6,264 research outputs found
A VLA Survey For Faint Compact Radio Sources in the Orion Nebula Cluster
We present Karl G. Janksy Very Large Array (VLA) 1.3 cm, 3.6 cm, and 6 cm
continuum maps of compact radio sources in the Orion Nebular Cluster. We
mosaicked 34 square arcminutes at 1.3 cm, 70 square arcminutes at 3.6 cm and
109 square arcminutes at 6 cm, containing 778 near-infrared detected YSOs and
190 HST-identified proplyds (with significant overlap between those
characterizations). We detected radio emission from 175 compact radio sources
in the ONC, including 26 sources that were detected for the first time at these
wavelengths. For each detected source we fit a simple free-free and dust
emission model to characterize the radio emission. We extrapolate the free-free
emission spectrum model for each source to ALMA bands to illustrate how these
measurements could be used to correctly measure protoplanetary disk dust masses
from sub-millimeter flux measurements. Finally, we compare the fluxes measured
in this survey with previously measured fluxes for our targets, as well as four
separate epochs of 1.3 cm data, to search for and quantify variability of our
sources.Comment: 13 pages, 6 figures, 4 tables, ApJ, in pres
Hierarchical Modeling Techniques to Analyze Contextual Effects: What Happened to the Aptitude by Treatment Design?
This article contrasts two analytical methods for making cross-level inferences between individual-level factors and group-level factors in school-effectiveness research, the aptitude by treatment interaction design and hierarchical linear modeling. Although the aptitude by treatment interaction method is suitable for making cross-level inferences when the intraclass correlations are low, partitioning the interaction into within-and between-contexts components is recommended to discern if the interaction is due to confounding contextual effects
The fact and the fiction: A prospective study of internet forum discussions on vaginal breech birth
© 2016 Australian College of Midwives Background Women with a breech baby late in pregnancy may use the internet to gather information to assist in decision-making for birth. The aim of this study was to examine how women use English language internet discussion forums to find out information about vaginal breech birth and to increase understanding of how vaginal breech birth is perceived among women. Method A descriptive qualitative study of internet discussion forums was undertaken. Google alerts were created with the search terms âbreech birthâ and âbreechâ. Alerts were collected for a one-year period (January 2013âDecember 2013). The content of forum discussions was analysed using thematic analysis. Results A total of 50 forum discussions containing 382 comments were collected. Themes that arose from the data were: Testing the watersâwhich way should I go?; Losing hope for the chance of a normal birth; Seeking support for optionsâwho will listen to me?; Considering vaginal breech birthâa risky choice?; Staying on the âsafe sideââcaesarean section as a guarantee; Exploring the positive potential for vaginal breech birth. Conclusion Women search online for information about vaginal breech birth in an attempt to come to a place in their decision-making where they feel comfortable with their birth plan. This study highlights the need for clinicians to provide comprehensive, unbiased information on the risks and benefits of all options for breech birth to facilitate informed decision-making for the woman. This will contribute to improving the woman's confidence in distinguishing between âthe fact and the fictionâ of breech birth discussions online
Does Basic Skills Education Work? Some Evidence from the National Adult Literacy Survey
No Abstract available
Periodic Optical Variability of Radio Detected Ultracool Dwarfs
A fraction of very low mass stars and brown dwarfs are known to be radio
active, in some cases producing periodic pulses. Extensive studies of two such
objects have also revealed optical periodic variability and the nature of this
variability remains unclear. Here we report on multi-epoch optical photometric
monitoring of six radio detected dwarfs, spanning the M8 - L3.5 spectral
range, conducted to investigate the ubiquity of periodic optical variability in
radio detected ultracool dwarfs. This survey is the most sensitive ground-based
study carried out to date in search of periodic optical variability from
late-type dwarfs, where we obtained 250 hours of monitoring, delivering
photometric precision as low as 0.15%. Five of the six targets exhibit
clear periodicity, in all cases likely associated with the rotation period of
