• Journal of Veterinary Clinics
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• v.32 no.3
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• pp.224-230
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• 2015

This study was designed in the fabricated poly (L-Lactic-co-${\varepsilon}$-Caprolactone) (PLCL) scaffold using chitosan-alginate hydrogel, which would be more suitable to maintain the biological and physiological functions continuing three dimensional spatial organizations for chondrocytes. As a scaffold, hydrogels alone is weak at endure complex loading within the body. In this study, we made cell hybrid scaffold constructs with poly (L-Lactic-co-${\varepsilon}$-Caprolactone) (PLCL) scaffold and hydrogels to make a three-dimensional composition of cells and extracellular matrix, which would be a mimic of a native cartilage. Using a particle leaching technique with NaCl, we fabricated a highly-elastic scaffold from PLCL with 85% porosity and $300-500{\mu}m$ pore size. A mixture of bovine chondrocytes and chitosan-alginate gel was seeded and compared with alginate as a control on the PLCL scaffold. The cell maturation, proliferation, extracellular matrix synthesis, glycosaminoglycans (sGAG) production and collagen type-II expressions were better in chondrocytes seeded in chitosan-alginate hydrogel than in alginate only. These results indicate that chondrocytes with chitosan-alginate gel on PLCL scaffolds provide an appropriate biomimetic environment for cell proliferation and matrix synthesis, which could successfully be used for cartilage repair and regeneration.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.9 no.1
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• pp.23-40
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• 1999

The analysis of thiodiglycolic acid in urine has been used as an index of biological exposure to vinyl chloride. Unfortunately thiodiglycolic acid has a strong hydrophilic character, because it has two carboxylic groups, so that it can only be extracted with organic solvent with a great difficulty. Underivatized thiodiglycolic acid tends to tail because of non-specific interaction with the inert support. Therefore, esterification is the obvious first choice for derivatization of thiodiglycolic acid, particularly for gas chromatography. In this study, the focus of interest is to compare two method of esterifications (methylation and silylation). Methylation is to make the methyl ester of thiodiglycolic acid by reaction with diazomethane. Silylation is to make the trimethylsilyl ester of thiodiglycolic acid by reaction with N-trimethylsily-ldiethylamine. The results and conclusions are as the following: 1. The detection limit (sensitivity) of methylated thiodiglycolic acid was $5.00{\mu}g/m{\ell}$ and silylated thiodiglycolic acid was $3.07{\mu}g/m{\ell}$ by gas chromatography with flame ionization detector. 2. The optimal liquid-liquid extraction of thiodiglycolic acid was as following: To each of the tubes, $15m{\ell}$ of urine, concentrated sulfuric acid (pH 1 - 2) and 5 gsodium sulfate were added. The samples was extracted three times with $5m{\ell}$ ethylacetate each time. 3. The methylated thiodiglycolic acid was more stable than silylated thiodiglycolic acid in extractional solvent which contained humidity. 4. The precision (pooled coefficient of variation for 4 days) of the analysis was 0.07324 in methylated thiodiglycolic acid with external standard calibration, and 0.07033 in methylated thiodiglycolic acid with internal standard calibration. 5. The precision (pooled coefficient of variation for 4 days) of the analysis was 0.10914 in silylated thiodiglycolic acid with external standard calibration, and 0.13602 in silylated thiodiglycolic acid with internal standard calibration. From the above results, the analysis of methylated thiodiglycolic acid was more sensitive (limit of detection) than silylated thiodiglycolic acid by gas chromatography. However, the methylated thiodiglycolic acid was stable in the humidity and was separated sharply on chromatogram. Also, analysis of methylated thiodiglycolic acid was more precise (pooled coefficient of variation for 4 days) than silylated thiodiglycolic acid. In conclusion, it is established that the analysis of methylated thiodiglycolic acid is appropriate for biological monitoring of exposure to vinyl chloride.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.17 no.2
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• pp.81-88
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• 2007

The aim of this study was to investigate whether the exposure to vinyl chloride monomer(VCM) induces lipid peroxidation in workers by evaluating the concentration of malondialdehyde(MDA) in the urine in order to assess worker's oxidative stress due to exposure of vinyl chloride monomer. The subjects investigated in the study were divided into the experimental group; 18 workers exposed to VCM, and the control group; 19 workers unexposed to VCM. A gas chromatography/pulsed flame photometric detector(GC/PFPD) was utilized to analyze thiodiglycolic acid(TDGA), which was methylated with trimethylsilyldiazomethane (2.0M in diethyl ether) in urine and the urinary MDA, the product of lipid peroxidation, was determined by high-performance liquid chromatography/ultraviolet-visible detector after derivatized with 2,4-dinitrophenylhydrazine(DNPH). The concentrations of urinary TDGA in controls and VCM exposure workers were 0.13(2.01)mg/g Cr. GM(GSD) and 0.35(1.96)mg/gCr. GM(GSD), respectively. The concentrations of urinary MDA were $0.12(2.21){\mu}mol/gCr$. GM(GSD) in controls and $1.35(1.79){\mu}mol/gCr$. GM(GSD) in VCM exposure workers. As a result of simple regressions analysis between urinary concentration of TDGA and MDA in VCM exposure workers, it was found that the $R^2$ value was 0.261 (p=0.03) and the drinking and smoking did not affect their level. In conclusion, the workers exposed to VCM have a potentially to suffered by oxidative stress due to VCM exposure and the urinary MDA can be applicable to the marker of effect to assess the level of worker's VCM exposure.

