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Search Results: 1 - 10 of 6847 matches for " Seung-Jae Lim "
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Cobalt-Alloy Implant Debris Induce HIF-1α Hypoxia Associated Responses: A Mechanism for Metal-Specific Orthopedic Implant Failure
Lauryn Samelko, Marco S. Caicedo, Seung-Jae Lim, Craig Della-Valle, Joshua Jacobs, Nadim J. Hallab
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0067127
Abstract: The historical success of orthopedic implants has been recently tempered by unexpected pathologies and early failures of some types of Cobalt-Chromium-Molybdenum alloy containing artificial hip implants. Hypoxia-associated responses to Cobalt-alloy metal debris were suspected as mediating this untoward reactivity at least in part. Hypoxia Inducible Factor-1α is a major transcription factor involved in hypoxia, and is a potent coping mechanism for cells to rapidly respond to changing metabolic demands. We measured signature hypoxia associated responses (i.e. HIF-1α, VEGF and TNF-α) to Cobalt-alloy implant debris both in vitro (using a human THP-1 macrophage cell line and primary human monocytes/macrophages) and in vivo. HIF-1α in peri-implant tissues of failed metal-on-metal implants were compared to similar tissues from people with metal-on-polymer hip arthroplasties, immunohistochemically. Increasing concentrations of cobalt ions significantly up-regulated HIF-1α with a maximal response at 0.3 mM. Cobalt-alloy particles (1 um-diameter, 10 particles/cell) induced significantly elevated HIF-1α, VEGF, TNF-α and ROS expression in human primary macrophages whereas Titanium-alloy particles did not. Elevated expression of HIF-1α was found in peri-implant tissues and synovial fluid of people with failing Metal-on-Metal hips (n = 5) compared to failed Metal-on-Polymer articulating hip arthroplasties (n = 10). This evidence suggests that Cobalt-alloy, more than other metal implant debris (e.g. Titanium alloy), can elicit hypoxia-like responses that if unchecked can lead to unusual peri-implant pathologies, such as lymphocyte infiltration, necrosis and excessive fibrous tissue growths.
Alpha-Synuclein Stimulation of Astrocytes: Potential Role for Neuroinflammation and Neuroprotection
He-Jin Lee,Changyoun Kim,Seung-Jae Lee
Oxidative Medicine and Cellular Longevity , 2010, DOI: 10.4161/oxim.3.4.12809
Abstract: Selective loss of neurons, abnormal protein deposition and neuroinflammation are the common pathological features of neurodegenerative diseases, and these features are closely related to one another. In Parkinson's disease, abnormal aggregation and deposition of α-synuclein is known as a critical event in pathogenesis of the disease, as well as in other related neurodegenerative disorders, such as dementia with Lewy bodies and multiple system atrophy. Increasing evidence suggests that α-synuclein aggregates can activate glial cells to induce neuroinflammation. However, how an inflammatory microenvironment is established and maintained by this protein remains unknown. Findings from our recent study suggest that neuronal α-synuclein can be directly transferred to astrocytes through sequential exocytosis and endocytosis and induce inflammatory responses from astrocytes. Here we discuss potential roles of astrocytes in a cascade of events leading to α-synuclein-induced neuroinflammation.
Alpha-Synuclein Stimulation of Astrocytes: Potential Role for Neuroinflammation and Neuroprotection
He-Jin Lee,Changyoun Kim,Seung-Jae Lee
Oxidative Medicine and Cellular Longevity , 2010, DOI: 10.4161/oxim.3.4.12809
Abstract: Selective loss of neurons, abnormal protein deposition and neuroinflammation are the common pathological features of neurodegenerative diseases, and these features are closely related to one another. In Parkinson's disease, abnormal aggregation and deposition of α-synuclein is known as a critical event in pathogenesis of the disease, as well as in other related neurodegenerative disorders, such as dementia with Lewy bodies and multiple system atrophy. Increasing evidence suggests that α-synuclein aggregates can activate glial cells to induce neuroinflammation. However, how an inflammatory microenvironment is established and maintained by this protein remains unknown. Findings from our recent study suggest that neuronal α-synuclein can be directly transferred to astrocytes through sequential exocytosis and endocytosis and induce inflammatory responses from astrocytes. Here we discuss potential roles of astrocytes in a cascade of events leading to α-synuclein-induced neuroinflammation.
