959 research outputs found
Simultaneous multi-frequency single-pulse properties of AXP XTE J1810-197
We have used the 76-m Lovell, 94-m equivalent WSRT and 100-m Effelsberg radio
telescopes to investigate the simultaneous single-pulse properties of the radio
emitting magnetar AXP XTE J1810-197 at frequencies of 1.4, 4.8 and 8.35 GHz
during May and July 2006. We study the magnetar's pulse-energy distributions
which are found to be very peculiar as they are changing on time-scales of days
and cannot be fit by a single statistical model. The magnetar exhibits strong
spiky single giant-pulse-like subpulses, but they do not fit the definition of
the giant pulse or giant micropulse phenomena. Measurements of the
longitude-resolved modulation index reveal a high degree of intensity
fluctuations on day-to-day time-scales and dramatic changes across pulse phase.
We find the frequency evolution of the modulation index values differs
significantly from what is observed in normal radio pulsars. We find that no
regular drifting subpulse phenomenon is present at any of the observed
frequencies at any observing epoch. However, we find a quasi-periodicity of the
subpulses present in the majority of the observing sessions. A correlation
analysis indicates a relationship between components from different
frequencies. We discuss the results of our analysis in light of the emission
properties of normal radio pulsars and a recently proposed model which takes
radio emission from magnetars into consideration.Comment: 15 pages, 11 figures, accepted for publication by MNRA
Utilization and Impact of Career Services Among Collegiate Athletes
Career readiness is a concern within the American educational system, particularly among student-athletes that must manage intense time commitments both on and off the field. Student services have emerged in higher education to support career preparation, but the utilization and impact of these services for collegiate athletes is largely unknown. The systems-theory framework (STF) of career development identifies a multitude of internal and external factors that influence individual career development. Guided by STF, the purpose of this study was to predict the factors that influence collegiate athletes\u27 utilization of career services and resulting perceived career skills. An online questionnaire was distributed to collegiate athletes at a Division I university, resulting in 143 collegiate athletes completing the questionnaire. Multiple regression analysis demonstrated collegiate athletes’ familiarity with career services significantly predicted their utilization of career services. In turn, utilization of only four of nine career services investigated (i.e., Careers Online, Career Fairs, Career Workshops, and Athletic Academic Advisor) significantly predicted perceived career skills positively. Implications for the design and marketing of career services for collegiate athletes are discussed
Structure in the Rotation Measure Sky
An analysis of structure in rotation measure (RM) across the sky based on the
RM catalog of Taylor et al. (2009) is presented. Several resolved RM structures
are identified with structure in the local ISM, including radio loops I, II,
and III, the Gum nebula, and the Orion-Eridanus super bubble. Structure
functions (SFs) of RM are presented for selected areas, and maps of SF
amplitude and slope across the sky are compared with H-alpha intensity and
diffuse polarized intensity. RM variance on an angular scale of 1 degree is
correlated with length of the line of sight through the Galaxy, with a
contribution from local structures. The slope of the SFs is less concentrated
to the Galactic plane and less correlated with length of the line of sight
through the Galaxy, suggesting a more local origin for RM structure on angular
scales ~ 10 degrees. The RM variance is a factor ~2 higher towards the SGP than
towards the NGP, reflecting a more wide-spread asymmetry between the northern
and southern Galactic hemispheres. Depolarization of diffuse Galactic
synchrotron emission at latitudes < 30 degrees can be explained largely by
Faraday dispersion related to small-scale variance in RM, but the errors allow
a significant contribution from differential Faraday rotation along the line of
sight.Comment: 13 pages, 14 figures. Figures 1-4 and 9-10 available as separate
files. Accepted for publication in the Astrophysical Journal A complete pdf
with all figures included is available at
http://www.ras.ucalgary.ca/~stil/Stil_2010_RM_structure.pd
Prevalence and causes of prescribing errors: the prescribing outcomes for trainee doctors engaged in clinical training (PROTECT) study
Objectives
Study objectives were to investigate the prevalence and causes of prescribing errors amongst foundation doctors (i.e. junior doctors in their first (F1) or second (F2) year of post-graduate training), describe their knowledge and experience of prescribing errors, and explore their self-efficacy (i.e. confidence) in prescribing.