the dwarf, with a marginal detection found for the sixth. Our data points to a
likely association between radio and optical periodic variability in
late-M/early-L dwarfs, although the underlying physical cause of this
correlation remains unclear. In one case, we have multiple epochs of monitoring
of the archetype of pulsing radio dwarfs, the M9 TVLM 513-46546, spanning a
period of 5 years, which is sufficiently stable in phase to allow us to
establish a period of 1.95958 0.00005 hours. This phase stability may be
associated with a large-scale stable magnetic field, further strengthening the
correlation between radio activity and periodic optical variability. Finally,
we find a tentative spin-orbit alignment of one component of the very low mass
binary LP 349-25.Comment: Accepted to The Astrophysical Journal; 22 pages; 12 figure
The role of planets in shaping planetary nebulae
In 1997 Soker laid out a framework for understanding the formation and
shaping of planetary nebulae (PN). Starting from the assumption that
non-spherical PN cannot be formed by single stars, he linked PN morphologies to
the binary mechanisms that may have formed them, basing these connections
almost entirely on observational arguments. In light of the last decade of
discovery in the field of PN, we revise this framework, which, although
simplistic, can still serve as a benchmark against which to test theories of PN
origin and shaping. Within the framework, we revisit the role of planets in
shaping PN. Soker invoked a planetary role in shaping PN because there are not
enough close binaries to shape the large fraction of non-spherical PN. In this
paper we adopt a model whereby only ~20% of all 1-8 solar mass stars make a PN.
This reduces the need for planetary shaping. Through a propagation of
percentages argument, and starting from the assumption that planets can only
shape mildly elliptical PN, we conclude, like in Soker, that ~20% of all PN
were shaped via planetary and other substellar interactions but we add that
this corresponds to only ~5% of all 1-8 solar mass stars. This may be in line
with findings of planets around main sequence stars. PN shaping by planets is
made plausible by the recent discovery of planets that have survived
interactions with red giant branch (RGB) stars. Finally, we conclude that of
the ~80% of 1-8 solar mass stars that do not make a PN, about one quarter do
not even ascend the AGB due to interactions with stellar and substellar
companions, while three quarters ascend the AGB but do not make a PN. Once
these stars leave the AGB they evolve normally and can be confused with
post-RGB, extreme horizontal branch stars. We propose tests to identify them.Comment: 23 pages, accepted by PAS
Summary Judgment: Let the Movant Beware.
Abstract Forthcoming
How do social discourses of risk impact on womenâs choices for vaginal breech birth? A qualitative study of womenâs experiences
© 2016 Informa UK Limited, trading as Taylor & Francis Group. In this article, we aim to explore the impact of social discourses of risk around childbirth on the decisions made for birth by women who planned to have a breech baby late in pregnancy. This article uses data from a qualitative descriptive study in New South Wales, Australia in 2013. In the study, we talked to 22 women about their decision-making process for planned a vaginal breech birth and the impact of social discourses of risk on this decision. In total, 12 of these women had a vaginal birth and the other 10 had a Caesarean section. In this article, we note that the mothers talked about their option for birth in a social setting in which the dominant discourse focused on the riskiness of breech birth and the vulnerability of female bodies that required medical surveillance, supervision and intervention to ensure a safe birth. Thus, for these mothers their pregnancy was seen through the societal lens of risk and medicalisation, with surgical intervention through a Caesarean section seen by society as the optimum choice. Women could resist this dominant discourse but such resistance required both justification and action, for example, the women who wanted a vaginal birth often had to resist the pressure from their families to have a Caesarean section. We identified four related strands in womenâs talk about resisting the dominate discourse: acknowledgment that they would be considered irrational for wanting a vaginal birth; having confidence in and believing that their body could give birth vaginally; convincing significant others that a vaginal birth was possible and desirable and looking for sources of support, for example, from new online social networks
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