• Korean Journal of Environmental Biology
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• v.21 no.4
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• pp.358-365
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• 2003

A bacterial strain capable of producing a novel bioflocculant was isolated from a biofilm sample and identified as Bacillus megaterium G31. The highest biopolymer yield was achieved when the organism was cultivated in a medium containing acetate as the sole carbon source and ($NH_4)_2HPO_4$as the nitrogen source. In kaolin suspension, the flocculating activity was highest at 170 mg I$^{-1}$ and decreased at the higher bioflocculant concentrations. The crude bioflocculant produced by the organism was purified by ethanol precipitation and gel permeation chromatography. The FTIR spectrum of the purified bioflocculant revealed that the bioflocculant might be a heterogeneous polysaccharide composed of hexosamines and neutral sugars. The analysis of sugar components of the bioflocculant using high performance anion-exchange chromatography showed that the sugar constituents of the bioflocculant were glucosamine, fucose, galactosamine, galactose, glucose, mannose in approximate molar ratio of 4 : 1 : 6 : 3 : 8 : 19. Its flocculating activity was stimulated by various cations. The bioflocculant was thermo-stable and retained 64% of its original activity after heating at $100^{\circ}C$ for 50 min.

• Journal of Korea Foundry Society
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• v.31 no.6
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• pp.342-346
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• 2011

A328 alloy is an attractive candidate for recycle-friendly aluminum alloy in the recycling of automotive components. In this study, A328 alloy melt was degassed by ultrasonic vibration and the effect of treatment time on the density, fluidity and mechanical properties was investigated. Experimental results reveal that a constant value of density can be reached after less than 180 seconds of ultrasonic treatment time, but the density decreased when the treatment time was 300 seconds. Ti which was dissolved from the horn during ultrasonic treatment reduced the fluidity of melt. After degassing by ultrasonic vibration for 180 seconds, tensile strength increased from 201MPa to 250MPa, and elongation increased from 2.38% to 3.50%, however, further treatment deteriorated the mechanical properties.

• Horticultural Science & Technology
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• v.32 no.1
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• pp.100-104
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• 2014

This study was conducted to determine the optimal MS medium strength to improve sprouting rate of apical meristem of strawberry 'Seolhyang' in vitro. Strawberry apical meristems at size (0.2 mm to 0.3 mm) with leaf primordials were cultured on the MS media with four strength levels, ($1/4{\times}$, $1/3{\times}$, $1/2{\times}$, and $1{\times}$) and the sprouting rate and growth characteristics were evaluated after eight weeks after cultivation. Shoot rate of 'Daewang' apical meristems was 93.6%whereas 'Seolhyang' apical meristems were sprouted with 31.6% on $1{\times}$ MS medium strength. Different sprouting rates were observed in 'Seolhyang' apical meristem with 31.6% in $1{\times}$ medium, 75.0% in $1/2{\times}$ medium, and 94.4% in $1/3{\times}$ medium. The sprouting rate was improved with the decrease of medium strength, but the shoot rate in $1/4{\times}$ medium decreased up to 54.5%. Shoot length was 0.9 cm in $1{\times}$ medium, 1.2 cm in $1/2{\times}$ medium, 1.6 cm in $1/3{\times}$ medium, and 1.9 cm in $1/4{\times}$ medium. Shoot length was longer as medium strength decreased and numbers of leaves and roots were not significant differences among the medium strengths. As a result, sprouting rate was highest and plant growth was best in $1/3{\times}$ MS medium compared to the others.

• Korean Journal of Food Science and Technology
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• v.31 no.6
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• pp.1635-1641
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• 1999

Bacillus subtilis PCA20-3 was isolated from meju and was found to produce a protease. The strain produced the maximum amount of enzyme in the medium containing soytone (0.2%), soluble starch (2%), $(NH_4)_2SO_4\;(0.1%),\;CaCl_2(0.1%),\;yeast\;extract\;(0.01%),\;K_2HPO_4\;(0.1%),\;and\;KH_2PO_4\;(0.1%)$. Protease was first concentrated by ammonium sulfate (80% saturation, w/v) precipitation of culture supernatant. Then the enzyme was purified by column chromatography using CM Sephadex C-50. The collected proteins were rechromatographed using Sephadex G-100 gel filtration column. The fraction with protease active from Sephadex G-100 gel chromatography was found to be pure when examined by SDS-polyacrylamide gel electrophoresis and YMC-pak reverse phase chromatography. Specific activity, yield and purity were 76 U/mg. 2.7%, and 7.6 fold, respectively. The molecular weight of the enzyme was estimated to be 31.5 kDa by SDS-PAGE. The number of amino acids calculated from molecular weight was evaluated about 321 residues. N-terminal sequence of the enzyme was $Val^1-Pro^2-Tyr^3-Gly^4-Val^5-Ser^6-Gln^7-Gly^8-Lys^9-Ala^{10}$.

