614 research outputs found
Optical spectroscopy of faint gigahertz peaked spectrum sources
We present spectroscopic observations of a sample of faint Gigahertz Peaked
Spectrum (GPS) radio sources drawn from the Westerbork Northern Sky Survey
(WENSS). Redshifts have been determined for 19 (40%) of the objects. The
optical spectra of the GPS sources identified with low redshift galaxies show
deep stellar absorption features. This confirms previous suggestions that their
optical light is not significantly contaminated by AGN-related emission, but is
dominated by a population of old (>9 Gyr) and metal-rich (>0.2 [Fe/H]) stars,
justifying the use of these (probably) young radio sources as probes of galaxy
evolution. The optical spectra of GPS sources identified with quasars are
indistinguishable from those of flat spectrum quasars, and clearly different
from the spectra of Compact Steep Spectrum (CSS) quasars. The redshift
distribution of the GPS quasars in our radio-faint sample is comparable to that
of the bright samples presented in the literature, peaking at z ~ 2-3. It is
unlikely that a significant population of low redshift GPS quasars is missed
due to selection effects in our sample. We therefore claim that there is a
genuine difference between the redshift distributions of GPS galaxies and
quasars, which, because it is present in both the radio-faint and bright
samples, can not be due to a redshift-luminosity degeneracy. It is therefore
unlikely that the GPS quasars and galaxies are unified by orientation, unless
the quasar opening angle is a strong function of redshift. We suggest that the
GPS quasars and galaxies are unrelated populations and just happen to have
identical observed radio-spectral properties, and hypothesise that GPS quasars
are a sub-class of flat spectrum quasars.Comment: LaTeX, 13 pages. Accepted by MNRAS. For related papers see
http://www.ast.cam.ac.uk/~snelle
Perceived and desired weight, weight related eating and exercising behaviours, and advice received from parents among thin, overweight, obese or normal weight Australian children and adolescents
BACKGROUND: Thin children are less muscular, weaker, less active, and have lower performance in measures of physical fitness than their normal weight peers. Thin children are also more frequently subjected to teasing and stigmatization. Little is known about thin children's weight perceptions, desired weight and attitudes and behaviours towards food and exercise. The study aimed to compare perceived weight status, desired weight, eating and exercise behaviours and advice received from parents among thin, overweight, obese or normal weight Australian children and adolescents. METHODS: The sample included 8550 school children aged 6 to 18 years selected from every state and territory of Australia. The children were weighed, measured and classified as thin, normal, overweight or obese using international standards. The main outcome measures were perceived and desired weight, weight related eating and exercising behaviours, and advice received from parents. RESULTS: The distribution of weight status was - thin 4.4%; normal weight 70.7%; overweight 18.3%; and obese 6.6%. Thin children were significantly shorter than normal weight, overweight or obese children and they were also more likely to report regularly consuming meals and snacks. 57.4% of thin children, 83.1% of normal weight children, 63.7% of overweight and 38.3% of obese children perceived their weight as "about right". Of the thin children, 53.9% wanted to be heavier, 36.2% wanted to stay the same weight, and 9.8% wanted to weigh less. Thin children were significantly less likely than obese children to respond positively to statements such as "I am trying to get fitter" or "I need to get more exercise." Parents were significantly less likely to recommend exercise for thin children compared with other weight groups. CONCLUSIONS: Thin children, as well as those who are overweight or obese, are less likely than normal weight children to consider their weight "about right'. Thin children differ from children of other weights in that thin children are less likely to desire to get fitter or be encouraged to exercise. Both extremes of the spectrum of weight, from underweight to obese, may have serious health consequences for the individuals, as well as for public health policy. Health and wellness programs that promote positive social experiences and encourage exercise should include children of all sizes
Discovery and partial genomic characterisation of a novel nidovirus associated with respiratory disease in wild shingleback lizards (Tiliqua rugosa)
A respiratory disease syndrome has been observed in large numbers of wild shingleback lizards (Tiliqua rugosa) admitted to wildlife care facilities in the Perth metropolitan region of Western Australia. Mortality rates are reportedly high without supportive treatment and care. Here we used next generation sequencing techniques to screen affected and unaffected individuals admitted to Kanyana Wildlife Rehabilitation Centre in Perth between April and December 2015, with the resultant discovery of a novel nidovirus significantly associated with cases of respiratory disease according to a case definition based on clinical signs. Interestingly this virus was also found in 12% of apparently healthy individuals, which may reflect testing during the incubation period or a carrier status, or it may be that this agent is not causative in the disease process. This is the first report of a nidovirus in lizards globally. In addition to detection of this virus, characterisation of a 23,832 nt segment of the viral genome revealed the presence of characteristic nidoviral genomic elements providing phylogenetic support for the inclusion of this virus in a novel genus alongside Ball Python nidovirus, within the Torovirinae sub-family of the Coronaviridae. This study highlights the importance of next generation sequencing technologies to detect and describe emerging infectious diseases in wildlife species, as well as the importance of rehabilitation centres to enhance early detection mechanisms through passive and targeted health surveillance. Further development of diagnostic tools from these findings will aid in detection and control of this agent across Australia, and potentially in wild lizard populations globally
