H Kobayashi

Nihon University, Edo, Tōkyō, Japan

Are you H Kobayashi?

Claim your profile

Publications (593)1550.91 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The magnetoresistance of λ-(BETS)2FeCl4 was measured along the needle axis of the crystal to determine the pressure and magnetic field dependences of the coupled metal-insulator and antiferromagnetic transition temperature (TMI, TN). TMI decreases when applying pressure and/or magnetic field. The TMI vs H curve shows an inflection point (H1). The anomaly observed around 1 T (H1) corresponds to the spin-flop transition observed by the SQUID measurements. The magnetization (M) of the oriented polycrystalline sample of λ-(BETS)2FeCl4 was measured at 2–15 K in a magnetic field of 0.01–7 T. The magnitude of the characteristic drop of M observed for the field parallel to the c axis (ΔM∥) becomes small above 1.2 T but remains almost constant above 4.5 T.
    Solid State Communications 01/2013; · 1.53 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Magnetic torque measurements have been carried out for two-dimensional magnetic-field-induced organic superconductor λ-(BETS)2FeCl4, where BETS stands for bis(ethylenedithio)tetraselenafulvalene, to investigate the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase. The in-plane upper critical field of the field-induced-superconducting phase steeply decreases with decreasing temperature below 2.2 K. The in-plane field dependence of the diamagnetic susceptibility shows a significant decrease below 25 T at low temperatures, showing that magnetic fluxes are less excluded from the sample. These results show the presence of the FFLO phase with the tricritical point between the FFLO, homogeneous superconducting, and paramagnetic metallic phases at 2.2 K and 23 T. The stability of the FFLO phase is also investigated as a function of the magnetic field angle and compared with theories.
    Physical review. B, Condensed matter 05/2012; 85(17). · 3.66 Impact Factor
  • S. Imaizumi, N. Aoki, H. Kobayashi, H. Kiya
    [Show abstract] [Hide abstract]
    ABSTRACT: We propose a key assignment scheme and applying it to control hierarchical access to multimedia content. By introducing a modified hash chain, the proposed scheme manages one key composed of a single segment. The managed key is not distributed to any users, providing security against key leakage. Collusion attacks are prevented by the order of key assignment. Our scheme also reduces the number of hash calculations. Analysis of performance demonstrated this scheme is valid.
    Intelligent Information Hiding and Multimedia Signal Processing (IIH-MSP), 2012 Eighth International Conference on; 01/2012
  • H. Kobayashi, M. Iwahashi, H. Kiya
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper proposes an extended median cut quantization method with special median values, which does not have a restriction that the number of signals after quantization is a power of 2. The proposed quantization performs fast and the quantization error of it becomes smaller than that of the linear quantization for images with sparse histogram. When the number of the quantization levels is large, it is confirmed that the quantization error of the proposed quantization becomes smaller than the median cut quantization, and becomes almost the same as the Lloyd-Max quantization for general images. Finally, we apply to a high bit rate lossy data compression system for sparse histogram images using the proposed quantization.
    Intelligent Signal Processing and Communications Systems (ISPACS), 2012 International Symposium on; 01/2012
  • Y. Tobe, S. Imaizumi, N. Aoki, H. Kobayashi
    [Show abstract] [Hide abstract]
    ABSTRACT: In this paper, an efficient data hiding scheme for printed color images is proposed that visualizes on printed color images embedded data that is invisible on a monitor. We accomplished this scheme by using the differences of color gamut between a monitor and printer. The proposed scheme visualizes embedded data by converting one piece of color information, either L*, a*, or b*, to a fixed value when printing. This feature can be easily applied to copyright protection for printed images. Simulation results show the effectiveness of our scheme.
    Intelligent Signal Processing and Communications Systems (ISPACS), 2012 International Symposium on; 01/2012
  • H. TANAKA, A. KOBAYASHI, H. KOBAYASHI
    [Show abstract] [Hide abstract]
    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 05/2010; 29(18).
  • H. B. Cui, D. Graf, J. S. Brooks, H. Kobayashi
    [Show abstract] [Hide abstract]
    ABSTRACT: A Reply to the Comment by Dafang Li, Yanming Ma, and Jun Yan.
