• Progress in Medical Physics
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• v.27 no.3
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• pp.105-110
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• 2016

Sparse angular sampling has been studied recently owing to its potential to decrease the radiation exposure from computed tomography (CT). In this study, we investigated the analytic reconstruction algorithm in sparse angular sampling using the sinogram interpolation method for improving image quality and computation speed. A prototype of the spectral CT system, which has a 64-pixel Cadmium Zinc Telluride (CZT)-based photon-counting detector, was used. The source-to-detector distance and the source-to-center of rotation distance were 1,200 and 1,015 mm, respectively. Two energy bins (23~33 keV and 34~44 keV) were set to obtain two reconstruction images. We used a PMMA phantom with height and radius of 50.0 mm and 17.5 mm, respectively. The phantom contained iodine, gadolinium, calcification, and lipid. The Feld-kamp-Davis-Kress (FDK) with the sinogram interpolation method and Maximum Likelihood Expectation Maximization (MLEM) algorithm were used to reconstruct the images. We evaluated the signal-to-noise ratio (SNR) of the materials. The SNRs of iodine, calcification, and liquid lipid were increased by 167.03%, 157.93%, and 41.77%, respectively, with the 23~33 keV energy bin using the sinogram interpolation method. The SNRs of iodine, calcification, and liquid state lipid were also increased by 107.01%, 13.58%, and 27.39%, respectively, with the 34~44 keV energy bin using the sinogram interpolation method. Although the FDK algorithm with the sinogram interpolation did not produce better results than the MLEM algorithm, it did result in comparable image quality to that of the MLEM algorithm. We believe that the sinogram interpolation method can be applied in various reconstruction studies using the analytic reconstruction algorithm. Therefore, the sinogram interpolation method can improve the image quality in sparse-angular sampling and be applied to CT applications.

• Investigative Magnetic Resonance Imaging
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• v.18 no.1
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• pp.70-74
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• 2014

Actinomycosis is caused by filamentous Gram positive anaerobic bacteria from the Actinomycetaceae family, and known as a rare cause of the infection at the eyeball. We report magnetic resonance findings of a 60-year-old Korean man with cervicofacial actinomycosis, including cellulitis in the eye and central nervous system actinomycosis. On orbital magnetic resonance imaging, gadolinium-enhanced T1-weight images showed multiple abnormal enhancing lesions in head and neck including right eye, and some include low signal intensities which considered as abscesses. The lesions was diagnosed as actinomycosis by incisional biopsy, and since then was cured by using antibiotics of penicillin family.

• Korean Journal of Materials Research
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• v.25 no.12
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• pp.703-707
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• 2015

In this study, we investigated the effect of annealing conditions on the ferromagnetic resonance(FMR) of yttrium iron garnet ($Y_3Fe_5O_{12}$, YIG) thin film prepared on gadolinium gallium garnet ($Gd_3Ga_5O_{12}$, GGG) substrate. The YIG thin films were grown by rf magnetron sputtering at room temperature and were annealed at various temperatures from 700 to $1000^{\circ}C$. FMR characteristics of the YIG thin films were investigated with a coplanar waveguide FMR measurement system in a frequency range from 5 to 20 GHz. X-ray diffraction(XRD) and X-ray photoelectron spectroscopy(XPS) were used to characterize the phase formation, crystal structure and composition of the YIG thin films. Field dependent magnetization curves at room temperature were obtained by using a vibrating sample magnetometer(VSM). The FMR measurements revealed that the resonance magnetic field was highly dependent on the annealing condition: the lowest FMR linewidth can be observed for the $800^{\circ}C$ annealed sample, which agrees with the VSM results. We also found that the Fe and O composition changes during the annealing process play important roles in the observed magnetic properties.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.26 no.3
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• pp.237-252
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• 2016

