• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.6 no.1
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• pp.40-48
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• 2001

The vertical distributions of temperature, salinity, dissolved oxygen, nutrients, chlorophyll, and primary production were investigated within the top 200m water depth in the south Pacific Ocean in February,2000. The study area ($24^{\circ}-41^{\circ}S,\;81^{\circ}-168^{\circ}W$) can be hydrologically divided into two regions. Upwelling was actively occurring in the eastern region of the $110^{\circ}S$ line, meanwhile it was not active in the western region. Accordingly, chemical properties in the surface waters were different between the two regions; nitrate+nitrite and phosphate concentrations were much higher in the eastern region than in the western region due to the active upwelling, but silicate concentration was higher in the western region. Among the nutrients, the major element influencing primary production was also different between the two regions; silicon would be a major element influencing primary production in the eastern region, but nitrogen may act as a major element for primary production in the western region. Primary production showed similar values in the two regions in spite of the large differences of nutrient concentrations in the surface waters, but the total chlorophyll integrated within the 200 m water depth was almost twice as much as in the western region than that in the eastern legion.

• Journal of Life Science
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• v.21 no.6
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• pp.819-828
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• 2011

To inspect norovirus contamination of groundwater in south eastern areas of Korea, a systematic survey of groundwater in Busan, Ulsan, and Gyeongsangnam-do was performed for two years from 2009 to 2010. For this purpose, we first optimized the nested reverse transcription-PCR condition by designing two sets of primers for the detection of norovirus genogroups, GI and GII. Of 145 samples, 21 (25.9%) and 15 (23.4%) were norovirus positive in the dry season (April to June) and wet season (July to August), respectively. The detection frequencies of norovirus in Busan, Ulsan, and Gyeongsangnam-do were 15%, 7%, and 32%, respectively, reflecting a geographical difference in their distribution. The GI and GII isolates were 5 and 31, respectively, indicating the prevalence of GII in the tested areas. According to phylogenetic analysis of their nucleotide sequences, all of the GI isolates were identified to genotype GI.5 whilst the GII isolates were divided into two genotypes, GII.3 and GII.4. Neither physical-chemical parameters such as pH, temperature, oxidation-reduction potential, and dissolved oxygen, nor microbial indicators of water quality such as total bacteria, total coliforms, and Escherichia coli were statistically correlated with contamination of norovirus in the groundwater. Interestingly, however, the presence of norovirus was closely correlated with low turbidity (<0.50 NTU). The present study suggests that periodical monitoring of norovirus in groundwater is necessary to prevent epidemic waterborne diseases and to secure better sanitary conditions for public health.

• Korean Journal of Ecology and Environment
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• v.33 no.3 s.91
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• pp.295-303
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• 2000

The water clarification efficiency was examined in a shallow wetland where dense vegetation was formed naturally in an abandoned paddy field. And, also two enclosure experiments were carried out to measure the effects of materials exchange between sediment and the overlying water with the existence of vegetation and accumulated litter. The hydraulic retention time of wetland was regulated in 1.2 day. The removal rates of SS (56%) and $NO_3-N$ (61%) were high, considering its short retention time. However, removal efficiencies of VSS (28%), COD (14%), DOC (1%),and TP (0.2%) were relatively lower. This low removal efficiencies were thought to be due to the release of dissolved form of organic matter and phosphorus from the sediment. Most of constituents except nitrate were higher in the enclosure at the beginning of enclosure installation than that of the outflowing water from wetland. And then, it has fluctuated and decreased with time. The wetland was in equilibrium state of settling, accumulation of organic debris, and regeneration of dissolved material from sediment. So ultimately high primary production by dense vegetation in the wetland may be the reason of unfavorable or low treatment efficiency of wetland after many years of operation for wastewater treatment. However, the water quality of effluent from the wetland showed smaller variation and better condition than that of inflow, especially during storm events. It can be concluded that this wetland is suitable for the improvement of water quality from nonpoint sources.

• Korean Journal of Ecology and Environment
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• v.38 no.1 s.110
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• pp.105-117
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• 2005

During the period of heavy rain from 2002 to 2004, the characteristics of the inflow, temporal and spatial fluctuations of high turbid water according to thermal stratification were studied on the Andong Reservoir which is the largest artificial lake in the Nakdong River basin, Korea. Thermal stratification was formed in June. Its structure determined to the pathway of inflowing turbid water and has affected by the transportation of high turbid water. Regardless of the time and amount of inflow, the high turbid water showed the shape of underflow at the riverine zone, separated from the bottom at the transition zone and moved to the lacustrine zone with the shape of density current. The plunging point depended on the time and amount of inflow. The distributions of thermal stratification and DO concentrations were changed by inflowing discharge. Two thermoclines and minimum DO layers were found out existing at metalimnion in a specific time, respectively. The layer of high turbid water which formed with the thickness of 20 m at the maximum below the depth of 15 m moved toward dam. Not settled to the bottom, the newly formed layer was discharged through the intake-outlet and dispersed into all layers by the circulation in the fall.