    Physical Review Letters 04/2010; 104(13). · 7.73 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The four-probe resistivity measurements were performed on the molecular crystals of TMTTeN (=tetramethyltetratelluronaphthalene) and [Ni(ptdt)2] (ptdt=propylenedithio tetrathiafulvalenedithiolate) by using a diamond anvil cell (DAC) up to 30 and 21GPa, respectively. In spite of extremely large enhancement of room-temperature conductivity (∼350Scm−1 at 25.4GPa) and metallic behavior at low temperatures (25–65K at 25.4GPa), the pressure-induced metallic state could not be observed in TMTTeN up to 30GPa at least around room temperature. The resistivity of [Ni(ptdt)2] decreased with increasing pressure and became approximately 10−2Ωcm at 18Gpa. The temperature dependence of the resistivity exhibited a weakly semiconducting behavior. At around 19.5GPa, [Ni(ptdt)2] showed weakly metallic behavior down to low temperature. However, this pressure-induced metallic state was not stable. At 20.7GPa, the resistivity increased again below 40K.The four-probe resistance measurements were also performed on the extremely brittle thin-plate microcrystals of single-component antiferromagnetic molecular conductor [Au(tmdt)2]. The resistance (R) decreased continuously with decreasing temperature (T). Except for a slight bending of the R−T curve at around the magnetic transition temperature (TN=110K), no resistance anomaly was observed. Nonetheless, the existence of the metallic state below TN was confirmed for the first time from the results of single-crystal resistance measurement.The precise crystal structure examinations were performed on [Au(tmdt)2] by the powder X-ray diffraction data at the temperature range of 9–300K.
    Physica B Condensed Matter 01/2010; 405(11). · 1.28 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 01/2010; 27(27).
  • [Show abstract] [Hide abstract]
    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 01/2010; 28(43).
  • [Show abstract] [Hide abstract]
    ABSTRACT: Shubnikov–de Haas and angular dependent magnetoresistance oscillations have been used to explore the role of anion size, magnetic moment, and disorder in the organic conductors κ‐(BETS)2GaBr4κ‐(BETS)2GaBr4 and κ‐(BETS)2FeCl2Br2κ‐(BETS)2FeCl2Br2 in the isomorphic class κ‐(BETS)2Ga1‐xFexCl4‐yBryκ‐(BETS)2Ga1‐xFexCl4‐yBry. The results, combined with previous work, show correlations between the anion composition (Ga1‐xFexCl4‐yBry)(Ga1‐xFexCl4‐yBry) and the superconducting transition temperature, effective mass, Fermi surface topology, and the mean free path.
    Physica B Condensed Matter 01/2010; 405(11):S295–S298. · 1.28 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Shubnikov-de Haas and angular dependent magnetoresistance oscillations have been used to explore the role of anion size, magnetic moment, and disorder in the organic conductors kappa-(BETS)_2GaBr_{4} and kappa-(BETS)_2FeCl_{2}_Br_{2} in the isomorphic class kappa-(BETS)_2Ga_{1-x}Fe_{x}Cl_{4-y}_Br_{y}. The results, combined with previous work, show correlations between the anion composition (Ga_{1-x}Fe_{x}Cl_{4-y}_Br_{y}) and the superconducting transition temperature, effective mass, Fermi surface topology, and the mean free path. Comment: 5 pages, 6 figures
    09/2009;
  • H B Cui, D Graf, J S Brooks, H Kobayashi
    [Show abstract] [Hide abstract]
    ABSTRACT: Germanium (Ge) becomes an "artificial metal" and a superconductor (T(c) approximately 5 K) above the pressure-induced semiconductor-(diamond structure)-to-metal (beta-Sn structure) transition at 10 GPa. We report single crystal resistance studies of the pressure-dependent metallic and metastable phases in the range 2.6 to 23 GPa, and show for a controlled pressure release, Ge is a metastable metal below 3 GPa. We find Ge has a superconducting upper critical field of 300 Oe (at 10.7 GPa and 1.8 K), above which a positive magnetoresistance consistent with that of a compensated closed orbit metal is observed.
    Physical Review Letters 07/2009; 102(23):237001. · 7.73 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: New bis(ethylenedithio)tetraselenafulvalene (BETS) based radical cation salts with tetrahedral dianions [CdBr4]2− and [HgBr4]2− of the (BETS)4MBr4(PhBr) composition were prepared by electrochemical crystallization. Room-temperature crystal structure of (BETS)4CdBr4(PhBr) determined by single crystal X-ray diffraction involves BETS radical cation layers of the θ-type packing and insulating layers consisting of [CdBr4]2− anions and PhBr molecules. In the neighboring conducting layers, the stacks are arranged perpendicular to each other. A metal-to-metal transition within 225–230K range was found in both (BETS)4CdBr4(PhBr) and (BETS)4HgBr4(PhBr). The behavior of electrical resistivity of these salts differs substantially along and across conducting layers. The study of magnetoresistance of (BETS)4HgBr4(PhBr) revealed weak Shubnikov-de Haas oscillations in fields higher than 6T.
    Synthetic Metals 01/2009; 159(11):1072-1076. · 2.11 Impact Factor
  • H. Kobayashi, K. Ohmi, K. Ichino, T. Kunimoto
    [Show abstract] [Hide abstract]
    ABSTRACT: In this paper, we discuss the present status of electroluminescence (EL) of inorganic materials. From 1970's, the main research was made on multicolor and fullcolor EL. Finally blue inorganic EL of BaAl2S4:Eu was developed, resulting in fullcolor EL-TV using “color by blue®” by iFire Technology. Very recently, a new ultra bright inorganic EL of dc driven at lower than 10 V has been developed. These three findings will stimulate the researches on inorganic EL, which slowed down and were not active in the past two decades. Some new findings are expected. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
