Absolute dimensions of the G7+K7 eclipsing binary star IM Virginis: Discrepancies with stellar evolution models

We report extensive spectroscopic and differential photometric BVRI observations of the active, detached, 1.309-day double-lined eclipsing binary IM Vir, composed of a G7-type primary and a K7 secondary. With these observations we derive accurate absolute masses and radii of M(1) = 0.981 +/- 0.012 M(Sun), M(2) = 0.6644 +/- 0.0048 M(Sun), R(1) = 1.061 +/- 0.016 R(Sun), and R(2) = 0.681 +/- 0.013 R(Sun) for the primary and secondary, with relative errors under 2%. The effective temperatures are 5570 +/- 100 K and 4250 +/- 130 K. The significant difference in mass makes this a favorable case for comparison with stellar evolution theory. We find that both stars are larger than the models predict, by 3.7% for the primary and 7.5% for the secondary, as well as cooler than expected, by 100 K and 150 K, respectively. These discrepancies are in line with previously reported differences in low-mass stars, and are believed to be caused by chromospheric activity, which is not accounted for in current models. The effect is not confined to low-mass stars: the rapidly-rotating primary of IM Vir joins the growing list of objects of near-solar mass (but still with convective envelopes) that show similar anomalies. The comparison with the models suggests an age of 2.4 Gyr for the system, and a metallicity [Fe/H] of approximately -0.3 that is consistent with other indications, but requires confirmation.Comment: 14 pages, 13 figures. Accepted for publication in Ap

On F-Algebroids and Dubrovin's Duality

In this note we introduce the concept of F-algebroid, and give its elementary properties and some examples. We provide a description of the almost duality for Frobenius manifolds, introduced by Dubrovin, in terms of a composition of two anchor maps of a unique cotangent F-algebroid.Comment: 13 pages; v2 has small changes, it has improved exposition. Revised version to appear in: "Archivum Mathematicum

The effect of magnetic activity on low-mass stars in eclipsing binaries

In recent years, analyses of eclipsing binary systems have unveiled differences between the observed fundamental properties of low-mass stars and those predicted by stellar structure models. Particularly, radius and effective temperatures computed from models are ~ 5-10% lower and ~ 3-5% higher than observed, respectively. These discrepancies have been attributed to different factors, notably to the high levels of magnetic activity present on these stars. In this paper, we test the effect of magnetic activity both on models and on the observational analysis of eclipsing binaries using a sample of such systems with accurate fundamental properties. Regarding stellar models, we have found that unrealistically high spot coverages need to be assumed to reproduce the observations. Tests considering metallicity effects and missing opacities on models indicate that these are not able to explain the radius discrepancies observed. With respect to the observations, we have tested the effect of several spot distributions on the light curve analysis. Our results show that spots cause systematic deviations on the stellar radii derived from light curve analysis when distributed mainly over the stellar poles. Assuming the existence of polar spots, overall agreement between models and observations is reached when ~ 35% spot coverage is considered on stellar models. Such spot coverage induces a systematic deviation in the radius determination from the light curve analysis of ~ 3% and is also compatible with the modulations observed on the light curves of these systems. Finally, we have found that the effect of activity or rotation on convective transport in partially radiative stars may also contribute to explain the differences seen in some of the systems with shorter orbital periods.Comment: 12 pages, 9 figures, accepted for publication in Ap

«Incursions en el Fileb» : notícia del Seminari Internacional

El text recull el conjunt de les aporacions dels participants en el Seminari «Incursions en el Fileb», celebrat a Coimbra els dies 2 i 3 de juliol de 2009. Les aportacions versen sobre diverses qüestions del text del Fileb i intenten oferir una lectura del tot del diàleg des de diverses perspectives.The text includes a sumari of all the contributions in the seminar «incursions into Philebus» held in Coimbra on 2 and 3 July 2009. The contributions, focusing on various issues of the Philebus’ text, aim to a comprehensive reading of the whole dialogue from different perspectives

