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Journal Articles

Gapless spin liquid in a square-kagome lattice antiferromagnet

Fujihara, Masayoshi*; Morita, Katsuhiro*; Mole, R.*; Mitsuda, Setsuo*; Toyama, Takami*; Yano, Shinichiro*; Yu, D.*; Sota, Shigetoshi*; Kuwai, Tomohiko*; Koda, Akihiro*; et al.

Nature Communications (Internet), 11(1), p.3429_1 - 3429_7, 2020/07

 Times Cited Count:8 Percentile:81.73(Multidisciplinary Sciences)

Journal Articles

Colossal barocaloric effects in plastic crystals

Li, B.*; Kawakita, Yukinobu; Kawamura, Seiko; Sugahara, Takeshi*; Wang, H.*; Wang, J.*; Chen, Y.*; Kawaguchi, Saori*; Kawaguchi, Shogo*; Ohara, Koji*; et al.

Nature, 567(7749), p.506 - 510, 2019/03

 Times Cited Count:85 Percentile:99.22(Multidisciplinary Sciences)

Refrigeration is of vital importance for modern society for example, for food storage and air conditioning- and 25 to 30% of the world's electricity is consumed for refrigeration. Current refrigeration technology mostly involves the conventional vapour compression cycle, but the materials used in this technology are of growing environmental concern because of their large global warming potential. As a promising alternative, refrigeration technologies based on solid-state caloric effects have been attracting attention in recent decades. However, their application is restricted by the limited performance of current caloric materials, owing to small isothermal entropy changes and large driving magnetic fields. Here we report colossal barocaloric effects (CBCEs) (barocaloric effects are cooling effects of pressure-induced phase transitions) in a class of disordered solids called plastic crystals. The obtained entropy changes in a representative plastic crystal, neopentylglycol, are about 389 joules per kilogram per kelvin near room temperature. Pressure-dependent neutron scattering measurements reveal that CBCEs in plastic crystals can be attributed to the combination of extensive molecular orientational disorder, giant compressibility and highly anharmonic lattice dynamics of these materials. Our study establishes the microscopic mechanism of CBCEs in plastic crystals and paves the way to next-generation solid-state refrigeration technologies.

Journal Articles

Liquid-like thermal conduction in intercalated layered crystalline solids

Li, B.; Wang, H.*; Kawakita, Yukinobu; Zhang, Q.*; Feygenson, M.*; Yu, H. L.*; Wu, D.*; Ohara, Koji*; Kikuchi, Tatsuya*; Shibata, Kaoru; et al.

Nature Materials, 17(3), p.226 - 230, 2018/03

 Times Cited Count:71 Percentile:96.98(Chemistry, Physical)

Journal Articles

Melting of Pb charge glass and simultaneous Pb-Cr charge transfer in PbCrO$$_{3}$$ as the origin of volume collapse

Yu, R.*; Hojo, Hajime*; Watanuki, Tetsu; Mizumaki, Masaichiro*; Mizokawa, Takashi*; Oka, Kengo*; Kim, H.*; Machida, Akihiko; Sakaki, Koji*; Nakamura, Yumiko*; et al.

Journal of the American Chemical Society, 137(39), p.12719 - 12728, 2015/10

 Times Cited Count:23 Percentile:65.97(Chemistry, Multidisciplinary)

no abstracts in English

Journal Articles

New PbTiO$$_{3}$$-type giant tetragonal compound Bi$$_{2}$$ZnVO$$_{6}$$ and its stability under pressure

Yu, R.*; Hojo, Hajime*; Oka, Kengo*; Watanuki, Tetsu; Machida, Akihiko; Shimizu, Keisuke*; Nakano, Kiho*; Azuma, Masaki*

Chemistry of Materials, 27(6), p.2012 - 2017, 2015/03

 Times Cited Count:21 Percentile:64.2(Chemistry, Physical)

no abstracts in English

Journal Articles

Origin of dramatic oxygen solute strengthening effect in titanium

Yu, Q.*; Qi, L.*; Tsuru, Tomohito; Traylor, R.*; Rugg, D.*; Morris, J. W. Jr.*; Asta, M.*; Chrzan, D. C.*; Minor, A. M.*

