• Economic and Environmental Geology
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• v.29 no.2
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• pp.119-127
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• 1996

Electrum-sulfide minerals of the Namsan Au-Ag mine were deposited in two stages of quartz and calcite veins that fill fault planes in Mesozoic granitic rocks (230~155 Ma). The K/Ar radiometric dating of hydrothermal sericite indicates that mineralization is early Cretaceous age ($127{\pm}3.0Ma$). Mineralogic, fluid inclusion and sulfur isotopic data show that ore minerals were deposited at temperatures between $340^{\circ}C$ and $200^{\circ}C$ from fluid with salinities of 3 to 6 equiv. wt % NaCl. Evidence of fluid boiling (and $CO_2$ effervescence) indicates a maximum pressures of 100 bars. The formation temperature and $fs_2$, of Au-mineralization from the Namsan mines are mainly $280{\sim}230^{\circ}C$ and $10^{-11}{\sim}10^{-13}$ atm, respectively. Au deposition was likely a result of boiling caused to chemical change (pH, $f_{O2}$, ${\Sigma}_{H_2S{\cdot}{\cdot}}$) of ore-fluids. Sulfur isotope composition of sulfide minerals (${\delta}^{34}S=5.1$ to 8.2‰) are consistent with ${\delta}^{34}S_{{\Sigma}{H2S}}$ value of +6 to +7‰, suggesting an igneous source of sulfur partially mixed with wall-rock sulfur.

• Polymer(Korea)
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• v.36 no.1
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• pp.98-103
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• 2012

Poly(2,6-dimethyl-1,4-phenylene ether) (PPE) was synthesized using $Cu(NO_2)_2{\cdot}3H_2O$ or CuCl catalyst with various amounts of ligand and base in several different solvent systems. CuCl/1-methylimidazole/ammonium hydroxide was found to be an effective catalyst system which showed the highest polymer yield and molecular weight. The effects of catalyst/monomer ratio, different amine ligands, and the content of mono-functional reagent 2,4,6-trimethylphenol (TMP) additive on the polymer yield and molecular weight were investigated. Among the co-solvent systems used in this polymerization, chloroform/methanol 9/1(v/v) gave the highest polymer yield and molecular weight ($\overline{M_n}$ 55 K, $\overline{M_w}$ 92 K, PDI 1.7). The catalytic activity between CuCl and CuI was compared by oxygen-uptake experiments and the formation of sideproduct, 5,5'-tetramethyl-4,4'-diphenoquinone (DPQ), was analyzed by ultraviolet spectroscopy.

• Microbiology and Biotechnology Letters
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• v.23 no.6
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• pp.687-694
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• 1995

Alkalophilic Bacillus sp. HJ-12 producing $\beta $-1, 4-D-arabinogalactanase was isolated from soil in the alkalic condition, pH 10.0. $\beta $-1, 4-D-arabinogalactanase was maximaly produced in the medium consisting of 2% soybean arabinogalactan (SAG), 0.5% yeast extract, 0.5% polypeptone, 0.5% NaCl, 0.1% K$_{2}$HPO$_{4}$, 0.02% MgSO$_{4}$$\cdot $7H$_{2}$O, 0.1% Na$_{2}$CO$_{3}$ under the aerobic condition (pH 8.2). $\beta $-1, 4-D-arabinogalactanase is inducible enzyme so that its activity has been increased 10 fold in the SAG medium than in the glucose medium. Through the ammonium sulfate precipitation, DEAE- Sephadex A-50 ion chromatography, and Sephadex G-75 gel chromatography procedures, this enzyme was purified with a single protein of 11% vield and 110 fold's purity. $\beta $-1, 4-D-arabinogalactanase is endo type enzyme producing ollgosaccharide from SAG.

