• 한국자원식물학회지
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• 제32권6호
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• pp.633-643
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• 2019

Long-term ultraviolet (UV) exposure accelerates the phenomenon of skin photo-aging by activating collagenase and elastase. In this study, we aimed to investigate the effects of a combination of grapefruit and rosemary extracts (cG&Re) on UVB-irradiated damage in HaCaT cells and dorsal mouse skin. In HaCaT cells, cG&Re recovered UVB-reduced cell viability and inhibited protein expression of mitogen-activated protein kinases (MAPKs), such as extracellular signal-regulated kinases (p-Erk), c-Jun N-terminal kinases (p-JNK), and a class of MAPKs (p-P38). Also, cG&Re suppressed UVB-induced collagen and elastin degradation by decreasing matrix metalloproteinases (MMPs) and nuclear factor kappa light chain enhancer of activated B cells (NF-κB) expression, which is a transcription factor. Similar results were observed in dorsal mouse skin. Taken together, our data indicate that cG&Re prevent UVB-induced skin photo-aging due to collagen/elastin degradation via activation of MAPKs, MMPs, and the NF-κB signaling pathway in vitro and in vivo.

• 동의생리병리학회지
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• 제31권2호
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• pp.105-110
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• 2017

Prolonged exposure to solar ultraviolet A (UVA) radiation has been known to cause premature skin aging (photo-aging). UVA radiation generates ROS thereby induce degenerative changes of skin such as degradation of dermal collagen, elastic fibers. Matrix metalloproteinases (MMPs), the proteolytic enzymes have been implicated as a major player in the development of UVA-induced photo-aging. Many studies have been conducted to block the harmful effects of UV radiation on the skin. Recently, we are interested in the availability of fermented red ginseng (FRG) as natural matrix metalloproteinases inhibitors (MMPIs). The efficacy difference between red ginseng and FRG has been compared. Both RG and FRG have no cytotoxic effects below the concentration of $300{\mu}g/ml$. Human dermal fibroblasts (HDFs) were pretreated with FRG or RG for 24h, followed by irradiation of UVA. Then, we measured the intracellular ROS production and the expression of MMP, $IL-1{\beta}$ at the mRNA level. We also examined the intracellular localization of $NF-{\kappa}B$ and MMP-9 on the FRG or RG treated and UVA-irradiated HDFs. FRG decreased the intracellular ROS production elicited by UVA. In addition, FRG decreased the mRNA expression of MMP-3, MMP-9, and $IL-1{\beta}$ more efficiently than RG. Furthermore, FRG suppressed the nuclear localization of $NF-{\kappa}B$, and the expression of MMP-9. Taken together, our results suggest that FRG is promising agents to prevent UVA-induced photo-aging by suppressing MMP expression and inflammation.

• 한국분말재료학회지
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• 제25권3호
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• pp.257-262
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• 2018

The coupling of two semiconducting materials is an efficient method to improve photocatalytic activity via the suppression of recombination of electron-hole pairs. In particular, the coupling between two different phases of $TiO_2$, i.e., anatase and rutile, is particularly attractive for photocatalytic activity improvement of rutile $TiO_2$ because these coupled $TiO_2$ powders can retain the benefits of $TiO_2$, one of the best photocatalysts. In this study, anatase $TiO_2$ nanoparticles are synthesized and coupled on the surface of rutile $TiO_2$ powders using a microemulsion method and heat treatment. Triton X-100, as a surfactant, is used to suppress the aggregation of anatase $TiO_2$ nanoparticles and disperse anatase $TiO_2$ nanoparticles uniformly on the surface of rutile $TiO_2$ powders. Rutile $TiO_2$ powders coupled with anatase $TiO_2$ nanoparticles are successfully prepared. Additionally, we compare the photocatalytic activity of these rutile-anatase coupled $TiO_2$ powders under ultraviolet (UV) light and demonstrate that the reason for the improvement of photocatalytic activity is microstructural.

