Jeonju, South Korea
Jeonju, South Korea

Chonbuk National University is a national research university founded in 1947, located in Jeonju, South Korea. As the flagship national university for the Jeollabuk-do province , Chonbuk National University has been ranked 501–550th in the world by QS Top Universities Ranking in 2010. Wikipedia.

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Chonbuk National University | Date: 2016-08-26

A method for manufacturing metal oxide-grown carbon fibers including immersing carbon fibers in a solution for forming a metal oxide seed layer and electrodepositing a metal oxide seed on the surfaces of carbon fibers, or irradiating microwave thereto to form a metal oxide seed layer, and irradiating microwave to the metal oxide seed layer-formed carbon fibers to grow metal oxide. The method for manufacturing metal oxide-grown carbon fibers can reduce process time, and improve process energy efficiency and production efficiency. The method for manufacturing metal oxide-grown carbon fibers can offer metal oxide-grown carbon fibers with improved interfacial shear stress.

The present invention relates to a composition and health functional food for preventing and treating male infertility using a mixed herbal mixture. Through an in vitro sperm mobility promotion effect evaluation method experiment for investigating effects of an herbal extract of Morinda officinalis, cuscuta seed, and/or Allium cepa of the present invention on changes in sperm count and mobility in human semen, it was verified that the samples of the present invention increased sperm mobility. In addition, through an in vivo varicocele animal model evaluation method for investigating effects of the herbal extract on changes in sperm count and mobility in an in vino varicocele animal model, it was verified that the samples of the present invention increased the sperm count in the semen obtained from spermiducts of a sample-administered group among varicocele-induced groups. Therefore, the herbal extract of the present invention can be usefully used in a pharmaceutical composition, health functional food, and health supplement food for preventing and treating male infertility.

Choi W.-Y.,Chonbuk National University | Choi J.-Y.,Chonbuk National University | Yoo J.-S.,Chonbuk National University
8th International Conference on Power Electronics - ECCE Asia: "Green World with Power Electronics", ICPE 2011-ECCE Asia | Year: 2011

This paper proposes a new bridgeless single-stage three-level ac-dc converter. The proposed converter integrates the operation of the bridgeless power factor correction (PFC) boost rectifier and the zero-voltage switching (ZVS) three-level dc-dc converter. The proposed converter provides high power factor and direct power conversion from the line voltage to an isolated dc output voltage without using the full-bridge diode rectifier. Conduction losses are lowered with a simple circuit structure. Voltage stresses of the power switches are reduced by the use of three-level topology. Switching losses are also reduced by achieving ZVS of the power switches. The effectiveness of the proposed converter is verified on a 400 W (48 V/8.33 A) experimental prototype at 90 Vrms line voltage. © 2011 IEEE.

Jeong J.,Chonbuk National University | Lee J.,Chonbuk National University
Liquid Crystals | Year: 2017

We reported an optical diode effect of a nematic liquid crystal (LC) sample induced by a plasma-treated surface. The LC sample whose one of the substrates was plasma treated transmitted or blocked the incident light depending on the sign of the applied electric field. On the other hand, the LC samples whose both substrates were plasma treated or none of the substrates were plasma treated showed the same transmittance regardless of the sign of the electric field. The optical diode effect was shown when the nematic LC materials contain strong dipole moments, while the same effect was not observed when the weak polar LC was used. A thin polar LC layer formed near the plasma-treated surface makes the net field in the positive and the negative frame to be different, resulting in the optical diode effect. © 2017 Informa UK Limited, trading as Taylor & Francis Group

Choi W.-Y.,Chonbuk National University | Yoo J.-S.,Chonbuk National University | Choi J.-Y.,Chonbuk National University
8th International Conference on Power Electronics - ECCE Asia: "Green World with Power Electronics", ICPE 2011-ECCE Asia | Year: 2011

This paper proposes a high efficiency dc-dc converter with high step-up gain for low PV voltage sources. The proposed converter converts the low dc voltage to a high dc voltage with a high-efficiency. The proposed converter uses the active-clamping circuit and voltage-doubler rectifier in order to achieve a high step-up ratio and soft-switching operation. The output diodes are turned off at zero-current, which can significantly reduce the switching power losses at high output voltage applications. The performance of the proposed converter is evaluated on a 260 W photovoltaic module integrated converter (PV-MIC) system. A high-efficiency of 97.5 % is achieved to generate 350V high output voltage from 36 V low PV module voltage. © 2011 IEEE.

Cho J.,Chonbuk National University | Park J.H.,Pohang University of Science and Technology | Kim J.K.,Pohang University of Science and Technology | Schubert E.F.,Rensselaer Polytechnic Institute
Laser and Photonics Reviews | Year: 2017

About twenty years ago, in the autumn of 1996, the first white light-emitting diodes (LEDs) were offered for sale. These then-new devices ushered in a new era in lighting by displacing lower-efficiency conventional light sources including Edison's venerable incandescent lamp as well as the Hg-discharge-based fluorescent lamp. We review the history of the conception, improvement, and commercialization of the white LED. Early models of white LEDs already exceeded the efficiency of low-wattage incandescent lamps, and extraordinary progress has been made during the last 20 years. The review also includes a discussion of advances in blue LED chips, device architecture, light extraction, and phosphors. Finally, we offer a brief outlook on opportunities provided by smart LED technology. (Figure presented.). © 2017 by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Shon I.-J.,Chonbuk National University
Journal of Korean Institute of Metals and Materials | Year: 2016

The low mechanical properties of SiC limit its wide application despite many attractive properties. To improve the mechanical properties, a second phase has been generally added to make a nanostructured composite. In this respect, graphene was evaluated as the reinforcing agent of SiC. SiC-graphene composites were sintered within 2 min by high-frequency induction heating under a pressure of 80 MPa. The rapid consolidation method allowed the retainment of the nano-scale microstructure by inhibiting the grain growth. The effect of graphene content on the microstructure and hardness of the SiC-graphene composite was investigated using FE-SEM and Vickers hardness tester. Copyright © The Korean Institute of Metals and Materials.

Jung K.,Chonbuk National University | Suh Y.,Chonbuk National University
ECCE 2016 - IEEE Energy Conversion Congress and Exposition, Proceedings | Year: 2016

This paper presents a neutral point deviation compensating control algorithm applied to a 3-level NPC converter. The neutral point deviation is analyzed with a focus on the current flowing out of or into the neutral point of the dc-link. Based on the zero sequence components of the reference voltages, this paper analyzes the neutral point deviation and balancing control for 3-level NPC converter. An analytical method is proposed to calculate the injected zero sequence voltage for neutral point balancing based on average neutral current. This paper also proposes a control scheme compensating for the neutral point deviation under generalized unbalanced grid operating conditions. The positive and negative sequence components of the pole voltages and ac input currents are employed to accurately explain the behavior of 3-level NPC converter. Simulation results are shown to verify the validity of the proposed algorithm. © 2016 IEEE.

Nguyen T.V.T.,Chonbuk National University | Seo Y.J.,Chonbuk National University
Tetrahedron Letters | Year: 2017

A novel thiophene attached anthracene (TA) based fluorescent compound was designed and synthesized. The TA showed a high quantum yield (Qy = 0.34) in regard to fluorescence. We applied this TA compound to detect specific metal compound and found that it could identify CuCl2 from other metals through dramatic fluorescence change at λmax = 460 nm. It showed strong quenching fluorescence property with CuCl2 while with other metal compounds it exhibited strong blue fluorescence emission. UV/Vis absorption spectroscopy clearly demonstrated that the quenching property of TA at λmax = 460 nm was due to overlapping of the fluorescence peak of TA at λmax = 460 nm and the absorption band of CuCl2 (from 190 nm to 525 nm). Binding constant (K′), which was 0.0895 mM− 2, indicated a complexation ratio between TA and CuCl2 as 1:2 and this interaction induced quenching property. © 2017 Elsevier Ltd

Choi J.,Chonbuk National University | Parida B.,Chonbuk National University | Palei S.,Chonbuk National University | Kim K.,Chonbuk National University
Solar Energy Materials and Solar Cells | Year: 2017

We investigated Schottky-type edge passivation of Si solar cells using Ag nanodots and the enhancement of cell conversion efficiency by improving the fill factor. The threshold voltage for the termination of photocurrent is increased by about 0.13 V compared to the reference sample without edge passivation. The cross-section of the pn junction depletion region forms an Ag/Si Schottky contact in the depletion layer of the space and the image charges with a width of about 28 nm. However, the p- and n-electrodes form Ohmic contacts with a contact depletion width of less than 5 nm for the carrier tunneling process. The edge Schottky contact reduces the carrier recombination and saturation current at the surrounding edge region and enhances the fill factor and the pn junction property with increased shunt resistance, indicating that metallic edge passivation is an important process for large-scale Si solar cell fabrication. © 2016 Elsevier B.V.

You B.R.,Chonbuk National University | Han B.R.,Chonbuk National University | Park W.H.,Chonbuk National University
Oncotarget | Year: 2017

Suberoylanilide hydroxamic acid (SAHA) as a histone deacetylase (HDAC) inhibitor has anti-cancer effect. Here, we evaluated the effect of SAHA on HDAC activity and cell growth in many normal lung and cancer cells. We observed that the HDAC activities of lung cancer cells were higher than that of normal lung cells. SAHA inhibited the growth of lung cancer cells regardless of the inhibitory effect on HDAC. This agent induced a G2/M phase arrest and apoptosis, which was accompanied by mitochondrial membrane potential (MMP: δψm) loss in lung cancer cells. However, SAHA did not induce cell death in normal lung cells. All tested caspase inhibitors prevented apoptotic cell death in SAHA-treated A549 and Calu-6 lung cancer cells. Treatment with tumor necrosis factor-alpha (TNF-α) enhanced apoptosis in SAHA-treated lung cancer cells through caspase-8 and caspase-9 activations. Especially, SAHA increased the expression level of TNF-α receptor 1 (TNFR1), especially acetylation of the region of TNFR1 promoter -223/-29 in lung cancer cells. The down-regulation of TNFR1 suppressed apoptosis in TNF-α and SAHA-treated lung cancer cells. In conclusion, SAHA inhibited the growth of lung cancer cells via a G2/M phase arrest and caspasedependent apoptosis. SAHA also enhanced apoptotic effect of TNF-α in human lung cancer cells through up-regulation of TNFR1. TNF-α may be a key to improve anticancer effect of HDAC inhibitors.

On S.Y.,Chonbuk National University | Kim M.S.,Korea Railroad Research Institute | Kim S.S.,Chonbuk National University
Composite Structures | Year: 2017

The mismatch in the coefficient of thermal expansion (CTE) between adherends and adhesives is one of the main reasons for the fracture and failure of adhesive bonding structures. Therefore, the adhesive layer requires reinforcing materials, which can reduce the CTE, enhance the reliability of the adhesive joints and improve the mechanical strength. In this work, electrospun meta-aramid nanofiber mats with a high specific strength and low CTE were used to reinforce the epoxy adhesive. Microwave treatment was introduced to improve the adhesion strength by enhancing the mechanical strength of the nanofiber mat. The surface morphology and fiber orientation of the nanofiber mats with respect to the microwave irradiation time were investigated using scanning electron microscopy (SEM). The residual solvent in the microwave-treated nanofiber mats was monitored via thermogravimetric analysis (TGA). Plasma treatment was conducted to functionalize the microwave-irradiated nanofiber mats with epoxy adhesive to improve the interfacial strength. The characteristics of the plasma-treated nanofiber mats were investigated using X-ray photoelectron spectroscopy (XPS). Thermo mechanical analysis (TMA) confirmed that the CTE of the post-treated meta-aramid nanofiber mat toughened the epoxy adhesive. The stress and strain distribution after the curing and during tensile testing of the single-lap joint were calculated by using finite element analysis (FEA). Single-lap tests were performed to estimate the effect of the reinforcing materials on the adhesion strength. As a result, the post-treated meta-aramid nanofiber mats exhibited an effectively reduced CTE of the adhesive layer and increased adhesion strength. © 2016 Elsevier Ltd

Shon I.-J.,Chonbuk National University
Journal of Korean Institute of Metals and Materials | Year: 2017

Despite of the many attractive properties of TiO2, its low fracture toughness limits many industrial applications. To improve its fracture toughness, the approach commonly utilized has been the addition of a second phase, to form composites, and to make nanostructured composites. In this regard, highly dense nanostructured TiO2 and TiO2-graphene composites were consolidated within one min at 1000 °C. The effect of graphene on the microstructure and the mechanical properties (hardness and fracture toughness) of TiO2-graphene composites was investigated. Copyright © The Korean Institute of Metals and Materials.

Shon I.-J.,Chonbuk National University | Kim W.-J.,Wonjin Aluminium
Journal of Ceramic Processing Research | Year: 2017

Nanopowders of Si and Al4C3 were made by high energy ball milling. The average grain sizes of Al4C3 and Si measured by Suryanarayana and Grant Norton’s formula were about 33 and 18 nm, respectively. Highly dense nanostructured 4Al-3SiC composite was consolidated by high-frequency induction heated sintering method within two minutes from the mechanically activated powders under the 80 MPa pressure. The microstructure and mechanical properties (hardness and fracture toughness) were investigated using FE-SEM and Vickers hardness tester. © 2017, Hanyang University. All rights reserved.

Byeon S.M.,Chonbuk National University | Lee M.H.,Chonbuk National University | Bae T.S.,Chonbuk National University
Materials | Year: 2017

As the proportion of adult orthodontic treatment increases, mainly for aesthetic reasons, orthodontic brackets are directly attached to yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) restorations. This, study analyzed the shear bond strength (SBS) between various surface treated Y-TZP and orthodontic metal brackets. The Y-TZP specimens were conditioned by 110 μm Al2O3 sandblasting, or sandblasting followed by coating with one of the primers (silane, MDP, or an MDP-containing silane primer). After surface treatment, the orthodontic metal bracket was bonded to the specimen using a resin cement, and then 24 h storage in water and thermal cycling (5000 cycles, 5-55°C), SBS was measured. Surface roughness was analyzed for surface morphology, and X-ray photoelectron spectroscopy (XPS) was employed for characterization of the chemical bond between the Y-TZP and the MDP-based primers (MDP, MDP containing silane primer). It was found that after surface treatment, the surface roughness of all groups increased. The groups treated with 110 μm Al2O3 sandblasting and MDP, or MDP-containing silane primer showed the highest SBS values, at 11.92 ± 1.51 MPa and 13.36 ± 2.31 MPa, respectively. The SBS values significantly decreased in all the groups after thermal cycling. Results from XPS analysis demonstrated the presence of chemical bonds between Y-TZP and MDP. Thus, the application of MDP-based primers after Al2O3 sandblasting enhances the resin bond strength between Y-TZP and the orthodontic metal bracket. However, bonding durability of all the surface-treated groups decreased after thermal cycling. © 2017 by the authors.

Ahmad R.,Chonbuk National University | Ahn M.-S.,Chonbuk National University | Hahn Y.-B.,Chonbuk National University
Journal of Colloid and Interface Science | Year: 2017

A promising field-effect transistor (FET) biosensor has been fabricated based on pyruvate oxidase (PyO) functionalized ZnO nanorods (ZnO NRs) array grown on seeded SiO2/Si substrate. The direct and vertically grown ZnO NRs on the seeded SiO2/Si substrate offers high surface area for enhanced PyO immobilization, which further helps to detect phosphate with higher specificity. Under optimum conditions, the fabricated FET biosensor provided a convenient method for phosphate detection with high sensitivity (80.57 μA mM−1 cm−2) in a wide-linear range (0.1 µM–7.0 mM). Additionally, it also showed very low effect of electroactive species, stability and good reproducibility. Encouraging results suggest that this approach presents a promising method to be used for field measurements to detect phosphate. © 2017

Harikishore Kumar Reddy D.,Chonbuk National University | Vijayaraghavan K.,Indian Institute of Technology Madras | Kim J.A.,Chonbuk National University | Yun Y.-S.,Chonbuk National University
Advances in Colloid and Interface Science | Year: 2017

Adsorption is a facile, economic, eco-friendly and low-energy requiring technology that aims to separate diverse compounds (ions and molecules) from one phase to another using a wide variety of adsorbent materials. To date, this technology has been used most often for removal/recovery of pollutants from aqueous solutions; however, emerging post-sorption technologies are now enabling the manufacture of value-added key adsorption products that can subsequently be used for (i) fertilizers, (ii) catalysis, (iii) carbonaceous metal nanoparticle synthesis, (iv) feed additives, and (v) biologically active compounds. These new strategies ensure the sustainable valorisation of post-sorption materials as an economically viable alternative to the engineering of other green chemical products because of the ecological affability, biocompatibility, and widespread accessibility of post-sorption materials. Fertilizers and feed additives manufactured using sorption technology contain elements such as N, P, Cu, Mn, and Zn, which improve soil fertility and provide essential nutrients to animals and humans. This green and effective approach to managing post-sorption materials is an important step in reaching the global goals of sustainability and healthy human nutrition. Post-sorbents have also been utilized for the harvesting of metal nanoparticles via modern catalytic pyrolysis techniques. The resulting materials exhibited a high surface area (> 1000 m2/g) and are further used as catalysts and adsorbents. Together with the above possibilities, energy production from post-sorbents is under exploration. Many of the vital 3E (energy, environment, and economy) problems can be addressed using post-sorption materials. In this review, we summarize a new generation of applications of post-adsorbents as value-added green chemical products. At the end of each section, scientific challenges, further opportunities, and issues related to toxicity are discussed. We believe this critical evaluation not only delivers essential contextual information to researchers in the field but also stimulates new ideas and applications to further advance post-sorbent applications. © 2016 Elsevier B.V.

Song J.,Chonbuk National University | Lee H.-S.,Chonbuk National University
Journal of Applied Biological Chemistry | Year: 2017

This study was conducted to evaluate the insecticidal effects of the Anethum graveolens and the Artemisia vulgaris oils against Sitophilus zeamais and Sitotroga cerealella, respectively, in granary. Insecticidal effects of the A. graveolens oil showed 100 % mortality against S. zeamais for 5 days. In the case of S. cerealella, the A. vulgaris oil showed 100 % mortality for 2 h. These results indicate that the A. graveolens and A. vulgaris oils have potential for development as insecticidal to control S. zeamais and S. cerealella, respectively. © The Korean Society for Applied Biological Chemistry 2017.

Romankov S.,Chonbuk National University | Park Y.C.,National Nanofab Center | Shchetinin I.V.,National University of Science and Technology "MISIS"
Journal of Alloys and Compounds | Year: 2017

Ni and Ti sheets were subjected to intense plastic deformation through ball collisions initiated within a mechanically vibrated vial. The Ti and Ni sheets were cut to discs and affixed to opposite sides of the vial. In this report, we demonstrate the development of plastic flow and intermixing of components on the Ni sheet. Grinding media fragments were transferred and embedded into the Ni surface via ball milling. The ball collisions generated a strong material flow, inducing mechanical intermixing of the introduced components. When different materials flowed together, the components split and penetrated each other along the grain boundaries, forming parallel layers. Nanolaminated structures were developed throughout the elongation process via a slip mechanism. Shearing forces pushed the introduced material along the developing lamella interface, forcing it to slide. The face centered cubic (Fe, Ni) phase developed on the basis of the Ni lamella when nanosized elemental lamellae slid in parallel layers. Component intermixing began at strain localization zones, gradually spreading over the entire deformation-processed volume, resulting in the formation of a continuous alloyed layer. The formation of an alloyed surface layer significantly increased the hardness of the Ni sheet. © 2016 Elsevier B.V.

Sarker M.A.L.,Chonbuk National University | Lee M.H.,Chonbuk National University
2016 International Conference on Information and Communication Technology Convergence, ICTC 2016 | Year: 2016

This paper presents an optimal transmit antenna selection technique to enhance the channel capacity in the case of high signal-To-noise ratio (SNR) multiple-input and multiple-output (MIMO) downlink correlated channel. Most related work has thus far considered optimal antenna selection technique with uncorrelated MIMO channel to reduce radio frequency (RF) module cost. Thus, we propose an optimal antenna selection technique in the case of the correlated MIMO downlink channel due to RF module cost. In this paper, we first design and develop the channel correlation matrices which reflect the correlations between the transmitter antennas, then apply an optimal transmit antenna selection technique for maximizing the channel mean capacity. Finally, simulation results show the channel capacity significantly enhance considering equal power transmission. © 2016 IEEE.

Kim J.S.,Chonbuk National University | Kwon S.H.,Chonbuk National University
Journal of Oral and Maxillofacial Surgery | Year: 2017

Purpose: Hemangioma is a common benign vascular lesion of the head and neck region. It rarely involves the mucous membranes of the nasal cavity and paranasal sinuses. It should be added to the differential diagnosis of nasal cavity masses when the presenting symptoms are epistaxis or nasal obstruction. Materials and Methods: A retrospective chart review was conducted of a histologic diagnosis of lobular capillary hemangioma or cavernous hemangioma of the sinonasal mucous membranes treated at the Chonbuk National University Hospital from January 1995 through December 2015. There were 1,479 patients diagnosed with hemangiomas in the total body area. Medical records were reviewed to gather data on clinical symptoms, demographic characteristics, site of tumor, imaging and histologic features, and treatment. A review of the literature on previously diagnosed cases of sinonasal hemangioma was performed. Results: Three hundred patients had hemangiomas in the head and neck region and only 37 patients (12.5%) had hemangiomas of the sinonasal mucous membranes. The most common complaint was nasal obstruction (59.5%), followed by epistaxis (51.4%). There were 18 male (48.6%) and 19 female (51.4%) patients. The predominant subsites were the nasal septum (40.5%), followed by the inferior turbinate (29.7%), the maxillary sinus (8.1%), and the uncinate process (8.1%). Lobular capillary hemangioma (24 of 37) was more common than cavernous hemangioma (13 of 37). There was a meaningful correlation between the histologic type and tumor site of the hemangioma. Conclusion: Sinonasal hemangiomas are relatively uncommon. Clinicians should be aware of the clinical, radiologic, and histologic features of sinonasal hemangiomas to avoid a misdiagnosis of a malignant tumor, angiofibroma, or other benign mass. © 2017.

Piao Z.,Chonbuk National University | Chung J.-G.,Chonbuk National University
ISOCC 2016 - International SoC Design Conference: Smart SoC for Intelligent Things | Year: 2016

Polar codes have recently become increasingly popular due to their simple structure and low decoding complexity. However, polar codes are still not suitable for real-Time applications because of the long decoding latency. In this paper, by analysis of the conventional architecture of SC decoder, a low latency SC decoder architecture is proposed. Using the proposed architecture, the decoding latency can be reduced by 25% compared with conventional architectures. © 2016 IEEE.

Yang E.,Chonbuk National University
Fuzzy Sets and Systems | Year: 2017

This paper deals with the standard completeness of involutive non-associative, non-commutative, substructural fuzzy logics and their axiomatic extensions. First, fuzzy systems based on involutively residuated mianorms (binary monotonic identity aggregation operations on the real unit interval [0,1]), their corresponding algebraic structures, and their algebraic completeness results are discussed. Next, completeness with respect to algebras whose lattice reduct is [0,1], known as standard completeness, is established for these systems via a construction in the style of Jenei-Montagna. These standard completeness results resolve a problem left open by Cintula, Horčík, and Noguera in the recent Handbook of Mathematical Fuzzy Logic and Review of Symbolic Logic. Finally, we briefly consider the similarities and differences between constructions of the author and Wang's Jenei-Montagna-style. © 2017 Elsevier B.V.

Choi S.-J.,Chonbuk National University | Pan J.-K.,Chonbuk National University
Optics InfoBase Conference Papers | Year: 2016

A twist dual cycling bending structure for ingenerating an optical fiber bending loss is proposed. The bending loss characteristics according to the interval between steel wires, wire radius, and number of steel wires are given.

Park J.-H.,Chonbuk National University | Lee H.-S.,Chonbuk National University
Applied Biological Chemistry | Year: 2017

Agricultural insects and stored-product insects are influenced by luminance intensities, exposure times, and wavelengths of light-emitting diodes (LEDs). Based on the phototactic behaviors of the agricultural insects, green or blue LEDs are most attractive for Bemisia tabaci, Trialeurodes vaporariorum, Myzus persicae, Liriomyza trifolii, Spodoptera exigua, and Spodoptera litura. Green LED attracts Plutella xylostella and Frankliniella occidentalis. Similarly, green or blue LEDs are more attractive to agricultural insects, such as Liriomyza sativae, Sogatella furcifera, and Nilaparvata lugens, than other wavelength LEDs. Concerning the phototactic behaviors of the stored-product insects, red LED is attractive for, in descending order Tribolium castaneum, Sitophilus zeamais, Lasioderma serricorne, and Tyrophagus putrescentiae. Blue LED captures most Sitophilus oryzae and Sitotroga cerealella. Red and blue LEDs are more attractive for stored-product insect pests rate than ultraviolet LED and green, yellow, white, and infrared LEDs. Based on the attraction rate of the stored-product insects on granary, red LED is most attractive for S. cerealella and Plodia interpunctella. These light sources are effective in controlling agricultural and stored-product insects. Applying LED technology for greenhouses and granaries along with conventional traps reduces crop loss due to moths, beetles, aphids, and weevils. LEDs have potential value in integrated pest management. © 2017 The Korean Society for Applied Biological Chemistry

Khan M.H.A.,Chonbuk National University | Lee M.H.,Chonbuk National University
APCC 2012 - 18th Asia-Pacific Conference on Communications: "Green and Smart Communications for IT Innovation" | Year: 2012

Coordinated Multi-Point (CoMP) transmission is a technology targeted for Long Term Evolution Advanced (LTE-A). The Joint Processing (JP) technique for CoMP can maximize system performance, which is achieved mainly with channel information-based beamforming algorithms. Precoding methods perform differently in various CoMP scenarios. In this paper, we propose a joint processing scheme in downlink CoMP transmission system. We apply block diagonal beamforming to downlink transmission, and assume perfect knowledge of downlink channels and transmit messages at each transmit point. © 2012 IEEE.

Zhang M.,Chonbuk National University | Kim S.,Chonbuk National University | Kim Y.,ETRI
APCC 2012 - 18th Asia-Pacific Conference on Communications: "Green and Smart Communications for IT Innovation" | Year: 2012

In this paper, we present a very simple soft demapping algorithm for M-ary PSK and QAM schemes and their universal implementation for adaptive modulation systems. The proposed scheme estimates soft bit information contained in a symbol, with complexity that increases linearly, with modulation order, and achieves approximating performance to maximum likelihood detection. In addition, universal implementation of any M order modulation enables simple single hardware implementation of a demodulator in adaptive systems employing multiple modulation orders. © 2012 IEEE.

Su-Yeon K.,Korea University | Hyeong-Eun K.,Chonbuk National University | Yong-Suk K.,Chonbuk National University
Food Control | Year: 2017

The aim of this study was to control Bacillus cereus growth and biogenic amines formation by using a starter in cheonggukjang fermentation. We used the four selected B. licheniformis strains for cheonggukjang fermentation and investigated whether the strains are effective in reducing both B. cereus level and biogenic amines content. We confirmed that the selected strains are able to reduce B. cereus level to below l log CFU/g after cheonggukjang fermentation from the initial level of 3–4 log CFU/g (artificial contamination). Tryptamine, β-phenylethylamine, putrescine, cadaverine, tyramine, spermidine, and spermine were detected whereas histamine, serotonin, noradrenaline, and dopamine were not detected in the cheonggukjang samples. Most of biogenic amines contents were lower than those of previous studies, indicating that the strains produced the low level of biogenic amines in cheonggukjang fermentation. The acceptable levels of amino-type nitrogen, free amino acids, and isoflavones were contained in the cheonggukjang samples. These results demonstrate that the selected strains are not only effective for reduction of both B. cereus contamination and biogenic amines but also suitable for preparation of cheonggukjang with good quality. © 2017 Elsevier Ltd

You S.H.,Chonbuk National University | Oh S.-H.,HIGH-TECH
Key Engineering Materials | Year: 2017

Demagnetizer has been used in the field of non-destructive test or processing as a tool for removing residual magnetic created on the surface of processed object. In case of residual magnetic left on the part, metal particles around them adhere with each other causing the destruction or abrasion on the part. This study is to develop automatic demagnetizing system for improving the quality of processed items by designing the residual magnetic measuring system, demagnetizing system, and total system to detect magnetic that is derived on parts in the middle of processing in application to bearing process. For this, control system, measuring system, and HMI program that managed them were developed making it feasible to expect the application of them on various automatic processing. © 2017 Trans Tech Publications.

Janardhanam V.,Chonbuk National University | Choi C.-J.,Chonbuk National University
Key Engineering Materials | Year: 2017

An investigation of the electrical and microstructural properties of gold (Au)/p-type silicon (Si) contact was performed as a function of rapid thermal annealing (RTA) temperatures. Au films reacted with Si and produced Au2Si and Au3Si phases during the deposition of the films at room temperature. The electrical properties of the Au contact to p-type Si degraded with increasing RTA temperature. Such a degradation of the electrical properties could be associated with the degradation of the surface and interface morphology caused by the formation of Au-silicide clusters. The RTA process at 500°C led to an increase in the size of the Au-silicide Island. This led to the further degradation of the electrical properties after annealing at 500°C. © 2017 Trans Tech Publications.

Kim S.,Chonbuk National University | Oh I.-S.,Chonbuk National University
Journal of Semiconductor Technology and Science | Year: 2017

In this paper, we propose a novel defect detection method using component tree representations of scanning electron microscopy (SEM) images. The component tree contains rich information about the topological structure of images such as the stiffness of intensity changes, area, and volume of the lobes. This information can be used effectively in detecting suspicious defect areas. A quasi-linear algorithm is available for constructing the component tree and computing these attributes. In this paper, we modify the original component tree algorithm to be suitable for our defect detection application. First, we exclude pixels that are near the ground level during the initial stage of component tree construction. Next, we detect significant lobes based on multiple attributes and edge information. Our experiments performed with actual SEM wafer images show promising results. For a 1000 × 1000 image, the proposed algorithm performed the whole process in 1.36 seconds. © 2017, Institute of Electronics Engineers of Korea. All rights reserved.

Hwangbo S.,Pohang University of Science and Technology | Lee I.-B.,Pohang University of Science and Technology | Han J.,Chonbuk National University
Applied Energy | Year: 2017

Existing energy-efficient management and development of alternative energy infrastructure are the most important issues in modern industry. The former has been mainly studied in terms of optimal design of utility supply network. The latter has been consistently researched in the field of strategic planning of future global hydrogen supply network. In this work, we develop an integrated network model of huge chemical industrial complexes to combine various utility supply networks with a global hydrogen supply network. To construct an integrated network model, the steam methane reforming process is used as a linkage between the two networks. The developed model is a two-stage stochastic mixed integer linear programming that optimizes total cost and also considers demand uncertainty about water, electricity, steam, and hydrogen that are consumed in each network. Finally, a case study in South Korea is conducted to validate the proposed model; it suggests reasonable scenarios to decision makers. © 2017 Elsevier Ltd

Jin Y.G.,Jeju National University | Kang Y.C.,Chonbuk National University
International Review of Electrical Engineering | Year: 2016

The wake effect due to aerodynamic interaction among wind turbines makes the wind farm control a challenging problem. The issues on the wind farm control considering the wake effect include the power generation control, reduction of structural loads, and maximization of energy capture. Among these issues, this paper focuses on the maximization of energy capture and proposes an iterative sequential optimization method (ISOM). The ISOM is not limited to a particular wake model and is based on the actual measurement of the generated power. The ISOM aims to reduce the number of iterations by exploiting the properties of the maximization problem, which include the iterative single-variable optimizations and the sequential optimization in the direction from upwind turbines to downwind ones. Further, the ISOM achieves a significant level of performance in terms of the generated power at the early stage of the iteration process. The effectiveness of the ISOM is verified by the simulations using a four-turbine wind farm and theHorns Rev wind farm. The results show that the ISOM can effectively search the optimal solution with the trade-off between the number of iterations and the precision of the solution. © 2016 Praise Worthy Prize S.r.l. - All rights reserved.

Oh J.,Kyungpook National University | Lee N.K.,Chonbuk National University
Biotechnology and Bioprocess Engineering | Year: 2017

Transactive response DNA binding protein 43 kDa (TDP-43, encoded by the TARDBP gene) is involved in transcriptional regulation and alternative splicing process. TDP-43 proteins are located in the nucleus and shuttles transcripts to the cytoplasm in normal neurons; however, they are observed in the forms of cytoplasmic inclusions in the degenerating cells. The abnormal accumulation of TDP-43 proteins is a pathologic feature of neurodegenerative diseases, such as Lou Gehrig’s disease and dementia including frontotemporal lobar degeneration and Alzheimer’s disease. In this study, we examined whether schizandrin, a main effective compound of Schisandra chinensis (Turcz.), so called omija in Korean, reduces TDP-43 accumulation in the hippocampal neurons in vitro. An immortalized mouse hippocampal neuronal cell line, HT22 cells, were treated with a proteasome inhibitor, MG132, in the absence or presence of schizandrin. We found that schizandrin treatment increased HT22 cell viability and reduced MG132-induced cytoplasmic accumulation of TDP-43. Our results suggest that schizandrin may be a promising compound for development of functional food materials beneficial to the neuronal protection against TDP-43 proteinopathies. © 2017, The Korean Society for Biotechnology and Bioengineering and Springer-Verlag Berlin Heidelberg.

You S.-H.,Chonbuk National University | Oh S.-H.,HIGH-TECH
Key Engineering Materials | Year: 2017

Carbon fiber-reinforced plastic has been applied in various industrial areas due to outstanding mechanic characteristics including high strength and hardness as well as light-weight. For the mechanic combination after the CFRP molding, hall processing is required. In this study, generally used carbide drill and TiAIN coating carbide drill were used to proceed the experiment. Afterwards, carbide drill where point angle was changed into 90° was manufactured while evaluating thrust force and tool wear. In the experiment of carbide drill and TiAIN coating carbide drill, thrust force was reduced when major axis rotating speed increased. However, it was not much influenced by changes in moving speed. In addition, TiAIN coating has not much influenced on the processing feature. Tools with point angle changed into were measured 90° with lower tool wear and thrust force compared to two other tools while obtaining outstanding tool performance. © 2017 Trans Tech Publications.

Kim J.S.,Chonbuk National University
Journal of the Korean Physical Society | Year: 2017

The problem of scalar wave scattering by a cylinder on or near a planar substrate is analytically solved. The solution is in the form of a coupled set of linear equations relating the coefficients of scattering and transmission of the cylinder and those of reflection and transmission of the planar substrate. The coupling is due to the process of multiple scattering by the two objects. Iterative substitution gives the solution in the form of a set of infinite series, and each term explicitly shows the effect of multiple scattering of increasing order. © 2017, The Korean Physical Society.

Ahmad R.,Chonbuk National University | Ahn M.-S.,Chonbuk National University | Hahn Y.-B.,Chonbuk National University
Electrochemistry Communications | Year: 2017

Herein, we report a non-enzymatic glucose sensor field-effect transistor (FET) based on vertically-oriented zinc oxide nanorods modified with iron oxide (Fe2O3-ZNRs). Compared with ZnO-based non-enzymatic glucose sensors, which show poor sensing performances, modification of ZnO with Fe2O3 dramatically enhances the sensing behavior of the fabricated non-enzymatic FET glucose sensor due to the excellent electrocatalytic nature of Fe2O3. The fabricated non-enzymatic FET sensor showed excellent catalytic activity for glucose detection under optimized conditions with a linear range up to 18 mM, detection limits down to ~ 12 μM, excellent selectivity, good reproducibility and long-term stability. Moreover, the fabricated FET sensor detected glucose in freshly drawn mouse whole blood and serum samples. The developed FET sensor has practical applications in real samples and the solution-based synthesis process is cost effective. © 2017 Elsevier B.V.

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.

Kim J.R.,Chonbuk National University | Lee J.H.,Chonbuk National University | Wang S.I.,Chonbuk National University
Knee Surgery, Sports Traumatology, Arthroscopy | Year: 2017

Although the proximal humerus is a common site of osteochondroma, osteochondroma arising from the lesser tuberosity of the proximal humerus is rare. Because of the anatomy of the shoulder, mechanical impingement can occur via direct contact of the protruding lesser tuberosity against the glenoid rim or coracoid. In younger patients, this may cause isolated tearing of the subscapularis. In this study, is presented a rare case of osteochondroma on the lesser tuberosity that caused a subscapularis tear after shoulder impingement in a 34-year-old male. This case was managed using an arthroscopic approach. One year after the surgery, the patient had recovered a normal range of motion, with the resolution of impingement symptoms and the tearing of the subscapularis. Level of evidence IV. © 2017 European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA)

Lee J.H.,Chonbuk National University | Kim J.R.,Chonbuk National University | Wang S.I.,Chonbuk National University
Knee Surgery, Sports Traumatology, Arthroscopy | Year: 2017

Golfers may injure themselves as a result of repetitive asymmetrical loads exerted on the body by poor swing mechanics. If the repetitive sub-maximal loading is not removed, this repetitive loading will exceed the adaptive capacity of bone, eventually resulting in a stress fracture. Stress fracture of the scapula due to golfing is extremely rare. Only two cases of acromion fracture have been reported. A rare case of nontraumatic coracoid fracture in a 50-year-old female beginner golfer is reported here. The mechanism of injury is also discussed. Level of evidence Level IV. © 2017 European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA)

Xu Y.,Chonbuk National University | Lim M.-S.,Chonbuk National University
APCC 2012 - 18th Asia-Pacific Conference on Communications: "Green and Smart Communications for IT Innovation" | Year: 2012

Spectrum sensing with multiple antennas for cognitive radio systems is analyzed as the detection probability with correlation among antennas. In order to reduce the adverse effect of the spatial correlation on spectrum sensing performance, we proposed to employ dual polarized multiple antennas at the secondary sensing nodes. The spectrum sensing performance degradation due to the antenna correlation is then investigated under LOS as well as multipath environment. The superiority of spectrum sensing with dual polarized multiple antennas over conventional multi antennas with only vertical polarization under multipath channel environment are verified by numerical simulation results. © 2012 IEEE.

Kim J.-Y.,Chonbuk National University | Kim H.-W.,Chonbuk National University
Water (Switzerland) | Year: 2017

Photoautotrophic microalgae offer high promise for a tertiary treatment of livestock wastewater owing to their rapid growth and nutrient uptake. To screen better microalga for the tertiary treatment, batch photobioreactor tests were conducted using Chlorella emersonii, Chlorella sorokiniana, and Botryococcus braunii. This study evaluated their specific growth rates, CO2 utilization rates, and nutrient removal rates to provide appropriate selection guidelines. Based on statistical comparisons, results indicate that selecting the right microalgae was the key to success in the tertiary treatment since each microalga responded differently, even under the same light, temperature, and nutrient conditions. Among the tested species, Chlorella emersonii was found to present the fastest photoautotrophic growth, total inorganic carbon (TIC) utilization, and nutrient removal for livestock wastewater treatment. Regression results identified that its specific growth and total nitrogen removal rates were as high as 0.51 day-1 and 0.18 day-1, respectively. Estimated TIC utilization over the supplied TIC was much higher (~34%) than those of others (11%-18%). This systemic evaluation of rate-limiting factors provides a quantitative understanding of the kinetic-based selection strategy of microalgae to polish livestock wastewater with better effluent quality. © 2017 by the authors.

