• Journal of the Korean Wood Science and Technology
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• v.25 no.3
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• pp.83-95
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• 1997

The degradation mode of lignocellulose by anaerobic ruminal cellulolytic bacterium Ruminococcus albus F-40 was investigated. Birchwood holocellulose and filter paper were incubated as the sole carbohydrate sources with using the Hungate techniques. After 2 or 4 days of incubation, samples were employed for chemical and electron microscopic evaluations. The degradation rate of cellulosic substrates and the adhesion rate of bacteria to the substrates increased proportionally with the decrease of relative crystallinity of cellulose, indicating the preferential breakdown of amorphous cellulose, by this bacterium. X-ray diffraction analyses and polarized light microscopy showed, however, that crystalline cellulose was also degraded by R. albus. FT-IR spectra indicated that not only cellulose but hemicellulose was also degraded by this bacterium. Electron microscopic investigations showed the protuberant structures on the surface of R. albus. These structures were much more significant when bacterial cells were grown in the media containing insoluble substrates, such as cellulose, indicating clearly that bacterial protuberant structures were induced by the substrates. Protuberant structures extended from the bacterial cells adhered tightly to the substrates and numerous vesicles covered the surface of cellulosic substrates affected. Cellulosome-like structures were distributed on the cellulose matrix. Electron microscopic works showed that diverse surface organells of R. albus were involved in the degradation of cellulosic materials. SEM examinations showed the breakdown of cellulose by R. albus was proceeded by severeal routes : short fiber formation, defibrillation and destrafication of cellulose microfibril.

• Restorative Dentistry and Endodontics
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• v.23 no.1
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• pp.468-476
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• 1998

The purpose of this study was to observe the morphologic change of dentinal surface, adhesion in interface between dentin and bonding agents, and penetration pattern of resin tags into dentinal tubles according to bonding procedure of ONE-STEP universal adhesive system. Ten extracted human molars were mounted in dental stone and sectioned to expose mid-coronal occlusal dentin and again sectioned tooth crown apically. Specimens were randomly assigned to three groups for dentin conditioning with 32% phoshoric acid, two coats of bonding agents after dentin conditioning, and bond of composite resin. The surfaces of dentin were treated with etch ant and applied bonding agent, and bonded composite resin according to the directions of manufacturer. Specimens which were boned composite were sectioned longitudinally for observing interfaces between resin and dentin. Two of specimens which were sectioned longitudinally were immersed in 6 N HCL for 30 seconds and 1% NaOCL for 12 hours to partially demineralize and deproteinize the dentin substrate. Each specimen was mounted on a brass stub, sputter-coated with gold and observed under SEM. The result were as follows : 1. On the dentinal surface which was conditioned with 32% phosphoric acid. the smear layer was completely removed. orifices of dentinal tubules were opened 3-$5{\mu}m$ wide. and dentinal surface was irregular. 2. On the dentinal surface which was applied ONE-STEP. bonding agent. resin particles were observed on the orifices of dentinal tubules and intertubular dentin. 3. There were close adaptation between dentin and resin and were the pattern which composite invaded into dentin. 4. 1-$3{\mu}m$-wide hybrid layer was visible in the interface between dentin and resin. 5. Long and funnel shaped resin tags were observed in demineralized specimens. and the surfaces of tags were rough.

• Journal of Radiation Industry
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• v.5 no.4
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• pp.365-370
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• 2011

Electrospun nanofibers prepared with synthetic biodegradable polymer have some limitations in regulating adhesion, proliferation, and spreading of cells because of their surface hydrophobicity and absence of cell-interaction. In this study, we functionalized the electrospun poly(L-lactide-co-${\varepsilon}$-caprolactone) (PLCL) nanofibers with acrylic acid (AAc) to modulate their surface hydrophilicity using electron-beam irradiation method and then measured grafting ratio of AAc, water contact angle, and ATR-FTIR of AAc-grafted nanofibers. A grafting ratio of AAc on the nanofibers was increased as irradiation dose and AAc concentration were increased. AAc-grafted nanofibers also have higher wettability than non-modified nanofibers. In conclusion, those surface-modified nanofibers may be an essential candidate to regulate cell attachment in tissue engineering applications.

