• Restorative Dentistry and Endodontics
• /
• v.42 no.3
• /
• pp.216-223
• /
• 2017

Objectives: The aim of this study was to compare the mechanical properties of various nickel-titanium (NiTi) files with similar tapers and cross-sectional areas depending on whether they were surface-treated. Materials and Methods: Three NiTi file systems with a similar convex triangular cross-section and the same ISO #25 tip size were selected for this study: G6 (G6), ProTaper Universal (PTU), and Dia-PT (DPT). To test torsional resistance, 5 mm of the straightened file's tip was fixed between polycarbonate blocks (n = 15/group) and continuous clockwise rotation until fracture was conducted using a customized device. To evaluate cyclic fatigue resistance, files were rotated in an artificial curved canal until fracture in a dynamic mode (n = 15/group). The torsional data were analyzed using 1-way analysis of variance and the Tukey post-hoc comparison test, while the cyclic fatigue data were analyzed using the Mann-Whitney U test at a significance level of 95%. Results: PTU showed significantly greater toughness, followed by DPT and G6 (p < 0.05). G6 showed the lowest resistance in ultimate torsional strength, while it showed a higher fracture angle than the other files (p < 0.05). In the cyclic fatigue test, DPT showed a significantly higher number of cycles to failure than PTU or G6 (p < 0.05). Conclusions: Within the limitations of this study, it can be concluded that the torsional resistance of NiTi files was affected by the cross-sectional area, while the cyclic fatigue resistance of NiTi files was influenced by the surface treatment.

• Restorative Dentistry and Endodontics
• /
• v.20 no.2
• /
• pp.699-720
• /
• 1995

This study was conducted to evaluate the effect of benzalkonium chloride solution as a wetting agent instead of water on dentin bonding with NTG-GMA/BPDM system (All-bond 2, Bisco.) and DSDM system (Aelitebond, Bisco.). Benzalkonium chloride solution is a chemical disinfectant widely used in medical and dental clinics for preoperative preparation of skin and mucosa due to its strong effect of cationic surface active detergent. Eighty freshly extracted bovine lower incisor were grinded labially to expose flat dentin surface, and then were acid-etched with 10 % phosphoric acid for 15 second, water-rinsed, and dried for 10 second with air syringe. The specimens were randomly divided into 8 groups of 10 teeth. The specimens of control group were remoistured with water and the specimens of experimental groups were remoistured with 0.1 %, 0.5 %, and 1.0 % benzalkonium chloride solution respectively. And then, the Aelitefil composite resin was bonded to the pretreated surface of the specimens by use of All-bond 2 dentin bonding system or Aelitebond dentin bonding system in equal number of the specimens. The bonded specimens were stored in $37^{\circ}C$ distilled water for 24 hours, then the tensile bond strength was measured, the mode of failure was observed, the fractured dentin surface were examined under scanning electron microscopy, and FT-IR spectroscopy was taken for the purpose of investigating the changes of the dentin surface pretreated with benzal konium chloride solution followed by each primer of the dentin bonding systems. The results were as follows : In the group of bonding with NTG-GMA/BPDM dentin bonding agent(All-bond 2), higher tensile bond strength was only seen in the experimental group remoistured with 0.1 % benzal konium chloride solution than that in water-remoistured control group(p<0.05). In the group of bonding with DSDM dentin bonding agent (Aelitebond), no significant differences were seen between the control and each one of the experimental group(p<0.05). Higher tensile bond strength were seen in NTG-GMAIBPDM dentin bonding agent group than in DSDM dentin bonding agent group regardless of remoistur ization with benzal konium chloride solution. On the examination of failure mode, cohesive and mixed failure were predominantly seen in the group of bonding with NTG-GMAIBPDM dentin bonding agent, while adhesive failure was predominantly seen in the group of bonding with DSDM dentin bonding agent. On SEM examination of fractured surfaces, no differences of findings of primed dentin surface between the groups with and without remoisturization with benzal konium chloride solution. FT-IR spectroscopy taken from the control and the experimental group reve::.led that some higher absorbance derived from the primers binding to dentin surface was seen at the group pretreated with 0.1 % benzal konium chloride solution than at the control group of remoisturizing with water.

