190 research outputs found
Optical implementation of visible gray-image morphology with the visual-area-coding technique
This paper was published in Optics Express and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://dx.doi.org/10.1364/AO.35.001234 Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law
Active Exploration based on Information Gain by Particle Filter for Efficient Spatial Concept Formation
Autonomous robots are required to actively and adaptively learn the
categories and words of various places by exploring the surrounding environment
and interacting with users. In semantic mapping and spatial language
acquisition conducted using robots, it is costly and labor-intensive to prepare
training datasets that contain linguistic instructions from users. Therefore,
we aimed to enable mobile robots to learn spatial concepts through autonomous
active exploration. This study is characterized by interpreting the `action' of
the robot that asks the user the question `What kind of place is this?' in the
context of active inference. We propose an active inference method, spatial
concept formation with information gain-based active exploration (SpCoAE), that
combines sequential Bayesian inference by particle filters and position
determination based on information gain in a probabilistic generative model.
Our experiment shows that the proposed method can efficiently determine a
position to form appropriate spatial concepts in home environments. In
particular, it is important to conduct efficient exploration that leads to
appropriate concept formation and quickly covers the environment without
adopting a haphazard exploration strategy
Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs) VIII. A less biased view of the early co-evolution of black holes and host galaxies
We present ALMA [CII] line and far-infrared (FIR) continuum observations of
three low-luminosity quasars () discovered by our
Subaru Hyper Suprime-Cam (HSC) survey. The [CII] line was detected in all three
targets with luminosities of , about one order
of magnitude smaller than optically luminous ()
quasars. The FIR continuum luminosities range from
(3 limit) to , indicating a wide range
in star formation rates in these galaxies. Most of the HSC quasars studied thus
far show [CII]/FIR luminosity ratios similar to local star-forming galaxies.
Using the [CII]-based dynamical mass () as a surrogate for bulge
stellar mass (), we find that a significant fraction of
low-luminosity quasars are located on or even below the local relation, particularly at the massive end of the galaxy mass
distribution. In contrast, previous studies of optically luminous quasars have
found that black holes are overmassive relative to the local relation. Given
the low luminosities of our targets, we are exploring the nature of the early
co-evolution of supermassive black holes and their hosts in a less biased way.
Almost all of the quasars presented in this work are growing their black hole
mass at much higher pace at than the parallel growth model, in which
supermassive black holes and their hosts grow simultaneously to match the local
relation at all redshifts. As the low-luminosity
quasars appear to realize the local co-evolutionary relation even at , they should have experienced vigorous starbursts prior to the currently
observed quasar phase to catch up with the relation.Comment: 19 pages, 11 figures, 4 tables. Accepted for publication in
Publications of the Astronomical Society of Japan (PASJ
Re-Evaluation of Nicotinic Acetylcholine Receptors in Rat Brain by a Tissue-Segment Binding Assay
Nicotinic acetylcholine receptors (nAChRs) of the cerebral cortex and cerebellum of rats were evaluated by a radioligand binding assay, employing tissue segments, or homogenates as materials. [3H]-epibatidine specifically bound to nAChRs in rat cortex or cerebellum, but the dissociation constants for [3H]-epibatidine differed between segments and homogenates (187 pM for segments and 42 pM for homogenates in the cortex and 160 pM for segments and 84 pM for homogenates in the cerebellum). The abundance of total nAChRs was approximately 310 fmol/mg protein in the segments of cortex and 170 fmol/mg protein in the segments of cerebellum, which were significantly higher than those estimated in the homogenates (115 fmol/mg protein in the homogenates of the cortex and 76 fmol/mg protein in the homogenates of the cerebellum). Most of the [3H]-epibatidine binding sites in the cortex segments (approximately 70% of the population) showed high affinity for nicotine (pKi = 7.9), dihydro-β-erythroidine, and cytisine, but the binding sites in the cerebellum segments had slightly lower affinity for nicotine (pKi = 7.1). An upregulation of nAChRs by chronic administration of nicotine was observed in the cortex segments but not in the cerebellum segments with [3H]-epibatidine as a ligand. The upregulation in the cortex was caused by a specific increase in the high-affinity sites for nicotine (probably α4β2). The present study shows that the native environment of nAChRs is important for a precise quantitative as well as qualitative estimation of nAChRs in rat brain
Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs) III. Star formation properties of the host galaxies at studied with ALMA
We present our ALMA Cycle 4 measurements of the [CII] emission line and the
underlying far-infrared (FIR) continuum emission from four optically
low-luminosity () quasars at discovered by
the Subaru Hyper Suprime Cam (HSC) survey. The [CII] line and FIR continuum
luminosities lie in the ranges
and , which are at least one
order of magnitude smaller than those of optically-luminous quasars at . We estimate the star formation rates (SFR) of our targets as
. Their line and continuum-emitting
regions are marginally resolved, and found to be comparable in size to those of
optically luminous quasars, indicating that their SFR or likely gas mass
surface densities (key controlling parameter of mass accretion) are accordingly
different. The ratios of the hosts, , are fully consistent with local star-forming
galaxies. Using the [CII] dynamics, we derived their dynamical masses within a
radius of 1.5-2.5 kpc as . By
interpreting these masses as stellar ones, we suggest that these faint quasar
hosts are on or even below the star-forming main sequence at , i.e.,
they appear to be transforming into quiescent galaxies. This is in contrast to
the optically luminous quasars at those redshifts, which show starburst-like
properties. Finally, we find that the ratios of black hole mass to host galaxy
dynamical mass of the most of low-luminosity quasars including the HSC ones are
consistent with the local value. The mass ratios of the HSC quasars can be
reproduced by a semi-analytical model that assumes merger-induced black
hole-host galaxy evolution.Comment: 20 pages, 9 figures, 4 tables. Accepted for publication in PAS
Subaru Hyper Suprime-Cam View of Quasar Host Galaxies at z < 1
Active galactic nuclei (AGNs) are key for understanding the coevolution of
galaxies and supermassive black holes (SMBHs). AGN activity is thought to
affect the properties of their host galaxies, via a process called "AGN
feedback", which drives the co-evolution. From a parent sample of 1151 z < 1
type-1 quasars from the Sloan Digital Sky Survey quasar catalog, we detected
host galaxies of 862 of them in the high-quality grizy images of the Subaru
Hyper Suprime-Cam (HSC) survey. The unprecedented combination of the survey
area and depth allows us to perform a statistical analysis of the quasar host
galaxies, with small sample variance. We fit the radial image profile of each
quasar as a linear combination of the point spread function and the Sersic
function, decomposing the images into the quasar nucleus and the host galaxy
components. We found that the host galaxies are massive, with stellar mass
Mstar > 10^(10) Msun, and are mainly located on the green valley. This trend is
consistent with a scenario in which star formation of the host galaxies is
suppressed by AGN feedback, that is, AGN activity may be responsible for the
transition of these galaxies from the blue cloud to the red sequence. We also
investigated the SMBH mass to stellar mass relation of the z < 1 quasars, and
found a consistent slope with the local relation, while the SMBHs may be
slightly undermassive. However, the above results are subject to our sample
selection, which biases against host galaxies with low masses and/or large
quasar-to-host flux ratios.Comment: Accepted for publication in PAS
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