Fundamental properties of lower main-sequence stars

The field of exoplanet research has revitalized interest in M dwarfs, which have become favorite targets of Doppler and transit surveys. Accurate measurements of their basic properties such as masses, radii, and effective temperatures have revealed significant disagreements with predictions from stellar evolution theory in the sense that stars are larger and cooler than expected. These anomalies are believed to be due to high levels of activity in these stars. The evidence for the radius discrepancies has grown over the years as more and more determinations have become available; however, fewer of these studies include accurate determinations of the temperatures. The ubiquitous mass-radius diagrams featured in many new discovery papers are becoming more confusing due to increased scatter, which may be due in part to larger than realized systematic errors affecting many of the published measurements. A discussion of these and other issues is given here from an observer's perspective, along with a summary of theoretical efforts to explain the radius and temperature anomalies.Comment: 7 pages, to appear in the Proceedings of the 17th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, eds. K. Strassmeier & M. Lopez-Morales (AN, Vol. 334

Hygroscopicity issues in powder and grain technology

The effect of hygroscopicity on flowability of powders and bulk solids with applications in the packaging industry is experimentally and numerically investigated. Firstly, four granular materials are tested at different water contents to study the impact of relative humidity on some hydro-mechanical properties, namely the hydraulic diffusivity on wetting, as well as the shear strength and compressibility properties of the materials. Next, a capillary model covering a wider water content range –compared to the previous tests– is applied to discrete element simulations of a granular column collapse set-up. These simulations give further insight into important aspects of grain hygroscopicity in packaging and other industrial applications (such as the kinematics of flow and flowability issues), which are outside the scope of conventional experimental testing.Postprint (published version

Astrid Morales Torres, Piano

Prelude and Fugue in C sharp Major, WTC I, BWV 848 / J.S. Bach; Impromptus, Op. 90 / F. Schubert; Concert Etude No. 3 / M.M. Ponce; Piano Concerto / M.M. Ponc

Paradoxes of Pain: A Dialogue between Plato and Contemporary Phenomenology

The paper presents a dialogue, between contemporary phenomenology and Plato, on the nature and complexity of pain. Taking as a departure point D. Leder's article «The experiential paradoxes of pain», the article delves into the essentially liminal character of pain and focusses afterwards in two paradoxes that this experiences reveals. The first one is the one that describes pain as a sensation and also as an interpretation; the second one is the one that describes pain as a destructive and also productive experience. Throughout the article we will see that the Platonic approach, although being much more holistic (in the sense of combining always the persona, ethical, political and also cosmological perspective), is not far away from the phenomenological one. That both approaches try to set limits and to describe an experience that escapes all limitations and determinations.El artículo presenta un diálogo entre la fenomenología contemporánea y Platón sobre la naturaleza complejidad del dolor. Tomando como punto de partida el artículo de D. Leder «Las paradojas experienciales del dolor», el escrito profundiza en el carácter esencialmente liminal del dolor y luego se centra en dos paradojas que revela esta experiencia. La primera es la que describe el dolor como una sensación y también como una interpretación; la segunda es el que lo describe como una experiencia destructiva y también productiva. A lo largo del artículo veremos que el enfoque platónico, aunque sea mucho más holístico (en el sentido de combinar siempre la perspectiva personal, ética, política y también cosmológica), no está muy lejos de la fenomenológica. Que ambos enfoques intentan establecer límites y describir una experiencia que escapa a todas las limitaciones y determinaciones

Protein Expression of Steroid Receptors in Macaca mulatta endometriotic Lesions

Endometriosis is pathologically defined as the presence of endometrial tissue in ectopic locations. Currently, there are no specific, non-invasive biomarkers and no cure for endometriosis. Non-human primates (NHP), including Macaca mulatta (rhesus macaques), have been highlighted as appropriate models to study endometriosis due to genetic, physiological, and anatomical similarities to humans. Research shows endometriosis might be associated with molecular deviations in human peritoneal endometriosis, such as increased levels of estrogen receptors and decreased levels of progesterone receptors. The aim of this study is to determine protein expression of steroid receptors in five endometriotic lesions of rhesus macaques. We propose that lesions of rhesus macaques will express elevated estrogen receptors and diminished progesterone receptors, similar to human endometriotic lesions. Endometriotic lesions of rhesus macaques were obtained at time of surgery from different locations, and steroid receptor expression was determined by immunohistochemistry. This study was able to determine the expression of steroid receptors in endometriotic lesions of rhesus macaques; however the results were not able to support our hypothesis. Results did not observe significant differences between estrogen and progesterone receptor protein expressions in glandular and stromal compartments of the endometriotic lesions. Still, this animal model represents a valuable tool to study endometriosis since they do develop spontaneous endometriosis. Future studies should match the location of lesions and classify the severity of endometriosis in the rhesus macaques