• KSBB Journal
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• v.11 no.5
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• pp.600-605
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• 1996

Optimum inoculum concentration for the production of taxol was determined in Taxus brevifolia and Taxus cuspidata cell suspension cultures. By fresh weight, 2.5, 5, 7.5, 10 g/flask of cells were inoculated and cell growth as well as taxol production were examined. In both Taxus cell cultures, the higher the inoculum concentration, the shorter the length of the lag period. The optimum inoculum concentration for taxol production was found to be 5 g/flask. To produce taxol in large quantity, utilization of proper medium was thought to be important. In case of using a production medium with 6% sucrose, taxol production was noticed. Its level reached the maximum at the 9th day of culture and decreased afterwards. However, taxol was not detected from cell cultures in growth medium.

• Applied Chemistry for Engineering
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• v.32 no.5
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• pp.581-588
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• 2021

In this study, soil slurry bioreactors were used to treat soils containing 16 polycyclic aromatic hydrocarbons (PAHs) for 35 days. Five different soil samples were taken from manufactured gas plant (MGP) and coal tar disposal sites. Soil properties, such as carbon content and particle distribution, were measured. These properties were significantly correlated with percent biodegradation and degradation rate. The cumulative amount of PAH degraded (P), degradation rate (K_m), and lag phase (𝜆) constants of PAHs in different MGP soils for 16 PAHs were successfully obtained from nonlinear regression analysis using the Gompertz equation, but only those of naphthalene, anthracene, acenaphthene, fluoranthene, chrysene, benzo[k]fluoranthene, benzo(a)pyrene, and benzo(g,h,i)perylene are presented in this study. A comparison between total non-carcinogenic and carcinogenic PAHs indicated higher maximum amounts of PAH degraded in the former than that in the latter owing to lower partition coefficients and higher water solubilities (S). The degradation rates of total non-carcinogenic compounds for all soils were more than four times higher than those of total carcinogenic compounds. Carcinogenic PAHs have the highest partitioning coefficients (K_oc), resulting in lower bioavailability as the molecular weight (MW) increases. Good linear relationships of K_m, 𝜆, and P with the octanol-water partitioning coefficient (K_ow), MW, and S were used to estimate PAH remaining, lag time, and biodegradation rate for other PAHs.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.5 no.4
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• pp.406-413
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• 1993

Among 2-dimensional coastal hydrodynamic finite element models time stepping ADCIRC and STEPM. and harmonic FUNDY and TEA models were compared in order to find out their characteristics and analyze ernr. General feasibility and capability of models were studied by comparing model results with an analytical solution on some reference points and L$_2$norm error in quarter annular domain where analytical solution can be obtained. According to these tests harmonic models FUNDY and TEA were nearly coinciding with analytical solutions and gave better results than time stepping models. STEPM was at least 5 times better than ADCIRC in L$_2$norm error test and it was 7 times worse than harmonic models. It was expected and concluded that these errors might come from phase lag due to cold start condition and nonlinear effect in basic equations of time stepping models.

• Journal of Microbiology and Biotechnology
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• v.7 no.4
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• pp.267-271
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• 1997

We developed a dermal equivalent (DE) which was engineered using human dermal fibroblasts and a matrix of collagen gel. The in vitro construction of the DE was accomplished by casting a porcine collagen type I solution plus concentrated medium with isolated and cultured fibroblasts. These constructs were attached to culture dishes or left floating in culture medium. Contraction of attached gels results in decreased gel thickness without a change in gel diameter, and contraction of floating gels results in decreased gel thickness and diameter. After contraction, there was no increase in cell number in floating gels, but cells in attached gels began to increase after about 4 days of the lag phase in cell growth curve. At this lag phase, addition of fibroblast growth factor (FGF) at a concentration of $0.1{\mu}$/ml promoted cell proliferation in the attached collagen gels, but no effect in floating gels. These results indicate that the method of contraction had an influence on the extracellular matrix (ECM) organization, and this influenced not only cell growth but also fibroblast responsiveness to FGF. This suggests that attached collagen gel is more suitable as a dermal equivalent than the floating gel. And the final contracted area of attached gel is much larger than that of the floating gel since floating gel is contracted in all directions but attached gel is contracted only vertically.

• Journal of Soil and Groundwater Environment
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• v.21 no.3
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• pp.82-87
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• 2016

This study investigates effects of an aging period on arsenic (As) chemical forms in soils and phytotoxicity using artificially As-contaminated soils with a range of As concentrations (0-300 mg/kg) and aging periods (0 and 3 months). A sequential extraction procedure showed that the increasing As concentration in soils increased the ratio of non-specifically and specifically bound As, which are known to be bioavailable. This resulted in increasing As uptake by tomatoes with increasing As concentration (R²=0.87 for exponential fitting); however, the seed germination was not sensitive to the As concentrations of the soil samples. The seed germination was also statistically similar in the soils with 75 and 150 mg-As/kg regardless of the aging period. The time taken until the seed germination (i.e., lag phase), on the other hand, decreased from 10 d to 3 d with aging for 3 months. This can be attributed to the decreased amount of bioavailable As with aging. Overall, this study shows that when the toxic effects of the As-contaminated soils are assessed using tomato plants, it is better to use more sensitive methods than seed germination such as the As accumulation or the lag phase for seed germination.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.3
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• pp.927-935
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• 2013

