321 research outputs found

    A Multi-Agent Systems Approach to Microeconomic Foundations of Macro

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    This paper is part of a broader project that attempts to gener- ate microfoundations for macroeconomics as an emergent property of complex systems. The multi-agents systems approach is seen to produce realistic macro properties from a primitive set of agents that search for satisfactory activities, "jobs", in an informationally constrained, computationally noisy environment. There is frictional and structural unemployment, inflation, excess capacity, fi- nancial instability along with the possibility of relatively smooth expansion. There is no Phillips curve but an inegalitarian distribution of income emerges as fundamental property of the system.Multi-agent system, agent-based models, microeconomic foundations, macroeconomics.

    KEYNESIAN AND NEOCLASSICAL CLOSURES IN AN AGENT-BASED CONTEXT

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    Since the "closure debate" of the 1980s it is well known that com- parative static derivatives in analytical macro models are highly sensitive to the closure rule selected. This led Keynesians to conclude that Keynesian closures were superior to those favored by the orthodoxy and vice-versa. It is argued that with the advent of agent-based or multi-agent systems, the clo- sure debate is superseded. While elements of both Keynesian and neoclassical models survive the transition to the more synthetic environment, an agent- based approach eliminates the need for drastic simplification that was at the root of the debate from the beginning.Agent-based models, multi-agent systems, macroeconomic closure.

    THE CURRENT MACROECONOMIC CRISIS

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    Professor Crotty once casually observed that in his view economics could not be properly thought of as a science. This paper investigates the implications of this view in light of the question of how the scientific method has recently contributed to the evolution of economic practice. It is argued that agent-based models might provide a platform for an integration of recent micro and macroeconomic theories.Agent-based models, macroeconomics, Keynes, James Crotty.

    The Structuralist Growth Model

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    This paper examines the underlying theory of structuralist growth models in an effort to compare that framework with the standard approach of Solow and others. Both the standard and structuralist models are solved in a common mathematical framework that emphasizes their similarities. It is seen that while the standard model requires the growth rate of the labor force to be taken as exogenously determined, the structuralist growth model must take investment growth to be determined exogenously in the long run. It is further seen that in order for the structuralist model to reliably converge to steady growth, considerable attention must be given to how agents make investment decisions. In many ways the standard model relies less on agency than does the structuralist. While the former requires a small number of plausible assumptions for steady growth to emerge, the structuralist model faces formidable challenges, especially if investment growth is thought to be determined by the rate of capacity utilization.

    The Leucine-Rich Amelogenin Peptide Alters the Amelogenin Null Enamel Phenotype

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    The amelogenin proteins secreted by ameloblasts during dental enamel development are required for normal enamel structure. Amelx null (KO) mice have hypoplastic, disorganized enamel similar to that of human patients with mutations in the AMELX gene, and provide a model system for studies of the enamel defect amelogenesis imperfecta. Because many amelogenin proteins are present in developing enamel due to RNA alternative splicing and proteolytic processing, understanding the function of individual amelogenins has been challenging

    Second Annual Transformative Vertical Flight Concepts Workshop: Enabling New Flight Concepts Through Novel Propulsion and Energy Architectures

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    On August 3rd and 4th, 2015, a workshop was held at the NASA Ames Research Center, located at the Moffett Federal Airfield in California to explore the aviation communities interest in Transformative Vertical Flight (TVF) Concepts. The Workshop was sponsored by the AHS International (AHS), the American Institute of Aeronautics and Astronautics (AIAA), the National Aeronautics and Space Administration (NASA), and hosted by the NASA Aeronautics Research Institute (NARI). This second annual workshop built on the success and enthusiasm generated by the first TVF Workshop held in Washington, DC in August of 2014. The previous Workshop identified the existence of a multi-disciplinary community interested in this topic and established a consensus among the participants that opportunities to establish further collaborations in this area are warranted. The desire to conduct a series of annual workshops augmented by online virtual technical seminars to strengthen the TVF community and continue planning for advocacy and collaboration was a direct outcome of the first Workshop. The second Workshop organizers focused on four desired action-oriented outcomes. The first was to establish and document common stakeholder needs and areas of potential collaborations. This includes advocacy strategies to encourage the future success of unconventional vertiport capable flight concept solutions that are enabled by emerging technologies. The second was to assemble a community that can collaborate on new conceptual design and analysis tools to permit novel configuration paths with far greater multi-disciplinary coupling (i.e., aero-propulsive-control) to be investigated. The third was to establish a community to develop and deploy regulatory guidelines. This community would have the potential to initiate formation of an American Society for Testing and Materials (ASTM) F44 Committee Subgroup for the development of consensus-based certification standards for General Aviation scale vertiport capable flight systems. These standards need to accommodate novel fixed wing concepts that do not fit within the existing Federal Aviation Administration (FAA) rotorcraft certification framework (Code of Federal Regulations, Title 14, Chapter I, Subchapter C, Part 27). The fourth desired outcome was to launch an information campaign to ensure key U.S. Government agencies understand the potential benefits and industry interest in establishing new vertiport capable flight markets. This record of the Workshop proceedings documents Workshop activities and products including summaries of the video recorded technical presentations, overviews of three breakout sessions (Missions Operational Concepts, Prioritized Technical Challenges, Regulatory Roadmap), and a preliminary draft roadmap framework for TVF

    Catching Element Formation In The Act

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    Gamma-ray astronomy explores the most energetic photons in nature to address some of the most pressing puzzles in contemporary astrophysics. It encompasses a wide range of objects and phenomena: stars, supernovae, novae, neutron stars, stellar-mass black holes, nucleosynthesis, the interstellar medium, cosmic rays and relativistic-particle acceleration, and the evolution of galaxies. MeV gamma-rays provide a unique probe of nuclear processes in astronomy, directly measuring radioactive decay, nuclear de-excitation, and positron annihilation. The substantial information carried by gamma-ray photons allows us to see deeper into these objects, the bulk of the power is often emitted at gamma-ray energies, and radioactivity provides a natural physical clock that adds unique information. New science will be driven by time-domain population studies at gamma-ray energies. This science is enabled by next-generation gamma-ray instruments with one to two orders of magnitude better sensitivity, larger sky coverage, and faster cadence than all previous gamma-ray instruments. This transformative capability permits: (a) the accurate identification of the gamma-ray emitting objects and correlations with observations taken at other wavelengths and with other messengers; (b) construction of new gamma-ray maps of the Milky Way and other nearby galaxies where extended regions are distinguished from point sources; and (c) considerable serendipitous science of scarce events -- nearby neutron star mergers, for example. Advances in technology push the performance of new gamma-ray instruments to address a wide set of astrophysical questions.Comment: 14 pages including 3 figure
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