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排序方式: 共有204条查询结果,搜索用时 15 毫秒
1.
Summary Well-defined living polymers of isobutyl vinyl ether were obtained in the polymerization initiated with ethylaluminum dichloride (EtAlCl2) in conjunction with a stoichiometric excess of dioxane (5–10 vol%) in n-hexane at 0°C. Under these conditions, the number-average molecular weight of the polymers increased in direct proportion to monomer conversion, while the molecular weight distribution stayed narrow (Mw/Mn = 1.1–1.25). In sharp contrast, the EtAlCl2-initiated polymerization in the absence of dioxane led to non-living polymers with a broad molecular weight distribution. It was concluded that the propagating carbocation is stabilized not by the counteranion but by an externally added basic compound (dioxane) that strongly interacts with the active end. 相似文献
2.
Nobuyoshi Koshino Masayuki Harada Yasuji Morita Toshiaki Kiikuchi Yasuhisa Ikeda 《Progress in Nuclear Energy》2005,47(1-4):406-413
We have developed a simple reprocessing process for spent FBR fuels using N-cyclohexyl-2-pyrrolidone (NCP) which has selective precipitation ability for UO22+ ions. It was confirmed that NCP has sufficient precipitation ability for UO22+ ions, decontamination capability (separation of UO22+ from simulated fission products), and resistance to γ-ray radiation in nitric acid solutions. These findings indicate that NCP is applicable to our reprocessing process. We have also evaluated performances of other precipitants such as N-n-propyl-2-pyrrolidone (NProP), N-n-butyl-2-pyrrolidone (NBP), and N-n-butyl-2-pyridone (NBPyr). It was found that higher decontamination factors (DFs) are obtained by using NProP and NBP. This can be interpreted that the hydrophobicity of NProP and NBP is lower than that of NCP. Furthermore, we have obtained an experimental result that the resistance of NBPyr to γ-ray radiation is superior to that of NCP. 相似文献
3.
Naoyuki Kanetake Yasuhisa Tozawa Toshio Otani 《International Journal of Mechanical Sciences》1983,25(5):337-345
The present study aims to calculate the height at each peripheral position of a cup drawn from polycrystalline sheet using texture data. In the analytical treatment the polycrystalline sheet is simplified to an aggregation of many single crystals with various orientations, and the texture is represented by a three-dimensional crystallite orientation distribution function. The ear is calculated crystallographically using the orientation distribution function as a volume fraction of a certain oriented crystal. In the experiment aluminium, Al-Mg alloy and copper sheets which are treated under various conditions of cold rolling and heat treatment are used. The average textures over the thicknesses of the sheets are measured by the Schulz reflection method. The calculated ears based on the measured textures are compared with the experimental ears for each material. The results show that all the principal features of the ears of drawn cups are predicted satisfactorily by the calculation. 相似文献
4.
Makoto Kobayashi Masashi Shimada Yuji Hatano Takuji Oda Brad Merrill Yasuhisa Oya Kenji Okuno 《Fusion Engineering and Design》2013,88(9-10):1749-1752
The deuterium trapping behaviors in tungsten damaged by light ions with lower energy (10 keV C+ and 3 keV He+) or a heavy ion with higher energy (2.8 MeV Fe2+) were compared by means of TDS to understand the effects of cascade collisions on deuterium retention in tungsten. By light ion irradiation, most of deuterium was trapped by vacancies, whose retention was almost saturated at the damage level of 0.2 dpa. For the heavy ion irradiation, the deuterium trapping by voids was found, indicating that cascade collisions by the heavy ion irradiation would create the voids in tungsten. Most of deuterium trapped by the voids was desorbed in higher temperature region compared to that trapped by vacancies. It was also found that deuterium could accumulate in the voids, resulting in the formation of blisters in tungsten. 相似文献
5.
