505 results on '"Takayuki Hirai"'
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102. Rapid, selective, and sensitive fluorometric detection of cyanide anions in aqueous media by cyanine dyes with indolium–coumarin linkages
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Kohei Yamamoto, Yasuhiro Shiraishi, Takayuki Hirai, and Masaya Nakamura
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Anions ,Indoles ,Cyanide ,Photochemistry ,Catalysis ,chemistry.chemical_compound ,Nucleophile ,Coumarins ,Nitriles ,Materials Chemistry ,Cyanine ,Fluorescent Dyes ,Detection limit ,Aqueous medium ,Chemistry ,Metals and Alloys ,Water ,General Chemistry ,Carbocyanines ,Coumarin ,Fluorescence ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Spectrometry, Fluorescence ,Ceramics and Composites ,Quantum Theory - Abstract
Cyanine dyes with indolium-coumarin linkages exhibit selective fluorescence enhancement for cyanide anions (CN(-)) via the nucleophilic interaction of CN(-) with their indolium carbon atoms. This facilitates rapid (detection time: 1 min) and sensitive (detection limit: 0.4 μM) sensing of CN(-) in aqueous media.
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- 2014
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103. Selective Photocatalytic Oxidation of Aniline to Nitrosobenzene by Pt Nanoparticles Supported on TiO2 under Visible Light Irradiation
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Satoshi Ichikawa, Hirokatsu Sakamoto, Yasuhiro Shiraishi, Takayuki Hirai, and Keisuke Fujiwara
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Inorganic chemistry ,Condensation ,General Chemistry ,Photochemistry ,Catalysis ,Nitrosobenzene ,chemistry.chemical_compound ,Aniline ,Deprotonation ,chemistry ,Photocatalysis ,Lewis acids and bases ,Visible spectrum - Abstract
Visible light irradiation (λ > 450 nm) of Pt nanoparticles supported on Degussa P25 TiO2 (Pt/P25 catalyst) promotes efficient and selective aerobic oxidation of aniline to nitrosobenzene. This is facilicated via the interband excitation of Pt atoms by visible light followed by the transfer of activated electrons to the TiO2 conduction band. The positive charges formed on the Pt surface oxidize substrates, and the conduction band electrons reduce O2, promoting photocatalytic cycles. The high activity of Pt/P25 is due to the high electron density of Pt particles. They behave as Lewis base sites for reductive deprotonation of aniline, thus promoting efficient aniline oxidation. The Pt/P25 catalyst, when photoirradiated at a low temperature (∼283 K), suppresses subsequent condensation of aniline and the formed nitrosobenzene, successfully producing nitrosobenzene with a very high selectivity (90%).
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- 2014
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104. Spiropyran-Modified Gold Nanoparticles: Reversible Size Control of Aggregates by UV and Visible Light Irradiations
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Yasuhiro Shiraishi, Satoshi Ichikawa, Hirokatsu Sakamoto, Eri Shirakawa, Takayuki Hirai, and Kazuya Tanaka
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Indoles ,Materials science ,Light ,Spectrophotometry, Infrared ,Photoisomerization ,Ultraviolet Rays ,Stacking ,Metal Nanoparticles ,Photochemistry ,chemistry.chemical_compound ,Isomerism ,Spectrophotometry ,medicine ,Benzopyrans ,General Materials Science ,Particle Size ,Spiropyran ,medicine.diagnostic_test ,Nitro Compounds ,chemistry ,Colloidal gold ,Quantum Theory ,Gold ,Self-assembly ,Isomerization ,Visible spectrum - Abstract
UV or visible light irradiation of gold nanoparticles (AuNPs) modified with a thiol-terminated spiropyran dye promotes reversible aggregation or dispersion of AuNPs. This is facilitated by the electrostatic repulsion/attraction between the AuNPs controlled by the ring-opening/closing photoisomerization of the surface dyes. This photochemical method successfully produces aggregates of AuNPs with tunable sizes (20–340 nm) and narrow size distributions (standard deviation
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- 2014
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105. Noble-Metal-Free Deoxygenation of Epoxides: Titanium Dioxide as a Photocatalytically Regenerable Electron-Transfer Catalyst
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Yoshiki Togawa, Yasuhiro Shiraishi, Takayuki Hirai, and Hiroaki Hirakawa
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Chemistry ,Reducing agent ,Alcohol ,General Chemistry ,engineering.material ,Photochemistry ,Catalysis ,chemistry.chemical_compound ,Electron transfer ,Titanium dioxide ,engineering ,Photocatalysis ,Noble metal ,Deoxygenation - Abstract
Catalytic deoxygenation of epoxides into the corresponding alkenes is a very important reaction in organic synthesis. Early reported systems, however, require noble metals, high reaction temperatures (>373 K), or toxic reducing agents. Here, we report a noble-metal-free heterogeneous catalytic system driven with alcohol as a reducing agent at room temperature. Photoirradiation (λ
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- 2014
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106. Fully bio-based polymer blend of polyamide 11 and Poly(vinylcatechol) showing thermodynamic miscibility and excellent engineering properties
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Takayuki Hirai, Mamiko Narita, Kotaro Satoh, Hisaaki Takeshima, Masami Kamigaito, Jumpei Kawada, and Taiji Ikawa
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Chemical resistance ,Materials science ,Polymers and Plastics ,Organic Chemistry ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Miscibility ,0104 chemical sciences ,Solvent ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Polyamide ,Materials Chemistry ,Polymer blend ,Polystyrene ,0210 nano-technology ,Glass transition ,Tensile testing - Abstract
Fully bio-based polyamide 11 (PA11) and poly(vinylcatechol) (PVCa) blends prepared by melt mixing demonstrate thermodynamic miscibility and excellent engineering properties. The glass transition temperature (Tg) of PA11 increases upon blending with PVCa; an 85/15 wt% PA11/PVCa blend exhibits a Tg 23–26 °C higher than that of PA11 devoid of additives. Morphological observations revealed that the PA11/PVCa blends do not phase-separate, confirming the homogeneity of PA11 and PVCa. Good chemical resistance of the PA11/PVCa blends was confirmed, with the blends resisting morphological changes even after immersion in methanol, which is a good solvent for PVCa. Tensile testing revealed that the PA11/PVCa blends have higher moduli and strengths than PA11. A PA11/nonpolar polystyrene blend was also examined by the same experimental procedure, which revealed that strong hydrogen bonding between PA11 and PVCa is the primary reason for the miscibility and excellent performance of PA11/PVCa blends.
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- 2019
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107. Blockade of Interleukin 6 Signaling Improves the Survival Rate of Transplanted Bone Marrow Stromal Cells and Increases Locomotor Function in Mice With Spinal Cord Injury
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Ying Tan, Hisatoshi Baba, Kenzo Uchida, Naoto Takeura, Alexander Rodriguez Guerrero, Shao-Yu Liu, Hideaki Nakajima, Shuji Watanabe, William E. B. Johnson, and Takayuki Hirai
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Male ,Necrosis ,Stromal cell ,Cell Survival ,Motor Activity ,Mesenchymal Stem Cell Transplantation ,Pathology and Forensic Medicine ,Proinflammatory cytokine ,Mice ,Cellular and Molecular Neuroscience ,stomatognathic system ,Neurotrophic factors ,medicine ,Animals ,Interleukin 6 ,Spinal cord injury ,Spinal Cord Injuries ,Neurons ,biology ,Interleukin-6 ,business.industry ,Mesenchymal Stem Cells ,Recovery of Function ,General Medicine ,medicine.disease ,Receptors, Interleukin-6 ,Survival Rate ,Transplantation ,Disease Models, Animal ,medicine.anatomical_structure ,Neurology ,Immunology ,Cancer research ,biology.protein ,Neurology (clinical) ,Bone marrow ,medicine.symptom ,business ,Signal Transduction - Abstract
Bone marrow stromal cells (BMSCs) have the potential to improve functional recovery in patients with spinal cord injury (SCI); however, they are limited by low survival rates after transplantation in the injured tissue. Our objective was to clarify the effects of a temporal blockade of interleukin 6 (IL-6)/IL-6 receptor (IL-6R) engagement using an anti-mouse IL-6R monoclonal antibody (MR16-1) on the survival rate of BMSCs after their transplantation in a mouse model of contusion SCI. MR16-1 cotreatment improved the survival rate of transplanted BMSCs, allowing some BMSCs to differentiate into neurons and astrocytes, and improved locomotor function recovery compared with BMSC transplantation or MR16-1 treatment alone. The death of transplanted BMSCs could be mainly related to apoptosis rather than necrosis. Transplantation of BMSC with cotreatment of MR16-1 was associated with a decrease of some proinflammatory cytokines, an increase of neurotrophic factors, decreased apoptosis rates of transplanted BMSCs, and enhanced expression of survival factors Akt and extracellular signal-regulated protein kinases 1/2. We conclude that MR16-1 treatment combined with BMSC transplants helped rescue neuronal cells and axons after contusion SCI better than BMSCs alone by modulating the inflammatory/immune responses and decreasing apoptosis.
