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171.
The stability enhancement of laser output power for the change of external cavity position in semiconductor lasers with optical feedback is observed by experiment. The relaxation oscillation frequency which plays an important role in the dynamics of the nonlinear system is also investigated as a function of the external cavity length. The period of the stability enhancement along the position of the external cavity is exactly coincident with the length corresponding to the relaxation oscillation frequency of the solitary laser. The experimental results are compared with theoretical and excellent coincidence between the two is found. 相似文献
172.
Matsuta K. Minamisono T. Tanigaki M. Fukuda M. Nojiri Y. Mihara M. Onishi T. Yamaguchi T. Harada A. Sasaki M. Miyake T. Minamisono K. Fukao T. Sato K. Matsumoto Y. Ohtsubo T. Fukuda S. Momota S. Yoshida K. Ozawa A. Kobayashi T. Tanihata I. Alonso J. R. Krebs G. F. Symons T. J. M. 《Hyperfine Interactions》1996,97(1):519-526
The magnetic moments of the proton drip-line nuclei13O(I
= 3/2–,T
1/2 = 8.6 ms) and 9C(I
= 3/2–,T
1/2 = 126 ms) have been determined for the first time through the combined techniques of polarized radioactive nuclear beams and-NMR detection. The observed magnetic moments are ¦(13O)¦ = 1.3891 ±0.0003
N and ¦(9C)¦ = 1.3914 ±0.0005
N. Spin expectation values are deduced to be 0.76 and 1.44 for13O and9C, respectively. While the of13O is consistent with the systematics from isospinT= 1/2 mirror pairs, the of9C is unusually large, even far larger than the single particle value, = 1. 相似文献
173.
Okauchi T Kakiuchi T Kitamura N Utsunomiya T Ichikawa J Minami T 《The Journal of organic chemistry》1997,62(24):8419-8424
alpha-Ester-substituted 1,3-dienylphosphonates 7 and 8, prepared by the Knoevenagel condensation, underwent intramolecular [2 + 2] cycloaddition in the presence of Lewis acid to form bicyclo[4.2.0] (26-57% yield) and bicyclo[3.2.0]skeleton (14-38% yield), respectively. Similar treatment of homologous 1,3-dienylphosphonate 11 and 1,3,5-trienylphosphonate 12 resulted in the formation of ionone derivatives (30-94% yield). The intramolecular cycloaddition reaction was applicable to several conjugated dienes bearing an ester group. 相似文献
174.
Paul D Suzumura A Sugimoto H Teraoka J Shinoda S Tsukube H 《Journal of the American Chemical Society》2003,125(38):11478-11479
Supramolecular complexation with 18-crown-6 significantly converted catalytically inactive cytochrome c (biological form) to catalytically active synzyme (artificial form). Although a family of cytochrome c proteins does not work as enzymes in nature, crown ether complexation modified their heme coordination structures and functionally activated them to promote the asymmetric oxidation of racemic sulfoxides at low temperature. Horse heart, pigeon breast, and yeast cytochrome c proteins were demonstrated to form supramolecular complexes with 18-crown-6 in methanol, which effectively oxidized (S)-isomers of naphthyl methyl sulfoxide, methyl tolyl sulfoxide, isopropyl phenyl sulfoxide, benzyl methyl sulfoxide, and 4-methylsulfenyl acetophenone at -40 degrees C. Because horse heart and pigeon breast cytochromes c exhibited more efficient and higher enantiomer-selective activities than yeast cytochrome c, a proper combination of cytochrome c and crown ether offers a new class of cold-active synzymes promoting nonbiological asymmetric oxidation. 相似文献
175.
Junji Mizukado Yasuhisa Matsukawa Heng-dao Quan Masanori Tamura Akira Sekiya 《Journal of fluorine chemistry》2005,126(3):365-369
ROCHF2-type fluorinated ethers were synthesized by the reaction of hexafluoropropene oxide (HFPO) with alcohol or phenol. In this reaction, although the insertion reaction of difluorocarbene to OH bond and the nucleophilic attack of alcohol or phenol to HFPO were competition, the insertion reaction proceeded predominantly to give fluorinated ether in the case of low nucleophilic alcohol or phenol. In addition, high reaction pressure is advantageous to the selectivity of the fluorinated ethers in the reaction of HFPO with (CF3)2CHOH or C6F5OH. 相似文献
176.
