• 대한수학교육학회지:수학교육학연구
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• 제17권2호
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• pp.147-162
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• 2007

본 논문은 교수를 위한 중학교 수학교사들의 수학적 지식을 조사한 저자의 학위논문의 일부분으로써, 19명의 한국 및 중국 중학교 수학교사들의 분수 나눗셈(division by fractions)에 대한 개념적 실생활 모델을 조사, 분석하였다. 분수 나눗셈에 대한 이론적 배경을 제공함과 동시에, 실제 현장 교사들이 가지고 있는 분수 나눗셈에 대한 개념적 이해를 조사, 분석함으로써 분수 나눗셈을 효과적으로 가르치기 위한 교사 지식의 구체적 예들을 제공하고 있다. 본 연구에서는, 연구에 참가한 교사들 대부분이 분수 나눗셈을 "역수 곱하기(invert and multiply)"와 같은 전통적 알고리즘에 기초하여 이해하고 있었으며, 분수 나눗셈의 의미를 실생활 모델로 나타내는 교수과제를 성공적으로 수행한 교사는 단 두 명에 뿐이었다. 이러한 현상은 그 교사들 대부분이 가지고 있는 범자연수 나눗셈 모델이 분할 모델 (partitive model)로 제한되어 있기 때문이었다. 하지만, 또 다른 흥미로운 연구 결과는, 교사가 분할모델 만을 가지고 있더라도, 그 모델의 개념적 구조(conceptual structure)를 깊이 이해하고 있을 때는, 그 기본적 개념 구조를 변형하여 분수 나눗셈의 실생활 모델을 응용해 내는 사고의 융통성을 보였다. 본 논문에서는 이러한 교사들의 성공적 사례뿐만 아니라, 주어진 교수 과제를 수행하는데 실패한 교사들의 인터뷰결과들도 분석, 해석하여 제공하였다.

• Food Science and Biotechnology
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• 제16권2호
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• pp.285-289
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• 2007

A 3% suspension of heat-stabilized defatted rice bran was treated with papain, followed by inactivating the enzyme by heat, and centrifuged. The supernatant was subjected to ultrafiltration, and fractions with various molecular sizes, F1 (>30 kDa), F2 (10-30 kDa), F3 (5-10 kDa), F4 (3-5 kDa), and F5 (3 kDa<), were freeze-dried, and evaluated for antimutagenicity by Ames test using Salmonella typhimurium TA 100 against phenazine methosulfate. The F3 fraction containing highest antimutagenicity from ultrafiltration was separated into 6 fractions by DEAE-Sephadex A-25 ion-exchange column chromatography (F3-1-F3-6). Each fractions having protein contents were pooled, dialyzed, freeze dried, and evaluated for antimutagenicity. Among the six fractions, the F3-1, F3-2, and F3-6 fractions showed antimutagenicity, which were 80.2, 53.4, and 58.6% at concentration of $100\;{\mu}g/plate$, respectively. These F3-1, F3-2, and F3-6 fractions were subjected to Sephadex G-50 gel filtration column chromatography for further purification. Among the purified fractions, the F3-1-1, F3-2-2, and F3-6-1 fractions showed antimutagenicity of 84.5, 58.6, and 69.8% at concentration of $100\;{\mu}g/plate$, respectively. It is thought that these peptides can find application for nutraceutical and pharmaceutical products.

• 대한수학교육학회지:학교수학
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• 제11권4호
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• pp.685-706
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• 2009

이 연구는 분수의 곱셈 나눗셈에 관련한 교수-학습을 의미 있게 도울 수 있는 맥락화가 왜 필요하며, 어떻게 가능한지, 또한 효과적인 맥락화의 활용 방안은 무엇인지를 탐구하는 것을 목적으로 한다. 이를 위해 자연수에 대하여 분수의 곱셈 나눗셈 상황의 차이는 무엇인지를 살펴보고, 그 차이에 따라 분수의 곱셈에서는 승수인 연산자의 역할을 이해할 수 이는 맥락을 설정하여, 단위의 변화에 대한 인식을 하도록 하였다. 분수의 나눗셈에서 포함제는 그 몫이 이산량인 경우이면 남은 양이 생길 수 있고, 연속량인 경우에는 분수로 그 몫을 표현해야 하는 맥락으로 구분지었다. 그리고 등분제의 맥락은 자연수의 등분제의 맥락과 연결시켜 새롭게 제시하여, 자연수의 나눗셈에서 분수의 나눗셈으로 형식화되는 3단계의 효과적인 학습 방법을 제안하였다. 이로써 교사와 학생들의 분수의 곱셈과 나눗셈의 교수-학습 과정에 있어서 유의미한 알고리즘의 습득에 도움을 줄 수 있을 것으로 기대한다.

