Positive interactions may decrease cooperation in social dilemma experiments.

A social dilemma appears in the public goods problem, where the individual has to decide whether to contribute to a common resource. The total contributions to the common pool are increased by a synergy factor and evenly split among the members. The ideal outcome occurs if everyone contributes the maximum amount.

Role-separating ordering in social dilemmas controlled by topological frustration.

''Three is a crowd" is an old proverb that applies as much to social interactions as it does to frustrated configurations in statistical physics models. Accordingly, social relations within a triangle deserve special attention. With this motivation, we explore the impact of topological frustration on the evolutionary dynamics of the snowdrift game on a triangular lattice.

Stochastic win-stay-lose-shift strategy with dynamic aspirations in evolutionary social dilemmas.

In times of plenty expectations rise, just as in times of crisis they fall. This can be mathematically described as a win-stay-lose-shift strategy with dynamic aspiration levels, where individuals aspire to be as wealthy as their average neighbor. Here we investigate this model in the realm of evolutionary social dilemmas on the square lattice and scale-free networks.

Evolutionary mixed games in structured populations: Cooperation and the benefits of heterogeneity.

Evolutionary games on networks traditionally involve the same game at each interaction. Here we depart from this assumption by considering mixed games, where the game played at each interaction is drawn uniformly at random from a set of two different games. While in well-mixed populations the random mixture of the two games is always equivalent to the average single game, in structured populations this is not always the case.

Effects of airway surface liquid height on the kinetics of extracellular nucleotides in airway epithelia.

Experimental techniques aimed at measuring the concentration of signaling molecules in the airway surface liquid (ASL) often require an unrealistically large ASL volume to facilitate sampling. This experimental limitation, prompted by the difficulty of pipetting liquid from a very shallow layer (~15 μm), leads to dilution and the under-prediction of physiologic concentrations of signaling molecules that are vital to the regulation of mucociliary clearance. Here, we use a computational model to describe the effect of liquid height on the kinetics of extracellular nucleotides in the airway surface liquid coating respiratory epithelia.

Distinguishing the opponents promotes cooperation in well-mixed populations.

Cooperation has been widely studied when an individual strategy is adopted against all coplayers. In this context, some extra mechanisms, such as punishment, reward, memory, and network reciprocity must be introduced in order to keep cooperators alive. Here, we adopt a different point of view.

Time-dependent properties of a simplified Fermi-Ulam accelerator model.

The chaotic low-energy region of a simplified Fermi-Ulam accelerator model is investigated numerically to determine the average energy and number of collisions as functions of time. We find that these properties exhibit scaling when the oscillation amplitude of the moving wall is small. Following a transient regime, the average energy increases in time, reaches a maximum and then shows a surprising slow decay.

On the scaling of mammalian long bones.

Although there is much data available on mammalian long-bone allometry, a theory explaining these data is still lacking. We show that bending and axial compression are the relevant loading modes and elucidate why the elastic similarity model failed to explain the experimental data. Our analysis provides scaling relations connecting bone diameter and length to the axial and transverse components of the force, in good agreement with experimental data.