• Radiation Oncology Journal
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• v.13 no.4
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• pp.397-402
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• 1995

Purpose : To determine the perturbation effect in the tissue downstream from surface layers of lesions located in the air/tumor-tissue interface of larynx using 6MV photon beam. Materials and Methods : Thermoluminescent dosimeters(TLDs), were embedded at 3 measurement locations in slab no. 7 of a humanoid phantom and exposed to forward and backward direction using various field sizes($4{\times}4cm^2\;-\;15{\times}15cm^2$). Results : At the air/tissue interface, forward dose perturbation factor(FDPF) is about 1.085 with $4{\times}4cm^2,\;1.05\;with\;7{\times}7cm^2,\;1.048\;with\;10{\times}10cm^2$ and $1.041\;with\;15{\times}15cm^2$. Backscatter dose perturbation factor(BDPF) is about 0.99 with $4{\times}4cm^2$, 0.981 with $7{\times}7cm^2$, 0.956 with $10{\times}10cm^2$ and 0.97 with $15{\times}15cm^2$. Conclusion : FDPF is greater as field size is smaller. And FDPF is smaller as the distance is further from the air/tissue interface.

• Journal of Radiation Protection and Research
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• v.1 no.1
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• pp.22-30
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• 1976

The perturbation of dose distribution adjacent to cavities in high energy electron has shown that the percentage of dose increase varies markedly as a function of the build-up layer, the length and thickness of the cavities, and the electron energy. The dose distribution showed that cavities similar in size to those encountered in the head and neck measured by industrial film dosimetry and corrected by ionization chambers. The most increased doses by measuring are resulted in a localized dose of up to 130% of that measured at the depth of maximum dose within a homogeneous tissue equivalent phantom. The measured values and correction factors of dose perturbation due to air cavities showed in diagrams and would be summarized as follows. 1. In $8{\sim}12MeV$ electron beams, the most marked dose is observed when the build-up layer thickness is 0.5cm and cavity volume is $2{\times}2{\times}2cm^3$. 2. The highest dose point is located under cavity when the energy is increased and cavity length is longer. 3. The cavity length at which the maximum percentage dose occurs decreases with increasing energy. 4. The highest percentage cavity doses are obtained when the energy is high, the build-up layer is thin, the thickness of the cavity is large, and the length of the cavity is approximately 1 to 3cm. 5. The doses of upper portion of cavity are less than the standard dose distribution as 5 to 10%. 6. The maximum range of electron beam are extended as much as thickness of cavity. 7. A cavity having a length of 5cm closely approximates a cavity of infinite length.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2006.08a
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• pp.97-97
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• 2006

• Progress in Medical Physics
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• v.29 no.1
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• pp.16-22
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• 2018

Current dosimetry protocols recommend the use of parallel-plate chambers in electron dosimetry because the electron fluence perturbation can be effectively minimized. However, substitutable methods to calibrate and measure the electron output and energy with the widely used cylindrical chamber should be developed in case a parallel-plate chamber is unavailable. In this study, we measured the correction factors and absolute dose-to-water of electrons with energies of 4, 6, 9, 12, 16, and 20 MeV using Farmer-type and Roos chambers by varying the dose rates according to the AAPM TG-51 protocol. The ion recombination factor and absolute dose were found to be varied across the chamber types, energy, and dose rate, and these phenomena were remarkable at a low energy (4 MeV), which was in good agreement with literature. While the ion recombination factor showed a difference across chamber types of less than 0.4%, the absolute dose differences between them were largest at 4 MeV at approximately 1.5%. We therefore found that the absolute dose with respect to the dose rate was strongly influenced by ion-collection efficiency. Although more rigorous validation with other types of chambers and protocols should be performed, the outcome of the study shows the feasibility of replacing the parallel-plate chamber with the cylindrical chamber in electron dosimetry.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1120-1124
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• 2005

We reviewed controllers with a time delay estimation in this paper. Time delay control (TDC) and sliding mode control (SMC) are well known robust control schemes. Basically, the TDC has a main characteristic called a time delay estimation from which we can estimate the total uncertainty of a system. . The TDC causes the stick-slip in the case of systems with a friction. The so-called TDCSA which are short for TDC with switching action was developed to reduce the stick-slip. The TDC has the additional switching action term in the TDC structure. In the other hand, the SMC dose not have a time delay estimation but instead it can estimate the system uncertainty through the switching action. The SMC has a difficulty to estimate the total uncertainty of a system because it does not have a time delay estimation. In order to solve the difficulty, some control schemes were developed. Among them, we need to focus our attention on two control schemes: SMCPE and SMCTE, which are short for sliding mode control with a perturbation estimation and sliding mode control with a time delay estimation, respectively. In this paper, we analyzed and compared the characteristic of above three controllers. Even though the motives for the development of three control schemes are different, three control schemes have much in common in terms of their controller structures.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2004.11a
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• pp.115-118
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• 2004

Respiratory motion in the thorax and abdomen is an important limiting factor in high-precision radiation therapy. The lung tumor and tumor(pancreas, stomach) in abdomen therefore are internal motion due to breathing. We will perform to measurement of dose distributions for these moving tumors. In preliminary study, we investigated displacement of moving tumor such as liver, lung tumor in abdomen with previously reported papers. With reference data, internal movements of tumor are displayed with phantom and moving control device(MCD), which appear three dimension (3-D) motion such as x, y and z axis. These devices are used to access dose delivered in tumor with and without internal motion. The MCD and phantom were used to evaluate a delivered dose under similar condition, although there are not same internal tumor motion. In future, we will obtain the exact evaluation of dose if improved in programed software of moving control device and measure precise internal motion using image modality such as fluoroscopy, simulator in based on this study.

