Showing papers by "Chonbuk National University published in 1999"

Stability and electronic structure of GaN nanotubes from density-functional calculations

Abstract: Density-functional calculations are used to predict the stability and electronic structures of GaN nanotubes. Strain energies of GaN nanotubes are comparable to those of carbon nanotubes, suggesting the possibility for the formation of GaN nanotubes. The zigzag nanotube is a semiconductor with direct band gap, whereas the armchair nanotube has an indirect band gap. The band gaps decrease with decreasing diameter, contrary to the case of carbon nanotubes. We further discuss possible ways of synthesizing GaN nanotubes in conjunction with carbon nanotubes.

Defect-Induced Oxidation of Graphite

Abstract: Atomic vacancies with controlled depth and size are generated on a graphite surface by low-energy ion bombardment. The reactivity of vacancies towards an oxygen molecule is investigated by using scanning tunneling microscopy (STM) and density functional theory. An oxygen molecule (i) exothermally dissociates and then chemisorbs at the top sites and/or the bridge sites of a vacancy, or (ii) forms a precursor state of molecular oxygen at a bridge site. Reaction pathways for oxidative etching are proposed to interpret serpentine and circular etching patterns observed by STM.

Synthesis of uniformly distributed carbon nanotubes on a large area of Si substrates by thermal chemical vapor deposition

Abstract: We have synthesized carbon nanotubes by thermal chemical vapor deposition of C2H2 on transition metal-coated silicon substrates. Multiwalled carbon nanotubes are uniformly synthesized on a large area of the plain Si substrates, different from previously reported porous Si substrates. It is observed that surface modification of transition metals deposited on substrates by either etching with dipping in a HF solution and/or NH3 pretreatment is a crucial step for the nanotube growth prior to the reaction of C2H2 gas. We will demonstrate that the diameters of carbon nanotubes can be controlled by applying the different transition metals.

Dynamic channel reservation based on mobility in wireless ATM networks

Abstract: We present a dynamic channel reservation scheme to improve the utilization of wireless network resources while guaranteeing the required QoS of handoff calls. The wireless channels are dynamically reserved by using the request probability determined by the mobility characteristics and channel occupancy to guarantee acceptable quality of handoff calls and keep the new call blocking probability as low as possible.

Enhanced T cell proliferative response to type II collagen and synthetic peptide CII (255-274) in patients with rheumatoid arthritis.

Abstract: Objective To determine the presence of specific immune recognition of type II collagen (CII) and its immunodominant epitope CII (255–274) in patients with rheumatoid arthritis (RA). Methods T cell proliferative responses to bovine CII and a synthetic peptide encompassing CII (255–274) in peripheral blood mononuclear cells (PBMC) and synovial fluid mononuclear cells (SFMC) from RA patients, and in PBMC from osteoarthritis (OA) patients and healthy controls were assayed by mixed lymphocyte culture. Results The stimulation index (SI) and the number of positive (SI ≥2) T cell responses to CII were higher in RA patients (n = 106) than in OA patients (n = 26) and healthy controls (n = 34). T cell responses to CII (255–274) were also enhanced in RA patients and correlated well with those to CII. In SFMC, positive responses to CII or CII (255–274) were detected in 61.9% of 42 RA patients. T cell responses to CII in SFMC were stronger and more prevalent than peripheral responses. The SI and positive responses to CII were higher in early RA than in late RA. Levels of IgG antibodies to CII in synovial fluid inversely correlated with T cell responses to CII. Conclusion T cell responses to CII or CII (255–274) were enhanced in RA, especially in early disease. Synthetic peptide CII (255–274), as well as native CII, could be recognized as immunogenic antigens by T cells, particularly in the synovial fluid. These observations suggest that CII-reactive T cells play an important role in the pathogenesis of RA. Peripheral tolerance induction using CII (255–274) might be useful in the treatment of RA.

