2,830 research outputs found
Plans for a Neutron EDM Experiment at SNS
The electric dipole moment of the neutron, leptons, and atoms provide a
unique window to Physics Beyond the Standard Model. We are currently developing
a new neutron EDM experiment (the nEDM Experiment). This experiment, which will
be run at the 8.9 A Neutron Line at the Fundamental Neutron Physics Beamline
(FNPB) at the Spallation Neutron Source (SNS) at the Oak Ridge National
Laboratory, will search for the neutron EDM with a sensitivity two orders of
magnitude better than the present limit. In this paper, the motivation for the
experiment, the experimental method, and the present status of the experiment
are discussed.Comment: 9 Pages, 4 Figures, submitted to the proceedings of the Second
Meeting of the APS Topical Group on Hadronic Physics, Nashville, TN, October
22-24, 200
On the X-ray variability of magnetar 1RXS J170849.0-400910
We present a long-term X-ray flux and spectral analysis for 1RXS
J170849.0-400910 using Swift/XRT spanning over 8 years from 2005-2013. We also
analyze two observations from Chandra and XMM in the period from 2003-2004. In
this 10-yr period, 1RXS J170849.0-400910 displayed several rotational glitches.
Previous studies have claimed variations in the X-ray emission associated with
some of the glitches. From our analysis we find no evidence for significant
X-ray flux variations and evidence for only low-level spectral variations. We
also present an updated timing solution for 1RXS J170849.0-400910, from RXTE
and Swift observations, which includes a previously unreported glitch at MJD
56019. We discuss the frequency and implications of radiatively quiet glitches
in magnetars.Comment: 9 pages, 2 figures, accepted for publication in Ap
Perspectives of frailty and frailty screening: Protocol for a collaborative knowledge translation approach and qualitative study of stakeholder understandings and experiences
Accompanying the unprecedented growth in the older adult population worldwide is an increase in the prevalence of frailty, an age-related clinical state of increased vulnerability to stressor events. This increased vulnerability results in lower social engagement and quality of life, increased dependency, and higher rates of morbidity, health service utilization and mortality. Early identification of frailty is necessary to guide implementation of interventions to prevent associated functional decline. Consensus is lacking on how to clinically recognize and manage frailty. It is unknown how healthcare providers and healthcare consumers understand and perceive frailty, whether or not they regard frailty as a public health concern; and information on the indirect and direct experiences of consumer and healthcare provider groups towards frailty are markedly limited.We will conduct a qualitative study of consumer, practice nurse, general practitioner, emergency department physician, and orthopedic surgeons' perspectives of frailty and frailty screening in metropolitan and non-metropolitan South Australia. We will use tailored combinations of semi-structured interviews and arts-based data collection methods depending on each stakeholder group, followed by inductive and iterative analysis of data using qualitative description.Using stakeholder driven approaches to understanding and addressing frailty and frailty screening in context is critical as the prevalence and burden of frailty is likely to increase worldwide. We will use the findings from the Perceptions of Frailty and Frailty Screening study to inform a context-driven identification, implementation and evaluation of a frailty-screening tool; drive awareness, knowledge, and skills development strategies across stakeholder groups; and guide future efforts to embed emerging knowledge about frailty and its management across diverse South Australian contexts using a collaborative knowledge translation approach. Study findings will help achieve a coordinated frailty and healthy ageing strategy with relevance to other jurisdictions in Australia and abroad, and application of the stakeholder driven approach will help illuminate how its applicability to other jurisdictions.Mandy M. Archibald, Rachel Ambagtsheer, Justin Beilby, Mellick J. Chehade, Tiffany K. Gill, Renuka Visvanathan, and Alison L. Kitso
Sdss J102347.6+003841: A Millisecond Radio Pulsar Binary that Had a Hot Disk During 2000-2001
