Showing papers by "Yonsei University published in 2000"

Complementarity, status similarity and social capital as drivers of alliance formation

Abstract: Using data on U.S. investment banking firms’ syndication in underwriting corporate stock offerings during the 1980s, this study explores the factors that drive alliance formation between two specific firms. We compare resource complementarity, status similarity, and social capital as a basis of alliance formation. The findings indicate that the likelihood of investment banks’ alliance formation is positively related to the complementarity of their capabilities, as well as their status similarity. Social capital arising from banks’ direct and indirect collaborative experiences also plays a very important role in alliance formation. The number of deals given by a lead bank to a potential partner over the past three years has an inverted U-shaped relationship to the probability that the lead bank will invite the potential partner to form an alliance. Our findings indicate that status similarity and social capital have a stronger effect on alliance formation in initial public offering deals than in secondary offering deals, as the former are more uncertain than the latter. Using these findings, we discuss the role of complementarity, status similarity, and social capital in alliance formation. Copyright © 2000 John Wiley & Sons, Ltd.

Wavelet compression of ECG signals by the set partitioning in hierarchical trees algorithm

Abstract: A wavelet electrocardiogram (ECG) data codec based on the set partitioning in hierarchical trees (SPIHT) compression algorithm is proposed in this paper. The SPIHT algorithm (A. Said and W.A. Pearlman, IEEE Trans. Ccts. Syst. II, vol. 6, p. 243-50, 1996) has achieved notable success in still image coding. The authors modified the algorithm for the one-dimensional case and applied it to compression of ECG data. Experiments on selected records from the MIT-BIH arrhythmia database revealed that the proposed codec is significantly more efficient in compression and in computation than previously proposed ECG compression schemes. The coder also attains exact bit rate control and generates a bit stream progressive in quality or rate.

Effect of metal particle size on coking during CO2 reforming of CH4 over Ni–alumina aerogel catalysts

Abstract: CO2 reforming of CH4 was carried out over Ni–alumina aerogel catalysts prepared with various Ni loadings. The preparation of alumina supported Ni catalysts via sol–gel synthesis and subsequent supercritical drying led to the formation of very small metal particles, which are evenly distributed over the alumina support. The activity of the aerogel catalysts increased along with increasing metal loading, and eventually, the SAA25 (0.25 in Ni/Al mole ratio) catalyst exhibited the high activity comparable to that of a 5 wt.% Ru/alumina catalyst (ESCAT44, Engelhard). Compared to the alumina-supported Ni catalyst prepared by conventional impregnation method, Ni–alumina aerogel catalysts showed a remarkably low coking rate due to highly dispersed metal particles. From TEM micrograph studies, it was observed that the formation of filamentous carbon was significantly influenced by the metal particle size and proceeded mostly over the metal particles larger than 7 nm. The loss of catalytic activity at 973 K was mainly caused by coke deposition and sintering.

Vitamin D3 Up-Regulated Protein 1 Mediates Oxidative Stress Via Suppressing the Thioredoxin Function

Abstract: As a result of identifying the regulatory proteins of thioredoxin (TRX), a murine homologue for human vitamin D3 up-regulated protein 1 (VDUP1) was identified from a yeast two-hybrid screen. Cotransfection into 293 cells and precipitation assays confirmed that mouse VDUP1 (mVDUP1) bound to TRX, but it failed to bind to a Cys32 and Cys35 mutant TRX, suggesting the redox-active site is critical for binding. mVDUP1 was ubiquitously expressed in various tissues and located in the cytoplasm. Biochemical analysis showed that mVDUP1 inhibited the insulin-reducing activity of TRX. When cells were treated with various stress stimuli such as H2O2 and heat shock, mVDUP1 was significantly induced. TRX is known to interact with other proteins such as proliferation-associated gene and apoptosis signal-regulating kinase 1. Coexpression of mVDUP1 interfered with the interaction between TRX and proliferation-associated gene or TRX and ASK-1, suggesting its roles in cell proliferation and oxidative stress. To investigate the roles of mVDUP1 in oxidative stress, mVDUP1 was overexpressed in NIH 3T3 cells. When cells were exposed to stress, cell proliferation was declined with elevated apoptotic cell death compared with control cells. In addition, c-Jun N-terminal kinase activation and IL-6 expression were elevated. Taken together, these results demonstrate that mVDUP1 functions as an oxidative stress mediator by inhibiting TRX activity.

