2,797 research outputs found
Melting of peridotites through to granites: a simple thermodynamic model in the system KNCFMASHTOCr
A new set of thermodynamic models is presented for calculating phase relations in bulk compositions extending from peridotite to granite, from 0.001 to 70 kbar and from 650â°C to peridotite liquidus temperatures, in the system K2OâNa2OâCaOâFeOâMgOâAl2O3âSiO2âH2OâTiO2âFe2O3âCr2O3 (KNCFMASHTOCr). The models may be used to calculate phase equilibria in partial melting of a large range of mantle and crustal compositions. They provide a good fit to experimental phase relation topologies and melt compositions across the compositional range of the model. Compared with the preliminary model of Jennings & Holland (2015) for peridotiteâbasalt melting relations, the inclusion of K2O and TiO2 allows for better modelling of small melt fractions in peridotite melting, and in reproducing rutile-bearing eclogite melting at high pressures. An improved orderâdisorder model for spinel is now incorporated. Above 10 kbar pressure, wet partial melting relations may be significantly affected by the dissolution of silicates in aqueous fluid, so the set of models includes an aqueous low-density silicate-bearing fluid in addition to a high-density H2O-bearing silicate melt. Oxygen fugacity may be readily calculated for the whole range of bulk compositions investigated, and the effect of water content on melt fO2 is assessed
The unmet needs of Aboriginal Australians with musculoskeletal pain: A mixed method systematic review
Objective: Musculoskeletal pain (MSP) conditions are the biggest cause of disability and internationally, Indigenous peoples experience a higher burden. There are conflicting reports about Aboriginal Australians and MSP. We conducted a systematic review to describe the prevalence, associated factors, impacts, care access, health care experiences, and factors associated with MSP among Aboriginal Australians.
Methods: A systematic search of quantitative and qualitative scientific and grey literature (PROSPERO number: CRD42016038342). Articles were appraised using the Mixed Methods Appraisal Tool. Due to study heterogeneity a narrative synthesis was conducted.
Results: Of 536 articles identified, 18 were included (14 quantitative, 4 qualitative), of high (n=11), medium (n=2) and low (n=5) quality. Prevalences of MSP in Aboriginal populations were similar to or slightly higher than the nonâAboriginal population (prevalence rate ratio 1.1 for back pain, 1.2â1.5 for osteoarthritis (OA), 1.0â2.0 for rheumatoid arthritis). Aboriginal people accessed primary care for knee or hip OA at around half the rate of nonâAboriginal people, and were less than half as likely to have knee or hip replacement surgery. Communication difficulties with health practitioners were the main reason why Aboriginal people with MSP choose not to access care. No articles reported interventions.
Conclusions: Findings provide preliminary evidence of an increased MSP burden amongst Aboriginal Australians and, particularly for OA, a mismatch between the disease burden and access to health care. To increase accessibility, health services should initially focus on improving Aboriginal patientsâ experiences of care, in particular by improving patientâpractitioner communication. Implications for care and research are outlined
Supernova Remnants in the Fossil Starburst in M82
We report the discovery of ten compact H-alpha-bright sources in the
post-starburst region northeast of the center of M82, ``M82 B.'' These objects
have H alpha luminosities and sizes consistent with Type II supernova remnants
(SNRs). They fall on the same H alpha surface brightness-diameter (Sigma-D)
relation defined by SNRs in other nearby star-forming galaxies, with the M82
candidates lying preferentially at the small diameter end. These are the first
candidates for optically-visible SNRs in M82 outside the heavily obscured
central starburst within ~250 pc from the galactic center. If these sources are
SNRs, they set an upper limit to the end of the starburst in region ``B2,''
about 500 pc from the galaxy's core, of ~50 Myr. Region ``B1,'' about 1000 pc
from the core, lacks good SNR candidates and is evidently somewhat older. This
suggests star formation in the galaxy has propagated inward toward the
present-day intense starburst core.Comment: Re-submitted to AJ, referee's comments taken into account, 15 pages
LaTeX preprint style, 4 postscript figures; full-resolution figures available
from http://www.astro.virginia.edu/~rd7a/snrs/ Changes: minor textual changes
and orientation/axes of Fig.
