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11.
p palan BS 《Physical review letters》1987,58(16):1597-1599
12.
Young-ah WooChang-hee Cho Hyo-jin Kim Jong-soo YangKi-yong Seong 《Microchemical Journal》2002,73(3):299-306
A rapid and nondestructive near infrared (NIR) method using soft independent modeling of class analogy (SIMCA) for the classification of cultivation area (Korea and China) was evaluated and confirmed. Raw, first, and second derivative NIR spectra were compared to develop a robust classification rule. The chemical properties of ginseng samples were also investigated to find out the differences between Korean samples and Chinese samples. These differences make NIR spectroscopic method viable. The average value of each Korean and Chinese ginseng sample for crude fiber, crude protein, starch, and 10 inorganic constituents were measured and compared with F-test and t-test. The inorganic constituents were also measured by induced coupled plasma-atomic emission spectroscopy (ICP-AES). It could be found that the amount of starch and ten inorganic elements for example Na, Mg, P, K, Ca, Mn, Fe, Ni, Cu and Zn in ginseng samples are considerably different based on cultivation area. SIMCA has been applied to the inorganic data to investigate the possibility of ICP-AES as classification tool. However, it was observed that the result was not equal to than NIR spectra data. The overall results showed the availability of NIR method using SIMCA would be adequate for classification of cultivation of ginseng, since NIR spectra includes useful and various information on chemical properties in spite of broad and overlapped bands. 相似文献
13.
Cheng-Zhu Wu Xing Fu Cai Seong Su Hong Eun-Kyoung Seo Ji-Xing Nan Jung Joon Lee 《Tetrahedron letters》2007,48(50):8861-8864
Two novel dimeric meroterpenoids, bisbakuchiols A and B, along with (S)-bakuchiol were isolated from the seeds of Psoralea corylifolia L. (Fabaceae). Bisbakuchiols A and B contain an unprecedented dimeric meroterpenoid skeleton in which two meroterpenes are linked through a dioxane bridge. All compounds were evaluated for their potential to inhibit hypoxia-inducible factor-1 (HIF-1) activation induced by hypoxia in a HIF-1-mediated reporter gene assay in AGS human gastric cancer cells. (S)-Bakuchiol inhibited hypoxic activation of HIF-1 with an IC50 value of 6.1 μM. 相似文献
14.
Seong J Rohrbacher A Li ZR Janda KC Tao FM Spiegelman F Halberstadt N 《The Journal of chemical physics》2004,120(16):7456-7463
The potential energy surface of He2Ne+ has been reinvestigated using a combination of ab initio and diatomics-in-molecule (DIM) calculations. In contrast to the reports of two recent studies the ion is found to have an asymmetric linear He-Ne-He structure, with no barrier to formation from the separated atoms on the ground-state surface. The He-Ne+ bond lengths at the potential minimum are 1.51 and 1.81 A, and the total bonding energy is 0.717 eV. Comparing the He2Ne+ energy to that of HeNe+, the bonding energy for the second helium atom is 0.06 eV, about 10% of that of the first He atom. The saddle point between the two equivalent minima is a symmetric structure, 0.0074 eV above the potential minimum. A symmetric geometry becomes the overall potential minimum if the 2s hole on the Ne is excluded from the reference states of a multireference configuration interaction calculation. A DIM potential was created for the HenNe+ family of ions. The DIM potential is consistent with the asymmetric He2Ne+ ion serving as a core; it predicts a slightly more asymmetric geometry than the ab initio results. Additional helium atoms form five-membered rings around the bonds of the core ion to fill the first shell and then add to the ends of the cluster. The asymmetric core ion and the highly compact structure help to account for the lack of apparent shell structure in the mass spectrometry of HenNe+ clusters. Finally, we recommend that the value De=0.63+/-0.04 eV be adopted for the ground state of HeNe+. 相似文献
15.
Sung Woo Moon Gun-Dae Lee Seong Soo Park Seong-Soo Hong 《Reaction Kinetics and Catalysis Letters》2004,82(2):303-310
Catalytic combustion of chlorobenzene over supported vanadium oxides has been investigated. TiO2 was prepared by the sol-gel method from titanium isopropoxide. The supported vanadium oxide catalysts have been prepared
by precipitation-deposition and impregnation method and characterized by XRD, FT-Raman and TPR. In the VOx/TiO2catalysts prepared using the impregnation method, when vanadium loading reaches 3 wt.%, the activity shows a maximum. However,
in the VOx/TiO2catalysts prepared by precipitation-deposition, when vanadium loading reaches 7 wt.%, the activity shows a maximum. This result
suggests that the precipitation-deposition can yield a higher metal loading on the support and a high dispersion compared
to the impregnation method.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
16.