• Korean Journal of Food Science and Technology
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• v.45 no.3
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• pp.364-369
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• 2013

Polychlorinated biphenyls (PCBs) have been studied during the past few decades because of their potential impacts on the environment and human health. PCBs are toxic environmental pollutants and persistent organic pollutants (POPs). This study was carried out to assess the dietary exposure and risk to PCBs for the general Korean population through food intake. Various samples (n=389) covering 28 kinds of food were collected from 5 cities in Korea. The PCB content was not detected-$182.4{\mu}g/kg$ (mean of $5.4{\mu}g/kg$) in the food. The mean dietary exposure of PCBs for the general population was 9.54 ng/kg bw/day with an intake of 0.19% of tolerable daily intake (TDI) ($5{\mu}g/kg$ bw/day). Therefore, the level of overall dietary exposure to PCBs for the Korean population through food intake is below the recommended TDI levels.

• Applied Chemistry for Engineering
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• v.18 no.4
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• pp.361-365
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• 2007

The precipitation reaction of some rare earth chlorides ($Ce/Nd/GdCl_3$) in a LiCl-KCl molten salt has been carried out by reaction with oxygen. Identification of rare earth precipitates by reaction with oxygen and effects of oxygen sparging time (max. 420 min) and molten salt temperature ($450{\sim}750^{\circ}C$) on conversion were investigated. In this study, regardless of the oxygen sparging time and the molten salt temperature, oxychlorides (REOCl) for $NdCl_3$ and $GdCl_3$, and an oxide ($REO_2$) for $CeCl_3$ are formed as a precipitate, which are identical with the estimation results of Gibbs free energy of reaction (${\Delta}G_r$). The conversion of rare-earth chlorides into insoluble precipitates was described by using a conversion ratio. The conversion ratio increased exponentially with the oxygen sparging time and finally showed asymptotic value, over 0.999 at $750^{\circ}C$ of the molten salt temperature and over 300 min of sparging time conditions. The conversion ratios were increased with the molten salt temperature. In case of $CeCl_3$, when the sparging time exceed 60 min, the values of the conversion ratio were nearly constant over 0.999 in all experimental temperature conditions.

• Applied Chemistry for Engineering
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• v.21 no.5
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• pp.532-536
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• 2010

A study on the volatile organic compounds (VOCs) and low molecular weight (LMW) amount which is contained within bisphenol A polycarbonate (PC) was performed by the solvent extraction with ketone type solvents (acetone, butanone, pentanone). The LMW amount of untreated PC was 2.6 wt%, but the values of treated samples with acetone and pentanone were 0.96 and 1.53 wt%, respectively. Acetone is a more effective solvent than pentanone on the LMW extraction. Methylene chloride (MC) and toluene were certified and quantified by GC-Mass experiments, and the quantitative results indicated the fact that the pentanone was the effective solvent on VOC extraction. Focused on the change of VOCs and LMW amount, the use of co-solvent might be more useful, and the experimental results of co-solvent extraction showed that the optimum condition was 50 : 50 volume percent.

• Korean Journal of Ecology and Environment
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• v.42 no.3
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• pp.271-279
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• 2009

Vinyl chloride (VC) is a known human carcinogen, and it is released to multi-environmental media via several exposure routes. VC was potentially evaluated as a water quality pollutant based on human health risk assessment in Korean water environments. In this study, we investigated physicochemical and toxicological properties of VC, human health and ecological risk assessment, and the regulation of VC as a water quality pollutant in developed countries. Currently there are no standard or guideline values of VC in Korean legal system for the protection of human health and aquatic ecosystem, except that it is designated as a specific toxic substance and a water quality pollutant. Human health risk assessment of VC was previously performed based on the limited water quality monitoring data. The monitoring level of VC in Korean water system is more higher than other countries'. VC was assessed as potential hazardous chemical based on the US EPA's cancer risk assessment. There were a few ecotoxicity data of VC available using very limited kinds of aquatic organisms, and the toxicity results obtained seem to be overestimated without considering the losses of VC in open exposure system. Therefore it is needed to monitor the VC in various areas and to carry out the ecotoxicity research using multi-level organisms. We expect that these results can be useful information for implementing VC as a water quality pollutant in legal system for the protection of human health and aquatic ecosystem in near future.

