• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.18 no.1
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• pp.141-158
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• 2023

From the perspective of an entrepreneur, one of the most important factors for understanding the inherent limitations of a startup, reducing the risk of failure, and succeeding is the composition of the talent, that is, the founding team. Therefore, a common concern experienced by entrepreneurs in the pre-entrepreneurship stage or the early stage of startup is the choice between independent startups and co-founding start-up. Nonetheless, in Korea, the share of independent entrepreneurship is significantly higher than that of co-founding start-up. On the other hand, focusing on the fact that many successful global innovative companies are in the form of co-founding start-up, the success factors of co-founding start-up were examined. Most of the related preceding studies are studies that identify the capabilities and characteristics of individual entrepreneurs as factors influencing the survival and success of entrepreneurship, and there is a lack of research on partnerships, that is, co-founding start-up, which are common in the field of entrepreneurship ecosystems. Therefore, this study attempted a multi-case study through in-depth interviews, collection of relevant data, analysis of contextual information, and consideration of previous studies targeting co-founders of domestic startups that succeeded in opportunistic startups. Through this, a model for deriving the phased characteristics and key success factors of co-founding start-up was proposed. As a result of the study, the key element of the preliminary start-up stage was 'opportunity', and the success factors were 'opportunity recognition through entrepreneur's experience' and 'idea development'. The key element in the early stages of start-up is "start-up team," and the success factor is "trust and complement of start-up team," and synergy is shown when "diversity and homogeneity of start-up team" are harmonized. In addition, conflicts between co-founders may occur in the early stages of start-ups, which has a large impact on the survival of start-ups. The conflict between the start-up team could be overcome through constant "mutual understanding and respect through communication" and "clear division of work and role sharing." It was confirmed that the core element of the start-up growth stage was 'resources', and 'securing excellent talent' and 'raising external funds' were important factors for success. These results are expected to overcome the limitations of start-up companies, such as limited resources, lack of experience, and risk of failure, in entrepreneurship studies, and prospective entrepreneurs preparing for a start-up in a situation where the form of co-founding start-up is attracting attention as one of the alternatives to increase the success rate. It has implications for various stakeholders in the entrepreneurial ecosystem.

• Korean journal of applied entomology
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• v.55 no.2
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• pp.149-160
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• 2016

Temperature-dependent development and fecundity of apterious Rhopalosiphum padi (L.) (Hemiptera: Aphididae) were examined at six constant temperatures (10, 15, 20, 25, 30 and $35{\pm}1.0^{\circ}C$, RH 50-70%, 16L:8D). Development time of nymphs decreased with increasing temperature and ranged from 42.9 days at $10^{\circ}C$ to 4.7 days at $30^{\circ}C$. The nymphs did not develop until adult at $35^{\circ}C$ because the nymphs died during the 2nd instar. The lower threshold temperature and thermal constant of nymph were estimated as $8.3^{\circ}C$ and 101.6 degree days, respectively. The relationships between development rates of nymph and temperatures were well described by the nonlinear model of Lactin 2. The distribution of development times of each stage was successfully fitted to the Weibull function. The longevity of apterious adults decreased with increasing temperature ranging from 24.0 days at $15^{\circ}C$ to 4.3 days at $30^{\circ}C$, with abnormally short longevity of 11.1 days at $10^{\circ}C$. R. padi showed the highest fecundity at $20^{\circ}C$ (38.2) and the lowest fecundity at $10^{\circ}C$ (3.9). In this study, we provided component sub-models for the oviposition model of R. padi: total fecundity, age-specific cumulative oviposition rate, and age-specific survival rate as well as adult aging rate based on the adult physiological age.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.14 no.6
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• pp.59-76
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• 2019

Most technology-based entrepreneurship(TBE) go through an process of decline or disappear without overcoming the valley of death(VoD). The purpose of this study is to identify the growth dimension of TBE and to test the influence of firms activities on firms growth over time. This study identified the two-dimensional growth dimension divided by size and profit through exploratory factor analysis(EFA) of a number of growth indicators. Then, we defined the discrete state of growth firm in four states, divided by size and profit, and five states, including the closure of business. Multi-nomial logit model is used to predict the effect of TBE activities on a discrete state of growth firm(size×profit, closure of business) based on multiple independent variables. The independent variables are based on five representative firms activities: employment, marketing, R&D, financial activities, and general management activities. The growth stage of TBE over time has been categorized into three stages: early stage, middle stage, and late stage of business, taking into account the main periods during which the survival rate of startups sharply decreases. The analytical data of this study was based on the secondary data of the start-up supporting companies of government and public institutions. The subjects of analysis were TBE within 10 years. As a result of the empirical analysis, the employment and marketing activities of TBE show that early and mid-term activities had an effect on the state of firms growth. However, if there is a difference, employment activities have both positive and negative effects, while marketing activities have only a positive effect on size and profit growth. And besides, R&D activities, financial activities, and general management activities throughout the entire process of firms growth were found to be firms activities that have both positive and negative effects on firms growth. In addition, the age of the founder, the firms' industry, and the geographic location of the firms, which are general characteristics of the company, were found to have a distinctive effect on the growth status of the firms according to the growth stage.

