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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.

Objective: This study investigated the cardiovascular risk factors associated with depression among Korean adults with coronary artery disease (CAD) and cerebrovascular disease (CBVD). Methods: A total of 487 coronary artery disease and 434 cerebrovascular disease subjects from the Fourth Korean National Health and Nutrition Examination Survey were analyzed according to sex using multiple logistic regression. Results: The prevalence of depression was 21.7% in those with CAD and 25.5% in those with CBVD. The associated risk factors for depression were female sex (odds ratio [OR] 15.77; 95% confidence interval [CI], 2.44-102.03, P=0.004), less education (OR 7.09 and 10.36, 95% CI, 1.24-40.75, 1.86-57.70 for an elementary and middle school education, respectively), and hypertension (OR 5.35; 95% CI, 1.48-19.40) in those with CAD and were female sex (OR 4.06, 95% CI, 1.12-14.76) and diabetes mellitus (OR 3.31, 95% CI, 1.36-8.05) in CBVD. These significant associations remained in males, but not in females in those with both CAD and CBVD. Conclusions: This study found the associations between hypertension and depression in those with CAD and diabetes mellitus and depression in those with CBVD in males, but not in females. Further studies are needed to explore the associated psychosocial factors of depression in those with different CAD kinds in females. © 2014 Wiley Publishing Asia Pty Ltd. Source

Lee D.E.,POSCO | Kim M.Y.,Chonbuk National University
Journal of Mechanical Science and Technology | Year: 2013

A mathematical model is developed to calculate temperature distribution of a slab in a hot rolled reheating furnace by considering thermal radiation in the furnace and transient conduction in the slab. The furnace is modeled as a radiating medium with spatially varying temperature. Radiative heat flux within the furnace, including the effects of the furnace walls, combustion gases, skid beams, and buttons, is calculated through finite volume method with weighted sum of gray gases model and is applied as the boundary condition in the transient conduction equation of the slab. After validating the predictions of the present models with experimental data, the variations in the heating characteristics of the slab are investigated with residence time in the furnace at two different charging and furnace gas temperatures. The optimum residence time for the slab in the furnace is examined with regard to slab exit temperature, temperature difference between the upper surface and centerline of the slab, and skid mark. © 2013 The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg. Source

Cao F.,China Jiliang University | Liu B.,China Jiliang University | Sun Park D.,Chonbuk National University
Neurocomputing | Year: 2013

In this work, a new image classification method is proposed based on extreme k-means (EKM) and effective extreme learning machine (EELM). The proposed method has image decomposition with curvelet transform, reduces dimensionality with discriminative locality alignment (DLA), generates a set of distinctive features with EKM, and has a classification with EELM. Since EKM has a better clustering performance than k-means and EELM has a better accuracy than ELM, the proposed EKM-EELM algorithm has a significant improvement in classification rate. Extensive experiments are performed using challenging databases and results are compared against state of the art techniques. Experimental results show that the proposed method has superior performances on classification rate than some other traditional methods for image classification. © 2012. Source

Hahn Y.-B.,Chonbuk National University
Korean Journal of Chemical Engineering | Year: 2011

Zinc oxide (ZnO) has been known as the next most important material for the fabrication of efficient nanodevices and nanosystems because of its versatile properties such as semiconducting, piezoelectric, and pyroelectric multiple properties. In this review, the state-of-the-art technologies related to the synthesis and characterization, the selective growth of ZnO nanostructures, and their applications for nanodevices are discussed. A special concern is focused on the controlled selective growth of ZnO nanostructures on wanted areas of substrates, which is crucial factor for devices applications. The device applications of ZnO nanostructures include field effect transistors (FETs), field-emission devices, piezoelectric nanogenerators, biosensors, p-n heterjunction diodes such as light-emitting diodes and photovoltaic cells, and so on. © 2011 Korean Institute of Chemical Engineers, Seoul, Korea. Source

Choi W.-Y.,Chonbuk National University
IEEE Transactions on Power Electronics | Year: 2013

This paper proposes a high-efficiency dc-dc converter with fast dynamic response for low-voltage photovoltaic (PV) sources. The voltage stress of power switches is reduced at low-voltage side. Zero-current turn-off of output diodes is achieved at high-voltage side. Power efficiency is improved by reducing switching power losses. A modified proportional and integral controller is also suggested to achieve fast output voltage control. The dynamic response of the proposed converter is improved. The performance of the proposed converter is verified based on an experimental prototype for a 200-W PV module. © 1986-2012 IEEE. Source

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. Source

Park W.H.,Chonbuk National University
Molecular Medicine Reports | Year: 2013

Reactive oxygen species (ROS) influence the signaling of mitogen-activated protein kinases (MAPKs) involved in cell survival and death. In the present study, the toxicological effect of hydrogen peroxide (H2O 2) on HeLa cervical cancer cells was evaluated following treatment with MAPK inhibitors [MAP kinase or ERK kinase (MEK), c-Jun N-terminal kinase (JNK) or p38], N-acetyl cysteine (NAC) and propyl gallate (PG) (well-known antioxidants), or L-buthionine sulfoximine [BSO; an inhibitor of glutathione (GSH) synthesis]. Treatment with 100 μM H2O2 inhibited the growth of HeLa cells and induced cell death, which was accompanied by loss of the mitochondrial membrane potential (MMP; Δψm). H 2O2 did not induce any specific phase arrests of the cell cycle. ROS levels increased, while GSH levels decreased in H2O 2-treated HeLa cells after 1 and 24 h of treatment. The MAPK inhibitors enhanced H2O2-induced HeLa cell death, while only p38 inhibitor increased ROS levels. Both NAC and PG attenuated H 2O2-induced HeLa cell growth inhibition and death together with the suppression of ROS levels. BSO increased ROS levels in H 2O2-treated HeLa cells without increasing cell death. The levels of MMP (Δψm) loss and GSH depletion were not closely associated with the levels of apoptosis in HeLa cells treated with the MAPK inhibitors, NAC, PG or BSO, in the presence of H2O2. In conclusion, H2O2 induced HeLa cell growth inhibition and death. MAPK inhibitors generally enhanced H2O2-induced HeLa cell death. In particular, p38 inhibitor increased ROS levels in H2O 2-treated HeLa cells, while NAC and PG attenuated H2O 2-induced HeLa cell death by suppressing ROS levels. Source

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. Source

Kim S.M.,Chonbuk National University
International Journal of Molecular Sciences | Year: 2016

Studies in humans have shown that 3,31-diindolylmethane (DIM), which is found in cruciferous vegetables, such as cabbage and broccoli, is effective in the attenuation of gastrointestinal cancers. This review presents the latest findings on the use, targets, and modes of action of DIM for the treatment of human gastrointestinal cancers. DIM acts upon several cellular and molecular processes in gastrointestinal cancer cells, including apoptosis, autophagy, invasion, cell cycle regulation, metastasis, angiogenesis, and endoplasmic reticulum (ER) stress. In addition, DIM increases the efficacy of other drugs or therapeutic chemicals when used in combinatorial treatment for gastrointestinal cancer. The studies to date offer strong evidence to support the use of DIM as an anticancer and therapeutic agent for gastrointestinal cancer. Therefore, this review provides a comprehensive understanding of the preventive and therapeutic properties of DIM in addition to its different perspective on the safety of DIM in clinical applications for the treatment of gastrointestinal cancers. © 2016 by the authors; licensee MDPI, Basel, Switzerland. Source

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. Source

For a stabilized Newmark time integration of dynamic contact problems of the rapidly sliding bodies, considering the equality and inequality contact constraints and a high-speed contact point motion sliding on the deforming contact surface, the velocity and acceleration contact constraints are derived. Also, to suppress the numerical oscillations accompanied by the node-to-segment contact of the finite element models, a pseudo-node-to-node contact technique is suggested with the linear shape function elements having the almost equal segment lengths on the contact surface. The numerical simulations are performed with a high-speed punch moving on the beam and the high-speed rotating disks to check the stability and accuracy of the solution. © 2013 Springer-Verlag Berlin Heidelberg. Source

Sun J.,University of Central Florida | Xu S.,University of Central Florida | Ren H.,Chonbuk National University | Wu S.-T.,University of Central Florida
Applied Physics Letters | Year: 2013

We report a simple reconfigurable printing method for fabricating submillisecond-response and scattering-free polymer network liquid crystal photonic devices, such as prism, grating, and lens. To suppress light scattering in the visible region, we reduce the domain sizes by controlling polymer concentration, selecting a high viscosity liquid crystal (LC) host, and performing UV curing at a low temperature. To demonstrate the configurability, we printed a LC micro-prism array with ∼300-μm feature size and a circular lens with 1.3-mm radius without any pre-patterned templates. This reconfigurable printing technique enables fast design iterations and should have widespread applications for fabricating display and photonic devices. © 2013 AIP Publishing LLC. Source

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. Source

Baek J.-A.,University of Rochester | Baek J.-A.,Chonbuk National University | Lan Y.,University of Rochester | Liu H.,University of Rochester | And 3 more authors.
Developmental Biology | Year: 2011

Cleft palate, including submucous cleft palate, is among the most common birth defects in humans. While overt cleft palate results from defects in growth or fusion of the developing palatal shelves, submucous cleft palate is characterized by defects in palatal bones. In this report, we show that the Bmpr1a gene, encoding a type I receptor for bone morphogenetic proteins (Bmp), is preferentially expressed in the primary palate and anterior secondary palate during palatal outgrowth. Following palatal fusion, Bmpr1a mRNA expression was upregulated in the condensed mesenchyme progenitors of palatal bone. Tissue-specific inactivation of Bmpr1a in the developing palatal mesenchyme in mice caused reduced cell proliferation in the primary and anterior secondary palate, resulting in partial cleft of the anterior palate at birth. Expression of Msx1 and Fgf10 was downregulated in the anterior palate mesenchyme and expression of Shh was downregulated in the anterior palatal epithelium in the Bmpr1a conditional mutant embryos, indicating that Bmp signaling regulates mesenchymal-epithelial interactions during palatal outgrowth. In addition, formation of the palatal processes of the maxilla was blocked while formation of the palatal processes of the palatine was significantly delayed, resulting in submucous cleft of the hard palate in the mutant mice. Our data indicate that Bmp signaling plays critical roles in the regulation of palatal mesenchyme condensation and osteoblast differentiation during palatal bone formation. © 2010 Elsevier Inc. Source

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. Source

Parastar A.,Yeungnam University | Kang Y.C.,Chonbuk National University | Seok J.-K.,Yeungnam University
IEEE Transactions on Industrial Electronics | Year: 2015

Recently, the interest in offshore wind farms has been significantly increased because of the stronger and more stable winds at sea, which will lead to a higher power production. DC/DC power conversion solutions are becoming more popular for fulfilling the growing challenges in the high-voltage (HV) dc-connected offshore wind power industry. This paper presents several multilevel modular dc/dc conversion systems based on the capacitor-clamped (CC) module concept for high-power offshore wind energy applications. Two types of the CC modules, namely, the double-switch (DS) module and the switchless (SL) module, are discussed. A soft-switching technique is adopted to achieve minimal switching losses and the maximum system efficiency. Theoretical analysis is carried out for the 2n+1-level cascaded configurations based on the CC modules. The inherent interleaving property of the proposed configurations effectively reduces the output voltage ripple without adding extra components. A cascaded hybrid topology is developed by the combination of DS and SL modules. The proposed hybrid topology achieves higher efficiency and lower component count. The cascaded hybrid approach is evaluated in terms of the power device count, reliability, and efficiency against other HV dc/dc topologies to demonstrate its advantage for HVDC-connected offshore wind farms. The experimental results of two 5-kW prototype CC converters are presented to validate the theoretical analysis and principles as well as attest the feasibility of the proposed topologies. © 1982-2012 IEEE. Source

Shon I.-J.,Chonbuk National University
Journal of Korean Institute of Metals and Materials | Year: 2014

Pulsed current activated sintering and spark plasma sintering enhance sinter-ability, The advantage of these processes is that they allow very quick densification to near theoretical density and inhibition of grain growth. Highly dense nanostructured intermetallic compounds, oxides, metal-ceramic composites, high temperature materials and hard materials were produced with a simultaneous application of pressure and a pulsed current within several minutes. The role of the current in sintering or synthesis has been the focus of several studies aimed at explaining enhanced sintering and improved properties. The role played by the current has had various interpretations, with the effect explained in terms of the fast heating rate due to Joule heating, the presence of plasma in pores separating powder particles, and the intrinsic contribution of the current to mass transport. Copyright © The Korean Institute of Metals and Materials. Source

ABSTRACT: Opsoclonus-myoclonus syndrome (OMS) is an involuntary multidirectional eye movement accompanied by myoclonic jerks and a subtype of paraneoplastic neurological syndromes. Clinical features of OMS include opsoclonus with myoclonic jerks and cerebellar ataxia. Although there have been a few studies on brain FDG PET in paraneoplastic neurological syndrome associated with some kinds of malignancies such as lung and gastric cancer, brain FDG PET of patients with OMS caused by a mature cystic teratoma has not been reported. Here, we described a case of brain FDG PET/CT studies performed in a woman with OMS provoked from a mature cystic teratoma. Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved. Source

Kim Y.,Chonbuk National University | Mylonakis E.,Harvard University
Infection and Immunity | Year: 2012

Although the immune response of Caenorhabditis elegans to microbial infections is well established, very little is known about the effects of health-promoting probiotic bacteria on evolutionarily conserved C. elegans host responses. We found that the probiotic Gram-positive bacterium Lactobacillus acidophilus NCFM is not harmful to C. elegans and that L. acidophilus NCFM is unable to colonize the C. elegans intestine. Conditioning with L. acidophilus NCFM significantly decreased the burden of a subsequent Enterococcus faecalis infection in the nematode intestine and prolonged the survival of nematodes exposed to pathogenic strains of E. faecalis and Staphylococcus aureus, including multidrug-resistant (MDR) isolates. Preexposure of nematodes to Bacillus subtilis did not provide any beneficial effects. Importantly, L. acidophilus NCFM activates key immune signaling pathways involved in C. elegans defenses against Gram-positive bacteria, including the p38 mitogen-activated protein kinase pathway (via TIR-1 and PMK-1) and the _-catenin signaling pathway (via BAR-1). Interestingly, conditioning with L. acidophilus NCFM had a minimal effect on Gram-negative infection with Pseudomonas aeruginosa or Salmonella enterica serovar Typhimurium and had no or a negative effect on defense genes associated with Gram-negative pathogens or general stress. In conclusion, we describe a new system for the study of probiotic immune agents and our findings demonstrate that probiotic conditioning with L. acidophilus NCFM modulates specific C. elegans immunity traits. © 2012, American Society for Microbiology. Source

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. Source

CoTi and ZrO2 nanopowders were mechanochemically synthesized from CoTiO3 and Zr powders according to the reaction (2CoTiO3+3Zr→2CoTi+3ZrO2). The milled powders were then consolidated using high frequency induction heated sintering (HFIHS) within one minute under the applied pressure of 80MPa. The average hardness and fracture toughness of the nanostructured 2CoTi-3ZrO2 composite sintered from high energy ball milled powder were 1205kg/mm2 and 6.9MPam1/2, respectively. The mechanical properties of composite were compared with those of monolithic CoTi and ZrO2, respectively. © 2016 Elsevier Ltd and Techna Group S.r.l. Source

Yoo W.-H.,Chonbuk National University
Rheumatology International | Year: 2012

A case of multiple organ tuberculosis (TBc) involving lung, pleura, and peritoneum in a 39-year-old man with long-standing ankylosing spondylitis (AS) treated with adalimumab was presented. The relationship between antitumor necrosis factor-α (anti-TNF-α) therapy and TBc was also reviewed. This case illustrates that TBc can develop in multiple organs during adalimumab therapy, and thus, the awareness of serious complications of multiple organs and atypical extrapulmonary pattern of TBc during anti-TNF-α therapy needs to be increased. © Springer-Verlag 2010. Source

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). Source

Komarov S.V.,Nippon Light Metal Company | Romankov S.E.,Chonbuk National University
Journal of the European Ceramic Society | Year: 2014

The present study examines the potentialities of a novel surface treatment process for the metallization of ceramics. The process combines the principles of ball milling and shot peening using the energy of ultrasonic vibrations. Experiments were performed by using alumina and powdered nickel as a ceramic substrate and metallizing agent, respectively. The main emphasis was placed on characterizing the deposited films and elucidating their formation mechanisms. The results showed that 3-min impact treatment at ambient temperature and pressure leads to the formation of 2-4 μm thin, dense, and highly adherent films of nanostructured Ni on the surface of alumina substrate. SEM and TEM observations revealed a very tight contact between the deposited films and substrate suggesting the shot-impact induced plastic flow in the Ni film. It is assumed that the van der Waals interaction is the main origin of the high adhesion strength observed. © 2013 Elsevier Ltd. Source

Long B.,University of Electronic Science and Technology of China | Kil T.C.,Chonbuk National University
International Review of Electrical Engineering | Year: 2012

This paper describes the modeling and control of energy recovery power battery testing system (PBTS) under charging mode, which was usually found in evaluating the performance of power battery used in electric vehicles. First, modeling of three-phase voltage source rectifier with step-down isolation transformer interface is put forward. An outer dc-link voltage loop combined with inner feed-forward power decoupling control loop PWM rectifier scheme is proposed, then, modeling of a non-isolating DC-DC buck chopper for charging test experiment is provided. Finally, combination of the two power circuit model as a wide range battery charging testing system is investigated. Simulation and experimental results are presented to support the theoretical analysis and to demonstrate the system performance. © 2012 Praise Worthy Prize S.r.l. - All rights reserved. Source

Yang G.S.,Chonbuk National University
Journal of Material Cycles and Waste Management | Year: 2014

