排序方式: 共有59条查询结果,搜索用时 311 毫秒
1.
Wang NH Taniguchi M Tsuji D Doi M Ohishi H Yoza K Baba K 《Chemical & pharmaceutical bulletin》2003,51(1):68-70
Four new guaianolides, sinodielides A-D (1-4), were isolated from Sinodielsia yunnanensis WOLFF together with a known polyacetylene, falcarindiol, and two known coumarins, bergapten and scopoletin. Their structures were established by spectral and X-ray analyses. 相似文献
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Yoshio Kitaoka Hidekazu Mukuda Shin-ichiro Tabata Akira Iyo 《Journal of Physics and Chemistry of Solids》2011,72(5):486-491
We reexamine the novel phase diagrams of antiferromagnetism (AFM) and high-Tc superconductivity (HTSC) for a disorder-free CuO2 plane based on an evaluation of local hole density (p) by site-selective Cu-NMR studies on multilayered copper oxides. Multilayered systems provide us with the opportunity to research the characteristics of the disorder-free CuO2 plane. The site-selective NMR is the best and the only tool used to extract layer-dependent characteristics. Consequently, we have concluded that the uniform mixing of AFM and SC is a general property inherent to a single CuO2 plane in an underdoped regime of HTSC. The T=0 phase diagram of AFM constructed here is in quantitative agreement with the theories in a strong correlation regime which is unchanged even with mobile holes. This Mott physics plays a vital role for mediating the Cooper pairs to make Tc of HTSC very high. By contrast, we address from extensive NMR studies on electron-doped iron-oxypnictides La1111 compounds that the increase in Tc is not due to the development of AFM spin fluctuations, but because the structural parameters, such as the bond angle α of the FeAs4 tetrahedron and the a-axis length, approach each optimum value. Based on these results, we propose that a stronger correlation in HTSC than in FeAs-based superconductors may make Tc higher significantly. 相似文献
3.
Kinouchi H Mukuda H Yashima M Kitaoka Y Shirage PM Eisaki H Iyo A 《Physical review letters》2011,107(4):047002
We report 75As nuclear quadrupole resonance studies on (Ca4Al2O(6-y))(Fe2As2) with T(c) = 27 K. Measurement of nuclear-spin-relaxation rate 1/T1 has revealed a significant development of two-dimensional antiferromagnetic spin fluctuations down to T(c) in association with the smallest As-Fe-As bond angle. Below T(c), the temperature dependence of 1/T1 without any trace of the coherence peak is well accounted for by a nodeless s(±)-wave multiple-gaps model. From the fact that its T(c) is comparable to T(c) = 28 K in the optimally doped LaFeAsO(1-y) in which antiferromagnetic spin fluctuations are not dominant, we remark that antiferromagnetic spin fluctuations are not a unique factor for enhancing T(c) among Fe-based superconductors, but a condition for optimizing superconductivity should be addressed from the lattice structure point of view. 相似文献
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Y. Tanaka A. Iyo K. Tokiwa T. Watanabe A. Crisan A. Sundaresan N. Terada 《Physica C: Superconductivity and its Applications》2010,470(20):1010-1012
Two-component superconductivity based on the two-band superconductor has a functional topology such as an inter-band phase difference soliton (i-soliton) to realize topological electronics (topolonics). Many gauge field theories are applied to investigate the topology of two-band superconductivity. To ease experimental and electronics applications, these theories should be refined. Weinberg–Salam theory and SU(2) (two-dimensional special unitary symmetry) gauge field theory are proper starting points. An effective extra force field because of the crystal structure and inter-band Josephson interaction, rather than spontaneous symmetry breaking, simplifies the conventional gauge field theory. 相似文献
6.
Y. Tanaka P.M. ShirageA. Iyo 《Physica C: Superconductivity and its Applications》2010,470(22):2023-2026
Competition between an interband Josephson interaction and a biquadratic interband interaction can break time-reversal symmetry when the interband interactions are very weak compared with the intraband interaction. We demonstrate this using the phenomenological Ginzburg–Landau free energy, taking into account terms essential for this phenomenon. This time-reversal symmetry-breaking state peels away a sheet of an interband phase difference soliton wall. This sheet is the domain wall between two different chiral states. The peeling reduces the formation energy of the domain wall. The domain wall can simultaneously erase the Meissner effect and the specific heat jump when the entropy invokes many domain walls, and its life time is prolonged by a pinning owing to an inhomogeneity such as surface roughness. 相似文献
7.
