1,065 research outputs found
Radio-continuum detections of Galactic Planetary Nebulae I. MASH PNe detected in large-scale radio surveys
We present an updated and newly compiled radio-continuum data-base for MASH
PNe detected in the extant large scale "blind" radio-continuum surveys (NVSS,
SUMSS/MGPS-2 and PMN) and, for a small number of MASH PNe, observed and
detected in targeted radio-continuum observations. We found radio counterparts
for approximately 250 MASH PNe. In comparison with the percentage of previously
known Galactic PNe detected in the NVSS and MGPS-2 radio-continuum surveys and
according to their position on the flux density-angular diameter and the radio
brightness temperature evolutionary diagrams we conclude, unsurprisingly, that
the MASH sample presents the radio-faint end of the known Galactic PNe
population. Also, we present radio-continuum spectral properties of a small
sub-sample of MASH PNe located in the strip between declinations -30arcdeg and
-40arcdeg, that are detected in both the NVSS and MGPS-2 radio surveys.Comment: 13 figures and 7 tables, accepted for publication in MNRA
The Role of Functional, Social, and Mobility Dynamics in Facilitating Older African Americans Participation in Clinical Research
Purpose: Older African Americans experience disproportionately higher incidence of morbidity and mortality related to chronic and infectious diseases, yet are significantly underrepresented in clinical research compared to other racial and ethnic groups. This study aimed to understand the extent to which social support, transportation access, and physical impediments function as barriers or facilitators to clinical trial recruitment of older African Americans. Methods: Participants (N=221) were recruited from six African American churches in Atlanta and surveyed on various influences on clinical trial participation
The planetary nebula Abell 48 and its [WN4] central star
We have conducted a multi-wavelength study of the planetary nebula Abell 48
and give a revised classification of its nucleus as a hydrogen-deficient star
of type [WN4]. The surrounding nebula has a morphology typical of PNe and
importantly, is not enriched in nitrogen, and thus not the 'peeled atmosphere'
of a massive star. Indeed, no WN4 star is known to be surrounded by such a
compact nebula. The ionized mass of the nebula is also a powerful discriminant
between the low-mass PN and high-mass WR ejecta interpretations. The ionized
mass would be impossibly high if a distance corresponding to a Pop I star was
adopted, but at a distance of 2 kpc, the mass is quite typical of moderately
evolved PNe. At this distance, the ionizing star then has a luminosity of ~5000
Lsolar, again rather typical for a PN central star. We give a brief discussion
of the implications of this discovery for the late-stage evolution of
intermediate-mass stars.Comment: EUROWD12 Proceeding
Flux calibration of the AAO/UKST SuperCOSMOS H-alpha Survey
The AAO/UKST SuperCOSMOS H Survey (SHS) was, when completed in 2003,
a powerful addition to extant wide-field surveys. The combination of areal
coverage, spatial resolution and sensitivity in a narrow imaging band, still
marks it out today as an excellent resource for the astronomical community. The
233 separate fields are available online in digital form, with each field
covering 25 square degrees. The SHS has been the motivation for equivalent
surveys in the north, and new digital H surveys now beginning in the
south such as VPHAS+. It has been the foundation of many important discovery
projects with the Macquarie/AAO/Strasbourg H planetary nebula project
being a particularly successful example. However, the full potential of the SHS
has been hampered by lack of a clear route to acceptable flux calibration from
the base photographic data. We have determined the calibration factors for 170
individual SHS fields, and present a direct pathway to the measurement of
integrated H fluxes and surface brightnesses for resolved nebulae
detected in the SHS. We also include a catalogue of integrated H fluxes
for 100 planetary and other nebulae measured from the SHS, and use these
data to show that fluxes, accurate to 0.10 - 0.14 dex (25-35 per
cent), can be obtained from these fields. For the remaining 63 fields, a mean
calibration factor of 12.0 counts pix R can be used, allowing the
determination of reasonable integrated fluxes accurate to better than 0.2
dex (50 per cent). We outline the procedures involved and the caveats
that need to be appreciated in achieving such flux measurements. This paper
