• Maxillofacial Plastic and Reconstructive Surgery
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• 제38권
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• pp.29.1-29.9
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• 2016

Background: The objective of this study was to evaluate xenograft degradation velocity when treated with 4-hexylresorcinol (4HR). Methods: The scapula of a cow was purchased from a local grocery, and discs (diameter 8 mm, thickness 1 mm) were prepared by trephine bur. Discs treated with 4HR were used as the experimental group. Untreated discs were used as the control. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), antibacterial test, endotoxin test, and scanning electron microscopy (SEM) were performed on the discs. In vivo degradation was evaluated by the rat calvarial defect model. Results: The XRD and FT-IR results demonstrated successful incorporation of 4HR into the bovine bone. The experimental disc showed antibacterial properties. The endotoxin test yielded results below the level of endotoxin contamination. In the SEM exam, the surface of the experimental group showed needle-shaped crystal and spreading of RAW264.7 cells. In the animal experiments, the amount of residual graft was significantly smaller in the experimental group compared to the control group (P = 0.003). Conclusions: In this study, 4HR was successfully incorporated into bovine bone, and 4HR-incorporated bovine bone had antibacterial properties. In vivo experiments demonstrated that 4HR-incorporated bovine bone showed more rapid degradation than untreated bovine bone.

• 한국환경보건학회지
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• 제46권5호
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• pp.599-609
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• 2020

Objectives: Coronavirus disease 2019 (COVID-19) first emerged in December 2019 in Wuhan, China, and has rapidly become a global pandemic with over 26.4 million confirmed cases and approximately 871,000 fatalities worldwide as of this writing. In the Republic of Korea, disease clusters frequently occurred in long-term care hospitals where the majority of residents are elderly with underlying medical conditions. Despite the fact that public health authorities and local community health centers have put tremendous efforts into preventing the spread of disease, positive cases have continued to occur. Thus, the Korea Centers for Disease Control & Prevention rapid response team decided to conduct an environmental investigation of a long-term care hospital to identify whether environmental contamination has remained and contributed to the spread of COVID-19. Methods: An environmental investigation was conducted at Hospital A. The characteristics of the facility and its HVAC system were assessed by checking the layout and interviewing the people in charge. A total of 64 surface samples were collected from areas of concern, including patient rooms, toilets, elevators, and nurses' station. These samples were tested by a regional health and environmental research institute using real-time reverse transcription polymerase chain reaction. Results: All samples from Hospital A were confirmed to be negative. Through interviews with high-level personnel at the regional community health center, we found that extensive disinfection is frequently performed on potentially contaminated areas in Hospital A in accordance with government guidelines. Conclusion: The environmental control measures implemented in Hospital A had been sufficient for mitigating the risk of further infection, suggesting that such measures may also be effective for other long-term health care facilities.

• 한국초지조사료학회지
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• 제12권4호
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• pp.201-210
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• 1992

This study was designed to investigate the content of inorganic nitrogen($NH_4$, $NO_3$) and its change in the 7 different sites; the permanent meadows of alfalfa, orchardgrass, and reed canarygrass, the fields of rye. corn, rice and a mountain region. the results from this study were summarized as follows; 1. The contents of ammonium and nitrate in meadows were 15.89-16.46 and 1.32-1.86ppm, respectively, showing the lower level than in other sites and no significant diffirences among three meadows. 2. In the rice field, the average content of ammonium(7.19ppm) was the highest among all sites, but the content of nitrate(1 l.l7ppm) was the lowest. In addition, almost all of nitrate were spreaded around the surface. 3. In the mountain region, the content of $NH_4$(5.79ppm) was slightly high, but the content of nitrate ( 15.18ppm) was very low. 4. In the rye field. the average content of $NO_3$ was 35.46ppm and show the highest (92.63ppm) at the deep part of soil in the specific season, but it decreased with increasing temperature. 5. In the corn field, which kept bare after harvesting the corn silage, the content of $NO_3$ was high, regardless of seasons and depths, and increased up to maximum of 103ppm. 6. The ground water concentrations of $NO_3$ were not more than 50ppm in the pasture. In the vegetable house, they were less than 30 ppm during the winter and spring and were 80-100ppm during the summer and fall. 7. The concentrations of $NO_3$ in Han river water were lower during the winter and spring(20-30ppm) and higher dxring the summer and fall (50-90ppm).

