• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.6
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• pp.147-153
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• 2018

PLGA microcapsule particles encapsulating BSA aqueous solutions were prepared using a water-in-oil-in-water emulsion method. The morphology, particle size, BSA encapsulating efficiency, and in-vitro release test were also studied using the microcapsule particles. In the outer aqueous phase, an emulsifier, e.g., PVA, was replaced with metal salts for surface solidification. Scanning electron microscopy (SEM) showed that the microcapsule particles had smooth surfaces and were between $1{\mu}m$ and $7{\mu}m$ in size. The microcapsule particle morphology was affected directly by the ratio between the polymer solution and inner aqueous solution, and composition of the outer aqueous solution. The factors also partially affected the BSA encapsulation efficiencies and in-vitro release rates. All the microcapsule particles showed an initial burst release through the in-vitro release test. On the other hand, the particles also showed a relatively long release period. Metal salts could be good choices to replace the emulsifier to solidify the microcapsule particle surfaces.

• Membrane and Water Treatment
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• v.7 no.2
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• pp.101-113
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• 2016

In this study, to improve the water flux of porous hydrophobic membranes, various water-soluble polymers including neutral, cationic and anionic polymers were adsorbed using 'salting-out' method. The adsorbed hydrophobic membrane surfaces were characterized mainly via the measurements of contact angles and scanning electron microscopy (SEM) images. To enhance the durability of the modified membranes, the water-soluble polymers such poly(vinyl alcohol) (PVA) were crosslinked with glutaraldehyde (GA) and found to be resistant for more than 2 months in vigorously stirred water. The water flux was much more increased when the ionic polymers used as the coating materials rather than the neutral polymer and in this case, about 70% of $0.31L/m^2{\cdot}h$ (LMH) to 0.50 LMH was increased when 300 mg/L of polyacrylamide (PAAm) was used as the coating agents. Among the cationic coating polymers such as poly(styrene sulfonic acid-co-maleic acid) (PSSA_MA), poly(acrylic acid-comaleic acid) (PAM) and poly(acrylic acid) (PAA), PSSA_MA was found to be the best in terms of contact angle and water flux. In the case of PSSA_MA, the water flux was enhanced about 80%. The low concentration of the coating solution was better to hydrophilize while the high concentration inclined to block the pores on the membrane surfaces. The best coating condition was found: (1) coating concentration 150 to 300 mg/L, (2) ionic strength 0.15, (3) coating time 20 min.

• Membrane Journal
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• v.9 no.3
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• pp.163-169
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• 1999

The effects of interactions between permeant molecules or permeant and membrane material have been investigated on the permeation behavior of permeants in pervaporation of water/alcohol mix¬tures. A poly(vinyl alcohol) (PVA) membrane crosslinked with glutaraldehyde was employed in this study. A homologous series of alcohols in aqueous solution were used as feed. The pervaporation experiments were carried out with feed having 70-97 wt.% of alcohol contents and at various feed temperatures. In a high alcohol content above 92 wt.%, the permeation rate was increased in the order of interaction strength between alcohol and water in feed. However, in a low alcohol content below 90 wt.%, the tendency of the permeation rate was found to be opposite. These observations were discussed in terms of changes in interaction between permeant/permeant or permeant/membrane in varying feed composition and feed temperature.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.4
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• pp.333-340
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• 2019

The effects of compaction methods on the sintering density, microstructures, and mechanical properties were investigated in ${\alpha}-alumina$ ceramics. ${\alpha}-Alumina$ powders were granulated with a 10% aqueous solution of polyvinyl alcohol (PVA). Uniaxially pressed (UAP) and cold isostatic-pressed (CIP) samples were prepared by pressing uniaxially at a pressure of 1 ton for 1 min, and isostatically at 200 MPa for 15 min, respectively. Subsequently, both types of samples were sintered at $1,200^{\circ}C$, $1,300^{\circ}C$, $1,400^{\circ}C$, $1,450^{\circ}C$, $1,500^{\circ}C$, $1,550^{\circ}C$, and $1,600^{\circ}C$ at a rate of $5^{\circ}C/min$ for 2 h. The CIP samples were better than the UAP samples for all properties measured, such as the sintering density, Vicker's hardness, and toughness. The CIP sample sintered at $1,400^{\circ}C$ showed the maximum Vicker's hardness and toughness; this may be attributed to the competing effects of a decrease in porosity and the growth of grains with increasing sintering temperature.

