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Visar resultat 1 - 5 av 34 avhandlingar som matchar ovanstående sökkriterier.

  1. 1. Ecological effects of pesticides in freshwater model ecosystems

    Författare :Lina Wendt-Rasch; Biologiska institutionen; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; marine biology; aquatic ecology; limnology; Marinbiologi; Hydrobiology; community; zooplankton; algae; herbicide; insecticide; pesticide mixture; macrophytes; cypermethrin; metsulfuron-methyl; risk assessment; pesticides; microcosms; limnologi; akvatisk ekologi;

    Sammanfattning : In this thesis I have investigated the effects of pesticide exposure on the ecosystem level using various types of experimental ecosystems, i.e. microcosms. The direct effect of exposure to cyperemthrin, a pyretroid insecticide, was a rapid decrease of crustancean zooplankton in enclosures in a lake. LÄS MER

  3. 2. Statistical modeling and design in forestry : The case of single tree models

    Författare :Leakemariam Berhe; Göran Arnoldsson; Göran Broström; Dieter Rasch; Umeå universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Forest data; Covariance structures; Nonlinear mixed effects models; Tree taper models; Ds-optimal design; Replication-free design.; Statistics; Statistik;

    Sammanfattning : Forest quantification methods have evolved from a simple graphical approach to complex regression models with stochastic structural components. Currently, mixed effects models methodology is receiving attention in the forestry literature. LÄS MER

  4. 3. A Facet Model of the Logical Operational Structures of Piaget's Theory : Guttman's Facet Design applied to Piaget's Theory

    Författare :Barbro Bergling; Siv Fischbein; Stockholms universitet; []
    Nyckelord :SAMHÄLLSVETENSKAP; SOCIAL SCIENCES; facet design; Piaget; operational thinking; Rasch; partial credit model; hierarchical model; psykologi; Psychology;

    Sammanfattning : This thesis explored whether the complex structure of Piaget's theory of operational thinking could be synthesized into a facet model by means of facet design. The aims were: (1) to deduce from detailed conceptual analyses of 12 of Piaget's classical experiments the essential parts of the operational structures (Study I); (2) to explore the internal structure of his constructs in terms of a mapping sentence (Study II); (3) to study the hierarchical structure of the interrelationships between the constructs (Study III); and (4) to apply the facet model in the development of test items (Study II and IV). LÄS MER

  5. 4. Muscle mass and function after total hip arthroplasty

    Författare :Anton Rasch; Karolinska Institutet; Karolinska Institutet; []
    Nyckelord :Osteoarthrosis; arthritis; joint disease; hip muscle strength; hip muscle function; outcome; elderly; attenuation; fatty infiltration; gait analysis; balance;

    Sammanfattning : Osteoarthritis (OA) of the hip is a common disease among elderly causing pain, joint stiffness and reduced mobility. Outcome studies have shown total hip arthroplasy (THA) to be a successful surgical procedure. Studies of muscle strength and function after THA are more scarce and results vary. LÄS MER

  7. 5. Microwave Gas and Multipactor Breakdown in Inhomogeneous Fields

    Författare :Joel Rasch; Chalmers tekniska högskola; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; corona; inhomogeneous fields; multipactor; Microwave breakdown;

    Sammanfattning : Microwave gas and multipactor breakdown remains to be one of the limiting factors for the maximum power in microwave devices. Above a certain electric field strength, the so-called breakdown threshold, free electrons can multiply by making ionizing impacts with neutral gas molecules, or causing secondary emission upon impact with system surfaces. LÄS MER