• 한국지하수토양환경학회지:지하수토양환경
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• 제25권3호
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• pp.43-51
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• 2020

About 90% of groundwater wells in Jeju Island are reported to be under the threat of contamination by infiltration of the surface pollutants. Most of those wells have improperly grouted annulus which is an empty space between the well and the inner casing. As a remedy to this problem, some of the wells were re-grouted by filling the annulus with cement without lifting an inner casing. In order to evaluate whether this method is appropriate for the geological structure of Jeju Island, two wells (W1 and W2) were selected and this method was applied. The water holding capacity did not decrease while the nitrate levels decreased from 16.8 and 20.2 to 6.8 and 13.8 mg/L in W1 and W2, respectively. The higher nitrate level in W2 is deemed to be influenced by the livestock farms located in the upper area of the well. In addition, transmissivity of the vedose zone was higher in W2 than W1, potentially facilitating the transport of nitrate to the groundwater. The overall result of this study suggests re-grouting of wells for the purpose of protecting water quality of goundwater should take into account geological structure of vadose zone as well as appropriate source control of the contaminants.

• Nuclear Engineering and Technology
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• 제52권6호
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• pp.1259-1265
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• 2020

A beta ray scanner was proposed for in-situ discrimination of beta and gamma ray radioactivity. This scanner is based on the principle that gamma and beta rays experience different changes in detection efficiency in scintillators with different geometries, especially with regard to the scintillator thickness. The ratios of the counting rates of gamma rays (R_gamma), beta rays (R_beta), and sample measurements (R_total) in a thick scintillator to those in a thin one are reported. The parameter X_thick, which represents the counting rate contributed by beta rays to the total counting rate in the thick scintillator, was derived as a function of those ratios. The values of R_gamma and R_beta for ⁶⁰Co and ⁹⁰Sr sources were estimated as 3.2 ± 0.057 and 0.99 ± 0.0049, respectively. The estimated beta ray contributions had relative standard deviations of 2.05-4.96%. The estimated range of the beta rays emitted from ⁹⁰Sr was 19 mm as per the Monte Carlo N-Particle simulation, and this value was experimentally verified. Homogeneous and surface contaminations of ⁶⁰Co and ⁹⁰Sr-⁹⁰Y were simulated for application of the proposed method. The counting rate contributed by the beta rays was derived and found to be proportional to the concentration of ⁹⁰Sr-⁹⁰Y contamination.

• 한국화재조사학회학술대회
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• 한국화재조사학회 2011년도 제20회 추계학술대회
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• pp.63-79
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• 2010

345 kV 케이블의 종단접속부에서는 다수의 아크흔적이 발견된다. 재료분석에 의하면 케이블은 양호한 것으로 판정된다. 제조 및 설계상의 문제점은 없는 것으로 판단된다. 시공상의 결함요인 중 절연유 레벨이 낮은 것으로 추정되었다. XLPE에서는 다수의 Arc trace가 나타난 것을 확인하였다. 그러나 Soots mark가 없고, Yellow band 확인되지 않았으며, 방사형의 spider leg와 연결되지 않은 아크흔적이 없다. 이견사항으로는 XLPE의 내부에 보이드, 이물질 또는 돌기로 의심되는 것은 발견되지 않았다. 따라서 XLPE에서 이물질의 부착에 의한 절연파괴인 것으로 판단된다.

• 한국물환경학회지
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• 제18권3호
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• pp.327-336
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• 2002

Disinfection process in water treatment plants (WTPs) is one of the most important step in order to inactivate waterborne disease. However, what is the necessary disinfection in WTPs was not properly established in Korea. This study was conducted to evaluate disinfection performance in nationwide water treatment plants (n=474). Disinfection requirement based on the SWTR (Surface Water Treatment Rule) of the U.S. (1-log Giardia removal) was chosen in estimating the compliance. The scope of unit process for evaluating disinfection performance includes postdisinfection process in clearwells, pipeline, and storage tank. The worst water quality condition in individual WTPs was applied for the disinfection performance evaluation. The major results are as follows. First, it was appeared that 184 WTPs (39 %) provided insufficient disinfection performance. Disinfection performance was significantly improved during past 2 years. The ratio of the number of WTPs providing insufficient disinfection performance in 1999 and 2001 was 78 % and 41 %, respectively. One of major factors for this improvement was due to the improvement of $T_{10}/T$ value in clearwell, as a result of modification of clearwell facility. Second, if disinfection criteria is 3-log Giardia inactivation at worst water quality condition, then 19 % of all WTPs can not meet this disinfection criteria. And if disinfection criteria is strengthened to 4-log Giardia inactivation, then 58 % of all WTPs can not meet this disinfection criteria. Since disinfection criteria is decided by contamination level of Giardia in source water, it also needs the investigation of Giardia occurrence in source water.