• 약학회지
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• 제52권2호
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• pp.117-124
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• 2008

The leaves of Perilla frutescens Britt. var. japonica Hara (Labiatae) are often used in gourmet food in several Asian countries. Two kinds of perilla cultivars, Namcheon (NC) and Bora (BR), have been respectively developed in Korea by the pure line of 'deulkkae' from the local variety and by the cross of 'deulkkae' and 'chajogi'. The present study evaluated and compared antioxidant and neuroprotective effects of the fractions prepared from the leaves of the two cultivars using cell-free bioassay systems and primary cultured rat cortical cells. We found that the spirit, chloroform, hexane and butanol fractions from NC and BR leaves inhibited lipid peroxidation initiated in rat brain homogenates by $Fe^{2+}$ and L-ascorbic acid. In contrast, only the spirit and butanol fractions from both cultivars exhibited 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity. Among the fractions tested, the butanol fractions from NC and BR leaves exhibited the most potent antioxidant properties, and the butanol fraction from BR was more potent than the NC fraction. In consistence with these findings, the butanol fractions from both cultivars protected primary cultured cortical cells from the oxidative damage induced by $H_2O_2$ or xanthine and xanthine oxidase, with the BR butanol fraction being more active. The butanol fractions from NC and BR did not produce cytotoxicity in our cultures treated for 24 h at the concentrations of up to $100\;{\mu}g/ml$. Taken together, these results indicate that the leaves of the two cultivars of Perilla frutescens exert antioxidant and neuroprotective effects, and that the butanol fraction from BR leaves exhibits the most potent antioxidative neuroprotection among the fractions tested in this study.

• 대한예방한의학회지
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• 제5권1호
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• pp.144-150
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• 2001

The cytotoxic activity of Cratalariae sessiliflorae on cultured NIH 3T3 fibroblasts and human oral epithelioid carcinoma cells (KB) were evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazoliumbromide (MTT) colorimetric method These fractions of methanol extract of Cratalariae sessiliflorae showed inhibitory effect in vitro in the milligram range against KB cell lines. In general, the antitumor activities of these fractions were does-dependent over the milligram range. The comparison of IC50 values of these fractions in tumor cell lines showed that their susceptibility to these fractions decrease in the following order: Fr. 4> Fr. 6> Fr. 10> Fr. 2> Fr. 11> Fr. 3> Fr. 8> Fr. 7> Fr. 9> Fr. 1> Fr. 5 by the MTT assay. These fractions were tested for their cytotoxic effects on NIH 3T3 fibroblasts using MTT assay. They exhibited potent cytotoxic activities in vitro in the milligram range against NIH 3T3 fibroblasts. In general, the cytotoxic activities of these fractions were does-dependent over the milligram range. The comparison of CD50 values of these fractions in NIH 313 fibroblasts shows that their susceptibility to these fractions in decrease the following order: Fr. 10> Fr. 9> Fr. 2 = Fr. 4> Fr. 8> Fr. 11> Fr. 1 = Fr. 7> Fr. 3> Fr. 5 = Fr. 6 by the MTT assay. These results suggests that fraction 5 has the most growth - inhibitory activity against KB cell lines.

