• Clean Technology
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• v.24 no.3
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• pp.198-205
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• 2018

This study investigated the influence of catalyst preparation on the activity of $Co-CeO_2$ catalyst for $N_2O$ decomposition. $Co-CeO_2$ catalysts were synthesized by co-precipitation and incipient wetness impregnation. In order to estimate the performance of the as prepared catalysts, direct catalytic $N_2O$ decomposition test was carried out under $250{\sim}375^{\circ}C$. As a result, the catalyst prepared by co-precipitation (CoCe-CP) showed an enhanced performance on $N_2O$ decomposition reaction even in the presence of $O_2$ and/or $H_2O$, whereas the impregnation catalyst (CoCe-IM) did not. In order to investigate the difference in catalytic activity, characterization such as XRD, BET, TEM, $H_2-TPR$, $O_2-TPD$, and XPS was conducted. It is confirmed that the particle size and specific surface area were changed depending on the catalyst preparation method and the synthesis process influenced the physical properties of the catalysts. In addition, the improvement in the activity of the catalyst prepared by co-precipitation is due to the enhanced reduction from $Co^{3+}$ to $Co^{2+}$ and the improved oxygen desorption rate. However, it has been confirmed that the surface electron state and binding energy, which are related to $N_2O$ decomposition, do not change depending on the preparation method.

• Applied Biological Chemistry
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• v.38 no.5
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• pp.468-472
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• 1995

Substantial amount of caryophyllene oxide (CPO) is present in the essential oils of traditionally-used folk medicinal plants and herbal spices. The CPO, produced via chemical and/or enzymatic reaction of caryophyllene (CP), has largely being used as a flavoring component and exhibited a variety of biological activities. Now, we report the antimutagenic activity of CPO determined by Ames's preincubation test. S-9 fraction was prepared from the liver of rats treated with Arochor 1254. Anatoxin $B_1\;(AFB_1)$ and 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) were used as mutagens. Reduction of mutagenicity of $AFB_1$ or IQ for S. typhimurium TA98 and TA100 by CPO was found to be a dose-dependant manner. CPO (500 ${\mu}g/plate$) reduced mutagenicity of AEB1 for S. typhimurium TA98 and TA100 to 89% and 71%, respectively. For IQ, similar results were observed against S. typhimurium TA98 and TA100, resulting in the inhibition percentage of 77% and 51%, respectively. CP also reduced mutagenicity of AEB1 and IQ for S. typhimurium TA98 and TA100, but the reduction rate was somewhat lowered relative to that of CPO. These results indicate that CPO could be developed as a potent antimutagenic flavoring agent.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.29 no.3
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• pp.345-356
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• 1996

Properties of enzymatic hydrolysates from ascidian tunic were assessed on supernatant ratio, solid yields and solid concentration. The concentartion of solid and yields in the extracts were increased as the enzyme concentration raised from $100\;{\mu}l\;to\;1000{\mu}l$ during the extraction period. The optima concentration and reaction time of each enzyme on digestion were $400\;{\mu}l$ 60 minutes, through treated with Duncan's multiple test. The percent of yields of solid, protein and carotenoids for 60 minutes extraction at $400\;{\mu}l$ were $32.32\%,\;1.34\%\;and\;74.60\;mg\%$, respectively, in Viscozyme systems. The extracts were composed with many kinds of carbohydrates such as arabinose, ribose, xylose, galactose, glucose, N-acetyl-D-galactosamine, and N-acetyl-D-glucosamine. Aspartic and glutamic arid were noted as predominant amino acids in all parts. Amino acid profiles of various ascidian tunic part were similiar to each other, but most of essential amino acids content of inter coat was higher than that of root and tunic (body). About sixty six fatty acids components were observed, and their distribution among neutral and polar lipids was compared. The main fatty acids were found to be 14:0, 16:0, 16:1n7, 18:0, 18:1n9, 18:1n7, 18:2n6, 20:5n3, and 22:6n3.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.91-93
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• 2003

