• International Journal of Oral Biology
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• v.38 no.3
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• pp.111-119
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• 2013

Objective. To investigate the effects of the hypoxia inducible factor-1 (HIF-1) activation-mimicking agent cobalt chloride ($CoCl_2$) on the osteogenic differentiation of human mesenchymal stem cells (hMSCs) and elucidate the underlying molecular mechanisms. Study design. The dose and exposure periods for $CoCl_2$ in hMSCs were optimized by cell viability assays. After confirmation of $CoCl_2$-induced HIF-$1{\alpha}$ and vascular endothelial growth factor expression in these cells by RT-PCR, the effects of temporary preconditioning with $CoCl_2$ on hMSC osteogenic differentiation were evaluated by RT-PCR analysis of osteogenic gene expression, an alkaline phosphatase (ALP) activity assay and by alizarin red S staining. Results. Variable $CoCl_2$ dosages (up to $500{\mu}M$) and exposure times (up to 7 days) on hMSC had little effect on hMSC survival. After $CoCl_2$ treatment of hMSCs at $100{\mu}M$ for 24 or 48 hours, followed by culture in osteogenic differentiating media, several osteogenic markers such as Runx-2, osteocalcin and osteopontin, bone sialoprotein mRNA expression level were found to be up-regulated. Moreover, ALP activity was increased in these treated cells in which an accelerated osteogenic capacity was also verified by alizarin red S staining. Conclusions. The osteogenic differentiation potential of hMSCs could be preserved and even enhanced by $CoCl_2$ treatment.

• Journal of Environmental Health Sciences
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• v.35 no.6
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• pp.454-460
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• 2009

The subway is the major public transportation system in Seoul with 2.2 million people using it everyday. Indoor air pollution in the subway can be a significant part of population exposure because of the number of people using the subway, time spent in transit and potentially high exposure for certain pollutants. The Korea Ministry of Environment has established the level 2 of recommended standards of $PM_{10}$ and $CO_2$ in subway trains. The aims of this study were to determine the airborne levels of $PM_{10}$, $CO_2$ and any correlation between pollutant levels and number of passenger in a subway train. The airborne $PM_{10}$ and $CO_2$ were measured on the inside of trains on line #4 for 4 different days from October to November in 2008. Average $PM_{10}$ and $CO_2$ levels were $113{\pm}25{\mu}g/m^3$ and $1402{\pm}442$ ppm, respectively. These levels did not exceed the level 2 of recommended standards of $250{\mu}g/m^3$ for $PM_{10}$ and 3500 ppm for $CO_2$. $PM_{10}$ level was not correlated with the number of passengers, while $CO_2$ levels were positively correlated with the number of passengers. The findings suggested that $PM_{10}$ in subway trains may have sources other than those directly associated with the number of passengers.

• The Journal of Engineering Geology
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• v.26 no.1
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• pp.117-128
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• 2016

Chemical reaction tests were performed to assess the properties of hardened specimens of cement pastes (KS-1 Portland and Class G) exposed to supercritical CO₂ for 1, 10, and 100 days. After exposure, the samples' measured permeability and strength were compared with values measured for pristine samples. The pristine cements had permeabilities of 0.009~0.025 mD, which increased by one order of magnitude after 100 days of exposure (to 0.11~0.29 mD). The enhancement of permeability is attributed to the stress release experienced by the samples after removal from the pressure vessel after exposure. Despite its enhancement, the measured permeability mostly remained lower than the API (American Petroleum Institute) recommended maximum value of 0.2 mD. The degradation of the cement samples due to exposure to supercritical CO₂ led to a layer of altered material advancing inwards from the sample edges. The Vickers hardness in the altered zone was much higher than that in the unaltered zone, possibly owing to the increase in density and the decrease in porosity due to the carbonation that occurred in the altered zone. Hardness close to the edge within the altered zone was found to have decreased significantly, which is attributed to the conversion of C-S-H into less-strong amorphous silica.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2005.06a
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• pp.523-530
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• 2005

