Integrated assurance assessment of a reconfigurable digital flight control system

The integrated application of reliability, failure effects and system simulator methods in establishing the airworthiness of a flight critical digital flight control system (DFCS) is demonstrated. The emphasis was on the mutual reinforcement of the methods in demonstrating the system safety

Hox-logic of preadaptations for social insect symbiosis in rove beetles

How symbiotic lifestyles evolve from free-living ecologies is poorly understood. Novel traits mediating symbioses may stem from preadaptations: features of free-living ancestors that predispose taxa to engage in nascent interspecies relationships. In Metazoa's largest family, Staphylinidae (rove beetles), the body plan within the subfamily Aleocharinae is preadaptive for symbioses with social insects. Short elytra expose a pliable abdomen that bears targetable glands for host manipulation or chemical defense. The exposed abdomen has also been convergently refashioned into ant- and termite-mimicking shapes in multiple symbiotic lineages. Here we show how this preadaptive anatomy evolved via novel Hox gene functions that remodeled the ancestral coleopteran groundplan. Using the model staphylinid Dalotia coriaria, we abolished activities of the five thoracic and abdominal Hox genes. We show that elytral shortening is a staphylinid-specific property of the Hox-less appendage ground state, which is overridden in the metathorax by Ultrabithorax to promote hind wing expansion. In the exposed abdomen, we present evidence that defensive gland development stems from novel combinatorial outputs of the Abdominal-A and Abdominal-B Hox proteins: in the posterior compartment of tergite VI they specify a chemical gland reservoir, an imaginal disc-like invagination of ectodermal secretory cells; in the anterior compartment of tergite VII Abdominal-A and Abdominal-B specify clusters of classical duct-bearing glands. These distinct gland cell types collectively synthesize a blend of benzoquinone irritants, surfactant esters and alkane solvent, a defensive chemistry, which in symbiotic species has been augmented with specialized volatiles that potently manipulate ant behavior. These results reveal how Hox-controlled body axis modifications caused a convergent trend towards evolving symbiosis in the Metazoa

Evolutionary dynamics of the most populated genotype on rugged fitness landscapes

We consider an asexual population evolving on rugged fitness landscapes which are defined on the multi-dimensional genotypic space and have many local optima. We track the most populated genotype as it changes when the population jumps from a fitness peak to a better one during the process of adaptation. This is done using the dynamics of the shell model which is a simplified version of the quasispecies model for infinite populations and standard Wright-Fisher dynamics for large finite populations. We show that the population fraction of a genotype obtained within the quasispecies model and the shell model match for fit genotypes and at short times, but the dynamics of the two models are identical for questions related to the most populated genotype. We calculate exactly several properties of the jumps in infinite populations some of which were obtained numerically in previous works. We also present our preliminary simulation results for finite populations. In particular, we measure the jump distribution in time and find that it decays as $t^{-2}$ as in the quasispecies problem.Comment: Minor changes. To appear in Phys Rev

Hierarchy Theory of Evolution and the Extended Evolutionary Synthesis: Some Epistemic Bridges, Some Conceptual Rifts

Contemporary evolutionary biology comprises a plural landscape of multiple co-existent conceptual frameworks and strenuous voices that disagree on the nature and scope of evolutionary theory. Since the mid-eighties, some of these conceptual frameworks have denounced the ontologies of the Modern Synthesis and of the updated Standard Theory of Evolution as unfinished or even flawed. In this paper, we analyze and compare two of those conceptual frameworks, namely Niles Eldredge’s Hierarchy Theory of Evolution (with its extended ontology of evolutionary entities) and the Extended Evolutionary Synthesis (with its proposal of an extended ontology of evolutionary processes), in an attempt to map some epistemic bridges (e.g. compatible views of causation; niche construction) and some conceptual rifts (e.g. extra-genetic inheritance; different perspectives on macroevolution; contrasting standpoints held in the “externalism–internalism” debate) that exist between them. This paper seeks to encourage theoretical, philosophical and historiographical discussions about pluralism or the possible unification of contemporary evolutionary biology

Effect of Pivot Point on Aerodynamic Force and Vortical Structure of Pitching Flat Plate Wings

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106512/1/AIAA2013-792.pd

Self-Organized Criticality Driven by Deterministic Rules

We have investigated the essential ingredients allowing a system to show Self Organized Criticality (SOC) in its collective behavior. Using the Bak-Sneppen model of biological evolution as our paradigm, we show that the random microscopic rules of update can be effectively substituted with a chaotic map without changing the universality class. Using periodic maps SOC is preserved, but in a different universality class, as long as the spectrum of frequencies is broad enough.Comment: 4 pages, RevTex (tar.gz), 4 eps-figures include

Self-organized criticality in deterministic systems with disorder

Using the Bak-Sneppen model of biological evolution as our paradigm, we investigate in which cases noise can be substituted with a deterministic signal without destroying Self-Organized Criticality (SOC). If the deterministic signal is chaotic the universality class is preserved; some non-universal features, such as the threshold, depend on the time correlation of the signal. We also show that, if the signal introduced is periodic, SOC is preserved but in a different universality class, as long as the spectrum of frequencies is broad enough.Comment: RevTex, 8 pages, 8 figure

Tangled Nature: A model of emergent structure and temporal mode among co-evolving agents

Understanding systems level behaviour of many interacting agents is challenging in various ways, here we'll focus on the how the interaction between components can lead to hierarchical structures with different types of dynamics, or causations, at different levels. We use the Tangled Nature model to discuss the co-evolutionary aspects connecting the microscopic level of the individual to the macroscopic systems level. At the microscopic level the individual agent may undergo evolutionary changes due to mutations of strategies. The micro-dynamics always run at a constant rate. Nevertheless, the system's level dynamics exhibit a completely different type of intermittent abrupt dynamics where major upheavals keep throwing the system between meta-stable configurations. These dramatic transitions are described by a log-Poisson time statistics. The long time effect is a collectively adapted of the ecological network. We discuss the ecological and macroevolutionary consequences of the adaptive dynamics and briefly describe work using the Tangled Nature framework to analyse problems in economics, sociology, innovation and sustainabilityComment: Invited contribution to Focus on Complexity in European Journal of Physics. 25 page, 1 figur