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31.
The dynamic changes in ferroelectric liquid crystal (FLC) molecular alignments under an applied electric field are examined
by observing the formation of conoscopic figures with a time resolution of 0.1 ms. Close agreements between observed and simulated
conoscopic figures under low voltage (30 V) were obtained. Under high voltage (120 V), however, the observed conoscopic figures
became blurred between 0.8 ms and 1.1 ms after reversal of the electric field. The light scattering producing the blurriness
occurred due to the development of fast transient molecular alignments during the switching transition above the applied voltage
70 V. 相似文献
32.
The vibration-rotation transitions for a fundamental band of SeO (X3Σ?) were studied by means of the infrared laser magnetic resonance (LMR) method employing a CO2 laser. The LMR spectra arising from five SeO isotopic species except 74SeO were detected and analyzed. Band origins for these species were determined. Molecular parameters ωe, ωeχe, Be, and αe, were obtained with the aid of the reduced mass relations. For 77SeO the axial component of magnetic hyperfine interaction was obtained. 相似文献
33.
We report on craters formed by balls dropped into dry, noncohesive, granular media. By explicit variation of ball density rho(b), diameter D(b), and drop height H, the crater diameter is confirmed to scale as the 1/4 power of the energy of the ball at impact: D(c) approximately equal (rho(b)D(3)(b)H)(1/4). Against expectation, a different scaling law is discovered for the crater depth: d approximately equal (rho(3/2)(b)D(2)(b)H)(1/3). The scaling with properties of the medium is also established. The crater depth has significance for granular mechanics in that it relates to the stopping force on the ball. 相似文献
34.
To evaluate individual expansion coefficients composing fitting parameters of the Born-Oppenheimer corrections to Dunham's coefficients Y(ij) that have been given analytically with the Delta(B) and Delta(omega) formalism, we examined the consistency of analytic expressions for those corrections with Watson's assertion of the experimental inseparability of nonadiabatic corrections Q(a, b)(r) for a molecule AB. Derived analytic expressions in terms of optimal fitting parameters for the corrections are essential to evaluate individual expansion coefficients. These expressions also reveal redundancies between empirical correction parameters Delta(ij). A method of evaluating nonadiabatic vibrational corrections Q(a, b)(r) and adiabatic corrections S(a, b)(r) separately consistent with Watson's assertion of inseparability is presented and is applied to an analysis of spectral data of LiH. Functions Q(a, b) and S(a, b) for LiH are thus successfully evaluated; S(H, Li)(r) values agree well with those predicted simply by wobble-stretch theory. Experimental values for optimal fitting parameters r(H)(1q) and r(H)(2q) are nearly equal to those of r(Li)(1q) and r(Li)(2q), respectively, in agreement with a theoretical relation r(a)(iq)=r(b)(iq). Copyright 2001 Academic Press. 相似文献
35.
Tse JS Uehara K Rousseau R Ker A Ratcliffe CI White MA MacKay G 《Physical review letters》2000,85(1):114-117
The postulated low thermal conductivity and the possibility of altering the electronic conductivity of metal-doped clathrates with semiconducting host elements have stimulated great interest in exploring these compounds as promising thermoelectric materials. The electronic and thermal properties of the prototypical Na xSi (46) system are studied in detail here. It is shown that, despite the fact that the Na/Si clathrate is metallic, its thermal conductivity resembles that of an amorphous solid. A theoretical model is developed to rationalize the structural stability of the peculiar structural topology, and a general scheme for rational design of high efficiency thermoelectric materials is presented. 相似文献
36.
Y. Uehara 《Surface science》2007,601(23):5643-5648
We have measured the scanning tunneling microscope (STM) light emission spectra of Ni(1 1 0)-streaky (1 × 2) surfaces. When the tip was fixed over atomic hydrogen adsorbed on the surfaces, two types of vibration-induced structure were observed in the STM light emission spectra. One is the periodic fine structures that were already reported in our previous paper [Y. Uehara, S. Ushioda, Phys. Rev. Lett. 92 (2004) 066102] and the other newly found in the present experiments is a stepwise structure that is located at the vibrational energy of hydrogen below the cutoff energy of the STM light emission. They are ascribed to different excitation mechanisms of the vibration in the STM light emission process; the periodic fine structures appear when the vibrating motion is directly excited by the electrons injected from the tip. Conversely, the stepwise structure is observed when it is excited by the electromagnetic fields confined in the tip-sample gap, i.e., by localized surface plasmons. 相似文献
37.
