• Journal of the Korea Concrete Institute
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• v.21 no.3
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• pp.245-253
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• 2009

The importance of chloride ions in the corrosion of steel in concrete has led to the concept for chloride threshold level (CTL). The CTL can be defined as the content of chlorides at the steel depth that is necessary to sustain local passive film breakdown and hence initiate the corrosion process. Despite the importance of the CTL, due to the uncertainty determining the actual limits in various environments for chloride-induced corrosion, conservative values such as 0.4% by weight of cement or 1.2 kg in 1 $m^3$ concrete have been used in predicting the corrosion-free service life of reinforced concrete structures. The paper studies the CTL for blended cement concrete by comparing the resistance of cementitious binder to the onset of chloride-induced corrosion of steel. Mortar specimens were cast with centrally located steel rebar of 10 mm in diameter using cementitious mortars with ordinary Portland cement (OPC) and mixed mortars replaced with 30% pulverized fuel ash (PFA), 60% ground granulated blast furnace slag (GGBS) and 10% silica fume (SF), respectively, at 0.4 of a free W/B ratio. Chlorides were admixed in mixing water ranging 0.0, 0.2, 0.4, 0.6, 0.8, 1.0, 1.5, 2.0, 2.5 and 3.0% by weight of binder(Based on $C1^-$). Specimens were curd 28 days at the room temperature, wrapped in polyethylene film to avoid leaching out of chloride and hydroxyl ions. Then the corrosion rate was measured using the polarization resistance method and the order of CTL for binder was determined. Thus, CTL of OPC, 60%GGBS, 30%PFA and 10%SF were determined by 1.6%, 0.45%, 0.8% and 2.15%, respectively.

• Journal of the Korean Magnetics Society
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• v.8 no.2
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• pp.67-73
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• 1998

Crystallographic and magnetic properties of perovskite $Gd_{1-x}Sr_xFeO_{3-y}$ (x=0.0, 0.5) substituted $Sr^{2+}$ having larger inoic radius than $Gd^{3+}$ at GdFeO$_3$have been studied by x-ary diffraction, M$\ "{o}$ssbauer spectroscopy, and VSM. The cystal structures are found to be orthorhombic with the lattice parameters : $a_o=5.53\;{\AA},\;b_o=5.608\;{AA},\;C_o=7.724\;{\AA}$ for $Gd_{0.5}Sr_{0.5}FeO_{3-y}$ (x=0.0, 0.5) have been investigated over temperature range from 4.2 to 690 K using the M$\ "{o}$ssbauer technique. The Neel temperatuer of $Gd_{1-x}Sr_xFeO_{3-y}$ system is 690 K with x value of 0.0 and 515 K with x value of 0.5. Analysis of M$\ "{o}$ssbauer spectra Mohr's salt analysis for $Gd_{1-x}Sr_xFeO_{3-y}$ demonstrated the existence of the mixed valence states of iron and the coordination state of $Fe^{3+}$ and $Fe^{4+}$ ions. The Corresponding hyperfine parameters for GdFeO$_3$ are compatible with S=5/2 $Fe^{3+}$ in octahedral cooedination.l cooedination.

• Journal of dental hygiene science
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• v.15 no.5
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• pp.577-584
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• 2015

The purpose of this study was to evaluate the effect of metal chloride infiltration treatment on color and strength changes of the yttria-stabilized tetragonal zirconia polycrystals (Y-TZP). Fifty disc specimens were prepared with a Y-TZP powder (ZPEX; Tosoh, Japan). Thirty different metal chloride solutions containing 0.03~0.08 wt% chromium and 0.03~0.07 wt% terbium ions were prepared. Presintered Y-TZP specimens were soaked in metal chloride coloring liquids for 3 minutes and sintered in air at $1,450^{\circ}C$ for 2 hours. The color of the specimens was measured with spectrophotometer and color difference (${\Delta}E^*$) was obtained based on the CIE $L^*$, $a^*$, $b^*$ color coordinate values. To evaluate the effect of metal chloride infiltration strength changes, the biaxial flexural test was performed at crosshead speed 0.5 mm/min. Colors of the sintered Y-TZP showed the colors of Vita shade guide A1, A2 and A3 with the infiltration of chromium and terbium chloride solutions. Density of the sintered Y-TZP increased by the infiltration of chromium and terbium chloride solutions. Bi-axial flexural strength of the sintered Y-TZP did not show statistically significant differences by the infiltration of chromium and terbium chloride solutions (p>0.05). Chromium and terbium chloride did not affect the crystal phase of zirconia, and all specimens showed tetragonal phase. Accordingly, this study suggests that chromium and terbium chlorides can make colored zirconia while adding in a liquid form. The color of colored zirconia differ from that of vita shade guide but it can use all ceramic restoration as substructure in dental clinic.