Profiling inflammatory markers in patients with pneumonia on intensive care
Clinical investigations lack predictive value when diagnosing pneumonia, especially when patients are ventilated and develop ventilator associated pneumonia (VAP). New tools to aid diagnosis are important to improve outcomes. This pilot study examines the potential for a panel of inflammatory mediators to aid in the diagnosis. Forty-four ventilated patients, 17 with pneumonia and 27 with brain injuries, eight of whom developed VAP, were recruited. 51 inflammatory mediators, including cytokines and oxylipins, were measured in patientsâ serum using flow cytometry and mass spectrometry. The mediators could separate patients admitted to ICU with pneumonia compared to brain injury with an area under the receiver operating characteristic curve (AUROC) 0.75 (0.61â0.90). Changes in inflammatory mediators were similar in both groups over the course of ICU stay with 5,6-dihydroxyeicosatrienoic and 8,9-dihydroxyeicosatrienoic acids increasing over time and interleukin-6 decreasing. However, brain injured patients who developed VAP maintained inflammatory profiles similar to those at admission. A multivariate model containing 5,6-dihydroxyeicosatrienoic acid, 8,9-dihydroxyeicosatrienoic acid, intercellular adhesion molecule-1, interleukin-6, and interleukin-8, could differentiate patients with VAP from brain injured patients without infection (AUROC 0.94 (0.80â1.00)). The use of a selected group of markers showed promise to aid the diagnosis of VAP especially when combined with clinical data
Streaming cold cosmic ray back-reaction and thermal instabilities across the background magnetic field
Using the multi-fluid approach, we investigate streaming and thermal
instabilities of the electron-ion plasma with homogeneous cold cosmic rays
drifting perpendicular to the background magnetic field. Perturbations across
the magnetic field are considered. The back-reaction of cosmic rays resulting
in the streaming instability is taken into account. The thermal instability is
shown not to be subject to the action of cosmic rays in the model under
consideration. The dispersion relation for the thermal instability has been
derived which includes sound velocities of plasma and cosmic rays, Alfv\'{e}n
and cosmic ray drift velocities. The relation between these parameters
determines the kind of thermal instability from Parker's to Field's type
instability. The results obtained can be useful for a more detailed the
investigation of electron-ion astrophysical objects such as galaxy clusters
including the dynamics of streaming cosmic rays.Comment: Submitted to MNRAS. arXiv admin note: substantial text overlap with
arXiv:1203.573
Observations of HI Absorbing Gas in Compact Radio Sources at Cosmological Redshifts
We present an overview of the occurrence and properties of atomic gas
associated with compact radio sources at redshifts up to z=0.85. Searches for
HI 21cm absorption were made with the Westerbork Synthesis Radio Telescope at
UHF-high frequencies (725-1200 MHz). Detections were obtained for 19 of the 57
sources with usable spectra (33%). We have found a large range in line depths,
from tau=0.16 to tau<=0.001. There is a substantial variety of line profiles,
including Gaussians of less than 10km/s, to more typically 150km/s, as well as
irregular and multi-peaked absorption profiles, sometimes spanning several
hundred km/s. Assuming uniform coverage of the entire radio source, we obtain
column depths of atomic gas between 1e19 and 3.3e21(Tsp/100K)(1/f)cm^(-2).
There is evidence for significant gas motions, but in contrast to earlier
results at low redshift, there are many sources in which the HI velocity is
substantially negative (up to v=-1420km/s) with respect to the optical
redshift, suggesting that in these sources the atomic gas, rather than falling
into the centre, may be be flowing out, interacting with the jets, or rotating
around the nucleus.Comment: 10 pages, accepted for publication in A&
A possible radio supernova in the outer part of NGC 3310
As part of an on-going radio supernova monitoring program, we have discovered
a variable, compact steep spectrum radio source ~65 arcsec (~4 kpc) from the
centre of the starburst galaxy NGC 3310. If the source is at the distance of
NGC 3310, then its 5 GHz luminosity is ~3 x 10^{19} WHz^-1. The source
luminosity, together with its variability characteristics, compact structure
(<17 mas) and its association with a group of HII regions, leads us to propose
that it is a previously uncatalogued type II radio supernova. A search of
archival data also shows an associated X-ray source with a luminosity similar
to known radio supernova.Comment: 5 pages, 3 figures. Accepted by MNRA
High-resolution double morphology of the most distant known radio quasar at z=6.12
Context: The highest redshift quasars at z>~6 receive considerable attention
since they provide strong constraints on the growth of the earliest
supermassive black holes. They also probe the epoch of reionisation and serve
as "lighthouses" to illuminate the space between them and the observer. The
source J1427+3312 (z=6.12) has recently been identified as the first and so far
the only known radio-loud quasar at z>6.
Aims: We investigated the compact radio structure of J1427+3312 on
milli-arcsecond (mas) angular scales, to compare it with that of the second
most distant radio-loud quasar J0836+0054 (z=5.77) and with lower-redshift
radio quasars in general. Methods: We observed J1427+3312 in phase-reference
mode with ten antennas of the European Very Long Baseline Interferometry (VLBI)
Network (EVN) at 1.6 GHz on 11 March 2007 and at 5 GHz on 3 March 2007.
Results: The source was clearly detected at both frequencies. At 1.6 GHz, it
shows a prominent double structure. The two components are separated by 8.3
mas, corresponding to a projected linear distance of ~160 pc. Both components
with sub-mJy flux densities appear resolved. In the position of the brightest
component at 1.6 GHz, we detected mas-scale radio emission at 5 GHz as well.
The radio spectrum of this feature is steep. The double structure and the
separation of the components of J1427+3312 are similar to those of the young
(<~10^4 yr) compact symmetric objects (CSOs).Comment: 4 pages, 2 figures, accepted for Astronomy & Astrophysics as a Letter
to the Edito
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