• The Journal of Korean Academy of Prosthodontics
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• v.35 no.1
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• pp.221-243
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• 1997

The objective of this study was to characterize the mechanical properties of $Y_{2}O_{3}$-containing glass infiltrated ceramic core material, which was made by pressureless powder packing method. A pure alumina powder with a grain size of about $4{\mu}m$ was packed without pressure is silicon mold to form a bar shaped sample, and applied PVA solution as a binder. Samples were sinterd at $1350^{\circ}C$ for 1 hour. After cooling, $Y_{2}O_{3}$-containing glass($SiO_{2},\;Y_{2}O_{3},\;B_{2}O_{3},\;Al_{2}O_{3}$, ect) was infiltrated to the sinterd samples at $1300^{\circ}C$ for 2 hours and cooled. Six different proportions $Y_{2}O_{3}$ of were used to know the effect of the mismatch of the thermal expansion coefficient between alumina powder and glass. The samples were ground to $3{\times}3{\times}30$ mm size and polished with $1{\mu}m$ diamond paste. Flexural strength, fracture toughness, hardness and other physical properties were obtained, and the fractured surface was examined with SEM and EPMA. Ten samples of each group were tested and compared with In-Ceram(tm) core materials of same size made in dental laboratory. The results were as follows : 1. The flexural strengths of group 1 and 3 were significantly not different with that of In-Ceram, but other experimental groups were lower than In-Ceram. 2. The shrinkage rate of samples was 0.42% after first firing, and 0.45% after glass infiltration. Total shrinkage rate was 0.87%. 3. After first firing, porosity rate of experimental groups was 50%, compared with 22.25% of In-Ceram. After glass infiltration, porosity rate of experimental groups was 2%, and 1% in In-Ceram. 4. There was no statistical difference in hardness between two materials tested, but in fracture toughness, group 2 and 3 were higher than In-Ceram. 5. The thermal expansion coefficients of experimental groups were varied to $4.51-5.35{\times}10^{-6}/^{\circ}C$ according to glass composition, also the flexural strengths of samples were varied. 6. In a view of SEM, many microparticles about $0.5{\mu}m$ diameter and $4{\mu}m$ diameter were observed in In-Ceram. But in experimental group, the size of most particles was about $4{\mu}m$, and a little microparticles was observed. The results obtained in this study showed that the mismatch of the thermal expansion coefficients between alumina powder and infiltrated glass affect the flexural strength of alumin/glass composite. The $Y_{2}O_{3}$-containing glass infiltrated ceramic core made by powder packing method will takes less time and cost with sufficient flexural strength similar to all ceramic crown made with slip casting technique.

• Journal of the Korean Chemical Society
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• v.19 no.4
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• pp.269-279
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• 1975

Photosensitive properties of naphthoquinone-1,2-diazide-5-sulfonyl esters (PGND, BEND and PVAND) of polyglyceryl phthalate(PG), bisphenol A-epichlorohydrin condensate(BE) and polyvinyl alcohol(PVA) were investigated by the change of solubility before and after exposing to light. Various samples coated on glass or quartz plates were exposed to light under various conditions and steeped in aqueous alkali solution, and then the yield of residual film(W/W0) was determined. The yield of residual film, which was closely related to the sensitivity of the film, was affected by the degree of polymerization of the backbone resin, sensitizers and their concentration. In polymer homologs, the sensitivity was dependent on the degree of polymerization(the higher, the better). And also, it was most effective when 5 % of sensitizers to esters was used. The minimum exposed time was 0.6 min. for PGND-1, 1.0 min. for BEND-1, and 3.0 min. for PVAND-1. Most effective sensitizers for PGND, BEND and PVAND among those used here were benzanthrone, 5-nitroacenaphthene and picramide, respectively. The spectral sensitivities of PGND, BEND and PVAND were examined by comparing their spectrograms with UV-spectra in a solid state. Also, the sensitization and spectral sensitivity of the above polymers were studied. All the polymers containing the sensitizers showed optical sensitization. From the fact that in either case of sensitized or unsensitized sample, the ranges of absorption-maximum wave length were almost consistent with sensitivity maximum wave length, it was proved that the light absorbed by a sample served efficiently for photochemical reactions. Benzanthrone was found to be an excellent sensitizer for PGND.

