• Journal of Korean society of Dental Hygiene
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• v.18 no.5
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• pp.831-842
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• 2018

Objectives: This study was conducted to reveal the biological basis of dental plaque and preschool children's dental health status through repetitive and continuous toothbrushing instruction to preschool children, using quantitative criteria, and to emphasize the importance of the role of an oral health manager for the prevention of dental caries. Methods: After IRB approval, toothbrushing instruction and oral microbial specimen collection were conducted with children of preschool age at the Daycare Center attached to D. University, Busan. Specimens from 27 children were characterized by analysis with real-time multi-chain enzymatic polymerization reaction technique at an agency specializing in genetic analysis. Results: In a survey of the children's dental health behaviors, 48.1% responded that the toothbrushing time is 91 to 150 seconds; 66.7% responded that the frequency of toothbrushing is more than three times per day; 81.5% stated that they performed tongue brushing; and 81.5% brushed their teeth. Regarding levels of dental cariogenic bacteria, after children received continuous toothbrushing instruction, there were reductions in both Streptococcus mutans and Streptococcus sobrinus. Regarding toothbrushing time, the time increased in relation to the presence of instruction. Regarding Quigley Hein Index, the index decreased in the early and middle periods upon addition of instruction, then increased in the middle and later periods. Conclusions: Through persistent and repetitive toothbrushing instruction, healthy behavior can be positively established in children of preschool age; it is necessary to prepare institutional measures so opportunities for dental health education can be consistently provided and maintained. In the future, it will be necessary to conduct a follow-up study to verify the factors affecting toothbrushing time and volume of oral pathogens.

• Analytical Science and Technology
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• v.8 no.1
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• pp.1-7
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• 1995

Spectrophotometric determination of U(VI) and Th(IV) by Flow injection method is described. Chrome Azurol S forms water soluble complexes with U(VI) and Th(IV) in the presence of cethyltrimethylammonium bromide. The maximum adsorption of U(VI) and Th(IV) complexes are at 600nm with molar absorptivity of $2.3{\times}10^5Lmol^{-1}cm^{-1}$ and 611nm with molar absorptivity of $3.8{\times}10^5Lmol^{-1}cm^{-1}$ in acetate buffer medium having pH 5.0 and 5.5. The calibration curves of U(VI) and Th(IV) are linear over the range of 0.1~0.8ppm and the correlation coefficients are ca. 0.9960 and 0.9930 respectively. The detection limits(S/N) are 20ppb for U(VI) and 15ppb for Th(IV). The relative standard deviation are ${\pm}1.8%$ for U(VI) and ${\pm}2.1%$ for Th(IV). The sample throughput was ca. $50hr^{-1}$.

• Journal of Animal Science and Technology
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• v.44 no.6
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• pp.809-816
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• 2002

Chitosan is the deacetylated product of chitin. Chitosan and its derivatives have many properties that make them attractive for a wide variety of health applications. This study was conducted to investigate change of oligosaccharide content and antiviral effect on rotavirus of chitooligosaccharide and water soluble chitosan after heat treatment. The quantitative analysis of oligosaccharide using colorimetry showed that oligosaccharide contents in water soluble chitosan and chitooligosaccharide were decreased from 62.67% to 60.45% and from 59.48% to 54.31%, respectively, after heating. The inhibitory effect of chitosan derivatives on MA-104 cell infected with human rotavirus(HRV) measured using AEC staining method. The inhibition level of 0.125% water-soluble chitosan against cell infection by human rotavirus was 91.98 3.09% in HRV S2 and was 89.92 1.68% in HRV Wa. But, chitooligosaccharide had not shown inhibitory effect against cell infection by HRV. It considered that most oligosaccharide of chitooligosaccharides consist of oligomer of lower polymerization degree. Heat treatment of water soluble chitosan and chitooligosaccharide did not influence their antiviral effects on rotavirus.