A comprehensive numerical study is carried out to investigate for the understanding of the flow evolution and flame development in a supersonic combustor with normal injection of ncumally injecting hydrogen in airsupersonic flows. The formulation treats the complete conservation equations of mass, momentum, energy, and species concentration for a multi-component chemically reacting system. For the numerical simulation of supersonic combustion, multi-species Navier-Stokes equations and detailed chemistry of H2-Air is considered. It also accommodates a finite-rate chemical kinetics mechanism of hydrogen-air combustion GRI-Mech. 2.11[1], which consists of nine species and twenty-five reaction steps. Turbulence closure is achieved by means of a k-two-equation model (2). The governing equations are spatially discretized using a finite-volume approach, and temporally integrated by means of a second-order accurate implicit scheme (3-5).The supersonic combustor consists of a flat channel of 10 cm height and a fuel-injection slit of 0.1 cm width located at 10 cm downstream of the inlet. A cavity of 5 cm height and 20 cm width is installed at 15 cm downstream of the injection slit. A total of 936160 grids are used for the main-combustor flow passage, and 159161 grids for the cavity. The grids are clustered in the flow direction near the fuel injector and cavity, as well as in the vertical direction near the bottom wall. The no-slip and adiabatic conditions are assumed throughout the entire wall boundary. As a specific example, the inflow Mach number is assumed to be 3, and the temperature and pressure are 600 K and 0.1 MPa, respectively. Gaseous hydrogen at a temperature of 151.5 K is injected normal to the wall from a choked injector.A series of calculations were carried out by varying the fuel injection pressure from 0.5 to 1.5MPa. This amounts to changing the fuel mass flow rate or the overall equivalence ratio for different operating regimes. Figure 1 shows the instantaneous temperature fields in the supersonic combustor at four different conditions. The dark blue region represents the hot burned gases. At the fuel injection pressure of 0.5 MPa, the flame is stably anchored, but the flow field exhibits a high-amplitude oscillation. At the fuel injection pressure of 1.0 MPa, the Mach reflection occurs ahead of the injector. The interaction between the incoming air and the injection flow becomes much more complex, and the fuel/air mixing is strongly enhanced. The Mach reflection oscillates and results in a strong fluctuation in the combustor wall pressure. At the fuel injection pressure of 1.5MPa, the flow inside the combustor becomes nearly choked and the Mach reflection is displaced forward. The leading shock wave moves slowly toward the inlet, and eventually causes the combustor-upstart due to the thermal choking. The cavity appears to play a secondary role in driving the flow unsteadiness, in spite of its influence on the fuel/air mixing and flame evolution. Further investigation is necessary on this issue. The present study features detailed resolution of the flow and flame dynamics in the combustor, which was not typically available in most of the previous works. In particular, the oscillatory flow characteristics are captured at a scale sufficient to identify the underlying physical mechanisms. Much of the flow unsteadiness is not related to the cavity, but rather to the intrinsic unsteadiness in the flowfield, as also shown experimentally by Ben-Yakar et al. [6], The interactions between the unsteady flow and flame evolution may cause a large excursion of flow oscillation. The work appears to be the first of its kind in the numerical study of combustion oscillations in a supersonic combustor, although a similar phenomenon was previously reported experimentally. A more comprehensive discussion will be given in the final paper presented at the colloquium.

• Journal of Korean Society of Forest Science
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• v.77 no.3
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• pp.259-268
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• 1988

For the purpose of examining the effects of simulated acid rain on nutrient contents of plant tissues in Pintos densiflora seedlings and Forsythia koreana rooted cuttings, the experimental design of randomized block arrangement with three replications was implemented in the experimental field of Yesan National Agricultural Junior College. One-year-old Pinus densiflora seedlings and Forsythia koreana cuttings were planted in the pots filled the mixed soils(nursery soil : forest soil of siliceous sandy loam=1 : 1 v/v) in the early spring of 1986. The regime of artificial acid rain, in terms of spray frequency per month and spray amount at single treatment per plot, was simulated on the basis of climatological data averaged from 30 years records. Simulated acid rain(pH 2.0, pH 4.0, and pH 5.5 as control) containing sulfuric and nutric acid in the ratio of 3 : 2(chemical equivalant basis) diluted with ground water were treated on the experimental plants under condition of cutting off the natural precipitation with vinyl tunnel, during the growing season(May 1 to August 31) in 1986. The results obtained in this study were as follow : (1) As for the nitrogen contents in plant tissues, P. densiflora increased significantly in one-year-old stembranch and root tissues, and F. koreana increased significantly in leaf and root tissues, as the pH levels of acid rain decreased. (2) The available phosphate contents in root tissues of P. densiflora, and in leaf and root tissues of F. koreana were significantly decreased, as the pH levels of acid rain decreased. (3) $K_2O$, CaO and MgO contents in plant tissues were significantly decreased in the both species as the pH levels decreased. And the effects of acid rain on F. koreana were higher than those of P. densiflora. (4) Sulfur contents of plant tissues in the both species were increased at pH 2.0 treatment. There were significant differences among three acid rain treatments in leaf and root tissues of P. densiflora, and in all parts of F. koreana. (5) In the effects of simulated acid rain on the both species and the tested soils, in general, F. koreana revealed higher sensitiveness than P. densiflora, and the lower pH levels of simulated acid rain were treated, the more sharp reaction was showed.

