Electromagnetic two-body problem: recurrent dynamics in the presence of state-dependent delay

We study the electromagnetic two-body problem of classical electrodynamics as a prototype dynamical system with state-dependent delays. The equations of motion are analysed with reference to motion along a straight line in the presence of an electrostatic field. We consider the general electromagnetic equations of motion for point charges with advanced and retarded interactions and study two limits, (a) retarded-only interactions (Dirac electrodynamics) and (b) half-retarded plus half-advanced interactions (Wheeler-Feynman electrodynamics). A fixed point is created where the electrostatic field balances the Coulombian attraction, and we use local analysis near this fixed point to derive necessary conditions for a Hopf bifurcation. In case (a), we study a Hopf bifurcation about an unphysical fixed point and find that it is subcritical. In case (b), there is a Hopf bifurcation about a physical fixed point and we study several families of periodic orbits near this point. The bifurcating periodic orbits are illustrated and simulated numerically, by introducing a surrogate dynamical system into the numerical analysis which transforms future data into past data by exploiting the periodicity, thus obtaining systems with only delays

Is there an integrative center in the vertebrate brain-stem? A robotic evaluation of a model of the reticular formation viewed as an action selection device

Neurobehavioral data from intact, decerebrate, and neonatal rats, suggests that the reticular formation provides a brainstem substrate for action selection in the vertebrate central nervous system. In this article, Kilmer, McCulloch and Blum’s (1969, 1997) landmark reticular formation model is described and re-evaluated, both in simulation and, for the first time, as a mobile robot controller. Particular model configurations are found to provide effective action selection mechanisms in a robot survival task using either simulated or physical robots. The model’s competence is dependent on the organization of afferents from model sensory systems, and a genetic algorithm search identified a class of afferent configurations which have long survival times. The results support our proposal that the reticular formation evolved to provide effective arbitration between innate behaviors and, with the forebrain basal ganglia, may constitute the integrative, ’centrencephalic’ core of vertebrate brain architecture. Additionally, the results demonstrate that the Kilmer et al. model provides an alternative form of robot controller to those usually considered in the adaptive behavior literature

Technical Integration of Hippocampus, Basal Ganglia and Physical Models for Spatial Navigation

Computational neuroscience is increasingly moving beyond modeling individual neurons or neural systems to consider the integration of multiple models, often constructed by different research groups. We report on our preliminary technical integration of recent hippocampal formation, basal ganglia and physical environment models, together with visualisation tools, as a case study in the use of Python across the modelling tool-chain. We do not present new modeling results here. The architecture incorporates leaky-integrator and rate-coded neurons, a 3D environment with collision detection and tactile sensors, 3D graphics and 2D plots. We found Python to be a flexible platform, offering a significant reduction in development time, without a corresponding significant increase in execution time. We illustrate this by implementing a part of the model in various alternative languages and coding styles, and comparing their execution times. For very large-scale system integration, communication with other languages and parallel execution may be required, which we demonstrate using the BRAHMS framework's Python bindings

BRAHMS: Novel middleware for integrated systems computation

Biological computational modellers are becoming increasingly interested in building large, eclectic models, including components on many different computational substrates, both biological and non-biological. At the same time, the rise of the philosophy of embodied modelling is generating a need to deploy biological models as controllers for robots in real-world environments. Finally, robotics engineers are beginning to find value in seconding biomimetic control strategies for use on practical robots. Together with the ubiquitous desire to make good on past software development effort, these trends are throwing up new challenges of intellectual and technological integration (for example across scales, across disciplines, and even across time) - challenges that are unmet by existing software frameworks. Here, we outline these challenges in detail, and go on to describe a newly developed software framework, BRAHMS. that meets them. BRAHMS is a tool for integrating computational process modules into a viable, computable system: its generality and flexibility facilitate integration across barriers, such as those described above, in a coherent and effective way. We go on to describe several cases where BRAHMS has been successfully deployed in practical situations. We also show excellent performance in comparison with a monolithic development approach. Additional benefits of developing in the framework include source code self-documentation, automatic coarse-grained parallelisation, cross-language integration, data logging, performance monitoring, and will include dynamic load-balancing and 'pause and continue' execution. BRAHMS is built on the nascent, and similarly general purpose, model markup language, SystemML. This will, in future, also facilitate repeatability and accountability (same answers ten years from now), transparent automatic software distribution, and interfacing with other SystemML tools. (C) 2009 Elsevier Ltd. All rights reserved

