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901.
902.
A combined structural refinement of Bi3.5La0.5Ti3O12 against both neutron and X-ray diffraction data was performed at 298 K on the basis of the Raman study. The upshift of Raman peaks suggested that the substitution sites of La atoms in Bi3.5La0.5Ti3O12 were only the Bi sites in the perovskite units. Of the two crystal structural models (orthorhombic and monoclinic systems) considered for the crystal structural system of Bi3.5La0.5Ti3O12, the weighted R factor, Rwp, and goodness-of-fit indicator, S (=Rwp/Re), of the monoclinic system were lower than those of the orthorhombic one. The final Rwp and S values based on the monoclinic system were 7.04% (6.34 and 7.76% for the neutron data and the X-ray data, respectively) and 1.45, respectively. The lattice parameters obtained from the combined structural refinement were a = 5.4321(1) A, b = 5.4161(1) A, and c = 32.8614(3) A. The beta angle was 89.95(4) degrees . Spontaneous polarizations calculated from the refined structural parameters were 27.0 microC/cm2 for the monoclinic system and 1.8 microC/cm2 for the orthorhombic one. 相似文献
903.
Sung Bin Park Byung Heung Park Sang Mun Jeong Jin Mok Hur Chung Seok Seo Seung-Hoon Choi Seong Won Park 《Journal of Radioanalytical and Nuclear Chemistry》2006,268(3):489-495
Summary Electrochemical behavior of the reduction of uranium oxide was studied in a LiCl-Li2O molten salt system with an integrated cathode assembly. The mechanism for the electrolytic reduction of uranium oxide was
studied through cyclic voltammetry. By means of a chronopotentiometry, the effects of the thickness of the uranium oxide,
the thickness of the MgO membrane and the material of the conductor of an integrated cathode assembly on the overpotential
of the cathode were investigated. From the voltamograms, the reduction potential of the uranium oxide and Li2O was obtained and the two mechanisms of the electrolytic reduction were considered with regard to the applied cathode potential.
From the chronopotentiograms, the exchange current, the transfer coefficient and the maximum allowable current based on the
Tafel behavior were obtained with regard to the thickness of the uranium oxide, and of the MgO membrane and the material of
the conductor of an integrated cathode assembly. 相似文献
904.
Yamada H Imahori H Nishimura Y Yamazaki I Ahn TK Kim SK Kim D Fukuzumi S 《Journal of the American Chemical Society》2003,125(30):9129-9139
A systematic series of ITO electrodes modified chemically with self-assembled monolayers (SAMs) of porphyrins and porphyrin-fullerene dyads have been designed to provide valuable insight into the development of artificial photosynthetic devices. First the ITO and gold electrodes modified chemically with SAMs of porphyrins with a spacer of the same number of atoms were prepared to compare the effects of energy transfer (EN) quenching of the porphyrin excited singlet states by the two electrodes. Less EN quenching was observed on the ITO electrode as compared to the EN quenching on the corresponding gold electrode, leading to remarkable enhancement of the photocurrent generation (ca. 280 times) in the porphyrin SAMs on the ITO electrode in the presence of the triethanolamine (TEA) used as a sacrificial electron donor. The porphyrin (H(2)P) was then linked with C(60) which can act as an electron acceptor to construct H(2)P-C(60) SAMs on the ITO surface in the presence of hexyl viologen (HV(2+)) used as an electron carrier in a three electrode system, denoted as ITO/H(2)P-C(60)/HV(2+)/Pt. The quantum yield of the photocurrent generation of the ITO/H(2)P-C(60)/HV(2+)/Pt system (6.4%) is 30 times larger than that of the corresponding system without C(60): ITO/H(2)P-ref/HV(2+)/Pt (0.21%). Such enhancement of photocurrent generation in the porphyrin-fullerene dyad system is ascribed to an efficient photoinduced ET from the porphyrin singlet excited state to the C(60) moiety as indicated by the fluorescence lifetime measurements and also by time-resolved transient absorption studies on the ITO systems. The surface structures of H(2)P and H(2)P-C(60) SAMs on ITO (H(2)P/ITO and H(2)P-C(60)/ITO) have been observed successfully in molecular resolution with atomic force microscopy for the first time. 相似文献
905.
