• Polymer(Korea)
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• v.31 no.6
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• pp.491-496
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• 2007

In the polymeric dental restorative composites, the resin matrix mainly contains 70 wt% 2,2-bis[4-(2-hydroxy-3-methacryloyloxy propoxy) phenyl] propane (Bis-GMA), as a base resin and 30 wt% triethylene glycol dimethacrylate (TEGDMA) as a diluent. Even though the viscosity of the resin matrix is rapidly decreased by adding TEGDMA, addition of TEGDMA to the Bis-GMA results in reduction in the mechanical properties and increase in the curing shrinkage of the dental composite. In order to fabricate dental composite exhibiting excellent properties by reducing TEGDMA content in the resin matrix, in this study, Bis-GMA derivatives, which do not contain hydroxyl groups, were used instead of Bis-GMA. The curing characteristics of Bis-GMA derivatives were similar with those of Bis-GMA, while the former exhibited lower viscosity and water absorption than the latter. Comparing the curing shrinkage of the dental composite containing Bis-GMA derivative with that prepared from Bis-GMA, the reduction in curing shrinkage was about 25%. Dental composites prepared from new resin matrices also exhibited low water uptake and better properties in mechanical strength.

• Journal of the Korean Data and Information Science Society
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• v.25 no.4
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• pp.829-846
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• 2014

Using complex sample design, this article analyzes the difference between sex and age groups of mental health, physical activity, suffering lifestyle diseases, drinking, and smoking using the fifth Korea national health and nutrition examination survey data (2011-2012), and then analyzes the effect of mental health, physical activity, suffering lifestyle diseases, drinking, and smoking on EQ-5D, a measure of health-related quality of life. The results show that mental health, physical activity, suffering lifestyle diseases, drinking and smoking are statistically different among gender and age groups, and that age group, education level, suffering diabetes, recognizing stress, thinking suicide are statistically influential on EQ-5D.

• KSBB Journal
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• v.18 no.2
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• pp.145-148
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• 2003

The hydrogen-producting bacterium was isolated from fresh water and identified as Enterbacter cloacae. The isolated was named Enterobacter cloacae YJ-1. In batch culture, The optimum cultivation temperature and pH of strain YJ-1 was 35$^{\circ}C$ and 7.5, respectively. All of the added glucose was consumed completely during fermentation even though pH was not controlled. Amount of hydrogen produced on each condition of 2% glucose, 4% sucrose and 5% fructose was 950, 1000 and 948 mL/L, respectively and resulted in increasing hydrogen production approximately 2.5-times more than controlled condition. The macimum hydrogen production was obtained when 50mM phosphate was added. was obtained when 50mM phosphate was added. In repeated0batch culture, yeast extract, but the production amount was not changed on the condition of over 0.5%, Most of the organic acides produced during the fermentation were formic and acetic acid, and propionic acid was moiety also generated.

• Child Health Nursing Research
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• v.24 no.2
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• pp.157-165
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• 2018

Purpose: The purpose of this study was to examine differences in the prevalence of vitamin D deficiency between male and female Korean adolescents and to investigate gender-specific factors associated with vitamin D deficiency. Methods: This cross-sectional descriptive study included 975 adolescents aged 12-18 years who participated in the fifth Korean National Health and Nutrition Examination Survey (2010~2011). Multiple logistic regression using complex sample analysis was performed to examine gender-specific factors associated with vitamin D deficiency with adjustments for covariates. Results: Among the participants, 82.9% had vitamin D deficiency. The prevalence of vitamin D deficiency was higher among female adolescents (88.4%) than their male counterparts (78.4%). A rural place of residence (OR, 0.40; 95% CI, 0.19~0.87; p=.021) and daily milk intake (OR, 0.23; 95% CI, 0.07~0.75; p=.015) were significant factors significantly associated with vitamin D deficiency in males, while body mass index (OR, 8.40; 95% CI, 1.05~67.04, p=.045) and having breakfast (OR, 0.22; 95% CI, 0.10~0.49; p<.001) showed significant relationships in females. Conclusion: The results of this study provide preliminary evidence for developing effective strategies to prevent vitamin D deficiency in Korean adolescents. The different factors influencing vitamin D deficiency in males and females should be considered when providing interventions.

• Journal of Nutrition and Health
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• v.41 no.3
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• pp.232-241
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• 2008

Moderate alcohol consumption has been known to be associated with reduced risk for coronary heart disease (CHD). We assessed the association between alcohol consumption and CHD-related risk factors [hypertension, diabetes mellitus (DM) , high total cholesterol, high triglyceride (TG), low HDL-cholesterol (HDL-C), and high LDL-cholesterol (LDL-C)] in Korean. After excluding those with extreme intake values, the number of final subjects included in the analysis was 4,662 Korean adults aged over 20 years (1,961 men, 2,701 women) who participate in the 2005 Korean National Health and Nutrition Examination Survey. The subjects were divided into four or five groups; none-alcohol consumption group, moderate alcohol consumption group (<15 or 15.0-29.9 g/d), heavy alcohol consumption group (30-69.9 g/d or ${\geq}$ 70 g/d in men, ${\geq}$ 30 g/d in women). Odds ratios (ORs) were estimated from logistic regression adjusting for potential covariates. Alcohol consumption was inversely associated with low HDL-C in both men and women. However, heavy alcohol intake (${\geq}$ 70 g/d) significantly increased risk for hypertension, DM, and hypertriglyceridemia in men. The frequency of alcohol intake was also associated with CHD risk. The risk for low HDLC was decreased with alcohol consumption (${\geq}$ 1 times/wk), but frequent alcohol intake (${\geq}$ 4 times/wk) increased the risk for hypertension. This study revealed that moderate alcohol consumption has protective effect on CHD-related risk factors in Korean population.