Regeneration of zeolite using microwave heating has been investigated focusing on the removal of toluene by desorption from zeolite samples. Studies were focused on the effect of physicochemical characteristics of three types of zeolite namely Na-rich natural zeolite (clinoptilolite), synthesized and heat treated on the toluene desorption ratio. In this work, it was shown that, in case of synthesized zeolite an increasing number of pores and their diffusion rate on the surface of samples caused by the sintering process resulted in an increase in the adsorption capacity compared to natural and heat-treated samples. The desorption experiment was carried out in MW irradiation time for about 1 h in which the temperature of zeolites samples was raised to almost 400 °C. Moisture had a significant effect on the desorption characteristics of zeolites. Maximum desorption ratios were obtained after approximately 30 min for heat-treated and synthesized samples when the moisture content was adjusted to 20 % of sample weight. In general, among the samples used in this study, synthesized zeolite showed the greatest absorption capacity and most efficient desorption ratio. © 2014 Springer Japan Source

Polyakov A.Y.,National University of Science and Technology "MISIS" | Lee I.-H.,Chonbuk National University
Materials Science and Engineering R: Reports | Year: 2015

New developments in theoretical studies of defects and impurities in III-Nitrides as pertinent to compensation and recombination in these materials are discussed. New results on experimental studies on defect states of Si, O, Mg, C, Fe in GaN, InGaN, and AlGaN are surveyed. Deep electron and hole traps data reported for GaN and AlGaN are critically assessed. The role of deep defects in trapping in AlGaN/GaN, InAlN/GaN structures and transistors and in degradation of transistor parameters during electrical stress tests and after irradiation is discussed. The recent data on deep traps influence on luminescent efficiency and degradation of characteristics of III-Nitride light emitting devices and laser diodes are reviewed. © 2015 Elsevier B.V. All rights reserved. Source

Choi J.-M.,Chonbuk National University
Journal of the Korean Physical Society | Year: 2012

The modulus of optical spatial coherence established by an incoherent light source was measured with a revised experimental setup of the Thompson and Wolf experiment. We used a liquid crystal display as a programmable aperture, which replaced the mechanical aperture controls used previously and provided a robust way to address the position-dependent spatial coherence. As a demonstration, the angular diameter, 0. 982′, of an extended light source was estimated from a visibility analysis of the diffraction fringes. © 2012 The Korean Physical Society. Source

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. Source

Hong Y.,Chonbuk National University
Revue Suisse de Zoologie | Year: 2011

Two new species of earthworms were found in a survey of lettuce cultivation fields, created by slash and burn. Amynthas hasamensis sp. n. and Amynthas samgaki sp. n. have simple intestinal caeca and no genital markings. Amynthas hasamensis sp. n. keys to the hawayanus group in Sims & Easton (1972) with three pairs of spermathecae in VI, VII, and VIII. Its male field areas in XVIII are complex with paired oval male discs bearing two transverse ridges with seminal grooves between the ridges. Amynthas samgaki sp. n. keys to the morrisi group with two pairs of spermathecae in VI and VII, and has a male field with large egg-shaped raised pads with transverse seminal grooves. Source

Huang K.-W.,National Sun Yat - sen University | Wu Y.-R.,National Sun Yat - sen University | Jeong K.-U.,Chonbuk National University | Kuo S.-W.,National Sun Yat - sen University
Macromolecular Rapid Communications | Year: 2013

A simple method is reported for the preparation of double-helical structures through a series of achiral random and block copolymers poly(styrene-co-4-vinylbenzyl triazolylmethyl methylthymine) (PS-co-PVBT) with various T units on the side chains through click reactions of poly(styrene-co-4-vinylbenzyl azide) (PS-co-PVBN3) with propargyl thymine (PT) and also the synthesis of the A-appended pyrene derivative (A-Py) through click chemistry. This double-helical structure is observed from achiral random-coil polystyrene (PS) main chains, stabilized through the combination of multiple A-T hydrogen bonds, and π-π stacking between pyrene units and single-walled carbon nanotubes (SWCNTs). A simple method is reported for the preparation of double-helical structure from achiral random-coil polystyrene (PS) main chains, stabilized through the combination of multiple A-T hydrogen bonds and π-π stacking between pyrene units and single-walled carbon nanotubes (SWCNTs). © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

The coexistence of Behçet's disease (BD) and ankylosing spondylitis (AS) is a rare combination and described only in case reports in the literature. Although the number of reports is increasing, vascular thrombosis, which is characteristic feature of BD, was not reported in this combination until now. We present a case of a male patient with both BD and AS, presenting with deep venous thrombosis. We also reviewed the clinical features of the cases with coexistence of BD and AS. © Springer-Verlag 2011. Source

Mishra S.C.,Indian Institute of Technology Guwahati | Krishna Ch.H.,Indian Institute of Technology Guwahati | Kim M.Y.,Chonbuk National University
Numerical Heat Transfer; Part A: Applications | Year: 2010

This article deals with the application of the modified discrete ordinate method (MDOM) to calculate volumetric radiative information with and without conduction in a concentric spherical enclosure containing a participating medium. With radiative information known from the MDOM, the energy equation of the combined mode transient conduction and radiation heat transfer is formulated and solved using the lattice Boltzmann method (LBM). Without conduction, for pure radiation case, two benchmark problems, representing nonradiative and radiative equilibrium situations are taken up. In the case of non-radiative equilibrium, an isothermal medium is bounded by cold walls and medium is the source of radiation, while in the case of radiative equilibrium, nonisothermal medium is confined between a hot and a cold wall, and the hot (inner sphere) wall is the radiation source. Depending upon the problem, heat flux, energy flow rate, emissive power, and temperature distributions in the medium are calculated for different values of parameters such as the extinction coefficient, the scattering albedo, the conduction-radiation parameter, the boundary emissivity, and the radius ratio. To validate the MDOM and the LBM-MDOM formulations, problems are also solved using the finite volume method (FVM) and the finite-difference method (FDM)-FVM approach, in which the FVM is used to calculate the volumetric radiation and the energy equation is also solved using the FDM. Results of the MDOM, LBM-MDOM, FVM and FDM-FVM are also benchmarked against those available in the literature. MDOM and LBM-MDOM have been found to provide accurate results. Copyright © Taylor & Francis Group, LLC. Source

Scleroderma (SSc) is a multisystem disorder characterized by fibrosis and collagen deposition in the dermis, but affects multiple organ systems, leading to esophageal dysmotility, renal failure, and interstitial lung disease (ILD). ILD is common manifestation of diffuse type of SSc and may be life threatening, and require aggressive therapy with cytotoxic agents. Although high-dose steroid and cyclophosphamide are most commonly used therapy for SSc-associated ILD, the efficacy is questionable in some cases and more effective and less toxic therapies are needed. Rituximab (RTX) is a chimeric mAb against human CD20 that depletes peripheral B cells and introduced for systemic rheumatic diseases. However, there were no enough evidences for SSc-associated ILD. We report herein a case of 47-year-old female with diffuse type of SSc with steroid and cyclophosphamide-resistant ILD that was successfully treated with RTX. Thus, we suggested that RTX could be an efficacious therapeutic modality for severe, conventional treatment-resistant SSc-associated ILD. © Springer-Verlag 2010. Source

Lee K.,Chonbuk National University
Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science | Year: 2014

By modifying the contact point displacement with a simple and systematic way, it has been explained that the node-to-segment contact solution can become as accurate as that of the node-to-node contact constraint. The accuracy of the solution is demonstrated by the numerical simulation using a punch sliding on the slab. © IMechE 2013. Source

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. Source

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. Source

Park S.-M.,Chonbuk National University
Journal of Bioscience and Bioengineering | Year: 2011

Recombinant acetyl xylan esterase (rAXE) of Aspergillus ficcum catalyzed the synthesis of peracetic acid (PAA) from ethyl acetate and hydrogen peroxide. Ten micrograms of rAXE catalyzed the synthesis of 1.34. mM of PAA, which can be used for the pretreatment of cellulosic biomass in situ. © 2011 The Society for Biotechnology, Japan. Source

Kim S.-M.,Pusan National University | Kim B.-Y.,Pusan National University | Eo S.-K.,Chonbuk National University | Kim C.-D.,Pusan National University | Kim K.,Pusan National University
Biochimica et Biophysica Acta - Molecular Basis of Disease | Year: 2015

We investigated the possibility that a cholesterol-rich milieu can accelerate response to pathogen-associated molecular patterns in order to elucidate mechanisms underlying aggravation of atherosclerosis after bacterial infection. The consumption of a high-cholesterol diet resulted in enhanced the expression of CD14 in arteries of ApoE-/- mice. 27-Hydroxycholesterol (27OHChol), the most abundant cholesterol oxide in atherosclerotic lesions, induced the significant expression of CD14 by THP-1 monocytic cells, but not by vascular smooth muscle cells or Jurkat T cells. Additions of lipopolysaccharide (LPS) to 27OHChol-treated THP-1 monocytic cells resulted in superinduction in terms of the gene transcription of CCL2 and the secretion of its gene product. In contrast, cholesterol did not cause increased the expression of CD14 in the aforementioned cells, and the addition of LPS to cholesterol-treated monocytic cells did not result in enhanced the expression of CCL2. The conditioned medium isolated from THP-1 cells exposed to 27OHChol plus LPS further induced the migration of monocytic cells in comparison with conditioned media obtained from THP-1 cells treated with 27OHChol or LPS alone. Treatment with 27OHChol also resulted in the enhanced secretion of MMP-9 and soluble CD14 (sCD14), and the secretion of sCD14 was blocked by a selective MMP-9 inhibitor. The inhibition of the ERK pathway resulted in significantly attenuated the secretion of sCD14 via mechanisms that were distinct from those by PI3K inhibition. We propose that 27OHChol can prime monocytes/macrophages by up-regulation of CD14 such that LPS-mediated inflammatory reaction is accelerated, thereby contributing to aggravated development of atherosclerotic lesions by enhancing recruitment of monocytic cells after infection with Gram-negative bacteria. © 2014 Elsevier B.V. Source

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. Source

You I.-C.,Chonbuk National University | Yoon K.-C.,Chonnam National University
Cornea | Year: 2012

PURPOSE: To investigate the efficacy of intravitreal triamcinolone acetonide (IVTA) injection in the treatment of endothelial graft rejection and the expression of T-helper type 1 (Th-1) chemokines in the aqueous humor. METHODS: Eleven patients (11 eyes) with acute endothelial graft rejection underwent IVTA (4 mg/0.1 mL) injection in addition to conventional treatment, including systemic and topical steroids and cyclosporine A (group A); 13 patients (13 eyes) received conventional treatment only (group B). Clinical characteristics were analyzed. In group A, Th-1 chemokines (CXCL-9, -10, and -11) in aqueous humor were measured by enzyme-linked immunosorbent assay and CXCR3 cells were counted by flow cytometry before treatment and at the period of improvement. RESULTS: There were no significant differences in visual acuity, intraocular pressure, and recurrence rate between the 2 groups. The mean time to improvement was 9.1 ± 3.9 days in group A and 15.4 ± 5.5 days in group B (P = 0.04). The concentrations of CXCL-9, -10, and -11 were 562.7 ± 109.4, 30293.1 ± 12537.1, and 228.3 ± 80.8 pg/mL before treatment and 6.7 ± 6.8 (P < 0.01), 207.5 ± 209.8 (P < 0.01), and 18.9 ± 19.5 (P < 0.01) pg/mL after treatment, respectively. The CXCL-10 level correlated with the time to improvement of graft rejection (P = 0.02). Flow cytometry demonstrated a significantly decreased number of CXCR3 and CXCR3CD4 cells in the aqueous humor after treatment. CONCLUSION: IVTA injection was effective in reducing the time to improvement of endothelial graft rejection. Increased expression of CXCL-9, -10, and -11, and their receptors in the aqueous humor of patients with endothelial graft rejection decreased after treatment. © 2012 by Lippincott Williams & Wilkins. Source

Son S.-W.,Korea Advanced Institute of Science and Technology | Son S.-W.,University of Calgary | Hong H.,Chonbuk National University
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2010

We consider globally coupled random frequency oscillators under thermal noise, and explore the synchronization transition with its critical behavior near the transition. In particular, we focus on the finite-size scaling behavior of the synchronization, and investigate how the thermal noise affects the correlation size exponent ν̄ of the synchronized oscillators. Extensive numerical simulations as well as mean-field analysis have been performed. We find that the correlation size exponent changes from ν̄ =5/2 without thermal noise to ν̄ =2 with strong thermal noise, where the value ν̄ =2 is the same as that for the usual equilibrium systems described by the Ginzburg-Landau mean-field theory. In order to see the effects of thermal fluctuation further, we remove the frequency-disorder fluctuations originating from the different realizations of natural frequencies of the oscillators, and examine the finite-size scaling behavior for the case only with the thermal fluctuation. It is found that ν̄ becomes 2 at much weak thermal noise strength, which implies that even very weak thermal fluctuations may lead to ν̄ =2 when frequency-disorder fluctuations are absent. © 2010 The American Physical Society. Source

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. Source

You M.-J.,Chonbuk National University
Parasitology International | Year: 2014

The oocysts of some of the recognized species of chicken coccidiosis are difficult to distinguish morphologically. Diagnostic laboratories are increasingly utilizing DNA-based technologies for the specific identification of Eimeria species. This study reports a multiplex polymerase chain reaction (PCR) assay based on internal transcribed spacer-1 (ITS-1) for the simultaneous diagnosis of the Eimeria tenella, Eimeria acervulina, Eimeria maxima, and Eimeria necatrix species, which infect domestic fowl. Primer pairs specific to each species were designed in order to generate a ladder of amplification products ranging from 20 to 25 bp, and a common optimum annealing temperature for these species was determined to be 52.5 °C. Sensitivity tests were performed for each species, showing a detection threshold of 1-5. pg. All the species were amplified homogeneously, and a homogenous band ladder was observed, indicating that the assay permitted the simultaneous detection of all the species in a single-tube reaction. In the phylogenic study, there was a clear species clustering, which was irrespective of geographical location, for all the ITS-1 sequences used. This multiplex PCR assay represents a rapid and potential cost-effective diagnostic method for the detection of some key Eimeria species that infect domestic fowl. © 2014 Elsevier Ireland Ltd. Source

Lee S.-J.,Chonbuk National University
ISIJ International | Year: 2013

An empirical model has been proposed to predict the grain growth of austenite for reheating alloy steels by considering the effect of various alloying elements. Additional elements such as Cu, Al, N were considered in the proposed model. The proposed model confirms that the austenite grain growth is suppressed by adding different alloying elements, whereas higher reheating temperatures increase the growth rate of austenite grains. the new predictive model is a function of composition and reheating conditions only, regardless of precipitate dissolution and formation. It is expected that the present model will be useful to predict the austenite grain growth of alloy steels adequately without requiring any thermodynamic calculations for the precipitation and dissolution of carbonitride-forming elements. Source

Ren H.,Chonbuk National University | Xu S.,University of Central Florida | Liu Y.,University of Central Florida | Wu S.-T.,University of Central Florida
Optics Express | Year: 2013

We demonstrate a flat polymeric lenticular microlens array using a mixture of rod-like diacrylate monomer and positive dielectric anisotropy nematic liquid crystal (LC). To create gradient refractive index profile in one microlens, we generate fringing fields from a planar top electrode and two striped bottom electrodes. After UV stabilization, the film is optically anisotropic and can stand alone. We then laminate this film on a 90° twisted-nematic LC cell, which works as a dynamic polarization rotator. The static polymeric lenticular lens exhibits focusing effect only to the extraordinary ray, but no optical effect to the ordinary ray. Such an integrated lens system offers several advantages, such as low voltage, fast response time, and temperature insensitivity, and can be used for switchable 2D/3D displays. © 2013 Optical Society of America. Source

Ren H.,Chonbuk National University | Xu S.,University of Central Florida | Wu S.-T.,University of Central Florida
Optics Letters | Year: 2013

We report a polymer-stabilized liquid crystal (LC) microlens array with a large dynamic range and fast response time. The top substrate has a planar indium-tin oxide (ITO) electrode, while the bottom substrate has two patterned ITO electrodes for generating a fringing field and uniform longitudinal field. The fringing field is utilized to create the desired gradient refractive index profile in the LC/monomer layer, which is later stabilized by UV curing to form polymer networks. To tune the focal length, we apply a longitudinal field to change the lens shape. This microlens array offers several attractive features, such as large dynamic range, fast response time, and good mechanical stability. © 2013 Optical Society of America. Source

Jung S.T.,Chonbuk National University
Journal of Pediatric Orthopaedics | Year: 2015

INTRODUCTION:: Posttraumatic pediatric distal tibiofibular synostosis is a rare complication following fracture. This is a retrospective, multicenter case series of synostosis of distal tibiofibular fractures in children. The purpose was to evaluate the incidence and pattern of posttraumatic distal tibiofibular synostosis in children. METHODS:: Of the 604 pediatric distal tibiofibular fractures, 20 patients (3.3%) with synostosis after treatment of distal tibiofibular fractures were identified at 3 tertiary referral centers. There were 12 boys and 8 girls, with a mean age of 8.4±2.0 years (range, 3.7 to 11.5 y) at the time of injury. Medical records were reviewed, and serial radiographs were analyzed to determine fracture configuration, pattern of synostosis, and changes in the relative positions of the proximal and distal tibial and fibular physes and in the alignment of the ankle. RESULTS:: The time from the occurrence of fracture until the recognition of the synostosis ranged from 2 to 6 months (mean, 2.8 mo). The most common fracture configuration was oblique tibial fracture combined with comminuted fibular fracture. There were 12 focal types and 8 extensive types. The proximal tibiofibular distance was decreased in 13 patients. Proximal migration of the distal fibular physis developed in all cases. Five patients exhibited ankle valgus of 10 degrees or greater with moderate or severe distal fibular shortening. Eight patients were symptomatic after synostosis and 12 patients were asymptomatic. CONCLUSIONS:: We identified 2 patterns of synostosis after the treatment of pediatric distal tibiofibular fracture: focal and extensive. The focal type was more prevalent than the extensive type, which was more likely to occur due to high-energy injury. When a tibiofibular cross-union develops, it creates growth abnormalities that warrant observation and potential treatment, as it may lead to progressive deformity or ankle pain. LEVEL OF EVIDENCE:: Level IV. Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved. Source