Science, 347(6222), p.635 - 639, 2015/02

 Times Cited Count:146 Percentile:97.59(Multidisciplinary Sciences)

Given that solute atoms interact weakly with the long-range elastic fields of screw dislocations, it has long been accepted that solution hardening is only marginally effective in materials with mobile screw dislocations. This accepted wisdom has recently been questioned by first-principles calculations suggesting that solutes may interact much more strongly with the screw dislocation core. We report here the results of a combined experimental and computational study undertaken to elucidate the profound hardening effect of oxygen in pure hexagonally-close-packed structured $$alpha$$-Ti. High resolution and in situ transmission electron microscopy nanomechanical characterization establish that the strengthening is due to the strong interaction between oxygen and the core of screw dislocations that mainly glide on prismatic planes. First-principles calculations of the screw dislocation core reveal a simple crystallographic source for the oxygen-dislocation interaction that is consistent with experimental observations. The distortion of the interstitial sites at the dislocation core creates a very strong but short-range repulsion for oxygen atoms. These mechanisms effectively pin the dislocation near the oxygen interstitial. These results establish a highly effective mechanism for strengthening by interstitial solutes that, contrary to prior understanding, may be significant in many structural alloys.

Journal Articles

Development of a GEM-TPC for H-dibaryon search experiment at J-PARC

Sako, Hiroyuki; Ahn, J. K.*; Baek, K. H.*; Bassalleck, B.*; Fujioka, H.*; Guo, L.*; Hasegawa, Shoichi; Hicks, K.*; Honda, R.*; Hwang, S. H.*; et al.

Journal of Instrumentation (Internet), 9(4), p.C04009_1 - C04009_10, 2014/04

 Times Cited Count:3 Percentile:18.85(Instruments & Instrumentation)

A TPC has been developed for J-PARC E42 experiment to search for H-dibaryon in ($$K^-$$, $$K^+$$) reaction. An event with 2 $$pi^-$$ and 2 protons decaying from H-dibaryon is searched for inside the TPC. The TPC has octagonal prism shape drift volume with about 50 cm diameter with 55 cm drift length filled with Ar-CH$$_{4}$$ (90:10) gas. At the end of the drift volume, 3-layer GEMs are equipped. In order to analyze momenta of produced particles, the TPC is applied with 1 T dipole magnetic field parallel to the drift electric field with a superconducting Helmholz magnet. In order to maximize the acceptance of H-dibaryon events, a diamond target is installed inside the TPC drift volume, in a cylindrical hole opened from the top to the middle of the drift volume. Since extremely high-rate $$K^-$$ beam is directly injected into the TPC drift volume to the target, a gating grid and GEMs are adopted to suppress positive-ion feedback.

Journal Articles

Diluted ferromagnetic semiconductor Li(Zn,Mn)P with decoupled charge and spin doping

Deng, Z.*; Zhao, K.*; Gu, B.; Han, W.*; Zhu, J. L.*; Wang, X. C.*; Li, X.*; Liu, Q. Q.*; Yu, R. C.*; Goko, Tatsuo*; et al.

Physical Review B, 88(8), p.081203_1 - 081203_5, 2013/08

 Times Cited Count:66 Percentile:92.87(Materials Science, Multidisciplinary)

Journal Articles

Benchmarking of mechanical test facilities related to ITER CICC steel jackets

Vostner, A.*; Pong, I.*; Bessette, D.*; Devred, A.*; Sgobba, S.*; Jung, A.*; Weiss, K.-P.*; Jewell, M. C.*; Liu, S.*; Yu, W.*; et al.

