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151.
Lysidicin A, which has been isolated from Lisidicie rhodostegia possesses complicated structure. A total synthesis of lysidicin A has been achieved and is described herein. The key reaction is single and cascade Claisen rearrangements. 相似文献
152.
J. Bellessa V. Voliotis T. Guillet D. Roditchev R. Grousson X.L. Wang M. Ogura 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,21(4):499-505
We report on time-resolved microphotoluminescence experiments in a single GaAs/GaAlAs V-shaped quantum wire as a function
of optical excitation intensity. At low pump power we observe that excitons are localized in quantum boxes formed by the local
potential minima existing along the wire axis. As the pump power is increased, state filling of the lowest lying levels of
the boxes appears. When two carriers occupy the first excited level of the box, a very efficient Auger scattering occurs,
leading to a transfer of carriers from one box to another neighbouring one. The intradot Auger scattering time has been measured
and is of the same order of magnitude as the LA-phonon emission rate.
Received 5 February 2001 相似文献
153.
Nagatomo T. Matsuta K. Hashimoto K. Ota M. Arimura K. Minamisono K. Sumikama T. Ogura M. Iwakoshi T. Miyake T. Kudo S. Akutsu K. Minamisono T. Fukuda M. Mihara M. Momota S. Nojiri Y. Kitagawa A. Torikoshi M. Kanazawa M. Suda M. Hirai M. Symons T. J. M. Krebs G. F. Alonso J. R. Zhu S. Y. Zhu J. Z. Xu Y. J. 《Hyperfine Interactions》2001,136(3-8):233-237
The nuclear spin alignments of the β-emitting fragments 12B(I
π=1+, T
1/2=20.2 ms) and 13B(I
π=3/2−, T
1/2=17.4 ms) produced in the 100A-MeV 13C, 15N + 9Be collisions respectively have been observed for the first time detecting asymmetric β-ray emission from these nuclei. By
means of the spin manipulation technique based on the hyperfine interaction of B isotopes in TiO2, both the polarization P and the alignment A were determined reliably. The obtained P and A were significantly smaller than the expectation from the kinematical model. From the fact that the quenching factors for
P and A are almost the same, there may be some depolarization mechanism in the collision process itself.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
154.
Minamisono T. Matsuta K. Minamisono K. Kudo S. Ogura M. Fukuda S. Sato K. Mihara M. Fukuda M. 《Hyperfine Interactions》2001,136(3-8):225-231
In order to precisely determine the |eqQ(41Sc)/h| of 41Sc(I
π=7/2−, T
1/2=0.596 s) implanted in a TiO2 single crystal the electric field gradient tensor and anisotropic chemical shift were determined by detecting the Fourier
Transformed Pulse-NMR of 45Sc(I
π=7/2−, stable) in the crystal at a high field of 7.0 T and 9.4 T. Combining the new |eqQ(41Sc)/h| value with the Q(45Sc)=−(23.6±0.2) fm2, also renewed by using the known atomic hyperfine interaction constants and Sternheimer polarization effect, the |Q(41Sc;I
π=7/2−,T
1/2=0.596 s)|=(15.6±0.3) fm2 has been precisely determined. The value is compared with the theoretical Q(41Sc) given by a shell model code.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
155.
We present a discrete correlation processor-2 (DCP-2), which is an optical processor with reconfigurability of interconnection patterns for large-fan-out optical interconnection systems. To our knowledge, there is no reconfigurable optical processor satisfying the requirements for large fan-outs such as high-speed reconfiguration of interconnection pattern, high optical efficiency, and high contrast ratio, because existing spatial light modulators (SLM#x0027;s) lack at least one of these features. The DCP-2 architecture fulfills the requirements by using a hybrid configuration composed of a high-speed image steerer and a spatial light modulator, which work in a complementary manner to shorten the setup time of the SLM. We constructed two kinds of prototype demonstrators based on this architecture. In the experiment, reconfiguration speed of the DCP-2 prototype with shift-invariant optical interconnections, in which a liquid crystal SLM cooperated with a two-dimensional acousto-optic beam deflector, was about 26,000 times faster than that of the standalone SLM at the cost of 50#x0025; energy loss by the deflector. 相似文献
156.
