• The Korean Journal of Ecology
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• 제22권1호
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• pp.39-43
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• 1999

중금속에 대한 내성을 나타낸 Serratia marcescens를 이용하여 카드뮴 흡착 기작에 관하여 조사하였다. 먼저 카드뮴에 대하여 민감성을 나타내는 돌연변이 균주인 PM을 개발하였으며 PM균주는 50ppm 이상의 카드뮴 농도에서 성장하지 못하였다. 카드뮴을 50ppm 처리한 균주에서 10회 이상 계대 배양하여 카드뮴에 적응을 유도한 PA균주는 PC, PM균주에 비해 성장 속도가 증가하였으며 세포 내 카드뮴 축적량도 4∼5배 증가하였다. PA균주는 100 ppm 카드뮴 처리군에서 처리량 중 23%를 세포내에 축적하였으며 세포막 부위보다 세포질 부위에 더욱 많은 카드뮴을 축적하였다. 카드뮴 처리시, 전 세포 단백질 양상에서 28 KDa과 64 KDa의 2개의 유도 단백질과 45 KDa의 감소 유도 단백질을 확인하였으며 원자 흡광 분석을 통하여 각각의 유도 단백질에 결합된 카드뮴 양은 단백질 1 g당 318.25 ㎍, 325.37 ㎍이 검출되었다. 세포내에 축적된 카드뮴을 전자현미경을 이용하여 카드뮴 결합 물질을 확인한 결과, 세포질의 단백질 분획에서 28 KDa크기의 유도 단백질이 카드뮴과 흡착한 것으로 나타났다. 카드뮴 흡착에 대한 DNA조사 결과 20 Kb 크기의 plasmid가 존재하였으며, curing agent로 plasmid를 제거한 결과 카드뮴 내성을 상실하여 본 분리 균주의 카드뮴 내성 유전자는 plasmid상에 위치하는 것으로 확인하였다.

• 한국지진공학회논문집
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• 제7권5호
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• pp.47-56
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• 2003

본 논문에서는 기존 IWAN 모델을 수정하여 사질토 지반의 반복경화 현상을 나타낼 수 있는 지반의 반복경화모델을 개발하였다. 일반적으로 동적하중을 받는 지반재료는 하중 반복회수에 따라 동적 거동특성이 변화하게 되며 이는 반복 경화 및 연화현상으로 나타난다. 본 논문에서는 등방 경화 또는 등방 연화 거동을 하는 스프링슬라이더 요소를 기존 병렬 IWAN 모델에 추가함으로써 지반의 동적 변형특성 표현이 가능하였다. 등방 경화 거동을 보이는 요소들의 항복 응력은 각각 반복 경화함수에 의하여 증가하도록 정의되었으며, 반복 경화함수는 대칭 한계를 가지는 동적 비틂전단 시험결과로부터 정의되었다. 이렇게 정의된 반복 경화함수는 지반의 동적 변형 특성을 묘사하기 위하여 하나의 독립 변수를 가지게 되며, 사용된 독립변수는 지반의 동적 한계 변형률의 특성을 포함하는 누적전단변형률로 사용되었다. 누적 전단변형률은 반복 전단한계 변형률 이상의 변형률의 누적으로 정의되며, 역재하 및 재재하 곡선에서는 Masing의 법칙을 적용하여 계산될 수 있다. 본 논문에서는 모델의 개발과정을 서술하였고, 모델에 대한 검증은 동반논문인 검증편에 설명하였다.

• Journal of Microbiology and Biotechnology
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• 제18권8호
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• pp.1408-1415
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• 2008

To produce polyhydroxyalkanoate (PHA) from inexpensive substrates by bacteria, vegetable-oil-degrading bacteria were isolated from a rice field using enrichment cultivation. The isolated Pseudomonas sp. strain DR2 showed clear orange or red spots of accumulated PHA granules when grown on phosphate and nitrogen limited medium containing vegetable oil as the sole carbon source and stained with Nile blue A. Up to 37.34% (w/w) of intracellular PHA was produced from corn oil, which consisted of three major 3-hydroxyalkanoates; octanoic (C8:0, 37.75% of the total 3-hydroxyalkanoate content of PHA), decanoic (C10:0, 36.74%), and dodecanoic (C12:0, 11.36%). Pseudomonas sp. strain DR2 accumulated up to 23.52% (w/w) of $PHA_{MCL}$ from waste vegetable oil. The proportion of 3-hydroxyalkanoate of the waste vegetable-oil-derived PHA [hexanoic (5.86%), octanoic (45.67%), decanoic (34.88%), tetradecanoic (8.35%), and hexadecanoic (5.24%)] showed a composition ratio different from that of the corn-oil-derived PHA. Strain DR2 used three major fatty acids in the same ratio, and linoleic acid was the major source of PHA production. Interestingly, the production of PHA in Pseudomonas sp. strain DR2 could not occur in either acetate- or butyrate-amended media. Pseudomonas sp. strain DR2 accumulated a greater amount of PHA than other well-studied strains (Chromobacterium violaceum and Ralstonia eutropha H16) when grown on vegetable oil. The data showed that Pseudomonas sp. strain DR2 was capable of producing PHA from waste vegetable oil.

