Faculty Profiles - OTSUKA, Yuichi

Papers - OTSUKA, Yuichi

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Quantum dot sensitized solar cells

Tachibana, Y; Akiyama, HY; Umekita, K; Otsuka, Y; Torimoto, T; Kuwabata, S

2008 2ND IEEE INTERNATIONAL NANOELECTRONICS CONFERENCE, VOLS 1-3 page： 160 - + 2008

Efficacy of STI571 for a patient with metastatic gastrointestinal stromal tumor

Sasaki, Y; Niwa, Y; Ando, N; Otsuka, Y; Ohmiya, N; Hirooka, Y; Itoh, A; Furuta, S; Goto, H

HEPATO-GASTROENTEROLOGY Vol. 52 ( 66 ) page： 1764 - 1767 2005.11

Inhibition of platelet adherence to mononuclear cells by alpha-tocopherol - Role of P-selectin

Murohara T, Ikeda H, Otsuka Y, Aoki M, Haramaki N, Katoh A, Takajo Y, Imaizumi T

CIRCULATION Vol. 110 ( 2 ) page： 141 - 148 2004.7

Usefulness of magnifying endoscopy in the diagnosis of early gastric cancer

Otsuka, Y; Niwa, Y; Ohmiya, N; Ando, N; Ohashi, A; Hirooka, Y; Goto, H

ENDOSCOPY Vol. 36 ( 2 ) page： 165 - 169 2004.2

Novel gene encoding a Ca2+-binding protein and under hexokinase-dependent sugar regulation

Otsuki S, Ikeda A, Sunako T, Muto S, Yazaki J, Nakamura K, Fujii F, Shimbo K, Otsuka Y, Yamamoto K, Sakata K, Sasaki T, Kishimoto N, Kikuchi S, Yamaguchi J

BIOSCIENCE BIOTECHNOLOGY AND BIOCHEMISTRY Vol. 67 ( 2 ) page： 347 - 353 2003.2

Vitamin E inhibits lysophosphatidylcholine-induced endothelial dysfunction and platelet activation

Murohara, T; Ikeda, H; Katoh, A; Takajo, Y; Otsuka, Y; Haramaki, N; Imaizumi, T

ANTIOXIDANTS & REDOX SIGNALING Vol. 4 ( 5 ) page： 791 - 798 2002.10

Platelet GPIIb/IIIa is activated and platelet-leukocyte coaggregates formed in vivo during hemodialysis

Kawabata, K; Nakai, S; Miwa, M; Sugiura, T; Otsuka, Y; Shinzato, T; Hiki, Y; Tomimatsu, I; Ushida, Y; Hosono, F; Maeda, K

NEPHRON Vol. 90 ( 4 ) page： 391 - 400 2002.4

Changes in Mac-1 and CD14 expression on monocytes and serum soluble CD14 level during push/pull hemodiafiltration

Kawabata, K; Nakai, S; Miwa, M; Sugiura, T; Otsuka, Y; Shinzato, T; Hiki, Y; Tomimatsu, I; Ushida, Y; Hosono, F; Maeda, K

NEPHRON Vol. 90 ( 3 ) page： 273 - 281 2002.3

Numerical simulation of gas flow through sand core

Maeda, Y; Nomura, H; Otsuka, Y; Tomishige, H; Mori, Y

INTERNATIONAL JOURNAL OF CAST METALS RESEARCH Vol. 15 ( 4 ) page： 441 - 444 2002

Imaging observations of midlatitude ionospheric disturbances during the geomagnetic storm of February 12, 2000

Sahai Y, Shiokawa K, Otsuka Y, Ihara C, Ogawa T, Igarashi K, Miyazaki S, Saito A

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 106 ( A11 ) page： 24481 - 24492 2001.11

CD31 expression on leukocytes is downregulated in vivo during hemodialysis

Kawabata, K; Nakai, S; Miwa, M; Sugiura, T; Otsuka, Y; Shinzato, T; Hiki, N; Tomimatsu, I; Ushida, Y; Hosono, F; Maeda, K

NEPHRON Vol. 89 ( 2 ) page： 153 - 160 2001.10

The assessment of vertical and lateral invasion of early gastric cancer by magnifying endoscopy

Otsuka, Y; Goto, H; Niwa, Y; Ohmiya, N; Kamiya, K; Sakata, T; Ando, N; Ito, B; Sasaki, Y; Hayakawa, T

GASTROINTESTINAL ENDOSCOPY Vol. 53 ( 5 ) page： AB212 - AB212 2001.4

The assessment of vertical and lateral invasion of early gastric cancer by magnifying endoscopy

Otsuka Y, Goto H, Niwa Y, Ohmiya N, Kamiya K, Sakata T, Ando N, Ito B, Sasaki Y, Hayakawa T

GASTROINTESTINAL ENDOSCOPY Vol. 53 ( 5 ) page： AB212 - AB212 2001.4

Diagnosis of gastrointestinal stromal tumor using endscopic ultrasonography-guided fine needle aspiration biopsy.

