Showing papers by "Korea University published in 2000"

International Data on Educational Attainment Updates and Implications

Abstract: This paper presents a data set that improves the measurement of educational attainment for a broad group of countries. We extend our previous estimates of educational attainment for the population over age 15 and over age 25 up to 1995 and provide projections for 2000. We discuss the estimation method for the measures of educational attainment and relate our estimates to alternative international measures of human capital stocks.

Economic Performance of Group-Affiliated Companies in Korea: Intragroup Resource Sharing and Internal Business Transactions

Abstract: This study examined the economic performance of the firms associated with Korean business groups by explicitly addressing groupwide resource sharing and internal business transactions. The results ...

Spurious Welfare Reversals in International Business Cycle Models

Abstract: Papers on international business cycles have documented spurious welfare reversals: incomplete markets produce a higher level of welfare than the complete market. This paper first demonstrates how conventional linearization, as used in King, Plosser, and Rebelo (1988), can generate approximation errors that can result in welfare reversals. Using a two-country production economy, we argue that spurious welfare reversals are not only possible but also plausible under reasonable values for model parameters including labor supply elasticity. As a constructive alternative, this paper then proposes an approximation method that modifies the conventional linearization by a bias correction - the linear approximation around a 'stochastic' steady state. We show that this method can be easily implemented and very well approximates the exact solution. The accuracy of the proposed method is by far better than that of the conventional linearization method and as good as that of a perturbation method involving a second-order expansion.

leafy hull sterile1 Is a Homeotic Mutation in a Rice MADS Box Gene Affecting Rice Flower Development

Abstract: Rice contains several MADS box genes. It has been demonstrated previously that one of these genes, OsMADS1 (for Oryza sativa MADS box gene1), is expressed preferentially in flowers and causes early flowering when ectopically expressed in tobacco plants. In this study, we demonstrated that ectopic expression of OsMADS1 in rice also results in early flowering. To further investigate the role of OsMADS1 during rice flower development, we generated transgenic rice plants expressing altered OsMADS1 genes that contain missense mutations in the MADS domain. There was no visible alteration in the transgenic plants during the vegetative stage. However, transgenic panicles typically exhibited phenotypic alterations, including spikelets consisting of elongated leafy paleae and lemmas that exhibit a feature of open hull, two pairs of leafy palea-like and lemma-like lodicules, a decrease in stamen number, and an increase in the number of carpels. In addition, some spikelets generated an additional floret from the same rachilla. These characteristics are very similar to those of leafy hull sterile1 (lhs1). The map position of OsMADS1 is closely linked to that of lhs1 on chromosome 3. Examination of lhs1 revealed that it contains two missense mutations in the OsMADS1 MADS domain. A genetic complementation experiment showed that the 11.9-kb genomic DNA fragment containing the wild-type OsMADS1 gene rescued the mutant phenotypes. In addition, ectopic expression of the OsMADS1 gene isolated from the lhs1 line resulted in lhs1-conferred phenotypes. These lines of evidence demonstrate that OsMADS1 is the lhs1 gene.

The trans-10,cis-12 Isomer of Conjugated Linoleic Acid Downregulates Stearoyl-CoA Desaturase 1 Gene Expression in 3T3-L1 Adipocytes

Abstract: Conjugated linoleic acids (CLA) are a group of positional and geometric conjugated dienoic isomers of linoleic acid. The objective of this study was to determine the effects of the cis-9,trans-11 and trans-10,cis-12 isomers of conjugated linoleic acid on lipid composition and gene expression during the differentiation of mouse 3T3-L1 preadipocytes. Treatment of differentiating 3T3-L1 preadipocytes with trans-10,cis-12 conjugated linoleic acid (CLA) resulted in a dose-dependent decrease in the expression of the stearoyl-CoA desaturase 1 gene (SCD1). The expression of other adipocyte genes such as adipose P2 (aP2), fatty acid synthase (FAS), SCD2 and the key adipogenic transcription factors, peroxisome proliferator-activated receptor gamma2 (PPARgamma2) and CCAAT enhancer binding protein alpha (C/EBPalpha), remained elevated. Cells treated with trans-10,cis-12 CLA exhibited smaller lipid droplets, with reduced levels of the major monounsaturated fatty acids, palmitoleate and oleate. By contrast, the cis-9,trans-11 isomer did not alter adipocyte gene expression. Repression of the stearoyl-CoA desaturase gene expression in adipocytes by the trans-10,cis-12 isomer may contribute to the mechanisms by which CLA reduces body fat in mice.

