1,306 research outputs found
A Broadband Study of the Emission from the Composite Supernova Remnant MSH 11-62
MSH 11-62 (G291.1-0.9) is a composite supernova remnant for which radio and
X-ray observations have identified the remnant shell as well as its central
pulsar wind nebula. The observations suggest a relatively young system
expanding into a low density region. Here we present a study of MSH 11-62 using
observations with the Chandra, XMM-Newton, and Fermi observatories, along with
radio observations from the Australia Telescope Compact Array (ATCA). We
identify a compact X-ray source that appears to be the putative pulsar that
powers the nebula, and show that the X-ray spectrum of the nebula bears the
signature of synchrotron losses as particles diffuse into the outer nebula.
Using data from the Fermi LAT, we identify gamma-ray emission originating from
MSH 11-62. With density constraints from the new X-ray measurements of the
remnant, we model the evolution of the composite system in order to constrain
the properties of the underlying pulsar and the origin of the gamma-ray
emission.Comment: 12 Pages, 12 figures. Accepted for publication in the Astrophysical
Journa
An Efficient Approach to Automatic Generation of Time-lapse Video Sequences
Time-lapse video sequences have recently become a highly utilised asset for marketing and advertising, particularly within the field of construction and landscape development. However, the manual generation of these videos, at a quality that can be used for marketing purposes, can be quite time-consuming. In this paper, a novel application for generating time-lapse videos is proposed, which will automatically select the optimal frames for time-lapse video generation, enhance these frames by applying a number of image pre- processing and machine learning techniques such as FAST super-resolution to improve the frames quality, and finally, provide an intuitive user interface to allow users to customise the time-lapse video with company branding. The auto-generated time-lapse videos will use techniques such as Laplacian filtering and temporal smoothing filtering to determine inactivity within the video sequence, classify day or night and, by use of optical character recognition, have the ability to remove unwanted artefacts such as the captured video date and time stamp. The obtained results from the proposed approach produce comparable video sequences to those produced manually, but with the advantage of being generated much faster and not requiring specialised video editing skills to complete
The Surface Mass Density and Structure of the Outer Disk of NGC 628
We study the kinematics of GALEX-selected H_alpha knots in the outer disk
(beyond R25) of NGC 628 (M74), a galaxy representative of large, undisturbed,
extended UV (Type 1 XUV) disks. Our spectroscopic target sample of 235 of the
bluest UV knots surrounding NGC 628 yielded 15 H_alpha detections (6%), roughly
the number expected given the different mean ages of the two populations. The
measured vertical velocity dispersion of the H_alpha knots between 1 - 1.8 R25
(13.5 - 23.2 kpc) is < 11 km/s. We assume that the H_alpha knots trace an
'intermediate' vertical mass density distribution (between the isothermal
sech(z)^2 and exponential distributions) with a constant scaleheight across the
outer disk (h_z = 700 pc) and estimate a total surface mass density of 7.5
solar masses/pc^2. This surface mass density can be accounted for by the
observed gas and stars in the outer disk (little or no dark matter in the disk
is required). The vertical velocity dispersion of the outer disk H_alpha knots
nearly matches that measured from older planetary nebulae near the outskirts of
the optical disk by Herrmann et al., suggesting a low level of scattering in
the outer disk. A dynamically cold stellar component extending nearly twice as
far as the traditional optical disk poses interesting constraints on the
accretion history of the galaxy.Comment: Accepted for publication in The Astrophysical Journal
Estimating the number needed to treat from continuous outcomes in randomised controlled trials: methodological challenges and worked example using data from the UK Back Pain Exercise and Manipulation (BEAM) trial
Background
Reporting numbers needed to treat (NNT) improves interpretability of trial results. It is unusual that continuous outcomes are converted to numbers of individual responders to treatment (i.e., those who reach a particular threshold of change); and deteriorations prevented are only rarely considered. We consider how numbers needed to treat can be derived from continuous outcomes; illustrated with a worked example showing the methods and challenges.
Methods
We used data from the UK BEAM trial (n = 1, 334) of physical treatments for back pain; originally reported as showing, at best, small to moderate benefits. Participants were randomised to receive 'best care' in general practice, the comparator treatment, or one of three manual and/or exercise treatments: 'best care' plus manipulation, exercise, or manipulation followed by exercise. We used established consensus thresholds for improvement in Roland-Morris disability questionnaire scores at three and twelve months to derive NNTs for improvements and for benefits (improvements gained+deteriorations prevented).