• Restorative Dentistry and Endodontics
• /
• v.16 no.2
• /
• pp.126-142
• /
• 1991

The purpose of this study was to evaluate the effect of various dentin surface treatments on shear bond strength, microhardness and fracture mode before and after thermocycling. Recently extracted 75 human molars were used. The teeth were sagittal sectioned faciolingually to obtain 150 specimens. They were randomly divided into six groups. Mesial and distal dentinal surfaces of specimens were exposed by grinding and treated respectively with GC-DENTIN CONDITIONER. 10-3 solution of 4-Meta, Cleansar and Primer of GLUMA, Scotchprep of Scotchbond 2, DENTIN CONDITIONER and PRIMER A, B of ALL BOND according to the manufacturers directions. Specimens of one group were not treated. Adhesive agent of Scotchbond 2, were applied and cured on the treated dentin surfaces. After P-50 were cured on them, specimens were stored in 31c water for 24 hours before shear bond strength measurement Shear bond strength was measured in 10 specimens of each group. 10 specimens of each group were thermocycled in $20^{\circ}C$, $60^{\circ}C$,$20^{\circ}C$, $4^{\circ}C$, $20^{\circ}C$ water in order, for 30 seconds respectively, 100 times a day for 7 days. After thermocycling shear bond strength was measured. Microhardness was checked on treated dentin surface and fractured dentin surface in 10 specimens respectievly. Francture modes were observed with SEM The following results were obtained. 1. Before thermocycling. shear bond strengths in the specimens treated with DENTIN CONDITIONER and PRIMER A, B of ALL BOND were significantly higher than those in other specimens(P<0.01). 2. After thermocycling. shear bond strengths in the specimens treated with Cleanser and Primer of GLUMA, Scotchprep of Scotchbond 2 and DENTIN CONDITIONER and PRIMER A, B of AIL BOND were significantly higher than those in specimens not: treated, treated with GC-DENTIN CONDITIONER and 10-3 solution of 4-Meta(P<0.01). Shear bond strengths in the specimens treated with GC-DENTIN CONDITIONER and PRIMER A, B of ALL BOND were significantly higher than those in other specimens except those treated with Scotchprep of Srotchbond 2(P<0.01). 3. Shear bond strengths after thermocycling were reduced in the specimens not treated, treated with GC-DENTIN CONDITIONER and 10-3 solution of 4-Meta and were increased in the specimens treated with Cleanser and Primer of GLUMA, Scotchprep of Scotchbond 2, without significance, compared with those before thermocycling. In the specimens treated with DENTIN CONDITIONER and PRIMER A, B of ALL BOND, shear bond strengths after thermocycling were significantly increased, compared with those before thermocycling(P<0.01). 4. Microhardnesses in the fractured surfaces after shear bond strength measurement were significantly increased in the specimens treated with 10-3 solution of 4-Meta and significantly decreased in the specimens treated with DENTIN CONDITIONER and PRIMER A, B of ALL BOND, compared with those in the treated dentin surfaces(P<0.01). 5. In the specimens treated with Cleanser and Primer of GLUMA, Scotchprep of Scotchbond 2 and DENTIN CONDITIONER and PRIMER A, B of ALL BOND, cohesive fracture modes were observed more than adhesive fracture modes.

• Restorative Dentistry and Endodontics
• /
• v.42 no.3
• /
• pp.206-215
• /
• 2017

Objectives: To determine the combined effect of fatigue cyclic loading and thermocycling (CLTC) on the shear bond strength (SBS) of a resin cement to zirconia surfaces that were previously air-abraded with aluminum oxide ($Al_2O_3$) particles at different pressures. Materials and Methods: Seventy-two cuboid zirconia specimens were prepared and randomly assigned to 3 groups according to the air-abrasion pressures (1, 2, and 2.8 bar), and each group was further divided into 2 groups depending on aging parameters (n = 12). Panavia F 2.0 was placed on pre-conditioned zirconia surfaces, and SBS testing was performed either after 24 hours or 10,000 fatigue cycles (cyclic loading) and 5,000 thermocycles. Non-contact profilometry was used to measure surface roughness. Failure modes were evaluated under optical and scanning electron microscopy. The data were analyzed using 2-way analysis of variance and ${\chi}^2$ tests (${\alpha}=0.05$). Results: The 2.8 bar group showed significantly higher surface roughness compared to the 1 bar group (p < 0.05). The interaction between pressure and time/cycling was not significant on SBS, and pressure did not have a significant effect either. SBS was significantly higher (p = 0.006) for 24 hours storage compared to CLTC. The 2 bar-CLTC group presented significantly higher percentage of pre-test failure during fatigue compared to the other groups. Mixed-failure mode was more frequent than adhesive failure. Conclusions: CLTC significantly decreased the SBS values regardless of the air-abrasion pressure used.

