3,110 research outputs found
A Connection Between an Exacltly Solvable Stochastic Optimal Control Problem and a Nonlinear Reaction Diffuison Equation
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
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