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Your search keyword '"Saitoh, Noriyuki"' showing total 35 results
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35 results on '"Saitoh, Noriyuki"'

1. The effect of supported metal Species on soot oxidation over PGM/CeO2-ZrO2.

Author

Kubo, Hitoshi, Ohshima, Yusuke, Kato, Shunsuke, Saitoh, Noriyuki, Yoshizawa, Noriko, Nakagoe, Osamu, and Tanabe, Shuji

Subjects
OXIDATION, CATALYSTS, METALS, OXYGEN, SOOT
Abstract

Herein is studied the soot oxidation over platinum group metal oxide/CeO2–ZrO2 (PGM/CZ) catalysts. The ability to capture gas-phase oxygen was in sequence of Ru/CZ > Rh/CZ > Ir/CZ > Pt/CZ > Pd/CZ. A soot oxidation test by TG-DTA showed that Ru/CZ, Rh/CZ, and Ir/CZ are highly active catalysts. It was found that there is a good correlation between the ability to capture gas-phase oxygen and soot oxidation activity. TEM observation revealed that soot oxidation mainly occurs at the interface between soot and CZ surfaces. The Ea values and soot oxidation test using labelled oxygen suggest that highly active catalysts oxidize soot by CZ lattice oxygen. For Ir/CZ, soot oxidation at 270 °C occurred due to the reduction by soot. Ru/CZ and Rh/CZ captured gas-phase oxygen spontaneously below 250 °C, resulting in soot oxidation at 270 °C. H2-TPR results suggest that the reactivity of lattice oxygen in the CZ surface, improved by PGM, is also related to soot oxidation activity. This suggests that the ability to capture gas-phase oxygen and the reactivity of lattice oxygen in the CZ surface determine the soot oxidation activity, and that Ru, Rh, and Ir have the effect of enhancing these properties. [ABSTRACT FROM AUTHOR]

Published
2024
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9. Three-step growth of highly photoresponsive BaSi2 light absorbing layers with uniform Ba to Si atomic ratios.

Author

Yamashita, Yudai, Sato, Takuma, Saitoh, Noriyuki, Yoshizawa, Noriko, Toko, Kaoru, and Suemasu, Takashi

Subjects
DEEP level transient spectroscopy, EPITAXY, MOLECULAR beam epitaxy, INTERFACIAL roughness, QUANTUM efficiency, CRYSTAL orientation
Abstract

Barium disilicide (BaSi2) shows great promise as a light absorbing material for solar cell applications. Thus, it is important to form high-quality BaSi2 films with a low defect density. We previously found that the photoresponsivity of a-axis-oriented BaSi2 epitaxial films was enhanced drastically when formed under Si-rich conditions by molecular beam epitaxy. However, the degree of a-axis crystal orientation normal to the sample surface was degraded. In this work, we investigated the origin of this degradation by cross-sectional transmission electron microscopy (X-TEM). It was found that excess Si atoms in BaSi2 films diffused out and precipitated around the BaSi2/Si interface, resulting in the formation of Si layers with an interface roughness of 0.2–0.3 μm when grown under Si-rich conditions. Furthermore, extended defects stemming from such rough interface regions were detected by deep level transient spectroscopy, and they acted as hole trap defects. To achieve high photoresponsivity in BaSi2 films under Si-rich conditions while avoiding such Si precipitation, we proposed a three-step growth method for BaSi2 films. X-TEM observations confirmed uniform Ba to Si atomic ratios throughout the entire layer and smooth BaSi2/Si interfaces. In addition, relative to films grown by the conventional two-step method, the a-axis orientation was improved significantly, and the photoresponsivity increased by approximately five times to reach 0.5 A/W at a wavelength of 800 nm under a bias voltage of −0.1 V. This corresponds to an external quantum efficiency above 90%. [ABSTRACT FROM AUTHOR]

Published
2019
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11. The effect of supported metal Species on soot oxidation over PGM/CeO2-ZrO2

Author

Kubo, Hitoshi, Ohshima, Yusuke, Kato, Shunsuke, Saitoh, Noriyuki, Yoshizawa, Noriko, Nakagoe, Osamu, and Tanabe, Shuji

Abstract

Herein is studied the soot oxidation over platinum group metal oxide/CeO2–ZrO2(PGM/CZ) catalysts. The ability to capture gas-phase oxygen was in sequence of Ru/CZ > Rh/CZ > Ir/CZ > Pt/CZ > Pd/CZ. A soot oxidation test by TG-DTA showed that Ru/CZ, Rh/CZ, and Ir/CZ are highly active catalysts. It was found that there is a good correlation between the ability to capture gas-phase oxygen and soot oxidation activity. TEM observation revealed that soot oxidation mainly occurs at the interface between soot and CZ surfaces. The Eavalues and soot oxidation test using labelled oxygen suggest that highly active catalysts oxidize soot by CZ lattice oxygen. For Ir/CZ, soot oxidation at 270 °C occurred due to the reduction by soot. Ru/CZ and Rh/CZ captured gas-phase oxygen spontaneously below 250 °C, resulting in soot oxidation at 270 °C. H2-TPR results suggest that the reactivity of lattice oxygen in the CZ surface, improved by PGM, is also related to soot oxidation activity. This suggests that the ability to capture gas-phase oxygen and the reactivity of lattice oxygen in the CZ surface determine the soot oxidation activity, and that Ru, Rh, and Ir have the effect of enhancing these properties.Graphical AbstractSoot oxidation over platinum group metal oxide/CeO2–ZrO2(PGM/CZ) occurs at the interface between soot and CZ surfaces by using CZ lattice oxygen. The ability to capture gas-phase oxygen and the reactivity of lattice oxygen in the CZ surface determine the soot oxidation activity. Ru, Rh, and Ir have the effect of enhancing these properties.

