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排序方式: 共有1103条查询结果,搜索用时 984 毫秒
981.
Narong?TouchEmail author Shinya?Nakashita Tadashi?Hibino 《Transport in Porous Media》2012,91(2):531-546
Mud transport in sand fractures has yielded a large body of information which is used to understand the sludge-ization of
tidal flats, to improve the tidal flat environment, and to design artificial tidal flats. Over the past decades, studies of
particle transport in saturated and unsaturated porous media provide a very clear understanding of the processes that govern
particle transport. It has been reported that the particle transport and capture in porous media are significantly governed
by hydraulic pressure gradient, porosity, and permeability distribution. The objective of this research is to present a study
of mud transport in saturated sand beds, aiming to delineate the effects of the organic properties of mud on the general behavior
of mud transport and deposition condition in pores. Laboratory experiments were undertaken to look into the effects of the
organic properties. The experiments were conducted at a flow rate of 1.3 cm3/s. Many types of muds that have differences in the organic properties were injected into different sand beds at a concentration
of 120 mg/L. It was observed that the deposition condition of mud in the beds was mostly due to the organic properties of
mud. Mud containing high amounts of organic matter easily remained in sand beds. Furthermore, it was found that mud deposited
in the pores as clusters rather than being separately adsorbed onto the surface of soil particles. 相似文献
982.
Fatemeh Abrishamian Shinichi Nagai Shinya Sato Masaaki Imai 《Optical and Quantum Electronics》2008,40(9):665-676
Spectral response of acoustically induced microbending through thin optical fiber is discussed from mode-coupling of core
and cladding modes. The thin fiber is analyzed in three-layered structure (core-cladding-air) to gain insights into acousto-optic
modulation. We explained the dependence of core and/or cladding diameters on acoustic source parameters from numerical calculations.
According to the calculations, we successfully fabricated all-optical tunable filter using this thin fiber that yields an
efficient mode-coupling at flexural wave frequencies less than 1MHz. To increase the acousto-optic effect, we used a specially
designed thin optical fiber (80 μm of cladding diameter) in the section where flexural wave is produced, and spliced both
ends of the thin fiber to the tapered 125 μm fibers. The frequency and voltage tuning of fabricated filter is also confirmed
by changing the driven frequency and applied voltage of the PZT, respectively. This result suggests a possibility of fiber-optic
device application as all-optical tunable filter at 1.55 μm. 相似文献
983.
Fumihiro Ishikawa Akimasa Miyanaga Hinano Kitayama Shinya Nakamura Isao Nakanishi Fumitaka Kudo Tadashi Eguchi Genzoh Tanabe 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(21):6980-6984
Adenylation (A) domains act as the gatekeepers of non‐ribosomal peptide synthetases (NRPSs), ensuring the activation and thioesterification of the correct amino acid/aryl acid building blocks. Aryl acid building blocks are most commonly observed in iron‐chelating siderophores, but are not limited to them. Very little is known about the reprogramming of aryl acid A‐domains. We show that a single asparagine‐to‐glycine mutation in an aryl acid A‐domain leads to an enzyme that tolerates a wide range of non‐native aryl acids. The engineered catalyst is capable of activating non‐native aryl acids functionalized with nitro, cyano, bromo, and iodo groups, even though no enzymatic activity of wild‐type enzyme was observed toward these substrates. Co‐crystal structures with non‐hydrolysable aryl‐AMP analogues revealed the origins of this expansion of substrate promiscuity, highlighting an enlargement of the substrate binding pocket of the enzyme. Our findings may be exploited to produce diversified aryl acid containing natural products and serve as a template for further directed evolution in combinatorial biosynthesis. 相似文献
984.
Masashi Ozaki Ai Shimazaki Mina Jung Yumi Nakaike Naoki Maruyama Shinya Yakumaru Alwani Imanah Rafieh Takahiro Sasamori Norihiro Tokitoh Piyasiri Ekanayake Yasujiro Murata Richard Murdey Atsushi Wakamiya 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(28):9489-9493
A high‐purity methylammonium lead iodide complex with intercalated dimethylformamide (DMF) molecules, CH3NH3PbI3?DMF, is introduced as an effective precursor material for fabricating high‐quality solution‐processed perovskite layers. Spin‐coated films of the solvent‐intercalated complex dissolved in pure dimethyl sulfoxide (DMSO) yielded thick, dense perovskite layers after thermal annealing. The low volatility of the pure DMSO solvent extended the allowable time for low‐speed spin programs and considerably relaxed the precision needed for the antisolvent addition step. An optimized, reliable fabrication method was devised to take advantage of this extended process window and resulted in highly consistent performance of perovskite solar cell devices, with up to 19.8 % power‐conversion efficiency (PCE). The optimized method was also used to fabricate a 22.0 cm2, eight‐cell module with 14.2 % PCE (active area) and 8.64 V output (1.08 V/cell). 相似文献
985.