Song Y.-R.,Korea Food Research Institute | Baik S.-H.,Chonbuk National University
Preparative Biochemistry and Biotechnology | Year: 2017

A gene encoding cinnamoyl esterase (CE), which breaks down chlorogenic acid (ChA) into caffeic and quinic acids, was cloned from Lactobacillus helveticus KCCM 11223. The gene with an open reading frame of 759 nucleotides was expressed in Escherichia coli, which resulted in a 51.6-fold increase in specific activity compared to L. helveticus KCCM 11223. The recombinant CE exists as a monomeric enzyme having a molecular weight of 27.4 kDa. Although the highest activity was observed at pH 7, the enzyme showed stable activity at pH 4.0–10.0. Its optimum temperature was 65°C, and it also possessed a thermophilic activity: the half-life of CE was 24.4 min at 65°C. The half-life of CE was 145.5, 80.5, and 24.4 min at 60, 62, and 65°C, respectively. The Km and Vmax values for ChA were 0.153 mM and 559.6 µM/min, respectively. Moreover, the CE showed the highest substrate specificity with methyl caffeate among other methyl esters of hydroxycinnamic acids such as methyl ferulate, methyl sinapinate, methyl p-coumarate, and methyl caffeate. Ca2+, Cu2+, and Fe2+ significantly reduced the relative activity on ChA up to 70%. This is the first report on a thermostable CE from lactic acid bacteria that can be useful to hydrolyze ChA from plant cell walls. © 2017 Taylor & Francis

Bak Y.-S.,Chonbuk National University | Lee Y.-U.,Chonbuk National University
Acta Geologica Sinica | Year: 2017

Paleoclimatic changes in the late Quaternary sediments deposited in the East Sea were analyzed by studying diatoms. A total of 95 species belonging to 47 genera were identified from the Core02GHP-02 of the Ulleung Basin in the East Sea, Korea. In the Core 02GHP-02, U-Oki (169–181 cm; 9.3 ka), AT (464–465.5 cm; 22 ka) and U–Ym (556–559 cm; 33 ka) tephra layers were recognized. The chronological divisions of 02GHP-02 may be correlated with the climatic changes from the glacial interval (730–620 cm; MIS3), to interstadial (620–500 cm; MIS3), to the last glacial maximum (500–390 cm; MIS 2), to the deglaciation (390–290 cm; MIS 2), to the late glacial (290–190 cm; MIS 1), and to the Holocene (190–10 cm; MIS 1). It is speculated that diatoms were rarely found during the glacial interval when the 02GHP-02 core was deposited; during the interstadial (MIS 3) and deglaciation, a mixture of warm-water and cold-water species were found. In particular, Fragilariopsis doliolus seems to have appeared in the East Sea after 8 kaBP. In the lower layers of the Holocene deposits, cold-water species such as Neodenticula seminae were frequently found, while in the upper layers, warm-water species such as Hemidiscus cuneiformis were found in relatively large abundance. Therefore, the findings indicate that the climate became warmer during the transition from the lower layer to the upper layer of the Holocene deposits. © 2017 Geological Society of China

Kim Y.S.,Chonbuk National University | Song J.S.,Chonbuk National University | Kannengiesser S.,Siemens AG | Seo S.Y.,Chonbuk National University
European Radiology | Year: 2017

Objective: To compare spin-echo echoplanar imaging (SE-EPI) and gradient recalled echo (GRE) MR elastography (MRE) at 3 T with and without gadoxetic acid administration. Methods: We included 84 patients who underwent MRE before and after gadoxetic acid administration, each time using SE-EPI and GRE sequences. Diagnostic performance for predicting clinical liver cirrhosis and high-risk oesophageal varices was assessed using the area under the receiver-operating characteristic curve (AUC). The relationships between T2* and success of MRE, and correlations of liver stiffness (LS) values between the two sequences or before and after gadoxetic acid administration, were investigated. Results: SE-EPI-MRE resulted in a significantly lower failure rate than GRE-MRE (1.19% vs. 10.71%, P = 0.018). Increased T2* was related to higher probability of successful LS measurement (odds ratio, 1.426; P = 0.004). The AUC of SE-EPI-MRE was comparable to that of GRE-MRE for the detection of clinical liver cirrhosis (0.938 vs. 0.948, P = 0.235) and high-risk oesophageal varices (0.839 vs. 0.752, P = 0.354). LS values were not significantly different before and after gadoxetic acid administration. Conclusion: SE-EPI-MRE can substitute for GRE-MRE for the detection of clinical liver cirrhosis and high-risk oesophageal varices. SE-EPI-MRE is particularly useful in patients with iron deposition, with lower failure rates than GRE-MRE. Key Points: • LS values are comparable between SE-EPI-MRE and GRE-MRE. • Administration of gadoxetic acid does not influence LS measurement. • The failure rate of SE-EPI-MRE is significantly lower than that of GRE-MRE. © 2017 European Society of Radiology

Han J.,Chonbuk National University
ACS Sustainable Chemistry and Engineering | Year: 2017

A biorenewable ϵ-caprolactam (EC) production strategy is presented based on experiment and process systems engineering studies. In this strategy, a corn stover is catalytically converted to γ-valerolactone (GVL) by using cellulose- and hemicellulose-derived GVL as a reaction solvent, and GVL is then upgraded to EC as a reaction intermediate. Experimental studies showed high yields (biomass-to-GVL: 41% and GVL-to-EC: 30%) using large amounts of GVL (more than five times the biomass), combined with difficulties in separation/purification. This work presents a systematic framework of process systems engineering studies for the strategy as follows: (1) synthesis of a commercial-scale integrated process, including catalytic conversion and separation subsystems, (2) design of a heat exchanger network to satisfy the total energy requirements of the process, and (3) demonstration of the economic feasibility of the process taking into account the minimum selling price of EC and a comparison with the petro-based process. © 2016 American Chemical Society.

Kim S.,Chonbuk National University | Han J.,Chonbuk National University
International Journal of Energy Research | Year: 2017

This study presents an integrated strategy for the co-production of bioenergy (biofuels: butene oligomers) and bio-based products (biomaterials: cyclopentanone (CPON) and alkylphenols) from hemicellulose (C5), cellulose (C6), and lignin fractions of lignocellulosic biomass based on experimental catalysis studies. To evaluate techno-economic feasibility of the strategy, we performed a system-level design study with three steps: process synthesis, energy analysis, and economic analysis. The results of process synthesis show that all biomass fractions are effectively converted with high numerical carbon yields (C6-to-butene oligomers: 52.5%, C5-to-CPON: 68.2%, and lignin-to-alkylphenols: 13.3%) but an efficient separation system for high recovery of bioenergy and bio-based products is crucial. Moreover, an efficient design of a heat exchanger network leads that the total energy requirements of the process are satisfied by the combustion of biomass degradation products (humins). Finally, an economic analysis is performed to estimate the minimum selling price of CPON as the highest energy material (201Mt/day of CPON production using 2000Mt/day of corn stover feedstock processing). This result shows that the process ($1.79/kg CPON) can be cost competitive with current petro-based production approaches. © 2017 John Wiley & Sons, Ltd.

Park W.H.,Chonbuk National University
Oncology Reports | Year: 2017

Gallic acid (GA; 3,4,5-triphydroxyl-benzoic acid) is widely dispersed in various plants, fruits and foods and it shows various biological properties including anticancer effects. This study investigated the effects of GA on HeLa cervical cancer cells in relation to cell death, reactive oxygen species (ROS) and glutathione (GSH). GA dose-dependently inhibited the growth of HeLa cells and human umbilical vein endothelial cells (HUVEC) at 24 or 72 h. The susceptibility of HeLa cells to GA was higher than that of HUVEC. GA induced apoptosis in HeLa cells, which was accompanied by the loss of mitochondrial membrane potential (MMP; Δm). GA increased ROS levels including O2 .- in HeLa cells at 24 h and it also induced GSH depletion. N-acetyl cysteine (NAC) increased the growth inhibition of GA-treated HeLa cells and enhanced the death of these cells. NAC differently influenced ROS levels in GA-treated HeLa cells and significantly increased GSH depletion in these cells. L-buthionine sulfoximine (BSO) increased MMP (Δm) loss, ROS levels and GSH depletion in GA-treated HeLa cells. In conclusion, GA significantly inhibited the growth of HeLa cells. GA-induced HeLa cell death was tightly related to GSH depletion rather than ROS level changes.

Zuo Z.-W.,Chonbuk National University | Pan J.-K.,Chonbuk National University
Optics InfoBase Conference Papers | Year: 2016

An intensity modulation-based fiber optic vibration sensor (FOVS) using serpentine spring with proof mass structure is proposed and demonstrated via experiments. The structure, operating principle, and characteristics of the proposed sensor are given. © OSA 2016.

Oh S.J.,Chonbuk National University | Cho J.,Chonbuk National University
Thin Solid Films | Year: 2017

Originating from a non-radiative recombination in the active region of a light-emitting diode (LED), the self-heating effect was investigated under continuous wave (cw) operation with a GaInN blue LED. Current-voltage (I-V) characteristics under pulse operation that lacked self-heating were measured and compared with the corresponding I-V measurement under the cw operation. Accordingly, a comparison of the measured I-V curves enabled estimation of the junction temperature of the LED during the cw operation. The junction temperature of the device increased as high as 323. K at an input current of 480. mA. The operating current showed a weaker temperature dependence in accordance with the bias increase, which is explained by the expansion of the Shockley diode equation. © 2017 Elsevier B.V.

Han J.,Chonbuk National University
Energy Conversion and Management | Year: 2017

In this work, an integrated strategy is developed for producing N-methylformanilide from the carbon dioxide of flue gas in a coal-fired power plant. Based on lab-scale experimental studies presenting maximum yields (96%) with low reaction concentrations (below 25 wt% reactants) using large volumes of gamma-valerolactone as a solvent and catalyst, the integrated strategy focuses on the development of commercial-scale processes that consist of a monoethanolamine-based carbon dioxide separation subsystem and a catalytic conversion subsystem of N-Methylaniline with carbon dioxide to N-methylformanilide. Moreover, a heat exchanger network is designed to minimize the total energy requirements by transferring the heat between subsystems. In the proposed integrated strategy, the energy efficiency after heat integration (77.5%) is higher than that before heat integration (74.5%). Economic analysis results show that the minimum selling price of N-methylformanilide ($1592.1 Mt−1 using the best possible parameters) for use in this integrated strategy is cost-competitive with the current market price ($2984 Mt−1). © 2017 Elsevier Ltd

Park S.-K.,Chonbuk National University
Acta dermato-venereologica | Year: 2017

is missing (Quiz).

Koh E.-J.,Chonbuk National University | Park J.-S.,Chonbuk National University
Medicine | Year: 2017

RATIONALE: Remote cerebellar hemorrhage (RCH) is a rare complication of supratentorial and spinal surgeries, seldom requiring intervention but occasionally causing significant morbidity or even mortality. Although a number of theories have been proposed, the exact pathophysiology of RCH remains incompletely understood.PATIENT CONCERNS: We present a 62-year-old patient with RCH encountered following surgical clipping of an unruptured middle cerebral artery bifurcation aneurysm in a patient with previous cerebellar infarction.LESSONS: It is extremely rare, but sometimes, RCH can be life-threatening. It is necessary to check the patient's general condition, underlying diseases and medical history. And controlled drainage of the CSF seems to be most important. Arachnoidplasty may be a consideration and the position of the drain string might have to be carefully determined.

Gao Y.,Chonbuk National University | Lee H.J.,Chonbuk National University
Multimedia Tools and Applications | Year: 2017

Face recognition techniques are widely used in many applications, such as automatic detection of crime scenes from surveillance cameras for public safety. In these real cases, the pose and illumination variances between two matching faces have a big influence on the identification performance. Handling pose changes is an especially challenging task. In this paper, we propose the learning warps based similarity method to deal with face recognition across the pose problem. Warps are learned between two patches from probe faces and gallery faces using the Lucas-Kanade algorithm. Based on these warps, a frontal face registered in the gallery is transformed into a series of non-frontal viewpoints, which enables non-frontal probe face matching with the frontal gallery face. Scale-invariant feature transform (SIFT) keypoints (interest points) are detected from the generated viewpoints and matched with the probe faces. Moreover, based on the learned warps, the probability likelihood is used to calculate the probability of two faces being the same subject. Finally, a hybrid similarity combining the number of matching keypoints and the probability likelihood is proposed to describe the similarity between a gallery face and a probe face. Experimental results show that our proposed method achieves better recognition accuracy than other algorithms it was compared to, especially when the pose difference is within 40 degrees. © 2017 Springer Science+Business Media New York

Kim S.,Chonbuk National University | Im D.,Chonbuk National University
2016 IEEE Asia Pacific Conference on Circuits and Systems, APCCAS 2016 | Year: 2016

The most popular tunable capacitor topologies in CMOS are the analog varactor and digitally controlled switched capacitor array (SCA). The conventional analog varactor shows a high quality factor (g-factor) in both the minimum capacitance (Cmin) and the maximum capacitance (Cmax) states with a wide tuning range, but it has a poor linearity performance due to the voltage dependent nonlinear capacitance. In case of the digitally controlled switched capacitor array, while it shows a very good linearity, its g-factor in Cmin state is strongly dependent on the substrate loss by the parasitic junction capacitances between p-well, deep n-well, and p-substrate and the substrate resistance. To overcome the aforementioned drawbacks of the analog varactor and the switched capacitor array, the digitally controlled binary-weighted accumulation-mode varactor array (AVA) is proposed. In the simulation, at 2.4 GHz frequency band, the proposed tunable capacitor shows a g-factor of greater than 60 over all states and a tuning range of 3. The inverter-based push-pull power amplifier (PA) with the tunable matching network (TMN) employing the proposed tunable capacitor extends the impedance coverage maintaining the output power of greater than 0 dBm under the worst case for antenna impedance mismatch. © 2016 IEEE.

Nam G.-B.,University of Ulsan | Ko K.-H.,University of Ulsan | Kim J.,Pusan National University | Park K.-M.,Inje University | And 4 more authors.
European Heart Journal | Year: 2010

AimsThe aim of the present study was to identify specific electrocardiogram (ECG) features that predict the development of multiple episodes of ventricular fibrillation (VF) in patients with an early repolarization (ER) pattern and to compare the mode of VF initiation with that observed in typical cases of Brugada syndrome (BrS).Methods and resultsThe mode of the onset and the coupling intervals of the premature ventricular contractions (PVCs) initiating VF episodes were analysed in patients with BrS (n = 8) or ER who experienced sudden cardiac death/syncope or repeated appropriate implantable cardioverter defibrillator shocks. Among the 11 patients with ER, 5 presented with electrical storm (ES, four or more recurrent VF episodes/day). The five ES patients displayed a dramatic but very transient accentuation of J waves across the precordial and limb leads prior to the development of ES. Ventricular fibrillation episodes were more commonly initiated by PVCs with a short-long-short (SLS) sequence in ER (42/58, 72.4) vs. BrS patients (13/86, 15.1, P < 0.01). Coupling intervals were significantly shorter in the ER group compared with those with BrS [328 (320, 340) ms vs. 395 (350, 404) ms, P < 0.01].ConclusionOur study provides additional evidence in support of the hypothesis that ER pattern in the ECG is not always benign. Transient augmentation of global J waves may be indicative of a highly arrhythmogenic substrate heralding multiple episodes of VF in patients with ER pattern. Ventricular tachycardia/VF initiation is more commonly associated with an SLS sequence, and PVCs display a shorter coupling interval in patients with ER pattern compared with those with BrS.

Lee S.H.,Sogang University | Hur N.,Sogang University | Jeong S.-K.,Chonbuk National University
Journal of Atherosclerosis and Thrombosis | Year: 2012

Aim: The aim of this study was to find a region of low wall shear stress (WSS) in a basilar artery using 3-dimensional (3D) geometric analysis and blood flow simulation. Methods: A 61-year-old patient who underwent follow-up time-of-flight magnetic resonance angiography (TOF-MRA) of the brain was recruited as the subject of the present study. In the basilar artery, the angle of the directional vector was calculated for the region of low WSS. The subject's 3D arterial geometry and blood flow velocity from a transcranial Doppler examination were used for a blood flow simulation study. The regions of low WSS identified by both geometric analysis and blood flow simulation were compared, and these methods were repeated for the basilar arteries of various geometries from other patients. Results: Two distinct arterial angulations along the basilar artery were identified: lateral and anterior angulations on the anteroposterior and lateral TOF-MR views, respectively. A low WSS region was observed in the distal portion along the inner curvatures of both angulations in the basilar artery. The directional vectors of the region of low WSS calculated by geometric analysis and blood flow simulation were very similar (correlation coefficient =0.996, p<0.001). Follow-up MRA confirmed the progression of plaque in the region of low WSS. Conclusion: Detailed geometric analysis and blood flow simulation of the basilar artery identified lateral and anterior angulations which determined the low WSS region in the distal portion along the inner curvatures of the angulations.

Noh Y.-J.,Kunsan National University | Na S.-I.,Chonbuk National University | Kim S.-S.,Kunsan National University
Solar Energy Materials and Solar Cells | Year: 2013

Efficient inverted polymer solar cells (PSCs) were fabricated with ZnO electron transport layers (ETLs) prepared by spray pyrolysis, which is a simple and cost efficient method producing a thin oxide layer by direct spray of precursor on hot substrate. To investigate the effect of substrate temperature on the structural and optical properties as well as performance of PSCs, ZnO ETLs were fabricated by spray pyrolysis on hot substrate controlled at 150, 250, and 350 C, respectively. The PSC with ZnO prepared by spray pyrolysis at 150 C exhibited poor power conversion efficiency (PCE) of 0.94% due to the mis-matched energy level and microscopic roughness of ZnO ETL. On the other hand, enhanced efficiency of 2.99% and 3.22% was obtained by using ZnO prepared by spray pyrolysis at 250 and 350 C, respectively. Enhancement of efficiency at higher temperature is attributed to better matching of ZnO coated ITO work-function with the lowest unoccupied molecular orbital (LUMO) energy level of PCBM and the formation of smooth and homogeneous polycrystalline ZnO, resulting in improved interfacial property and electron transport. In the durability test, inverted ZnO solar cell was retained above 80% during 9 days in an ambient atmosphere without any encapsulation, while conventional solar cells showed dramatic decrease of efficiency. © 2013 The Authors.

Yeo J.-S.,Gwangju Institute of Science and Technology | Yun J.-M.,Gwangju Institute of Science and Technology | Kim D.-Y.,Gwangju Institute of Science and Technology | Kim S.-S.,Kunsan National University | Na S.-I.,Chonbuk National University
Solar Energy Materials and Solar Cells | Year: 2013

Abstract We report an effective 2-step solvent treatment combined with a polar solvent vapor annealing process (PSVA) and a dipping process using polar solvents (DP) to enhance the electrical conductivity of poly(3,4- ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films, which is highly desirable for the fabrication of solution-processed organic photovoltaics (OPVs) on flexible substrates. The PSVA and DP-treated PEDOT:PSS films showed conductivities up to 1475 S/cm. The changes in conductivity, surface morphology, composition, and conformational PEDOT chains are investigated to elucidate the effect of the 2-step PSVA and DP treatment on PEDOT:PSS films. The highly segregated-PSS component induced by PSVA was effectively removed from the PEDOT:PSS films after successive DP treatments, eventually resulting in an enhanced conductivity of bulk films. We also employed optimized PEDOT:PSS films treated by the 2-step PSVA and DP-process as transparent anodes for indium tin oxide (ITO)-free OPVs fabricated on flexible substrates. The device performance of flexible OPVs with PSVA and DP-treated films was further improved due to the increased conductivity and decreased series resistance of devices and showed highly comparable cell-efficiency with ITO-based flexible OPVs. These results suggest that the 2-step solvent-treated PEDOT:PSS film is a promising alternative to ITO for realization of high-efficiency, flexible, and low-cost ITO-free OPVs with facile manufacturing process. © 2013 Elsevier B.V. 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.

Khan H.A.A.,Bahauddin Zakariya University | Akram W.,University of Agriculture at Faisalabad | Shad S.A.,Bahauddin Zakariya University | Lee J.-J.,Chonbuk National University
PLoS ONE | Year: 2013

House flies, Musca domestica L., are important pests of dairy operations worldwide, with the ability to adapt wide range of environmental conditions. There are a number of insecticides used for their management, but development of resistance is a serious problem. Insecticide mixtures could enhance the toxicity of insecticides in resistant insect pests, thus resulting as a potential resistance management tool. The toxicity of bifenthrin, cypermethrin, deltamethrin, chlorpyrifos, profenofos, emamectin benzoate and fipronil were assessed separately, and in mixtures against house flies. A field-collected population was significantly resistant to all the insecticides under investigation when compared with a laboratory susceptible strain. Most of the insecticide mixtures like one pyrethroid with other compounds evaluated under two conditions (1:1-"A" and LC50: LC50-"B") significantly increased the toxicity of pyrethroids in the field population. Under both conditions, the combination indices of pyrethroids with other compounds, in most of the cases, were significantly below 1, suggesting synergism. The enzyme inhibitors, PBO and DEF, when used in combination with insecticides against the resistant population, toxicities of bifenthrin, cypermethrin, deltamethrin and emamectin were significantly increased, suggesting esterase and monooxygenase based resistance mechanism. The toxicities of bifenthrin, cypermethrin and deltamethrin in the resistant population of house flies could be enhanced by the combination with chlorpyrifos, profenofos, emamectin and fipronil. The findings of the present study might have practical significance for resistance management in house flies. © 2013 Khan et al.

Jiang X.,Peking University | Tong M.,Peking University | Kim H.,Chonbuk National University
Journal of Colloid and Interface Science | Year: 2012

The significance of natural organic matter (NOM, both humic acid and alginate) on the transport and deposition kinetics of ZnO nanoparticles (NPs) in irregular quartz sand was examined by direct comparison of both breakthrough curves and retained profiles with NOM present in NPs suspension versus those obtained without NOM. Packed column experiments were conducted in both NaCl and CaCl2 solutions under a series of environmentally relevant ionic strengths. Under all examined conditions, breakthrough plateaus with NOM even at concentration as low as 1mgL-1 of total organic carbon (TOC) were higher than those without NOM, indicating that presence of NOM in NPs suspensions enhanced ZnO NPs transport. Although hyper-exponential retained profiles were observed both in the presence and absence of NOM, the amount of retained ZnO NPs acquired in the presence of NOM decreased slowly as the transport distance increased. Straining induced by concurrent aggregation is found to cause the hyper-exponential decrease. In the presence of NOM, electrosteric interaction effectively reduced the ZnO NPs deposition on collector surfaces and NPs-NPs aggregation. Subsequently, the amount of NPs that jammed in the column inlet in the absence of NOM were markedly decreased, which therefore exhibited as flatter retained profiles. © 2012 Elsevier Inc.

Jiang X.,Peking University | Tong M.,Peking University | Lu R.,Peking University | Kim H.,Chonbuk National University
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2012

The impact of ionic strength and cation valence on the transport and deposition kinetics of ZnO nanoparticles in saturated porous media was systematically investigated in this research. Packed column experiments were performed over a series of environmentally relevant ionic strength in both NaCl (ranging from 1 to 20mM) and CaCl 2 (ranging from 0.1 to 1mM) solutions. Solution chemistries (ionic strength and ion types) greatly affected the transport of ZnO nanoparticles in saturated quartz sand. Flat breakthrough plateaus were observed at relatively low ionic strength in both NaCl (1 and 5mM) and CaCl 2 (0.1-0.5mM) solutions, whereas, ripening was observed at high ionic strength (10 and 20mM in NaCl, and 1mM CaCl 2) conditions. Deposition of nanoparticle increased with increasing solution ionic strength in both monovalent and divalent salt solutions. The presence of divalent ions in solutions increased nanoparticle deposition in quartz sand. Under all examined conditions, nanoparticles mainly retained at segments near the column inlet. The retained ZnO nanoparticle concentrations versus transport distance decreased faster than the theory prediction of log-linear decrease under all examined conditions. Our study found that concurrent aggregation of ZnO nanoparticles occurred during the transport process, which contributed to the hyper-exponential retained profiles. © 2012 Elsevier B.V.

Solehati N.,Chonbuk National University | Bae J.,Chonbuk National University | Sasmito A.P.,National University of Singapore
Journal of Industrial and Engineering Chemistry | Year: 2012

Operating conditions is one of the key factors required to ensure high performance PEM fuel cell stack; careful balance between performance and parasitic loads has to be taken into account to achieve optimum output. This study evaluates numerically key operating parameters of liquid-cooled PEM fuel cell stack with regard to the stack performance, stack efficiency and viability to enhance efficiency utilizing waste heat for combined heat and power. The results indicate that high stack performance does not always associate with high stack efficiency due to higher parasitic load; it is recommended to optimize the operating parameters in terms of efficiency. © 2011 The Korean Society of Industrial and Engineering Chemistry.

Jiang X.,Peking University | Wang X.,Peking University | Tong M.,Peking University | Kim H.,Chonbuk National University
Environmental Pollution | Year: 2013

The significance of biofilm on the transport and deposition behaviors of ZnO nanoparticles were examined under a series of environmentally relevant ionic strength at two fluid velocities of 4 m-d-1 and 8 m-d-1. Biofilm enhanced nanoparticles retention in porous media under all examined conditions. The greater deposition was also observed in extracellular polymeric substances (EPS) coated surfaces by employment of quartz microbalance with dissipation (QCM-D) system. Derjaguin-Landau-Verwey-Overbeek (DLVO) failed to interpret more ZnO nanoparticles deposition on biofilm (EPS) coated silica surfaces. Chemical interaction and physical morphology of biofilm contributed to this greater deposition (retention). Biofilm affected the spacial distribution of retained ZnO nanoparticles as well. Relatively steeper slope of retained profiles were observed in the presence of biofilm, corresponding to the greater deviation from colloid filtration theory (CFT). Pore space constriction via biofilm induced more nanoparticle trapped in the column inlet, leading to greater deviations (σln kf) from the CFT. © 2012 Elsevier B.V. All rights reserved.

Kwak I.S.,Engineering Randnter | Won S.W.,Chonbuk National University | Chung Y.S.,Chonbuk National University | Yun Y.-S.,Chonbuk National University
Bioresource Technology | Year: 2013

A fibrous bacterial biosorbent was developed to bind precious metal-organic complexes in batch and column processes. Polyethylenimine (PEI)-modified bacterial biosorbent fiber (PBBF) was prepared by spinning Corynebacterium glutamicum biomass-chitosan blends, coating them with PEI and cross-linking with glutaraldehyde. When an acetic acid waste solution containing 1822.9. mg/L Ru was used as a model waste solution, Ru uptake by the PBBF was 16.5 times higher than that of the commercial ion exchange resin, Lewatit MonoPlus M600. The maximum amounts of Ru uptake were 110.5, 16.0 and 6.7. mg/g for PBBF, raw biomass, and Lewatit MonoPlus M600, respectively. In a flow-through packed bed, PBBF exhibited the breakthrough time of 42.32. h. Therefore, PBBF can be considered as an alternative sorbent for recovery of anionic metal-organic complexes from waste solutions. © 2012 Elsevier Ltd.

McMahon C.G.,Australian Center for Sexual Health | Lee G.,University of Kuala Lumpur | Park J.K.,Chonbuk National University | Adaikan P.G.,National University of Singapore
Journal of Sexual Medicine | Year: 2012

Introduction. Premature ejaculation (PE) is a common male sexual dysfunction. The prevalence of PE in the Asia-Pacific region has not been comprehensively studied. Aim. The aim of this study is to evaluate PE prevalence in nine Asia-Pacific countries and the impact of PE on sufferers. Methods. A random sample of heterosexual males aged 18-65years in a stable sexual relationship currently or in the past 2years completed a 48-question survey by computer-assisted interviewing, online, or in-person; the survey and recruitment methodologies varied by location. The survey included demographic questions, the five-question Premature Ejaculation Diagnostic Tool (PEDT), the five-question Sexual Health Inventory for Men (SHIM), and the 10-question Index of Premature Ejaculation (IPE). Separately, men self-reported having PE (lifelong or acquired) or erectile dysfunction (ED). Main Outcome Measures. The PEDT was used to diagnose PE or probable PE; the SHIM was used to diagnose ED; and the IPE was used to assess respondent's attitudes toward PE. Results. Of the 4,997 men who completed the survey, the prevalences of PEDT-diagnosed PE, PEDT-diagnosed probable PE, and self-reported PE were 16%, 15%, and 13%, respectively. Less than half of men with PEDT-diagnosed PE (N=816) or probable PE (N=738) self-reported the condition (40% and 19%, respectively), and 6% of men with a PEDT diagnosis of no PE self-reported PE. In contrast, more respondents self-reported ED (8%) than had SHIM-diagnosed moderate or severe ED (5%). IPE responses indicated that 45%, 46%, and 23% of men with PEDT-diagnosed PE were somewhat or very dissatisfied with the length of intercourse before ejaculation, their control over ejaculation, and with sexual intercourse, respectively. Conclusions. In this study, PE was more prevalent than ED in the Asia-Pacific countries surveyed, but only 40% of men with PEDT-diagnosed PE self-reported PE. © 2011 International Society for Sexual Medicine.

Vijayaraghavan K.,National University of Singapore | Joshi U.M.,National University of Singapore | Kamala-Kannan S.,Chonbuk National University
Ecological Engineering | Year: 2012

Biosorption is a well established remediation technology for heavy metal ions; however, little is known about their practical applications. Effluents generated in research laboratories are creating severe treatment problems for various organizations, owing to their complex nature. This article utilizes the well-defined biosorption technology for the treatment of complex synthetic laboratory wastewaters. Three seaweeds, Sargassum, Ulva and Turbinaria were employed to remediate wastewater found to comprise of eight different heavy metal ions (Cu(II), Co(II), Cd(II), Cr(III), Ni(II), Mn(II), Pb(II) and Zn(II)) at 0.016. M total concentration. Among the seaweeds, Turbinaria conoides performed well in both batch and continuous-mode of operation with total uptake capacities of 3.20 and 3.01. mmol/g, respectively. This article also discusses mechanism of seaweeds biosorption along with the practical problems associated with biosorption process in real applications, including process design, cost, biosorbent availability, mode of operation, quality of the final effluent and ultimate disposal of biosorbent. © 2012 Elsevier B.V.

Bradford S.A.,U.S. Department of Agriculture | Torkzaban S.,CSIRO | Kim H.,Chonbuk National University | Simunek J.,University of California at Riverside
Water Resources Research | Year: 2012

The transport and fate of colloids, microorganisms, and nanoparticles in subsurface environments is strongly influenced by transients in solution ionic strength (IS). A sophisticated dual-permeability transport model was modified and a theory was developed to mechanistically account for the transport, retention, and release of colloids with transients in IS. In particular, colloid release in the model was directly related to the balance of applied hydrodynamic and resisting adhesive torques that determined the fraction of the solid surface area that contributed to colloid immobilization (Sf). The colloid sticking efficiency (α) and Sf were explicit functions of IS that determined the rates of colloid interaction with the solid, immobilization on the solid, colloid release from the solid and back into the bulk aqueous phase, and the maximum amount of colloid retention. The developed model was used to analyze experimental transport and release data with transients in IS for 1.1 and 0.11 mm latex microspheres, E. coli D21g, and coliphage φX174. Comparison of experimental values of Sf (IS) with predictions based on mean interaction energies indicated that predictions needed to account for the influence of physical and/or chemical heterogeneity on colloid immobilization. This was especially true for smaller colloids because they were more sensitive to microscopic heterogeneities that produced mainly irreversible interaction in a primary minimum and greater hysteresis in S f (IS) with IS. Significant deviations between experimental and predicted values of a(IS) were observed for larger colloids when hydrodynamic forces were not accounted for in the predictions. A sensitivity analysis indicated that colloid release with IS transients was not diffusion controlled, but rather occurred rapidly and with low levels of dispersion. The calibrated model provided a satiSfactory description of the observed release behavior for a range of colloid types and sizes and a general theoretical foundation to develop predictions for the influence of solution chemistry on the transport, retention, and release of colloids. © 2012. American Geophysical Union. All Rights Reserved.

Chua L.,University of California at Berkeley | Sbitnev V.,University of California at Berkeley | Sbitnev V.,RAS Petersburg Nuclear Physics Institute | Kim H.,Chonbuk National University
International Journal of Bifurcation and Chaos | Year: 2012

This paper presents a rigorous and comprehensive nonlinear circuit-theoretic foundation for the memristive Hodgkin-Huxley Axon Circuit model. We show that the Hodgkin-Huxley Axon comprises a potassium ion-channel memristor and a sodium ion-channel memristor, along with some mundane circuit elements. From this new perspective, many hitherto unresolved anomalous phenomena and paradoxes reported in the literature are explained and clarified. The yet unknown nonlinear dynamical mechanisms which give birth to the action potentials remain hidden within the memristors, and the race is on for uncovering the ultimate truth. © 2012 World Scientific Publishing Company.

Bradford S.A.,Us Salinity Laboratory | Wang Y.,University of California at Riverside | Kim H.,Chonbuk National University | Torkzaban S.,CSIRO | Simunek J.,University of California at Riverside
Journal of Environmental Quality | Year: 2014

An understanding of microbial transport and survival in the subsurface is needed for public health, environmental applications, and industrial processes. Much research has therefore been directed to quantify mechanisms influencing microbial fate, and the results demonstrate a complex coupling among many physical, chemical, and biological factors. Mathematical models can be used to help understand and predict the complexities of microbial transport and survival in the subsurface under given assumptions and conditions. This review highlights existing model formulations that can be used for this purpose. In particular, we discuss models based on the advection-dispersion equation, with terms for kinetic retention to solid-water and/or air-water interfaces; blocking and ripening; release that is dependent on the resident time, diffusion, and transients in solution chemistry, water velocity, and water saturation; and microbial decay (first-order and Weibull) and growth (logistic and Monod) that is dependent on temperature, nutrient concentration, and/or microbial concentration. We highlight a tworegion model to account for microbe migration in the vicinity of a solid phase and use it to simulate the coupled transport and survival of Escherichia coli species under a variety of environmentally relevant scenarios. This review identifies challenges and limitations of models to describe and predict microbial transport and survival. In particular, many model parameters have to be optimized to simulate a diversity of observed transport, retention, and survival behavior at the laboratory scale. Improved theory and models are needed to predict the fate of microorganisms in natural subsurface systems that are highly dynamic and heterogeneous. © American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America.

Han Y.,Hanyang University | Kim H.,Chonbuk National University | Tong M.,Peking University
Materials Chemistry and Physics | Year: 2012

Ceramic foams with different relative densities (i.e., different extension ratios) were successfully prepared from stone powder sludge (SPS) via a foaming and gelcasting method. Ceramic foams with various relative densities were characterized in terms of porosity, specific surface area, and water absorption capacity. The porosity of the ceramic foams ranged from 35% to 78%, depending on the extension ratio. The specific surface area and water absorption capacity increased as the relative density decreased (i.e., increasing extension ratio), resulting in enhanced pore connectivity. The feasibility of the SPS foams as microorganism-immobilized carriers and the effect of inner pores on simultaneous nitrification/denitrification were tested through wastewater treatment experiments. The results from fixed-bed reactors packed by SPS carriers with different relative densities revealed that the organic removal efficiency for all reactors was greater than 90%. In addition, the nitrification/ denitrification experimental results suggested that the increase of the NH 4 +-N loading rate resulted in the improvement of nitrification efficiency and the decrease of nitrogen loss in all reactors. However, no significant correlation between relative density (i.e., extent of inner pore development) and nitrification/denitrification efficiency was found. © 2012 Elsevier B.V. All rights reserved.

Binupriya A.R.,Chonbuk National University | Sathishkumar M.,National University of Singapore | Vijayaraghavan K.,National University of Singapore | Yun S.-I.,Chonbuk National University
Journal of Hazardous Materials | Year: 2010

Bioreduction efficacy of both active (AB) and inactive (IB) cells/biomass of Aspergillus oryzae var. viridis and their respective cell-free extracts (ACE and ICE) to convert trivalent aurum to gold nanoparticles were tested in the present study. Strong plasmon resonance of gold nanoparticles was observed between 540 and 560. nm in the samples obtained from AB, IB, ACE and ICE. Transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX) and X-ray diffraction (XRD) were performed to examine the formation of gold nanoparticles. Comparing all four forms of A. oryzae var. viridis, ICE showed high gold nanoparticle productivity. The nanoparticles formed were quite uniform in shape and ranged in size from 10 to 60. nm. In addition some triangle, pentagon and hexagon-shaped nanoplates with size range of 30-400. nm were also synthesized especially at lower pH. Organics from the inactive cells are believed to be responsible for reduction of trivalent aurum to nano-sized gold particles. Organic content of the ICE was found to be double the amount of ACE. High productivity of gold nanoparticles by metabolic-independent process opens up an interesting area of nanoparticle synthesis using waste fungal biomass from industries. © 2009 Elsevier B.V.

Lynch D.,National Jewish Health | Chawla A.,Sri Aurobindo Institute of Medical science | Garg K.,Aurora University | Tammemagi M.C.,Brock University | And 3 more authors.
Radiology | Year: 2013

Purpose: To determine the prevalence of interstitial lung abnormalities (ILAs) at initial computed tomography (CT) examination and the rate of progression of ILAs on 2-year follow-up CT images in a National Lung Screening Trial population studied at a single site. Materials and Methods: The study was approved by the institutional review board and informed consent was obtained from all participants. Image review for this study was HIPAA compliant. We reviewed the CT images of 884 cigarette smokers who underwent low-dose CT at a single site in the National Lung Screening Trial. CT findings were categorized as having no evidence of ILA, equivocal for ILA, or ILA. We categorized the type of ILA as nonfibrotic (ground-glass opacity, consolidation, mosaic attenuation), or fibrotic (ground glass with reticular pattern, reticular pattern, honeycombing). We evaluated the temporal change of the CT findings (no change, improvement, or progression) of ILA at 2-year follow-up. A x2 with Fisher exact test or unpaired t test was used to determine whether smoking parameters were associated with progression of ILA at 2-year follow-up CT. Results: The prevalence of ILA was 9.7% (86 of 884 participants; 95% confidence interval: 7.9%, 11.9%), with a further 11.5% (102 of 884 participants) who had findings equivocal for ILA. The pattern was fibrotic in 19 (2.1%), nonfibrotic in 52 (5.9%), and mixed fibrotic and nonfibrotic in 15 (1.7%) of the 86 participants with ILA. The percentage of current smokers (P = .001) and mean number of cigarette pack-years (P = .001) were significantly higher in those with ILA than those without. At 2-year follow-up of those with ILA (n = 79), findings of nonfibrotic ILA improved in 49% of cases and progressed in 11%. Fibrotic ILA improved in 0% and progressed in 37% of cases. Conclusion: ILA is common in cigarette smokers. Nonfibrotic ILA improved in about 50% of cases, and fibrotic ILA progressed in about 37%. © 2013 RSNA.

