• Journal of Science Education
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• v.45 no.1
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• pp.11-22
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• 2021

The purpose of this study is to identify the main issues of international STEM education by synthesizing the findings in the field of global STEM education. The data in this study are the results of meta-analysis or systematic literature studies that reflect key issues of STEM education through the review of selection criteria and groups of experts. The following issues of STEM education were selected by conducting a qualitative meta-analysis of a total of 23 studies. First, STEM education is a global educational trend and has been studied in many countries such as the United States, Canada, Australia, Republic of Korea, and Turkey. Second, STEM education contributes positively to the improvement of students' cognitive, affective, psychomotor, and career domains. Third, STEM education has been studied with the use of various instructional tools and technologies. Furthermore, the growth of teachers' expertise in STEM education is one of the main factors for the implementation of successful STEM education. In addition, issues such as diversity, equity, and valid and reliable research design were discussed for the successful practice of STEM education. This study provides implications for the direction of convergence education and practical strategies in South Korea and gives suggestions for future research.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.11
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• pp.263-266
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• 1997

Three dimensional numerical model based on the finite element method(FEM) were developed to predict the mechanical behavior of hip implants. The purpose of this study is to investigate the stress distribution of two types of cementless total hip replacement femoral component -a straight stem and a curved stem, and to compare their effect on the stress shielding between two types by three dimensional finite element method. The authors analyzed von Mises stress in the cortex & stem and compared the stress between the straight and the curved stem. In comparison of stresses between two different design of femoral stem, there was 25% more decrease of stress in straight stem than curved stem in the medial cortex at proximal region. The straight stem had consistently much lower stresses than the curved stem throughout the whole medial cortex with maximum 70% reduction of stress. However, there was little change in stress between nature and 2 implanted femur throughout the lateral cortex. Stress of femoral stem was much higher in the straight stem than the curved stem up to 60%. The straight stem had more chance of stress shielding and a risk of fatigue fracture of the stem compared with the curved stem in noncement hip arthroplasty. In design of femoral stem still we have to consider to develop design to distribute more even stress on the proximal medial cortex.

• Korean Journal of Computational Design and Engineering
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• v.5 no.2
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• pp.122-126
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• 2000

A major mechanical problem with total hip replacement is the loosening of the femoral component. The loss of proximal support, with firm fixation distally, has been thought to be a major caused of fatigue failure of femoral stems. While many causes have been proposed, the most frequently suggested cause of the calcar resorption is the disuse atrophy of the cortex of the calcar due to the stress shielding of the proximal bone by the metal femoral stem. In this research, the new-designed stem(modified collar stem) was considered which made a hole inside stem and had a 3 mm thickness. Using the 3-dimensional finite element methods, the common collar stem and the modified colla stem was modeled and analysed. Also, the two models was compared. The results showed that the modified collar stem decreased the stress-shielding and it made a effective load transfer at the entire femoral region.

• IMMUNE NETWORK
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• v.8 no.2
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• pp.53-58
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• 2008

Background: Molecular mechanisms of natural killer (NK) cell development from hematopoietic stem cells (HSCs) have not been clearly elucidated, although the roles of some genes in NK cell development have been reported previously. Thus, searching for molecules and genes related NK cell developmental stage is important to understand the molecular events of NK cell development. Methods: From our previous SAGE data-base, Gpnmb (Glycoprotein non-metastatic melanoma protein B) was selected for further analysis. We confirmed the level of mRNA and protein of Gpnmb through RT-PCR, quantitative PCR, and FACS analysis. Then we performed cell-based ELISA and FACS analysis, to know whether there are some molecules which can bind to Gpnmb. Using neutralizing antibody, we blocked the interaction between NK cells and OP9 cells, and checked IFN-${\gamma}$ production by ELISA kit. Results: Gpnmb expression was elevated during in vitro developmental stage and bound to OP9 cells, but not to NK precursor cells. In addition, we confirmed that the levels of Gpnmb were increased at NK precursor stage in vivo. We confirmed syndecan4 as a candidate of Gpnmb's binding molecule. When the interaction between NK cells and OP9 cells were inhibited in vitro, IFN-${\gamma}$ production from NK cells were reduced. Conclusion: Based on these observations, it is concluded that Gpnmb has a potential role in NK cell development from HSCs.

• Journal of Periodontal and Implant Science
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• v.41 no.4
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• pp.192-200
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• 2011

Purpose: The aim of this study is to compare the gene expression profile in mesenchymal stem cells derived from dental tissues and bone marrow for characterization of dental stem cells. Methods: We employed GeneChip analysis to the expression levels of approximately 32,321 kinds of transcripts in 5 samples of bone-marrow-derived mesenchymal stem cells (BMSCs) (n=1), periodontal ligament stem cells (PDLSCs) (n=2), and dental pulp stem cells (DPSCs) (n=2). Each cell was sorted by a FACS Vantage Sorter using immunocytochemical staining of the early mesenchymal stem cell surface marker STRO-1 before the microarray analysis. Results: We identified 379 up-regulated and 133 down-regulated transcripts in BMSCs, 68 up-regulated and 64 down-regulated transcripts in PDLSCs, and 218 up-regulated and 231 down-regulated transcripts in DPSCs. In addition, anatomical structure development and anatomical structure morphogenesis gene ontology (GO) terms were over-represented in all three different mesenchymal stem cells and GO terms related to blood vessels, and neurons were over-represented only in DPSCs. Conclusions: This study demonstrated the genome-wide gene expression patterns of STRO-$1^+$ mesenchymal stem cells derived from dental tissues and bone marrow. The differences among the expression profiles of BMSCs, PDLSCs, and DPSCs were shown, and 999 candidate genes were found to be definitely up- or down-regulated. In addition, GOstat analyses of regulated gene products provided over-represented GO classes. These data provide a first step for discovering molecules key to the characteristics of dental stem cells.

