• Journal of Radiation Protection and Research
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• 제42권1호
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• pp.63-68
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• 2017

Background: The combined effect of the low energy electron (LEE) irradiation and $Cu^{2+}$ ion on DNA damage was investigated. Materials and Methods: Lyophilized pBR322 plasmid DNA films with various concentrations (1-15 mM) of $Cu^{2+}$ ion were independently irradiated by monochromatic LEEs with 5 eV. The types of DNA damage, single strand break (SSB) and double strand break (DSB), were separated and quantified by gel electrophoresis. Results and Discussion: Without electron irradiation, DNA damage was slightly increased with increasing Cu ion concentration via Fenton reaction. LEE-induced DNA damage, with no Cu ion, was only 6.6% via dissociative electron attachment (DEA) process. However, DNA damage was significantly increased through the combined effect of LEE-irradiation and Cu ion, except around 9 mM Cu ion. The possible pathways of DNA damage for each of these different cases were suggested. Conclusion: The combined effect of LEE-irradiation and Cu ion is likely to cause increasing dissociation after elevated transient negative ion state, resulting in the enhanced DNA damage. For the decrease of DNA damage at around 9-mM Cu ion, it is assumed to be related to the structural stabilization due to DNA inter- and intra-crosslinks via Cu ion.

• Journal of Radiation Protection and Research
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• 제45권1호
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• pp.11-15
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• 2020

Background: There have been various studies to investigate the mechanisms of DNA damage from low-energy electrons. To understand the mechanism of these strand breaks, it is necessary to investigate the dissociation mechanism of the DNA constituents, that is, bases, sugars, and phosphates. Materials and Methods: We studied the dissociation of thymine base upon interaction with low-energy electrons. For this experiment, thymine powder was pressed onto the indium base and irradiated by 5 eV electrons. Results and Discussion: Non-irradiated and irradiated thymine samples were compared and analyzed using the X-ray photoelectron spectroscopic technique to analyze the dissociation patterns of the molecular bonds after low-energy electron irradiation of thymine. Conclusion: With 5 eV electron irradiation, C-C and N-C = O bonds are the primary dissociations that occur in thymine molecules.

• Journal of Radiation Protection and Research
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• 제36권4호
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• pp.190-194
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• 2011

After the first report that electrons with sub-ionization energy of DNA could cause single strand breaks or double strand breaks to DNA, there have been various studies to investigate the mechanisms of DNA damage by low-energy electrons. In this paper, we examined the possibility of using X-ray photoelectron spectroscopy (XPS) to analyze the dissociation patterns of the molecular bonds by electron irradiation on DNA thin films and tried to establish the method as a general tool for studying the radiation damage of biomolecules by low energ yelectrons. For the experiment, pBR322 plasmid DNA solution was formed into the films on tantalum plates by lyophilization and was irradiated by 5-eV electrons. Un-irradiated and irradiated DNA films were compared and analyzed using the XPS technique.

• Journal of Radiation Protection and Research
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• 제40권2호
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• pp.87-91
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• 2015

We have employed X-ray photoelectron spectroscopy (XPS) technique to examine the combined effects of low-energy electron (LEE) irradiation and $Fe^{3+}$ ion on DNA damage. pBR322 plasmid DNA extracted from E. coli ER2420 was used for preparing DNA-$Fe^{3+}$ sample. The C1s XPS spectra were scanned for LEE-irradiated and LEE-unirradiated samples and then curve-fitted. For the samples with LEE irradiation only or with Fe ion only, no significant changes from pure DNA samples were observed - a single effect of either $Fe^{3+}$ ion or LEE irradiation did not cause a significant damage. However, when these two components were combined, the DNA damage was increased quite significantly, compared to the sum of DNA damages caused by $Fe^{3+}$ ion and by LEE irradiation independently. This observation is consistent with our previous results [Radiat. Res. 177, 775 (2012)] which was done using gel-electrophoresis technique. Partial interpretation of the observed spectrum peaks was also attempted.

