• 원예과학기술지
• /
• 제29권5호
• /
• pp.488-493
• /
• 2011

Callus culture initiation of strawberry (Fragaria${\times}$ananassa Duch.) was investigated at different Murashige and Skoog (MS) medium strengths, types and concentrations of plant growth regulators, and incorporating a cold pretreatment period to determine the optimal nutritional and environmental conditions. No high quality callus was induced on MS media without auxin regardless of medium strength. When 6-benzylaminopurine (BA) was combined with indole acetic acid (IAA), naphthalene acetic acid (NAA), and 2,4-dichlorophenoxyacetic acid (2,4-D), high quality callus were highly induced compared to medium supplemented with auxin alone. When $0.5mg{\cdot}L^{-1}$ BA was combined with IAA, NAA, and 2,4-D, high quality callus induction was more effective than the medium supplemented with the other BA concentrations. The best combination of auxin and cytokinin for high quality callus induction was $1.0mg{\cdot}L^{-1}$ NAA and $0.5mg{\cdot}L^{-1}$ BA. Although the differences in callus induction were not significant, high quality callus induction at half strength MS medium was more effective than at full strength medium. When $30g{\cdot}L^{-1}$ sucrose was added to the half strength MS medium, the rate of high quality callus induction increased. The optimum cold pretreatment temperature and period for high quality callus induction were $4^{\circ}C$ and 72 h, respectively. Regeneration rate of high quality callus increased in MS medium supplemented with thidiazuron.

• The Journal of Advanced Prosthodontics
• /
• 제7권4호
• /
• pp.317-322
• /
• 2015

PURPOSE. The aim was to evaluate the effect of curing mode and different dentin surface pretreatment on microtensile bond strength (${\mu}TBS$) of self-adhesive resin cements. MATERIALS AND METHODS. Thirty-six extracted human permanent molars were sectioned horizontally exposing flat dentin surface. The teeth were divided into 12 groups (3 teeth/group) according to the dentin surface pretreatment methods (control, 18% EDTA, 10% Polyacrylic acid) and curing mode (self-curing vs. light-curing) of cement. After pretreatment, composite resin blocks were cemented with the following: (a) G-CEM LinkAce; (b) RelyX U200, followed by either self-curing or light-curing. After storage, the teeth were sectioned and ${\mu}TBS$ test was performed using a microtensile testing machine. The data was statistically analyzed using one-way ANOVA, Student T-test and Scheffe's post-hoc test at P<.05 level. RESULTS. For G-CEM LinkAce cement groups, polyacrylic acid pretreatment showed the highest ${\mu}TBS$ in the self-cured group. In the light-cured group, no significant improvements were observed according to the dentin surface pretreatment. There were no significant differences between curing modes. Both dentin surface pretreatment methods helped to increase the ${\mu}TBS$ of RelyX U200 resin cement significantly and degree of pretreatment effect was similar. No significant differences were found regarding curing modes except control groups. In the comparisons of two self-adhesive resin cements, all groups within the same pretreatment and curing mode were significantly different excluding self-cured control groups. CONCLUSION. Selecting RelyX U200 used in this study and application of dentin surface pretreatment with EDTA and polyacrylic acid might be recommended to enhance the bond strength of cement to dentin.

• Composites Research
• /
• 제24권3호
• /
• pp.1-5
• /
• 2011

환경 문제가 대두 됨에 따라 세계 각국에서는 환경규제를 통해서 산업계에 친환경 제품의 개발을 독려하고 있어 생분해성 재료에 대한 산업계의 관심이 높아지고 있다. 생분해성 재료인 Polylactic acid(PLA)는 강성과 내화학성이 뛰어나지만 내열성과 내충격성이 낮아서 자동차용 재료로서 요구되는 성능을 만족시킬 수 없다. 이에 본 연구에서는 천연섬유(황마)를 강화재로 사용하여 PLA의 내열성과 내충격성을 향상 시키기 위한 실험을 수행하였다. 특히 PLA와 황마 계면 간의 결합력을 증가시키기 위해 다양한 표면처리를 수행하였고 내충격성이 향상됨을 확인하였다. 또, 어닐링 처리를 통해서 PLA의 내열성이 크게 증가함을 보였다.

