2,418 research outputs found
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A game theoretical model of kleptoparasitism with incomplete information
Kleptoparasitism, the stealing of food from one animal by another, is a common natural phenomenon that has been modelled mathematically in a number of ways. The handling process of food items can take some time and the value of such items can vary depending upon how much handling an item has received. Furthermore this information may be known to the handler but not the potential challenger, so there is an asymmetry between the information possessed by the two competitors. We use game-theoretic methods to investigate the consequences of this asymmetry for continuously consumed food items, depending upon various natural parameters. A variety of solutions are found, and there are complex situations where three possible solutions can occur for the same set of parameters. It is also possible to have situations which involve members of the population exhibiting different behaviours from each other. We find that the asymmetry of information often appears to favour the challenger, despite the fact that it possesses less information than the challenged individual
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Evolutionary games on graphs and the speed of the evolutionary process
In this paper, we investigate evolutionary games with the invasion process updating rules on three simple non-directed graphs: the star, the circle and the complete graph. Here, we present an analytical approach and derive the exact solutions of the stochastic evolutionary game dynamics. We present formulae for the fixation probability and also for the speed of the evolutionary process, namely for the mean time to absorption (either mutant fixation or extinction) and then the mean time to mutant fixation. Through numerical examples, we compare the different impact of the population size and the fitness of each type of individual on the above quantities on the three different structures. We do this comparison in two specific cases. Firstly, we consider the case where mutants have fixed fitness r and resident individuals have fitness 1. Then, we consider the case where the fitness is not constant but depends on games played among the individuals, and we introduce a ‘hawk–dove’ game as an example
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Models of kleptoparasitism on networks: the effect of population structure on food stealing behaviour
The behaviour of populations consisting of animals that interact with each other for their survival and reproduction is usually investigated assuming homogeneity amongst the animals. However, real populations are non-homogeneous. We focus on an established model of kleptoparasitism and investigate whether and how much population heterogeneities can affect the behaviour of kleptoparasitic populations. We consider a situation where animals can either discover food items by themselves or attempt to steal the food already discovered by other animals through aggressive interactions. Representing the likely interactions between animals by a network, we develop pairwise and individual-based models to describe heterogeneities in both the population structure and other individual characteristics, including searching and fighting abilities. For each of the models developed we derive analytic solutions at the steady state. The high accuracy of the solutions is shown in various examples of populations with different degrees of heterogeneity. We observe that highly heterogeneous structures can significantly affect the food intake rate and therefore the fitness of animals. In particular, the more highly connected animals engage in more conflicts, and have a reduced food consumption rate compared to poorly connected animals. Further, for equivalent average level of connectedness, the average consumption rate of a population with heterogeneous structure can be higher
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The Evolution of Kleptoparasitism under Adaptive Dynamics Without Restriction
A Hawk-Dove game in kleptoparasitic populations
Kleptoparasitism, the parasitism by theft, is a widespread biological phenomenon. In this paper we extend earlier models to investigate a population of conspecifics involved in foraging and, potentially, kleptoparasitism. We assume that the population is composed of two types of individuals, Hawks and Doves. The types differ according to their strategic choices when faced with an opportunity to steal and to resist a challenge. Hawks use every opportunity to steal and they resist all challenges. Doves never resist and never steal. The fitness of each type of individual depends upon various natural parameters, for example food density, the handling time of a food item, density of the population, as well as the duration of potential fights over the food. We find the Evolutionarily Stable States (ESSs) for all arameter combinations and show that there are three possible ESSs, pure Hawks, pure Doves, and a mixed population of Hawks and Doves. We show that for any set of parameter values there is exactly one ESS. We further investigate the relationship between our findings and the classical Hawk-Dove game as defined in Maynard Smith 1982. We also show how our model extends the classical on
The effect of very low-calorie diets on renal and hepatic outcomes : a systematic review
Peer reviewedPublisher PD
A qualitative study of hospital pharmacists and antibiotic governance: Negotiating interprofessional responsibilities, expertise and resource constraints Organization, structure and delivery of healthcare
© 2016 Broom et al. Background: Antibiotic treatment options for common infections are diminishing due to the proliferation of antimicrobial resistance (AMR). The impact of Antimicrobial Stewardship (AMS) programs seeking to preserve viable antibiotic drugs by governing their use in hospitals has hitherto been limited. Pharmacists have been delegated a critical role in antibiotic governance in AMS teams within hospitals but the experience of pharmacists in influencing antibiotic use has received limited attention. In this study we explore the experiences of pharmacists in antibiotic decision-making in two Australian hospitals. Methods: We conducted 19 semi-structured interviews to explore hospital-based pharmacists' perceptions and experiences of antibiotic use and governance. The analysis was conducted with NVivo10 software, utilising the framework approach. Results: Three major themes emerged in the pharmacist interviews including (1) the responsibilities of pharmacy in optimising antibiotic use and the interprofessional challenges therein; (2) the importance of antibiotic streamlining and the constraints placed on pharmacists in achieving this; and (3) the potential, but often under-utilised expertise, pharmacists bring to antibiotic optimisation. Conclusions: Pharmacists have a critical role in AMS teams but their capacity to enact change is limited by entrenched interprofessional dynamics. Identifying how hospital pharmacy's antibiotic gatekeeping is embedded in the interprofessional nature of clinical decision-making and limited by organisational environment has important implications for the implementation of hospital policies seeking to streamline antibiotic use. Resource constraints (i.e. time limitation and task prioritisation) in particular limit the capacity of pharmacists to overcome the interprofessional barriers through development of stronger collaborative relationships. The results of this study suggest that to enact change in antibiotic use in hospitals, pharmacists must be supported in their negotiations with doctors, have increased presence on hospital wards, and must be given opportunities to pass on specialist knowledge within multidisciplinary clinical teams
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The effect of network topology on optimal exploration strategies and the evolution of cooperation in a mobile population
We model a mobile population interacting over an underlying spatial structure using a Markov movement model. Interactions take the form of public goods games, and can feature an arbitrary group size. Individuals choose strategically to remain at their current location or to move to a neighbouring location, depending upon their exploration strategy and the current composition of their group. This builds upon previous work where the underlying structure was a complete graph (i.e. there was effectively no structure). Here, we consider alternative network structures and a wider variety of, mainly larger, populations. Previously, we had found when cooperation could evolve, depending upon the values of a range of population parameters. In our current work, we see that the complete graph considered before promotes stability, with populations of cooperators or defectors being relatively hard to replace. By contrast, the star graph promotes instability, and often neither type of population can resist replacement. We discuss potential reasons for this in terms of network topology
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Two results on evolutionary processes on general non-directed graphs
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