• Journal of the Korean Crystal Growth and Crystal Technology
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• v.4 no.1
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• pp.11-20
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• 1994

GaAs and AlGaAs epi-layers were grown on semi-insulating (100) GaAs substrate by molecular beam epitaxy (MBE) and their electrical and optical properties have been investigated by several measurements. In undoped GaAs, the p-type GaAs layers with the good surface morphology were obtained under the growth conditions of the substrate temperatures ranging from 570 to $585^{\circ}C$ and the $As_4$/Ga ratios from 17 to 22. In the samples with the growth rates of the ranges of $0.9~1.1 {\mu}m/h$, the impurity concentrations were in the ranges of $1.5{\times}10^{14}~5.6{\times}10^{14}cm^{-3}$ with the Hall mobilities of $590~410cm^2/V-s$. In the Si-doped GaAs, the n-type GaAs layers with low electro trap, only two hole deep levels were observed with uniform doping profiles (<1%). AlGaAs layers with good surface morphology and crystallinity were grown under an optimum condition of the substrate temperature, $600^{\circ}C $. 8 deep level defects were observed between 0.17~0.85eV in undoped AlGaAs layers.

• Korean Journal of Food Science and Technology
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• v.35 no.5
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• pp.914-917
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• 2003

This study was undertaken to find the optimum condition for the Maillard browning reaction of tagatose and glycine model solution by applying the response surface methodology. Independent variables were pH (3, 5, 7), temperature (70, 85, $100^{\circ}C$), and time (60, 180, 300 min), while the dependent variables were absorbance, yellowness, color difference, and organoleptic score. The quadratic models with the cross-product proved to be suitable, due to the high coefficients of determination and the lack of fit results. Since all the dependent variables had saddle points, the optimal points were determined through ridge analysis. For absorbance, yellowness, and color difference, the optimal points were the lowest values; in contrast, the optimal point of organoleptic score was the highest value.

• Korean Journal of Microbiology
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• v.45 no.4
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• pp.362-367
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• 2009

Among total 176 strains with antialgal effects isolated from So-ok stream in Korea, Pseudomonas aeruginosa AJ1 showed the highest removal efficiency for an algal species Microcystis aeruginosa (clear zone of diameter 50.0 mm on algal lawn after 20 days). The algal growth was suppressed even when the supernatant of AJ1 culture was applied, suggesting that extracellular substances are responsible for its antialgal activity. The removal activity of AJ1 was optimal under the following condition: pH 8, $30^{\circ}C$, and mannitol as a carbon source. The antialgal activity of AJ1 appeared to be dependent of the growth phase of M. aeruginosa, i.e., the highest at the early phase, but not its own phase. As expected, the algicidal effect was improved as the amount of the treated supernatant was increased; the highest removal efficiency (80.3%) was achieved when 40 ml/L of the supernatant was used. Interestingly, however, the removal rate was opposite. The highest removal rate ($8.2{\mu}g$ chl-a/ml supernatant/day) was achieved when low concentration (10 ml/L) was applied. These results suggest that P. aeruginosa AJ1 is a promising biological agent to control the problematic algal bloom.

• Korean Journal of Ecology and Environment
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• v.47 no.spc
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• pp.74-82
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• 2014

A perennial plant species of Ranunculaceae, Pulsatilla tongkangensis is a very rare species only found in limestone vegetation of South Korea. It is not only rare but also has great value as a horticultural resource, thus resulting in serious problems of overexploitation and habitat disturbance. For the conservation of the rare species and its development as a resource, the study was conducted with the following three aims: first, to investigate any new geographical distribution of the species; second, to identify the site condition and vegetation structure of its habitat; and third, to compare the ecology of P. tongkangensis in other microhabitats such as rock, slope and ridge area. A new distribution was found in limestone vegetation at Danyang-gun, Chungcheongbuk-do. It was, therefore, confirmed that the distribution of P. tongkangensis exactly coincides with the area of distribution of limestone, indicating a possibility that the species might be a calcicole. 87% of the microhabitats found in rocks. Compared to P. tongkangensis, at ridges or slopes, number of P. tongkangensis plants were few in rocks. It is possibly due to the lack of microhabitats that could settle in rocky areas. Once established on rocks, however, plants grew large enough to flower with higher number of leaves and flowers per plant, resulting in higher flowering rate on rocky areas. Cracks in/between rocks are likely to be safe places for the plants with favorable light conditions, abundant fine particles to root down and reduced competition for resources. Yet, further research is necessary in terms of determining whether the species is indeed a calcicole, whether other limiting factors work in its establishment stage, and genetic diversity exists in the population.