• KSBB Journal
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• v.17 no.4
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• pp.409-415
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• 2002

A certain group of phytochemicals such as isoflavone have been proven to act as a phytoestrogen. After thorough the study of different bibliographic herbs excluding soybeans, dates, pomegranates, and other publicized plants, three different edible herbs by Korean Food Regulation were extracted for the animal study on the effect of estrogen replacement. The herbal extract(FGF271) has been orally administered into 51 weeks old partial ovariectomized rats for 5 weeks with the different dosages of 100 and 1,000 mg/kg, respectively. It was observed that 1) serum estrogen level was increased in both 100 and 1,000 mg/kg group, 2) the distension of uterus was made dose dependently and significantly different in 1,000 mg/kg group (p.0.05) from control in the gross findings, 3) the weight of uterus was increased in 1,000 mg/kg group, and 4) the action on reproductive tissues was clear in the microscopic findings in terms of hyperplasia of endometrial epithelial cell, cystic change of submucosa, dilatation of uterus (significantly increased in 1,000 kg/mg), and follicular cystic changes in ovary. As a result, FGF271 seemed to act as a phytoestrogen by inducing the change in ovary and uterus and by increasing the serum estrogen concentration.

• Polymer(Korea)
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• v.25 no.2
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• pp.246-253
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• 2001

Amino terminated PES-CTBN-PES triblock copolymer was synthesized from PES oligomer and commercial CTBN rubber (CTBN1300$\times$13), and molecular weight of the copolymer was controlled to be 15000 g/mole. The copolymer was utilized to toughen diglycidyl ether of bisphenol-A (DGEBA) epoxy resin which was cured with 4,4'-diaminodi-phenylsulfone (DDS) and subjected to the measurement of thermal properties, fracture toughness ( $K_{IC}$), flexural properties and solvent resistance. The properties were compared with those from the samples modified by CTBN/PES blends. The maximum loading of copolymer into the epoxy resin was 40 wt% without utilizing solvent, at which $K_{IC}$ fracture toughness of 2.21 MPa${\cdot}m^{0.5}$ was obtained without sacrificing flexural properties and chemical resistance. However, the epoxy resin modified with PES/CTBN blend exhibited much lower $K_{IC}$ and flexural properties compared to the epoxy resins toughened by PES-CTBN-PES copolymers.

• Polymer(Korea)
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• v.24 no.5
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• pp.610-620
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• 2000

Vinyl acetate (VAc) was polymerized at 30, 40, and 5$0^{\circ}C$ using 2,2'-azobis (2,4-dimethylvaleronitrile) (ADMVN) and tertiary butyl alcohol (TBA) as the initiator and the solvent, respectively. High molecular weight (HMW) atactic poly(vinyl alcohol) (PVA) was prepared by saponifying the poly(vinyl acetate) (PVAc) synthesized. The effect of polymerization conditions were investigated in terms of conversion, degree of branching for acetyl group of PVAc, and molecular weight of both PVAc and PVA. The polymerization rate of VAc in TBA was proportional to the 0.49th power of ADMVN concentration in good accordance with the theoretical value of 0.5. HMW-PVA with high yield could be obtained successfully, probably due to lower polymerization temperature and decreased chain transfer reaction rate which was achieved by adopting ADMVN and TBA. PYAc having average degree of polymerization (P$_{n}$) of 10000~13000 was obtained at the conversion of 35~70%. Saponification of so prepared PVAc yielded PVA having P$_{n}$ of 2400~6100. The syndiotactic diad content increased with decreasing polymerization temperature and increasing VAc concentration due to a steric hindrance effect of TBA during polymerization.

• Polymer(Korea)
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• v.35 no.2
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• pp.183-188
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• 2011

Pentaerytritol triacrylate (PETA) was synthesized by a condensation reaction between pentaerytritol and acrylic acid. The highest yield of PETA was obtained when heptane was used as a solvent under the 1:4 mole ratio of pentaerytritol and acrylic acid. The 6-functional urethane acrylates(UA) were also synthesized by a condensation reaction between PETA and diisocyanate. Cured films were prepared from the mixtures of UA oligomer, reactive diluents and UV initiator to investigate their physical properties. The thermal stability of the aliphatic urethane acrylate was better than that of the aromatic urethane acrylate. The UA-2 showed good hardness and scratch resistance properties while the UA-l with a high degree of curing density exhibited a better chemical resistance. All the UA oligomers showed fairly good adhesion strengths but the other physical properties of UA-3 were poor due to its low curing density.

• Journal of Adhesion and Interface
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• v.20 no.4
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• pp.140-145
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• 2019

In view of environmental considerations, the control of carbon dioxide (CO₂) and volatile organic compounds (VOCs) is one of important issues in the film and coating industries. Therefore, UV-curable system has been developed due to minimize emissions of VOCs and reduce CO₂ emission due to low energy consumption from fast curing. Also, biodegradable polymers economically are attractive because of environmental and economic concerns associated with huge waste plastics. In this study, UV-curable polyurethane acrylates with different compositions of biodegradable polylactide (PLA) diol and poly(ethylene glycol) as diols were synthesized and curing reaction of their end-capped acrylates was performed by UV exposure. Tensile strength, elongation, and Tg of the UV-cured polyurethane acrylates increased with PLA diol content in the diol while their hydrophilicity and thermal stability increased with the PEG content. These results indicated a property of UV-cured polyurethane acrylates could be controlled by environment-friendly diols.