Ando, N; Goto, H; Niwa, Y; Hirooka, Y; Koijima, S; Hosoi, T; Shinkai, M; Sakata, T; Otsuka, Y; Hayakawa, T

GASTROINTESTINAL ENDOSCOPY Vol. 51 ( 4 ) page： AB162 - AB162 2000.4

Multi‐Event Analysis of STEVE, SAR Arc, and Red/Green Arc at Subauroral Latitudes Using Data From Ground Optical and Radio Instruments and the Arase and Van Allen Probes Satellites

Rei Sugimura, Kazuo Shiokawa, Yuichi Otsuka, Shin‐ichiro Oyama, Arto Oksanen, Martin Connors, Akira Kadokura, Igor Poddelsky, Nozomu Nishitani, Simon G. Shepherd, J. Michael Ruohoniemi, Charles Smith, Harlan Spence, Geoff Reeves, Herbert O. Funsten, Yoshizumi Miyoshi, Iku Shinohara, Yoshiya Kasahara, Fuminori Tsuchiya, Atsushi Kumamoto, Atsuki Shinbori, Kazushi Asamura, Shoichiro Yokota, Yoichi Kazama, C.‐W. Jun, Shiang‐Yu Wang, Sunny W. Y. Tam, Tzu‐Fang Chang, Bo‐Jhou Wang, Satoshi Kasahara, Kunihiro Keika, Tomoaki Hori, Ayako Matsuoka

Journal of Geophysical Research: Space Physics Vol. 130 ( 2 ) 2025.2

Publishing type：Research paper (scientific journal) Publisher：American Geophysical Union (AGU)

Abstract

Strong Thermal Emission Velocity Enhancement (STEVE) is a latitudinally narrow, purple‐band emission observed at subauroral latitudes. Stable Auroral Red (SAR) arcs characterized by major red emission, and red/green arcs with both red and green emissions also occur at subauroral latitudes. Characteristics of magnetospheric source plasma and electromagnetic fields of these three types of arcs have not been fully understood because of the limited conjugate observations between magnetosphere and the ground. In this study, we report 11 conjugate observations (2 STEVEs, 7 SAR arcs, and 2 red/green arcs), using all‐sky images obtained at seven ground stations over more than four years from January 2017 to April 2021 and magnetospheric satellites (Arase and Van Allen Probes). We found that, in the inner magnetosphere, the source region of STEVEs and red/green arcs were located outside the plasmasphere, and that of the SAR arc was in the region of spatial overlap between the plasmasphere and ring current region. Electromagnetic waves at frequencies below 1 Hz were observed for STEVEs and red/green arcs. SuperDARN radar data showed a strong westward plasma flow in the ionosphere, especially during STEVE events, whereas the plasma flows associated with SAR arcs and red/green arcs were generally weaker and variable. The STEVE and SAR arc can appear simultaneously at slightly different latitudes and STEVEs and red/green arcs can transform into SAR arcs. These first comprehensive ground‐satellite measurements of three types of subauroral‐latitude auroras increase our understanding on similarlity, differences, and coupling of these auroras in the ionosphere and the magnetosphere.

DOI： 10.1029/2024JA032793

Web of Science

Midlatitude Plasma Blob-like Structures Along With Super Equatorial Plasma Bubbles During the May 2024 Great Geomagnetic Storm

Wenjie Sun, Guozhu Li, Biqiang Zhao, Shun Rong Zhang, Yuichi Otsuka, Lianhuan Hu, Guofeng Dai, Xiukuan Zhao, Haiyong Xie, Yi Li, Jianfei Liu, Yu Li, Baiqi Ning, Libo Liu, Atsuki Shinbori, Michi Nishioka, Septi Perwitasari

Geophysical Research Letters Vol. 51 ( 21 ) 2024.11

Publishing type：Research paper (scientific journal)

