83 research outputs found

    Improving ecological realism in the risk assessment of chemicals : development of an integrated model

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    The use of population models for copper (Cu) risk assessment : improving ecological relevance : partim Acipenser transmontanus

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    Unexpected recovery and non-effects predicted with a mixture toxicity implementation in a population model

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    Current regulations in risk assessment are very substance-based and only regard effects observed in lab-standardized tests on individual organisms. However, in the environment organisms are exposed to mixtures of chemicals that vary in concentration and composition. In addition, effects on individuals will have an effect on populations and higher levels of organisation in the ecosystem. Mechanistic, individual-based models have been proposed to tackle this issue as they can integrate effects observed at the individual level to make an extrapolation of effects at the population level. In addition, mechanistic models can be used to describe the effects of mixtures. Mixture toxicity implementations of the GUTS and DEBtox theory are applied here: damage addition and independent action. Integrating these models in an individual-based implementation, a model is obtained that describes effects of mixtures on Daphnia magna populations. Two population experiment were conducted exposing Daphnia magna mixtures of different compounds (Cu, Zn, alfa-HCH, dicofol and pyrene). These compounds have been selected for their suspected toxicological mode of action. The populations were exposed for 2 months to these compounds, their binary mixtures, and a ternary mixture. The population density over time was recorded bi-weekly in all of the treatments. We calibrated an individual-based model for D. magna based on the individual-level effects of the different substances. We validated the implementation at the population level with the data from the population experiment. We evaluated the different mixture toxicity implementations (i.e. damage addition vs independent action). For Cu, the model was able to predict (unexpectedly) recovery of effects over time. The independent action approach was able to predict the effects for the Cu and Zn mixtures. Overall, we highlight the applicability of mechanistic population models for predicting mixture toxicity effects at the population, based on effects observed on the individual level with individual substances

    Multimedia teaching aid for students of basics of control theory in MATLAB and SIMULINK

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    The paper deals with the multimedia teaching aid which was created for students of the Bachelor curriculum entitled as Information and control technology. It helps mainly students of distance curriculum to study the slight introduction to control theory and programming in MATLAB from their home. They could run the DVD at home and watch how the controller is programmed or created. © 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license

    PIN-driven auxin transport emerged early in streptophyte evolution

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    PIN-FORMED (PIN) transporters mediate directional, intercellular movement of the phytohormone auxin in land plants. To elucidate the evolutionary origins of this developmentally crucial mechanism, we analysed the single PIN homologue of a simple green alga Klebsormidium flaccidum. KfPIN functions as a plasma membrane-localized auxin exporter in land plants and heterologous models. While its role in algae remains unclear, PIN-driven auxin export is probably an ancient and conserved trait within streptophytes
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