kg of body weight, dosages that are effective for treating iron overload. No reduction in asexual intra-erythrocytic parasites was observed during or after deferiprone treatment. The mean peak plasma concentration of deferiprone (108.9 ± 24.9 μmol/L) achieved was within the range demonstrated to inhibit the growth of P. falciparum in vitro, but the systemic exposure as determined by the 24-hr plasma concentration-time curve would not be predicted inhibit growth in vivo. No evidence of deferiprone- associated hematological toxicity was noted in this short-term study of these subjects, all of whom had clinical evidence of normal body iron stores. Because of the risk of neutropenia and other adverse effects with higher doses or prolonged use of the chelator, additional trials of deferiprone as a sole anti-malarial agent would not seem to be justified. In contrast, further efforts are needed to develop other orally active iron-chelating agents specifically for their antimalarial action
Prioritized Sweeping Neural DynaQ with Multiple Predecessors, and Hippocampal Replays
During sleep and awake rest, the hippocampus replays sequences of place cells
that have been activated during prior experiences. These have been interpreted
as a memory consolidation process, but recent results suggest a possible
interpretation in terms of reinforcement learning. The Dyna reinforcement
learning algorithms use off-line replays to improve learning. Under limited
replay budget, a prioritized sweeping approach, which requires a model of the
transitions to the predecessors, can be used to improve performance. We
investigate whether such algorithms can explain the experimentally observed
replays. We propose a neural network version of prioritized sweeping
Q-learning, for which we developed a growing multiple expert algorithm, able to
cope with multiple predecessors. The resulting architecture is able to improve
the learning of simulated agents confronted to a navigation task. We predict
that, in animals, learning the world model should occur during rest periods,
and that the corresponding replays should be shuffled.Comment: Living Machines 2018 (Paris, France
Revealing Nuclear Pions Using Electron Scattering
A model for the pionic components of nuclear wave functions is obtained from
light front dynamical calculations of binding energies and densities. The
pionic effects are small enough to be consistent with measured nuclear di-muon
production data and with the nucleon sea. But the pion effects are large enough
to predict substantial nuclear enhancement of the cross section for
longitudinally polarized virtual photons for the kinematics accessible at
Jefferson Laboratory.Comment: 9 pages, 4 figure
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