• Economic and Environmental Geology
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• v.45 no.6
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• pp.661-672
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• 2012

Lab scale experiments to investigate the dissolution reaction among supercritical $CO_2$-sandstone-groundwater by using sandstones from Gyeongsang basin were performed. High pressurized cell system (100 bar and $50^{\circ}C$) was designed to create supercritical $CO_2$ in the cell, simulating the sub-surface $CO_2$ storage site. The first-order dissolution coefficient ($k_d$) of the sandstone was calculated by measuring the change of the weight of thin section or the concentration of ions dissolved in groundwater at the reaction time intervals. For 30 days of the supercritical $CO_2$-sandstone-groundwater reaction, physical properties of sandstone cores in Gyeongsang basin were measured to investigate the effect of supercritical $CO_2$ on the sandstone. The weight change of sandstone cores was also measured to calculate the dissolution coefficient and the dissolution time of 1 g per unit area (1 $cm^2$) of each sandstone was quantitatively predicted. For the experiment using thin sections, mass of $Ca^{2+}$ and $Na^+$ dissolved in groundwater increased, suggesting that plagioclase and calcite of the sandstone would be significantly dissolved when it contacts with supercritical $CO_2$ and groundwater at $CO_2$ sequestration sites. 0.66% of the original thin sec-tion mass for the sandstone were dissolved after 30 days reaction. The average porosity for C sandstones was 8.183% and it increased to 8.789% after 30 days of the reaction. The average dry density, seismic velocity, and 1-D compression strength of sandstones decreased and these results were dependent on the porosity increase by the dissolution during the reaction. By using the first-order dissolution coefficient, the average time to dissolve 1 g of B and C sandstones per unit area (1 $cm^2$) was calculated as 1,532 years and 329 years, respectively. From results, it was investigated that the physical property change of sandstones at Gyeongsang basin would rapidly occur when the supercritical $CO_2$ was injected into $CO_2$ sequestration sites.

• Microbiology and Biotechnology Letters
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• v.41 no.2
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• pp.198-206
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• 2013

The five anti-complementary polysaccharides (MFKF-NP, MFKF-AP1${\alpha}$, ${\beta}$, and MFKF-AP2${\alpha}$, ${\beta}$) were separated from hot water extracts of fruiting bodies of Fomes fomentarius by two subsequent column chromatography using DEAE-sepharose FF and Concanavalin A-sepharose 4B. The order of anti-complementary activity was MFKF-AP1${\beta}$ > MFKF-AP1${\alpha}$ > MFKF-AP2${\alpha}$ > MFKF-AP2${\beta}$ > MFKF-NP > Polysaccharide Krestine (PSK). Especially, MFKF-AP1${\beta}$ among those showed the most excellent anti-complementary activity (70% of ITCH50 value at $20{\mu}g/ml$). The monosaccharide composition analysis by gas chromatography indicates that MFKF-AP1${\alpha}$ and ${\beta}$ are a kind of homoxylan consisted mainly of xylose above 97%. Molecular weight of MFKF-AP1${\beta}$, major anti-complementary polysaccharide, was estimated to be about 12,000 by high performance liquid chromatography (HPLC). After the incubation of the serum with MFKF-AP1${\beta}$ in the presence or absence of $Mg^{++}$ and $Ca^{++}$ ions, its anti-complementary activity was investigated. This result indicated that MFKF-AP1${\beta}$ seems to be activator both on the classical and the alternative pathway of complement activation.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.250-250
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• 2012

