Hwang I.Y.,Kyung Hee UniversityGyeonggi do |
Lee S.H.,Korea Research Institute of Chemical Technology |
Choi Y.S.,Chungnam National University |
Park S.J.,Myongji UniversityGyeonggido |
And 7 more authors.
Journal of Microbiology and Biotechnology | Year: 2014
Methane is considered as a next-generation carbon feedstock owing to the vast reserves of natural and shale gas. Methane can be converted to methanol by various methods, which in turn can be used as a starting chemical for the production of value-added chemicals using existing chemical conversion processes. Methane monooxygenase is the key enzyme that catalyzes the addition of oxygen to methane. Methanotrophic bacteria can transform methane to methanol by inhibiting methanol dehydrogenase. In this paper, we review the recent progress made on the biocatalytic conversion of methane to methanol as a key step for methane-based refinery systems and discuss future prospects for this technology. © 2014 by The Korean Society for Microbiology and Biotechnology.
Hwang I.Y.,Kyung Hee UniversityGyeonggi do |
Hoon Hur D.,Kyung Hee UniversityGyeonggi do |
Hoon Lee J.,Kyung Hee UniversityGyeonggi do |
Park C.-H.,Kyung Hee UniversityGyeonggi do |
And 3 more authors.
Journal of Microbiology and Biotechnology | Year: 2015
Recently, methane has attracted much attention as an alternative carbon feedstock since it is the major component of abundant shale and natural gas. In this work, we produced methanol from methane using whole cells of Methylosinus trichosporium OB3b as the biocatalyst. M. trichosporium OB3b was cultured on NMS medium with a supply of 7:3 air/methane ratio at 30oC. The optimal concentrations of various methanol dehydrogenase inhibitors such as potassium phosphate and EDTA were determined to be 100 and 0.5 mM, respectively, for an efficient production of methanol. Sodium formate (40 mM) as a reducing power source was added to enhance the conversion efficiency. A productivity of 49.0 mg/l·h, titer of 0.393 g methanol/l, and conversion of 73.8% (mol methanol/mol methane) were obtained under the optimized batch condition. © 2015 by The Korean Society for Microbiology and Biotechnology.
Lee J.H.,Kyung Hee UniversityGyeonggi do |
Choi S.H.,Kyung Hee UniversityGyeonggi do |
Hwang I.Y.,Kyung Hee UniversityGyeonggi do |
Park J.B.,Ewha Womans University |
And 4 more authors.
Process Biochemistry | Year: 2016
Crude castor oil hydrolysates mainly consisting of ricinoleic acid can be biologically converted to 11-hexyloxy-9-undecenoic acid (C18) with an unsaturated bond and an ester bond which is utilized as a fertile chemical platform. The platform chemical of 11-hexyloxy-9-undecenoic acid can be converted to ω-hydroxyundec-9-enoic acid or dicarboxylic acid via simple chemical or biological conversion. In this study, the biotransformation was directly performed from crude castor oil hydrolysates containing 82% ricinoleic acid using the recombinant Escherichia coli BL21 with two plasmids containing Micrococcus luteus alcohol dehydrogenase and Pseudomonas putida KT2440 Baeyer-Villiger monooxygenase, respectively. The recombinant cells were cultured in Riesenberg medium at pH 6.9 and 20°C for 28.5 h. For biotransformation at 35°C for 2 h, 2.54 g/L 11-hexyloxy-9-undecenoic acid was obtained from crude castor oil hydrolysates with the final concentration of 2.98 g/L ricinoleic acid. The yield and volumetric productivity were 81.34% and 1.22 g/L/h, respectively. Herein, direct conversion of crude castor oil hydrolysates to value-added 11-hexyloxy-9-undecenoic acid was successfully demonstrated. © 2015 Elsevier Ltd. All rights reserved.