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- 2013
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108. Pt–Cu Bimetallic Alloy Nanoparticles Supported on Anatase TiO2: Highly Active Catalysts for Aerobic Oxidation Driven by Visible Light
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Yoshitsune Sugano, Yasuhiro Shiraishi, Hirokatsu Sakamoto, Satoshi Ichikawa, and Takayuki Hirai
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Anatase ,Materials science ,General Engineering ,General Physics and Astronomy ,Nanoparticle ,Heterojunction ,Photochemistry ,Catalysis ,chemistry.chemical_compound ,chemistry ,Titanium dioxide ,Photocatalysis ,General Materials Science ,Bimetallic strip ,Visible spectrum - Abstract
Visible light irradiation (λ450 nm) of Pt-Cu bimetallic alloy nanoparticles (~3-5 nm) supported on anatase TiO2 efficiently promotes aerobic oxidation. This is facilicated via the interband excitation of Pt atoms by visible light followed by the transfer of activated electrons to the anatase conduction band. The positive charges formed on the nanoparticles oxidize substrates, and the conduction band electrons reduce molecular oxygen, promoting photocatalytic cycles. The apparent quantum yield for the reaction on the Pt-Cu alloy catalyst is ~17% under irradiation of 550 nm monochromatic light, which is much higher than that obtained on the monometallic Pt catalyst (~7%). Cu alloying with Pt decreases the work function of nanoparticles and decreases the height of the Schottky barrier created at the nanoparticle/anatase heterojunction. This promotes efficient electron transfer from the photoactivated nanoparticles to anatase, resulting in enhanced photocatalytic activity. The Pt-Cu alloy catalyst is successfully activated by sunlight and enables efficient and selective aerobic oxidation of alcohols at ambient temperature.
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- 2013
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109. Rutile Crystallites Isolated from Degussa (Evonik) P25 TiO2: Highly Efficient Photocatalyst for Chemoselective Hydrogenation of Nitroaromatics
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Yoshitsune Sugano, Yoshiki Togawa, Yasuhiro Shiraishi, Hiroaki Hirakawa, Satoshi Ichikawa, and Takayuki Hirai
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Hydrogen ,Inorganic chemistry ,chemistry.chemical_element ,General Chemistry ,Photochemistry ,Catalysis ,chemistry.chemical_compound ,Adsorption ,Hydrofluoric acid ,chemistry ,Rutile ,Titanium dioxide ,Photocatalysis ,Crystallite - Abstract
We report that the rutile crystallites, isolated from Degussa (Evonik) P25 TiO2 by a hydrofluoric acid treatment, behave as a highly efficient photocatalyst for hydrogenation of nitroaromatics. Photoirradiation (λ >300 nm) of the isolated rutile particles with alcohol as a hydrogen source successfully promotes chemoselective hydrogenation of nitroaromatics to anilines, with an activity higher than that of commercially available rutile TiO2. The high activity of the isolated rutile particles is due to the specific distribution of structural defects (oxygen vacancy sites) on the particles. These particles contain a relatively small number of inner defects behaving as recombination centers for photoformed electron (e–) and positive hole (h+) pairs, and a relatively large number of surface defects behaving as reduction sites for nitroaromatics. Photoexcitation of the isolated particles therefore promotes efficient charge separation between e– and h+, and facilitates rapid reduction of nitroaromatics adsorbed ...
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- 2013
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110. Selective Hydrogen Peroxide Formation by Titanium Dioxide Photocatalysis with Benzylic Alcohols and Molecular Oxygen in Water
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Daijiro Tsukamoto, Takayuki Hirai, Yasuhiro Shiraishi, Shunsuke Kanazawa, Akimitsu Shiro, and Yoshitsune Sugano
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Hydrogen ,Inorganic chemistry ,chemistry.chemical_element ,Alcohol ,General Chemistry ,Photochemistry ,Peroxide ,Oxygen ,Catalysis ,chemistry.chemical_compound ,chemistry ,Titanium dioxide ,Photocatalysis ,Hydrogen peroxide - Abstract
Photocatalytic production of hydrogen peroxide (H2O2) on semiconductor catalysts with alcohol as a hydrogen source and molecular oxygen (O2) as an oxygen source has attracted much attention as a potential method for safe H2O2 synthesis, because the reaction can be carried out without the use of explosive H2/O2 mixed gases. Early reported photocatalytic systems with aliphatic alcohol as a hydrogen source, however, produce only a few millimolar levels of H2O2. We found that benzylic alcohols, when used as a hydrogen source for photoreaction in water with titanium dioxide (TiO2) photocatalyst, produce a very high concentration of H2O2 (ca. 40 mM). Raman spectroscopy and electron spin resonance analysis revealed that the enhanced H2O2 formation is due to the efficient formation of side-on coordinated peroxo species on the photoactivated TiO2 surface, via the reaction of benzylic alcohol and O2. The peroxo species is readily transformed to H2O2, thus facilitating highly efficient H2O2 production.
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- 2013
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111. Supported Au-Cu Bimetallic Alloy Nanoparticles: An Aerobic Oxidation Catalyst with Regenerable Activity by Visible-Light Irradiation
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Shunsuke Tanaka, Takayuki Hirai, Daijiro Tsukamoto, Satoshi Ichikawa, Yasuhiro Shiraishi, and Yoshitsune Sugano
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Materials science ,Visible light irradiation ,Alloy ,Nanoparticle ,Degussa p25 ,General Chemistry ,General Medicine ,engineering.material ,Photochemistry ,Catalysis ,Catalytic oxidation ,engineering ,Irradiation ,Bimetallic strip ,Nuclear chemistry - Abstract
Visible-light irradiation (
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- 2013
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112. Colorimetric Sensing of Cu(II) in Aqueous Media with a Spiropyran Derivative via a Oxidative Dehydrogenation Mechanism
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Kazuya Tanaka, Yasuhiro Shiraishi, and Takayuki Hirai
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Spiropyran ,Indoles ,Luminescent Agents ,Ligand ,Imine ,Substituent ,Ab initio ,Nitro Compounds ,Photochemistry ,chemistry.chemical_compound ,chemistry ,Benzopyrans ,Colorimetry ,General Materials Science ,Amine gas treating ,Dehydrogenation ,Imines ,Amines ,Oxidation-Reduction ,Copper ,Derivative (chemistry) - Abstract
A spiropyran derivative containing a simple NO bidentate ligand (2) was synthesized. The ligand acts as a colorimetric chemodosimeter for selective Cu(2+) detection in aqueous media. The ligand, even when treated at elevated temperature (60 °C), exists as a spirocyclic form and shows almost no absorption in the visible region. This is because the electron donation by an amine substituent suppresses spirocycle-opening. Treatment of the solution with Cu(2+) at 60 °C, however, creates a strong absorption at 450-650 nm, whereas other metal cations do not promote spectral change. IR, NMR, and ab initio calculation revealed that Cu(2+) is coordinated with two 2 ligands and produces 1:2 Cu(2+)-amine complex intermediately. This is converted to the 1:2 Cu(+)-imine complex via oxidative dehydrogenation of amine moieties, along with the reduction of Cu(2+). The formation of the imine complex decreases the electron density of nitrogen atoms and weakens the electron donation ability. This thus promotes thermal spirocycle opening and facilitates coloration of the solution.
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- 2013
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113. N-Monoalkylation of Amines with Alcohols by Tandem Photocatalytic and Catalytic Reactions on TiO2 Loaded with Pd Nanoparticles
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Yasuhiro Shiraishi, Satoshi Ichikawa, Takayuki Hirai, Keisuke Fujiwara, and Yoshitsune Sugano
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chemistry.chemical_classification ,Imine ,Nanoparticle ,chemistry.chemical_element ,General Chemistry ,Photochemistry ,Aldehyde ,Catalysis ,chemistry.chemical_compound ,chemistry ,Alcohol oxidation ,Photocatalysis ,Amine gas treating ,Palladium - Abstract
TiO2 loaded with Pd particles (Pd/TiO2), when photoirradiated at λ > 300 nm in alcohol containing primary amine, efficiently promotes N-monoalkylation of amine with alcohol, producing the corresponding secondary amine with almost quantitative yields. This occurs via tandem photocatalytic and catalytic reactions: (i) Pd-assisted alcohol oxidation on the photoactivated TiO2, (ii) condensation of the formed aldehyde with amine on the TiO2 surface, and (iii) hydrogenation of the formed imine by the surface H atoms on the Pd particles. The rate-determining step is the imine hydrogenation, and the reaction depends strongly on the size of the Pd particles. The catalyst with 0.3 wt % Pd, containing 2–2.5 nm Pd particles, shows the highest activity for imine hydrogenation, and smaller or larger Pd particles are inefficient. Calculations of the number of surface Pd atoms based on the cuboctahedron particle model revealed that the Pd atoms on the triangle site of Pd particles are the active site for hydrogenation. L...
