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Sol-Precipitation법으로 제조된 WO<sub>3</sub> 나노분말을 이용한 후막 센서의 NO<sub>2</sub> 감지 특성
류현욱,박경희,김인천,홍광준,박진성,Ryu, Hyun-Wook,Park, Kyung-Hee,Kim, In-Chun,Hong, Kwang-Joon,Park, Jin-Seong 한국재료학회 2002 한국재료학회지 Vol.12 No.12
Nanosized $WO_3$ powders were synthesized by the sol-precipitation process using $WCl_{6}$ as the starting material, ethanol as a solvent and $NH_4$OH solution as a precipitant, followed by a washing-drying treatment and calcination. The effects on the powder crystallinity and microstructure of calcination temperature were investigated with XRD and FE-SEM. The $WO_3$ powders calcined at $500^{\circ}C$ and $700^{\circ}C$ showed good crystallinity and their mean particle size was 30nm and 70nm, respectively. These powders were used for the preparation of pastes which were printed as thick films on alumina substrates with comb-type Pt electrodes. The particle size strongly influenced the $NO_2$ gas sensing property of the thick films. A significant reduction in the $NO_2$ sensitivity was observed for the film prepared from larger particle size, having thus a larger grain size. For the film having a smaller grain size, on the other hand, the higher $NO_2$ sensitivity was observed and the sensitivity increased with $NO_2$ concentration.
Influence of Toxicologically Relevant Metals on Human Epigenetic Regulation
류현욱,이동훈,원혜림,김경환,성연정,권소희 한국독성학회 2015 Toxicological Research Vol.31 No.1
Environmental toxicants such as toxic metals can alter epigenetic regulatory features such as DNA methylation,histone modification, and non-coding RNA expression. Heavy metals influence gene expression byepigenetic mechanisms and by directly binding to various metal response elements in the target gene promoters. Given the role of epigenetic alterations in regulating genes, there is potential for the integration oftoxic metal-induced epigenetic alterations as informative factors in the risk assessment process. Here, wefocus on recent advances in understanding epigenetic changes, gene expression, and biological effectsinduced by toxic metals.
하악골 결손부의 치조골 신장술을 이용한 임플란트 식립 증례보고
류현욱,Ryu, Hyun-Wook 대한악안면성형재건외과학회 2009 Maxillofacial Plastic Reconstructive Surgery Vol.31 No.4
Objective : This is to report the effectiveness of intraoral distraction osteogenesis, iliac bone graft for alveolar augmentation in the extremely atrophied alveolar defects after infected allobone grafted area. Subjects and Methods : Anterior segmental osteotomy was performed and the trans-oral alveolar distractors (Martin, Germany) were applied in patient with the severe acquired anterior mandibular and mandibular defect after ameloblastoma enucleation. Iliac bone grafts were performed in defect sites and distraction osteogenesis were treated. After latent period for 1 week, the osteomized alveolar segments were distracted by 0.75 mm a day (0.25 mm/1 turn) for 10 days The consolidation period was about 12 weeks. Thereafter, 2 titanium threaded implants were simultaneously installed with removal of distractor. For oral rehabilitiation, The implants were installed in maxilla, mandible. It was tested with clinically and radiographically. Results : Amounts of acquired alveolar bone were 10 mm with the increased width of the ridge crests and soft tissue expansion. Dental implants installated on the augmented alveolar ridges in 12 weeks after distraction were confirmed as in good osseointegration and in good function without any complications. Conclusion : Intraoral distraction osteogenesis can be a good option for alveolar ridge augmentation of the severely atrophied ridges and soft-tissue defects.
대한응급의학회지에 게재된 연구의 부적절한 사후‐검정력 분석
류현욱,이미진,최마이클승필,김종근 대한응급의학회 2013 대한응급의학회지 Vol.24 No.4
Purpose: Negative studies provide valuable information. However, conducting studies with inadequate power is unethical and an inefficient use of resources. Moreover,inaccurate interpretations from underpowered studies result in false conclusions that alter clinical interventions and deter further research. The purpose of this study was to determine the prevalence of negative studies with inadequate power in the Journal of the Korean Society of Emergency Medicine (JKEM). Methods: We assessed all papers in JKEM from 2009 to 2012. We sought published evidence that a post-hoc power analysis had been performed in association with the main hypothesis of the paper. All clinical research studies containing the phrase “no difference” were identified. Data necessary for power calculation were extracted from applicable studies. Results: There were a total of 351 papers in which a statistical comparison was undertaken. Out of 351 original articles,170(48.4%) were negative studies that contained enough information for analysis. Out of 126 negative studies in JKEM, only 21(16.7%) had performed a power analysis demonstrating adequate sample size. In addition, only 6.3% of dichotomous variable articles and 10.3% of continuous variable articles had adequate power. Levels of adequate power in negative studies did not improve over time (p=0.148). Conclusion: Many negative studies in JKEM are inconclusive because they lack the adequate power to detect even large differences between groups. Therefore, it is imperative to consider power when interpreting the literature. When designing future research, power calculations should be performed to ensure sufficient patient recruitment to attain clinically meaningful results.
플라즈마 가스와 RF 파워에 따른 NiO 박막의 우선배향성 및 표면형상 변화
류현욱,최광표,노효섭,박용주,권용,박진성,Ryu Hyun-Wook,Choi Gwang-Ryo,Noh Whyo-Sup,Park Yong-Ju,Kwon Yong,Park Jin-Seong 한국재료학회 2004 한국재료학회지 Vol.14 No.2
Nickel oxide (NiO) thin films were deposited on Si(100) substrates at room temperature by RF magnetron sputtering from a NiO target. The effects of plasma gas and RF power on the crystallographic orientation and surface morphology of the NiO films were investigated. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM) were employed to characterize the deposited film. It was found that the type of plasma gases affected the crystallographic orientation, deposition rate, surface morphology, and crystallinity of NiO films. Highly crystalline NiO films with (100) orientation were obtained when it was deposited under Ar atmosphere. On the other hand, (l11)-oriented NiO films with poor crystallinity were deposited in $O_2$. Also, the increase in RF power resulted in not only higher deposition rate, larger grain size, and rougher surface but also higher crystallinity of NiO films.