• Journal of the Korean Society of Marine Environment & Safety
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• v.15 no.4
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• pp.297-313
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• 2009

Long-term trends and distribution patterns of water quality were investigated in the Gunsan coastal areas of Yellow Sea, Korea from 1972 to 2006. Water samples were collected at 6 stations and physicochemical parameters were analyzed including water temperature, salinity, suspended solids(SS), chemical oxygen demand(COD), dissolved oxygen(DO) and nutrients. Spatial distribution patterns of temperature, DO and SS were not clear among stations but the seasonal variations were distinct except COD and SS. The trend analysis by principal component analysis(PCA) during 24 years revealed the significant variations in water quality in the study area. Spatial water qualities were clearly classified into 3 clusters by PCA; station cluster 1, 2~4, and 5~6. Annual water qualities were clearly classified into 4 surface water clusters and 5 bottom water clusters by PCA. By this multi-variate analysis. The annual trends were summarized as follows; Salinity, pH and DO tended to increase since late 1970's, COD to increase since 1987, and SS to decrease and nutrients to increase in Gunsan coastal waters due to the input of fresh water from land same as in Kyoungin coastal area, Asan coastal area and Choensoo bay.

• Korean Journal of Microbiology
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• v.34 no.3
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• pp.108-114
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• 1998

Salmonella Pathgenicity Island 2 plays an important role in Salmonella pathogenicity, especially invasion into host cell. We have investigated the effect of various environmental factors, such as oxygen level, osmolarity, pH, carbon starvation and glycerol addition on the expression of SPI2. For this research, we constructed the reporter plasmids, in which the promoter-less lac operons are fused with the regulatory regions (including promoter) of ssaJ and ssaK, major genes in SPI2. The study using the reporters showed that low oxygen, low osmolarity, or weak alkali conditions increased the expression levels of ssaJ and ssaK and when these three conditions exist simultaneously, the expression levels of ssaJ and ssaK are the highest. However carbon starvation and glycerol addition did not affect the expression of ssaJ and ssaK. These environmental effects on the expression levels of ssaJ and ssaK are the same in three Salmonella typhimurium wild types, LT2, UK1, and SL1344. In addition, we confirmed that the mutation in hilA, a regulatory gene encoding a transcriptional activator of SPI1, had no effect on the expression of ssaJ and ssaK. Thus, these results strongly suggest that the expressions of SPI2 and SPI1 are regulated by different control systems.

• Ecology and Resilient Infrastructure
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• v.2 no.1
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• pp.22-32
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• 2015

This study investigated the difference in fish community structures in a main channel and an isolated former channel, considering the environmental factors in the Mangyeong River, Korea. Principal component analysis (PCA) with environmental factors showed that former channels were composed of a fine substrate covered by in-stream vegetation, whereas the main channel was covered by a wide range of substrates with a higher dissolved oxygen and conductivity. The result of the hierarchical cluster analysis with species abundance delineated to the four main groups; three abandoned channel groups and one main channel group. Non-metric multidimensional scaling (NMDS) showed that fish community structures of each study site differed from environmental factors: former channel fish communities were positively related to in-stream vegetation cover, whereas main channel fish communities were positively associated with dissolved oxygen and conductivity. The results indicated that channelization, where there was a separation between the former channel and the main channel, had detrimental effects on fish community structures of both the main channel and the abandoned channel in the Mangyeong River. In conclusion, this study suggested that the connectivity between the main channel and abandoned channel were required to enhance both habitat structural diversity and species diversity of the Mangyeong River.

• Nutrition Research and Practice
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• v.16 no.1
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• pp.33-45
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• 2022

BACKGROUND/OBJECTIVES: Ginseng extract (GSE) and taurine (TR) are widely used antifatigue resources in functional foods. However, the mechanism underlying the antifatigue effects of GSE and TR are still unclear. Hence, we investigated whether GSE and TR have synergistic effects against fatigue in mice. MATERIALS/METHODS: L6 cells were treated with different concentrations of TR and GSE, and cell viability was determined using 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium. Oxidative stress was analyzed by immunocytochemistry using MitoTracker^TM Red FM and an anti-8-oxoguanine antibody. Respiratory gas analysis was performed to investigate metabolism. Expression of an activated protein kinase was analyzed using immunohistochemistry. Gene expression of cluster of differentiation 36 and pyruvate dehydrogenase lipoamide kinase isozyme 4 was measured using reverse transcription-polymerase chain reaction. Mice were orally administered TR, GSE, or their combination for 30 days, and then fatigue-related parameters, including lactate, blood urea nitrogen, and glycogen, were measured after forced swimming. RESULTS: TR and GSE reduced oxidative stress levels in hydrogen peroxide-stimulated L6 cells and enhanced the oxygen uptake and lipid metabolism in mice after acute exercise. After oral administration of TR or GSE for 30 days, the fatigue-related parameters did not change in mice. However, the mice administered GSE (400 mg/kg/day) alone for 30 days could swim longer than those from the other groups. Further, no synergistic effect was observed after the swimming exercise in mice treated with the TR and GSE combination for 30 days. CONCLUSIONS: Taken together, our data suggest that TR and GSE may exert antifatigue effects in mice after acute exercise by enhancing oxygen uptake and lipid oxidation.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.31 no.3
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• pp.343-352
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• 1998