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- 2013
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114. FUNDAMENTAL INVESTIGATION ON COLOR, MECHANICAL PROPERTIES, AND THERMAL SHADING/INSULATING PROPERTIES OF CEMENTITIOUS MATERIALS INCLUDING PIGMENT
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Makoto Yamaguchi, Sho-ichi Kondo, and Takayuki Hirai
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Materials science ,General Medicine ,Composite material - Abstract
To investigate the usability of concrete colored by pigment for building wall members, experimental investigations were conducted regarding various fundamental properties of cement-based materials including pigment. The main results obtained are as follows:1)it is expected that the pigment mixing rate from which the coloring effect reaches at its peak exists;2)the color of mortar linearly changes in the L*a*b*color space by varying of the pigment mixing rate;3)mechanical characteristics of mortar are hardly influenced by the pigment mixing rate;4)the lightness of surface of cement paste specimen tends to be larger than that of inside of the specimen, and the tendency does not change after the outdoor exposure for six months;and 5)it is effective in improving the indoor thermal environment of reinforced concrete facilities to mix suitable pigment into the concrete.無機顔料混入により着色したコンクリートの建築壁材への利用に資するため、顔料混入セメント系材料の各種基礎物性について実験的検討を行った。その結果として、①着色効果が最大となる顔料混入率が存在する可能性が認められること、②顔料混入により、モルタルの色彩はL*a*b*色空間を直線的に変化すること、③顔料混入がモルタルの力学的特性に及ぼす影響は小さいこと、④顔料混入セメントペーストの色彩は、内部よりも表面で高明度となり、その傾向は6か月間の屋外暴露を経ても殆ど変化しないこと、⑤適切な顔料の使用が鉄筋コンクリート造建築物の屋内温熱環境を制御する上で有効となり得ること、等の知見が得られた。
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- 2013
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115. Carbon Nitride-Aromatic Diimide-Graphene Nanohybrids: Metal-Free Photocatalysts for Solar-to-Hydrogen Peroxide Energy Conversion with 0.2% Efficiency
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Hirokatsu Sakamoto, Yusuke Kofuji, Yuki Isobe, Satoshi Ichikawa, Shunsuke Tanaka, Takayuki Hirai, and Yasuhiro Shiraishi
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Graphene ,chemistry.chemical_element ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Photochemistry ,01 natural sciences ,Biochemistry ,Catalysis ,0104 chemical sciences ,law.invention ,Organic semiconductor ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,chemistry ,law ,Diimide ,Photocatalysis ,Moiety ,Water splitting ,0210 nano-technology ,Carbon ,Carbon nitride - Abstract
Solar-to-chemical energy conversion is a challenging subject for renewable energy storage. In the past 40 years, overall water splitting into H2 and O2 by semiconductor photocatalysis has been studied extensively; however, they need noble metals and extreme care to avoid explosion of the mixed gases. Here we report that generating hydrogen peroxide (H2O2) from water and O2 by organic semiconductor photocatalysts could provide a new basis for clean energy storage without metal and explosion risk. We found that carbon nitride-aromatic diimide-graphene nanohybrids prepared by simple hydrothermal-calcination procedure produce H2O2 from pure water and O2 under visible light (λ420 nm). Photoexcitation of the semiconducting carbon nitride-aromatic diimide moiety transfers their conduction band electrons to graphene and enhances charge separation. The valence band holes on the semiconducting moiety oxidize water, while the electrons on the graphene moiety promote selective two-electron reduction of O2. This metal-free system produces H2O2 with solar-to-chemical energy conversion efficiency 0.20%, comparable to the highest levels achieved by powdered water-splitting photocatalysts.
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- 2016
116. Coumarin-Spiropyran Dyad with a Hydrogenated Pyran Moiety for Rapid, Selective, and Sensitive Fluorometric Detection of Cyanide Anion
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Yasuhiro Shiraishi, Takayuki Hirai, Masaya Nakamura, and Naoto Hayashi
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Spiropyran ,Nucleophilic addition ,Quantum yield ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Photochemistry ,Coumarin ,01 natural sciences ,Fluorescence ,0104 chemical sciences ,Analytical Chemistry ,chemistry.chemical_compound ,chemistry ,Pyran ,Molecule ,Moiety ,0210 nano-technology - Abstract
We synthesized a coumarin-spiropyran dyad with a hydrogenated pyran moiety (2), behaving as an off-on type fluorescent receptor for rapid, selective, and sensitive detection of cyanide anion (CN(-)) in aqueous media. The receptor itself shows almost no fluorescence with a quantum yield0.01, due to the delocalization of π-electrons over the molecule. Selective nucleophilic addition of CN(-) to the spirocarbon of the molecule rapidly promotes spirocycle opening within only 3 min. This leads to localization of π-electrons on the coumarin moiety and exhibits strong light-blue fluorescence at 459 nm with very high quantum yield (0.52). As a result of this, the receptor facilitates rapid, selective, and sensitive fluorometric detection of CN(-) as low as 1.0 μM.
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- 2016
117. Phase I study of NK105, a nanomicellar paclitaxel formulation, administered on a weekly schedule in patients with solid tumors
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Takayuki Hirai, Tetsuya Hamaguchi, Taito Esaki, Hirofumi Mukai, Yoshihiro Nambu, Ken Kato, Rika Goda, Shouzou Ohsumi, Yasuo Hozomi, Yasuhiro Matsumura, and Nobuaki Matsubara
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0301 basic medicine ,Adult ,Male ,medicine.medical_specialty ,Maximum Tolerated Dose ,Paclitaxel ,Neutropenia ,Gastroenterology ,Drug Administration Schedule ,DDS ,03 medical and health sciences ,chemistry.chemical_compound ,0302 clinical medicine ,Breast cancer ,Pharmacokinetics ,Internal medicine ,Neoplasms ,Phase I Studies ,medicine ,Humans ,Pharmacology (medical) ,Tissue Distribution ,Survival rate ,Aged ,Neoplasm Staging ,Pharmacology ,Aged, 80 and over ,business.industry ,Cancer ,Middle Aged ,medicine.disease ,Prognosis ,NK105 ,Antineoplastic Agents, Phytogenic ,Surgery ,Phase i study ,Survival Rate ,030104 developmental biology ,chemistry ,Oncology ,030220 oncology & carcinogenesis ,Toxicity ,Polymeric micelles ,Female ,business ,Follow-Up Studies - Abstract
Previous studies have established the rationale for NK105, a nanomicellar formulation of paclitaxel, administered every 3 weeks. The aim of this phase I study was to determine the recommended dose and pharmacokinetics of weekly administered NK105. NK105 was administered by a 30-min infusion once weekly for three consecutive weeks in each 4-week cycle. In the dose-escalation phase, three to seven patients with solid tumors were enrolled to each of the four dose levels (50–100 mg/m2; n = 16). At a dose level of 100 mg/m2, predefined dose-limiting toxicity (DLT) manifested in only one out of six evaluable patients, whereas a dose delay due to neutropenia during the first course occurred two patients. None of the three patients given 80 mg/m2 had a dose reduction, while a dose delay occurred in two. NK105 exhibited linear pharmacokinetics at doses of 50–100 mg/m2, and approximately 5 % of total paclitaxel was released from micelles. Thus, the recommended dose was set at 80 mg/m2, and an additional 10 advanced breast cancer (ABC) patients were given this dose in the dose-expansion phase. DLT manifested in two patients, and grade ≥ 3 neutropenia was found in eight patients. Among the nine patients who completed the first cycle, four had a dose reduction, mostly because of neutropenia. Of the 10 patients, six achieved partial response (PR), and four achieved stable disease (SD) status. Overall, weekly NK105 was well tolerated and had a desirable antitumor activity profile. Further investigations of NK105 in ABC patients are currently underway.
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- 2016
118. Highly Efficient and Selective Hydrogenation of Nitroaromatics on Photoactivated Rutile Titanium Dioxide
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Shunsuke Tanaka, Yasuhiro Shiraishi, Takayuki Hirai, Yoshiki Togawa, and Daijiro Tsukamoto
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Anatase ,Inorganic chemistry ,General Chemistry ,Photochemistry ,Catalysis ,chemistry.chemical_compound ,Adsorption ,Aniline ,chemistry ,Rutile ,Titanium dioxide ,Photocatalysis ,Selectivity - Abstract
We report that photoactivated rutile titanium dioxide (TiO2) catalyzes a highly efficient and selective hydrogenation of nitroaromatics with alcohol as a hydrogen source. Photoirradiation (λ >300 nm) of rutile TiO2 suspended in alcohol containing nitroaromatics at room temperature and atmospheric pressure produces the corresponding anilines with almost quantitative yields, whereas common anatase and P25 TiO2 show poor activity and selectivity. The Ti3+ atoms located at the oxygen vacancies on the rutile surface behave as the adsorption site for nitroaromatics and the trapping site for photoformed conduction band electrons. These effects facilitate rapid and selective nitro-to-amine hydrogenation of the adsorbed nitroaromatics by the surface-trapped electrons, enabling aniline formation with significantly high quantum yields (>25% at
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- 2012
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119. Platinum Nanoparticles Supported on Anatase Titanium Dioxide as Highly Active Catalysts for Aerobic Oxidation under Visible Light Irradiation
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Yoshitsune Sugano, Shunsuke Tanaka, Takayuki Hirai, Daijiro Tsukamoto, Yasuhiro Shiraishi, Satoshi Ichikawa, and Akimitsu Shiro
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Anatase ,Materials science ,Schottky barrier ,chemistry.chemical_element ,Nanoparticle ,General Chemistry ,Platinum nanoparticles ,Photochemistry ,Catalysis ,chemistry ,Photocatalysis ,Platinum ,Visible spectrum - Abstract
Visible light irradiation (λ >450 nm) of platinum (Pt) nanoparticles supported on anatase titanium dioxide (TiO2) promotes efficient aerobic oxidation at room temperature. This occurs via the electronic excitation of Pt particles by visible light followed by the transfer of their electrons to anatase conduction band. The positively charged Pt particles oxidize substrates, whereas the conduction band electrons are consumed by the reduction of molecular oxygen. The activity of this photocatalysis depends on the height of Schottky barrier and the number of perimeter Pt atoms created at the Pt/anatase heterojunction, which are affected by the amount of Pt loaded and the size of Pt particles. The catalyst loaded with 2 wt % Pt, containing 3–4 nm Pt particles, creates a relatively low Schottky barrier and a relatively large number of perimeter Pt atoms and, hence, facilitates smooth Pt→anatase electron transfer, resulting in very high photocatalytic activity. This catalyst is successfully activated by sunlight ...
