• Journal of Microbiology and Biotechnology
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• 제13권5호
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• pp.809-814
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• 2003

${\beta}-amyloid$ ($A{\beta}$) peptides from the proteolytic processing of ${\beta}-amyloid$ precursor protein (${\beta}-APP$) aggregates in the brain to form senile plaques, and their aggregation plays a key role in pathogenesis of Alzheimer's disease (AD). To isolate an active compound that has an $A{\beta}$ aggregation-inhibitory activity, 2,000 microbial metabolite libraries were screened based on their ability to inhibit $A{\beta}$ aggregation by using both Congo red and thioflavin T assays. As a result, a water-soluble fraction of a soil microorganism, KK565, showed a potent $A{\beta}$ aggregation-inhibitory activity. The strain was identified as Streptomyces species, based on the cultural and morphological characteristics, the presence of diaminopimelic acid in the cell wall, and the sugar patterns for the whole-cell extract. In addition, the purification of active principle resulted in identifying a heat-unstable protein responsible for the $A{\beta}$ aggregation-inhibitory activity.

• 한국농공학회논문집
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• 제51권4호
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• pp.43-47
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• 2009

Soil aggregation is an important part of influencing the soil behaviors in reducing rainfall-runoff and soil erosion, aeration, infiltration, and root penetration. Some inorganic materials such as clay minerals, Fe and Al oxides/hydroxides, and calcium carbonate can act as cementing agents within macroaggregates. The objective of this study was to determine the effects of different cementing agents (Fe, Mn, and Al) on soil aggregate formation in reclaimed tidelands. Water stable aggregate ratio and MWD (mean weight diameter) were higher in iron dioxides treatment than two other treatments. This result indicates significant correlation between soil aggregate formation and iron dioxides.

• 한국토양비료학회지
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• 제40권1호
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• pp.57-63
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• 2007

토양의 입단은 토양의 물리적 구조를 형성함에 있어서 매우 중요한 특성이며 토양의 양분 및 수분의 이동 및 토양관리방법 등과 매우 밀접한 연관이 있다. 그러나 토양의 입단과 토양특성에 대한 상호관계에 관한 연구가 매우 미흡하다. 본 연구에서는 토양의 내수성 입단과 토양 물리화학적 특성관계를 구명하고자 토양의 토양물리 화학성과 함께 내수성 입단을 측정하여 상관관계를 분석한 결과, 토양의 내수성 토양입단형성에 미치는 토양물리성 입자 중 미사($r=0.82^{***}$)와 점토($r=0.75^{***}$) 함량은 유의성이 있는 정의 상관을 보였으며, 모래($r=-0.82^{***}$)는 유의성 있는 부의 상관을 나타내었다. 토양화학적 특성은 Ca > Mg > CEC > OM > K > Al 순으로 내수성 토양입단 함량과 통계적으로 유의한 상관성을 나타내었다. Middleton의 분산율 (0.05mm 이하)과 내수성 토양입단함량과는 통계적으로 유의한 상관 ($r=-0.76^{***}$)을 나타내었다. 내수성 입단 함량 추정을 위한 Middleton의 분산율의 유의한 회귀모형이 산출되었다 (Y=-0.79X+96.49; $r^2=0.58^{**}$). 결론적으로, Middleton의 분산율을 이용하여 토양의 내수성 토양 입단함량을 간편하고 빠르게 측정할 수 있었다.

• 한국토양비료학회지
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• 제38권5호
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• pp.231-237
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• 2005

