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Search Results: 1 - 10 of 43862 matches for " Ik Yong Kim "
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Quantitative Measurement of Elasticity of the Appendix Using Shear Wave Elastography in Patients with Suspected Acute Appendicitis
Seung-Whan Cha, Ik Yong Kim, Young Wan Kim
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0101292
Abstract: Introduction Shear wave elastography (SWE) has not been studied for diagnosing appendicitis. We postulated that an inflamed appendix would become stiffer than a normal appendix. We evaluated the elastic modulus values (EMV) by SWE in healthy volunteers, patients without appendicitis, and patients with appendicitis. We also evaluated diagnostic ability of SWE for differentiating an inflamed from a normal appendix in patients with suspected appendicitis. Materials and Methods Forty-one patients with clinically suspected acute appendicitis and 11 healthy volunteers were prospectively enrolled. Gray-scale ultrasonography (US), SWE and multi-slice computed tomography (CT) were performed. The EMV was measured in the anterior, medial, and posterior appendiceal wall using SWE, and the highest value (kPa) was recorded. Results Patients were classified into appendicitis (n = 30) and no appendicitis groups (n = 11). One case of a negative appendectomy was detected. The median EMV was significantly higher in the appendicitis group (25.0 kPa) compared to that in the no appendicitis group (10.4 kPa) or in the healthy controls (8.3 kPa) (p<0.001). Among SWE and other US and CT features, CT was superior to any conventional gray-scale US feature or SWE. Either the CT diameter criterion or combined three CT features predicted true positive in 30 and true negative in 11 cases and yielded 100% sensitivity and 100% specificity. An EMV of 12.5 kPa for the stiffest region of the appendix predicted true positive in 28, true negative in 11, and false negative in two cases. The EMV (≥12.5 kPa) yielded 93% sensitivity and 100% specificity. Conclusion Our results suggest that EMV by SWE helps distinguish an inflamed from a normal appendix. Given that SWE has high specificity, quantitative measurement of the elasticity of the appendix may provide complementary information, in addition to morphologic features on gray-scale US, in the diagnosis of appendicitis.
Smart Learning Services Based on Smart Cloud Computing
Svetlana Kim,Su-Mi Song,Yong-Ik Yoon
Sensors , 2011, DOI: 10.3390/s110807835
Abstract: Context-aware technologies can make e-learning services smarter and more efficient since context-aware services are based on the user’s behavior. To add those technologies into existing e-learning services, a service architecture model is needed to transform the existing e-learning environment, which is situation-aware, into the environment that understands context as well. The context-awareness in e-learning may include the awareness of user profile and terminal context. In this paper, we propose a new notion of service that provides context-awareness to smart learning content in a cloud computing environment. We suggest the elastic four smarts (E4S)—smart pull, smart prospect, smart content, and smart push—concept to the cloud services so smart learning services are possible. The E4S focuses on meeting the users’ needs by collecting and analyzing users’ behavior, prospecting future services, building corresponding contents, and delivering the contents through cloud computing environment. Users’ behavior can be collected through mobile devices such as smart phones that have built-in sensors. As results, the proposed smart e-learning model in cloud computing environment provides personalized and customized learning services to its users.
Stellar Populations and the Local Group Membership of the Dwarf Galaxy DDO 210
Myung Gyoon Lee,Antonio Aparicio,Nikolay Tikonov,Yong-Ik Byun,Eunhyeuk Kim
Physics , 1999, DOI: 10.1086/300988
Abstract: We present deep BVI CCD photometry of the stars in the dwarf galaxy DDO 210. The color-magnitude diagrams of DDO 210 show a well-defined red giant branch (RGB) and a blue plume. The tip of the RGB is found to be at I_TRGB = 20.95 +/- 0.10 mag. From this the distance to DDO 210 is estimated to be d = 950 +/- 50 kpc. The corresponding distance of DDO 210 to the center of the Local Group is 870 kpc, showing that it is a member of the Local Group. The mean metallicity of the red giant branch stars is estimated to be [Fe/H] = -1.9 +/- 0.1 dex. Integrated magnitudes of DDO 210 within the Holmberg radius (r_H=110 arcsec = 505 pc) are derived to be M_B=-10.6 +/- 0.1 mag and M_V=-10.9 +/- 0.1 mag. B and V surface brightness profiles of DDO 210 are approximately consistent with an exponential law with scale lengths r_s(B) = 161 pc and r_s(V) = 175 pc. The brightest blue and red stars in DDO 210 (BSG and RSG) are found to be among the faintest in the nearby galaxies with young stellar populations: _{BSG} = -3.41 +/- 0.11 mag and _{RSG} = -4.69 +/- 0.13 mag. An enhancement of the star formation rate in the recent past (several hundred Myrs) is observed in the central region of DDO 210. The opposite trend is observed in the outer region of the galaxy, suggesting a possible two-component structure of the kind disk/halo found in spiral galaxies. The real nature of this two-component structure must, however, be confirmed with more detailed observations.