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- 2012
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120. Gold Nanoparticles Located at the Interface of Anatase/Rutile TiO2 Particles as Active Plasmonic Photocatalysts for Aerobic Oxidation
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Shunsuke Tanaka, Takayuki Hirai, Daijiro Tsukamoto, Yoshitsune Sugano, Yasuhiro Shiraishi, and Satoshi Ichikawa
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Anatase ,Time Factors ,Light ,Photochemistry ,Metal Nanoparticles ,chemistry.chemical_element ,Electrons ,Biochemistry ,Catalysis ,Electron transfer ,Colloid and Surface Chemistry ,Titanium ,Binding Sites ,Chemistry ,Temperature ,General Chemistry ,Oxygen ,Models, Chemical ,Colloidal gold ,Rutile ,Alcohols ,Alcohol oxidation ,Photocatalysis ,Gold ,Visible spectrum - Abstract
Visible-light irradiation (λ450 nm) of gold nanoparticles loaded on a mixture of anatase/rutile TiO(2) particles (Degussa, P25) promotes efficient aerobic oxidation at room temperature. The photocatalytic activity critically depends on the catalyst architecture: Au particles with5 nm diameter located at the interface of anatase/rutile TiO(2) particles behave as the active sites for reaction. This photocatalysis is promoted via plasmon activation of the Au particles by visible light followed by consecutive electron transfer in the Au/rutile/anatase contact site. The activated Au particles transfer their conduction electrons to rutile and then to adjacent anatase TiO(2). This catalyzes the oxidation of substrates by the positively charged Au particles along with reduction of O(2) by the conduction band electrons on the surface of anatase TiO(2). This plasmonic photocatalysis is successfully promoted by sunlight exposure and enables efficient and selective aerobic oxidation of alcohols at ambient temperature.
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- 2012
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121. Photocatalytic H2O2 Production from Ethanol/O2 System Using TiO2 Loaded with Au–Ag Bimetallic Alloy Nanoparticles
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Yoshitsune Sugano, Akimitsu Shiro, Shunsuke Tanaka, Takayuki Hirai, Yasuhiro Shiraishi, Satoshi Ichikawa, and Daijiro Tsukamoto
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Materials science ,Alloy ,Inorganic chemistry ,Nanoparticle ,Heterojunction ,General Chemistry ,engineering.material ,Catalysis ,chemistry.chemical_compound ,Adsorption ,Chemical engineering ,chemistry ,Titanium dioxide ,engineering ,Photocatalysis ,Bimetallic strip - Abstract
TiO2 loaded with Au–Ag bimetallic alloy particles efficiently produces H2O2 from an O2-saturated ethanol/water mixture under UV irradiation. This is achieved via the double effects created by the alloy particles. One is the efficient photocatalytic reduction of O2 on the Au atoms promoting enhanced H2O2 formation, due to the efficient separation of photoformed electron–hole pairs at the alloy/TiO2 heterojunction. Second is the suppressed photocatalytic decomposition of formed H2O2 due to the decreased adsorption of H2O2 onto the Au atoms.
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- 2012
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122. Visible light-induced partial oxidation of cyclohexane on WO3 loaded with Ptnanoparticles
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Yoshitsune Sugano, Yasuhiro Shiraishi, Takayuki Hirai, and Satoshi Ichikawa
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chemistry.chemical_compound ,Cyclohexane ,chemistry ,Photocatalysis ,Cyclohexanol ,Cyclohexanone ,Partial oxidation ,Photochemistry ,Selectivity ,Catalysis ,Visible spectrum - Abstract
Photocatalytic oxidation of cyclohexane (CHA) with molecular oxygen (O2) was carried out using WO3 loaded with Pt nanoparticles (Pt/WO3) under irradiation of visible light (λ > 420 nm). The Pt/WO3 catalysts promote oxidation of CHA and give rise to partial oxidation products such as cyclohexanol (CHA-ol) and cyclohexanone (CHA-one) with ca. 93% selectivity. Among the catalysts, Pt/WO3 with 0.2 wt% Pt shows the highest activity. The high selectivity for partial oxidation on Pt/WO3 is because subsequent photocatalytic decomposition of partial oxidation products is suppressed. In the Pt/WO3 system, the photoformed electrons on the conduction band of WO3 are consumed by a multi-electron reduction of O2 on the Pt particles (formation of H2O and H2O2), where a single-electron reduction of O2 is unfavored. This suppresses the formation of a superoxide anion (O2˙−) that promotes decomposition of CHA-ol and CHA-one and, hence, results in selective formation of partial oxidation products.
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- 2012
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123. INFLUENCES OF SLAB COMPOSITION USING PRECAST SMALL ELEMENTS ON BLAST RESISTANCE
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Kiyoshi Murakami, Takayuki Hirai, Makoto Yamaguchi, Yoshiyuki Mitsui, and Koji Takeda
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Materials science ,business.industry ,Detonation ,Local failure ,Building and Construction ,Fiber-reinforced concrete ,Structural engineering ,Polyethylene ,law.invention ,chemistry.chemical_compound ,chemistry ,law ,Precast concrete ,Architecture ,Slab ,Composite material ,business - Published
- 2012
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124. AN EXPERIMENTAL STUDY ON BLAST-RESISTANT STRENGTHENING OF REINFORCED CONCRETE SLABS USING CONTINUOUS FIBER REINFORCEMENTS
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Yoshiyuki Mitsui, Nobuhiro Hisabe, Koji Takeda, Takayuki Hirai, Kiyoshi Murakami, and Makoto Yamaguchi
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Materials science ,business.industry ,Architecture ,Local failure ,Building and Construction ,Fiber ,Structural engineering ,Composite material ,Reinforced concrete ,Reinforcement ,business - Published
- 2012
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125. Colorimetric sensing of cyanide anion in aqueous media with a fluorescein–spiropyran conjugate
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Shigehiro Sumiya, Takayuki Doi, Yasuhiro Shiraishi, and Takayuki Hirai
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Spiropyran ,Aqueous solution ,Nitrile ,Cyanide ,Organic Chemistry ,Photochemistry ,Biochemistry ,chemistry.chemical_compound ,chemistry ,Absorption band ,Drug Discovery ,Merocyanine ,Absorption (chemistry) ,Conjugate - Abstract
A fluorescein–spiropyran conjugate (2) behaves as a receptor for colorimetric sensing of cyanide anion (CN−) in aqueous media under irradiation of UV light. The compound 2, which exists as a spirocycle-closed (SP) form in the dark condition, is isomerized to the spirocycle-opened merocyanine (MC) form upon irradiation of UV light and shows absorption bands at 467 and 568 nm. Addition of CN− to the solution leads to a decrease in these bands and an appearance of new absorption band at 512 nm, via a nucleophilic interaction between CN− and the spirocarbon of MC form. This absorption change occurs selectively with CN− and enables ratiometric quantification of CN− by absorption analysis.
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- 2012
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126. High-Mobility Group Box-1 and Its Receptors Contribute to Proinflammatory Response in the Acute Phase of Spinal Cord Injury in Rats
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Hisatoshi Baba, Wei-Ying Ma, Takayuki Hirai, Ke-Bing Chen, Hideaki Nakajima, Shao-Yu Liu, Ping Zhu, Shigeru Kobayashi, Alexander Rodriguez Guerrero, Kenzo Uchida, and Takafumi Yayama
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Pathology ,medicine.medical_specialty ,Time Factors ,Immunoelectron microscopy ,Immunoblotting ,Receptor for Advanced Glycation End Products ,Fluorescent Antibody Technique ,Proinflammatory cytokine ,RAGE (receptor) ,Anterior Horn Cells ,Animals ,Medicine ,Orthopedics and Sports Medicine ,HMGB1 Protein ,Receptors, Immunologic ,Acute-Phase Reaction ,Microscopy, Immunoelectron ,Receptor ,Spinal cord injury ,Spinal Cord Injuries ,Neurons ,Interleukin-6 ,Tumor Necrosis Factor-alpha ,business.industry ,Macrophages ,medicine.disease ,Spinal cord ,Immunohistochemistry ,Toll-Like Receptor 2 ,Rats ,Toll-Like Receptor 4 ,medicine.anatomical_structure ,Immunology ,TLR4 ,Cytokines ,Tumor necrosis factor alpha ,Neurology (clinical) ,Inflammation Mediators ,business ,Interleukin-1 ,Protein Binding - Abstract
Study design To examine the localization and expression of high-mobility group box-1 (HMGB-1) protein and its receptors after rat spinal cord injury. Objective To elucidate the contribution of HMGB-1 and its receptors as potential candidates in a specific upstream pathway to the proinflammatory response leading to a cascade of secondary tissue damage after spinal cord injury. Summary of background data HMGB-1 was recently characterized as a key cytokine with a potential role in nucleosome formation and regulation of gene transcription. No studies have investigated the role of HMGB-1 in spinal cord injury. Methods Injured thoracic spinal cord from 62 rats aged 8 to 12 weeks and spinal cord from 20 control rats were examined. HMGB-1 was localized by immunofluorescence staining, costaining with cell markers, and by immunoelectron microscopy. The expression of HMGB-1 and its receptors, receptor for advanced glycation end products (RAGE), toll-like receptor (TLR)2, and TLR4 were also examined by immunohistochemistry. Results HMGB-1 expression appeared earlier than that of tumor necrosis factor-α, interleukin (IL)-1β, and IL-6 in the spinal cord injury rats, with the HMGB-1 produced by both macrophages and neurons. HMGB-1 translocated from nucleus to cytoplasm in some neurons at an early stage after neural injury. Increased expression of HMGB-1, RAGE, and TLRs was observed after injury, and interaction of HMGB-1 with RAGE or TLRs, particularly in macrophage, was confirmed at 3 days after injury. Conclusion Our results demonstrated an earlier onset in the expression of HMGB-1 than in tumor necrosis factor-α, IL-1β, and IL-6 after spinal cord injury. The release of HMGB-1 from neurons and macrophages is mediated through the HMGB-1/RAGE or TLR pathways. HMGB-1 seems to play at least some roles in the proinflammatory cascade originating the secondary damage after the initial spinal cord injury.
