• Korean Chemical Engineering Research
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• v.55 no.3
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• pp.436-442
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• 2017

Fischer-Tropsch synthesis is the technology of converting a syngas (CO+$H_2$) derived from such as coal, natural gas and biomass into a hydrocarbon using a catalyst. The catalyst used in the Fischer-Tropsch synthesis consists of active metal, promoter and support. The types of these components and composition affect the reaction activity and product selectivity. In this study, we manufactured an iron catalyst using ${\gamma}-Al_2O_3/SiO_2$ mixed support (100/0 wt%, 75/25 wt%, 50/50 wt%, 25/75 wt%, 0/100 wt%) by an impregnation method to investigate how the composition of ${\gamma}-Al_2O_3/SiO_2$ mixed support effects on the reaction activity and product selectivity. The physical properties of catalyst were analyzed by $N_2$ physical adsorption and X-Ray diffraction method. The Fischer-Tropsch synthesis was conducted at $300^{\circ}C$, 20bar in a fixed bed reactor for 60h. According to the results of the $N_2$ physical adsorption analysis, the BET surface area decreases as the composition of ${\gamma}-Al_2O_3$ decreases, and the pore volume and pore average diameter increase as the composition of ${\gamma}-Al_2O_3$ decreases except for the composition of ${\gamma}-Al_2O_3/SiO_2$ of 50/50 wt%. By the results of the X-Ray diffraction analysis, the particle size of ${\alpha}-Fe_2O_3$ decreases as the composition of ${\gamma}-Al_2O_3$ decreases. As a result of the Fischer-Tropsch synthesis, the CO conversion decreases as the composition of ${\gamma}-Al_2O_3$ decreases, and the selectivity of C1-C4 decreases until the composition of ${\gamma}-Al_2O_3$ was 25 wt%. In contrast, the selectivity of C5+ increases until the composition of ${\gamma}-Al_2O_3$ is 25 wt%.

• Polymer(Korea)
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• v.36 no.1
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• pp.71-75
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• 2012

In this study, silver nanoparticles (AgNPs) have been prepared by using aqueous $AgNO_3$ solution in the poly(vinyl alcohol) (PVA) hydrogels. PVA powders were dissolved in deionized water, and then irradiated by gamma-ray with a radiation dose of 50 kGy to make hydrogels. PVA hydrogels were dipped into 0.01 and 0.05 M $AgNO_3$ solution for 1 h respectively. After that, the swollen hydrogels were irradiated by gamma-ray at various doses to form AgNPs. UV-vis analysis indicated that the concentration of Ag NPs was enhanced by increasing absorbed dose and the concentration of $AgNO_3$. FE-SEM measurements provided further evidence for the successful formation of Ag NPs in PVA hydrogels. Also, the antibacterial effect of PVA hydrogels stabilized AgNPs against Gram-negative bacteria (S.aureus and E.coli) in liquid as well as on solid growth media has been investigated. The AgNPs consolidated in PVA hydrogel networks have an excellent antibacterial effect.

• Nuclear Engineering and Technology
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• v.52 no.7
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• pp.1524-1531
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• 2020

The aim of this work is to develop a Geiger-Muller (GM) detector system for robot to look for a radioactive source in case of a nuclear emergency or in a high radiation environment. In order to find a radiation source easily, a detector system, including 3 detectors, was designed to search γ-ray radiation sources autonomously. First, based on GEANT4 simulation, radiation dose rates in 3 Geiger-Muller (GM) counters were simulated at different source-detector distances, distances between detectors and angles. Various sensitivity analyses were performed experimentally to verify the simulated designed detector system. A mono-energetic ¹³⁷Cs γ-ray source with energy 662 keV and activity of 1.11 GBq was used for the observation. The simulated results were compared with the experimental dose rate values and good agreements were obtained for various cases. Only based on the dose rates in three detectors, the radiation source with a specific source activity and angle was localized in the different location. A method was adopted with the measured dose rates and differences of distances to find the actual location of the lost γ-ray source. The corresponding angles of deviation and detection limits were calculated to determine the sensitivity and abilities of our designed detector system. The proposed system can be used to locate radiation sources in low and high radiation environments.