• Bulletin of the Korean Chemical Society
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• v.14 no.4
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• pp.439-444
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• 1993

The aerobic oxidation of the Fe(II) complex of 1,4,8,11-tetraazacyclotetradecane, [Fe(cyclam)$(CH_3CN)_2](ClO_4)_2$, in MeCN in the presence of a few drops of $HClO_4$ leads to low spin Fe(III) species [Fe(cyclam)$(CH_3CN)_2](ClO_4)_3$. The Fe(III) cyclam complex is further oxidized in the air in the presence of a trace of water to produce the deep green binuclear bismacrocyclic Fe(II) complex $[Fe_2(C_{20}H_{36}N_8)(CH_3CN)_4](ClO_4)_4{\cdot}2CH_3CN$. The Fe(II) ions of the complex are six-coordinated and the bismacrocyclic ligand is extensively unsaturated. $[Fe_2(C_{20}H_{36}N_8)(CH_3CN)_4](ClO_4)_4{\cdot}2CH_3CN$ crystallizes in the monoclinic space group $P2_1/n$ with a= 13.099 (1) ${\AA}$, b= 10.930 (1) ${\AA}$, c= 17.859 (1) ${\AA}$, ${\beta}$= 95.315 $(7)^{\circ}$, and Z= 2. The structure was solved by heavy atom methods and refined anisotropically to R values of R= 0.0633 and $R_w$= 0.0702 for 1819 observed reflections with F > $4{\sigma}$ (F) measured with Mo K${\alpha}$ radiation on a CAD-4 diffractometer. The two macrocyclic units are coupled through the bridgehead carbons of ${\beta}$-diimitie moieties by a double bond. The double bonds in each macrocycle unit are localized. The average bond distances of $Fe(II)-N_{imine}$, $Fe(II)-N_{amine}$, and $Fe(II)-N_{MeCN}$ are 1.890 (5), 2.001 (5), and 1.925 (6) ${\AA}$, respectively. The complex is diamagnetic, containing two low spin Fe(II) ions in the molecule. The complex shows extremely intense charge transfer band in the near infrared at 868 nm with ${\varepsilon}$= 25,000 $M^{-1}cm^{-1}$. The complex shows a one-electron oxidation wave at +0.83 volts and two one-electron reduction waves at -0.43 and-0.72 volts vs. Ag/AgCl reference electrode. The complex reacts with carbon monoxide in $MeNO_2$ to form carbonyl adducts, whose $v_{CO}$ value (2010 $cm^{-1}$) indicates the ${\pi}$-accepting property of the present bismacrocyclic ligand.

• Transactions on Electrical and Electronic Materials
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• v.6 no.6
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• pp.245-248
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• 2005

The physical and electrical properties of polycrystalline $\beta$-SiC were studied according to different nitrogen doping concentration. Nitrogen-doped SiC films were deposited by LPCVD(1ow pressure chemical vapor deposition) at $900^{\circ}C$ and 2 torr using $100\%\;H_2SiCl_2$ (35 sccm) and $5 \%\;C_2H_2$ in $H_2$(180 sccm) as the Si and C precursors, and $1\%\;NH_3$ in $H_2$(20-100 sccm) as the dopant source gas. The resistivity of SiC films decreased from $1.466{\Omega}{\cdot}cm$ with $NH_3$ of 20 sccm to $0.0358{\Omega}{\cdot}cm$ with 100 sccm. The surface roughness and crystalline structure of $\beta$-SiC did not depend upon the dopant concentration. The average surface roughness for each sample 19-21 nm and the average surface grain size is 165 nm. The peaks of SiC(111), SiC(220), SiC(311) and SiC(222) appeared in polycrystalline $\beta$-SiC films deposited on $Si/SiO_2$ substrate in XRD(X-ray diffraction) analysis. Resistance of nitrogen-doped SiC films decreased with increasing temperature. The variation of resistance ratio is much bigger in low doping, but the linearity of temperature dependent resistance variation is better in high doping. In case of SiC films deposited with 20 sccm and 100 sccm of $1\%\;NH_3$, the average of TCR(temperature coefficient of resistance) is -3456.1 ppm/$^{\circ}C$ and -1171.5 ppm/$^{\circ}C$, respectively.