Statistical Properties of Galactic δ Scuti Stars: Revisited
Seo-Won Chang,Pavlos Protopapas,Dae-Won Kim,Yong-Ik Byun
Physics , 2013, DOI: 10.1088/0004-6256/145/5/132
Abstract: We present statistical characteristics of 1,578 {\delta} Scuti stars including nearby field stars and cluster member stars within the Milky Way. We obtained 46% of these stars (718 stars) from the works done by Rodr\'{i}guez and collected the remaining 54% stars (860 stars) from other literatures. We updated the entries with the latest information of sky coordinate, color, rotational velocity, spectral type, period, amplitude and binarity. The majority of our sample are well characterized in terms of typical period range (0.02-0.25 days), pulsation amplitudes (<0.5 mag) and spectral types (A-F type). Given this list of {\delta} Scuti stars, we examined relations between their physical properties (i.e., periods, amplitudes, spectral types and rotational velocities) for field stars and cluster members, and confirmed that the correlations of properties are not significantly different from those reported in the Rodr\'{i}guez's works. All the {\delta} Scuti stars are cross-matched with several X-ray and UV catalogs, resulting in 27 X-ray and 41 UV-only counterparts. These counterparts are interesting targets for further study because of their rarity and uniqueness in showing {\delta} Scuti-type variability and X-ray/UV emission at the same time. The compiled catalog can be accessed through the web interface http://stardb.yonsei.ac.kr/DeltaScuti
QSO Selection Algorithm Using Time Variability and Machine Learning: Selection of 1,620 QSO Candidates from MACHO LMC Database
Dae-Won Kim,Pavlos Protopapas,Yong-Ik Byun,Charles Alcock,Roni Khardon,Markos Trichas
Physics , 2011, DOI: 10.1088/0004-637X/735/2/68
Abstract: We present a new QSO selection algorithm using a Support Vector Machine (SVM), a supervised classification method, on a set of extracted times series features including period, amplitude, color, and autocorrelation value. We train a model that separates QSOs from variable stars, non-variable stars and microlensing events using 58 known QSOs, 1,629 variable stars and 4,288 non-variables using the MAssive Compact Halo Object (MACHO) database as a training set. To estimate the efficiency and the accuracy of the model, we perform a cross-validation test using the training set. The test shows that the model correctly identifies ~80% of known QSOs with a 25% false positive rate. The majority of the false positives are Be stars. We applied the trained model to the MACHO Large Magellanic Cloud (LMC) dataset, which consists of 40 million lightcurves, and found 1,620 QSO candidates. During the selection none of the 33,242 known MACHO variables were misclassified as QSO candidates. In order to estimate the true false positive rate, we crossmatched the candidates with astronomical catalogs including the Spitzer Surveying the Agents of a Galaxy's Evolution (SAGE) LMC catalog and a few X-ray catalogs. The results further suggest that the majority of the candidates, more than 70%, are QSOs.
Detecting Variability in Massive Astronomical Time-Series Data II: Variable Candidates in the Northern Sky Variability Survey
Min-Su Shin,Hahn Yi,Dae-Won Kim,Seo-Won Chang,Yong-Ik Byun
Physics , 2011, DOI: 10.1088/0004-6256/143/3/65
Abstract: We present variability analysis of data from the Northern Sky Variability Survey (NSVS). Using the clustering method which defines variable candidates as outliers from large clusters, we cluster 16,189,040 light curves, having data points at more than 15 epochs, as variable and non-variable candidates in 638 NSVS fields. Variable candidates are selected depending on how strongly they are separated from the largest cluster and how rarely they are grouped together in eight dimensional space spanned by variability indices. All NSVS light curves are also cross-correlated to the Infrared Astronomical Satellite, AKARI, Two Micron All Sky Survey, Sloan Digital Sky Survey (SDSS), and Galaxy Evolution Explorer objects as well as known objects in the SIMBAD database. The variability analysis and cross-correlation results are provided in a public online database which can be used to select interesting objects for further investigation. Adopting conservative selection criteria for variable candidates, we find about 1.8 million light curves as possible variable candidates in the NSVS data, corresponding to about 10% of our entire NSVS samples. Multi-wavelength colors help us find specific types of variability among the variable candidates. Moreover, we also use morphological classification from other surveys such as SDSS to suppress spurious cases caused by blending objects or extended sources due to the low angular resolution of the NSVS.
A Refined QSO Selection Method Using Diagnostics Tests: 663 QSO Candidates in the LMC
Dae-Won Kim,Pavlos Protopapas,Markos Trichas,Michael Rowan-Robinson,Roni Khardon,Charles Alcock,Yong-Ik Byun
Physics , 2011, DOI: 10.1088/0004-637X/747/2/107
Abstract: We present 663 QSO candidates in the Large Magellanic Cloud (LMC) selected using multiple diagnostics. We started with a set of 2,566 QSO candidates from our previous work selected using time variability of the MACHO LMC lightcurves. We then obtained additional information for the candidates by crossmatching them with the Spitzer SAGE, the MACHO UBVI, the 2MASS, the Chandra and the XMM catalogs. Using this information, we specified six diagnostic features based on mid-IR colors, photometric redshifts using SED template fitting, and X-ray luminosities in order to further discriminate high confidence QSO candidates in the absence of spectra information. We then trained a one-class SVM (Support Vector Machine) model using the diagnostics features of the confirmed 58 MACHO QSOs. We applied the trained model to the original candidates and finally selected 663 high confidence QSO candidates. Furthermore, we crossmatched these 663 QSO candidates with the newly confirmed 144 QSOs and 275 non-QSOs in the LMC fields. On the basis of the counterpart analysis, we found that the false positive rate is less than 1%.
