On the choosability of claw-free perfect graphs

It has been conjectured that for every claw-free graph $G$ the choice number of $G$ is equal to its chromatic number. We focus on the special case of this conjecture where $G$ is perfect. Claw-free perfect graphs can be decomposed via clique-cutset into two special classes called elementary graphs and peculiar graphs. Based on this decomposition we prove that the conjecture holds true for every claw-free perfect graph with maximum clique size at most $4$

Disproving the normal graph conjecture

A graph $G$ is called normal if there exist two coverings, $\mathbb{C}$ and $\mathbb{S}$ of its vertex set such that every member of $\mathbb{C}$ induces a clique in $G$, every member of $\mathbb{S}$ induces an independent set in $G$ and $C \cap S \neq \emptyset$ for every $C \in \mathbb{C}$ and $S \in \mathbb{S}$. It has been conjectured by De Simone and K\"orner in 1999 that a graph $G$ is normal if $G$ does not contain $C_5$, $C_7$ and $\overline{C_7}$ as an induced subgraph. We disprove this conjecture

Average Deactivation Time of theHeterogeneous Reaction2 A+B2→2AB

In the present paper we exactly solve the distributed parameter stochastic modelof the heterogeneous catalytic reaction2A+B2→2ABand calculate the averagenumber of reactive steps necessary to deactivate the lattice first,. Resultsare compared with Monte Carlo simulations.shows a nonmonotonic behaviorwith the sticking coefficient probabilitysand the desorption probabilitypd, reachinga maximum value that depends ons,pdand the lattice sizeNFil: Pastor, Veronica Estela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Dammig Quiña, Pablo Leandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Salvatierra, Lucas Matías. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina. Pont. Universidad Catolica Arg."sta.maria de Los Bs.as.". Facultad de Química E Ingeniería-rosario; ArgentinaFil: Irurzun, Isabel Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Mola, Eduardo Elías. Pont. Universidad Catolica Arg."sta.maria de Los Bs.as.". Facultad de Química E Ingeniería-rosario; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentin

Jamming transition in air transportation networks

In this work we present a model of an air transportation traffic system from the complex network modelling viewpoint. In the network, every node corresponds to a given airport, and two nodes are connected by means of flight routes. Each node is weighted according to its load capacity, and links are weighted according to the Euclidean distance that separates each pair of nodes. Local rules describing the behavior of individual nodes in terms of the surrounding flow have been also modelled, and a random network topology has been chosen in a baseline approach. Numerical simulations describing the diffusion of a given number of agents (aircraft) in this network show the onset of a jamming transition that distinguishes an efficient regime with null amount of airport queues and high diffusivity (free phase) and a regime where bottlenecks suddenly take place, leading to a poor aircraft diffusion (congested phase). Fluctuations are maximal around the congestion threshold, suggesting that the transition is critical. We then proceed by exploring the robustness of our results in neutral random topologies by embedding the model in heterogeneous networks. Specifically, we make use of the European air transportation network formed by 858 airports and 11170 flight routes connecting them, which we show to be scale-free. The jamming transition is also observed in this case. These results and methodologies may introduce relevant decision making procedures in order to optimize the air transportation traffic

Estudio e implementación de un sistema de pick and place de piezas en cinta transportadora usando visión por computador y robots industriales

El trabajo consiste en desarrollar una aplicación completa con dos robots para poder testear la mayor cantidad posible de las funcionalidades de éstos en un caso práctico. Por un lado, tendremos una estación en la que llegarán piezas por una cinta transportadora y que se identificarán empleando visión artificial. Una vez identificadas, las piezas serán recogidas por un robot y depositadas en otra cinta de salida. Dicha cinta será la entrada de la otra estación, en la que las piezas serán detectadas por un sensor fotoeléctrico, que se activará cada vez que pase una pieza por debajo. Esta señal se mapeará a otro robot que recogerá dicha pieza y la colocará en la cinta de entrada del robot que emplea visión para la detección. Esta pieza no se colocará siempre en la misma posición, sino que se generará un número aleatorio para decidir su coordenada horizonta

Efficient enumeration of maximal split subgraphs and sub-cographs and related classes