Junji Furukawa Eiichi Kobayashi Shiro Nagata T
hei Moritani 《Journal of polymer science. Part A, Polymer chemistry》1974,12(8):1799-1807
13C NMR spectra of acrylic monomers complexed with a Lewis acid were measured and their electronic structures discussed in relation to their alternating copolymerizability. The β-carbon of acrylonitrile and methacrylonitrile showed a downfield shift due to the complex formation with the Lewis acid, while the α-carbon showed an upfield shift and the nitrile carbon showed no significant shift. The degree of shift of olefinic carbons decreased in the following order: AlCl3 > EtAlCl2 > Et1.5AlCl1.5 > Et2AlCl > SnCl4, EtOAlCl2 > Et(EtO)AlCl, which seems to run parallel to the Lewis acidity and acid strength. On the other hand, the chemical shift of olefinic carbons of methyl acrylate, methyl methacrylate, and olefinic diesters was influenced little by complex formation with Lewis acids, whereas the carbonyl and alkoxyl carbons were deshielded significantly by the complex formation. These results are discussed in terms of electron distribution on the carbons and an alternating polymerization mechanism. 相似文献
177.
[reaction: see text] A cyclic phosphoric acid derivative, derived from (R)-BINOL, was used as a chiral Br?nsted acid (10 mol %) in hydrophosphonylation of aldimines with diisopropyl phosphite at room temperature. Alpha-amino phosphonates were obtained with good to high enantioselectivities. 相似文献
178.
Junji Furukawa Eiichi Kobayashi Takahiro Kawagoe 《Journal of polymer science. Part A, Polymer chemistry》1978,16(7):1609-1625
Copolymerization of acetylenic monomers and 1,3-dienes was carried out by use of nickel naphthenate–diethylaluminum chloride catalyst. The molecular weight of the copolymers is rather low, and the copolymers are suitable as prepared for direct use as coating vehicles. In the system of acetylene and 1,3-dienes, the order of the copolymerization rate decreases in the following order: butadiene > isoprene > 2,3-dimethylbutadiene > chloroprene. 1,3-Dienes substituted at 1-and/or 4-position were scarcely copolymerized with acetylene. Methylacetylene and dienes tend to form cyclized copolymers. In the system of phenylacetylene and dienes, polyphenylacetylene was the main product; the copolymer was not obtained. The copolymer composition and the sequence distribution of linear copolymers were evaluated by 1H-NMR spectra. Comparison of dyad fractions of copolymers evaluated from NMR spectra and those calculated by assuming random polymerization indicated that the copolymers of acetylene and dienes were random, and that the copolymers of methylacetylene and dienes were somewhat blocky. The coordination of monomers on the catalyst may play an important role in controlling the copolymerizability. 相似文献
179.
Horikiri H Hirano N Tanaka Y Oishi J Hatakeyama H Kawamura K Nagase H 《Chemical & pharmaceutical bulletin》2004,52(6):664-669
Syntheses of 10-oxo, 10alpha-hydroxy, and 10beta-hydroxy derivatives of a potent kappa-opioid receptor selective agonist, TRK-820, are described. These derivatives were supposed to be potential degradation products in formulation of TRK-820 as a result of autoxidation. 10-Oxo-TRK-820 11 was derived from 10-oxo-4,5-epoxymorphinan 14 in 10 steps in 32% overall yield. Reduction of the 10-oxo group in 4,5-epoxymorphinan with NaBH(4) gave 10beta-hydroxy-4,5-epoxymorphinan, exclusively. A stepwise inversion method of the 10beta-hydroxy group to produce 10alpha-hydroxy-4,5-epoxymorphinan was established. By HPLC analyses, 10alpha-hydroxy-TRK-820 12 was confirmed to be one of the degradation products in developing formulation of TRK-820. 相似文献
180.
T. Minamisono T. Ohtsubo S. Fukuda I. Minami Y. Nakayama M. Fukuda K. Matsuta Y. Nojiri 《Hyperfine Interactions》1993,80(1-4):1315-1319
The -NMR technique has been modified in order to detect efficiently the nuclear quadrupole effects in the NMR spectra. -NMR is detected as a function of coupling frequency; all RFs that correspond to the coupling frequency were applied simultaneously. 相似文献