• Journal of Digital Convergence
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• v.15 no.7
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• pp.415-424
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• 2017

The purpose of this study was to examine the relationship among public's risk characteristics, risk severity, risk perception and risk acceptability of human stem cell technology. The subjects were 300 Koreans selected. The data were analyzed by the exploratory factor analysis, confirmatory factor analysis, correlation analysis and structural equation modeing analysis. The results were as followed. First, public's risk characteristics on human stem cell technology influenced positively on risk severity. Second, public's risk characteristics on human stem cell technology influenced positively on risk perception. Third, public's risk severity on human stem cell technology influenced positively on risk perception. Fourth, public's risk characteristics on human stem cell technology influenced negatively on risk acceptability. Fifth, public's risk severity on human stem cell technology influenced not significantly on risk acceptability. Sixth, public's risk perception on human stem cell technology influenced not significantly on risk acceptability. These results will contribute to develop the risk communication strategy on the acceptability of human stem cell technology.

• Proceedings of the KOSOMBE Conference
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• v.1996 no.11
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• pp.337-346
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• 1996

Debonding of cement-femoral stem interface has been suggested as a initial focus of loosening mechanism in many previous studies of cemented total hip replacement. The purpose of this study was to investigate the effect of debonding of cement-femoral stem interface to the bone-cement interface by using three-dimensional non-liner finite element analysis. Three cases of partial debonded, full debonded, full bonded cement-bone interface were modelled with partial bonding of distal 70mm from the tip of femoral stem. Each situation was studied under loading stimulating one-leg stanced gait of 68kg patient. The results showed that under partial and full debonded cement-stem interface condition the peak von Mises stress(3.1 MPa) were observed at the cement of bone-cement interface just under the calcar of proximal medial of femur, and sudden high peak stresses(3.5MPa) were developed at the distal tip of femoral stem at the lateral bone-cement interface in all 3 cases of bonding. The stresses were transfered very little to the cement of upper lateral bone-cement interface in partial and full debonded cases. Thus, once partial or full debonded cement-femoral stem interface occured, 3 times higher stress concentration were developed on the cement of proximal medial bone-cement interface than full bonded interface, and these could cause loosening of cemented total hip replacement. Clinically, preservation of more rigid cement-femoral stem interface may be important factor to prevent loosening of femoral stem.

• Journal of Biomedical Engineering Research
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• v.15 no.2
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• pp.183-188
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• 1994

In clinical orthopaedics, bone resoption in the cortex is often seen post operatively on X-rays or bone densitometry after total hip replacement (THR) in the form of cortical osteoporosis or atropy. Stress shielding of bone occurs, when a load, normally carried by the bone alone, is shared with an implant as a result, the bone stresses are abnormal and with remodelling analysis this may cause extensive proximal bone resoption, possibly weakening the bone bed to the point of failure. The author made finite element models of the cemented and non-cemented type implanted femoral stem with bone resorption of the proximal medial femur and studied the feed back effect of the various degree of bone resoption to THR system by parametric analysis on the stress of the femoral stem and interface. The results of the present finite element analysis implied that the extent of proximal bone resorption has the effect of more increasing stress on the distal stem tip, cement mantle and interface in both type of femoral stem and this high distal stress possibly can cause the mechanical failure of loosening or failure after THR.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.11 s.188
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• pp.126-134
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• 2006

In this study, the effect of stem-end design on contact pressure and stress distribution in revision TKR was investigated using finite element method. The finite element model of tibia, including the cortical bone, the cancellous bone and canal, was developed based on CT images. The implant models with various stem lengths, diameters, friction coefficients, and press-fit effects were considered. The results showed that the longer stem length, the stronger press-fit, the bigger stem diameter, and the higher friction coefficient increased both peak contact pressure and Von-Mises stress distributions. The results supported the clinical hypothesis that peak contact pressure and stress are related to the stem end pain. The results of this study will be useful to design the stem and reduce the end-of-stem pain in revision TKR.

• Molecules and Cells
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• v.45 no.11
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• pp.820-832
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• 2022

As a potential candidate to generate an everlasting cell source to treat various diseases, embryonic stem cells are regarded as a promising therapeutic tool in the regenerative medicine field. Cohesin, a multi-functional complex that controls various cellular activities, plays roles not only in organizing chromosome dynamics but also in controlling transcriptional activities related to self-renewal and differentiation of stem cells. Here, we report a novel role of the α-kleisin subunits of cohesin (RAD21 and REC8) in the maintenance of the balance between these two stem-cell processes. By knocking down REC8, RAD21, or the non-kleisin cohesin subunit SMC3 in mouse embryonic stem cells, we show that reduction in cohesin level impairs their self-renewal. Interestingly, the transcriptomic analysis revealed that knocking down each cohesin subunit enables the differentiation of embryonic stem cells into specific lineages. Specifically, embryonic stem cells in which cohesin subunit RAD21 were knocked down differentiated into cells expressing neural alongside germline lineage markers. Thus, we conclude that cohesin appears to control the fate determination of embryonic stem cells.