• Mycobiology
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• v.36 no.4
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• pp.249-254
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• 2008

Minimal growth inhibitory concentrations (MICs) of chitosan acetate (M.W. 60 kDa) on heterotrophic bacteria (strains MK1, S, and R) isolated from the soft-rotten tissues of Neungee mushroom (Sarcodon aspratus) were measured. The slimy substance produced by the MK1 strain was responsible for the diseased mushroom’s appearance. The S and R strains were members of the Burkholderia cepacia complex. These strains showed different levels of susceptibility toward chitosan acetate. The MIC of chitosan acetate against the MK1 and S strains was 0.06%. The MIC against the R strain was greater than 0.10%. Survival fractions of the MK1 and S strains at the MIC were $3\;{\times}\;10^{-4}$ and $1.4\;{\times}\;10^{-3}$ after 24 h, and $2\;{\times}\;10^{-4}$ and $7\;{\times}\;10^{-4}$ after 48 h, respectively. Survival fractions of the R strain after 24 and 48 hr at 0.1% chitosan acetate were $1\;{\times}\;10^{-2}$ and $6.9\;{\times}\;10^{-3}$, respectively. Compared to the MK1 and S strains, the low susceptibility of the R stain towards chitosan acetate could be due to the ability of the R strain to utilize chitosan as a carbon source. Thirty-eight percent of Neungee pieces treated in a 0.06% chitosan acetate solution for $2{\sim}3$ second did not show any bacterial growth at 4 days, whereas bacterial growth around untreated mushroom pieces occurred within 2 days. These data suggest that chitosan acetate is highly effective in controlling growth of indigenous microorganisms on Neungee. The scanning electron micrographs of the MK1 strain treated with chitosan revealed a higher degree of disintegrated and distorted cellular structures.

• Korean Journal of Medicinal Crop Science
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• v.8 no.3
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• pp.274-282
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• 2000

Physico-chemical characteristics and chemical composition of seed oil of Sapium japonicum were determined by various analysis methods. Physio-chemical characteristics of the extracted oil from fresh seed were specific gravity (0.928), refraction index (1.477), acid value (2.30), saponification number (190.0), and iodine value (126.0). Neutral lipid (93%) in seed oil was identified as major components, followed by glycolipid (4.9%) and phospholipid (1.3%). In GC analysis, nine fatty acids were presented in the seed oil. Among fatty acids, predominant fatty acids were oleic acid (45.8%) and linoleic acid (35.6%). The contents of fatty acids of seed oil somewhat varied with their storage period. Composition of fatty acids from lipid fractions which were isolated on silica open column was investigated. Major fatty acids in three lipid fractions were linoleic acid and linolenic acid. The fatty acid contents of fresh seed oil derived from each lipid fraction were generally high comapred to storage seed oil. From the above results, seed oil of Sapium Japonicum could be useful in cosmetics, detergents and a few pharmaceuticals.

• Journal of the Korean Wood Science and Technology
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• v.44 no.3
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• pp.398-405
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• 2016

The cellulose nanofibers (CNFs) were prepared by wet disk-milling (WDM) and fractionated by settling method into supernatant, middle and sediment fractions. The diameter and its distribution of the fractionated CNFs were investigated. With increasing WDM passing number, precipitation became delayed. Weight fraction at sediment fraction was decreased, whereas those at supernatant and middle fractions were increased with increasing WDM passing number. Diameter distribution of CNFs at supernatant fraction was narrowest and became broaden at middle and sediment fraction. Filtration time was longer in order of supernatant, middle and sediment fraction.

• School Mathematics
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• v.11 no.4
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• pp.643-664
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• 2009

This study was aimed to understand the problems that students experience during the self--directed study of a mathematics digital textbook and to find the implications for the design of digital textbook. For this study, we analyzed the process of self-directed learning on 'division of fractions with same denominator' using digital textbook by eight 6th graders. Students asked to use think aloud method while they study the unit. Their learning process was videotaped and analyzed by researchers after the experiment. After the self-directed learning, students filled out a test items and participated interview with a researcher. The result showed that students experienced several misconceptions and errors while using a digital textbook. The types of misconceptions and errors were cataegorized as "misconceptions and errors caused by a mathematics textbook" and "misconceptions and errors caused by a digital textbook". Especially, students showed several important misconceptions and errors because of the design factors. This implies we need to consider the causes of misconceptions for the design of a digital textbook.

• Food Science and Preservation
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• v.14 no.3
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• pp.323-327
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• 2007

Moderate consumption of maesil(Prunus mune) was associated with pharmaceutical and physiological effects on human health. The object of this study was to determine the inhibitory effects of Prunus mune extracts(PME) on food spoilage microorganisms. PME was found to have an antibacterial effect on Colletotrichum fragariae. The hydrophilic fractions of PME showed more effective inhibition than did the hydrophobic fractions. In addition, the hydrophilic fractions of PME seemed to inhibit(12-40%) metabolic enzymes related to energy production, including glucose-6-phosphate dehydrogenase, succinate dehydrogenase, malate dehydrogenase, and hexokinase. Our data suggest that hydrophilic components of PME might control food spoilage microorganisms because of suppression of membrane enzymatic function.