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. Source

Lee J.-H.,Chonbuk National University | Yoon T.-H.,Pusan National University
Journal of Applied Physics | Year: 2013

Spontaneous formation of chiral domains such as a helical filament and a bent-broom texture was observed from the mixture of a rod-like liquid crystal octylcyano-biphenyl (8CB) and a tri boomerang-shaped 2,4,6-triphenoxy-1,3,5- triazine (triphenoxy) molecule. Although the constituent molecules were achiral, their mixture showed the chiral domains with the equal fraction of the opposite handedness. No tilt of 8CB molecules in the smectic layer was observed, implying the chirality is not due to the polar packing and tilt of the molecules. In addition, the splay and bend elastic constant of 8CB was decreased after doping triphenoxy. A structural conformation of triphenoxy and an orientational coupling between 8CB and triphenoxy are considered to be related to the chiral domain formation. © 2013 AIP Publishing LLC. Source

Different continental collision belts show contrasting metamorphic trend along their length, including the distribution of extreme metamorphism; i.e., ultrahigh-pressure (>100. km depth) and ultrahigh-temperature (900-1150°C) metamorphisms. However, no previous study has succeeded in explaining these trends. The present study investigates the main factors that control the metamorphic trends along collision belts, with reference to the Dabie-Hongseong collision belt between the North and South China blocks and the Himalayan collision belt between the Indian and Asian blocks. In the Dabie-Hongseong collision belt, collision began in the east before 245. Ma and propagated westward until ca. 220. Ma. In the eastern part of the belt, the amount of oceanic slab that subducted before collision was insufficient to pull down the continental crust to the depths of ultrahigh-pressure metamorphism; however, ultrahigh-pressure metamorphism occurred in the western part of the belt. Slab break-off also migrated from east to west, with a westward increase in the depth of break-off (from ca. 10. kbar in the west to ca. 35. kbar in the east). These lateral trends along the belt resulted in a westward change from ultrahigh-temperature (915-1160°C, 9.0-10.6. kbar) to high-pressure (835-860°C, 17.0-20.9. kbar) and finally ultrahigh-pressure metamorphism (680-880°C, 30-40. kbar). In the Himalayan collision belt, collision started from the west at 50. Ma and propagated eastward. The amount of oceanic slab subducted prior to collision was sufficient to pull down the continental crust to the depths of ultrahigh-pressure metamorphism in the west, but not in the east. Slab break-off started in the west at ca. 46. Ma and propagated eastward, with an eastward decrease in the depth of slab break-off from 27-29 to 17-18. kbar. Consequently, the metamorphic trend along the belt changes eastward from ultrahigh-pressure (690-750°C, 27-29. kbar) to high-pressure and finally high-pressure granulite facies metamorphism (890°C, 17-18. kbar). The differences in metamorphic trend between the Dabie-Hongseong and Himalayan collision belts reflect the amount of oceanic crust subducted prior to collision and the depth and timing of slab break-off along each belt. © 2010 Elsevier Ltd. Source

Yang E.,Chonbuk National University
Fuzzy Sets and Systems | Year: 2015

This paper addresses standard completeness for non-associative, non-commutative, substructural fuzzy logics and their axiomatic extensions. First, fuzzy systems, which are based on mianorms (binary monotonic identity aggregation operations on the real unit interval [0,1]), their corresponding algebraic structures, and algebraic completeness results are discussed. Next, completeness with respect to algebras whose lattice reduct is [0,1], so-called standard completeness, is established for these systems using construction in the style of Jenei-Montagna. Finally, some axiomatic extensions of the non-associative, non-commutative core fuzzy logics having axioms corresponding to the structural rule(s) of exchange and/or associativity are considered. © 2015 Elsevier B.V. Source

So E.S.,Chonbuk National University
Journal of Aging and Health | Year: 2014

Objective: This study aims to explore the impact of differential degrees of obesity on health-related quality of life (HRQL) by sex in the Korean elderly. Method: We analyzed data on those aged between 65 and 74 years from the Korean National Health and Nutrition Examination Survey (KNHANES) using multiple regression analysis. Results: Compared with the lowest waist circumference (WC) quintile, the women in the fourth and fifth quintiles demonstrated significantly lower unadjusted HRQL but not the men in any quintiles. Whereas higher WC quintiles impaired mobility, usual activities, and pain/discomfort in women, the fourth WC quintile improved usual activities in men. After adjustment, only the women of the highest WC quintile reported impaired mobility. Discussion: Extreme obesity worsens mobility, and comorbidity in combination with obesity worsens HRQL in elderly women. Monitoring and controlling comorbidity and maintaining adequate WC decreases the risks of lowered HRQL in Korean elderly women. © The Author(s) 2014. Source

Song K.-J.,Chonbuk National University
Neurosurgery Quarterly | Year: 2015

Cervical osteochondroma is a rare tumor. However, because minor trauma in patients with a history of cervical osteochondroma can lead to serious neurological damage, spinal evaluation using computed tomography in hereditary multiple exostosis patients including patients with no presenting symptoms is required; in addition, sufficient explanation of the possibility of neurological damage after minor trauma to the head should be given to the patient and guardians. © 2015 Wolters Kluwer Health, Inc. All rights reserved. Source

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. Source

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. Source

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). Source

Lee C.,Chonbuk National University
Journal of Supercomputing | Year: 2013

Owing to the recent development in mobile network technologies, users may enjoy streaming media services anytime, anywhere using personal mobile communication devices. Wireless mobile streaming media services, however, have such problems as delay, congestion, and crosstalk due to narrow network bandwidth and limited resources. These problems degrade not only Quality of Service (QoS), but also responsiveness and reliability of the streaming media service. To solve this problem, this paper proposes a Fuzzy Similarity-Based Transcoding Proxy (FSTP) mechanism. The proposed FSTP mechanism analyzes the fuzzy similarity of partitioned segment versions of media objects to construct a Fuzzy Similarity-Based Transcoding Graph (FSTG). The constructed FSTG determines transcoding for the partitioned media object segment versions. The determined transcoding improves Delay Saving Ratios (DSR), Cache Hit Precision Ratio (CHPR), and Cache Hit Recall Ratio (CHRR). Therefore, the more relevant media object segment versions, determined by the fuzzy similarity, are transcoded and cached first to reduce the start delay time and network traffic. The proposed mechanism is simulated to evaluate various performance parameters. The simulation results show that the proposed mechanism achieves improved performance in DSR, CHPR, and CHRR compared with those of other existing mechanisms. © 2012 Springer Science+Business Media, LLC. Source

Yanagimoto T.,Kyushu University | Yu Y.-T.,Chonbuk National University | Kaneko K.,Kyushu University
Sensors and Actuators, B: Chemical | Year: 2012

Au/SnO 2 core-shell structure NPs were prepared by a precipitation method and a microwave hydrothermal synthesis method, and their CO responses were measured by a high resistance meter. It was found that the CO response of the sample prepared by the precipitation method was extremely low, 0.18, with comparison to the one by the hydrothermal synthesis method, 0.965. Microstructures achieved by two-dimensional TEM characterization showed that both samples maintained the similar core-shell structures with their sizes ranging between 30 and 50 nm, as the core consists of Au NP and the shell consists of SnO 2 NPs. The average grain sizes of SnO 2 NPs of precipitation method and hydrothermal synthesis method were measured as 5.2 nm and 8.3 nm, respectively. The thickness and the porosity variation of SnO 2-shell layers were characterized further by three-dimensional electron tomography, and correlated with the sensing properties. It was found that the porosity within SnO 2-shell layers prepared by the precipitation method was lower than the one prepared by the hydrothermal synthesis method. Since Au NP could act as the catalyst for CO oxidation reaction, high porosity within SnO 2-shell layers would have lead the accessibilities of Au NP to the CO gas molecules and resulted high CO responses. © 2011 Elsevier B.V. All rights reserved. Source

Oh H.K.,Chonbuk National University
Bulletin of the Korean Chemical Society | Year: 2011

The aminolysis of O-methyl S-aryl thiocarbonates with benzylamines are studied in acetonitrile at -45.0°C. The βX (βnuc) values are in the range 0.62-0.80 with a negative cross-interaction constant, ρXZ = -0.42, which are interpreted to indicate a concerted mechanism. The kinetic isotope effects involving deuterated benzylamine nucleophiles (XC 6H 4CH 2ND 2) are large, kH/kD = 1.29-1.75, suggesting that the N-H(D) bond is partially broken in the transition state by forming a hydrogen-bonded four-center cyclic structure. The concerted mechanism is enforced by the strong push provided by the MeO group which enhances the nucleofugalities of both benzylamine and arenethiolate from the putative zwitterionic tetrahedral intermediate. Source

Oh H.K.,Chonbuk National University
Bulletin of the Korean Chemical Society | Year: 2011

The aminolysis reactions of phenyl N-benzyl thiocarbamate with benzylamines in acetonitrile at 50.0 °C are investigated. The reactions are first order in both the amine and the substrate. Under amine excess, pseudo-first coefficient (k obs) are obtained, plot of k obs vs free amine concentration are linear. The signs of ρ XZ (< 0) are consistent with concerted mechanism. Moreover, the variations of ρ X and ρ Z with respect to the sustituent in the substrate and large ρ XZ value indicate that the reactions proceed concerted mechanism. The normal kinetic isotope effects (k H/k D = 1.3 ∼ 1.5) involving deuterated benzylamine nucleophiles suggest a hydrogen-bonded, four-centered-type transition state. The activation parameters, ΔH†and AS†, are consistent with this transition state structure. Source

Chang B.-Y.,Pukyong National University | Lee H.J.,Chonbuk National University | Park S.-M.,Ulsan National Institute of Science and Technology
Electroanalysis | Year: 2011

We report an extraction-reconstruction strategy for obtaining a novel voltammogram for a specific electrochemical process. While a conventional voltammogram is obtained from potentiodynamic currents, our voltammogram is obtained from a large body of potentiodynamic electrochemical impedance spectra by taking advantage of their highly resolvable power. As a proof of concept, construction of a mass transfer admittance voltammogram (MTAV) is demonstrated, which is made up of purely mass transfer admittances plotted vs. potential, excluding effects from other interfering electrochemical components. We also compare the MTAV with the AC voltammogram to show its enhanced accuracy and apply the novel voltammetry to clearly determine the number of electrons transferred and diffusion coefficients, which may vary depending on experimental conditions, for a complex electrochemical reaction. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

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: 2011

Based on dielectrophoretic effect, we report a novel approach which can extensively spread a liquid crystal (LC) interface. With interdigitated striped electrodes, the droplets can be stretched along the striped electrode direction; while with zigzag interdigitated electrodes, the droplets can be further stretched sidewise. In our demonstration, the occupied area of a 1.9-mm-aperture LC droplet doped with 1.2 wt% black dye could be expanded over ∼3.5× at 78 Vrms. The spreading and recovering times were measured to be ∼0.39 s and ∼0.75 s, respectively. The slower response time confirms the extreme expanding of the LC surface. The contrast ratio is over ∼120:1 in transmissive mode. Color light switch was also demonstrated by spreading colored-dye doped LC droplets. The mechanical stability of the device was also evaluated. Liquid devices based on this cell structure have the advantages of good stability, simple operation and low power consumption. This work opens a new gateway for voltage controllable, polarization-insensitive, and broadband liquid photonic devices which may find numerous applications in switchable windows, variable optical attenuators, and displays. This journal is © The Royal Society of Chemistry. Source

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. Source

Eun H.-J.,Chonbuk National University
International Journal of Software Engineering and its Applications | Year: 2015

Web-based specialized retrieval systems for scientific fields extremely restrict the expression for user's information requests. Therefore the process of information content analysis and that of the information acquisition become inconsistent. In this paper, we apply the fuzzy retrieval model to solve the high time complexity of the retrieval system by constructing a reduced term set for the term's relatively important degree. We also perform a cluster retrieval to reflect the user's query exactly through the similarity relation matrix satisfying the characteristics of the fuzzy compatibility relation. This paper proves the performance of a proposed re-ranking model based on the union of similarity of the fuzzy retrieval model and the document cluster retrieval model. © 2015 SERSC. Source

Park H.-S.,Kent State University | Kang S.-W.,Chonbuk National University | Tortora L.,Kent State University | Kumar S.,Kent State University | Lavrentovich O.D.,Kent State University
Langmuir | Year: 2011

We use optical and fluorescence microscopy, densitometry, cryo-transmission electron microscopy (cryo-TEM), spectroscopy, and synchrotron X-ray scattering to study the phase behavior of the reversible self-assembled chromonic aggregates of an anionic dye Sunset Yellow (SSY) in aqueous solutions crowded with an electrically neutral polymer polyethylene glycol (PEG) and doped with the salt NaCl. PEG causes the isotropic SSY solutions to condense into a liquid-crystalline region with a high concentration of SSY aggregates, coexisting with a PEG-rich isotropic (I) region. PEG added to the homogeneous nematic (N) phase causes separation into the coexisting N and I domains; the SSY concentration in the N domains is higher than the original concentration of PEG-free N phase. Finally, addition of PEG to the highly concentrated homogeneous N phase causes separation into the coexisting columnar hexagonal (C) phase and I phase. This behavior can be qualitatively explained by the depletion (excluded volume) effects that act at two different levels: at the level of aggregate assembly from monomers and short aggregates and at the level of interaggregate packing. We also show a strong effect of a monovalent salt NaCl on phase diagrams that is different for high and low concentrations of SSY. Upon the addition of salt, dilute I solutions of SSY show appearance of the condensed N domains, but the highly concentrated C phase transforms into a coexisting I and N domains. We suggest that the salt-induced screening of electric charges at the surface of chromonic aggregates leads to two different effects: (a) increase of the scission energy and the contour length of aggregates and (b) decrease of the persistence length of SSY aggregates. © 2011 American Chemical Society. Source

Yoo J.,Hanyang University | Kwon H.-H.,Chonbuk National University | Kim T.-W.,Hanyang University | Ahn J.-H.,Seokyeong University
Journal of Hydrology | Year: 2012

Analyses of drought frequency require long-term historical data to ensure reliable quantile estimates. Estimation of quantiles is difficult, because drought extremes are rare by definition, and the durations of extremes are often too short for reliable point frequency analysis. Regional frequency analysis provides a solution for these problems by using data from multiple sites, provided the sites are homogeneous, and this type of analysis yields appropriate estimates of quantiles at sites of interest. This study aims to develop a practical drought frequency analysis method based on a bivariate distribution by incorporating regional drought attributes that are associated with drought frequency (e.g., duration and severity). This study employed a kernel density function to describe joint probabilistic behavior of drought. Given the proposed approach, we estimated return periods according to the most severe drought events on record at each site, and ultimately assess the risks for occurrence of droughts exceeding the most severe droughts over the next 10, 50, 100, and 150. years. © 2011 Elsevier B.V. Source

Jang J.-S.,University of Delaware | Varischetti J.,University of Nevada, Reno | Lee G.W.,University of Nevada, Reno | Lee G.W.,Chonbuk National University | Suhr J.,University of Delaware
Composites Part A: Applied Science and Manufacturing | Year: 2011

This study involves the investigation of mechanical damping and thermal stability of hybrid epoxy composites with two types of fillers, graphitized carbon nanofiber (CNF) and micron size silicon dioxide (SiO2) particles. While viscoelastic properties of the composites were characterized for the study of mechanical damping, the linear coefficient of thermal expansion (CTE) was evaluated for investigation of thermal stability of the hybrid composites. The effect of filler loading was investigated with respect to both mechanical and thermal stability of the hybrid composite materials. It has been found that the addition of 3% weight fraction of SiO2 particles along with 3% weight fraction of CNF can improve damping loss factors by up to 15.6% at room temperature while at the same time improving thermal stability with up to 15% reductions in CTE. This study also presents semi-empirical models which can account for both the fillers in prediction of viscoelastic properties and CTE of the hybrid composites. It is observed that there is reasonable agreement in both mechanical damping and CTE for the hybrid composites between the experimental data and the predicted data. © 2010 Elsevier Ltd. All rights reserved. Source

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

A simple approach for preparing gradient polymer network liquid crystal (PNLC) with a large refractive index change is demonstrated. To control the effective refractive index at a given cell position, we applied a voltage to a homogeneous cell containing LC/diacrylate monomer mixture to generate the desired tilt angle and then stabilize the LC orientation with UV-induced polymer network. By varying the applied voltage along with the cells' movement, a PNLC with a gradient refractive index distribution is obtained. In comparison with conventional approaches using patterned photomask or electrode, our method offers following advantages: large refractive index change, freedom to design specific index profile, and large panel capability. Potential applications include tunable-focus lenses, prism gratings, phase modulators, and other adaptive photonic devices. © 2012 Optical Society of America. Source

Lee D.,Chonbuk National University | Pernicka H.,Missouri University of Science and Technology
International Journal of Aeronautical and Space Sciences | Year: 2011

