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排序方式: 共有169条查询结果,搜索用时 31 毫秒
21.
Chaudhuri C Chang RY Chen WX Fang WC Cheng JP Whang TJ Tsai CC 《The journal of physical chemistry. A》2007,111(39):9764-9768
The 71Pig Rydberg state of Na2 correlating with the separated atom limit Na(3s) + Na(5p) has been observed using high-resolution cw optical-optical double resonance spectroscopy. A total of 104 identified rovibrational levels in the range v = 0-12 and 11 = J = 44 have been assigned to the 71Pig state. Dunham coefficients were determined, and the Rydberg-Klein-Rees potential curve in the range of R = 2.99-4.66 A was derived for the 71Pig state using the observed quantum levels. The important molecular properties are the potential minimum Te = 36 633.00(23) cm-1 at Re = 3.6313(29) A, omegae = 115.75(13) cm-1, and Be = 0.111 22(17) cm-1. A detailed discussion of this investigation of the 71Pig state is provided. 相似文献
22.
23.
Heo J Lim CK Whang DR Shin J Jeong SY Park SY Kwon IC Kim S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(28):8699-8704
Colorless 1,3-bis(dicyanomethylidene)indan is an organic acid (pK(a) ≈3.0) that turns blue in polar media owing to self-deprotonation. Moreover, its colored conjugate base shows potential as a minimal anionic polymethine dye for probing biomolecules in cells and in vivo through noncovalent complexation and near-infrared fluorescence signaling. 相似文献
24.
Jung-Kyu Park Ji-Wook Yoon Kyung-Hyun Whang Sung-Hak Cho 《Applied Physics A: Materials Science & Processing》2012,108(2):269-274
The effective removal of nanoparticles from a silicon wafer surface was demonstrated using the self-channeled plasma filament excited by a femtosecond (130?fs) Ti:sapphire laser (?? p=790?nm). The photoinduced self-channeled plasma filament in air reached a length of approximately 110?C130?mm from the first focal spot with diameters ranging from 40 to 50???m at input intensities of more than 1.0×1014?W/cm2. By the scan of wafer using the X?CY?CZ stage during self-channeled plasma filament, the removal variation of nanoparticles on surface was observed in situ before and after the plasma filament occurred. The cleaning efficiency was strongly dependent on the gap distance between the plasma filament and the surface. The removal efficiency of nanoparticles reached 96?% with no damage to the surface when the gap was 150???m. 相似文献
25.
Diabetes is a chronic metabolic disease that is a constant problem. Previous studies have reported that Benincasa cerifera Savi. extracts are effective in treating diabetes and its complications. Benincasae Exocarpium (BE) is a fruit peel of B. cerifera that has been reported to be used for the prevention and treatment of metabolic diseases such as hyperglycemia, obesity, and hyperlipidemia. However, there are not enough studies on the compounds and bioassays to support the efficacy of BE. The inhibitory activity of the BE extracts and fractions against advanced glycation end-products (AGE) formation and α-glucosidase activity was evaluated. These assays are relevant for the treatment of type 2 diabetes and its complications. Based on these results, compounds 1–11 were isolated through bioassay-guided isolation. In addition, we developed a high-performance liquid chromatography (HPLC) method that can simultaneously analyze these 11 compounds. Activity evaluation of the compounds was also conducted, and eight compounds exhibited significant activity. Among these, flavonoid compounds showed strong activity. A quantitative evaluation of eight bioactive compounds (2, 5–11) was conducted. In conclusion, this study demonstrated the potential of BE for prevention and treatment of type 2 diabetes and its complications. 相似文献
26.
T.G. Kim J.H. Lee J.H. Song K.H. Chae S.W. Shin H.M. Hwang J. Lee K. Jeong C.N. Whang J.-S. Lee K.-B. Lee 《Journal of magnetism and magnetic materials》2006
The irradiation effect of 1 MeV C+ on the interface and magnetic anisotropy of epitaxial Cu/Ni system with a perpendicular magnetic anisotropy was investigated by using magneto-optical Kerr effects, grazing incident diffraction and X-ray reflectivity. The magnetic easy-axis was altered from the direction along the surface normal to in-plane and the strain in the Ni layer was relaxed after ion irradiation. Though the interface between the top Cu layer and the Ni layer becomes rough, the contrast of electron densities of Cu and Ni layer increases and the grain-growth occurs during ion irradiation. These phenomena arise from thermo-chemical driving force, i.e. heat of formation, which may be a crucial factor in determining the interface shape in the case of indirect energy transfer mechanism. Therefore, the change of the magnetic anisotropy of the Ni/Cu system after ion irradiation is not due to the formation of the intermixed layer at the interface. The ion irradiation effects on the grain-growth and enhancement of the electronic contrast between Ni and Cu are explained by the interfacial atomic movement caused by thermo-chemical driving force. 相似文献
27.
