• Restorative Dentistry and Endodontics
• /
• 제26권5호
• /
• pp.379-386
• /
• 2001

This study was performed to evaluate the sealing ability of various retrograde filling materials by using bacterial penetration and dye penetration test. One hundred and forty extracted human teeth with single, straight canals and mature apiece were collected and used for this study. All canals were instrumented using an engine driven Ni-Ti file (ProFile). After removing 3mm from the apex of tooth, a standardized 3mm root end cavity was prepared using an ultrasonic instrument. The 70 teeth were randomly divided into 7 groups : 6 groups for retrograde filling using Super-EBA, ZOE, Chelon-Silver, IRM, ZPC and amalgam. The 7th group was used as a negative control. Nail varnish was applied to all external root surfaces to the level of the reseated root ends to prevent lateral microleakages. The specimens were then sterilized in an ethylene oxide sterilizer for 24 hours. 2 mm of the reseated root was immersed in a culture chamber containing a Tripticase Soy Broth with a phenol red indicator. The coronal access of each specimen was inoculated every 72 hours with suspension of Proteus vulgaris. The culture media were observed every 24hours for color change indicating bacterial contamination. The specimens were observed for 4weeks. The remaining 70 teeth were submitted to a dye penetration test. The canals of all teeth were first sealed with AH26 and obturated using an Obtura II system. Root resection, root end preparation and retrograde filling was performed as above. All specimens were suspended in 2% methylene blue dye for 72 hours before being ion gitudinally split. The degree of dye penetration was then measured using a stereomicroscope at 10 magnification and evaluated. The results were as floows : 1. In the bacterial penetration, the degree of leakage was the lowest in the Super-EBA, followed by, in ascending order, ZOE, Chelon-Silver IRM and ZPC. The amalgam showed highest bacterial leakage of all(p<0.01). 2. In the dye penetration, the degree of microleakage was the lowest in the Chelon-Silver and Super-EBA, followed by, in ascending order, IRM, ZPC. The ZOE and amalgam showed the highest microleakage of all (p<0.05). These results suggested that the eugenol based cement, Super-EBA, have excellent sealing ability as a retrograde filling material.

• 한국축산식품학회지
• /
• 제35권5호
• /
• pp.674-682
• /
• 2015

The objective of this study was to evaluate the risk of illness from Campylobacter spp. on ham. To identify the hazards of Campylobacter spp. on ham, the general characteristics and microbial criteria for Campylobacter spp., and campylobacteriosis outbreaks were investigated. In the exposure assessment, the prevalence of Campylobacter spp. on ham was evaluated, and the probabilistic distributions for the temperature of ham surfaces in retail markets and home refrigerators were prepared. In addition, the raw data from the Korea National Health and Nutrition Examination Survey (KNHNES) 2012 were used to estimate the consumption amount and frequency of ham. In the hazard characterization, the Beta-Poisson model for Campylobacter spp. infection was used. For risk characterization, a simulation model was developed using the collected data, and the risk of Campylobacter spp. on ham was estimated with @RISK. The Campylobacter spp. cell counts on ham samples were below the detection limit (<0.70 Log CFU/g). The daily consumption of ham was 23.93 g per person, and the consumption frequency was 11.57%. The simulated mean value of the initial contamination level of Campylobacter spp. on ham was −3.95 Log CFU/g, and the mean value of ham for probable risk per person per day was 2.20×10⁻¹². It is considered that the risk of foodborne illness for Campylobacter spp. was low. Furthermore, these results indicate that the microbial risk assessment of Campylobacter spp. in this study should be useful in providing scientific evidence to set up the criteria of Campylobacter spp..

• Corrosion Science and Technology
• /
• 제6권5호
• /
• pp.219-226
• /
• 2007

Pre-construction primer (PCP), or shopprimer, have been applied to steel plates to control temporary corrosion during ship fabrication. For surface preparation at ship block stage, in common shipyard practices, welding beads, burnt and rusted areas shall be blasted or power tool cleaned and the contamination such as zinc salt shall be removed with blasting or power tool. Whereas, the sound film of PCP needs not to be removed or roughened as the paint having good compatibility with PCP is used for the first coat. In many cases, however, full blasting or sweep blasting on the sound PCP treated block assemblies was requested. There still has been argument about the legitimacy of this practice, thus, it is critical to evaluate the quality of the coating system applied on the sound PCP retained condition, comparing with the one applied on the full blasted or sweep blasted condition. In this study, two different epoxy systems for water ballast tank were applied on the surfaces with sound PCP condition, full blasted condition, and sweep blasted condition. Coating performances such as durability, anti-corrosion, cathodic disbondment resistance were evaluated. The test results clearly indicated that the sound film of PCP needed not to be removed or roughened as the paint having good compatibility with PCP based on inorganic zinc silicate.

• 한국화재소방학회논문지
• /
• 제34권3호
• /
• pp.8-17
• /
• 2020

본 논문은 오염물질에 따른 HFIX 절연전선 피복의 특성변화에 관한 연구이다. HFIX 절연전선 피복을 오염시키기 위해 전선의 내수성시험 항목인 KS C IEC 60811-1-3 규격을 인용, 오염물질을 선정하고 선정된 오염물질에 시료를 노출시켜 주차 별 최대 4주간 노출된 실험시료를 제작하였다. 그 후 주차 별 시료들을 대상으로 최대인장하중 및 신장률을 측정하였다. 오염노출 기간이 길어짐에 따라 최대인장하중이 상온시료의 경우 6.22%, 고온시료 6.52%, 방청윤활제 19.94% 감소하였고, 신장률 또한 급격하게 감소하여 피복 특성저하가 뚜렷하게 나타났다. 추가적인 주사전자현미경을 이용한 표면 분석결과 오염기간이 길어짐에 따라 천공, 갈라짐, 용융 등의 구조 변경 현상이 발생되어 기계적 특성이 감소되는 것으로 나타났다. 따라서 절연전선의 성능저하를 방지하기 위해 검사주기 및 보수시기의 마련이 필요할 것으로 생각된다.

• 마이크로전자및패키징학회지
• /
• 제16권3호
• /
• pp.53-59
• /
• 2009

PCB 표면 개질 및 세정에 있어서 저압 수은 램프를 이용한 UV 장비가 널리 사용되어왔다. 본 연구에서는 공정의 생산성을 향상 시키기 위하여 기존 UV 장비를 대체하여 리모트 DBD 방식의 대기압플라즈마 장비를 새로이 개발하였다. 두 장비의 생산성 비교는 처리 시간 증가에 따른 표면 접촉각의 변화를 측정함으로써 정량적으로 비교할 수 있었다. 측정 결과 대기압 플라즈마 장비의 생산성이 UV 장비에 비하여 매우 우수한 것으로 확인 되었다. 또한 XPS를 이용한 표면 조성 측정 결과 동일한 접촉각 수준에서 UV 및 대기압 처리의 효과는 유사한 것으로 파악되었다. 즉, 유기 오염 수준이 감소되었으며 표면 일부 표면 원소가 산회되었다. 최종적으로 대기압 플라즈마를 BGA제조의 플럭스 도포 공정에 적용하였는데, 대기압 플라즈마를 처리함으로써 도포 공정의 균일도가 향상되는 결과를 얻을 수 있었다.

• Tribology and Lubricants
• /
• 제31권6호
• /
• pp.281-286
• /
• 2015

Automotive transmission systems are assembled with a large number of gears and shafts, and rolling bearings are used to ensure their smooth operation. Gear oil in the gear box contains solid particles such as wear debris from contacting gears and metallic chips. This particle-enriched lubricating oil can cause premature failure of the rolling bearings. Research aimed at improving the service life of these rolling bearings has been confined mainly to design and lubrication of the inner/outer rings and the rolling elements. In this paper, we redesigned the shape of the cage pocket of a deep groove ball bearing to reduce the premature failure due to particle contamination. Test bearings are assembled with this new cage design containing a hole punched in the cage pocket. Endurance tests are carried out using the contaminated lubricating oil with miracle grid as hard particle. The duration and damaged bearing component shapes are compared for two different cages. The B₁₀ life of bearing with new cage is increased by about 66% compared to the conventional cage. This is because the hard particles can be easily discharged through the pocket hole without staying for a long time in the lubrication regions. This greatly decreases abrasive wear and dents on the highly stressed ball bearing surfaces. Therefore, the cage design of this study, containing a pocket hole, can significantly delay the premature failure of rolling bearings and improve the endurance life.

• Parasites, Hosts and Diseases
• /
• 제51권1호
• /
• pp.139-142
• /
• 2013

Pinworm infection can occur through contact with contaminated surfaces followed by ingestion or even through inhalation of infective eggs. We have limited information regarding environmental contamination by eggs of Enterobius vermicularis. In order to determine environmental risk factors associated with the rate of E. vermicularis infection, we investigated possible environmental risk factors using a questionnaire from 46 kindergartens in 3 different cities of the southeast area of Korea. In total, using the cellotape anal swab technique, 3,422 children were examined for E. vermicularis infection. We evaluated E. vermicularis egg of books, educational materials, toys, room door handles, dusts of window edges, desks, chairs, tables, and dusts of classrooms. The overall egg-positive rate for E. vermicularis was 6.0%, and the prevalence of enterobiasis in each kindergarten ranged between 0% and 16.9%. We found that 78.9% of egg positive kindergartens were managed by private foundations, which was significantly higher, compared with kindergartens managed by public foundations or the nation. Compared with public or national kindergartens, most private kindergartens were located in residential areas and the number of children in these areas was significantly higher. In conclusion, numbers of children in kindergartens was found to be an environmental risk factor associated with transmission of enterobiasis in Korea.

• Journal of Periodontal and Implant Science
• /
• 제49권3호
• /
• pp.193-204
• /
• 2019

Purpose: The reaction of cells to a titanium implant depends on the surface characteristics of the implant which are affected by decontamination. The aim of this study was to evaluate the cytocompatibility of titanium disks treated with various decontamination methods, using salivary bacterial contamination with dental pellicle formation as an in vitro model. Methods: Sand-blasted and acid-etched (SA) titanium disks were used. Three control groups (pristine SA disks [SA group]; salivary pellicle-coated SA disks [pellicle group]; and biofilm-coated, untreated SA disks [NT group]) were not subjected to any decontamination treatments. Decontamination of the biofilm-coated disks was performed by 14 methods, including ultrasonic instruments, rotating instruments, an air-powder abrasive system, a laser, and chemical agents. MG63 cells were cultured in the presence of the treated disks. Cell proliferation assays were performed on days 2 and 5 of cell culture, and cell morphology was analyzed by immunofluorescence and scanning electron microscopy (SEM). A vascular endothelial growth factor (VEGF) assay was performed on day 5 of culture. Results: The cell proliferation assay revealed that all decontaminated disks, except for the 2 groups treated using a plastic tip, showed significantly less cell proliferation than the SA group. The immunofluorescence and SEM analyses revealed that most groups showed comparable cell density, with the exception of the NT group, in which the cell density was lower and bacterial residue was observed. Furthermore, the cells grown with tetracycline-treated titanium disks showed significantly lower VEGF production than those in the SA group. Conclusions: None of the decontamination methods resulted in cytocompatibility similar to that of pristine SA titanium. However, many methods caused improvement in the biocompatibility of the titanium disks in comparison with the biofilm-coated, untreated titanium disks. This suggests that decontamination is indispensable for the treatment of peri-implantitis, even if the original biocompatibility cannot be restored.

• Journal of Animal Science and Technology
• /
• 제64권2호
• /
• pp.343-352
• /
• 2022

Pig slaughterhouses harbor high humidity because of the necessary cleaning that takes place simultaneously with slaughter, which facilitates the existence of mold. Due to the enclosed space, there are several limitations to the control of mold growth with respect to cleaning, ventilation, and drying. In this study, the prevalence of fungi was investigated in four pig slaughterhouses in Korea. Four fungi (Aspergillus niger, Penicillium commune, Penicillium oxalicum, and Cladosporium cladosporioides) were detected with the highest frequency. These four strains were subjected to various treatments to reduce their growth. The fungi were inoculated onto stainless steel (SS) chips and treated with ultraviolet (UV)-C irradiation and hot water. Individual treatments with UV-C (15, 30, 90, 150, 300, and 600 mJ/cm²), and hot water (60, 65, 70, and 83℃) were performed to sanitize the SS chips. Simultaneous cleaning with 60℃ hot water and more than 150 mJ/cm² of UV-C reduced the fungal incidence by > 6.5 Log from 6.6-7.0 Log CFU/cm² (initial count). Our results demonstrate that a combined treatment of UV-C and hot water is the most economical and convenient way to prevent microbiological contamination of small tools (such as knives and sharpeners) and steel surfaces in slaughterhouses.

• 반도체디스플레이기술학회지
• /
• 제22권3호
• /
• pp.130-135
• /
• 2023

Plasma-resistant ceramic (PRC) is a material used to prevent internal damage in plasma processing equipment for semiconductors and displays. The challenge is to suppress particles falling off from damaged surfaces and increase retention time in order to improve productivity and introduce the latest miniaturization process. Here, we confirmed the effect of suppressing plasma deterioration and reducing the etch rate through surface treatment of existing PRC with an initial illumination level of 200 nm. In particular, quartz glass showed a decrease in etch rate of up to 10%. Furthermore, it is believed that micro-scale secondary particles formed on the microstructure of each material grow as crystals during the fluoridation process. This is a factor that can act as a killer defect when dropped, and is an essential consideration when analyzing plasma resistance. The plasma etching suppression effect of the initial illumination is thought to be due to partial over etching at the dihedral angle of the material due to the sputtering of re-emission of Ar+-based cations. This means that plasma damage due to densification can also be interpreted in existing PRC studies. The research results are significant in that they present surface treatment conditions that can be directly applied to existing PRC for mass production and a new perspective to analyze plasma resistance in addition to simple etching rates.