Results
At three months, NNT estimates ranged from 5.1 (95% CI 3.4 to 10.7) to 9.0 (5.0 to 45.5) for exercise, 5.0 (3.4 to 9.8) to 5.4 (3.8 to 9.9) for manipulation, and 3.3 (2.5 to 4.9) to 4.8 (3.5 to 7.8) for manipulation followed by exercise. Corresponding between-group mean differences in the Roland-Morris disability questionnaire were 1.6 (0.8 to 2.3), 1.4 (0.6 to 2.1), and 1.9 (1.2 to 2.6) points.
Conclusion
In contrast to small mean differences originally reported, NNTs were small and could be attractive to clinicians, patients, and purchasers. NNTs can aid the interpretation of results of trials using continuous outcomes. Where possible, these should be reported alongside mean differences. Challenges remain in calculating NNTs for some continuous outcomes
The SAMI Galaxy Survey: Global stellar populations on the size-mass plane
We present an analysis of the global stellar populations of galaxies in the
SAMI Galaxy Survey. Our sample consists of 1319 galaxies spanning four orders
of magnitude in stellar mass and includes all morphologies and environments. We
derive luminosity-weighted, single stellar population equivalent stellar ages,
metallicities and alpha enhancements from spectra integrated within one
effective radius apertures. Variations in galaxy size explain the majority of
the scatter in the age--mass and metallicity--mass relations. Stellar
populations vary systematically in the plane of galaxy size and stellar mass,
such that galaxies with high stellar surface mass density are older, more
metal-rich and alpha-enhanced than less dense galaxies. Galaxies with high
surface mass densities have a very narrow range of metallicities, however, at
fixed mass, the spread in metallicity increases substantially with increasing
galaxy size (decreasing density). We identify residual correlations with
morphology and environment. At fixed mass and size, galaxies with late-type
morphologies, small bulges and low Sersic n are younger than early-type, high
n, high bulge-to-total galaxies. Age and metallicity both show small residual
correlations with environment; at fixed mass and size, galaxies in denser
environments or more massive halos are older and somewhat more metal rich than
those in less dense environments. We connect these trends to evolutionary
tracks within the size--mass plane.Comment: 25 pages, 18 figures, MNRAS in press Corrected typo in author lis
Gas Metallicities in the Extended Disks of NGC 1512 and NGC 3621. Chemical Signatures of Metal Mixing or Enriched Gas Accretion?
(Abridged) We have obtained spectra of 135 HII regions located in the inner
and extended disks of the spiral galaxies NGC 1512 and NGC 3621, spanning the
range of galactocentric distances 0.2-2 x R25 (from 2-3 kpc to 18-25 kpc). We
find that the excitation properties of nebulae in the outer (R>R25) disks are
similar to those of the inner disks, but on average younger HII regions tend to
be selected in the bright inner disks. Reddening by dust is not negligible in
the outer disks, and subject to significant large-scale spatial variations. For
both galaxies the radial abundance gradient flattens to a constant value
outside of the isophotal radius. The outer disk O/H abundance ratio is highly
homogeneous, with a scatter of only ~0.06 dex. Based on the excitation and
chemical (N/O ratio) analysis we find no compelling evidence for variations in
the upper initial mass function of the ionizing clusters of extended disks. The
O/H abundance in the outer disks of the target galaxies corresponds to 35% of
the solar value (or higher, depending on the metallicity diagnostic). This
conflicts with the notion that metallicities in extended disks of spiral
galaxies are necessarily low. The observed metal enrichment cannot be produced
with the current level of star formation. We discuss the possibility that metal
transport mechanisms from the inner disks lead to metal pollution of the outer
disks. Gas accretion from the intergalactic medium, enriched by outflows,
offers an alternative solution.Comment: Accepted for publication in the Astrophysical Journa
Cobalt and nickel in the Peru upwelling region : a major flux of labile cobalt utilized as a micronutrient
Author Posting. © American Geophysical Union, 2004. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 18 (2004): GB4030, doi:10.1029/2003GB002216.The geochemistry of cobalt in the Peru upwelling region is dominated by its importance as a micronutrient. A large and previously undocumented flux of labile cobalt behaved as a micronutrient with correlations with major nutrients (nitrate, phosphate; r 2 = 0.90, 0.96) until depleted to ≤50 pM of strongly complexed cobalt. Co:P utilization ratios were an order of magnitude higher than in the North Pacific, comparable to utilization rates of zinc in other oceanic regions. Cobalt speciation measurements showed that available cobalt decreased over 4 orders of magnitude in this region, with shifts in phytoplankton assemblages occurring at transitions between labile and nonlabile cobalt. Only small changes in total dissolved nickel were observed, and nickel was present in a labile chemical form throughout the region. In the Peru upwelling region, cobalt uptake was highest at the surface and decreased with depth, suggesting phytoplankton uptake was a more important removal mechanism than co-oxidation with microbial manganese oxidation. These findings show the importance of cobalt as a micronutrient and that cobalt scarcity and speciation may be important in influencing phytoplankton species composition in this economically important environment.This work was supported by the
