1,544 research outputs found
Is it time to ask whether facility based birth is safe for low risk women and their babies?
Despite evidence to the contrary, homebirth remains a controversial choice in maternity care, with strong opinions expressed by consumers, health providers and the media [1]. There is rarely any differentiation between the media reporting of adverse outcomes associated with freebirth or homebirth attended by registered health providers [2]. This can cause health services to resist consumer demand for system integrated homebirth [3]. Research shows that homebirth is as safe as hospital birth for women who are low risk and attended by professional midwives who, in turn, are well networked into a responsive health system [4]. It can be less safe for the baby when women with significant risk factors choose homebirth, or when they give birth without regulated health providers in attendance. When systems are overly restrictive and there is significant variation in guidance on homebirth [5], confusion and conflict inevitably arises amongst and between consumers, policy makers and health providers. Internationally, rates of homebirth attended by registered health professionals (usually a midwife) range from 13% in the Netherlands [6] to 0.3% in Australia [7]. In some countries, homebirth is deemed illegal and midwives are being prosecuted or jailed for supporting women who make this choice [8]
Characterizing the contaminating distance distribution for Bayesian supernova cosmology
Measurements of the equation of state of dark energy from surveys of
thousands of Type Ia Supernovae (SNe Ia) will be limited by spectroscopic
follow-up and must therefore rely on photometric identification, increasing the
chance that the sample is contaminated by Core Collapse Supernovae (CC SNe).
Bayesian methods for supernova cosmology can remove contamination bias while
maintaining high statistical precision but are sensitive to the choice of
parameterization of the contaminating distance distribution. We use simulations
to investigate the form of the contaminating distribution and its dependence on
the absolute magnitudes, light curve shapes, colors, extinction, and redshifts
of core collapse supernovae. We find that the CC luminosity function dominates
the distance distribution function, but its shape is increasingly distorted as
the redshift increases and more CC SNe fall below the survey magnitude limit.
The shapes and colors of the CC light curves generally shift the distance
distribution, and their effect on the CC distances is correlated. We compare
the simulated distances to the first year results of the SDSS-II SN survey and
find that the SDSS distance distributions can be reproduced with simulated CC
SNe that are ~1 mag fainter than the standard Richardson et al. (2002)
luminosity functions, which do not produce a good fit. To exploit the full
power of the Bayesian parameter estimation method, parameterization of the
contaminating distribution should be guided by the current knowledge of the CC
luminosity functions, coupled with the effects of the survey selection and
magnitude-limit, and allow for systematic shifts caused by the parameters of
the distance fit.Comment: 17 pages, 5 figures; accepted for publication in the Astrophysical
Journa
The Deepest Supernova Search is Realized in the Hubble Ultra Deep Field Survey
The Hubble Ultra Deep Field Survey has not only provided the deepest optical
and near infrared views of universe, but has enabled a search for the most
distant supernovae to z~2.2. We have found four supernovae by searching spans
of integrations of the Ultra Deep Field and the Ultra Deep Field Parallels
taken with the Hubble Space Telescope paired with the Advanced Camera for
Surveys and the Near Infrared Multi Object Spectrometer. Interestingly, none of
these supernovae were at z>1.4, despite the substantially increased sensitivity
per unit area to such objects over the Great Observatories Origins Deep Survey.
We present the optical photometric data for the four supernovae. We also show
that the low frequency of Type Ia supernovae observed at z>1.4 is statistically
consistent with current estimates of the global star formation history combined
with the non-trivial assembly time of SN Ia progenitors.Comment: 24 pages (6 figures), submitted to the Astronomical Journa
Cost analysis of the CTLB Study, a multitherapy antenatal education programme to reduce routine interventions in labour
Objective: To assess whether the multitherapy antenatal education ‘CTLB’ (Complementary Therapies for Labour and Birth) Study programme leads to net cost savings.
Design: Cost analysis of the CTLB Study, using analysis of outcomes and hospital funding data.
Methods: We take a payer perspective and use Australian Refined Diagnosis-Related Group (AR-DRG) cost data to estimate the potential savings per woman to the payer (government or private insurer). We consider scenarios in which the intervention cost is either borne by the woman or by the payer. Savings are computed as the difference in total cost between the control group and the study group.
Results: If the cost of the intervention is not borne by the payer, the average saving to the payer was calculated to be A659 since the average cost of delivering the programme was A659 to $A808 per woman. Compared with the average cost of birth in the control group, we conclude that the programme could lead to a reduction in birth-related healthcare costs of approximately 9%.
Trial registration number: ACTRN12611001126909
A Novel Approach to Recreational Reading: Creating a Virtual Collection on a Shoestring
Reading for recreation has been tied to academic achievement and lifelong learning, but not all academic libraries have the capacity to offer a separate recreational reading collection for their users. A low/no-cost option is to create a virtual recreational reading collection that allows patrons to browse for print titles by genre or book cover, much as they would in a bookstore or physical collection. The authors recently implemented this solution at their institution by dynamically compiling records of existing titles belonging to genres that are often of interest to recreational readers. This article addresses the justification for investing staff time in promoting recreational reading, discusses the technology employed to create and maintain a virtual collection, and shares the impacts of this effort on circulation
The Dwarf Starburst Host Galaxy of a Type Ia SN at z = 1.55 from CANDELS
We present VLT/X-shooter observations of a high redshift, type Ia supernova
host galaxy, discovered with HST/WFC3 as part of the CANDELS Supernova project.
