• Korean Journal of Materials Research
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• v.13 no.6
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• pp.404-408
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• 2003

SiC nanorods have been grown on Si (100) substrate directly. Tetramethylsilane and Ni were used for SiC nanorod growth. After 3minute, SiC nanorod had grown by CVD. Growth regions ware divided by two regions with diameter. The First region consisted of thin SiC nanorods having below 10 nm diameter, but second region's diameter was 10∼50 nm. This appearance shows by reduction of growth rate. The effect of temperature and growth time was investigated by scanning electron microscopy. Growth temperature and time affected nanorod's diameter and morphology. With increasing growth time, nanorod's diameter increased because of the deactivation effect. But growth temperatures affected little. By TEM characterization, grown SiC nanorods consisted of the polycrystalline grain.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.693-694
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• 2006

In order to develop a high temperature superconducting(HTS) coil for the fault current limiter(FCL), the over-current characteristics in YBCO coated conductor(CC) with Ni-W alloy substrate are analyzed. The HTS wire is wound by bifilar winding method for resistive current limitation and it is operated in 65K sub-cooled nitrogen. In order to analyze the resistance and the temperature characteristics of the CC wire, an analysis program is developed considering all the composition materials except the buffer layer. Using this program, the temperature rise, the resistance development and the current limitation of CC are calculated depending on the applied voltage and the stabilizer materials. According to the analysis results, under the temperature restriction of 300K, the maximum voltage per meter is determined as 40V/m if the stabilizer is $25{\mu}m$ thick stainless steel at each side. Finally, the wire length needed for the distribution level HTS FCL is estimated.

• YAKHAK HOEJI
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• v.47 no.3
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• pp.184-189
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• 2003

Peptide deformylase (PDF) is essential and unique to bacteria, thus making it an attractive target for the discovery of novel antibacterial drugs. PDF deformylates the N-formylmethionine of newly synthesized polypeptides in prokaryotes. In this study, a pdf gene from Staphylococcus aureus 6538p was cloned in pET-14b vector and PDF protein was over-produced in Escherichia coli BL21 (DE3). NH$_2$-terminal His-tagged PDF protein was purified by nickel-nitrilotriacetic acid (Ni-NTA) metal-affinity chromatography. Enzymatic activity of purified 6xHis-tagged PDF was tested on the substrate (formyl-Methionine-Alanine-Serine) by formate dehydrogenase-coupled spectrometric assay of peptide deformylase. For the discovery of new PDF inhibitors from chemical libraries and culture broths of soil bacteria, a target-oriented screening system using a 96-well plate was developed. About 3,000 commercial chemical libraries were tested in this screening system, and 2 chemicals (0.07％) among them showed an inhibitory activity against PDF enzyme. This result showed that a new screening system can be used for the discovery of new PDF inhibitors.

• Fisheries and Aquatic Sciences
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• v.13 no.1
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• pp.49-55
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• 2010

A bacterial strain with phytase and glucose-1-phosphatase activity was isolated from seawater. The colony was identified as an Enterobacter cloacae strain and named E. cloacae B11. A gene, agpEnB11, coding for an intracellular acid glucose phosphatase was cloned from the strain and sequenced. It comprised 1,242 nucleotides and encoded a polypeptide of 413 amino acids. Recombinant glucose-1-phosphatase (AgpEn) was overexpressed in Escherichia coli and purified using Ni-NTA column under native conditions. Purified protein displayed a single band of 47 kDa on SDS-PAGE. AgpEn hydrolyzed a wide variety of phosphorylated compounds, with high activity for glucose-1-phosphate and glucose-6-phosphate. Optimum pH and temperature for enzyme activity were pH 5.0 and $50^{\circ}C$, respectively. Enzyme activity was stimulated by $Ca^{2+}$ and $Co^{2+}$, and inhibited by $Cu^{2+}$.

• YAKHAK HOEJI
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• v.35 no.3
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• pp.222-230
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• 1991

Polyphenol oxidase (PPO) was purified from an extract of Perillae Folium by ammonium sulfate fractionation and sephadex G-150 gel filtration, which molecular weight estimated 65,000$\pm$1,000 in SDS-gel electrophoresis, and pI value was 4.8. The pH and temperature optima were 6.0 and $30^{\circ}C$ respectively. $K_{m}$ values of the PPO for various phenolics derived from Lineweaver-Burk plots were 4.0$\times$10$^{-4}$, caffeic acid; 4.2$\times$10$^{-3}$M, 4-methylcatechol. The inhibition by 4-nitrocatechoi, potassium cyanide, cysteine, 2-mercaptoethanol was competitive with $K_{i}$ values of 7.6$\times$10$^{-5}$M, 7.2$\times$10$^{-5}$M, 3.6$\times$10$^{-5}$M, 2.2$\times$10$^{-5}$M, respectively. Among the divalent cations, Cu$^{2+}$ ion was strong activator on PPO and Zn$^{2+}$, Ni$^{2+}$ ions were little effect on PPO activity. In comparing the amino acid composition of Perillae Folium PPO with that of wheat isozyme, grape, spinach showed similarity. But the content of glycine phenylalanine was abundant relatively.

