984 resultados para 774
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Distribution of dimethylsulfide (DMS) and/or particulate dimethylsulfoniopropionate (DMSPp) concentrations in the Jiaozhou Bay, Zhifu Bay and East China Sea were investigated during the period of 1994 - 1998. Both DMS and DMSPp levels showed remarkable temporal and spatial variations. High values occurred in the coastal or shelf waters and low values in the offshore waters. The highest levels were observed in spring or summer and lowest in autumn. DMS or DMSPp distribution patterns were associated with water mass on a large geographical scale, while biological and chemical factors were more likely influential on smaller-scale variations. Diatoms could play an important role in total DMS or DMSPp abundance in coastal waters. Nitrate was found to have a two-phase relationship with DMSPp concentrations: positive when nitrate concentration was lower than 1 mumol/L, and negative when it was above. Anthropogenic factors such as sewage input and aquaculture also showed influences on DMS or DMSPp concentration.
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为了给青海高原春小麦改良提供资料,分析了于海育成和国内外引进的125个春小麦品种(系)的HMW-GS等位基因变异,并测定了其中58个品种(系)在青海高原环境下的面团流变学特性。结果表明:(1)参试春小麦品种(系)的HMW-GS存在广泛的变异,Glu-A1位点出现3个等位基因,Glu-B1位点出现5个等位基因,Glu-D1位点出现4个等位基因;共出现了22种HMW-GS组合形式,其中1,7+8,2+12和N,7+8,2+12组合类型出现频率最高,并发现了个别罕见的变异类型,如2+10,10。(2)亚基组合类型对沉淀值、形成时间、稳定时间、评价值等品质性状影响较大,对籽粒蛋白质含量、出粉率和面粉吸水率的影响不显著。试验还表明,HMW-GS组成与面粉的筋力有密切关系。
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Metagentiana striata is an alpine annual herbaceous plant endemic to the east of the Qinghai-Tibet (Q-T) Plateau and adjacent areas. The phylogeography of M. striata was studied by sequencing the chloroplast DNA (cpDNA) trnS-trnG intergenic spacer. Ten haplotypes were identified from an investigation of 232 individuals of M. striata from 14 populations covering the entire geographical range of this species. The level of differentiation amongst populations was very high (G(ST) = 0.746; N-ST = 0.774) and a significant phylogeographical structure was observed (P < 0.05). An analysis of molecular variance found a high variation amongst populations (76%), with F-ST = 0.762 (highly significant, P < 0.001), indicating that little gene flow occurred amongst the different regions; this was explained by the isolation of populations by high mountains along the Q-T Plateau and adjacent areas (N-m = 0.156). Only one ancestral haplotype (A) was common and widespread throughout the distributional range of M. striata. The populations of the Hengduan Mountains region of the south-eastern Q-T Plateau showed high diversity and uniqueness of haplotypes. It is suggested that this region was the potential refugium of M. striata during the Quaternary glaciation, and that interglacial and postglacial range expansion occurred from this refugium. This scenario was in good agreement with the results of nested clade analysis, which inferred that the current spatial distribution of cpDNA haplotypes and populations resulted from range expansion, together with past allopatric fragmentation events. (c) 2008 The Linnean Society of London.
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针对激光焊接机器人对焊缝跟踪的实时性要求高的特点,设计了基于视觉的激光焊接机器人跟踪曲线焊缝系统,并建立了相应的焊缝跟踪视觉模型.通过机器人示教确定曲线焊缝的轨迹,然后机器人沿着轨迹行走,当发现焊缝偏差时,通过视觉伺服控制进行焊缝偏差补偿.保证了焊缝跟踪的实时性,提高了跟踪精度。
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以0.01mol·L^-1 CaCl2和0.005mol·L^-1 1DTPA作为提取剂,用简化的3步连续提取法对贵州省赫章县土法炼锌污染土壤中Zn、Cd的形态进行了分析.结果显示,污染土壤中Zn、Cd主要以残渣态的形式存在,CaCl2提取态和DTPA提取态Zn、CA平均仅占全量的0.63%、3.91%和lO.94%、10.13%.土壤中不同形态Zn、Cd含量与玉米中Zn、CA含量的相关分析结果显示,CaCl2提取态金属与玉米中金属含量投有显著的相关关系,而DTPA提取态、残渣态以及总量Zn、Cd与玉米根、茎叶中Zn、Cd含量显著正相关.这些结果表明CaCl2提取态Zn、Cd对土壤中该元素的植物有效态可能不具重要贡献,而DTPA提取态金属和金属总量在一定程度上能作为评价土壤中元素植物有效性的标准.
