• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.10
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• pp.21-26
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• 2003

In this research, the change of coefficient of thermal expansion (CTE) of graphite/epoxy composite laminate under space environment was measured using fiber optic sensors. Two fiber Bragg grating (FBG) sensors have been adopted for the simultaneous measurement of thermal strain and temperature. Low Earth Orbit (LEO) conditions with high vacuum, ultraviolet and thermal cycling environments were simulated in a thermal vacuum chamber. As a pre-test, a FBG temperature sensor was calibrated and a FBG strain sensor was verified through the comparison with the electric strain gauge (ESG) attached on an aluminun specimen at high and low temperature respectively. The change of the CTE in a composite laminate exposed to space environment was measured for intervals of aging cycles in real time. As a whole, there was no abrupt change of the CTE after 1000 aging cycles. After aging, however, the CTE decreased a Little all over the test temperature range. These changes are caused by outgassing, moisture desorption, matrix cracking etc.

• Analytical Science and Technology
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• v.25 no.3
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• pp.197-206
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• 2012

Ambers are composed of polymer molecules which contain aromatic moieties such as benzene, naphthalene, phenanthrene and anthracene. They emit fluorescence when irradiated with ultraviolet light, which was used for confirming an amber. The fluorescence of amber, however, tends to decrease as the surface of amber is weathered with light, heat, oxygen for a long time. In this study, the reliability of confirming amber with its fluorescence by measuring the changes of fluorescence after artificial aging. Aging factors were UV light (${\lambda}$=340 nm), oxygen with heat (100%, $90^{\circ}C$) and heat ($90^{\circ}C$) and aging time was for 5, 15, 30 and 60 days, respectively. In the excitation and emission spectra of amber, the intensity decreased and the maximal wavelength was shifted to longer wavelength with artificial aging time. Especially, there was a drastic decrease in the intensity of spectra to 1.7% of initial value after 60 days aging under oxygen with heat. Only in Colombian amber there showed an increase of fluorescence intensity for a certain aging time, which could be explained by the production of aromatic ring in the presence of light and heat. Conclusively, the fluorescence can be lessened by the natural weathering with light, heat and oxygen and it is not accurate to recognize amber just with UV irradiation method.

• Journal of Nutrition and Health
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• v.49 no.6
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• pp.429-436
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• 2016

Purpose: Solar ultraviolet (UV) radiation causes inflammation and matrix metalloproteinase (MMP) overexpression and extracellular matrix depletion, leading to skin photoaging such as wrinkle formation, dryness, and sagging. Activation of MMP is influenced by various molecules such as reactive oxygen species (ROS), proinflammatory cytokines, and transient receptor potential vanilloid type (TRPV)-1, which are increased in UV-irradiated skin cells. Aralia elata (AE) ethanolic extract was reported to inhibit ROS generation caused by UVB-irradiation in keratinocytes. In this study, we investigated the photoprotective effect of AE ethanolic extract on UVB-irradiated human keratinocytes (HaCaT) and human dermal fibroblasts (HDF). Methods: AE was freeze-dried, extracted in 70% ethanol, and concentrated. Skin cells were treated with AE extract for 24 h and then exposed to UVB ($55mJ/cm^2$). After 48 h of incubation, proinflammatory cytokines, MMP-1, type-1 procollagen, and TRPV-1 levels were measured by ELISA or Western blotting. Results: Treatment with AE extract ($100{\mu}g/mL$) significantly inhibited UVB-induced IL-6, IL-8, and $PGE_2$ production in HaCaT by 25.6%, 5.3%, and 70.2%, respectively, and also inhibited elevation of MMP-1 and TRPV-1 caused by UVB irradiation by 20.0% and 41.9%, respectively (p < 0.05). In HDF, AE extract treatment significantly inhibited both elevation of MMP-1 and reduction of type-1 procollagen caused by UVB irradiation (p < 0.05). In addition, type-1 procollagen was elevated by AE extract treatment in normal HDFs (p < 0.05). Conclusion: AE 70% ethanol extract has photoprotective ability via reduction of proinflammatory mediators, TRPV-1 and MMP-1 production, and elevation of collagen synthesis. Our findings suggest that AE extract might be a good natural material to protect against UVB-induced premature skin aging.

