• Analytical Science and Technology
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• v.16 no.2
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• pp.143-151
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• 2003

In the present study, we made measurements of PM-bound metal concentrations from seven different urbanized locations in Seoul for the period covering March 2001 through May 2002. The measurement data were analyzed to explore the possible influences of spatial factors on metal distribution characteristics. To check for the importance of such aspects on metal distribution characteristics, the measured data were compared between different metals and between different sites by several criteria including (1) coefficient of variation (CV) values; (2) temporal variability; and (3) the abundance of strongly correlated pairs. The overall results of our study indicate strong diversity in the distribution characteristics of different metals. It is found that some metals (like Fe, Mn, and Pb) tend to exhibit strong compatibility among different study sites. However, no such compatibility appears to exist for certain metals like Cu. To account for the importance of spatial factors, complex relationships between source/sink processes and geochemical characteristics of a given metallic component may have to be examined in a systematic manner.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.10
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• pp.1025-1029
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• 2005

A simple analysis of atmospheric sulfur dioxide($SO_2$) pollution in industrial region was investigated using badge type passive samplers. It were set up in 76 locations and the $SO_2$ distribution evaluated along the boundary of land use type. It changed considerably both monthly and seasonally. Soil samples were also collected in 120 locations to investigate influence of sulfur dioxide pollution on soil and heavy metal distribution in the study area, where the sulfur dioxide pollutants from industrial area could affect the soil environment of near residential and green areas. The relationship between the $SO_2$ concentrations in the atmosphere and heavy metal(Cu, Pb) concentrations in the soil were analyzed, by using the correlation coefficient values and the results were 0.17 and 0.08 in industrial area. And this study indicated that the atmospheric pollution in industrial region affect the level of the soil pollution adjacent to the residential and green area. The study result may be used to define correlativity for establishing an exposure index. It will subsequently be used for a more precise assessment measuring the exposure of plants and inhabitants, for the purposes of a study en effects on health.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.4 no.3
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• pp.198-207
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• 1999

Five core sediments acquired from the Lake Shihwa are analyzed for variations of sedimentary environment and heavy metal pollution after the Shihwa seawall construction. The depositional environment of the study area is divided into anoxic, oxic and mixed suboxic conditions based on the C/N ratio and C/S ratios of organic matters. Controlling factors for redox condition are the water depth and the difference in industrial effluents supply. Correlations among geochemical elements (Mn, U, Mo) show a distinctive difference and thus can be used as an indicator of redox condition. The content of Al, Ti are dependent on the sediment characteristics, and the contents of heavy metals (Cr, Ni, Cu, Zn, and Pb) indicate heavy metal pollution. The concentrations of heavy metals are higher near Shiswa-Banwol industrial complexies than the central part of Lake Shihwa. Especially, the accumulation of the heavy metal at the surface sediments near Shihwa-Banwol industrial complex are two to eight times higher than in the center of Lake Shihwa.

• 한국초전도학회:학술대회논문집
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• v.10
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• pp.65-65
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• 2000

Microwave response of intrinsic Josephson junctions in mesa structure formed on HgI2-intercalated Bi2Sr2CaCu2O8+x single crystals was studied in a wide range of microwave frequency. With irradiation of 73${\sim}$76 GHz microwave, the supercurrent branch becomes resistive above a certain onset microwave power. At low current bias, the current-voltage characteristics show linear behavior, while at high current bias, the resistive branch splits into multiple sub-branches. The voltage spacing between neighboring sub-branches increase with the microwave power and the total number of sub-branches is almost identical to the number of intrinsic Josephson junctions in the mesa. All the experimental results suggest that each sub-branch represents a specific mode of collective motion of Josephson vortices generated by the microwave irradiation. With irradiation of microwave of microwave of frequency lower than 20 GHz, on the other hand, no branch splitting was observed and the current-voltage characteristics exhibited complex behavior at hlgh blas currents. This result can be explained in terms of incoherent motion of Josephson vortices generated by non-uniform microwave irradiation.

