• Journal of Microbiology
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• v.33 no.3
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• pp.178-183
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• 1995

The recombinant plasmid of pCU103 constructed by cloning pcbCD genes in pBluescript SK(+) was studied for the effect of temperature on its persistence in different waters by the methods of electrophoresis, Southern hybridization, quantification, and transformation. The plasmid was very rapidly degraded out in non-sterile FW water without regards to water temperature, probably due to the effect of biochemical factor such as nucleases. The pCU103 was most persistent at 4$^{\circ}C$ in any water environments, moderately persistant at 15$^{\circ}C$ but least stable at 3$0^{\circ}C$ such results could be explained by the facts that hydrogen bonds in double-stranded plasmid DNAs become unstable and that nucleases are activated by increasing temperature. The intact structure of pCU1-3 was generally observed by gel electrophoresis under the conditions which the plasmid should be 2.0 ng/$\mu\textrm{l}$ or higher in concentration and that about 10$^2$ CFU/ml or more transformant cells should be recovered.

• Journal of Microbiology
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• v.34 no.2
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• pp.144-150
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• 1996

During growth of the genetically engineered E. coli CU103 in different media, extracellular DNAs released from the cells were studied. The extracellular DNAs released in the medium were concentrated by an thanol precipitation method and then quantified by a fluorescence method using Hoechst 33258. The released extracellular DNAs were also examined by gel electrophoresis and identified by Southern hybridization for the cloned pcbCD genes. The chromosomal DNAs and recombinant plasmid containing the cloned genes were observed to be released in an exponential growth phase. In Luria-Bertani (LB) broth and MM2-GLUCOSE, 210 and 69 ng/ml of DNAs were detected, respectively, after 3-4 days incubation at $30^{\circ}C$ and at pH 7.0. But the released DNAs were measured to be about 10-15 ng/ml in filtered river water (FW) and Tris-EDTA (TE). The at both $15^{\circ}C$ and $4^{\circ}C$, but the released DNAs were more easily degraded at the higher temperature. The extracellular DNAs were produced about 2 times more at pH 7.0 than at both pH 5.0 and pH 9.0 in MM2-glucose medium at $30^{\circ}C$. Therefore, the extracellular DNAs were found to be released actively from the cells during growth in liquid media.

• Korean Journal of Materials Research
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• v.15 no.8
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• pp.528-535
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• 2005

It is inclined to increase that use of hazardous substances such as lead(Pb), mercury (Hg), cadmium(Cd) etc. are prohibited in the electronics according to environmental friendly policies of an advanced nation for protecting environment of earth. As this reasons, many researches for ensuring the reliability were proceeding in Pb free soldering process. n the flux remains on the PCB(printed circuit board) in the soldering process or the electronics exposed to corrosive environment, it becomes the reasons of breakdown or malfunction of the electronics caused by corrosion. Therefore in this studies we researched the polarization and Tafel properties of Sn40Pb and SnCu system solders based on the electrochemical theory. The experimental polarization curves were measured in distilled ionized water and 1 mole $3.5 wt\%$ NaCl electrolyte of $40^{\circ}C$, pH 7.5. Ag/AgCl and graphite were utilized by reference and counter electrodes, respectively. To observe the electrochemical reaction, polarization test was conducted from -250mV to +250mV. From the polarization curves composed of anodic and cathodic curves, we obtained Tafel slop, reversible electrode potential(Ecorr) and exchange current density((cow). In these results, we compared the corrosion rate of SnPb and SnCu solders.

• The Korean Journal of Ecology
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• v.18 no.1
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• pp.109-120
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• 1995

As the genetically modified microorganisms (GMMs) and their recombinant plasmid DNAs could be released into natural environments, their stabilities and impacts to indigenous microorganisls have become very importhant research subjects concerning with environmental and ecological aspects. In this study, the genetically modified E. coli CU103 and its recombinant pCU103 plasmid DNA, in which pcbCD genes involving in degradation of biphenyl and 4-chlorobiphenyl were cloned, were studied for their survival and stability in several different waters established under laboratory conditions. E. coli CU103 and its host E. coli XL1-Blue survived longer in sterile distilled water (SDW) and filtered autoclaved river water (FAW) than in filtered river water (FW). A lot of extracellular DNAs were released from E. coli CU103 by lytic action of phages in FW and the released DNAs were degraded by DNase dissolved in the water. Such effects of the factors in FW on stability of the recombinant pCU103 plasmid were also observed in the results of gel electrophoresis, quantitative analysis with bisbenzimide, and transformation assay. Therefore, the recombinant plasmids of pCU103 were found to be readily liberated from the genetically modified E. coli CU103 into waters by normal metabolic processes and lysis of cells. And the plasmid DNAs were quite stable in waters, but their stabilities could be affected by physicoKDICical and biological factors in non-sterile natural waters.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.7
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• pp.377-386
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• 2016

The purposes of this research are to examine soil pollution in the nation and to explore the contaminated soil management of the public housing agency in public land for residential development. In so doing, the primary and secondary data were utilized, the former made use of the public data annually released by the Korea Ministry of Environment, and the latter relied on a self-administerd questionnaire survey conducted in the staff of the public housing agency, particularly those in charge of soil contamination in large-scale land, housing and urban development projects. The findings reveal that the national concentrations of 21 inorganic and organic soil contaminants (e.g., Cd, Cu, As, Hg, Pb, Cr, Zn, Ni, F, P, PCB, CN, Phenol, BTEX, TPH, TCE, PCE, Benzo(a)pyrene, and pH) in the land were extracted to be well below the risk level designated by the statutory guidance while industrial areas had them at a relatively modest level. In addition, the survey results indicate that the public housing agency didn't establish specific and clear guidelines for soil pollution and its remediation in the residential land development, so that contaminated sites have been primarily remediated by outsourcing companies. As the unexpected occurrence of contaminated sites causes the incurring expenses added to total project budget, the provision of both professional training and on-site manuals with the sufficient information on techniques and methods of soil contamination is critical to promptly and systematically deal with soil pollution.