Rational Combinatorics

We propose a categorical setting for the study of the combinatorics of rational numbers. We find combinatorial interpretation for the Bernoulli and Euler numbers and polynomials.Comment: Adv. in Appl. Math. (2007), doi:10.1016/j.aam.2006.12.00

TX Active: fotocatalisis contra la contaminación

El cemento es el material más utilizado en el sector de la construcción presente de manera continua en casi todos los espacios de nuestra vida diaria, los cuales soportan unos niveles de contaminación elevados. Aprovechando la capacidad de absorción de contaminantes orgánicos e inorgánicos de los fabricados con cemento, Italcementi ha desarrollado TX Active, principio activo con propiedades fotocatalíticas. La fotoquímica desempeña un importante papel tanto en los procesos químicos, biológicos y medioambientales. La demanda de un medio ambiente más limpio y la búsqueda de la mejora de la calidad de vida hacen que la idea de la luz con una finalidad medioambiental se haya convertido una línea de investigación muy importante. La tecnología fotoquímica aplicada a los materiales de construcción puede ser una buena solución, la intensa investigación en este campo ha sentado las bases para su amplia aplicación en varios sectores industriales. En particular, la reducción de la contaminación constituye una prometedora línea de trabajo y desarrollo, dentro de este reto, Italcementi ha desarrollado cementos fotocatalíticos capaz de responder a las preocupaciones medioambientales mediante la aplicación del principio TX Active® en los materiales de construcción, dotando a los materiales de capacidad autolimpiante y descontaminante

Elementos constitutivos del homicidio

Fil: Laplaza, Francisco P. Universidad de Buenos Aires. Facultad de Derecho. Buenos Aires, ArgentinaTemas de Derecho Penal I

The Role of Body Surface Area in Quantity Discrimination in Angelfish (Pterophyllum scalare)

Although some fish species have been shown to be able to discriminate between two groups (shoals) of conspecifics differing in the number of members, most studies have not controlled for continuous variables that covary with number. Previously, using angelfish (Pterophyllum scalare) we started the systematic analysis of the potential influence of such continuous variables, and found that they play different roles in shoal discrimination depending on whether large (≥ 4 fish) or small (<4 fish) shoals were contrasted. Here, we examine the potential role of the overall body surface area of stimulus fish in shoal preference, a prominent variable not yet examined in angelfish. We report that both when numerically large (5 versus 10 fish) and when small (2 versus 3 fish) shoals were contrasted, angelfish were unable to discriminate the numerically different shoals as long as the surface area of the contrasted shoals was equated. Thus, we conclude that body surface may be an important continuous variable in shoal discrimination. This conclusion was further supported by the analysis of preference when shoals of the same numerical size but different body surface area were contrasted. We found subjects to spend significantly more time close to the shoals with the greater overall surface area. Last, we conducted an experiment in which we simultaneously controlled a set of continuous variables, including overall surface area, and found angelfish to use the number of shoal members as a cue only in large shoal contrasts but not in small shoal contrasts. This result suggests the potential existence of different processing systems for large and small numbers in fish

Spectra associated to symmetric monoidal bicategories

We show how to construct a Gamma-bicategory from a symmetric monoidal bicategory, and use that to show that the classifying space is an infinite loop space upon group completion. We also show a way to relate this construction to the classic Gamma-category construction for a bipermutative category. As an example, we use this machinery to construct a delooping of the K-theory of a bimonoidal category as defined by Baas-Dundas-Rognes.Comment: 27 pages; originally submitted as: "An Infinite Loop Space Structure for K-theory of Bimonoidal Categories", this version has essentially the same content, but the organization is differen

A bonding evolution theory study on the catalytic Noyori hydrogenation reaction

The electronic rearrangements involved in Noyori hydrogenation reactions with double bonds (ethene and formaldehyde) are analysed using the bonding evolution theory. The study and analysis of the changes on the electron localisation function topology along a given reaction path reveals fluxes of electron density, allowing to unambiguously identify the main chemical events happening along the chemical reactions. This analysis shows that the first hydrogen transfer (with hydride character) occurs before the transition state (TS), while the second hydrogen transfer (with proton character) takes places after having reached the TS. The lower energy barrier found for formaldehyde over ethene is explained by two reasons. First, the hydride transfer is favoured for the C = O bond over C = C due to the electrophilic character of the carbon atom. Second, a negatively charged CH3–X (X = CH2, O) hidden intermediate is formed in the proximities of the TS region. The oxygen atom is able to stabilise this negatively charged species more effectively than the CH2 group due to its higher electronegativity and the presence of V(O) lone pairs. The obtained analysis explains and rationalises catalyst chemoselectivity (C = O vs. C = C). Finally, a curly arrow representation diagram accounting for the electronic rearrangements is proposed on the basis of BET results

A first step towards quantum energy potentials of electron pairs

A first step towards the construction of a quantum force field for electron pairs in direct space is taken. Making use of topological tools (Interacting Quantum Atoms and the Electron Localisation Function), we have analysed the dependency of electron pairs electrostatic, kinetic and exchange-correlation energies upon bond stretching. Simple correlations were found, and can be explained with elementary models such as the homogeneous electron gas. The resulting energy model is applicable to various bonding regimes: from homopolar to highly polarized and even to non-conventional bonds. Overall, this is a fresh approach for developing real space-based force fields including an exchange-correlation term. It provides the relative weight of each of the contributions, showing that, in common Lewis structures, the exchange correlation contribution between electron pairs is negligible. However, our results reveal that classical approximations progressively fail for delocalised electrons, including lone pairs. This theoretical framework justifies the success of the classic Bond Charge Model (BCM) approach in solid state systems and sets the basis of its limits. Finally, this approach opens the door towards the development of quantitative rigorous energy models based on the ELF topology

Aprendizaje automático basado en las extensiones de la integral de Sugeno

Uno de los problemas más importantes enel ámbitodel aprendizaje automático es el problema de la clasifcación. Entre los métodos más utilizados para resolverlos se encuentras las redes neuronales, redes bayesianas o árboles de decisión. Sin embargo, en este trabajo nos centramos en un tipo de clasifcadores que todavía no han recibido mucha atención en esta rama de la Inteligencia Artifcial, los clasifcadores de Sugeno. El clasifcador de Sugeno fue propuesto por el científco alemán Eyke Hülermeier en [1] como método para la clasifcación binaria, en el que la integral de Sugeno se utiliza como función de agregación que combina varias evaluaciones locales de una instancia en una única evaluación global. Gracias a los resultados del estudio experimental que realizó, comprobamos la gran capacidad de predicción que posee el clasifcador de Sugeno. Posteriormente se han publicado varias extensiones de esta integral y, por este motivo, nos preguntamos cómodeprecisos serán los clasifcadores basados en dichas extensiones. Así, nuestro objetivo es proponer cinco posibles nuevos métodos de clasifcación binarios basados en extensiones de la integral de Sugeno. En este trabajo estudiamos tanto la integral de Sugeno como el algoritmo de clasifcación del clasifcador de Sugeno junto con los procesos de aprendizaje correspondientes, y proponemos nuevos métodos de clasifcación binaria. Para estudiar el comportamiento de estas propuestas, utilizamos ocho conjuntos de datos reales y realizamos un análisis estadístico para apoyar las conclusiones obtenidas. Con el objetivo de comprobar la calidad de los métodos de clasifcación propuestos, llevamos a cabo una comparativa del clasifcador de Sugeno con cada una de nuestras propuestas. Los resultados experimentales muestran la competitividad de los métodos de clasifcación desarrollados y la utilidad de las extensiones de la integral de Sugeno como funciones de agregación en este contexto