• Journal of Radiation Industry
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• v.11 no.3
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• pp.145-149
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• 2017

The cel7A sequence variation was analyzed between the wild type (Lentinula edodes KACC42378) and its cellulase activity enhanced mutant LER277. LER277 was induced by using gamma ray radiation ($^{60}Co$) at the $LD_{99}$ dose (0.94 kGy). Cloning and sequencing results showed that the cel7A coding DNA sequence (CDS) of LER277 had five nucleotide substitutions ($T{\rightarrow}C$, 201, 285 and 744 nt; $A{\rightarrow}G$, 525 nt; $C{\rightarrow}T$, 540 nt) and one hexanucleotide repeat insertion (GGCACC, within 1375-1392 nt) compared to that of the wild type. The Five nucleotide substitutions did not change the deduced amino acids and the hexanucleotide insertion elongated the GT repeat in a serine/threonine/glycine-rich linker. These results suggest that the enhancement of the cellulase activity in LER277 partly stemmed from cel7A changes by which the GT repeat of the linker is elongated.

• Food Science and Preservation
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• v.9 no.3
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• pp.345-350
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• 2002

This study was carried out to determine the effect of gamma irradiated Puerariae radix extract on color removal, antioxidative, DPPH radical scavenging and antimicrobial efftcts. Puerariae radix were extracted with methanol and acetone and irrdiated 10, 20 and 30 kGy with gamma ray. Hunter color L-value increased by irrdiation in a dose dependent manner, resulting in brighter color. But a and b values decreased by irradiation in a dose dependent manner. Antioxidant activities of the Puerariae radix extract in soybean oil emulsion were higher in methanol extract than acetone extract. Scavenging effect of Puerariae radix extracts on DPPH radical with methanol was not changed by irradiation but acetone decreased Acetone extract from Puerariae radix showed antimicrobial activities in B. subtilis, B, natto, B, megaterium S, aureus, Sal, typhymurium and E. coli methanol extract also had the antimicrobial activities but weaker for Sal. typhymurium and E. coli. Results suggested that Puerariae radix extracts have a potential as a natural food preservatives and cosmetic raw material.

• Nuclear Engineering and Technology
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• v.55 no.5
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• pp.1757-1762
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• 2023

Radiological hazards from external exposure of naturally occurring radioactive materials (NORM) scales residues, generated during the extraction process of oil and gas production in southern Algeria, are evaluated. The activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K were measured using high-purity gamma-ray spectrometry (GeHP). Mean activity concentration of ²²⁶Ra, ²³²Th and ⁴⁰K, found in scale samples are 4082 ± 41, 1060 ± 38 and 568 ± 36 Bq kg^-1, respectively. Radiological hazard parameters, such as radium equivalent (Ra_eq), external and internal hazard indices (H_ex, H_in), and gamma index (I_γ) are also evaluated. All hazard parameter values were greater than the permissible and recommended limits and the average annual effective dose value exceeded the dose constraint (0.3 mSv y^-1). However, for occasionally exposed workers, the dose rate of 0.65 ± 0.02 mSv y^-1 is lower than recommended limit of 1 mSv y^-1 for public.

• Journal of Applied Biological Chemistry
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• v.59 no.1
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• pp.49-56
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• 2016

The current study investigated the anti-obesity effect of Cissus quadrangularsis extracts (CQR-300) and its molecular action mechanism on obese mice induced high-fat diet (HFD). To induce the obesity, mice were fed a HFD for 6 weeks and then fed HFD only or HFD with CQR-300 at 50 and 200 mg/kg. Then, body weight gain and white adipose tissue weights were measured. We investigated the reduction in body fat and the regulation of fatty acid synthesis was measured by dual energy X-ray absorptiometry and real-time PCR with Western blot, respectively. In vitro study, CQR-300 inhibited pancreatic lipase activity. The CQR-300 treatment was significantly decreased the body weight gain and adipocytes size as well as white adipose tissues weights in HFD-induced obese mice. Furthermore, CQR-300 reduced the body fat and fat mass with regulating of adipose tissue hormones as leptin. Treatment with 50 mg/kg CQR-300 showed effectively lower expression levels of adipogenesis/lipogenesis related genes and proteins such as CCAAT/enhancer binding protein ${\alpha}$ ($C/EBP{\alpha}$), peroxisome proliferator-activated receptor ${\gamma}$ ($PPAR{\gamma}$), Sterol regulatory element binding protein-1c (SREBP-1c), and fatty acid synthase (FAS) in white adipose tissue (WAT) as compared with the HFD fed only mice. These results suggest that the CQR-300 has an anti-obesity effect via inhibition of lipase activity, decrease the body fat mass by regulating the adipogenesis and lipogenesis related genes and proteins in epididymal adipose tissue with evaluate body fat reduce in the HFD-induced obese mice.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.17 no.3
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• pp.321-328
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• 2019

