• Elastomers and Composites
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• v.31 no.3
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• pp.175-182
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• 1996

Polymer latices, prepared from the emulsion polymerization of vinyl monomer compounds, are widely used for many industrial applications. Included among these are uses in paints, adhesives, flocculants, and heavy-duty plastics as well as their original use in synthetic rubber compounds. The emulsion polymerization process with chemical initiator has chemical disadvantage such as removal of initiator which was left after polymerization. In this study, polystyrene latex was prepared by using ultrasonic irradiation which generate the free radical, and then it was analyzed by GPC. Reaction temperature hardly have an effect on average molecular weight. Average molecular weight is increased by increasing amount of surfactant, i.e. SDS, but polydispersity is decreased. After 90 minutes of reaction time, increase and decrease of average molecular weight Is repeated. It is proposed that monodisperse polymer is obtained by controlling ultrasonic irradiation time and surfactant concentration.

• Journal of the Korean Data and Information Science Society
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• v.10 no.2
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• pp.319-327
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• 1999

Zero-Inflated Poisson distributions have been widely used for defect-free products in manufacturing processes. It is very interesting to check the shift after the unknown changepoint. If the detectives are caused by the two different types of factor, we should use bivariate zero-inflated model. In this paper, likelihood ratio tests were used to detect the shift of changes after the changepoint. Some inferences for the parameters in this model were made.

• Fibers and Polymers
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• v.6 no.1
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• pp.1-5
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• 2005

In this study, we attempted to evaluate a novel use of sericin-fixed silk fiber (SFx) as an immobilization support of enzyme. Sericin was fixed on the silk fiber using glutaraldehyde as a fixation reagent. After 6 hours of fixation, the degree of fixation increases linearly with linear decrease of the amount of bound $\alpha$-chymotrypsin (CT). This suggests that the increase of the degree of fixation is due to the further crosslinking of free aldehyde groups on the surface of sericin-fixed silk fiber (SFx). Even though perfect fixation was not achieved, sericin did not dissolve seriously and could be removed by further washing. The specific activity did not differ significantly after 6 hours of fixation. The activity of immobilized CT on SFx decreased to its half after 6 hours of incubation at 50$^{\circ}C$. However, it retained $78\%$ of initial activity even after 1 hour of treat­ment with $100\%$ ethanol. As a result, the SFx could be used as an immobilization support of enzyme in non-aqueous media at ambient temperature.

• Microbiology and Biotechnology Letters
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• v.14 no.6
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• pp.455-460
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• 1986

Dane particle was prepared from the plasma of chronic HBsAg carrier with high levels of HBsAg activity. DNA extracted front Dane particle core after a DNA polymerase reaction with $\alpha$-($^{32}$P) dNTP, was identified as HBV DNA by liquid scintillation counter and agarose gel electrophoresis-G.M. counting. To produce Hepatitis B surface antigen for use as a vaccine against Hepatitis B virus infection, yeast strains harboring recombinant plasmid with Apase promoter was used. Recombinant plasmid was construced from pHBV 130 and pAN 82, transformed into E coli, and then transferred into yeast strains. HBsAg was produced by derepression in Burkholder minimal medium with controlled inorganic phosphate concentration. The kinetics of HBsAg production was also investigated. Total HBsAg activity increased rapidly between 3 and 6 hours after transfer to phosphate-free medium and reached a maximum at around 9th hour. The transfer into phosphate-free medium after 6 hours in high phosphate cell growth medium gave maximum activity.

