When is a Network a Network? Multi-Order Graphical Model Selection in Pathways and Temporal Networks

We introduce a framework for the modeling of sequential data capturing pathways of varying lengths observed in a network. Such data are important, e.g., when studying click streams in information networks, travel patterns in transportation systems, information cascades in social networks, biological pathways or time-stamped social interactions. While it is common to apply graph analytics and network analysis to such data, recent works have shown that temporal correlations can invalidate the results of such methods. This raises a fundamental question: when is a network abstraction of sequential data justified? Addressing this open question, we propose a framework which combines Markov chains of multiple, higher orders into a multi-layer graphical model that captures temporal correlations in pathways at multiple length scales simultaneously. We develop a model selection technique to infer the optimal number of layers of such a model and show that it outperforms previously used Markov order detection techniques. An application to eight real-world data sets on pathways and temporal networks shows that it allows to infer graphical models which capture both topological and temporal characteristics of such data. Our work highlights fallacies of network abstractions and provides a principled answer to the open question when they are justified. Generalizing network representations to multi-order graphical models, it opens perspectives for new data mining and knowledge discovery algorithms.Comment: 10 pages, 4 figures, 1 table, companion python package pathpy available on gitHu

Certificação IEA.

Dada a dimensão territorial ocupada pelo cultivo da cana, pelos impactos ambientais e sociais gerados pelo setor sucroalcooleiro, pela existência de iniciativas de certificação e devido ao fato da não adoção até o momento de certificação socioambiental por nenhum grupo empresarial do setor, é clara a necessidade de se discutir este tema assim como deixar clara a necessidade de gerar subsídios para a implementação de políticas públicas nesta direção. O intuito deste trabalho é justamente o de apresentar informações para colocar em discussão como políticas de pesquisa e tecnológicas podem levar a modos de produção mais desejáveis e auxiliar na definição de políticas públicas que auxiliem na elaboração de certificação socioambiental para o setor sucroalcooleiro. No decorrer do texto são relatados dados da situação atual do setor, bem como cenários futuros, inclusive de opções tecnológicas, como argumento para justificar as propostas de políticas e agendas de pesquisas futuras, que são apresentadas no final

A new analysis of the GJ581 extrasolar planetary system

We have done a new analysis of the available observations for the GJ581 exoplanetary system. Today this system is controversial due to choices that can be done in the orbital determination. The main ones are the ocurrence of aliases and the additional bodies - the planets f and g - announced in Vogt et al. 2010. Any dynamical study of exoplanets requires the good knowledge of the orbital elements and the investigations involving the planet g are particularly interesting, since this body would lie in the Habitable Zone (HZ) of the star GJ581. This region,for this system, is very attractive of the dynamical point of view due to several resonances of two and three bodies present there. In this work, we investigate the conditions under which the planet g may exist. We stress the fact that the planet g is intimately related with the orbital elements of the planet d; more precisely, we conclude that it is not possible to disconnect its existence from the determination of the eccentricity of the planet d. Concerning the planet f, we have found one solution with period $\approx 450$ days, but we are judicious about any affirmation concernig this body because its signal is in the threshold of detection and the high period is in a spectral region where the ocorruence of aliases is very common. Besides, we outline some dynamical features of the habitable zone with the dynamical map and point out the role played by some resonances laying there.Comment: 12 pages, 9 figure

Objetivos do ensino de ciências no discurso de professores : um olhar sociocultural

O debate sobre as contribuições da Educação em Ciências no sentido de melhor servir aos interesses da coletividade nos levou ao objetivo de investigar o discurso de professores de ciências sobre as finalidades da educação e sua relação com a realidade social. Analisamos os enunciados de 27 professores (de Física, Química, Biologia e Matemática) e a influência da linguagem acadêmica no discurso comprometido com o social. Apenas dez professores indicaram objetivos relacionados à realidade social, tendo os demais enfatizado a realidade natural ou o indivíduo. A influência de contextos acadêmicos de formação continuada parece influenciar a preocupação social dos professores. De toda a forma, os resultados apontam para a necessidade de envidar esforços na formação dos professores das ciências naturais no sentido de favorecer a abordagem de problemas sociais

Measure of thermal transmittance of two different infill wall built with bamboo cultivated in Tuscany

ArticleBamboo is used in different scenarios of application, its physical and mechanical characteristics guarantee a high flexibility of use especially in the buildings constructions. The experience gained in civil constructions demonstrates that bamboo can be considered a sustainable material able to replace wood in many constructive elements with structural functions. The applications of bamboo aimed at carrying out structural functions are thoroughly studied. For this reason the present research focuses on the thermal insulation performance. To ensure an approach focused on the sustainability of potential exploitation, the research examined only local material coming from three bamboo fields located in the Tuscany region (Italy). The material harvested and suitably treated was utilized for the realization of two different kind of wall, undergone later to experimental tests in compliance with the ISO 9869 standard for the calculation of the transmittance values. The measure of transmittance enabled to know the characteristics of thermal conduction of bamboo walls. The first wall was made of cut throw longitudinal axis bamboo culms; the second one was made of cut throw longitudinal axis bamboo culms coated in internal face with a sustainable mortar. The test was carried out using insulating thermal box with internal temperature under control. The calculation of the transmittance in place was compared with the images captured by thermal camera. Thermal imagine allowed to highlight the behaviour of the material subjected to a thermal stress induced by the experimental test