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排序方式: 共有117条查询结果,搜索用时 46 毫秒
51.
M. Karppinen H. YamauchiT. Nakane K. FujinamiK. Lehmus P. NachimuthuR.S. Liu J.M. Chen 《Journal of solid state chemistry》2002,166(1):229-236
Generation of holes is facilitated in the Cu(Ba0.8Sr0.2)2 (Yb1−xCax)Cu2O6+z (Cu-1212) system by two independent ways, i.e., by Ca substitution (0≤x≤0.35) and O doping (0<z<1). The distribution of holes between the CuO2-(Yb1−xCax)-CuO2 block containing two identical superconductive CuO2 planes and the “charge-reservoir” block consisting of a single CuOz chain has been quantitatively investigated by means of O K-edge and Cu L2,3-edge X-ray absorption near-edge structure (XANES) spectroscopy. The resultant values for the CuO2-plane hole concentration are compared with those calculated employing the bond-valence-sum (BVS) method from the neutron powder diffraction (NPD) data previously reported for the same samples. The results of the two methods are in good agreement. The two independent hole-doping ways are found to result in different distributions of holes over the crystal, i.e., different ratios of hole numbers at the CuO2 plane and the CuOz chain. With Ca substitution holes are directed efficiently into the CuO2 plane, while for O doping holes are more homogeneously distributed between the CuO2 plane and the CuOz chain. Moreover, the value of Tc at a fixed CuO2-plane hole concentration is shown to be higher for Ca-substituted than for O-doped samples. 相似文献
52.
The v3 mode of CH3F was excited by irradiation with a TEA CO2 laser pulse, and the time-resolved emission spectra of the v3 overtone and the 3 μ;m region were observed. The results indicate that the population of the v4 level behaves kinetically in the same manner as that of 2v3 or 3v3. This suggests an efficient energy transfer between these levels. 相似文献
53.
In the previous work we reported five A-seco-rearranged lanostane triterpenoids as antibacterial constituents from the ethyl acetate soluble fraction of Abies sachalinensei leaves. In further study on the isolation of constituents from the ethyl acetate soluble fraction, two new rearranged lanostane and lanostane-type triterpenoids (3, 4) and three reported compound (1, 2, 5) were isolated. The structures of new compound 3 and 4 were determined to be 3,4-seco-4(28),6,8(14),24-mariesatetraen-26,23-olide-23-hydroxy-3-oic acid and 3,4-seco-4(28),7,24-lanostatrien-26,23-olide-23-hydroxy-3-oic acid, respectively, by spectral studies on HR-MS, (1)H-NMR, (13)C-NMR, and 2D-NMR spectra. Compound 1 was identified with pindrolactone and its structure was revised as 7,14,22Z,24-mariesatetraen-26,23-olide-3alpha-ol. Structures of 2 and 5 were determined as 7,14,24-mariesatrien-26,23-olide-3alpha,23-diol and 3alpha-hydroxy-7,14,24E-mariesatrien-23-oxo-26-oic acid. Of these compounds, 2, 3 and 4 were obtained as lactol tautomer mixtures at gamma-lactone structures of side chains. 相似文献
54.
Satoshi Nakane Sho Yoshinaka Shoutaro Iwase Yoshihiro Shuto Paul Bunse Bernhard Wünsch Shinji Tanaka Masato Kitamura 《Tetrahedron》2018,74(38):5069-5084
Asymmetric NaBH4 reduction catalyzed by the Co(II) complex of a chiral diamidine-type sp2N ligand, Naph-diPIM-dioxo-iPr, was successfully applied to 3-silyloxycinnamate substrates without over-reduction, giving quantitatively 3-silyloxy-3-arylpropionates with an enantiomer ratio of up to 99:1. The high utility was confirmed on a 30-g scale using 0.1?mol% catalyst. Both Z and E substrates could be converted to a single enantiomeric product by changing the ligand chirality. The relationship between the Z/E stereochemistry and the absolute configuration of the 1,4-reduction product provided important information about the mechanism underlying enantioface selection. Combination of the asymmetric catalysis with two other key steps, Suzuki coupling with an N-protected tetrahydropyridine boronic acid derivative and intramolecular bromo etherification, realized an efficient synthetic route to both enantiomers of fluspidine. The new strategy permits the introduction of substituents on the two aryl groups and piperidine ring, allowing for structural variations toward the development of higher performance σ1 receptor antagonists. 相似文献
55.
