• 대한수학교육학회지:수학교육학연구
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• 제22권3호
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• pp.311-329
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• 2012

본 연구는 초등학교 3학년 학생들을 대상으로 연속량과 이산량 맥락에서 전체-부분으로서의 분수에 대한 이해를 분석하였다. 동형인 문제에 대해 맥락별로 성취도의 차이를 살펴보았는데 예상과 달리 연속량의 성취도가 이산량의 성취도보다 약간 낮았다. 각 맥락별로 드러나는 전형적인 오류를 분석하고 이에 대한 원인을 살펴본 결과 학생들이 맥락별로 적용하는 전략에 차이가 있었고, 그에 따라 겪는 어려움의 원인이 달랐다. 이와 같은 연구 결과를 바탕으로 본 논문은 각 맥락에 적합한 교과서 구성 및 교수 학습에 대한 시사점을 제공하고자 한다.

• 한국토양비료학회지
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• 제45권1호
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• pp.30-36
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• 2012

The active fraction of soil organic matter, which includes organic debris and light organic fraction, plays a major role in nutrient cycling. In addition, particulate organic matter is a valuable index of labile soil organic matter and can reflect differences in various soil behaviors. Since soil organic matter bound to soil mineral particles has its density lower than soil minerals, we partitioned soil organic matter into debris ($<1.5g\;cm^{-3}$), light fraction ($1.5-2.0g\;cm^{-3}$), and heavy fraction ($>2.0g\;cm^{-3}$), based on high density $ZnCl_{2-}$ sucrose solutions. Generally, partitioned organic bands were clearly separated, demonstrating that the $ZnCl_{2-}$ sucrose solutions are useful for such a density gradient centrifugation. The available gradient ranges from 1.2 to $2.0g\;cm^{-3}$. Although there was not a statistically meaningful difference in organic debris and organomineral fractions among the examined soils, there was a general trend that a higher content of organic debris resulted in a higher proportion of light organomineral fraction. In addition, high clay content was associated with increased fraction of light organomineals. Partitioning of soil organic carbon revealed that carbon content is reduced in the heavy fraction than in the light fraction, reflecting that the light fraction contains more fresh and abundant carbon than the passive resistant fraction. It was also found that carbon contents in the overall organic matter, debris, light fraction, and heavy fractions may differ considerably in response to different farming practices.

• 대한수학교육학회지:학교수학
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• 제14권1호
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• pp.29-43
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• 2012

이 논문은 균등분배상황이 문장제나 수식 형태의 나눗셈으로 주어졌을 때, 아이들이 그 문제 상황을 도형으로 표현하고 그 도형을 분할하는 전략이 그 분할 결과를 다양한 형태의 분수로 수량화시키는 작업과 연관해 구성하는 개념적 스키머에 대하여 조사하였다. 그리고 이 때 분자와 분모 간, 제수와 피제수 간의 인수와 배수 관계들이 그 과정에 어떤 영향을 미치는지를 연구하였다. 아이들의 분할 전략은 다음 순서로 발달했다: 반복적인 이등분 수준${\rightarrow}$ 전체 양 모두 사용하기 수준${\rightarrow}$ 자연수 물건 남기기 수준${\rightarrow}$ 단수 물건 해석/복수 물건 해석 수준${\rightarrow}$ 직접 사상(mapping) 수준. 또한, 아이들이 단수 물건 해석을 복수 물건 해석과 연관시킬 수 있을 때, 그들은 마침내 나눗셈을 분수로, 분수를 나눗셈으로 개념화할 수 있었다.

• Archives of Pharmacal Research
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• 제21권3호
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• pp.260-265
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• 1998

Angiogenic activity of Aloe vera gel was investigated by in vitro assay. We obtained the most active fraction from dichloromethane extract of Aloe vera gel by partitioning between hexane and 90% aqueous methanol. The most active fraction (F3) increased the proliferation of calf pulmonary artery endothelial (CPAE) cells. In addition, F3 fraction induced CPAE cells to invade type I collagen gel and form capillary-like tube through in vitro angiogenesis assay, and increased the invasion of CPAE cells into matrigel through in vitro invasion assay. Furthermore, the effect on the MRNA expression of proteolytic enzymes which are key participants in the regulation of extracellular matrix degradation was investigated by northern blot analysis. F3 fraction enhanced mRNA expression of urokinase-type plasminogen activator (u-PA), matrix metalloproteinase-2 (MMP-2), and membrane-type MMP (MT-MMP) in CPAE cells whereas the expression of plasminogen activator inhibitory (PAl-1) mRNA was not changed.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2002년도 총회 및 춘계학술발표회
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• pp.330-333
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• 2002

Immobilization isotherms for methyl tort-buty1 ether (MTBE) in sodium dodecy1 sulfate(SDS) and cetylpyridinium chloride (CPC) were investigated for application to micellar enhanced remediation. Headspace solid-phase microextraction was used to analyze immobilization isotherms. Maximum partitioning coefficients of MTBE were 48 L/mol and 9 L/mol for SDS and CPC, respectively, The values decreased gradually as the MTBE mole fraction in the micelles increased.

• 한국응용약물학회:학술대회논문집
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• 한국응용약물학회 1998년도 Proceedings of UNESCO-internetwork Cooperative Regional Seminar and Workshop on Bioassay Guided Isolation of Bioactive Substances from Natural Products and Microbial Products
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• pp.166-166
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• 1998

Gliricidia sepium is a medicinal plant that has been established to have antidermatophytic activity. This research was able to isolate an antidermatophytic agent from the leaves of the plant. Leaves of Gliricidia sepium, locally known as kakaoati, were collected from the College of Science area of the University of the Philippines, Diliman, Quezon City. These were air dried, grounded and immersed in methanol. Different fractions were obtained by partitioning with hexane, chloroform, and ethyl acetate. These fractions were bioassayed to determine the fractions with the most antifungal activity using Trichophyton mentagrophytes as test organism. Inhibitory zone in millimeters was obtained and it was found out that the most active fraction was the hexane fraction with an inhibition zone of 25 mm as compared to chloroform with 16 mm and ethyl acetate with 18 mm.

