999 resultados para Superficial change


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Five village soundscapes toim./ed. R. M. Schafer. kirjan liitteinä olevista CD-levyistä kaksi liittyy teokseen Acoustic environments in change ja kaksi teokseen Five village soundscapes. Five villages soundscapes. 1st ed. Vancouver : A.R.C. Publications, cop. 1977.

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The metal distribution in the surface sediment fractions of the Cachoeira River was evaluated based on the fractionation method using a five-step sequential extraction. The determination of metals was made by flame atomic absorption spectrophotometry (F AAS). Zn, Pb and Cu exhibit higher concentrations in the residual fraction of the sediment from sites that receive discharges from urban and industrial zones. High levels of Ni (60 ± 1 to 447 ± 9 µg L-1) were found in the river water, which may be detrimental to the "health" of rural communities that utilize the river water for domestic purposes without treatment.

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The sea surface microlayer (SML), although poorly understood, is important in biogeochemical cycling and sea - air exchanges; it is a source or a sink for a range of pollutants. In this paper, an overview of sampling techniques and the role of SML in biogeochemical cycles and climate is presented. The chemical and biological nature of the ocean surface film and its interaction with atmospheric aerosols are discussed. Special attention is given to organic constituents, gel-like compounds, surfactants, halogenated compounds, and metals. Estimates of air - sea exchange fluxes-with focus on organic carbon, polycyclic aromatic hydrocarbons, and polychlorinated biphenyls-are compiled. In addition, research gaps in the chemical composition of marine aerosols and their relationship with SML are described.

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Precise surface area is needed for accurate characterization of self-assembled monolayers (SAMs) on metallic surfaces. The aim of this manuscript was to emphasize that miscalculation of surface area is the major source of errors in SAM electrochemical characterization. Limitations are discussed and recommendations given for beginners in analyses of SAM functionalized electrodes. The electrochemical measurements and examples were based on bare gold electrode immobilized with dodecanethiol. The degree of compression of the monolayer properties of formation and reproducibility of the electrochemical response depends on roughness factor, with values closer to the unit being better.

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This dissertation discusses Holocene palaeoenvironmental and palaeomagnetic secular variation (PSV) records reconstructed from sediments preserved in Lake Lehmilampi (63º37´N, 29º06´E) and Lake Kortejärvi (63º37´N, 28º56´E) in eastern Finland. Several piston and freeze cores were obtained from both lakes for varve and magnetic analyses. Sediment samples were impregnated in low-viscosity epoxy and physical parameters of varves, including varve thickness and relative grey-scale values, were recorded using x-ray densitometry combined with semiautomatic digital image analysis. On average, varve records of Lehmilampi and Kortejärvi cover 5122 and 3902 years, respectively. Past solar activity, as estimated by residual 14C data, compares favourably with varve thicknesses from Lehmilampi during the last 2000 years. This indicates the potential of clastic-organic varves to record sensitively climatic variations. Bulk magnetic parameters, including magnetic susceptibility together with natural, anhysteretic and isothermal remanent magnetizations, were measured to describe mineral magnetic properties and geomagnetic palaeosecular variation recorded in the sediments. Main stages in the development of the investigated lakes are reflected in the variations in the mineral magnetic records, sediment lithology and composition. Similar variations in magnetic parameters and sediment organic matter suggest contribution of bacterial magnetite in the magnetic assemblages of Lehmilampi. Inclination and relative declination records yielded largely consistent results, attesting to the great potential of these sediments to preserve directional palaeosecular variation in high resolution. The PSV data from Lehmilampi and Kortejärvi were stacked into North Karelian PSV stack, which may be used for dating homogenous lake sediments in the same regional context. Reconstructed millennial variations in relative palaeointensity results are approximately in agreement with those seen in the absolute palaeointensity data from Europe. Centennial variations in the relative palaeointensity, however, are influenced by environmental changes. Caution is recommended when using varved lake sediments in reconstructing relative palaeointensity.

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Estudou-se a distribuição de Cr, Ni, Cu, Cd e Pb em frações de substâncias húmicas (SH) de diferentes tamanhos moleculares. As SH foram extraídas de amostras de água (SHA) e de sedimentos de superfície (SHSS), interface/água (SHSI) e fundo (SHSF) coletados no reservatório de captação de água superficial Anhumas, localizado no município de Araraquara-SP. Para a extração das SH utilizaram-se os procedimentos recomendados pela Sociedade Internacional de Substâncias Húmicas. Após purificação por diálise, as SH foram fracionadas com base no tamanho molecular utilizando-se sistema de fracionamento seqüencial por ultrafiltração e fluxo tangencial. O fracionamento das amostras de SHA permitiu caracterizar uma distribuição de massa relativamente uniforme dentre as frações de diferentes tamanhos moleculares, com valores maiores nas frações F2 (20,8%) e F4 (23,8%). Exceto para os íons Pb(II) e Cu(II) os quais apresentaram concentrações relativamente mais altas nas frações F2 e F4, respectivamente, de maneira geral, crômio, níquel, cádmio e chumbo têm distribuições similares nas cinco frações com tamanhos moleculares maiores e médios (F1 a F5). Quanto às distribuições de massa nas diferentes frações de substâncias húmicas extraídas de amostras de sedimento de superfície (SHSS), sedimento interface/água (SHSI) e sedimento de fundo (SHSF), as três amostras apresentaram 42-48% das SH nas frações com maiores tamanhos moleculares (F1 e F2), 29-31% nas frações intermediárias (F3 e F4) e 13-20% nas frações com menores tamanhos moleculares (F5 e F6). De modo geral, caracterizaram-se para os íons metálicos, distribuições similares dentre as respectivas frações F1 a F6. Exceções para Pb(II) e Ni(II) em sedimento de superfície com concentrações relativamente menores nas frações F2 e F4, respectivamente.

