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Search Results: 1 - 10 of 4382 matches for " Tae-Hyun Um "
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Chair-rising and 3-min walk: A simple screening test for functional mobility  [PDF]
Tae-Woong Oh, Izumi Tabata, Jin-Hwan Kim, Tae-Hyun Lee, Tatsuki Naka
Open Journal of Preventive Medicine (OJPM) , 2012, DOI: 10.4236/ojpm.2012.21013
Abstract: Aging induces decrease of locomotor capacity and its decrease is associated with an increased risk of falls. Several lines of evidence indicate that both change in muscle power and aerobic fitness are causative. Mobility tests are usually based on a maximal exercise stress test; however, this test is often difficult and sometimes frightening to older persons. Therefore, the objective of this study was to examine age and gender differences in 3-min walk distance test (3WDT), and time of chair-rising test (CRT) of functional mobility. 153 men and 159 women aged from 20 to 78 years were recruited as subjects of the present study. The body composition measured the height, body mass (BM), body mass index (BMI), lean tissue mass (LTM), and waist circumference (WC). The Functional mobility tests measured the peak oxygen uptake (VO2peak), 3WDT, leg extension strength (LES), and times of CRT. Both in men and women, height and BMI, WC decreased and increased, respectively, with age. Height, BM, LTM, WC in men are higher than in women. We found no correlation between ages and 3WDT in women and a significant, negative correlation in men. All parameters of fitness performance were negatively correlated with age. Both in men and women, all parameters of fitness performance were positively correlated with sex. Both in men and women, VO2peak, 3WDT, and LES decreased with age. All parameters of fitness performance in men are higher than in women. Both in men and women were observed for the correlation between 3WDT and VO2peak, LES and CRT respectively. Although as the correlation coefficient between 3WTD and VO2peak, LES and CRT were low (r = 0.28 - 0.38), an error may occur, this study shows that 3WDT and CRT test can be a feasible method of providing the information for muscle power and aerobic fitness, possibly avoiding the need for a maximal stress test.
New Design Criteria for Robust PCA and a Compliant Bayesian-Inspired Algorithm
Tae-Hyun Oh,David Wipf,Yasuyuki Matsushita,In So Kweon
Computer Science , 2015,
Abstract: Commonly used in computer vision and other applications, robust PCA represents an algorithmic attempt to reduce the sensitivity of classical PCA to outliers. The basic idea is to learn a decomposition of some data matrix of interest into low rank and sparse components, the latter representing unwanted outliers. Although the resulting optimization problem is typically NP-hard, convex relaxations provide a computationally-expedient alternative with theoretical support. However, in practical regimes performance guarantees break down and a variety of non-convex alternatives, including Bayesian-inspired models, have been proposed to boost estimation quality. Unfortunately though, without additional a priori knowledge none of these methods can significantly expand the critical operational range such that exact principal subspace recovery is possible. Into this mix we propose a novel pseudo-Bayesian algorithm that explicitly compensates for design weaknesses in many existing non-convex approaches leading to state-of-the-art performance with a sound analytical foundation.
Simple and Versatile Molecular Method of Copy-Number Measurement Using Cloned Competitors
Hyun-Kyoung Kim, Hai-Li Hwang, Seong-Yeol Park, Kwang Man Lee, Won Cheol Park, Han-Seong Kim, Tae-Hyun Um, Young Jun Hong, Jin Kyung Lee, Sun-Young Joo, Ju-Young Seoh, Yeong-Wook Song, Soo-Youl Kim, Yong-Nyun Kim, Kyeong-Man Hong
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0069414
Abstract: Variations and alterations of copy numbers (CNVs and CNAs) carry disease susceptibility and drug responsiveness implications. Although there are many molecular methods to measure copy numbers, sensitivity, reproducibility, cost, and time issues remain. In the present study, we were able to solve those problems utilizing our modified real competitive PCR method with cloned competitors (mrcPCR). First, the mrcPCR for ERBB2 copy number was established, and the results were comparable to current standard methods but with a shorter assay time and a lower cost. Second, the mrcPCR assays for 24 drug-target genes were established, and the results in a panel of NCI-60 cells were comparable to those from real-time PCR and microarray. Third, the mrcPCR results for FCGR3A and the FCGR3B CNVs were comparable to those by the paralog ratio test (PRT), but without PRT's limitations. These results suggest that mrcPCR is comparable to the currently available standard or the most sensitive methods. In addition, mrcPCR would be invaluable for measurement of CNVs in genes with variants of similar structures, because combination of the other methods is not necessary, along with its other advantages such as short assay time, small sample amount requirement, and applicability to all sequences and genes.
