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739 results on '"Kato, Satoru"'

288. A Study on Clustering Method by Self-Organizing Map and Information Criteria.

Author

Kato, Satoru, Horiuchi, Tadashi, and Itoh, Yoshio

Abstract

In this paper, we propose a clustering method by SOM and information criteria. In this method, initial cluster-candidates are derived by SOM, and then these candidates are merged appropriately based on information criterion such as BIC or AIC (Akaike Information Criterion). Through the clustering experiments for the artificial datasets and UCI Machine Learning Repository΄s datasets, we confirm that our proposed method can extract clusters more accurately and stably than the SOM-only method. [ABSTRACT FROM AUTHOR]

Published
2009
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289. Measurement of liquid water distribution in GDL under cross-flow-inducing parallel flow field using operando synchrotron X-ray radiography

Author

Suzuki, Takahisa, Kato, Akihiko, Yamaguchi, Satoshi, Nagai, Yasutaka, Hayashi, Daisuke, and Kato, Satoru

Abstract

Baffles in flow field channels for air in a polymer electrolyte fuel cell are known to enhance the performance by inducing convective flow through the gas diffusion layer (GDL) with smaller pressure loss than interdigitated flow fields. This work experimentally correlates performance enhancement with the amount of liquid water in a GDL. A parallel flow field (PFF) that has different inlet and outlet opening sizes is applied to induce cross-flow in the GDL under the rib between adjacent air channels. Operando synchrotron X-ray radiography experiments are conducted to compare the amount of water in the GDL with that for a PFF having the same inlet and outlet sizes. The performance enhancement by application of different opening sizes increases with decreasing relative humidity and increasing air flow rate. A significant performance enhancement is observed when the amount of water in the GDL substrate under the rib becomes almost zero. No performance enhancement is observed under over-humidified conditions, although a decrease in the amount of water in the GDL is still observed, which suggests that the performance becomes insensitive to the difference in the liquid water saturation as the saturation increases.

Published
2023
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290. Equation Elucidating the Catalyst-Layer Proton Conductivity in a Polymer Electrolyte Fuel Cell Based on the Ionomer Distribution Determined Using Small-Angle Neutron Scattering

Author

Harada, Masashi, Kadoura, Hiroaki, Takata, Shin-ichi, Iwase, Hiroki, Kajiya, Shuji, Suzuki, Takahisa, Hasegawa, Naoki, Shinohara, Akihiro, and Kato, Satoru

Abstract

The performance of a polymer electrolyte fuel cell can be enhanced by improving the proton conductivity of the catalyst layer, where the oxygen reduction reaction generates electrochemical power. Protons are conducted through the ionomer coatings on catalyst-supporting carbon particles, which form porous structures that facilitate oxygen diffusion during the reaction within the catalyst layer. Therefore, while a higher ionomer content in the catalyst layer is favorable, the proton conductivity is additionally governed by the type of carbon support. As the influence of the ionomer distribution is not fully understood, we introduce a novel proton conductivity model for use in simulating catalyst layers with various amounts of ionomers and different carbon types. This proton conductivity model considers that several ionomers occur as thin films with drastically suppressed proton conductivities. Although evaluating the thin-film ionomer fraction is challenging, proton-conducting ion clusters in thick-film ionomers have been detected by characterizing the catalyst layers via small-angle neutron scattering. Our model reveals that reducing the fraction of the thin-film ionomer or avoiding factors that suppress its proton conduction improves the performance of the catalyst layer.

Published
2023
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291. Upregulation of Transglutaminase in the Goldfish Retina During Optic Nerve Regeneration.

