Showing papers by "Korea University published in 1999"

Exotic plant species invade hot spots of native plant diversity

Abstract: Some theories and experimental studies suggest that areas of low plant spe- cies richness may be invaded more easily than areas of high plant species richness. We gathered nested-scale vegetation data on plant species richness, foliar cover, and frequency from 200 1-m 2 subplots (20 1000-m 2 modified-Whittaker plots) in the Colorado Rockies (USA), and 160 1-m 2 subplots (16 1000-m 2 plots) in the Central Grasslands in Colorado, Wyoming, South Dakota, and Minnesota (USA) to test the generality of this paradigm. At the 1-m 2 scale, the paradigm was supported in four prairie types in the Central Grasslands, where exotic species richness declined with increasing plant species richness and cover. At the 1-m 2 scale, five forest and meadow vegetation types in the Colorado Rockies contradicted the paradigm; exotic species richness increased with native-plant species richness and foliar cover. At the 1000-m 2 plot scale (among vegetation types), 83% of the variance in exotic species richness in the Central Grasslands was explained by the total percentage of nitrogen in the soil and the cover of native plant species. In the Colorado Rockies, 69% of the variance in exotic species richness in 1000-m 2 plots was explained by the number of native plant species and the total percentage of soil carbon. At landscape and biome scales, exotic species primarily invaded areas of high species richness in the four Central Grasslands sites and in the five Colorado Rockies vegetation types. For the nine vegetation types in both biomes, exotic species cover was positively correlated with mean foliar cover, mean soil percentage N, and the total number of exotic species. These patterns of invasibility depend on spatial scale, biome and vegetation type, spatial autocorrelation effects, availability of resources, and species-specific responses to grazing and other disturbances. We conclude that: (1) sites high in herbaceous foliar cover and soil fertility, and hot spots of plant diversity (and biodiversity), are invasible in many landscapes; and (2) this pattern may be more closely related to the degree resources are available in native plant communities, independent of species richness. Exotic plant in- vasions in rare habitats and distinctive plant communities pose a significant challenge to land managers and conservation biologists.

Relationship between Helicobacter pylori iceA, cagA, and vacA Status and Clinical Outcome: Studies in Four Different Countries

Abstract: There is continuing interest in identifying Helicobacter pylori virulence factors that might predict the risk for symptomatic clinical outcomes. It has been proposed that iceA and cagA genes are such markers and can identify patients with peptic ulcers. We compared H. pylori isolates from four countries, looking at the cagA and vacA genotypes, iceA alleles, and presentation of the infection. We used PCR to examine iceA, vacA, and cagA status of 424 H. pylori isolates obtained from patients with different clinical presentations (peptic ulcer, gastric cancer, and atrophic gastritis). The H. pylori isolates examined included 107 strains from Bogota, Colombia, 70 from Houston, Tex., 135 from Seoul, Korea, and 112 from Kyoto, Japan. The predominant genotype differed among countries: the cagA-positive iceA1 vacA s1c-m1 genotype was predominant in Japan and Korea, the cagA-positive iceA2 vacA s1b-m1 genotype was predominant in the United States, and the cagA-positive iceA2 vacA s1a-m1 genotype was predominant in Colombia. There was no association between the iceA, vacA, or cagA status and clinical outcome in patients in the countries studied. iceA status shows considerable geographic differences, and neither iceA nor combinations of iceA, vacA, and cagA were helpful in predicting the clinical presentation of an H. pylori infection.

Development of advanced edible coatings for fruits

Abstract: Edible coatings can provide an additional protective coating for fresh products and can also give the same effect as modified atmosphere storage in modifying internal gas composition. Recently, several edible coatings for preserving fruits such as oranges, apples, and grapefruits were successfully applied. But, in some cases, edible coatings were not successful. In fact, fruit quality was worse. The success of edible coatings for fresh products totally depends on the control of internal gas composition. This article is designed to help develop a systematic means of selecting edible coatings to maximize quality and shelf life of fresh fruits and vegetables. Methods will be introduced to select edible coatings based on their gas permeation properties relative to controlling internal gas composition of target products.

