• Korean Journal of Food Science and Technology
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• v.34 no.3
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• pp.396-399
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• 2002

Electron spin resonance (ESR) spectroscopy was used to investigate the effect of irradiation dose and storage time on the free radical concentrations in gamma-irradiated sesame (Korean and Sudan) and perilla seeds (Korea). The samples were sealed with packed pyrex tube (50 g respectively) and then irradiated with doses of 0, 1, 5 and 10 kGy at room temperature using a Co-60 irradiator. Each sample in ESR quartz tube were calculated with ESR signals by Bruker-EPR spectrometer for 4 weeks. Free radicals detected for irradiated and unirradiated samples were higher than those of unirradiated ones. Since the free radical concentrations linearly incresed with the applied doses $(1{\sim}10\;kGy)$, highly positive correlation coefficients $(R^2=0.9926{\sim}0.9994)$ were obtained between irradiation doses and free radical concentrations right after irradiation. Although the free radical concentrations decreased with storage time, the signals of free radical in irradiated samples were observed even after 4 weeks of storage at room temperature.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.31 no.1 s.49
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• pp.73-78
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• 2005

This work was carried out to investigate the antioxidative effects of Acanthopnax sessiliflorus from Jeongseon County for the purpose of development of a novel antioxidant from natural products. The antioxidant activity was determined by using electron paramagnetic resonance (EPR), not measuring the radical scavenging effect on 1,1-diphenyl-2-picrylhydrazyl (DPPH) which have bun used for antioxidant activity of natural sources. Although DPPH radical scavenging activity assay have been generally used for antioxidant activity, this assay is nut appropriated for determinating which radical is scavenged by extracts from natural products. Using EPR, we determinated whether A. sessiliflorus extracts from Jeongseon County scavenge specific radicals or not. On experiment of scavenging superoxide anion radical, hydroxyl radical, nitrogen dioxide and peroxinitrite. Extracts from A. sessiliflorus showed high antioxidant activities to reactive oxygen and nitrogen species. These result suggest that extracts from A. sessiliflorus act as an antioxidant by scavenging reactive oxygen and nitrogen species and used as new cosmetic ingredients for anti-oxidative stress in skin.

• Korean Journal of Food Science and Technology
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• v.33 no.4
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• pp.423-426
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• 2001

Electron spin resonance (ESR) spectroscopy was used to investigate the effect of irradiation dose on irradiated dried fruits. Dried banana, pineapple and pistachio were irradiated with doses of 0, 0.5, 1, 2 and 5 kGy at room temperature using a Co-60 irradiator. Multiplet ESR signals were observed in irradiated dried banana and pineapple, and singlet ESR signal was observed in irradiated pistachio, while these characteristic signals were not detected in non-irradiated samples. Since the amount of free radicals linearly increased with the applied doses $(0.5{\sim}5\;kGy)$, highly positive correlation coefficients $(R^2=0.9874{\sim}0.9974)$ were obtained between the irradiation doses and the corresponding free radical concentrations. The characteristic ESR signals were observed in irradiated samples even after 40 days of storage at room temperature.

• Journal of the Korean Vacuum Society
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• v.21 no.3
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• pp.171-177
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• 2012

The computer program (EPR-NMR program version 6.2) employed here sets up the spin Hamiltonian matrices and determines their eigenvalues using exact diagonalization. We study the electron spin resonance for $Mn^{2+}$ in ferroelectric $LiNbO_3$ single crystals. The self-energy is obtained using the projection operator method developed by Argyres and Sigel. The self-energy is calculated to be axially symmetric about the by the spin Hamiltonian. The line-widths decreased as the temperature increased; we assume that the hyperfine structure transition is a more dominant scattering than the other transitions. We conclude that the calculation process presented in this study is useful for quantum optical transitions.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.2
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• pp.300-312
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• 1993

The material deterioration of service-exposed boiler tube steels in fossil power plant was evaluated by using the electrochemical technique namely, modified electrochemical potentiokinetic reactivation(EPR). It was focused that the passivation of Mo$_{6}$C carbide which governs the mechanical properties of Mo alloyed steels did not occur even in the passivity region of steel in sodium molybdate solution and the reactivation peak current (Ip) observed as the result of non-passivation indicating the precipitation of Mo$_{6}$C carbides. To obtain the optimal test conditions for the field test by using the specially designed electrochemical cell, the effects of scan rate, the surface roughness and the pH of electrolyte on Ip value were also investigated. Furthermore, the change of mechanical properties occurred during the long time exposure at high temperature was evlauated quantitatively by small punch(SP) tests and micro hardness test taking account of the metallurgical changes. It is known that reactivation peak current (Ip) has a good relationship with Larson-Miller Parameter(LMP) which represents the information about material deterioration occurred at high temperature environment. In addition it was possible to estimate the ductile-brittle transition temperature (DBTT) by means of the SP test. The Sp test could be, therefore, suggested as a reliable test method for evaluating the material degradation of boiler tube steels. From the good correaltion between the SP DBTT and Ip values shown in this study, it was knows that the change of mechanical properties could be evaluated non-destructively by measurring only Ip values.ues.

• Journal of Marine Bioscience and Biotechnology
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• v.1 no.4
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• pp.252-259
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• 2006

Extracts which were prepared by four different extractions - 80% methanol extracts (ME) at high ($70^{\circ}C$) and a room temperature ($20^{\circ}C$), respectively and aqueous extracts (AE) at both temperatures with the residue after the methanol extracts - of 10 green, 19 brown and 25 red seaweeds collected in Jeju Island coast were examined for their DPPH free radical scavenging activity using a ESR (electron spin resonance) spectroscopy. A variety of the extracts showed positive scavenging effect against DPPH free radical (except the green seaweeds). Among the extracts, the brown seaweed extracts exhibited the highest scavenging activity. Especially, Sargassum spp. of the brown seaweeds have remarkable scavenging activities - both methanolic and aqueous at the both temperatures ($20^{\circ}C$ and $70^{\circ}C$). On the other hand, ME showed better scavenging activity than AE in the red seaweed extracts. These results indicate that autogenous seaweeds in Jeju will be potential natural antioxidants for functional food compounds.

