• Corrosion Science and Technology
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• 제20권3호
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• pp.158-168
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• 2021

Austenitic 316 stainless steel was irradiated with protons accelerated by an energy of 2 MeV at 360 ℃, the various defects induced by this proton irradiation were characterized with microscopic equipment. In our observations irradiation defects such as dislocations and micro-voids were clearly revealed. The typical irradiation defects observed differed according to depth, indicating the evolution of irradiation defects follows the characteristics of radiation damage profiles that depend on depth. Surface oxidation tests were conducted under the simulated primary water conditions of a pressurized water reactor (PWR) to understand the role irradiation defects play in surface oxidation behavior and also to investigate the resultant irradiation assisted stress corrosion cracking (IASCC) susceptibility that occurs after exposure to PWR primary water. We found that Cr and Fe became depleted while Ni was enriched at the grain boundary beneath the surface oxidation layer both in the non-irradiated and proton-irradiated specimens. However, the degree of Cr/Fe depletion and Ni enrichment was much higher in the proton-irradiated sample than in the non-irradiated one owing to radiation-induced segregation and the irradiation defects. The microstructural and microchemical changes induced by proton irradiation all appear to significantly increase the susceptibility of austenitic 316 stainless steel to IASCC.

• 대한약리학회지
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• 제32권3호
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• pp.335-345
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• 1996

허혈/재관류 뇌손상에서 활성산소류의 역할이 중요시되고 있다. 본 연구에서는 모래쥐의 총경동맥을 묶었다 풀어줌으로써 실험적 허혈/재관류 손상을 유도하고 산화성 스트레스 발생 유무와 이러한 산화성 스트레스가 세포손상으로 연결되는지를 알아보고자 하였다. 해마는 뇌조직 중에서도 특히 산화성 스트레스에 취약한 부분이므로 해마에서 얻은 조직을 대뇌피질에서 얻은 조직과 비교분석하였다. 또한, 이들 부위에서 heat shock protein 70(HSP70)의 발현이 허혈/재관류 손상에 미치는 영향도 검색하고자 하였다. 허혈/재관류에 의한 산화성 스트레스의 지표로써 글루타치온 산화정도, GSSG/(GSH+2xGSSG)를 측정하였을 때 주로 해마에서 산화지표가 상승됨을 관찰하였다. 한편 산화성 스트레스가 세포손상으로 연결되는지를 알아보고자 지질과산화물을 측정하였다. 두 부위 모두에서 지질과산화물 형성의 증가가 있었으며 대뇌피질에서보다 해마에서 더 증가됨을 알 수 있었다. 지질과산화물 형성의 정도나 시간적 변화양상이 글루타치온 산화의 그것들과 유사하였다. 이러한 결과들은 허혈/재관류에 의해 산화성 스트레스가 형성되며 동시에 이러한 산화성 스트레스가 세포 손상을 초래함을 보여준다. 또한 산화성 스트레스 및 산화성 세포손상 정도가 대뇌피질보다는 해마에서 더 큰 것을 알 수 있었다. 그러나, 피질과 해마에서 HSP70의 기초발현(basal level) 정도는 차이가 없었다. 이는 해마의 취약성이 HSP70 발현 결핍에 기인하지 않았음을 나타낸다. 반면 허혈/재관류에 의한 HSP70의 발현유도는 해마조직에서 제대로 이주어지지 않았고 northern blot결과 이는 전사단계에서의 부친에 의한 것으로 나타났다. 이러한 결과들로 볼 때 허혈/재관류에 의한 뇌손상에서 HSP70 유도정도를 측정하는 것이 세포의 취약성을 예측할 수 있는 지표로 유용하게 사용될 수 있을 것으로 사료된다.

• Biotechnology and Bioprocess Engineering:BBE
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• 제5권6호
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• pp.422-430
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• 2000

Mechanism of lignin biodegradation caused by basidiomycetes and the history of lignin biodegradation studies were briefly reviewed. The important roles of fungal extracellular ligninolytic enzymes such as lignin and manganese peroxidases (LiP and MnP) were also summarized. These enzymes were unique in their catalytic mechanisms and substrate specificities. Either LiP or MnP system is capable of oxidizing a variety of aromatic substrates via a one-electron oxidation. Extracellular fungal system for aromatic degradation is non-specific, which recently attracts many people working a bioremediation field. On the other hand, an intracellular degradation system for aromatic compounds is rather specific in the fungal cell. Structurally similar compounds were prepared and metabolized, indicating that an intracellular degradation strategy consisted of the cellular systems for substrate recognition and metabolic response. It was assumed that lignin-degrading fungi might be needed to develop multiple metabolic pathways for a variety of aromatic compounds caused by the action of non-specific ligninolytic enzymes on lignin. Our recent results on chemical stress responsible factors analyzed using mRNA differential display techniques were also mentioned.

• Fibers and Polymers
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• 제4권4호
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• pp.145-150
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• 2003

Polypropylene nonwoven fabrics were exposed to He/$O_2$ atmospheric pressure glow discharge plasma. Surface chemical analysis and contact angle measurement revealed the surface oxidation by formation of new functional groups after plasma treatment. Weight loss (%) measurement and scanning electron microscopy analysis showed a significant plasma etching effect. It was investigated in low-stress mechanical properties of the fabrics using Kawabata Evaluation System (KES-FB). The surface morphology change by plasma treatment increased surface friction due to an enhancement of fiber-to-fiber friction, resulting in change of other low-stress mechanical properties of fabric.

