Daejeon, South Korea
Daejeon, South Korea

Chungnam National University is one of ten Flagship Korean National Universities. It is recognized as one of the most prestigious five national universities in Korea. Wikipedia.

Time filter

Source Type

Chungnam National University | Date: 2016-09-22

The present invention relates to a transfer-free method for forming a graphene layer, in which a high-quality graphene layer having excellent crystallinity can be easily formed over a large area at low temperature by a transfer-free process so that it can be applied directly to a base substrate, which is used in a transparent electrode, a semiconductor device or the like, without requiring a separate transfer process, and to an electrical device comprising a graphene layer formed by the method. More specifically, the transfer-free method for forming a graphene layer comprises the steps of: depositing a Ti layer having a thickness of 3-20 m on a base substrate by sputtering; and growing graphene on the deposited Ti layer by chemical vapor deposition.

Chungnam National University | Date: 2016-12-09

A method for cell-free protein synthesis is characterized in that pH is controlled by using an enzyme. For example, by using an amino acid decarboxylase, the pH is controlled according to removal of hydrogen ions that are produced during regeneration of ATP. The method for cell-free protein synthesis of the present invention has an advantage that not only the expression amount of protein is enhanced but also the expressed protein can be directly used for activity analysis without undergoing any separation or purification.

Samsung, Chungnam National University and Korea Research Institute of Chemical Technology | Date: 2016-09-23

An electrically conductive composite including: a polymer matrix including a cellulose, and a plurality of electrically conductive carbon nanoparticles dispersed in the polymer matrix, wherein the electrically conductive carbon nanoparticles have a multiple hydrogen bonding moiety covalently bound to a surface thereof.

Kim M.,Chung - Ang University | Cho S.,Chungnam National University | Lee J.-H.,Chung - Ang University
Pain Medicine (United States) | Year: 2016

Objective. This preliminary study aimed to investigate the effects of long-term frequent ketamine treatment on cognitive function in [AQ-A] CRPS patients. Design. A total of 30 CRPS patients were divided into two groups based on both the duration and frequency of ketamine treatment; the long-term frequent ketamine treatment (LF) group (N 5 = 14) and the Non-LF group (N 5 = 16). Participants were asked to complete a questionnaire packet including demographic and clinical characteristics and potential variables affecting cognitive function. Then, they performed the neuropsychological test. Results. Results indicated that the LF group performed significantly poorer than the Non-LF group on the digit span, digit symbol, Controlled Oral Word Association Test, and Trail Making Test, but not the Stroop task. Conclusions. Patients with CRPS receiving longterm frequent ketamine treatment showed impairment in cognitive function (specifically executive function) compared with those who do not. These findings may have implications for clinical assessment and rehabilitation of cognitive function in CRPS patients. © 2016 American Academy of Pain Medicine. All rights reserved.

Cho J.-S.,Kyungpook National University | Bae H.-J.,Chungnam National University | Cho B.-K.,Chungnam National University | Moon K.-D.,Kyungpook National University
Food Chemistry | Year: 2017

Qualitative properties of roasting defect coffee beans and their classification methods were studied using hyperspectral imaging (HSI). The roasting defect beans were divided into 5 groups: medium roasting (Cont), under developed (RD-1), over roasting (RD-2), interior under developed (RD-3), and interior scorching (RD-4). The following qualitative properties were assayed: browning index (BI), moisture content (MC), chlorogenic acid (CA), trigonelline (TG), and caffeine (CF) content. Their HSI spectra (1000–1700 nm) were also analysed to develop the classification methods of roasting defect beans. RD-2 showed the highest BI and the lowest MC, CA, and TG content. The accuracy of classification model of partial least-squares discriminant was 86.2%. The most powerful wavelength to classify the defective beans was approximately 1420 nm (related to O[sbnd]H bond). The HSI reflectance values at 1420 nm showed similar tendency with MC, enabling the use of this technology to classify the roasting defect beans. © 2016

Kim S.-K.,Korea Institute of Oriental Medicine | Nam S.J.,Chungnam National University | Kim S.H.,Korea Institute of Oriental Medicine
BMC Complementary and Alternative Medicine | Year: 2017

Background: Much research has been done in Northeast Asia to show the efficacy of traditional medicine. While MEDLINE contains many biomedical articles including those on traditional medicine, it does not categorize those articles by specific research area. The aim of this study was to provide a method that searches for articles only on traditional medicine in Northeast Asia, including traditional Chinese medicine, from among the articles in MEDLINE. Results: This research established an SVM-based classifier model to identify articles on traditional medicine. The TAK + HM classifier, trained with the features of title, abstract, keywords, herbal data, and MeSH, has a precision of 0.954 and a recall of 0.902. In particular, the feature of herbal data significantly increased the performance of the classifier. By using the TAK + HM classifier, a total of about 108,000 articles were discriminated as articles on traditional medicine from among all articles in MEDLINE. We also built a web server called DisArticle (http://informatics.kiom.re.kr/disarticle), in which users can search for the articles and obtain statistical data. Conclusions: Because much evidence-based research on traditional medicine has been published in recent years, it has become necessary to search for articles on traditional medicine exclusively in literature databases. DisArticle can help users to search for and analyze the research trends in traditional medicine. © 2017 The Author(s).

An H.,Chungnam National University | Cha H.,Chungnam National University
ECCE 2016 - IEEE Energy Conversion Congress and Exposition, Proceedings | Year: 2016

This paper proposes a new senseless start-up method using a closed loop current control and a flux estimator without position sensor, and it is composed of four step sequence. Step 1 is applied for detection of the initial rotor position, and an initial rotor position is estimated around 1% of accuracy within 150ms. Step 2 is applied for a stable start-up state from the standstill through a closed loop current control, and is up to 3% of the rated speed of synchronous machine. Step 3 and 4 are used in the range generating a sufficient back-emf, and employ a flux estimator. The flux estimator consists of field flux model and flux voltage model, and rotor position/speed are estimated by using a phase locked loop. Field flux model is applied up to 5% of the rated speed. Performance of the proposed start-up method is evaluated by Simpower/Matlab simulation at overall speed range. To verify a feasibility of the proposed method, a 5kVA prototype of load commutated inverter (LCI) system is implemented. Experimental results show the proposed sensorless start-up method works well in the overall sequence region. © 2016 IEEE.

Jung S.,Chungnam National University
International Conference on Control, Automation and Systems | Year: 2016

This paper presents a neuro-sliding mode control method for a robot manipulator. The sliding mode controller requires to identify robot models to lessen the work of the controller although it can be used as a non model-based nonlinear controller. Selection of the gain for the nonlinear function becomes important and affects the performance. To make it easy of selecting the gain, a neural network is used to compensate for the modeling error to form a neuro-sliding control method. Stability analysis for the neuro-sliding control method is provided. Simulation studies of controlling joints of the three-link robot manipulator are presented. © 2016 Institute of Control, Robotics and Systems - ICROS.

Lee S.D.,Chungnam National University | Jung S.,Chungnam National University
2016 IEEE International Conference on Information and Automation, IEEE ICIA 2016 | Year: 2016

Disturbance observer(DOB) has been known as a simple robust control method to reject disturbances. Design of Q filters is considered as the most important design technique for the DOB design to compensate for the possible improperness of the inverse model of the plant as well as a non minimum phase. Many efforts on Q-filter design have been accomplished to realize a stable filter for the inverse of the nominal model in the DOB. In this paper, a recursive least square approach to a disturbance observer (RbDOB) for modeling the plant is proposed. A recursive least square method is used to estimate model parameters of the 2nd order model through an input-output FIR filtering. Experimental studies of balancing control performances of a single-wheel robot by DOB and RbDOB are compared. © 2016 IEEE.

Lee S.-D.,Chungnam National University | Jung S.,Chungnam National University
International Conference on Control, Automation and Systems | Year: 2016

In this paper, a fuzzy compensation (FC) technique along with the on-line system identification of two actuator systems of a one-wheel robot. Recursive least square (RLS) algorithm is used to identify the system with FIR-typed moving average filters for both a gimbal and a body system. To compensate for uncertainties in the modeling process, a fuzzy compensator is designed. Experimental studies of balancing a one-wheel robot are conducted. Performances by different control schemes, FC without RLS and FC with RLS are compared. © 2016 Institute of Control, Robotics and Systems - ICROS.

Kim J.H.,Korea Aerospace Research Institute | Kim B.,Chungnam National University
Advances in Engineering Software | Year: 2017

The thermal model reduction method is introduced to condense a huge satellite panel thermal model into a simplified model in order to make efficient calculations in the thermal analysis of a satellite in orbit. The static condensation algorithm with a substitution matrix manipulation is employed to handle the huge matrices without any numerical restriction. The relevant mathematical procedures of reduction are described step-by-step. The thermal model example of a satellite panel is illustrated to demonstrate the developed reduction method and its results are discussed. The influence of generated meshes for the reduced thermal model is reviewed. The calculation times are assessed and comparison between the developed method and the classical block-form LU decomposition method is also performed. © 2017 Elsevier Ltd

Gil E.-S.,Chungnam National University | Song H.,Chungnam National University | Chun K.-H.,Chungnam National University
International Journal of Mechanical Engineering and Robotics Research | Year: 2017

In this paper, a Modular-Multilevel-Converter based high voltage direct current (MMC-HVDC) system is considered. It is assumed that the grid is strong. The effects of load change and, PLL errors can cause voltage, current, and active/reactive power changes on the grid side. It is assumed that active/reactive power and q-axis voltage are disturbances. Based on the H∞ theory, a robust controller is designed to deal with external disturbances. Purpose of controller maintains active/reactive power at the inverter station. The designed H∞ controller is validated by a simulation using MATLAB/Simulink. © 2017 Int. J. Mech. Eng. Rob. Res.

Park P.,Chungnam National University | Di Marco P.,KTH Royal Institute of Technology | Di Marco P.,Ericsson AB | Johansson K.H.,KTH Royal Institute of Technology
IEEE Transactions on Industrial Electronics | Year: 2017

When multiple control processes share a common wireless network, the communication protocol must provide reliable performance in order to yield stability of the overall system. In this paper, the novel cross-layer optimized control (CLOC) protocol is proposed for minimizing the worst case performance loss of multiple industrial control systems. CLOC is designed for a general wireless sensor and actuator network where both sensor to controller and controller to actuator connections are over a multihop mesh network. The design approach relies on a constrained max-min optimization problem, where the objective is to maximize the minimum resource redundancy of the network and the constraints are the stability of the closed-loop control systems and the schedulability of the communication resources. The optimal operation point of the protocol is automatically set in terms of the sampling rate, scheduling, and routing, and is achieved by solving a linear programming problem, which adapts to system requirements and link conditions. The protocol has been experimentally implemented and evaluated on a testbed with off-the-shelf wireless sensor nodes, and it has been compared with a traditional network design and a fixed-schedule approach. Experimental results show that CLOC indeed ensures control application stability and fulfills communication constraints while maximizing the worst case redundancy gain of the system performance. © 2017 IEEE.

Kim J.,Chungnam National University | Lee J.,Chungnam National University
Journal of Institute of Control, Robotics and Systems | Year: 2017

This paper proposes a novel method for real-time ground surface identification on rough terrain based on the estimation of soil resistance, which can be distinguished depending on the material type such as sand or firm soil. Soil resistance is considered a crucial feature for classifying materials while a mobile robot is traversing rough terrain where wheel slip can easily occur such as sand, gravel, grass, etc. This paper, which illustrates the proposed method, is largely divided into two parts. First, a method of material identification is theoretically discussed from some equations related to the estimation of soil resistance and the classification of material type. Second, the proposed method is verified by one-wheel driving experiments using a testbed for the analysis of wheelterrain interaction in a laboratory and by real robot experiments in outdoor environments such as sand, grass, firm soil, and asphalt. © ICROS 2017.

Lee Y.-H.,Chungnam National University | Lambert S.R.,Stanford University
American Journal of Ophthalmology | Year: 2017

Purpose To compare the effectiveness of superior rectus transposition and medial rectus recession (SRT/MRc) vs inferior and superior rectus transposition (VRT) for acquired sixth nerve palsy. Design Consecutive, interventional case series. Methods The medical records of a consecutive series of patients with acquired sixth nerve palsy who underwent VRT or SRT/MRc by a single surgeon were reviewed. The preoperative and postoperative findings were compared between the 2 groups. Results Eight patients (mean age, 46.8 years) underwent SRT/MRc and 8 patients underwent VRT (mean age, 51.1 years). Lateral fixation was performed on all but 4 patients in the VRT group. Preoperative esotropia in primary position and abduction deficit were similar in both groups (SRT/MRc, 41.9 prism diopter [PD], −4.6; VRT, 55.6 PD, −4.5; P =.195, 1.0). The SRT/MRc group underwent a mean MR recession of 6 (range, 5–7) mm. Four patients in the VRT later underwent MR recession (mean 5.3 mm, range 5–6 mm). In addition, 5 patients in the VRT group had 1 or more botulinum toxin injections in the medial rectus muscle. No additional procedures were performed in the SRT/MR group. Fewer additional procedures were performed with SRT/MR (SRT/MR, 0; VRT, 1.8 ± 1.2; P <.010). At last follow-up, residual esotropia (SRT/MRc, 7.1 PD; VRT, 10.3 PD; P =.442) was similar in both groups, but abduction was better in the SRT/MRc group (SRT/MR, −3.0 ± 0.7; VRT, −3.8 ± 0.4; P =.038). There were no new persistent vertical deviations or torsional diplopia. Conclusions Final outcomes were similar with SRT/MRc vs VRT. However, fewer additional surgical procedures were needed with SRT/MR. © 2017 Elsevier Inc.

Kang L.H.,Chungnam National University | Seo Y.B.,Chungnam National University
Palpu Chongi Gisul/Journal of Korea Technical Association of the Pulp and Paper Industry | Year: 2016

For the development of high loaded printing paper, in-situ calcium carbonate formation on wood pulp fines were studied. Fines were generated from hardwood chemical pulp, and they were processed by in-situ calcium carbonate (CaCO3) formation method with the fines to calcium carbonate ratios of 1:10, 1:30 and 1:50 by weight at 20°C and 40°C. The handsheet results revealed that the CaCO3 covered fines at 40°C improved smoothness and opacity greatly, and kept solid content after wet pressing compared to the control, where ground calcium carbonate (GCC) were added to fiber furnish, at the equivalent ash levels. Lowering reaction temperature of the in-situ CaCO3 formation from 40°C to 20°C lowered opacity and solid content of the handsheet. Covering fines with CaCO3 increased drainage rate and solid content.

Kim D.-S.,Chungnam National University | Sung Y.J.,Chungnam National University
Palpu Chongi Gisul/Journal of Korea Technical Association of the Pulp and Paper Industry | Year: 2016

The pretreatments of rice husk with chlorine dioxide were conducted in order to increase the silica extraction efficiency of rice husk. The temperature of chlorine dioxide treatment had significant effects on the morphological properties and the chemical composition of treated rice husk. The severer treatment conditions resulted in the higher loss in the yield and the lignin of treated rice husk. The ash contents of the treated rice husk were increased, which showed the chlorine dioxide treatment had no significant effects on the silica in rice husk. The reduction in the organic components including the lignin of rice husk and the changes in the structure by the pretreatment leaded to the increase in the alkali extraction of silica from the treated rice husk. Those results showed the silica extraction efficiency could be improved by the chlorine dioxide pretreatment.

Choi J.S.,Chungnam National University | Seo Y.B.,Chungnam National University
Palpu Chongi Gisul/Journal of Korea Technical Association of the Pulp and Paper Industry | Year: 2016

High filler loading in printing paper is desirable for papermakers because they can reduce production cost and carbon dioxide emission, if all the paper properties are acceptable. Two new filler preparation methods were presented and compared in this study. The hybrid calcium carbonate (HCC) was prepared by the in-situ calcium carbonate (CaC03) formation on the pre-flocculated mixture of grounded calcium carbonate (GCC) and calcium oxide particles in aqueous medium. For the preparation of 'Post HCC', only GCC particles were pre-flocculated firstly, calcium oxide was added to the pre-flocculated GCC secondly, and carbon dioxide were introduced lastly until the pH of the aqueous medium becomes neutral. Both methods increased tensile strength, stiffness, and bulk, but kept smoothness when compared to the case of simple GCC addition at equivalent ash level in the handsheet study. Post HCC gave higher solid content and higher stiffness than HCC.

Kang L.H.,Chungnam National University | Seo Y.B.,Chungnam National University
Palpu Chongi Gisul/Journal of Korea Technical Association of the Pulp and Paper Industry | Year: 2016

High filler loading and energy saving without forgiving any physical property loss in printing paper is a long-cherished wish for papermakers because reduction of production cost and carbon dioxide emission are expected. In this study, the fines generated from wood pulp were covered with calcium carbonate (CaCO3) by the in-situ calcium carbonate formation method with the fines to calcium carbonate ratios of 1:10, 1:30 and 1:50, and were used to prepare handsheets. The handsheet results revealed that the CaCO3 covered fines by in-situ method improved breaking length, bulk, stiffness and double folds greatly compared to the control, where ground calcium carbonate (GCC) were added to fiber furnish, at equivalent ash levels. Lowering reaction temperature of in-situ CaCO3 formation from 40°C to 20°C deteriorated most of strength properties.

Park M.S.,Chungnam National University | Kim K.T.,Chungnam National University | Kang J.S.,Chungnam National University
Journal of Chromatography B: Analytical Technologies in the Biomedical and Life Sciences | Year: 2017

Bee pollen collected by honeybees, which is in powdered form, is a good nutritional supplement. Nitrofuran antibiotics are assumed not to be present in bee pollen, which is important as the level of antibiotics in bee pollen is strongly regulated in many countries. A liquid chromatography–tandem mass spectrometry (LC–MS/MS) method to detect nitrofurans in honey has been developed, but this method is not suitable for bee pollen because of it being in powdered form. During preparation of bee pollen samples, the dispersal of powder particles in an aqueous solution often makes them susceptible to forming an emulsion with solvent components such as hexane and ethyl acetate. This may reduce the reproducibility and sensitivity of analyses of nitrofuran levels in bee pollen. Therefore, we attempted to optimize the sample preparation conditions to detect nitrofurans in bee pollen by determining three nitrofuran residues, namely, 3-amino-2-oxazolidinone (AOZ), 3-amino-5-methyl-morpholino-2-oxazolidinone (AMOZ), and 1-aminohydantoin (AHD), using LC–MS/MS. The optimized method prevented the formation of powder-induced emulsion. To verify the reproducibility and sensitivity of this method, it was validated using nitrofuran-free bee pollen spiked with analytes with different side chains at 1.0, 2.0, and 5.0 μg kg−1. The accuracy levels were 94.1%–104.0% and the coefficients of variation were less than 12%. The limits of detection for AOZ, AMOZ, and AHD were 0.18, 0.25, and 0.30 μg kg−1, respectively, while their limits of quantitation were 0.59, 0.83, and 1.00 μg kg−1. The LC–MS/MS method developed to analyze nitrofuran in bee pollen should contribute to the quality control of bee pollen and food safety. © 2016 Elsevier B.V.

Lee W.-Y.,Chungnam National University | Hwang D.-S.,Chungnam National University | Noh C.-K.,Chungnam National University
Journal of Korean Medical Science | Year: 2017

We analyzed the causes leading to total hip arthroplasty (THA), aimed to clarify the incidence of femoroacetabular impingement (FAI) among the causes, and compared the incidence in Korea with those in other countries. From January 2000 to December 2014, 1,206 hips of 818 patients who underwent primary THA at our institute were reviewed retrospectively in terms of radiographs and electronic charts. The radiographs and radiographic parameters were reviewed and measured by 2 of the authors, who are orthopedic surgeons. Patients were categorized in terms of the causes leading to THA as primary osteoarthritis (OA), rheumatoid arthritis (RA), posttraumatic arthritis, post infectious arthritis, avascular necrosis (AVN) of the femoral head, fracture of the femoral head or neck, ankylosing spondylitis (AS), developmental dysplasia of the hip (DDH), Legg- Calvé-Perthes disease (LCPD), FAI, and others. There were 32 patients (3.91%) in the primary OA group, 41 (5.01%) in the RA group, 84 (10.27%) in the posttraumatic arthritis group, 39 (4.77%) in the post infectious arthritis group, 365 (44.62%) in the AVN group, 39 (4.77%) in the fracture group, 21 (2.57%) in the AS group, 52 (6.36%) in the DDH group, 71 (8.68%) in the LCPD group, 52 (6.36%) in the FAI group, and 22 (2.69%) in the 'other' group. The causes leading to THA in Korea differ from those in Western countries. FAI could be causes of severe secondary OA that requires THA in Korea, therefore symptomatic FAI should not be neglected. © 2017 The Korean Academy of Medical Sciences.

Jang S.-J.,Chungnam National University | Yun H.-D.,Chungnam National University | Lee M.-S.,Hanyang University
Archives of Civil and Mechanical Engineering | Year: 2017

This paper describes the experimental results of tests of the structural behavior of structural silicone glazing (SSG) sealant connections in a curtain wall system in which structural sealant is placed between an aluminum frame and laminated glass panel. Cases often have been found where the structural sealant has been applied at a 45° angle from the inside of the curtain wall. Thus, assessment of the structural behavior of the SSG connections between the aluminum frame and glass panel in a curtain wall system is required. The tests conducted in this research include variables such as the use of Norton tape, the application (or omission) of end sealant, the thickness of the stiffening sealant applied on top of the structural sealant, and the span length of the glass panel. The test results indicate that the use of Norton tape directly affects the initial stiffness and strength values of the SSG connection and that the application of end sealant improves the strength and ductility of the SSG connection. However, the change in the maximum load per unit length caused by the application of stiffening sealant on the existing structural sealant was found to be insignificant. © 2016 Politechnika Wrocławska

Choi W.-C.,Gachon UniversityGyeonggido | Jang S.-J.,Chungnam National University | Yun H.-D.,Chungnam National University
Composites Part B: Engineering | Year: 2017

An experimental study was conducted to examine the effect of hybrid fiber, polyethylene (PE) and steel fiber, reinforcement on the bond and cracking characteristics of lap-spliced reinforcing bars embedded in strain-hardening cementitious composite (SHCC) in the tension zone and subjected to monotonic and cyclic tension loads. This study focused on the confinement effects with respect to the compressive strength of SHCC mixtures with hybrid fiber reinforcement. The SHCC mixtures contained two types of reinforcing fibers: polyethylene and steel fiber with aspect ratios of 1000 and 79, respectively. The test parameters include normal compressive strength (30 MPa) and high strength (100 MPa) and spliced lengths in tension (40% and 60% of the splice length recommended by ACI 318) for the SHCC mixtures. The results indicate that SHCC mixtures can be used effectively to reduce the development length of rebar up to 60% of the splice length required by the American Concrete Institute 318 equation according to splitting failure control by multiple cracking behavior of SHCC mixtures. © 2016 Elsevier Ltd

Lee S.,Chosun University | Kim J.,Chungnam National University
Energy | Year: 2017

This paper investigates a component-sizing method and a power-control algorithm for series-hybrid military vehicles equipped with hybrid energy storages that comprise batteries and super-capacitors. Component sizing of the powertrain is determined by the performance specification that is related to mission profiles and power-flow control methods. In order to minimize the effects of mission profiles and power-flow control methods, the linear programming (LP) technique is employed. The LP problem for minimizing the output energy from the engine under different conditions of driving cycles and capacities of the energy storage system (ESS) is solved to eliminate the effect of the power distribution. Through analyzing the effects of different power and energy ratings of the ESS, the optimal values of power and energy capacities of the ESS are determined. The design approaches are extensively verified with simulations and experimental results of a reduced-scale per-unit equivalent system of the 10-ton series-hybrid electric vehicle (SHEV). © 2016 Elsevier Ltd

Park H.-J.,Chungnam National University | Baik K.-H.,Chungnam National University
Korean Journal of Materials Research | Year: 2017

Doped-LaCrO3 perovskites, because of their good electrical conductivity and thermal stability in oxidizing and/or reducing environments, are used in high temperature solid oxide fuel cells as a gas-tight and electrically conductive interconnection layer. In this study, perovskite (La0.8Ca0.2)(Cr0.9Co0.1)O3 (LCCC) coatings manufactured by atmospheric plasma spraying followed by heat treatment at 1200 °C have been investigated in terms of microstructural defects, gas tightness and electrical conductivity. The plasma-sprayed LCCC coating formed an inhomogeneous layered structure after the successive deposition of fully-melted liquid droplets and/or partially-melted droplets. Micro-sized defects including unfilled pores, inter-splat pores and micro-cracks in the plasma-sprayed LCCC coating were connected together and allowed substantial amounts gas to pass through the coating. Subsequent heat treatment at 1200 °C formed a homogeneous granule microstructure with a small number of isolated pores, providing a substantial improvement in the gas-tightness of the LCCC coating. The electrical conductivity of the LCCC coating was consequently enhanced due to the complete elimination of inter-splat pores and microcracks, and reached 53 S/cm at 900 °C. © Materials Research Society of Korea.

Park K.-T.,Chungnam National University | Yoon S.-G.,Chungnam National University
Korean Journal of Materials Research | Year: 2017

In this paper, synthesis of terephthalate intercalated Zn-Al: Layered double hydroxides (LDHs) was studied. We designed freestanding Zn-Al: Carbonate LDH nanosheets for a facile exchange technique. The as-prepared Zn-Al carbonate LDHs were converted to terephthalate intercalated Zn-Al:LDHs by ion exchange method. Initially, Al-doped ZnO (AZO) thin films were deposited on p-Si (001) by facing target sputtering. For synthesis of free standing carbonate Zn-Al:LDH, we dipped the AZO thin film in naturally carbonated water for 3 hours. Further, Zn-Al: Carbonate LDH nanosheets were immersed in terepthalic acid (TA) solution. The ion exchange phenomena in the terephthalate assisted Zn-Al:LDH were confirmed using FT-IR analysis. The crystal structure of terephthalate intercalated Zn-Al:LDH was investigated by XRD pattern analysis with different mole concentrations of TA solution and reaction times. The optimal conditions for intercalation of terephthalate from carbonated Zn-Al LDH were established using 0.3 M aqueous solution of TA for 24 hours. © Materials Research Society of Korea.

Lee J.-H.,Chungnam National University | Kim H.,Chungnam National University
Polymer (Korea) | Year: 2017

The effect of surface oxidation of polyethylene on the secure fusion of pipe was investigated. Oxidative functional group such as carbonyl group was formed on polyethylene pipe by both thermal and ultraviolet oxidation conditions which were usually applied during storage and fusion process. The bonding strength of fusion part of polyethylene pipe decreased significantly due to the poor chain entanglement at the fusion interface as the degree of surface oxidation increased. The deformation on debonded fracture surface of fusion pan was reduced significantly as the degree of surface oxidation increased.

Park S.-H.,Agency for Defense Development | Kim J.-H.,Chungnam National University
Solar Energy | Year: 2017

The analysis of long term data for degradation of PV modules suffers from volatility and uncertainty due to intrinsic and extrinsic factors. The low rate of degradation causes analysis complexity and ambiguity. In this study, methods used to estimate the PV module lifetimes were reviewed in terms of degradation of power output with time. Under the assumption that degradation is continuous, gradual, and monotonic, the gamma process model can explain the sampling and temporal uncertainties of lifetime data. Examples are provided to demonstrate the use of gamma process model for long term and accelerated lifetime test (ALT) data. Three types of lifetime estimation method were compared for long term operation data. Although they all gave similar estimated lifetime, the gamma process model gave the most applicable results to determine warranty life. The gamma process model can also express the condition variation at inspection and the lifetime variation at failure level as probability distributions. A method to determine warranty life is proposed using an age based replacement policy. For ALT data, we estimated the lifetime from degradation data using the Arrhenius equation for standard environmental conditions and applied the gamma process model to obtain time varying probability distributions for condition and lifetime. Service life was estimated as the median, while warranty life was estimated as the minimum rate of increase of optimal replacement time. © 2017 Elsevier Ltd

Trung T.N.,Chungnam National University | Kim D.-O.,Chungnam National University | Kim E.-T.,Chungnam National University
RSC Advances | Year: 2017

We report the direct and self-selective synthesis of Ag nanowires (NWs) on graphene patterns through a modified citrate reduction reaction approach. High-density NWs were selectively formed only on the graphene areas, whereas NWs were not synthesized on the SiO2/Si and glass substrates. The size and density of the Ag NWs gradually increased with increasing reaction time and AgNO3 concentration. When the Ag NWs were synthesized with 60 mM AgNO3 at 90 °C for 30 min, the average width and length of the NWs were approximately 150 nm and 3 μm, respectively. Graphene-Ag NW hybrids showed excellent light transmittance (91.5% at 550 nm) with low sheet resistance (102 Ω sq-1). These properties can be further optimized by manipulating the size and density of the Ag NWs. This simple and cost-effective process for the fabrication of graphene-Ag NW hybrid electrode patterns is useful for a variety of applications. © The Royal Society of Chemistry.

Gusev E.S.,Russian Academy of Sciences | Siver P.A.,Connecticut College | Shin W.,Chungnam National University
Cryptogamie, Algologie | Year: 2017

Species from the Mallomonas bronchartiana complex were examined using material from Vietnam, the U.S.A. and South Korea. The original description of Mallomonas bronchartiana is expanded and descriptions of two new taxa, M. pseudobronchartiana and M. velari, are given. All taxa possess body scales that are large, broad, with an asymmetrically-placed posterior rim, an internal honeycomb reticulation, and are covered externally with a layer containing papillae. A distinct V-rib is lacking on Mallomonas bronchartiana scales. Scales of M. pseudobronchartiana have a thin V-shaped rib situated on the scale surface, while the V-rib of M. velari is formed from an upward folding of the surface of the scale. Scales of Mallomonas velari are also easily separated from the other species by the presence of a large forward projecting wing. The positions of all three taxa within the genus are discussed, and placement in section Quadratae is proposed. The distributions and habitat conditions of each species are summarized. © 2017 Adac. Tous droits réservés.

Park Y.,Hannam University | Lee Y.-H.,Chungnam National University
Proceedings of the 30th Pacific Asia Conference on Language, Information and Computation, PACLIC 2016 | Year: 2016

This paper took an experimental approach and investigated how Korean EFL learners process the English island constructions. Since there are some controversies on the existence of the island effects in Korean, the L1 transfer effect may make it difficult for the Korean EFL learners to learn island constructions in English. To examine if the difference between English and Korean affects the acquisition of English island constructions, four different types of target sentences were made for English island phenomena: Complex-NP, whether, subject, and adjunct island. The acceptabilit ENGLy scores of Korean EFL learners were measured with Magnitude Estimation (ME). Then, the collected data were statistically analyzed. The analysis results showed that, unlike previous studies, the Korean EFL learners correctly identified all of the English island constructions. This finding showed that the island status of the Korean language did not affect the acquisition of island constructions in English.

Park C.H.,Chungnam National University | Kang Y.,Chungnam National University
Proceedings - 2016 IEEE International Conference on Big Data, Big Data 2016 | Year: 2016

In analyzing streaming data in which the underlying data distribution may change or the concept of interest may drift over time, the ability of a classifier to adapt to drifted concepts is very important to maintaining the prediction performance. However, the true class labels of data samples are often available only after some period of time or they are obtained by experts' efforts. In this paper, we develop an effective method for active learning on data streams with concept drift. The proposed method combines active learning and adaptive incremental learning. For unlabeled data samples, the degree of concept drift is estimated and used for both data selection for labeling and adaptive incremental learning of the current classifier. Experimental results on five artificial data sets and two real data sets demonstrate a competent performance of the proposed method. © 2016 IEEE.

Lee S.-H.,Chungnam National University | Yoon S.-G.,Chungnam National University
Korean Journal of Materials Research | Year: 2016

We have investigated the properties of thin film transistors(TFT) fabricated using zinc tin oxide(ZTO) thin films deposited via on-axis sputtering and FTS methods. ZTO thin films deposited by FTS showed lower root-mean-square(RMS) roughness and more uniformity than those deposited via on-axis sputtering. We observed enhanced electrical properties of ZTO TFT deposited via FTS. The ZTO films were deposited at room temperature via on-axis sputtering and FTS. The as-deposited ZTO films were annealed at 400 °C. The TFT using the ZTO films deposited via FTS process exhibited a high mobility of 12.91 cm2 /V.s, a low swing of 0.80 V/decade, Vth of 5.78 V, and a high Ion/off ratio of 2.52 × 106. © 2016, Materials Research Society of Korea.

Lee M.,Agency for Defense Development | Kim J.,Chungnam National University
30th Congress of the International Council of the Aeronautical Sciences, ICAS 2016 | Year: 2016

Two previously developed failure criteria (the average stress failure criterion and the point stress failure criterion), which are used to predict the uniaxial compressive strength of a laminated composite containing through-the-thickness material discontinuities (notches), are subjected to further experimental scrutinization. This paper contains predictions, using the two failure criteria, for compressive fracture strength in open hole laminates. This is accomplished by obtaining experimental data on the carbon/epoxy material system, in conjunction with unnotched multidirectional laminates and open hole multidirectional laminates. The composite material used in this paper is a carbon/epoxy unidirectional (UD) tape prepreg (Cycom G40-800/5276-1) cured at a 350°F (177°C). The operating temperature is -60°F ∼ +200°F (-55°C∼+95°C). A total of 84 compression tests were conducted on specimens from 6 distinct laminates that were laid up by standard angle layers (0°, +45°, -45° and 90°). The ASTM-D-6484D standard was used for the test method. Results are presented for the fracture compressive strengths of several carbon/epoxy laminates containing a circular hole. The point stress failure criterion was more reasonable than the average stress failure criterion to predict the observed strengths in all cases considered.

Beers T.C.,University of Notre Dame | Placco V.M.,University of Notre Dame | Carollo D.,University of Notre Dame | Rossi S.,University of Sao Paulo | And 5 more authors.
Astrophysical Journal | Year: 2017

We obtain estimates of stellar atmospheric parameters for a previously published sample of 1777 relatively bright (9 < B < 14) metal-poor candidates from the Hamburg/ESO Survey. The original Frebel et al. analysis of these stars was able to derive estimates of [Fe/H] and [C/Fe] only for a subset of the sample, due to limitations in the methodology then available. A new spectroscopic analysis pipeline has been used to obtain estimates of Teff , log g, [Fe/H], and [C/Fe] for almost the entire data set. This sample is very local-about 90% of the stars are located within 0.5 kpc of the Sun. We consider the chemodynamical properties of these stars in concert with a similarly local sample of stars from a recent analysis of the Bidelman and MacConnell 'weak metal' candidates by Beers et al. We use this combined sample to identify possible members of the halo stream of stars suggested by Helmi et al. and Chiba & Beers, as well as stars that may be associated with stripped debris from the putative parent dwarf of the globular cluster Omega Centauri, suggested to exist by previous authors. We identify a clear increase in the cumulative frequency of carbon-enhanced metal-poor (CEMP) stars with declining metallicity, as well as an increase in the fraction of CEMP stars with distance from the Galactic plane, consistent with previous results. We also identify a relatively large number of CEMP stars with kinematics consistent with the metal-weak thick-disk population, with possible implications for its origin. © 2017. The American Astronomical Society. All rights reserved.

Baatar A.,Chungnam National University | Ha R.,Chungnam National University | Yu Y.,Chungnam National University
Environmental Science and Pollution Research | Year: 2017

We separated dust particles from the mesh-filtered sets of rainwaters collected on rainy days with daily precipitations exceeding 10 mm per day. A total of 136 rainwaters (or snow during the winter season) samples collected from February 2009 to February 2013 were analyzed. In particular, 33 out of 136 rainwaters were collected during or just after the Asian dust storm (ADS) events. Values of pH were relatively higher during warmer seasons. During ADS events, precipitations were alkaline, possibly due to abundant supply of alkaline minerals from the deserts source area to the precipitation. Compositional analysis on particulate matter (PM) indicated that Fe (and Al, K, and Mg) enriched the dusts collected during ADS, with respect to events than those without ADS. We found that ADS rainfall events are effective in selectively eliminating dust particles. However, high rainfall does not necessarily indicate more dilution of dusts. On microscopic examination, we observed natural soils, natural dust of pedogenesis or weathering origin, anthropogenic C–Fe-rich particles, and anthropogenic C-rich particles. Because of its small size, the stoichiometry of ADS-related, Fe-rich dust particles was inferred from the magnetic analysis. Presence of Verwey transition near 100–120 K and experimental determination of Curie points near 580 °C indicate that magnetic mineral responsible for the magnetic properties of ADS-related dusts was magnetite. © 2017 The Author(s)

Heo H.,Chungnam National University | Ryou J.,Chungnam National University
International Journal of Services, Technology and Management | Year: 2017

We propose a lightweight network access control (NAC) technique applied to wireless router. It authenticates users and devices whether they are trusted or not and it controls the access of the devices according to their security state. As the age of internet of things and bring your own device has begun, NAC technique has become more important. However, it is hard to adopt the NAC from small and medium sized enterprise because of the cost problem. For this reason, we suggest lightweight NAC on wireless router. To do this, we developed an advanced NAC module added to OpenWrt, open source wireless router firmware, which allows to establish secure network environment without additional NAC appliance. We also developed agent programs for PC and mobile to examine the security state of device and identify the trusted users and devices.

Hui C.Y.,Chungnam National University | Lee J.,Chungnam National University | Takata J.,Huazhong University of Science and Technology | Ng C.W.,University of Hong Kong | Cheng K.S.,University of Hong Kong
Astrophysical Journal | Year: 2017

By comparing the properties of non-recycled radio-loud γ-ray pulsars and radio-quiet γ-ray pulsars, we have searched for the differences between these two populations. We found that the γ-ray spectral curvature of radio-quiet pulsars can be larger than that of radio-loud pulsars. Based on the full sample of non-recycled γ-ray pulsars, their distributions of the magnetic field strength at the light cylinder are also found to be different. We note that this might result from an observational bias. By reexamining the previously reported difference of γ-ray-to-X-ray flux ratios, we found that the significance can be hampered by their statistical uncertainties. In the context of the outer gap model, we discuss the expected properties of these two populations and compare with the possible differences that are identified in our analysis. © 2017. The American Astronomical Society. All rights reserved..

Kong K.-B.,Chungnam National University
Applied Computational Electromagnetics Society Journal | Year: 2017

A Ka-band doubly curved reflector antenna for a warning radar system for the road was designed based on the curve-deformation equations. This antenna requires a cosecant-squared radiation pattern in the vertical and horizontal planes. Using curve-deformation equations, the shaped reflector antenna was designed to satisfy the desired beam pattern. The curve-deformation equations include the parameters which determine the shape of the curve, and these parameters are obtained by the optimization process. The simulated result shows the designed antenna satisfies the specifications of the antenna for the road radar system. © ACES.

Kim W.-N.,Chungnam National University | Hong S.I.,Chungnam National University
Kovove Materialy | Year: 2017

Tri-layered Cu/Al-Mg-Si/Cu clad composite was cold roll-bonded, and its mechanical/ electrical properties were studied. In the roll-bonded and aged Cu/Al-Mg-Si/Cu clad composite, neither interfacial reaction layer nor interface defects were observed. The strength as high as 415MPa with the conductivity of 82 % IACS was attained in 3-ply light-weight Cu/Al-Mg-Si/Cu clad composite. The ductility and conductivity of clad composite are increased appreciably with heat treatment at 175°C. After mechanical testing, the interface crack propagation and fracture in the well-bonded interface between metallic Cu and Al occurred in softer Al matrix. The increase of detached Al lumps onto the separated Cu side in clad composite heat-treated at 175°C strongly supports that the interface bonding can be enhanced during aging of Al-Mg-Si alloy layer in Cu/Al-Mg-Si/Cu clad composite. The increased ductility in the aged Cu/Al-Mg-Si/Cu clad composite can be attributed to the enhanced interface bonding and precipitation in Al-Mg-Si layers.