Antitumor-promoting constituents from Chaenomeles sinensis KOEHNE and their activities in JB6 mouse epidermal cells 总被引:2,自引:0,他引:2
Gao H Wu L Kuroyanagi M Harada K Kawahara N Nakane T Umehara K Hirasawa A Nakamura Y 《Chemical & pharmaceutical bulletin》2003,51(11):1318-1321
Primary screening of antitumor-promoting activity using soft agar colony assays with JB6 cells was employed to isolate 22 compounds from Chaenomeles sinensis KOEHNE. These compounds were lyoniresinol-2a-O-alpha-L-rhamnopyranoside (1), lyoniresinol-2a-O-beta-D-glucopyranoside (2), aviculin (3), betulinic acid (4), betulin (5), 3-O-(E)-p-coumaroylbetulin (6), 3-O-(E)-caffeoylbetulin (7), 3-O-(Z)-p-coumaroylbetulin (8), 3-O-(E)-caffeoyllupeol (9), alphitolic acid (10), sorbikortal II (11), tormentic acid (12), euscaphic acid (13), corosolic acid (14), maslinic acid (15), erythrodiol (16), 1-beta-D-glucopyranosyloxy-3,4,5-trimethoxybenzene (17), avicularin (18), 7-O-beta-D-glucopyranosylkaempferol (19), 5-O-beta-D-glucopyranosylgenistein (20), 7-O-beta-D-glucopyranosylgenistein (21), epicatechin (22), and beta-sitosterol (23) and were identified using spectral data such as MS, (1)H- and (13)C-NMR. Compound 1, having a rhamnosyl group, showed greater activity than 2, having a glucosyl group, and 3, which was a bis-demethoxy derivative of 1. Betulinic acid (4), having a C-28 carboxyl group, 3-O-(E)-caffeoylbetulin (7), and tormentic acid (12) showed more potent activity than betulin (5), which has a C-28 hydroxymethyl group. 相似文献
56.
S. Nakane 《Journal of Mathematical Analysis and Applications》2008,338(1):552-562
The dynamics of regular polynomial endomorphisms of two variables is investigated. Especially, the landing points of the external rays for maps associated with Chebyshev maps are completely characterized. 相似文献
57.
58.
Germacrone (1) and (4S,5S)-germacrone-4,5-epoxide (2) were isolated, along with guaiane and secoguaiane-type sesquiterpenes, from Curcuma aromatica plants. Compound 2 was derived from 1 and cyclized through transannular (T-A) reactions into various guaiane and secoguaiane-type sesquiterpenes in C. aromatica. The cyclization reaction of 2 was initiated by protonation at an epoxide oxygen atom, followed by cleavage of the epoxide ring and the formation of a C-C bond between C-1 and C-5 to give guaiane-type derivatives. Acidic and thermal treatments of 2 produced twelve sesquiterpenes having guaiane and secoguaiane skeletons. The structures of these products were elucidated by spectral methods, including 2D-NMR spectroscopy. Most were identified as sesquiterpenes isolated from C. aromatica as natural products. The T-A cyclization of 2 occurred via two transition states, a cross conformation and a parallel conformation. The mechanism of the T-A cyclization reaction of 2 is discussed. 相似文献
59.
60.
D. Satoh Y. Iwamoto M. Hagiwara H. Iwase H. Yashima T. Sato A. Endo Y. Sakamoto Y. Nakane H. Nakashima T. Nakamura A. Tamii K. Hatanaka 《Radiation measurements》2010,45(10):1159-1162
Angular differential neutron elastic scattering cross sections have been measured by using a 7Li(p,n) quasi-monoenergetic neutron beam. The neutron beam whose peak energy is 134 MeV was incident upon a natural carbon sample, and the scattering neutrons were measured by liquid organic scintillators with the time-of-flight (TOF) technique. The results were compared with the existing experimental data measured by a recoil-proton telescope, and the evaluated nuclear data of JENDL/HE-2007 and ENDF/B-VII.0. 相似文献