• Nuclear Engineering and Technology
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• v.1 no.2
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• pp.91-101
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• 1969

Resistivity changes of n-type float-zone silicon crystals with 6.4$\times$10$^{14}$ to 1.25$\times$10$^{17}$ phosphorus atoms/㎤ due to irradiation by (1) 1 MeV electrons, (2) two types of research reactors, and (3) $Co^{60}$ ${\gamma}$-ray sources were investigated. The results were analyzed on the basis of a simple exponential formula derived by Buehler. While the formula gave a fair fit in the low fluence range in most cases, the deviation was quite appreciable in the case of 1 MeV electron irradiation, and a linear change gave better fit in some cases. The large change in the carrier removal rate in electron-irradiated samples in the high fluence range was analyzed in detail in terms of the Fermi level cross-over of the defect levels. Based on the damage constants evaluated from the initial portion of data where the formula was applicable, the relative effectiveness of various radiation sources in causing the resistivity change in n-type silicon was compared. The TRIGA Mark II reactor neutrons, for example, were found to be about 40 times more effective than 1 MeV electrons. The dependence of the damage constant on the initial carrier concentration was also examined. The physical basis of the exponential law and the effect of the Fermi level cross-over of the defect levels on the resistivity change in the high fluence ranges are discussed.

• Journal of Radiation Protection and Research
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• v.44 no.3
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• pp.118-126
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• 2019

Background: Government conducts environmental radioactivity surveillance for verification purpose around nuclear facilities based on the Nuclear Safety Law and issues a surveillance report every year. This study aims to evaluate the short and the long-term fluctuation of radionuclides detected above MDC and their origins using concentration ratios between these radionuclides. Materials and Methods: Sample media for verification surveillance are air, rainwater, groundwater, soil, and milk for terrestrial samples, and seawater, marine sediment, fish, and seaweed for marine samples. Gamma-emitting radionuclides including $^{137}Cs$, $^{90}Sr$, Pu, $^3H$, and $^{14}C$ are evaluated in these samples. Results and Discussion: According to the result of the environmental radioactivity verification surveillance in the vicinity of nuclear power facilities in 2017, the anthropogenic radionuclides were not detected in most of the environmental samples except for the detection of a trace level of $^{137}Cs$, $^{90}Sr$, Pu, and $^{131}I$ in some samples. Radioactivity concentration ratios between the anthropogenic radionuclides ($^{137}Cs/^{90}Sr$, $^{137}Cs/^{239+240}Pu$, $^{90}Sr/^{239+240}Pu$) were similar to those reported in the environmental samples, which were affected by the global fallout of the past nuclear weapon test, and Pu atomic ratios ($^{240}Pu/^{239}Pu$) in the terrestrial sample and marine sample showed significant differences due to the different input pathway and the Pu source. Radioactive iodine ($^{131}I$) was detected at the range of < $5.6-190mBq{\cdot}kg-fresh^{-1}$ in the gulfweed and sea trumpet collected from the area of Kori and Wolsong intake and discharge. A high level of $^3H$ was observed in the air (Sangbong: $0.688{\pm}0.841Bq{\cdot}m^{-3}$) and the precipitation (Meteorology Post: $199{\pm}126Bq{\cdot}L^{-1}$) samples of the Wolsong nuclear power plant (NPP). $^3H$ concentration in the precipitation and pine needle samples showed typical variation pattern with the distance and the wind direction from the stack due to the gaseous release of $^3H$ in Wolsong NPP. Conclusion: Except for the detection of a trace level of $^{137}Cs$, $^{90}Sr$, Pu, and $^{131}I$ in some samples, anthropogenic radionuclides were below MDC in most of the environmental samples. Overall, no unusual radionuclides and abnormal concentration were detected in the 2017's surveillance result for verification. This research will be available in the assessment of environment around nuclear facilities in the event of radioactive material release.

• Journal of the Korean Society of Radiology
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• v.13 no.1
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• pp.125-132
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• 2019

Potassium cyanate (KCN) is an inorganic reagent and can induce the post-translation carbamylation of proteins. The carbamylated reaction in the body is involved in cell death in various diseases. According the results in our previous study, KCN enhances the radiosensitivity of human colorectal cancer cell line, HCT 116 cells. However, it was not enough to confirm the mechanism that KCN works in these cells. To determinated the mechanisms of KCN in the cells with increased radiosensitivity, HCT 116 cells were treated KCN with low-dose gamma-radiation. And then, we examined alteration of the cell cycle, cell proliferation, cytokine level and the activation of cell signaling protein. As a result, cell cycle arrest and cell death were induced by the activation of caspase-3 and PARP in the irradiated cells with KCN treatment. These changes of the irradiated cell with KCN treatment were induced by the release of $TNF-{\alpha}$ via $NF-{\kappa}B$ activation. In conclusions, enhanced radio-sensitivity mediated by KCN induced cell death and it occurs by $NF-{\kappa}B$-dependent $TNF-{\alpha}$ production.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.26 no.4
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• pp.318-323
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• 1981