• 한국세라믹학회지
• /
• 제55권5호
• /
• pp.446-451
• /
• 2018

In this study, different formulations of magnesium oxide and various modifiers (phosphoric acid, ferrous sulfate, pure acrylic emulsion, silicone acrylic emulsion, glass fiber, and polypropylene fiber) were used to prepare magnesium oxychloride cement composites. The compressive strength of the magnesium oxychloride cement was tested, and the softening coefficients of the composites after soaking in water were also calculated. The results showed that a magnesium oxychloride cement sample could not be coagulated when the MgO activity was 24.3%, but the coagulation effect of the magnesium oxide cement sample was excellent when the MgO activity was 69.5%. While pure acrylic emulsion, silicon-acrylic emulsion, and glass fiber showed insignificant modification effects on the magnesium oxychloride cement, ferrous sulfate heptahydrate, phosphoric acid, and polypropylene fiber could effectively improve its water resistance and compressive strength. When the phosphoric acid, ferrous sulfate heptahydrate, and polypropylene fiber contents were 0.47%, 0.73%, and 0.25%, respectively, the softening coefficient of a composite soaked in water reached 0.93 after 7 days, and the compressive strength reached 64.3 MPa.

• The Journal of Advanced Prosthodontics
• /
• 제5권2호
• /
• pp.98-103
• /
• 2013

PURPOSE. To evaluate the effects of hydrofluoric acid etching and Er,Cr:YSGG laser irradiation on the shear bond strength of resin cement to lithium disilicate ceramic. MATERIALS AND METHODS. Fifty-five ceramic blocks ($5mm{\times}5mm{\times}2mm$) were fabricated and embedded in acrylic resin. Their surfaces were finished with 1000-grit silicon carbide paper. The blocks were assigned to five groups: 1) 9.5% hydrofluoric-acid etching for 60 s; 2-4), 1.5-, 2.5-, and 6-W Er,Cr:YSGG laser applications for 60 seconds, respectively; and 5) no treatment (control). One specimen from each group was examined using scanning electron microscopy. Ceramic primer (Rely X ceramic primer) and adhesive (Adper Single Bond) were applied to the ceramic surfaces, followed by resin cement to bond the composite cylinders, and light curing. Bonded specimens were stored in distilled water at $37^{\circ}C$ for 24 hours. Shear bond strengths were determined by a universal testing machine at 1 mm/min crosshead speed. Data were analyzed using Kruskal-Wallis and Mann-Whitney U-tests (${\alpha}$=0.05). RESULTS. Adhesion was significantly stronger in Group 2 ($3.88{\pm}1.94$ MPa) and Group 3 ($3.65{\pm}1.87$ MPa) than in Control group ($1.95{\pm}1.06$ MPa), in which bonding values were lowest (P<.01). No significant difference was observed between Group 4 ($3.59{\pm}1.19$ MPa) and Control group. Shear bond strength was highest in Group 1 ($8.42{\pm}1.86$ MPa; P<.01). CONCLUSION. Er,Cr:YSGG laser irradiation at 1.5 and 2.5 W increased shear bond strengths between ceramic and resin cement compared with untreated ceramic surfaces. Irradiation at 6 W may not be an efficient ceramic surface treatment technique.

• KSBB Journal
• /
• 제10권5호
• /
• pp.491-498
• /
• 1995

Cyclodextrin의 고순도 분획, 정제를 위한 CD adsorbent의 제조에 척합한 matnx를 선별하기 위하여 capric acid를 ligand로 각종 이온교환수지를 비교 검토한 결과 DEAE Cellulose가 가장 적합함을 알았다. DEAE Cellulose와 capric acid간의 결합 안정성은 온도, ionic strength의 변화에 영향을 받았으며, ethanol 농도의 변화에는 안정하였다. CD adsorbent의 흡착량, 탈착량, 그리고 ${\alpha}$-, ${\beta}$- 및 ${\gamma}$-CD 의 용출양상을 규명하였다. 탄소쇄가 다른 각종 포화, 불포화 fatty acid를 ligand로 하여 specific adsorbent를 제조하였으며, ${\alpha}$-, ${\beta}$- 및 ${\gamma}$-CD의 회수율과 분리능을 비교 검토 하였다. 그 결과 steanc a acid는 ${\alpha}$-CD 그리고 linoleic acid는 ${\beta}$-CD에 대하여 높은 회수율과 선택성을 보였으며, 선택성은 fatty acid의 탄소쇄 길이와 이중결합 유무에 의하여 영향을 받았다. Stearic acid와 linoleic acid CD adsorbents를 이용하여 CD 혼합물로부터${\alpha}$-, ${\beta}$- 및 ${\gamma}$-CD의 분획양상을 검토하였다.

