890 research outputs found
All-Sky spectrally matched UBVRI-ZY and u'g'r'i'z' magnitudes for stars in the Tycho2 catalog
We present fitted UBVRI-ZY and u'g'r'i'z' magnitudes, spectral types and
distances for 2.4M stars, derived from synthetic photometry of a library
spectrum that best matches the Tycho2 BtVt, NOMAD Rn and 2MASS JHK_{2/S}
catalog magnitudes. We present similarly synthesized multi-filter magnitudes,
types and distances for 4.8M stars with 2MASS and SDSS photometry to g<16
within the Sloan survey region, for Landolt and Sloan primary standards, and
for Sloan Northern (PT) and Southern secondary standards.
The synthetic magnitude zeropoints for BtVt, UBVRI, ZvYv, JHK_{2/S},
JHK_{MKO}, Stromgren uvby, Sloan u'g'r'i'z' and ugriz are calibrated on 20
calspec spectrophotometric standards. The UBVRI and ugriz zeropoints have
dispersions of 1--3%, for standards covering a range of color from -0.3 < V-I <
4.6; those for other filters are in the range 2--5%.
The spectrally matched fits to Tycho2 stars provide estimated 1-sigma errors
per star of ~0.2, 0.15, 0.12, 0.10 and 0.08 mags respectively in either UBVRI
or u'g'r'i'z'; those for at least 70% of the SDSS survey region to g<16 have
estimated 1-sigma errors per star of ~0.2, 0.06, 0.04, 0.04, 0.05 in u'g'r'i'z'
or UBVRI.
The density of Tycho2 stars, averaging about 60 stars per square degree,
provides sufficient stars to enable automatic flux calibrations for most
digital images with fields of view of 0.5 degree or more. Using several such
standards per field, automatic flux calibration can be achieved to a few
percent in any filter, at any airmass, in most workable observing conditions,
to facilitate inter-comparison of data from different sites, telescopes and
instruments.Comment: 36 pages, 30 figures, 3 printed tables, several electronic tables,
accepted PASP Dec 201
Fundamental Properties of O-Type Stars
We present a comprehensive analysis of high-resolution, far-UV HST/STIS,
FUSE, and optical spectra of 17 O stars in the SMC. Our analysis is based on
NLTE metal line-blanketed model atmospheres calculated with our NLTE code
TLUSTY. We systematically explore the sensitivity of various UV and optical
lines to different stellar parameters. We have obtained consistent fits of the
UV and the optical spectrum to derive the effective temperature, surface
gravity, surface composition, and microturbulent velocity of each star. Stellar
radii, masses, luminosities and ages then follow. Similarly to more limited
recent studies, we derive cooler temperatures than the standard Teff
calibration of O stars. We propose a new calibration between the spectral type
and effective temperature based on our results from UV metal lines as well as
optical hydrogen and helium lines. For stars of the same spectral subtype, we
find a general good agreement between Teff determinations obtained with TLUSTY,
CMFGEN, and FASTWIND models. We derive ionizing luminosities that are smaller
by a factor of 3 compared to luminosities inferred from previous standard
calibrations. The chemical composition analysis reveals that the surface of
about 3/4 of the program stars is moderately to strongly enriched in nitrogen,
while showing the original helium, carbon, and oxygen abundances. Our results
support the new stellar evolution models that predict that the surface of fast
rotating stars becomes N-rich during the main sequence phase because of
rotationally-induced mixing. Most stars exhibit the ``mass discrepancy''
problem. This discrepancy too is a result of fast rotation which lowers the
measured effective gravity. Our study thus emphasizes the importance of
rotation in our understanding of the properties of massive stars. (abridged)Comment: Submitted to Astrophysical Journal; 69 page
Land resource survey of Rottnest Island - an aid to land use planning
This report provides a description of the landforms, soils and vegetation of Rottnest Island. In addition, it provides a discussion of the relative capability of each of the landforms of the island to sustain various forms of development. The primary objective of this work is to direct development into areas of high capability (low risk of land degradation) in preference to areas of lower capability (higher risk of land degradation).
Rottnest Island is located approximately 30 km west of Perth. The proximity of the island to the capital city of Western Australia, its warm Mediterranean climate and the subsequent likelihood of further development, mean that there will be increasing pressure on the natural resources of the island. This report details the nature and inherent stability of those natural resources, and provides a guide for their management.https://researchlibrary.agric.wa.gov.au/bulletins/1062/thumbnail.jp
What makes for prize-winning television?
We investigate the determinants of success in four international television awards festivals between 1994 and 2012. We find that countries with larger markets and greater expenditure on public broadcasting tend to win more awards, but that the degree of concentration in the market for television and rates of penetration of pay-per-view television are unrelated to success. These findings are consistent with general industrial organisation literature on quality and market size, and with media policy literature on public service broadcasting acting as a force for quality. However, we also find that âhome countriesâ enjoy a strong advantage in these festivals, which is not consistent with festival success acting as a pure proxy for television quality
Paraphrases and summaries: A means of clarification or a vehicle for articulating a preferred version of student accounts?