본 연구는 간척지 토양인 계화도의 세사양토 와 김제 진봉의 미사질양토에 대하여 이수석고, 팽화왕겨, zeolite 등의 토양개량제가 입단형성에 미치는 영향을 조사하였다. 이수석고 처리 후 세사양토의 입단화율은 60일째의 경우 대조군 보다 Kbfg1과 Kbfg2에서 2 mm 이상의 입자비율이 증가하였고, 90일째는 Kbfg2의 입자크기 증가율이 높았으며, 120일째는 Kbfg1, Kbfg2, Kbfg3에서 0.1 mm 이하의 입자비율이 감소하였고, 다른 크기의 입자비율이 증가되었는데 특히 Kbfg2와 Kbfg3가 양호하였다. 또한 미사질양토의 업단화율은 60일째 대조군보다 Mbfg2에서 2.0-1.0 mm, 1.0-0.5 mm의 입자비율이 증가되었고, 90일째 Mbfg1과 Mbfg2에서 0.5-0.25 mm 이상부터 뚜렷한 증가를 나타내었으며, 120일째 모든 시험구가 입단화를 촉진하였고, 특히 Mbfg2에서 0.5-0.25 mm의 입자비율이 뚜렷하게 증가되었다. 팽화왕겨 처리 후 세사양토의 입단화율은 60일째 Kbfh1에서만 2.0-1.0 mm의 입자비율이 증가하였고, 90일째 Kbfh1에서 2.0 mm 이상 및 2.0-1.0 mm가 증가하였으며, 120일째는 Kbfh1가 양호하였다. 또한 미사질양토의 경우 입단화율은 60일째 Mbfh2에서 2.0 mm 이상과 2.0-1.0 mm가 증가하였고, 90일째는 Mbfh1과 Mbfh2가 양호하였으며, 120일째는 Mbfh3가 양호하였다. 팽화왕겨와 제오라이트 처리 후 세사양토의 입단화율은 60일째 Kbfhz1, Kbfhz2, Kbfhz3에서 2 mm 이상의 입자비율이 증가하였고, 90일째는 Kbfhz1에서 1.0-0.5 mm 이상의 입자비율이 증가하였으며, 120일째는 모든 시험구에서 0.1 mm 이하의 입자비율이 감소한 대신 다른 입자비율이 증가하였고, 특히 Kbfhz3에서 2 mm 이상 및 1.0-0.5 mm의 입자비율이 증가하였다. 또한 미사질양토의 입단화율은 60일째 Mbfhz1, Mbfhz2, Mbfhz3에서 2 mm 이상의 입자비율이 증가하였고, 90일째는 Mbfhz1, Mbfhz2, Mbfhz3에서 0.25 mm 이상의 입자비율이 증가한 가운데 특히, Mbfhz1이 양호하였다. 120일째는 모든 시험구에서 0.1 mm 이하의 입자비율이 감소한 대신 다른 입자의 비율이 증가하였고, 특히 Mbfhz2가 우수하였다.

• 한국환경농학회지
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• 제26권4호
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• pp.279-285
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• 2007

Soil physical properties in organic farming apple orchard were evaluated in relation to conventional farming to better understand the effects of organic farming system on soil quality. Two adjacent apple orchards, matched by soil type, were chosen to ensure the same pedological conditions except management system. Soil samples were collected from middle of two adjacent trees along the tree line at two depths of 5-20 and 20-35 cm in September 2006. Contents of organic matter in organic farming soil were twice as much as those found in soil of conventional farming. The higher level of organic matter in organic farming soil was reflected through a consequent trend in improved soil physical properties. Organic farming produced greater aggregation in >2 mm size and increased aggregate stability. Bulk density was lower by 13% and hence porosity was higher in soils of organic farming as compared with conventional farming. Water holding capacity was significantly greater with organic farming by >17% over conventional farming. The capacity of organic farming to improve soil physical properties can be contributed to the regular application of relatively large amount of organic materials and the sustainable ground-cover managements, mulching with compost and cover crop cultivation.

• 한국응용곤충학회지
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• 제34권2호
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• pp.120-126
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• 1995

잣나부 인공조임지의 식생과 임상 토질에 서식하는 날개응애류의 군집지수를 분석한 결과를 요약하면 다음과 같다. 종다양도의 Shannon-Wiener index와 균등도지수는 조임년수가 경과할수톡 낮아지는 경향이었으며 1월에 최고치를, 9月에 최저치를 나타냈다. 종풍부경지수는 6월에 최고치를 5月에 최저치를 나타냈다. 우점도지수는 조림연수가 경과할수록 증가하는 경향이고, 4월과 5월에 최고치를, 1월에 최저치를 나타냈다. 집중도지수는 평균 1.9로서 집중분포를 나타냈으며, 조림연수가 경과할수록 증가하는 경향이고, 4월과 8월에 최고치를 1월에 최저치를 나타냈다. 군집지수간의 상관관계에 있어서는 고도의 유의성이 인정되었으며 풍부도지수와 Shannon-Wiener, 균등도지수는 I정의 상관관계가 우점도, 집중도지수와 Shannon-Wiener, 균등도, 풍부도지수는 부의상관 관계가 인정되었다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1992년도 가을학술발표회 논문집
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• pp.55-60
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• 1992

