Expectation-driven interaction: a model based on Luhmann's contingency approach

We introduce an agent-based model of interaction, drawing on the contingency approach from Luhmann's theory of social systems. The agent interactions are defined by the exchange of distinct messages. Message selection is based on the history of the interaction and developed within the confines of the problem of double contingency. We examine interaction strategies in the light of the message-exchange description using analytical and computational methods.Comment: 37 pages, 16 Figures, to appear in Journal of Artificial Societies and Social Simulation

Casanovas are liars : behavioral syndromes, sperm competition risk, and the evolution of deceptive male mating behavior in live-bearing fishes [version 2; referees: 2 approved, 1 approved with reservations]

Male reproductive biology can by characterized through competition over mates as well as mate choice. Multiple mating and male mate choice copying, especially in internally fertilizing species, set the stage for increased sperm competition, i.e., sperm of two or more males can compete for fertilization of the female’s ova. In the internally fertilizing fish Poecilia mexicana, males respond to the presence of rivals with reduced expression of mating preferences (audience effect), thereby lowering the risk of by-standing rivals copying their mate choice. Also, males interact initially more with a non-preferred female when observed by a rival, which has been interpreted in previous studies as a strategy to mislead rivals, again reducing sperm competition risk (SCR). Nevertheless, species might differ consistently in their expression of aggressive and reproductive behaviors, possibly due to varying levels of SCR. In the current study, we present a unique data set comprising ten poeciliid species (in two cases including multiple populations) and ask whether species can be characterized through consistent differences in the expression of aggression, sexual activity and changes in mate choice under increased SCR. We found consistent species-specific differences in aggressive behavior, sexual activity as well as in the level of misleading behavior, while decreased preference expression under increased SCR was a general feature of all but one species examined. Furthermore, mean sexual activity correlated positively with the occurrence of potentially misleading behavior. An alternative explanation for audience effects would be that males attempt to avoid aggressive encounters, which would predict stronger audience effects in more aggressive species. We demonstrate a positive correlation between mean aggressiveness and sexual activity (suggesting a hormonal link as a mechanistic explanation), but did not detect a correlation between aggressiveness and audience effects. Suites of correlated behavioral tendencies are termed behavioral syndromes, and our present study provides correlational evidence for the evolutionary significance of SCR in shaping a behavioral syndrome at the species level across poeciliid taxa

Searching for Communities in Bipartite Networks

Bipartite networks are a useful tool for representing and investigating interaction networks. We consider methods for identifying communities in bipartite networks. Intuitive notions of network community groups are made explicit using Newman's modularity measure. A specialized version of the modularity, adapted to be appropriate for bipartite networks, is presented; a corresponding algorithm is described for identifying community groups through maximizing this measure. The algorithm is applied to networks derived from the EU Framework Programs on Research and Technological Development. Community groups identified are compared using information-theoretic methods.Comment: 12 pages, 4 figures, to appear in "Proceedings of the 5th Jagna International Workshop: Stochastic and Quantum Dynamics of Biomolecular Systems," C. C. Bernido and M. V. Carpio-Bernido, editors. A version with full-quality figures and larger file size is available at http://ccm.uma.pt/publications/Barber-Faria-Streit-Strogan-2008.pd

Resíduos Plásticos: capacitando a comunidade sobre reciclagem

Anais do 35º Seminário de Extensão Universitária da Região Sul - Área temática: Meio AmbienteA reciclagem, se conduzida de forma correta, traz inúmeros benefícios ambientais, sociais e econômicos. Nesse aspecto foi desenvolvido um projeto de pesquisa pelo LAPAM para a reciclagem de resíduos plásticos. Este projeto contou com atividades de extensão de forma a capacitar selecionadores de materiais recicláveis, comunidade acadêmica e setor empresarial através de treinamento teórico-prático e workshop. As capacitações permitiram o intercâmbio de experiências e conhecimentos, resultando na boa aceitação do público-alv

Einfluss von lebenden Mulchen auf die Begleitflora und die Weizenerträge unter Bedingungen des Ökolandbau

For the success of no-tillage in organic farming, new tools have to be developed to control weeds. One possible strategy could be sowing the main crop into an earlier established living mulch of easily controllable cover crops. Field trials were carried out in the Swiss midlands to investigate the impact of different legume cover crops on weed populations and grain yield of directly drilled winter wheat (Triticum aestivum L.) in a living mulch system. In general, weed suppressing effect was best with highly productive legumes. A significant reduction of the weed density of dicotyle, monocotyle, and spring germinating species was observed. Though, effective weed suppression resulted also in strong competition with the winter wheat. In order to improve the practicability of such systems, seeding technique of the main crop and living mulch management should be investigated

An alternative heavy Higgs mass limit

After commenting on the present value of the Higgs particle mass from radiative corrections, we explore the phenomenological implications of an alternative, non-perturbative renormalization of the scalar sector where the mass of the Higgs particle does not represent a measure of observable interactions at the Higgs mass scale. In this approach the Higgs particle could be very heavy, even heavier than 1 TeV, and remain nevertheless a relatively narrow resonance.Comment: 17 pages. Version accepted for publication in Journal of Physics