This study was conducted to establish an effective radiation treatment and selection method for induced mutants in M_1 population of soybean treated with gamma-ray. About 64% of total M_1 plants was reduced in plant height up to 50 - 60% and among which 60 - 70% of the plants were contained mutations in M_2 generation. About 60% of the MI plants have born 6 - 15 seeds per plant and 50 - 60% of their progenies produced mutants in M_2 generation. Positive correlation between plant height and number of seeds per plant in M_1 population was found. Higher visible macro-mutation rate in M_2 was observed in the groups of reduced plant height and seed number in the M_1 generation, whereas the frequency of chlorophyll mutation was increased in the group of less damaged plants. The size of mutation sector was increased with reduction in number of seeds per M_1 plant and the mutants were occurred at random in all the parts of M_1 plants. For the effective selection of mutants in soybean mutation breeding, the M_1 seeds should be harvested from the radiation damaged M_1 plants with the application of higher doses of mutagens, and handling M_2 generation by bulk population method is recommendable.

• Journal of Radiation Protection and Research
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• v.41 no.1
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• pp.49-55
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• 2016

Background: For the purpose of baseline data collection and enhancement of environmental monitoring the distribution studies of $^{137}Cs$ and $^{90}Sr$ in the soil of Uljin province was performed and the relation between surface soil activities and soil properties (pH, TOC and median of the surface soil) was analyzed. Materials and Methods: For 14 spots within 10 km from the NPP surface soil samples were collected and soils for depth profile were sampled for 3 spots in April 2011. Using ${\gamma}$-ray spectrometry with HPGe detector, the concentrations of $^{137}Cs$ were determined and the concentrations of $^{90}Sr$ were measured by counting ${\beta}$-activity of $^{90}Y$ (in equilibrium with $^{90}Sr$) in a gas flow proportional counter. Results and Discussion: The concentration ranges of $^{137}Cs$ and $^{90}Sr$ were $<0.479-39.6Bq{\cdot}(kg-dry)^{-1}$ (avg. $7.51Bq{\cdot}(kg-dry)^{-1}$) and $0.209-1.85Bq{\cdot}(kg-dry)^{-1}$ (avg. $0.74Bq{\cdot}(kg-dry)^{-1}$) which were similar to the reported values from other regions in Korea. The activity ratio of $^{137}Cs$ to $^{90}Sr$ in surface soils was around 9.67, which is much bigger than the initial value of 1.75 for worldwide fallouts because of faster downward movement of $^{90}Sr$ after fallout than that of $^{137}Cs$. For depth profile studies soils were collected down to 40 cm depth for the locations of Deokgu, Hujeong and Maehwa. The $^{137}Cs$ concentration distribution of the first two showed maximum values at top soils and decreased rapidly in exponential manner, while $^{90}Sr$ showed two local maximum values for soils near top and about 30 cm depth. Through linear fittings between the $^{137}Cs$ and $^{90}Sr$ concentrations of surface soil and pH, TOC and median of the surface soil, the only probable relationship obtained was between $^{137}Cs$ and TOC (determination coefficient $R^2=0.6$). Conclusion: The concentration ranges of $^{137}Cs$ and $^{90}Sr$ in Uljin were similar to the reported values from other regions in Korea. The only probable relationship obtained between activities and soil properties was between $^{137}Cs$ and TOC.

• Horticultural Science & Technology
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• v.28 no.4
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• pp.648-655
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• 2010

This study is the first comprehensive report on the molecular cloning, structural characterization, sequence comparison between wild and mutant types, copy number in the genome, expression features and activities of a gene encoding 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) in Korean lawn grass ($Zoysia$ $japonica$). The full length cDNA of the EPSPS from Korean lawn grass ($zj$EPSPS) obtained from a 3' and 5' RACE method was 1540 bp, containing a 1176 bp ORF, a 144 bp leader sequence (5' UTR) and a 220 bp 3' UTR, which was eventually decoded 391 amino acid residues with a molecular mass of 41.74 kDa. The Southern blot detection of the $zj$EPSPS showed that the gene exists as a single copy in the Korean lawn grass genome. Sequence comparison of the $zj$EPSPS gene demonstrated that the glyphosate-tolerant mutant (GT) having a Pro-53 to Ser substitution in the gene seems to have a preferred binding activity of the enzyme to phosphoenol pyruvate(PEP) over glyphosate, which allows the continuous synthesis of aromatic amino acids in the shikimate pathway. From the Northern blotting analysis, the $zj$EPSPS was found to be highly expressed, with continuous increase until 36 hours after 0.5% glyphosate treatment in both wild and mutant samples, but 1.5-fold higher EPSP synthase activity was observed in the tolerant mutant when exposed to the glyphosate treatment. The molecular information of the $zj$EPSPS gene obtained from this study needs to be further dissected to be more effectively applied to the development of gene-specific DNA markers and zoysiagrass cultivars; nevertheless, the glyphosate-tolerant mutant having the featured $zj$EPSPS gene can be provided to turfgrass managers for weed problems with timely adoptable management options.

