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132 results on '"Matsumura D"'

1. Formation of orbital molecules on a pyrochlore lattice induced by A-O bond covalency

Author

Krajewska, A., Yaresko, A., Nuss, J., Gibbs, A. S., Bette, S., Blankenhorn, M., Dinnebier, R. E., Sari, D. P., Watanabe, I., Bertinshaw, J., Gretarsson, H., Ishii, K., Matsumura, D., Tsuji, T., Isobe, M., Keimer, B., Takagi, H., and Takayama, T.

Subjects
Condensed Matter - Strongly Correlated Electrons
Abstract

The pyrochlore ruthenate In$_2$Ru$_2$O$_7$ displays a subtle competition between spin-orbital entanglement and molecular orbital formation. At room temperature, a spin-orbit-entangled singlet state was identified. With decreasing temperature, In$_2$Ru$_2$O$_7$ undergoes multiple structural transitions and eventually forms a nonmagnetic ground state with semi-isolated Ru$_2$O units on the pyrochlore lattice. The dominant hopping through the Ru-O-Ru linkage leads to molecular orbital formation within the Ru$_2$O units. This molecular orbital formation is unique in that it involves the O$^{2-}$ anions, unlike the transition-metal dimers observed in systems with edge-sharing octahedra. We argue that the covalent character of In-O bonds plays a pivotal role in the structural transitions and molecular orbital formation and such bonding character of "$A$-site" ions is an important ingredient for electronic phase competition in complex transition metal oxides.

Published
2021

3. Anomalous metallic state in the vicinity of Metal to Valence Bond Solid insulator transition in LiVS2

Author

Katayama, N., Uchida, M., Hashizume, D., Niitaka, S., Matsuno, J., Matsumura, D., Nishihata, Y., Mizuki, J., Takeshita, N., Gauzzi, A., Nohara, M., and Takagi, H.

Subjects
Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Materials Science
Abstract

We investigate LiVS2 and LiVSe2 with a triangular lattice as itinerant analogues of LiVO2, known for the formation of valence bond solid (VBS) state out of S = 1 frustrated magnet. LiVS2, which is located at the border between a metal and a correlated insulator, shows a first ordered transition from a paramagnetic metal to a VBS insulator at Tc ~ 305 K upon cooling. The presence of VBS state in the close vicinity of insulator-metal transition may suggest the importance of itinerancy in the formation of VBS state. We argue that the high temperature metallic phase of LiVS2 has a pseudo-gap, likely originating from the VBS fluctuation. LiVSe2 was found to be a paramagnetic metal down to 2 K., Comment: 4 pages, 4 figures

Published
2009
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4. General Synthesis of Single-Atom Catalysts for Hydrogen Evolution Reactions and Room-Temperature Na-S Batteries

Author

Lai W-H, Wang H, Zheng L, Jiang Q, Yan Z-C, Wang L, Yoshikawa H, Matsumura D, Sun Q, Wang Y-X, Gu Q, Wang J-Z, Liu H-K, Chou S-L, and Dou S-X

Subjects
Organic Chemistry, 03 Chemical Sciences
Abstract

Herein, we report a comprehensive strategy to synthesize a full range of single-atom metals on carbon matrix, including V, Mn, Fe, Co, Ni, Cu, Ge, Mo, Ru, Rh, Pd, Ag, In, Sn, W, Ir, Pt, Pb, and Bi. The extensive applications of various SACs are manifested via their ability to electro-catalyze typical hydrogen evolution reactions (HER) and conversion reactions in novel room-temperature sodium sulfur batteries (RT-Na-S). The enhanced performances for these electrochemical reactions arisen from the ability of different single active atoms on local structures to tune their electronic configuration. Significantly, the electrocatalytic behaviors of diverse SACs, assisted by density functional theory calculations, are systematically revealed by in situ synchrotron X-ray diffraction and in situ transmission electronic microscopy, providing a strategic library for the general synthesis and extensive applications of SACs in energy conversion and storage.

Published
2020

6. Synthesis and characterization of iodovanadinite using PdI2, an iodine source for the immobilisation of radioiodine

Author

Johnstone, E.V., Bailey, D.J., Lawson, S., Stennett, M.C., Corkhill, C.L., Kim, M., Heo, J., Matsumura, D., and Hyatt, N.C.

Abstract

The synthesis of a palladium-containing iodovanadinite derivative, hypothetically “PdPb9(VO4)6I2”, was attempted using PdI2 as a source of iodine in searching for a novel waste form for radioiodine. Stoichiometric amounts of Pb3(VO4)2 and PdI2 were batched and reacted at elevated temperatures in sealed vessels. Batched material was also subjected to high-energy ball-milling (HEBM) in order to reduce reaction time and the potential for iodine volatilization during subsequent reaction at 200–500 °C. The resulting products were characterized using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray analysis, IR spectroscopy, thermal analysis and Pd K XANES. Results showed that PdI2 can function as a sacrificial iodine source for the formation of iodovanadinite, prototypically Pb10(VO4)6I2, however, the incorporation of Pd into this phase was not definitively observed. The sacrificial reaction mechanism involved the decomposition of PdI2 to Pd metal and nascent I2, with the latter incorporated into the iodovanadinite Pb10(VO4)6I2 phase. In comparison to processing using standard solid state reaction techniques, the use of HEBM prior to high temperature reaction generates a more homogeneous end-product with better iodine retention for this system. Overall, the key novelty and importance of this work is in demonstrating a method for direct immobilisation of undissolved PdI2 from nuclear fuel reprocessing, in a composite wasteform in which I-129 is immobilised within a durable iodovandinite ceramic, encapsulating Pd metal.

