Intrinsic adaptation in autonomous recurrent neural networks

A massively recurrent neural network responds on one side to input stimuli and is autonomously active, on the other side, in the absence of sensory inputs. Stimuli and information processing depends crucially on the qualia of the autonomous-state dynamics of the ongoing neural activity. This default neural activity may be dynamically structured in time and space, showing regular, synchronized, bursting or chaotic activity patterns. We study the influence of non-synaptic plasticity on the default dynamical state of recurrent neural networks. The non-synaptic adaption considered acts on intrinsic neural parameters, such as the threshold and the gain, and is driven by the optimization of the information entropy. We observe, in the presence of the intrinsic adaptation processes, three distinct and globally attracting dynamical regimes, a regular synchronized, an overall chaotic and an intermittent bursting regime. The intermittent bursting regime is characterized by intervals of regular flows, which are quite insensitive to external stimuli, interseeded by chaotic bursts which respond sensitively to input signals. We discuss these finding in the context of self-organized information processing and critical brain dynamics.Comment: 24 pages, 8 figure

Synthetic LISA: Simulating Time Delay Interferometry in a Model LISA

We report on three numerical experiments on the implementation of Time-Delay Interferometry (TDI) for LISA, performed with Synthetic LISA, a C++/Python package that we developed to simulate the LISA science process at the level of scientific and technical requirements. Specifically, we study the laser-noise residuals left by first-generation TDI when the LISA armlengths have a realistic time dependence; we characterize the armlength-measurements accuracies that are needed to have effective laser-noise cancellation in both first- and second-generation TDI; and we estimate the quantization and telemetry bitdepth needed for the phase measurements. Synthetic LISA generates synthetic time series of the LISA fundamental noises, as filtered through all the TDI observables; it also provides a streamlined module to compute the TDI responses to gravitational waves according to a full model of TDI, including the motion of the LISA array and the temporal and directional dependence of the armlengths. We discuss the theoretical model that underlies the simulation, its implementation, and its use in future investigations on system characterization and data-analysis prototyping for LISA.Comment: 18 pages, 14 EPS figures, REVTeX 4. Accepted PRD version. See http://www.vallis.org/syntheticlisa for information on the Synthetic LISA software packag

New risks and opportunities for food security: scenario analyses for 2015 and 2050

