• Molecules and Cells
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• v.41 no.7
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• pp.631-638
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• 2018

Spermatogonial stem cells (SSCs) derived from mouse testis are unipotent in regard of spermatogenesis. Our previous study demonstrated that SSCs can be fully reprogrammed into pluripotent stem cells, so called germline-derived pluripotent stem cells (gPS cells), on feeder cells (mouse embryonic fibroblasts), which supports SSC proliferation and induction of pluripotency. Because of an uncontrollable microenvironment caused by interactions with feeder cells, feeder-based SSC reprogramming is not suitable for elucidation of the self-reprogramming mechanism by which SSCs are converted into pluripotent stem cells. Recently, we have established a Matrigel-based SSC expansion culture system that allows longterm SSC proliferation without mouse embryonic fibroblast support. In this study, we developed a new feeder-free SSC self-reprogramming protocol based on the Matrigel-based culture system. The gPS cells generated using a feeder-free reprogramming system showed pluripotency at the molecular and cellular levels. The differentiation potential of gPS cells was confirmed in vitro and in vivo. Our study shows for the first time that the induction of SSC pluripotency can be achieved without feeder cells. The newly developed feeder-free self-reprogramming system could be a useful tool to reveal the mechanism by which unipotent cells are self-reprogrammed into pluripotent stem cells.

• IMMUNE NETWORK
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• v.1 no.3
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• pp.179-186
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• 2001

Bone marrow stroma is a complex tissue encompassing a number of cell types and supports hematopiesis, differentiation of erythreid, nyel and lymphoid lineages, and also maintains undifferentiated hematopoietic stem cells. Marrow-derived stem cells were composed of two populations, namely, hematopoietic stem cells that can differentiate into blood elements and mesenchymal stem cells that can give rise to connective tissues such as bone, cartilage, muscle, tendon, adipose and stroma. Differentiation requires environmental factors and unique intracellular signaling. For example, $TGF-{\beta}$ or BMP2 induces osteoblastic differentiation of mesenchymal stem are very exciting. However, the intrinsic controls involved in differentiation of stem cells are yet to be understood properly in order to exploit the same. This review presents an overview of the recent developments made in mesenchymal stem cell research with respect to osteogenesis.

• Tribology and Lubricants
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• v.20 no.4
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• pp.204-208
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• 2004

This paper presents the oil leakage characteristics of the valve stem system in gasoline engines. For the oil leakage investigation, four study models have been prepared as functions of used poppet valve and used valve stem seal, used poppet valve and unused valve stem seal, unused poppet valve and used valve stem seal, and unused poppet valve and unused valve stem seal. With four models, the experimental study on the oil leakage has been investigated for the oil temperature, intake pressure, and camshaft speed. The experimental results show that the sealing performance of the valve stem seal plays an important role on the leakage of the valve stem system. And the appropriate replacement of a stem seal with used poppet valve shows good sealing performance in oil leakage in compared with a new valve system.

• Journal of Engineering Education Research
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• v.20 no.3
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• pp.13-24
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• 2017

This study investigated student engagement of STEM-specialized higher education institutions in comparison with students from humanities & social science and STEM majors, respectively. By doing so, the study aimed to find the effects of the characteristics of STEM disciplines and organizational culture of STEM-specialized small-sized institutions on student engagement. The students majoring STEM disciplines, regardless of the organizational types, showed lower reflective-integrative learning experiences compared to students on humanities & social science disciplines. In contrast, students of STEM-specialized institutions reported significantly higher levels of peer relationship and student-faculty interaction in comparison with humanities & social science students and STEM students of general higher education institutions. Finally, the study suggests policy implications for STEM education.

