• Journal of Technologic Dentistry
• /
• v.28 no.2
• /
• pp.355-366
• /
• 2006

The purpose of this study was to determine if repeated casting has a detrimental effect on the corrosion behavior of nickel-chrome casting alloys. The X-ray diffraction analysis, vickers hardness test, SEM, EDX and corrosion test were performed to determine the effects of recasting on chemical composition, microstructure, physical property, castability and corrosion behavior of nickel-chrome casting alloys. The X-ray diffraction analysis results for the cast and recast specimens of the VeraBond and the Rexillium V showed that major crystal phase contained nickel-chrome compounds, Nickel carbide and Chrome carbide. Microstructure analysis results for the cast and recast specimens of the VeraBond and the Rexillium V showed recasting has no effect on microstructure. EDX analysis results indicated the percentage of the main component nickel(Ni) in the specimens of the VeraBond showed a tendency to increase with recasting, but those of other components Carbon(C) showed a tendency to decrease with recasting, Chrome(Cr), Silicon(Si), Aluminium(Al) and molybdenum(Mo) showed no changes in the percentage. The percentage of the main component nickel(Ni) in the specimens of the Rexillium V showed a tendency to increase with recasting, but those of other components silicon(Si), carbon(C) and molybdenum(Mo) showed a tendency to decrease with recasting, chrome(Cr) and aluminium(Al) showed no changes in the percentage. The vickers hardness results for the cast and recast specimens of the VeraBond and the Rexillium V showed a tendency to decrease with recasting, but the differences for the first to fifth cast were not statistically significant. The castability results for the cast and recast specimens of the VeraBond and the Rexillium V showed a tendency to decrease with recasting, but the differences for the first to fifth cast were not statistically significant. The cast and recast specimens of the VeraBond and the Rexillium V showed no differences in the corrosion resistance. The results indicate that the VeraBond and the Rexillium V can be safely recast.

• Journal of the Korean Magnetics Society
• /
• v.17 no.1
• /
• pp.47-50
• /
• 2007

[ $ZnCr_2O_4$ ] shows geometrically frustrated magnet. Recently, $CoCr_2O_4$ has been investigated for multiferroic property and dielectric anomalies by spin-current model. Polycrystalline $CoCr_2O_4$ and $CoCrFeO_4$ compounds was prepared by wet-chemical process. Crystallographic and magnetic properties of $CoCr_2O_4$ and $CoCrFeO_4$ were investigate by using the x-ray diffractometer(XRD), vibrating sample magnetometer(VSM), superconducting quantum interference device magnetometer(SQUID), and $M\"{o}ssbauer$ spectroscopy. The crystal structure was found to be single-phase cubic spinel with space group of Fd3m. The lattice constants of $CoCr_2O_4$ and $CoCrFeO_4$ $a_0$ were determined to be 8.340 and 8.377 ${\AA}$, respectively. The ferrimagnetic transition temperature for the both samples were observed at 97 K and 320 K. The $M\"{o}ssbauer$ absorption spectra at 4.2 K show that the well developed two sextets are superposed with small difference of hyperfine field($H_{hf1}=507\;and\;H_{hf2}=492\;kOe$). Isomer shift values($\delta$) of the two sextets are found to be 0.33 and 0.34 mm/s relative to the Fe metal, respectively, which are consistent with the high spin $Fe^{3+}$ charge state.

• Microbiology and Biotechnology Letters
• /
• v.26 no.4
• /
• pp.316-322
• /
• 1998

An ${\alpha}$-D-galactosidase (${\alpha}$-D-galactoside galactohydrolase, EC 3. 2. 1. 22) from sunflower seed was purified by affinity chromatography using N-$\varepsilon$-aminocaproyl-${\alpha}$-D-galactopyranosylamine coupled to sepharose and its properties were examined. The specific activity of the purified enzyme, tested with p-nitrophenyl-${\alpha}$-D-galactopyranoside as substrate, was 291.66 units/mg protein, representing an 115-folds purification of the original crude extract. The final preparation obtained from by Sephadex G-25 chromatography showed a single band on SDS-polyacrylamide gel electrophoresis. The molecular weight was determined to be 42,000 by SDS-polyacrylamide gel electrophoresis. The purified galactosidase showed maximum activity at pH 4.5 and 55$^{\circ}C$, and was stable in the pH and temperature ranges of 4.0 to 5.0 and 30 to 55$^{\circ}C$, respectively. The enzyme activity was inhibited by Ag$\^$2+/, Hg$\^$2+/ and Co$\^$2+/. The enzyme activity was not affected considerably by treatment with other metal compounds. The enzyme liberated galactose from melibiose, raffinose, copra galactomannan, guar gum and locust bean gum by TLC, and also the hydrolysis rate of substrate was compared by HPLC.

