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1,144 results on '"Sato, Kazunori"'

156. Transmembrane helix 5 is critical for the high water permeability of aquaporin

Author

Kuwahara, Michio, Shinbo, Itsuki, Sato, Kazunori, Terada, Yoshio, Marumo, Fumiaki, and Sasaki, Sei

Subjects
Proteins -- Structure, Membrane proteins -- Research, Biological sciences, Chemistry
Abstract

Helix 5 and loop E of aquaporin-2 contribute to the high water permeability of the protein. This protein is a water channel regulated by vasopressin that concentrates urine.

Published
1999

159. 高い出生率をもつ集団における侵入速度の過大評価の改善 (第13回生物数学の理論とその応用 : 連続および離散モデルのモデリングと解析)

Author

Shikayama, Daisuke and Sato, Kazunori

Abstract

集団がその個体数を増やし, 新天地に侵入し生息地を獲得する現象は, 身の回りに多く存在する. これは, 拡散と侵入のメカニズムが, 直観的に連想される生物の繁殖による拡散のみならず, 森林で発生した火事の広がりや, 噂が伝わっていく様子にも適用できるためである. そのため侵入と拡散の解析方法の進歩が, 生態学や医学, 社会学への貢献へつながり, 非常に有用なものになると考えられる. 現在, 拡散と侵入の解析には大きく分けて2種類の方法が存在する. 1つは連続的な空間での集団の拡散を想定し, このダイナミクスを拡散方程式として決定論的に記述する方法, もう1つは, 多角形格子状の空間を想定し, 各格子点の状態を出生, 死亡, 移動などルールに従い遷移させることで確率論的な要素を加えた解析を行う方法である. Ellner et al. (1998)では, 1次元及び2次元の格子空間を用いた解析方法としてペアエッジ法を提唱した. これは, 格子空間上の集団を, ペア近似を基盤として解析したときに, その集団の先端がどのような挙動を示しているかに注目した手法であり, 比較的単純な計算式で, 集団の侵入速度や拡散可能なパラメータの臨界値を求めることが出来る. しかし当時紹介されていた計算方法は, 2次元の格子空間に対して空間のサイズに制約を設ける必要があった. この計算については, これ以降進展がない状態であったため, 我々はEllner et al. (1998)が提唱した2次元格子空間上の計算を, 空間サイズの拡張, 集団の先端の形状に対してより現実に近いモデルに適用しつつ, 侵入速度及び拡散可能な出生率の臨界値の観点から, 精度の維持が可能な算出方法を模索した. Ellner et al (1998)で提唱された計算方法は, 死亡と出生のみを考慮したモデルに限り良い精度の計算結果を得ることが出来るが, 個体の移動を考慮した場合に精度を著しく落とすことが分かった. 一方, 先端の形状をより詳細に決定した計算方法の場合, 計算方法は煩雑になるが, 移動の有無に関わらず, 非常に良い精度の計算結果を求めることが出来た. 本論では, Ellner et al. (1998)で提唱された計算方法を紹介した後, 格子空間の行数先頭走者付近の集団の状態のそれぞれに注目した場合の計算方法の拡張を行い, その結果と考察を述べる.

Published
2017

178. Intrinsic defect formation and the effect of transition metal doping on transport properties in a ductile thermoelectric material α-Ag2S: a first-principles study.

Author

Ngoc Nam, Ho, Yamada, Ryo, Okumura, Haruki, Nguyen, Tien Quang, Suzuki, Katsuhiro, Shinya, Hikari, Masago, Akira, Fukushima, Tetsuya, and Sato, Kazunori

Abstract

In this paper, the electronic structure and transport properties of a ductile thermoelectric material α-Ag2S are examined using first-principles calculations combined with the Boltzmann transport equation within a constant relaxation-time approximation. The use of the exchange–correlation functional SCAN + rVV10 successfully describes the geometric and electronic structure of α-Ag2S with a direct bandgap value of 0.99 eV, which is consistent with the previous experimental observations. Based on the calculations of the formation energy of typical intrinsic defects, it is found that intrinsic defect formation greatly affects the conductivity of the system where silver vacancy and interstitial silver act as p-type and n-type defects, respectively. Large Seebeck coefficients at room-temperature, of around −760 μV K−1 for n-type and 1400 μV K−1 for p-type, are realized. It is also suggested that the doping of fully filled d-block elements such as Cu and Au not only maintained the Seebeck coefficients at high values but also improved electrical conductivity by more than 1.4 times, leading to the improvement of the power factor by up to 40% compared to the non-doped sample at low carrier concentration. [ABSTRACT FROM AUTHOR]

Published
2021
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184. Balance and Gait Improvements of Postoperative Rehabilitation in Patients with Parkinson’s Disease Treated with Subthalamic Nucleus Deep Brain Stimulation (STN-DBS)

Author

Sato, Kazunori, primary, Aita, Noriaki, additional, Hokari, Yoshihide, additional, Kitahara, Eriko, additional, Tani, Mami, additional, Izawa, Nana, additional, Hatori, Kozo, additional, Nakamura, Ryota, additional, Sasaki, Fuyuko, additional, Sekimoto, Satoko, additional, Jo, Takayuki, additional, Oyama, Genko, additional, Hatano, Taku, additional, Shimo, Yasushi, additional, Iwamuro, Hirokazu, additional, Umemura, Atsushi, additional, Hattori, Nobutaka, additional, and Fujiwara, Toshiyuki, additional

Published
2019
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198. Usefulness of C-11-methionine-positron emission tomography for the diagnosis of progressive multifocal leukoencephalopathy

Author

Shirai, Shinichi, Yabe, Ichiro, Kano, Takahiro, Shimizu, Yuka, Sasamori, Toru, Sato, Kazunori, Hirotani, Makoto, Nonaka, Takayuki, Takahashi, Ikuko, Matsushima, Masaaki, Minami, Naoya, Nakamichi, Kazuo, Saijo, Masayuki, Hatanaka, Kanako C., Shiga, Tohru, Tanaka, Shinya, and Sasaki, Hidenao

Subjects
Mefloquine, Progressive multifocal leukoencephalopathy, F-18-fluorodeoxyglucose-positron emission tomography, C-11-methionine-positron emission tomography
Abstract

Progressive multifocal leukoencephalopathy (PML) is a subacute demyelinating disease of the brain caused by the JC virus that occurs mainly in immunocompromised patients. The prognosis is very poor. As the lesion looks like non- specific leukoencephalopathy, making a diagnosis at the early stage is very difficult. We report three PML cases in which there was a mismatch between C-11-methionine-positron emission tomography (MET-PET) uptake and F-18-fluorodeoxyglucose-positron emission tomography (FDG-PET) uptake. All three cases demonstrated the hyper-uptake of MET around the white matter lesions and hypo-uptake of FDG inside the lesions. We speculate that the infection had ended inside the white matter lesions of these patients, while JC virus infection was ongoing around the lesions, resulting in the increase of methionine metabolism, and the glucose metabolism was reduced or intermediate because inflammatory cells infiltrate PML lesions rarely. Two patients who were diagnosed and treated with mefloquine while the JC virus was at a low level in the cerebrospinal fluid are still alive. We suggest the usefulness of MET-PET for the early diagnosis of PML and early treatment with mefloquine.

Published
2014

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