Term Graph Representations for Cyclic Lambda-Terms

We study various representations for cyclic lambda-terms as higher-order or as first-order term graphs. We focus on the relation between `lambda-higher-order term graphs' (lambda-ho-term-graphs), which are first-order term graphs endowed with a well-behaved scope function, and their representations as `lambda-term-graphs', which are plain first-order term graphs with scope-delimiter vertices that meet certain scoping requirements. Specifically we tackle the question: Which class of first-order term graphs admits a faithful embedding of lambda-ho-term-graphs in the sense that: (i) the homomorphism-based sharing-order on lambda-ho-term-graphs is preserved and reflected, and (ii) the image of the embedding corresponds closely to a natural class (of lambda-term-graphs) that is closed under homomorphism? We systematically examine whether a number of classes of lambda-term-graphs have this property, and we find a particular class of lambda-term-graphs that satisfies this criterion. Term graphs of this class are built from application, abstraction, variable, and scope-delimiter vertices, and have the characteristic feature that the latter two kinds of vertices have back-links to the corresponding abstraction. This result puts a handle on the concept of subterm sharing for higher-order term graphs, both theoretically and algorithmically: We obtain an easily implementable method for obtaining the maximally shared form of lambda-ho-term-graphs. Also, we open up the possibility to pull back properties from first-order term graphs to lambda-ho-term-graphs. In fact we prove this for the property of the sharing-order successors of a given term graph to be a complete lattice with respect to the sharing order. This report extends the paper with the same title (http://arxiv.org/abs/1302.6338v1) in the proceedings of the workshop TERMGRAPH 2013.Comment: 35 pages. report extending proceedings article on arXiv:1302.6338 (changes with respect to version v2: added section 8, modified Proposition 2.4, added Remark 2.5, added Corollary 7.11, modified figures in the conclusion

Analysis of domestic tourism between the Spanish peninsular autonomous communities: specialization and competitive advantage

This paper presents an implementation of shift share analysis ofnational tourism between the Spanish peninsular autonomous communities withovernight stays in hotels data. Thus, it achieves a more complete interpretation ofthe available statistical information. Among other things, it allows us to know theposition which each region has in terms of specialization and competitive advantageand, hence, the potential markets for development can be identified

Polymer coated vermiculite-iron composites: Novel floatable magnetic adsorbents for water spilled contaminants

Magnetic adsorbents based on vermiculite-iron have been prepared and characterized by magnetic measurements, BET surface area, Mössbauer spectroscopy, powder X-ray diffraction, scanning electron microscopy, thermogravimetric and differential scanning calorimetric analyses. These magnetic materials show two important features for the remediation of contaminated sites: (i) they float on water and can be used to adsorb/ absorb spilled oils and (ii) after adsorption they can be easily removed from the medium by a simple magnetic separation procedure. These magnetic materials have been coated/hydrophobized with polymers such as epoxy resin and polystyrene improving their oil remotion capacity, floatability and the chemical and mechanical resistance.Fil: Machado, L. C. R.. Universidade Federal de Minas Gerais; BrasilFil: Lima, F. W. J.. Universidade Federal de Minas Gerais; BrasilFil: Paniago, R.. Universidade Federal de Minas Gerais; BrasilFil: Ardisson, J. D.. Universidade Federal de Minas Gerais; BrasilFil: Sapag, Manuel Karim. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich". Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich"; ArgentinaFil: Lago, Rochel Montero. Universidade Federal de Minas Gerais; Brasi

Simulation of networks of spiking neurons: A review of tools and strategies

We review different aspects of the simulation of spiking neural networks. We start by reviewing the different types of simulation strategies and algorithms that are currently implemented. We next review the precision of those simulation strategies, in particular in cases where plasticity depends on the exact timing of the spikes. We overview different simulators and simulation environments presently available (restricted to those freely available, open source and documented). For each simulation tool, its advantages and pitfalls are reviewed, with an aim to allow the reader to identify which simulator is appropriate for a given task. Finally, we provide a series of benchmark simulations of different types of networks of spiking neurons, including Hodgkin-Huxley type, integrate-and-fire models, interacting with current-based or conductance-based synapses, using clock-driven or event-driven integration strategies. The same set of models are implemented on the different simulators, and the codes are made available. The ultimate goal of this review is to provide a resource to facilitate identifying the appropriate integration strategy and simulation tool to use for a given modeling problem related to spiking neural networks.Comment: 49 pages, 24 figures, 1 table; review article, Journal of Computational Neuroscience, in press (2007

Discusión sobre la política de innovación y de fomento del emprendimiento en Europa

Los indicadores sobre I+D y emprendimiento en Europa muestran su desventaja respecto a otros potencias económicas. Sobre esa base, se están articulando políticas que persiguen un simple aumento de los gastos o la promoción de la innovación y el espíritu empresarial. Sin embargo, aún no está disponible el protocolo para alcanzar innovaciones exitosas. Además, habría que considerar los costes sociales en los que se incurren cuando se estimula la búsqueda de la innovación entre empresas que compiten en los mismos mercados.ABSTRACTIndicators about R & D and entrepreneurship in Europe show a disadvantage compared to other economies. On that basis, policies have been implemented in order to pursue a simple increase in expenditure or to foster innovation and entrepreneurship. However, no protocol is available to achieve successful innovations. Furthermore, we should consider the social costs when the search for innovation among firms which compete in the same markets is being encouraged