• Tuberculosis and Respiratory Diseases
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• v.50 no.1
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• pp.29-41
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• 2001

Background : The appearance of multiple-drug-resistant Mycobacterium tuberculosis strains has been seriously compromising successful control of tuberculosis. Rifampin-resistance, caused by mutations in the rpoB gene, can be indicative of multiple-drug-resistance, and its detection is of great importance. The present study aimed to develop an oligonucleotide chip for accurate and convenient screening of drug-resistance. Methods : In order to detect point mutations in the rpoB gene, an oligonucleotide chip was prepared by immobilizing specific probe DNA to a microscopic slide glass by a chemical reaction. The probe DNA that was selected from the 81 bp core region of the rpoB gene was designed to have mutation sites at the center. A total of 17 mutant probes related to rifampin-resistance including 8 rifabutin-sensitive mutant probes were used in this study. For accurate determination, wild type probes were prepared for each mutation position with an equal length, which enabled a direct comparison of the hybridization intensities between the mutant and wild type. Results : Mycobacterial genomic DNA from clinical samples was tested with the oligonucleotide chip and the results were compared with those of the drug-susceptibility test in addition to sequencing and INNO-LiPA Rif. TB kit test in some cases. Out of 15 samples, the oligonucleotide chip results of 13 samples showed good agreement with the rifabutin-sensitivity results. The two samples with conflicting result also showed a discrepancy between the other tests, suggesting such possibilities as existence of mixed strains and difference in drug-sensitivity. Further verification of these samples in addition to more case studies are required before the final evaluation of the oligonucleotide chip can be made. Conlcusion : An oligonucleotide chip was developed for the detection of rpoB gene mutations related to drugsusceptibility. The results to date show the potential for using the oligonucleotide chip for accurate and convenient screening of drug-resistance to provide useful information in antituberculosis drug therapy.

• Journal of Life Science
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• v.19 no.7
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• pp.839-844
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• 2009

This experiment was conducted to evaluate pollen viability of Nakdongbyeo, transgenic rice lines, an F$_1$ hybrid from a cross between Milyang weedy rice and ABC-promoter transgenic rice line containing basta-resistant (bar) gene and subsequent selfed progenies, F$_2$ and F$_3$. The reaction of pollen with 3-{4,5 dimethylthiazolyl-2}-2,5-diphenyl monotetrazolium bromide (MTT) as a staining chemical immediately after pollen shedding showed maximum pollen viability of 86% in Nakdongbeyo, 75% in ABC-promoter transgenic rice line, 62% in ubiquitin-promoter transgenic line, 68% in F$_1$, 79% in F$_2$ and 78% in F$_3$. Viability gradually declined during subsequent observations at 20-minute intervals. However, there was a drastic decline in pollen viability after 40 minutes of pollen shedding. The mean difference of pollen viability among rice lines and time was highly significant, indicating significantly different pollen viabilities at different time intervals. Maximum viability of 36.2% was observed in F$_3$ and minimum viability of 3.5% was found in F$_2$ at 90 min after pollen shedding. Results of this experiment on pollen viability and longevity elucidate potential risks of pollen-mediated flow of herbicide-resistant gene from transgenic rice lines and possible integration of it into the weedy rice population.