• Applied Chemistry for Engineering
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• v.32 no.3
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• pp.320-325
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• 2021

In this study, an optimization for the production of water emulsion was designed by adding an extract of wheat sprout, which is known to contain a large amount of antioxidants. The central composite design of reaction surface analysis method (CCD-RSM) was used for the optimization process. The amount of emulsifier, emulsification time, and added amount of wheat sprout extract were selected as independent variables based on our preliminary experiments. The mean droplet size (MDS), viscosity, and emulsion stability index (ESI) were set as the responses to evaluate the stability of the emulsion. For each independent variable, the P-value and coefficient of determination were evaluated to verify the reliability of the experiments. From the result of CCD-RSM, optimum conditions for the emulsification were determined as 23.6 min, 7.7 wt.%, and 3.9 wt.% for the emulsification time, amount of emulsifier, and amount of sprout, respectively. From the optimized condition obtained, MDS, viscosity, and ESI after 7 days from reaction were estimated as 252.3 nm, 616.7 cP, and 88.7%, respectively. The overall satisfaction was 0.9137, which supported the validity of the experiments, and the error rate was measured at 0.5% or less by advancing the experiments. Therefore, an optimized process for producing an emulsion by adding the malt extract was designed by the CCD-RSM.

• Journal of the Mineralogical Society of Korea
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• v.23 no.1
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• pp.1-13
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• 2010

The Yugeum deposit in Youngduk in Gyungsangbuk-do is emplaced in the Cretaceous granitoids located in the Northeastem Gyeongsang Basin. Gold-bearing quartz veins filling the fracture with a direction of $N19^{\circ}{\sim}38^{\circ}W$ are most abundantly distributed within the Younghae granodiorite body. The formation of quartz veins can be classified into three main stages: barren quartz stage, auriferous quartz vein stage, and finally the extensive sulfide mineralization stage. Various sulfide minerals such as pyrite, chalcopyrite, galena, sphalerite, and arsenopyrite were precipitated during the hydrothermal gold mineralization process. Gold commonly occurs as fine-grained electrum in sulfides with high Au concentration (up to 93 wt%) compared to Ag. During the early gold mineralization stage, the temperature and pressure of the fluids are in the range of $220{\sim}250^{\circ}C$ and 730~1800 bar, and the oxygen fugacity is between $10^{-27}$ and $10^{-31.7}$ atm. On the other hand, the fluids of the late stage mineralization are characterized by temperature of $290{\sim}350^{\circ}C$ and pressure of 206~472 bar, and the oxygen fugacity is in the range of $10^{-26.3}{\sim}10^{-28.6}$ atm. The sulfur isotope compositions of sulfide minerals are in the range of $0.2{\sim}4.2^{\circ}/_{\circ\circ}$, while the ${\delta}^{34}SH_2S$ values range from 1.0 to $3.7^{\circ}/_{\circ\circ}$. The Ag/Au atomic ratios of electrum ranges from 0.15 to 1.10, and Au content is higher than Ag in most electrum. During the main gold mineralization stage at the relatively high temperature condition and with pH from 4.5 to 5.5, the stability of ${AuCl_2}^-$ increased while the stability of ${Au(HS)_2}^-$ decreased. Considering the pressure estimated in this deposit, the temperature of the ore fluid reached higher than $350^{\circ}C$ and ${AuCl_2}^-$ became an important species for the gold transportation. As mineralization proceeded with decreasing temperature and increasing pH and $f_{o2}$, the precipitation of sulfide minerals and accompanying electrum occurred.

• Journal of the Korean Society of Clothing and Textiles
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• v.32 no.12
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• pp.1963-1970
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• 2008

Natural indigo dye in powder form was prepared by modifying traditional Niram method, using $Ca(OH)_2$ instead of baked oyster powder for precipitating indigo dye. The prepared dye was applied to dyeing Tencel fabrics to investigate the effect of experimental conditions for the optimization of dyeing process. The indigo dye powder contained 15.2%(w/w) of indigo content and 0.757%(w/w) of indirubin content on the basis of HPLC analysis. Maximum dye uptake was obtained at $60^{\circ}C$ for 20min. Almost saturated dye uptake was obtained at 2g/L of sodium hydrosulfite concentration up to 4g/L of indigo dye and then slowly increased for further increase of sodium hydrosulfite. Whereas at higher indigo dye concentration(8g/L) more than 3g/L of reducing agent concentration was required for obtaining the maximum dye uptake. At the same indigo dye and reducing agent concentration, K/S value of the sample dyed without sodium hydroxide(pH 5.75) was 15.19, much higher than one dyed in alkaline condition(K/S 5.76). There was no difference in colorfastness ratings among samples with different color strength. However, more fading was occurred for the sample with low color strength.

