• Education of Primary School Mathematics
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• v.27 no.1
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• pp.91-110
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• 2024

The purpose of this study is to explore visual models for deriving the fractional division algorithm, to see how students understand this integrated model, the rectangular partition model, when taught in elementary school classrooms, and how they structure relationships between fractional division situations. The conclusions obtained through this study are as follows. First, in order to remind the reason for multiplying the reciprocal of the divisor or the meaning of the reciprocal, it is necessary to explain the calculation process by interpreting the fraction division formula as the context of a measurement division or the context of the determination of a unit rate. Second, the rectangular partition model can complement the detour or inappropriate parts that appear in the existing model when interpreting the fraction division formula as the context of a measurement division, and can be said to be an appropriate model for deriving the standard algorithm from the problem of the context of the inverse of a Cartesian product. Third, in the context the inverse of a Cartesian product, the rectangular partition model can naturally reveal the calculation process in the context of a measurement division and the context of the determination of a unit rate, and can show why one division formula can have two interpretations, so it can be used as an integrated model.

• Korean Journal of Food Science and Technology
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• v.48 no.5
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• pp.508-514
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• 2016

Effects of the ethyl acetate fraction from gomchwi (Ligularia fischeri) extract against high $glucose/H_2O_2-induced$ oxidative stress and in vitro neurodegeneration were investigated to confirm the physiological property of the extract. The ethyl acetate fraction of gomchwi extract showed the highest total phenolic contents than the other solvent fractions. An anti-hyperglycemic activity of the ethyl acetate fraction was evaluated using the ${\alpha}-glucosidase$ inhibitory assay, and the half maximal inhibitory concentration ($IC_{50}$) value for ${\alpha}-glucosidase$ was found to be $727.64{\mu}g/mL$. In addition, the ethyl acetate fraction showed excellent 2,2'-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) diammonium salt radical scavenging activity, and inhibition of malondialdehyde production. The ethyl acetate fraction also decreased intracellular reactive oxygen species, whereas neuronal cell viability against high glucose/$H_2O_2$-induced cytotoxicity was found to be increased. Finally, 3,5-dicaffeoylquinic acid as a main phenolic compound in the ethyl acetate fraction was analyzed by high-performance liquid chromatography. These results suggest that gomchwi might be a good natural source of functional materials to prevent diabetic neurodegeneration.

• Korean Journal of Pharmacognosy
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• v.48 no.4
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• pp.314-319
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• 2017

To evaluate the longevity property of Allium hookeri (Liliaceae) leaves, this study was performed. Ethanol extract of A. hookeri was successively partitioned as methylene chloride, ethyl acetate, n-butanol and $H_2O$ soluble fractions, and lifespan-extending effects of the fractions were checked using Caenorhabditis elegans model system. The most active ethyl acetate-soluble fraction elevated heat stress tolerance, and increased expression of stress resistance protein. Further studies were performed to investigate several aging-related factors such as reproduction, food intake, growth and movement of C. elegans. The results revealed that there were no significant changes in aging-related factors including reproduction and food intake, however, ethyl acetate-soluble fraction treatment led to up-regulation of locomotory ability and growth of aged worms, suggesting ethyl acetate-soluble fraction affected healthspan as well as lifespan of nematode.

• Polymer(Korea)
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• v.38 no.3
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• pp.272-277
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• 2014

We studied in-line monitoring the dispersion of highly energetic material simulant by a twin screw extruder having a high temperature ultrasonic system. The simulant suspension system consisted of ethylene vinyl acetate and Dechlorane plus 25 as binder and filler, respectively. With increasing filling fraction, the ultrasonic velocity was not changed but the attenuation linearly decreased. It was possible to estimate the solid fraction of well dispersed suspension system by measuring ultrasonic attenuation. The ultrasonic attenuation of samples filled over 60 v% approached straight line with increasing filling fraction when the samples was extruded repeatedly. It was due to the enhanced dispersion of solid particles in the suspension system. It was believed that the degree of dispersion and filling fraction could be obtained by combination of on-line measurement like ultrasonic attenuation and off-line analysis like TGA and SEM with image analyzer.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.135-135
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• 1999