Park M.-J.,Kyung Hee University | Choi B.-C.,Chungnam National University
Mathematical Problems in Engineering | Year: 2017

We consider a single-machine scheduling problem with an outsourcing option in an environment where the processing time and outsourcing cost are uncertain. The performance measure is the total cost of processing some jobs in-house and outsourcing the rest. The cost of processing in-house jobs is measured as the total weighted completion time, which can be considered the operating cost. The uncertainty is described through either an interval or a discrete scenario. The objective is to minimize the maximum deviation from the optimal cost of each scenario. Since the deterministic version is known to be NP-hard, we focus on two special cases, one in which all jobs have identical weights and the other in which all jobs have identical processing times. We analyze the computational complexity of each case and present the conditions that make them polynomially solvable. © 2017 Myoung-Ju Park and Byung-Cheon Choi.

Eun J.W.,Namseoul University | Lee J.-H.,Chungnam National University
IEICE Electronics Express | Year: 2017

In this paper, a new design method of the dual-band bandpass filter which consists of feed line with stepped-impedance resonator (SIR) structure, open-loop ring resonator (OLRR) with SIR, and uniform OLRR is proposed. The SIR structure which can control harmonic frequencies is used to provide the maximum magnetic coupling at the same positions of both the upper and lower feed lines, irrespective of the first passband and the second passband of the dual-band bandpass filter and improve characteristic of stopband between the first and second passbands. This proposed design method was confirmed to be useful from measured results for dual-band bandpass filter operated at 2.4 GHz and 5.5 GHz. © IEICE 2017.

Pyo G.,Korea Advanced Institute of Science and Technology | Kim C.-Y.,Chungnam National University | Hong S.,Korea Advanced Institute of Science and Technology
IEEE Transactions on Microwave Theory and Techniques | Year: 2017

This paper presents a CMOS transceiver IC for a single-antenna frequency-modulated continuous wave (FMCW) radar. Since transmitter (Tx) leakage is critical in a single antenna radar with CMOS technology, a comprehensive leakage canceling technique is proposed. It is able to cancel all the leakages caused by antenna reflection, asymmetry of a balanced structure, and lossy substrate without additional power or area. Even-order harmonic leakages from the power amplifier (PA) are also reduced by an even-harmonic filter, which is implemented simply by removing the real ground from the symmetrical point of the PA output transformer. Matching networks are simplified by using a modified coupler structure. A low-noise combining amplifier is used to make the combining circuit compact. As a result, the transceiver achieves the output power of -1.6 dBm, the phase noise of -105.44 dBc/Hz at 1MHz offset, the receiver (Rx) gain of 15.3 dB, and the noise figure of 11.6 dB. Tx leakages are canceled so that the isolation between Tx and Rx is 47.3 dB. The chip consumes 74.1 mA from a 1.5-V power supply. Despite the high integration level, the chip area including pads is 1.7 mm × 0.9 mm. A K -band FMCW radar module with a single antenna is implemented with this chip. © 1963-2012 IEEE.

Kim I.J.,Chungnam National University | Ramalingam M.,Chungnam National University | Son Y.-A.,Chungnam National University
Sensors and Actuators, B: Chemical | Year: 2017

A conjugated naphthoquinone-benzothiazole (R) system was developed and characterized and its cyanide sensing properties were monitored in 80% aqueous DMF solution. Cyanide ions react with the receptor through a nucleophilic addition reaction, resulting in immediate color change that can be viewed and monitored colorimetrically and fluorimerically. Optical properties of R were not affected by the addition of other common anions in the presence and absence of cyanide ions. A test strip based on R was fabricated and could act as a convenient test kit to detect cyanide ions. Thus, the receptor can be used as an effective probe to detect cyanide ions in aqueous solution. © 2017 Elsevier B.V.

Lee W.,Chungnam National University | Kim S.H.,Yonsei University | Park J.,Yonsei University | Min B.-K.,Yonsei University
Journal of Cleaner Production | Year: 2017

Optimizing the machining condition is one of the effective ways for reducing the energy consumption of machine tools at a unit process level. Based on statistical approaches with design of experiments, various methods have been developed to reduce the energy consumption by optimizing the machining condition. However, the methods cannot be easily utilized when the optimization target or machine tool design is modified because the optimal solution is determined based on the experimentally measured data. In this study, a simulation-based method that utilizes a virtual machine tool (VMT) to optimize the machining condition is proposed. The VMT model is designed to focus on estimating the energy consumption during machining and is developed by replicating real machine tools. Based on the VMT model, a genetic algorithm is used to optimize the machining condition to reduce the energy consumption. The changes in the optimization target or machine tool design are easily considered by modifying the cost function or component model, respectively. The proposed method is applied to reduce the energy consumption of a three-axis milling machine. The optimal feed rate and spindle speed are obtained for each line of the part program when the thrust force is limited. An experimental setup of the machine tool with an energy consumption monitoring system is constructed to demonstrate the effectiveness of the proposed method. The results show that the total energy consumption of the machine tool reduces by 13% owing to the optimization. © 2017 Elsevier Ltd

Choi W.-C.,Gachon University | Kim S.-W.,Chungnam National University | Jang S.-J.,Chungnam National University | Yun H.-D.,Chungnam National University
Magazine of Concrete Research | Year: 2017

Research into the fire resistance of structural concrete in South Korea has been ongoing since 2000 and incorporates studies on concrete materials, columns, construction methods and finishing materials. Recently, experiments and analytical studies have been undertaken to include diverse materials and structures for fire resistance. Based on the results of these studies, the South Korean government recognised the need for performance criteria for legal fire-resistant construction and published Regulations for Egress/Fire Protection Construction in 2015. In light of this previous work, this paper provides a review of recent research results for the prevention of the explosive fracture of concrete exposed to high temperatures, analysis of the fire resistance of concrete and recent fire mitigation construction methods. In addition, the paper briefly describes existing specifications for fire resistance design methods in South Korea. © 2017, ICE Publishing. All rights reserved.

Kim J.-C.,Chungnam National University | Jung K.,Chungnam National University
Water Resources Management | Year: 2017

This paper investigates positively skewed shape of instantaneous unit hydrograph (IUH), one of the universal features of hydrologic response function. An analytical expression of statistical moments for IUH is derived in the framework of width function based geomorphologic IUH (GIUH) theory being interpreted by the concept of hydrodynamic, geomorphologic and kinematic dispersion. Within the extent of a river basin there is a significant scale difference between hillslope and channel flow path length. Even though the former has much smaller length scale its variation coefficient tends to be higher and skewness coefficient has a different trend than the latter. Kinematic heterogeneity has larger influence on the shape of IUH rather than hydrodynamic heterogeneity. Furthermore, its combined effect with geomorphologic heterogeneity can be a major cause of skewing hydrologic response function. Through transformation of width function into GIUH statistical properties of hillslope and channel flow path length can be imprinted on the shape of hydrologic response function in the form of dimensionless statistics. © 2017, Springer Science+Business Media Dordrecht.

Yan J.,Chungnam National University | Jeong Y.G.,Chungnam National University
Composites Science and Technology | Year: 2017

We report the electrical, dielectric and piezoelectric properties of flexible PDMS-based nanocomposite generators, which are tunable by different contents of multi-walled carbon nanotube (MWCNT, 0.0–5.0 wt%) and BaTiO3 nanofiber (10–50 wt%). The BaTiO3 nanofiber with tetragonal structure was manufactured by an electrospinning and following calcination process. For the first series of nanocomposite generators with 30 wt% BaTiO3 nanofiber and 0.0–5.0 wt% MWCNT, both electrical and dielectric properties were dramatically enhanced at a critical MWCNT content of 0.47 wt% owing to the formation of percolating networks of MWCNT in the presence of BaTiO3 nanofibers, as verified by SEM analysis. Accordingly, the nanocomposite generator with 30 wt% BaTiO3 and 5.0 wt% MWCNT achieved the highest conductivity of 0.12 S/cm and dielectric constant of 4474 at 1 kHz, whereas the nanocomposite generator with 30 wt% BaTiO3 and 2.0 wt% MWCNT attained the best piezoelectric performance by harvesting average output voltage of ∼3.00 V, current of ∼0.82 μA, and power of ∼0.14 μW. In cases of the second series of nanocomposite generators with 2.0 wt% MWCNT and 10–50 wt% BaTiO3 nanofiber, the electrical conductivity and dielectric constant increased with the increment of BaTiO3 content up to 40 wt%. Overall, the nanocomposite generator with 2.0 wt% MWCNT and 40 wt% BaTiO3 nanofiber generated the highest average output voltage of ∼3.73 V, current of ∼1.37 μA, and power of ∼0.33 μW, which was feasible to light up commercial LEDs and to charge a capacitor after rectification, revealing the potentiality in powering self-sufficient nanodevices and wireless electronics. © 2017 Elsevier Ltd

Oh H.-J.,Chungnam National University | Dao V.-D.,Chungnam National University | Choi H.-S.,Chungnam National University
Journal of Alloys and Compounds | Year: 2017

This work presents the synthesis of CoxPd1-x alloys (0 ≤ x ≤ 1) on a reduced graphene oxide (RGO) surface using the dry plasma reduction method. The formation of CoPd alloys on the RGO surface is confirmed through high-resolution scanning electron microscopy (HRSEM) and X-ray photoelectron spectroscopy (XPS) measurements, and transmittance electron microscopy (TEM). Then, the developed materials are applied as Pt-free counter electrodes (CEs) in dye-sensitized solar cells (DSCs). In order to obtain efficient CEs, the chemical composition of the CoxPd1-x/RGO is controlled through optimizing the volume ratio of the Co and Pd precursors during the synthesizing process. Due to the optimization of the charge-transfer resistance (Rct) and the diffusion impedance (Zw) values of the Co0.9Pd0.1/RGO CE, the device using the Co0.9Pd0.1/RGO CE exhibits the highest efficiency among the fabricated cells. Note that the cells using Co/RGO and Pd/RGO exhibit efficiencies of 5.17% and 5.41%, respectively. The proposed strategy is simple and efficient; thus, it is promising for fabricating highly efficient and low-cost CE materials for DSCs. © 2017 Elsevier B.V.

Oh D.-S.,Chungnam National University | Phillips F.Y.,Yuan Ze University
PICMET 2016 - Portland International Conference on Management of Engineering and Technology: Technology Management For Social Innovation, Proceedings | Year: 2016

Globalization and information/communication technology, as well as new modes of assessment, have opened new prospects for the practice of technology assessment. These prospects hold the potential for realizing the technology assessment role that has long heen recommended for UNESCO and other United Nations agencies. They may also solve the problem of research parks that, as 'hyhrid organizations,' have failed to mesh with the cultural values of their surrounding communities. This paper highlights the new prospects for assessment, and identifies the institutional gaps in assessment practice. We propose, as a solution, that assessment become a function of an international network of research parks, with the official recognition and clearinghouse services of an international agency. We find this proposal aligns well with the recent technology assessment literature and its implications, and we put forth the Daejeon/ UNESCO Global Innovation Forum as a possible network platform. © 2016 Portland International Conference on Management of Engineering and Technology, Inc.

Thao N.P.,Chungnam National University | Lee J.S.,Chungnam National University | Kim Y.H.,Chungnam National University
Bioorganic and Medicinal Chemistry Letters | Year: 2017

The aim of this study was to search for potential therapeutic agents by identifying novel inhibitors of soluble epoxide hydrolase (sEH) from natural plants using an in silico approach. We found that an ethanolic extract from the roots of Cimicifuga dahurica (Turcz.) Maxim. significantly inhibited sEH in vitro. In a phytochemical investigation using assay-guided fractionation of the dichloromethane extract of C. dahurica, we isolated two new indolinone alkaloids (5 and 6) and five related constituents (1–4, and 7) and established their structures based on an extensive analysis using 1D and 2D NMR, and MS methods. All of the isolated compounds inhibited sEH enzymatic activity in a dose-dependent manner, with IC50 values ranging from 0.8 ± 0.0 to 2.8 ± 0.4 μM. A kinetic analysis of compounds 1–7 revealed that compound 2 was non-competitive; 1, 3, and 7 were mixed-type; and 4–6 were competitive inhibitors. Molecular docking was employed to further elucidate their receptor-ligand binding characteristics. These results demonstrated that compounds from C. dahurica are potential sEH inhibitors. © 2017 Elsevier Ltd

Park S.,Agency for Defense Development | Cha H.,Chungnam National University
19th International Conference on Electrical Machines and Systems, ICEMS 2016 | Year: 2016

An LC3L type Isolated bidirectional dc/dc converter is analyzed, including the effect of a high frequency transformer by using ac complex circuit approximation. Its solution is derived and is used to obtain the characteristics of the proposed converter. The analyses show the comparison of voltage gain with T-equivalent transformer results in introduction of magnetizing and leakage inductance at conventional LC3L dc/dc converter with ideal transformer. The theoretical solution and simulation results that observed introduction of a transformer in the converter had considerable effect on the performance, especially in the case of low output voltage and large load. © 2016 The Institute of Electrical Engineers of Japan.

Choi J.,Chungnam National University | Jang Y.-C.,Chungnam National University | Kim J.-G.,Chonbuk National University
Science of the Total Environment | Year: 2017

Polybrominated diphenyl ethers (PBDEs), a class of brominated flame retardants, have been widely used in many applications in industry such as automobiles, textiles, and electronics. This study focused on a quantitative substance flow analysis (SFA) of PBDEs in automobiles in order to identify their flow by life cycle and treatment pathways of PBDEs-containing materials in end-of-life vehicles (ELVs) in Korea. In addition, this study has estimated environmental releases of PBDEs in automobiles by life cycle in Korea. During this study, PBDEs were analyzed for the samples collected from several ELVs treatment facilities using X-ray fluorescence and gas chromatography/mass spectrometry (GC/MS) methods. The system boundary for SFA of PBDEs ranged from manufacturing/trade to disposal stage of automobiles by life cycle. Based on the result of the SFA, it was found that the amount of PBDEs in automobiles were the highest in use stage (7748 ton/year), followed by production stage (1743 ton/year) in 2014. In disposal stage, automobile shredded residues (ASR) and seat fabrics were the main components with relatively high levels of PBDEs in ELVs. The major treatment methods of such components included incineration (84%), energy recovery (9%), and landfilling (6%). This research indicates that PBDEs were emitted the highest amount from interior components during the use stage of automobiles, followed by recycling processes such as dismantling and shredding. This study suggests that PBDEs in ASR and seat fabrics should be properly managed to prevent the widespread dispersion in the environment. © 2016 Elsevier B.V.

Membranous nephropathy (MGN) is the most common cause of the nephrotic syndrome in adults. Most cases of MGN are primary, but secondary MGN are frequently encountered. Determination of secondary MGN is crucial for initiation of appropriate treatment. The diagnostic performance of the phospholipase A2 receptor (PLA2R) and immunoglobulin G4 (IgG4) detection based on immunohistochemistry were evaluated using biopsy tissues of 59 primary and 56 secondary MGN cases for discrimination between primary MGN and secondary MGN. The PLA2R and IgG4 detection based on immunohistochemistry were dominantly positive in primary MGN cases. Sensitivity and specificity values for identification of primary MGN were 83% and 88% for PLA2R, and 76% and 86% for IgG4. Both PLA2R and IgG4 positivity showed a high specificity of 96.4% for identifying primary MGN. A meta-analysis was performed for analysis of the diagnostic accuracy of histologic PLA2R and IgG4 deposition for differentiation of primary from secondary MGN. The overall sensitivity, specificity, and area under curve of summary receiver operating characteristics were 76%, 86%, 0.93 for histologic PLA2R deposition, and 80%, 69%, 0.82 for histologic IgG4 deposition. PLA2R and IgG4 detection based on immunohistochemistry can be useful for differentiation of primary MGN from secondary MGN. Copyright 2017 Wolters Kluwer Health, Inc. All rights reserved.

Jung S.,Chungnam National University
International Journal of Control, Automation and Systems | Year: 2017

Neural network control for robot manipulators is aimed to compensate for uncertainties in the robot dynamics. The location of a compensating point differentiates the control scheme into two categories, the feedback error learning (FEL) scheme and the reference compensation technique (RCT). The RCT scheme is relatively less used although it has several structural advantages. In this paper, the global stability of the RCT scheme is analyzed on the basis of Lyapunov function. The analysis turns out that the stability depends upon the magnitude of the controller gains. Simulation studies of controlling the position of a two-link robot manipulator are conducted. © 2017 Institute of Control, Robotics and Systems and The Korean Institute of Electrical Engineers and Springer-Verlag Berlin Heidelberg

Go J.-I.,Chungnam National University | Park J.-S.,Chungnam National University
5th Asian-Australian Rotorcraft Forum, ARF 2016 | Year: 2016

This work conducts a validation study for the XH-59A helicopter using a rigid coaxial rotor system in order to establish the techniques of the conceptual design and performance analysis for the lift-offset compound rotorcraft. As a tool for conceptual design and performance analysis, NDARC (NASA Design and Analysis of Rotorcraft) is used for the present study. An assumed mission profile is considered for the conceptual design of the XH-59A. As a validation result of the design, the dimensions and weight of the XH-59A are appropriately designed when compared to the target values since the relative error is less than 0.5%. Then, performance analyses are conducted for the designed XH-59A model with and without auxiliary propulsion in hover and forward flight conditions. The present analyses show good validity since the prediction results compare well with both the flight test and previous analyses. Therefore, the techniques for the conceptual design and performance analysis of the lift-offset compound helicopter are overall considered to be appropriately established. In addition, this study investigates the influence of the lift-offset on the rotor effective lift-to-drag ratio of the XH-59A helicopter with auxiliary propulsion. As a result, the improvement of the rotor effective lift-to-drag ratio can be obtained by appropriately increasing the lift-offset in high-speed flight. Copyright © 2016 by the American Helicopter Society International, Inc. All rights reserved.

Park M.-S.,Chungnam National University | Lee S.,Chungnam National University | Lee Y.-S.,Chungnam National University
Carbon Letters | Year: 2017

The effects of ammonia-treated graphene oxide (GO) on composites based on epoxy resin were investigated. Ammonia solutions of different concentrations (14–28%) were used to modify GO. Nitrogen functional groups were introduced on the GO surfaces without significant structural changes. The ammonia-treated GO-based epoxy composites exhibited interesting changes in their mechanical properties related to the presence of nitrogen functional groups, particularly amine (C-NH2) groups on the GO surfaces. The highest tensile and impact strength values were 42.1 MPa and 12.3 J/m, respectively, which were observed in an epoxy composite prepared with GO treated with a 28% ammonia solution. This improved tensile strength was 2.2 and 1.3 times higher than those of the neat epoxy and the non-treated GO-based epoxy composite, respectively. The amine groups on the GO ensure its participation in the cross-linking reaction of the epoxy resin under amine curing agent condition and enhance its interfacial bonding with the epoxy resin. © Korean Carbon Society.

Kim C.-K.,EH R&C Co. | Choi M.S.,Chungnam National University
Ocean Science Journal | Year: 2017

Mediterranean (blue) mussels (Mytilus galloprovincialis) collected from a reference site were transplanted to 15 stations in coastal areas around Ulsan and Onsan Bays, an extensively metal polluted area in Korean coastal waters, to assess metal contamination in the coastal oceans of Korea. During the biomonitoring periods (June 30 to July 20, 2003; 21 days), transplanted mussels, seawater, and particulate materials were collected for analysis of 15 metals (Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Sb, Se, Sn, and Zn). Transplanted mussels showed metal enrichment compared to initial concentrations and spatial gradients consistent with dissolved and/or particulate metal concentrations in seawaters. Based on Q mode factor analysis, stations were clustered into three groups. The first group, located on Onsan Bay, showed high Ag, Cd, Cu, Hg, Pb, Sb and Zn enrichment, presumably arising from non-ferrous metal refineries and chemical industries in this area. The second group was located near the mouth of the Oehwang River and was enriched in Co from petrochemical industries. The third group comprised a site intermediate between Group 1 and Group 2, an isolated station with independent metal sources located in Jangsaengpo harbor, where a number of ship repairing and building companies operate, and a less contaminated station near a small fishing village. Metal accumulation rates (%·day-1) in mussels were estimated to be between 8% (Cr) and 281% (Pb), based on accumulated metal concentrations over 21 days. The active biomonitoring technique using M. galloprovincialis demonstrated here is a useful monitoring method because it reflects the present status of seawaters; furthermore, physiological factors can be standardized, and bioavailable and time-integrated metal concentrations can be obtained. Furthermore, this method can be applied even in coastal seawaters so heavily contaminated that living organisms would not normally survive. © 2017, Korea Ocean Research & Development Institute (KORDI) and the Korean Society of Oceanography (KSO) and Springer Science+Business Media Dordrecht.

Kim H.-G.,Chungnam National University | Song K.B.,Chungnam National University
Journal of Microbiology and Biotechnology | Year: 2017

Combined treatment with gaseous and aqueous chlorine dioxide (ClO2) was performed to improve the microbiological safety and quality of paprika. A single treatment of 50 ppmv ClO2 gas for 30 min decreased the populations of Escherichia coli O157:H7 and Salmonella2 Typhimurium by 2.33 and 2.91 log CFU/g, respectively. In addition, a single treatment of aqueous ClO2 (50 ppm) for 5 min decreased these populations by 1.86 and 1.37, respectively. The most dramatic effects were achieved by combined treatment of 50 ppm aqueous and2 gaseous ClO2 for 30 min, which decreased populations of E. coli O157:H7 and S. Typhimurium by 4.11 and 3.61 log CFU/g, respectively. With regard to the qualities of paprika, no adverse2 effects were elicited by the combined treatment. Thus, combined treatment with aqueous and gaseous ClO2 is a suitable approach that can be used to improve the microbial safety and quality of paprika.2 © 2017 by The Korean Society for Microbiology and Biotechnology

Kang J.H.,Chungnam National University | Song K.B.,Chungnam National University
Journal of Microbiology and Biotechnology | Year: 2017

An aqueous chlorine dioxide (ClO2) treatment combined with highly activated calcium oxide (CaO) and mild heat was tested for inactivating naturally existing bacteria and Escherichia coli O157:H7 inoculated on fresh-cut kale. Kale samples were treated with different concentrations of ClO2 (10, 30, and 50 ppm), CaO (0.01%, 0.05%, 0.1%, and 0.2%), and mild heat (25°C, 45°C, 55°C, and 65°C) as well with combinations of 30 or 50 ppm ClO2 and 0.2% CaO at 55°C for 3 min. An increasing concentration of ClO2 and CaO significantly reduced the microbial population compared with the control. In addition, mild heating at 55°C elicited greater microbial reduction than the other temperatures. A combined treatment of 50 ppm ClO2 and 0.2% CaO at 55°C reduced the population of naturally existing bacteria on kale by 3.10 log colony forming units (CFU)/g, and the counts of E. coli O157:H7 were below the detection limit (1 log CFU/g). In addition, no significant differences in the Hunter color values were evident in any treatment during storage. Therefore, a combined treatment of ClO2 and active CaO at 55°C can be an effective sanitizing method to improve the microbiological safety of fresh-cut kale without affecting its quality. © 2017 by The Korean Society for Microbiology and Biotechnology.

Song J.-H.,Chungnam National University | Ahn K.-J.,Chungnam National University
Journal of Asia-Pacific Biodiversity | Year: 2017

Aleochara (Emplenota) hayamai Yamamoto & Maruyama and Tetrasticta brevipennis (Bernhauer) are recorded for the first time in Korea. Photographs of habitus and diagnoses are provided. © 2017 National Science Museum of Korea (NSMK) and Korea National Arboretum (KNA).

Song J.-H.,Chungnam National University | Ahn K.-J.,Chungnam National University
Journal of Asia-Pacific Biodiversity | Year: 2017

The beetle family Clambidae, represented by Clambus formosanus japonicus Endrödy-Younga, is identified for the first time in Korea. A habitus photograph, diagnosis, and illustrations of diagnostic characters of the species are provided. © 2017 National Science Museum of Korea (NSMK) and Korea National Arboretum (KNA).

Bae K.-H.,Chungnam National University | Dao V.-D.,Chungnam National University | Choi H.-S.,Chungnam National University
Journal of Colloid and Interface Science | Year: 2017

This study presents the synthesis of PtNi alloys with different volume ratios of Pt and Ni precursors in mixture solutions using dry plasma reduction under atmospheric pressure and low temperature. The developed materials are applied as efficient counter electrodes (CEs) in dye-sensitized solar cells (DSCs). The investigation of the Pt utility in PtNi alloys for electrocatalytic activity, and cost effective and highly efficient DSCs are also investigated. Compared with the reference electrodes (Pt and Ni CEs), the developed PtNi alloy CEs exhibit better reversibility as indicated by the peak-to-peak separation and better catalytic activity for the regeneration of iodide ions from triiodide ions. Thus, the DSC with the developed PtNi CEs provides higher efficiency than that of the device fabricated with the reference electrodes. © 2017 Elsevier Inc.

Ssessanga N.,Chungnam National University | Kim Y.H.,Chungnam National University | Jeong S.-H.,Chungnam National University
Journal of Geophysical Research: Space Physics | Year: 2017

A statistical study on the relationship between the perturbation component (ΔTEC (total electron content)) and the F2 layer peak height (hmF2) during nighttime medium-scale traveling ionospheric disturbances is presented. The results are obtained by using a time-dependent computerized ionospheric tomography (CIT) technique. This was realized by using slant total electron content observations from a dense Global Positioning System receiver network over Japan (with more than 1000 receivers), together with a multiplicative algebraic reconstruction technique. Reconstructions from CIT were validated by using ionosonde and occultation measurements. A total of 36 different time snapshots of the ionosphere when medium-scale traveling ionospheric disturbances (MSTIDs) were eminent were analyzed. These were obtained from a data set covering years from 2011 to 2014. The reconstructed surface wavefronts of ΔTEC and hmF2 structure were found to be aligned along the northwest-southeast direction. These results confirm that nighttime MSTIDs are driven by electrodynamic forces related to Perkins instability which explains the northwest-southeast wavefront alignment based on the F region electrodynamics. Furthermore, from the statistical analysis hmF2 varied quasiperiodically in altitude with dominant peak-to-peak amplitudes between 10 and 40km. In addition, ΔTEC and hmF2 were 60% anticorrelated. © 2017. American Geophysical Union. All Rights Reserved.

Sok S.-W.,Electronics and Telecommunications Research Institute | Jung Y.-W.,Electronics and Telecommunications Research Institute | Lee C.-H.,Chungnam National University
Journal of Physics: Conference Series | Year: 2017

This paper introduces ViMo-S, a type 1 hypervisor for ARMv7 and ARMv8-based ARM server systems. It supports full virtualization to run existing operating systems and applications unmodified. It uses ARM hardware virtualization extensions to optimize the performance of virtual machines, especially system call latency. Therefore, its virtual machines' system call latency is near physical machine's, while other hypervisors like Xen and KVM show relatively slower and unstable performances in benchmark tests. © Published under licence by IOP Publishing Ltd.

Son H.-J.,Chungnam National University | Song K.B.,Chungnam National University
Journal of Microbiology and Biotechnology | Year: 2017

This study examined the antimicrobial activity of flaxseed meal extract (FME) against Staphylococcus aureus and Escherichia coli O157:H7 inoculated on red mustard. With the treatment of 0.7% FME for 3 min, the reduction levels of S. aureus and E. coli O157:H7 populations were 1.23 and 1.83 log CFU/g, respectively. In addition, the combined treatment of 0.7% FME at 50°C for 3 min reduced the populations of the pathogenic bacteria by 2.28 and 2.41 log CFU/g, respectively. The color and the vitamin C content were not significantly different between treatments. Thus, FME can be used as a novel antimicrobial agent in fresh-cut vegetables. © 2017 by The Korean Society for Microbiology and Biotechnology.

Tsunetsugu Y.,Japan Forestry and Forest Products Research Institute | Lee J.,Korea Forest Service | Park B.-J.,Chungnam National University | Tyrvainen L.,Finnish Forest Research Institute | And 2 more authors.
Landscape and Urban Planning | Year: 2013

The present study investigated the physiological and psychological effects of viewing urban forest landscapes on 48 young male urban residents. Four forested areas and four urban areas located in central and western Japan were used as the test sites. We found that in the forested areas, the subjects exhibited (i) significantly lower diastolic blood pressure, (ii) significantly higher parasympathetic nervous activity, but significantly lower sympathetic nervous activity, and (iii) significantly lower heart rate. The forest landscapes (iv) obtained better scores in subjective ratings, and (v) induced significantly less negative and more vigorous moods. Taken as whole, these findings suggest that even a short-term viewing of forests has relaxing effects. We have thus concluded that the approach taken in this study is useful in exploring the influences of urban green space on humans, as well as contributing to the planning and design of a healthy environment for urban residents. © 2013 Elsevier B.V.

Cho S.E.,Korea Water Resources Corporation | Park H.C.,Chungnam National University
International Journal for Numerical and Analytical Methods in Geomechanics | Year: 2010

Geotechnical engineering problems are characterized by many sources of uncertainty. Some of these sources are connected to the uncertainties of soil properties involved in the analysis. In this paper, a numerical procedure for a probabilistic analysis that considers the spatial variability of cross-correlated soil properties is presented and applied to study the bearing capacity of spatially random soil with different autocorrelation distances in the vertical and horizontal directions. The approach integrates a commercial finite difference method and random field theory into the framework of a probabilistic analysis. Two-dimensional cross-correlated non-Gaussian random fields are generated based on a Karhunen-Loéve expansion in a manner consistent with a specified marginal distribution function, an autocorrelation function, and cross-correlation coefficients. A Monte Carlo simulation is then used to determine the statistical response based on the random fields. A series of analyses was performed to study the effects of uncertainty due to the spatial heterogeneity on the bearing capacity of a rough strip footing. The simulations provide insight into the application of uncertainty treatment to geotechnical problems and show the importance of the spatial variability of soil properties with regard to the outcome of a probabilistic assessment. Copyright © 2009 John Wiley & Sons, Ltd.

Um I.K.,Korea Institute of Geoscience and Mineral Resources | Choi M.S.,Chungnam National University | Bahk J.J.,Korea Institute of Geoscience and Mineral Resources | Song Y.H.,Chungnam National University
Marine Geology | Year: 2013

In order to discriminate the origins of Ulleung Basin (East/Japan Sea) sediments using rare earth elements (REEs), sediments from 15 box cores and one piston core collected in the shelf, slope, and basin were analyzed for major elements (Al, Fe, Ca, and Mn) and REEs. The major sedimentary components in this basin were presumed to be detrital materials from land, even in the basin sediments, based on Al and organic contents (carbon and opal). Post-depositional recycling processes involving Fe and Mn were identified in the basin sediments. Thus, the Ce anomaly and the fractionation factors of light REEs (LREEs) and middle REEs (MREEs) relative to heavy REEs (HREEs) could not be used as provenance indicators in the deep basin sediments (>2000m of water depth) based on a feasibility check using their covariation with Fe and Mn. For the shelf, slope, and basin B (sites near islands; water depths of 1200-1800m) regions, the Eu anomaly, LREEN/HREEN, and MREEN/HREEN could be successfully used to discriminate possible provenances, including Nakdong River sediments (NRS), Chinese River sediments (CRS), Ulleungdo volcanic rocks (UVR), and Dokdo volcanic rocks (DVR).From the provenance indicators, slope as well as the shelf sediments (called the Korea Strait shelf mud; KSSM) in the Ulleung Basin can be regarded as mixtures of NRS and CRS with decreasing portions of NRS in the KSSM with distance from the Nakdong River. Basin B sediments were mixtures of UVR or DVR and CRS. These findings can be explained if sediments discharged from the Nakdong River were transported and deposited (KSSM) northward within the strong coastal front in normal periods and if sediment flumes from summer floods flowed out across the coastal front, were carried with the Tsushima Warm Current, and then deposited in the slope area. This study indicated that CRS were very important detrital sediments and that REE compositions can be successfully used as a provenance indicator in even hemipelagic sediments close to land. © 2013 Elsevier B.V.

Long X.,Jiangsu University | Oh K.,Chungnam National University | Cheng G.,Peking University
Journal of Cleaner Production | Year: 2013

This paper investigates the effects of environmental policy on environmental conditions resulting from China's accession to the WTO. We estimate environmental technological efficiency under both weak and strong disposability assumptions and use the difference to calculate the pollution abatement cost (PAC). We then undertake Tobit regression analysis on several explanatory variables, including dummies for different time periods and regions. Generally, our findings show that China's accession to the WTO did not guarantee better environmental conditions even though China adopted stronger regulations to meet the higher standards. In particular, the eastern region does not seem to be strictly regulated. These interesting results may be partly attributable to China's need to attract foreign investment and may represent a case in which institutional regulations are not always effective in practice. © 2012 Elsevier Ltd. All rights reserved.

Lee J.-W.,Chungnam National University | Park C.-M.,Chonbuk National University | Rhee H.,University of Montana
Land Degradation and Development | Year: 2013

Decomposed granite roadcuts are difficult to revegetate after losing the topsoil and vegetation cover. We developed a new drilling machine, Digger, to efficiently drill six holes simultaneously on decomposed granite roadcuts to facilitate revegetation. The Digger consists of a base machine (0.7m3-level excavator) and a mounting body with six hydraulic motors instead of a bucket. We tested its performance on two roadcuts in southwest Korea using time-motion studies, which showed that the Digger can drill 240m2 of decomposed granite roadcuts daily. The unit cost of the Digger was less than a half of other roadcut stabilization and revegetation techniques in Korea, making the Digger a cost-effective revegetation technology. Field germination and growth tests were also conducted to identify appropriate diameter and depth of drilling holes, suitable revegetation species, and mulching treatment. We drilled holes with three different diameters and depths, filled the holes with a mixture of plant seeds and cultivated soil, applied mulching treatments (coir geotextile, shade net, and no mulching), and measured the germination and growth results at two field plots after 1month and 1year. The results showed that drilling diameter 10cm and depth 10cm were large enough to result in better plant germination and growth. Erosion control species, Poa pratensis L. and Eragrostis curvula (Schrad.) Nees, survived and grew better than native woody species. Coir geotextile improved the plant germination and growth. The time-motion and revegetation results show that the Digger can be a promising technology to restore decomposed granite roadcuts. © 2013 John Wiley & Sons, Ltd.

Ko H.,Sogang University | Lee J.,Sogang University | Kim Y.,Sogang University | Lee B.,Sogang University | And 5 more authors.
Advanced Materials | Year: 2014

Active, paper-based, microfluidic chips driven by electrowetting are fabricated and demonstrated for reagent transport and mixing. Instead of using the passive capillary force on the pulp to actuate a flow of a liquid, a group of digital drops are transported along programmed trajectories above the electrodes printed on low-cost paper, which should allow point-of-care production and diagnostic activities in the future. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Patra A.K.,Korea Institute of Geoscience and Mineral Resources | Kim D.-J.,Korea Institute of Geoscience and Mineral Resources | Chung H.-S.,Konyang University | Lee S.-W.,Chungnam National University
Hydrometallurgy | Year: 2013

Two step leaching experiments were carried out to extract nickel, vanadium, and molybdenum present in spent refinery catalyst. A bioleaching process was applied in the first step. Pulp density, initial Fe(II) concentration, initial pH, particle size, and temperature were varied to optimize the bioleaching process. Ni, V, and Mo were leached out with maximum recoveries of 97%, 92% and 53%, respectively, at an optimized bioleaching condition of initial ferrous ion of 2 g/L, initial pH of 2, pulp density of 10% (w/v), particle size of (-106+45) μm, and a temperature of 35 °C. As the Mo leaching rate was very low, a second leaching step for the bioleached residue was applied with different concentrations of (NH4)2CO3, Na 2CO3, or H2SO4. The second step leaching was optimum at a concentration of 30 g/L (NH4) 2CO3 with respect to Mo extraction. The rate of Mo dissolution with respect to concentration of lixiviant in the second leaching step was evaluated. The percentages of Ni, V, and Mo leached were 97%, 97% and 99%, respectively, by combining the first step under optimized conditions and the second step with 30 g/L (NH4)2CO3. © 2012 Elsevier B.V. All rights reserved.

Ko Y.B.,Chungnam National University | Nam S.L.,Chungnam National University | Yang J.B.,Chungnam National University
Cellular Signalling | Year: 2014

High-mobility group box 1 (HMGB1) was shown to be strongly implicated in high incidences of metastasis and the poor clinical pathologic conditions found in various human tumors. In this study, we explored the possible mechanism of HMGB1 in tumor metastases in vitro, using a human carcinoma cell system. BTB, as a negative regulator of cell cycle progression, was identified as a HMGB1 interacting partner. The ectopic expression of HMGB1 activates cell growth by suppressing BTB-induced cell death, decreasing Bax and p53 expression, while enhancing Bcl-xL, Bcl-2, cyclin D1, and NF-κB expression. HMGB1 activates the FAK/PI3K/mTOR signaling cascade, and BTB prominently inhibits HMGB1-induced oncogenesis. The effect of HMGB1 on FAK/mTOR signaling was also confirmed through the silencing of HMGB1 expression. These insights provide evidence that HMGB1 enhances cell proliferation and suppresses apoptosis. Collectively, our results show an underlying mechanism for an HMGB1-associated promotion of carcinoma cells. © 2014 Elsevier Inc.

Aldredge D.,University of California at Davis | An H.J.,Chungnam National University | Tang N.,Agilent Technologies | Waddell K.,Agilent Technologies | Lebrilla C.B.,University of California at Davis
Journal of Proteome Research | Year: 2012

Glycosylation is one of the most common post-translational modifications of proteins and has been shown to change with various pathological states including cancer. Global glycan profiling of human serum based on mass spectrometry has already led to several promising markers for diseases. The changes in glycan structure can result in altered monosaccharide composition as well as in the linkages between the monosaccharides. High-throughput glycan structural elucidation is not possible because of the lack of a glycan template to expedite identification. In an effort toward rapid profiling and identification of glycans, we have constructed a library of structures for the serum glycome to aid in the rapid identification of serum glycans. N-Glycans from human serum glycoproteins are used as a standard and compiled into a library with exact structure (composition and linkage), liquid chromatography retention time, and accurate mass. Development of the library relies on highly reproducible nanoLC-MS retention times. Tandem MS and exoglycosidase digestions were used for structural elucidation. The library currently contains over 300 entries with 50 structures completely elucidated and over 60 partially elucidated structures. This database is steadily growing and will be used to rapidly identify glycans in unknown biological samples. © 2012 American Chemical Society.

Kim J.-H.,Chungnam National University | An H.J.,Chungnam National University | Garrido D.,University of California at Davis | German J.B.,University of California at Davis | And 2 more authors.
PLoS ONE | Year: 2013

Bifidobacterium longum subsp. infantis is a common member of the intestinal microbiota in breast-fed infants and capable of metabolizing human milk oligosaccharides (HMO). To investigate the bacterial response to different prebiotics, we analyzed both cell wall associated and whole cell proteins in B. infantis. Proteins were identified by LC-MS/MS followed by comparative proteomics to deduce the protein localization within the cell. Enzymes involved in the metabolism of lactose, glucose, galactooligosaccharides, fructooligosaccharides and HMO were constitutively expressed exhibiting less than two-fold change regardless of the sugar used. In contrast, enzymes in N-Acetylglucosamine and sucrose catabolism were induced by HMO and fructans, respectively. Galactose-metabolizing enzymes phosphoglucomutase, UDP-glucose 4-epimerase and UTP glucose-1-P uridylytransferase were expressed constitutively, while galactokinase and galactose-1-phosphate uridylyltransferase, increased their expression three fold when HMO and lactose were used as substrates for cell growth. Cell wall-associated proteomics also revealed ATP-dependent sugar transport systems associated with consumption of different prebiotics. In addition, the expression of 16 glycosyl hydrolases revealed the complete metabolic route for each substrate. Mucin, which possesses O-glycans that are structurally similar to HMO did not induced the expression of transport proteins, hydrolysis or sugar metabolic pathway indicating B. infantis do not utilize these glycoconjugates. © 2013 Kim et al.

