65 research outputs found
Avoiding the 'costly' crisis: Informing renal services design and delivery for Aboriginal people in rural/regional New South Wales, Australia
Australian Aboriginal people experience at least eight times the incidence of chronic kidney disease progressing to end-stage kidney disease than non-Aboriginal Australians. No previous studies in rural Australia have explored the experience of Aboriginal patients with haemodialysis or renal services delivery. Methods An Indigenist research paradigm and community based participatory research methods informed interviews conducted with 18 Aboriginal haemodialysis recipients and 29 health professionals providing treatment or care. Results ‘Family’ was the motivator for persevering with haemodialysis. Comparison of both data sets revealed significant congruence between Aboriginal and provider perspectives. A combined thematic analysis produced a supervening theme of Avoiding the ‘costly’ crisis. Four sub themes were: better screening for early detection; flexible family-focussed care; system redesign to demonstrate cultural understanding; managing patient fear of mainstream services. Institutional racism emerged as a barrier to effective care for Aboriginal renal patients. Health system redesign to meet participant’s perceptions of culturally acceptable care was the greatest challenge but with potential to improve quality of care and outcomes. Conclusion Health services need to address less than optimal services for rural Aboriginal haemodialysis patients. Addressing residual institutionalised racism and the ongoing impact of past overt racism on Aboriginal people within health services will provide more culturally competent and effective treatment and care
Probing the Coevolution of Supermassive Black Holes and Quasar Host Galaxies
At low redshift, there are fundamental correlations between the mass of
supermassive black holes (MBH) and the mass (Mbulge) and luminosity of the host
galaxy bulge. We investigate the same relation at z>=1. Using virial mass
estimates for 11 quasars at z >~2 to measure their black hole mass, we find
that black holes at high z fall nearly on the same MBH versus R-band magnitude
(MR) relation (to ~0.3 mag) as low-redshift active and inactive galaxies,
without making any correction for luminosity evolution. Using a set of
conservative assumptions about the host galaxy stellar population, we show that
at z>~2 (10 Gyrs ago) the ratio of MBH/Mbulge was 3--6 times larger than today.
Barring unknown systematic errors on the measurement of MBH, we also rule out
scenarios in which moderately luminous quasar hosts at z>~2 were fully formed
bulges that passively fade to the present epoch. On the other hand, 5 quasar
hosts at z~1 are consistent with current day MBH-MR relationship after taking
into account evolution, appropriate for that of E/S0 galaxies. Therefore, z~1
host galaxies appear to fit the hypothesis they are fully formed early-type
galaxies. We also find that most quasar hosts with absolute magnitudes brighter
than MR = -23 cannot fade below L* galaxies today, regardless of their stellar
population makeup, because their black hole masses are too high and they must
arrive at the local MBH-MR relationship by z=0.Comment: 16 pages, 3 figures, 2 tables. ApJ in press. Corrected for minor
typographical error
Rotation Curve Measurement using Cross-Correlation
Longslit spectroscopy is entering an era of increased spatial and spectral
resolution and increased sample size. Improved instruments reveal complex
velocity structure that cannot be described with a one-dimensional rotation
curve, yet samples are too numerous to examine each galaxy in detail.
Therefore, one goal of rotation curve measurement techniques is to flag cases
in which the kinematic structure of the galaxy is more complex than a
single-valued curve.
We examine cross-correlation as a technique that is easily automated and
works for low signal-to-noise spectra. We show that the technique yields
well-defined errors which increase when the simple spectral model (template) is
a poor match to the data, flagging those cases for later inspection.