• Progress in Medical Physics
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• v.22 no.2
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• pp.99-105
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• 2011

The purpose of this study is to evaluate the accuracy of IMRT in our clinic from based on TG119 procedure and establish action level. Five IMRT test cases were described in TG119: multi-target, head&neck, prostate, and two C-shapes (easy&hard). There were used and delivered to water-equivalent solid phantom for IMRT. Absolute dose for points in target and OAR was measured by using an ion chamber (CC13, IBA). EBT2 film was utilized to compare the measured two-dimensional dose distribution with the calculated one by treatment planning system. All collected data were analyzed using the TG119 specifications to determine the confidence limit. The mean of relative error (%) between measured and calculated value was $1.2{\pm}1.1%$ and $1.2{\pm}0.7%$ for target and OAR, respectively. The resulting confidence limits were 3.4% and 2.6%. In EBT2 film dosimetry, the average percentage of points passing the gamma criteria (3%/3 mm) was $97.7{\pm}0.8%$. Confidence limit values determined by EBT2 film analysis was 3.9%. This study has focused on IMRT commissioning and quality assurance based on TG119 guideline. It is concluded that action level were ${\pm}4%$ and ${\pm}3%$ for target and OAR and 97% for film measurement, respectively. It is expected that TG119-based procedure can be used as reference to evaluate the accuracy of IMRT for each institution.

• Journal of Soil and Groundwater Environment
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• v.22 no.1
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• pp.27-32
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• 2017

Cesium (Cs) generated by nuclear accidents is one of the most hazardous radionuclides because of its gamma radiation and long half-life. Especially, when Cs is exposed on the soil environments, Cs is mainly adsorbed on the topsoil and is strongly combined with tiny soil particle including clay minerals. The adsorption of Cs onto soil can vary depending on various physicochemical properties of soil. In this study, the adsorption characteristics between soil and Cs were investigated according to various physicochemical properties of soil including organic matter contents, cation exchange capacity (CEC), soil particle size, and the types of clay minerals. Soil organic matter inhibited the adsorption of Cs onto the soil because organic matter was blocking the soil surface. In addition, it was estimated that the CEC of the soil influenced the adsorption of Cs onto the soil. Moreover, more Cs was adsorbed as the soil particles size decreased. It was estimated that Cs was mostly adsorbed onto the topsoil, this is related to the clay mineral. Therefore, soil organic matter, CEC, soil particle size, and clay minerals are considered the key factors that can influence the adsorption characteristics between soil and Cs.

• The Korean Journal of Nuclear Medicine
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• v.23 no.1
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• pp.7-12
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• 1989

The pain, swelling of salivary glands and dry mouth are not infrequent complication of the high dose radioiodine treatment in the patients with differentiated thyroid cancer. The purpose of this study was, by the dynamic salivary scintigraphy, to observe the change of the salivary function after the high dose $(150\sim200mci)$ radioiodine treatment. From May 1987 to April 1988, the dynamic salivary scintigraphy with 5mci of $^{99m}Tc-pertechnetate$ and gamma camera was performed before and 7 days after the radiolodine treatment in 7 patients with differentiated thyroid cancer. Just after the dynamic scintigraphy, the stimulation test with vitamin C solution of pH3.0 and poststirnulation scintigraphy were done, and the radioactivity uptake index, excretion fraction and salivary clearance after the stimulation were calculated for each gland. There was positive correlation between the radioactivity uptake index and excretion fraction after the stimulation. The salivary clearance after the stimulation was $18.96{\pm}8.95ml/min$ in the pretreatment state, and $14.37{\pm}7.7ml/min$ after the radioioine treatment. After the radioiodine treatment, the radioactivity uptake index, excretion fraction and salivary clearance after the stimulation were significantly reduced in the parotid glands, but only the excretion fraction was reduced in the submandibular glands. The more the pretreatment salivary clearance after the stimulation was, the % change after the treatment was smaller. Further studies on the relation between the radiation dose in the salivary glands and the change of their function, and the long-term observation for the recovery of function are expected.

• Journal of Korean Neurosurgical Society
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• v.61 no.4
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• pp.427-433
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• 2018

Obsessive compulsive disorder is a debilitating condition characterized by recurrent obsessive thoughts and compulsive reactions. A great portion of the obsessive compulsive disorder (OCD) patients are managed successfully with psychiatric treatment such as selective serotonin-reuptake inhibitor and cognitive behavioral psychotherapy, but more than 10% of patients are remained as non-responder who needs neurosurgical treatments. These patients are potential candidates for the neurosurgical management. There had been various kind of operation, lesioning such as leucotomy or cingulotomy or capsulotomy or limbic leucotomy, and with advent of stereotaxic approach and technical advances, deep brain stimulation was more chosen by neurosurgeon due to its characteristic of reversibility and adjustability. Gamma knife radiosurgery are also applied to make lesion targeting based on magnetic resonance (MR) imaging, but the complication of adverse radiation effect is not predictable. In the neurosurgical field, MR guided focused ultrasound has advantage of less invasiveness, real-time monitored procedure which is now growing to attempt to apply for various brain disorder. In this review, the neurosurgical treatment modalities for the treatment of OCD will be briefly reviewed and the current state of MR guided focused ultrasound for OCD will be suggested.