• Geomechanics and Engineering
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• 제34권5호
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• pp.481-489
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• 2023

Drained cyclic triaxial tests were conducted on a saturated sand to examine its deformation characteristics under either axial or lateral cyclic loading condition. To apply lateral cyclic loading, the cell pressure was cycled while maintaining a constant vertical stress. The strain accumulations and flow direction in the soil were presented and discussed considering various initial stress ratios (η₀), cyclic stress amplitudes and cyclic stress paths. The results indicate that axial strain accumulation shows an exponential increase with the maximum stress ratio (η^max). The initial deviatoric stress has comparable effects with lateral cyclic stress amplitude on the accumulated axial strain. In contrast, the accumulated volumetric strain is directly proportional to the lateral cyclic stress amplitude but not much affected by η₀ values. Due to the anisotropy of the soil, the accumulated axial and lateral bulging strains are greater in lateral cyclic loading when compared to axial cyclic loading even though η^max is the same. It is also found that η^max affects soil's lateral deformation and increasing the ratio could change the lateral deformation from contraction to bulging. The flow direction depends on η^max in the sand under lateral cyclic loading, regardless of η₀ values and the cyclic stress amplitudes, and a large η^max could lead to great deviatoric strain but a little volumetric strain accumulation.

• 한국토양비료학회지
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• 제34권3호
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• pp.185-191
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• 2001

호남지역 농경지에 수년간 사용되어 온 타로닐, 만코지, 벤타존 및 부타클로르약제에 대한 내성균의 밀도를 조사하고 이들 내성균주를 분리하여 미생물속의 분포 및 타로닐의 분해정도를 검토한 결과는 다음과 같다. 호남지역 농경지에 분포한 타로닐을 비롯한 4개약제 $500{\mu}g\;ml^{-1}$에 생존하는 내성균의 밀도는 $10^3cfu\;g^{-1}$이 상으로 시설재배지> 밭> 논토양 순으로 높았고, 약제별로는 벤타존> 부타클로르> 타로닐> 만코지 순으로 높았으며, 이들4개 약제 $500{\mu}g\;ml^{-1}$에서 분리된 내성균주의균속 분포율은 Acinetobacter속과 Corynebacterium속이 높게 나타났으나 Moraxella속은 낮게 나타났다. 타로닐 연용 밭토양에 $0{\sim}100{\mu}g\;g^{-1}$까지 처리후 20일간 배양시 사상균수는 초기보다 감소하였으나 호기성3, 방선균 및 타로닐내성균수는 크게 증가하였고, 멸균 토양중에서 다코닐약제 분해균주의 밀도는 $10{\mu}g\;g^{-1}$처리시 접종후 5일경에 가장 높았고, TD-25균주는 TC-23균주보다 높은 밀도로 나타났다. 다코닐 약제처리후 20일째의 약제잔류농도는 고농도처리에서 높았고 약제분해는 TD-25균주> 무멸균토양 함유균주> TC-23균주 순으로 나타났다.

• Journal of Ginseng Research
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• 제21권2호
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• pp.91-97
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• 1997

In order to elucidate the mechanism of red-colored phenomena(RCP) in ginseng(Panax ginseng C.A. Meyer), distribution of inorganic elements of ginseng root and its surrounding soil, and microflora in the soil were investigated. Red brown colored-substances were accumulated in the cell wall of epidermis at early stage of red-colored ginseng (RCG). Cell wall of the late stage of RCG was disordered and microorganisms were shown in the disordered cell wall. Al, Si and Fe contents among inorpanic elements in the epidermis of RCG were higher at two or three times than that of healthy ginseng. On the other hand, K content was higher at three times in healthy ginseng than that of RCG. Especially, Fe content was higher at three times in lateral roots of RCG than that of healthy ginseng. Total 21 strains of microorganisms were isolated on the 523 medium from surface soil, surrounding soil of both healthy and RCG, and RCG. Six strains of microorganisms among them were resistant to 2 mM Fe. Two species in Bacillus app. and Lactobacillus app. , and one species in Micrococcus sp. and Npisseria sp. respectively were identified. It seemed that RCP was closely related with the distribution and uptake of inorganic elements, was also correlated Fe-independent metabolism of microorganisms.