• Tuberculosis and Respiratory Diseases
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• v.60 no.2
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• pp.180-186
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• 2006

Background : Para-aminosalicylic acid(PAS) is a 2nd-line drug that can cause severe adverse reactions leading to poor patient compliance. This study evaluated the relapse rate according to the discontinuance of PAS at a certain point after bacteriological conversion during the course of chemotherapy for multidrug-resistant tuberculosis(MDR-TB). Methods : 42 out of 452 MDR-TB patients were enrolled in this study. All subjects were receiving chemotherapy including PAS at National Masan TB Hospital between Jan. 1, 2000 and Dec. 31, 2001. The relapse rate was evaluated after the discontinuance of PAS from their initial regimen as a result of the severe adverse reactions at a certain point after the bacteriological conversion during the course of chemotherapy for MDR-TB. Results : The male to female ratio was 2.5:1, and the mean age was 47.2 years old. The average number of past histories, used drugs and resistant drugs was 1.2, 3.9 and 4.3. The mean number of sensitive drugs included in the inirial regimen was 3.9. The mean time for bacteriological conversion and discontinuance of the PAS was 2.3 months after initiating treatment and 6 months after bacteriological conversion, respectively. There was no relapse after discontinuing PAS during a mean follow up period of 31.6 months. Conclusion : PAS may be discontinued in the cases of serious gastrointestinal problems approximately 6 months after bacteriological conversion without concern about relapse.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.2
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• pp.646-652
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• 2014

It is the primary aim of this paper to propose the empirical fatigue crack propagation model fit to describe a crack growth behavior of AZ31 magnesium alloys under the different specimen thickness conditions. The empirical models estimated are Paris-Erdogan model, Walker model, Forman model, and modified-Forman model. The parameters of each model are estimated by maximum likelihood method. The statistical crack growth data needed for an estimation of empirical models are obtained by fatigue crack propagation tests under the three cases of specimen thickness. It is found that the good empirical models fit to describe a crack growth behavior of AZ31 magnesium alloys under the different specimen thickness conditions are Paris-Erdogan model and Walker model. It is also verified that a fatigue crack growth rate exponent of a empirical model may be a material constant at the specimen thickness conditions of 4.75mm and 6.60mm.

• Bulletin of the Korean Chemical Society
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• v.31 no.3
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• pp.653-663
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• 2010

Enantioselective total synthesis of (-)-clavosolide A and B was reported in full including the synthesis of proposed structure of (-)-clavosoldie A (1), revised structure of (-)-clavosoldie A (5), and revised structure of (-)-clavosoldie B (6). The relative and absolute stereochemistries of the natural products were confirmed unambiguously by comparing the optical rotation values and $^1H$ and $^{13}C$ NMR spectra of them.

• Journal of Welding and Joining
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• v.31 no.3
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• pp.31-38
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• 2013

The transition of serrated grain boundary and its effect on liquation behavior in the simulated weld heat-affected zone (HAZ) have been investigated in a wrought Ni-based superalloy Alloy 263. Recently, the present authors have found that grain boundary serration occurs in the absence of adjacent coarse ${\gamma}^{\prime}$ particles or $M_{23}C_6$ carbides when a specimen is direct-aged with a combination of slow cooling from solution treatment temperature to aging temperature. The present study was initiated to determine the interdependence of the serration and HAZ property with a consideration of this serration as a potential for the use of a hot-cracking resistant microstructure. A crystallographic study indicated that the serration led to a change in grain boundary character as special boundary with a lower interfacial energy as those terminated by low-index {111} boundary planes. It was found that the serrated grain boundaries are highly resistant to boron enrichment, and suppress effectively grain coarsening in HAZ. Furthermore, the serrated grain boundaries showed a higher resistance to susceptibility of liquation cracking. These results was discussed in terms of a significant decrease in interfacial energy of grain boundary by the serration.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.6
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• pp.469-475
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• 2014

The roll to roll (RTR) imprint process is an integrated imprinting process where steps ranging from assignment of a function to a flexible rolled substrate to rewinding of the same substrate in a roll are performed. RTR imprint is a green, low-cost technology without limitations. In RTR imprint, it is important to manufacture the mold precisely and maintain uniform process condition. To this, process conditions have to include precision tension control, optimization of process parameters. We introduced RTR imprint to fabricate planar lightwave circuit (PLC) device for communication, by new schematic design and process optimization, we fabricated successfully optical device. The fabricated optical device showed the optical performance which was satisfied to meet international standard.

• Journal of the Korean Applied Science and Technology
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• v.33 no.4
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• pp.717-725
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• 2016

This study was designed to examine the in vitro antioxidant, antimicrobial and anti-inflammation effects of essential oils of Erigeron annuus L. Flower. Erigeron annuus L. essential oils were obtained by solvent extraction. Antioxidative ability was evaluated by bioassays using ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid diammonium salt) radical scavenging effect and 2, 2-diphenyl-1-1-picrydrazyl (DPPH) free radical scavenging activity. Erigeron annuus L. essential oil exhibited free radical scavenging activity on ABTS and DPPH 98.6%, 48.3% respectively, at a concentration of $500{\mu}g/ml$. Antimicrobial activity of essential oils of Erigeron annuus L. were tested against Staphylococcus aureus (S. aureus), Propionibacterium acnes (P. acne) and Escherichia coli (E. coli) by paper disc method, MIC and MBC. Erigeron annuus L. essential oil showed excellent antibacterial activities against S. aureus with MIC and MBC values of 0.31 mg/mL. The clear zone, indicating antimicrobial activity against P. acnes, was 14 mm, MIC and MBC values 0.31 mg/mL, 0.63 mg/mL, respectively. For the anti-inflammatory activity in RAW 264.7 cell, the Erigeron annuus L. essential oils inhibited not only NO production but also the expression of pro-inflammatory cytokines such as, TNF-${\alpha}$, IL-6 in a dose-dependent manner. These results suggested that Erigeron annuus L. essential oils has considerable potential as a cosmetic ingredient with antioxidative, antimicrobial and anti-inflammation effects.