• Journal of Korea Foundry Society
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• v.27 no.1
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• pp.24-30
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• 2007

The effects of C, Si and RE additions on the tendency of chill formation of ductile cast iron obtained from metal mold casting were investigated. In case of metal mold cast, the ductile cast iron with 2.5%Si had pearlitic matrix, and specimens with 2.9%Si had bull's eye type regardless of C contents. As-cast specimen with a large amount of fine graphites could be obtained by adding 0.2% RE. Normalizing process was necessary to remove carbide and form a large amount of spheroidal graphites for the as-cast specimens. Good mechanical properties could be obtained by heat-treatment of as-cast specimens with pearlitic matrix. Normalizing the specimens with RE caused the reduction in mechanical properties.

• Bulletin of the Korean Chemical Society
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• v.19 no.3
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• pp.354-358
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• 1998

The effect of thermal conditions on the clustering of sulfonated polystyrene ionomers was investigated. It was found that when the zinc-sulfonated ionomer was dried above a matrix glass transition temperature (Tg), the cluster Tg was observed at ca. 310 ℃, which is ca. 45 ℃ higher than that for the ionomer dried below the matrix Tg. This difference is believed to be the result of the increase in chain mobility at higher temperatures, which improves the multiplet formation and clustering; thus the cluster Tg increases. In the lithium ionomer case, however, the increase in the cluster Tg was ca. 6 ℃ upon annealing. From the results, it was suggested that in the zinc ionomer, the zinc ion is soft and divalent, which results in weaker interactions in multiplets, and thus decreases the stability of the multiplets. Therefore, the thermal effect is more significant for the zinc ionomers than for the lithium ionomers.

• Korean Journal of Pharmacognosy
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• v.37 no.4 s.147
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• pp.253-257
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• 2006

We examined anti-angiogenic effects of water extracts from 32 plant materials (20 Korean medicinal plants and 12 western herbs) using cell-based anti-angiogenic assay, HUVEC tube formation assay, and then we found that 7 plant extracts inhibited HUVEC tube formation strongly. The plant materials which showed anti-angiogenic effects are Cinnamomi Ramulus, Atractylodis Rhizoma alba, Polygalae Radix, Myristicae Semen, Artemisiae Iwayomogii Herba, leaves of Rosmarinus officinalis, and leaves of Melissa officinalis. We also investigated inhibitory effects of these anti-angiogenic herbal extracts on MMP (matrix metalloproteinase) activity which has important roles in angiogenesis. Among extracts tested in this study, water extract of Melissa officinalis showed the most potent anti-angiogenic and MMP inhibitory activity.

• Journal of Pharmaceutical Investigation
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• v.41 no.2
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• pp.91-94
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• 2011

The purpose of this study was to investigate the effect of peptide charge on the interaction between peptide and poly(D,L-lactide-co-glycolide) (PLGA) for evaluating mechanism of acylated peptide formation in PLGA matrix. As a model peptide, octreotide, a synthetic somatostatin analogue and active ingredient of commercial PLGA product, was used. The disulfide group of octreotide was reduced with dithiothreitol and the sulfhydryl groups were modified with N-${\beta}$-maleimidopropionic acid (BMPA) to neutralize octreotide with positive charge in physiological conditions. The BMPA-conjugated octreotide was identified by measuring the molecular mass with liquid chromatography-mass spectrometry. In the interaction study with PLGA, native octreotide showed initial adsorption to PLGA and substantial production of acylated peptides (56% of overall peptide), whereas BMPA-conjugated octreotide showed minimal adsorption to PLGA and no acylation products for 42 days. Consequently, the neutralization of octreotide completely inhibited the peptide acylation by preventing interaction of peptide with PLGA. In conclusion, this study demonstrates that the initial polymer interaction of peptide is important step for peptide acylation in PLGA matrix and suggests the modulation of peptide charge as strategy for inhibiting the formation of acylated peptide impurities.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.28 no.1
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• pp.71-79
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• 2002

