Diffusion equations for nonhomogeneous media. Existence of similarity solutions

We study the invariance of the diffusion equation δP(x,t)/δt = (δ/δx)[D(x)δP(x,t)/δx] under continuous groups of transformations. We show the conditions which D(x) must satisfy for the existence of similarity solutions

New classes of stable exact solutions for a nonlinear rotational DNA model

We consider a system of two coupled nonlinear partial differential equations for describing the rotational motions of bases in both polynucleotide chains of the DNA molecule. The model was proposed by L.V. Yakushevich and it is well known that the model supports, for some operating regimes, traveling wave solutions as kink–(antikink) soliton solutions. We have tried to make some progress by performing an analysis of the classical symmetries of this model. Our study shows that the model does not have enough symmetries as to reduce the equations to ordinary differential equations. Nevertheless, the known symmetries have been useful for finding several classes of exact solutions, by imposing adequate Ansätze. Some of them are kink–(antikink) like solutions, but other ones are not traveling wave solutions. For some of the new solutions, we have carried out a qualitative study and analyzed some stability properties. We think that they could be significant for the description of the DNA molecule as well as for some other applications.DGYCYT project MTM2006-05031Junta de Andalucía FQM 201. P06-FQM-0144

Analysis of columns with sheardeformation using finite element method and equivalent distributedloads

En este trabajo se aplica un procedimiento basado en el concepto de Acción Repartida Equivalente (ARE) al análisis, por el Método de Elementos Finitos (MEF) formulado en desplazamientos y solución nodal exacta, de pilares con deformación por cortante de acuerdo con la teoría de Timoshenko. Los resultados obtenidos con la metodología ARE-MEF, en los casos analizados, ponen de manifiesto que con un número muy reducido de elementos (uno y dos en los ejemplos desarrollados) se alcanza gran exactitud en desplazamientos, giros y esfuerzos. Sin embargo con otras metodologías formuladas en desplazamientos, como por ejemplo la de integración reducida, se requiere del orden de 40 elementos para alcanzar resultados similares. Asimismo en el presente trabajo, a partir del MEF con solución nodal exacta se determinan de una forma directa y sistemática las funciones de estabilidad y la carga de pandeo para el pilar de Timoshenko.This paper describes a procedure based on the concept of Equivalent Distributed Loads (EDL) applied to the Finite Elements Method (FEM) based on displacements and exact nodal solution of columns subject to shear deformation in accordance with the Timoshenko beam theory. The results obtained using this “EDL-FEM” methodology, in the cases studied, show that a high level of exactness in displacements, rotations as well as shear force and bending moment is obtained with a very small number of elements (one or two in the examples developed). Other methodologies based on displacements, such as reduced integration, require on the order of 40 elements to achieve similar results. The stability functions and buckling load for the Timoshenko beam are also determined in a direct and systematic way from the FEM with exact nodal solution.Peer Reviewe

Análisis florístico de las sierras de María y Orce (provincias de Almería y Granada, España)

11 páginas, 4 tablas y 3 figuras[EN]We carried out a floristic analysis of the María and Orce mountain ranges, situated in the north of Almería and Granada provinces, respectively, in a región of continentalized climate with a climatic irregularity of 37.5%. The biological spectrum was compared with other peninsular and north african áreas. Being a montane zone, the dominant biotype is hemicryptophytic, but a relatively high proportion of therophytes is also present, which indicates a southeast semiarid peninsular influence. Data obtained from analysis of floristic elements present (mediterranean, 51 %; iberian, 18.5 %; ibero-northafrican, 10.3 %; etc.) allow these mountain ranges to be characterized as an área of conjunction between diverse floras, specifically betic (central and eastern andalusian), eastern peninsular (taxa of the southeastern and eastern peninsular regions which may also be present in the central or southern peninsular regions), and Murcia-Almerian (southeast semiarid). The área possesses 6 local endemics: Brassica repanda (Willd.) DC. subsp. almeriensis Gómez-Campo, Nepeta hispanica Boiss. & Reuter in Boiss, subsp. hispanica, Sideritis stachydioidesV/iWk., Sideritis x sagredoi O. Socorro, J. Molero, M. Casares & F. Pérez Raya, Centaurea mariana Nyman and Centaurea Xpüfontiana Fernández Casas & Susanna. The distribution of taxa in bioclimatic belts was also studied. There was a predominance of those taxa which occur in both the mesomediterranean and the supramediterranean. Analysis of the degree of conservation of the flora according to the categories of the IUCN (25.7 % of the flora was found to be threatened to a certain degree) indicates that 85.7 % of threatened taxa are present in the supra- and oromediterranean. Lastly, we give the distribution of floristic elements according to the bioclimatic belts, noting that the endemics of most limited range are present in the summit zones, with the exception of the Almenan endemics, whose área of distribution is the basal belt of the semiarid Murcia-Almerian región.[ES]La idea de evaluar la importancia de las áreas naturales, bien sea para su conservación o para otros fines, ha evolucionado en época reciente y ha encontrado una amplia aplicación (MARGULES & USHER, 1981; GOLDSMITH, 1983). La evaluación de áreas naturales implica factores subjetivos y objetivos que, a menudo, no pueden separarse fácilmente (ROOME, 1984). SMITH & THEBERGE (1986) analizaron los criterios usados en 22 sistemas de evaluación, encontrando que los más utilizados son los de rareza y singularidad, seguidos del de diversidad. En este trabajo se realiza un análisis florístico de las sierras de María y Orce, tomando como base el estudio de CUETO (1989). Dichas sierras están situadas al norte de las provincias de Almería y Granada, respectivamente; constituyen un núcleo montano con una altura media de 1326 m, que alcanza los 2045 m de altitud en el pico María. Ocupan un área virtual sobre el plano de 202,14 km2. Por su situación geográfica, presentan un clima continental, que se suaviza algo en las vertientes sur, como consecuencia de la influencia del Mediterráneo. La irregularidad climática es del 37,5% (MONTERO & GONZÁLEZ REBOLLAR, 1983); esto favorece la existencia de una flora rica y variada, puesto que los cambios de clima propician la presencia de táxones que se desarrollan dentro de límites climáticos muy diversos. Las precipitaciones anuales en la zona oscilan entre los 340 y los 640 mm; las mínimas se presentan en el extremo noroccidental del área, lo cual indica la influencia de la depresión de Orce, mientras que las máximas se recogen en las cotas superiores de la Sierra de María. Las temperaturas medias anuales se sitúan entre los 7 °C de las cumbres de la Sierra de Maria y los 12 °C que se alcanzan en el extremo noroccidental y en las zonas bajas de la vertiente sur de ambas sierras.Estación Experimental de Zonas Áridas, C.S.I.C. General Segura, 1.04001 Almería. Departamento de Biología Vegetal, Facultad de Ciencias. Fuentenueva, s/n. 18001 Granada. Centro de Ciencias Medioambientales, C.S.I.C. Serrano, 115 duplicado. 28006 Madrid.Peer reviewe