Method
A three-part mixed-methods design was used, comprising: prospective observational study; semi-structured interviews and cross-sectional survey. All doctors prescribing in eight purposively selected hospitals in Scotland participated. All foundation doctors throughout Scotland participated in the survey. The number of prescribing errors per patient, doctor, ward and hospital, perceived causes of errors and a measure of doctors' self-efficacy were established.
Results
4710 patient charts and 44,726 prescribed medicines were reviewed. There were 3364 errors, affecting 1700 (36.1%) charts (overall error rate: 7.5%; F1:7.4%; F2:8.6%; consultants:6.3%). Higher error rates were associated with : teaching hospitals (p<0.001), surgical (p = <0.001) or mixed wards (0.008) rather thanmedical ward, higher patient turnover wards (p<0.001), a greater number of prescribed medicines (p<0.001) and the months December and June (p<0.001). One hundred errors were discussed in 40 interviews. Error causation was multi-factorial; work environment and team factors were particularly noted. Of 548 completed questionnaires (national response rate of 35.4%), 508 (92.7% of respondents) reported errors, most of which (328 (64.6%) did not reach the patient. Pressure from other staff, workload and interruptions were cited as the main causes of errors. Foundation year 2 doctors reported greater confidence than year 1 doctors in deciding the most appropriate medication regimen.
Conclusions
Prescribing errors are frequent and of complex causation. Foundation doctors made more errors than other doctors, but undertook the majority of prescribing, making them a key target for intervention. Contributing causes included work environment, team, task, individual and patient factors. Further work is needed to develop and assess interventions that address these.</p
Seabed Mining and Approaches to Governance of the Deep Seabed
Commercial seabed mining seems imminent, highlighting the urgent need for coherent, effective policy to safeguard the marine environment. Reconciling seabed mining with the United Nations Sustainable Development Goals will be difficult because minerals extraction will have irreversible consequences that could lead to the loss of habitats, species and ecosystems services. A dialog needs to take place around social, cultural, environmental and economic costs and benefits. Governance of human interactions with the seabed is fragmented and lacks transparency, with a heavy focus on facilitating exploitation rather than ensuring protection. In the light of high uncertainties and high stakes, we present a critical review of proposed policy options for the regulation of seabed mining activities, recommend actions to improve seabed governance and outline the alternatives to mining fragile deep-sea ecosystems
Novel interactions between alien pathogens and native plants increase plant–pathogen network connectance and decrease specialization
1. Alien plant pathogens are a threat to native plants and are increasingly integrating into native plant–pathogen networks, but how these novel plant–pathogen networks are structured remains unclear. Theory predicts that novel antagonists are likely to be generalists, resulting in interaction networks with greater nestedness as well as lower modularity and specialization than native networks. 2. We tested these predictions by quantifying associations between native plants and their native and alien pathogens using a comprehensive database of plant–fungal associations in New Zealand. We compared the host ranges of alien and native pathogens and the structure of native and alien pathogen subnetworks. 3. As predicted, alien pathogens associated with a greater number and diversity of native plant host species than native pathogens. The alien pathogen subnetwork was more nested and connected, but less modular and less specialized than the native pathogen subnetwork, consistent with expectations for novel interactions. Alien pathogens altered the overall native plant–pathogen network structure, making the full network more connected and less specialized than the native network. Modules in the native and alien subnetworks were clustered by host phylogeny but did not show a clear signal associated with host habitat or region. 4. Synthesis. Our study provides some of the first empirical insights into the structure of novel plant–pathogen networks and the changes that occur when alien pathogens invade a native network. Because alien pathogens interacted with more hosts than native pathogens, alien pathogens have an increased risk of adverse indirect effects, including pathogen spillover, host jumps and network destabilization