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- 2011
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127. Thermoresponsive Copolymer Containing a Coumarin–Spiropyran Conjugate: Reusable Fluorescent Sensor for Cyanide Anion Detection in Water
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Shigehiro Sumiya, Takayuki Hirai, Kenji Manabe, and Yasuhiro Shiraishi
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Anions ,Spiropyran ,chemistry.chemical_classification ,Cyanides ,Indoles ,Polymers ,Biosensing Techniques ,Polymer ,Nitro Compounds ,Photochemistry ,Fluorescence ,chemistry.chemical_compound ,chemistry ,Nucleophile ,Coumarins ,Polymer chemistry ,Copolymer ,Moiety ,Benzopyrans ,General Materials Science ,Merocyanine ,Water Pollutants, Chemical ,Conjugate - Abstract
A simple copolymer consisting of N-isopropylacrylamide and coumarin-conjugated spiropyran (CS) units, poly(NIPAM-co-CS), has been synthesized. This polymer enables selective fluorometric detection of cyanide anion (CN(-)) in water at room temperature. The polymer itself shows almost no fluorescence, but shows a strong blue fluorescence in the presence of CN(-) under irradiation of UV light. The fluorescence enhancement occurs via a nucleophilic interaction between CN(-) and the photoformed merocyanine form of the CS unit, leading to a localization of π-electrons on the coumarin moiety. The polymer enables accurate determination of very low levels of CN(-) (0.5 μM). The polymer can be recovered from water by simple centrifugation at high temperature (40 °C), due to the heat-induced aggregation of the polymer. In addition, the polymer is regenerated by simple acid treatment, and the resulting polymer is successfully reused for further CN(-) sensing without loss of sensitivity.
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- 2011
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128. Visible-Light-Induced Partial Oxidation of Cyclohexane by Cr/Ti/Si Ternary Mixed Oxides with Molecular Oxygen
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Takayuki Hirai, Daijiro Tsukamoto, Akimitsu Shiro, and Yasuhiro Shiraishi
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Materials science ,Cyclohexane ,Inorganic chemistry ,Oxide ,Cyclohexanol ,Cyclohexanone ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Catalysis ,law.invention ,Tetraethyl orthosilicate ,chemistry.chemical_compound ,General Energy ,chemistry ,law ,Calcination ,Partial oxidation ,Physical and Theoretical Chemistry - Abstract
Cr/Ti/Si ternary mixed oxides (CrTiSi) were prepared by a hydrolysis of tetraethyl orthosilicate (TEOS), Cr(NO3)3, and titanium tetraisopropoxide (TTIP) followed by calcination. These oxides were used as catalysts for partial oxidation of cyclohexane with molecular oxygen under irradiation of visible light (λ > 400 nm). The CrTiSi catalysts produce cyclohexanol and cyclohexanone with high selectivity (>91%) and show much higher activity than the CrSi binary oxides. Among them, the catalyst with equimolar amounts of Cr and Ti shows the highest activity. Visible-light irradiation of the CrSi catalyst promotes a reduction of tetrahedrally coordinated Cr oxide species (Td6+) and produces the excited state (Td4+*), which behaves as an active site for oxidation. In contrast, the CrTiSi catalyst contains tetrahedrally coordinated Cr and Ti oxide species that are connected through the Cr–O–Ti bond. The photoformed Td4+* species is strongly stabilized due to delocalization of excited electrons on the Cr–O–Ti speci...
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- 2011
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129. Tumor Necrosis Factor-α Antagonist Reduces Apoptosis of Neurons and Oligodendroglia in Rat Spinal Cord Injury
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Kenzo Uchida, Shao-Yu Liu, Shigeru Kobayashi, Takayuki Hirai, Wei-Ying Ma, Ke-Bing Chen, Hideaki Nakajima, Alexander Rodriguez Guerrero, Shuji Watanabe, Takafumi Yayama, and Hisatoshi Baba
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Male ,musculoskeletal diseases ,Pathology ,medicine.medical_specialty ,Recombinant Fusion Proteins ,Apoptosis ,Receptors, Tumor Necrosis Factor ,Luxol fast blue stain ,Etanercept ,Rats, Sprague-Dawley ,Myelin ,medicine ,Animals ,Orthopedics and Sports Medicine ,Spinal cord injury ,Spinal Cord Injuries ,Neurons ,TUNEL assay ,Tumor Necrosis Factor-alpha ,business.industry ,medicine.disease ,Spinal cord ,Rats ,Oligodendroglia ,medicine.anatomical_structure ,Terminal deoxynucleotidyl transferase ,Immunoglobulin G ,Anesthesia ,Acute Disease ,Tumor necrosis factor alpha ,Neurology (clinical) ,business ,medicine.drug - Abstract
Study Design. To examine the effects of a tumor necrosis factor (TNF)-α antagonist (etanercept) on rat spinal cord injury and identify a possible mechanism for its action. Objective. To elucidate the contribution of etanercept to the pathologic cascade in spinal cord injury and its possible suppression of neuronal and oligodendroglial apoptosis. Summary of Background Data. Etanercept has been recently used successfully for treatment of inflammatory disorders. However, only a few studies have examined its role in suppressing neuronal and oligodendroglial apoptosis in spinal cord injury. Methods. Etanercept or saline (control) was administered by intraperitoneal injection 1 hour after thoracic spinal cord injury in rats. The expressions and localizations of TNF-α, TNF receptor 1 (TNFR1), and TNF receptor 2 (TNFR2) were examined by immunoblot and immunohistochemical analyses. Spinal cord tissue damage between saline- and etanercept-treated groups was also compared after hematoxylin-eosin and luxol fast blue (LFB) staining. The Basso-Beattie-Bresnahan (BBB) scale was used to evaluate rat locomotor function after etanercept administration. Terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick end labeling (TUNEL)-positive cells were counted and the immunoreactivity to active caspase-3 and caspase-8 was examined after etanercept administration. Results. Immunoblot and double immunofluorescence staining revealed suppression of TNF-α, TNFR1, and TNFR2 expression after administration of etanercept in the acute phase of spinal cord injury. LFB staining demonstrated potential myelination in the etanercept-treated group from 2 week after spinal cord injury, together with an increased BBB locomotor score. Double immunofluorescence staining showed a significant decrease in TUNEL-positive neurons and oligodendroglia from 12 hour to 1 week in the gray and white matters after etanercept administration. Immunoblot analysis demonstrated overexpression of activated caspase-3 and caspase-8 after spinal cord injury, which was markedly inhibited by etanercept. Conclusion. Our results indicated that etanercept reduces the associated tissue damage of spinal cord injury, improves hindlimb locomotor function, and facilitates myelin regeneration. This positive effect of etanercept on spinal cord injury is probably attributable to the suppression of TNF-α, TNFR1, TNFR2, and activated caspase-3 and caspase-8 overexpressions, and the inhibition of neuronal and oligodendroglial apoptosis.
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- 2011
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130. Selective Photocatalytic Oxidation of Alcohols to Aldehydes in Water by TiO2 Partially Coated with WO3
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Takayoshi Hara, Shunsuke Tanaka, Yasuhiro Shiraishi, Takayuki Hirai, Makoto Ikeda, Daijiro Tsukamoto, and Nobuyuki Ichikuni
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chemistry.chemical_classification ,Organic Chemistry ,technology, industry, and agriculture ,General Chemistry ,Photochemistry ,Aldehyde ,Catalysis ,law.invention ,chemistry.chemical_compound ,Adsorption ,chemistry ,law ,Alcohol oxidation ,Photocatalysis ,Tungstic acid ,Calcination ,Selectivity - Abstract
Semiconductor TiO(2) particles loaded with WO(3) (WO(3)/TiO(2)), synthesized by impregnation of tungstic acid followed by calcination, were used for photocatalytic oxidation of alcohols in water with molecular oxygen under irradiation at λ>350 nm. The WO(3)/TiO(2) catalysts promote selective oxidation of alcohols to aldehydes and show higher catalytic activity than pure TiO(2). In particular, a catalyst loading 7.6 wt % WO(3) led to higher aldehyde selectivity than previously reported photocatalytic systems. The high aldehyde selectivity arises because subsequent photocatalytic decomposition of the formed aldehyde is suppressed on the catalyst. The TiO(2) surface of the catalyst, which is active for oxidation, is partially coated by the WO(3) layer, which leads to a decrease in the amount of formed aldehyde adsorbed on the TiO(2) surface. This suppresses subsequent decomposition of the aldehyde on the TiO(2) surface and results in high aldehyde selectivity. The WO(3)/TiO(2) catalyst can selectively oxidize various aromatic alcohols and is reusable without loss of catalytic activity or selectivity.