The galaxy exhibits strong emission lines of Ly{\alpha}, [O II], H{\beta}, [O
III], and H{\alpha} at z = 1.54992(+0.00008-0.00004). From the emission-line
fluxes and SED fitting of broad-band photometry we rule out AGN activity and
characterize the host galaxy as a young, low mass, metal poor, starburst galaxy
with low intrinsic extinction and high Ly{\alpha} escape fraction. The host
galaxy stands out in terms of the star formation, stellar mass, and metallicity
compared to its lower redshift counterparts, mainly because of its high
specific star-formation rate. If valid for a larger sample of high-redshift SN
Ia host galaxies, such changes in the host galaxy properties with redshift are
of interest because of the potential impact on the use of SN Ia as standard
candles in cosmology.Comment: 25 pages, 8 figures. Accepted for publication in Ap
The Diffuse Supernova Neutrino Background is detectable in Super-Kamiokande
The Diffuse Supernova Neutrino Background (DSNB) provides an immediate
opportunity to study the emission of MeV thermal neutrinos from core-collapse
supernovae. The DSNB is a powerful probe of stellar and neutrino physics,
provided that the core-collapse rate is large enough and that its uncertainty
is small enough. To assess the important physics enabled by the DSNB, we start
with the cosmic star formation history of Hopkins & Beacom (2006) and confirm
its normalization and evolution by cross-checks with the supernova rate,
extragalactic background light, and stellar mass density. We find a sufficient
core-collapse rate with small uncertainties that translate into a variation of
+/- 40% in the DSNB event spectrum. Considering thermal neutrino spectra with
effective temperatures between 4-6 MeV, the predicted DSNB is within a factor
4-2 below the upper limit obtained by Super-Kamiokande in 2003. Furthermore,
detection prospects would be dramatically improved with a gadolinium-enhanced
Super-Kamiokande: the backgrounds would be significantly reduced, the fluxes
and uncertainties converge at the lower threshold energy, and the predicted
event rate is 1.2-5.6 events /yr in the energy range 10-26 MeV. These results
demonstrate the imminent detection of the DSNB by Super-Kamiokande and its
exciting prospects for studying stellar and neutrino physics.Comment: 14 pages, 5 figures, 4 tables, some added discussions, accepted for
publication in Physical Review
Synoptic Sky Surveys and the Diffuse Supernova Neutrino Background: Removing Astrophysical Uncertainties and Revealing Invisible Supernovae
The cumulative (anti)neutrino production from all core-collapse supernovae
within our cosmic horizon gives rise to the diffuse supernova neutrino
background (DSNB), which is on the verge of detectability. The observed flux
depends on supernova physics, but also on the cosmic history of supernova
explosions; currently, the cosmic supernova rate introduces a substantial
(+/-40%) uncertainty, largely through its absolute normalization. However, a
new class of wide-field, repeated-scan (synoptic) optical sky surveys is coming
online, and will map the sky in the time domain with unprecedented depth,
completeness, and dynamic range. We show that these surveys will obtain the
cosmic supernova rate by direct counting, in an unbiased way and with high
statistics, and thus will allow for precise predictions of the DSNB. Upcoming
sky surveys will substantially reduce the uncertainties in the DSNB source
history to an anticipated +/-5% that is dominated by systematics, so that the
observed high-energy flux thus will test supernova neutrino physics. The
portion of the universe (z < 1) accessible to upcoming sky surveys includes the
progenitors of a large fraction (~ 87%) of the expected 10-26 MeV DSNB event
rate. We show that precision determination of the (optically detected) cosmic
supernova history will also make the DSNB into a strong probe of an extra flux
of neutrinos from optically invisible supernovae, which may be unseen either
due to unexpected large dust obscuration in host galaxies, or because some
core-collapse events proceed directly to black hole formation and fail to give
an optical outburst.Comment: 11 pages, 6 figure
Empirical Delay Time Distributions of Type Ia Supernovae From The Extended GOODS/HST Supernova Survey
Using the Hubble Space Telescope ACS imaging of the GOODS North and South
fields during Cycles 11, 12, and 13, we derive empirical constraints on the
delay-time distribution function for type Ia supernovae. We extend our previous
analysis to the three-year sample of 56 SNe Ia over the range 0.2<z<1.8, using
a Markov chain Monte Carlo to determine the best-fit unimodal delay-time
distribution function. The test, which ultimately compares the star formation
rate density history to the unbinned volumetric SN Ia rate history from the
GOODS/HST-SN survey, reveals a SN Ia delay-time distribution that is tightly
confined to 3-4 Gyrs (to >95% confidence). This result is difficult to resolve
with any intrinsic delay-time distribution function (bimodal or otherwise), in
which a substantial fraction (e.g., >10%) of events are ``prompt'', requiring
less than approximately 1 Gyr to develop from formation to explosion. The
result is, however, strongly motivated by the decline in the number of SNe Ia
at z>1.2. Sub-samples of the HST-SN data confined to lower redshifts (z<1) show
plausible delay-time distributions that are dominated by prompt events, which
is more consistent with results from low-redshift supernova samples and
supernova host galaxy properties. Scenarios in which a substantial fraction of
z>1.2 supernovae are extraordinarily obscured by dust may partly explain the
differences in low-z and high-z results. Other possible resolutions may include
environmental dependencies (such as gas-phase metallicity) that affect the
progenitor mechanism efficiency, especially in the early universe.Comment: 12 pages, 9 figures, accepted to the Astrophysical Journa
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