• 대한수학교육학회지:학교수학
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• 제18권4호
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• pp.793-818
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• 2016

본 연구의 목적은 2009 개정 교육과정에 의한 초등학교 수학 교과서로 이분모분수의 덧셈을 학습한 학생들이 이분모분수의 덧셈에서 전체 단위의 고정성, 통분의 필요성, 재귀적 분할 및 이분모분수 덧셈의 알고리즘에 대해 어떻게 이해하고 있는지를 구체적으로 살펴보는 것이다. 이를 위해, 15명의 5학년 학생들을 대상으로 교수 실험을 진행하였다. 연구 결과 대부분의 학생들은 이분모분수 덧셈의 핵심 아이디어에 절차적으로 접근하는 경향을 보였다. 그러나 일부 학생들은 이분모분수의 덧셈 상황에 양적으로 접근하고 단위의 구조에 초점을 맞추면서 이분모분수의 의미 및 알고리즘을 개념적으로 이해할 수 있었다. 이에 대한 논의를 바탕으로 이분모분수의 덧셈 지도 방안에 구체적인 시사점을 제공하고자 한다.

• Asian Pacific Journal of Cancer Prevention
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• 제15권2호
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• pp.617-622
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• 2014

Voacanga globosa (Blanco), a plant endemic to the Philippines, is traditionally used especially by indigenous people of Bataan in the treatment of ulcers, wounds and tumorous growths. This study aimed to provide scientific evidence to therapeutic properties by determining cytotoxic and pro-apoptotic activity of HPLC fractions from leaves on HCT116 human colon carcinoma and A549 human lung carcinoma cell lines. Ethanolic extraction was performed on V globosa leaves followed by hexane and ethyl acetate partitioning. Silica gel column chromatography and high performance liquid chromatography (HPLC) produced MP1, MP2 and MP3 fractions. Cytotoxic activity of the fractions was determined through MTT assay against the cancer cell lines HCT116 and A549 and the non-cancer AA8 Chinese hamster ovarian cell line. Pro-apoptotic activities of the most active fractions were further assessed through DAPI staining, TUNEL assay and JC-1 mitochondrial membrane potential assay with HCT116 cells. While the MPI fraction exerted no significant activity against all cell lines tested, MP2 and MP3 fractions demonstrated high toxicity against HCT116 and A549 cells. The MP3 fraction induced formation of apoptotic bodies, condensed DNA and other morphological changes consistent with apoptosis of HCT116 cells and TUNEL assay showed significant increase in DNA fragmentation over time. In these cells, the MP3 fraction also induced mitochondrial membrane destabilization, which is generally associated with the beginning of apoptosis. Phytochemical analysis demonstrated the presence only of saponins and terpenoids in the MP3 fraction. The results indicate that the MP3 fraction exerts cytotoxic activity on HCT116 cells via induction of apoptosis triggered by loss of mitochondrial membrane potential crucial for cell survival.

• 대한수학교육학회지:수학교육학연구
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• 제24권2호
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• pp.165-180
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• 2014

본 연구는 제7차부터 2009 개정 교육과정에 제시된 몫으로서의 분수 관련 내용을 바탕으로 수학과 교과용 도서를 분석하였다. 분석 결과, 몫으로서의 분수와 관련하여 현재 수학과 교과용 도서에 몇 가지 재고의 여지가 있는 부분이 드러났다. 첫째, 제7차 수학과 교육과정에 비해 2007 수학과 교육과정에서 몫으로서의 분수를 다루는 비중이 크게 줄었다. 둘째, 3, 4학년에서 배우는 자연수의 나눗셈 상황과 5학년에서 배우는 몫으로서의 분수 상황이 자연스럽게 연결되어 있지 않고 분리되어 있다. 셋째, 교과서에 제시된 문장제, 모델 및 분할전략, 형식화과정들이 어느 한 부분에 집중되어 있거나 지나치게 약화되어 있다. 이에 대한 논의를 바탕으로 초등학교 수학교과서의 몫으로서의 분수 관련 내용 구성 및 지도 방향에 시사점을 제공하고자 한다.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2003년도 추계학술발표회
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• pp.409-412
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• 2003

Total extraction of stream sediments in the Kwangyang mine area shows their significant pollution with most trace metals such as Cr, Co, Fe, Pb, Cu, Ni, Zn and Cd, due to sulfide oxidation in waste dumps. Calculations of enrichment factor shows that Chonam-ri creek sediments are more severely contaminated than Sagok-ri sediments. Using the weak acid (0.1N HCl) extraction and sequential extraction techniques, the transport and sediment-water partitioning of heavy metals in mine drainage were examined for contaminated sediments in the Chonam-ri and Sagok-ri creeks of the Kwangyang Au-Ag mine area. Calculated distribution coefficient (Kd) generally decreases in the order of Pb $\geq$Al > Cu > Mn > Zn > Co > Ni $\geq$ Cd. Sequential extraction of Chonam-ri creek sediments shows that among non-residual fractions the Fe-Mn oxide fraction is most abundant for most of the metals. This indicates that precipitation of Fe hydroxides plays an important role in regulating heavy metal concentrations in water, as shown by field observations.