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131.
Yuji Shibahara Yoko Akiyama Yoshinobu Izumi Shigehiro Nishijima Yoshihide Honda Norio Kimura Seiichi Tagawa Goro Isoyama 《Journal of Polymer Science.Polymer Physics》2008,46(1):1-7
The thermal degradation of Nafion membrane was analyzed with age‐momentum correlation (AMOC) measurement and four‐electrode AC impedance measurement. In the heated sample, the decrease in proton conductivity was observed. The lifetimes and corresponding relative intensities showed fairly good agreement between heated and nonheated samples within the experimental error. In the analysis of the photopeak of annihilation γ‐ray, on the other hand, the difference between those two kinds of samples was observed, and this difference was found to be caused by the annihilation of free positrons with low energy electrons by using AMOC method. The decrease in proton conductivity was caused by the low energy electrons, namely sulfonic radicals. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1–7, 2008 相似文献
132.
The influence of simple salts on the ion exchange and protonation equilibria of an amphoteric ion-exchange resin, which has strong base and weak acid moieties in a single functional group fixed onto the styrene-DVB matrix, has been investigated. Concentrations of ionic species in the amphoteric ion-exchange resin in equilibrium with various sodium salt solutions were estimated by (23)Na NMR spectroscopy. For the NaClO(4) system, the ratio of sodium ion concentration in the resin phase to that in the equilibrium solution was greater than 1 and increased with a decrease in the salt concentration. In contrast to an ordinary cation-exchange resin, the ion exchange behavior of Mg(2+) and Ca(2+) on the amphoteric ion-exchange resin showed a marked dependence on the kinds of salts: the distribution coefficients for the NaCl system were independent of the salt concentration, while the log D vs. log[Na(+)] plots for the NaClO(4) system showed linear relationships with slopes being neither -2 nor 0. Apparent protonation constants of the carboxylate in the functional group of the resin in equilibrium with NaClO(4) solutions were greater than those with NaCl solutions. The ion exchange and protonation properties of the amphoteric ion-exchange resin were elucidated on the basis of the information about the salt concentrations in the resin phase estimated by the NMR method. 相似文献
133.
134.
Aiko Fukazawa Dr. Yasunori Ichihashi Youhei Kosaka Shigehiro Yamaguchi Prof. Dr. 《化学:亚洲杂志》2009,4(11):1729-1740
The intramolecular trans‐halophosphanylation of 2‐(aminophosphanyl)phenylacetylenes mediated by PBr3 followed by the oxidation with H2O2, produces 3‐bromobenzo[b]phosphole oxide derivatives. This cyclization is also used for the synthesis of a 3‐iodo derivative by conducting the reaction in the presence of LiI. Based on this synthetic method, various benzophosphole‐containing π‐conjugated compounds, including a phosphoryl and methylene‐bridged stilbene 10 , 2,3,6,7‐tetraphenylbenzo[1,2‐b:4,5‐b′]diphosphole‐P,P′‐dioxides 11 , and their phosphine sulfide derivatives 12 , are synthesized. The study of the structure–property relationships in a series of the bridged stilbenes, including a bis(methylene)‐bridged stilbene 10 , and a bis(phosphoryl)‐bridged stilbene, reveals that as the contribution of the phosphoryl groups increased, the absorption and emission maxima substantially shift to longer wavelengths. The intrinsic substituent effects of the phosphoryl group in this skeleton are to decrease the oscillator strength of the electronic transition and thus decrease the radiative decay rate constants from the singlet excited state. Nevertheless, these compounds maintain high fluorescence quantum yields (ΦF>0.8) owing to the significantly retarded nonradiative decay process. In the study of the benzodiphosphole derivatives 11 and 12 , their cyclic voltammetry revealed that both of the phosphoryl and phosphine sulfide derivatives have low reduction potentials (?1.7 to ?1.8 V vs ferrocene/ferrocenium couple) with the high reversibility of the redox waves. These compounds also showed high thermal stabilities with the high glass transition temperatures of 147–159 °C, indicative of their potential utilities as amorphous materials. 相似文献
135.
To acquire high-resolution T(1)-weighted images of the liver in rats, for which breath-holding cannot be ensured, respiratory triggering is essential. At the respiratory rate of 30-60 times/min in rats, however, T(1)-weighted images cannot be obtained with simple triggering. As a simple solution to this, we applied multiple repeated acquisitions with one trigger signal. With this technique, sufficient T(1) contrast could be easily achieved in rat liver enhanced by gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid infusion. 相似文献
136.
Nagura K Saito S Fröhlich R Glorius F Yamaguchi S 《Angewandte Chemie (International ed. in English)》2012,51(31):7762-7766
Give and take: The introduction of NHC-borane moieties to thiophene-based π?skeletons endows a zwitterionic character, which makes the π?system electron-donating, while the NHC ring acts as an electron-accepting moiety. The NHC-borane-substituted thiophene underwent a clean photoisomerization with a drastic color change, however, the expanded bithiophene derivatives were inert to this photoreaction, showed low oxidation potentials, and formed a slipped π-stacked array in the crystal. 相似文献
137.
138.
A mathematical model was developed to determine the soil trajectory of motion on the moldboard plow surface. With the use of the model, trajectory lines of soil particle travel were calculated based on the shape of the moldboard plow surface. Also, with the use of the values of soil properties, soil-metal coefficient of friction, the travel speed of plow and the soil modulus of elasticity, equations of forces were solved for equilibrium condition of the furrow slice passing over the moldboard surface. The use of the model can be xtended to the approximation of the soil reaction forces occurring the plowing operation. Laboratory experiments were conducted to verify the validity of the model. the moldboard shape factors used were derived from the coordinates of points describing the contours of the plow surface as measured by a profilograph. 相似文献
139.
[reaction: see text] A new intramolecular triple cyclization of bis(o-haloaryl)diacetylenes, via dilithiation followed by reaction with chalcogen elements, produces pi-conjugated compounds containing heterole-1,2-dichalcogenin-heterole fused tricyclic skeletons. The subsequent dechalcogenation with copper metal affords a series of thiophene- and selenophene-based heteroacenes. 相似文献
140.