De macht van de grootte

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The use of species sensitivity distributions and monitoring to predict the ecological effect of longitudinal training dams

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Sensitivity of native and introduced fish species to changes in flow velocity of European rivers

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Generic physiologically based kinetic modelling for farm animals: Part I. Data collection of physiological parameters in swine, cattle and sheep

Abstract Physiologically based kinetic (PBK) models for farm animals are of growing interest in food and feed safety with key applications for regulated compounds including quantification of tissue concentrations, kinetic parameters and the setting of safe exposure levels on an internal dose basis. The development and application of these models requires data for physiological, anatomical and chemical specific parameters. Here, we present the results of a structured data collection of anatomical and physiological parameters in three key farm animal species (swine, cattle and sheep). We performed an extensive literature search and meta-analyses to quantify intra-species variability and associated uncertainty of the parameters. Parameters were collected for organ weights and blood flows in all available breeds from 110 scientific publications, of which 29, 48 and 33 for cattle, sheep, and swine, respectively. Organ weights were available in literature for all three species. Blood flow parameter values were available for all organs in sheep but were scarcer in swine and cattle. Furthermore, the parameter values showed a large intra-species variation. Overall, the parameter values and associated variability provide reference values which can be used as input for generic PBK models in these species

The full greenhouse gas balance of an abandoned peat meadow

International audienceGlobally, peat lands are considered to be a sink of CO2, but a source when drained. Additionally, wet peat lands are thought to emit considerable amounts of CH4 and N2O. Hitherto, reliable and integrated estimates of emissions and emission factors for this type of area have been lacking and the effects of wetland restoration on methane emissions have been poorly quantified. In this paper we estimate the full GHG balance of a restored natural peat land by determining the fluxes of CO2, CH4 and N2O through atmosphere and water, while accounting for the different GWP's. This site is an abandoned agricultural peat meadow, which has been converted into a wetland nature reserve ten years ago by raising the water level. GHG fluxes were measured continuously with an eddy-correlation system (CO2) and flux chamber measurements (CH4 and N2O). Meteorological and hydrological measurements were done as well. With growing seasons of respectively 192 and 155 days, the net annual CO2 uptake was 276±61 g C m?2 for 2004 and 311±58 g C m?2 for 2005. Ecosystem respiration was estimated as 887±668 g C m?2 for 2004 and 866±666 g C m?2 for 2005. CH4 fluxes from water, saturated land and relatively dry land varied: total annual CH4 fluxes are 10.4±19.2 g C m?2 yr?1, 101 g C m?2 yr?1±30 and 37.3±10.9 g C m?2 yr?1, respectively, and a annual weighed total CH4 emission of 31.27±20.44 g C m?2 yr?1. N2O fluxes were too low to be of significance. The carbon-balance consists for the largest part of CO2 uptake, CO2 respiration and CH4 emission from wet land and water. CO2 emission has decreased significantly as result of the raised water table, while CH4 fluxes have increased. In global warming potentials the area is a very small sink of 71 g CO2-equiv m?2 (over a 100-year period)

A compact and stable eddy covariance set-up for methane measurements using off-axis integrated cavity output spectroscopy

A Fast Methane Analyzer (FMA) is assessed for its applicability in a closed path eddy covariance field set-up in a peat meadow. The FMA uses off-axis integrated cavity output spectroscopy combined with a highly specific narrow band laser for the detection of CH<sub>4</sub> and strongly reflective mirrors to obtain a laser path length of 2–20×10<sup>3</sup> m. Statistical testing and a calibration experiment showed high precision (7.8×10<sup>−3</sup> ppb) and accuracy (<0.30%) of the instrument, while no drift was observed. The instrument response time was determined to be 0.10 s. In the field set-up, the FMA is attached to a scroll pump and combined with a 3-axis ultrasonic anemometer and an open path infrared gas analyzer for measurements of carbon dioxide and water vapour. The power-spectra and co-spectra of the instruments were satisfactory for 10 Hz sampling rates. <br><br> Due to erroneous measurements, spikes and periods of low turbulence the data series consisted for 26% of gaps. Observed CH<sub>4</sub> fluxes consisted mainly of emission, showed a diurnal cycle, but were rather variable over. The average CH<sub>4</sub> emission was 29.7 nmol m<sup>−2</sup> s<sup>−1</sup>, while the typical maximum CH<sub>4</sub> emission was approximately 80.0 nmol m<sup>−2</sup> s<sup>−1</sup> and the typical minimum flux was approximately 0.0 nmol m<sup>−2</sup> s<sup>−1</sup>. The correspondence of the measurements with flux chamber measurements in the footprint was good and the observed CH<sub>4</sub> emission rates were comparable with eddy covariance CH<sub>4</sub> measurements in other peat areas. <br><br> Additionally, three measurement techniques with lower sampling frequencies were simulated, which might give the possibility to measure CH<sub>4</sub> fluxes without an external pump and save energy. Disjunct eddy covariance appeared to be the most reliable substitute for 10 Hz eddy covariance, while relaxed eddy accumulation gave reliable estimates of the fluxes over periods in the order of days or weeks

Quadruple junction polymer solar cells with four complementary absorber layers

A monolithic two‐terminal solution‐processed quadruple junction polymer solar cell in an n–i–p (inverted) configuration with four complementary polymer:fullerene active bulk‐heterojunction layers is presented. The subcells possess different optical bandgaps ranging from 1.90 to 1.13 eV. Optical modeling using the transfer matrix formalism enables prediction of the fraction of absorbed photons from sunlight in each subcell and determine the optimal combination of layer thicknesses. The quadruple junction cell features an open‐circuit voltage of 2.45 V and has a power conversion efficiency of 7.6%, only slightly less than the modeled value of 8.2%. The external quantum efficiency spectrum, determined with appropriate light and voltage bias conditions, exhibits in general an excellent agreement with modeled spectrum. The device performance is presently limited by bimolecular recombination, which prevents using thick photoactive layers that could absorb light more efficiently