In the aged skin especially in the face and eyelid, deep and slight wrinkles are one of the remarkable phenomena of aging and the cause of wrinkle is various. Among the cause of wrinkles an oxidative stress plays an important roles in wrinkle formation process. It caused the lipid peroxidation of cell membrane, the increase of the MMPs(MatrixMetalloProteinase) gene expression and cellular DNA damage. These ROS induced materials may cause the degradation of collagen matrix system in the dermis and cause the formation of skin wrinkle. So, it is very important for protecting skin wrinkle formation to regulate ROS activity. In this study, we developed one active ingredient having multi functional activities such as activation of collagen synthesis, inhibition of MMPs activity, lipid peroxidation and free radical scavenging activity and inhibition of free radical induced DNA damage in vitro. Pericarpium castaneae extracts showed collagen synthesis increase in Normal Human Fibroblast and the inhibition of elastase activity (IC$\_$50/ of Elastase: 43.9$\mu\textrm{g}$/㎖). It showed also anti-oxidative activity (IC$\_$50/ : 48$\mu\textrm{g}$/㎖) and free radical scavenging activity(IC$\_$50/: 7.6$\mu\textrm{g}$/㎖). Conclusively, Pericarpium castaneae extracts may be used as an ingredient for new anti-wrinkle cosmetics.

• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1165-1167
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• 1995

The Cu-Si alloy has been proposed as a new matrix materal for filamentary Nb-Ti wires in AC use. The Cu-Si alloy shows approprite mechanical and electrical properties, and is economically more favourable than the Cu-Ni alloy matrix used currently. Moreover, the addition of Si to Cu prevents the formation of intermetallic compounds around the filaments. After we investigated resistivity and hardness of Cu-Si alloy as matrix materal, investigated CuSi/NbTi interface reactions and superconductivities of superconducting wires that were made by various heat treatment.

• Journal of the Korean Ceramic Society
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• v.30 no.6
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• pp.457-468
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• 1993

In oxide matrix-SiC(W) composites, instability and glassy phase formation due to oxidation at the high temperature and the diffusion of Si, respectively, cause brittle fracture and low reliability for ceramic materials. The mode of contribution in each mechanisms induced by matrix-whisker debonding, varies with the morphology of matrix-whisker interfaces. This work has described the dispersion behaviours and stabilization mechanisms in slip systems, and multiple toughening mechanisms by dint of two second phase different from each other when spherical ZrO2 and chemically stable Al2O3(W) is respectively added in Al2O3 matrix. To obtain complexshaped components, slip casted bodies were sintered at 1$600^{\circ}C$, 2hrs up to 98~99% R.D.. Multiple toughening mechanisms in comparison with theories reported until now will be discussed as a result of the phase analysis of ZrO2 by athermal behaviours and microstructural characterizations as well as measured mechanical properties.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.42 no.5
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• pp.456-460
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• 2009

Biofilm is a structured community of microorganism encapsulated within a self-developed polymeric matrix and adherent to a living or a solid surface. In this study, we investigated the effects of various substrates on the formation of biofilm in Vibrio parahaemolyticus. We found that biofilm formation profoundly increased in a substrate, that consisted of calcium chloride, calcium nitrate, and calcium sulfate in 1% peptone water. On the other hand, a dramatic reduction in biofilm formation was observed in a substrate, that consisted of glucose and ferric chloride in LB broth. These results suggest that V. parahaemolyticus prefer to form a biofilm on the surface of a crustacean or a clam, where calcium ion is rich, and also where seawater temperature is relatively lower. In contrast, high levels of glucose in a crustacean or a clam body resulting from increased seawater temperature, can make V. parahaemolyticus detach from it and lead to free floating.

• Nuclear Engineering and Technology
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• v.52 no.3
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• pp.610-613
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• 2020

Specimens of austenitic stainless steel were irradiated with 6 MeV Xe ions to two doses of 7 and 15 dpa at room temperature and 300 ℃ respectively. Then partial irradiated specimens were subsequently thermally annealed at 550 ℃. Irradiation-induced BCC-phase formation and magnetism were analyzed by grazing incidence X-ray diffraction (GIXRD) and vibrating sample magnetometer (VSM). It has been shown that irradiation damage level, irradiation temperature and annealing temperature have significant effect on BCC-phase formation. This BCC-phase changes the magnetic behavior of austenitic stainless steel. The stress relief and compositional changes in matrix are the driving forces for BCC-phase formation in austenitic stainless steel during ion irradiation.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.237-239
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• 2002

The effect of particle sizes of the metal matrix composites containing 10 wt.%SiCp was investigated with using various tools. The results showed that tool life decreased considerably with increasing particle size and cutting speed. The wear resistance of TiC-coated tools was considerably higher than that of the other tools. It was observed that abrasive wear was the main responsible mechanism for wear of the tool thermal cracks were at high speed while a built-edge formation was also evident at lower speed.