Disimplicial arcs, transitive vertices, and disimplicial eliminations

In this article we deal with the problems of finding the disimplicial arcs of a digraph and recognizing some interesting graph classes defined by their existence. A diclique of a digraph is a pair $V \to W$ of sets of vertices such that $v \to w$ is an arc for every $v \in V$ and $w \in W$. An arc $v \to w$ is disimplicial when $N^-(w) \to N^+(v)$ is a diclique. We show that the problem of finding the disimplicial arcs is equivalent, in terms of time and space complexity, to that of locating the transitive vertices. As a result, an efficient algorithm to find the bisimplicial edges of bipartite graphs is obtained. Then, we develop simple algorithms to build disimplicial elimination schemes, which can be used to generate bisimplicial elimination schemes for bipartite graphs. Finally, we study two classes related to perfect disimplicial elimination digraphs, namely weakly diclique irreducible digraphs and diclique irreducible digraphs. The former class is associated to finite posets, while the latter corresponds to dedekind complete finite posets.Comment: 17 pags., 3 fig

Unemployment rates and population changes in Spain

This paper discusses the long run effect of changes in the age distribution of Spanish population on the unemployment rate, disaggregated by sex and age segments in the light of cointegration theory given the non stationarity of the series. Four main results are obtained. First, empirical analysis does not provide a clear scheme concerning the long run relationships between population variables and the specificunemployment rates for different groups. Second, as a first approximation one can detect the existence of, at least, one long run equilibrium relationship in all sex-age groups, except for the ones including the middle aged unemployed female workers and oldest unemployed female workers. Third, a more thorough analysis enables us to justify the existence of such long run relationships for the youngest male workers and middle aged male workers. One cannot argue, however, a joint evolution of population variables and the unemployment rates associated with female workers and to the oldest male workers. Fourth, the short run dynamics of unemployment rates for the youngest (male and female workers) and the middle age male workers is affected by the transitory deviations from these long run relationships. Hence, from an applied economics point of view, the result stresses the likely failure of employment policies which do not take into account the heterogeneous composition of unemployed workers. It stresses the need to design particular policies for specific groups of workers depending on their age and sex characteristics.unemployment rates, population aging, cointegration

Advanced anode materials for sodium ion batteries: H2Ti3O7and TMNCN (TM=Mn2+, Fe2+, Co2+, Ni2+, Cu2+ and Zn2+) carbodiimides

207 p.La futura escasez de los combustibles fósiles (principal fuente de energía) y la contaminación generada por su utilización genera una necesidad de cambio del sistema energético actual. Por tanto, es necesario el aprovechamiento de las fuentes de energía renovables mediante el almacenamiento de energía en baterías. A pesar de las buenas prestaciones de las baterías de ion litio, la necesidad de buscar una tecnología más limpia y barata de alta densidad energética como son las baterías de ion sodio. Sin embargo, la imposibilidad de usar grafito como ánodo en estas baterías es la mayor desventaja. Por tanto, el proyecto de investigación se centra en el estudio de la caracterización estructural y electroquímica en dos diferentes familias de materiales para ser utilizados como electrodos negativos (ánodos) para baterías de ion sodio. En este trabajo se han estudiado las prestaciones electroquímicas de titanatos y carbodiimidas de metales de transición, así como experimentos de celdas completas para una buena caracterización del material. Para ello se han utilizado una gran variedad de técnicas experimentales de caracterización tanto estructural como electroquímica, que nos permite conocer los diferentes mecanismos de reacción de los materiales que presentan estos materiales dentro de la batería

Motherhood Versus Metropolis: Maternity Practices in Native Cultures of the Chronicles of Peru

Motherhood and colonization, why should we put these two notions together, and what do we know about the changes in childbearing patterns during the colonization of the America’s as a signal of a broader cultural change? Even when all human life on this planet is born from a woman, we know more about the air we breathe, and the seas we travel, than about the nature and meaning of motherhood as Adrienne Rich famously said (1976: 11). The production of life remains a marginal issue in the study of modernity and its consequences. The colonization of America marked a significant shift in how Western minds understood themselves and was pivotal in the overall concept of motherhood and by combining both these cultural phenomena we can illuminate many aspects of society, then and now

Supramolecular chemistry of bis-porphyrins

(Base de datos de tesis doctorales TESEO) En este trabajo de tesis doctoral se desarrollan básicamente dos aspectos. El primero, es la síntesis de receptores bis-porfirínicos metalados con zinc, tanto acíclicos como cíclicos, y con diferente grado de saturación de las cadenas carbonadas, y el segundo, trata sobre los estudios de complejación llevados a cabo con ligandos de diferente tipo y propiedades: aminas y fullerenos. Los primeros se unen mediante enlaces de coordinación metal-nitrógeno, mientras que los segundos se basan en interacciones  entre el anillo aromático de la porfirina y la estructura con un marcado carácter aromático de los fullerenos.Además, se exponen los resultados obtenidos al derivar uno de los ciclopéptidos del grupo de investigación del Prof. J.R. Granja con una o dos porfirinas de zinc y emplear el ensamblaje supramolecular tipo "sándwich" entre bis-porfirinas y aminas ditópicas para controlar la mezcla regioisomérica que tiene lugar en el proceso de autoensamblaje entre los ciclopéptidos.(Base de datos de tesis doctorales TESEO) English versionIn this doctoral thesis two main aspects are developed. The first is the synthesis of bis-porphyrin receptors metallated with zinc, both acyclic and cyclic, and with different degrees of saturation of the carbon chain, and the second deals with the studies of complexation with ligands of different types and properties: amines and fullerenes. The first ligands are connected by metal-nitrogen coordination between the nitrogen of the ligand and the zinc of the porphyrin ring, while the latter are    interactions between the aromatic ring of the porphyrin and the fullerenes.In addition, we present the results obtained when derive one of the cyclopeptides of the research group of Prof. J.R. Granja with one or two zinc porphyrins, using the motif: "sandwich" complexes between bis-porphyrins and ditopic amines, in order to control the regioisomeric mixture that takes place in the self-assembly of the cyclopeptides

