• Journal of Korean Society on Water Environment
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• v.31 no.4
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• pp.399-406
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• 2015

A sequencing batch reactor was operated under different pH conditions to see the influence of free ammonia (FA) and free nitrous acid (FNA) to microbial community on ammonium partial nitrification. Long-term influences of FA and FNA were evaluated by polymerase chain reaction-denaturing gradient gel electrophoresis and fluorescence in situ hybridization. Nitrite accumulation was successfully achieved at pH 8.2 and 6.3. The shifts in the microbial community were observed when influent ammonia concentration increased to 1 g $NH_4$-N/L at pH 8.2, and then when pH was dropped to 6.3. Both Nitrosomonas and Nitrosospira were selected during the startup of the reactor, and eventually became dominant members as ammonia-oxidizing bacteria. The results of molecular microbiological analysis strongly suggested that the composition of microbial community was changed according to the method used to control nitrite-oxidizing bacteria.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.339-340
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• 2007

Gradient system에 spiral waveform 입력을 가하면 Hardware limitation에 의하여 만들어지는 gradient fields에 Transient time delay가 발생한다. 이를 보상하기 위하여, Gradient system을 R-L-C 회로로 모델링하여 재구성에 필요한 k-space trajectory를 보정하여 개선된 image를 획득하였다.

• Communications of the Korean Mathematical Society
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• v.31 no.3
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• pp.625-635
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• 2016

In this paper, we study certain doubly-warped products which admit gradient Ricci solitons with harmonic Weyl curvature and non-constant soliton function. The metric is of the form $g=dx^2_1+p(x_1)^2dx^2_2+h(x_1)^2\;{\tilde{g}}$ on ${\mathbb{R}}^2{\times}N$, where $x_1$, $x_2$ are the local coordinates on ${\mathbb{R}}^2$ and ${\tilde{g}}$ is an Einstein metric on the manifold N. We obtained a full description of all the possible local gradient Ricci solitons.

• Journal of Embryo Transfer
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• v.14 no.1
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• pp.23-29
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• 1999

The objectives of the study were to establish sperm separation method and duration of insemination for bovine IVF. Oocytes from slaughterhouse ovaries were matured and fertilized using general protocol. After 18 or 42 h of insemination, six to ten embryos were placed into a 30${mu}ell$ drop of each medium, and the embryos were examined 7~10d post in semination without medium renewal. First, we compared Percoll gradient will swim-up technique for sperm separation. There was no difference in cleavage rates between them, but the development rates over morula stage of oocytes fertilized with sperm separated by Percoll gradient was significantly higher than that sperm selected by swim-up technique (p<0.05). Second, we evaluated development of bovine embryos derived from the IVF procedure with different durations(18 vs 42 h) of fertilization. There was also no difference in cleavage rates, but the development to blastocyst stage of oocytes exposed in cleavage rates, but the development to blastocyst stage of oocytes exposed to sperm for 42 h was significantly higher than that exposed for 18 h (p<0.05). In conclusion, Percoll gradient can be used for sperm selecton, improving of embryonic development. Also, 42h of IVF may improve the development of bovine embryos.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.5
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• pp.513-523
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• 2017

We evaluated the viability of phytoplankton along the salinity gradient in the flood and ebb tides of spring tide of February and the ebb tide of neap tide of March 2017 in the Seomjin River Estuary. Additional laboratory experiments were also conducted to determine the reason of the pH changes along the salinity gradient using the field natural sample in February. In field, saltwater was well mixed at downstream vertically and the salinity gradient was horizontally appeared toward upstream of freshwater zone. There were strong negative correlations between salinity and nutrient (nitrate + nitrite R=0.99, p<0.001, and silicate R=0.98, p<0.001), implying that those two nutrients of freshwater origin were gradually diluted with mixing the saltwater. On the other hands, relatively high phosphate concentration was kept in the stations of saltwater over 15 psu, indicating that it was caused by resuspended sediments of Gwangyang Bay and downstream by tidal water mixing.Among phytoplankton community structure in winter, Eucampia zodiacus have occupied to be c.a. 70 % in the most stations. Based on the field survey results for survivability of phytoplankton by phytoPAM instrument, there was positive correlations between salinity and chlorophyll a (R=0.82, p<0.001) and, salinity and active chlorophyll a (R=0.80, p<0.001), implying that the dominant marine diatom species may have significantly damaged in low salinity conditions of upstream. Also, maximum mortality rate of phytoplankton caused by low salinity shock was appered to be 75% in the upstream station. In particular, the pH in spring tides of February had tended to increase with high phytoplankton accmulated stations, suggesting that it was related with absorption of $CO_2$ by the photosynthesis of dominant diatom. In laboratory experiments, phytoplankton mass-mortality caused by low salinity shock was also occurred, which is confirmed with reducing the photosynthetic electron transport activity. Following the phytoplankton mass-mortality, bacteria abundance was significantly increased in 24 hours. As a result, the mass-proliferating bacteria can produce the $CO_2$ in the process of biodegradation of diatoms, which can lead to pH decrease. Therefore, marine phytoplankton species was greatly damaged in freshwater mixing area, depending on along the salinity gradient that was considered to be an important role in elevating and reducing of pH in Seomjin River Estuary.