• Composites Research
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• 제31권3호
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• pp.83-87
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• 2018

An object in the Low Earth Orbit (LEO) is affected by many environmental conditions unlike earth's surface such as, Atomic oxygen (AO), Ultraviolet Radiation (UV), thermal cycling, High Vacuum and Micrometeoroids and Orbital Debris (MMOD) impacts. The effect of all these parameters have to be carefully considered when designing a space structure, as it could be very critical for a space mission. Polybenzimidazole (PBI) is a high performance thermoplastic polymer that could be a suitable material for space missions because of its excellent resistance to these environmental factors. A thin coating of PBI polymer on the carbon epoxy composite laminate (referred as CFRP) was found to improve the energy absorption capability of the laminate in event of a hypervelocity impact. However, the overall efficiency of the shield also depends on other factors like placement and orientation of the laminates, standoff distances and the number of shielding layers. This paper studies the effectiveness of using a PBI coating on the front bumper in a multi-shock shield design for enhanced hypervelocity impact resistance. A thin PBI coating of 43 micron was observed to improve the shielding efficiency of the CFRP laminate by 22.06% when exposed to LEO environment conditions in a simulation chamber. To study the effectiveness of PBI coating in a hypervelocity impact situation, experiments were conducted on the CFRP and the PBI coated CFRP laminates with projectile velocities between 2.2 to 3.2 km/s. It was observed that the mass loss of the CFRP laminates decreased 7% when coated by a thin layer of PBI. However, the study of mass loss and damage area on a witness plate showed CFRP case to have better shielding efficiency than PBI coated CFRP laminate case. Therefore, it is recommended that PBI coating on the front bumper is not so effective in improving the overall hypervelocity impact resistance of the space structure.

• 한국지하수토양환경학회지:지하수토양환경
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• 제20권7호
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• pp.70-79
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• 2015

A sample of soil humic acid (HA) was divided by ultrafiltration (UF) into five fractions of different molecular size (UF₁: > 300, UF₂: 100~300, UF₃: 30~100, UF₄: 10~30, UF₅: 1~10 kilodaltons). Apparent average molecular weight (M_w) of the HA fractions were measured using high performance size exclusion chromatography (HPSEC), and the chemical and structural properties of the five HA fractions were characterized by elemental compositions (H/C, O/C and w ((2O + 3NH)/ C)) and ultraviolet-visible absorption ratios (SUVA, A_4/6). The organic carbon normalized-sorption coefficients (Koc) for the binding of phenanthrene to the HA fractions were determined by fluorescence quenching and relationship between the sorption coefficients and structural characteristics of the HA fractions were investigated. The elemental analysis and UV-vis spectral data indicated that the HA fractions with higher molecular weights have grater aliphatic character and lower contents of oxygen, while the HA fractions with lower molecular size have greater aromatic character and molecular polarity that correspond to greater SUVA and internal oxidation values (w). The log Koc values (L/kg C) were gradual increased from 4.45 for UF₅ to 4.87 for UF1. The correlation study between the structural descriptors of the HA fractions and log Koc values of phenanthrene show that the magnitude of Koc values positively correlated with $M_w$ and H/C, while negatively correlated with the independent descriptors of the O/C, w, SUVA and A_4/6.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.194.1-194.1
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• 2015

Transition metal dichalcogenide (TMD) with layered structure, has recently been considered as promising candidate for next-generation flexible electronic and optoelectronic devices because of its superior electrical, optical, and mechanical properties.[1] Scalability of thickness down to a monolayer and van der Waals expitaxial structure without surface dangling bonds (consequently, native oxides) make TMD-based thin film transistors (TFTs) that are immune to the short channel effect (SCE) and provide very high field effect mobility (${\sim}200cm^2/V-sec$ that is comparable to the universal mobility of Si), respectively.[2] In addition, an excellent photo-detector with a wide spectral range from ultraviolet (UV) to close infrared (IR) is achievable with using $WSe_2$, since its energy bandgap varies between 1.2 eV (bulk) and 1.8 eV (monolayer), depending on layer thickness.[3] However, one of the critical issues that hinders the successful integration of $WSe_2$ electronic and optoelectronic devices is the lack of a reliable and controllable doping method. Such a component is essential for inducing a shift in the Fermi level, which subsequently enables wide modulations of its electrical and optical properties. In this work, we demonstrate n-doping method for $WSe_2$ on poly-4-vinylphenol and poly (melamine-co-formaldehyde) (PVP/PMF) insulating layer and adjust the doping level of $WSe_2$ by controlling concentration of PMF in the PVP/PMF layer. We investigated the doping of $WSe_2$ by PVP/PMF layer in terms of electronic and optoelectronic devices using Raman spectroscopy, electrical measurements, and optical measurements.

