Structure and dynamics of penumbral filaments

High-resolution observations of sunspots have revealed the existence of dark cores inside the bright filaments of the penumbra. Here we present the stationary solution of the heat transfer equation in a stratified penumbra consisting of nearly horizontal magnetic flux tubes embedded in a stronger and more vertical field. The tubes and the external medium are in horizontal mechanical equilibrium. This model produces bright filaments with dark cores as a consequence of the higher density of the plasma inside the flux tube, which shifts the surface of optical depth unity toward higher (cooler) layers. Our results suggest that the surplus brightness of the penumbra is a natural consequence of the Evershed flow, and that magnetic flux tubes about 250 km in diameter can explain the morphology of sunspot penumbra.Comment: 6 pages, 4 figures, conference proceedings: SEA, 2008, Santander, Spai

Fluxtube model atmospheres and Stokes V zero-crossing wavelengths

First results of the inversion of Stokes I and V profiles from plage regions near disk center are presented. Both low and high spatial resolution spectra of FeI 6301.5 and FeI 6302.5 A obtained with the Advanced Stokes Polarimeter (ASP) have been considered for analysis. The thin flux tube approximation, implemented in an LTE inversion code based on response functions, is used to describe unresolved magnetic elements. The code allows the simultaneous and consistent inference of all atmospheric quantities determining the radiative transfer with the sole assumption of hydrostatic equilibrium. By considering velocity gradients within the tubes we are able to match the full ASP Stokes profiles. The magnetic atmospheres derived from the inversion are characterized by the absence of significant motions in high layers and strong velocity gradients in deeper layers. These are essential to reproduce the asymmetries of the observed profiles. Our scenario predicts a shift of the Stokes V zero-crossing wavelengths which is indeed present in observations made with the Fourier Transform Spectrometer.Comment: To appear in ApJ Letters (1997) (in press

Photospheric structure of an extended penumbra

The photospheric structure of an extended penumbra belonging to a complex spot observed near disk center is investigated by means of the inversion of the full Stokes vector of two Fe I lines at 1.56 μm. An attempt is made to classify the observed Stokes V profiles in terms of their shapes. It turns out that about 28% of the profiles have abnormal shapes indicative of two different magnetic-field components within the resolution element. The spatial distribution of abnormal Stokes V profiles is studied. It is found that such profiles are evenly distributed in the penumbra, without any particular tendency to concentrate near the so-called neutral line. Anomalous profiles are not only seen in the outer penumbra and beyond, but also in the middle part of it. A Milne-Eddington–like inversion is carried out first, revealing a smooth picture of the spatial distribution of magneticfield vector and velocities along the line of sight. In particular, dark spines with stronger and more vertical magnetic fields are seen to coexist with nearly horizontal magnetic fields throughout the penumbra. A full inversion allowing for gradients of the atmospheric parameters along the line of sight indicates the existence of cool magnetic tubes returning back to the solar surface (inclination angles greater than 90◦) and carrying the largest material flows

The differentiated effects of CSR actions in the service industry

Purpose – The purpose of this study is to attempt to explain why the impact of Corporate Social Responsibility (CSR) initiatives may be different and/or more important in service firms compared to manufacturing firms. CSR is becoming a common strategy, hence its extensive research. Central to it is the analysis of the effect of CSR on a firm’s performance, whose outcome depends on firm-specific and industry-related factors. Design/methodology/approach – The event study methodology is applied to all the 248 companies that have ever traded on the Spanish Stock Market between 1990 and 2007. A regression analysis examines potential different effects of CSR on service and goods firms. Findings – The results show that CSR activities have a positive impact on firm performance that is higher for service firms than for manufacturing firms. Actions related to the environment, responsible labor relationships and good corporate governance are especially important in the service context. Research limitations/implications – This research is focused on shareholders’ performance, but it does not consider other stakeholders, such as real consumer behavior or employees’ commitment and productivity. Practical implications – Service firms are likely to gain from focusing on some CSR activities (environment, employees and good corporate governance) and should use their responsible behavior as a valuable tool for public relations and differentiation in the market. Originality/value – This article is the first attempt to empirically test and explain why the relationship between CSR and firm performance may be different (more positive) for service vs manufacturing firms.The authors would like to thank the Spanish Ministry of Science for financially supporting this research under Contract No. ECO2008-05487

On the validity of the 630 nm Fe I nm lines for the magnetometry of the internetwork quiet Sun

The purpose of this work is to analyze the reliability of the magnetic field strengths inferred from the 630 nm pair of Fe I lines at internetwork quiet Sun regions. Some numerical experiments have been performed that demonstrate the inability of these lines to recover the magnetic field strength in such low flux solar regions. It is shown how different model atmospheres, with magnetic field strengths ranging from few hundred Gauss to kiloGauss, give rise to Stokes profiles that can not be distinguished. The reasons for this degeneracy are discussed.Comment: Accepted for publication in A&