Yoo H.J.,Chungnam National University | Lee K.H.,Chungnam National University
Cellular Signalling | Year: 2012

Recent studies have shown DAPk as a molecular modulator induced by the second messenger, responsible for controlling cell destiny decisions, but the detailed mechanism mediating the role of DAPk1 during cell death is still not fully understood. In this present report, we attempted to characterize the effects of TNF-α and INF-γ on DAPk1 in human ovarian carcinoma cell lines, OVCAR-3. Both TNF-α and INF-γ significantly induce DAPk1 levels in a time-dependent manner. At the same time, they both arrested cell cycle progression in the G0-G1 and G2/M phase, down-regulated cyclin D1, CDK4 and NF-κB expression, while also up-regulating p27 and p16 expression. Subsequently, the efficacy of the combined treatment with DAPk1 was investigated. In the presence of DAPk1, TNF-α or INF-γ-induced apoptosis was additively increased, while TNF-α or INF-γ-induced NF-κB activity was inhibited. Conversely, TNF-α or INF-γ-dependent NF-κB activity was further enhanced by the inhibition of DAPk1 with its specific siRNA. The activity of NF-κB was dependent on the level of DAPk1, indicating the requirement of DAPk1 for the activation of NF-κB. Low levels of DAPk1 expression were frequently observed in different human patient's tissue and cancer cell lines compared to normal samples. In addition, over-expression of DAPk1 from either TNF-α or INF-γ-treatment cells suppressed the anti-apoptosis protein XIAP as well as COX-2 and ICAM-1, more than control. Taken together, our data findings suggest that DAPk1 can mediate the pro-apoptotic activity of TNF-α and INF-γ via the NF-κB signaling pathways. © 2012 Elsevier Inc..

Hua S.,University of California at Davis | Lebrilla C.,University of California at Davis | An H.J.,Chungnam National University
Bioanalysis | Year: 2011

The glycome, that is, the glycan components of a biological source, has been widely reported to change with disease states. However, mining the glycome for biomarkers is complicated by glycan structural heterogeneity. Nanoflow LC, or nano-LC, significantly addresses the problem by providing a highly sensitive and quantitative method of separating and profiling glycans. This review summarizes recent advances in analytical technology and methodology that enhance and augment the advantages offered by nano-LC. (e.g., reversed phase, hydrophilic interaction and porous graphitized carbon chromatography, as well as associated derivatization strategies), detectors (e.g., fluorescence and MS), and technology platforms (particularly chip-based nano-LC) are examined in detail, along with their application to biomarker discovery. Particular emphasis is placed on methods and technologies that allow structure-specific glycan profiling. © 2011 Future Science Ltd.

Yang Y.,University of California at Davis | Li J.,University of California at Davis | Li J.,Nanjing University | Wu H.,University of California at Davis | And 3 more authors.
Nano Letters | Year: 2012

We report a simple, controlled doping method for achieving n-type, intrinsic, and p-type lead sulfide (PbS) nanowires (NWs) grown by chemical vapor deposition without introducing any impurities. A wide range of carrier concentrations is realized by adjusting the ratio between the Pb and S precursors. The field effect electron mobility of n-type PbS NWs is up to 660 cm2/(V s) at room temperature, in agreement with a long minority carrier diffusion length measured by scanning photocurrent microscopy (SPCM). Interestingly, we have observed a strong dependence of minority carrier diffusion length on gate voltage, which can be understood by considering a carrier concentration dependent recombination lifetime. The demonstrated ambipolar doping of high quality PbS NWs opens up exciting avenues for their applications in photodetectors and photovoltaics. © 2012 American Chemical Society.

Cho S.,Chungnam National University | Kim G.-S.,Sangji University | Lee J.-H.,Chung - Ang University
Health and Quality of Life Outcomes | Year: 2013

Background: Sleep Hygiene Index (SHI) was designed to assess sleep hygiene. Although the SHI has shown adequate psychometric properties in a nonclinical sample, it has not been validated in a sample with chronic pain. Also, its factor structure, measurement error, and incremental validity over and above other factors affecting sleep quality have not been investigated in a nonclinical sample. Thus, this present study aimed to extend prior psychometric investigation of the SHI. Specifically, we evaluated the factor structure, measurement error, and incremental validity as well as the reliabilities and concurrent validity of the SHI in a sample with chronic pain.Methods: A total of 161 patients seeking treatment in a tertiary pain center located in Seoul, Korea participated. To explore the factor structure of the SHI, we performed an exploratory factor analysis using principal component with varimax. Cronbach's alphas and intraclass correlation coefficients were computed to investigate internal consistency and 2-week test-retest stability of the SHI, respectively. Measurement error was estimated using standard error of measurement and minimum detectable change (MDC) of the SHI. For concurrent validity, Pearson correlations were calculated to examine the relations between the SHI and outcome measures including background variables. Also for incremental validity, a hierarchical multiple regression was performed in relation to sleep quality.Results: Results indicated that two-factor solution is most appropriate; sleep disturbing behavior and environment (B/E) and irregular sleep-wake schedule. Results also showed that the internal consistencies and test-retest stability estimates of the SHI were deemed acceptable. At the 95% confidence level, the MDCs were 5.75 for 'sleep disturbing B/E,' 3.65 for 'irregular sleep-wake schedule,' and 7.49 points for total. The SHI was significantly correlated with age, depression, pain-related anxiety, and sleep quality. Also, sleep quality was significantly predicted by the irregular sleep-wake schedule subscale of the SHI, over and above background variables, pain intensity, depression, pain-related anxiety.Conclusions: The SHI has the reliability, measurement error, and concurrent and incremental validity support for assessing sleep hygiene in a sample with chronic pain. © 2013 Cho et al.; licensee BioMed Central Ltd.

Paik M.-J.,Sunchon National University | Kang J.S.,Chungnam National University | Huang B.-S.,National University of Kaohsiung | Carey J.R.,National University of Kaohsiung | Lee W.,Chosun University
Journal of Chromatography A | Year: 2013

Chiral crown ethers have been widely used in the resolution of various chiral compounds containing a primary amino group. Covalently bonded chiral stationary phases derived from (18-crown-6)-2,3,11,12-tetracarboxylic acid (18-C-6-TA) were developed in our groups and utilized for the resolution for several types of analytes. By use of NMR spectroscopy, chiral discrimination studies were performed for α-amino acids and their esters using 18-C-6-TA. Here, advances in the development and application of chiral stationary phases and chiral solvating agents using 18-C-6-TA for enantiomer resolution are described in relationship to recent chiral recognition mechanism studies. © 2012 Elsevier B.V.

Kim K.M.,Chungnam National University | Hoarau G.G.,University of Nordland | Boo S.M.,Chungnam National University
Aquatic Botany | Year: 2012

Gelidium elegans Kützing is commonly found in Korea, China, and Japan, and is the economically most important agarophyte in the northwest Pacific. To assess the genetic structure of the Korean species, we analyzed 1200 base pairs of the mitochondrial cox1 gene from 272 individuals collected from 36 locations. A total of 34 haplotypes were found, most of which were unique, including 27 (79%) 'private' haplotypes. The nucleotide and haplotype diversities of cox1 within G. elegans were 0.711±0.028 (H) and 0.00736±0.00038 (π), respectively. The distribution of cox1 haplotypes, pairwise F ST values, results of neutrality tests, AMOVA, and mismatch distribution revealed the existence of a deep genetic break between central Pacific Japan and all the other locations, corresponding to the surface seawater current patterns as well as the genetic signature of potential demographic expansion. © 2011 Elsevier B.V.

Zhou J.,National University of Singapore | Ong C.-N.,National University of Singapore | Hur G.-M.,Chungnam National University | Shen H.-M.,National University of Singapore
Biochemical Pharmacology | Year: 2010

Andrographolide (Andro), a diterpenoid lactone isolated from a traditional herbal medicine Andrographis paniculata, is known to possess potent anti-inflammatory and anticancer properties. In this study, we sought to examine the effect of Andro on signal transducer and activator of transcription 3 (STAT3) pathway and evaluate whether suppression of STAT3 activity by Andro could sensitize cancer cells to a chemotherapeutic drug doxorubicin. First, we demonstrated that Andro is able to significantly suppress both constitutively activated and IL-6-induced STAT3 phosphorylation and subsequent nuclear translocation in cancer cells. Such inhibition is found to be achieved through suppression of Janus-activated kinase (JAK)1/2 and interaction between STAT3 and gp130. For understanding the biological significance of the inhibitory effect of Andro on STAT3, we next investigated the effect of Andro on doxorubicin-induced apoptosis in human cancer cells. In our study the constitutive activation level of STAT3 was found to be correlated to the resistance of cancer cells to doxorubicin-induced apoptosis. Both the short-term MTT assay and the long-term colony formation assay showed that Andro dramatically promoted doxorubicin-induced cell death in cancer cells, indicating that Andro enhances the sensitivity of cancer cells to doxorubicin mainly via STAT3 suppression. These observations thus reveal a novel anticancer function of Andro and suggest a potential therapeutic strategy of using Andro in combination with chemotherapeutic agents for treatment of cancer. © 2009 Elsevier Inc. All rights reserved.

Lee H.-I.,Korea Electric Power Research Institute | Noh M.D.,Chungnam National University
IEEE Transactions on Industrial Electronics | Year: 2011

Toroidally wound brushless dc (BLDC) machines are compact, economical, and can operate across large air gaps. In this paper, we provide analytical design equations for a radial-flux toroidally wound BLDC machine. The validity of the design equations is checked against finite-element analyses (FEAs) and experiments. It is found that the motor constant calculated by the design equations is off only by 5% from the results by the FEAs or experiments. We also provide an optimization metric that corresponds to the maximization of machine torque while maintaining minimum power loss. Two optimal design cases are presented. © 2011 IEEE.

Poudyal C.P.,Chungnam National University | Chang C.,Chungnam National University | Oh H.-J.,Korea Institute of Geoscience and Mineral Resources | Lee S.,Korea Institute of Geoscience and Mineral Resources
Environmental Earth Sciences | Year: 2010

This study considers landslide susceptibility mapping by means of frequency ratio and artificial neural network approaches using geographic information system (GIS) techniques as a basic analysis tool. The selected study area was that of the Panchthar district, Nepal. GIS was used for the management and manipulation of spatial data. Landslide locations were identified from field survey and aerial photographic interpretation was used for location of lineaments. Ten factors in total are related to the occurrence of landslides. Based on the same set of factors, landslide susceptibility maps were produced from frequency ratio and neural network models, and were then compared and evaluated. The weights of each factor were determined using the back-propagation training method. Landslide susceptibility maps were produced from frequency ratio and neural network models, and they were then compared by means of their checking. The landslide location data were used for checking the results with the landslide susceptibility maps. The accuracy of the landslide susceptibility maps produced by the frequency ratio and neural networks is 82.21 and 78.25%, respectively. © 2010 Springer-Verlag.

Baek S.H.,Korea Electric Power Research Institute | Park H.Y.,Korea Electric Power Research Institute | Ko S.H.,Chungnam National University
Fuel | Year: 2014

This paper describes the numerical investigations of the influence of the blending method on the combustion characteristics and NOx emission in a 500 MW, tangentially coal-fired boiler. The in-furnace and out-furnace blending methods are simulated with the blend of 60% bituminous and 40% subbituminous coals on a weight basis. The simulation shows the blending method has a great effect on carbon in ash, but a little effect on NOx emission. The in-furnace blending method which burns bituminous coal at lower burners and subbituminous coal at upper burners gives the least carbon in ash. For two blending methods, carbon in ash is mainly attributed to the middle burner sets in the furnace. The field tests at a 500 MW coal-fired power plant showed that the in-furnace blending method substantially reduces in NOx and carbon in ash, compared with the out-furnace blending method. © 2014 Published by Elsevier Ltd.

Duong T.-T.,Chungnam National University | Choi H.-J.,Chungnam National University | He Q.-J.,Shanghai University | Le A.-T.,HIGH-TECH | Yoon S.-G.,Chungnam National University
Journal of Alloys and Compounds | Year: 2013

SnO2 blocking layers of various thicknesses were tested for an enhancement to the efficiency of dye-sensitized solar cells (DSSCs). The blocking layers were placed onto FTO/glass substrates at 240 °C using a nanocluster deposition (NCD) technique. The root mean square (rms) roughness of the FTO with 120 nm-thick SnO2 blocking layers showed an increase of about 15% compared with that of a bare- FTO, and the transmittance of the SnO2/FTO structures was not changed compared with that of the bare-FTO. The SnO2 blocking layer prepared by NCD played an important role in increasing the contact area between TiO2 thick films and FTO, which helped prevent electron movement back to the electrolyte, and decreased the contact resistance at the TiO2/FTO interface. The energy-conversion efficiency of the 120 nm-thick SnO2/FTO-based DSSCs was significantly improved, by about 12.1%, compared with that of a bare FTO-based DSSC. © 2013 Elsevier B.V. All rights reserved.

Xu B.,Hong Kong Baptist University | Sung C.,Chungnam National University
International Journal of Medicinal Mushrooms | Year: 2014

Telomerase has been widely accepted as a cancer marker and a promising therapeutic target for novel anticancer drugs. The aim of this study was to investigate the in vitro telomerase inhibitory effects of mushrooms and their anticancer properties. The inhibitory effects of mushrooms and lichens against telomerase activity of HL-60 cells were systematically assessed using polymerase chain reaction based on assay of telomeric repeat amplification protocol. Telomerase inhibitory samples were further tested for antiproliferation effects against the gastric cell line SNU-1 using the MTT method. Ethyl acetate extract of Pleurotus ostreatus, ethyl acetate and water extracts of Lasiosphaera fenzlii, hexane extract of Strobilomyces foccopus, water extract of Sarcodon aspratus, and hexane, ethyl acetate, and water extracts from Umbilicaria esculenta showed strong positive telomerase inhibitory activity. Hexane extract of S. foccopus and water extracts from the edible lichen U. esculenta exhibited strong anticancer effects against SNU-1 cells through antiproliferation assay. The water extract of U. esculenta has a great potential to be developed into an anticancer agent that targets telomerase. © 2014 Begell House, Inc.

Kim J.-I.,Chungnam National University | Park S.-J.,Chungnam National University | Kim S.-B.,Korea Institute of Geoscience and Mineral Resources
Fluid Phase Equilibria | Year: 2010

Phase equilibriums were studied with related extractive solvents of Molybdenum (Mo). Tri-butylphosphate, tri-octylamine and heavy alcohols are used in the extraction of Mo from the acidic media of Mo roasted ore, as a selective solvent or modifier. Solid-liquid equilibrium (SLE) between these solvents and modifiers were determined by visual technique. The combination of solvent and modifier were binary systems of tri-butylphosphate. +. 1-octanol, tri-butylphosphate. +. 1-decanol and 1-octanol. +. 1-decanol. They have a single eutectic point. Non-random two liquid (NRTL) and universal quasi chemical (UNIQUAC) models were used for the description of the determined SLE data.The extraction process of Mo usually progressed with solvents in the kerosene diluents. In order to analyze solvent capability, liquid-liquid equilibrium (LLE) for the ternary systems 1-decane. +. tri-butylphosphate. +. water and 1-decane. +. tri-octylamine. +. water were determined because 1-decane is usually considered as a model compound of kerosene. The measured ternary LLE data were correlated well with NRTL and UNIQUAC model. © 2010 Elsevier B.V.

Graham R.,University of California at Davis | Miller C.,University of California at Davis | Oh E.,Chungnam National University | Yu D.,University of California at Davis
Nano Letters | Year: 2011

We determined the minority carrier diffusion length to be ∼1 μm in single PbS nanowire field effect transistors by scanning photocurrent microscopy. PbS nanowires grown by the vapor-liquid-solid method were p-type with hole mobilities up to 49 cm2/(V s). We measured a photoresponse time faster than 14 μs with near-unity charge separation efficiency at the contacts. For the first time, we also observed a field-dependent photocurrent decay length, indicating a drift dominant carrier transport at high bias. © 2010 American Chemical Society.

Kim C.-S.,Chungnam National University | Seong G.J.,Yonsei University | Lee N.-H.,Chungnam National University | Song K.-C.,Province of Chungcheongnamdo
Ophthalmology | Year: 2011

Purpose To assess the prevalence of primary open-angle glaucoma (POAG) in the Namil-myon area in central South Korea. Design A cross-sectional, epidemiologic study in a defined population. Participants Residents aged ≥40 years in Namil-myon, a rural agricultural area in central South Korea. Methods Each subject underwent a screening that consisted of an interview and ophthalmic examinations, including visual acuity measurement, autorefraction, anterior segment evaluation by optical biometry, slit-lamp examination, Goldmann applanation tonometry, binocular optic disc evaluation, fundus photography, pachymetry, gonioscopy, and screening visual field test using frequency doubling technology. Subjects with suspected glaucoma were referred for definitive examinations. Standard automated field tests and retinal nerve fiber layer analysis using optical coherence tomography (Stratus OCT) or scanning laser polarimetry (GDx VCC) were performed. A diagnosis of glaucoma was made based on the optic disc shape, retinal nerve fiber layer appearance, perimetric results, and other ocular findings. Main Outcome Measures Prevalence of POAG, mean intraocular pressure (IOP), and mean central corneal thickness (CCT). Results Of 1928 eligible residents in the area, 1532 (79.5%) participated in this study. The estimated prevalence of POAG in the population aged ≥40 years was 3.5% (95% confidence interval [CI], 2.7%-4.3%). The prevalence of POAG with an IOP of ≤21 mmHg was 2.7% (95% CI, 2.1%-3.3%), and the prevalence of POAG with an IOP of ≥22 mmHg was 0.8% (95% CI, 0.4%-1.2%). The mean IOP for POAG eyes (16.3±4.6 mmHg) was significantly higher than nonglaucomatous eyes (13.3±2.7 mmHg; P = .001). The mean CCT of POAG eyes with an IOP of ≤21 mmHg was 528±26 μm, and that of POAG eyes with an IOP ≥22 mmHg was 531±37 μm; these values were not significantly different from that of nonglaucomatous eyes (530±31 μm; P = .943 and .996, respectively). Conclusions The prevalences of POAG and POAG with an IOP ≤21 mmHg in the Namil-myon region of central South Korea were higher than that in most previous reports worldwide, but were similar to the reported rates in black and Japanese populations. The mean IOP of POAG eyes was higher than nonglaucomatous eyes, but the mean CCTs were not different. Financial Disclosure(s) The authors have no proprietary or commercial interest in any of the materials discussed in this article. © 2011 American Academy of Ophthalmology.

Moon Y.-E.,Chungnam National University | Yun J.,Chungnam National University | Yun J.,University of Wollongong | Kim H.-I.,Chungnam National University
Journal of Industrial and Engineering Chemistry | Year: 2013

Polymer nanocomposites were prepared by in situ polymerization of aniline with graphite oxide (GO), γ-Fe2O3, and BaTiO3 as electromagnetic interference (EMI) shielding materials. GO, γ-Fe2O3, and BaTiO3 nanoparticles were incorporated in the nanocomposites to improve the electromagnetic properties. The nanocomposites showed the significant improvement in both EMI shielding efficiency (SE) and thermal property due to the thermal conductivity of GO, the magnetic effect of γ-Fe2O3, and the electric effect of BaTiO3. The EMI SE of nanocomposites was improved due to the synergetic effect of reflection and absorption of electromagnetic interference by GO, γ-Fe2O3, and BaTiO3 additives. © 2012 The Korean Society of Industrial and Engineering Chemistry.

Beers T.C.,University of Notre Dame | Norris J.E.,Australian National University | Placco V.M.,Gemini Observatory | Lee Y.S.,Chungnam National University | And 3 more authors.
Astrophysical Journal | Year: 2014

A new set of very high signal-to-noise (S/N > 100/1), medium-resolution (R ∼ 3000) optical spectra have been obtained for 302 of the candidate "weak-metal" stars selected by Bidelman & MacConnell. We use these data to calibrate the recently developed generalization of the Sloan Extension for Galactic Exploration and Understanding and Exploration (SEGUE) Stellar Parameter Pipeline, and obtain estimates of the atmospheric parameters (Teff, log g, and [Fe/H]) for these non-Sloan Digital Sky Survey/SEGUE data; we also obtain estimates of [C/Fe]. The new abundance measurements are shown to be consistent with available high-resolution spectroscopic determinations, and represent a substantial improvement over the accuracies obtained from the previous photometric estimates reported in Paper I of this series. The apparent offset in the photometric abundances of the giants in this sample noted by several authors is confirmed by our new spectroscopy; no such effect is found for the dwarfs. The presence of a metal-weak thick-disk (MWTD) population is clearly supported by these new abundance data. Some 25% of the stars with metallicities -1.8 < [Fe/H] ≤-0.8 exhibit orbital eccentricities e < 0.4, yet are clearly separated from members of the inner-halo population with similar metallicities by their location in a Lindblad energy versus angular momentum diagram. A comparison is made with recent results for a similar-size sample of Radial Velocity Experiment stars from Ruchti et al. We conclude, based on both of these samples, that the MWTD is real, and must be accounted for in discussions of the formation and evolution of the disk system of the Milky Way. © 2014 The American Astronomical Society. All rights reserved.

Park S.-J.,Wonkwang University | Li Z.,Chungnam National University | Hwang I.-N.,Chonnam National University | Huh K.M.,Chungnam National University | Min K.-S.,Chonbuk National University
Journal of Endodontics | Year: 2013

Introduction: Hydrogels have been widely studied as tissue engineering scaffolds over the past 2 decades because of their favorable biological properties. Recently, a new biodegradable glycol chitin-based thermoresponsive hydrogel scaffold (GC-TRS) was developed that can be easily applied as a mild viscous solution at room temperature but quickly transforms into a durable hydrogel under physiological conditions. The aim of this study was to investigate the effects of GC-TRS on the proliferation and odontogenic differentiation of colony-forming human dental pulp cells (hDPCs) in the presence of enamel matrix derivative. Methods: Glycol chitin was synthesized by N-acetylation of glycol chitosan. The morphology of the thermoresponsive hydrogel scaffold was observed by using scanning electron microscopy. The sol gel phase transition of the aqueous solution of glycol chitin was investigated by using the tilting method and rheometer studies. hDPCs were isolated based on their ability to generate clonogenic adherent cell clusters. The effect of GC-TRS and collagen on cell viability was examined by performing 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Expression of markers for odontogenic/osteogenic differentiation (ie, dentin sialophosphoprotein, dentin matrix protein-1, osteonectin, and osteopontin) was analyzed by performing real-time polymerase chain reaction. Results: GC-TRS exhibited a highly macroporous and well-interconnected porous structure. The polymer solution existed in a mildly viscous sol state, but it transitioned to a gel state and did not flow above approximately 37 C. Rheometer studies showed that the glycol chitin solution exhibited a fast sol gel transition approximately at body temperature. GC-TRS and collagen did not inhibit cell viability until 7 days. Dentin sialophosphoprotein and dentin matrix protein-1 were expressed by cells cultured in GC-TRS at a higher level than that in cells cultured in collagen (P <.05). In both the scaffold groups, dentin sialophosphoprotein, dentin matrix protein-1, and osteopontin messenger RNA was up-regulated significantly in EMD-treated hDPCs when compared with the nontreated cells (P <.05). Conclusions: GC-TRS allowed the proliferation and odontogenic differentiation of hDPCs. Furthermore, the differentiation was facilitated by EMD. These results suggest that GC-TRS has the potential to be used in tissue engineering techniques for dentin regeneration. © 2013 American Association of Endodontists.

Han N.S.,Chungbuk National University | Kim T.-J.,Chungbuk National University | Park Y.-C.,Kookmin University | Kim J.,Chungnam National University | Seo J.-H.,Seoul National University
Biotechnology Advances | Year: 2012

Human milk contains a large variety of oligosaccharides (HMOs) that have the potential to modulate the gut flora, affect different gastrointestinal functions, and influence inflammatory processes. This review introduces the recent advances in the microbial and coupled enzymatic methods to produce HMOs with grouping them into trisaccharides (sialyllactose and fucosyllactose) and complex oligosaccharides (lacto- N-biose derivatives). The high purity and low cost of HMOs should make their use possible in new fields such as the food or pharmaceutical industries. © 2011 Elsevier Inc.

Yoo C.S.,Ulsan National Institute of Science and Technology | Luo Z.,University of Connecticut | Lu T.,University of Connecticut | Kim H.,Chungnam National University | Chen J.H.,Sandia National Laboratories
Proceedings of the Combustion Institute | Year: 2013

The effect of thermal stratification, spark-ignition, and turbulence on the ignition of a lean homogeneous iso-octane/air mixture at constant volume and high pressure is investigated by direct numerical simulations (DNS) with a new 99-species reduced kinetic mechanism developed for very lean mixtures from a detailed mechanism. Two-dimensional DNS are performed in a fixed volume with two-dimensional isotropic velocity spectrums, temperature fluctuations, and an ignition source superimposed on the initial scalar fields. The influence of variations in the initial temperature field imposed by changing the variance of temperature, the ignition-timing by changing the time at which the ignition source is superimposed, and the turbulence intensity and length scale on ignition of a lean iso-octane/air mixture is elucidated. The mean heat release rate increases more slowly and ignition delay decreases with increasing thermal stratification under homogeneous charge compression-ignition (HCCI) conditions since the present mean temperature lies far outside of the negative temperature coefficient (NTC) regime. The spark-ignition induces relatively short ignition delay under spark-assisted compression ignition (SACI) conditions while mildly spreading out the mean heat release rate. For SACI combustion, high turbulence intensity decreases the ignition delay more by increasing the turbulent flame area. Displacement speed and Damköhler number analyses reveal that the high degree of thermal stratification induces deflagration at the reaction fronts, and hence, the mean heat release rate is smoother subsequent to thermal runaway occurring at the highest temperature regions in the domain. For SACI combustion, the heat release rate occurs solely by deflagration prior to the occurrence of the maximum heat release rate and subsequently by mixed modes of deflagration and spontaneous ignition. These results suggest that thermal stratification provides smooth operation of HCCI engines and moreover, spark-ignition can precisely control the ignition timing for SACI combustion. © 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Choi W.-J.,Chonnam National University | Lee M.-S.,Chonnam National University | Choi J.-E.,Chungnam National University | Yoon S.,Chonnam National University | Kim H.-Y.,Chonnam National University
Global Change Biology | Year: 2013

Here, we experimentally examined how an episodic lack of sunshine (ELS), as an extreme weather event, would affect rice productivity under warming with elevated [CO2]. In 2009 and 2010, rice plants were grown at two levels of [CO2] (ca. 390 and 650 μl l-1) and three levels of warming (≈ambient, +1.2 °C, and +2.2/2.4 °C) in six independent temperature gradient field chambers (three each for ambient and elevated [CO2]). At panicle initiation (PI), booting (BT), or flowering (FL), rice plants were exposed to ELS (ca. 18% of full sunlight) for 10-14 days consecutively. As expected, ELS elicited a significant reduction in aboveground biomass (AGB) and yields. However, elevated [CO2] had the potential to relieve the ELS-induced reduction in AGB and yield, whereas warming had the reverse effect for yields, without a significant warming × [CO2] interaction. When ELS applied at PI, BT, and FL, the extents to which warming-reduced yields (averaged across [CO2] levels) ranged from 9 to 25%, 7 to 14, and 10 to 18% at +1.2 °C, and ranged from 24 to 56%, 22 to 55%, and 18 to 46% at +2.2/2.4 °C across two seasons, respectively. Meanwhile, under normal sunshine they ranged from 1 to 3% at +1.2 °C and 7 to 21% at +2.2/2.4 °C. Warming predisposed rice plants that had experienced ELS to be more sensitive to spikelet sterility and spikelet number per panicle, accounting for most of the yield reductions. These findings provide evidence that an expected warming could further exacerbate rice productivity if ELS occurs simultaneously during reproductive stages. Our results collectively suggest that it might be critically important to consider extreme events for a holistic evaluation of the potential impact of warming and [CO2] on crop productivity, when considering changing climate. © 2012 Blackwell Publishing Ltd.

Kim S.,Chungnam National University | Cho S.,Anyang University, South Korea
Journal of the American Society for Information Science and Technology | Year: 2013

Korea, along with Asia at large, is producing more and more valuable academic materials. Furthermore, the demand for academic materials produced in non-Western societies is increasing among English-speaking users. In order to search among such material, users rely on keywords such as author names. However, Asian nations such as Korea and China have markedly different methods of writing personal names from Western naming traditions. Among these differences are name components, structure, writing customs, and distribution of surnames. These differences influence the Anglicization of Asian academic researchers' names, often leading to them being written in various fashions, unlike Western personal names. These inconsistent formats can often lead to difficulties in searching and finding academic materials for Western users unfamiliar with Korean and Asian personal names. This article presents methods for precisely understanding and categorizing Korean personal names in order to make academic materials by Korean authors easier to find for Westerners. As such, this article discusses characteristics particular to Korean personal names and furthermore analyzes how the personal names of Korean academic researchers are currently being written in English. © 2012 ASIS&T.

Choi G.,Pratt Institute | Chung H.,Chungnam National University
International Journal of Human-Computer Interaction | Year: 2013

With their heavy traffic and technological capabilities, social networking sites (SNS) introduced a new means of building and maintaining perceived social capital. This study aims to identify underlying factors and causal relationships that affect behavioral intention to use SNS. For this purpose, this research developed an extended technology acceptance model, incorporating subjective norm and perceived social capital for predicting SNS acceptance and usage. Exploratory correlation and path analyses were conducted to identify the relationships between five constructs: perceived usefulness, perceived ease of use, subjective norm, perceived social capital, and intention to use. The results showed that perceived usefulness and perceived ease of use had robust effects on the user's intention to use SNS. The research findings also demonstrated that subjective norm and perceived social capital were significant predictors of both perceived usefulness and perceived ease of use and therefore should be considered as potential variables for extending the technology acceptance model. © 2013 Copyright Taylor and Francis Group, LLC.

Kim H.M.,Chungnam National University | Lee H.,Korea Basic Science Institute | Hong K.S.,Chungnam National University | Hong K.S.,Korea Basic Science Institute | And 4 more authors.
ACS Nano | Year: 2011

Here, we describe an easy but robust chemical strategy to synthesize high-performance magnetic resonance (MR)/near-infrared (NIR) multimodal imaging nanoprobes. Poly(γ-glutamic acid) was used for the convenient phase transfer of MnFe2O4 nanoparticles dispersed in organic solvents into aqueous solutions and facilitated further ionic gelation with poly(l-lysine). During the gelation process, MnFe2O4 nanoparticulate satellites were encapsulated in the ionic nanocomplex, which induced synergistic magnetism and resulted in huge T2 relaxivity (r2). The positively charged outer surfaces were assembled with other negatively charged NIR emitting fluorescent nanocrystals and enabled the highly efficient delivery of the magnetofluorescent polyelectrolyte nanocomposites (MagFL-PEN) into cancer cells. The enhancement of negative contrast of MagFL-PEN at 2 μg/mL concentration was similar to that of Resovist at 20 μg/mL concentration. The NIR fluorescence microscopy images of the MagFL-PEN-labeled cells even at 12.5 pM were able to be clearly observed. The labeling efficiency of MagFL-PEN was approximately 65-fold higher compared to that of the commercialized fluorescent nanocrystals, only after 3 h incubation period, even at the test concentration (100 pM). Due to the high-performance capabilities both in materials properties and cell labeling efficiency, the MagFL-PEN is expected to be used as a highly efficient MR/NIR dual-modality imaging nanoprobe in the detection of cancer cells and monitoring of therapeutic cells in vivo. © 2011 American Chemical Society.

Nguyen T.-H.,Soonchunhyang University | Lee K.-H.,Chungnam National University | Lee B.-T.,Soonchunhyang University
Materials Science and Engineering C | Year: 2010

In this study, the antimicrobial substance, silver nanoparticles (Ag NPs) loaded in poly (vinyl alcohol) (PVA) nanowire mats were fabricated by conjugation of the electro-spinning method and the microwave-assisted process. The best PVA nanowire mats were fabricated by through control of electro-spinning conditions, which were applied for fabrication of Ag NPs loaded in PVA nanowires. PVA was used not only as a carrier for loading of Ag NPs but also as a reduction agent with which the Ag+ ion was already reduced to a large number of Ag NPs by irradiation with a microwave. Ag NPs were synthesized inside the PVA solution depending on the time of microwave irradiation - whether for 60 s or 90 s. Size distribution of Ag NPs was 5-10 nm in diameter for 60 s; and 10-20 nm in diameter for 90 s of irradiation. Presence of Ag NPs acquired through microwave assisted irradiation was confirmed by X-ray diffraction profiles (XRD). Microstructure, particle size distribution, and morphology of both the nanowire mats and the Ag particles were investigated using SEM and TEM techniques. The effect of Ag-NPs on the PVA mechanical property of nano-fibrous mats was investigated according to tensile strength. Antibacterial activity of PVA loaded Ag NPs at different irradiation times was tested on Gram-positive bacteria, Staphylococcus aureus Gram-negative bacteria, and Escherichia coli. © 2010 Elsevier B.V. All rights reserved.

Cho W.K.,Chungnam National University | Kang S.M.,Pukyong National University | Lee J.K.,Kyungpook National University
Journal of Nanoscience and Nanotechnology | Year: 2014

Nanoarchitectured polymer thin films are playing an increasingly pivotal role in a wide range of areas such as interfacial reactions, biomedical devices/implants, biosensors, food packing, and marine equipment. This review highlights recent research results in the field of the non-biofouling polymer films, including current understanding of the mechanisms of non-biofouling efficacy against bioentities (for example, proteins, cells, and bacteria) under different biological conditions. We also discuss current advances in the fabrication of non-biofouling coatings and micropatterns of cells on solid substrates and suggest a guideline when designing a non-biofouling polymer films, according to application requirements. © 2014 American Scientific Publishers.

Noh Y.-W.,Chungnam National University | Park H.S.,Chungnam National University | Sung M.-H.,Kookmin University | Lim Y.T.,Chungnam National University
Biomaterials | Year: 2011

Sentinel lymph node (SLN) biopsy techniques have been widely used in the diagnosis of cancer metastasis because lymph node metastasis is one of the most important prognostic signs. Indocyanine green (ICG) has potential application as a molecular imaging probe for SLN mapping due to its fluorescent properties emitting in the near-infrared (NIR) region, where light transmission through biological tissue is maximized. However, its low photostability in an aqueous solution at the physiological temperature and its rapid diffusion behavior through SLN into the second lymph node have limited its wide use in real clinical fields. In this study, we developed a new NIR imaging contrast system consisting of ICG and poly (γ-glutamic acid) (γ-PGA) polymers for efficient sentinel lymph node mapping. By a combination of clinically used ICG and the biocompatible anionic polyelectrolyte, γ-PGA, the photostabilities of aqueous ICG solutions at room and body temperatures were drastically enhanced. When the ICG/γ-PGA complex was injected subcutaneously into the front paw of a mouse, it entered the lymphatics and migrated to the axillary sentinel lymph node (SLN) within 2 min. Furthermore, the NIR fluorescent signal intensity and retention time of ICG/γ-PGA complex in lymph node were superior to those of ICG only. In addition, a histofluorescentstudy of the SLN resected under NIR imaging revealed that ICG and γ-PGA were co-localized in the lymph node.Taken together, the experimental results on the enhanced photostability and retention time of the ICG/γ-PGA complex provide strong evidence that it has promising potential for improved sentinel lymph node mapping. © 2011 Elsevier Ltd.

Nurunnabi M.,Korea National University of Transportation | Khatun Z.,Korea National University of Transportation | Huh K.M.,Chungnam National University | Park S.Y.,Korea National University of Transportation | And 3 more authors.
ACS Nano | Year: 2013

Photoluminescent graphene quantum dots (GQDs) have fascinating optical and electronic properties with numerous promising applications in biomedical engineering. In this work, we first studied the in vivo biodistribution and the potential toxicity of carboxylated photoluminescent GQDs. KB, MDA-MB231, A549 cancer cells, and MDCK normal cell line were chosen as in vitro cell culture models to examine the possible adverse effects of the carboxylated photoluminescent GQDs. The carboxylated GQDs are desirable for increased aqueous solubility. All cancer cells efficiently took up the carboxylated GQDs. No acute toxicity or morphological changes were noted in either system at the tested exposure levels. A long-term in vivo study revealed that the GQDs mainly accumulated in liver, spleen, lung, kidney, and tumor sites after intravenous injection. To reveal any potential toxic effect of the GQDs on treated mice, serum biochemical analysis and histological evaluation were performed. The toxicity results from serum biochemistry and complete blood count study revealed that the GQDs do not cause appreciable toxicity to the treated animals. Finally, we observed no obvious organ damage or lesions for the GQDs treated mice after 21 days of administration at 5 mg/kg or 10 mg/kg dosages. With adequate studies of toxicity, both in vitro and in vivo, photoluminescent GQDs may be considered for biological application. © 2013 American Chemical Society.

Ba Linh N.T.,Soonchunhyang University | Lee K.-H.,Chungnam National University | Lee B.-T.,Soonchunhyang University
Journal of Biomedical Materials Research - Part A | Year: 2013

New biodegradable mats was successfully obtained by functional polyvinyl alcohol (PVA)/Gelatin (GE) blend fiber mats containing different BCP amounts (20, 40, and 50 w/v%) of biphasic calcium phosphate (BCP) nanoparticles for bone regeneration. BCP nanoparticles were loaded and dispersed successfully in the PVA/GE fibrous matrix. The addition of BCP was found to have increased fiber diameter, tensile strength, osteoblast cell adhesion, proliferation, and protein expression. Compared to the others, the 50% BCP-loaded electrospun PVA/GE fibers had the most favorable mechanical properties, cell attachment and growth, and protein expression. In vivo bone formation was examined using rat models, and increased bone formation was observed for the 50% BCP-loaded electrospun PVA/GE blends within 2 and 4 weeks. This result suggests that the 50% BCP-PVA/GE composite nanofiber mat has high potential for use in the field of bone regeneration and tissue engineering. Copyright © 2013 Wiley Periodicals, Inc.

Park H.S.,Kyungpook National University | Nam K.Y.,Chungnam National University | Kim J.Y.,Chungnam National University
Graefe's Archive for Clinical and Experimental Ophthalmology | Year: 2011

Background: To introduce a case of Vogt-Koyanagi-Harada (VKH) disease in which the serous retinal detachment (SRD), refractory to the systemic steroid therapy, was resolved in a short time after an intravitreal injection of bevacizumab. Methods: Interventional case report to show the effect of bevacizumab for the SRD in a VKH patient. Results: A 42-year-old woman, diagnosed with VKH disease, showed decreased visual acuities and multiple SRDs in both eyes. The best-corrected visual acuity (BCVA) was FC 30 cm in both eyes. On optical coherence tomography (OCT), multiple SRDs were confirmed. On OCT, the height of SRD in the central fovea area was 1119 μm in the right eye and 1151 μm in the left eye. After high-dose steroid treatment for 5 weeks, the SRD in the left eye was completely resolved, however, the SRD in the right eye was persisted. At the time, the height of SRD in the right eye was 884 μm and the BCVA was 0.1. For the treatment of persistent SRD causing a decreased visual acuity despite a long-term high-dose course of systemic steroid therapy, an intravitreal injection of 1.25 mg bevacizumab was performed for the right eye, following an informed consent. One week later, there was fast and complete reabsorption of multiple SRDs in the right eye. The retinal thickness in the foveal area was measured to be 189μm by OCT and the BCVA was improved to 0.7. Discussion: An intravitreal injection of bevacizumab combined with systemic steroid in VKH is expected to shorten the time for the persistent presence of SRD and to prevent the permanent visual impairment. © 2010 Springer-Verlag.