New frame rate up-conversion using bi-directional motion estimation

Abstract: We propose a new frame rate up-conversion algorithm for high quality video. In the proposed scheme, bi-directional motion estimation (ME) is performed to construct the motion vector (MV) field for the frame to be interpolated. Unlike conventional motion-compensated interpolation (MCI) algorithms, the proposed technique does not produce any overlapped pixel and hole region in the interpolated frame, and thus can utilize the overlapped block motion compensation technique to reduce the blocking artifacts. The proposed algorithm is very simple to implement on consumer products when compared to conventional MCI methods. Computer simulation shows a high visual performance of the proposed frame rate up-conversion algorithm.

High frequency electromagnetic interference shielding response of mixtures and multilayer films based on conducting polymers

Abstract: The electromagnetic interference (EMI) shielding efficiency (SE) is measured for conductive polyaniline and its mixtures containing conducting powders. The frequency ranges of the EMI SE is 10 MHz–1 GHz by using the ASTM D4935-89 technique. The EMI SE of hydrochloric acid doped polyaniline containing silver (Ag) powder is ∼46 dB at room temperature, which indicates that the materials can be commercially applied to shielding against electromagnetic (EM) radiation. The theoretical SE is calculated by using measured dc conductivity, which is compared to the experimental data. We observe that the SE increases with increasing dc conductivity. A model to account for the increase of the SE through the chemical doping and mixing process is presented. The theory for the calculation of the EMI SE of multilayer films based on conducting polymers is discussed in terms of boundary conditions for electric and magnetic fields of EM plane waves. The high frequency (⩾300 MHz) EMI shielding response of the monolayer and mu...

Growth model of bamboo-shaped carbon nanotubes by thermal chemical vapor deposition

Abstract: Vertically aligned carbon nanotubes were grown on iron-deposited silicon oxide substrate by thermal chemical vapor deposition of acetylene The carbon nanotubes have no encapsulated iron particles at the closed tip and a bamboo structure in which the curvature of compartment layers is directed to the tip A base growth model is suggested for the bamboo-shaped carbon nanotubes grown under our experimental conditions

Hepatic expression, synthesis and secretion of a novel fibrinogen/angiopoietin-related protein that prevents endothelial-cell apoptosis

Abstract: Using degenerate PCR we isolated a cDNA encoding a novel 406- and 410-amino acid protein from human and mouse embryonic cDNAs and have designated it ‘hepatic fibrinogen/angiopoietin-related protein’ (HFARP). The N-terminal and C-terminal portions of HFARP contain the characteristic coiled-coil domains and fibrinogen-like domains that are conserved in angiopoietins. In human and mouse tissues, HFARP mRNA is specifically expressed in the liver. HFARP mRNA and protein are mainly present in the hepatocytes. HFARP has a highly hydrophobic region at the N-terminus that is typical of a secretory signal sequence and one consensus glycosylation site. Recombinant HFARP expressed in COS-7 cells is secreted and glycosylated. HFARP protein is present not only in the hepatocytes, but also in the circulating blood. Recombinant HFARP acts as an apoptosis survival factor for vascular endothelial cells, but does not bind to Tie1 or Tie2 (endothelial-cell tyrosine kinase receptors). These results suggest that HFARP may exert a protective function on endothelial cells through an endocrine action.

Charge pump with perfect current matching characteristics in phase-locked loops

Abstract: Conventional CMOS charge pump circuits have some current mismatching characteristics. The current mismatch of the charge pump in the PLLs generates a phase offset, which increases spurs in the PLL output signals. In particular, it reduces the locking range in wide range PLLs with a dual loop scheme. A new charge pump circuit with perfect current matching characteristics is proposed. By using an error amplifier and reference current sources, one can achieve a charge pump with good current matching characteristics. It shows nearly perfect current matching characteristics over the whole VCO input range, and the amount of the reference spur is <-75 dBc in the PLL output signal. The charge pump circuit is implemented in a 0.25 /spl mu/m CMOS process.