• Korean Journal of Microbiology
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• v.50 no.1
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• pp.22-26
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• 2014

Protocatechualdehyde (PA) is phenolic compound having antioxidative and antitumor activities. PA was purified from supernatant of Streptomyces lincolnensis M-20. In the presence of copper ion, PA acted as pro-oxidant. The antioxidant activity was assessed with the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay, and the pro-oxidant effect of PA on DNA damage as pBR322 plasmid DNA-cleaving agents in the presence of Cu(II) ions was investigated. The involvement of reactive oxygen species (ROS) in the DNA damage was confirmed by the inhibition of the DNA breakage by using glutathione (GSH), specific scavenger of ROS. When the increase in ROS reaches a certain level (the toxic threshold), it may trigger cell death. The formation of the PA/Cu(II) chelate complex was confirmed by reaction with ethylenediamine-tetraacetic acid (EDTA), a well-known chelating agent for metal ions, by using UV/Vis spectroscopic analysis.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.77-77
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• 2009

ELV(; End of Life Vehicles)를 비롯한 최근 환경 동향은 자동차 전장 모듈에 대하여 다양한 무연 솔더 적용을 요구하고 있다. 특히 자동차 엔진룸과 트랜스미션은 가동 중 고온 및 진동의 지속적인 영향을 받기 때문에 이와 유사한 환경에서의 신뢰성 연구가 필요한 시점이다. 이에 본 연구에서는 Sn3.5Ag, Sn0.7Cu, Sn5.0Sb 솔더 조성에 대하여 복합환경 조건하에서 접합부 신뢰성을 평가하였다. 복합환경을 구현하기 위하여 $-40{\sim}150^{\circ}C$ 범위의 온도 사이클과 랜덤 진동을 동시에 인가하였으며, 진동 가속도 3G, 진동주파수는 10~1000Hz 로 설정하여 자동차 환경을 충족하였다. 복합시험의 1 cycle 은 20 시간이며, 총 120 시간의 시험 동안 진동의 영향 및 진동과 고온이 동시에 작용하였을 경우의 영향에 대해 비교하였다. 테스트 모듈 제작을 위해 450 um 의 솔더볼이 적용되었으며, 각 조성의 솔더볼을 이용하여 BGA test chip 제작하였고, 제작된 BGA test chip 은 다시 daisy chain PCB 위에 실장 및 리플로우 공정을 통해 접합되었다. 테스트 동안 In-situ 로 저항의 변화를 관찰하여 파단의 유무를 판단하였고 전자주사현미경을 통해 파괴 기전을 평가하였다. 복합시험 시간에 따른 전단강도를 측정하였으며, 각 조성에 대하여 상이한 전단강도 변화를 관찰하였다. 계면 IMC 형상은 전단강도 변화에 영향을 주었으며, 특히 높은 온도가 IMC 성장을 촉진시켜 전단강도 감소에 영향을 주었다. 본 복합환경 시험 조건에서는 Sn0.7Cu 가 가장 안정적이었으며, 파단면을 관찰한 결과 연성파괴 모드가 관찰되었다.

• Analytical Science and Technology
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• v.8 no.4
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• pp.561-568
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• 1995

Two methods, precipitation and ultrafiltration, were applied in order to recover platinum group metals(PGM) by complexing them with water-soluble polyelectrolytes, e.g., polyethyleneimine [PEl], poly(2-vinylpyridine) [2-PVP], poly (4-vinylpyridine) [4-PVP], and poly (styrene sulfonic acid) [PSSA]. In the precipitation method, the PGM-polyelectrolyte complex that was formed by mixing first with polybase, e.g.,4-PVP at pH 1 was precipitated by further mixing with polyacid, e.g., PSSA. However, the recovery of PGM obtained by this method was not quantitative(less than 70%). The "sandwiching" binding between the metal anions and two polyelectrolytes was examined by X-ray photoelectron spectroscopy(XPS). The XPS studies indicated that the PGM atom was bound with the acdic and basic polyelectrolyte via its oxygen and nitrogen atom, respectively. The recovery of PGM using polyelectrolyte was further studied by ultrafiltration methods as follows : The PGM ions, eomplexed at pH 1 with polyelectrolyte, allowed the applicntion of membrane filtration by virtue of the great differences in molecular weights between PGM and other low molecular weight species. By applying this method, Pd and Pt (ca. $10^{-4}M$) were selectively separated almost quantitatively from coexisting metal ions, e.g., $Cu^{2+}$ and $Ni^{2+}$. The EPR spectra and viscosity measurements indicated that these polyelectrlytes were not bound to $Cu^{2+}$ and $Ni^{2+}$ ions at this pH, which provided the basis for selective separation of PGM(Pd, Pt and Rh) from these coexisting ions.

