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- O'Gorman, Eoin J., et al.
(författare)
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Impacts of Warming on the Structure and Functioning of Aquatic Communities : Individual-to Ecosystem-Level Responses
- 2012
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Ingår i: Advances in Ecological Research, Vol 47. - : Elsevier. - 9780123983152 ; , s. 81-176
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Bokkapitel (refereegranskat)abstract
- Environmental warming is predicted to rise dramatically over the next century, yet few studies have investigated its effects in natural, multi-species systems. We present data collated over an 8-year period from a catchment of geothermally heated streams in Iceland, which acts as a natural experiment on the effects of warming across different organisational levels and spatiotemporal scales. Body sizes and population biomasses of individual species responded strongly to temperature, with some providing evidence to support temperature size rules. Macroinvertebrate and meiofaunal community composition also changed dramatically across the thermal gradient. Interactions within the warm streams in particular were characterised by food chains linking algae to snails to the apex predator, brown trout These chains were missing from the colder systems, where snails were replaced by much smaller herbivores and invertebrate omnivores were the top predators. Trout were also subsidised by terrestrial invertebrate prey, which could have an effect analogous to apparent competition within the aquatic prey assemblage. Top-down effects by snails on diatoms were stronger in the warmer streams, which could account for a shallowing of mass-abundance slopes across the community. This may indicate reduced energy transfer efficiency from resources to consumers in the warmer systems and/or a change in predator-prey mass ratios. All the ecosystem process rates investigated increased with temperature, but with differing thermal sensitivities, with important implications for overall ecosystem functioning (e.g. creating potential imbalances in elemental fluxes). Ecosystem respiration rose rapidly with temperature, leading to increased heterotrophy. There were also indications that food web stability may be lower in the warmer streams.
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- Carmelo, J. M. P., et al.
(författare)
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Correlation effects in one-dimensional systems
- 2007
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Ingår i: Strongly Correlated Systems, Coherence and Entanglement. - Hackensack, N.J. : World Scientific. - 9789812705723 ; , s. 3-27
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- We review developments concerning the effect of correlations on the electronic properties of one-dimensional systems, focusing our analysis on the one-dimensional Hubbard model. We consider methods used to describe the exotic properties of these systems, ranging from bosonization associated with the Tomonaga and Luttinger liquid behavior, to the Bethe ansatz solution, referring to all energy scales of solvable quantum problems and the pseudoparticle description. We use that description to study the model energy spectrum and the low-energy quantities. In the ensuing companion chapter we discuss the relation of the electronic operators to these quantum objects.
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- Carmelo, J. M. P., et al.
(författare)
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Dynamical and spectral properties of low dimensional materials
- 2007
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Ingår i: Strongly Correlated Systems, Coherence and Entanglement. - Hackensack, N.J. : World Scientific. - 9789812705723 ; , s. 29-59
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- This chapter follows its companion, chapter 1. Here we review different methods based on the Bethe ansatz solution of the one-dimensional Hubbard model, in order to study quantities related to charge transport and the momentum dependent conductivity. Moreover, we report recent developments on finite-energy dynamical properties. This is achieved by introducing new entities called pseudofermions which are basically free, in the sense that their energies are additive, and where the effect of the interactions appears through phase shifts that are absorbed by their discrete momentum values. The resulting pseudofermion dynamical theory enables the evaluation of matrix elements between energy eigen-states and hence the derivation of finite energy expressions for the one- and two-electron correlation and spectral functions. Comparison with experimental results is also discussed.
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- Milrad, Marcelo, et al.
(författare)
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Developing Tools that Support Effective Mobile and Game Based Learning: The COLLAGE Platform
- 2010. - 1
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Ingår i: Architectures for Distributed and Complex M-Learning Systems: Applying Intelligent Technologies. - Hershey, PA, USA : IGI Global. - 9781605668826 ; , s. 1-34
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- This chapter presents the COLLAGE (collaborative learning platform using game-like enhancements) project as a good practice example of mobile and game-based learning that aims to integrate formal and informal learning settings through an innovative pedagogical approach. In this learning environment, students learn in context while participating in ready-made game activities or creating their own games: they gather data from their environments (at school, during visits to museums and science centres, on field trips, at home) and interpret it as information useful for learning, either on their own or through platform-mediated peer collaboration. This chapter describes the pedagogical background and technical details of the COLLAGE system, which was developed in the framework of an EU-supported e-learning project in 2005-2007. The aim of the project was to investigate the impact of the COLLAGE system focusing on results and changes the introduction of mobile game-based learning may produce in the learning process.
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