It is well known that Raman spectroscopy is powerful tool in analysis of sp3/sp3 bonding fraction in diamond-like carbon(DLC) films. Raman spectra of DLC film is composed of D-peak centered at 1350cm-1 and G-peak centered at 1530cm-1. The sp3/sp3 fraction is qualitatively acquired by deconvolution method. However, in case of DLC film, it is generally observed that G-peak position shifts toward low wavenumber as th sp3 fraction increases. However, opposite results were frequently observed in ta-C films. ta-C film has much higher residual compressive stress due to its high sp3 fraction compared to the DLC films deposited by CVD method. Effect of residual stress on G-peak position is most recommendable parameter in Raman analysis of ta-C, due to its smallest fitting error among many parameters acquired by peak deconvolution of symmetric spectra. In current study, the effect of residual stress on Raman spectra was quantitatively evaluated by free-hang method. ta-C films of different residual stress were deposited on Si-wafer by modifying DC-bias voltage during deposition. The variation of the G-peak position along the etching depth were observed in the free-hangs of 20~30${\mu}{\textrm}{m}$ etching depth. Mathematical result based on Airy stress function, was compared with experimental results. The more reliable analysis excluding stress-induced shift was possible by elimination of the Raman shift due to residual compressiove stress.

• Natural Product Sciences
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• v.11 no.3
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• pp.165-169
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• 2005

Chlorophytum borivilianum Baker (Antharicaceae) commonly referred as 'Safed Musli' has been widely used in the Indian traditional systems of medicine to treat various diseases like rheumatism apart from having immunomodulating property and is used as general tonic. It is also known as 'Ayurvedic viagra' for its aphordisiac properties. C. borivilianum was screened for the first time to determine its antioxidant activity, isolation of the sapogenins and standardization of the isolated sapogenin fraction using HPTLC. Potent antioxidant activity of ethanolic extract was found by their ability to scavenge DPPH (84.51%), hydroxyl radical (48.95 %), ferryl bi-pyridyl complex (84.53%) along with the inhibition of lipid peroxidation (67.17%) at $100\;{\mu}g/ml$ concentration. The ethanolic extract also exhibited significant inhibition of superoxide anion radical generated by photochemiluminescence. Thus, the potent antioxidant activity validates the innumerable therapeutic claims of the plant in the traditional system especially its use as a Rasayana drug.

• KSBB Journal
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• v.24 no.5
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• pp.469-476
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• 2009

The antioxidant activities of two crude extracts ($CH_2Cl_2$ and MeOH) and their solvent fractions (n-hexane, 85% aq. MeOH, n-BuOH, and $H_2O$ fractions) from Corydalis heterocarpa were determined by evaluating authentic $ONOO^-$ and $ONOO^-$ generated from SIN-1 (3-morpholinsydnonimine) in vitro as well as by measuring the degree of occurrence of intracellular reactive oxygen species (ROS) and nitric oxide (NO). Scavenging activities of solvent fractions on authentic $ONOO^-$ increased in the order of n-BuOH > 85% aq. MeOH > $H_2O$ > n-hexane fractions, while those on $ONOO^-$ generated from SIN-1 increased in the order of n-BuOH > 85% aq. MeOH > $H_2O$ > n-hexane fractions. In addition, all solvent fractions effectively inhibited the intracellular ROS and NO levels. The n-BuOH fraction especially exhibited the strongest ROS scavenging effect. Further purification of n-BuOH fraction led to the isolation of cnidimoside A, which presented the potent ROS scavenging effect at $10\;{\mu}M$. From these results, extracts of C. heterocarpa and its component, cnidimoside A, were predicted to be potentially useful as ingredients for protecting against oxidation.