Kim Y.S.,Kyung Hee UniversityGyeonggi Do |
Khatiwoda P.,University of Minnesota |
Park B.H.,Pusan National University |
Lee H.Y.,University of Minnesota
Social Work in Public Health | Year: 2016
Existing studies report a negative association between health literacy and hospital/emergency room use. Despite substantial research on this topic among older Americans, little is known about the link between health literacy and healthcare services use among older Koreans. This study investigates this link, using a sample of 596 adults, 65 and older, from Korea's three largest cities. Andersen's behavior model guided the study. Findings revealed that participants with higher health literacy were significantly less likely to use emergent health services. Enhanced health literacy will likely promote better health outcomes for older Koreans and reduce Korea's healthcare costs. © 2016 Taylor & Francis Group, LLC.
Jung J.Y.,Kyung Hee UniversityGyeonggi do |
Lee Y.,Kyung Hee UniversityGyeonggi do |
Lee E.Y.,Kyung Hee UniversityGyeonggi do
Applied Chemistry for Engineering | Year: 2016
Due to the high price volatility and environmental concern of petroleum, biofuels such as bioethanol produced from lignocellulosic biomass have attracted much attention. It is also expected that the amount of lignin residue generated from pretreatment of lignocellulosic biomass will increase as the volume of cellulosic bioethanol increases. Lignin is a natural aromatic polymer and has very complex chemical structures with chemical functional groups. Chemical modification of lignin such as oxypropylation and epoxidation has also been applied to the production of value-added bioplastics such as polyurethane and polyester with enhanced thermal and mechanical properties. In addition, lignin can be used for carbon fiber production in automobile industries. This review highlights recent progresses in utilizations and chemical modifications of lignin for the production of bioplastics, resins, and carbon fiber. © 2016 The Korean Society of Industrial and Engineering Chemistry. All rights reserved.
Lee H.-K.,Kyung Hee UniversityGyeonggi do |
Na J.-Y.,Kyung Hee UniversityGyeonggi do |
Moon Y.-J.,Kyung Hee UniversityGyeonggi do |
Seong T.-Y.,Korea University |
Kim S.-K.,Kyung Hee UniversityGyeonggi do
Current Applied Physics | Year: 2015
We designed a near-unity transmittance dielectric/Ag/ITO electrode for high-efficiency GaN-based light-emitting diodes by using the scattering matrix method. The transmittance of an ultrathin metal layer, sandwiched between a dielectric layer and an ITO layer, was investigated as a function of the thickness and the optical constant of each constituent layer. Three different metals (Ag, Au, and Al) were examined as the metal layer. The analytical simulation indicated that the transmittance of a dielectric/metal/ITO multilayer film is maximized with an approximately 10-nm-thick Ag layer. Additionally, the transmittance also tends to increase as the refractive index of the upper dielectric layer increases. By tailoring the thickness of the dielectric layer and the ITO layer, the dielectric/Ag/ITO structure yielded a transmittance of 0.97, which surpasses the maximum transmittance (0.91) of a single ITO film. Furthermore, this extraordinary transmittance was present for other visible wavelengths of light, including violet and green colors. A complex phasor diagram model confirmed that the transmittance of the dielectric/metal/ITO multilayer film is influenced by the interference of reflected partial waves. These numerical findings underpin a rational design principle for metal-based multilayer films that are utilized as transparent electrodes for the development of efficient light-emitting diodes and solar cell devices. © 2015 Elsevier B.V.All rights reserved.
Song Y.R.,Kyung Hee UniversityGyeonggi do |
Lim C.W.,Hannam University |
Kim T.W.,Kyung Hee UniversityGyeonggi do
Luminescence | Year: 2016
New blue-emitting materials based on 1,2-diphenylindolizine were designed and synthesized through a microwave-assisted Suzuki coupling reaction. The photophysical, electrochemical, and thermal properties of the 1,2-diphenylindolizine derivatives were investigated using UV-visible and fluorescence spectroscopy, cyclic voltammetry, thermogravimetric analysis, and differential scanning calorimetry. The 1,2-diphenylindolizine derivatives had band gaps of 3.1-3.4eV and indicated proper emission of around 450nm without significant difference between in solution and thin solid film. The indolizine derivatives show an enhanced thermal stability (δTm>100°C), compared with 1,2-diphenylindolizine. These results suggest the 1,2-diphenylindolizine derivatives are suitable for blue-emitting materials in organic light-emitting devices. Copyright © 2015 John Wiley & Sons, Ltd.