• Journal of the Korean Electrochemical Society
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• v.8 no.3
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• pp.139-145
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• 2005

[ $SnO_x$ ] films on the flexible substrate of PET film were prepared at ambient temperature under a $(CH_3)_4Sn(TMT: tetra-methyl tin)-H_2-O_2$ atmosphere in order to obtain transparent conductive polymer by using ECR-MOCVD(Electro Cyclotron Resonance Metal Organic Chemical Yfpor Deposition) system. The prepared $SnO_x$ thin films show generally over $90\%$ of optical transmittance at wavelength range of 380-780nm and about $1\times10^{-2\~3}ohm{\cdot}cm$ of electrical resistivity. In the present study, effects of $O_2/TMT\;and\;H_2/TMT$ mole ratio on the properties of $SnO_x$ films are investigated and the other process parameters such as microwave power, magnetic current power, substrate distance and working pressure are fixed. Based on our experimental results, the $SnO_x$ film composition ratio of Sn and O directly influences on the electrical and optical properties of the films prepared. The $SnO_x$ film with low electric resistivity and high transmittance could be obtained by controlling the process parameters such as $O_2/TMT\;and\;H_2/TMT$ mole ratio, which play an important role to change the composition ratio between Sn and O. An increase of $O_2/TMT$ mole ratio brought on the increases 0 content in the $SnO_x$ film. On the other hand, an increase of $H_2/TMT$ mole ratio lead to decreases the oxygen content in the film. The optimized composition ratio of oxygen : tin Is determined as 2.4: 1 at $O_2/TMT$ of 80 and $H_2/TMT$ of 40 mole ratio, respectively.

• Economic and Environmental Geology
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• v.37 no.3
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• pp.303-309
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• 2004

Pyrochlores were known as promising materials for the immobilization of radioactive actinide. Accordingly, we synthesized pyrochlores with Gd$_2$Ti$_2$$O_7$ and Gd$_2$Zr$_2$$O_7$compositions by sintering method, and studied its properties and phase relations in Gd-Ti-O and Gd-Zr-O system. The mixed powders were pressed into pellets under 200-400 kgf/cm$^2$ at room temperature. and then sintered at 1000-1$600^{\circ}C$ for 0.5-40 hours. The synthesized samples were analyzed and were identified with XRD and SEM/EDS analyses. The optimal synthetic conditions of pyrochlores with Gd$_2$Ti$_2$$O_7$composition were at 140$0^{\circ}C$/0.5hrs, 130$0^{\circ}C$/3hrs and 120$0^{\circ}C$/20hrs. Its chemical composition was $Gd_{2.0-2.1}$$Ti_{1.9-2.0}$$O_7$ and similar to the stoichiometric composition without any relationship in temperature and atmosphere. The optimal synthetic conditions of pyrochlores with $Gd_{2}$$Zr_{2}$$O_7$composition were at 155$0^{\circ}C$/40hrs and 1$600^{\circ}C$/30hrs. The compositions of pyrochlore synthesized from these optimal conditions were irregular with $Gd_{1.5-2.4}$$Zr_{1.7-2.4}$$O_7$. Such heterogeneity indicates that the reaction rate of pyrochlore with Gd$_2$Zr$_2$$O_7$composition is very low, and then its equilibrium state could not be attained even for 40 hours which was the longest sintering time in this research.

• Korean Journal of Soil Science and Fertilizer
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• v.6 no.2
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• pp.75-81
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• 1973

The morphological, physical, and chemical properties of Sonjeong series derived from acidic crystalline rocks are presented. Also it deals with the genesis and classification of the Songjeong series. Morphologically these soils have brown to dark brown loam A horizons and yellowish red to red clay loam Bt horizons with moderate, medium subangular blocky structure and thin patchy clay cutans on the ped faces. C horizons are very deep, yellowish red to yellowish brown fine sandy loam or sandy loam with original rock structure. Physically distribution of particle size indicates that clay increases with depth up to argillic horizons but below the argillic horizons clay content decrease. The moisture holding capacity is fairly good in Songjeong soils. Chemically soil reaction is strongly to very strongly acid throughout the profile and content of organic matter is less than 1 per cent except A horizons. Cation exchange capacity ranges from 5 to 9 me/100g of soils and base saturation is less than 35 per cent throughout the profile. The natural fertility of Songjeong soils are usually low. It needs lime, organic matter, and heavy application of fertilizer for the crop land. These soils occur temperate and humid climate under coniferous, deciduous, and mixed forest vegetation. Songjeong soils are classified as Red-Yellow Soils. Characteristically Songjeong soils are similar to Red-Yellow Podzolic soils in the United States but lack of A2 horizons and are quite liket Red-Yellow Soils of the Japan. According to new classification system which is 7th approximation of USDA Songjeong soils can be classified as fine loamy, mesic family of Typic Hapludults and in the FAO/UNESCO project World Soil Map as Orthic Acrisols.