• Radiation Oncology Journal
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• v.24 no.4
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• pp.280-284
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• 2006

$\underline{Purpose}$: To evaluate biological characteristics of neutron beam generated by MC50 cyclotron located in the Korea Institute of Radiological and Medical Sciences (KIRAMS). $\underline{Materials\;and\;Methods}$: The neutron beams generated with 15 mm Beryllium target hit by 35 MeV proton beam was used and dosimetry data was measured before in-vitro study. We irradiated 0, 1, 2, 3, 4 and 5 Gy of neutron beam to EMT-6 cell line and surviving fraction (SF) was measured. The SF curve was also examined at the same dose when applying lead shielding to avoid gamma ray component. In the X-ray experiment, SF curve was obtained after irradiation of 0, 2, 5, 10, and 15 Gy. $\underline{Results}$: The neutron beams have 84% of neutron and 16% of gamma component at the depth of 2 cm with the field size of $26{\times}26\;cm^2$, beam current $20\;{\mu}A$, and dose rate of 9.25 cGy/min. The SF curve from X-ray, when fitted to linear-quadratic (LQ) model, had 0.611 as ${\alpha}/{\beta}$ ratio (${\alpha}=0.0204,\;{\beta}=0.0334,\;R^2=0.999$, respectively). The SF curve from neutron beam had shoulders at low dose area and fitted well to LQ model with the value of $R^2$ exceeding 0.99 in all experiments. The mean value of alpha and beta were -0.315 (range, $-0.254{\sim}-0.360$) and 0.247 ($0.220{\sim}0.262$), respectively. The addition of lead shielding resulted in no straightening of SF curve and shoulders in low dose area still existed. The RBE of neutron beam was in range of $2.07{\sim}2.19$ with SF=0.1 and $2.21{\sim}2.35$ with SF=0.01, respectively. $\underline{Conclusion}$: The neutron beam from MC50 cyclotron has significant amount of gamma component and this may have contributed to form the shoulder of survival curve. The RBE of neutron beam generated by MC50 was about 2.2.

• The Korean Journal of Financial Management
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• v.24 no.2
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• pp.147-181
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• 2007

Our article investigates the risk implication of ownership structure in life insurance companies. We set up a model to identify the priority structure of policyholder's and shareholder's cashflow claims, and to derive its implications. Current literature on this issue has focused on the agency paradigm or the risk-sharing efficiency. Fama and Jensen(1983a, 1983b) and Mayers and Smith(1981, 1986, 1988, 1990, 1994) argue that the survival of both the corporate and the mutual form of organization is due in part to the relative efficiencies in controlling agency problems. With regard to insurance business, agency problems arise because of the three functions inherent in the organizations:manager, risk-bearer(owner), and policyholder. Stock insurers are characterized by the potentially complete separation of all three functions while mutual insurers merger the policyholder with the ownership function. Doherty and Dionne(1993) and Doherty(1991) concentrate their analysis on differences in the efficiency of risk sharing between participating and non-participating policies. They argue that when the undiversifiable risk has higher portion in business risk, combining policy and equity claims into a single package is a more efficient risk-sharing contract than a simple prepaid risk-transfer. Among various methods for assembling the policy/equity package, Doherty and Dionne(1993) and Doherty(1991) suggest that policy/equity package offered by the mutual is the most efficient risk-sharing arrangement. There has been a controversy on the property of participating policies sold by life insurance corporations in Korea. Some scholars argue that participating policyholders of Korean life insurance companies have shared the cashflow risk with shareholders. They emphasize that insurance firms have used dividend reserves to supplement for equity deficits. Thus, they argue that the economic entities of Korean life insurance companies are mutual companies though their legal entities are corporations. Our article explicitly sets up each stakeholder's cashflow claim in stock and mutual insurers, and thus identify risk differences in shareholder and policyholder. Using our model, we could derive direct implications on the controversy. Our model shows that life insurance companies would sell participating policies since policyholders would have the incentive to share the risk inherent in their primary claims with equityholders. And there exists a fundamental difference in shareholder's risk and equityholder's.

