• Korean Journal of Environmental Biology
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• v.18 no.1
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• pp.1-20
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• 2000

There are increasing evidences of climate change in the Antarctic and Arctic Oceans, especially elevated temperature due to the continuous burning of the fossil fuels and ultraviolet B(UV-B) flux within the ozone hole. Light-dependent, temperature-sensitive, and fast-growing organisms respond to these physical and biogeochemical changes. Polar marine phytoplankton, which are pioneer endemic species and important carbon contributors in the polar waters, are therefore highly suitable biological indicators of such changes. By virtue of light requirement, the primary producers are exposed to extreme seasonal fluctuations in temperature, photosynthetically active radiation, and UV radiation. Local environmental warming and increased UV-B radiation during ozone depletion may have profound effects on the primary producers that are primary carbon producers in the polar water. Small changes in climate temperature and solar radiation may have profound effects on the activity threshold of the polar phytoplanktion. To demonstrate biological response to the environmental changes, standardized representative natural and biological parameters are needed so that replicate samples (including controls) can be taken over extended periods of time. In this paper, we review general characteristics of polar phytoplankton, their environment, environmental changes in the polar waters, the effects on the environmental changes to the polar phytoplankton, and the importance of the polar phytoplankton to understand the global environmental changes. [Biological indicators, Global environmental change, Polar phytoplankton, UV].

• Applied Chemistry for Engineering
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• v.28 no.6
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• pp.705-713
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• 2017

A novel material, $Bi_2WO_6-GO-TiO_2$ composite, was successfully synthesized using a facile hydrothermal method. During the hydrothermal reaction, the loading of $Bi_2WO_6$ and $TiO_2$ nanoparticles onto graphene sheets was achieved. The obtained $Bi_2WO_{6-GO-TiO2}$ composite photo-catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM), Raman spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy (UV-vis-DRS), and X-ray photoelectron spectroscopy (XPS). The $Bi_2WO_6$ nanoparticle showed an irregular dark-square block nanoplate shape, while $TiO_2$ nanoparticles covered the surface of the graphene sheets with a quantum dot size. The degradation of rhodamine B (RhB), methylene blue trihydrate (MB), and reactive black B (RBB) dyes in an aqueous solution with different initial amount of catalysts was observed by UV spectrophotometry after measuring the decrease in the concentration. As a result, the $Bi_2WO_6-GO-TiO_2$ composite showed good decolorization activity with MB solution under visible light. The $Bi_2WO_6-GO-TiO_2$ composite is expected to become a new potential material for decolorization activity. Photocatalytic reactions with different photocatalysts were explained by the Langmuir-Hinshelwood model and a band theory.

• Horticultural Science & Technology
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• v.31 no.6
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• pp.813-820
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• 2013

Monoterpenoids were recently found as main biologically active compounds which is responsible for various physiological effect in goat's beard (Aruncus dioicus). Ethyl acetate extract of A. dioicus (ADE) was treated to B16F10 melanoma cells for the examination of whitening activity. MTT assay was performed to evaluate cell toxicity and the result showed that slight cell toxicity (> 10%) by over $500{\mu}g{\cdot}mL^{-1}$. Thus, 0, 5, 10, or $50{\mu}g{\cdot}mL^{-1}$ ADE was used for further experiments. We found that tyrosinase activity was decreased according to ADE concentration, and the total melanin content was also dramatically reduced. Especially with $50{\mu}g{\cdot}mL^{-1}$ ADE treatment tyrosinase activity was reduced to 35.6%, and 58.8% of melanin content was lowered. In addition, whitening related proteins including tyrosinase, tyrosinase related protein 1 (TRP1), TRP2, microphthalmia associated transcription factor (MITF) and cAMP and protein kinase A (PKA) were reduced by ADE treatment. It caused decreased phosphorylation of cAMP response binding protein (CREB) but increased phosphorylation of extracellular signal related kinase (ERK). Therefore, in this paper we would like to suggest the potent usage of A. dioicus natively grown in Ulleungdo, Korea as materials of functional cosmetics by confirming whitening activity related with melanin content.

• Korean Journal of Plant Resources
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• v.33 no.6
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• pp.604-614
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• 2020