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- 2011
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131. A benzoxadiazole–thiourea conjugate as a fluorescent chemodosimeter for Hg(II) in aqueous media
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Yasuhiro Shiraishi, Takahiro Sugii, Takayuki Hirai, and Shigehiro Sumiya
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Quenching (fluorescence) ,Chemistry ,General Chemical Engineering ,General Physics and Astronomy ,General Chemistry ,Photochemistry ,Fluorescence ,Photoinduced electron transfer ,chemistry.chemical_compound ,Aniline ,Thiourea ,Moiety ,Derivative (chemistry) ,Conjugate - Abstract
A benzoxadiazole–thiourea conjugate ( 1 ) was synthesized and used for chemodosimetric detection of Hg 2+ in aqueous media. The compound 1 shows a selective and quantitative fluorescence quenching upon addition of Hg 2+ . This is promoted via a Hg 2+ -induced desulfurization of the thiourea moiety, leading to a formation of an imidazoline derivative, 2 . Ab initio molecular orbital calculation reveals that the formation of imidazoline moiety by the reaction of 1 with Hg 2+ promotes a photoinduced electron transfer from the aniline moiety to the excited state benzoxadiazole moiety and results in fluorescence quenching.
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- 2011
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132. Rapid colorimetric sensing of cyanide anion in aqueous media with a spiropyran derivative containing a dinitrophenolate moiety
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Masataka Itoh, Yasuhiro Shiraishi, and Takayuki Hirai
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Spiropyran ,Aqueous solution ,Nucleophilic addition ,Cyanide ,Organic Chemistry ,Photochemistry ,Biochemistry ,chemistry.chemical_compound ,chemistry ,Drug Discovery ,Moiety ,Merocyanine ,Selectivity ,Derivative (chemistry) - Abstract
A spiropyran derivative containing a dinitrophenolate moiety ( 2 : 1′,3′,3′-trimethyl-6,8-dinitro-spiro-[2 H -1-benzopyran-2,2′-indoline]) behaves as a receptor for selective detection of cyanide anion (CN − ) in aqueous media. Compound 2 , when dissolved in aqueous media, spontaneously produces the spirocycle-opened merocyanine (MC) form even in dark condition. The absorption band of the MC form decreases selectively upon addition of CN − , via a nucleophilic addition of CN − to the spirocarbon of the MC form. The nucleophilic addition occurs very rapidly (within 1 min) and enables rapid and selective quantification of very low levels of CN − (>0.8 μM) by an absorption analysis.
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- 2011
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133. Colorimetric response of spiropyran derivative for anions in aqueous or organic media
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Yasuhiro Shiraishi, Takayuki Hirai, and Masataka Itoh
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Spiropyran ,Nucleophilic addition ,Aqueous solution ,Nitrile ,Chemistry ,Organic Chemistry ,Protonation ,Photochemistry ,Biochemistry ,chemistry.chemical_compound ,Nucleophile ,Drug Discovery ,Acetonitrile ,Derivative (chemistry) - Abstract
We previously found that a simple spiropyran derivative (1:1′,3′,3′-trimethyl-6-nitro-spiro-[2H-1-benzopyran-2,2′-indoline]) behaves as a selective and sensitive cyanide anion (CN−) receptor in aqueous media under UV irradiation 13 . The receptor, when irradiated by UV light in a water/MeCN mixture, creates a CN−-selective absorption band via a nucleophilic addition of CN− to 1 (formation of the 1–CN− species) and allows quantitative determination of very low levels of CN−. In the present work, effects of pH and water content on the response of 1 to anions were studied to clarify the detailed properties of 1. In aqueous media, 1 reacts selectively with CN−regardless of pH and water content, but the reaction is suppressed by a decrease in pH and an increase in water content due to the protonation of CN−. In contrast, in pure MeCN, addition of F− also creates a new absorption band, as does CN−. This is promoted via a nucleophilic interaction between 1 and F− in a 1:2 stoichiometry (formation of the 1–2F− species). The 1–CN− and 1–2F− species have different photochemical properties; the 1–CN− species is stable upon UV irradiation, while the UV irradiation of the 1–2F− species leads to a decomposition of the spiropyran platform.
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- 2011
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134. Cu(II)-selective fluorescence of a bis-quinolylimine derivative
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Yasuhiro Shiraishi, Takayuki Hirai, and Chizuru Ichimura
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Ligand ,General Chemical Engineering ,Condensation ,Quinoline ,General Physics and Astronomy ,General Chemistry ,Photochemistry ,Fluorescence ,chemistry.chemical_compound ,chemistry ,Moiety ,Acetonitrile ,Stoichiometry ,Derivative (chemistry) - Abstract
A new bis-quinolylimine ligand containing an azadiene moiety, 1,4-bis(2-quinolyl)-2,3-diaza-1,3-buthadiene (1), was synthesized by one-step facile condensation. This simple ligand, when dissolved in acetonitrile, shows a Cu2+-selective fluorescence enhancement. Coordination of 1 with Cu2+ produces two kinds of complexes with 1:1 and 1:2 stoichiometries. The 1:2 complex shows a strong fluorescence (ΦF = 0.37), while the 1:1 complex does not (ΦF
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- 2011
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135. Fabrication of defocus graded-index optical waveguide for evanescent wave optical amplifier
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Eisuke Nihei and Takayuki Hirai
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Optical amplifier ,Dye laser ,Materials science ,business.industry ,Physics::Optics ,Waveguide (optics) ,Atomic and Molecular Physics, and Optics ,Transverse mode ,Slot-waveguide ,Optics ,Optoelectronics ,Radiation mode ,business ,Plastic optical fiber ,Nonlinear Sciences::Pattern Formation and Solitons ,Refractive index - Abstract
This is the first report on an evanescent wave optical amplifier with a plastic waveguide that can amplify a CW signal transmitted by a plastic optical fiber. The waveguide with a concave refractive index distribution was fabricated by an interfacial-gel polymerization technique. Since the waveguide increases the number of reflections at the boundary surface of the waveguide and the laser dye solution, the enhancement of amplification efficiency can be realized. The function of the fabricated waveguide was confirmed by calculations and experiments. The obtained results indicate that the fabricated fiber generated a larger evanescent field than the waveguide without a refractive index distribution.
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- 2014
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136. Association of Nodular Hyperplasia With Resistance to Cinacalcet Therapy for Secondary Hyperparathyroidism in Hemodialysis Patients
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Norihisa Takasugi, Takayuki Hirai, Noriaki Yorioka, and Ayumu Nakashima
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medicine.medical_specialty ,Hyperparathyroidism ,Cinacalcet ,biology ,business.industry ,medicine.medical_treatment ,Hematology ,Hyperplasia ,medicine.disease ,Gastroenterology ,Surgery ,N-terminal telopeptide ,Nephrology ,Internal medicine ,medicine ,Osteocalcin ,biology.protein ,Secondary hyperparathyroidism ,Hemodialysis ,Prospective cohort study ,business ,medicine.drug - Abstract
There have been few long-term prospective studies investigating the effect of cinacalcet on secondary hyperparathyroidism with or without nodular hyperplasia. We examined whether the effect of cinacalcet on secondary hyperparathyroidism differed between patients with or without nodular hyperplasia. Stable hemodialysis patients with secondary hyperparathyroidism resistant to conventional treatment received cinacalcet for 12 months. Based on ultrasonography findings, patients were divided into group S (gland < 500 mm(3) without nodular hyperplasia) and group L (gland ≥ 500 mm(3) with nodular hyperplasia). Serum levels of intact parathyroid hormone, bone-specific alkaline phosphatase, osteocalcin, and cross-linked N-terminal telopeptide of type 1 collagen were measured. Thirty-one patients completed the study. The changes of parameters from the baseline did not differ significantly between the two groups after 6 months. However, the percentage reduction of each parameter was significantly smaller in group L compared with group S after 12 months. Nodular hyperplasia is associated with resistance to cinacalcet therapy in patients on chronic dialysis with secondary hyperparathyroidism.
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- 2010
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137. Local Viscosity Analysis of Triblock Copolymer Micelle with Cyanine Dyes as a Fluorescent Probe
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Yasuhiro Shiraishi, Takuya Inoue, and Takayuki Hirai
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Quantum yield ,Concentration effect ,Surfaces and Interfaces ,Poloxamer ,Condensed Matter Physics ,Photochemistry ,Micelle ,Fluorescence ,Viscosity ,chemistry.chemical_compound ,chemistry ,Excited state ,Electrochemistry ,Organic chemistry ,General Materials Science ,Cyanine ,Spectroscopy - Abstract
The local viscosity of Pluronic F127 triblock copolymer micelles in water was determined with cyanine dyes as fluorescent probes. These dyes show very weak fluorescence at a low temperature, but show enhanced fluorescence at a temperature higher than the critical micellization temperature (T(cm)). This is because a viscous environment within the micelle suppresses the formation of a nonradiative twisted intramolecular charge transfer (TICT) excited state of the dyes. The good correlation between the fluorescence quantum yields of the dyes and the viscosity and the temperature of the media allows a determination of local viscosity of micelle based on the fluorescence quantum yields. The local viscosity of both core and corona regions of micelles increases atT(cm) and shows a maximum at a temperature 7-9 °C higher than T(cm), and decreases at higher temperature due to the increased fluidity. The core viscosity is larger than that of the corona, and the corona viscosity increases toward the micelle center. The polymer concentration has different effects on the core and corona viscosity: the corona viscosity increases with a polymer concentration increase at the entire temperature range, whereas the core viscosity increases only at a low temperature. The corona viscosity increase is due to the condensation of a large number of polyethylene oxide (PEO) blocks. In contrast, the dehydration degree of polypropylene oxide (PPO) blocks in the core scarcely changes, and the core has a similar composition regardless of polymer concentration. The larger polymer concentration promotes a micelle formation at lower temperature where the fluidity increase is very weak, resulting in larger core viscosity.