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以往研究表明锡成矿与S型花岗岩具有密切的成因联系。近年来随着大量与A型花岗岩有关的锡矿床的发现,有关锡成矿与A型花岗岩关系的研究成为地学界关注的热点。 芙蓉超大型锡多金属矿床位于我国著名的南岭钨锡多金属成矿带上,锡矿体位于骑田岭A型花岗岩体的内部或者岩体与围岩的内外接触带。成岩成矿年代学研究表明,成岩与成矿为前后相继的地质事件,具有密切的时空关系。本论文以与芙蓉超大型锡多金属矿床有密切时空关系的骑田岭A型花岗岩为研究对象,在详细野外地质调查的基础上,运用岩石学、矿物学、矿物化学、同位素地球化学、流体地球化学等学科的理论和方法,对骑田岭花岗岩的岩石学特征、岩石成因、成岩物理化学条件、岩浆分异的流体特征、挥发性组分特征以及成岩与成矿的关系等方面进行详细的分析,探讨骑田岭花岗岩成岩过程中流体聚集的机制及其对锡成矿的制约,初步揭示A型花岗岩与锡成矿之间的本质联系。本论文主要取得以下成果和认识: (1)通过对与锡矿有关的骑田岭花岗岩体的主量、微量、稀土元素、同位素和花岗岩中黑云母的微量、稀土元素分析研究发现:骑田岭角闪石黑云母花岗岩和黑云母花岗岩为高度分异演化的花岗岩,具有高硅、富铝、富碱、高钾的特征。随着岩体分异演化程度的增加,花岗岩总体向富硅、富碱的方向演化。岩体轻重稀土分异明显,表现为右倾型模式,Eu负异常明显,表现为中等-强烈的负Eu异常。岩体明显富集Rb、Th等大离子亲石元素及Zr、Hf等高场强元素,而亏损Ba、Nb、Sr、P、Ti。骑田岭花岗岩两个阶段岩石有着相似的Sr、Nd同位素特征,揭示其具有相同的物质来源,是同源岩浆演化的产物,为具壳幔混合特征的A2型花岗岩。 (2)对骑田岭花岗岩体矿物学和矿物化学特征、全岩Sn含量分析研究发现:角闪石黑云母花岗岩的结晶温度为774~796℃,氧逸度(logfO2)为-15.30~-15.0。黑云母花岗岩的结晶温度为714~784℃,氧逸度(logfO2)为-17.5~-20.0。随着岩浆的演化,从角闪石黑云母花岗岩到黑云母花岗岩随着结晶温度的降低,氧逸度也随之减小。随着岩浆的演化,岩体中Cl含量不断的减少,而F含量有所增加,Cl趋向分配进入流体相。随着岩浆分异演化程度的增加,岩体成岩温度降低,氧逸度减小,岩体中Sn含量不断的减少,Sn趋向分配进入富Cl流体,表明岩浆演化过程中分异出富Cl、富Sn的流体。 (3)骑田岭花岗岩石英斑晶中的包裹体研究表明:骑田岭角闪石黑云母花岗岩和黑云母花岗岩在岩浆演化过程中经历了两个阶段,即岩浆阶段和岩浆-热液阶段,分别以出现熔融包裹体、流体-熔融包裹体为特征,其中流体-熔融包裹体的出现是岩浆分异流体的直接证据。结合矿物的结构、构造特征,研究发现骑田岭花岗岩浆演化过程分异出流体。骑田岭花岗岩原生流体包裹体地球化学研究表明,岩浆分异出的流体为H2O-CO2-NaCl-KCl-CaCl2不混溶体系,具有盐度高(32.98~52.04Wt%NaCleq.),密度低(0.27~0.95g/cm3),均一温度较高(190~ 494℃)的特征,压力为600~800bar,成岩过程中发生了沸腾现象。 (4)对芙蓉超大型锡矿床和骑田岭花岗岩研究表明,锡矿与花岗岩有着密切的时间、空间和成因联系。矿体产在花岗岩体内部或者岩体与围岩的接触带,成岩与成矿时限一致,随着岩浆分异演化程度的增加,岩体成岩温度降低,氧逸度降低,岩体中的挥发性组分Cl含量减小,而F含量增加,Cl趋向分配进入流体相,这种流体萃取熔体中的成矿元素Sn,并以氯络合物形式迁移。可以认为,随着岩浆的演化,骑田岭花岗岩岩浆结晶期后分异出的热液流体具有富Cl和Sn的特征。芙蓉超大型锡多金属矿床的成矿流体应主要来源于黑云母花岗岩岩浆结晶期后分异出的岩浆热液。
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Los cambios producidos en los procesos de enseñanza– aprendizaje requieren de los docentes formación competencial que motive a los alumnos para que sean capaces de desarrollarse como personas y realizar aprendizajes significativos a lo largo de toda su vida. En línea con este objetivo es necesaria una formación específica del profesorado que promueva el desarrollo de las competencias de tipo emocional. En el contexto educativo, una de las claves del éxito (la consecución de un proceso de enseñanza–aprendizaje efectivo y de calidad) se encuentra en el modo en el cual se establecen las dinámicas interpersonales. Un buen docente es aquel que no sólo “sabe”, sino que “es”. La presencia del docente en el aula, su cercanía al alumno, su capacidad para gestionar sus emociones, para comunicarse de modo eficaz y empatizar con él, son todos ellos aspectos que inciden sin lugar a dudas en el clima de trabajo, en el grado de motivación del alumno, en los resultados de aprendizaje, y claro está, en su desarrollo personal. Cuando hablamos de aspectos