• Journal of the korean academy of Pediatric Dentistry
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• v.27 no.2
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• pp.351-360
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• 2000

The purpose of this study was to evaluate the microleakage of class V compomers according to acid etching treatment and treatment times. Extracted 180 sound human molar teeth were selected then prepared physiologic pulpal pressure far this experiment. In this study class V cavities were prepared on buccal surface with gingival margin located in 1mm superior to CEJ under simulate physiological conditions. These specimens were randomly divided into 6 groups of 30 each and restored following methods : A: Dyract AP + Prime&Bond 2.1 Group 1 : No acid etching, according to manufacturer's instruction. Group 2 : 15 seconds acid etching and same method with Group 1. Group 3 : 30 seconds acid etching and same method with Group 1. B: F2000 groups + Single Bond adhesive Group 1 : No acid etching, according to manufacturer's instruction. Group 2 : 15 seconds acid etching and same method with Group 1 Group 3 : 30 seconds acid etching and same method with Group 1. After 500 thermocycling between $5^{\circ}C\;and\;55^{\circ}C$, the specimens were sealed with glass ionomer and nail varnish then placed in 5% methylene blue dye for 5 hours and rinsed with tab water. The specimens were embedded in orthodontic clear resin, then sectioned buccolingually through the center of restoration with a low speed diamond saw. The dye penetration on each of the specimens were then observed with a stereomicroscope at $\times20$ magnification. The results of this study were statistically analyzed using the indepedent sample t-test and analysis of variance. Results were as follows, 1. In occlusal walls, microleakage were significantly reduced in acid etched group restored with Dyract AP but no statistically significance in F2000 groups. 2. In gingival walls, microleakage were significantly reduced in group 2 restored with Dyract AP, and group 2 and group 3 in F2000 groups. 3. All groups, except group 3 in Dyract AP, showed significantly less microleakage in occlusal wall than gingival wall. 4. No statistical significance were showed between group 2 and group 3 in both materials.

• Journal of Animal Science and Technology
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• v.47 no.4
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• pp.679-690
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• 2005

This study was carried out to evaluate the quality characteristics of aerobic packed pork during storage after fermentation with soy sauce, red pepper and soybean paste seasonings. The ham of pork were cut to cube($7{\time}10{\time}2$cm) and Korea traditional seasonings such as soy sauce(T1), red pepper paste(T2), soybean paste(T3) were seasoned by the proportions of meat to seasonings(1:1), respectively. The seasoned sample were fermented by fill into plastic box at $1{\pm}1^{\circ}C$ for 10 days. And then, the fermented meat from each pack was aerobic packed and stored at $1{\pm}1^{\circ}C$ for up to 28 days. The pH of T1 were significantly(P<0.05) lower compared to T2 and T3 at 1 day of storage, but were significantly(P<0.05) higher at 14 and 28 days of storage. The water-holding capacity of T1were significantly(P<0.05) higher compared to T2 and T3 at 1 and 28 days of storage. The shear force of T3 were significantly(P<0.05) lower compared to T1 during storage. The surface meat L* values of T3 were significantly(P<0.05) higher than those of T1 and T2, but a* and b* values of T2 were significantly(P<0.05) higher. The volatile basic nitrogen(VBN) of T3 were significantly(P<0.05) lower compared to T2 at 1 and 14 days of storage, but T1 were significantly(P<0.05) lower at 28 days of storage. The thiobarbituric acid reactive substances(TBARS) of T3 were significantly(P<0.05) lower compared to T1 and T2. The total plate counts of T1 were significantly(P<0.05) lower compared to T2 and T3 at 1 day of storage, but T2 were significantly(P<0.05) lower at 14 and 28 days of storage. The Escherichia coli of T1 and T3 were significantly(P<0.05) lower compared to T2 at 1 day of storage. The Lactobacilli spp. of T2 were significantly(P<0.05) lower compared to T1 and T3.