Takaya Ikeuchi Shinsuke Inuki Shinya Oishi Hiroaki Ohno 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(23):7874-7878
A gold‐catalyzed reaction of phenylene‐tethered allenynes with benzofurans gave 1‐(naphth‐1‐yl)cyclopropa[b]benzofuran derivatives, whereas the reaction of 1‐allenyl‐2‐ethynyl‐3‐methylbenzene derivatives in the absence of benzofurans gave acenaphthenes in good yields. These results can be rationalized by nucleophilic attack of the alkyne moiety on an activated allene to form a vinyl cation intermediate. 相似文献
986.
Masashi Ozaki Ai Shimazaki Mina Jung Yumi Nakaike Naoki Maruyama Shinya Yakumaru Alwani Imanah Rafieh Takahiro Sasamori Norihiro Tokitoh Piyasiri Ekanayake Yasujiro Murata Richard Murdey Atsushi Wakamiya 《Angewandte Chemie (International ed. in English)》2019,58(28):9389-9393
A high‐purity methylammonium lead iodide complex with intercalated dimethylformamide (DMF) molecules, CH3NH3PbI3?DMF, is introduced as an effective precursor material for fabricating high‐quality solution‐processed perovskite layers. Spin‐coated films of the solvent‐intercalated complex dissolved in pure dimethyl sulfoxide (DMSO) yielded thick, dense perovskite layers after thermal annealing. The low volatility of the pure DMSO solvent extended the allowable time for low‐speed spin programs and considerably relaxed the precision needed for the antisolvent addition step. An optimized, reliable fabrication method was devised to take advantage of this extended process window and resulted in highly consistent performance of perovskite solar cell devices, with up to 19.8 % power‐conversion efficiency (PCE). The optimized method was also used to fabricate a 22.0 cm2, eight‐cell module with 14.2 % PCE (active area) and 8.64 V output (1.08 V/cell). 相似文献
987.
Yoshiro Imura Ryota Akiyama Shinya Furukawa Ryota Kan Clara Morita‐Imura Takayuki Komatsu Takeshi Kawai 《化学:亚洲杂志》2019,14(4):547-552
Shape‐controlled metal nanocrystals, such as nanowires and nanoflowers, are attractive owing to their potentially novel catalytic properties and bimetallic nanocrystals composed of two distinct metals are expected to act as highly active catalysts. However, their catalytic activities are limited because of the capping agents adsorbed on the metal surfaces, which are necessary for the preparation and dispersion of these nanocrystals in solvents. Therefore, the preparation of bimetallic shape‐controlled noble metal nanocrystals with clean surfaces, devoid of almost all capping agents, are expected to have high catalytic activity. Herein, we report the preparation of bimetallic Au–Ag nanoflowers using melamine as the capping agent. The bimetallic Au–Ag nanoflowers with a clean surface were subsequently obtained by a support and extraction method. The bimetallic nanoflowers with a clean surface were then used for the aerobic oxidation of 1‐phenylethyl alcohol and they exhibited high rates for the formation of acetophenone compared to Au nanoflowers and spherical nanoparticles with almost the same size and Au/Ag ratio. We also show that Au–Ag nanoflowers containing only 1 % Ag (Au99–Ag1NFs) exhibit the highest rate of acetophenone formation among Au–Ag nanoflowers with different Au/Ag ratios owing to an increase in the electron density of the Au atoms that act as active sites for the oxidation of 1‐phenylethyl alcohol. 相似文献
988.
Hattori T Toraishi T Tsuneda T Nagasaki S Tanaka S 《The journal of physical chemistry. A》2005,109(45):10403-10409
The axial water exchange on glycinatocopper(II) complexes was theoretically investigated by using density functional theory (DFT) calculations. Glycinatocopper(II) complexes are well-known by the diffusion controlled exchange of axial ligands. Calculations using explicitly coordinating water molecules and solvent models showed that bis-glycinatocopper(II) complexes have a four-coordinate planar structure, in which waters are excluded from the axial positions of Cu(II) due to the Jahn-Teller effect. This may be because coordinating axial waters induce the discrepancy in the most stable ligand field splittings of inner 3d and outer 4d orbitals of the Cu(II) cation. To estimate the reactivity of the axial water exchange, we calculated the rate constant by calculating Gibbs free energies for the activation. As a result, we obtained the rate constant as k = 3.61 x 10(10) s(-1) in aqueous solution at T = 298.15 K. This rate constant is slightly larger than that of the diffusion controlled exchange of axial waters, which is experimentally observed in the order of 10(9) s(-1). Finally, we determined the structures of tris-glycinatocopper(II) complexes. It was consequently found that the third glycine is coordinated to Cu with the amino groups as experimentally observed. 相似文献
989.
Sasaki M Takaishi S Miyasaka H Sugiura K Yamashita M 《Journal of the American Chemical Society》2005,127(43):14958-14959
Scanning tunneling microscopy (STM) has been measured in quasi-one-dimensional (Quasi-ID) bromo-bridged Ni(III) complexes. In the STM image of [Ni(pn)2Br]Br2 (pn = (R)-1,2-diaminopropane), the bright spots are fluctuated zigzags. Such a result indicates that the methyl groups of the pn ligands are not arranged on the right- and left-hand alternatively along the chains, but in the domain structures or fluctuated structures. This is the first direct observation of the disorder of the methyl group of pn ligands in real space. 相似文献
990.