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Search Results: 1 - 10 of 13556 matches for " Sang-Ho Choi "
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Arteriovenous Graft Modeling and Hemodynamic Interpretation  [PDF]
Hyoung-Ho Kim, Young Ho Choi, Sang-Ho Suh, Young Hoon Jung, Young Ho So, Jeong Sang Lee
Open Journal of Fluid Dynamics (OJFD) , 2012, DOI: 10.4236/ojfd.2012.24A040
Abstract: Arteriovenous graft (AVG) is artificially made with graft for hemodialysis in the patients with renal failure. Stenosis in the arterial or venous anastomosis of AVG results in its malfunction. Here, we made an AVG hemodynamic model with three different anastomotic angles (20°, 30°, 40°) and analyzed hemodynamic parameters such as velocity vectors, WSS and OSI in the arterial and venous anastomosis to find what helps in developing new surgical techniques to reduce stenosis in the anastomosis. Recirculation flow, low WSS and high OSI in the venous anastomosis were demonstrated in 30° and 40° models, and recirculation flow, high WSS and high OSI in the arterial anastomosis were shown in all models. Conclusively, higher anastomosis angle in the venous anastomosis cause stenosis, but stenosis in the arterial anastomosis happens irregardless of anastomosis angle.
3D-QSAR and Cell Wall Permeability of Antitubercular Nitroimidazoles against Mycobacterium tuberculosis
Sang-Ho Lee,Minsung Choi,Pilho Kim,Pyung Keun Myung
Molecules , 2013, DOI: 10.3390/molecules181113870
Abstract: Inhibitory activities of monocyclic nitroimidazoles against Mycobacterium tuberculosis (Mtb) deazaflavin-dependent nitroreductase (DDN) were modeled by using docking, pharmacophore alignment and comparative molecular similarity indices analysis (CoMSIA) methods. A statistically significant model obtained from CoMSIA was established based on a training set using pharmacophore-based molecular alignment. The leave-one out cross-validation correlation coefficients q 2 (CoMSIA) were 0.681. The CoMSIA model had a good correlation (/CoMSIA = 0.611) between the predicted and experimental activities against excluded test sets. The generated model suggests that electrostatic, hydrophobic and hydrogen bonding interactions all play important roles for interaction between ligands and receptors. The predicted cell wall permeability ( logPapp) for substrates with high inhibitory activity against Mtb were investigated. The distribution coefficient (logD) range was 2.41 < logD < 2.89 for the Mtb cell wall membrane permeability. The larger the polar surface area is, the better the permeability is. A larger radius of gyration ( rgry) and a small fraction of rotatable bonds ( frtob) of these molecules leads to higher cell wall penetration ability. The information obtained from the in silico tools might be useful in the design of more potent compounds that are active against Mtb.
Early use of imipenem/cilastatin and vancomycin followed by de-escalation versus conventional antimicrobials without de-escalation for patients with hospital-acquired pneumonia in a medical ICU: a randomized clinical trial
Jong Kim, Joowon Chung, Sang-Ho Choi, Hang Jang, Sang-Bum Hong, Chae-Man Lim, Younsuck Koh
Critical Care , 2012, DOI: 10.1186/cc11197
Abstract: We compared the early use of broad-spectrum antimicrobials plus subsequent de-escalation (DE) with conventional antimicrobial treatment (non-de-escalation, NDE) in critically ill patients with hospital-acquired pneumonia (HAP). This open-label, randomized clinical trial was performed in patients in a tertiary-care center medical intensive care unit (MICU) in Korea. Patients (n = 54) randomized to the DE group received initial imipenem/cilastatin plus vancomycin with subsequent de-escalation according to culture results, whereas patients randomized to the NDE group (n = 55) received noncarbapenem, nonvancomycin empiric antimicrobials.Between November 2004 and October 2006, 109 MICU patients with HAP were enrolled. Initial antimicrobial adequacy was significantly higher in the DE than in the NDE group for Gram-positive organisms (100% versus 14.3%; P < 0.001), but not for Gram-negative organisms (64.3% versus 85.7%; P = 0.190). Mean intensive care unit (ICU) stay, and 14-day, 28-day, and overall mortality rates did not differ in the two groups. Among culture-positive patients, mortality from methicillin-resistant Staphylococcus aureus (MRSA) pneumonia was higher in the DE group, even after early administration of vancomycin. Multidrug-resistant organisms, especially MRSA, were more likely to emerge in the DE group (adjusted hazard ratio for emergence of MRSA, 3.84; 95% confidence interval, 1.06 to 13.91).The therapeutic advantage of early administration of broad-spectrum antimicrobials, especially with vancomycin, was not evident in this study.Early use of broad-spectrum antimicrobials and subsequent de-escalation (DE) after microbiologic culture results may minimize the emergence of drug-resistant organisms [1-3] and costs [1] during the treatment of patients with hospital-acquired pneumonia (HAP). This strategy may reduce the overall duration of antimicrobial treatment [4] and mortality rates [5,6]. These studies, however, were observational, with successful DE indi
Bertrand-Cournot Comparison in a Mixed Duopoly with Advertisement  [PDF]
Chul-Hi Park, Dmitriy Li, Sang-Ho Lee
Theoretical Economics Letters (TEL) , 2016, DOI: 10.4236/tel.2016.62017
Abstract: We examine the Bertrand-Cournot comparison with advertisement in a differentiated mixed duopoly market, and compare with the social optimum. We show that not only both firms’ quantities but also both firms’ advertisements are higher (lower) in Cournot (Bertrand) than the social optimum. Thus, both firms engage in excessive (insufficient) advertisement in Cournot (Bertrand). We also show that despite lower both firms’ prices in Cournot, both firms’ profits and social welfare are strictly higher in Bertrand and thus, both firms prefer Bertrand to Counrnot.