• Journal of the Korean Society of Food Science and Nutrition
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• v.33 no.5
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• pp.785-790
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• 2004

Kimchi is well known as a traditional Korean food containing various antioxidative compounds and it has been demonstrated that dietary kimchi inhibit the tissue oxidation and aging in many related studies. Ultraviolet B (UVB) radiation is the most potent among the many related factor to skin photo-aging. This experiment is designed to elucidate the inhibitory effect of solvent fractionation of various kimchi on UVB induced oxidation and erythema formation. Among solvent fractions, phenol content mostly existed in dichloromethane / ethylacetate fraction of buchu kimchi, dichloromethane fraction of Korean cabbage kimchi and ethylacetate / dichloromethane fraction of mustard leaf kimchi. Free radical scavenging activities were higher in dichloromethane and ethylacetate fraction from buchu kimchi, dichloromethane fraction from Korean cabbage kimchi, and ethylacetate fraction from mustard leaf kimchi. When the damage of photo-oxidation by UVB irradiation was tested in the presence of solvent fractions of kimchi, dichloromethane / ethylacetate fraction of buchu kimchi, ethylacetate fraction from Korean cabbage and from mustard leaf kimchi showed the higher protective activities than others. The erythema formations which were induced by UVB irradiation were decreased in solvent fractions of kimchi that hate higher antioxidant activities. In conclusion, kimchi solvent fractions having antioxidant compounds mostly inhibited photo-oxidation and erythema formation by UV-irradiation, therefore kimchi consumption can retard skin aging due to the presence of antioxidative compounds.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.31 no.4 s.54
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• pp.323-327
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• 2005

Although many studies have been performed to elucidate the molecular consequence of ultraviolet irradiation on an aging, little is known about the effect of natural products. Matrix metalloproteinases (MMPs) we known to play an important role in (a) photoaging. Hete we investigated the effect of $1,2,4,6-tetra-O-galloyl-{\beta}-{_D}-gluco- pyranose (1)$ and 3,4,5-trihydroxybenzoic acid (2) on the expression of MMP-1 in UVA-irradiated human skin fibroblasts (products), (on the) activity of MMP-1, and (on the) scavenging activities of free radicals. Compounds 1 and 2 were isolated from Melothria heterophylla (Cucurbitaceae). These compounds were found to scavenge free radicals and reactive oxygen species (ROS) and were measured to have the $SC_{50}$ values of $3.9{\mu}M\;and\;13.3{\mu}M$ against the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals and $4.3{\mu}M\;and\; 4.0{\mu}M$ against superoxide radicals in the xanthine/xanthine oxidase system, respectively. Compounds 1 and 2 showed a dose-dependent inhibitory effect on the e):pression and activity of MMP-1 in the UVA-irradiated human skin fibroblasts. Therefore, we concluded that compounds 1 and 2 significantly inhibited MMP-1 expression at the protein level. Also, these compounds were determined to have a potent antioxidant activity. From these results, we suggest that these compounds nay be used as (a) new anti-aging agents for the photo-damaged skin.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.41 no.4
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• pp.351-359
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• 2015

Acute and chronic ultraviolet (UV) irradiation triggers severe skin photoaging processes, which directly disrupt the normal three-dimensional integrity of skin. UV light stimulates the expression of matrix metalloproteinases (MMPs) which degrade constituents of extracellular matrix (ECM) proteins. These MMPs reduce collagen synthesis and decrease skin elasticity and integrity, resulting in wrinkle formation. In this study, we identified Rosa multiflora hip extract (RME) as an effective anti-photoaging ingredient. First, cell proliferation activity of RME was verified using Hs68 human dermal fibroblast cell line. RME downregulated MMPs expression through the inhibition of activator protein (AP)-1. In addition, type I and IV collagen expressions were increased with RME treatment and UVB-induced inflammatory responses were also reduced after RME treatment. In conclusion, R. multiflora hip extract may effectively improve UVB-induced skin aging and wrinkle formation which may provide as an anti-aging, anti-wrinkle, and anti-inflammation ingredient in cosmetic industry.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.50 no.1
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• pp.85-93
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• 2024

