• 폴리머
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• 제38권3호
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• pp.307-313
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• 2014

Poly(ethylene-co-vinyl acetate) (EVA) 중에 포함된 비닐아세테이트의 함량을 0~40 wt% 범위에서 변화시키면서, 관능화 그래핀 쉬트(functionalized graphene sheet, FGS)/EVA 복합재료의 물성 변화를 조사하였다. EVA 중 극성을 가진 비닐아세테이트의 함량이 증가할수록 FGS와의 혼화성이 증가하여, FGS의 분산이 좋아지면서 EVA의 표면 저항 감소, 모듈러스 증가가 효과적으로 발현되었다. EVA 중 비닐아세테이트의 함량이 적어 FGS와의 상호작용이 작은 경우는 계면에서의 접착력이 낮아 인장력을 부가한 경우 파괴가 급격히 진행되어 파괴점에서의 신도가 크게 감소하였다. 복합재료에서 EVA의 결정화는 FGS와의 상호작용으로 대체적으로 감소하였다. 하지만, 비닐아세테이트 함량이 작은 EVA에 소량의 FGS를 첨가한 경우는 기핵효과에 의한 결정화 촉진이 관찰되었다.

• 대한치과보철학회지
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• 제45권3호
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• pp.375-381
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• 2007

Statement of problem. Prior to determining an optimal width of micropatterned grooves provided on titanium substrata, we have done a pilot study using surface topographies in combined microm and submicrom levels. Purpose. The purpose of this study was twofold 1) to assess the proliferation and 2) to analyze the expression of genes encoding the intracellular signaling proteins involved in cell-substratum adhesions and adhesion-dependent G1 phase cell cycle progression of human gingival fibroblasts plated on smooth and microgrooved/acid-etched titanium substrata. Material and methods. Three groups of titanium discs as NE0 (smooth Ti substrata), E15 (Ti substrata with microgrooves of $15{\mu}m$ of spacing and $3.5{\mu}m$ in depth and with further acidetching), and E30 (Ti substrata with microgrooves of $30{\mu}m$ spacing and $3.5{\mu}m$ in depth and with further acid-etching) served as the human gingival fibroblasts' substrata. Viability and proliferation of fibroblasts were determined using an XTT assay. Gene expressions of fibronectin, ${\alpha}5$ integrin, CDK4, and $p27^{kip}$ were analyzed in RT-PCR. Cell-substratum interactions were analyzed in SEM. Results. From the XTT assay at 24 h incubation, the mean optical density (OD) value of E15 was significantly greater than the values of E30 and NE0. At 48 and 96 h however, the mean OD values of E30 were significantly greater than the values of E15 and NE0. No differences in the expression of PCR transcripts at 96 h incubations were noted between groups, whereas at 48 h, an unexpected increase in the expression of all the transcripts were noted in E15 compared with other two groups. Fibroblasts were observed to orient and adhere inside the microgrooves. Conclusion. Micropatterned grooves and acid-etching on Ti substrata alter viability and gene expression of adhered human gingival fibroblasts.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제21권2호
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• pp.120-130
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• 1999

This investigation studied the effect of ovariectomy on the temporomandibular joint (TMJ) of rat. Forty female Sprauge-Dawley strain white rats, each weighing about 200grams were used and divided into two groups. The one group was performed ovariectomy, and the other was performed sham operation. Both group were killed at the intervals of 3 days, 1, 2, 4, and 8 weeks postoperatively, paraffin section were stained with H&E, MT and histomorphometric study of the TMJ was performed in a synchronous manner with an sham operated control group The result were as follows: 1. At 4 weeks after ovariectomy, an adhesion between the inferior surface of the articular disc and the condyle was observed in the central portion. At 8 weeks after ovariectomy, a focal thickening of the bone (osteophyte) was observed in anterior portion and there was a marked decrease in the trabecular bone in the posterior region. 2. The thickness of cartilage zone was increased at 2 weeks postopratively in the central portion, and decreased at 4 weeks postopratively in the posterior portion. The thickness of transitional zone was decreased at 1 week postoperatively in the anterior and proliferating zone was decreased postoperatively. The thickness of articular zone was decreased at 3 days postopratively in the anterior portion, and decreased at 1 week postoperatively in the central portion. From the above finding, we could conclue that estrogen deficiency in rats causes alteration of TMJ in marked early stage.

