• Nuclear Engineering and Technology
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• v.55 no.8
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• pp.2757-2772
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• 2023

The fluid retention effect of the Volume Control Tank (VCT) leads to a long time delay in Reactor Coolant System (RCS) concentration during the boration process. A coupled model combining a lumped-parameter sub-model and a computational fluid dynamics sub-model is currently used to investigate the concentration dynamic characteristic of RCS during the boration process. This model is validated by comparison with experimental data, and the predicted results show excellent agreement with experimental data. We provide detailed fields in VCT and concentration variations of RCS to study the interaction between mixing in VCT and the transient responses of RCS. Moreover, the impacts of the inlet flow rate, inlet nozzle diameter, original concentration, and replenishing temperature of VCT on the RCS concentration characteristic are studied. The inlet flow rate and nozzle diameter of VCT remarkably affect the RCS concentration characteristic. Too-large or too-small inlet flow rates and nozzle diameters will lead to unacceptable long delays. In this work, the optimal inlet flow rate and nozzle diameter of VCT are 5 m³/h and 58.8 mm, respectively. Besides, the impacts of the original concentration and replenishing temperature of VCT are negligible under normal operating conditions.

• Proceedings of the Mineralogical Society of Korea Conference
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• 2001.06a
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• pp.38-39
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• 2001

The seasonal changes in pH, Fe, Al and SO$_4$$\^$2-/ contents of acid drainage released from coal mine dumps play a major role in precipitation of metal hydroxides in the Taebaek coal field area, southeastern Korea. Precipitates in the creeks underwent a cycle of the color change showing white, reddish brown and brownish yellow, which depends on geochemical factors of the creek waters. White precipitates consist of Al-sulfate (basaluminite and hydrobasaluminite) and reddish brown ones are composed of ferrihydrite and brownish yellow ones are of schwertmannite. Goethite coprecipitates with ferrihydrite and schwertmannite. Ferrihydrite formed at higher values than pH 5.3 and schwertmannite precipitated below pH 4.3, and goethite formed at the intermediate pH range between the two minerals. With the pH being increased from acid to intermediate regions, Fe is present both as schwertmannite and goethite. From the present observation, the most favorable pH that basauluminte can precipitate is in the range of pH 4.45-5.95. SEM examination of precipitates at stream bottom shows that they basically consist of agglomerates of spheroid and rod-shape bacteria. Bacteria species are remarkably different among bottom precipitates and, to a less extent, there are slightly different chemical compositions even within the same bacteria. The speciation and calculation of the mineral saturation index were made using MINTEQA2. In waters associated with yellowish brown precipitates mainly composed of schwertmannite, So$_4$ species is mostly free So$_4$$\^$2-/ ion with less AlSo$_4$$\^$+/, CaSo$\sub$(aq)/, and MgSo$\sub$4(aq)/. Ferrous iron is present mostly as free Fe$\^$2+/, and FeSo$\sub$4(aq)/ and ferric iron exists predominantly as Fe(OH)$_2$$\^$+/, with less FeSo$\sub$4(aq)/, Fe(OH)$_2$$\^$-/, FeSo$_4$$\^$-/ and Fe$\^$3+/, respectively Al exists as free Al$\^$3+/, AlOH$_2$$\^$-/, (AlSo$_4$)$\^$+/, and Al(So$_4$)$\^$2-/. Fe is generally saturated with respect to hematite, magnetite, and goethite, with nearly saturation with lepidocrocite. Aluminum and sulfate are supersaturated with respect to predominant alunite and less jubanite, and they approach a saturation state with respect to diaspore, gibbsite, boehmite and gypsum. In the case of waters associated with whitish precipitates mainly composed of basaluminite, Al is present as predominant Al$\^$3+/ and Al(SO$_4$)$\^$+/, with less Al(OH)$\^$2+/, Al(OH)$_2$$\^$+/ and Al(SO$_4$)$\^$2-/. According to calculation for the mineral saturation, aluminum and sulfate are greatly supersaturated with respect to basaluminite and alunite. Diaspore is flirty well supersaturated while jubanite, gibbsite, and boehmite are already supersaturated, and gypsum approaches its saturation state. The observation that the only mineral phase we can easily detect in the whitish precipitate is basaluminite suggests that growth rate of alunite is much slower than that of basaluminite. Neutralization of acid mine drainage due to the dilution caused by the dilution effect due to mixing of unpolluted waters prevails over the buffering effect by the dissolution of carbonate or aluminosilicates. The main factors to affect color change are variations in aqueous geochemistry, which are controlled by dilution effect due to rainfall, water mixng from adjacent creeks, and the extent to which water-rock interaction takes place with seasons. pH, Fe, Al and SO$_4$ contents of the creek water are the most important factors leading to color changes in the precipitates. A geochemical cycle showing color variations in the precipitates provides the potential control on acid mine drainage and can be applied as a reclamation tool in a temperate region with four seasons.

