979 research outputs found
Ecological models of the maintenance of sexual reproduction
No full textA generic model of the interaction between sexual and asexual morphs in an ecological context was developed from the lotka-Volterra model of the population dynamics of two competing species (Doncaster, Pound & Cox, 2000). This revealed the threshold difference between the resource niches of sexual and asexual populations that allows coexistence between the two morphs. Coexistence depended on the respective carrying capacities of the sexual and asexual competitors, which we showed to be contingent upon the intrinsic growth capacity of the sexual population. The analytical model was extended to study (a) competition between a sexual population and numerous asexual clones; (b) competition between two metapopulation. A special formulation of Slatkin’s (1974) three-dimensional model of two competing metapopulations was developed with Lotka-Volterra dynamics, which yielded novel predictions for the behaviour of local and regional communities of species.Coexistence between sexual and asexual morphs maybe unsustainable due to the accumulation of clonal diversity over time, and indeed coexistence is rarely observed in nature. To study the dynamics of this accumulation, a stochastic model was developed for competition between asexual clones and a genetically diverse sexual population that exploits a range of resource niches. A model of the accumulation of deleterious mutations over time was incorporated into this framework. Monte-Carlo simulations demonstrated that a sexual population may, over time, exclude asexual clones whose fitness deteriorates due to the accumulation of deleterious mutations. These results suggest that whilst coexistence between sexual and asexual morphs is possible over ecological timescales the long-term outcome of an asexual invasion is determined by: 1) The relationship between genetic variation and niche breadth in the sexual population. 2) The rate as which the relative fitness of the asexual population declines with mutation accumulation. Reciprocal scenarios of the invasion of an asexual population by sexual mutants and sexual colonists are also considered
Grid middleware for engineering design search and optimisation.
No full textDesign search and optimisation algorithms can be used by engineers to yield improved designs. Design search involving the analysis of the aerodynamic properties of a design, using Computational Fluid Dynamics, is both computationally and data intensive, making this problem well matched to Grid computing. Evaluation of the quality of a design (the objective function) may require commercial and user supplied software packages to be called in sequence, data transferred to and from suitable compute resources, in addition to pre- and post-processing. To allow engineers to express these necessarily complex workflows we expose a suite of Grid-enabled tools to a high-level scripting language. These tools include client functionality to Globus compute resources, and to a job submission Web service which exposes a cycle-scavenging Condor pool. These tools are exposed as functions to the Matlab environment that can be used directly by the engineer, or integrated into higher level functions for design search and optimisation. Here the benefits of the scripting approach are discussed, together with details of the Grid middleware used and the implementation of the client functionality
Ezra Pound and the rhetoric of science, 1901-1922
No full textThis thesis identifies science as Ezra Pound’s first extended extra-poetic interest.
This reference to science in Pound’s poetic theory and poetry is portrayed as rhetoric, with
its emphasis on the linguistic signifier or word rather than the actual concepts and data of
science. The material covers over two decades between 1901, when Pound entered
university, and 1922, after he left London. Beginning with Pound’s exposure to philology,
the thesis establishes a correlation between his educational background and his use of
scientific rhetoric in his prose. As he attempted to establish a professional status for the
poet, he used metaphors linking literature to the natural sciences and comparisons between
the poet and the scientist. Additionally, Pound attempted to organize poetic movements that
resembled the professional scientific organizations that were beginning to form in America.
In his writings promoting these movements, Pound developed a hygienic theory of poetry—
itself an extensive rhetorical project—which produced a clean, bare poem and further linked
Pound’s poetic output with the sciences. Beyond his rhetorical use of science, Pound
attempted to study the sciences and even adopted a doctor persona for his friends with
illnesses—both diagnosing and prescribing cures. When Pound was planning to leave
London, he also considered entering medical school—a biographical fact to which Pound
scholarship has paid little attention. His decision not to formally study the sciences
reinforced his identity as a poet and his representations of scientific knowledge as mere
rhetoric. This interest in the sciences, and medicine in particular, influenced Pound’s poetry
and prose because of their frequent references and their alignment with literature.
