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111.
[reaction: see text] A novel and efficient synthetic method is described for (2S,3S)-3-amino-2-hydroxy-4-phenyl butyric acid derivatives, which are useful intermediates of enzyme inhibitors. This involves a Pummerer rearrangement of a beta-ketosulfoxide derived from l-phenylalanine followed by highly stereoselective acyl migration. From these studies, it appears that nitrogen-protecting groups exert a substantial influence over stereoselectivity. The mechanism of the rearrangement is discussed. beta-Amino alpha-hydroxy carboxylic acids are important pharmaceutical intermediates, and this method may provide a versatile synthesis from various amino acids in a few steps. 相似文献
112.
Summary CuGaS2 crystals grown by iodine transport exhibit room temperature photoluminescences at 2.45 eV and at 1.44 eV. The spectral distribution
of the green emission is shown to be relatively well described by the calculated curve for a direct band-to-band transition
withk-selection. The heterojunction formation has been tried between sulfur-treated CuGaS2 crystals and low-resistivity amorphous ZnS films prepared by sputtering at room temperature. TheI–V characteristic of the diode shows rectifying behaviour, but no injection luminescence has been observed.
Paper presented at the ?V International Conference on Ternary and Multinary Compounds?, held in Cagliari, September 14–16,
1982. 相似文献
113.
Matsuo Maeda Sadao Hibi Fumihiro Itoh Shunji Nomura Tatsuro Kawaguchi Hiromichi Kawai 《Journal of Polymer Science.Polymer Physics》1970,8(8):1303-1322
A mathematical representation of the transformation of an orientation function between two sets of Cartesian coordinates is discussed in terms of a series expansion of the distribution function in generalized spherical harmonics. A general procedure for calculating the mechanical anisotropy of a single-phase system (a polycrystalline material) from the orientation of its structural units and the intrinsic mechanical anisotropy of the structural unit is discussed in relation to the transformation of the orientation distribution function, i.e., mutual conversion of the coefficients in the expansion of the distribution function between the two sets of Cartesian coordinates. The procedure is extended to a two-phase systems (semicrystalline polymers) containing structural units composed of crystalline and noncrystalline materials in three different geometrical arrangements. 相似文献
114.
Double-exposure holographic interferometry is applied to measure the elastic deformation of rotating objects. The first exposure is made in the rotating state and the second in the static state. The precise positioning of the object between the two exposures is obtained by using holographically produced Haidinger's fringes. 相似文献
115.
A convenient method is described for the selective determination of pentoses, hexoses and 6-deoxyhexoses by dual-wavelength spectrophotometry with the l-cysteine—phenol—sulfuric acid system. Excellent linearity was observed for 25–250 nmol of pentoses, and for 25–500 nmol of hexoses and 6-deoxyhexoses. These aldoses in those sample ranges could be determined selectively with high accuracy and precision by the k -factor mode. The appropriate, wavelength of λ2 was 462, 499 and 398 nm for pentoses, hexoses and 6-deoxyhexoses, respectively, whereas that of λ1 was commonly 424 nm. 相似文献
116.
A discrete model of interfaces with self-similarity is proposed to show the power-law decay of the total area. In the case that the similarity dimension is equal to the spatial dimension a law appears. 相似文献
117.
Optical near-field plasmon-enhancement techniques have made marked contributions to the field of subwavelength optical beam
spot generation for photonic devices. However, the metal material used is not sufficiently heat resistant for high-temperature
operating requirements, such as laser-assisted magnetic recording storage. Therefore, it is preferable to use a dielectric
material as a heat source for this application. To realize a subwavelength optical beam spot size using a dielectric material,
we extensively analyze a leaky mode dielectric waveguide with a thin core. Finally, we show a new ridge-type dielectric waveguide
using a leaky mode operation for a subwavelength beam spot. 相似文献
118.
Takemoto H Honda K Masaki S Shimada Y Fujimoto I 《The Journal of the Acoustical Society of America》2006,119(2):1037-1049
A 3D cine-MRI technique was developed based on a synchronized sampling method [Masaki et al., J. Acoust. Soc. Jpn. E 20, 375-379 (1999)] to measure the temporal changes in the vocal tract area function during a short utterance /aiueo/ in Japanese. A time series of head-neck volumes was obtained after 640 repetitions of the utterance produced by a male speaker, from which area functions were extracted frame-by-frame. A region-based analysis showed that the volumes of the front and back cavities tend to change reciprocally and that the areas near the larynx and posterior edge of the hard palate were almost constant throughout the utterance. The lower four formants were calculated from all the area functions and compared with those of natural speech sounds. The mean absolute percent error between calculated and measured formants among all the frames was 4.5%. The comparison of vocal tract shapes for the five vowels with those from the static MRI method suggested a problem of MRI observation of the vocal tract: data from static MRI tend to result in a deviation from natural vocal tract geometry because of the gravity effect. 相似文献
119.
Hidetaka Hamada Tatsuhiro Honda Gabriela Kohr 《Journal of Mathematical Analysis and Applications》2006,317(1):302-319
Let B be the unit ball in Cn with respect to an arbitrary norm and let f(z,t) be a g-Loewner chain such that e−tf(z,t)−z has a zero of order k+1 at z=0. In this paper, we obtain growth and covering theorems for . Moreover, we consider coefficient bounds and examples of mappings in . 相似文献
120.
Zhi C Bando Y Tang C Honda S Sato K Kuwahara H Golberg D 《The journal of physical chemistry. B》2006,110(4):1525-1528
An effective method was proposed to remove obstinate boron nitride phase impurities in boron nitride nanotubes (BNNTs). The method is based on strong interactions between BNNTs and a conjugated polymer wrapping them and significant weight and size difference between BNNTs and impurities. The as-grown samples and purified samples were compared through detailed characterization, using scanning electron microscopy, transmission electron microscopy, and Raman and Fourier transformed infrared spectroscopy. The results reveal that impurities are effectively removed and resultant BNNTs possess perfect crystallization. 相似文献