• 생태와환경
• /
• 제45권4호
• /
• pp.420-443
• /
• 2012

An Individual-Based Model (IBM) was developed by employing natural and toxic survival rates of individuals to elucidate the community responses of benthic macroin-vertebrates to anthropogenic disturbance in the streams. Experimental models (dose-response and relative sensitivity) and mathematical models (power law and negative exponential distribution) were applied to determinate the individual survival rates due to acute toxicity in stressful conditions. A power law was additionally used to present the natural survival rate. Life events, covering movement, exposure to contaminants, death and reproduction, were simulated in the IBM at the individual level in small (1 m) and short (1 week) scales to produce species abundance distributions (SADs) at the community level in large (5 km) and long (1~2 years) scales. Consequently, the SADs, such as geometric series, log-series, and log-normal distribution, were accordingly observed at severely (Biological Monitoring Working Party (BMWP<10), intermediately (BMWP<40) and weakly (BMWP${\geq}50$) polluted sites. The results from a power law and negative exponential distribution were suitably fitted to the field data across the different levels of pollution, according to the Kolmogorov-Smirnov test. The IBMs incorporating natural and toxic survival rates in individuals were useful for presenting community responses to disturbances and could be utilized as an integrative tool to elucidate community establishment processes in benthic macroin-vertebrates in the streams.

• Toxicological Research
• /
• 제20권1호
• /
• pp.21-29
• /
• 2004

We used cDNA microarray to assess gene expression profiles in hematopoetic cell line, U-937, exposed to low doses of ionizing irradiation. The 1,000 DNA elements on this array were PCR-amplified cDNAs selected from named human cancer related genes. According to the strength of irradiation, the levels of some gene expression were increased or decreased as dose-dependent manner. The gene expressions of Tubulin alpha, protein kinase, interferon-alpha, -beta, -omega receptor and ras homolog gene family H were significantly increased. Especially, Tubulin gene was shown 2.5 fold up-regulated manner under stress of 500 rad irradiation than 200 rad. On the other hand, fibroblast growth factor 12 and four and a half LIM domains, etc. were significantly down-regu-lated. Also, tumor protein 53(TP53) related genes that p53 inducible protein, tumor protein 53-binding protein looks of little significance as radiation sensitive manner. The radio-sensitivity of tubulin gene etc. that we proposed could be useful to rapid and correct survey for the bio-damage by exposure to low dose irradiation.

• Nuclear Engineering and Technology
• /
• 제36권1호
• /
• pp.47-52
• /
• 2004

Recently, a new sintered pellet-type LiF:Mg,Cu,Na,Si TL detector which has a high sensitivity and good reusability, named KLT-300(KAERI LiF:Mg,Cu,Na,Si TL detector), was developed by the variation of the dopants concentrations and the parameters of the preparation procedure at KAERI (Korea Atomic Energy Research Institute). In this study, the thermoluminescent characteristics of the newly developed TL detectors were investigated. The sensitivity of the TL detector was compared with that of the TLD-100 by light integration. The dose linearity of the detector was tested from $10^{-6}$ Gy up to 30 Gy. The dose response was very linear up to 10 Gy and a sublinear response was observed at higher doses. The energy response of the detector was studied for photon energies from 20 keV to 662 keV. The result shows that a maximum response of 1.004 at 53 keV and a minimum response of 0.825 at 20 keV were observed. The reproducibility study for the TL detector was also carried out. The coefficients of variation for each detector separately did not exceed 0.016, and for all the 10 detectors collectively was 0.0054. Lower limit of detection for the detector was investigated at 70 nGy by the Harshaw 4500 TLD Reader and the residual signal of the TL detector was found to be $0.57\%$.