Consistency of expert product reviews: an application to wine guides

Purpose. The purpose of this study is to examine the internal consistency of wine guides by comparing the judgements of experts who taste and review wines. It further classifies the wines into categories to establish whether expert reviews of similar wines are coherent. Design/methodology/approach. Sentiment analysis based on natural language processing techniques was used to compare quantitative and qualitative reviews between experts. In addition, a finite mixture model was used to classify wines into categories to analyse internal consistency between ratings. Findings. The results for a sample of more than 200,000 Wine Enthusiast ratings reveal significant differences between the experts’ reviews, which shows that there are no standard criteria for reviewing the wines included in the guide. Originality. Wine guides are amongst the most widely used marketing resources in the wine industry. They provide a signal to consumers about the quality of wines, guiding their purchase decisions, whilst also influencing the reputation of brands and the performance of the companies producing these wines. Thus, the main contribution of this study is to improve comparisons of the assessments by wine guide experts in relation to the wines they taste. This analysis will make it possible to verify their effectiveness as a source of information for consumers and will allow wine producers to make more accurate assessments of the potential impact of experts on their performance

Models and Observations of Sunspot Penumbrae

The mysteries of sunspot penumbrae have been under an intense scrutiny for the past 10 years. During this time, some models have been proposed and refuted, while the surviving ones had to be modified, adapted and evolved to explain the ever-increasing array of observational constraints. In this contribution I will review two of the present models, emphasizing their contributions to this field, but also pinpointing some of their inadequacies to explain a number of recent observations at very high spatial resolution. To help explaining these new observations I propose some modifications to each of them. These modifications bring those two seemingly opposite models closer together into a general picture that agrees well with recent 3D magneto-hydrodynamic simulations.Comment: 9 pages, 1 color figure. Review talk to appear in the proceedings of the International Workshop of 2008 Solar Total Eclipse: Solar Magnetism, Corona and Space Weather--Chinese Space Solar Telescope Scienc

On the Magnetic Nature of an Exploding Granule as Revealed by Sunrise/IMaX

We study the photospheric evolution of an exploding granule observed in the quiet Sun at high spatial ($0.3^{\prime\prime}$) and temporal (31.5 s) resolution by the imaging magnetograph Sunrise/IMaX in June 2009. These observations show that the exploding granule is cospatial to a magnetic flux emergence event occurring at mesogranular scale (up to 12 Mm$^{2}$ area). Using a modified version of the SIR code for inverting the IMaX spectropolarimetric measurements, we obtain information about the magnetic configuration of this photospheric feature. In particular, we find evidence of highly inclined emerging fields in the structure, carrying a magnetic flux content up to $4 \times 10^{18}$ Mx. The balance between gas and magnetic pressure in the region of flux emergence, compared with a very quiet region of the Sun, indicates that the additional pressure carried by the emerging flux increases by about 5% the total pressure and appears to allow the granulation to be modified, as predicted by numerical simulations. The overall characteristics suggest that a multi-polar structure emerges into the photosphere, resembling an almost horizontal flux sheet. This seems to be associated with exploding granules. Finally, we discuss the origin of such flux emergence events.Comment: 19 pages, 12 figure + Appendix, accepted for ApJ. Figure 1 and Figure 5 are a low-quality version of the original one

Plasmodium falciparum Choline Kinase Inhibition Leads to a Major Decrease in Phosphatidylethanolamine Causing Parasite Death

This work was supported by Agencia Aragonesa para la Investigación y Desarrollo (ARAID), Ministerio de Economía y Competitividad (CTQ2013-44367-C2-2-P to R.H.-G.) and Diputación General de Aragón (DGA; B89 to R.H.-G.) and the EU Seventh Framework Programme (2007–2013) under BioStruct-X (grant agreement 283570 and BIOSTRUCTX 5186, to R.H.-G.). T.K.S. was supported by the Wellcome Trust grant 093228 and European Community’s Seventh Framework Programme under grant agreement No. 602773 (Project KINDRED).Malaria is a life-threatening disease caused by different species of the protozoan parasite Plasmodium, with P. falciparum being the deadliest. Increasing parasitic resistance to existing antimalarials makes the necessity of novel avenues to treat this disease an urgent priority. The enzymes responsible for the synthesis of phosphatidylcholine and phosphatidylethanolamine are attractive drug targets to treat malaria as their selective inhibition leads to an arrest of the parasite’s growth and cures malaria in a mouse model. We present here a detailed study that reveals a mode of action for two P. falciparum choline kinase inhibitors both in vitro and in vivo. The compounds present distinct binding modes to the choline/ethanolamine-binding site of P. falciparum choline kinase, reflecting different types of inhibition. Strikingly, these compounds primarily inhibit the ethanolamine kinase activity of the P. falciparum choline kinase, leading to a severe decrease in the phosphatidylethanolamine levels within P. falciparum, which explains the resulting growth phenotype and the parasites death. These studies provide an understanding of the mode of action, and act as a springboard for continued antimalarial development efforts selectively targeting P. falciparum choline kinase.Publisher PDFPeer reviewe