IEEE Transactions on Applied Superconductivity, 23(3), p.9500705_1 - 9500705_5, 2013/06

 Times Cited Count:11 Percentile:55.01(Engineering, Electrical & Electronic)

The ITER Cable-In-Conduit Conductor (CICC) used in the superconducting magnet system consists of a cable made of 300 to 1440 strands housed in a stainless steel tube (a.k.a. jacket or conduit). There are circular, square, as well as circle-in-square jackets, made of either a very low carbon AISI 316LN grade stainless steel or a high Mn austenitic stainless steel developed for ITER called JK2LB. Selected mechanical properties of the base material and weld joint were tested at room temperature and/or cryogenic temperatures ($$<$$ 7 K). The Domestic Agencies (DAs) reference laboratories and the ITER-IO appointed reference laboratories, CERN and Karlsruhe Institute of Technology (KIT) performed mechanical tests. This paper will compare the test results (e.g. elongation to failure) from different laboratories.

Journal Articles

Test results of ITER conductors in the SULTAN facility

Bruzzone, P.*; Stepanov, B.*; Wesche, R.*; Mitchell, N.*; Devred, A.*; Nunoya, Yoshihiko; Tronza, V.*; Kim, K.*; Boutboul, T.*; Martovetsky, N.*; et al.

Proceedings of 24th IAEA Fusion Energy Conference (FEC 2012) (CD-ROM), 8 Pages, 2013/03

Starting March 2007, over 60 ITER cable-in-conduit conductors (CICC) have been tested in the SULTAN test facility, Switzerland. For the NbTi CICC, the results confirm the prediction from the strand data, which are made taking the peak field over the conductor cross section as operating field. All the NbTi samples passed the supplier qualification phase. For the Nb$$_{3}$$Sn CICC, the performance prediction is not straightforward because of the irreversible degradation caused by filament damage occurring during cyclic loading. At the first run of the test campaign, the performance of all the Nb$$_{3}$$Sn samples largely meets the target for all the tested samples. Contrary to the NbTi CICC case, the n-index of the transition is substantially lower than in the strands, providing evidence of irreversible degradation. The performance loss upon load cycles and thermal cycles has a broad range among the various conductor samples.

Journal Articles

Positron annihilation study of 4H-SiC by Ge$$^+$$ implantation and subsequent thermal annealing

Yu, R. S.*; Maekawa, Masaki; Kawasuso, Atsuo; Wang, B. Y.*; Wei, L.*

Nuclear Instruments and Methods in Physics Research B, 270, p.47 - 49, 2012/01

 Times Cited Count:4 Percentile:36.4(Instruments & Instrumentation)

Journal Articles

Li(Zn,Mn)As as a new generation ferromagnet based on a I-II-V semiconductor

Deng, Z.*; Jin, C. Q.*; Liu, Q. Q.*; Wang, X. C.*; Zhu, J. L.*; Feng, S. M.*; Chen, L. C.*; Yu, R. C.*; Arguello, C.*; Goko, Tatsuo*; et al.

Nature Communications (Internet), 2, p.1425_1 - 1425_5, 2011/08

 Times Cited Count:137 Percentile:93.89(Multidisciplinary Sciences)

In a prototypical ferromagnet (Ga,Mn)As based on a III-V semiconductor, substitution of divalent Mn atoms into trivalent Ga sites leads to severely limited chemical solubility and metastable specimens available only as thin films. The doping of hole carriers via (Ga,Mn) substitution also prohibits electron doping. To overcome these difficulties, Masek et al. theoretically proposed systems based on a I-II-V semiconductor LiZnAs, where isovalent (Zn,Mn) substitution is decoupled from carrier doping with excess/deficient Li concentrations. Here we show successful synthesis of Li$$_{1+y}$$(Zn$$_{1-x}$$Mn$$_x$$)As in bulk materials. We reported that ferromagnetism with a critical temperature of up to 50 K is observed in nominally Li-excess compounds, which have p-type carriers.

Journal Articles

Validation of on- and off-axis neutral beam current drive against experiment in DIII-D

Park, J. M.*; Murakami, Masanori*; Petty, C. C.*; Heidbrink, W. W.*; Osborne, T. H.*; Holcomb, C. T.*; Van Zeeland, M. A.*; Prater, R.*; Luce, T. C.*; Wade, M. R.*; et al.