We compare the technique to the more traditional, parametric technique of
simultaneous emission line fitting. When the line profile at a single slit
position is non-Gaussian, the techniques disagree. For our model spectra with
two well-separated velocity components, assigned velocities from the two
techniques differ by up to ~52% of the velocity separation of the model
components. However, careful use of the error statistics for either technique
allows one to flag these non-Gaussian spectra.Comment: LaTeX document with 26 pages, including 12 figures; published in PAS
Structural Evolution of Early-type Galaxies to z=2.5 in CANDELS
Projected axis ratio measurements of 880 early-type galaxies at redshifts
1<z<2.5 selected from CANDELS are used to reconstruct and model their intrinsic
shapes. The sample is selected on the basis of multiple rest-frame colors to
reflect low star-formation activity. We demonstrate that these galaxies as an
ensemble are dust-poor and transparent and therefore likely have smooth light
profiles, similar to visually classified early-type galaxies. Similar to their
present-day counterparts, the z>1 early-type galaxies show a variety of
intrinsic shapes; even at a fixed mass, the projected axis ratio distributions
cannot be explained by the random projection of a set of galaxies with very
similar intrinsic shapes. However, a two-population model for the intrinsic
shapes, consisting of a triaxial, fairly round population, combined with a flat
(c/a~0.3) oblate population, adequately describes the projected axis ratio
distributions of both present-day and z>1 early-type galaxies. We find that the
proportion of oblate versus triaxial galaxies depends both on the galaxies'
stellar mass, and - at a given mass - on redshift. For present-day and z<1
early-type galaxies the oblate fraction strongly depends on galaxy mass. At z>1
this trend is much weaker over the mass range explored here
(10^10<M*/M_sun<10^11), because the oblate fraction among massive (M*~10^11
M_sun) was much higher in the past: 0.59+-0.10 at z>1, compared to 0.20+-0.02
at z~0.1. In contrast, the oblate fraction among low-mass early-type galaxies
(log(M*/M_sun)1 to
0.72+-0.06 at z=0. [Abridged]Comment: accepted for publication in ApJ; 14 pages; 10 figures; 4 table
The Majority of Compact Massive Galaxies at z~2 are Disk Dominated
We investigate the stellar structure of massive, quiescent galaxies at z~2,
based on Hubble Space Telescope/WFC3 imaging from the Early Release Science
program. Our sample of 14 galaxies has stellar masses of M* > 10^{10.8} Msol
and photometric redshifts of 1.5 < z < 2.5. In agreement with previous work,
their half-light radii are <2 kpc, much smaller than equally massive galaxies
in the present-day universe. A significant subset of the sample appears highly
flattened in projection, which implies, considering viewing angle statistics,
that a significant fraction of the galaxies in our sample have pronounced
disks. This is corroborated by two-dimensional surface brightness profile fits.
We estimate that 65% +/- 15% of the population of massive, quiescent z~2
galaxies are disk-dominated. The median disk scale length is 1.5 kpc,
substantially smaller than the disks of equally massive galaxies in the
present-day universe. Our results provide strong observational evidence that
the much-discussed ultra-dense high-redshift galaxies should generally be
thought of as disk-like stellar systems with the majority of stars formed from
gas that had time to settle into a disk.Comment: published versio
The Majority of Compact Massive Galaxies at z~2 are Disk Dominated
We investigate the stellar structure of massive, quiescent galaxies at z~2,
based on Hubble Space Telescope/WFC3 imaging from the Early Release Science
program. Our sample of 14 galaxies has stellar masses of M* > 10^{10.8} Msol
and photometric redshifts of 1.5 < z < 2.5. In agreement with previous work,
their half-light radii are <2 kpc, much smaller than equally massive galaxies
in the present-day universe. A significant subset of the sample appears highly
flattened in projection, which implies, considering viewing angle statistics,
that a significant fraction of the galaxies in our sample have pronounced
disks. This is corroborated by two-dimensional surface brightness profile fits.
