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RISS 인기검색어
- 검색키워드
- 저자 : Joong Yeol Choi (검색결과 130 건)
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최창혁,최기열,이중배 大韓齒科器材學會 2004 대한치과재료학회지 Vol.31 No.1
The purpose of this study was to evaluate the galvanic corrosion behavior of NT by coupling with other dental alloys in artificial saliva. The variation of galvanic current and common potential (mixed potential) were monitored as a function of time, and interpreted in terms of the electrochemical properties of each alloy. The effects of adding some constituents such as acid or chloride to the ordinary composition of artificial saliva were also estimated. For most cases of coupling, the significant current was observed only at early stage for several seconds or several minutes, then gradually diminished. The current value was affected by the excessive amount of acid or chloride added to artificial saliva, depending on their aggressiveness on each alloy ; the current was increased in the couples with HG, LG, VT, and decreased in the couples with AM and G2. The results were more complicated in the couples with AP and TC, where some mixed reaction occurred. The common potential was always between two corrosion potentials of alloys involved in the couple, and did not exceed the breakdown potential of alloy acted as anode except the case of coupling with AM in acid-containing artificial saliva. The coupling with AM was found to be the most susceptible to galvanic corrosion.
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치과용 콤포짓트 레진의 적정중합을 위한 최소 광조사 시간 평가
임범순,이용근,김철위,최기열,이중배 大韓齒科器材學會 2004 대한치과재료학회지 Vol.31 No.1
The aim of this study was to estimate the minimum irradiation time for dental composites using a dynamic mechanical analyzer (DMA) and FT-IR. Six commercially available dental composites with A3 shade were tested: Heliomolar RO (Vivadent, Liechtenstein), Charisma (Kulzer, Germany), Herculite XRV Enamel (Kerr, USA), Aelitefil (Bisco, USA), Z100 (3M, USA), and Z250 (3M, USA). Storage modulus was measured by using DMA (StressTech Rheometer, Rheologica Instrument, Sweden) with fast oscillation mode (1 Hz). After disk-type (4 ㎜ ?1 ㎜) samples were irradiated with 500 mW/cm2 for 1, 2, 3, 4, 5, 10, 15, 20, and 30 s, storage modulus was recorded continuously for 60 min. Degree of conversion was also measured using FT-IR spectroscopy (FTS-165, Biorad Win-IR, Perkin-Elmer, USA) at 60 min after irradiation with same curing condition as DMA test. Sample irradiated with 500 mW/cm2 for 120 s was used as a control. The average of results for five specimens was compared using Tukey multiple comparison test (p=0.05) and the minimum irradiation time of composites was determined. The minimum irradiation time to get adequate polymerization was different depending on the dental composites. Both Z100 and Z250 require short irradiation times (5 s) and Charisma requires long irradiation time (15 s).
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Choi, Wonjun,Kim, Hwan-Yeol,Park, Rae-Joon,Kim, Sung Joong Atomic Energy Society of Japan 2017 Journal of nuclear science and technology Vol.54 No.3
<P>During a steam generator tube rupture (SGTR) accident, direct release of radioactive nuclides into the environment is postulated via bypassing the containment building. This conveys a significant threat in severe accident management (SAM) for minimization of radionuclide release. To mitigate this risk, a numerical assessment of SAM strategies was performed for an SGTR accident of an Optimized Power Reactor 1000 MWe (OPR1000) using MELCOR code. Three in-vessel mitigation strategies were evaluated and the effect of delayed operation action was analyzed. The MELCOR calculations showed that activation of a prompt secondary feed and bleed (F&B) operation using auxiliary feed water and use of an atmospheric dump valve could prevent core degradation. However, depressurization using the safety depressurization system could not prevent core degradation, and the injection of coolant via high-pressure safety injection without the use of reactor coolant system (RCS) depressurization increased fission product release. When mitigation action was delayed by 30 minutes after SAMG entrance, a secondary F&B operation failed in depressurizing the RCS sufficiently, and a significant amount of fission products were released into the environment. These results suggest that appropriate mitigation actions should be applied in a timely manner to achieve the optimal mitigation effects.</P>
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Examples of rehabilitation exercises utilizing the virtual reality
( Joong Sook Lee ),( Ki Hoon Han ),( Kang Ho Bae ),( Jin Hyung Shin ),( Hee Yeon Lee ),( Doe Yeol Choi ) 한국체육학회 2016 국제스포츠과학 학술대회 Vol.2016 No.1
Purpose: Virtual reality is a technology created by using computers that can function to allow the user to feel the immersion and interact through the experience of human senses such as sight, touch, smell. To overcome various limitations, such as the environment and the place can be a good mediator because virtual reality is processing program, not reality. Let``s know about the plan and the development direction of rehabilitation exercise utilizing these virtual realities. Method: The processing program of the virtual reality may serve as one of the mediators that can overcome the various limitations, such as the environment and location. The stimulation applied to a variety of human movement and sensory organs to the development of virtual reality technology makes it even more similar to reality. We search for rehabilitation exercise equipment and program cases using virtual reality. Through this, we propose for the future direction of the rehabilitation exercise utilizing virtual reality. Result: Exercise rehabilitation program utilizing virtual reality is mostly composed of simple content such as game with strength training and utilizing biological signals using isokinetic equipment. In rehabilitation exercises, practical applications of virtual reality can be found without difficulty. In Korea, COWALK made from Korea Institute of Science and Technology (KIST) is designed to reflect in gait rehabilitation aimed at extracting the EMG palsy, Plantar Foot Pressure, EEG data. The Man & tel measure and evaluate muscle strength and range of motion in the joints of patients, and it has been implemented a muscular reinforcement and body stabilization exercises. Overseas, the US Microsoft has developed a military physical therapy equipment using the Kinect to recognize your movement. Upper limb rehabilitation robot Armeo, Lower limb rehabilitation robotic Lokomat from Switzerland Hocoma have developed applying software for controlling the treatment strength and the difficulty level depending on the cognitive abilities of a patient. In fact, it has been implemented as seen the virtual reality screen and configured along with the virtual character. Conclusion: Virtual reality technology has not yet presented the exact evidence on how it affects your brain and cognitive abilities because it is not the same as reality. Due to the expensive equipment and data fees, it will find it difficult to secure popularity. But virtual reality is a technology that meets the inherent human desire with a technology that makes it all possible is not possible in reality. Virtual reality content users are thought to increase. With increasing number of users of the virtual reality system, virtual reality can be improved and the stability of the VR device will be consistently proven. Value of the exercise and rehabilitation fusion VR is believed to be raised.
