• Advances in concrete construction
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• 제10권1호
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• pp.13-20
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• 2020

Steel corrosion in embedded steel causes a significant durability problems and this usually propagates to structural degradation. Large-scaled concrete structures, PSC (Pre-stressed Concrete) or RC (Reinforced Concrete) structures, are usually constructed with mass concrete and require quite a long construction period. When they are located near to sea shore, chloride ion penetrates into concrete through direct or indirect exposure to marine environment, and this leads durability problems. Even if the structures are sheltered from chloride ingress outside after construction, the chloride contents which have been penetrated into concrete during the long construction period are differently evaluated from the initially mixed chloride content. In the study, chloride profiles in cores extracted from anchorage concrete block in two large-scaled suspension bridge (K and P structure) are evaluated considering the exposure periods and conditions. Total 21 cores in tendon room and chamber room were obtained, and the acid-soluble chlorides and compressive strength were evaluated for the structures containing construction period around 3 years. The test results like diffusion coefficient and surface chloride content from the construction joint and cracked area were also discussed with the considerations for maintenance.

• Biomolecules & Therapeutics
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• 제7권4호
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• pp.322-328
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• 1999

In this study, it was tested whether the changes of catecholamines and its metabolites are related with the changes of blood pressure(BP) induced by different levels of lead exposure. Adult male SD rats were exposed to lead by giving drinking water containing 50(low doses), 200 and 1,000 ppm(high doses) of lead(as lead acetate) or sodium acetate(for control groups, supplying an identical amount of acetate) for 7 or 16 weeks. The systolic BP was measured in the unanesthetized state by the tail-cuff technique. Levels of catecholamines and its metabolites in urine were measured by HPLC-ECD. Rats receiving 200 and 1,000 ppm developed an elevation of systolic BP at 3 and 7 weeks compared with week 0, but blood pressure levels at 16 weeks returned to normal. For the 50 ppm lead treated group, systolic BP increased significantly at 7 weeks and 16 weeks. The concentrations of norepinephrine and VMA in the urine of lead exposed rats changed similarly to the changes of blood pressure, but blood viscosity levels in all lead treated rats increased continuously during all lead treatment periods. This result suggests that the changes of catecholamines and its metabolites in urine by lead intoxication may influence the changes of blood pressure.

• Journal of the Korean Wood Science and Technology
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• 제46권6호
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• pp.627-636
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• 2018

This research was performed to supplement the previous research about the driving rain index (DRI) for Korea determined by using daily weather data for 30 years. The average annual driving rain index (AADRI) was calculated from the hourly weather data, and the magnitude of DRI was investigated according to wind directions. The hourly climate data were obtained from the Korea Meteorological Administration (KMA) for the period 2009 to 2017. Of 82 locations investigated, seven were classified into regions where the level of exposure of walls to rain was high. The result showed quite a difference from the previous results, in which no high exposure regions were observed. Since the hourly-based and the daily-based annual driving rain index (ADRI) values showed only a slight difference, the result may be explained by the length of the periods used in both studies. The change of DRI according to wind directions showed that there was a certain range of wind directions in which driving rain easily approached building walls. It suggests that the consideration of wind directions with high DRI would be useful to develop a good design of wooden buildings from the point of wood preservation and maintenance.

• 한국수산과학회지
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• 제36권2호
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• pp.107-112
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• 2003

Effect of PCBs on the skin and gill development of olive flounder, Paralichthys olivaceus were investigated by histological methodology and morphometric data. The olive flounder were exposed to limit concentration of effulent of PCBs (3.0 ${\mu}g/L$) for 60 days. Skin development can be classified into four stages: SSEL (simple squamous epithelial layer), MCA (mucous cell appearance) & CCA (club cell appearance) DLA (dermal layer appearance), and SEL (startification of epidermal layer) stages. Gill development had five stages: GFA (gill filament appearance), IGFE (identification of early gill filament epithelial cell) MCA (mucous cell appearance), PCA (pillar cell appearance), and FGL (formation of gill lamella) stages. The periods of structural completion of skin and gill were 22-30 days and 23-30 days after hatching in the exposure group respectively. The process of development of skin and gill of the exposure group was very similar to that of the control group. Therefore, PCBs (3 ${\mu}g/L$) have no influence on the development of skin and gill in the larval stage of olive flounder.