• IMMUNE NETWORK
• /
• v.6 no.2
• /
• pp.86-92
• /
• 2006

Background: Germanium compounds are increased to use in nutrient foods and medicines in terms of antibiotics to microbes, anticancer, modulation of immune system and neutralizing heavy metal toxins. Geranti Bio-Ge Yeast, containing stable organic germanium and bound to the yeast protein was developed by Geranti Pharm. LTD. and the modulation effect in the immune system was examined in vivo and in vitro. Methods: The compound, Geranti Bio-Ge Yeast, was fed to female Balb/c mice (each group has 10 mice) for 4 weeks and the yeast powder and steamed red ginseng powder were used as control during the same feeding time points. During 4 weeks there was no symptom to be considered, and after 4 weeks feeding all mice were sacrificed to check the changes of related immune cells and subsidiary responses (i.e. cell counting, FACS, MTT, LDH, PFC assay). Results: In pre-post comparison, B cell population was increased in the group of Geranti Bio-Ge Yeast in a dose dependent manner (100 to 800 mg/kg). However, the population of T cell, dendritic cell and macrophage was not comparably changed in all doses. The ability of cytokine production and proliferation was almost same level as shown in control group. In contrast, PFC assay informed that the compound increase the antibody production ability when fed over 200 mg/kg implying that the increase of PFC number might be due to the increase of B cells. Conclusion: Over the entire study, we concluded that the compound, Geranti Bio-Ge Yeast has better potential in immune response in terms of B cell proliferation than that of positive control, red ginseng, and the compound can be one of the future candidates for a new supplementary source improving immune system activity.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.06a
• /
• pp.169-169
• /
• 2008

To keep pace with scaling trends of CMOS technologies, high-k metal oxides are to be introduced. Due to their high permittivity, high-k materials can achieve the required capacitance with stacks of higher physical thickness to reduce the leakage current through the scaled gate oxide, which make it become much more promising materials to instead of $SiO_2$. As further studying on high-k, an understanding of the relation between the etch characteristics of high-k dielectric materials and plasma properties is required for the low damaged removal process to match standard processing procedure. There are some reports on the dry etching of different high-k materials in ICP and ECR plasma with various plasma parameters, such as different gas combinations ($Cl_2$, $Cl_2/BCl_3$, $Cl_2$/Ar, $SF_6$/Ar, and $CH_4/H_2$/Ar etc). Understanding of the complex behavior of particles at surfaces requires detailed knowledge of both macroscopic and microscopic processes that take place; also certain processes depend critically on temperature and gas pressure. The choice of $BCl_3$ as the chemically active gas results from the fact that it is widely used for the etching o the materials covered by the native oxides due to the effective extraction of oxygen in the form of $BCl_xO_y$ compounds. In this study, the surface reactions and the etch rate of $Al_2O_3$ films in $BCl_3/Cl_2$/Ar plasma were investigated in an inductively coupled plasma(ICP) reactor in terms of the gas mixing ratio, RF power, DC bias and chamber pressure. The variations of relative volume densities for the particles were measured with optical emission spectroscopy (OES). The surface imagination was measured by AFM and SEM. The chemical states of film was investigated using X-ray photoelectron spectroscopy (XPS), which confirmed the existence of nonvolatile etch byproducts.

• Korean Chemical Engineering Research
• /
• v.56 no.5
• /
• pp.725-731
• /
• 2018

The effects of catalysts addition on the carbonization reaction of biomass have been studied in a thermogravimetric analyzer (TGA). The sample biomasses were Bamboo and Pine. The catalysts tested were K, Zn metal compounds. The carbonization reactions were tested in the nonisothermal condition from the room temperature to $850^{\circ}C$ at a heating rate $1{\sim}10^{\circ}C/min$ on the flowing of $N_2$ purge gases. Also, the effects of catalyst on the torrefaction were tested in the temperature condition of 220, 250, $280^{\circ}C$ at 30 min. Combustion characteristic for the torrefied catalyst biomass were studied in the nonisothermal conditions of $200{\sim}850^{\circ}C$. As the results, the initial decomposition temperatures of the volatile matters ($T_i$) and the temperature of maximum reaction rate ($T_{max}$) were decreased with increasing the catalyst amounts in the sample biomass. The char amounts remained after carbonization at $400^{\circ}C$ increased with the catalyst amounts. Therefore catalysts addition can be decreased the energy for carbonization process and improved the heating value of product char. The catalysts reduced the optimum torrefaction conditions from $250^{\circ}C$ to $220^{\circ}C$. The torrefied catalyst biomass have lower activated energy from 46.5~58.7 kJ/mol to 25.1~27.0 kJ/mol in the nonisothermal combustion reaction.