• Journal of the Korean Chemical Society
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• v.20 no.6
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• pp.494-499
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• 1976

The extraction-polarographic method applied to the determination of micro amount of chromium (Ⅵ). Chromium(Ⅵ) was extracted into methylisobuthylketone(MIBK) layer containing diethyldithiocarbamate(DDTC) as Cr(Ⅲ)-DDTC complex from acetate buffered aqueous, solution of pH 5.4 and the direct current polarogram for the extract was recorded after addition of sodium perchlorate as supporting electrolyte. The reduction current was diffusion controlled. And the half wave potential of this reduction wave was -0.81 volt vs. SCE. The diffusion current was proportional to the chromium concentraticn in aqueous solution in the range of 8∼160 ppm. And the chromium(Ⅵ) could be selectively determined in the presence of chromium(Ⅲ), since the chromium(Ⅲ) did not interfere up to twice the amount of chromium(Ⅵ). Many of other metals such as Mn(Ⅱ), Cu(Ⅲ), Zn(Ⅱ), Mg(Ⅱ), Ni(Ⅱ) and Ag(Ⅰ) were found to have no effect even when present in 1000 times the amount of chromium (Ⅵ).

• Journal of the Korean Chemical Society
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• v.29 no.6
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• pp.637-645
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• 1985

To predict speciation of copper and cadmium in natural waters, the stability constant of complexes formed between copper or cadmium and natural organic ligands have been determined by the ion selective electrodes at pH 6. The stability constants for copper and cadmium, log $K'_{CuL} = 5.80\;and\;log K'_{CdL}=3.82$, were incorporated inot MINEQL computer program and prediction of chemical species of copper and cadmium in a model fresh water system was made by using this computer program. The natural organic ligands form complex with cupric ions at the concentration of $10^{-6}$ moles/l and with cadmium ions at the concentration of $10^{-5}$ moles/l. This result showed that prediction of chemical species of heavy metals in natural waters was not possible without taking into account the presence of the natural organic ligands.

• Bulletin of the Korean Chemical Society
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• v.27 no.12
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• pp.2002-2010
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• 2006

This study examined the quenching of ofloxacin (OFL) and flumequine (FLU) fluorescence by $Cuj^{2+}$, $Ni^{2+}$, $Co^{2+}$ and $Mn^{2+}$ in an aqueous solution. The change in the fluorescence intensity and lifetime was measured at various temperatures as a function of the quencher concentration. According to the Stern-Volmer plots, the fluorescence emission was quenched by both collisions (dynamic quenching) and complex formation (static quenching) with the same quencher but the effect of static quenching was larger than that of dynamic quenching. Large static and dynamic quenching constants for both OFL and FLU support significant ion-dipole and orbital-orbital interactions between fluorophore and quencher. For both molecules, the static and dynamic quenching constants by $Cu^{2+}$ were the largest among all the metal quenchers examined in this study. In addition, both the static and dynamic quenching mechanisms by $Cu^{2+}$ were somewhat different from the quenching caused by other metals. Between $Ni^{2+}$ and FLU, a different form of chemical interaction was observed compared with the interaction by other metals. The change in the absorption spectra as a result of the addition of a quencher provided information on static quenching. With all these metals, the static quenching constant of FLU was larger than those of OFL. The fluorescence of OFL was quite insensitive to both the dynamic and static quenching compared with FLU. This property of OFL can be explained by the twisted intramolecular charge transfer in the excited state.