• Microbiology and Biotechnology Letters
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• v.14 no.2
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• pp.125-131
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• 1986

In order to obtain the optimum conditions for intact yeast cell transformation in the various yeast host-vector systems, 3 yeast plasmid vectors, YRp7, YEpl3 and YIp5 were introduced into 5 yeast hosts, Saccaromyces cervisiae Dl3-1A, DKD-5D, DBY-746, MC-16 and S2022D with various transformation conditions, and plasmid stabilities in all the transformants were also observed. The highest transformation frequencies in all the host-vector system were obtained in the 16 hour Cultured cell (5.4 $\times$ 10$^6$ - 2.4 $\times$ 10$^8$cells/$m{\ell}$) treated with 0.1-0.2 M lithium chloride in 0.1 M tris-HCl (pH 7.6), 35% polyethylene glycol 4000, and heat-shocked at 42$^{\circ}C$ for 5 minutes after 60 minutes of induction. The intact cell transformation got more transformation frequency in DKD-5D (YRp7) and DBY-746 (YEpl3) than protoplast transformation, but reverse tendency was observed in DKD-5D (YEp13) and Dl3-lA (YRp7). The transformants, D13-1A (YRp7) and DKD-5D (YRp7) were very unstable in selective medium, with 80 to 85% of the transformants losing the plasmid after 70 generations, but the transformants, DKD-5D (YEpl3) and DBY-746 (YEpl3) were quite stable, with 35% of the transformants losing the plasmid.

• Korean Journal of Food Science and Technology
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• v.25 no.6
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• pp.794-800
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• 1993

A lipid producing yeast was screened from leaves of Albabiscus and was identified as a Rhodotorula graminis SW 214. During the shakining incubation of 8 days at $25^{\circ}C$, the yeast produced extracellular lipids of 7.3g/l of the media. The relative concentration of carbon and nitrogen sources in the media influenced the extracellular lipid production greatly. When with nitrogen sources in the media were almost exhausted for growth of the yeast the sufficient carbon sources, the lipid production proceeded vigorously. Eight days of batch cultivation with 8% glucose, 2.5g/l of yeast extract, $KH_{2}PO_{4}(1g/l)\;MgSO_{4}\;(0.2g/l)$ and pH 6 gave maximum biomass and extracellular lipid production of 8.05g/l and 8.89g/l, respectively. The acid value, saponificatio value, the iodine value, ad the unsaponifiable matter of the extracellular lipids of Rhodotorula graminis SW 214 were 2.6, 534, 5.1 and 2.4, respectively. Lipid was constituted 75.2% triglyceride, 5.9% free fatty acid, 10.8% phospholipid, 4.9% esterified sterol and 3.3% free sterol. Major fatty acids found were 3-hydroxypentadecanoate, 3-hydroxyhexadecanate, trans-9-octadecanate, cis-9-hexadecanate (hydroxy palmitic), 15-methylhexadecanate (oleic), 18-methylno-nadecanate, octadecanate (stearic) and 3-hydroxytridecante.

• Korean Journal of Agricultural and Forest Meteorology
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• v.6 no.3
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• pp.183-189
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• 2004

This study was conducted to examine the changes in the seed physical characters and germinative properties of three tree species at three different storage times in order to determine the most suitable storage time and condition. Seed physical characters and germinative properties were examined from seeds of Fraxinus rhynchophylla, Zanthoxylum schinifolium and Staphylea bumalda that were stored at -18C for 1, 3 and 10 years, and the growth performance and physiological characters of their seedlings were analyzed. Seed physical characters and germinative properties showed significant differences between three storage times as well as three tree species. Seed moisture content of F rhynchophylla and S. bumalda and seed fresh weight of Z. schinifolium decreased with increase of storage time. Storage time represented negative correlation with moisture content and fresh weight (r = -0.822, P<0.01). Seed percent germination of Z. schinifolium and S. bumalda stored for 3 and 10 years decreased less than 15% and 10.7% respectively. Mean germination times for seed of F. rhynchophylla, Z. schinifolium and S. bumalda were delayed 11.9, 5.7 and 9.7 days after a storage time of 10 years, respectively. However the growth and viability of seedlings didn't show a special pattern for storage time and tree species.