• Korean Journal of Materials Research
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• 제26권2호
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• pp.67-72
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• 2016

$BaMoO_4:Tb^{3+}$ phosphor powders were synthesized with different concentrations of $Tb^{3+}$ ions using the solid-state reaction method. XRD patterns showed that all the phosphors, irrespective of the concentration of $Tb^{3+}$ ions, had tetragonal systems with two main (112) and (004) diffraction peaks. The excitation spectra of the $Tb^{3+}$-doped $BaMoO_4$ phosphors consisted of an intense broad band centered at 290 nm in the range of 230-330 nm and two weak bands. The former broad band corresponded to the $4f^8{\rightarrow}4f^75d^1$ transition of $Tb^{3+}$ ions; the latter two weak bands were ascribed to the $^7F_2{\rightarrow}^5D_3$ (471 nm) and $^7F_6{\rightarrow}^5D_4$ (492 nm) transitions of $Tb^{3+}$. The main emission band, when excited at 290 nm, showed a strong green band at 550 nm arising from the $^5D_4{\rightarrow}^7F_5$ transition of $Tb^{3+}$ ions. As the concentration of $Tb^{3+}$ increased from 1 to 10 mol%, the intensities of all the emission lines gradually increased, approached maxima at 10 mol% of $Tb^{3+}$ ions, and then showed a decreasing tendency with further increase in the $Tb^{3+}$ ions due to the concentration quenching effect. The critical distance between neighboring $Tb^{3+}$ ions for concentration quenching was calculated and found to be $12.3{\AA}$, which indicates that dipole-dipole interaction was the main mechanism for the concentration quenching of the $^5D_4{\rightarrow}^7F_5$ transition of $Tb^{3+}$ in the $BaMoO_4:Tb^{3+}$ phosphors.

• Applied Chemistry for Engineering
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• 제19권3호
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• pp.326-331
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• 2008

The purpose of this work is to develope sodium-containing nonstoichiometric apatitic coatings on solid substrate. The apatitic coatings prepared at different concentrations of sodium salt indicated that the presence of sodium ions exerted significant effects on the physicochemical properties of the apatitic coating including surface morphology, chemical state, and Ca/P ratio. The variation of these properties was sustained up to 0.01 mM of sodium ion concentration. The ratio of calcium to phosphorus was varied from 2.18 to 2.03 which indicated the apatitic coating prepared in this study was calcium-rich nonstoichiometric apatite. The structure of all the samples appeared to be low crystalline. In the presence of sodium ion within the apaptitic coating, the adhesion of human osteoblast-like SaOS-2 cells was significantly promoted. On the other hand, the proliferation of the cells on the apatitic coatings was decreased with the increase of sodium ions. This reverse response of SaOS-2 cells indicates that the interaction between SaOS-2 and apatitic surface triggered considerable changes in intracellular mechanisms including cellular signal transductions.

• Journal of the Korean Geotechnical Society
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• 제29권12호
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• pp.35-44
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• 2013

In this study, a particle method without using grid was applied for analysing large deformation problems in soil flows instead of using ordinary finite element or finite difference methods. In the particle method, a continuum equation was discretized by various particle interaction models corresponding to differential operators such as gradient, divergence, and Laplacian. Soil behavior changes from solid to liquid state with increasing water content or external load. The Mohr-Coulomb failure criterion was incorporated into the particle method to analyze such three-dimensional soil behavior. The yielding and hardening behavior of soil before failure was analyzed by treating soil as a viscous liquid. First of all, a sand column test without confining pressure and strength was carried out and then a self-standing clay column test with cohesion was carried out. Large deformation from such column tests due to soil yielding or failure was used for verifying the developed particle method. The developed particle method was able to simulate the three-dimensional plastic deformation of soils due to yielding before failure and calculate the variation of normal and shear stresses both in sand and clay columns.

• Journal of Microbiology and Biotechnology
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• 제29권10호
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• pp.1495-1505
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• 2019