Two distinct mechanisms are involved in 6-hydroxydopamine- and MPP+- induced dopaminergic neuronal cell death: Role of caspases, ROS, and JNK

Abstract: In this study, we examined the possibility that MPTP and 6-hydroxydopamine (6-OHDA) act on distinct cell death pathways in a murine dopaminergic neuronal cell line, MN9D. First, we found that cells treated with 6-OHDA accompanied ultrastructural changes typical of apoptosis, whereas MPP+ treatment induced necrotic manifestations. Proteolytic cleavage of poly(ADP-ribose)polymerase by caspase was induced by 6-OHDA, whereas it remained uncleaved up to 32 h after MPP+ treatment and subsequently disappeared. Accordingly, 6-OHDA- but not MPP+-induced cell death was significantly attenuated in the presence of a broad-spectrum caspase inhibitor, N-benzyloxy-carbonyl-Val-Ala-Asp-fluomethylketone (Z-VAD-fmk). As measured by fluorometric probes, the level of reactive oxygen species (ROS) significantly increased after 6-OHDA treatment. In contrast, the level of dihydroethidium-sensitive ROS following MPP+ treatment remained unchanged while a slight increase in dichlorofluorescin-sentive ROS was temporarily observed. As demonstrated by immunoblot analysis, the level of superoxide dismutase was down-regulated following 6-OHDA treatment, whereas it remained unchanged after MPP+ treatment. Cotreatment of cells with antioxidants such as N-acetylcysteine or Mn(III)tetrakis(4-benzoic acid)porphyrin chloride (MnTBAP, cell-permeable superoxide dismutase mimetic) rescued 6-OHDA- but not MPP+-induced cell death, whereas inclusion of catalase or NG-nitro-l-arginine had no effect in both cases. In addition, 6-OHDA induced ROS-mediated c-Jun N-terminal kinase (JNK) activation that was attenuated in the presence of N-acetylcysteine or MnTBAP but not catalase or Z-VAD-fmk. In contrast, MPP+ has little effect on JNK activity, indicating that ROS and/or ROS-induced cell death signaling pathway seems to play an essential role in 6-OHDA–mediated apoptosis but not in MPP+-induced necrosis in a mesencephalon-derived, dopaminergic neuronal cell line. J. Neurosci. Res. 57:86–94, 1999. © 1999 Wiley-Liss, Inc.

Efficient video indexing scheme for content-based retrieval

Abstract: Extracting a small number of key frames that can abstract the content of video is very important for efficient browsing and retrieval in video databases. In this paper, the key frame extraction problem is considered from a set-theoretic point of view, and systematic algorithms are derived to find a compact set of key frames that can represent a video segment for a given degree of fidelity. The proposed extraction algorithms can be hierarchically applied to obtain a tree-structured key frame hierarchy that is a multilevel abstract of the video. The key frame hierarchy enables an efficient content-based retrieval by using the depth-first search scheme with pruning., Intensive experiments on a variety of video sequences are presented to demonstrate the improved performance of the proposed algorithms over the existing approaches.

Fast digital image stabilizer based on Gray-coded bit-plane matching

Abstract: A fast digital image stabilizer based on the Gray-coded bit-plane matching is proposed which is robust to irregular conditions such as moving objects and intentional panning. The proposed digital image stabilization (DIS) system performs motion estimation using the Gray-coded bit-plane of video sequences, greatly reducing the computational load. This motion estimation method can be realized using only binary Boolean functions which have significantly reduced computational complexity, while the accuracy of motion estimation is maintained. In order to further improve the computational efficiency, the Gray-coded bit-plane matching with the three-step search (3SS) is proposed. Experimental results indicate that the proposed digital image stabilizer is a computationally efficient alternative to existing DIS systems.

