• Polymer(Korea)
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• v.27 no.3
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• pp.217-225
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• 2003

We fabricated the 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU, carmustine)-loaded PLGA wafers containing poly(N-vinylpyrrolidone) (PVP) or tedium chloride (NaCl) in order to control the release profile of drug in special shape (3 in diameter, 1 mm in thickness) by direct compression method. In vitro release profiles of BCNU could be controlled by additives contained in the wafers. Initial release amount, release rate and duration of BCNU could be controlled with presence of PVP or NaCl. In vitro antitumor activity accessed using 9L gliosarcoma cell line has been evaluated by assaying the viability of cells treated with BCNU released from the wafers containing additives resulting in continuous growth inhibition of 9L gliosarcoma tumor cells. Specially, the continuous growth inhibition of BCNU-loaded PLGA wafers containing additives was more effective than that of non-additive BCNU-loaded PLGA wafers. The cytotoxic effect of the drug from the wafers containing NaCl as compared to wafers containing PVP was more enhanced.

• Fire Science and Engineering
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• v.26 no.2
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• pp.75-83
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• 2012

An experimental study was conducted to investigate the effects of change in heat release rate on unsteady fire characteristics of under-ventilated fire in a semi-closed compartment. A standard doorway width of the full-scale ISO 9705 room was modified to 0.1 m and the flow rate of heptane fuel was increased linearly with time using a spray nozzle located at the center of enclosure. Temperature, heat flux, species concentrations and heat release rate were continuously measured and then global equivalence ratio (GER) concept was adopted to represent the unsteady thermal and chemical characteristics inside the compartment. It was observed that there was a significant difference in unsteady behavior between global and local combustion efficiency, and the GERs predicted by ideal and measured heat release rate were also shown different results in time. The unsteady behaviors of temperature, heat flux and species concentrations were represented well using the GER concept. It was important to note that CO concentration was gradually decreased with the increase in GER after reaching its maximum value in the range of 2.0~3.0 of global equivalence ratio. In addition, the experimental data on unsteady thermal and chemical behaviors obtained in a semi-closed compartment will be usefully used to validate a realistic fire simulation.

• Journal of Wetlands Research
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• v.22 no.3
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• pp.171-177
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• 2020

To improve the nitrogen reduction capability of stormwater treatment systems subjected to intermittent saturation, organic materials are often added as filter media. However, these materials can be an additional source of organic carbon and increase the chemical oxygen demand (COD) in the outflow. In this study, different types of organic filter media were subjected to a batch leaching test to observe and quantify the release of COD. Results reveal that the initial pH of the tap water used for soaking which is 7.5-7.7 is conducive to the release of organics from the media to the leachate. The highest amount of COD released was observed in yard clippings and woodchip followed by compost and bark mulch. The leaching of organics also increased as the size of the media decreases due to higher surface area per volume. In addition, empirical regression analysis predicted that COD from these organic media will be exhausted from the material in 3-5 months to up to 26 months depending on the type of media. The results of this study can serve as a guide in estimating the potential release of COD in organic media in order to ensure their safe application in stormwater treatment facilities.

• Polymer(Korea)
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• v.31 no.5
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• pp.447-453
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• 2007

In this study, we fabricated recrystallized PLGA (rPLGA) particles using the vacuum drying method. In order to investigate an applicability of the rPLGA particles for controlled release system of 5-fluorouracil (5-FU) loaded PLGA wafer, we prepared three different wafers using; 1) untreated PLGA (uPLGA), 2) rPLGA, and 3) uPLGA and rPLGA (4 : 1, 1 : 1 or 1 : 4). The rPLGA particles were characterized using NMR, IR and GPC to compare with uPLGA particles. The surface and cross section morphology of the prepared wafers were observed by the scanning electron microscope. The release profile of the 5-FU loaded wafer was measured by HPLC. The 5-FU/rPLGA wafer released the incorporated 5-FU in a sustained manner with low initial burst compared to 5-FU/uPLGA. These results showed that the ratio of pure PLGA/recrystallized PLGA can affect the release behaviors.

• Elastomers and Composites
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• v.37 no.3
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• pp.159-169
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• 2002

The improvement of flame retardancy of the foams based on NBR/GTR compounds was conducted by formulating various materials i.e. NBR, GTR, inorganic and phosphorus containing flame retardants, foaming agent, cross-linking agent and activator. The foaming properties, morphology, smoke density and flame retardancy of the specimens were investigated using SEM, LOI tester, smoke density control system and cone calorimeter. The phosphorus containing flame retardant reduces heat release rate, increases the limiting oxygen index and a char formation. The inorganic flame retardant increases the limiting oxygen index and reduces heat release rate with an increased CO yield by char formation, and smoke suppressing effect. The formed char seemed to intercept the oxygen transport and heat transfer into the core area. When the composition ratios of the compounds of NBR/GTR were $100{\sim}80/0{\sim}20 wt.%$, and the ratios of the rubbers/flame retardants were $1/1.55{\sim}3.60 wt.%$, we could developed foams with low heat release rate, high limiting oxygen index($28.0{\sim}39.3$), closed or semi-closed cell of uniformity and reasonable expandability($225{\sim}250 %$).

