181 research outputs found
Reliability of measuring abductor hallucis muscle parameters using two different diagnostic ultrasound machines
<p>Abstract</p> <p>Background</p> <p>Diagnostic ultrasound provides a method of analysing soft tissue structures of the musculoskeletal system effectively and reliably. The aim of this study was to evaluate within and between session reliability of measuring muscle dorso-plantar thickness, medio-lateral length and cross-sectional area, of the abductor hallucis muscle using two different ultrasound machines, a higher end Philips HD11 Ultrasound machine and clinically orientated Chison 8300 Deluxe Digital Portable Ultrasound System.</p> <p>Methods</p> <p>The abductor hallucis muscle of both the left and right feet of thirty asymptomatic participants was imaged and then measured using both ultrasound machines. Interclass correlation coefficients (ICC) with 95% confidence intervals (CI) were used to calculate both within and between session intra-tester reliability. Standard error of the measurement (SEM) calculations were undertaken to assess difference between the actual measured score across trials and the smallest real difference (SRD) was calculated from the SEM to indicate the degree of change that would exceed the expected trial to trial variability.</p> <p>Results</p> <p>The ICCs, SEM and SRD for dorso-plantar thickness and medial-lateral length were shown to have excellent to high within and between-session reliability for both ultrasound machines. The between-session reliability indices for cross-sectional area were acceptable for both ultrasound machines.</p> <p>Conclusion</p> <p>The results of the current study suggest that regardless of the type ultrasound machine, intra-tester reliability for the measurement the abductor hallucis muscle parameters is very high.</p
Optimized Photometric Redshifts for the Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey (CANDELS)
We present the first comprehensive release of photometric redshifts
(photo-z's) from the Cosmic Assembly Near-Infrared Deep Extragalactic Legacy
Survey (CANDELS) team. We use statistics based upon the Quantile-Quantile
(Q--Q) plot to identify biases and signatures of underestimated or
overestimated errors in photo-z probability density functions (PDFs) produced
by six groups in the collaboration; correcting for these effects makes the
resulting PDFs better match the statistical definition of a PDF. After
correcting each group's PDF, we explore three methods of combining the
different groups' PDFs for a given object into a consensus curve. Two of these
methods are based on identifying the minimum f-divergence curve, i.e., the PDF
that is closest in aggregate to the other PDFs in a set (analogous to the
median of an array of numbers). We demonstrate that these techniques yield
improved results using sets of spectroscopic redshifts independent of those
used to optimize PDF modifications. The best photo-z PDFs and point estimates
are achieved with the minimum f-divergence using the best 4 PDFs for each
object (mFDa4) and the Hierarchical Bayesian (HB4) methods, respectively. The
HB4 photo-z point estimates produced and
outlier fraction = 0.067/0.019 for spectroscopic and
3D-HST redshifts, respectively. Finally, we describe the structure and provide
guidance for the use of the CANDELS photo-z catalogs, which are available at
https://archive.stsci.edu/hlsp/candels.Comment: 35 pages, 19 figures, submitted to ApJ, data available at
https://archive.stsci.edu/hlsp/candel
Investigating the Effect of Galaxy Interactions on Star Formation at 0.5<z<3.0
Observations and simulations of interacting galaxies and mergers in the local
universe have shown that interactions can significantly enhance the star
formation rates (SFR) and fueling of Active Galactic Nuclei (AGN). However, at
higher redshift, some simulations suggest that the level of star formation
enhancement induced by interactions is lower due to the higher gas fractions
and already increased SFRs in these galaxies. To test this, we measure the SFR
enhancement in a total of 2351 (1327) massive () major
() spectroscopic galaxy pairs at 0.5<z<3.0 with
km s (1000 km s) and projected separation <150 kpc selected from
the extensive spectroscopic coverage in the COSMOS and CANDELS fields. We find
that the highest level of SFR enhancement is a factor of 1.23
in the closest projected separation bin (<25 kpc) relative to a stellar mass-,
redshift-, and environment-matched control sample of isolated galaxies. We find
that the level of SFR enhancement is a factor of higher at 0.5<z<1
than at 1<z<3 in the closest projected separation bin. Among a sample of
visually identified mergers, we find an enhancement of a factor of
1.86 for coalesced systems. For this visually identified
sample, we see a clear trend of increased SFR enhancement with decreasing
projected separation (2.40 vs.\ 1.58 for
0.5<z<1.6 and 1.6<z<3.0, respectively). The SFR enhancement seen in our
interactions and mergers are all lower than the level seen in local samples at
the same separation, suggesting that the level of interaction-induced star
formation evolves significantly over this time period.Comment: 23 pages, 13 figures, Accepted for publication in Ap
Ultrasound evaluation of the abductor hallucis muscle: Reliability study
© 2008 Cameron et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens
A spatially resolved analysis of star-formation burstiness by comparing UV and H in galaxies at z1 with UVCANDELS
The UltraViolet imaging of the Cosmic Assembly Near-infrared Deep
Extragalactic Legacy Survey Fields (UVCANDELS) program provides HST/UVIS F275W
imaging for four CANDELS fields. We combine this UV imaging with existing
HST/near-IR grism spectroscopy from 3D-HST+AGHAST to directly compare the
resolved rest-frame UV and H emission for a sample of 979 galaxies at
spanning a range in stellar mass of . Since
both rest-UV and H are sensitive to on-going star-formation but over
different timescales, their resolved comparison allows us to infer the
burstiness in star-formation as a function of galaxy structural parameters. We
generate homogenized maps of rest-UV and H emission for all galaxies in
our sample and stack them to compute the average UV-to-H luminosity
ratio as a function of galactocentric radius. We find that galaxies below
stellar mass of , at all radii, have a UV-to-H
ratio higher than the equilibrium value expected from constant star-formation,
indicating a significant contribution from bursty star-formation. Even for
galaxies with stellar mass , the UV-to-H ratio
is elevated towards in their outskirts (), suggesting that
bursty star-formation is likely prevalent in the outskirts of even the most
massive galaxies but is likely over-shadowed by their brighter cores.
Furthermore, we present the UV-to-H ratio as a function of galaxy
surface brightness, a proxy for stellar mass surface density, and find that
regions below are consistent with bursty
star-formation, regardless of their galaxy stellar mass, potentially suggesting
that local star-formation is independent of global galaxy properties at the
smallest scales.Comment: 19 pages, 8 figures; submitted to Ap
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