1,625 research outputs found
Time management situation assessment (TMSA)
TMSA is a concept prototype developed to support NASA Test Directors (NTDs) in schedule execution monitoring during the later stages of a Shuttle countdown. The program detects qualitative and quantitative constraint violations in near real-time. The next version will support incremental rescheduling and reason over a substantially larger number of scheduled events
Time management displays for shuttle countdown
The Intelligent Launch Decision Support System project is developing a Time Management System (TMS) for the NASA Test Director (NTD) to use for time management during Shuttle terminal countdown. TMS is being developed in three phases: an information phase; a tool phase; and an advisor phase. The information phase is an integrated display (TMID) of firing room clocks, of graphic timelines with Ground Launch Sequencer events, and of constraints. The tool phase is a what-if spreadsheet (TMWI) for devising plans for resuming from unplanned hold situations. It is tied to information in TMID, propagates constraints forward and backward to complete unspecified values, and checks the plan against constraints. The advisor phase is a situation advisor (TMSA), which proactively suggests tactics. A concept prototype for TMSA is under development. The TMID is currently undergoing field testing. Displays for TMID and TMWI are described. Descriptions include organization, rationale for organization, implementation choices and constraints, and use by NTD
Large-scale annotated dataset for cochlear hair cell detection and classification
Our sense of hearing is mediated by cochlear hair cells, of which there are two types organized in one row of inner hair cells and three rows of outer hair cells. Each cochlea contains 5-15 thousand terminally differentiated hair cells, and their survival is essential for hearing as they do not regenerate after insult. It is often desirable in hearing research to quantify the number of hair cells within cochlear samples, in both pathological conditions, and in response to treatment. Machine learning can be used to automate the quantification process but requires a vast and diverse dataset for effective training. In this study, we present a large collection of annotated cochlear hair-cell datasets, labeled with commonly used hair-cell markers and imaged using various fluorescence microscopy techniques. The collection includes samples from mouse, rat, guinea pig, pig, primate, and human cochlear tissue, from normal conditions and following in-vivo and in-vitro ototoxic drug application. The dataset includes over 107,000 hair cells which have been identified and annotated as either inner or outer hair cells. This dataset is the result of a collaborative effort from multiple laboratories and has been carefully curated to represent a variety of imaging techniques. With suggested usage parameters and a well-described annotation procedure, this collection can facilitate the development of generalizable cochlear hair-cell detection models or serve as a starting point for fine-tuning models for other analysis tasks. By providing this dataset, we aim to give other hearing research groups the opportunity to develop their own tools with which to analyze cochlear imaging data more fully, accurately, and with greater ease
The properties of extragalactic radio sources selected at 20 GHz
We present some first results on the variability, polarization and general
properties of radio sources selected in a blind survey at 20 GHz, the highest
frequency at which a sensitive radio survey has been carried out over a large
area of sky. Sources with flux densities above 100 mJy in the AT20G Pilot
Survey at declination -60 to -70 were observed at up to three epochs during
2002-4, including near-simultaneous measurements at 5, 8 and 18 GHz in 2003. Of
the 173 sources detected, 65% are candidate QSOs, BL Lac objects or blazars,
20% galaxies and 15% faint (b > 22 mag) optical objects or blank fields.
On a 1-2 year timescale, the general level of variability at 20 GHz appears
to be low. For the 108 sources with good-quality measurements in both 2003 and
2004, the median variability index at 20 GHz was 6.9% and only five sources
varied by more than 30% in flux density.
Most sources in our sample show low levels of linear polarization (typically
1-5%), with a median fractional polarization of 2.3% at 20 GHz. There is a
trend for fainter sources to show higher fractional polarization.
At least 40% of sources selected at 20GHz have strong spectral curvature over
the frequency range 1-20 GHz. We use a radio `two-colour diagram' to
characterize the radio spectra of our sample, and confirm that the radio-source
population at 20 GHz (which is also the foreground point-source population for
CMB anisotropy experiments like WMAP and Planck) cannot be reliably predicted
by extrapolating the results of surveys at lower frequencies. As a result,
direct selection at 20 GHz appears to be a more efficient way of identifying 90
GHz phase calibrators for ALMA than the currently-proposed technique of
extrapolation from all-sky surveys at 1-5 GHz.Comment: 14-page paper plus 5-page data table. Replaced with published versio
A pilot feasibility study of daily rTMS to modify corticospinal excitability during lower limb immobilization
Short term immobilization of the lower limb is associated with increased corticospinal excitability at 24 hours post cast removal. We wondered whether daily stimulation of the motor cortex might decrease brain reorganization during casting. We tested the feasibility of this approach. Using transcranial magnetic stimulation (TMS), resting motor threshold and recruitment curves were obtained at baseline in 6 healthy participants who then had leg casts placed for 10 days. On 7 of the 10 days subjects received 20 minutes of 1 Hz repetitive TMS (rTMS). TMS measures were then recorded immediately after and 24 hours post cast removal. Four of 6 subjects completed the study. At the group level there were no changes in excitability following cast removal. At the individual level, two participants did not show any change, 1 participant had higher and one lower excitability 24 hours after cast removal. Daily rTMS over motor cortex is feasible during casting and may modify neuroplastic changes occurring during limb disuse. A prospective double blind study is warranted to test whether daily rTMS might improve outcome in subjects undergoing casting, and perhaps in other forms of limb disuse such as those following brain injury or weightlessness in space flight
