1,064 research outputs found
Derivation of a macroscopic model for transport of strongly sorbed solutes in the soil using homogenization theory
No full textIn this paper we derive a model for the diffusion of strongly sorbed solutes in soil taking into account diffusion within both the soil fluid phase and the soil particles. The model takes into account the effect of solutes being bound to soil particle surfaces by a reversible nonlinear reaction. Effective macroscale equations for the solute movement in the soil are derived using homogenization theory. In particular, we use the unfolding method to prove the convergence of nonlinear reaction terms in our system. We use the final, homogenized model to estimate the effect of solute dynamics within soil particles on plant phosphate uptake by comparing our double-porosity model to the more commonly used single-porosity model. We find that there are significant qualitative and quantitative differences in the predictions of the models. This highlights the need for careful experimental and theoretical treatment of plant-soil interaction when trying to understand solute losses from the soil
Growth model for arbuscular mycorrhizal fungi
No full textIn order to quantify the contribution of arbuscular mycorrhizal (AM) fungi to plant phosphorus nutrition, the development and extent of the external fungal mycelium and its nutrient uptake capacity are of particular importance. We develop and analyse a model of the growth of AM fungi associated with plant roots, suitable for describing mechanistically the effects of the fungi on solute uptake by plants. The model describes the development and distribution of the fungal mycelium in soil in terms of the creation and death of hyphae, tip–tip and tip–hypha anastomosis, and the nature of the root–fungus interface. It is calibrated and corroborated using published experimental data for hyphal length densities at different distances away from root surfaces. A good agreement between measured and simulated values was found for three fungal species with different morphologies: Scutellospora calospora (Nicol. & Gerd.) Walker & Sanders; Glomus sp.; and Acaulospora laevis Gerdemann & Trappe associated with Trifolium subterraneum L. The model and findings are expected to contribute to the quantification of the role of AM fungi in plant mineral nutrition and the interpretation of different foraging strategies among fungal specie
Impact of growth and uptake patterns of arbuscular mycorrhizal fungi on plant phosphorus uptake—a modelling study
No full textIn this paper we present a mathematical model for estimating external mycelium growth of arbuscular mycorrhizal fungi and its effect on root uptake of phosphate (P). The model describes P transport in soil and P uptake by both root and fungi on the single root scale. We investigate differences in soil P depletion and overall P influx into a mycorrhizal root by assuming that different spatial regions of mycelia are active in P uptake.When all external hyphae contribute to P uptake, overall uptake is dominated by the fungus and the most effective growth pattern appears to be the one using a high level of anastomosis. The same is true when only the proportion of external hyphae assumed to be active contributes to uptake. When uptake is restricted to the tips, hyphal contribution to overall P uptake is less dominant; the most effective growth pattern appears to be the one characterised by nonlinear branching where branching stops at a given maximal hyphal tip density. Comparison to measured P depletion in the literature suggests that the scenario where active hyphae are contributing to P uptake is likely to fit the data best. These quantitative predictions promote our understanding of the mycorrhizal symbiosis and its role in plant P nutrition
A mathematical model for simultaneous spatio-temporal dynamics of calcium and inositol 1,4,5-trisphosphate in Madin–Darby canine kidney epithelial cells
No full textThe landmark paper by Hirose et al. (Hirose, K., Kadowaki, S., Tanabe, M., Takeshima, H., Iino, M., Science 284:1527–1530, 1999) presented experimental investigations to show that not only can calcium upregulate IP3, but that it can also have an inhibitory effect on IP3. In this paper, we present a preliminary model, which is consistent with these experiments. This model includes positive and negative feedback between calcium and IP3 and is able to reproduce more precisely the data presented in Hirose et al. (Hirose, K., Kadowaki, S., Tanabe, M., Takeshima, H., Iino, M., Science 284:1527–1530, 1999). In the second part of the paper, the intracellular and intercellular calcium movement in Madin–Darby canine kidney epithelial cells is investigated. With the aid of the model we are able to identify the aspects of IP3 and calcium signalling, which should be studied further experimentally before refining the mode
Stability analysis of high-frequency interactions between a converter and HVDC grid resonances
No full textsponsorship: This work was supported in part by the Energy Transition Fund, FOD Economy, Belgium, and in part by the FWO under Grant G0D2319N. The work of Thomas Roose was supported by a research grant from the Research Foundation -Flanders (FWO) and VITO under Grant 1182519N. The work of Jef Beerten was supported by the FWO under Grant 12D1117N. (Corresponding author: Thomas Roose.) (Energy Transition Fund, FOD Economy, Belgium, FWO|G0D2319N, FWO|12D1117N, Research Foundation -Flanders (FWO), VITO|1182519N)status: Publishe
Rezension zu: Jochen Roose, Mike S. Schäfer & Thomas Schmidt-Lux (Hrsg.) (2010). Fans. Soziologische Perspektiven. Wiesbaden: VS Verlag, 2010. 442 S. ISBN 978-3-531-16096-2, 34.95 €
No full textRiedl L. Rezension zu: Jochen Roose, Mike S. Schäfer & Thomas Schmidt-Lux (Hrsg.) (2010). Fans. Soziologische Perspektiven. Wiesbaden: VS Verlag, 2010. 442 S. ISBN 978-3-531-16096-2, 34.95 €. Sport und Gesellschaft - Sport and Society. 2010;7(3):265-274
Use of a coupled soil-root-leaf model to optimise phosphate fertiliser use efficiency in barley
No full textFiles used to compute the figures for the paper Heppell, J., Payvandi, S., Talboys, P., Zygalakis, K., Langton, D., Sylvester-Bradley, R., Edwards, A.C., Walker, R., Withers, P., Jones, D.L. and Roose, T. (2016) Use of a coupled soil-root-leaf model to optimise phosphate fertiliser use efficiency in barley. Plant and Soil, 1-29. (doi:10.1007/s11104-016-2883-4)</span
Fans und Emotionen
No full textDie Soziologie der Emotionen ist vergleichsweise jung. Entstanden in den USA der 1970er, fasste sie erst in den 1980ern in Deutschland Fuß, hat sich seither aber rasant entwickelt und verfügt mittlerweile über ein ansehnliches Theorien und Methodenrepertoire. Dieses Repertoire ist für die Analyse von Fans prädestiniert - schließlich stellen Emotionen ein konstitutives, vielleicht das konstitutive Charakteristikum von Fans dar, die von unterschiedlichen Autoren und auch in diesem Band als Personen verstanden werden, die sich vornehmlich durch ihre intensive emotionale Beziehung zu einem für sie externen Fanobjekt auszeichnen (vgl. die Einleitung in diesem Band sowie Fritzsche 2003: 265ff.; Hills 2002: 90; Schäfer/Roose 2005: 49; Winter 1993: 71). Entsprechend wird im Folgenden dargelegt, welche emotionssoziologischen Blickwinkel bereits für die Analyse von Fans genutzt wurden und welche dahingehend künftig fruchtbar sein könnten. Dazu werden zunächst die Grundperspektiven der Emotionssoziologie skizziert und anschließend auf Fans bezogen
The study of asymptotically fine wrinkling in nonlinear elasticity using a boundary layer analysis
No full text- …