Yang H.,Peking University | Kim H.,Chonbuk National University | Tong M.,Peking University
Colloids and Surfaces B: Biointerfaces | Year: 2012

The significance of natural organic matter (NOM) on the transport of bacteria in packed porous media (quartz sand) was examined in both NaCl and CaCl2-NaCl mixing solutions at pH 6.0. Three representative cell types (with EPS), Rhodococcus sp. QL2 (Gram-positive, non-motile), Escherichia coli BL21 (Gram-negative, non-motile), and E. coli C3000 (Gram-negative, motile), were utilized to systematically determine the influence of NOM (Suwannee River humic acid (SRHA)) on cell transport behavior. To investigate the significance of SRHA on transport of bacteria without EPS on cell surfaces, experiments for treated cells with the removal of EPS from cell surfaces were also performed. The breakthrough plateaus for all examined bacteria with the presence of SRHA (1mgL-1) in solutions were higher than those with the absence of SRHA under all examined conditions, indicating that the presence of SRHA in solutions enhanced cell transport regardless of cell types (Gram-negative or Gram-positive), motility (non-motile or motile), presence or absence of EPS on cell surfaces, and solution chemistry (ionic strength and ion valence). Zeta potentials for bacteria and quartz sand with the presence of SRHA were similar as those without SRHA present in solutions, suggesting that SRHA did not alter the surface charge of bacteria or sand, thus the enhanced cell transport by SRHA was not likely driven by alteration in the surface charge of either cell or quartz sand. SRHA pre-equilibration experiments demonstrated that the site competition by a portion of SRHA and the repelling deposition by suspended SRHA contributed to the decreased cell deposition observed with the presence of SRHA in bacteria suspension. © 2011 Elsevier B.V.

Moon H.,Sogang University | Kim H.,Sogang University | Kumar D.,Korea University | Sim C.,Sogang University | And 3 more authors.
ACS Nano | Year: 2015

We report a strongly amplified photoacoustic (PA) performance of the new functional hybrid material composed of reduced graphene oxide and gold nanorods. Due to the excellent NIR light absorption properties of the reduced graphene oxide coated gold nanorods (r-GO-AuNRs) and highly efficient heat transfer process through the reduced graphene oxide layer, r-GO-AuNRs exhibit excellent photothermal stability and significantly higher photoacoustic amplitudes than those of bare-AuNRs, nonreduced graphene oxide coated AuNRs (GO-AuNRs), or silica-coated AuNR, as demonstrated in both in vitro and in vivo systems. The linear response of PA amplitude from reduced state controlled GO on AuNR indicates the critical role of GO for a strong photothermal effect of r-GO-AuNRs. Theoretical studies with finite-element-method lab-based simulation reveal that a 4 times higher magnitude of the enhanced electromagnetic field around r-GO-AuNRs can be generated compared with bare AuNRs or GO-AuNRs. Furthermore, the r-GO-AuNRs are expected to be a promising deep-tissue imaging probe because of extraordinarily high PA amplitudes in the 4-11 MHz operating frequency of an ultrasound transducer. Therefore, the r-GO-AuNRs can be a useful imaging probe for highly sensitive photoacoustic images and NIR sensitive therapeutics based on a strong photothermal effect. © 2015 American Chemical Society.

Hagensen M.K.,Institute of Clinical Medicine | Vanhoutte P.M.,Chonbuk National University | Bentzon J.F.,Institute of Clinical Medicine
Cardiovascular Research | Year: 2012

For more than a decade, a prevailing hypothesis in research related to arterial disease has been that circulating endothelial progenitor cells (EPCs) provide protection by their innate ability to replace dysfunctional or damaged endothelium. This paradigm has led to extensive investigation of EPCs in the hope of finding therapeutic targets to control their homing and differentiation. However, from the very beginning, the nomenclature and the phenotype of EPCs have been subject to controversy and there are currently no specific markers that can unambiguously identify these cells. Moreover, many of the initial observations that EPCs differentiate to endothelial cells in the course of arterial disease have been criticized for methodological problems. The present review discusses the contrasting experimental evidence as to the role of EPCs in contributing to relining of the endothelium and highlights some of the methodological pitfalls and terminological ambiguities that confuse the field. © The Author 2012.

Tong M.,Peking University | Kim H.,Chonbuk National University
Environmental Science and Technology | Year: 2012

The significance of clay particles on the transport and deposition kinetics of bacteria in irregular quartz sand was examined by direct comparison of both breakthrough curves and retained profiles with clay particles in bacteria suspension versus those without clay particles. Two representative cell types, Gram-negative strain E. coli DH5α and Gram-positive strain Bacillus subtilis were utilized to systematically determine the influence of clay particles (bentonite) on cell transport behavior. Packed column experiments for both cell types were conducted in both NaCl (5 and 25 mM ionic strengths) and CaCl2 (5 mM ionic strength) solutions at pH 6.0. The breakthrough plateaus with bentonite in solutions (30 mg L-1 and 50 mg L -1) were lower than those without bentonite for both cell types under all examined conditions, indicating that bentonite in solutions decreased cell transport in porous media regardless of cell types (Gram-negative or Gram-positive) and solution chemistry (ionic strength and ion valence). The enhanced cell deposition with bentonite particles was mainly observed at segments near to column inlet, retained profiles for both cell types with bentonite particles were therefore steeper relative to those without bentonite. The increased cell deposition with bentonite observed in NaCl solutions was attributed to the codeposition of bacteria with bentonite particles whereas, in addition to codeposition of bacteria with bentonite, the bacteria-bentonite- bacteria cluster formed in suspensions also contributed to the increased deposition of bacteria with bentonite in CaCl2 solution. © 2012 American Chemical Society.

Xu M.,Chonbuk National University | Ren H.,Chonbuk National University | Lin Y.-H.,National Chiao Tung University
Optics Letters | Year: 2015

We report an adaptive iris using dielectric liquids and a radial-interdigitated electrode. A black liquid is confined by a circular gasket with a donut shape. The surrounding of the black liquid is filled with an immiscible liquid. In the relaxing state, the black liquid obtains the largest clear aperture. By applying a voltage, the surface of the black liquid is stretched by the generated dielectric force, resulting in a reduction of its aperture. For the demonstrated iris, the diameter of the aperture can be changed from ∼4.7 mm to ∼1.2 mm when the voltage is applied from 0 to 70 Vrms. The aperture ratio is ∼94%. Owing to the radial-interdigitated electrode, the aperture size of the iris can be effectively switched with a reasonably fast response time. The optical switch is polarization-insensitive. The potential applications of our iris are light shutters, optical attenuators, biomimicry, and wearable devices. © 2015 Optical Society of America.

Jin Y.,Peking University | Dai Z.,Peking University | Liu F.,Peking University | Kim H.,Chonbuk National University | And 2 more authors.
Water Research | Year: 2013

Ag2O/TNBs were fabricated by depositing Ag2O nanoparticles on the surface of TiO2 nanobelts (TNBs). The disinfection activities of Ag2O/TNBs on two representative bacterial types: Gram-negative Escherichia coli ATCC15597 and Gram-positive Bacillus subtilis, were examined under both dark and visible light conditions. Ag2O/TNBs exhibited stronger bactericidal activities than Ag2O nanoparticles and TNBs under both dark and light conditions. For both cell types, disinfection effects of Ag2O/TNBs were greater under light conditions relative to those under dark conditions. The bactericidal mechanisms of Ag2O/TNBs under both dark and light conditions were explored. Ag+ ions released from Ag2O/TNBs did not contribute to the bactericidal activity of Ag2O/TNBs under dark conditions, whereas the released Ag+ ions showed bactericidal activity under visible light irradiation conditions. Active species (H2O2, O2-·, and e-) generated by Ag2O/TNBs played important roles in the disinfection processes under both dark and visible light irradiation conditions. Without the presence of active species, the direct contact of Ag2O/TNBs with bacterial cells had no bactericidal effect. © 2013 Elsevier Ltd.

Noh Y.-J.,Chonbuk National University | Noh Y.-J.,Korea Institute of Science and Technology | Kim S.-S.,Kunsan National University | Kim T.-W.,Korea Institute of Science and Technology | Na S.-I.,Chonbuk National University
Solar Energy Materials and Solar Cells | Year: 2014

Abstract We demonstrate cost-effective, indium tin oxide (ITO)-free organic solar cells (OSCs) fabricated with a silver nanowire (AgNW)-poly(3,4- ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) composite electrode. The composite films were prepared with a one-step spray-coating of a mixture composed of AgNW and a highly conductive, dimethylsulfoxide (DMSO)-treated PEDOT:PSS (hcPEDOT). The film-thickness, optical transmittance, and sheet resistance of AgNW-hcPEDOT hybrid electrodes were easily controlled by varying the spray deposition time. With AgNW-hcPEDOT composite electrodes, the devices exhibited high power conversion efficiencies of up to 2.16% under 100 mW cm -2 and AM 1.5G illumination conditions. In addition, the surface of the AgNW-hcPEDOT composite electrodes was further smoothened with an additional spray-coated PEDOT:PSS buffer layer, leading to reduced shorting and improved cell-efficiency. As a result, the best performing devices with a AgNW-hcPEDOT electrode and spray-coated PEDOT buffer exhibited efficiencies of up to 2.65%, which approaches that of conventional ITO-based devices. These results indicate that the one-step spray-coated AgNW-hcPEDOT composite-based film is a viable alternative to the high-cost and vacuum-deposited ITO for mass-production and low-cost roll-to-roll based solar cells. © 2013 Elsevier B.V.

Jeon Y.-J.,Chonbuk National University | Yun J.-M.,Gwangju Institute of Science and Technology | Kim D.-Y.,Gwangju Institute of Science and Technology | Na S.-I.,Chonbuk National University | Kim S.-S.,Kunsan National University
Solar Energy Materials and Solar Cells | Year: 2012

As an alternative to the poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) hole transporting layer (HTL) in polymer solar cells (PSCs), moderately reduced graphene oxide (GO) films fabricated by simple and fast thermal treatment of solution processed GO were investigated. PSC with thermally treated GO at 250 °C exhibited best performance with a power conversion efficiency (PCE) of 3.98%, compared to the PSC containing conventional PEDOT:PSS HTL with a PCE of 3.85%. Furthermore, the PSC with thermally treated GO showed superior stability compared to the PSC with conventional PEDOT:PSS HTL under the atmosphere condition without any encapsulation process. Our demonstration suggests that moderately reduced GO by simple thermal treatment could be promising HTL replacing PEDOT:PSS in PSCs as well as other organic electronics. © 2012 Elsevier B.V.

Unnithan A.R.,Chonbuk National University | Gnanasekaran G.,Chonnam National University | Sathishkumar Y.,Chonbuk National University | Lee Y.S.,Chonbuk National University | Kim C.S.,Chonbuk National University
Carbohydrate Polymers | Year: 2014

In this study, an antibacterial electrospun nanofibrous scaffolds with diameters around 400-700 nm were prepared by physically blending polyurethane (PU) with two biopolymers such as cellulose acetate (CA) and zein. Here, PU was used as the foundation polymer, was blended with CA and zein to achieve desirable properties such as better hydrophilicity, excellent cell attachment, proliferation and blood clotting ability. To prevent common clinical infections, an antimicrobial agent, streptomycin sulfate was incorporated into the electrospun fibers and its antimicrobial ability against the gram negative and gram positive bacteria were examined. The interaction between fibroblasts and the PU-CA and PU-CA-zein-drug scaffolds such as viability, proliferation, and attachment were characterized. PU-CA-zein-drug composite nanoscaffold showed enhanced blood clotting ability in comparison with pristine PU nanofibers. The presence of CA and zein in the nanofiber membrane improved its hydrophilicity, bioactivity and created a moist environment for the wound, which can accelerate wound recovery. © 2013 Elsevier Ltd.

Rim H.,ASE Korea | Ryoung Park H.,Chonnam National University | Youp Song M.,Chonbuk National University
Ceramics International | Year: 2013

LiNi1-yCoyO2 (y=0.1, 0.3 and 0.5) cathode materials were synthesized by a solid-state reaction method at different temperatures using Li2CO3 as a Li source, NiCO3 as a Ni source, and Co3O4 as a Co source. The electrochemical properties of the synthesized samples were then investigated. Structures of the synthesized LiNi1-yCoyO2 (y=0.1, 0.3 and 0.5) samples were analyzed, and microstructures of the samples were observed. Voltage vs. x in LixNi1-yCo yO2 curves for the first and second charge-discharge cycles and intercalated and deintercalated Li quantity Δx were studied. LiNi0.9Co0.1O2 synthesized at 800 °C had the largest first discharge capacity (152 mAh/g) and quite good cycling performance, with a discharge capacity of 146 mAh/g at n=5. It had a discharge capacity fading rate of 1.4 mAh/g/cycle. © 2012 Elsevier Ltd and Techna Group S.r.l.

Ambade R.B.,Chonbuk National University | Ambade S.B.,Chonbuk National University | Shrestha N.K.,Nepal Academy of Science and Technology | Nah Y.-C.,Korea University of Technology and Education | And 4 more authors.
Chemical Communications | Year: 2013

We report exceptional electrochemical specific capacitance (640 F g -1) for polythiophene (PTh) infiltrated into TiO2 nanotubes (TNTs) by a controlled electropolymerization route. The resulting PTh-TNTs also exhibit excellent electrochemical behavior with long-term stability. This reproducible and superior performance of PTh-TNT electrodes makes them attractive candidates for energy storage. This journal is © The Royal Society of Chemistry.

Jung S.,Florida A&M University | Arda Vanli O.,Florida A&M University | Kwon S.-D.,Chonbuk National University
Applied Energy | Year: 2013

A new Bayesian approach is proposed to estimate the annual energy production (AEP) of a site where construction of wind turbines is considered. The approach uses long-term wind speeds of a nearby weather station and short-term wind speeds near the target site. Uncertainties exist due to the limited amount of data in the target site, in addition to the inherent uncertainties in the wind speed, the air density, the surface roughness exponent, and the power performance of the turbine. The proposed method systematically addresses these uncertainties and provides the distribution of the AEP. For illustration, we used the wind speed data near Yeosu, Korea, and the power performance curve of a 3. MW turbine. For the site and the turbine studied, the range given by the 95% confidence interval corresponded to 8.9% of the mean AEP, and the range given by the 99% confidence interval corresponded to 11.9% of the mean AEP. Benefits of using the Bayesian approach compared to the classical statistical inference was also illustrated with the case study. The proposed approach provides a more conservative estimation considering the uncertainties due to the limited amount of data. Distributions of parameters of the prediction model are also provided, which enables a more detailed analysis of the prediction. © 2012 Elsevier Ltd.

Jung S.,Florida A&M University | Kwon S.-D.,Chonbuk National University
Applied Energy | Year: 2013

This paper presents the application of the artificial neural network (ANN) to predict long-term wind speeds of a particular site, and to estimate the annual energy production of wind turbines using the predicted wind speeds. A major finding in this study is that an ANN trained with a conventional error measure may significantly underestimate the annual energy production. An accurate prediction of the mean wind speed does not guarantee an accurate prediction of the energy production when the variance of the wind speed is underestimated. To improve the accuracy in estimating the energy production, we proposed two ANNs that are based on weighted error functions. They use the frequency of the wind speed and the power performance curve to develop the weighted form of the error function. For the site and the turbine studied in this paper, the proposed ANNs showed 8-12% improvement in predicting the annual energy production compared to the conventional ANN. © 2013 Elsevier Ltd.

Lee I.C.,Pohang University of Science and Technology | Hong S.W.,Chonnam National University | Whang S.S.,Chonbuk National University | Lim P.O.,Jeju National University | And 2 more authors.
Plant and Cell Physiology | Year: 2011

Leaf senescence, which constitutes the final stage of leaf development, involves programmed cell death and is intricately regulated by various internal and environmental signals that are incorporated with age-related information. ABA plays diverse and important physiological roles in plants, and is involved in various developmental events and stress responses. ABA has long been regarded as a positive regulator of leaf senescence. However, the cellular mediators of ABA-induced senescence have not been identified. We sought to understand the ABA-induced senescence signaling process in Arabidopsis by examining the function of an ABA- and age-induced gene, RPK1, which encodes a membrane-bound, leucine-rich repeat-containing receptor kinase (receptor protein kinase 1). Loss-of-function mutants in RPK1 were significantly delayed in age-dependent senescence. Furthermore, rpk1 mutants exhibited reduced sensitivity to ABA-induced senescence but little change to jasmonic acid- or ethylene-induced senescence. RPK1 thus mediates ABA-induced leaf senescence as well as age-induced leaf senescence. Conditional overexpression of RPK1 at the mature stage clearly accelerated senescence and cell death, whereas induction of RPK1 at an early developmental stage retarded growth without triggering senescence symptoms. Therefore, RPK1 plays different roles at different stages of development. Consistently, exogenously applied ABA affected leaf senescence in old leaves but not in young leaves. The results, together, showed that membrane-bound RPK1 functions in ABA-dependent leaf senescence. Furthermore, the effect of ABA and ABA-inducible RPK1 on leaf senescence is dependent on the age of the plant, which in part explains the mechanism of functional diversification of ABA action. © 2011 The Author.

Cha K.S.,Chonbuk National University | Bae J.H.,Chonnam National University
Energy Policy | Year: 2011

This study investigates the impacts of high international oil prices on the bioethanol and corn markets in the US. Between 2007 and 2008, the prices of major grain crops had increased sharply, reflecting the rise in international oil prices. These dual price shocks had caused substantial harm to the global economy. Employing a structural vector auto-regression model (SVAR), we analyze how increases in international oil prices could impact the prices of and demand for corn, which is used as a major bioethanol feedstock in the US. The results indicate that an increase in the oil price would increase bioethanol demand for corn and corn prices in the short run and that corn prices would stabilize in the long run as corn exports and feedstock demand for corn decline. Consequently, policies supporting biofuels should encourage the use of bioethanol co-products for feed and the development of marginal land to mitigate increases in the feedstock price. © 2010 Elsevier Ltd.

Lee E.-K.,Mogam Biotechnology Research Institute | Lee E.-K.,Seoul National University | Kim D.-G.,Chonbuk National University | Kim J.-S.,Mogam Biotechnology Research Institute | Yoon Y.,Mogam Biotechnology Research Institute
Cancer Research | Year: 2011

The cell-cycle regulator Cks1 has recently been implicated in Skp2-mediated ubiquitination of the tumor suppressor protein p27. In this article, we report that Cks1 exerts a Skp2-independent regulation of NF-κB that promotes interleukin-8 (IL-8) expression, which is critical to hepatocellular carcinoma (HCC) growth. Cks1 was upregulated frequently in human HCC tissues and cell lines. Cks1 knockdown in HCC cells elevated p27 levels and decreased tumorigenicity in a manner that was also associated with a strong downregulation of IL-8 expression. IL-8 downregulation was not phenocopied by either RNAi-mediated knockdown of Skp2 or ectopic overexpression of p27. However, attenuation of IL-8 expression itself was sufficient to blunt HCC growth. Mechanistic investigations revealed that IL-8 was controlled at a transcriptional level by Cks1 targeting of the NF-κB regulator IκBa, which led to NF-κB activation and IL-8 expression, through a p27-independent regulation of IκB kinase complex components. Collectively, our findings support the hypothesis that Cks1 supports hepatocarcinogenesis by NF-κB-mediated regulation of IL-8 expression, broadening the function of Cks1 in cancer beyond its role as a Skp2 cofactor in p27 ubiquitination. ©2011 AACR.

Chaudhary G.,Chonbuk National University | Jeong Y.,Chonbuk National University | Lim J.,Soonchunhyang University
IEEE Transactions on Microwave Theory and Techniques | Year: 2012

This paper presents a novel approach to the design of tunable dual-band bandpass filter with broadband harmonic suppression characteristics. The proposed filter structure offers the possibility of two tunable passbands, as well as a fixed first passband and controllable second passband. The tunable passband frequency usually causes a shift of the harmonics, which need to be suppressed to improve out-of the passband characteristics. In order to suppress the harmonics over a broad bandwidth, defected ground structures are used at input and output feeding lines without degrading the passbands characteristics. Both theory and experiment are provided to validate the proposed filter. From the experimental results, it is found that the proposed filter exhibits a first passband center frequency tunable range of 34.14% from 0.85 to 1.2 GHz with the almost constant 3-dB fractional bandwidth (FBW) of 13% and second passband center frequency tunable range of 41.81% from 1.40 to 2.14 GHz with the 3-dB FBW of 11%. The measured results of the proposed filters show a rejection level of 20 dB up to more than ten times of second passband frequency can be obtained, thereby ensuring broad harmonics rejection characteristics without degradation of passbands. The measurement data have good agreement with the simulation. © 1963-2012 IEEE.

Kim H.-A.,Chonnam National University | Kim K.-J.,Chonnam National University | Seo K.H.,Jeollanamdo Biopharmaceutical Research Center | Lee H.-K.,Chonbuk National University | Im S.-Y.,Chonnam National University
FEBS Letters | Year: 2012

In this study, we investigated the role of PTEN (phosphatase and tensin homolog deleted on chromosome 10) in a platelet-activating factor (PAF)-induced experimental pulmonary tumor metastasis model. An adenovirus carrying PTEN cDNA (Ad-PTEN) reversed PAF-induced increase in phosphorylation of AKT as well as pulmonary metastasis of B16F10. PAF-induced pulmonary metastasis was inhibited by MAPK inhibitors, but not by PI3K inhibitor. Ad-PTEN abrogated PAF-induced phosphorylation of MAPKs. These data indicate PTEN/MAPK pathways play a key role in PAF-induced tumor metastasis. © 2012 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

Park D.,Kyungpook National University | Yun Y.-S.,Chonbuk National University | Park J.M.,Pohang University of Science and Technology
Biotechnology and Bioprocess Engineering | Year: 2010

The discovery and further development of biosorption phenomena provide a basis for a whole new technology aimed at the removal of various pollutants or the recovery of valuable resources from aqueous systems. Today, biosorption is one of the main components of environmental and bioresource technology. Since the status of scientific development of a technology can be reflected through analyses of the literatures pertaining to it, in this review, we qualitatively examine almost all aspects of biosorption research. A range of subjects are covered, including the initial history, raw materials, mechanisms, instrumental tools, process factors, modification and immobilization methods, recovery and regeneration, continuous processes, commercial application, and modeling studies of biosorption. Finally, we summarized the important considerations of the current research on biosorption, as well as the suggestions for its future directions. We believe that this review will prove to be useful for scientists and engineers in the performance of their research into biosorption. © KSBB.

Kwak Y.J.,Chonbuk National University | Park H.R.,Chonnam National University | Song M.Y.,Chonbuk National University
Metals and Materials International | Year: 2013

Magnesium with oxides or transition elements prepared by mechanical grinding under H2 (reactive mechanical grinding) showed relatively high hydriding and dehydriding rates when the content of additives was about 20 wt%. Ni, Fe2O3, and Fe were chosen as the oxides or transition elements to be added. Ti was also selected since it was considered to increase the hydriding and dehydriding rates by forming Ti hydride. Samples Mg-14Ni-3Fe2O3-3Ti (Sample A) and Mg-14Ni-2Fe 2O3-2Ti-2Fe (Sample B) were prepared by reactive mechanical grinding, and their hydrogen storage properties were compared. The activated Sample A had a little smaller hydriding rate than the activated Sample B, but a higher dehydriding rate than the activated Sample B. Sample A exhibits quite a larger dehydriding rate and quantity of hydrogen desorbed for 60 min than any other Mg-xNi-yFe2O3-zM (M=transition metals) samples. An addition of a relatively larger amount of Ti is considered to lead to quite a high hydriding rate and a high dehydriding rate of Sample A. © 2013 The Korean Institute of Metals and Materials and Springer Science+Business Media Dordrecht.

Park C.-G.,Chonbuk National University | Hwang J.-C.,Kyungpook National University | Hwang J.-C.,Korea Institute for Advanced Study | Noh H.,Korea Astronomy and Space Science Institute
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

Axion as a coherently oscillating scalar field is known to behave as cold dark matter in all cosmologically relevant scales. For conventional axion mass with 10 -5eV, the axion reveals a characteristic damping behavior in the evolution of density perturbations on scales smaller than the Solar System size. The damping scale is inversely proportional to the square root of the axion mass. We show that the axion mass smaller than 10 -24eV induces a significant damping in the baryonic density power spectrum in cosmologically relevant scales, thus deviating from the cold dark matter in the scale smaller than the axion Jeans scale. With such a small mass, however, our basic assumption about the coherently oscillating scalar field is broken in the early Universe. This problem is shared by other dark matter models based on the Bose-Einstein condensate and the ultralight scalar field. We introduce a simple model to avoid this problem by introducing evolving axion mass in the early Universe and present observational effects of a present-day low-mass axion on the baryon density power spectrum, the cosmic microwave background radiation temperature power spectrum, and the growth rate of baryon density perturbation. In our low-mass axion model, we have a characteristic small-scale cutoff in the baryon density power spectrum below the axion Jeans scale. The small-scale deviations from the cold dark matter model in both matter and cosmic microwave background radiation power spectra clearly differ from the ones expected in the cold dark matter model mixed with the massive neutrinos as a hot dark matter component. © 2012 American Physical Society.

Shin Y.S.,Chonbuk National University | Zhao C.,Shanghai JiaoTong University | Park J.K.,Chonbuk National University
Urology | Year: 2013

Objective: To introduce a new repair technique, inverted V-shape, for penile paraffinoma without necrosis of the ventral skin anastomosed. Materials and Methods: From March 2006 to July 2012, 34 patients underwent penile paraffinoma repair using the T-style or a new operation procedure, the inverted V-shape anastomosis with a bilateral scrotal flap. The patients were subdivided into 2 groups. In group 1, each patient underwent the T-style anastomosis. In group 2, each patient underwent the inverted V-shape anastomosis. Two circumferential incisions were made, one at the skin just proximal to the corona of the penis and one at the penoscrotal junction. Complete removal of the involved skin and subcutaneous tissue, including paraffinoma, was performed. Both scrotal flaps were drawn to the mid-dorsal portion of the corona after scrotal flaps were incised appropriately and sutured with a T-style anastomosis between the coronal and scrotal flaps. The ventral skin was anastomosed end to end to avoid the T-style anastomosis, similar to a dorsal anastomosis. We created an inverted V incision 1 cm below from the anastomosis site. The scrotal flaps were sutured layer by layer. Results: All 14 flaps survived completely without the necrosis of the ventral skin. The results were successful and without any major complications. Conclusion: Penile resurfacing without the T-style anastomosis at the ventral corona with bilateral scrotal flaps is a new technique for repair of penile paraffinoma. It is an effective and reliable method, especially for the saving corona and scrotal flap anastomosed to the ventral penile body. © 2013 Elsevier Inc.

Noh H.,Korea Astronomy and Space Science Institute | Park C.-G.,Chonbuk National University | Hwang J.-C.,Kyungpook National University | Hwang J.-C.,Korea Institute for Advanced Study
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2013

We prove that the axion as a coherently oscillating scalar field acts as a cold dark matter (CDM) to the second-order perturbations in all cosmological scales including the super-horizon scale. The proof is made in the axion-comoving gauge. For a canonical mass, the axion pressure term causes deviation from the CDM only on scales smaller than the Solar System size. Beyond such a small scale the equations of the axion fluid are the same as the ones of the CDM based on the CDM-comoving gauge which are exactly identical to the Newtonian equations to the second order. We also show that the axion fluid does not generate the rotational (vector-type) perturbation even to the second order. Thus, in the case of axion fluid, we have the relativistic/Newtonian correspondence to the second order, even considering the rotational perturbation. Our analysis is made in the presence of the cosmological constant, and can be easily extended to the realistic situation including other components of fluids and fields. © 2013 Elsevier B.V.

Kim S.-K.,Seoul National University | Shoeib M.,Environment Canada | Kim K.-S.,Chonbuk National University | Park J.-E.,Chonbuk National University
Environmental Pollution | Year: 2012

Despite concerns to their increasing contribution to ecological and human exposure, the atmospheric levels of poly- and perfluoroalkyl substances (PFASs) have been determined mainly in Europe and North America. This study presents the indoor and outdoor air concentrations of volatile PFASs [fluorotelomer alcohols (FTOHs), and perfluoroalkyl sulfonamides/sulfonamidoethanols/sulfonamide ethyl acetate (FOSAs/FOSEs/FOSEA)] for the first time in Korean cities. In contrast to the good agreement observed for indoor FTOHs levels in Korea and Europea/North America, FOSAs/FOSEs levels were 10-100-fold lower in Korean indoor air, representing a cultural difference of indoor source. Korean outdoor air contained higher PFAS levels than indoor air, and additionally showed different PFAS composition profile from indoor air. Thus, indoor air would not likely be a main contributor to atmospheric PFAS contamination in Korea, in contrast to western countries. Inhalation exposure of volatile PFASs was estimated to be a minor contributor to PFOA and PFOS exposure in Korea. © 2011 Elsevier Ltd. All rights reserved.

Song M.Y.,Chonbuk National University | Kwon S.N.,Chonbuk National University | Park H.R.,Chonnam National University
Journal of Korean Institute of Metals and Materials | Year: 2013

In this work, Mg-x wt% Fe2O3 wt% Ni alloys were prepared by mechanical grinding under hydrogen (reactive mechanical grinding) using a planetary ball mill, and pressure-composition isotherms of the samples were subsequently obtained. By measuring the absorbed hydrogen quantity as a function of number of cycles, the cycling properties of a Mg-5 wt% Fe 2O3-15 wt% Ni alloy was investigated. The Mg-10 wt% Fe2O3-5 wt% Ni alloy showed an equilibrium plateau pressure of 1.92 bar at 593 K and had a hydrogen storage capacity of 5.47 wt% at 593 K. The absorbed hydrogen quantity decreased as the number of cycles increased. The Ha value varied almost linearly with the number of cycles. The maintainability of absorbed hydrogen quantity at n = 150 was 73.8% for the hydriding reaction time of 60 min. Copyright © The Korean Institute of Metals and Materials.

Song M.Y.,Chonbuk National University | Kwak Y.J.,Chonbuk National University | Lee S.H.,Chonbuk National University | Park H.R.,Chonnam National University
Journal of Korean Institute of Metals and Materials | Year: 2013

In order to investigate the formation of a high pressure form of magnesium hydride, Y-MgH2, X-ray diffraction patterns before and after the hydriding reaction were obtained for samples of MgH2, MgH 2after reactive mechanical grinding (RMG), and 94 wt% MgH 2-6 wt% Ni after reactive mechanical grinding. In addition, absorbed hydrogen quantity versus time curves at the first cycle were examined. The MgH2 sample did not contain Y-MgH2. However, the MgH 2 after RMG and the 94 wt% MgH2-6 wt% Ni after RMG contained Y-MgH2. All these results prove that after reactive mechanical grinding, y-MgH2, one of the high pressure forms of MgH2, was formed in the MgH2 and 94 wt% MgH2-6 wt% Ni samples under low hydrogen pressures. © The Korean Institute of Metals and Materials.

Yoon K.-C.,Chonnam National University | Choi W.,Chonnam National University | You I.-C.,Chonbuk National University | Choi J.,Eun Hospital
Cornea | Year: 2011

Purpose:: To investigate the efficacy of umbilical cord serum eyedrops for the treatment of patients with recurrent corneal erosions. Methods:: Thirty-five eyes of 35 patients with recurrent corneal erosions were studied. Eighteen eyes were treated with 20% umbilical cord serum eyedrops in addition to artificial tears (group A), and 17 eyes received artificial tears only (group B). Frequency of recurrence of corneal erosions was compared between the 2 groups. Results:: The study included 17 male and 18 female patients. Mean age was 46.6 ± 13.4 years, and mean follow-up duration was 14.7 ± 2.5 months. No significant differences in age, sex, and follow-up duration were observed between the 2 groups. In group A, recurrence occurred 2 times in 3 eyes, 1 time in 3 eyes, and did not occur in 12 eyes. In group B, recurrence occurred 5 times in 1 eye, 3 times in 5 eyes, 2 times in 8 eyes, 1 time in 2 eyes, and did not occur in 1 eye. The mean frequency of recurrence was 0.50 ± 0.79 (0.04 ± 0.07 per month) in group A and 2.24 ± 1.09 (0.15 ± 0.08 per month) in group B (P < 0.01). No significant complications associated with serum use were observed. Conclusions:: In the treatment of recurrent corneal erosions, umbilical cord serum eyedrops may be effective in reducing the number of recurrences.

Moon C.-M.,Chonnam National University | Yang J.-C.,Chonbuk National University | Jeong G.-W.,Chonnam National University
Journal of Affective Disorders | Year: 2015

Background Generalized anxiety disorder (GAD) is associated with brain function and morphological alterations. This study investigated explicit verbal memory impairment in patients with GAD in terms of brain functional deficits in combination with morphologic changes. Methods Seventeen patients with GAD and 17 healthy controls matched for age, sex, and education level underwent high-resolution T1-weighted MRI and fMR imaging at 3 T during explicit verbal memory tasks with emotionally neutral and anxiety-inducing words. Results In response to the neutral words, the patients showed significantly lower activities in the regions of the hippocampus (Hip), middle cingulate gyrus (MCG), putamen (Pu) and head of the caudate nucleus (HCd) compared with healthy controls. In response to the anxiety-inducing words, the patients showed significantly higher activities in the ventrolateral prefrontal cortex and precentral gyrus. However, they showed lower activities in the Hip, MCG, Pu and HCd. In addition, patients with GAD showed a significant reduction in gray matter volumes, especially in the regions of the Hip, midbrain, thalamus, insula and superior temporal gyrus, compared with healthy controls. Limitations This study examined a small sample sizes in each of the groups, and there was no consideration of a medication effect on brain activity and volume changes. Conclusions This study provides evidence for the association between brain functional deficits and morphometric alterations in an explicit verbal memory task for patients with GAD. This finding is helpful for understanding explicit verbal memory impairment in connection with GAD symptoms. © 2015 Elsevier B.V. All rights reserved.

Chaudhary G.,Chonbuk National University | Jeong Y.,Chonbuk National University | Lim J.,Soonchunhyang University
IEEE Transactions on Microwave Theory and Techniques | Year: 2014

This paper presents a novel approach to the design and implementation of a distributed transmission line negative group delay filter (NGDF) with a predefined negative group delay (NGD) time. The newly proposed filter is based on a simple frequency transformation from a low-pass filter to a bandstop filter. The NGD time can be purely controlled by the resistors inserted into the resonators. The performance degradation of the NGD time and signal attenuation (SA) of the proposed NGDF according to the temperature dependent resistance variation is also analyzed. From this analysis, it is shown that the NGD time and SA variations are less sensitive to the resistance variation compared to those of the conventional NGD circuit. For an experimental validation of the proposed NGDF, a two-stage distributed microstrip line NGDF is designed, simulated, and measured at an operating center frequency of 1.962 GHz. These results show a group delay time of-7.3 ns with an SA of 22.65 dB at the center frequency and have good agreement with the simulations. The cascaded response of two NGDFs operating at different center frequencies is also presented in order to obtain broader NGD bandwidth. NGDFs with good reflection characteristics at the operating frequencies are also designed and experimentally verified. © 2014 IEEE.

Feletou M.,Institute Of Recherches Servier | Kohler R.,University of Southern Denmark | Kohler R.,Aragon Institute of Health science | Vanhoutte P.M.,University of Hong Kong | Vanhoutte P.M.,Chonbuk National University
Annals of Medicine | Year: 2012

The present review first summarizes the complex chain of events, in endothelial and vascular smooth muscle cells, that leads to endothelium- dependent relaxations (vasodilatations) due to the generation of nitric oxide (NO) by endothelial nitric oxide synthase (eNOS) and how therapeutic interventions may improve the bioavailability of NO and thus prevent/cure endothelial dysfunction. Then, the role of other endothelium-derived mediators (endothelium-derived hyperpolarizing (EDHF) and contracting (EDCF) factors, endothelin-1) and signals (myoendothelial coupling) is summarized also, with special emphasis on their interaction(s) with the NO pathway, which make the latter not only a major mediator but also a key regulator of endothelium-dependent responses. © 2012 Informa UK, Ltd.

Chaudhary G.,Chonbuk National University | Jeong Y.,Chonbuk National University | Lim J.,Soonchunhyang University
IEEE Transactions on Microwave Theory and Techniques | Year: 2013

This paper presents a novel approach to the design of tunable dual-band bandpass filter (BPF) with independently tunable passband center frequencies and bandwidths. The newly proposed dual-band filter principally comprises two dual-mode single band filters using common input/output lines. Each single BPF is realized using a varactor-loaded transmission-line dual-mode resonator. The proposed filter also offers switchable characteristics to select either of the passbands (either the first or the second passband only). To suppress the harmonics over a broad bandwidth, defected ground structures are used at input/output feeding lines without degrading the passbands characteristics. From the experimental results, it was found that the proposed filter exhibited the first passband center frequency tunable range from 1.48 to 1.8 GHz with a 3-dB fractional bandwidth (FBW) variation from 5.76% to 8.55% and the second passband center frequency tunable range from 2.40 to 2.88 GHz with the 3-dB FBW variation from 8.28% to 12.42%. The measured harmonic results of the proposed filters showed a rejection level of 19 dB, which is up to more than ten times of the highest center frequency of the first passband without degradation of the passbands. © 1963-2012 IEEE.

Yoon K.-C.,Chonnam National University | Im S.-K.,Chonnam National University | Kim H.-G.,Chonnam National University | You I.-C.,Chonbuk National University
Cornea | Year: 2011

Purpose: To determine the relative staining characteristics of the nasal and temporal conjunctiva as compared with other measures of dry eye and evaluate the qualitative clinical impression of the utility of the double vital staining with fluorescein and lissamine green. Methods: Ocular surface staining was performed with a mixture of 1% fluorescein and 1% lissamine green in 50 patients with dry eye (12 patients with Sjögren syndrome and 38 patients with non-Sjögren syndrome). Ocular surface disease index (OSDI), tear breakup time (BUT), and Schirmer test were evaluated. Digital photographs were taken after vital staining on the ocular surface, and the grade of staining in various areas was assessed. Correlation among the degrees of staining, OSDI, and ocular surface parameters was analyzed. Results: The nasal conjunctiva evidenced greater staining compared with the temporal conjunctiva and cornea (P = 0.04). Staining of the nasal conjunctiva showed significant correlation with OSDI (P < 0.01) and BUT (P = 0.03). Staining of the temporal conjunctiva correlated significantly with OSDI (P = 0.01), and staining of the cornea correlated with BUT (P = 0.02). Conclusions: Double vital staining with 1% fluorescein and 1% lissamine green correlates with symptoms and some ocular surface parameters in patients with dry eye and helps to identify ocular surface changes easily. It may be a useful method for the diagnosis of dry eye and the assessment of the therapeutic effect in patients with dry eye syndrome. Copyright © 2011 by Lippincott Williams & Wilkins.

Song M.Y.,Chonbuk National University | Kwon S.N.,Chonbuk National University | Hong S.-H.,Korea Institute of Machinery and Materials | Park H.R.,Chonnam National University
Metals and Materials International | Year: 2012

Mg-5wt%Ni-2.5wt%Fe-2.5wt%Ti (referred to as Mg-5Ni-2.5Fe-2.5Ti) hydrogen storage material was prepared by reactive mechanical grinding, after which the hydrogen absorption and desorption kinetics were investigated using a Sievert-type volumetric apparatus. A nanocrystalline Mg-5Ni-2.5Fe-2.5Ti sample was prepared by reactive mechanical grinding and hydriding-dehydriding cycling. Analysis by the Williamson- Hall method from an XRD pattern of this sample after 10 hydriding-dehydriding cycles showed that the crystallite size of Mg was 37.0 nm and that its strain was 0.0407%. The activation of Mg-5Ni-2.5Fe-2.5Ti was completed after three hydriding-dehydriding cycles. The prepared Mg-5Ni-2.5Fe-2.5Ti sample had an effective hydrogen-storage capacity near 5 wt% H. The activated Mg-5Ni-2.5Fe-2.5Ti sample absorbed 4.37 and 4.90 wt% H for 5 and 60 min, respectively, at 593K under 12 bar H2, and desorbed 1.69, 3.81, and 4.85 wt% H for 5, 10 and 60 min, respectively, at 593K under 1.0 bar H 2. © KIM and Springer.