• Korean Journal of Environmental Biology
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• v.26 no.2
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• pp.76-86
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• 2008

The seasonal variations of primary production were investigated by phyto-PAM chlorophyll fluorometry as well as classical methods (standing crops of phytoplanktons and chlorophyll ${\alpha}$) in the Beopsu Marsh, Haman-gun, Gyeongsangnam-do. The amounts of turbidity, SS, T-N, T-P, BOD, COD, Ca$^{2+}$ and Cl$^-$ were the highest at the station 3, where located in flowout site of wastewater treated by the filtration plants. The water quality was the third level by the standard of BOD and COD. The amount of chlorophyll a (268.8 mg L$^{-1}$) was the highest at the station 2 in April because the cell density (2,677 cells mL$^{-1}$) of Micractinium pusillum increased suddenly from February (180 cells mL$^{-1}$). The patterns of primary production of phytoplankton by phyto-PAM chlorophyll fluorometry were fallen in with those of standing crops and chlorophyll a of phyto-planktons. The primary production was varied according to stations and seasons. The water environments of the Beopsu Marsh as a natural mounument should be under the control of a regular examination in order to preserve the ecosystem.

• Korean Journal of Ecology and Environment
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• v.43 no.2
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• pp.232-241
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• 2010

Epilithic diatom communities and water quality were monitored to evaluate the ecological impact of the inflow of Wonju-stream passing through the urban area in the Seom River Watershed. We selected the 14 sampling stations (5 main stream sites and 9 tributary sites), and collected diatom and water samples between October 2007 and September 2008, on the seasonal basis. The results indicate that most water quality parameters showed the site-specific patterns over the study, except for water temperature and dissolved oxygen. The levels of water quality parameters were highest at the site of Wonju stream, whereas the lowest in the upstream sites, and intermediate or gradually decreased in the downstream sites of the Seom river. One species, Achnanthes convergens, showed the highest biomass and frequency over the sites, while three saprophilous species-Navicula goeppertiana, Navicula subminuscula, Nitzschia palea were appeared only in Wonju Stream and other polluted sites. According to trophic diatom index (TDI) values, which were highly correlated with nutrients and EC, the study sites were classified into three classes: upstream and tributary (Class A and B), Wonju Stream (Class D), and mixed zone and downstream (Class C). A cluster analysis supported the result of TDI classification. Therefore, Wonju-stream located in populated urban area exerted the adverse ecological effects on the epilithic diatom community and water quality of the lower Seom River System, although its severity gradually decreased downstream.

• Korean Journal of Environment and Ecology
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• v.29 no.3
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• pp.410-420
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• 2015

In order to estimate the influence of environmental factors on zooplankton communities in lentic freshwater ecosystems, 20 reservoirs and wetlands were monitored by season in 2013. A total of 109 species of zooplankton were identified during the study period. Zooplankton assemblage showed a different distribution in its density and diversity in accordance with the seasons. In particular, the density of zooplankton (98 species and 603ind. L-1) was the most in autumn when compared to the other seasons. In order to effectively analyze zooplankton distribution that are affected by various environmental factors, a Self-Organizing Map (SOM) was used, which extracts information through competitive and adaptive properties. A total of 11 variables (8 environment factors and 3 groups of zooplankton) were patterned on to the SOM. Based on a U-matrix, four clusters were identified from the model. Among zooplankton communities, rotifer displayed a positive relationship with water temperature, and cladocerans and copepod were positively related to conductivity, chlorophyll a, and nutrient factor (i. e. TN and TP). In contrast, high dissolved oxygen appeared to have a negative effect on zooplankton distribution. Consequently, the SOM results depicted a clear pattern of zooplankton density clusters partitioned by environmental factors, which play a key role in determining the seasonal distribution of zooplankton groups in lentic freshwater ecosystem.