Human Body Tracking and Pose Estimation Using Modified Camshift Algorithm  [PDF]
Seung-Jun Hwang, Jae-Hong Min, In-Gyu Kim, Seung-Jae Park, Gwang-Pyo Ahn, Joong-Hwan Baek
Journal of Software Engineering and Applications (JSEA) , 2013, DOI: 10.4236/jsea.2013.65B008
Abstract: In this paper, we propose multiple CAMShift Algorithm based on Kalman filter and weighted search windows that extracts skin color area and tracks several human body parts for real-time human tracking system. The CAMShift Algorithm we propose searches the skin color region by detecting the skin color area from background model. Kalman filter stabilizes the floated search area of CAMShift Algorithm. Each occlusion areas are avoided by using weighted window of non-search areas and main-search area. And shadows are eliminated from background model and intensity of shadow. The proposed modified Camshaft algorithm can estimate human pose in real-time and achieves 96.82% accuracy even in the case of occlusions.
Torsional Stiffness Effects on the Dynamic Stability of a Horizontal Axis Wind Turbine Blade
Min-Soo Jeong,In Lee,Seung-Jae Yoo,Kwang-Choon Park
Energies , 2013, DOI: 10.3390/en6042242
Abstract: Aeroelastic instability problems have become an increasingly important issue due to the increased use of larger horizontal axis wind turbines. To maintain these large structures in a stable manner, the blade design process should include studies on the dynamic stability of the wind turbine blade. Therefore, fluid-structure interaction analyses of the large-scaled wind turbine blade were performed with a focus on dynamic stability in this study. A finite element method based on the large deflection beam theory is used for structural analysis considering the geometric nonlinearities. For the stability analysis, a proposed aerodynamic approach based on Greenberg’s extension of Theodorsen’s strip theory and blade element momentum method were employed in conjunction with a structural model. The present methods proved to be valid for estimations of the aerodynamic responses and blade behavior compared with numerical results obtained in the previous studies. Additionally, torsional stiffness effects on the dynamic stability of the wind turbine blade were investigated. It is demonstrated that the damping is considerably influenced by variations of the torsional stiffness. Also, in normal operating conditions, the destabilizing phenomena were observed to occur with low torsional stiffness.
Spatial and Temporal Variation in PBL Height over the Korean Peninsula in the KMA Operational Regional Model
Seung-Jae Lee,Juwon Lee,Steven J. Greybush,Minseok Kang,Joon Kim
Advances in Meteorology , 2013, DOI: 10.1155/2013/381630
Abstract: Spatial and temporal variations in planetary boundary layer height (PBLH) over the Korean Peninsula and its surrounding oceans are investigated using a regional grid model operated at the Korea Meteorological Administration (KMA). Special attention is placed on daily maximum mixing height for evaluation against two radiosonde observation datasets. In order to construct a new high-resolution PBLH database with 3-hour time and 10?km spatial resolution, short-term integrations with the regional model are carried out for a one-year period from June 2010 to May 2011. The resulting dataset is then utilized to explore the seasonal patterns of horizontal PBLH distribution over the peninsula for one year. Frequency distributions as well as monthly and diurnal variations of PBLH at two selected locations are examined. This study reveals specific spatiotemporal structure of boundary layer depth over the Korean Peninsula for the first time at a relatively high-resolution scale. The results are expected to provide insights into the direction for operational tuning and future development in the model boundary layer schemes at KMA. 1. Introduction The diurnally evolving structure of the planetary boundary layer (PBL) for a typical synoptic high-pressure system is described by Stull [1]. The depth of the PBL provides important information for numerical weather prediction (NWP) and atmospheric dispersion models. It has been used as a key parameter in the trigger function for convection in cumulus parameterization schemes in many NWP models (e.g., [2, 3]). Accurate prediction of PBL’s vertical extent is crucial in determining whether harmful gases (e.g., those erupted from a volcano) would reach the ground or not [4]. It affects near-surface atmospheric pollutant concentrations (e.g., [5]), low-level moisture availability, and updraft conditions prior to thundershowers (e.g., [6]). In particular, daytime mixed-layer (ML) height has been regarded as the location of a capping temperature inversion atop the convective boundary layer. Raupach et al. [7] and Denmead et al. [8] formularized the relationship between carbon dioxide concentration and ML depth through entrainment processes. To identify the ML top, there have been several methods for which radiosondes, wind profilers, and ceilometer/light detection and ranging (LIDAR) were utilized (e.g., [9–14]). These kinds of techniques to extract PBLH information have been also applied over the Korean Peninsula to surface flux [15–17], radiosonde [18, 19], LIDAR [20], and wind profiler [21] data. Most of the researchers
3-D Worm Tracker for Freely Moving C. elegans
Namseop Kwon, Jaeyeon Pyo, Seung-Jae Lee, Jung Ho Je
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0057484
Abstract: The manner in which the nervous system regulates animal behaviors in natural environments is a fundamental issue in biology. To address this question, C. elegans has been widely used as a model animal for the analysis of various animal behaviors. Previous behavioral assays have been limited to two-dimensional (2-D) environments, confining the worm motion to a planar substrate that does not reflect three-dimensional (3-D) natural environments such as rotting fruits or soil. Here, we develop a 3-D worm tracker (3DWT) for freely moving C. elegans in 3-D environments, based on a stereoscopic configuration. The 3DWT provides us with a quantitative trajectory, including the position and movement direction of the worm in 3-D. The 3DWT is also capable of recording and visualizing postures of the moving worm in 3-D, which are more complex than those in 2-D. Our 3DWT affords new opportunities for understanding the nervous system function that regulates animal behaviors in natural 3-D environments.