• Fisheries and Aquatic Sciences
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• 제25권4호
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• pp.189-201
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• 2022

Jellyfish is an emerging aquaculture species, farmed for Oriental cuisines and nutraceutical ingredients. This study aimed to examine antioxidative and antimicrobial potentials of various fractions of the jellyfish, Acromitus hardenbergi. The bell and oral arms of the jellyfish were sequentially extracted with petroleum ether (PE), dichloromethane (DCM), chloroform (CHCl₃), methanol (MeOH), and water (H₂O) to extract its bioactive in an increasing polarity gradient. Test fractions were assayed for antiradical activities using electron spin resonance spectrometry, β-carotene-linoleate model and Folin-Ciocalteu assay; and antimicrobial activity against 2 Gram-negative bacteria, 4 Gram-positive bacteria and 2 fungal species using the disc diffusion assay. All fractions were also subjected to Fourier Transform Infrared (FTIR) analysis to identify types of functional groups present. It was found that the hydrophilic extracts (H₂O fractions) possessed the most effective radical scavenging activity (p < 0.05) while the lipophilic extracts (PE fractions) the most active antimicrobial activity, especially against Gram-positive bacteria (p < 0.05). Total oxidation substrates content was found to be highest in the PE fractions of jellyfish bell and oral arms (p < 0.05). FTIR data showed that the H₂O and MeOH fractions contains similar functional groups including -OH, -C=O, -N-H and -S=O groups, while the PE, DCM, and CHCl₃ fractions, the -CH₃, -COOH groups. This study showed that A. hardenbergi contains antioxidants and antimicrobials, thereby supporting the traditional claim of the jellyfish as an anti-aging and health-promoting functional food. Bioassay-guided fractionation approach serves as a critical milestone for the strategic screening, purification, and elucidation of therapeutically significant actives from jellyfish.

• 대한수학회지
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• 제34권4호
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• pp.949-957
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• 1997

The purpose of this paper is to establish connection between certain complex of modules of generalized fractions and the concept of cosequence in commutative algebra. The main theorem of the paper leads to characterization, in terms of modules of generalized fractions, of regular (co) sequences.

• Kyungpook Mathematical Journal
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• 제51권4호
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• pp.419-427
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• 2011

In this paper, making use of transformation due to S. N. Singh [21], an at-tempt has been made to establish certain results involving basic bilateral hypergeometric series and continued fractions.

• 한국수학교육학회지시리즈D:수학교육연구
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• 제17권1호
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• pp.15-27
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• 2013

Division of fractions is always a difficult topic for primary school students. Most of the presentations in teaching the topic in textbooks are procedural, asking students to invert the second fraction and multiply it with the first one, that is, $$\frac{a}{b}{\div}\frac{c}{d}=\frac{a}{b}{\times}\frac{d}{c}$$. Such procedural approach in teaching diminishes both the understanding of structure in mathematics and the interest in learning the subject. This paper discussed the formulation of teaching the division of fractions, which based on research lessons in some primary five classrooms. The formulated lessons started with an analogy to division of integers and working with division of fractions with equal denominators and then extended to division of fractions in general. It is found that the using of analogy helps students to invent their procedure in working the division problem. Some procedures found by students are discussed, with the focus on the development of their invention and mathematical thinking.

• 한국식품영양과학회지
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• 제30권3호
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• pp.547-551
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• 2001

The comparative activities of acetone, ethanol, and aqueous fractions extracted from fruit powder of Cudrania tricuspidata by different temperature were tested by in vitro experimental models; peroxidation of linoleic acid and autooxidation of rat hepatic and renal microsomes by using thiobarbituric acid (TBA) for assay of free malondialdehyde production, and scavenging activities of free radicals by DPPH (α, α'-diphenyl-β-picrylhydrazyl). In DPPH method, acetone fraction extracted at 30℃ showed the highest free radical scavenging activities and acetone fractions extracted at 30℃ and 60℃ and ethanol fraction extracted at 30℃ showed stronger than BHT (butylated hydroxitoluene) although used ten-fold lower concentrations. In thiocyanate method used linoleic acid an inhibitory effects of all fractions showed higher than control treatment. TBA method used linoleic acid showed the highest antioxidative activity in acetone fraction extracted at 30℃ and 60℃. an inhibition activity against lipid peroxidation in hepatic microsomes of rats showed the highest at acetone faction extracted at acetone fraction among extracted fractions was shown to be the most potent antioxidative properties and this action was more potent in fractions extracted at 30℃ than those extracted at 60℃.