Analysis of class separation and combination of class-dependent features for handwriting recognition

Abstract: In this paper, we propose a new approach to combine multiple features in handwriting recognition based on two ideas: feature selection-based combination and class dependent features. A nonparametric method is used for feature evaluation, and the first part of this paper is devoted to the evaluation of features in terms of their class separation and recognition capabilities. In the second part, multiple feature vectors are combined to produce a new feature vector. Based on the fact that a feature has different discriminating powers for different classes, a new scheme of selecting and combining class-dependent features is proposed. In this scheme, a class is considered to have its own optimal feature vector for discriminating itself from the other classes. Using an architecture of modular neural networks as the classifier, a series of experiments were conducted on unconstrained handwritten numerals. The results indicate that the selected features are effective in separating pattern classes and the new feature vector derived from a combination of two types of such features further improves the recognition rate.

A study of the systematics of Theileria spp. based upon small-subunit ribosomal RNA gene sequences.

Abstract: The systematics of benign and moderately pathogenic Theileria isolates from cattle and deer originating from different geographic regions was undertaken by small-subunit ribosomal RNA (SSU rRNA) gene nucleotide-sequence analysis. A maximum-likelihood phylogenetic tree constructed from these sequences resulted in two major divisions, each with a common ancestor. One major division branches into four relatively divergent groups, including (1) bovine Theileria sp. Type D (USA and Korea), (2) T. mutans Intona and Theileria sp. MSD (Africa), (3) T. cervi (USA), and (4) well-characterized pathogenic Theileria spp. (Africa). The other major division branches into two groups: (1) T. buffeli Warwick and T. buffeli Marula and (2) a second branch of closely related isolates with SSU rRNA gene Types B, B1, C, E, and H. Putative geographically associated diversity was noted only in the Korean bovine Theileria spp. with SSU rRNA gene types C and H and in African T. mutans Intona and Theileria sp. MSD. The current results show that the United States bovine Theileria isolates are not T. mutans because they have T. buffeli Marula (Type A) and/or Type D (species undesignated) SSU rRNA gene sequences. The taxonomic separation of T. buffeli Warwick from African T. mutans is confirmed in this study.

Trading costs and price discovery across stock index futures and cash markets

Abstract: The focus of this article is to test the trading cost hypothesis of price leadership, which predicts that the market with the lowest overall trading costs will react most quickly to new information. In an attempt to hold market microstructure effects constant and in contrast to previous studies, we examine intraday price leadership across the S&P 500, NYSE Composite, and MMI futures, and across the respective cash indexes—rather than between each futures and its associated cash index. We find that, among the futures, the S&P 500 exhibits price leadership over the other index futures, whereas among the cash indexes the MMI leads. Both findings are consistent with the trading cost hypothesis. © 1999 John Wiley & Sons, Inc. Jrl Fut Mark 19: 475–498, 1999

Amplified CDK2 and cdc2 activities in primary colorectal carcinoma.

Abstract: BACKGROUND Cyclins are overexpressed in various malignancies, including carcinoma of the colorectum, esophagus, lung, larynx, and breast. However, to the authors' knowledge, the protein levels and activities of cyclin-dependent kinases (CDKs), which are the functional cyclin partners in the cell cycle, have not been investigated previously. METHODS Eight samples of cancer tissue and adjacent normal tissue were taken from 23 patients with Stage B2–C1 (AJCC/UICC Stage II–III) colorectal carcinoma during curative resection. The protein levels of cyclin and CDKs were determined by Western blot analysis. The activities of CDKs were determined by the phosphorylation amount using specific substrates after immunoprecipitations. RESULTS The protein expression of cyclin (D1, D3, E, and A) and CDKs (CDK4, CDK2, and cdc2) was higher in primary colorectal carcinoma tissue than in adjacent normal tissue. Whereas only 3 of 8 patients had increased CDK4 activity in cancer tissue, 8 of 8 and 7 of 8 patients had increased CDK2 and cdc2 activities, respectively, in cancer tissue compared with adjacent normal tissue. However, there were no positive correlations among the pathologic staging or differentiation status and the increased ratio of cyclin protein, CDK protein, or CDK activity. CONCLUSIONS These results indicate that significant activation of S and M phases of the cell cycle occurs in primary colorectal carcinoma. Cancer 1999;85:546–53. © 1999 American Cancer Society.

