• The Korean Journal of Pharmacology
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• v.32 no.2
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• pp.201-209
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• 1996

Restoration of the blood flow after a period of ischemia is accompanied by generation of toxic oxygen radicals. This phenomenon may account for the occurrence of reperfusion-mediated tissue injury in ischemic hearts. In in vitro studies, although oxygen radicals can be generated from a variety of sources, including xanthine oxidase system, activated leucocytes, mitochondria and others, the most important source and mechanism of oxygen radical production in the post-ischemic reperfused hearts is unclear. In the present study, we tested the hypothesis that the respiratory chain of mitochondria might be an important source of oxygen radicals which are responsible for the development of the reperfusion injury of ischemic hearts. Langendorff-perfused, isolated rat hearts were subjected to 30 min of global ischemia at $37^{\circ}C$, followed by reperfusion. Amytal, a reversible inhibitor of mitochondrial respiration, was employed to assess the mitochondrial contributions to the development of the reperfusion injury. Intact mitochonria were isolated from the control and the post-ischemic reperfused hearts. Mitochondrial oxygen radical generation was measured by chemiluminescence method and the oxidative tissue damage was estimated by measuring a lipid peroxidation product, malondialdehyde(MDA). To evaluate the extent of the reperfusion injury, post-ischemic functional recovery and lactate dehydrogenase(LDH) release were assessed and compared in Amytal-treated and -untreated hearts. Upon reperfusion of the ischemic hearts, MDA release into the coronary effluent was markedly increased. MDA content of mitochondria isolated from the post-ischemic reperfused hearts was increased to 152% of preischemic value, whereas minimal change was observed in extramitochondrial fraction. The generation of superoxide anion was increased about twice in mitochondria from the reperfused hearts than in those from the control hearts. Amytal inhibited the mitochondrial superoxide generation significantly and also suppressed MDA production in the reperfused hearts. Additionally, Amytal prevented the contractile dysfunction and the increased release of LDH observed in the reperfused hearts. In conclusion, these results indicate that the respiratory chain of mitochondria may be an important source of oxygen radical formation in post-ischemic reperfused hearts, and that oxygen radicals originating from the mitochondria may contribute to the development of myocardial reperfusion injury.

• Proceedings of the Korean Society of Food Science and Nutrition Conference
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• 2004.11a
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• pp.265-270
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• 2004

Coronary heart disease (CHD) has been the number one killer in western society for a long time, and CHD in most instances is due to atherosclerosis. One of the earliest events in atherogenesis is the intracellular accumulation of lipids, particularly cholesterol esters, in the aortic intima. The lipids presumably came from the uptake of plasma lipoproteins, particularly from LDL. These foam cells were identified as being predominantly as macrophages. Currently, it is believed that oxidation of low density lipoprotein (LDL) might contribute to the generation of foam cells. An outcome of the oxidation hypothesis is that the consumption of antioxidants would be beneficial. In this study, Boldine, an alkaloid of Peumus boldus was tested for their antioxidant potency both in, in vitro oxidation system and in mouse models. Boldine decreased the ex-vivo oxidation of Low-density lipoprotein (LDL). In vivo studies were performed to study the effect of these compounds on the atherosclerotic lesion formation in LDL r-/- mice. Three groups of LDL r-/- mice (N=12 each) were fed an atherogenic diet. Group 1 was given vehicle and group 2 and 3 were given 1 and 5 mg of Boldine/day in addition to the atherogenic diet. The results indicated that there was a decrease in lesion formation reaching a 40% reduction due to Boldine compared to controls. The in vivo tolerance of Boldine in humans (has been used as an herbal medicine in other diseases) should make it an attractive alternative to vitamin E.