• The Journal of Advanced Prosthodontics
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• v.14 no.5
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• pp.305-314
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• 2022

PURPOSE. The aim of this study was to evaluate the flexural strength of a 3D-printed denture base resin (Cosmos Denture), after different immediate repair techniques with surface treatments and thermocycling. MATERIALS AND METHODS. Rectangular 3D-printed denture base resin (Cosmos Denture) specimens (N = 130) were thermocycled (5,000 cycles, 5℃ and 55℃) before and after the different repair techniques (n = 10 per group) using an autopolymerized acrylic resin (Jet, J) or a hard relining resin (Soft Confort, SC), and different surface treatments: Jet resin monomer for 180 s (MMA), blasting with aluminum oxide (JAT) or erbium: yttrium-aluminum-garnet laser (L). The control group were intact specimens. A three-point flexural strength test was performed, and data (MPa) were analyzed by ANOVA and Games-Howell post hoc test (α = 0.05). Each failure was observed and classified through stereomicroscope images and the surface treatments were viewed by scanning electron microscope (SEM). RESULTS. Control group showed the highest mean of flexural strength, statistically different from the other groups (P < .001), followed by MMA+J group. The groups with L treatment were statistically similar to the MMA groups (P > .05). The JAT+J group was better than the SC and JAT+SC groups (P < .05), but similar to the other groups (P > .05). Adhesive failures were most observed in JAT groups, especially when repaired with SC. The SEM images showed surface changes for all treatments, except JAT alone. CONCLUSION. Denture bases fabricated with 3D-printed resin should be preferably repaired with MMA+J. SC and JAT+SC showed the worst results. Blasting impaired the adhesion of the SC resin.

• Structural Engineering and Mechanics
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• v.84 no.1
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• pp.17-33
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• 2022

An experimental study is carried out to investigate the performance of the cutting tool regarding the insert wear, surface roughness, cutting forces, cutting power and material removal rate of three coated carbides GC2015 (TiCN-Al₂O₃-TiN), GC4215 (Al₂O₃-Ti(C,N)) and GC1015 (TiN) during the dry turning of AISI4140 steel. For this purpose, a Taguchi design (L₉) was adopted for the planning of the experiments, the effects of cutting parameters on the surface roughness (R_a), tangential cutting force (F_z), the cutting power (P_c) and the material removal rate (MRR) were studied using analysis of variance (ANOVA), the response surface methodology (RSM) was used for mathematical modeling, with which linear mathematical models were developed for forecasting of R_a, F_z, P_c and MRR as a function of cutting parameters (V_c, f, and a_p). Then, Multi-Objective Ant Lion Optimizer (MOALO) has been implemented for multi-objective optimization which allows manufacturers to enhance the production performances of the machined parts. Furthermore, in order to characterize and quantify the flank wear of the tested tools, some machining experiments were performed for 5 minutes of turning under a depth of 0.5 mm, a feed rate of 0.08 mm/rev, and a cutting speed of 350 m/min. The wear results led to a ratio (V_B-GC4215/V_B-GC2015) of 2.03 and (V_B-GC1015/V_B-GC2015) of 4.43, thus demonstrating the efficiency of the cutting insert GC2015. Moreover, SEM analysis shows the main wear mechanisms represented by abrasion, adhesion and chipping.

• Composites Research
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• v.22 no.5
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• pp.8-14
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• 2009

Interfacial evaluation of glass fiber reinforced carbon nanotube (CNT)-epoxy nanocomposite was investigated by micromechanical technique in combination with wettability test. The contact resistance of the CNT-epoxy nanocomposite was measured using a gradient specimen, containing electrical contacts with gradually-increasing spacing. The contact resistance of CNT-epoxy nanocomposites was evaluated by using the two-point method rather than the four-point method. Due to the presence of hydrophobic domains on the heterogeneous surface, the static contact angle of CNT-epoxy nanocomposite was about $120^{\circ}$, which was rather lower than that for super-hydrophobicity. For surface treated-glass fibers, the tensile strength decreased dramatically, whereas the tensile modulus exhibited little change despite the presence of flaws on the etched fiber surface. The interfacial shear strength (IFSS) between the etched glass fiber and the CNT-epoxy nanocomposites increased due to the enhanced surface energy and roughness. As the thermodynamic work of adhesion, $W_a$ increased, both the mechanical IFSS and the apparent modulus increased, which indicated the consistency with each other.

• The Journal of Korean Academy of Prosthodontics
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• v.41 no.3
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• pp.300-318
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• 2003

Statement of problem: The success of implants depends on intimate and direct contact of implant material on bone tissue and on functional relationship with soft tissue contact. Creation and maintenance of osseointegration depend on the understanding of the tissue's healing, repairing, and remodeling capacity and these capacities rely on cellular behavior. Altering the surface properties can modify cellular responses such as cell adhesion, cell motility, bone deposition, Therefore, various implant surface treatment methods are being developed for the improved bone cell responses. Purpose: The purpose of this study was to evaluate the responses of osteoblast-like cells to surface-modified titanium. Materials and Methods: The experiment was composed of four groups. Group 1 represented the electropolished surface. Group 2 surfaces were machined surface. Group 3 and Group 4 were anodized surfaces. Group 3 had low roughness and Group 4 had high roughness. Physicochemical properties and microstructures of the discs were examined and the responses of osteoblast-like cells to the discs were investigated. The microtopography was observed by SEM. The roughness was measured by three-dimension roughness measuring system. The microstructure was analyzed by XRD, AES. To evaluate cell responses to modified titanium surfaces, osteoblasts isolated from calvaria of neonatal rat were cultured. Cell count, morphology, total protein measurement and alkaline phosphatase activities of the cultures were examined. Results and Conclusion: The results were as follows 1. The four groups showed specific microtopography respectively. Anodized group showed grain structure with micropores. 2. Surface roughness values were, from the lowest to the highest, electropolished group, machined group, low roughness anodized group, and high roughness anodized group. 3. Highly roughened anodized group was found to have increased surface oxide thickness and surface crystallinity. 4. The morphology of cells, flattened or spherical, were different from each other. In the electropolished group and machined group, the cells were almost flattened. In two anodized groups, some cells were spherical and other cells were flattened. And the 14 day culture cells of all of the groups were nearly flattened due to confluency. 5. The number of attached cells was highest in low roughness anodized group. And the machined group had significantly lower cell count than any other groups(P<.05). 6. Total protein contents showed no difference among groups. 7. The level of alkaline phosphatase activities was higher in the anodized groups than electropolished and machined groups(P<.05).

• Journal of the Korean Society of Clothing and Textiles
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• v.31 no.2 s.161
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• pp.292-299
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• 2007

Development of portable device measuring the vital sign continuously with no limit of time and space is absolutely prerequisite for the U-health care that grafts the ubiquitous concept into medical system. Accordingly, it requires to develop a garment style apparatus for measuring vital-sign that is easy to wear on for a long time period. This study suggests a method to improve the insulation of electric cable and the skin adhesion of electrode by integrating the electric conductive material to garment, in order to develop a garment apparatus for measuring ECG for U-health care. Results of the research are as follows; In order to provide the adjacent conductive yarns with insulation, braid with narrow woven end was interlaced using polyester yarn. As a result, the direct contact between electric conductive yarns was restrained, which would be interposed into pin-tuck structured cable. Washable silicone gel applied around the electrode made of electric conductive fabric improved the adhesion, which prevents electrodes from dropping off from the skin surface during body movement. ECG signals on the human subject were tested using the garment apparatus developed by the above method. And the result was that the clear QRS wave formation in the typical form of ECG could be measured in both conditions of still and moving state as well. The result of this study is expected to contribute for the production of U-health care related medical apparatus by accelerating the practical uses of the garment measuring vital sign at a reasonable price.

• Journal of Adhesion and Interface
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• v.13 no.3
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• pp.109-115
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• 2012

Monodisperse blue-colored poly(styrene-co-acrylic acid) latices were successfully prepared by seeded emulsion polymerization. Blue-colored latices with carboxyl anionic charge on the surface were synthesized at the second stage with the introduction of Blue 606 dye, acrylic acid, and 0.21 ${\mu}m$-polystyrene seed. All the blue-colored latices synthesized in this study were in the size range of 0.25~0.42 ${\mu}m$ and all uniform with less than 1.01 in PSD. The particle size increased with the addition of acrylic acid being delayed and colloidally stable latices were obtained over 30 min after its addition. The blue-colored latex with 20 wt% acrylic acid showed -145 mV of zeta-potential and $-9.4{\times}10^{-6}\;cm^2/Vs$ of electrophoretic mobility, and with 25 wt% of DVB showed high $T_g$ at 396.7 K.

• Journal of Adhesion and Interface
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• v.10 no.3
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• pp.117-126
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• 2009

Epoxy/anhydride systems with silica filler were studied to improve the cure behavior and characteristics. To study the curing process of epoxy/anhydride using DSC and a stress rheometer, it was observed that gelation temperature increased by increasing the thermal rate or in high isothermal conditions, while it was observed that the degree of cure at gelation decreased. Thermal stability of the epoxy/anhydride system showed any increment by increasing silica contents, except slight decrease of weight by containing humidity. The epoxy resin cured with 30% of silica filler decreased coefficient thermal expansion (CTE) about 33% to show $40ppm/^{\circ}C$. Specimens filled with 30 wt% of silica showed 60% increase in storage modulus at $30^{\circ}C$ to show 3909 MPa compared with neat resin to 2,377 MPa. Epoxy/anhydride systems with surface treated silica by silane coupling agent decreased storage modulus.