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91.
The interrogation of fiber-Bragg-grating (FBG) sensors using a vertical-cavity surface-emitting laser (VCSEL) is discussed. A long-wavelength (1.54 μm) VCSEL was used as a wavelength-tunable source by variation in the current. Temperature stabilization was performed with a thermoelectric device. Characteristics of temperature and strain sensing were investigated. FBGs with different reflectivities were compared. For temperature sensing, the root-mean-square error in the measurement was reduced to 1/3 that without temperature stabilization. The dependence of the measurement error on the reflectivities of the FBGs was investigated. The measurement error was larger for FBGs with lower reflectivities in both temperature and strain sensing. Improvement on the sensing with low-reflectivity FBGs is discussed. 相似文献
92.
Tsuchiya H Enoto T Yamada S Yuasa T Kawaharada M Kitaguchi T Kokubun M Kato H Okano M Nakamura S Makishima K 《Physical review letters》2007,99(16):165002
A report is made on a comprehensive observation of a burstlike gamma-ray emission from thunderclouds on the Sea of Japan, during strong thunderstorms on 6 January 2007. The detected emission, lasting for approximately 40 sec, preceded cloud-to-ground lightning discharges. The burst spectrum, extending to 10 MeV, can be interpreted as consisting of bremsstrahlung photons originating from relativistic electrons. This ground-based observation provides the first clear evidence that strong electric fields in thunderclouds can continuously accelerate electrons beyond 10 MeV prior to lightning discharges. 相似文献
93.
Kun'ichi Miyazawa Takuro Nagai Koji Kimoto Masaru Yoshitake Yumi Tanaka 《Surface and interface analysis : SIA》2021,53(1):84-89
We analyzed the surface atomic structure of highly oriented pyrolytic graphite (HOPG) substrate exfoliated with adhesive tape, using high‐resolution transmission electron microscopy and scanning transmission electron microscopy‐electron energy‐loss spectroscopy (STEM‐EELS). The surface step height of the exfoliated HOPG substrate was determined using high‐angle annular dark‐field‐scanning transmission electron microscopy (HAADF‐STEM) images and the depth profiles of the EELS spectra of a cross‐sectioned thin foil specimen prepared via focused ion beam milling. The exfoliated surface of the HOPG substrate presented disordered and curved graphene layers. The STEM‐EELS measurements indicated that upon exfoliation, the surface of the HOPG substrate reacted with atmospheric water and oxygen molecules. 相似文献
94.
Dr. Masayuki Iwasaki Miki Iyanaga Yuta Tsuchiya Yugo Nishimura Wenjuan Li Prof. Dr. Zhiping Li Prof. Dr. Yasushi Nishihara 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(9):2459-2462
A catalytic variant of the direct thiolation of arenes, bearing directing groups, with disulfides or thiols has been developed under palladium and copper co‐catalysis. Both sulfenyl moieties of the disulfide could be incorporated into the thiolated products, therefore, the reactions reached completion with only half an equivalent of disulfide, with respect to the starting arene. Experimental evidence suggested that the reaction proceeds through a PdII/PdIV mechanism. 相似文献
95.
Direct Asymmetric Mannich‐Type Reaction of α‐Isocyanoacetates with Ketimines using Cinchona Alkaloid/Copper(II) Catalysts
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Masashi Hayashi Masaru Iwanaga Noriyuki Shiomi Dr. Daisuke Nakane Prof. Dr. Hideki Masuda Prof. Dr. Shuichi Nakamura 《Angewandte Chemie (International ed. in English)》2014,53(32):8411-8415
The enantioselective direct Mannich‐type reaction of ketimines with α‐isocyanoacetates has been developed. Excellent yields and enantioselectivity were observed for the reaction of various ketimines and α‐isocyanoacetates using cinchona alkaloid/Cu(OTf)2 and a base. Both enantiomers of the products could be obtained by using pseudoenantiomeric chiral catalysts. This process offers an efficient route for the synthesis of α,β‐diamino acids. 相似文献
96.
Jie Zhu Dr. Ryota Osuga Prof. Ryo Ishikawa Prof. Naoya Shibata Prof. Yuichi Ikuhara Prof. Junko N. Kondo Prof. Masaru Ogura Prof. Jihong Yu Prof. Toru Wakihara Prof. Zhendong Liu Prof. Tatsuya Okubo 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(44):19837-19842
Encapsulating metal nanoclusters into zeolites combines the superior catalytic activity of the nanoclusters with high stability and unique shape selectivity of the crystalline microporous materials. The preparation of such bifunctional catalysts, however, is often restricted by the mismatching in time scale between the fast formation of nanoclusters and the slow crystallization of zeolites. We herein demonstrate a novel strategy to overcome the mismatching issue, in which the crystallization of zeolites is expedited so as to synchronize it with the rapid formation of nanoclusters. The concept was demonstrated by confining Pt and Sn nanoclusters into a ZSM-5 (MFI) zeolite in the course of its crystallization, leading to an ultrafast, in situ encapsulation within just 5 min. The Pt/Sn-ZSM-5 exhibited exceptional activity and selectivity with stability in the dehydrogenation of propane to propene. This method of ultrafast encapsulation opens up a new avenue for designing and synthesizing composite zeolitic materials with structural and compositional complexity. 相似文献
97.
Elaine Tsui Anthony J. Metrano Yuto Tsuchiya Robert R. Knowles 《Angewandte Chemie (International ed. in English)》2020,59(29):11845-11849
We report a catalytic, light‐driven method for the intramolecular hydroetherification of unactivated alkenols to furnish cyclic ether products. These reactions occur under visible‐light irradiation in the presence of an IrIII‐based photoredox catalyst, a Brønsted base catalyst, and a hydrogen‐atom transfer (HAT) co‐catalyst. Reactive alkoxy radicals are proposed as key intermediates, generated by direct homolytic activation of alcohol O?H bonds through a proton‐coupled electron‐transfer mechanism. This method exhibits a broad substrate scope and high functional‐group tolerance, and it accommodates a diverse range of alkene substitution patterns. Results demonstrating the extension of this catalytic system to carboetherification reactions are also presented. 相似文献
98.
Masaru Yoshida Masaharu Asano Hideki Omichi Masaharu Miyajima Yasuo Takahashi Hidetoshi Yamanaka Noriyuki Yonezawa Ryoichi Katakai 《Macromolecular theory and simulations》1993,2(3):377-384
The loosely cross-linked poly(acryloyl-L -proline methyl ester) gel, which is known as one of the typical thermo-responsive gels, shows a volume transition around approximately 14°C in pure water. This volume transition is shifted to higher temperature by treatment in aqueous sodium dodecyl sulfate (SDS). The analysis of the swelling-temperature curve (frequency distribution) was performed according to a moment analysis, in which the area under the swelling-temperature curve (AUC), mean swelling transition temperature (MSTT) and variance of swelling transition temperature (VSTT) were calculated. It is shown that the apparent volume transition temperature can be estimated from MSTT and that VSTT can be used to characterize the shape of the corresponding curves. 相似文献
99.
100.