• Journal of Life Science
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• v.16 no.5
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• pp.734-739
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• 2006

This study investigated the hepatoprotective effects of mesangi (Capsosiphon fulvecens) in carbon tetrachloride $(CCI_4)$-induced liver injury. Thirty healthy male Sprague-Dawley rats were divided into three groups : the normal (Normal), $CCI_4$-treated $(CCI_4)$, and mesangi-treated (Exp-CF) groups. Administration of $CCI_4$ increased the levels of GOT, GPT, and LDH in serum, while the levels were significantly decreased by the addition of mesangi. Higher levels of HDL-cholesterol were found in the Normal and Exp-CF groups, which has lower levels of total and LDL-cholesterol. Administration of $CCI_4$ also increased IGFBP-1 expression in serum, but it was decreased in the Exp-CF group. This suggests that $CCI_4$ is involved in the change in IGFBP-1 expression via its hepatotoxicity. The results indicate that mesangi has a hepatoprotective effect in rats given $CCI_4$.

• Fire Science and Engineering
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• v.31 no.6
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• pp.91-98
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• 2017

The present paper is a study on the tracking characteristics depending on accelerated degradation of PVC insulation material. In order to insulation degradation of PVC insulation material, the Arrhenius equation, a type of accelerated degradation test formula, was used to conduct accelerated degradation experiments with experiment samples prepared at the following age equivalents: 0, 10, 20, 30 and 40 years. Afterwards, a tracking experiment was conducted on the accelerated experiment samples as part of the KS C IEC 60112 criteria. When measuring the PVC tracking features according to the accelerated aging, the results showed that when 0.1% of ammonium chloride was added to the PVC insulating material, but no tracking occurred. However, depending on the age equivalent, The results of analyzing the current waveform and voltage waveform of the tracking propagation process showed the age equivalent from 0 years to 40 years displayed a break down in insulation resistance and even the BDB(before dielectric breakdown) sections did not maintain the same functionality of the original material. Based on a criterion of an age equivalent of 0 years, material with an age equivalent of 10 years posed a 1.4 times greater risk, material with an age equivalent of 20 years posed a 2 times greater risk, material with an age equivalent of 30 years posed a 4.6 times greater risk, and material with an age equivalent of 40 years posed a 7 times greater risk.

• Korean journal of food and cookery science
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• v.31 no.4
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• pp.465-476
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• 2015

The purpose of this study was to develop sodium reduced foods for 10 representative high sodium foods often served in the food service industry, and to conduct sensory evaluation on the foods. The foods are kimchi, cucumber salad, banquet noodle, seaweed soup, ahuk soup, pork kimchi stew, red pepper paste pork chops, beef bulgogi, grilled mackerel and saury stew selected based on data from the 2010 national health and nutrition examination survey. The sodium contents of chinese cabbage kimchi were 688.1 mg in the control, 587.3 mg in the 15% reduced sodium sample group (level 1), and 486.5 mg in the 30% reduced sodium sample group (level 2). The corresponding sodium contents of cucumber salad were 406.4 mg, 345.5 mg, and 284.6 mg. The sodium contents of banquet noodle were 1080.2 mg, 912.2 mg, and 765.8 mg, respectively. The sodium contents of seaweed soup were 459.4 mg, 392.1 mg, and 333.0 mg, respectively. The sodium contents of ahuk soup were 615.3 mg, 534.9 mg, and 434.4 mg respectively. The sodium contents of pork kimchi stew were 1156.2 mg, 988.3 mg, and 820.2 mg respectively. The sodium contents of grilled mackerel were 624.6 mg, 557.4 mg, and 456.9 mg respectively. The sodium contents of red pepper paste pork chops were 723.7 mg, 615.0 mg, and 505.3 mg, respectively. The sodium contents of beef bulgogi were 678.3 mg, 561.9 mg, and 473.3 mg, respectively. The sodium contents of saury stew were 676.0 mg, 574.6 mg, and 470.9 mg respectively. Sensory evaluation was conducted with a total of 30 samples consisting of 10 control food groups, 15%, and 30% reduced sodium food groups. Results showed sodium reduction up to level 1 or 2 in chinese cabbage kimchi, cucumber salad, pork kimchi stew, red pepper paste pork chops, beef bulgogi, grilled mackerel and saury stew. However, the soups and noodles showed significant differences between the control and the 15% reduced sodium (level 1) food groups, specifically in banquet noodle, seaweed soup, ahuk soup.