Kim J.-N.,Korea Institute of Energy Research | Ko C.H.,Chonnam National University | Yi K.B.,Chungnam National University
International Journal of Hydrogen Energy | Year: 2013

Catalytic absorbents containing CaO and Ca12Al 14O33 and metallic Ni in one body were prepared in combination of precipitation and hydration and tested for sorption enhanced hydrogen production (SEHP). Adding aluminum precursor in the precipitation step induced the formation of Ca12Al14O33 and FIB-TEM analysis revealed that Ca12Al14O33 provides spacious pathway for CO2 diffusion by forming porous structure. In thermogravimetric analysis, Ca12Al14O 33 was identified as an excellent support material providing superior cyclic stability for Ca-based sorbent. Catalytic absorbents were prepared with adding various amount of Ni precursor (3, 5, 7, and 10 wt %). The SEHP test with the catalytic absorbents showed that 7wt% of Ni loading resulted in excellent performance in terms of H2 production and CH4 conversion. Ni agglomeration was observed when 10 wt% of Ni is loaded on the catalytic absorbent. Copyright © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Byeon Y.,Chonnam National University | Lee K.,Chonnam National University | Park Y.-I.,Chungnam National University | Park S.,Chonnam National University | Back K.,Chonnam National University
Journal of Pineal Research | Year: 2013

Serotonin N-acetyltransferase (SNAT) catalyzes conversion of serotonin into N-acetylserotonin, which is a direct precursor for melatonin biosynthesis in all organisms. Molecular cloning of plant SNAT from rice led to a screening for SNAT homolog genes in other species. We identified a cyanobacterium SNAT-like gene (cSNAT) that showed 56% amino acid homology with the rice SNAT. To confirm whether cSNAT encoded SNAT enzyme activity, we expressed cSNAT DNA in Escherichia coli and purified the cSNAT protein as a C-terminal His-tagged form. The purified cSNAT protein exhibited SNAT enzyme activities, transferring the acetyl group into either serotonin or tryptamine substrates. The optimum temperature was 55°C, but it was still highly active at 70°C, suggesting that cSNAT is a thermotolerant enzyme. The Km and Vmax were 823 μm and 1.6 nmol/min/mg protein, respectively. The cSNAT gene is highly conserved in all cyanobacterial taxa and seems to be an origin of SNAT in higher plants. The thermotolerance of cSNAT suggests that melatonin plays a role in the response to high-temperature stress. Further analysis of this role of melatonin in higher plants is needed. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Kim D.-H.,Korea University of Technology and Education | Lee G.-W.,Chungnam National University | Kim Y.-C.,Korea University of Technology and Education
Solid State Communications | Year: 2012

Interaction of a zinc interstitial (Zn i) with an oxygen vacancy (V O) was investigated to understand an origin of natively n-type characteristics of ZnO using density functional theory with the hybrid functional. The V O-Zn i complex is formed with a formation of 3.82 eV and is a shallow donor with 1 charge state near the conduction band minimum. Its formation energy, however, is not low enough to be stable thermodynamically. Energy barrier for Zn i migration in the V O-Zn i complex is studied to consider its existence from kinetic aspect, and a high value of 1.3 eV is obtained with the kick-out process. Therefore, the bound Zn i to V O can exist and supply electrons for native n-type ZnO kinetically. © 2012 Elsevier Ltd. All rights reserved.

Cho Y.,Kyungpook National University | Kim Y.H.,Korea Basic Science Institute | Kim Y.H.,Green Nano Materials Research Center | Kim S.,Kyungpook National University | Kim S.,Chungnam National University
Analytical Chemistry | Year: 2011

Planar limits, defined as lines generated by connecting maximum double-bond equivalence (DBE) values at given carbon numbers, are proposed as a means of predicting and understanding the molecular structure of compounds in crude oil. The slopes and y-intercepts of the lines are determined by the DBE/carbon number ratios of functional groups defining the planar limits. For example, the planar limit generated by a serial addition of saturated cyclic rings has a slope of 0.25. The planar limit formed by the linear and nonlinear addition of benzene rings yields lines with slopes of 0.75 and 1, respectively. The y-intercepts of these lines were determined by additional functional groups added within a series of molecules. Plots of DBE versus carbon number for S1 class compounds observed by Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) showed that saturates/aromatics/resins/asphaltenes (SARA) fractions exhibited unique slopes and y-intercepts. The slope of the planar limit observed from a saturates fraction matched well with the slope of a planar limit generated by the serial addition of saturated cyclic rings. The slopes of planar limits of aromatics and resins fractions were very similar to that obtained from the linear addition of benzene rings. Finally, the slope of the asphaltenes fraction was almost identical to the slope obtained from the nonlinear addition of benzene rings. Simulated and experimental data show that SARA fractions exhibit different molecular structure characteristics. On the basis of the slope and y-intercept of the planar limit, the structures of molecules in SARA fractions were predicted and suggested. The use of planar limits for structural interpretation is not limited to crude oil compounds but can also be used to study other organic mixtures such as humic substances or metabolites. © 2011 American Chemical Society.

Choi J.-I.,Chonnam National University | Kim H.-J.,Chungnam National University
Carbohydrate Polymers | Year: 2013

Fucoidan is a marine sulfated polysaccharide with a wide variety of biological activities. Recently, it has been reported that low molecular weight fucoidan has the enhanced antioxidant and anticoagulative activities. However, degradation techniques such as enzymolysis and acid hydrolysis for obtaining low molecular weight fucoidan, have the disadvantages such as narrow substrate specificity and unfavorable hydrolysis of side groups, respectively. In this study, low molecular weight fucoidan was prepared by gamma-irradiation. When fucoidan was gamma-irradiated, the molecular weight rapidly dropped to 38 kDa when the sample was irradiated at 10 kGy, then gradually dropped to 7 kDa without the significant elimination of the sulfate groups. Low molecular weight fucoidan had higher cytotoxicity than native fucoidan in cancer cells, such as AGS, MCF-7, and HepG-2. In addition, low molecular weight fucoidan showed higher inhibitory activity of cell transformation, which resulted in higher anticarcinogenicity. This result suggests that low molecular weight fucoidan with enhanced biological activities can be produced by a simple irradiation method without changing the functional groups. © 2013 Elsevier Ltd. All rights reserved.

Han O.H.,Korea Basic Science Institute | Han O.H.,Chungnam National University | Han O.H.,Kyungpook National University
Progress in Nuclear Magnetic Resonance Spectroscopy | Year: 2013

The article focuses on NMR investigations of electrochemical reactions and dynamic properties closely related to electrochemical reactions in low temperature FCs operating in acidic conditions such as polymer electrolyte membrane FCs and direct alcohol FCs, mainly reported over the last 10 years. The first in situ NMR investigation of FCs was carried out with a homemade toroid cavity detector NMR probe dedicated for in situ NMR analyses of the electrochemical reactions on the different anode catalysts, such as carbon supported PtRu, and Pt in real direct methanol FCs. Compounds in the anode exhausts of direct ethanol FCs have been detected under operating conditions by using high performance liquid chromatography and gas chromatography, however, sequential trapping of the electrochemical reaction products was necessary to convert the products to chemicals detectable by high performance liquid chromatography and a cold trap to collect anode products was used for the gas chromatography analyses.

Uddin N.,Kyungpook National University | Choi T.H.,Chungnam National University | Choi C.H.,Kyungpook National University
Journal of Physical Chemistry B | Year: 2013

The pKa values of HF, HCOOH, CH3COOH, CH 3CH2COOH, H2CO3, HOCl, NH 4 +, CH3NH3 +, H 2O2, and CH3CH2OH in aqueous solution were predicted by QM/MM-MD in combination with umbrella samplings adopting the flexible asymmetric coordinate (FAC). This unique combination yielded remarkably accurate values with the maximum and root-mean-square errors of 0.45 and 0.22 in pKa units, respectively, without any numerical or experimental adjustments. The stability of the initially formed Coulomb pair rather than the proton transfer stage turned out to be the rate-determining step, implying that the stabilizations of the created ions require a large free energy increase. A remarkable correlation between DWR (degree of water rearrangements) and pKa was observed. As such, the large pK a of ethanol can be, in part, attributed to the large water rearrangement, strongly suggesting that proper samplings of water dynamics at dissociated regions are critical for accurate predictions of pKa. Current results exhibit a promising protocol for direct and accurate predictions of pKa. The significant variations in the gas phase deprotonation energies with level of theory appear to be mostly canceled by the similar changes in the averaged solute-solvent interactions, yielding accurate results. © 2013 American Chemical Society.

Kim J.Y.,Chungnam National University | Kim S.Y.,Kyungpook National University
Investigative Ophthalmology and Visual Science | Year: 2011

PURPOSE. To compare the prophylactic effects of intravenous moxifloxacin and vancomycin for Staphylococcus epidermidis endophthalmitis in a rabbit model. METHODS. Albino rabbits (n = 60) were divided into three groups. Intravenous moxifloxacin was injected into 20 animals (group 1), and intravenous vancomycin was injected into 20 animals (group 2). In group 3, 20 animals received 0.9% normal saline. After these prophylactic intravenous injections, the right eyes of the 60 rabbits were injected intravitreally with 105 colony-forming units of S. epidermidis. Intravenous antibiotic injection was repeated on days 1, 2, and 3 after infection. Clinical features were evaluated on days 1, 3, 5, and 7 after infection, and 10 eyes per group were then enucleated for histopathologic examination. Vitreous aspirates were obtained for bacterial culture on days 1, 3, 5, and 7 after infection from the other 10 eyes per group. RESULTS. The moxifloxacin group showed significant clinical effects at days 1, 3, 5, and 7 (P =0.019, < 0.001, < 0.001, and < 0.001, respectively); bacteriologic results at days 1, 3, 5, and 7 (P = 0.001, 0.002, 0.01, and 0.002, respectively); and histopathologic results, with less severe inflammation and relatively well-preserved retinal architecture. However, no difference was detected between the vancomycin group and control group in any aspect examined. CONCLUSIONS. Intravenously administered moxifloxacin showed a significant prophylactic effect against S. epidermidis endophthalmitis. Thus, intravenous moxifloxacin may be a useful prophylactic medication against postoperative endophthalmitis. © 2011 The Association for Research in Vision and Ophthalmology, Inc.

Park J.,Kyungpook National University | Yi K.B.,Chungnam National University
International Journal of Hydrogen Energy | Year: 2012

A novel and economical method for preparing CaO-based high-temperature CO 2 absorbents for sorption-enhanced hydrogen production is introduced. CaO-MgO absorbents prepared by the co-precipitation method show excellent cyclic stability but poor absorption capacity (∼8-14 g CO 2/100 g absorbent). An additional hydration process provided spacious CO 2 pathways resulting in a significant increase of the absorption capacity (∼17.4-47.8 g CO 2/100 g absorbent) with excellent cyclic stability. As the MgO content increased, the absorption ratio of the absorbent and the degree of CaO conversion also increased. In addition, XRD analysis revealed that the hydration process followed by calcination at 900 °C led to the formation of a partial solid solution in the CaO-MgO absorbent containing 25 wt% MgO. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Kim S.-H.,Kyungpook National University | Hwang I.-J.,Kyungpook National University | Gwon S.-Y.,Kyungpook National University | Son Y.-A.,Chungnam National University
Dyes and Pigments | Year: 2010

A thermoresponsive poly(NIPAM-co-SPO-co-fluorophore) hydrogel comprising poly(N-isopropylacrylamide) that was partially modified using an electron donor-π-conjugated-electron acceptor (D-π-A) pyran-based fluorescent dye using radical copolymerization as well as a photochromic spironaphthoxazine unit displayed a lower critical solution temperature transition from 28 to 50 °C in aqueous solution. The poly(NIPAM-co-SPO-co-fluorophore) copolymer exhibited excellent photochromic behavior in both aqueous solution and hydrogel state. The fluorescence intensity of the poly(NIPAM-co-SPO-co-fluorophore) was temperature-dependent. The relationship between fluorescence intensity change and size of the polymer aggregates was determined using dynamic light scattering. Reversible modulation of fluorescence intensity was achieved using alternating irradiation with UV and visible light. The internal microstructure of the poly(NIPAM-co-SPO-co-fluorophore) hydrogel was investigated using SEM. © 2010 Elsevier Ltd. All rights reserved.

Bioleaders Corporation, Kookmin University, Korea Research Institute of Bioscience, Biotechnology, Chungnam National University and Chungbuk National University | Date: 2012-05-02

The present invention relates to an adjuvant composition containing poly-gamma-glutamic acid-chitosan nanoparticles and a vaccine composition containing the adjuvant composition, and more particularly to an adjuvant composition containing nanoparticles prepared by ionic bonding between poly-gamma-glutamic acid having ensured safety and chitosan, and a vaccine composition containing the poly-gamma-glutamic acid-chitosan nanoparticles and an antigen. The adjuvant containing the poly-gamma-glutamic acid-chitosan nanoparticles has little or no toxicity and side effects and is added to human or animal vaccines for the prevention and treatment of viral and bacterial infections and cancers to increase the production of antibodies.

Bioleaders Corporation, Korea Research Institute of Bioscience, Biotechnology, Chungnam National University, Kookmin University and Chungbuk National University | Date: 2010-06-17

The present invention relates to a new microorganism Weissella cibaria BLS13, and more specifically, to a Kimchi-derived new microorganism Weissella cibaria BLS13 which activates an inhibitory effect on avian influenza viruses, and to uses thereof. According to the present invention, the Weissella cibaria BLS13 or a culture medium thereof contains a substance having an anti-viral function, and thus can be used advantageously in feed additives, fermentation products, foods and medicine.

Bioleaders Corporation, Chungnam National University, Korea Research Institute of Bioscience, Biotechnology and Kookmin University | Date: 2011-12-07

The present invention relates to a novel microorganism producing L-type poly-gamma-glutamic acid and an L-type poly-gamma-glutamic acid produced thereby and, more particularly, to Bacillus megaterium Toha (KCTC11752BP) isolated from salt-fermented Toha shrimps (Korean traditional fermented food) and an L-type poly-gamma-glutamic acid produced thereby. The novel microorganism Bacillus megaterium Toha (KCTC11752BP) has the ability to produce L-type poly-gamma-glutamic acid which can be used in high-value-added microbial agents, probiotic agents, immune-activating agents, animal drugs, cosmetics, moisture absorbers, thickeners, biodegradable plastics, etc.

Bioleaders Corporation, Korea Research Institute of Bioscience, Biotechnology, Chungnam National University and Kookmin University | Date: 2011-11-10

The present invention provides a medical adhesive composition containing poly-gamma-glutamic acid or its salt; and sugar or sugar alcohol, which is edible, water-soluble, anionic and biodegradable. The invention also provides a thickener composition containing poly-gamma-glutamic acid, which can be used as a moisture-absorbing agent, a moisturizing agent and a raw material for cosmetic products.

Bioleaders Corporation, Kookmin University and Chungnam National University | Date: 2011-11-18

The present invention relates to an optical imaging probe for detecting a sentinel lymph node, which contains a complex of poly-gamma-glutamic acid and an optical imaging dye, and more particularly to an optical imaging probe for detecting a sentinel lymph node, which contains a poly-gamma-glutamic acid/optical imaging dye complex that, when injected subcutaneously in vivo, remains in the sentinel lymph node for a relatively long period of time and has a low tendency to migrate to other lymph nodes. The present invention provides a poly-gamma-glutamic acid/fluorescent dye complex, which contains no radiopharmaceutical and is harmless to the human body. The use of the poly-gamma-glutamic acid/fluorescent dye complex makes it possible to accurately detect the position of a sentinel lymph node in real time without concerns about radioactive contamination.

Li L.,Chungnam National University | Nurunnabi M.,Korea National University of Transportation | Nafiujjaman M.,Korea National University of Transportation | Jeong Y.Y.,Chonnam National University | And 2 more authors.
Journal of Materials Chemistry B | Year: 2014

A multifunctional nanomedicine combining magnetic resonance imaging (MRI) and photodynamic therapy (PDT) functionalities is a promising integrated platform that allows for targeted drug delivery, noninvasive monitoring of therapeutic responses, and simultaneous cancer diagnosis and treatment. A hybrid nanoparticle (NP) system with a core/shell-structured magnetic iron oxide/gold (Fe3O4/Au) NP and a photosensitizer (PS)-conjugated heparin surface layer is investigated as a novel multifunctional carrier in PDT. A thiolated heparin-pheophorbide a (PhA) conjugate (H-PhA), which is a macromolecular PS, is synthesized and introduced onto the NP surface through a gold-thiol interaction. The photoactivity of the PhA moieties on the NP surface is significantly suppressed by the quenching effect of the Fe3O 4/Au NP. However, their photoactivity can be restored in a glutathione (GSH)-rich intracellular environment, which allows GSH-mediated switchable photoactivity in the hybrid NP system. As a result, marked phototoxicity and strong fluorescence signals are observed in NP-treated A549 cells under light irradiation. In an animal tumor model, Fe3O 4/Au/H-PhA NPs are efficacious in photodynamic cancer treatment and exhibit prolonged circulation characteristics, enhanced tumor specificity, and higher therapeutic efficacy compared with free PhA. In addition, in vitro MRI studies reveal that the NPs could potentially serve as MRI contrast agents in cancer diagnosis and may be used to monitor the photodynamic treatment response used to accurately guide light irradiation. The present findings show that the Fe3O4/Au/H-PhA NP is a promising nanomedicine platform in PDT and cancer diagnosis. © 2014 the Partner Organisations.

Jung C.-R.,Korea Research Institute of Bioscience and Biotechnology | Lim J.H.,Korea Research Institute of Bioscience and Biotechnology | Choi Y.,Korea Research Institute of Bioscience and Biotechnology | Kim D.-G.,Chonbuk National University | And 3 more authors.
Journal of Clinical Investigation | Year: 2010

The human E3 ubiquitin ligase murine double minute 2 (MDM2) targets the tumor suppressor p53 for ubiquitination and degradation but also promotes its own ubiquitination and subsequent degradation. As the balance between MDM2 and p53 levels plays a crucial role in regulating cell proliferation and apoptosis, we sought to identify factors selectively inhibiting MDM2 self-ubiquitination. Here we have shown that the LIM domain protein Enigma directly interacts with MDM2 to form a ternary complex with p53 in vitro and in human hepatoma and colon carcinoma cell lines and mouse embryonic fibroblasts. We found that Enigma elicited p53 degradation by inhibiting MDM2 self-ubiquitination and increasing its ubiquitin ligase activity toward p53 in cells. Moreover, mitogenic stimuli such as serum, FGF, and HGF increased Enigma transcription via induction of serum response factor (SRF), leading to MDM2 stabilization and subsequent p53 degradation. We observed similar results in the livers of mice treated with HGF. In humans, we found SRF and Enigma coexpressed with MDM2 but not p53 in several liver and stomach tumors. Finally, we showed that Enigma promoted cell survival and chemoresistance by suppressing p53-mediated apoptosis in both cell lines and a mouse xenograft model. Our findings suggest a role for Enigma in tumorigenesis and uncover a mechanism whereby mitogens attenuate p53 antiproliferative activity through an SRF/Enigma/MDM2 pathway.

Lee B.Y.,Chonnam National University | Kim Y.Y.,Chungnam National University | Yi S.-T.,Inha Technical College | Kim J.-K.,Korea Advanced Institute of Science and Technology
Structure and Infrastructure Engineering | Year: 2013

In the present work, an image processing technique that automatically detects and analyses cracks in the digital image of concrete surfaces is proposed. The image processing technique automates the measurement of crack characteristics including the width, length, orientation and crack pattern. In the proposed technique, a morphological technique was applied to correct the non-uniform brightness of the background, and enhanced binarisation and shape analysis were used to improve the detection performance; furthermore, detailed algorithms to calculate the crack width, length, orientation and an artificial neural network to recognise crack patterns including horizontal, vertical, diagonal (-45°), diagonal (+45°), and random cracks are proposed. An image processing program was developed for the proposed algorithm and a series of experimental and analytical investigations were performed to assess the validity of the algorithm. Then, the crack characteristics measured using the proposed technique were compared with those obtained using a conventional technique. The test results showed that the crack characteristics can be accurately measured and analysed using the proposed technique. © 2013 Copyright Taylor and Francis Group, LLC.

Noh Y.-W.,Chungnam National University | Kong S.-H.,Seoul National University | Choi D.-Y.,Kookmin University | Park H.S.,Chungnam National University | And 6 more authors.
ACS Nano | Year: 2012

Sentinel lymph node (SLN) mapping has been widely used to predict the metastatic spread of primary tumor to regional lymph nodes in clinical practice. In this research, a new near-infrared (NIR)-emitting polymer nanogel (NIR-PNG) having a hydrodynamic diameter of about 30 nm, which is optimal for lymph node uptake, was developed. The NIR-emitting polymer nanoprobes were designed and synthesized by conjugating IRDye800 organic dye to biodegradable pullulan-cholesterol polymer nanogels. The NIR-PNG nanoprobes were found to be photostable compared with the IRDye800-free dye at room temperature. Upon intradermal injection of the NIR-PNG into the front paw of a mouse, the nanoprobes entered the lymphatic system and migrated to the axillary lymph node within 2 min. The NIR fluorescence signal intensity and retention time of NIR-PNG in the lymph node were superior to the corresponding properties of the IRDye800-free dye. A immunohistofluorescence study of the SLN resected under NIR imaging revealed that the NIR-PNG nanoprobes were predominantly co-localized with macrophages and dendritic cells. Intradermal injection of NIR-PNG nanoprobes into the thigh of a pig permitted real-time imaging of the lymphatic flow toward the SLN. The position of the SLN was identified within 1 min with the help of the NIR fluorescence images. Taken together, the experimental results demonstrating the enhanced photostability and retention time of the NIR-PNG provide strong evidence for the potential utility of these polymer probes in cancer surgery such as SLN mapping. © 2012 American Chemical Society.

Hyundai Mobis and Chungnam National University | Date: 2015-01-15

Provided is an apparatus for determining an available driving space, including a laser distance sensor installed in a vehicle and configured to sense a region in front of the vehicle by a predetermined distance to generate distance information, a signal processing unit configured to generate plane distance information by using the distance information generated by the laser distance sensor, a curb searching unit configured to determine correlation and similarity between the generated plane distance information and previous plane distance information to search for a curb, and a determining unit configured to determine whether the region in front of the vehicle by the predetermined distance is an available driving space depending on whether a route of a curb searched by the curb searching unit is included in a driving region.

Chonnam National University and Chungnam National University | Date: 2010-12-10

There is provided a communication middleware apparatus for a host device, including: a profile manager configured to receive specification information of a guest device through a Low-rate Wireless Personal Area Network (LR-WPAN) module; an application program manager configured to search for an application program for a host device that has to be newly installed or updated, based on the specification information of the guest device, and to install or update the found application program for the host device in the host device; and a firmware manager configured to search for firmware for the guest device that has to be updated based on the specification information of the guest device, and to transmit the found firmware for the guest device to the guest device through the LR-WPAN module.

Bioleaders Corporation, Kookmin University, Chungbuk National University, Chungnam National University, Korea Research Institute of Bioscience and Biotechnology | Date: 2010-06-25

The present invention relates to an adjuvant composition containing poly-gamma-glutamic acid-chitosan nanoparticles and a vaccine composition containing the adjuvant composition, and more particularly to an adjuvant composition containing nanoparticles prepared by ionic bonding between poly-gamma-glutamic acid having ensured safety and chitosan, and a vaccine composition containing the poly-gamma-glutamic acid-chitosan nanoparticles and an antigen. The adjuvant containing the poly-gamma-glutamic acid-chitosan nanoparticles has little or no toxicity and side effects and is added to human or animal vaccines for the prevention and treatment of viral and bacterial infections and cancers to increase the production of antibodies.

Bioleaders Corporation, Chungnam National University, Korea Research Institute of Bioscience, Biotechnology and Kookmin University | Date: 2013-06-04

The present invention relates to nanomicelles composed of a complex of a lipophilic compound and a poly-gamma-glutamic acid wherein a portion of carboxyl groups are substituted with an amine group, and more particularly, to nanomicelles composed of a complex of a lipophilic compound and a poly-gamma-glutamic acid wherein a portion of carboxyl groups are substituted with an amine group, a preparation method thereof, and a drug delivery system employing the mucous membrane-adhesive property of the nanomicelles. According to the present invention, the nanomicelle drug delivery system based on poly-gamma-glutamic acid that is a natural biopolymer can be used for the delivery of a drug to mucous membranes to thereby increase the in vivo stability and effectiveness of the drug.

Lee S.,KAIST | Kong S.,KAIST | Kim C.-Y.,Chungnam National University | Hong S.,KAIST
Digest of Papers - IEEE Radio Frequency Integrated Circuits Symposium | Year: 2012

This paper presents a low power UWB radar transceiver IC, which is used to make a radar system with precise range accuracy. The range accuracy is allowed by a variable delay circuit which can control the delay by 5 ps resolution. The detecting range of the transceiver is from 0.15 m to 8.4 m. The measurement results show that the maximum error is 3.75 mm. The circuit is implemented in a 0.13 μm CMOS process with the die area of 1.28 × 1.07 mm 2. The total power consumption of the core circuit is 6.89 mA with the supply voltage of 1.5 V. © 2012 IEEE.

Beak I.-H.,Chungnam National University | Kim M.-S.,Inje University
Chemical and Pharmaceutical Bulletin | Year: 2012

In this study, amorphous solid dispersions containing dutasteride and various excipients, manufactured by spray-drying processes, were characterized to determine the effects on their ability to form supersaturated solutions and to identify the effects of supersaturation on increasing the bioavailability of dutasteride. The excipients included Eudragit E, hydroxypropyl-β- cyclodextrin (HP-β-CD), hydroxypropyl cellulose (HPC), hydroxypropylmethyl cellulose (HPMC), and polyvinylpyrrolidone (PVP K30). A solid dispersion with Eudragit E displayed a high maximum supersaturation with extended supersaturation, compared with a water-soluble polymer. The maximum concentration and the degree of supersaturation increased in the following order: PVP K30

Bartolome L.,KAIST | Imran M.,King Saud University | Lee K.G.,University of Michigan | Sangalang A.,KAIST | And 2 more authors.
Green Chemistry | Year: 2014

There have been numerous studies to develop catalysts for the chemical recycling of poly(ethylene terephthalate) (PET) via glycolysis. However, in the field of PET glycolysis, only a few have attempted to recover and reuse the catalysts. This research utilized easily recoverable superparamagnetic γ-Fe2O3 nanoparticles as a reusable catalyst for PET glycolysis. γ-Fe2O3 nanoparticles were produced by calcining Fe3O4 nanoparticles prepared by the co-precipitation method. The produced γ-Fe2O3 nanoparticles had an average size of 10.5 ± 1.4 nm, and a very high surface area reaching 147 m2 g-1. Its superparamagnetic property was also confirmed. Glycolysis reactions were carried out, and the γ-Fe2O3 catalysts were recovered after the reactions by simple magnetic decantation. The use of magnetic iron oxide allowed the easy recovery of the catalyst from the glycolysis products. At 300 °C and a 0.05 catalyst/PET weight ratio, the maximum bis(2-hydroxyethlyl) terephthalate (BHET) monomer yield reached more than 90% in 60 min. At 255 °C and a 0.10 catalyst/PET weight ratio, the BHET yield reached more than 80% in 80 min. The catalyst was reused 10 times, giving almost the same BHET yield each time. © 2014 The Royal Society of Chemistry.

Qu B.,Chungnam National University | Eu Y.-J.,Chungnam National University | Jeong W.-J.,Korea Research Institute of Bioscience and Biotechnology | Kim D.-P.,Pohang University of Science and Technology
Lab on a Chip - Miniaturisation for Chemistry and Biology | Year: 2012

An efficient cell transformation method is presented that utilizes droplet electroporation on a microfluidic chip. Two types of green microalgae, a wall-less mutant and a wild type of Chlamydomonas reinhardtii, are used as model cells. The PDMS-glass electroporation chip is simply composed of a flow-focusing microstructure for generating cell-encapsulating droplets and a serpentine channel for better mixing of the content in the droplet, and five pairs of parallel microelectrodes on the glass slide, without involving any expensive electrical equipment. The transformation efficiency via the microfluidic electroporation is shown to be more than three orders of magnitude higher for the wall-less mutant, and more than two orders of magnitude higher for the wild type, which has its cell wall intact, than bulk phase electroporation under identical conditions. Furthermore, the microfluidic transformation is remarkably efficient even at a low DNA/cell ratio, facilitating ways of controlling the transgenic copy number, which is important for the stability of the transgene expression. © 2012 The Royal Society of Chemistry.

Kim W.,Pohang University of Science and Technology | Chun Ryu J.,Chungnam National University | Kweon Suh Y.,Dong - A University | Hyoung Kang K.,Pohang University of Science and Technology
Applied Physics Letters | Year: 2011

We present a method of pumping dielectric (or non-polar) liquids. The pumping method relies on the electrohydrodynamic flow generated by field dependent electrical conductivity (Onsager effect). Adding a small amount of polar liquid increases the field-dependency of conductivity. Applying either dc or ac voltage produces a fast and regular flow around electrodes. Flow speed is proportional to cube of electric-field strength and inversely to applied frequency. The experimental results agreed well with numerical analysis based on our theoretical model. © 2011 American Institute of Physics.

Bang S.R.,Inje University | Kim Y.H.,Chungnam National University | Kim G.S.,Sungkyunkwan University
Clinical Transplantation | Year: 2011

Introduction: The aim of this study was to determine the effects of in vitro hemodilution with 6% HES (130/0.4) solution on thrombelastograph® (TEG) parameters in whole blood samples from patients with end-stage liver disease (ESLD). Methods: Enrollment consisted of 95 patients with ESLD undergoing liver transplantation. Blood was diluted by 11%, 22%, and 33% with 6% HES (130/0.4) solution. Normal saline was used as a control diluent. Results: When blood was diluted by 33% with normal saline, only the reaction time (r) was increased (p<0.0001) compared to the baseline value. When blood was diluted with 6% HES (130/0.4), 11% dilution decreased maximum amplitude (MA) (p=0.003) compared to baseline. At 33% dilution, the r (p<0.0001, vs. baseline) and K (p<0.0001, vs. baseline; p<0.0001, vs. normal saline) increased, and the MA, alpha angle, and coagulation index (p<0.0001, vs. baseline; p<0.0001, vs. normal saline) decreased. Conclusion: Hemodilution with 6% HES (130/0.4) solution results in TEG abnormalities even with 11% hemodilution, in whole blood samples of patients with ESLD undergoing liver transplantation. © 2010 John Wiley & Sons A/S.

Han J.,Korea Advanced Institute of Science and Technology | Koh Y.J.,Korea Advanced Institute of Science and Technology | Moon H.R.,Korea Advanced Institute of Science and Technology | Ryoo H.G.,Korea Advanced Institute of Science and Technology | And 5 more authors.
Blood | Year: 2010

The stromal vascular fraction (SVF) in adipose tissue contains a pool of various stem and progenitor cells, but the existence of hematopoietic stem and progenitor cells (HSPCs) in the SVF has not been seriously considered. We detected the presence of HSPCs in the SVF by phenotypically probing with Lin-Sca-1+c-kit+ (LSK) and functionally confirming the presence using colony-forming cell assay and assessing the long-term multilineage reconstitution ability after SVF transplantation. The LSK population in the SVF was 0.004% plus or minus 0.001%, and 5 × 10 5 freshly isolated SVF cells gave rise to 13 plus or minus 4 multilineage colonies. In addition, 0.15% plus or minus 0.03% of SVF cells was home to bone marrow (BM), especially near vascular and endosteal regions, 24 hours after blood transplantation. SVF transplantation was capable of generating a long-term (> 16 weeks), but variable extent (2.1%-32.1%) multilineage reconstitution in primary recipients, which was subsequently transferred to the secondary recipients by BM transplantation. All HSPCs within the SVF originated from the BM. Furthermore, the granulocyte-colony-stimulating factor (G-CSF) mobilization of HSPCs from BM markedly elevated the number of phenotypic and functional HSPCs in the SVF, which induced a high efficiency long-term reconstitution in multilineage hematopoiesis in vivo. Our results provide compelling evidence that adipose tissue is a novel extramedullary tissue possessing phenotypic and functional HSPCs. © 2010 by The American Society of Hematology.

Choi H.,Ulsan National Institute of Science and Technology | Ko S.-J.,Ulsan National Institute of Science and Technology | Choi Y.,Ulsan National Institute of Science and Technology | Joo P.,Ulsan National Institute of Science and Technology | And 10 more authors.
Nature Photonics | Year: 2013

The coupling of surface plasmons and excitons in organic materials can improve the performance of organic optoelectronic devices. Here, we prepare carbon-dot-supported silver nanoparticles (CD-Ag nanoparticles) using the carbon dots both as a reducing agent and a template to fabricate solution-processable polymer light-emitting diodes and polymer solar cells. The surface plasmon resonance effect of CD-Ag nanoparticles allows significant radiative emission and additional light absorption, leading to remarkably enhanced current efficiency of 27.16 cd A -1 and a luminous efficiency of 18.54 lm W -1 in polymer light-emitting diodes as well as a power conversion efficiency of 8.31% and an internal quantum efficiency of 99% in polymer solar cells compared with control devices (current efficiency = 11.65 cd A -1 and luminous efficiency = 6.33 lm W -1 in polymer light-emitting diodes; power conversion efficiency = 7.53% and internal quantum efficiency = 91% in polymer solar cells). These results demonstrate that CD-Ag nanoparticles constitute a versatile and effective route for achieving high-performance polymer optoelectronic devices. © 2013 Macmillan Publishers Limited. All rights reserved.

Heo M.,Ulsan National Institute of Science and Technology | Cho H.,Ulsan National Institute of Science and Technology | Jung J.-W.,Chungnam National University | Jeong J.-R.,Chungnam National University | And 2 more authors.
Advanced Materials | Year: 2011

The surface plasmon effect on polymer solar cells and polymer light-emitting diodes is demonstrated by using metal nanoparticles prepared from block copolymer templates. Light absorption of the polymer thin layer is increased with the incorporation of metallic nanostructures, resulting in a significant surface plasmon effect in the optoelectronic devices. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Kim B.J.,Pohang University of Science and Technology | Choi Y.S.,Chungnam National University | Cha H.J.,Pohang University of Science and Technology
Angewandte Chemie - International Edition | Year: 2012

Sticky stuff: The novel composite nanofibrous scaffolds based on mussel adhesive proteins (MAPs) provide a mechanically durable structural backbone with the function of bioactive peptides. It can also be easily coated with a variety of biomolecules. This biofunctionalized nanofiber platform could be a promising tool for successful tissue-engineering applications. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Jeong H.-H.,Chungnam National University | Jin S.H.,Chungnam National University | Lee B.J.,Chungnam National University | Kim T.,Ulsan National Institute of Science and Technology | Lee C.-S.,Chungnam National University
Lab on a Chip - Miniaturisation for Chemistry and Biology | Year: 2015

Quorum sensing (QS) is a type of cell-cell communication using signal molecules that are released and detected by cells, which respond to changes in their population density. A few studies explain that QS may operate in a density-dependent manner; however, due to experimental challenges, this fundamental hypothesis has never been investigated. Here, we present a microfluidic static droplet array (SDA) that combines a droplet generator with hydrodynamic traps to independently generate a bacterial population gradient into a parallel series of droplets under complete chemical and physical isolation. The SDA independently manipulates both a chemical concentration gradient and a bacterial population density. In addition, the bacterial population gradient in the SDA can be tuned by a simple change in the number of sample plug loading. Finally, the method allows the direct analysis of complicated biological events in an addressable droplet to enable the characterization of bacterial communication in response to the ratio of two microbial populations, including two genetically engineered QS circuits, such as the signal sender for acyl-homoserine lactone (AHL) production and the signal receiver bacteria for green fluorescent protein (GFP) expression induced by AHL. For the first time, we found that the population ratio of the signal sender and receiver indicates a significant and potentially interesting partnership between microbial communities. Therefore, we envision that this simple SDA could be a useful platform in various research fields, including analytical chemistry, combinatorial chemistry, synthetic biology, microbiology, and molecular biology. © The Royal Society of Chemistry 2015.

Jee G.,Korea Polar Research Institute | Lee H.-B.,Korea Polar Research Institute | Lee H.-B.,Chungnam National University | Solomon S.C.,High Altitude Observatory
Journal of Geophysical Research: Space Physics | Year: 2014

The last solar minimum period was anomalously extended and low in EUV irradiance compared with previous solar minima. It can readily be expected that the thermosphere and the ionosphere must be correspondingly affected by this low solar activity. While there have been unanimous reports on the thermospheric changes, being cooler and lower in its density as expected, the ionospheric responses to low solar activity in previous studies were not consistent with each other, probably due to the limited ionospheric observations used for them. In this study, we utilized the measurements of total electron content (TEC) from TOPEX and JASON-1 satellites during the periods of 1992 to 2010, which includes both the last two solar minimum periods, in order to investigate how the ionosphere responded to the extremely low solar activity during the last solar minimum compared with previous solar minimum. Although the global daily mean TECs show negligible differences between the two solar minimum periods, the global TEC maps reveal that there are significant systematic differences ranging from about -30% to +50% depending on local time, latitude, and season. The systematic variations of the ionospheric responses seem to mainly result from the relative effects of reduced solar EUV production and reduced recombination rate due to thermospheric changes during the last solar minimum period. Key Points The comparison between the global ionospheric TECs during the last two solar minima was performed The daily mean TECs show negligible differences between the two solar minima The global TEC maps show large differences with systematic variations ©2014. American Geophysical Union. All Rights Reserved.

Son D.W.,Korea Forestry Research Institute | Kang S.-G.,Chungnam National University
Journal of the Korean Wood Science and Technology | Year: 2014

The purpose of this study is to analyze fundamental combustion characteristics of woods used for indoor applications. The combustion characteristics such as heat release rate, total heat release, gas yield, and mass loss were analyzed by the method of cone calorimeter or thermogravimetry. These analysis results show that material properties of wood are closely related to flammability. It was shown that the relationship between the mass loss and gas emission. The results of combustion properties of woods would be useful for fundamentals of guiding the safe use of wood indoor application.

Yim S.,Chungnam National University | Park Y.,KAIST
Vehicle System Dynamics | Year: 2011

This paper presents a method to design a rollover prevention controller for vehicle systems. The vehicle rollover can be prevented by a controller that minimises the lateral acceleration and the roll angle. Rollover prevention capability can be enhanced if the controlled vehicle system is robust to the variation of the height of the centre of gravity and the speed of the vehicle. For this purpose, a robust controller is designed with linear matrix inequality-based trajectory sensitivity minimisation. Differential braking and active suspension are adopted as actuators that generate yaw and roll moments, respectively. The newly proposed method is shown to be effective in preventing rollover by the simulation on a non-linear multibody dynamic simulation software, CarSim®. © 2011 Taylor & Francis.

