• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.6
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• pp.673-680
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• 2017

Research and commercialization of wood chips-urethane resin mixtures as paving materials for park trails and tourist attractions are underway. The aim of this study was to expand the use of such paving materials to the playgrounds, where vigorous physical movements occur frequently. For this purpose, the physical properties and safety of the paving material, in which some or all of the wood chips(passing through a 10mm sieve and remaining in a 3mm sieve) were replaced with sawdust, were studied experimentally. Strength, elastic modulus, slip resistance, shock absorption and heavy metal content tests were carried out by varying the mixing ratio of urethane resin, sawdust and wood chip. As a result, in the case of wood chip-resin mixtures with mass ratios of the resin to total mass of sawdust and wood chips of 1.0 and 1.2 and having a ratio of sawdust mass to total mass of sawdust and wood chips of 0-0.4, it was found that the properties satisfied KS F 3888-2. On the other hand, in case of using sawdust only as a woody material, the shock absorbability was below standard, and the mass ratio of resin to sawdust required 1.2 or more to ensure the specified tensile strength.

• Journal of Environmental Health Sciences
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• v.37 no.4
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• pp.279-288
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• 2011

Objectives: This study investigated the levels and components of floor-settled dust in two elementary schools located at different sites (one near the Shihwa industrial complex and the other in a rural area) in order to evaluate the amounts of trace metal elements (As, Cd, Co, Cr, Cu, Ni, Pb and Zn) and microorganisms. Methods: Over twenty settled-dust samples were collected from the two elementary schools. Trace metal elements were extracted from the dust using hydrochloric acid and nitric acid, and the amounts were measured by ICP-OES. Microbiological analysis was performed by bacterial culturing using R2A medium and denaturing gradient gel electrophoresis (DGGE). Results: The results showed that the amounts of three metal elements (Cr, Pb, and Zn) were significantly different between the schools (${\alpha}$=0.05, p<0.04). In addition, microbial communities in each school were highly correlated with one another. Among the identified microorganisms, a number of potentially opportunistic microorganisms, including antibiotic-resistant bacteria such as Acinetobacter baumannii, were found. Conclusions: This study will provide preliminary data for assessing levels and types of chemical and microbiological agents in elementary schools and for further evaluating human health risks associated with the agents.

• Korean Journal of Veterinary Research
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• v.30 no.2
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• pp.203-214
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• 1990

A total of 166 strains of Salmonella (S) typhimurium var copenhagen isolated from pigeons (164 strains) and aquatic birds (2 strains) were examined for the biochemical characteristics and plasmid profiles. All the strains were sensitive to ampicillin, chloramphenicol, gentamicin, kanamycin and sulfadimethoxine. But 13 strains(7.8%) were resistant to streptomycin (Sm), 2 (1.2%) to tetracycline, 2 (1.2%) to rifampicin, and 1 (0.6%) to nalidixic acid. Among drug resistant strains, only one strain resistant to Sm contained conjugative R plasmid which was fertility inhibition and incompatibility group $I_{\alpha}$. All the strains were sensitive to cobalt chloride, cupric sulfate, lead nitrate, mercuric chloride and silver nitrate. Of 166 isolates, 6 (3.6%) were resistant to sodium arsenate and 1 (0.6%) to potassium tellurite. Among 166 isolates, 1 (0.6%) was colicinogenic, 12 (7.2%) sucrose fermenters, and 166 (100%) maltose fermenters. Plasmid profiles were confirmed as being 4 or 5 plasmids, and their molecular weight ranged 3.2 to 60 megadalton (MD). All the strains harbored 60 Md plasmid. There are three patterns by the plasmid profile, 150 isolates (90.4%) were pattern I (3.2, 3.5, 33, 60Md), 14 (8.4%) pattern II (3.2, 3.5, 29, 60Md), and 2 (1.2%) pattern III (4.2, 7.8, 8.5, 15, 60Md). S typhimurium var copenhagen strains containing 60Md plasmid were resistant to killing by 90% normal guinea pig serum.

