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가시광을 이용한 ZnS/ZnO 상에서의 광촉매 반응에 의한 물로부터의 수소생성
서승광,윤필상,이한수,이호인 한국공업화학회 2003 응용화학 Vol.7 No.2
The pure ZnS can not absorb visible light because of its large band gap of 3.6eV. The ZnO/ZnS was obtained from partial oxidation of ZnS, and its band gap was 2.5eV where visible light can be absorbed. From XRD analysis, it was confirmed that only ZnO was formed during oxidation process but not ZnSO₄. In case of ZnO/ZnS, the quantum efficiency for the hydrogen evolution from water was 0.87% under visible light irradiation. In order to improve the interaction between ZnO and ZnS, ZnS/ZnO was prepared by precipitating ZnS on ZnO. After calcination of ZnS/ZnO, the band gap became narrow. The pure ZnO and the physically mixed ZnS-ZnO could not absorb visible light, but the ZnS-doped ZnO (ZnS/ZnO) could do. The band gap of pure ZnO was 3.2 eV and that of ZnS/ZnO was 2.5ev. The best activity was obtained when clcination temperature and time were 500 ℃ and 1 h, respectively. The quantum efficiency of ZnS/ZnO for the reaction was 3.29%.
오승필,김도익,예윤해,-- 경희대학교 레이저공학연구소 2001 레이저공학 Vol.12 No.-
We propose a signal processing method for white light interferometry which requires a series of analog signal processing circuitry to locate the central interference fringe with high speed. The method is applied to a fiber optic sensor consisted of an ELED, a sensing Fabry-Perot interferometer, and a Michelson interferometer for phase-matching and phase modulation. The temporal shift of sensor response is measured by the shift of the central fringe position. The test results show that the WLI sensor system is able to differentiate the change of 0.02℃ when it is implemented as a temperature sensor.
레이저 스페클간섭법에 있어서 스페클크기와 측정 한계에 관한 연구
윤성운,김경석,양승필,정현철,김정호,이도윤 한국공작기계학회 1996 한국생산제조학회지 Vol.5 No.1
The high coherence of laser beam has made it possible to observe interference effects even in the light scattered from rough surfaces. That's why, when object with a scattering surface is illuminated with laser light, we do see a speckled appearance due to random interference. This sort of unique property of laser speckle has brought into existence the new noncontacting techniques such as speckle metrology method of measuring deformation, displacement, and vibration etc of objects with high optical sensitivity. The measurable range of speckle metrology especially used to measure in-plane information, however, is limited by some factors, the so-called strain, rotation, tilt of surface and out of displacement perpendicular to the plane of analysis. This restrictions severly limits the measurable range of speckle metrology by causing the decorrelation of speckle patterns. It is the purpose of this paper to give a survey on the measurable limitation of speckle photography method that is one of speckle metrology. Namely we will discuss the mutual relationships and problems of each limitations adding the restriction of the largest and smallest displacement measurable with speckle methods.
Yun, Seung Pil,Yoon, Yeo Min,Lee, Jun Hee,Kook, Minjee,Han, Yong-Seok,Jung, Seo Kyung,Lee, Sang Hun MDPI 2018 INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES Vol.19 No.2
<P>Mesenchymal stem cells (MSCs) could be a promising solution in the treatment of various diseases including chronic kidney disease (CKD). However, endoplasmic reticulum (ER) stress induced by ischemia in the area of application limits the integration and survival of MSCs in patients. In our study, we generated ER stress-induced conditions in MSCs using <I>P</I>-cresol. As <I>P</I>-cresol is a toxic compound accumulated in the body of CKD patients and induces apoptosis and inflammation through reactive oxygen species (ROS), we observed ER stress-induced MSC apoptosis activated by oxidative stress, which in turn resulted from ROS generation. To overcome stress-induced apoptosis, we investigated the protective effects of tauroursodeoxycholic acid (TUDCA), a bile acid, on ER stress in MSCs. In ER stress, TUDCA treatment of MSCs reduced ER stress-associated protein activation, including GRP78, PERK, eIF2α, ATF4, IRE1α, and CHOP. Next, to explore the protective mechanism adopted by TUDCA, TUDCA-mediated cellular prion protein (PrP<SUP>C</SUP>) activation was assessed. We confirmed that PrP<SUP>C</SUP> expression significantly increased ROS, which was eliminated by superoxide dismutase and catalase in MSCs. These findings suggest that TUDCA protects from inflammation and apoptosis in ER stress via PrP<SUP>C</SUP> expression. Our study demonstrates that TUDCA protects MSCs against inflammation and apoptosis in ER stress by PrP<SUP>C</SUP> expression in response to <I>P</I>-cresol exposure.</P>