Published
2020

18. Methionine imbalance and toxicity in calves

Author

Abe, M., Okada, H., Matsumura, D., Sato, H., and Funaba, M. Iriki, T.

Subjects
Methionine -- Physiological aspects, Calves -- Food and nutrition, Zoology and wildlife conservation
Abstract

The occurrence of methionine imbalance and toxicity was examined using 70- and 100-kg Holstein bull calves. The animals had been trained to maintain reflex closure of the reticular groove after weaning at 5 wk of age, and Trials 1(n = 30) and 2 (n = 24) were conducted on animals at 7 and 12 wk of age, respectively. Calves received a corn-soybean meal diet in Trial 1 and a corn-corn gluten meal diet in Trial 2. In Trial 1, postruminal administration of 6 g of DL-methionine/d increased ADG, feed intake, gain/feed, and N retention compared with a control group receiving N-free supplement. However, the administration of 12 g Of DL-methionine/d did not improve these variables, whereas both 18 and 24 g/d resulted in BW loss and decreased gain/feed and N utilization efficiency. In Trial 2, postruminal administration of 16 g/d of L-lysine from L-lysine monohydrochloride increased ADG, gain/feed, and N utilization efficiency compared with a control group receiving a N-free supplement. The administration of 8 g of DL-methionine/d in addition to L-lysine did not exert an adverse effect on these variables. However, the additional supplementation of 16 and 24 g of DL-methionine/d negated the improvement, whereas 32 g/ d resulted in BW loss and decreased gain/feed and N utilization efficiency. These results showed that a methionine imbalance and toxicity occurred in calves with even a modest excess Of DL-methionine, and 70-kg calves were more susceptible to methionine toxicity than 100kg calves. Plasma concentrations of branched-chain amino acids and phenylalanine linearly decreased with increasing amounts of additional DL-methionine from 0 to 32 g/d in Trial 2. However, such a decrease occurred mainly within the range from 0 to 12 g/d in Trial 1. This decrease was suggested to occur in relation to methionine metabolism via the transsulfuration pathway. Key Words: Branched Chain Amino Acids, Calves, Imbalance, Lysine, Methionine, Toxicity

Published
2000

25. Observation of all-in type tetrahedral displacements in nonmagnetic pyrochlore niobates

Author

Torigoe, S., primary, Ishimoto, Y., additional, Aoishi, Y., additional, Murakawa, H., additional, Matsumura, D., additional, Yoshii, K., additional, Yoneda, Y., additional, Nishihata, Y., additional, Kodama, K., additional, Tomiyasu, K., additional, Ikeda, K., additional, Nakao, H., additional, Nogami, Y., additional, Ikeda, N., additional, Otomo, T., additional, and Hanasaki, N., additional

Published
2016
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26. Effects of Fe doping on anomalous specific heat and XAFS oscillation in antiferromagnetic metal Mn3Si.

Author

Hiraka, H., Ohoyama, K., Kosaka, M., and Matsumura, D.

Subjects
IRON, DOPING agents (Chemistry), ANTIFERROMAGNETIC materials
Abstract

The specific heat of Mn3−xFexSi was measured over a wide temperature range. Aside from the lattice and electronic specific heat components, another component had a significant contribution to the specific heat at low temperatures in the case of x = 0.2; however, its contribution decreased when x = 1.0. It is observed that the net component was retained at temperatures significantly higher than TN for both x. The XAFS spectra of the Mn K-edge for x = 0 not only indicated a smooth structure near the edge, but also an unusually small amplitude in the extended high energy region; however, these features disappeared with Fe doping. The specific heat and XAFS data were discussed in terms of the charge degree of freedom or electronic inhomogeneity. [ABSTRACT FROM AUTHOR]

Published
2018
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29. Trench-channel MOSFET using C-H Diamond Surface

Author

Saito, T., primary, Kobayashi, M., additional, Yamada, T., additional, Xu, D., additional, Kitabayashi, Y., additional, Matsumura, D., additional, Inaba, M., additional, Hiraiwa, A., additional, and Kawarada, H., additional

Published
2015
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46. Electron correlation effects in Co nanoscale islands on a nitrogen-covered Cu(001) surface

Author

Nakatsuji, Kan, Yoshimoto, Y., Sekiba, D., Doi, S., Iimori, T., Yagyu, K., Takagi, Y., Ohno, S. Y., Miyaoka, H., Yamada, M., Komori, F., Amemiya, K., Matsumura, D., and Ohta, T.

Subjects
Materials science, Electronic correlation, Absorption spectroscopy, Scattering, Electron, Condensed Matter Physics, Spectral line, Electronic, Optical and Magnetic Materials, law.invention, Absorption edge, law, Scanning tunneling microscope, Atomic physics, Absorption (electromagnetic radiation)
Abstract

The electronic states of cobalt nanoislands on a nitrogen-saturated Cu 001 c 2 2 -N surface have been investigated by means of x-ray absorption spectroscopy. In the case of low coverages, when the surface is covered by small Co islands, a shoulder structure in the Co L-edge absorption spectrum is observable at an energy about 3 eV higher than the absorption edge. By considering the unoccupied Co 3d state calculated by first-principles method, x-ray photoelectron spectra and the multiple scattering during the absorption process, the shoulder is attributed to the correlation among 3d electrons. The satellite intensity decreases with the increase in the Co island size. The perimeter Co atoms of the island are assigned as the origins of the correlation satellite by comparing its intensity with the morphology of the islands observed using scanning tunneling microscopy. The polarization dependent satellite intensity suggests that the electron correlation in the in-plane 3d orbital of the perimeter atoms is larger than that in the out-of-plane one.

Published
2008

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