• 상하수도학회지
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• 제18권2호
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• pp.121-127
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• 2004

It is necessary to supply external carbon source for enhancement of biological nitrogen removal from domestic wastewater with low influent C/N ratio. Sulfide was chosen as a cost effective electron donor and reaction stoichiometry for autotrophic denitrification was investigated by conducting bench-scale experiments in this study. Higher sulfur to nitrogen (S/N) ratio than the calculated value from theoretical reaction stoichiometry was required when the anoxic reactor was operated at open condition because dissolved oxygen introduced by surface aeration reacted with sulfide with ease. In addition, higher sulfate production and lower yield of microorganism could be observed under the same condition. It was possible to obtain reliable reaction stoichiometry for autotrophic denitrification by establishing pure anoxic condition. Linear relationship between bacterial growth and consumption of nitrate, sulfide, alkalinity, and sulfate production enabled to derive a relatively correct reaction stoichiometry for autotrophic denitrification when sulfide was used as an electron donor.

• 대한기계학회논문집B
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• 제36권6호
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• pp.625-632
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• 2012

본 논문은 고분자 전해질 연료전지 공기극 유로 내부에서 당량비에 따라 발생하는 플러딩 현상을 가시화를 통해 확인하고, 전류 변화에 따른 물의 운송 특성에 관한 연구를 수행하였다. 공기극 당량비는 1.5, 2.0, 연료극 당량비는 1.5로 고정하여 실험을 수행하였다. 연료전지 공기측 당량비 2.0로 공급하였을 때 1.5와 비교하여 짧은 시간에 물이 생성되기 시작하였으며, 플러딩 영역이 빠르게 생성되는 결과가 나타났다. 또한, 공기극 당량비 1.5로 유지하는 경우 플러딩 영역 이후에 건조화 7.8A 이후 구간에서 건조화가 진행되며, 8A 이후구간에서 건조화가 시작되는 공기극 당량비 2.0에서 작동하는 연료전지와 비교하여 넓은 영역에서 물 생성이 활발하게 이루어져 MEA의 내구성과 수소이온전도도가 우수한 결과를 확인하였다.

• 한국물환경학회지
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• 제30권6호
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• pp.665-672
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• 2014

Elemental cellular stoichiometry of natural phytoplankton communities was examined in six large dam reservoirs in the Han River system. Carbon (C) and nitrogen (N) contents of the phytoplankton-dominated seston from Lake Soyang was higher than that from other lakes. Phosphorus (P) content showed slight variations among six lakes in the range of $0.04{\sim}0.18{\mu}mol$ P mg $DW^{-1}$. The phosphorus concentrations of lake water showed obvious positive relationship with P and C contents of the phytoplankton-dominated seston. In all six lakes, N:P ratios and C:P ratios in the phytoplankton-dominated seston were more than 23 and 133 respectively, indicating the phytoplankton communities in six lakes have been exposed in phosphorus limited condition. The relative abundance of diatoms showed significant negative correlation with C, N, P contents of the phytoplankton-dominated seston and that of cyanobacteria showed significant positive correlation. Elemental stoichiometry of diatoms-dominated seston showed distinctive less content than that of cyanobacteria-dominated seston. The cellular N:P ratios of diatoms- and cyanobacteria-dominated seston indicate that both main classes of phytoplankton in six lakes are in phosphorus deficiency. Elemental stoichiometry of the phytoplankton-dominated seston in this study could be used for the further ecological stoichiometric studies in six lakes.

• 한국과학교육학회지
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• 제25권1호
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• pp.1-15
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• 2005

This study examined two students' problem solving approaches: the similarities and the differences in their problem solving approaches, and the general problem solving strategies (heuristics) the students employed were discussed. The two students represent differences not only in terms of grades earned, but also in terms of participation, motivation, attention to detail, and approaches to answering questions and problem solving. Three separate problems were selected for this study: A stoichiometry problem; a fruit salad problem; and a limiting reactant problem. Each student was asked individually on three separate occasions to contribute to this study. There are more similarities in the students' problem solving strategies than there are differences. Both students were able to correctly solve the stoichiometry and the fruit salad problems, and were unable to correctly solve the limiting reactant problem. They recognized that an algorithm could be used for both chemistry problems(a stoichiometry problem & a limiting reactant problem). Both students were unable to correctly solve the limiting reactant problem and to demonstrate a clear understanding of the Law of Conservation of Mass. Nor did they show an ability to apply it in solving the problem. However, there was a difference in each one's ability to extend what had been learned/practiced/quizzed in class, to a related but different problem situation.

• The Korean Journal of Ceramics
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• 제4권2호
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• pp.72-77
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• 1998

A defect model for UO$_2$ fuel containing soluble fission products was devised based on the defect structure of pure and doped uranias. Using the equilibrium between fuel solid-solution and fission-products and the material balance within the fuel, a tracing method to get the stoichiometry change of urania fuel with burnup was made. This tracing method was applied to high burnup urania fuel and DUPIC fuel. The oxygen potential of urania fuel turned out to increase slightly with burnup. The stoichiometry change was calculated to be negligible due to the buffering role f Mo. The oxygen potential of DUPIC fuel out to be sensitive to the initial chemical state of Mo in the fuel.

