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3. The Rising Sun Envelope Method: an automatic and accurate peak location technique for XANES measurements

Author

Monteiro, Rafael, Miyazato, Itsuki, and Takahashi, Keisuke

Subjects
Condensed Matter - Materials Science, Electrical Engineering and Systems Science - Signal Processing, Physics - Chemical Physics
Abstract

The lack of theoretical understanding of X-Ray Absorption Near Edge Structure (XANES) spectroscopy makes the development of analysis tools for its study a necessity. Here, an algorithm for judicious choice of local minima and maxima points of XANES spectrum (experimental or simulated) is proposed, without any loss of information on peaks location nor on peak strength. We call it the Rising Sun Envelope Method, since it is based on successive regularizations of the spectral measurement that, according to parameter choices that are intrinsic to the measurements, keep peaks location and strength as invariants. This is the first method that finds peaks in XANES automatically, without depending on first derivative information. Nevertheless, a direct computation of Absorption-Edge is provided, where we avoid the issue inflection point computations based on the XANES second derivative, dealing instead with simpler computations of inflection points of higher quality cubic spline approximation. Besides applications of the algorithm to XANES, we illustrate further applications in Electron Energy Loss Spectroscopy (EELS) and Raman spectra., Comment: 10 pages, 12 figures

Published
2019
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7. Committee machine that votes for similarity between materials

Author

Nguyen, Duong-Nguyen, Pham, Tien-Lam, Nguyen, Viet-Cuong, Ho, Tuan-Dung, Tran, Truyen, Takahashi, Keisuke, and Dam, Hieu-Chi

Subjects
Physics - Computational Physics, Condensed Matter - Materials Science
Abstract

We developed a method for measuring the similarity between materials, focusing on specific physical properties. The obtained information can be utilized to understand the underlying mechanisms and to support the prediction of the physical properties of materials. The method consists of three steps: variable evaluation based on non-linear regression, regression-based clustering, and similarity measurement with a committee machine constructed from the clustering results. Three datasets of well-characterized crystalline materials represented by critical atomic predicting variables are used as test beds. Herein, we focus on the formation energy, lattice parameter, and Curie temperature of the examined materials. Based on the information obtained on the similarities between the materials, a hierarchical clustering technique is applied to learn the cluster structures of the materials that facilitate interpreting the mechanism, and an improvement of regression models is introduced for predicting the physical properties of the materials. Our experiments show that rational and meaningful group structures can be obtained and that the prediction accuracy of the materials physical properties can be significantly increased, confirming the rationality of the proposed similarity measure., Comment: 13 pages

Published
2018

9. Revealing the multi-bonding state between hydrogen and graphene-supported Ti clusters

Author

Takahashi, Keisuke, Isobe, Shigehito, Omori, Kengo, Mashoff, Torge, Convertino, Domenica, Miseikis, Vaidotas, Coletti, Camilla, Tozzini, Valentina, and Heun, Stefan

Subjects
Physics - Chemical Physics, Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

Hydrogen adsorption on graphene-supported metal clusters has brought much controversy due to the complex nature of the bonding between hydrogen and metal clusters. The bond types of hydrogen and graphene-supported Ti clusters are experimentally and theoretically investigated. Transmission electron microscopy shows that Ti clusters of nanometer-size are formed on graphene. Thermal desorption spectroscopy captures three hydrogen desorption peaks from hydrogenated graphene-supported Ti clusters. First principle calculations also found three types of interaction: Two types of bonds with different partial ionic character and physisorption. The physical origin for this rests on the charge state of the Ti clusters: when Ti clusters are neutral, H2 is dissociated, and H forms bonds with the Ti cluster. On the other hand, H2 is adsorbed in molecular form on positively charged Ti clusters, resulting in physisorption. Thus, this work clarifies the bonding mechanisms of hydrogen on graphene-supported Ti clusters.

