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991.
992.
The excited-state tautomerization dynamics of 7-hydroxyquinoline in the water pools of reverse micelles has been investigated by monitoring time-resolved fluorescence spectra and kinetics as well as static absorption and emission spectra with a variation of water content and isotopic fractionation. The normal and the tautomeric species are found to reside preferentially in the bound- and the free-water regions of the micelles, respectively. The excited-state tautomerization of the normal species in the bound-water layers is suggested to occur via two different channels, depending on rotamers at the moment of excitation. The cis tautomerizes via proton relay from the enol group to the imino group along a hydrogen-bonded water bridge, unusual in water but common in alcohols, whereas the trans tautomerizes via the stepwise individual acid-base reactions of two prototropic groups as found in bulk water. Proton relay can take place because water in the pools has substantially reduced polarity and disrupted hydrogen-bond networks compared with bulk water. 相似文献
993.
Azamerone, a terpenoid phthalazinone from a marine-derived bacterium related to the genus Streptomyces (Actinomycetales) 总被引:1,自引:0,他引:1
A novel meroterpenoid, azamerone, was isolated from the saline culture of a new marine-derived bacterium related to the genus Streptomyces. Azamerone is composed of an unprecedented chloropyranophthalazinone core with a 3-chloro-6-hydroxy-2,2,6-trimethylcyclohexylmethyl side chain. The structure was rigorously determined by NMR spectroscopy and X-ray crystallography. A possible biosynthetic origin of this unusual ring system is proposed. [structure: see text] 相似文献
994.
Jin-Bok Lee Sang-Yong Jeong Bong-Jun Park Chel-Jong Choi Kwon Hong Sung-Jin Whang Tae-Yeon Seong 《Superlattices and Microstructures》2010
We have investigated the effects of a NiCo interlayer on the electrical and thermal properties of nickel silicide as a function of the annealing temperature. For the interlayered samples, 3 nm-thick NiCo(10 at.% Co) films are electron-beam evaporated on Si substrates, on which 27 nm-thick Ni films are deposited without breaking the vacuum. It is shown that all the samples exhibit a distinctive increase in the sheet resistance at temperatures above 900 °C. However, the NiCo interlayer sample produces the lowest sheet resistance at 900 \circC. X-ray diffraction results show that the Ni only and NiCo interlayer samples produce NiSi and NiSi2 phases, while NiCo full samples give NiSi and Ni1−xCoxSi2 phases. Scanning electron microscopy results exhibit that for all the samples, the surfaces become degraded with numerous arbitrarily-shaped spots, corresponding to areas uncovered by the silicides. The areal fractions of the silicides for the Ni only, NiCo full, and NiCo interlayer samples are about 57%, 72%, and 81%, respectively. The temperature dependence of the electrical properties of the silicide samples is explained in terms of the formation of resistive phases and the agglomeration of the silicide. 相似文献
995.
Seung Kwon Hong Hye Young Koo You Na Ko Jung Hyun Kim Jang Heui Yi Yun Chan Kang 《Applied Physics A: Materials Science & Processing》2010,98(3):671-677
Eu-doped B2O3–ZnO–PbO glass phosphor powders with spherical shape and fine size were directly prepared by spray pyrolysis. The glass phosphor
powders prepared at a temperature of 1100°C had broad XRD peak at around 28°. One glass phosphor powder was formed from one
droplet at the preparation temperature range from 900 to 1100°C. The mean size of the glass phosphor powders was 0.75 μm.
The glass transition temperature (T
g
) of the glass phosphor powders prepared by spray pyrolysis was 378.5°C. The excitation spectrum of the glass phosphor powders
prepared at the optimum preparation temperature of 1100°C had bands at 362, 381, 392, 463, 525, and 532 nm. The glass phosphor
powders had emission spectra with bands at 579, 614, and 653 nm. The glass phosphor powders with doping concentration of Eu
of 7 wt% had the maximum photoluminescence intensity. The glass phosphor layer formed from the glass phosphor powders had
high transparencies above 90%. 相似文献
996.
Doyle TE Goodrich JB Ambrose BJ Patel H Kwon S Pearson LH 《The Journal of the Acoustical Society of America》2010,128(5):EL229-EL235
Normal and malignant mammary epithelial cells were studied using laboratory measurements, wavelet analysis, and numerical simulations of monolayer cell cultures to determine whether microscopic breast cancer can be detected in vitro with high-frequency ultrasound. Pulse-echo waveforms were acquired by immersing a broadband, unfocused 50-MHz transducer in the growth media of cell culture well plates and collecting the first reflection from the well bottoms. The simulations included a multilayer pulse-reflection model and a model of two-dimensional arrays of spherical cells and nuclei. The results show that normal and malignant cells produce time-domain signals and spectral features that are significantly different. 相似文献
997.
Supercritical carbon dioxide (scCO2) processing was performed with mixtures of CO2-soluble peracetylated-β-cyclodextrin (PAc-β-CD) heptakis(2,3,6-tri-O-acetyl)-β-cyclodextrin, and highly water-soluble drug molsidomine (MOL) to prepare inclusion complexes of MOL and PAc-β-CD. The MOL/PAc-β-CD inclusion complex was confirmed by differential scanning calorimetry, X-ray diffractometry, and 1H NMR analyses. The complexes were further investigated for their potential use in controlled drug delivery applications. The in-vitro release of MOL from the peanut oil suspensions into aqueous phase was found to be significantly retarded by the complexation with PAc-β-CD, mainly due to the hydrophobic properties associated with the PAc-β-CD. 相似文献
998.
Kwon MS 《Optics letters》2010,35(22):3835-3837
This Letter theoretically proposes and investigates an integrated plasmonic sensor that is based on a grating-assisted coupling between a surface plasmon polariton (SPP) and a dielectric waveguide (DW) mode. It consists of a glass slide with a gold film for the propagation of an SPP and a separate DW with a long-period grating. For sensing, the two parts are temporarily combined. After sensing, the former is replaceable, and so the sensor has disposability. The design procedure and analysis method for the sensor are explained. The designed sensor is shown to be very compact. Its characteristics of sensing a change of the refractive index of liquid are analyzed and discussed. 相似文献
999.
Jun‐Gill Kang Jung‐Pyo Hong Sung Kwon Kang 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(10):e432-e433
In the title compound, Na+·C6H8NO6?·2H2O, the sodium ion is coordinated in a distorted octahedral manner by two carboxylate O atoms and two water O atoms. Each of these water molecules bridges two adjacent Na ions, resulting in two four‐membered rings of the type Na–O–Na–O. 相似文献
1000.
Yunghee Oh Byoung‐Chul Shin Dale Swenson Harold M. Goff Sung Kwon Kang 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(2):m57-m59
The title compound, [Fe(C44H8F20N4)]·2C6H6, contains a four‐coordinated FeII atom, which lies on a center of symmetry. The porphyrin macrocycle is planar, and the Fe—N bond distances are in the range 1.9891 (13)–1.9982 (13) Å. The spin state of the FeII atom is intermediate (S = 1), as confirmed by NMR spectroscopy. The asymmetric unit contains two half benzene molecules, each lying about an independent inversion centre; one of the benzene rings is located just below (and by inversion symmetry, another is just above) the Fe atom, where it interacts weakly with the porphyrin ring. 相似文献