Protection from Hemolytic Uremic Syndrome by Eyedrop Vaccination with Modified Enterohemorrhagic E. coli Outer Membrane Vesicles
Kyoung Sub Choi, Sang-Hyun Kim, Eun-Do Kim, Sang-Ho Lee, Soo Jung Han, Sangchul Yoon, Kyu-Tae Chang, Kyoung Yul Seo
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0100229
Abstract: We investigated whether eyedrop vaccination using modified outer membrane vesicles (mOMVs) is effective for protecting against hemolytic uremic syndrome (HUS) caused by enterohemorrhagic E. coli (EHEC) O157:H7 infection. Modified OMVs and waaJ-mOMVs were prepared from cultures of MsbB- and Shiga toxin A subunit (STxA)-deficient EHEC O157:H7 bacteria with or without an additional waaJ mutation. BALB/c mice were immunized by eyedrop mOMVs, waaJ-mOMVs, and mOMVs plus polymyxin B (PMB). Mice were boosted at 2 weeks, and challenged peritoneally with wild-type OMVs (wtOMVs) at 4 weeks. As parameters for evaluation of the OMV-mediated immune protection, serum and mucosal immunoglobulins, body weight change and blood urea nitrogen (BUN)/Creatinin (Cr) were tested, as well as histopathology of renal tissue. In order to confirm the safety of mOMVs for eyedrop use, body weight and ocular histopathological changes were monitored in mice. Modified OMVs having penta-acylated lipid A moiety did not contain STxA subunit proteins but retained non-toxic Shiga toxin B (STxB) subunit. Removal of the polymeric O-antigen of O157 LPS was confirmed in waaJ-mOMVs. The mice group vaccinated with mOMVs elicited greater humoral and mucosal immune responses than did the waaJ-mOMVs and PBS-treated groups. Eyedrop vaccination of mOMVs plus PMB reduced the level of humoral and mucosal immune responses, suggesting that intact O157 LPS antigen can be a critical component for enhancing the immunogenicity of the mOMVs. After challenge, mice vaccinated with mOMVs were protected from a lethal dose of wtOMVs administered intraperitoneally, conversely mice in the PBS control group were not. Collectively, for the first time, EHEC O157-derived mOMV eyedrop vaccine was experimentally evaluated as an efficient and safe means of vaccine development against EHEC O157:H7 infection-associated HUS.
Analysis of Pools of Targeted Salmonella Deletion Mutants Identifies Novel Genes Affecting Fitness during Competitive Infection in Mice
Carlos A. Santiviago equal contributor,M. Megan Reynolds equal contributor,Steffen Porwollik,Sang-Ho Choi,Fred Long,Helene L. Andrews-Polymenis ,Michael McClelland
PLOS Pathogens , 2009, DOI: 10.1371/journal.ppat.1000477
Abstract: Pools of mutants of minimal complexity but maximal coverage of genes of interest facilitate screening for genes under selection in a particular environment. We constructed individual deletion mutants in 1,023 Salmonella enterica serovar Typhimurium genes, including almost all genes found in Salmonella but not in related genera. All mutations were confirmed simultaneously using a novel amplification strategy to produce labeled RNA from a T7 RNA polymerase promoter, introduced during the construction of each mutant, followed by hybridization of this labeled RNA to a Typhimurium genome tiling array. To demonstrate the ability to identify fitness phenotypes using our pool of mutants, the pool was subjected to selection by intraperitoneal injection into BALB/c mice and subsequent recovery from spleens. Changes in the representation of each mutant were monitored using T7 transcripts hybridized to a novel inexpensive minimal microarray. Among the top 120 statistically significant spleen colonization phenotypes, more than 40 were mutations in genes with no previously known role in this model. Fifteen phenotypes were tested using individual mutants in competitive assays of intraperitoneal infection in mice and eleven were confirmed, including the first two examples of attenuation for sRNA mutants in Salmonella. We refer to the method as Array-based analysis of cistrons under selection (ABACUS).