Song M.Y.,Chonbuk National University | Mumm D.R.,University of California at Irvine | Park C.K.,Chonbuk National University | Park H.R.,Chonnam National University
Metals and Materials International | Year: 2012

The LiNi 1-yMyO 2 specimens with compositions of LiNiO 2, LiNi 0.975Ga 0.025O 2, LiNi 0.975Al 0.025O 2, LiNi 0.995 Ti 0.005O 2, and LiNi 0.990Al 0.005Ti 0.005O 2 were synthesized by wet milling and a solid-state reaction method. Among all the specimens, LiNi 0.990Al 0.005Ti 0.005O 2 has the largest first discharge capacity of 196.3 mAh/g at a rate of 0.1 C. At n=50, LiNiO 2 has the largest discharge capacity of 126.7 mAh/g. LiNiO 2 has the best cycling performance, its degradation rate of discharge capacity being 0.73 mAh/g/cycle. LiNi 0.975Al 0.025O 2 shows the lowest decrease rate of the first discharge capacity with C rate. An equation describing the variation of the discharge capacity with the number of charge-discharge cycles, n, is obtained. The Williamson- Hall method is applied to calculate the crystallite size and the strain of the samples before and after charge-discharge cycling. © KIM and Springer.

Song M.Y.,Chonbuk National University | Lee D.S.,LILB Process Engineering Team | Park H.R.,Chonnam National University
Materials Research Bulletin | Year: 2012

LiNi 1-yTi yO 2 (y = 0.000, 0.012, 0.025, 0.050, 0.100, and 0.150) and LiNi 0.975M 0.025O 2 (M = Zn, Al, and Ti) were synthesized by the solid-state reaction method. The voltage vs. discharge capacity curves for y = 0.012 and y = 0.025 exhibit four distinct plateaus corresponding to phase transitions. Among LiNi 1-yTi yO 2, LiNi 0.975Ti 0.025O 2 has the largest first discharge capacity, 154.8 mAh/g, at a rate of 0.1 C, and a relatively good cycling performance (77% at n = 10). Among LiNi 0.975M 0.025O 2 (M = Zn, Al, and Ti) samples, the LiNi 0.975Ti 0.025O 2 sample had the largest first discharge capacity. The LiNi 0.975Ti 0.025O 2 sample has sharper peaks for the -dx/dV vs. V curves than the LiNi 0.975M 0.025O 2 (M = Zn and Al). The LiNi 0.975Al 0.025O 2 sample, with the first discharge capacity of 128.5 mAh/g at a rate of 0.1 C, has the best cycling performance (98% at n = 10). © 2012 Elsevier Ltd. All rights reserved.

Ahn T.,Chonnam National University | Yun C.-H.,Chonnam National University | Kim H.-R.,Wonkwang University | Chae H.-J.,Chonbuk National University
Cell Calcium | Year: 2010

We investigated the effects of phospholipid composition in membranes and Bcl-2 homology (BH) domains of the Bcl-2 family on Ca 2+/H + antiporter activity of human recombinant Bax inhibitor-1 (BI-1) reconstituted into membranes. Cardiolipin (CL) and phosphatidylserine (PS) stimulated the proton-mediated efflux of Ca 2+ ions encapsulated into proteoliposomes when compared to Ca 2+ efflux from 100% phosphatidylcholine (PC) membranes in a CL or PS concentration-dependent manner. Concomitantly, the anionic phospholipids also enhanced H + ion influx into the membranes. Lateral segregations of CL and PS were observed through the fluorescence properties of fluorophore-labeled phospholipids upon BI-1 reconstitution in PC/CL or PC/PS binary systems. However, other anionic phospholipids, such as phosphatidic acid, phosphatidylglycerol, and phosphatidylinositol did not influence the stimulation of BI-1 functions in membranes. The peptide corresponding to the BH4 domain of Bcl-2 and Bcl-xL proteins stimulated the BI-1 activities in 100% PC membranes. The peptide also showed an additive effect with CL or PS. Furthermore, the CL, PS, and BH4 domains specifically increased oligomerization levels such as dimer and tetramer of BI-1 in membranes. Taken together, these results suggest that the CL, PS, and BH4 domains were stimulating factors for the Ca 2+/H + antiporter activities of BI-1 through protein oligomerization. © 2010 Elsevier Ltd.

Kim S.-H.,University of Ulsan | Hong S.-B.,University of Ulsan | Yun S.-C.,University of Ulsan | Choi W.-I.,Keimyung University | And 5 more authors.
American Journal of Respiratory and Critical Care Medicine | Year: 2011

Rationale: Administration of adjuvant corticosteroids to patients with pandemic influenza A/H1N1 2009 (pH1N1) may reduce in-flammation and improve outcomes. Objectives: To assess the effect of adjuvant corticosteroid treatment on the outcome of critically ill patients with pH1N1 infection. Methods: All adult patients with confirmed pH1N1 admitted to the intensive care unit of 28 hospitals in South Korea from September 2009 to February 2010 were enrolled. Patients with and without adjuvant corticosteroid treatment were retrospectively compared bytworisk stratification models:(1)a retrospective cohort study that used propensity score analysis to adjust for confounding by treatment assignment and (2) a propensity-matched case-control study. Measurements and Main Results: A total of 245 patients were enrolled in the cohort study, 107 of whom (44%) received adjuvant steroid treatment. In the cohort study, the 90-day mortality rate of patients given steroids (58%, 62 of 107) was significantly higher than that of those not given steroids (27%, 37 of 138) (P < 0.001). The steroid group was more likely to have superinfection such as secondary bacterial pneumonia or invasive fungal infection, and had more prolonged intensive care unit stays than the no-steroid group. Multivariate analysis indicated that steroid treatment was associated with increased 90-day mortality when independent predictors for 90-day mortality and propensity score were considered (adjusted odds ratio, 2.20; 95% confidence interval, 1.03-4.71). In the case-control study, the 90-day mortality rate in the steroid group was 54% (35 of 65) and 31% (20 of 65) in the no-steroid group (McNemar test, P = 5 0.004). Conclusions: Adjuvant corticosteroids were significantly associated with higher mortality in critically ill patients with pH1N1 infection. Copyright © 2011 American Thoracic Society.

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 J.H.,Chonbuk National University | Lee B.S.,University of Illinois at Urbana - Champaign
Computational Materials Science | Year: 2012

Modal analysis of single-walled carbon nanotubes (SWCNTs) and nanocones (SWCNCs) was performed using a finite element method (FEM) with ANSYS. The vibrational behaviors of fixed beam and cantilever SWCNTs with different section types of a circle and an ellipse were modeled using three-dimensional elastic beams of carbon bonds and point masses. Also, the vibrational behaviors of fixed beam and cantilever SWCNCs with different disclination angles of 120°, 180°, and 240° were modeled using the same method. The beam element natural frequencies were calculated by considering the mechanical characteristics of the covalent bonds between the carbon atoms in the hexagonal lattice. Each mass element of the carbon atoms was assigned as a point mass at the nodes of the FEM elements. The natural frequencies of zigzag and armchair SWCNTs and SWCNCs were also computed. There were some differences between the findings obtained in this study and the molecular structural mechanics data available in the literature. The natural frequencies of SWCNCs were estimated depending on the geometrical type and disclination angle with different boundary conditions. The natural frequencies of the SWCNCs with disclination angles of 120°, 180°, and 240° increased significantly at higher modes of vibration. © 2011 Elsevier B.V. All rights reserved.

Choi J.-M.,Chonbuk National University | Noh H.,Kookmin University
Journal of the Korean Physical Society | Year: 2015

In vectorial diffraction theory, tight focusing of a linearly-polarized laser beam produces an anisotropic field distribution around the focal plane. We present a numerical investigation of the electromagnetic field distribution of a focused beam in terms of the input beam’s polarization state and the associated effects on the trap stiffness asymmetry of optical tweezers. We also explore the symmetry change of a polarization-dependent optical force due to the electromagnetic field redistribution in the presence of dielectric spheres of selected diameters ranging from the Rayleigh scattering regime to the Mie scattering regime. © 2015, The Korean Physical Society.

Ryu B.-G.,KAIST | Kim J.,KAIST | Kim K.,KAIST | Choi Y.-E.,Chonbuk National University | And 2 more authors.
Bioresource Technology | Year: 2013

Waste spent yeast from brewery industry was used as a sole growth substrate to grow an oleaginous yeast Cryptococcus curvatus for the purpose of biodiesel production. Approximately 7. g/l/d of biomass productivity was obtained using only spent yeast (30. g/l) without additional nutrients and pretreatment of any kind. To make best use of available nutrients in the spent yeast, stepwise cultivation was carried out in a batch culture mode and the highest biomass and lipid content, which were 50.4. g/l and 37.7%, respectively, were obtained at 35:1 of C/N ratio. Lipid from C. curvatus was found to be a quality-sufficient source of oil as a transportation fuel in terms of cetane, iodine values, and oxidation stability, although the values of cold filter plugging point were less desirable. Economic evaluation revealed that the use of the spent yeast could significantly reduce the unit cost of yeast-based biodiesel production. © 2012 Elsevier Ltd.

Choi S.Y.,Chonbuk National University | Muhlleitner M.M.,Karlsruhe Institute of Technology | Zerwas P.M.,German Electron Synchrotron
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2013

We chart the theoretical basis of radiative decays of the Higgs boson, H→γγ and Zγ, for measuring the spin of the Higgs particle. These decay channels are complementary to other rare modes such as real/virtual Z-boson pair decays. In systematic helicity analyses the angular distribution for zero-spin is confronted with hypothetical spin-2± and higher assignments to quantify the sensitivity. © 2012 Elsevier B.V.

Park B.-Y.,Chonbuk National University | Park B.-Y.,University of Pennsylvania | Saint-Jeannet J.-P.,University of Pennsylvania
Gene Expression Patterns | Year: 2010

Runx genes encode a family of proteins defined by the highly conserved runt DNA-binding domain. Studies in several organisms have shown that these transcription factors regulate multiple aspects of embryonic development and are responsible for the pathogenesis of several human diseases. Here we report the cloning and expression of Runx3 during Xenopus development and compare its expression pattern to other Runx family members, Runx1 and Runx2, and to Cbfb, the obligatory binding partner of Runx proteins. Using in situ hybridization in the whole embryo and on sections we show that Runx3 is coexpressed with Runx1 in the hematopoietic lineage and in Rohon-Beard sensory neurons. In contrast Runx3 and Runx2 are co-expressed in craniofacial cartilage elements. Runx3 shows also unique expression domains in a number of derivatives of the neurogenic placodes, including the ganglia of the anteroposterior and middle lateral line nerves, and ganglia of the trigeminal, glossopharyngeal, facial and vagal nerves. These observations suggest a critical role for Runx3 in the development of cranial sensory neurons, while in other tissues its co-expression with Runx1 or Runx2 may signify functional redundancy between these family members. © 2010 Elsevier B.V. All rights reserved.

Lu M.,Columbia University | Lall U.,Columbia University | Schwartz A.,University of Strasbourg | Kwon H.,Chonbuk National University
Water Resources Research | Year: 2013

Atmospheric Rivers (ARs) are being increasingly identified as associated with some extreme floods. More generally, such floods may be associated with tropical moisture exports (TMEs) that exhibit relatively robust teleconnections between moisture source regions and flood regions. A large-scale flood event that persisted over Western Europe in January 1995 is studied here. During the last 10 days of the month, two rare flooding events, associated with heaviest rainfall in 150 years, occurred in two places, one over Brittany (West of France), and the second in the France-Germany border region and parts of neighboring countries. In this paper, we explore the month-long evolution of TMEs and their connection to the precipitation events that led to the Brittany event. The persistent large-scale atmospheric circulation patterns that led to the birth, death, and evolution of these TMEs as ARs with landfalls in Western Europe are identified, and the relationship of daily extreme precipitation to these patterns is examined. Singular value decomposition analysis and a generalized linear model are used to assess whether knowledge of the atmospheric circulation patterns from the prior record is useful for explaining the occurrence of their rare events. The analysis establishes the importance of both global and regional atmospheric circulation modes for the occurrence of such persistent events and the hydrologic importance of diagnosing global atmospheric moisture pathways. Key Points Association between extreme precipitation and atmospheric circulations Moisture sources and transports that lead to persistent extreme precipitation Precipitation predictability using identified circulation patterns ©2013. American Geophysical Union. All Rights Reserved.

Yoo G.,KAIST | Park W.-K.,KAIST | Kim C.W.,KAIST | Choi Y.-E.,Chonbuk National University | Yang J.-W.,KAIST
Bioresource Technology | Year: 2012

High-cost downstream process is a major bottleneck for producing microalgal biodiesel at reasonable price. Conventional lipid extraction process necessitates biomass drying process, which requires substantial amount of energy. In this regard, lipid extraction from wet biomass must be an attractive solution. However, it is almost impossible to recover lipid directly from wet microalgae with current technology. In this study, we conceived osmotic shock treatment as a novel method to extract lipid efficiently. Osmotic shock treatment was applied directly to wet Chlamydomonas reinhardtii biomass with water content >99%, along with both polar and non-polar organic solvents. Our results demonstrated that osmotic shock could increase lipid recovery approximately 2 times. We also investigated whether the presence of cell wall or different cell stages could have any impact on lipid recovery. Cell wall-less mutant stains and senescent cell phase could display significantly increased lipid recovery. Taken together, our results suggested that osmotic shock is a promising technique for wet lipid extraction from microalgal biomass and successfully determined that specific manipulation of biomass in certain cell phase could enhance lipid recovery further. © 2012 Elsevier Ltd.

Li L.,University of Sichuan | Liu C.,University of Sichuan | Ren H.,Chonbuk National University | Wang Q.-H.,University of Sichuan | Wang Q.-H.,Sichuan University
Optics Letters | Year: 2013

We report a tunable iris using two immiscible liquids. One liquid is opaque and conductive, while the other liquid is clear and insulating. The opaque liquid forms an iris-like opening in its central area on one glass substrate surface. The clear liquid is used to fill the outside space of the opaque liquid. In the voltage-off state, the opening presents the smallest aperture. When a voltage is applied to the liquids, the diameter of the iris is enlarged due to the electro-wetting effect. Our results show that the aperture of the iris can be tuned from ∼2.3 to ∼6.1 mm as the applied voltage is changed from 0 to ∼65 V. The response time and the transmittance in the opening area were measured to be ∼200 ms and ∼85%, respectively. Our adaptive iris has potential applications in beam controls, light shutters, and lab-on-a-chip devices. © 2013 Optical Society of America.

Song J.-S.,Chonbuk National University | Choi B.-W.,Inje University | Song K.-J.,Chonbuk National University
Journal of Clinical Neuroscience | Year: 2014

This study aimed to determine the risk factors for developing adjacent segment disease (ASDz) after anterior cervical arthrodesis for the treatment of degenerative cervical disease by analyzing patients treated with various fusion methods. We enrolled 242 patients who had undergone anterior cervical fusion for degenerative cervical disease, and had at least 5 years of follow-up. We evaluated the development of ASDz and the rate of revision surgery. To identify the risk factors for ASDz, the sagittal alignment, spinal canal diameter, range of motion of the cervical spine, number of fusion segments, and fusion methods were evaluated. The patients were divided into three groups according to the fusion method: Group A contained patients who had received autogenous bone graft only (53 patients), Group B contained patients who received autogenous bone graft and plate augmentation (62 patients), and Group C contained patients who underwent cage and plate augmentation (127 patients). ASDz occurred in 33 patients, of whom 19 required additional surgery. The risk of developing ASDz was significantly higher in male patients (p = 0.043), patients whose range of motion of the cervical spine was >30° (p = 0.027), and patients with spinal canal stenosis (p = 0.010). The rate of development of ASDz was not different depending on the number of fusion segments. The rate of development of ASDz was 41.5% in Group A, 9.6% in Group B, and 5.51% in Group C (p = 0.03). In patients who underwent anterior cervical arthrodesis for degenerative disease, the occurrence of ASDz was related to age, the cervical spine range of motion, and spinal canal stenosis. Additional plate augmentation for anterior cervical arthrodesis surgery can lower the rate of ASDz development. © 2013 Elsevier Ltd. All rights reserved.

Chon J.,earthmine | Kim H.,Chonbuk National University | Lin C.-S.,University of Missouri
ISPRS Journal of Photogrammetry and Remote Sensing | Year: 2010

This paper presents a novel algorithm that selects seam-lines for mosaicking image patches. This technique uses Dijkstra's algorithm to find a seam-line with the minimal objective function. Since a segment of seam-line with significant mismatch, even if it is short, is more visible than a lengthy one with small differences, a direct summation of the mismatch scores is inadequate. Limiting the level of the maximum difference along a seam-line should be part of the objective in the seam-line selection process. Our technique first determines this desired level of maximum difference, then applies Dijkstra's algorithm to find the best seam-line. A quantitative measure to evaluate a seam-line is proposed. The measure is defined as the sum of a fixed number of top mismatch scores. The proposed algorithm is compared with other techniques quantitatively and visually about various types of images. © 2009 International Society for Photogrammetry and Remote Sensing, Inc. (ISPRS).

Park J.W.,Pohang University of Science and Technology | Seo Y.J.,Chonbuk National University | Kim B.H.,Pohang University of Science and Technology
Chemical Communications | Year: 2013

Systematic modification of the 4A loop region of the Rb gene with PyA fluorophore units allows discrimination of the fluorescence signals corresponding to structural dynamics from single-stranded to i-motif structures. © 2014 The Royal Society of Chemistry.

Kim K.T.,Pohang University of Science and Technology | Veedu R.N.,University of Queensland | Seo Y.J.,Chonbuk National University | Kim B.H.,Pohang University of Science and Technology
Chemical Communications | Year: 2014

We have identified quencher-free molecular beacons that allow the sensitive probing of CAG repeat oligonucleotides, including mRNA fragments of trinucleotide repeat diseases, with significant increases in fluorescence intensity mediated by disruption of the stacking of their PyU units. This journal is © The Royal Society of Chemistry.

Lee D.G.,Chonbuk National University | Kim I.S.,Chonbuk National University | Park J.W.,Pohang University of Science and Technology | Seo Y.J.,Chonbuk National University
Chemical Communications | Year: 2014

We developed a multiplexed fluorophore system on a DNA scaffold (MFD) that produced new and diverse fluorescence properties depending on the mixing pattern and sequence that could not be obtained from each monomer fluorophore. Our approach for producing new fluorescence properties is relatively facile: simply mixing fluorophores on a DNA scaffold provides large variations in the color and intensity using only one excitation wavelength with high "Stokes shifts" (∼190 nm). Furthermore these special fluorescence properties could be controlled by the hybridization pattern and were therefore dependent on the structural changes in DNA. © 2014 the Partner Organisations.

Oh C.,Korea Polar Research Institute | Philippe M.,University Claude Bernard Lyon 1 | Kim K.,Chonbuk National University
Acta Palaeontologica Polonica | Year: 2015

The distribution of fossil wood genera has been demonstrated to be an effective proxy for Mesozoic terrestrial climates. In this study, we investigated the phytocoenoses, which were associated with Xenoxylon confirmed to be a marker for a cool and/or wet climate in a boreal hemisphere (i.e., Xenoxylon-phytocoenoses) during the Mesozoic, using specimens of fossil wood. It was confirmed that Xenoxylon co-occurs more often with some wood genera than with others. For example, Protocedroxylon, a wood that is most likely related to the Pinaceae, is the genus most often associated with Xenoxylon-phytocoenoses. Although Taxodioxylon is also found in Xenoxylon-phytocoenoses, it is not found, however, as consistently as Protocedroxylon. The distribution and diversity of Xenoxylon-phytocoenoses changed throughout the Mesozoic. During the Late Triassic and Late Cretaceous, Xenoxylon-phytocoenoses had low diversity and were restricted to higher palaeolatitudes during the Late Cretaceous. However, during the Early to Middle Jurassic, Xenoxylon-phytocoenoses were distributed much farther south, while their diversity concomitantly increased sharply. From the Late Jurassic to the Early Cretaceous, the distribution of Xenoxylon-phytocoenoses moved northward in Europe and even more so in East Asia. The changes in the distribution of Xenoxylon-phytocoenoses are in agreement with changes in both global and regional climates. Our results also demonstrated that, within the Xenoxylon distribution range, the corresponding phytocoenoses were differentiated along a latitudinal gradient and according to the global climate change patterns during the Mesozoic. Copyright © 2015 C. Oh et al.

Ahsanulhaq Q.,Chonbuk National University | Kim J.H.,Chonbuk National University | Lee J.S.,Pohang University of Science and Technology | Hahn Y.B.,Chonbuk National University
Electrochemistry Communications | Year: 2010

A method for measuring the electrical characteristics of aligned ZnO nanorod arrays (NRAs) directly grown on a pre-patterned four-point probe system in solution was proposed. This four-probe method enabled us to perform electrical measurements directly on the as-grown ZnO nanorod arrays without any additional processing. The location, shape and length of the rods directly grown on the four-probe electrodes were well controlled. The current-voltage characteristics showed a low turn-on voltage and a high saturation current. These ZnO NRAs devices were implemented as gas sensors for detecting hydrogen. The sensitivity increased with the concentration of H2 and the operating temperature. © 2010 Elsevier B.V. All rights reserved.

Choi B.-W.,Inje University | Song K.-J.,Chonbuk National University | Chang H.,Inje University
Asian Spine Journal | Year: 2011

Ossification of the posterior longitudinal ligament (OPLL) is most commonly found in men, in the elderly, and in Asian patients. The disease can start with mild or no symptoms, but some patients progress slowly to develop symptoms of myelopathy. An accurate diagnosis through the use plain radiograph, computed tomography, and magnetic resonance imaging findings is very important to monitor the development of symptoms and to make decisions regarding a treatment plan. When symptoms are mild and non-progressive, conservative treatments and periodic observations are good enough, but once symptoms of myelopathy are present and neurologic symptoms are progressive, the treatment of choice is surgery to relieve spinal cord compression. Surgical management of OPLL continues to be controversial. Each surgical technique has some advantages and disadvantages, and the choice of operation should be decided carefully with various considerations. The patient's neurological condition, location and extent of pathology, cervical kyphosis, presence or absence of accompanied instability, and the individual surgeon's experience must be an important factors that should be considered before surgery. © 2011 by Korean Society of Spine Surgery.

Chang D.W.,Ulsan National Institute of Science and Technology | Lee H.J.,Chonbuk National University | Kim J.H.,Seoul National University | Park S.Y.,Seoul National University | And 4 more authors.
Organic Letters | Year: 2011

Novel quinoxaline-based organic sensitizers using vertical (RC-21) and horizontal (RC-22) conjugation between an electron-donating triphenylamine unit and electron-accepting quinoxaline unit have been synthesized and used for dye-sensitized solar cells (DSSCs), leading to the relatively high power conversion efficiencies of 3.30 and 5.56% for RC-21 and RC-22, respectively. This result indicates that the quinoxaline electron-accepting unit is quite a promising candidate in organic sensitizers. © 2011 American Chemical Society.

Kwon J.-M.,Hanbat National University | Choi W.-Y.,Chonbuk National University | Kwon B.-H.,Pohang University of Science and Technology
IEEE Transactions on Industrial Electronics | Year: 2011

A single-stage quasi-resonant flyback converter is proposed for a cost-effective plasma display panel (PDP) sustain power module. The proposed converter operates at the boundary of the continuous- and discontinuous- conduction modes to reduce the switching loss of the primary switch. The bulk capacitor voltage can be independent of the output load and maintained within a practical range for the universal line input. By integrating two power conversion stages into one, the proposed converter provides a simple structure and high efficiency for the PDP sustain power module. The operational principle and theoretical analysis are presented. A prototype converter was built and tested for a 32-in PDP, which requires 150-W (180-V/0.83-A) sustain power. The experimental results verify the feasibility of the proposed scheme. © 2010 IEEE.

Jin H.,Pohang University of Science and Technology | Choi S.,Pohang University of Science and Technology | Velu R.,Pohang University of Science and Technology | Kim S.,Pohang University of Science and Technology | Lee H.J.,Chonbuk National University
Langmuir | Year: 2012

A multilayer of CdSe quantum dots (QDs) was prepared on the mesoporous surface of a nanoparticulate TiO 2 film by a layer-by-layer (LBL) assembly using the electrostatic interaction of the oppositely charged QD surface for application as a sensitizer in QD-sensitized TiO 2 solar cells. To maximize the absorption of incident light and the generation of excitons by CdSe QDs within a fixed thickness of TiO 2 film, the experimental conditions of QD deposition were optimized by controlling the concentration of salt added into the QD-dissolved solutions and repeating the LBL deposition a few times. A proper concentration of salt was found to be critical in providing a deep penetration of QDs into the mesopore, thus leading to a dense and uniform distribution throughout the whole TiO 2 matrix while anchoring the oppositely charged QDs alternately in a controllable way. A series of post-treatments with (1) CdCl 2, (2) thermal annealing, and (3) ZnS-coating was found to be very critical in improving the overall photovoltaic properties, presumably through a better connection between QDs, effective passivation of QD's surface, and a high impedance of recombination, which were proved by transmission electron microscopy (TEM) and electrochemical impedance spectroscopy (EIS) experiments. With a proper post-treatment of multilayered QDs as a sensitizer, the overall power conversion efficiency in the CdSe QD-sensitized TiO 2 solar cells could reach 1.9% under standard illumination condition of simulated AM 1.5G (100 mW/cm 2). © 2012 American Chemical Society.

Lee Y.-H.,Chonbuk National University | Lee Y.-H.,University of Pennsylvania | Saint-Jeannet J.-P.,University of Pennsylvania
Genesis | Year: 2011

The Sox family of transcriptional regulators has been implicated in the control of a broad array of developmental processes. One member of this family SOX9 was first identified as a candidate gene for campomelic dysplasia (CD), a human syndrome affecting skeletal, and testis development. In these patients most endochondral bones of the face fail to develop resulting in multiple defects such as micrognathia, cleft palate, and facial dysmorphia. In this review we describe Sox9 expression during embryonic development and summarize loss of function experiments in frog, fish, and mouse embryos highlighting the role of Sox9 in regulating morphogenesis of the face. We also discuss the mutations in and around SOX9 responsible for craniofacial defects in CD patients. © 2011 Wiley-Liss, Inc.

Jin H.,Pohang University of Science and Technology | Choi S.,Pohang University of Science and Technology | Lee H.J.,Chonbuk National University | Kim S.,Pohang University of Science and Technology
Journal of Physical Chemistry Letters | Year: 2013

A multilayer of quantum dots (QDs) is preferred for QD-sensitized solar cells over a monolayer counterpart to fully utilize the sunlight incident into a relatively thin-film-based photovoltaic device. A controlled assembly of QD multilayers such as layer-by-layer (LbL) assemblies can provide a model system to study the interactions between the QD layers and can offer an optimal device configuration for efficient solar power conversion. Recently, we have proposed a LbL QD assembly using electrostatic interactions of the surface charges and have successfully prepared a controlled multilayer of QD on the surface of mesoporous metal oxide films. The as-prepared tailor-made QD multilayers not only guaranteed the sufficient absorption of incident solar light but also provided a toolbox for the study and optimization of electron/energy transfers between QD layers. © 2013 American Chemical Society.

Zhang S.,Nanjing Southeast University | Zhang S.,University of Delaware | Xia X.-G.,University of Delaware | Xia X.-G.,Chonbuk National University | Wang J.,University of Kent
IEEE Journal on Selected Areas in Communications | Year: 2012

In this paper, the error rate performance and diversity gain of amplify-and-forward (AF) wireless relay networks are studied. The distributed space-time block code (DSTBC) in a synchronous relay network with multiple relay nodes is considered. The distributed linear dispersion code is used at the relays. The symbol (or codeword) error rate is studied in terms of upper and lower bounds through rigorous derivations, and the diversity gain of the DSTBC is derived, for any number of relay nodes. As a corollary, a necessary and sufficient condition is obtained for achieving full cooperative diversity. Arbitrary coding matrices at the relays, path loss and general linear power allocation are considered. Finally, the orthogonal frequency division multiplexing (OFDM)-based space-time transmission scheme in asynchronous cooperative networks is also discussed. © 2012 IEEE.

Cho S.H.,Samsung | Lee H.J.,Chonbuk National University | Ko Y.,Ulsan National Institute of Science and Technology | Park S.-M.,Ulsan National Institute of Science and Technology
Journal of Physical Chemistry C | Year: 2011

Effects of a few solubilizers on electrochemical oxidation of 3,4-ethylenedioxythiophene (EDOT) in aqueous media and on electrochemical, morphological, and electronic properties of its resultant thin polymer (PEDOT) films have been investigated by Fourier transform electrochemical impedance spectroscopic and current sensing atomic force microscopic experiments. Two different types of solubilizers including hydroxypropyl-β-cyclodextrin (HpβCD) forming an inclusion complex with a hydrophobic species and two anionic surfactants forming micelles, sodium dodecylsulfate (SDS) and sodium dodecylsulfonate (SDBS), were used due to the low solubility of the EDOT monomer in aqueous media. Results indicate that anionic surfactant micelles protect electrogenerated cationic species of monomers and oligomers by encapsulating them, leading to formation of polymer films of better properties. The polymer growth characteristics were shown to be closely related to electrical properties of resultant polymer films; PEDOT films obtained in the presence of SDS showed the best growth, ion transport, electrochemical, and electronic properties. © 2011 American Chemical Society.

Song K.-J.,Chonbuk National University | Choi B.-W.,Inje University | Jeon T.-S.,Inje University | Lee K.-B.,Chonbuk National University | Chang H.,Inje University
European Spine Journal | Year: 2011

Introduction The purpose of this study was to determine whether fusion causes adjacent segment degeneration or whether degeneration is due to disease progression. Materials and methods Eighty-seven patients that had undergone single level anterior cervical decompression and fusions with at least 5 years of follow-up were enrolled in this retrospective study. Segments adjacent to fusion levels (above or below) were allocated to group A, and all others were allocated to group B. Radiographic evaluations of adjacent level changes included assessments of; disc degenerative changes, anterior ossification formation, and segmental instability. The developments of new clinical symptoms were also evaluated. Results In group A, adjacent segment degenerative change developed in 28 segments (16%) and two cases (2%) developed new clinical symptoms. In group B, adjacent segment degenerative change developed in 10 segments (3%), and two cases (0.7%) also developed new clinical symptoms. Additional operations were performed in one patient in each group. Conclusion Although, fusion per se can accelerate the severity of adjacent level degeneration, no significant difference was observed between adjacent and non-adjacent segments in terms of the incidence of symptomatic disease. The authors conclude that adjacent segment disease is more a result of the natural history of cervical spondylosis than the presence of fusion. © Springer-Verlag 2011.

Yang J.,Ulsan National Institute of Science and Technology | Heo M.,Ulsan National Institute of Science and Technology | Lee H.J.,Chonbuk National University | Park S.-M.,Ulsan National Institute of Science and Technology | And 2 more authors.
ACS Nano | Year: 2011

The assembly of reduced graphene oxide (rGO) and fullerene (C60) into hybrid (rGO/C60) wires was successfully performed by employing the liquid-liquid interfacial precipitation method. The rGO sheets spontaneously wrapped C60 wires through the π-π interaction between rGO and C60. Structural characterization of the rGO/C60 wires was carried out by using UV/visible spectroscopy, scanning electron microscopy, and transmission electron microscopy. FET devices with rGO/C60 wires were fabricated to investigate their electrical properties. The I ds-Vg curves of the hybrid wires exhibited p-type semiconducting behavior both in vacuum and in air, indicating hole transport through rGO as a shell layer, whereas pure C60 wires and rGO sheets showed n-type and ambipolar behaviors, respectively, under vacuum. Possible application of the fabricated wires, such as photovoltaic devices, was also demonstrated. © 2011 American Chemical Society.

News Article | January 29, 2016

The editors of Current Applied Physics have given their recommendations for articles recently published in the journal. Editor in Chief, Eun Kyung Suh, Professor at Chonbuk National University and Executive Editor, Sungkyun Park, from Pusan National University, have recommended the following titles, all of which are free to download: Structural, morphological, compositional, and optical properties of single step electrodeposited Cu2ZnSnS4 (CZTS) thin films for solar cell application (Volume 14, Issue 3, March 2014, Pages 254–258. Authors: Seul Gi Lee, Jongmin Kim, Huyn Suk Woo, Yongcheol Jo, A.I. Inamdar, S.M. Pawar, Hyung Sang Kim, Woong Jung, Hyun Sik Im) A new era for liquid crystal research: Applications of liquid crystals in soft matter nano-, bio- and microtechnology (Volume 12, Issue 6, November 2012, Pages 1387–1412. Authors: Jan P.F. Lagerwall, Giusy Scalia)

Marvel S.A.,University of Michigan | Hong H.,Chonbuk National University | Papush A.,Cornell University | Strogatz S.H.,Cornell University
Physical Review Letters | Year: 2012

Some of the most pivotal moments in intellectual history occur when a new ideology sweeps through a society, supplanting an established system of beliefs in a rapid revolution of thought. Yet in many cases the new ideology is as extreme as the old. Why is it then that moderate positions so rarely prevail? Here, in the context of a simple model of opinion spreading, we test seven plausible strategies for deradicalizing a society and find that only one of them significantly expands the moderate subpopulation without risking its extinction in the process. © 2012 American Physical Society.

Kwon S.N.,Chonbuk National University | Song J.,Cornell University | Mumm D.R.,University of California at Irvine
Ceramics International | Year: 2011

LiNiO 2 was synthesized by the combustion method with various excess lithium amount z in Li 1 + zNiO 2 (z = 0.04, 0.08, 0.10, 0.12, and 0.15). The sample with z = 0.10 has the largest first discharge capacity of 195 mAh/g at 0.1 C rate and voltage range 2.7-4.4 V with the weight ratio of active material:acetylene black:binder = 85:10:5. The LiNiO 2 cathodes, in which the excess lithium amount z for the synthesis of LiNiO 2 was 0.10, were fabricated with various weight ratios of active material:acetylene black:binder (85:10:5, 85:12:3, and 90:7:3). The cathode with the ratio of active material:acetylene black:binder 85:10:5 has the best electrochemical properties. The variation, with C-rate, of discharge capacity vs. number of cycles curve for the LiNiO 2 cathode with the weight ratio of active material:acetylene black:binder = 85:10:5 was investigated. At 0.1 C rate, the LiNiO 2 cathode has the largest first discharge capacity, the discharge capacity degradation rate of 0.70 mAh/g/cycle and a discharge capacity at n = 50 of 134 mAh/g. © 2011 Elsevier Ltd and Techna Group S.r.l.

Vatankhah-Varnoosfaderani M.,Chonbuk National University | Vatankhah-Varnoosfaderani M.,Amirkabir University of Technology | Hashmi S.,Chonbuk National University | Hashmi S.,NED University of Engineering and Technology | And 2 more authors.
Polymer Chemistry | Year: 2014

Marine and freshwater mussels secrete proteinaceous adhesive materials for adherence to the substrates upon which they reside. It is well known that 3,4-dihydroxyphenylalanine (DOPA) is the key to understanding these mussel adhesive proteins (MAPs). In order to gain a better understanding of their complex formation and quick recovery upon rupturing, novel water soluble copolymers of N-isopropylacrylamide and dopamine methacrylate were synthesized in such a way that they have 1, 2.5, and 5 mole percent dopamine monomer with respect to the NIPAM monomer on average. The statistical distribution of DOPA-functionalities along the chain makes the material a close synthetic equivalent of the byssal thread proteins of mytili. At acidic pH, the aqueous copolymer solution behaves like an unentangled copolymer solution, but at basic pH, these catechol functionalities form a dicomplex with H3BO 3, thereby crosslinking two chains, proven by 11B-NMR and gelation. The polymer solution is thermosensitive with a pH-dependent lower critical solution temperature (LCST) between 21 and 33 °C, depending on the DOPA-content. If 2 or more functionalities per chain are present, a gel is formed that is self-healing with very quick recovery from sustained damage. The moduli of the gels depend on the concentration of functionalities. Hence, triple stimuli responsive copolymers were obtained. © 2014 The Royal Society of Chemistry.

Jeong H.-J.,Hoseo University | Shin S.-Y.,Kyung Hee University | Oh H.-A.,Kyung Hee University | Kim M.-H.,Chonbuk National University | And 2 more authors.
Journal of Pathology | Year: 2011

IL-32 is a described pro-inflammatory cytokine produced by T lymphocytes, natural killer cells, monocytes, and epithelial cells. However, the specific mechanism of IL-32 on allergic rhinitis (AR) has not been elucidated. Here, we report a significant increase of IL-32 protein and mRNA in the nasal mucosa of AR patients. In addition, in nasal mucosa tissue from AR patients, the level of IL-32 production correlated with inflammation, IL-1β, IL-18, and granulocyte-macrophage colony-stimulating factor (GM-CSF). In an AR animal model, IL-32 significantly increased IgE and inflammatory cytokine levels. IL-32 expression was induced by recombinant human GM-CSF via activation of caspase-1 in eosinophils. In addition, depletion of IL-32 prevents the production of inflammatory cytokines in eosinophils. In conclusion, IL-32 is an important cytokine involved in the inflammation of AR. The regulation of IL-32 expression may form the basis of a new strategy for the treatment of AR. Copyright © 2011 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Stadler F.J.,Friedrich - Alexander - University, Erlangen - Nuremberg | Stadler F.J.,Chonbuk National University | Karimkhani V.,Amirkabir University of Technology
Macromolecules | Year: 2011

Different rheological quantities, such as the zero shear-rate viscosity η 0 and the linear steady-state elastic compliance J e 0 of long-chain branched metallocene-catalyzed ethene homopolymers and ethene-/α-olefin copolymers with a polydispersity M w/M n≈ 2, were correlated with the molar mass M w and degree of long-chain branching λ. A linear reference for the δ(|G *|) plot was used to show the effect of long-chain branches on this rheological property. The linear steady-state elastic compliance J e 0 correlated with the zero shear-rate viscosity increase factor η 0/η 0 lin and the characteristic phase angle δ c. However, the latter only works when compensating for the influence of the molar mass on J e 0 by the relationship between J e 0 and M w established elsewhere (Stadler and Münstedt, JoR, 2008). The characteristic phase angle δ c and zero shear-rate viscosity enhancement factor η 0/η 0 lin are linked to each other by the linear dependencies for the type I and type II viscosity functions. © 2011 American Chemical Society.

Hong H.,Chonbuk National University | Strogatz S.H.,Cornell University
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2011

We consider a variant of the Kuramoto model in which all the oscillators are now assumed to have the same natural frequency, but some of them are negatively coupled to the mean field. These contrarian oscillators tend to align in antiphase with the mean field, whereas, the positively coupled conformist oscillators favor an in-phase relationship. The interplay between these effects can lead to rich dynamics. In addition to a splitting of the population into two diametrically opposed factions, the system can also display traveling waves, complete incoherence, and a blurred version of the two-faction state. Exact solutions for these states and their bifurcations are obtained by means of the Watanabe-Strogatz transformation and the Ott-Antonsen ansatz. Curiously, this system of oscillators with identical frequencies turns out to exhibit more complicated dynamics than its counterpart with heterogeneous natural frequencies. © 2011 American Physical Society.