New autofocusing technique using the frequency selective weighted median filter for video cameras

Abstract: Most conventional autofocusing techniques based on the gradient estimator are very sensitive to noise. A new autofocusing technique which is resistive to noise generated by the CCD of video cameras is proposed. In the proposed scheme, the frequency selective weighted median (FSWM) filter is utilized to estimate the degree of focus and the fast hill-climbing search (HCS) strategy is exploited to determine the best focused image. Since the FSWM filter can not only extract high frequency components from the image, but also eliminate impulsive noise, the proposed autofocusing method employing the FSWM criterion function can estimate the degree of focus precisely. Furthermore, the proposed real-time HCS algorithm enables the video camera to continuously focus on dynamic images. Experimental results demonstrate that the proposed technique outperforms existing techniques by enhancing the accuracy of the focus value of the video camera without the influence of noise.

Comparison of Protein Extraction Solutions for Rice Starch Isolation and Effects of Residual Protein Content on Starch Pasting Properties

Abstract: Protein extraction solutions such as aqueous solutions of sodium hydroxide (0.1 and 0.2 %), sodium lauryl sulfate (SLS, 1.2 %) containing sodium sulfite (0.12 %), and dodecylbenzene sulfonate (DoBS, 1.2 %) containing sodium sulfite (0.12 %) were compared in their protein removal efficiencies during isolation of starch from a rice flour (Ilpumbyo, a nonwaxy Korean rice variety). In addition, the pasting properties of the isolated starch was compared. More than 80 % of the flour protein was extracted in 1 h by stirring the dispersion (1:3, w/v) at room temperature. Repeating the extractions (1 or 2 h for each step) with fresh solution significantly increased the protein removal efficiency. When the extraction in 0.2 % NaOH was repeated four times (1 h for each step) at 25°C, the residual protein content in the isolated rice starch was 0.9 % (DB), equivalent to 86 % removal of the rice protein. Raising the extraction temperature slightly increased the protein solubility, but starch loss also became significant. Among the solutions, DoBS was most effective in removing rice protein whereas SLS was least. The residual protein content had a critical role in determining the pasting characteristics of the isolated starch, showing a negative correlation to the peak viscosity of the starch paste, but a positive correlation to the pasting temperature.

The impact of modes of entry and resource fit on modes of exit by multibusiness firms

Abstract: This study examines the choices of modes of entry and exit in the process of new business exploration. We find that exit mode choices are determined by a different set of factors from those that are important for the entry mode decision and the exit decision per se. Our study indicates that when the resource profiles of a parent firm and the business unit are more dissimilar, and there has been less development of firm-specific idiosyncratic assets, firms are more likely to sell businesses than dissolve them. Further, the study reports a strong relationship between the mode of exit from a line of business (sell-off vs. dissolution) and the original mode of entry (acquisition versus internal development). Copyright © 1999 John Wiley & Sons, Ltd.

A novel angiogenic factor derived from Aloe vera gel: beta-sitosterol, a plant sterol.

Abstract: Aloe vera gel has a beneficial effect on wound healing. Because angiogenesis is an essential process in wound healing, we hypothesized that Aloe vera gel might contain potent angiogenic compounds. Here we demonstrate that Aloe vera gel and its extracts are angiogenic on the chorioallantoic membrane (CAM) of chick embryo. Out of the three compounds purified from the final fraction of Aloe vera gel, beta-sitosterol showed a potent angiogenic activity in the CAM assay. In the presence of heparin, beta-sitosterol stimulated neovascularization in the mouse Matrigel plug assay and the motility of human umbilical vein endothelial cells in an in vitro wound migration assay. Thus beta-sitosterol is a novel plant-derived angiogenic factor which may have potential pharmaceutical applications for the management of chronic wounds.

Terminal sliding mode control of second‐order nonlinear uncertain systems

Abstract: In this paper, a terminal sliding mode control scheme is proposed for second-order nonlinear uncertain systems. By using a function augmented sliding hyperplane, it is guaranteed that the output tracking error converges to zero in finite time which can be set arbitrarily. In addition, the proposed scheme eliminates the reaching phase problem so that the closed-loop system always shows the invariance property to parameter uncertainties. Copyright © 1999 John Wiley & Sons, Ltd.

