• Journal of the Korean Applied Science and Technology
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• v.31 no.2
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• pp.231-237
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• 2014

The supercritical fluids (SCFs) have been widely used for material synthesis and processing due to their remarkable properties including low viscosity, high diffusivity and low surface tension. Carbon dioxide is one of the suitable solvents in SCFs processes in terms of its advantages such as easy processibility (with low critical temperature and pressure), inexpensive, nonflammable, nontoxic, and readily available. However, it has generally low solubility for high molecular weight polymers with the exception of fluoropolymers and siloxane polymers. Therefore, hydrocarbon solvents and hydrochlorofluorocarbons have been used for various SCFs process by its high solubility for high molecular weight polymers. In this report, a PMMA/clay nanocomposites were fabricated by using supercritical fluid process. The $Na^+$-MMT(montmorillonites)was modified by a fluorinated surfactant which is able to enhance compatibility with the chlorodifluoromethane(HCFC-22) and thus, improve dispersability of the clay in the polymer matrix. The PMMA/fluorinated surfactant modified clay nanocomposite shows enhanced mechanical and thermal properties which characterized by X-raydiffraction(XRD), Thermo gravimetric analysis(TGA), Dynamic mechanical analysis (DMA) and Transmission electron microscopy (TEM).

• Journal of the Korean Society of Food Science and Nutrition
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• v.44 no.12
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• pp.1905-1911
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• 2015

Melanin is one of the most important factors affecting skin color. Melanogenesis is the bioprocess of melanin production by melanocytes in the skin and hair follicles and is mediated by several enzymes, such as tyrosinase, tyrosinase related protein (TRP)-1, and TRP-2. Convenient enzymatic transformation of the simple phenol pyrogallol with polyphenol oxidase originating from pear to an oxidative product, purpurogallin, was efficient. The structure of the pyrogallol oxidation product was identified on the basis of spectroscopic methods. The biotransformation product purpurogallin showed significant inhibitory effects against both melanin synthesis and tyrosinase activity in a dose-dependent manner in B16 melanoma cells. In addition, purpurogallin significantly attenuated melanin production by inhibiting TRP-1, and TRP-2 expression through modulation of their corresponding transcription factors, and microphthalamia- associated transcription factor in B16 cells. Consequently, purpurogallin derived from convenient enzymatic transformation of pyrogallol might be a beneficial material for reducing skin hyperpigmentation.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.363-363
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• 2014

Ruthenium (Ru) has attractive material properties due to its promising characteristics such as a low resistivity ($7.1{\mu}{\Omega}{\cdot}cm$ in the bulk), a high work function of 4.7 eV, and feasibility for the dry etch process. These properties make Ru films appropriate for various applications in the state-of-art semiconductor device technologies. Thus, it has been widely investigated as an electrode for capacitor in the dynamic random access memory (DRAM), a metal gate for metal-oxide semiconductor field effect transistor (MOSFET), and a seed layer for Cu metallization. Due to the continuous shrinkage of microelectronic devices, better deposition processes for Ru thin films are critically required with excellent step coverages in high aspect ratio (AR) structures. In these respects, atomic layer deposition (ALD) is a viable solution for preparing Ru thin films because it enables atomic-scale control of the film thickness with excellent conformality. A recent investigation reported that the nucleation of ALD-Ru film was enhanced considerably by using a zero-valent metallorganic precursor, compared to the utilization of precursors with higher metal valences. In this study, we will present our research results on the synthesis and characterization of novel ruthenium complexes. The ruthenium compounds were easy synthesized by the reaction of ruthenium halide with appropriate organic ligands in protic solvent, and characterized by NMR, elemental analysis and thermogravimetric analysis. The molecular structures of the complexes were studied by single crystal diffraction. ALD of Ru film was demonstrated using the new Ru metallorganic precursor and O2 as the Ru source and reactant, respectively, at the deposition temperatures of $300-350^{\circ}C$. Self-limited reaction behavior was observed as increasing Ru precursor and O2 pulse time, suggesting that newly developed Ru precursor is applicable for ALD process. Detailed discussions on the chemical and structural properties of Ru thin films as well as its growth behavior using new Ru precursor will be also presented.