N. Yasuda K. Uchikawa K. Amemiya N. Watanabe H. Takahashi M. Nakazawa M. Yamamoto K. Ogura 《Radiation measurements》2001,34(1-6):45-49
As a frame work of the study for the latent track size measurement using atomic force microscope, we have measured the minute etch pits and the extremely small amount of bulk etch of CR-39 at the beginning of chemical etching, and obtained its growth curves in nanometer dimensions. The pieces of CR-39 were exposed to 6 MeV/nC and Fe ions with normal incidence angle and were etched in 70°C 7 N NaOH solution for 0.5,1,2,3,5 min. The diameters of latent track were estimated to be 17 nm for Fe ions and 8 nm for C ions, respectively. These values are comparable to the experimental data on the average ‘track core diameters’ that have been obtained by various experimental techniques. 相似文献
157.
Ryuya Yokoo Keisuke Goto Jiro Kasahara Venkat Athmanathan James Braun Guillermo Paniagua Terrence R. Meyer Akira Kawasaki Ken Matsuoka Akiko Matsuo Ikkoh Funaki 《Proceedings of the Combustion Institute》2021,38(3):3759-3768
The internal flow structures of detonation wave were experimentally analyzed in an optically accessible hollow rotating detonation combustor with multiple chamber lengths. The cylindrical RDC has a glass chamber wall, 20 mm in diameter, which allowed us to capture the combustion self-luminescence. A chamber 70 mm in length was first tested using C2H4O2 and H2–O2 as propellants. Images with a strong self-luminescence region near the bottom were obtained, confirming the small extent of the region where most of the heat release occurs as found in our previous research. Based on the visualization experiments, we tested RDCs with shorter chamber walls of 40 and 20 mm. The detonation wave was also observed in the shorter chambers, and its velocity was not affected by the difference in chamber length. Thrust performance was also maintained compared to the longer chamber, and the short cylindrical RDC had the same specific impulse tendency as the cylindrical (hollow) or annular 70-mm chamber RDC. Finally, we calculated the pressure distributions of various chamber lengths, and found they were also consistent with the measured pressure at the bottom and exit. We concluded that the short-chamber cylindrical RDC with equal length and diameter maintained thrust performance similar to the longer annular RDC, further expanding the potential of compact RDCs. 相似文献
158.
The magnetic properties and the hyperfine interactions of Fe4N and Fe4C under high pressures are discussed on the basis of first-principles electronic structure calculations performed by the KKR
Green's function method and its extention into a full potential scheme (FP-KKR). The results show that both Fe4N and Fe4C undergo a weak first order transition from high to low spin states under pressure. This transition is sensitively reflected
not only by H
hf but also by EFG. The calculated Curie temperature, magnetic moments and H
hf well reproduce the experimental observations. 相似文献
159.
Tsuneo Itoh Ikuko Fujii Yasuo Tomii Ichiro Ishikawa Hamo Ogura Yoshihisa Mizuno Norio Kawahara 《Journal of heterocyclic chemistry》1987,24(5):1453-1455
An improved and efficient synthesis of 1,3-dialkylpyrido[2,3-d]pyrimidine-2,4-(1H,3H)-diones from 6-methylaminouracils and methyl propiolate or diethyl ethoxymethylenemalonate is described. 相似文献
160.
M Nakamura K Furuhata K Yamazaki H Ogura H Kamiya H Ida 《Chemical & pharmaceutical bulletin》1989,37(8):2204-2206
A method for analysis of 3-deoxy-D-glycero-D-galacto-2-nonulopyranosonic acid (KDN) by high-performance liquid chromatography (HPLC) with a strongly basic anion-exchange resin was developed. The method was applied to detect free KDN in water used to rinse of fertilized eggs of chum salmon, Oncorhynchus keta. Furthermore, KDN was isolated from the water as a fully protected derivative. 相似文献