Paclitaxel, 5-fluorouracil, and cisplatin combination chemotherapy for the treatment of advanced gastric carcinoma

Abstract: BACKGROUND Although the clinical efficacy of paclitaxel in the treatment of gastric carcinoma has not been clearly defined, recent reports have suggested a possible role in the treatment of upper gastrointestinal carcinomas in vitro and in vivo. In this study, the authors evaluated the efficacy and toxicity of a combination chemotherapy that included paclitaxel, 5-fluorouracil (5-FU), and cisplatin in the treatment of patients with advanced gastric carcinoma. METHODS Forty-one gastric carcinoma patients with metastatic disease, unresectable advanced disease, or relapsed disease were treated with the following regimen, administered every 28 days: paclitaxel 175 mg/m2 by 3-hour intravenous (i.v.) infusion on Day 1, 5-FU 750 mg/m2 by 24-hour continuous i.v. infusion on Days 1–5, and cisplatin 20 mg/m2 by 2-hour i.v. infusion on Days 1–5. Twenty-six patients had measurable disease, and 15 had evaluable disease. All patients were assessable for toxicity. RESULTS Twenty-one of the 41 patients (51%; 95% confidence interval [CI], 36.5–65.7%) demonstrated an objective response, including 4 complete responses (10%; 95% CI, 3.9–22.5%). Sixty-five percent of the patients with measurable disease (17of 26; 95% CI, 58–92.5%) and 27% of the patients with evaluable disease (4 of 15: 95% CI, 11.1–52.3%) achieved a complete response or a partial response. The median response duration was 17 weeks (range, 4–90 weeks), and the median survival duration for all patients was 26 weeks (range, 8 to 118+ weeks). The major toxicity of this treatment was myelosuppression with neutropenia of World Health Organization Grade 3 and 4 in 24% and 10% of the patients, respectively. Nonhematologic toxicity included mucositis, nausea/vomiting, diarrhea, neurotoxicity, and alopecia. Fluid retention occurred in two patients, and one patient had an anaphylatic reaction. Dose reduction was necessary for one patient, because Grade 4 neutropenia and mucositis occurred. CONCLUSIONS Paclitaxel, 5-FU, and cisplatin was an active combination regimen in the treatment of advanced gastric carcinoma. The toxicity of this regimen was tolerable. Based on these findings, this combination regimen could be an attractive treatment in the preoperative setting. Cancer 1999;85:295–301. © 1999 American Cancer Society.

Structure-based identification of a novel NTPase from Methanococcus jannaschii

Abstract: Almost half of the entire set of predicted genomic products from Methanococcus jannaschii are classified as functionally unknown hypothetical proteins. We present a structure-based identification of the biochemical function of a protein with an as yet unknown function from a M. jannaschii gene, Mj0226. The crystal structure of Mj0226 protein determined at 2.2 A resolution reveals that the protein is a homodimer and each monomer folds into an elongated α/β structure of a new fold family. Comparisons of Mj0226 protein with protein structures in the database, however, indicate that one part of the protein is homologous to some of the nucleotide-binding proteins. Biochemical analysis shows that Mj0226 protein is a novel nucleotide triphosphatase that can efficiently hydrolyze nonstandard nucleotides such as XTP to XMP or ITP to IMP, but not the standard nucleotides, in the presence of Mg2+ or Mn2+ ions.

Neoliberalism and the decline of the developmental state

Abstract: Since the 1980s, the Korean state has witnessed significant challenges from big business (chaebol) as well as from organized labor and popular sector. Regime transition has influenced the social and political relations between the state and big business. Thus the central argument is therefore that the developmental state has gradually eroded as the power and capability of the developmental state was increasingly affected by economic liberalization and political democratization. At the same time the state and big business are increasingly connected within more institutionalized networks. The argument will be advanced that the traditional relationship between the state and big business, which was characterized as one of state domination and the subordination of big business, has been changing more radically than the statist analysts presumed.