Whiteness and loss in outer East London: tracing the collective memories of diaspora space

This paper explores collective memory in Newham, East London. It addresses how remembering East London as the home of whiteness and traditional forms of community entails powerful forms of forgetting. Newham's formation through migration – its ‘great time’ – has ensured that myths of indigeneity and whiteness have never stood still. Through engaging with young people's and youth workers' memory practices, the paper explores how phantasms of whiteness and class loss are traced over, and how this tracing reveals ambivalence and porosity, at the same time as it highlights the continued allure of race. It explores how whiteness and class loss are appropriated across ethnic boundaries and how they are mobilized to produce new forms of racial hierarchy in a ‘super-diverse’ place

Effects of antiplatelet therapy on stroke risk by brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases: subgroup analyses of the RESTART randomised, open-label trial

Background Findings from the RESTART trial suggest that starting antiplatelet therapy might reduce the risk of recurrent symptomatic intracerebral haemorrhage compared with avoiding antiplatelet therapy. Brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases (such as cerebral microbleeds) are associated with greater risks of recurrent intracerebral haemorrhage. We did subgroup analyses of the RESTART trial to explore whether these brain imaging features modify the effects of antiplatelet therapy

Crop Updates 2008 - Lupins, Pulses and Oilseeds

This session covers twenty six papers from different authors: Regional Roundup 1. SOUTH EAST AGRICULTURAL REGION, Mark Seymour Department of Agriculture and Food, and Robert Johnson CBH Group, Esperance 2. CENTRAL AGRICULTURAL REGION, Ian Pritchard, Department of Agriculture and Food 3. GREAT SOUTHERN AND LAKES REGION, Raj Malik, Department of Agriculture and Food 4. NORTHERN AGRICULTURAL REGION, Wayne Parker and Martin Harries, Department of Agriculture and Food LUPINS 5. Cropping lupins in wide rows in Western Australia, Martin Harries and Bob French, Department of Agriculture and Food 6. The effect of sowing time and radish density on lupin yield, Martin Harries and Jo Walker, Department of Agriculture and Food 7. Lupin agronomy affects crop competitiveness with annual ryegrass, Bob French and Laurie Maiolo, Department of Agriculture and Food 8. Identification of lupin mutants with tolerance to isoxaflutole, Leigh Smith, Department of Agriculture and Food PULSES 9. Chickpea 2007 Crop Variety Testing (CVT) and National Variety Testing (NVT), Alan Harris, Rod Hunter, Tanveer Khan and Jenny Garlinge, Department of Agriculture and Food 10. Desi chickpea breeding: Evaluation of advanced lines, Tanveer Khan1, Poran Gaur2, Kadambot Siddique3, Heather Clarke4, Neil Turner4, William MacLeod4, Stuart Morgan1, Alan Harris1, 1Department of Agriculture and Food, 2International Crop Research Institute for the Semi Arid Tropics (ICRISAT); 3The University of Western Australia; 4Centre for Legumes in Mediterranean Agriculture 11. Can wide rows buffer chickpea growth against dry environments? Bob French and Wendy Vance, Department of Agriculture and Food, and School of Environmental Sciences, Murdoch University 12. Field pea 2007 Crop Variety Testing (CVT) and National Variety Testing (NVT), Alan Harris, Rod Hunter, Tanveer Khan and Jenny Garlinge, Department of Agriculture and Food 13. Australian Field Pea improvement Program (AFPIP): Evaluation of advanced breeding lines, Tanveer Khan1, Phillip Chambers1, Chris Veitch1, Stuart Morgan1, Alan Harris1, and Tony Leonforte 2, 1Department of