Remission in models of type 1 diabetes by gene therapy using a single-chain insulin analogue

Abstract: A cure for diabetes has long been sought using several different approaches, including islet transplantation, regeneration of β cells and insulin gene therapy1. However, permanent remission of type 1 diabetes has not yet been satisfactorily achieved. The development of type 1 diabetes results from the almost total destruction of insulin-producing pancreatic β cells by autoimmune responses specific to β cells2,3,4,5,6. Standard insulin therapy may not maintain blood glucose concentrations within the relatively narrow range that occurs in the presence of normal pancreatic β cells7. We used a recombinant adeno-associated virus (rAAV) that expresses a single-chain insulin analogue (SIA), which possesses biologically active insulin activity without enzymatic conversion, under the control of hepatocyte-specific L-type pyruvate kinase (LPK) promoter, which regulates SIA expression in response to blood glucose levels. Here we show that SIA produced from the gene construct rAAV-LPK-SIA caused remission of diabetes in streptozotocin-induced diabetic rats and autoimmune diabetic mice for a prolonged time without any apparent side effects. This new SIA gene therapy may have potential therapeutic value for the cure of autoimmune diabetes in humans.

Driving force for γ → ε martensitic transformation and stacking fault energy of γ in Fe-Mn binary system

Abstract: A regular solution model for the difference of the chemical free energy between γ and e phases during γ→e martensitic transformation in the Fe-Mn binary system has been reexamined and partly modified based on many articles concerning the M s and A s temperatures of Fe-Mn alloys. Using the regular solution model, the measured M s temperatures, and a thermodynamic model for the stacking fault energy (SFE) of austenite (γ), the driving force for γ→e martensitic transformation, and the SFE of γ have been calculated. The driving force for γ→e martensitic transformation increases linearly from − 68 to − 120 J/mole with increasing Mn content from 16 to 24 wt pct. The SFE of γ decreases to approximately 13 at. pct Mn and then increases with increasing Mn content, which is in better agreement with Schumann’s result rather than Volosevich et al.’s result.

Effects of native defects on optical and electrical properties of ZnO prepared by pulsed laser deposition

Abstract: ZnO thin film has been deposited on a sapphire (001) at a temperature of 400°C using a pulsed laser deposition (PLD) with oxygen pressures of 50, 200, 300 and 500 mTorr. As the oxygen pressure for the thin film deposition increases, the crystallinity of the samples degrades as measured by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). In contrast, the photoluminescence (PL) intensity of ultra-violet (UV) luminescence increases as the oxygen pressure increases up to 300 mTorr. This is probably because the stoichiometry of oxygen-deficient ZnO film is improved by increasing oxygen pressure. According to the results from Hall measurements, the oxygen vacancy as a native donor defect in the ZnO decreases in concentration as the pressure increases. It is concluded that the UV luminescence intensity strongly depends on the stoichiometry in the ZnO film rather than the micro-structural quality of the crystal.

Bridging the spheres: political and personal conversation in public and private spaces

Abstract: For some theorists, talk about politics is infrequent, difficult, divisive, and, to be efficacious, must proceed according to special rules in protected spaces. We, however, examined ordinary political conversation in common spaces, asking Americans how freely and how often they talked about 9 political and personal topics at home, work, civic organizations, and elsewhere. Respondents felt free to talk about all topics. Most topics were talked about most frequently at home and at work, suggesting that the electronic cottage is wired to the public sphere. Political conversation in most loci correlated significantly with opinion quality and political participation, indicating that such conversation is a vital component of actual democratic practice, despite the emphasis given to argumentation and formal deliberation by some normative theorists.

The Korean "Examination Hell": Long Hours of Studying, Distress, and Depression.

Abstract: The goal of this study was to investigate whether the higher rates of clinical depression found among Korean than American adolescents was related to Korean's daily ordeal of studying and schoolwork in preparation for the competitive college entrance examination. A sample of 56 high school seniors in Korea and 62 seniors in the United States provided time-sampling data on the amount of time they spent in daily activities and their affect states during these activities. The Korean adolescents were found to spend much more time in schoolwork and less time in discretionary activities than their American counterparts. Korean adolescents' affect states across daily activities were more negative relative to American adolescents. In the combined sample of Korean and American adolescents spending less time in active leisure activities and experiencing more negative affect states during schoolwork, socializing, and passive leisure activities were related to higher depression. These findings suggest that the effect of the college exam in generating depression in Korean adolescents may be partly mediated through its effect on their daily experience.