• Journal of Microbiology and Biotechnology
• /
• v.23 no.5
• /
• pp.689-698
• /
• 2013

The production and characterization of an active recombinant N-acetylgalactosamine-6-sulfate sulfatase (GALNS) in Escherichia coli BL21(DE3) has been previously reported. In this study, the effect of the signal peptide (SP), inducer concentration, process scale, and operational mode (batch and semi-continuous) on GALNS production were evaluated. When native SP was presented, higher enzyme activity levels were observed in both soluble and inclusion bodies fractions, and its removal had a significant impact on enzyme activation. At shake scale, the optimal IPTG concentrations were 0.5 and 1.5 mM for the strains with and without SP, respectively, whereas at bench scale, the highest enzyme activities were observed with 1.5 mM IPTG for both strains. Noteworthy, enzyme activity in the culture media was only detected when SP was presented and the culture was carried out under semi-continuous mode. We showed for the first time that the mechanism that in prokaryotes recognizes the SP to mediate sulfatase activation can also recognize a eukaryotic SP, favoring the activation of the enzyme, and could also favor the secretion of the recombinant protein. These results offer significant information for scaling-up the production of human sulfatases in E. coli.

• Restorative Dentistry and Endodontics
• /
• v.32 no.5
• /
• pp.445-458
• /
• 2007

The purpose of this study was to evaluate the bond strength of a new Single step system with different curing mode composites, and to evaluate the effect of the intermediate resins which have different hydrophilicity on bonding ability by means of the micro shear bond testing and TEM examination for the adhesive interface. The adhesive used in this study was an experimental single step system (Bisco Inc., Schaumburg IL). Experimental groups were produced by using six kinds of intermediate resin having different hydrophilicity that was hydrophilic, hydrophobic and most hydrophobic resin and as filled or not after applying adhesive. Each experimental group was further divided into two subgroups whether the adhesive was light cured or not. Dual cured composite (Bis Core, Bisco Ltd., Schaumburg, IL) was placed on the adhesive layer as light cure or self cure mode. The results or bond strength were statistically analyzed using one way ANOVA and multiple comparisons are made using Tukey's test at ${\alpha}\;<\;0.05$ level. The results of this study were as follows ; 1. The application of intermediate resin did not increase the bond strength for light cured composite. 2. The bond strength of an experimental adhesive with self cured composite was significantly increased by the application of intermediate resin layer. 3. The bond strength of adhesive was irrespective of the cure or not of itself before intermediate resin layer applied. 4. As applied hydrophilic resin layer was, the initial bond strength was higher than both hydrophobic and most hydrophobic one used but there was no significance. Using a single step adhesive with dual/self cured composite, the incompatibility between both of them should be solved by the application of intermediate hydrophobic resin to reduce the adhesive permeability. However, Single step adhesive can be used in the light cured composite restoration without any decrease of the initial bond strength.

• Korean Journal of Soil Science and Fertilizer
• /
• v.50 no.4
• /
• pp.293-305
• /
• 2017