• Journal of Life Science
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• v.26 no.1
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• pp.68-74
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• 2016

Perchlorate (ClO₄⁻) is an emerging pollutant detected in surface water, soil, and groundwater. Previous studies provided experimental evidence of autotrophic ClO₄⁻ removal with elemental sulfur (S⁰) particles and activated sludge, which are inexpensive and easily available, respectively. In addition, ClO₄⁻ removal efficiency was shown to increase when an enrichment culture was used as an inoculum instead of activated sludge. PCR-DGGE was employed in the present study to investigate the microbial community in the enrichment culture that removed ClO₄⁻ autotrophically. Microorganisms in the enrichment culture showed 99.71% or more ClO₄⁻ removal efficiency after a 7-day incubation when the initial concentration was approximately 120 mg ClO₄⁻/l. Genomic DNA was isolated from the enriched culture and its inoculum (activated sludge), and used for PCR-DGGE analysis of 16S rRNA genes. Microbial compositions of the enrichment culture and the activated sludge were different, as determined by their different DGGE profiles. The difference in DGGE banding patterns suggests that environmental conditions of the enrichment culture caused a change in the microbial community composition of the inoculated activated sludge. Dominant DGGE bands in the enrichment culture sample were affiliated with the classes β-Proteobacteria, Bacteroidetes, and Spirochaetes. Further investigation is warranted to reveal the metabolic roles of the dominant populations in the ClO₄⁻ degradation process, along with their isolation.

• Korean Journal of Soil Science and Fertilizer
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• v.32 no.4
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• pp.383-397
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• 1999

For sites to be investigated, the results of such an investigation can be used in determining foals for cleanup, quantifying risks, determining acceptable and unacceptable risk, and developing cleanup plans t hat do not cause unnecessary delays in the redevelopment and reuse of the property. To do this, it is essential that an appropriately detailed study of the site be performed to identify the cause, nature, and extent of contamination and the possible threats to the environment or to any people living or working nearby through the analysis of samples of soil and soil gas, groundwater, surface water, and sediment. The migration pathways of contaminants also are examined during this phase. Key aspects of cost-effective site assessment to help standardize and accelerate the evaluation of contaminated soils at sites are to provide a simple step-by-step methodology for environmental science/engineering professionals to calculate risk-based, site-specific soil levels for contaminants in soil. Its use may significantly reduce the time it takes to complete soil investigations and cleanup actions at some sites, as well as improve the consistency of these actions across the nation. To achieve the effective site assessment, it requires the criteria for choosing the type of standard and setting the magnitude of the standard come from different sources, depending on many factors including the nature of the contamination. A general scheme for site-specific assessment consists of sequential Phase I, II, and III, which is defined by workplan and soil screening levels. Phase I are conducted to identify and confirm a site's recognized environmental conditions resulting from past actions. If a Phase 1 identifies potential hazardous substances, a Phase II is usually conducted to confirm the absence, or presence and extent, of contamination. Phase II involve the collection and analysis of samples. And Phase III is to remediate the contaminated soils determined by Phase I and Phase II. However, important factors in determining whether a assessment standard is site-specific and suitable are (1) the spatial extent of the sampling and the size of the sample area; (2) the number of samples taken: (3) the strategy of taking samples: and (4) the way the data are analyzed. Although selected methods are recommended, application of quantitative methods is directed by users having prior training or experience for the dynamic site investigation process.

• Economic and Environmental Geology
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• v.48 no.2
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• pp.147-160
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• 2015