• 한국추진공학회지
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• 제17권5호
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• pp.95-100
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• 2013

동적 기밀구조에 사용되는 고체윤활재의 선택에 있어 중요 설계 변수들은 기밀성, 내마멸성, 윤활막의 형성 등이 있다. 본 연구에서 그라파이트의 고체유할 특성에 영향을 미치는 영향인자들이 분석되었고 다양한 시험 조건들에 대하여 발생하는 마모거동이 왕복동 마모시험으로부터 얻은 결과들과 비교되었다. 또한 윤활 막들의 생성에 대한 최적조건들이 그라파이트 소재의 특성들을 평가하기 위하여 조사되었다. 마멸입자의 생성, 윤활 막의 생성, 윤활 막의 소멸의 과정을 반복하는 과정이 마모 깊이의 변화와 통하여 마모 메커니즘을 평가하였다. 따라서 그라파이트 씰의 윤활막은 마모된 표면위에 마모 입자들의 응착에 의해 발생한 윤활막이 발생되었고 이는 마모특성에 매우 유용하였다.

• 대한기계학회논문집B
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• 제35권11호
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• pp.1229-1235
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• 2011

본 연구에서는 세포의 성장속도, 배양표면 부착, 체내 특이성을 유지에 중요한 요소인 세포외 기질 물질에 따른 심근세포주(HL-1 cell)의 성장, 생존률 및 표현형 등을 분석했다. 서로 다른 5 가지의 세포외 기질 환경을 조성하여 세포 성장에 미치는 영향에 대하여 분석했다. 세포외 기질 물질이 처리된 배양 표면의 물리적인 형태는 원자현미경을 통하여 분석했으며, 세포의 표면부착, 성장 및 증식과 생존률 및 표현형은 역상형광현미경 및 면역염색법을 통해 분석했다. 본 연구를 통하여 서로 다른 세포외 기질 물질이 세포의 부착 및 성장 속도에 영향을 미치며, 심근세포의 특이성을 나타내는 단백질의 형성에도 차이를 보이는 것을 확인했다.

• Elastomers and Composites
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• 제47권2호
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• pp.162-167
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• 2012

거대분자의 표면개질은 고분자재료의 물성을 향상시키기 위한 점진적이고 바람직한 방안을 제공하며 고분자의 주요 물성을 손상시키지 않고 고분자 표면의 전도도, 젖음성, 안정성, 접착 및 항박테리아성 등을 개선시킨다. PE 또는 PP 등의 polyolefin을 관능성 단량체로서 MAH와 용액상에서 그래프트시켰다. FTIR측정을 통하여 그래프팅이 일어났음을 확인하였다. 그래프팅율은 화학적정에 의하여 결정하였다. MAH량이 많아질수록 접촉각은 낮은 값을 얻었다. 또한 MAH량이 증가함에 따라 polyolefin-g-MAH의 융점($T_m$)은 감소하는 한편 분해온도($T_d$)는 증가하는 경향을 보였다.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2002년도 춘계 기술심포지움 논문집
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• pp.193-197
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• 2002

The tribological properties and van der Waals attractive forces and the thermal stability of films are very important characteristics of highly hydrophobic fluorocarbon (FC) films for the long-term reliability of nano system. The effect of thermal annealing on films and van der Waals attractive forces and friction coefficient of films have been investigate d in this study. It was coated Al wafer which was treated O2 and Ar that ocatfluorocyclobutane ($C_4_{8}$) and Ar were supplied to the CVD chamber in the ratio of 2:3 for deposition of FC Films. Static contact angle and dynamic contact angle were used to characterize FC films. Thickness of films was measured by variable angle spectroscopy ellipsometer (VASE). Nanotribological data was got by atomic force microscopy (AFM) to measure roughness, lateral force microscopy (LFM) to measure friction force, and force vs. distance (FD) curve to evaluate adhesion force. FC films were cured in N2 and vacuum. The film showed the slight changes in its properties after 3 hr annealing. FTIR ATR studies showed the decrease of C-F peak intensity in the spectra as the annealing time increased. A significant decrease of film thickness has been observed. The friction force of Al surface was at least thirty times higher than ones with FC films. The adhesive force of bare Al was greater than 100 nN. After deposit FC films adhesive force was decreased to 40 nN. The adhesive force of films was decreased down to 10 nN after 24 hr annealing. During 24 hr annealing in $N_2$and vacuum at $100^{\circ}C$ film properties were not changed so much.