Author

Back, Nathan, Cohen, Irun R., Kritchevsky, David, Lajtha, Abel, Paoletti, Rodolfo, Hollyfield, Joe G., Anderson, Robert E., LaVail, Matthew M., Sugitani, Kayo, Matsukawa, Toru, Maeda, Ari, and Kato, Satoru

Abstract

To elucidate the molecular involvement of transglutaminase (TG) in central nervous system (CNS) regeneration, we cloned a full-length cDNA for neural TG (TGN) from axotomized goldfish retinas and produced a recombinant TGN protein from this cDNA. The levels of TGN mRNA and protein were increased at 10-30 days after optic nerve transection, and this increase in TGN was only localized in the ganglion cells in goldfish retinas. In retinal explant cultures, the recombinant TGN protein induced a drastic enhancement of neurite outgrowth, while TGN-specific RNAi significantly suppressed this neurite outgrowth. Taken together, these data strongly indicate that TGN is a key regulatory molecule for CNS regeneration. [ABSTRACT FROM AUTHOR]

Published
2006
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292. Activation of Cell Survival Signals in the Goldfish Retinal Ganglion Cells after Optic Nerve Injury.

Author

Back, Nathan, Cohen, Irun R., Kritchevsky, David, Lajtha, Abel, Paoletti, Rodolfo, Hollyfield, Joe G., Anderson, Robert E., LaVail, Matthew M., Koriyama, Yoshiki, Homma, Keiko, and Kato, Satoru

Abstract

Generally, nerve injury of adult mammalian CNS neurons leads to a retrograde neuronal degeneration and cell death. The retinal ganglion cells (RGCs) of rat fail to regenerate and become apoptotic after optic nerve injury. In contrast, goldfish RGCs can survive and regrow their axons after injury. Focusing on this different response of RGCs in both species to optic nerve injury, we compared cell death and cell survival signals in the rat and goldfish RGCs after optic nerve injury. In goldfish retina, levels of phospho-Akt (p-Akt) and phospho-Bad (p-Bad) first rapidly increased at 3-5 days after optic nerve injury. Subsequently, levels of Bcl-2 increased and caspase-3 activity decreased at 10 days after nerve injury. In rat retina, levels of p-Akt and p-Bad first rapidly decreased at 1-2 days after optic nerve injury. Subsequently, levels of Bax and caspase-3 activity increased 6 days after optic nerve crush. These changes after optic nerve injury were all morphologically localized only in the RGCs. The data suggest that goldfish RGCs are warranted the cell survival by rapid p-Akt and subsequent Bcl-2 activations during the optic nerve regeneration, whereas rat RGCs are made a progress of the cell death by rapid inactivation of p-Akt and subsequent activation of Bax after optic nerve crush. [ABSTRACT FROM AUTHOR]

Published
2006
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296. A simple method to measure through-plane effective gas diffusivity of a gas diffusion layer for polymer electrolyte fuel cells.

Author

Yoshimune, Wataru, Kato, Satoru, Inagaki, Masahide, and Yamaguchi, Satoshi

Subjects
*PROTON exchange membrane fuel cells, *DIFFUSION, *CARBON dioxide detectors, *FICK'S laws of diffusion, *KIRKENDALL effect, *CARBON monoxide detectors, *INFRARED absorption, *MICROPOROSITY
Abstract

• A simple and robust method using an infrared adsorption CO 2 sensor is presented. • The effective through-plane diffusivity in gas diffusion layers was measured. • In a comparison with previous studies, the obtained gas diffusivity was reasonable. Gas diffusivity in a gas diffusion layer for polymer electrolyte fuel cells is strongly related to the fuel cell performance. In this work, we develop a straightforward experimental apparatus for measuring the through-plane effective diffusion coefficient in gas diffusion layers. The apparatus consists of an infrared absorption carbon dioxide sensor and a custom-built sample holder. The gas chamber of the sensor is separated from the air by gas diffusion layers in the sample holder. After the gas chamber is purged with carbon dioxide through the gas diffusion layer, its decay is examined. The decay curve is fitted using Fick's law for one-dimensional diffusion, and the diffusivity is calculated by dividing the effective diffusion coefficient by the bulk diffusion coefficient. As a case study, we examined the gas diffusivity for a commercial carbon paper (TGP-H060, Toray). The calculated diffusivity for TGP-H060 was evaluated to be 0.36 ± 0.02 at 25 °C. This value is consistent with the data presented in previous reports. [ABSTRACT FROM AUTHOR]

Published
2022
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