876 research outputs found
Evolutionary prisoner's dilemma games with optional participation
Competition among cooperators, defectors, and loners is studied in an
evolutionary prisoner's dilemma game with optional participation. Loners are
risk averse i.e. unwilling to participate and rather rely on small but fixed
earnings. This results in a rock-scissors-paper type cyclic dominance of the
three strategies. The players are located either on square lattices or random
regular graphs with the same connectivity. Occasionally, every player
reassesses its strategy by sampling the payoffs in its neighborhood. The loner
strategy efficiently prevents successful spreading of selfish, defective
behavior and avoids deadlocks in states of mutual defection. On square
lattices, Monte Carlo simulations reveal self-organizing patterns driven by the
cyclic dominance, whereas on random regular graphs different types of
oscillatory behavior are observed: the temptation to defect determines whether
damped, periodic or increasing oscillations occur. These results are compared
to predictions by pair approximation. Although pair approximation is incapable
of distinguishing the two scenarios because of the equal connectivity, the
average frequencies as well as the oscillations on random regular graphs are
well reproduced.Comment: 6 pages, 7 figure
Spectro-Electrochemical Investigation of the bc1 Complex from the Yeast Saccharomyces cerevisiae using Surface Enhanced B-Band Resonance Raman Spectroscopy
Stochastic differential equations for evolutionary dynamics with demographic noise and mutations
We present a general framework to describe the evolutionary dynamics of an
arbitrary number of types in finite populations based on stochastic
differential equations (SDE). For large, but finite populations this allows to
include demographic noise without requiring explicit simulations. Instead, the
population size only rescales the amplitude of the noise. Moreover, this
framework admits the inclusion of mutations between different types, provided
that mutation rates, , are not too small compared to the inverse
population size 1/N. This ensures that all types are almost always represented
in the population and that the occasional extinction of one type does not
result in an extended absence of that type. For this limits the use
of SDE's, but in this case there are well established alternative
approximations based on time scale separation. We illustrate our approach by a
Rock-Scissors-Paper game with mutations, where we demonstrate excellent
agreement with simulation based results for sufficiently large populations. In
the absence of mutations the excellent agreement extends to small population
sizes.Comment: 8 pages, 2 figures, accepted for publication in Physical Review
Phase transitions and volunteering in spatial public goods games
Cooperative behavior among unrelated individuals in human and animal
societies represents a most intriguing puzzle to scientists in various
disciplines. Here we present a simple yet effective mechanism promoting
cooperation under full anonymity by allowing for voluntary participation in
public goods games. This natural extension leads to rock--scissors--paper type
cyclic dominance of the three strategies cooperate, defect and loner i.e. those
unwilling to participate in the public enterprise. In spatial settings with
players arranged on a regular lattice this results in interesting dynamical
properties and intriguing spatio-temporal patterns. In particular, variations
of the value of the public good leads to transitions between one-, two- and
three-strategy states which are either in the class of directed percolation or
show interesting analogies to Ising-type models. Although volunteering is
incapable of stabilizing cooperation, it efficiently prevents successful
spreading of selfish behavior and enables cooperators to persist at substantial
levels.Comment: 4 pages, 5 figure
Critical dynamics in the evolution of stochastic strategies for the iterated Prisoner's Dilemma
The observed cooperation on the level of genes, cells, tissues, and
individuals has been the object of intense study by evolutionary biologists,
mainly because cooperation often flourishes in biological systems in apparent
contradiction to the selfish goal of survival inherent in Darwinian evolution.
In order to resolve this paradox, evolutionary game theory has focused on the
Prisoner's Dilemma (PD), which incorporates the essence of this conflict. Here,
we encode strategies for the iterated Prisoner's Dilemma (IPD) in terms of
conditional probabilities that represent the response of decision pathways
given previous plays. We find that if these stochastic strategies are encoded
as genes that undergo Darwinian evolution, the environmental conditions that
the strategies are adapting to determine the fixed point of the evolutionary
trajectory, which could be either cooperation or defection. A transition
between cooperative and defective attractors occurs as a function of different
parameters such a mutation rate, replacement rate, and memory, all of which
affect a player's ability to predict an opponent's behavior.Comment: 27 pages, including supplementary information. 5 figures, 4 suppl.
figures. Version accepted for publication in PLoS Comp. Bio
Variable outcomes of human heart attack recapitulated in genetically diverse mice.
Clinical variation in patient responses to myocardial infarction (MI) has been difficult to model in laboratory animals. To assess the genetic basis of variation in outcomes after heart attack, we characterized responses to acute MI in the Collaborative Cross (CC), a multi-parental panel of genetically diverse mouse strains. Striking differences in post-MI functional, morphological, and myocardial scar features were detected across 32 CC founder and recombinant inbred strains. Transcriptomic analyses revealed a plausible link between increased intrinsic cardiac oxidative phosphorylation levels and MI-induced heart failure. The emergence of significant quantitative trait loci for several post-MI traits indicates that utilizing CC strains is a valid approach for gene network discovery in cardiovascular disease, enabling more accurate clinical risk assessment and prediction
Variable outcomes of human heart attack recapitulated in genetically diverse mice
Clinical variation in patient responses to myocardial infarction (MI) has been difficult to model in laboratory animals. To assess the genetic basis of variation in outcomes after heart attack, we characterized responses to acute MI in the Collaborative Cross (CC), a multi-parental panel of genetically diverse mouse strains. Striking differences in post-MI functional, morphological, and myocardial scar features were detected across 32 CC founder and recombinant inbred strains. Transcriptomic analyses revealed a plausible link between increased intrinsic cardiac oxidative phosphorylation levels and MI-induced heart failure. The emergence of significant quantitative trait loci for several post-MI traits indicates that utilizing CC strains is a valid approach for gene network discovery in cardiovascular disease, enabling more accurate clinical risk assessment and prediction
10-Year Associations Between Tumor Necrosis Factor Receptors 1 and 2 and Cardiovascular Events in Patients With Stable Coronary Heart Disease:A CLARICOR (Effect of Clarithromycin on Mortality and Morbidity in Patients With Ischemic Heart Disease) Trial Substudy
Circulating endostatin as a risk factor for cardiovascular events in patients with stable coronary heart disease:A CLARICOR trial sub-study
Searches at HERA for Squarks in R-Parity Violating Supersymmetry
A search for squarks in R-parity violating supersymmetry is performed in e^+p
collisions at HERA at a centre of mass energy of 300 GeV, using H1 data
corresponding to an integrated luminosity of 37 pb^(-1). The direct production
of single squarks of any generation in positron-quark fusion via a Yukawa
coupling lambda' is considered, taking into account R-parity violating and
conserving decays of the squarks. No significant deviation from the Standard
Model expectation is found. The results are interpreted in terms of constraints
within the Minimal Supersymmetric Standard Model (MSSM), the constrained MSSM
and the minimal Supergravity model, and their sensitivity to the model
parameters is studied in detail. For a Yukawa coupling of electromagnetic
strength, squark masses below 260 GeV are excluded at 95% confidence level in a
large part of the parameter space. For a 100 times smaller coupling strength
masses up to 182 GeV are excluded.Comment: 32 pages, 14 figures, 3 table
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