The Fractal Dimension of SAT Formulas

Modern SAT solvers have experienced a remarkable progress on solving industrial instances. Most of the techniques have been developed after an intensive experimental testing process. Recently, there have been some attempts to analyze the structure of these formulas in terms of complex networks, with the long-term aim of explaining the success of these SAT solving techniques, and possibly improving them. We study the fractal dimension of SAT formulas, and show that most industrial families of formulas are self-similar, with a small fractal dimension. We also show that this dimension is not affected by the addition of learnt clauses. We explore how the dimension of a formula, together with other graph properties can be used to characterize SAT instances. Finally, we give empirical evidence that these graph properties can be used in state-of-the-art portfolios.Comment: 20 pages, 11 Postscript figure

The Mental Construction of Reality in James Joyce

[Abstract] The purpose of this study is to analyse how James Joyce builds a large part of his narrative through a verbal tissue that is born from the cognitive experience, from the deep interaction between mind and environment. Beyond the psychoanalytic approach or Psychological realism, Joyce, particularly in Ulysses, displays this reading of reality in which a series of cognitive events form a narrative continuum. Reality appears before us through the perceptions of the protagonists, and that is the reason why we only access an incomplete view of reality itself. Partiality or incompleteness is a fundamental characteristic of Ulysses. However, Joyce aspires to build up a coherent and solid universe. Joyce creates a continuous reality through the semantic flow, often chaotic and blurry. Joycean language reveals the inconsistencies and instabilities of one's life, when it is impossible to transmit what cannot be apprehended completely, whether due to mental dysfunctions, hallucinations or other causes, as in Finnegans Wake. In this study, we also consider etymology as a tool that provides stability and linguistic richness to Joyce’s narrative, although subjecting it to hard transformations or mutation processes. Joyce finds great stylistic possibilities in the words used as semantic repositories that come from the past, and, with his passion for language, is able to build cognitive moments that rely on etymology. In the light of the most recent cognitive theories applied to Joyce's work, this study shows how the combination of mind, body and environment builds reality in Joyce, especially in Ulysses, overcoming traditional analyses around the inner monologue or the individual mind. Confirming previous studies, we consider that Joyce builds reality through microhistories, sketches, discursive or introspective cognitive events. However, to form a continuous substrate, that contributes to the construction of identity in Ulysses, Joyce deploys strategic frameworks, such as paternity or adultery.[Resumen] El propósito de este estudio es analizar cómo James Joyce construye una gran parte de su narrativa a través de un tejido verbal que nace de la experiencia cognitiva, de la interacción profunda entre la mente y el entorno. Más allá del enfoque psicoanalítico o del realismo psicológico, Joyce, particularmente en Ulises, muestra esta lectura de la realidad en la que una serie de eventos cognitivos forman un continuo narrativo. La realidad aparece ante nosotros a través de las percepciones de los protagonistas, y esa es la razón por la cual solo accedemos a una visión incompleta de la realidad misma. La parcialidad o incompletitud es una característica fundamental de Ulises. Sin embargo, Joyce aspira a construir un universo coherente y sólido. Joyce crea una realidad continua a través del flujo semántico, a menudo caótico y borroso. El lenguaje de Joyce revela las inconsistencias e inestabilidades de la vida, cuando es imposible transmitir lo que no puede ser aprehendido por completo, ya sea debido a disfunciones mentales, alucinaciones u otras causas, como en Finnegans Wake. En este estudio, también consideramos la etimología como una herramienta que proporciona estabilidad y riqueza lingüística a la narrativa de Joyce, aunque la somete a transformaciones difíciles o procesos de mutación. Joyce encuentra grandes posibilidades estilísticas en las palabras utilizadas como depósitos semánticos que provienen del pasado y, con su pasión por el lenguaje, es capaz de construir momentos cognitivos que dependen de la etimología. A la luz de las teorías cognitivas más recientes aplicadas al trabajo de Joyce, este estudio muestra cómo la combinación de mente, cuerpo y entorno construye la realidad en Joyce, especialmente en Ulises, superando los análisis tradicionales en torno al monólogo interior o la mente individual. Confirmando estudios previos, consideramos que Joyce construye la realidad a través de microhistorias, bocetos, eventos cognitivos discursivos o introspectivos. Pero, para formar un sustrato continuo, que contribuya a la construcción de la identidad en Ulises, Joyce despliega marcos estratégicos, como la paternidad o el adulterio

