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141.
A new and reliable procedure for constructing five- to seven-membered carbocycles via an endo-mode ring-closing reaction of 1-phenylsulfonylallenes with a substituent that has a terminal active methine moiety at the C1-position has been developed. Trisubstituted 1-phenylsulfonylallenes underwent a similar endo-mode ring-closing reaction to produce the corresponding five- to seven-membered carbocycles, while the formation of six- and seven-membered carbocycles from the corresponding tetrasubstituted allene was not realized. In addition, the introduction of an aromatic ring to the alkyl side chain of the starting allenes made possible the construction not only of normal-sized carbocycles but also an eight-membered framework. 相似文献
142.
A. Sasoh K. Watanabe Y. Sano N. Mukai 《Applied Physics A: Materials Science & Processing》2005,80(7):1497-1500
When a pulsed laser beam is focused onto a metal plate in water, a high-pressure pulse can be generated. This paper investigates the formation and behavior of bubbles that appear after the high-pressure-pulse generation. A 200-mJ, second-harmonic Nd:YAG laser pulse (duration of 7 ns) is incident on a stainless steel (SUS 304) plate to form a 1.1-mm-diameter spot. A bubble is formed and expands over the spot, which generates a hemispherical blast wave around the spot. The bubble grows in a period of the order of 400 s after the laser pulse to reach a radius of about 5 mm. The behavior of the bubble is strongly affected by the thickness of the plate. When the plate thickness is 10 mm, the bubble keeps its hemispherical shape during the period of the first bounce. However, with a thin plate, for example of 0.1-mm thickness, the bubble is pinched and its head separates; moreover, another bubble is generated on the other side of the plate. Since these bubbles have different bounce motions, the acoustic field between 400 and 900 s significantly differs depending on the thickness of the plate. PACS 47.40.Nm; 68.45.-v; 42.62.Cf 相似文献
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145.
Takehito Hayakawa Tetsuro Komatsubara Jun Lu Junko Mukai Kohei Furuno 《Zeitschrift für Physik A Hadrons and Nuclei》1997,358(1):15-24
Low-lying states in 57 128 La and 56 128 Ba have been investigated by γ-ray spectroscopy after the β decays of 58 128 Ce and 57 128 La. For the EC+β+ decay of 128Ce, a new halflife has been determined to be 4.1 ± 0.3 min. In 128La a new β-unstable isomeric state with a halflife shorter than 2 min is suggested in addition to a previously known isomeric state with the halflife of 5.2 min. A tentative level scheme of 128La at low excitation energies has been constructed from the γ?γ coincidence measurement after the β decay of 128Ce. The γ?γ angular correlation for γ rays from 128Ba after the β decay of 128La suggests that the spin-parity assignment of I π = 4? or 5+ is preferable for the 2424.9 keV level which is populated via the β decay of the 5.2-min isomeric state with a log ft value of 5.6. For the 2877.1 keV level observed with log ft = 5.8, a preferable spin-parity assignment is 5? or 6+. On the basis of these decay properties and low-lying excited states in neighboring odd mass nuclei, the spins and parities of isomeric states in 128La are proposed to be (1+ or 2+) for the low-spin state, while (5± or 6+) for the high-spin state, within the limit of zero order approximation to the proton-neutron couplings. 相似文献
146.
We have measured the intensity noise from symmetric low-Q cavity laser diodes (LD's) operated far above threshold in a constant-current mode. The single-sided output noise exhibits significant dependence on the mirror reflectivities of the laser cavity, in good agreement with the theoretical predictions based on a quantum-mechanical traveling-wave analysis. In an antireflection-coated LD with a residual mirror reflectivity of 5%, intensity noise as large as 9 dB above the shot-noise level was observed at a pumping rate of 10 times the threshold. This is caused by amplification of the vacuum-field fluctuations coupled by the low-reflectivity mirrors into the laser cavity. 相似文献
147.
J. Mukai A. Odahara R. Nakatani Y. Haruta H. Tomura B. J. Min K. Heiguchi S. Suematsu S. Mitarai T. Kuroyanagi 《Zeitschrift für Physik A Hadrons and Nuclei》1992,342(4):393-396
The neutron deficient isotope79Y has been firstly identified and the decay properties were studied from-decay measurements in the reaction of54Fe(28Si,p2n at 92 MeV. Three rays of 152.5, 177.4, and 1106 keV were observed concerning the decay. The half life and QEC value were determined to be 14.9 ± 0.6 s and 7.12 ± 0.45 MeV, respectively. The decay scheme including spin-parity is discussed, and 5/2+ assignment for the ground state is proposed.We would like to thank to Dr. Y. Maeda for his valuable advice about the electroplating method of iron targets. We also thank to Mr. T. Maeda and Mr. S. Niiya for preparation of hardware for data-taking. 相似文献
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149.
在InGaN发光二极管中,尽管存在着大量的位错,但其效率还是相当高的.用InGaN作为有源层是很重要的.在InGaN基LED的情况下,为产生光发射需要较高的激发功率.横向大面积外延生长的GaN激光二极管(LDs)是在厚的GaN衬底上外延制备成的.在温度250℃、30mW输出的连续工作状态下,其工作电流小于42mA,600℃、30mW输出的连续工作状态下的寿命约为15 000小时.这些结果表明,螺旋位错密度的降低延长了激光二极管的寿命.此外,良好的散热也是很重要的. 相似文献
150.
Tomoyuki Akiyama Haruhiko Kuwatsuka Takashi Simoyama Yoshiaki Nakata Kohki Mukai Mitsuru Sugawara Osamu Wada Hiroshi Ishikawa 《Optical and Quantum Electronics》2001,33(7-10):927-938
Ultrafast gain dynamics in quantum-dot optical amplifiers has been studied by using the pump-probe and four-wave mixing (FWM) techniques. It was found that there are at least three nonlinear processes, which are attributed to carrier relaxation to the ground states, phonon scattering, and carrier capture from the wetting layers into the quantum dots (QDs). The relevant time constants were evaluated to be ~90 fs, ~260 fs, and ~2 ps, respectively, under a 50 mA bias condition. The compressed gain recovered to 3% of its initial value in 4 ps, and no recovery component slower than 2 ps could be seen in the temporal range tested. This is quite different from the feature in quantum wells, where a very slow component (> 50 ps) exists. This suggests a possibility of enhancing the operation speed of semiconductor optical amplifiers by using QDs as an active layer. The third-order optical susceptibility (χ(3)) has been evaluated by means of both nonlinear transmission and FWM experiments. The results show that the nonlinearity expressed by χ(3)/g 0 is quite similar to that of bulk and quantum wells, which can be explained by the similar relaxation times. 相似文献