Hong H.,Chonbuk National University | Strogatz S.H.,Cornell University
Physical Review Letters | Year: 2011

We consider a generalization of the Kuramoto model in which the oscillators are coupled to the mean field with random signs. Oscillators with positive coupling are "conformists"; they are attracted to the mean field and tend to synchronize with it. Oscillators with negative coupling are "contrarians"; they are repelled by the mean field and prefer a phase diametrically opposed to it. The model is simple and exactly solvable, yet some of its behavior is surprising. Along with the stationary states one might have expected (a desynchronized state, and a partially-synchronized state, with conformists and contrarians locked in antiphase), it also displays a traveling wave, in which the mean field oscillates at a frequency different from the population's mean natural frequency. © 2011 American Physical Society.

Wu D.,Mount Sinai Medical Center | Wu D.,Chonbuk National University | Kraut J.A.,University of California at Los Angeles
American Journal of Nephrology | Year: 2014

Background: Metabolic acidosis is associated with impaired cellular function. This has been attributed to the accompanying reduction in intracellular and interstitial pH of the myocardium. Recent studies suggest that activation of the cellular Na+-H+ exchanger NHE1 might contribute to myocardial dysfunction. This review examines the experimental evidence which supports the role of NHE1 in the genesis of acidosis-induced cellular dysfunction, the benefits of its inhibition, and the type of acidosis that might benefit from therapy. Summary: Information was obtained by searching MEDLINE for articles published between 1969 and 2013 using the terms: NHE1, metabolic acidosis, lactic acidosis, ischemia-reperfusion, shock, resuscitation, high anion gap acidosis, and non-gap acidosis. Each article was also reviewed for additional suitable references. Nineteen manuscripts published between 2002 and 2013 assessed the impact of inhibition of NHE1 on cellular function. They revealed that NHE1 is activated with metabolic acidosis associated with hypoxia, hypoperfusion, hemorrhagic shock, and sepsis. This was associated with a rise in cellular sodium and calcium and cardiac dysfunction including reduced contractility and a predisposition to cardiac arrhythmias. Inhibition of NHE1 with specific inhibitors improved cardiac function, reduced blood and tissue levels of proinflammatory cytokines, and decreased mortality. Key Message: These results suggest that use of inhibitors of NHE1 might be worthwhile in the treatment of some types of acute metabolic acidosis, specifically the lactic acidosis associated with hypoxia, hemorrhagic shock, and cardiac arrest. Its potential role in the treatment of other forms of acute metabolic acidosis remains to be determined. © 2014 S. Karger AG, Basel.

Koo H.,University of Rochester | Xiao J.,University of Rochester | Klein M.I.,University of Rochester | Jeon J.G.,Chonbuk National University
Journal of Bacteriology | Year: 2010

Streptococcus mutans is a key contributor to the formation of the extracellular polysaccharide (EPS) matrix in dental biofilms. The exopolysaccharides, which are mostly glucans synthesized by streptococcal glucosyltransferases (Gtfs), provide binding sites that promote accumulation of microorganisms on the tooth surface and further establishment of pathogenic biofilms. This study explored (i) the role of S. mutans Gtfs in the development of the EPS matrix and microcolonies in biofilms, (ii) the influence of exopolysaccharides on formation of microcolonies, and (iii) establishment of S. mutans in a multispecies biofilm in vitro using a novel fluorescence labeling technique. Our data show that the ability of S. mutans strains defective in the gtfB gene or the gtfB and gtfC genes to form microcolonies on saliva-coated hydroxyapatite surfaces was markedly disrupted. However, deletion of both gtfB (associated with insoluble glucan synthesis) and gtfC (associated with insoluble and soluble glucan synthesis) is required for the maximum reduction in EPS matrix and biofilm formation. S. mutans grown with sucrose in the presence of Streptococcus oralis and Actinomyces naeslundii steadily formed exopolysaccharides, which allowed the initial clustering of bacterial cells and further development into highly structured microcolonies. Concomitantly, S. mutans became the major species in the mature biofilm. Neither the EPS matrix nor microcolonies were formed in the presence of glucose in the multispecies biofilm. Our data show that GtfB and GtfC are essential for establishment of the EPS matrix, but GtfB appears to be responsible for formation of microcolonies by S. mutans; these Gtf-mediated processes may enhance the competitiveness of S. mutans in the multispecies environment in biofilms on tooth surfaces. Copyright © 2010, American Society for Microbiology. All Rights Reserved.

Kim M.-H.,Chonbuk National University | Seo J.-H.,Chonbuk National University | Kim H.-M.,Kyung Hee University | Jeong H.-J.,Hoseo University
European Journal of Pharmacology | Year: 2014

Zinc (Zn) is an essential trace metal for eukaryotes. The roles of Zn in the numerous physiological functions have been elucidated. Bamboo salt contains Zn that was shown to have anti-inflammatory effect and other health benefits. Nanoparticles of various types have found application in the biology, medicine, and physics. Here we synthesized tetrapod-like, zinc oxide nanoparticles (ZO-NP; diameter 200 nm, source of Zn) using a radio frequency thermal plasma system and investigated its effects on mast cell-mediated allergic inflammatory reactions. ZO-NP was found to inhibit the productions and mRNA expressions of inflammatory cytokines such as interleukin (IL)-1β, IL-6, and tumor necrosis factor-α on the phorbol 12-myristate 13-acetate plus A23187 (PMACI)-stimulated human mast cell line, HMC-1 cells. In these stimulated cells, caspase-1 and nuclear factor-κB activations were abolished by ZO-NP, and the expressions of receptor interacting protein2 (RIP2) and IκB kinaseβ (IKKβ) induced by PAMCI were reduced. On the other hand, ZO-NP alone increased the expressions of RIP2 and IKKβ in normal condition. ZO-NP inhibited the phosphorylation of extracellular signal-regulated protein kinase in the PMACI-stimulated HMC-1 cells. Furthermore, ZO-NP significantly inhibited passive cutaneous anaphylaxis activated by anti-dinitrophenyl IgE. These findings indicate that ZO-NP effectively ameliorates mast cell-mediated allergic inflammatory reaction, and suggest that ZO-NP be considered a potential therapeutic for the treatment of mast cell-mediated allergic diseases. © 2014 Elsevier B.V.

Lee K.-M.,University of North Texas | Lee S.-K.,Chonbuk National University | Choi T.-Y.,University of North Texas
Applied Physics A: Materials Science and Processing | Year: 2012

We developed a reliable and highly reproducible way of fabricating a one-stop measurement platform for characterizing the thermoelectric properties of individual nanowires (NWs) using a focused ion beam and a nanomanipulator. 3-ω and 1-ω signals obtained by the four-point-probe method were used in measuring the thermal and electrical conductivities of the NW. Subsequently, the Seebeck coefficient was measured by using additional nanoelectrodes including a nanoheater. The thermal conductivity of the single β-SiC NW was obtained at 86.5±3.5 W/mK. The Seebeck coefficient was obtained to be -1.21 mV/K by using the same measurement platform. Thus, the dimensionless figure of merit, ZT=σS 2 T/k, was measured to be ∼0.12. This value is around 120 times higher than the reported maximum value of bulk β-SiC. © 2011 Springer-Verlag.

Hashmi S.,NED University of Engineering and Technology | Ghavaminejad A.,Chonbuk National University | Obiweluozor F.O.,Chonbuk National University | Vatankhah-Varnoosfaderani M.,Amirkabir University of Technology | Stadler F.J.,Chonbuk National University
Macromolecules | Year: 2012

Hybrid hydrogels of poly(N-isopropylacrylamide) (pNIPAM) containing carboxylate carbon nanotubes (CNTs) and/or zwitterions are synthesized by free radical polymerization. The supramolecular interactions among zwitterionic monomers and CNTs influence the mechanical properties and diffusion mechanism in hybrid hydrogel systems. These supramolecular interactions and response behavior of hybrid hydrogels were tested mechanically and with respect to their swelling characteristics. Hybrid hydrogels of pNIPAM and CNT or pNIPAM, zwitterions, and CNT follow a Fickian diffusion behavior, while adding zwitterions leads to an anomalous triple-stage swelling behavior and stiffening of the gel due to the interactions of the zwitterions with each other, which significantly increase the viscous dissipation and change the microscopic structure. While CNT itself stiffens the gel and slightly increases the diffusion speed, it complexes zwitterions, which leads to a novel property profile that is both potentially antibiotic and electrically conductive. CNT affords a relaxation process at long relaxation times, while zwitterion attachment and detachment lead to dissipation predominantly at high frequencies. Dynamic rheological measurements were performed during swelling of these complex materials. © 2012 American Chemical Society.

Mishra S.C.,Indian Institute of Technology Guwahati | Kim M.Y.,Chonbuk National University | Maruyama S.,Tohoku University
International Journal of Heat and Mass Transfer | Year: 2012

This article reports results of the four popular and widely used numerical methods, viz., the Monte Carlo method (MCM), the discrete transfer method (DTM), the discrete ordinates method (DOM) and the finite volume method (FVM) used to calculate radiative information in any thermal problem. Different classes of problems dealing with radiation and/or conduction heat transfer problems in a 2-D rectangular absorbing, emitting and scattering participating medium have been considered. In radiative equilibrium and non-radiative equilibrium cases, the MCM results have been used as the benchmark data for comparing the performances of the DTM, the DOM and the FVM. In the combined radiation and conduction mode problem, the energy equation has been formulated using the lattice Boltzmann method (LBM). To compare the performance of the DTM, the DOM and the FVM, the required radiative field data computed using these methods have been provided to the LBM formulation. Temperature distributions obtained using the four methods and those obtained from the LBM in conjunction with the DTM, the DOM and the FVM have been compared for different parameters such as the extinction coefficient, the scattering albedo, the conduction-radiation parameter, the wall emissivity, the aspect ratio and heat generation rate. In all the cases, results of these methods have been found in good agreements. Computationally, the DTM was found the most time consuming, and the DOM was computationally the most efficient. © 2012 Elsevier Ltd. All rights reserved.

Park O.-K.,Korea Institute of Science and Technology | Park O.-K.,Chonbuk National University | Hahm M.G.,Rice University | Lee S.,Korea Institute of Science and Technology | And 6 more authors.
Nano Letters | Year: 2012

Highly conductive reduced graphene oxide (GO) polymer nanocomposites are synthesized by a well-organized in situ thermochemical synthesis technique. The surface functionalization of GO was carried out with aryl diazonium salt including 4-iodoaniline to form phenyl functionalized GO (I-Ph-GO). The thermochemically developed reduced GO (R-I-Ph-GO) has five times higher electrical conductivity (42 000 S/m) than typical reduced GO (R-GO). We also demonstrate a R-I-Ph-GO/polyimide (PI) composites having more than 10 4 times higher conductivity (∼1 S/m) compared to a R-GO/PI composites. The electrical resistances of PI composites with R-I-Ph-GO were dramatically dropped under ∼3% tensile strain. The R-I-Ph-GO/PI composites with electrically sensitive response caused by mechanical strain are expected to have broad implications for nanoelectromechanical systems. © 2012 American Chemical Society.

Mahmoudi T.,Chonbuk National University | Karimkhani V.,Amirkabir University of Technology | Song G.S.,Chonbuk National University | Lee D.S.,Chonbuk National University | Stadler F.J.,Chonbuk National University
Macromolecules | Year: 2013

A resin mixture of vinyl ester and carboxyl terminated butadiene diluted with styrene shows an increase of viscosity when shearing the sample. Unlike previous reports on rheopexy and shear induced gelation of unfilled systems, this behavior leads to permanently elevated levels of viscosity. FT-IR found no indication of a chemical reaction, and therefore, the changes must be physical in nature - believed to be an increase in the number of hydrogen bonds. On the basis of the results, it is concluded that a physical network based on supramolecular attractions between the -COOH groups of the carboxyl terminated butadiene is formed, which leads to a time-dependent behavior and increase in viscosity at certain shear rate, at longer shearing times. This is a new effect, which we call "irreversible shear induced gelation by supramolecular bonding". © 2013 American Chemical Society.

Lee K.M.,University of North Texas | Choi T.Y.,University of North Texas | Lee S.K.,Chonbuk National University | Poulikakos D.,ETH Zurich
Nanotechnology | Year: 2010

Control of one-dimensional (1D) nanostructures is demonstrated in this paper by selectively placing and aligning silicon carbide (β-SiC) nanowires (NWs). We developed a reliable and highly reproducible way of placing a single or double SiC NW on pre-patterned electrodes by using a focused ion beam and a nanomanipulator. 3-ω signals obtained by the four-point-probe method were used in measuring the thermal conductivity of the NWs. The thermal conductivities of the placed single and double β-SiC NWs were obtained at 82 ± 6WmK- 1 and 73 ± 5WmK- 1, respectively. The proposed technique offers new possibilities for manipulating and evaluating 1D nanoscale materials. © 2010 IOP Publishing Ltd.

Mishra S.C.,Indian Institute of Technology Guwahati | Krishna C.H.,Chonbuk National University | Kim M.Y.,Tohoku University
Numerical Heat Transfer; Part A: Applications | Year: 2011

This article deals with the analysis of radiative transport with and without conduction in a finite concentric cylindrical enclosure containing absorbing, emitting, and scattering medium. Isothermal medium as the radiation source confined between the cold cylinders and a nonisothermal medium with the inner cylinder as the radiation source are the two nonradiative and radiative equilibrium problems. They involve only calculation of radiative information. In the third problem, a conducting-radiating medium is thermally perturbed by raising the temperature of the inner cylinder. In all problems, radiative information is computed using the modified discrete ordinate method (MDOM), and in the third problem, the lattice Boltzmann method (LBM) is used to formulate and solve the energy equation. Depending on the problems, effects of various parameters such as the extinction coefficient, the scattering albedo, the boundary emissivity, the conduction-radiation parameter, and the radius ratio are studied on temperature and heat flux distributions. The MDOM and the LBM-MDOM results are compared with those available in the literature. To further establish the accuracy of the MDOM and the LBM-MDOM results, in all problems, comparisons are made with the results obtained from the finite volume method (FVM) and the finite difference method-FVM approach, in which FVM provides the radiative information. The selection of the FDM-FVM for the third problem is also with the objective that for this problem, not much work is reported in which the FVM is used to calculate the radiative information. MDOM and LBM-MDOM results are found to compare well with those available in the literature, and in all cases they are in excellent agreement with FVM and FDM-FVM approaches. Copyright © Taylor & Francis Group, LLC.

Romankov S.,Chonbuk National University | Hayasaka Y.,Tohoku University | Shchetinin I.V.,National University of Science and Technology "MISIS" | Yoon J.M.,Chonbuk National University
Acta Materialia | Year: 2012

Ni-Al-Ti sheets were fabricated using a ball-collision technique at room temperature in an ambient atmosphere. The 0.5 mm thick Ni, Al and Ti foils were stacked and fixed at the top of a vibration chamber and ball-treated for durations of between 5 and 30 min. The microstructural evolution of the sheets was investigated as a function of the processing time and the mass of the ball. Joining of materials was considered to have occurred when materials at the interface plasticized, flowed and came into intimate contact under the high pressure developed by the ball collisions. The key parameters of the process were impact energy and processing time. Larger balls with higher impact energy were more effective for joining, and smaller balls were more effective for grain refinement. The transformation difference in grain refinement was attributed to the impact frequency, which appeared to be higher for the smaller balls. Ball collisions may have refined the grains of the Ni and Ti sheets to the nanometer scale, thereby destroying the initial rolling texture and inducing the formation of the fiber texture. The formation and stability of the 〈1 1 1〉 fiber texture in Ni were affected by the ball mass. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Hong H.,Chonbuk National University | Strogatz S.H.,Cornell University
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2012

We consider a variant of the Kuramoto model of coupled oscillators in which both attractive and repulsive pairwise interactions are allowed. The sign of the coupling is assumed to be a characteristic of a given oscillator. Specifically, some oscillators repel all the others, thus favoring an antiphase relationship with them. Other oscillators attract all the others, thus favoring an in-phase relationship. The Ott-Antonsen ansatz is used to derive the exact low-dimensional dynamics governing the system's long-term macroscopic behavior. The resulting analytical predictions agree with simulations of the full system. We explore the effects of changing various parameters, such as the width of the distribution of natural frequencies and the relative strengths and proportions of the positive and negative interactions. For the particular model studied here we find, unexpectedly, that the mixed interactions produce no new effects. The system exhibits conventional mean-field behavior and displays a second-order phase transition like that found in the original Kuramoto model. In contrast to our recent study of a different model with mixed interactions, the π state and traveling-wave state do not appear for the coupling type considered here. © 2012 American Physical Society.

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.

El-Deen A.G.,Chonbuk National University | Barakat N.A.M.,Chonbuk National University | Barakat N.A.M.,Minia University | Khalil K.A.,King Saud University | Kim H.Y.,Chonbuk National University
Journal of Materials Chemistry A | Year: 2013

Among the various carbonaceous materials, carbon nanofibers (CNFs) are widely utilized in different applications because of their superior mechanical and physicochemical characteristics. However, due to the low surface area compared to other nanocarbonaceous materials, CNFs performance as an electrode in capacitive deionization (CDI) units is comparatively low. In this study, this problem has been overcome by preparing multi-channel carbon nanofibers having a total surface area 10 times more than the conventional CNFs, by creating numerous channels on the nanofibers surface. The modified CNFs have been synthesized using a low cost, high yielding and facile method; an electrospinning technique. Typically, the stabilization and graphitization of electrospun nanofiber mats composed of polyacrylonitrile (PAN) and poly(methyl methacrylate) (PMMA) leads to the formation of multi-channel CNFs due to the difference in the physicochemical characteristics of the two polymers and the complete thermal decomposition of the PMMA during the graphitization step. Three formulations were prepared; 0, 25 and 50 wt% PMMA with respect to the PAN. To properly evaluate the introduced modified CNFs, graphene was prepared using the chemical route. The utilized characterizations indicated that the CNFs obtained from the electrospun solution having 50% PMMA possess a surface area of 181 m2 g-1, which is more than all the investigated formulations including graphene. Accordingly, these nanofibers revealed a salt removal efficiency of ∼90% and a specific capacitance of 237 F g -1. Overall, the present study introduces an effective and simple strategy to distinctly improve the surface area of CNFs, which can strongly enhance their application in CDI technology. © 2013 The Royal Society of Chemistry.

El-Deen A.G.,Chonbuk National University | Barakat N.A.M.,Chonbuk National University | Barakat N.A.M.,Minia University | Kim H.Y.,Chonbuk National University
Desalination | Year: 2014

Due to its marvelous characteristics, huge surface area and excellent electric conductivity, graphene is an optimum electrode in the capacitive deionization (CDI) units if the specific capacitance could be improved. In this study, novel strategy for rapid transformation of graphite into graphene-intercalated with nanostructure MnO2 with morphology control is introduced by one-pot reaction, low-time consuming and eco-environmentally method. Conversion of graphite into the graphene structure was suggested through vigorous oxidation using ammonium peroxysulphate and hydrogen peroxide in the presence of manganese sulfate followed by a reduction step using piperidine under a microwave irradiation. It was demonstrated that formation of MnO2 nanostructures during the exfoliation process has a great impact to separate the graphene sheets as the metallic nanostructures wedged among the sheets. Interestingly, morphology control could be performed; MnO2-nanorods and MnO2-nanparticles at graphene could be prepared. As an electrode in the CDI unit, the synthesized MnO2-nanorods at graphene revealed excellent results in specific capacitance (292F/g), distinct electrosorptive capacity (5.01mg/g), amazing salt removal efficiency (~93%) and distinguished recyclability. Overall, this work introduces an effective technique to improve the interfacial contact area between MnO2 and graphene nanosheets which enhances the electrochemical performance and recommends utilizing the introduced material as a promising electrode for CDI units. © 2014 Elsevier B.V.

El-Deen A.G.,Chonbuk National University | Barakat N.A.M.,Chonbuk National University | Barakat N.A.M.,Minia University | Khalil K.A.,King Saud University | Kim H.Y.,Chonbuk National University
New Journal of Chemistry | Year: 2014

Capacitive deionization (CDI) is strongly recommended as an environmentally friendly and economical technique for removing salt ions from saline water. In this study, highly efficient hollow carbon nanofiber electrodes for capacitive deionization were prepared using co-axial electrospinning of poly(methyl methacrylate) (core) and poly(acrylonitrile) (shell) polymer solutions, followed by oxidative stabilization and then carbonization. The morphology, pore structure and electrochemical performance were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), nitrogen adsorption-desorption isotherms, and cyclic voltammetry, respectively. The synthesized hollow carbon nanofibers had a specific capacitance of 222.3 F g-1, which is almost 4 times higher than the corresponding value for solid carbon nanofibers (63 F g-1). Moreover, the surface area of the hollow nanofibers (186 m2 g-1) was 10 times greater compared to the surface area of solid carbon nanofibers (17.7 m2 g-1). Accordingly, the salt ion electrosorption capacity of the modified carbon nanofibers was greatly enhanced; the hollow nanofibers exhibited an excellent desalination performance (∼86%) and a better cycling ability. These properties are attributed to the hollow structure. Overall, the proposed modification to carbon nanofibers makes them adequate not only for use as promising electrodes for the CDI process but also for any application requiring carbonaceous materials with a high specific surface area. This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2014.

Abdal-Hay A.,Chonbuk National University | Barakat N.A.M.,Chonbuk National University | Barakat N.A.M.,Minia University | Lim J.K.,Chonbuk National University
Ceramics International | Year: 2013

The corrosion behavior of magnesium and its alloys in the electrolytic physiological environment is extremely poor; this imposes a limitation for their use in orthopedic applications. In the present study, the effect of spray coating AZ31 magnesium alloy with membrane films of pristine and hydroxyapatite-doped poly(lactic acid) on corrosion behavior and bioactivity is investigated. Polymer concentration was found to have a strong impact on the pore size of the coating layer. However, addition of HAp NPs distinctly stimulated the precipitation of an apatite-like compound upon soaking the samples in a simulated body fluid (SBF). Magnesium coated samples revealed three orders of magnitude less corrosion compared to the naked samples, which indicates a stable electrochemical corrosion resistance. During a 15 days in-vitro test, pH variation, weight loss, and bending strength were lower for the coated samples (with average values of 8.5%, 7.2% and 10%, respectively) than the control sample (10.5%, 15.5%, and 25%, respectively). Moreover, the coated samples showed good bending strength characteristics. Cytocompatibility studies on MC3T3 cells revealed a continuous increase in cell growth with the coated samples. Overall, the suggested strategy might open a new avenue to widen utilization of Mg alloys as implant materials for orthopedic applications. © 2012 Elsevier Ltd and Techna Group S.r.l.

Lee K.H.,Chonbuk National University | Han S.-W.,Chonbuk National University | Kwon K.-Y.,Gyeongsang National University | Park J.B.,Chonbuk National University
Journal of Colloid and Interface Science | Year: 2013

Graphene has been modified with palladium nanoparticles (Pd NPs) to develop high performance catalysts for the Sonogashira cross coupling reaction. In this research, graphite oxide (GO) sheets exfoliated from graphite were impregnated with Pd(OAc)2 to prepare Pd2+/GO. Thermal treatments of the Pd2+/GO in H2 flow at 100°C produced Pd/graphene (Pd/G) nanocomposites. TEM images show that Pd NPs were distributed quite uniformly on the graphene sheet without obvious aggregation, and the mean size of Pd NPs was determined to be less than 2nm in diameter. Morphological and chemical structures of the GO, Pd2+/GO, and Pd/G were investigated using FT-IR, XRD, XPS, and XAFS. The resulting Pd/G showed excellent catalytic efficiency in the Sonogashira reaction and offers significant advantages over inorganic supported catalysts such as simple recovery and recycling. Finally, deactivation process of the Pd/G in recycling was investigated. We believe that the remarkable reactivity of the Pd/G catalyst toward the Sonogashira reaction is attributed to the high degree of the Pd NP dispersion and thus the increased low coordination numbers of smaller Pd NPs. © 2013.

Kim Y.-H.,Korea Electronics Technology Institute | Kim H.S.,Korea Electronics Technology Institute | Han J.-I.,Dongguk University | Park S.K.,Chonbuk National University
Applied Physics Letters | Year: 2010

We investigated solvent-mediated threshold voltage (VTH) shift in solution-processed zinc-tin oxide (ZTO) thin film transistors (TFTs). The ZTO TFTs showed negative VTH shift when exposed to various organic solvents such as hexane, isopropanol, and chlorobenzene. Additionally the magnitude of the shift showed a close relationship with the dielectric constant or electronegativity of the solvent molecules. From the experiments, one of the origins of the VTH shift in the transparent oxide TFTs appears to be closely correlated with the dipole interaction of the solvent molecules and ZTO back channel surface. © 2010 American Institute of Physics.

Barakat N.A.M.,Chonbuk National University | Barakat N.A.M.,Minia University | Abdelkareem M.A.,Minia University | Kim H.Y.,Chonbuk National University
Applied Catalysis A: General | Year: 2013

Novel electrocatalyst based on non precious metals (Co and Cd) is introduced to be used as anode in the ethanol fuel cells. Cd-doped Cobalt nanoparticles encapsulated in graphite shell have been synthesized using simple sol-gel technique. The introduced electrocatalyst can be prepared from a sol-gel composed of cadmium acetate, cobalt acetate and poly(vinyl alcohol) based on the polycondensation possibility of the acetates. Grinding and calcination in Ar atmosphere of the prepared gel leads to produce Cd-doped Co nanoparticles encapsulated in a thin graphite layer. High current density (70 mA cm -2) and considerably low onset potential (∼585 mV vs. NHE) were obtained when the synthesized nanoparticles have been exploited as electrocatalyst for ethanol (concentration 1 M) oxidation in basic media (1 M KOH). Considering that the introduced nanoparticles composed of non precious metals and the obtained electrochemical results are satisfactory, the introduced study might open new avenues to the cobalt-based nanostructures to be used as novel electrocatalysts in the fuel cells applications. © 2013 Elsevier B.V. All rights reserved.

Park S.-I.,LS Nikko Copper Inc. | Kwak I.S.,Engineering R and nter | Won S.W.,Chonbuk National University | Yun Y.-S.,Chonbuk National University
Journal of Hazardous Materials | Year: 2013

Glutaraldehyde (GA)-crosslinked chitosan beads (GA-CS) are prepared with coagulating solution containing sodium tripolyphosphate and GA, and used for the adsorption of metals from binary-metal solution Au(III) and Pd(II). GA-CS exhibited selective sorption of Au(III) in the Au(III)-Pd(II) mixture. X-ray diffraction analyses showed that Au(III) was reduced to Au(0) following sorption, while Pd(II) was present as unreduced divalent form. Increased GA led to more selectivity toward Au(III), indicating that Au(III) selectivity is attributed to reduction-couple sorption of Au(III) with a reducing agent GA. Furthermore, a 2-step desorption process enabled selective recovery of Pd and Au using 5. M HCl and 0.5. M thiourea-1. M HCl, respectively, leading to pure Pd(II) and Au(III)-enriched solutions. This finding may open a new way to design reduction-coupled selectivity-tunable metal sorbents by combination of redox potentials of metal ions and reducing agents. © 2013 Elsevier B.V.

Barakat N.A.M.,Chonbuk National University | Barakat N.A.M.,Minia University
Applied Catalysis A: General | Year: 2013

Due to the axial ratio feature, bimetallic nanofibers are expected to have novel characteristics. In this study, Pd-doped Co nanofibers could be successfully prepared using simple, low cost, high yield and effective technique; electrospinning. The introduced nanofibers have been synthesized by calcination of electrospun nanofibers composed of Pd NPs/cobalt acetate tetrahydrate/poly(vinyl alcohol) in a vacuum atmosphere. The utilized physicochemical characterizations indicated that the introduced bimetallic nanofibers are chemically protected by a sheath of graphite layer. Interestingly, the introduced nanofibers can be utilized in hydrolysis of ammonia borane in an aqueous solutions using two different simultaneous mechanisms; normal and photo catalysis. The solar radiation improves the performance as the stoichiometric hydrogen has been obtained within few minutes under the sunlight because of the photohydrolysis influence. Reusability is a distinct feature for the introduced nanofibers as they could be utilized for several successive times with the same efficiency. Moreover, due to the carbon sheathing, no metallic ions release was observed in the final solution. Photohydrolysis mechanism of ammonia borane might open a new avenue to utilize different class of materials to release the embedded hydrogen in the ammonia borane complex. © 2012 Elsevier B.V.

Choo B.K.,Chonbuk National University | Roh S.-S.,Daegu Haany University
Experimental and Therapeutic Medicine | Year: 2013

This study was performed to investigate the effects of berberine (BB) in a rat model of gastroesophageal reflux disease (GERD), induced by pylorus and forestomach ligation. We evaluated cytotoxicity and proinflammatory biomarkers (nitric oxide, interleukin (IL)-1β and prostaglandin E2) in RAW 264.7 cells in vitro and anti-inflammatory effects in vivo. A total of 54 Sprague Dawley rats were divided into six groups: intact control rats; refux esophagitis (RE) control rats; RE rats treated with 20 mg/kg omeprazole and RE rats treated with BB at doses of 20, 40 and 60 mg/kg, respectively. All rats were fasted. RE was induced by pylorus and forestomach ligation one hour subsequent to the oral treatment. Six hours subsequent to the surgery, the rats were sacrificed, blood was collected from the abdominal vein and the esophagus and stomach were dissected. The gastric volume and the pH of the gastric juice were evaluated, prior to the esophagus being cut longitudinally and an inner mucosal area being imaged, to analyze mucosal damage indices. Proinflammatory biomarkers in the serum, including tumor necrosis factor (TNF)-α, IL-1β, IL-6 and monocyte chemoattractant protein (MCP)-1 were analyzed using an enzyme-linked immunosorbent assay (ELISA) kit, while the mRNA expression of TNF-α, IL-1β, IL-6 and plasminogen activator inhibitor (PAI)-1 was analyzed using a quantitative polymerase chain reaction (qPCR). Esophagic tissue damage in the BB groups was dose-dependently decreased compared with that in the RE control group. This result was consistent with significant reductions in the levels of proinflammatory biomarkers in the serum and in the expression of proinflammatory mRNA, specifically, TNF-α, IL-1β, IL-6 and PAI-1. The results suggest that the anti-inflammatory and protective effects of BB may attenuate the severity of RE and prevent esophageal mucosal damage, in addition to validating the use of BB as a pharmacological treatment for esophageal reflux disease.

Lee H.-S.,Chonbuk National University | Ka S.-O.,Chonbuk National University | Lee S.-M.,Chonbuk National University | Lee S.-I.,Gyeongsang National University | And 2 more authors.
Arthritis and Rheumatism | Year: 2013

Objective Sirtuin 6 (SIRT-6) is an NAD+-dependent deacetylase and mono-ADP-ribosyltransferase. It is known to interfere with the NF-κB signaling pathway and thereby has an antiinflammatory function. Due to the central role of NF-κB in rheumatoid arthritis (RA) development, we undertook this study to test our hypothesis that SIRT-6 could have antiarthritic effects. Methods An adenovirus containing SIRT-6 complementary DNA (Ad-SIRT6) was used to deliver SIRT-6 to human RA fibroblast-like synoviocytes in vitro as well as to mice with collagen-induced arthritis (CIA) in vivo via bilateral intraarticular injections into the ankle joints. Results In vitro experiments demonstrated that SIRT-6 overexpression suppressed NF-κB target gene expression induced by tumor necrosis factor α. SIRT-6 overexpression inhibited osteoclast differentiation induced by macrophage colony-stimulating factor and RANKL in bone marrow-derived macrophages. Mice with CIA had an increased incidence of disease and developed arthritis in the hind paws. In contrast, mice injected with Ad-SIRT6 showed attenuated severity of arthritis based on clinical scores, hind paw thickness, and radiographic and pathologic findings. Moreover, the injection of Ad-SIRT6 down-regulated local and systemic levels of proinflammatory cytokines. After induction of CIA, mice injected with Ad-SIRT6 showed significantly decreased arthritis severity, from the onset of clinical signs to the end of the study. Conclusion These results suggest that blocking the NF-κB pathway by SIRT-6 in rheumatoid joints reduces both the inflammatory response and tissue destruction. Therefore, the development of an immunoregulatory strategy based on SIRT-6 may have therapeutic potential for the treatment of RA. Copyright © 2013 by the American College of Rheumatology.

Raghavan P.,Gyeongsang National University | Manuel J.,Gyeongsang National University | Zhao X.,Gyeongsang National University | Kim D.-S.,Gyeongsang National University | And 2 more authors.
Journal of Power Sources | Year: 2011

Electrospun membranes of polyacrylonitrile are prepared, and the electrospinning parameters are optimized to get fibrous membranes with uniform bead-free morphology. The polymer solution of 16 wt.% in N,N-dimethylformamide at an applied voltage of 20 kV results in the nanofibrous membrane with average fiber diameter of 350 nm and narrow fiber diameter distribution. Gel polymer electrolytes are prepared by activating the nonwoven membranes with different liquid electrolytes. The nanometer level fiber diameter and fully interconnected pore structure of the host polymer membranes facilitate easy penetration of the liquid electrolyte. The gel polymer electrolytes show high electrolyte uptake (>390%) and high ionic conductivity (>2 × 10-3 S cm -1). The cell fabricated with the gel polymer electrolytes shows good interfacial stability and oxidation stability >4.7 V. Prototype coin cells with gel polymer electrolytes based on a membrane activated with 1 M LiPF 6 in ethylene carbonate/dimethyl carbonate or propylene carbonate are evaluated for discharge capacity and cycle property in Li/LiFePO4 cells at room temperature. The cells show remarkably good cycle performance with high initial discharge properties and low capacity fade under continuous cycling. © 2010 Elsevier B.V. All rights reserved.

Noh J.,Chungnam National University | Chae B.-J.,Chonbuk National University | Ku B.-C.,Korea Institute of Science and Technology | Lee T.S.,Chungnam National University
Journal of Polymer Science, Part A: Polymer Chemistry | Year: 2014

Conjugated polymers containing triphenylamine group are synthesized via Suzuki coupling polymerization. Fluorescent-conjugated polymer nanoparticles (CPN) are prepared by reprecipitation method using the newly synthesized conjugated polymer. CPN can be encapsulated with polyarginine by electrostatic interaction. The CPN modified with polyarginine exhibit excellent interaction with graphene oxide (GO) which is chemically modified with hydrophilic groups that possesses negative charge, which, in turn, induces the quenching of the fluorescence of CPN upon formation of CPN-GO nanohybrid. Upon exposure to trypsin, the quenched fluorescence is recovered by release of CPN from the nanohybrid, because trypsin cleaves the polyarginine linkage, resulting in weakening of interaction between CPN and GO. Copyright © 2014 Wiley Periodicals, Inc.

Srivastava M.,Chonbuk National University | Elias Uddin M.,Chonbuk National University | Singh J.,Delhi Technological University | Kim N.H.,Chonbuk National University | Lee J.H.,Chonbuk National University
Journal of Alloys and Compounds | Year: 2014

NiCo2O4 nanoparticles dispersed on reduced graphene oxide (RGO) are prepared by simultaneously reducing graphene oxide (GO), nickel and cobalt nitrate via a hydrothermal method assisted by post annealing at low temperature. The method involves formation of hydroxides on GO using ammonia under hydrothermal conditions. Subsequent thermal treatment at 300 C led to the conversion of hydroxides into single-phase NiCo2O4 atop the RGO. The synthesized products are characterized through several techniques including X-ray diffraction (XRD), ultraviolet-visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy (RS), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The FE-SEM investigations reveal the growth of a layer by layer assembly of NiCo2O 4-RGO (2:1) nanocomposite, where the NiCo2O4 nanoparticles are tightly packed between the layers of RGO. Further, the catalytic properties of the NiCo2O4-RGO nanocomposite are investigated for the oxygen evolution reaction (OER) through cyclic voltammetry (CV) measurements. It is observed that the special structural features of the NiCo2O4-RGO (2:1) nanocomposite, including layer by layer assembly, integrity and excellent dispersion of the NiCo2O 4 nanoparticles atop the RGO, produced a synergistic effect and therefore significantly improved the electrochemical performance. The oxidation potential (0.135 V) of NiCo2O4-RGO (2:1) nanocomposite was observed to be lower than that of bare NiCo2O4 nanoparticles (0.33 V), whereas the corresponding current densities were measured to be 4.1 mA/cm2 and 3.11 mA/cm2, respectively. © 2013 Elsevier B.V. All rights reserved.

Wang X.,Harbin Institute of Technology | Chen Y.,Harbin Institute of Technology | Xu L.,Harbin Institute of Technology | Liu Z.,Harbin Institute of Technology | Woo K.-D.,Chonbuk National University
Materials and Design | Year: 2013

In this work Ti-35Nb-xSn/15hydroxyapatite (HA, x=2.5, 5, 10wt.%) bulk biocomposites were fabricated by high energy mechanical milling (HEMM) and pulse current activated sintering (PCAS). The microstructure and characteristics of Ti-35Nb-xSn/15HA milled powders and bulk composites sintered from powders milled for 12h were studied. The results indicate that α-Ti transforms into β-Ti completely in 12h milled Ti-35Nb-2.5Sn/15HA powders due to the solid solution of Nb into Ti lattice. The ultrafine grains are obtained in the bulk Ti-35Nb-2.5Sn/15HA composites. All bulk Ti-35Nb-xSn/15HA composites have high compression strength and low elastic modulus (21-23GPa). The corrosion current density of bulk Ti-35Nb-2.5Sn/15HA composites is about 0.18μA/cm2 in Hank's solution. Cell culture results reveal that MC-3T3 osteoblast cells have good growing and spreading ability on the surface of bulk Ti-35Nb-xSn/15HA composites. Cell viability for bulk Ti-35Nb-2.5Sn/15HA composite is 0.4 times higher than that for CP Ti. The results demonstrate that bulk Ti-35Nb-xSn/15HA composites are promising biomaterials. © 2013 Elsevier Ltd.

Won S.W.,Gyeongsang National University | Kotte P.,Chonbuk National University | Wei W.,Chonbuk National University | Lim A.,Chonbuk National University | Yun Y.-S.,Chonbuk National University
Bioresource Technology | Year: 2014

Biosorption is a promising technology not only for the removal of heavy metals and dyes but also for the recovery of precious metals (PMs) from solution phases. The biosorptive recovery of PMs from waste solutions and secondary resources is recently getting paid attractive attention because their price is increasing or fluctuating, their available deposit is limited and maldistributed, and high-tech industries need more consumption of PMs. The biosorbents for recovery of PMs require specifications which differ from those for the treatment of wastewaters containing heavy metals and dyes. In this review, the previous works on biosorbents and biosorption for recovery of PMs were summarized. Especially, we discuss and suggest the required specifications of biosorbents for recovery of PMs and strategies to give the required properties to the biosorbents. We believe this review will provide useful information to scientists and engineers and hope to give insights into this research frontier. © 2014 Elsevier Ltd.

