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단섬유로 강화된 Nylon 6.6/Ionomer 복합재료의 물리적 특성
서광석,박광석,이철호 고려대학교 공학기술연구소 1999 공학논문집 Vol.37 No.1
Physical properties of short glass fiber-reinforced nylon 6,6 and ionomer (Surlyn 9020) composites were studied. While ionomer content was increased from 0 to 30phr, tensile strength and flexural strength were decreased, whereas impact strength had maximum value at 20phr. Permittivity, tans, and volume resistivity had no remarkable difference with the variation of ionomer content, In PEA (Pulsed electroacoustic) experiments, for moisture-free specimens, homocharges were accumulated near electrodes and increased with the increase of ionomer content up to 20phr. It was found that moisture uptake rate of nylon 6,6 was declined due to hydrophobicity of ionomer. For moisture-contained specimens, homocharges were increased with moisture content at first, and then decreased while moisture content saturated. Moisture-ionomer interaction was a major mechanism of homocharge formation.
서광석,이창용,강창균 고려대학교 공학기술연구소 1991 고려대학교 생산기술연구소 생기연논문집 Vol.27 No.1
Electrical conduction characteristics of low density polyethylene with a silicon-oil layer at the surface have been investigated at medium fields ranging from about 75 to 650 ㎸/㎝ over the temperature range of 20 to 100℃. The conduction current of polyethylene increases exponentially with the electric field and gets higher as the temperature increases. The observed conduction behavior was explained in term of the SCLC and tunneling effect. Activation energy ranges from 0.54 to 0.44 eV over the field range of 90∼450 ㎸/㎝ and the charge mobility was estimated from a Child law to be in the order of 10^(-16)∼10^(-14)㎡/V·s. Silicone oil layer modifies the conduction behaviors in polyethylene. Major changes are (1) an increase in conduction currents, (2) a suppression in a rate of change of conduction currents, and (3) a decrease in activation energy.
광섬유 센서를 이용한 절연유의 방전신호 및 감쇄특성 측정
김태영,김상준,남진호,서광석,이수묵 고려대학교 공학기술연구소 1999 공학논문집 Vol.37 No.1
This paper presents the preliminary results on the application of optical fiber sensor(OFS) for the measurements of discharging signal and degradation in insulation oil such as transformer and silicone oil. An OFS system using a Mach-Zehnder interferometry technique was built to detect attenuation of acoustic signal produced by discharging. Simultaneous measurements were made of electrical signal and OFS signal from discharge. It was found that the arcing signal produced by needle-sphere electrode system could be detected by OFS installed in an oil bath. With increasing OFS distance from an arcing spot, the attenuation of acoustic signal became greater. From the results of sound attenuation for various insulation oils, the linear relationship was observed between the attenuation signal and viscosity in log scale. Details of these results are discussed.
( Ju Yeun Lee ),( Yul Hee Kim ),( Nam Joon Yi ),( Hyang Sook Kim ),( Hye Suk Lee ),( Byung Koo Lee ),( Hye Young Kim ),( Young Rok Choi ),( Geun Hong ),( Kwang Woong Lee ),( Yung Suk Suh4 ) 대한간학회 2014 Clinical and Molecular Hepatology(대한간학회지) Vol.20 No.2
Background/Aims: The most commonly used immunosuppressant therapy after liver transplantation (LT) is a combination of tacrolimus and steroid. Basiliximab induction has recently been introduced; however, the most appropriate immunosuppression for hepatocellular carcinoma (HCC) patients after LT is still debated. Methods: Ninety-three LT recipients with HCC who took tacrolimus and steroids as major immunosuppressants were included. Induction with basiliximab was implemented in 43 patients (46.2%). Mycophenolate mofetil (MMF) was added to reduce the tacrolimus dosage (n=28, 30.1%). The 1-year tacrolimus exposure level was 7.2 ± 1.3 ng/mL (mean ± SD). Results: The 1- and 3-year recurrence rates of HCC were 12.9% and 19.4%, respectively. Tacrolimus exposure, cumulative steroid dosages, and MMF dosages had no impact on HCC recurrence. Induction therapy with basiliximab, high alpha fetoprotein (AFP; >400 ng/mL) and protein induced by vitamin K absence/antagonist-II (PIVKA-II; >100 mAU/mL) levels, and microvascular invasion were significant risk factors for 1-year recurrence (P<0.05). High AFP and PIVKA-II levels, and positive 18fluoro-2-deoxy-d-glucose positron-emission tomography findings were significantly associated with 3-year recurrence (P<0.05). Conclusions: Induction therapy with basiliximab, a strong immunosuppressant, may have a negative impact with respect to early HCC recurrence (i.e., within 1 year) in high-risk patients. (Clin Mol Hepatol 2014;20:192-203)
