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51.
Md. Khorshed Alam Ryuji Miura Hideyuki Tsuboi Akira Endou Momoji Kubo 《Applied Surface Science》2010,257(5):1383-1389
Ceria plays an important role in catalysis, due to its ability to store and release oxygen depending on the condition present in the catalyst environment. To analyze the role of ceria in catalytic reactions, it is necessary to know the details of the interaction of ceria surface with environmentally sensitive molecules. This study was conducted using ultra accelerated quantum chemical molecular dynamics. Its purpose was to investigate the reduction process of the (1 1 1) and (1 1 0) surfaces of ceria with atomic hydrogen as well as water desorption mechanisms from the surfaces. This simulation demonstrated that when a high-energy colliding hydrogen atoms are adsorbed on the ceria, it pulls up an O atom from the ceria surfaces and results in the formation of a H2O molecule. This is the first dynamics simulation related to such reduction processes based on quantum chemistry. 相似文献
52.
Dielectric properties of vinyl acetate and methyl methacrylate oligomers having chemically different end groups were compared. Dielectric measurements were carried out over the frequency range between 23 and 3 MHz and the temperature range between +50 and ?50°C. The static dielectric constants of these oligomers are between 10 and 20. The relaxations were analyzed with the Havriliak–Negami equation. The dielectric properties depend on the chain end groups on the oligomers. The distribution of relaxation times of the vinyl acetate oligomers was wider than that of poly(vinyl acetate). It was concluded that two cooperative motions, that of the principal chain and that of the chain and that of the chain end group, take part in the dielectric relaxation of these short chain molecules. 相似文献
53.
Hong FL Minoshima K Onae A Inaba H Takada H Hirai A Matsumoto H Sugiura T Yoshida M 《Optics letters》2003,28(17):1516-1518
A frequency comb spanning more than one octave has been achieved by injecting the second-harmonic generation (780 nm) of a mode-locked fiber laser (1.56 microm) into a photonic crystal fiber. We propose and realize a novel interferometric scheme for observing the carrier-envelope offset frequency of the frequency comb. Frequency noise has been observed on the measured carrier-envelope offset frequency, which has been confirmed to be generated in the photonic crystal fiber by comparing the measured beat frequencies between cw lasers and frequency combs before and after the photonic crystal fiber. The mode-locked fiber laser is considered to be an important candidate for the light source used in realizing a compact optical frequency measurement system including applications in the telecommunication bands. 相似文献
54.
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
55.
Toshio Nishi Hideyuki Nukaga So Fujinami Ken Nakajima 《高分子科学》2007,(1):35-41
Atomic force microscopy (AFM) has the advantage of obtaining mechanical properties as well as topographic information at the same time. By analyzing force-distance curves measured over two-dimensional area using Hertzian contact mechanics, Young's modulus mapping was obtained with nanometer-scale resolution. Furthermore, the sample deformation by the force exerted was also estimated from the force-distance curve analyses. We could thus reconstruct a real topographic image by incorporating apparent topographic image with deformation image. We applied this method to carbon black reinforced natural rubber to obtain Young's modulus distribution image together with reconstructed real topographic image. Then we were able to recognize three regions; rubber matrix, carbon black (or bound rubber) and intermediate regions. Though the existence of these regions had been investigated by pulsed nuclear magnetic resonance, this paper would be the first to report on the quantitative evaluation of the interfacial region in real space. 相似文献
56.
Yoshikazu Shizuri Yoshishige Okuno Hideyuki Shigemori Shosuke Yamamura 《Tetrahedron letters》1987,28(52):6661-6664
(±)-8,14-Cedranoxide has been synthesized starting from 3,4-dimethoxyphenol, wherein 6-acetoxymethyl-2,6-dimethyl-9-methoxytricyclo[5.3.1.01,5]undec-9-en-8,11-dione as a key intermediate has been produced efficiently by means of electrochemical methods. 相似文献
57.
Wada M Yokota C Ogata Y Kuroda N Yamada H Nakashima K 《Analytical and bioanalytical chemistry》2008,391(3):1057-1062
A sensitive high-performance liquid chromatography (HPLC)–fluorescence method for determination of morphine (Mor) in rat brain
and blood microdialysates was developed using 4-(4,5-diphenyl-1H-imidazol-2-yl)benzoyl chloride (DIB-Cl) as a label. Mor was labeled with DIB-Cl under mild reaction conditions (at room temperature
for 10 min). The separation of DIB-Mor was carried out on an octadecylsilica (ODS) column with CH3CN/0.1 M acetate buffer (pH 5.4) within 14 min. The detection limits of Mor in brain and blood microdialysates at a signal-to-noise
ratio of 3 were 0.4 and 0.6 ng mL−1, respectively. The proposed method was successfully applied to the preliminarily study of potential pharmacokinetic interaction
between Mor and diclofenac. 相似文献
58.
Tei T Sato Y Hagiya K Tai A Okuyama T Sugimura T 《The Journal of organic chemistry》2002,67(19):6593-6598
The stereocontrol mechanism of the 2,4-pentanediol (PD)-tethered reaction was studied in detail using a reaction system consisting of phenyl and rhodium carbenoid moieties. Different tethers were examined to analyze the effects of the methyl groups on the PD tether. Among the reactions with these tethers, the PD tether achieves an unmeasurably high stereoselectivity in a diastereomeric ratio of >500. Another tether showing a high but measurable stereoselectivity in a ratio of 41 is mostly controlled by the entropy term. To clarify the role of the methyl groups on the chiral tethers, which are the origin of the stereocontrol, the "chiral perturbation factor" is introduced. This parameter is defined as the rate of a chiral reaction relative to that of an achiral reference reaction. By analyzing the temperature dependence of the chiral perturbation factors for different chiral-tethered reactions, high potentials of the PD-tethered reaction in its stereocontrol are concluded to be due to the entropy term. 相似文献
59.
Satoshi Kaneco Kensuke Hayashi Hideyuki Katsumata Tohru Suzuki 《International journal of environmental analytical chemistry》2013,93(13):1381-1388
A preconcentration method by adsorption of cadmium on a niobium wire was developed for the environmental waters, followed by electrothermal atomic absorption spectrometry with a tungsten tube atomizer. After the preconcentration, the niobium wire was directly inserted into the tungsten tube atomizer. In the preconcentration (adsorption) process of cadmium, the optimal immersing time was 60?s. The effects of large amounts of concomitants on the preconcentration of cadmium were evaluated. When 103–104 fold excess of matrix elements existed in aqueous solution at pH 4 and 9, the cadmium response was profoundly affected by the matrix elements. However, the cadmium absorption signal was not significantly influenced at pH 7. Therefore, pH 7 was selected for the application into the real environmental samples. Under the optimal conditions, the detection limit (3S/N) for cadmium by the niobium wire preconcentration method was 7.0?pg?mL?1 and the relative standard deviation was 6.8%. The method with preconcentration on a niobium wire was applied to the determination of cadmium in water and proved to be sensitive, simple and convenient. Because this preconcentration method can be utilized in the in situ treatment of trace cadmium in environmental water samples, it was unnecessary to carry the water samples to the analytical work place. The technique was shown to be useful for the determination of cadmium in environmental water samples at 0.1–1?µg?L?1 levels. 相似文献
60.