Nitric oxide negatively regulates c-Jun N-terminal kinase/stress-activated protein kinase by means of S-nitrosylation

Abstract: NO, produced from l-arginine in a reaction catalyzed by NO synthase, is an endogenous free radical with multiple functions in mammalian cells. Here, we demonstrate that endogenously produced NO can suppress c-Jun N-terminal kinase (JNK) activation in intact cells. Treatment of BV-2 murine microglial cells with IFN-gamma induced endogenous NO production, concomitantly suppressing JNK1 activation. Similarly, IFN-gamma induced suppression of JNK1 activation in RAW264.7 murine macrophage cells and rat alveolar macrophages. The IFN-gamma-induced suppression of JNK1 activation in BV-2, RAW264.7, or rat alveolar macrophage cells was completely prevented by N(G)-nitro-l-arginine, a NO synthase inhibitor. Interestingly, the IFN-gamma-induced suppression of JNK1 activation was not affected by 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, an inhibitor of guanylyl cyclase. 8-Bromo-cGMP, a membrane-permeant analogue of cGMP, did not change JNK1 activation in intact cells either. In contrast, S-nitro-N-acetyl-dl-penicillamine (SNAP), a NO donor, inhibited JNK1 activity in vitro. Furthermore, a thiol reducing agent, DTT, reversed not only the in vitro inhibition of JNK1 activity by SNAP but also the in vivo suppression of JNK1 activity by IFN-gamma. Substitution of serine for cysteine-116 in JNK1 abolished the inhibitory effect of IFN-gamma or SNAP on JNK1 activity in vivo or in vitro, respectively. Moreover, IFN-gamma enhanced endogenous S-nitrosylation of JNK1 in RAW264.7 cells. Collectively, our data suggest that endogenous NO mediates the IFN-gamma-induced suppression of JNK1 activation in macrophage cells by means of a thiol-redox mechanism.

Corporate and industry effects on business unit competitive position

Abstract: We partition the variances of market shares, which we use as surrogates for competitive position, of the business units of all public manufacturing companies available in the Trinet data base into industry factors, corporate parent-specific factors, and business unit-specific factors. Our results differ somewhat from Rumelt's (1991), which decomposed variances in profitability. We find that corporate parent effects on market share are considerably greater than zero when lines of business are defined more narrowly, when small business units are included, and when firms are medium-sized. Our results suggest that the relative importance of corporate, industry, and business unit effects depends on the types of criteria, such as the level of industry aggregation, whether small business units are included, and firm size, that are used to construct samples. Copyright © 2000 John Wiley & Sons, Ltd.

Antitumor Action of Physiological Estradiol on Tamoxifen-stimulated Breast Tumors Grown in Athymic Mice

Abstract: The estrogen receptor (ER)-positive MCF-7 breast cancer cell line can be transplanted into athymic mice and grown into tumors with estradiol (E2) support. Tamoxifen (TAM) blocks E2-stimulated tumor growth; however, continuous TAM treatment results in transplantable tumors within a year that will grow with either E2 or TAM (M. M. Gottardis and V. C. Jordan, Cancer Res., 48: 5183-5187, 1988). Although this model may represent the development of TAM resistance for the treatment of advanced breast cancer, no laboratory model exists to study the exposure of breast cancer to 5 years of adjuvant TAM therapy. We have addressed this issue and report the development and characterization of two tumor lines, MCF-7TAM and MT2, which have been serially transplanted into TAM-treated athymic mice for >5 years. The MCF-7TAM tumor rapidly regresses in response to E2 and then about 50% of tumors regrow in response to E2. Interestingly, tumor regression does not occur if TAM treatment is stopped, probably because E2 levels are too low in ovariectomized athymic mice. The development of the antitumor effect of E2 was documented for MT2 tumors over a 1-year period; TAM-stimulated tumor growth was retained, but E2 caused progressively less of a stimulatory effect. Most importantly, E2-stimulated tumors that regrew after initial tumor regression in both MCF-7TAM and MT2 lines were again responsive to TAM to block E2-stimulated growth. Unlike MCF-7 tumors, the MT2 tumor line contains a single point mutation, Asp351Tyr, in the ER, which was retained after the development of E2-stimulated regrowth. The mutation is associated with increased estrogen-like actions for the TAM-ER complex (A. S. Levenson et al., Br. J. Cancer, 77: 1812-1819, 1998), but we conclude that the mutant ER is not required for TAM resistance. On the basis of the new breast cancer models presented, we propose a cyclic sensitivity to TAM that may have important clinical implications: (a) it is possible that a woman's own estrogen may produce an antitumor effect on the presensitized micrometastatic disease after 5 years of TAM. Long-term antitumor action occurs because the drug is stopped, but resistance accumulates and tumors start to grow if adjuvant therapy is continued; and (b) although in the clinic TAM-resistant tumors respond to second-line therapies that cause estrogen withdrawal, e.g., pure antiestrogens or aromatase inhibitors, estrogen therapy may also be effective and return the tumor to TAM responsiveness. In this way, a hormone-responsive tumor may be controlled longer in the patient with advanced disease.

