Food webs under stress : The structure, stability and functioning of stressed soil food webs

Verhoef, H.A. [Promotor]Gestel, C.A.M. van [Copromotor

Recent and ancient sedimentation; two aspects of one subject

Geology has thrived on the application of the maxim, the present is the key to the past. Investigation of the phenomena and active processes of the surrounding world has proved to supply the most trustworthy foundation for interpreting the features of ancient rocks and unravelling the geological history of the earth\u27s crust. But one chapter of geology has formed an exception, that of ancient marine sediments. Considering the extent as well as the economic and paleontologic importance of these rocks, it is a huge chapter. In this domain geologists have attempted the opposite procedure, namely to deduce the submarine processes from the features of their consolidated rocks

Unveiling the Expressivity of Complexity: Drifting in Design Research

Design research is regarded to be a mode of inquiry particularly suited to engage with complex topics. In our work, we are interested in unpacking the complexity at the heart of an embodied aesthetic experience. In this article, through our digital and physical artefacts and a methodological reflection, we illustrate an ongoing design research project that a multi-disciplinary team of interaction designers, professional dancers, software developers, artists and 3D modelling experts are carrying out to develop insights on how to understand this complexity and how to use such insights as inspiration for interaction design-related projects. By embracing combinations of design, new technologies and simple visualisation tools, the project investigates the complex and hidden expressivity embedded in the skills of dancers in a programmatic design research approach. This investigation leads to insights on different levels. Firstly, cycles of formulation, realisation and reflection on design programs express parts of this complexity and this lets new research interests emerge. Secondly, as a body of work, reflecting on these cycles exposes how our “drifting” within this programmatic approach has started to unveil the complexities inherent in our research program. In this article we aim at contributing to the growing understanding of what designerly ways of knowing might be and how a practice aimed at expanding and contributing such knowledge unfolds

Anaerobic oxidation of thiosulfate to tetrathionate by obligately heterotrophic bacteria, belonging to the Pseudomonas stutzeri group

A number of strains of heterotrophic bacteria were isolated from various environments on the basis of their potential to oxidize inorganic sulfur compounds to tetrathionate. The isolates were screened for the ability to oxidize thiosulfate under denitrifying conditions. Many of them could grow anaerobically with acetate and nitrate, and eight strains could oxidize thiosulfate to tetrathionate under the same conditions. In batch cultures with acetate as carbon and energy source, most active anaerobic thiosulfate oxidation occurred with N2O as electron acceptor. The level of anaerobic thiosulfate-oxidizing activity in cultures and cell suspensions supplied with nitrate correlated with the activity of nitrite reductase in cell suspensions. Some strains converted thiosulfate to tetrathionate equally well with nitrite, nitrate and N2O as electron accepters. Others functioned best with N2O during anaerobic thiosulfate oxidation. The latter strains appeared to have a lower level of nitrite reductase activity. Thiosulfate oxidation under anaerobic conditions was much slower than in the presence of oxygen, and was obviously controlled by the availability of organic electron donor. The strains had DNA-DNA similarity levels higher than 30%. Sequence analysis of the 16S rRNA gene of four selected isolates showed their affiliation to specific genomovars of Pseudomonas stutzeri and the proposed new species, Pseudomonas balearica. As shown by 16S rRNA sequence analysis and DNA-DNA hybridization, the previously misnamed 'Flavobacterium lutescans' (ATCC 27951) is also a P. stutzeri strain which can oxidize thiosulfate to tetrathionate aerobically and anaerobically in the presence of N2O. The data suggest that tetrathionate-forming heterotrophic bacteria, in particular those belonging to the P. stutzeri 'superspecies', can play a much mole significant role in the biogeochemical cycles than was previously recognized. (C) 1999 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved