• The Journal of the Korea Contents Association
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• v.19 no.5
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• pp.511-519
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• 2019

The purpose of this study was to investigate the status of infection control in dental office and the degree of infection control practice of dental hygienists. A self-reported questionnaire was answered by 193 dental hygienists working in dental hospitals or dental clinics in Gyeonggi and Incheon areas. The number of bacteria was measured sample of surface dental unit chair shoulder backrests and light handles from 19 dental hospitals and 28 dental clinics. It was responded that impression or occlusion bodies were routinely disinfected in 52.6% of the dental hospitals and dental prosthesis were routinely disinfected in 46.4% in dental clinics. The dental hospital and clinics disinfect the surface each 26.3%, 25% after the patient treatment. The dental hospital and clinic were detected bacteria $5.02^*10\^3CFU/mL$, $1^*10\^4CFU/mL$, from dental unit chair backrest, respectively and $8.32^*10\^3CFU/mL$, $4.26^*10\^4CFU/mL$ from light handles, respectively. At the conclusion of this investigation, it can be kept from infection source in dental office is to make the right selection and use of the personal protective equipments and to improve the practice level by regular and active education. The same infection control practice should be done by institutionalizing and mandating infection control practice.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2004.06a
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• pp.407-417
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• 2004

This study is to verify radiation detection method by using $\alpha$-spectroscopy and ${\gamma}$-spectroscopy for concretes and components which will be generated during the decommissioning of the uranium conversion plant. Components and inside walls of the building were contaminated with natural uranium materials. Some parts of the stainless steel pipes and concretes of the walls were sampled and analyzed their alpha and gamma activities respectively. Alpha and gamma activities are well matched each other in the range of high activity region to 0.01 Bq/g and gamma activities are over estimated comparing alpha activities corresponded in below 0.005 Bq/g region for the natural uranium of AUC sample. The $^{238}U$ originated from natural products of conversion process could be distinguished by measuring $^{214}Pb$ or $^{214}Bi$ and $^{234}Th$ or $^{234m}Pa$. Uranium contaminations mainly are in the wall surface of the plant. Decontamination process of generating wastes which can be reached tp background level gamma activities measured by gamma spectroscopy can also be used to conservative assessment data.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.38
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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.

• Journal of Environmental Health Sciences
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• v.46 no.5
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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.

• Journal of The Korean Society of Grassland and Forage Science
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• v.12 no.4
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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).

• Journal of Soil and Groundwater Environment
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• v.25 no.3
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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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• v.52 no.6
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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.

• Congress of the korean instutite of fire investigation
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• 2010.12a
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• pp.63-79
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• 2010

It is found to the arc trace on the junction termination of 345kV cable. According to the analysis of the cable material is judged to be good. Manufacturing and design problems are not considered. In construction defects, it was estimated to the low level of insulation oil. In the majority of the arc trace appeared XLPE is found. However, there is no Soots mark, yellow band has not been confirmed, not associated with a radial arc of the spider leg is not evidence. In other opinions, void, contamination or jut are not found on the inside of XLPE. Thus, by the attachment of the impurities in surface of XLPE insulation is judged to the breakdown.

• Journal of Korean Society on Water Environment
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• v.18 no.3
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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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• v.43 no.4
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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.