• Journal of Environmental Health Sciences
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• v.36 no.3
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• pp.236-246
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• 2010

In preparative anti-corrosive coating experiments, polyaniline was obtained by reacting an oxidizing agent with the monomer aniline. Further, the primer coating was prepared using a variety of widely-used materials such as urethane resin. For the top coating, epoxy resin and acrylic urethane resin were used. Characteristics of the coatings were assessed according to KS and ASTM specifications, and the structure of the polyaniline was characterized using FT-IR and TGA. For analysis of anti-corrosive properties in salt-spray experiments, measurements of the oxidation state of iron and surface atomic analysis were conducted using XPS and SEM-EDX. Unlike general anti-corrosive coatings which exhibit anti-corrosive effects only as a primer coating, the anti-corrosive coatings using polyaniline as the anti-corrosive pigment showed a marked synergistic effect with the top coatings. In other words, the top coatings not only produce a fine view effect, but also increase, through interaction with the primer coatings, the resistance to diffusion of corrosive factors from the external environment. It was also found that, unlike the heavy metal oxide-forming layer of the passive barrier alone, the polyaniline anti-corrosive pigment oxidized iron at the interface with the iron substrate to form a passive barrier in the oxidic layer, and itself formed a potential barrier layer with anti-corrosive factors from the external environment. Although the passive layer was damaged, the damaged area did not become completely oxidized iron; on the contrary, it showed a tendency to reduction. This can be interpreted such that a passive layer is formed again on the damaged area, and that at the same time there is a tendency to self-healing.

• Ecology and Resilient Infrastructure
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• v.2 no.3
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• pp.237-246
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• 2015

Heavy metal pollution in soil, such as lead contamination, has become an area of interest in Korea because of urbanization and atmospheric deposition from neighboring countries. Therefore, in this research, eco-physiological responses such as chlorophyll contents, antioxidant enzyme activity, photosynthetic rate, biomass and phytoaccumulation abilities were investigated for 4 commonly used native roadside tree species to suggest suitable tree species to cope with lead contamination. The target species, Ginkgo biloba, Prunus yedoensis, Zelkova serrata and Chionanthus retusus showed lead toxicity by significant changes of chlorophyll contents and antioxidant enzyme activities on treatments over 200 mg Pb/kg. However, biomass and photosynthetic rates only showed significant responses of plants in the highest level (5,000 mg/kg) treatment. Especially, G. biloba did not show any significant changes of antioxidant enzyme activity, photosynthetic rate, and biomass even in the highest level treatment. In low level - environmentally realistic treatments, G. biloba and P. yedoensis showed the highest phytoaccumulation rate of lead from soil. Selecting and planting species like G. biloba which have good phytoaccumulation abilities and resistance to lead contamination by further research will be required to deal with emerging lead contamination.

• Journal of Microbiology and Biotechnology
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• v.29 no.2
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• pp.274-282
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• 2019

Mercury-resistant ($Hg^R$) bacteria were isolated from heavy metal polluted wastewater and soil collected near to tanneries of district Kasur, Pakistan. Bacterial isolates AZ-1, AZ-2 and AZ-3 showed resistance up to $40{\mu}g/ml$ against mercuric chloride ($HgCl_2$). 16S rDNA ribotyping and phylogenetic analysis were performed for the characterization of selected isolates as Bacillus sp. AZ-1 (KT270477), Bacillus cereus AZ-2 (KT270478) and Bacillus cereus AZ-3 (KT270479). Phylogenetic relationship on the basis of merA nucleotide sequence confirmed 51-100% homology with the corresponding region of the merA gene of already reported mercury-resistant Gram-positive bacteria. The merE gene involved in the transportation of elemental mercury ($Hg^0$) via cell membrane was cloned for the first time into pHLV vector and transformed in overexpressed C43(DE3) E. coli cells. The recombinant plasmid (pHLMerE) was expressed and the native MerE protein was obtained after thrombin cleavage by size exclusion chromatography (SEC). The purification of fusion/recombinant and native protein MerE by Ni-NTA column, dialysis and fast protein liquid chromatography (FPLC/SEC) involved unfolding/refolding techniques. A small-scale reservoir of wastewater containing $30{\mu}g/ml$ of $HgCl_2$ was designed to check the detoxification ability of selected strains. It resulted in 83% detoxification of mercury by B. cereus AZ-2 and B. cereus AZ-3, and 76% detoxification by Bacillus sp. AZ-1 respectively (p < 0.05).