In this study, we prepared fractions from Cynanchum paniculatum (C. paniculatum) with ethyl acetate and identified the structure and content of paeonol, an indicator substance. Fractions were obtained by sequential solvent fractions using n-hexane, methylene chloride, ethyl acetate, n-butanol, and distilled water, and showed the highest paeonol content in ethyl acetate (EtOAc). The structure of the ethyl acetate fraction (EA) was confirmed by nuclear magnetic resonance (NMR) and the content was determined by high performance liquid chromatography (HPLC) analysis. The antioxidant activity of EA was tested through its ability to scavenge 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), and its ability to inhibit nitric oxide (NO) production in RAW 264.7 cells induced by lipopolysaccharide (LPS) was tested for its ability to inhibit NO production in a concentration-dependent manner. Furthermore, MMP-1 production induced by ultraviolet B (UVB) was decreased in a concentration-dependent manner by the EA, and the ability to produce procollagen type-I was increased in a concentration-dependent manner. In addition, as a result of conducting clinical trials using cosmetic formulations containing EA, the effect of improving wrinkles around the eyes was confirmed. Thus, it is expected that Cynanchum paniculatum can be used as a natural functional cosmetic material with antioxidant and anti-aging effects.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.443-446
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• 2009

In this study, a series of degradation test for structural adhesives was performed to investigate the possibility of replacement of the alternative adhesives to the conventional adhesives. Four types of the adhesives were exposed to combined environmental conditions over 1000 hours at an accelerated aging tester, which can simulate natural weather conditions such temperature, moisture and ultraviolet. Mechanical and chemical properties of the adhesives were evaluated through material testing system and FT/IR spectrometer. According to the results, the conventional adhesives can be replaced by the alternative adhesives because the alternative adhesives were more stable to environmental conditions rather than the conventional adhesives.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 1999.04b
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• pp.296-301
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• 1999

Different papers such as toilet and towel tissue, newsprint and copy paper made from reclaimed fibres were characterized using UV-VIS reflectance and fluorescence spectroscopy. The emission properties of the extracts of the papers were also evaluated. Photochemical irradiation at ambient temperatures, and thermal aging of the copy papers at 105$^{\circ}C$ and 150$^{\circ}C$ were performed. Post-colour numbers (PC) were calculated from the reflectance values measured from the corresponding UV-VIS reflectance spectra. Light absorption coefficient spectra were calculated before and after irradiation, and the changes in absorption coefficient were related to the content of chromophores in the papers. Photochemical and thermal discolouration of the copy papers, similar to that of virgin fibres, was readily observed. The influence of changes in the concentrations of fluorescent brightening agents and dyes on the spectral properties was also assessed. Photostabilization studies of the copy papers were performed with the use of polymer additives polyethylene glycol (PEG) and polytetrahydrofuran (PTHF).

• Journal of Surface Science and Engineering
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• v.47 no.2
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• pp.57-62
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• 2014

The biogas holder is composed of an outer membrane and an inner membrane which are subject to outdoor exposure and gas exposure respectively. The influence of weathering conditions on the photo-degradation of a biogas holder was investigated. Tests were performed under three different methods - outdoor exposure tests (Seosan, Arizona), accelerated tests (Xenon-are lamp) with the outer-membrane of biogas. Moreover, the changes in the aging process were monitored using color difference, gloss, the contact angle and an optical microscope. Changes in physical properties, such as decrease reduction in gloss, decrease in the contact angle, increase in color difference were observed in the aging process. The comparison between membrane 3B, 4B and membrane 5B under xenon-arc were discussed. Membrane 5B was very sensitive to ultraviolet (UV) ray. There were many difficulties in the outdoor exposure test due to acid rain, dust, and stain resistance.