The detection performances of the NaI(Tl), $LaBr_3$(Ce) and $CeBr_3$ scintillation detectors, which can be used to rapidly evaluate the major artificial radionuclides deposited on the soil surface in a nuclear accident or radiological emergency, were compared. Detection performance was assessed by calculating the minimum detectable activity (MDA). The detection efficiency of each detector for artificial radionuclides was semi-empirically determined using mathematical modelling and point-like sources having certified radioactivity. The background gamma-ray energy spectrum for MDA evaluation was obtained from relatively wide and flat grassland, and the MDA values of each detector for the major artificial radionuclides that could be released in nuclear accidents were calculated. As a result, the relative MDA values of each detector regarding surface deposition distribution at normal environmental radiation level were evaluated as high in the order of the NaI(Tl), $LaBr_3$(Ce), and $CeBr_3$ detectors. These results were compared based on each detector's intrinsic and measurement environment background, detection efficiency, and energy resolution for the gamma-ray energy region of the radionuclide of interest.

• Radiation Oncology Journal
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• v.11 no.2
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• pp.205-217
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• 1993

In order to evalute the effects of radiation on mammalian neuronal system, we have examined the effect of gamma-ray radiation on the monoamine oxidase (MAO) activity in monoaminergic neurons. Following the whole body irradiation, MAO activity in the rat brain was measured as well as in the liver for the comparative studies between the neuronal and nonneuronal system. The effects of some radiation protectors and sensitizers were also examined in addition to the $O_2$ effect. The results can be summarized as follows. 1) The MAO activity of rat brain was minimally affected by the radiation dose up to 1,700 cGy Radiation dose above 2,500 cGy inhibited the brain MAO activity by no less than $l0\%.$ MAO-A form was found to be particularly sensitive to radiation. The liver MAO was somewhat inhibited (by about $5\%$) but hardly dependent on the dose of radiation. 2) The inhibitory effect on the brain was initiated immediately by the radiation dose of 2,500 cGy. On the contrary, for the liver, the inhibitory effect became apparent only 2 days after irradiation. 3) Two days after a dose of 2,500 cGy, Vmax and Km of the brain mitochondrial MAO decreased. For liver, Vmax decreased while Km increased, which indicates the kinetic patterns for the neuronal and nonneruronal systems are not affected similarly by radiation. 4) The effect of several known radiation protectors and sensitizers on MAO activity was tested ut no definite results were obtained. The level of -SH group increased in some degree upon radiation but not by the compounds. 5) MAO activity was not affected by $O_2$ concentration, while an elevated level of lipid peroxidase was found under the same condition. The results described here indicate that characteristics of MAO, one of the most important central nervous system enzymes, are liable to radiation, which is partially differentiated from the liver MAO. Also indicated are that the -SH groups are hardly related to the effect of radiation but the production of the lipid peroxide seems to be somewhat correlated to the effect of radiation.

• Journal of Radiation Protection and Research
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• v.42 no.1
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• pp.33-41
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• 2017

Background: Phosphate rock and its by-product are widely used in various industries to produce phosphoric acid, gypsum, gypsum board, and fertilizer. Owing to its high level of natural radioactive nuclides (e.g., $^{238}U$ and $^{226}Ra$), the radiological safety of workers who work with phosphate rock should be systematically managed. In this study, $^{238}U$, $^{232}Th$, $^{226}Ra$, and $^{40}K$ levels were measured to analyze the transport characteristics of these radionuclides in the production cycle of phosphate rock. Materials and Methods: Energy dispersive X-ray fluorescence and gamma spectrometry were used to determine the activity of $^{238}U$, $^{232}Th$, $^{226}Ra$, and $^{40}K$. To evaluate the extent of secular disequilibrium, the analytical results were compared using statistical methods. Finally, the distribution of radioactivity across different stages of the phosphate rock production cycle was evaluated. Results and Discussion: The concentration ratios of $^{226}Ra$ and $^{238}U$ in phosphate rock were close to 1.0, while those found in gypsum and fertilizer were extremely different, reflecting disequilibrium after the chemical reaction process. The nuclide with the highest activity level in the production cycle of phosphate rock was $^{40}K$, and the median $^{40}K$ activity was $8.972Bq{\cdot}g^{-1}$ and $1.496Bq{\cdot}g^{-1}$, respectively. For the $^{238}U$ series, the activity of $^{238}U$ and $^{226}Ra$ was greatest in phosphate rock, and the distribution of activity values clearly showed the transport characteristics of the radionuclides, both for the byproducts of the decay sequences and for their final products. Conclusion: Although the activity of $^{40}K$ in k-related fertilizer was relatively high, it made a relatively low contribution to the total radiological effect. However, the activity levels of $^{226}Ra$ and $^{238}U$ in phosphate rock were found to be relatively high, near the upper end of the acceptable limits. Therefore, it is necessary to systematically manage the radiological safety of workers engaged in phosphate rock processing.