• Korean Journal of Materials Research
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• v.16 no.10
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• pp.624-628
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• 2006

In this study, divalent europium-activated $NaCaPO_4$ green phosphor powders were prepared by the chemical synthetic method followed by heat treatment in reduced atmosphere, and the crystal structures, morphologies and photoluminescent properties of the powders were investigated by x-ray powder diffraction, scanning electron microscope and spectrometer for the first time. The effects of Ca/P and Na/Ca mole ratios on the final products were also investigated. The influences of input amount change of europium as the activator on the light emission intensity were studied, and the resulting concentration quenching phenomenon was observed. The optimized synthesis conditions obtained in this study were Ca/P mole ratio 1.2, Na/Ca mole ratio 3.0 and 4 mole%Eu. The peak wavelength was 505 nm for all the samples. The result of excitation spectrum measurement indicated that the excitation efficiency was high for the long-wavelength UV region. It was thus concluded that the samples prepared in this study can be successfully applied for the light-emitting devices such as LED excited with long-wavelength UV light sources.

• Korean Journal of Food Science and Technology
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• v.20 no.1
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• pp.40-44
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• 1988

This paper was carried out to investigate the relation of pH, aciidity and sourness during Kimchi fermentation and preservatives on Kimchi fermentation. Na-acetate, Na-malate, K-sorbate and K-sorbate+acetic acid were added to Kimchi samples. These Kimchi samples were fomented for 7 days at $37^{\circ}C$ and $20^{\circ}C$. In the experiment about the sourness and buffer action by organic salts which showed that the intensity of sourness was differented by the difference of pH in the same acidity. Na-acetate (0.3%) and Na-malate (0.3%) acted as good buffer, whereas K-sorbate (0.1%) and K-sorbate (0.1%)+acetic acid (0.05%) acted as lactobacilli growth enhancer in the fermentation.

• Food Science of Animal Resources
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• v.38 no.2
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• pp.417-430
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• 2018

This study was conducted to determine the effects of NaCl concentration and cooking temperature on the color and pigment characteristics of presalted ground chicken breasts. Four treatments with different salt concentrations (0%, 1%, 2%, and 3%) were prepared and stored for 7 d prior to cooking. Each sample was cooked to four endpoint temperatures ($70^{\circ}C$, $75^{\circ}C$, $80^{\circ}C$, and $85^{\circ}C$). The salt concentration affected the color and pigment properties of the cooked ground chicken breasts. As the salt concentration increased, the cooking yield and residual nitrite content also increased. However, the samples with 1%, 2%, and 3% NaCl showed similar nitrosyl hemochrome and total pigment contents. Among the products containing salt, the samples with 3% NaCl showed the lowest percentage myoglobin denaturation (PMD) and the lowest CIE $a^*$ values. The cooking temperature had limited effects on the pigment properties of cooked ground chicken breasts. The oxidation-reduction potential and residual nitrite contents increased with cooking temperature, while the PMD, nitrosyl hemochrome, total pigment contents and CIE $a^*$ values were similar in the samples cooked at different temperatures. These results indicated that the addition of up to 2% salt to ground chicken breasts and storage for 7 d could cause the pink color defect of cooked products. However, the addition of 3% NaCl could reduce the redness of the cooked products.

• Nuclear Engineering and Technology
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• v.24 no.2
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• pp.163-167
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• 1992

Nondestructive neutron activation analysis of copper in high purity Aluminum samples which can be used as a parameter of impurity is investigated and determined. Other 23 trace impurity elements in the samples are also determined. In the analysis of copper, the new irradiation method using thermal column was applied to reduce the interfering activity of 24Na produced by 27Al(n,$\alpha$)24Na reaction induced by fast neutron. As a result, the interference can be reduced to 100 times more than other activation methods. Also the influence by activity of 24Na is found in the range of 2~3 %. It has been observed that the copper contents in so-ratted“six nine”class standard aluminum samples are about 0.54 $\pm$ 0.08 ppm. By the comparison with other values re-ported, our results are reasonable and can be available as a improved routine analysis.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.28 no.6
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• pp.770-778
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• 1995