Recently, multiferroic materials have attracted much attention due to their fascinating fundamental physical properties and potential technological applications in magnetic/ferroelectric data storage systems, quantum electromagnets, spintronics, and sensor devices. Among single-phase multiferroic materials, $BiFeO_3$, in particular, has received considerable attention because of its very interesting magnetoelectric properties for application to spintronics. Enhanced ferromagnetism was found by Fe-site ion substitution with magnetic ions. In this study, $BiFe_{1-x}Ni_xO_3$ (x=0 and 0.05) bulk ceramic compounds were prepared by solid-state reaction and rapid sintering. High-purity $Bi_2O_3$, $Fe_3O_4$ and NiO powders were mixed with the stoichiometric proportions, and calcined at $450^{\circ}C$ for 24 h to produce $BiFe_{1-x}Ni_xO_3$. Then, the samples were directly put into the oven, which was heated up to $800^{\circ}C$ and sintered in air for 20 min. The crystalline structure of samples was investigated at room temperature by using a Rigaku Miniflex powder diffractometer. The Raman measurements were carried out with a Raman spectrometer with 514.5-nm-excitation Ar+-laser source under air ambient condition on a focused area of $1-{\mu}m$ diameter. The field-dependent magnetization and the temperature-dependent magnetization measurements were performed with a vibrating-sample magnetometer. The x-ray diffraction study demonstrates the compressive stress due to Ni substitution at the Fe site. $BiFe_{0.95}Ni_{0.05}O_3$ exhibits the rhombohedral perovskite structure R3c, similar to $BiFeO_3$. The lattice constant of $BiFe_{0.95}Ni_{0.05}O_3$ is smaller than of $BiFeO_3$ because of the smaller ionic radius of Ni3+ than that of Fe3+. The field-dependent magnetization of $BiFe_{0.95}Ni_{0.05}O_3$ exhibits a clear hysteresis loop at 300 K. The magnetic properties of $BiFe_{0.95}Ni_{0.05}O_3$ were improved at room temperature because of the existence of structurally compressive stress.

• Korean Journal of Optics and Photonics
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• v.8 no.1
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• pp.31-36
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• 1997

We measured refractive indices and thicknesses of SiO$_2$ thin films that have been plated on LCD glass substrate for the purpose of preventing the out-diffusion of sodium ions. The best experimental condition to determine refractive index and thickness of SiO$_2$ thin film by using ellipsometry is searched for, where ⅰ) the film thickness is increased uniformly by 20 $\AA$ from 0 $\AA$ to the period thickness while the angle of incidence is fixed and ⅱ) the angle of incidence is increased uniformly by 1$^{\circ}$ from 45$^{\circ}$ to 70$^{\circ}$ while the film thickness is fixed. We estimated the errors in determining the refractive index and thickness by comparing the measurement error of $\Delta$ and Ψ with the calculated one. The ellipsometric constants of SiO$_2$ thin film on LCD glass substrate are measured at several angle of incidence around the Brewster angle, which is the best angle if the experimental error of ellipsometer is not sensitive to the incident angle. Also the best fit refractive index and thickness of SiO$_2$ thin film to these ellipsometric constants measured at several angle of incidenc eas well as the best fit ones to the SE data are obtained using regressional analysis.

• Clinical and Experimental Reproductive Medicine
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• v.26 no.1
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• pp.75-81
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• 1999

The beneficial effect of glucose and phosphate ions in culture medium on the development of human embryos in vitro has not been fully elucidated. The purpose of this study was to evaluate the influence of fertilization and culture of embryos in glucose/phosphate-free m-TALP medium on pregnancy rates in IVF-ET program. The patients in 244 IVF-ET cycles received GnRH agonist + HMG regimens. A does of 10,000 IU HCG was administered when two or more dominent follicles reached 18mm in diameter. Thirty-six hours after HCG, oocytes were recovered transvaginally using ultrasound guidance. Aspirated oocytes were matured for 4 to 6 h in TCM-199 supplemented with 10% follicular fluid (FF). Insemination was carried out with 50,000 motile spermatozoa in TCM-199 + 10% FF or m-TALP + 5% FF + 5% fetal cord serum (FCS) according to experimental design. After 6 h, oocytes were washed 3 to 4 times and cultured in each fresh medium. After 20 h, oocytes were freed from cumulus/corona cells and examined for the presence of pronuclei. Fertilized oocytes were transferred into each co-culture drops and cultured for further incubation. On day 3, embryo transfer was performed with grade 1 and 2 embryos. Monolayers for co-culture of embryos were prepared by plating $1{\times}10^5$ cumulus cells/ml in 10ul drop of TCM-199 + 10% FF or m-TALP + 5% FF + 5% FCS media 24 h prior to the onset of co-culture. Development to 4 to 16 cell stage was observed at 70x magnification following two days of incubation. Pregnancy was confirmed by detecting increasing serum ${\beta}$-hCG concentrations for 11 days following embryo transfer. Data were analyzed by ${\chi}^2$-test. Oocytes from 244 IVF-ET cycles were randomized. The number of cycles and mean age of patients were 97 and 147, 31.3 yrs and 31.2 yrs for TCM-199 (control) and m-TALP groups, respectively. The mean number of retrieved oocytes/cycle, fertilization rates, number of embryos transferred/ET and pregnancy rates were 11.1 and 10.3, 65.1% and 67.3%, 4.1 and 4.7, 28.9% and 43.8% for TCM-199 and m-TALP groups, respectively. Differences in the pregnancy rates were found between control and m-TALP groups (p<0.05). The pregnancy rate of patients divided according to maternal age groups of ${\leq}30$, 31-35, $36{\leq}$ were 44.4% and 49.0%, 26.1% and 41.3%, 29.2% and 41.2% for control and m-TALP groups, respectively. These data indicate that culture of human embryos in glucose/phosphate-free m-TALP medium improves pregnancy rates.