In this paper, we are interested in algorithms that take in input an arbitrary graph $G$, and that enumerate in output all the (inclusion-wise) maximal "subgraphs" of $G$ which fulfil a given property $\Pi$. All over this paper, we study several different properties $\Pi$, and the notion of subgraph under consideration (induced or not) will vary from a result to another. More precisely, we present efficient algorithms to list all maximal split subgraphs, sub-cographs and some subclasses of cographs of a given input graph. All the algorithms presented here run in polynomial delay, and moreover for split graphs it only requires polynomial space. In order to develop an algorithm for maximal split (edge-)subgraphs, we establish a bijection between the maximal split subgraphs and the maximal independent sets of an auxiliary graph. For cographs and some subclasses , the algorithms rely on a framework recently introduced by Conte & Uno called Proximity Search. Finally we consider the extension problem, which consists in deciding if there exists a maximal induced subgraph satisfying a property $\Pi$ that contains a set of prescribed vertices and that avoids another set of vertices. We show that this problem is NP-complete for every "interesting" hereditary property $\Pi$. We extend the hardness result to some specific edge version of the extension problem

A Model for Evaluating Soil Vulnerability to Erosion Using Remote Sensing Data and A Fuzzy Logic System

Soil vulnerability is the capacity of one or more of the ecological functions of the soil system to be harmed. It is a complex concept which requires the identification of multiple environmental factors and land management at different temporal and space scales. The employment of geospatial information with good update capabilities could be a satisfactory tool to assess potential soil vulnerability changes in large areas. This chapter presents the application of two land degradation case studies which is simple, synoptic, and suitable for continuous monitoring model based on the fuzzy logic. The model combines topography and vegetation status information to assess soil vulnerability to land degradation. Topographic parameters were obtained from digital elevation models (DEM), and vegetation status information was derived from the computation of the normalized difference vegetation index (NDVI) satellite images. This spectral index provides relevance and is updated for each scene, evidences about the biomass and soil productivity, and vegetation density cover or vegetation stress (e.g., forest fires, droughts). Modeled output maps are suitable for temporal change analysis, which allows the identification of the effect of land management practices, soil and vegetation regeneration, or climate effects

Correlatos psicofisiológicos periféricos de regulación emocional

II Jornadas de investigación para los estudiantes de la Facultad de Ciencias de la SaludIntroducción: La regulación emocional puede definirse como la capacidad para influir sobre qué emociones tenemos, cuándo las tenemos y cómo las experimentamos y expresamos. La mayoría de estudios se han centrado en la reevaluación cognitiva, básicamente utilizando medidas centrales (fmri o erp). Sin embargo, pocos trabajos se han interesado por los correlatos psicofisiológicos periféricos de estos procesos (por ejemplo, reflejo de sobresalto, actividad electrodérmica o variabilidad cardíaca). Método: Tomando como grupo de referencia a la población adulta, en este trabajo se realiza una revisión sistemática de estudios recientes que, utilizando metodologías diversas, aportan evidencia empírica acerca de distintos correlatos psicofisiológicos de regulación emocional. Resultados: El análisis de la literatura experimental permite observar una clara modulación del reflejo de sobresalto, en función de las instruccio- nes de la tarea (i.e., aumento o disminución de emociones negativas o positivas). De manera similar, la conductancia de la piel y la variabilidad cardíaca varían dependien- do del contenido específico y de las instrucciones de la tarea. Conclusión: Estos re- sultados sugieren que los correlatos psicofisiológicos periféricos son un índice fiable de regulación voluntaria del afecto, mostrando cómo ciertas estrategias (como la ree- valuación cognitiva) pueden modular las respuestas fisiológicas.Introduction: Emotional regulation is defined as the ability to influence what emotions we have, when we have them, and how we experience and express them. One of the most investigated strategies of emotional regulation is cognitiva reappraisal, basically using brain measures (fMRI or ERP). However, only a few studies have focused on peripheral psychophysiological correlates of these processes (e.g., startle reftex, electrodermal acivity or cardiac variability). Method: Here, we systematically review recent research focused on heallhy adult population that using diverse methodologies provide empirical evidence regarding different psychophysiological correlates of emotional regulatlon. Results: Results show that startle blink responses are modulated depending on the picture category and task instructions (i.e., increase or decrease of negative and positive emotions). Similarly, skin conductance and heart rate variability differ dependlng on the speclflc content and task instructions. Conclusion: These results suggest that peripheral psychophysiological correlates are a reliable index of voluntary regulation of affect, showing how certain strategies (such as cognitive reappraisal) can modulate physiological responses