• Journal of Life Science
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• v.17 no.1 s.81
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• pp.76-81
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• 2007

Inhibitory effects of methanol extracts and several solvent fractions from meju on mutagenicity in vitro genotoxicity (SOS chromotest) and growth of human cancer cells (AGS gastric adenocarcinoma and Hep 3B hepatocellular cancinoma cells) were studied. The treatment of meju methanol extracts $(100{\mu}g/assay)$ to SOS chromotest system inhibited N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) induced mutagenicity by 36%. However, the ethylacetate and dichloromethane fractions from meju methanol extracts showed the stronger antimutagenic effects (91% and 91%, respectively) in SOS chromotest. In sulforhodamine B (SRB) assay, the treatments of ethylacetate and dichloromethane fractions (2 mg/assay) significantly inhibited the growth of AGS and Hep 3B cancer cells by 64% and 71%, respectively. These results indicated that meju had inhibitor)r effects on MNNG in SOS mutagenic system and growth of human cancer cells, suggesting that its antimutagenic effect may be relative to activity of doenjang.

• The Mathematical Education
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• v.53 no.3
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• pp.329-355
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• 2014

The purpose of this study is to understand the difference of cognitive structure depending on the level of the 6th graders' problem-solving abilities about the division of fraction and to propose a method for improving the 6th graders' understanding about the division of fraction through the word association test. The following is the findings from this study. 1)The lower level students' is, the lower the step that the chunk appeared in cognitive structure is. 2)The basic level students' association frequency between any two concepts was less than the excellent level students and the ordinary level students' it. 3)The basic level students' connection number between concepts was far less than the excellent level students and the ordinary level students' it. 4)The connection between natural number and unit fractions, subtraction of fraction and division of fraction, division of fraction and reduction to common denominator, and division of fraction and common multiple that expected in this study did not appear in the three groups.

• Journal of the Korean Wood Science and Technology
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• v.33 no.5 s.133
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• pp.86-91
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• 2005

Six compounds were isolated from the EtOAc and $Et_2O$ fractions of the bark of Rhus chinensis by repeated column chromatography with $SiO_2$ and Sephadex LH-20. The structures were determined by instrumental analysis using MS and NMR spectrophotometer as: gallic acid (1), methyl gallate (2), 6, 7-dimethoxycoumarin (3), orcinol-${\beta}$-D-glucoside (4), scopoletin (5), semialactone (6). Among these compounds, 6,7-dimethoxycoumarin (3) was isolated from this plant for the first time. To measure the antioxidant activity, the DPPH radical scavenging activity test was performed. Gallic acid (1) showed the strongest activity, while orcinol-${\beta}$-D-glucoside (4), semialactone (5) and scopoletin (6) had the low activities.

• Journal of Applied Biological Chemistry
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• v.53 no.1
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• pp.21-24
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• 2010

In recent years, many agricultural scientists are studying on eco-friendly farming methods. Among of lots of the methods, the natural insecticides are highly motivated and interested due to their safety and biodegradable issues, and readily available source of bioinsecticides. In this study, the crude extract of custard apple (Annona reticulata L.) seed and its three fractions which were separated based on polarity indexes were examined for their insecticidal activities against Myzus persicae Sulzer and Nilaparvata lugens S.. The crude extract (Aceton/MeOH) showed strong insecticidal activities against both insects at 3.00 mg/mL ($LD_{50}$=0.45mg/mL for M. persicae S. and 1.42 mg/mL for N. lugens S.). Furthermore, simple fractionation with hexane, chloroform, and water lead to increase three-folds insecticidal activity on chloroform fraction ($LD_{50}$=0.13mg/mL for M. persicae S. and 1.14 mg/mL for N. lugens S.). The results suggest that A. reticulata extracts might be used to control for M. persicae effectively.

• Journal of Elementary Mathematics Education in Korea
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• v.18 no.1
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• pp.105-122
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• 2014

In this paper, fraction division algorithms in Korean elementary mathematics textbooks are analyzed as a part of the groundwork to improve teaching methods for fraction division algorithms. There are seemingly six fraction division algorithms in ${\ll}Math\;5-2{\gg}$, ${\ll}Math\;6-1{\gg}$ textbooks according to the 2006 curriculum. Four of them are standard algorithms which show the multiplication by the reciprocal of the divisors modally. Two non-standard algorithms are independent algorithms, and they have weakness in that the integration to the algorithms 8 is not easy. There is a need to reconsider the introduction of the algorithm 4 in that it is difficult to think algorithm 4 is more efficient than algorithm 3. Because (natural number)${\div}$(natural number)=(natural number)${\times}$(the reciprocal of a natural number) is dealt with in algorithm 2, it can be considered to change algorithm 7 to algorithm 2 alike. In textbooks, by converting fraction division expressions into fraction multiplication expressions through indirect methods, the principles of calculation which guarantee the algorithms are explained. Method of using the transitivity, method of using the models such as number bars or rectangles, method of using the equivalence are those. Direct conversion from fraction division expression to fraction multiplication expression by handling the expression is possible, too, but this is beyond the scope of the curriculum. In textbook, when dealing with (natural number)${\div}$(proper fraction) and converting natural numbers to improper fractions, converting natural numbers to proper fractions is used, but it has been never treated officially.