• Journal of Information Technology Services
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• v.8 no.2
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• pp.229-245
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• 2009

The Korean mobile telecommunication service market is faced with a tremendous competitive period, in which the market is entering into the maturity stage with launching of the 3rd generation service and with introduction of mobile number portability. In general, it is more important to sustain the old customers than to attracting new customers, as the life cycle of an industry is entering the maturity stage in which the growth rate of new customers is decreasing gradually or becoming stagnant. Thus, mobile telecommunication business has to seek a way to maintain the existing customers instead of promoting new customers. So this study investigates whether the service quality of mobile telecommunication could have effects on the switching barrier of the industry. In order to test the hypothesis on the effects of service quality of mobile telecommunication in Korea on switching barrier, this study collected the questionnaire response data of students including middle and high school students and undergraduates, who are regarded as the major customers in that mobile telecommunication industry.

• Biomedical Science Letters
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• v.24 no.1
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• pp.50-54
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• 2018

N-nitroso-N-methylurea (NMU) and N-nitroso-N-ethylurea (NEU), direct alkylating chemical mutagens and carcinogens, are shown to be the upregulators of cellular $NF-{\kappa}B$, regulating various genes that mediate tumorigenesis and carcinogenesis. Nitric oxide (NO), a toxic reactive radical gas, has been known to induce programmed cell death or apoptosis in various cells. Therefore, the assessment of NO production was examined to elucidate the possible contribution of NO release to the chemical carcinogenic potency of NMU and NEU in human skin cells. NMU and NEU did not alter the NO production, but they caused a significant downregulation of the NO generation on lipopolysaccharide (LPS)-induced NO production at concentrations ranging from $2{\sim}5{\mu}M$. The degree of downregulation of NO by NMU and NEU decreased up to 15% and 20%, respectively, compared to the control. These results demonstrate that the LPS-inducible keratinocytes NO synthase is involved in modulating carcinogenic potency by NMU and NEU, and the regulation of the cellular $NF-{\kappa}B$ activity by NMU and NEU is negatively correlated with the level of LPS-induced NO production in human skin cells. The findings of this study suggest the hypothesis that NMU and NEU-induced carcinogenesis may be associated with the downregulation of NO production, and the inducible NO may play an important role in NMU and NEU-induced carcinogenicity in human epidermal keratinocytes.

• The Journal of Asian Finance, Economics and Business
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• v.7 no.7
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• pp.369-378
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• 2020

The paper aims to identify the determinants that influence entrepreneurial intention among National Economics University graduates. For the sample size, we conducted a questionnaire survey of 250 full-time third-year undergraduates at the National Economics University, with convenience sampling technique. Of those 250 undergraduates, 150 were Business Administration students and 100 Economy Management students. After eliminating invalid responses due to lack of information or low quality information, 215 responses were used (93.07% of respondents) for data analysis. The results show that the factor "Perceived desirability" has the strongest impact on the intention to start a business. It is followed by the factor "Perceived feasibility" in which the "ability to search and plan for start-up" has a stronger influence on undergraduates' entrepreneurial intention than the "leadership and ability to overcome adversity". The hypothesis of a positive relationship between undergraduates' propensity to act and their intention to start a business is also supported in this study. Based on the results, we suggest some recommendations for the university and State management agencies to nurture and develop entrepreneurial intention of undergraduates, forming the young generation of potential entrepreneurs to contribute to the development of emerging countries such as Vietnam, the case study.

• Transactions on Control, Automation and Systems Engineering
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• v.3 no.1
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• pp.10-14
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• 2001

We studied the use of time-related information, with and without prediction, to support human operators performing moni-toring and control tasks in the process. Based on monitoring and control techniques used for Project Management we developed a display design for the process industries. A simulated power plant was used to test the hypothesis that availability of predictions along with information on past trends can improve the performances of the human operator handling faults. Several designs of dis-plays were tested in the experiment in which human operators had to detect and handle two types of faults(local and systems wide) in the simulated electricity generation process. Analysis of the results revealed that temporal data, with and without prediction, signifi-cantly reduced response time. Our results encourage the integration of temporal information and prediction in displays used for the control processes to enhance the capabilities of the human operators. Based on the analysis we proposed some guidelines for the de-signer of the human interface of a process control system.