Positivity and the Construction of Life Satisfaction Judgments: Global Happiness is Not the Sum of its Parts

Abstract: The present study investigated how reports of satisfaction with specific versus global domains can be used to assess a disposition towards positivity in subjective well-being reports. College students from 41 societies (N = 7167) completed measures of life satisfaction and ratings of global and specific aspects of their lives. For example, participants rated satisfaction with their education (global) and satisfaction with their professors, textbooks, and lectures (specific). It was hypothesized that global measures would more strongly reflect individual differences in dispositional positivity, that is, a propensity to evaluate aspects of life in general as good. At both the individual and national levels, positivity predicted life satisfaction beyond objective measures. Also, positivity was associated with norms about ideal life satisfaction such that countries and individuals who highly valued positive emotions were more likely to display positivity. The difference between more global versus more concrete measures of satisfaction can be used as an indirect and subtle measure of positivity.

Increased Expression of Vascular Endothelial Growth Factor and Angiogenesis in the Early Stage of Multistep Hepatocarcinogenesis

Abstract: Background.—Hepatocellular carcinoma (HCC) is known to receive its blood supply principally from the hepatic arteries. Recent studies have reported differences in the vascular supply, espe...

Species identification of mycobacteria by PCR-restriction fragment length polymorphism of the rpoB gene.

Abstract: PCR-restriction fragment length polymorphism analysis (PRA) using the novel region of the rpoB gene was developed for rapid and precise identification of mycobacteria to the species level. A total of 50 mycobacterial reference strains and 3 related bacterial strains were used to amplify the 360-bp region of rpoB, and the amplified DNAs were subsequently digested with restriction enzymes such as MspI and HaeIII. The results from this study clearly show that most of the mycobacterial species were easily differentiated at the species level by this PRA method. In addition, species with several subtypes, such as Mycobacterium gordonae, M. kansasii, M. celatum, and M. fortuitum, were also differentiated by this PRA method. Subsequently, an algorithm was constructed based on the results, and a blinded test was carried out with more than 260 clinical isolates that had been identified on the basis of conventional tests. Comparison of these two sets of results clearly indicates that this new PRA method based on the rpoB gene is more simple, more rapid, and more accurate than conventional procedures for differentiating mycobacterial species.

Angiocentric Lymphoma of the Head and Neck: Patterns of Systemic Failure After Radiation Treatment

Abstract: PURPOSE: To investigate the patterns of systemic failure and the clinical outcome in patients with angiocentric lymphoma of the head and neck who were treated with radiation alone, and to discuss the optimal mode of treatment for these patients. PATIENTS AND METHODS: We reviewed the records of 92 patients with stage I or II angiocentric lymphoma who were treated at Yonsei Cancer Center between 1976 and 1994. All patients were treated with involved-field irradiation. Radiation doses ranged from 40 to 60 Gy (median dose, 50.4 Gy). Treatment response, patterns of treatment failure including systemic failure, and clinical outcome after radiation treatment were analyzed. RESULTS: The most frequently involved site was the nasal cavity, either alone or in conjunction with other sites. In 16 patients (17.4%), angiocentric lymphoma was accompanied by cervical lymphadenopathy. Disease was classified as stage I in 62 patients (67.4%) and stage II in 30 patients (32.6%). After completion of radiation treatment, 61 pa...

Connexin26 mutations associated with nonsyndromic hearing loss.

Abstract: Objective Mutations in the GJB2 gene are a major cause of autosomal recessive and sporadic types of congenital deafness. The 35delG mutation is the most frequent type of mutation in white populations. However, several other forms were reported, such as 167delT among Ashkenazi Jews and R143W in Africans. The present study investigated the mutations of connexin26 (Cx26) found in patients with nonsyndromic hearing loss (NSHL) and newborns in the Korean population. Study Design The sequencing data for 147 unrelated patients with congenital NSHL and 100 audiologically screened newborns were included in this prospective study. Methods Genomic DNA samples from all patients and newborns were sequenced in both directions for detection of Cx26 mutations. Results Thirteen different types of mutations were found in the patients and newborns. V27I and E114G are the popular types of polymorphic mutations in both groups. 235delC—deletion and frameshift—was detected in patients (15 in 294 alleles) and newborns (1 in 200 alleles). 35delG was rarely found in both group. In addition to above mutations, several types of mutations—S85P, K41R, S72C, V84A, 176-191del, and 299-300del—were identified. The family study of the 235delC showed a typical autosomal recessive trait of NSHL in their audiological evaluation of hearing threshold. Conclusion The frequency of 235delC allele showed much higher in the patients (5%) than in newborns (0.5%). We rarely found 35delC mutant in both groups. These results suggest that the different types of Cx26 mutations affect autosomal recessive NSHL according to ethnic background.