Anchovy Engraulis japonica boiled and dried was stored at $20^{\circ}C$ for 5 months after that treatment of sodium-erythorbate (Na-ery) or deoxygenizer (Deoxy). During storage, peroxide value (POV), thiobarbituric acid (TBA) value, lipid content, and lipid class compositions were determined to evaluate the quality of the samples. pay was decreased rapidly for the first 3 months storage and its decrease was Deoxy group>Control group>Na-ery group in that order. TBA values increased for the first 4 months and then decreased rapidly, and it's increase was the highest in Control group, followed by Na-ery and Deoxy group. Total lipid contents in all samples declined during storage. Especially, phospholipid decreased mainly in Na- ery and Deoxy group, while neutral lipid mainly in Control group. Triglyceride (TG), phosphatidylethanolamine(PE), and phosphatidylcholine(PC) decreased, while free fatty acid (FFA) and lyso-PC (LPC) increased during storage. The decrease of TG was the highest in Control group and that of PE and PC was higher in Na-ery group than in other sample. The decrease of PE in all samples (except Deoxy group) was higher than that of pc. The increase of FFA and LPC were higher in Control and Na-ery group than in Deoxy group. These results indicated that the lipid deterioration of the boiled and dried-anchovy was effectively suppressed by the enclosed deoxygenizer during storage at $20^{\circ}C$.

• Restorative Dentistry and Endodontics
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• v.40 no.3
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• pp.195-201
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• 2015

Objectives: The use of chitosan nanoparticles (CNPs) in endodontics is of interest due to their antibiofilm properties. This study was to investigate the ability of bioactive CNPs to remove the smear layer and inhibit bacterial recolonization on dentin. Materials and Methods: One hundred bovine dentin sections were divided into five groups (n = 20 per group) according to the treatment. The irrigating solutions used were 2.5% sodium hypochlorite (NaOCl) for 20 min, 17% ethylenediaminetetraacetic acid (EDTA) for 3 min and 1.29 mg/mL CNPs for 3 min. The samples were irrigated with either distilled water (control), NaOCl, NaOCl-EDTA, NaOCl-EDTA-CNPs or NaOCl-CNPs. After the treatment, half of the samples (n = 50) were used to assess the chelating effect of the solutions using portable scanning electronic microscopy, while the other half (n = 50) were infected intra-orally to examine the post-treatment bacterial biofilm forming capacity. The biovolume and cellular viability of the biofilms were analysed under confocal laser scanning microscopy. The Kappa test was performed for examiner calibration, and the non-parametric Kruskal-Wallis and Dunn tests (p < 0.05) were used for comparisons among the groups. Results: The smear layer was significantly reduced in all of the groups except the control and NaOCl groups (p < 0.05). The CNPs-treated samples were able to resist biofilm formation significantly better than other treatment groups (p < 0.05). Conclusions: CNPs could be used as a final irrigant during root canal treatment with the dual benefit of removing the smear layer and inhibiting bacterial recolonization on root dentin.

• Restorative Dentistry and Endodontics
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• v.44 no.1
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• pp.8.1-8.7
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• 2019

Objectives: Irrigants are imperative in endodontic therapy for the elimination of pathogens from the infected root canal. The present study compared the antimicrobial efficacy of octenidine dihydrochloride (OCT) with chlorhexidine (CHX) and sodium hypochlorite (NaOCl) against Staphylococcus epidermidis (S. epidermidis) for root canal disinfection. Materials and Methods: The minimum inhibitory concentration (MIC) was obtained using serial dilution method. The agar diffusion method was then used to determine the zones of inhibition for each irrigant. Lastly, forty 6-mm dentin blocks were prepared from human mandibular premolars and inoculated with S. epidermidis. Samples were randomly divided into 4 groups of 10 blocks and irrigated for 3 minutes with saline (control), 2% CHX, 3% NaOCl, or 0.1% OCT. Dentin samples were then collected immediately for microbial analysis, including an analysis of colony-forming units (CFUs). Results: The MICs of each tested irrigant were 0.05% for CHX, 0.25% for NaOCl, and 0.0125% for OCT. All tested irrigants showed concentration-dependent increase in zones of inhibition, and 3% NaOCl showed the largest zone of inhibition amongst all tested irrigants (p < 0.05). There were no significant differences among the CFU measurements of 2% CHX, 3% NaOCl, and 0.1% OCT showing complete elimination of S. epidermidis in all samples. Conclusions: This study showed that OCT was comparable to or even more effective than CHX and NaOCl, demonstrating antimicrobial activity at low concentrations against S. epidermidis.

