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101.
Lee SK Heo S Lee JG Kang KT Kumazawa K Nishida K Shimbo Y Takanishi Y Watanabe J Doi T Takahashi T Takezoe H 《Journal of the American Chemical Society》2005,127(31):11085-11091
Two chiral bent-core mesogens Pn-O-PIMB(n - 2)* (n = 9 and 10) and their oxygen analogues Pn-O-PIMB(n - 2)*-(n - 4)O (n = 8, 9, and 10) with omega-[(S)-amyloxy]alkoxy terminal groups were prepared, and their phase structures were investigated by means of electro-optic, polarization reversal current and second harmonic generation measurements in order to clarify the effect of the interlayer steric interaction on the emergence of polar orderings. The odd-even behavior for the alternative appearance of ferroelectricity and antiferroelectricity was observed in two homologous series; the bent-core mesogens P10-O-PIMB8*, P8-O-PIMB6*-4O, and P10-O-PIMB8*-6O in addition to the previously reported P6-O-PIMB4* and P8-O-PIMB6*, where the length of chains n is even, exhibited ferroelectric phases. On the contrary, the mesogens P7-O-PIMB5*, P9-O-PIMB7*, and P9-O-PIMB7*-5O, where n is odd, showed antiferroelectric phases. It is obvious that the interlayer steric interaction plays a major role for the emergence of a variety of phase structures. 相似文献
102.
Synthesis and catalytic properties of barium hexaaluminates incorporated with chromium and lanthanum 总被引:4,自引:0,他引:4
Sang Gun Lee Hyun Lee Chang Hee Lee Jae Yul Kwon Hee Chan Park Seong Soo Hong Seong Soo Park 《Reaction Kinetics and Catalysis Letters》2005,86(2):299-306
Summary Barium hexaaluminates incorporated with chromium and lanthanum (Ba1-xLaxCrAl11O19-a) were synthesized from aqueous metal nitrates and sulfates through the precipitation, and then followed by crystallization
at 1300oC for 2 h. They had the ability to maintain heat resistance and high conversion of CH4in methane combustion at elevated temperature. 相似文献
103.
The effect of representing dielectric properties in terms of the complex polarizability c = – i is examined. Loss curves ( and tan ) are shifted towards higher frequencies, revealing the existence of new relaxations and allowing the clarifications of ones already known. We have calculated the shift ratios (at maximum or tan )/ (at maximum or tan ) from the more conventional empirical equations representing the dielectric behavior. Some examples are given. 相似文献
104.
105.
Gun J. Lev O. Regev O. Pevzner S. Kucernak A. 《Journal of Sol-Gel Science and Technology》1998,13(1-3):189-193
A new method for the formation of reticular silicate and organically modified silicate is introduced. Monoliths were prepared by incorporating a few percent hydrogen peroxide in the sol-gel starting solution. For example, incorporation of 6–10% (v) hydrogen peroxide in base catalyzed sol-gel precursors of methyl-Ormosil yielded macroporous monoliths with a bi-modal pore size distribution. The average characteristic pore diameters were approximately 1.2 nm and 0.7 m, depending on the sol-gel precursors used and the preparation protocol. The specific surface area was approximately 160 m2/g, contributed mainly by the microporous structure. A similar preparation procedure without hydrogen peroxide yielded only fractured or powdery materials. Presumably, the decomposition of the hydrogen peroxide yielded microbubbles, which formed templates for the polycondensation reaction. SEM, nitrogen adsorption isotherms and small angle X-ray spectroscopy were used to characterize the reticular materials. 相似文献
106.
Optics and Spectroscopy - A new technique for estimating the efficiency of electron transfer from a CdSe/ZnS quantum dot (QD) to TiO2 nanoparticles based on the generation of reactive oxygen... 相似文献
107.
108.
Dr. Anna Hedström Dr. Zakieh Izakian Irma Vreto Dr. Carl‐Johan Wallentin Prof. Dr. Per‐Ola Norrby 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(15):5946-5953
The radical nature of iron‐catalyzed cross‐coupling between Grignard reagents and alkyl halides has been studied by using a combination of competitive kinetic experiments and DFT calculations. In contrast to the corresponding coupling with aryl halides, which commences through a classical two‐electron oxidative addition/reductive elimination sequence, the presented data suggest that alkyl halides react through an atom‐transfer‐initiated radical pathway. Furthermore, a general iodine‐based quenching methodology was developed to enable the determination of highly accurate concentrations of Grignard reagents, a capability that facilitates and increases the information output of kinetic investigations based on these substrates. 相似文献
109.
A Fourier spectral scheme is proposed for solving the periodic problem of nonlinear Klein-Gordon equation. Its stability and convergence are investigated. Numerical results are also presented. 相似文献
110.