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A reação de eletro-oxidação do metanol foi estudada sobre eletrocatalisadores de Pt/C, PtRu/C e PtMo/C preparados pelo método do ácido fórmico em diferentes composições atômicas. Os produtos da oxidação do metanol foram monitorados pela técnica de DEMS. O desempenho dos catalisadores frente a reação de oxidação do metanol foi estudado através dos perfis voltamétricos e experimentos de cronoamperoometria.

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By interpreting research results about textbooks this study tries to answer the question: how should texts be formulated to optimize the learning of the reading pupil? Seven perspectives structure the research: History. The amount of information available in a society influences the learning offered by textbooks. A compressed description indicates that memorizing activities have turned to tendencies for critical reading. Curriculum. The decentralization of curriculum development accentuates the importance of the textbook authors as interpreters of significant information. Because of the authority of textbooks, the way that information is presented can function as an unintended curriculum. Use. In the use of textbooks different functions can be identified. Thus the textbooks have, for instance, an authoritarian, a cohesive and a disciplinary function. Level of difficulty. A text that optimally matches the skills of the readers ina class should both provide facilitating scaffolds for the learning and at the same time challenge especially capable students by not being too obvious. Changing of preconceptions. The only possible starting point for teaching is the knowledge developed earlier by the student. In certain areas misconceptions are usual, which motivates the use of conceptual change texts that enhance the transformation of earlier obtained knowledge. Coherence. Well structured texts can usually be considered beneficial for learning. The same applies to the use of meta-discourse guiding the reader through the text. If the structuring is too obvious, the content may not, at least by capable students, be processed on a deep level. Content. The analysis underlines the need for deep approaches in textbooks. Though this is a relative statement, textbooks from a learning perspective seem to have been too superficial in their presentations. Ten principles were developed as a concluding interpretation of the good textbook. Though these principles capture important tendencies for developing a good textbook, textbook writing has to be considered as an art that cannot be captured in a short formula. The paradoxes identified indicate that the results should be seen as a starting point for further research.

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Konsistens och förändring i finländsk etermediapolitik. Implementering av digital television och en jämförelse med Kanada Avhandlingen handlar om hur det finländska televisionssystemet förändrades i slutet av 1990-talet från en nationell institution till ett dualistiskt system som präglas av stark marknadsorientering. Syftet med avhandlingen är att förstå på vilket sätt en så snabb förändring kunde ske och analysera de institutionella faktorerna bakom utvecklingen. På teoretisk nivå diskuteras tesen om det nära sambandet mellan statliga politiska institutioner och rundradioverksamhetens institutioner. Avhandlingen består av två fallstudier. Den första sätter fokus på de första åren av den finländska televisionens digitaliseringsprocess som startade med starka industriell-nationalistiska motiveringar. Analysen, som baserar på offentliga dokument, sträcker sig framtill hösten 2001 då de digitala televisionssändningarna startade och regeringspropositionen om den nya kommunikationsmarknadslagen lämnades till riksdagen. Dessa policy-processer analyseras som en ”marknadisering” av de traditionella styrningsprinciper och idéer gällande finländsk rundradioverksamheten. En jämförelse mellan Finlands och Kanadas nationella rundradiopolitik gör att man kan koppla slutsatserna till den internationella utvecklingen. Jämförelsen visar hur kommunikationspolitiska linjen i de två länderna har kommit att likna varandra trots att ländernas tv-system och deras styrordningar är mycket olika. Exemplet med Kanada visar att den särskilda teknologin inte är viktig utan snarare de kommersiella intressen som står bakom och som beslutsfattare gärna döljer i en nationalistisk retorik. Studien visar att det är viktigt att beakta vilken tyngd man i politiken ger de två sidor som rundradioverksamheten består av: sändningsteknologin och verksamheten som en speciell kulturform. Nationalstatens handlingsutrymme minskar inom fältet om målet är att vara framgångsrik i konkurrensen i den nya internationella ekonomin. Enligt de nyliberalistiska principer som det politiska systemet överlag har tillägnat sig det är önskvärd men också helt inhemska institutionella traditioner och praxis som följdes i den finländska digitaliseringsprocessen främjade utvecklingen som ledde till att nästan alla ursprungliga nationella syften föll sönder.