• Journal of the Korean Society of Radiology
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• v.14 no.3
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• pp.279-287
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• 2020

Recently, interest in radiation protection is increasing because of the occurrence of accidents related to exposure dose. So, the nuclear safety act provides to install the shields to avoid exceeding the dose limit. In particular, when the worker conducts the non-destructive testing (NDT) without the fixed shielding structure, we should monitor the access to the workplace based on a constant dose rate. However, when we apply for permits for NDT work in these work environments, the consideration factors to the estimation of the distance and exposure dose are not legally specified. Therefore, we developed the excel model that automatically calculates the distance, exposure dose, and cost if we input the factors. We applied the assumption data to this model. As a result of the application, the distance change rate was low when the thickness of the lead blanket and collimator is above 25 mm, 21.5 mm, respectively. However, we didn't consider the scattering and build-up factor. And, we assumed the shape of the lead blanket and collimator. Therefore, if we make up for these limitations and use the actual data, we expect that we can build a database on the distance and exposure dose.

• Journal of the Korean Society of Radiology
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• v.11 no.7
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• pp.597-603
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• 2017

High-dose $^{131}I$ therapy has been generally carried out to remove remaining thyroid tissue or to cure metastasize lesion of patients who received full thyroidectomy due to differentiated thyroid cancers. In case high-dose $^{131}I$ therapy is carried out for a patient, the patient should be hospitalized being isolated for a certain period in order to restrict the amount of exposure to radiation of people at large from the patient within the limit of a level of radiation. Effective half-life is an important value to calculate how family members are exposed to radiation from a patient or to decide the period of isolation of the patient from the family members. Therefore, in this study we calculated the effective decay constant, effective half-life and period of isolation of high-dose $^{131}I$ therapy patient using NM670 SPECT/CT. As a result of carrying out this study, the effective half-life of high-dose $^{131}I$ therapy patients was derived and the time to reach the discharge level of 1.2 GBq was confirmed. When they were compared with each other in each of curative doses, the effective half-life did not have significant difference, but the time when the level of radiation remaining in the interior of the body to reach the criteria of isolation and discharge showed significant difference and it could be confirmed that the higher the curative dose the longer the period of isolation becomes. When the effective half-lives in each type of preparation were compared with each other, they did not show significant difference. However, When the times to reach the level of radiation that is the criteria of isolation and discharge in each type of preparations, they showed significant difference. The cause of the shortening of the isolation period for rhTSH patients group is decided to be low curative dose. Accordingly, if the current national health insurance (the insurance is applied to using of rhTSH in 3.7 GBq or lower) is maintained, while discerning them in each of types of preparation, we would be able to discharge patients at the time earlier than the current period of isolation (2 nights and 3 days).

• Applied Chemistry for Engineering
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• v.20 no.1
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• pp.87-93
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• 2009

Pd/activated carbon (Pd/AC) and Pd/alumina (Pd/AO) catalysts were prepared by the impregnation of palladium into activated carbon and alumina. The catalytic characteristics according to the kinds of support materials were compared. The decomposition efficiencies of ozone according to kinds of support materials are about the same when these were compared by adding 10 g of catalysts into the water saturated with ozone. The decomposition efficiencies and the oxidation characteristics (TOC, $COD_{Cr}$) of dichloroacetic acid were compared with the ozone only process and the catalytic ozonations using Pd/activated carbon and Pd/alumina catalysts. The decomposition efficiencies of dichloroacetic acid by catalytic ozonations were better than the one by ozone only process, but there was slight difference of the one between Pd/activated carbon and Pd/alumina catalyst. The decomposition efficiency of dichloroacetic acid was increased with increasing ozone dose at a constant concentration of dichloroacetic acid, but the one was little increased with increasing ozone dose at more than 1.0 L/min of ozone dose. It was seemed that the bicarbonate and the chloric ion formed throughout the decomposition of dichloroacetic acid acted as the scavenger of hydroxyl radical.

• Biomolecules & Therapeutics
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• v.19 no.2
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• pp.261-266
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• 2011