Barakat N.A.M.,Chonbuk National University | Barakat N.A.M.,Minia University | Motlak M.,University of Anbar
Applied Catalysis B: Environmental | Year: 2014

In this study, CoxNiy-decorated graphene is introduced as novel, super effective and stable non-precious electro-catalyst for methanol oxidation. The obtained results have indicated that utilizing graphene as a support strongly enhances the electro-catalytic activity as the current density was doubled ten times, moreover a negative onset potential (-40mV vs. Ag/AgCl) was obtained which is a distinct progress in the non-precious electro-catalysts research field. The electronic structure which is controlled by the alloy composition showed strong influence on the electro-catalytic activity; Co0.2Ni0.2 alloy nanoparticles revealed the best performance while Co0.1Ni0.3 nanoparticles were the worst. Due to the alloy structure, the introduced graphene-supported electro-catalyst reveals distinguished stability. In-situ decoration of graphene by CoxNiy alloy nanoparticle is utilized to produce the introduced electro-catalyst. Briefly, cobalt acetate and nickel acetate were added to the reaction media during graphene preparation using a modified chemical route. Later on, the resultant material was calcined in argon atmosphere at 850°C. The utilized physicochemical characteristics affirmed formation of multi-layer graphene sheets decorated by solid solution CoxNiy alloy nanoparticle. © 2014 Elsevier B.V.

Song K.-J.,Chonbuk National University | Choi B.-Y.,Presbyterian Medical Center
Asian Spine Journal | Year: 2014

Anterior cervical discectomy and fusion (ACDF) is a safe and effective procedure for degenerative cervical spinal disease unresponsive to conservative management and its outstanding results have been reported. To increase fusion rates and decrease complications, numerous graft materials, cage, anterior plating and total disc replacement have been developed, and better results were reported from those, but still there are areas that have not been established. Therefore, we are going to analyze the treatment outcome with the various procedure through the literature review and determine the efficacy of ACDF. © 2014 by Korean Society of Spine Surgery.

Barakat N.A.M.,Chonbuk National University | Barakat N.A.M.,Minia University
Materials Letters | Year: 2013

Hydrolysis of the ammonia borane complex is the optimum procedure to obtain the incorporated hydrogen. In this study, MnO-doped cobalt nanofibers are introduced as effective catalyst for ammonia borane hydrolysis. Compared to cobalt NPs which could release only 1.1 mol of hydrogen, the introduced nanofibers revealed better performance as all the equivalent hydrogen (3 mol) were obtained at room temperature in a short time. The hydrolysis mechanism was investigated. The nanofibers were synthesized using the electrospinning process. Briefly, electrospun nanofibers composed of poly(vinyl alcohol), cobalt acetate and manganese acetate were vacuously dried and calcined in Ar atmosphere at 850 C. © 2013 Elsevier B.V.

Barakat N.A.M.,Chonbuk National University | Barakat N.A.M.,Minia University
Journal of Materials Science | Year: 2012

Among the reported nanostructural shapes, nanofibers have special interest due to the long axial ratio which has a distinct impact on many chemical and physical properties. In this study, synthesis of the desirable maghemite iron oxide (γ-Fe 2O 3) nanofibers is introduced. Calcination of electrospun mats composed of ferrous acetate and poly(vinyl alcohol) in argon atmosphere resulted in producing maghemite nanofibers. Detailed characterization affirmed that the obtained γ-Fe 2O 3 nanofibers are free of other iron oxides. Due to the axial ratio impact, the synthesized nanofibers which have an average diameter of ∼70 nm do have magnetic properties resemble γ-Fe 2O 3 nanoparticles having an average diameter of ∼5 nm. Accordingly, the produced nanofibers are considerable candidate for biomagnetic separation of the biomaterials. The prepared γ-Fe 2O 3 nanofibers can be easily handled as they were obtained in the form of strong mats. Electrical properties study indicated that the introduced nanofibers behave as a semiconducting material. Moreover, the synthesized γ-Fe 2O 3 nanofibers have band gap energy of ∼4.2 eV. Based on the simplicity, effectiveness, highyield, and low-cost features of the utilized preparation process and the studied physiochemical properties of the obtained product, the synthesized γ-Fe 2O 3 nanofibers might have considerable application fields. © Springer Science+Business Media, LLC 2012.

Oh K.-Y.,KEPCO E&C | Kim J.-Y.,KEPCO E&C | Lee J.-S.,KEPCO E&C | Ryu K.-W.,Chonbuk National University
Renewable Energy | Year: 2012

In recent years, many countries have been endeavoring to exploit the offshore wind energy in terms of overcoming the limitations of on-land wind energy. Considering that mountains cover 70 percent of the Korean Peninsula and arable plains for wind energy are negligibly small, Korean government aggressively drives the offshore wind development of the Korean Peninsula. In this context, KEPCO-RI (Korea Electric Power Corporation-Research Institute) has been performing a feasibility study for construction of the first offshore wind farm in Korea, including wind resource assessments around the Korean Peninsula. This paper provides a summary of the offshore wind resources of the Korean Peninsula, by analyzing marine buoy datasets measured at 5 positions over the period of 12 years, the QuikSCAT satellite data measured over 9 years, and a numerical wind map based on meteorological data measured for 4 years. Based on these datasets, wind resources are assessed, and economical efficiency is evaluated by means of the expected capacity factor. The analyzing results will be utilized to decide location of the first offshore wind farm in Korea. © 2011 Elsevier Ltd.

Choi H.S.,Beth Israel Deaconess Medical Center | Gibbs S.L.,Beth Israel Deaconess Medical Center | Lee J.H.,Beth Israel Deaconess Medical Center | Kim S.H.,Beth Israel Deaconess Medical Center | And 9 more authors.
Nature Biotechnology | Year: 2013

The signal-to-background ratio (SBR) is the key determinant of sensitivity, detectability and linearity in optical imaging. As signal strength is often constrained by fundamental limits, background reduction becomes an important approach for improving the SBR. We recently reported that a zwitterionic near-infrared (NIR) fluorophore, ZW800-1, exhibits low background. Here we show that this fluorophore provides a much-improved SBR when targeted to cancer cells or proteins by conjugation with a cyclic RGD peptide, fibrinogen or antibodies. ZW800-1 outperforms the commercially available NIR fluorophores IRDye800-CW and Cy5.5 in vitro for immunocytometry, histopathology and immunoblotting and in vivo for image-guided surgery. In tumor model systems, a tumor-to-background ratio of 17.2 is achieved at 4 h after injection of ZW800-1 conjugated to cRGD compared to ratios of 5.1 with IRDye800-CW and 2.7 with Cy5.5. Our results suggest that introducing zwitterionic properties into targeted fluorophores may be a general strategy for improving the SBR in diagnostic and therapeutic applications. © 2013 Nature America, Inc. All rights reserved.

Qurashi A.,Chonbuk National University | Qurashi A.,King Fahd University of Petroleum and Minerals | Kim J.H.,Chonbuk National University | Hahn Y.-B.,Chonbuk National University
Electrochemistry Communications | Year: 2012

To avoid a traditional pick-and-place method of nanodevice fabrication and directly measure the electrical characteristics of as-grown nanorods (NRs), the ZnO NR arrays were fabricated directly on-chip system by the site-selective growth of nanorods thus forming nanorod-array bridges between two-point gold electrodes. This is attractive, realistic, straightforward and highly reproducible technique to grow nanostructures onto the electrodes. The ZnO NR arrays were grown at 70 °C on the pre-patterned two-point electrode system without damaging the electrodes structure and geometry. The electrodes remain completely intact in the chemical solution for 6 h growth of NRs. The effect of oxygen-plasma treatment on the electrical properties of the ZnO NR arrays based two-point electrodes system was investigated in detail. © 2012 Elsevier B.V.

Jeon Y.J.,CHA Medical University | Kim O.J.,CHA Medical University | Kim S.Y.,CHA Medical University | Oh S.H.,CHA Medical University | And 3 more authors.
Arteriosclerosis, Thrombosis, and Vascular Biology | Year: 2013

Objective-: MicroRNAs play a role in atherosclerosis-related diseases, such as cerebrovascular or cardiovascular disease. However, the effect of miR-146a, miR-149, miR-196a2, and miR-499 polymorphisms on stroke and silent brain infarction (SBI) susceptibility has not been reported. METHODS AND RESULTS-: Using polymerase chain reaction-amplified DNA, microRNA polymorphisms were analyzed in 678 patients with ischemic stroke, 373 patients with SBI, and 553 control subjects. The miR-146aC>G polymorphism and miR-146aG/-149T/-196a2C/- 499G allele combination was significantly associated with ischemic stroke prevalence. For SBI prevalence, there were no statistically significant genetic markers. However, some allele combinations were associated with increased SBI incidence (C-T-C-G and G-T-T-A of miR-146a/-149/-196a2/-499). In subgroup analyses, miR-146aC>G increased stroke risk in female, normotensive, and nondiabetic groups. There were significant combined effects between microRNA polymorphisms and homocysteine/folate levels on ischemic stroke and SBI prevalence. CONCLUSION-: The miR-146aG allele and miR-146aG/-149T/-196a2C/-499G allele combination were associated with ischemic stroke pathogenesis. The combined effects between microRNA polymorphisms and homocysteine/folate levels may contribute to stroke and SBI prevalence. © 2012 American Heart Association, Inc.

Lee S.J.,Chonbuk National University | Michel S.L.J.,University of Maryland, Baltimore
Accounts of Chemical Research | Year: 2014

ConspectusZinc finger (ZF) proteins are a large family of metalloproteins that utilize zinc for structural purposes. Zinc coordinates to a combination of cysteine thiol and histidine imidazole residues within the ZF polypeptide sequence resulting in a folded and functional protein. Initially, a single class of ZFs were identified. These ZFs, now referred to as the "classical" ZFs, utilize a Cys2His2 (CCHH) ligand set to bind zinc. Upon Zn coordination, the classical ZFs fold into a structure made up of an α helix and an antiparallel β sheet. When folded, classical ZFs recognize and bind to specific DNA targets and function as transcription factors. With the advent of genome sequencing and proteomics, many additional classes of ZFs were identified based upon their primary amino acid sequences. At least 13 additional classes of ZFs are known, and collectively these "nonclassical" ZFs differ in the ligand set involved in Zn(II) coordination, the organization of the ligands within the polypeptide sequence and the macromolecular targets. Some nonclassical ZFs are DNA binding "transcription factors", while others are involved in RNA regulation and protein recognition. Much less is known about these nonclassical ZFs with regards to the roles of metal coordination in fold and function. This Account focuses on our laboratorys efforts to characterize two families of "nonclassical" ZFs: the Cys3His (or CCCH) ZF family and the Cys2His2Cys (or CCHHC) ZF family.Our work on the CCCH ZF family has focused on the protein Tristetraprolin (TTP), which is a key protein in regulating inflammation. TTP contains two CCCH domains that were proposed to be ZFs based upon their sequence. We have shown that while this protein can coordinate Zn(II) at the CCCH sites, it can also coordinate Fe(II) and Fe(III). Moreover, the zinc and iron bound forms of TTP are equally adept at discriminating between RNA targets, which we have demonstrated via a fluorescence anisotropy based approach. Thus, CCCH type ZFs appear to be promiscuous with respect to metal preference and a role for iron coordination in CCCH ZF function is proposed.The CCHHC family of ZFs is a small family of nonclassical ZFs that are essential for the development of the central nervous system. There are three ZFs in this family: neural zinc finger factor-1 (NZF-1), myelin transcription factor-1 (MyT1), and suppressor of tumorgenicity 18 (ST18). All three proteins contain multiple clusters of "CCHHC" domains, which are all predicted to be Zn binding domains. We have focused on a tandem-CCHHC domain construct of NZF-1, which recognizes β-RARE DNA, and we have identified key residues required for DNA recognition. Unlike classical ZFs, for which a few conserved residues are required for DNA recognition, the CCHHC class of ZFs utilize a few nonconserved residues to drive DNA recognition leading us to propose a new paradigm for ZF/DNA binding. © 2014 American Chemical Society.

Chong K.-H.,Agency for Defense Development | Choi W.-S.,Agency for Defense Development | Chong K.-T.,Chonbuk National University
Applied Optics | Year: 2016

Analysis of the dead zone is among the intensive studies in a closed-loop fiber optic gyroscope. In a dead zone, a gyroscope cannot detect any rotation and produces a zero bias. In this study, an analysis of dead zone sources is performed in simulation and experiments. In general, the problem is mainly due to electrical cross coupling and phase modulation drift. Electrical cross coupling is caused by interference between modulation voltage and the photodetector. The cross-coupled signal produces spurious gyro bias and leads to a dead zone if it is larger than the input rate. Phase modulation drift as another dead zone source is due to the electrode contamination, the piezoelectric effect of the LiNbO3 substrate, or to organic fouling. This modulation drift lasts for a short or long period of time like a lead-lag filter response and produces gyro bias error, noise spikes, or dead zone. For a more detailed analysis, the cross-coupling effect and modulation phase drift are modeled as a filter and are simulated in both the open-loop and closed-loop modes. The sources of dead zone are more clearly analyzed in the simulation and experimental results. © 2015 Optical Society of America.

Park J.-H.,Chonbuk National University | Kim M.-H.,Chonbuk National University | Kissinger S.,Jubail University College | Lee C.-R.,Chonbuk National University
Nanoscale | Year: 2013

We demonstrate the fabrication of n-GaN:Si/p-GaN:Mg nanowire arrays on (111) silicon substrate by metal organic chemical vapor deposition (MOCVD) method. The nanowires were grown by a newly developed two-step growth process. The diameter of as-grown nanowires ranges from 300-400 nm with a density of 6-7 × 107 cm-2. The p- and n-type doping of the nanowires is achieved with Mg and Si dopant species. Structural characterization by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) indicates that the nanowires are relatively defect-free. The room-temperature photoluminescence emission with a strong peak at 370 nm indicates that the n-GaN:Si/p-GaN:Mg nanowire arrays have potential application in light-emitting nanodevices. The cathodoluminscence (CL) spectrum clearly shows a distinct optical transition of GaN nanodiodes. The nano-n-GaN:Si/p-GaN: Mg diodes were further completed using a sputter coating approach to deposit Au/Ni metal contacts. The polysilazane filler has been etched by a wet chemical etching process. The n-GaN:Si/p-GaN:Mg nanowire diode was fabricated for different Mg source flow rates. The current-voltage (I-V) measurements reveal excellent rectifying properties with an obvious turn-on voltage at 1.6 V for a Mg flow rate of 5 sccm (standard cubic centimeters per minute). © The Royal Society of Chemistry 2013.

Kim H.,Korea Advanced Institute of Science and Technology | Jo H.,Chonbuk National University | Lee J.,Sungkyunkwan University
IEEE Transactions on Computers | Year: 2011

Since a virtual machine independently uses its own caching policy, redundant disk operations exacerbate the I/O virtualization overhead when virtual machines access large amounts of data on shared storage. This paper presents XHive, an efficient cooperative caching system that is implemented at the virtualization layer, for consolidated environments. Our proposed scheme globally manages buffer caches of consolidated virtual machines in order to accommodate a shared working set in machine memory. A singlet, which is a block cached solely by a virtual machine, is preferentially given more chances to be cached in machine memory by XHive, when it is evicted by a guest operating system. For efficient use of limited memory, singlets are cached in memory that is collaboratively donated from idle memory of virtual machines. Our evaluation shows that XHive significantly reduces disk I/O operations for shared working sets, thereby achieving high read performance and scalability. Improved scalability enables a high degree of workload consolidation with respect to virtual machines that have shared working sets. © 2011 IEEE.

Majhi S.M.,Chonbuk National University | Rai P.,Indian Institute of Technology Kanpur | Yu Y.-T.,Chonbuk National University
ACS Applied Materials and Interfaces | Year: 2015

We successfully prepared Au@ZnO core-shell nanoparticles (CSNPs) by a facile low-temperature solution route and studied its gas-sensing properties. The obtained Au@ZnO CSNPs were carefully characterized by X-ray diffraction, transmission electron microscopy (TEM), high-resolution TEM, and UV-visible spectroscopy. Mostly spherical-shaped Au@ZnO CSNPs were formed by 10-15 nm Au NPs in the center and by 40-45 nm smooth ZnO shell outside. After the heat-treatment process at 500 C, the crystallinity of ZnO shell was increased without any significant change in morphology of Au@ZnO CSNPs. The gas-sensing test of Au@ZnO CSNPs was examined at 300 C for various gases including H2 and compared with pure ZnO NPs. The sensor Au@ZnO CSNPs showed the high sensitivity and selectivity to H2 at 300 C. The response values of Au@ZnO CSNPs and pure ZnO NPs sensors to 100 ppm of H2 at 300 C were 103.9 and 12.7, respectively. The improved response of Au@ZnO CSNPs was related to the electronic sensitization of Au NPs due to Schottky barrier formation. The high selectivity of Au@ZnO CSNPs sensor toward H2 gas might be due to the chemical as well as catalytic effect of Au NPs. © 2015 American Chemical Society.

Hu R.-H.,Chonbuk National University | Hu R.-H.,Huanghe Science and Technology College | Sun M.-Y.,Chonbuk National University | Lim J.-K.,Chonbuk National University
Materials and Design | Year: 2010

In this research, aging behaviors of short jute fiber/Polylactide (PLA) composite material in hygrothermal environment were investigated. The material was fabricated by using film stacking hot pressed method. The aging was carried out for uncoated samples and adhesive tape coated samples in saturated vapor at 70°C. Moisture absorption rates of the samples were measured during the aging process. It is found that the moisture absorption process of uncoated samples includes three stages: a short and quick moisture uptaking stage, a slow stable uptaking stage and an abrupt very quick moisture uptaking stage. Microstructures of the samples in different aging stages were observed. The main defects occurred during the aging process include pores, microcracks, delamination and complete relaxation in the whole structure. The results reveal that the moisture absorption and aging process can be effectively retarded by coating. The molecular weight measurement by gel permission chromatography (GPC) indicated that the PLA matrix was severely degraded in hygrothermal environment. Tensile strength severely decreased after aging. © 2010 Elsevier Ltd.

Chonbuk National University and Beth Israel Deaconess Medical Center | Date: 2013-09-13

The present invention includes a vanillyl alcohol-containing copolyoxalate copolymer (PVAX). The present invention also includes a PVAX microparticle comprising PVAX. In one aspect, the compositions of the invention can be used as a drug delivery system, an antioxidant or anti-inflammatory composition, a composition for preventing or treating ischemic disease, a composition for inhibiting the side effects of anticancer drugs, a contrast agent, and/or a composition for diagnosing ischemic disease.

Ahsanulhaq Q.,Chonbuk National University | Ahsanulhaq Q.,King Fahd University of Petroleum and Minerals | Kim J.H.,Chonbuk National University | Hahn Y.-B.,Chonbuk National University
Solar Energy Materials and Solar Cells | Year: 2012

A facile and cost effective solution method was used for the large-scale selective area growth of well-aligned ZnO nanorod arrays (NRAs) on a pre-patterned ZnO/Si. Conventional photolithography is employed to develop negative and positive circular ZnO NRAs micro-patterns with the help of low cost and economical flexible photo (polymer) mask. Unlike complex photolithography procedures, our patterning process does not require wet or dry-etching processes, and thus prove to be a simple, fast and low cost technique. Field emission scanning electron microscopy analysis reveals that the selectively grown ZnO nanorods have an average diameter and length of ∼55±5 and ∼650±50 nm. The structural analysis of ZnO nanorods showed that the nanorods were single-crystalline and grown along the c-axis direction. The photoluminescence spectrum shows a strong ultra violet emission at 381 nm and a broad deep-level visible emission at 580 nm. Such large-sized ZnO patterned substrate will be effective in light trapping and localized surface trapping, which can lead to significant enhancement in light absorption of solar cells. © 2011 Elsevier B.V. All rights reserved.

Rai P.,Chonbuk National University | Khan R.,Chonbuk National University | Raj S.,Chonbuk National University | Majhi S.M.,Chonbuk National University | And 4 more authors.
Nanoscale | Year: 2014

Au@Cu2O core-shell nanoparticles (NPs) were synthesized by a solution method at room temperature and applied for gas sensor applications. Transmission electron microscopy (TEM) images showed the formation of Au@Cu 2O core-shell NPs, where 12-15 nm Au NPs were covered with 60-30 nm Cu2O shell layers. The surface plasmon resonance (SPR) peak of Au NPs was red-shifted (520-598 nm) after Cu2O shell formation. The response of Au@Cu2O core-shell NPs was higher than that of bare Cu2O NPs to CO at different temperatures and concentrations. Similarly, the response of Au@Cu2O core-shell NPs was higher than that of bare Cu2O NPs for NO2 gas at low temperature. The improved performance of Au@Cu2O core-shell NPs was attributed to the pronounced electronic sensitization, high thermal stability and low screening effect of Au NPs. © 2014 The Royal Society of Chemistry.

Choi J.,Samsung | Batchelor B.,Texas A&M University | Won C.,Chonbuk National University | Chung J.,Samsung
Chemosphere | Year: 2012

A kinetic study of nitrate reduction by green rust (GR), a group of layered Fe(II)-Fe(III) hydroxide solids, was performed using a batch reactor system. The reduction rate of nitrate by GRs was affected by the anion content in the interlayer of GRs. GR containing F - (GR-F) showed the fastest reduction rate while GR-SO 4 showed 9 times slower reaction rate than GR-F. The addition of 1mM Pt or Cu to GR that contained 85mM Fe(II) improved the reduction kinetics of nitrate by up to 200 times. Pt was an effective activating agent for all GRs. The sequential step reaction model that we proposed appropriately simulated the experimental data. The fastest nitrate reduction by GR-F with Pt was achieved at pH 9 among 7.5 to 11. At that condition, 1mM nitrate transformed completely into ammonium within 23min. © 2011 Elsevier Ltd.

Oh J.-W.,Seoul National University | Lim D.-K.,Chonbuk National University | Kim G.-H.,Seoul National University | Suh Y.D.,Korea Research Institute of Chemical Technology | Nam J.-M.,Seoul National University
Journal of the American Chemical Society | Year: 2014

The design, synthesis and control of plasmonic nanostructures, especially with ultrasmall plasmonically coupled nanogap (∼1 nm or smaller), are of significant interest and importance in chemistry, nanoscience, materials science, optics and nanobiotechnology. Here, we studied and established the thiolated DNA-based synthetic principles and methods in forming and controlling Au core-nanogap-Au shell structures [Au-nanobridged nanogap particles (Au-NNPs)] with various interior nanogap and Au shell structures. We found that differences in the binding affinities and modes among four different bases to Au core, DNA sequence, DNA grafting density and chemical reagents alter Au shell growth mechanism and interior nanogap-forming process on thiolated DNA-modified Au core. Importantly, poly A or poly C sequence creates a wider interior nanogap with a smoother Au shell, while poly T sequence results in a narrower interstitial interior gap with rougher Au shell, and on the basis of the electromagnetic field calculation and experimental results, we unraveled the relationships between the width of the interior plasmonic nanogap, Au shell structure, electromagnetic field and surface-enhanced Raman scattering. These principles and findings shown in this paper offer the fundamental basis for the thiolated DNA-based chemistry in forming and controlling metal nanostructures with ∼1 nm plasmonic gap and insight in the optical properties of the plasmonic NNPs, and these plasmonic nanogap structures are useful as strong and controllable optical signal-generating nanoprobes. © 2014 American Chemical Society.

Wu D.,Mount Sinai Medical Center | Wu D.,Chonbuk National University | Kraut J.A.,Medical And Res Ser Veterans Admini Greater Los Angeles Healthcare Syt | Abraham W.M.,Mount Sinai Medical Center
PLoS ONE | Year: 2013

Introduction: Acute metabolic acidosis impairs cardiovascular function and increases the mortality of critically ill patients. However, the precise mechanism(s) underlying these effects remain unclear. We hypothesized that targeting pH-regulatory protein, Na+/H+ exchanger (NHE1) could be a novel approach for the treatment of acute metabolic acidosis. The aim of the present study was to examine the impact of a novel NHE1 inhibitor, sabiporide, on cardiovascular function, blood oxygen transportation, and inflammatory response in an experimental model of metabolic acidosis produced by hemorrhage-induced hypovolemia followed by an infusion of lactic acid. Methods and Results: Anesthetized pigs were subjected to hypovolemia for 30 minutes. The animals then received a bolus infusion of sabiporide (3 mg/kg) or vehicle, followed by an infusion of lactic acid for 2 hours. The animals were continuously monitored for additional 3 hours. Hypovolemia followed by a lactic acid infusion resulted in a severe metabolic acidosis with blood pH falling to 6.8. In association with production of the acidemia, there was an excessive increase in pulmonary artery pressure (PAP) and pulmonary vascular resistance (PVR). Treatment with sabiporide significantly attenuated the increase in PAP by 38% and PVR by 67%, as well as significantly improved cardiac output by 51%. Sabiporide treatment also improved mixed venous blood oxygen saturation (55% in sabiporide group vs. 28% in control group), and improved systemic blood oxygen delivery by 36%. In addition, sabiporide treatment reduced plasma levels of TNF-α (by 33%), IL-6 (by 63%), troponin-I (by 54%), ALT (by 34%), AST (by 35%), and urea (by 40%). Conclusion: These findings support the possible beneficial effects of sabiporide in the treatment of acute metabolic acidosis and could have implications for the treatment of metabolic acidosis in man. © 2013 Wu et al.

Wang W.,Xi'an Jiaotong University | Xia X.-G.,University of Delaware | Xia X.-G.,Chonbuk National University
IEEE Transactions on Signal Processing | Year: 2010

Chinese remainder theorem (CRT) reconstructs an integer from its multiple remainders that is well-known not robust in the sense that a small error in a remainder may cause a large error in the reconstruction. A robust CRT has been recently proposed when all the moduli have a common factor and the robust CRT is a searching based algorithm and no closed-from is given. In this paper, a closed-form robust CRT is proposed and a necessary and sufficient condition on the remainder errors for the closed-form robust CRT to hold is obtained. Furthermore, its performance analysis is given. It is shown that the reason for the robustness is from the remainder differential process in both searching based and our proposed closed-form robust CRT algorithms, which does no exist in the traditional CRT. We also propose an improved version of the closed-form robust CRT. Finally, we compare the performances of the traditional CRT, the searching based robust CRT and our proposed closed-form robust CRT (and its improved version) algorithms in terms of both theoretical analysis and numerical simulations. The results demonstrate that the proposed closed-form robust CRT (its improved version has the best performance) has the same performance but much simpler form than the searching based robust CRT. © 2006 IEEE.

Mun S.P.,Chonbuk National University | Cai Z.,U.S. Department of Agriculture | Zhang J.,Mississippi State University
Materials Letters | Year: 2013

Wood char, a by-product from the fast-pyrolysis process of southern yellow pine wood for bio-oil production, was carbonized with Fe nanoparticles (FeNPs) as a catalyst to prepare carbon-encapsulated Fe nanoparticles. A magnetic separation method was tested to isolate carbon-encapsulated Fe nanoparticles from the carbonized char. X-ray diffraction pattern clearly shows that Fe-containing materials were completely separated from the carbonized wood char mixture using a magnet. The amorphous carbon in the material which adhered to the magnetic bar was significantly decreased in comparison with the non-adhered material. Carbon graphitic layers encapsulated FeNPs were observed in the adhered material through high-resolution transmission electron microscopy. In addition, many long and tangled-multi-layered graphitic carbon structures grew from the surface of carbon-encapsulated Fe nanoparticles. © 2013 Elsevier B.V.

Ryu N.,Electronics and Telecommunications Research Institute | Jang S.,Electronics and Telecommunications Research Institute | Lee K.C.,Electronics and Telecommunications Research Institute | Jeong Y.,Chonbuk National University
IEEE Journal of Solid-State Circuits | Year: 2014

This paper presents a novel CMOS Doherty power amplifier (PA) with an impedance inverter using a variable balun transformer (VBT) and adaptive bias control of an auxiliary amplifier. Unlike a conventional quarter-wavelength λ/4 transmission line impedance inverter of a Doherty PA, the proposed VBT impedance inverter can achieve load modulation without any phase delay circuit. As a result, a λ /4 phase compensation circuit at the input path of the auxiliary amplifier can be removed, and the total size of the Doherty PA can be reduced. Additionally, an enhancement of the power efficiency at backed-off power levels can successfully be achieved with an adaptive gate bias in a common gate stage of the auxiliary amplifier. The PA, fabricated with 0.13-μm CMOS technology, achieved a 1-dB compression point (P1 dB) of 31.9 dBm and a power-added efficiency (PAE) at P1 dB of 51%. When the PA is tested with 802.11g WLAN orthogonal frequency division multiplexing (OFDM) signal of 54 Mb/s, a 25-dB error vector magnitude (EVM) compliant output power of 22.8 dBm and a PAE of 30.1% are obtained, respectively. © 1966-2012 IEEE.

Arunachalam S.,Bharathidasan University | Tirupathi Pichiah P.B.,Chonbuk National University | Achiraman S.,Bharathidasan University
FEBS Letters | Year: 2013

Doxorubicin-treated animals show elevated serum triglyceride and blood glucose levels. Adipocytes play an important role in buffering blood glucose and lipids. A raise in serum lipid level triggers adipogenesis in order to increase the lipid absorption capacity of adipose tissue. Doxorubicin inhibits adipogenesis through the down-regulation of PPARγ, a crucial component of the lipid metabolic pathway which controls the expression of glucose and fatty acid transporters. Doxorubicin-mediated down-regulation of PPARγ inhibits blood glucose and lipid clearance thereby causing hyperglycemia and hyperlipidemia resulting in lipotoxicity, glucotoxicity, inflammation and insulin resistance. Therefore we hypothesize that doxorubicin treatment could mimic a type 2 diabetic condition. © 2012 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

Lee K.S.,Chonbuk National University | Croft W.B.,University of Massachusetts Amherst
Information Processing and Management | Year: 2013

Typical pseudo-relevance feedback methods assume the top-retrieved documents are relevant and use these pseudo-relevant documents to expand terms. The initial retrieval set can, however, contain a great deal of noise. In this paper, we present a cluster-based resampling method to select novel pseudo-relevant documents based on Lavrenko's relevance model approach. The main idea is to use overlapping clusters to find dominant documents for the initial retrieval set, and to repeatedly use these documents to emphasize the core topics of a query. The proposed resampling method can skip some documents in the initial high-ranked documents and deterministically construct overlapping clusters as sampling units. The hypothesis behind using overlapping clusters is that a good representative document for a query may have several nearest neighbors with high similarities, participating in several different clusters. Experimental results on large-scale web TREC collections show significant improvements over the baseline relevance model. To justify the proposed approach, we examine the relevance density and redundancy ratio of feedback documents. A higher relevance density will result in greater retrieval accuracy, ultimately approaching true relevance feedback. The resampling approach shows higher relevance density than the baseline relevance model on all collections, resulting in better retrieval accuracy in pseudo-relevance feedback.

Jung E.,Chonbuk National University | Kim M.S.,Electronics and Telecommunications Research Institute | Kim H.,Chonbuk National University
IEEE Transactions on Electron Devices | Year: 2013

The contributing factors that determine the reliability characteristics of GaN-based white light-emitting diodes (WLEDs) with dual degradation kinetics were investigated. For this study, an aging test of WLEDs was performed at temperatures of 60 °C, 80°C, and 100°C under a constant dc of 300 mA. Evidence for dual degradation kinetics could be observed by the optical output degradation occurring with the modification of chromatic properties (due to the deterioration of packaging materials) and the evolution of leakage currents (due to the generation of nonradiative defects). By comparing temperature-dependent output degradation with the modification of chromatic properties or the evolution of leakage currents, the contributing factor that predominantly determines the reliability characteristics was estimated, i.e., the contributing factor for generated nonradiative defects versus the degraded packaging materials was 75:25 at 60°C and 32:68 at 100°C. This indicates that the predominant degradation kinetics change as the aging temperature varies. The activation energy of WLEDs was shown to be as low as 0.33 eV using Arrhenius plots of half-lifetime, which is attributed to the dual degradation kinetics. © 1963-2012 IEEE.

Seo H.-K.,Colorado State University | Ameen S.,Chonbuk National University | Akhtar M.S.,Chonbuk National University | Shin H.S.,Chonbuk National University
Talanta | Year: 2013

Reliable sensing properties towards hazardous phenol chemical were detected by the novel working electrode of layered polyaniline (PANI) nanosheets. The layered PANI nanosheets were synthesized by the chemical polymerization of aniline monomer in the presence of hydrochloric acid and ammonium persulphate at 5 °C. The morphological, structural, optical, electrical and electrochemical properties of layered PANI nanosheets were extensively studied. The electrochemical behavior of layered PANI nanosheets based electrode was demonstrated by the electrochemical impedance spectroscopy (EIS) and cyclovoltametry (CV) measurements. The layered PANI nanosheets electrode showed reasonably good electrocatalytic activity towards the detection of phenol chemical, which resulted from the high redox current and low RCT. The current-voltage (I-V) characteristics were used to elucidate the sensing parameters of the fabricated phenol chemical sensor with layered PANI nanosheets electrode. The fabricated phenol chemical sensor with layered PANI nanosheets electrode significantly attained the high sensitivity of ∼1485.3 μA mM-1 cm-2 and the detection limit of ∼4.43 μM with correlation coefficient (R) of ∼0.9981 and short response time (10 s). © 2012 Elsevier B.V.

Jung J.-H.,Seoul National University | Seo P.J.,Chonbuk National University | Park C.-M.,Seoul National University
Journal of Biological Chemistry | Year: 2012

The timing of flowering is coordinated by a web of gene regulatory networks that integrates developmental and environmental cues in plants. Light and temperature are two major environmental determinants that regulate flowering time. Although prolonged treatment with low nonfreezing temperatures accelerates flowering by stable repression of FLOWERING LOCUS C (FLC), repeated brief cold treatments delay flowering. Here, we report that intermittent cold treatments trigger the degradation of CONSTANS (CO), a central activator of photoperiodic flowering; daily treatments caused suppression of the floral integrator FLOWERING LOCUS T (FT) and delayed flowering. Cold-induced CO degradation is mediated via a ubiquitin/ proteasome pathway that involves the E3 ubiquitin ligase HIGH EXPRESSION OF OSMOTICALLY RESPONSIVE GENE 1 (HOS1). HOS1-mediated CO degradation occurs independently of the well established cold response pathways. It is also independent of the light signaling repressor CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1) E3 ligase and light wavelengths. CO has been shown to play a key role in photoperiodic flowering. Here, we demonstrated that CO served as a molecular hub, integrating photoperiodic and cold stress signals into the flowering genetic pathways. We propose that the HOS1-CO module contributes to the fine-tuning of photoperiodic flowering under short term temperature fluctuations, which often occur during local weather disturbances. © 2012 by The American Society for Biochemistry and Molecular Biology, Inc.

Seo H.-K.,Colorado State University | Elliott C.M.,Colorado State University | Shin H.-S.,Chonbuk National University
ACS Applied Materials and Interfaces | Year: 2010

TiO2 nanoparticles were synthesized by a facile method of dielectric barrier discharge jet (DBD jet) for the dye-sensitized solar cell (DSSC) and other potential applications. DBD jet is utilized as a method for deposition of TiO2 nanoparticles with a 9 μm/min growth rate which is more than × 25 faster than reported previously. Their performance was compared with cells fabricated using commercial TiO2 nanoparticles (P25). The crystallinity and chemical bonding states of samples were characterized by XRD and XPS. Photoanodes fabricated by the DBD jet method resulted in approximately 50% higher photoconversion efficiency than ones prepared from P25 nanoparticles. © 2010 American Chemical Society.

Park J.H.,Chonbuk National University | Morizumi T.,University of Toronto | Li Y.,Charité - Medical University of Berlin | Hong J.E.,Chonbuk National University | And 5 more authors.
Angewandte Chemie - International Edition | Year: 2013

Receptor-ligand interaction: Olfactory receptors (ORs) are G-protein-coupled receptors (GPCRs), which detect signaling molecules such as hormones and odorants. The structure of opsin, the GPCR employed in vision, with a detergent molecule bound deep in its orthosteric ligand-binding pocket provides a template for OR homology modeling, thus enabling investigation of the structural basis of the mechanism of odorant-receptor recognition. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Khayyat S.A.,King Abdulaziz University | Akhtar M.S.,Chonbuk National University | Umar A.,Najran University
Materials Letters | Year: 2012

This paper reports the successful synthesis of ZnO nanocapsules and their utilization as a photocatalyst for photocatalytic degradation of thionine. The nanocapsules were synthesized by facile hydrothermal process and characterized in detail in terms of their morphological, structural and optical properties. The detailed studies revealed that the synthesized nanocapsules possess well-crystalline and good optical properties. By utilizing the as-synthesized ZnO nanocapsules as a photocatalyst, significant photocatalytic degradation was observed towards thionine dye under light illumination. The considerable photo-degradation of thionine dye was due to the unique morphology and high surface area of synthesized ZnO nanocapsules which might import the effective electron/hole separation and might generate the large number of oxy-radicals. © 2012 Elsevier B.V. All rights reserved.

Ryu N.,Electronics and Telecommunications Research Institute | Park B.,Electronics and Telecommunications Research Institute | Jeong Y.,Chonbuk National University
IEEE Microwave and Wireless Components Letters | Year: 2015

This paper proposes a CMOS linear power amplifier (PA) design scheme for IEEE 802.11g (WLAN) application. The proposed PA consists of a programmable gain amplifier and a high power stage which is composed of a main amplifier with class AB bias and an auxiliary amplifier with class C bias. Based on the un-even bias scheme, the power stage can improve linearity and reduce current consumption in the low power region. It is fabricated with a TSMC 40 nm standard RF CMOS process. The measurements show that the designed PA reaches a 1 dB gain compression output power of 24.6 dBm and a peak drain efficiency of 38% with a 3.3 V power supply at 2.4 GHz operating frequency range. When the PA was tested with an IEEE 802.11g OFDM signal of 20 MHz channel bandwidth, the obtained -25 dB EVM compliant output power and drain efficiency are 18.5 dBm and 14%, respectively. © 2001-2012 IEEE.

Kumar R.,JCDAV College | Kumar G.,JCDAV College | Akhtar M.S.,Chonbuk National University | Umar A.,Najran University
Journal of Alloys and Compounds | Year: 2015

A simple, facile and rapid solution combustion method utilizing dextrose as fuel was employed to synthesize zinc oxide (ZnO) nano-aggregates at high temperature 450 °C. The synthesized nanomaterials were characterized in terms of their morphological, structural, compositional, optical and photocatalytic properties. The detailed characterizations confirmed that the synthesized ZnO nano-aggregate possessed high density and exhibit well-crystallinity with good optical properties. The sonophotocatalytic properties of the synthesized ZnO nano-aggregates was carried out by performing the degradation of methyl orange (MO) dye under UV light. A strong synergism was observed between UV light and ZnO nano-aggregates for the photodegradation process, whereas sonolytic and photolytic degradation processes were found to operate independently. The presence of air in the aqueous suspensions of MO dye was also shown a significant impact in the photodegradation rate. © 2015 Elsevier B.V. All rights reserved.

Bandara N.,Chonbuk National University | Jo J.,Chonbuk National University | Ryu S.,Seoul National University | Kim K.-P.,Chonbuk National University
Food Microbiology | Year: 2012

Bacillus cereus is a foodborne bacterial pathogen that causes diarrhea and vomiting. In this study, the usefulness of bacteriophages to eradicate B. cereus from fermented foods was investigated. A total of 13 phages were isolated from Korean fermented food products, and 2 (BCP1-1 and BCP8-2) were further characterized. Transmission electron microscopy (TEM), restriction enzyme digestion pattern analysis, and SDS-PAGE of the structural proteins suggest that both phages belong to the family Myoviridae, containing approximately 150 kbp-long genomes. The host ranges of both phages were limited to B. cereus group species (12/13), as they were not able to lyse other Gram-positive or negative strains including Bacillus subtilis. Purified phages were used to inhibit B. cereus growth in a model fermented food system, cheonggukjang, a fast-fermented soybean paste product. BCP1-1 and BCP8-2 were able to effectively eradicate B. cereus from the food only if divalent cations (Ca 2+, Mg 2+, or Mn 2+) were added to the medium. Further studies reveal that divalent cations are essential for phage adsorption, while a monovalent cation (Na +) is required for the post-adsorption phase of phage infection. Taken together, our findings imply that a phage could be an ideal anti-bacterial agent for use in fermented food products that require the presence of beneficial microflora and, during phage application, optimization of phage reaction conditions is critical for the successful utilization of phage biocontrol. © 2012 Elsevier Ltd.