Published
2016
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17. Development of an Intra-Layer No-Insulation (LNI) REBCO Coil Implemented With a Resistance-Controlled (RC) Interface

Author

Tanaka, Yuya, Suetomi, Yu, Kawahata, Mizuho, Takahashi, Keisuke, Takao, Tomoaki, Kobayashi, Kensuke, Piao, Renzhong, Yamazaki, Toshio, and Yanagisawa, Yoshinori

Abstract

The intra-layer no-insulation (LNI) method achieves self-protection characteristics against quenching in a layer-wound REBCO coil, owing to a current bypass function associated with the copper sheet inserted in each layer. The self-protection is strongly influenced by the electrical contact resistivity (ρct) of the interface between conductors and copper sheets. In particular, a coil requires a high ρct value, typically of the 100 mΩcm2-class. However, the ρct value of a coil substantially changes due to external disturbances such as thermal cycles and electromagnetic forces. Therefore, it is vital to develop a technology to form an interface that provides a desired ρct value and that is stable against external disturbances. In the present work, we developed a basic method to form a resistance-controlled (RC) interface with a layer thickness as thin as ∼30 μm, using epoxy resin mixed with conductive and insulating fillers, which respectively act as current bypassing paths and spacers. A certain value of the mixing ratio of the conductive fillers provides a target ρct value from a wide range from 1 mΩcm2 to 1,000 mΩcm2. An RC interface-implemented LNI-REBCO coil exhibits a stable ρct value under thermal cycles and self-protection against an overcurrent quench in liquid nitrogen.

Published
2024
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19. Platelet-activating factor contracts guinea pig esophageal muscularis mucosae by stimulating extracellular Ca2+influx through diltiazem-insensitive Ca2+channels

Author

Obara, Keisuke, Ichimura, Aina, Arai, Taichi, Fujiwara, Mako, Otake, Miho, Yamada, Nana, Yoshioka, Kento, Kusakabe, Taichi, Takahashi, Keisuke, Kato, Keisuke, and Tanaka, Yoshio

Abstract

Platelet-activating factor (PAF) is expected to increase esophageal motility. However, to the best of our knowledge, this has not been examined. Thus, we investigated the contractile effects of PAF on guinea pig (GP) esophageal muscularis mucosae (EMM) and the extracellular Ca2+influx pathways responsible. PAF (10−9–10−6 M) contracted EMM in a concentration-dependent manner. PAF (10−6 M)-induced contractions were almost completely suppressed by apafant (a PAF receptor antagonist, 3 × 10−5 M). In EMM strips, PAF receptor and PAF-synthesizing/degrading enzyme mRNAs were detected. PAF (10−6 M)-induced contractions were abolished by extracellular Ca2+removal but were not affected by diltiazem [a voltage-dependent Ca2+channel (VDCC) inhibitor, 10−5 M]. PAF (10−6 M)-induced contractions in the presence of diltiazem were significantly suppressed by LOE-908 [a receptor-operated Ca2+channel (ROCC) inhibitor, 3 × 10−5 M], SKF-96365 [an ROCC and store-operated Ca2+channel (SOCC) inhibitor, 3 × 10−5 M], and LOE-908 plus SKF-96365. Among the tested ROCC/SOCC-related mRNAs, Trpc3, Trpc6, and Trpv4/Orai1, Orai3, and Stim2were abundantly expressed in EMM strips. These results indicate that PAF potently induces GP EMM contractions that are dependent on extracellular Ca2+influx through ROCCs/SOCCs, and VDCCs are unlikely to be involved.

Published
2024
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30. Study on Addition of Surfactants Agents to Improve the Behavior of High Water Content Sediment for Rare Earth Mining in Deep Sea

Author

Sasaoka, Takashi, Hamanaka, Akihiro, FUNATSU, Takahiro, Shimada, Hideki, and TAKAHASHI, Keisuke

Subjects
high water content sediment, deep sea mining, rare earth, surfactants agent
Abstract

Importance of rare mineral metal resources is increasing currently. Therefore, the rare earth elements rich mud which exist on the deep-sea floor has the potential to be developed to fulfill their demand. As one of the effective mining method, a suction mining method is expected to apply to seabed mining. The seabed sediment containing rare earth element shows the very high water content, more than 100%. And the sediment movement during the suction is greatly affected by the water content (WC) and liquid limit (WL) of the material. Therefore, it is important to modify the liquid limit by adding a chemical agent to control the behavior of sediment. We selected eight different surfactants which can be divided into three types. They are dispersant type, water retention type, and thickener type. We carried out a liquid limit test and viscosity measurement of the sediment mixed with the agents. It is found that the water-absorbing polymer and the hydroxyethyl cellulose increase the liquid limit and viscosity. Whereas, the alkyl ammonium salt surfactant and the alkyl ammonium salt, alkyl aryl sulfonate blend decrease the liquid limit and viscosity. It is possible to control sediment behavior by adding suitable surfactants.