Objectives: This study was conducted in order to improve the current understanding of rare earths(RE) and to provide supporting data for establishing occupational health policies by reviewing the toxicological data and issues caused by the use of RE compounds in various fields. Methods: To evaluate the potential toxicity of RE from the viewpoint of occupational health, we summarized extensive reviews of relevant articles in the toxicology(animals and cells), occupational health and safety, and epidemiologic literature. Results: Although occupational RE exposure occurs extensively from ore mining and refining to end users in various industrial applications, epidemiologic study has not been performed among workers up to now. Bioaccumulation and adverse effects of RE have also been mentioned in ore mining regions and nearby residences, but safety standards for each process are insufficient. Moreover, because new commercial recycling technology will soon be applied to various industries, regulation and policies are needed for preventing abuse of recycling. In the results of animal toxicity for a few REs(mostly cerium, lanthanum, and gadolinium), toxicities of liver, lung, blood, and the nervous system were identified due to oxidative stress, but study of long-term RE exposure is required. Understanding the dual effect for RE and discovery of biomarkers pose a scientific challenge in further mechanism studies. Conclusions: In the future, additional hazard evaluation based on animal experiments is required, alongside continuous research for developing analytical methods and discovering biomarkers. Finally, RE occupational health and safety management needs to be integrated into the sustainable use of these materials.

• Journal of the Korean Society of Radiology
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• v.12 no.2
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• pp.167-172
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• 2018

This study evaluated absorbed dose of brachytherapy according to the nanoparticle in prostate cancer which many occurred in Korean man and provided basic data. Absorbed dose evaluation was using MCNPX program which was applied Monte Carlo simulation. Source was applied $^{192}Ir$ which was many using in Korean HDR machine and gold, ferric oxide, gadolinium and iodine nanoparticle were applied. Prostate absorbed dose result was increased when using nanoparticle, in particular gold nanoparticle was the highest result as $3.13E-03J/kg{\cdot}e$. Absorbed dose of surrounding organs and distance was similar between using nanoparticle and non-using nanoparticle. Therefore, brachytherapy was used nanoparticle was increased therapeutic ratio and efficiency of radiation therapy.

• Archives of Pharmacal Research
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• v.26 no.12
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• pp.1079-1086
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• 2003

The aim of this study was to investigate the effect of trauma on cytochrome P450 (CYP) gene expression and to determine the role of Kupffer cells in trauma-induced alteration of CYP isozymes. Rats underwent closed femur fracture (FFx) with associated soft-tissue injury under anesthesia. To deplete Kupffer cells in vivo, gadolinium chloride ($GdCl_3$) was intravenously injected at 7.5 mg/kg body wt., 1 and 2 days prior to FFx surgery. At 72 h of FFx, liver tissues were isolated to determine the mRNA and protein expression of CYP isozymes and NADPH-P450 reductase by reverse transcription-polymerase chain reaction and Western immunoblotting, respectively. In addition, the mRNA levels of tumor necrosis factor alpha (TNF-$\alpha$), inducible nitric oxide synthase (iNOS) and heme oxygenase-1 (HO-1) were evaluated. FFx increased the mRNA level of CYP1A1; an increase that was not prevented by $GdCl_3$. There were no significant differences in the mRNA expression of CYP1A2, 2B1 and 2E1 among any of the experimental groups. The protein levels of CYP2B1 and 2E1 were significantly decreased by FFx; a decrease that was not prevented by $GdCl_3$ treatment. The gene expression of NADPH-P450 reductase was unchanged by FFx. FFx significantly increased the expression of TNF-$\alpha$ mRNA; an increase that was attenuated by $GdCl_3$. The mRNA expression of HO-1 was increased by FFx, but not by $GdCl_3$ . Our findings suggest that FFx differentially regulates the expression of CYP isozyme through Kupffer cell-independent mechanisms.

