3,815 research outputs found
Evidence for a developing gap in a 10 Myr old protoplanetary disk
We have developed a self-consistent model of the disk around the nearby 10
Myr old star TW Hya which matches the observed spectral energy distribution and
7mm images of the disk. The model requires a significant dust size evolution
and a partially-evacuated inner disk region, as predicted by theories of planet
formation. The outer disk, which extends to at least 140 AU in radius, is very
optically thick at IR wavelengths and quite massive ~0.06 Msun for the
relatively advanced age of this T Tauri star. This implies long viscous and
dust evolution timescales, although dust must have grown to sizes of order ~1cm
to explain the sub-mm and mm spectral slopes. In contrast, the negligible
near-infrared excess emission of this system requires that the disk be
optically thin inside ~4 AU.This inner region cannot be completely evacuated;
we need ~0.5 lunar mass of ~1 micron particles remaining to produce the
observed 10 micron silicate emission. Our model requires a distinct transition
in disk properties at ~4 AU, separating the inner and outer disk. The inner
edge of the optically-thick outer disk must be heated almost frontally by the
star to account for the excess flux at mid-IR wavelengths. We speculate that
this truncation of the outer disk may be the signpost of a developing gap due
to the effects of a growing protoplanet; the gap is still presumably evolving
because material still resides in it, as indicated by the silicate emission,
the molecular hydrogen emission, and by the continued accretion onto the
central star (albeit at a much lower rate than typical of younger T Tauri
stars). TW Hya thus may become the Rosetta stone for our understanding of the
evolution and dissipation of protoplanetary disks.Comment: 23 pages including 5 figures, Accepted by AP
AP/Linux - initial implementation
The AP1000+ is a distributed-memory parallel computer based on SuperSPARC processors, which incorporates message-passing hardware which can be accessed safely from user mode. We are in the process of porting the Linux kernel to this machine and extending it to support execution of parallel programs. This report outlines the motivation and background of this effort, and describes the current status and future directions for the work. The reader may also refer to our WWW page at http://cap.anu.edu.au/cap/projects/linux for up to date information on the progress of the port
The Milky Way Heart: Investigating molecular gas and gamma-ray morphologies in the Central Molecular Zone
Since the discovery of a broad distribution of very high energy (VHE; >0.1
TeV) gamma-rays in the Central Molecular Zone (CMZ) of the Galaxy in 2006 by
the HESS collaboration, the correlation of this emission with the integrated
intensity of the CS(1-0) molecular line emission has inferred a hadronic origin
for the gamma-rays. Here we describe the beginning of our investigation into
the strength of this correlation utilising new multi-line millimeter data from
the Mopra CMZ and HOP surveys and multi-wavelength GBT radio continuum
observations towards the CMZ and compare these in detail with the diffuse TeV
gamma-ray emission from HESS. The benefit of these new data is that they allow
us to simultaneously observe and analyse correlations using a large number
(>10) of molecular species, some of which contain their isotopologue pairs. The
use of isotopologue pairs is especially powerful, since it allows one to
analyse the optical depth of a number of different molecular species, thus
investigating the nature of the correlation over a range of different physical
conditions. Here we begin by comparing the integrated line emission and
continuum radio emission with the diffuse gamma-ray emission, and, by using
isotopologue pairs such as HCN/HCN, obtain optical depths throughout the
CMZ corresponding to regions of both strong and weak gamma-ray emission. We
find that the radio continuum better matches the peak of the gamma-ray
emission, which corresponds to the more compact -- compared to the relatively
coarse resolution of the gamma-ray images -- sources in the CMZ. Using the
isotopologue pairs, we find that the optical depth at all positions and
velocities within the CMZ are about 2--4. This is similar to that found for the
CS(1--0) line and would underestimate the mass of the CMZ, potentially
explaining why molecular line emission peaks appear offset from the gamma-ray
peaks.Comment: 8 pages, 5 figures. Accepted to the Proceedings of the 25th Texas
Symposium on Relativistic Astrophysics (Heidelberg, 2010
ALMA Observations of Circumnuclear Disks in Early Type Galaxies: 12CO(2-1) and Continuum Properties
We present results from an Atacama Large Millimeter/submillimeter Array
(ALMA) Cycle 2 program to map CO(2-1) emission in nearby early-type galaxies
(ETGs) that host circumnuclear gas disks. We obtained resolution
Band 6 observations of seven ETGs selected on the basis of dust disks in Hubble
Space Telescope images. We detect CO emission in five at high signal-to-noise
ratio with the remaining two only faintly detected. All CO emission is
coincident with the dust and is in dynamically cold rotation. Four ETGs show
evidence of rapid central rotation; these are prime candidates for
higher-resolution ALMA observations to measure the black hole masses. In this
paper we focus on the molecular gas and continuum properties. Total gas masses
and H column densities for our five CO-bright galaxies are on average
and cm over the kpc-scale
disks, and analysis suggests that these disks are stabilized against
gravitational fragmentation. The continuum emission of all seven galaxies is
dominated by a central, unresolved source, and in five we also detect a
spatially extended component. The 230 GHz nuclear continua are modeled as