A new approach for spacecraft absolute attitude estimation based on the unscented Kalman filter (UKF) is extended to relative attitude estimation and navigation. This approach for nonlinear systems has faster convergence than the approach based on the standard extended Kalman filter (EKF) even with inaccurate initial conditions in attitude estimation and navigation problems. The filter formulation employs measurements obtained from a vision sensor to provide multiple line(-) of(-) sight vectors from the spacecraft to another spacecraft. The line-of-sight measurements are coupled with gyro measurements and dynamic models in an UKF to determine relative attitude, position and gyro biases. A vector of generalized Rodrigues parameters is used to represent the local error-quaternion between two spacecraft. A multiplicative quaternion-error approach is derived from the local error-quaternion, which guarantees the maintenance of quaternion unit constraint in the filter. The scenario for bounded relative motion is selected to verify this extended application of the UKF. Simulation results show that the UKF is more robust than the EKF under realistic initial attitude and navigation error conditions, © The Korean Society for Aeronautical & Space Sciences. Source

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. Source

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. Source

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. Source

Baik S.-H.,Chonbuk National University
Food Science and Biotechnology | Year: 2010

In order to investigate the optimal conditions for raffinose synthesis, α-galactosidase was purified from Absidia corymbifera IFO8084 with a recovery yield of approximately 8.1% (8.36 mg). The molecular weight of the wild-type α-galactosidase was about 83 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDSPAGE). The native molecular mass of the enzyme was approximately 330 kDa by gel filtration chromatography, indicating that α-galactosidase from A. corymbifera IFO8084 is a homotetrameric enzyme. The purified enzyme displayed optimal enzyme activity at pH 4.5 and 60°C. When the purified α-galactosidase was incubated in a substrate solution of sucrose and D-galactose for 48 hr at 37°C, raffinose was synthesized and was confirmed by thin layer chromatography (TLC), high performance liquid chromatography (HPLC), and 13C-nuclear magnetic resonance (13C-NMR) spectrometer analysis. Maximum rates of conversion were observed with 1.67 M galactose, 2.04 M sucrose, and 100 U α-galactosidase at pH 6.0 and 70°C. Under the optimized conditions, the overall conversion ratio was 10%(w/v), representing 2.5 times the synthesis yield that would be possible without the optimized conditions. © KoSFoST and Springer 2010. Source

Kwon S.-D.,Chonbuk National University | Park J.,Stanford University | Law K.,Stanford University
Smart Materials and Structures | Year: 2013

This paper investigates the applicability of an electromagnetic generator with repulsively stacked magnets for harvesting energy from traffic-induced bridge vibrations. First, the governing equation for electro-mechanical coupling is presented. The magnetic field for repulsive pole arrangements is discussed and the model is validated from a magnet falling test. The detailed design, fabrication, and test results of a prototype device are presented in the paper. An experimental vibration shaker test is conducted to assess the performance of the energy harvester. Field test and numerical simulation at the 3rd Nongro Bridge in South Korea shows that the device can generate an average power of 0.12 mW from an input rms acceleration of 0.25 m s-2 at 4.10 Hz. With further frequency tuning and design improvement, an average power of 0.98 mW could be potentially harvested from the ambient vibration of the bridge. © 2013 IOP Publishing Ltd. Source

For the numerical analysis of dynamic contact problem where the contact constraint is imposed by a very stiff massless spring between the bodies, it is shown that a stabilized time integration solution can be obtained without spurious oscillations by imposing the velocity and acceleration constraints as well as the displacement constraint on the contact point. For the velocity and acceleration contact constraints which are crucial for the numerical stability, the time derivatives of the spring deformation are computed by using the Newmark time integration rule of structural dynamics. With the numerical experiments the necessity of the velocity and acceleration contact constraints and the necessity of unconditionally stable time integration rule for the very stiff spring are demonstrated. © Springer-Verlag 2010. Source

Choi S.Y.,Chonbuk National University | Choudhury D.,University of Delhi | Freitas A.,University of Pittsburgh | Kalinowski J.,University of Warsaw | And 2 more authors.
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2011

The Higgs sector is extended in R-symmetric supersymmetry theories by two iso-doublets Rd,u which complement the standard iso-doublets Hd,u. We have analyzed masses and interactions of these novel states and describe their [non-standard] decay modes and their production channels at the LHC and e+e- colliders. © 2011 Elsevier B.V. Source

Park N.-M.,Electronics and Telecommunications Research Institute | Choi C.-J.,Chonbuk National University
Nano Research | Year: 2014

A new method for growing silicon nanowires is presented. They were grown in an aqueous solution at a temperature of 85 °C under atmospheric pressure by using sodium methylsiliconate as a water-soluble silicon precursor. The structure, morphology, and composition of the as-grown nanowires were characterized by scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray spectrometry. It was also confirmed by X-ray powder diffraction and Raman spectroscopy that the silicon nanowire has a hexagonal structure. It was possible to grow the crystalline silicon nanowires at low temperature under atmospheric pressure because potassium iodide, which was used as a gold etchant, sufficiently increased the surface energy and reactivity of gold as a metal catalyst for the reaction of the Si precursor even at low temperature. [Figure not available: see fulltext.] © 2014 Tsinghua University Press and Springer-Verlag Berlin Heidelberg. Source

Wang H.-M.,Xian Jiaotong University | Xia X.-G.,University of Delaware | Xia X.-G.,Chonbuk National University
IEEE Transactions on Wireless Communications | Year: 2010

Time asynchronism is a practical issue need to be addressed for a general distributed two-way relay network, where two terminal nodes exchange information through multiple spatial-separated relay nodes. In this letter, we propose an analog network coding (ANC) scheme for a time asynchronous two-way relay network. In the proposed scheme, each relay node linearly transforms the received mixed asynchronous signals in the first time-slot by a Toeplitz matrix, and then broadcasts them back to the terminals in the second time-slot. A sufficient condition is derived for the proposed ANC to achieve full cooperative diversity using only linear receivers at the terminal nodes, such as zero-forcing (ZF), or minimum mean square error (MMSE) receivers, with any delay profiles of the timing errors. The decoding of the proposed ANC scheme is computationally efficient and the symbol rate can approach 1, when the coding block length is sufficiently large compared to the number of relay nodes R and the timing errors. © 2006 IEEE. Source

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. Source

Lee S.-J.,Chonbuk National University | Matlock D.K.,Colorado School of Mines | Van Tyne C.J.,Colorado School of Mines
Computational Materials Science | Year: 2013

A finite element subroutine code, named CTDT (Carburization and Thermal Distortion with Transformation kinetics), has been developed. CTDT simulates a carburizing process of heat-treatable steel components. In the present study, CTDT is compared with the commercial heat treatment code DANTE. The same carburizing process condition with a simple cylindrical sample is used to compare the two different codes. The differences in results, such as carbon profile at surface, temperature change, microstructure distribution, hardness, residual stress, and quenching distortion after carburizing treatment are primarily caused by the different transformation kinetics models and material properties used in each code. However, the simulation results show reasonable agreement with experimental results. The flexibility for updating or changing the transformation kinetics model and material properties is the advantage of the CTDT code. © 2012 Elsevier B.V. All rights reserved. Source

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. Source

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. Source

Kim H.-C.,Korea Institute for Knit Industry | Chung Y.S.,Chonbuk National University
Fibers and Polymers | Year: 2013

Chitin and chitosan have been extensively investigated as a matrix of organic/inorganic composite. Barium, one of the radiopaque inorganic materials, can provide chitosan with radiopaque property by blending of chitosan and BaSO4. The filtered and deaerated chitosan/BaCl2 solutions were extruded into NaOH and Na2SO4 coagulation bath through a nozzle by gear pump. BaSO4 was synthesized by the reaction between BaCl2 and Na2SO4 in the coagulation bath, in which acidic chitosan solution was also solidified at the same time. In XRD, the introduction of BaSO4 into chitosan fibers reduced the inherent peak of chitosan fibers. In angiographic observation, chitosan/BaSO4 hybrid fibers exhibited the clear contrast images which become clear with an increase in BaSO4 content. © 2013 The Korean Fiber Society and Springer Science+Business Media Dordrecht. Source

Jeong S.-Y.,Chonbuk National University
Neurosurgery Quarterly | Year: 2015

The purpose of this study is to report a case of massive, spontaneous, subcutaneous hematoma in a neurofibromatosis type 1 (NF1) patient. NF is rarely associated with spontaneous hemorrhage. Massive, spontaneous, subcutaneous hemorrhage in the lower back is also rare. Patients with NF1 should understand the potential complications of their disease and surgeons and physicians should be prepared to promptly manage such complications in these patients. © 2015 Wolters Kluwer Health, Inc. All rights reserved. Source

Imayama T.,Nagoya University | Imayama T.,Chonbuk National University | Suzuki K.,Nagoya University
American Mineralogist | Year: 2013

Chemical Th-U-total Pb isochron method (CHIME) of monazite and xenotime from three leucogranites in far-eastern Nepal revealed the presence of Carboniferous inherited grains of monazite and intense intrusion of leucogranites around 18-16 Ma in the High Himalaya. In garnet-bearing sillimanite-muscovite-biotite leucogranite, most monazite grains have inherited cores with the chemical dates of ∼504-418 and ∼342-272 Ma, which were overgrown by Early Miocene mantles and rims of 17.9 ± 1.5 Ma. Early Ordoviciain and Carboniferous ages are rarely found in the same euhedral-subhedral cores. In addition to the previously recognized Early Paleozoic magmatism, monazite cores with Carboniferous ages in Early Miocene leucogranites provide evidence for two periods of magmatism at the base of the High Himalaya prior to the Cenozoic Himalayan orogeny. In muscovite-biotite leucogranite, no inherited domains were observed in monazite and xenotime grains. They yielded the CHIME monazite and xenotime dates of 16.1 ± 2.0 and 19.8 ± 6.5 Ma, respectively. Monazite grains adjacent to xenotime have significantly lower concentrations of UO2 and Y 2O3 compared to those isolated from xenotime. These results imply that xenotime influences Y and U contents in monazite, reflecting local equilibrium system. In aplitic leucogranite, monazite grains yielded the mean of apparent chemical date of 18.0 ± 2.2 Ma. The CHIME monazite ages of ∼18-16 Ma in three leucogranites reflect the timing of melt crystallization. Source

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. Source

Kim Y.,Chonbuk National University
Journal of Korean Institute of Metals and Materials | Year: 2011

This paper presents a study of the tensile behavior of carbon and glass fiber reinforced epoxy hybrid laminates manufactured by vacuum assisted resin transfer molding (VARTM). The objective of this study was to develop and characterize carbon fiber reinforced plastic hybrid composite material that is low cost and light-weight and that possesses adequate strength and stiffness. The effect of position and content of the glass fabric layer on the tensile properties of the hybrid laminates was examined. The strength and stiffness of the hybrid laminates showed a steady decrease with an increase of the glass fabric content this decrease was almost linear. Fracture strain of these laminates showed a slight increasing trend when glass fabric content was increased up to 3 layers, but at a glass fabric content > 3 layers the strain was almost constant. When glass fabric layers were at both outer surfaces, the hybrid laminate exhibited a slightly higher tensile strength and elastic modulus due to the small amount of glass yarn pull-out. Source

Han Y.-H.,Chonbuk National University
Clinical Nuclear Medicine | Year: 2016

ABSTRACT: A 37-year-old woman with chronic renal insufficiency underwent bone scintigraphy to evaluate renal osteodystrophy (ROD). Markedly increased uptakes were shown in the maxilla and the mandible, which suggested extensive maxillary and mandibular hypertrophy. CT image revealed that diffuse bony thickening and ground-glass appearance in the skull, maxilla, and mandible with poor distinction of the corticomedullary junction. Whole-body bone scintigraphy images also demonstrated various skeletal characteristics of ROD. This case emphasizes the utility of bone scintigraphy for the surveillance of the whole body in ROD. Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved. Source

A combination of low-temperature scanning tunneling microscopy and density functional theory calculations was used to determine the adsorption characteristics of single pyridine molecules on Ag(1 1 0) surfaces. Pyridine was chemisorbed onto Ag(1 1 0) surfaces at 13 K in either the stand-up or flat-lying configuration. The fractional ratio of the two configurations depended on the molecular coverage: at very low coverage, the flat-lying pyridine predominated on the surface; however, the molecules stood up with increasing surface coverage until the stand-up configuration was favored. The adsorption configurations were characterized by distinct C-H stretching vibrational energies, hopping barriers, and binding characteristics: (i) The C-H stretching energy for the flat-lying configuration was lower than that of the stand-up configuration. (ii) The hopping barrier for the stand-up configuration along the [1over(1, ̄) 0] direction was the lowest. (iii) The electrostatic interaction was the dominant contribution to the binding of pyridine on Ag surfaces in both configurations, although the interaction was especially strong for the flat-lying configuration. © 2009 Elsevier B.V. All rights reserved. Source

In this article, the effect of an incomplete frequency range on relaxation spectra calculated with the new spline-based method (Stadler and Bailly, Rheol Acta 48(1):33-49, 2009) presented before is discussed. The range, in which the spectrum can be determined, is limited by the range of the input data, but not directly by the inverse frequency. The actual limits depend on the range of input data. Depending on the shape of the spectrum the relaxation spectrum can be determined from the input data in a range up to three decades larger than the input data. This can be explained by the influence of the modes outside the inverse frequency range. For this purpose, a new concept, the relevance factor analysis, was introduced, which allows for a determination of the limits of spectrum calculation. The characteristic relaxation times are discussed in comparison for to the calculation of Je 0 and η0 from the spectrum. © 2010 Springer-Verlag. Source

Direct one-step aminolysis of high free fatty acid containing triglycerides of used cotton seed oil, karanja oil and jatropha oil was investigated using a new heterogeneous catalyst. The catalyst, 2.5-NaOH/CaO, was prepared in nanocrystalline form by using simple wet chemical method. Complete conversion of used cotton seed oil (99%) to fatty alkanolamides has been obtained in 45 min with the prepared catalyst when 5 wt% of catalyst amount and 6:1 M ratio of diethanolamine/oil were used. The catalyst was equally active for the transesterification reaction of similar feed stocks. The prepared fatty acid alkanolamides was found to improve lubricity of diesel fuel significantly. © 2015 Elsevier Ltd. All rights reserved. Source

Cho I.S.,Chonbuk National University
Journal of Mechanical Science and Technology | Year: 2015

Numerous studies have been conducted on hydraulic systems operating under high pressure. However, such systems are difficult to realize because of mechanical limitations as a result of tribological problems between relative sliding parts. Design techniques, manufacturing techniques, and tribological characteristics must be improved or innovated to operate such systems under increased pressure. The stress distributions and optimum design factors needed to satisfy these requirements under maximum pressure are determined by analyzing the stress on the valve plate of a hydraulic axial piston pump. This pump is among the most important relative sliding parts. As per the result of the analysis conducted using an orthogonal array, the extent of the influence of the design factors on maximum stress value is ordered as follows: [z > M > h > r]. Moreover, the maximum stress value of the optimum model is 13.3% lower than that of the standard model. Results also show that the stress characteristic of the optimum model is more stable than that of the standard model. © 2015, The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg. Source

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. Source

Ryu S.H.,Chonbuk National University
International Journal of Precision Engineering and Manufacturing | Year: 2015

In this research, eco-friendly electrochemical machining (ECM) characteristics for drilling and milling stainless steel using microwire and microfoil electrodes in citric acid electrolyte are investigated. According to cell configuration and applied pulse conditions, extraordinary phenomena such as tool electrode cut-off due to Joule heating followed by fractured tool welding to the work substrate, electrolyte capillary action around the tool electrode, and tool shaking by evolved bubbles are observed and their effects on micro ECM performances are discussed. Complex micro/nano textures were found on the inner wall of the drilled holes under strict pulse conditions and their generation mechanism is described. Metal structure formed on the bottom of the blind hole under weak electric conditions hinders further drilling. By adjusting electrochemical conditions, micro holes, 37 μm in diameter with 100 μm depth and 26 μm in diameter with 50 μm depth, are drilled using a 10 μm thick tungsten wire electrode. A complex micro hand pattern is fabricated by electrochemical milling on SS 304 substrate. Furthermore, high quality micro grooves with dimension of 34 μm wide and 17 μm deep are machined using 20 μm thick stainless steel foil electrode. Finally, micro electrochemical reverse drilling technique is newly suggested and its effectiveness on machining time reduction is validated. © 2015, Korean Society for Precision Engineering and Springer-Verlag Berlin Heidelberg. Source

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. Source

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. Source

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. Source

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. Source

Radi M.,University of Technology Malaysia | Dezfouli B.,University of Technology Malaysia | Bakar K.A.,University of Technology Malaysia | Lee M.,Chonbuk National University
Sensors | Year: 2012

A wireless sensor network is a large collection of sensor nodes with limited power supply and constrained computational capability. Due to the restricted communication range and high density of sensor nodes, packet forwarding in sensor networks is usually performed through multi-hop data transmission. Therefore, routing in wireless sensor networks has been considered an important field of research over the past decade. Nowadays, multipath routing approach is widely used in wireless sensor networks to improve network performance through efficient utilization of available network resources. Accordingly, the main aim of this survey is to present the concept of the multipath routing approach and its fundamental challenges, as well as the basic motivations for utilizing this technique in wireless sensor networks. In addition, we present a comprehensive taxonomy on the existing multipath routing protocols, which are especially designed for wireless sensor networks. We highlight the primary motivation behind the development of each protocol category and explain the operation of different protocols in detail, with emphasis on their advantages and disadvantages. Furthermore, this paper compares and summarizes the state-of-the-art multipath routing techniques from the network application point of view. Finally, we identify open issues for further research in the development of multipath routing protocols for wireless sensor networks. © 2012 by the authors; licensee MDPI, Basel, Switzerland. Source

Zhao J.,China Jiliang University | Wang Z.,China Jiliang University | Park D.S.,Chonbuk National University
Neurocomputing | Year: 2012