NSF under grant OCE-9618729 and OCE-0327225
Establishing psychological safety in online design-thinking education: a qualitative study
Design thinking, an approach traditionally used to develop or improve products, services, or processes within design and engineering sectors, has emerged as a novel pedagogical approach. As design thinking becomes more widely established within education contexts, it is important to gain deeper insight as to how such learning environments operate. The aim of this study was to explore online design thinking through the lens of psychological safety. We used a qualitative single-case study design to investigate nine students’ experiences across a nine-week design-thinking project. Data were collected via semi-structured interviews and reflective journal entries, and analysed through reflexive thematic analysis. Our findings suggested that psychological safety is a valuable consideration in the design and implementation of online design-thinking learning environments. Facilitators of psychological safety included having collaborative environments, encouraging leadership, and a focus on team formation. Barriers to psychological safety included difficulties connecting, fear of speaking, and cultural considerations. Our findings also highlighted several outcomes of psychologically safe team climates, including creativity, collaboration, and the development of approaches to working with uncertainty
Galaxy-scale Star Formation on the Red Sequence: the Continued Growth of S0s and the Quiescence of Ellipticals
This paper examines star formation (SF) in relatively massive, primarily
early-type galaxies (ETGs) at z~0.1. A sample is drawn from bulge-dominated
GALEX/SDSS galaxies on the optical red sequence with strong UV excess and yet
quiescent SDSS spectra. High-resolution far-UV imaging of 27 such ETGs using
HST ACS/SBC reveals structured UV morphology in 93% of the sample, consistent
with low-level ongoing SF (~0.5 Ms/yr). In 3/4 of the sample the SF is extended
on galaxy scales (25-75 kpc), while the rest contains smaller (5-15 kpc) SF
patches in the vicinity of an ETG - presumably gas-rich satellites being
disrupted. Optical imaging reveals that all ETGs with galaxy-scale SF in our
sample have old stellar disks (mostly S0 type). None is classified as a true
elliptical. In our sample, galaxy-scale SF takes the form of UV rings of
varying sizes and morphologies. For the majority of such objects we conclude
that the gas needed to fuel current SF has been accreted from the IGM, probably
in a prolonged, quasi-static manner, leading in some cases to additional disk
buildup. The remaining ETGs with galaxy-scale SF have UV and optical
morphologies consistent with minor merger-driven SF or with the final stages of
SF in fading spirals. Our analysis excludes that all recent SF on the red
sequence resulted from gas-rich mergers. We find further evidence that
galaxy-scale SF is almost exclusively an S0 phenomenon (~20% S0s have SF) by
examining the overall optically red SDSS ETGs. Conclusion is that significant
number of field S0s maintain or resume low-level SF because the preventive
feedback is not in place or is intermittent. True ellipticals, on the other
hand, stay entirely quiescent even in the field.Comment: Accepted for publication in ApJ. Contains color figures, but
compatible with non-color printer
Calibrating Single-Ended Fiber-Optic Raman Spectra Distributed Temperature Sensing Data
Hydrologic research is a very demanding application of fiber-optic distributed temperature sensing (DTS) in terms of precision, accuracy and calibration. The physics behind the most frequently used DTS instruments are considered as they apply to four calibration methods for single-ended DTS installations. The new methods presented are more accurate than the instrument-calibrated data, achieving accuracies on the order of tenths of a degree root mean square error (RMSE) and mean bias. Effects of localized non-uniformities that violate the assumptions of single-ended calibration data are explored and quantified. Experimental design considerations such as selection of integration times or selection of the length of the reference sections are discussed, and the impacts of these considerations on calibrated temperatures are explored in two case studies
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