• Journal of environmental and Sanitary engineering
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• v.14 no.1
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• pp.88-96
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• 1999

The effect of acute cadmium-neuropathy on phospholipid metabolism in rat sciatic nerve was investigated. An animal model of cadmium neuropathy was induced by feeding diet containing cadmium to Sprague-Dawley rat for two weeks. Four weeks aged Sprague-Dawley rats were divided into four groups : normal control group, 10ppm-cadmium treated group, 100ppm-cadmium treated group, 1000ppm-cadmium treated group, reference drug, myo-inositol-treated group. All rats were sacrificed at the end of two weeks. The rate of incorporation of 2-[3H]myo-inositol into polyphosphinositide was significantly decreased while the rates of incorporation into phospholipid of titratedserine, ethanolamine and choline were unchanged in sciatic nerve obtained from cadmium-treated rat. Continuously the activities of three enzymes concerned with inositol phospholiped metabolism were measured in homogenates of rat sciatic nerves. Cystidine diglyceride transferase and phophatidylinositol kinase showed significantly decreased activities while phosphatidylinositol-4-phosphate kinase did not show any significant change in activity by cadmium treatment. However these deficits of inositol phospholipid metabolism were ameliorated by myo-inositol administration and these effectiveness were more potent in lower dose cadmiumtreated rats than higher dose cadmium-treated rats. These results suggest that cadmium intoxicated peripheral nerve with perturbation of the ployphosphoinositide metabolism and alteration of the enzyme activity which concerned with myo-inositol metabolism.

• BMB Reports
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• v.38 no.4
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• pp.391-398
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• 2005

3-hydrogenwadaphnin (3-HK) is a new daphnane-type diterpene ester isolated from Dendrostellera lessertii with strong anti-tumoral activity in animal models and in cultures. Here, prolonged effects of this new agent on proliferation and viability of several different cancerous cell lines were evaluated. Using [$^3H$]thymidine incorporation, it was found that the drug inhibited cell proliferation and induced G1/S cell cycle arrest in leukemic cells 24 h after a single dose treatment. The cell viability of Jurkat cells was also decreased by almost 10%, 31% and 40% after a single dose treatment (7.5 nM) at 24, 48 and 72 h, respectively. The drug-treated cells were stained with acridine orange/ethidium bromide to document the chromatin condensation and DNA fragmentation. These observations were further confirmed by detection of DNA laddering pattern in the agarose gel electrophoresis of the extracted DNA from the treated cells. Treatment of K562 cells with the drug at 7.5, 15 and 30 nM caused apoptosis in 25%, 45% and 65% of the cells, respectively. Exogenous addition of $25-50\;{\mu}M$ guanosine and/or deoxyguanosine to the cell culture of the drug-treated cells restored DNA synthesis, released cell arrest at G1/S checkpoint and decreased the apoptotic cell death caused by the drug. These observations were not made using adenosine. However, the drug effects on K562 cells were potentiated by hypoxanthine. Based on these observations, perturbation of GTP metabolism is considered as one of the main reasons for apoptotic cell death by 3-HK.

• Journal of the Korean Magnetic Resonance Society
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• v.21 no.3
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• pp.102-108
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• 2017

Escherichia coli responds to ever-changing external and internal stresses by rapidly adjusting its physiology for better survival. This adjustment occurs at all levels including metabolites as well as mRNAs and proteins. Although there has been many reports describing E. coli's adaptation to various stresses regarding transcriptomics or proteomics, only a few investigations have been reported regarding this adaptation viewed from metabolites' perspective. We applied four different types of stresses at four different doses as imposed by NaCl, sorbitol, ethanol, and pH to investigate the similarities or differences among the stresses, and which stress causes the largest perturbation of the metabolite composition. We profiled the metabolites under such external stresses by using two-dimensional NMR spectroscopy and identified 39 metabolites including amino acids, sugars, organic acids, and nucleic acids. According to our statistical analysis, the osmotic stress caused by sorbitol differentiated itself from others, while NaCl showed the largest dose dependent metabolic perturbations. We hope this work will form a foundation on which an approach to a successful protein production is systematically provided by a favorable metabolic environment by imposing proper external stresses.

• BMB Reports
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• v.49 no.1
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• pp.45-50
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• 2016

Salsolinol (SAL), a compound derived from dopamine metabolism, is the most probable neurotoxin involved in the pathogenesis of Parkinson's disease (PD). In this study, we investigated the modification and inactivation of human ceruloplasmin (hCP) induced by SAL. Incubation of hCP with SAL increased the protein aggregation and enzyme inactivation in a dose-dependent manner. Reactive oxygen species scavengers and copper chelators inhibited the SAL-mediated hCP modification and inactivation. The formation of dityrosine was detected in SAL-mediated hCP aggregates. Amino acid analysis post the exposure of hCP to SAL revealed that aspartate, histidine, lysine, threonine and tyrosine residues were particularly sensitive. Since hCP is a major copper transport protein, oxidative damage of hCP by SAL may induce perturbation of the copper transport system, which subsequently leads to deleterious conditions in cells. This study of the mechanism by which ceruloplasmin is modified by salsolinol may provide an explanation for the deterioration of organs under neurodegenerative disorders such as PD. [BMB Reports 2016; 49(1): 45-50]