Showing papers by "Chonbuk National University published in 2007"

Fabrication and Mechanical Properties of Completely Biodegradable Hemp Fiber Reinforced Polylactic Acid Composites

Abstract: Biodegradable composite materials can be produced by the combination of biodegradable polymers and natural fibers. In this study, a new biodegradable composite of hemp fiber reinforced polylactic acid (PLA) was fabricated using the hot press method. Mechanical properties of composites with different fiber volume fractions were tested. The optimum fiber content was determined according to the test results. Effects of alkali treatment on the fiber surface morphology and the mechanical properties of the composites were investigated. Test results show that the composite with 40% volume fraction of alkali treated fiber has the best mechanical properties. The tensile strength, elastic modulus, and flexural strength of the composite with 40% treated fiber are 54.6 MPa, 8.5 Gpa, and 112.7 MPa respectively, which are much higher than those of PLA alone. The composites have lower densities, which were measured to be from 1.19 g/cm3 to 1.25 g/cm3. Specific strengths were also calculated. Surface morphologies of fibe...

Induction Machine Condition Monitoring Using Neural Network Modeling

Abstract: Condition monitoring is desirable for increasing machinery availability, reducing consequential damage, and improving operational efficiency. Model-based methods are efficient monitoring systems for providing warning and predicting certain faults at early stages. However, the conventional methods must work with explicit motor models, and cannot be applied effectively for vibration signal diagnosis due to their nonadaptation and the random nature of vibration signal. In this paper, an analytical redundancy method using neural network modeling of the induction motor in vibration spectra is proposed for machine fault detection and diagnosis. The short-time Fourier transform is used to process the quasi-steady vibration signals to continuous spectra for the neural network model training. The faults are detected from changes in the expectation of vibration spectra modeling error. The effectiveness of the proposed method is demonstrated through experimental results, and it is shown that a robust and automatic induction machine condition monitoring system has been produced

Growth of aligned ZnO nanorods and nanopencils on ZnO/Si in aqueous solution: growth mechanism and structural and optical properties

Abstract: Well-aligned ZnO nanorod and nanopencil arrays were synthesized in a high density on ZnO/Si substrate by a low-temperature aqueous solution technique. Detailed structural characterizations revealed that the as-synthesized nanorods and nanopencils were single crystalline, with a hexagonal phase, and with growth along the [0001] direction. The room-temperature photoluminescence spectra showed a strong ultraviolet emission at 381 nm, a weak blue band at 460 nm, and a broad green emission at 580 nm. A detailed growth mechanism has been proposed for the formation of nanorods and nanopencils based on the different crystallographic habits of wurtzite hexagonal ZnO.

Cisplatin cytotoxicity of auditory cells requires secretions of proinflammatory cytokines via activation of ERK and NF-κB

Abstract: The ototoxicity of cisplatin, a widely used chemotherapeutic agent, involves a number of mechanisms, including perturbation of redox status, increase in lipid peroxidation, and formation of DNA adducts. In this study, we demonstrate that cisplatin increased the early immediate release and de novo synthesis of proinflammatory cytokines, including TNF-α, IL-1β, and IL-6, through the activation of ERK and NF-κB in HEI-OC1 cells, which are conditionally immortalized cochlear cells that express hair cell markers. Both neutralization of proinflammatory cytokines and pharmacologic inhibition of ERK significantly attenuated the death of HEI-OC1 auditory cells caused by cisplatin and proinflammatory cytokines. We also observed a significant increase in the protein and mRNA levels of proinflammatory cytokines in both serum and cochleae of cisplatin-injected rats, which was suppressed by intraperitoneal injection of etanercept, an inhibitor of TNF-α. Immunohistochemical studies revealed that TNF-α expression was mainly located in the spiral ligament, spiral limbus, and the organ of Corti in the cochleae of cisplatin-injected rats. NF-κB protein expression, which overlapped with terminal deoxynucleotidyl transferase-mediated dUTP nick-end-labeling-positive signal, was very strong in specific regions of the cochleae, including the organ of Corti, spiral ligament, and stria vascularis. These results indicate that proinflammatory cytokines, especially TNF-α, play a central role in the pathophysiology of sensory hair cell damage caused by cisplatin.

