• Journal of the Korean Chemical Society
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• v.55 no.6
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• pp.936-939
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• 2011

Thiamine hydrochloride (VB1) has been used as an acid catalyst in organic synthesis. One pot three component Biginelli condensation of dimedone, urea/thiourea and substituted aromatic aldehydes catalyzed by 10 mol % of thiamine hydrochloride (VB1) in solvent free condition under microwave irradiation in good to excellent yields has been investigated. Utilization of microwave irradiation, simple reaction conditions, short reaction time, ease of product isolation, and purification makes this manipulation very interesting from an economic and environmental perspective.

• Proceedings of the Korean Magnetic Resonance Society Conference
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• 2000.08a
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• pp.41-41
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• 2000

• Applied Chemistry for Engineering
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• v.9 no.6
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• pp.864-869
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• 1998

In this work, the solid-liquid equilibria (SLE) of some aromatic organic mixtures including benzene, widely used as an industrial solvent, were measured by static method using our own made experimental apparatus. The accuracy and reproducibility of apparatus were tested by comparing experimental results with literature values for 1-dodecanol+cyclohxane and benzene + p-xylene systems. The SLE for new binary systems of benzene+aniline, benzene+nitrobenzene, p-xylene+cyclohexane were measured afterwards and compared with the calculated values by modified UNIFAC(Dortmund) equation.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.174-174
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• 2006

By condensing two different functional monomers, highly fluorescent aromatic polymers were prepared to produce a conjugated- conjugated spacer-type copolymer or conjugated-non-conjugated spacer-type copolymer. As synthesized polymers were soluble in an organic solvent and showed significantly enhanced optical properties compared to its monomer. Variation in the monomer composition afforded polymers having multifunctionaility such as photochromic-fluorescent polymers. Transparent thin films of the polymer as a solid medium were prepared using spin coating method and fabricated as a photoswitch, which showed photo-induced conductivity switching properties depending on the core monomeric unit in the polymers.

• Journal of the Korean Society of Safety
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• v.15 no.3
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• pp.83-87
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• 2000

Combustion characteristics of immobilized benzene and toluene in sands were studied. Experiments were performed by burning benzene and toluene immobilized on sands(particle size 0.1~0.5mm) to measure combustion rate and combustion temperature. The longer time from ignition to extinguishment was resulted from the larger particle size exhibited the higher mass burning rate. Of aromatic compounds tested the relative magnitude of facilitation of combustion was benzene and toluene. Combustion temperature of benzene and toluene without regard to the types of benzene and toluene was not increased with smaller sand. However, with larger sands, combustion temperature of benzene and toluene were increased by 50~$100^{\circ}C$ and the highest combustion temperature was obtained with larger sands.

• Journal of the Korean Chemical Society
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• v.38 no.10
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• pp.726-733
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• 1994

Supercritical fluid extraction (SFE) followed by gas chromatographic separation and mass spectrometric (MS) detection were used in rapid analysis of polycyclic aromatic hydrocarbons (PAH's) in air particulate material extracted for 30 min with 10 ml of supercritical $N_2O$ without another sample preparation step. Two samples, urban dust in Seoul area and a certified air particulate reference material 1649 supplied by the NBS (National Bureau of Standards), were processed for the purpose of evaluating extraction and analysis methods. As a result, the quantitative recovery of PAH's in the SFE method was relatively lower than conventional organic solvent extraction methods, but reproducibility was resonable, and analysis time was reduced remarkably. The method has proved to be suitable for monitoring of PAH's in air particulate material.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.9 no.1
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• pp.156-172
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• 1999

Potential chemical hazards encountered in painting operation of four shipyards and a ship-repair shop were investigated through the material safety data sheets (MSDS). Material safety data sheets (MSDS) for 307 paints, 50 thinners and 34 binders were collected and reviewed. It was shown that various organic solvents such as aromatic hydrocarbons, aliphatic hydrocarbons, ketones, alcohols, glycols, glycol ether acetates and esters were contained in painting materials. Of these solvents, xylene was found in the largest number of painting materials. sixty percent of the thinners contained xylene in the contents of 20-100%. Other most frequently found solvents were 1-methoxypropanol, 1-methoxypropyl acetate, n-butanol, methyl isobutyl ketone, toluene, isopropanol, and n-butyl acetate, etc. Glycol ethers such as 2-methoxyethanol (2-ME), 2-methoxyethyl acetate (2-MEA), 2-ethoxyethanol (2-EE), 2-ethoxyethyl acetate (2-EEA) and 2-butoxyethanol (2-BA) were regarded as having the potential to cause adverse reproductive effects, embryotoxic effect and hematotoxic effects, and were found in some epoxy panting materials. Coal tar pitch was included in some paints(13%) where polynuclear aromatic hydrocarbons (PAHs) could be contaminated. Inorganic pigments such as lead chromate and zinc potassium chromate were found in some paints (8%). The epoxy resin based paints, which may contain isocyanates such as toluene diisocyanates and hexamethylene diisocyanates causing potential sensitization and asthma to upper respiratory organ, were mostly used in the shipyards. The constituents in the MSDS were significantly different from the results analyzed using gas chromatography/mass detector: minor constituents or impurities were omitted in many MSDS. In conclusion, xylene was the most frequent organic solvent in painting materials, and glycol ethers, including 2-ME, 2-MEA, 2-EE, 2-EEA and 2-BA, were found some products. Also, painting workers may be exposed to PAHs, lead, chromate, isocyanates, organic tin and other various chemicals. The compositions of chemicals in painting materials were variable significantly, and the hazards were changed. These facts should be considered in environmental monitoring and control of the hazards.

