Effects of punishment in a mobile population playing the prisoner’s dilemma game

We deal with a system of prisoner’s dilemma players undergoing continuous motion in a two-dimensional plane. In contrast to previous work, we introduce altruistic punishment after the game. We find punishing only a few of the cooperator-defector interactions is enough to lead the system to a cooperative state in environments where otherwise defection would take over the population. This happens even with soft nonsocial punishment (where both cooperators and defectors punish other players, a behavior observed in many human populations). For high enough mobilities or temptations to defect, low rates of social punishment can no longer avoid the breakdown of cooperation

Characterization and Control Strategies of an Integrated Chemical-Biological System for the Remediation of Toxic Pollutants in Wastewater: A case of study

In a previous work, a hybrid system consisting of an advanced oxidation process (AOP) named Photo-Fenton (Ph-F) and a fixed bed biological treatment operating as a sequencing batch biofilm reactor (SBBR) was started-up and optimized to treat 200 mg·L-1 of 4-chlorophenol (4-CP) as a model compound. In this work, studies of reactor stability and control as well as microbial population determination by molecular biology techniques were carried out to further characterize and control the biological reactor. Results revealed that the integrated system was flexible and even able to overcome toxic shock loads. Oxygen uptake rate (OUR) in situ was shown to be a valid tool to control the SBBR operation, to detect toxic conditions to the biomass, and to assess the recovery of performance. A microbial characterization by 16S rDNA sequence analysis reveals that the biological population was varied, although about 30% of the bacteria belonged to the Wautersia genus.

Imperfectly informed voters and strategic extremism

We analyze a unidimensional model of two-candidate electoral competition where voters have im- perfect information about the candidates' policy proposals, that is, voters cannot observe the exact policy proposals of the candidates but only which candidate offers the most leftist/rightist platform. We assume that candidates are purely office motivated and that one candidate enjoys a valence advan- tage over the other. We characterize the unique Sequential Equilibrium in very-weakly undominated strategies of the game. In this equilibrium the behavior of the two candidates tends to maximum extremism, due to the voters' lack of information. But it may converge or diverge depending on the size of the advantage. For small values of the advantage candidates converge to the extreme policy most preferred by the median and for large values of the advantage candidates strategies diverge: each candidate specializes in a different extreme policy. These results are robust to the introduction of a proportion of well informed voters. In this case the degree of extremism decreases when the voters become more informed.

On the structure of cooperative and competitive solutions for a generalized assignment game

We study cooperative and competitive solutions for a many- to-many generalization of Shapley and Shubik (1972)'s assignment game. We consider the Core, three other notions of group stability and two al- ternative definitions of competitive equilibrium. We show that (i) each group stable set is closely related with the Core of certain games defined using a proper notion of blocking and (ii) each group stable set contains the set of payoff vectors associated to the two definitions of competitive equilibrium. We also show that all six solutions maintain a strictly nested structure. Moreover, each solution can be identified with a set of ma- trices of (discriminated) prices which indicate how gains from trade are distributed among buyers and sellers. In all cases such matrices arise as solutions of a system of linear inequalities. Hence, all six solutions have the same properties from a structural and computational point of view.

¿Qué entienden los jóvenes universitarios por monogamia y sexo sin penetración, como estrategias preventivas de la transmisión sexual del virus del SIDA? = What university students understand by monogamy and sex without penetration as preventive strategies of sexual transmission of AIDS virus?

Monogamy and sex without penetration are behaviors recommended by the WHO to avoid AIDS virus sexual transmission. Seven hundred and fifty university students from 18 to 25 years (67.7% women) were surveyed and they were asked to give a maximum of three free definitions of the words monogamy and sex without penetration to prevent AIDS virus sexual transmission. Their participation was voluntary and anonymous. Although the majority of the answers was correct, there was a considerable percentage of wrong answers, either for monogamy (3.7% masturbation; 2.1% to have many partners; 0.9% homosexual relations), or for sex without penetration (20.5% oral sex; 1.1% anal coitus; 0.8% coitus without orgasm; 0.4% coitus interruptus). Some definitions or examples differ by gender. The amount of wrongs or incomplete answers put researchers on the alert about insufficient preventive knowledge in a population with a high educational level