• 제목/요약/키워드: free play

검색결과 701건 처리시간 0.036초

황환원 세균의 quorum-sensing 유사 현상

  • 박지은;장덕진
    • 한국생물공학회:학술대회논문집
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    • 한국생물공학회 2001년도 추계학술발표대회
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    • pp.545-548
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    • 2001
  • Microbiologically influenced corrosion (MIC) of metal is common in the natural environment and sulfate reducing bacteria are representative microorganisms for MIC. We found that biofilm fomlation by SRB on the metal surface might be controlled by quorum sensing, which is a cell density dependent regulation of cell metabolism. As cell free culture fluids (spent media) of Desulfovibrio vulgaris and D. desulfuricans were tested for quontrn sensing related test strains, it was found that spent media of two SRB induced increased luminescence of Vibrio harveyi BB886 (sensor 1+, sensor 2-) and BB170 (sensor 1-, sensor 2+). Quorum activities of D. vulgaris and D. desulfuricans appeared to be parallel to growth patterns, i.e., it was low in the lag phase, highly increased in the exponential phase, and reached maximum in the stationary phase. Interestingly, however, luminescence of V. harveyi BB886 and BB170 induced by a unit cell mass of the SHB showed a maximal peak in the late lag phase. Hence, it was suspected that quorum sensing of these two SHB play unknown roles in shifting cells from dormant to growth stages.

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Effects of low temperature and salicylic acid on chilling tolerance in cucumber seedlings

  • Jung, Sang-Duck;Jung, You-Jin;Kim, Tae-Yun;Hong, Jung-Hee
    • 한국환경과학회:학술대회논문집
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    • 한국환경과학회 2002년도 봄 학술발표대회 발표논문집
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    • pp.468-471
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    • 2002
  • The present study was undertaken to Investigate the effects of low temperature and salicylic acid (SA) on chilling tolerance In acclimated and nonacclimated cucumber seedlings. Acclimation significantly affected survival and shoot dry weights. Injuries of acclimated seedlings at the third leaf stage were on the average smaller by half than those of the nonacclimated ones. Chilling caused a large increase in free proline levels, regardless of acclimation status. Exogenous treatment with SA resulted in improvement in growth and survival of acclimated, chilled seedlings, indicating SA and acclimation have common effects. Cycloheximide treatment In the presence of SA restored acclimation-induced chilling tolerance. An elevated proline level was observed in cold-treated and SA- treated plants and the level was more pronounced in the light than in the dark at chilled temperature, indicating that endogenous proline may play a role in chilling tolerance.

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유아의 애착 및 어머니-유아 상호작용과 또래 상호작용간의 관계 (The Relation of Attachment and Mother-Child Interactions to Peer Interactions)

  • 이영;나유미
    • 아동학회지
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    • 제20권3호
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    • pp.19-32
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    • 1999
  • This study analyzed the relation of children's attachment security and mother-child interaction to children's peer interactions. The subjects were 51 preschoolers, 44 to 57 months of age and their mothers. Attachment was assessed using the Attachment Q-set (Waters, 1987), mother-child interactions at home were observed with the use of the Teaching Strategies Rating Scales (Erickson, Sroufe, Egeland, 1985), and peer interactions were observed during free play time, using the Holloway and Erickson(1988) categories. Pearson correlation and multiple regression showed that attachment security scores were negatively related to dependency toward peers. Mother's "structure and limit setting" and "respect for child's autonomy" were positively related to "helping with peers" and negatively to "asking for help" and "physical attack". The variables accounting for dependency toward peers were mother's hostility and attachment security.

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자유놀이 상황에 나타난 어머니의 대화 양식과 유아의 의사소통 의도 (Maternal Conversation Style and Communicative Intent of Young Children during Free Play)

  • 성미영
    • 아동학회지
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    • 제24권5호
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    • pp.77-89
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    • 2003
  • The relationship of communicative intent of infants and the conversation style of mothers were investigated with 20 mothers and their 2- and 3-year old children. They conversed in naturalistic settings while playing with Lego blocks. Cluster analyses revealed 2 maternal styles: a conversation-eliciting and a directive style. Children of conversation-eliciting mothers provided more information than those of directive mothers. Children of directive mother requested more permission than those of conversation-eliciting mothers. Implications of these two maternal styles for children's communicative abilities were discussed.

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보육시설에서의 영아-교사 상호작용과 영아의 발달수준, 교사의 민감성 및 초기 가정환경 간의 관련성에 관한 연구 (Infant-Child Care Teacher Interaction : Infant Development, Teachers' Sensitivity and Early Home Environment)

  • 최은정;하지영;서소정
    • 아동학회지
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    • 제30권2호
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    • pp.71-95
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    • 2009
  • This study investigated relationships among infant development, teacher's sensitivity, home literacy environment, and infant-teacher interaction in the child care setting. Verbal and behavioral interactions between 30 2-year-old infant-teacher pairs were video-recorded during free play activities; teachers' sensitivity was observed by trained observers; infant development was assessed by teachers; data on the early home literacy environment were gathered through maternal self-reported questionnaires. Data were analyzed by descriptive statistics, t-tests, and correlation analyses. Results indicated that boys showed more naming; girls showed more physical contact with teachers. Infants high in overall developmental level showed more behavioral interaction with teachers. Teacher's sensitivity correlated positively with behavioral imitating and negatively with questioning and nodding. Verbal interaction in the home correlated positively with nodding.