• 한국지하수토양환경학회지:지하수토양환경
• /
• 제22권4호
• /
• pp.33-48
• /
• 2017

An optimum disposal plan of disused sealed radioactive sources (DSRSs) should be established to ensure long-term disposal safety at the low- and intermediate-level radioactive waste (LILW) disposal facility in Gyeongju. In this study, an optimum disposal system was suggested and preliminary post-closure safety assessment was performed. The DSRSs disposal system was composed of a rock cavern and near surface disposal facilities at the Gyeongju LILW disposal facility. The assessment was conducted using GoldSim program, and probabilistic assessment and sensitivity analysis were implemented to evaluate the uncertainties in the input parameters of natural barriers. Deterministic and probabilistic calculations indicated that the maximum dose was below the regulatory limits ($0.1mSvyr^{-1}$ for the normal scenario, $1mSvyr^{-1}$ for the well scenario). It was concluded that the DSRSs disposal system would maintain environmental safety over a long-time. Moreover, the partition coefficient of Np in host rock, Darcy velocity in host rock, and density of the host rock were the most sensitive parameters in predicting exposure dose in the safety assessment.

• Nuclear Engineering and Technology
• /
• 제56권4호
• /
• pp.1425-1430
• /
• 2024

This study develops superheated emulsion detectors that are both sensitive to fast neutrons, and thermal neutrons owing to the exergonic ⁶₃Li(n, α)³₁H capture reaction caused by the ⁶Li-containing compound dispersed throughout the gel-like medium. The experimental research was conducted on two SEDs. One detector was an ordinary Freon-12 detector and the other was a Freon-12 detector containing 3.4 % (by weight) LiCl. In order to investigate the sensitivity of lithium-containing SEDs to thermal neutrons, two types of SEDs were simultaneously exposed to various flux levels of thermal neutrons from ²⁴¹Am-Be neutron source inside a cylindrical tank filled with water. A Boron-lined proportional counter was used to estimate the thermal neutron flux and the relevant MCNP code was developed for flux and dose calculations in the prepared set-up around ²⁴¹Am-Be source. The results demonstrate that there is a proportional relationship between the variations of SED response and the change in thermal neutron flux and dose. Also, the sensitivity of SED was estimated.

• Radiation Oncology Journal
• /
• 제17권3호
• /
• pp.256-260
• /
• 1999

목적 : 얇은 박막을 위에 얹은 TLD 선량계의 반응 값에 영향을 미치는 인자를 조사하였고, 특히, 금속박막을 얹은 TLD 선량계의 광자에너지와 표면 흡수선량에 대한 의존성을 조사하였다. 방법 및 재료 : 본 연구에서는 TLD-100과 TLD-100 위에 얹은 Slt은 물질로는 주석, 금, 그리고 TE 플라스틱 판을 사용하였다. 각 금속 박막의 두께는 0.1 mm, TE 플라스틱 판의 두께는 1 mm였고 각 박막의 면적은 TLD-100의 면적과 같이 하였다. 방사선치료에 많이 산이는 6 MV에서 15 MV사이의 광자에너지에 대한 TLD-100의 반응감도와 금박막을 얹은 TLD-100의 반응감도, 그리고 주석 박막을 얹은 TLD-100의 반응감도를 비교해 보았다. 결과 : 금속 박막을 얹은 TLD의 경우 표면 흡수선량의 증가가 명백히 나타나고, 금 박막을 얹은 TLD의 경우 10MV에서 정상 TLD보다 약 1.83배 정도 과잉 반응하는 것으로 관측되었으며, 흡수선량에 따른 반응감도의 변화는 주석을 얹은 TLD의 경우가 가장 작았다 금속 박막을 얹은 TLD의 일반 TLD에 대한 상대 반응감도는 에너지에 대한 의존성을 거의 나타내지 않았다. 그리고 311은 박막의 조직에 대한 등가 두께에 따라 반응감도가 증가하였다. 결론 : 금속박막을 얹은 TLD 선량계의 반응값이 고 에너지(6-15 MV)에 대한 의존성을 거의 나타내지 않았으며, 흡수선량에 대한 선형성도 뛰어난 것으로 관측되었다. 따라서 금속박막을 얹은 TLD 선량계는 매우 작은 크기의 광자빔과 표면흡수선량의 측정에 매우 적합한 것으로 사료된다.