Yun, Seung Pil,Han, Yong-Seok,Lee, Jun Hee,Kim, Sang Min,Lee, Sang Hun The Korean Society of Applied Pharmacology 2018 Biomolecules & Therapeutics(구 응용약물학회지) Vol.26 No.4
p-Cresol, found at high concentrations in the serum of chronic kidney failure patients, is known to cause cell senescence and other complications in different parts of the body. p-Cresol is thought to mediate cytotoxic effects through the induction of autophagy response. However, toxic effects of p-cresol on mesenchymal stem cells have not been elucidated. Thus, we aimed to investigate whether p-cresol induces senescence of mesenchymal stem cells, and whether melatonin can ameliorate abnormal autophagy response caused by p-cresol. We found that p-cresol concentration-dependently reduced proliferation of mesenchymal stem cells. Pretreatment with melatonin prevented pro-senescence effects of p-cresol on mesenchymal stem cells. We found that by inducing phosphorylation of Akt and activating the Akt signaling pathway, melatonin enhanced catalase activity and thereby inhibited the accumulation of reactive oxygen species induced by p-cresol in mesenchymal stem cells, ultimately preventing abnormal activation of autophagy. Furthermore, preincubation with melatonin counteracted other pro-senescence changes caused by p-cresol, such as the increase in total 5'-AMP-activated protein kinase expression and decrease in the level of phosphorylated mechanistic target of rapamycin. Ultimately, we discovered that melatonin restored the expression of senescence marker protein 30, which is normally suppressed because of the induction of the autophagy pathway in chronic kidney failure patients by p-cresol. Our findings suggest that stem cell senescence in patients with chronic kidney failure could be potentially rescued by the administration of melatonin, which grants this hormone a novel therapeutic role.
Yun, Seung Pil,Han, Yong-Seok,Lee, Jun Hee,Yoon, Yeo Min,Yun, Chul Won,Rhee, Peter,Lee, Sang Hun SPANDIDOS PUBLICATIONS 2017 MOLECULAR MEDICINE REPORTS Vol.16 No.5
<P>Cellular prion protein (PrP<SUP>C</SUP>) can replace other pivotal molecules due to its interaction with several partners in performing a variety of important biological functions that may differ between embryonic and mature stem cells. Recent studies have revealed major advances in elucidating the putative role of PrP<SUP>C</SUP> in the regulation of stem cells and its application in stem cell therapy. What is special about PrP<SUP>C</SUP> is that its expression may be regulated by hypoxia-inducible factor (HIF)-1α, which is the transcriptional factor of cellular response to hypoxia. Hypoxic conditions have been known to drive cellular responses that can enhance cell survival, differentiation and angiogenesis through adaptive processes. Our group recently reported hypoxia-enhanced vascular repair of endothelial colony-forming cells on ischemic injury. Hypoxia-induced AKT/signal transducer and activator of transcription 3 phosphorylation eventually increases neovasculogenesis. In stem cell biology, hypoxia promotes the expression of growth factors. According to other studies, aspects of tissue regeneration and cell function are influenced by hypoxia, which serves an essential role in stem cell HIF-1α signaling. All these data suggest the possibility that hypoxia-mediated PrP<SUP>C</SUP> serves an important role in angiogenesis. Therefore, the present review summarizes the characteristics of PrP<SUP>C</SUP>, which is produced by HIF-1α in hypoxia, as it relates to angiogenesis.</P>
Magnetic resonance imaging evaluation of Yukatan minipig brains for neurotherapy applications
Seung Pil Yun,Dong Hyun Kim,Jung Min Ryu,Jae Hong Park,Su Shin Park,Ji Hoon Jeon,Bit Na Seo,Hyun-Jeong Kim,Jun-Gyu Park,Kyoung-Oh Cho,Ho Jae Han 한국실험동물학회 2011 Laboratory Animal Research Vol.27 No.4
Magnetic resonance imaging (MRI) of six Yukatan minipig brains was performed. The animals were placed in stereotaxic conditions currently used in experiments. To allow for correctpositioning of the animal in the MRI instrument, landmarks were previously traced on the snout of the pig. To avoid movements, animal were anesthetized. The animals were placed in a prone position in a Siemens Magnetom Avanto 1.6 System with a head coil. Axial T2-weighted and sagittal T1-weighted MRI images were obtained from each pig. Afterwards, the brains of the pigs were fixed and cut into axial sections. Histologic and MR images were compared. The usefulness of this technique is discussed.