• Korean Journal of Crystallography
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• v.4 no.2
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• pp.74-85
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• 1993

Single crystals of LiNbO3 have found extensive application in electro-optic and nonlinear optic devices. However, laser-induced refartive index inhomogeneities, which have been labeled opical damage impose limits on device optical damage in LiNbO3 is imporved if more than 4.5 rml% MgO is added to the melt The laser damage thrueshold increased as much as 100 times better then that of undoped crystals. The MgO doped cystal has thus been urterlsiv81y studied since then. In the study, Mgo:LiNbOs(MLA) single crystals dopsd with 0, 2.5, 5.0, 7.5, 10.0 mol% MgO have been grown by the czocrualski technique. The metls were prepared in the platinum crluible and 15∼20mm diameter crystals were grown with a length of 20∼30mm in a resitance heater. The growth rate was 2.5mm/hr, the rotation speed 15rpn. Before sawing MLN single crystals were annealed for 24 hours under atmosphere at a temperature of 1080℃. After sawing, we have found an annual ring cross section of MNA crystals only in the direction of perpendicilar to the c-axis. Nonuniform dispusion of MgO was pointed out that the cuties of the state of oxide were strongly affected by oxygen partial pressure in.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.6
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• pp.617-623
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• 2001

To predict the seasonal variation of dissolved oxygen (DO) in Hakata bay, Japan, possible 20 time-series of different hourly-solar-radiation intensities were generated based on stochastically changing solar radiation intensity, and a numerical simulation on dissolved oxygen (DO) was carried out for each time series by using the Sediment-Water Ecological Model (SWEM). The model, consisting of two sub-models with hydrodynamic and biological models, simulates the circulation process of nutrient between water column and sediment, such as nutrient regeneration from sediments as well as ecological structures on the growth of phytoplankton and zooplankton, The results of the model calibration followed the seasonal variation of observed water quality well, and generated cumulative-frequency-distribution (CFD) curves of daily solar radiation agreed well with observed ones, The simulation results indicated that the exchange of sea water would have a great influence on the DO concentration, and that the concentration could change more than 1 mg/L in a day. This prediction method seems to be an effective way to examine a solution to minimize fishery damage when DO is depleted.

• Journal of Periodontal and Implant Science
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• v.36 no.4
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• pp.863-878
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• 2006

Porphyromonas gingivalis는 치주질환을 야기하는 독성세균으로서, 구강상피세포에 p. gingivalis가 감염되었을 때, 세포형태에 변화를 초래함으로 인해 방어기작이 작동하게 된다. 치주질환과 관련되어 생성된 활성 산소종의 소거에 관여하는 항산화성분은 p. gingivalis 이 감염된 구강상피세포에서 그 분포와 발현수준이 달라지리라 예상된다. 따라서 이번 연구에서는 구강상피세포(KB 세포)에 p. gingivalis가 감염되었을 때 야기되는 활성산소종과 이를 소거하는 역할을 하는 항산화단백들의 역할들을 규명하고자 하였다. 활성산소종 형성을 조절하는 NADPH oxidase 중 NOX4와 Rac1 전사체는 구강상피세포에서 p. gingivalis세균에 의해 증가하였으며 $gp91^{phox}$, Rac2, $p47^{phox}$와 $p67^{phox}$는 세균에 의한 변화가 관찰되지 않았다. 반면에 $p40^{phox}$ 전사체는 감소하는 경향을 보였다. NOX1 전사체는 p. gingivalis 처리 30분 후 감소하였다가 60분 후에는 다시 증가하는 양상을 보였다. 같은 시간에 NOX 활성화 단백인 NOXA1은 감소하고, NOX 구성단백질인 NOXO1은 증가하는 경향을 보였다. p. gingivalis가 감염된 구강상피세포를 방어하는 항산화단백 발현수준을 평가한 결과, SOD1, 2, 3 모두 p. gingivalis 처리시간에 따라 증가하는 양상을 보였다. GPx 발현 양상도 SOD와 유사하게 나타났다. $H_2O_2$를 소거하는 Prx는 감염된 KB 세포에서 Prx4와 Prx5가 4-6배 증가하는 것을 알 수 있었다. 반면 endocytosis 과정 중 $H_2O_2$ 생산은 변화되지 않았다. 이번 연구의 결과, p. gingivalis의 감염은 KB 세포의 NOX4와 Rac1의 NADPH oxidase 발현을 증가시켰으며, NOX1은 NOXA1과 NOXO1의 조절에 의해 영향을 받음을 알 수 있었다. 또한 항산화기작으로는 SOD, GPx, Prx가 증가하였는데, 이것은 Prx4와 Prx5가 중요한 역할을 할 것을 시사하였다.