As recent reports suggest that nanoparticles may penetrate into cell membrane and effect DNA condition, it is necessary to assay possible cytotoxic and genotoxic risk. Three different sizes of magnetic nanoparticle silica (MNP@$SiO_2$) (50, 100 and 200 nm diameter) were tested for cytotoxicity and DNA damage using L5178Y cell. MNP@$SiO_2$ had constant physicochemical characteristics confirmed by transmission electron microscope, electron spin resonance spectrometer and inductively coupled plasma-atomic emission spectrometer for 48 h. Treatment of MNP@$SiO_2$ induced dose and time dependent cytotoxicity. At 6 h, 50, 100 or 200 nm MNP@$SiO_2$ decreased significantly cell viability over the concentration of 125 ${\mu}g/ml$ compared to vehicle control (p<0.05 or p<0.01). Moreover, at 24 h, 50 or 100 nm MNP@$SiO_2$ decreased significantly cell viability over the concentration of 125 ${\mu}g/ml$(p<0.01). And treatment of 200 nm MNP@$SiO_2$ decreased significantly cell viability at the concentration of 62.5 ${\mu}g/ml$ (p<0.05) and of 125, 250, 500 ${\mu}g/ml$ (p<0.01, respectively). Furthermore, at 48 h, 50, 100 or 200 nm MNP@$SiO_2$ decreased significantly cell viability at the concentration of 62.5 ${\mu}g/ml$ (p<0.05) and of 125, 250, 500 ${\mu}g/ml$ (p<0.01, respectively). Cellular location detected by confocal microscope represented they were existed in cytoplasm, mainly around cell membrane at 2 h after treatment of MNP@$SiO_2$. Treatment of 50 nm MNP@$SiO_2$ significantly increased DNA damage at middle and high dose (p<0.01), and treatment of 100 nm or 200 nm significantly increased DNA damage in all dose compared to control (p<0.01). Taken together, treatment of MNP@$SiO_2$ induced cytotoxicity and enhanced DNA damage in L5178Y cell.

• Korean Journal of Food Science and Technology
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• v.35 no.1
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• pp.67-71
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• 2003

Alginates were irradiated in an aqueous solution with $Co^{60}$ gamma rays in the dose ranges from 0 to 100 kGy, and investigated the relationship between the intrinsic viscosity $([{\eta}])$ and the molecular weight $(M_w)$ of alginates. The molecular weight of alginate was measured by gel permeation chromatography and the ranges from 1,894 to 135,174 Da were obtained. The molecular weight of alginate decreased markedly with increasing the degree of ${\gamma}-ray$ dose rate. The intrinsic viscosity of alginate solution after ${\gamma}-irradiation$ showed the ranges from 9.83 (g/g) to 602.69 (g/g), depending upon the ${\gamma}-irradiation$ dose. The molecular weight of alginate dependence of the intrinsic viscosity of the alginate solution would be expressed by Mark-Houwink equation. With a linearization of molecular weight and the intrinsic viscosity of the alginate solution, Mark-Houwink equation could be expressed with constant variables and the real data fitted to the equation of $[{\eta}]=2.2{\times}10^{-6}\;{M_w}^{1.656}\;(R^2=0.998)$.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.713-716
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• 2013

The device performances of N-channel Tunneling FET have been characterized with different intrinsic length between drain and gate($L_{in}$), drain and source doping, permittivity and oxide thickness when the total effective channel length is constant. N-channel Tunneling FET of SOI structure have been used in characterization. $L_{in}$ was from 30nm to 70nm, dose concentration of drain and source were from $2{\times}10^{12}cm^{-2}$ to $2{\times}10^{15}cm^{-2}$ and from $1{\times}10^{14}cm^{-2}$ to $3{\times}10^{15}cm^{-2}$, permittivity was from 3.9 to 29, and oxide thickness was from 3nm to 9nm. The device performances were characterized by Subthreshold slope(S-slope), On/off ratio, and leakage current. From the simulation results, the leakage current have been reduced for long $L_{in}$ and low drain doping. S-slope have been reduced for high source doping, high permittivity and thin oxide thickness. With considering the leakage current and S-slope, it is desirable that are long $L_{in}$, low drain doping, high source doping, high permittivity and thin oxide thickness to optimize device performance in n-channel Tunneling FET.

• Radiation Oncology Journal
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• v.15 no.4
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• pp.393-402
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• 1997

Purpose : When an x-ray beam of small field size is irradiated to target area containing an air cavity, such as larynx, the underdosing effect is observed in the region near the interfaces of air and soft tissue. With a larynx model, air cavity embedded in tissue-equivalent material, this study is intonded for examining Parameters, such as beam quality, field size, and cavity size, to affect the dose distribution near the air cavity. Materials and Methods : Three x-rar beams, 4-, 6- and 10-MV, were employed to Perform a measurement using a 2cm $(width){\times}L$ (length in cm, one side of x-ray field used 2cm (height) air cavity in the simulated larynx. A thin window parallel-plate chamber connected to an electrometer was used for a dosimetry system. A ratio of the dose at various distances from the cavity-tissue interface to the dose at the same points in a homogeneous Phantom (ebservedlexpected ratio, O/E) normalized buildup curves, and ratio of distal surface dose to dose at the maximum buildup depth were examined for various field sizes. Measurement for cavity size effect was performed by varying the height (Z) of the air cavity with the width kept constant for several field sizes. Results : No underdosing effect for 4-MV beam for fields larger than $5cm\times5cm$ was found For both 6- and 10-MV beams, the underdosing portion of the larynx at the distal surface was seen to occur for small fields, $4cm\times4cm\;and\;5cm\times5cm$. The underdosed tissue was increased in its volume with beam energy even for similar surface doses. The relative distal surface dose to maximum dose was changed to 0.99 from 0.95, 0.92, and 0.91 for 4-, 6-, and 10-MV, respectively, with increasing field size, $4cm\times4cm\;to\;8cm\times8cm$, For 6- and 10-MV beams, the dose at the surface of the cavity is measured less than the predicted by about two and three percent. respectively. but decrease was found for 4-MV beam for $5cm\times5cm$ field. For the $4cm\timesL\timesZ$ (height in cm). varying depth from 0.0 to 4.8cm, cavity, O/E> 1.0 was observed regardless of the cavity size for any field larger than about $8cm\times8cm$. Conclusion : The magnitude of underdosing depends on beam energy, field size. and cavity size for the larynx model. Based on the result of the study. caution must be used when a small field of a high quality x-ray beam is irradiated to regions including air cavities. and especially the region where the tumor extends to the surface. Low quality beam. such as. 4-MV x-ray, and larger fields can be used preferably to reduce the risk of underdosing, local failure. In the case of high quality beams such as 6- and 10-MV x-rays, however. an additional boost field is recommended to add for the compensation of the underdosing region when a typically used treatment field. $8cm\times8cm$, is employed.

