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

The massive multiple system HD 64315

The O6 Vn star HD 64315 is believed to belong to the star-forming region known as NGC 2467, but previous distance estimates do not support this association. We explore the multiple nature of this star with the aim of determining its distance, and understanding its connection to NGC 2467. A total of 52 high-resolution spectra have been gathered over a decade. We use their analysis, in combination with the photometric data from All Sky Automated Survey and Hipparcos catalogues, to conclude that HD 64315 is composed of at least two spectroscopic binaries, one of which is an eclipsing binary. HD 64315 contains two binary systems, one of which is an eclipsing binary. The two binaries are separated by 0.09 arcsec (or 500 AU) if the most likely distance to the system, around 5 kpc, is considered. The presence of fainter companions is not excluded by current observations. The non-eclipsing binary (HD 64315 AaAb) has a period of 2.70962901+/-0.00000021 d. Its components are hotter than those of the eclipsing binary, and dominate the appearance of the system. The eclipsing binary (HD 64315 BaBb) has a shorter period of 1.0189569+/-0.0000008 d. We derive masses of 14.6+-2.3 M$_\odot$ for both components of the BaBb system. They are almost identical; both stars are overfilling their respective Roche lobes, and share a common envelope in an overcontact configuration. The non-eclipsing binary is a detached system composed of two stars with spectral types around O6 V with minimum masses of 10.8 M$_\odot$ and 10.2 M$_\odot$, and likely masses aprox. 30 M$_\odot$. HD 64315 provides a cautionary tale about high-mass star isolation and multiplicity. Its total mass is likely above 90 M$_\odot$,but it seems to have formed without an accompanying cluster. It contains one the most massive overcontact binaries known, a likely merger progenitor in a very wide multiple system.Comment: 14 pages, 13 figures, 8 Table

Interaction-induced chaos in a two-electron quantum-dot system

A quasi-one-dimensional quantum dot containing two interacting electrons is analyzed in search of signatures of chaos. The two-electron energy spectrum is obtained by diagonalization of the Hamiltonian including the exact Coulomb interaction. We find that the level-spacing fluctuations follow closely a Wigner-Dyson distribution, which indicates the emergence of quantum signatures of chaos due to the Coulomb interaction in an otherwise non-chaotic system. In general, the Poincar\'e maps of a classical analog of this quantum mechanical problem can exhibit a mixed classical dynamics. However, for the range of energies involved in the present system, the dynamics is strongly chaotic, aside from small regular regions. The system we study models a realistic semiconductor nanostructure, with electronic parameters typical of gallium arsenide.Comment: 4 pages, 3ps figure

Traces de metalls contaminants en biomasses

La contaminació dels ecosistemes terrestres per elements traça ha anat augmentant progressivament durant les últimes dècades a moltes regions del món, incloent la Mediterrània europea. El CREAF investiga des de fa anys l'afectació que representa aquest fenomen per als ecosistemes terrestres de Catalunya. Aquests estudis de control ambiental de grans territoris presenten certes dificultats, en part degudes a la baixa concentració dels elements i al gran nombre de mostres a analitzar. Els recents avenços en el camp de l'espectroscòpia d'absorció atòmica amb atomització electrotèrmica (ETAAS) poden suposar un avenç en la instrumentació usada en aquests tipus d'anàlisi. Científics del CREAF han efectuat un estudi metodològic per escatir els millors i més moderns mètodes analítics per determinar arsènic (As), cadmi (Cd), coure (Cu), mercuri (Hg) i plom (Pb) en biomasses mitjançant ETAAS.La contaminación de los ecosistemas terrestres por elementos traza haido aumentando progresivamente durante las últimas décadas enmuchas regiones del mundo, incluyendo el Mediterráneo europeo. ElCREAF investiga desde hace años la afectación que representa estefenómeno para los ecosistemas terrestres de Cataluña. Estos estudiosde control ambiental de grandes territorios presentan ciertas dificultades,en parte debidas a la baja concentración de los elementos y al grannúmero de muestras a analizar. Los recientes avances en el campo dela espectroscopia de absorción atómica con atomización electrotérmica(ETAAS) pueden suponer un avance en la instrumentación usada eneste tipo de análisis. Científicos del CREAF han efectuado un estudiometodológico para dilucidar los mejores y más modernos métodos analíticos para determinar arsénico (As), cadmio (Cd), cobre (Cu),mercurio (Hg) y plomo (Pb) en biomasas mediante ETAAS

Las diferencias individuales en el proceso de envejecimiento humano

This article reviews the main trends in human aging research during the XX century upto and including the study of differences between individuals in groups, between individuals and intra-individuals. Descriptive data are presented which demonstrate the need to take into account individual differences in the study of the aging process. These variables include sex, age, marital status, and the personality dimensions of extraversion and neuroticism. A comparison is made between the subjective data drawn from self-perceptions recorded via partially structured interviews and objective data, including general psychological and physical health.En este articulo se repasan los diferentes objetos de estudio que a lo largo del siglo XX han tenido las investigaciones sobre el proceso de envejecimiento humano, hasta llegar al estudio de las diferencias individuales entre grupos, entre individuos e intra-individuales. Se presentan algunos datos descriptives generales que demuestran la existencia de diferencias individuales a tener en cuenta en el estudio del proceso de envejecimiento: sexo, edad, estado civil y personalidad, según las dimensiones extraversión y neuroticismo. Además, se comparan datos subjetivos, resultado de las autopercepciones registradas mediante la entrevista estructurada, con datos objetivos que incluyen la salud fisica y psicológica en general