• Advances in nano research
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• v.4 no.1
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• pp.1-14
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• 2016

Superparamagnetic iron oxide nanoparticles (Nps), composed of magnetite, $Fe_3O_4$, or maghemite, ${\gamma}-Fe_2O_3$, core and biocompatible polymer shell, such as dextran or chitozan, have recently found wide applications in magnetic resonance imaging, contrast enhancement and hyperthermia therapy. For different diagnostic and therapeutic applications, current attempt is focusing on the synthesis and biomedical applications of various ferrite Nps, such as $CoFe_2O_4$ and $MnFe_2O_4$, differing from iron oxide Nps in charge, surface chemistry and magnetic properties. This study is focused on the synthesis of manganese ferrite, $MnFe_2O_4$, Nps by most commonly used chemical way pursuing better control of their size, purity and magnetic properties. Co-precipitation syntheses were performed using aqueous alkaline solutions of Mn(II) and Fe(III) salts and NaOH within a wide pH range using various hydrothermal treatment regimes. Different additives, such as citric acid, cysteine, glicine, polyetylene glycol, triethanolamine, chitosan, etc., were tested on purpose to obtain good yield of pure phase and monodispersed Nps with average size of ${\leq}20nm$. Transmission electron microscopy (TEM), X-ray diffraction, energy dispersive X-ray spectroscopy (EDX), $M\ddot{o}ssbauer$ spectroscopy down to cryogenic temperatures, magnetic measurements and inductively coupled plasma mass spectrometry were employed in this study.

• Korean Journal of Food Science and Technology
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• v.31 no.1
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• pp.158-163
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• 1999

The quality change of black rice during storage at $20^{\circ}C$ was measured to determine a packaging material for black rice storage, using polyethylene film (PE), polypropylene film (PP) and laminated film with PE and PP (PE/PP). Water activity of black rice was 0.642 at initial time and changed little in 8 months during storage at $20^{\circ}C$. Acidity of black rice was 25 mg KOH at initial time and was the lowest, 33.16 mg KOH, within PE/PP of 0.10 mm in thickness in 8 months during storage at $20^{\circ}C$. L, a and b values, hunter color value of black rice were not changed significantly in all packaging materials during 8 month storage. Hardness of the black rice was increased a little, but changed the smallest in PF/PP and the largest in PE with 0.05mm in thickness in 8 months. During storage, hexanal content was increased the smallest in PE/PP and the largest in 0.05 mm PE. Among fatty acid of black rice, linoleic acid was changed the smallest in PE/PP and the largest in 0.05 mm PE. In conclusion, PE/PP was better for the storage of black rice than PE and PP.

• Journal of Conservation Science
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• v.31 no.2
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• pp.87-94
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• 2015

Plastic artwork can be appeared crack, change of color and whitening event by various environment conditions. A large scale plastic artwork often exhibits in outside it will be directly degraded by physical and chemical degradation factor such as strong sunlight, high humidity and rainfall. We should know degradation characteristic of plastics to prevent these damages. In this study, we studied degradation characteristic of plastics (5 types of wide use plastics; polypropylene, polystyrene, polyethylene, polyvinyl chloride, polyurethane) depending on various artificial degradation conditions such as high temperature, ultraviolet and these complex conditions (high temperature and ultraviolet). As a result, polypropylene, polystyrene and polyethylene show the most visible change especially polypropylene, polystyrene. Polypropylene didn't show a great change degree of tensile strength and contact angle, on the other hand polystyrene did. Polypropylene and polystyrene weakened by photo degradation, polyvinyl chloride and polyurethane had relatively good light stability. Also the high temperature and complex conditions were most degradation characteristic. High temperature worked for degradation catalyst because its energy can not enough worked for cut off binding energy of plastics while ultraviolet condition effected as directly degradation condition. Though following results, we expect it can be applied to investigation of degradation factor depending on plastic artwork materials and basic result of plastic artworks conservation.