Arecibo timing observations of 17 pulsars along the Galactic plane
We present phase-coherent timing solutions obtained for the first time for 17
pulsars discovered at Arecibo by Hulse & Taylor (1975ab) in a 430-MHz survey of
the Galactic plane. This survey remains the most sensitive of the Galactic
plane at 430 MHz and has comparable equivalent sensitivity to the 1400-MHz
Parkes multibeam survey. Comparing both surveys we find that, as expected, the
one at 430 MHz is limited in depth by interstellar dispersion and scattering
effects; and that the detection rate of pulsars with high spin-down luminosity
( erg s) at the low frequency is a factor of 5 smaller
than at high frequency. We also present scatter-broadening measurements for two
pulsars and pulse nulling and mode-changing properties for two others.Comment: 10 pages, 3 figures, accepted for publication in A
The characteristics of millisecond pulsar emission: I. Spectra, pulse shapes and the beaming fraction
We have monitored a large sample of millisecond pulsars using the 100-m
Effelsberg radio telescope in order to compare their radio emission properties
to the slowly rotating population. With some notable exceptions, our findings
suggest that the two groups of objects share many common properties. A
comparison of the spectral indices between samples of normal and millisecond
pulsars demonstrates that millisecond pulsar spectra are not significantly
different from those of normal pulsars. There is evidence, however, that
millisecond pulsars are slightly less luminous and less efficient radio
emitters compared to normal pulsars. We confirm recent suggestions that a
diversity exists among the luminosities of millisecond pulsars with the
isolated millisecond pulsars being less luminous than the binary millisecond
pulsars. There are indications that old millisecond pulsars exhibit somewhat
flatter spectra than the presumably younger ones. We present evidence that
millisecond pulsar profiles are only marginally more complex than those found
among the normal pulsar population. Moreover, the development of the profiles
with frequency is rather slow, suggesting very compact magnetospheres. The
profile development seems to anti-correlate with the companion mass and the
spin period, again suggesting that the amount of mass transfer in a binary
system might directly influence the emission properties. The angular radius of
radio beams of millisecond pulsars does not follow the scaling predicted from a
canonical pulsar model which is applicable for normal pulsars. Instead they are
systematically smaller. The smaller inferred luminosity and narrower emission
beams will need to be considered in future calculations of the birth-rate of
the Galactic population.Comment: 40 pages, 14 figures, accepted for publication in Ap
Radially Extended Kinematics in the S0 Galaxy NGC 2768 from Planetary Nebulae, Globular Clusters and Starlight
There are only a few tracers available to probe the kinematics of individual
early-type galaxies beyond one effective radius. Here we directly compare a
sample of planetary nebulae (PNe), globular clusters (GCs) and galaxy starlight
velocities out to ~4 effective radii, in the S0 galaxy NGC 2768. Using a
bulge-to-disk decomposition of a K-band image we assign PNe and starlight to
either the disk or the bulge. We show that the bulge PNe and bulge starlight
follow the same radial density distribution as the red subpopulation of GCs,
whereas the disk PNe and disk starlight are distinct components. We find good
kinematic agreement between the three tracers to several effective radii (and
with stellar data in the inner regions). Further support for the distinct
nature of the two galaxy components come from our kinematic analysis. After
separating the tracers into bulge and disk components we find the bulge to be a
slowly rotating pressure-supported system, whereas the disk reveals a rapidly
rising rotation curve with a declining velocity dispersion profile. The
resulting V/sigma ratio for the disk resembles that of a spiral galaxy and
hints at an origin for NGC 2768 as a transformed late-type galaxy. A
two-component kinematic analysis for a sample of S0s will help to elucidate the
nature of this class of galaxy.Comment: 10 pages, 5 figures, accepted for publication in MRA
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