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Your search keyword '"Mazaki, H."' showing total 129 results
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129 results on '"Mazaki, H."'

2. Lower critical fields of Bi2Sr2CaCu2O8+d and YBa2Cu3O7-d single crystals

Author

Tochihara, S., Yasuoka, H., Mazaki, H., Osada, M., and Kakihana, M.

Subjects
Crystals -- Research, Superconducting quantum interference devices -- Usage, Physics
Abstract

The temperature dependence of the lower critical fields of Hc1(T) of Bi2Sr2CaCu2O8+d and YBa2Cu3O7-d single crystals was studied for both orientations of the applied fields, parallel and perpendicular to the c axis. The magnetization curves of the samples were measured by utilizing a superconducting quantum interference device. Findings indicated that the temperature dependence of the coherence length in the ab plane plays an important role.

Published
1999

3. Magnetic response of Y/Pb dopped single-crystal Bi2Sr2CaCu2O(sub 8+d) superconductors

Author

Tochihara, S., Goto, A., Yasuoko, H., Mazaki, H., Osada, M., and Kakihana, M.

Subjects
Magnetic fields -- Research, Magnetometer -- Usage, Superconductors -- Magnetic properties, Business, Electronics, Electronics and electrical industries
Abstract

A study was conducted to determine the magnetic properties of Y/Pb dopped single-crystal Bi2Sr2CaCu2O(sub 8+d) superconductors. By analyzing the magnetization curves of the superconductors through a SQUID magnetometer, the close correlation of magnetic response and carrier concentration was revealed. It was also noted that the samples' lower critical field and pinning force increase with the rise of carrier concentration in the CuO2 plane.

Published
1999

5. Critical currents of ceramic superconductors induced by pulsed magnetic fields

Author

Yasuoka, H., Mazaki, H., Tochihara, S., Kakihana, M., and Yoshimura, M.

Subjects
Superconductors -- Magnetic properties, Magnetic fields -- Analysis, Physics
Abstract

Signal patterns induced in ceramic superconductors by pulsed magnetic fields to measure critical current density, Jc, either decrease monotonically to zero as a time function or show a cyclic pattern tending to zero. Jc is evaluated by simulating signal patterns from magnetization relations in the Bean and Kim-Anderson reproduction models. Jc evaluation is achieved by considering an external field that depends on the simulated signal profiles.

Published
1993

32. Fluorinated Amphiphilic Vinyl Ether Block Copolymers:  Synthesis and Characteristics of Their Micelles in Water

Author

Matsumoto, K., Mazaki, H., and Matsuoka, H.

Abstract

Fluorine-containing amphiphilic block copolymers, poly(2-hydroxyethyl vinyl ether)-block-poly(2-(2,2,2-trifluoroethoxy)ethyl vinyl ether)) (poly(HOVE-b-TFEOVE) (m = 78, n = 23)), poly(2-hydroxyethyl vinyl ether)-block-poly(2-(2,2,3,3,3-pentafluoropropoxy)ethyl vinyl ether) (poly(HOVE-b-PFPOVE) (m = 74, n = 22)), and poly(2-hydroxyethyl vinyl ether)-block-poly(2-(2,2,3,3,4,4,4-heptafluorobutoxy)ethyl vinyl ether) (poly(HOVE-b-HFBOVE) (m = 79, n = 19)) were synthesized along with the non-fluorine-containing amphiphilic block copolymer, poly(2-hydroxyethyl vinyl ether)-block-poly(n-butyl vinyl ether) (poly(HOVE-b-NBVE) (m = 70, n = 22)), where m and n are polymerization degrees of hydrophilic segment and hydrophobic segment, respectively. These fluorine-containing block copolymers considerably reduced the surface tension of the aqueous solutions, indicating the high surface activity of the block copolymers. They formed core−shell rodlike and/or core−shell spherical micelles in aqueous solutions, which were evaluated by small-angle neutron scattering (SANS), small-angle X-ray scattering (SAXS), and dynamic light scattering (DLS) analyses. A qualitative trend was observed, that is, the fraction of rodlike micelles increased, as the number of fluorine atoms in a hydrophobic segment increased. The fluorine-containing block copolymer selectively solubilized the hydrophobic fluorinated dye into water phase and the fluorinated dye selectivity increased as the number of the fluorine atoms in the hydrophobic monomer unit increased. Solubilization of a low molecular weight compound strongly affected the copolymer micelle structure, which was also confirmed by SANS, SAXS, and DLS analyses.

Published
2004

33. Perfluoroalkyl-philic Character of Poly(2-hydroxyethyl vinyl ether)-block-poly[2-(2,2,2-trifluoroethoxy)ethyl vinyl ether] Micelles in Water:  Selective Solubilization of Perfluorinated Compounds

Author

Matsumoto, K., Mazaki, H., Nishimura, R., Matsuoka, H., and Yamaoka, H.

