排序方式: 共有46条查询结果,搜索用时 31 毫秒
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Kunihito Miyake Yasuhiro Masaki Ikuya Miyamoto Shozo Yanagida Takeshi Ohno Akio Yoshimura Chyongjin Pac 《Photochemistry and photobiology》1993,58(5):631-636
We have investigated the photosensitized monomerization of the cis,syn -cyclobutane dimer of 1,3-di-methylthymine using riboflavin tetraacetate and a 5-deazaflavin derivative as photosensitizer. Although little monomerization of the dimer is induced by photoexcitation of the flavins in the absence of any additives, the flavins can function as an efficient photosensitizer in the presence of magnesium perchlorate. Mechanistic studies involving spectroscopic, quantum-yield and flash-photolysis measurements demonstrated that the photosensitized monomerization exclusively proceeds through electron transfer from the dimer to the triplet flavins complexed with Mg2+ . The effects of magnesium perchlorate are compared with those on the chloranil-photosensitized monomerization and also with the effects of HClO4 on the flavin-photosensitized reaction. 相似文献
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Masuda Y Itoh T Itoh M Koumoto K 《Langmuir : the ACS journal of surfaces and colloids》2004,20(13):5588-5592
We developed a novel self-assembly process to fabricate an orderly array of particle wires constructed from a close-packed colloidal crystal without preparation of patterned templates. A substrate was immersed vertically into a SiO2 colloidal solution, and the liquid surface moved downward upon evaporation of solution. Particles formed a mono-/multiparticle layer, which was cut by the periodic drop-off of solution. The orderly array of particle wires was successfully fabricated, showing the suitability of the self-assembly process for the fabrication of nano-/microstructures constructed from nano-/microparticles or blocks. The mechanism of the assembly process and control of thickness, width, and interval of particle wires were further discussed. Moreover, an array of particle wires constructed not from close-packed face-centered cubic (or hexagonal close packed) structure but from two kinds of particles was realized to fabricate an array of particle wires with NaCl structure by this self-assembly process. 相似文献
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Masuda Y Itoh T Koumoto K 《Langmuir : the ACS journal of surfaces and colloids》2005,21(10):4478-4481
We developed a self-assembly process of silica particles to fabricate desired patterns of colloidal crystals having high feature edge acuity and high regularity. A micropattern of colloidal methanol prepared on a self-assembled monolayer in hexane was used as a mold for particle patterning, and slow dissolution of methanol into hexane caused shrinkage of molds to form micropatterns of close-packed SiO2 particle assemblies. This result is a step toward the realization ofnano/micro periodic structures for next-generation photonic devices by a self-assembly process. 相似文献
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Kiyofumi Katagiri Keiko Ohta Kunihito Koumoto Kei Kurosu Yoshihiro Sasaki Kazunari Akiyoshi 《Colloid and polymer science》2013,291(6):1375-1380
Novel organic–inorganic hybrid nanoparticles consisting of polymer–hydrogel nanoparticles (nanogels) and iron oxide were developed for potential biomedical applications. Hybrid nanoparticles were prepared by a simple procedure using polysaccharide nanogels as a reactive site for iron oxide formation. The hybrid nanoparticles have a narrow size distribution with a diameter of approximately 30 nm and show high colloidal stability. These nanohybrid particles could be used as a contrast medium for magnetic resonance imaging or for magnetic hyperthermia therapy. 相似文献
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The underlying mechanism for Adaptive Feedback Control in the experimental photoisomerization of 3,3'-diethyl-2,2'-thiacyanine iodide (NK88) in methanol is exposed theoretically. With given laboratory limitations on laser output, the complicated electric fields are shown to achieve their targets in qualitatively simple ways. Further, control over the cis population without laser limitations reveals an incoherent pump-dump scenario as the optimal isomerization strategy. In neither case are there substantial contributions from quantum multiple-path interference or from nuclear wave packet coherence. Environmentally induced decoherence is shown to justify the use of a simplified theoretical model. 相似文献