Yoon J.-H.,Chosun University | Ahn S.-G.,Chosun University | Lee B.-H.,Seoul National University | Jung S.-H.,Chonbuk National University | Oh S.-H.,Chosun University
Biochemical Pharmacology | Year: 2012

Capsaicin treatment was previously reported to reduce the sensitivity of breast cancer cells, but not normal MCF10A cells, to apoptosis. The present study shows that autophagy is involved in cellular resistance to genotoxic stress, through DNA repair. Capsaicin treatment of MCF-7 cells induced S-phase arrest and autophagy through the AMPKα-mTOR signaling pathway and the accumulation of p53 in the nucleus and cytosol, including a change in mitochondrial membrane potential. Capsaicin treatment also activated δ-H2AX, ataxia telangiectasia mutated (ATM), DNA-dependent protein kinase catalytic subunit (DNA-PKcs), and poly(ADP-ribose) polymerase (PARP)-1. Genetic or pharmacological disruption of autophagy attenuated capsaicin-induced phospho-ATM and phospho-DNA-PKcs and enhanced apoptotic cell death. ATM inhibitors, including Ku55933 and caffeine, and the genetic or pharmacological inhibition of p53 prevented capsaicin-induced DNA-PKcs phosphorylation and stimulated PARP-1 cleavage, but had no effect on microtubule-associated protein light chain 3 (LC3)-II levels. Ly294002, a DNA-PKcs inhibitor, boosted the capsaicin-induced cleavage of PARP-1. In M059K cells, but not M059J cells, capsaicin induced ATM and DNA-PKcs phosphorylation, p53 accumulation, and the stimulation of LC3II production, all of which were attenuated by knockdown of the autophagy-related gene atg5. Ku55933 attenuated capsaicin-induced phospho-DNA-PKcs, but not LC3II, in M059K cells. In human breast tumors, but not in normal tissues, AMPKα, ATM, DNA-PKcs, and PARP-1 were activated and LC3II was induced. The induction of autophagy by genotoxic stress likely contributes to the sustained survival of breast cancer cells through DNA repair regulated by ATM-mediated activation of DNA-PKcs and PARP-1. © 2011 Elsevier Inc.

Ahmad R.,Chonbuk National University | Tripathy N.,Chonbuk National University | Kim S.H.,Najran University | Umar A.,Najran University | And 2 more authors.
Electrochemistry Communications | Year: 2014

Zinc oxide nanotube (ZNT) arrays were grown on Si/Ag substrate by one-step chemical process in an aqueous solution and further used as a working electrode to fabricate an enzyme-based cholesterol biosensor through immobilization of cholesterol oxidase (ChOx). The fabricated biosensors exhibit high and reproducible sensitivity of 79.40 μA/mM/cm2, wide linear range from 1.0 μM to 13.0 mM, fast response time of ~ 2 s and ultra-low detection limit of 0.5 nM (S/N = 3) for cholesterol sensing. The anti-interference ability and long-term stability of the biosensor were also assessed. Finally, the biosensor was applied to analyze cholesterol concentration in human serum samples. © 2013 Elsevier B.V.

Abdal-Hay A.,Chonbuk National University | Abdal-Hay A.,South Valley University | Pant H.R.,Chonbuk National University | Lim J.K.,Chonbuk National University
European Polymer Journal | Year: 2013

The present study was aimed at designing a novel bimodal fiber diameter distributed electrospun hydroxyapatite/nylon-6 (HAp/N6) biocomposite nanofiber mat for bone tissue engineering. The manufacturing of pure N6 fibers and biocomposite fibers was explored by an electrospinning process. The synthesized HAp/N6 composite mats were characterized by XRD, TGA, FE-SEM, EDS, and TEM analyses and water contact angle measurements. The results revealed that fibers of distinct sizes (nano and true-nano scale) were obtained with the addition of a wide range (1-10 wt.%) of HAp. Conversion of pristine hydrophobic N6 fibers (130.3°) to super-hydrophilic (0°) composite fibers by simple blending of different amounts of HAp with N6 solution prior to electrospinning could make N6 more biocompatible for hard tissue engineering. Biomineralization was carried out by immersing the composite into simulated body fluid for different lengths of time. Results showed that the nanocomposite had a better ability to form apatite layers on the surface of the fibers compared to the pristine fibers. Therefore, our results suggest that this newly developed HAp/N6 hybrid scaffold may have potential for bone tissue engineering. © 2013 Elsevier B.V. All rights reserved.

Oh S.-Y.,Chonbuk National University | Kim J.-S.,Seoul National University | Yang T.-H.,Chonbuk National University | Shin B.-S.,Chonbuk National University | Jeong S.-K.,Chonbuk National University
Journal of Neurology | Year: 2013

To clarify the changes of cervical (cVEMP) and ocular (oVEMP) vestibular evoked myogenic potentials induced by air-conducted sound (ACS) and bone-conducted vibration (BCV) in patients with vestibular neuritis (VN), patients with VN (n = 30) and normal controls (n = 45) underwent recording of cVEMP and oVEMP in response to ACS (1,000 Hz, 5 ms, tone bursts) and BCV (500 Hz, short tone burst). Patients with VN showed a high proportion of oVEMP abnormalities in response to both ACS (80.0 %) and BCV at the forehead (Fz, 73.3 %) or the mastoid (76.7 %). In contrast, cVEMPs were mostly normal with both ACS and BCV in the patients. The dissociations in the abnormalities of cVEMP and oVEMP induced by ACS and BCV at the mastoids and at the forehead in patients with VN suggest that oVEMP reflects functions of the superior vestibular nerve and most likely the utricular function. The results of our study suggest that oVEMP induced by either ACS or BCV appears to depend on integrity of the superior vestibular nerve, possibly due to the utricular afferents travelling in it. In contrast, cVEMP elicited by either ACS or BCV may reflect function of the saccular afferents running in the inferior vestibular nerve. © 2013 Springer-Verlag Berlin Heidelberg.

Hwang S.J.,Korea Institute of Science and Technology | Kim S.-K.,Korea Institute of Science and Technology | Kim S.-K.,Chung - Ang University | Lee J.-G.,Korea Institute of Science and Technology | And 6 more authors.
Journal of the American Chemical Society | Year: 2012

The design of electrocatalysts for polymer electrolyte membrane fuel cells must satsify two equally important fundamental principles: optimization of electrocatalytic activity and long-term stability in acid media (pH <1) at high potential (0.8 V). We report here a solution-based approach to the preparation of Pt-based alloy with early transition metals and realistic parameters for the stability and activity of Pt3M (M = Y, Zr, Ti, Ni, and Co) nanocatalysts for oxygen reduction reaction (ORR). The enhanced stability and activity of Pt-based alloy nanocatalysts in ORR and the relationship between electronic structure modification and stability were studied by experiment and DFT calculations. Stability correlates with the d-band fillings and the heat of alloy formation of Pt3M alloys, which in turn depends on the degree of the electronic perturbation due to alloying. This concept provides realistic parameters for rational catalyst design in Pt-based alloy systems. © 2012 American Chemical Society.

Bradford S.A.,U.S. Department of Agriculture | Kim H.,Chonbuk National University
Journal of Environmental Quality | Year: 2010

Column experiments were conducted to study chemical factors that influence the release of clay (kaolinite and quartz minerals) from saturated Ottawa sand of different sizes (710, 360, and 240 μm). A relatively minor enhancement of clay release occurred when the pH was increased (5.8 to 10) or the ionic strength (IS) was decreased to deionized (DI) water. In contrast, clay release was dramatically enhanced when monovalent Na+ was exchanged for multivalent cations (e.g., Ca2+ and Mg2+) on the clay and sand and then the solution IS was reduced to DI water. This solution chemistry sequence decreased the adhesive force acting on the clay as a result of an increase in the magnitude of the clay and sand zeta potential with cation exchange, and expansion of the double layer thickness with a decrease in IS to DI water. The amount of clay release was directly dependent on the Na + concentration of the exchanging solution and on the initial clay content of the sand (0.026-0.054% of the total mass). These results clearly demonstrated the importance of the order and magnitude of the solution chemistry sequence on clay release. Column results and scanning electron microscope (SEM) images also indicated that the clay was reversibly retained on the sand, despite predictions of irreversible interaction in the primary minimum. One plausible explanation is that adsorbed cations increased the separation distance between the clay-solid interfaces as a result of repulsive hydration forces. A cleaning procedure was subsequently developed to remove clay via cation exchange and IS reduction; SEM images demonstrated the effectiveness of this approach. The transport of Cu2+ was then shown to be dramatically enhanced by an order of magnitude in peak concentration by adsorption on clays that were released following cation exchange and IS reduction. Copyright © 2010 by the American Society of Agronomy.

Kim Y.K.,Chonbuk National University | Kim C.S.,Chonbuk National University | Han Y.M.,Chonbuk National University | Yu H.C.,Samsung | Choi D.,Chonbuk National University
Investigative Radiology | Year: 2011

Purpose: To investigate the diagnostic efficacy of gadoxetic acid-enhanced magnetic resonance imaging (MRI) at 3.0 T for the detection of hepatocellular carcinomas (HCC) and compare with that at 1.5 T. MATERIALS: Forty patients with 54 HCCs (size range: 0.6-2.0 cm) underwent gadoxetic acid-enhanced MRIs at both 1.5 and 3.0 T with 3 to 8 days interval. The MRIs were compared quantitatively by measuring tumor-liver contrast-to-noise ratio, and qualitatively by evaluating tumor-liver contrast using matched pairs analysis. Diagnostic accuracy and sensitivity were also evaluated by the consensus readings of 2 reviewers using the alternative-free response receiver operator characteristic (ROC) method. Results: Although the tumor-liver contrast-to-noise ratio for the arterial phase was significantly higher at 3.0 T than at 1.5 T (30.2 ± 21.4 vs. 35.2 ± 22.9; P = 0.04), we found similar values for the hepatocyte phase (38.2 ± 24.6 vs. 38.4 ± 25.3; P = 0.762). Matched pairs analysis indicated that the relative tumor-liver contrast was better in 7 and 9 lesions in the arterial phase and hepatocyte phase at 3.0 T, respectively, than those at 1.5 T. The diagnostic accuracy and sensitivity of 3.0-T imaging [Az, 0.988; 92.6% (n = 50)] were slightly higher than those of 1.5-T imaging [Az, 0.981; 88.9% (n = 48)], but the difference was not statistically significant (P = 0.487). Conclusions: Gadoxetic acid-enhanced MRIs at 1.5 and 3.0 T showed similar diagnostic performances for detecting small HCCs. However, there was a tendency toward increased reader confidence for the arterial phase and hepatocyte phase with 3.0 T compared with 1.5 T.Copyright © 2011 by Lippincott Williams & Wilkins.

Bradford S.A.,U.S. Department of Agriculture | Kim H.,Chonbuk National University
Journal of Contaminant Hydrology | Year: 2012

Experiments were designed to better understand the causes and implications of colloid and microorganism retention hysteresis with transients in solution ionic strength (IS). Saturated packed column experiments were conducted using two sizes of carboxyl modified latex (CML) microspheres (0.1 and 1.1 μm) and microorganisms (coliphage φX174 and E. coli D21g) under various transient solution chemistry conditions, and 360 μm Ottawa sand that was subject to different levels of cleaning, namely, a salt cleaning procedure that removed clay particles, and a salt + acid cleaning procedure that removed clay and reduced microscopic heterogeneities due to metal oxides and surface roughness. Comparison of results from the salt and salt + acid treated sand indicated that microscopic heterogeneity was a major contributor to colloid retention hysteresis. The influence of this heterogeneity increased with IS and decreasing colloid/microbe size on salt treated sand. These trends were not consistent with calculated mean interaction energies (the secondary minima), but could be explained by the size of the electrostatic zone of influence (ZOI) near microscopic heterogeneities. In particular, the depth of local minima in the interaction energy has been predicted to increase with a decrease in the ZOI when the colloid size and/or the Debye length decreased (IS increased). The adhesive interaction was therefore largely irreversible for smaller sized 0.1 μm CML colloids, whereas it was reversible for larger 1.1 μm CML colloids. Similarly, the larger E. coli D21g exhibited greater reversibility in retention than φX174. However, direct comparison of CML colloids and microbes was not possible due to differences in size, shape, and surface properties. Retention and release behavior of CML colloids on salt + acid treated sand was much more consistent with mean interaction energies due to reduction in microscopic heterogeneities. © 2012 Elsevier B.V.

Yang S.J.,Seoul National University | Cho J.H.,Seoul National University | Nahm K.S.,Chonbuk National University | Park C.R.,Seoul National University
International Journal of Hydrogen Energy | Year: 2010

We report on an easy synthesis method for the preparation of a hybrid composite of Pt-loaded MWCNTs@MOF-5 [Zn4O(benzene-1,4-dicarboxylate) 3] that greatly enhanced hydrogen storage capacity at room temperature. To prepare the composite, we first prepared Pt-loaded MWCNTs, which were then incorporated in-situ into the MOF-5 crystals. The obtained composite was characterized by various techniques such as powder X-ray diffractometry, optical microscopy, porosimetry by nitrogen adsorption, and hydrogen adsorption. The analyses confirmed that the product has a highly crystalline structure with a Langmuir specific surface area of over 2000 m2/g. The hybrid composite was shown to have a hydrogen storage capacity of 1.25 wt% at room temperature and 100 bar, and 1.89 wt% at cryogenic temperature and 1 bar. These H2 storage capacities represent significant increases over those of virgin MOF-5s and Pt-loaded MWCNTs. © 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.

Kim M.J.,Seoul National University | Park M.-J.,Seoul National University | Seo P.J.,Chonbuk National University | Song J.-S.,Seoul National University | And 2 more authors.
Biochemical Journal | Year: 2012

Controlled proteolytic activation of membrane-anchored transcription factors provides an adaptation strategy that guarantees rapid transcriptional responses to abrupt environmental stresses in both animals and plants. NTL6 is a plant-specific NAC [NAM/ATAF1/2/CUC2] transcription factor that is expressed as a dormant plasma membrane-associated form in Arabidopsis. Proteolytic processing of NTL6 is triggered by abiotic stresses and ABA (abscisic acid). In the present study, we show that NTL6 is linked directly with SnRK (Snf1-related protein kinase) 2.8-mediated signalling in inducing a drought-resistance response. SnRK2.8 phosphorylates NTL6 primarily at Thr142. NTL6 phosphorylation by SnRK2.8 is required for its nuclear import. Accordingly, a mutant NTL6 protein, in which Thr142was mutated to an alanine, was poorly phosphorylated and failed to enter the nucleus. In accordance with the role of SnRK2.8 in drought-stress signalling, transgenic plants overproducing either NTL6 or its active form 6ΔC (35S:NTL6 and 35S:6ΔC) exhibited enhanced resistance to water-deficit conditions such as those overproducing SnRK2.8 (35S:SnRK2.8). In contrast, NTL6 RNAi (RNA interference) plants were susceptible to dehydration as observed in the SnRK2.8-deficient snrk2.8-1 mutant. Furthermore, the dehydration-resistant phenotype of 35S:NTL6 transgenic plants was compromised in 35S:NTL6 X snrk2.8-1 plants. These observations indicate that SnRK2.8-mediated protein phosphorylation, in addition to a proteolytic processing event, is important for NTL6 function in inducing a drought-resistance response. © The Authors Journal compilation © 2012 Biochemical Society.

Seo P.J.,Chonbuk National University | Park M.-J.,Seoul National University | Park C.-M.,Seoul National University
Planta | Year: 2013

Transcription factors play a central role in the gene regulatory networks that mediate various aspects of plant developmental processes and responses to environmental changes. Therefore, their activities are elaborately regulated at multiple steps. In particular, accumulating evidence illustrates that post-transcriptional control of mRNA metabolism is a key molecular scheme that modulates the transcription factor activities in plant responses to temperature fluctuations. Transcription factors have a modular structure consisting of distinct protein domains essential for DNA binding, dimerization, and transcriptional regulation. Alternative splicing produces multiple proteins having different structural domain compositions from a single transcription factor gene. Recent studies have shown that alternative splicing of some transcription factor genes generates small interfering peptides (siPEPs) that negatively regulate the target transcription factors via peptide interference (PEPi), constituting self-regulatory circuits in plant cold stress response. A number of splicing factors, which are involved in RNA binding, splice site selection, and spliceosome assembly, are also affected by temperature fluctuations, supporting the close association of alternative splicing of transcription factors with plant responses to low temperatures. In this review, we summarize recent progress on the temperature-responsive alternative splicing of transcription factors in plants with emphasis on the siPEP-mediated PEPi mechanism. © 2013 The Author(s).

Kwon C.,State University of New York at Buffalo | Lee T.,Chonbuk National University | Berglund P.,Norfolk Southern Corporation
Naval Research Logistics | Year: 2013

We consider a robust shortest path problem when the cost coefficient is the product of two uncertain factors. We first show that the robust problem can be solved in polynomial time by a dual-variable enumeration with shortest path problems as subproblems. We also propose a path enumeration approach using a K -shortest paths finding algorithm that may be efficient in many real cases. An application in hazardous materials transportation is discussed, and the solution methods are illustrated by numerical examples. © 2013 Wiley Periodicals, Inc. Naval Research Logistics, 2013 Copyright © 2013 Wiley Periodicals, Inc.

Lee M.-J.,Chonbuk National University | Chae J.-S.,Seoul National University
Vector-Borne and Zoonotic Diseases | Year: 2010

The salivary gland (SG) of tick plays an important role as a route in the dissemination of tick-borne pathogens to their hosts. We evaluated the presence of these pathogens in the SGs of Haemaphysalis longicornis ticks, and these ticks were collected from grazing cattle in Jeju Island, Korea. Of total 463 one-side SGs, 56 (12.1%) SGs were positive for Ehrlichia chaffeensis and 11 (2.4%) were positive for Anaplasma bovis. In addition, two (0.4%) SGs were co-infected with both E. chaffeensis and A. bovis. In conclusion, we specifically describe the presence of E. chaffeensis and A. bovis in the SGs of H. longicornis ticks in Korea. © 2010, Mary Ann Liebert, Inc.

Samsung and Chonbuk National University | Date: 2014-04-08

An inspection apparatus for detecting a defect of a substrate is provided. The inspection apparatus includes a liquid crystal modulator, a light emitting unit, a beam splitter, and a measurement unit. The liquid crystal modulator includes a reflection layer, a liquid crystal layer, an electrode, and a polarizer. The reflection layer reflects a light. The sensor layer includes a hybrid aligned nematic liquid crystal. The electrode is provided on the liquid crystal layer. The polarizer is provided on the electrode.

Postech Academy Industry Foundation and Chonbuk National University | Date: 2013-03-04

An exemplary embodiment of the present invention provides a three-dimensional virtual liver surgery planning system including: a digital imaging and communications in medicine (DICOM) receiving module which receives an abdomen computer tomography (CT) volume data set from a picture archiving and communication system (PACS) server; a DICOM loading and noise removing module which loads the received abdomen CT volume data set and remove noises; a standard liver volume estimation module which estimates a standard liver volume (SLV) from the denoised abdomen CT volume data set; a liver extraction module which extracts a three-dimensional liver region; a vessel extraction module which extracts a three-dimensional vessel region including a portal vein, a hepatic artery, a hepatic vein, and an inferior vena cava (IVC); a tumor extraction module which extracts a three-dimensional tumor region; a liver segmentation module which divides the extracted three-dimensional liver region into several segments using landmarks which are selected by a user or a segmentation sphere; and a liver surgery planning module which makes a three-dimensional liver surgery plan using a resection surface, a liver segments, or the segmentation sphere.

Electronics, Telecommunications Research Institute and Chonbuk National University | Date: 2010-06-29

A method includes: placing a Radio Frequency Identification (RFID) tag for underground use under a ground surface, wherein a ground plate which has a diameter greater than that of the RFID tag or a tag antenna and on a top of which the RFID tag is mounted is placed underground such that the RFID tag protrudes above the ground surface or a bottom of the RFID tag is aligned with the ground surface.

A liquid crystal composition including about 70 percent by weight to about 98 percent by weight of a liquid crystal molecule; and about 2 percent by weight to about 30 percent by weight of a hydrogel agent, each based on a total weight of the liquid crystal composition.

Chonbuk National University, Electronics and Telecommunications Research Institute | Date: 2013-06-18

A loop antenna includes first and second loops that are formed with respective conductive wires. In this case, the second loop is formed with a double loop having current paths of opposite directions.

A liquid crystal device that includes two substrates that face each other, a liquid crystal cell interposed between the two substrates, and a liquid crystal alignment layer interposed between the liquid crystal cell and at least one of the two substrates, the liquid crystal alignment layer includes a plurality of spherical or spherical-like core particles having a diameter of 10 nm to 1 m.

Abdal-Hay A.,Chonbuk National University | Dewidar M.,South Valley University | Lim J.K.,Chonbuk National University
Applied Surface Science | Year: 2012

The present study was ultimately aimed to design novel adhesive biodegradable polymer, poly(vinyl acetate) (PVAc), coatings onto Mg based alloys by the dip-coating technique in order to control the degradation rate and enhance the biocompatibility of magnesium alloys. The influence of various solvents on PVAc surface topography and their protection of Mg alloys were dramatically studied in vitro. Electrochemical polarization, degradation, and PVAc film cytocompatibility were also tested. Our results showed that the solvent had a significant effect on coating quality. PVAc/dichloromethane solution showed a porous structure and solution concentration could control the porous size. The coatings prepared using tetrahydrofuran and dimethylformamide solvents are exceptional in their ability to generate porous morphology even at low polymer concentration. In general, the corrosion performance appears to be different on different PVAc-solvent system. Immersion tests illustrated that the porous morphology on PVAc stabilized corrosion rates. A uniform corrosion attack in artificial simulation body fluid was also exhibited. The cytocompatibility of osteoblast cells (MC3T3) revealed high adherence, proliferation, and survival on the porous structure of PVAc coated Mg alloy, which was not observed for the uncoated samples. This novel PVAc coating is a promising candidate for biodegradable implant materials, which might widen the use of Mg based implants. Copyright © 2012 Published by Elsevier B.V. All rights reserved.

Wang H.-M.,Xi'an Jiaotong University | Yin Q.,Xi'an Jiaotong University | Xia X.-G.,University of Delaware | Xia X.-G.,Chonbuk National University
IEEE Transactions on Signal Processing | Year: 2012

In this paper, we address the security of a two-way relay network in the presence of an eavesdropper, where each node is only equipped with single antenna. We propose two-phase distributed analog network coding, or distributed beamforming and power allocation to enhance the secrecy sum rate of the data exchange. In the first phase, the two terminals broadcast their information data simultaneously to all the relay nodes. In the second phase, three different security schemes are proposed: optimal beamforming, null-space beamforming, and artificial noise beamforming. In the first scheme, the objective is to achieve the maximum secrecy sum rate of the two terminals. Mathematically, the objective function is difficult to optimize. In the second scheme, we maximize the total information exchanged while we eliminate the information leakage completely, subject to the total transmission power constraint. We show that the problem has a unique and global optimum, which can be solved using bisection method. When the instantaneous channel state information of the eavesdropper is not available, we propose an artificial noise beamforming in the third scheme. We minimize the information transmission power so that the artificial noise power is maximized to eliminate information leakage, under the constraints of quality of service (QoS) required by terminals. It is a second-order convex cone programming (SOCP) problem, thus can be efficiently solved using interior point methods. Numerical results are provided and analyzed to show the properties and efficiency of the proposed designs. © 2012 IEEE.

Yun D.,Seoul National University | Kim S.,Chonbuk National University | Ha S.,Seoul National University
IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems | Year: 2012

A virtual prototyping system is constructed by replacing real processing components with component simulators running concurrently. The performance of such a distributed simulation decreases drastically as the number of component simulators increases. Thus, we propose a novel parallel simulation technique to boost up the simulation speed. In the proposed technique, a simulator wrapper performs time synchronization with the simulation backplane on behalf of the associated component simulator itself. Component simulators send null messages periodically to the backplane to enable parallel simulation without any causality problems. Since excessive communication may degrade the simulation performance, we also propose a novel performance analysis technique to determine an optimal period of null message transfer, considering both the characteristics of a target application and the configurations of the simulation host. Through intensive experiments, we show that the proposed parallel simulation achieves almost linear speedup to the number of processor cores if the frequency of null message transfer is optimally decided. The proposed analysis technique could predict the simulation performance with more than 90% accuracy in the worst case for various target applications and simulation environments we have used for experiments. © 2011 IEEE.

Kim K.J.,Inha University | Fan Y.,Princeton University | Iltis R.A.,University of California at Santa Barbara | Poor H.V.,Princeton University | Lee M.H.,Chonbuk National University
IEEE Transactions on Vehicular Technology | Year: 2012

A new precoder that reduces the feedback overhead in an orthogonal frequency-division multiplexing (OFDM)-based relay network is proposed. A joint singular value decomposition (SVD) and QR decomposition is employed on the source-destination link and the source-relay-destination link. Using the proposed precoder, only one precoding matrix needs to be fed back, independent of the total number of subcarriers. Kernel density estimation is applied to determine approximate forms of unknown distributions of the end-to-end effective channel powers obtained by this precoder. Using approximated probability density functions (pdfs) for these effective channel powers, closed-form expressions for the link achievable average sum-rate and the outage probability can be derived and then their accuracies verified via Monte Carlo simulations. The achievable sum-rates are also compared with that of SVD-based precoders and for varying codebook size. © 2012 IEEE.

Anygen Inc., Samsung, Snu R&D Foundation and Chonbuk National University | Date: 2016-01-13

The present invention relates to a pharmaceutical composition for treating or preventing erectile dysfunction, containing LDD175 as an active ingredient. Furthermore, the present invention relates to a co-administration preparation for treating or preventing erectile dysfunction, containing LDD175 and a PDE5 inhibitor as active ingredients. The LDD175 of the present invention has an excellent corporal smooth muscle relaxation effect, and thus significantly improved erectile function. Since the LDD175 of the present invention acts on BK_(Ca )channels, and thus is expected to have little adverse cardiovascular effects. The LDD175 of the present invention exhibits an erectile dysfunction therapeutic ability equivalent to that of udenafil, which is a PDE5 inhibitor, and showed a synergistic corporal smooth muscle relaxation effect when being co-administered with udenafil.

Samsung and Chonbuk National University | Date: 2015-06-19

An LCD panel, comprises substrates facing each other, a liquid crystal layer disposed between the substrates and liquid crystal alignment layers, each sandwiched between the liquid crystal layer and a respective one of the substrates, wherein the liquid crystal alignment layers comprises hydrocarbon derivative having perfluorocarbon group.

Chonbuk National University, Electronics and Telecommunications Research Institute | Date: 2011-12-22

Disclosed herein is a circularly polarized antenna with a wide beam width, in which four U-shaped metal strips are disposed in a circular shape, and four signals having the same magnitude and phase difference intervals of 90 degrees are fed to the respective metal strips so as to transceive circularly polarized waves. The disclosed circularly polarized antenna includes a ground plane, a central patch formed in the center of an upper surface of the ground plane, and a plurality of radiation patches disposed above the ground plane and around the central patch in a circular shape, wherein signals having the same magnitude and preset phase differences are fed to respective radiation patches.

Chonbuk National University, Electronics and Telecommunications Research Institute | Date: 2011-10-18

A communication method and apparatus using a symbol interleaver in a long term evolution (LTE)-based satellite communication system are provided. The communication method may include determining whether to use an interleaver based on service information, and interleaving the data using the symbol interleaver designed based on interleaver information. Also, the communication method may include generating random data using a timer and interleaving the random data.

Mishra A.,Chonbuk National University | Tripathy S.K.,Korea University | Tripathy S.K.,Korea University | Yun S.-I.,Chonbuk National University
Process Biochemistry | Year: 2012

Biological systems employing microorganisms have been used as an alternative to conventional chemical techniques for synthesizing gold nanoparticles. In the present study, gold nanoparticles have been synthesized from the supernatant broth (SB) and live cell filtrate (LCF) of the industrially important fungus Penicillium rugulosum. Additionally, potato dextrose broth (PDB) medium which is used for the growth of the fungus has also been able to synthesize gold nanoparticles. The size of the particles has been investigated by Bio-TEM before purification as well as after purification to find the difference in morphology pattern of the nanoparticles. Different characterization techniques like X-ray diffraction (XRD), infra-red (FTIR), X-ray photoelectron (XPS) and UV-vis spectroscopy have been used for analysis of the particles. SB of the fungus has yielded nanoparticles with better morphology and hence further optimization studies were conducted for controlling the size and shape of the above by altering pH and concentration of gold salt. A pH range of 4-6 has favored the synthesis process whereas increasing concentration of gold salt (beyond 2 mM) has resulted in the formation of bigger sized and aggregated nanoparticles. The optimized nanoparticles have been used to conjugate with isolated genomic DNA of bacteria Escherichia coli and Staphylococcus aureus. Visual observation of agarose gel electrophoresis images confirmed the binding of gold nanoparticles (4 μL and 6 μL) with isolated DNA (2 μL) fragments of both the organisms. The slight red shift of the surface plasmon (SP) band and minor aggregations noticed in Bio-TEM images for the DNA conjugated gold nanoparticles indicates that the genomic DNA could stabilize the particles against aggregation owing to negatively charged phosphate backbone. © 2012 Elsevier Ltd. All rights reserved.

Cui X.-D.,Chonbuk National University | Lee M.-J.,Chonbuk National University | Kim J.-H.,Chonbuk National University | Hao P.-P.,Chonbuk National University | And 3 more authors.
Hepatology | Year: 2013

Eph receptor 2 (EphA2) overexpression is frequently accompanied by the loss of its cognate ligand during tumor progression. However, the molecular mechanism of this ligand-independent promotion of tumor by EphA2 remains unclear in highly malignant and fatal cholangiocarcinoma (CC). We examined the biological role of EphA2 in tumor growth and metastasis in CC tissues and cells according to the degree of differentiation and we explored the downstream signaling pathways of EphA2. Growth factor-mediated EphA2 overexpression itself leads to the activation of the mammalian target of rapamycin complex 1 (mTORC1) and extracellular signal-regulated kinase (ERK) pathways through ligand-independent activation of EphA2 (phosphorylation of S897). An in vitro soft agar assay and in vivo orthotopic or subcutaneous tumor model showed that EphA2 enhanced colony formation and accelerated tumor growth, and which seemed to be mainly associated with Akt (T308)/mTORC1 activation. Aberrant expression and activation of EphA2 was also associated with poorer differentiation and higher metastatic ability. Enhanced metastatic ability was also observed in an orthotopic tumor model or lung metastasis model, correlating with Pyk2(Y402)/c-Src/ERK activation in addition to activation of the canonical Raf/MEK/ERK pathway. The mTORC1 and Raf/Pyk2 pathways also appeared to affect each other. These results suggest that growth factor-mediated EphA2 might be involved in tumor growth and metastasis through activation of the mTORC1 and Raf/Pyk2 pathways. Therapeutic strategies that target EphA2 and its downstream effectors may be useful to control CC. © 2013 American Association for the Study of Liver Diseases.

Lee M.,Chonbuk National University | Gatton T.M.,National University of La Jolla
Sensors | Year: 2010

Ubiquitous home healthcare systems have been playing an increasingly significant role in the treatment and management of chronic diseases, such as diabetes and hypertension, but progress has been hampered by the lack of standardization in the exchange of medical health care information. In an effort to establish standardization, this paper proposes a home healthcare monitoring system data exchange scheme between the HL7 standard and the IEEE1451 standard. IEEE1451 is a standard for special sensor networks, such as industrial control and smart homes, and defines a suite of interfaces that communicate among heterogeneous networks. HL7 is the standard for medical information exchange among medical organizations and medical personnel. While it provides a flexible data exchange in health care domains, it does not provide for data exchange with sensors. Thus, it is necessary to develop a data exchange schema to convert data between the HL7 and the IEEE1451 standard. This paper proposes a schema that can exchange data between HL7 devices and the monitoring device, and conforms to the IEEE 1451 standard. The experimental results and conclusions of this approach are presented and show the feasibility of the proposed exchange schema. © 2010 by the authors.

Zhao Y.,University of Hong Kong | Vanhoutte P.M.,University of Hong Kong | Vanhoutte P.M.,Chonbuk National University | Leung S.W.S.,University of Hong Kong
Journal of Pharmacology and Experimental Therapeutics | Year: 2013

In the aorta of male spontaneously hypertensive rats (SHR), but not in that of normotensive Wistar-Kyoto rats (WKY), contractions to phenylephrine obtained in the presence of L-NAME [inhibitor of nitric oxide synthase (NOS)] and indomethacin (inhibitor of cyclooxygenase) are inhibited by an unknown endothelium-derived factor. The present study aimed to identify the mechanism underlying this endothelium-dependent inhibition in the SHR aorta. Aortic rings of male SHR and WKY, with and without endothelium, were suspended in organ chambers in the presence of indomethacin and L-NAME for the measurement of isometric tension. Contractions to phenylephrine were smaller in SHR aortae with endothelium than in those without, but were similar in the two types of preparations of WKY aortae. The endothelium-dependent, NOS-independent inhibition of phenylephrine-induced contraction was abolished by oxyhemoglobin [extracellular NO scavenger], carboxy-PTIO (NO scavenger) and ODQ (inhibitor of soluble guanylyl cyclase). It was unmasked not only by indomethacin but also by apocynin (antioxidant), but inhibited by diphenyleneiodonium (inhibitor of flavoproteins including cytochrome P450 reductase). The cytochrome P450 reductase protein expression was similar in SHR and WKY aortae. However, the level of nitrate and nitrite, substrates of cytochrome P450 reductase, were higher in SHR than WKY plasma and aortae. Therefore, in SHR but not WKY aortae, eNOS-independent NO is formed by cytochrome P450 reductase. Copyright © 2013 by The American Society for Pharmacology and Experimental Therapeutics.

Li F.Y.L.,University of Hong Kong | Lam K.S.L.,University of Hong Kong | Tse H.-F.,University of Hong Kong | Chen C.,University of Hong Kong | And 4 more authors.
Circulation | Year: 2012

Background-Endothelial damage and dysfunction are crucial mediators that link diabetes mellitus with atherosclerotic cardiovascular disease. AMP-activated kinase (AMPK) has been implicated in regulation of both energy metabolism and vascular homeostasis. The present study investigated whether endothelium-selective activation of AMPK prevents diabetes mellitus-induced endothelial damage and vascular dysfunction by improving reendothelialization in mice. Methods and Results-Transgenic mice with endothelium-selective expression of a constitutively active (CA) AMPK were generated and rendered diabetic by the injection of streptozotocin. Relaxation and reendothelialization of carotid arteries and circulating numbers of endothelial progenitor cells (EPCs) were examined after wire-induced denudation. Bone marrow-derived EPCs were isolated to monitor their in vivo and in vitro function. Compared with wild-type littermates, the CA-AMPK transgenic mice were resistant to diabetes mellitus-induced impairment in endothelium-dependent relaxation and reendothelialization of their injured carotid arteries. These changes in the transgenic mice were accompanied by increased mobilization of EPCs and enhanced incorporation of EPCs into injured blood vessels. Furthermore, EPCs from the transgenic mice exhibited augmented adhesion, migration, and tube formation capacities. At the molecular level, the expression of heme oxygenase (HO)-1 and the secretion of stromal cell-derived factor (SDF)-1α were upregulated in EPCs derived from the transgenic mice, whereas AMPK-mediated elevation of serum SDF-1α levels and improvements of EPC function and reendothelialization were all abrogated by pharmacological inhibition of heme oxygenase-1. Conclusions-Endothelium-specific AMPK activation is sufficient to protect against diabetes mellitus-induced aggravation of vascular injury by promoting EPC function and reendothelialization via upregulation of heme oxygenase-1 and SDF-1α. © 2012 American Heart Association, Inc.

Yan G.H.,Yanbian University | Choi Y.H.,Chonbuk National University
Journal of Pharmacological Sciences | Year: 2014

Salidroside is a biologically active ingredient of Rhodiola rosea, which has several interesting biological properties, including anti-oxidant and anti-inflammatory; however, its anti-allergic effects are poorly understood. The objective of this study is to determine whether salidroside attenuates the inflammatory response in an ovalbumin (OVA)-induced asthma model. OVA-sensitized/challenged mice show airway hyperresponsiveness (AHR) to inhaled methacholine and have an increased amount of T-helper2 type cytokines [interleukin (IL)-4, IL-5, and IL-13] and eosinophils in their bronchoalveolar lavage fluids and lung tissues. However, three successive intraperitoneal administrations of salidroside before the last OVA challenge result in significant inhibition of these asthmatic reactions. Moreover, OVA significantly increases the activation of nuclear factor-kappa B (NF-κB) and p38 mitogen-activated protein kinase (MAPK) in lung tissues, whereas salidroside markedly suppresses NF-κB translocation and reduces phosphorylation of p38 MAPK. Furthermore, salidroside attenuates the expression of intercellular adhesion molecule 1 and IL-6 through modulating the activities of p38 MAPK and NF-κB in the BEAS-2B cells stimulated by proinflammatory cytokines. These findings indicate that salidroside protects against OVA-induced airway inflammation and AHR, at least in part via downregulation of NF-κB and p38 MAPK activities. Our data support the utility of salidroside as a potential medicine for the treatment of asthma. © The Japanese Pharmacological Society.

Feletou M.,Institute Recherches Servier | Huang Y.,Chinese University of Hong Kong | Vanhoutte P.M.,University of Hong Kong | Vanhoutte P.M.,Chonbuk National University
Pflugers Archiv European Journal of Physiology | Year: 2010

In cardiovascular diseases and during aging, endothelial dysfunction is due in part to the release of endothelium-derived contracting factors that counteract the vasodilator effect of the nitric oxide. Endotheliumdependent contractions involve the activation of endothelial cyclooxygenases and the release of various prostanoids, which activate thromboxane prostanoid (TP) receptors of the underlying vascular smooth muscle. The stimulation of TP receptors elicits not only the contraction and the proliferation of vascular smooth muscle cells but also diverse physiological/pathophysiological reactions, including platelet aggregation and activation of endothelial inflammatory responses. TP receptor antagonists curtail endothelial dysfunction in diseases such as hypertension and diabetes, are potent antithrombotic agents, and prevent vascular inflammation. © Springer-Verlag 2009.