• Clean Technology
• /
• v.6 no.2
• /
• pp.121-127
• /
• 2000

There are several kinds of hazardous materials in incinerator flue gas, such as particulate matter, acid gas, heavy metal, dioxin, etc. The activated carbon adsorption is considered as one of the methods removing dioxin from flue gas. Without any additional equipment and facilities, the activated carbon was mixed with lime and sprayed in the semi-drying reactor of an incinerator and filtered in the bag filter, and its efficiency of removing hazardous organic material was investigated. 1,2-dichlorobenzene (o-DCB) was used as a precursor material of dioxin and the effects of the activated carbon amount, the operating temperature of the reactor, and the atomizer r.p.m were measured and analyzed. Experimental results showed that the optimum outlet temperature of the reactor was $145^{\circ}C$ considering the performance of the bag filter, and the adsorption performance improved with the increase of the atomizer r.p.m. Also the performance of removing o-DCB in the bag filter is higher than of the semi-drying reactor.

• Journal of Ginseng Research
• /
• v.42 no.3
• /
• pp.327-333
• /
• 2018

Background: Bioactive compounds in plant extracts are able to reduce metal ions to nanoparticles through the process of green synthesis. Panax ginseng is an oriental medicinal herb and an adaptogen which has been historically used to cure various diseases. In addition, the P. ginseng leaves-mediated gold nanoparticles are the value-added novel materials. Its potential as a cosmetic ingredient is still unexplored. The aim of this study was to evaluate the antioxidant, moisture retention and whitening properties of gold nanoparticles (PgAuNPs) in cosmetic applications. Methods: Cell-free experiments were performed to evaluate PgAuNP's antioxidant and moisture retention properties and inhibition activity on mushroom tyrosinase. Furthermore, in vitro cell cytotoxicity was evaluated using normal human dermal fibroblast and murine B16BL6 melanoma cells (B16) after treatment with increasing concentrations of PgAuNPs for 24 h, 48 h, and 72 h. Finally, in vitro cell assays on B16 cells were performed to evaluate the whitening effect of PgAuNPs through reduction of cellular melanin content and tyrosinase activity. Results: In vitro DPPH radical scavenging assay results revealed that PgAuNPs exhibited antioxidant activity in a dose-dependent manner. PgAuNPs exhibited moisture retention capacity and effectively inhibited mushroom tyrosinase. In addition, 3-(4,5-dimethyl-thiazol-2yl)-2,5-diphenyl tetrazolium bromide results revealed that PgAuNPs were not toxic to human dermal fibroblast and B16 cells; in addition, they significantly reduced melanin content, tyrosinase activity, and mRNA expression of melanogenesis-associated transcription factor and tyrosinase in B16 cells. Conclusion: Our study is the first report to provide evidence supporting that P. ginseng leaves-capped gold nanoparticles could be used as multifunctional ingredients in cosmetics.

• The Korean Journal of Mycology
• /
• v.19 no.1
• /
• pp.32-40
• /
• 1991

Mitochondria in Pleurotus ostreatus were isolated and purified by the stepped sucrose density gradient centrifugation, to investigate the effects of the light on the enzymatic activity of the mitochondrial ATP synthase. This enzyme, which was illuminated by the light ranging from 400 nm to 700 nm, showed that the specific activity was stimulated at 490 nm for 15 sec. Effects of organic compounds on the mitochondrial ATP synthase were also investigated at the optimum conditions; The activities of this enzyme were increased to 168 percent by the addition of 2,6-dichlo­rophenol indophenol(DCPIP), 224 percent by phenazine methosulfate(PMS), but inhibited 91 per­cent by oligomycin, 14 percent by 2-heptyl-4-hydroxyquinoline-N-oxide(HQNO) and 75 percent by 2,4-dinitrophenol (DNP), respectively. Effects of metal ions of the mitochondrial ATP synthase were investigated at the optimum conditions. The activities of the enzyme were inhibited 35 percent by $Ca^{2+}$, 14 percent by $Co^{2+}$ and 73 percent by $Mn^{2+}$. For effects of anions, the activities of this enzyme were inhibited 80 percent by $CN^{-}$, 52 percent by $SO_{4}\;^{2-}$, 28 percent by each of $CO_{3}\;^{2-}$­and $NO_{3}\;^{-}$, respectively.

• Journal of Adhesion and Interface
• /
• v.12 no.2
• /
• pp.47-55
• /
• 2011

UV-curable coatings have been used in various industries due to their advantages such as high mechanical property, good solvent resistance, fast curing process and low volatile organic compounds. However, a lack of flexibility of UV-cured films is a weak point for the pre-coated system of roll-to-roll process. In this study, UV-curable polycarbonate-based methacrylates were synthesized with polycarbonate diol, isophorone diisocyanate and 2-hydroxyethylmethacrylate to improve flexibility of the UC-cured films. The effects of polyol molecular weight, content of photoinitiator and monomers on the UV-curing behavior, flexibility and properties were investigated. The UV-curing behavior was measured by a photo-DSC, the pendulum hardness, tensile strength, viscoelastic properties were also evaluated.