Repertoire of human antibodies against the polysaccharide capsule of Streptococcus pneumoniae serotype 6B.

Abstract: We examined the repertoire of antibodies to Streptococcus pneumoniae 6B capsular polysaccharide induced with the conventional polysaccharide vaccine in adults at the molecular level two ways In the first, we purified from the sera of seven vaccinees antipneumococcal antibodies and determined their amino acid sequences Their VH regions are mainly the products of VH3 family genes (candidate genes, 3-23, 3-07, 3-66, and 3-74), but the product of a VH1 family gene (candidate gene, 1-03) is occasionally used All seven individuals have small amounts of polyclonal κ+ antibodies (Vκ1 to Vκ4 families), although κ+ antibodies are occasionally dominated by antibodies formed with the product of the A27 Vκ gene In contrast, λ+ anti-6B antibodies are dominated by the antibodies derived from one of 3 very similar Vλ2 family genes (candidate genes, 2c, 2e, and 2a2) and Cλ1 gene product The Vλ2+ antibodies express the 812 idiotype, which is expressed on anti-double-stranded-DNA antibodies In one case, Vλ is derived from a rarely expressed Vλ gene, 10a In the second approach, we studied a human hybridoma (Dob1) producing anti-6B antibody Its VH region sequence is closely related to those of the 3-15 VH gene (88% nucleotide homology) and JH4 (92% homology) Its VL region is homologous to the 2a2 Vλ2 gene (91%) and Jλ1/Cλ1 Taken together, the V region of human anti-6B antibodies is commonly formed by a VH3 and a Vλ2 family gene product

Simultaneous synthesis and densification of Ti5Si3 and Ti5Si3–20 vol% ZrO2 composites by field-activated and pressure-assisted combustion

Abstract: A method to simultaneously synthesize and consolidate the silicide Ti 5 Si 3 and the composite Ti 5 Si 3 –20 vol% ZrO 2 from powders of Ti, Si, and ZrO 2 was investigated Combustion synthesis was carried out under the combined effect of an electric field and mechanical pressure The final density of the products increased nearly linearly with the applied pressure Highly dense Ti 5 Si 3 and Ti 5 Si 3 –20 vol% ZrO 2 with relative densities of up to 98% were produced under the simultaneous application of a 60 MPa pressure and a 3000 A current on the reactant powders The percentages of the total shrinkage occurring before and during the synthesis reaction were 22 and 78% for the case of Ti 5 Si 3 , and 18 and 82% for the case of Ti 5 Si 3 –20 vol% ZrO 2 , respectively The respective Vickers microhardness values for these materials were 85 and 60 GPa From indentation crack measurements, the fracture toughness values for Ti 5 Si 3 and Ti 5 Si 3 –20 vol% ZrO 2 were calculated to be 3 and 9 MPa m 1/2 , respectively

Neutral invertase is a novel type of sucrose-cleaving enzyme

Abstract: Metabolism of sucrose, a mobile source of energy and carbon, is an absolute requirement for the survival of heterotrophic plant organs. In these organs, different isoforms of invertase with discrete subcellular locations hydrolyze the disaccharide into hexoses and, thereby, feed sucrose into various biochemical pathways. In contrast to the invertases with acidic pH optima and a vacuolar or extracellular location, knowledge about the molecular nature of the cytoplasmic invertases (neutral and alkaline invertases) is still in its infancy. Here we report the cDNA cloning of a neutral invertase from carrot based on a partial peptide sequence from the purified enzyme. The function of the encoded polypeptide was confirmed by expression of the cDNA in Escherichia coli. The recombinant protein cleaved sucrose into glucose and fructose with the highest activity between pH 6.5 and 7.0. Unlike acid invertase, neutral invertase does not have the characteristics of a typical plant β-fructofuranosidase and sucrose akppears to be its sole substrate. The deduced amino acid sequence shares no similarity with sequences of acid invertases. The polypeptide is cysteine-rich and homologous sequences were only detected in the genomes of plants and photosynthetic bacteria. Hence, this protein must have evolved independently of other sucrose-cleaving enzymes. Transcripts for neutral invertase were found in all organs at different stages of development with slightly higher levels in developing organs, suggesting a more general and possibly a growth-related function of the enzyme in carrot sucrose metabolism.

