Origin of coherent structures in a discrete chaotic medium

Using as an example a large lattice of locally interacting Hindmarsh-Rose chaotic neurons, we disclose the origin of ordered structures in a discrete nonequilibrium medium with fast and slow chaotic oscillations. The origin of the ordering mechanism is related to the appearance of a periodic average dynamics in the group of chaotic neurons whose individual slow activity is significantly synchronized by the group mean field. Introducing the concept of a "coarse grain" as a cluster of neuron elements with periodic averaged behavior allows consideration of the dynamics of a medium composed of these clusters. A study of this medium reveals spatially ordered patterns in the periodic and slow dynamics of the coarse grains that are controlled by the average intensity of the fast chaotic pulsation

RP-DeLP: a weighted defeasible argumentation framework based on a recursive semantics

In this paper we first define a recursive semantics for warranted formulas in a general defeasible argumentation framework by formalizing a notion of collective (non-binary) conflict among arguments. The recursive semantics for warranted formulas is based on the fact that if the argument is rejected, then all arguments built on it should also be rejected. The main characteristic of our recursive semantics is that an output (extension) of a knowledge base is a pair of sets of warranted and blocked formulas. Arguments for both warranted and blocked formulas are recursively based on warranted formulas but, while warranted formulas do not generate any collective conflict, blocked conclusions do. Formulas that are neither warranted nor blocked correspond to rejected formulas. Second we extend the general defeasible argumentation framework by attaching levels of preference to defeasible knowledge items and by providing a level-wise definition of warranted and blocked formulas. Third we formalize the warrant recursive semantics for the particular framework of Possibilistic Defeasible Logic Programming, we call this particular framework Recursive Possibilistic Defeasible Logic Programming (\mbox{RP-DeLP} for short), and we show its relevance in the scope of Political debates. An RP-DeLP program may have multiple outputs in case of circular definitions of conflicts among arguments. So, we tackle the problem of which output one should consider for an RP-DeLP program with multiple outputs. To this end we define the maximal ideal output of an RP-DeLP program as the set of conclusions which are ultimately warranted and we present an algorithm for computing them in polynomial space and with an upper bound on complexity equal to P^{NP}. Finally, we propose an efficient and scalable implementation of this algorithm that is based on implementing the two main queries of the system, looking for valid arguments and collective conflicts between arguments, using SAT encodings. We perform an experimental evaluation of our SAT based approach when solving test sets of instances with single and multiple preference levels for defeasible knowledge.The authors are very thankful to the anonymous reviewers for their helpful and constructive comments. This research was partially supported by the Spanish projects ARINF (TIN2009- 14704-C03-01), TASSAT (TIN2010-20967-C04-03), EdeTRI (TIN2012-39348-C02-01) and AT (CONSOLIDER- INGENIO 2010, CSD2007-00022)

Formalisation and logical properties of the maximal ideal recursive semantics for weighted defeasible logic programming

Possibilistic defeasible logic programming (P-DeLP) is a logic programming framework which combines features from argumentation theory and logic programming, in which defeasible rules are attached with weights expressing their relative belief or preference strength. In P-DeLP,a conclusion succeeds if there exists an argument that entails the conclusion and this argument is found to be undefeated by a warrant procedure that systematically explores the universe of arguments in order to present an exhaustive synthesis of the relevant chains of pros and cons for the given conclusion. Recently, we have proposed a new warrant recursive semantics for P-DeLP, called Recursive P-DeLP (RP-DeLP for short), based on the claim that the acceptance of an argument should imply also the acceptance of all its sub-arguments which reflect the different premises on which the argument is based. This paper explores the relationship between the exhaustive dialectical analysis-based semantics of P-DeLP and the recursive-based semantics of RP-DeLP, and analyses a non-monotonic inference operator for RP-DeLP which models the expansion of a given program by adding new weighted facts associated with warranted conclusions. Given the recursive-based semantics of RP-DeLP, we have also implemented an argumentation framework for RP-DeLP that is able to compute not only the output of warranted and blocked conclusions, but also explain the reasons behind the status of each conclusion. We have developed this framework as a stand-alone application with a simple text-based input/output interface to be able to use it as part of other artificial intelligence systemsThis research was partially supported by the Spanish projects EdeTRI (TIN2012-39348-C02-01) and AT (CONSOLIDER- INGENIO 2010, CSD2007-00022)

