• Title/Summary/Keyword: Peroxy radical

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Detection of Radiation Degradation of LDPE by ESR Spectroscopy (전자스핀공명을 이용한 저밀도 폴리에틸렌의 방사선 열화 검지)

  • Kim Ki-Yup;Lee Chung;Ryu Boo-Hyung
    • Journal of the Korean Society of Safety
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    • v.20 no.1 s.69
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    • pp.81-86
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    • 2005
  • This study has investigated radiation degradation of low density polyethylene(LDPE). Samples were irradiated up to 800kGy using a $Co^{60}\;\gamma-ray$ at a dose rate of 5kGy/hr in the presence of air atmosphere at room temperature. After irradiation, storing for 2 weeks, free radical measurement of LDPE has established by electron spin resonance(ESR). ESR measurement showed that free radical concentration(FRC) was increased with radiation dose and decreased with the time. The radical types showed alkyl, allyl, and peroxy radical with the irradiation, these changed to peroxy radical with the time.

Comparison of Antioxidant Activities of Various Meat Broths Served with Oriental Noodles (동양 면요리 육수의 항산화 활성의 비교)

  • Kim, Sung-Hun;Park, Inshik
    • The Korean Journal of Food And Nutrition
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    • v.26 no.1
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    • pp.150-153
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    • 2013
  • The objective of this research was to compare the antioxidant activities of meat broths served with oriental noodles. For this purpose, we estimated DPPH, ABTS radical scavenging, and SOD-like activities as well as reducing power of meat broth of oriental noodles such as Korean, Chinese and Japanese style. DPPH radical scavenging activities of Korean, Chinese and Japanese meat broth at the concentration of 2 $mg/m{\ell}$ were 2.78%, 25.37%, and 40.74%, respectively. The Korean and Chinese meat broths exhibited little hydroxyl radical scavenging activities, whereas Japanese broth showed 59.06% hydroxyl radical scavenging activity at the concentration of 0.5 $mg/m{\ell}$. The peroxy radical scavenging activities ($IC_{50}$) of Korean, Chinese and Japanese meat broth were 0.121 $mg/m{\ell}$, 0.222 $mg/m{\ell}$, and 0.013 $mg/m{\ell}$, respectively. The Korean and Japanese meat broth exhibited higher ABTS radical scavenging activity than that of Chinese.

New Mechanism for the Reaction of Thianthrene Cation Radical Perchlorate with tert-Butyl Peroxide

  • Park, Bo-Kyung;Sohn, Chang-Kook;Lee, Wang-Keun
    • Bulletin of the Korean Chemical Society
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    • v.23 no.1
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    • pp.103-106
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    • 2002
  • A new reaction mechanism is proposed for the reaction of thianthrene cation radical perchlorate $(Th^{+{\cdot}}CIO_4^-}$ and tert-butyl peroxide in acetonitrile at room temperature on the basis of experimental and theoretical results. Rapid C-O bond rupture instead of O-O bond cleavage was observed by a good peroxy radical trapping agent, thianthrene cation radical. Products were N-tert-butyl acetamide, thianthrene 5-oxide (ThO), thianthrene 5,5-dioxide $(SSO_2)$, and thianthrene (Th). Thianthrene 5,10-dioxide (SOSO) was not obtained. A comparative computational study of the cation radical of tert-butyl peroxide is made by using B3LYP and CBS-4. The computational results are helpful to explain the reaction mechanism.

Relative Contribution of the Oxidation of VOCs to the Concentrations of Hydroxyl (OH) and Peroxy Radicals in the Air of Seoul Metropolitan Area (서울에서의 VOCs의 히드록실 및 페록시 라디칼 농도에 대한 상대적 기여도 연구)

  • Shon, Zang-Ho
    • Journal of Korean Society for Atmospheric Environment
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    • v.22 no.6
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    • pp.779-790
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    • 2006
  • This study examines relative contributions of volatile organic compounds (VOCs) to the formation of hydroxyl (OH) and peroxy radicals such as $HO_2$ and $RO_2$ during the intensive sampling period (Jun. $1{\sim}30$, 2004) in the air of Seoul metropolitan area. As to the contribution of VOCs to $HO_x$ levels, the impact of individual VOC concentration change on $HO_2$ concentration change was more than an order of magnitude higher than that on OH concentration change during the study period. The contribution of change in isoprene concentration to $HO_2$ concentration change was 38 times higher than OH and that in the concentration of alkene compounds to $HO_2$ concentration change was 31 times higher than OH. Moreover, the concentration changes of isoprene and aromatic compounds (AROM) played significant roles in $HO_x$ concentration changes. On the other hands, aldehydes (ALD2) and alkanes (ALKA) showed anti-correlation (negative) in $HO_x$ concentration changes with low contribution ($-4{\times}10^{-3}$ pptv/ppbv (OH) and $-58{\times}10^{-3}$ ($HO_2$) for ALD2; $-1{\times}10^{-3}$ (OH) and $-15{\times}10^{-3}$ ($HO_2$) for ALKA). Unlike other VOCs, $C_2H_6$ and $C_3H_8$ showed positive or negative contribution to peroxy radicals, depending on ambient air conditions. The contribution of VOC concentration changes to changes in $CH_3O_2$ and $RO_2$ concentration showed similar pattern to $HO_x$ contribution.