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- 2010
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138. Plasma osteoprotegerin, arterial stiffness, and mortality in normoalbuminemic Japanese hemodialysis patients
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Norihisa Takasugi, Noriaki Yorioka, Ayumu Nakashima, Juan Jesus Carrero, Toshinori Ueno, Yoshihiko Taniguchi, Takayuki Hirai, Abdul Rashid Qureshi, and Bengt Lindholm
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Male ,musculoskeletal diseases ,medicine.medical_specialty ,Brachial Artery ,Endocrinology, Diabetes and Metabolism ,medicine.medical_treatment ,Osteoporosis ,Vascular Stiffness ,Osteoprotegerin ,Renal Dialysis ,Internal medicine ,medicine ,Humans ,Risk factor ,Pulse wave velocity ,Serum Albumin ,Aged ,business.industry ,Middle Aged ,Prognosis ,medicine.disease ,Rheumatology ,Surgery ,medicine.anatomical_structure ,Cardiovascular Diseases ,Cardiology ,Arterial stiffness ,Kidney Failure, Chronic ,Female ,Hemodialysis ,Epidemiologic Methods ,business ,Biomarkers ,Blood Flow Velocity ,Artery - Abstract
A high circulating osteoprotegerin (OPG) level may be a risk factor for vascular calcification and mortality in hemodialysis patients. OPG and pulse wave velocity (PWV) were measured at baseline in 151 normoalbuminemic, long-term (3 years) Japanese hemodialysis patients who were prospectively followed for 6 years. In long-term normoalbuminemic Japanese hemodialysis patients, OPG levels were strongly linked with both arterial stiffness and worse outcome.A high circulating OPG level is reported to be a risk factor for vascular calcification and mortality in Western chronic kidney disease (CKD) patients but it is not known if this is true for Japanese CKD patients, where a different risk profile may operate.OPG and PWV were measured at baseline in 151 normoalbuminemic, long-term (3 years) Japanese hemodialysis patients (median age 62 years) who were prospectively followed for 6 years.OPG levels were associated in multivariate analysis with age, dialysis vintage, history of cardiovascular disease (CVD) and parathyroid hormone levels. C-reactive protein levels did not correlate with OPG. Patients with clinical history of CVD had significantly higher OPG levels and OPG levels were positively correlated to PWV, an index of arterial stiffness. These associations were independent of age, sex, dialysis vintage, and diabetes. During the follow-up period, 40 deaths, including 25 cardiovascular deaths, were recorded. In crude analysis, each unit of increase in OPG was associated with increased all-cause (hazard ratios 1.14, 95% confidence interval 1.08-1.20) and CVD mortality (1.14 [1.07-1.21]), which persisted after adjustment for age, sex, dialysis vintage, diabetes, and baseline CVD (1.12 [1.05-1.19] and 1.11 [1.02-1.19], all-cause and CVD mortality, respectively).In long-term normoalbuminemic Japanese hemodialysis patients, with low prevalence of inflammation, OPG levels were strongly linked with both arterial stiffness and worse outcome.
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- 2010
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139. Fluorescence properties of polyamines bearing two terminal quinoline fragments in water
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Takayuki Hirai, Yasuhiro Shiraishi, and Chizuru Ichimura
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Ligand ,Stereochemistry ,Organic Chemistry ,Quinoline ,Ethylenediamine ,Biochemistry ,Fluorescence ,chemistry.chemical_compound ,Crystallography ,chemistry ,Triethylenetetramine ,Stability constants of complexes ,Drug Discovery ,Diethylenetriamine ,Polyamine - Abstract
Fluorescence properties of polyamines bearing two terminal quinoline fragments with different polyamine chain length, such as ethylenediamine ( L0 ), diethylenetriamine ( L1 ), and triethylenetetramine ( L2 ), have been studied in water. These ligands show Zn 2+ -induced fluorescence enhancement, while showing almost no enhancement with other cations. However, stability constants for Zn 2+ coordination and fluorescence response against Zn 2+ depend strongly on the polyamine chain length. The chain length also affects the fluorescence wavelength. The Zn 2+ – L1 and Zn 2+ – L2 complexes show emission at 410 nm, while Zn 2+ – L0 complexes show a blue-shifted emission at 375 nm due to the partial charge transfer from the excited state quinoline to the Zn 2+ center.
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- 2010
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140. Photosensitized isomerization of olefin with benzophenone-conjugated amphiphilic graft copolymers
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Takayuki Hirai, Yasuhiro Shiraishi, and Takeshi Suzuki
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Olefin fiber ,Photoisomerization ,General Chemical Engineering ,General Physics and Astronomy ,General Chemistry ,Conjugated system ,Photochemistry ,Micelle ,chemistry.chemical_compound ,chemistry ,Polymer chemistry ,Benzophenone ,Methyl methacrylate ,Isomerization ,Acrylic acid - Abstract
Two kinds of amphiphilic graft copolymers, PAA-g-P(MMA-co-BP) and P(AA-co-BP)-g-PMMA, consisting of polar poly(acrylic acid) (PAA), less polar poly(methyl methacrylate) (PMMA), and benzophenone (BP) photosensitizing units, have been synthesized. These polymers, when used as a photosensitizer for isomerization of trans-β-methylstyrene, show a sensitization activity controlled by solvents. In benzene and chloroform, P(AA-co-BP)-g-PMMA forms a micelle structure consisting of aggregated P(AA-co-BP) core with dissolved PMMA units at the outer sphere. This suppresses a triplet energy transfer (TET) from the excited state BP units to olefin and, hence, shows lower sensitization activity than a bulk sensitizer (4-methoxybenzophenone: MBP). In methanol, both polymers form a weak aggregate of less polar PMMA units containing dissolved PAA units. The internal cavity of the aggregate is less polar and stabilizes the excited state BP units. This accelerates a TET from the excited state BP units to olefin and shows higher sensitization activity than MBP.
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- 2010
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141. A distyryl BODIPY derivative as a fluorescent probe for selective detection of chromium(III)
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Takayuki Hirai, Yasuhiro Shiraishi, and Dongping Wang
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musculoskeletal diseases ,Denticity ,Chemistry ,Organic Chemistry ,chemistry.chemical_element ,chemical and pharmacologic phenomena ,hemic and immune systems ,Photochemistry ,Biochemistry ,Fluorescence ,Metal ,chemistry.chemical_compound ,Chromium ,visual_art ,parasitic diseases ,Drug Discovery ,visual_art.visual_art_medium ,Molecule ,BODIPY ,Derivative (chemistry) ,Red fluorescence - Abstract
A new boradiazaindacene (BODIPY) derivative (1a) bearing simple NO bidentate ligands has been synthesized. The 1a molecule behaves as a fluorescent probe for Cr3+ and shows strong red fluorescence upon coordination with Cr3+, while showing almost no fluorescence for other metal cations.
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- 2010
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142. Highly Efficient Methyl Ketone Synthesis with Photoactivated Acetone and Olefins Assisted by Mg(II)-Exchanged Zeolite Y
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Yasuhiro Shiraishi, Takayuki Hirai, and Daijiro Tsukamoto
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chemistry.chemical_classification ,Magnetic Resonance Spectroscopy ,Ketone ,Photochemistry ,Organic Chemistry ,Free-radical reaction ,Stereoisomerism ,Alkenes ,Ketones ,Crystallography, X-Ray ,Hydrogen atom abstraction ,Catalysis ,Acetone ,chemistry.chemical_compound ,Models, Chemical ,chemistry ,Zeolites ,Moiety ,Magnesium ,Selectivity ,Magnesium ion - Abstract
We previously found that photoirradiation of an acetone/water mixture containing olefins affords the corresponding methyl ketones highly efficiently and selectively via a water-assisted C-C coupling between the acetonyl radical and olefins (Org. Lett. 2008, 10, 3117-3120). The reaction proceeds at room temperature without any additives and has a potential to be a powerful method for methyl ketone synthesis. Here we report that an addition of Mg(2+)-exchanged zeolite Y (MgY) to the above photoreaction system accelerates the methyl ketone formation, while maintaining high selectivity. Ab initio molecular orbital calculation reveals that the accelerated methyl ketone formation is due to the electrostatic interaction between Mg(2+) and excited-state acetone. This leads to a charge polarization of the carbonyl moiety of excited-state acetone and accelerates the hydrogen abstraction from ground-state acetone (acetonyl radical formation). This promotes efficient addition of the acetonyl radical to olefins, resulting in methyl ketone formation enhancement. Adsorption experiments reveal that accumulation of olefins inside the zeolite pore also affects efficient radical addition to olefins. The present process successfully produces various methyl ketones with very high yield, and the MgY recovered can be reused for further reaction without loss of activity.
- Published
- 2010
- Full Text
- View/download PDF
143. Visible light-induced photosensitized decomposition of organic pollutants with polymer nanocapsules encapsulating Fe(bpy)32+ complex
- Author
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Takayuki Hirai, Kenji Manabe, and Yasuhiro Shiraishi
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Chemistry ,Process Chemistry and Technology ,Radical ,Inorganic chemistry ,chemistry.chemical_element ,Photochemistry ,Heterogeneous catalysis ,Decomposition ,Oxygen ,Catalysis ,Nanocapsules ,Bipyridine ,chemistry.chemical_compound ,Photosensitizer ,General Environmental Science ,Visible spectrum - Abstract
Cross-linked polymer nanocapsules (PC) encapsulating an iron tris(bipyridine) complex, Fe(bpy)32+@PC, have been synthesized by a ship-in-a-bottle method. This was used as a photosensitizer for the decomposition of organic pollutant in water under visible light irradiation with molecular oxygen. The Fe(bpy)32+@PC promotes efficient decomposition of organic pollutant, whereas noncapsulated Fe(bpy)32+ is inactive. The enhanced sensitization activity of Fe(bpy)32+ within PC is due to the interaction with the PC wall. This lengthens the lifetime of the excited state Fe(bpy)32+ and promotes efficient production of hydroxyl radicals. The sensitization activity of Fe(bpy)32+@PC depends on the thickness of the PC wall. The Fe(bpy)32+@PC with an appropriate PC wall thickness allows accumulation of pollutant within the PC and, hence, promotes efficient decomposition of pollutant.
