On the Wilson-Bappu relationship in the Mg II k line

An investigation is carried out on the Wilson-Bappu effect in the Mg II k line at 2796.34 A. The work is based on a selection of 230 stars observed by both the IUE and HIPPARCOS satellites, covering a wide range of spectral type and absolute visual magnitudes. The Wilson-Bappu relationship here provided is considered to represent an improvement over previous recent results for the considerably larger data sample used as well as for a proper consideration of the measurement errors. No evidence has been found for a possible dependence of the WB effect on stellar metallicity and effective temperature.Comment: 8 pages, 8 figures Accepted for publication on A&

A study of the Mg II 2796.34 A emission line in late--type normal, and RS CVn stars

We carry out an analysis of the Mg II 2796.34 A emission line in RS CVn stars and make a comparison with the normal stars studied in a previous paper (Paper I). The sample of RS CVn stars consists of 34 objects with known HIPPARCOS parallaxes and observed at high resolution with IUE. We confirm that RS CVn stars tend to possess wider Mg II lines than normal stars having the same absolute visual magnitude. However, we could not find any correlation between the logarithmic line width log Wo and the absolute visual magnitude Mv (the Wilson--Bappu relationship) for these active stars, contrary to the case of normal stars addressed in Paper I. On the contrary, we find that a strong correlation exists in the (Mv, log L) plane (L is the absolute flux in the line). In this plane, normal and RS CVn stars are distributed along two nearly parallel straight lines with RS CVn stars being systematically brighter by about 1 dex. Such a diagram provides an interesting tool to discriminate active from normal stars. We finally analyse the distribution of RS CVn and of normal stars in the (log L, log Wo) plane, and find a strong linear correlation for normal stars, which can be used for distance determinations.Comment: 10 pages, 7 figures, latex, to be published in A&

Can morphotaxa be assessed with photographs? Estimating the accuracy of two-dimensional cranial geometric morphometrics for the study of threatened populations of African monkeys

The classification of most mammalian orders and families is under debate and the number of species is likely greater than currently recognized. Improving taxonomic knowledge is crucial, as biodiversity is in rapid decline. Morphology is a source of taxonomic knowledge, and geometric morphometrics applied to two dimensional (2D) photographs of anatomical structures is commonly employed for quantifying differences within and among lineages. Photographs are informative, easy to obtain, and low cost. 2D analyses, however, introduce a large source of measurement error when applied to crania and other highly three dimensional (3D) structures. To explore the potential of 2D analyses for assessing taxonomic diversity, we use patas monkeys (Erythrocebus), a genus of large, semi-terrestrial, African guenons, as a case study. By applying a range of tests to compare ventral views of adult crania measured both in 2D and 3D, we show that, despite inaccuracies accounting for up to one-fourth of individual shape differences, results in 2D almost perfectly mirror those in 3D. This apparent paradox might be explained by the small strength of covariation in the component of shape variance related to measurement error. A rigorous standardization of photographic settings and the choice of almost coplanar landmarks are likely to further improve the correspondence of 2D to 3D shapes. 2D geometric morphometrics is, thus, appropriate for taxonomic comparisons of patas ventral crania. Although it is too early to generalize, our results corroborate similar findings from previous research in mammals, and suggest that 2D shape analyses are an effective heuristic tool for morphological investigation of small differences

Hadron detection with a dual-readout fiber calorimeter

In this paper, we describe measurements of the response functions of a fiber-based dual- readout calorimeter for pions, protons and multiparticle "jets" with energies in the range from 10 to 180 GeV. The calorimeter uses lead as absorber material and has a total mass of 1350 kg. It is complemented by leakage counters made of scintillating plastic, with a total mass of 500 kg. The effects of these leakage counters on the calorimeter performance are studied as well. In a separate section, we investigate and compare different methods to measure the energy resolution of a calorimeter. Using only the signals provided by the calorimeter, we demonstrate that our dual-readout calorimeter, calibrated with electrons, is able to reconstruct the energy of proton and pion beam particles to within a few percent at all energies. The fractional widths of the signal distributions for these particles (sigma/E) scale with the beam energy as 30%/sqrt(E), without any additional contributing terms

Phosphorylation of acetylhexosamines

originalFil: Leloir, Luis Federico. Instituto de Investigaciones Bioquímicas Fundación Campomar; ArgentinaFil: Cardini, Carlos E.. Instituto de Investigaciones Bioquímicas Fundación Campomar; ArgentinaFil: Olavarría, José M.. Instituto de Investigaciones Bioquímicas Fundación Campomar; ArgentinaBlanco y negro4 páginas en pdfLFL-PI-O-ART. Artículos científicosUnidad documental simpleAR-HYL-201

Direct transfer of zinc between plants is channelled by common mycorrhizal network of arbuscular mycorrhizal fungi and evidenced by changes in expression of zinc transporter genes in fungus and plant

The role that common mycorrhizal networks (CMNs) play in plant-to-plant transfer of zinc (Zn) has not yet been investigated, despite the proved functions of arbuscular mycorrhizal fungi (AMF) in crop Zn acquisition. Here, two autotrophic Medicago truncatula plants were linked by a CMN formed by Rhizophagus irregularis. Plants were grown in vitro in physically separated compartments (Donor-C and Receiver-C) and their connection ensured only by CMN. A symbiosis-defective mutant of M. truncatula was used as control in Receiver-C. Plants in both compartments were grown on Zn-free medium, and only the leaves of the donor plants were Zn fertilized. A direct transfer of Zn was demonstrated from donor leaves to receiver shoots mediated by CMN. Direct transfer of Zn was supported by changes in the expression of fungal genes, RiZRT1 and RiZnT1, and plant gene MtZIP2 in roots and MtNAS1 in roots and shoots of the receiver plants. Moreover, Zn transfer was supported by the change in expression of MtZIP14 gene in AM fungal colonized roots. This work is the first evidence of a direct Zn transfer from a donor to a receiver plant via CMN, and of a triggering of transcriptional regulation of fungal-plant genes involved in Zn transport-related processes

Internal rotation of red giants by asteroseismology

We present an asteroseismic approach to study the dynamics of the stellar interior in red-giant stars by asteroseismic inversion of the splittings induced by the stellar rotation on the oscillation frequencies. We show preliminary results obtained for the red giant KIC4448777 observed by the space mission Kepler.Comment: 3 pages, 4 figures, the 40th Liege International Astrophysical Colloquium Liac40, 'Ageing low mass stars: from red giants to white dwarfs', to be published on EPJ Web of Conference