Abstract

Two types of amphiphilic block copolymer, poly(2-hydroxyethyl vinyl ether)-block-poly[2-(2,2,2-trifluoroethoxy)ethyl vinyl ether] (poly(HOVE-b-TFEOVE)) (m:n = 78:23) and poly(2-hydroxyethyl vinyl ether)-block-poly(n-butyl vinyl ether) (poly(HOVE-b-NBVE)) (m:n = 74:23), having the same ratios of polymerization degree in hydrophilic and hydrophobic segments with the same total chain length were synthesized, and the properties of their aqueous solutions were investigated, where m and n represent number-averaged polymerization degree of HOVE and TFEOVE or NBVE, respectively. By water surface tension measurements, the critical micelle concentrations (cmc's) of poly(HOVE-b-TFEOVE) and poly(HOVE-b-NBVE) were both estimated at 1.0 × 10-4 mol/L. Solubilization of various fluoro and non-fluoro compounds using these polymer aqueous solutions was examined. It was confirmed that poly(HOVE-b-TFEOVE) solubilized more decafluorobiphenyl than did poly(HOVE-b-NBVE), whereas poly(HOVE-b-NBVE) solubilized more 2,6-dimethylnaphthalene than did poly(HOVE-b-TFEOVE). When a mixture of decafluorobiphenyl and 2,6-dimethylnaphthalene was added to the polymer solutions, poly(HOVE-b-TFEOVE) selectively solubilized decafluorobiphenyl, while poly(HOVE-b-NBVE) solubilized 2,6-dimethylnaphthalene predominantly, which was observed by the UV absorption spectrum of the polymer solutions.

Published
2000

37. Search for superconducting effect on the decay of99mTc

Author

Mazaki, H., Kakiuchi, S., and Shimizu, S.

Abstract

An experimental investigation of the influence of superconductivity on the decay rate of99mTc,?T, has been performed by means of a differential method. The99mTc samples containing99Tc as a carrier were prepared by electrodeposition on a copper plated tungsten wire. For production of metallic technetium the samples were reduced in pure hydrogen gas at 800~1000°C. X-ray analysis of the samples showed they were surely metallic with anhcp structure. The lattice constants observed area=2.741 Å andc=4.398 Å. The transition temperature was found to be 7.5±0.2K. Comparison of two sources, normal (room temperature) and superconducting (4.2 K), did not show an appreciable effect of superconductivity on the decay rate of99mTc exceeding the limit of uncertainty of our experiment:??/?T=(1.1±2.7) × 10-4.

Published
1978
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39. Tunneling measurements on superconductor/insulator/superconductor junctions using single-crystal YBa2Cu3O7-x thin films.

Author

Hirata, K., Yamamoto, K., Iijima, K., Takada, J., Terashima, T., Bando, Y., and Mazaki, H.

Subjects
THIN films, COPPER oxide superconductors, HIGH temperature superconductors
Abstract

We have, for the first time, made quasi-particle tunneling measurements on a YBa2Cu3O7-x(001)/Y2O3 (001)/YBa2 Cu3 O7-x (001)junction, which was epitaxially grown on a MgO(100) substrate in an in-situ process. Both layers of YBa2 Cu3 O7-x showed the same superconducting transition of Tc end =86 K with ΔT(R=10–90%)=1.5 K. Quasi-particle tunneling in the direction perpendicular to the Cu-O planes was measured. A gap parameter Δ(4.5 K) of 9.0±0.2 meV and a value of 2Δ/kTc of 3.5+0.4-0.6 were obtained. [ABSTRACT FROM AUTHOR]

Published
1990
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40. Tunnel junctions using oxide superconducting thin films epitaxially grown on SrTiO3.

Author

Takada, J., Terashima, T., Bando, Y., Mazaki, H., Iijima, K., Yamamoto, K., and Hirata, K.

Subjects
THIN films, SUPERCONDUCTORS, STRONTIUM compounds
Abstract

Normal-metal/insulator/superconductor (NIS) junctions were fabricated using thin films of YBa2Cu3O7-x (YBCO) or ErBa2Cu3O7-x. These were epitaxially grown on single-crystal SrTiO3 by the activated reactive evaporation method. For some NIS junctions prepared on SrTiO3 (110) substrates, we observed multipeaks in the differential conductance versus voltage curve. NIS junctions using single-crystal YBCO films on SrTiO3 (100) showed a set of peaks, from which we obtained a gap parameter of 11.5±1.5 meV at 4.4 K and a coupling constant of 3.2±0.4. [ABSTRACT FROM AUTHOR]

Published
1988
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