Non-transitive maps in phase synchronization

Concepts from the Ergodic Theory are used to describe the existence of non-transitive maps in attractors of phase synchronous chaotic systems. It is shown that for a class of phase-coherent systems, e.g. the sinusoidally forced Chua's circuit and two coupled R{\"o}ssler oscillators, phase synchronization implies that such maps exist. These ideas are also extended to other coupled chaotic systems. In addition, a phase for a chaotic attractor is defined from the tangent vector of the flow. Finally, it is discussed how these maps can be used to real time detection of phase synchronization in experimental systems

Tracing the spiral arms in IP Pegasi

We report the analysis of time-resolved spectroscopy of IP Pegasi in outburst with eclipse mapping techniques to investigate the location and geometry of the observed spiral structures. We were able to obtain an improved view of the spiral structures with the aid of light curves extracted in velocity bins matching the observed range of velocities of the spiral arms combined with a double default map tailored for reconstruction of asymmetric structures. Two-armed spiral structures are clearly seen in all eclipse maps. The arms are located at different distances from the disc centre. The “blue” arm is farther out in the disc (R = 0.55 ± 0.05 R L1 ) than the “red” arm (R = 0.30 ± 0.05 R L1 ). There is evidence that the velocity of the emitting gas along the spiral pattern is lower than the Keplerian velocity for the same disc radius. The discrepancy is smaller in the outer arm (measured velocities 10–15 per cent lower than Keplerian) and is more significant in the inner arm (observed velocities up to 40 per cent lower than Keplerian). We measured the opening angle of the spirals from the azimuthal intensity distribution of the eclipse maps to be φ = 25◦ ± 3◦ . A comparison with similar measurements on data at different outburst stages reveals that the opening angle of the spiral arms in IP Peg decreases while the outbursting accretion disc cools and shrinks, in agreement with the expected evolution of a tidally driven spiral wave. The sub-Keplerian velocities along the spiral pattern and the clear correlation between the opening angle of the spirals and the outburst stage favors the interpretation of these asymmetric structures as tidally-induced spiral shocks

Accretion and activity on the post-common-envelope binary RR~Cae

Current scenarios for the evolution of interacting close binaries - such as cataclysmic variables (CVs) - rely mainly on our understanding of low-mass star angular momentum loss (AML) mechanisms. The coupling of stellar wind with its magnetic field, i.e., magnetic braking, is the most promising mechanism to drive AML in these stars. There are basically two properties driving magnetic braking: the stellar magnetic field and the stellar wind. Understanding the mechanisms that drive AML therefore requires a comprehensive understanding of these two properties. RRCae is a well-known nearby (d=20pc) eclipsing DA+M binary with an orbital period of P=7.29h. The system harbors a metal-rich cool white dwarf (WD) and a highly active M-dwarf locked in synchronous rotation. The metallicity of the WD suggests that wind accretion is taking place, which provides a good opportunity to obtain the mass-loss rate of the M-dwarf component. We analyzed multi-epoch time-resolved high-resolution spectra of RRCae in search for traces of magnetic activity and accretion. We selected a number of well-known activity indicators and studied their short and long-term behavior. Indirect-imaging tomographic techniques were also applied to provide the surface brightness distribution of the magnetically active M-dwarf, and reveals a polar feature similar to those observed in fast-rotating solar-type stars. The blue part of the spectrum was modeled using a atmosphere model to constrain the WD properties and its metal enrichment. The latter was used to improve the determination of the mass-accretion rate from the M-dwarf wind. The presence of metals in the WD spectrum suggests that this component arises from accretion of the M-dwarf wind. A model fit to the WD gives Teff=(7260+/-250)K and logg=(7.8+/-0.1) dex with a metallicity of =(-2.8+/-0.1)dex, and a mass-accretion rate of dotMacc=(7+/-2)x1e-16Msun/yr.Comment: 14 pages, 7 Figures, 6 Table

The Omnipaper metadata RDF/XML prototype implementation

Omnipaper (Smart Access to European Newspapers, IST-2001-32174) is a project from the European Commission IST program (Information Society Technologies) that investigates and proposes ways for access to different types of distributed information sources. This article intends to introduce the technology Resource Description Framework - RDF, developed by W3C for the Web based on metadata, and its practical use in the Omnipaper project, which the authors are involved. We intend to achieve the implementation of a prototype that enables users (professional journalists and occasional users) to have simultaneous and structured access to the articles of a large number of digital European news providers. Omnipaper is not a project about digitalization of news, but about bringing digitized news originating from various sources (and in various formats) together. In this article will be described the procedure implemented in the description of our newspaper articles using the RDF technology, followed by a elaborated description on the manipulation process and treatment of the information structured in RDF, through the RDF Gateway

Vantagens e desvantagens da relação entre plantas e fungos

Apresentação efetuada nas III Jornadas Micológicas, Braga, 2011Os fungos são capazes de estabelecer múltiplas associações/relações com as plantas. Apesar de muitas dessas relações se revelarem prejudiciais, outras apresentam vantagens significativas ao nível do desenvolvimento, nutrição e sanidade das plantas. Nesta comunicação será particularmente abordada a associação sirnbiótica que ocorre entre raízes e fungos do solo - micorrização - referindo-se as vantagens que daí advêm para plantas, fungos e inclusivamente para o Homem

Network Mutual Information and Synchronization under Time Transformations

We investigate the effect of general time transformations on the phase synchronization (PS) phenomenon and the mutual information rate (MIR) between pairs of nodes in dynamical networks. We demonstrate two important results concerning the invariance of both PS and the MIR. Under time transformations PS can neither be introduced nor destroyed and the MIR cannot be raised from zero. On the other hand, for proper time transformations the timing between the cycles of the coupled oscillators can be largely improved. Finally, we discuss the relevance of our findings for communication in dynamical networks.Comment: 15 p

Navegação semântica sobre uma base de metadados RDF implementada no projecto OmniPaper

O projecto OmniPaper (Smart Access to European Newspapers) é um projecto do programa IST (Information Society Technologies) da comissão europeia, que visa fomentar um acesso distribuído a diferentes tipos de fontes de informação. Com este projecto pretende-se chegar a um protótipo de um sistema que permita aos utilizadores (quer ocasionais, quer profissionais) um acesso estruturado, personalizado e multilingue a todo um conjunto de artigos de notícias disponibilizados pelas empresas parceiras (a que denominamos por arquivos locais). Este artigo pretende descrever o trabalho desenvolvido na implementação do protótipo RDF no âmbito do projecto OmniPaper, focando a utilização dos IPTC Subject Codes na definição de uma camada de navegação semântica sobre as descrições de metadados codificados em RDF/XML

The extension of the omnipaper system in the context of scientific publications

Today the Internet is an important information source, which facilitates the search and access to information contents on the Web. In fact, the Internet has become an important tool used daily by scholars in the development of their work. However the contents published on the Web increase daily and consequently difficult the identification of new contents published in various information sources. In this context the RSS technology introduces a new dimension in the access and dis-tribution mechanisms of new contents published by distributed information sources. In the scope of scientific contents the use of RSS technology helps the scholars to be up to date of new scientific resources provided by several and dis-tributed information sources. An instance of the OmniPaper RDF prototype has been developed in order to instantiate the mechanisms of distributed information retrieval investigated in the context of the news published in newspapers and use them in the context of scientific contents. In addition a central metadatabase was developed through the RSS approach, in order to enable the scientific content syn-dication. This paper intends to describe the steps involved in the development of the instantiation system of the OmniPaper RDF prototype