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251.
Ryotaro Sekine Takashi Shibuya Kazuhiko Ukai Shinichi Komatsu Masayuki Hattori Toshifumi Mihashi Naoki Nakazawa Yoko Hirohara 《Optical Review》2006,13(4):207-211
The measurement of human ocular aberration is now frequently performed because of the increase in refractive surgery on the
human cornea. The Hartmann-Shack (H-S) wavefront sensor is considered to be the most useful wavefront sensor, and a calculation
method for wavefront aberration has been established. New methods of measuring wavefront aberrations of human eyes, using
the Talbot image of a two-dimensional grating as a wavefront sensor and local shift of the Talbot image to calculate tilt
of the wavefront are shown. The shift of the Talbot image was determined by comparing the phases of fundamental spatial frequency
between the grating and the local patch of the Talbot image by Fourier transformation. The actual experiment was performed
using a modified commercially available wavefront analyzer. Using these methods, Talbot images were obtained from model eyes
and a human eye, and wavefront shapes were successfully reconstructed. Wavefront aberrations can be measured even when the
obtained image is degraded by defocusing or scattering. 相似文献
252.
Satoshi Hamatani Kazuhide Tsuji Akio Kawai Kazuhiko Shibuya 《Chemical physics letters》2002,360(5-6):466-472
We measured the laser-induced fluorescence (LIF) and dispersed fluorescence (DF) spectra of jet-cooled -, o- and m-chlorobenzyl radicals after they were generated by the 193 nm photolysis of the corresponding parent molecules. The vibronically resolved spectra were obtained to analyze their D1–D0 transitions. The fluorescence lifetimes of -, o-, m- and p-chlorobenzyls in the zeroth vibrational levels of the D1 states were measured to estimate the oscillator strengths of a series of benzyl derivatives. It was found that the -substitution is inefficient to break the ‘accidental forbiddenness' of the D1–D0 transition of benzyl, while the ring-substitution enhances the oscillator strength by 50%. 相似文献
253.
Dr. Ming Zhang Dr. Kenji Watanabe Masafumi Tsukamoto Ryozo Shibuya Dr. Hiroyuki Morimoto Dr. Takashi Ohshima 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(10):3937-3941
An increased supply of scarce or inaccessible natural products is essential for the development of more sophisticated pharmaceutical agents and biological tools, and thus the development of atom‐economical, step‐economical and scalable processes to access these natural products is in high demand. Herein we report the development of a short, scalable total synthesis of (?)‐α‐kainic acid, a useful compound in neuropharmacology that is, however, limited in supply from natural resources. The synthesis features sequential platinum‐catalyzed direct allylic aminations and thermal ene‐cyclization, enabling the gram‐scale synthesis of (?)‐α‐kainic acid in six steps and 34 % overall yield. 相似文献
254.
Juzo Nakayama Ayako Kaneko Yoshiaki Sugihara Akihiko Ishii Akihiro Oishi Isao Shibuya 《Heteroatom Chemistry》2000,11(6):434-440
It was shown that dimethyl 2‐thiono‐1,3‐dithiole‐4,5‐dicarboxylate ( 2 ) and dimethyl acetylenedicarboxylate (DMAD) undergo a 1,3‐dipolar cycloaddition to produce a short‐lived ylide intermediate ( 3 ). The 1,3‐dipolar cycloaddition took place even at room temperature, although sluggishly, but took place much more rapidly under application of a high pressure of 500 MPa. The 1,3‐dipolar cycloaddition is reversible and the ylide 3 immediately splits into 2 and DMAD. When the reaction of 2 with DMAD was carried out at room temperature without solvent, a spiro‐1,3‐dithiole ( 11 ) was formed in 11% yield, whereas the reaction at 150°C provided a thiophene derivative ( 13 ) in 41% yield. It was found that 11 undergoes a thermal rearrangement to 13 . Results of attempted chemical trapping of the ylide 3 are also reported. © 2000 John Wiley & Sons, Inc. Heteroatom Chem 11:434–440, 2000 相似文献