Hwang H.,Ulsan National Institute of Science and Technology | Kim Y.,Ulsan National Institute of Science and Technology | Cho J.,Chungnam National University | Lee J.-Y.,Chungnam National University | And 2 more authors.
Analytical Chemistry | Year: 2013

In this study, we describe a novel platform based on centrifugal microfluidics for simultaneous determination of nitrite, nitrate and nitrite, ammonium, orthophosphate, and silicate in water samples. All processes from sample metering to detection were integrated and automatically conducted on a rotating disc-shaped device. Fluid transfer was controlled by laser irradiation on the ferrowax-based microvalves. Liquid samples and reagents were pumped by centrifugal force in the rotating disc, and their positions and movements were controlled through a programmable light from a laser diode. This novel water analysis platform required only 500 μL of sample (100 μL for each nutrient) and 10-30 μL of reagents for colorimetric detection. In addition, the fully automated parallel processes and efficient mixing in the rotating disc allowed for a significant reduction in total analysis time (∼7 min 40 s) and increased accuracy. Validation with a seawater certified reference material indicated that the platform accurately measured nutrient concentrations in water samples. In addition, we showed that the nutrients in the seawater collected from Chunsu Bay in Korea measured by the proposed lab-on-a-disc and by a commercialized autoanalyzer are comparable. © 2013 American Chemical Society.

So H.-S.,Chungnam National University | Rao B.A.,Chungnam National University | Hwang J.,Chungnam National University | Yesudas K.,Gandhi Institute of Technology and Management | Son Y.-A.,Chungnam National University
Sensors and Actuators, B: Chemical | Year: 2014

We report the design and synthesis of a novel squaraine-bis(rhodamine-6G) (SR)-based indicator for selective detection of Hg2+ ion. Sensing behavior toward various metal ions (M = Li+, Na+, Mg 2+, K+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Ag+, Cs+, Hg 2+, and Pb2+) was investigated by UV-vis and fluorescence spectroscopy in acetonitrile solution. The indicator exhibited highly selective and sensitive colorimetric and "turn-on" fluorescent responses compared with the other investigated metal ions because of the soft-acid nature and large size of mercuric ion. The obvious change from colorless to pink upon the addition of Hg2+ could make it a suitable "naked eye" indicator for Hg2+. Finally, we proposed a reversible ring-opening mechanism (OFF-ON) of the rhodamine spirolactam induced by Hg2+ binding and forming a 1:1 stoichiometric complex of SR-Hg2+ which is supported by the density functional theory calculations. More significantly, the sensor displayed a remarkable blue-to-green fluorescence switch in the presence of Hg2+ ions. © 2014 Elsevier B.V.

Kim I.G.,Pohang University of Science and Technology | Jo B.H.,Pohang University of Science and Technology | Kang D.G.,Pohang University of Science and Technology | Kim C.S.,Pohang University of Science and Technology | And 2 more authors.
Chemosphere | Year: 2012

Recently, as a mimic of the natural biomineralization process, the use of carbonic anhydrase (CA), which is an enzyme catalyzing fast reversible hydration of carbon dioxide to bicarbonate, has been suggested for biological conversion of CO 2 to valuable chemicals. While purified bovine CA (BCA) has been used in previous studies, its practical utilization in CO 2 conversion has been limited due to the expense of BCA preparation. In the present work, we investigated conversion of CO 2 into calcium carbonate as a target carbonate mineral by using a more economical, recombinant CA. To our knowledge, this is the first report of the usage of recombinant CA for biological CO 2 conversion. Recombinant α-type CA originating in Neisseria gonorrhoeae (NCA) was highly expressed as a soluble form in Escherichia coli. We found that purified recombinant NCA which showed comparable CO 2 hydration activity to commercial BCA significantly promoted formation of solid CaCO 3 through the acceleration of CO 2 hydration rate, which is naturally slow. In addition, the rate of calcite crystal formation was also accelerated using recombinant NCA. Moreover, non-purified crude recombinant NCA also showed relatively significant ability. Therefore, recombinant CA could be an effective, economical biocatalyst in practical CO 2 conversion system. © 2012 Elsevier Ltd.

Cho W.S.,Korea Basic Science Institute | Kim D.,University of Florida | Kong K.,University of Kansas | Lim S.H.,Korea Basic Science Institute | And 4 more authors.
Physical Review Letters | Year: 2016

We discuss nonstandard interpretations of the 750 GeV diphoton excess recently reported by the ATLAS and CMS Collaborations which do not involve a new, relatively broad resonance with a mass near 750 GeV. Instead, we consider the sequential cascade decay of a much heavier, possibly quite narrow, resonance into two photons along with one or more additional particles. The resulting diphoton invariant mass signal is generically rather broad, as suggested by the data. We examine three specific event topologies - the "antler," the "sandwich," and the two-step cascade decay - and show that they all can provide a good fit to the observed published data. In each case, we delineate the preferred mass parameter space selected by the best fit. In spite of the presence of extra particles in the final state, the measured diphoton pT spectrum is moderate due to its anticorrelation with the diphoton invariant mass. We comment on the future prospects of discriminating with higher statistics between our scenarios, as well as from more conventional interpretations. © 2016 American Physical Society.

Bae J.S.,Inje University | Kim O.K.,Inje University | Kim J.M.,Chungnam National University
Diabetes Research and Clinical Practice | Year: 2011

We sought to investigate the peripheral nerve excitability property of early diabetic neuropathy (DN) and provide a logical hypothesis regarding the pathophysiology of subclinical/early stage of DN. The automated nerve excitability test (NET) utilizing the threshold tracking technique (TTT) was performed to measure multiple excitability indices in 30 early DN and 30 normal subjects. Early DN was defined as N0 or N1 stage of Dyck's staging method. The protocols calculated strength-duration time constant (SDTC) from duration-charge curve, parameters of threshold electrotonus (TE) and current-threshold relationship (CTR) from sequential sub-threshold current, and recovery cycle (RC) from double supra-threshold stimulation. Each parameter of test was co-analyzed with clinical and laboratory data including age, sex, BMI, HgbA1c, lipid profile, and estimated glomerular filtration rate (eGFR). Compared to normal or N0 groups, N1 group had 'fanning-in' phenomenon in TE, increased refractory period, and decreased supernormality/subnormality. Linear regression showed that parameters associated with vascular factor were significantly related with STDC: absolute TG values were positively associated with STDC, whereas eGFR values were inversely related with STDC. Nerve excitability can be altered even in the early mild DN. The pattern of alteration suggests depolarizing nerve or nerve ischemia in pathophysiology of subclinical/early DN. © 2010 Elsevier Ireland Ltd.

Choi H.,Ulsan National Institute of Science and Technology | Lee J.-P.,Ulsan National Institute of Science and Technology | Ko S.-J.,Ulsan National Institute of Science and Technology | Jung J.-W.,Chungnam National University | And 6 more authors.
Nano Letters | Year: 2013

We demonstrate high-performance polymer solar cells using the plasmonic effect of multipositional silica-coated silver nanoparticles. The location of the nanoparticles is critical for increasing light absorption and scattering via enhanced electric field distribution. The device incorporating nanoparticles between the hole transport layer and the active layer achieves a power conversion efficiency of 8.92% with an external quantum efficiency of 81.5%. These device efficiencies are the highest values reported to date for plasmonic polymer solar cells using metal nanoparticles. © 2013 American Chemical Society.

Kim K.N.,Chungnam National University | Jeoung J.W.,Seoul National University | Park K.H.,Seoul National University | Kim D.M.,Seoul National University | And 2 more authors.
American Journal of Ophthalmology | Year: 2014

Purpose To investigate the relationship between preferred sleeping position and asymmetric visual field (VF) loss in open-angle glaucoma (OAG) patients. Design Retrospective, cross-sectional study. Methods Six hundred and ninety-two (692) patients with bilateral normal-tension glaucoma (NTG) or high-tension glaucoma were consecutively enrolled. A questionnaire to determine the preferred sleeping position was administered to each patient. Asymmetric VF loss was defined as a difference in mean deviation between the 2 eyes of at least 2 dB. According to these values, the better eye and worse eye were defined. Among the patients with asymmetric VF loss, the numbers preferring the worse eye-dependent lateral decubitus position and the better eye-dependent lateral decubitus position were compared. Results Among the enrolled patients, 309 (60.6%) with NTG and 121 (66.5%) with high-tension glaucoma had asymmetric VF between the 2 eyes. Among the 309 NTG patients, 100 (32.4%) preferred the lateral decubitus position. Of these, 66 (66.0%) preferred the worse eye-dependent lateral decubitus position (P =.001). Among the 121 high-tension glaucoma patients, 32 (26.4%) preferred the lateral decubitus position, and of these, 23 (71.9%) preferred the worse eye-dependent lateral decubitus position (P =.013). Conclusion Our results suggest that the sleep position habitually preferred by glaucoma patients may be associated with greater VF loss.

Choi W.-C.,North Carolina A&T State University | Yun H.-D.,Chungnam National University | Cho C.-G.,Chosun University | Feo L.,University of Salerno
Composite Structures | Year: 2014

High performance fiber-reinforced cement composite (HPFRCC) exhibits several desirable characteristics, such as strain-hardening, multiple fine cracks, energy dissipation and crack damage tolerance. These attractive properties have allowed the industry and researchers to apply HPFRCC mixtures successfully to various concrete structures. This paper presents the results of HPFRCC research efforts that range from the study of fundamental properties to practical applications for reinforced concrete structures in South Korea. The findings of this study indicate that HPRFCC can be used to retrofit reinforced concrete structures and to enhance their strength, ductility and seismic performance. © 2013 Elsevier Ltd.

Cho C.-G.,Chosun University | Kim Y.-Y.,Chungnam National University | Feo L.,University of Salerno | Hui D.,University of New Orleans
Composite Structures | Year: 2012

The brittleness of concrete raises several concerns due to the lack of strength and ductility in the plastic hinge region of reinforced concrete columns. In this study, in order to improve the seismic strength and performance of reinforced concrete columns, a new method of seismic strengthened reinforced concrete composite columns was attempted by applying High Performance Fiber Reinforced Cementitious composites (HPFRCs) instead of concrete locally in the plastic hinge region of the column. HPFRC has high-ductile tensile strains about 2-5% with sustaining the tensile stress after cracking and develops multiple micro-cracking behaviors. A series of column tests under cyclic lateral load combined with a constant axial load was carried out. Three specimens of reinforced concrete composite cantilever columns by applying the HPFRC instead of concrete locally in the column plastic hinge zone and one of a conventional reinforced concrete column were designed and manufactured. From the experiments, it was known that the developed HPFRC applied reinforced concrete columns not only improved cyclic lateral load and deformation capacities but also minimized bending and shear cracks in the flexural critical region of the reinforced concrete columns. © 2012.

Kwon Y.H.,LG Chemical Ltd. | Woo S.-W.,LG Chemical Ltd. | Jung H.-R.,LG Chemical Ltd. | Yu H.K.,LG Chemical Ltd. | And 8 more authors.
Advanced Materials | Year: 2012

The mechanical flexibility of a cable-type battery reaches levels far beyond what is possible with conventional designs. The hollow-spiral (helical) multi-helix anode architecture is critical to the robustness under mechanical stress and facilitates electrolyte wetting of the battery components. This design enables the battery to reliably power an LED screen or an MP3 player even under severe mechanical twisting and bending. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Yoon S.M.,Pohang University of Science and Technology | Lee J.,Chungnam National University | Je J.H.,Pohang University of Science and Technology | Choi H.C.,Pohang University of Science and Technology | Yoon M.,Chungnam National University
ACS Nano | Year: 2011

Lasing action by planar-, fiber-, or ring-type waveguide has been extensively investigated with different types of microcavities such as thin films, wires, cylindrical tubes, or ribbons. However, the lasing action by sharp bending waveguide, which promises efficient interconnection of amplified light in the photonic circuits, remains unexplored. Here, we report the first observation of microcavity effects in the organic rectangular microtubes (RMTs) with sharp bends (ca. 90°) and subwavelength nanoscale wall thicknesses, based on single crystalline and themostable tetra(4-pyridyl)porphyrin (H 2TPyP)-RMTs synthesized by the VCR process. A bright tip emission is observed from the sharp bending edges of a single RMT upon laser excitation, demonstrating a clear waveguiding behavior in RMT. The appearance of a peak from the (0-1) band at a threshold tube length and the gradual decrease of its full width at half-maximum (fwhm) suggest that amplification of spontaneous emission (ASE) is developed by stimulated emission along the walls of the RMTs. The ehancement of the ASE peak together with the narrowing of its fhwm over a threshold pump power and the tube size (width and length) dependence of the mode spacing strongly support vibronic lasing action in the RMTs. The stimulated emission by the subwavelength bending waveguide demonstrates that the organic RMTs can be applied as new building blocks for micromanipulation of optical path and amplification in the integrated circuits for efficient photonic devices. © 2011 American Chemical Society.

Ge K.,CAS Institute of Geology and Geophysics | Ge K.,University of Chinese Academy of Sciences | Williams W.,University of Edinburgh | Liu Q.,CAS Institute of Geology and Geophysics | Yu Y.,Chungnam National University
Geochemistry, Geophysics, Geosystems | Year: 2014

The relationship between magnetic hysteresis parameters and the degree of oxidation of ultrafine magnetite particles is examined by both experimental measurements (distributed particle assemblage with median grain size of ∼80 nm and standard deviation 0.43) and micromagnetic simulations (single particles from 40 nm to 140 nm). Experimental results show that both coercivity (B c) and the ratio of saturation remanence to saturation magnetization (Mrs/Ms) increase slowly, as the oxidation parameter z increases from 0 to ∼0.9. Thereafter, both parameters decrease sharply as magnetite becomes completely oxidized to maghemite. Numerical simulations of hysteresis loop and microstructure using a micromagnetic model with a core-shell geometry (a stoichiometric core surrounded by an oxidized shell) show three categories of behavior for magnetic grains during oxidation. First, the coercivity of SD particles decreases as oxidation proceeds, but their remanence magnetization remains in a uniform state. Second, for PSD sized particles near the critical SD boundary (80 nm to 100 nm), the initial vortex domain structure changes to a SD as oxidation occurs and returns to a vortex state upon complete maghemitization, resulting in an initial rise and then fall of Bc and Mrs. Finally, larger PSD grains remain a vortex state throughout the maghemitization, with less variations of Bc and Mrs. The predicted magnetic properties exhibit good agreement with experimental observations and suggest that the domain arrangement is likely to be dominated by a core-shell structure with strong exchange coupling at their interface. Overall, the partially oxidized magnetite in SD-PSD range can reliably record palaeomagnetic signals. Key Points The low-temperature oxidation is very common in natural environments Experiments and micromagnetic modeling are studied The partially oxidized magnetite can record palaeomagnetic signals © 2014. American Geophysical Union. All Rights Reserved.

Joo J.-Y.,Cancer Research Institute | Park J.-Y.,Cancer Research Institute | Yoon Y.-H.,Cancer Research Institute | Choi B.,Chungnam National University | And 4 more authors.
Journal of Clinical Endocrinology and Metabolism | Year: 2012

Context: Few reports have determined whether preoperative detection of the BRAF V600E mutation in fine-needle aspiration biopsy (FNAB) may influence determination of surgical extent such as prophylactic central lymph node dissection (CLND) in patients with papillary thyroid carcinoma (PTC). Objectives: Our objectives were to investigate whether preoperative BRAF analysis may assist determination of surgical extent, including prophylactic CLND with variable clinicopathological risk factors for central lymph node metastasis, in patients with PTC and clinically node-negative neck. Patients and Methods: From July 2009 to May 2011, we prospectively enrolled 148 PTC patients with clinically node-negative neck who received a total thyroidectomy and prophylactic CLND. BRAF mutation by pyrosequencing was tested on preoperative FNAB specimens. The relationships between occult central lymph node metastasis and preoperative BRAF mutation or clinicopathological factors were analyzed. Additionally, we assessed the associations between preoperative BRAF mutation status and various clinicopathological characteristics of PTC revealed postoperatively. Results: The prevalence of the BRAF V600E mutation was 53.4%, and the rate of occult central lymph node metastasis was 25.7%. Multivariate analysis showed that tumor size over 1 cm [P = 0.006; odds ratio (OR) = 3.559], perithyroidal invasion (P = 0.023; OR = 2.893), and preoperative positive BRAF mutation (P = 0.029; OR = 2.727) were independent risk factors for the presence of occult central lymphnodemetastasis. BRAF mutation examined in FNAB specimens, compared with the wild-type allele, strongly predicted perithyroidal invasion (48 vs. 29%; P = 0.017), extracapsular spread (65 vs. 45%; P = 0.017), occult central lymph node metastasis (35 vs. 15%; P = 0.004), and advanced TNM stage (44 vs. 28%; P = 0.035). In the multivariate analysis, patients with preoperative positive BRAF mutation were significantly more likely (P = 0.023; OR = 2.848) to have occult central lymph node metastasis. Conclusion: Preoperative BRAF analysis by FNAB and primary tumor size based on ultrasonography may assist in predicting occult central lymph node metastasis in patients with PTC and clinically node-negative neck. Copyright © 2012 by The Endocrine Society.

Fabri M.,University of California at Los Angeles | Fabri M.,University of Cologne | Realegeno S.E.,University of California at Los Angeles | Jo E.-K.,Chungnam National University | Modlin R.L.,University of California at Los Angeles
Current Opinion in Immunology | Year: 2011

There is compelling evidence demonstrating a key role for autophagy in host defense against microbial infections. Induction and regulation of autophagy involves complex pathways including signaling molecules that have widespread roles in cell biological functions. For example, inhibiting mTOR by rapamycin, the most widely used chemical approach to induce autophagy, can also result in immunosupression. Nevertheless, advances in our understanding of autophagy provide a new opportunity to modulate host cellular responses as a potential therapeutic strategy to combat microbial infections in humans. © 2010 Elsevier Ltd.

Kim D.,Korea Institute of Nuclear Safety | Cha H.,Chungnam National University
Conference Proceedings - 2012 IEEE 7th International Power Electronics and Motion Control Conference - ECCE Asia, IPEMC 2012 | Year: 2012

Lead-acid batteries are used for DC power system in nuclear power plants. Standards of periodic surveillance and determining battery capacity for the batteries in the nuclear power plant are summarized. This paper is investigated for environment service condition, specification, advantages and disadvantages of Class 1E battery bank. Class 1E batteries of nuclear power plants in Korea are summarized in terms of specification, such as capacity, discharge rate, bank configuration, discharge end voltage, etc. This paper summarizes standards, and performance test results of the battery in the nuclear power plant. Also this paper analyses performance test results during 12 years and compared performance degradation in the battery bank. © 2012 IEEE.

Nam Y.S.,Chungnam National University | Park W.H.,Chungnam National University | Ihm D.,Hoseo University | Hudson S.M.,North Carolina State University
Carbohydrate Polymers | Year: 2010

Chitin and chitosan nanofibers with different degrees of deacetylation (DD) were fabricated by electrospinning using 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) as the spinning solvent and by subsequent deacetylation using a 40% aqueous NaOH solution at 100 °C for 0-150 min. The thermal decomposition behavior of the chitin and chitosan nanofibers was examined by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The thermal stability of the chitin/chitosan nanofibers was decreased with increasing the DD and the peak temperature for thermal decomposition on the TGA curves was shifted to a lower temperature. The activation energies for the thermal degradation of the chitin/chitosan nanofibers were calculated from the TGA curves. The two exotherms corresponding to the decomposition of N-acetyl-d-glucosamime and d-glucosamine units in the chitin/chitosan molecular chains were observed on the DSC thermograms. This suggests that the residual N-acetyl groups had a blocky distribution in the molecular chain, possibly due to heterogeneous deacetylation. © 2009 Elsevier Ltd. All rights reserved.

Lee J.,Korea Institute of Nuclear Safety | Cha H.,Chungnam National University
Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC | Year: 2016

In this paper, a new DSC-PLL (Delayed Signal Cancellation Phase Locked Loop) with FLL (Frequency Locked Loop) based on RDFT(recursive discrete fourier transform) method is proposed for coping with frequency variation. This method shows significant performance improvement for detection of fundamental positive sequence component voltage when the grid voltage is polluted by grid harmonics and frequency variation. The frequency detection technique of DSC-PLL tracks frequency drift by the RDFT. These compensation algorithms can correct for discrepancies of changing the frequency within maximum 28ms and improve traditional DSC-PLL. To verify feasibility of the proposed DSC-PLL, Matlab/Simulink results show good agreement with the analysis. © 2016 IEEE.

Santos-Lima R.,University of Sao Paulo | Santos-Lima R.,University of Wisconsin - Madison | Lazarian A.,University of Wisconsin - Madison | De Gouveia Dal Pino E.M.,University of Sao Paulo | And 2 more authors.
Astrophysical Journal | Year: 2010

The diffusion of astrophysical magnetic fields in conducting fluids in the presence of turbulence depends on whether magnetic fields can change their topology via reconnection in highly conducting media. Recent progress in understanding fast magnetic reconnection in the presence of turbulence reassures that the magnetic field behavior in computer simulations and turbulent astrophysical environments is similar, as far as magnetic reconnection is concerned. This makes it meaningful to perform MHD simulations of turbulent flows in order to understand the diffusion of magnetic field in astrophysical environments. Our studies of magnetic field diffusion in turbulent medium reveal interesting new phenomena. First of all, our three-dimensional MHD simulations initiated with anti-correlating magnetic field and gaseous density exhibit at later times a de-correlation of the magnetic field and density, which corresponds well to the observations of the interstellar media. While earlier studies stressed the role of either ambipolar diffusion or time-dependent turbulent fluctuations for de-correlating magnetic field and density, we get the effect of permanent de-correlation with one fluid code, i.e., without invoking ambipolar diffusion. In addition, in the presence of gravity and turbulence, our three-dimensional simulations show the decrease of the magnetic flux-to-mass ratio as the gaseous density at the center of the gravitational potential increases. We observe this effect both in the situations when we start with equilibrium distributions of gas and magnetic field and when we follow the evolution of collapsing dynamically unstable configurations. Thus, the process of turbulent magnetic field removal should be applicable both to quasi-static subcritical molecular clouds and cores and violently collapsing supercritical entities. The increase of the gravitational potential as well as the magnetization of the gas increases the segregation of the mass and magnetic flux in the saturated final state of the simulations, supporting the notion that the reconnection-enabled diffusivity relaxes the magnetic field + gas system in the gravitational field to its minimal energy state. This effect is expected to play an important role in star formation, from its initial stages of concentrating interstellar gas to the final stages of the accretion to the forming protostar. In addition, we benchmark our codes by studying the heat transfer in magnetized compressible fluids and confirm the high rates of turbulent advection of heat obtained in an earlier study. © 2010 The American Astronomical Society. All rights reserved.

Lee Y.-H.,Dankook University | Kim B.,Chungnam National University | Kim H.-J.,Gyeongnam National University of Science and Technology
Computers and Mathematics with Applications | Year: 2012

Localizing an object within an image is a common task in the field of computer vision, and represents the first step towards the solution of the recognition problem. This paper presents an efficient approach to object localization for image retrieval using query-by-region. The new algorithm utilizes correlogram back-projection in the YCbCr chromaticity components to handle the problem of subregion querying. Utilizing similar spatial color information enables users to detect and locate primary location and candidate regions accurately without the need for further information about the number of objects. Comparing this new approach to existing methods, an improvement of 21% was observed in experimental trials. These results reveal that color correlograms are markedly more effective than color histograms for this task. © 2011 Elsevier Ltd. All rights reserved.

Abbas M.,Chungnam National University | Takahashi M.,Chungnam National University | Takahashi M.,Tohoku University | Kim C.,Chungnam National University
Journal of Nanoparticle Research | Year: 2013

Monodisperse magnetite nanocubes with uniform particle size of about 80 nm have been synthesized in aqueous medium by single reaction sonochemical method using inexpensive and non-toxic metal salt (FeSO4·7H 2O) as reactant. The crystallinity of the magnetite nanocube is enhanced by annealing treatment up to 600 C with uniform shape and size distribution, after that a distortion in shape and a broad size distribution are obtained at 700 C annealing temperature. The magnetic characterization of the nanoparticles reveals saturation magnetization of 91 emu/g at 5 K for as-synthesized sample and 94.8 emu/g for the sample which annealed at the temperature of 600 C in a vacuum chamber. However, the saturation magnetization has been observed to decrease with further increase in annealing temperature and this has been attributed to the presence of a thin magnetic dead layer at the surface caused by shape anisotropy distortion and broken exchange bonds, and spin canting on the surface of the particles in addition to the formation of a small amount of maghemite phase. © 2012 Springer Science+Business Media Dordrecht.

Kim M.S.,Jeju National University | Kim S.Y.,Chungnam National University | Nelson W.,NIWA - National Institute of Water and Atmospheric Research
Botanica Marina | Year: 2010

Symphyocladia lithophila sp. nov. is newly described using both morphological and molecular analyses of samples collected from the southeastern coast of Korea. The new species is characterized by small size, ecorticate thallus, with 8-10 pericentral cells, lacking trichoblasts, and having 5-7 segments of congenital fusions. S. lithophila was observed to be a winter species, producing tetrasporangia from December to February. Plastid-encoded rbcL sequences were determined in four samples of S. lithophila from different locations and 21 samples of four putative relatives, including the most related genus Pterosiphonia. All four Symphyocladia lithophila replicates from three different locations had almost identical rbcL sequences, and interspecific sequence divergences were sufficient to warrant its separation as a natural entity. The phylogeny of the rbcL sequences also indicated monophyly of the genus Symphyocladia, which is separated from the genus Pterosiphonia. The specimens of Pterosiphonia, including the type species P. cloiophylla from its type locality in South Africa, form a monophyletic group. © 2010 by Walter de Gruyter Berlin New York.

Kim S.,Chungnam National University | Rey S.-C.,Chungnam National University | Rey S.-C.,Johns Hopkins University | Lisker T.,University of Heidelberg | Tony Sohn S.,US Space Telescope Science Institute
Astrophysical Journal Letters | Year: 2010

We present ultraviolet (UV) color-magnitude relations (CMRs) of early-type dwarf galaxies in the Virgo cluster, based on Galaxy Evolution Explorer (GALEX) UV and Sloan Digital Sky Survey (SDSS) optical imaging data.We find that dwarf lenticular galaxies (dS0s), including peculiar dwarf elliptical galaxies (dEs) with disk substructures and blue centers, show a surprisingly distinct and tight locus separated from that of ordinary dEs,which is not clearly seen in previous CMRs. The dS0s in UV CMRs follow a steeper sequence than dEs and show bluer UV-optical color at a given magnitude. We also find that the UV CMRs of dEs in the outer cluster region are slightly steeper than that of their counterparts in the inner region, due to the existence of faint, blue dEs in the outer region. We explore the observed CMRs with population models of a luminosity-dependent delayed exponential star formation history. We confirm that the feature of delayed star formation of early-type dwarf galaxies in the Virgo cluster is strongly correlated with their morphology and environment. The observed CMR of dS0s is well matched by models with relatively long delayed star formation. Our results suggest that dS0s are most likely transitional objects at the stage of subsequent transformation of late-type progenitors to ordinary red dEs in the cluster environment. In any case, UV photometry provides a powerful tool to disentangle the diverse subpopulations of early-type dwarf galaxies and uncover their evolutionary histories. © 2010. The American Astronomical Society. All rights reserved.

Kobayashi H.,Ishikawa Prefectural Nursing University | Park B.-J.,Chungnam National University | Miyazaki Y.,Chiba University
Journal of Physiological Anthropology | Year: 2012

Background: This study aimed to present normative reference values of heart rate variability and salivary alphaamylase in a healthy young male population with a particular focus on their distribution and reproducibility. Methods: The short-term heart rate variability of 417 young healthy Japanese men was studied. Furthermore, salivary alpha-amylase was measured in 430 men. The average age of the subjects were 21.9 years with standard deviation of 1.6 years. Interindividual variations in heart rate variability indices and salivary alpha-amylase levels were plotted as histograms. Data are presented as the mean, median, standard deviation, coefficient of variation, skewness, kurtosis, and fifth and 95th percentiles of each physiological index. Results: Mean recorded values were heart period 945.85 ms, log-transformed high frequency component 9.84 lnms 2, log-transformed low frequency component 10.42 ln-ms 2, log-transformed low frequency to high frequency ratio 0.58 ln-ratio, standard deviation of beat-to-beat interval 27.17 ms and root mean square of successive difference 37.49 ms. The mean value of raw salivary alpha-amylase was 17.48 U/mL, square root salivary alphaamylase 3.96 sqrt[U/mL] and log-transformed salivary alpha-amylase 2.65 ln[U/mL]. Log-transformed heart rate variability indices exhibited almost symmetrical distributions; however, time-domain indices of heart rate variability (standard deviation of beat-to-beat interval and root mean square of successive difference) exhibited right-skewed (positive skewness) distributions. A considerable right-skewed distribution was observed for raw salivary alphaamylase. Logarithmic transformation improved the distribution of salivary alpha-amylase, although square root transformation was insufficient. The day-to-day reproducibility of these indices was assessed using intraclass correlation coefficients. Intraclass correlation coefficients of most heart rate variability and salivary indices were approximately 0.5 to 0.6. Intraclass correlation coefficients of raw salivary markers were approximately 0.6, which was similar to those of heart rate variability; however, log transformation of the salivary markers did not considerably improve their reproducibility. Correlations between sympathetic indicators of heart rate variability and salivary alpha-amylase were not observed. Conclusion: Because the sample population examined in this study involved limited age and gender variations, the present results were independent of these factors and were indicative of pure interindividual variation. © 2012 Kobayashi et al.

Wu W.,University of Tennessee at Knoxville | An K.,Oak Ridge National Laboratory | Huang L.,University of Tennessee at Knoxville | Lee S.Y.,Chungnam National University | Liaw P.K.,University of Tennessee at Knoxville
Scripta Materialia | Year: 2013

The deformation dynamics and the effect of deformation history on plastic deformation in a wrought magnesium alloy at room temperature have been studied by real-time in situ neutron diffraction measurements under a continuous loading condition. The experimental results reveal that no detwinning occurred during unloading after compression and even in an elastic region during reverse tension. It is found that the serration behavior is closely related to the twinning- and detwinning-dominated deformation. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Ryu D.,Chungnam National University | Schleicher D.R.G.,University of Gottingen | Treumann R.A.,ISSI | Tsagas C.G.,Aristotle University of Thessaloniki | Widrow L.M.,Queen's University
Space Science Reviews | Year: 2012

Magnetic fields appear to be ubiquitous in astrophysical environments. Their existence in the intracluster medium is established through observations of synchrotron emission and Faraday rotation. On the other hand, the nature of magnetic fields outside of clusters, where observations are scarce and controversial, remains largely unknown. In this chapter, we review recent developments in our understanding of the nature and origin of intergalactic magnetic fields, and in particular, intercluster fields. A plausible scenario for the origin of galactic and intergalactic magnetic fields is for seed fields, created in the early universe, to be amplified by turbulent flows induced during the formation of the large scale structure. We present several mechanisms for the generation of seed fields both before and after recombination. We then discuss the evolution and role of magnetic fields during the formation of the first starts. We describe the turbulent amplification of seed fields during the formation of large scale structure and the nature of the magnetic fields that arise. Finally, we discuss implications of intergalactic magnetic fields. © 2011 Springer Science+Business Media B.V.

Widrow L.M.,Queen's University | Ryu D.,Chungnam National University | Schleicher D.R.G.,University of Gottingen | Subramanian K.,University of Pune | And 2 more authors.
Space Science Reviews | Year: 2012

We review current ideas on the origin of galactic and extragalactic magnetic fields. We begin by summarizing observations of magnetic fields at cosmological redshifts and on cosmological scales. These observations translate into constraints on the strength and scale magnetic fields must have during the early stages of galaxy formation in order to seed the galactic dynamo. We examine mechanisms for the generation of magnetic fields that operate prior during inflation and during subsequent phase transitions such as electroweak symmetry breaking and the quark-hadron phase transition. The implications of strong primordial magnetic fields for the reionization epoch as well as the first generation of stars are discussed in detail. The exotic, early-Universe mechanisms are contrasted with astrophysical processes that generate fields after recombination. For example, a Biermann-type battery can operate in a proto-galaxy during the early stages of structure formation. Moreover, magnetic fields in either an early generation of stars or active galactic nuclei can be dispersed into the intergalactic medium. © 2011 Springer Science+Business Media B.V.

Park B.-Y.,Chungnam National University | Kim J.-I.,Florida State University | Rho M.,CEA Saclay Nuclear Research Center | Rho M.,Hanyang University
Physical Review C - Nuclear Physics | Year: 2010

Dense hadronic matter at low temperatures is expected to be in a crystalline state and at high density to make a transition to a chirally restored but color-confined state, which is a novel phase hitherto unexplored. This phase transition is predicted in both skyrmion matter in four dimensions and instanton matter in five dimensions, the former in the form of half-skyrmions and the latter in the form of half-instantons or dyons. We predict that when K-'s are embedded in this half-skyrmion or half-instanton (dyonic) matter, which may be reached not far past the normal density, there arises an enhanced attraction from both the soft dilaton field figuring for the trace anomaly of QCD and the Wess-Zumino term. This attraction may have relevance for a possible strong binding of antikaons in dense nuclear matter and for kaon condensation in neutron-star matter. Such kaon property in the half-skyrmion phase is highly nonperturbative and may not be accessible by low-order chiral perturbation theory. Relevance of the half-skyrmion or dyonic matter to compact stars is discussed. © 2010 The American Physical Society.

Dao V.-D.,Chungnam National University | Kim S.-H.,Chungnam National University | Choi H.-S.,Chungnam National University | Kim J.-H.,Bioneer Co. | And 2 more authors.
Journal of Physical Chemistry C | Year: 2011

[Pt hollow spheres] electrodes and [Pt-sputtered + Pt hollow spheres] electrodes were fabricated on fluorine-doped tin oxide (FTO) glass as counter electrodes for dye-sensitized solar cells (DSCs), after sputtering platinum (Pt) on polystyrene microspheres and annealing them at 500 °C for 30 min. Electrochemical impedance measurement revealed that the charge transfer resistances of [Pt hollow spheres] electrodes and [Pt-sputtered + Pt hollow spheres] electrodes were 0.91 ω cm 2 and 0.48 ω cm 2, respectively, which were less than that of 1.28 ω cm 2 obtained from [Pt-sputtered] electrode. Furthermore, the DSCs with [Pt hollow spheres] and [Pt-sputtered + Pt hollow spheres] electrodes exhibited high energy-conversion efficiencies of 8.20(±0.10)% and 8.53(±0.08)%, respectively, which were both higher than the 7.89(±0.05)% efficiency of the DSC with [Pt-sputtered] electrodes. © 2011 American Chemical Society.

Srivastava R.K.,Banaras Hindu University | Srivastava R.K.,Rice University | Srivastava S.,Banaras Hindu University | Srivastava S.,National Physical Laboratory India | And 7 more authors.
ACS Nano | Year: 2012

Figure Persented: Multilayered graphene (MLG) is an interesting material for electrochemical sensing and biosensing because of its very large 2D electrical conductivity and large surface area. We propose a less toxic, reproducible, and easy method for producing functionalized multilayer graphene from multiwalled carbon nanotubes (MWCNTs) in mass scale using only concentrated H 2SO 4/HNO 3. Electron microscopy results show the MLG formation, whereas FTIR and XPS data suggest its carboxylic and hydroxyl-functionalized nature. We utilize this functionalized MLG for the fabrication of a novel amperometric urea biosensor. This biosensor shows linearity of 10-100 mg dL -1, sensitivity of 5.43 μA mg -1 dL cm -2, lower detection limit of 3.9 mg dL -1, and response time of 10 s. Our results suggest that MLG is a promising material for electrochemical biosensing applications. © 2011 American Chemical Society.

Yoo J.-M.,Chungnam National University | Sok D.-E.,Chungnam National University | Kim M.R.,Chungnam National University
International Immunopharmacology | Year: 2013

Recently, some endocannabinoids were reported to show anti-inflammatory and anti-allergic activities. In this respect, various arachidonoyl endocannabinoids were screened for the inhibition of allergic response in IgE-activated RBL-2H3 cells. Among arachidonoyl endocannabinoids with a low cytotoxicity, only NA-5HT remarkably inhibited the release of β-hexosaminidase (IC50, 13.58 μM), a marker of degranulation, and tumor necrosis factor-α (IC50, 12.52 μM), a pro-inflammatory cytokine, in IgE-activated RBL-2H3 cells. Additionally, NA-5HT markedly suppressed the formation of prostaglandin D2 (PGD2) with IC 50 value of 1.27 μM and leukotriene B4 (LTB 4) with IC50 value of 1.20 μM, and slightly LTC 40. When effect of NA-5HT on early stage of Fc?RI cascade was investigated, it significantly inhibited phosphorylation of Syk, but not Lyn. Furthermore, NA-5HT suppressed phosphorylation of PLCγ1/2 and PKCλ, related to degranulation process, as well as phosphorylation of LAT, ERK1/2, p38, JNK, Gab2, PI3K and Akt, implicated in the expression of pro-inflammatory cytokines. Relative to its effect on the late stage, NA-5HT slightly reduced phosphorylation of 5-lipoxygenase (5-LO) and cyclooxygenase-2 (COX-2). Additionally, NA-5HT significantly reduced the level of p40phox, and partially inhibited the expression of p47phox and p67phox. From these results, it is suggested that NA-5HT expresses anti-allergic action by suppressing the activation of Syk, LAT, p38, JNK, PI3K and Akt, as well as the expression of ERK1/2 and NADPH oxidase subunits. Further, a strong inhibition of PGD2 or LTB4 biosynthesis by NA-5HT may be an additional mechanism for its anti-allergic action. Such anti-allergic actions of NA-5HT may contribute to further information about its biological functions. © 2013 Elsevier B.V. All rights reserved.

Cho K.H.,Chungnam National University | Lee S.S.,Chungnam National University
Annals of Rehabilitation Medicine | Year: 2012

Objective: To investigate the eff ect of radiofrequency (RF) sacral rhizotomy of the intolerable neurogenic bladder in spinal cord injured patients. Method: Percutaneous RF sacral rhizotomy was performed on 12 spinal cord injured patients who had neurogenic bladder manifested with urinary incontinence resisted to an oral and intravesical anticholinergic instillation treatment. Various combinations of S2, S3, and S4 RF rhizotomies were performed. Th e urodynamic study (UDS) was performed 1 week before RF rhizotomy. The voiding cystourethrogram (VCUG) and voiding diaries were compared 1 week before and 4 weeks after therapy. Total volume of daily urinary incontinence (ml/day) and clean intermittent catheterization (ml/time) volume of each time were also monitored. Results: After RF sacral rhizotomy, bladder capacity increased in 9 patients and the amount of daily urinary incontinence decreased in 11 patients. The mean maximal bladder capacity increased from 292.5 to 383.3 ml (p<0.05) and mean daily incontinent volume decreased from 255 to 65 ml (p<0.05). Bladder trabeculation and vesicoureteral reflux findings did not change 4 weeks after therapy. Conclusion: This study revealed that RF sacral rhizotomy was an effective method for neurogenic bladder with uncontrolled incontinence using conventional therapy among spinal cord injured patients. © 2012 by Korean Academy of Rehabilitation Medicine.

Ryu M.-H.,Korea Institute of Energy Research | Ryu M.-H.,Chungnam National University | Jung K.-N.,Korea Institute of Energy Research | Shin K.-H.,Korea Institute of Energy Research | And 2 more authors.
Journal of Physical Chemistry C | Year: 2013

N-doped mesoporous carbon decorated TiO2 nanofibers were synthesized for the first time by a facile electrospinning process combined with subsequent heat treatment and investigated as an anode material for lithium-ion battery applications. The N-doped mesoporous carbon decorated TiO2 nanofibers had continuous one-dimensional (1-D) geometry with a smooth surface and an average thickness of ∼250 nm. The nanofibers comprised both interconnected polycrystalline TiO2 and numerous mesopores in N-doped carbon. After 100 cycles at current density of 33 mA/g, the N-doped mesoporous carbon decorated TiO2 nanofibers still exhibited a high capacity of 264 mAh/g. This superior electrochemical performance is attributed to small TiO2 crystallites, N-doped mesoporous carbon, favorable 1-D nanostructures, and smooth accommodation of the strain occurring during the charge-discharge process. © 2013 American Chemical Society.