• Journal of Ecology and Environment
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• 제43권4호
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• pp.461-468
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• 2019

Background: This study aimed to identify NO₃^--N sources using the stable isotope δ¹⁵N in Chydorus sphaericus (OF Müller), to investigate hydrological characteristics and nutrient states in artificial wetlands near the Nakdong River. Chydorus sphaericus is dominant in wetlands where aquatic plants are abundant, occurring in high density, and is sensitive to wetland water pollution, making it suitable for identification of NO₃^--N sources. Results: NO₃^--N sources for each wetland were strongly dependent on hydrological characteristics. Wetlands with sewage or rainfall/groundwater as their main sources had high levels of NO₃^--N, whereas wetlands with surface water as their main input had comparatively lower levels. Since wetlands with sewage and rainfall/groundwater as their main water sources were mostly detention ponds, their inputs from tributaries or the main river stream were limited and nutrients such as NO₃^--N easily become concentrated. Changes in NO₃^--N levels at each wetland were closely associated with δ¹⁵N of C. sphaericus. Interestingly, regression analysis also showed positive correlation between δ¹⁵N of C. sphaericus and NO₃^--N level. Conclusions: We conclude that the nitrate stable isotope (δ¹⁵N) of C. sphaericus can be used to elucidate the hydrological characteristics of riverine wetlands. This information is important for maintenance and conservation of artificial wetlands at the Nakdong River.

• 한국농공학회논문집
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• 제63권1호
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• pp.89-102
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• 2021

Soils in agricultural lands contain large amount of organic matter and nutrients due to the injected fertilizers and manure. During heavy rain, surface water and base runoff pollutants flows into a nearby stream or lake with eroded soil from agricultural lands. On the other hands, agricultural lands near the lake are inundated due to the increase of the water level in the lake, leading to organic matter and nutrient release from the inundated soil. In this study, releasing rates of nutrient salts and organic substances were analyzed for the soil in the agricultural land, where cultivation activities has been carried out and periodically flooded, to account for the possibility of contamination from the inundated agricultural land in reservoir areas The experiment results have shown that COD was released from the soil in anaerobic conditions, and T-P was released in both anaerobic and aerobic conditions. However, in the case of T-N, it was found that the runoff by soil was not made before the rainfall occurred, and when the soil was impound due to rainfall, the elution occurred under the aerobic conditions. Through the results of this study, it was possible to account for the effect of flooded agricultural lands on the water quality in the lake, and this could be reflected in an efficient agricultural non-point pollution management policy. In order to determine the precise releasing rate for each agricultural land, it is believed that the leaching experiment for paddy fields and grasslands are needed.

• 급식외식위생학회지
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• 제3권1호
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• pp.8-18
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• 2022

Dry-aging is one of the traditional aging processes, especially for beef. This aging process is being popular, because it produces unique brown/roasted flavor and texture that consumers prefer. However, as it is exposed to outside without packaging food safety concerns have been raised. The objective of this study was to investigate the presence of total aerobic bacteria (TAB) and pathogenic bacteria in manufacturing environment and suggest the safety management plan for the production of dry-aged meat. Surface samples from 66 environmental and 6 beef carcass samples were collected. According to the monitoring results, the contamination levels of TAB were in the order of shelves (5.4±1.1 Log CFU/cm²), cotton gloves (2.9±0.2 Log CFU/cm²), and door knobs (2.8±0.4 Log CFU/cm²) in the dry-aging room. In the door knobs, the level of mold was higher than that of yeast. These results indicate that the mold spores may be cross-contaminated with environmental factors inside the aging room. The risk factors that may occur during the manufacturing process were presented and possibility of risk was determined. From the aspect of microbiology, aging and trimming steps were determined as the critical control points. The temperature of the aging room should be maintained below 10℃ and the humidity below 75-85%. Based on the monitoring and the risk assessment of the dry-aging process, we prepared the safety management plan for the production of dry-aged meat, and it should be useful in improving the food safety of dry-aged meat.