• Nuclear Engineering and Technology
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• v.35 no.2
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• pp.133-143
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• 2003

Stem-stem nut coefficient of friction(COF) in motor-operated gate/globe valves is one of the important factors which determine the performance of the valve/actuators. The COF is affected greatly by the type and condition of the stem-stem nut lubricants, environmental parameters, surface condition of the stem/stem-nuts, and the number of strokes after the lubrication. In this paper, the measured data of the COFs at stem threads of some safety-related motor-operated gate/globe valves in domestic nuclear power plants are presented. In addition, the performance of the lubricants is evaluated by comparing the COFs among those valves. The results show that the measured COF at torque switch trip are higher than the unwedging COF and conservatively applicable to the unwedging COF. It is also shown that the lubricating performance based on the measured COFs varies with the lubricants.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.48 no.2
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• pp.71-78
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• 2022

This study was conducted to review the efficacy of different sources of stem cells in bone regeneration of cleft palate patients. The majority of previous studies focused on the transplantation of bone marrow mesenchymal stem cells. However, other sources of stem cells have also gained considerable attention, and dental stem cells have shown especially favorable outcomes. Additionally, approaches that apply the co-culture and co-transplantation of stem cells have shown promising results. The use of different types of stem cells, based on their accessibility and efficacy in bone regeneration, is a promising method in cleft palate bone regeneration. In this regard, dental stem cells may be an ideal choice due to their efficacy and accessibility. In conclusion, stem cells, despite the lengthy procedures required for culture and preparation, are a suitable alternative to conventional bone grafting techniques.

• Medical Lasers
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• v.9 no.2
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• pp.134-141
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• 2020

The use of stem cell therapy to treat various diseases has become a promising approach. The ability of stem cells to self-renew and differentiate can contribute significantly to the success of regenerative medical treatments. In line with these expectations, there is a great need for an efficient research methodology to differentiate stem cells into their specific targets. Photobiomodulation (PBM), formerly known as low-level laser therapy (LLLT), is a relatively non-invasive technique that has a therapeutic effect on damaged tissue or cells. Recent advances in adapting PBM to stem cell therapy showed that stem cells and progenitor cells respond favorably to light. PBM stimulates different types of stem cells to enhance their migration, proliferation, and differentiation in vitro and in vivo. This review summarizes the effects of PBM on targeted differentiation across multiple stem cell lineages. The analytical expertise gained can help better understand the current state and the latest findings in PBM and stem cell therapy.

• Korean Journal of Otorhinolaryngology-Head and Neck Surgery
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• v.56 no.12
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• pp.749-753
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• 2013

Basically stem cells have characteristics of multi-potency, differentiation into multiple tissue types, and self-renew through proliferation. Recent advances in stem cell biology can make identifying the stem-cell like cells in various mammalian tissues. Stem cells in various tissues can restore damaged tissue. Stem cells from the adult nervous system proliferate to form clonal floating colonies called spheres in vitro, and recent studies have demonstrated sphere formation by cells in the tympanic membrane, vestibular system, spiral ganglion, and partly in the organ of Corti. The presence of stem cells in the ear raises the possibilities for the regeneration of the tympanic membrane & inner ear hair cells & neurons. But the gradual loss of stem cells postnatally in the organ of Corti may correlate with the loss of regenerative capacity and limited hearing restoration. Future strategies using endogenous stem cells in the ear can be the another treatment modality for the patients with intractable inner ear diseases.

• Journal of Engineering Education Research
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• v.11 no.2
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• pp.90-101
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• 2008

This study was conducted to develop pre-engineering educational program model based on STEM integration approach. To accomplish this purpose literature review and content validity ratio survey were carried out. The main results of this study were as follows: First, the conceptual model of STEM integration approach was constituted. Second, the conceptual model of pre-engineering educational program model based on STEM integration approach was proposed. Third, the formation steps of inquiry project activity, problem solving activity, and creative engineering design activity were developed to structure the educational program.

• Journal of Korean Institute of Industrial Engineers
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• v.41 no.5
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• pp.488-498
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• 2015

Research on stem cells can be divided into three categories : pluripotent stem cell, adult stem cell, and induced pluripotent stem cell. Technology life cycle (TLC) on research stage is analyzed for the three stem cell categories based on diffusion model. Three diffusion models-logistic, Bass, and Bass model with integration constant (BMIC)-are applied to the number of articles related to each stem cell category in SCOPUS lists. Two different parameter estimation methods is used for each of logistic and Bass model. Results show that (1) the current year, 2015, lies in growth period at pluripotent stem cell and adult stem cell, and lies in growth period or maturity period at induced pluripotent stem cell. (2) Model fitness is the highest at BMIC model. (3) Imitation effect works best at the research area of induced pluripotent stem cell.