The ensemble of online sequential extreme learning machine (EOS-ELM), an average of several online sequential extreme learning machines (OS-ELMs), can learn data one-by-one or chunk-by-chunk with fixed or varying chunk size. EOS-ELM provides higher accuracy with fewer training time, better generalization performance and stability than other popular sequential learning algorithms. However, in plenty of practical applications such as stock forecast, weather forecast, etc., training data often have timeliness, that is, each datum has a period of validity. In order to reflect the timeliness of training data in the process of learning, an improved EOS-ELM, called online sequential extreme learning machine with forgetting mechanism (FOS-ELM), is proposed in this paper. The proposed FOS-ELM cannot only retain the advantages of EOS-ELM, but also improve the learning effects by discarding the outdated data quickly in the process of learning to reduce their bad affection to the following learning. Detailed performance comparisons of FOS-ELM are carried out with EOS-ELM in the stock price short-term predictions. The experimental results show that FOS-ELM has higher accuracy with fewer training time, better stability and short-term predictability than EOS-ELM. © 2012 Elsevier B.V. Source

In this paper, the bending properties of woven carbon/glass and carbon/aramid fabric-reinforced polymer laminates is studied using a combination of experimental analysis and fracture observation. Six types of each hybrid composite were manufactured by lamination of the carbon/aramid fabric and carbon/glass fabric using VARTM. Bending behaviors were fundamentally evaluated for the six types of monolithic composites laminated by the same fabric. The objective was to achieve a good bending strength by effective combination of composite structures using limited amounts of a raw material. It was shown that the bending property was different, depending on the type of fiber, lamination structure, and the number of layers. © 2016, The Korean Fiber Society and Springer Science+Business Media Dordrecht. Source

Kwon S.-D.,Chonbuk National University
Applied Physics Letters | Year: 2010

This paper proposes a T-shaped piezoelectric cantilever for generating electric power from fluid flow. The working principle of the device is based on aeroelastic flutter and utilizes a bimorph cantilever with T-shape which hastens occurrence of flutter at a low fluid speed. A prototype device (100×60×30 mm3) was tested in a wind tunnel. The device was found to provide power from a wind speed of 4 m/s and a continuous peak electrical power output of 4.0 mW. The simplicity of the present device consisting of only a bimorph cantilever is considered to be cost effective. © 2010 American Institute of Physics. Source

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. Source

Clarkson J.,University of Otago | Han S.-K.,Chonbuk National University | Liu X.,University of Otago | Lee K.,University of Otago | Herbison A.E.,University of Otago
Molecular and Cellular Endocrinology | Year: 2010

Studies undertaken in many species indicate that kisspeptin-Gpr54 signaling is essential for the activation of gonadotropin-releasing hormone (GnRH) neurons to bring about puberty. Investigations in transgenic mouse models, in particular, have highlighted the importance of kisspeptin signaling at the level of the GnRH neuron itself in this process. This review aims to highlight current understanding of the neurobiological mechanisms underlying the kisspeptin activation of postnatal GnRH neurons. The three key features of the kisspeptin-Gpr54-GnRH neuron axis leading up to puberty are (i) the expression of adult-like levels of Gpr54 mRNA in GnRH neurons well in advance of puberty, (ii) a modest increase in the electrical response of GnRH neurons to Gpr54 activation across postnatal development and (iii), the " sudden" appearance of kisspeptin fibers surrounding GnRH neuron cell bodies/proximal dendrites just prior to puberty onset. These kisspeptin fibers are likely to originate from the kisspeptin population located in the rostral periventricular region of the third ventricle (RP3V). Together, available data suggest that the key step in the kisspeptin control of puberty lies in the control of kisspeptin synthesis within RP3V kisspeptin neurons that innervate GnRH neurons. This has recently been shown to be dependent upon circulating estradiol concentrations. As such, we propose that RP3V kisspeptin neurons represent a critical estradiol-dependent amplification mechanism brought into play relatively late in pubertal development to activate GnRH neurons and complete the process of puberty onset. Subsequently, in the adult female, this same circuitry is used to activate GnRH neurons to generate the cyclical preovulatory GnRH/LH surge. © 2010 Elsevier Ireland Ltd. Source

The present work reports on the process of modeling chairs and occupants to closely approximate the sound absorption of occupied full scale theatre chairs and explains how the best form of model listener was determined. Modifying the form of the model listeners to have shorter upper legs and narrower lower legs, led to improved agreement between model and full scale occupied chairs at all frequencies including at 125 Hz. The measured absorption coefficients of single blocks of model chairs with or without model listeners agreed well with the measured values for both full scale types E and G chairs. However, the estimated values for larger sample blocks of model chairs with P/A = 0.5 m-1 showed better agreement with the measured values for full scale type G chairs than type E chairs due to the different slopes of the regression lines versus P/A. The present results demonstrate that the model chair and listener accurately simulate the sound absorption characteristics of a particular type of quite absorptive full scale occupied chairs for all sample sizes of the full scale chairs. © 2013 Elsevier Ltd. All rights reserved. Source

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. Source

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. Source

Jo S.-U.,Kumoh National Institute of Technology | Kim D.-H.,Kumoh National Institute of Technology | Yang J.-S.,Korea Institute of Science and Technology | Baek K.,Chonbuk National University
Electrochimica Acta | Year: 2012

In South Korea, the agricultural use of greenhouses has increased gradually. Salt accumulation in greenhouses is an important issue because of their unique characteristics, including high temperatures and interception of rainfall. Even though an electrokinetic process could remove salts from the soil, energy consumption is a major barrier to widespread application of these systems. In this study, the effectiveness of a pulsed electrokinetic process in reducing the electrical energy consumption during the restoration of saline soil was investigated. The pulsed electrokinetic process lowered the electrical energy consumption to 42% of that of the conventional process, while producing a similar decrease in salinity. The frequency of on/off switching did not influence the total reduction in salinity, but the amounts of sulfate and Ca removed were correlated with the on/off frequency positively and negatively, respectively. From these results, it was concluded that a pulsed electrokinetic process is an effective technique for reducing energy consumption in the electrokinetic restoration of saline soil. © 2012 Elsevier Ltd. All rights reserved. Source

Lee C.-S.,Chonbuk National University
Journal of the Korean Medical Association | Year: 2010

Influenza viruses cause annual epidemics and occasional pandemics that have claimed the millions of lives. On December 4th 2009, more than 207 countries and overseas territories have reported laboratory confirmed cases of pandemic influenza H1N1 2009, which has claimed at least 8768 lives. Up to this date, the pandemic influenza H1N1 2009 has spread throughout the world with unprecedented speed. Accurate and rapid diagnosis of this influenza virus is critical for minimizing further spread, combined with timely implementation of antiviral treatment and public health based measures. Recently, the percentage of oseltamivir- resistant human seasonal H1N1 has increased to 98.5% in USA, and 99.8% in Korea. Fortunately, the pandemic influenza H1N1 2009 is sensitive to neuraminidase inhibitors, including oseltamivir. However, the percentage oseltamivir-resistant pandemic influenza H1N1 2009 is expected to increase with time. In this review, the various diagnostic method and the antiviral agents that have been reported in the literature will be discussed. Source

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. Source

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. Source

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. Source

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. Source

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. Source

It is well known that androgen deprivation relates to penile fibrosis, so we hypothesize that long-term treatment with 5-alphareductase inhibitors (5ARIs) may increase the risk of fibrosis of prostate. Thirty-two BPH patients who underwent transurethral resection of the prostate were enrolled. The patients were divided into two groups: group one, 16 patients underwent TURP who had been treated with tamsulosin for 2 years; group two, 16 patients underwent TURP who had been treated with combination of tamsulosin and dutasteride for at least 1 year. We evaluated the expressions of nNOS, iNOS, eNOS, TGF-β1, TGF-β2, phosphorylated-Smad2/3 (p-Smad2/3), E-cadherin, N-cadherin, and α-smooth muscle actin in the resected prostate tissues by western blotting, and the TGF-β concentration was determined by ELISA kit. The expressions of 3 isoforms of NOS were significantly increased in group 2 except of eNOS in lateral prostate, and the expressions of TGF-β1, TGF-β2, and p-Smad2/3 increased about 2-fold compared with group 1. In group 2, the E-cadherin expression decreased while N-cadherin expression increased significantly. The overexpression of nNOS may contribute to prostate smooth muscle relaxation; however, long-time treatment with 5 ARI increases the risk of fibrosis of prostate. Source

Park W.H.,Chonbuk National University
Molecular Medicine Reports | Year: 2011

Gallic acid (GA) has various biological properties, including an anti-cancer effect. However, little is known about the toxicological effect of GA in primary normal cells in relation to mitogen-activated protein kinase (MAPK) signaling. In this study, we investigated the effects of MAPK (MEK, JNK or p38) inhibitors on GA-treated human pulmonary fibroblast (HPF) cells in relation to cell growth inhibition, cell death, reactive oxygen species (ROS) and glutathione (GSH). GA induced HPF cell growth inhibition and cell death at 24 h, which was accompanied by the loss of mitochondrial membrane potential (MMP; ΔΨ m). GA increased ROS levels and GSH-depleted cell numbers in the HPF cells. The MEK inhibitor did not affect cell growth inhibition, cell death, ROS and GSH levels in the GA-treated HPF cells. The JNK inhibitor slightly enhanced cell growth inhibition by GA, while the p38 inhibitor significantly prevented the growth inhibition. Both JNK and p38 inhibitors did not affect cell death, ROS and GSH levels in the GA-treated HPF cells. In conclusion, MAPK inhibitors differentially affected the growth inhibition of GA-treated HPF cells, which were not related to cell death, ROS and GSH levels. Source

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. Source

Jeong S.-K.,Chonbuk National University | Cho Y.I.,Drexel University | Duey M.,ProMetrics Consulting Inc. | Rosenson R.S.,Mount Sinai School of Medicine
Cardiovascular Drugs and Therapy | Year: 2010

To date, all major clinical trials for anemia correction using erythrocyte stimulating agents (ESAs) failed to show improved outcomes for cardiovascular disease (CVD), stroke, and vascular thrombosis. Even moderate elevations in hemoglobin (e.g., to 13 g/dL) using erythropoietin have been associated with significantly increased risk of thrombotic cardiovascular events and heart failure. This review presents a biophysical rationale for increased risk of CVD among certain patients treated with ESAs and suggests a risk management approach based on blood viscosity. Whole blood viscosity is a key determinant of the work of the heart, and elevated blood viscosity appears to be both a strong predictor of cardiovascular disease and an important pathophysiological factor in the development of atherothrombosis. Blood donation has been shown to reduce viscosity. Reflecting these findings, studies in male blood donors and in women of premenopausal age with regular menstruation have shown reduced incidence of cardiovascular events such as myocardial infarction, angina, stroke, and the requirement for procedures such as percutaneous transluminal coronary angioplasty and coronary artery bypass graft compared with non-donors and postmenopausal women, respectively. We propose that blood viscosity monitoring should be considered as part of a cardiovascular risk assessment, whenever an increased cardiovascular risk is detected and particularly in the context of anemia correction. © 2010 Springer Science+Business Media, LLC. Source

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. Source

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. Source

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. Source

Park S.,Korea Advanced Institute of Science and Technology | Youn Moon S.,Chonbuk National University | Choe W.,Korea Advanced Institute of Science and Technology
Applied Physics Letters | Year: 2013

As many as eight multiple plasma bullets produced at atmospheric pressure were observed in one voltage period in a capillary helium dielectric barrier plasma jet. We found that the number of the bullets strongly depends on the nitrogen fraction added to the helium supply gas. Using optical emission spectroscopy and ionization rate calculation, this study demonstrates that nitrogen gas plays an important role in the generation and dynamics of multiple plasma bullets through Penning ionization of nitrogen by helium metastables. © 2013 AIP Publishing LLC. Source

Cho I.S.,Chonbuk National University
Journal of Mechanical Science and Technology | Year: 2015

The performance of a reciprocating compressor in refrigeration and air-conditioning systems is influenced by the lubrication characteristics of the critical sliding components. Improvements in design and performance of reciprocating compressors therefore depend in part upon the lubrication characteristics between the crankshaft and journal bearing. Current studies have explored experimental and theoretical methods, yet difficulties arise when applying these results to practical designs in the field. The present study seeks to enhance the energy efficiency ratio, and to improve the reliability of the reciprocating compressor for refrigeration and air conditioning systems by studying the influence of boundary conditions on the lubrication characteristics between the crankshaft and journal bearing. The results demonstrate that appropriate boundary conditions, when applied to theoretical analysis, improve both the speed and ease of the design process. © 2015, The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg. Source

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. Source

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. Source

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. Source

Lee H.-S.,Chonbuk National University
Journal of Applied Biological Chemistry | Year: 2015

The composition of the essential oil of Ligustrum japonicum leaves was determined by GC-MS analysis. The major constituents of L. japonicum leaf oil were germacrene D (40.50%), α-pinene (13.63%), (−)-β-elemene (6.42%), β-caryophyllene (5.73%), and δ-cadinene (5.47%). The acaricidal activities of L. japonicum oil were evaluated against acaridae and pyroglyphid mites. In the fumigant bioassay, the LD50 values of L. japonicum oil were 16.48, 12.38, and 15.63 μg/cm3 against Tyrophagus putrescentiae, Dermatophagoides farinae, and D. pteronyssinus, respectively. In the contact bioassay, the LD50 values of L. japonicum oil were 8.02, 5.02, and 7.67 μg/cm2 against T. putrescentiae, D. farinae, and D. pteronyssinus, respectively. © The Korean Society for Applied Biological Chemistry 2015. Source

Jeong T.W.,Backje daero | Ahn J.Y.,Chonbuk National University | Lee C.D.,Backje daero
International Journal of Innovative Computing, Information and Control | Year: 2013

Transcoding has a significant effect on streaming media services in wireless networks. The goal of this paper is to reduce network traffic due to high network bandwidth demand and streaming constraints, and enhance the performance of streaming media services. Therefore, we propose a new OVT (object version transcoding) mechanism based on fuzzy similarity. This work derives a media object relationship to calculate the individual fuzzy similarity of certain versions of a media object. We take into account transcoding constraints such as media object characteristics, cache capacity and the properties of the object versions. Based on the given constraints, the proposed mechanism reduces the startup delay and congestion, and it increases the response rate and cache hit rate. We obtained excellent results in terms of QoS (Quality of service) metrics, average service response ratio, startup latency and cache-hit ratio. © 2013 ICIC International. Source

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. Source

Imayama T.,Chonbuk National University
Swiss Journal of Geosciences | Year: 2014

Metabasites exposed in far-eastern Nepal provide an important insight into the metamorphic evolution of the Himalayan orogen independent from data obtained on metapelites. The P-T conditions and formation process of mafic granulite intercalated within Early Oligocene migmatites and two amphibolites surrounded by Early Miocene metapelites were inferred from pseudosection modeling and conventional geothermobarometry combined with the occurrences of field and microstructures. A mafic granulite in the Higher Himalaya Crystalline Sequence (HHCS) yields P-T conditions of 6.5-8 kbar, 730-750 °C. The similar peak P-T condition and retrograde path with low P/T gradient of mafic granulite and surrounding migmatite indicate that both rocks were simultaneously metamorphosed and exhumed together along the tectonic discontinuities in the HHCS. In contrast, the P-T conditions (2-5 kbar, 500-600 °C) of highly-deformed amphibolite block above the Main Central Thrust (MCT) records significantly lower pressure than garnet-mica gneisses in the country rock, suggesting that the amphibolite block derived from upper unit of the MCT zone and became tectonically mixed with the gneisses of hanging wall near the surface. An amphibolite lense below the MCT preserves the prograde P-T conditions (6-7.5 kbar, 550-590 °C) of Early Miocene syn-tectonic metamorphism that occurred in the MCT zone. This study indicates the top-to-the south movement of the MCT zone results in the tectonic assembly of rocks with different P-T-t conditions near the MCT. © 2014 Swiss Geological Society. Source

Choi S.Y.,Chonbuk National University | Englert C.,University of Glasgow | Zerwas P.M.,German Electron Synchrotron
European Physical Journal C | Year: 2013

We develop a phenomenological formalism for mixing effects between the Standard Model and hidden-sector fields, motivated by dark matter in the Universe as well as string theories. The scheme includes multiple Higgs-portal interactions in the scalar sector as well as multiple gauge-kinetic mixings in the abelian gauge sector. While some of the mixing effects can be cast in closed form, other elements can be controlled analytically only by means of perturbative expansions in the ratio of standard scales over large hidden scales. Higgs and vector-boson masses and mixings are illustrated numerically for characteristic processes. © 2013 Springer-Verlag Berlin Heidelberg and Società Italiana di Fisica. Source

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. Source

Lee C.-S.,University of Pittsburgh | Lee C.-S.,Chonbuk National University | Doi Y.,University of Pittsburgh
Infection and Chemotherapy | Year: 2014

The prevalence of carbapenem-resistant gram-negative bacterial pathogens (CRGNs) has increased dramatically during the last 10 years, but the optimal treatment for CRGN infections is not well established due to the relative scarcity of robust clinical data. The polymyxins remain the most consistently active agents against CRGNs in vitro. Tigecycline, based on its in vitro antibacterial spectrum, could also be considered as a therapeutic option in the treatment of infections caused by certain CRGNs. Other agents, including aminoglycosides, rifampin, trimethoprim-sulfamethoxazole, fosfomycin and fluoroquinolones, could be considered as monotherapy or combination therapy against CRGNs in appropriate contexts, as combination therapy with two or more in vitro active drugs appears to be more effective than monotherapy based on some clinical data. Several promising new agents are in late-stage clinical development, including ceftolozane-tazobactam, ceftazidime-avibactam and plazomicin. Given the shortage of adequate treatment options, containment of CRGNs should be pursued through implementation of adequate infection prevention procedures and antimicrobial stewardship to reduce the disease burden and prevent future outbreaks of CRGNs. © 2014 by The Korean Society of Infectious Diseases. Source