Oh S.Y.,University of Delaware | Yi Y.,Chungnam National University | Bieber J.W.,University of Delaware
Solar Physics | Year: 2010

The diurnal variation of the galactic cosmic ray (GCR) count rates measured by a ground-based neutron monitor (NM) station represents an anisotropic flow of GCR at 1 AU. The variation of the local time of GCR maximum intensity (we call the phase) is thought in general to have a period of two sunspot cycles (22 years). However, other interpretations are also possible. In order to determine the cyclic behavior of GCR anisotropic variation more precisely, we have carried out a statistical study on the diurnal variation of the phase. We examined 54-year data of Huancayo (Haleakala), 40-year data from Rome, and 43-year data from Oulu NM stations using the 'pile-up' method and the F-test. We found that the phase variation has two components: of 22-year and 11-year cycles. All NM stations show mainly the 22-year phase variation controlled by the drift effect due to solar polar magnetic field reversal, regardless of their latitudinal location (cut-off rigidity). However, the lower the NM station latitude is (the higher the cut-off rigidity is), the higher is the contribution from the 11-year phase variation controlled by the diffusion effect due to the change in strength of the interplanetary magnetic fields associated with the sunspot cycle. © 2010 Springer Science+Business Media B.V.

Swaraz A.M.,Chungnam National University | Park Y.-D.,Kyung Hee University | Hur Y.,Chungnam National University
Plant Science | Year: 2011

SmD3 is a core protein of small nuclear ribonucleoprotein (snRNP) essential for splicing of primary transcripts. To elucidate function of SmD3 protein in plants, phenotypes and gene expression of SmD3 knock-out and overexpressing mutants in Arabidopsis have been analyzed. smd3- a knock-out mutant or SmD3- a and SmD3- b overexpressors did not show phenotypic alteration. Knock-out of SmD3- b resulted in the pleotropic phenotypes of delayed flowering time and completion of life cycle, reduced root growth, partially defective leaf venation, abnormal numbers of trichome branches, and changed numbers of floral organs. Microarray data revealed that the smd3- b mutant had altered expression of genes related to the above phenotypes, indirectly suggesting that changed splicing of these genes may cause the observed phenotypes. Splicing of selected genes was either totally blocked or reduced in the smd3- b mutant, indicating the important role of SmD3-b in the process. A double knock-out mutant of smd3- a and smd3- b could not be generated, indicating possible redundant function of these two genes. All data indicate that SmD3-b may be major component of the spliceosomal snRNP in Arabidopsis, but the function of SmD3-a may be redundant. © 2011 Elsevier Ireland Ltd.

Tam P.H.T.,National Tsing Hua University | Kong A.K.H.,National Tsing Hua University | Hui C.Y.,Chungnam National University | Cheng K.S.,University of Hong Kong | And 2 more authors.
Astrophysical Journal | Year: 2011

Globular clusters (GCs) are emerging as a new class of γ-ray emitters, thanks to the data obtained from the Fermi Gamma-ray Space Telescope. By now, eight GCs are known to emit γ-rays at energies >100 MeV. Based on the stellar encounter rate of the GCs, we identify potential γ-ray emitting GCs out of all known GCs that have not been studied in detail before. In this paper, we report the discovery of a number of new γ-ray GCs: Liller 1, NGC6624, and NGC6752, and evidence of γ-ray emission from M80, NGC6139, and NGC6541, in which γ-rays were found within the GC tidal radius. With one of the highest metallicities among all GCs in the Milky Way, the γ-ray luminosity of Liller 1 is found to be the highest of all known γ-ray GCs. In addition, we confirm a previous report of a significant γ-ray emitting region next to NGC6441. We briefly discuss the observed offset of γ-rays from some GC cores. The increasing number of known γ-ray GCs at distances out to 10 kpc is important for us to understand the γ-ray emitting mechanism and provides an alternative probe to the underlying millisecond pulsar populations of the GCs. © 2011. The American Astronomical Society. All rights reserved.

Kumar Challa K.,Chungnam National University | Goswami S.K.,Chungnam National University | Oh E.,Chungnam National University | Kim E.-T.,Chungnam National University
Applied Physics Letters | Year: 2011

TiO 2/CdS core-shell nanowires were synthesized using a simple thermal oxidation treatment of a Ti film, followed by O 2 plasma treatment and CdS coating via low-cost chemical bath deposition. The 5 and 20 nm thick CdS films were uniformly coated onto TiO 2 nanowires using 200 and 40 ml aqueous solvent, respectively. Time-resolved photoluminescence (PL) measurements on the TiO 2/CdS (5 nm) nanowires showed a remarkably increased PL lifetime of 420 ps compared with the 60 ps of the TiO 2/CdS (20 nm) nanowires. This result can be attributed to the enhanced electron-hole separation due to the more upshifted quantized electron energy levels of the 5 nm thick CdS film with respect to the TiO 2 conduction band edge. © 2011 American Institute of Physics.

Chung M.G.,Chungnam National University | Rhee Y.H.,Chungnam National University
Bioscience, Biotechnology and Biochemistry | Year: 2012

The (R)-specific enoyl-CoA hydratase gene (phaJ HS21) from Pseudomonas chlororaphis HS21 was overexpressed in various Pseudomonas strains, alone and in combination with the polyhydroxyalkanoate synthase gene (phaC HS21), for the biosynthesis of polyhydroxyalkanoates (PHAs) of altered monomer composition. Recombinant Pseudomonas strains harboring phaC HS21 and phaJ HS21 generated saturated and unsaturated monomers of C12-C14 in their PHAs. In particular, the level of the 3-hydroxytetradecenoate monomer in recombinant P. chlororaphis HS21 increased by approximately 260%. PhaJ HS21 is expected to be useful in the biosynthesis of PHAs consisting of unusual monomer units.

Background: Food allergies are important etiologic factors in atopic dermatitis. CD19 is a B-cell-specific cell-surface molecule, with a critical role in B-cell activation. Recently, B cells showed independent two subpopulations as CD19hi and CD19low. The allergen-specific responses of the CD19high and CD19low B-cell subpopulations were investigated in patients with non-IgE-mediated food allergy. Methods: Five milk-allergic subjects and eight milk-tolerant subjects were selected by a double-blind placebo-controlled food challenge. Peripheral blood mononuclear cells (PBMCs) were stimulated in vitro with casein or ovalbumin and stained with monoclonal antibodies to distinguish the B-cell subsets. Results: After allergen stimulation, CD19high B cells increased in the number and the fraction in PBMCs in the milk-tolerant group, whereas those remained unchanged in the milk-allergic group. These responses were constant, regardless of the kind of food allergen (milk or egg). The resulting CD19high/CD19low B-cell ratio increased markedly in the milk-tolerant group after allergen stimulation, but was unchanged in the milk-allergic group. IL-10, IL-17, IL-32 and TGF-p-producing regulatory B cells and Foxp3-expressing regulatory B cells were identified predominantly on CD19 low and CD5(+) B cells. Conclusions: The response of the CD19high B-cell subpopulation to allergen stimulation is decisive for immune tolerance of non-IgE-mediated food allergy in atopic dermatitis. CD19 high and CD5(+) B cells dominantly produce cytokines and express Foxp3. Especially, IL-17 and IL-32 expressing B cells (Br17 & Br32) are present. The exact immunological role of CD19 and cytokines including IL-17 and IL-32 around B cells in immune tolerance requires further investigation. © 2012 Bentham Science Publishers.

Noh Y.-W.,Korea Research Institute of Bioscience and Biotechnology | Noh Y.-W.,Chonbuk National University | Jang Y.-S.,Chonbuk National University | Ahn K.-J.,Catholic University of Korea | And 2 more authors.
Biomaterials | Year: 2011

We report the fabrication of a one-pot antigen system that delivers antigen to dendritic cells (DCs) and tracks their in vivo migration after injection. Multifunctional polymer nanoparticles containing ovalbumin protein, magnetic resonance imaging contrast agents (iron oxide nanoparticles), and near-infrared fluorophores (indocyanine green, ICG), MPN-OVA, were prepared using a double emulsion method. The MPN-OVA was efficiently taken up by the dendritic cells and subsequently localized in the lysosome. Flow cytometry analysis revealed an increase in the uptake of OVA antigen by MPN-OVA at 37 °C, when compared with soluble OVA protein. We found that MPN-OVA had no effect on DC surface expression of MHC class I, costimulatory (CD80, CD86) or adhesion (CD54) molecules or the ability of DCs to mature in response to LPS. Following the uptake of MPN-OVA, exogenous OVA antigen was delivered to the cytoplasm, and OVA peptides were presented on MHC class I molecules, which enhanced OVA antigen-specific cross-presentation to OT-1 T cells and CD8OVA1.3 T cell hybridoma in vitro. The immunization of mice with MPN-OVA-treated DCs induced OVA-specific CTL activity in draining lymph nodes. The presence of MPN allowed us to monitor the migration of DCs via lymphatic drainage using NIR fluorescence imaging, and the homing of DCs into the lymph nodes was imaged using MRI. This system has potential for use as a delivery system to induce T cell priming and to image DC-based immunotherapies. © 2011 Elsevier Ltd.

Kim H.,Chungnam National University | Song T.,Chungnam National University | Ahn K.-H.,Chungnam National University
Applied Physics Letters | Year: 2011

Hair cells in biological hearing organs transform mechanical stimuli into neuronal signals with great sensitivity, sharp frequency selectivity, and wide range of intensity. By combining principle of adaptation in hair cells with electronic engineering, we have produced a biomimetic force sensor under water showing all these features. For the nano-Newton force signal, the biomimetic sensor showed that more than an order of magnitude increases in sensitivity and frequency selectivity compared to the passive sensor. The nonlinear amplification mechanism in the hair cell is demonstrated by showing that the hair cell can precisely detect pulse signals weaker than noise. © 2011 American Institute of Physics.

Kang H.,Pusan National University | Ryu D.,Chungnam National University
Astrophysical Journal | Year: 2011

We examine diffusive shock acceleration (DSA) of the pre-existing as well as freshly injected populations of non-thermal, cosmic-ray (CR) particles at weak cosmological shocks. Assuming simple models for thermal leakage injection and Alfvénic drift, we derive analytic, time-dependent solutions for the two populations of CRs accelerated in the test-particle regime. We then compare them with the results from kinetic DSA simulations for shock waves that are expected to form in intracluster media and cluster outskirts in the course of large-scale structure formation. We show that the test-particle solutions provide a good approximation for the pressure and spectrum of CRs accelerated at these weak shocks. Since the injection is extremely inefficient at weak shocks, the pre-existing CR population dominates over the injected population. If the pressure due to pre-existing CR protons is about 5% of the gas thermal pressure in the upstream flow, the downstream CR pressure can absorb typically a few to 10% of the shock ram pressure at shocks with a Mach number M ≲ 3, yet the re-acceleration of CR electrons can result in a substantial synchrotron emission behind the shock. The enhancement in synchrotron radiation across the shock is estimated to be about a few to several for M ∼ 1.5 and 10 2-103 for M ∼ 3, depending on the detail model parameters. The implication of our findings for observed bright radio relics is discussed. © 2011. The American Astronomical Society. All rights reserved.

Kim D.,University of Florida | Park J.-C.,Chungnam National University
Physics of the Dark Universe | Year: 2016

We propose a novel mechanism enabling us to have a continuum bump as a signature of gamma-ray excess in indirect detection experiments of dark matter (DM), postulating a generic dark sector having (at least) two DM candidates. With the assumption of non-zero mass gap between the two DM candidates, the heavier one directly communicates to the partner of the lighter one. Such a partner then decays into a lighter DM particle along with an "axion-like" particle (ALP) or dark "pion", which subsequently decays into a pair of photons, via a more-than-one step cascade decay process. Since the cascade is initiated by the dark partner obtaining a non-trivial fixed boost factor, a continuum γ-ray energy spectrum naturally arises even with a particle directly decaying into two photons. We apply the main idea to the energy spectrum of the GeV γ-rays from around the Galactic Center (GC), and find that the relevant observational data is well-reproduced by the theory expectation predicted by the proposed mechanism. Remarkably, the relevant energy spectrum has a robust peak at half the mass of the ALP or dark pion, as opposed to popular DM models directly annihilating to Standard Model particles where physical interpretations of the energy peak are not manifest. Our data analysis reports substantially improved fits, compared to those annihilating DM models, and ~900. MeV mass of the ALP or dark pion. © 2016 Elsevier B.V.

Eom I.,Korea Basic Science Institute | Ahn S.-H.,Korea Basic Science Institute | Rhee H.,Korea Basic Science Institute | Rhee H.,Chungnam National University | And 2 more authors.
Physical Review Letters | Year: 2012

We demonstrate that a single-pulse characterization of electronic optical activity-free induction decay, which carries information on both circular dichroism and optical rotatory dispersion, is experimentally feasible. Employing a self-referencing scheme, we show that a highly reliable interferometric chiroptical measurement free from power and phase fluctuations is achievable on a shot-by-shot basis. © 2012 American Physical Society.

Tran T.H.,Chungnam National University | Nguyen C.T.,Chungnam National University | Kim D.-P.,Chungnam National University | Lee Y.-K.,Chungbuk National University | Huh K.M.,Chungnam National University
Lab on a Chip - Miniaturisation for Chemistry and Biology | Year: 2012

This paper demonstrates the highly efficient synthesis of amphiphilic heparin-folic acid-retinoic acid (HFR) bioconjugates with a high drug coupling ratio by a microfluidic approach. The microfluidic synthesis enabled the conjugation of 17 molecules of retinoic acid to each heparin chain with 21 possible groups for attachment after reacting for several minutes. In contrast, about 11 molecules of the drug were covalently conjugated to one heparin chain after 4 days in the bulk reaction. The microfluidic based-HFR bioconjugates readily self-assembled in aqueous media to form uniform nanoparticles, while the product from the bulk reaction formed non-uniform nanoparticles with broad size distribution. The HFR nanoparticles with high drug content effectively delivered the drug to folate receptor-positive cancer cells with superior cellular uptake and selective cytotoxicity in vitro compared to HFR nanoparticles synthesized in bulk reaction. With the ability to achieve high drug content in heparin carrier within a short reaction time, the microfluidic technique offers new alternatives for the efficient synthesis of polymer-based conjugates for drug delivery. © 2012 The Royal Society of Chemistry.

Akahori T.,Chungnam National University | Ryu D.,Chungnam National University
Astrophysical Journal | Year: 2011

We investigate the Faraday rotation measure (RM) due to the intergalactic magnetic field (IGMF) through the cosmic web up to cosmological distances, using a model IGMF based on turbulence dynamo in the large-scale structure of the universe. By stacking the IGMF and gas density data up to redshift z = 5 and taking account of the redshift distribution of polarized background radio sources against which the RM is measured, we simulate the sky map of the RM. The contribution from galaxy clusters is subtracted from the map, based on several different criteria of X-ray brightness and temperature. Our findings are as follows. The distribution of RM for radio sources of different redshifts shows that the rms value increases with redshift and saturates for z ≳ 1. The saturated value is RMrms several rad m-2. The probability distribution function of |RM| follows the lognormal distribution. The power spectrum has a broad plateau over the angular scale of 1°-01 with a peak around 0°15. The second-order structure function has a flat profile in the angular separation of ≳ 0°2. Our results could provide useful insights for surveys to explore the IGMF with the Square Kilometer Array (SKA) and upcoming SKA pathfinders. © 2011 The American Astronomical Society. All rights reserved.

Maurya R.A.,Chungnam National University | Hoang P.H.,Chungnam National University | Kim D.-P.,Chungnam National University
Lab on a Chip - Miniaturisation for Chemistry and Biology | Year: 2012

Efficient and continuous monoacylation of symmetrical diamines performed in microreactors yielded superior selectivity to that predicted by statistical considerations. It is highly valuable that the kinetically controlled product in high yields was achieved without any special catalyst at ambient temperature. © 2012 The Royal Society of Chemistry.

Yao L.,Tulane University | Han C.,Tulane University | Song K.,Tulane University | Zhang J.,Tulane University | And 2 more authors.
Cancer Research | Year: 2015

Prostaglandin E2 (PGE2) is a proinflammatory lipid mediator that promotes cancer growth. The 15-hydroxyprostaglandin dehydrogenase (15-PGDH) catalyzes oxidation of the 15(S)-hydroxyl group of PGE2, leading to its inactivation. Therefore, 15-PGDH induction may offer a strategy to treat cancers that are driven by PGE2, such as human cholangiocarcinoma. Here, we report that omega-3 polyunsaturated fatty acids (ω-3 PUFA) upregulate 15-PGDH expression by inhibiting miR-26a and miR-26b, thereby contributing to ω-3 PUFA-induced inhibition of human cholangiocarcinoma cell growth. Treatment of human cholangiocarcinoma cells (CCLP1 and TFK-1) with ω-3 PUFA (DHA) or transfection of these cells with the Fat-1 gene (encoding Caenorhabditis elegans desaturase, which converts ω-6 PUFA to ω-3 PUFA) significantly increased 15-PGDH enzymes levels, but with little effect on the activity of the 15-PGDH gene promoter. Mechanistic investigations revealed that this increase in 15-PGDH levels in cells was mediated by a reduction in the expression of miR-26aandmiR-26b, which target 15-PGDH mRNA and inhibit 15-PGDH translation. These findings were extended by the demonstration that overexpressing miR-26a or miR-26b decreased 15-PGDH protein levels, reversed ω-3 PUFA-induced accumulation of 15-PGDH protein, and prevented ω-3 PUFA-induced inhibition of cholangiocarcinoma cell growth. We further observed that ω-3 PUFA suppressed miR-26a and miR-26b by inhibiting c-myc, a transcription factor that regulates miR-26a/b. Accordingly, c-myc overexpression enhanced expression of miR-26a/b and ablated the ability of ω-3 PUFA to inhibit cell growth. Taken together, our results reveal a novel mechanism for ω-3 PUFA-induced expression of 15-PGDH in human cholangiocarcinoma and provide a preclinical rationale for the evaluation of ω-3 PUFA in treatment of this malignancy. © 2015 American Association for Cancer Research.

Jo S.,Chungnam National University | Kim D.,Chungnam National University | Son S.-H.,Chungnam National University | Kim Y.,Chungnam National University | Lee T.S.,Chungnam National University
ACS Applied Materials and Interfaces | Year: 2014

Conjugated polymer of poly(fluorene-co-quinoxaline) was synthesized via Suzuki coupling polymerization. The emission color of the polymer can be tuned depending on the concentration of the polymer in solution. A low-energy bandgap is observed both in the concentrated solution and in the solid state, caused by aggregation of the polymer chains, resulting in long wavelength emission from the quinoxaline moiety, while short wavelength emission can be seen in diluted, well-dissolved solution. The presence of quinoxaline units enables us to demonstrate fluorescence switching and imaging. Paper-based strips containing the polymer are prepared via simple immersion of filter paper in the polymer solution for practical use in the detection of nerve agents. The emission of the paper-based strip is quenched upon exposure to diethyl chlorophosphate (DCP), a nerve agent simulant, and the initial emission intensity can be almost restored by treatment with aqueous sodium hydroxide solution, making a possible reversible paper-based sensor. © 2013 American Chemical Society.

Kim J.Y.,Chungnam National University | Kim H.J.,Chungnam National University | Lim G.O.,Chungnam National University | Jang S.A.,Chungnam National University | Song K.B.,Chungnam National University
Postharvest Biology and Technology | Year: 2010

The combined effect of aqueous chlorine dioxide (ClO2) or fumaric acid with ultraviolet-C (UV-C) on postharvest quality of "Maehyang" strawberries was examined. The strawberries were treated with distilled water, 50 mg L-1 ClO2, 0.5% fumaric acid, 5 kJ m-2 UV-C irradiation, and a combination of 50 mg L-1 ClO2/5 kJ m-2 UV-C and 0.5% fumaric acid/5 kJ m-2 UV-C. The combined treatment of fumaric acid/UV-C reduced the initial populations of total aerobic bacteria and yeast and molds in the strawberries by 2.25 and 2.01 log CFU g-1, respectively. Sensory evaluation results indicated that the combined treatment provided better sensory scores than did the control. These results suggest that postharvest treatments of either ClO2 or fumaric acid with UV-C can be useful for maintaining the quality of 'Maehyang' strawberries. © 2010 Elsevier B.V. All rights reserved.

Kim H.-C.,Chungnam National University | Kim T.-W.,Chungnam National University | Kim T.-W.,University of California at Berkeley | Kim D.-M.,Chungnam National University
Process Biochemistry | Year: 2011

Although glucose can be used as an economical and efficient energy source for driving cell-free protein synthesis, use of high concentrations of glucose can cause accumulation of organic acids, which inhibits protein synthesis through the decrease in pH of reaction mixture. In this study, instead of directly using glucose, we used soluble starch as a glucose-releasing energy reservoir molecule. When compared to previously reported methods using glucose as the primary energy source, the use of starch alleviated the problem of a pH drop, thereby allowing a prolonged cell-free protein synthesis. As a result, protein synthesis continued over 12 h in a reaction mixture employing starch as an energy source, and approximately 1.7 ± 0.1 mg/mL of the target protein accumulated in the reaction mixture. Moreover, homeostatic maintenance of the reaction conditions and controlled rate of translation led to substantially larger amounts of proteins being obtained in a soluble form. © 2011 Elsevier Ltd. All rights reserved.

Choi Y.L.,Korea Research Institute of Chemical Technology | Choi Y.L.,Korea University | Lim H.S.,Korea Research Institute of Chemical Technology | Lim H.S.,Chungnam National University | And 3 more authors.
Organic Letters | Year: 2012

A one-pot transition-metal-free, base-mediated synthesis of dibenzo[b,f]oxepins was developed. The reaction of 2-halobenzaldehydes with (2-hydroxyphenyl)acetonitriles proceeds via a sequential aldol condensation and intramolecular ether formation reaction in the presence of Cs2CO 3 and molecular sieves in toluene. © 2012 American Chemical Society.

Yan J.,Chungnam National University | Jeong Y.G.,Chungnam National University
ACS Applied Materials and Interfaces | Year: 2016

Piezoelectric nanogenerators, harvesting energy from mechanical stimuli in our living environments, hold great promise to power sustainable self-sufficient micro/nanosystems and mobile/portable electronics. BaTiO3 as a lead-free material with high piezoelectric coefficient and dielectric constant has been widely examined to realize nanogenerators, capacitors, sensors, etc. In this study, polydimethylsiloxane (PDMS)-based flexible composites including BaTiO3 nanofibers with different alignment modes were manufactured and their piezoelectric performance was examined. For the study, BaTiO3 nanofibers were prepared by an electrospinning technique utilizing a sol-gel precursor and following calcination process, and they were then aligned vertically or horizontally or randomly in PDMS matrix-based nanogenerators. The morphological structures of BaTiO3 nanofibers and their nanogenerators were analyzed by using SEM images. The crystal structures of the nanogenerators before and after poling were characterized by X-ray diffraction. The dielectric and piezoelectric properties of the nanogenerators were investigated as a function of the nanofiber alignment mode. The nanogenerator with BaTiO3 nanofibers aligned vertically in the PDMS matrix sheet achieved high piezoelectric performance of an output power of 0.1841 μW with maximum voltage of 2.67 V and current of 261.40 nA under a low mechanical stress of 0.002 MPa, in addition to a high dielectric constant of 40.23 at 100 Hz. The harvested energy could thus power a commercial LED directly or be stored into capacitors after rectification. © 2016 American Chemical Society.

Kim B.-K.,Chungnam National University | Han M.,Chungnam National University
Industrial and Engineering Chemistry Research | Year: 2012

Reactive distillation, which combines reaction and distillation in a single vessel, is receiving increasing attention because of its great potential for use in process intensification. The superposition of reaction and separation in a single processing unit can introduce new patterns of dynamic behavior such as multiplicity and oscillation. Acetic acid was effectively recovered from its dilute aqueous solution in the form of methyl acetate by reactive distillation. The reactive distillation column converting the acetic acid to the methyl acetate was highly nonlinear and showed steady-state multiplicity under certain conditions. The dynamic behavior of the column under multiple steady states was demonstrated to be well explained by nonlinear wave propagation theory. If the maximum conversion was obtained under the condition where the multiplicity appears, then a conventional control scheme could not deal with the control difficulty due to the multiplicity. A profile position control scheme based on wave propagation theory was proposed for the control of the column under multiple steady states, and the performance of the proposed controller was compared with that of conventional controllers. The proposed control scheme using profile positions as controlled variables was shown to give an excellent performance for the control of the reaction conversion and product purity in the reactive distillation. © 2012 American Chemical Society.

Yuvakkumar R.,Chungnam National University | Suresh J.,Alagappa University | Nathanael A.J.,Yeungnam University | Sundrarajan M.,Alagappa University | Hong S.I.,Chungnam National University
Materials Science and Engineering C | Year: 2014

In the present investigation, we report a sustainable novel green synthetic strategy to synthesis zinc oxide nanocrystals. This is the first report on sustainable biosynthesis of zinc oxide nanocrystals employing Nephelium lappaceum L., peel extract as a natural ligation agent. Green synthesis of zinc oxide nanocrystals was carried out via zinc-ellagate complex formation using rambutan peel wastes. The successful formation of zinc oxide nanocrystals was confirmed employing standard characterisation studies. A possible mechanism for the formation of ZnO nanocrystals with rambutan peel extract was also proposed. The prepared ZnO nanocrystals were coated on the cotton fabric and their antibacterial activity were analyzed. ZnO nanocrystals coated cotton showed good antibacterial activity towards Escherichia coli (E. coli), gram negative bacteria and Staphylococcus aureus (S. aureus), gram positive bacteria. © 2014 Elsevier B.V.

Kim H.D.,Chungnam National University | Kim G.,Chungnam National University
Tetrahedron Letters | Year: 2013

Aza-cyclization of α,β-unsaturated carbonyl moieties with free amine has been studied. An azepine alkaloid, hexahydroapoerysopine, has been synthesized from an enone-ester in a concise manner through the aza-cyclization followed by reductions. © 2012 Elsevier Ltd. All rights reserved.

Lee G.H.,Chungnam National University | Jung S.,Chungnam National University
International Journal of Advanced Robotic Systems | Year: 2013

This article presents the development and control of a two-wheeled mobile robot as the base of a human carrier for an amusement/transportation vehicle. The robot has a combined structure of two systems: a line tracking mobile robot and an inverted pendulum system that maintains balance while following a line on the floor. The mobile robot is purposely designed to carry a human operator or humanoid arms. The robot has the capability to follow the line on the floor using visual feedback, as well as maintaining its balance on two wheels. A visual servoing technique allows the robot to follow the line on the floor captured by a camera as the desired trajectory. Controllers are designed to have good line tracking and balancing performance using sensor fusion techniques. Experimental studies involving the robot following a line demonstrate the feasibility of it being an amusement vehicle. © 2013 Lee and Jung; licensee InTech.

Dung N.Q.,Chungnam National University | Patil D.,Chungnam National University | Jung H.,Chungnam National University | Kim J.,Chungnam National University | Kim D.,Chungnam National University
Sensors and Actuators, B: Chemical | Year: 2013

Porous nickel-decorated single-walled carbon nanotubes (Ni-SWCNTs) were grown on indium tin oxide (ITO)-coated glass substrate through the arc-discharge method. Oxidation followed at 400 C in the air for 2 h to synthesize the NiO-SWCNT/ITO electrode. The Ni nanoparticles distributing among the SWCNTs were oxidized to become NiO as the effective sensing probes. The surface morphology and crystalline structure of the NiO-SWCNT/ITO electrode were characterized by SEM, EDS and Raman spectroscopy. The response of the NiO-SWCNT/ITO electrode to glucose was examined using the electrochemical method. The obtained cyclic voltammograms revealed the electrocatalytic behavior of the NiO-SWCNT/ITO electrode with glucose in 0.1 M NaOH solution. The amperometric response of the NiO-SWCNT/ITO electrode to glucose was investigated at a potential of 0.5 V in 0.1 M NaOH that showed a linear range of the detection from 1 μM to 1000 μM, as well as a low detection limit of 0.3 μM and a high sensitivity at 907 μA mM-1 cm-2. © 2013 Elsevier B.V.

Lee H.-R.,Korea Institute of Machinery and Materials | Chung K.-Y.,Korea Institute of Machinery and Materials | Jhang K.-S.,Chungnam National University
Journal of Information Processing Systems | Year: 2013

Maintenance Access Hatches are used to ensure urban safety and aesthetics while facilitating the management of power lines, telecommunication lines, and gas pipes. Such facilities necessitate affordable and effective surveillance. In this paper, we propose a FiCHS (Fixed Cluster head centralized Hierarchical Static clustering) routing protocol that is suitable for underground maintenance hatches using WSN (Wireless Sensor Network) technology. FiCHS is compared with three other protocols, LEACH, LEACH-C, and a simplified LEACH, based on an ns-2 simulation. FiCHS was observed to exhibit the highest levels of power and data transfer efficiency. © 2013 KIPS.

Kang J.-G.,Chungnam National University | Jung Y.,Chungnam National University | Min B.-K.,Yeungnam University | Sohn Y.,Yeungnam University
Applied Surface Science | Year: 2014

Crystalline hexagonal phase Eu(OH)3 nanorods were prepared by a hydrothermal method, and cubic phase Eu2O3 nanorods were obtained by a post-annealing treatment, after which their physicochemical properties were fully characterized by X-ray diffraction (XRD) crystallography, scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimetry/thermogravimetric analysis (DSC/TGA), Raman, FT-IR, UV-vis absorption, photoluminescence imaging, X-ray photoelectron spectroscopy, and a temperature-programmed reduction experiment. © 2014 Elsevier B.V.

Kim I.-K.,Chungnam National University | Hong S.I.G.,Chungnam National University
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science | Year: 2013

The deformation and fracture behaviors of roll-bonded tri-layered Mg/Al/stainless steel (SST) composite plates were studied. Brittle interfacial reaction compounds were observed at the Mg/Al interface upon annealing at and above 573 K (300 C), whereas no visible interfacial reaction compounds were observed at Al/SST interfaces even after annealing up to 673 K (400 C). The strength of the tri-layered Mg/Al/SST clad plates is in close agreement with those calculated from the strength data of the separated Mg, Al, and ST layers using the rule of mixture. The fracture strain components of the tri-layered clad in the absence of brittle interfacial intermetallic layer far exceed those calculated based on the fracture strain data of separated Mg, Al, and SST sheets. The enhanced ductility of the clad composites is due to the suppression of the localized deformation in a metallic layer by other metallic layers caused by the mutual constraint imposed by an adjacent layer. On the other hand, the fracture strain was found to be reduced in the presence of intermetallic layers between the metallic substrates. Cracks perpendicular to the stress axis were observed in the intermetallic compound layer between Mg and Al, inducing the localized slip in the vicinity of intermetallic cracks and premature fracture of the Mg alloy layer. © 2013 The Minerals, Metals & Materials Society and ASM International.

Park B.J.,Philadelphia University | Choi C.-H.,Chungnam National University | Kang S.-M.,Chungnam National University | Tettey K.E.,Philadelphia University | And 2 more authors.
Soft Matter | Year: 2013

We present the behaviour of particles with chemical and geometrical anisotropy at a planar oil-water interface. We find that Janus cylinders with a small aspect ratio adopt an upright configuration, whereas the particles with a large aspect ratio exhibit both the upright and tilted configurations, which can be explained by the presence of two minima in the attachment energy profile. Such unique configurations significantly affect their assembly structure and lateral interactions. In particular, we observe strong capillary attractions between two tilted Janus cylinders and show that the scaling behaviour of the interaction depends on the lateral alignments of two cylinders. Consequently, this capillarity leads to a variety of assembled structures, which we attribute to the quasi-quadrupolar interface deformation observed around each particle. © 2013 The Royal Society of Chemistry.

Han H.,Korea Research Institute of Standards and Science | Kim B.,Korea Research Institute of Standards and Science | Lee S.G.,Korea Research Institute of Chemical Technology | Kim J.,Chungnam National University
Food Chemistry | Year: 2013

Isotope dilution-liquid chromatography/mass spectrometry (ID-LC/MS) has been established as a candidate reference method for the accurate determination of growth promoters (zeranol, taleranol, and diethylstilbesterol) in raw meat samples. Sample preparation processes including an enzymatic hydrolysis, extraction, and SPE clean-up were optimised. The sensitivity difference of trans- and cis-diethylstilbestrol (isomerizing in sample preparation processes) by the LC/MS was measured by running a trans/cis mixture (ratio measured by a quantitative NMR) with and without sample matrices, and applied for the determination of total diethylstilbestrol. Validity, repeatability, and reproducibility of the analytical method were tested by measuring gravimetrically fortified samples (chicken breast, bovine muscles, and porcine muscle) in a number of different time periods. Measurement results agreed with the fortified values within their uncertainties. The method provided accurate results of the target analytes in the range of 0.05-15 μg/kg with the relative expanded uncertainty of 2-15%. © 2013 Elsevier Ltd. All rights reserved.

Choi J.M.,Chungnam National University | Lee C.W.,North Dakota State University
Journal of Plant Nutrition | Year: 2012

The relationship between the total amount of micronutrients absorbed by the above-ground plant tissue and the occurrence of visible micronutrient deficiency symptoms in two strawberry cultivars as influenced by elevated phosphorus (P) levels in fertigation solution was investigated. The plants were cultured with a fertilizer solution containing 0, 0.5, 1, 2, 4, or 6 mM P and tissue nutrient content were determined at 120 days after transplanting. Young leaves of the plants grown with nutrient solution P levels higher than 4 mM and 2 mM, respectively, in 'Keumhyang' and 'Seonhong', developed interveinal chlorosis. Tissue concentrations (mg·kg-1 dry weight) of metallic micronutrients [iron (Fe), copper (Cu), manganese (Mn), and zinc (Zn)] in both cultivars did not decrease, but the total amount absorbed by the aboveground plant tissue decreased in the treatments in which nutrient deficiencies were observed. These results indicate that total amount of micronutrients is a better indicator of P-induced micronutrient deficiency. © 2012 Copyright Taylor and Francis Group, LLC.

Zhang T.,Chungnam National University
Nature communications | Year: 2013

Constitutive NF-κB activation in cancer cells is caused by defects in the signalling network responsible for terminating the NF-κB response. Here we report that plant homeodomain finger protein 20 (PHF20) maintains NF-κB in an active state in the nucleus by inhibiting the interaction between PP2A and p65. We show that PHF20 induces canonical NF-κB signalling by increasing the DNA-binding activity of NF-κB subunit p65. In PHF20 overexpressing cells, the termination of tumour necrosis factor-induced p65 phosphorylation is impaired whereas upstream signalling events triggered by tumour necrosis factor are unaffected. This effect strictly depends on the interaction between PHF20 and methylated lysine residues of p65, which hinders recruitment of PP2A to p65, thereby maintaining p65 in a phosphorylated state. We further show that PHF20 levels correlate with p65 phosphorylation levels in human glioma specimens. Our work identifies PHF20 as a novel regulator of NF-κB activation and suggests that elevated expression of PHF20 may drive constitutive NF-κB activation in some cancers.

Dao V.-D.,Chungnam National University | Nang L.V.,Chungnam National University | Kim E.-T.,Chungnam National University | Lee J.-K.,Korea Institute of Science and Technology | Choi H.-S.,Chungnam National University
ChemSusChem | Year: 2013

Crystal clear: Dry plasma reduction is used for continuously immobilizing platinum nanoparticles on CVD-grown graphene under atmospheric pressure without using any toxic chemicals while keeping the temperature low. The PtNPs/graphene-coated counter electrode exhibits a reasonably low charge-transfer resistance and a high optical transmittance. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hoa N.D.,Chungnam National University | An S.Y.,Chungnam National University | Dung N.Q.,Chungnam National University | Van Quy N.,Chungnam National University | Kim D.,Chungnam National University
Sensors and Actuators, B: Chemical | Year: 2010

Nanostructured CuO thin films are synthesized by deposition and thermal oxidation of Cu on SiO2 substrates. The effects of oxidation temperatures on the morphologies and crystallinity of the CuO thin films are investigated by SEM, XRD, and XPS. The electrical and hydrogen sensing properties of CuO are studied by electrical resistance measurements. In addition, the effects of carrier gases on the gas response of CuO are investigated. The results showed that Cu was oxidized into monoclinic cupric oxide in the investigated temperature range from 300 to 800 °C. The p-type semiconducting CuO thin film showed increases in electrical resistance upon exposure to hydrogen. The CuO thin film oxidized at 400 °C showed the highest response as compared to others, and it was 3.72 for 6% H2 at an operating temperature of 250 °C. The carrier gases played very important roles in the hydrogen sensing by CuO. That is, the sensor showed good response-and-recovery with a carrier gas of air but not with nitrogen. © 2010 Elsevier B.V. All rights reserved.

Jeon S.-I.,Korea Institute of Energy Research | Jeon S.-I.,Chungnam National University | Park H.-R.,Korea Institute of Energy Research | Park H.-R.,Chungnam National University | And 5 more authors.
Energy and Environmental Science | Year: 2013

A capacitive deionization process utilizing flow-electrodes (FCDI) was designed and evaluated for use in seawater desalination. The FCDI cell exhibited excellent removal efficiency (95%) with respect to an aqueous NaCl solution (salt concentration: 32.1 g L-1), demonstrating that the FCDI process could effectively overcome the limitations of typical CDI processes. © 2013 The Royal Society of Chemistry.

Nguyen C.C.,Chungnam National University | Nguyen C.C.,Hanwha Chemical Co. | Choi H.,Chungnam National University | Choi H.,Hanwha Chemical Co. | Song S.-W.,Chungnam National University
Journal of the Electrochemical Society | Year: 2013

Film model electrodes of silicon oxide (SiOx) with various oxygen content (x = 0.4, 0.85, 1.0 and 1.3) have been studied for the effects of oxygen content and interfacial reaction behavior on cycling ability. IR and XPS analyses on the origin of initial charge plateau in 1M LiPF6/EC:DEC indicate that the contribution of electrolyte reduction to the plateau is far larger than the formation of lithium silicates, lithium oxide and silicon. Higher oxygen content of SiOx induces to decrease initial electrolyte reduction, whereas larger fraction of oxides is subjected to dissolution by acid (e.g., HF)-etching. Cycling ability at higher oxygen content however is remarkably improved when constructing a surface protective siloxane network at the electrodes using silane electrolyte additive. The SiO1.0 electrode exhibits superior capacity retention of 84% at the 200th cycle delivering discharge capacity of 1206-1017 mAh/g. The SEI layer formed over surface siloxane network consists of a plenty of organic compounds and lithium carbonate, in contrast to mainly inorganic salts and organic phosphorus fluoride compounds upon cycling without silane adidtive. A better protection and passivation of electrode surface should be of the effects of siloxane network, and in that fashion cycling ability is greatly stabilized. © 2013 The Electrochemical Society. All rights reserved.

