• 과학교육연구지
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• 제45권1호
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• pp.11-22
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• 2021

이 연구의 목적은 국제 STEM 교육 분야의 연구 결과를 종합하여 국제 STEM 교육의 주요 이슈를 파악하는 데 있다. 이 연구의 분석 대상 자료는 선정 기준과 전문가 그룹의 검토를 통해 다양한 STEM 교육의 이슈를 반영하고 있는 메타분석 또는 체계적 문헌연구의 결과이다. 총 23개의 연구를 대상으로 질적 메타 분석을 하여 다음과 같은 STEM 교육의 이슈를 선정하였다. 첫째, STEM 교육은 국제적인 교육 동향으로 미국, 캐나다, 호주, 한국, 터키 등 많은 국가에서 연구되고 있다. 둘째, STEM 교육은 학생들의 인지적, 정의적, 심동적, 그리고 진로 영역의 향상에 긍정적으로 기여하고 있다. 셋째, STEM 교육은 다양한 수업 도구와 기술의 사용과 함께 연구되어 왔다. 또한, STEM 교육에 대한 교사의 전문성 신장이 성공적인 STEM 교육의 실현의 주요 요인들 중 하나이다. 그 외에 STEM 교육의 성공적인 실천을 위해 다양성, 평등, 타당하고 신뢰로운 연구 설계 등의 이슈에 대해 논의하였다. 또한 이 연구는 우리나라 융합교육의 방향과 실천 전략을 위한 함의점을 제공할 수 있으며 향후 연구에 대한 제언을 줄 수 있다.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1997년도 추계학술대회
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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.

• 한국CDE학회논문집
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• 제5권2호
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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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• 제8권2호
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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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• 제41권4호
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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.

• 디지털융복합연구
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• 제15권7호
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• pp.415-424
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• 2017

본 연구는 공중의 체세포복제기술에 대한 위험특성, 위험심각성, 위험인식 및 위험수용의 관계를 살펴보기 위하여 서울에 거주하는 한국인 300명을 대상으로 IBM SPSS 21 프로그램과 IBM AMOS 21 프로그램을 활용하여 탐색적 요인분석과 확인적 요인분석, 상관관계 분석, 구조모형분석을 수행하였다. 주요결과를 요약 제시하면 다음과 같다. 첫째, 공중의 체세포복제기술에 대한 위험특성은 위험심각성에 통계적으로 유의한 정적 영향을 미치는 것으로 나타났다. 둘째, 공중의 체세포복제기술에 대한 위험특성은 위험인식에 통계적으로 유의한 정적 영향을 미치는 것으로 나타났다. 셋째, 공중의 체세포복제기술에 대한 위험심각성은 위험인식에 통계적으로 유의한 정적 영향을 미치는 것으로 나타났다. 넷째, 공중의 체세포복제기술에 대한 위험특성은 위험수용에 통계적으로 유의한 부적 영향을 미치는 것으로 나타났다. 다섯째, 공중의 체세포복제기술에 대한 위험심각성은 위험수용에 통계적으로 유의한 영향을 미치지 못하였다. 여섯째, 공중의 체세포복제기술에 대한 위험인식은 위험수용에 통계적으로 유의한 영향을 미치지 못하였다.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1996년도 추계학술대회
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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.

• 대한의용생체공학회:의공학회지
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• 제15권2호
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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.

• 한국정밀공학회지
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• 제23권11호
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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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• 제45권11호
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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.