• Clinical and Experimental Reproductive Medicine
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• v.18 no.1
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• pp.81-87
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• 1991

There studies were carried for evaluation of the efficiency of freezing of hamster oocytes for use in a human sperm penetration assay. The hamster oocytes fully equilibrated in various cryoprotectant agents and inseminated with human sperm. After insemination with hamster oocytes, there was no difference in penetrated rates. Cumulus free oocytes equilibrated in 1.5M various cryoprotective agents and slowely cooled to temperature $-30^{\circ}C$ before rapid cooling and storage in nitrozen tank. After rapid thawing, survival rates of frozen oocytes according to cryo-protective agents were examined and the human sperm penetration assay with zona free hamster oocytes was conducted. 1. Survival rates of oocytes after cryoprotectants exposure have no significant difference (range 88-91%) and peneration rate was 51.1%. 2. Recovery and survival rate of frozen-thawed oocytes were 85.1 and 66.8%. There was no significant difference on cryoprotective agents. 3. Penetration rates of the frozen-thawed and intact oocytes were 69.0 and 77.0%, respectively. 4. Hamster oocytes cryopreservation provides a convenient way of supplying and trans-porting hamster oocytes for the assessment of the fertilizing potential of human spermatozoa.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.217-220
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• 2009

Conductive adhesives have been investigated for use in microelectronics packaging as a lead-free solder substitute due to their advantages, such as low bonding temperature. However, high resistivity and poor mechanical behavior may be the limiting factors for the development of conductive adhesives. The metal fillers and the polymer resins provide electrical and mechanical interconnections between surface mount device components and a substrate. As metal fillers used in conductive adhesives, silver is the most commonly used due to its high conductivity and the stability. However the cost of conductive adhesives with silver fillers is much higher than usual lead-free solders and silver has poor electro-migration performance. So, copper can be a promising candidate for conductive filler metal due to its low resistivity and low cost, but oxidation causes this metal to lose its conductivity. In this study, electrically conductive adhesives (ECAs) using surface modified copper fillers were developed. Especially, in order to overcome the problem associated with the oxidation of copper, copper particles were coated with silver, and the silver-coated copper was tested as a filler metal. Especially the effect of silver coating on the electrical resistance just after curing and after aging was investigated. As a result, it was found that the electrical resistance of ECA with silver-coated copper filler was clearly lower and more stable than that of ECA with pure copper filler after curing process. And, during high temperature storage test, the degradation rate of electrical resistance for ECA with silver coated copper filler was quite slower than that for ECA with pure copper filler.

• The Journal of Korean Academy of Prosthodontics
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• v.18 no.1
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• pp.73-86
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• 1980

Recently, the controversy continues as to whether maximum intercuspation of teeth should occur at the terminal hinge position(the condylar theory) or at the myo-co(the neuromuscular theory). There is also much controversy regarding the antero-posterior position of myo-co. The object of this study was to measure and compare with the positional relations of centric relation, centric occlusion and myo-co, and free-way space using Mandibular Kinesiograph and Myo-monitor in the 40 subjects without stomatognathic problems. Mandibular Kinesiograph(M.K.G.) was originally conceived as a research instrument to track mandibular movement and position. As its use in research progressed, its great diagnostic value became apparent in case by case. And Myo-monitor was developed as a means of applying the neuromuscular approach to occlusion. Thus the Myo-monitor technique is an intra-systemic approach to occlusal positioning using patient's own musculature, and Myo-monitor is used to relax the musculature by a light myopulse induced electronically. From this experiment, the following results were obtained. 1. The adaptive free-way space before muscle relaxation was an average of $1.6{\pm}60mm$, and the true free-way space after muscle relaxation using Myo-monitor was an average of $2.4{\pm}0.74mm$. 2. It took an average of $25{\pm}3.11$ minutes to relax the mandibular musculature by Myo-monitor and administration of 5mg. Diazepam and an average of $38{\pm}4.73$ minutes by Myo-monitor without administration of Diazepam. 3. Myo-co existed anterior to centric occlusion, with an average of $0.53{\pm}0.31$ mm, and centric relation existed posterior to centric occlusion, with an average of $0.57{\pm}0.58mm$ before muscle relaxation and with an average of $0.57{\pm}0.43mm$ after muscle relaxation. 4. Centric relation coincided with centric occlusion in 5 of 40 subjects(12.5%), and posterior to centric occlusion in the rest of cases (87.5%). 5. Myo-co existed anterior to centric occlusion in 38 of 40 subjects(95%), except 1 subject that coincided with centric occlusion and 1 subject that existed posterior to centric occlusion. 6. Myo-co and centric relation existed inferior to centric occlusion and the lateral displacement was various with individual difference. 7. The total displacement from centric occlusion to centric relation was an average of $0.74{\pm}0.64mm$ before muscle relaxation, and an average of $0.68{\pm}0.53mm$ after muscle relaxation, and the total displacement from centric occlusion to myo-co was an average of $1.07{\pm}0.58mm$.