- Published
- 2010
- Full Text
- View/download PDF
144. INFLUENCES OF ADDITIVE RATE OF SUPERPLASTICIZER AND USE OF CRUSHED SAND AS FINE AGGREGATE ON MECHANICAL CHARACTERISTICS OF POLYETHYLENE FIBER REINFORCED CONCRETE
- Author
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Kiyoshi Murakami, Koji Takeda, Takayuki Hirai, and Makoto Yamaguchi
- Subjects
chemistry.chemical_compound ,Materials science ,Aggregate (composite) ,chemistry ,law ,Superplasticizer ,General Medicine ,Fiber-reinforced concrete ,Polyethylene ,Composite material ,law.invention - Published
- 2010
- Full Text
- View/download PDF
145. BLAST RESISTANCE OF DOUBLE-LAYERED SLABS COMPOSED OF PRECAST THIN PLATES
- Author
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Makoto Yamaguchi, Kiyoshi Murakami, Takayuki Hirai, and Yoshiyuki Mitsui
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endocrine system ,Toughness ,animal structures ,Materials science ,business.industry ,Rapid construction ,Detonation ,Building and Construction ,Fiber-reinforced concrete ,Structural engineering ,Polyethylene ,Spall ,law.invention ,chemistry.chemical_compound ,chemistry ,law ,Precast concrete ,Architecture ,Slab ,Composite material ,business - Abstract
For rapid construction of blast-resistant structures and better blast resistance of PEFRC (polyethylene fiber-reinforced concrete) slab, the double-layered PEFRC slabs composed of precast thin plates with 50 mm thick were proposed and supplied for contact detonation tests. Based on the test results, numerical simulation with the ANSYS AUTODYN code was conducted to clarify fracture mechanism of double-layered normal concrete slab with an air space. The main results obtained are as follows: 1) making an air space of 15 mm thick in the middle of the double-layered PEFRC slab is effective in reducing spall damage, however, an air space is disadvantageous in normal concrete; 2) breach in the lower layer of the air-sandwiched normal concrete slab is due to impact of concrete fragments occurred in the back surface of the upper layer; and 3) good blast resistance of the air-sandwiched PEFRC slab can be explained qualitatively, considering high toughness of both layers due to bridging effects of polyethylene short fibers.
- Published
- 2010
- Full Text
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146. Functionally graded Pd/γ-alumina composite membrane fabricated by electroless plating with emulsion of supercritical CO2
- Author
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Hideo Kameyama, Takayuki Hirai, Yakichi Higo, Md. Mizanur Rahman, Masato Sone, Makoto Sakurai, Minoru Ozawa, and Masahiro Seshimo
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Supercritical carbon dioxide ,Materials science ,Nanoporous ,Metallurgy ,Filtration and Separation ,Penetration (firestop) ,Biochemistry ,Supercritical fluid ,Catalysis ,Membrane ,Pulmonary surfactant ,Chemical engineering ,Emulsion ,General Materials Science ,Physical and Theoretical Chemistry - Abstract
This paper proposes a functionally graded Pd/γ-alumina composite membrane fabricated by a novel method for electroless plating by combining supercritical fluid technology and Pd electroless plating in a hybrid technique. The electroless plating reactions on catalyzed nanoporous γ-alumina surfaces were carried out in an emulsion of supercritical carbon dioxide (sc-CO 2 ) and an electroless plating solution with fluorinated surfactant F(CF(CH 3 )CF 2 O) 3 CF(CF 3 )COO(CH 2 CH 2 O)CH 3 . Pd/γ-alumina graded membrane produced by electroless plating with sc-CO 2 had thicker Pd/γ-alumina graded layer and smoother surface than conventional electroless plating. In electroless plating with sc-CO 2 , the penetration into the nanoporous γ-alumina pores was dominant reaction because the deposited Pd particles were smaller and, moreover, the electroless plating media with dispersed CO 2 has lower viscosity than conventional electroless plating. The Pd membrane formed in the emulsion of sc-CO 2 was about 1 μm thickness and composed of a composite membrane of 0.45 mol m −2 min −1 as hydrogen flux, while 0.30 mol m −2 min −1 of the Pd membrane formed by conventional electroless plating.
- Published
- 2009
- Full Text
- View/download PDF
147. Spiropyran as a Selective, Sensitive, and Reproducible Cyanide Anion Receptor
- Author
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Yasuhiro Shiraishi, Kenichi Adachi, Masataka Itoh, and Takayuki Hirai
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Anions ,Spiropyran ,Cyanides ,Indoles ,Aqueous medium ,Ultraviolet Rays ,Organic Chemistry ,food and beverages ,Nitro Compounds ,Photochemical Processes ,Photochemistry ,Biochemistry ,chemistry.chemical_compound ,chemistry ,Benzopyrans ,Irradiation ,Physical and Theoretical Chemistry ,Receptor ,Cyanide anion ,Derivative (chemistry) ,Environmental Monitoring ,Visible spectrum - Abstract
A spiropyran derivative (1) behaves as a selective and sensitive cyanide anion receptor in aqueous media under UV irradiation. The receptor can be reproduced just by irradiation with visible light.
- Published
- 2009
- Full Text
- View/download PDF
148. A BODIPY–indole conjugate as a colorimetric and fluorometric probe for selective fluoride anion detection
- Author
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Takayuki Hirai, Takahiro Sugii, Yasuhiro Shiraishi, Dongping Wang, and Hajime Maehara
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Indole test ,Hydrogen bond ,Organic Chemistry ,Inorganic chemistry ,Photochemistry ,Biochemistry ,Fluorescence ,Ion ,chemistry.chemical_compound ,chemistry ,Drug Discovery ,BODIPY ,Fluoride ,Stoichiometry ,Conjugate - Abstract
A BODIPY–indole conjugate, 1, behaves as a colorimetric and fluorometric probe for selective and sensitive detection of F−. Compound 1 interacts with F− in a 1:1 stoichiometry via a hydrogen bonding interaction between the indolic NH proton and F−, leading to clear color change from blue to green and quenching of orange fluorescence.
- Published
- 2009
- Full Text
- View/download PDF
149. Effects of alkyl chain length on Cu(II)-selective green fluorescence of rhodamine–diacetic acid conjugates
- Author
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Yasuhiro Shiraishi, Takayuki Hirai, Xuan Zhang, and Shigehiro Sumiya
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chemistry.chemical_classification ,Steric effects ,General Chemical Engineering ,General Physics and Astronomy ,chemistry.chemical_element ,General Chemistry ,Photochemistry ,Fluorescence ,Copper ,Rhodamine ,chemistry.chemical_compound ,chemistry ,Amide ,Self-assembly ,Alkyl ,Conjugate - Abstract
Fluorescence properties of rhodamine–diacetic acid conjugates ( 1a – e ), with different alkyl chain length (C2–C6) between the rhodamine and the diacetic acid moieties, have been studied in the presence of Cu 2+ and Hg 2+ . Without cations or with other cations, these probes show almost no fluorescence; however, addition of Cu 2+ creates strong green fluorescence at around 530 nm, while Hg 2+ addition shows weak orange fluorescence at around 580 nm. The Cu 2+ -induced green fluorescence originates from self-assembled aggregates of the probes formed by coordination association with multiple Cu 2+ ions. Coordination association of the probes with Cu 2+ is weakened with an increase in the chain length of the probes due to longer distance between the amide oxygen and the diacetic acid binding sites. In contrast, the green fluorescence intensity is not related to the coordination association strength; some probes show high fluorescence intensity. This is probably because alkyl chains sterically affect the alignment of the probes during aggregation interaction and, hence, produces aggregates with different fluorescence property.
- Published
- 2009
- Full Text
- View/download PDF
150. Effect of substrate polarity on photocatalytic activity of titanium dioxide particles embedded in mesoporous silica
- Author
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Takayuki Hirai, Yasuhiro Shiraishi, Yoshitsune Sugano, and Daisuke Inoue
- Subjects
Inorganic chemistry ,technology, industry, and agriculture ,Substrate (chemistry) ,Mesoporous silica ,Catalysis ,Titanium oxide ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Reagent ,Titanium dioxide ,Photocatalysis ,Reactivity (chemistry) ,Physical and Theoretical Chemistry - Abstract
Photocatalytic activity of TiO 2 particles embedded in mesoporous silica (TiO 2 @MPS), prepared by surfactant-templating method with a TiO 2 colloidal suspension, has been studied in water with molecular oxygen. Photocatalytic reactions of several kinds of aromatic molecules with TiO 2 @MPS reveal that less polar substrates show high reactivity, while polar substrates show much lower reactivity. Electron spin resonance analysis with spin-trapping reagents reveals that less polar substrates diffuse easily into the pore of the catalysts and react efficiently with short-lived hydroxyl ( OH) radicals formed at the surface of inner TiO 2 particles, resulting in a high reactivity. In contrast, polar substrates cannot diffuse into the pores and hence, shows a low reactivity. The photocatalytic activity of TiO 2 @MPS driven by the substrate polarity is applicable to selective transformation of a less polar reactant to a polar product, such as hydroxylation of benzene to phenol with high selectivity (>69%).
- Published
- 2009
- Full Text
- View/download PDF
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