X-ray flares on the UV Ceti-type star CC Eridani: a "peculiar" time-evolution of spectral parameters

Context: Weak flares are supposed to be an important heating agent of the outer layers of stellar atmospheres. However, due to instrumental limitations, only large X-ray flares have been studied in detail until now. Aims: We used an XMM-Newton observation of the very active BY-Dra type binary star CC Eri in order to investigate the properties of two flares that are weaker than those typically studied in the literature. Methods: We performed time-resolved spectroscopy of the data taken with the EPIC-PN CCD camera. A multi-temperature model was used to fit the spectra. We inferred the size of the flaring loops using the density-temperature diagram. The loop scaling laws were applied for deriving physical parameters of the flaring plasma. We also estimated the number of loops involved in the observed flares. Results: A large X-ray variability was found. Spectral analysis showed that all the regions in the light curve, including the flare segments, are well-described by a 3-T model with variable emission measures but, surprisingly, with constant temperatures (values of 3, 10 and 22 MK). The analysed flares lasted ~ 3.4 and 7.1 ks, with flux increases of factors 1.5-1.9. They occurred in arcades made of a few tens of similar coronal loops. The size of the flaring loops is much smaller than the distance between the stellar surfaces in the binary system, and even smaller than the radius of each of the stars. The obtained results are consistent with the following ideas: (i) the whole X-ray light curve of CC Eri could be the result of a superposition of multiple low-energy flares, and (ii) stellar flares can be scaled-up versions of solar flares.Comment: 14 pages, 12 figures. Accepted for publication in Astronomy & Astrophysic

Homoclinic Signatures of Dynamical Localization

It is demonstrated that the oscillations in the width of the momentum distribution of atoms moving in a phase-modulated standing light field, as a function of the modulation amplitude, are correlated with the variation of the chaotic layer width in energy of an underlying effective pendulum. The maximum effect of dynamical localization and the nearly perfect delocalization are associated with the maxima and minima, respectively, of the chaotic layer width. It is also demonstrated that kinetic energy is conserved as an almost adiabatic invariant at the minima of the chaotic layer width, and that the system is accurately described by delta-kicked rotors at the zeros of the Bessel functions J_0 and J_1. Numerical calculations of kinetic energy and Lyapunov exponents confirm all the theoretical predictions.Comment: 7 pages, 4 figures, enlarged versio

Universal scaling laws of chaotic escape in dissipative multistable systems subjected to autoresonant excitations

A theory concerning the emergence and control of chaotic escape from a potential well by means of autoresonant excitations is presented in the context of generic, dissipative, and multistable systems. Universal scaling laws relating both the onset and lifetime of transient chaos with the parameters of autoresonant excitations are derived theoretically using vibrational mechanics, Melnikov analysis, and energy-based autoresonance theory. Numerical experiments show that these scaling laws are robust against both the presence of noise and re-shaping.Comment: 4 pages, 5 figure

Bean Genome Diversity Reveals the Genomic Consequences of Speciation, Adaptation, and Domestication

Here we review whether genomic islands of speciation are repeatedly more prone to harbor within-species differentiation due to genomic features, such as suppressed recombination, smaller effective population size, and increased drift, across repeated hierarchically nested levels of divergence. Our discussion focuses on two species of Phaseolus beans with strong genepool and population substructure and multiple independent domestications each. We overview regions of species-associated divergence, as well as divergence recovered in within-species between-genepool comparisons and in within-genepool wild-cultivated comparisons. We discuss whether regions with overall high relative differentiation coincide with sections of low SNP density and with between-species pericentric inversions, since these convergences would suggest that shared variants are being recurrently fixed at replicated comparisons, and in a similar manner across different hierarchically nested levels of divergence, likely as the result of genomic features that make certain regions more prone to accumulate islands of speciation as well as within-species divergence. We conclude that neighboring signatures of speciation, adaptation, and domestication in Phaseolus beans seem to be influenced by ubiquitous genomic constrains, which may continue shaping, fortuitously, genomic differentiation at various other scales of divergence. This pattern also suggests that genomic regions important for adaptation may frequently be sheltered from recombination

The effect of magnetic activity saturation in chromospheric flux-flux relationships

We present a homogeneous study of chromospheric and coronal flux-flux relationships using a sample of 298 late-type dwarf active stars with spectral types F to M. The chromospheric lines were observed simultaneously in each star to avoid spread due to long term variability. Unlike other works, we subtract the basal chromospheric contribution in all the spectral lines studied. For the first time, we quantify the departure of dMe stars from the general relations. We show that dK and dKe stars also deviate from the general trend. Studying the flux-colour diagrams we demonstrate that the stars deviating from the general relations are those with saturated X-ray emission and that those stars also present saturation in the H$\alpha$ line. Using several age spectral indicators, we show that they are younger stars than those following the general relationships. The non-universality of flux-flux relationships found in this work should be taken into account when converting between fluxes in different chromospheric activity indicators.Comment: Accepted for publication in the Monthly Notices of the Royal Astronomical Societ