• Corrosion Science and Technology
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• v.16 no.6
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• pp.305-316
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• 2017

Austenitic stainless steels have been widely used for various systems of nuclear power plants. Among these stainless steels, small pipes with diameter less than 14 inch have been produced in the form of seamless pipe. Annealing and cooling process during the manufacturing process can affect corrosion properties of seamless stainless steels. Therefore, 12 inch-diameter of as-received 304L stainless steel pipe was annealed and aged in this study. Intergranular corrosion resistance was evaluated by ASTM A262 Practice A, C, and E methods. The degree of sensitization was determined using a DL-EPR test. U-bend method in an autoclave was used to evaluate the SCC resistance in 0.01 M $Na_2S_4O_6$ or 40% NaOH solution at $340^{\circ}C$. As-received specimen showed relatively high degree of sensitization and intergranular corrosion rate. Carbon segregation was also observed near grain boundaries. Annealing treatment could give the dissolution of segregated carbon into the matrix. Aging treatment could induce segregation of carbon and finally form carbides. Microstructural analysis confirmed that high intergranular corrosion rate of the as-received seamless pipe was due to micro-galvanic corrosion between carbon segregation and grains.

• Bulletin of the Korean Chemical Society
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• v.18 no.11
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• pp.1166-1172
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• 1997

[FeⅢ(BLPA)DBC]BPh4, a new functional model for the catechol dioxygenases, has been synthesized, where BLPA is bis((6-methyl-2-pyridyl)methyl)(2-pyridylmethyl)amine and DBC is 3,5-di-tert-butylcatecholate dianion. The BLPA complex has a structural feature that iron center has a six-coordinate geometry with N4O2 donor set. It exhibits EPR signals at g=5.5 and 8.0 which are typical values for the high-spin FeⅢ (S=5/2) complex with axial symmetry. The BLPA complex reacts with O2 within a few hours to afford intradiol cleavage (75%) and extradiol cleavage (15%) products which is very unique result of all [Fe(L)DBC] complexes studied. The iron-catecholate interaction of BLPA complex is significantly stronger, resulting in the enhanced covalency of the metal-catecholate bonds and low energy catecholate to FeⅢ charge transfer bands at 583 and 962 nm in CH3CN. The enhanced covalency is also reflected by the isotropic shifts exhibited by the DBC protons, which indicate increased semiquinone character. The greater semiquinone character in the BLPA complex correlates well with its high reactivity towards O2. Kinetic studies of the reaction of the BLPA complex with 1 atm O2 in CH3OH and CH2Cl2 under pseudo-first order conditions show that the BLPA complex reacts with O2 much slower than the TPA complex, where TPA is tris(2-pyridylmethyl)amine. It is presumably due to the steric effect of the methyl substituent on the pyridine ring. Nevertheless, both the high specificity and the fast kinetics can be rationalized on the basis of its low energy catecholate to FeⅢ charge transfer bands and large isotropic NMR shifts for the BLPA protons. These results provide insight into the nature of the oxygenation mechanism of the catechol dioxygenases.

• Corrosion Science and Technology
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• v.17 no.6
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• pp.279-286
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• 2018

Austenitic stainless steels used in nuclear power plants mainly use pipes made of seamless pipes, which depend on imports. The manufacturing process and high cost are some of the problems associated with seamless pipes. Therefore, in this study, the corrosion characteristics of the seamless pipe and the SAW pipe were assessed to determine the safety and reliability of the SAW pipe in a bid to replace the seamless pipe. Microstructure was analyzed using an optical microscope and the degree of hardness was measured using a Rockwell B scale. Intergranular corrosion resistance was evaluated by ASTM A262 Practice A, C, and E methods. The degree of sensitization was determined using a DL-EPR test. Anodic polarization test was performed in deaerated 1% NaCl solution at $30^{\circ}C$ and the U-bend method was used to evaluate the SCC resistance in 0.01 M $Na_2S_4O_6$ at $340^{\circ}C$ and 40% NaOH solution at $290^{\circ}C$. Weld metal of the SAW pipe specimen showed relatively high degree of sensitization and intergranular corrosion rate. However, annealing to SAW pipes improved the corrosion properties in comparison to that of the seamless pipe.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.32 no.4 s.59
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• pp.241-247
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• 2006

This work was carried out to investigate the anti-inflammatory effects of Paulownia coreana Uyeki on abirritant, atopy and acne skin. Paulownia coreana Uyeki has been used as a traditional medicine having anti-febrile, anti-inflammation effect in Korea, Paulownia coreana Uyeki loaves were extracted with 70% EtOH. Its superoxide anion radical scavenging activity and inhibitory effect on LPS-induced NO production were examined. The extract inhibitied the generation of NO and $PGE_2$ induced by LPS in the macrophage cell line (Raw 264.7). Consistent with the inhibitory effects on No and $PGE_2$ generation, the extract inhibited expression of iNOS and COX-2. In further study, it was found that the extract prevented $IkB-{\alpha}$ degradation, as demonstrated by western blot analysis of $IkB-{\alpha}$ protein level. However, the extract treatment did not affect cell viability at $100{\mu}g/mL$ concentration in both human skin fibroblast and Raw 264.7 cells in vitro. Thus, the present study suggests that Paulownia coreana Uyeki leaves extract have significant anti-inflammatory activity and potential as an anti-irritation material.