    Physica Status Solidi (A) Applications and Materials 01/2008; 205(1):11 - 14. · 1.53 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Magnetotransport properties of two isostructural salts, the superconducting λ-(BETS)2GaCl4 phase and the first organic conductor containing magnetic Fe3+ ions, λ-(BETS)2FeCl4, where BETS is bis(ethylenedithio)tetraselenafulvalene, have been studied up to 37 T. The previously reported sharp metal-insulator phase transition occurring at 8 K under ambient pressure for λ-(BETS)2FeCl4 is suppressed when applying magnetic fields > 10 T. This unusual phenomenon may be connected to a field-induced ferromagnetic ordering of the Fe3+-ions moments. This could result in some kind of "decondensation" of the carriers, initially condensed below 8 K, into a field-restored highly conducting state (FRHCS). The temperature-magnetic-field (T-H) phase diagram is presented. The angle dependence of the critical field Hc2 has been determined for the superconducting λ-(BETS)2GaCl4 phase at 4.2 K.
    EPL (Europhysics Letters) 07/2007; 28(6):427. · 2.26 Impact Factor
  • Journal of Low Temperature Physics 06/2007; 142:609-612. · 1.18 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Chiral magnets are obtained by inclusion of chiral guest molecules into the channels of an achiral nanoporous ferrimagnet consisting of the Mn3(HCOO)6 (1) framework. Insertion of the R or the S enantiomer of 2-chloropropan-1-ol (CH3C*HClCH2OH) in the chiral pores of the previously emptied framework (space group P21/c) results in the two corresponding chiral solids (1R and 1S, space group P21), while insertion of a racemic mixture of the two enantiomers retains the achirality of the host for the meso solid (1RS, space group P21/c). The R guest is ordered in the M channels while the S guest is ordered in the P channels. In contrast, the R guests in the P channels and the S guests in the M channels are disordered on two crystallographic orientations. For the racemic mixture of the two enantiomers in 1RS, random disorder of guests in both channels is observed. Thus, the localization of the guest molecule depends on the nature of the surface to recognize the guest of a particular chirality. The guest inclusion compounds are thermally stable. The 1R and 1S compounds are optically active. All the compounds adopt a ferrimagnetic ground state. Compared to the host framework of 1 without guest, the Curie temperature decreases for both 1R and 1S but increases for 1RS. The additional interactions between the framework and the inserted guest alcohols strengthen the lattice via hydrogen bonds and other electrostatic forces, and it might account for the significant lowering of the lattice contribution as well as the magnetic component to the specific heat capacity upon guest loading.
    Advanced Functional Materials 01/2007; 17(4):577 - 584. · 10.44 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Se77-NMR spectrum and frequency shift measurements in the paramagnetic metal and antiferromagnetic insulating phases are reported for a small single crystal of the organic conductor lambda-(BETS)2FeCl4 as a function of temperature (T) and field alignment for an applied magnetic field B0=9T . The results show that in the low T limit, where the localized Fe3+ spins (Sd=5/2) are almost fully polarized, the conduction electrons (Se pi electrons, spin spi=1/2 ) in the BETS molecules experience an exchange field (Bpid) from the Fe3+ spins with a value of -32.7±1.5T at 5K and 9T aligned opposite to B0 . This large negative value of Bpid is consistent with that predicted by the resistivity measurements and supports the Jaccarino-Peter internal field-compensation mechanism being responsible for the origin of field-induced superconductivity.
    Physical review. B, Condensed matter 01/2007; 76. · 3.66 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Magneto-optical measurements have been performed in organic conductors β''-(BEDT-TTF)2CsCd(SCN)4 and λ-(BETS)2FeCl4. Although the zero magnetic field ground state of β''-(BEDT-TTF)2CsCd(SCN)4is considered as the density wave state, periodic orbit resonances (POR's) attributed to quasi-one-dimensional (Q1D) and quasi-two-dimensional (Q2D) Fermi surfaces (FS's) have been observed above 6 T. The existence of these FS's are predicted by the band calculation based on room temperature lattice parameters. This result may suggest the destruction of the density wave state at 6 T, and the primal metallic state revives in the high field phase above 6 T. In the case of λ-(BETS)2FeCl4, large changes of the transmission intensity of electromagnetic waves around 10 T, which correspond to the insulator-metal transition, have been observed. However, no POR-like resonance has been observed. This may be due to the restriction of the observed frequency-field region.
    Journal of Physics Conference Series 12/2006; 51(1):359.