• Clinical and Experimental Pediatrics
• /
• 제59권4호
• /
• pp.178-182
• /
• 2016

Purpose: Medium-dose (1 g/kg) intravenous immunoglobulin (IVIG) is effective in the majority of patients with Kawasaki disease (KD) but some patients who do not respond to medium-dose IVIG are at high risk for the development of coronary artery lesions (CALs). The purpose of this study was to identify the clinical predictors associated with unresponsiveness to medium-dose IVIG and the development of CALs. Methods: A retrospective study was performed in 91 children with KD who were treated with mediumdose IVIG at our institution from January 2004 to December 2013. We classified the patients into responders (group 1; n=68) and nonresponders (group 2; n=23). We compared demographic, laboratory, and echocardiographic data between the 2 groups. Results: Multivariate logistic regression analysis identified 6 variables as predictors for resistance to medium-dose IVIG. We generated a predictive scoring system assigning 1 point each for percentage of neutrophils ${\geq}65%$, C-reactive protein ${\geq}100mg/L$, aspartate aminotransferase ${\geq}100IU/L$, and alanine aminotransferase ${\geq}100IU/L$, as well as 2 points for less than 5 days of illness, and serum sodium level ${\leq}136mmol/L$. Using a cutoff point of ${\geq}4$ with this scoring system, we could predict nonresponsiveness to medium-dose IVIG with 74% sensitivity and 71% specificity. Conclusion: If a patient has a low-risk score in this system, medium-dose IVIG can be recommended as the initial treatment. Through this process, we can minimize the adverse effects of high-dose IVIG and incidence of CALs.

• Nuclear Engineering and Technology
• /
• 제54권8호
• /
• pp.2871-2876
• /
• 2022

The sensitivity of polymer-based capacitive relative humidity (RH) sensors after irradiation with neutrons, electrons and protons was measured. Degradation consists of the decreasing of the upper RH limit that can be measured. At the same time, low RH-level sensitivity is almost stable. After 30 krad of absorption dose, RH cut off is equal to 85% of max value, after 60 krad-40%. Degradation reduces after annealing which indicates high radiation sensitivity of the internal circuit in comparison to RH-sensing polymer film.

• 한국방사선학회논문지
• /
• 제13권2호
• /
• pp.313-318
• /
• 2019

민감도 향상을 위해 블록형 섬광체를 사용한 검출기를 개발하였다. 픽셀형 섬광체는 섬광체에서 발생된 빛을 최대한 광센서로 이동시키기 위해 픽셀 사이에 반사체가 위치하며, 반사체 부분으로 민감도 손실이 발생한다. 민감도를 향상시키고 픽셀형 섬광체의 특징을 가지게 하기 위해 블록형 섬광체를 레이저 각인을 통해 픽셀 형태의 섬광체로 가공하였다. 본 섬광체를 위치민감형 광전증배관과 결합하여 평면 영상을 획득하였고, 각 픽셀별 에너지 스펙트럼과, 에너지 분해능을 측정하였으며, GATE 시뮬레이션을 통해 블록형 섬광체와 픽셀 섬광체의 민감도 분석을 수행하였다. 측정된 전체 에너지 분해능은 20.7%를 보였으며, 민감도는 픽셀 섬광체에 비해 18.5% 높은 결과를 나타내었다. 본 검출기를 감마카메라 및 양전자방출단층촬영기기 등의 영상화 기기에 활용할 경우 높은 민감도 향상을 통해 촬영시간의 단축 및 적은 방사선원 사용으로 환자의 피폭선량 감소를 이룰 수 있을 것이다.

• 한국균학회지
• /
• 제34권1호
• /
• pp.34-38
• /
• 2006

양성자 빔 조사 후 조사선량에 따른 느타리버섯(Pleurotus ostreatus) 담자포자 발아율 및 균사체 생존율이 $10{\sim}100\;Gy$조사선량에서 시그모이드 곡선을 그리며 증가하였으며, 이후 500y 이상 조사시 유의성있게 감소하였다. 50% 치사율($L_{50}$)을 나타내는 조사선량은 담자포자가 500 Gy, 균사체가 400 Gy로 나타났으며, $D_{10}$값($D_{10}\;=\;-l/slope(b)$, y = a + bx) 은 각각 750 Gy와 1,250 Gy로 나타났다. 느타리버섯 돌연변이원으로서 양성자 빔 이용시 적정 조사선량은 담자포자의 경우 $500{\sim}750\;Gy$, 균사체의 경우 $400{\sim}1,000\;Gy$가 바람직하다고 판단되었다.