• Journal of Microbiology and Biotechnology
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• v.17 no.8
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• pp.1271-1283
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• 2007

A fibrinolytic protease (PoFE) was purified from the cultured mycelia of the edible oyster mushroom Pleurotus ostreatus, using a combination of various chromatographies. The purification protocol resulted in an 876-fold purification of the enzyme, with a final yield of 6.5%. The apparent molecular mass of the purified enzyme was estimated to be 32 kDa by SDS-PAGE, fibrin-zymography, and size exclusion using FPLC. The optimal reaction pH value and temperature were pH 6.5 and $35^{\circ}C$, respectively. PoFE effectively hydrolyzed fibrinogen, preferentially digesting the $A{\alpha}$-chain and the $B{\beta}$-chain over the ${\gamma}$-chain. Enzyme activity was enhanced by the addition of $Ca^{2+},\;Zn^{2+},\;and\;Mg^{2+}$ ions. Furthermore, PoFE activity was potently inhibited by EDTA, and it was found to exhibit a higher specificity for the chromogenic substrate S-2586 for chymotrypsin, indicating that the enzyme is a chymotrypsin-like metalloprotease. The first 19 amino acid residues of the N-terminal sequence were ALRKGGAAALNIYSVGFTS, which is extremely similar to the metalloprotease purified from the fruiting body of P. ostreatus. In addition, we cloned the PoFE protein, encoding gene, and its nucleotide sequence was determined. The cDNA of cloned PoFE is 867 nucleotides long and consists of an open reading frame encoding 288 amino acid residues. Its cDNA showed a high degree of homology with PoMEP from P. ostreatus fruiting body. The mycelia of P. ostreatus may thus represent a potential source of new therapeutic agents to treat thrombosis.

• Journal of Microbiology
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• v.44 no.6
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• pp.622-631
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• 2006

In this study we purified a fibrinolytic enzyme from Cordyceps militaris using a combination of ion-exchange chromatography on a DEAE Sephadex A-50 column, gel filtration chromatography on a Sephadex G-75 column, and FPLC on a HiLoad 16/60 Superdex 75 column. This purification protocol resulted in a 191.8-fold purification of the enzyme and a final yield of 12.9 %. The molecular mass of the purified enzyme was estimated to be 52 kDa by SDS-PAGE, fibrin-zymography, and gel filtration chromatography. The first 19 amino acid residues of the N-terminal sequence were ALTTQSNV THGLATISLRQ, which is similar to the subtilisin-like serine protease PR1J from Metarhizium anisopliae var. anisopliase. This enzyme is a neutral protease with an optimal reaction pH and temperature of 7.4 and $37^{\circ}C$, respectively. Results for the fibrinolysis pattern showed that the enzyme rapidly hydrolyzed the fibrin $\alpha$-chain followed by the $\gamma$-$\gamma$ chains. It also hydrolyzed the $\beta$-chain, but more slowly. The A$\alpha$, B$\beta$, and $\gamma$ chains of fibrinogen were also cleaved very rapidly. We found that enzyme activity was inhibited by $Cu^{2+}$ and $Co^{2+}$, but enhanced by the additions of $Ca^{2+}$ and $Mg^{2+}$ ions. Furthermore, fibrinolytic enzyme activity was potently inhibited by PMSF and APMSF. This enzyme exhibited a high specificity for the chymotrypsin substrate S-2586 indicating it's a chymotrypsin-like serine protease. The data we present suggest that the fibrinolytic enzyme derived from the edible and medicinal mushroom Cordyceps militaris has fibrin binding activity, which allows for the local activation of the fibrin degradation pathway.