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Your search keyword '"Kawasaki, Toshiyuki"' showing total 209 results
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209 results on '"Kawasaki, Toshiyuki"'

4. Effects of initial surfactant concentration on plasma-induced liquid flows.

Author

Kawasaki, Toshiyuki, Kamasaki, Masahiro, Takeuchi, Nozomi, and Mitsugi, Fumiaki

Subjects
*SURFACE tension, *PARTICLE image velocimetry, *CRITICAL micelle concentration, *SURFACE active agents, *MARANGONI effect, *LIQUIDS
Abstract

Clarifying the mechanisms of liquid flows induced by plasma irradiation is necessary to understand the plasma–liquid interaction. In the present work, we studied the effects of the initial surfactant (lauryl betaine) concentration on the plasma-induced liquid flows using particle image velocimetry. The results indicated that the initial surfactant concentration affected the generation characteristics of a liquid flow that linearly moved in the depth direction of the liquid. The intensity of the driving force strongly depended on the initial surfactant concentration and varied with the plasma-irradiation time. At a concentration of 20 mg/l, the liquid flow changed in the opposite direction during plasma irradiation. In the concentration range of 50–150 mg/l, the liquid flows were mostly enhanced in the same direction. The liquid flows became extremely weak in the surfactant solution above a critical micelle concentration (approximately 400 mg/l). We focused on the Marangoni flow generated by a surface-tension gradient as the driving force. The surface tension was measured before and after plasma irradiation. The difference in the surface tension due to plasma irradiation was also maximum in the concentration range of 50–150 mg/l. The experimental results demonstrated that the change in the surface-tension difference due to plasma irradiation was strongly related to the direction and intensity of the liquid flows. The mechanisms of the plasma-induced liquid flows were qualitatively explained in relation to the initial surfactant concentration. [ABSTRACT FROM AUTHOR]

Published
2021
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6. Local supply of reactive oxygen species into a tissue model by atmospheric-pressure plasma-jet exposure.

Author

Kawasaki, Toshiyuki, Mitsugi, Fumiaki, Koga, Kazunori, and Shiratani, Masaharu

Subjects
*REACTIVE oxygen species, *PLASMA jets, *ATMOSPHERIC pressure, *TISSUES, *MEDICAL model
Abstract

The supply of reactive oxygen species (ROSs) into a tissue by plasmas must be controlled for the safe and effective use of plasma technologies in biomedical applications. In this study, the two-dimensional distributions of ROSs after passing through an agarose tissue model by the plasma-jet exposures were visualized using a KI-starch gel reagent to evaluate the local ROS supply. Partial ROS supply on the tissue model surface induced the local ROS supply in a pointlike shape just under the plasma-exposed spot. The O3-containing gas exposure without direct plasma contact could not induce the local ROS supply. Therefore, the local ROS supply was assumed to be induced by plasma-specific effects. However, the results also indicated that the plasma jet coming in direct contact with the tissue model surface did not necessarily induce the local ROS supply. The effects of the tissue model thickness on the local ROS supply were also studied; the local ROS supply could penetrate to a depth of 2 mm in the tissue model under the given experimental conditions. [ABSTRACT FROM AUTHOR]

Published
2019
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19. The selective metabotropic glutamate 2/3 receptor agonist MGS0028 reverses psychomotor abnormalities and recognition memory deficits in mice lacking the pituitary adenylate cyclase-activating polypeptide

Author

Ago, Yukio, Hiramatsu, Naoki, Ishihama, Toshihiro, Hazama, Keisuke, Hayata-Takano, Atsuko, Shibasaki, Yasuhiro, Shintani, Norihito, Hashimoto, Hitoshi, Kawasaki, Toshiyuki, Onoe, Hirotaka, Chaki, Shigeyuki, Nakazato, Atsuro, Baba, Akemichi, Takuma, Kazuhiro, and Matsuda, Toshio

Published
2013
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30. ac surface discharge on dielectric materials observed by advanced Pockels effect technique

Author

Kawasaki, Toshiyuki, Terashima, Tokihiro, Suzuki, Saburo, and Takada, Tatsuo

Subjects
Electric discharges -- Research, Dielectrics -- Research, Physics
Abstract

Surface charge distribution on dielectric films is observed by a new measurement method which uses the electrooptic Pockels effect of Bi12SiO20 single crystals coupled with a high-speed charge coupled device camera. The observation process includes the image processing method for quantification and visualization of the image of the latent electric charge. The observation reveals that the electrical surface discharge pattern depends on the dielectric film characteristics when a 50 Hertz alternating current is applied.

Published
1994

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