Crescimento reduzido por salinidade, fotoquímica PS2 e conteúdo de clorofila em rabanete

Abstract: When plants are grown under saline conditions, photosynthetic activity decreases leading to reduced plant growth, leaf area, chlorophyll content and chlorophyll fluorescence. Seeds and seedlings of radish (Raphanus sativus L.) were grown in NaCl solutions under controlled greenhouse conditions. The NaCl concentrations in complete nutrient solutions were 0 (control), 4.7, 9.4 and 14.1 dS m-1. The salinity reduced germination percentage and also delayed the germination rate as the salt level increased. Lengths and fresh weights of root and shoot decreased with the increasing salt concentration. Furthermore, photochemical efficiency of PS2 (Fv/Fm), photochemical quenching coefficient (qP), non photochemical quenching coefficient (qN), leaf area and chlorophyll content (SPAD value) were also reduced (P < 0.001) by salt stress. In contrast, the Fo/Fm ratio increased with increasing salt concentration while salinity showed no effect on the efficiency of excitation captured by open PS2 (Fv'/Fm'), electron transport rate (ETR), and leaf water content. Linear regression shows that the photochemical efficiency of PS2 (Fv/Fm) had a positive relationship with the photochemical quenching coefficient (qP), leaf area and chlorophyll content but had no relation with Fv'/Fm', Fo/Fm, and qN.

Importance of pericytes and mechanisms of pericyte loss during diabetes retinopathy.

Abstract: Pericytes are distinctive regulators of angiogenesis and are adumbrated to provide vessel stability and control of endothelial proliferation. The present article spotlights the persona of pericytes in physiological angiogenesis, recruitment of pericytes and different mechanisms of pericyte depletion. Developing retina appears particularly dependent on pericytes, and pericyte loss is considered as hallmark of early diabetic retinopathies. Several factors are contemplated to be engaged in pericyte conscription including angiopoietin-1 and its receptor tyrosine kinase Tie-2, vascular endothelial growth factor-A and its receptor flk-1 and the platelet-derived growth factor PDGF-B/PDGF-beta system. At present, the mechanisms by which diabetes persuade apoptosis in the retinal microvasculature remain indecisive, albeit oxidative stress, formation of advanced glycation end products , upregulation of protein kinase C, increased polyol pathway flux and focal leukostasis may be important. In this context, accelerated microvascular cell death may become a constructive surrogate end-point in pharmacological studies of experimental diabetic.

Corrosion studies of carbon nanotubes–Zn composite coating

Abstract: Zn–carbon nanotubes composite coatings were obtained from a sulphate bath containing dispersed carbon nanotubes (CNTs). The electrochemical and weight loss measurements were made to find the corrosion behavior of composite coating. The presence of carbon nanotubes shifts the potential of zinc deposit to more positive values. The composite coatings were porous free and the service life of coating was examined by salt spray test. The electrochemical studies revealed higher resistance of composite coatings to corrosion. The surface morphology was investigated by recording the SEM images of coating before and after corrosion. The mechanism of action against corrosion was established.

Antibody Recognition of Cell Surface-Associated NS1 Triggers Fc-γ Receptor-Mediated Phagocytosis and Clearance of West Nile Virus-Infected Cells

Abstract: Previous studies have suggested that monoclonal antibodies (MAbs) to flavivirus nonstructural protein-1 (NS-1) protect against infection in mice through an Fc-γ receptor-dependent pathway. To identify a specific mechanism, we evaluated the protective activity of anti-NS1 MAbs to WNV using mice and cells with deficiencies of specific Fc-γ receptors. Our results suggest that only MAbs that recognize cell surface-associated NS1 trigger Fc-γ receptor I- and/or IV-mediated phagocytosis and clearance of WNV-infected cells. These findings may be relevant for generating novel therapeutic MAbs or vaccines against flaviviruses that target the NS1 protein.

The Late Permian to Triassic Hongseong-Odesan Collision Belt in South Korea, and Its Tectonic Correlation with China and Japan

Abstract: We propose a new correlation of Middle Triassic (ca. 230 Ma) eclogites from the Hongseong area of the southwest Gyeonggi Massif, South Korea, with the Dabie-Sulu collision belt of China. Late Permian (ca. 257 Ma) mangerites that intrude the Odesan area in the eastern part of the Gyeonggi Massif show geochemical characteristics of collisional tectonic settings, implying that the Hongseong collision belt extends to the Odesan area. In the Higo terrain of southernmost Japan, sapphirine-bearing granulites and related high-temperature metamorphic rocks reveal ca. 245 Ma ultrahigh-temperature (UHT) metamorphic conditions. This metamorphism is well matched with the 245 ± 10 Ma UHT metamorphism estimated for spinel granulite in the Odesan area, suggesting that the Dabie-Sulu collision zone continues through the Hongseong-Odesan belt into the Higo area and that Paleozoic subduction complexes in southwest Japan represent an eastern extension of the Dabie-Sulu collision belt. The Paleozoic subduction complexes in Ja...

