• The Journal of Engineering Geology
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• v.23 no.1
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• pp.1-17
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• 2013

It is sometimes necessary to change the location of the collection conduit, which is constructed in shallow sediments in a stream, if the concentrations of $Fe^{2+}$ and $Mn^{2+}$ become too high for water treatment. A total of nine wells, including four shallow wells with a depth of 3 m and five deeper wells with a depth of 6 m, were installed in the study area at Naeseong-cheon in Yecheon-gun. The change in hydrogeochemical features of groundwater and the concentrations of $Fe^{2+}$ and $Mn^{2+}$ were examined at the wells during 5 hours of pumping. As pumping was performed, the velocity of groundwater flow was increased around the pumping well and aeration conditions were developed to precipitate iron and manganese oxides in an oxidizing environment. In addition, the concentrations of $Ca^{2+}$ and $Cl^-$ at the pumping well were increased following the mixing of surface water and groundwater. It is suggested that the center region of the stream would be more suitable for a new collection conduit, considering the concentrations of $Fe^{2+}$ and $Mn^{2+}$ in groundwater and their reducing effect during pumping. The installation of a collection conduit based on field tests performed to ensure water quality enables a reduction in the construction and management costs at water treatment facilities.

• Bulletin of the Korean Chemical Society
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• v.34 no.6
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• pp.1684-1688
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• 2013

A rapid and sensitive method for determining usnic acid of Lethariella cladonioides in rat was established using high performance liquid chromatography (HPLC) quadrupole time-of-flight (QTOF) tandem mass (MS/MS). Rat plasma was pretreated by mixture of acetonitrile and chloroform to precipitate plasma proteins. Chromatographic separation was achieved on a column ($50{\times}2.1$ mm, $5{\mu}m$) with a mobile phase consisting of water (containing $5{\times}10^{-3}$ M ammonium formate, pH was adjusted to 3.0 with formic acid) and acetonitrile (20:80, v/v) at a flow rate of 0.3 mL/min. A tandem mass spectrometric detection with an electrospray ionization (ESI) interface was conducted via collision induced dissociation (CID) under negative ionization mode. The MS/MS transitions monitored were m/z 343.0448 ${\rightarrow}$ m/z 313.2017 for usnic acid and m/z 153.1024 ${\rightarrow}$ m/z 136.2136 for protocatechuic acid (internal standard). The linear range was calculated to be 2.0-160.0 ng/mL with a detection limit of 3.0 pg/mL. The inter- and intra-day accuracy and precision were within ${\pm}7.0%$. Pharmacokinetic study showed that the apartment of usnic acid in vivo confirmed to be a two compartment open model. The method was fully valid and will probably be an alternative for pharmacokinetic study of usnic acid.

• Journal of Life Science
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• v.18 no.7
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• pp.992-998
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• 2008

We evaluated proanthocyanidin contents out of total polyphenolic compounds in two pine needle extracts prepared by combined extraction methods and compared their antioxidative activities. Amounts of total polyphenolic compounds of sub-supercritical hotwater precipitate (SSHP) and sub-supercritical hotwater supermatant (SSHS) were 225.4 and 116.6 mg/g, respectively. Amounts of proanthocyanidin of SSHP and SSHS were 9.9 and 3.6 mg/g, respectively. Thus, the ratio of proanthocyanidin contents over total polyphenolic compounds of SSHP and SSHS were 4.3 and 3.9%, respectively. Antioxidative activities ($IC_{50}$) of SSHP and SSHS measured by DPPH radical scavenging were 41.5 and $50.7\;{\mu}g/ml$, respectively. These results indicates that two combined extracts, SSHP and SSHS showed higher antioxidative activities than extract prepared by hot water or sub-supercritical. In conclusion, extraction procedures for SSHP and SSHS could be useful methods for preparing the effective components of functional food products.

• Economic and Environmental Geology
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• v.37 no.1
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• pp.133-142
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• 2004

The purpose of this study is to evaluate a laboratory test on arsenic removal effciency for ARD(Acid Rock Drain-age) using limestone and apatite, and on heavy metals removal efficiencies for AMD(Acid Mine Drainage) using apatite and fish bone. As a result of the laboratory test, pH, arsenic removal rate of limestone & apatite are inversely proportional to flow rates and apatite removes 100% of arsenic while limestone removes 37% of arsenic at 0.6$m{ell}$/min/kg flow rate in case of ARD treatment. And the dissolution amount of apatite is twenty five times higher than that of limestone. In case of AMD treatment, fish bone shows higher dissolution rate than apatite, and pH of outlet water reacted with fish bone is higher than that reacted with apatite. The heavy metal removal rates of fish bone are also higher than that of apatite except arsenic removal rate. The precipitate resulted from fish bone reaction with AMD seems to be biological sludge type while that resulted from apatite with AMD is inorganic solid which can settle easily compared with the biological sludge and can be cemented by gypsum. As the results, apatite can be used as a precipitant for the polluted mine waters showing wide range of pH and fish bone can be used for highly contaminated AMD.