• Journal of Microbiology and Biotechnology
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• v.24 no.5
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• pp.639-647
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• 2014

Laccases have a broad range of industrial applications. In this study, we immobilized laccase on $SiO_2$ nanoparticles to overcome problems associated with stability and reusability of the free enzyme. Among different reagents used to functionally activate the nanoparticles, glutaraldehyde was found to be the most effective for immobilization. Optimization of the immobilization pH, temperature, enzyme loading, and incubation period led to a maximum immobilization yield of 75.8% and an immobilization efficiency of 92.9%. The optimum pH and temperature for immobilized laccase were 3.5 and $45^{\circ}C$, respectively, which differed from the values of pH 3.0 and $40^{\circ}C$ obtained for the free enzyme. Immobilized laccase retained high residual activities over a broad range of pH and temperature. The kinetic parameter $V_{max}$ was slightly reduced from 1,890 to 1,630 ${\mu}mol/min/mg$ protein, and $K_m$ was increased from 29.3 to 45.6. The thermal stability of immobilized laccase was significantly higher than that of the free enzyme, with a half-life 11- and 18-fold higher at temperatures of $50^{\circ}C$ and $60^{\circ}C$, respectively. In addition, residual activity was 82.6% after 10 cycles of use. Thus, laccase immobilized on $SiO_2$ nanoparticles functionally activated with glutaraldehyde has broad pH and temperature ranges, thermostability, and high reusability compared with the free enzyme. It constitutes a notably efficient system for biotechnological applications.

• Archives of Plastic Surgery
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• v.40 no.3
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• pp.251-255
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• 2013

We present a case of a 57-year-old male patient who presented with squamous cell carcinoma on his mouth floor with cervical and mandibular metastases. Wide glossectomy with intergonial mandibular ostectomy, and sequential reconstruction using fibular osteomyocutaneous free flap were planned. When the anastomosis between the peroneal artery of the fibular free flap and the right lingual artery was performed, no venous flow was observed at the vena comitans. Then re-anastomosis followed by topical application of papaverine and lidocaine was attempted. However, the blood supply was not recovered. Warm saline irrigation over 30 minutes was also useless. Microvascular thromboses of donor vessels were clinically suspected, so a solution of 100,000 units of urokinase was infused once through a 26-gauge angiocatheter inserted into the recipient artery just at the arterial anastomotic site, until the solution gushed out through the flap vena comitans. Immediately after the application of urokinase, arterial flow and venous return were restored. There were no complications during the follow-up period of 11 months. We believe that vibrating injuries from the reciprocating saw during osteotomies and flap insetting might be the cause of microvascular thromboses. The use of urokinase may provide a viable option for the treatment of suspicious intraoperative arterial thrombosis.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.1
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• pp.33-42
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• 2003

This paper deals with the FEM analysis of nonlinear sloshing of incompressible, invicid and irrotational flow in two dimensional rectangular tank. We use laplace equation based on potential theory as governing equation. For large amplitude sloshing motion, kinematic and dynamic free surface conditions derived from Bernoulli equation are applied. This problem is solved by FEM using 9-node elements. For the time integration and accurate velocity calculation, we introduce predictor-corrector time marching scheme and least square method. Also, numerical stability in tracking of free surface is obtained by direct calculation of free surface location to time variation. Numerical results of sloshing induced by harmonic excitations, while comparing with those of linear theory and references, prove the accuracy and stability. After verification of our program, we analyze sloshing response characteristics to the fluid height and the excitation amplitude.