• Journal of the Korean Wood Science and Technology
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• v.27 no.2
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• pp.15-22
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• 1999

Polymeric meterials that are used for noise and vibration damper in wood/polymer/wood sandwich composites, must have a high loss factor(tan ${\delta}$), and at the same time the storage modulus(E) of $5{\times}10^7$ to $10^9$ dyne/$cm^2$ must withstand over a wide temperature and frequency ranges. In this study, the series of epoxy resinlpolyacrylate interpenetrating polymer networks(IPNs) were synthesized by simultaneous polymerization. Their dynamic tensile properties were measured at 110Hz using Rheovibron instrument. Composite damping factor(tan ${\delta}_c$) and dynamic bending modulus($E_c,\;E_^{\prime\prime}c$) of wood/polymer/wood sandwich composites were measured at 110Hz using a Rheovibron in bending mode of vibration. These dynamic tensile studies indicated that cured epoxy resin/polyacrylates IPNs were semicompatible in the sense that both the shifting of T($E^{\prime\prime}_{max}$) or T(tan ${\delta}_{max}$) and the broadening of glass transition temperature range were observed. Especially, the cured Epikote871/P(n-BMA) IPNs of composition 70/30 to 50/50 showed a relatively high tan a and appropriate E' value over a wide temperature range; consequently the tan a e curves of wood/IPNs/wood sandwich composites was broadened over a wide temperature range.

• Applied Chemistry for Engineering
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• v.1 no.2
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• pp.190-196
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• 1990

The biological active monomer, 1-(methacryloyloxymethyl)-5-fluorouracil(MAOMFU) was synthesized from 2, 4-bis(trimethylsilyloxy)-5-fluoropyrimidine. Poly(MAOMFU) poly(1-methacryloyloxymethyl-5-f1uorouracil-co-methyl methacrylate), and poly(MAOMFU-co-MMA) were also obtained by radical polymerization at $60^{\circ}C$. The monomer reactivity ratios, $r_1$ and $r_2$ were determined by $Kelen-T\ddot{u}d\ddot{o}s$ method ; $r_1(MAOMFU)=0.72$, and $r_2(MMA)=1.24$. These reactivity values imply that the copolymerization was mainly affected by the steric hindrance of MAOMFU. It was found from kinetic measurements that the rate constants of solvolysis are given as $6.42{\times}10^{-5}sec^{-1}$ and $7.40{\times}10^{-6}sec^{-6}$, respectively, for MAOMFU and poly(MAOMFU).

• Applied Chemistry for Engineering
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• v.10 no.6
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• pp.954-959
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• 1999

Radiation-induced grafting of 2-hydroxyethyl methacrylate(HEMA), acrylic acid(AAc) and methacrylic acid(MAAc) onto polypropylene microfiltration membrane has been studied. The effect of grafting conditions such as solvent composition(MeOH and $H_2O$) and monomer concentration on the grafting yield in investigated. The highest degree of grafting is obtained at a solvent composition of 25% $H_2O$:75% MeOH for HEMA, pure water for AAc and 50% $H_2O$:50% MeOH for MAAc. Modification of the PP membranes with hydrophilic monomers is shown to cause an increase in the water permeation flux of the membranes. It is found that HEMA is the best monomer to increase the water permeation flux and the highest water permeation flux is obtained at 99% degree of grafting. The water permeation flux of AAc-grafted PP membrane and MAAc-grafted PP membrane is very sensitive to environmental pH and $Cu^{2+}$ ion, but the water permeation flux of HEMA-grafted PP membrane scarcely depends on pH and $Cu^{2+}$ ion.

• Applied Chemistry for Engineering
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• v.25 no.2
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• pp.121-133
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• 2014

Block copolymers including ABA triblock architectures are useful as thermoplastic elastomers and toughened plastics depending on the relative glassy and rubbery content. These materials can be blended with other polymers and utilized as additives, toughening agents, and compatibilizers. Most of commercially available block copolymers are derived from petroleum. Renewable alternatives are attractive considering the finite supply of fossil resources on earth and the overall economic and environmental expenses involved in the recovery and use of oil. Furthermore, tomorrow's sustainable materials are demanding the design and implementation with programmed end-of-life. The present review focuses on the preparation and evaluation of new classes of renewable ABA triblock copolymers and also emphasizes on the use of carbohydrate-derived poly(lactide) or plant-based poly(olefins) having a high glass transition temperature and/or high melting temperature for the hard phase in addition to the use of bio-based amorphous hydrocarbon polymers with a low glass transition temperature for the soft components. The combination of multiple controlled polymerizations has proven to be a powerful approach. Precision-controlled synthesis of these hybrid macromolecules has led to the development of new elastomers and tough plastics offering renewability, biodegradability, and high performance.