Hereditary biclique-Helly graphs: recognition and maximal biclique enumeration

A biclique is a set of vertices that induce a complete bipartite graph. A graph G is biclique-Helly when its family of maximal bicliques satisfies the Helly property. If every induced subgraph of G is also biclique-Helly, then G is hereditary biclique-Helly. A graph is C4-dominated when every cycle of length 4 contains a vertex that is dominated by the vertex of the cycle that is not adjacent to it. In this paper we show that the class of hereditary biclique-Helly graphs is formed precisely by those C4-dominated graphs that contain no triangles and no induced cycles of length either 5 or 6. Using this characterization, we develop an algorithm for recognizing hereditary biclique-Helly graphs in O(n 2 +αm) time and O(n+m) space. (Here n, m, and α = O(m1/2 ) are the number of vertices and edges, and the arboricity of the graph, respectively.) As a subprocedure, we show how to recognize those C4-dominated graphs that contain no triangles in O(αm) time and O(n + m) space. Finally, we show how to enumerate all the maximal bicliques of a C4-dominated graph with no triangles in O(n 2 + αm) time and O(αm) space.Fil: Eguía, Martiniano. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Computación; ArgentinaFil: Soulignac, Francisco Juan. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Computación; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Reconstruyendo la red de lazos personales : metodología egocéntrica para investigación sociocéntrica

Este artículo presenta los avances de investigación en un modelo computacional que permite describir una red social observada por medio de encuestas muestrales representativas de sus nodos. El modelo tiene también el objetivo de servir a estimar la fiabilidad de la encuesta así como estimar medidas globales de la red. De esta forma, el trabajo propone un camino alternativo al análisis egocéntrico de datos representativos de redes personales, obteniendo con un modelo de multiagente de simulación un análisis sociocéntrico de la información parcial de una red. La medición que se utiliza como marco de referencia empírico del modelo es la producida por la Encuesta de la Deuda Social Argentina en el año 2006. Esta encuesta se aplica anualmente en 1500 hogares del país sobre una muestra polietápica representativa de adultos en Gran Buenos Aires, Córdoba, Mendoza, Neuquén, Salta, Resistencia y Bahía Blanca.This article introduces the preliminary results of a computational network model research approach. The aim of this model is to help estimating sampling errors of an ongoing personal network survey, as well as to describe the network observed. In this way, it presents an alternative path to the egocentric analysis of representative data of personal networks, using a simulation multiagent model in order to make a sociocentric analysis on partial information of a network. The survey used as empirical reference frame for the model is the Encuesta de la Deuda Social Argentina (2006), which is applied annually to 1500 household along the country, using a multistage representative sample of adults in 7 large Argentinean cities (Gran Buenos Aires, Córdoba, Mendoza, Neuquén, Salta, Resistencia and Bahía Blanca)

Valoración de factores pronósticos en las lesiones de osteocondritis disecante de la rodilla del adulto

El objetivo de este trabajo es la valoración de la influencia de diferentes variables lesionales en los resultados terapéuticos obtenidos en pacientes adultos afectos de osteocondritis. Hemos realizado un estudio retrospectivo de 85 pacientes con diagnóstico artroscópico de osteocondritis disecante realizado en el periodo comprendido entre mayo de 1988 y mayo de 1997. Considerando los casos con afectación bilateral, 91 rodillas han sido intervenidas. A todos los pacientes se les realizó una valoración clínica preartroscópica y post-operatoria durante un año siguiendo la encuesta epidemiológica y exploratoria protocolarizada en nuestra unidad. Acompañando a esta valoración clínica se realizó una valoración de métodos complementarios de imagen. Se recogieron 14 variables según las diferentes características epidemiológicas y lesionales de cada paciente. Se realizó un análisis estadístico de la influencia de estas variables en los resultados funcionales, no obteniendo ningún resultado como significativo (p>0,05).The aim of this study is the valuation of the influence of different lesional variables in the clinical results obtained in adults affected of osteochondritis. We have studied retrospectivally 85 patients diagnosed of osteochondritis dissecans realized in the period of time between May 1988 and May 1997. Considering the cases with bilateral affectation, 91 knees have been operated. We realized a prearthroscopic clinical valuation of all patients and a post-operation valuation during one year using an epidemiological inquiry and a protocolarized examination. At the same time made an imagin study. There were 14 variables obtained using the different epidemiological and lesional characteristics of every patient. Statistical analysis of the influence of these variables in the functional results, showed no significant results (p>0,05)

Production of environmentally innocuous coatings

It is known the biofouling phenomenon, as well as the negative consequences that it means for the artificial structures in contact with seawater in form of structural defects and of additional expenses for the companies which develop their work in the marine scope due to the processes of cleaning and prevention, the evolution in the world of the technology of antifouling paintings, once we analysed the serious environmental problems caused by an indiscriminate use of byocides of high toxicity in its composition as they are the organic derivatives of tin compounds made up and of the uncontrolled emission of volatile organic compounds (VOC) to the atmosphere, according to the present environmental norm, has as only aim to develop environmentally innocuous coverings based on water in which extracts of the very same marine world are used as byocides compound