power laws ranging from to within the
observed frequency band. The extended continuum profiles of the two
radio-bright (and CO-faint) galaxies are roughly aligned with their radio jet
and suggests resolved synchrotron jets. The extended continua of the CO-bright
disks are coincident with optically thick dust absorption and have spectral
slopes that are consistent with thermal dust emission.Comment: 20 pages, 10 figures; accepted for publication in Ap
Augmented pain behavioural responses to intra-articular injection of nerve growth factor in two animal models of osteoarthritis
Acknowledgements The authors would like to thank Paul Millns for his technical assistance with tissue (dorsal root ganglia) collection. Competing interests None. Provenance and peer review Not commissioned; externally peer reviewedPeer reviewedPublisher PD
The potential for modification in cloning and vitrification technology to enhance genetic progress in beef cattle in Northern Australia
AbstractRecent advances in embryology and related research offer considerable possibilities to accelerate genetic improvement in cattle breeding. Such progress includes optimization and standardization of laboratory embryo production (in vitro fertilization â IVF), introduction of a highly efficient method for cryopreservation (vitrification), and dramatic improvement in the efficiency of somatic cell nuclear transfer (cloning) in terms of required effort, cost, and overall outcome. Handmade cloning (HMC), a simplified version of somatic cell nuclear transfer, offers the potential for relatively easy and low-cost production of clones. A potentially modified method of vitrification used at a centrally located laboratory facility could result in cloned offspring that are economically competitive with elite animals produced by more traditional means. Apart from routine legal and intellectual property issues, the main obstacle that hampers rapid uptake of these technologies by the beef cattle industry is a lack of confidence from scientific and commercial sources. Once stakeholder support is increased, the combined application of these methods makes a rapid advance toward desirable traits (rapid growth, high-quality beef, optimized reproductive performance) a realistic goal. The potential impact of these technologies on genetic advancement in beef cattle herds in which improvement of stock is sought, such as in northern Australia, is hard to overestimate
Cognitive and affective reassurance and patient outcomes in primary care:a systematic review
In the context of uncertainty about aetiology and prognosis, good clinical practice commonly recommends both affective (creating rapport, showing empathy) and cognitive reassurance (providing explanations and education) to increase self-management in groups with nonspecific pain conditions. The specific impact of each of these components in reference to patients' outcomes has not been studied. This review aimed to systematically evaluate the evidence from prospective cohorts in primary care that measured patient-practitioner interactions with reference to patient outcomes. We carried out a systematic literature search and appraisal of study methodology. We extracted measures of affective and cognitive reassurance in consultations and their associations with consultation exit and follow-up measures of patients' outcomes. We identified 16 studies from 16,059 abstracts. Eight studies were judged to be high in methodological quality. Pooling could not be achieved as a result of heterogeneity of samples and measures. Affective reassurance showed inconsistent findings with consultation exit outcomes. In 3 high-methodology studies, an association was found between affective reassurance and higher symptom burden and less improvement at follow-up. Cognitive reassurance was associated with higher satisfaction and enablement and reduced concerns directly after the consultations in 8 studies; with improvement in symptoms at follow-up in 7 studies; and with reduced health care utilization in 3 studies. Despite limitations, there is support for the notion that cognitive reassurance is more beneficial than affective reassurance. We present a tentative model based on these findings and propose priorities for future research. © 2013 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved
Development of a root caries prediction model in a population of dental attenders
Acknowledgement This study was conducted as part of the doctoral thesis of P.A.F. We would like to thank the participating dental practice teams and patients without whose valuable contribution this study could not have taken place. We would like to thank our colleagues in the INTERVAL Trial team Funding INTERVAL was funded by the NIHR HTA programme [project numbers 06/35/05 (Phase I) and 06/35/99 (Phase II)]. No additional funding was obtained to conduct the prediction study presented in this paper. The views expressed are those of the author(s) and not necessarily those of NIHR, the NHS or the Department of Health and Social Care.Peer reviewedPublisher PD
Development of a Root Caries Prediction Model in a Population of Dental Attenders
Acknowledgement This study was conducted as part of the doctoral thesis of P.A.F. We would like to thank the participating dental practice teams and patients without whose valuable contribution this study could not have taken place. We would like to thank our colleagues in the INTERVAL Trial team Funding INTERVAL was funded by the NIHR HTA programme [project numbers 06/35/05 (Phase I) and 06/35/99 (Phase II)]. No additional funding was obtained to conduct the prediction study presented in this paper. The views expressed are those of the author(s) and not necessarily those of NIHR, the NHS or the Department of Health and Social Care.Peer reviewedPublisher PD
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