363 research outputs found
Convergence Stability of Depth-Depth-Matching-Based Steepest Descent Method in Simulated Liver Surgery
We recently established that our digital potential function was globally stable at the point where a virtual liver coincided with its real counterpart. In particular, because three rotational degrees of freedom are frequently used in a surgical operation on a real liver, stability of the potential function concerning three rotational degrees of freedom was carefully verified in the laboratory, using fluorescent lamps and sunlight. We achieved the same stability for several simulated liver operations using a 3D printed viscoelastic liver in a surgical operating room equipped with two light-emitting diode shadowless lamps. As a result, with increasing number of lamps, stability of our depth-depth matching in the steepest descendent algorithm improved because the lamps did not emit an infrared spectrum such as the one emitted by our depth camera. Furthermore, the slower the angular velocity in a surgical sequence, the more overall stability improved
MOIRCS Deep Survey. X. Evolution of Quiescent Galaxies as a Function of Stellar Mass at 0.5<z<2.5
We study the evolution of quiescent galaxies at 0.5<z<2.5 as a function of
stellar mass, using very deep NIR imaging data taken with the Multi-Object
Infrared Camera and Spectrograph on the Subaru Telescope in the GOODS-North
region. The deep NIR data allow us to construct a stellar mass-limited sample
of quiescent galaxies down to ~10^{10} Msun even at z~2 for the first time. We
selected quiescent galaxies with age/tau>6 by performing SED fitting of the
multi broad-band photometry from the U to Spitzer 5.8um bands with the
population synthesis model of Bruzual & Charlot (2003) where exponentially
decaying star formation histories are assumed. The number density of quiescent
galaxies increases by a factor of ~3 from 1.0<z<1.5 to 0.5<z<1.0, and by a
factor of ~10 from 1.5<z<2.5 to 0.5<z<1.0, while that of star-forming galaxies
with age/tau<4 increases only by factors of ~2 and ~3 in the same redshift
ranges. At 0.5<z<2.5, the low-mass slope of the stellar mass function of
quiescent galaxies is alpha ~ 0 -- 0.6, which is significantly flatter than
those of star-forming galaxies (alpha ~ -1.3 -- -1.5). As a result, the
fraction of quiescent galaxies in the overall galaxy population increases with
stellar mass in the redshift range. The fraction of quiescent galaxies at
10^{11}-10^{11.5} Msun increases from ~20-30% at z~2 to ~40-60% at z~0.75,
while that at 10^{10}-10^{10.5} Msun increases from <~ 5% to ~15% in the same
redshift range. These results could suggest that the quenching of star
formation had been more effective in more massive galaxies at 1<~z<~2. Such a
mass-dependent quenching could explain the rapid increase of the number density
of ~M* galaxies relative to lower-mass galaxies at z >~ 1-1.5.Comment: 12 pages, 7 figures, accepted for publication in PASJ (Subaru special
issue). Updated to accepted versio
Synthetic data generation method for hybrid image-tabular data using two generative adversarial networks
The generation of synthetic medical records using generative adversarial
networks (GANs) has become increasingly important for addressing privacy
concerns and promoting data sharing in the medical field. In this paper, we
propose a novel method for generating synthetic hybrid medical records
consisting of chest X-ray images (CXRs) and structured tabular data (including
anthropometric data and laboratory tests) using an auto-encoding GAN
({\alpha}GAN) and a conditional tabular GAN (CTGAN). Our approach involves
training a {\alpha}GAN model on a large public database (pDB) to reduce the
dimensionality of CXRs. We then applied the trained encoder of the GAN model to
the images in original database (oDB) to obtain the latent vectors. These
latent vectors were combined with tabular data in oDB, and these joint data
were used to train the CTGAN model. We successfully generated diverse synthetic
records of hybrid CXR and tabular data, maintaining correspondence between
them. We evaluated this synthetic database (sDB) through visual assessment,
distribution of interrecord distances, and classification tasks. Our evaluation
results showed that the sDB captured the features of the oDB while maintaining
the correspondence between the images and tabular data. Although our approach
relies on the availability of a large-scale pDB containing a substantial number
of images with the same modality and imaging region as those in the oDB, this
method has the potential for the public release of synthetic datasets without
compromising the secondary use of data.Comment: 14 page
エジプト紅海沿岸のマングローブ林の林分構造
Established mangrove forests along the coastal area of the Arabian Peninsula and African side of the Red Sea are uniquely different from mangrove forests in other parts of the world because of their low biodiversity and harsh habitat of arid and highly saline conditions. Therefore mangrove forests in this area appear in patchy and scattered patterns at mouths of wadi or in sheltered lagoons with rare and irregular flooding. Most of them are pure forests of Avicennia marina, occasionally mixed with Rhizophora mucronata in the southern part of the Red Sea. In this study, we analyze the forest structure of A. marina and discuss the regeneration strategy and the forest dynamics of this unique mangrove species. Three experimental plots of 1000 to 2000 trees/ha were selected from north to south along the Red Sea coast. The highest tree size (6.8m) suggested severe effects of the high salinity of the Red Sea (3.2 to 4.9%) on tree growth. Dense mantle vegetation had developed at the forest edge facing the open sea to protect the forest interior against strong waves and wind. Tree growth was also prevented by severe drought on the landside edge of the forest. All the forests had a dense seedling bank throughout the forest floor, with a very high rate of turnover and regeneration, which seldom occurred in other forests
MOIRCS Deep Survey. VII: NIR Morphologies of Star-forming Galaxies at Redshift z~1
We investigate rest-frame near-infrared (NIR) morphologies of a sample of 139
galaxies with M_{s} >= 1 x 10^{10} M_{sun} at z=0.8-1.2 in the GOODS-North
field using our deep NIR imaging data (MOIRCS Deep Survey, MODS). We focus on
Luminous Infrared Galaxies (LIRGs), which dominate high star formation rate
(SFR) density at z~1, in the sample identified by cross-correlating with the
Spitzer/MIPS 24um source catalog. We perform two-dimensional light profile
fitting of the z~1 galaxies in the Ks-band (rest-frame J-band) with a single
component Sersic model. We find that at z~1, ~90% of LIRGs have low Sersic
indices (n<2.5, similar to disk-like galaxies) in the Ks-band, and those
disk-like LIRGs consist of ~60% of the whole disk-like sample above M_{s} >= 3
x 10^{10} M_{sun}. The z~1 disk-like LIRGs are comparable or ~20% small at a
maximum in size compared to local disk-like galaxies in the same stellar mass
range. If we examine rest-frame UV-optical morphologies using the HST/ACS
images, the rest-frame B-band sizes of the z~1 disk-like galaxies are
comparable to those of the local disk-like galaxies as reported by previous
studies on size evolution of disk-like galaxies in the rest-frame optical band.
Measuring color gradients (galaxy sizes as a function of wavelength) of the z~1
and local disk-like galaxies, we find that the z~1 disk-like galaxies have 3-5
times steeper color gradient than the local ones. Our results indicate that (i)
more than a half of relatively massive disk-like galaxies at z~1 are in violent
star formation epochs observed as LIRGs, and also (ii) most of those LIRGs are
constructing their fundamental disk structure vigorously. The high SFR density
in the universe at z~1 may be dominated by such star formation in disk region
in massive galaxies.Comment: 16 pages, 15 figures, accepted for publication in PASJ. Catalog data
will be available at http://astr.tohoku.ac.jp/MODS/wiki/index.php soo
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