Measurement of the Higgs Boson Mass with a Linear e+e- Collider

The potential of a linear e+e- collider operated at a centre-of-mass energy of 350 GeV is studied for the measurement of the Higgs boson mass. An integrated luminosity of 500 fb-1 is assumed. For Higgs boson masses of 120, 150 and 180 GeV the uncertainty on the Higgs boson mass measurement is estimated to be 40, 65 and 70 MeV, respectively. The effects of beam related systematics, namely a bias in the beam energy measurement, the beam energy spread and the luminosity spectrum due to beamstrahlung, on the precision of the Higgs boson mass measurement are investigated. In order to keep the systematic uncertainty on the Higgs boson mass well below the level of the statistical error, the beam energy measurement must be controlled with a relative precision better than 10-4.Comment: 19 pages, 10 Figure

Chemical analysis of carbon stars in the Local Group. II. The Carina dwarf spheroidal galaxy

Astronomy and Astrophysics, 481, pp. 161-168, http://dx.doi.org./10.1051/0004-6361:20079114International audienc

Evolution, nucleosynthesis and yields of low mass AGB stars at different metallicities (II): the FRUITY database

By using updated stellar low mass stars models, we can systematically investigate the nucleosynthesis processes occurring in AGB stars, when these objects experience recurrent thermal pulses and third dredge-up episodes. In this paper we present the database dedicated to the nucleosynthesis of AGB stars: the FRUITY (FRANEC Repository of Updated Isotopic Tables & Yields) database. An interactive web-based interface allows users to freely download the full (from H to Bi) isotopic composition, as it changes after each third dredge-up episode and the stellar yields the models produce. A first set of AGB models, having masses in the range 1.5 < M/Msun < 3.0 and metallicities 1e-3 < Z < 2e-2, is discussed here. For each model, a detailed description of the physical and the chemical evolution is provided. In particular, we illustrate the details of the s-process and we evaluate the theoretical uncertainties due to the parametrization adopted to model convection and mass loss. The resulting nucleosynthesis scenario is checked by comparing the theoretical [hs/ls] and [Pb/hs] ratios to those obtained from the available abundance analysis of s-enhanced stars. On the average, the variation with the metallicity of these spectroscopic indexes is well reproduced by theoretical models, although the predicted spread at a given metallicity is substantially smaller than the observed one. Possible explanations for such a difference are briefly discussed. An independent check of the third dredge-up efficiency is provided by the C-stars luminosity function. Consequently, theoretical C-stars luminosity functions for the Galactic disk and the Magellanic Clouds have been derived. We generally find a good agreement with observations.Comment: Accepted for Publication on The Astrophysical Journal Supplement

Galactic Cosmic Rays from Superbubbles and the Abundances of Lithium, Beryllium, and Boron

In this article we study the galactic evolution of the LiBeB elements within the framework of a detailed model of the chemical evolution of the Galaxy that includes galactic cosmic ray nucleosynthesis by particles accelerated in superbubbles. The chemical composition of the superbubble consists of varying proportions of ISM and freshly supernova synthesized material. The observational trends of 6 LiBeB evolution are nicely reproduced by models in which GCR come from a mixture of 25% of supernova material with 75% of ISM, except for 6 Li, for which maybe an extra source is required at low metallicities. To account for 7 Li evolution several additional sources have been considered (neutrino-induced nucleosynthesis, nova outbursts, C-stars). The model fulfills the energetic requirements for GCR acceleration.Comment: 25 pages, 9 figures. Accepted for publication in the Astrophysical Journa

Cross-Over between Discrete and Continuous Protein Structure Space: Insights into Automatic Classification and Networks of Protein Structures