Distributed reinforcement learning in multi-agent decision systems

Proceeding of: 6th Ibero-American Conference on AI (IBERAMIA '98),Lisbon, Portugal, October 5–9, 1998Decision problems can be usually solved using systems that implement different paradigms. These systems may be integrated into a single distributed system, with the expectation of obtaining a group performance more satisfactory than individual performances. Such a distributed system is what we call a Multi Agent Decision System (MADES), a special kind of Multi Agent System, that integrates several heterogeneous autonomous decision systems (agents). A MADES must produce a single solution proposal for the problem instance it faces, despite the fact that its decision making is distributed, and every agent produces solution proposals according to its local view and to its idiosyncrasy. We present a distributed reinforcement algorithm for learning how to combine the decisions the agents make in a distributed way, into a single group decision (solution proposal).Publicad

Age and growth of four spot megrim (Lepidorhombus boscii) in northern Iberian waters corroborated by cohort tracking

Age and growth are key biological aspects for the age-structured assessment of exploited fish populations. Confirming the consistency of fish age interpretation by validation/corroboration studies is essential for providing accurate age estimates to the stock assessment process. The Atlantic Iberian stock of four-spot-megrim (Lepidorhombus boscii), an important exploited demersal fish, is annually assessed by age-structured models in ICES, and specimens are routinely aged by IEO expert readers for this purpose. A total of 11,741 otoliths of this stock were aged from 23 annual groundfish surveys carried out in Cantabrian Sea and Galician waters (ICES Div. VIIIc, IXa) and following internationally standardized protocols. Annual age-length-keys were built using the respective age estimates and applied to the length distribution of each survey, thus obtaining a matrix of abundance indices by age and year. Similar mean lengths are obtained for each age group along most of the time-series. The von Bertalanffy growth parameters for the time-series are estimated (L∞: 49.0; k: 0.13; t0: 1.13) and the results are compared with previous studies. The annual growth pattern estimated for L. boscii is here corroborated by tracking cohort abundance indices in the surveys. The current otolith age estimation criterion used and the resulting age estimates obtained by the age readers can be considered valid. Strong and weak cohorts are well tracked along most of their age classes, and the correlations between age abundance indices are statistically significant up to the age 6, which represent around 95% of the total number of this species caught in the surveys. The findings here presented on the age of L. boscii and its corroboration can help to reduce the uncertainty in the estimation of its demographic structure and hence, ultimately, it will be important for a better understanding of its relevance in the functioning of the benthic community of the shelf.Versión del edito

Análisis de las lesiones más frecuentes en pruebas de velocidad, medio fondo y fondo

El propósito de este trabajo fue el de revisar y analizar la tipología de las lesiones más frecuentes derivadas de la práctica del atletismo, en sus modalidades de carrera de velocidad, medio-fondo y fondo, y que podían ocurrir durante su práctica continuada. Los datos de este trabajo se extrajeron de un estudio descriptivo transversal, realizado por muestreo aleatorio simple en Galicia durante el año 2002, sobre un total de 135 atletas. Los instrumentos de recogida de datos fueron: cuestionario formado por 30 ítems y entrevista personal. La duración de la recogida de datos fue de 5 meses. Del análisis de los datos, se identificaron las lesiones más frecuentes, a la vez que se analizaron sus posibles causas y factores de riesgo. Como conclusión del trabajo se propone un plan de prevención, relacionado con aquellas lesiones más frecuentes, detectadas en el estudio