Chemically Related 4,5-Linked Aminoglycoside Antibiotics Drive Subunit Rotation in Opposite Directions
Dynamic remodelling of intersubunit bridge B2, a conserved RNA domain of the bacterial ribosome connecting helices 44 (h44) and 69 (H69) of the small and large subunit, respectively, impacts translation by controlling intersubunit rotation. Here we show that aminoglycosides chemically related to neomycin-paromomycin, ribostamycin and neamine-each bind to sites within h44 and H69 to perturb bridge B2 and affect subunit rotation. Neomycin and paromomycin, which only differ by their ring-I 6\u27-polar group, drive subunit rotation in opposite directions. This suggests that their distinct actions hinge on the 6\u27-substituent and the drug\u27s net positive charge. By solving the crystal structure of the paromomycin-ribosome complex, we observe specific contacts between the apical tip of H69 and the 6\u27-hydroxyl on paromomycin from within the drug\u27s canonical h44-binding site. These results indicate that aminoglycoside actions must be framed in the context of bridge B2 and their regulation of subunit rotation
A Sino-German 6 cm polarization survey of the Galactic plane II. The region from 129 degree to 230 degree longitude
Linearly polarized Galactic synchrotron emission provides valuable
information about the properties of the Galactic magnetic field and the
interstellar magneto-ionic medium, when Faraday rotation along the line of
sight is properly taken into account. We aim to survey the Galactic plane at 6
cm including linear polarization. At such a short wavelength Faraday rotation
effects are in general small and the Galactic magnetic field properties can be
probed to larger distances than at long wavelengths. The Urumqi 25-m telescope
is used for a sensitive 6 cm survey in total and polarized intensities. WMAP
K-band (22.8 GHz) polarization data are used to restore the absolute zero-level
of the Urumqi U and Q maps by extrapolation. Total intensity and polarization
maps are presented for a Galactic plane region of 129 degree < l < 230 degree
and |b| < 5 degree in the anti-centre with an angular resolution of 9'5 and an
average sensitivity of 0.6 mK and 0.4 mK Tb in total and polarized intensity,
respectively. We briefly discuss the properties of some extended Faraday
Screens detected in the 6 cm polarization maps. The Sino-German 6 cm
polarization survey provides new information about the properties of the
magnetic ISM. The survey also adds valuable information for discrete Galactic
objects and is in particular suited to detect extended Faraday Screens with
large rotation measures hosting strong regular magnetic fields.Comment: 17 pages, 20 figures, accepted by A&A. Resolutions of the figures
have been significantly reduced. For version with full resolution, see
http://159.226.88.6/zmtt/6cm/papers/gao.paper2.pd
Radio emission from the Cygnus Loop and its spectral characteristics
We present a new sensitive 2675 MHz radio continuum map of the Cygnus Loop,
which is used in conjunction with 408 MHz, 863 MHz and 1420 MHz maps from both
the Effelsberg 100-m telescope and the DRAO Synthesis Telescope for a spectral
analysis. Between 408 MHz and 2675 MHz we find an overall integrated spectral
index of (), close to
previous results. There is no indication of a spectral break in the integrated
spectrum. Spatially highly varying and rather strong spectral curvature was
previously reported, but is not confirmed on the basis of new, higher
sensitivity observations. We found spectral variations across the Cygnus Loop
reaching up to from a TT-plot analysis. The flattest
spectra are seen towards enhanced emission areas. Spectral index maps produced
between different frequency pairs, as well as all four maps, revealed that
there are at least three flat spectrum regions. In regions interior to the high
emission filaments, we have detected at least two spectral components across
the whole object with and towards northern and
southern parts of the object, respectively.Comment: 22 pages, 13 figures in jpeg format, accepted for publication in
Astrophysics & Astronom
Study of the Composite Supernova Remnant MSH 11-62
We present the analysis of the X-ray data collected during an observation of
the supernova remnant (SNR) MSH 11-62 by the Advanced Satellite for Cosmology
and Astrophysics (ASCA). We show that MSH 11-62 is a composite remnant whose
X-ray emission comes from two distinct contributions. Nonthermal, synchrotron
emission, localized to a region of radius (~~)3' (consistent with a point
source) dominates the total flux above 2 keV. A second contribution comes from
a thermal component, extended up to a radius of (~~)6' and detected only at
energies below 2keV. The spatial and spectral analysis imply the presence of a
neutron star losing energy at a rate of about (10**36 - 10**37) ergs/s. No
pulsed emission is detected and we set a limit on the pulsed fraction of 10%.
This is consistent with the lack of a radio pulsar in the remnant, which may
indicate that the pulsed emission from the rapidly rotating compact object that
should be powering the synchrotron nebula is beamed and our viewing direction
is unfavorable. In either event, the central neutron star deposits much of its
spin-down energy into the surrounding synchrotron nebula where, through direct
imaging with broadband satellites such as ASCA, it is possible to study the
energetics and evolution of the compact remnant.Comment: 30 pages, including 5 figures, Latex. To appear in ApJ (May 20, 1998
issue, Vol. 499.
Radio Frequency Spectra of 388 Bright 74 MHz Sources
As a service to the community, we have compiled radio frequency spectra from
the literature for all sources within the VLA Low Frequency Sky Survey (VLSS)
that are brighter than 15 Jy at 74 MHz. Over 160 references were used to
maximize the amount of spectral data used in the compilation of the spectra,
while also taking care to determine the corrections needed to put the flux
densities from all reference on the same absolute flux density scale. With the
new VLSS data, we are able to vastly improve upon previous efforts to compile
spectra of bright radio sources to frequencies below 100 MHz because (1) the
VLSS flux densities are more reliable than those from some previous low
frequency surveys and (2) the VLSS covers a much larger area of the sky
(declination >-30 deg.) than many other low frequency surveys (e.g., the 8C
survey). In this paper, we discuss how the spectra were constructed and how
parameters quantifying the shapes of the spectra were derived. Both the spectra
and the shape parameters are made available here to assist in the calibration
of observations made with current and future low frequency radio facilities.Comment: Accepted to ApJ
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