Takehiko Tsukahara Hiroyasu Hotokezaka Masayuki Harada Yoshikuni Kikutani Manabu Tokeshi Yasuhisa Ikeda 《Microfluidics and nanofluidics》2013,14(6):989-994
We have developed a novel microchip equipped with a microchannel and Pt microelectrode array for electrochemically controlling valences of actinide (An) species. The square wave voltammograms of the redox reaction of potassium hexacyanoferrate(II) in the microchannel were measured. We found that the fabricated Pt microelectrode array has superior performances for the detection of the electrochemically active species in the microchannel. Therefore, the potentiostatic electrolysis experiments of uranium ions were carried out in the microchannel, and the concentration changes of uranium ions accompanied by the potentiostatic electrolysis were examined using thermal lens microscope. The results showed that the redox reactions between U(VI) and U(IV) can be performed completely in a microchannel in a few minutes, that is, the microscale reaction is accelerated by a factor of more than 10 compared with the bulk solution reactions taking hours mostly. The developed microchip was found to have enough performances for realizing rapid and highly efficient redox reactions for An species, which are impossible in the bulk reactions. 相似文献
6.
Yasuhisa Oda Ken Kajiwara Koji Takahashi Atsushi Kasugai Michael A. Shapiro Richard J. Temkin Keishi Sakamoto 《Journal of Infrared, Millimeter and Terahertz Waves》2010,31(8):949-957
The preliminary results of mode measurement in the ITER relevant 40 m long transmission test line composed from 63.5 mm diameter
corrugated waveguides and miter bends are presented. The field patterns were measured by taking temperature profiles on a
paper screen placed in front of the waveguide end using an infrared imaging camera. The complex electric field at the waveguide
end was retrieved from the measured temperature profiles. As a result, the transmission power includes 87% of HE11 mode and 6% of LP11 odd (HE21+TE01) mode and small ratios of other modes. The mode content had small dependence on length of the transmission line. This result
indicated that the higher order mode content generated at the input of the transmission line is conserved and propagated through
the transmission line. This suggests that the initial RF coupling to the waveguide is critical since it affects the launcher
efficiency. 相似文献
7.
We report an analysis for the morphology and breaking behavior of deposits of spherical latex particles (1 and 3.6 μm in diameter) at a cylindrical collector in a microfluidic channel fabricated by soft-lithography. In-situ observation of particle deposition over a large range of flow rate conditions evidence the relationship between deposit morphology and mode of particle transport toward the collector. For low Pe?clet number (Pe), particle deposits are nearly uniform all over the collector surface except at the rear where particles do not attach. Upon increase of Pe, deposits gradually adopt a columnar morphology at the collector stagnation point. These results are qualitatively consistent with previously reported Monte Carlo simulations of deposits formation in stagnation point flow systems. However, these simulations fail to quantitatively predict the observed deposition at the rear of the collector for sufficiently high flow rate. Additional deposit breaking experiments together with numerical evaluations of particle flux around the collector suggest that such "anomalous" deposition at large Pe is significantly governed by concomitant detachment of deposited particles at the stagnation point and the presence of recirculation flow at the collector rear. Finally, kinetics of deposition are discussed in connection with particle size-dependence of deposit breaking features. 相似文献
8.
Uchida T Oshita S Ohmori M Tsuno T Soejima K Shinozaki S Take Y Mitsuda K 《Nanoscale research letters》2011,6(1):295
Unique properties of micro- and nanobubbles (MNBs), such as a high adsorption of impurities on their surface, are difficult
to verify because MNBs are too small to observe directly. We thus used a transmission electron microscope (TEM) with the freeze-fractured
replica method to observe oxygen (O2) MNBs in solutions. MNBs in pure water and in 1% NaCl solutions were spherical or oval. Their size distribution estimated
from TEM images close to that of the original solution is measured by light-scattered methods. When we applied this technique
to the observation of O2 MNBs formed in the wastewater of a sewage plant, we found the characteristic features of spherical MNBs that adsorbed surrounding
impurity particles on their surface. 相似文献
9.