• 청정기술
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• 제14권3호
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• pp.193-203
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• 2008

피혁 제조 공정에서 계면활성제는 세정목적, 분산성 그리고 고착성 등을 부여하기 위해 사용되고 있다. 그러나 기존의 피혁 공정에서 사용되고 있는 계면활성제는 친수성기가 다량 포함되어 있어 향후 피혁 시장에서 요구될 것으로 기대되는 내오염성, 내수성, 내구성 통의 고기능성 특성을 재현하는데 문제점이 있다. 본 연구에서는 기존의 탄화수소 계열의 계면활성제의 문제점을 보완하기 위해서, 탄소-불소의 강한 결합에너지로 인한 표면장력 감소, 분산력 증대, 세정효과, 크롬 흡착력 증대 등의 특성을 나타내는 불소계 계면활성제를 제조하였다. 불소계 계면활성제의 사용으로 피혁 제조 공정의 분산성 증대, 침투력 상승 및 결합력을 향상시켜 크롬 흡착률 증가, 탄닝 폐수 배액의 크롬 함량 감소, 생물학적 산소 요구량, 화학적 산소 요구량의 함량 감소 및 물리적 특성이 향상되는 것을 확인하였다.

• The Journal of Advanced Prosthodontics
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• 제1권1호
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• pp.56-61
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• 2009

STATEMENT OF PROBLEM. The success of titanium implants is due to osseointegration or the direct contact of the implant surface and bone without a fibrous connective tissue interface. PURPOSE. The purpose of this study was to evaluate the osteoblast precursor response to titanium-10 tantalum-10 niobium(Ti-Ta-Nb) alloy and its sputtered coating. MATERIAL AND METHODS. Ti-Ta-Nb coatings were sputtered onto the Ti-Ta-Nb disks. Ti6-Al-4V alloy disks were used as controls. An osteoblast precursor cell line, were used to evaluate the cell responses to the 3 groups. Cell attachment was measured using coulter counter and the cell morphology during attachment period was observed using fluorescent microscopy. Cell culture was performed at 4, 8, 12 and 16 days. RESULTS. The sputtered Ti-Ta-Nb coatings consisted of dense nanoscale grains in the range of 30 to 100 nm with alpha-Ti crystal structure. The Ti-Ta-Nb disks and its sputtered nanoscale coatings exhibited greater hydrophilicity and rougher surfaces compared to the Ti-6Al-4V disks. The sputtered nanoscale Ti-Ta-Nb coatings exhibited significantly greater cell attachment compared to Ti-6Al-4V and Ti-Ta-Nb disks. Nanoscale Ti-Ta-Nb coatings exhibited significantly greater ALP specific activity and total protein production compared to the other 2 groups CONCLUSIONS. It was concluded that nanoscale Ti-Ta-Nb coatings enhance cell adhesion. In addition, Ti-Ta-Nb alloy and its nanoscale coatings enhanced osteoblast differentiation, but did not support osteoblast precursor proliferation compared to Ti-6Al-4V. These results indicate that the new developed Ti-Ta-Nb alloy and its nanoscale Ti-Ta-Nb coatings may be useful as an implant material.

• The Journal of Advanced Prosthodontics
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• 제7권6호
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• pp.484-495
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• 2015

PURPOSE. This study was to evaluate the effects of bacterial cellulose (BC) membranes as a barrier membrane on guided bone regeneration (GBR) in comparison with those of the resorbable collagen membranes. MATERIALS AND METHODS. BC membranes were fabricated using biomimetic technology. Surface properties were analyzed, Mechanical properties were measured, in vitro cell proliferation test were performed with NIH3T3 cells and in vivo study were performed with rat calvarial defect and histomorphometric analysis was done. The Mann-Whitney U test and the Wilcoxon signed rank test was used (${\alpha}<.05$). RESULTS. BC membrane showed significantly higher mechanical properties such as wet tensile strength than collagen membrane and represented a three-dimensional multilayered structure cross-linked by nano-fibers with 60 % porosity. In vitro study, cell adhesion and proliferation were observed on BC membrane. However, morphology of the cells was found to be less differentiated, and the cell proliferation rate was lower than those of the cells on collagen membrane. In vivo study, the grafted BC membrane did not induce inflammatory response, and maintained adequate space for bone regeneration. An amount of new bone formation in defect region loaded with BC membrane was significantly similar to that of collagen membrane application. CONCLUSION. BC membrane has potential to be used as a barrier membrane, and efficacy of the membrane on GBR is comparable to that of collagen membrane.