• 대한수학회보
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• 제30권1호
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• pp.83-89
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• 1993

Applications of the classical Knaster-Kuratowski-Mazurkiewicz theorem [KKM] and the fixed point theory of multifunctions defined on convex subsets of topological vector spaces have been greatly improved by adopting the concept of convex spaces due to Lassonde[L]. Recently, this concept has been extended to pseudo-convex spaces, contractible spaces, or spaces having certain families of contractible subsets by Horvath[H1-4]. In the present paper we give a far-reaching generalization of the best approximation theorem of Ky Fan[F1, 2] to pseudo-metric spaces and improved versions of the well-known fixed point theorems due to Brouwer [B] and Schauder [S] for spaces having certain families of contractible subsets. Our basic tool is a generalized Fan-Browder type fixed point theorem in our previous works [P3, 4].

• 한국작물학회지
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• 제51권2호
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• pp.179-185
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• 2006

The Ministry of Agriculture and Forestry announced in 2001 that the overall amount of paddy land set aside for rice will be cut down by 12% by 2005, decreasing from 1.08 million to 953,000 hectares. When evaluating the value of paddy rice systems, the multi-function of paddy systems in the monsoon climate is vital importance. The main functions of paddy rice systems are to conserve biodiversity and maintain sustainability. Some crucial environmental benefits of the paddy rice systems include: flood prevention, recharge of water resources, water purification, soil erosion and landslide prevention, soil purification, landscape preservation and air purification. The paddy rice systems in Korea, which are more diverse than upland crop systems, are known to be composed of 14 orders, 36 families and 134 species. The sustain ability of paddy rice production systems can never be overestimated. Rice is part of the culture and even the heart of spiritual life in the area under the monsoon climate. Therefore paddy rice systems should be preserved with the highest priority being the enhancement of the systems' multi-function. As an outlook to future research, the need of joint and interdisciplinary research projects between economists and natural scientists at inland as well as international levels were emphasized in establishing the development of counter-measure logic through actual proofed analysis.

• 대한수학회논문집
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• 제26권1호
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• pp.135-149
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• 2011

Using (r, s)-preopen sets [14] and pre-${\omega}_t$-closures [6], a new kind of covering property $P^t_{({\omega}_r,s)}$-closedness is introduced in a bitopological space and several characterizations via filter bases, nets and grills [30] along with various properties of such concept are investigated. Two new types of cluster sets, namely pre-(${\omega}_r$, s)t-${\theta}_f$-cluster sets and (r, s)t-${\theta}_f$-precluster sets of functions and multifunctions between two bitopological spaces are introduced. Several properties of pre-(${\omega}_r$, s)t-${\theta}_f$-cluster sets are investigated and using the degeneracy of such cluster sets, some new characterizations of some separation axioms in topological spaces or in bitopological spaces are obtained. A sufficient condition for $P^t_{({\omega}_r,s)}$-closedness has also been established in terms of pre-(${\omega}_r$, s)t-${\theta}_f$-cluster sets.

• Biomolecules & Therapeutics
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• 제25권4호
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• pp.441-451
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• 2017

Imperatorin, a major bioactive furanocoumarin with multifunctions, can be used for treating neurodegenerative diseases. In this study, we investigated the characteristics of imperatorin transport in the brain. Experiments of the present study were designed to study imperatorin transport across the blood-brain barrier both in vivo and in vitro. In vivo study was performed in rats using single intravenous injection and in situ carotid artery perfusion technique. Conditionally immortalized rat brain capillary endothelial cells were as an in vitro model of blood-brain barrier to examine the transport mechanism of imperatorin. Brain distribution volume of imperatorin was about 6 fold greater than that of sucrose, suggesting that the transport of imperatorin was through the blood-brain barrier in physiological state. Both in vivo and in vitro imperatorin transport studies demonstrated that imperatorin could be transported in a concentration-dependent manner with high affinity. Imperatorin uptake was dependent on proton gradient in an opposite direction. It was significantly reduced by pretreatment with sodium azide. However, its uptake was not inhibited by replacing extracellular sodium with potassium or N-methylglucamine. The uptake of imperatorin was inhibited by various cationic compounds, but not inhibited by TEA, choline and organic anion substances. Transfection of plasma membrane monoamine transporter, organic cation transporter 2 and organic cation/carnitine transporter 2/1 siRNA failed to alter imperatorin transport in brain capillary endothelial cells. Especially, tramadol, clonidine and pyrilamine inhibited the uptake of [$^3H$]imperatorin competitively. Therefore, imperatorin is actively transported from blood to brain across the blood-brain barrier by passive and carrier-mediated transporter.

• 한국토양환경학회지
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• 제1권1호
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• pp.47-54
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• 1996

중금속으로 오염된 토양질을 평가할 수 있는 토양오염지표(SPI, Soil Pollution Indices)를 고안하였다. 토양오염지표는 토양을 농경지, 주거지, 공원 여가지, 공장 산업지역으로 분류하고, 토양의 이용 용도별 토양오염기준을 이용하여 토양의 다기능성을 고려하였다. 토양의 이용 용도별로 토양중 5종류의 중금속 및 비소의 농도가 생태계에 미치는 영향을 나타내는 수리적 수치를 가산한 토양오염 점수(SPS, Soil Pollution Score)를 산출하였다. 토양의 이용 용도별로 산출된 토양오염점수에 따라 토양을 4등급의 토양오염등급(SPC, Soil Pouution Class)으로 구분하였다. 1등급은 점수 <100, 2등급은 점수 100-200, 3등급은 점수 >200-300, 4등급은 점수 >300으로 설정하였다. 토양오염점수와 토양등급의 실용화 가능성을 타진하기 위하여 1994년 토양측정망의 운영결과로 도출된 5종류의 중금속 및 비소 농도를 이용하여 토양중의 중금속 농도를 토양오염점수, 토양등급으로 환산하였다. 토양 측정망 측정지역의 비소 및 중금속 농도를 토양오염기준과 비교할 때, 대상지역의 토양환경은 대부분이 건전한 상태로 판단되나, 토양측정 망 측정지 점 의 약 3.0∼4.0%는 토양오염이 우려되거나 오염된 지역으로 판단된다. 토양측정망 측정 지역의 평균 토양오염 점수는 66.2로 토양측정망 대부분이 지역이 건전한 상태를 유지하는 것으로 나타났다. 토양오염점수를 4등급으로 분류하였을 때, 전체 측정지역에서 1등급(토양질 건전지역) 87.0%, 2등급(토양질 검증지역 1) 9.4%, 3등급(토양질 검증지역2) 2.4%, 4등급(토양질의 오염우려지역) 1.2%로 산출되었다. 토양오염지표로 고안된 토양오염점수와 토양오염등급은 오염물질에 의한 토양의 오염상태를 종합적으로 판단할 수 있는 방법으로 평가되며, 토양오염지표를 개발한 방법은 5종류의 중금속 및 비소를 포함하여 유 무기 오염물질에 의한 토양오염의 판단에 적용할 수 있을 것으로 사료된다.