Hydraulically filled ground is formed by the settling of soil grains from the mixture of soil grains and water. It was generally known that the settling speed of the soil grains in governed by Stokes low. In the case of clayed dredged material, the shape of soil grains is not round, the surface of the soil grains is relatively large compared to the weight of soil grains and inter-grain ionic force is relatively large compared to the wight of soil grains. By this reason the settling and consolidation behavior of hydraulically filled quite different from that of Stokes law. This study investigated the settling and consolidation behavior of hydraulically filled materials of Yeochon industrial complex by large scale laboratory settling & consolidation container. The test results showed tat actual settling speed of soil grains in quite large compared to that of Stokes law. It was turned out that this phenomenon was due to the aggregation of soil grains. Also, it was truned out that the void ration and water content after the completion of settling process was 8.7 and 322% respectively. The consolidtion settlement of clayey hydraulic fill material was predicated better by "incremental small strain" consolidation concept than classical Terzaghj's consolidation concept (infinitesimal strain).

• Geomechanics and Engineering
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• 제28권3호
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• pp.239-253
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• 2022

Suitable techniques to stabilize organic soil and improve its engineering behaviour are in demand. Despite various alternatives, nano-additives proved to be an effective stabilizer owing to their strength enhancing properties. The study focuses on using nano-silica as a potential stabilizer to improve organic silt. Soil was treated with four dosages of nano-silica namely 0.2%, 0.4%, 0.6% and 0.8% of dry weight of the soil. Nano-silica treated soil showed a strength increase of nearly 25% at a dosage of 0.4% after curing for two hours. Strength of the treated soil improved with age. Strength improved by nearly 62.9% after 28 days of curing and 221.4% after 180 days of curing due to formation of Calcium - Silicate - Hydrate (CSH) gel in the soil matrix. Dosage of 0.6% nano-silica is observed to be the optimum dosage. Coefficient of permeability and compression index showed an increase by 13.32 and 5.5 times respectively owing to aggregation of particles and creation of void spaces as visualized from the scanning electron micrographs. Further model foundation study and numerical parametric studies using PLAXIS 2D indicate that optimized and economic results can be obtained by varying the additive dosage with depth.

• 한국토양비료학회지
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• 제47권2호
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• pp.107-112
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• 2014

Glomalin has been suggested as an enhancer for soil stability by promoting the aggregation. In this study, we examined the concentrations of glomalin and microbial characteristics in 25 controlled horticultural soils sampled from Gyeongnam Province. Total glomalin had a significant positive correlation with soil organic matter (p < 0.01), soil microbial biomass carbon (p < 0.05), and dehydrogenase activity (p < 0.05) in controlled horticultural soils. In addition, the total glomalin had a significant positive correlation with concentrations of total fatty acid methyl esters, Gram-negative and Gram-positive bacteria, fungi, and arbuscular mycorrhizal fungi in controlled horticultural soils (p < 0.001). In conclusion, the concentration of total glomalin could be an indicator of microbial biomass richness for sustainable agriculture in controlled horticultural soils.

• 한국농공학회지
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• 제34권4호
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• pp.69-79
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• 1992

To estimate soil behavior and structural characteristics under the conditions of cyclic loading, freezing & thawing and initial state, several testing was performed and obtained following results. 1.After repeated freezing and thawing processes, original soil structure was destroyed and changed to globular structure from honeycomb or tube in its structure types. Also above processes resulted increasing the soil compression strain while decreasing the failure stress in stress-strain relationship and reached the soil structure into the mode of brittle fracture. Under cyclic loading conditions, soil cluster which was originally dispersed structure colloided with each other, seperated, and finally the soil failed due to the effect of overcompaction. 2.Through the stabilization processes seperated by four steps, the structure of soil skeleton was changed to quite different globular type. The degree of compressibility of soil was decreased in the normally consolidated zone, while the strength against external load increased due to soil particle stabilization. 3.Soil stress-strain chracteristics were largely influenced by repeated up and down processes of temperature. The maximum deformation was obtained in the case of temperature between 0 10˚C by the reseon of particle cluster reformation. 4.Soil compressibility was largely influenced by the optimum moisture content. Under freezing process, swelling could be found and its magnitude was proportional to the density of soil. 5.Density of soil was decreased as increasing the number or repeated freezing and thawing processes and the largest decreasing rate was found at the first turning point from freezing to thawing cycle.