• 방사선산업학회지
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• 제11권3호
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• pp.123-130
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• 2017

Concerns about high radiation exposure to the hands of radiation workers who may contact with radioactive contamination on surfaces in a nuclear power plant (NPP) had been raised, and the Korean regulatory body required the extremity dose estimation during contact tasks with radioactive materials. Korean NPPs conducted field tests to identify the incident radiation to the hands of radiation workers who may contact with radioactive contamination during maintenance periods. The results showed that the radiation fields for contact tasks are dominated by high energy photons. It was also found that the radiation doses to the hands of radiation workers in Korean NPPs were much less than the annual dose limits for extremities. This approach can be applicable to measure and estimate the extremity dose to the hands of medical workers who handle the radioactive materials in a hospital.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 춘계학술발표회논문집(1)
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• pp.571-576
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• 1996

Currently most nuclear power plants(NPPs) are adopted the mid-loop operation to minimize the overhaul period and save the operating cost. For mid-loop operation it is essential to install nozzle dam between RCS pipe and steam generator(SG). Because SG remains more highly contaminated with radioactive material than any other parts of the NPPs, the repairmen are very reluctant to carry out installing nozzle dam inside the SG. Until now, unfortunately, it appears that no practically applicable device was developed to provide the longstanding demand. Also the accidents have been reported by licenser event report during this operation mode due to loss of residual heat removal(RHR). The purpose of this paper is to conduct remotely blocking and disintegration of nozzle of a SG which has the highest radiation exposure during the maintenance in NPPs. The remote nozzle blocking device of a SG includes three bladders, hubs, air controller provisions to supply and contact air pressure into the bladders. This remote nozzle block device will give the larger operation margin to prevent the loss of RHR and minimize the radiation exposure dose to the repairman and shorten the overhaul periods.

• 환경생물
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• 제39권3호
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• pp.298-310
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• 2021

Prediction of the behavior of heavy metals over time is important to evaluate the heavy metal toxicity in algae species. Various modeling studies have been well established, but there is a need for an improved model for predicting the chronic effects of metals on algae species to combine the metal kinetics and biological response of algal cells. In this study, a kinetic dynamics model was developed to predict the copper behavior(5 ㎍ L^-1, 10 ㎍ L^-1, and 15 ㎍ L^-1) for two freshwater algae (Pseudokirchneriella subcapitata and Chlorella vulgaris) in the chronic exposure experiments (8 d and 21 d). In the experimental observations, the rapid change in copper mass between the solutions, extracellular and intracellular sites occurred within initial exposure periods, and then it was slower although the algal density changed with time. Our model showed a good agreement with the measured copper mass in each part for all tested conditions with an elapsed time (R² for P. subcapitata: 0.928, R² for C. vulgaris: 0.943). This study provides a novel kinetic dynamics model that is compromised between practical simplicity and realistic complexity, and it can be used to investigate the chronic effects of heavy metals on the algal population.

• Journal of Periodontal and Implant Science
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• 제33권4호
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• pp.585-597
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• 2003