• Applied Biological Chemistry
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• v.22 no.4
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• pp.210-216
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• 1979

RNA degrading bacteria were isolated from soil of Korea. One strain (no. JSC-114), having strong 5'-phosphodiesterase activity, was identified as belonging to the genus Streptomyces on the basis of taxonomic characteristics. The optimum conditions of 5'-phophosdiesterase production were found at $30^{\circ}C$ for 4 day in a medium containing 4.5% of soluble starch, 0.15% of peptone, 0.6% of yeast extract, 0.1% of $MgSO_4{\cdot}7H_2O$, 0.01% of $CaCl_2{\cdot}2H_2O$, 0.25% of $KNO_3$, and 0.5% of $KH_2PO_4$(pH 7.0). The maximum production rate of 5'-nucleotides from yeast RNA was 95% at $40-45^{\circ}C$ for 4hrs, and the products were identified as 5'-IMP, 5'-GMP, 5'-CMP and 5'-UMP(5.5 : 5.0 : 4.9 : 5.0).

• Economic and Environmental Geology
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• v.36 no.5
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• pp.365-374
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• 2003

Various deleterious chemicals can be introduced to existing concrete structures from various external sources. The deterioration of concrete by seawater attack is involved in complex processes due to various elements contained in seawater. In the present study, attention was paid to the formation of secondary minerals and characteristics of mineralogical and micro-structural changes involved in concrete deterioration caused by the influence of major seawater composition. The characteristics of deterioration occurred in existing concrete structures was carefully observed and samples were collected at many locations of coastal areas in Busan-Kyungnam. The petrographic, XRD, SEM/EDAX analyses were conducted to determine chemical, mineralogical and micro-structural changes in the aggregate and cement paste of samples. The experimental concrete deteriorations were performed using various chloride solutions (NaCl, CaCl, $MgCl_2$ and $Na_2SO_4$ solution. The experimental results were compared with the observation results in order to determine the effect of major elements in seawater on the deterioration. The alkalies in seawater appear to accelerate alkali-silica reaction (ASR). The gel formed by ASR is alkali-calcium-silica gel which known to cause severe expansion and cracking in concrete. Carbonation causes the formation of abundant less-cementitious calcite and weaken the cement paste. Progressive carbonation significantly affects on the composition and stability of some secondary minerals. Abundant gypsum generally occurs in concretes subjected to significant carbonation, but thaumasite ({$Ca_6/[Si(OH)_6]_2{\cdot}24H_2O$}${\cdot}[(SO_4)_2]{\cdot}[(CO_3))2]$) occurs as ettringite-thaumasite solid solution in concretes subjected to less significant carbonation. Experimentally, ettringite can be transformed to trichloroaluminate or decomposed by chloride ingress under controlled pH conditions. Mg ions in seawater cause cement paste deterioration by forming non-cementitious brucite and magnesium silicate hydrate (MSH).

• Korean Journal of Materials Research
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• v.21 no.6
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• pp.352-356
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• 2011

[ $Zn_{2(1-x)}Mn_xSiO_4$ ]$0.07{\leq}x{\leq}0.15$) green phosphor was prepared by solid state reaction. The first heating was at $900^{\circ}C-1250^{\circ}C$ in air for 3 hours and the second heating was at $900^{\circ}C$ in $N_2/H_2$(95%/5%) for 2 hours. The size effect of $SiO_2$ in forming $Zn_2SiO_4$ was investigated. The temperature for obtaining single phase $Zn_2SiO_4$ was lowered from $1100^{\circ}C$ to $1000^{\circ}C$ by decreasing the $SiO_2$ particle size from micro size to submicro size. The effect of the activators for the Photoluminescence (PL) intensity of $Zn_2SiO_4:Mn^{2+}$ was also investigated. The PL intensity properties of the phosphors were investigated under vacuum ultraviolet excitation (147 nm). The emission spectrum peak was between 520 nm and 530 nm, which was involved in green emission area. $MnCl_2{\cdot}4H_2O$, the activator source, was more effective in providing high emission intensity than $MnCO_3$. The optimum conditions for the best optical properties of $Zn_2SiO_4:Mn^{2+}$ were at x = 0.11 and $1100^{\circ}C$. In these conditions, the phosphor particle shape was well dispersed spherical and its size was 200 nm.

