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Moret M.A.,Programa de Modelagem Computacional
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2014

In this paper we study the time series of sunspots by using two different approaches, analyzing its self-affine behavior and studying its distribution. The long-range correlation exponent α has been calculated via Detrended Fluctuation Analysis and the power law vanishes to values greater than 11 years. On the other hand, the distribution of the sunspots obeys a q-exponential decay that suggests a non-extensive behavior. This observed characteristic seems to take an alternative interpretation of the sunspots dynamics. The present findings suggest us to propose a dynamic model of sunspots formation based on a nonlinear Fokker-Planck equation. Therefore its dynamic process follows the generalized thermostatistical formalism. © 2013 Elsevier B.V.

Henrique T.,State University of Feira de Santana | Fadigas I.S.,State University of Feira de Santana | Rosa M.G.,State University of Feira de Santana | Pereira H.B.B.,Programa de Modelagem Computacional | Pereira H.B.B.,Bahia State University
Social Network Analysis and Mining | Year: 2014

Continuous technological advances have resulted in analysis techniques that can be used in network theory. Topological characterisation, study of cohesion, and analysis of prominence are relevant techniques through which vertices (e.g., words) and their relationships are considered. The goal of this paper is to produce a comparative study on semantic networks based on titles of scientific papers in the field of mathematics education in Portuguese (Brazil) and English to ascertain the topological structure of these semantic networks and to present reflections thereafter concerning the diffusion of mathematics education. The vertices of proposed semantic networks are words with intrinsic meaning belonging to the titles of scientific papers and two words are connected if both belong to the same title. Methods and metrics from social and complex network analysis have been used to develop a diagnosis of the characterisation of this type of semantic network. Within this context, this study could be used to offer support to facilitate the process of diffusing knowledge in specific areas. © 2014, Springer-Verlag Wien.

Fox A.J.,European Southern Observatory | Fox A.J.,University of Cambridge | Ledoux C.,European Southern Observatory | Petitjean P.,CNRS Paris Institute of Astrophysics | And 2 more authors.
Astronomy and Astrophysics | Year: 2011

We present VLT/UVES spectroscopy of the quasar Q0841+129, whose spectrum shows a proximate damped Ly-α (PDLA) absorber at z = 2.47621 and a proximate sub-DLA at z = 2.50620, both lying close in redshift to the QSO itself at zem = 2.49510 ± 0.00003. This fortuitous arrangement, with the sub-DLA acting as a filter that hardens the QSO's ionizing radiation field, allows us to model the ionization level in the foreground PDLA, and provides an interesting case-study on the origin of the high-ion absorption lines Si iv, C iv, and O vi in DLAs. The high ions in the PDLA show at least five components spanning a total velocity extent of 160 km s-1, whereas the low ions exist predominantly in a single component spanning just 30 km s-1. We examine various models for the origin of the high ions. Both photoionization and turbulent mixing layer models are fairly successful at reproducing the observed ionic ratios after correcting for the non-solar relative abundance pattern, though neither model can explain all five components. We show that the turbulent mixing layer model, in which the high ions trace the interfaces between the cool PDLA gas and a hotter phase of shock-heated plasma, can explain the average high-ion ratios measured in a larger sample of 12 DLAs. © 2011 ESO.

Moret M.A.,Programa de Modelagem Computacional
Physica A: Statistical Mechanics and its Applications | Year: 2011

The major factor that drives a protein toward collapse and folding is the hydrophobic effect. At the folding process a hydrophobic core is shielded by the solvent-accessible surface area of the protein. We study the fractal behavior of 5526 protein structures present in the Brookhaven Protein Data Bank. Power laws of protein mass, volume and solvent-accessible surface area are measured independently. The present findings indicate that self-organized criticality is an alternative explanation for the protein folding. Also we note that the protein packing is an independent and constant value because the self-similar behavior of the volumes and protein masses have the same fractal dimension. This power law guarantees that a protein is a complex system. From the analyzed data, q-Gaussian distributions seem to fit well this class of systems. © 2011 Elsevier B.V. All rights reserved.

Fadigas I.S.,State University of Feira de Santana | Pereira H.B.B.,Programa de Modelagem Computacional | Pereira H.B.B.,Bahia State University
Physica A: Statistical Mechanics and its Applications | Year: 2013

The characterization of complex networks is a procedure that is currently found in several research studies. Nevertheless, few studies present a discussion on networks in which the basic element is a clique. In this paper, we propose an approach based on a network of cliques. This approach consists not only of a set of new indices to capture the properties of a network of cliques but also of a method to characterize complex networks of cliques (i.e., some of the parameters are proposed to characterize the small-world phenomenon in networks of cliques). The results obtained are consistent with results from classical methods used to characterize complex networks. © 2013 Elsevier B.V. All rights reserved.

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