Published
2020

40. Ca2+ imaging with two-photon microscopy to detect the disruption of brain function in mice administered neonicotinoid insecticides.

Author

Hirai, Anri, Sugio, Shouta, Nimako, Collins, Nakayama, Shouta M. M., Kato, Keisuke, Takahashi, Keisuke, Arizono, Koji, Hirano, Tetsushi, Hoshi, Nobuhiko, Fujioka, Kazutoshi, Taira, Kumiko, Ishizuka, Mayumi, Wake, Hiroaki, and Ikenaka, Yoshinori

Subjects
NEONICOTINOIDS, THIAMETHOXAM, NICOTINIC acetylcholine receptors, IMIDACLOPRID, SOMATOSENSORY cortex, CENTRAL nervous system, INSECTICIDES, MICROSCOPY
Abstract

Neonicotinoid pesticides are a class of insecticides that reportedly have harmful effects on bees and dragonflies, causing a reduction in their numbers. Neonicotinoids act as neuroreceptor modulators, and some studies have reported their association with neurodevelopmental disorders. However, the precise effect of neonicotinoids on the central nervous system has not yet been identified. Herein, we conducted in vivo Ca2+ imaging using a two-photon microscope to detect the abnormal activity of neuronal circuits in the brain after neonicotinoid application. The oral administration of acetamiprid (ACE) (20 mg/kg body weight (BW) in mature mice with a quantity less than the no-observed-adverse-effect level (NOAEL) and a tenth or half of the median lethal dose (LD50) of nicotine (0.33 or 1.65 mg/kg BW, respectively), as a typical nicotinic acetylcholine receptor (nAChR) agonist, increased anxiety-like behavior associated with altered activities of the neuronal population in the somatosensory cortex. Furthermore, we detected ACE and its metabolites in the brain, 1 h after ACE administration. The results suggested that in vivo Ca2+ imaging using a two-photon microscope enabled the highly sensitive detection of neurotoxicant-mediated brain disturbance of nerves. [ABSTRACT FROM AUTHOR]

Published
2022
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45. Application of Cement-based Sealants for Prevention and Remediation of Environmental Impact of Submarine Resource Mining

Author

Takahashi, Keisuke, Yamanaka, Toshiro, Shimada, Hideki, and Sasaoka, Takashi

Subjects
cement, sealant, Submarine resource mining, hydrothermal deposit, environmental remediation
Abstract

Recurrent studies on submarine hydrothermal deposits have been directed toward the practical mine development and the corresponding environmental impacts. Even after the extraction of submarine resources, the original environment shall be maintained in order to prevent harmful effects on the marine ecosystem. Nonetheless, relatively little research about mineral exploitation on the seafloor has been focused on how to prevent its environmental disturbances and rehabilitate the mining site. The author invented an environment-friendly underwater mining method that aims to control the dispersion of seabed surface sediments and fill the extracted areas by sealing a submerged mine site with an anti-washout cement-based material. This work investigates technological properties and environmental impacts of sealants with different cementitious binders and anti-washout agents on a laboratory scale. Using the remotely operated vehicle Hyper-Dolphin, field trials were conducted in the marine submerged Wakamiko crater. The results indicate that a sealant with particular types of cement and anti-washout agent showed superior anti-washout, filling and hardening properties under submarine hydrothermal conditions. Less dispersion of surface sediments was observed after covering the seafloor surface with the sealant during the field-scale experimental exploitation. Sealants had less negative effects on the seafloor ecosystem.

Published
2017

46. The Seimei telescope project and technical developments

Author

Kurita, Mikio, primary, Kino, Masaru, primary, Iwamuro, Fumihide, primary, Ohta, Kouji, primary, Nogami, Daisaku, primary, Izumiura, Hideyuki, primary, Yoshida, Michitoshi, primary, Matsubayashi, Kazuya, primary, Kuroda, Daisuke, primary, Nakatani, Yoshikazu, primary, Yamamoto, Kodai, primary, Tsutsui, Hironori, primary, Iribe, Masatsugu, primary, Jikuya, Ichiro, primary, Ohtani, Hiroshi, primary, Shibata, Kazunari, primary, Takahashi, Keisuke, primary, Tokoro, Hitoshi, primary, Maihara, Toshinori, primary, and Nagata, Tetsuya, primary

Published
2020
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