• Preventive Nutrition and Food Science
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• v.6 no.2
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• pp.126-132
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• 2001

Methanol extracts form four kinds of kimchi, which were differently prepared in kinds and levels of sub-ingredients, were given to Balb/c mice for 3 weeks (0.5 mg/kg/day). Peritoneal macrophages isolated from mice treated with kimchi extracts and saline were stimulated by lipopolysaccharide (LPS). K3 and K4 kimchis, containing more red pepper powder, garlic, Chinese pepper powder, mustard leaf and organically cultivated Korean cabbage, significantly increased NO production by the activated macrophages (p<0.05). K1, K2, K3 and K4 kimchi extracts (0.01, 0.1, 1.0 $\mu\textrm{g}$) significantly reduced the increased TGF-$\beta$1 production of H.pylori lysate (0.01 $\mu\textrm{g}$)-activated human epithelial RPMI 2650 cells (5$\times$10$^{4}$ cells/mL) at 24 and 48 hrs of treatment (p<0.01). However, the decreased TGF-$\beta$1 $\alpha$ production of RPMI 2650 cells by H. pylori lysate increased by treatment with kimchi extract for 72 hrs. Especially, K4 kimchi (containing organically cultivated Korean cabbage and more ingredients, modulated TGF-$\beta$1 production of H. pylori lysate-activated RPMI 2650 cells to the normal level (control) by treatment for 48 hrs. The treatment of K1 and K4 kimchi enhanced the LPS (0.01 $\mu\textrm{g}$/mL)-induced IL-6 production of splenocytes. The results suggest that kimchi might have an beneficial effect on cancer prevention due in part to the function enhancing NO production of activated macrophages. Our data suggest that kimchi could modulate TGF-$\beta$1 production by cancer cells and IL-6 production of splenocytes, thereby possibly contributing to control carcinogenesis and the immune system.

• Journal of Korean society of Dental Hygiene
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• v.14 no.4
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• pp.601-608
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• 2014

Objectives : The purpose of the study is to examine the apoptotic effects of Pseudomonas aeruginosa exotoxin A(PEA) in squamous cell carcinoma(SCC) 25 cells. Methods : Cell growth reduction and apoptosis induced by PEA were confirmed by WST-1 assay, Hoechst 33258 staining, flow cytometry analysis, and Western blot assay. Results : The PEA treatment decreased the cell viability in a dose and time dependent manner: control; $100{\pm}0^e$(p<0.01), 0.1875 nM; $87{\pm}4.36^d$(p<0.01), 0.375 nM; $82{\pm}0.58^d$(p<0.01), 0.75 nM; $72{\pm}1.67^c$(p<0.01), 1.5 nM; $51{\pm}1.53^{bc}$(p<0.01), 7.5 nM; $31{\pm}1.20^{ab}$(p<0.01), 15 nM; $26{\pm}0.67^a$(p<0.01), control; $100{\pm}0^a$(p<0.05), 24 h; $51{\pm}1.53^b$(p<0.05), 48 h; $16{\pm}0.5^c$(p<0.05), 72 h; $12{\pm}1.67^d$%(p<0.05). The PEA was observed on SCC 25 cells with the half maximal inhibitory concentration(IC50) value of 1.5 nM at 24 hours. The PEA treated SCC 25 cells demonstrated several types of apoptotic indications, such as nuclear condensation, the increase of sub G1, and the cleavage of PARP-1 and DFF 45. Conclusions : PEA showed anti-cancer activity against SCC 25 cells via apoptosis. PEA may potentially contribute to human oral cancer treatment.

• Applied Chemistry for Engineering
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• v.7 no.6
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• pp.1034-1042
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• 1996

Various $TiO_2-SiO_2$ composite powders were prepared by the modified sol-gel method using 1-dodecanol as DCCA (Dryng Control Chemical Additive ). Their characterizations were carried out and their photocatalytic catalysis was examined on the evolution reaction of hydrogen. The weight losses at $500^{\circ}C$ of only $TiO_2$ and $SiO_2$ powders were 33. 0wt% and 42.5wt%, respectively, and those of the $TiO_2/SiO_2$ powders ($TiO_2/SiO_2=25/75$, 50/50 and 75/25) were about $70.0{\pm}3.0wt%$. The released substances from the powders were almost organic matters. The as-prepared powders except only $TiO_2$ powder were amorphous. Transformation of anatase to rutil was hindered by $SiO_2$ component and the crystallinity of anatase was decreased with increasing $SiO_2$ contents. The as-prepared powders were bulky states. By heating at $600^{\circ}C$ for 1 hr $TiO_2-SiO_2$ powders ($TiO_2=100%$, $TiO_2/SiO_2=75/25,\;50/50$) showed agglomerates consisted of particles in submicron, but those of $TiO_2/SiO_2=25/75$ and $SiO_2=100%$ were still bulky states. Specific surface area of the powders heat-treated at $600^{\circ}C$ for 1hr was increased with $SiO_2$ concents and their pore sizes were also depended on $SiO_2$ contents. The photocatalytic activity of $TiO_2/SiO_2=75/25$ heat-treated at $600^{\circ}C$ for 1hr was 0.240mo1/h.g-cat as $H_2$ evolution rate. This value was about 2.0 times that of P-25(Degussa P-25) as a standard photocatalyst.