Genotype, phenotype, and developmental biology of molar tooth characters

Abstract: Primate molar shapes reflect developmental and ecological processes. Development may constrain as well as facilitate evolution of new tooth shapes, affecting how reliable dental characters are in phylogenetic studies. Much of the genetic machinery of development uses the same genes among different organs, including teeth, limbs, and feathers. Furthermore, within a tooth, the development of individual cusps repeatedly uses the same set of developmental genes, forming a "developmental module." The repeated activation of the developmental module can explain the cumulative variation in later-developing cusps. Therefore short, later-developing cusps may be evolvable but also more homoplastic. This patterning cascade mode of cusp development can be used to explain the variational properties of dental characters and character states related to cusp initiation. The developmental basis and variational properties of crown termination, cusp shape, and cusp configuration characters are currently less well understood. It is unlikely that there is a simple "gene to phenotype" map for dental characters. Rather, the whole cusp pattern is a product of a dynamic developmental program manifested in the activation of the developmental modules.

Effect of Dietary Patterns on Serum Homocysteine Results of a Randomized, Controlled Feeding Study

Abstract: Background—Elevated blood levels of homocysteine are associated with an increased risk of atherosclerotic cardiovascular disease. Although numerous studies have assessed the impact of vitamin supplements on homocysteine, the effect of dietary patterns on homocysteine has not been well studied. Methods and Results—During a 3-week run-in, 118 participants were fed a control diet, low in fruits, vegetables, and dairy products, with a fat content typical of US consumption. During an 8-week intervention phase, participants were then fed 1 of 3 randomly assigned diets: the control diet, a diet rich in fruits and vegetables but otherwise similar to control, or a combination diet rich in fruits, vegetables, and low-fat dairy products and reduced in saturated and total fat. Between the end of run-in and intervention periods, mean change in homocysteine was +0.46 μmol/L in the control diet, +0.21 μmol/L in the fruits and vegetables diet (P=0.47 compared with control), and −0.34 μmol/L in the combination diet (P=0.0...

The KSTAR project: An advanced steady state superconducting tokamak experiment

Abstract: The Korea Superconducting Tokamak Advanced Research (KSTAR) project is the major effort of the national fusion programme of the Republic of Korea. Its aim is to develop a steady state capable advanced superconducting tokamak to establish a scientific and technological basis for an attractive fusion reactor. The major parameters of the tokamak are: major radius 1.8 m, minor radius 0.5 m, toroidal field 3.5 T and plasma current 2 MA, with a strongly shaped plasma cross-section and double null divertor. The initial pulse length provided by the poloidal magnet system is 20 s, but the pulse length can be increased to 300 s through non-inductive current drive. The plasma heating and current drive system consists of neutral beams, ion cyclotron waves, lower hybrid waves and electron cyclotron waves for flexible profile control in advanced tokamak operating modes. A comprehensive set of diagnostics is planned for plasma control, performance evaluation and physics understanding. The project has completed its conceptual design and moved to the engineering design and construction phase. The target date for the first plasma is 2002.

The pedunculopontine nucleus: its role in the genesis of movement disorders.