• Journal of the Korean association of regional geographers
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• v.5 no.1
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• pp.163-185
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• 1999

The purpose of this study is to develop the model of constructivist multimedia-assisted instruction(CMAI) and to analyze the effect of it in the secondary school geography. The main results are as follows : (1) The conceptual model of CMAI can be defined as an instruction aiming at making a person who has self-directed learning ability through constructivism and multimedia. The procedural model of CMAI based on PIDA instructional strategy is divided into four stages : prediction & explanation, inquiry activity, discussion & fixation, application & synthesis stage. (2) CMAI is typed by offline CMAI and online CMAI. that is, O/WCMAI(online CMAI by web-based courseware). Offline CMAI is subdivided into P/TCMAI(offline CMAI by presentation-based courseware) and C/RCMAI(offline CMAI by cd-rom based courseware) according to authoring tool and function. (3) Offline constructivist multimedia course-ware(offline courseware) was developed for 2 periods as the material to analyze the effect of CMAI. Offline courseware is received development level of it. (4) After offline courseware being applied to the class, the effect of it according the types of the CMAI instruction(lecture instruction, whole teaching, individualized learning, cooperative learning) was analyzed. As the result of analyzing the descriptive statistics of the level of learning achievement and instruction response, there isn't big relationship between them. As the result of analyzing the inferential statistics of the level of learning achievement, there wasn't significant difference between the types of CMAI instruction in whole student of the classes and certain students who improved their grades. But as the result of analyzing of the level of instruction response, there was significant difference between lecture instruction and other types of the CMAI instruction(whole teaching, individualized learning, cooperative learning).

• Journal of Life Science
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• v.26 no.12
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• pp.1477-1486
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• 2016

Lactulose (4-O-${\beta}$-D-galactopyranosyl-D-fructose) is a non-digestible synthetic ketose disaccharide which can used in food and pharmaceutical fields due to its useful functions for encephalopathy, chronic constipation, hyperammonemia, etc. Therefore, the lactulose is regarded as one of the most important disaccharides and have been concentrated much interesting as an attractive functional material in the current industry. From this reason, the research related on the production of lactulose has been carried out various academic and industrial research groups. To produce lactulose, two main methods, chemical production and enzymatic production have been used. Commercially lactulose produced by alkaline isomerization of lactose as chemical production method but it has many disadvantages such as rapid lactulose degradation, purification, and waste management. From these reasons, lactulose produced by enzymatic method which solves these problems has been suggested as a proper method for lactulose production. Two different enzymatic methods have been reported as methods for lactulose production. Lactulose can be obtained through hydrolysis and transfer reaction catalyzed by a ${\beta}$-galactosidase which requires fructose as co-substrate and exhibits a low conversion. Alternatively, lactulose can be produced by direct isomerization of lactose to lactulose catalyzed by cellobiose 2-epimerase which requires lactose as a single substrate and achieves a high lactulose yield. This review summarizes the current state of lactulose production by chemical and biological methods.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.120-120
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• 2011

Graphene is a carbon based material and it has great potential of being utilized in various fields such as electronics, optics, and mechanics. In order to develop graphene-based logic systems, graphene field-effect transistor (GFET) has been extensively explored. GFET requires supporting devices, such as volatile memory, to function in an embedded logic system. As far as we understand, graphene has not been studied for volatile memory application, although several graphene non-volatile memories (GNVMs) have been reported. However, we think that these GNVM are unable to serve the logic system properly due to the very slow program/read speed. In this study, a GVM based on the GFET structure and using an engineered graphene channel is proposed. By manipulating the deposition condition, charge traps are introduced to graphene channel, which store charges temporarily, so as to enable volatile data storage for GFET. The proposed GVM shows satisfying performance in fast program/erase (P/E) and read speed. Moreover, this GVM has good compatibility with GFET in device fabrication process. This GVM can be designed to be dynamic random access memory (DRAM) in serving the logic systems application. We demonstrated GVM with the structure of FET. By manipulating the graphene synthesis process, we could engineer the charge trap density of graphene layer. In the range that our measurement system can support, we achieved a high performance of GVM in refresh (>10 ${\mu}s$) and retention time (~100 s). Because of high speed, when compared with other graphene based memory devices, GVM proposed in this study can be a strong contender for future electrical system applications.

• Journal of Applied Biological Chemistry
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• v.60 no.4
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• pp.327-332
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• 2017

In this study, the whitening activity of Nymphoides indica extract in B16F10 cells were measured. Inhibition rate of tyrosinase from mushroom was 42% at $1,000{\mu}g/mL$. And inhibition of tyrosinase and melanin biosynthesis in B16F10 cells were 26 and 25% at $5{\mu}g/mL$, respectively. The expression levels of cAMP and protein kinase A (PKA), which are higher levels of melanin-related factors, were found to be decreased in a dose-dependent manner. In addition, the expression rate of protein and mRNA of tyrosinase, tyrosinase related protein 1 (TRP1), tyrosinase related protein 2 (TRP2) and microphthalmia associated transcription factor (MITF). In this study, it was confirmed that the N. indica extract effectively inhibited the activity of tyrosinase, TRP1, TRP2 and MITF as well as the activity of PKA by effectively inhibiting cAMP. Therefore, it was confirmed that the N. indica extract has high value as a functional material.

