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Tunneling Magnetoresistance of a Ramp-Type Junction with a Si3N4 Barrier
Sang-SukLee,Do-GuwnHwang,KungwonRhie,김선욱 한국물리학회 2002 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.41 No.5
The tunneling magnetoresistance (TMR) of a ramp-edge-type junction has been studied. The samples were prepared using sputtering and were etched using electron cyclotron resonance (ECR) argon-ion milling. The junction structure was NiO(60 nm)/Co(10 nm)/NiO(60 nm)/Si3N4(2-6 nm)/NiFe(10 nm). We obtained nonlinear I-V characteristics for ramp-type tunneling junctions which had distinctive differences with and without an applied field. The voltage dependence of the TMR was stable up to a bias voltage of 10 V with a negative TMR of about -10 %, which is a very peculiar magnetic tunneling property for an asymmetric tunneling process between a wedge Co-pinned layer and a NiFe free layer.
Sang-SukLee,Do-GuwnHwang,Jong-KeeKim,KungwonRhie 한국물리학회 2002 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.40 No.3
The change in the magnetoresistance (MR) of dual NiO spin valves was investigated while the samples were etched by electron cyclotron (ECR) oxygen ion milling. The samples were prepared by sputtering, and the structure was NiO(600 A)/NiFe(31 A)/Co(7 A)/Cu(20 A)/Co(7)/NiFe(41 A)/Co(7 A)/Cu(20 A)/Co(7 A)/NiFe(31 A)/NiO(600 A). The MR ratios of the as-grown single NiO(bottom)/NiFe/Co/Cu/Co/NiFe spin valve with naturally oxidized surface layers were enhanced. The maximum MR ratios of the dual spin valve and the milled single spin valve were about 14 15 %, which might have been due to the specular eect at the interface caused by the forming of a very thin oxide-free layer with good flatness.
Kyu-SukLee,Won-SukLee,Seong-IlSuh,Sang-PyoKim,Sung-RyongLee,Young-WookRyoo,Byung-ChunKim 생화학분자생물학회 2003 Experimental and molecular medicine Vol.35 No.4
UV radiation is known to cause photoaging of the skin and is considered one of the leading cause of developing skin carcinogenesis. Melatonin which has a highly lipophilic molecular structure facilita-ting penetration of cel membranes and serving as an extra- and intracellular free radical scavenger has been demonstrated to protect photodamage of have examined the role of melatonin in response to UVB induced photodamaging proces, using human skin fibroblasts in vitro. Cell survival cur-ves after UVB iradiation showed dose-dependent decrease. Only 60% of fibroblasts were survived at 140 mJ/cm2UVB irradiation. By pre-cultivation of cells with melatonin (10 nM), a significant number of cels remained unaffected. After UVB iradiation with 70 mJ/cm2, the level of putrescine was 1.70.3 fold increased compared to mela-transcriptional level of ornithine decarboxylase (ODC) gene expression was increased by UVB ir-radiation and prohibited by melatonin. These re-sults indicated that melatonin was effectively able to neutralize membrane peroxidation when present in relevant concentration during UVB irradiation and diminishes the UVB-induced increase of poly-amine synthesis and ODC gene expression. Col-lectively, ODC response to UVB induced changes are possibly involves a melatonin or antioxidant sensitive regulatory pathway in normal human skin fibroblast.