• Proceedings of the Membrane Society of Korea Conference
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• 1993.10a
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• pp.7-12
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• 1993

Preparation of asymmetric polyimide membranes by the phase inversion process was investigated to develop ultrafiltration, reverse osmosis and pervaporation membranes for organic solutions, using a commercially available solvent-soluble polymaide. The influences of the various factors such as the composition of a cast solution, casting conditions, gelating solutions and others on membrane structure and performance were studied in detail, and it was made clear that a wide variety of asymmetric polyimide membranes ranging from UF to RO for organic solutions could be prepared from the aromatic polyimide used. It was also found that the chemical stability and separation performance of the asymmetric polyimide membranes could be improved by annealing in a liquid or a vacuum at above 200$\circ$. The membrane annealed at 300$\circ$ in a vacuum exhibited the separation factor $\alpha(H_2O/EtOH)$ of 900 with the flux of 1.0 kg/$m^2\cdot h$ at 60$\circ$C for an aqueous ethanol solution of 95 vol%.

• Safety and Health at Work
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• v.2 no.4
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• pp.365-374
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• 2011

Objectives: This study was designed to investigate whether long-term, low-level exposure to monocyclic aromatic hydrocarbons (MAHs) induced insulin resistance. Methods: The subjects were 110 male workers who were occupationally exposed to styrene, toluene, and xylene. One hundred and ten age-matched male workers who had never been occupationally exposed to organic solvents were selected as a control group. Cytokines, which have played a key role in the pathogenesis of insulin resistance, and oxidative stress indices were measured. Assessment of exposure to MAHs was performed by measuring their ambient levels and their urinary metabolites in exposed workers, and the resulting parameters between the exposed group and non-exposed control groups were compared. Results: There was no significant difference in general characteristics and anthropometric parameters between the two groups; however, total cholesterol, fasting glucose, fasting insulin, and homeostasis model assessment of insulin resistance levels were significantly higher in the exposed group. Phenylglyoxylic acid levels showed significant association with tumor necrosis factor-${\alpha}$, total oxidative status, and oxidative stress index via multiple linear regression analysis. Further, there was a negative correlation between methylhippuric acid levels and total anti-oxidative capacity, and there was a significant relationship between MAHs exposure and fasting glucose levels, as found by multiple logistic regression analysis (odds ratio = 3.95, 95% confidence interval = 1.074-14.530). Conclusion: This study indicated that MAHs increase fasting glucose level and insulin resistance. Furthermore, these results suggested that absorbing the organic solvent itself and active metabolic intermediates can increase oxidative stress and cytokine levels, resulting in the changes in glucose metabolism and the induction of insulin resistance.

• Bulletin of the Korean Chemical Society
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• v.33 no.8
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• pp.2724-2730
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• 2012

A new heterogeneous acidic catalyst was successfully prepared by impregnation of silica (Aerosil 300) by an acidic ionic liquid, named 1-(4-sulfonic acid)butylpyridinium hydrogen sulfate [$PYC_4SO_3H$][$HSO_4$], and characterized using FT-IR spectroscopy, the $N_2$ adsorption/desorption analysis (BET), thermal analysis (TG/DTG), and X-ray diffraction (XRD) techniques. The amount of loaded acidic ionic liquid on Aerosil 300 support was determined by acid-base titration. This new solid acidic supported heterogeneous catalyst exhibits excellent activity in the synthesis of 2-aryl-2,3-dihydroquinazolin-4(1H)-ones by cyclocondensation reaction of 2-aminobenzamide with aromatic aldehydes under solvent-free conditions and the desired products were obtained in very short reaction times with high yields. This catalyst has the advantages of an easy catalyst separation from the reaction medium and lower problems of corrosion. Recycling of the catalyst and avoidance of using harmful organic solvent are other advantages of this simple procedure.