This experiment was conducted to evaluate the effect of leachate replacement frequency on solid state anaerobic digestion (SSAD) of dairy manure using 22 L volume lab-scale digesters at mesophilic temperature ($37^{\circ}C$) in batch mode. Three different leachate replacement strategies (no replacement, once every three days, and once every nine days) were applied and three digesters per each treatment were operated for 45 days. Results showed that leachate replacement test unit every nine days resulted in 1.6 times more methane production ($53.8N{\cdot}mL\;g^{-1}{\cdot}VS$) from SSAD compared to test unit every three days ($34.0N{\cdot}mL\;g^{-1}{\cdot}VS$). No leachate replacement strategy applied group showed slightly higher methane production ($56.3N{\cdot}mL\;g^{-1}{\cdot}VS$) than every nine days replaced one. When added the methane production potential of replaced leachate itself to the methane produced from digester, leachate replacement every nine days resulted in quite similar methane production ($56.5N{\cdot}mL\;g^{-1}{\cdot}VS$) to no leachate replacement group. Even though methane production potential of replaced leachate itself added to the methane produced from digester, every three days replacement showed only $34N{\cdot}mL$ methane production per gram of volatile solids. These results suggest that farmers do not need to replace leachate during SSAD of dairy manure and sawdust mixture in order to maximize methane production. If there are any concerns with accumulation of inhibiting substances in the digester, the 9-day cycle leachate replacement is appropriate.

• Structural Engineering and Mechanics
• /
• v.76 no.2
• /
• pp.153-162
• /
• 2020

Aiming at the mechanical and structural characteristics of the contact zone composite rock, the shear tests and numerical studies were carried out. The effects of the differences in mechanical properties of different materials and the normal stress on shear properties of contact zone composite samples were analyzed from a macro-meso level. The results show that the composite samples have high shear strength, and the interface of different materials has strong adhesion. The differences in mechanical properties of materials weakens the shear strength and increase the shear brittleness of the sample, while normal stress will inhibit these effect. Under low/high normal stress, the sample show two failure modes, at the meso-damage level: elastic-shearing-frictional sliding and elastic-extrusion wear. This is mainly controlled by the contact and friction state of the material after damage. The secondary failure of undulating structure under normal-shear stress is the nature of extrusion wear, which is positively correlated to the normal stress and the degree of difference in mechanical properties of different materials. The increase of the mechanical difference of the sample will enhance the shear brittleness under lower normal stress and the shear interaction under higher normal stress.

• Corrosion Science and Technology
• /
• v.12 no.6
• /
• pp.274-279
• /
• 2013

Flow accelerated corrosion (FAC) of the carbon steel piping in nuclear power plants (NPPs) has been major issue in nuclear industry. During the FAC, a protective oxide layer on carbon steel dissolves into flowing water leading to a thinning of the oxide layer and accelerating corrosion of base material. As a result, severe failures may occur in the piping and equipment of NPPs. Effect of alloying elements on FAC of pipe materials was studied with rotating cylinder FAC test facility at $150^{\circ}C$ and at flow velocity of 4m/s. The facility is equipped with on line monitoring of pH, conductivity, dissolved oxygen(DO) and temperature. Test solution was the demineralized water, and DO concentration was less than 1 ppb. Surface appearance of A 106 Gr. B which is used widely in secondary pipe in NPPs showed orange peel appearance, typical appearance of FAC. The materials with Cr content higher than 0.17wt.% showed pit. The pit is thought to early degradation mode of FAC. The corrosion product within the pit was enriched with Cr, Mo, Cu, Ni and S. But S was not detected in SA336 F22V with 2.25wt.% Cr. The enrichment of Cr and Mo seemed to be related with low, solubility of Cr and Mo compared to Fe. Measured FAC rate was compared with Ducreaux's relationship and showed slightly lower FAC rate than Ducreaux's relationship.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.45 no.1
• /
• pp.91-96
• /
• 2008

In this paper, a monopulse fled for three mode $2{\times}2$ array feed horn antenna was designed. Gain of single feed was 8.25dB. Increasing property of gain and rectangular waveguide and reflection of free space is decreased because it has structure extending to electric plane at connected part from transformation to free space. When fled port1 and port2 is placed vertically and thickness of aperture hem is reduced, isolation is satisfied with property of lower -25dB. Also, at higher frequency, it is confirmed that isolation is improved. Combination of electric field occurs less influence because port1 and port3 is placed horizontally and distribution of electric field is connected to parallel. However, because of combination of electric field, it is more improved from 2dB to 6dB than isolation of port1 and port2. Direct combination occult less effect at port1 and port4 than effect of port2 and port3, it is lower -35dB.