• Agricultural and Biosystems Engineering
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• v.3 no.2
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• pp.79-84
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• 2002

The seawater involving diverse chemical elements was mixed with wasted coals to improve the quality. The thermal and chemical characteristics of these seawater-mixed coals were investigated and compared with those of original coals. The contents of MgO, $Na_2O$, and $K_2O$ were increased by mixing seawater in wasted coals. The content of $Na_2O$ in these coal samples was greatly increased due to the sodium, which was the main component of seawater. Thus, it was expected that fusion temperatures of these coal samples were decreased. Coal samples mixed with seawater showed that the rapid weight loss was started at the lower temperature than those of original coal samples. In these coal samples, the temperatures of maximum heat emission were lowered by average $61^{\circ}C.$. Thus, it is suggested that some chemical constituents of the seawater act an important role on lowering the ignition temperature of wasted coal. By mixing seawater into wasted coals, the calorific values were increased. Especially, calorific values were greatly increased in the coal samples of lower quality as Baksan A and B with the improvement of 15~20%.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.32 no.4
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• pp.371-380
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• 2022

Objectives: To ensure that employers handling petroleum compounds understand whether petroleum-based UVCB (unknown or variable composition, complex reaction products, or biological materials) substances contain hazardous substances and comply with the Occupational Safety and Health Act, petroleum-based UVCB substances were analyzed and the results from samples were compared with MSDS (Material Safety Data Sheet) contents. Methods: Twenty-one petroleum samples were analyzed using GC-MS (Gas Chromatography-Mass Spectrometry), targeting ten volatile organic compounds regulated by the Occupational Safety and Health Act. Results: The target chemicals were detected in 13 out of 21 samples. All 13 samples were in the naphtha (low boiling point naphthas (gasolines)) group. There were also naphtha group samples containing 2% benzene. Some naphtha samples used as solvents contained about 1% benzene. Conclusions: This study shows that naphtha group petroleum substances contain hazardous chemicals in many cases. In particular, if benzene, n-hexane, and toluene with low occupational exposure limits are contained above the limit concentration. Such information should be delivered in the article on MSDS legal regulations.

• Journal of Korean Society on Water Environment
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• v.34 no.1
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• pp.77-83
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• 2018

This paper aims to evaluate the results of toxicity testing with Daphnia magna and Vibrio fischeri on wastewater samples which might be influenced by ion imbalance. The effluents from factories were found to be more toxic with high salinity levels than those from public wastewater treatment plant (WTP) and sewage treatment plant (SWP). Clion composition was highest in the effluent, in terms of percentage, which was followed by $Na^+$, $SO_4^{2-}$ and $Ca^{2+}$. $K^+$ and $Mg^{2+}$ ion was relatively low. The sensitivity of D. magna test results was higher than V. fischeri. Among samples which were proved by V. fischeri testing to be nontoxic, the composition ratio of each ion whether toxic samples or nontoxic samples which were decided by D. magna toxicity testing, were compared. $Na^+$, $K^+$, $Ca^{2+}$, $Mg^{2+}$ ion composition ratio showed high level in nontoxic samples whereas $SO_4^{2-}$ and $Cl^-$ ion composition ratio was high in toxic samples. Accordingly, $SO_4^{2-}$ and $Cl^-$ ion seemed to be considered the ions causing toxicity in effluent. Toxicity from some categories of industries (Mining of non-metallic minerals, Manufacture of basic organic petrochemicals, Manufacture of other basic organic chemicals, Manufacture of other chemical products etc.) seemed to be influenced by salinity. The Ion concentration in influent and effluent were similar. Concentration of $Na^+$, $Cl^-$, $K^+$, $Ca^{2+}$ ions were high in influent, however $Mg^{2+}$ and $SO_4^{2-}$ ions were high in effluent.