Physics of Plasmas, 16(9), p.092508_1 - 092508_10, 2009/09

 Times Cited Count:20 Percentile:62.48(Physics, Fluids & Plasmas)

Neutral beam current drive (NBCD) experiments in DIII-D using vertically shifted plasmas to move the current drive away from the axis have clearly demonstrated robust off-axis NBCD. Time-dependent measurements of magnetic pitch angles by the motional Stark effect diagnostic are used to obtain the evolution of the poloidal magnetic flux, which indicates a broad off-axis NBCD profile with a peak at about half the plasma radius. In most cases, the measured off-axis NBCD profile is consistent with calculations using an orbit-following Monte-Carlo code for the beam ion slowing down including finite-orbit effects, provided there is no large-scale MHD activity such as Alfv$'e$n eigenmodes modes or sawteeth. Good agreement is found between the measured pitch angles and those from simulations using transport-equilibrium codes. Two-dimensional image of Doppler-shifted fast ion D$$alpha$$ light emitted by neutralized energetic ions shows clear evidence for a hollow profile of beam ion density, consistent with classical beam ion slowing down. The magnitude of off-axis NBCD is sensitive to the alignment of the beam injection relative to the helical pitch of the magnetic field lines. If the signs of B and I yield the proper helicity, both measurement and calculation indicate that the efficiency is as good as on-axis NBCD because the increased fraction of trapped electrons reduces the electron shielding of the injected ion current, in contrast with electron current drive schemes where the trapping of electrons degrades the efficiency. The measured off-axis NBCD increases approximately linearly with the injection power, although a modest amount of fast ion diffusion is needed to explain an observed difference in the NBCD profile between the measurement and the calculation at high injection power.

Journal Articles

Off-axis neutral beam current drive for advanced scenario development in DIII-D

Murakami, Masanori*; Park, J. M.*; Petty, C. C.*; Luce, T. C.*; Heidbrink, W. W.*; Osborne, T. H.*; Prater, R.*; Wade, M. R.*; Anderson, P. M.*; Austin, M. E.*; et al.

Nuclear Fusion, 49(6), p.065031_1 - 065031_8, 2009/06

 Times Cited Count:39 Percentile:83.07(Physics, Fluids & Plasmas)

Modification of the two existing DIII-D neutral beam lines is planned to allow vertical steering to provide off-axis neutral beam current drive (NBCD) peaked as far off-axis as half the plasma minor radius. New calculations for a downward-steered beam indicate strong current drive with good localization off-axis so long as the toroidal magnetic field, BT, and the plasma current, Ip, point in the same direction. This is due to good alignment of neutral beam injection (NBI) with the local pitch of the magnetic field lines. This model has been tested experimentally on DIII-D by an injecting equatorially-mounted NBs into reduced size plasmas that are vertically displaced with respect to the vessel midplane. The existence of off-axis NBCD is evident in the changes seen in sawtooth behavior in the internal inductance. By shifting the plasma upward or downward, or by changing the sign of the toroidal field, measured off-axis NBCD profiles measured with motional Stark effect data and internal loop voltage show a difference in amplitude (40%-45%) consistent with predicted differences predicted by the changed NBI alignment with respect to the helicity of the magnetic field lines. The effects of NB injection direction relative to field line helicity can be large even in ITER: off-axis NBCD can be increased by more than 20% if the BT direction is reversed. Modification of the DIII-D NB system will strongly support scenario development for ITER and future tokamaks as well as providing flexible scientific tools for understanding transport, energetic particles and heating and current drive.

Journal Articles

New method to measure the rise time of a fast pulse slicer for laser ion acceleration research

Mori, Michiaki; Yogo, Akifumi; Kiriyama, Hiromitsu; Nishiuchi, Mamiko; Ogura, Koichi; Orimo, Satoshi; Ma, J.*; Sagisaka, Akito; Kanazawa, Shuhei; Kondo, Shuji; et al.