Theoretical study of frequency chirping and extinction ratio of wavelength-converted optical signals by XGM and XPM using SOA's

Abstract: We develop a complete large-signal dynamic model of semiconductor optical amplifier (SOA)-based wavelength converters using cross-gain modulation (XGM) and cross-phase modulation (XPM). The large-signal dynamic model has been implemented using the modified transfer matrix method (TMM). This model takes into account longitudinal variations of carrier-induced refractive index, n-parameter, internal reflection, photon density, and amplified spontaneous emission noise at each small section. Therefore, we can accurately estimate frequency chirping, optical pulse patterns, and the extinction ratio as well as the dynamic characteristics of SOA's. Frequency chirping and the extinction ratio have been calculated for various parameters such as signal power and wavelength, CW power and wavelength, and facet reflectivity. Modulation bandwidth, defined by the 3-dB drop as the eye opening ratio (EOR) is investigated with current density, confinement factor, and cavity length.

Structure and mechanism of glutamate racemase from Aquifex pyrophilus.

Abstract: Glutamate racemase (MurI) is responsible for the synthesis of D-glutamate, an essential building block of the peptidoglycan layer in bacterial cell walls. The crystal structure of glutamate racemase from Aquifex pyrophilus, determined at 2.3 A resolution, reveals that the enzyme forms a dimer and each monomer consists of two α/β fold domains, a unique structure that has not been observed in other racemases or members of an enolase superfamily. A substrate analog, D-glutamine, binds to the deep pocket formed by conserved residues from two monomers. The structural and mutational analyses allow us to propose a mechanism of metal cofactor-independent glutamate racemase in which two cysteine residues are involved in catalysis.

Enhanced photodecomposition of 4-chlorophenol in aqueous solution by deposition of CdS on TiO2

Abstract: The photocatalyzed degradation of 4-chlorophenol (4-CP) in water is comparatively examined with TiO 2 powder, TiO 2 /CdS powder, TiO 2 thin film electrodes and TiO 2 /CdS thin film electrodes in the initial stages of the reaction. The apparent intermediates of 4-CP photodegradation with TiO 2 and TiO 2 /CdS powders in suspensions are found to be 1,4-benzoquinone (BQ) and hydroquinone (HQ), with HQ rapidly converting into BQ with TiO 2 and TiO 2 /CdS electrodes at an applied anodic potential of 0.6 V vs Ag/AgCl. The apparent reaction rate constants using the Langmuir–Hinshelwood equation with TiO 2 /CdS powder and the TiO 2 /CdS electrode are obtained to be about 90% and 33% larger than with TiO 2 powder and the TiO 2 electrode, respectively, indicating that the TiO 2 /CdS catalysts have more photocatalytic activities than the TiO 2 catalysts in the initial stages. The adsorption coefficient ( K ) of 4-CP on TiO 2 /CdS powder is one and a half times larger than that on TiO 2 powder. With the electrode catalysts at 0.6 V, the value of K increases several times with respect to the corresponding powder catalysts and shows essentially no difference between the TiO 2 /CdS electrode and the TiO 2 electrode. Thus, the value of K may strongly depend on the electrostatic interaction between 4-CP and the electrode surface, but not very much on the type of electrode surface.

Macromodeling of single-electron transistors for efficient circuit simulation

Abstract: In this study, the possibility of compact modeling in single-electron circuit simulation has been investigated. It is found that each Coulomb island in single-electron circuits can be treated independently when the interconnections between single-electron transistors are large enough and a quantitative criterion for this condition is given. It is also demonstrated that, in those situations, SPICE macromodeling of single-electron transistors can be used for efficient circuit simulation. The developed macromodel produces simulation results with reasonable accuracy and with orders of magnitude less CPU time than usual Monte Carlo simulations.