Regulation of patterned dynamics of local exocytosis in growth cones by netrin-1

Axonal guidance and synaptic specification depends on specific signaling mechanisms that occur in growth cones. While several signaling pathways implicated in cone navigation have been identified, membrane dynamics in growth cones remains largely unknown. We took advantage of SynaptopHluorin and high-speed optical recordings to monitor the patterns of membrane dynamics in rat hippocampal growth cones. We show that exocytosis occurs both at the peripheral and central domains, including filopodia, and that SynaptopHluorin signals occur as spontaneous patterned peaks. Such transients average approximately two per minute and last ∼30 s. We also demonstrate that the chemoattractant Netrin-1 elicits increases in the frequency and slopes of these transients, with peaks averaging up to six per minute in the peripheral domain. Netrin-1-dependent regulation of exocytotic events requires the activation of the Erk1/2 and SFK pathways. Furthermore, we show that domains with high SynaptopHluorin signals correlate with high local calcium concentrations and that local, spontaneous calcium increases are associated with higher SynaptopHluorin signals. These findings demonstrate highly stereotyped, spontaneous transients of local exocytosis in growth cones and that these transients are positively regulated by chemoattractant molecules such as Netrin-1

Análisis biogeográfico y clave de géneros de los helechos y licofitos del Parque Nacional Mburucuyá, Corrientes, Argentina

The diversity of ferns and lycophytes of Corrientes province, Argentina is not well understood. Our field work in the Mburucuyá National Park in Corrientes province as well as a literature review fi nds 29 genera and 48 infrageneric taxa of ferns and lycophytes for this Park. A comparison of the Park's species diversity with other protected areas in northeastern Argentina using Jaccard's similarity coeffi cient and the infrageneric taxa biodiversity index proposed by Squeo et al. (1998) are analized. A key to the Park's ferns and lycophytes genera is provided.El Parque Nacional Mburucuyá, cuenta con una superficie de 176.80 km2, se encuentra en la provincia de Corrientes, Argentina, dentro de una región ecotonal entre los dominios Chaqueños y Amazónicos. En esta área se registraron 29 géneros y 48 taxones infragenéricos de helechos y liocófi tos fueron registrados. Las especies registradas son comparadas con las áreas protegidas ya estudiadas del noreste de Argentina utilizando el coeficiente de similitud de Jaccard y el índice de biodiversidad de Squeo et al. (1998) a nivel infragenérico. En este trabajo se proporciona una clave para diferenciar los géneros presentes en el Parque.Facultad de Ciencias Naturales y Muse

Análisis biogeográfico y clave de géneros de los helechos y licofitos del Parque Nacional Mburucuyá, Corrientes, Argentina

The diversity of ferns and lycophytes of Corrientes province, Argentina is not well understood. Our field work in the Mburucuyá National Park in Corrientes province as well as a literature review fi nds 29 genera and 48 infrageneric taxa of ferns and lycophytes for this Park. A comparison of the Park's species diversity with other protected areas in northeastern Argentina using Jaccard's similarity coeffi cient and the infrageneric taxa biodiversity index proposed by Squeo et al. (1998) are analized. A key to the Park's ferns and lycophytes genera is provided.El Parque Nacional Mburucuyá, cuenta con una superficie de 176.80 km2, se encuentra en la provincia de Corrientes, Argentina, dentro de una región ecotonal entre los dominios Chaqueños y Amazónicos. En esta área se registraron 29 géneros y 48 taxones infragenéricos de helechos y liocófi tos fueron registrados. Las especies registradas son comparadas con las áreas protegidas ya estudiadas del noreste de Argentina utilizando el coeficiente de similitud de Jaccard y el índice de biodiversidad de Squeo et al. (1998) a nivel infragenérico. En este trabajo se proporciona una clave para diferenciar los géneros presentes en el Parque.Facultad de Ciencias Naturales y Muse

Mechanisms of resistance in postharvest fruit-pathogen interaction

The objective of this review was to bring together concepts related to studies aimed at elucidating defense mechanisms against disease-causing agents, mainly in postharvest. Like plants, fruits are exposed to attack by pathogens that cause rot during postharvest storage, resulting in considerable losses. To control these pathogens, synthetic chemicals are used; however, since they are toxic, genetic resistance is regarded as a viable alternative. Fruits can withstand pathogens by means of physical barriers (presence of thick cuticular or trichome layers) and chemical ones, or through induced defenses that are activated once the host detects the presence of the pathogen, triggering the oxidative burst during the early hours of interaction. This burst entails the generation of reactive oxygen species (ROS), such as superoxide (O2ˉ), hydroxyl radical (OHˉ) or hydrogen peroxide (H2O2), and the activation of genes involved in several metabolic pathways. The study of such mechanisms may allow detecting disease-resistant genetic materials, thus reducing the use of toxic products.Este trabajo ha sido financiado por el gobierno español a través del proyecto AGL2011-30519-C03-03 y por el Consejo Nacional de Ciencia y Tecnología de México a través de los Fondos FOMIX-QRO-2010-C01-145514