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41.
Controllable photoinduced optical attenuation in a single-mode optical fiber by irradiation of a femtosecond pulse laser 总被引:1,自引:0,他引:1
Novel optical attenuation fibers were fabricated by the irradiation of a focused infrared femtosecond pulsed laser onto the core of a silica glass single-mode optical fiber. Optical attenuation at a wavelength of 1.55 microm proportionally increased with increasing numbers of irradiation points and was controllable under laser irradiation conditions. The single-mode property of the waveguide and the mode-field diameter of the optical fiber were maintained after irradiation of the femtosecond laser. It is suggested that the attenuation results from optical scattering at photoinduced spots formed inside the fiber core. 相似文献
42.
Kazuki Nakanishi Yosuke Sato Yayat Ruyat Kazuyuki Hirao 《Journal of Sol-Gel Science and Technology》2003,26(1-3):567-570
Silica gels with hierarchical macropores and mesopores have been prepared by inducing phase separation in the alkoxide-based sol-gel system with an addition of alkyltrimethylammonium salt. Narrowly distributed mesopores were observed in the heat-treated gel samples possibly as a result of supramolecular templating of silica oligomers in the reacting solution. The ionic attractive interaction and hydrophobicity of the attached alkyl group cooperatively determined the phase separation tendency. No indication of long-range order of the mesopores was obtained. 相似文献
43.
A new tridentate cyclometalated platinum(II) complex derived from N,2-diphenyl-8-quinolinamine, which consists of two crystallographic independent molecules with two intermolecular N-H-Cl-Pt hydrogen bonds forming a dimer, exhibited a low-energy luminescence at ca. 740 nm in a 1 × 10−3 M dichloromethane solution and a strong emission centered at 670 nm in a solid state, but the analogous palladium(II) complex was nonemissive at room temperature. 相似文献
44.
Shimizu A Hirao Y Matsumoto K Kurata H Kubo T Uruichi M Yakushi K 《Chemical communications (Cambridge, England)》2012,48(45):5629-5631
An anthracene-linked bisphenalenyl Kekulé molecule with very significant singlet biradical character has shown a prominent covalent bonding interaction between molecules in a molecular aggregate. High aromatic stabilization energy in the anthracene linker is responsible for the significant singlet biradical character. 相似文献
45.
Guizhou Yue Kaining Lei Hajime Hirao Jianrong Zhou 《Angewandte Chemie (International ed. in English)》2015,54(22):6531-6535
Asymmetric reductive Heck reaction of aryl halides is realized in high stereoselectivity. Hydrogen‐bond donors, trialkylammonium salts in a glycol solvent, were used to promote halide dissociation from neutral arylpalladium complexes to access cationic, stereoselective pathways. 相似文献
46.
Shimizu M Sakakura M Kanehira S Nishi M Shimotsuma Y Hirao K Miura K 《Optics letters》2011,36(11):2161-2163
We report on the formation mechanism of element distribution in glass under high-repetition-rate femtosecond laser irradiation. We simultaneously focused two beams of femtosecond laser pulses inside a glass and confirmed the formation of characteristically shaped element distributions. The results of the numerical simulation in which we considered concentration- and temperature-gradient-driven diffusions were in excellent qualitative agreement with the experimental results, indicating that the main driving force is the sharp temperature gradient. Since the composition of a glass affects its refractive index, absorption, and luminescence property, the results in this study provide a framework to fabricate a functional optical device such as optical circuits with a high-repetition-rate femtosecond laser. 相似文献
47.
Kumar D Hirao H de Visser SP Zheng J Wang D Thiel W Shaik S 《The journal of physical chemistry. B》2005,109(42):19946-19951
Density functional theory (DFT) is applied to the dark section of the catalytic cycle of the enzyme cytochrome P450, namely, the formation of the active species, Compound I (Cpd I), from the ferric-hydroperoxide species (Cpd 0) by a protonation-assisted mechanism. The chosen 96-atom model includes the key functionalities deduced from experiment: Asp(251), Thr(252), Glu(366), and the water channels that relay the protons. The DFT model calculations show that (a) Cpd I is not formed spontaneously from Cpd 0 by direct protonation, nor is the process very exothermic. The process is virtually thermoneutral and involves a significant barrier such that formation of Cpd I is not facile on this route. (b) Along the protonation pathway, there exists an intermediate, a protonated Cpd 0, which is a potent oxidant since it is a ferric complex of water oxide. Preliminary quantum mechanical/molecular mechanical calculations confirm that Cpd 0 and Cpd I are of similar energy for the chosen model and that protonated Cpd 0 may exist as an unstable intermediate. The paper also addresses the essential role of Thr(252) as a hydrogen-bond acceptor (in accord with mutation studies of the OH group to OMe). 相似文献
48.
Shinobu Onoda Toshio Hirao Takeshi Ohshima Hisayoshi Itoh 《Radiation Physics and Chemistry》2009,78(12):1116-1119
The effect of radial ion-track distribution on the transient current in semiconductors caused by a high-energy heavy ion strike was studied. Reasonable agreement was observed in experimental and calculated transient currents for ion energies ranging from several to several hundred MeV when the radius of the ion track used in the numerical simulations was shorter or equivalent to that of the penumbra radius. 相似文献
49.
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