• Bulletin of the Korean Chemical Society
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• v.31 no.5
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• pp.1143-1148
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• 2010

We investigated the separation of nitrogen heterocyclic compound (NHC) contained in a model coal tar fraction comprising four kinds of NHC [indole (In), quinoline (Q), iso-quinoline (iQ), quinaldine (Qu)], three kinds of bicyclic aromatic compound (BAC) [1-methylnaphthalene (1MN), 2-methylnaphthalene (2MN), dimethylnaphthalene (DMN) mixture with ten structural isomers (DMNs; regarded as one component)], biphenyl (Bp) and phenyl ether (Pe) by liquid membrane permeation (LMP). A batch-stirred tank was used as the permeation unit. An aqueous solution of saponin and n-hexane were used as the liquid membrane and the outer oil phase, respectively. Yield and selectivity of individual NHC was much larger than that of BAC, Bp and Pe. Increasing the initial mass fraction of the saponin to the membrane solution ($C_{sap,0}$) and the initial volume fraction of O/W emulsion to total liquid in a stirred tank (${\phi}_{OW,0}$) resulted in deteriorating the yield of individual NHC, but increasing the stirring speed (N) resulted in improving the yield of each NHC. With increasing $C_{sap,0}$, the selectivity of each NHC based on DMNs increased. Increasing ${\phi}_{OW,0}$ and N resulted in decreasing the selectivity of individual NHC based on DMNs. At an experimental condition fixed, the sequence of the yield and selectivity in reference to DMNs for each NHC was Q > Qu = iQ > In. Furthermore, we compared LPM method with methanol extraction method in view of the separation efficiency (yield, selectivity) of NHC.

• Toxicological Research
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• v.30 no.2
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• pp.131-138
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• 2014

Radix Astragali, the root of Astragalus (A.) membranaceus, has been applied in a variety of diseases for a long time in Asian countries such as Korea and China. In addition, the aerial parts such as leaves and stems of A. membranaceus have received a great deal of attention. Recently, the polysaccharide fraction showing a potent immunomoduating activity was isolated from the aerial parts of A. membranaceus. Thus, the aerial parts of A. membranaceus would be worthy enough for a food material and a dietary supplement. However, they should be safe even though valuable. In our previous study, it was estimated that NOAEL for female rats are 5000 mg/kg/day of the crude polysaccharide fraction from A. membranaceus-aboveground parts. As a series of safety evaluation, genotoxicity test for the crude polysaccharide fraction was carried out in this study. In conclusion, the three genotoxicity assays provided strong overall support that the crude polysaccharide fraction lacks mutagenic and/or clastogenic potential under the GLP-based test conditions. This indicates the aerial parts of A. membranaceus would be safe enough for a food material and a dietary supplement.

• Korean Journal of Pharmacognosy
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• v.48 no.2
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• pp.141-147
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• 2017

As an ongoing study about Allium hookeri (Liliaceae), this study was performed to evaluate the anti-oxidative effect of the leaves of this plant. Ethanol extract of A. hookeri leaves was successively partitioned as methylene chloride, ethyl acetate, n-butanol and $H_2O$ soluble fractions. The ethyl acetate soluble fraction showed the most potent DPPH radical scavenging and superoxide quenching activities among those fractions. To prove antioxidant activity of ethyl acetate fraction of A. hookeri leaves, we checked the activities of superoxide dismutase (SOD) and catalase, and intracellular ROS level and oxidative stress tolerance in Caenorhabditis elegans. In addition, to verify if increased stress tolerance of C. elegans by treating of ethyl acetate fraction was due to regulation of stress-response gene, we checked SOD-3 expression using transgenic strain. As a consequence, the ethyl acetate fraction increased SOD and catalase activity of C. elegans, and reduced intracellular ROS accumulation in a dose-dependent manner. Besides, the ethyl acetate fraction-treated CF1553 worms showed higher SOD-3::GFP intensity.