"Given the number of undernourished people in the developing world and the increasingly complex risks to food security, policymakers are faced with an enormous agenda. Freeing people from hunger will require more and better-targeted investments, innovations, and policy actions, driven by a keen understanding of the dynamic risks and forces that shape the factors affecting people's access to food and the links with nutrition. The International Food Policy Research Institute's (IFPRI's) International Model for Policy Analysis of Agricultural Commodities and Trade (IMPACT) provides insight into the management of these risks through appropriate policy actions. By projecting future global food scenarios to 2050, IMPACT explores the potential implications of policy action and inaction in several main risk areas as well as the effects on child malnutrition in the developing world, commodity prices, demand, cereal yields, production, and net trade. In the progressive policy actions scenario, which assumes increased investment in rural development, health, education, and agricultural research and development, developing country governments and the international community are able to dramatically reduce the number of food-insecure people, leading to a worldwide decline in hunger. Under these conditions, Latin America and China are able to virtually eliminate child malnutrition by 2050. Bolstered by the development and dissemination of improved technologies and better infrastructure, crop production and yields increase in developing countries. Notably, the bulk of the growth in production is driven by yield increases rather than by expanding land area. Spurred by growth in the agricultural sector, average incomes in developing countries increase. Rising incomes bolster demand for high-value agricultural products, such as meat, dairy, and fruits and vegetables; global livestock production more than doubles, for example. Average per capita calorie supplies for developing countries exceed 3,400 per day, well in excess of minimum requirements. The policy failure scenario assumes greater political discord and more extensive agricultural protectionism, together with the failure of policies to deal with food emergencies related to conflict. Slow growth and trade restrictions lead to stagnation in average per capita calorie availability, which remains only slightly above minimum requirements until after 2030, when availability increases. In addition, crucial investments in agriculture, rural development, and poverty reduction are forgone or displaced. Because of limited investment in agricultural research and technology, this scenario has a high level of crop area expansion as a result of relatively rapid population growth and slim yield improvements in developing countries. This scenario also results in flat maize prices, declining per capita cereal demand, falling beef prices, and relatively flat meat demand. As a result of the policies in this scenario, the number of malnourished children in developing countries rises between 1997 and 2015, after which there are only modest declines. In the technology and natural resource management failure scenario, yield growth falls even more than under the preceding scenario, forcing farmers to move into marginal producing areas, which causes a more rapid expansion of cereal area into less productive land that does not compensate for the yield shortfalls (and causes environmental degradation). As a result, cereal prices rise substantially through 2030 and then fall off only gradually. Beef and other meat prices, which are affected by the price of feed, follow a similar pattern. Developing-country per capita calorie availability is essentially unchanged over 1997–2050 and remains at a barely adequate average level. Given unequal access to the food that is available, millions of people actually consume less than the minimum. The occurrence of child undernourishment is even higher than under the policy failure scenario in all developing-country regions. Overall, the technology and natural resource management failure scenario results in the worst impact on food security and child malnourishment in the developing world. The progressive policy scenario outlines several of the most crucial positive steps. National governments and the international community must assume a new focus on agricultural growth and rural development, along with increasing their investments in education, social services, and health. Policies to encourage synergistic growth in the nonfarm sectors are also needed to spur broad-based economic growth. Underpinning these strategies and research agendas must be a firm commitment to reducing hunger and improving the welfare of the world's undernourished people." From Authors' Executive SummaryImpact model, Caloric intake, Safety nets,

Bell's Theorem from Moore's Theorem

It is shown that the restrictions of what can be inferred from classically-recorded observational outcomes that are imposed by the no-cloning theorem, the Kochen-Specker theorem and Bell's theorem also follow from restrictions on inferences from observations formulated within classical automata theory. Similarities between the assumptions underlying classical automata theory and those underlying universally-unitary quantum theory are discussed.Comment: 12 pages; to appear in Int. J. General System

Calibration and data quality of warm IRAC

We present an overview of the calibration and properties of data from the IRAC instrument aboard the Spitzer Space Telescope taken after the depletion of cryogen. The cryogen depleted on 15 May 2009, and shortly afterward a two-month- long calibration and characterization campaign was conducted. The array temperature and bias setpoints were revised on 19 September 2009 to take advantage of lower than expected power dissipation by the instrument and to improve sensitivity. The final operating temperature of the arrays is 28.7 K, the applied bias across each detector is 500 mV and the equilibrium temperature of the instrument chamber is 27.55 K. The final sensitivities are essentially the same as the cryogenic mission with the 3.6 μm array being slightly less sensitive (10%) and the 4.5 μm array within 5% of the cryogenic sensitivity. The current absolute photometric uncertainties are 4% at 3.6 and 4.5 μm, and better than milli-mag photometry is achievable for long-stare photometric observations. With continued analysis, we expect the absolute calibration to improve to the cryogenic value of 3%. Warm IRAC operations fully support all science that was conducted in the cryogenic mission and all currently planned warm science projects (including Exploration Science programs). We expect that IRAC will continue to make ground-breaking discoveries in star formation, the nature of the early universe, and in our understanding of the properties of exoplanets

Warren McCulloch and the British cyberneticians

Warren McCulloch was a significant influence on a number of British cyberneticians, as some British pioneers in this area were on him. He interacted regularly with most of the main figures on the British cybernetics scene, forming close friendships and collaborations with several, as well as mentoring others. Many of these interactions stemmed from a 1949 visit to London during which he gave the opening talk at the inaugural meeting of the Ratio Club, a gathering of brilliant, mainly young, British scientists working in areas related to cybernetics. This paper traces some of these relationships and interaction