Suh, Kwang Sik,Choi, Eun-Mi,Kwon, Mikwang,Chon, Suk,Oh, Seungjoon,Woo, Jeong-Taek,Kim, Sung Woon,Kim, Jin-Woo,Kim, Young Seol Pharmaceutical Society of Japan 2009 Biological & pharmaceutical bulletin Vol.32 No.4
<P>Reducing sugar, 2-deoxy-<SMALL>D</SMALL>-ribose (dRib), produces reactive oxygen species through autoxidation and protein glycosylation and causes osteoblast dysfunction. Kaempferol, a natural flavonoid, was investigated to determine whether it could influence dRib-induced cellular dysfunction and oxidative cell damage in the MC3T3-E1 mouse osteoblastic cell line. Osteoblastic cells were treated with 30 m<SMALL>M</SMALL> dRib in the presence or absence of kaempferol (10<SUP>−9</SUP>—10<SUP>−5</SUP> <SMALL>M</SMALL>) and markers of osteoblast function and lipid peroxidation were subsequently examined. Kaempferol (10<SUP>−9</SUP>—10<SUP>−5</SUP> <SMALL>M</SMALL>) significantly inhibited the dRib-induced decrease in growth of MC3T3-E1 osteoblastic cells. In addition, treatment with kaempferol resulted in a significant elevation of alkaline phosphatase (ALP) activity, collagen content, and mineralization in the cells. Treatment with kaempferol increased osteoprotegerin (OPG) secretion and decreased malondialdehyde (MDA) contents of MC3T3-E1 osteoblastic cells in the presence of 30 m<SMALL>M</SMALL> dRib. Taken together, these results suggest that kaempferol inhibits dRib-induced osteoblastic cell damage and may be useful for the treatment of diabetes-related bone disease.</P>
Actein protects against methylglyoxal‐induced oxidative damage in osteoblastic MC3T3‐E1 cells
Suh, Kwang Sik,Chon, Suk,Choi, Eun Mi John Wiley Sons, Ltd 2017 Journal of the Science of Food and Agriculture Vol.97 No.1
<P>CONCLUSIONThis study demonstrates that actein reduces MG-induced damage in osteoblastic MC3T3-E1 cells by enhancing antioxidant defenses, the glyoxalase system and mitochondrial biogenesis. (c) 2016 Society of Chemical Industry</P>
Suh, Kwang Sik,Chon, Suk,Choi, Eun Mi Elsevier Pub. Co 2017 Chemico-biological interactions Vol.278 No.-
<P><B>Abstract</B></P> <P>Methylglyoxal (MG) is a potent protein glycating agent and an important precursor of advanced glycation end products, which are involved in the pathogenesis of diabetic osteopathy. In this study, we investigated the effects of limonene on MG-induced damage in osteoblastic MC3T3-E1 cells. Pretreating cells with limonene prevented MG-induced protein adduct formation, tumor necrosis factor alpha and interleukin-6 release, mitochondrial superoxide production, and cardiolipin peroxidation. In addition, limonene increased glyoxalase I activity, and glutathione and heme oxygenase-1 levels in the presence of MG. Pretreatment with limonene prior to MG exposure reduced MG-induced mitochondrial dysfunction by preventing mitochondrial membrane potential dissipation and adenosine triphosphate loss, and reduced the levels of adenosine monophosphate-activated protein kinase, peroxisome proliferator activated receptor γ coactivator 1α, and nitric oxide. These results demonstrate that limonene may prevent the development of diabetic osteopathy.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Limonene prevented MG-induced protein adduct formation. </LI> <LI> Limonene increased glyoxalase I activity and glutathione levels. </LI> <LI> Limonene reduced MG-induced ROS, inflammatory cytokines, and mitochondrial dysfunction. </LI> <LI> Limonene increased the levels of AMPK, PGC1α, and NO. </LI> </UL> </P>