Oh S.W.,Chonbuk National University
Journal of the Korean Wood Science and Technology | Year: 2016

This study investigated electrical properties and far-infrared ray emission according to the carbonizing temperature and phenol-formaldehyde (PF) resin impregnation ratio of ceramics manufactured using sawdust and rice husk. The far-infrared ray emission values and emission energy values decreased as the carbonizing temperature increased. The far-infrared ray emission values of the ceramics manufactured using a carbonizing process at 600°C and a board with a PF resin impregnation ratio of 60 percent was 0.930; the emission energy presented the highest value of 4.32 × 10 w/m2. The electric resistance decreased as the carbonizing temperature increased. For the increase in the carbonizing temperature above 1200°C, ceramics was very close to a conductor due to the small resistance. The power consumption increased by the decrease of electric resistance and increase of the electric current in the case of a higher resin impregnation ratio. Source

Ragetly G.,Urbana University | Griffon D.J.,Urbana University | Chung Y.S.,Chonbuk National University
Acta Biomaterialia | Year: 2010

The biocompatibility of chitosan and its similarity to glycosaminoglycans (GAG) make it attractive for cartilage tissue engineering. We have previously reported improved chondrogenesis but limited cell adhesion on chitosan scaffolds. Our objectives were to produce chitosan scaffolds coated with different densities of type II collagen and to evaluate the effect of this coating on mesenchymal stem cell (MSC) adhesion and chondrogenesis. Chitosan fibrous scaffolds were obtained by a wet spinning method and coated with type II collagen at two different densities. A polyglycolic acid mesh served as a reference group. The scaffolds were characterized by Fourier-transform infrared spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and type II collagen content. Constructs were analyzed after MSCs seeding via live/dead assay, weight and DNA evaluations, SEM, and TEM. Constructs were cultured in chondrogenic medium for 21 days prior to quantitative analysis (weight, DNA, and GAG), SEM, TEM, histology, immunohistochemistry, and quantitative real time polymerase chain reaction. The cell attachment and distribution after seeding correlated with the density of type II collagen. The cell number, the matrix production, and the expression of genes specific for chondrogenesis were improved after culture in collagen coated chitosan constructs. These findings encourage the use of type II collagen for coating chitosan scaffolds to improve MSCs adhesion and chondrogenesis, and confirm the importance of biomimetic scaffolds for tissue engineering. © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Source

Huh C.,Electronics and Telecommunications Research Institute | Kim K.-H.,Electronics and Telecommunications Research Institute | Kim B.K.,Electronics and Telecommunications Research Institute | Kim W.,Electronics and Telecommunications Research Institute | And 3 more authors.
Advanced Materials | Year: 2010

The light output power and wall-plug efficiency of the Si nanocrystal (nc-Si) light-emitting diode (LED) were significantly enhanced by employing the multiple-luminescent structures. This improvement was attributed to a strong confinement of carriers in the SiNx luminescent layers containing the nc-Si due to the band offset between the luminescent layer and barrier layer. Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Lee H.-S.,Chonbuk National University
Journal of Applied Biological Chemistry | Year: 2011

The inhibitory effects of Rubia tinctorum root-derived materials against nitric oxide (NO) production were assessed by evaluation of NO production and inducible NO synthase (iNOS) expression, and compared to those of trihydroxyanthraquinone derivatives. The inhibitory effect of 1,2,4-trihydroxyanthraquinone (purpurin) from R. tinctorum roots against NO production was 60.7 and 38.5% at 2.5 and 1.25 μg/mL, respectively. Inhibitory effect of 1,2,7-trihydroxyanthraquinone was 52.5% at 2.5 μg/mL. Suppression effects of 1,2,4-trihydroxyanthraquinone on iNOS expression were confirmed by western blot analysis. Source

Kim Y.-H.,Korea Electronics Technology Institute | Kim Y.-H.,Seoul National University | Han M.-K.,Seoul National University | Han J.-I.,Korea Electronics Technology Institute | Park S.K.,Chonbuk National University
IEEE Transactions on Electron Devices | Year: 2010

We report the combinatorial study on surface morphology and electrical properties of solution-processed amorphous indium-gallium-zinc-oxide (α-IGZO) thin-film transistors (TFTs). The sol-gel-processed α-IGZO thin films typically have shown an amorphous structure and critical dependence of mobility, carrier concentration, and surface roughness on the In, Ga, and Zn molar ratio in the solution phase. Based on efficient control of the metallic components from the sol-gel process, the solution-processed α-IGZO TFTs with a mobility of 0.5-2 cm2/V·s, on/off current ratio > 107, and a subthreshold slope of as steep as 1.5 V/dec were obtained. © 2010 IEEE. Source

Hong S.-H.,Korea Institute of Machinery and Materials | Song M.Y.,Chonbuk National University
Metals and Materials International | Year: 2013

Fe-Ti alloys were prepared by applying a pulsed electric current through compacted mixtures of iron, manganese and titanium oxide (with carbon) or titanium hydride (without carbon). After ball milling the mixture into a fine powder, the mixture was heated up to 1373-1573 K in a carbon mold by applying a pulsed electric current, and the temperature was maintained for 3-10 min. When TiO2 was used as a starting material, TiC was formed. Fe was alloyed into FeTi and Fe2Ti, with Ti also observed. When the C content was lowered to 8.136 wt%, the remaining C content after pulsed current application decreased to 4.64 wt%. When using TiH2 as a starting material, Fe was alloyed into FeTi and Fe2Ti, and Ti, Mn, Fe, and FeMn2 were also observed. For a Fe-Ti alloy prepared using titanium hydride as a starting material, hydrogen content vs. absorption time curves were obtained at various numbers of cycles and temperatures. © 2013 The Korean Institute of Metals and Materials and Springer Science+Business Media Dordrecht. Source

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

We report on a pixel whose aperture can be varied electrically. The pixel is confined by a hole-patterned polymer wall and a dielectric liquid forms a ring shape around the wall surface. Without an electric field, the pixel has the largest aperture. The applied fringing field stretches the liquid surface, leading to a decrease in the aperture size. The switchable aperture ratio of the pixel is over 80% and the response time is ̃10 ms. Such a device is useful for an optical attenuator, a light shutter, an adaptive iris, and an information display. © 2012 Optical Society of America. Source

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. Source

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. Source

Choi B.-Y.,Chonbuk National University
Journal of Korean Institute of Metals and Materials | Year: 2010

We fabricated flanged outer races for wheel bearing units using 0.52%C clean steels, and then characterized and studied the transformation behavior. The outer races produced by hot forging and high frequency induction hardening in this study were analyzed through microstructural characterization using OM, SEM, TEM, and X-ray diffractometer and their microhardness depth profiles of the raceway contacted by balls were measured using MVH tester. The surface hardened layers with a uniform hardness profile in the raceway consisting of very fine martensite with sub-micron sized retained austenite could be formed for very short time during high frequency induction hardening after hot forging. The very fine martensite may be transformed on rapid cooling, from the inhomogeneous austenite nucleated on rapid heating in small particles of pearlitic cementite fragmentated by hot forging. On the other hand the sub-micron sized retained austenite may be chemically stabilized due to their extremely small size, from the small austenite nucleated at the grain boundaries. Source

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. Source

Choi Y.-J.,Chonbuk National University
Applied Acoustics | Year: 2013

The present study investigates the application of periodic type diffusers for improving the acoustics in classrooms and proposes an optimum combination of absorptive and diffusing treatments for achieving preferred acoustics in classrooms. The measurements were carried out in a 1/10 scale model classroom, adding different amounts of absorptive and diffusing materials to one or more of five surfaces of the room. Adding absorptive materials on the entire ceiling area and diffusers on each wall increased early-to-late arriving sound ratio (C50) values corresponding to higher clarity. Adding diffusers on 25% of the ceiling area with the other 75% absorptive was more beneficial for achieving higher G50 and G values than adding absorptive materials on the entire ceiling. Diffusers were beneficial for enhancing the early arriving reflection energy (G50) at the most distant seats and they resulted in achieving more uniform acoustical conditions across the room. The treatment of the front wall with diffusers was found to lead to better acoustical conditions than treating the rear and side walls with diffusers. Adding diffusers on the ceiling and lower front wall or side wall and adding diffusers on the ceiling and absorptive materials on the lower front wall were selected for consideration as the more successful treatments for classroom acoustic design. © 2012 Elsevier Ltd All rights reserved. Source

Seo K.-W.,Kyung Hee University | Lee J.-H.,Kyung Hee University | Kim H.-J.,Kyung Hee University | Kim H.-K.,Kyung Hee University | Na S.-I.,Chonbuk National University
Applied Physics Letters | Year: 2014

We investigated characteristics of Ti-doped In2O3 (TIO)/Ag nanowire (NW)/TIO films as potential transparent and flexible electrodes for flexible organic solar cells. Effective insertion of metallic Ag NW between TIO layers led to improvement of electrical and mechanical properties of sputtered TIO film. At optimized conditions, we achieved a flexible TIO/Ag NW/TIO multilayer with a low sheet resistance of 9.01 Ω/square and a high optical transmittance of 85.14%. In addition, the TIO/Ag NW/TIO multilayer electrode showed small inner and outer bending radius of 5 and 6.5 mm indicating good flexibility. This indicates that hybridization of sputtered TIO films and printed Ag NW network is a promising solution to solve critical problems of high resistance and brittle TIO film and Ag NW network with poor adhesion. © 2014 AIP Publishing LLC. Source

Jeong J.K.,Chonbuk National University
Neurobiology of aging | Year: 2012

The human prion protein fragment, PrP (106-126), may contain a majority of the pathological features associated with the infectious scrapie isoform of PrP, known as PrP(Sc). Based on our previous findings that hypoxia protects neuronal cells from PrP (106-126)-induced apoptosis and increases cellular prion protein (PrP(C)) expression, we hypothesized that hypoxia-related genes, including hypoxia-inducible factor-1 alpha (HIF-1α), may regulate PrP(C) expression and that these genes may be involved in prion-related neurodegenerative diseases. Hypoxic conditions are known to elicit cellular responses designed to improve cell survival through adaptive processes. Under normoxic conditions, a deferoxamine-mediated elevation of HIF-1α produced the same effect as hypoxia-inhibited neuron cell death. However, under hypoxic conditions, doxorubicin-suppressed HIF-1α attenuated the inhibitory effect on neuron cell death mediated by PrP (106-126). Knock-down of HIF-1α using lentiviral short hairpin (sh) RNA-induced downregulation of PrP(C) mRNA and protein expression under hypoxic conditions, and sensitized neuron cells to prion peptide-mediated cell death even in hypoxic conditions. In PrP(C) knockout hippocampal neuron cells, hypoxia increased the HIF-1α protein but the cells did not display the inhibitory effect of prion peptide-induced neuron cell death. Adenoviruses expressing the full length Prnp gene (Ad-Prnp) were utilized for overexpression of the Prnp gene in PrP(C) knockout hippocampal neuron cells. Adenoviral transfection of PrP(C) knockout cells with Prnp resulted in the inhibition of prion peptide-mediated cell death in these cells. This is the first report demonstrating that expression of normal PrP(C) is regulated by HIF-1α, and PrP(C) overexpression induced by hypoxia plays a pivotal role in hypoxic inhibition of prion peptide-induced neuron cell death. These results suggest that hypoxia-related genes, including HIF-1α, may be involved in the pathogenesis of prion-related diseases and as such may be a therapeutic target for prion-related neurodegenerative diseases. Copyright © 2012 Elsevier Inc. All rights reserved. Source

Choi B.H.,Chonbuk National University | Hahn S.J.,Catholic University of Korea
Acta Pharmacologica Sinica | Year: 2010

K + channels, which are ubiquitous membrane proteins, play a central role in regulating the resting membrane potential and the shape and duration of the action potential in pancreatic Β-cells. There are at least three types of K + channels (K ATP, K Ca, and Kv2.1 channels) that are involved in glucose-stimulated insulin secretion in pancreatic Β-cells, and one type (Kv1.3) that is associated with the regulation of insulin sensitivity in peripheral target tissues. This article reviews the function of Kv1.3 channels that contribute to mediating insulin action in insulin-sensitive tissues. Pharmacological strategies for targeting Kv1.3 are then discussed with a focus on a rationale for the potential therapeutic use of Kv1.3 blocker in diabetic treatment. © 2010 CPS and SIMM All rights reserved. Source

Bak Y.-S.,Chonbuk National University
Quaternary International | Year: 2015

Diatoms from the KS2009 core sediment on the coast of the West Sea, Kunsan-si and the KR07 trench sediment collected from the neighboring Sabsi island, Korea, were analyzed for Holocene sea-level fluctuations. In KS2009 core sediment, results of AMS 14C dating identified five stratigraphic horizons ranging from 2200 to 9100BP. The results obtained by measuring the radiocarbon dating from the KR07 were as follows:-0.34m.a.s.l: 6108BP,-0.74m: 6488BP,-1.46m: 6838BP, and-1.58m: 7208BP. Diatom assemblages from KS2009 indicated: Facies A (barren zone: KS2009 (-23.5to-20.3m))→Facies B (high tidal flat: KS2009 (-20.3to-14.6m)): Holocene marine transgression→Facies C (mid tidal flat: KS2009 (-14.6to-2.0m)): falling sea-level-rising sea-level→Facies D (high tidal flat: KS2009 (-2to2m)): rising sea-level. Thus, after seawater influx started at 8300BP, seawater rose with fluctuations (rising and falling). The KR-07 trench deposit of Sabsi island showed: Facies A' (barren zone: KR07 (-1.58to-1.18m))→Facies B' (bog: KR07 (-1.18to-0.76m))→Facies C' (tidal marsh: KR07 (-0.76to-0.52m))→Facies D' (tidal flat: KR07 (-0.52to-0.28m))→Facies E' (tidal marsh: KR07 (-0.28to-0.08m))→ Facies F' (tidal flat: KR07 (-0.08 to 0.06m)). Transgression occurred first about 8,300BP at the west coast of Korea: around 6300-6000BP, there was a drop in the sea-level and around 6000-4000BP, there was a rapid rise. Also, Repetition of falling and rising occurred since 4500BP. © 2014 Elsevier Ltd and INQUA. Source

Park M.S.,Chonbuk National University
Journal of orthopaedic surgery (Hong Kong) | Year: 2010

PURPOSE: To investigate the cause of failure in matte-surface cemented stems in second-generation metal-on- metal total hip arthroplasty (THA). METHODS: Records of 26 men and 11 women (39 hips) aged 29 to 72 years who underwent primary cementless THAs by a single surgeon using second-generation metal-on-metal prostheses and were followed up for a mean of 122 (range, 120-141) months were reviewed. Two types of femoral stems were used: a cementless Ti-alloy stem (n=21) and a matte-surface, iron-based alloy, cemented stem (n=18). Clinical outcomes were measured using the Harris hip score. Radiographs were assessed for stem loosening and osteolysis. Patient activity levels were graded. Surfaces of the retrieved femoral stems and periprosthetic tissue samples were examined. Metallic and cement particles were studied. Hypersensitivity to metal was tested. RESULTS: None of the cementless stems were revised; no osteolysis or stem loosening occurred. In contrast, 7 of 18 matte-surface cemented stems were revised owing to stem loosening or osteolysis. Periprosthetic tissues revealed abundant cement-related particles; 90% were zirconium oxides but a few were iron particles. Histological examination of periprosthetic tissues showed perivascular infiltration of lymphocytes and macrophages containing tiny foreign materials. Metal hypersensitivity was not associated with aseptic loosening. CONCLUSION: Metal-on-metal THA with cementless components could be recommended for young, active patients to prevent wear and osteolysis. The matte-surface cemented stem is more likely to fail owing to friction during the earlier stage and cement-related biological processes during the later stage. Source

Lee H.W.,Chonbuk National University
PLoS ONE | Year: 2013

Ssangjungri (SJ), an open-air site with several Paleolithic horizons, was recently discovered in South Korea. Most of the identified artifacts are simple core and flake tools that indicate an expedient knapping strategy. Bifacially worked core tools, which might be considered non-classic bifaces, also have been found. The prolific horizons at the site were dated by accelerator mass spectrometry (AMS) to about 30 kya. Another newly discovered Paleolithic open-air site, Jeungsan (JS), shows a homogeneous lithic pattern during this period. The dominated artifact types and usage of raw materials are similar in character to those from SJ, although JS yielded a larger number of simple core and flake tools with non-classic bifaces. Chronometric analysis by AMS and optically stimulated luminescence (OSL) indicate that the prime stratigraphic levels at JS also date to approximately 30 kya, and the numerous conjoining pieces indicate that the layers were not seriously affected by post-depositional processes. Thus, it can be confirmed that simple core and flake tools were produced at temporally and culturally independent sites until after 30 kya, supporting the hypothesis of a wide and persistent use of simple technology into the Late Pleistocene. © 2013 Hyeong Woo Lee. Source

Xu S.,University of Central Florida | Ren H.,Chonbuk National University | Wu S.-T.,University of Central Florida
Journal of Physics D: Applied Physics | Year: 2013

Tunable optofluidic devices exhibit some unique characteristics that are not achievable in conventional solid-state photonic devices. They provide exciting opportunities for emerging applications in imaging, information processing, sensing, optical communication, lab-on-a-chip and biomedical engineering. A dielectrophoresis effect is an important physical mechanism to realize tunable optofluidic devices. Via balancing the voltage-induced dielectric force and interfacial tension, the liquid interface can be dynamically manipulated and the optical output reconfigured or adaptively tuned in real time. Dielectrophoretically tunable optofluidic devices offer several attractive features, such as rapid prototyping, miniaturization, easy integration and low power consumption. In this review paper, we first explain the underlying operation principles and then review some recent progress in this field, covering the topics of adaptive lens, beam steering, iris, grating, optical switch/attenuator and single pixel display. Finally, the future perspectives are discussed. © 2013 IOP Publishing Ltd. Source