The relationship between summer hypoxia in bottom water layer and benthic community structure was discussed at forty sampling stations in semi-enclosed Youngsan River estuarine bay, Korea. The oxygen deficient layer less than $2.0 mg/\ell$ was widely developed in the inner estuarine stations in summer due to the summer stratification. A total of 141 species was occurred, with a mean density of $1,923 ind./m^2$ and biomass of $79.44\;g/m^2$ in summer season. The species number was significantly increased with the increment of the bottom dissolved oxygen, whereas density and biomass were partially correlated within the low oxygen level of $2.0\;mg/\ell$. These results imply that benthic community structures are affected by bottom oxygen depletion in summer. Cluster analysis showed that the benthic community could be classified into three station groups. These station groups from the species composition coincided with the groups based on the environmental factors. This fact suggests that the overall spatial distribution of macrozoobenthos in Youngsan River estuarine bay in summer should be controlled by the summer hypoxia and clay content of the area. Group-I was located the innermost estunrine bay from Mokpo Harbour to near the dike, where summer hypoxia was developed and one bivalve Theora fragilis, two polychaetes, Tharyx sp. and Lumbrineris longifolia were dominated. Group-II, the central transitory area of the estuarine bay between two another stational groups, where two bivalves Theora fragilis, Raetellops pulchella and a polychaete Tharyx sp. predominated with relatively low density compared to that of Group-I. Group-III, the mouth part of the estunrine bay exposed to the open sea, where a polychaetes Poecilochaetus johnsoni and a bivalve Yoldia Johanni predominated.

• Journal of Welding and Joining
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• v.15 no.4
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• pp.126-135
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• 1997

$H_2/O_2$ 비에 따른 Hybrid HVOF 용사된 $Cr_3C_2$-7wt%(NiCr) 용사층의 특성 및 산화거동 This study was performed to investigate the influence of fuel/oxygen ratio (F/O=3.2, 3.0, 2.8) on the characteristics and the oxidation behavior of the hybrid-HVOF sprayed $Cr_3C_2$-7wt%NiCr coatings. Decomposition and the oxidation of the $Cr_3C_2$was occured during spraying. The degree of transformation from $Cr_3C_2$to $Cr_7C_3$ was increased with decreasing the F/O ratio. The microstructural differences of the as sprayed coating with F/O ratio can not be distinguished, However, large pores were diminished and then the coatings became dense by heat treatment. Microhardness of the as-sprayed specimen which sprayed with F/O=3.0 condition was hightest ($Hv_{300}$=1140) and the hardness was increased to 1500 after heat treatment at $600^{\circ}C$ for 50hrs in air. It was supposed that hardness was increased due to the formation of $Cr_2O_3$ within $Cr_3C_2$/$Cr_7C_3$matrix and the densification of coating layer during heat treatment. Apparent activation energy for oxidation was varied from 21.2 kcal$mol^{-1}K^{-1}$ to 23.8 kcal$mol^{-1}K^{-1}$ with respect to the F/O ratio. The surface morphology was changed to porous and oxide chusters were grown after oxidation $1000^{\circ}C$ for 50 hours by the aggressive evolution of gas phase ($CrO_3$ and$CO_2$). The oxide cluster was composed of Ni and Cr.

• Journal of Ecology and Environment
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• v.34 no.2
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• pp.175-191
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• 2011

Colonization patterns and community changes in benthic macroinvertebrates in the Cheonggye Stream, a functionally restored stream in downtown Seoul, Korea, were studied from November 2005 to November 2007. Benthic macroinvertebrates were quantitatively sampled 15 times from five sites in the stream section. Taxa richness (59 species in total) increased gradually over the first year, whereas the density revealed seasonal differences with significantly lower values in the winter season and after flood events. The benthic macroinvertebrate fauna may have drifted from the upstream reaches during floods and from the Han River, arrived aerially, or hitchhiked on artificially planted aquatic plants. Oligochaeta, Chironommidae, Psychodidae, and Hydropsychidae were identified as major community structure contributors in the stream. Swimmers and clingers colonized relatively earlier in the upper and middle reaches, whereas burrowers dominated particularly in the lower reaches. Collector-gatherers colonized at a relatively early period throughout the stream reaches, and collector-filterers, such as the net-spinning caddisfly (Cheumatopyche brevilineata), predominated in the upper and middle reaches after a 1-year time period. Cluster analyses and multi-response permutation procedures demonstrated that the Cheonggye Stream shares more similarities with the Jungnang Stream than with the Gapyeong Stream. Detrended correspondence analysis and nonmetric multidimensional scaling demonstrated that physical environmental factors (depth, current velocity, dissolved oxygen, and pH) as well as nutrients (total nitrogen and total phosphorous), water temperature, and conductivity could affect the distribution of benthic macroinvertebrates in the study streams.

