3,272 research outputs found
Synthetic Stellar Clusters for Pop III
We present preliminary results of an incoming theoretical work concerning the
integrated properties of the Population III clusters of stars. On the basis of
synthetic Color-Magnitude Diagrams, we provide a grid of optical and near-IR
colors of Simple Stellar Populations with very low metallicity (Z=10
and Z=10) and age which spans from 10 Myr to 15 Gyr. A comparison with
higher metallicities up to 0.006 is also shown, disclosing sizable differences
in the CMD morphology, integrated colors and Spectral Energy Distribution
(SED).Comment: 2 pages, incl. 2 figures, "The First Stars", Proceedings of the
second MPA/ESO workshop, Eds.: Weiss, Abel, Hill, Springer, Heidelberg, 200
Geometric phase and gauge theory structure in quantum computing
We discuss the presence of a geometrical phase in the evolution of a qubit
state and its gauge structure. The time evolution operator is found to be the
free energy operator, rather than the Hamiltonian operator.Comment: 5 pages, presented at Fifth International Workshop DICE2010:
Space-Time-Matter - current issues in quantum mechanics and beyond,
Castiglioncello (Tuscany), September 13-17, 201
On the observational properties of He-burning stars: some clues on the tilt of the HB in metal rich clusters
We investigate the predicted Color-Magnitude distribution of metal-rich
Horizontal Branch (HB) stars, discussing selected theoretical models computed
under various assumptions about the star metallicity and the efficiency of
super-adiabatic convection. We find that canonical Zero Age Horizontal Branches
with metallicity larger or of the order of Z=0.002 should be all affected by a
tilt, by an amount which increases when the metallicity is increased and/or the
mixing length is decreased, reaching a tilt of 0.2 mag in the
case of solar metallicity when a mixing length value =1.6 is assumed
( is the magnitude difference between the top of the blue HB and the
fainter magnitude reached by the red HB). Uncertainties in the luminosity of
the red HB due to uncertainty in the mixing length value are discussed. We
finally discuss the much larger tilt observed in the clusters NGC 6441 and NGC
6388, reporting additional evidence against suggested non-canonical
evolutionary scenarios. Numerical experiments show that differential reddening
could produce such sloped HBs. Further, HST-PC imaging of NGC 6441 gives clear
indications about the occurrence of differential reddening across the cluster.
However, the same imaging shows that the observed slope of the red HB {\em is
not} an artifact of differential reddening. We finally show that sloping red
HBs in metal rich clusters are a common occurrence not necessarily correlated
with the appearance of extended blue HB.Comment: 14 pages, 9 figures, Accepted by Ap
Taxonomic remarks and distribution of Smyrnium dimartinoi (Apiaceae)
Smyrnium L., an Eurasian genus of the family Apiaceae, includes about 20 taxa of which only 7 are accepted at specific rank; among these, 5 are native to Europe (Tutin & al. 1968; Gomez 2003). In the Italian flora, the genus is represented by 3 taxa also occurring in Sicily (Pignatti 1982; Giardina & al. 2007); these are Smyrnium olusatrum L., S. perfoliatum L. and S. rotundifolium Mill. The last one has also been treated at the rank of subspecies under S. perfoliatum [S. perfoliatum subsp. rotundifolium (Mill.) Hartvig] (Strid 1986; Conti & al. 2005), or as a variety [S. perfoliatum var. rotundifolium (Mill.)Fiori (Fiori 1925)]. In Sicily, same populations related to S. perfoliatum differ from this taxon for both morphological and ecological characteristics, especially on the Madonie Mountains and the Mountains around Palermo.
The study of the morphological characteristics \u2013 namely of the root, stem, and leaf \u2013 allowed to clearly distinguish these populations that, therefore, represented a taxonomically and perhaps even chorologically critical case, since similar plants occurring in Greece were described as S. rotundifolium var. ovatifolium Hal\ue1csy (Hal\ue1csy 1901). In Sicily the same population was finally described as a new species named Smyrnium dimartinoi (Raimondo et al., 2015) to commemorate Andrea Di Martino (1926-2009), professor of botany and director of the Botanical Garden and Herbarium Mediterraneum in the Palermo University.
The occurrence of the new taxon related to S. perfoliatum \u2013 ascertained only in Central-Western Sicily and in Crete \u2013 has also been supposed in other countries of the Mediterranean Europe; this, owing to some critical specimens observed in PAL and PAL-Gr.
In this contribution, the analytical key of S. perfoliatum group is presented. Furthermore, the geographical distribution of S. dimartinoi is specified after the study of selected exsiccata from other Italian and foreign herbaria. The results found in this research show that S. dimartinoi belongs to the Eurimediterranean element, spread in various countries of the Southern Europe, from Greece to Italy and Spain
Genetic variation patterns in some groups of Centaurea (Asteraceae) in Italy
In the current work the data of the isozyme analysis of all the twenty studied Italian Centaurea
taxa were compared. They belong to Centaurea parlatoris, C. cineraria, C. tenorei and C. jacea
groups. The following parameters of the genetic variability were considered: the total number
of the alleles, the mean number of alleles per locus (A), the mean percentage of polymorphic
loci (P95), the expected heterozygosity (He) that is a measure of the intra-population diversity,
the Wright’s fixation index (F) and inbreeding coefficient (FIS) that are measures for the deviation
from the Hardy-Weinberg equilibrium.
The present study contributes to insight some aspects of the genetic diversity related to the distribution
range (endemics or widespread taxa) of the studied Centaurea species. The mean proportion
of polymorphic loci and the mean number of alleles per locus (A) in the endemic
species are comparable with the widespread ones, while the intra-population diversity (He)
results about 40% higher in the populations of the widespread taxa than the endemics. The loci
with a major role for the processes of differentiation and evolution of the genus Centaurea in
South Italy and Sicily are: Mdh-1, Pgi-2 and Idh-1.
Italian Centaurea species with the highest genetic diversity usually inhabit extreme habitats (rocky,
sandy places, etc.) and localities with significant human impact or the borderline of their area of distribution.
Sicily could be considered a centre of differentiation of the endemic groups of C. cineraria
and C. parlatoris which show relatively high intra-population variability
The LHC string2 supervision system
This paper describes the implementation of the supervision system for the LHC Prototype Full-Cell also known as String 2. The supervision application is based on a commercial package targeted to industrial controls, but because of the complexity and the specifics of such a system, integration with custom components is necessary in order to merge the industrial requirements with the specificity of the accelerator controls
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