Chronological aging and photoaging affect appearance, causing wrinkles, pigmentation, texture changes, and loss of elasticity in the skin. Phragmites communis is a tall perennial herb used for its high nutritional value and for medicinal purposes, such as relief from fever and vomiting and facilitation of diuresis. In this study, we investigated the effects of ethanol extract of P. communis rhizome (PCE) on skin aging. The total flavonoid and total phenolic content in PCE were 2.92 ± 0.007 ㎍ of quercetin equivalents (QE) and 231.8 ± 0.001 ㎍ of gallic acid equivalents (GAE) per 100 mg of dried extract (n = 3). The half-maximal inhibitory concentration (IC50) values of PCE for 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) and hydrogen peroxide scavenging activities were 0.96 and 0.97 mg/mL, respectively. PCE showed inhibitory effects on tyrosinase when L-tyrosine (IC50 = 1.25 mg/mL) and L-3,4-dihydroxyphenylalanine (IC50 = 0.92 mg/mL) were used as substrates. PCE treatment up to 200 ㎍/mL for 24 h did not cause any significant cytotoxicity in B16F10 melanocytes, human dermal fibroblasts (HDFs), and HaCaT keratinocytes. In B16F10 melanocytes, PCE (25 and 50 ㎍ /mL) inhibited melanin production and cellular tyrosinase activity after challenge with α-melanocyte-stimulating hormone (α-MSH; p < 0.05). In HDFs, PCE suppressed the mRNA expression of matrix metalloproteinase-1 (MMP-1) and reduced the activity of elastase (p < 0.05). In addition, ultraviolet B (UVB)-mediated downregulation of hyaluronic acid synthase-2 gene expression in HaCaT keratinocytes was also effectively suppressed by PCE treatment. Overall, our results showed that PCE has potential anti-skin aging activity associated with the suppression of hyperpigmentation, wrinkle formation, and reduction in dryness. PCE is a promising candidate for the development of an anti-skin aging cosmetic ingredient.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.05a
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• pp.142-145
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• 2005

AC-PDP에서 발광 휘도와 발광 효율의 개선은 매우 중요한 과제중의 하나이다. 높은 발광 휘도와 발광 효율을 위해선 VUV의 높은 발광 효율이 요구되어진다. 이 실험에서는 AC-PDP에서 Ne-Xe의 2원 혼합기체와 He-Ne-Xe의 3원 혼합기체의 VUV 발광 세기를 측정하였다. 기체 압력은 200 Torr, 300 Torr, 400 Torr, 500 Torr로 유지하였고, Xe 혼합비는 1%, 2%, 4%, 7%, 10%, 15%를 사용하였다. 진공자외선 발광 세기는 He-Ne-Xe의 3원 혼합기체가 Ne-Xe의 2원 혼합기체보다 발광 세기가 훨씬 높다는 것을 알 수 있었다. 그리고 Xe 함량이 증가함에 따라 공명선인 147 nm의 발광 세기는 Xe 혼합비가 약 10%까지는 증가하다가 10% 이후에는 포화되고, 반면 분자선인 173 nm은 Xe 함량과 가스 압력이 증가함에 따라 발광 세기가 증가하였다.

• Journal of the Korean Vacuum Society
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• v.15 no.6
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• pp.581-586
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• 2006

We have generated the argon plasma in the diode chamber based on the established coaxial electrode type and investigated the emitted visible light for emission spectroscopy. We applied various voltages $2\sim3.5kV$ to the device by 0.5kV, and obtained the emission spectrum data for the focused plasma in the diode chamber on the argon pressure of 330 mTorr. The Ar I and Ar II emission line are observed. The electron temperature and ion density have been measured by the Boltzmann plot and Saha equation from assumption of local thermodynamic equilibrium (LTE) The Ar I and Ar II ion densities have been calculated to be $\sim10^{15}/cc\;and\;~10^{13}/cc$, respectively, from Saha equation.

• Korean Journal of Heritage: History & Science
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• v.46 no.4
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• pp.78-89
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• 2013

For safe conservation treatment of damaged accessory relics that were unearthed, the quality of the material should be accurately identified through a nondestructive analysis and failure analysis. This study provides the basic conservational scientific data regarding material analyses and conservation treatment that were conducted for 11 relics, including amber and agate that were discovered during the repair of Geumsansa Temple's Hall of Maitreya Buddha and Left Attendant Buddhas in June 2008. An ultraviolet analysis, SEM-EDS analysis and FT-IR microscope analysis revealed that the physical and chemical characteristics of the 11 relics are the same as those of amber. It is inferred that the cracks and exfoliation of the surface of most amber relics is attributable to darkening of the color due to C=C bond oxidation. It is also assumed that cracks and exfoliation occurred from the weathered layer on the amber surface. As such, it is appropriate to engage in conservation treatment of the damaged amber relics by using $Paraloid^{(R)}$ B67 reinforcing agent that is diluted in nonpolar solvent. The greatest care is needed for future handling of organic artifacts.