Inhibitory Effects of Anthocyanins on Secretion of Helicobacter pylori CagA and VacA Toxins
Sa-Hyun Kim, Min Park, Hyunjun Woo, Nagendran Tharmalingam, Gyusang Lee, Ki-Jong Rhee, Yong Bin Eom, Sang Ik Han, Woo Duck Seo, Jong Bae Kim
International Journal of Medical Sciences , 2012,
Abstract: Anthocyanins have been studied as potential antimicrobial agents against Helicobacter pylori. We investigated whether the biosynthesis and secretion of cytotoxin-associated protein A (CagA) and vacuolating cytotoxin A (VacA) could be suppressed by anthocyanin treatment in vitro. H. pylori reference strain 60190 (CagA+/VacA+) was used in this study to investigate the inhibitory effects of anthocyanins; cyanidin 3-O-glucoside (C3G), peonidin 3-O-glucoside (Peo3G), pelargonidin 3-O-glucoside (Pel3G), and malvidin 3-O-glucoside (M3G) on expression and secretion of H. pylori toxins. Anthocyanins were added to bacterial cultures and Western blotting was used to determine secretion of CagA and VacA. Among them, we found that C3G inhibited secretion of CagA and VacA resulting in intracellular accumulation of CagA and VacA. C3G had no effect on cagA and vacA expression but suppressed secA transcription. As SecA is involved in translocation of bacterial proteins, the down-regulation of secA expression by C3G offers a mechanistic explanation for the inhibition of toxin secretion. To our knowledge, this is the first report suggesting that C3G inhibits secretion of the H. pylori toxins CagA and VacA via suppression of secA transcription.
Metabolic syndrome is associated with erosive esophagitis
Jung Ho Park, Dong IL Park, Hong Joo Kim, Yong Kyun Cho, Chong IL Sohn, Woo Kyu Jeon, Byung Ik Kim
World Journal of Gastroenterology , 2008,
Abstract: AIM: To clarify whether insulin resistance and metabolic syndrome are risk factors for erosive esophagitis.METHODS: A case-control study was performed using the database of the Kangbuk Samsung Hospital Medical Screening Center.RESULTS: A total of 1679 cases of erosive esophagitis and 3358 randomly selected controls were included. Metabolic syndrome was diagnosed in 21% of the cases and 12% of the controls (P < 0.001). Multiple logistic regressions confirmed the association between erosive esophagitis and metabolic syndrome (Odds ratio, 1.25; 95% CI, 1.04-1.49). Among the components of metabolic syndrome, increased waist circumference, elevated serum triglyceride levels and hypertension were significant risk factors for erosive esophagitis (all P < 0.01). Furthermore, increased insulin resistance (Odds ratio, 0.91; 95% CI, 0.85-0.98) and fatty liver, as diagnosed by ultrasonography (Odds ratio, 1.39; 95% CI, 1.20-1.60), were also related to erosive esophagitis even after adjustment for a series of confounding factors.CONCLUSION: Metabolic syndrome and increased insulin resistance are associated with an increased risk of developing erosive esophagitis.
Dynamic Sensor Interrogation Using Wavelength-Swept Laser with a Polygon-Scanner-Based Wavelength Filter
Yong Seok Kwon,Myeong Ock Ko,Mi Sun Jung,Ik Gon Park,Namje Kim,Sang-Pil Han,Han-Cheol Ryu,Kyung Hyun Park,Min Yong Jeon
Sensors , 2013, DOI: 10.3390/s130809669
Abstract: We report a high-speed (~2 kHz) dynamic multiplexed fiber Bragg grating (FBG) sensor interrogation using a wavelength-swept laser (WSL) with a polygon-scanner-based wavelength filter. The scanning frequency of the WSL is 18 kHz, and the 10 dB scanning bandwidth is more than 90 nm around a center wavelength of 1,540 nm. The output from the WSL is coupled into the multiplexed FBG array, which consists of five FBGs. The reflected Bragg wavelengths of the FBGs are 1,532.02 nm, 1,537.84 nm, 1,543.48 nm, 1,547.98 nm, and 1,553.06 nm, respectively. A dynamic periodic strain ranging from 500 Hz to 2 kHz is applied to one of the multiplexed FBGs, which is fixed on the stage of the piezoelectric transducer stack. Good dynamic performance of the FBGs and recording of their fast Fourier transform spectra have been successfully achieved with a measuring speed of 18 kHz. The signal-to-noise ratio and the bandwidth over the whole frequency span are determined to be more than 30 dB and around 10 Hz, respectively. We successfully obtained a real-time measurement of the abrupt change of the periodic strain. The dynamic FBG sensor interrogation system can be read out with a WSL for high-speed and high-sensitivity real-time measurement.
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