• Journal of the Korean Chemical Society
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• v.35 no.6
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• pp.612-616
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• 1991

Metachromatic behavior of methylene blue (MB) in solutions of aqueous sodium dodecyl sulfate (SDS), chondroitin sulfate and L-${\alpha}$-lecithin vesicle at $18~52^{\circ}$C has been studied by absorption spectroscopy. MB was clustered in the matrix of the vesicle with high concentration of L-${\alpha}$-lecithin. The metachromasy of MB was found to be independent of phase transition temperature of vesicles. These results suggest that the dyes were aggregated on the hydrophilic surfaces of vesicle. In the vesicular system, the metachromatic effect of MB was dramatically decreased in the presence of hexadecyltrimethylammonium bromide (CTAB) than SDS. It is estimated that the intercalation site of these surfactants on vesicle surfaces was different, that is, the intercalation of CTAB was more effective than that of SDS.

• Bulletin of the Korean Chemical Society
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• v.26 no.2
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• pp.241-247
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• 2005

A series of proton conductive inorganic-organic hybrid membranes doped with phosphoric acid ($H_3PO_4$) and/or triethylphosphate (PO(OEt)$_3$) have been prepared by sol-gel process with 3-glycidoxypropyltrimethoxysilane (GPTMS), 3-aminopropyltriethoxysilane (APTES) and tetraethoxysilane (TEOS) as precursors. High proton conductivity of 3.0 ${\times}$ $10^{-3}$ S/cm with composition of 50TEOS-30GPTMS-20APTES-50$H_3PO_4$ was obtained at 120 ${^{\circ}C}$ under 50% relative humidity. Thermal stability of membrane was significantly enhanced by the presence of SiO$_2$ framework up to 250 ${^{\circ}C}$. XRD revealed that the gels are amorphous. IR spectra showed a good complexation of $H_3PO_4$ in the matrix. The conductivity under 75% relative humidity was significantly improved by addition of APTES due to the increase in concentration of defected site in hybrid matrix. The effect of PO(OEt)$_3$, humidifying time, and heat-treatment were also investigated. PO(OEt)$_3$ had no improvement on conductivity and conductivity increased with humidifying time, however, decreased with heating temperature.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.4
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• pp.573-584
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• 2006

This study was carried out to investigate the causes of fish kills in the Yudeung Stream in Daejeon, Korea using literature reviews, governmental and our water quality monitoring data of the study site, rainfall data, intensive water quality monitoring during rainfall events, sediment pollutant contents and laboratory bioassay tests. Fish kill in urban streams can be caused by combined effect of reduction in dissolved oxygen concentration, increase in toxic material or increase in turbidity in waterbody due to introduction of surface runoff or effluent of combined sewer overflows after rainfall from the watershed areas. Despite of extensive and intensive field surveys and laboratory tests, it was found that those conventional methods have limitations to identify causes of fish kills in urban streams. It would be necessary to use dynamic water quality modeling to predetermine the range and level of water pollution in the stream and automatic water quality monitoring system that can collect water samples and detect water quality continuously.

• Journal of Korean Tunnelling and Underground Space Association
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• v.4 no.2
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• pp.113-121
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• 2002

This study is focused on establishing influence zone caused by tunnelling in limestone site. Therefore, the numerical analysis using the FLAC2D was performed considering various locations and magnitudes of cavities. To reduce the stress concentration, the shape of cavities was designed to ellipse. This parametric study reveals that the cavities located at crown part and edge part of tunnel greatly have influenced on stability of tunnel. The effect of distance between tunnel and cavity which is larger than 1-0D (Tunnel diameter) dose not directly related to stability of tunnel, but the nearer a cavity location was, the larger displacement and stress of reinforcement occured within 0.25D.

• Asian-Australasian Journal of Animal Sciences
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• v.15 no.5
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• pp.637-642
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• 2002

Thirty Holstein calves were used to determine effects of age, environment and sex on blood metabolite concentrations during 1 to 90 d of age. Calves were weaned at 75 d of age. Environmental effects are grouped by the difference in month at birth and site of feeding. Blood samples were obtained every 2 or 3 d. The mean metabolite concentration every 3 d was used for the statistical analysis. Dairy bodyweight gain was not affected by environmental group and sex effect. Concentrations of plasma glucose, nonesterified fatty acids (NEFA), triglyceride, total cholesterol and total ketone changed with growth. These developmental changes in metabolite levels would be caused by ruminal maturation with increment of grain intake. Levels of plasma urea nitrogen, glucose, NEFA, triglyceride and total cholesterol drastically changed during a few weeks after birth, indicating that the physiological state in calves greatly changed during that time. Effects of the environmental group and sex were significant in almost all metabolites. Temperature influenced plasma metabolite concentrations. The plasma metabolite concentrations were affected more intensely by heat stress in the infant period than in the neonatal period.