• Fibers and Polymers
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• 제6권2호
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• pp.113-120
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• 2005

Helium-oxygen plasma treatments were conducted to modify poly(trimethylene terephthalate) (PIT) and poly(ethylene terephthalate) (PET) warp knitted fabrics under atmospheric pressure. Lubricant and contamination removals by plasma etching effect were examined by weight loss $(\%)$ measurements and scanning electron microscopy (SEM) analysis. Surface oxidation by plasma treatments was revealed by x-ray photoelectron spectroscopy (XPS) analyses, resulting in formation of hydrophilic groups and moisture regain $(\%)$ enhancement. Low-stress mechanical properties (evaluated by Kawabata evaluation system) and bulk properties (air permeability and bust strength) were enhanced by plasma treatment. Increasing interfiber and interyarn frictions might play important roles in enhancing surface property changes by plasma etching effect, and then changing low-stress mechanical properties and bulk properties for both fabrics.

• Corrosion Science and Technology
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• 제2권3호
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• pp.155-160
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• 2003

Plasma spraying technique was used to fabricate functionally graded coating (FGC) of NiCrAIY/YSZ 8wt%$Y_2O_3-ZrO_2$ on a Co-base superalloy (HAYNES 188) substrate. Six layers were coated on the substrate for building up compositionally graded architecture. Conventional thermal barrier coating (TBC) of NiCrAIY/SZ with sharp interface was also fabricated. As-coated FGC and TBC samples were exposed at the temperature of $1100^{\circ}C$ for 10, 50, 100 hours in air. Microstructural change of thermally exposed samples was examined. Pores and microcracks were formed in YSZ layer due to evolution of thermal internal stress at high temperature. The amount of pores and microcracks in YSZ layer were increased with increasing exposure time at high temperature. High temperature oxidation of coatings occurred mainly at the NiCrAIY/YSZ interface. In comparison with the case of TBC. the increased area of the NiCrAIY/YSZ interface in FGC is likely to attribute to forming the higher amount of oxides.

• 한국세라믹학회지
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• 제43권9호
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• pp.544-551
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• 2006

The sealing technique between a glass tube and a copper heat pipe in an evacuated tube solar collector is studied. In this study two different sealing techniques, such as flame method and furnace firing, are examined. After the sealing of a copper to a glass, the oxidation state of the copper and its bonding morphology were examined by SEM and XRD. Its oxidation was retarded by coating of borate solution on the copper, and $Cu_2O(cuprite)$ turned into CuO(tenorite) with increase in a firing temperature and firing time. Porous structure was found in the oxide layer when CuO formed. The best sealing morphology was observed when the thickness of the oxidation layer was less than $20{\mu}m$. The sealing technique performed in a furnace was promising and the satisfactory result was obtained when the sample was fired at $950^{\circ}C$ for 5 min under $N_2$ atmosphere. Annealing procedure is recommended to remove the stress left at the bonding zone.

• 한국수소및신에너지학회논문집
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• 제10권2호
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• pp.101-106
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• 1999

Hydrogen solubility in internally oxidized Pd-Mo(Al) alloys has been studied at 323 K from the measurements of pressure-composition(p-c) isotherms. Internal oxidation of $Pd_{0.985}Al_{0.015}$ and $Pd_{0.97}Mo_{0.03}$ alloys results in the precipitation of Al and Mo particles in a matrix of pure Pd. It has been observed that the presence of the aluminum and molybdenum oxide precipitates results in an enhanced hydrogen solubility in the dilute phase region of Pd-H in a Pd/aluminum(molybdenum)oxide composites. Hydrogen solubility enhancements due to the presence of residual stresses around ceramic particles have been observed from p-c isotherms determined at 323 K after oxidation at 1073 K. The solubility enhancements in completely internally oxidized alloys are greater than that in partially oxidized alloys. The stress fields near the ceramic precipitates are the major source of the solubility enhancements. Transmission electron microscopy indicates that alumina precipitates are nanometer-sized and coherent with the Pd matrix after oxidation.

• Molecules and Cells
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• 제24권1호
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• pp.113-118
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• 2007

The brains of Alzheimer's disease (AD) patients are characterized by large deposits of amyloid beta peptide ($A{\beta}$). $A{\beta}$ is known to increase free radical production in nerve cells, leading to cell death that is characterized by lipid peroxidation, free radical formation, protein oxidation, and DNA/RNA oxidation. In this study, we selected an extract of Gardenia jasminoides by screening, and investigated its ameliorating effects on $A{\beta}$-induced oxidative stress using PC12 cells. The effects of the extract were evaluated using the 2',7'-dichlorofluorescein diacetate (DCF-DA) assay and the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction assay. To find the active component, the ethanol extract was partitioned with hexane, chloroform, and ethyl acetate, respectively, and the active component was purified by silica-gel column chromatography and HPLC. The results suggested that Gardenia jasminoides extract can reduce the cytotoxicity of $A{\beta}$ in PC 12 cells, possibly by reducing oxidative stress.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제54권4호
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• pp.154-160
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• 2005

We have investigated thermal properties showed by changing the content of carbon black which is the component parts of semiconductive shield in underground power transmission cable. Specimens were made of sheet with the nine of those for measurement. Density of specimens was measured by density meter, and then stress-strain of specimens was measured by TENSOMETER 2000. A speed of measurement was 200[mm/min], ranges of stress and strain were 400(Kgf/$cm^2$) and 600[$\%$]. In addition, tests of stress-strain were progressed by aging specimens at air oven. Finally surface profile was shown in order to looking for protrusion of specimens by using smoothness tester. Density was highly measured according to increasing the content of carbon black from this experimental result, and stress was decreased, while strain was increased according to increasing the content of carbon black. And stress-strain were decreased some after aging because of oxidation reaction of chemical defect. Lastly surface of specimens smoothed generally.