• Journal of Electrical Engineering and Technology
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• 제12권1호
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• pp.288-294
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• 2017

This paper contains results of the theoretical studies of the electrical breakdown properties in sulfur hexafluoride. Since the strong interaction of high-energy electrons with the polyatomic sulfur hexafluoride molecule causes their rapid deceleration to the lower energy of electron capture and dissociative attachment, the breakdown is only possible at relatively high field strengths. From the breakdown voltage curves, the effective yields that characterize secondary electron productions have been estimated. Values of the effective yields are found to be more consistent if they are derived from the experimentally determined values of the ionization coefficient and the breakdown voltages. In addition, simulations were performed using an one-dimensional Particle-in-cell/Monte Carlo collision code. The obtained simulation results agree well with the available experimental data with an error margin of less than 10% over a wide range of pressures and the gap sizes. The differences between measurements and calculations can be attributed to the differences between simulation and experimental conditions. Simulation results are also compared with the theoretical predictions obtained by using expression that describes linear dependence of the breakdown voltage in sulfur hexafluoride on the pressure and the gap size product.

• Journal of Radiation Protection and Research
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• 제33권2호
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• pp.53-59
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• 2008

X선과 같은 고에너지 방사선에 의한 DNA 손상 중 간접적인 손상을 확인하기 위하여 탄탈륨(Ta) 박막위에 동결건조 과정으로 만들어진 pGEM-3Zf(-) plasmid DNA 단일층(monolayer)의 박막을 만든 다음, 에너지가 1.5 keV인 Al $K{\alpha}$ X선을 0분, 3분, 7분, 10분 동안 초고진공 상태에서 이 DNA 단일층에 조사하여 평균 흡수선량(mean absorbed dose)의 변화에 따른 DNA 손상을 관찰하였다. 또한 3 eV의 낮은 에너지 전자선을 조사하여 그 결과를 X선을 조사한 경우와 비교하였다. X선과 낮은 에너지 전자선으로 조사된 plasmid DNA를 전기영동(electrophoresis) 방법을 이용해 supercoiled DNA와 unsupercoiled DNA로 분리한 후 각각을 정량적으로 분석하였다. Supercoiled DNA는 X선과 3 eV 전자선의 조사에 따른 평균흡수선량이 증가함에 따라 선형적으로 감소했다. 그와 반대로 circular DNA와 crosslinked form 1 DNA는 평균흡수선량이 증가함에 따라 선형적으로 증가했다. 이것은 supercoiled DNA가 낮은 에너지 전자와 상호작용하여 외가닥 절단(single strand break)을 일으켰고 그 결과 unsupercoiled DNA로 변화되었음을 보여준다. 본 실험을 통해 X선과 같은 고에너지 방사선에 의한 DNA의 간접적 손상이 일어남을 관찰할 수 있었고, DNA의 이온화 에너지보다 작은 에너지($0{\sim}10\;eV$)를 갖는 전자에 의해서도 DNA 손상이 일어날 수 있음을 확인할 수 있었다.

• 공업화학
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• 제18권2호
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• pp.136-141
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• 2007

본 연구에서는 열플라즈마를 이용하여 클로로메탄 즉 사염화탄소($CCl_4$), 삼염화탄소($CCl_3H$), 이염화탄소($CCl_2H_2$)를 분해하는 실험을 수행하였으며 열플라즈마분해공정의 특성에 대한 연구를 진행하였다. Factsage program을 이용하여 열역학적 평형조성을 알아보았으며, 또한 Gas chromatography를 이용하여 농도, 캐리어 가스의 유량 및 quenching 속도등 세가지 변수의 변화에 따른 분해율을 살펴보았다. 실험 결과 92%이상의 높은 분해율을 얻었다. FT-IR을 이용하여 최종 생성물을 확인한 결과 중성 분위기에서는 주로 카본, 염소, 염화수소가 생성되었고 산화 분위기에서는 카본의 생성이 억제되었으며 주로 이산화탄소, 염화수소, 염소가 생성되었다. FT-IR생성물에 대한 분석과 Factsage program에 의한 온도 분포 별 생성된 라디칼 및 기타 입자의 종류와 결부하여 이에 따른 분해 메커니즘에 대해 알아보았다. 분해 경로는 주로 라디칼에 의한 산화반응과 전자 부착에 의한 분해 반응으로 이루어짐을 확인하였다.