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Yuji Utsunomiya Takashi Kajiwara Takashi Nishiyama Kunihito Nagayama Shiro Kubota 《Applied Physics A: Materials Science & Processing》2010,99(3):641-649
We studied a new pulse laser ablation phenomenon on a liquid surface layer, which is caused by the difference between the
refractive indices of the two materials involved. The present study was motivated by our previous study, which showed that
laser ablation can occur at the interface between a transparent material and a gas or liquid medium when the laser pulse is
focused through the transparent material. In this case, the ablation threshold fluence is reduced remarkably. In the present
study, experiments were conducted in water and air in order to confirm this phenomenon for a combination of two fluid media
with different refractive indices. This phenomenon was observed in detail by pulse laser shadowgraphy. A high-resolution film
was used to record the phenomenon with a Nd:YAG pulse laser with 10-ns duration as a light source. The laser ablation phenomenon
on the liquid surface layer caused by a focused Nd:YAG laser pulse with 1064-nm wavelength was found to be followed by the
splashing of the liquid surface, inducing a liquid jet with many ligaments. The liquid jet extension velocity was around 1000
m/s in a typical case. The liquid jet decelerated drastically due to rapid atomization at the tips of the ligaments. The liquid
jet phenomenon was found to depend on the pulse laser parameters such as the laser fluence on the liquid surface, laser energy,
and laser beam pattern. The threshold laser fluence for the generation of a liquid jet was 20 J/cm2. By increasing the incident laser energy with a fixed laser fluence, the laser focused area increased, which eventually led
to an increase in the size of the plasma column. The larger the laser energy, the larger the jet size and the longer the temporal
behavior. The laser beam pattern was found to have significant effects on the liquid jet’s velocity, shape, and history. 相似文献
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Wilfried Wunderlich Hiromichi Ohta Kunihito Koumoto 《Physica B: Condensed Matter》2009,404(16):2202-2212
The effective mass is one of the main factors determining the Seebeck coefficient and electrical conductivity of thermo-electrics. In this ab-initio LDA-GGA study the effective mass is estimated from the curvature of electronic bands by one-band-approximation and is in excellent agreement with experimental data of Nb- and La-doped SrTiO3. It is clarified that the deformation of SrTiO3 crystals has a significant influence on the bandgap, effective electronic DOS-mass and band-mass, but the electronic effect due to the eg-band flattening near the Γ-point due to Nb-doping up to 0.2 at% is the main factor for the effective mass increase. Doping of La shows a linear decrease of the effective mass; this can be explained by the different surroundings of A- and B-sites in perovskite. Substitution with other elements such as Ba on the A-site and V on the B-site in SrTiO3 increases the effective mass as well. 相似文献
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Matsuda Y Hoki K Maeda S Hanaue K Ohta K Morokuma K Mikami N Fujii A 《Physical chemistry chemical physics : PCCP》2012,14(2):712-719
Ionization dynamics of acetone and its dimer in supersonic jets is investigated by a combination of experimental and theoretical techniques, both of which have recently been developed. In experiments, the neutral and the cationic structures are explored by infrared predissociation spectroscopy with the vacuum-ultraviolet photoionization detection schemes. Reaction paths following the one-photon ionization of the acetone monomer and its dimer have been studied by the joint use of several theoretical methods including the ab initio molecular dynamics, the global reaction route mapping, the intrinsic reaction coordinate, and the artificial force induced reaction calculations. Upon one-photon ionization, the dimer isomerizes to the H-bonded form, in which the enol cation of acetone is bound to the neutral molecule, while this enolization is energetically forbidden in the acetone monomer. The enolization of the dimer cation occurs through a two-step proton-transfer from the methyl group of the ionized moiety, and is catalyzed by the neutral moiety within the dimer cation. 相似文献