• Journal of the Korean institute of surface engineering
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• v.49 no.6
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• pp.595-603
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• 2016

Rare-earth zirconates, including lanthanum zirconate and gadolinium zirconate, have been investigated as ones of the most promising candidates for next-generation thermal barrier coating (TBC) materials due to their excellent properties such as low thermal conductivity, chemical stability at high temperature and so on. In this study, TBCs with three compositions, in the $La_2O_3-Gd_2O_3-ZrO_2$ system with reduced rare-earth contents from $RE_2Zr_2O_7$ compositions, were fabricated by using suspension plasma spray with different suspension preparation methods. The phase formation, microstructure, and thermal properties of TBCs were examined. In particular, each coating exhibited single fluorite phase and a dense, vertically-separated microstructure. The potential of coatings with rare-earth zirconates for TBC applications was also discussed.

• Journal of the Korean institute of surface engineering
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• v.49 no.6
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• pp.604-611
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• 2016

In order to comply with demand for high efficient gas turbines operating at higher temperatures, considerable amounts of research efforts have been performed with searching for the next-generation thermal barrier coatings (TBCs) with respect to coating materials as well as processing methods. In this study, thermal barrier coatings in the $(La_{1-x}Gd_x)_2Zr_2O_7$ system, which is one of the most versatile materials replacing yttria-stabilized zirconia (YSZ), are fabricated by suspension plasma spray with suspension made of synthesized powders via solidstate reaction. Dense, $100{\sim}400{\mu}m$ thick coatings of fluorite-phase zirconate with moderate amount of segmented microstructures are obtained by using suspension plasma spray. Phase formation and thermal diffusivity are characterized with coating compositions. The feasibility of $(La_{1-x}Gd_x)_2Zr_2O_7$ coatings for TBC applications is also discussed.

• Nuclear Engineering and Technology
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• v.48 no.1
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• pp.164-168
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• 2016

Lean duplex stainless steels with 0.087 wt.% gadolinium (Gd) were inert arc-melted and cast in molds of size $10mm{\times}10mm{\times}20mm$. The micro-hardnesses of the rolling direction (RD), transverse direction (TD) and short transverse (ST) direction were $258.5H_V$, $292.3H_V$, and $314.7H_V$, respectively. A 33% cold rolled specimen had the crystallographic texture that (100) pole was mainly concentrated to the normal direction (ND) and (110) pole was concentrated in the center of ND and RD. The corrosion potential and corrosion rate in artificial seawater and $0.1M\;H_2SO_4$ solution were in the range of $105.6-221.6mV_{SHE}$, $0.59-1.06mA/cm^2$, and $4.75-8.25mV_{SHE}$, $0.69-1.68mA/cm^2$, respectively. The friction coefficient and wear loss of the 0.087 w/o Gd-lean duplex stainless steels in artificial seawater were about 67% and 65% lower than in air, whereas the wear efficiency was 22% higher. The corrosion and wear behaviors of the 0.087 w/o Gd-lean duplex stainless steels significantly depended on the Gd phases.

• Journal of the Korean Ceramic Society
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• v.53 no.5
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• pp.494-499
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• 2016

In this work, the effects of different sintering inhibitors added to $La_{0.8}Sr_{0.2}MnO_{3-{\partial}}$ (LSM) were studied to obtain an optimum cathode material for cathode-supported type of Solid oxide fuel cell (SOFC) in terms of phase stability, mechanical strength, electric conductivity and porosity. Four different sintering inhibitors of $Al_2O_3$, $CeO_2$, NiO and gadolinium doped ceria (GDC) were mixed with LSM powder, sintered at $1300^{\circ}C$ and then they were evaluated. The phase stability, sintering behavior, electrical conductivity, mechanical strength and microstructure were evaluated in order to assess the performance of the mixture powder as cathode support material. It has been found that the addition of $Al_2O_3$ undesirably decreased the electrical conductivity of LSM; other sintering inhibitors, however, showed sufficient levels of electrical conductivity. GDC and NiO addition showed a promising increase in mechanical strength of the LSM material, which is one of the basic requirements in cathode-supported designs of fuel cells. However, NiO showed a high reactivity with LSM during high temperature ($1300^{\circ}C$) sintering. So, this study concluded that GDC is a potential candidate for use as a sintering inhibitor for high temperature sintering of cathode materials.