• Journal of Applied Biological Chemistry
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• v.63 no.3
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• pp.267-274
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• 2020

The dissipation characteristics and kinetics of fungicide mandipropamid and insecticide thiamethoxam in lettuce under greenhouse conditions were investigated at three different lettuce-growing fields for estimating the pre-harvest residue limits (PHRLs). The analytical methods were fully validated for the quantitation of pesticide residues using High-Performance Liquid Chromatography-Photo Diode Array detector or Ultraviolet-Visible Detector and applied to real samples. The lettuces suitable for shipment were harvested during 10 days including pre-harvest interval after treatment at the recommended dose by safe-use guidelines. The initial mean residues in different fields were 6.68-17.87 and 4.96-8.31 mg/kg for mandipropamid and thiamethoxam, respectively, which decreased to 16-54 and 14-44% in 10 days. The clothianidin, a metabolite of thiamethoxam, was detected in <0.02 to 0.37 mg/kg. The dissipation of both pesticides followed first-order kinetics over a period of 10 days after application. Based on the residue data, the mean dissipation rate constant (λ) and biological half-lives (T_1/2) were estimated to be -0.1060 and 6.5 days of mandipropamid and -0.1236 and 5.6 days of thiamethoxam. The PHRLs for lettuce on the 10th and 5th day before harvesting were calculated to be 63.24 and 43.56 mg/kg for mandipropamid, and 44.66 and 25.88 mg/kg for thiamethoxam, with -0.0746 and -0.1091 of the upper 95% confidence intervals of dissipation rate constant, respectively. This work would be useful as guidance for adjusting the shipment date and contribute to stabilizing the income of farmers in Korea.

• Journal of Photoscience
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• v.9 no.2
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• pp.454-456
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• 2002

It is important to determine the action spectrum of UV-B radiation contained in the sunlight to estimate the risk of skin cancer. We have investigated action spectra for induction of apoptosis and reproductive cell death in L5178Y cells using the Okazaki Large Spectrograph at NIBB. L5178Y cells were exposed to light at different wavelengths in UV-B or UV-A region. Frequencies of apoptosis induction and reproductive cell death were determined by counting cells with chromatin condensation, and by the colony formation assay, respectively. The measured sensitivity spectra for the two end-points were in very good agreement. Sensitivity decreased steeply with increase of wavelength in UV-B region and remains nearly constant in UV-A region. The action spectra were also slightly steeper than that for the minimum erythematic dose (MED), but very similar to the light absorption spectrum of DNA in UV-B region. On the other hand, the spectra for both endpoints were similar to MED spectrum but not DNA spectrum in the UV-A region. Also different time-course and morphological difference of apoptosis were found between UV-B (long time, fragmentation) and UV-A (short time, shrinkage) region. These results suggest that DNA damage induced by UV-B light triggers apoptosis and reproductive cell death, but other damaged targets (membrane, protein and so on) trigger these effects in UV-A region.

• Journal of the Korean Data and Information Science Society
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• v.17 no.4
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• pp.1349-1364
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• 2006

An analytic approach that provides explicit estimates of risk on cataract and epilation data is evaluated by reasonableness of conceivable relative risk models regarding a simple, odds, logistic or Gompertz regression method, assuming a binomial distribution. In these analyses, we apply relative risk models with two thresholds between epilators and nonepilators from a highly characteristic lesion of which radiation cataract does not occur around 2 gray for a single acute exposure. The risk models are fitted to the data assuming 10 as a constant relative biological effectiveness of neutron. The likelihood of observing the entire data set in these models fitted is evaluated by an individual binary-response array. Estimation of a threshold with or without severe epilation and the 100 ($1-\alpha$)% confidence limits are derived from the maximum likelihood approach. The relative risk model with two thresholds can be expressed as a formula with structure of Background $\times$ RR, where RR includes threshold models with or without epilation. The radiosensitivity of ionizing radiation to cataracts has been examined for the relationship between epilators and nonepilators.