In this study, maximum exposure rate at DAW(Dry Active Waste) drum surface which is satisfying regulation limit was calculated for conceptual design of IP(Industrial Package). DAW can be classified as combustible and non-combustible waste and the calculation was conducted for single and mixed radionuclide for each type of waste. In case of combustible waste that mixed radionuclide is uniformly distributed, the maximum exposure rates at drum surface were 3.60E-01, 8.85E-01 and 1.27E+01 mSv/hr for IP Type 1, 2-a and 2-b, respectively. and 3.60E-01, 8.85E-01, 1.27E+01 mSv/hr for single radionuclide(Co-60). In case of non-combustible waste that mixed radionuclide is uniformly distributed, the maximum exposure rates at drum surface were 7.14E-01, 1.83E+00, 2.69E+01 mSv/hr for IP Type 1, 2-a and 2-b, respectively. and 7.13E-01, 1.81E-01, 2.62E+01 mSv/hr for single radionuclide(Co-60). Through this study, the maximum amount of DAW can be transported by IP was suggested as maximum exposure rate at drum surface and the calculation for the other types of waste will be conducted.

• Proceedings of the Korea Society of Environmental Toocicology Conference
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• 2003.05a
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• pp.166-166
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• 2003

In terms of the risk assessment, qualitative and quantitative informations are needed to estimate the exposures of environmental pollutants, which may be potentiality of risks, and those are the information about the changes caused by the chemical transportation among environmental media and transformation in environmental media by duration. The various fate mechanism of chemical is possible for estimation of chemical concentration in environmental media. Since there are limitations in measuring the change of chemical concentration within all medium according to the time period, estimating method through modeling are developed.

• Journal of the Korean Institute of Gas
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• v.17 no.4
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• pp.18-25
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• 2013

It may occur health hazards or death by suffocation or acute poisoning in case of oxygen deficiency in ambient or exposure to harmful gas. As a part of accident prevention, we studied the change of activity and lethal dose by changing the concentration of several hazardous gas with inhalation exposure chamber and laboratory animals. We investigated the lethality and motility change during either the 4 hrs whole body exposure to oxygen, nitrogen, toluene, $H_2S$, CO and 48 recovery. As results, it is estimated that 5% oxygen concentration as lethal concentration and 5.5% as $LC_{50}$ (rat, 4 hrs) with statistics for dose-response. The results of lethality in oxygen deficient condition (approximately 6%), the lethalities were 40%, 20% with 20 ppm $H_2S$, 600 ppm CO respectively, and was not increased the lethality with 8% CO. Thus, it was confirmed that the $H_2S$, CO had influence to lethal dose, while toluene had low fluence.

• Proceedings of the KSAR Conference
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• 2003.06a
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• pp.62-62
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• 2003