IEEE Transactions on Plasma Science, 36(4), p.1872 - 1877, 2008/08

 Times Cited Count:7 Percentile:30.94(Physics, Fluids & Plasmas)

A dependence of cut-off proton kinetic energy on laser prepulse duration has been observed. ASE pedestal duration is controlled by a fast electro-optic pulse slicer where the risetime is estimated to be 130 ps. We demonstrate a new correlated spectral technique for determining this risetime using a stretched, frequency chirped pulse.

Journal Articles

The H-Invitational Database (H-InvDB); A Comprehensive annotation resource for human genes and transcripts

Yamasaki, Chisato*; Murakami, Katsuhiko*; Fujii, Yasuyuki*; Sato, Yoshiharu*; Harada, Erimi*; Takeda, Junichi*; Taniya, Takayuki*; Sakate, Ryuichi*; Kikugawa, Shingo*; Shimada, Makoto*; et al.

Nucleic Acids Research, 36(Database), p.D793 - D799, 2008/01

 Times Cited Count:51 Percentile:74.53(Biochemistry & Molecular Biology)

Here we report the new features and improvements in our latest release of the H-Invitational Database, a comprehensive annotation resource for human genes and transcripts. H-InvDB, originally developed as an integrated database of the human transcriptome based on extensive annotation of large sets of fulllength cDNA (FLcDNA) clones, now provides annotation for 120 558 human mRNAs extracted from the International Nucleotide Sequence Databases (INSD), in addition to 54 978 human FLcDNAs, in the latest release H-InvDB. We mapped those human transcripts onto the human genome sequences (NCBI build 36.1) and determined 34 699 human gene clusters, which could define 34 057 protein-coding and 642 non-protein-coding loci; 858 transcribed loci overlapped with predicted pseudogenes.

Journal Articles

Positron microscopic analysis of crack failure in stainless steels

Yu, R.; Maekawa, Masaki; Miwa, Yukio; Hirade, Tetsuya; Nishimura, Akihiko; Kawasuso, Atsuo

Physica Status Solidi (C), 4(10), p.3577 - 3580, 2007/09

 Times Cited Count:4 Percentile:74.98

Employing a positron beam with lateral resolution of about 30 micometer, we performed one and two dimensional scan of crack tips in mechanically fatigued as well as stress corrosion cracked (SCC) stainless steels. Results suggest the existence of quite different crack failure mechanisms in the two types of specimen. In agreement with normal crack propagation principal, creation of dislocations and vacancies close to a crack in the mechanically fatigued sample lead to an expected narrowing of the positron annihilation 511 keV Doppler broadening $$gamma$$-ray peak (S(crack)/S(bulk)=1.01). Contrarily, widening of the Doppler broadening peak was observed for the SCC specimen (S(crack)/S(bulk)=0.97). Such phenomenon was ascribed to the micro-compositional and micro-structural differences between the studied samples.

Journal Articles

Design of a positron microprobe using magnetic lenses

Maekawa, Masaki; Yu, R.; Kawasuso, Atsuo

Physica Status Solidi (C), 4(10), p.4016 - 4019, 2007/09

 Times Cited Count:4 Percentile:74.98

no abstracts in English

Journal Articles

Characterization of ion beam-induced SiC-OI structures by positron annihilation spectroscopy

Maekawa, Masaki; Yu, R.; Kawasuso, Atsuo

Physica Status Solidi (C), 4(10), p.3680 - 3683, 2007/09

 Times Cited Count:0 Percentile:0.07

no abstracts in English

Journal Articles

Characterization of ion beam-induced quantum structures using a slow positron beam

Maekawa, Masaki; Yu, R.; Kawasuso, Atsuo

JAEA-Review 2006-042, JAEA Takasaki Annual Report 2005, P. 152, 2007/02

no abstracts in English

29 (Records 1-20 displayed on this page)