Porphyromonas gingivalis has been implicated as an important periodontophathic bacterium in the etiology and progression of periodontal diseases. It has been reported that P.gingivalis may mediate periodontal destruction not only directly through its virulence factors, but also indirectly by including complex host mediated inflammatory reponses. The purpose of this study was t o evaluate the effects of P.gingivalis on the bone formation and resorption by osteoblasts. For this purpose, after determining the concentration below which sonicated P.gingivalis extracts (SPEs) have no cytotoxicity on mouse calvarial primary osteoblastic (POB) cells, we investigated the effects of SPEs on the alkaline phosphatase (ALP) activity, matrix metalloproteinase (MMP) expression (MMP-2, -9, 13), and prostaglandin $E_2$ ($PGE_2$) release in POB cells by treatment with SPEs below that concentration. The results were as follows; 1. SPEs showed no cytotoxic effect on POB cells up to a concentration of 1 ${\mu}m$/ml. 2. The treatment with SPEs reduced ALP activity in a dose-dependent manner in POB cells, In addition, when we investigated the effect of SPEs (1 ${\mu}m$/ml) on ALP activity for different exposure periods, statistically significant inhibition of ALP activity was shown at 2 days of exposure, and further significant inhibition occurred by extending the periods of exposure. 3. The treatment with SPEs stimulated the gene expression of MMP-9 in POB cells. 4. The pre-treatment with SPEs increased the amount of $PGE_2$ released in POB cells. In summary, the present study shows that P.gingivalis could inhibit osteogenesis and stimulate bone resorption not only by reducing ALP activity but also by increasing MMP-9 mRNA expression in osteoblasts, possibly through an endogenous $PGE_2$ pathway. In addition, our results suggest that if P.gingivalis affects osteoblasts in early differentiation stage, such effects by P. gingivalis could be irreversible.

• 농약과학회지
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• 제12권2호
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• pp.155-161
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• 2008

수단과 우리나라에서 수집된 12 가지 식물체 추출물(메탄올 추출 9종, 헥산추출 3종)을 이용하여 실내에서 뿌리혹선충(Meloidogyne incognita)의 부화에 미치는 영향을 조사하였다. 10,000 ppm, 1,000 ppm, 100 ppm 농도의 식물체 추출물에 뿌리혹선충 알을 넣고, 3일과 7일, 21일 후 부화 된 알의 수를 조사하였다 모든 식물체 추출물 처리에서 무처리에 비해 뿌리혹선충 난의 부화억제 활성이 있었다. 농도가 높을수록 부화억제 활성이 높았는데, 10,000 ppm 농도에서는 Quisqalis indica 처리를 제외하고 소수의 개체만이 부화하였다 그리고 Q. indica 처리에서만 7일과 21일째 84.4%와 54.4%가 부화하였고, 대부분의 처리에서는 7일째 이후에 부화되는 알이 없었다. 1,000 ppm농도에서는 10,000 ppm 농도에 비해 부화율이 높았는데, Cucumis mello var agrestis 처리에서 부화율이 가장 낮아 3, 7, 21일 후에 각각 2%와 8%, 3% 만이 부화하였다. 100 ppm 처리에서는 Desmodium caudatum 처리에서 처리 3일과 7일째 부화되는 알의 수가 가장 적었다.

• 한국환경보건학회:학술대회논문집
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• 한국환경보건학회 2004년도 International Conference Global Environmental Problems and their Health Consequences
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• pp.185-187
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• 2004

The co-administration of BPA and BBP induced slow weight gain compared with single administration in dams. Also, such mixture induced low neonatal body weights in next generation. The dams treated with BPA and BBP showed significant organ weight changes in liver, spleen exposed during lactational periods. But the dams exposed during lactational periods showed significant organ weight changes not only in liver, spleen but also in kidney, uterus and ovary. The F1 female rats exposed during lactation periods showed significant organ weight changes in liver, spleen, ovary. The F1 male rats showed significant organ weight changes in liver, kidney, epididymis, vesicular glands, prostate. However no clear synergistic effects of BPA and BBP could be found. Estrogen receptor ${\alpha}$ expression by BPA and BBP in the uterus(dam, F1 female) and testis(F1 male) were studied. There was no significant different $ER{\alpha}$ expression pattern between control and treated groups. But $ER{\alpha}$ expression were increased in F1 male testis and female uterus. F1 male showed distinct $ER{\alpha}$ expression, especially in the group of lactational combined exposure. Synergistic $ER{\alpha}$ expression was found by combined treatment of BPA and BBP.