Lim H.S.,Chungnam National University
Laser Therapy | Year: 2011

Background and Aims: This study demonstrated the development of a laser system for cancer treatment with photodynamic therapy (PDT) based on a 635 nm laser diode. In order to optimize efficacy in PDT, the ideal laser system should deliver a homogeneous nondivergent light energy with a variable spot size and specific wavelength at a stable output power. Materials and Methods: We developed a digital laser beam controller using the constant current method to protect the laser diode resonator from the current spikes and other fluctuations, and electrical faults. To improve the PDT effects, the laser system should deliver stable laser energy in continuous wave (CW), burst mode and super burst mode, with variable irradiation times depending on the tumor type and condition. Results and Comments: The experimental results showed the diode laser system described herein was eminently suitable for PDT. The laser beam was homogeneous without diverging and the output power increased stably and in a linear manner from 10 mW to 1500 mW according to the increasing input current. Variation between the set and delivered output was less than 7%. Conclusions: The diode laser system developed by the author for use in PDT was compact, user-friendly, and delivered a stable and easily adjustable output power at a specific wavelength and user-set emission modes. © 2011 JMLL, Tokyo, Japan.

Kang S.K.,Chungnam National University
Acta Crystallographica Section E: Structure Reports Online | Year: 2013

In the title compound (systematic name: {[(phenylformamido)carbonyl]amino} methanethioamide), C9H9N3O2S, both benzoyl and terminal thiourea fragments adopt transoid conformations with respect to the central carbonyl O atom. The benzoyl and thiobiuret groups are almost coplanar, making a dihedral angle of 4.40 (8)°. The molecular structure is stabilized by two intramolecular N - H⋯O hydrogen bonds. In the crystal, N - H⋯O and N - H⋯S hydrogen bonds link the molecules into a tape running along [101].

Ma H.,Chungnam National University | Joo C.W.,Chungnam National University
Fibers and Polymers | Year: 2011

This study developed a novel PHB-lignin-jute biodegradable composite with preferable mechanical properties and low water absorption. The appearances of fracture surface of composites were analyzed by scanning electron microscope. The result suggested a Gaussian-like distribution of the size particles supporting the presence of lignin with a radius smaller than 0. 5 μm. According to X-ray diffraction, the presence of lignin and jute fibers was decreased the crystallization of PHB. Moreover, the glass transition temperature of PHB increased, and the endotherm during glass transition was decreased. The maximum tensile strength and modulus of composites were obtained with 30 wt% jute fiber contents and 4 wt% lignin contents. The presence of jute fibers was largely increased the water absorption of composites. However, the presence of lignin was effectively decreased the water absorption of composites at saturation levels. © 2011 The Korean Fiber Society and Springer Netherlands.

A taxonomic review of the Atheta Thomson subgenus Microdota Mulsant & Rey in Korea is presented. The subgenus is represented in Korea by 15 species including two new species, Atheta (Microdota) jangtaesanensis Lee & Ahn, sp. n. and A. (M.) pasniki Lee & Ahn, sp. n. Four species [A. (M.) kawachiensis Cameron, A. (M.) muris Sawada, A. (M.) spiniventris Bernhauer, and A. (M.) spinula (Sawada)] are new to the Korean Peninsula and two [A. (M.) formicetorum Bernhauer and A. (M.) subcrenulata Bernhauer] to South Korea. Two other species [A. (M.) kobensis Cameron and A. (M.) scrobicollis (Kraatz)] previously recorded in North Korea had been identified incorrectly. A key, descriptions, habitus photographs and illustrations of the diagnostic features are provided. Species distributions and diversity in East Asia are discussed. © Seung-Gyu Lee, Kee-Jeong Ahn.

Jeon M.-J.,Chungnam National University | Song J.-H.,National Institute of Biological Resources | Ahn K.-J.,Chungnam National University
Zoologica Scripta | Year: 2012

A phylogenetic analysis of the marine littoral genus Cafius Stephens is presented based on molecular characters. The data set comprised partial mitochondrial COI (910bp), COII (369bp), 12S rDNA (351-354bp), 16S rDNA (505-509bp) and nearly complete sequences of 18S rDNA (1814-1830bp) for 37 species. Twenty-seven Cafius species, representing five of six subgenera, two Remus Holme species, three Phucobius Sharp species, monotypic Thinocafius Steel and four outgroups were included. The sequences were analysed simultaneously by parsimony analysis in Tree Analysis Using New Technology (TNT) with traditional manual alignment, direct optimization (DO) in the program POY4 under a variety of gap costs and partitioned Bayesian analysis for the combined data. The genus Cafius and nearly all of its subgenera were not supported as being monophyletic. Instead, all analyses (parsimony trees, DO tree under equal weighting and Bayesian tree) showed monophyly of Cafius+Phucobius + Remus+Thinocafius (clade Z) and all seven nested clades (A-G). However, the phylogenetic relationships among clades A-G differed among the analyses. The genus Phucobius was recovered as a monophyletic group within Cafius. The genus Remus was not monophyletic but formed a clade with C. rufescens Sharp and C. rufifrons Bierig within Cafius. The genus Thinocafius formed a clade with C. caviceps Broun, C. litoreus (Broun) and C. quadriimpressus (White) within Cafius. We propose new concepts for the genus Cafius and its related genera, and the seven nested clades. © 2012 The Authors. Zoologica Scripta © 2012 The Norwegian Academy of Science and Letters.

Noh G.,Chungnam National University | Lee J.H.,Chungnam National University
Inflammation and Allergy - Drug Targets | Year: 2012

Food allergies are classified as IgE-mediated and non-IgE mediated type. The number of successful reports of immunotherapy, namely tolerance induction for food allergy (TIFA) are increasing, bringing hope for meaningful positive and radical treatment of food allergy. Therapeutic characteristics of the clinical course in TIFA for NFA are different from TIFA for IFA. Cytokines including IL-10, TGF-β and IFN-γ and regulatory cells such as Treg and Breg, are involved in immune tolerance. IFN-γ has been used for tolerance induction of food allergy as an immunomodulatory biologics. A definitive distinction between IgE-mediated and non-IgE-mediated food allergies is absolutely essential for diagnostic and therapeutic purposes. Original SOTI using IFN-γ is more effective then conventional SOTI without IFN-γ. Especially, IFN-γ is absolutely necessary for the tolerance induction of NFA. This review highlights and updates the advances in the conceptual immunological background and the clinical characteristics of oral tolerance induction for food allergy. © 2012 Bentham Science Publishers.

Noh G.,Chungnam National University | Lee J.H.,Chungnam National University
Inflammation and Allergy - Drug Targets | Year: 2012

Atopic dermatitis is an allergic inflammatory skin disease that is characterized by late eczematous skin lesions which result from non-IgE-mediated immune responses. It is well known that food allergy is an important cause of atopic dermatitis. Moreover, with recent advances in the diagnosis and treatment of food allergy, it becomes possible to elucidate the role of IgE- and non-IgE-mediated food allergies. Interprerations for blood eosinophil counts and total serum IgE levels are updated based on the immunopathogenesis of AD relating with these IgE- and non-IgE-mediated food allergies. The clinical significances of skin prick test and allergen-specific IgE are re-evaluated according to the out-to in and in-to out sensitization. Atopic march is reconsturcted by the sequential sensitization of foods and aeroallergens. In this review, the revized immunopathogenesis and relevant interpretations of food allergy in atopic dermatitis are described for the evaluation of precise clinical status of AD. © 2012 Bentham Science Publishers.

Noh G.,Chungnam National University | Lee J.H.,Chungnam National University
Recent Patents on Inflammation and Allergy Drug Discovery | Year: 2012

Atopic dermatitis is an immunologic disease that results in allergic inflammations of the skin. Cytokines are involved in the negative regulation of immunopathogenesis of atopic dermatitis. Negative immune regulation is also achieved by immune cells in addition to cytokines which are subsequently regulated by a counter-regulatory mechanism. Allergen tolerance is an important aspect of the treatment of atopic dermatitis. Recently, the IL-27, IL-21, and IL-10 cytokines were found to be important components of the counter regulatory mechanism that terminates immune response, and protects the host from excessive immune responses. IL-10 and TGF-β are well-known to be involved in the immune tolerance. IL-10 and IFN-γ are promising cytokines with respect to the prevention of allergen sensitization and the induction of allergen-specific tolerance. In particular, IFN-γ has unique tolerogenic effects with respect to pre-sensitized allergens, especially in atopic dermatitis. In this review, the role of cytokines in the immune tolerance and relevant patents are reviewed, and therapeutic strategies are presented based on the immunologic architecture of AD. © 2012 Bentham Science Publishers.

Kim D.,Chungnam National University | Lee T.S.,Chungnam National University
Chemical Communications | Year: 2014

A highly sensitive and selective detection of thrombin is accomplished using an emission color-tunable conjugated polyelectrolyte. The implementation of a combined logic gate is realized upon emission modulation of the system including the polymer, fibrinogen, thrombin, and heparin. This journal is © the Partner Organisations 2014.

Kim M.Y.,Chungnam National University
Journal of medicinal food | Year: 2010

The beneficial effect of Spirulina (Spirulina platensis) on tissue lipid peroxidation and oxidative DNA damage was tested in the hypercholesterolemic New Zealand White rabbit model. After hypercholesterolemia was induced by feeding a high cholesterol (0.5%) diet (HCD) for 4 weeks, then HCD supplemented with 1% or 5% Spirulina (SP1 or SP5, respectively) was provided for an additional 8 weeks. Spirulina supplementation significantly reduced the increased lipid peroxidation level in HCD-fed rabbits, and levels recovered to control values. Oxidative stress biomarkers such as glutathione, glutathione peroxidase, glutathione reductase, and glutathione S-transferase were significantly improved in the liver and red blood cells of rabbits fed SP1. Furthermore, SP5 induced antioxidant enzyme activity by 3.1-fold for glutathione, 2.5-fold for glutathione peroxidase, 2.7-fold for glutathione reductase, and 2.3-fold for glutathione S-transferase in liver, compared to the HCD group. DNA damage in lymphocytes was significantly reduced in both the SP1 and SP5 groups, based on the comet assay. Findings from the present study suggest that dietary supplementation with Spirulina may be useful to protect the cells from lipid peroxidation and oxidative DNA damage.

Cha S.M.,Chungnam National University
Journal of Pediatric Orthopaedics Part B | Year: 2015

Solitary osteochondromas originating from the carpal bones are very uncommon; when they occur, they usually arise from the scaphoid or capitate. We report a solitary, unilobed osteochondroma arising from the hamate that was excised, with no evidence of recurrence at the 3-year follow-up. Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.

Kim H.,Chungnam National University | Rao B.A.,Chungnam National University | Son Y.-A.,Chungnam National University
Fibers and Polymers | Year: 2013

The novel pyrene based dye sensor was designed and synthesized through the reaction between pyrene-1-carboxaldehyde and 4-phenylthiosemicarbazide. This dye sensor showed selectivity and sensitivity binding properties toward F- ion with showing absorption and emission changes in DMSO. These optical properties were investigated by using UV-vis spectrometer and emission spectrophotometer. In addition, electron distributions and HOMO/LUMO values of this dye sensor were simulated and calculated with theoretical calculations of Material Studio 4.3. © 2013 The Korean Fiber Society and Springer Science+Business Media Dordrecht.

Roh J.-L.,University of Ulsan | Kim J.-M.,Chungnam National University | Park C.I.,Chungnam National University
Annals of Surgical Oncology | Year: 2011

Background: Although subclinical cervical lymph node (LN) metastases in papillary thyroid carcinoma (PTC) are common, the efficacy of prophylactic central LN dissection (CLND) is unclear. Few prospective studies have assessed the relationships between complete pathologic information regarding tumors and metastatic nodes in the central compartment. We therefore investigated the pattern and predictive indicators of central LN metastasis, morbidity, and recurrence in patients who underwent total thyroidectomy and prophylactic CLND for unilateral PTC and clinically node-negative neck (cN0) disease. Methods: This prospective study involved 184 patients with previously untreated unilateral PTC and cN0 who underwent total thyroidectomy and bilateral CLND. Nodal samples were divided into the prelaryngeal/pretracheal and ipsilateral and contralateral paratracheal regions, with each assessed for clinicopathologic predictors of central metastases. Postoperative morbidity and recurrence were assessed. Results: Rates of metastasis to ipsilateral and contralateral central compartments were 42.9 and 9.8%, respectively. Multivariate analysis showed that tumor size >1 cm and extrathyroidal extension were independent predictors of ipsilateral metastasis, and ipsilateral metastases independently predicted contralateral metastases (P < 0.05 each). Permanent hypoparathyroidism and incidental recurrent nerve paralysis were found in 1.6 and 0% of patients, respectively. After a mean follow-up of 46 months, none of these patients had recurrence in the central compartment. Conclusions: Subclinical metastases are highly prevalent in the ipsilateral central neck of patients with PTC >1 cm. Contralateral central metastases, although uncommon, are associated with ipsilateral central metastases. These findings may guide the necessity and extent of prophylactic bilateral or unilateral CLND. © 2011 Society of Surgical Oncology.

Bae J.,Chungnam National University | Kim S.,University of Seoul
Queueing Systems | Year: 2010

We consider a G/M/1 queue in which the patience time of the customers is constant. The stationary distribution of the workload of the server, or the virtual waiting time, is derived by the level crossing argument. To this end, we obtain the expected downcrossings of a level in the workload process during a busy cycle and then the expected length of a busy cycle. For both the expectations, we use the dual property between the M/G/1 and G/M/1 queue. © 2010 Springer Science+Business Media, LLC.

Lee J.H.,Chungnam National University | Noh G.,Pyeongtaek International Hospital
Cytokine | Year: 2013

Background: AD patients exhibit sensitisation to multiple allergens due to a Th1/Th2 imbalance. Until now, it was impossible to improve the polysensitised status and elevated serum total IgE levels. In this study, the effects of IFN-gamma on systemic polysensitisation to multiple allergens and on serum total IgE levels are investigated. Methods: A total of 44 AD patients whose food allergies were completely controlled and who were polysensitised to multiple allergens according to the SPT were selected. Twenty-two of these patients received IFN-gamma therapy twice a week for 2. months, and 22 patients did not receive this therapy. The blood eosinophil % and serum total IgE levels were assessed, and a skin prick test for 51 allergens was performed before and after the IFN-gamma therapy. Results: With IFN-gamma therapy, the polysensitisation status was improved, as demonstrated by a decrease in the positive allergen count and skin reactivity (systemic polydesensitisation). The improvement in the polysensitised status was accompanied by a decrease in serum total IgE levels. The change in serum total IgE levels was significantly correlated with the change in polysensitisation status. Conclusions: IFN-gamma therapy resulted in systemic polydesensitisation with reduced levels of serum total IgE. IFN-gamma is indicated in AD patients with high serum total IgE levels whose food allergies are well controlled and who are polysensitised to multiple allergens. © 2013 Elsevier Ltd.

Park Y.-W.,Chungnam National University | Jung H.-J.,Chungnam National University | Yoon S.-G.,Chungnam National University
Sensors and Actuators, B: Chemical | Year: 2011

Single crystalline Bi2O3 nanowires were prepared by annealing in oxygen ambient using pure Bi nanowires grown at a low vacuum (∼10-6 Torr) with Bi-Al co-sputtered films. The ability to grow Bi nanowires using Bi-Al co-sputtered films can be attributed to the suppression of the oxidation of the bismuth by the preferred oxidation of aluminum in co-sputtered ambient (∼mTorr). The Bi nanowires from the Bi-Al co-sputtered films could be grown even at the low temperature of 230 °C in low-vacuum ambient. The Bi2O3 nanowires prepared from the Bi nanowires showed a single crystalline structure with (1 1 1), (1̄22), (1 2 0), and (0 1 2) planes. The current-voltage (I-V) relationship of the Bi 2O3 nanowire revealed that the Bi2O3 nanowire exhibited a semiconducting property with a resistivity of 14.6 Ω-cm. Variations in resistance of the Bi2O3 single nanowire as a function of time at 350 °C showed reproducible response and recovery time characteristics for each concentration of NO. The electric resistance of the Bi2O3 single nanowire was sensitive to NO gas even at 10 ppm. © 2011 Elsevier B.V. All Rights Reserved.

Choi S.-Y.,Chungbuk National University | Yun J.,Korea Research Institute of Bioscience and Biotechnology | Lee O.-J.,Chungbuk National University | Han H.-S.,Chungbuk National University | And 3 more authors.
Placenta | Year: 2013

Introduction Preeclampsia (PE) is a leading cause of maternal and neonatal mortality and morbidity worldwide. However, the pathophysiology of this disease is not yet fully understood. MiRNA plays an important role in post-transcriptional gene regulation. Recent studies have suggested that dysregulation of miRNAs in placental tissue is involved in the pathogenesis of PE. Therefore, we investigated miRNA profiles in PE placenta to understand the miRNA function in PE pathogenesis. Methods MiRNA profiling was performed in 20 formalin-fixed and paraffin-embedded samples (10 placentas from severe PE and 10 from a control group). We used a hybridization-based microarray with a PNA-probe comprised of 158 miRNAs. Results Thirteen miRNAs (miR-92b, miR-197, miR-342-3p, miR-296-5p, miR-26b, miR-25, miR-296-3p, miR-26a, miR-198, miR-202, miR-191, miR-95, and miR-204) were significantly overexpressed and two miRNAs (miR-21 and miR-223) were underexpressed in PE compared with the control group. Among 15 differentially expressed miRNAs, miR-26b, miR-296-5p, and miR-223 were found to be consistent with results from previous studies. We identified 893 genes that were predicted by at least three of four computational algorithms. Target genes participated in several signaling pathways, adherens junction, focal adhesion, and regulation of the actin cytoskeleton. Conclusions Several miRNAs are found to be dysregulated in placentas of PE patients and they seem to be closely associated with the early pathogenesis of PE. Further study is necessary to develop tools for early detection and management. © 2013 Elsevier Ltd. All rights reserved.

Yu C.,Chungnam National University
Cell Death and Differentiation | Year: 2016

Cumulative damage caused by oxidative stress results in diverse pathological conditions. Therefore, elucidating the molecular mechanisms underlying cell death following oxidative stress is important. Here, we describe a novel role for Fas-associated factor 1 (FAF1) as a crucial regulator of necrotic cell death elicited by hydrogen peroxide. Upon oxidative insult, FAF1 translocated from the cytoplasm to the nucleus and promoted the catalytic activation of poly(ADP-ribose) polymerase 1 (PARP1) through physical interaction. Moreover, FAF1 depletion prevented PARP1-linked downstream events involved in the triggering of cell death, including energetic collapse, mitochondrial depolarization and nuclear translocation of apoptosis-inducing factor (AIF), implying that FAF1 has a key role in PARP1-dependent necrosis in response to oxidative stress. We further investigated whether FAF1 might contribute to the pathogenesis of Parkinson’s disease through excessive PARP1 activation. Indeed, the overexpression of FAF1 using a recombinant adeno-associated virus system in the mouse ventral midbrain promoted PARP1 activation and dopaminergic neurodegeneration in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of Parkinson’s disease. Collectively, our data demonstrate the presence of an FAF1–PARP1 axis that is involved in oxidative stress-induced necrosis and in the pathology of Parkinson’s disease.Cell Death and Differentiation advance online publication, 23 September 2016; doi:10.1038/cdd.2016.99. © 2016 Macmillan Publishers Limited, part of Springer Nature.

Park M.,Chungnam National University
IFMBE Proceedings | Year: 2013

Purpose: The purpose of this study were to apply rough set model to nursing knowledge discovery process. Method: Data mining based on rough set model was conducted on a large clinical data set containing Nursing Minimum Data Set elements. Randomized patient data were selected from Uniform Hospital Discharge Data which had the frequently used nursing diagnoses. Patient and care characteristics including nursing diagnoses, interventions and outcomes were analyzed to derive the decision rules. Results: Number of comorbidity, marital status, nursing diagnosis related to risk for infection and nursing intervention related to infection protection, and discharge status were the predictors to determine the length of stay. Age, impaired skin integrity, pain, and discharge status were identified as valuable predictors for nursing outcome, relived pain. Age, pain, potential for infection, marital status, and primary disease were identified as important predictors for mortality. Conclusion: This study demonstrated the utilization of Rough Set Model through a large data set with standardized language format to identify the contribution of specific care to patient's health. © 2013 IFMBE.

Kang Y.,Chungnam National University | Kang Y.,Johns Hopkins University | Rey S.-C.,Chungnam National University | Bianchi L.,Johns Hopkins University | And 3 more authors.
Astrophysical Journal, Supplement Series | Year: 2012

We present a comprehensive catalog of 700 confirmed star clusters in the field of M31 compiled from three major existing catalogs. We detect 418 and 257star clusters in Galaxy Evolution Explorer near-ultraviolet and far-ultraviolet (FUV) imaging, respectively. Our final catalog includes photometry of star clusters in up to 16 passbands ranging from FUV to NIR as well as ancillary information such as reddening, metallicity, and radial velocities. In particular, this is the most extensive and updated catalog of UV-integrated photometry for M31star clusters. Ages and masses of star clusters are derived by fitting the multi-band photometry with model spectral energy distribution (SED); UV photometry enables more accurate age estimation of young clusters. Our catalog includes 182 young clusters with ages less than 1Gyr. Our estimated ages and masses of young clusters are in good agreement with previously determined values in the literature. The mean age and mass of young clusters are about 300Myr and 10 4 M ⊙, respectively. We found that the compiled [Fe/H] values of young clusters included in our catalog are systematically lower (by more than 1dex) than those from recent high-quality spectroscopic data and our SED-fitting result. We confirm that most of the young clusters' kinematics shows systematic rotation around the minor axis and association with the thin disk of M31. The young cluster distribution exhibits a distinct peak in the M31 disk around 10-12kpc from the center and follows a spatial distributions similar to other tracers of disk structure such as OBstars, UVstar-forming regions, and dust. Some young clusters also show concentration around the ring splitting regions found in the southern part of the M31 disk and most of them have systematically younger (<100Myr) ages. Considering the kinematical properties and spatial distribution of young clusters, they might be associated with the well-known 10kpc star formation ring structure in the M31 disk. Consequently, we suggest that various properties of young clusters in M31 might be in line with the scenarios that a satellite galaxy had passed through the disk of M31 less than few hundred million years ago. © © 2012. The American Astronomical Society. All rights reserved.

E-cadherin and β-catenin are molecules that mediate cell-cell adhesion in normal epithelium. Aberrant expression of these adhesion molecules results in the loss of intercellular adhesion, with possible cell transformation and tumour progression. We determined the role of E-cadherin and β-catenin in the pathogenesis of sinonasal inverted papilloma (IP) and its malignant transformation. We determined the expression of E-cadherin and β-catenin by immunohistochemistry in paraffin-embedded tissue of 21 subjects with nasal polyps, 56 with IPs, 7 IPs with dysplasia and 18 IPs with squamous cell carcinoma (SCC). The clinicopathological variables of the IPs with SCC correlated with the degree of expression of E-cadherin and β-catenin. The degree of expression of E-cadherin and β-catenin in the cell membrane was significantly lower in IPs with SCC than in nasal polyps and IPs. The degree of expression of β-catenin was significantly lower in IPs with SCC with a malignant proportion > 50% compared to a malignant proportion ≤ 50%. However, there was no significant association between the degree of expression of E-cadherin and β-catenin and clinicopathological variables, such as age, gender, T stage, tumour differentiation, or SCC type (metachronous vs. synchronous). In addition, there was no significant relationship between recurrence or survival rate in IPs with SCC and the degree of expression of E-cadherin or β-catenin in the cell membrane or nuclear β-catenin. Decreased expression of E-cadherin and β-catenin in the cell membrane may be associated with carcinogenesis of IPs and help predict malignant transformation in sinonasal IPs.

Kim K.C.,Chungnam National University | Shin H.D.,Chungnam National University | Cha S.M.,Chungnam National University | Park J.Y.,Chungnam National University
American Journal of Sports Medicine | Year: 2014

Background: A few studies have compared high-grade partial-thickness articular- and bursal-side rotator cuff tears postoperatively. Purpose: To compare the clinical and radiological outcomes of high-grade partial-thickness rotator cuff tears treated with arthroscopic conversion to full-thickness tears, followed by repair. Study Design: Cohort study; Level of evidence, 3. Methods: Forty-three consecutive shoulders with high-grade partial-thickness rotator cuff tears (20 articular- and 23 bursal-side lesions) treated with arthroscopic conversion to full-thickness tears, followed by repair using the suture-bridge technique, were evaluated. The final functional evaluation was conducted at a mean of 35.53 months (range, 24-54 months). Radiological outcomes were evaluated at a minimum of 1 year postoperatively. The following outcome measures were used in this study: the American Shoulder and Elbow Surgeons (ASES) score, the University of California, Los Angeles (UCLA) Shoulder Rating Scale, the Constant score, and range of motion. Results: At the final follow-up, the mean ASES, UCLA, and Constant scores improved significantly to 91.80, 32.70, and 75.85, respectively, in the articular-side group (all P < .001). The mean ASES, UCLA, and Constant scores improved significantly to 90.80, 32.52, and 83.00, respectively, in the bursal-side group (all P<.001). The UCLA and ASES scores did not differ significantly between the 2 groups (P = .821 and .869, respectively), while the Constant scores did (P = .048). The retear rate was 0% in the articular-side group and 9.5% in the bursal-side group; this difference was not significant (P = .204). Conclusion: The arthroscopic repair of partial-thickness bursal-side tears resulted in comparable or superior postoperative functional outcomes compared with that of articular-side tears. However, the postoperative retear rate did not differ significantly between the 2 groups. © 2013 The Author(s).

Kim N.K.,Chungnam National University | Choi S.H.,Chungnam National University
Lithos | Year: 2016

To constrain the source and tectonomagmatic processes that gave rise to the Andong Ultramafic Complex (AUC) in South Korea, we determined the clinopyroxene Sr–Nd–Hf–Pb isotope and trace element compositions as well as the whole-rock and mineral compositions for the Late Triassic (ca. 222 Ma) ultramafic rocks from the complex. They are composed of dunites, wehrlites, pyroxene/hornblende peridotites, and pyroxenites. The constituent minerals are olivines, diopsides/augites, bronzites, calcic-amphiboles, and spinels. Clinopyroxenes exhibit a convex-upward rare earth element (REE) pattern, with an apex at Sm. The whole-rock compositions plot away from the residual mantle peridotite trends, with variable but lower Al2O3 and SiO2 contents, and higher CaO, FeO*, and TiO2 contents at a given value of MgO. Estimated equilibrium temperatures for the AUC rocks range from 420 to 780 °C. These observations, together with the absence of reaction or melt impregnation textures, indicate that the AUC ultramafic rocks are magmatic cumulates emplaced within the crust rather than residual mantle or mantle-melt reaction products. The AUC clinopyroxenes have compositions intermediate between the oceanic island basalt- and arc basalt-related cumulate clinopyroxenes. The AUC spinels have lower Cr#s than the arc-related magmatic cumulate spinels. They plot within the field for spinels from mid-ocean ridge basalts (MORB) on a TiO2 vs. Cr# diagram. However, the AUC clinopyroxenes have much more radiogenic Sr ([87Sr/86Sr]i = 0.70554 to 0.70596), unradiogenic Nd ([εNd]i = − 1.0 to − 0.3), and Hf ([εHf]i = + 4.4 to + 6.6) isotopic compositions than those of the MORB or fore-arc basalts (FAB). In the Sr–Nd isotopic correlation diagram, the AUC clinopyroxenes plot in the enriched extension of the “mantle array”. They also have more elevated 207Pb/204Pb ratios at a given 206Pb/204Pb than those of the MORB or FAB. In the Nd-Hf isotope space, the AUC clinopyroxenes have somewhat elevated 176Hf/177Hf ratios at a given 143Nd/144Nd compared to the “mantle–crust” array. These observations indicate that the sub-continental lithospheric mantle (SCLM) overprinted by secondary volatile-rich silicate melts might be the principal source of the AUC magmatism. Heat from the upwelling asthenosphere, through the slab window produced by detachment of the oceanic slab from the buoyant continental lithosphere during continental collision between the North and South China Cratons, might lead to partial melting of the overlying metasomatized SCLM, resulting in the post-collisional Triassic magmatism in South Korea. © 2016 Elsevier B.V.

Jeong Y.G.,Chungnam National University | An J.-E.,H&SHighTech Corporation
Macromolecular Research | Year: 2014

UV-cured epoxy hybrid composite films were manufactured by efficient and facile cationic photochemical polymerization of 3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexane carboxylate mixtures including 5.0 wt% carbon nanofillers of different graphene/multi-walled carbon nanotube (MWCNT) compositions of 10/0, 9/1, 7/3, 5/5, 3/7, and 0/10 by weight ratio. TEM images confirmed that the mixed carbon nanofillers of graphene and MWCNT were well dispersed in the UV-cured epoxy matrix, while MWCNT as a single carbon nanofiller component was aggregated in the matrix. The electrical resistivity of the composite films was thus varied with the increment of the relative MWCNT content in 5.0 wt% carbon nanofillers, i.e., ∼160 Ωcm for the epoxy/graphene composite film, 30∼80 Ωcm for the epoxy/graphene/MWCNT composite films, and ∼16,200 Ωcm for the epoxy/MWCNT composite film. The decreased electrical resistivity of the epoxy/graphene/MWCNT composite films was associated with the interconnected network formation of graphene sheets and MWCNTs. Thus the UV-cured epoxy/graphene and epoxy/graphene/MWCNT composite films exhibited excellent electric heating performance in terms of rapid temperature response, stable maximum temperature, and high electric power efficiency. In addition, the UV-cured epoxy hybrid composite films as electric heating materials were found to be thermally stable up to ∼290 °C.[Figure not available: see fulltext.]. © 2014, The Polymer Society of Korea and Springer Sciene+Business Media Dordrecht.

Yuvakkumar R.,Chungnam National University | Nathanael A.J.,Yeungnam University | Hong S.I.,Chungnam National University
RSC Advances | Year: 2014

Sustainable new insights into the development of Co3O4 as a natural litigation agent via cobalt-ellagate complex formation were revealed using Nephelium lappaceum L. peel-waste resources. Suggestive cell (3T3) suffering was more obvious at 500 μg ml-1 Co3O4 dosages, with a decrease in cell viability of ∼30%. This material is a potentially suitable candidate for applications in biomedicine and sustainable materials development. © 2014 the Partner Organisations.

Bianchi L.,Johns Hopkins University | Efremova B.,Sigma Space Corporation | Hodge P.,University of Washington | Kang Y.,Johns Hopkins University | Kang Y.,Chungnam National University
Astronomical Journal | Year: 2012

We studied the young stellar populations of 22 star-forming regions in the Andromeda galaxy (M31), with Hubble Space Telescope (HST) multi-band imaging from far-UV to I. The regions were selected from Galaxy Evolution Explorer (GALEX) wide-field far-UV imaging; they sample different environments and galactocentric distances from 6 to 22kpc. They were imaged with 30 HST fields (360 distinct images, in six bandpasses), with a pixel scale of 0.38pc projected on the sky, at the distance of M31. This study is part of HST treasury survey program HST-GO-11079, which includes star-forming regions in eight Local Group galaxies. We provide a merged catalog of six-band stellar photometry in the 30 M31 fields, containing 118,036 sources brighter than V and B ∼ 23mag. Each HST field covers about 0.3kpc 2 in M31, and contains up to ∼7000 stars, of which the number varies by a factor of >7 among the target regions; a large fraction of the sample are hot massive stars, due to our choice of filters and exposures. We derived stellar physical parameters and interstellar extinction for individual sources by spectral energy distribution analysis with model-atmosphere colors, and used the results to infer ages, massive stars content, and extinction of the star-forming regions. Reddening is up to E(B - V) ≲ 0.6mag in some OB associations, and lowest in the outermost regions (average of ≲0.12mag in OB184 at 21.9kpc). We examined the spatial distribution (clustering) of the hot massive stars, and defined OB associations on various spatial scales from compact to wider, more spread out ones. A hierarchical structuring is observed, with small compact groups arranged within large complexes. Their areas vary from less than 10 to 10 5pc 2, and masses are up to 10 5 M ⊙, in the scales sampled by our analysis. Their cumulative mass distribution follows a power law, at least in part of the sampled regime. Hot-star counts in the young regions compare very well with integrated measurements of UV flux from GALEX. © 2012. The American Astronomical Society. All rights reserved.

You Y.,Chungnam National University
The American journal of emergency medicine | Year: 2012

Intravenous fat emulsion (IFE) therapy is an adjunct therapy administered to hemodynamically compromised patients with glyphosate-surfactant intoxication when they respond poorly to conventional therapies such as fluid resuscitation or vasopressors [1,2]. However, the use of IFE as an adjunct therapy in collapsed patients with glyphosate intoxication has not been reported previously. Here, we describe the case of a patient with glyphosate-surfactant-induced cardiovascular collapse who responded to IFE.

Lee S.,Chungnam National University | Kwag J.,Chungnam National University | Lee H.,Chungnam National University | Jo Y.,Chungnam National University | Kim J.Y.,Chungnam National University
Retina | Year: 2013

PURPOSE:: To investigate longitudinal changes in retinal nerve fiber layer (RNFL) thickness after panretinal photocoagulation (PRP) in diabetic retinopathy patients. METHODS:: This prospective study examined 31 eyes in 25 patients undergoing PRP, who were diagnosed with severe nonproliferative diabetic retinopathy or non-high-risk proliferative diabetic retinopathy. Optical coherence tomography was conducted before PRP and at 3, 6, 12, and 24 months after PRP to investigate changes in peripapillary RNFL thickness. RESULTS:: Superior, nasal, inferior, temporal, and mean peripapillary RNFL thickness increased until 6 months after PRP and then decreased. Superior RNFL thickness increased significantly at 3 and 6 months and decreased significantly at 24 months compared with the baseline RNFL thickness. Nasal RNFL thickness declined significantly at 24 months compared with the baseline RNFL thickness without any significant increase in thickness during the follow-up period. Inferior RNFL thickness increased significantly at 6 months and decreased significantly at 24 months compared with its baseline RNFL thickness. Temporal thickness increased significantly at 3, 6, 12, and 24 months compared with the baseline RNFL thickness. Mean RNFL thickness increased significantly at 6 months and decreased significantly at 24 months. Central subfield thickness increased significantly at 3, 6, 12, and 24 months compared with its baseline thickness. CONCLUSION:: Peripapillary RNFL thickness increased at 6 months after PRP and then decreased at 24 months after PRP compared with baseline peripapillary RNFL thickness in diabetic retinopathy patients. This finding suggests that in addition to diabetes itself, diabetic retinopathy, and associated glaucoma, PRP may be a cause of RNFL thickness loss in patients with diabetes.

Park S.-J.,Chungnam National University | Hwang I.-C.,Chungnam National University | Shin S.-H.,Chungnam National University
Journal of Chemical and Engineering Data | Year: 2014

The ternary liquid-liquid equilibria (LLE) at atmospheric pressure of the following systems have been studied at several temperatures in stirred, thermo-regulated cells: water + anisole + methyl phenyl carbonate (MPC) at 308.15 K, water + methanol + MPC at 308.15 K, water + dimethyl carbonate (DMC) + MPC at 308.15 K, water + phenol + MPC at 318.15 K, and water + diphenyl carbonate (DPC) + MPC at 358.15 K. The experimental ternary LLE data have been satisfactorily correlated with the well-known two activity coefficient models: the Non-Random Two-Liquid (NRTL) and UNIversal QUAsiChemical (UNIQUAC). In addition, the distribution coefficients and the selectivity values of MPC for anisole, methanol, DMC, phenol, and DPC were derived from the tie-line data. © 2014 American Chemical Society.

Jeong L.,Chungnam National University | Park W.H.,Chungnam National University
International Journal of Molecular Sciences | Year: 2014

Ag nanoparticles (NPs) were synthesized in formic acid aqueous solutions through chemical reduction. Formic acid was used for a reducing agent of Ag precursor and solvent of gelatin. Silver acetate, silver tetrafluoroborate, silver nitrate, and silver phosphate were used as Ag precursors. Ag+ ions were reduced into Ag NPs by formic acid. The formation of Ag NPs was characterized by a UV-Vis spectrophotometer. Ag NPs were quickly generated within a few minutes in silver nitrate (AgNO3)/formic acid solution. As the water content of formic acid aqueous solution increased, more Ag NPs were generated, at a higher rate and with greater size. When gelatin was added to the AgNO3/formic acid solution, the Ag NPs were stabilized, resulting in smaller particles. Moreover, gelatin limits further aggregation of Ag NPs, which were effectively dispersed in solution. The amount of Ag NPs formed increased with increasing concentration of AgNO3 and aging time. Gelatin nanofibers containing Ag NPs were fabricated by electrospinning. The average diameters of gelatin nanofibers were 166.52 ± 32.72 nm, but these decreased with the addition of AgNO3. The average diameters of the Ag NPs in gelatin nanofibers ranged between 13 and 25 nm, which was confirmed by transmission electron microscopy (TEM). © 2014 by the authors; licensee MDPI, Basel, Switzerland.

Bui V.-T.,Chungnam National University | Ko S.H.,U.S. National Institute of Standards and Technology | Choi H.-S.,Chungnam National University
Chemical Communications | Year: 2014

Thin films of bio-compatible poly(lactic acid) with highly ordered hexagonal patterns were successfully fabricated under normal ambient conditions without using any surfactant via an improved phase separation method. The patterned surface was successfully applied to fabricate silicon/copper dome-patterned electrodes for high-performance hybrid capacitors. This journal is © the Partner Organisations 2014.

Song S.-M.,Chungnam National University | Kim I.H.,Chungnam National University
Korean Journal of Chemical Engineering | Year: 2013

Separation of immunoglobulin Y (IgY) from hen eggs is an interesting topic for investigating antibody purification. Understanding of IgY separation by chromatography is necessary to prepare antibody. IgY preparation in SMB was simulated by Aspen chromatography and was experimented by assembling a 3-zone simulated moving bed (SMB). With change of stream flow rates, the SMB performance was studied. Simulation of IgY batch HPLC chromatography was also done and confirmed by HPLC experiments. Based on these, good operating conditions of SMB chromatography were determined. Three-zone SMB equipment was set up by connecting three C18-HPLC columns, four HPLC pumps, and six multiposition valves. Batch chromatography of IgY was conducted to determine the isotherms of IgY and contaminating impurity. The outlet streams of SMB, raffinate and extract were sampled and analyzed by analytical HPLC system. The adsorption isotherms of IgY and impurity were determined as HIgY=0.1 and Himpure=1.1. The highest experimental purity of IgY from SMB was obtained as 98% for the operating parameters of Qfeed=0.2mL/min, Qdesorbent=0.31 mL/min, Qextract=0.2 mL/min, Qraffinate=0.3 mL/min, and switching time=8.47 min. © 2013 Korean Institute of Chemical Engineers, Seoul, Korea.

Song N.-B.,Chungnam National University | Jo W.-S.,Chungnam National University | Song H.-Y.,Chungnam National University | Chung K.-S.,Korea Research Institute of Bioscience and Biotechnology | And 2 more authors.
Food Hydrocolloids | Year: 2013

To prepare chicken feather protein (CFP)/nano-clay composite films and to evaluate the effects of various plasticizers and nano-clay concentrations on the mechanical properties of the films, CFP composite films with various concentrations of Cloisite Na+ were prepared, and their physical properties such as tensile strength (TS), elongation at break (E), and water vapor permeability (WVP) were investigated. Optimal CFP films were formed with 5 g of CFP, 0.5 g of glycerol, and 1.5 g of sorbitol in 100 mL of film-forming solution; the TS, E, and WVP of the film were 4.74 MPa, 10.08%, and 3.11 × 10-9 g m/m2 s Pa, respectively. After the nano-clay was incorporated into the CFP film-forming solution, scanning electron microscopy and X-ray diffraction studies were conducted to examine the structural characteristics of the CFP/nano-clay composite films. The incorporation of nano-clay improved the physical properties of the CFP films. The TS of the CFP/nano-clay composite film containing 7% Cloisite Na+ increased by 1.21 MPa, and the WVP of the composite film decreased by 1.15 × 10-9 g m/m2 s Pa compared to the CFP film. Therefore, these results suggest that CFP composite films can be prepared with improved mechanical property by the addition of nano-clay and used as a food packaging material in the food industry. © 2012 Elsevier Ltd.

