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357 results on '"Sato, Takafumi"'

2. Ongoing EEG artifact correction using blind source separation

Author

Ille, Nicole, Nakao, Yoshiaki, Shumpei, Yano, Taura, Toshiyuki, Ebert, Arndt, Bornfleth, Harald, Asagi, Suguru, Kozawa, Kanoko, Itabashi, Izumi, Sato, Takafumi, Sakuraba, Rie, Tsuda, Rie, Kakisaka, Yosuke, Jin, Kazutaka, and Nakasato, Nobukazu

Subjects
Quantitative Biology - Quantitative Methods, Electrical Engineering and Systems Science - Signal Processing, Statistics - Methodology
Abstract

Objective: Analysis of the electroencephalogram (EEG) for epileptic spike and seizure detection or brain-computer interfaces can be severely hampered by the presence of artifacts. The aim of this study is to describe and evaluate a fast automatic algorithm for ongoing correction of artifacts in continuous EEG recordings, which can be applied offline and online. Methods: The automatic algorithm for ongoing correction of artifacts is based on fast blind source separation. It uses a sliding window technique with overlapping epochs and features in the spatial, temporal and frequency domain to detect and correct ocular, cardiac, muscle and powerline artifacts. Results: The approach was validated in an independent evaluation study on publicly available continuous EEG data with 2035 marked artifacts. Validation confirmed that 88% of the artifacts could be removed successfully (ocular: 81%, cardiac: 84%, muscle: 98%, powerline: 100%). It outperformed state-of-the-art algorithms both in terms of artifact reduction rates and computation time. Conclusions: Fast ongoing artifact correction successfully removed a good proportion of artifacts, while preserving most of the EEG signals. Significance: The presented algorithm may be useful for ongoing correction of artifacts, e.g., in online systems for epileptic spike and seizure detection or brain-computer interfaces., Comment: 16 pages, 4 figures, 3 tables

Published
2023
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42. Quasi‐Homoepitaxial Growth of Highly Strained Alkali‐Metal Ultrathin Films on Kagome Superconductors.

Author

Kato, Takemi, Nakayama, Kosuke, Li, Yongkai, Wang, Zhiwei, Sugawara, Katsuaki, Tanaka, Kiyohisa, Takahashi, Takashi, Yao, Yugui, and Sato, Takafumi

Subjects
THIN films, PHOTOELECTRON spectroscopy, FERMI liquids, SUBSTRATES (Materials science), QUANTUM states, EPITAXY
Abstract

Applying lattice strain to thin films, a critical factor to tailor their properties such as stabilizing a structural phase unstable at ambient pressure, generally necessitates heteroepitaxial growth to control the lattice mismatch with substrate. Therefore, while homoepitaxy, the growth of thin film on a substrate made of the same material, is a useful method to fabricate high‐quality thin films, its application to studying strain‐induced structural phases is limited. Contrary to this general belief, here the quasi‐homoepitaxial growth of Cs and Rb thin films is reported with substantial in‐plane compressive strain. This is achieved by utilizing the alkali‐metal layer existing in bulk crystal of kagome metals AV3Sb5 (A = Cs and Rb) as a structural template. The angle‐resolved photoemission spectroscopy measurements reveal the formation of metallic quantum well states and notable thickness‐dependent quasiparticle lifetime. Comparison with density functional theory calculations suggests that the obtained thin films crystalize in the face‐centered cubic structure, which is typically stable only under high pressure in bulk crystals. These findings provide a useful approach for synthesizing highly strained thin films by quasi‐homoepitaxy, and pave the way for investigating many‐body interactions in Fermi liquids with tunable dimensionality. [ABSTRACT FROM AUTHOR]

Published
2024
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