• Composites Research
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• v.29 no.3
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• pp.111-116
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• 2016

The tilting pad journal bearing for the turbo compressor application has a role to support high speed and heavy loading rotor. White metal has been widely used for the bearing material but the conventional bearing is immediately suspended and induces serious serious damage to the rotor under the unexpected oil cut situation or the insufficient oil film formation. The carbon fiber reinforced composite having high specific stiffness, specific strength and excellent tribological characteristics can solve these seizure problems. In this work, the study on the durability of high thermal resistance carbon fiber/epoxy composite tilting pad journal bearing under oil cut situation was conducted. The material properties of the composite materials including tensile, compressive and interlaminar properties were measured at room and high temperature of oil cut situation. To investigate the possibility of failure of composite tilting pad journal bearing under oil cut situation, the stress distribution of the composite bearing was analyzed via finite element analysis and the Tsai-Wu Failure index was calculated. To verify the failure analysis results, the oil cut tests for the composite tilting pad journal bearing were conducted using industrial test bench.

• Applied Microscopy
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• v.32 no.4
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• pp.411-419
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• 2002

Metallothionein (MT) is a family of ubiquitous, low molecular weight ($6,000{\sim}7,000D$), cysteine-rich ($30{\sim}35%$) inducible protein with a high affinity to metal ions and has no aromatic amino acids and histidine. Some of the known functions of MT include detoxification of heavy metals and alkylating agents and neutralization of free radicals. Also, this protein has been reported to involve in tumor pathophysiology and therapy resistance. MT expression may affect a number of cellular processes including gene expression, apoptosis, proliferation and differentiation. Many reports on the physiological and biochemical properties of MT have been published, but ultrastructural reports on the localization of MT in human gastric cancer tissues are extremely rare. The present study was undertaken to examine the ultrastructural features and the localization of MT within the gastric adenocarcinoma. Ultrastructures of gastric cancer cells were characterized by the high nuclear cytoplasmic ratio, the interdigitation between cells, the irregular nucleus containing much heterochromatin and the wide distribution of free ribosomes in the cytoplasm. Immunohistochemical reaction for MT was prominent in the gastric adenocarcinoma. And the immunogold labellings were more prominent within the nucleus than the cytoplasm. Particularly, immunogold particles were numerously seen at nulcleolus or nucleolar associated heterochromatin. These results suggest that MT expression by gastric cancer cells is associated with cell proliferative activity and is possibly synthesized in the cytoplasm, and then the protein is transported into the nucleus to participate in any transcriptional steps.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.1
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• pp.200-207
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• 2019

Cement is one of the most commonly used materials in the construction and civil engineering industry. However, emissions of carbon dioxide generated during the production of cement have been linked to climate change and environment pollutants. In order to replace cement, many studies have been actively performed research to utilizing Blast Furnace Slag(BFS), which is a byproduct of the steel industry. This study aims to investigate the physiochemical properties of the BFS powder based grout to determine whether it can be used as an environment-friendly grout material. As a fine powder, BSF can be used instead of cement grout due to its potential hydraulic property. BSF has also been known for its ability to strengthen materials long-term and to densify the internal structure of concrete. In order to investigate the physicochemical properties of the BFS powder based grout as a grout material, in this study assessment tests were performed through a gel-time measurement, uniaxial compressive strength, and chemical resistance tests, and heavy-metal leaching test. Characteristics and advantages of the slag were studied by comparing slag and cement in various methods.

• Korean Journal of Microbiology
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• v.55 no.1
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• pp.69-73
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• 2019

During screening of microbes for compounds having cosmetic benefits, we isolated Marinobacter salarius HL2708#2 from lava seawater on Jeju Island, Republic of Korea. The complete genome sequence was determined. Strain HL27080#2 features a circular chromosome of 4,304,603 bp with 57.21% G+C content and a 244,163 bp plasmid with 53.14% G+C. There were 4,180 protein coding sequences identified, along with 49 transfer RNA and 18 ribosomal RNA noncoding genes. The genome harbored genes for the utilization of alcohol, maltose/starch, and monosaccharide as sole carbon sources. Genes responsible for halophilic characteristics and heavy metal resistance could be annotated, as well as aromatic and alkane hydrocarbons. Contrary to the prior report that M. salarius is negative for nitrate and nitrite reduction, nitrate/nitrite reductase along with nitrate/nitrate transporters and nitronate monooxygenase were evident, suggesting that strain HL2708#2 may be able to denitrify extracellular nitroalkenes to ammonia.