• Advances in materials Research
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• v.3 no.4
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• pp.227-232
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• 2014

$Ce^{4+}$, $Eu^{3+}$, $Tb^{3+}$ co-doped $Ca_3Si_3O_8F_2$ phosphor was synthesized via solid state reaction method using $CaF_2$, $CaCO_3$ and $SiO_2$ as raw materials for the host and $Eu_2O_3$, $CeO_2$, and $Tb_4O_7$ as activators. The luminescent properties of the phosphor was analysed by spectrofluorophotometer at room temperature. The effect of excitation wavelengths on the luminescent properties of the phosphor i.e. under near-ultraviolet (nUV) and visible excitations was investigated. The emission peaks of $Ce^{4+}$, $Eu^{3+}$, $Tb^{3+}$ co-doped $Ca_3Si_3O_8F_2$ phosphor lays at 480(blue band), 550(green band) and 611nm (red band) under 380nm excitation wavelength, attributed to the $Ce^{4+}$ ion, $Tb^{3+}$ ion and $Eu^{3+}$ ions respectively. The results reveal that the phosphor emits white light upon nUV (380nm) / visible (465nm) illumination, and a red light upon 395nm / 535nm illumination. RE ions doped $Ca_3Si_3O_8F_2$ is a promising white light phosphor for LEDs. The emission colours can be seen using Commission international de l'eclairage (CIE) co-ordinates. A single host phosphor emitting different colours under different excitations indicates that it is a potential phosphor having applications in many fields.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.189-189
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• 2015

Plasmonics, sensor, field effect transistors, solar cells 등 다양한 적용분야를 가지는 실리콘 구조체는 제작공정에 의해 전기적 및 광학적 특성이 달라지기 때문에 적합한 나노구조 제작방법이 요구되고 있다. 나노구조체 제작방법으로는 Photo lithography, Extreme ultraviolet lithography (EUV), Nano imprinting lithography (NIL), Block copolymer (BCP) 방식의 방법들이 연구되고 있으며, 특히 BCP는 direct self-assembly 특성을 가지고 있으며 가격적인 면에서도 큰 장점을 가진다. 하지만 BCP를 mask로 사용하여 식각공정을 진행할 경우 BCP가 버티지 못하고 변형되어 mask로서의 역할을 하지 못한다. 이러한 문제를 해결하기 위하여 본 논문에서는 BCP와 질화막을 이용한 double mask 방법을 사용하였다. 기판 위에 BCP를 self-assembly 시키고 mask로 사용하여 hole 부분으로 노출된 기판을 Ion gun을 통해 질화 시킨 후에 BCP를 제거한다. 기판 위에 hole 모양의 질화막 표면은 BCP와 다르게 etching 공정 중 변형되지 않는다. 이러한 질화막 표면을 mask로 사용하여 pillar pattern의 실리콘 나노구조체를 제작하였다. 질화막 mask로 사용되는 template은 PS와 PMMA로 구성된 BCP를 사용하였다. 140kg/mol의 polystyrene과 65kg/mol의 PMMA를 톨루엔으로 용해시키고 실리콘 표면 위에 spin coating으로 도포하였다. Spin coat 후 230도에서 40시간 동안 열처리를 진행하여 40nm의 직경을 가진 PS-b-PMMA self-assembled hole morphology를 형성하였다. 질화막 형성 및 etching을 위한 장비로 low-energy Ion beam system을 사용하였다. Reactive Ion beam은 ICP와 3-grid system으로 구성된 Ion gun으로부터 형성된다. Ion gun에 13.56 MHz의 frequency를 갖는 200W 전력을 인가하였다. Plasma로부터 나오는 Ion은 $2{\Phi}$의 직경의 hole을 가지는 3-grid hole로 추출된다. 10~70 voltage 범위의 전위를 plasma source 바로 아래의 1st gird에 인가하고, 플럭스 조절을 위해 -150V의 전위를 2nd grid에 인가한다. 그리고 3rd grid는 접지를 시켰다. chamber내의 질화 및 식각가스 공급은 2mTorr로 유지시켰다. 그리고 기판의 온도는 냉각칠러를 이용하여 -20도로 냉각을 진행하였다. 이와 같은 공정 결과로 100 nm 이상의 높이를 갖는 40 nm직경의 균일한 Silicon pillar pattern을 형성 할 수 있었다.

• Journal of the Korean Home Economics Association
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• v.45 no.10
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• pp.73-81
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• 2007

The purpose of this study was to increase the ultraviolet-light (UV)-cut ability of cellulose fabrics (cotton, ramie, and rayon) dyed with safflower yellow colorants. For this purpose, samples treated with UV-cut agent and tannic-acid were compared with the untreated samples after UV exposure in terms of K/S value, color changes(${\Delta}E$), SEM, and strength retention. The K/S value rapidly decreased after 28 days exposure, whereas the K/S value of the samples treated with both UV-cut agent and tannic-acid decreased to less than that of the untreated samples. In color changes, $L^*$ increased while $a^*$ and $b^*$ decreased, indicating less red and yellow character in color. This induced a change in the hue, value and chroma values. However the color change(${\Delta}E$) of the samples treated with both UV-cut agent and tannic-acid was less than that of the untreated samples. Scanning electron microscopy (SEM) pictures showed a severe degradation by exposure in all samples. Tensile strength rapidly decreased after 28 days for cotton and rayon, and after 21 days for ramie. However, the strength retention of the samples treated with UV-cut agent and tannic-acid was higher than that of the untreated samples.