• The Journal of Korean Academy of Prosthodontics
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• v.60 no.3
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• pp.231-238
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• 2022

Purpose. This study aimed to investigate the effect of different veneering methods on the tensile bond strength between polyetherketoneketone (PEKK) and denture base resins. Materials and methods. A total of 80 PEKK T-shaped specimens were fabricated and the primer (Visio.link) was applied after airborne-particle abrasion with 110 ㎛ alumina oxide powder. According to the veneering method, the specimens were divided into four groups (n = 20) to be veneered with the gingival colored packable photopolymerized composite resin (SR Adoro); flowable photopolymerized composite resin, (Crea.lign); heat-polymerized resin (Vertex); and self-polymerized resin (ProBase Cold). Each group was divided into two subgroups (n = 10) according to the artificial thermal aging. After the tensile bond strength measurement via universal testing machine, the fracture sections of all specimens were observed. Two-way ANOVA and Tukey's HSD post hoc test were used for the statistical analysis (α = .05). Results. The results of the two-way ANOVA showed statistically significant differences in the tensile bond strength according to the veneering method and artificial thermal aging of denture base resins (P<.001). The highest tensile bond strength showed in the packable photopolymerized resin group before and after the artificial thermal aging. The lowest tensile bond strength showed in the heat-polymerized resin group. The mixed and adhesive fracture showed in all groups. Conclusion. The veneering method and artificial thermal aging can influence in the tensile bond strength between the resin and PEKK. The artificial thermal aging can reduce the tensile bond strength.

• Journal of the Korean Wood Science and Technology
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• v.48 no.6
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• pp.791-806
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• 2020

In this study, a block shear strength test was conducted to compare and analyze the strength and failure mode on the glued laminated timber, CLT, and Ply-lam CLT, which are mainly used for the construction of wood construction as engineering wood. Through this, the Ply-lam CLT manufacturing conditions for optimum production, such as the type of lamina, plywood, adhesive, and layer composition, were investigated. The results are as follow. Through block shear strength test, it showed high strength in the order of glued laminated timber, Ply-lam CLT and CLT. In particular, the shear strength of Ply-lam CLT, which is made of a composite structure of larch plywood and larch lamina, passed 7.1 N/㎟, which is a Korean industrial standards for block shear strength of structural glued laminated timber. In addition, in this study, there was no different in shear strength according to the adhesive type used for glulam, CLT, and Ply-lam CLT adhesion. However, in the case of Ply-lam CLT, the difference in shear strength of Ply-lam CLT was shown according to the type of lamina and plywood. The results showed high strength in the order of Larix kaempferi > Mixed light hardwood ≒ Pinus densiflora, sieb, et, Zucc plywood. The optimal configuration of Ply-lam CLT is when larch plywood and larch lamina are used, and it is decided that the adhesive can be used by selecting PRF and PUR according to the application. The results of block shear strength failure mode by type of wood based materials were analyzed. The failure mode showed shear parallel-to-grain for glulam, rolling shear for CLT, and shear parallel-to-grain and rolling for ply-lam CLT. This is closely related to shear strength results and is decided to indicate higher shear strength in Ply-lam CLT than in CLT due to rolling shear.

• Food Science and Preservation
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• v.16 no.4
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• pp.472-481
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• 2009

Response surface methodology (RSM) is frequently used for optimization studies. In the present work, RSM was used to determine the antimicrobial activitiesof grapefruit seed extract (GFSE) and a lactic acid mixture (LA) against Staphylococcus aureus, Bacillus cereus, Escherichia coli, Salmonella typhimurium, Pseudomonas fluorescens, and Vibrio parahaemolyticus. A central composite design was used to investigate the effects of independent variables on dependent parameters. One set of antimicrobial preparations included mixtures of 1% (w/w) GFSE and 10% (w/w) LA, in which the relative proportions of component antimicrobials varied between 0 and 100%. In further experiments, the relative proportions were between 20% and 100%. Antimicrobial effects against various microorganisms were mathematically encoded for analysis. The codes are given in parentheses after the bacterial names, and were S. aureus ($Y_1$), B. cereus ($Y_2$), E. coli ($Y_3$), S. typhimurium ($Y_4$), P. fluorescens ($Y_5$), and V. parahaemolyticus ($Y_6$). The optimum antimicrobial activity of the 1% (w/w) GFSE:10% (w/w) LA mixture against each microorganism was obtained by superimposing contour plots ofantimicrobial activities on measures of response obtained under various conditions. The optimum rangesfor maximum antimicrobial activity of a mixture with a ratio of 1:10 (by weight) GFSE and LA were 35.73:64.27 and 56.58:43.42 (v/v), and the optimum mixture ratio was 51.70-100%. Under the tested conditions (a ratio of 1% [w/w] GFSE to 10% [w/w] LA of 40:60, and a concentration of 1% [w/w] GFSE and 10% [w/w] LA, 70% of the highest value tested), and within optimum antimicrobial activity ranges, the antimicrobial activities of the 1% (w/w) GFSE:10% (w/w) LA mixture against S. aureus ($Y_1$), B. cereus ($Y_2$), E. coli ($Y_3$), S. typhimurium ($Y_4$), P. fluorescens ($Y_5$), and V. parahaemolyticus ($Y_6$) were 24.55, 25.22, 20.20, 22.49, 23.89, and 28.04 mm, respectively. The predicted values at optimum conditions were similar to experimental values.

