5,482 research outputs found

    Information entropy of classical versus explosive percolation

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    We study the Shannon entropy of the cluster size distribution in classical as well as explosive percolation, in order to estimate the uncertainty in the sizes of randomly chosen clusters. At the critical point the cluster size distribution is a power-law, i.e. there are clusters of all sizes, so one expects the information entropy to attain a maximum. As expected, our results show that the entropy attains a maximum at this point for classical percolation. Surprisingly, for explosive percolation the maximum entropy does not match the critical point. Moreover, we show that it is possible determine the critical point without using the conventional order parameter, just analysing the entropy's derivatives.Comment: 6 pages, 6 figure

    Books that Matter. The Case of Tocqueville’s Democracy in America

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    This article addresses a puzzle in the history of academic disciplines: Why is Alexis de Tocqueville’s Democracy in America, once considered a sociological classic, nowadays mostly praised as a classic in political philosophy? Existing approaches emphasize either aspects internal to the text or to the figure of the author, or external factors such as historical contexts and disciplinary dynamics. Our explanation questions the assumption that texts are stable and explores the pragmatic interplay between text-artifact-metaphor. The result is a pragmatic genealogy of the successive material incarnations of Democracy since 1945. This allows us to account for the various meanings that have been associated with Democracy (and Tocqueville) at key historical moments in terms of the cultural work of collectives of agents around the text and its material form so as to make it the icon of certain political and disciplinary projects

    Manual de interpretação de trilhas: explorando os conceitos de ecologia e conservação de floresta na Reserva do Caju.

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    Electron transfer driven decomposition of adenine and selected analogs as probed by experimental and theoretical methods

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    We report on a combined experimental and theoretical study of electron transfer induced decomposition of adenine and a selection of analogue molecules in collisions with potassium atoms (K). Time-of-flight negative ion mass spectra have been obtained in a wide collision energy range (6–68 eV in the centre-of-mass frame), providing a comprehensive investigation of the fragmentation patterns of purine, adenine, 9-methyl adenine, 6-dimethyl adenine and 2-D adenine. Following our recent communication about selective hydrogen loss from the transient negative ions (TNI) produced in these collisions [T. Dunha et al. J. Chem. Phys. 148, 021101 (2018)], this work focuses on the production of smaller fragment anions. In the low-energy part of the present range, several dissociation channels that are accessible in free electron attachment experiments are absent from the present mass spectra, notably NH2 loss from adenine and 9-methyl adenine. This can be understood in terms of a relatively long transit time of the K+ cation in the vicinity of the TNI tending to enhance the likelihood of intramolecular electron transfer. In this case, the excess energy can be redistributed through the available degrees of freedom inhibiting fragmentation pathways. Ab initio theoretical calculations were performed for 9-methyl adenine (9-mAd) and adenine (Ad) in the presence of a potassium atom and provided a strong basis for the assignment the lowest unoccupied molecular orbitals accessed in the collision process

    Rendimento industrial de cenourete® em função do tamanho da matéria-prima e do tempo de processamento.

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