The Sloan Digital Sky Survey (SDSS) source J102347.6+003841 was recently revealed to be a binary 1.69 ms radio pulsar with a 4.75 hr orbital period and a ~0.2 M ☉ companion. Here, we analyze the SDSS spectrum of the source in detail. The spectrum was taken on 2001 February 1, when the source was in a bright state and showed broad, double-peaked hydrogen and helium lines—dramatically different from the G-type absorption spectrum seen from 2002 May onward. The lines are consistent with emission from a disk around the compact primary. We derive properties of the disk by fitting the SDSS continuum with a simple disk model, and find a temperature range of 2000-34,000 K from the outer to inner edge of the disk. The disk inner and outer radii were approximately 109 and 5.7×1010 cm, respectively. These results further emphasize the unique feature of the source: it is a system likely at the end of its transition from an X-ray binary to a recycled radio pulsar. The disk mass is estimated to have been ~1023 g, most of which would have been lost due to pulsar wind ablation (or due to the propeller effect if the disk had extended inside the light cylinder of the pulsar) before the final disk disruption event. The system could undergo repeated episodes of disk formation. Close monitoring of the source is needed to catch the system in its bright state again, so that this unusual example of a pulsar-disk interaction can be studied in much finer detail
The SCUBA 8-mJy survey - I: Sub-millimetre maps, sources and number counts
We present maps, source lists, and number counts from the largest, unbiassed,
extragalactic sub-mm survey so far undertaken with the SCUBA camera on the
JCMT. Our maps cover 260 sq. arcmin, to a noise level S(850)=2.5 mJy/beam. We
have reduced the data using both SURF, and our own pipeline which produces
zero-footprint maps and noise images. The uncorrelated noise maps produced by
the latter approach have allowed application of a maximum-likelihood method to
measure the statistical significance of each peak, leading to properly
quantified flux-density errors for all potential sources. We detect 19 sources
with S/N > 4, 38 with S/N > 3.5, and 72 with S/N > 3. To assess completeness
and the impact of source confusion we have applied our source extraction
algorithm to a series of simulated images. The result is a new estimate of the
sub-mm source counts in the flux-density range S(850)=5-15mJy, which we compare
with other estimates, and with model predictions. Our estimate of the
cumulative source count at S(850) > 8 mJy is 320 (+80,-100) per square degree.
Assuming that the majority of sources have z > 1.5, the co-moving number
density of high-z galaxies forming stars at a rate >1000 solar masses per year
is 10^-5 per Mpc^3, with only a weak dependence on the precise redshift
distribution. This number density corresponds to that of massive ellipticals
with L > 3-4 L* at low redshift and is also the same as the co-moving number
density of comparably massive, passively-evolving objects in the redshift band
1<z<2 inferred from recent surveys of extremely red objects. Thus the bright
sub-mm sources can plausibly account for the formation of all present-day
massive ellipticals. Improved z constraints, and a proper measurement of sub-mm
clustering can refine or refute this picture.Comment: Minor revisions. 27 pages, 13 figures. Higher resolution versions of
Figs 5,6,7 and 8 are available from the autho
Evidence of strong stabilizing effects on the evolution of boreoeutherian (Mammalia) dental proportions.
The dentition is an extremely important organ in mammals with variation in timing and sequence of eruption, crown morphology, and tooth size enabling a range of behavioral, dietary, and functional adaptations across the class. Within this suite of variable mammalian dental phenotypes, relative sizes of teeth reflect variation in the underlying genetic and developmental mechanisms. Two ratios of postcanine tooth lengths capture the relative size of premolars to molars (premolar-molar module, PMM), and among the three molars (molar module component, MMC), and are known to be heritable, independent of body size, and to vary significantly across primates. Here, we explore how these dental traits vary across mammals more broadly, focusing on terrestrial taxa in the clade of Boreoeutheria (Euarchontoglires and Laurasiatheria). We measured the postcanine teeth of NÂ =Â 1,523 boreoeutherian mammals spanning six orders, 14 families, 36 genera, and 49 species to test hypotheses about associations between dental proportions and phylogenetic relatedness, diet, and life history in mammals. Boreoeutherian postcanine dental proportions sampled in this study carry conserved phylogenetic signal and are not associated with variation in diet. The incorporation of paleontological data provides further evidence that dental proportions may be slower to change than is dietary specialization. These results have implications for our understanding of dental variation and dietary adaptation in mammals
The 2016 outburst of PSR J1119-6127: cooling & a spin-down dominated glitch
We report on the aftermath of a magnetar outburst from the young,
high-magnetic-field radio pulsar PSR J1119-6127 that occurred on 2016 July 27.