• Journal of Chest Surgery
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• v.39 no.5 s.262
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• pp.359-365
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• 2006

Background: Arterial grafts have been used to achieve better long-term results for coronary revascularization. Bilateral internal thoracic artery (ITA) grafts have a better results, but it may be not used in some situations such as diabetes and chronic obstructive pulmonary disease (COPD). We evaluated the clinical and angiographic results of composite left internal thoracic artery-radial artery (LITA-RA) Y graft. Material and Method: Between April 2002 and September 2004, 119 patients were enrolled in composite Y graft for coronary bypass surgery. The mean age was $62.6{\pm}8.8$ years old and female was 34.5%. Preoperative cardiac risk factors were as follows: hypertension 43.7%, diabetes 33.6%, smoker 41.2%, and hyperlipidemia 22.7%, There were emergency operation (14), cardiogenic shock (6), left ventricle ejection fraction (LVEF) less than 40% (17), and 17 cases of left main disease. Coronary angiography was done in 35 patients before the hospital discharge. Result: The number of distal anastomoses was $3.1{\pm}0.91$ and three patients (2.52%) died during hospital stay. The off-pump coronary artery bypass (OPCAB) was applied to 79 patients (66.4%). The LITA was anastomosed to left anterior descending system except three cases which was to lateral wall. The radial Y grafts were anastomosed to diagonal branches (4), ramus intermedius (21), obtuse marginal branches (109), posterolateral branches (12), and posterior descending coronary artery (8). Postoperative coronary angiography in 35 patients showed excellent patency rates (LITA 100%, and RA 88.5%; 3 RA grafts which anastomosed to coronary arteries <70% stenosed showed string sign with competitive flow). Conclusion: The LITA-RA Y composite graft provided good early clinical and angiographic results in multivessel coronary revascularization. But it should be cautiously used in selected patients.

• Food Science and Preservation
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• v.16 no.6
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• pp.908-914
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• 2009

A central composite design was used to optimize extraction of propolis materials using ethanol. The independent variables in extraction experiments were ethanol concentration (50, 60, 70, 80, 90%, v/v) and extraction time (1, 2, 3, 4, and 5 h). Higher ethanol concentration and shorter extraction time increased total polyphenol content, but total polyphenol concentration began to decrease when ethanol concentration was higher than 80% (v/v). Ethanol concentration was more important than extraction time in optimization of total polyphenol content in propolis extracts. Electron-donating ability increased with ethanol concentration and shorter extraction time, with ethanol concentration being of greater significance. Antioxidant ability in extracts was optimal at an ethanol concentration of 65 - 75% and with an extraction time of 2.2 - 3.6 h. Nitrite-scavenging ability was increased with use of higher ethanol concentration and shorter extraction time. Total flavonoid content was maximized with an ethanol concentration of 68 - 82% and an extraction time of 2.4 - 3.7 h. Total flavonoid content was affected by both ethanol concentration and extraction time. By superimposition of contour plots, an ethanol concentration of 72 - 82% and an extraction time of 2.2 - 3.3 h were optimal for preparation of propolis extracts.

• Food Science and Preservation
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• v.12 no.6
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• pp.591-599
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• 2005

This study was conducted to optimize the extraction conditions from cabbage by a response surface methodology. In extraction conditions based on the central composite design with variations, the ratio of solvent to sample ($10\~30$mL/g), ethanol concentration ($0\~100\%$) and extraction temperature ($35\~95^{circ}C$) coefficients of determinations ($R^2$) were 0.8162(p<0.1), 0.8173(p<0.1), 0.9374(p<0.01) and 0.9116(p<0.05) in extraction yield, electron donating ability, tyrosinase inhibition and SOD-like ability, respectively. Estimated extraction conditions for the maximizing yield, electron donating ability and SOD-like ability were $15\~30$ mL/g in ratio of solvent to sample, $40\~80\%$; ethanol concentration, and $50\~90^{\circ}C$ ; extraction temperature. Predicted values at the optimum condition (25 mL/g solvent to sample, $50\%$ ethanol concentration and $70^{\circ}C$ in extraction temperature) were in good agreement with observed values.