Abstract: The pedunculopontine nucleus (PPN) is located in the dorso-lateral part of the ponto-mesencephalic tegmentum. The PPN is composed of two groups of neurons: one containing acetylcholine, and the other containing non-cholinergic neurotransmitters (GABA, glutamate). The PPN is connected reciprocally with the limbic system, the basal ganglia nuclei (globus pallidus, substantia nigra, subthalamic nucleus), and the brainstem reticular formation. The caudally directed corticolimbic-ventral striatal-ventral pallidal-PPN-pontomedullary reticular nuclei-spinal cord pathway seems to be involved in the initiation, acceleration, deceleration, and termination of locomotion. This pathway is under the control of the deep cerebellar and basal ganglia nuclei at the level of the PPN, particularly via potent inputs from the medial globus pallidus, substantia nigra pars reticulata and subthalamic nucleus. The PPN sends profuse ascending cholinergic efferent fibers to almost all the thalamic nuclei, to mediate phasic events in rapid-eye-movement sleep. Experimental evidence suggests that the PPN, along with other brain stem nuclei, is also involved in anti-nociception and startle reactions. In idiopathic Parkinson's disease (IPD) and parkinson plus syndrome, overactive pallidal and nigral inhibitory inputs to the PPN may cause sequential occurrences of PPN hypofunction, decreased excitatory PPN input to the substantia nigra, and aggravation of striatal dopamine deficiency. In addition, neuronal loss in the PPN itself may cause dopamine-resistant parkinsonian deficits, including gait disorders, postural instability and sleep disturbances. In patients with IPD, such deficits may improve after posteroventral pallidotomy, but not after thalamotomy. One of the possible explanations for such differences is that dopamine-resistant parkinsonian deficits are mediated to the PPN by the descending pallido-PPN inhibitory fibers, which leave the pallido-thalamic pathways before they reach the thalamic targets.

Firm Value, Risk, and Growth Opportunities

Abstract: We show that Tobin's q, as proxied by the ratio of the firm's market value to its book value, increases with the firm's systematic equity risk and falls with the firm's unsystematic equity risk Further, an increase in the firm's total equity risk is associated with a fall in q The negative relation between the change in total risk and the change in q is robust through time for the whole sample, but it does not hold for the largest firms

Role of sea surface temperature and soil-moisture feedback in the 1998 Oklahoma–Texas drought

Abstract: The drought that affected the US states of Oklahoma and Texas in the summer of 1998 was strong and persistent, with soil moisture reaching levels comparable to those of the 1930s ‘dust bowl’1,2. Although other effects of the record-strength 1997–98 El Nino were successfully predicted over much of the United States, the Oklahoma–Texas drought was not3. Whereas the response of the tropical atmosphere to strong anomalies in sea surface temperature is quite predictable, the response of the extratropical atmosphere is more variable4,5. Here we present results from mechanistic experiments to clarify the origin and maintenance of this extratropical climate extreme. In addition to global atmospheric models6,7,8,9,10,11, we use a regional model12,13 to isolate regional climate feedbacks. We conclude that during April and May 1998, sea surface temperature anomalies combined with a favourable atmospheric circulation to establish the drought. In June–August, the regional positive feedback associated with lower evaporation and precipitation contributed substantially to the maintenance of the drought. The drought ended in the autumn, when stronger large-scale weather systems were able to penetrate the region and overwhelm the soil-moisture feedback. Our results show the potential for numerical models including appropriate physical processes to make skilful predictions of regional climate.

PAPR reduction in OFDM transmission using Hadamard transform

Abstract: An OFDM signal with large peak-to-average power ratio (PAPR) can cause power degradation (inband distortion) and spectral spreading (out-of-band radiation) by being clipped passing through a power amplifier. The PAPR characteristics are analyzed in two different aspects. From the foundation of the analysis, we propose Hadamard transform, which is ascribed to the relationship between the autocorrelation function and PAPR. Extensive computer simulations show that Hadamard transform is an effective technique to reduce PAPR.

An animal model of neuropathic pain employing injury to the sciatic nerve branches.

Abstract: The present study was conducted to develop a new animal model of neuropathic pain employing injury to the distal sciatic nerve branches. Under halothane anesthesia, the tibial, sural, and/or common peroneal nerves were injured and neuropathic pain behaviors were compared among different groups of rats. Different types of injury produced different levels of neuropathic pain. Rats with injury to the tibial and sural nerves showed the most vigorous mechanical allodynia, cold allodynia, and spontaneous pain. These neuropathic pain behaviors were not relieved by functional sympathectomy using guanethidine. The results suggested that injury to the tibial and sural nerves, while leaving the common peroneal nerve intact, can be used as a new animal model of neuropathic pain and that this model represents sympathetically independent pain (SIP). The present animal model is very simple to produce injury and can produce profound and reliable pain behaviors. These features enable the new animal model to be a useful tool in elucidating the mechanisms of neuropathic pain, especially SIP.