• The Korean Journal of Physiology and Pharmacology
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• v.2 no.4
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• pp.427-433
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• 1998

In brain hypoxic-ischemia, an excess release of glutamate and a marked production of reactive oxygen species (ROS) occur in neuronal and non-neuronal cells. The present study investigated the effect of the biological antioxidants dihydrolipoic acid (DHLA) and lipoic acid (LA) on N-methyl-D-aspartate (NMDA)- and ROS-induced neurotoxicity in cultured rat cortical neurons. DHLA enhanced NMDA-evoked rises in intracellular calcium concentration ($[Ca^{2+}]_i$). In contrast, LA did not alter the NMDA-evoked calcium responses but decreased after a brief treatment of dithiothreitol (DTT), which possesses a strong reducing potential. Despite the modulation of NMDA receptor-mediated rises in $[Ca^{2+}]_i$, neither DHLA nor LA altered the NMDA receptor-mediated neurotoxicity, as assessed by measuring the amount of lactate dehydrogenase released from dead or injured cells. DHLA, but not LA, prevented the neurotoxicity induced by xanthine/xanthine oxidase-generated superoxide radicals. Both DHLA and LA decreased the glutathione depletion-induced neurotoxicity. The present data may indicate that biological antioxidants DHLA and LA protect neurons from ischemic injuries via scavenging oxygen free radicals rather than modulating the redox modulatory site(s) of NMDA receptor.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.819-835
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• 2009

In order to investigate the field application of selected stabilization methods(cover soil method, surface and total interval treatment of embankment method) on rice paddies contaminated by heavy metals, column test was carried out with heavy metal-contaminated soils collected from rice paddies around abandoned mine site. Columns were made by acrylic and filled with untreated soil, treated soil mixed with amendments(lime stone and steel refining slag) and uncontaminated cover soil according to the design report. Distilled water was discharged into the columns with the velocity of 1 pore volume/day. During test, pH, EC, and heavy metal concentration were measured in the regular term. The column test result showed that the selected stabilization methods were effective remediation method to stabilize heavy metals in paddy soils, but it was also expected that application of surface treatment methods was required the careful observation on pH variation due to the lowest increment.

• Journal of Wetlands Research
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• v.16 no.2
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• pp.275-280
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• 2014

Because ammonia in water body can cause water pollution as a result of generating ammonium ion, it is of importance in the management of water quality. This work performed to analyze the ammonium ion by measuring the color band length on the basis of modifying the indophenol method. When 1-naphthol was employed as a coloring agent, the maximum absorbance was shown near 720nm, where the proper injection was in the range of 0.5-1.5ml. About 80% of absorbance was observed after the color development was made within the 20 minutes. In the manufacturing of coloring agent, the proper concentration of NaOH was 1.5-2.5M, and the effect of pH on the color development is negligible. In addition, the color development was effectively in the region of room temperature.

• Archives of Pharmacal Research
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• v.29 no.10
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• pp.928-933
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• 2006

Percutaneous delivery of NSAIDs has advantages of avoiding hepatic first pass effect and delivering the drug for extended period of time at a sustained, concentrated level at the inflammation site that mainly acts at the joint and the related regions. To develop the new topical formulations of pranoprofen that have suitable bioadhesion, the gel was formulated using hydroxypropyl methylcellulose (HPMC) and poloxamer 407. The effects of temperature on drug release was performed at $32^{\circ}C$, $37^{\circ}C$ and $42^{\circ}C$ according to drug concentration of 0.04%, 0.08%, 0.12%, 0.16%, and 0.2% (w/w) using synthetic cellulose membrane at $37{\pm}0.5^{\circ}C$. The increase of temperature showed the increased drug release. The activation energy (Ea), which were calculated from the slope of lop P versus 1000/T plots was 11.22 kcal/ mol for 0.04%, 10.79 kcal/mol for 0.08%, 10.41 kcal/mol for 0.12% and 8.88 kcal/mol for 0.16% loading dose from the pranoprofen gel. To increase the drug permeation, some kinds of penetration enhancers such as the ethylene glycols, the propylene glycols, the glycerides, the non-ionic surfactants and the fatty acids were incorporated in the gel formulation. Among the various enhancers used, propylene glycol mono laurate showed the highest enhancing effects with the enhancement factor of 2.74. The results of this study suggest that development of topical gel formulation of pranoprofen containing an enhancer is feasible.

• Journal of The Korean Society of Agricultural Engineers
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• v.46 no.1
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• pp.107-117
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• 2004

Hourly monitoring data from Saemangeum estuary, which is expected to become freshwater, was analyzed to evaluate the water quality characteristics. Higher algal growth at spring season than winter influenced the high ratio of organic nitrogen to total nitrogen and concentration of chemical oxygen demand (COD). About 87.9％ and 59.7％ of organic nitrogen was observed at winter season and spring season, respectively. Daily salinity analysis at the mouth of two main rivers demonstrated that the Dongjin in river was more influenced by tidal effect and showed higher variation than the Mankyung river. The ratio of nitrogen to phosphorus (N/P ratio) was different with site (estuary versus sea area) and season (winter versus spring) remarkably. The N/P ratio was highest (32.74 ∼ 43.93) at estuary in winter and was lowest (1.78 ∼ 3.06) at sea in spring. The high N/P ratio at estuary area implies that phosphorus can be the limiting nutrient factor for algal growth as in general freshwater river, therefore, water quality management practice considering river characteristics rather might be needed in the Saemangeum estuary. The Saemangeum project is nationally recognized for its environmental issues, and especially water quality concern is a critical factor to make policy decision and further assessment with continued monitoring is strongly recommended.