Plasma blob is generally a low-latitude phenomenon occurring at the poleward edge of equatorial plasma bubble (EPB) during post-sunset periods. Here we report a case of midlatitude ionospheric plasma blob-like structures occurring along with super EPBs over East Asia around sunrise during the May 2024 great geomagnetic storm. Interestingly, the blob-like structures appeared at both the poleward and westward edges of EPBs, reached up to 40°N magnetic latitudes, and migrated westward several thousand kilometers together with the bubble. The total electron content (TEC) inside the blob-like structures was enhanced by ∼50 TEC units relative to the ambient ionosphere. The blob-like structure at the EPB poleward edge could be partly linked with field-aligned plasma accumulation due to poleward development of bubble. For the blob-like structure at the EPB west side, one possible mechanism is that it was formed and enhanced accompanying the bubble evolution and westward drift.

DOI： 10.1029/2024GL111638

Web of Science

Scopus

Monitoring of Ionospheric Variability Using the Low lAtitude Long Range Ionospheric raDar (LARID): Capabilities, Advantages and Limitations

Wenjie Sun, Guozhu Li, Baiqi Ning, Lianhuan Hu, Yuichi Otsuka, Guofeng Dai, Haiyong Xie, Xiukuan Zhao, Yi Li, Atsuki Shinbori, Michi Nishioka, Septi Perwitasari, Chi Wang

Space Weather Vol. 22 ( 11 ) 2024.11

Publishing type：Research paper (scientific journal)

A Low lAtitude long Range Ionospheric raDar (LARID), which was built recently at Dongfang (19.2°N, 108.8°E, magnetic latitude 13.9°), Hainan Is., China, is employed to study the ionospheric variability over a large region. The LARID consists of two high frequency (HF) coherent backscatter radars, looking toward east and west, respectively, with a field-of-view covering a wide longitude from Africa to Pacific. Here we report some results by the LARID, with main focus on its capabilities, advantages and limitations in monitoring ionospheric variability. The results show that the LARID can detect various ionospheric variations at low latitudes, including (a) sequentially generated equatorial plasma bubbles over a longitude span of ∼80°, (b) near-range E region irregularities drifting across more than 1,000 km, (c) ionospheric background information retrieved from ground scatters, (d) traveling ionospheric disturbances, and (e) sporadic E structures reflecting HF radio waves at low elevation angles. It is demonstrated that the LARID provides an important tool for investigating different types of ionospheric variability over a broad region, especially over the Indian Ocean and west Pacific, and will contribute significantly to the regional ionospheric weather forecasting.

DOI： 10.1029/2024SW004134

Web of Science

Scopus

Solar activity dependence for the relationship between nighttime medium-scale traveling ionospheric disturbance and sporadic E (Es) layer activities in summer during 1998–2019 over Japan Reviewed International coauthorship

Veera Kumar Maheswaran, Yuichi Otsuka, James A. Baskaradas, Venkata Ratnam Devanaboyina, Sriram Subramanian, Atsuki Shinbori, Takuya Sori, Michi Nishioka, Septi Perwitasari

Earth, Planets and Space Vol. 76 ( 1 ) 2024.6

Publishing type：Research paper (scientific journal)

To investigate solar activity dependence of the coupling between medium-scale traveling ionosphere disturbance (MSTID) and sporadic E (Es) layer, we analyzed the total electron content (TEC) obtained from a Japanese global positioning system (GPS) receivers and ionosonde at Kokubunji (35.7° N, 139.5° E) in Japan during the summer period of May–August from 1998 to 2019. To obtain perturbation TEC caused by MSTIDs, the detrended TEC is calculated by subtracting 1-h moving averages from the measured TEC for each pair of GPS satellite and receiver. The detrended TEC data are mapped on to the geographical coordinates to make detrended 2-D maps with spatial resolution of 0.15° × 0.15° in longitude and latitude. The MSTID activity is defined as a ratio of the standard deviation to the background TEC over Kokubunji in Japan. Day-to-day variations of the MSTID activity during summer nights was compared to Es layer parameters [critical frequency (foEs) and Δfo-b≡foEs-fbE, where fbEs is blanketing frequency] derived from ionosonde station at Kokubunji. We have found that the correlation coefficient between the MSTID activity and foEs(Δfo-b) between 1998 and 2019 is 0.5 3 (0.46) on average, suggesting that there is an electrodynamical coupling between the Es layer and F region could generate nighttime MSTIDs. We also have found that the correlation coefficient positively correlates with solar activity. This finding indicates that in the high solar activity conditions, when the growth rate of Perkins instability is relatively low, generation of the polarization electric fields in the Es layer could play a more important role to grow MSTIDs than in the low solar activity conditions. Graphical Abstract: (Figure presented.)