The photoinduced charge transfer that had been suggested to result in the dissociation of phenol on Ag(111) was investigated by two-photon photoemission spectroscopy. An unoccupied intermediate state was positively identified, which was found to be located 3.22 eV above the Fermi level. From the photoelectron energy dispersion, the effective mass of the intermediate state was determined to be (15 +/- 10)m(e) for a 1 ML coverage of phenol. This implies that the excited electron is localized mainly on the adsorbed phenol, forming a molecular resonance state. Polarization dependence of the photoelectron intensity suggested that the initial photoexcitation of the substrate produces hot electrons that scatter into the molecular resonance state, leading ultimately to the dissociation of the adsorbate. These results are the first two-photon photoemission study to characterize the transient anionic state involved in photodissociation of a molecule adsorbed on a metal surface. 相似文献
17.
Jae Ha Kim Young Tae Jeong Seong Ihl Woo 《Journal of polymer science. Part A, Polymer chemistry》1994,32(15):2979-2987
Highly active catalysts for copolymerization have been prepared by the precipitation of MgCl2/ToCl4 complex with or without high surface area silica. Copolymerization of ethylene and 1-butene has been tested by using the prepared catalysts at various concentrations of 1-butene. The catalytic activities are 20–80 kg/g Ti h. The rate of copolymerization is strongly affected by the addition of 1-butene. The decay rate of copolymerization is first order with respect to time. Analyses of copolymers with solvent extraction, DSC, IR, XRD, and NMR were performed. Ethylene reactivity ratio (k11) for TiCl4/MgCl2/THF catalyst is calculated to be about 26 by NMR spectrum. © 1994 John Wiley & Sons, Inc. 相似文献
18.
Peng CY Nam WJ Fonash SJ Gu B Sen A Strawhecker K Natarajan S Foley HC Kim SH 《Journal of the American Chemical Society》2003,125(31):9298-9299
We describe the use of hard etching methods to create nanodimensional channels and their use as templates for the formation of polymer filament arrays with precise dimensional and orientational control in a single integrated step. The procedure is general as illustrated by the radical, coordination, and photochemical polymerizations that were performed in these nanochannels. The nanochannel templates (20 nm high, 20-200 nm wide, and 100 mum long) were fabricated by the combined use of electron-beam lithography and a sacrificial metal line etching technique. Radical polymerization of acrylates, metal-catalyzed polymerization of norbornene, and photochemical polymerization of 1,4-diiodothiophene were carried out in these nanochannels. The polymers grown follow the dimensions and orientation of the channels, and the polymer filaments can be released without breaking. The approach opens up the possibility of just-in-place manufacturing and processing of patterns and devices from nanostructured polymers using well-established polymer chemistry. 相似文献
19.
Lee KB Kim DJ Lee ZW Woo SI Choi IS 《Langmuir : the ACS journal of surfaces and colloids》2004,20(7):2531-2535
The micropatterns of biological ligands (biotin and RGD peptides) were generated on a flat surface of biodegradable polymer, poly(glycolic acid) (PGA). The immobilization of biological ligands onto the surface of biodegradable polymers (especially aliphatic polyesters) is usually hampered by the absence of functionalizable groups on the polymer backbone. We demonstrate herein that PGA polymer films were modified by surface hydrolysis to introduce carboxylic acid groups on the film surfaces, which were subsequently used for patterning amine-terminated ligands by microcontact printing. Fluorescence microscopy was used to verify the pattern of biotin on the surface of the PGA films after complexation with fluorescein-conjugated streptavidin. In addition, the cellular micropatterns were obtained from micropatterns of RGD peptides on the surface-hydrolyzed PGA films. 相似文献
20.
Thiam Seong Chong 《Journal of organometallic chemistry》2006,691(4):687-692
The rate constant for the methyl abstraction reaction of CpFe(CO)2Me has been measured with the benzyl radical clock as (1.1 ± 0.2) × 105 M−1 s−1 at room temperature. Time-resolved Fourier-transform Infrared (FTIR) absorption spectroscopy pointed towards the formation of the CpFe(CO)2 radical upon benzyl abstraction. The main stable product has been established by a linear scan of the reaction mixture as Cp2Fe2(CO)4 produced by the dimerization of the CpFe(CO)2 radicals. The transition state structure for the abstraction process was also found at UB3LYP/6-311+G* level of theory to contain a planar CH3 group. 相似文献