An Automatic Programming ACO-Based Algorithm for Classification Rule Mining

In this paper we present a novel algorithm, named GBAP, that jointly uses automatic programming with ant colony optimization for mining classification rules. GBAP is based on a context-free grammar that properly guides the search process of valid rules. Furthermore, its most important characteristics are also discussed, such as the use of two different heuristic measures for every transition rule, as well as the way it evaluates the mined rules. These features enhance the final rule compilation from the output classifier. Finally, the experiments over 17 diverse data sets prove that the accuracy values obtained by GBAP are pretty competitive and even better than those resulting from the top Ant-Miner algorith

Cluster analysis for validated climatology stations using precipitation in Mexico

Annual average of daily precipitation was used to group climatological stations into clusters using the k-means procedure and principal component analysis with varimax rotation. After a careful selection of the stations deployed in Mexico since 1950, we selected 349 characterized by having 35 to 40 complete years of observations. The clustering of stations was performed three times: firstly according to the amount of precipitation; secondly according to their anomalies from the mean, resulting in their standard deviations grouping; and thirdly using the standardized anomalies, which resulted in a clustering according to the features of the trend and the structural changes of the series over the observing period. We identified two clusters that occupy northwestern and north-central Mexico; another at the center of the territory, between Sierra Madre Oriental and Sierra Madre Occidental; the following over the Sierra Madre Oriental; and a last one in the southeast of the territory, the southern coast of the Pacific Ocean and the Yucatán Peninsula, that overlaps with Sierra Madre Oriental group. Some stations of Yucatán Peninsula show similar characteristics to the northwestern cluster. The groupings were compared with the results of previous studies. The comparison indicates that regions are invariant in time and space and independent of the method of agregation and the stations sampled

High hole mobility and light-harvesting in discotic nematic dendrimers prepared: Via 'click' chemistry

We report a new family of liquid crystalline porphyrin-core dendrimers with coumarin units at the periphery of the dendrimer. These compounds have been prepared by copper-catalyzed azide-alkyne "click" cycloaddition (CuAAC). The mesomorphic properties have been investigated via polarized optical microscopy (POM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The peripheral coumarin units play a key role in the liquid crystal behavior, contributing to the appearance of discotic nematic mesophases with hole mobility values among the highest values reported for discotic liquid crystals (of the order of 1 cm 2 V -1 s -1 ). It has also been demonstrated that excitation of the coumarin moieties leads to energy transfer (antenna effect) to the luminescent porphyrin core. Therefore, this strategy, which involves ''click'' chemistry, has been proven to be a powerful and elegant synthetic tool for the preparation of optoelectronic materials based on complex dendritic architectures

Generating Semantic Snapshots of Newscasts Using Entity Expansion

textabstractTV newscasts report about the latest event-related facts occurring in the world. Relying exclusively on them is, however, insufficient to fully grasp the context of the story being reported. In this paper, we propose an approach that retrieves and analyzes related documents from the Web to automatically generate semantic annotations that provide viewers and experts comprehensive information about the news. We detect named entities in the retrieved documents that further disclose relevant concepts that were not explicitly mentioned in the original newscast. A ranking algorithm based on entity frequency, popularity peak analysis, and domain experts’ rules sorts those annotations to generate what we call Semantic Snapshot of a Newscast (NSS). We benchmark this method against a gold standard generated by domain experts and assessed via a user survey over five BBC newscasts. Results of the experiments show the robustness of our approach holding an Average Normalized Discounted Cumulative Gain of 66.6%

Estudio del crecimiento de gallinas ponedoras de 18 hasta 60 semanas de edad criadas en jaulas enriquecidas sometidas a diferentes intensidades de iluminación. 2. Tasa de crecimiento

El objetivo del estudio fue comparar la tasa de crecimiento de gallinas ponedoras criadas en jaulas enriquecidas sometidas a diferentes intensidades de iluminación de acuerdo con el esquema factorial 2x3: iluminación del pasillo (lateral y central) versus iluminación del piso (bajo, intermedio y alto) evaluada en el periodo de 18 hasta 60 semanas de edad de acuerdo con el modelo no linear de Gompertz. Las gallinas fueron alojadas en dos bateríasde 3 pisos, con dos filas por piso y cinco jaulas por fila (25 aves/jaula), con un total de 1.50