DOI： 10.1186/s40623-024-02023-6

Web of Science

Scopus

Regional Ionospheric Super Bubble Induced by Significant Upward Plasma Drift During the 1 December 2023 Geomagnetic Storm Reviewed International coauthorship

Wenjie Sun, Guozhu Li, Shun Rong Zhang, Lianhuan Hu, Guofeng Dai, Biqiang Zhao, Yuichi Otsuka, Xiukuan Zhao, Haiyong Xie, Yi Li, Baiqi Ning, Libo Liu, Atsuki Shinbori, Michi Nishioka, Septi Perwitasari

Journal of Geophysical Research: Space Physics Vol. 129 ( 6 ) 2024.6

Publishing type：Research paper (scientific journal)

An unseasonal equatorial plasma bubble (EPB) event occurred in the East/Southeast Asian sector during the geomagnetic storm on 1 December 2023, causing strong amplitude scintillations from equatorial to middle latitudes. Based on the observations from multiple instruments over a large latitudinal and longitudinal region, the spatial features of the super EPB were investigated. The EPB developed vertically at a fast rising speed ∼470 m/s over the magnetic equator and extended to a very high middle latitude more than 40°N, despite that the storm intensity was not very strong with the minimum SYM-H index −132 nT. In the zonal direction, the super EPB covered over a specific region ∼95–140°E, where the local sunset roughly coincided with southward turning of interplanetary magnetic field (IMF) Bz component. Before the onset of the super EPB, significant upward plasma drift up to ∼110 m/s was observed over the magnetic equator, which could amplify the growth rate of Rayleigh-Taylor instability and lead to the generation of the super EPB. The significant drift was likely caused by eastward penetration electric field (PEF) due to sharp southward turning of IMF Bz. The local time of storm onset and duration of IMF Bz southward turning during the storm main phase may partly determine the onset region and zonal coverage of the EPB.

DOI： 10.1029/2024JA032430

Web of Science

Scopus

Statistical Analysis of Low-Latitude Boundary of Polar-Type Medium-Scale Traveling Ionospheric Disturbances Observed by a 630-nm Airglow Imager at Nyrölä, Finland Reviewed International coauthorship

Masaki Sato, Kazuo Shiokawa, Shin ichiro Oyama, Yuichi Otsuka, Atsuki Shinbori, Arto Oksanen

Journal of Geophysical Research: Space Physics Vol. 129 ( 4 ) 2024.4

Language：English Publishing type：Research paper (scientific journal)

Medium-scale traveling ionospheric disturbances (MSTIDs) are one of the ionospheric plasma density structures and are observable through 630-nm airglow images. Previous studies using airglow images at Tromsø (69.6°N, 19.2°E; magnetic latitude: 66.7°N), Norway, reported high-latitude MSTIDs (here we call them as polar-type MSTIDs) whose propagation direction changes associated with auroral brightening and magnetic field disturbances. However, there has been little statistical analysis on the connection of MSTIDs occurring at high and middle latitudes. In this study, we statistically analyzed the MSTIDs observed by an airglow imager at Nyrölä (62.3°N, 25.5°E; magnetic latitude: 59.4°N), Finland, which is located ∼7° south of Tromsø, corresponding to subauroral latitudes. The period analyzed was from 23 January 2017, to 30 September 2021. We found 11 cases of MSTIDs during this period. Eight cases were found to be the polar-type MSTIDs whose motion changes associated with auroral brightening and magnetic field disturbances. We found that 9 cases of MSTID show the low-latitude boundary at 61° ± 2°N for geographic latitude and 58° ± 2°N for magnetic latitude, indicating disconnection between high- and mid-latitude MSTIDs. We also derived occurrence probability, velocity, wavelength, period, wave front direction, and propagation direction of these MSTIDs. The occurrence probability of MSTIDs at Nyrölä is 1.9%, which is much lower than those at high (Tromsoe, more than 50%) and middle (Japan, ∼30%) latitudes. We discuss these MSTID characteristics at subauroral latitudes based on possible difference of generation mechanisms of nighttime MSTIDs at high and middle latitudes.

DOI： 10.1029/2023JA032077

Web of Science

Scopus

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Papers - OTSUKA, Yuichi