In this study, reservoir routings for 1 hour-50 year precipitation frequency were carried out at the Engineering Water Fall and the Amphitheater located at the downstream of Seoul National University Dam. Main analysis was focus on the following matters: (1) storage amount by the tank; (2) reduction of the outflow and the peak water surface elevation; (3) change of phase lag time; and (4) design of new boxes at the inlet and outlet of storage tank. As for the storage tank of $25,000m^3$ built in the Amphitheater area, the tank induced 49.43 % storage effect, 28 min. phase lag time, and reduced the peak outflow by 49.64 %. In addition, the peak water surface elevation was lowered by 35 cm compared with that of $15,000m^3$ storage tank. It is concluded that combined management of previous storage facility and new underground storage tank would control the excessive rainfall runoff efficiently.

• Journal of the Korea Organic Resources Recycling Association
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• v.21 no.2
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• pp.88-96
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• 2013

The objective of this research was to evaluate the suitability of sigmoidal and firstorder kinetic equations for simulating the methane production from solid wastes. The sigmoidal kinetic equations used were modified Gompertz and Logistic equations. Statistical criteria used to evaluate equation performance were analysis of goodness-of-fit (Residual sum of squares, Root mean squared error and Akaike's Information Criterion). Akaike's Information Criterion (AIC) was employed to compare goodness-of-fit of equations with same and different numbers of parameters. RSS and RMSE were decreased for first-order kinetic equation with lag-phase time, compared to the first-order kinetic equation without lag-phase time. However, first-order kinetic equations had relatively higher AIC than the sigmoidal kinetic equations. It seemed that the sigmoidal kinetic equations had better goodness-of-fit than the first-order kinetic equations in order to simulate the methane production.

• Journal of Wetlands Research
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• v.14 no.2
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• pp.289-301
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• 2012

Tidal artificial lake capable of inflow and outflow of seawater is planned for waterfront and eco-friendly space at Songdo, Incheon, Korea. This study for hydrodynamic behaviors of tidal artificial lake was carried out and predicted about water level and velocity within the lake corresponding to width of channel or waterway using by 1 dimensional numerical model(CEA) and 2 dimensional numerical model(FLOW2DH). As a result, the proper width, 100.0m of the channel between the lake and the open sea was calculated reasonable conclusions such as tidal phase lag and maximum velocity from CEA. Also, water level and velocity of each point within the lake was predicted and compared to the measured data from FLOW2DH. FLOW2DH was added to the gate control case for maintenance and administration purpose of the lake and obtained the results that the velocity was decreased by approximately 20% at flood and 50% at ebb than the case without gate control.

• Korean Journal of Environmental Agriculture
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• v.16 no.4
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• pp.341-346
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• 1997

The degradation of fungicide oxadixyl in soil amended with manure, chemical fertilizers, heavy metals and detergent was studied. The degradation of oxadixyl in the soil was slow, but became to be fast after the lag phase of about 14 days. The half-life was 10.5 days. The degradation rate was accelerated largely by the amendment of manure. Potassium also promoted the degradation rate but nitrogen and phosphate did not. The heavy metals inhibited the degradation rate, in order of Ni, Cd, Cr, Cu, and Zn. The degradation rate was declined greatly with the addition of synthetic detergent. The microbial biomass and the respiration rate in the soil were increased by the amendment of manure and chemical fertilizers, but decreased by the addition of heavy metals and cleaner. The degradation rate of oxadixyl was positively correlated with the microbial biomass and the respiration rate.

• Ocean and Polar Research
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• v.41 no.3
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• pp.203-211
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• 2019

Diatom growth is affected by associated bacteria that probably provide useful substances like vitamins. In the present study, we analysed the variation of vitamins $B_1$, $B_7$ and $B_{12}$ on the growth stages of the marine diatom Cyclotella meneghiniana and assessed putative vitamin-producing bacteria (e.g., ${\alpha}$- and ${\gamma}$-proteobacteria). HPLC analysis showed that total amounts of vitamins $B_1$ and $B_{12}$ decreased with cell growth, whereas vitamin $B_7$ increased gradually on the growth stages. $B_1$ and $B_{12}$ measured 0.5% and 0.18% at the stationary phase, following 0.25% and 0.72% at the lag phase. They considerably increased to 0.75% and 0.77% at the death stage. 16S pyrosequencing showed relatively high ratios of ${\alpha}$- and ${\gamma}$-proteobacteria in all the growth stages of the C. meneghiniana. In addition, we detected previously-reported vitamin-producing bacteria, such as Marinobacter, in high numbers. The species was dorminant in the lag (relative abundance 72%) and exponetial (72%) stages, whareas it decreased in the stationary (49%) and death (48%) stages. These results suggest that vitamins $B_1$ or $B_{12}$ may be necesaary for diatom growth and that associated bacteria, including Marinobacter, may produce these substances for the cell growth of C. meneghiniana.