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排序方式: 共有2238条查询结果,搜索用时 15 毫秒
61.
Shinpei Kado Yuuhei Takeshima Yoshio Nakahara Keiichi Kimura 《Journal of inclusion phenomena and macrocyclic chemistry》2012,72(1-2):227-232
It is well-known that cholesteric liquid crystals have an optical property, selective reflection, due to changes in the pitch of their helical structure. This unique property of cholesteric liquid crystals can be used to attain a visual sensing system showing color changes as the detection signal. In this paper, we report a visual sensing membrane comprising cholesteric liquid crystals, in which a 15-crown-5 derivative was incorporated as ion recognizing sites, for K+ in aqueous solution. The resulting CLC membrane showed a shift of the reflection peak sensitive to K+ in water. We have also designed polymer-dispersed liquid crystal membranes that showed ion-selective reflection peak shifts with improved response time. 相似文献
62.
Abstract The non-linear dielectric relaxation spectroscopy has been recently developed and applied to soft materials such as polymers. We have applied this new method to the S*C phases of some ferroelectric liquid crystals. Under a weak AC electric field, the original and third order harmonic frequency components of electric displacement are proportional to the first and third powers of the applied electric field, respectively. The linear spectrum obtained from the original frequency component shows the relaxation of Debye type and the third order non-linear spectrum shows the relaxation with an extended form of Debye type to the non-linear case. The third order non-linear dielectric increment is found to be negative, which implies that the dielectric non-linearity of the liquid crystal in the S*C phase is due to the saturation of molecular dipole moments induced by the applied electric field. The temperature dependence of the linear and third order non-linear spectra in the S*C phase are also studied. Both spectra do not change their forms much through the whole temperature range of the S*C phase. In the vicinity of the SA–S*C transition temperature, the critical behaviour is more remarkable in the third order spectrum than in the linear one. 相似文献
63.
J.-B. Laloë T. Yang T. Kimura Y. Otani 《Journal of magnetism and magnetic materials》2009,321(22):3829-3832
We investigate the injection of a pure spin current into a non-magnetic Cu wire in a lateral spin valve. We detect the spin accumulation occurring at the interfaces between the magnetic nanopillars and the non-magnetic wire in the non-local geometry. We confirm that the accumulated spins diffuse equally in the Cu wire irrespective of the presence of a charge current. The inversion of the injector and detector magnetic nanopillars does not affect the spin signal, in agreement with analytical predictions for this system. 相似文献
64.
Masayuki Hagiwara Shojiro Kimura Haruhiko Yashiro Takanari Kashiwagi Hironori Yamaguchi Koichi Kindo 《Applied magnetic resonance》2009,36(2-4):269-274
We have developed high-field and multifrequency (HFMF) electron spin resonance (ESR) apparatus for the magnetic fields up to 65 T at frequencies up to about 6 THz. In addition to this pulsed field ESR apparatus, we are making a multifrequency ESR apparatus with very high sensitivity in a static field. We report the results of ESR studies on BaCoV2O8 and NiGa2S4, followed by recent developments and future plans of our HFMF ESR apparatus. 相似文献
65.
Keiichi Kimura Akira Matsui Yoshiaki Inaki Kiichi Takemoto 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(8):1231-1241
Polymerization of acrylonitrile initiated by triazole-copper(II) complexes was studied in dimethylsulfoxide solution. It was found that the polymerization proceeds by a free radical mechanism; however, the complexes can hardly homopolymerize methyl methacrylate and styrene. Ability of the complexes to initiate polymerization seems to depend on the substituents of triazole, the sort of solvents, and the counterions of copper(n) salts. From the data of visible spectroscopy and the spin trapping, the initiation mechanism was discussed in terms of reduction of copper(II) followed by forming active species. 相似文献
66.
Dr. Takuya Nakashima Kyohei Yamamoto Yuka Kimura Prof. Tsuyoshi Kawai 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(50):16972-16980
Herein, we designed chiral photoresponsive tetra(2‐phenylthiazole)s, which induce a diastereoselective 6π‐electrocyclization reaction in a helically folded structure to freeze the conformational interconversions. The folding conformation with one helical turn of tetra(2‐phenylthiazole)s was supported by multiple intramolecular noncovalent interactions including vicinal S???N interheteroatom interactions and CH–π and π–π stacking interactions between nonadjacent units, as found in X‐ray crystal structures as well as quantum chemical calculations. The introduction of a chiral group at both ends of tetra(2‐phenylthiazole) dictates the preferential folding into a one‐handed helix conformation by the simultaneous operation of S???O and multiple CH–π interactions that involve the chiral end groups. Since the tetra(2‐phenylthiazole)s possess two equivalent photoreactive 6π‐electron systems and the folded conformation is suitable for photoinduced electrocyclization reaction, they undergo a photocyclization reaction in a stereoselective manner to memorize the chirality of the helix in a resulting diastereomeric closed form. 相似文献
67.