• Asian-Australasian Journal of Animal Sciences
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• v.17 no.5
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• pp.612-616
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• 2004

This study was carried out to compare the semen characteristics, frozen-thawed sperm viability and testosterone concentration and in vitro fertilization (IVF) and development of in vitro matured pig oocytes between two Yorkshire boars. Semen and blood samples were collected once per week from October to November 2002 from two adult Yorkshire boars at 18 months of age with 170 kg body weight. Sperm were deep frozen in 5 ml maxi-straws with lactose-egg yolk and N-acetyl-D-glucosamine (LEN) diluent and stored in liquid nitrogen. Blood samples were obtained at 10 a.m. by inserting a 21 gauge, hypodermic needle attached to 10 ml syringe into surface veins in the ear. The concentration of testosterone was determined by Competitive Enzyme Immunoassay. Ovaries were collected from prepubertal gilts at a local slaughter house. Cumulus oocyte complexes were aspirated from antral follicles (3 to 6 mm in diameter). The medium used for oocyte maturation was modified TCM 199. After about 22 h of culture, oocytes were cultured without cysteamine and hormones for 22 h at $38.5^{\circ}C$, 5% $CO_2$ in air. For IVF, one frozen 5 ml straw was thawed at $52^{\circ}C$in 40 sec and was diluted with 20 ml Beltsville thawing solution at room temperature. Sperm were washed 2 times in mTLP-PVA and inseminated without preincubation after thawing. Oocytes were inseminated with $2{\times}10^7$/ml sperm concentration. Oocytes were coincubated for 6 h in 500 ${\mu}$l mTBM fertilization medium. At 6 h after IVF, oocytes were transferred into 500 ${\mu}$l NCSU-23 culture medium for further culture of 48 and 144 h. There were no significant differences in the semen volume, motility, normal acrosome morphology and sperm concentration of raw semen between A and B of Yorkshire boar. However, motility and normal acrosome of boar A were higher than those of boar B at 0.5, 2, 3, 4, 5 and 6 h incubations of frozen-thawed sperm. Testosterone concentration (3.75 ng/ml) of boar A was higher than that (2.34 ng/ml) of boar B. The rate of blastocyst formation (15.1%) of boar A was higher than that (10.4%) of boar B. In conclusion, serum testosterone concentration of boar showed very important role for the frozen-thawed sperm viability and the blastocyst formation of pig oocytes matured in vitro.

• Analytical Science and Technology
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• v.19 no.6
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• pp.482-489
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• 2006

Two electrode-based lactate biosensor was prepared by immobilizing lactate oxidase (LOD) obtained from pediococcus species in a poly(vinyl alcohol). Hydrogen peroxide ($H_2O_2$) produced by the reaction of lactate and LOD was detected on the Pt-black that was electrochemically deposited on the Au electrode. Sensors fabricated with Pt-black deposited Au electrode provided a high current of $H_2O_2$ oxidation at a substantially lowered applied potential (+300 mV vs. Ag/AgCl), resulting in reduced interferences from easily oxidizable species such as ascorbic acid, acetaminophen, and uric acid. An outer membrane is formulated by adjusting water uptake of hydrophilic polyurethane (HPU). The sensor performance was evaluated in vitro with both flow-through arrangement and static mode. The sensor showed a linear range from 0.1 mM to about 9.0 mM in 0.05 M phosphate buffer (pH 7.6) containing 0.05 M NaCl. Storing the sensors prepared in this work at $4^{\circ}C$ buffer solution while not in use, they provided same electrochemical performance for more than 25 days.