Additionally, this early use of rhetoric and an exploration into extra-poetic materials
prepares Pound for his later, better-known and often infamous explorations of economics
and social theory
The accumulation of deleterious mutations within the frozen niche variation hypothesis
No full textThe frozen niche variation hypothesis proposes that asexual clones exploit a fraction of a total resource niche available to the sexual population from which they arise. Differences in niche breadth may allow a period of coexistence between a sexual population and the faster reproducing asexual clones. Here, we model the longer term threat to the persistence of the sexual population from an accumulation of clonal diversity, balanced by the cost to the asexual population resulting from a faster rate of accumulation of deleterious mutations. We use Monte-Carlo simulations to quantify the interaction of niche breadth with accumulating deleterious mutations. These two mechanisms may act synergistically to prevent the extinction of the sexual population, given: (1) sufficient genetic variation, and consequently niche breadth, in the sexual population; (2) a relatively slow rate of accumulation of genetic diversity in the clonal population; (3) synergistic epistasis in the accumulation of deleterious mutations
Tuning GENIE earth system model components using a Grid enabled data management system
No full textWe present the Grid enabled data management system that has been deployed for the GENIE project and demonstrate its use in tuning studies of an Earth system model. A Matlab client to the
system provides a common environment for the project Virtual Organization to share scripts, binaries and output data. By using tools available in the Geodise toolkits we have scripted the execution of tuning studies which exploit multiple heterogeneous computational resources and use the database repository to steer computation using multi-dimensional optimisation methods
Matlab functions provide client functionality to the Grid
No full textSeveral toolboxes have been developed by the Geodise project to enable engineers to perform Grid-enabled design search and optimisation from the Matlab technical computing environment. The toolboxes provide a suite of Matlab functions that facilitate the composition of scripts to automate the evaluation of engineering designs by design search and optimisation tools. The generic functionality provided by these toolboxes includes access to compute resources, data management, file transfer, and certificate management tools. The functions provide a simple interface that is intuitive to users familiar with the Matlab environment. In addition we provide higher-level composite functions that build upon the core functions to perform problem specific tasks. By integrating Grid client functionality into Problem Solving Environments used day-to-day by engineers we are lowering the barriers to entry for professionals wishing to exploit Grid technologie
User deployment of grid toolkits to engineers
No full textRecently a full-scale deployment of the Geodise toolboxes has been performed in the Computational Engineering and Design Centre, University of Southampton. This deployment included the following steps: installation of required software components such as Globus, Condor, Oracle, and Webspere Application Server; installation of Geodise tools; configuring available software packages; training researchers via documents and workshops; and administering the whole infrastructure. In this paper we present our hands-on experience from deploying the toolboxes along with the challenges that may arise while Grid-enabling an existing computational cluster of an organisation. A special emphasis will be given to problems and proposed solutions of accessing COndor pools across a NAT firewall using the existing Grid infrastructure
GeodiseLab: making the grid usable
No full textThe GeodiseLab project is supported by the OMII managed programme to extend and improve the Geodise toolboxes which provide Grid client functionality to Problem Solving Environments (PSEs) used by engineers and scientists. The three key areas of development in the Geodise toolboxes have been: extending the functionality of the toolboxes, supporting additional environments, and hardening the toolboxes for public release. The Geodise computational toolboxes now support additional Grid technologies, including Condor and the OMII_1 platform. Recent enhancements to the Geodise Database and XML Toolbox are described. The Jython scripting environment is now supported in addition to the Matlab technical computing environment. We also discuss the software engineering process used to harden the toolboxes for public release, and the usability issues highlighted by feedback from users. Finally, a new application of the Geodise toolboxes in the domain of Electric Impedance Tomography is presented
A grid-enabled problem solving environment (PSE) for design optimisation within matlab
No full textThe process of design search and optimisation using Computational Fluid Dynamics (CFD) is computationally and data intensive, a problem well-suited to Grid computing. The Geodise toolkit is a suite of Grid-enabled design optimisation and search tools within the Matlab environment. The use of these tools by the engineer is facilitated by intelligent design advisers targeted initially at CFD. The role of remote computation and data access in constructing a Grid-enabled Problem Solving Environment is discussed. The use of the Geodise toolkit for design optimisation from within the Matlab environment is considered with an exemplar problem
Multiobjective tuning of Grid-enabled Earth System Models using a Non-dominated Sorting Genetic Algorithm (NSGA-II)
No full textThe tuning of parameters in climate models is essential to provide reliable long-term forecasts of Earth system behaviour. In this paper we present the first application of the multiobjective non-dominated sorting genetic algorithm (NSGA-II) to the GENIE-1 Earth System Model (ESM). Twelve model parameters are tuned to improve four objective measures of fitness to observational data. Grid computing and data handling technology is harnessed to perform the concurrent simulations that comprise the generations of the genetic algorithm. Recent advances in the method exploit Response Surface Modelling to provide surrogate models of each objective. This enables more extensive and efficient searching of the design space. We assess the performance of the NSGA-II using surrogates by repeating a tuning exercise that has been performed using a proximal analytical centre plane cutting method and the Ensemble Kalman Filter on the GENIE-1 model. We find that the multiobjective algorithm locates Pareto-optimal solutions which are of comparable quality to those obtained using the single objective optimisation methods
- …