This study was carried out to investigate the effects of activation agents on parthenogenetic activation of pig oocytes matured in vitro. The medium used for oocyte maturation was tissue culture medium (TCM) 199 supplemented with 26.19 mM sodium bicarbonate, 0.9 mM sodium pyruvate, 10 $\mu\textrm{g}$/ml insulin, 2 $\mu\textrm{g}$/ml vitamin $B_{l2}$, 25 mM Hepes, 10 $\mu\textrm{g}$/ml bovine apotransferrin, 150 $\mu$M cysteamine, 10 IU/ml PMSG, 10 IU/ml hCG, 10 ng/ml EGF, 0.4% BSA, 75 $\mu\textrm{g}$/ml sodium penicillin G, 50 $\mu\textrm{g}$/ml streptomycin sulfate and 10% pFF. 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. Cumulus-free oocytes involving first polar body were activated by exposure to various concentrations of ethanol and exposure time of ethanol in Hepes-buffered NCSU23 medium. Also, oocytes were activated by electric pulse alone or combination with ethanol. For electrical activation, oocytes were rinsed twice in 0.3 M mannitol solution supplemented with 0.1 mM CaC1$_2$, 0.2 mM MgC1$_2$, 0.5 mM Hopes and 0.01% BSA, and transferred to a chamber consisting of two electrodes 1 mm apart which was overlaid with the same activation solution. Oocytes were activated with a single DC pulse of 1.3 ㎸/cm for 30 $\mu$sec. After activation treatments, oocytes were washed three times with Hepes-buffered NCSU23 medium and were washed twice with NCSU23 culture medium containing 0.4% BSA, and then cultured in 500 ${mu}ell$ of the same medium for 20 h at 38.5$^{\circ}C$, 5% $CO_2$ in air. The activation rates of oocytes were higher in 6, 7 and 8% ethanol concentrations compared with 0, 5, 9 and 10% ethanol concentrations. Significantly more oocytes (29.3~33.7%) were activated in the exposure for 8, 10, 12 and 15 min than those in the exposure for 0 and 5 min, but there was no difference due to exposure to 8% ethanol for 8 to 15 min. Electric pulse treatment followed by exposure to ethanol significantly improved the rate of oocyte activation (61.9%) compared with that of other 3 treatments. In conclusion, the optimal activation treatment of ethanol exposure alone for the in-vitro matured pig oocytes was 8% ethanol for 8 to 15 min. Electric pulse treatment followed by ethanol exposure significantly improved the rate of activation.n.

• Journal of Korean Society for Atmospheric Environment
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• v.5 no.2
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• pp.30-35
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• 1989

To effectively develop and evaluate air pollution control measures, health risk rates due to air pollution must be identified. This article describes the application of a visual analysis and an air pollution-health risk model for determining the impacts of carbon monoxide (CO) exposure on angina pectoris patients in a metropolitan area. The procedures used for analyzing the relationship between CO exposure and the related increase in angina angina attacks for stable angina pectoris patients are described through a case study in the city of Seoul, Korea and the findings show that air-pollution-health risk model and visual analysis can be effective tools for environmental decision-makers, allowing air pollution control scenarios to be developed and evaluated for environmental protection. One of the features of this study is to provide a methodology for translating clinical findings into estimates of the relative contributions of air pollution to all causes of a particular disease. Therefore, there must be appropriate recognition of the uncertainties involved in the study.

• Journal of Information Display
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• v.12 no.4
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• pp.205-208
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• 2011

Herein, the integration of solution-processed polymer thin-film transistors (TFTs) that were fabricated using selective wettability through ultraviolet (UV) exposure into a reflective liquid crystal display is demonstrated. From the experimental results of energy-dispersive spectroscopy, the composition of carbon and fluorine enhancing the hydrophobicity in the polymer chains was found to play a critical role in the wetting selectivity upon UV exposure. The polymer TFTs fabricated through the wettability-patterning process exhibited long-term stability and reliability. This wetting-selectivity-based patterning technique will be useful for constructing different types of solution-processed electronic and optoelectronic devices.

• Polymer(Korea)
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• v.28 no.6
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• pp.445-454
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• 2004

The requirement for a much finer line width circuits on semiconductors needs new developers such as supercritical fluid to prevent the collapse of the photoresist micro-patterns. The copolymers contain t-butyl methacrylate having an acid-cleavable t-butyl group and supercritical fluid $CO_2$ soluble perfluorinated decyl methacrylate segments. The supercritical fluid $CO_2$-philic properties of the photoresist changed to supercritical fluid $CO_2$-phobic properties after the deprotection reaction by exposure, which made the exposed resist insoluble in the supercritical fluid $CO_2$ developer. The synthesized copolymers containing more than 30% of perfluorinated decyl methacrylate were found to be soluble in supercritical fluid $CO_2$. The variation of film thickness before and after exposure was largest when the mole ratio of perfluorinated decyl methacrylate in the copolymer was 30%.