Interlayer Structure of Bioactive Molecule, 2-Aminoethanesulfonate, Intercalated into Calcium-Containing Layered Double Hydroxides
Tae-Hyun Kim,Hyoung Jun Kim,Jae-Min Oh
Journal of Nanomaterials , 2012, DOI: 10.1155/2012/987938
Abstract: We have successfully intercalated 2-aminoethanesulfonate, a well-known biomolecule taurine, into calcium-containing layered double hydroxides via optimized solid phase intercalation. According to X-ray diffraction patterns and infrared spectroscopy, it was revealed that the intercalated taurine molecules were each directly coordinated to other calcium cation and arranged in a zig-zag pattern. Scanning electron microscopy showed that the particle size and morphology of the LDHs were not affected by the solid phase intercalation, and the surface of intercalates was covered by organic moieties. From ninhydrin amine detection tests, we confirmed that most of the taurine molecules were well stabilized between the calcium-containing LDH layers.
Thermal Stability of the R Phase of a Rapidly Solidified Ti-47.3Ni (at%) Alloy
Tae-hyun Nam,Hyo-jung Moon,Su-jin Chun,Yinong Liu
Transactions on Electrical and Electronic Materials , 2012,
Abstract: Transformation behavior of rapidly solidified Ti-47.3Ni (at%) alloy ribbons and thermal stability of the R phase in theribbons were investigated by means of differential scanning calorimetry (DSC), X-ray diffraction, and transmissionelectron microscopy. Rapidly solidified Ti-47.3Ni alloy ribbons showed the two-stage B2-R-B19' martensitictransformation behavior. The B2-R transformation in the ribbons was observed even after annealing at 1,223 K,which was attributed to the fact that a specific orientation relationship between Ti2Ni and matrix in the ribbons ismaintained after annealing at 1,223 K. The DSC peak temperature of the B2-R transformation (TR*) decreased withraising annealing temperature, which was attributed to the increased volume fraction of Ti2Ni, thus causing anincreased Ni content in the matrix.
Fast Randomized Singular Value Thresholding for Nuclear Norm Minimization
Tae-Hyun Oh,Yasuyuki Matsushita,Yu-Wing Tai,In So Kweon
Computer Science , 2015,
Abstract: Rank minimization can be boiled down to tractable surrogate problems, such as Nuclear Norm Minimization (NNM) and Weighted NNM (WNNM). The problems related to NNM (or WNNM) can be solved iteratively by applying a closed-form proximal operator, called Singular Value Thresholding (SVT) (or Weighted SVT), but they suffer from high computational cost of computing Singular Value Decomposition (SVD) at each iteration. We propose a fast and accurate approximation method for SVT, that we call fast randomized SVT (FRSVT), where we avoid direct computation of SVD. The key idea is to extract an approximate basis for the range of a matrix from its compressed matrix. Given the basis, we compute the partial singular values of the original matrix from a small factored matrix. In addition, by adopting a range propagation technique, our method further speeds up the extraction of approximate basis at each iteration. Our theoretical analysis shows the relationship between the approximation bound of SVD and its effect to NNM via SVT. Along with the analysis, our empirical results quantitatively and qualitatively show that our approximation rarely harms the convergence of the host algorithms. We assess the efficiency and accuracy of our method on various vision problems, e.g., subspace clustering, weather artifact removal, and simultaneous multi-image alignment and rectification.
Partial Sum Minimization of Singular Values in Robust PCA: Algorithm and Applications
Tae-Hyun Oh,Yu-Wing Tai,Jean-Charles Bazin,Hyeongwoo Kim,In So Kweon
Computer Science , 2015,
Abstract: Robust Principal Component Analysis (RPCA) via rank minimization is a powerful tool for recovering underlying low-rank structure of clean data corrupted with sparse noise/outliers. In many low-level vision problems, not only it is known that the underlying structure of clean data is low-rank, but the exact rank of clean data is also known. Yet, when applying conventional rank minimization for those problems, the objective function is formulated in a way that does not fully utilize a priori target rank information about the problems. This observation motivates us to investigate whether there is a better alternative solution when using rank minimization. In this paper, instead of minimizing the nuclear norm, we propose to minimize the partial sum of singular values, which implicitly encourages the target rank constraint. Our experimental analyses show that, when the number of samples is deficient, our approach leads to a higher success rate than conventional rank minimization, while the solutions obtained by the two approaches are almost identical when the number of samples is more than sufficient. We apply our approach to various low-level vision problems, e.g. high dynamic range imaging, motion edge detection, photometric stereo, image alignment and recovery, and show that our results outperform those obtained by the conventional nuclear norm rank minimization method.