A critical assessment of methods for the intrinsic analysis of liquid interfaces. 1. surface site distributions

Substantial progress in our understanding of interfacial structure and dynamics has stemmed from the recent development of algorithms that allow for an intrinsic analysis of fluid interfaces. These work by identifying the instantaneous location of the interface, at the atomic level, for each molecular configuration and then computing properties relative to this location. Such a procedure eliminates the broadening of the interface caused by capillary waves and reveals the underlying features of the system. However, a precise definition of which molecules actually belong to the interfacial layer is difficult to achieve in practice. Furthermore, it is not known if the different intrinsic analysis methods are consistent with each other and yield similar results for the interfacial properties. In this paper, we carry out a systematic and detailed comparison of the available methods for intrinsic analysis of fluid interfaces, based on a molecular dynamics simulation of the interface between liquid water and carbon tetrachloride. We critically assess the advantages and shortcomings of each method, based on reliability, robustness, and speed of computation, and establish consistent criteria for determining which molecules belong to the surface layer. We believe this will significantly contribute to make intrinsic analysis methods widely and routinely applicable to interfacial systems

A critical assessment of methods for the intrinsic analysis of liquid interfaces: 2. density profiles

Substantial improvements in the molecular level understanding of fluid interfaces have recently been achieved by recognizing the importance of detecting the intrinsic surface of the coexisting condensed phases in computer simulations (i.e., after the removal of corrugations caused by capillary waves) and by developing several methods for identifying the molecules that are indeed located at the boundary of the two phases. In our previous paper [J. Phys. Chem. C 2010, 114, 11169], we critically compared those methods in terms of reliability, robustness, and computation speed. Once the intrinsic surface of a given phase is detected, various profiles, such as the density profiles of the components, can be calculated relative to this intrinsic surface rather than to the macroscopically planar Gibbs dividing surface. As a continuation of our previous study, here we present a detailed and critical comparison of various methods that can be used to calculate intrinsic density profiles once the full set of truly interfacial molecules has been identified. Two of the methods, the Fourier function and the Voronoi tessellation, are already described in the literature; two other methods, the covering surface and the triangular interpolation, are newly proposed algorithms; one method, the modified grid-based intrinsic profile (GIP) method, is an improvement over an existing procedure. The different methods are again compared in terms of accuracy and computational cost. On the basis of this comparison, we propose a fast and accurate protocol to be routinely used for intrinsic surface analyses in computer simulations

METIS D3.4: Final workshops packages: workshops for different educational levels and education contexts

Several decades of research in technology-enhanced learning (TEL) have clearly demonstrated the potential of digital technology to transform education. Yet the impact of TEL research on daily teaching-learning practices is still far from fulfilling this potential. Arguably, this is a gap in the capacity for learning design: educators need the tools and competencies which would allow them to identify educational challenges, describe the context in which they arise, identify the opportunities afforded by technology, project the insights derived from research, and devise new learning experiences. To address this gap, educators need tools and practices. Tools that would support them through the cycle of learning design – from conception to deployment and evaluation of techno-educational innovations. Professional practices that use such tools to ensure the robustness and effectiveness of their innovations and make learning design a daily habit and part of their professional identity. The METIS project (http://metis-project.org/) aims to contribute to this aim, by providing educators with an Integrated Learning Design Environment (ILDE) (Hernández-Leo, Asensio-Pérez, Derntl, Prieto, & Chacón, 2014; Hernández-Leo et al., 2015) and a workshop package for training educators in using the ILDE to support effective learning design. Work Package 3, led by the OU (UK), is concerned with the design and development of the workshop package. This deliverable is the final version of the METIS workshop package. It includes • a meta-design for METIS workshops that provides a flexible reusable structure so that workshops can be customised to meet different needs , • a description of the rationale and pedagogical methodology on which the meta-design is based • guidance for instantiating the meta-design in different contexts and • example workshop packages based on the meta-design for three different educational sectors. This document provides educators with a basis for delivering workshops about using the ILDE to support effective learning design. To create and run a workshop suitable for your own context, please proceed in the following way. Firstly, consider the meta-design; then choose one of the example workshop packages closest to your context; finally, use the guidelines to adapt it for your needs