Free radical scavenging phenolic compounds of the leaves of Juglans sinensis

  • Kim, Mi-Hee;Ko, Eun-Kyung;Jun, Jung-Yang;Li-Xun;Oh, Myung-Hun;An, Nyeon-Hyoung;Kim, Youn-Chul
    • Proceedings of the PSK Conference
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    • 2002.10a
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    • pp.381.3-382
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    • 2002
  • Free radical-mediated cell damage and free radical attack on polyunsaturated fatty acids result in the formation of lipid radicals. These lipid radicals react readily with molecular oxygen to produce peroxy radicals responsible for initiating lipid peroxidation. The peroxidation of cellular membrane lipid can lead to cell necrosis and considered to be implicated in a number of pathophysiological conditions as well as in the toxicity of many xenobiotics. DPPH is known to abstract labile hydrogen and the ability to scavenge the DPPH radical is related to the inhibition of lipid peroxidation. (omitted)

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Measurement of Atmospheric Nitrous Acid(HONO) using DNPH/HPLC in Seoul (DNPH/HPLC에 의한 서울시 대기 중의 Nitrous Acid 측정)

  • 정용국;홍상범;이재훈
    • Proceedings of the Korea Air Pollution Research Association Conference
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    • 2001.11a
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    • pp.325-326
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    • 2001
  • 오존은 태양광선의 존재 하에 질소산화물과 VOCs가 관련하여 발생하는 생성물이다. 대기중의 VOCs 는 히드록실 라디칼(hydroxyl radical, OHㆍ)과 같은 자유 라디칼(free radical)과 반응하여 하이드로퍼옥시 라디칼(hydroperoxy radical, HO$_2$ㆍ)과 알킬 퍼옥시 라디칼(alkyl peroxy radical, RO$_2$ㆍ)을 생성해 낸다. 이 퍼옥시 라디칼들은 NO를 NO$_2$ㆍ로 산화시키며 또한 히드록실 라디칼을 재생하며 이 히드록실 라디칼은 다시 VOCs와 반응한다. 그리고, 이때 산화된 NO$_2$는 햇빛에 의해 NO와 자유산소원자(free oxygen atom)로 광분해 되는데, 여기서 생성된 자유산소인자는 산소분자와 반응하여 오존을 생성한다. (중략)

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A study on radiation degradation of LDPE by using ESR (ESR을 이용한 저밀도 폴리에틸렌의 방사선 열화에 관한 연구)

  • Kim, Ki-Yup;Kim, Jin-Ah;Lee, Chung;Kim, Pyeong-Jong;Ryu, Boo-Hyung
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2004.07a
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    • pp.473-476
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    • 2004
  • This study has investigated radiation degradation of low density polyethylene(LDPE). Samples were irradiated using a $Co^{60}\;\gamma-ray$ and ray up to 800 kGy at a dose rate of 5 kGy/hr in the presence of air atmosphere at room temperature. After irradiation, free radical measurement of LDPE has established by electron spin resonance(ESR). Then, each sample was stored for 2 weeks. ESR measurement showed that free radical concentration(FRC) was increased with radiation dose and changed from alkyl, allyl radical to peroxy radical with time.

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Free Radical Scavenging Compounds of Polygoni Multiflori Ramulus

  • Li-Xun;Kim, Mi-Hee;Ko, Eun-Kyung;Jun, Jung-Yang;Oh, Myung-Hun;Shin, Hwa-Woo;Kim, Youn-Chul
    • Proceedings of the PSK Conference
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    • 2002.10a
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    • pp.381.2-381.2
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    • 2002
  • There is now increasing evidence that free radicals and active oxygen species are involved in a variety of pathological events. often associated with ageing. Free radical-mediated cell damage and free radical attack on polyunsaturated fatty acids result in the formation of lipid radicals. These lipid radicals react readily with molecular oxygen to produce peroxy radicals responsible for initiating lipid peroxidation. The peroxidation of cellular membrane lipid can lead to cell necrosis and considered to be implicated in a number of pathophysiological conditions as well as in the toxicity of many xenobiotics. (omitted)

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MEK-PO 분해 폭발사고 사례 연구

  • 김관응;이근원;김기영;박상현
    • Proceedings of the Korean Institute of Industrial Safety Conference
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    • 2003.10a
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    • pp.54-59
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    • 2003
  • 유기과산화물은 분자구조내에 과산화결합(Peroxy, -O-O-)을 갖고 있는 유기화합물로서 매우 불안정한 과산화수소(H-O-O-H)의 유도체이다. 과산화물을 특징짓는 산소-산소(-O-O-) 과산화결합은 C-H, C-O, C-C 등의 결합에 비하여 결합에너지가 작아서 열이나 빛에 의해서 쉽게 균형분해(Homolysis)가 일어나 두 개의 유리기인 라디칼(Free radical)을 생성하게 되는데, 이때 생성된 라디칼은 비닐중합반응을 개시시킬 수 있고, 또한 다른 자유 라디칼 반응을 유발시킬 수 있다.(중략)

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Effect of Storage Conditions on Graft of Polypropylene Non-woven Fabric Induced by Electron Beam (전자선 조사된 폴리프로필렌 부직포의 그라프트에 있어 보관조건이 미치는 영향)

  • Lee, Jin Young;Jeun, Joon-Pyo;Kang, Phil-Hyun
    • Journal of Radiation Industry
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    • v.9 no.2
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    • pp.57-62
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    • 2015
  • In this study, we fabricated effect of storage conditions on graft of polypropylene (PP) non-woven fabric induced by electron beam. The electron beam irradiations on PP non-woven fabric were carried out over a range of irradiation doses from 25 to 100 kGy to make free radicals on fabric surface. The radical measurement was established by electron spin resonance (ESR) for confirming the changes of the alkyl radical and peroxy radical according to effect of storage time, storage temperature and atmosphere. It was observed that the free radicals were increased with irradiation dose and decreased with storage time due to the continuous oxidation. However, the radical extinction was significantly delayed due to reduced mobility of radicals at extremely low temperature. The degree of graft based on the analysis of ESR was investigated. The conditions of graft reaction were set at a temperature: $60^{\circ}C$, reaction time: 6 hours and styrene monomer concentration: 20 wt%.