Aem Nuylert Dr. Fumihiro Motojima Prof. Dr. Chartchai Khanongnuch Prof. Dr. Tipparat Hongpattarakere Prof. Dr. Yasuhisa Asano 《Chembiochem : a European journal of chemical biology》2020,21(1-2):181-189
Because the synthesis of chiral compounds generally requires a broad range of substrate specificity and stable enzymes, screening for better enzymes and/or improvement of enzyme properties through molecular approaches is necessary for sustainable industrial development. Herein, the discovery of unique hydroxynitrile lyases (HNLs) from two species of passion fruits, Passiflora edulis forma flavicarpa (yellow passion fruit, PeHNL-Ny) and Passiflora edulis Sims (purple passion fruit, PeHNL-Np), isolated and purified from passion fruit leaves is reported. These are the smallest HNLs (comprising 121 amino acids). Amino acid sequences of both enzymes are 99 % identical; there is a difference of one amino acid in a consensus sequence. PeHNL-Np has an Ala residue at position 107 and is nonglycosylated at Asn105. Because it was confirmed that natural and glycosylated PeHNL-Ny showed superior thermostability, pH stability, and organic tolerance to that of PeHNL-Np, it has been speculated that protein engineering around the only glycosylation site, Asn105, located at the C-terminal region of PeHNL-Ny, might contribute to the stabilization of PeHNL. Therefore, the focus is on improved stability of the nonglycosylated PeHNL by truncating its C-terminal region. The C-terminal-truncated PeHNLΔ107 was obtained by truncating 15 amino acids from the C terminus followed by expression in Escherichia coli. PeHNLΔ107 expressed in E. coli was not glycosylated, and showed improved thermostability, solvent stability, and reusability similar to that of the wild-type glycosylated form of PeHNL expressed in Pichia pastoris. These data reveal that the lack of the high-flexibility region at the C terminus of PeHNL might be a possible reason for improving the stability of PeHNL. 相似文献
10.
Biocatalytic Synthesis of Nitriles through Dehydration of Aldoximes: The Substrate Scope of Aldoxime Dehydratases 下载免费PDF全文
Tobias Betke Jun Higuchi Philipp Rommelmann Keiko Oike Dr. Taiji Nomura Prof.Dr. Yasuo Kato Prof.Dr. Yasuhisa Asano Prof.Dr. Harald Gröger 《Chembiochem : a European journal of chemical biology》2018,19(8):768-779
Nitriles, which are mostly needed and produced by the chemical industry, play a major role in various industry segments, ranging from high‐volume, low‐price sectors, such as polymers, to low‐volume, high‐price sectors, such as chiral pharma drugs. A common industrial technology for nitrile production is ammoxidation as a gas‐phase reaction at high temperature. Further popular approaches are substitution or addition reactions with hydrogen cyanide or derivatives thereof. A major drawback, however, is the very high toxicity of cyanide. Recently, as a synthetic alternative, a novel enzymatic approach towards nitriles has been developed with aldoxime dehydratases, which are capable of converting an aldoxime in one step through dehydration into nitriles. Because the aldoxime substrates are easily accessible, this route is of high interest for synthetic purposes. However, whenever a novel method is developed for organic synthesis, it raises the question of substrate scope as one of the key criteria for application as a “synthetic platform technology”. Thus, the scope of this review is to give an overview of the current state of the substrate scope of this enzymatic method for synthesizing nitriles with aldoxime dehydratases. As a recently emerging enzyme class, a range of substrates has already been studied so far, comprising nonchiral and chiral aldoximes. This enzyme class of aldoxime dehydratases shows a broad substrate tolerance and accepts aliphatic and aromatic aldoximes, as well as arylaliphatic aldoximes. Furthermore, aldoximes with a stereogenic center are also recognized and high enantioselectivities are found for 2‐arylpropylaldoximes, in particular. It is further noteworthy that the enantiopreference depends on the E and Z isomers. Thus, opposite enantiomers are accessible from the same racemic aldehyde and the same enzyme. 相似文献