Boundary flows in general coset theories

Abstract: In this paper we study the boundary effects for off-critical integrable field theories which have close analogues with integrable lattice models. Our models are the coset conformal field theories perturbed by an integrable boundary and bulk operators. The boundary interactions are encoded into the boundary reflection matrix. Using the thermodynamic Bethe ansatz (TBA) method, we verify the flows of the conformal BCs by computing the boundary entropies. These flows of the BCs have direct interpretations for the fusion restricted solid-on-solid (RSOS) lattice models. For super conformal field theories (CFTs) (k = 2) we show that these flows are possible only for the Neveu-Schwarz sector and are consistent with the lattice results. The models we consider cover a wide class of integrable models. In particular, we show how the impurity spin is screened by electrons for the k-channel Kondo model by taking the limit. We also study the problem using an independent method based on the boundary roaming TBA. Our numerical results are consistent with the boundary CFTs and RSOS TBA analysis.

Serum insulin-like growth factor (IGF)-I and IGF-binding proteins in lung cancer patients.

Abstract: Many studies have shown that insulin-like growth factors (IGF-I & IGF-II) are implicated in the autocrine and paracrine growth of various tumors. Alterations in serum IGFs and IGF-binding proteins (IGFBPs) profiles have been reported in lung cancer. In this study, we measured serum levels of IGF-I and IGFBPs in 41 patients with lung cancer (small cell lung cancer, SCLC, 9; non-small cell lung cancer, NSCLC, 32) by radioimmunoassay and Western ligand blot (WLB). The serum IGF-I level in patients with lung cancer was significantly lower than in controls (207.9+/-62.6 vs 281.3+/-53.9 ng/mL, p 0.05). The concentration of IGFBP-3 in lung cancer was 48% of that found in controls by WLB. The serum level of IGFBP-2 was markedly elevated in patients with lung cancer compared with controls (1303.7+/-618.0 vs 696.2+/-300.5, p<0.01). However, there was no significant difference between SCLC and NSCLC groups. This result showed that serum level of IGF-I/IGFBPs may be useful markers for diagnosing and identifying tumor types in lung cancer and further studies are needed.

Ultraviolet-ozone jet cleaning process of organic surface contamination layers

Abstract: To understand the ultraviolet (UV)-ozone jet cleaning process of organic surface contamination layers, adventitious hydrocarbon layers on Si, self-assembled octadecyltrichlorosilane monolayers on Si, and self-assembled C60H–(CH2)12–SH monolayers on Au were cleaned with pure ozone jet and UV irradiation. Cleaned surfaces were analyzed with in situ x-ray photoelectron spectroscopy measurements. Ozone molecules could react with the unsaturated C–C bonds in self-assembled C60H–(CH2)12–SH monolayers on Au surfaces at room temperature. However, the saturated C–C bonds in OTS hydrocarbon molecules adsorbed on Au surfaces reacted not with ozone molecules but with oxygen radicals generated by the dissociation of ozone molecules under UV irradiation. For adventitious carbon contamination on Si surfaces, only a fraction could be cleaned by ozone at room temperature but it could be almost cleaned with UV-ozone jet.

