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91.
Bischolic acid derivative 1 linked by m-xylylene dicarbamate at the 3,3'-position was synthesized and the single ion channel properties were examined. Compound 1 showed two clearly distinct conductances, 9.5 (type A) and 25.3 pS (type B), under 500 mM KCl symmetric salt conditions, whereas various conductances, ranging from 5-20 pS, were observed in the tetramethylether analogue reported previously. Results indicate that the replacement of four methylether groups with hydroxyls at the 7, 7', 12, and 12' positions in the bischolic acid framework influences the stability of aggregated (supramolecular) ion channel structures. Ion permeability ratios (potassium/chloride and potassium/sodium) for each type of channel were also determined. 相似文献
92.
Highly efficient frequency conversions were conducted to obtain deep-ultraviolet single-mode coherent light by use of two-stage external cavities. A power of 154 mW at approximately 252 nm was obtained with a conversion efficiency of more than 8% by doubly resonant sum-frequency mixing of 373-nm light from the first-stage conversion and 780-nm light from a single-mode Ti:sapphire laser. The output performance of the deep-ultraviolet light source is sufficient for use in the laser cooling of neutral silicon atoms. 相似文献
93.
T.?Okato P.A.?Atanasov R.I.?Tomov M.?Obara Email author 《Applied Physics A: Materials Science & Processing》2003,77(6):775-778
Highly textured single-oriented (110)Nd-doped potassium gadolinium tungstate [Nd:KGd(WO4)2 or Nd:KGW] thin films were successfully fabricated on (100)Si substrate by introducing a (100)CeO2 buffer layer using KrF-excimer-laser pulsed laser deposition (PLD) at precisely controlled experimental conditions. The CeO2 buffer layer was also prepared by PLD. Home-made potassium-enriched ceramic targets were prepared and used in order to prevent K deficiency in the film during the deposition. Depositions were performed in both Ar and O2 environments. The optimal growing conditions achieved from the viewpoint of best crystallinity, optical properties and surface morphology were: dT–S=4 cm, P(O2)=0.08 mbar and Tsub=700 °C, respectively. Improvement of the properties of the as-grown films was examined by post-deposition annealing between 700 °C and 900 °C in air. Optical waveguide loss and the photoluminescence spectrum in the 800–1400-nm range were measured. PACS 81.15.Fg; 42.79.Gn; 42.79.Hj 相似文献
94.
Jun TakayamaSeiko Fukuda Yoshiaki SugiharaAkihiko Ishii Juzo Nakayama 《Tetrahedron letters》2003,44(28):5159-5162
Hetero Diels-Alder reactions of 3,4-di-tert-butylthiophene 1-oxide (1) with thioaldehydes and thioketones take place exclusively, except the reaction with thiobenzophenone, at the syn-π-face of 1 with respect to the SO bond. The π-face selectivity was explained in terms of the extent of conformational changes of 1 that are brought about in the process to the transition states. 相似文献
95.
Nomoto A Mitsuoka H Ozeki H Kobuke Y 《Chemical communications (Cambridge, England)》2003,(9):1074-1075
Introducing a porphyrin bearing electron acceptor onto a self-assembled monolayer (SAM) using a supramolecular method to form a hetero-dimer increased the photocurrent value compared with using porphyrin without an electron acceptor. 相似文献
96.
Simple bis(imidazolyl)porphyrin cobalt(III) complex was found to form a long polymeric array by complementary coordination of imidazole to cobalt ion. Formation of higher ordered assemblies was also observed. 相似文献
97.
98.
Tobe M Isobe Y Tomizawa H Nagasaki T Aoki M Negishi T Hayashi H 《Chemical & pharmaceutical bulletin》2003,51(9):1109-1112
We investigated the chemical modifications of the nitroquinazoline derivative (1) through the replacement of the NH group at the C(4)-position with several N-alkyl groups to increase the lipophilicity at the C(4)-position. Among them, we found that the N-methyl analogue (5a) showed a 2-fold loss in the inhibitory activity toward tumor necrosis factor-alpha (TNF-alpha) production in vitro as compared with the NH analogue (1); however, 5a exhibited an oral inhibitory activity on TNF-alpha production with an ED50 value of 26 mg/kg, whereas 1 did not. Moreover, the oral bioavailability of 5a was higher than that of 1 (1, F=1%; 5a, F=21%), and the calculated ClogP value for 5a was higher than that for 1. These results suggest that the improved lipophilicity of 5a compared with that of 1 reflects its greater inhibitory activity on TNF-alpha production in vivo as well as oral bioavailability. 相似文献
99.
100.
We developed a deep-UV single-mode coherent light source through two-stage highly efficient frequency conversions by use of external cavities. In the first stage, second-harmonic power of 500 mW was obtained by frequency doubling of a 746-nm Ti:sapphire laser with a conversion efficiency of 40%. In the second stage, 50-mW power at ~252nm was obtained by doubly resonant sum-frequency mixing of 373-nm light from the first-stage conversion and 780-nm light from a diode laser. The output performance of this deep-UV light source is sufficient for laser cooling of neutral silicon atoms. 相似文献