forms a handy reference source that will significantly increase the scientific
utility of the SHS.Comment: 14 pages, 12 figures, 2 tables (plus 7 pp. of supplementary online
information). Version to appear in MNRA
The planetary nebula Abell 48 and its [WN] nucleus
We have conducted a detailed multi-wavelength study of the peculiar nebula
Abell 48 and its central star. We classify the nucleus as a helium-rich,
hydrogen-deficient star of type [WN4-5]. The evidence for either a massive WN
or a low-mass [WN] interpretation is critically examined, and we firmly
conclude that Abell 48 is a planetary nebula (PN) around an evolved low-mass
star, rather than a Population I ejecta nebula. Importantly, the surrounding
nebula has a morphology typical of PNe, and is not enriched in nitrogen, and
thus not the `peeled atmosphere' of a massive star. We estimate a distance of
1.6 kpc and a reddening, E(B-V) = 1.90 mag, the latter value clearly showing
the nebula lies on the near side of the Galactic bar, and cannot be a massive
WN star. The ionized mass (~0.3 M_Sun) and electron density (700 cm^-3) are
typical of middle-aged PNe. The observed stellar spectrum was compared to a
grid of models from the Potsdam Wolf-Rayet (PoWR) grid. The best fit
temperature is 71 kK, and the atmospheric composition is dominated by helium
with an upper limit on the hydrogen abundance of 10 per cent. Our results are
in very good agreement with the recent study of Todt et al., who determined a
hydrogen fraction of 10 per cent and an unusually large nitrogen fraction of ~5
per cent. This fraction is higher than any other low-mass H-deficient star, and
is not readily explained by current post-AGB models. We give a discussion of
the implications of this discovery for the late-stage evolution of
intermediate-mass stars. There is now tentative evidence for two distinct
helium-dominated post-AGB lineages, separate to the helium and carbon dominated
surface compositions produced by a late thermal pulse. Further theoretical work
is needed to explain these recent discoveries.Comment: 19 pages, 10 figures, to appear in MNRAS. Version 3 incorporates
proof correction
Haplotype analysis of the PPARgamma Pro12Ala and C1431T variants reveals opposing associations with body weight.
BACKGROUND: Variation at the PPARG locus may influence susceptibility to type 2 diabetes and related traits. The Pro12Ala polymorphism may modulate receptor activity and is associated with protection from type 2 diabetes. However, there have been inconsistent reports of its association with obesity. The silent C1431T polymorphism has not been as extensively studied, but the rare T allele has also been inconsistently linked to increases in weight. Both rare alleles are in linkage disequilibrium and the independent associations of these two polymorphisms have not been addressed. RESULTS: We have genotyped a large population with type 2 diabetes (n = 1107), two populations of non-diabetics from Glasgow (n = 186) and Dundee (n = 254) and also a healthy group undergoing physical training (n = 148) and investigated the association of genotype with body mass index. This analysis has demonstrated that the Ala12 and T1431 alleles are present together in approximately 70% of the carriers. By considering the other 30% of individuals with haplotypes that only carry one of these polymorphisms, we have demonstrated that the Ala12 allele is consistently associated with a lower BMI, whilst the T1431 allele is consistently associated with higher BMI. CONCLUSION: This study has therefore revealed an opposing interaction of these polymorphisms, which may help to explain previous inconsistencies in the association of PPARG polymorphisms and body weight
Confirmation of G6.31+0.54 as a part of a Galactic supernova remnant
A combination of archival multi-frequency radio observations with narrow-band
HAlpha optical imagery and new confirmatory optical spectroscopy have shown
that candidate supernova remnant G6.31+0.54 can now be confirmed as part of a
Galactic supernova remnant (SNR). It has non-thermal emission, an optical
emission line spectrum displaying shock excitation and standard SNR line
ratios, fine filamentary structures in HAlpha typical of optical remnants and
closely overlapping radio and optical footprints. An X-ray ROSAT source 1RXS
J175752.1-231105 was also found that matches the radio and optical emission
though a definite association is not proven. Nevertheless, taken together, all
these observed properties point to a clear SNR identification for this source.