The Burkholderia cepacia complex (BCC) is capable of remaining viable in low-nutrient environments and harsh conditions, posing a contamination risk in non-sterile pharmaceutical products as well as a challenge for detection. To develop optimal recovery methods to detect BCC, three oligotrophic media were evaluated and compared with nutrient media for the recovery of BCC from autoclaved distilled water or antiseptic solutions. Serial dilutions ($10^{-1}$ to $10^{-12}CFU/ml$) of 20 BCC strains were inoculated into autoclaved distilled water and stored at $6^{\circ}C$, $23^{\circ}C$ and $42^{\circ}C$ for 42 days. Six suspensions of Burkholderia cenocepacia were used to inoculate aqueous solutions containing $5{\mu}g/ml$ and $50{\mu}g/ml$ chlorhexidine gluconate (CHX) and $10{\mu}g/ml$ benzalkonium chloride (BZK), and stored at $23^{\circ}C$ for a further 199 days. Nutrient media such as Tryptic Soy Agar (TSA) or Tryptic Soy Broth (TSB), oligotrophic media (1/10 strength TSA or TSB, Reasoner's $2^{nd}$ Agar [R2A] or Reasoner's $2^{nd}$ Broth [R2AB], and 1/3 strength R2A or R2AB) were compared by inoculating these media with BCC from autoclaved distilled water and from antiseptic samples. The recovery of BCC in water or antiseptics was higher in culture broth than on solid media. Oligotrophic medium showed a higher recovery efficiency than TSA or TSB for the detection of 20 BCC samples. Results from multiple comparisons allowed us to directly identify significant differences between TSA or TSB and oligotrophic media. An oligotrophic medium pre-enrichment resuscitation step is offered for the United States Pharmacopeia (USP) proposed compendial test method for BCC detection.

• Journal of the Korean Magnetics Society
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• 제5권5호
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• pp.782-785
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• 1995

In this paper, $Mn^{2+}$ ion was doped in Y-Ba-Cu-O as an EPR probe. The following samples were prepared by conventional solid-state reaction method : $YBa_{2}Cu_{2.96}Mn_{0.04}O_{7-\delta}$ (MN-I), annealed $YBa_{2}Cu_{2.96}Mn_{0.04}O_{7-\delta}$ (AMN) and $YBa_{2}Cu_{2.94}Mn_{0.06}O_{7-\delta}$ (MN-II). AMN sample was obtained from MN-I by annealing for 1 hr under the Ar gas atmosphere at $600^{\circ}C$. X-band (~9.05 GHz) EPR spectra were measured from 103 K to room temperature by employing a JES-RE3X spectroscopy with a $TE_{0.11}$ cylindrical cavity and 100 kHz modulation frequency. In MN-I we have observed only the $Cu^{2+}$ signal. The fact that no $Mn^{2+}$ signal was observed, in spite of $Mn^{2+}$ being a very sensitive EPR probe, indicates that most likely isolated $Mn^{2+}$ ions don't exist in the MN-I sample. Most probably $Mn^{2+}$ ions in the MN-I sample interact antiferromagnetically and hence are EPR silent. The AMN spectra of at room temperature and 103 K indicate not only the $Cu^{2+}$ signal but also an extra signal, which increases with decreasing temperature. It is suggested that the extra signal originates from Mn ions that were antiferromagnetically coupled before the annealing process. In MN-II, from 103 K to room temperature, also, the extra signal was observed together with the $Cu^{2+}$ signal. The extra signal in MN-II, however, decreases with decreasing temperature and nearly disappears at 103 K. The signal originates from Mn ions in impurity phases that include $Mn^{2+}$ ions. We suppose that there exist at least two $Mn^{2+}$ doped phases in Y-Ba-Cu-O. The $Mn^{2+}$ signal of one phase is undectable at all temperature and that of another phase decreases with decreasing temperature and disappears around 103 K.

• Nuclear Engineering and Technology
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• 제1권2호
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• pp.91-101
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• 1969

Resistivity changes of n-type float-zone silicon crystals with 6.4$\times$10$^{14}$ to 1.25$\times$10$^{17}$ phosphorus atoms/㎤ due to irradiation by (1) 1 MeV electrons, (2) two types of research reactors, and (3) $Co^{60}$ ${\gamma}$-ray sources were investigated. The results were analyzed on the basis of a simple exponential formula derived by Buehler. While the formula gave a fair fit in the low fluence range in most cases, the deviation was quite appreciable in the case of 1 MeV electron irradiation, and a linear change gave better fit in some cases. The large change in the carrier removal rate in electron-irradiated samples in the high fluence range was analyzed in detail in terms of the Fermi level cross-over of the defect levels. Based on the damage constants evaluated from the initial portion of data where the formula was applicable, the relative effectiveness of various radiation sources in causing the resistivity change in n-type silicon was compared. The TRIGA Mark II reactor neutrons, for example, were found to be about 40 times more effective than 1 MeV electrons. The dependence of the damage constant on the initial carrier concentration was also examined. The physical basis of the exponential law and the effect of the Fermi level cross-over of the defect levels on the resistivity change in the high fluence ranges are discussed.