• Journal of Microbiology and Biotechnology
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• v.28 no.5
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• pp.718-731
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• 2018

The beneficial effects of lactic acid bacteria (LAB) have been intensively investigated in recent decades with special focus on modulation of the host intestinal microbiota. Numerous discoveries of effective probiotics are driven by a significantly increasing demand for dietary supplements. Consequently, technological advances in the large-scale production and lyophilization are needed by probiotic-related industries for producing probiotic LAB for commercial use. Our study had a dual objective, to determine the optimum growth medium composition and to investigate appropriate cryoprotective additives (CPAs) for Lactobacillus salivarius, and compare its responses with other Lactobacillus species. The one-factor-at-a-time method and central composite design were applied to determine the optimal medium composition for L. salivarius cultivation. The following composition of the medium was established (per liter): 21.64 g maltose, 85 g yeast extract, 1.21 ml Tween 80, 6 g sodium acetate, $0.2g\;MgSO_4{\cdot}7H_2O$, $0.02g\;MnSO_4{\cdot}H_2O$, $1g\;K_2HPO_4$, $1.5g\;KH_2PO_4$, $0.01g\;FeSO_4{\cdot}7H_2O$, and 1 g sodium citrate. A cryoprotective additive combination comprising 10% (w/v) skim milk and 10% (w/v) sucrose supplemented with 2.5% (w/v) sodium glutamate was selected for L. salivarius, and its effectiveness was confirmed using culture-independent methods in the freeze-dried cells of the Lactobacillus strains. In conclusion, the optimized medium enhanced the species-specific cultivation of L. salivarius. On the other hand, the cryoprotective effects of the selected CPA mixture may also be dependent on the bacterial strain. This study highlights the necessity for precise and advanced processing techniques for large-scale production of probiotics in the food and feed industries.

• Journal of Life Science
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• v.21 no.8
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• pp.1083-1093
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• 2011

A microorganism utilizing rice hulls as a substrate for the production of carboxymethylcellulase (CMCase) was isolated from seawater and identified as Bacillus lincheniformis by analyses of its 16S rDNA sequences. The optimal carbon and nitrogen sources for production of CMCase were found to be rice hulls and ammonium nitrate. The optimal conditions for cell growth and the production of CMCase by B. lincheniformis LBH-52 were investigated using the response surface method (RSM). The analysis of variance (ANOVA) of results from central composite design (CCD) indicated that a highly significant factor ("probe>F" less than 0.0001) for cell growth was rice hulls, whereas those for production of CMCase were rice hulls and initial pH of the medium. The optimal conditions of rice hulls, ammonium nitrate, initial pH, and temperature for cell growth extracted by Design Expert Software were 48.7 g/l, 1.8 g/l, 6.6, and 35.7$^{\circ}C$, respectively, whereas those for the production of CMCase were 43.2 g/l, 1.1 g/l, 6.8, and 35.7$^{\circ}C$. The maximal production of CMCase by B. lincheniformis LBH-52 from rice hulls under optimized conditions was 79.6 U/ml in a 7 l bioreactor. In this study, rice hulls and ammonium nitrate were developed to be substrates for the production of CMCase by a newly isolated marine microorganism, and the time for production of CMCase was reduced to 3 days using a bacterial strain with submerged fermentation.

• Journal of the Korean Society of Food Science and Nutrition
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• v.34 no.4
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• pp.549-556
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• 2005

Response surface methodology (RSM) was applied in steaming and roasting processes of Polygonatum odoratum roots in order to monitor hypoglycemic components and sensory property. In steaming and roasting processes based on the central composite design with variations in steaming time $(60\~180\;min)$, roasting temperature $(110\~150^{\circ}C)$ and roasting time $(10\~50\;min)$, coefficients of determinations $(R^2)$ were 0.8691 (p<0.05), 0.8253 (p<0.l0), 0.8727 (p<0.05), 0.8706 (p<0.05) and 0.8316 (p<0.10) in soluble solid, stigmasterol, $\beta-sitosterol$, hypoglycemic component (total), and overall acceptability, respectively. The maximum value of soluble solid was $71.47\%$ in 65.24 min of steaming time, $126.93^{\circ}C$ of roasting temperature and 37.58 min of roasting time. The maximum value of hypoglycemic component (total) was $764.10\;{\mu}g/g$ in 107.76 min, $117.78^{\circ}C$ and 14.70 min. Meantime, the maximum value of overall acceptability was 6.89 in 126.04 min, $115.79^{\circ}C$ and 43.93 min. The predicted values in optimum conditions for hypoglycemic components and sensory property were in good agreement with experimental values.

• Journal of the Korean Society of Food Science and Nutrition
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• v.36 no.8
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• pp.1062-1069
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• 2007

Response surface methodology was employed to optimize extraction conditions for finding the maximizing the functional properties of roasted Pleurotus eryngii. Based on the central composite design, independent variables were ethanol concentration ($0{\sim}100%$), extraction time ($1{\sim}9$ min) and microwave power ($25{\sim}125$ W). Soluble solid content, electron donating ability and nitrite-scavenging ability were mainly affected by ethanol concentration, but ACE inhibition activity was largely affected by extraction time. The optimum ranges of extraction conditions resulting from superimposing the response surface were predicted to be ethanol concentration ($25{\sim}50%$), extraction time ($3{\sim}9$ min) and microwave power ($80{\sim}125$ W). Total protein and total phenolic compound content of optimal extracts were 45.80 mg/g and 7.42 mg/g, respectively. In phenolic compounds of roasted Pleurotus eryngii extracts, protocatechuic acid was the highest concentration at 1226.32 ${\mu}g/g$, followed by salicylic acid, catechin, p-hydroxybenzoic acid, caffeic acid, coumaric acid and hesperidin.