• Korean Journal of Food Science and Technology
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• v.20 no.6
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• pp.856-861
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• 1988

A new method developed for simultaneous purification of enterotoxin A and C from Staphylococcus aureus strain L 350/1 consisted of chromatography on carboxymethyl (CM)-cellulose using a buffer of variable pH, gel filtration on Ultro gel, and fast protein liquid chromatography(FPLC) using a buffer of variable pH. The enterotoxin A and C were purified by three steps: batchwise adsorption from culture supernatant on Amberlite CG-50; chromatography on CM-cellulose using a buffer of constant pH and molarity; and gel filtration on Sephadex G-75. The purified enterotoxin appeared homogeneous by gel diffusion and polyacrylamide gel electrophoresis. Upon treatment with CM-cellulose using a elution of variable pH, enterotoxin A and C were so close that they were not separated completely. After elution from gels, the enterotoxins appeared as a single peak at the same position. Gel filtration gave a reaction of complete identity to enterotoxin A and C in Ouchterlony immunodiffusion. In FPLC using a CM-cellulose, enterotoxin A and C were simultaneously separated at pH 8.6 and 6.8. When each fraction was performed to gel immunodiffusion, at peak of enterotoxin A and C were not detected each other. In a method of elution by pH-gradient was to be more efficient as a simultaneous separation method in terms of speed, yields and simplicity. The purified toxin A and C were identical to type A and C reference enterotoxin on both disc electrophoresis and Ouchterlony gel diffusion.

• Journal of Plant Biology
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• v.37 no.3
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• pp.271-276
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• 1994

The possibility that 1-aminocyclopropane-1-carboxylic acid (ACC)-uptake may be dependent on the H+-gradient established across the plsma membrane was tested in protoplasts isolated from 2.5 day old mungbean hypocotyls. The ACC-induced ethylene production was inhibited when the H+-gradient was collapsed by the treatment with carbonycyamide-p-trifluro-methoxy-phenylhydrazone (FCCP). Moreover, the treatment with o-vanadate, a specific inhibitor of plasma membrane H+-ATPase, caused the inhibition of ethylene production. The ACC-induced ethylene production was inhibited by the treatemnt with verapamil (Ca2+-channel blocker), or ethylene glycol-bis($\beta$-aminoethyl ether) N, N, N', N'-tetraacetic acid (EGTA) (Ca2+-chelator). In contrast, the ehtylene production was stimulated by the application of A23187 (Ca2+ ionophore). The inhibitory effect of EGTA in the ethylene producton was magnified in the presence of A23187. From these results, we suggest that the external Ca2+ influx to the cytosol resulted in the stimulatin of ACC oxidase activity after ACC-uptake resulting from a H+-gradient across the plasma membrane.

• Geomechanics and Engineering
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• v.13 no.6
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• pp.947-961
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• 2017

An innovative spiral variable-section capillary model is established for piping critical hydraulic gradient of cohesion-less soils causing water/mud inrush in tunnels. The relationship between the actual winding seepage channel and grain-size distribution, porosity, and permeability is established in the model. Soils are classified into coarse particles and fine particles according to the grain-size distribution. The piping critical hydraulic gradient is obtained by analyzing starting modes of fine particles and solving corresponding moment equilibrium equations. Gravities, drag forces, uplift forces and frictions are analyzed in moment equilibrium equations. The influence of drag force and uplift force on incipient motion is generally expounded based on the mechanical analysis. Two cases are studied with the innovative capillary model. The critical hydraulic gradient of each kind of sandy gravels with a bimodal grain-size-distribution is obtained in case one, and results have a good agreement with previous experimental observations. The relationships between the content of fine particles and the critical hydraulic gradient of seepage failure are analyzed in case two, and the changing tendency of the critical hydraulic gradient is accordant with results of experiments.

• Journal of Environmental Science International
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• v.23 no.3
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• pp.483-492
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• 2014

DNA damage such as genotoxicity was identified with comet assay, which blood cell of a marine parrot fish (Oplegnathus fasciatus) was exposed to an acidified seawater, lowered pH gradient making of $CO_2$ gas. The gradient of pH were 8.22, 8.03, 7.81, 7.55 with control as HBSS solution with pH 7.4. DNA tail moment of fish blood cell was $0.548{\pm}0.071$ exposed seawater of pH 8.22 condition, on the other hand, DNA tail moment $1.601{\pm}0.197$ exposed acidified seawater of pH 7.55 lowest condition. The approximate difference with level of DNA damage was 2.9 times between highest and lowest of pH. DNA damage with decreasing pH was significantly increased with DNA tail moment on blood cell of marine fish (ANOVA, p < 0.001). Ocean acidification, especially inducing the leakage of sequestered $CO_2$ in geological structure is a consequence from the burning of fossil fuels, and long term effects on marine habitats and organisms are not fully investigated. The physiological effects on adult fish species are even less known. This result shown that the potential of dissolved $CO_2$ in seawater was revealed to induce the toxic effect on genotoxicity such as DNA breakage.

• KSBB Journal
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• v.18 no.1
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• pp.35-38
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• 2003

Analysis of proteome in amniotic fluid was performed by 2-D PAGE (polyacrylamide gel electrophoresis). Proteins in amniotic fluid were separated by centrifugation and solubilized in buffer solution for IEF, using an IPG strip of pH 4-7L. Both a homogeneous slab gel of 12.5% and a gradient gel of 8-18%, were used. After 2-D PAGE, spots were stained with silver nitrate and picked up for in-gel digestion. Digested peptides were analyzed by MALDI-TOF and proteins were further identifical. More protein spots were detected in the gradient gels and a protein not previously reported was identified.