• 접착 및 계면
• /
• 제9권3호
• /
• pp.27-33
• /
• 2008

무기계 킬레이트의 일종인 aluminum acetylacetonate (AlACA)를 점착제의 -COOH 당량비에 따라 0, 0.25, 0.5, 0.75, 1의 비율로 변화 시키고, 점착제는 acrylic acid의 함량을 3 wt%, 7 wt%, 10 wt%으로 변화를 시켜 그에 따른 경화거동을 살펴 보았다. 킬레이트의 함량이 증가하면서 가교 구조가 형성되고, 이에 따라 probe tack의 fibrillation이 줄어들고, peel strength도 줄어드는 경향을 보였다. SAFT의 경우 점착제의 acrylic acid 함량이 증가함에 따라 확연히 증가하였다. 본 연구 결과, aluminum acetylacetonate는 점착물성을 크게 변화시키지 않는 범위에서 점착제를 가교 시킬 수 있음을 확인하였다.

• 한국임상수의학회지
• /
• 제25권6호
• /
• pp.494-500
• /
• 2008

The aim of this study was to determine the effectiveness of hyaluronic acid-carboxymethylcellulose membrane (GUARDIX-$MB^{(R)}$) barriers on prevention against post-operative peritoneal adhesions. In this study, fourteen mongrel dogs were divided into two experimental groups: 0.1 % hyaluronic acid (0.1HA) group and hyaluronic acidcarboxymethylcellulose membrane (HA-CMC) group. In order to induce adhesions, the anti-mesenteric serosa of the ileum was exteriorized and then abraded in a standard manner by scraping with a scalpel blade to create homogenous petechial hemorrhagic surface over a $1\;{\times}\;1cm$ area. Solution of 0.1HA were simply coated over the abraded tissues, $1.5\;{\times}\;1.5cm$ HA-CMC membrane was placed over the abraded tissues, allowed to spread across the intra-abdominal organs before closure of the abdomen. On day 1 before and day 1, 4, 7, 14, and 21 after operation, venous blood specimens were collected for measurement of fibrinogen and total WBC. The adhesions were blindly assessed 3 weeks later by using a computerized tensiometer. The fibrinogen and total WBC values of two groups showed no statistical significances. The mean tensile strength (gram force, gf) of formed adhesions day 21 after surgery was $88.1\;{\pm}\;55.70gf$ in the 0.1 % HA group and $24.8\;{\pm}\;22.69gf$ in the HA-CMC group. The tensile strength values of adhesion separation HA-CMC membrane group was significantly lower than the 0.1HA group (p<0.05). Therefore, we suggest that HACMC membrane reduce peritoneal adhesions may be applicable to preventing post-operative intraperitoneal adhesions in dogs.

• 방사선산업학회지
• /
• 제6권2호
• /
• pp.165-169
• /
• 2012

This study was conducted to determine the prevention effect of poly-gamma-glutamic acid (${\gamma}-PGA$) on tissue damage induced by gamma irradiation for development of xenograft. Porcine tendons were treated at various doses of ${\gamma}-PGA$ (0.1, 0.5, 1 and 5%) and then gamma-irradiated (30 kGy). Prevention effects on tissue damage were measured as the result of tensile strength, hydroxyproline contents and viscosity of ${\gamma}-PGA$. Tensile strength was remarkably decrease in gamma-irradiated porcine ligament, but increased by ${\gamma}-PGA$ treated one. Among the ${\gamma}-PGA$ treatment doses, 1% treated group showed the highest values of tensile strength compared to non-treated group. Hydroxyproline contents was significantly increased by gamma irradiation, but decreased by the ${\gamma}-PGA$ treatment. Particularly, 1 and 5% ${\gamma}-PGA$ treated group were exhibited lower values of hydroxyproline contents than other group. In the result of viscosity, gamma-irradiated ${\gamma}-PGA$ (1%) was remarkably increased. Base on the results, it demonstrated that gamma irradiation induces severe alteration of mechanical property and collagen contents on porcine ligament, but ${\gamma}-PGA$ can effectively prevent these tissue damage.

• Bulletin of the Korean Chemical Society
• /
• 제8권5호
• /
• pp.427-428
• /
• 1987