Um J.,Korea Institute for Advanced Study | Hong H.,Chonbuk National University | Marchesoni F.,University of Camerino | Park H.,Korea Institute for Advanced Study
Physical Review Letters | Year: 2012

We demonstrate that a large ensemble of noiseless globally coupled-pinned oscillators is capable of rectifying spatial disorder with spontaneous current activated through a dynamical phase transition mechanism, either of first or second order, depending on the profile of the pinning potential. In the presence of an external weak drive, the same collective mechanism can result in an absolute negative mobility, which, though not immediately related to symmetry breaking, is most prominent at the phase transition. Our results apply to a tug-of-war by competing molecular motors for bidirectional cargo transport. © 2012 American Physical Society. Source

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. Source

Lehwald N.,Stanford University | Lehwald N.,Heinrich Heine University Dusseldorf | Tao G.,Stanford University | Jang K.Y.,Stanford University | And 4 more authors.
Gastroenterology | Year: 2011

Background & Aims: Ischemia and reperfusion injury are common causes of oxidative tissue damage associated with many liver diseases and hepatic surgery. The Wntβ-catenin signaling pathway is an important regulator of hepatic development, regeneration, and carcinogenesis. However, the role of Wnt signaling in the hepatocellular response to ischemia-reperfusion (I/R) injury has not been determined. Methods: Hepatic injury following ischemia or I/R was investigated in hepatocyte-specific, β-catenindeficient mice, as well as Wnt1-overexpressing and wild-type (control) mice. Results: Wntβ-catenin signaling was affected by the cellular redox balance in hepatocytes. Following ischemia or I/R, mice with β-catenindeficient hepatocytes were significantly more susceptible to liver injury. Conversely, mice that overexpressed Wnt1 in hepatocytes were resistant to hepatic I/R injury. Hypoxia inducible factor (HIF)-1α signaling was reduced in β-catenindeficient liver but increased in hepatocytes that overexpressed Wnt1 under hypoxia and following I/R, indicating an interaction between β-catenin and HIF-1α signaling in the liver. The mechanism by which Wnt signaling protects against liver injury involves the role of β-catenin as a transcriptional coactivator of HIF-1α signaling, which promotes hepatocyte survival under hypoxic conditions. Conclusions: Cellular redox balance affects Wntβ-catenin signaling, which protects against hypoxia and I/R injury. These findings might be used to develop strategies for protection of hepatocytes, regeneration of liver, and inhibition of carcinogenesis. © 2011 AGA Institute. Source

Kim J.,Chonbuk National University | Lee H.,Google
Proceedings - International Conference on Data Engineering | Year: 2012

Similarity searches are essential in many applications including data cleaning and near duplicate detection. Many similarity search algorithms first generate candidate records, and then identify true matches among them. A major focus of those algorithms has been on how to reduce the number of candidate records in the early stage of similarity query processing. One of the most commonly used techniques to reduce the candidate size is the prefix filtering principle, which exploits the document frequency ordering of tokens. In this paper, we propose a novel partitioning technique that considers multiple token orderings based on token co-occurrence statistics. Experimental results show that the proposed technique is effective in reducing the number of candidate records and as a result improves the performance of existing algorithms significantly. © 2012 IEEE. Source

Sun J.,Chonbuk National University | Teng J.T.C.,University of Texas at Arlington
Computers in Human Behavior | Year: 2012

Information Systems Use (ISU) is an essential part of the human behaviors in utilizing computers in organizations. The construct has been widely used to measure IS adoption or IS success. However, few studies attempt to understand ISU in a job and organizational setting where employees use various types of IS for different tasks. To better understand ISU, it is necessary to contextualize the construct in users' overall work related activities. We classified the overall IS/IT use in an organization into three different types of IS; Information Reporting Systems (IRSs), Decision Support Systems (DSSs), and Group Support System (GSSs). Based on this classification, we developed four items for each type of ISU behaviors. The resulting ISU instrument was tested using a dataset of 231 responses collected in a survey. Both exploratory factor analysis and PLS are employed to successfully establish reliability, convergent/discriminate validity, and predictive validity. The contribution of this research is to provide better and more robust measurements for the ISU construct, which should help to lay a firmer foundation for further research on IS success. © 2012 Elsevier Ltd. All rights reserved. Source

Romankov S.,Chonbuk National University | Park Y.C.,National NanoFab Center
Journal of Alloys and Compounds | Year: 2015

We observed the moment of material escape from a surface of CoFeNi/Cu/Zr(Al)O2 composite into the amorphous carbon layer when we studied the phase transformation of the structure using in situ transmission electron microscopy (TEM) technique at 800 °C. To protect the top surface of the TEM specimen against focused-ion beam process damage, the specimen had been coated with an amorphous carbon layer, a thin Pt film and a W protective layer. During our high-temperature experiments at 800 °C, we detected that the CoFeNi nanoparticles moved from the surface of the TEM specimen into the amorphous carbon layer. A porous amorphous carbon layer had a large impact on the visualization of this phenomenon. Liquid-like behavior of the CoFeNi phase, which possessed some crystalline order, was detected before the material escaped from the surface. After heating, the carbon layer became tightly packed with small particles and single atoms. The majority of the particles in the carbon layer were in the size range of 1-4 nm. The particles were assigned to the CoFeNi, FePt, and W phases. The CoFeNi particles escaped directly from the specimen surface, while the FePt and W particles were formed in the carbon layer during heating as a result of atomic reactions. The single atoms observed in the carbon layer were attributed to the heavy elements Pt and W. © 2015 Elsevier B.V. Source

Romankov S.,Chonbuk National University | Park Y.C.,National NanoFab Center
Journal of Alloys and Compounds | Year: 2014

A nanolaminated amorphous/crystalline composite structure with a mean lamellar thickness of around 10 nm was fabricated on a Cu plate. The crystalline phase was a multicomponent non-equilibrium face-centered cubic (fcc) Cu(CoFeNi) solid solution, and the amorphous phase was a Zr-based compound containing Al, Cu, and Fe. The composite's thermal stability and microstructural transformation was studied over the temperature range of 200-900 °C. The lamellae maintained their shape during heating up to 600 °C. Transformation of the structure began with separation of the elements inside the crystalline lamellae. In early stages of the transformation, hardening occurred. At 600 °C, an interconnected CoFe phase started to appear with an ordered body-centered cubic (bcc) crystal structure. When the temperature was increased further, the nanolaminated structure degraded and the bcc CoFe phase grew. At 750 °C, the bcc CoFe phase formed a complex network that surrounded the formerly amorphous regions, and the bcc CoFe phase started transforming to the fcc configuration. The Cu atoms segregated to the grain boundaries of the fcc CoFe(Ni) phase. The amorphous phase gradually crystallized into nanometer-sized polycrystalline grains that were attributed to the Zr(Al)O2phase. As a result of these transformations, heating at 900 °C produced a morphologically complex nanocomposite structure consisting of branched grains of Zr(Al)O2and fcc CoFe(Ni) with Cu inclusions. When the nanolaminated structure had completely transformed, the layer was softer than it had been in the initial annealing steps, but was still almost five times as hard as the initial Cu plate. © 2014 Elsevier B.V. All rights reserved. Source

Kim H.,Chonbuk National University | Kim K.-K.,Korea Polytechnic University | Lee S.-N.,Korea Polytechnic University | Baik K.-H.,Korea Electronics Technology Institute
Optics Express | Year: 2011

The fabrication process and design issues for the fabrication of vertical-injection GaN-based light-emitting diodes were investigated. The process yield was reduced according to the adhesion of reflective p-electrodes, the exposure of electroplated metal in plasma, and wet-etching induced surface textures. The chip design utilizing current blocking layer and branched n-electrode was found to significantly affect the power efficiency of LEDs. © 2011 Optical Society of America. Source

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. Source

Stadler F.J.,Chonbuk National University | Van Ruymbeke E.,Catholic University of Louvain
Macromolecules | Year: 2010

A study was conducted to propose an improved method to obtain direct rheological evidence of monomer density reequilibration for entangled polymer melts. Investigations revealed that all polymers except PS-275K were 1,4-polybutadienes with a very high stereoregularity, given by the low T g around -99 °C. The temperature was controlled between -95 and +100 °C and frequency sweeps were carried out to ensure a shift factor around 100 between the individual temperatures. The relaxation spectra of all samples were calculated using a self-programmed spectrum calculation routine based on determining the spectrum as a spline instead of individual relaxation modes similar to most other calculation routines. This method ensured a very precise calculation of the relaxation spectrum. Source

Moon I.D.,Hyundai Engineering | Oh C.Y.,Chonbuk National University
International Journal of Automotive Technology | Year: 2012

This paper develops a computational model that can analyze the kinematics and compliance characteristics of the front suspension of a commercial vehicle. This computational model is called the flexible multi-body dynamic model because it is developed by interfacing the finite element model of the multi-leaf spring with the dynamic model of the front suspension. In this paper, the bump mode and roll mode tests are performed with a suspension parameter measuring device (SPMD). An excitation load for creating the bump mode and roll mode motion is applied on the left and right tires slowly in in-phase and out-of-phase modes. In the test, wheel rate, toe angle change, caster angle change, and camber angle change, which together represent the wheel alignment, are measured along with the longitudinal and lateral wheel center loci which together represent the wheel center trajectory change. The reliability of the developed computational model is verified by comparing the simulation results with the SPMD test results. The developed flexible multi-body computational model will provide useful information on kinematics and compliance characteristics in the earliest stages of the commercial vehicle design process. © 2012 The Korean Society of Automotive Engineers and Springer-Verlag Berlin Heidelberg. Source

Abdullah A.H.,University of Technology Malaysia | Enayatifar R.,University of Technology Malaysia | Lee M.,Chonbuk National University
AEU - International Journal of Electronics and Communications | Year: 2012

The security of digital images has attracted much attention recently. In this study, a new method based on a hybrid model is proposed for image encryption. The hybrid model is composed of a genetic algorithm and a chaotic function. In the first stage of the proposed method, a number of encrypted images are constructed using the original image and the chaotic function. In the next stage, these encrypted images are used as the initial population for the genetic algorithm. In each stage of the genetic algorithm, the answer obtained from the previous iteration is optimized to produce the best-encrypted image. The best-encrypted image is defined as the image with the highest entropy and the lowest correlation coefficient among adjacent pixels. The use of genetic algorithms in image encryption has been attempted for the first time in this paper. Analyzing the results from the performed experiments, a high level of resistance of the proposed method against brute-force and statistical invasions is obviously illustrated. The obtained entropy and correlation coefficients of the method are approximately 7.9978 and -0.0009, respectively. © 2012 Elsevier GmbH. All rights reserved. Source

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. Source

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. Source

Kim J.,Chonbuk National University
Information Systems | Year: 2015

In this paper, we study edit similarity query processing to find strings similar to a query string from a collection of strings. To solve the problem, many algorithms have been proposed under a filter-and-verification framework, where candidate strings are generated and refined using a few filters and then verified to find true matches. A major focus of those algorithms has been on generating candidates as small as possible in an early stage of the query processing. A typical approach to generate candidates is to extract some signatures from a query and take union of string ids in the inverted lists of the extracted signatures. However, the number of candidates generated from existing techniques is extremely larger than the number of answer strings and costs for refinement and verification are expensive. To address the problem, we propose an intersection-based candidate generation scheme, which generates a substantially smaller number of candidates. Given some signatures of a query, the proposed scheme first categorizes signatures into several groups. Then, it takes intersection of string ids in the inverted lists of the signatures in each group. Finally, it takes union of the intersections to generate candidates. To minimize the number of candidates under our scheme, we propose a novel algorithm which judiciously selects an optimal signature group. We show through experiments that our technique is very effective in reducing the number of candidates and significantly improves the performance. © 2014 Elsevier Ltd. Source

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. Source

Park J.H.,University of Texas at Austin | Park J.H.,Chonbuk National University | Boika A.,University of Texas at Austin | Park H.S.,University of Texas at Austin | And 2 more authors.
Journal of Physical Chemistry C | Year: 2013

We report that conductive single nanoparticle (NP) collisions can involve a significant component of the mass transport to the electrode of the charged NPs by migration. Previously, collision events of catalytic NPs were described as purely diffusional using random walk theory. However, the charged NP can also be attracted to the electrode by the electric field in solution (i.e., migration) thereby causing an enhancement in the collision frequency. The migration of charged NPs is affected by the supporting electrolyte concentration and the faradaic current flow. A simplified model based on the NP transference number is introduced to explain the migrational flux of the NPs. Experimental collision frequencies and the transference number model also agreed with more rigorous simulation results based on the Poisson and Nernst-Planck equations. © 2013 American Chemical Society. Source

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. Source

Yakimov E.B.,National University of Science and Technology "MISIS" | Polyakov A.Y.,Chonbuk National University
Physica Status Solidi (C) Current Topics in Solid State Physics | Year: 2015

Dislocations in the ELOG n-GaN films have been studied by the Electron Beam Induced Current (EBIC) method. The effect of dopant concentration and diffusion length values on the dislocation EBIC profile is revealed. It is shown that the width of dislocation image in the EBIC mode decreases with a diffusion length decrease and the dopant concentration increase. In the crystals with the submicron diffusion length the individual dislocations can be separated in the EBIC images up to the dislocation densities higher that 109cm-2. The radius of dislocation related defect cylinder was found to increase with the dopant concentration decreasing that could be explained under an assumption that dislocations in GaN are charged. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Islam M.S.,Chonbuk National University | Kang S.H.,Kyung Hee University
Talanta | Year: 2011

A novel, quantitative analytical method for measuring C-reactive protein (CRP) levels in human serum has been developed based on the catalytic activity of gold nanoparticles (GNPs) and luminol-H 2O 2 chemiluminescence (CL). The CL intensity in the presence of CRP and its ligand, O-phosphorylethanolamine (PEA), was greatly enhanced due to the aggregation of GNPs after the addition of 0.5 M NaCl. Any pretreatment steps, such as covalent functionalization of GNPs, addition of antibodies, or labeling of CRP, were not needed for CL detection. The CL enhancement was linearly proportional to CRP concentration in the range of 1.88 fM to 1.925 pM. The detection limit of CRP in serum samples was estimated to be as low as 1.88 fM. The detection sensitivity was increased more than 164 times of magnitude over that of the conventional, enzyme-linked immunosorbent assay (ELISA) method. This proposed GNP-based CL detection method offers the advantages of simplicity, rapidity, and sensitivity. © 2011 Elsevier B.V. All rights reserved. All rights reserved. Source

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. Source

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. Source

Lee J.-H.,Kyung Hee University | Shin H.-S.,Kyung Hee University | Na S.-I.,Chonbuk National University | Kim H.-K.,Kyung Hee University
Solar Energy Materials and Solar Cells | Year: 2013

We have investigated the characteristics of transparent and flexible PEDOT:PSS electrodes passivated by thin InZnSnO (IZTO) film for flexible organic solar cells (FOSCs). Using damage-free linear facing target sputtering (LFTS), an IZTO passivation layer was deposited on the gravure printed PEDOT:PSS electrode without causing plasma damage. The thickness of the IZTO passivation layer was found to critically affect electrical and optical properties of the IZTO/PEDOT multilayer because the continuity and morphology of the thin IZTO passivation layer were greatly influenced by thickness. At optimized IZTO passivation thickness of 20 nm, the IZTO/PEDOT:PSS multilayer electrode exhibited decreased sheet resistance of 353.6 ω/sq and optical transmittance of 83.09% without flexibility degradation. The FOSC with an optimized IZTO/PEDOT:PSS electrode showed better performances than the FOSC with PEDOT:PSS electrodes due to the effect of a stable IZTO passivation layer. This indicates that IZTO passivation on the PEDOT:PSS electrode using a LFTS is one of the key solutions for improving the properties and stability of flexible PEDOT:PSS electrodes for high performance FOSCs. © 2012 Elsevier B.V. Source

Oxidative stress-induced cytotoxicity in cervical cancer cells may be of toxicological interest. In the present study, the effects of exogenous H2O2 on cell growth and death in HeLa cervical cancer cells were investigated, and the anti-apoptotic effects of various caspase (pan-caspase, caspase-3, -8 or -9) inhibitors on H2O2-treated HeLa cells were also evaluated with regard to reactive oxygen species (ROS) and glutathione (GSH) levels. Based on MTT assays, H2O2 inhibited the growth of HeLa cells with an IC50 value of ~75 μM at 24 h. H2O2 increased the number of dead cells and Annexin V-FITC-positive cells in the HeLa cells, which was accompanied by the activation of caspase-3 and the loss of mitochondrial membrane potential (MMP; δΩm). However, relatively higher doses of H2O2 induced necrosis in HeLa cells. Caspase inhibitors significantly prevented H2O2-induced HeLa cell death. H2O2 increased ROS including O2•- at 24 h and increased the activity of catalase in HeLa cells. H2O2 also increased the ROS level at 1 h, and several caspase inhibitors attenuated the increased level at 1 h but not at 6, 12 and 24 h. H2O2 decreased the GSH level in HeLa cells at 1 h, and several caspase inhibitors attenuated the decreased level of GSH at this time. H2O2 induced GSH depletion at 24 h. In conclusion, H2O2 inhibited the growth of HeLa cells via apoptosis and/or necrosis, which was accompanied by intracellular increases in ROS levels and GSH depletion. Caspase inhibitors are suggested to suppress H2O2-induced oxidative stress to rescue HeLa cells at the early time point of 1 h. Source

Guak S.,Chonbuk National University | Neilsen D.,Agriculture and Agri Food Canada
Horticulture Environment and Biotechnology | Year: 2013