Prioritizing the Best Areas for Treated Wastewater Use Using RCP 8.5  [PDF]
Sang-Mook Jeon, Eun-Sung Chung, Yeonjoo Kim, Sang-ho Lee
Journal of Environmental Protection (JEP) , 2013, DOI: 10.4236/jep.2013.41B011
Abstract: The goal of this study is to develop a new framework that prioritizes the best sites for treated wastewater (TWW) use considering climate change impacts. Fuzzy TOPSIS which is a kind of multi-criteria decision making techniques was introduced to reflect the uncertainty of input data and criteria weighting values. Representative concentration pathway 8.5 scenario was included into the hydrologic simulations for the climate change impact to hydrologic regimes using hydrological simulation program-Fortran (HSPF). Furthermore, all year scenarios were considered to determine the rankings, respectively. It can take into consideration the uncertainty of time periods which always exists in all climate change scenarios. This study can be a baseline to start to combine the fuzzy multi-criteria decision making techniques with robust prioritization for climate change adaptation strategies.
Aging Risk and Health Care Expenditure in Korea
Byongho Tchoe,Sang-Ho Nam
International Journal of Environmental Research and Public Health , 2010, DOI: 10.3390/ijerph7083235
Abstract: This paper analyzes the impact of population aging on health care expenditures in Korea. Examination of the age-expenditure profile reveals that health care resources are allocated more for the older cohort of population over time, suggesting significant growth of health care expenditures due to population aging. We contend, however, that population aging is considered as a parameter rather than an independent variable to explain rising health care expenditures. This paper shows that population aging is not found to be a significant determinant of health care expenditures according to the econometric analysis using OECD health data and time-series data for Korea. Using the components decomposition method, which measures the contribution of each component of health care expenditure, we estimate that population aging contributes only less than 10 percent.
Association of Mannose-Binding Lectin 2 Gene Polymorphisms with Persistent Staphylococcus aureus Bacteremia
Yong Pil Chong, Ki-Ho Park, Eun Sil Kim, Mi-Na Kim, Sung-Han Kim, Sang-Oh Lee, Sang-Ho Choi, Jin-Yong Jeong, Jun Hee Woo, Yang Soo Kim
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0089139
Abstract: Objectives Mannose-binding lectin (MBL) is an important component of innate immunity. Structural and promoter polymorphisms in the MBL2 gene that are responsible for low MBL levels are associated with susceptibility to infectious diseases. The objective of this study was to investigate the association of serum MBL levels and MBL2 polymorphisms with persistent Staphylococcus aureus bacteremia (SAB) in adult Korean patients. Methods We conducted a case-control study nested in a prospective cohort of patients with SAB. The study compared 41 patients with persistent bacteremia (≥7 days) and 46 patients with resolving bacteremia (<3 days). In each subject, we genotyped six single-nucleotide polymorphisms in the promoter region (alleles H/L, X/Y, and P/Q) and exon 1 (alleles A/B, A/C, and A/D) of the MBL2 gene and measured serum MBL concentrations. We also compared MBL2 genotypes between SAB patients and healthy people. Results Patients with persistent bacteremia were significantly more likely to have low/deficient MBL-producing genotypes and resultant low serum MBL levels, than were patients with resolving bacteremia (P = 0.019 and P = 0.012, respectively). Independent risk factors for persistent bacteremia were metastatic infection (adjusted odds ratio [aOR], 34.7; 95% confidence interval [CI], 12.83–196.37; P = 0.003), methicillin resistance (aOR, 4.10; 95% CI, 3.19–29.57; P = 0.025), and low/deficient MBL-producing genotypes (aOR, 7.64; 95% CI, 4.12–63.39; P = 0.003). Such genotypes were significantly more common in patients with persistent bacteremia than in healthy people (OR, 2.09; 95% CI, 1.03–4.26; P = 0.040). Conclusions This is the first demonstration of an association of low MBL levels and MBL2 polymorphisms responsible for low or deficient MBL levels with persistent SAB. A combination of factors, including clinical and microbiological characteristics and host defense factors such as MBL levels, may together contribute to the development of persistent SAB.
On Initialization of Ml DOA Cost Function for Uca
Joon-Ho Lee;Sang-Ho Jo
PIER M , 2008, DOI: 10.2528/PIERM08052702
Abstract: Maximum likelihood (ML) direction-of-arrival (DOA) estimation is essentially an optimization of multivariable nonlinear cost function. Since the final estimate is highly dependent on the initial estimate, an initialization is critical in nonlinear optimization. Alternating Projection (AP) initialization has been proposed as computationally efficient method for the initialization of the ML DOA cost function. In this paper, we propose a multi-dimensional (M-D) search scheme of uniform exhaustive search and improved exhaustive search. Improved exhaustive search is used to reduce the computational load of uniform exhaustive search. In the improved exhaustive search algorithm, the two-step procedure is applied to reduce the computational load of the uniform exhaustive search initialization scheme. In numerical results, it is shown that the performance of the proposed scheme is better than that of AP initialization.
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