• Title/Summary/Keyword: Kyung Keun

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Regioselective synthesis of .alpha.-L-fucosyl-containing benzyl disaccharides by use of .alpha.-L-fucosidases of aspergillus niger

  • Chung, Yong-Za;Kwak, Hong-Keun;Sung, Yung-Ki
    • Archives of Pharmacal Research
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    • v.19 no.4
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    • pp.307-311
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    • 1996
  • The activity of fucosidase shows different value depending on disease, eg) fucosidosis and I cell disease are characterized by the absence or deficiences of .alpha.-fucosidase, and sera of ovarian cancer patients exhibited a statistically significant deficiency of .alpha.-L-fucosidase activity (Zielke et al., 1972; Kress et al., 1980; Barlow et al., 1981). For the purpose of diagnosis of these disease easily, the manual of test can be developed by preparing kits of hydrophobic-binding substrate of fucosidase that bind C18-column.

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Hemifacial Spasm Caused by Epidermoid Tumor at Cerebello Pontine Angle

  • Choi, Seok-Keun;Rhee, Bong-Arm;Lim, Young-Jin
    • Journal of Korean Neurosurgical Society
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    • v.45 no.3
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    • pp.196-198
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    • 2009
  • Hemifacial spasm (HFS) is almost always induced by vascular compression but in some cases the cause of HFS are tumors at cerebellopontine angle (CPA) or vascular malformations. We present a rare case of hemifacial spasm caused by epidermoid tumors and the possible pathogenesis of HFS is discussed. A 36-year-old female patient presented with a 27-month history of progressive involuntary facial twitching and had been treated with acupuncture and herb medication. On imaging study, a mass lesion was seen at right CPA. Microvascular decompression combined with mass removal was undertaken through retrosigmoid approach. The lesion was avascular mass and diagnosed with an epidermoid tumor pathologically. Eventually, we found a offending vessel (AICA : anterior inferior cerebellar artery) compressing facial nerve root exit zone (REZ). In case of HFS caused by tumor compression on the facial nerve REZ, surgeons should try to find an offending vessel under the mass. This case supports the vascular compression theory as a pathogenesis of HFS.

Stability of Amorphous Silicon Thin-Film Transistor using Planarized Gate

  • Choi, Young-Jin;Woo, In-Keun;Lim, Byung-Cheon;Jang, Jin
    • 한국정보디스플레이학회:학술대회논문집
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    • 2000.01a
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    • pp.15-16
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    • 2000
  • The gate bias stress effect of the hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFTs) with a $SiN_x/BCB$ gate insulator have been studied. The gate planarization was carried out by spin-coating of BCB (benzocyclobutene) on Cr gates. The BCB exhibits charge trappings during a high gate bias, but the stability of the TFT is the same as conventional one when it is between -25 V and +25 V. The charge trap density in the BCB increases with its thickness.

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The Analysis of Discharge Characteristics for Discharge Excited KrF Laser System (방전여기 KrF 레이저 장치의 방전특성 해석)

  • Jeong, Jae-Keun;Choi, Boo-Yeon;Lee, Choo-Hie
    • Proceedings of the KIEE Conference
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    • 1988.07a
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    • pp.393-396
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    • 1988
  • In discharge excited excimer laser, it is hard to say that the analysis of laser operation was well explained until now. But this can be improved by analysis the nonlinear discharge characteristics in the cavity. The nonlinear characteristics can be analysed by solving the nonlinear resistance which depends on electron mobility and number density. We can calculate the electron mobility and number density each other using Boltzmann equation and Kinetics equation. So we calculated the nonlinear resistance and analysed nonlinear discharge characteristics.

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Power Dependence on Formation of Polyynes by Laser Ablation in Water

  • Park, Young Eun;Shin, Seung Keun;Park, Seung Min
    • Bulletin of the Korean Chemical Society
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    • v.34 no.4
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    • pp.1039-1042
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    • 2013
  • Polyynes were prepared by liquid laser ablation of a graphite target in deionized water at various physical conditions such as laser power (20 and 40 mJ/pulse) and ablation wavelengths (355, 532, and 1064 nm). The effects of physical parameters on the linear carbon chain length were examined by analyzing the densities of polyynes with different carbon numbers ($C_6H_2$, $C_8H_2$, and $C_{10}H_2$) as well as their branching ratios. We concluded the photophysical processes turned out to play a more significant role than thermal ones in the formation of polyynes.

Inhibitory Activity of Isorhamnetin from Persicaria thunbergii on Farnesyl Protein Transferase

  • Oh Hyun Mi;Kwon Byoung-Mog;Baek Nam-In;Kim Sung-Hoon;Chung In-Sik;Park Mi-Hyun;Park Hee Wook;Lee Jae Hyeok;Park Hye Won;Kim Eun Jeong;Kim Dae Keun
    • Archives of Pharmacal Research
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    • v.28 no.2
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    • pp.169-171
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    • 2005
  • The methanolic extract of the aerial parts of Persicaria thunbergii was found to show inhibitory activity on Farnesyl Protein Transferase (FPTase). Bioassay-guided fractionation of the methanolic extract resulted in the isolation of isorhamnetin, as an inhibitor on FPTase. This compound inhibited FPTase activity in a dose-dependent manner, and the $IC_{50}$ value of isorhamnetin was $37.5\;{\mu}M$.

The Solvent Effects on the Formation of Polyynes by Laser Ablation

  • Park, Young-Eun;Shin, Seung-Keun;Park, Seung-Min
    • Bulletin of the Korean Chemical Society
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    • v.33 no.7
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    • pp.2439-2442
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    • 2012
  • In order to explore the effects of the solvent on the formation rate of polyynes, we investigated the absorption spectra of polyynes obtained by laser ablation of a graphite target in different solvents at 1064 nm. Polyynes so produced were confirmed by the Raman band around $2200cm^{-1}$ which corresponds to the carbon triple bonds. The production of polyynes by laser ablation turned out to be significantly affected by the ratio of the hydrogen and carbon atoms in the solvent molecule. No clear correlations were observed in the formation of polyynes for other properties of the solvent such bond dissociation energy, thermal conductivity, and total mass of hydrogen atoms per volume of solvent.