Role of Transcription Factor Modifications in the Pathogenesis of Insulin Resistance
Mi-Young Kim,Jin-Sik Bae,Tae-Hyun Kim,Joo-Man Park,Yong Ho Ahn
Experimental Diabetes Research , 2012, DOI: 10.1155/2012/716425
Abstract: Non-alcoholic fatty liver disease (NAFLD) is characterized by fat accumulation in the liver not due to alcohol abuse. NAFLD is accompanied by variety of symptoms related to metabolic syndrome. Although the metabolic link between NAFLD and insulin resistance is not fully understood, it is clear that NAFLD is one of the main cause of insulin resistance. NAFLD is shown to affect the functions of other organs, including pancreas, adipose tissue, muscle and inflammatory systems. Currently efforts are being made to understand molecular mechanism of interrelationship between NAFLD and insulin resistance at the transcriptional level with specific focus on post-translational modification (PTM) of transcription factors. PTM of transcription factors plays a key role in controlling numerous biological events, including cellular energy metabolism, cell-cycle progression, and organ development. Cell type- and tissue-specific reversible modifications include lysine acetylation, methylation, ubiquitination, and SUMOylation. Moreover, phosphorylation and O-GlcNAcylation on serine and threonine residues have been shown to affect protein stability, subcellular distribution, DNA-binding affinity, and transcriptional activity. PTMs of transcription factors involved in insulin-sensitive tissues confer specific adaptive mechanisms in response to internal or external stimuli. Our understanding of the interplay between these modifications and their effects on transcriptional regulation is growing. Here, we summarize the diverse roles of PTMs in insulin-sensitive tissues and their involvement in the pathogenesis of insulin resistance.
Transcriptional Regulation of Glucose Sensors in Pancreatic β-Cells and Liver: An Update
Jin-Sik Bae,Tae-Hyun Kim,Mi-Young Kim,Joo-Man Park,Yong-Ho Ahn
Sensors , 2010, DOI: 10.3390/s100505031
Abstract: Pancreatic β-cells and the liver play a key role in glucose homeostasis. After a meal or in a state of hyperglycemia, glucose is transported into the β-cells or hepatocytes where it is metabolized. In the β-cells, glucose is metabolized to increase the ATP:ADP ratio, resulting in the secretion of insulin stored in the vesicle. In the hepatocytes, glucose is metabolized to CO2, fatty acids or stored as glycogen. In these cells, solute carrier family 2 (SLC2A2) and glucokinase play a key role in sensing and uptaking glucose. Dysfunction of these proteins results in the hyperglycemia which is one of the characteristics of type 2 diabetes mellitus (T2DM). Thus, studies on the molecular mechanisms of their transcriptional regulations are important in understanding pathogenesis and combating T2DM. In this paper, we will review a recent update on the progress of gene regulation of glucose sensors in the liver and β-cells.
The impact of pretransplant 25-hydroxy vitamin D deficiency on subsequent graft function: An observational study
Hyunwook Kim, Shin-Wook Kang, Tae-Hyun Yoo, Myoung Kim, Soon Kim, Yu Kim, Kyu Choi
BMC Nephrology , 2012, DOI: 10.1186/1471-2369-13-22
Abstract: We analyzed 106 patients who underwent KT and for whom 25-hydroxy vitamin D (25-OHD) levels were measured during hospitalization prior to transplantation. We measured estimated glomerular filtration rates (eGFR) using the Modification of Diet in Renal Disease (MDRD) formula at baseline and at six-month intervals up to 36 months after KT.38.7% of the patients were diagnosed with 25-OHD deficiency defined as less than 10 ng/mL. Recipient gender (female vs. male, odds ratio [OR] 3.30, 95% CI 1.33-8.21, P = 0.010), serum albumin level (per 1 mg/dl increase, OR 0.35, 95% CI 0.13-0.98, P = 0.047), and predominant renal replacement therapy modality before KT (P < 0.001) were found to be independent pretransplant risk factors for 25-OHD deficiency by multivariate logistic regression analysis. Subsequent repeated measures analysis of covariance revealed that 25-OHD level had the only significant main effect on eGFR during the 36-month follow-up period [F (1, 88) = 12.07, P = 0.001].Pretransplant 25-OHD deficiency was significantly associated with a lower post-transplant eGFR, suggesting that 25-OHD may play an important role in maintaining graft function after KT.25-hydroxy vitamin D (25-OHD) is not only the stored form of vitamin D in the human body but also the predominant circulating form of vitamin D in the blood. Due to its long half-life and high concentration in plasma, the serum 25-OHD level is considered to be the best measure of vitamin D status. In addition to its classical role in maintenance of bone and neuromuscular health, several reports have demonstrated that poor vitamin D status is associated with a higher prevalence of hypertension, chronic heart failure, malignancy [1-3], and increased mortality not only in patients with chronic kidney disease not on dialysis, but also in incident hemodialysis patients [4,5]. Moreover, several clinical and experimental studies have reported a protective role for vitamins D against both diabetic and non-diabetic renal inj
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