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Dive into the research topics where Yoshihiko Yamada is active.

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Featured researches published by Yoshihiko Yamada.


Cellular and Molecular Life Sciences | 1998

Scavenger receptor family proteins: roles for atherosclerosis, host defence and disorders of the central nervous system

Yoshihiko Yamada; Takefumi Doi; Takao Hamakubo; Tatsuhiko Kodama

Abstract. In this review, we summarize the structure and function of the scavenger receptor family of proteins including class A (type I and II macrophage scavenger receptors, MARCO), class B (CD36, scavenger receptor class BI), mucinlike (CD68/macrosialin, dSR-CI) and endothelial (LOX-1) receptors. Two motifs have been identified as ligand-binding domains a charged collagen structure of type I and II receptors, and an immunodominant domain of CD36. These structures can recognize a wide range of negatively charged macromolecules, including oxidized low-density lipoproteins, damaged or apoptotic cells, and pathogenic microorganisms. After binding, these ligands can be either internalized by endocytosis or phagocytosis, or remain at the cell surface and mediate adhesion or lipid transfer through caveolae. Under physiological conditions, scavenger receptors serve to scavenge or clean up cellular debris and other related materials, and they play a role in host defence. In pathological states, they mediate the recruitment, activation and transformation of macrophages and other cells which may be related to the development of atherosclerosis and to disorders caused by the accumulation of denatured materials, such as Alzheimers disease.


Proceedings of SPIE | 2012

Hyper Suprime-Cam

Satoshi Miyazaki; Yutaka Komiyama; Hidehiko Nakaya; Yukiko Kamata; Yoshi Doi; Takashi Hamana; Hiroshi Karoji; Hisanori Furusawa; Satoshi Kawanomoto; Yuki Ishizuka; Kyoji Nariai; Yoko Tanaka; Fumihiro Uraguchi; Yousuke Utsumi; Yoshiyuki Obuchi; Yuki Okura; Masamune Oguri; Tadafumi Takata; Daigo Tomono; Tomio Kurakami; Kazuhito Namikawa; Tomonori Usuda; Hitomi Yamanoi; Tsuyoshi Terai; Hatsue Uekiyo; Yoshihiko Yamada; Michitaro Koike; Hiro Aihara; Yuki Fujimori; Sogo Mineo

Hyper Suprime-Cam (HSC) is an 870 Mega pixel prime focus camera for the 8.2 m Subaru telescope. The wide field corrector delivers sharp image of 0.25 arc-sec FWHM in r-band over the entire 1.5 degree (in diameter) field of view. The collimation of the camera with respect to the optical axis of the primary mirror is realized by hexapod actuators whose mechanical accuracy is few microns. As a result, we expect to have seeing limited image most of the time. Expected median seeing is 0.67 arc-sec FWHM in i-band. The sensor is a p-ch fully depleted CCD of 200 micron thickness (2048 x 4096 15 μm square pixel) and we employ 116 of them to pave the 50 cm focal plane. Minimum interval between exposures is roughly 30 seconds including reading out arrays, transferring data to the control computer and saving them to the hard drive. HSC uniquely features the combination of large primary mirror, wide field of view, sharp image and high sensitivity especially in red. This enables accurate shape measurement of faint galaxies which is critical for planned weak lensing survey to probe the nature of dark energy. The system is being assembled now and will see the first light in August 2012.


Ophthalmology | 2010

High-resolution imaging of resolved central serous chorioretinopathy using adaptive optics scanning laser ophthalmoscopy.

Sotaro Ooto; Masanori Hangai; Atsushi Sakamoto; Akitaka Tsujikawa; Kenji Yamashiro; Yumiko Ojima; Yoshihiko Yamada; Hideo Mukai; Susumu Oshima; Takashi Inoue; Nagahisa Yoshimura