• Journal of Science and Technology Studies
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• v.3 no.2 s.6
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• pp.61-82
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• 2003

In a new paradigm of competition, firms face a multiple industry in a generation and compete with existing capabilities and resources in a new industry. Firms need to increase dynamic capabilities to adjust to a radical change in terms of technologies for survival and sustainable growth in a new industry. But we lack a clear conceptual model explaining evolutionary process of firms facing a emerging industry with different experiences in a prior industry and where heterogeneity in firms' technological portfolios come from. How we explaining firms' heterogeneity arising in a new industiy? In this article, I suggest hypothesis explaining firms' heterogeneity in a new industry with the concept of existent industry's technological trajectories, available assets, core processes and show the possibility of model to explain the heterogeneity of firms.

• Journal of Korea Trade
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• v.25 no.7
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• pp.56-74
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• 2021

Purpose - This study aims to identify consumer tendencies in Korea and Vietnam, focusing on the online platform called cross-border, to derive revenue generation measures and use them for strategies to advance into ASEAN. Design/methodology - The questionnaire collected 420 copies from December 1 to December 31, 2020, of which 408 were used for statistical processing. The structural equation model (SEM) and moderating effect analysis with Amos was used to test hypothesis in this research. Findings - The hypotheses were set as factors that positively influence the intention to use e-commerce, such as effort expectancy, social influence, facilitating conditions and variety seeking showed statistically significant results. Among them, the social influence factor had the greatest influence, followed by facilitating condition. The sample was divided into countries, Korea and Vietnam, and these changes and differences in influence were confirmed through moderating effect analysis. Originality/value - The moderating effect on both countries (Korea and Vietnam) was found to have a moderating effect on the intention to use. For Korean consumers, significant results were found in the effort expectancy, social influence, facilitating conditions, and variety seeking, but for Vietnamese consumers, there were significant effects on the social influence and facilitating conditions, but the effort expectancy and variety seeking had no significant effect.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.8
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• pp.271-285
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• 2021

The aim of this research was to look into the relationship between leadership; transformational leadership, transactional leadership, and employee innovation, as well as the mediating impact of cultural diversity between leadership and employee innovation. Structured questionnaire was used to collect the data from 633 public and private universities' employees in the United Arab Emirates (UAE) with the help of the stratified sampling technique, and hypothesis verified through structural equations modelling (AMOS-21). Findings of the study shows that leadership has positive impact on employee innovation and cultural diversity partially mediates the relationship between leadership and innovative performance of UAE universities' employees. Practical implication of the study is to understand how universities can enhance their employees' innovation which is crucial for their competitiveness and survival. Moreover, the increasing prevalence of cultural diversity, as work arrangements in universities, raises the question of how to successfully manage employees. Although few studies have looked into how transformational and transactional leadership styles affect employees' innovation performance, this study expands on the topic by concentrating on sub-dimensions of leadership that foster innovation through idea generation and execution at the United Arab Emirates universities. This study offers valuable insights for educational leaders and throws light on the main characteristics of leadership which helps the employees to perform better in terms of innovation.

• Journal of The Korean Association For Science Education
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• v.28 no.3
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• pp.197-210
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• 2008

The purpose of this study is to explore the cases and features of the abductive inference used by young children when trying to explain natural phenomena in everyday life. From observing a 5-year-old's daily activities with his family, and analyzing the data according to the criterion extracted from the form of abductive inference described by C. S. Peirce, a few cases where the child used abductive inferences to explain natural phenomena were found. The abductive inferences in the cases were conducted: (a) based on figural resemblance and behavioral resemblance (b) under the influence by individual belief and communal belief, then (c) resulted in new categorization accompanied by over generalization. Such features of the abductive inference showed the 'double faces'; sometimes encourages and sometimes discourages children's generating better scientific hypotheses and explanations. These results suggest that even young children use abductive inference to explain doubtful natural phenomena in everyday life, although we need to consider carefully with the double aspects of the features of abductive inference for the practical applications to the fields of science education. Finally, several suggestions and following studies for science education are proposed.