Feletou M.,Institute Of Recherches Servier | Vanhoutte P.M.,University of Hong Kong | Verbeuren T.J.,Chonbuk National University
Journal of Cardiovascular Pharmacology | Year: 2010

The stimulation of thromboxane/endoperoxide receptors (TP) elicits diverse physiological/pathophysiological reactions, including platelet aggregation and contraction of vascular smooth muscle. Furthermore, the activation of endothelial TP promotes the expression of adhesion molecules and favors adhesion and infiltration of monocytes/macrophages. In various cardiovascular diseases, endothelial dysfunction is predominantly the result of the release of endothelium-derived contracting factors that counteract the vasodilator effect of nitric oxide produced by the endothelial nitric oxide synthase. Endothelium-dependent contractions involve the activation of cyclooxygenases, the production of reactive oxygen species along with that of endothelium-derived contracting factors, which diffuse toward the vascular smooth muscle cells and activate their TP. TP antagonists curtail the endothelial dysfunction in diseases such as hypertension and diabetes, are potent antithrombotic agents, and reduce vascular inflammation. Therefore, TP antagonists, because of this triple activity, may have a unique potential for the treatment of cardiovascular disorders. © 2010 by Lippincott Williams & Wilkins.

Vatankhah-Varnoosfaderani M.,Chonbuk National University | Vatankhah-Varnoosfaderani M.,Islamic Azad University | Ghavaminejad A.,Chonbuk National University | Hashmi S.,Chonbuk National University | And 2 more authors.
Chemical Communications | Year: 2013

Novel covalent gels were prepared by complexation of polymer-bound catechols with NaBH4 at pH ≈ 9. These gels can absorb humidity, which changes the catechol-borate covalent bonds from irreversible to reversible. Furthermore, humidity induces self-healing, proven by rheological data. © The Royal Society of Chemistry 2013.

Baretella O.,University of Hong Kong | Xu A.,University of Hong Kong | Vanhoutte P.M.,University of Hong Kong | Vanhoutte P.M.,Chonbuk National University
Pflugers Archiv European Journal of Physiology | Year: 2014

Changes in pH modulate the responsiveness of vascular smooth muscle cells to vasoconstrictor stimuli, but their effect on endothelium-dependent responses is unknown. Therefore, the influence of moderate changes in pH on responses to endothelium-dependent and -independent agonists was determined in aortae and carotid arteries of 15- to 26-week-old male C57BL/6N mice. Isolated rings were suspended in Halpern-Mulvany myographs for isometric tension recording. The preparations were exposed to either acidic (pH 7), control (pH 7.4) or alkaline (pH 7.8) modified Krebs-Ringer bicarbonate buffer solutions and their contractions and relaxations compared. Endothelium-dependent relaxations to acetylcholine (in the presence of meclofenamate or of the thromboxane-prostanoid (TP) receptor antagonist S18886) were comparable at the three pH values tested in contracted aortic or carotid arterial rings. Endothelium-dependent contractions of quiescent carotid arteries were reduced in acidosis and potentiated in alkalosis compared to control; these effects were reversible. The carotid arteries produced equal amounts of 6-keto prostaglandin F 1α and thromboxane B2 at the different pH values tested. Contractions to the full TP receptor agonist U46619 were similar in the three milieus, but after inducing partial TP receptor blockade (with low concentrations of the TP receptor antagonist S18886) they were depressed in acidosis compared to alkalosis. Prostacyclin as a partial TP receptor activator also induced weaker contractions at low than at high pH, whereas its vasodilator effect was not affected. These findings demonstrate that changes in pH modulate endothelium-dependent contractions in mouse arteries primarily by altering the sensitivity of TP receptors of vascular smooth muscle to endothelium-derived contracting factors. © 2013 Springer-Verlag Berlin Heidelberg.

Park J.H.,University of Texas at Austin | Park J.H.,Chonbuk National University | Thorgaard S.N.,University of Texas at Austin | Thorgaard S.N.,Winona State University | And 2 more authors.
Journal of the American Chemical Society | Year: 2013

We describe the electrochemical detection of single nanoparticle (NP) attachment on a nanoelectrode by the increase in the active electrode area. The attachment of gold NP-decorated single wall carbon nanotubes (Au-SWCNTs) was observed by their current-time transients for ferrocenemethanol (FcMeOH) oxidation. Since the attached Au-SWCNT increases the electroactive area available for FcMeOH oxidation, the current increases after attachment of the particle. The "staircase" shape of the current response establishes that the particles do not become deactivated for the outer-sphere electron transfer reaction after attachment. Au-SWCNTs migrate to and are held at the nanoelectrode by an electric field. However, SWCNTs that are not decorated with a gold NP produce only a sharp transient ("blip") response. © 2013 American Chemical Society.

Feletou M.,Institute Of Recherches Servier | Kohler R.,University of Southern Denmark | Vanhoutte P.M.,University of Hong Kong | Vanhoutte P.M.,Chonbuk National University
Current Hypertension Reports | Year: 2010

Endothelial cells regulate vascular tone by releasing various contracting and relaxing factors including nitric oxide (NO), arachidonic acid metabolites (derived from cyclooxygenases, lipoxygenases, and cytochrome P450 monooxygenases), reactive oxygen species, and vasoactive peptides. Additionally, another pathway associated with the hyperpolarization of the underlying smooth muscle cells plays a predominant role in resistance arteries. Endothelial dysfunction is a multifaceted disorder, which has been associated with hypertension of diverse etiologies, involving not only alterations of the L-arginine NO-synthase-soluble guanylyl cyclase pathway but also reduced endothelium-dependent hyperpolarizations and enhanced production of contracting factors, particularly vasoconstrictor prostanoids. This brief review highlights these different endothelial pathways as potential drug targets for novel treatments in hypertension and the associated endothelial dysfunction and end-organ damage. © 2010 The .Author(s).

Choi Y.H.,Chonbuk National University | Jin G.Y.,Yanbian University | Li L.C.,Yanbian University | Yan G.H.,Yanbian University
PLoS ONE | Year: 2013

Vascular endothelial growth factor (VEGF) is supposed to contribute to the pathogenesis of allergic airway disease. VEGF expression is regulated by a variety of stimuli such as nitric oxide, growth factors, and hypoxia-inducible factor-1 alpha (HIF-1α). Recently, inhibition of the mammalian target of rapamycin (mTOR) has been shown to alleviate cardinal asthmatic features, including airway hyperresponsiveness, eosinophilic inflammation, and increased vascular permeability in asthma models. Based on these observations, we have investigated whether mTOR is associated with HIF-1α-mediated VEGF expression in allergic asthma. In studies with the mTOR inhibitor rapamycin, we have elucidated the stimulatory role of a mTOR-HIF-1α-VEGF axis in allergic response. Next, the mechanisms by which mTOR is activated to modulate this response have been evaluated. mTOR is known to be regulated by phosphoinositide 3-kinase (PI3K)/Akt or protein kinase C-delta (PKC δ) in various cell types. Consistent with these, our results have revealed that suppression of PKC α by rottlerin leads to the inhibition of PI3K/Akt activity and the subsequent blockade of a mTOR-HIF-1α-VEGF module, thereby attenuating typical asthmatic attack in a murine model. Thus, the present data indicate that PKC d is necessary for the modulation of the PI3K/Akt/mTOR signaling cascade, resulting in a tight regulation of HIF-1α activity and VEGF expression. In conclusion, PKC δ may represent a valuable target for innovative therapeutic treatment of allergic airway disease. © 2013 Choi et al.

Nho J.-H.,University of Ulsan | Kim S.R.,Chonbuk National University | Kwon Y.S.,University of Ulsan
Supportive Care in Cancer | Year: 2014

Purpose: The reported prevalence of malnutrition and related factors in gynecologic cancer varies. We aimed to describe nutritional status and to identify demographic, clinical, psychological, and nutritional factors contributing to malnutrition in gynecologic cancer patients.Methods: We used a descriptive cross-sectional design. A total of 129 subjects were enrolled. Subjects agreed to undergo a face-to-face interview, including measurement of body mass index (BMI) and administration of structured questionnaires including the Patient-Generated Subjective Global Assessment (PG-SGA), the Beck Depression Inventory (BDI), and the Simplified Nutritional Appetite Questionnaire (SNAQ).Results: Mean BMI was 23.4 kg/m2 (range, 14.6–36.7 kg/m2) and median body weight was 55.0 kg (range, 38.5–91.3 kg). Sixty-nine (53.5 %) of 129 patients reported severe malnutrition according to the PG-SGA. Malnutrition among patients who had received chemotherapy was more common than among patients who had not received chemotherapy within 6 months. Depression and appetite were significant factors predicting malnutrition in patients with gynecologic cancer. However, malnutrition was not related to age, marital status, level of education, or annual income among demographic factors, nor age at onset of cancer, cancer type, stage, or duration of cancer among clinical factors.Conclusions: Assessment of nutritional status should be considered along with depression and appetite in patients with gynecologic cancer. In addition, regular and consistent nutritional assessment is essential in gynecologic cancer patients because of the high prevalence of malnutrition in these patients. © 2014, Springer-Verlag Berlin Heidelberg.

Seo J.,Korea University | Choi S.-G.,Korea University | Oh C.W.,Chonbuk National University
Gondwana Research | Year: 2010

The Gwangcheon intrusive rocks occur in the Hongseong collision belt of South Korea, which is thought to represent the eastern extension of the Dabie-Sulu collision zone of China. The central part of the Gwangcheon intrusive complex consists of orthopyroxene-bearing monzonite (mangerite), and the marginal part is composed of syenite. North of the Gwangcheon mangerite, the post-collisional (233±2Ma) Haemi biotite granite contains syenite enclaves. SHRIMP U-Pb zircon analysis yields ages of 232±3Ma for the mangerite and 230±3Ma for a syenite enclave within the Haemi biotite granite. The mangerite-syenite complex and syenite enclaves exhibit a shoshonitic affinity, with a total alkalinity (Na2O+K2O) of 7.38-9.64wt.%, high K2O, Mg#, Ba, Sr, Cr, Ni, and LREE contents, and insignificant negative Eu anomalies. Geochemical data indicate that the mangerite-syenite intrusion and the syenite enclaves are post-collisional igneous rocks formed by the partial melting of an enriched lithospheric mantle. The heat for this melting was derived from asthenospheric upwelling following oceanic slab break-off. The SHRIMP age data suggest that both the Gwangcheon intrusives and the syenite enclaves formed after the Triassic continental collision of the North and South China blocks in Korea. © 2009 International Association for Gondwana Research.

Kang J.W.,Massachusetts Institute of Technology | So P.T.C.,Massachusetts Institute of Technology | Dasari R.R.,Massachusetts Institute of Technology | Lim D.-K.,Chonbuk National University | Lim D.-K.,Korea University
Nano Letters | Year: 2015

We report a method to achieve high speed and high resolution live cell Raman images using small spherical gold nanoparticles with highly narrow intra-nanogap structures responding to NIR excitation (785 nm) and high-speed confocal Raman microscopy. The three different Raman-active molecules placed in the narrow intra-nanogap showed a strong and uniform Raman intensity in solution even under transient exposure time (10 ms) and low input power of incident laser (200 μW), which lead to obtain high-resolution single cell image within 30 s without inducing significant cell damage. The high resolution Raman image showed the distributions of gold nanoparticles for their targeted sites such as cytoplasm, mitochondria, or nucleus. The high speed Raman-based live cell imaging allowed us to monitor rapidly changing cell morphologies during cell death induced by the addition of highly toxic KCN solution to cells. These results strongly suggest that the use of SERS-active nanoparticle can greatly improve the current temporal resolution and image quality of Raman-based cell images enough to obtain the detailed cell dynamics and/or the responses of cells to potential drug molecules. © 2015 American Chemical Society.

Suardana N.P.G.,Udayana University | Suardana N.P.G.,Chonbuk National University | Ku M.S.,Chonbuk National University | Lim J.K.,Chonbuk National University
Materials and Design | Year: 2011

The flammability, thermal stability and mechanical properties of natural fiber-reinforced thermoplastic bio-composites were measured using a horizontal burning test, thermogravimetric analyzer, and universal testing machine, respectively. The composites were fabricated from film resins (Polylactic-acid, PLA and Polypropylene, PP) and natural fibers (coconut filter and jute fiber) by a hot press machine. To improve the flame retardancy of the bio-composites, various diammonium phosphates (DAP) were treated into the fibers. In general, the results indicate that increasing the percentage of DAP used to treat the fibers effectively improves the flame resistant, weight loss rate, and flexural modulus but decreases the flexural and tensile strengths of the bio-composites. Bio-composites with DAP-treated fibers showed a greater flexural modulus than those with untreated fibers, and the flexural modulus was even greater than that of neat polymers (PLA and PP). Also, increasing the percentage of DAP for treatment of the fibers in the composites decreases the temperature required for 5% weight loss and the decomposition rate, but increases the char residual at 500 °C. The best linear burning rate and weight loss rate were observed for fiber treatment with 5% DAP. The compressive and wear properties of these bio-composites were also studied. © 2010 Elsevier Ltd.

Lee J.-C.,University of Kentucky | Lee J.-C.,Chonbuk National University | Son Y.-O.,University of Kentucky | Pratheeshkumar P.,University of Kentucky | Shi X.,University of Kentucky
Free Radical Biology and Medicine | Year: 2012

Occupational and environmental exposures to metals are closely associated with an increased risk of various cancers. Although carcinogenesis caused by metals has been intensively investigated, the exact mechanisms of action are still unclear. Accumulating evidence indicates that reactive oxygen species (ROS) generated by metals play important roles in the etiology of degenerative and chronic diseases. This review covers recent advances in (1) metal-induced generation of ROS and the related mechanisms; (2) the relationship between metal-mediated ROS generation and carcinogenesis; and (3) the signaling proteins involved in metal-induced carcinogenesis, especially intracellular reduction-oxidation-sensitive molecules. © 2012 Elsevier Inc. All rights reserved.

Takayama K.,University of Vienna | Sun B.-Y.,Chonbuk National University | Stuessy T.F.,University of Vienna
Annals of Botany | Year: 2012

Background and AimAnagenesis (also known as phyletic speciation) is an important process of speciation in endemic species of oceanic islands. We investigated genetic variation in Acer okamotoanum, an anagenetically derived species endemic to Ullung Island, South Korea, to infer genetic consequences of anagenesis in comparison with other groups that have undergone cladogenesis (and adaptive radiation). Methods We examined genetic variation based on eight polymorphic microsatellite markers from 145 individuals of A. okamotoanum and 134 individuals of its putative progenitor A. mono. We employed standard population genetic analyses, clustering analyses, Bayesian clustering analyses in STRUCTURE and bottleneck analyses. Key Results Based on both the NeighborJoining tree and Bayesian clustering analyses, clear genetic distinctions were found between the two species. Genetic diversity in terms of allelic richness and heterozygosity shows slightly lower levels in A. okamotoanum in comparison with A. mono. Bayesian clustering analyses showed a relatively high F-value in the cluster of A. okamotoanum, suggesting a strong episode of genetic drift during colonization and speciation. There was no clear evidence of a bottleneck based on allelic frequency distribution and excess of observed heterozygotes, but the M-ratio indicated a historical bottleneck in several populations of A. okamotoanum. No geographical genetic structure within the island was found, and the genetic variation among populations of A. okamotoanum was quite low. Conclusions We hypothesized that genetic consequences of oceanic-endemic plants derived via anagenesis would be quite different from those derived via cladogenesis. Populations of A. okamotoanum form a cluster and are clearly differentiated from A. mono, which suggests a single origin for the anagenetically derived island endemic. No pattern of geographical differentiation of populations occurs in A. okamotoanum, which supports the concept of initial founder populations diverging through time by accumulation of mutations in a relatively uniform environment without further specific differentiation. © 2011 The Author.

Tang E.H.C.,Harvard University | Vanhoutte P.M.,University of Hong Kong | Vanhoutte P.M.,Chonbuk National University
Pflugers Archiv European Journal of Physiology | Year: 2010

Endothelial dysfunction is a common feature of hypertension, and it results from the imbalanced release of endothelium-derived relaxing factors (EDRFs; in particular, nitric oxide) and endothelium-derived contracting factors (EDCFs; angiotensin II, endothelins, uridine adenosine tetraphosphate, and cyclooxygenase-derived EDCFs). Thus, drugs that increase EDRFs (using direct nitric oxide releasing compounds, tetrahydrobiopterin, or l-arginine supplementation) or decrease EDCF release or actions (using cyclooxygenase inhibitor or thromboxane A2/prostanoid receptor antagonists) would prevent the dysfunction. Many conventional antihypertensive drugs, including angiotensin-converting enzyme inhibitors, calcium channel blockers, and third-generation β-blockers, possess the ability to reverse endothelial dysfunction. Their use is attractive, as they can address arterial blood pressure and vascular tone simultaneously. The severity of endothelial dysfunction correlates with the development of coronary artery disease and predicts future cardiovascular events. Thus, endothelial dysfunction needs to be considered as a strategic target in the treatment of hypertension. © 2010 Springer-Verlag.

Zhang W.,University of New South Wales | Xu T.,University of Delaware | Xia X.-G.,University of Delaware | Xia X.-G.,Chonbuk National University
IEEE Transactions on Information Theory | Year: 2012

A partial interference cancellation (PIC) group decoding based space-time block code (STBC) design criterion was recently proposed by Guo and Xia, where the decoding complexity and the code rate traeoff is dealt when the full diversity is achieved. In this paper, two designs of STBC are proposed for any number of transmit antennas that can obtain full diversity when a PIC group decoding (with a particular grouping scheme) is applied at receiver. With the PIC group decoding and an appropriate grouping scheme for the decoding, the proposed STBC are shown to obtain the same diversity gain as the ML decoding, but have a low decoding complexity. The first proposed STBC is designed with multiple diagonal layers and it can obtain the full diversity for two-layer design with the PIC group decoding and the rate is up to 2 symbols per channel use. With PIC-SIC group decoding, the first proposed STBC can obtain full diversity for any number of layers and the rate can be full. The second proposed STBC can obtain full diversity and a rate up to 9/4 with the PIC group decoding. Some code design examples are given and simulation results show that the newly proposed STBC can well address the rate-performance-complexity tradeoff of the MIMO systems. © 2012 IEEE.

Kim S.T.,Korea University | Kim D.-J.,Chonbuk National University | Kim T.-J.,Korea University | Seo D.-W.,Chonbuk National University | And 5 more authors.
Nano Letters | Year: 2010

Silicon nanowires (SiNWs) offer promising inorganic nanostructures for biomedical application. Here, we report the development of a novel SiNW array designed for isolating primary CD4+ T lymphocytes from the heterogeneous mixture of cell populations. Our system employed the specific high-affinity binding features of streptavidin (STR)-functionalized SiNW with biotin-labeled CD4+ T lymphocytes. Fabricated SiNW arrays easily separated the CD4+ T lymphocytes from the mouse whole splenocytes with over ∼88% purity and demonstrated tight attachment to CD4+ T lymphocytes by scanning electron microscopy. Thus, our STR-SiNW arrays provide a potential tool for specific cell separation and further present a possibility to be applied to the other area of biomedical applications. © 2010 American Chemical Society.

Li Z.,University of Hong Kong | Wang Y.,University of Hong Kong | Vanhoutte P.M.,University of Hong Kong | Vanhoutte P.M.,Chonbuk National University
Hypertension | Year: 2011

Heme oxygenase converts heme to carbon monoxide, biliverdin (subsequently converted to bilirubin), and free iron. Pharmacological induction of heme oxygenase 1 has an antihypertensive effect in the spontaneously hypertensive rat. The present study investigated whether upregulation of heme oxygenase 1 by hemin reduces endothelial dysfunction in this animal. Thirty-six-week- old rats were divided into a hemin treatment (50 mg/kg, IP injection, once) and a control group. Aortas were isolated for the measurement of isometric tension, production of reactive oxygen species, and heme oxygenase activity, as well as gene and protein expressions. Hemin treatment augmented the expression and activity of heme oxygenase 1. This in vivo induction of heme oxygenase 1, but not in vitro incubation with the heme oxygenase products carbon monoxide or bilirubin, led to an improvement of endothelial function in that acetylcholine-induced relaxations were potentiated and acetylcholine-and calcium ionophore-induced contractions were attenuated. Free radical production was suppressed by hemin treatment, judging from the results of 2',7'- dichlorodihydrofluoresein diacetate staining, dihydroethidium staining, and lucigenin chemiluminescence, which was explained by the decreased expressions of NADPH oxidase 2 and cyclooxygenase 1. The production of prostacyclin was decreased by heme oxygenase 1 induction, which was explained by a lower expression of cyclooxygenase 1. Contractions to vasoconstrictor concentrations of prostacyclin and its mimetic iloprost were attenuated, suggesting that the responsiveness of thromboxane-prostanoid receptors to prostacyclin was decreased in hemin-treated rats. The suppressed production of free radicals and prostacyclin and the decrease of thromboxane-prostanoid receptors sensitivity concur to explain the impairment of endothelium-dependent contractions caused by heme oxygenase 1 induction by hemin. © 2011 American Heart Association, Inc.

Im H.S.,Korea University | Cho Y.J.,Korea University | Lim Y.R.,Korea University | Jung C.S.,Korea University | And 4 more authors.
ACS Nano | Year: 2013

Sn-based nanostructures have emerged as promising alternative materials for commercial lithium-graphite anodes in lithium ion batteries (LIBs). However, there is limited information on their phase evolution during the discharge/charge cycles. In the present work, we comparatively investigated how the phases of Sn, tin sulfide (SnS), and tin oxide (SnO2) nanocrystals (NCs) changed during repeated lithiation/delithiation processes. All NCs were synthesized by a convenient gas-phase photolysis of tetramethyl tin. They showed excellent cycling performance with reversible capacities of 700 mAh/g for Sn, 880 mAh/g for SnS, and 540 mAh/g for SnO2 after 70 cycles. Tetragonal-phase Sn (β-Sn) was produced upon lithiation of SnS and SnO2 NCs. Remarkably, a cubic phase of diamond-type Sn (α-Sn) coexisting with β-Sn was produced by lithiation for all NCs. As the cycle number increased, α-Sn became the dominant phase. First-principles calculations of the Li intercalation energy of α-Sn (Sn8) and β-Sn (Sn4) indicate that Sn4Lix (x ≤ 3) is thermodynamically more stable than Sn8Lix (x ≤ 6) when both have the same composition. α-Sn maintains its crystalline form, while β-Sn becomes amorphous upon lithiation. Based on these results, we suggest that once α-Sn is produced, it can retain its crystallinity over the repeated cycles, contributing to the excellent cycling performance. © 2013 American Chemical Society.

Lee M.H.,Chonbuk National University | Borissov Y.L.,Bulgarian Academy of Science
Electronics Letters | Year: 2010

Lee and colleagues have introduced a generalised reverse jacket transform (GRJT) as a multi-phase or multilevel generalisation of the WHT and the even-length DFT. The matrix representing a primary GRJT is permutation- equivalent to the DFT matrix of even order, and in addition possesses the property to have a border consisting entirely of ±1's. To the authors' knowledge, the problem of existence of such transform matrices in the case of odd order, has attracted minor attention in the existing literature. In this Letter, a contribution is made regarding this problem in respect to an extended class of matrices. © 2010 The Institution of Engineering and Technology.

Park J.,Chonbuk National University | Jeong S.Y.,International St Marys Hospital
Clinics in Orthopedic Surgery | Year: 2014

Background: The minimally invasive plate osteosynthesis (MIPO) technique using periarticular locking plates may be a good option for the repair of displaced proximal humeral fractures. However, axillary nerve complications related to this technique may be underestimated. The purpose of this study is to evaluate the outcomes of the minimally invasive plating, focusing on the complications. Methods: The records of 21 consecutive patients treated for proximal humerus fractures using the MIPO technique with locking plates were retrospectively reviewed. These patients were treated between March 2009 and March 2011 with a minimum one-year follow-up. The clinical function, complications, and radiological bony union were evaluated. Results: All of the patients, with one exception, showed at least 90 degrees of flexion and abduction at the shoulder joint six months postoperatively. The average Constant scores at three months, six months, and one year follow-ups were 74.0 (range, 62 to 90), 79.4 (range, 64 to 91), and 82.7 (range, 66 to 92), respectively. All of the patients achieved bony union within the average of 3.2 months (range, 2 to 6 months). There was one case of delayed union, one case of intra-articular screw penetration, and one case of axillary nerve paresis (incomplete injury), which did not completely recover during the one year of follow-up. Conclusions: The MIPO technique using periarticular locking plates is a useful option for the treatment of selected cases of displaced proximal humeral fractures. However, nerve complications such as axillary nerve paresis should be considered along with implant-related complications when choosing patients for minimally invasive plating. © 2014 by The Korean Orthopaedic Association.

Liang C.-F.,University of Hong Kong | Liu J.T.,University of Hong Kong | Wang Y.,University of Hong Kong | Xu A.,University of Hong Kong | And 2 more authors.
Arteriosclerosis, Thrombosis, and Vascular Biology | Year: 2013

OBJECTIVE: To analyze the role of toll-like receptor 4 in modulating metabolism and endothelial function. APPROACH AND RESULTS: Type 2 diabetic mice with mutated toll-like receptor 4 (DWM) were protected from hyperglycemia and hypertension, despite an increased body weight. Isometric tension was measured in arterial rings with endothelium. Relaxations to acetylcholine were blunted in aortae and mesenteric arteries of Lepr mice, but not in DWM mice; the endothelial NO synthase dimer/monomer ratio and endothelial NO synthase phosphorylation levels were higher in DWM preparations. These differences were abolished by apocynin. Contractions to acetylcholine (in the presence of L-NAME) were larger in carotid arteries from Lepr mice than from DWM mice and were inhibited by indomethacin and SC560, demonstrating involvement of cyclooxygenase-1. The release of 6-ketoprostaglandin F1α was lower in DWM mice arteries, implying lower cyclooxygenase-1 activity. Apocynin, manganese(III) tetrakis(1-methyl-4-pyridyl) porphyrin, catalase, and diethyldithiocarbamate inhibited endothelium-dependent contractions. The mRNA and protein levels of NADPH oxidase isoforms NOX1 and NOX4 were downregulated in DWM mice arteries. The in vivo and in vitro administration of lipopolysaccharide caused endothelial dysfunction in the arteries of wild-type, but not toll-like receptor 4-mutated mice. CONCLUSIONS: Toll-like receptor 4 plays a key role in obesity and diabetes-associated endothelial dysfunction by increasing oxidative stress. © 2013 American Heart Association, Inc.

Cheng G.,Chonbuk National University | Xiong J.,CAS Lanzhou Institute of Chemical Physics | Stadler F.J.,Chonbuk National University
New Journal of Chemistry | Year: 2013

3D desertrose-like BiOCl nanoarchitectures were synthesized via a facile refluxing method in the polyol triethylene glycol (TEG) without templates or surfactants. They were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared (FTIR), UV-vis diffuse reflectance (UV-DRS) and nitrogen adsorption analyses. On the basis of a series of contrast experiments, the probable growth mechanism and the fabrication process of the products were proposed. These BiOCl nanoarchitectures composed of numerous nanosheets exhibit higher photocatalytic performance than BiOCl nanoparticles, nanoplates and P25 under visible light irradiation. The enhancement of photocatalytic activity of the desertrose-like BiOCl nanoarchitectures compared to other nanostructures is mainly attributed to their larger surface area, higher dye loading, special hierarchitecture, and narrow band gap. © 2013 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.

Liu Y.,Xidian University | Xia X.-G.,University of Delaware | Xia X.-G.,Chonbuk National University | Zhang H.,Xidian University
IEEE Transactions on Wireless Communications | Year: 2012

In this paper, we propose two distributed linear convolutional space-time coding (DLC-STC) schemes for full-duplex (FD) asynchronous cooperative communications. The DLC-STC Scheme 1 is for the case of the complete loop channel cancellation, which achieves the full asynchronous cooperative diversity. The DLC-STC Scheme 2 is for the case of the partial loop channel cancellation and amplifying, where some loop signals are used as the self-coding instead of treated as interference to be directly cancelled. We show this scheme can achieve full asynchronous cooperative diversity. We then evaluate the performance of the two schemes when loop channel information is not accurate and present an amplifying factor control method for the DLC-STC Scheme 2 to improve its performance with inaccurate loop channel information. Simulation results show that the DLC-STC Scheme 1 outperforms the DLC-STC Scheme 2 and the delay diversity scheme if perfect or high quality loop channel information is available at the relay, while the DLC-STC Scheme 2 achieves better performance if the loop channel information is imperfect. © 2012 IEEE.

Tak Y.-S.,Korea University | Kim J.,Chonbuk National University | Hwang E.,Korea University
Engineering Applications of Artificial Intelligence | Year: 2012

With the recent development of ubiquitous technologies, many new applications have been emerging for smart home implementation. Usually, such applications are based on diverse sensors. One fundamental operation in the applications is to find out semantically meaningful events or activities from huge sensor data stream. Usually, such event or activity is represented by a salient sequence pattern. Among the diverse research issues, detecting salient sequence patterns of human motions from image sensor data stream has received much attention for security and surveillance purposes. In the case of detecting human motions from image sensor data, finding and matching their salient sequence patterns could become more complicated since semantically same motions could show diverse variations such as different motion time. Based on this observation, in this paper, we propose a new querying and answering scheme for continuous sensor data stream to detect abnormal human motions. More specifically, we first present a new hierarchical querying scheme to consider variable length of semantically same human motions. Secondly, we present an indexing scheme to efficiently find semantically meaningful motion sequences in the sensor data stream. Thirdly, we present Dynamic Group Warping algorithm to effectively filter out unnecessary human motions. Through extensive experiments, we show that our proposed method achieves outstanding performance. © 2012 Elsevier Ltd. All rights reserved.

Li Y.,Zhejiang University | Ngebani I.,Zhejiang University | Xia X.-G.,University of Delaware | Xia X.-G.,Chonbuk National University | Host-Madsen A.,University of Hawaii at Manoa
IEEE Transactions on Signal Processing | Year: 2012

Vector Orthogonal Frequency Division Multiplexing (OFDM) for single transmit antenna systems is a general transmission scheme, where OFDM and Single-Carrier Frequency Domain Equalization (SC-FDE) can be treated as two special/extreme cases. Due to its flexibility, it has drawn more and more attention recently. So far, all the studies about Vector OFDM assume the Maximum Likelihood (ML) receiver. In this paper, we investigate the performance of Vector OFDM with linear receivers, i.e., the Zero-Forcing (ZF) and Minimum Mean Square Error (MMSE) receivers. We first show that the detection SNR gap between the MMSE and ZF receivers increases with both channel SNR and the vector blocks (VB) size defined in Vector OFDM. Then, it is proved that for both ZF andMMSE receivers, all the transmitted symbols have equal performance. This is different from the Vector OFDM with ML receiver, where different VBs may have different coding gain, and thus may have different performances. We analyze the diversity order for Vector OFDM with MMSE receiver, and show that, regardless of the Vector OFDM symbol length , the diversity order can be represented as , where is the VB size, is the spectrum efficiency in bits/symbol, and is the maximum delay of the multipath channel. For Vector OFDM with ZF receiver, we show that the diversity order equals 1 and the performance is the same as the conventional OFDM at high SNR. © 2012 IEEE.

Li Y.,Zhejiang University | Wang H.,Hangzhou Dianzi University | Xia X.-G.,University of Delaware | Xia X.-G.,Chonbuk National University
IEEE Transactions on Wireless Communications | Year: 2012

As a space- and cost-efficient antenna configuration, dual-polarized antennas are widely deployed in real field MIMO wireless communication systems. The Quasi-Orthogonal Space-Time Block Code (QOSTBC), due to its advantages in the transmission rate and the decoding complexity, is an important transmit diversity scheme for more than 2 transmit antennas. In this paper, we investigate the performance of QOSTBC for dual-polarized MIMO channels. We show that when QOSTBC is used with dual-polarized antennas, we need to connect the power amplifiers (PAs) to the differently polarized antennas carefully, in order to avoid more than 1dB performance loss at high cross-polar discrimination (XPD). Also, we show that, if the QOSTBC with constellation rotations, which achieves full diversity in uni-polarized MIMO channels, is used, the performance loss due to the bad PA-to-antenna connections is mitigated. However, when the XPD is high, the QOSTBC without full diversity, if connected properly, can achieve better performance than the QOSTBC with full diversity when connected badly, which shows the importance of a proper connection at high XPD. So, to guarantee robust performance of QOSTBC at any XPD, besides designing codes to have full diversity and good diversity product, connecting the PAs and the antennas properly is also important. © 2012 IEEE.

Ren H.,Chonbuk National University | Xu S.,University of Central Florida | Wu S.-T.,University of Central Florida
Lab on a Chip - Miniaturisation for Chemistry and Biology | Year: 2013

We report a dielectrically actuated liquid crystal (LC) pump. A small volume of LC forms a pillar-like droplet in a cylindrical hole which partially touches the bottom substrate with embedded interdigitated electrodes. By applying a voltage, the LC droplet can be largely stretched along the electrode direction by the generated dielectric force, which in turn exerts a pressure to displace a small volume of fluid on the opposite side of the chamber. Once the voltage is removed, the LC droplet returns to its initial state. The LC droplet with such a reciprocating movement behaves like a pump. In this work, the actuation mechanism of the LC pump is presented and the performance evaluated experimentally. Our LC pump has the following advantages: simple structure, easy fabrication, compact size, high precision, low power consumption, and relatively fast response time. It is promising for applications in lens actuators, biotechnology, drug delivery, and other lab-on-a-chip devices. © The Royal Society of Chemistry.

Ka S.-O.,Chonbuk National University | Song M.-Y.,Chonbuk National University | Bae E.J.,Woosuk University | Park B.-H.,Chonbuk National University
Journal of Endocrinology | Year: 2015

Inflammation is an important factor in the development of insulin resistance. SIRT1, a class 3 histone/protein deacetylase, has anti-inflammatory functions. Myeloid-specific deletion of Sirt1 promotes macrophage infiltration into insulin-sensitive organs and aggravates tissue inflammation. In this study, we investigated how SIRT1 in macrophages alters tissue inflammation in the pancreas as well as liver and adipose tissue, and further explored the role of SIRT1 in locomotion of macrophages. Myeloid-specific Sirt1-deleted mice (mS1KO) and WT littermates were fed a 60% calorie high-fat diet (HFD) for 16 weeks. Tissue inflammation and metabolic phenotypes were compared. Bone marrow macrophages (BMMs) from WTor mS1KO mice were used in in vitro chemotaxis assays and macrophage polarization studies. mS1KO mice fed a HFD exhibited glucose intolerance, reduced insulin secretion, and insulin sensitivity with a slight decrease in body weight. Consistent with these results, pancreatic islets of mS1KO mice fed a HFD displayed decreased mass with profound apoptotic cell damage and increased macrophage infiltration and inflammation. Liver and adipose tissues from mS1KO HFD mice also showed greater accumulation of macrophages and tissue inflammation. Results from in vitro experiments indicated that deletion of myeloid Sirt1 stimulated proinflammatory M1-like polarization of BMMs and augmented the adipocyte-mediated macrophage chemotaxis. The latter effect was accompanied by increased expression and acetylation of focal adhesion kinase, as well as nuclear factor kappa B. Our results indicate that myeloid SIRT1 plays a crucial role in macrophage polarization and chemotaxis, and thus regulates the development of HFD-induced pancreatic inflammation and insulin secretion, and metabolic derangements in liver and adipose tissue. © 2015 Society for Endocrinology.

Ren H.,Chonbuk National University | Xu S.,University of Central Florida | Ren D.,University of Central Florida | Wu S.-T.,University of Central Florida
Optics Express | Year: 2011

We demonstrated a novel optical switch with a reconfigurable dielectric liquid droplet. The device consists of a clear liquid droplet (glycerol) surrounded by a black liquid (dye-doped liquid crystal). In the voltage-off state, the incident light passing through the clear liquid droplet is absorbed by the black liquid, resulting in a dark state. In the voltage-on state, the dome of the clear liquid droplet is uplifted by the dielectric force to form a light pipe which in turn transmits the incident light. Upon removing the voltage, the droplet recovers to its original shape and the switch is closed. We also demonstrated a red color light switch with ̃10:1 contrast ratio and ̃300 ms response time. Devices based on such an operation mechanism will find attractive applications in light shutter, tunable iris, variable optical attenuators, and displays. © 2011 Optical Society of America.

Xu S.,University of Central Florida | Ren H.,Chonbuk National University | Sun J.,University of Central Florida | Wu S.-T.,University of Central Florida
Optics Express | Year: 2012

A polarization independent variable optical attenuator (VOA) based on a dielectrically stretched liquid crystal (LC) droplet is demonstrated. In the voltage-off state, the proposed VOA has the smallest attenuation. As voltage increases, the LC droplet is stretched by a dielectrophoretic force, which gradually deflects the beam leading to an increased attenuation. Such a VOA can cover the entire C-Band. At λ = 1550 nm, the following results are obtained: dynamic range ∼32 dB insertion loss ∼0.7 dB, polarization dependent loss ∼0.3 dB, and response time ∼20 ms. ©2012 Optical Society of America.

Kim J.S.,Gyeongbuk Institute for Marine Bioindustry | Lee I.K.,Chonbuk National University | Yun B.S.,Chonbuk National University
PLoS ONE | Year: 2015

Yeast biosurfactants are important biotechnological products in the food industry, and they have medical and cosmeceutical applications owing to their specific modes of action, low toxicity, and applicability. Thus, we have isolated and examined biosurfactant-producing yeast for various industrial and medical applications. A rapid and simple method was developed to screen biosurfactant-producing yeasts for high production of eco-friendly biosurfactants. Using this method, several potential niches of biosurfactant-producing yeasts, such as wild flowers, were investigated. We successfully selected a yeast strain, L3-GPY, with potent surfactant activity from a tiger lily, Lilium lancifolium Thunb. Here, we report the first identification of strain L3-GPY as the black yeast Aureobasidium pullulans. In addition, we isolated a new low-surface-tension chemical, designated glycerol-liamocin, from the culture supernatant of strain L3-GPY through consecutive chromatography steps, involving an ODS column, solvent partition, silica gel, Sephadex LH-20, and an ODS Sep-Pak cartridge column. The chemical structure of glycerol-liamocin, determined by mass spectrometry and nuclear magnetic resonance spectroscopy, indicates that it is a novel compound with the molecular formula C33 H62O12. Furthermore, glycerol-liamocin exhibited potent biosurfactant activity (31 mN/m). These results suggest that glycerol-liamocin is a potential novel biosurfactantfor use in various industrial applications. Copyright: © 2015 Kim et al.

Song M.Y.,Chonbuk National University | Baek S.H.,Chonbuk National University | Bobet J.-L.,CNRS Laboratory of Condensed Matter Chemistry, Bordeaux | Hong S.-H.,Korea Institute of Machinery and Materials
International Journal of Hydrogen Energy | Year: 2010

A sample composition has been designed based on previously reported data. An 80 wt%Mg-13.33 wt%Ni-6.67 wt%Fe (referred to as Mg-13.33Ni-6.67Fe) sample exhibited higher hydriding and dehydriding rates after activation and a larger hydrogen storage capacity compared to those of other mixtures prepared under similar conditions. After activation (at n = 3), the sample absorbed 4.60 wt%H for 5 min and 5.61 wt%H for 60 min at 593 K under 12 bar H2. The sample desorbed 1.57 wt%H for 5 min and 3.92 wt%H for 30 min at 593 K under 1.0 bar H2. Rietveld analysis of the XRD pattern using FullProf program showed that the as-milled Mg-13.33Ni-6.67Fe sample contained Mg(OH)2 and MgH2 in addition to Mg, Ni, and Fe. The Mg(OH)2 phase is believed to be formed through the reaction of Mg or MgH2 with water vapor in the air. The dehydrided Mg-13.33Ni-6.67Fe sample after hydriding-dehydriding cycling contained Mg, Mg2Ni, MgO, and Fe. © 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.