• Korean journal of applied entomology
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• v.57 no.3
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• pp.127-135
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• 2018

Climate change can affect variables related to the life cycle of insects, including growth, development, survival, reproduction and distribution. As it encourages alien insects to rapidly spread and settle, climate change is regarded as one of the direct causes of decreased biodiversity because it disturbed ecosystems and reduces the population of native species. Hypera postica caused a great deal of damage in the southern provinces of Korea after it was first identified on Jeju lsland in the 1990s. In recent years, the number of individuals moving to estivation sites has concerned scientists due to the crop damage and national proliferation. In this study, we examine how climate change could affect inhabitation of H. postica. The MaxEnt model was applied to estimate potential distributions of H. postica using future climate change scenarios, namely, representative concentration pathway (RCP) 4.5 and RCP 8.5. As variables of the model, this study used six bio-climates (bio3, bio6, bio10, bio12, bio14, and bio16) in consideration of the ecological characteristics of 66 areas where inhabitation of H. postica was confirmed from 2015 to 2017, and in consideration of the interrelation between prediction variables. The fitness of the model was measured at a considered potentially useful level of 0.765 on average, and the warmest quarter has a high contribution rate of 60-70%. Prediction models (RCP 4.5 and RCP 8.5) results for the year 2050 and 2070 indicated that H. postica habitats are projected to expand across the Korean peninsula due to increasing temperatures.

• Clinical and Experimental Reproductive Medicine
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• v.27 no.1
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• pp.47-57
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• 2000

Objective: The effects of cryopreservation with or without coculture on the in vitro development of blastomere-biopsied 8-cell mouse embryos were investigated. This experimental study was originally designed for the setup of a preclinical mouse model for the preimplantation genetic diagnosis (PGD) in human. Methods: Eight-cell embryos were obtained after in vitro fertilization (IVF) from F1 hybrid mice (C57BL(표현불가)/CBA(표현불가)). Using micromanipulation, one to four blastomeres were aspirated through a hole made in the zona pellucida by zona drilling (ZD) with acid Tyrode's solution (ATS). A slow-freezing and rapid-thawing protocol with 1.5M dimethyl sulfoxide (DMSO) and 0.1M sucrose as cryoprotectant was used for the cryopreservation of blastomere- biopsied 8-cell mouse embryos. After thawing, embryos were cultured for 110 hours in Ham's F-10 supplemented with 0.4% bovine serum albumin (BSA). In the coculture group, embryos were cultured for 110 hours on the monolayer of Vero cells in the same medium. The blastocyst formation was recorded, and the embryos developed beyond blastocyst stage were stained with 10% Giemsa to count the total number of nuclei in each embryo. Results: The survival rate of embryos after cryopreservation was significantly lower in the blastomere-biopsied (7/8, 6/8, 5/8, and 4/8 embryos) groups than in the non-biopsied, zona intact (ZI) group. Without the coculture, the blastocyst formation rate of embryos after cryopreservation was not significantly different among ZI, the zona drilling only (ZD), and the balstomere-biopsied groups, but it was significantly lower than in the non-cryopreserved control group. The mean number of cells in embryos beyond blastocyst stage was significantly higher in the control group ($50.2{\pm}14.0$) than in 6/8 ($26.5{\pm}6.2$), 5/8 ($25.0{\pm}5.5$), and 4/8 ($17.8{\pm}7.8$) groups. With the coculture using Vero cells, the blastocyst formation rate of embryos after cryopreservation was significantly lower in 5/8 and 4/8 groups, compared with the control, 7/8, and 6/8 groups. The mean number of cells in embryos beyond blastocyst stage was also significantly lower in 4/8 group ($25.9{\pm}10.2$), compared with the control ($50.2{\pm}14.0$), 7/8 ($56.0{\pm}22.2$), and 6/8 ($55.3{\pm}25.5$) groups. Conclusion: After cryopreservation, blastomere-biopsied mouse embryos have a significantly impaired developmental competence in vitro, but this detrimental effect might be prevented by the coculture with Vero cells in 8-cell mouse embryos biopsied one or two blastomeres. Biopsy of mouse embryos after ZD with ATS is a safe and highly efficient preclinical model for PGD of human embryos.