Agriculture and Food, 2Department of Primary Industries, Victoria 14. Ability of semi-leafless field peas to recover after rolling, Mark Seymour and Rodger Beermier, Department of Agriculture and Food 15. Field pea germplasm enhancement for black spot resistance, Tanveer Khan, Stuart Morgan, Alan Harris and Phillip Chambers, Department of Agriculture and Food 16. Application of ‘Blackspot Manager’ model to identifying a low risk sowing date for field pea in South Australia and Western Australia in 2007, Moin Salam1, Jenny Davidson2, Jean Galloway1, Pip Payne2, Tess Humphries2, Bill MacLeod1 and Art Diggle1, 1Department of Agriculture and Food, 2SARDI, South Australia 17. Late post emergent herbicide sprays for field pea, Mark Seymour and Rodger Beermier, Department of Agriculture and Food 18. Adding triasulfuron to croptopping mixes does not affect the yield of field pea, Mark Seymour, Department of Agriculture and Food 18. Herbicide tolerance of field pea varieties, Harmohinder Dhammu and Mark Seymour, Department of Agriculture and Food 19. Breeding highlights of the PBA lentil program, Michael Materne1, Kerry Regan2, Chris Veitch2 and Phil Chambers2, 1Department of Primary Industries, Victoria 2Department of Agriculture and Food CANOLA 20. How late can I sow canola in 2008? Mohammad Amjad, Andy Sutherland and Pat Fels, Department of Agriculture and Food 21. Direct harvesting canola, Glen Riethmuller1, Wallace Cowling2, Milton Sanders2, Eliot Jones2 and Chris Newman1, 1Department of Agriculture and Food, Western Australia, 2Canola Breeders Western Australia Pty Ltd 22. Agronomic performance of new hybrid canola and juncea canola in low, medium and high rainfall environments of Western Australia, Mohammad Amjad, Andy Sutherland and Pat Fels, Department of Agriculture and Food 23. Comparative performance of new canola varieties in commercial-scale field trials of Oilseeds WA – 2007, Mohammad Amjad1, John Duff2 and David Sermon3 1Department of Agriculture and Food, 2Oilseeds Western Australia and John Duff & Associates, Perth; 3ConsultAg, Perth 24. The effect of rotation crops, trash retention and prophylactic sprays on arthropod abundance in a following canola crop, Svetlana Micic, Anthony Dore and Geoff Strickland, Department of Agriculture and Food OATS 25. Fungicide options for controlling disease in oats, Raj Malik and Blakely Paynter, Department of Agriculture and Food 26. Herbicide tolerance of new oat varieties, Harmohinder Dhammu, Vince Lambert and Chris Roberts, Department of Agriculture and Foo

Forced Moves or Good Tricks in Design Space? Landmarks in the Evolution of Neural Mechanisms for Action Selection

This review considers some important landmarks in animal evolution, asking to what extent specialized action-selection mechanisms play a role in the functional architecture of different nervous system plans, and looking for “forced moves” or “good tricks” (see Dennett, D., 1995, Darwin’s Dangerous Idea, Penguin Books, London) that could possibly transfer to the design of robot control systems. A key conclusion is that while cnidarians (e.g. jellyfish) appear to have discovered some good tricks for the design of behavior-based control systems—largely lacking specialized selection mechanisms—the emergence of bilaterians may have forced the evolution of a central ganglion, or “archaic brain”, whose main function is to resolve conflicts between peripheral systems. Whilst vertebrates have many interesting selection substrates it is likely that here too the evolution of centralized structures such as the medial reticular formation and the basal ganglia may have been a forced move because of the need to limit connection costs as brains increased in size