We estimate that 65% +/- 15% of the population of massive, quiescent z~2
galaxies are disk-dominated. The median disk scale length is 1.5 kpc,
substantially smaller than the disks of equally massive galaxies in the
present-day universe. Our results provide strong observational evidence that
the much-discussed ultra-dense high-redshift galaxies should generally be
thought of as disk-like stellar systems with the majority of stars formed from
gas that had time to settle into a disk.Comment: published versio
What turns galaxies off? The different morphologies of star-forming and quiescent galaxies since z~2 from CANDELS
We use HST/WFC3 imaging from the CANDELS Multicycle Treasury Survey, in
conjunction with the Sloan Digital Sky Survey, to explore the evolution of
galactic structure for galaxies with stellar masses >3e10M_sun from z=2.2 to
the present epoch, a time span of 10Gyr. We explore the relationship between
rest-frame optical color, stellar mass, star formation activity and galaxy
structure. We confirm the dramatic increase from z=2.2 to the present day in
the number density of non-star-forming galaxies above 3e10M_sun reported by
others. We further find that the vast majority of these quiescent systems have
concentrated light profiles, as parametrized by the Sersic index, and the
population of concentrated galaxies grows similarly rapidly. We examine the
joint distribution of star formation activity, Sersic index, stellar mass,
inferred velocity dispersion, and stellar surface density. Quiescence
correlates poorly with stellar mass at all z<2.2. Quiescence correlates well
with Sersic index at all redshifts. Quiescence correlates well with `velocity
dispersion' and stellar surface density at z>1.3, and somewhat less well at
lower redshifts. Yet, there is significant scatter between quiescence and
galaxy structure: while the vast majority of quiescent galaxies have prominent
bulges, many of them have significant disks, and a number of bulge-dominated
galaxies have significant star formation. Noting the rarity of quiescent
galaxies without prominent bulges, we argue that a prominent bulge (and
perhaps, by association, a supermassive black hole) is an important condition
for quenching star formation on galactic scales over the last 10Gyr, in
qualitative agreement with the AGN feedback paradigm.Comment: The Astrophysical Journal, in press; 20 pages with 13 figure
Continuous flow analysis methods for sodium, magnesium and calcium detection in the Skytrain ice core
Dissolved and particulate sodium, magnesium and calcium are analyzed in ice cores to determine past changes in sea ice extent, terrestrial dust variability and atmospheric aerosol transport efficiency. They are also used to date ice cores if annual layers are visible. Multiple methods have been developed to analyze these important compounds in ice cores. Continuous flow analysis (CFA) is implemented with instruments that sample the meltstream continuously. In this study, CFA with ICP-MS (inductively coupled-plasma mass spectrometry) and fast ion chromatography (FIC) methods are compared for analysis of sodium and magnesium. ICP-MS, FIC and fluorescence methods are compared for analysis of calcium. Respective analysis of a 10 m section of the Antarctic WACSWAIN Skytrain Ice Rise ice core shows that all of the methods result in similar levels of the compounds. The ICP-MS method is the most suitable for analysis of the Skytrain ice core due to its superior precision (relative standard deviation: 1.6% for Na, 1.3% for Mg and 1.2% for Ca) and sampling frequency compared to the FIC method. The fluorescence detection method may be preferred for calcium analysis due to its higher depth resolution (1.4 cm) relative to the ICP-MS and FIC methods (~4 cm)
Childhood obesity prevention in general practice : supporting implementation through co-ideation
Background Childhood obesity is associated with physical and psychological complications thus the prevention of excess weight gain in childhood is an important health goal. Relevant to the prevention of childhood obesity, Australian general practice-specific, preventive care guidelines recommend General Practitioners (GPs) conduct growth monitoring and promote a number of healthy behaviours. However, challenges to providing preventive care in general practice may impact implementation. In October and November, 2022, a series of three workshops focusing on the prevention of childhood obesity were held with a group of Australian GPs and academics. The objective of the workshops was to determine practical ways that GPs can be supported to address barriers to the incorporation of obesity-related prevention activities into their clinical practice, for children with a healthy weight. Methods This paper describes workshop proceedings, specifically the outcomes of co-ideation activities that included idea generation, expansion of the ideas to possible interventions, and the preliminary assessment of these concepts. The ecological levels of the individual, interpersonal, and organisation were considered. Results Possible opportunities to support childhood obesity prevention were identified at multiple ecological levels within the clinic. The preliminary list of proposed interventions to facilitate action included GP education and training, clinical audit facilitation, readily accessible clinical guidelines with linked resources, a repository of resources, and provision of adequate growth monitoring tools in general practice. Conclusions Co-ideation with GPs resulted in a number of proposed interventions, informed by day-to-day practicalities, to support both guideline implementation and childhood obesity prevention in general practice
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