Competing associations in six-species predator-prey models

We study a set of six-species ecological models where each species has two predators and two preys. On a square lattice the time evolution is governed by iterated invasions between the neighboring predator-prey pairs chosen at random and by a site exchange with a probability Xs between the neutral pairs. These models involve the possibility of spontaneous formation of different defensive alliances whose members protect each other from the external invaders. The Monte Carlo simulations show a surprisingly rich variety of the stable spatial distributions of species and subsequent phase transitions when tuning the control parameter Xs. These very simple models are able to demonstrate that the competition between these associations influences their composition. Sometimes the dominant association is developed via a domain growth. In other cases larger and larger invasion processes preceed the prevalence of one of the stable asociations. Under some conditions the survival of all the species can be maintained by the cyclic dominance occuring between these associations.Comment: 8 pages, 9 figure

A model-independent approach to infer hierarchical codon substitution dynamics

<p>Abstract</p> <p>Background</p> <p>Codon substitution constitutes a fundamental process in molecular biology that has been studied extensively. However, prior studies rely on various assumptions, e.g. regarding the relevance of specific biochemical properties, or on conservation criteria for defining substitution groups. Ideally, one would instead like to analyze the substitution process in terms of raw dynamics, independently of underlying system specifics. In this paper we propose a method for doing this by identifying groups of codons and amino acids such that these groups imply closed dynamics. The approach relies on recently developed spectral and agglomerative techniques for identifying hierarchical organization in dynamical systems.</p> <p>Results</p> <p>We have applied the techniques on an empirically derived Markov model of the codon substitution process that is provided in the literature. Without system specific knowledge of the substitution process, the techniques manage to "blindly" identify multiple levels of dynamics; from amino acid substitutions (via the standard genetic code) to higher order dynamics on the level of amino acid groups. We hypothesize that the acquired groups reflect earlier versions of the genetic code.</p> <p>Conclusions</p> <p>The results demonstrate the applicability of the techniques. Due to their generality, we believe that they can be used to coarse grain and identify hierarchical organization in a broad range of other biological systems and processes, such as protein interaction networks, genetic regulatory networks and food webs.</p

Excellence seekers, pragmatists, or sceptics : Ways of applying performance‐based research funding systems at new universities and university colleges in Sweden

The Swedish system of research funding has undergone major changes, while competitive funding schemes gradually have gained popularity, at the expense of institutional block grants. In recent years, there has been a strong drive to improve research performance in universities as a result of governmental desires, resulting in performance-based research funding systems (PRFS) being introduced to distribute block grants. The study on which this article reports sought to understand the development of increased government intent to steer resources for research, by investigating the behaviour of universities and university colleges in Sweden in terms of internal organisation and distribution of funding. The article investigates the structure of and motives for applying PRFS at seven new universities and university colleges through a document and interview study. We identified three categories of higher education institutions: the excellence seekers, the pragmatists and the sceptics. Universities rhetorically ignal compliance with governmental propositions to distribute funding according to performance measures, but their actions are limited. Thus, national incentives, models and measures influence decisions at lower institutional levels in a rather modest way.Special Issue: Expansion and retrenchment of internationalisation in higher education: Theories, methods and data</p