The Australia Telescope 20GHz (AT20G) Survey: analysis of the extragalactic source sample
The Australia Telescope 20 GHz (AT20G) survey is a blind survey of the whole
Southern sky at 20 GHz with follow-up observations at 4.8, 8.6, and 20 GHz
carried out with the Australia Telescope Compact Array (ATCA). In this paper we
present an analysis of radio spectral properties in total intensity and
polarisation, sizes, optical identifications, and redshifts of the sample of
the 5808 extragalactic sources in the survey catalogue of confirmed sources
over the whole Southern sky excluding the strip at Galactic latitude
|b|<1.5deg. The sample has a flux density limit of 40 mJy. Completeness has
been measured as a function of scan region and flux density. Averaging over the
whole survey area the follow-up survey is 78% complete above 50mJy and 93%
complete above 100mJy. 3332 sources with declination <-15deg have good quality
almost simultaneous observations at 4.8, 8.6, and 20GHz. The spectral analysis
shows that the sample is dominated by flat-spectrum sources. The fraction of
flat-spectrum sources decreases from 81% for 20GHz flux densities S>500mJy, to
60% for S<100mJy. There is also a clear spectral steepening at higher
frequencies with the median spectral index decreasing from -0.16 between 4.8
and 8.6GHz to -0.28 between 8.6 and 20GHz. Simultaneous observations in
polarisation are available for all the sources at all the frequencies. 768
sources have a good quality detection of polarised flux density at 20GHz; 467
of them were also detected in polarisation at 4.8 and/or at 8.6GHz so that it
has been possible to compare the spectral behaviour in total intensity and
polarisation. We have found that the polarised fraction increases slightly with
frequency and decreases with flux density. Cross matches and comparisons have
been made with other catalogues at lower radio frequencies, and in the optical,
X-ray and gamma-ray bands. Redshift estimates are available for 825 sources.Comment: 15 pages, 16 figures, accepted for publication in MNRA
The Transit Light Curve Project. XII. Six Transits of the Exoplanet XO-2b
We present photometry of six transits of the exoplanet XO-2b. By combining
the light-curve analysis with theoretical isochrones to determine the stellar
properties, we find the planetary radius to be 0.996 +0.031/-0.018 rjup and the
planetary mass to be 0.565 +/- 0.054 mjup. These results are consistent with
those reported previously, and are also consistent with theoretical models for
gas giant planets. The mid-transit times are accurate to within 1 min and are
consistent with a constant period. However, the period we derive differs by 2.5
sigma from the previously published period. More data are needed to tell
whether the period is actually variable (as it would be in the presence of an
additional body) or if the timing errors have been underestimated.Comment: Accepted for publication in AJ. 20 pages, 3 tables, 4 figure
The Australia Telescope 20 GHz Survey: The Source Catalogue
We present the full source catalogue from the Australia Telescope 20 GHz
(AT20G) Survey. The AT20G is a blind radio survey carried out at 20 GHz with
the Australia Telescope Compact Array (ATCA) from 2004 to 2008, and covers the
whole sky south of declination 0 deg. The AT20G source catalogue presented here
is an order of magnitude larger than any previous catalogue of high-frequency
radio sources, and includes 5890 sources above a 20 GHz flux-density limit of
40 mJy. All AT20G sources have total intensity and polarisation measured at 20
GHz, and most sources south of declination -15 deg also have near-simultaneous
flux-density measurements at 5 and 8 GHz. A total of 1559 sources were detected
in polarised total intensity at one or more of the three frequencies. We detect
a small but significant population of non-thermal sources that are either
undetected or have only weak detections in low-frequency catalogues. We
introduce the term Ultra-Inverted Spectrum (UIS) to describe these radio
sources, which have a spectral index alpha(5, 20) > +0.7 and which constitute
roughly 1.2 per cent of the AT20G sample. The 20 GHz flux densities measured
for the strongest AT20G sources are in excellent agreement with the WMAP 5-year
source catalogue of Wright et al. (2009), and we find that the WMAP source
catalogue is close to complete for sources stronger than 1.5 Jy at 23 GHz.Comment: 21 pages, accepted for publication in MNRA
The Australia Telescope 20 GHz (AT20G) Survey: The Bright Source Sample
The Australia Telescope 20 GHz (AT20G) Survey is a blind survey of the whole
Southern sky at 20 GHz (with follow-up observations at 4.8 and 8.6 GHz) carried
out with the Australia Telescope Compact Array (ATCA) from 2004 to 2007. The
Bright Source Sample (BSS) is a complete flux-limited subsample of the AT20G
Survey catalogue comprising 320 extragalactic (|b|>1.5 deg) radio sources south
of dec = -15 deg with S(20 GHz) > 0.50 Jy. Of these, 218 have near simultaneous
observations at 8 and 5 GHz. In this paper we present an analysis of radio
spectral properties in total intensity and polarisation, size, optical
identifications and redshift distribution of the BSS sources. The analysis of
the spectral behaviour shows spectral curvature in most sources with spectral
steepening that increases at higher frequencies (the median spectral index
\alpha, assuming S\propto \nu^\alpha, decreases from \alpha_{4.8}^{8.6}=0.11
between 4.8 and 8.6 GHz to \alpha_{8.6}^{20}=-0.16 between 8.6 and 20 GHz),
even if the sample is dominated by flat spectra sources (85 per cent of the
sample has \alpha_{8.6}^{20}>-0.5). The almost simultaneous spectra in total
intensity and polarisation allowed us a comparison of the polarised and total
intensity spectra: polarised fraction slightly increases with frequency, but
the shapes of the spectra have little correlation. Optical identifications
provided an estimation of redshift for 186 sources with a median value of 1.20
and 0.13 respectively for QSO and galaxies.Comment: 34 pages, 19 figures, tables of data included, replaced with version
published in MNRA
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