Jung S.,Chungnam National University
Journal of Intelligent and Robotic Systems: Theory and Applications | Year: 2014

This article presents the contact force control approach for a quad-rotor system to perform tasks of interacting with the environment. The hovering capability of the quad-rotor system allows the force in the altitude direction to be regulated by realizing the impedance function. To obtain the better force control performance, inherent and external disturbances to the quad-rotor system are suppressed by designing the acceleration-based disturbance observer (AbDOB). Force tracking impedance control is applied to regulate the contact force to the environment. Simulation studies of force tracking control for changing a light bulb on the ceiling are performed to evaluate the feasibility of the proposed force control task for a quad-rotor system. © Springer Science+Business Media Dordrecht 2013.

Park C.H.,Chungnam National University
Signal Processing | Year: 2014

Query by humming (QBH) is to retrieve songs in the music database by using user's humming. In QBH, the huge size of a song database requires an efficient search method. Recently, local sensitive hashing (LSH) has been applied in QBH and showed its superior performance. In this paper, we propose a method for QBH which uses multiple spectral hashing (MSH) and scaled open-end dynamic time warping (SOEDTW). We construct multiple binary embedding spaces by utilizing eigenvectors obtained from spectral hashing, so we call this approach as multiple spectral hashing (MSH). We also apply an improved OEDTW method for similarity matching. The experimental results demonstrate that the proposed method can improve retrieval performance greatly. © 2014 Elsevier B.V. All rights reserved.

Kim K.C.,Chungnam National University | Shin H.D.,Chungnam National University | Lee W.Y.,Chungnam National University | Han S.C.,Chungnam National University
American Journal of Sports Medicine | Year: 2012

Background: Only a few studies have examined repair integrity and functional outcome after arthroscopic suture-bridge rotator cuff repair procedure. In addition, no reported study has compared outcomes between the suture-bridge and double-row techniques.Purpose: This study compared the functional outcome and repair integrity of arthroscopic double-row and conventional suture-bridge repair in full-thickness rotator cuff tears.Study Design: Cohort study; Level of evidence, 2.Methods: Fifty-two consecutive full-thickness rotator cuff tears with 1 to 4 cm of anterior to posterior dimension that underwent arthroscopic rotator cuff repair were included. A double-row technique was used in the first 26 consecutive shoulders, and a conventional suture-bridge technique was used in the next 26 consecutive shoulders. Fifty shoulders (92.5%) underwent magnetic resonance imaging or ultrasonography postoperatively. Clinical outcomes were evaluated a minimum 2 years (mean, 37.2 months; range, 24-54) postoperatively using the University of California at Los Angeles (UCLA), American Shoulder and Elbow Surgeons (ASES), and Constant scores. The postoperative cuff integrity was evaluated a mean of 33.0 (range, 10-54) months postoperatively.Results: At the final follow-up, the average UCLA, ASES, and Constant scores improved significantly, to 32.3, 90.5, and 80.7, respectively, in the double-row group and to 30.6, 88.5, and 74.0, respectively, in the suture-bridge group. The UCLA, ASES, and Constant scores improved in both groups postoperatively (all P <.001); however, there was no significant difference between the 2 groups at final follow-up (P =.185,.585, and.053, respectively). The retear rate was 24% in the shoulders that underwent double-row repair and 20% in the shoulders that underwent suture-bridge repair; this difference was not statistically significant (P =.733).Conclusion: The arthroscopic conventional suture-bridge technique resulted in comparable patient satisfaction, functional outcome, and rates of retear compared with the arthroscopic double-row technique in full-thickness rotator cuff tears. © 2012 American Orthopaedic Society for Sports Medicine.

Kim J.,Chungnam National University
Mass Spectrometry Letters | Year: 2015

This article reviews the fundamentals of sample preparation used in matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS). MALDI is a soft ionization method used to generate analyte ions in their intact forms, which are then detected in MS analysis. MALDI-MS boasts fast analysis times and easy-to-use operation. The disadvantages of MALDI-MS include the occurrence of matrix-associated peaks and inhomogeneous distribution of analyte within the matrix. To overcome the disadvantages of MALDI-MS, various efforts have been directed such as using different matrices, novel matrix systems, various additives, and different sample preparation methods. These various efforts will be discussed in detail. This article will benefit those who would like to obtain basic knowledge of MALDI sample preparation and those who would like to use MALDI-MS in their chemical analyses. © 2015, Korean Society for Mass Spectrometry. All rights reserved.

An H.-J.,Chungnam National University | Lee H.,Chungnam National University | Paik S.-G.,Chungnam National University
Molecules and Cells | Year: 2011

We have previously shown that Ras mediates NO-induced BNIP3 expression via the MEK-E RK-HIF-1 pathway i n mouse macrophages, and that NO-induced death results at least in part from the induction of BNIP3. In the present study, we describe another aspect of Ras regulation of BNIP3 expression in pancreatic cancer cells. Human BNIP3 promoter-driven luciferase activity was efficiently induced by activated Ras in AsPC-1, Miapaca-2, PK-1 and PANC-1 cells. However, expression of endogenous BNIP3 was not induced, and BNIP3 up-regulation by hypoxia was also inhibited. Treatment of the cells with the DNMT inhibitor, 5-aza-2-deoxycytidine, restored BNIP3 induction, indicating that DNA methylation of the BNIP3 promoter was responsible for the inhibition of BNIP3 induction. Furthermore, inhibition of the MEK pathway with U0126 reduced DNMT1 expression, but not that of DNMT3a and 3b, and restored the hypoxia-inducibility of BNIP3, suggesting that the DNA methylation of the BNIP3 promoter was mediated by DNMT1 via the MEK pathway. © 2011 The Korean Society for Molecular and Cellular Biology and Springer Netherlands.

Kim S.-W.,Chungnam National University | Yun H.-D.,Chungnam National University
Engineering Structures | Year: 2013

To investigate the bond behavior of deformed bars in recycled aggregate concrete (RAC), 144 tests were performed. In this paper, the following variables were considered: the aggregate size, four types of recycled coarse aggregate (RCA) replacement ratios, two reinforcing bar directions (vertical and horizontal), and two reinforcing bar locations (75 and 225. mm from the bottom). In addition, the effect of concrete aging on the bond behavior between the bar and the concrete was evaluated. Based on the test results, the RAC-I specimens (with 20. mm of maximum RCA size) had a greater bond strength than the RAC-II specimens (with 25. mm of maximum RCA size) under the same RCA replacement ratio. Thus, the bond strength of RCA is affected by the aggregate size because the shape of the RAC is generally spherical. For both RAC-I and -II specimens, as RCA replacement ratio increased, compressive strength showed a tendency to decrease proportionally. In terms of aging, regardless of the RCA replacement ratio, RAC-I pullout specimens showed similar bond strength under the same age although the compressive strength showed a downward trend with the RCA replacement ratio. In view of the top-bar effect, a significant difference was detected between the top and bottom bars at all ages; this does not confirm the provision of the ACI and CSA codes that require all of the top bars to have more than 300. mm of concrete below them. In particular, the bond stress was not uniformly distributed along the length of the bar in the RAC-II specimens due to settlement of the coarse aggregates. © 2012 Elsevier Ltd.

Mallick S.,Chungnam National University | Choi J.S.,Chungnam National University
Journal of Nanoscience and Nanotechnology | Year: 2014

Since the revolutionary discovery that phospholipids can form closed bilayered structures in aqueous systems, liposomes have become a very interesting topic of research. Because of their versatility and amazing biocompatibility, the use of liposomes has been widely accepted in many scientific disciplines. Their applications, especially in medicine, have yielded breakthroughs with anticancerdrug carriers over the past few decades. Specifically, their easy preparation and various structural aspects have given rise to a broadly usable way to internalize biomolecules such as drugs, DNA, RNA and even imaging probes. This review article reports recent developments in liposomal drug delivery and gene delivery, and thoroughly covers the synthesis and different kinds of liposomal surface modification techniques that have resulted in higher stability and efficiency with respect to the use of liposomes in tumor cell targeting, site-specific release, and extending blood retention times. Copyright © 2014 American Scientific Publishers All rights reserved.

Park J.S.,Chungnam National University
Biosciences Biotechnology Research Asia | Year: 2016

Rhododendron is one of the largest shrubs and is well known as a garden plant because of their evergreen leaves and various flower colors. The present study investigated the variation in amino acids in the differently colored flowers of Rhododendron schlippenbachii. Analysis of the Rhododendron flowers revealed 22 types of amino acids. The amino acid content varied greatly depending on the different colors of the flowers. Violet Rhododendron flowers had the highest total quantity of amino acids, which was 2.24 and 1.31 times higher than the total amino acid content in the red and white flowers, respectively. Violet Rhododendron flowers also contained the highest quantities of aspartate, glutamate, glutamine, histidine, 3-aminobutyric acid (GABA), and methionine while white Rhododendron flowers contained the highest quantities of serine, threonine, alanine, valine, norvaline, tryptophan, phenylalanine, isoleucine, and leucine. Compared to the violet flowers, white flowers had 1.24, 1.35, 2.34, and 2.46 times higher amounts of serine, tryptophan, phenylalanine, isoleucine, and leucine, respectively. Although the total amino acid content was the lowest in the red flowers, these flowers contained the highest quantities of Asparagine, Vitamin U, Glutamine, Glycine, Tyrosine, Cysteine, and Lysine. The content of Asparagine was much higher in red flowers than in any other color of Rhododendron flower. Red flowers contained 3.70 and 2.48 times higher levels of asparagine than that measured in white and violet colored Rhododendron flowers, respectively. Our results demonstrate that Rhododendron flowers with different colors contain variable quantities of amino acids, with the highest total amount of amino acids observed in the violet flowers.

Shin J.W.,Korea Aerospace Research Institute | Lee Y.-S.,Chungnam National University | Kim S.J.,Korea Aerospace Research Institute
Acta Mechanica | Year: 2013

The transient response of an interface crack between two dissimilar functionally graded piezoelectric material (FGPM) layers under anti-plane shear impact loading is analyzed using the integral transform method. The properties of the FGPM layers vary continuously along the thickness, and the two layers are connected weak-discontinuously. Laplace transform and Fourier transform are used to reduce the problem to two sets of dual integral equations, which are then expressed to the Fredholm integral equations of the second kind. Numerical values on the dynamic energy release rate are presented for the FGPM to show the effects on the electric loading, variation and gradient of material properties, and thickness of layers. Following things are helpful to increase the resistance of transient fracture of interface crack in FGPMs: (a) increase of the material properties from the interface to the upper or lower free surface; (b) decrease of weak discontinuity at the interface; (c) increase of the gradient of material properties; (d) certain direction and magnitude of the electric loading; and (e) increase of the thickness of the FGPM layer. © 2012 Springer-Verlag Wien.

Lee S.,Seoul National University | Ryi J.,Chungnam National University | Choi J.-S.,Chungnam National University
Journal of Mechanical Science and Technology | Year: 2013

To reduce airfoil self-noise from a 10 kW wind turbine, we modified the airfoil shape and planform of a wind turbine blade. To obtain the optimal blade design, we used optimization techniques based on genetic algorithms. The optimized airfoil was first determined based on a section of the rotor blade, and then the optimized blade was designed with this airfoil. The airfoil self-noise from the rotor blades was predicted by using a semi-empirical model. The numerical analysis indicates that the level of the airfoil self-noise from the optimized blade is 2. 3 dB lower than that from the baseline blade at the rated wind speed. A wind tunnel experiment was also performed to validate the design optimization. The baseline and optimized rotors were scaled down by a factor of 5. 71 for the wind tunnel test. The experimental results showed that airfoil self-noise is reduced by up to 2. 6 dB. © 2013 The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.

A recent paper by H.-J. Kim, J.-H. Kim, C.S.S.P. Kumar, D. Punnoose, S.-K. Kim, C.V.V.M. Gopi, S.S. Rao [1] provides a facile chemical bath deposition of CuS nano peas like structure as a high efficient counter electrode for quantum-dot-sensitized solar cells, but makes an unjustified approximation in the film thickness. Herein, the film thickness was carefully analyzed again based on the original paper. © 2015 Elsevier B.V.

Choi J.H.,Chungnam National University
Food and chemical toxicology : an international journal published for the British Industrial Biological Research Association | Year: 2013

Ginseng contains many bioactive constituents, including various ginsenosides that are believed to have anti-allergic, anti-oxidant, and immunostimulatory activities; however, its effects on atopic dermatitis (AD) remain unclear. In the current study, we hypothesized that cultivated ginseng (CG) would inhibit 2,4-dinitrochlorobenzene (DNCB)-induced AD-like skin lesions in NC/Nga mice by regulating the T helper (Th)1/Th2 balance. Also, CG inhibits TNF-α/IFN-γ-induced thymus- and activation-regulated chemokine (TARC) expression through nuclear factor-kappa B (NF-κB)-dependent signaling in HaCaT cells. CG ameliorated DNCB-induced dermatitis severity, serum levels of IgE and TARC, and mRNA expression of TARC, TNF-α, IFN-γ, IL-4, IL-5, and IL-13 in mice. Histopathological examination showed reduced thickness of the epidermis/dermis and dermal infiltration of inflammatory cells in the ears. Furthermore, CG suppressed the TNF-α/IFN-γ-induced mRNA expression of TARC in HaCaT cells. CG inhibited TNF-α/IFN-γ-induced NF-κB activation. These results suggest that CG inhibited the development of the AD-like skin symptoms by modulating Th1 and Th2 responses in the skin lesions in mice and TARC expression by suppressing TNF-α/IFN-γ-induced NF-κB activation in keratinocytes, and so may be a useful tool in the therapy of AD-like skin symptoms. Copyright © 2013 Elsevier Ltd. All rights reserved.

Ju Chae D.,Korea University | Yoon Kim D.,Korea University | Geun Kim T.,Korea University | Mo Sung Y.,Korea University | Doeck Kim M.,Chungnam National University
Applied Physics Letters | Year: 2012

In this paper, improved electrical and optical properties of aluminum gallium nitride (AlGaN)-based ultraviolet light-emitting diodes using fluorine-doped indium tin oxide (F-ITO) electrodes are reported. F-doping was found to increase the work function as well as the energy bandgap of the ITO and, thereby, reduce the Shottky barrier height in contact with p-(Al)GaN. As a result, the optical transmittance increased from 79.7 to 86.9 at 380 nm, while the specific contact resistance decreased from 1.04 10 -3 cm 2 to 9.12 10 -4 cm 2 after F-doping, which led to an increase in the output power from 2.41 mW to 5.99 mW. © 2012 American Institute of Physics.

Ahn K.-J.,Chungnam National University | Jeon M.-J.,National Institute of Biological Resources | Branham M.A.,University of Florida
Cladistics | Year: 2010

A phylogenetic analysis of the tribe Liparocephalini Fenyes is presented based on morphological and molecular characters. The data set comprised 50 adult morphological characters, partial COI (907 bp), COII (366 bp) and 12S rDNA (325-355 bp), and nearly complete sequences of 18S rDNA (1768-1902 bp) for 21 species. Eighteen species of liparocephaline beetles from all eight genera and three outgroups, are included. The sequences were analysed separately and simultaneously with morphological characters by direct optimization in the program POY4 and by partitioned Bayesian analysis for the combined data. The direct optimization (DO) tree for the combined data under equal weighting, which also shows a minimum incongruence length difference value, resulted in a monophyletic Liparocephalini with the following patterns of phylogenetic relationships (outgroup ((Baeostethus, Ianmoorea) (Paramblopusa ((Amblopusa, Halorhadinus) (Liparocephalus, Diaulota))))). A sensitivity analysis using 16 different parameter sets for the combined data shows the monophyly of the liparocephalines and all its genera under all parameter sets. Bayesian analysis resulted in topological differences in comparison with the DO tree under equal weighting only in the position of the genus Paramblopusa and clade (Amblopusa + Halorhadinus), which were reversed. Historical biogeography and the stepwise evolutionary colonization of intertidal habitat in the Liparocephalini are discussed. Based on the biogeographical analyses, we hypothesize that the ancestor of the Liparocephalini occurred along the Panthallassan Ocean, the direct antecedent of the Pacific Ocean, followed by repeated dispersals to the Nearctic from the Palearctic. We also hypothesize that ancestors of the Liparocephalini appear to have arisen in the littoral zone of beaches and then colonized rocky reef areas in the low tidal zone later through high- to mid-tide zones. © The Willi Hennig Society 2009. © The Willi Hennig Society 2009.

Cho J.,Chungnam National University
Journal of the Korean Physical Society | Year: 2014

When the magnetic field is so strong that the magnetic energy density is much larger than that of matter, magnetic perturbations propagate along the magnetic field lines, and the speed of propagation approaches the speed of light. As in the non-relativistic case, counter-traveling waves in this relativistic limit can interact and generate turbulence. In the present paper, we discuss the properties of the magnetohydrodynamic (MHD) turbulence generated by such interactions. First, we discuss the scaling relations for driven, balanced, relativistic MHD turbulence, in which the amplitudes of counter-traveling wave packets are similar. Second, we discuss the scaling relations of imbalanced relativistic MHD turbulence, in which the amplitudes of counter-traveling wave packets are different. Numerical simulations show that the scaling relations of relativistic MHD turbulence for both cases are very similar to those for their non-relativistic counterparts. © 2014, The Korean Physical Society.

Ko M.O.,Chungnam National University | Kim S.-J.,Chungnam National University | Kim J.-H.,Chungnam National University | Lee B.W.,Fiberpro | Jeon M.Y.,Chungnam National University
Optics Express | Year: 2014

We demonstrate for the first time to our knowledge a dynamic measurement for an electric field sensor using a nematic liquid crystal (NLC) Fabry-Perot etalon and a wavelength-swept laser. It is well known that the wavelengths of the transmitted peaks of the NLC Fabry-Perot etalon depend on the applied electric field. The change in the effective refractive index of the NLC is measured according to the applied static electric field. The effective refractive index decreases from 1.67 to 1.51 as the applied the electric field intensity is increased. In addition, we measure the frequency of the dynamic variation in the electric field using a highspeed wavelength-swept laser. By measuring the modulation frequency of the transmitted peaks in the temporal domain, the frequency of the amplitude-modulated electric field can be estimated. The frequencies of the measured dynamic variations show a close agreement with the amplitude modulation frequencies of the induced electric field. © 2014 Optical Society of America.

Frank J.H.,University of Florida | Ahn K.-J.,Chungnam National University
ZooKeys | Year: 2011

We provide a list of the 392 described species of Staphylinidae confined to coastal habitats worldwide. The list is in taxonomic sequence by subfamily, tribe, and genus and includes 91 genera. We provide the page reference of the original description of every species and genus listed and of many synonyms. We note the existence of recent reviews, phylogenies and keys of each of the tribes and genera included. Coastal Staphylinidae contain eight subfamilies: Microsilphinae, Omaliinae, Pselaphinae, Aleocharinae, Oxytelinae, Scydmaeninae, Paederinae, and Staphylininae. By 'coastal habitats' we mean habitats existing on the sea coast and subject to inundation or at least splashing by the very highest tides. This includes rocky, boulder, coral, sandy, and muddy seashores, and at least portions of salt-marshes, estuaries, and mangrove swamps. We exclude the sand dune habitat and higher parts of sea-cliffs. The list notes distribution of all the species, first according to the ocean or sea on whose shores it has been recorded, and second by country (and for the larger countries by province or state). Although this distribution is undoubtedly incomplete, it provides a basis for future development of a dedicated database. The 'Habitats, Habits, and Classificatory Notes' section is designed to provide ecologists with further taxonomic and ecological information. It includes references to descriptions of the immature stages, behavior of adults and immatures, their food, natural enemies, and habitat. We would have preferred to separate these entities, but current knowledge of ecology is developed in few instances beyond natural history. The Pacific Ocean basin was the origin and contributed to the dispersal of the majority of specialist coastal Staphylinidae at the level of genus. However, at the level of species, species belonging to noncoastal- specialist genera are about as likely to occur on the shores of other oceans as on the shores of the Pacific. This difference is a reflection of the antiquity of coastal genera and species. A complete bibliography, and habitat and habitus photographs of some representative coastal Staphylinidae species are provided. © J.H. Frank, K.-J. Ahn.

Sung Y.J.,Chungnam National University | Shin S.-J.,Chungbuk National University
Biomass and Bioenergy | Year: 2011

The effects of electron beam irradiation on chemical decomposition of industrial hemp biomass were evaluated at doses of 150, 300, and 450 kGy. The quantity of decomposed components was indirectly estimated by measuring changes in alkaline extraction. The more severe degradation of structural components induced by higher irradiation doses resulted in larger amounts of alkaline extract. Carbohydrate compositional analysis using 1H-NMR spectroscopy was applied to quantitatively investigate changes in the polysaccharides of the industrial hemp. The xylose peak intensity in the NMR spectra decreased with increasing electron irradiation dose, indicating that xylan was more sensitive to electron beam irradiation than cellulose. © 2011 Elsevier Ltd.

Moon J.,Korea University | Lim N.-H.,Chungnam National University | Lee H.-E.,Korea University
Thin-Walled Structures | Year: 2013

Corrugated steel plates have several advantages such as high resistance for shear without stiffeners, minimization of welding process, and high fatigue resistance. To take advantage of these benefits, several researchers have attempted to use corrugated steel plate as a web for I-girders. The flexural- torsional buckling is the major design aspect of such I-girders. However, the flexural-torsional buckling of the I-girder with corrugated steel webs still needs to be investigated especially for a real loading condition such as non-uniform bending. This paper investigated the flexural-torsional buckling strength of an I-girder with corrugated steel webs under linear moment gradient by using finite element analysis. From the results, it was found that the buckling behavior of the I-girder with corrugated steel webs differed depending on the number of periods of the corrugation. Also, a simple equation for the moment gradient correction factor for the I-girder with corrugated steel webs was suggested. The inelastic flexural-torsional buckling strength of the I-girder with corrugated steel webs was then discussed based on current design equations for ordinary I-girders and inelastic finite element analysis considering initial imperfection and residual stresses. © 2012 Elsevier Ltd. All rights reserved.

Lee C.-H.,Kongju National University | Jeong M.-K.,Kongju National University | Fatih Kilicaslan M.,Kastamonu University | Lee J.-H.,Chungnam National University | And 2 more authors.
Waste Management | Year: 2013

In this study, a method which is environmentally sound, time and energy efficient has been used for recovery of indium from used liquid crystal display (LCD) panels. In this method, indium tin oxide (ITO) glass was crushed to micron size particles in seconds via high energy ball milling (HEBM). The parameters affecting the amount of dissolved indium such as milling time, particle size, effect time of acid solution, amount of HCl in the acid solution were tried to be optimized. The results show that by crushing ITO glass to micron size particles by HEBM, it is possible to extract higher amount of indium at room temperature than that by conventional methods using only conventional shredding machines. In this study, 86% of indium which exists in raw materials was recovered about in a very short time. © 2012 Elsevier Ltd.

Jang M.-S.,Chungnam National University | Lee S.-J.,Chungnam National University | Kim C.-J.,Chungnam National University | Lee C.-W.,Sungkyunkwan University | Kim E.,Chungnam National University
Oncogene | Year: 2011

Phosphorylation of the Fas-associated death domain (FADD) protein sensitizes cancer cells to various chemotherapeutics. However, the molecular mechanism underlying chemosensitization by phosphorylated FADD (P-FADD) is poorly understood. In this study, we describe the physical interactions and functional interplay between Polo-like kinase 1 (Plk1) and FADD. Plk1 phosphorylates FADD at Ser-194 in response to treatment with taxol. Overexpression of a phosphorylation-mimicking mutant, FADD S194D, caused degradation of Plk1 in an ubiquitin-independent manner, and delayed cytokinesis, consistent with the expected cellular phenotype of Plk1 deficiency. This demonstrates that Plk1 is regulated via a negative feedback loop by its substrate, FADD. Overexpression of FADD S194D sensitized HeLa cells to a low dose of taxol independently of caspase activation, whereas overexpression of FADD S194D resulted in caspase activation in response to a high dose of taxol. Therefore, we examined whether the death potential of P-FADD affected Plk1-mediated tumorigenesis. Transfection of FADD S194D inhibited colony formation by Plk1-overexpressing HeLa cells (HeLa-Plk1). Moreover, overexpression of FADD S194D suppressed tumorigenesis in nude mice xenografted with HeLa-Plk1. Therefore, this study reports the first in vivo validation of tumor-suppressing activity of P-FADD. Collectively, our data demonstrate that in response to taxol, Plk1 endows death-promoting and tumor-suppressor functions to its substrate, FADD. © 2011 Macmillan Publishers Limited All rights reserved.

Hui C.-Y.,Chungnam National University
Journal of Astronomy and Space Science | Year: 2014

The nature of the exotic stellar corpses which reincarnate by consuming their companion is reviewed. Apart from sucking life from their partners, they are actually eating the doomed companions away by their deadly and powerful particle/radiation beams. Such situation resembles that a female "black widow" spider that eats its mate after mating. These celestial zombies are called - Millisecond pulsars (MSPs). In this review article, I will focus on the effort of Fermi Asian Network (FAN) in exploring these intricating objects over the last five years. Two special classes of MSPs are particularly striking. Since Fermi Gamma-ray Space Telescope has started surveying the gamma-ray sky, the population of "black widows" has been boosted. Another dramatic class is so-called "redbacks" (Australian cousin of "black widows") which has just emerged in the last few years. These MSPs provide us with a long-sought missing link in understanding the transition between accretion-powered and rotation-powered systems. The strategy of hunting MSPs through mulitwavelength observations of the unidentified Fermi objects is also reviewed. © The Korean Space Science Society.

Hwang Y.P.,Chungnam National University | Oh K.N.,Natural Resources Research Institute | Yun H.J.,Chungnam National University | Yun H.J.,Chosun University | Jeong H.G.,Chungnam National University
Journal of Dermatological Science | Year: 2011

Background: Ultraviolet (UV) irradiation causes major changes in skin connective tissues as a result of the degradation of collagen, a major structural component of the extracellular matrix. This process is likely mediated by matrix metalloproteinases (MMPs). Such changes in collagenous skin tissues have been suggested to be causes of cutaneous aging and skin cancer. Objective: We investigated the protective effects of apigenin and luteolin on immortalized human keratinocytes (HaCaT) against UVA damage. We then explored the inhibitory effects of apigenin and luteolin on UVA-induced MMP-1 and investigated the molecular mechanism underlying those effects. Methods: HaCaT cells were treated with apigenin and luteolin for the indicated times followed by irradiation with UVA. Those effects were assessed by semi-quantitative PCR, Western blotting and enzymic activity assays. Results: These two compounds, at concentrations of 1-5μM, increased the viability of, and inhibited ROS production in HaCaT cells exposed to UVA irradiation. Pre-treatment of HaCaT cells with apigenin and luteolin also inhibited UVA-induced production of the collagenases MMP-1. They also suppressed UVA-induced expression of c-Jun and c-Fos and the phosphorylation of three MAP kinases, upstream modulators of AP-1. Furthermore, the same two flavonoids decreased the UVA-induced influx of Ca2+ into HaCaT cells and the phosphorylation of Ca2+/calmodulin-dependent kinases (CaMKs). Conclusion: The results indicate that apigenin and luteolin inhibited UVA-induced collagenolytic MMP-1 production by interfering with Ca2+-dependent MAPKs and AP-1 signaling. They may thus be potentially useful in the prevention and treatment of skin photoaging. © 2010 Japanese Society for Investigative Dermatology.

Choi S.,Chungnam National University | Oh J.-Y.,Hallym University | Kim S.-J.,Hallym University
Journal of Cellular Biochemistry | Year: 2011

The cancer chemoprevention effects of ginseng saponins have been demonstrated against a variety of experimental tumors; however, their molecular mechanisms in vitro and in in vivo models are not well studied. This study was undertaken to gain insights into the molecular mechanisms of ginsenoside Rh2 (Rh2)-induced cell death in human breast cancer cell lines as well as in in vivo xenografts. Rh2 treatment significantly inhibited viability of both MCF-7 and MDA-MB-231 human breast cells in a concentration-dependent manner, which correlated with mitochondria-mediated apoptosis. Rh2-induced apoptosis was accompanied by the down-regulation of antiapoptotic proteins Bcl-2, Bcl-xL, and Mcl-1. It also caused induction of the proapoptotic members Bak, Bax, and Bim leading to mitochondrial translocation of Bax and activation of caspases. Moreover, Rh2-induced apoptosis was partially, yet significantly protected by transient transfection of MCF-7 cells with Bax- and Bak-targeted siRNAs. Oral gavage of 5mg Rh2/kg of mouse (three times a week) significantly caused apoptosis of MDA-MB- 231 xenografts. An increase in Bax and Bak and a decrease in Bcl-2 and Bcl-xL transcript levels, in accordance with their protein expression, were observed in tumor tissue. Tumors from Rh2-treated mice exhibited a markedly higher count of apoptotic bodies and reduced proliferation index compared with control tumors. Our data suggest that Rh2 used in traditional oriental medicine for the treatment of various ailments, may be an attractive agent for the treatment and/or prevention of human breast cancers. J. Cell. Biochem. 112: 330-340, 2011. © 2010 Wiley-Liss, Inc.

Kim C.S.,Chungnam National University | Nam K.Y.,Chungnam National University | Kim J.Y.,Chungnam National University
Retina | Year: 2011

Purpose: Brimonidine (0.15%), which is used to lower intraocular pressure, is an α-2-adrenergic agonist that has vasoconstrictive effects. This study examined whether the administration of brimonidine (0.15%) before intravitreal injection prevents subconjunctival hemorrhage. Methods: A prospective, randomized, double-masked single-center study. Two hundred and forty-four patients (244 eyes) who underwent intravitreal injection were prospectively examined. The control group (118 eyes) was given normal saline, while the experimental group received 0.15% brimonidine (126 eyes) 30 minutes before the intravitreal injection. On Days 1 and 7, the treatment outcome was assessed using slit-lamp microscopy. The severity of subconjunctival hemorrhage was scored on a scale of 1 (mild) to 3 (severe). To determine the size of the affected area, the lengths of the short and long axes of the subconjunctival hemorrhage were measured in millimeters and then multiplied. To consider both the severity and the size of subconjunctival hemorrhage, the severity score was multiplied by the size of the subconjunctival hemorrhage. Results: Subconjunctival hemorrhage occurred as a result of intravitreal injection in 13.5% (17 eyes) of the brimonidine group and in 29.7% (35 eyes) of the control group (P = 0.003). On Days 1 and 7, the severity and size of the subconjunctival hemorrhage and the product of these 2 parameters were significantly lower in the brimonidine group. Conclusion: The administration of 0.15% brimonidine before an intravitreal injection decreased the incidence, severity, and size of subconjunctival hemorrhage. © The Ophthalmic Communications Society, Inc.

Most cell membrane proteins are known or predicted to be glycosylated in eukaryotic organisms, where surface glycans are essential in many biological processes including cell development and differentiation. Nonetheless, the glycosylation on cell membranes remains not well characterized because of the lack of sensitive analytical methods. This study introduces a technique for the rapid profiling and quantitation of N- and O-glycans on cell membranes using membrane enrichment and nanoflow liquid chromatography/mass spectrometry of native structures. Using this new method, the glycome analysis of cell membranes isolated from human embryonic stem cells and somatic cell lines was performed. Human embryonic stem cells were found to have high levels of high mannose glycans, which contrasts with IMR-90 fibroblasts and a human normal breast cell line, where complex glycans are by far the most abundant and high mannose glycans are minor components. O-Glycosylation affects relatively minor components of cell surfaces. To verify the quantitation and localization of glycans on the human embryonic stem cell membranes, flow cytometry and immunocytochemistry were performed. Proteomics analyses were also performed and confirmed enrichment of plasma membrane proteins with some contamination from endoplasmic reticulum and other membranes. These findings suggest that high mannose glycans are the major component of cell surface glycosylation with even terminal glucoses. High mannose glycans are not commonly presented on the surfaces of mammalian cells or in serum yet may play important roles in stem cell biology. The results also mean that distinguishing stem cells from other mammalian cells may be facilitated by the major difference in the glycosylation of the cell membrane. The deep structural analysis enabled by this new method will enable future mechanistic studies on the biological significance of high mannose glycans on stem cell membranes and provide a general tool to examine cell surface glycosylation.

Rao B.A.,Chungnam National University | Lee J.-Y.,Chungnam National University | Son Y.-A.,Chungnam National University
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2014

A short, high-yielding route to pyranylidene Iminium (Imi) salts using a new pyrylium salt reaction between N,N-Dimethylformamide (DMF) and acetic anhydride is reported. The Imi salt-sensing behavior toward various anions has been investigated using UV-Visible spectroscopy. The Imi salt demonstrates high selectively for CN- when various other anions, such as CN -, Cl-, Br-, I-, SCN-, ClO4-, NO3-, HSO4-, PF6- and N3-, are present because it is highly reactive towards nucleophiles. The selective detection of CN- with the Imi unit gave rise to a significant hypochromic shift in the CH3CN solution at λmax = 444 nm and 423 nm and creation of new peak at 252 nm. These studies indicated that CN- had high affinity toward Imi, forming a 1:1 complex; this observation agrees with the current understanding of these materials. © 2014 Elsevier B.V. All rights reserved.

Park S.I.,Electronics and Telecommunications Research Institute | Lim H.,Electronics and Telecommunications Research Institute | Kim H.M.,Electronics and Telecommunications Research Institute | Wu Y.,Communications Research Center Canada | Oh W.,Chungnam National University
IEEE Transactions on Broadcasting | Year: 2012

In this paper, we propose a novel Augmented Data Transmission (ADT) system which can transmit an additional data stream in the Advanced Television Systems Committee (ATSC) terrestrial DTV system. The proposed ADT system can offer an additional data of rate up to a few megabits per second (Mbps) based on hierarchical modulation, DTV signal cancellation, and advanced error correction code. The proposed ADT system significantly enhances capability compared with the data transmission schemes used in the transmitter identification (TxID) system. Since the proposed ADT system uses the in-band hierarchical modulation, it does not require any additional RF spectrum to increase the data capacity in a 6 MHz RF channel. Meanwhile, the ADT system has negligible impact to legacy receivers, if the proposed ADT system is deployed over the frequency bands occupied by ATSC A/53 or A/153 services. © 2012 IEEE.

Yu J.-S.,Chungnam National University | Ha D.-H.,Korea Research Institute of Standards and Science | Kim J.-H.,Chungnam National University
Nanotechnology | Year: 2012

The electronic properties of graphene depend critically on its lattice orientation and edge type. However, it is very difficult to identify them, and they are accessible only using sophisticated tools. In this paper, we show an easy and reliable way to reveal the lattice orientation and edge type of graphene and graphite flakes, i.e.multi-layered graphene. Nematic liquid crystals have the potential to align themselves into three symmetric and equivalent orientations on crystalline graphite. The director of macroscopic texture due to the elasticity indicates the lattice orientation of the top graphite layer. By analyzing the director orientation using a polarizing optical microscope, we were able to show the lattice orientation, chiral angle and edge type of graphene and graphite flakes on the macroscopic scale. As liquid crystals are soft and easily removable, our technique has little chance of influencing the following processes for graphene manipulation. © 2012 IOP Publishing Ltd.

Kwak N.-S.,Chungnam National University | Koo J.S.,Chungnam National University | Hwang T.S.,Chungnam National University
Macromolecular Research | Year: 2012

Vinyl benzyl trimethyl ammonium chloride (VBTAC) was grafted onto poly(ethylene-co-tetrafluoroethylene) (ETFE) film by γ-ray using simultaneous irradiation graft copolymerization in the presence of 2-hydroxyl ethyl methacrylate (HEMA). The structure of the ETFE-g-(VBTAC-co-HEMA) anion membrane was confirmed by Fourier transform infrared spectroscopy and thermogravimetric analysis. The degree of grafting (DG) of the membrane increased with total irradiation dose and VBTAC monomer concentration. The highest DG of an ETFE-g-(VBTAC-co-HEMA) membrane was 92%, which was synthesized by the treating of an ETFE film with a 0.8 M solution of VBTAC monomer in the presence of 50 kGy irradiation. Different properties of the anion membrane, such as water uptake and ion exchange capacity, increased as DG increased. The permeability and vanadium redox-flow battery performance were measured for a membrane with a DG of 92%. The average voltage efficiency, coulombic efficiency, and energy efficiency were 0.79, 0.88, and 0.70, respectively, all of which remained stable as the number of cycles increased. [Figure not available: see fulltext.] © 2012 The Polymer Society of Korea and Springer Netherlands.

Jung C.-H.,Korea Atomic Energy Research Institute | Hwang I.-T.,Korea Atomic Energy Research Institute | Choi J.-H.,Chungnam National University
Radiation Physics and Chemistry | Year: 2014

In this study, poly(lactic acid) (PLA)/poly(ethylene glycol)-functionalized polyhedral oligomeric silsesquioxane (PEG-POSS) nanocomposites with or without triallyl isocyanurate (TAIC) were investigated by melt blending and electron beam irradiation to enhance the flexibility of PLA. Based on the results of the crosslinking degree measurements, the PLA/PEG-POSS nanocomposites were crosslinked by electron beam irradiation in the presence of triallyl isocyanurate (TAIC) and their crosslinking degree reached up to 80% based on the absorbed dose and their compositions. From the results of the FE-SEM and EDX Si-mapping, the crosslinked PLA/PEG-POSS nanocomposites were homogenous without a micro-phase separation or radiation-induced morphological change. Based on the results of the tensile test, the PLA/PEG-POSS nanocomposites containing 15. wt% PEG-POSS exhibited the highest flexibility, and their tensile strength showed a maximum value of 44.5. MPa after electron beam irradiation at an absorbed dose of 100. kGy in the presence of TAIC, which is comparable to non-biodegradable polypropylene. The results of the dynamic mechanical analysis revealed that the crosslinked PLA/PEG-POSS nanocomposites exhibited a higher thermal resistance above their melting temperature in comparison to that of the neat PLA, although their glass transition temperature was lower than that of the neat PLA. The enzymatic biodegradation test revealed that the PLA/PEG-POSS nanocomposites were biodegradable even though their biodegradability was deteriorated in comparison to that of the neat PLA. © 2014 Elsevier Ltd.

Kim J.-J.,Chungnam National University | Jo E.-K.,Chungnam National University
Journal of Korean Medical Science | Year: 2013

The inflammasome is a multi-protein complex that induces maturation of inflammatory cytokines interleukin (IL)-1ß and IL-18 through activation of caspase-1. Several nucleotide binding oligomerization domain-like receptor family members, including NLRP3, recognize unique microbial and danger components and play a central role in inflammasome activation. The NLRP3 inflammasome is critical for maintenance of homeostasis against pathogenic infections. However, inflammasome activation acts as a double-edged sword for various bacterial infections. When the IL-1 family of cytokines is secreted excessively, they cause tissue damage and extensive inflammatory responses that are potentially hazardous for the host. Emerging evidence has shown that diverse bacterial pathogens or their components negatively regulate inflammasome activation to escape the immune response. In this review, we discuss the current knowledge of the roles and regulation of the NLRP3 inflammasome during bacterial infections. Activation and regulation of the NLRP3 inflammasome should be tightly controlled to prevent virulence and pathology during infections. Understanding the roles and regulatory mechanisms of the NLRP3 inflammasome is essential for developing potential treatment approaches against pathogenic infections.