A Study on Group Key Agreement in Sensor Network Environments Using Two-Dimensional Arrays
Seung-Jae Jang,Young-Gu Lee,Kwang-Hyung Lee,Tai-Hoon Kim,Moon-Seog Jun
Sensors , 2011, DOI: 10.3390/s110908227
Abstract: These days, with the emergence of the concept of ubiquitous computing, sensor networks that collect, analyze and process all the information through the sensors have become of huge interest. However, sensor network technology fundamentally has wireless communication infrastructure as its foundation and thus has security weakness and limitations such as low computing capacity, power supply limitations and price. In this paper, and considering the characteristics of the sensor network environment, we propose a group key agreement method using a keyset pre-distribution of two-dimension arrays that should minimize the exposure of key and personal information. The key collision problems are resolved by utilizing a polygonal shape’s center of gravity. The method shows that calculating a polygonal shape’s center of gravity only requires a very small amount of calculations from the users. The simple calculation not only increases the group key generation efficiency, but also enhances the sense of security by protecting information between nodes.
A genetic screen for modifiers of Drosophila caspase Dcp-1 reveals caspase involvement in autophagy and novel caspase-related genes
Young-Il Kim, Taewoo Ryu, Judong Lee, Young-Shin Heo, Joohong Ahnn, Seung-Jae Lee, OokJoon Yoo
BMC Cell Biology , 2010, DOI: 10.1186/1471-2121-11-9
Abstract: We screened ~15,000 EP lines and identified 72 Dcp-1-interacting genes that were classified into 10 groups based on their functions and pathways: 4 apoptosis signaling genes, 10 autophagy genes, 5 insulin/IGF and TOR signaling pathway genes, 6 MAP kinase and JNK signaling pathway genes, 4 ecdysone signaling genes, 6 ubiquitination genes, 11 various developmental signaling genes, 12 transcription factors, 3 translation factors, and 11 other unclassified genes including 5 functionally undefined genes. Among them, insulin/IGF and TOR signaling pathway, MAP kinase and JNK signaling pathway, and ecdysone signaling are known to be involved in autophagy. Together with the identification of autophagy genes, the results of our screen suggest that autophagy counteracts Dcp-1-induced apoptosis. Consistent with this idea, we show that expression of eGFP-Atg5 rescued the eye phenotype caused by Dcp-1 GF. Paradoxically, we found that over-expression of full-length Dcp-1 induced autophagy, as Atg8b-GFP, an indicator of autophagy, was increased in the eye imaginal discs and in the S2 cell line. Taken together, these data suggest that autophagy suppresses Dcp-1-mediated apoptotic cell death, whereas Dcp-1 positively regulates autophagy, possibly through feedback regulation.We identified a number of Dcp-1 modifiers that genetically interact with Dcp-1-induced cell death. Our results showing that Dcp-1 and autophagy-related genes influence each other will aid future investigations of the complicated relationships between apoptosis and autophagy.Apoptosis, or programmed cell death, is an evolutionarily conserved, genetically regulated process, whereby cells that are no longer needed undergo self-destruction through the activation of a cell suicide program [1,2]. This cell death program is associated with characteristic morphological alterations, such as condensation of the nucleus and cytoplasm, fragmentation of nuclear DNA, reorganization of the cytoskeleton, and reduction of the cell
Detrimental Effect of Interfacial Dzyaloshinskii-Moriya Interaction on Perpendicular Spin-Transfer-Torque Magnetic Random Access Memory
Peong-Hwa Jang,Kyoungmi Song,Seung-Jae Lee,Seo-Won Lee,Kyung-Jin Lee
Physics , 2015, DOI: 10.1063/1.4936089
Abstract: Interfacial Dzyaloshinskii-Moriya interaction in ferromagnet/heavy metal bilayers is recently of considerable interest as it offers an efficient control of domain walls and the stabilization of magnetic skyrmions. However, its effect on the performance of perpendicular spin transfer torque memory has not been explored yet. We show based on numerical studies that the interfacial Dzyaloshinskii-Moriya interaction decreases the thermal energy barrier while increases the switching current. As high thermal energy barrier as well as low switching current is required for the commercialization of spin torque memory, our results suggest that the interfacial Dzyaloshinskii-Moriya interaction should be minimized for spin torque memory applications.
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