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Choi, Sun-Hye,Kim, Hyeon-Joong,Cho, Hee-Jung,Park, Sang-Deuk,Lee, Na-Eun,Hwang, Sung-Hee,Rhim, Hyewon,Kim, Hyoung-Chun,Cho, Ik-Hyun,Nah, Seung-Yeol The Korean Society of Ginseng 2019 Journal of Ginseng Research Vol.43 No.2
Background: Gintonin is a ginseng-derived exogenous ligand of the G protein-coupled lysophosphatidic acid (LPA) receptor. We previously reported that gintonin stimulates gliotransmitter release in primary cortical astrocytes. Astrocytes play key roles in the functions of neurovascular systems. Although vascular endothelial growth factor (VEGF) is known to influence the normal growth and maintenance of cranial blood vessels and the nervous system, there is little information about the effect of gintonin on VEGF regulation in primary astrocytes, under normal and hypoxic conditions. Methods: Using primary cortical astrocytes of mice, the effects of gintonin on the release, expression, and distribution of VEGF were examined. We further investigated whether the gintonin-mediated VEGF release protects astrocytes from hypoxia. Results: Gintonin administration stimulated the release and expression of VEGF from astrocytes in a concentration- and time-dependent manner. The gintonin-mediated increase in the release of VEGF was inhibited by the LPA1/3 receptor antagonist, Ki16425; phospholipase C inhibitor, U73122; inositol 1,4,5- triphosphate receptor antagonist, 2-APB; and intracellular $Ca^{2+}$ chelator, BAPTA. Hypoxia further stimulated astrocytic VEGF release. Gintonin treatment stimulated additional VEGF release and restored cell viability that had decreased due to hypoxia, via the VEGF receptor pathway. Altogether, the regulation of VEGF release and expression and astrocytic protection mediated by gintonin under hypoxia are achieved via the LPA receptor-VEGF signaling pathways. Conclusion: The present study shows that the gintonin-mediated regulation of VEGF in cortical astrocytes might be neuroprotective against hypoxic insults and could explain the molecular basis of the beneficial effects of ginseng on the central nervous system.
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Choi, Sun-Hye,Lee, Byung-Hwan,Kim, Hyeon-Joong,Hwang, Sung-Hee,Lee, Sang-Mok,Nah, Seung-Yeol The Korean Society of Pharmacology 2013 The Korean Journal of Physiology & Pharmacology Vol.17 No.3
The calcium-activated $K^+$ ($BK_{Ca}$) channel is one of the potassium-selective ion channels that are present in the nervous and vascular systems. $Ca^{2+}$ is the main regulator of $BK_{Ca}$ channel activation. The $BK_{Ca}$ channel contains two high affinity $Ca^{2+}$ binding sites, namely, regulators of $K^+$ conductance, RCK1 and the $Ca^{2+}$ bowl. Lysophosphatidic acid (LPA, 1-radyl-2-hydroxy-sn-glycero-3-phosphate) is one of the neurolipids. LPA affects diverse cellular functions on many cell types through G protein-coupled LPA receptor subtypes. The activation of LPA receptors induces transient elevation of intracellular $Ca^{2+}$ levels through diverse G proteins such as $G{\alpha}_{q/11}$, $G{\alpha}_i$, $G{\alpha}_{12/13}$, and $G{\alpha}s$ and the related signal transduction pathway. In the present study, we examined LPA effects on $BK_{Ca}$ channel activity expressed in Xenopus oocytes, which are known to endogenously express the LPA receptor. Treatment with LPA induced a large outward current in a reversible and concentration-dependent manner. However, repeated treatment with LPA induced a rapid desensitization, and the LPA receptor antagonist Ki16425 blocked LPA action. LPA-mediated $BK_{Ca}$ channel activation was also attenuated by the PLC inhibitor U-73122, $IP_3$ inhibitor 2-APB, $Ca^{2+}$ chelator BAPTA, or PKC inhibitor calphostin. In addition, mutations in RCK1 and RCK2 also attenuated LPA-mediated $BK_{Ca}$ channel activation. The present study indicates that LPA-mediated activation of the $BK_{Ca}$ channel is achieved through the PLC, $IP_3$, $Ca^{2+}$, and PKC pathway and that LPA-mediated activation of the $BK_{Ca}$ channel could be one of the biological effects of LPA in the nervous and vascular systems.
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