• Journal of Environmental Health Sciences
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• v.41 no.2
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• pp.90-101
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• 2015

Objective: This study was conducted to develop a chemical oxygen demand (COD) regression model using water quality monitoring data (January, 2014) obtained from the Han River auto-monitoring stations. Methods: Surface water quality data at 198 sampling stations along the six major areas were assembled and analyzed to determine the spatial distribution and clustering of monitoring stations based on 18 WQPs and regression modeling using selected parameters. Statistical techniques, including combined genetic algorithm-multiple linear regression (GA-MLR), cluster analysis (CA) and principal component analysis (PCA) were used to build a COD model using water quality data. Results: A best GA-MLR model facilitated computing the WQPs for a 5-descriptor COD model with satisfactory statistical results ($r^2=92.64$,$Q{^2}_{LOO}=91.45$,$Q{^2}_{Ext}=88.17$). This approach includes variable selection of the WQPs in order to find the most important factors affecting water quality. Additionally, ordination techniques like PCA and CA were used to classify monitoring stations. The biplot based on the first two principal components (PCs) of the PCA model identified three distinct groups of stations, but also differs with respect to the correlation with WQPs, which enables better interpretation of the water quality characteristics at particular stations as of January 2014. Conclusion: This data analysis procedure appears to provide an efficient means of modelling water quality by interpreting and defining its most essential variables, such as TOC and BOD. The water parameters selected in a COD model as most important in contributing to environmental health and water pollution can be utilized for the application of water quality management strategies. At present, the river is under threat of anthropogenic disturbances during festival periods, especially at upstream areas.

• The Journal of Korean Physical Therapy
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• v.15 no.3
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• pp.295-345
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• 2003

This study investigated activation of cerebral cortex in patients with hemiplegia that was caused by neural damage. Key-point control movement therapy of Bobath was performed for 9 weeks in 3 subjects with hemiplegia and fMRI was used to compare and analyze activated degree of cerebral cortex in these subjects. fMRI was conducted using the blood oxygen level-dependent(BOLD) technique at 3.0T MR scanner with a standard head coil. The motor activation task consisted of finger flexion-extension exercise in six cycles(one half-cycles = 8 scans = $3\;sec{\times}\;8\;=\;24\;sec$). Subjects performed this task according to visual stimulus that sign of right hand or left hand twinkled(500ms on, 500ms off). After mapping activation of cerebral motor cortex on hand motor function, below results were obtained. 1. Activation decreased in primary motor area, whereas it increased in supplementary motor area and visual association area(p<.001). 2. Activation was observed in bilateral medial frontal gyrus, middle frontal gyrus of left cerebrum, inferior frontal gyrus, inter-hemispheric, fusiform gyrus of right cerebrum, superior parietal lobule of parietal lobe and precuneus in subjedt 1, parahippocampal gyrus of limbic lobe and cingulate gyrus in subject 2, and inferior frontal gyrus of right frontal lobe, middle frontal gyrus, and inferior parietal lobule of left cerebrum in subject 3 (p<.001). 3. Activation cluster extended in declive of right cellebellum posterior lobe in subject 1, culmen of anterior lobe and declive of posterior lobe in subject 2, and dentate gyrus of anterior lobe, culmen and tuber of posterior lobe in subject 3 (p<.001). In conclusion, these data showed that Key-point control movement therapy of Bobath after stroke affect cerebral cortex activation by increasing efficiency of cortical networks. Therefore mapping of brain neural network activation is useful for plasticity and reorganization of cerebral cortex and cortico-spinal tract of motor recovery mechanisms after stroke.

• Journal of the Korean Vacuum Society
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• v.13 no.2
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• pp.79-85
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• 2004

Secondary ion mass spectrometry(SIMS) and glow discharge mass spectrometry(GDMS) were used to determine the impurity concentrations of hydrogen, carbon, and oxygen elements in the Cu and Ta films, and the results of SIMS and GDMS analysis were carefully considered. The Cu and Ta films were deposited on Si (100) substrates at zero substrate bias voltage and a substrate bias voltage of -50 V(Cu films) or -125 V(Ta films) using a non-mass separated ion beam deposition method. As a result of SIMS with Cs+ ion beam, in the case of the Cu and Ta films deposited without the substrate bias voltage, many strong peaks were observed, which is considered to be detected as a the cluster state such as CxHx, OxHx, CxOxHx. All the peaks of SIMS results could be interpreted by the combination of these dominant impurities. Moreover, it was confirmed that the quantitative results of GDMS analysis were accordant to the SIMS results.