Published
2024
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15. Three-step growth of highly photoresponsive BaSi2 light absorbing layers with uniform Ba to Si atomic ratios

Author

TOKO, Kaoru, SUEMASU, Takashi, Yamashita, Yudai, Sato, Takuma, Saitoh, Noriyuki, and Yoshizawa, Noriko

Abstract

Barium disilicide (BaSi2) shows great promise as a light absorbing material for solar cell applications. Thus, it is important to form high-quality BaSi2 films with a low defect density. We previously found that the photoresponsivity of a-axis-oriented BaSi2 epitaxial films was enhanced drastically when formed under Si-rich conditions by molecular beam epitaxy. However, the degree of a-axis crystal orientation normal to the sample surface was degraded. In this work, we investigated the origin of this degradation by cross-sectional transmission electron microscopy (X-TEM). It was found that excess Si atoms in BaSi2 films diffused out and precipitated around the BaSi2/Si interface, resulting in the formation of Si layers with an interface roughness of 0.2–0.3 μm when grown under Si-rich conditions. Furthermore, extended defects stemming from such rough interface regions were detected by deep level transient spectroscopy, and they acted as hole trap defects. To achieve high photoresponsivity in BaSi2 films under Si-rich conditions while avoiding such Si precipitation, we proposed a three-step growth method for BaSi2 films. X-TEM observations confirmed uniform Ba to Si atomic ratios throughout the entire layer and smooth BaSi2/Si interfaces. In addition, relative to films grown by the conventional two-step method, the a-axis orientation was improved significantly, and the photoresponsivity increased by approximately five times to reach 0.5 A/W at a wavelength of 800 nm under a bias voltage of −0.1 V. This corresponds to an external quantum efficiency above 90%.

Published
2019

23. Mechanism of Soot Oxidation over CeO2–ZrO2under O2Flow

Author

Kubo, Hitoshi, Ohshima, Yusuke, Yamashita, Takeshi, Kikuhara, Shunji, Saitoh, Noriyuki, Yoshizawa, Noriko, Nakagoe, Osamu, and Tanabe, Shuji

Abstract

Soot oxidation over CeO2–ZrO2(CZ) has been studied herein. The soot-CZ mixtures were observed under different contact conditions using transmission electron microscopy (TEM) and evaluated using thermogravimetric-differential thermal analysis (TG-DTA). These results indicate that the soot ignition temperature depends on the soot/CZ contact degree, and the soot oxidation rate depends on the soot/CZ contact area. The TEM observation of soot-CZ mixture quenched at T50(50% soot conversion) indicates that soot oxidation occurs only at the soot/CZ interface. Furthermore, the soot oxidation under 18O2flow and under He flow suggests that CZ lattice oxygen is a more active oxygen species than the adsorbed oxygen on the CZ. The CZ lattice oxygen mainly oxidizes soot; however, the adsorbed oxygen on the CZ surface does not oxidize soot at lower temperatures. Thus, the adsorbed oxygen oxidizes the reaction intermediates such as adsorbed CO on the CZ surface, which shows that CZ lattice is more active than the adsorbed oxygen.Soot oxidation over CeO2–ZrO2(CZ) occurs at the interface between soot and CZ. CZ lattice oxygen oxidizes soot (carbon). The reaction intermediate, such as adsorbed CO, is oxidized by the adsorbed oxygen species on the CZ surface. The driving force of soot oxidation is the gas-phase oxygen capture of CZ related to the reduction of CZ by soot.

Published
2018
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35. [Central clinical laboratory and infection control team: an essential partnership controlling health care-associated infections].

Author

Kayaba H, Tobita M, Tomita N, Kobayashi N, Fukui R, Saitoh N, Ueki S, Kobayashi Y, Sakurada N, and Chihara J

Subjects
Anti-Bacterial Agents, Cross Infection epidemiology, Cross Infection prevention & control, Disease Outbreaks, Drug Monitoring, Drug Resistance, Multiple, Bacterial, Drug Utilization Review, Hospitals, University, Humans, Intensive Care Units, Japan, Methicillin Resistance, Prevalence, Staphylococcal Infections epidemiology, Staphylococcal Infections prevention & control, Vancomycin, Infection Control economics, Infection Control methods, Infection Control organization & administration, Laboratories, Hospital, Patient Care Team
Abstract

Infection Control Committee (ICC) of Akita University Hospital was established in 1980's, when methicillin-resistant Staphylococcus aureus (MRSA) spread in teaching hospitals in Japan. After 20 years from the establishment of ICC, we needed to shake up some of the outdated infection control systems. Infection Control Team (ICT) was established in 2002 to reinforce ICC. ICT was consisted of five infection control doctors (ICD), two infection control nurses (ICN), two medical technicians in bacteriological division of clinical laboratory, one pharmacist and three administrative officials in the hospital. Monitoring of multiple drug-resistant pathogens, antibiotic use, surgical site infections and bloodstream infections are mandatory. Personnel training and educational activity are also required. After the establishment of ICT, inappropriate use of antibiotics and prevalence of MRSA were dramatically decreased. The hospital saved more than 30,000,000 yen annually. However, with a great regret, we experienced an outbreak of MRSA in a department of our hospital in 2003. MRSA infection was judged as a cause of death in three patients in the outbreak. MRSA was thought to transmit via medical personnel since pulsed-field gel electrophoresis revealed common genotype in 11 out of 15 patients studied. Prevention of healthcare-associated infections is a crucial in the management of hospitals. In this paper, we verified the efforts to control the outbreak and analyzed factors interfering infection control activities. A crucial role of a clinical laboratory in controlling healthcare associated infections was also discussed.

Published
2005

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