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The protective effects of trace elements against side effects induced by ionizing radiation

  • Hosseinimehr, Seyed Jalal
    • Radiation Oncology Journal
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    • 제33권2호
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    • pp.66-74
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    • 2015
  • Trace elements play crucial role in the maintenance of genome stability in the cells. Many endogenous defense enzymes are containing trace elements such as superoxide dismutase and metalloproteins. These enzymes are contributing in the detoxification of reactive oxidative species (ROS) induced by ionizing radiation in the cells. Zinc, copper, manganese, and selenium are main trace elements that have protective roles against radiation-induced DNA damages. Trace elements in the free salt forms have protective effect against cell toxicity induced by oxidative stress, metal-complex are more active in the attenuation of ROS particularly through superoxide dismutase mimetic activity. Manganese-complexes in protection of normal cell against radiation without any protective effect on cancer cells are more interesting compounds in this topic. The aim of this paper to review the role of trace elements in protection cells against genotoxicity and side effects induced by ionizing radiation.

What Can Caenorhabditis elegans Tell Us About Nematiocides and Parasites\ulcorner

  • Dent, Joseph A.
    • Biotechnology and Bioprocess Engineering:BBE
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    • 제6권4호
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    • pp.252-263
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    • 2001
  • Nematode infections compromise human health and reduce agricultural productivtiy. Experiments that exploit the powerful molecular genetics of the free-living nematode Caenorhabdl - elegans have contributed to our understanding of how the major classes of anthelmintic nema-tocides kill worms and how worms might evolve resistance to these drugs In C. elegans, as in parasites, benzimidixoles interfere with microtubule polyumerization the imidazothiazoles/tetra-hydropyrimidines activate nicotinic acetylcholine receptors, and the macrocyclic la ctones activate qlutamate-gate chloride chanels. Mutant alleles of genes that encode drug targes often confer resistance in C. elegans. Preliminary evidence suggests that alleles of homologous genes in parasites will, in many cases, also play a role in resistance. Thus information acquired from C. elegans can be usefully applied to understand the mechanisms of drug sensitivity and the genetics of resis-tance in parasites.

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콘크리트 균열진행의 유한요소 정규화 (Finite Element Regularization of Progressive Cracks in Concrete)

  • 송하원;변근주;이주영;서철;심별
    • 한국콘크리트학회:학술대회논문집
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    • 한국콘크리트학회 1994년도 가을 학술발표회 논문집
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    • pp.279-284
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    • 1994
  • Fracture mechanics does work for concrete, provided that one used a proper, nonlinear form of fracture mechanics in which a finite nonlinear zone at fracture front is being considered. The fracture process zone is a region ahead of a traction-free crack, in which two major mechanisms, microcracking and bridging, play important rules. The toughness due to bridging is dominant compared to the toughness induced by the microcracking, so that the bridging is the dominant mechanism governing the fracture process of concrete. In this paper the bridging zone, which is a part of extended macrocrck with stresses transmitted by aggregates in concrete, is modelled by a Dugdale-Barenblatt type model with lenear tension-softening curve for the analyses of crack growth in concrete Finite element technique is shown for inplementation of the model.

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비정질 칼코게나이드 재료를 이용한 PMC소자 제작 (The PMC fabrication using the amorphous chalcogenide materials)

  • 정홍배;허정화;손정우;박인애;조동환;김성진;남기현
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 2009년도 제40회 하계학술대회
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    • pp.1262_1263
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    • 2009
  • Programmable Metallization Cell (PMC) is a memory device based on the electrolytical characteristic of chalcogenide materials. In this study, we investigate the nature of thin films formed by photo doping of Ag ions into chalcogenide materials for use in solid electrolyte of programmable metallization cell devices. We were able to do more economical approach by using copper which play an electrolyte ions role. The results imply that a Ag-rich phase separates owing to the reaction of Ag with free atoms from chalcogenide materials.

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4절 링크구조를 응용한 플랙셔 힌지 기반 모듈형 나노포지셔너 (Modularized Flexure-Hinge Nanopositioner Based on Four-Bar-Link-Mechanism)

  • 채기운;배진현;정영훈
    • 한국정밀공학회지
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    • 제28권7호
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    • pp.851-858
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    • 2011
  • Nanopositioning technologies play an important role in the progress of electronics, optics, bio-engineering and various nano-scale technologies. As a result, various practical nanopositioning methods have been successfully introduced. Flexure mechanism is a valuable method in nanopositioning because of smooth and friction-free motion and the infinitesimal movement near to sub-nm. In this study a modularized nanopositioner based on parallelogram four-bar linkage structure with right-circular flexure hinge was developed. The positioning performance of a single axis nanopositioner and a XY nanopositioner which was extended from single axis one were demonstrated using control experiments. Consequently, it was shown that the developed single axis nanopositioner possessed high performance and could be extended to various multi-axis nanopositioners.