Prof. Dr. Mutsumi Kimura Junya Masuo Yuki Tohata Kazumichi Obuchi Naruhiko Masaki Takurou N. Murakami Nagatoshi Koumura Kojiro Hara Atsushi Fukui Ryohsuke Yamanaka Prof. Dr. Shogo Mori 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(3):1028-1034
A series of panchromatic ruthenium sensitizers ( MJ sensitizers) with attached thiophene and phenyl units bearing alkyl chains was synthesized. A new synthetic route was used to examine all possible positions for the alkyl chains. The absorption spectra showed the sum of a ruthenium complex and peripheral organic chromophore units. The hypochromic effect and blueshift of the metal‐to‐ligand charge‐transfer band observed in the modified ruthenium sensitizers were suppressed by changing the positions of the alkyl chains on the attached thiophene ring. Changing only one alkyl chain also influenced the performance of dye‐sensitized solar cells. Ruthenium sensitizer MJ‐10 with bulky substituent harvests visible and near‐infrared light, and solar cells sensitized by MJ‐10 exhibit an efficiency of 9.1 % under 1 sun irradiation. 相似文献
68.
Xiaobo Su Satoshi Kimura Masahisa Wada Ung-Jin Kim Shigenori Kuga 《Cellulose (London, England)》2013,20(3):1023-1029
Adsorption–complexation of cellulose by hydrazine solutions in water and toluene was studied for native cellulose of varied crystallinity. Penetration of hydrazine into cellulose takes place more readily in hydrazine solution of higher concentration and with cellulose of lower crystallinity, but the equilibrium uptake was nearly independent of crystallinity. Complexation from toluene solution takes place at lower hydrazine concentration in toluene than in water, presumably because of the difference in hydrazine–solvent interaction. The adsorption isotherm of hydrazine in water is likely to be sigmoid, implying a cooperative sorption mechanism. It can presumably be ascribed to the disordered structure in the course of complexation. 相似文献
69.
Ryohei Yoshisaki Dr. Shinya Kimura Dr. Masashi Yokoya Prof. Dr. Masamichi Yamanaka 《化学:亚洲杂志》2021,16(14):1937-1941
Maltose is a ubiquitous disaccharide produced by the hydrolysis of starch. Amphiphilic ureas bearing hydrophilic maltose moiety were synthesized via the following three steps: I) construction of urea derivatives by the condensation of 4-nitrophenyl isocyanate and alkylamines, II) reduction of the nitro group by hydrogenation, and III) an aminoglycosylation reaction of the amino group and the unprotected maltose. These amphiphilic ureas functioned as low molecular weight hydrogelators, and the mixtures of the amphipathic ureas and water formed supramolecular hydrogels. The gelation ability largely depended on the chain length of the alkyl group of the amphiphilic urea; amphipathic urea having a decyl group had the highest gelation ability (minimum gelation concentration=0.4 mM). The physical properties of the supramolecular hydrogels were evaluated by measuring their thermal stability and dynamic viscoelasticity. These supramolecular hydrogels underwent gel-to-sol phase transition upon the addition of α-glucosidase as a result of the α-glucosidase-catalyzed hydrolysis of the maltose moiety of the amphipathic urea. 相似文献
70.
Dr. Manuela Leticia Kim Dr. Deicy Barrera Dr. Mutsumi Kimura Prof. Dr. Juan P. Hinestroza Prof. Dr. Karim Sapag Dr. Eugenio Hernán Otal 《化学:亚洲杂志》2021,16(9):1086-1091
We report on a detailed textural analysis of mechanochemically synthesized MOF-199 including N2 adsorption-desorption and CO2 adsorption isotherms data at 77 K and 273 K (up to atmospheric pressure), respectively, and CH4 adsorption data at 298 K (up to 35 bar). We used the isotherm adsorption data to determine the micropore volume of the MOF-199 structures, to establish their methane uptake capacity and to understand how these properties depended on the Ethanol/BTC ratio used during the synthesis. The maximum methane uptake capacity for our specimens was recorded at 130 v/v at 35 bars. These results open an avenue for a better understanding of alternative manufacturing processes of MOF structures for gas storage applications. 相似文献