comunicativos, aquellos de tipo no verbal cobran una gran importancia. Los docentes apenas reciben formación de tipo experiencial sobre aspectos relacionados con la presencia del cuerpo y su expresión. El conocimiento enactivo a través de un programa de concienciación corporal y comunicación no –verbal posibilita el desarrollo de competencias intra e interpersonales. Se presentan en este trabajo los resultados preliminares de un programa de formación realizado en este ámbito con profesores universitarios de distintas áreas de conocimiento.
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Davison, G. and Gleeson, M. (2005). Influence of Acute Vitamin C and/or Carbohydrate Ingestion on Hormonal, Cytokine, and Immune Responses to Prolonged Exercise. International Journal of Sport Nutrition and Exercise Metabolism. 15(5), pp.465-479 RAE2008
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http://www.archive.org/details/humanprogressthr00bartuoft
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Four non-destructive tests for determining the length of fatigue cracks within the solder joints of a 2512 surface mount resistor are investigated. The sensitivity of the tests is obtained using finite element analysis with some experimental validation. Three of the tests are mechanically based and one is thermally based. The mechanical tests all operate by applying different loads to the PCB and monitoring the strain response at the top of the resistor. The thermal test operates by applying a heat source underneath the PCB, and monitoring the temperature response at the top of the resistor. From the modelling work done, two of these tests have shown to be sensitive to cracks. Some experimental results are presented but further work is required to fully validate the simulation results.
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Gas-solids two phase systems are widely employed within process plant in the form of pneumatic conveyors, dust extraction systems and solid fuel injection systems. The measurement of solids phase velocity therefore has wide potential application in flow monitoring and, in conjunction with density measurement instrumentation, solids mass flow rate measurement. Historically, a number of authors have detailed possible measurement techniques, and some have published limited test results. It is, however, apparent that none of these technologies have found wide application in industry. Solids phase velocity measurements were undertaken using real time cross correlation of signals from two electrostatic sensors spaced axially along a pipeline conveying pulverised coal (PF). Details of the measurement equipment, the pilot scale test rig and the test results are presented.