La tercera revolución : comunicación, tecnología y su nomenclatura en inglés

[Resumen] La informacion es, hoy en dia, un elemento esencial en la toma de decisiones por parte de los grupos de poder. Las tecnologias que la hacen posible forman un conglomerado de conceptos y de terminos, la mayoria de ellos originalmente en ingles. Aunque lo verdaderamente significativo de las nuevas tecnologias es que se hallan siempre en constante evolucion. En los inicios del siglo XXI, en los que nos encontramos, resulta evidente que estamos inmersos en una tercera revolucion: la de la tecnologia de la comunicacion y la de Internet. Y todos sabemos que el conocimiento de esta tecnologia resulta irrenunciable, no solo en el puesto de trabajo, sino en el ocio, en la calle y en el hogar. A lo largo del texto, descubriremos el cumulo de conceptos y terminos que conforman el universo de las tecnologias de la informacion y de la comunicacion (TICs). Tanto los mas elementales como los mas complejos. Asi, el lector podra recorrer desde los componentes fisicos del propio ordenador, junto con el sistema operativo, el software de produccion, las redes de comunicacion, Internet, los sistemas de informacion, la produccion del propio software, etc., hasta las consideraciones eticas derivadas de todo el proceso de cambio que conlleva la revolucion actual, ademas de un analisis de las principales salidas laborales derivadas de las TICs. Pero el libro quiere ir mas alla, como se manifiesta desde el primer capitulo, La era tecnologica. Quiere analizar el enorme impacto de Internet y de la realidad virtual en nuestras vidas, aventurar el futuro que nos espera a la luz de los ultimos avances tecnologicos y, en suma, profundizar en los cambios drasticos que nuestra sociedad y nuestros modos de vida experimentaran en los proximos años. Cambios que, de hecho, estamos experimentando ya

A Distributed Solution to the PTE Problem

Proceeding of: AAAI Spring Symposium on Predictive Toxicology, AAAI Press, Stanford, March 1999A wide panoply of machine learning methods is available for application to the Predictive Toxicology Evaluation (PTE) problem. The authors have built four monolithic classification systems based on Tilde, Progol, C4.5 and naive bayesian classification. These systems have been trained using the PTE dataset, and their accuracy has been tested using the unseen PTE1 data set as test set. A Multi Agent Decision System (MADES) has been built using the aforementioned monolithic systems to build classification agents. The MADES was trained and tested with the same data sets used with the monolithic systems. Results show that the accuracy of the MADES improves the accuracies obtained by the monolithic systems. We believe that in most real world domains the combination of several approaches is stronger than the individuals. Introduction The Predictive Toxicology Evaluation (PTE) Challenge (Srinivasan et al. 1997) was devised by the Oxford University Computing Laboratory to test the suitability ...Publicad

HSPG Modification by the Secreted Enzyme Notum Shapes the Wingless Morphogen Gradient

AbstractThe secreted signaling protein Wingless acts as a morphogen to pattern the imaginal discs of Drosophila. Here we report identification of a secreted repressor of Wingless activity, which we call Notum. Loss of Notum function leads to increased Wingless activity by altering the shape of the Wingless protein gradient. When overexpressed, Notum blocks Wingless activity. Notum encodes a member of the α/β-hydrolase superfamily, with similarity to pectin acetylesterases. We present evidence that Notum influences Wingless protein distribution by modifying the heparan sulfate proteoglycans Dally-like and Dally. High levels of Wingless signaling induce Notum expression. Thus, Wingless contributes to shaping its own gradient by regulating expression of a protein that modifies its interaction with cell surface proteoglycans

Nuevos retos moleculares en la conservación animal

The contribution of genetics to wildlife conservation has been stressed often forgetting the existing theoretical and empirical limitations in the use of genetic information to solve ecological and demographic problems. The possibilities of molecular analyses are extensive and the automation of procedures is increasing the efficiency and reducing the cost of molecular technology. With large amounts of molecular data already available, the interest is switching towards the analysis of these data and the interpretation of genetic variability within and across species from a functional perspective. The understanding of the link between genetic variation and fitness or survival is essential in conservation biology and this understanding needs the combination of molecular data with non–molecular (e.g. physiological, behavioural and ecological) data. Progress in this promising field will depend on the trust and collaboration between molecular and field biologists.La contribución de la genética a la conservación de la vida salvaje ha sido enfatizada, olvidándose a menudo que existen limitaciones teóricas y empíricas sobre el uso de la información genética para solucionar problemas ecológicos y demográficos. Los análisis moleculares ofrecen numerosas posibilidades y la automatización de los procesos está incrementando la eficiencia y reduciendo los costes de la tecnología molecular. Con grandes cantidades de datos moleculares ya disponibles, el interés se está desplazando hacia el análisis de dichos datos y la interpretación de la variabilidad genética intraespecífica e interespecífica desde una perspectiva funcional. La comprensión del vínculo entre variabilidad genética y eficacia biológica o supervivencia es esencial en la biología de la conservación, requiriendo esta comprensión la combinación de datos moleculares con datos no moleculares (por ejemplo fisiológicos, de comportamiento y ecológicos). El progreso en este campo tan prometedor debe basarse en la confianza y la colaboración entre biólogos moleculares y de campo