Zhang P.,Kyung Hee UniversityGyeonggi do |
Park S.,Seoul National UniversityGyeonggi do |
Kang S.H.,Kyung Hee UniversityGyeonggi do
Bulletin of the Korean Chemical Society | Year: 2015
Fast microchip electrophoretic (ME) separation of native super-paramagnetic nanoparticles (SPMNPs) with different functional groups (i.e., - NH2, - OH, and - COOH) was investigated at the single-particle level using enhanced dark-field illumination detection with high signal-to-noise ratio. The dynamics provide evidence of the random motion of individual native nanoparticles and their real-time velocities within a microchip with or without an electric field. The SPMNPs were introduced into the microchip by magnetic force, and separation was performed at different electric field strengths; neither low (≤30 V/cm) nor high (≥70 V/cm) applied electric field strengths provided separation above baseline (resolution > 1.5) due to the random motion of the nanoparticles. Based on the optimized separation conditions obtained at the single-particle level, the individual SPMNPs were separated successfully from the model nanoparticle mixture within ∼75 s using differences in acid dissociation constants and zeta potentials. © 2015 Korean Chemical Society, Seoul & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Santisteban R.D.B.,Kyung Hee UniversityGyeonggi do |
Kim Y.L.,Purdue University |
Kim Y.L.,Kyung Hee UniversityGyeonggi do |
Farooq U.,Kyung Hee UniversityGyeonggi do |
And 3 more authors.
International Journal of Environmental Research and Public Health | Year: 2016
As the prevalence of overweight and obesity has been increasing in South Korea, it is critical to better understand possible associations between environmental surroundings and general health status. We characterize key health test readings and basic demographic information from 10,816 South Koreans, obtained from two Ubiquitous Healthcare (U-Healthcare) centers that have distinct surrounding neighborhood characteristics. One is located in a rural area in Busan, the other is located in an urban area in Daegu surrounded by a highly crowded residential and commercial business area. We analyze comprehensive health data sets, including blood pressure, body mass index, pulse rate, and body fat percentage from December 2013 to December 2014 to study differences in overall health test measurements between users of rural and urban U-Healthcare centers. We conduct multiple regression analyses to evaluate differences in general health status between the two centers, adjusting for confounding factors. We report statistical evidence of differences in blood pressure at the two locations. As local residents are major users, the result indicates that the environmental surroundings of the centers can influence the demographics of the users, the type of health tests in demand, and the users' health status. We further envision that U-Healthcare centers will provide public users with an opportunity for enhancing their current health, which could potentially be used to prevent them from developing chronic diseases, while providing surveillance healthcare data. © 2016 by the authors; licensee MDPI, Basel, Switzerland.
Kim J.-H.,Korea University |
Kim D.-H.,Korea University |
Kim S.-K.,Kyung Hee UniversityGyeonggi do |
Bae D.,Hexa Solution Co.Gyeonggi do |
And 2 more authors.
Ceramics International | Year: 2016
We modified the refractive index (n) of TiO2 by annealing at various temperatures to obtain a high figure of merit (FOM) for TiO2/Ag/TiO2 (45 nm/17 nm/45 nm) multilayer films deposited on glass substrates. Unlike the as-deposited and 300 °C-annealed TiO2 films, the 600 °C-annealed sample was crystallized in the anatase phase. The as-deposited TiO2/Ag/as-deposited TiO2 multilayer film exhibited a transmittance of 94.6% at 550 nm, whereas that of the as-deposited TiO2/Ag/600 °C-annealed TiO2 (lower) multilayer film was 96.6%. At 550 nm, n increased from 2.293 to 2.336 with increasing temperature. The carrier concentration, mobility, and sheet resistance varied with increasing annealing temperature. The samples exhibited smooth surfaces with a root-mean-square roughness of 0.37–1.09 nm. The 600 °C-annealed multilayer yielded the highest Haacke's FOM of 193.9×10−3 Ω−1. © 2016 Elsevier Ltd and Techna Group S.r.l.