In 2014, on 31 August and 1 September, the emissions of $CH_4$, $CO_2$, and $O_2$ gases were measured six times using the closed chamber method from exposed tidal flat sediments in the same position relative to the low point of the tidal cycle in the Eoeun-ri, Taean-gun, on the Mid-western Coast of Korea. The concentrations of $CH_4$ in the air sample collected in the chamber were measured using gas chromatography with an EG analyzer, model GS-23, within 6 hours of collection, and the other gases were measured in real time using a multi-gas monitor. The gas emission fluxes (source (+), and sink (-)) were calculated from a simple linear regression analysis of the changes in the concentrations over time. In order to see the surrounding parameters (water content, temperature, total organic carbon, average mean size of sediments, and the temperature of the inner chamber) were measured at the study site. On the first day, across three measurements during 5 hours 20 minutes, the observed $CO_2$ flux absorption was -137.00 to $-81.73mg/m^2/hr$, and the $O_2$ absorption, measured simultaneously, was -0.03 to $0.00mg/m^2/hr$. On the second day using an identical number of measurements, the $CO_2$ absorption was -20.43 to $-2.11mg/m^2/hr$, and the $O_2$ absorption -0.18 to $-0.14mg/m^2/hr$. The $CH_4$ absorption before low tide was $-0.02mg/m^2/hr$ (first day, Pearson correlation coefficient using the SPSS statistical analysis is -0.555(n=5, p=0.332, pronounced negative linear relationship)), and $-0.15mg/m^2/hr$ (second day, -0.915(n=5, p=0.030, strong negative linear relationship)) on both measurement days. The emitted flux after low tide on both measurement days reached a minimum of $+0.00mg/m^2/hr$ (+0.713(n=5, p=0.176, linear relationship which can be almost ignored)), and a maximum of $+0.03mg/m^2/hr$ (+0.194(n=5, p=0.754, weak positive linear relationship)) after low tide. However, the absolute values of the $CH_4$ fluxes were analyzed at different times. These results suggest that rate for $CH_4$ fluxes, even the same time and area, were influenced by changes in the tidal cycle characteristics of surface sediments for understanding their correlation with these gas emissions, and surrounding parameters such as physiochemical sediments conditions.

• The Korean Journal of Quaternary Research
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• v.14 no.1
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• pp.7-31
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• 2000

Quaternary Geological and geophysical investigation was performed at the Eurimji reservoir of Jaechon City in order to interprete depositional environment and genesis of lake sediments. For this purpose, echo sounding, bottom sampling and columnar sampling by drilling on board and GPR survey were employed for a proper field investigation. Laboratory tests cover grain size population analysis, pollen analysis and $^{14}C$ datings for the lake sediments. The some parts of lake bottom sediments anthropogenically tubated and filled several times to date, indicating several mounds on the bottom surface which is difficult to explain by bottom current. Majority of natural sediments were accumulated both as rolling and suspended loads during seasonal flooding regime, when flash flow and current flow are relatively strong not only at bridge area of the western part of Eurimji, connected to stream valley, but at the several conduit or sewage system surrounding the lake. Most of uniform suspend sediments are accumulated at the lake center and lower bank area. Some parts of bottom sediments indicate the existence of turbid flow and mudflow probably due to piezometric overflowing from the lake bottom, the existence of which are proved by CM patterns of the lake bottom sediments. The columnar samples of the lake sediments in ER-1 and ER-3-1 boreholes indicate good condition without any human tubation. The grain size character of borehole samples shows poorly sorted population, predominantly composed of fine sand and muds, varying skewness and kurtosis, which indicate multi-processed lake deposits, very similar to lake bottom sediments. Borehole columnar section, echo sounding and GPR survey profilings, as well as processed data, indicate that organic mud layers of Eurimji lake deposits are deeper and thicker towards lower bank area, especially west of profile line-9. In addition the columnar sediments indicate plant coverage of the Eurimji area were divided into two pollen zones. Arboreal pollen ( AP) is predominant in the lower pollen zone, whreas non-aboreal pollen(NAP) is rich in the upper pollen zone. Both of the pollen zones are related to the vegetation coverage frequently found in coniferous and deciduous broad-leaved trees(mixed forest) surrounded by mountains and hilly areas and prevailing by aquatic or aquatic margin under the wet temperate climate. The $^{14}C$ age of the dark gray organic muds, ER1-12 sample, is 950$\pm$40 years B.P. As the sediments are anthropogenetically undisturbed, it is assumed that the reliability of age is high. Three $^{14}C$ ages of the dark gray organic muds, including ER3-1-8, ER3-1-10, ER3-1-11 samples, are 600$\pm$30 years B.P., 650$\pm$30 years B.P., 800$\pm$40 years B.P. in the descending order of stratigraphic columnar section. Based on the interpretation of depositional environments and formation ages, it is proved that Eurimji reservoir were constructed at least 950$\pm$40 years B.P., the calibrated ages of which ranges from 827 years, B.P. to 866 years B.P. Ancient people utilize the natural environment of the stream valley to meet the need of water irrigation for agriculture in the local valley center and old alluvium fan area.