• Applied Biological Chemistry
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• v.32 no.4
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• pp.416-423
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• 1989

In order to produce clear and favorable citrus wine from Citrus unshiu produced in Cheju island, chemical and microbiological processes for alcoholic fermentation were investigated. The ratio of pressed juice passed below 100 mesh sieve and peel of mandarin orange were 55.9% and 25.6% respectively. Orange juice for fermentation source contained 8.85% total sugar, 1.43% total acid and 0.056% volatile acid. Pressed juice was adjusted to 24 degree Brix with cane sugar, and was fermented at $20^{\circ}C$ for one month. Starter screened and selected was Saccharomyces cerevisiae IAM 4274. As principal fermentation proceeded for one week, suspended solids began to precipitate slowly after then. After fermentation, clear citrus wine consisted of about 8 degree Brix residual sugar, $13.3{\sim}14.4%$ ethanol, $0.78{\sim}1.11%$ total acid, $0.05{\sim}0.07%$ methanol and $2.25{\sim}3.29%$ extract, was obtained. Color, flavor and taste of citrus wine found good with panel test. Citrus wine which was treated with fungal enzyme derived from Aspergillus niger CCM-4 was cleared much faster, and could be filtered more rapidly than the untreated. The enzyme-producing strain was isolated from field soil of Cheju island and identified.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.1
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• pp.169-178
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• 1998

The crystal phases precipitated in various compositions glass of CaO-$SiO_2-P_2O_5$ system, were identified by XRD. E composition (CaO 49.4, $SiO_2\;36.8,\;P_2O_5$ 8.8 wt%) glass in which both apatite(($Ca_{10}(PO_4)_6O$ and $\beta$-wollastonite($CaSiO_3$) crystals would precipitate by heating, was selected as an experimental composition to prepare the glass ceramics with high bending strength and good bioactivity to the living bone. Glass powders of E composition were unidirectionally crystallized at $1050^{\circ}$C in the temperature-gadient furnace and the resultant glass ceramics were characterized. Bending strength of the glass ceramics was also measured. To investigate the bond forming ability between the glass ceramics and living bone tissue, soaking test of glass ceramics in simulated body fluid was carried out. Densed glass ceramics composed of apatite and $\beta$-wollastonite crystal were prepared by unidirectional crystallization under the optimum conditions. (2 0 2) plane of $\beta$-wollastonite crystals tended to grow perpendicularly to the crystallization direction. Average bending strength of this glass ceramics was 186.9 MPa, higher than that of the glass ceramics prepared by isothermal (not directional) crystallization In soaking test, a thin layer of apatite crystallite was formed on surface of the glass ceramics in 3 days. Apatite crystals formed on the glass ceramics could be act a role to make the chemical bond between the glass ceramics and living bone tissue.

• Journal of the Korean Ceramic Society
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• v.39 no.3
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• pp.315-320
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• 2002

Treatment effects of dilute hydrofluoric acid (6 wt% HF) on the surface properties of $Al(OH)_3$ were investigated at the molar ratio of F/Al(fluoride/aluminum)=0.15. Temperature and pH variations in the reaction system were recorded to analyze reaction mechanism between $Al(OH)_3$ and aqueous Hf. The reaction of HF to the surface of $Al(OH)_3$ accompanied with a quantity of heat evolution, resulting in increasing temperature of a reactionsystem. And also the reaction was proceeded as transitional state which metastable ${\alpha}-form\;AlF_3{\cdot}3H_2O$ was transferred to insoluble ${\beta}$-form. The resulting ${\beta}-form\;AlF_3{\cdot}3H_2O$ formed by a surface treatment was identified by FT-IR and X-ray diffractormetry. The formation of ${\beta}$-form aluminum fluoride hydrates with diameter less than $1{\mu}m$ on the surface of $Al(OH)_3$ could be visulaized by SEM imgae, making up a coating layer as precipitate-like. The surface whiteness of $Al(OH)_3$ treated with aqueous HF was furthermore increased approximately 6.6% due to the formation of surface hydrates.