A new rehabilitation training system for postural balance control using virtual reality technology

Abstract: A new rehabilitation training system, designated as a virtual cycling system, was developed to improve postural balance control by combining virtual reality (VR) technology with a bicycle. Several parameters including path deviation, path deviation velocity, cycling time, and head movement were extracted and evaluated to quantify the extent of control. The system was effective as a training device and, in addition, the technology might have a wider applicability to the rehabilitation field.

Glucocorticoids prevent NF-κB activation by inhibiting the early release of platelet-activating factor in response to lipopolysaccharide

Abstract: Lipopolysaccharide (LPS) is a known inducer of numerous pro-inflammatory events including the production of platelet-activating factor (PAF). PAF released in response to LPS is a major contributor to the pathological events associated with endotoxemia. The present study demonstrates that dexmethasone (DEX) inhibited the LPS-induced early plasma PAF raise in a dose- and time-dependent manner. In addition, DEX prevented the subsequent PAF-mediated pathological phenomena such as anaphylactic shock-like symptoms, symptoms of disseminated intravascular coagulation and hemorrhage in renal medullae. DEX or the PAF antagonist BN 50739 significantly inhibited LPS-induced NF-kappaB activation. The inhibition of NF-kappaB activation by DEX was overcome by the injection of exogenous PAF. Administration of PAF or LPS resulted in a rapid loss of IkappaBalpha protein. The LPS-induced degradation of IkappaBalpha was prevented by pretreatment with BN 50739, suggesting that PAF is a critical intermediate in the LPS-triggered degradation of IkappaBalpha protein. DEX prevented the LPS-induced IkappaBalpha degradation, which was also reversed by exogenous PAF. Administration of DEX or BN 50739 caused an increase in cytoplasmic IkappaBalpha level. Our results indicate that DEX inhibits IkappaBalpha degradation and subsequent NF-kappaB activation through blocking the initial release of PAF.

Modulation of endocardial natriuretic peptide receptors in right ventricular hypertrophy.

Abstract: Natriuretic peptide (NP) receptors (NPRs) located at the endocardial endothelium are suggested to be involved in regulating myocardial contractility. However, the characteristics and modulation of ...

Epidermal grafts for treatment of stable and progressive vitiligo.

Abstract: Background: Previous reports have shown the effectiveness of epidermal grafts for patients with stable vitiligo. Objective: Our purpose was to evaluate the effectiveness and complications of epidermal grafts in patients with stable and progressive vitiligo and to compare the results in both groups. Methods: Epidermal grafting with suction blisters was performed in 40 patients with vitiligo (26 stable and 14 progressive). The grafted sites and donor sites were examined for repigmentation for longer than 3 months, up to 2.5 years. Results: Complete repigmentation was observed in 19 patients with stable (73.1%) and 10 with progressive vitiligo (71.4%). Of the 29 patients who experienced complete repigmentation, we noted recurrences in 2 patients with stable disease (10.5%) and 4 with progressive disease (40%). Conclusion: Although patients with progressive vitiligo showed more frequent recurrence than those with stable disease, epidermal grafting may be an effective treatment not only for stable vitiligo but also for progressive vitiligo. (J Am Acad Dermatol 1999;40:412-7.)

Direct electrochemical regeneration of NADH from NAD+ using cholesterol-modified gold amalgam electrode

Abstract: The efficiency of the direct electrochemical regeneration of NADH from NAD+ was enhanced by applying a cholesterol-modified gold amalgam electrode. The modified electrode was prepared by immersing gold plate in mercury and casting few drops of cholesteryl oleate solution over the gold amalgam. Coenzymatically active NADH was formed from NAD+ directly at the cholesterol-modified gold amalgam electrode which is supposed to hinder the dimerization of the NAD radicals on its membrane surface. The direct electrochemical NAD+ reduction process was used favorably to drive an enzymatic reduction of pyruvate to d-lactate. d-Lactate of 18.2 mm was obtained from pyruvate of 25.3 mm at 21 h of total reaction time in the electrolysis of 50 cm3 solution with the electrode of 6 cm2area. The turnover number for NAD+ was estimated as 1400.