Structural classifications of proteins assume the existence of the fold, which is an intrinsic equivalence class of protein domains. Here, we test in which conditions such an equivalence class is compatible with objective similarity measures. We base our analysis on the transitive property of the equivalence relationship, requiring that similarity of A with B and B with C implies that A and C are also similar. Divergent gene evolution leads us to expect that the transitive property should approximately hold. However, if protein domains are a combination of recurrent short polypeptide fragments, as proposed by several authors, then similarity of partial fragments may violate the transitive property, favouring the continuous view of the protein structure space. We propose a measure to quantify the violations of the transitive property when a clustering algorithm joins elements into clusters, and we find out that such violations present a well defined and detectable cross-over point, from an approximately transitive regime at high structure similarity to a regime with large transitivity violations and large differences in length at low similarity. We argue that protein structure space is discrete and hierarchic classification is justified up to this cross-over point, whereas at lower similarities the structure space is continuous and it should be represented as a network. We have tested the qualitative behaviour of this measure, varying all the choices involved in the automatic classification procedure, i.e., domain decomposition, alignment algorithm, similarity score, and clustering algorithm, and we have found out that this behaviour is quite robust. The final classification depends on the chosen algorithms. We used the values of the clustering coefficient and the transitivity violations to select the optimal choices among those that we tested. Interestingly, this criterion also favours the agreement between automatic and expert classifications. As a domain set, we have selected a consensus set of 2,890 domains decomposed very similarly in SCOP and CATH. As an alignment algorithm, we used a global version of MAMMOTH developed in our group, which is both rapid and accurate. As a similarity measure, we used the size-normalized contact overlap, and as a clustering algorithm, we used average linkage. The resulting automatic classification at the cross-over point was more consistent than expert ones with respect to the structure similarity measure, with 86% of the clusters corresponding to subsets of either SCOP or CATH superfamilies and fewer than 5% containing domains in distinct folds according to both SCOP and CATH. Almost 15% of SCOP superfamilies and 10% of CATH superfamilies were split, consistent with the notion of fold change in protein evolution. These results were qualitatively robust for all choices that we tested, although we did not try to use alignment algorithms developed by other groups. Folds defined in SCOP and CATH would be completely joined in the regime of large transitivity violations where clustering is more arbitrary. Consistently, the agreement between SCOP and CATH at fold level was lower than their agreement with the automatic classification obtained using as a clustering algorithm, respectively, average linkage (for SCOP) or single linkage (for CATH). The networks representing significant evolutionary and structural relationships between clusters beyond the cross-over point may allow us to perform evolutionary, structural, or functional analyses beyond the limits of classification schemes. These networks and the underlying clusters are available at http://ub.cbm.uam.es/research/ProtNet.phpThis work was supported by the Ramon y Cajal program of the Spanish Science Ministry of Education and Science, Project ‘Centrosoma 3DBioinformatics’ of the program Consolider-Ingenio 2010 of the Spanish Ministry of Education and Science, Project BIO2005-0576 from the Spanish Ministry of Education and Science, Project 200520M157 from the Comunidad de Madrid, and Research Foundation ‘‘Ramon Areces’’.Peer reviewe

12^{12}C/13^{13}C ratio in planetary nebulae from the IUE archives

We investigated the abundance ratio of $^{12}$C/$^{13}$C in planetary nebulae by examining emission lines arising from \ion{C}{3} 2s2p ^3P_{2,1,0} \to 2s^2 ^1S_0. Spectra were retrieved from the International Ultraviolet Explorer archives, and multiple spectra of the same object were coadded to achieve improved signal-to-noise. The $^{13}$C hyperfine structure line at 1909.6 \AA was detected in NGC 2440. The $^{12}$C/$^{13}$C ratio was found to be $\sim4.4\pm$1.2. In all other objects, we provide an upper limit for the flux of the 1910 \AA line. For 23 of these sources, a lower limit for the $^{12}$C/$^{13}$C ratio was established. The impact on our current understanding of stellar evolution is discussed. The resulting high signal-to-noise \ion{C}{3} spectrum helps constrain the atomic physics of the line formation process. Some objects have the measured 1907/1909 flux ratio outside the low-electron density theoretical limit for $^{12}$C. A mixture of $^{13}$C with $^{12}$C helps to close the gap somewhat. Nevertheless, some observed 1907/1909 flux ratios still appear too high to conform to the presently predicted limits. It is shown that this limit, as well as the 1910/1909 flux ratio, are predominantly influenced by using the standard partitioning among the collision strengths for the multiplet $^1S_0$--$^3P_J$ according to the statistical weights. A detailed calculation for the fine structure collision strengths between these individual levels would be valuable.Comment: ApJ accepted: 19 pages, 3 Figures, 2 Table

Microarray-based identification of antigenic variants of foot-and-mouth disease virus: a bioinformatics quality assessment

BACKGROUND: The evolution of viral quasispecies can influence viral pathogenesis and the response to antiviral treatments. Mutant clouds in infected organisms represent the first stage in the genetic and antigenic diversification of RNA viruses, such as foot and mouth disease virus (FMDV), an important animal pathogen. Antigenic variants of FMDV have been classically diagnosed by immunological or RT-PCR-based methods. DNA microarrays are becoming increasingly useful for the analysis of gene expression and single nucleotide polymorphisms (SNPs). Recently, a FMDV microarray was described to detect simultaneously the seven FMDV serotypes. These results encourage the development of new oligonucleotide microarrays to probe the fine genetic and antigenic composition of FMDV for diagnosis, vaccine design, and to gain insight into the molecular epidemiology of this pathogen. RESULTS: A FMDV microarray was designed and optimized to detect SNPs at a major antigenic site of the virus. A screening of point mutants of the genomic region encoding antigenic site A of FMDV C-S8c1 was achieved. The hybridization pattern of a mutant includes specific positive and negative signals as well as crosshybridization signals, which are of different intensity depending on the thermodynamic stability of each probe-target pair. Moreover, an array bioinformatic classification method was developed to evaluate the hybridization signals. This statistical analysis shows that the procedure allows a very accurate classification per variant genome. CONCLUSION: A specific approach based on a microarray platform aimed at distinguishing point mutants within an important determinant of antigenicity and host cell tropism, namely the G-H loop of capsid protein VP1, was developed. The procedure is of general applicability as a test for specificity and discriminatory power of microarray-based diagnostic procedures using multiple oligonucleotide probes