• KSBB Journal
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• v.22 no.1
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• pp.30-36
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• 2007

The water-soluble or ethanol-soluble materials extracted from fruit bodies and cultured products (mycelium and broth) of H. erinaceum were prepared, and their inhibitory effect on acetylcholinesterase (AChE) activity from Electrophorous electricus was investigated. Inhibition of 75-85% for AChE activity at concentration of 10 mg/ml was obtained and the mechanism was due to general non-competitive inhibition. Especially, the supernatant of culture broth by ethanol treatment, exhibited a strong inhibition activity of 94% at 10 mg/ml. The samples from fruit body, mycelium and broth (supernatant and precipitate by ethanol treatment) which were extracted from H. erinaceum, were very effective to inhibit the initial stage oxidation of a linoleic acid at concentration of 0.1 mg/ml. The antioxidative activity of these samples were superior than rutin, vitamin C and tocopherol as antioxidative standards by FTC (ferric thiocyanate) method, and also showed the very strong antioxidative activity of 95% without significant difference of the samples by TBA-RS (thiobarbituric acid-reactive substance) method.

• Korean Journal of Materials Research
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• v.20 no.11
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• pp.606-610
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• 2010

Films consisting of a silicon quantum dot superlattice were fabricated by alternating deposition of silicon rich silicon nitride and $Si_3N_4$ layers using an rf magnetron co-sputtering system. In order to use the silicon quantum dot super lattice structure for third generation multi junction solar cell applications, it is important to control the dot size. Moreover, silicon quantum dots have to be in a regularly spaced array in the dielectric matrix material for in order to allow for effective carrier transport. In this study, therefore, we fabricated silicon quantum dot superlattice films under various conditions and investigated crystallization behavior of the silicon quantum dot super lattice structure. Fourier transform infrared spectroscopy (FTIR) spectra showed an increased intensity of the $840\;cm^{-1}$ peak with increasing annealing temperature due to the increase in the number of Si-N bonds. A more conspicuous characteristic of this process is the increased intensity of the $1100\;cm^{-1}$ peak. This peak was attributed to annealing induced reordering in the films that led to increased Si-$N_4$ bonding. X-ray photoelectron spectroscopy (XPS) analysis showed that peak position was shifted to higher bonding energy as silicon 2p bonding energy changed. This transition is related to the formation of silicon quantum dots. Transmission electron microscopy (TEM) and electron spin resonance (ESR) analysis also confirmed the formation of silicon quantum dots. This study revealed that post annealing at $1100^{\circ}C$ for at least one hour is necessary to precipitate the silicon quantum dots in the $SiN_x$ matrix.

• Korean Journal of Materials Research
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• v.20 no.11
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• pp.586-591
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• 2010

Solar cells have been more intensely studied as part of the effort to find alternatives to fossil fuels as power sources. The progression of the first two generations of solar cells has seen a sacrifice of higher efficiency for more economic use of materials. The use of a single junction makes both these types of cells lose power in two major ways: by the non-absorption of incident light of energy below the band gap; and by the dissipation by heat loss of light energy in excess of the band gap. Therefore, multi junction solar cells have been proposed as a solution to this problem. However, the $1^{st}$ and $2^{nd}$ generation solar cells have efficiency limits because a photon makes just one electron-hole pair. Fabrication of all-silicon tandem cells using an Si quantum dot superlattice structure (QD SLS) is one possible suggestion. In this study, an $SiO_x$ matrix system was investigated and analyzed for potential use as an all-silicon multi-junction solar cell. Si quantum dots with a super lattice structure (Si QD SLS) were prepared by alternating deposition of Si rich oxide (SRO; $SiO_x$ (x = 0.8, 1.12)) and $SiO_2$ layers using RF magnetron co-sputtering and subsequent annealing at temperatures between 800 and $1,100^{\circ}C$ under nitrogen ambient. Annealing temperatures and times affected the formation of Si QDs in the SRO film. Fourier transform infrared spectroscopy (FTIR) spectra and x-ray photoelectron spectroscopy (XPS) revealed that nanocrystalline Si QDs started to precipitate after annealing at $1,100^{\circ}C$ for one hour. Transmission electron microscopy (TEM) images clearly showed SRO/$SiO_2$ SLS and Si QDs formation in each 4, 6, and 8 nm SRO layer after annealing at $1,100^{\circ}C$ for two hours. The systematic investigation of precipitation behavior of Si QDs in $SiO_2$ matrices is presented.