• Applied Chemistry for Engineering
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• v.25 no.2
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• pp.174-180
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• 2014

A plasma hydrophobic coating on commercial fish feed was conducted to prolong the floating time of feed, thereby enhancing the feed consumption rate and reducing the contamination of water in fish farms. The hydrophobic coating on the fish feed was prepared using an atmospheric-pressure dielectric barrier discharge (DBD) plasma with hexamethyldisiloxane (HMDSO), toluene and n-hexane as the precursors. The effect of the parameters such as input power, precursor type and coating time on the coating performance were examined. The physicochemical properties of the coating layer were analyzed using a Fourier transform infrared (FTIR) spectrometer and a contact angle (CA) analyzer. The water CA increased after the coating preparation, indicating that the surface changed from hydrophilic to hydrophobic. The FTIR characterization revealed that the hydrophobic layer was comprised of functional groups such as $CH_3$, Si-O-Si and Si-C. As a result of the hydrophobic coating, the floating time of the fish feed increased from several seconds to 3 minutes, which suggested that the plasma coating method could be a viable means for practical applications. Compared to the water CA measured as soon as the coating layer was prepared, the 6-day aged sample exhibited a substantial CA increase, confirming the aging effect on the improvement of the hydrophobicity.

• Korean Journal of Food Science and Technology
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• v.26 no.3
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• pp.310-316
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• 1994

The phenolic substances contents of 45 plant foods in Korean diet were determined by different methods. Total phenolics contents by Folin-Denis method were $0.1{\sim}5.8%$ (dry matter basis), in which persimmon leaf, chestnut's inner skin, Chinese quince, walnut, sunflower seed and arrowroot exhibited the higher levels above 2%. Condensed tannin contents by vanillin method were $0{\sim}48%$, in which Chinese quince and chestnut's inner layer gave very high levels. Protein-precipitable phenolic substances ranged from 0.4% to 2.2%, in which chestnut's inner layer, walnut and Chinese quince had the highest content. The ability of phenolics to form precipitate was higher with pepsin and albumin than with trypsin. Among different phenolics content, total phenlolics correlated significantly with protein-precipitable phenolics (r=0.65) and condensed tannin (r=0.56). Chinese quince, chestnut's inner skin and sorghum showed a relatively lower degree of polymerization, as expressed by vanillin/FolinDenis ratio. Processed foods from buckwheat, acorn, mugwort and arrowroot showed a lower content of phenolic substances, suggesting a negligible adverse effect on the bioavailability of food proteins, if any.

• Korean Journal of Food Science and Technology
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• v.19 no.2
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• pp.113-118
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• 1987

An intermediate moisture model food system was used to investigate the effects of water activity (Aw), temperature, pH and polyethyleneglycol (PEG) on the Maillard reaction. The initial molar ratio of glucose to lysine was varied from one half to four. The maximum Maillard reaction was obtained from an initial glucose/lysine molar ratio of approximately three. The rate of Maillard reaction showed a maximum in the range of water activity of a normal intermediate moisture food. 'the model food system was prepared to hold water activity range of 0.47-0.84 and the samples were held at various temperatures. The maximum browning rate occurred at an Aw value of approximately 0.89 at $40^{\circ}C$ and $60^{\circ}C$, 0.74 at $30^{\circ}C$ and 0.67 at $20^{\circ}C$, respectively. The Arrhenius activiation energies for nonenzymatic browning pigment production were 18.03, 15.18 and 9.90 Kcal/mole for the sample with Aw 0.84, 0.74 and 0.67. When the pH of the model system was increased, a significant increase in the browning reaction was observed. On the inhibitive effects of PEG, the higher degree of polymerization, the more inhibition of browning reaction.