The effects of water absorption on hydrophilic polymer matrices based on carboxylic functionalized glucose (glucose maleic acid ester vinyl resin) and epoxy resins were studied as a function of curing temperature. The matrix cured at higher temperature shows compact crosslinks due to the higher concentration of ether bonds comparing to the matrix cured at the lower temperature. The polymer matrices cured at different temperatures were immersed in water at room temperature for 1000 h and the thermomechanical properties of the cured polymers were characterized using DMA and TGA. Two types of sorbed water were identified. Type I sorbed water contributed mainly to increasing the weight and to the decrease in Tg due to a plasticizer effect. Type II sorbed water was not removed after heating the polymer to 110 °C for an hour. Type II sorbed water causes changes in the mechanical properties of the polymers cured at different temperatures depending on the crosslinks of the matrix. The cured matrix at the higher temperature has the comparatively tight crosslinks in the network structure and the sorbed water molecule disturbed the polymer network resulting in the degradation of the matrix such as microcracks. 相似文献
906.
Yoon I Seo J Lee JE Song MR Lee SY Choi KS Jung OS Park KM Lee SS 《Dalton transactions (Cambridge, England : 2003)》2005,(14):2352-2354
By virtue of simple one donor variations of O(2)S(2)X-donor macrocycles (L(1): X=S, L(2): X=O and L(3): X=NH) towards silver(I) perchlorates, four supramolecular complexes (1-3) with different topologies have been isolated; L(1) afforded solvent- and anion-free sandwich complex (1), otherwise L(2) and L(3) gave the dimeric (2a), 1-D polymeric (2b), and tetrameric bowl-type (3) complexes with solvent or anion coordination. 相似文献
907.
Background
The conventional solution-phase Chemical Cleavage of Mismatch (CCM) method is time-consuming, as the protocol requires purification of DNA after each reaction step. This paper describes a new version of CCM to overcome this problem by immobilizing DNA on silica solid supports. 相似文献908.
Lee MK Hwang BY Lee SA Oh GJ Choi WH Hong SS Lee KS Ro JS 《Chemical & pharmaceutical bulletin》2003,51(4):409-411
The inhibitory compound of monoamine oxidase (MAO) activity was isolated from the CH(2)Cl(2) fraction of the fructus of Evodia rutaecarpa and identified as 1-methyl-2-undecyl-4(1H)-quinolone (1). Compound 1 showed a selective inhibition of type B MAO (MAO-B) activity with the IC(50) value of 15.3 microM using a substrate kynuramine, but did not inhibit type A MAO (MAO-A) activity. The kinetic analysis using Lineweaver-Burk plots indicated that compound 1 competitively inhibited MAO-B activity with the K(i) value of 9.91 microM. The inhibition of MAO-B by compound 1 was found to be irreversible by dialysis of the incubation mixture. These results suggest that compound 1 is a potent irreversible inhibitor of MAO-B, and may regulate catecholamine content in the neurons. 相似文献
909.
Young Bok Ryu Man Sig Lee Seong Soo Park Gun-Dae Lee Seong-Soo Hong 《Reaction Kinetics and Catalysis Letters》2005,84(1):101-108
Summary TiO2 nanoparticles were prepared by the hydrolysis of titanium tetraisopropoxide (TTIP) using TMA (tetramethylamine) as a peptizer in the hydrothermal method. The photocatalytic degradation of Orange II has been studied in a batch reactor under UV light. The particle size was similar to that from hydrothermal treatment at 120-170oC, but it increased to 23 nm at 200oC. The titania particles prepared at 170oC and calcined at 600oC showed the highest activity in the photocatalytic decomposition ofOrange II. 相似文献
910.
To generate an active site that consisted of one Cp2ZrCl2 molecule and 1-2 MAO molecules inside supercage of NaY zeolite, two preparation ways for supported catalyst were estimated. First, higher concentration of MAO and Cp2ZrCl2, and long reaction time were introduced during the preparation of supported catalyst. It showed activity in ethylene polymerization without any additional MAO. It indicates that Cp2ZrCl2 coordinated with only 1-2 MAO molecules could be an active site due to the fact that supercage has nano-scaled diameter of supercage, 1.2 nm, and it could contain only 1-2 MAO molecules inside it theoretically. In situ generation of active site between NaY/MAO and homogeneous Cp2ZrCl2 also showed experimental evidence that an active site was generated inside the supercage of NaY zeolite. It showed low activity with long activation time, suggesting the presence of a diffusion effect of Cp2ZrCl2 in the pore of NaY. However, NaY/Cp2ZrCl2 and homogeneous MAO system showed the characteristic PE polymerization with homogeneous catalyst, indicating that active site was not generated inside the supercage of NaY. 相似文献