A study of through-thickness texture gradients in rolled sheets

Abstract: A method to simulate shear effects and through-thickness texture gradients in rolled sheet materials is introduced. The strain history during a rolling pass is idealized by superimposing a sine-shaped evolution of the \(\dot \varepsilon \)13 shear component to a plane-strain state. These generic strain histories are enforced in a visco-plastic self-consistent (VPSC) polycrystal deformation model to simulate texture evolution as a function of through-thickness position. The VPSC scheme is deemed superior to a full constraints (FC) or relaxed constraints (RC) approach, because it allows one to fully prescribe diagonal and shear-strain-rate components while still accounting for grain-shape effects. The idealized strain states are validated by comparison with deformation histories obtained through finite-element method (FEM) calculations. The through-thickness texture gradients are accounted for by introducing a relative variation of the sine-shaped \(\dot \varepsilon \)13 shear with respect to the plane-strain component. The simulation results are validated, in turn, by comparison with typical examples of through-thickness texture gradients observed experimentally in rolled plates and in sheets of fcc and bcc materials.

Financial Crisis and Credit Crunch in Korea: Evidence from Firm-Level Data

Abstract: This paper analyzes the credit crunch following the recent financial crisis in Korea. Using enterprise-level data, we find that there were big differences in the magnitude of the credit contraction across different types of firms. In particular, chaebol (conglomerate)-affiliated firms appeared to have lost the preferential access to credit they enjoyed in the pre-crisis period, and credit appears to have been reallocated in favor of more efficient firms. This suggests that the credit crunch suffered by certain sectors can be attributed to the adjustment by banks and enterprises to the restructuring of the financial sector, rather than to tight monetary policy or an external credit constraint.

Free-Standing GaN Substrates by Hydride Vapor Phase Epitaxy

Abstract: Thick gallium nitride films 250–350 µm in thickness were grown on 2-inch-diameter (0001) sapphire wafers by hydride vapor phase epitaxy. The size of the free-standing GaN substrates without cracks separated from the sapphire substrates by laser processing was equal to that of the initial sapphire substrates. The origin of bowing and the broad photoluminescence (PL) spectra of GaN films was considered the difference in the residual strain between the front and bottom surfaces caused by threading dislocations.

OmpR Regulates the Stationary-Phase Acid Tolerance Response of Salmonella enterica Serovar Typhimurium

Abstract: Bacteria in nature are often exposed to dramatic fluctuations in external pH that threaten viability. Survival, therefore, depends on the presence of adaptive mechanisms that sense an acidifying environment and coordinate an appropriate molecular response (15, 17). Salmonella enterica serovar Typhimurium employs several strategies to avoid or repair damage associated with acid stress. Two major low-pH-inducible systems, known as acid tolerance responses (ATR), have been identified. They are classified based on the growth phase at which each becomes induced. Most studies have focused on the log-phase ATR system induced when exponentially growing cells suddenly undergo a rapid transition to low pH (16). Over 50 acid shock proteins (ASPs) are produced during this response (14). The regulatory genes rpoS, encoding an alternative sigma factor, and fur, encoding the major iron regulator, are required for log-phase acid tolerance and control the production of subsets of the ASPs (15, 17, 19, 33). The second ATR system, referred to as the stationary-phase ATR, is induced by exposing stationary-phase cells to low pH (34). It is distinct from the general stress response system that is induced by entry into stationary phase regardless of the culture pH. The general stress response system requires stationary-phase induction of the alternative sigma factor ςS, while the acid-induced stationary-phase ATR does not. The Fur protein, also required for log-phase ATR, is not involved in the stationary-phase ATR, indicating that the two acid-inducible acid tolerance systems are functionally distinct. Consistent with this idea, 10 stationary-phase ASPs have been found that are not log-phase ASPs (34). However, the identities of these proteins and their genetic regulation have not been characterized. In this study, we present the first report of an acid-induced gene required for the stationary-phase ATR of serovar Typhimurium.