• The Plant Pathology Journal
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• 제24권1호
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• pp.8-16
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• 2008

Aurofusarin is a polyketide pigment produced by some Fusarium species. The PKS12 and GIP1 genes, which encode a putative type I polyketide synthase (PKS) and a fungal laccase, respectively, are known to be required for aurofusarin biosynthesis in Gibberella zeae (anamorph: Fusarium graminearum). The ten additional genes, which are located within a 30 kb region of PKS12 and GIP1 and regulated by a putative transcription factor (GIP2), organize the aurofusarin biosynthetic cluster. To determine if they are essential for aurofusarin production in G. zeae, we have employed targeted gene deletion, complementation, and chemical analyses. GIP7, which encodes O-methyltransferase, is confirmed to be required for the conversion of norrubrofusarin to rubrofusarin, an intermediate of aurofusarin. GIP1-, GIP3-, and GIP8-deleted strains accumulated rubrofusarin, indicating those gene products are essential enzymes for the conversion of rubrofusarin to aurofusarin. Based on the phenotypic changes in the gene deletion strains examined, we propose a possible pathway for aurofusarin biosynthesis in G. zeae. Our results would provide important information for better understanding of naphthoquinone biosynthesis in other fdarnentous fungi as well as the aurofusarin biosynthesis in G. zeae.

• 한국식물병리학회지
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• 제10권4호
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• pp.305-313
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• 1994

Typically susceptible lesions were developed on pepper (cv. Hanbyul) leaves inoculated with the compatible strains Ds 1 of Xanthomonas campestris pv. vesicatoria. The lesions appeared first water-soaked and then turned yellow with a chlorotic area. In contrast, the leaves inoculated with the incompatible strain 81-23 initially turned yellow and then developed local necrosis. Multiplication of x. c. pv. vesicatoria in pepper leaves also were distinctly different between the two strains. The strain Ds 1 multiplied more greatly than did the strain 81-23 in the infected leaves. X. c. pv. vesicatoria infection of pepper leaves induced the synthesis of soluble proteins, especially more greatly in the compatible than in the incompatible interactions. Some pathogenesis-related (PR) proteins were detected in the intercellular washing fluid (IWF) and extracts of the infected pepper leaves. In particular, the 32 kDa protein on SDS-PAGE gels appeared intensely in the incompatible interaction. In contrast, some proteins with moluecular masses of 65, 71, and 75 kDa disappeared in the infected pepper leaves. Isoelectric focusing could identify the pIs of soluble proteins in infected pepper leaves. The accumulation of the IWF from infected leaves was more conspicuous in the incompatible than the compatible interaction. These results suggest that some extremely acidic and basic proteins were induced and accumulated in the intercellular spaces of infected pepper leaves.

• Journal of Welding and Joining
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• 제15권5호
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• pp.64-73
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• 1997

Deformations of structures due to welding appear much complicated and deformated modes are also complex. As parameters governing deformations are various and effect of parameters on deformations is not well known, precise prediction of deformation due to welding has been a difficult problem. Until now, many research papers as to welding deformation have been published, but the research results can explain only one aspect of welding deformation have been published, but the research results can explain only one aspect of welding deformation and are hard to be used in reasonable prediction of welding deformations in complicated structures. In this study, based on the accumulated results concerning to welding deformations, a practical method to predict complicated welding deformations of large structure is proposed. A simplified model to estimate residual plastic strains is suggested and main parameters affecting residual plastic strains are shown to be heat input and joint restaints. Inherent strain theory and experimental data are combined with the finite element method and welding deformations of large structures are calculated by elastic analysis. Comparison of calculated results with experimental data shows the accuracy and validity of the proposed method.

• 한국미생물·생명공학회지
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• 제45권4호
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• pp.343-353
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• 2017

In the present study, the isolation of selenium (Se)-enriched bacteria from rumen fluid and hot spring water was carried out. Rumen fluid samples were taken from cannulated goats fed a basal diet and the water samples were collected from Selayang hot spring, Selangor-Malaysia. A total number of 140 Se-tolerant isolates were obtained aerobically using an Se-enriched medium and spread plate technique. All the isolates were initially screened for the ability to transform the Se-containing medium to a red-orange culture using a spectrophotometer. Twenty isolates of dark red-orange medium were selected for a screening of the highest Se-containing protein accumulating strains using the dialysis technique and icp.ms to measure the Se content. Four isolates, identified as Enterobacter cloacae (ADS1, ADS7, and ADS11), and Klebsiella pneumoniae (ADS2) from rumen fluid origin, as well as, one isolate from hot spring water (Stenotrophomonas maltophilia (ADS18)), were associated with the highest biomass organic Se-containing protein when grown in a medium enriched with $10{\mu}g/ml$ sodium selenite. In addition, around $50{\mu}g/100{\mu}g$ of the absorbed inorganic Se was accumulated as an organic form. Organic Se-containing protein in all the selected strains showed antioxidant properties in the range of 0.306 to 0.353 Trolox equivalent antioxidant capacity (TEAC) mg/ml. Therefore, these strains may offer a potential source of organic Se due to their Se-tolerant nature and higher biomass organic to inorganic Se ratio.