• 대한본초학회지
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• 제20권4호
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• pp.1-10
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• 2005

Objectives : We investigated the anti-aging effect on skin with the extract of the needles of red pine, Pinus densiflora. Methods : We measured various effects related to skin such as the anti-oxidant effect, the protection against ultraviolet (UV) irradiation, the inhibition of reactive oxygen species (ROS) generation, the induction of heat shock protein 70 (HSP70), the reduction of matrix metalloproteinase-2 (MMP-2) synthesis and senescent cell. Results : The results were as follows : The extract of the needles of red pine (RP) had the potent anti-oxidant effect and the ROS scavenging effect. Also RP preserved the systemic anti-oxidant enzyme system (superoxide dismutase and catalase) from UVB irradiation. RP protected the cell membrane from the damages induced by UVB irradiation. RP induced HSP70, a mediator of resistance to UVB irradiation. RP reduced the synthesis of MMP-2 induced by UVB irradiation. And RP inhibited the amount of senescent-associated (SA) ${\beta}-galactosidase$ staining, as a marker of replicative senescence. Conclusions : The results of our study indicate that the extract of the needles of red pine, Pinus densiflora, has anti-aging effects on skin.

• 천문학논총
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• 제32권1호
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• pp.257-261
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• 2017

We built a $8{\mu}m$ selected sample of galaxies in the NEP-AKARI field by defining 4 redshift bins with the four AKARI bands at 11, 15, 18 and 24 microns (0.15 < z < 0.49, 0.75 < z < 1.34, 1.34 < z < 1.7 and 1.7 < z < 2.05). Our sample contains 4079 sources, 599 are securely detected with Herschel/PACS. Also adding ultraviolet (UV) data from GALEX, we fit the spectral energy distributions using the physically motivated code CIGALE to extract the star formation rate, stellar mass, dust attenuation and the AGN contribution to the total infrared luminosity ($L_{IR}$). We discuss the impact of the adopted attenuation curve and that of the wavelength coverage to estimate these physical parameters. We focus on galaxies with a luminosity close the characteristic $L^*_{IR}$ in the different redshift bins to study the evolution with redshift of the dust attenuation in these galaxies.

• 한국식품위생안전성학회지
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• 제35권3호
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• pp.205-212
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• 2020

본 논문은 수산물에 사용되는 식용 코팅의 다양한 천연성분에 대한 소재 및 특성에 대하여 조사하였으며, 화학적 항균 물질 및 항산화제와 물리적 살균 기술을 병합한 허들 기술(hurdle technology)에 대하여 서술하였다. 다양한 원인으로 인한 식중독 사고가 빈번히 발생하고 있으며 주된 원인은 오염된 식품의 섭취와 관련이 있다. 특히, 식품 중에서도 수산물은 수분함량이 많고 미생물에 오염되기 쉽기 때문에 저장 기한이 짧다. 이에 대한 해결방안으로 여러 가지 대안들이 적용되고 있는데, 가식성을 가지고 독성이 없는 장점을 가진 식용 코팅이 주목을 받고 있다. 식용 코팅은 미생물의 성장을 억제하고 수분 손실을 지연시킴으로써 수산물의 품질을 유지할 수가 있다. 또한 항균 물질 및 항산화제를 첨가하거나 물리적인 살균 기술과도 병합할 수 있다. 하지만 식용 코팅과의 병합 처리 기술이 소수 보고되고 있어 다양한 허들 기술에 대한 연구가 필요하다.

• 폴리머
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• 제30권4호
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• pp.357-361
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• 2006

생체 내에서 생성되는 알파 리포산은 산화방지, 혈당량 조절뿐만 아니라 식욕 억제, 비만 억제 효과 등을 가지고 있다. 약물로도 이용되고 있는 이 물질은 두 개의 황을 함유하고 있는 오각형 고리구조를 가지고 있어, 열과 자외선에 의해서 쉽게 개환되고 나아가 고분자로 중합될 수 있어서 약물로서 투여했을 경우 생체 이용률이 낮아지는 문제가 보고되어 있다. 본 연구는 개환에 따른 고분자화를 위한 다양한 조건을 조사하였다. 리포산은 녹는점이 지나야만 개환이 발생하였지만 그 이상의 온도에서는 온도의존성이 없었다. $70^{\circ}C$에서 개환율은 시간에 비례하였고 농도에 반비례하였다. 1시간 동안, $70^{\circ}C$ 아세트산에서 자외선과 함께 개환된 경우 개환율은 가장 높은 70% 였다. 이렇게 개환된 알파 리포산들은 대부분이 이황 고분자로 변했고, 개환율이 커질수록 고분자의 분자량 도 증가하였다.