An early response regulatory cluster induced by low temperature and hydrogen peroxide in seedlings of chilling-tolerant japonica rice

Abstract: Background Plants respond to low temperature through an intricately coordinated transcriptional network. The CBF/DREB-regulated network of genes has been shown to play a prominent role in freeze-tolerance of Arabidopsis through the process of cold acclimation (CA). Recent evidence also showed that the CBF/DREB regulon is not unique to CA but evolutionarily conserved between chilling-insensitive (temperate) and chilling-sensitive (warm-season) plants. In this study, the wide contrast in chilling sensitivity between indica and japonica rice was used as model to identify other regulatory clusters by integrative analysis of promoter architecture (ab initio) and gene expression profiles.

Toward a Theory of Motivation and Personality with Application to Word-of-Mouth Communications

Abstract: Numerous scales have been developed to measure constructs relevant to consumer behavior, marketing, and management problems. Until recently, there has been no theory or model capable of providing an organizational structure for understanding the relationships among these numerous constructs. This paper presents the 3M Model of Motivation and Personality (Mowen 2000) as a viable theoretical approach for organizing constructs into an ordered nomological net. In addition, this effort illustrates how the 3M Model approach can be applied to personality research via an empirical study that investigates the trait antecedents of enduring dispositions to send and receive marketplace information across the U.S. and Korean cultures.

A new classification of pattern hair loss that is universal for men and women: Basic and specific (BASP) classification

Abstract: Background Pattern hair loss (PHL) can be classified into several patterns. Currently, the Hamilton–Norwood classification system for men and the Ludwig grade system for women are commonly used to describe patterns of hair loss. However, these pre-existing classifications have some limitations. Objective To establish an acceptable, universal, and accurate standard of both male and female pattern hair loss and to report its use in determining the incidence of PHL. Methods We developed a new classification system (BASP classification) and then applied this system to classify the types of PHL. The BASP classification was based on observed patterns of hair loss. The basic (BA) types represent the shape of the anterior hairline, and the specific types (SP) represent the density of hair on distinct areas (frontal and vertex). There are four basic types (L, M, C, and U) and two specific types (F and V). The final type is decided by the combination of the assigned basic and specific types. Between November 2004 and June 2005, 2213 Korean subjects, comprised of 1768 males and 445 females, were classified according to the BASP classification at 13 university dermatologic centers nationwide throughout South Korea, as a multicenter study of the Korean Hair Research Society. Results For both sexes, the majority of patients enrolled in the study were in the third and fourth decade of life (65.1% of males and 56.68% of females). In males, the older group as well as the younger group in the study were more likely to have little recession of the frontal hairline (classified as type M1∼2) and diffuse thinning over the top of scalp (type F1∼2). The women in the study developed typical female PHL. Limitations The subjects of our study were mostly outpatients and some inpatients who complained about hair loss, not the general population of Korea. Conclusion The BASP classification is a new stepwise, systematic, and universal classification system for PHL, regardless of sex.

Galactosylated chitosan-graft-polyethylenimine as a gene carrier for hepatocyte targeting

Abstract: Chitosans have been proposed as alternative, biocompatible cationic polymers for nonviral gene delivery. However, the low transfection efficiency and low specificity of chitosan need to be addressed before clinical application. We prepared galactosylated chitosan-graft-polyethylenimine (GC-g-PEI) copolymer by an imine reaction between periodate-oxidized GC and low-molecular-weight PEI. The molecular weight and composition were characterized using gel permeation chromatography column with multi-angle laser scattering and 1H nuclear magnetic resonance, respectively. The copolymer was complexed with plasmid DNA in various copolymer/DNA (N/P) charge ratios, and the complexes were characterized. GC-g-PEI showed good DNA-binding ability and superior protection of DNA from nuclease attack and had low cytotoxicity compared to PEI 25K. GC-g-PEI/DNA complexes showed higher transfection efficiency than PEI 25K in both HepG2 and HeLa cell lines. Transfection efficiency into HepG2, which has asialoglycoprotein receptors, was higher than that into HeLa, which does not. GC-g-PEI/DNA complexes also transfected liver cells in vivo after intraperitoneal (i.p.) administration more effectively than PEI 25K. These results suggest that GC-g-PEI can be used in gene therapy to improve transfection efficiency and hepatocyte specificity in vitro and in vivo.