Pepper gene encoding a basic pathogenesis‐related 1 protein is pathogen and ethylene inducible

Abstract: A new basic pathogenesis-related (PR)-1 cDNA (CABPR1) was isolated from a cDNA library of pepper leaves infected with Xanthomonas campestris pv. vesicatoria. The full-length clone contains an open reading frame of 531 nucleotides encoding 177 amino acid residues with a predicted molecular mass of 20241 and pI of 8.1. The deduced amino acid sequence of CABPR1 has a high level of identity with PR-1 proteins from tobacco and tomato. Expression of the CABPR1 mRNA was greatly induced in an incompatible interaction of pepper leaves with X. campestris pv. vesicatoria. Accumulation of the basic PR-1 mRNA in the bacteria-infected leaves was intrinsically associated with the induction of ethylene biosynthesis. Treatment with 1-aminoethoxyvinylglycine, an inhibitor of ethylene biosynthesis, strongly suppressed the induction of PR-1 mRNA expression in the bacteria-infected leaves. These data suggest that ethylene may function as a strong signal elicitor in the activation of PR-1 genes, eventually mediating the plant defence response. Phytophthora capsici infection also distinctly stimulated ethylene biosynthesis, together with accumulation of PR-1 mRNA. Expression of the basic PR-1 mRNA was also induced in the pepper leaves by treatment with dl-β-amino-n-butyric acid or salicylic acid, but not by wounding. Treatment with methyl jasmonate, in combination with salicylic acid, strongly induced the PR-1 transcripts. The basic PR-1 gene expression occurred in untreated roots, flowers and green fruit of pepper but not in leaf, stem or red fruit.

Fast scene change detection using direct feature extraction from MPEG compressed videos

Abstract: In order to process video data efficiently, a video segmentation technique through scene change detection must be required. This is a fundamental operation used in many digital video applications such as digital libraries, video on demand (VOD), etc. Many of these advanced video applications require manipulations of compressed video signals. So, the scene change detection process is achieved by analyzing the video directly in the compressed domain, thereby avoiding the overhead of decompressing video into individual frames in the pixel domain. In this paper, we propose a fast scene change detection algorithm using direct feature extraction from MPEG compressed videos, and evaluate this technique using sample video data, First, we derive binary edge maps from the AC coefficients in blocks which were discrete cosine transformed. Second, we measure edge orientation, strength and offset using correlation between the AC coefficients in the derived binary edge maps. Finally, we match two consecutive frames using these two features (edge orientation and strength). This process was made possible by a new mathematical formulation for deriving the edge information directly from the discrete cosine transform (DCT) coefficients. We have shown that the proposed algorithm is faster or more accurate than the previously known scene change detection algorithms.

Occurrence of aflatoxin M1 in Korean dairy products determined by ELISA and HPLC.

Abstract: The occurrence of aflatoxin M1 (AFM1)in pasteurized milk and dairy products was investigated by using direct competitive enzyme-linked immunosorbent assay (ELISA) and high-performance liquid chromatography (HPLC). The recoveries of AFM1 from the samples spiked at levels between 5 and 500 pg/ml were 88.0–106.5% for pasteurized milk and 84.0–94.0% for yoghurt by ELISA. By HPLC, the recoveries were 103–120% for pasteurized milk and 87.0–93.0% for yoghurt. The limits of detection were found to be 2 pg/ml by ELISA and 10 pg/ml by HPLC. Among a total of 180 samples collected in Seoul, Korea, the incidence of AFM1 in pasteurized milk, infant formula, powdered milk and yoghurt was 76, 85, 75, and 83%, respectively, with a mean concentration of 18, 46, 200, and 29 pg/g, respectively, when determined by ELISA. These results obtained by ELISA were closely related to those by HPLC for AFM1 (r2 = 0.9783).

Microsatellite instability in gastric intestinal metaplasia in patients with and without gastric cancer.

Abstract: The role and significance of microsatellite instability (MSI) in gastric carcinogenesis remain unknown. This study determined the chronology of MSI in gastric carcinogenesis by examining intestinal metaplasia (IM) from patients with and without gastric cancer. DNA was obtained from gastric specimens of 75 patients with gastric IM (30 cancer, 26 peptic ulcer, and 19 chronic gastritis patients) and was amplified with a set of eight microsatellite markers. Eight (26.7%) tumors and seven (9.3%) IM samples (three from cancer-free patients) displayed high-level MSI (three or more loci altered). Low-level MSI (one or two loci altered) was detected in 50. of the tumors, in 40% of IM samples coexisting with cancer, and in 38% of IM tissues of cancer-free individuals. Among the 30 cancer patients, microsatellites were more frequently altered in IM coexisting with tumors that showed MSI ( P = 0.003). In addition, patients with low-level MSI in the tumor tissues were more likely to have active Helicobacter pylori infection than those with stable tumors ( P = 0.02). In conclusion, this study indicates that MSI occurs not only in gastric IM of patients with gastric carcinoma, but also in IM of cancer-free individuals. These data suggest that the progressive accumulation of MSI in areas of IM may contribute to gastric cancer development, representing an important molecular event in the multistep gastric carcinogenesis cascade.