• KSBB Journal
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• v.28 no.4
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• pp.260-268
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• 2013

Transgenic plant cell cultures are an attractive expression system for the production of industrial and pharmaceutical proteins because of their advantages in safety and low production cost. Human cytotoxic T-lymphocyte antigen 4-immunoglobulin (hCTLA4Ig) was produced and secreted when sugar was depleted in culture medium by transgenic rice cell lines (Oryza sativa L.) using RAmy3D promoter. Due to the production of the target protein by sugar depletion, concomitant occurrence of cell death is inevitable. For that reason, inhibition of cell death for enhancing productivity was necessary for the production period without energy sources. Supplementation of 0.1 mM sodium nitroprusside improved cell viability by 1.4-fold and maximum hCTLA4Ig production by 1.3-fold compared to those of control. Addition of 1 and 10 mM glutathione, N-acetylcysteine (NAC), and nicotinamide inhibited apoptotic-like programmed cell death by decreasing the activity of reactive oxygen species. Production hCTLA4Ig was enhanced 1.4-, 1.25-, and 1.15-fold with 10 mM NAC, 1 mM NAC, and 1 mM glutathione, respectively. In addition, it was found that the supplementation of NAC enhanced the cell viability.

• ALGAE
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• v.27 no.2
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• pp.125-134
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• 2012

Germanium dioxide ($GeO_2$) has been used for many years in the cultivation of red and green algae as a means of controlling the growth of diatoms. Brown algae are sensitive to $GeO_2$, however, the basis of this sensitivity has not been characterized. Here we use embryos of $Fucus$ $vesiculosus$ to investigate morphological and physiological impacts of $GeO_2$ toxicity. Morphometric features of embryos were measured microscopically, and physiological features were determined using pulse amplitude modulated (PAM) fluorometry. At 5 mg $L^{-1}$ $GeO_2$, embryos grew slower than controls and developed growth abnormalities. After 24 h, initial zygote divisions were often oblique rather than transverse. Rhizoids had inflated tips in $GeO_2$ and were less branched, and apical hairs were deformed, with irregularly aligned, spheroidal cells. Minimum fluorescence ($F_0$) showed minor differences over the 10 days experiment, and pigment levels (chlorophylls $a$, $c$ and total carotenoids) showed no difference after 10 days. Optimum quantum yield increased from ca. 0.52 at 24 h to 0.67 at 5 days, and $GeO_2$-treated embryos had higher mean values (significant at 3 and 5 days). Optimum quantum yield of photosystem II (${\Phi}_{PSII}$) was stable in control thalli after 5 days, but declined significantly in $GeO_2$. Addition of silica (as $SiO_2$) did not reverse the effects of $GeO_2$. These results suggest that $GeO_2$ toxicity in brown algae is associated with negative impacts at the cytological level rather than metabolic impacts associated with photosynthesis.

• Journal of Ecology and Environment
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• v.40 no.1
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• pp.12-19
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• 2016

Background: Direct impact of inorganic carbon (i.e., carbon dioxide ($CO_2$)) on the periphyton community is important to understand how and to what extent atmospheric conditions can affect the structure and dynamics of these communities in lotic systems. We investigated the influence of elevated $CO_2$ concentration on the periphyton community in the artificially constructed channels during the winter period. The channels made of acrylic paneling were continuously supplied with surface water discharged from a small reservoir, which was supported with ground water, at a flow rate of 5 L/min, and water temperature ranging $4-5^{\circ}C$. The effects of elevated $CO_2$ concentrations (790 ppm) were evaluated in comparison with the control (395 ppm $CO_2$) by analyzing pH, water carbon content and nutrients in water, periphyton composition and biomass, chlorophyll-a, ash-free dry-matter at 2-day intervals for 10 days. Results: After the addition of $CO_2$, significant decreases of pH, $NH_3-N$, and $PO_4-P$ (p < 0.05) and increases of chlorophyll-a, ash-free dry-matter, and the cell density of periphyton (p < 0.01) were observed, whereas the species composition of periphyton and water carbon content did not change. Conclusions: These results suggest that elevated $CO_2$ in flowing water system with low temperature could facilitate the growth of periphyton resulting in biomass increase, which could further influence water quality and the consumers throughout the food web.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.4
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• pp.1923-1930
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• 2012

Mn-Cu catalysts were tested for selective catalytic reduction of NOx with NH3. Influence of initial reaction temperature was studied for NOx conversion in which reaction temperature was changed three patterns. NOx conversion of catalysts calcined at 200, 300 and $340^{\circ}C$ was measured during the changing temperature. Hydrogen conversion efficiency of calcined catalysts was also measured in the $H_2$-TPR system. The deactivation effect of $SO_2$ on catalyst was investigated with the on-off control of $SO_2$ supply. The catalyst which calcined above $340^{\circ}C$ was somewhat deactivated with thermal shock. The reason of deactivation was draw from the results of surface area and hydrogen conversion.