• Journal of Applied Biological Chemistry
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• v.62 no.4
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• pp.391-398
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• 2019

The antioxidant, whitening, and anti-wrinkle activity of Spirodela polyrhiza extracts and fractions were evaluated to determine its efficacy as a functional cosmetic material. 1,1-diphenyl-2-picrylhydrazyl and 2,2'-azinobis-3-ethylbenzothiazoline-6-sulfonic acid radical scavenging activities were 44.2 and 74.3%, respectively, at 100 ㎍/mL of SE-E (the ethyl acetate fraction of 70% ethanol extract). To measure anti-wrinkle effects, procollagen biosynthesis and matrix metalloproteinase-1 (MMP-1) inhibition activity were determined. At 25 ㎍/mL of SE (70% ethanol extract), the biosynthesis activity was 48.5%, and SE-E showed the best activity (57.8%) at the same concentration. MMP-1 inhibition activity of SE and SE-E was 13.4 and 28.5%, respectively, at 25 ig/mL. Finally, the inhibition of cellular melanin synthesis and cellular tyrosinase were measured to determine the whitening effect; at 25 ㎍/mL, the inhibition activities of SE were 9.6 and 13.8%, respectively, and those for SE-E were 15.4 and 22.0%, respectively. Our results confirmed the possibility of SE and SE-E as effective functional materials. Further research investigating the antimicrobial, anti-inflammatory, and anticancer activities of S. polyrhiza is necessary to confirm its potential use in the food, cosmetics, and drug industries.

• Journal of Applied Biological Chemistry
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• v.63 no.1
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• pp.75-82
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• 2020

In this study, extracts from the Green ball apple peel (GBE) and the newly bred green ball apple from Korea showed inhibition effects on photo-aging factor regulation associated with skin aging. To investigate the inhibition effect on photo-aging factor regulation in skin, GBE was treated with UVB to induce photo-aging related factors in CCD986sk fibroblast cells. Photo-aging factor regulation effects showed that GBE inhibited UVB-stimulated matrix metalloproteinase (MMP)-1 and MMP-9 protein synthesis in collagen type I alpha 2 chain (COL1A2), MMP-1, MMP-9, and tissue inhibitors of metalloproteinase (TIMP)-1 protein expression. The expression of COL1A2 and TIMP-1 protein was significantly increased. The mRNA expression levels of COL1A2, MMP-1, MMP-9, hyaluronan synthase (HAS)2, transforming growth factor (TGF)-β, and TIMP-1 were decreased by GBE. The expression of TIMP-1 and TGF-β, which are regulators involved in matrix metalloproteinase and type I procollagen expression, was found to increase with increasing expression of COL1A2. The expression of HAS2, which is involved in the production of hyaluronic acid, one of the structural proteins constituting the skin, was also confirmed. Therefore, GBE showed excellent efficacy against photo-aging factor regulation and could be used as functional material to prevent and treat skin aging.

• Applied Chemistry for Engineering
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• v.23 no.1
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• pp.105-111
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• 2012

Manganese (Mn) catalysts were generated using $CeO_2$ and $ZrO_2$supports synthesized by the supercritical hydrothermal method and two different Mn precursors, aimed at an application for a low-temperature selective catalytic reduction process. Manganese acetate (MA) and manganese nitrate (MA) were used as Mn precursors. Effects of the kind and the concentration of the Mn precursor used for catalyst generation on the NOx removal efficiency were investigated. The characteristics of the generated catalysts were analyzed using $N_2$ adsorption-desorption, thermo-gravimetric analysis, X-ray diffraction, and X-ray photoelectron spectroscopy. De-NOx experiments were carried out to measure NOx removal efficiencies of the catalysts. NOx removal efficiencies of the catalysts generated using MA were superior to those of the catalysts generated using MN at every temperature tested. Analyses of the catalyst characteristics indicated that the higher NOx removal efficiencies of the MA-derived catalysts stemmed from the higher oxygen mobility and the stronger interaction with support material of $Mn_2O_3$ produced from MA than those of $MnO_2$ produced from MN.