Publication Stats

5k Citations
1,550.91 Total Impact Points

Institutions

  • 2009–2012
    • Nihon University
      • Department of Chemistry
      Edo, Tōkyō, Japan
    • Florida State University
      • Department of Physics
      Tallahassee, FL, United States
  • 1998–2010
    • Tottori University
      • Department of Electrical and Electronic Engineering
      TTJ, Tottori, Japan
  • 1987–2010
    • The University of Tokyo
      • • Department of Chemistry
      • • Department of Applied Physics
      • • Institute for Solid State Physics
      Edo, Tōkyō, Japan
    • Higashi Nippon International University
      Higashimurayama-shi, Tōkyō, Japan
  • 1984–2010
    • Toho University
      • • Department of Chemistry
      • • Department of Biomolecular Science
      • • Faculty of Science
      Edo, Tōkyō, Japan
  • 1999–2007
    • Institute for Molecular Science
      Okazaki, Aichi, Japan
    • Nagoya University
      • Division of Radiology
      Nagoya-shi, Aichi-ken, Japan
    • Gakushuin University
      • Department of Physics
      Tokyo, Tokyo-to, Japan
  • 2006
    • National Institute for Materials Science
      Tsukuba, Ibaraki, Japan
    • Tokushima Bunri University
      Shido, Kagawa, Japan
  • 1990–2004
    • Niigata University
      • • Faculty of Medicine
      • • Division of Neuropathology
      Niahi-niigata, Niigata, Japan
  • 1982–2004
    • Hokkaido University
      • • Department of Dermatology
      • • Laboratory of Plant Pathology
      • • Division of Chemistry
      • • Department of Medicine II
      Sapporo, Hokkaidō, Japan
  • 2003
    • University of Florida
      • Department of Physics
      Gainesville, FL, United States
  • 2001
    • Tsukuba Research Institute
      Edo, Tōkyō, Japan
    • Nikko Memorial Hospital
      Hidachi, Ibaraki, Japan
    • Center for Infertility and Human Reproduction
      Barcino, Catalonia, Spain
  • 1999–2001
    • Tokyo Women's Medical University
      • Department of Urology
      Edo, Tōkyō, Japan
  • 1998–2001
    • Juntendo University
      • Department of Medicine
      Edo, Tōkyō, Japan
  • 1992–2001
    • Osaka University
      • • Department of Integrated Medicine
      • • Division of Applied Chemistry
      Ōsaka-shi, Osaka-fu, Japan
    • Iwate Medical University
      • Department of Internal Medicine
      Morioka, Iwate, Japan
  • 1967–2001
    • Hokkaido University Hospital
      • Division of Dermatology
      Sapporo, Hokkaidō, Japan
  • 2000
    • Nippon Zenyaku Kogyo Co., Ltd.
      Hukusima, Fukushima, Japan
  • 1996–1999
    • Health Sciences University of Hokkaido
      • • Department of Oral and Maxillofacial Surgery
      • • School of Dentistry
      Tōbetsu, Hokkaido, Japan
    • Kyoto Daini Red Cross Hospital
      Kioto, Kyōto, Japan
  • 1990–1995
    • Central Research Institute of Electric Power Industry
      Edo, Tōkyō, Japan
  • 1994
    • Nagoya Second Red Cross Hospital
      Nagoya, Aichi, Japan
  • 1993–1994
    • Tokyo Medical and Dental University
      • Department of Neuropathology
      Edo, Tōkyō, Japan
    • Tokyo University of Science
      Edo, Tōkyō, Japan
  • 1991
    • Paul Sabatier University - Toulouse III
      Tolosa de Llenguadoc, Midi-Pyrénées, France
    • Edward Hines, Jr. VA Hospital
      Hines, Oregon, United States
  • 1988–1991
    • Keio University
      • • School of Medicine
      • • Department of Electronics and Electrical Engineering
      Tokyo, Tokyo-to, Japan
  • 1989
    • Sapporo Medical University
      Sapporo, Hokkaidō, Japan
  • 1986
    • Harbin Medical University
      Charbin, Heilongjiang Sheng, China