• Journal of Life Science
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• v.31 no.8
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• pp.710-718
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• 2021

Placenta-derived mesenchymal stem cells (PD-MSCs) are promising candidates for cell-based therapy in regenerative medicine. The migration and homing potential of PD-MSCs to injured sites is a critical property of MSC engraftment. MicroRNAs (miRNAs) have recently been shown to regulate the critical functions of MSCs, such as proliferation, survival, and migration. The objective of the present study was to identify the miRNA and target genes involved in PD-MSCs homing in a bile duct ligation (BDL) rat model. We selected candidate miRNAs targeting genes for PD-MSCs homing based on microarray analysis. PD-MSC engraftment in BDL-injured rat liver was identified by immunofluorescence assay and human-specific Alu gene expression by quantitative real-time polymerase chain reaction (qRT-PCR) one week after transplantation. Compared with migrated naïve PD-MSCs under hypoxic and normoxic conditions (Hyp/Nor), the transplanted group with PD-MSCs (Tx) showed distinct differences in miRNA expressions in BDL-injured rat liver. We also validated the miRNAs and their target genes for PD-MSCs homing. The expressions of integrin α4 (ITGA4) and integrin α5 (ITGA5) target genes for miR-199a-5p and miR-148a-3p were significantly upregulated in the Tx group (p<0.05). In addition, integrin β1 (ITGB1) and integrin β8 (ITGB8) were upregulated by suppressing miR-183-5p and miR-145-5p, respectively. These results demonstrated that PD-MSCs regulate miRNA expression related to the integrin family for their homing effects on the BDL-injured rat liver. The findings further suggest that miRNA-mediated regulation of the integrin family contributes to the therapeutic efficacy of PD-MSCs in the rat hepatic fibrosis model by BDL.

• Journal of Embryo Transfer
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• v.24 no.3
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• pp.199-205
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• 2009

This study was carried out to investigate the effective genetic resources preservation system using the frozen boar semen. The porcine oocytes were matured for 44 hours in NCSU-23 medium with or without 10% Porcine Follicle Fluid (PFF), 0.5 ${\mu}g/ml$ porcine FSH, 0.5 ${\mu}g/ml$ equine LH, 1.0 ${\mu}g/ml$ 17 $\beta$-estradiol ($E_2$) and 10 ng/ml Epidermal Growth Factor (EGF) under mineral oil at $38.5^{\circ}C$ in humidified atmosphere of 5% $CO_2$ in air. After 44 h of culture, the oocytes were inseminated with frozen-thawed semen and fresh semen prepared with mTBM medium for 6 h. Later, set of 50 presumptive zygotes were transferred into 4-well dish (500 ${\mu}l$) of IVC medium. for embryos freezing, slow-freezing and vitrification methods were used as a cryopreservation. Differences among treatments were analyzed using General Linear Model Procedure by SAS Package (version 6.12) differences were considered significant when p<0.05. Following IVF and IVC, the rates of cleavage and blastocysts formation were significantly higher (p<0.05) in hormone supplemented group than that of hormone-free group (25.7 vs, 12.1). The development rates to cleavage and blastocysts were significantly higher in PZM-5 group than NCSU-23 group (60.3%, 46.6% vs 27.4%, 11.1%). Further improvement was achieved when PZM-5 was supplemented with FBS. Cleavage rates was significantly higher in fresh semen source group than frozen semen (66.7% vs 43.7%). However in blastocysts rates was similar two groups. Post-thaw survival rates of embryos were 1.2% and 2.2% in slow-frezing and vitrification groups, respectively. The results of our study suggest that it is still possible to improve the culture conditions and boar semen cryopreservation for enhance reproductive technology and animal genetic resources conservation.

• Tuberculosis and Respiratory Diseases
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• v.73 no.4
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• pp.224-230
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• 2012

Background: We evaluated the clinical outcomes and prognostic factors of patients requiring prolonged mechanical ventilation (PMV), defined as ventilator care for ${\geq}21$ days, who were admitted to the medical intensive care unit (ICU) of a university hospital in Korea. Methods: During the study period, a total of 2,644 patients were admitted to the medical ICU, and 136 patients (5.1%) were enrolled between 2005 and 2010. Results: The mean age of the patients was $61.3{\pm}14.5$ years, and 94 (69.1%) were male. The ICU and six-month cumulative mortality rates were 45.6 and 58.8%, respectively. There were 96 patients with tracheostomy placement after admission and their mean period from admission to the day of tracheostomy was $21.3{\pm}8.4$ days. Sixty-three patients (46.3%) were successfully weaned from ventilator care. Of the ICU survivors (n=74), 34 patients (45.9%) were transferred to other hospitals (not university hospitals). Two variables (thrombocytopenia [hazard ratio (HR), 1.964; 95% confidence interval (CI), 1.225~3.148; p=0.005] and the requirement for vasopressors [HR, 1.822; 95% CI, 1.111~2.986; p=0.017] on day 21) were found to be independent factors of survival on based on the Cox proportional hazard model. Conclusion: We found that patients requiring PMV had high six-month cumulative mortality rates, and that two clinical variables (measured on day 21), thrombocytopenia and requirement for vasopressors, may be associated with prognostic indicators.