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61.
62.
The phase-matched second harmonic generation by periodic structures composed of laminae of nonlinear optical crystals has been studied experimentally. It is shown that the intensity of the second harmonic is approximately proportional to the square of the number of laminae under phase-matched condition, which is satisfied over a broad frequency range by the variation of the angle of incidence when a laminar structure with a period much larger than the coherence length is used. 相似文献
63.
Masakatsu Okada 《Optics Communications》1980,34(2):153-158
Instability in the transient response of hybrid bistable optical devices is discussed. It is applied to determine the precise conditions for optical regenerative oscillation and monostable pulse generation in three types of electrooptic bistable devices. Theoretical results explain well the sequential behaviors of these phenomena. 相似文献
64.
65.
Satoru Isoda Hiromichi Shimada Masakatsu Kochi Hirotaro Kambe 《Journal of Polymer Science.Polymer Physics》1981,19(9):1293-1312
Molecular aggregation in a commercial polyimide film, Du Pont Kapton, was investigated by small-angle x-ray scattering (SAXS). From the analysis of the desmeared SAXS curve, it is concluded that aggregation in the Kapton film can be elucidated in terms of a two-phase structure having electron density fluctuations within the phases. For comparison with the molecular aggregation in Kapton, molecular aggregation in polyimides synthesized in our laboratory was also investigated. It was found in this case that molecular aggregation is controlled by the initial imidization temperature. Molecular aggregation of polyamic acid and polyimide cyclized at a low temperature gives amorphous structures. On the other hand, molecular aggregation of polyimide cyclized at high temperatures gives two-phase structures like that of Kapton film. The SAXS curve for a polyimide having the two-phase structure shows a peak due to interference between ordered regions. The two-phase structure of the polyimide can be explained in terms of a one-dimensional model. The more ordered phase is produced at the higher initial imidization temperature. The relative density difference between two phases is only a few percent for polyimide films cyclized at high temperatures. This result shows that the two-phase structure of aromatic polyimide differs essentially from that of ordinary crystalline polymers. 相似文献
66.
67.
Masakatsu Shintomi Yuuichi Tazuke Haruyuki Takahashi 《Molecular Crystals and Liquid Crystals》2013,570(2):27-32
Abstract Magnetic and neutron studies are done about iron-intercalated titanium diselenide, FexTiSe2 with 0<x≤0.5. A neutron diffraction measurement shows that Fe-atoms are located between neighboring selenium layers. Magnetic measurements show that FexTiSe2 are spin glasses for 0. 15≤x≤0.22 and antiferromagnets for 0.25≤x≤0.5. T-x magnetic phase diagram is determined. This diagram is slightly different from that determined by Huntley et al. The difference may be caused by a formation of Fe-clusters in their samples. The x-dependence of the parameters of paramagnetic susceptibilities is determined. 相似文献
68.
Pandur Venkatesan Balaji Lennart Brewitz Naoya Kumagai Masakatsu Shibasaki 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(9):2670-2674
Thioureas have emerged as effective hydrogen‐bonding catalysts over the last two decades, and they are broadly utilized in asymmetric catalysis. We report that achiral trisubstituted thioureas function as beneficial secondary ligands to CuI catalysts, thereby enabling highly diastereo‐ and enantioselective addition of α‐fluoronitriles to imines. The structure of the thiourea significantly affects the reaction outcome, and kinetic experiments indicate that the thioureas enhance the stereocontrol by binding to the CuI complex. The reaction products can be readily transformed into valuable β‐amino acid derivatives bearing a fluorinated tetrasubstituted stereogenic center. 相似文献
69.
Nucleophilic and Electrophilic Activation of Non‐Heteroaromatic Amides in Atom‐Economical Asymmetric Catalysis 下载免费PDF全文
Dr. Naoya Kumagai Prof. Dr. Masakatsu Shibasaki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(43):15192-15200
Recent advances in catalytic asymmetric carbon–carbon bond‐forming reactions of non‐heteroaromatic amide substrates are highlighted. Among carbonyl compounds, amides have received limited attention in catalytic asymmetric transformations mainly owing to their lower reactivity. Amides are reluctant to form enolates for nucleophilic addition, and α,β‐unsaturated amides exhibit diminished electrophilicity at the β‐carbon. Recent advances in asymmetric catalysis rendered these amides amenable to enantioselective reactions with perfect atom economy, producing synthetically useful chiral building blocks. This Minireview summarizes recent developments in the field. 相似文献
70.
Nobuko Watanabe Ayu Wakatsuki Hisako K. Ijuin Yoshio Kabe Masakatsu Matsumoto 《Tetrahedron letters》2018,59(11):971-977
Organic superbases represented by TBD (1,5,7-triazabicyclo[4.4.0]dec-5-ene) effectively induced the decomposition of hydroxyaryl-substituted dioxetanes in acetonitrile to give bright light. The color of the chemiluminescence from a dioxetane bearing a 4-(benzoxazol-2-yl)-3,5-dihydroxyphenyl moiety varied depending on the base used. In addition to this change in the color of emission, TBD increased the chemiluminescence efficiency 2- to 5-fold compared to the results with other base systems and accelerated decomposition of the dioxetane. These unique effects of TBD may be due to its “bifunctional” character, which is different from those of other organic superbases. Chemiluminescent decomposition of the dioxetane was effectively induced by superbases even in apolar p-xylene. 相似文献