Temperature-controlled experiments were conducted to determine the relative contribution of temperatures to dormancy completion of floral buds in 'Gala' apple (Malus domestica Borkh.) and 'Sweetheart' sweet cherry (Prunus avium L.). Shoots were collected right before chill inception, and exposed continuously to seven different temperatures in the range of -2°C and 16. 8°C for 1320 hours. Chilling requirements were determined on sequential field samples from plots of days to bud break against sampling date. Temperature-response curves, which were best fit in a four parameter logistic nonlinear regression, indicated that optimum chilling temperatures were between -2°C and 5. 5°C for 'Gala' and between -2°C and 7°C for 'Sweetheart', with no chilling effect above 13°C in both species. The derived chill unit models predicted that chill unit accumulations required for dormancy completion averaged 921 for 'Gala' and 740 for 'Sweetheart' over the three year period. The year-to-year variation in 'Gala' apple was smaller with our 'Gala' model than with the 'Utah' model (14% vs 23. 5% coefficients of variation), while similar to each other in 'Sweetheart' sweet cherry. © 2013 Korean Society for Horticultural Science. Source

Lee C.,Chonbuk National University
International Journal of Innovative Computing, Information and Control | Year: 2014

This paper proposes a new conceptual object grouping method for usercentric streaming media services in wireless multimedia service zones with fuzzy filtering. The proposed method can be used to automatically compose similarity relations between the objects by fuzzy relation to conceptual objects extracted from the client's request of wireless multimedia service domains. These conceptual objects are grouped to improve throughput and quality of service (QoS), and fuzzy filtering is used to decide on a similarity relation, for which μ-cut, fuzzy similarity (FS), and direct similarity relation (DSR) are applied. These techniques group related conceptual objects easily. In order to show the performance of the proposed method, about 5,000 conceptual objects were simulated. The simulation was conducted using a grouping method, a non-grouping method, and category-based method. The results show that the proposed method provides better performance than the non-grouping method and category-based method. © 2014 ISSN 1349-4198. Source

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. Source

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. Source

Choi J.-M.,Chonbuk National University
New Physics: Sae Mulli | Year: 2016

The working range of optical tweezers deep inside a suspension medium is severely limited by the refractive-index-mismatch spherical aberration (RIMSA) due to the presence of media with different indices of refraction, e.g., an immersion medium, a coverslip, and a suspension medium. In this case study, the feasibility of versatile optical tweezers with a moderate NA objective is investigated with a wavefront correction method. The effect of RIMSA on a tightly-focused beam through planar interfaces is described with the angular spectrum representation based on the rigorous vectorial diffraction theory, and the associated effects on optical tweezers are presented by evaluating the light-matter interaction in the Rayleigh region. Finally, I show that a stable optical trap for 70-nm silica spheres 100 μm deep inside a suspension medium can be realized with a 780-nm laser beam of a few tens of mW by using a moderate NA objective lens having a centimeter-long working distance. Source

Lee C.,Chonbuk National University
International Journal of Innovative Computing, Information and Control | Year: 2014

Proxy-driven streaming service in wireless multimedia service zones (WMS Z) is challenging due to rate distortion and high channel error rate. To facilitate proxy-driven streaming media services in wireless multimedia service zones, streaming operations such as distortion detection, distortion adjustment, and caching management should be considered. A new proxy-driven streaming service (PDSS) is proposed to support high streaming quality in IEEE 802.11-based wireless multimedia service zones. The proposed mechanism performs disjunction mapping-based management operation, conjunction mapping-based management operation, and filer mapping-based management operation to derive the optimized proxy caching for the individual versions of a media object. The goal of this study is to reduce the distortion due to limited bandwidth, high bit rate error, and proxy constraints, and to enhance the throughput of streaming media service. Simulation results show that the proposed method has better performance than the existing server-only streaming method, resource-based caching method, and frequency-based caching method. © 2014 ICIC International. Source

Osteoblasts (OBs) are indispensable for the maintenance of hematopoietic stem cells (HSCs) in the bone marrow microenvironment. Here we investigated how Smad4 modulates HSC fate at distinct stages of OB development. For this, we conditionally knocked out Smad4 in cells expressing type I collagen (Col1a1) and osteocalcin (OC), respectively. Col1a1-expressing OBs were widely present in both the trabecular and cortical compartment, whereas OC-expressing OBs were predominantly located in the cortical compartment. HSCs from Col1a1 mutants displayed senescence-associated phenotypes. OC mutants did not exhibit HSC senescence-related phenotypes, but instead showed preferential HSC death. Of note, stromal cell-derived factor 1 expression was lower in Col1a1 mutants than control littermates, suggesting potential impairment of CXCR4–CXCL12-mediated HSC retention. Disruption of the CXCR4–CXCL12 axis by AMD3100 administration led to an increase in the senescence-associated β-galactosidase activity and low competitive potential. Collectively, our findings indicate that deletion of Smad4 in OBs differentially modulates HSC fate in a stage-dependent manner.Leukemia advance online publication, 7 June 2016; doi:10.1038/leu.2016.133. © 2016 Macmillan Publishers Limited Source

Oh S.-W.,Pusan National University | Park B.W.,Pusan National University | Lee J.-H.,Chonbuk National University | Yoon T.-H.,Pusan National University
Applied Optics | Year: 2013

We propose an achromatic optical-compensation method using uniaxial films to eliminate the off-axis light leakage at the dark state in a homogeneously aligned liquid crystal cell. Three uniaxial films with different dispersion characteristics are used so that they can compensate each other to achieve achromatic effective phase retardation at off-axis. The retardation values are optimized with the aid of the Poincare sphere and through numerical research. A contrast ratio of higher than 20001 is predicted over the entire -60 viewing cone for a homogeneously aligned LC cell with zero pretilt angle. © 2013 Optical Society of America. Source

Kim H.,Chonbuk National University | Lee S.-N.,Korea Polytechnic University
Journal of the Electrochemical Society | Year: 2010

We report theoretical considerations regarding current spreading in GaN-based light emitting diodes (LEDs) fabricated with top-emission geometry, in which sheet resistances of both top transparent electrodes and n-layers are taken into consideration, whereas vertical resistance associated with the p-contact and the p-layer is neglected. The current spreading length (L s) is inversely proportional to the injected current density (J 0), namely, Ls J0-1/2, and can be increased as the sheet resistances of either the transparent electrode or the n-layer are reduced. The effects of the material parameters (sheet resistances of transparent electrode and n-layer) on current spreading and hence the LED performance are discussed. © 2010 The Electrochemical Society. Source

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. Source

Lee D.-W.,Chonbuk National University
Acta Mathematica Scientia | Year: 2014

In this paper we study the properties of homotopy inverses of comultiplications and algebraic loops of co-H-spaces based on a wedge of spheres. We also investigate a method to construct new comultiplications out of old ones by using a group action. We are primarily interested in the algebraic loops which have inversive, power-associative and Moufang properties for some comultiplications. © 2014 Wuhan Institute of Physics and Mathematics. Source

Auhl D.,Friedrich - Alexander - University, Erlangen - Nuremberg | Auhl D.,Catholic University of Louvain | Stadler F.J.,Friedrich - Alexander - University, Erlangen - Nuremberg | Stadler F.J.,Chonbuk National University | Munstedt H.,Friedrich - Alexander - University, Erlangen - Nuremberg
Macromolecules | Year: 2012

Polypropylene (PP) irradiated with electrons or electromagnetic waves (gamma-rays) undergoes chain scission, and the macroradicals generated form branched molecules as shown by size-exclusion chromatography coupled with laser scattering. Information on the irradiation modification of the molecular structure of PP is still limited in the literature, especially with respect to the controlled generation of long-chain branches (LCB). This paper examines the branching structure of an electron-beam- and gamma-irradiated polypropylene. In general, appropriate irradiation conditions lead to the formation of LCB, which were analyzed in detail by rheological means. At smaller doses, the zero shear-rate viscosities η 0 of the electron-beam-irradiated PP lie above the values for the unmodified PP with the same M w but are distinctly lower than the linear reference at higher doses. This result can be interpreted by the change from a starlike to a treelike branching topography. The gamma-irradiation leads to η 0 values smaller than those of the linear reference, giving rise to the assumption of the generation of treelike molecules. The measurements of the elongational viscosities support this molecular picture. An explanation of these findings is given along the line that the electron irradiation conducted at dose rates higher than the gamma-irradiation creates a larger concentration of short-living radicals, which will partially annihilate each other, but favor the growth of some long branches, which get branched themselves at higher doses. The structure of the gamma-irradiated samples is postulated to consist of a blend of linear and treelike molecules. © 2012 American Chemical Society. Source

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. Source

Lee S.-J.,Chonbuk National University | Van Tyne C.J.,Colorado School of Mines
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science | Year: 2013

A hot-rolled and controlled rolled 16MnCr5 steel was analyzed after similar industrial cooling conditions. The hot rolled steel had a ferrite-bainite microstructure whereas the controlled rolled steel had a ferrite-pearlite microstructure. The prior austenite grain size was found to be the controlling factor based on a cooling analysis. The effect of prior austenite grain size on the bainite start temperature had to be considered in the transformation model. © 2013 The Minerals, Metals & Materials Society and ASM International. Source

Lee K.-A.,Soonchunhyang University | Chae J.-I.,Chonbuk National University | Shim J.-H.,Soonchunhyang University
Journal of Biomedical Science | Year: 2012

Background: Malignant pleural mesothelioma (MPM) is a highly aggressive cancer with a very poor prognosis. Several clinical studies such as immunotherapy, gene therapy and molecular targeting agents have been tried for treatment of malignant mesothelioma, however, there is no application for effective clinical treatment. Coffee has various biological functions such as anti-oxidant, anti-inflammatory, anti-mutagenic and anti-carcinogenic activities. The therapeutic activities of the bioactive compounds in coffee was sugested to influence intracellular signaling of MPM. Regarding to the cancer-related functions, In this study, suppression of Sp1 protein level followed by induction of MSTO-211H cell apoptosis by cafestol and kahweol were investigated in oreder to determine Sp1's potential as a significant target for human MPM therapy as well. Methods: Cells were treated separately with final concentration of cafestol and kahweol and the results were analyzed by MTS assay, DAPI staining, PI staining, luciferase assay, RT-PCR, and immunoblotting. Results: Viability of MSTO-211H and H28 cells were decreased, and apoptotic cell death was increased in MSTO-211H as a result of cafestol and kahweol treatment. Cafestol and kahweol increased Sub-G1 population and nuclear condensation in MSTO-211H cells. Roles of Sp1 in cell proliferation and apoptosis of the MSTO-211H cells by the Sp1 inhibitor of Mithramycin A were previously confirmed. Cafestol and kahweol significantly suppressed Sp1 protein levels. Kahweol slightly attenuated Sp1 mRNA, while Cafestol did not affect in MSTO-211H cells. Cafestol and kahweol modulated the promoter activity and protein expression level of the Sp1 regulatory genes including Cyclin D1, Mcl-1, and Survivin in mesothelioma cells. Apoptosis signaling cascade was activated by cleavages of Bid, Caspase-3, and PARP with cafestol and by upregulation of Bax, and downregulation of Bcl-xl by kahweol. Conclusions: Sp1 can be a novel molecular target of cafestol and kahweol in human MPM. © 2012 Lee et al.; licensee BioMed Central Ltd. Source

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. Source

Hong Y.K.,Korea Advanced Institute of Science and Technology | Baek S.W.,Korea Advanced Institute of Science and Technology | Kim M.Y.,Chonbuk National University
Numerical Heat Transfer; Part A: Applications | Year: 2010

Inverse thermal problem is applied to natural convective flow with radiative heat transfer. The bottom wall temperature in the 2-D cavity domain is estimated by using gas temperature measurements in the flow field. The inverse problem is solved through a minimization of an objective function using the conjugate gradient method with adjoint problem. The effects of functional form of bottom wall temperature profile, the number and the position of measurement points, and the measurement errors are investigated and discussed. The conjugate gradient method is found to work well in estimating the bottom wall temperature, even when natural convection with radiation phenomena is involved. Copyright © Taylor & Francis Group, LLC. Source

Lee G.-H.,Wonkwang University | Kim H.-R.,Chonbuk National University | Kim H.-R.,Wonkwang University | Chae H.-J.,Wonkwang University
International Journal of Biochemistry and Cell Biology | Year: 2012

In this study, we explored the role of Bax inhibitor-1 (BI-1) on the expression of P450 2E1 and related ROS production. P450 2E1 protein, not mRNA, was expressed at relatively low levels in BI-1 plasmid-transfected cells (BI-1 cells) compared with neomycin-resistant vector-transfected cells (Neo cells). When exposed to ER stress, P450 2E1 expression and activity and ER membrane lipid peroxidation increased in both Neo cells and BI-1 cells, but to a lesser degree in BI-1 cells. This observation correlated with the lower level of ER stress in BI-1 cells than Neo cells. To examine the BI-1-associated P450 2E1 degradation mechanism, cells were treated with the lysosome inhibitor, bafilomycin and the proteasome inhibitor, MG132. Bafilomycin recovered the reduced P450 2E1 expression in BI-1 cells, but did not affect P450 2E1 expression in Neo cells. Next, proteosomal and lysosomal activities in Neo cells were compared to those in BI-1 cells. Although proteosomal activity was similar between Neo and BI-1 cells, LysoTracker and acridine orange labeling, lysosomal V-ATPase activity, and lysosomal cathepsin B expression were higher in BI-1 cells than in Neo cells. In the presence of ER stress, lysosomal activities decreased in Neo cells but did not change in BI-1 cells. P450 2E1 expression and ER membrane lipid peroxidation were greater in the hepatocytes and livers of BI-1 knock-out mice than in BI-1 wild-type cells and mice. Our results suggest that the BI-1-mediated enhancement of lysosomal activity regulates P450 2E1 expression and resultant ROS accumulation. © 2012 Elsevier Ltd. All rights reserved. Source

Bekemeier B.,University of Washington | Chen A.L.-T.,University of Washington | Chen A.L.-T.,Chonbuk National University | Kawakyu N.,International Training and Education Center for Health | Yang Y.,University of Washington
American Journal of Preventive Medicine | Year: 2013

Background Local health department leaders are expected to improve the health of their populations as they "use and contribute to" the evidence base for practice, but effectively providing and utilizing data and evidence for local public health decision making has proven difficult. Purpose This study was conducted in 2011 and initiated by Washington State's public health practice-based research network to identify factors influencing local resource allocation and programmatic decisions among public health leaders facing severe funding losses. Methods Quantitative data informed sampling for the collection of interview data. Qualitative methods were used to capture diverse insights of Washington State's local public health leaders in making decisions regarding resource allocation. Results Local decision-making authority was perceived as greatly restricted by what public health activities were legally mandated and the categoric nature of funding sources, even as some leaders exercised deliberate strategic approaches. One's workforce and board of health were also influential in making decisions regarding resource allocations. Challenges were expressed regarding making use of data and research evidence for decision making. Data were analyzed in 2011-2012. Conclusions Programmatic mandates, funding restrictions, local stakeholders, and workforce capacity appear to trump factors such as research evidence and perceived community need in public health resource allocation. Study findings highlight tensions between the literature descriptions of what "should" influence decision making in local public health and the realities of practice. Advancements in practice-based research and evidence-based decision making, however, provide opportunities for strengthening the development of evidence and research translation for local decision making to maximize resources and promote effective service provision. © 2013 American Journal of Preventive Medicine. Source

Abstract Many attempts have been made to fabricate lightweight, high-performance, and low-cost polymeric composites. To improve the mechanical performance of the same material compared to conventional composites, paired hybrid materials were manufactured with different lamination structures. Each of six types of hybrid composite was designed by lamination pairing of carbon/aramid fabric and carbon/glass fabric using VARTM. The dependence of the mechanical properties of the samples on the pairing effects of the lamination structures was investigated. All pairing materials did not lead to a large increase of tensile strength due to the domination of carbon fiber, but the mechanical properties of specific laminates were clearly changed by the particular pairing sequence used. Using the limited material, the design of an effective structure was the central laminating condition with a good tensile and bending properties. Laminating position of the carbon fiber was found to play an important role in the stacking design of hybrid composites. © 2015 Elsevier Ltd. All rights reserved. Source

Park B.-Y.,Chonbuk National University | Hong C.-S.,Daegu University | Weaver J.R.,University of Pennsylvania | Rosocha E.M.,University of Pennsylvania | Saint-Jeannet J.-P.,University of Pennsylvania
Developmental Biology | Year: 2012

Lower vertebrates develop a unique set of primary sensory neurons located in the dorsal spinal cord. These cells, known as Rohon-Beard (RB) sensory neurons, innervate the skin and mediate the response to touch during larval stages. Here we report the expression and function of the transcription factor Xaml1/Runx1 during RB sensory neurons formation. In Xenopus embryos Runx1 is specifically expressed in RB progenitors at the end of gastrulation. Runx1 expression is positively regulated by Fgf and canonical Wnt signaling and negatively regulated by Notch signaling, the same set of factors that control the development of other neural plate border cell types, i.e. the neural crest and cranial placodes. Embryos lacking Runx1 function fail to differentiate RB sensory neurons and lose the mechanosensory response to touch. At early stages Runx1 knockdown results in a RB progenitor-specific loss of expression of Pak3, a p21-activated kinase that promotes cell cycle withdrawal, and of N-tub, a neuronal-specific tubulin. Interestingly, the pro-neural gene Ngnr1, an upstream regulator of Pak3 and N-tub, is either unaffected or expanded in these embryos, suggesting the existence of two distinct regulatory pathways controlling sensory neuron formation in Xenopus. Consistent with this possibility Ngnr1 is not sufficient to activate Runx1 expression in the ectoderm. We propose that Runx1 function is critically required for the generation of RB sensory neurons, an activity reminiscent of that of Runx1 in the development of the mammalian dorsal root ganglion nociceptive sensory neurons. © 2011 Elsevier Inc. Source

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. Source

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. Source