Kimata M Terashima T Kurita N Satsukawa H Harada A Kodama K Sato A Imai M Kihou K Lee CH Kito H Eisaki H Iyo A Saito T Fukazawa H Kohori Y Harima H Uji S 《Physical review letters》2010,105(24):246403
We report the results of the angular-dependent magnetoresistance oscillations (AMROs), which can determine the shape of bulk Fermi surfaces (FSs) in quasi-two-dimensional (Q2D) systems, in a highly hole-doped Fe-based superconductor KFe2As2 with Tc ≈ 3.7 K. From the AMROs, we determined the two Q2D FSs with rounded-square cross sections, correspond to 12% and 17% of the first Brillouin zone. The rounded-squared shape of the FS cross section is also confirmed by the analyses of the interlayer transport under in-plane fields. From the obtained FS shape, we infer the character of the 3d orbitals that contribute to the FSs. 相似文献
8.
K. Nishikawa T. Masui H. Eisaki A. Iyo 《Journal of Physics and Chemistry of Solids》2008,69(12):3074-3077
We report Raman scattering spectra for single crystals of overdoped Tl2Ba2CuO6+δ (Tl-2201) at low temperatures. It was observed that the pair-breaking peaks in A1g and B1g spectra radically shift to lower energy with carrier doping. We interpret it as s-wave component mixing into d-wave, although the crystal structure is tetragonal. Since similar phenomena were observed also in YBa2Cu3Oy and Bi2Sr2CaCu2Oz, we conclude that s-wave mixing is a common property for overdoped high-Tc superconductors. 相似文献
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Recyclable carbon fiber‐reinforced plastics (CFRP) containing degradable acetal linkages: Synthesis,properties, and chemical recycling 下载免费PDF全文
Ayaka Yamaguchi Tamotsu Hashimoto Yoshinori Kakichi Michio Urushisaki Toshikazu Sakaguchi Kazumasa Kawabe Keiichi Kondo Hirohumi Iyo 《Journal of polymer science. Part A, Polymer chemistry》2015,53(8):1052-1059
Two epoxy resins containing degradable acetal linkages were synthesized by the reaction of cresol novolak‐type phenolic resin (CN) with vinyl ethers containing a glycidyl group [cyclohexane dimethanol vinyl glycidyl ether (CHDMVG) and 4‐vinyloxybutyl glycidyl ether (VBGE). Carbon fiber‐reinforced plastics (CFRPs) were prepared by heating laminated prepreg sheets with CN‐CHDMVG resin (derived from CN and CHDMVG) and CN‐VBGE resin (derived from CN and VBGE), in which carbon fibers are impregnated with epoxy resins containing curing agents [dicyandiamide (DICY)] and curing accelerator [3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea (DCMU)]. CN‐CHDMVG‐based CFRPs and CN‐VBGE‐based CFRPs exhibited almost the same tensile strength as the conventional bisphenol‐A‐based CFRPs. CN‐CHDMVG‐based CFRPs and CN‐VBGE‐based CFRPs underwent smooth breakdown with the treatment of hydrochloric acid in tetrahydrofuran at room temperature for 24 h to regenerate strands of carbon fibers. The surface conditions of the recovered carbon fibers had little changes during degradation and recovery processes on the basis of scanning electron microscopy (SEM) and X‐ray photoelectron spectroscopy (XPS). The recovered carbon fibers exhibited almost the same tensile strength as virgin carbon fibers and hence would be reused for the production of CFRPs. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1052–1059 相似文献
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P.M. Shirage K. Miyazawa H. Kito H. Eisaki A. Iyo 《Physica C: Superconductivity and its Applications》2009,469(15-20):898-900
Here we report on the invention of the Co-doped induced superconductivity in PrFe1−xCoxAsO (x = 0 and 0.075). Polycrystalline samples were prepared by high-pressure synthesis method. The PrFe1−xCoxAsO (x = 0 and 0.075) crystallizes with the ZrCuSiAs type crystal structure (P4/nmm). The PrFeAsO is a parent compound with non-superconducting phase which can be transformed to superconductor by replacement 7.5% of Fe by Co. The magnetic susceptibility measurement shows the onset of superconducting transition temperature at 15 K. 相似文献