High-performance liquid chromatography (HPLC) coupled with the reverse-pulse amperometric (RPA) detection method has been developed for the analysis of triorganotin compounds in aqueous solutions. The major advantage of RPA vs. conventional amperometric detection is its ‘in situ’ elimination of interference from dissolved oxygen in the chromatographic eluent; therefore, no extra chemicals or apparatus are required for oxygen removal. With a Partisil-10 SCX column and an eluent of methanol/0.01 M sodium acetate buffer (70:30, pH 5.5), the four triorganotins, viz., trimethyl-, triethyl-, tripropyl-, and tributyltin, can be totally separated. Detection by RPA was performed with a static dropping mercury electrode with an initial potential of ?1.15 V and a final potential of +0.15 V. The absolute detection limit (S/N = 3) ranged from 12 ng of tributyltin (as tin) to 0.3 μg of trimethyltin (as tin). Applications of the method to the analysis of trace tributyltin in marine antifoulant leachate and sea water are described. 相似文献
28.
Y. K. Kim E. Y. Kim C. M. Whang Y. H. Kim W. I. Lee 《Journal of Sol-Gel Science and Technology》2005,33(1):87-91
Nanophase silica-titania particles were prepared by two different synthetic routes, namely, sol–gel and hydrothermal processing. The crystallinity and crystallographic phases, particle size and surface area of the materials were controlled by varying the calcination temperature, and/or the ratio of Si to Ti. It was determined by XRD that the crystallite sizes of SiO2-TiO2 prepared by sol–gel and hydrothermal processing decreased from 11 to 6 nm and 12 to 9 nm, respectively, as the mole fraction of silica was increased from 0.1 to 0.4. It is proposed that the presence of the amorphous silica suppresses the growth of anatase TiO2 grains and their phase transformation to rutile. The photocatalytic decomposition rate of 1,4-dichlorobenzene (DCB) in aqueous solution with the sol–gel derived SiO2-TiO2 powder prepared at 750 °C was about 10 ± 5% higher than that observed with Degussa P25, whereas the SiO2-TiO2 samples prepared by hydrothermal processing at 250 °C showed a slightly lower decomposition rate than P25. 相似文献
29.
Park KM Whang D Lee E Heo J Kim K 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(2):498-508
This paper reports a synthetic strategy to construct one- and two-dimensional (1D and 2D) polyrotaxanes, in which a number of rings are threaded onto a coordination polymer, by the combination of self-assembly and coordination chemistry. Our approach to construct polyrotaxanes with high structural regularity involves threading a cucurbituril (CB) "bead" with a short "string" to form a stable pseudorotaxane, followed by linking the pseudorotaxanes with metal ions as "linkers" to organize into a 1D or 2D polyrotaxane. A 4- or 3-pyridylmethyl group is attached to each end of 1,4-diaminobutane or 1,5-diaminopentane to produce the short "strings", which then react with the cucurbituril "bead" to form stable pseudorotaxanes. The reaction of the pseudorotaxanes with various transition metal ions including CuII, CoII, NiII, AgI, and CdII produces 1D or 2D polyrotaxanes, in which many molecular "beads" are threaded onto 1D or 2D coordination polymers as confirmed by X-ray crystallography. The overall structure of a polyrotaxane is the result of interplay among various factors that include the coordination preferences of the metal ion, spatial disposition of the donor atoms with respect to the CB beads in the pseudorotaxane, and the size and coordination ability of the counteranion. 相似文献
30.
Kinetic studies on the pyridinolysis of aryl furan-2-carbodithioates 1 are carried out at 60.0 degrees C in acetonitrile. The biphasic rate dependence on the pyridine basicity with a breakpoint at pK(a) degrees = 5.2 is interpreted to indicate a change of the rate-limiting step from breakdown (beta(X) = 0.7-0.8) to formation (beta(X) = 0.2) of the tetrahedral intermediate, T(+/-), at the breakpoint as the basicity of the pyridine nucleophile is increased. Observation of the breakpoint is possible with pyridines since the expulsion rate of the pyridine (k(-)(a)) from T(+/-) is sufficiently low, with the low k(-)(a)/k(b) ratio leading to a low breakpoint, pK(a) degrees. The clear-cut change in the cross-interaction constants, rho(XZ), from a positive (rho(XZ) = +0.86) to a small negative (rho(XZ) = -0.11) value at the breakpoint supports the mechanistic change proposed. The magnitudes of rho(Z) and activation parameters are also consistent with the proposed mechanism. 相似文献