The use of group discussions as a means to facilitate learning from experiences is well documented in adventure education literature. Priest and Naismith (1993) assert that the use of the circular discussion method, where the leader poses questions to the participants, is the most common form of facilitation in adventure education. This paper draws on transcripts of facilitation sessions to argue that the widely advocated practice of leader summaries or paraphrases of student responses in these sessions functions as a potential mechanism to control and sponsor particular knowledge(s). Using transcripts from recorded facilitation sessions the analysis focuses on how the leader paraphrases the studentsâ responses and how these paraphrases or âformulationsâ function to modify or exclude particular aspects of the studentsâ responses. I assert that paraphrasing is not simply a neutral activity that merely functions to clarify a student response, it is a subtle means by which the leader of the session can, often inadvertently or unknowingly, alter the studentâs reply with the consequence of favouring particular knowledge(s). Revealing the subtle work that leader paraphrases perform is of importance for educators who claim to provide genuine opportunities for students to learn from their experience
Fracture and damage localization in volcanic edifice rocks from El Hierro, Stromboli and Tenerife
© 2018 The Author(s). We present elastic wave velocity and strength data from a suite of three volcanic rocks taken from the volcanic edifices of El Hierro and Tenerife (Canary Islands, Spain), and Stromboli (Aeolian Islands, Italy). These rocks span a range of porosity and are taken from volcanoes that suffer from edifice instability. We measure elastic wave velocities at known incident angles to the generated through-going fault as a function of imposed strain, and examine the effect of the damage zone on P-wave velocity. Such data are important as field measurements of elastic wave tomography are key tools for understanding volcanic regions, yet hidden fractures are likely to have a significant effect on elastic wave velocity. We then use elastic wave velocity evolution to calculate concomitant crack density evolution which ranges from 0 to 0.17: highest values were correlated to the damage zone in rocks with the highest initial porosity
Terminal velocities of luminous, early-type SMC stars
Ultraviolet spectra from the Space Telescope Imaging Spectrograph (STIS) are
used to determine terminal velocities for 11 O and B-type giants and
supergiants in the Small Magellanic Cloud (SMC) from the Si IV and C IV
resonance lines. Using archival data from observations with the Goddard
High-Resolution Spectrograph and the International Ultraviolet Explorer
telescope, terminal velocities are obtained for a further five B-type
supergiants. We discuss the metallicity dependence of stellar terminal
velocities, finding no evidence for a significant scaling between Galactic and
SMC metallicities for Teff < 30,000 K, consistent with the predictions of
radiation driven wind theory for supergiant stars. A comparison of the
ratio between the SMC and Galactic samples, while
consistent with the above statement, emphasizes that the uncertainties in the
distances to galactic O-stars are a serious obstacle to a detailed comparison
with theory. For the SMC sample there is considerable scatter in this ratio at
a given effective temperature, perhaps indicative of uncertainties in stellar
masses.Comment: 28 pages, 8 figures, accepted by ApJ; minor revisions prior to
acceptanc
The 1.2 Millimeter Image of the beta Pictoris Disk
We present millimeter imaging observations in the 1200 micron continuum of
the disk around beta Pictoris. With the 25 arcsec beam, the beta Pic disk is
unresolved perpendicularly to the disk plane (< 10 arcsec), but slightly
resolved in the northeast-southwest direction (26 arcsec). Peak emission is
observed at the stellar position. A secondary maximum is found 1000 AU along
the disk plane in the southwest, which does not positionally coincide with a
similar feature reported earlier at 850 micron. Arguments are presented which
could be seen in support of the reality of these features. The observed
submm/mm emission is consistent with thermal emission from dust grains, which
are significantly larger than those generally found in the interstellar medium,
including mm-size particles, and thus more reminiscent of the dust observed in
protostellar disks. Modelling the observed scattered light in the visible and
the emission in the submm/mm provides evidence for the particles dominating the
scattering in the visible/NIR and those primarily responsible for the thermal
emission at longer wavelengths belonging to different populations.Comment: 6 pages, 3 postscript figures, accepted for publication in Astronomy
and Astrophysic
Descriptive analysis of a 1:1 physiotherapy outpatient intervention post primary lumbar discectomy: One arm of a small-scale parallel randomised controlled trial across two UK sites
Objective: There is a lack of high-quality evidence for physiotherapy post lumbar discectomy. Substantial heterogeneity in treatment effects may be explained by variation in quality, administration and components of interventions. An optimised physiotherapy intervention may reduce heterogeneity and improve patient benefit. The objective was to describe, analyse and evaluate an optimised 1:1 physiotherapy outpatient intervention for patients following primary lumbar discectomy, to provide preliminary insights. Design: A descriptive analysis of the intervention embedded within an external pilot and feasibility trial. Setting: Two UK spinal centres. Participants: Participants aged .18; post primary, single level, lumbar discectomy were recruited. Intervention: The intervention encompassed education, advice, mobility and core stability exercises, progressive exercise, and encouragement of early return to work/activity. Patients received .8 sessions for .8 weeks, starting 4 weeks post surgery (baseline). Outcomes: Blinded outcome assessment at baseline and 12 weeks ( post intervention) included the Roland Morris Disability Questionnaire. STarT Back data were collected at baseline. Statistical analyses summarised participant characteristics and preplanned descriptive analyses. Thematic analysis grouped related data. Findings: Twenty-two of 29 allocated participants received the intervention. STarT Back categorised n=16 (55%) participants 'enot at low risk'f. Physiotherapists identified reasons for caution for 8 (36%) participants, commonly risk of overdoing activity (n=4, 18%). There was no relationship between STarT Back and physiotherapists'f evaluation of caution. Physiotherapists identified 154 problems (mean (SD) 5.36 (2.63)). Those 'enot at low risk'f, and/or requiring caution presented with more problems, and required more sessions (mean (SD) 3.14 (1.16)). Conclusions: Patients present differently and therefore require tailored interventions. These differences may be identified using clinical reasoning and outcome data. Trial registration number: ISRCTN33808269; post results
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