We present the results of a monitoring campaign using the Neil Gehrels Swift
X-ray Telescope, NuSTAR, and XMM-Newton. After reaching a peak luminosity of
~300 times the quiescent luminosity, the pulsar's X-ray flux declined by factor
of ~50 on a time scale of several months. The X-ray spectra are well described
by a blackbody and a hard power-law tail. After an initial rapid decline during
the first day of the outburst, we observe the blackbody temperature rising from
kT = 0.9 keV to 1.05 keV during the first two weeks of the outburst, before
cooling to 0.9 keV. During this time, the blackbody radius decreases
monotonically by a factor of ~4 over a span of nearly 200 days. We also report
a heretofore unseen highly pulsed hard X-ray emission component, which fades on
a similar timescale to the soft X-ray flux, as predicted by models of
relaxation of magnetospheric current twists. The previously reported spin-up
glitch which accompanied this outburst was followed by a period of enhanced and
erratic torque, leading to a net spin-down of Hz, a
factor of ~24 over-recovery. We suggest that this and other radiatively loud
magnetar-type glitch recoveries are dominated by magnetospheric processes, in
contrast to conventional radio pulsar glitch recoveries which are dominated by
internal physics.Comment: Submitted to Ap
Development of methods for the genetic manipulation of Flavobacterium columnare
<p>Abstract</p> <p>Background</p> <p><it>Flavobacterium columnare </it>is the causative agent of columnaris disease, a disease affecting many freshwater fish species. Methods for the genetic manipulation for some of the species within the <it>Bacteroidetes</it>, including members of the genus <it>Flavobacterium</it>, have been described, but these methods were not adapted to work with <it>F. columnare</it>.</p> <p>Results</p> <p>As a first step toward developing a robust set of genetic tools for <it>F. columnare</it>, a protocol was developed to introduce the <it>E. coli </it>– <it>Flavobacterium </it>shuttle vector pCP29 into <it>F. columnare </it>strain C#2 by conjugal mating at an efficiency of 1.5 × 10<sup>-3 </sup>antibiotic-resistant transconjugants per recipient cell. Eight of eleven <it>F. columnare </it>strains tested were able to receive pCP29 using the protocol. pCP29 contains the <it>cfxA </it>and <it>ermF </it>genes, conferring both cefoxitin and erythromycin resistance to recipient cells. Selection for pCP29 introduction into <it>F. columnare </it>was dependent on <it>cfxA</it>, as <it>ermF </it>was found not to provide strong resistance to erythromycin. This is in contrast to other <it>Flavobacterium </it>species where <it>ermF</it>-based erythromycin resistance is strong. The green fluorescent protein gene (<it>gfp</it>) was introduced into <it>F. columnare </it>strains under the control of two different native <it>Flavobacterium </it>promoters, demonstrating the potential of this reporter system for the study of gene expression. The transposon Tn<it>4351 </it>was successfully introduced into <it>F. columnare</it>, but the method was dependent on selecting for erythromycin resistance. To work, low concentrations of antibiotic (1 μg ml<sup>-1</sup>) were used, and high levels of background growth occurred. These results demonstrate that Tn<it>4351 </it>functions in <it>F. columnare </it>but that it is not an effective mutagenesis tool due to its dependence on erythromycin selection. Attempts to generate mutants via homologous recombination met with limited success, suggesting that RecA dependent homologous recombination is rare in <it>F. columnare</it>.</p> <p>Conclusion</p> <p>The conjugation protocol developed as part of this study represents a significant first step towards the development of a robust set of genetic tools for the manipulation of <it>F. columnare</it>. The availability of this protocol will facilitate studies aimed at developing a deeper understanding of the virulence mechanisms of this important pathogen.</p
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