We provide a rough estimate for the kinematic distance to G6.31+0.54 of
~4.5kpc. The detected optical filaments are some ~10arcminutes in extent (or
about 13 pc at the assumed distance). However, as only a partial arcuate
structure of the SNR can be seen (and not a full shell) the full angular extent
of the SNR is unclear. Hence the physical extent of the observed partial shell
is also difficult to estimate. If we assume an approximately circular shell
then a conservative fit to the optical arc shaped filaments gives an angular
diameter of ~20 arcminutes corresponding to a physical diameter of ~26 pc that
shows this to be an evolved remnant.Comment: Accepted for publishing in MNRAS 8 pages, 8 figure
Provider Insight on Surmounting Specialty Practice Challenges to Improve Tdap Immunization Rates among Pregnant Women
Background Pertussis, or “whooping cough,” is an acute, contagious pulmonary disease that, despite being vaccine-preventable, has become an increasingly widespread problem in the United States. As a result, the Advisory Committee on Immunization Practices and American College of Obstetricians and Gynecologists updated recommendations stating clinicians should give a Tdap dose during every pregnancy, preferably at 27–36 weeks. Despite this recommendation, reported Tdap vaccine receipt rates during pregnancy vary from 16–61%, and previous studies have shown that clinician recommendation and vaccine administration are strongly associated with vaccine uptake among pregnant women. Methods Our aim was to inform new strategies to increase uptake of the Tdap vaccine among pregnant women and, ultimately, reduce pertussis-related morbidityand mortality in infants. We conducted interviewswith a sample of 24 ob-gyns. We subsequently performed grounded theory analyses of transcripts using deductive and inductive coding strategies followed by intercoder reliability assessment. Results All physicians interviewed were familiar with the most recent recommendation of giving the Tdap vaccine during the third trimester of every pregnancy, and the majority of physicians stated that they felt that the vaccine was important and effective due to the transfer of pertussis antibodies from the mother to the fetus. Most physicians indicated that they recommended the vaccine to patients during pregnancy, but not all reported administering it on site because it was not stocked at their practice. Implementation challenges for physicians included insurance reimbursement and other challenges (i.e., patient refusal). Tdap vaccinationduring pregnancy was a lower clinical priority for some physicians. Physicians recognized the benefits associated with Tdap vaccination during pregnancy. Conclusions Findings indicate while most ob-gyns recognize the benefits of Tdap and recommend vaccination during pregnancy, barriers such as insurance reimbursement and financial concerns for the practice can outweigh the perceived benefits. This resulted in some ob-gyns reporting choosing not to stock and administer the vaccine in their practice. Recommendations to address these concerns include 1) structural support for Tdap vaccine administration in ob-gyns practices; 2) Continuing medical education-equivalent educational interventions that address management techniques, vaccine coding, and other relevant information; and 3) interventions to assist physicians in communicating the importance of Tdap vaccination during pregnancy
AAOmega radial velocities rule out current membership of the planetary nebula NGC 2438 in the open cluster M46
We present new radial velocity measurements of 586 stars in a one-degree
field centered on the open cluster M46, and the planetary nebula NGC 2438
located within a nuclear radius of the cluster. The data are based on
medium-resolution optical and near-infrared spectra taken with the AAOmega
spectrograph on the Anglo-Australian Telescope. We find a velocity difference
of about 30 km/s between the cluster and the nebula, thus removing all
ambiguities about the cluster membership of the planetary nebula caused by
contradicting results in the literature. The line-of-sight velocity dispersion
of the cluster is 3.9+/-0.3 km/s, likely to be affected by a significant
population of binary stars.Comment: 6 pages + 5 figures, accepted for publication in MNRA
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