• Current Research on Agriculture and Life Sciences
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• v.14
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• pp.111-122
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• 1996

S. chibaensis J-59 produced an extracellular xylanase in a CSL medium composed of 1.5% com steep liquor, 0.1% $MgSO_4{\cdot}7H_2O$, 0.012% $CoCl_2{\cdot}6H_2O$, and 0.15% glucose containing xylan. but it did not produce in the culture medium containing xylose. The production of enzyme reached to a maximum level (0.83 uints/ml) when bacteria were cultured in 2.5 l jar fermentor for 48hrs at $30^{\circ}C$ and pH 7.0. Furthermore, S. chibaensis J-59 produced an intracellular glucose isomerase in a medium containing xylan and/or xylose. Xylanase was purified 29-fold over the culture supernatants of S. chibaensis J-59 by ammonium sulfate fractionation, chromatography on DEAE-Sephadex A-50, and gel filtration on Sephadex G-200. The purified enzyme is a monomeric enzyme with a native molecular mass of 25 kDa and a subunit molecular mass of 25 kDa. The purified enzyme requires $Mg^{2+}$ for activity, $Ca^{2+}$, $Co^{2+}$ is not an inhibitor but inhibit by $Fe^{3+}$, $Hg^{2+}$, and $Cu^{2+}$, sodium dodecyl sulfate, N-bromosuccinide. Pattern of hydrolysis demonstrated that the xylanase was an endo-splitting enzyme able to break down birchwood xylan at random giving xylobiose, xylotriose and xylotetrose as the main end products.

• KSBB Journal
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• v.27 no.6
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• pp.352-360
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• 2012

Bacillus clausii I-52 which produced SDS- and $H_2O_2$-tolerant extracellular alkaline protease (BCAP) was isolated from heavily polluted tidal mud flat of West Sea in Incheon, Korea and stable strain (transformant C5) of B. clausii I-52 harboring another copy of BCAP gene in the chromosome was developed using the chromosome integration vector, pHPS9-fuBCAP. When investigated the production of BCAP using B. clausii transformant C5 through pilot-scale submerged fermentation (500 L) at $37^{\circ}C$ for 30 h with an aeration rate of 1 vvm and agitation rate of 250 rpm, protease yield of approximately 105,700 U/mL was achieved using an optimized medium (soybean meal 2%, wheat flour 1%, sodium citrate 0.5%, $K_2HPO_4$ 0.4%, $Na_2HPO_4$ 0.1%, NaCl 0.4%, $MgSO_4{\cdot}7H_2O$ 0.01%, $FeSO_4{\cdot}7H_2O$ 0.05%, liquid maltose 2.5%, $Na_2CO_3$ 0.6%). The enzyme stability of BCAP was increased by addition of polyols (10%, v/v) and also, the stabilities of BCAP towards not only the thermal-induced inactivation at $50^{\circ}C$ but also the SDS and $H_2O_2$-induced inactivation at $50^{\circ}C$ were enhanced. Among the polyols examined, the best result was obtained with propylene glycol (10%, v/v). The BCAP supplemented with propylene glycol exhibited extreme stability against not only the detergent components such as ${\alpha}$-orephin sulfonate (AOS) and zeolite but also the commercial detergent preparations. The granulized enzyme of BCAP was prepared with approximately 1,310,000 U/g of granule. Wash performance analysis using EMPA test fabrics revealed that BCAP granule exhibited high efficiency for removal of protein stains in the presence of anionic surfactants as well as bleaching agents. When compared to Savinase 6T$^{(R)}$ and Everlase 6T$^{(R)}$ manufactured by Novozymes, BCAP under this study probably showed similar or higher efficiency for the removal of protein stains. These results suggest that the alkaline protease produced from B. clausii transformant C5 showing high stability against detergents and high wash performance has significant potential and a promising candidate for use as a detergent additive.