OBJECTIVEnTo compare pathologic changes in photoreceptors in eyes with resolved central serous chorioretinopathy (CSC) seen on high-resolution images obtained by adaptive optics scanning laser ophthalmoscopy (AO SLO) with visual acuity (VA) and findings on spectral-domain optical coherence tomography (SD OCT).nnnDESIGNnObservational case series.nnnPARTICIPANTSnForty-five eyes of 38 patients with resolved CSC and 20 normal eyes of 20 volunteer subjects.nnnMETHODSnAll patients underwent a full ophthalmologic examination, SD OCT, and imaging with an original prototype AO SLO system fabricated using liquid crystal-on-silicon technology.nnnMAIN OUTCOME MEASURESnCone mosaic patterns and cone density on AO SLO images and VA in eyes with CSC.nnnRESULTSnIn normal eyes, AO SLO images showed a regular photoreceptor mosaic pattern and average cone densities 0.2, 0.5, and 1.0 mm from the central fovea of 67,900, 33,320, and 14,450 cones/mm(2). In eyes with CSC, cone densities were significantly lower at each distance from the central fovea (P = 0.009 at 0.2 mm, P = 0.007 at 0.5 mm, and P = 0.004 at 1.0 mm), and 2 distinct cone mosaic patterns were seen. Group 1 CSC eyes had regular cone mosaic patterns with small dark regions. Group 2 CSC eyes had irregular mosaic patterns with large dark regions. Compared with group 1, group 2 had significantly lower average cone density and worse average logarithm of the minimum angle of resolution (logMAR) VA (P<0.001). Mean cone density in eyes with disruptions in the photoreceptor inner and outer segment (IS/OS) junction or in the intermediate line on SD OCT images was significantly lower than that in eyes with an intact IS/OS junction or intermediate line (P<0.001 for both). Cone density 0.2 mm from the central fovea correlated with logMAR VA and mean foveal thickness (1-mm diameter area) measured on SD OCT images (P<0.001 for both).nnnCONCLUSIONSnAdaptive optics SLO images showed abnormal cone mosaic patterns and reduced cone densities in eyes with resolved CSC, and these abnormalities were associated with VA loss, suggesting that AO SLO is a useful means to detect and measure cone abnormalities associated with VA loss in these eyes.


The Astrophysical Journal | 2012

DEEP NEAR-INFRARED SPECTROSCOPY OF PASSIVELY EVOLVING GALAXIES AT z ≳ 1.4*

M. Onodera; A. Renzini; Marcella Carollo; Michele Cappellari; C. Mancini; V. Strazzullo; Emanuele Daddi; Nobuo Arimoto; R. Gobat; Yoshihiko Yamada; H. J. McCracken; O. Ilbert; P. Capak; Alessandro Cimatti; Mauro Giavalisco; Anton M. Koekemoer; Xu Kong; S. J. Lilly; Kentaro Motohara; Kouji Ohta; D. B. Sanders; N. Z. Scoville; Naoyuki Tamura; Yoshiaki Taniguchi

We present the results of new near-IR spectroscopic observations of passive galaxies at z ≳ 1.4 in a concentration of BzK-selected galaxies in the COSMOS field. The observations have been conducted with Subaru/MOIRCS, and have resulted in absorption lines and/or continuum detection for 18 out of 34 objects. This allows us to measure spectroscopic redshifts for a sample that is almost complete to K_AB = 21. COSMOS photometric redshifts are found in fair agreement overall with the spectroscopic redshifts, with a standard deviation of ~0.05; however, ~30% of objects have photometric redshifts systematically underestimated by up to ~25%. We show that these systematic offsets in photometric redshifts can be removed by using these objects as a training set. All galaxies fall in four distinct redshift spikes at z = 1.43, 1.53, 1.67, and 1.82, with this latter one including seven galaxies. SED fits to broadband fluxes indicate stellar masses in the range of ~4-40 × 10^10 M_☉ and that star formation was quenched ~1 Gyr before the cosmic epoch at which they are observed. The spectra of several individual galaxies have allowed us to measure their Hδ_F indices and the strengths of the 4000 A break, which confirms their identification as passive galaxies, as does a composite spectrum resulting from the co-addition of 17 individual spectra. The effective radii of the galaxies have been measured on the COSMOS HST/ACS i_(F814W)-band image, confirming the coexistence at these redshifts of passive galaxies, which are substantially more compact than their local counterparts with others that follow the local effective radius-stellar mass relation. For the galaxy with the best signal-to-noise spectrum we were able to measure a velocity dispersion of 270 ± 105 km s^(–1) (error bar including systematic errors), indicating that this galaxy lies closely on the virial relation given its stellar mass and effective radius.


Publications of the Astronomical Society of Japan | 2018

The Hyper Suprime-Cam software pipeline

James Bosch; Robert Armstrong; Steven J. Bickerton; Hisanori Furusawa; Hiroyuki Ikeda; Michitaro Koike; Robert H. Lupton; Sogo Mineo; Paul A. Price; Tadafumi Takata; M. Tanaka; Naoki Yasuda; Yusra AlSayyad; Andrew Cameron Becker; William R. Coulton; Jean Coupon; Jose A. Garmilla; Song Huang; K. Simon Krughoff; Dustin Lang; Alexie Leauthaud; Kian-Tat Lim; Nate B. Lust; Lauren A. MacArthur; Rachel Mandelbaum; Hironao Miyatake; Satoshi Miyazaki; Ryoma Murata; Surhud More; Yuki Okura