• Polymer(Korea)
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• v.32 no.3
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• pp.284-289
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• 2008

Polymer is a critical component of local drug delivery to prevent restenosis. This study tested whether poly(n-butylmethacrylate)(PBMA) and poly(3-hydroxybutyrate-co-4-hydroxybutyrate)(PHA) was candidates for this purpose. In vitro release of paclitaxel from PBMA and PHA loaded with 10% paclitaxel exhibited a triphasic release profile, with a fast initial and intermediate second phase followed by a slow release phase. Perivascular delivery of paclitaxel using these films inhibited neointimal hyperplasia in balloon-injured rat carotid arteries. The paclitaxel-loaded PBMA or PHA groups showed significant neointimal formation reductions versus the control groups (PBMA vs control: $0.03{\pm}0.02$ vs $0.10{\pm}0.01\;mm^2$, p<0.05; PHA vs control: $0.04{\pm}0.03$ vs $0.09{\pm}0.01\;mm^2$, p<0.05). This study suggests that PBMA and PHA could be good candidate polymers of local drug delivery to prevent restenosis. Perivascular delivery using these films represents a possible approach for prevention of restenosis. These can be candidate polymers for drug eluting stents.

• Journal of Sensor Science and Technology
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• v.6 no.1
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• pp.35-42
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• 1997

The optical biosensor using the electrically controlled release of reactive reagent is developed for the detection of peroxide. Rapid degradation of polymer complex of PEOx and PMAA occurs as the applied current increases and thus released amount of HPA increases. The degradation velocity of polymer and the amount of HPA released are linearly proportional to the applied current. Peroxide is reacted with the released reagent by peroxidase and then the product, a fluorescent dimer DBDA, is formed. The monochromic light from light source (150W Xe arc ramp) excites the DBDA and the excited light is transmitted through an optical fiber to be detected by a photodiode array. The change of fluorescence intensity is related to the change of peroxide concentration. The peroxidase is entrapped in Ca-alginate get on the inner surface. The biosensor has the linear signal range of 0.025mM-10.mM peroxide. By applying the step function of peroxide, reproducibility of biosensor has been investigated. The mathematical model is constructed by the combination of enzyme kinetics with reactor flow model. Good agreement is obtained between the experimental result and model prediction in the sensor signal.

• KSBB Journal
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• v.23 no.5
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• pp.452-459
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• 2008

To obtain maximal efficacy with minimal systemic side-effects, many studies have been carried out to achieve the controlled release of 5-fluorouracil (5-FU). In this study, biodegradable poly(L-lactide) (L-PLA) microparticles containing 5-FU were prepared by a process, called aerosol solvent extraction system (ASES), utilizing supercritical carbon dioxide. The effects of various organic solvents, drug/polymer feeding ratio, polymer molecular weight, and blending with the same polymers with different molecular weights on the formation of 5-FU loaded microparticles were investigated under a predetermined operating condition from our previous study. The drug recovery, entrapment efficiency, and in vitro drug release kinetics were determined by HPLC assays. The drug recovery obtained from the ASES process was found to be very high, whereas the drug entrapment efficiency was considerably low in all the experiments due to the poor affinity between L-PLA and 5-FU. These results indicated that the precipitation rate of L-PLA might be quite different from that of 5-FU so that there was little chance to form 5-FU loaded L-PLA microparticles.

• Korean Chemical Engineering Research
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• v.43 no.5
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• pp.632-636
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• 2005

In this work, the effect of chemical treatments on surface properties of SiC was investigated in thermal and mechanical interfacial behaviors of SiC/PMMA nanocomposites. The acid/base value, contact angles, and FT-IR analysis were performed for the study of surface characteristics of the SiC studied. The thermal stabilities of the SiC/PMMA nanocomposites were investigated by thermogravimetric analysis (TGA). Also the mechanical interfacial properties of the composites were studied in critical stress intensity factor ($K_{IC}$) and critical strain energy release rate ($G_{IC}$) measurements. As a result, the acidically treated SiC (A-SiC) had higher acid value than that of untreated SiC (V-SiC) or basically treated SiC (B-SiC). The acidic solution treatment led to an increase in surface free energy of the SiC, mainly due to the increase of its specific component. Thermal and mechanical interfacial properties of the SiC/PMMA nanocomposites, including initial decomposition temperature (IDT), $K_{IC}$, and $G_{IC}$ had been improved in the acidic treatment on SiC. This was due to the improvement in the interfacial bonding strength, resulting from the acid-base interfacial interactions between the fillers and polymeric matrix.

• Journal of Environmental Health Sciences
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• v.45 no.5
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• pp.465-473
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• 2019

Objectives: A variety of industries handling hazardous chemicals emit odorous substances. Based on the emission characteristics of major odor substances from the results of hazardous chemical substance emissions, we will define basic data for improving the management methods of odorous substances. Methods: A survey of hazardous pollutant emissions for 2010-2016 was conducted through the Pollutant Release and Transfer Register homepage. Eight kinds of designated odor substances (ammonia, hydrogen sulfide, dimethyl disulfide, acetaldehyde, styrene, toluene, xylene, methyl ethyl ketone) provided the study subjects. The status of chemical accidents for the target substances was analyzed using the Chemistry Safety Clearing-house system. Results: From 2010 to 2016, it was found that more than 30% of businesses that emitted odorous substances accounted for more than 50% of the total emissions of the eight substances. Emissions of xylene, toluene, methyl ethyl ketone, and ammonia were found, in that order, and they made up more than 90% of the total emitted. By region, about 70% of odorous substances were emitted in the top-four regions: Gyeongsangnam-do Province, Ulsan, Gyeonggi-do Province, and Jeollanam-do Province. Conclusion: Recently, the amount of chemical emissions has been continuously increasing, including those that can cause odor. Odorous substances can be a serious risk to the lives of local residents. Systematic research is needed for the health protection of residents.