Kenji Kinashi Yuki Kambe Masahiro Misaki Yasuko Koshiba Kenji Ishida Yasukiyo Ueda 《Journal of polymer science. Part A, Polymer chemistry》2012,50(24):5107-5114
Three types of bi‐functionalized copolymers ( P1FAz , P2FAz , and P3FAz ) with different numbers of fluorene units and an azobenzene unit were synthesized and characterized using UV–vis and polarized absorption spectroanalysis. The trans‐cis photoisomerization was conformed under 400 nm light irradiation for all copolymers in chloroform. However, in the film state, only the trans‐cis photoisomerization occurred by mono‐fluorene attached copolymer poly[(9,9‐di‐n‐octylfluorenyl‐2,7‐diyl)‐alt‐4,4′‐azobenzene)] ( P1FAz ). Photo‐induced alignment was achieved using the P1FAz film after irradiation with linear polarized 400 nm light and subsequent annealing at 60 °C. Surface orientation of a spin‐coating film of poly(9,9‐didodecylfluorene) ( F12 ) was achieved using the photo‐induced alignment layer of the P1FAz film after annealing at 90 °C. The photo‐induced alignment layer of P1FAz has potential application to the surface orientation technique for appropriate polymers, which will be useful for the fabrication of optoelectronics devices. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
38.
Shin-ichi Matsuoka Naoto Ogiwara Yosuke Uehara Takashi Ishizone 《Macromolecular Symposia》2006,240(1):206-212
Ring-opening polymerizations of [3.3.1]propellane derivatives, 1,3-dehydroadamantane ( 1 ) and 5-butyl-1,3-dehydroadamantane ( 2 ), were carried out with CF3SO3H in CH2Cl2 at 0 °C for 6–42 h. The central σ-bonds in 1 and 2 were exclusively opened to afford novel poly([3.3.1]propellane)s, poly(1,3-adamantane)s, in 52–95% yields. The resulting poly( 2 ) possessing flexible butyl substituent was soluble in chloroform, THF, and 1,2-dichlorobenzene, and the degree of polymerization was estimated to be greater than 30, while the poly( 1 ) was hardly soluble in the common organic solvents. All aliphatic poly( 1 ) and poly( 2 ) showed high thermal stability, their 10% weight loss temperatures were 421 and 486 °C, respectively. 相似文献
39.
Enantioenriched synthesis of cyclopropenes with a quaternary stereocenter, versatile building blocks
Uehara M Suematsu H Yasutomi Y Katsuki T 《Journal of the American Chemical Society》2011,133(2):170-171
Ir(salen) complexes were found to catalyze enantioselective cyclopropenation efficiently. Cyclopropenation can be carried out using either a donor/acceptor- or an acceptor/acceptor-substituted diazo compound such as α-aryl-α-diazoacetates, α-phenyl-α-diazophosphonate, 2,2,2-trifluoro-1-phenyl-1-diazoethane, and α-cyano-α-diazoacetamide as carbenoid precursors. The reactions provide highly enantioenriched cyclopropenes (84-98% ee) with a functionalized quaternary carbon as versatile building blocks. 相似文献
40.
Itoh A Saitoh T Tani K Uchigaki M Sugimoto Y Yamada J Nakajima H Ohshiro H Sun S Tanahashi T 《Chemical & pharmaceutical bulletin》2011,59(8):947-951
From the embryos of the seeds of Nelumbo nucifera, three bisbenzylisoquinoline alkaloids, nelumboferine and nelumborines A and B, were isolated along with four known compounds, neferine, liensinine, isoliensinine and anisic acid. The structures of the new alkaloids were determined mainly by spectroscopic methods. 相似文献