In this paper, we describe the optical imaging data processing pipeline developed for the Subaru Telescopes Hyper Suprime-Cam (HSC) instrument. The HSC Pipeline builds on the prototype pipeline being developed by the Large Synoptic Survey Telescopes Data Management system, adding customizations for HSC, large-scale processing capabilities, and novel algorithms that have since been reincorporated into the LSST codebase. While designed primarily to reduce HSC Subaru Strategic Program (SSP) data, it is also the recommended pipeline for reducing general-observer HSC data. The HSC pipeline includes high level processing steps that generate coadded images and science-ready catalogs as well as low-level detrending and image characterizations.


The Astrophysical Journal | 2012

Stellar Populations and Structural Properties of Ultra Faint Dwarf Galaxies, Canes Venatici I, Boötes I, Canes Venatici II, and Leo IV

Sakurako Okamoto; Nobuo Arimoto; Yoshihiko Yamada; M. Onodera

We take deep images of four ultra faint dwarf (UFD) galaxies, Canes Venatici I (CVn I), Booetes I (Booe I), Canes Venatici II (CVn II), and Leo IV, using the Suprime-Cam on the Subaru Telescope. Color-magnitude diagrams (CMDs) extend below main-sequence turnoffs (MSTOs) and yield measurements of the ages of stellar populations. The stellar populations of three faint galaxies, the Booe I, CVn II, and Leo IV dwarf spheroidal galaxies (dSphs), are estimated to be as old as the Galactic globular cluster M92. We confirm that Booe I dSph has no intrinsic color spread in the MSTO and no spatial difference in the CMD morphology, which indicates that Booe I dSph is composed of an old single stellar population. One of the brightest UFDs, CVn I dSph, shows a relatively younger age ({approx}12.6 Gyr) with respect to Booe I, CVn II, and Leo IV dSphs, and the distribution of red horizontal branch (HB) stars is more concentrated toward the center than that of blue HB stars, suggesting that the galaxy contains complex stellar populations. Booe I and CVn I dSphs show the elongated and distorted shapes. CVn II dSph has the smallest tidal radius of a Milky Way satellite andmorexa0» has a distorted shape, while Leo IV dSph shows a less concentrated spherical shape. The simple stellar population of faint UFDs indicates that the gases in their progenitors were removed more effectively than those of brighter dSphs at the occurrence of their initial star formation. This is reasonable if the progenitors of UFDs belong to less massive halos than those of brighter dSphs.«xa0less


The Astrophysical Journal | 2010

A z=1.82 ANALOG OF LOCAL ULTRA-MASSIVE ELLIPTICAL GALAXIES

M. Onodera; Emanuele Daddi; R. Gobat; Michele Cappellari; Nobuo Arimoto; A. Renzini; Yoshihiko Yamada; H. J. McCracken; C. Mancini; P. Capak; Marcella Carollo; Alessandro Cimatti; Mauro Giavalisco; O. Ilbert; Xu Kong; S. J. Lilly; Kentaro Motohara; K. Ohta; D. B. Sanders; N. Z. Scoville; Naoyuki Tamura; Y. Taniguchi

We present observations of a very massive galaxy at


Monthly Notices of the Royal Astronomical Society | 2006

A Subaru/Suprime-Cam wide-field survey of globular cluster populations around M87 – II. Colour and spatial distribution

Naoyuki Tamura; Ray M. Sharples; Nobuo Arimoto; Masato Onodera; Kouji Ohta; Yoshihiko Yamada

z


The Astrophysical Journal | 2006

Stellar populations of elliptical galaxies in virgo cluster. I. The data and stellar population analysis

Yoshihiko Yamada; Nobuo Arimoto; A. Vazdekis; Reynier F. Peletier

=1.82 which show that its morphology, size, velocity dispersion and stellar population properties that are fully consistent with those expected for passively evolving progenitors of todays giant ellipticals. These findings are based on a deep optical rest-frame spectrum obtained with the Multi-Object InfraRed Camera and Spectrograph (MOIRCS) on the Subaru telescope of a high-


The Astrophysical Journal | 2004

The Full-fledged Dwarf Irregular Galaxy Leo A

Vladas Vansevičius; Nobuo Arimoto; Takashi Hasegawa; Chisato Ikuta; Pascale Jablonka; D. Narbutis; Kouji Ohta; Rima Stonkutė; Naoyuki Tamura; Valdas Vansevičius; Yoshihiko Yamada

z

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Satoshi Miyazaki

Graduate University for Advanced Studies

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A. Vazdekis

University of La Laguna

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