• Food Science and Preservation
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• 제16권4호
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• pp.459-462
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• 2009

'Fuyu' (Diospyros kaki L.) is an important sweet persimmon cultivar, and the fruits are often stored in a modified atmosphere after harvesting in South Korea. However, blossom-end browning and darkening of fruit often occur after harvest or during storage, which decreases fruit quality in the fresh fruit market. High fruit calcium concentration would reduce oxidation of phenolic compounds in the cytoplasm such oxidation is responsible for fruit browning. This study investigated the effects of soluble calcium fertilization and foliar application, and indole-3-butyric acid (IBA) fertilization on fruit quality and browning. Trees received one of the following five treatments: 1) control (no calcium or IBA); 2) calcium fertilization (Ca FG, 2 mL per tree); 3) calcium foliar application (Ca FA, 2 mL); 4) calcium and IBA fertilization (Ca+IBA) 5) IBA fertilization (IBA, 2 mL. Fruit calcium concentration was highest in trees treated by Ca FA, and lowest in control trees. Generally, fruit calcium concentration was high in the stem end but low in the blossom end, which usually first develops fruit-browning symptoms. There were no apparent differences in fruit qualities such as firmness, soluble solid content, and weight among treatments. Fruit browning occurred at frequencies of about 14%, 20%, and 50% on Ca FA, Ca FG, and control trees, respectively. Therefore, the improved fruit calcium level seen when trees received Ca or IBA application tended to prevent fruit browning, which increased fruit quality and storage properties.

• Korean Journal of Soil Science and Fertilizer
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• 제39권6호
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• pp.409-414
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• 2006

Sulfur-oxidizing bacteria were enumerated and isolated from a steady-state anaerobic master culture reactor (MCR) operated for over six months under a semi-continuous mode and nitrate-limiting conditions using thiosulfate as an electron donor. Most are Gram-negative bacteria, which have sizes up to 12 m. Strains AD1 and AD2 were isolated from the plate count agar (PCA), and strains BD1 and BD2 from the solid thiosulfate/nitrate medium. Based on the morphological, physiological, FAME and 16S rDNA sequence analyses, the two dominant strains, AD1 and AD2, were identified as Paracoccus denitrificans and Paracoccus versutus (formerly Thiobacillus versutus), respectively. From the physiological results, glucose was assimilated by both strains AD1 and AD2. Heterotrophic growth of strains AD1 and AD2 could be a more efficient way of obtaining a greater amount of biomass for use as an inoculum. Even though facultative autotrophic bacteria grow under heterotrophic conditions, autotrophic denitrification would not be reduced.

• Journal of the Korean Society of Radiology
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• 제15권5호
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• pp.715-721
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• 2021

In radiation brachytherapy, the wrong source location may cause excessive dose to normal tissue. Therefore, research on digital dosimeters is being made to replace the analog detection method. Therefore, in this study, a lead (II) oxide (PbO) dosimeter applied with a passive layer (PL) was fabricated as a basic study to improve the dosimeter performance. Afterwards, reproducibility, linearity, and distance dependence were evaluated to analyze the performance of the Ir-192 source under irradiation conditions. The reproducibility of the PL-PbO dosimeter was 0.40%, which satisfies the evaluation criteria of 1.5%, and showed improved results compared to the PbO dosimeter. Linear function R2 showed excellent results as 0.9995, and slope analysis through regression analysis of the linear function was excellent in PL-PbO. The distance dependence of the PL-PbO dosimeter was +0.599 higher than that of PbO when the slope obtained through regression analysis of the power function was compared with the inverse square value. This study presents the effects and measurement variables according to the measurement configuration of the solid-state dosimeter, and can be used in various radiation detection fields.

• Herbal Formula Science
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• 제26권4호
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• pp.295-306
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• 2018

Schisandra chinensis (SC) and Lycium chinense (LC) were widely distributed in Asia and the fruit has been used traditionally for medicinal herbs. The processing method was solid-state fermentation using Aspergillus oryzae for 48 h after stir-frying treatment at $220^{\circ}C$ for 12 min. In this study, in vitro the anti-inflammatory effect and in vivo hangover reduction were compared to unprocessed SC and LC water extract. Anti-inflammatory effects have been evaluated in pro-inflammatory mediators which were secreted by lipopolysaccharide (LPS)-induced RAW 264.7 macrophages. Nitric oxide (NO) was determined using Griess reaction. Proinflammatory cytokines such as tumor necrosis factor $(TNF)-{\alpha}$ and interleukin $(IL)-1{\beta}$ were measured by enzyme-linked immunosorbent assays (ELISA). Alcohol dehydrogenase (ADH) and acetaldehyde dehydrogenase (ALDH) activities were compared to processed SC or LC and mixtures thereof (1:1). In vivo study was compared to hangover relief in alcohol-fed mice. After administering a mixture of SC and LC (300 mg/kg) water extract (1:1), mice were fed 3 g/kg of ethanol. Serum was collected at 1, 3, and 5 h intervals to analyze ethanol and acetaldehyde levels using a colorimetric assay kit. The processed SC and LC water extracts compared to raw materials significantly inhibited LPS-induced NO and inflammatory cytokine production in RAW 264.7 cells. The results of the hangover mouse model are also consistent with anti-inflammatory effects. These results suggest that processed SC and LC extracts may be functional materials for the treatment of inflammation and hangover.