• 한국과학교육학회지
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• 제15권4호
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• pp.437-451
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• 1995

Middle and high school students' conceptual understanding about stoichiometry, gas laws, and diffusion was compared with essay type test and multiple choice test. Whereas achievement of high school students was higher in stoichiometry, that of middle school students who were expected to go to high schools was higher in gas laws and diffusion. When students' achievement was compared to that of American college students, Korean students' achievement was higher in stoichiometry and was similar in gas laws. These results indicate that algorithmic problem solving is more emphasized than conceptual understanding in high schools and that quantitative aspects focused in chemistry education are not helpful in concept understanding. Nevertheless relatively smaller difference between concept understanding and algorithmic problem solving for high school students in this study seems to be from concept learning in middle schools.

• 한국지하수토양환경학회지:지하수토양환경
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• 제8권2호
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• pp.70-77
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• 2003

유해유기물질의 미생물 분해시 일어나는 총괄반응을 이론적으로 예측하는 방법을 기술하였다. 열역학적 이론을 바탕으로 하는 반쪽반응 방법을 사용하,였고, 최근에 도입된 이론들인 중간체 생성 반응, oxygenation반응, 그룹이론에 의한 표준 자유생성에너지 예측기법 등을 적용하였다. 대표적인 유해유기물질인 phenanthrene과 함께 glucose, hexadecane의 미생물 분해 반응식을 실제로 계산하였다. 예측된 총괄반응식을 이용하여 미생물 수율, 산소 요구량, 질소 요구량, 무기화율 등의 정보를 얻을 수 있었으며, 이는 오염된 지하수/토양의 생물복원 공법 설계 및 자연정화평가 등에 유용하게 적용될 수 있을 것으로 기대한다.

• 한국미생물·생명공학회지
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• 제21권1호
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• pp.23-29
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• 1993

토양으로부터 nucleoside oxidase 생산균주를 분리하고 Flavobacterium meningosepticum으로 동정하였다. 생산균주의 cell free extract로부터 본 효소를 정제배율 180배, 수율 18로 전기영동적으로 균일하게 정제하였으며 정제효소의 기질 특이성을 검토한 결과 nucleoside만을 산화시키는 전형적인 nucleoside oxidase이었다. Adenosine을 기질로 한 표준효소반응계에서 stoichiometry를 검토한 결과 본 효소는 lmol adenosine을 중간 생성물인 adenosice 5'-aldeh-yde로 산화 후 1 mol adenosine 5'-carboxylic acid까지 2단계로 산화시키면서 동시에 2 mol H2O2를 생성하는 새로운 type의 nucleoside oxidase로 확인되었다. 본 효소의 높은 기질 특이성과 H2O2를 생성하는 반응성은 nucleoside의 신속 간편한 효소학적정량볍 및 임상진단용 시약의 개발에 응용될 수 있음을 시사하였다.

• 대한화학회지
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• 제68권1호
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• pp.25-31
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• 2024

The p97 adenosine triphosphatase is a key player in protein homeostasis, responsible for unfolding ubiquitylated substrates. It engages with various adaptor proteins through its N-terminal domain, with the p97-p47 complex attracting particular attention for its involvement in membrane remodeling. Although the structures of p97 in complex with the Ubiquitin regulatory X (UBX) domain from various adaptors have been reported, the stoichiometry is conflicting. Here, we report the crystal structure of the p97 N-D1 hexamer in complex with the p47 UBX domain at a resolution of 2.7 Å. The structure reveals a stoichiometry of 6:6 between the p97 N-D1 and the p47 UBX domain. These findings provide valuable insights into the binding stoichiometry of p97 N-D1 and p47 UBX domain, which are crucial for understanding the role of p97 and adaptor proteins in cellular processes such as the ubiquitin-proteasome pathway, membrane fusion, and cell cycle regulation.

• Journal of Forest and Environmental Science
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• 제40권1호
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• pp.9-14
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• 2024

Quantitative evaluation of nutrient status and stoichiometry on the forest floor is a good indicator of litter quality in various vegetation types. This study was conducted to determine the effects of vegetation type on the nutrient concentration and stoichiometry of forest floors at a regional scale. Forest floor samples were collected from four vegetation types of evergreen coniferous forests including Cryptomeria japonica, Chamaecyparis obtusa, evergreen broadleaf, and bamboo spp. forests in southern Korea. The dry weight of the forest floor was higher in the C. japonica and C. obtusa forests than in the evergreen broadleaf and bamboo forests. The mean carbon (C) concentrations of the forest floor were highest in the broadleaf forest, followed by the bamboo forest, C. japonica and C. obtusa forests. Mean nitrogen (N) and phosphorous (P) concentrations in the the coniferous forests were lower than those in the broadleaf and bamboo forests. The mean C:N ratio was the highest in C. obtusa forest (118±25), followed by C. japonica (66±6), evergreen broadleaf (41±1), and bamboo (30±1) forests. However, C:P and N:P ratios were lower in the coniferous forests than in the broadleaf forest indicating that the stoichiometry of the forest floor varies across vegetation types. The C, N, and P stocks on the forest floor were higher in the C. obtusa forest than in the broadleaf or bamboo forests. These results highlight that vegetation type-dependent stoichiometric ratio is an useful indicator for understanding interspecific difference in quality and quantity of the forest floor.