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In order to reduce the weight of the blow motor case and to maintain the strength of the motor joint, the mechanical joining strength is to be predicted. The true stress - true strain curves for finite element analysis were obtained through tensile tests of HGI and DP 780 steel. The mechanical joining strength was predicted through an explicit finite element analysis and the accuracy of the predicted results was verified by actual sample test. The regression equation for predicting the mechanical joining strength to the thickness of the DP 780 steel was derived. The minimum thickness of DP 780(1.2mm), which is equivalent to the joining strength of HGI(2.6mm), was derived from the equation.
Blended natural polymers composed of β-chitosan (Cs) and gelatin (G) with various composition ratios were produced as candidate materials for biomedical application. Novel cross-linked porous scaffold compared of gelatin/chitosan 7:3 5:5 3:7 and different amounts of genipin concentration (0.001, 0.01 and 0.03 mg/ml). Genipin was used to crosslinking agent of gelatin/β-chitosan blends, promoting the formation of primary amine and tertiary amine between chitosan and gelatin, or by itself. The effects of composition and crosslinking on the physical-chemical properties of GCs composite scaffolds were evaluated by ATR-FTIR analysis, water uptake, degradation and in vitro cell viability test. The SEM analysis showed that the pore size of gelatin/chitosan porous scaffolds were increased with increasing blend ratio of chitosan. The ATR-FTIR showed that the amount of amine group of gelatin/ chitosan was decreased with increasing genipin concentration. As the genipin concentration in the scaffold decreased resulting in an enhanced water uptake ability. In this study, NIH3T3 cells were seeded gelatin/β-chitosan porous scaffolds for the cell cytotoxicity, cell proliferation. The porous scaffolds did not affect cell growth because of low cytotoxicity. The porous cross-linked scaffold with the improved characterization and cell viability may be suitable as a biocompatable scaffold for tissue engineering.
A hot forming of large thick Al plate using a grid-type hybrid die is a process to make a shell plate for the production of a spherical LNG tank. This process is characterized by using a grid-typed die with an additional air cooling system for reducing the cooling time of the heated plate after hot forming. The process consists of the plate's feeding, heating, forming and cooling in detail and each of them is continuously performed along the rail. This paper was designed to propose the analytical and experimental methods for determining the convection and interfacial heat transfer coefficients required in hot forming analysis of Al plate. These values in the analysis are to reproduce numerically the cooling performance of grid-typed die and cooling device. Interfacial heat transfer was obtained from the heat transfer experiments for different pressures and inverse analysis method. To verify the efficiency of the coefficient values obtained from above methods, FE analysis and experiment of the hot spherical-forming process were conducted for a smallscaled model. The convection coefficient was also calculated from flow analysis of air released by cooling device within grid-typed die using ANSYS-CFX.
본 연구는 단백질약물이 고정화된 주사제 형태의 수화젤을 제조하는데 목적을 두었다. 생체적합성, 생분해성의 특징을 가지는 천연고분자 히알루론산을 이용하여 azidophenyl 히알루론산 유도체(Az-HA)를 제조하였다. FTIR 및 ¹H NMR 분석을 통하여 hyaluronic acid에 azido기가 성공적으로 도입되었음을 확인하였다. 또한 유변학적 분석을 통하여 제조된 유도체의 수화젤 특성 유지여부를 검토하였다. 광고정화방법을 이용하여 단백질의 고정화 가능여부를 형광현미경으로 확인하였다. Az-HA 유도체에 고정화된 단백질약물이 지속적으로 방출되는 여부를 확인하기 위해 단백질 방출 실험을 실시하였다. 세포 독성 실험을 통하여 Az-HA의 생체적합성과 광고정화된 섬유아세포 성장인자(FGF)의 세포증식 촉진효과를 확인하였다. 위와 같은 실험결과로부터 본 연구에서 제조한 Az-HA는 효과적으로 약물 전달이 가능한 의료용 생체소재로서 활용가능성을 가질 수 있을 것으로 사료된다. The aim of this study was to prepare injectable hydrogels that can effectively deliver drugs. Azidophenyl-hyaluronic acid derivatives (Az-HA) were prepared using natural polymer hyaluronic acid with biocompatibility and biodegradability. It was confirmed that azido group was successfully introduced into hyaluronic acid by FTIR and ¹H NMR analysis. In addition, The maintenance of hydrogel properties of the prepared derivatives was examined using rheological analysis. Protein immobilization was confirmed using the photo-immobilization method, and the protein release experiment was conducted to confirm whether the protein drug immobilized with Az-HA derivative was continuously released. Through cytotoxicity test, the biocompatibility of Az-HA was confirmed. As a result of the intracellular administration of Az-HA immobilized with fibroblast growth factor (FGF), cell proliferation was confirmed. According to the result of the above experiments, the prepared UV-curable Az-HA are considered to have applicability as a biomedical material capable of effective delivery of drugs.
Osteoclasts regulate bone homeostasis and have a key role in bone degenerative processes. Mouse RAW264.7 macrophage cells have been shown to retain the capacity to differentiate into osteoclast-like cells in the presence of a receptor activator of nuclear factor kappa B ligand(RANKL), which is essential and sufficient to promote the maturation of osteoclasts. When treated with RANKL, RAW264.7 cells express high levels of osteoclastassociated genes such as tartrate-resistant acid phosphatase(TRAP), which has been widely used to assess bone resorption. In this study, we hypothesized that alendronate prevents RANKL-induced osteoclast-like cells, which are known to play important roles in the bone-resorptive responses. We investigated that occurred TRAP-positive area and the expression patterns of two important proteolytic enzymes, cathepsin K and Matrix Metalloproteinase- 9(MMP-9) during RANKL-induced osteoclast differentiation in RAW264.7 cells. These results showed that increased TRAP-positive staining and both cathepsin K and MMP-9 mRNA expression levels on RANKL-induced osteoclast differentiation during 4 days. Especially, alendronate increased caspase-3 expression for apoptosis with Western blot analysis. These results showed that alendronate cause apoptosis and thus osteoclast differentiation inhibit. This finding may help the understanding of the osteolytic and osteoporotic processes responsible for bone diseases, including osteoporosis and periodontal diseases.
Blended natural polymer composed of β-chitosan and gelatin scaffold was prepared for bone tissue scaffold. After hydrolyzing the scaffold in 1 N NaOH, recombinant human bone morphogenic protein-2(rhBMP-2), which has amine groups was immobilized onto the caboxylic groups on the surface, was immobilized on the surface of scaffold to improve cell viability and bone differentiation. Dental pulp stem cells(DPSCs) were seeded on the series of scaffold(non-treated, hydrolyzed, and BMP-2 immobilized gelatin/β-chitosan porous scaffolds). BMP-2 singnificently increased ALP activity, alizarin red for a week differentiation period compared with non-treated and hydrolyzed scaffolds in vitro. These results indicated that BMP-2-immobilyzed gelatin/β-chitosan porous scaffold would be valuable for bone tissue regeneration.