• Mycobiology
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• v.37 no.2
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• pp.109-113
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• 2009

The mineral contents of the cultivation substrates, fruiting bodies of the mushrooms, and the postharvest cultivation substrates were determined in cultivated edible mushrooms Pleurotus eryngii, Flammulina velutipes, and Hypsizigus marmoreus. The major mineral elements both in the cultivation substrates and in the fruiting bodies were K, Mg, Ca, and Na. Potassium was particularly abundant ranging 10${\sim}$13 g/kg in the cultivation substrates and 26${\sim}$30 g/kg in the fruiting bodies. On the contrary, the calcium content in the fruiting bodies was very low despite high concentrations in the cultivation substrates, indicating Ca in the cultivation substrates is in a less bio-available form or the mushrooms do not have efficient Ca uptake channels. Among the minor mineral elements determined in this experiment, Cu, Zn, and Ni showed high percentage of transfer from the cultivation substrates to the fruiting bodies. It is noteworthy that the mineral contents in the postharvest cultivation substrates were not changed significantly which implies that the spent cultivation substrates are nutritionally intact in terms of mineral contents and thus can be recycled as mineral sources and animal feeds.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.6
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• pp.546-549
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• 2007

As a rule, high temperature superconducting coated conductors have multi-layered buffers consisting of seed, diffusion barrier and cap layers. Multi-buffer layer deposition requires longer fabrication time. This is one of main reasons which increases fabrication cost. Thus, single buffer layer deposition seems to be important for practical coated conductor process. In this study, a single layered buffer deposition of $CeO_2$ for low cost coated conductors has been tried using thermal evaporation technique. 100 nm-thick $CeO_2$ layers deposited by thermal evaporation were found to act as a diffusion layer. $1\;{\mu}m-thick$ SmBCO superconducting layers were deposited by thermal co-evaporation on the $CeO_2$ buffered Ni-5%W substrate. Critical current of 90 A/cm was obtained for the SmBCO coated conductors.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.5
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• pp.415-420
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• 2008

AAO films were fabricated on two kinds of substrates such as $Al/SiO_2/Si$ and Al/Ni/Ti/Si. To obtain well-aligned AAO film, we optimized process condition for buffer layer, electrolyte and voltage. In the case of oxalic acid, the AAO film with pore size of approximately 45 nm was obtained at voltage of 40 V, temperature of $10^{\circ}C$, oxalic acid of 0.3 M and widening time of 60 min. Then the thickness of barrier is less than 600 nm. In the case of sulfuric acid, the AAO film has pore size of 40 nm and barrier thickness of 400 nm with optimum conditions such as voltage of 25 V, temperature of $8^{\circ}C$, sulfuric acid of 0.3 M and widening time of 60 min.

• Proceedings of the KOSOMBE Conference
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• v.1996 no.05
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• pp.133-136
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• 1996

We investigated how hydroxyapatite (HA) coating onto a porous super stainless steel (S.S.S, 22Cr-20Ni-6Mo-0.25N) affects bone ingrowth in a dog transcortical femoral model. Implants were histologically evaluated after 4 and 48 weeks of implantation, and the bone bonding strength at the bone/implant interface was examined by employing the pull-out test. The direct osseous tissue bonding onto the HA-coated S.S.S was observed, but the uncoated stainless steels had thin fibrous tissue layers. The mean interface strength of the HA-coated S.S.S was 1.5 and 2.5 times greater than those of the S.S.S and the 316L SS after one year of implantation, respectively. In preliminary studies, no toxic responce was observed from a cytotoxicity test of the S.S.S, having similar corrosion resistance to titanium. Our results suggest that early osteoconductive nature of HA coating may induce long term osteointegration for a bioinert substrate.

• Journal of Welding and Joining
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• v.7 no.4
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• pp.30-37
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• 1989

Effect of heat treatment on mechanical properties of an overlay weldment was investigated. Over welding was carried out on the structural C-Mn mild steel substrate to take required test specimens. Shielded metal arc welding process with 13Cr-0.2Ni stick electrode was applied. The heat treatment temperatures and holding times were $450{\circ}C., 550{\circ}C., 650{\circ}C., 750{\circ}C., 850{\circ}C.$ and 0.5hr, 2hr, 10hr, respectively. Mechanical tests and microscopic inspection were also carried out to investigate welds soundness. Test results indicated that carbon migration was dominant near bonded zone. At temperature of around 650.deg. C, carburized layer and decarburized layer were formed remarkably along overlay welds region and C-Mn mild steel region, respectively. The wideth of these layers became wider with increasing heat treatment temperature and/or holding time at the elevated temperature, and this relationship agreed with Larson-Miller parameter. Side bending test results demonstrated that the crack free region of overlay welds could be deduced from the relationship between temperature and holding time.